US20050019180A1

US20050019180A1 - Pump

Info

Publication number: US20050019180A1
Application number: US10/866,119
Authority: US
Inventors: Takeshi Seto; Kunihiko Takagi
Original assignee: Seiko Epson Corp
Current assignee: Seiko Epson Corp
Priority date: 2003-06-17
Filing date: 2004-06-14
Publication date: 2005-01-27
Also published as: EP1489306A2; DE602004006802T2; EP1489306A3; JP2005133704A; JP4678135B2; DE602004006802D1; CN100398821C; CN1573102A; EP1489306B1

Abstract

To provide a pump capable of discharging gas bubbles and thus maintaining a discharging ability, even when the gas bubbles stay inside a pump chamber, a pump includes a primary pump chamber whose volume can be varied by driving a diaphragm, an inlet passage to allow a working fluid to flow into the primary pump chamber, an outlet passage to allow the working fluid to flow out of the primary pump chamber, and check valves to open and close at least the inlet passage. A resultant inertance value of the inlet passage is set to be smaller than a resultant inertance value of the outlet passage. A bubble discharging device to discharge gas bubbles remained in the primary pump chamber is further provided. As a result, it is possible to provide a pump capable of discharging gas bubbles with the bubble discharging device and thus maintain a discharging ability, even when the gas bubbles stay in the primary pump chamber.

Description

BACKGROUND OF THE INVENTION

1. Field of Invention
The present invention relates to a pump to move a working fluid by varying a volume of a pump chamber by a piston or a movable wall, such as a diaphragm, and specifically to a small high-power pump.
2. Description of Related Art
In the related art, there are pumps having a construction in which check valves are provided between an inlet passage and a pump chamber having a variable volume and between an outlet passage and the pump chamber, respectively. Further, in a case of a pump having a purpose of transferring liquid, there is a related art structure that a thin wall portion is provided at an upstream side or downstream side passage of a pump chamber and thus pulsation due to the liquid intermittently driven is reduced through deformation of the passage (see, Japanese Unexamined Patent Application Publication No. 2000-265963.
Furthermore, there is a related art high-power pump with high reliability, which was suggested by the present inventor, etc., capable of coping with high load pressure and high frequency driving by employing a passage structure having a large inertance value in place of a valve in an outlet passage and thus by using a force of fluid inertia. In a pump having such a structure, for the purpose of preventing a suction efficiency of the pump from being decreased due to pulsation in an inlet passage, a deformable structure is used in the inlet passage (see, Japanese Unexamined Patent Application Publication No. 2002-322986.
Furthermore, there is a related art volume pump including a diaphragm to be driven with a piezoelectric element, such as a PZT, a pump chamber whose volume can be varied by the diaphragm, a hole to allow a fluid to flow into the pump chamber, and a hole to allow the fluid to flow out of the pump chamber, check valves being provided in the respective holes (see, for example, Japanese Unexamined Patent Application Publication No. 61-171891.

