GB2267934A - I.C engine or compressor rotary valve arrangement. - Google Patents

Abstract

A resiliently deformable sleeve 17 has a slit which extends along the entire axial length thereof whereby the sleeve can deform to allow deformation of the rotary valve 19 and abutments 16a, 16b are biased into abutment with the exterior surface of the sleeve and moveable relative to the sleeve to allow deformation of the sleeve. The abutments 16a, 1 6b are movable in two dimensions against the biasing force and abut the sides 47 of the valve cavity. A seal 36 is spring and gas pressure biased against the sleeve 17. The valve stator 20 may be angularly adjustable and may provide respective passages (55b, 56b, 60, 61, Figs. 7 and 8) for air and air/fuel mixture. Details of valve lubrication are given in the specification. <IMAGE>

Description

ROTARY VALVE ARRANGEMENT The present invention relates to an internal combustion engine or compressor with a novel rotary valve arrangement.

The present invention arose through development of the rotary valve system described in PCT application No. PCT/GB 91/00990 of the applicants (published as WO91/19889 on the 26th December 1991). Numerous references will be made to the International application PCT/GB 91/00990 throughout the specification and the preferred embodiments of the present invention will be described with reference to the apparatus described in the earlier International application and to the particular application of the present invention in a two-stroke engine.

Whilst the invention will be described with reference to its application two-stroke engine, the invention should not be considered so limited and in fact a rotary valve according the invention could be used in any internal combustion engine or compressor.

Referring to the system described in WO91/19889, it was found that the rotary valve used in the system required large running clearances to allow for thermal distortion and also for distortion of the valve due to the forces on it arising from pressures in the working cylinder. It was found that the cooling effect of the incoming charge air was insufficient to prevent thermal distortion of the valve. Furthermore, it was found that since the same section of the valve was heated in each cycle, an assymetric thermal loading was imposed on the valve which lead to assymetric deformation which required large running clearance to prevent seizure. The large running clearance required gave inadequate sealing for the engine.

Rotary valves are well known in the prior art and an example can be seen in US 4597321 of Gabelish. Gabelish also includes a discussion of rotary valve arrangements and points out that deformation may be a problem which leads to seizure. Earlier proposals for rotary valves are discussed in the Gabelish patent and it is pointed out that they suffer generally from the drawbacks that they are costly to manufacture and lack durability and ruggedness and consume large amounts of oil.

Gabelish proposes a rotary valve assembly for use in an internal combustion engine in which a rotary valve is supported on roller bearings within the cylinder head. A split seal is provided which surrounds the rotary valve as a sleeve. The split seal is located in a split housing provided for the split seal. The split housing is mounted in a suitable cavity machined in the cylinder head of the internal combustion engine and is able to move within the cavity. The split housing is split into upper and lower parts. The lower part of the housing provides a surface exposed to pressures within the working cylinder associated with the rotary valve arrangement. Both parts of the split housing are moveable with respect to the cylinder head and with respect to each other. The two parts of the split housing and the split seal are in floating relationship to one another.

Deformation of the components of the rotary valve is taken up by the rotary valve housing arrangement by movement of the split seal and also of the split housing for the split seal. The components of the split housing are biased together by springs and the springs enable sealing contact to be maintained between the components, despite movement, so that gas cannot flow from the working cylinder of the engine past the rotary valve arrangement.

Gas pressure is prevented from escaping between the cylinder head and the split housing from the split seal by a 'V' section resilient ring. The 'V' section ring also helps to maintain sealing contact between the split seal and the rotary valve. The gas pressure of gas in the working cylinder on the expbsed surface of the lower part of the split housing also aids the sealing contact between the split seal and the rotary valve.

The split seal has two lubricated zones and one non-lubricated zone which covers the cylinder head part.

The close proximity of the non-lubricated zone of the split seal to the rotary valve provides sealing, and the lubricated zones provide hydrodynamic seals. The oil films in the lubricated zones take the force of the gas pressure on the lower part of the split housing, the force reducing clearances when needed most.

The Gabelish rotary valve arrangement is not suitable for many applications for several reasons.

