GB2580626A

GB2580626A - A rotary valve internal combustion engine

Info

Publication number: GB2580626A
Application number: GB1900656.8A
Authority: GB
Inventors: Lawes Keith; Mason Brian
Original assignee: RCV Engines Ltd
Current assignee: RCV Engines Ltd
Priority date: 2019-01-17
Filing date: 2019-01-17
Publication date: 2020-07-29
Also published as: GB2580733A; TW202039991A; GB201912690D0; GB201900656D0; GB2580733B

Abstract

A rotary valve internal combustion engine comprising a combustion chamber being defined in part by the piston and the combustion end of the cylinder, a valve housing 8 fixed at an outer portion of the combustion end of the cylinder and defining a bore and a rotary valve 5 carried by a ball bearing 7 being rotatable in the bore about a rotary valve axis 5a. The rotary valve is mounted in the valve housing for rotation by the crankshaft through a gear drive train, the drive train having a driven gear 9 rotationally fast with the rotary valve. A gap or clearance 32 is provided between the bearing and the driven gear and contains a resilient element, such as a wave spring (24, fig.4), to bias the valve into engagement with the bearing.

Description

A rotary valve internal combustion engine The present invention relates to a rotary valve internal combustion engine in which the control of the intake and exhaust gases of combustion gases is achieved by means of a rotary valve.

A rotary valve internal combustion engine is known comprising: a piston connected to a crankshaft and reciprocatable in a cylinder, the cylinder having a combustion end, a combustion chamber being defined in part by the piston and the combustion end of tne cylinder, a valve housing fixed at an outer portion of the combustion end of the cylinder and defining a bore and a rotary valve rotatable about a rotary valve axis in the bore in the valve housing, the rotary valve having a hollow valve body having an interior volume forming a part of the combustion chamber, wherein the interior volume of the hollow valve body is subjected to combustion gases throughout the combustion process, and further havina in a wall part thereof a port givino, during rotation of the valve. fluid communication successively to and from the combustion chamber via inlet and exhaust ports in the valve housing.

The present invention seeks to provide such an engine with p ved constructional features..

According to the present invention there is provided a rotary valve internal combustion engine comprising a piston connected to a crankshaft and reciprocatable in a cylinder, the cylinder having a combustion end, a combustion chamber being defined in part by the piston and the combustion end of the cylinder, a valve housing fixed at an outer portion of the combustion end of the cylinder and defining a bore and a rotary valve rotatable about a rotary valve axis in the bore in the valve housing, the rotary valve having a hollow valve body having an interior volume forming a part of the combustion chamber, wherein the interior volume of the hollow valve body is subjected to combustion gases throughout the combustion process, and further having in a wall part thereof a port giving, during rotation of the valve, fluid communication successively to and from the combustion chamber via inlet and exhaust ports in the valve housing, wherein the rotary valve is mounted in the valve housing for rotation by the crankshaft through a gear drive train, the drive train including a driven gear rotatable about the rotary valve axis, the driven gear being rotationally fast with the rotary valve. wherein there is provided, a predetermined axial gap between the driven gear and the bearing in which the rotary valve is mounted, resilient means being located in the axial gap.

In a preferred embodiment, the bearing has an inner race, the predetermined axial gap being between the driven gear and the inner race of the bearing.

Preferably the driven gear has an annular rib aligned with the inner race of the bearing, the axial gap being formed between the annular rib and the inner race of the bearing.

Preferably, tne space between the inner and outer races of the bearing is closed by a seal to prevent combustion gases passing through the bearing.

Preferably, the seal is formed of metal and in a preferred form comprises a wave spring element.

Preferably, the resilient element is formed of a metal.

Preferably the resilient element is annular eing co-axial with the rotary valve' Preferably the resilient element is a wave spring in a preferred embodiment, a vent passage is provided to vent combustion gases ping from between the space between the valve body and the valve housing back into the inlet port.

Preferred embodiments of the present invention will now be described y way of example with reference to the accompanying drawings, in which:-Figure 1 shows a cross-sectional view of a single cylinder air cooled rotary valve' internal combustion engine, Figure 2 is an enlarged schematic view of part of the rotary valve body and drive gear, and Figure 3 shows a plan view of the rotary valve drive and driven gears Figure 4 shows an enlarged sectional view of the rotary valve and drive gear Figures 5a-5c show, respectively, plans and side views of a wave spring Figure 6 shows a view of the valve and a driven gear Figure 7 shows a view of the valve and a ball bearing, and Figure 8 shows the:path of escaping combustion gases.

Referring now to Figure 1, there is snown a single cylinder air cooled engine. The engine has a cylinder housing containing the cylinder 2. A piston 1 is connected in the conventional manner to a crankshaft 3 mounted for rotation in a crankcase 14 for reciprocation in the cylinder 2. The upper part of the cylinder 2 is closed by a combustion chamber 4 in a combustion chamber housing. The flow of inlet air/fuel mix and exhaust gas into and out of the combustion chamber 4 is controlled by a rotary valve 5. In this embodiment, the valve 5 is rotatable in a valve==housing 8 in the combustion chamber housing about an axis 5a which is co-axial with the axis of the cylinder 2. In other embodiments, the axis of rotation of the valve body is offset from the axis 5a of the cylinder 2.

