US3822682A

US3822682A - Rotary valve engine

Info

Publication number: US3822682A
Application number: US00268139A
Authority: US
Inventors: N Sherwood
Original assignee: Textron Inc
Current assignee: Textron Inc
Priority date: 1972-06-30
Filing date: 1972-06-30
Publication date: 1974-07-09
Anticipated expiration: 1991-07-09

Abstract

The crank case of a twin cylinder engine is divided into two compartments, one for each cylinder. An intake chamber provided in the crank case between the two compartments has a port opening into each of the compartments. A valve disc on the crank shaft in each of the compartments overlies the port opening into the respective compartment and has an opening registrable with the port when the crank shaft is in a selected angular position to permit entry of a charge from the intake chamber into the respective compartment of the crank case. The charge may be a fuel-air mixture or, in the case of fuel injection into the crank case or the cylinder, it may be air. In either event oil may be included in the charge for lubrication. A seal is provided between the port of the intake chamber and the valve disc by a floating sealing ring of low friction material having a flat face which is pressed against the valve disc by a pressure ring of elastomeric material which may, for example, be of sponge structure or may be formed with a base portion and a selected number of flexible webs which press against the sealing ring and forming passageways for entry of crankcase gas under pressure between the base portion of the elastomeric ring and the sealing ring to partially balance pressure tending to unseat the sealing ring.

Description

[ July 9, 1974 [5 7] ABSCT The crank case of a twin cylinder engine is divided into two compartments, one for each cylinder. An intake chamber provided in the crank case between the two compartments has a port opening into each of the compartments. A valve disc on the crank shaft in each of the compartments overlies the port opening into the respective compartment and has an opening registrable with the port when the crank shaft is in a selected angular position to permit entry of a charge from the intake chamber into the respective compartment of the crank case. The charge may be a fuel-air mixture or, in the case of fuel injection into the crank case or the cylinder, it may be air. In either event oil may be included in' the charge for lubrication. A seal is provided between the port of the intake chamber and the valve disc by a floating sealing ring of low friction ma- ROTARY VALVE ENGINE Noble Sherwood, Greenwich, Conn.

Assignee: Textron, Inc, Providence, RI.

June 30, 1972 Appl. No.: 268,139

US. Cl..... 123/73 D, 123/190 AA, 123/190 D 123/190 E Int. F011 7/12, F011 7/16 Field of Search............l23/73 V, 73 D, 73 A 190 AA, 123/190 DA ,190E, 190 1 References Cited UNITED STATES PATENTS Sargent.....

United States Patent Sherwood terial having a flat face which is pressed against the valve disc by a pressure ring of elastomeric material which may, for example, be of sponge structure or ADD A a 0 7 ww Mil 2 u Seifert....... Kottsieper. Kiekhaefer Dworak may be formed with a base portion and a selected number of flexible webs which press against the seal- 123/190 D ing ring and forming passageways for entry of crankcase gas under pressure between the base portion of the elastomeric ring and the sealing ring to partially balance pressure tending to unseat the sealing ring.

11 Claims, 7 Drawing Figures FOREIGN PATENTS OR APPLICATIONS 832,953 7/1949 Germany........................

Primary Examiner-Charles J. Myhre Assistant ExaminerW. Rutledge, Jr. Attorney, Agent, or FirmRobert E. Burns; Emmanuel J. Lobato; Bruce L. Adams PATENTEDJm 91914 SHEU 2 BF 4 PATENTEDJUL 9:974 3822.682

sum 3 BF a 1 ROTARY VALVE ENGINE FIELD OF INVENTION The present invention relates to internal combustion engines and in particular to valving in the fuel-air mixture intake system of two cycle engines, for example, of a size such as those used on snowmobiles.