First, the two components of the rotary valve housing of Gabelish are moveable in the cavity of the engine against bias only relative to each other in one direction, upward and downward. This constrains the deformation rotary valve and the sleeve and can lead to a loss of circular cross-section the rotary valve, inhibiting rotation of the rotary valve.

Secondly, it requires a special shaping of the cylinder head which does not allow the most favourable combustion chamber shape. The arrangement necessitates a high position for the valve within a cylinder head.

Thirdly, it necessitates provision of a cylinder head of significant size, to accomodate both parts of the split housing.

The present invention provides an internal combustion engine or compressor having at least one working chamber and a rotary valve arrangement for controlling the flow of fluid into and/or out of the working chamber through a port in the working chamber comprising; a rotary valve and means to rotate the rotary valve in timed relationship with the operation of the engine or compressor, a resiliently deformable sleeve member which surrounds the rotary valve and which has a slit which extends along the entire axial length thereof whereby the sleeve member can deform to allow deformation of the rotary valve, the sleeve member having a port therein to allow fluid flow from the rotary valve to the working chamber and/or vice versa, biasing means for applying a biasing force on the sleeve member to bias the sleeve member towards the rotary valve, which biasing means comprises abutment means biased into abutment with the exterior surface of the sleeve member and moveable relative to the sleeve member to allow deformation of the sleeve member, wherein the rotary valve, the sleeve member and the biasing means are located in a rotary valve cavity provided in the engine or compressor, which rotary valve cavity communicates with the working chamber via the port of the working chamber, characterised in that the abutment means of the biasing means is moveable in two dimensions against the biasing force.

The rotary valve arrangement of the invention thus allows radial deformation of the rotary valve whilst the biasing means ensures the sleeve member stays in close proximity to the rotary valve.

It should be appreciated that the word "fluid" used in this specification is a general term to cover liquids, gases and gas/liquid mixtures.

The present invention also provides an internal combustion engine or compressor having at least one working chamber and a rotary valve arrangement for controlling the flow of fluid into and/or out of the working chamber through a port of the working chamber comprising: a rotary valve and means to rotate the rotary valve in timed relationship with the operation of the engine or compressor, a resiliently deformable sleeve member which surrounds the rotary valve and which has a slit which extends along the entire axial length thereof whereby the sleeve member can deform to allow deformation of the rotary valve, the sleeve member having a port therein to allow fluid flow from the rotary valve to the working chamber and/or vice versa, biasing means for applying a biasing force on the sleeve member to bias the sleeve member towards the rotary valve, which biasing means comprises abutment means biased into abutment with the exterior surface of the sleeve member and moveable relative to the sleeve member to allow deformation of the sleeve member, wherein the rotary valve, the sleeve member and the biasing means are located in a rotary valve cavity provided in the engine or compressor, which rotary valve cavity communicates with the working chamber via the port of the working chamber, characterised in that the abutment means of the biasing means is biased into direct abutment with the surface of the rotary valve cavity to establish a seal between the rotary valve and the surface of the rotary valve cavity.

The invention thus also provides a rotary valve arrangement which ensures there is good heat flow path between the rotary valve and the body of the engine or compressor, thereby limiting the deformation of the rotary valve. The biasing means also establishes a good seal between the sleeve member and the wall of the housing which remains intact despite deformation of the rotary valve.

Preferably the abutment means comprises a plurality of abutment members each having a tapered surface and wherein the rotary valve cavity has matched tapered surfaces, the tapered surface of each abutment member being biased into abutment with a tapered surface of the cavity, the matched tapered surfaces allowing two dimensional motion.

The tapered surface allows the biasing means two dimensional motion against a biasing force and provides a good contact area for heat conduction and also provides a seal which remains intact despite deformation.

Preferably each abutment member has an abutment surface for abutting the exterior of the sleeve member which is shaped to match the exterior surface of the sleeve member.

By shaping the abutment means to match the sleeve member good heat flow from the rotary valve is assured and a good seal is maintained.