SUMMARY OF THE INVENTION

However, in the construction of Japanese Unexamined Patent Application Publication No. 2000-265963 there is a problem that it is not possible to cope with the high load pressure or high frequency driving, because the inlet passage and the outlet passage all require the check valve serving as a fluid resistance element. Thus, the pressure loss of the fluid is large through the two check valves. In a case where gas bubbles stay in the pump chamber, there is a problem that it is not possible to obtain a predetermined amount of discharge, because the pressure of the liquid in the pump chamber is not raised enough in the course of reducing the volume of the pump chamber.
Furthermore, in the pumps having the constructions of Japanese Unexamined Patent Application Publication No. 2002-322986 and Japanese Unexamined Patent Application Publication No. 61-171891, since the variation in volume of the pump chamber due to the deformation of the diaphragms is small, the pressure of the liquid in the pump chamber is not raised enough in the course of reducing the volume of the pump chamber when gas bubbles stay in the pump chamber. As a result, the flow characteristics of the pump are largely deteriorated. If things come to the worst, it may be impossible to discharge the liquid.
The present invention provides a pump capable of discharging gas bubbles and thus maintaining a discharging ability, even when the gas bubbles stay inside a pump chamber.
A pump according to an aspect of the present invention includes a pump chamber whose volume can be varied by driving a piston or a movable wall, an inlet passage to allow a working fluid to flow into the pump chamber, an outlet passage to allow the working fluid to flow out of the pump chamber, and a fluid resistance element to open and close at least the inlet passage. A resultant inertance value of the inlet passage is set to be smaller than a resultant inertance value of the outlet passage. A bubble discharging device to discharge gas bubbles remaining in the pump chamber is further provided.
Here, a diaphragm, which is driven with an actuator, such as a piezoelectric element, may be used as the movable wall. Further, a check valve may be used as the fluid resistance element.
Furthermore, as the bubble discharging device, details of which will be described later, for example, a secondary pump chamber, a pressurizing mechanism, a heating section, etc., which is used to apply a pressure to the pump chamber, may be used.
According to this construction, since the pump includes the bubble discharging device, the pump can be started even when gas bubbles stay in the pump chamber. Specifically, even when the working fluid is not filled in the pump chamber. Further, when the gas bubbles stay in the pump chamber, although it is considered that the pressure in the pump chamber is not sufficiently raised, the staying gas bubbles can be discharged in driving the pump, due to the aforementioned bubble discharging device. So it is possible to maintain performance of the pump, specifically, the discharge amount of the working fluid.
Further, in the aforementioned construction, the pump chamber may include a primary pump chamber which communicates with the outlet passage and whose volume can be varied by driving a piston or a movable wall, and a secondary pump chamber which communicates with the inlet passage and functions as the bubble discharging device and whose volume can be varied by driving a movable wall.
According to this construction, since the secondary pump chamber as the bubble discharging device is provided at the inlet passage side, the working fluid of the inlet passage can be transferred to the primary pump chamber by driving the secondary pump chamber. Thus the pressure in the primary pump chamber can be raised, so that it is possible to discharge the gas bubbles in the primary pump chamber.
The pump having the above construction may include a primary pump chamber inlet passage to allow the working fluid to flow into the primary pump chamber; a primary pump chamber outlet passage to allow the working fluid to flow out of the primary pump chamber; a secondary pump chamber inlet passage to allow the working fluid to flow into the secondary pump chamber; and a secondary pump chamber outlet passage to allow the working fluid to flow out of the secondary pump chamber, and the primary pump chamber inlet passage be the secondary pump chamber outlet passage.
According to this construction, since the primary pump chamber inlet passage is also used as the secondary pump chamber outlet passage, the flow passage of the working fluid is shortened. Thus the size of the pump can be decreased, so that it is possible to reduce the fluid resistance of the flow passage.
The pump according to an aspect of the present invention may include a fluid resistance element to open and close the primary pump chamber inlet passage; a fluid resistance element to open and close the secondary pump chamber inlet passage; and a fluid resistance element to open and close the secondary pump chamber outlet passage, and the fluid resistance element to open and close the primary pump chamber inlet passage may be the fluid resistance element to open and close the secondary pump chamber outlet passage.
According to this construction, for example, when the movable wall of the secondary pump chamber is driven, a check valve, as the fluid resistance element of the secondary pump chamber inlet passage, is closed. Then the working fluid, of which the pressure has been raised in the secondary pump chamber, flows into the primary pump chamber. Further, when the working fluid is discharged from the primary pump chamber, a check valve as the fluid resistance element of the primary pump chamber inlet passage is closed. In this way, since the inside pressure of the primary pump chamber can be raised, the gas bubbles staying in both pump chambers can be compressed and then discharged to the outside of the pump chambers.
Furthermore, since the fluid resistance element to open and close the primary pump chamber inlet passage is the fluid resistance element to open and close the secondary pump chamber outlet passage, two check valves, as the fluid resistance elements, are enough for two pump chambers. So it is possible to simplify the structure of the pump, to reduce the number of components, and thus to accomplish low cost. Furthermore, it is also possible to reduce the fluid resistance.
In the pump having the aforementioned construction, the movable wall provided in the secondary pump chamber may be a diaphragm in which a piezoelectric element is attached to at least one surface thereof, and the secondary pump chamber and the diaphragm constitute a unimorph pump or a bimorph pump.
According to this construction, the secondary pump chamber can be constructed using a piezoelectric element attached to the diaphragm used in related art pulsation reducing device for a flow passage. Further, since the unimorph pump and the bimorph pump have a large amount of displacement of the diaphragm even under a low pressure, they can combine the functions of the secondary pump chamber as a pulsation absorbing device and the aforementioned bubble discharging device.
The pump having the above construction may include a driving switch control unit for switching the driving between the secondary pump chamber and the primary pump chamber.
By the driving switch control unit, for example, when the driving of the pump is started, the inner gas bubbles can be discharged by first driving the secondary pump chamber and then driving the primary pump chamber. Then the primary pump chamber is continuously driven or the primary pump chamber and the secondary pump chamber can be alternately driven, so that it is possible to obtain a stable discharge amount of working fluid during the driving of the pump.
Furthermore, a driving electrode and a detecting electrode may be formed in the piezoelectric element.
According to this construction, the state of the secondary pump chamber can be detected. Specifically, variation in the inside pressure of the secondary pump chamber can be detected as displacements of the piezoelectric element. It is thus possible to control the primary pump chamber and the secondary pump chamber correspondingly to the variation in pressure by using the above-mentioned driving switch control unit.
Furthermore, the pump according to an aspect of the present invention may include a pressure detecting section to detect an inside pressure of the primary pump chamber.
According to this construction, the state inside the primary pump chamber can be detected. So it is possible to efficiently drive the pump correspondingly to the state inside the primary pump chamber.
Further, by combining the state inside the primary pump chamber with the state inside the secondary pump chamber detected through the detecting electrode of the secondary pump chamber, it is possible to drive the pump more efficiently than a case of driving the pump correspondingly to both states of both pump chambers.
The above-mentioned pump according to an aspect of the present invention may include a pressurizing mechanism serving as the bubble discharging device to raise and maintain the pressure of the working fluid existing in the pump chamber.
According to this construction, when the inside pressure of the pump chamber is reduced due to the gas bubbles staying in the pump chamber and thus the working fluid cannot be discharged, the pressure of the working fluid in the pump chamber can be raised and maintained by the pressurizing mechanism. As a result, since the volume of the gas bubbles is decreased, it is possible to discharge the gas bubbles in the pump chamber by compressing the volume of the pump chamber through driving the piston or the movable wall, such as a diaphragm.
In the above-mentioned construction, the pressurizing mechanism may include a variable-volume chamber and a flow passage to allow the variable-volume chamber and the outlet passage to communicate with each other.
According to this construction, since the variable-volume chamber communicates with the outlet passage by pressing the variable-volume chamber, the pressurizing mechanism can simply generate a high pressure in the pump chamber communicating with the outlet passage.
In the above-mentioned construction, the variable-volume chamber may be formed of an elastic member.
According to this construction, by forming the variable-volume chamber out of the elastic member, the pressure can be smoothly raised due to the introduction of the working fluid into the variable-volume chamber. Damages on the components constituting the pump due to the pressure can be reduced or prevented. Further, the variable-volume chamber also functions to reduce the pressure pulsation in the outlet passage. As a result, it is possible to reduce or prevent the variation in pump ability from occurring due to influence of an external pipe to be connected to the outlet passage.
Furthermore, in the above-mentioned construction, the pressurizing mechanism may include a volume varying mechanism to apply a pressure to vary the volume of the variable-volume chamber.
Here, an actuator may be employed as the volume varying mechanism.
According to this construction, since the volume varying mechanism to vary the volume of the variable-volume chamber is provided, it is possible to control the volume of the variable-volume chamber correspondingly to the state of the pump chamber.
In an aspect of the present invention, the pressurizing mechanism may include a passage switching section to switch between a first mode where the working fluid flowing out of the pump chamber is introduced into the variable-volume chamber and a second mode where the working fluid flowing out of the pump chamber is isolated from the variable-volume chamber.
According to this construction, for example, when it is detected that gas bubbles exist in the pump chamber, it is possible to surely press the working fluid in the pump chamber with the elastic force of the elastic member constituting the variable-volume chamber, by setting the first mode where the working fluid flowing out of the pump chamber is introduced into the variable-volume chamber. When the gas bubbles do not exist in the pump chamber, the working fluid is controlled not to be introduced into the variable-volume chamber but to be discharged out of the pump chamber, so that it is possible to efficiently drive the pump.
The pump having the above construction may include a pressure detecting section to detect an inside pressure of the variable-volume chamber.
In this way, by providing the pressure detecting device to detect the inside pressure of the variable-volume chamber, it is possible to control the inside pressure of the variable-volume chamber within a proper range of pressure.
In the aforementioned pump, the pressure detecting device may be provided in the pump chamber.
As a result, by detecting the inside pressure of the pump chamber and determining whether the gas bubbles stay in the pump chamber, it is possible to suitably control the driving of the pump chamber and the pressurizing mechanism.
In the above construction, the inside pressure of the variable-volume chamber, which is pressurized by the pressurizing mechanism, may range from about one atmosphere to about five atmospheres in a gauge pressure.
According to this construction, it is possible to reduce the volume of the gas bubbles staying in the pump chamber as enough as possible to discharge without damaging the components constituting the pump by the pressure.
Furthermore, the pressurizing mechanism may include a variable-volume chamber, a flow passage communicating with the outlet passage, and an opening and closing member to open and close the flow passage. The pressurizing mechanism may be detachable from the outlet passage. The variable-volume chamber and the outlet passage may be allowed to communicate with each other by fitting the pressurizing mechanism into the outlet passage.
In this way, when the detachable pressurizing mechanism is fitted into the outlet passage, the outlet passage and the pressurizing mechanism communicate with each other. Thus the pressure in the variable-volume chamber is raised, so that the gas bubbles in the pump chamber are discharged. When the gas bubbles do not stay in the pump chamber, it is possible to realize a small and light pump in a state where the pressurizing mechanism is detached.
Furthermore, the pump according to an aspect of the present invention may include a heating section serving as the bubble discharging device provided in the pump chamber.
According to this construction, the gas bubbles are moved from the stagnation points in the pump chamber by heating the staying gas bubbles with the heating section provided in the pump chamber and thus increasing the volume of the staying gas bubbles, so that it is possible to easily discharge the gas bubbles.
The heating section may be received inside the wall of the pump chamber, or be arranged in a comer portion of the pump chamber.
In the pump chamber, the gas bubbles tend to stay at the comer portions of the pump chamber or at the protruded wall portions of the pump chamber. Accordingly, by receiving the heating section inside the wall of the pump chamber without generating any protruded portion, or by arranging the heating section at least at the comer portion of the pump chamber, it is possible to make the gas bubbles not stay or to discharge the staying gas bubbles from the corner portions of the pump chamber where the gas bubbles tend to stay.
Furthermore, a plurality of the heating sections may be provided.
In this way, by arranging the plurality of heating devices, it is possible to reduce the amount of energy per unit time to be supplied to the heating device. It is also possible to rapidly discharge the staying gas bubbles while reducing or preventing destruction of the pump.
Furthermore, the above-mentioned pump may include a pressure detecting section for detecting an inner pressure of the pump chamber.
As a result, by detecting the inside pressure of the pump chamber and checking whether the gas bubbles stay in the pump chamber, it is possible to suitably control the driving of the pump.
Furthermore, when the piston or the movable wall is being driven, a heating signal may be input to the heating section.
As a result, by heating the working fluid in the pump chamber with the heating section while allowing the piston or the diaphragm to operate, it is possible to raise the inside pressure of the pump chamber and thus to discharge the gas bubbles staying in the pump chamber.
In the above construction, a pulse-shaped heating signal may be input to the heating section. The piston or the movable wall may be driven in synchronism with the heating signal.
