WO2008026882A1

WO2008026882A1 - Capacitance type leakage sensor

Info

Publication number: WO2008026882A1
Application number: PCT/KR2007/004165
Authority: WO
Inventors: Jong Gu Park; Eung Shin Lee
Original assignee: Rechner Korea Co., Ltd.
Priority date: 2006-08-30
Filing date: 2007-08-29
Publication date: 2008-03-06
Also published as: KR100726935B1

Abstract

Disclosed is a capacitance type leakage sensor, which withstands poor environments surrounding the sensor so as to use a conventional capacitance type sensor as a leakage sensor, and correctly finds out which chemical is leaked with a desired precision. The capacitance type leakage sensor for sensing whether or not a target object to be sensed is leaked, includes an electrode constituent unit including first and second electrode terminals, having different polarities, provided on both surfaces of an insulating substrate, and an auxiliary electrode terminal, having the same polarity as that of the first electrode terminal, provided at the outside of the second electrode terminal; and a circuit unit substrate for determining whether or not the target object is leaked according to capacitance varied between both electrodes of the electrode constituent unit.

Description

[DESCRIPTION]

[invention Title]

CAPACITANCE TYPE LEAKAGE SENSOR

[Technical Field]

The present invention relates to a capacitance type leakage sensor, and more particularly to a capacitance type leakage sensor, which senses leakage of water and a chemical liquid in early stages of semiconductor or LCD manufacturing equipment.

[Background Art]

In industrial equipment using a liquid, a leakage sensor, which is installed around a container containing the liquid or below a joint of a pipe line transporting the liquid, senses the leakage of water or a chemical. Till now, optical sensors (also referred to as 'photosensors' ) using light have been mostly used as leakage sensors. In this case, an optical type leakage sensor senses the leakage of a liquid by detecting a variation in the intensity of illumination of light reflected by an absorbent paper, which is installed below the optical type leakage sensor, when the liquid soaks into the absorbent paper. In the conventional optical type leakage sensor, the absorbent paper is replaced with a new one whenever the liquid soaks into the absorbent paper, and is discolored due to moisture in air or vapor of a chemical after a designated time after the installation of the sensor has elapsed and the intensity of illumination of light is changed. Thus, the conventional optical type leakage sensor may be abnormally operated even when the leakage of the liquid does not occur. Accordingly, the conventional optical type leakage sensor needs to clean a white wet paper having a high absorptiveness in a sensing region at all times so as to maintain the uniform intensity of illumination, and does not sense the leakage of a chemical having a small variation in intensity of illumination even when the chemical is leaked and soaks into the paper according to circumstances.

A conventional capacitance type sensor is used as a leakage sensor for sensing the leakage of a liquid having a high dielectric constant. However, the use of such a capacitance type sensor as a leakage sensor has several problems, as follows.

First, the conventional capacitance type sensor, which is a proximity sensor, adjusts a sensing region sensing the leakage of a chemical close to a leakage spot, differing from an optical sensor. Thus, in the case that the chemical has a high melting property, the external surface of the sensor is melted and a circuit in the sensor is spoiled, or the circuit partially shorts and sparks. Then, the chemical having a high inflammability may catch fire.

Second, the conventional capacitance type sensor may have a structure, in which a variation in dielectric constant of a target object 1, to be sensed, between two electrodes 111 and 112 is sensed, as shown in FIG. IA. This structure, in which the electrodes 111 and 112 are separated from each other so as to sense a chemical flowing into a space therebetween, is complicated, and does not satisfy the requirements of the industry having a simple structure of a conventional sensor.

Third, the conventional capacitance type sensor has a sensing region, which is broadly formed at the front of the main body of the sensor, and thus detects a variation in distance of a target object, to be sensed, entering the sensing region due to vertical movement or whether or not an object having a high dielectric constant exists. However, the leakage sensor must correctly sense a variation in dimensions of a liquid flowing from the side into a sensing region, and thus have a difficult problem to precisely restrict a desired sensing region.

Fourth, the conventional capacitance type sensor may have a structure, in which two electrodes 121 and 122 are disposed in series, as shown in FIG. IB, or one electrode 131 is disposed at the rear of the other electrode 132, as shown in FIG. 1C, other than the structure in which the two electrodes are separated so as to sense a variation in dielectric constant of a target object disposed therebetween. In the case that the capacitance type sensor having the above disposition of electrodes is applied to a leakage sensor, when an object having a high dielectric constant passes by an electrode, being opposed to the sensing region, the sensor is abnormally operated.