BACKGROUND OF THE INVENTION In a two cycle engine, a fuel-air mixture (which may also contain lubricating oil) is supplied to the crank case of the engine where it is precompressed by downward movement of the piston. When the piston reaches approximately the bottom of its stroke, it uncovers an intake port communicating with the crank case so as to permit the flow of fuel-air mixture from the crank case into the cylinder to displace the burned gases from the previous charge which are discharged through an exhaust port likewise uncovered by the piston. The charge of fuel-air mixture in the cylinder is compressed by the upstroke of the piston and is then ignited to provide the next power stroke. The supply of fuel-air mixture to the crank case is controlled by valving which opens to permit flow of fuel-air mixture from an intake chamber or manifold into the crank case during the upstroke of the piston and closes to provide precompression of the fuel-air mixture during the downstroke of the piston. Reed valves have been used for this purpose but their capacity is somewhat limited and their operating characteristics undesirably limit engine power and efficiency. The most popular two cylinder engines now on the market have a fuel intake system comprising a piston-ported axial flow fan. However, pistonporting of the fuel-air mixture does not permit maximum engine efficiency over a wide speed range.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a two cycle internal combustion engine having the characteristics of superior power, wider operating range, reduced fire hazard, smoother idling, compact size, lighter weight and greater reliability. The intake system in accordance with the present invention is particularly suitable for two cylinder engines but may, if desired, also be used with. single cylinder engines or engines having more than two cylinders. The invention is applicable to engines having a carburetor in which event the intake charge is a fuel-air mixture and to engines in which fuel is injected into the crank case or the cylinder in which event the charge is air. In either event, the charge may contain oil mist for lubrication.

In accordance with the present invention, the supply of air or fuel-air mixture from an intake chamber to the crank case of the engine is controlled by a rotary valve comprising a valve member which is provided on the crank shaft of the engine and engages a floating valve seat surrounding a port opening from an intake chamber into the crank case to control the opening and closing of the port in selected constant timed relation with the rotation of the crank shaft. The floating valve seat permits wider manufacturing tolerances and compensates for thermal expansion. The rotary intake valve permits unsymmetrical intake timing for inducting the fresh charge into the crank case without depending on pressure wave action (as in piston porting) which is effective over only a limited speed range. The unsymmetrical intake valve action also results in smoother idling and, because it opens more slowly and at a time when the pressure differential across it is small, intake noise is less than in piston ported engines. Moreover, fire hazard is reduced by eliminating carburetor spit-back caused by the symmetrical intake valve timing of piston ported engines. Although such spit-back may be reduced with suitable shields and screens, these safety devices are not fully effective and moreover are sometimes removed by users in an effort to increase engine power. The elimination of the piston ported intake also makes it possible to decrease the engine stroke with the result of obtaining lower piston acceleration and reducing shaking forces. An engine in accordance with the present invention has been found to be noticeably smoother in its operation than other engines presently available.

The rotary intake valve system of the present invention is particularly suitable for use in two cylinder engines in which the crank case is divided into two compartments, one for each cylinder. An intake chamber provided in the crank case between the two compartments has ports which open respectively into each of the compartments and are controlled by rotary valve members fixed in selected angular position on the crank shaft of the engine. However, the invention is also applicable to single cylinder engines and to engines having a number of cylinders greater than two in which event an air intake chamber is provided between the crank case chambers of two adjacent cylinders.

BRIEF DESCRIPTION OF. DRAWINGS The objects and advantages of the invention will be more fully understood from the following description of a preferred embodiment in conjunction with the accompanying drawings in which:

FIG. 1 is a perspective view of the crank shaft and lower portion of the crank case of an engine having rotary intake valves in accordance with the present invention;

FIG. 2 is a vertical section taken approximately on the line 22 in FIG. 1 and including also part of the upper portion of the crank case of the engine;

FIG. 3 is a horizontal section taken approximately on the line 3-3 in FIG. 1;

FIG. 4 is a schematic view of a rotary valve in accordance with the present invention;

FIGS. 5 and 6 are perspective views of a sealing ring of the rotary valve; and

FIG. 7 is a perspective view of an alternative form of pressure ring for pressing the sealing ring into engagement with the rotary valve member.