Furthermore, since the aforementioned pump allows the heating section to heat the working fluid in a pulse shape and allows the diaphragm to operate in synchronism with the pulse, it is possible to reduce the amount of energy consumed in the heating section, and to effectively discharge the gas bubbles staying in the pump chamber.
In the above pump, the heating section may heat the working fluid to change the phase of the working fluid in contact with the heating section.
As a result, since the gas bubbles can be generated in the pump chamber due to the change of phase and a complex and non-stagnated flow flowing out to the outlet passage can be caused in the pump chamber, it is possible to easily discharge the gas bubbles staying in the pump chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-sectional schematic illustrating a pump according to a first exemplary embodiment of the present invention;
FIG. 2 is a graph illustrating inner states of the pump according to the first exemplary embodiment of the present invention;
FIG. 3 is a schematic illustrating a driving circuit of the pump according to the first exemplary embodiment of the present invention;
FIG. 4 is a schematic illustrating a diaphragm for a secondary pump chamber of a pump according to a second exemplary embodiment of the present invention;
FIG. 5 is a vertical cross-sectional schematic illustrating a part of a pump according to a third exemplary embodiment of the present invention;
FIG. 6 is a schematic illustrating a driving circuit of the pump according to the third exemplary embodiment of the present invention;
FIG. 7 is a vertical cross-sectional schematic illustrating a pump according to a fourth exemplary embodiment of the present invention;
FIG. 8 is a schematic illustrating a driving circuit of the pump according to the fourth exemplary embodiment of the present invention;
FIG. 9 is a vertical cross-sectional schematic illustrating a pump according to a fifth exemplary embodiment of the present invention;
FIG. 10 is a vertical cross-sectional schematic illustrating a pressurizing mechanism according to a sixth exemplary embodiment of the present invention;
FIG. 11 is a vertical cross-sectional schematic illustrating a part of a pump according to the sixth exemplary embodiment of the present invention;
FIG. 12 is a vertical cross-sectional schematic illustrating a part of a pump according to a seventh exemplary embodiment of the present invention;
FIG. 13 is a schematic illustrating a heater according to the seventh exemplary embodiment of the present invention;
FIG. 14 is a schematic illustrating a modified example of the heater according to the seventh exemplary embodiment of the present invention;
FIG. 15 is a schematic illustrating a driving circuit of the pump of the seventh exemplary embodiment of the present invention;
FIG. 16 is a schematic illustrating another modified example of the heater according to the seventh exemplary embodiment of the present invention; and
FIG. 17 is a vertical cross-sectional schematic illustrating a pump according to another exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Now, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.
The exemplary embodiments of the present invention are shown in FIGS. 1 to 17.
First Exemplary Embodiment
FIGS. 1 to 3 show a pump 10 according to a first exemplary embodiment.
FIG. 1 is a vertical cross-sectional schematic illustrating a structure of the pump 10 according to the first exemplary embodiment of the present invention. In FIG. 1, the pump 10 includes a cup-shaped case 50 to which a laminated piezoelectric element 70 is fixed, an inflow passage 21 to introduce a working fluid, an outflow passage 28 to discharge the working fluid, and a pump case 20 having a secondary pump chamber 24 and a primary pump chamber 27.
One end of the laminated piezoelectric element 70 is fixed to an inside bottom portion of the case 50 through a fixing device, such as adhesive. A primary pump chamber diaphragm 60 is closely fixed to both of a top surface of an edge portion of the case 50 and a top surface of the other end of the laminated piezoelectric element 70. The pump case 20 is fixed to the circumferential edge portion of the top surface of the primary pump chamber diaphragm 60 such that the airtightness of the fixed portions is maintained. The primary pump chamber 27 is formed in a space between the primary pump chamber diaphragm 60 and a concave portion formed in a lower portion of the pump case 20.
A concave portion is provided in an upper portion of the pump case 20. The secondary pump chamber diaphragm 45 is airtightly fixed to a top surface of an edge portion of the concave portion, thereby forming the secondary pump chamber 24. The secondary pump chamber diaphragm 45 is formed out of a plate member thinner than the primary pump chamber diaphragm 60, and is deformable with the inside pressure of the secondary pump chamber 24. A plate-shaped piezoelectric element 71 is fixed to a top surface of the secondary pump chamber diaphragm 45. The secondary pump chamber diaphragm 45 and the plate-shaped piezoelectric element 71 form a unimorph actuator.
The plate-shaped piezoelectric element 71 may be attached to both surfaces of the secondary pump chamber diaphragm 45 to form a bimorph actuator. In this case, the close attachment of the plate-shaped piezoelectric element 71 in contact with the working fluid should be noted, while an actuator having a larger displacement can be formed.
Next, a construction along the flow passage of the working fluid will be described. The inflow passage 21 is formed in an inlet connection tube 30 protruded from the pump case 20, and communicates with the secondary pump chamber 24 through an inlet valve hole 22 for the secondary pump chamber and an inlet valve fitting hole 23 for the secondary pump chamber. An inlet check valve 41 for the secondary pump chamber as a fluid resistance element to open and close the inlet valve hole 22 for the secondary pump chamber is fixed to the edge of the inlet valve fitting hole 23 for the secondary pump chamber. An inlet valve hole 25 for the primary pump chamber and an inlet valve fitting hole 26 for the primary pump chamber are provided between the secondary pump chamber 24 and the primary pump chamber 27. An inlet check valve 42 for the primary pump chamber as a fluid resistance element, including an opening and closing member which can open and close the inlet valve hole 25 for the primary pump chamber, is fixed to the edge of the inlet valve fitting hole 26 for the primary pump chamber.
The primary pump chamber 27 communicates with the outflow passage 28. The outflow passage 28 has a narrow tube portion connected to the primary pump chamber 27 and a wide tube portion of which a sectional area is enlarged from an intermediate portion of the narrow tube portion, which are formed continuously. An outer circumferential portion of the outlet passage constitutes the outlet connection tube 31.
Further, although not shown, tubes made of silicon rubber having elasticity are connected to the inlet connection tube 30 and the outlet connection tube 31.
Next, an inertance value L of a flow passage is defined. Supposed that a sectional area of the flow passage is S, a length of the flow passage is r, and a density of the working fluid is ρ, the following equation is obtained: L=ρ×r/S. Supposed that a pressure difference of the flow passage is ΔP and a flow volume of the working fluid flowing in the flow passage is Q. The following equation is obtained by deforming a dynamic equation of the fluid in the flow passage using the inertance value L: ΔP=L×dQ/dt.
The inertance value L indicates a degree of influence of a unit pressure on a variation of flow volume per unit time, where the variation of flow volume per unit time becomes smaller with increase of the inertance value L and the variation of flow volume per unit time becomes larger with decrease of the inertance value L.
The resultant inertance value, about a parallel connection of a plurality of flow passages or a serial connection of a plurality of flow passages having different shapes may be calculated by composing inertance values of the respective flow passages similarly to the parallel connection or the serial connection of inductances in electric circuits. For example, when two flow passages having inertance values of L1 and L2, respectively, are connected in series, the resultant inertance value is given as L1+L2.
The inlet passage described hereinafter refers to a flow passage extending from the inside of the primary pump chamber 27 to an inlet end surface of the inlet valve hole 25 for the primary pump chamber. In the first exemplary embodiment of the present invention, since the secondary pump chamber 24 having the secondary pump chamber diaphragm 45 as a pulsation absorbing device is connected to an intermediate portion of the flow passage, the inlet passage refers to a flow passage extending from the inside of the primary pump chamber 27 to a connection portion of the pulsation absorbing device.
Therefore, when the secondary pump chamber diaphragm 45 has a high rigidity and thus a small pulsation absorbing effect, it is necessary to calculate the resultant inertance value of the primary pump chamber inlet passage up to the position of the pulsation absorbing device, such as a tube at the upstream of the secondary pump chamber 24.
The outlet passage refers to a flow passage extending up to an outlet end surface of the outflow passage 28, because the tube serving as the pulsation absorbing device is connected to the outlet connection tube 31.
Next, the inertance value of an opening and closing member of the check valve is defined. The inertance value of the opening and closing member is associated almost with a mass of the opening and closing member and a sectional area of the flow passage (a valve hole) which is closed by the opening and closing member, and is given as (the inertance value of the opening and closing member)=((the mass of the opening and closing member)/(the sectional area of the flow passage which is closed by the opening and closing member)²). For a time when the flow volume is small, by opening the flow passage from a state where the opening and closing member closes the flow passage entirely, the inertance value of the opening and closing member indicates a degree of influence of a unit pressure on the variation of flow volume per unit time, similarly to the inertance value of the flow passage, where the variation of flow volume per unit time becomes smaller with increase of the inertance value and the variation of flow volume per unit time becomes larger with decrease of the inertance value.
Next, an internal state of the pump, according to the first exemplary embodiment when the pump operates, will be described with reference to FIG. 2. FIG. 1 will be also referred to.
FIG. 2 is a graph illustrating as waveforms relations of a driving voltage (V) of the laminated piezoelectric element 70 and a pressure (MPa) of the primary pump chamber 27 expressed in an absolute pressure with respect to a time (ms), when the primary pump chamber 27 and the secondary pump chamber 24 are filled with the working fluid which is a liquid (water) in the pump 10 according to the first exemplary embodiment of the present invention. In FIG. 2, since the laminated piezoelectric element 70 is expanded with increase of the driving voltage, the primary pump chamber diaphragm 60 is raised, thereby compressing the volume of the primary pump chamber 27. In FIG. 2, it can be seen that the pressure starts its increase due to the compression of the primary pump chamber 27 after passing through a trough of the driving voltage. The inside pressure of the primary pump chamber 27 is rapidly decreased after passing through a point of the driving voltage having an largest upward slope, and is dropped substantially down to an absolute pressure of 0.
Specifically, first, when the primary pump chamber 27 is compressed in a state where the inlet check valve 42 for the primary pump chamber is closed, the inside pressure of the primary pump chamber 27 is largely increased due to the large inertance of the outflow passage (outlet passage) 28. With the increase of the inside pressure of the primary pump chamber 27, the working fluid in the small tube portion is accelerated. Thus the kinetic energy generating an inertia effect is accumulated. When the slope of the expansion and contraction speed of the laminated piezoelectric element 70 is decreased, the working fluid tends to continuously flow due to the inertia effect from the kinetic energy of the working fluid in the outlet passage accumulated in the meantime, so that the inside pressure of the primary pump chamber 27 is rapidly dropped, and thus becomes smaller than the inside pressure of the secondary pump chamber 24.
At this time point, the inlet check valve 42 for the primary pump chamber is opened due to the pressure difference, so that the working fluid flows in the primary pump chamber 27 from the secondary pump chamber 24. At that time, since the sum of the resultant inertance value of the inlet passage of the primary pump chamber 27 and the inertance value of the inlet check valve 42 for the primary pump chamber serving as the opening and closing member is smaller enough than the inertance value of the outlet passage described above, the efficient inflow of the working fluid is caused.
This state where the outflow and inflow to the primary pump chamber 27 occur simultaneously is continued until the laminated piezoelectric element 70 is compressed and then is expanded again. This denotes the flat portion of the inside pressure of the primary pump chamber 27 in FIG. 2.
Specifically, in the pump 10 according to the first exemplary embodiment of the present invention, since the discharge and suction are continued for a long time, it is possible to allow a large flow volume to flow. Since the inside of the pump chamber has a very high pressure, it is possible to cope with a high load pressure.
At that time, in the secondary pump chamber 24, the secondary pump chamber diaphragm 45 absorbs the pulsation through deformation by the inside pressure of the secondary pump chamber 24. As a result, the inflow of the working fluid from the inflow passage 21 having a large inertance value to the secondary pump chamber 24 is a static flow having a small pulsation, and the inlet check valve 41 for the secondary pump chamber is continuously opened. In this way, the secondary pump chamber diaphragm 45 has an effect of suppressing the pulsation of the inflow passage 21 while keeping the inertance value of the inlet passage of the primary pump chamber 27 small through its deformation. At that time, since the opened state of the inlet check valve 41 for the secondary pump chamber is continued, a problem such as generation of fluid resistance or fatigue failure does not occur.
Next, a priming action when the pump 10 starts its operation will be described with reference to FIGS. 1 and 3.
FIG. 3 is a schematic of a driving circuit system according to the first exemplary embodiment of the present invention. A priming action is an action that in a case where gas bubbles stay in the pump, a liquid is filled using another pump when the primary pump chamber 27, not having an ability of voluntarily absorbing the liquid, is started. In FIG. 3, the driving circuit system of the pump 10 includes the laminated piezoelectric element 70 to drive the primary pump chamber diaphragm 60, the plate-shaped piezoelectric element 71 to drive the secondary pump chamber diaphragm 45, a switching circuit 85 serving as a driving switch control unit to switch the driving between the laminated piezoelectric element 70 and the plate-shaped piezoelectric element 71, and a pump driving control circuit 80 to control the driving of the pump 10.
In a case where the working fluid is not filled in the primary pump chamber 27, a driving voltage generated by the pump driving control circuit 80 is applied to the plate-shaped piezoelectric element 71 attached to the secondary pump chamber diaphragm 45 by he switching circuit 85 at an initial stage of the pump operation. The driving voltage has, for example, a sine waveform. Since the secondary pump chamber 45 is formed out of a thin plate member and constitutes a unimorph actuator having a large amount of displacement, the second pump chamber 24 causes large variation in volume with the driving voltage. The inlet check valve 41 for the secondary pump chamber is arranged at the inlet side of the secondary pump chamber 24, and the inlet check valve 42 for the primary pump chamber is arranged at the outlet side thereof. The inlet check valve 42 for the primary pump chamber functions as the outlet check valve of the secondary pump chamber 24.