As shown in FIG. 2, since an electric field between the two electrodes are broadly distributed above and below the electrodes, the conventional capacitance type sensor has a poor sensing capacity to a target liquid flowing into the sensing region. Further, in equipment, such as semiconductor manufacturing equipment, in which many capacitance type sensors serving as leakage sensors are installed, when a person or a tool for repairing or checking the equipment passes by the sensors, many sensors generate an abnormally operational signal frequently.

Since the electric field is broadly distributed around the sensor, in the case that a circuit of the sensor is adjusted such that the sensing capacity of the sensor is increased, the sensor is abnormally operated when the humidity in air is increased or vapor of a chemical is generated although the target object is not substantially leaked. [Disclosure] [Technical Problem]

Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a capacitance type leakage sensor, which withstands poor environments surrounding the sensor so as to use a conventional capacitance type sensor as a leakage sensor, and correctly finds out which chemical is leaked with a desired precision. It is another object of the present invention to provide a capacitance type leakage sensor having a novel constitution of electrodes, which precisely senses the leakage of a chemical when the leaked chemical reaches a designated area or more in a sensing region of the sensor It is yet another object of the present invention to provide a capacitance type leakage sensor, which exhibits a safely and reliably high sensing capacity without trouble, even when the sensor is exposed to a chemical, the leakage of which is sensed.

[Technical Solution]

In accordance with an aspect of the present invention, the above and other objects can be accomplished by the provision of a capacitance type leakage sensor for sensing whether or not a target object to be sensed is leaked, comprising an electrode constituent unit including first and second electrode terminals, having different polarities, provided on both surfaces of an insulating substrate, and an auxiliary electrode terminal, having the same polarity as that of the first electrode terminal, provided at the outside of the second electrode terminal; and a circuit unit substrate for determining whether or not the target object is leaked according to capacitance varied between both electrodes of the electrode constituent unit.

The first electrode terminal and the auxiliary electrode terminal may maintain an equi-potential surface.

The electrode constituent unit may further include an auxiliary ring provided outside the insulating substrate, the first electrode terminal, and the auxiliary electrode terminal for preventing the outflow of an electric field.

An LED for checking whether or not the leakage of the target object is sensed may be provided on the circuit unit substrate . The electrode constituent unit and the circuit unit substrate may be hermetically sealed with a housing and a protection lid; and the inside of the housing may be filled with epoxy.

A sensing region formed by the electrode constituent unit may be adjusted by an area ratio of the second electrode terminal and the auxiliary electrode terminal . [Advantageous Effects]

The present invention provides a capacitance type leakage sensor, which employs small and flat electronic components as a unit for sensing leakage of water or a chemical and a circuit unit for treating the leakage using a double-sided or multi-layered substrate so that the sensor can be miniaturized and easily installed, and includes a part for protecting the sensor so that the sensor can be installed at a desired place using a holder. Thus, the capacitance type leakage sensor is usefully applied to semiconductor or LCD manufacturing equipment, and solves several problems caused by a conventional optical type leakage sensor, thus being substituted for the conventional leakage sensor. Further, the capacitance type leakage sensor of the present invention is filled with a specific epoxy, and thus prevents the sensor from floating due to the self weight even when a large amount of a liquid is leaked and prevents the chemical from permeating into the sensor so as to increase the durability of the sensor, thereby being semi-permanently used.

Further, in the case that the technique of the present invention is applied to a conventional industrial capacitance type sensor, the distance sensing capacity of the sensor is improved, and the sensing region of the sensor is reduced so that the sensor cannot be operated abnormally even when an object having a high capacitance is located in a region other than the sensing region.

[Description of Drawings]

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIGs. IA, IB, and 1C are schematic views illustrating constitutions of electrodes of general capacitance type sensors;

FIG. 2 is a view illustrating the distribution of an electric field of the capacitance type sensor having the disposition of the electrodes as shown in FIG. 1C; FIG. 3 is a schematic view illustrating a method, which senses an object using a capacitance type leakage sensor in accordance with one embodiment of the present invention;

FIGs . 4A and 4B illustrate examples of the capacitance type leakage sensor of FIG. 3, and more particularly:

FIG. 4A illustrates the capacitance type leakage sensor having a multi-layer substrate; and

FIG. 4B illustrates the capacitance type leakage sensor having a divisional substrate;

FIG. 5 is a schematic view illustrating the constitution of electrodes of the capacitance type leakage sensor of FIG. 3; FIG. 6 is a view illustrating the distribution of an electric field of the capacitance type leakage sensor having the disposition of the electrodes as shown in FIG. 5;