At its end remote from the combustion chamber 4, the rotary valve 5 has a concentric drive shaft 6 carrying a single race ball bearing 7 which rotatabiy supports the valve 5 in the valve housing 8. The valve driveshaft 6 is secured to a coaxial driven gear 9 which meshes with a drive gear 10 of a drive arrangement 11 through which the driven gear 9 and hence the rotary valve 5 is connected to the crankshaft 3. The drive arrangement 11 includes a drive shaft 12 which is located in a channel or tube 17 in the cylinder housing and mounted for rotation in an upper bearing 18 adjacent the drive gear 10 and a lower bearing 13 adjacent the crankshaft 3. The channel or tube 17 is cast into the cylinder housing The channel or tube 17 is formed integrally with the cylinder housing, which may be formed by a casting process. The driveshaft 11 carries a bevel gear 15 which meshes with a corresponding bevel gear 16 secured on the crankshaft for rotation with the crankshaft 3. Thus, the rotation of the crankshaft 3 and hence the piston movement is coordinated with the rotation of the rotary valve 5 so that the engine operates on the conventional four stroke cycle. To achieve this, the diameter of the driven gear 9 is twice that of the drive gear 10 so that the rotary valve 5 rotates at half engine speed.

Referring now to Figure 2 also there is shown more detail of the rotary valve 5 which comprises a generally cylindrical rotary valve body 5 rotatable about a rotary valve axis 5a with a close sliding fit in the bore in the valve housing 8, the rotary vaive 5 having a hollow valve body 16 having an interior volume 19 forming a part of the combustion chamber. The valve has a generally cylindrical body part comprising the valve body 16 itself which is slightly larger in diameter than the shaft 6, which forms a shoulder 14 against which the inner race 28 of the ball bearing 7 is located. The valve body 16 extends into the combustion chamber and has in its interior a volume 20 which forms part of the combustion chamber 4 and which is subject to combustion gases at all stages of the combustion process. The valve body 19 is rotatable in a bore in a valve housing 8 with a close sliding fit.. The valve 5 and the valve housing 8 are formed of aluminium.

The shaft 6 part of the rotary valve 5 is only slightly smaller in diameter than the valve body 19 to provide the shoulder 14. The shaft is solid to provide a good oath for conducting heat from the valve body 16 to the exterior The rotary valve body port 21, during rotation of the valve, enables fluid communication successively to and from the interior volume of the valve and hence the combustion chamber via inlet and exhaust ports in the valve housing. In this embodiment the port 21 is in the form of a recess formed in the lower peripheral edge 22 of the wall 23 of the valve body adjacent to'the combustion chamber 4 the recess extending upwardly from this lower edge of the wall of the valve to form the port 21 in the side of the valve Referring further to Figure 2 and Figure 3, there is shown the connection between the driven gear 9 and the rotary valve 5. The driven gear 9 is secured coaxiafly to the rotary valve 5 by means of a counter sunk screw 30. The driven gear 9 has a concentric recess which accommodates the outer end of the shaft 6 and the recess has an annular rib 31 which is aligned with the inner race 28 of the ball bearing 7. An axial clearance 32 is provided between the annular ring 31 sand the inner race 28 to allow a small degree of axial float which means that the valve 5 is not clamped to the inner race 28 and can therefore move slightly radially to accommodate any small concentric offset between the bearing 7 and the valve bore in which the rotary valve rotates.

In operation, the forces generated by the combustion gases tend to move tne valve body axially relative to the valve housing. To prevent hammering of the shoulder 14 against the inner race 28 of the bearing 7 caused by axial movement of the valve body 16 reiative to the inner race 28 of the bearing, which would otherwise occur during every combustion cycle, a resilient element in the form of a wave spring 24 biases driven gear 9 to urge the shoulder 14 of the valve body 16 upwards into contact with the lower face of the inner race 28, as shown in Figure 4, with a sufficient force to prevent hammering or chattering between the two components during operation but not too powerful to prevent the slight radial movement of the valve body necessary to accommodate slight misalignment between the valve and the valve housing which will occur in practice as a result of slight differences caused by manufacturing tolerances of the components.

As shown in Figures 5a-5c, the wave spring consists of a generally annular plate-like body. Throughout its annular length, the wave sprina 24 has a plurality of wave forms curving the spring out of a radial plane as shown particularly in Figures 5b and 5c. In this embodiment the wave spring is formed out a spring steel. The spring element could be formed of other materials, designs or profiles, providing they meet the objective of being able to provide the resilient damping effect required and being able to cope with the harsh environmental conditions in the engine.