As a result, since the secondary pump chamber 24 includes the check valves at both of the inlet and outlet and thus has a large amount of variation in volume, the secondary pump chamber functions as a pump capable of transferring both gas and liquid. Since the secondary pump chamber 24 and the primary pump chamber 27 discharge the gas and thus are filled with the liquid which is the working fluid, the pump can operate through variation in volume of the primary pump chamber 27. The switching circuit 85 is switched to apply the driving voltage to the laminated piezoelectric element 70 after sufficient time passes through a timer (not shown), thereby automatically enabling high-power operation.
Furthermore, during operation of the primary pump chamber 27, it is possible to detect the operating condition of the secondary pump chamber diaphragm 45 by detecting a terminal voltage of the plate-shaped piezoelectric element 71. In a case where gas bubbles in the working fluid stay in the primary pump chamber 27 to deteriorate the pump ability, the amount of operation of the secondary pump chamber diaphragm 45 is decreased. At that time, by allowing the secondary pump chamber diaphragm 45 to operate by the plate-shaped piezoelectric element 71, thus discharging the gas bubbles, and then switching the driving voltage such that the primary pump chamber diaphragm 60 is driven by the laminated piezoelectric element 70, the pump ability can be recovered. The priming action is executed by performing the aforementioned driving control.
Therefore, in the aforementioned first exemplary embodiment, since the secondary pump chamber 24 includes the check valves 41, 42 at both of the inlet and outlet and thus has a large amount of variation in volume, the secondary pump chamber functions as a pump capable of transferring both of the gas and the liquid. Since the secondary pump chamber 24 and the primary pump chamber 27 discharge the gas and thus are filled with the liquid which is the working fluid, the pump can operate through variation in volume of the primary pump chamber 27.
The switching circuit 85 is switched to apply the driving voltage to the laminated piezoelectric element 70 of the primary pump chamber 27 after sufficient time passes through the timer, thereby automatically enabling the high-power operation.
Furthermore, during operation of the primary pump chamber 27, it is possible to detect the operating condition of the secondary pump chamber diaphragm 45 by detecting the terminal voltage of the plate-shaped piezoelectric element 71. In a case where gas bubbles in the working fluid stay in the primary pump chamber 27 to deteriorate the pump ability, the amount of operation of the secondary pump chamber diaphragm 45 is decreased. At that time, by allowing the secondary pump chamber diaphragm 45 to operate by he plate-shaped piezoelectric element 71, thus discharging the gas bubbles, and then switching the driving voltage such that the primary pump chamber diaphragm 60 is driven by the laminated piezoelectric element 70, the pump ability can be recovered.
Furthermore, since the primary pump chamber inlet passage is the secondary pump chamber outlet passage and the fluid resistance element (the check valve 42) to open and close the primary pump chamber inlet passage is the fluid resistance element to open and close the secondary pump chamber outlet passage, the flow passage of the working fluid is shortened, so that it is possible to reduce the fluid resistance of the flow passage. As a result, it is possible to simplify the structure of the pump 10 and to reduce the number of components, thereby realizing low cost.
In the first exemplary embodiment described above, a case where the diaphragm 60 is used to cause the variation in volume of the primary pump chamber 27 has been described, but this may be also accomplished by using a piston.
Second Exemplary Embodiment
Next, a second exemplary embodiment of the present invention will be described with reference to FIG. 4.
The pump according to the second exemplary embodiment has a basic structure similar to the aforementioned first exemplary embodiment, but is different from the first exemplary embodiment in that a part of a driving electrode 52 attached to the plate-shaped piezoelectric element 71 of the secondary pump chamber 24 is separated and forms a detecting electrode 53.
FIG. 4 is a schematic of the pump according to the second exemplary embodiment as seen from the secondary pump chamber diaphragm side. In FIG. 4, a part of the electrode 52 formed on the plate-shaped piezoelectric element 71 attached to the top surface of the secondary pump chamber diaphragm 45 is separated to form the detecting electrode 53.
Next, a function of the detecting electrode will be described. During the priming action, such as the time of starting the pump, the driving voltage is applied to the plate-shaped piezoelectric element 71 in the aforementioned first exemplary embodiment. However, in the second exemplary embodiment, since the detecting electrode 53 is isolated, it is possible to detect movement of the secondary pump chamber diaphragm 45 even during the priming action (when the driving voltage is applied to the plate-shaped piezoelectric element 71). When the gas in the secondary pump chamber 24 is discharged through the operation of the secondary pump chamber diaphragm 45 and thus the liquid is filled in the secondary pump chamber 24, the movement of the secondary pump chamber diaphragm 45 is decreased due to difference in compression rate thereof, and shortly thereafter the primary pump chamber 27 is thus filled with the working fluid. Therefore, when a long tube is connected to the inflow side, timing when the priming action is completed can be detected more accurately than a case where time management is performed, so that it is possible to switch the driving voltage toward the laminated piezoelectric element 70 attached to the primary pump chamber diaphragm 60 for a short time.
Furthermore, by independently connecting the driving circuits to the respective piezoelectric elements of the primary pump chamber diaphragm 60 and the second pump chamber diaphragm 45, and always monitoring the detecting electrode 53, it is possible to correctly perform the priming action without switching the circuits even in a case of operation failure due to interfusion of gas bubbles, etc. during operation of the pump.
Therefore, according to the second exemplary embodiment described above, since the detecting electrode 53 is isolated, it is possible to detect the movement of the secondary pump chamber diaphragm 45 during the priming action, and to accurately detect the timing when the priming action is completed, so that it is possible to switch the driving voltage toward the laminated piezoelectric element 70 of the primary pump chamber diaphragm 60 for a short time.
Furthermore, by independently connecting the driving circuits to the respective piezoelectric elements of the primary pump chamber diaphragm 60 and the second pump chamber diaphragm 45, and always monitoring the detecting electrode, it is possible to correctly perform the priming action without switching the circuits even in a case of operation failure due to interfusion of gas bubbles, etc. during operation of the pump.
Third Exemplary Embodiment
Next, a third exemplary embodiment of the present invention will be described with reference to FIGS. 5 and 6. The pump according to the third exemplary embodiment has a basic structure similar to the aforementioned first exemplary embodiment, but is different from the first exemplary embodiment in that the pump includes a pressure sensor 90 in the primary pump chamber 27. Descriptions of constituent elements common to the first exemplary embodiment will be omitted.
FIG. 5 is a vertical cross-sectional schematic of the pump according to the third exemplary embodiment of the present invention, and FIG. 6 is a schematic of the driving circuit of the pump according to the third exemplary embodiment. In FIG. 5, two-stepped concave portion 35 is formed in an inside top wall of the primary pump chamber 27. The pressure sensor 90 made of the same material as the aforementioned plate-shaped piezoelectric element 71 is fixed to the step of the concave portion 35 toward the primary pump chamber 27. An electrode, not shown, is formed on the surface of the pressure sensor 90. The pressure sensor is connected to the pump driving control circuit 80 (see FIG. 6) to be described later. The concave portion 35 has a gap so that the pressure sensor 90 does not come in contact with the wall when it is bent.
In FIG. 6, the driving circuit system of the pump 10 includes the laminated piezoelectric element 70 to drive the primary pump chamber diaphragm 60, the plate-shaped piezoelectric element 71 to drive the secondary pump chamber diaphragm 45, the pressure sensor 90 to detect the inside pressure of the primary pump chamber 27, and the pump driving control circuit 80 to control the driving of the pump 10.
In FIGS. 5 and 6, when gas bubbles stay in the primary pump chamber 27, the inside pressure of the primary pump chamber 27 is decreased. This state is detected by the pressure sensor 90. A driving signal is output to the plate-shaped piezoelectric element 71 from the pump driving control circuit 80, so that the secondary pump chamber diaphragm 45 is driven to increase the inside pressure of the secondary pump chamber 24. Accordingly, the gas bubbles staying in the primary pump chamber 27 are discharged from the pump chamber. Specifically, the plate-shaped piezoelectric element 71 of the secondary pump chamber diaphragm 45 is driven in synchronism with variation of the inside pressure of the primary pump chamber 27.
In the first to third exemplary embodiments, the pump not including a check valve at the outflow passage 28 side of the primary pump chamber 27 has been constructed. But in the pump including the check valve and requiring the priming action, the similar advantages can be obtained.
Therefore, according to the third exemplary embodiment, since the pressure sensor 90 is provided in the primary pump chamber 27, it is possible to accurately detect the operation failure due to interfusion of the gas bubbles into the primary pump chamber 27. Furthermore, in the third exemplary embodiment of the present invention, since the plate-shaped piezoelectric element 71 of the secondary pump chamber diaphragm 45 can be driven in synchronism with the primary pump chamber diaphragm 60, it is possible to further enhance the suction efficiency of the primary pump chamber 27, so that it is possible provide a higher-power pump.
Fourth Exemplary Embodiment
Next, a pump according to a fourth exemplary embodiment of the present invention will be described with reference to FIGS. 7 and 8. The fourth exemplary embodiment basically has the technical spirit of the first exemplary embodiment, but is different from the first exemplary embodiment in that a pressurizing mechanism 150 is provided as a bubble exclusion unit in place of the secondary pump chamber 24 (see FIG. 1).
FIG. 7 is a vertical cross-sectional schematic of the pump according to the fourth exemplary embodiment of the present invention. In FIG. 7, the pump 100 basically includes the cup-shaped case 50 to which the laminated piezoelectric element 70 is fixed, an inflow passage 121 to introduce the working fluid, an outflow passage 128 to discharge the working fluid, a pump case 120 having a pump chamber 127, and a pressurizing mechanism 150 (surrounded with a broken line in the figure) to apply pressure to the pump chamber 127.
In the cup-shaped case 50, one end of the laminated piezoelectric element 70 is fixed to an inside bottom portion thereof. The diaphragm 60 is fixed to the edge portion of the case 50 and a top surface of the other end of the laminated piezoelectric element 70. A pump case 120 is airtightly fixed to the top surface of the diaphragm 60. The pump chamber 127 is formed in a space between the diaphragm 60 and the bottom of the pump case 120.
The inflow passage 121 and the outflow passage 128 are formed toward the pump chamber 127. In the inflow passage 121, a check valve 122 as a fluid resistance element to open and close the inflow passage 121 is provided at a connection portion with the pump chamber 127. A part of the outer circumference of a cylindrical portion constituting the inflow passage 121 functions as an inlet connection tube 130 to be connected to an external tube, not shown. The outflow passage 128 includes a narrow tube portion connected to the pump chamber 127 and a wide tube portion of which a sectional area is enlarged in the way, which are formed continuously. The outer circumference of a cylindrical portion constituting the outflow passage 128 functions as an outlet connection tube 131 to be connected to an external tube, not shown. Here, for example, tubes made of silicon rubber can be used as the external tubes.
The pressure sensor 90 as the pressure detecting section to detect the inside pressure of the pump chamber 127 is fixed to the inside top wall of the pump chamber 127.
The pump 100 is provided with the pressurizing mechanism 150 surrounded with a broken line in the figure.
The pressurizing mechanism 150 includes a metallic bellows 151, which is an elastic member, an actuator 170 formed out of a piezoelectric element as a volume varying mechanism of the bellows 151, and an shutoff valve 140 to shut off the movement of the working fluid in the outflow passage 128. The bellows 151 is closely fixed to a side surface of the outlet connection tube 131. Its opening portion 152 is connected to the flow passage 132 communicating with the outflow passage 128.
A variable-volume chamber is formed inside the bellows 151. A pressure sensor 91, as the pressure detecting section to detect the inside pressure of the bellows 151, is provided inside the bellows. The volume of the bellows 151 is varied by the actuator 170.
In the fourth exemplary embodiment, an end of the actuator 170 opposite to the bellows 151 is fixed to the side of the inlet connection tube 130. The actuator is reciprocated by a driving section, not shown. The actuator includes a pressing section 171 to compress the bellows 151. The pressing section is driven by the pump driving control circuit 180 (see FIG. 8).
The sectional area of the wide tube portion of the outflow passage 128 at a position connected to the bellows 151 is double the sectional area of the narrow tube portion. For this reason, the flow rate of the fluid passing through the flow passage 132 connected to the bellows 151 is decreased, so that the energy loss of the fluid during passing the flow passage can be reduced.
The inertance value relation important in driving the pump according to an aspect of the present invention has been described in the first exemplary embodiment, and thus its description is omitted. The inlet passage and the outlet passage in the fourth exemplary embodiment will be defined.
In the flow passage to allow the working fluid to flow into the pump chamber 127, the flow passage extending from the opening portion of the pump chamber 127 to the connection with a pulsation absorbing device is defined as the inlet passage. Here, the pulsation absorbing device sufficiently reduces the variation in the inside pressure of the flow passage. In addition, a flow passage made of material, such as silicon rubber, resin, thin metal, which can be easily deformed with the inside pressure, an accumulator connected to the flow passage, a composition flow passage to compose pressure variations having a plurality of different phases, etc. correspond to the pulsation absorbing device.
In the fourth exemplary embodiment, since the external tube, such as a silicon rubber tube, is connected to the inlet connection tube 130, the flow passage extending from the opening portion of the pump chamber 127 to the end surface of the connection side of the silicon rubber tube in the inflow passage 121, that is, the inflow passage 121 itself, is defined as the inlet passage.
The outlet passage is defined similarly to the inlet passage. In the flow passage to which the working fluid is discharged from the pump chamber 127, a flow passage extending from the opening portion of the pump chamber 127 to a connection portions with the pulsation absorbing device is defined as the outlet passage. In the fourth exemplary embodiment according to the present invention, since the bellows 151 in the way of the outflow passage 128 has a function of absorbing the pressure pulsation in a discharge mode to be described later, the outflow passage 128 extending from the opening portion of the pump chamber 127 to the connection portion with the bellows 151 is defined as the outlet passage.
Next, a case where the pump 100 according to the fourth exemplary embodiment is driven in the discharge mode will be described.