FIG. 7 is a block diagram of the circuit constitution of a circuit unit substrate among components of the capacitance type leakage sensor of FIG. 3;

FIGs. 8 and 9 illustrate examples of the installation of the capacitance type leakage sensor of the present invention, and more particularly: FIG. 8 illustrates one example of the installation of the capacitance type leakage sensor using a metallic holder; and

FIG. 9 illustrates one example of the installation of the capacitance type leakage sensor using a nonmetallic holder;

FIG. 10 is a schematic view illustrating the constitution of electrodes of a capacitance type leakage sensor in accordance with another embodiment of the present invention; and FIG. 11 is a graph illustrating variations of sensitivity of a conventional capacitance type leakage sensor and the capacitance type leakage sensor of the present invention according to a variation in leakage.

[Mode for Invention]

Now, a capacitance type leakage sensor of the present invention will be described in detail with reference to the annexed drawings.

FIG. 3 is a schematic view illustrating a method, which senses an object using a capacitance type leakage sensor in accordance with one embodiment of the present invention. FIGs. 4A and 4B illustrate examples of the capacitance type leakage sensor of FIG. 3, and more particularly FIG. 4A illustrates the capacitance type leakage sensor having a multi-layer substrate, and FIG. 4B illustrates the capacitance type leakage sensor having a divisional substrate. FIG. 5 is a schematic view illustrating the constitution of electrodes of the capacitance type leakage sensor of FIG. 3. FIG. 6 is a view illustrating the distribution of an electric field of the capacitance type leakage sensor having the disposition of the electrodes as shown in FIG. 5. FIG. 7 is a block diagram of the circuit constitution of a circuit unit substrate among components of the capacitance type leakage sensor of FIG. 3. FIGs. 8 and 9 illustrate examples of the installation of the capacitance type leakage sensor of the present invention, and more particularly FIG. 8 illustrates one example of the installation of the capacitance type leakage sensor using a metallic holder, and FIG. 9 illustrates one example of the installation of the capacitance type leakage sensor using a nonmetallic holder. FIG. 10 is a schematic view illustrating the constitution of electrodes of a capacitance type leakage sensor in accordance with another embodiment of the present invention. FIG. 11 is a graph illustrating variations of sensitivity of a conventional capacitance type leakage sensor and the capacitance type leakage sensor of the present invention according to a variation in leakage.

In order to allow a capacitance type sensor for sensing leakage to form an electric field uniformly in a desired direction to restrict a sensing region, the disposition of electrodes provided in an electrode constituent unit 40, as shown in FIG. 5, is important.

As shown in FIG. 3, the disposition of electrodes of the electrode constituent unit 40 is preferably configured such that the leakage sensor 84 has a sensing region 85 restricted just below the electrodes when a target object 82, the leakage of which is sensed, drops below a joint of a pipe line 81 transporting a chemical or a container containing the chemical, is gathered in a support 83, and flows into an area below the leakage sensor 84.

In the case that the conventional capacitance type sensor having the disposition of electrodes, as shown in FIG. 1C, is used, an electric field formed by the electrodes is widely distributed, as shown in FIG. 2. Accordingly, even though the target object 82 drops onto the support 83 and flows into the area below the leakage sensor 84, a variation in capacitance is not high before and after the target object 82 enters the sensing region 85, and thus cannot be correctly sensed. FIG. HB illustrates the variation in capacitance in the conventional capacitance type sensor. As shown in FIG. 11B, the variation in capacitance even within the sensing region 85 formed below the electrodes is not high, and thus the conventional capacitance type sensor has a low efficiency of sensing the target object 82.

In the case that the circuit of the leakage sensor 84 is modified such that the sensing capacity of the leakage sensor 84 is excessively high, the leakage sensor 84 not only senses the leakage of the target object 82 when the target object 82 is substantially leaked, but also is abnormally operated and thus determines that the target object 82 is leaked when the humidity is increased or an object passes by the leakage sensor 84. Accordingly, the leakage sensor 84 needs to effectively sense the target object 82 while not having an excessively high sensing capacity.

Thus, the capacitance type leakage sensor of the present invention has a disposition of electrodes such that an electric field formed around the electrodes of the electrode constituent unit 40 is concentrated onto the sensing region 85 so as to restrict the sensing region 85, as shown in FIG. 3.