Figure 6 illustrates a schematic perspective view of the rotary valve 5 and the driven gear 9 with the wave spring 24 in position between the inner race 28 of the bearing and the driven gear 9. Figure 7 illustrates a similar schematic perspective view of the rotary valve 5 and the driven gear 9 with the single race ball bearing 7 in position. As shown also in Figure 8, th space between the inner and outer races 28 and 29 of the bearing 7 is dosed at its lower edge by a metal seal 26.

It has been found that in practice some combustion gases escape between the interface between the rotary valve body 5 and the valve housing 8. These waste combustion gases can pass through the bearing 7 past the balls 25 and into the chamber containing the driven gear and the wave spring causing a buildup of carbon which adversely affects the performance and durability of the valve and the high temperature and corrosive action of the hot gases can cause premature failure of the wave spring.. To prevent, or at least minimise, the combustion gases leaking across the bearing 7, the seal 26 closes the gap between the inner and outer races 28 and 29 of the bearing The seal is formed of a metal to cope with the harsh environmental conditions.. Furthermore, the seal prevents the escaping combustion gases from damaging or destroying the resilient spring.

Referring now to Figure 8 tnere is shown an enlarged view of the valve and bearing arrangement illustrating an improvement in which a vent passage 37 is provided from the narrow annular space 28 between the annular metal seal 26 and the valve housing leading into the inlet port as illustrated by the black arrows 40. This has the advantage that the escaping combustion gases are led back into the inlet port 39 where they are recycled through the engine to improve the engine emissions performance.

The correct location of the rotary valve 5 relative to the valve gear, which determines the timing of the engine, is achieved by a timing pin 33. The drive gear 10 has "a timing mark 34 which indicates when the engine is at top dead centre, The driven gear 9 connected to the rotary valve has a timing hole 35 adapted to receive the timing pin 33 and the driven gear has a corresponding timing hole through which the timing pin is inserted to secure the driven gear 9 to the rotary valve 5 to hold the rotary valve in its top dead centre position The counter sunk screw 30 is then inserted to secure the driven gear 9 to the rotary valve 5 in the correct timing position and the counter sunk head of the screw 30 engages the end of the timing pin 30 to secure this in position. Other means such as a washer on the screw 30 may be used to secure the timing pin 33 in position.

Because the rotary valve has a port 21 cut in its peripheral wall; it is recognised that the mass of the valve is not uniformly disposed about its periphery and this generates out of balance forces as the rotary valve rotates in practice In a further embodiment of the engine, a counterbalance or counterbalancing mass is created on the valve train. particularly by adding material to the driven gear 9 or by removing material at an appropriate position in the driven gear 9. The embodiment described is a single cylinder air cooled engine but it will be understood that the invention is equally applicable to multicylinder and/or watercooled engines.

Claims

CLAIMSA rotary valve internal combustion engine comprising: a piston connected to a crankshaft and reciprocatable in a cylinder, the cylinder having a combustion end, a combustion chamber being defined in part by the piston and the combustion end of the cylinder, a valve housing fixed at an outer portion of the combustion end of the cylinder and defining a bore and a rotary valve rotatable about a rotary valve axis in the bore in the valve housing, the rotary valve having a hollow valve body having an interior volume forming a part of the combustion chamber, wherein the interior volume of the hollow valve body is subjected to combustion gases throughout the combustion process, and further having in a wall part thereof a port giving, during rotation of the valve, fluid communication successively to and from the combustion chamber via inlet and exhaust ports in the valve housing, a sealing function being carried out between the surface of the main body of the rotary valve and a contiguous surface of the bore in the valve housing, wherein the rotary valve is mounted in the valve housing for rotation by the crankshaft through a gear drive train, the drive train including a driven gear rotatable about the rotary valve axis, the driven gear being rotationally fast with the rotary valve, wherein there is provided a predetermined axial cap between the driven gear and the bearing in which the rotary valve is mounted, a resilient element being located in the axial gap.
2 A rotary valve internal combustion engine according to claim 1 wherein, the predetermined axial gap is between' the driven gear and an inner race of the bearing.
A rotary valve internal combustion engine according to claim 1 or 2 wherein the bearing comprises a single race ball bearing, and the driven gear has an annular rib aligned with the inner race of the bearing, the axial gap being formed between the annular rib and the inner race of the bearing.
4. A rotary valve internal combustion engine according to claims or 3 wherein the space between the inner and outer races of the bearing is closed by a seal to prevent combustion gases passing through the bearing.
5. A rotary valve internal combustion engine according to claim 4 wherein the seal is formed of metal 6. A rotary valve internal combustion engine according to any one of the preceding claims wherein a vent passage is provided to vent combustion gases escaping from between the space between the valve body and the valve housing back into the inlet port.
6 A rotary valve internal combustion engine accord. .g to any one of the preceding claims, wherein the resilient element is formed of a metal.
7. A rotary valve internal combustion engine according to any one of the preceding claims wherein the resilient element is annular, being co-axial with the rotary valve 6. A rotary valve internal combustion engine according to any one of the preceding claims wherein the resilient element is a wave spring.