Preferably the abutment memberts abut only the exterior surface of the half of the sleeve member furthest from the port of the working chamber.

The arrangement enables the positioning of the rotary valve arrangement adjacent to the working chamber port and enables optimum design of the working chamber.

It also enables a cylinder head to be used that is smaller than that required by US 4697321.

Preferably the majority of the exterior surface of the half the sleeve member furthest from the port of the working chamber is abutted by the abutment means. Thus a large area is provided for heat conduction.

Preferably sealing means is provided between the lower half of the sleeve member and the cavity, which sealing means surrounds the port of the working chamber and the aligned port in the sleeve member to inhibit flow of fluid from the working chamber between the sleeve member and the surface of the rotary valve cavity.

This ensures adequate sealing of the working chamber.

Preferably the sealing means comprises one or more members moveable in recesses machined in the surface of the rotary valve cavity and biased into engagement with the sleeve member.

The sealing members are thus moveable to allow movement of the sleeve member.

Preferably a clearance is provided between the sleeve member and the surface of the rotary valve cavity in the region between the port of the working chamber and the sealing members, whereby the pressure of the fluid in the working chamber is communicated to the sealing members and forces the sealing members into abutment with the walls of the recesses and the sleeve member.

The clearance between the sleeve member and the rotary valve cavity enables the sleeve member to move to compensate for thermal distortion and enables the pressure of the gas in the cylinder is thus used to ensure that a seal is established between the sleeve member and the cavity surface. This is particularly advantageous since the tightest seal is established when needed most, i.e.

when the gas pressure in the working chamber is highest.

Preferably a clearance is provided between the exterior surface of at least part of the lower half of the sleeve member and the surface of rotary valve cavity through which fluid from the working chamber passes between the exterior surface sleeve member and the surface of the rotary valve cavity, whereby fluid pressure can be applied on the sleeve member to force it into abutment with the exterior surface of the rotary valve.

The pressure of the gas in the cylinder is thus used to ensure efficient sealing between the sleeve member and the rotary valve. The gas pressure is supplied directly to the sleeve member and thus efficient sealing can be ensured when required.

Preferably there is provided means to supply oil to form a lubricating film between the sleeve member and the rotary valve in two zones spaced axially apart on the sleeve member, each zone being axially spaced from the part of the sleeve aligned with the port of the working chamber and clearances being provided between the sleeve member and the rotary valve in the lubricated zones which are tapered to increase in depth towards the ends of the sleeve member.

The tapering in the lubricated zones ensures that lubricating oil is directed away from the port of the working chamber and therefore oil losses due to migrating into the working chamber are avoided.

In a first preferred embodiment a second port is provided in the sleeve member diametrically opposite the port of the sleeve member aligned with the port of the working chamber and conduit means is provided which communicates with the second port, the rotary valve being adapted to allow radial flow of fluid from the conduit means to the working chamber during a range of rotational positions thereof.

In the first preferred embodiment a radial feed rotary valve arrangement is provided. This is advantageous for two reasons. First, since the rotary valve has to rotate through only 1800 for ports to align 0 rather than the 360 needed by axial delivery rotary valves, the rotary valve can rotate at a slower speed.

Secondly, when the arrangement is used in an engine the heat inputs from successive combustions are applied to diametrically opposite sections of the rotary valve, which minimises thermal distortion.

In one preferred embodiment the present invention provides an internal combustion engine with the aforementioned features when the conduit means is divided into two passages and air under pressure is supplied through one passage and fuel/air mixture through the other passage, the rotary valve having two corresponding passages whereby air under pressure can be delivered to the working chamber separately from fuel/air mixture.

The advantages of supplying air under pressure separately from fuel/air mixture are fully discussed in W091/19889. The present invention provides a radial feed rotary valve arrangement which can deliver pressurised air to a working chamber of an engine separately from fuel/air mixure.

In all embodiments of the invention the rotary valve preferably comprises a rotor which is rotated about a stator in final relationship to the speed on the engine or compressor, the rotor being a sleeve surrounding the stator and having at least one port therein, the stator having at least one fluid passage and the rotary valve allowing flow of fluid to or from the working chamber when the port of the rotor aligns with the passage of the stator. In such embodiments a control system is preferably provided to rotate the stator with changes in operational speed of the engine or compressor, thereby varying the rate of flow of fluid to or from the working chamber in each working cycle.