The discharge mode refers to an operation mode in which the working fluid is allowed to flow out toward the downstream of the outflow passage 128, and is performed in a case where the working fluid is filled in the pump chamber 127 and thus gas bubbles do not stay therein. At that time, the shutoff valve 140 does not shut off the outflow passage 128. The pressing section 171 of the actuator 170 is separated from the bellows 151, as shown in FIG. 7. As a result, the bellows 151 can be freely deformed elastically with the inside pressure. The bellows 151 functions to reduce the pressure pulsation in the outflow passage 128. Accordingly, even if an external tube, made of any material, is connected to the outlet connection tube 131, the inertance value of the outlet passage is not influenced, so that it is possible to reduce or prevent change in the pump ability due to the external tube. Only if a variable-volume chamber is formed of an elastic member in place of the bellows 151, can the same advantage be obtained.
Next, the internal state of the pump 100 according to the fourth exemplary embodiment when it is driven will be described. The internal state of the pump 100 is similar to the above first exemplary embodiment (see FIG. 2), the description thereof is omitted. Thus features of the fourth exemplary embodiment will be described in detail.
The features are described with reference to FIGS. 2 and 7. In FIG. 2, as can be seen from the fact that the inside pressure of the pump chamber 127 is raised up to about 2 MPa, the pump 100 according to the fourth exemplary embodiment causes a high pressure in the pump chamber 127, thereby obtaining a high power. For this reason, specifically when gas bubbles stay in the pump chamber 127, the variation in volume (hereinafter, referred to as exclusion volume) of the pump chamber 127 generated due to the deformation of the diaphragm 60 is used to compress the gas bubbles during the time when the laminated piezoelectric element 70 turns to the state where it is most expanded from the state where it is most contracted, and thus does not contribute to increase the inside pressure of the pump chamber 127, so that the pump cannot operate properly. For this reason, it is important to exclude the staying gas bubbles rapidly.
Subsequently, a case where the pump 100 according to the fourth exemplary embodiment is driven in a bubble discharge mode will be described with reference to FIGS. 7 and 8.
FIG. 8 is a schematic of the driving circuit of the pump 100 according to the fourth exemplary embodiment. Here, the bubble discharge mode refers to an operation mode to be performed when the gas bubbles stay in the pump chamber 127. In FIG. 8, the driving circuit system of the pump 100 includes the pressure sensor 90 (see FIG. 7) to detect the inside pressure of the pump chamber 127, the pressure sensor 91 to detect the inside pressure of the bellows 151, the pressurizing mechanism 150, and a pump driving control circuit 180 to control them.
Next, the discharge of gas bubbles existing by means of the pressurizing mechanism 150 when the pump is driven in the bubble discharge mode will be described.
When the maximum inside pressure of the pump chamber detected by the pressure sensor 90 is smaller than, specifically a half or less of, the maximum inside pressure of the pump chamber in the normal driving under the driving condition, the pump driving control circuit 180 determines that gas bubbles stay in the pump chamber 127. Then, the pump driving control circuit 180 gives an instruction to the pressurizing mechanism 150. In response to the instruction, first, the shutoff valve 140 is switched not to shut off the outflow passage 128. Next, the actuator 170 in FIG. 7 allows the pressing section 171 to extend left and to come in contact with the bellows 151, and then compresses the bellows 151 in the left direction, so that the volume of the chamber formed out of the bellows 151 is largely reduced. As a result, the gas bubbles staying in the chamber formed out of the bellows 151 can be allowed to flow out to the downstream from the shutoff valve 140.
Next, the shutoff valve 140 shuts off the outflow passage 128, and the actuator 170 allows the pressing section 171 to be contracted and separated from the bellows 151. Since the bellows 151 is formed of an elastic member, it is recovered to the original state with its own elastic force. In this way, the working fluid is filled in the bellows 151. Subsequently, the actuator 170 is allowed to compress the bellows 151 again. As a result, the pressure of the working fluid existing from the inside of the bellows 151 to the pump chamber 127 can be raised.
The volume of the gas bubbles staying in the pump chamber 127 is decreased through the pressing, and the volume of the gas bubbles can be made to be smaller enough than the exclusion volume. At that time, it is necessary to set the chamber of the bellows 151 to about one atmosphere or more in a gauge pressure, preferably a pressure between about one atmosphere and five atmospheres. By allowing the pump driving control circuit 180 to control the actuator 170 to compress the bellows 151 on the basis of the detected value by the pressure sensor 91 to detect the pressure of the chamber formed out of the bellows 151, it is possible to raise the inside pressure of the bellows 151 up to a proper pressure.
Subsequently, when the laminated piezoelectric element 70 is driven, like in the discharge mode, the inside pressure of the pump chamber 127 is raised enough and the working fluid is discharged from the pump chamber 127 to the outflow passage 128. The gas bubbles staying in the pump chamber 127 flows in the bellows 151 with the flow of the working fluid in the pump chamber 127.
The pump driving control circuit 180 includes a timer (not shown) to count the time when the laminated piezoelectric element 70 is driven after the shutoff valve 140 shuts off the outflow passage 128. After a predetermined time interval, as a time interval enough to discharge the gas bubbles staying in the pump chamber 127, is counted with the timer, the shutoff valve 140 releases the shutoff of the outflow passage 128 and the actuator 170 is contracted up to the position where it is separated from the bellows 151. Thereafter, the bubble discharge mode is finished.
At that time, the inside pressure of the bellows 151 is raised due to the working fluid discharged from the pump chamber 127. But the bellows is designed such that the deformation due to the pressure is suppressed within an allowable range of elastic deformation. In this way, by forming the variable-volume chamber out of an elastic member, the pressure can be made to be smoothly raised due to the introduction of the working fluid, so that it is possible to prevent destruction of the constituent elements of the pump 100.
In addition, the pump driving control circuit 180 may be allowed to control the actuator 170 by using values detected by the pressure sensor 91 provided in the bellows 151, so that it may be possible to suppress the inside pressure of the bellows 151 from being raised.
The pump may be constructed so that a relief valve is provided in the bellows 151, and it is possible to surely suppress the inside pressure of the bellows 151 from being raised by opening the relief valve when the inside pressure of the bellows 151 is too high.
Therefore, in the fourth exemplary embodiment, since the pressurizing mechanism 150 to raise and maintain the pressure of the working fluid existing in the pump chamber 127 is provided, it is possible to raise and maintain the pressure of the working fluid existing in the pump chamber 127, when the gas bubbles stay in the pump chamber 127, the inside pressure of the pump chamber 127 is reduced. Thus it is not possible to discharge the working fluid. As a result, the volume of the gas bubbles is decreased, so that it is possible to discharge the gas bubbles in the pump chamber by compressing the volume of the pump chamber 127 through the operation of the diaphragm 60.
The pressurizing mechanism 150 presses the bellows 151. But since the variable-volume chamber of the bellows 151 communicates with the outflow passage 128, it is possible to simply generate a high pressure in the pump chamber 127 communicating with the outflow passage 128.
Furthermore, by forming the variable-volume chamber out of an elastic member, the increase in pressure due to introduction of the working fluid into the variable-volume chamber is smoothed, so that it is possible to prevent the constituent elements of the pump from being damaged due to the pressure. Furthermore, by forming the variable-volume chamber out of an elastic member, the variable-volume chamber can be allowed to have a function of reducing the pressure pulsation in the outlet passage. As a result, it is possible to reduce or prevent the pump ability from be varied due to influence of the external tube connected to the outlet passage.
First Modified Example of Fourth Embodiment
In a modified example of the fourth exemplary embodiment described above, the detected value of the pressure sensor 90 in the pump chamber 127 may be checked, for example, by arbitrarily setting the time interval to be counted by the timer of the pump driving control circuit 180 and allowing the pump to operate in the discharge mode after the bubble discharge mode is finished.
According to this modified example, by repeatedly performing the operation of the bubble discharge mode until the gas bubbles are discharged, it is possible to surely discharge the gas bubbles.
In the fourth exemplary embodiment described above, since the operation of the bubble discharge mode is executed when it is determined using the pressure sensor 90 in the pump chamber 127 that the gas bubbles stay, the operation of the bubble discharge mode is not executed wastefully. But the operation of the bubble discharge mode may be executed at proper time intervals.
In this case, the pressure sensor 90 can be omitted, so that it is possible to simplify the structure.
Furthermore, when the inflow passage 121 and the outflow passage 128 are connected to the external tubes, it is possible to raise and maintain the inside pressure of the pump chamber 127 by pressing the bellows 151 with the actuator 170 without the shutoff valve 140, thereby obtaining the same advantage. Furthermore, although the actuator 170 is provided to press the bellows 151, the same advantage can be obtained, even when a display device through which a user can view an output of the pressure sensor 91 is provided and the user manipulates the shutoff valve 140 to press the bellows 151.
Second Modified Example of Fourth Embodiment
In the fourth exemplary embodiment, the pressure sensor 90 has been provided as the pressure detecting device for the pump chamber in the pump chamber 127, but a different device may be employed.
For example, the inside pressure of the pump chamber 127 may be calculated by measuring the deformation of the diaphragm 60 with a strain gauge or a displacement sensor.
Further, the inside pressure of the pump chamber 127 may be calculated by measuring the deformation of the case 50 with a strain gauge.
Furthermore, the inside pressure of the pump chamber 127 may be calculated by measuring the deformation of the opening and closing member in a state where the check valve 122 is closed, with a strain gauge or a displacement sensor.
Furthermore, the inside pressure of the pump chamber 127 may be calculated by measuring current to drive the laminated piezoelectric element 70 with a current sensor. Furthermore, by providing a strain gauge in the laminated piezoelectric element 70, the inside pressure of the pump chamber 127 may be calculated on the basis of a voltage applied to the laminated piezoelectric element 70 and the measured value by the strain gauge. At that time, any type of strain gauge which detects the quantity of deformation by using variation in resistance, variation in capacitance, or variation in voltage may be used as the strain gauge. As the inside pressure detecting device of the bellows 151, a structure of calculating the pressure by detecting the deformation of the bellows 151 with a strain gauge may used.
Third Modified Example of Fourth Embodiment
In the fourth exemplary embodiment described above, a piezoelectric element has been employed as the actuator 170. But an electromagnetic type actuator, a shape-memory alloy type actuator, etc. in addition to the piezoelectric element may be employed. Since the shape-memory alloy type actuator can realize a large quantity of deformation with a simple structure, it is preferable.
Furthermore, the elastic member forming the variable-volume chamber may be made of rubber or resin material. But the elastic member made of metal is specifically preferable because it can reduce or prevent vaporization of the working fluid. Furthermore, the variable-volume chamber may have a film shape or a diaphragm shape. But since the bellows shape described in the fourth exemplary embodiment can cause a large quantity of deformation and the laminated piezoelectric element 70 can be driven in the bubble discharge mode continuously for a long time, it is preferable in that the gas bubbles can be easily discharged.
Therefore, according to the construction of the modified example of the fourth exemplary embodiment, it is possible to obtain the advantage similar to the fourth exemplary embodiment.
Fifth Exemplary Embodiment
Next, a pump according to a fifth exemplary embodiment of the present invention will be described with reference to FIG. 9.
The pump according to the fifth exemplary embodiment has the basic structure similar to the fourth exemplary embodiment (see FIG. 7), but is different from the fourth exemplary embodiment in that the pump has a structure of switching between a first mode where the working fluid flowing out of the pump chamber 127 is introduced into the chamber formed out of the bellows 151 and a second mode where the chamber formed out of the bellows 151 is shut off from the flow of the working fluid flowing out of the pump chamber 127. Therefore, the difference will be paid attention to. The same functional members are denoted by the same reference numerals as the fourth exemplary embodiment (see FIG. 7).
FIG. 9 shows a vertical cross-sectional schematic of the pump 100 according to the fifth exemplary embodiment. In FIG. 9, the pressurizing mechanism 150 surrounded with a broken line is provided in the outflow passage 128. The pressurizing mechanism 150 includes the metallic bellows 151 formed of an elastic member, and a switching valve 190 (surrounded with two-dot chain line in the drawing) which is a passage switching device. The switching valve 190 includes a switching valve 182 to open and close the flow passage 132 communicating with the outflow passage 128 at the opening portion 152 of the chamber formed out of the bellows 151, and a switching valve 183 to open and close the outflow passage 128.
The switching valve 190 functions as switching a first connection state where, the outflow passage 128 extending from the pump chamber 127 to the switching valve 182, and the outflow passage 128 at the downstream side thereof, communicates with each other, by opening the switching valve 183, and the chamber formed out of the bellows 151 is shut off from the outflow passage 128 by closing the switching valve 182, and a second connection state where, the outflow passage 128 extending from the pump chamber 127 to the switching valve 182 and the chamber formed out of the bellows 151 communicate with each other, and the outflow passage 128 at the more downstream side than the switch valve 183, is shut off by closing the switching valve 183.
In the outflow passage 128, the sectional area of the outflow passage 128 at the position at which the switching valve 183 is arranged is double the sectional area of the narrow flow passage portion of the outflow passage 128 connected to the pump chamber 127. The reason has been described in the fourth exemplary embodiment. The pressure sensor 91 as an inside pressure detecting device of the bellows to detect the pressure of the chamber formed out of the bellows 151, is provided in the bellows 151.
Here, definitions of the inlet passage and the outlet passage, and relations of the inertance values in the fifth exemplary embodiment are similar to the fourth exemplary embodiment.
Next, a case where the pump 100 according to the fifth exemplary embodiment is driven in the discharge mode will be described. In the fifth exemplary embodiment, in the discharge mode, the switching valve 190 is switched into the first connection state to allow the working fluid to flow out toward the downstream of the outflow passage 128. At that time, the pressure waveform in the pump chamber 127 when the laminated piezoelectric element 70 is driven is similar to the first exemplary embodiment (see FIG. 2). For this reason, similarly to the first exemplary embodiment, since the discharge and the absorption simultaneously occur, a large flow volume can be transferred. Since the pump chamber has a very high inside pressure, it is possible to cope with a high load pressure. When the gas bubbles stay in the pump chamber 127, it has been already described in the first exemplary embodiment that the pump does not operate properly.