That is, as shown in FIG. 5, a first electrode 41 is broadly disposed on the upper surface of an insulating substrate 42, a second electrode 44 having a pole opposite to that of the first electrode 41 is disposed on the lower surface of the insulating substrate 42, and an auxiliary electrode 43 is disposed around the second electrode 44 such that the auxiliary electrode 43 forms an equi-potential surface with the first electrode 41 and surrounds the second electrode 44. Here, the first electrode 41 is grounded so as to have an electric potential of 0 constantly, and an AC voltage of a high-frequency RC circuit (not shown) is applied to the second electrode 44. That is, the second electrode 44 has the positive pole (+) , and the first electrode 41 and the auxiliary electrode 43 are grounded.

In order to form the proper sensing region 85 through the electric field, as shown in FIG. 6, the first electrode 41 of the electrode constituent unit 40 is disposed on one surface of the insulating substrate 42, and the area ratio of the second electrode 44 and the auxiliary electrode 43, which are disposed on the other surface of the insulating substrate 42, is adjusted, thus being capable of finely controlling the direction of the electric field. Here, a small hole for connecting the first electrode 41 and the auxiliary electrode 43 so as to have the same electric potential is formed through the insulating substrate 42.

Further, as shown in FIG. 10, an auxiliary ring 70 made of a metal may be disposed around the insulating substrate 42 so as to adjust the degree of deviating the electric field from the sensing region. That is, the first electrode 41, the auxiliary electrode 43 surrounding the second electrode 44, and the auxiliary ring 70 surrounding the insulating substrate 42 are connected and grounded, and thus the upper portion and the outside of the electrode constituent unit 40 form an equi-potential surface, thereby causing the capacitance to scarcely vary even though an external disturbance exists. Accordingly, since the electric field formed in the sensing region 85 has a higher potential difference than the electric field formed in other regions, when a liquid or the target object having a high dielectric constant enters the sensing region 85, the variation in capacitance is high and thus the sensing capacity to the target object 82 is high. In the capacitance type leakage sensor of the present invention, after the electrode constituent unit 40 is obtained by locating the first electrode 41 on the upper surface of the insulating substrate 42 and the auxiliary electrode 43 and the second electrode 44 on the lower surface of the insulating substrate 42, as described above, the electrode constituent unit 40 has a divisional structure, as shown in FIG. 4B, or has a multi-layer structure, as shown in FIG. 4A.

A circuit unit substrate 20 including treating units for sensing a variation in current according to a variation in capacitance and outputting converted signals, a housing 30 for protecting the electrodes 41, 43 an 44 and the insulating substrate 42 of the electrode constituent unit 40 and the circuit unit substrate 20, the auxiliary ring 70 disposed between the circuit unit substrate 20 and the housing 30 for intercepting the external disturbance of the capacitance, are provided, and a cable 50 for supplying power to the circuit unit substrate 20 and transmitting the output signal of the circuit unit substrate 20 is connected to the circuit unit substrate 20 through the housing 30. With reference to FIGs. 4A and 4B, a light emitting diode (LED) 60 for displaying the operating state of the leakage sensor 84 is attached to the circuit unit substrate 20, and a hole is formed through the housing 30 such that the LED 60 can be exposed to the outside through the hole. Instead of the hole, a transparent window may be formed in the housing 30 such that the LED 60 can be exposed to the outside through the transparent window.

As described above, the capacitance type leakage sensor of the present invention has a multi-layer structure such that the electrodes 41, 43 and 44 for sensing a target object, the leakage of which is sensed, the insulating substrate 42 for fixing the electrodes 41, 43, and 44, and the circuit unit substrate 20 for detecting the variation in capacitance are stacked, and electronic components for forming a circuit are attached thereto. Thereby, the capacitance type leakage sensor of the present invention is miniaturized.

The circuit unit substrate 20 is stacked on the electrodes 41, 43, and 44 and the insulating substrate 42 of the electrode constituent unit 40, and includes several components for detecting the variation in capacitance. As shown in FIG. 7, the circuit unit substrate 20 includes a high-frequency oscillatory circuit 21, a detector circuit 22, an amplifier circuit 23, and an output circuit unit 24.

Further, in the capacitance type leakage sensor of the present invention, as shown in FIGs. 8 and 9, various electronic components, such as the electrode constituent unit 40 and the circuit unit substrate 20, are installed in the housing 30 and are hermetically sealed by a protection lid 30. The housing 30, which serves to isolate the internal components from a chemical, is mainly made of fluororesin in a gas, such as polytetrafluoroethylene (PTFE), which has a low capacitance and a high resistance to leaked water or liquid or a chemical in a gas state, and is made of polyethylene (PE), polyvinyl chloride (PVC), poly carbonate (PC), or polyetheretherketone (PEEK).