DESCRIPTION OF PREFERRED EMBODIMENT The embodiment of the invention illustrated by way of example in the drawings is a two cylinder, two cycle engine. For convenience of reference the engine cylinders are assumed to be vertical although it will be understood that the engine can be operated in any desired position. In the drawings only those parts of the engine have been shown that are relevant to the present invention. It will be understood that insofar as the present invention is concerned, other parts of the engine may be of known construction.

The engine is shown as comprising a crank shaft 1 which is rotarably mounted by suitable bearings in a crank case 2 comprising an upper portion 2a and lower portion 2b which are secured to one another, for example by suitable bolts 2c. The engine cylinders (not shown) are mounted on the upper portion 2a of the crank case in known manner. The crank shaft I has a crank 30 connected by a connecting rod to the piston in one cylinder of the engine and a crank 3b connected by a connecting rod to the piston in the other cylinder. The connecting rods and pistons may be of known construction and are hence not shown in the drawings. Counterbalancing

masses

4a, 4b, 4c and 4d are provided as cheeks of the

cranks

3a and 3b of the crank shaft. The crank shaft including the cranks and counter weights is preferably formed as a single piece.

The crank case 2 is divided by a central partition transverse of the crank shaft axis to provide two compartments 5a and 51:, one for each cylinder. The compartment 5a accommodates the crank of the crank shaft and communicates in known manner with an inlet port of the respective cylinder. The compartment 5b accommodates the crank 3b of the crank shaft and communicates in known manner with an inlet port of the other cylinder. The crank case further provides a fuel intake chamber 6 disposed centrally between the

compartments

5a and 5b. The intake chamber 6 has an inlet opening 7 connected to suitable means for supplying a fuel-air mixture. For example a carburetor 8 is mounted on the crank case by means of an adapter 9 so as to supply fuel-air mixture to the intake chamber 6.

The fuel intake chamber 6 has a port Ila opening into the crank case compartment 5a and a port 11b opening into the crank case compartment 512. The ports are arranged symmetrically with respect to a central plane perpendicular to the axis of the crank shaft and the intake chamber is contoured so as to provide smooth flow of fuel-air mixture from the inlet opening 7 to both ports. A valve member 12a shown in the form of a flat disc is provided on the crank shaft in position to cooperate with the port Ila to control flow of fuelair mixture from the intake chamber 6 to the crank case compartment 5a. Likewise, a second valve disc 12b on the crank shaft cooperates with the port 11b to control flow of fuel-air mixture from the intake chamber 6 into the crank case compartment 5b. While the

valve discs

12a and 12b can, if desired, be formed inte grally with the crank shaft, they are shown as separate disc members which are secured by bolts 13 to the

counterweights

4 b and 4c and suitable lugs provided on the crank shaft. This permits replacement of the valve discs and also angular adjustment relative to the crank shaft in order to control the timing of the valve opening.

Means is provided for forming a seal between the ports 11a and 11b and the

respective valve discs

12a and 12b. The sealing means comprises sealing

rings

14a and 14b which conform in shape to the ports Ila and 11b. As seen in FIGS. 4, 5 and 6, the sealing rings 14a and 14b are approximately D-shapecl. The flat side is disposed inwardly toward the crank shaft while the outer curved side is approximately concentric with the axis of the crank shaft and thus conforms with the outer periphery of the respective valve disc. As seen in FIGS. 2, 5 and 6, the sealing rings 14a and 14b are of angular cross section with a flat face that engages the valve disc and an angularly projecting flange surrounding the opening in the ring. The sealing rings are made of low friction, wear resisting material such as synthetic material or pressed metal containing a lubricant such as graphite.

