Rotary valve internal combustion engine

Abstract

A rotary valve internal combustion engine has a piston (1) connected to a crankshaft (3) and reciprocatable in a cylinder (2), a combustion chamber 4 being defined in part by the piston. The engine has a rotary valve (5) rotatable with a close sliding fit in a valve housing (8) fixed relative to the cylinder (2), the rotary valve having a valve body containing a volume (9) defining, in part, the combustion chamber 4 and further having in a wall part (11) thereof a port (1)2 giving, during rotation of the valve, fluid communication successively to and from the combustion chamber via inlet and exhaust ports (13), (14) in the valve housing. The rotary valve and the valve housing are both formed of aluminum.

Claims

1. 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 with a close sliding fit 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 base material of both the valve body and valve housing is aluminium, a sealing function being carried out between a surface of the main body of the rotary valve and a contiguous surface of the bore in the valve housing, wherein the sealing function is carried out between the surface of the body of the rotary valve and the surface of the valve housing only, there being no additional sealing devices incorporated between the rotary valve and the valve housing.

2. The rotary valve internal combustion engine according to claim 1, wherein the aluminium is an aluminium alloy with a copper content of up to 5%.

3. The rotary valve internal combustion engine according to claim 1, wherein the aluminium is a eutectic aluminium.

4. The rotary valve internal combustion engine according to claim 1, wherein the interface surface of one or both of the valve body and the valve housing is provided with a hardened surface.

5. The rotary valve internal combustion engine according to claim 4, wherein the hardened surface of the valve body comprises one of: anodised aluminium, a ceramic coating, a silicon carbide coating, a DLC (Diamond like Carbon) coating, or a plasma nitrided surface.

6. The rotary valve internal combustion engine according to claim 4, wherein the hardened surface of the valve housing comprises one of: anodised aluminium, a ceramic coating, a silicon carbide coating, a DLC (Diamond like Carbon) coating, or a plasma nitrided surface.

7. The rotary valve internal combustion engine according to claim 1, wherein the port in the valve is a recess formed in the lower peripheral edge of the wall of the valve body adjacent to the combustion chamber, the recess extending upwardly from this lower edge of the wall of the valve to form the port in the side of the valve.

8. The rotary valve internal combustion engine according to claim 1, wherein the port in the valve is a bore in the wall part of the valve body, the wall having a lip formed below the port adjacent to the combustion chamber.

9. The rotary valve internal combustion engine according to claim 1, wherein there are no thermal expansion restricting devices incorporated between the rotary valve and the valve housing.

Description

(1) Preferred embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which:

(2) FIG. 1 shows a cross-sectional view of a single cylinder air cooled engine,

(3) FIG. 2 is a schematic view of one embodiment of the rotary valve body.

(4) Referring now to FIG. 1, there is shown a single cylinder air cooled engine. The cylinder 2 has a piston 1 connected to a crankshaft 3 in the conventional manner for reciprocation in the cylinder 2. As shown particularly in FIG. 2, the upper part of the cylinder 2 is closed by a combustion chamber 4. 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 is rotatable in a valve housing in the combustion chamber housing about an axis 5a which is parallel to the axis of rotation 3a of the crankshaft 3.

(5) At its end remote from the combustion chamber 4, the rotary valve 5 has a driven pulley 17 mounted thereon which is connected to a drive pulley 18 on the engine crankshaft 3 by a belt drive arrangement, comprising an endless belt 19 having a toothed profile on its inner surface which drivingly engage with corresponding teeth on the pulleys 17 and 18. The pulleys, and hence the endless belt 19 also, lie in a common plane 20. 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 pulley 17 is twice that of the drive pulley 18 so that the rotary valve 5 rotates at half engine speed.

(6) Referring now to FIG. 2 also, there is shown more detail of the rotary valve 5. The rotary valve consists of a plain active valve having a first cylindrical part in the form of a shaft 6 mounted on a ball bearing arrangement comprising a single race ball bearing 7, located on a side of the valve 5 remote from the combustion chamber 4. The valve has a slightly larger cylindrical body part comprising the valve body 11 itself which forms a shoulder 12 against which the ball bearing 7 is located. The valve body 11 extends into the combustion chamber and has in its interior a volume 9 which forms part of the combustion chamber 4. The valve body 11 is rotatable in a bore in a valve housing 8 in which the valve body 11 is a close sliding fit. Typically, the clearance is within the range of 10-30 microns between the rotary valve 5 and the bore of the valve housing 8. The valve 5 and the valve housing 8 are formed of aluminium.

(7) Preferably, the aluminium may be an aluminium alloy with a high copper content, up to 5%, which gives good heat dissipation properties and good bearing qualities. A preferred aluminium is that designated as aluminium 2618. In further developments of the invention, one or both of the interface surfaces of the valve body 5 and the valve housing 8 may be provided with a hard coating such as anodised aluminium, a ceramic or silicon carbide coating such as Nikasil (a registered trademark), a DLC (Diamond like Carbon) coating or a plasma nitride treatment.

(8) The shaft 6 part of the rotary valve 5 is only slightly smaller in diameter than the valve body 11 to provide the shoulder. The shaft part is solid to provide a good path for conducting heat from the valve body 11 to the exterior. The shaft, on its end remote from the combustion chamber, to which the driven pulley 17 is connected, may have additional cooling means such as a heat sink 13 which may include fins or a fan rotatable with the driven pulley 17.

(9) The rotary valve, the valve body has a port 14 which, during rotation of the valve, enables fluid communication successively to and from the combustion chamber via inlet and exhaust ports in the valve housing. In this embodiment the port is in the form of a recess formed in the lower peripheral edge 16 of the wall 15 of the valve body adjacent to the combustion chamber the recess extending upwardly from this lower edge of the wall of the valve to form the port 14 in the side of the valve. In an alternative construction (not shown), the port is a bore in the wall part of the valve body, the wall having a lip formed below the port at the lower peripheral edge 16 of the wall 15 adjacent to the combustion chamber.

(10) Although described as a single cylinder engine, it will be understood that the invention is equally applicable to multi cylinder engines which may be of in-line, Vee or horizontally opposed configuration. Furthermore, although described as a spark ignition engine the invention is equally applicable to a compression ignition engine.

(11) Although the example given is for an engine with the axis of rotation of the rotary valve parallel to the axis of the crankshaft, it will be understood that the invention is equally applicable to rotary valve engines where the axis of rotation of the valve is perpendicular to the axis of rotation of the crankshaft, or indeed at any intermediate angle.