Next, the bubble discharge mode, which is executed when the gas bubbles stay in the pump chamber, will be described. Further, although not shown, in the switching valve control system, if the pump driving control circuit determines that the gas bubbles stay in the pump chamber 127, the pump driving control circuit gives an instruction to the switching valve 190. Thus the switching valve 190 is switched into the second connection state from the first connection state.
At that time, since the inside of the bellows 151 is pressurized up to about one atmosphere or more in a gauge pressure, preferably to a pressure between about one atmosphere and five atmospheres, the pump chamber 127 is almost pressurized up to the above pressure. In this way, by forming the variable-volume chamber out of an elastic member, it is possible to apply the pressure only with the elastic force of the elastic member.
Since the volume of the gas bubbles staying in the pump chamber 127 becomes smaller than the exclusion volume of the pump chamber 127 through the pressing, the gas bubbles are discharged into the bellows 151 through the driving of the laminated piezoelectric element 70, as described in the fourth exemplary embodiment. Since the pump driving control circuit includes a timer (not shown) to count the time interval when the laminated piezoelectric element 70 is driven after the switching valve 190 is switched into the second connection state, a predetermined time interval is counted as the time interval enough to discharge the gas bubbles staying in the pump chamber 127 by using the timer, the switching valve 190 is then switched into the first connection state, and then the bubble discharge mode is finished.
At that time, the inside pressure of the bellows 151 is raised by the working fluid discharged from the pump chamber 127. But the bellows is designed so that the deformation due to the inside pressure is suppressed within an allowable range for elastic deformation. Further, the pump may be constructed so that a relief valve, not shown, is provided in the bellows 151, and it is possible to suppress the inside pressure of the bellows 151 from being raised by opening the relief valve when the inside pressure of the bellows 151 is too high. Thus it is possible to maintain the inside pressure at a constant value of about one atmosphere or more in a gauge pressure and preferably a constant value between about one atmosphere and five atmospheres. In the bubble discharge mode, the staying gas bubbles are excluded, so that it is possible to recover the pump ability.
Next, a bellows pressing mode, which is performed to maintain the inside pressure of the bellows 151 to about one atmosphere or more in a gauge pressure and preferably a value between about one atmosphere and five atmospheres, will be described with reference to FIG. 8.
The inside pressure of the bellows 151 is detected by the pressure sensor 91 provided in the bellows 151. When the detected pressure is smaller than about one atmosphere in a gauge pressure, an instruction is given to the pressurizing mechanism 150 from the pump driving control circuit 180, so that the switching valve 190 is switched to the second connection state. Next, the diaphragm 60 is driven by the laminated piezoelectric element 70, so that the fluid is allowed to flow out of the pump chamber 127 to the outflow passage 128, similarly to the discharge mode.
Then, the working fluid flows in the bellows 151 through the switching valve 182, so that the inside of the chamber formed out of the bellows 151 is compressed. When the pump driving control circuit 180 confirms on the basis of the detected value of the pressure sensor 91 that the inside pressure of the bellows 151 reaches about one atmosphere or more in a gauge pressure and preferably a value between about one atmosphere and five atmospheres, an instruction is given to the pressurizing mechanism 150 from the pump driving control circuit 180, the switching valve 190 is thus switched to the first connection state, and then the bellows pressing mode is finished. By performing this operation mode, even when leakage occurs in the switching valve 190, etc., the inside of the bellows 151 can be always maintained to the set pressure, so that it is possible to wait for the bubble discharge mode.
In the above fifth exemplary embodiment, the switching valve 190 includes two valves. But an integrated three-way valve, etc. may be used. Since a hole (not shown in the figures), which can be airtightly closed, is provided in the bellows 151, it is possible to discharge the gas bubbles through the hole when too many gas bubbles are gathered in the bellows 151.
In a modified example of the above fifth exemplary embodiment, in a case where the relationship between the time and the amount of leakage from the bellows 151 is known, the bellows pressing mode may be performed every predetermined time interval without providing the pressure sensor 91 in the bellows. In this case, by converting the amount of leakage from the time until the current bellows pressing mode is started after the previous bellows pressing mode is finished, it is possible to drive the laminated piezoelectric element 70 for the time required to allow the working fluid having the same volume as the amount of leakage to flow into the bellows 151 from the pump chamber 127.
Furthermore, by providing a relief valve, not shown, in the chamber formed out of the bellows 151 without providing the pressure sensor 91, the bellows pressing mode may be performed every predetermined time interval. As a result, if the inside of the bellows 151 is compressed above the pressure set with the relief valve when the bellows pressing mode is performed, the relief valve is opened. Thus the working fluid is leaked, so that it is possible to maintain the inside of the bellows 151 at a constant pressure.
In the above description, the pressure sensors described in the fourth exemplary embodiment can be similarly used as the pressure sensor 90 in the pump chamber 127 to detect the inside pressure of the pump chamber 127 and the pressure sensor 91 in the bellows 151.
Therefore, according to the fifth exemplary embodiment, the pressurizing mechanism 150 is provided with the passage switching device to switch between the first mode in which the working fluid flowing out of the pump chamber 127 is introduced into the chamber of the bellows 151 and the second mode in which the chamber of the bellows 151 is shut off from the flow of the working fluid flowing out of the pump chamber 127. As a result, it is possible to surely compress the working fluid in the pump chamber 127 with the elastic force of the elastic member constituting the variable-volume chamber.
Furthermore, since the pressure sensor 91 to detect the inside pressure of the variable-volume chamber is provided, it is possible to control the inside pressure of the variable-volume chamber within a proper pressure range. Furthermore, since the pressure sensor 90 is provided in the pump chamber 127, it is possible to determine whether the gas bubbles stay in the pump chamber 127.
Furthermore, since the pressure applied from the pressurizing mechanism 150 is set to a value between about one atmosphere and five atmospheres in a gauge pressure, it is possible to reduce the volume of the gas bubbles staying in the pump chamber as small as possible to discharge, without damaging the constituent components of the pump due to the pressure.
Sixth Exemplary Embodiment
Next, a pump according to a sixth exemplary embodiment of the present invention will be described with reference to FIGS. 10 and 11.
The sixth exemplary embodiment of the present invention has a basic structure similar to the above fourth exemplary embodiment except for the pressurizing mechanism, and thus differences therebetween will be described in detail. The pump according to the sixth exemplary embodiment is used without connecting an external tube to the outflow passage 128, has a structure not requiring the switching valve (see FIGS. 7 and 9) described in the fourth and fifth exemplary embodiments, and is characterized in that the pressurizing mechanism 150 is provided detachably from the outflow passage 128.
FIG. 10 shows a vertical cross-sectional schematic of the independent pressurizing mechanism according to the sixth exemplary embodiment. In FIG. 10, the pressurizing mechanism 150 includes the bellows 151 and a valve case 153 to which the bellows 151 is fixed and receives a valve 156.
As described in the above fourth exemplary embodiment, the variable-volume chamber in which the working fluid stay and an opening portion 152 are formed in the bellows 151, which is closely fixed to an end of the valve case 153.
The valve case 153 includes the opening portion 152 communicating with the bellows 151, an entry hole 155 into which the outlet connection tube 131 (see FIG. 11) of the pump 100 is inserted, a valve fitting hole 154 which communicates with the opening portion 152 and an entry hole 155 and to which the valve 156 is fitted, and a rod inserting hole 160 into which a rod 159 of the valve 156 is inserted. A seal member 165 to prevent the working fluid from being leaked from the connected portion of the outlet connection tube 131 and the entry hole 155 is fitted into an intermediate portion of the entry hole 155.
The valve 156 is connected to the rod 159 with the rod inserting hole 160 therebetween and a washer 157 to fix the rod 159. Through-holes 158 through which the working fluid passes are formed in the washer 157. In addition, a coil spring 161 to apply force to the valve 156 in order to seal the rod inserting hole 160 is provided between the washer 157 and the inside wall of the entry hole 155.
The variable-volume chamber of the bellows 151 is compressed within a range of about one atmosphere to five atmospheres in a gauge pressure by means of the elastic force of the bellows 151, similarly to the fourth and fifth exemplary embodiment.
FIG. 11 is a partially vertical cross-sectional schematic illustrating a state where the above pressurizing mechanism 150 is fitted into the outlet connection tube 131 of the pump 100. In FIG. 11, the entry hole 155 of the pressurizing mechanism 150 is inserted into the outlet connection tube 131. At that time, the front end portion of the outlet connection tube 131 comes in contact with the washer 157 and compresses the coil spring 161, so that the valve 156 is moved to a position to open the rod inserting hole 160. At that time, the outflow passage 128 and the chamber surrounded with the bellows 151 communicates with each other, so that the working fluid can flow through the through-holes 158 therebetween.
Next, a case where the gas bubbles do not stay in the pump 100 according to the sixth exemplary embodiment will be described. This case will be described with reference to FIGS. 10 and 11.
In a normal state where the gas bubbles do not stay in the pump 100 according to the sixth exemplary embodiment, the pressurizing mechanism 150 is separated from the outflow passage 128 to discharge the working fluid from the outflow passage 128. In this case, a principle of discharging the working fluid to the outflow passage 128 is similar to that of the first exemplary embodiment. Therefore, when the gas bubbles stay in the pump chamber 127, increase in pressure of the pump chamber is hindered and the pump ability is thus deteriorated largely, so that it is important to rapidly exclude the gas bubbles.
Next, a case where the gas bubbles stay in the pump chamber 127 will be described.
When the gas bubbles stay, the outflow amount of the working fluid from the outflow passage 128 is decreased largely. Therefore, when a user observes the decrease of the outflow amount from the outflow passage 128, the user fits the pressurizing mechanism 150 into the outlet connection tube 131 (see FIG. 11). In FIG. 11, by pressing the washer 157 with the end portion of the outlet connection tube 131 by a force larger than the elastic force of the coil spring 161, the coil spring 161 is contracted, the valve 156 is thus opened, and the through-holes 158 for the working fluid provided in the washer 157 and the opened valve 156 communicate with each other, so that the outflow passage 128 is connected to the inside (the chamber) of the bellows 151.
In this way, since the volume of the gas bubbles staying in the pump chamber 127 is reduced by means of compression of the inside of the pump chamber 127, the staying gas bubbles can be discharged into the bellows 151 from the outflow passage 128, as described in the fourth and fifth exemplary embodiments. At that time, a lock mechanism to prevent the connection of the outflow passage 128 and the bellows 151 from going amiss may be provided.
In this exemplary embodiment, the inside pressure of the bellows may be suppressed from being raised by providing a relief valve in the bellows 151. Furthermore, by providing a hole that can be airtightly closed in the bellows 151, the gas bubbles staying in the bellows can be discharged.
Therefore, according to the sixth exemplary embodiment, since the pressurizing mechanism is freely detachable, when the pressurizing mechanism is fitted into the outlet passage, the outlet passage and the pressurizing mechanism communicate with each other. The inside pressure of the variable-volume chamber is raised, thereby discharging the gas bubbles in the pump chamber. When the gas bubbles do not stay in the pump chamber, by separating the pressurizing mechanism, it is possible to realize a small and light pump.
Seventh Exemplary Embodiment
Next, a pump according to a seventh exemplary embodiment of the present invention will be described with reference to FIGS. 12 to 14. The seventh exemplary embodiment has the same basic structure and discharge operation of working fluid as the first to sixth exemplary embodiments described above, but is different from them in that a heating section is provided as the bubble excluding device of the pump chamber.
Therefore, a relationship between the heating section and the bubble exclusion will be described in detail.
FIG. 12 shows a vertical cross-section of the pump 200 according to the seventh exemplary embodiment. In FIG. 12, the pump 200 includes a cup-shaped case 50 to which a laminated piezoelectric element 70 is fixed, an inflow passage 221 to introduce a working fluid, an outflow passage 228 to discharge the working fluid, a pump case 220 having a pump chamber 227, and a ring-shaped heater 212 provided in the pump chamber 227.
In the case 50, one end portion of the laminated piezoelectric element 70 is fixed to the inside bottom portion, and a diaphragm 60 is fixed to both of the edge portion of the case 50 and the other end portion of the laminated piezoelectric element 70. The pump case 220 is airtightly fixed to the top surface of the diaphragm 60. The pump chamber 227 is formed in a space between the diaphragm 60 and the bottom portion of the pump case 220.
The inflow passage 221 and the outflow passage 228 are formed toward the pump chamber 227. In the inflow passage 221, a check valve 222 as a fluid resistance element to open and close the inflow passage 221 is provided at a connecting portion with the pump chamber 127. A part of the outer circumference of a cylindrical portion constituting the inflow passage 221 functions as an inlet connection tube 230 to be connected to an external tube, not shown. A part of the outer circumference of a cylindrical portion constituting the outflow passage 228 functions as an outlet connection tube 231 to be connected to an external tube, not shown. Here, as the external tubes, not shown, for example, tubes made of silicon rubber can be used.
Here, the inflow passage 221 itself is defined as an inlet passage. The outflow passage 228 itself is defined as an outlet passage. In a relationship of inertance values, as described above, the resultant inertance value of the inlet passage side is set to be smaller than the inertance value of the outlet passage side.
A ring-shaped heater 212 is fixed to the outer circumferential comer portion of the inside top wall of the pump chamber 227. The heater 212 is airtightly inserted and fixed to the comer portion of the top wall of the pump chamber 227, so that the heater is not protruded from the top wall surface of the pump chamber 227 toward the pump chamber.
FIG. 13 is a schematic of the pump case 220 shown in FIG. 12 as seen from the pump chamber side.
In FIG. 13, the heater 212 is arranged at a position in the comer portion of the pump chamber 227 where gas bubbles easily stay. The heater 212 is formed by fixing a resistance member to a ceramics substrate of alumina, etc., and then coating an insulating film thereon. Various members may be used as the resistance member. But members having a high melting point, specifically, platinum or platinum alloy, may be used. Although not shown, a lead wire to supply power to the heater 212 is drawn out through the pump case 220.