The sealing rings 14a and 14b are resiliently pressed against the

respective valve discs

12a and 12b by

pressure rings

15a and 15b acting between the sealing rings and seats provided around the ports 11a and Mb. The pressure rings 15a and 15b are preferably formed of elastomeric material and may for example be of sponge construction as illustrated in FIGS. 2 and 3 or may comprise a flat base with projecting transverse ribs as illustrated in FIG. 7. If a sponge material is used for the pressure rings the density and firmness of the material are selected to provide the desired pressure of the sealing rings against the valve discs. With the embodiments shown in FIG. 7 the durometer of the elastomeric mate rial and the thickness and spacing of the ribs which engage the sealing ring are selected to provide the desired pressure. The form shown in FIG. 7 has the advantage that, with reference to the lower part of FIG. 3, gas under pressure in the crank case can flow between the sealing ring and the base portion of the pressure ring to partially balance the pressure tending to unseat the sealing ring. The sealing rings pressed against the valve discs by the pressure rings constitute in effect floating valve seats which are engaged by the valve discs to control the flow of fuel-air mixture from the intake chamber 6 to the crank case compartments 5a and 51) respectively.

As seen in FIG. 4, the valve disc is solid except for an opening which is registrable with the respective port of the intake chamber 6 to permit the flow of fuel-air mixture from the intake chamber to the respective compartment of the crank case. Instead of a single opening, the valve disc has a plurality of openings 16a, 16b and 16c which are separated from one another by narrow partition portions and 17b connected with arcuate peripheral portions and 18b. The

portions

17a, 17b and 18a, 18b provide support for the sealing ring and prevent it from being pressed into the opening of the valve disc when the opening is in full registry with the respective port.

The size of the ports 11a and 11b and the corresponding size and location of the openings in the

valve discs

12a and 12b make it possible to control the flow of fuel-air mixture from the intake chamber 6 into the respective crank case compartments 5a and 5b in such manner as to achieve maximum engine power and efficiency. Moreover, with the construction in accordance with the present invention the intake ports can be made of relatively large size so that the engine is free breathing. As seen in FIG. 4 the ports and the openings in the valve discs have an angular extent of approximately 90 circumferentially of the valve discs and a radial extent of approximately half the radius of the discs. The pressure drop characteristic of reed valves is thereby avoided. Moreover, the streamlined contour of the intake chamber promotes the smooth flow of fuel-air mixture from the carburetor into the respective crank case compartments.

While a preferred embodiment of the invention has been illustrated in the drawings and is herein particularly described, it will be understood that the invention is in no way limited to the illustrated embodiment.

What I claim and desire to secure by Letters Patent 1. In an internal combustion engine, the combination of a crank case having two compartments, a crank shaft rotatable in the crank case, an intake chamber disposed between said two compartments of the crank case and having a port opening into each of said compartments, means to supply air or fuel-air mixture to said intake chamber, a valve disc on said crank shaft in each of said compartments and rotatable with said crank shaft, each said valve disc overlying the port opening into the respective compartment and having an opening registrable with said port when the crank shaft is in a selected angular position, and sealing means providing a seal between said port and said valve disc, said sealing means comprising a seat surrounding each of said ports and spaced uniformly from the respective valve disc, a continuous sealing ring disposed between said seat and said valve disc and having a face engaging said valve disc and a continuous ring of elastomeric material between said sealing ring and said seat, said ring of elastomeric material being elastically compressible in a direction normal to said valve disc and being compressed between said seat and said sealing ring to press said sealing ring into sealing engagement with said disc and to provide a fluid tight seal between said sealing ring and said seat, said elastomeric ring comprising a base portion having on one face a surface engaging said seat and on the opposite face recessed portions forming passageways for entry of crank case gas under pressure between said base portion of said elastomeric ring and said sealing ring to partially balance pressure tending to unseat the sealing ring.

2. The combination according to claim 1, in which said sealing ring has in cross section a flat face portion engaging said valve disc and a flange projecting angularly away from said valve disc at the inner periphery of said ring.