The applicant has appreciated that a sleeve member can be used to surround a rotary valve which has a rotor which is a sleeve for a stator. This enables use of a control system to rotate the stator to vary the area through which fluid can pass into or from the working chamber. The advantages of doing so are fully discussed in WO91/19889.

The present invention will be described with reference to the accompanying drawings in which; Figure 1 is a transverse cross-section of a rotary valve arrangement according to an embodiment of the invention.

Figure 2 is a cross-section of the rotary valve arrangement shown in Figure 1, taken in a plane along the axis of the rotary valve.

Figure 3 is a projected view of the split sealing ring shown in Figures 1 and 2 Figure 4 is a sectional view of part of the rotary valve arrangement of Figures 1. and 2.

Figure 5 is an illustration of a static sealing grid as used in the rotary valve arrangement shown in Figures 1 and 2.

Figure 6 is a projected view of a part of the static sealing grid as shown in Figure 5.

Figure 7 is a transverse cross-section of the rotary valve arrangement of a second embodiment of the invention.

Figure 8 is a transverse cross-section of the rotary valve arrangement of a third embodiment of the invention.

Referring to Figure 1 the rotary valve arrangement of a first embodiment of the invention can be seen. The rotary valve arrangement is provided in the first embodiment in a two-stroke internal combustion engine comprising a working piston 10 reciprocating within a cylinder 11 in a cylinder block 12. The rotary valve arrangement is indicated generally by the reference numeral 13 is provided in the cylinder head 14 of the internal combustion engine.

The rotary valve arrangement 13 comprises a retaining cover 15, a split seal housing 16, a split floating seal 17 which is a sleeve member surrounding a rotary valve 18 comprising a rotor 19 rotatable about a stator 20. Springs 21 are provided to act between the retaining cover 15 and the split seal housing 16.

The split seal housing 16 comprises two parts 16a and 16b. Each part 16a and 16b has a curved surface which matches the exterior of the split seal 17. Each part 16a and 16b has a flat uppermost surface. Each part 16a and 16b also has a tapered lower portion 40a,40b, the purpose of which will be discussed later. Each part 16a and 16b has a flat side surface 49a,49b which in use is situated opposite a side of the cavity in the cylinder head 14.

Clearances 57 and 58 are provided between the sides 49a and 49b and the sides of the cavity in the cylinder head 14. A sealing ring 22 is provided between the retaining cover 15 and the two parts of the split seal housing 16a and 16b.

A static sealing grid which comprises members 23 and 36 is provided between the split floating seal 17 and the cylinder head 14. This will be described in greater detail later with reference to later figures. A radial clearance 46 exists between lower region of the split seal 17 and the cylinder head 14.

The radial clearance is necessary to allow for distortion of the rotary valve 18 due to thermal loading and loading due to the gas pressure in the cylinder 11.

This clearance is particularly necessary if the cylinder head 14 and rotary valve 19 are made of different materials, which is often the case since the alloys can be preferable for the components of the rotary valve 18. The radial clearance 46 also allows the transmission of gas pressure to the static sealing grid, the advantage of which will be discussed later.

In Figure 2 it can be seen that the split floating seal 17 extends axially along only a portion of the rotary valve 18. The rotor 19 of the rotary valve 18 is mounted in the cylinder head 14 for rotation therein and is journalled in bearings 24. Two sealing rings 25 and 26 are provided circumferentially of the rotor 19.

The static sealing grid 23 can be seen in the Figure 2, as can the outline of the cylinder 11, which is shown in dotted lines.