The inside of the pump chamber 227 is provided with a pressure sensor 90, not shown (see FIG. 15).
Next, a modified example of the heater 212 according to the seventh exemplary embodiment will be described with reference to FIG. 14.
In FIG. 14, the heater 212 is formed as a thin plate having a circular plate shape, and is fixed to a wide range of the top wall surface of the pump chamber 227 other than the circumferential portion of the inflow passage 221 and outflow passage 228. The heater 212 is inserted into the top wall of the pump chamber 227 so that it is not protruded from the top wall surface.
Next, a case where the pump 200 according to the seventh exemplary embodiment is driven in a discharge mode of the working fluid will be described.
The discharge mode is a mode in which power is not supplied to the heater 212 and a voltage is applied only to the piezoelectric element 70. Since the discharge mode has been described in the first to sixth exemplary embodiments described above, the description thereof will be omitted. At that time, as described above, when the gas bubbles stay in the pump chamber 227, the inside pressure of the pump chamber is decreased and the pump ability is deteriorated, so that a bubble discharge mode is performed.
Next, a case where the pump 200 according to the seventh exemplary embodiment is driven in the bubble discharge mode will be described with reference to FIG. 15 (also, see FIG. 12).
FIG. 15 is a schematic of a driving circuit system of the pump 200. In FIG. 15, the driving circuit system of the pump 200 includes a pressure sensor 90 as a pressure detecting device in the pump chamber 227, a heater 212, a power distribution circuit 265 to control the heater 212, and a pump driving control circuit 280 to control the driving of the pump 200.
In a case where the maximum inside pressure of the pump chamber detected by the pressure sensor 90 when the pump 200 is driven in the discharge mode is smaller, specifically by 50% or less, than the maximum inside pressure of the pump chamber when the pump is normally driven, the pump driving control circuit 280 determines that the gas bubbles stay in the pump chamber 227, and thus switches the driving mode to the bubble discharge mode from the discharge mode. Then, the pump driving control circuit 280 sends a signal to the power distribution circuit 265. Then the power distribution circuit 265 starts the power distribution to the heater 212 in response to the signal.
Since the heater 212 is arranged at the comer portion in which the flow is stagnated and the gas bubbles easily stay as described above, the staying gas bubbles existing in the vicinity thereof are heated by the heater 212, so that it is possible to expand the volume of the gas bubbles. As a result, if the size of the staying gas bubbles is not received in the stagnated area completely, the staying gas bubbles are moved along the flow inside the pump chamber 227 due to the driving of the diaphragm 60 and thus can be discharged out of the outflow passage 128. The bubble discharge mode is set to be finished after a predetermined time interval.
At that time, in a case where a plurality of heaters 212 are provided, by constructing the power distribution circuit 265 to sequentially switch the power distributions to the respective heaters with time, the distributed current can be reduced without change of the heat quantity of the heaters supplied with electricity, so that the power distribution circuit 265 can be miniaturized.
By generating a heat quantity with which the working fluid existing on the surface of the heaters 212 changes its phase, the gas bubbles due to the phase change may be generated from the respective surface portions of the heaters 212. In this method, the working fluid corresponding to the volume of the generated gas bubbles is discharged to the outflow passage 228. When the power distribution to the heaters 212 is stopped and the change of phase is finished, the working fluid having an amount corresponding to the volume of the discharged working fluid is introduced into the pump chamber 227 through the check valve 222 from the inflow passage 221. At that time, since the gas bubbles due to the change of phase are generated from the respective surface portions of the heaters 212, the flow inside the pump chamber 227 is complex and not stagnated, so that it is possible to discharge the staying gas bubbles gathered at the comer portions of the pump chamber which is the stagnated area in the discharge mode.
Furthermore, by generating a heat quantity enough to allow the working fluid existing on the surface of the heater 212 to reach an overheated state through the power distribution from the power distribution circuit 265, a film boiling such that a film-shaped gas bubble is generated from the whole surface of the heater 212 may be caused. In this method, since the volume of the gas bubbles generated due to the change of phase is increased and the volume of the working fluid discharged to the outflow passage 228 from the pump chamber 227 with one power distribution is increased, it is easy to discharge the gas bubbles.
FIG. 16 shows a modified example of the heater 212. In FIG. 16, the heater 212 includes two of a heater 213 arranged at the inflow passage 221 side and a heater 214 arranged at the outflow passage 228 side.
At that time, the phases of the distributed current to the respective heaters are deviated by using the power distribution circuit 265 (see FIG. 15). As a result, after the inside pressure of the gas bubbles generated through the film boiling on the surface of one heater exceeds the maximum value, the inside pressure of the gas bubbles generated through the film boiling on the surface of the other heater reaches the maximum value.
Furthermore, it is preferable that the heater 213 close to and the heater 214 far from the opening portion of the pump chamber 227 of the outflow passage 228 are provided, the power distribution to the far heater 214 is first started, and the power distribution to the heater 213 is started later, so that the flow from the comer portion of the pump chamber 227 toward the outflow passage 228 can be easily generated. Of course, the number of heaters 212 may be two or more.
When the phase of the working fluid on the surface of the heater 212 is changed, the diaphragm 60 may have any one of the stopped state and the driven state. But it is preferable that the diaphragm 60 is driven, so that the flow inside the pump chamber becomes complex and thus the staying gas bubbles can be easily excluded.
In the seventh exemplary embodiment, the pump driving control circuit 280 and the power distribution circuit 265 may be controlled so that the heater 212 is allowed to emit heat in a pulse shape by performing the power distribution to the heater 212 using a pulse current. The diaphragm 60 is driven in a direction in which the volume of the pump chamber 227 is reduced in synchronism with the heat emitting.
As a result, it is possible to effectively discharge the gas bubbles staying in the pump chamber while reducing the energy consumption of the heating section.
Furthermore, when the start and stop of the power distribution to the heater 212 are repeated several times during one bubble discharge mode, a more complex flow is generated inside the pump chamber. Thus, the staying gas bubbles are more easily discharged. Furthermore, the detected value by the pressure sensor 91 may be checked by driving the pump in the discharge mode after the bubble discharge mode is finished, so that it is possible to repeat the driving of the bubble discharge mode until the staying gas bubbles are discharged.
Therefore, according to the seventh exemplary embodiment, since the inside pressure of the pump chamber 227 is raised by providing the heater 212 inside the pump chamber 227 and thus the volume of the gas bubbles is compressed, it is possible to discharge the gas bubbles in the pump chamber 227.
Furthermore, since the heater 212 is fitted into the wall of the pump chamber 227 so that the heater is not protruded from the wall, and the heater is arranged at least at the comer portion of the pump chamber 227, the gas bubbles can be prevented from staying in a protruded portion in which the gas bubbles is easily stagnated. It is also possible to discharge the staying gas bubbles at the comer portion of the pump chamber 227.
Furthermore, when a plurality of heaters 212 are provided, it is possible to reduce the quantity of energy per unit time to be supplied to the heaters 212, and to rapidly discharge the staying gas bubbles while preventing the destruction of the pump.
Furthermore, since the pressure sensor 90 is provided in the pump chamber 227, it is possible to determine whether the gas bubbles stay in the pump chamber 227, thereby discharge the gas bubbles in the pump chamber 227 as described above.
Furthermore, since the heater 212 emits heat in a pulse shape and the diaphragm 60 is driven in synchronism with the pulse, it is possible to effectively discharge the gas bubbles staying in the pump chamber 227 while reducing the energy consumption of the heater 212.
Furthermore, by performing the heating process to generate the heat quantity with which the working fluid in contact with the heater 212 changes its phase, the gas bubbles due to the change of phase is generated in the pump chamber 227, so that the complex and non-stagnated flow flowing toward the outflow passage 228 can be caused in the pump chamber 227. As a result, it is possible to discharge the gas bubbles staying in the pump chamber 227.
Furthermore, in the above description, since the bubble discharge mode is performed when it is determined by the pressure sensor 91 that the gas bubbles stay, the bubble discharge mode is not performed wastefully. But the bubble discharge mode may be performed every predetermined time interval. In this case, since the pressure sensor 91 can be omitted, it is possible to simplify the structure.
Furthermore, in the above description, the construction that the pressure sensor as the pressure detecting device for the pump chamber is provided in the pump chamber 227 has been described. But different constructions may be employed. In one different construction, for example, the inside pressure of the pump chamber 227 may be calculated by measuring the deformation of the diaphragm 60 with a strain gauge or a displacement sensor. Further, the inside pressure of the pump chamber 227 may be calculated by measuring the deformation of the valve member in a state where the check valve 222 is closed, with a strain gauge or a displacement sensor. Furthermore, the inside pressure of the pump chamber 227 may be calculated by measuring current to drive the piezoelectric element 70 with a current sensor. Furthermore, by providing a strain gauge in the piezoelectric element 70, the inside pressure of the pump chamber 227 may be calculated on the basis of the voltage applied to the piezoelectric element 70 and the measured value by the strain gauge. At that time, any type of strain gauges that detect the quantity of deformation by using variation in resistance, variation in capacitance, or variation in voltage may be used as the strain gauge.
The shape of the diaphragm 60 is not limited to the circular shape. Further, the check valve 222 is not limited to the passive valve which performs the opening and closing due to the pressure difference of the fluid, but an active valve which can control the opening and closing with different forces may be used as the check valve.
The present invention is not limited to the above exemplary embodiments, but the present invention includes modifications and enhancements.
In the seventh exemplary embodiment, for example, the resultant inertance value of the inlet passage side is smaller than the resultant inertance value of the outlet passage side, and the heater 212 as the bubble discharging device is employed in the small high-pressure pump having an inertia effect of the working fluid. However, the bubble discharge device may be employed, for example, in a pump using a unimorph type diaphragm shown in FIG. 17.
FIG. 17 is a vertical cross-sectional schematic of the pump employing the unimorph type diaphragm. In FIG. 17, constituent elements different from the seventh exemplary embodiment will be described in detail. The pump 200 includes a unimorph type diaphragm 260 as a diaphragm, and check valves 222, 242 as the fluid resistance elements provided in both of the inflow passage 221 and the outflow passage 228. In FIG. 17, the diaphragm 260 is airtightly fixed to the edge portion of the cup-shaped case 250. The plate-shaped piezoelectric element 71 is fixed to the surface of the diaphragm 260 facing the case 250. The pump case 220 is airtightly fixed to the top of the diaphragm 260, and the pump chamber 227 is formed between the diaphragm 260 and the pump case 220.
The inflow passage 221 and the outflow passage 228 communicate with the pump chamber 227. The check valve 222, as the fluid resistance element, is provided in the inflow passage 221. The check valve 242, as the fluid resistance element, is provided in the outflow passage 228. The plane-shaped heater 212, as the heating section, is provided on the top wall surface constituting the pump chamber 227 of the pump case 220. The heater 212 is airtightly fitted into the pump case 220, so that the heater is not protruded from the pump case 220 toward the pump chamber.
The shape and material of the heater 212, and the position in which the heater is fitted into the pump case 220 are similar to the seventh exemplary embodiment and the modified example of the seventh exemplary embodiment. Thus descriptions thereof will be omitted.
The discharge mode of the pump will be described.
If a voltage is applied to the plate-shaped piezoelectric element 71, the diaphragm 260 is deformed to have a convex surface toward the pump chamber 227 through the diametrical deformation of the plate-shaped piezoelectric element 71. If the application of voltage is stopped, the diaphragm is restored to the original shape. In this pump, when the check valves 222 and 242 close the flow passage, the diaphragm 260 is deformed in the direction in which the volume of the pump chamber 227 is decreased by using the deformation of the diaphragm 226, thereby pressing the liquid inside the pump chamber 227. If the inside pressure of the pump chamber 227 becomes higher than the downstream pressure of the check valve 242, the check valve 222 is opened. Thus the liquid is discharged to the outflow passage 228.
Next, by deforming the diaphragm 260 in the direction in which the volume of the pump chamber 227 is increased, the inside pressure of the pump chamber 227 is decreased. Then, the check valve 242 is first closed. If the inside pressure of the pump chamber 227 becomes lower than the upstream pressure of the check valve 222, the check valve 222 is opened, so that the liquid is introduced into the pump chamber 227 from the inflow passage 221. By repeating the above actions, the working fluid is transferred.
By providing the heater 212 as the bubble discharge device in the pump having the above structure, it is possible to allow the gas bubbles inside the pump chamber to flow out, and to suitably maintain the inside pressure of the pump chamber, so that it is possible to secure the amount of working fluid to be discharged.
In the above exemplary embodiments, the diaphragms 60, 45 have a circular shape, but the shape is not limited to the circular shape. Further, the check valves 41, 42 are not limited to the passive valves that perform the opening and closing process due to the pressure difference of the fluid, but active valves that can control the opening and closing process with different forces may be used as the check valves. Furthermore, any element may be used as the piezoelectric element to drive the diaphragm 60, only if it can be contracted and expanded. However, in this pump structure, since the piezoelectric element and the diaphragm are connected to each other without a displacement enlarging mechanism and thus the diaphragm can be driven at a high frequency, it is possible to increase the flow volume with a high frequency driving by employing a piezoelectric element having a high response frequency as in the embodiments, so that it is possible to realize a small and high-power pump. Similarly, a super magnetic distortion element having a high frequency characteristic may be employed. Different liquid, such as oil may be used as the working fluid, in addition to water.
Therefore, according to the first to seventh exemplary embodiments described above, since the bubble discharging device is provided, it is possible to provide a pump capable of discharging the gas bubbles and thus maintaining a discharging ability thereof, even when the gas bubbles stay in the pump chamber.