3. The combination according to claim 1, in which said elastomeric ring comprises said base portion and a multiplicity of transverse web portions interposed between said base portion of said elastomeric ring and said sealing ring.

4. The combination according to claim ii, in which said sealing ring is generally D-shaped.

5. The combination according to claim 1, in which said opening in said valve disc is divided into at least two adjacent opening portions with a portion of said disc between adjacent opening portions engageable with said sealing means to prevent entry of said sealing means into said opening of said valve disc.

6. The combination according to claim 1, in which a counterweight is provided on said crank shaft and said valve disc is removable fixed to said counterweight.

7. The combination according to claim 1, in which a single carburetor mounted on the crank case supplies a fuel-air mixture to said intake chamber for both of said compartments.

8. The combination according to claim 1, in which at least a portion of said opening in said valve disc entends to the periphery of said valve disc.

9. The combination according to claim 1, in which a portion of said sealing ring extends radially beyond the periphery of said valve disc 10. The combination according to claim 1, in which said port and said opening have an angular extent of approximately circumferentially of said disc and a radial extent of approximately half the radius of said disc.

11. in an internal combustion engine, the combination of a crank case having a compartment for precompression of a charge and an intake chamber having a port opening into said compartment, a crank shaft rotatable in the crank case, means to supply air or fuel-air mixture to said intake chamber, a valve disc on said crank shaft in said compartment and rotatable with said crank shaft, said valve disc overlying the port opening from said intake chamber into said compartment and having an opening registrable with said port when the crank shaft is in selected angular position, said port being surrounded by a seat, a floating sealing between said seat and said valve disc conforming to the shape of said port and engaging said valve disc, and a continuous pressure ring of elastomeric material between said seat and said sealing ring, said pressure ring being elastically compressible in a direction normal to said disc and being compressed between said seat and said disc to press said sealing ring against said valve disc with selected pressure to maintain said sealing ring in sealing contact with said valve disc despite manufacturing tolerances and thermal expansion of engine parts and to provide a fluid tight seal between said sealing ring and said seat, said elastomeric ring comprising a base portion having on one face a surface engaging said seat and on the opposite face recessed portions forming passageways for entry of crank case gas under pressure between said base portion of said elastomeric ring and said sealing ring to partially balance pressure tending to unseat the sealing ring.

Claims

1. In an internal combustion engine, the combination of a crank case having two compartments, a crank shaft rotatable in the crank case, an intake chamber disposed between said two compartments of the crank case and Having a port opening into each of said compartments, means to supply air or fuel-air mixture to said intake chamber, a valve disc on said crank shaft in each of said compartments and rotatable with said crank shaft, each said valve disc overlying the port opening into the respective compartment and having an opening registrable with said port when the crank shaft is in a selected angular position, and sealing means providing a seal between said port and said valve disc, said sealing means comprising a seat surrounding each of said ports and spaced uniformly from the respective valve disc, a continuous sealing ring disposed between said seat and said valve disc and having a face engaging said valve disc and a continuous ring of elastomeric material between said sealing ring and said seat, said ring of elastomeric material being elastically compressible in a direction normal to said valve disc and being compressed between said seat and said sealing ring to press said sealing ring into sealing engagement with said disc and to provide a fluid tight seal between said sealing ring and said seat, said elastomeric ring comprising a base portion having on one face a surface engaging said seat and on the opposite face recessed portions forming passageways for entry of crank case gas under pressure between said base portion of said elastomeric ring and said sealing ring to partially balance pressure tending to unseat the sealing ring.

4. The combination according to claim 1, in which said sealing ring is generally D-shaped.

9. The combination according to claim 1, in which a portion of said sealing ring extends radially beyond the periphery of said valve disc.

10. The combination according to claim 1, in which said port and said opening have an angular extent of approximately 90* circumferentially of said disc and a radial extent of approximately half the radius of said disc.