In both Figure 1 and in Figure 2 the rotary valve 18 is in a position wherein gas can flow into the combustion chamber 11 through the rotary valve 18. The aperture 27 in the rotor 19 ' has aligned with the bottom aperture provided in the stator 20 and the aperture 28 of the rotor has aligned with the top aperture of the stator 20. The split floating seal 17 is provided with a top aperture 30 which is in alignment with an aperture 32 provided in the retaining cover 15. In the position shown in Figures 1 and 2, fuel/air mixture can be provided to the chamber 11 by passing through the aperture 32 in the retaining cover 15, the aperture 30 in the split floating seal 17, the upper aperture 28 in the rotor 20, the lower aperture 27 of the rotor 19, the lowermost aperture 31 provided in the split floating seal 17 and finally a cylinder head port machined in the cylinder head 14.

Referring to Figure 3 the floating seal 17 can be seen in greater detail. The apertures 30 and 31 can be seen in the Figure 3, as defined by the split floating seal 17. The split 33 in the split floating seal can be clearly seen.

Two grooves 34 shown in figure 3 receive the rings 25 and 26 which are shown in Figure 2. Between the grooves 34 the split floating seal remains unlubricated and outside the two grooves 34 and 35 lubricated bearing zones are provided. Oil can be supplied to the lubricated zones via the two oil supply ports 35. The arrow shown in Figure 3 indicates the direction of rotation of the rotary valve.

Two radial slots 43 and 44 are symetrically positioned either side of the upper port 30 of the split seal 17. When the rotary valve arrangement is assembled the slots 43 and 44 engage with ring pegs provided on the two parts 16a and 16b of the split housing 16 to prevent rotation of the split seal 17. The ring pegs also prevent leakage of air from the port 30 to the lubricated areas of the split seal via the split 33.

The split 33 extends axially through the port 30 and the two radial slots 43 and 44. The sides of the split 33 are parallel in the non-lubricated zone of the split seal 17, but one side of the split 33 is at an angle extending away from the other side in each of the lubricated zones.

Referring to Figure 4, a preferred cross-section for the split floating seal 17 is shown, wherein the lubricated bearing zones of the split floating seal 17 are of tapered radial depth, with the taper increasing in depth towards the ends of the split floating seal 17.

Figure 5 shows an underneath view of the exterior of the split floating seal illustrating the positioning of the static sealing grid 23. The static sealing grid is mounted in grooves 45 provided in the cylinder head 17 (see Figures 1 and 2). Resilient biasing means are preferably provided in the grooves to spring load the grid into engagement with the exterior of the split seal 17.

The static sealing grid has two members 23 of arcuate shape, which follow the external curved surface of the split seal 17. The static sealing grid also has two members 36 which extend between the arcuate members 23.

The four members of the static sealing grid are provided such that they surround the lower port 31 of the split floating seal 17.

Figure 6 shows a corner of the static sealing grid, showing how corner pieces are provided to provide seals between the arcuate members 23 and the members 36. The members 23 and 36 will each typically be made of cast iron and silicon sealant will typically be used at the corners to ensure adequate sealing.

The operation of the rotary valve arrangement 13 will now be described. In use, the rotor 19 will be driven to rotate in timed relationship to the movement of the piston 10, opening and sealing the combustion chamber 11. If used in a two-stroke engine, as illustrated, the rotor 19 would be rotated at half engine speed. This is advantageous since the heat applied to the rotor 19 during combustion is applied at diametrically opposite portions of the rotor 18 in successive combustion. This, combined with the symmetrical design of the rotor helps to maintain a straight rotational axis for the rotor, keeping distortion to a minimum.

Fuel/air mixture will be fed to the cylinder 11 radially through the rotary valve arrangement, the rotor 17 rotating through 1800 during each cycle of the two-stroke engine, so that the ports 27 and 28 are reversed for successive fuel/air inlet operation.

Obviously, fuel/air charge can only be admitted into the chamber 11 when the apertures 28 and 31 align with the apertures 31 and 30 in the split floating seal 17, which are themselves respectively in alignment with an inlet port provided in the cylinder head 14 for the chamber 11 and the aperture provided the retaining cover 15.

The rotary valve arrangement of the invention is designed to allow for thermal expansion of the components. The split floating seal 17 can expand or contract due to the split 33 provided in it. Thus it can expand or contract to deal with any deformation of the rotor 19. The full circumferential contact between the split seal 17 and the rotor 19 ensures good sealing and provides a large surface area for good heat conduction.