A specific epoxy for firmly fixing the internal components fills the inside of the housing 30, and thus prevents the inside of the housing 30 from shaking so as to protect the inside of the housing 30 from vibration or impact and prevents the housing 30 from floating in a leaked liquid due to the self weight even when a large amount of the liquid is leaked. Further, the epoxy fills up the inside of the housing 30, thereby preventing the leaked liquid from permeating into the housing 30 and thus increasing the durability of the housing 30. Under the condition that the inside of the housing 30 is filled with the epoxy and is hermetically sealed so as not to prevent any liquid from permeating into the housing 30, the capacitance type leakage sensor of the present invention is installed at a position, where a target liquid to be sensed is leaked and then gathered, using a holder 90 or 91 serving as a fixing unit, as shown in FIGs. 8 and 9. The holder 90 or 91 is made of metal, PTFE, or PVC.

The above-described capacitance type leakage sensor of the present invention correctly senses the leakage of the liquid when the liquid is leaked and reaches a desired position. The electric field formed around the capacitance type leakage sensor of the present invention is concentrated onto an area below the electrode constituent unit 40, as shown in FIG. 10. When the target object 82 flows into the sensing region 85 of the leakage sensor 84, the leakage sensor 84 exhibits a specific curve having a variation in capacitance, as shown in FIG. UA, and. It is verified that the capacitance type leakage sensor of the present invention has a great variation in capacitance of the target object 82 below the electrodes and thus has a high sensing capacity, compared with a conventional capacitance type leakage sensor exhibiting a curve having a variation in capacitance, as shown in FIG. HB.

The conventional capacitance type leakage sensor exhibiting the curve of FIG. HB has a small variation in capacitance between when the leaked liquid flows near the sensor and when the leaked liquid flows into the sensing region 85, thus causing a difficulty in detecting a sensing point of time. Further, in the case that the circuit of the conventional capacitance type leakage sensor is electronically modified so as to increase the sensitivity of the sensor, when an object having a high capacitance passes by the conventional capacitance type leakage or the humidity is increased, the conventional capacitance type leakage may be operated abnormally. On the other hand, the capacitance type leakage sensor of the present invention exhibiting the curve of FIG. HA has a variation in capacitance such that the capacitance maintains a small value when a liquid is located at the outside of the sensing region 85 and is highly varied when the liquid flows into the sensing region 85. Accordingly, it is possible to adjust that a point of time, when how many percent of the total capacitance value is varied when the liquid flows into an area corresponding to how many percent of the sensing region 85, is set to a sensing point of time to the target object 82. This adjustment is achieved according to the area ratio of the second electrode 44 and the auxiliary electrode 43. When the area of the second electrode 44 located within the auxiliary electrode 43 is decreased, the sensing region 85 of the leakage sensor 84 is reduced, and when the area of the second electrode 44 is increased, the sensing region of the leakage sensor 85 is expanded.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

[CLAIMS]

[Claim l] A capacitance type leakage sensor for sensing whether or not a target object to be sensed is leaked, comprising: an electrode constituent unit including first and second electrode, having different polarities, provided on both surfaces of an insulating substrate, and an auxiliary electrode, having the same polarity as that of the first electrode, provided at the outside of the second electrode; and a circuit unit substrate for determining whether or not the target object is leaked according to capacitance varied between both electrodes of the electrode constituent unit.

[Claim 2] The capacitance type leakage sensor according to claim 1, wherein the first electrode and the auxiliary electrode maintain an equi-potential surface.

[Claim 3] The capacitance type leakage sensor according to claim 2, wherein the electrode constituent unit further includes an auxiliary ring provided outside the insulating substrate, the first electrode, and the auxiliary electrode for preventing the outflow of an electric field.

[Claim 4] The capacitance type leakage sensor according to claim 2, wherein an LED for checking whether or not the leakage of the target object is sensed is provided on the circuit unit substrate.

[Claim 5] The capacitance type leakage sensor according to claim 2, wherein: the electrode constituent unit and the circuit unit substrate are hermetically sealed with a housing and a protection lid; and the inside of the housing is filled with epoxy.

[Claim 6] The capacitance type leakage sensor according to claim 2, wherein a sensing region formed by the electrode constituent unit is adjusted by an area ratio of the second electrode and the auxiliary electrode.