INDUSTRIAL APPLICABILITY

The pump according to aspects of the present invention can be applied to various industries requiring a small liquid transfer pump.

Claims

1. A pump, comprising:

a pump chamber whose volume can be varied by driving a piston or a movable wall;

an inlet passage to allow a working fluid to flow into the pump chamber;

an outlet passage to allow the working fluid to flow out of the pump chamber,

a fluid resistance element to open and close at least the inlet passage, a resultant inertance value of the inlet passage being set to be smaller than a resultant inertance value of the outlet passage; and

a bubble discharging device to discharge gas bubbles remaining in the pump chamber.

2. The pump according to claim 1,

the pump chamber including a primary pump chamber which communicates with the outlet passage and whose volume can be varied by driving a piston or a movable wall, and a secondary pump chamber which communicates with the inlet passage and functions as the bubble discharging device and whose volume can be varied by driving a movable wall.

3. The pump according to claim 2, further comprising:

a primary pump chamber inlet passage to allow the working fluid to flow into the primary pump chamber;

a primary pump chamber outlet passage to allow the working fluid to flow out of the primary pump chamber;

a secondary pump chamber inlet passage to allow the working fluid to flow into the secondary pump chamber; and

a secondary pump chamber outlet passage to allow the working fluid to flow out of the secondary pump chamber, the primary pump chamber inlet passage also functioning as the secondary pump chamber outlet passage.

4. The pump according to claim 3, further comprising:

a fluid resistance element to open and close the primary pump chamber inlet passage;

a fluid resistance element to open and close the secondary pump chamber inlet passage; and

a fluid resistance element to open and close the secondary pump chamber outlet passage,

the fluid resistance element to open and close the primary pump chamber inlet passage also functioning as the fluid resistance element to open and close the secondary pump chamber outlet passage.

5. The pump according to claim 2,

the movable wall provided in the secondary pump chamber being a diaphragm in which a piezoelectric element is attached to at least one surface thereof, and the secondary pump chamber and the diaphragm including a unimorph pump or a bimorph pump.

6. The pump according to claim 2, further comprising:

a driving switch control unit to switch the driving between the secondary pump chamber and the primary pump chamber.

7. The pump according to claim 5,

a driving electrode and a detecting electrode are formed in the piezoelectric element.

8. The pump according to claim 2, further comprising:

a pressure detecting section to detect an inside pressure of the primary pump chamber.

9. The pump according to claim 1, further comprising:

a pressurizing mechanism serving as the bubble discharging device to raise and maintain the pressure of the working fluid existing in the pump chamber.

10. The pump according to claim 9,

the pressurizing mechanism, comprises:

a variable-volume chamber and a flow passage to allow the variable-volume chamber and the outlet passage to communicate with each other.

11. The pump according to claim 10,

the variable-volume chamber being formed of an elastic member.

12. The pump according to claim 10,

the pressurizing mechanism, further comprises:

a volume varying mechanism to apply a pressure to vary the volume of the variable-volume chamber.

13. The pump according to claim 9,

the pressurizing mechanism, comprises:

a passage switching section to switch between a first mode where the working fluid flowing out of the pump chamber is introduced into the variable-volume chamber, and a second mode where the working fluid flowing out of the pump chamber is isolated from the variable-volume chamber.

14. The pump according to claim 10, further comprising:

a pressure detecting section to detect an inside pressure of the variable-volume chamber.

15. The pump according to claim 9,

a pressure detecting device being provided in the pump chamber.

16. The pump according to claim 12,

the inside pressure of the variable-volume chamber, which is pressurized by the pressurizing mechanism, ranging from about one atmosphere to about five atmospheres in a gauge pressure.

17. The pump according to claim 9,

the pressurizing mechanism, comprises:

a variable-volume chamber;

a flow passage communicating with the outlet passage; and

an opening and closing member to open and close the flow passage, and

the pressurizing mechanism being detachable from the outlet passage, and the variable-volume chamber and the outlet passage being allowed to communicate with each other by fitting the pressurizing mechanism into the outlet passage.

18. The pump according to claim 1,

a heating section serving as the bubble discharging device being provided in the pump chamber.

19. The pump according to claim 18,

the heating section being received inside the wall of the pump chamber, or being arranged in a comer portion of the pump chamber.

20. The pump according to claim 18,

a plurality of the heating sections being provided.

21. The pump according to claim 18, further comprising:

a pressure detecting section to detect an inner pressure of the pump chamber.

22. The pump according to claim 18,

when the piston or the movable wall is being driven, a heating signal being input to the heating section.

23. The pump according to claim 18,

a pulse-shaped heating signal being input to the heating section, and the piston or the movable wall being driven in synchronism with the heating signal.

24. The pump according to claim 19,

the heating section heating the working fluid to change the phase of the working fluid in contact with the heating section.