It is important to ensure good heat contraction away from the rotor 19 to minimise thermal distortion of the rotor 19 and to ensure that the rotor 19, split seal 17 and split housing 16 remain at roughly equal temperatures such that the differences between rates of thermal expansion of components are minimised. Obviously large differences between rates of thermal expansion could lead to reduced sealing efficiencies.

The expansion or contraction of the split floating seal 17 is accomodated by movement of the split housing 16 relative to the cylinder. The two portions 16a and 16b of the split housing each comprise tapered portions 40a and 40b. The cylinder head 40 is machined such that the cavity for receiving the rotary valve is defined with a lowermost portion that has a surface which matches the cylindrical exterior of the split floating seal 17 with the radial clearance 46 provided. The cavity has outwardly tapering sides 47 extending from the lowermost portion to an uppermost portion 48 of rectangular transverse cross-section.

The tapered portions 40a and 40b of the components 16a and 16b of the split housing 16 extend into the tapered cavities defined between the exterior of split floating seal 17 and the tapered portion 47 of the cavity in the cylinder head 14. The components 16a and 16b of the split housing 16 are urged into abutment with the cylinder head 14 and the split floating seal 17 by the springs 21, which act between the components 16a and 16b and the retaining cover 15. In this way, a seal between the cylinder head 14 and the split housing 16 can be maintained whilst the split housing 16 can move relative to the cylinder head 14 to accomodate any movement of the split floating seal 17.

The clearances 57 and 58 between the sides 49a and 49b of housing members 16a and 16b and the sides of the cavity in the rectangular cross-section region 48 allow the components 16a and 16b to ride freely up and down the tapered portion 47 of the cavity.

As mentioned before, the cavity in the cylinder head 14 is machined such that a clearance 46 is provided between the exterior of the split floating seal 17 and the lowermost portion of the cavity. The members 23 and 36 of the static sealing grid provide for a seal between the cylinder head 14 and the split floating seal 17. The members 23 and 36 of the static sealing grid are biased toward the split seal 17 by resilient biasing means in the grooves 45 defined in the cylinder head 14. The springs 21 also act, indirectly, to push the members 23 and 36 of the static sealing grid into sealing engagement with the split floating seal 17.

The sealing engagement between the members of the static sealing grid and both the cylinder head 14 and the split seal 17 is aided by gas pressure in the combustion chamber 11. This gas pressure is communicated through the radial clearance between the split seal 17 and the cylinder head 14 to the sealing members 17 and 23. Gas pressure supplied to the grooves 45 in the cylinder head 14 force the members 23 and 36 against one face of the grooves 45 in the cylinder head 14 and also force the members 23 and 36 into engagement with the split floating seal 17. Thus efficient sealing is provided when most required, ensuring efficient performance of the engine 52.

The sealing of the engine is also aided by the hydrodynamic seals provided by lubrication of parts of the split floating seal 17. Oil is dripped into the oil supply ports 34 and 35 to lubricate the adjacent surfaces of rotary valve and split seal 17 to reduce friction and is distributed over adjacent surfaces of the split floating seal 17 and the rotary valve 19 by rotation of the rotary valve 19. The oil films formed provide good hydrodynamic seals which prevent escape of gas from the combustion chamber 11 between the split seal housing 17 and the rotor 19.

It is important to ensure that oil from the oil films in the lubricated regions of the split seal 17 does not reach the portion of the rotor 17 which opens and closes the combustion chamber 11, since otherwise oil will be combusted and the engine will use large amounts of oil in operation, whilst producing undesirable emissions of burnt oil. For this purpose, the rings 25 and 26 which extend circumferentially of the rotor 19 act as oil barriers to prevent migration of oil. Also, the split floating seal 17 is provided with two tapered surfaces 41 and 42 which act to direct lubricating oil towards the ends of the split floating seal 17 to a drainage area provided between the edges of the split seal 17 and the bearings 24. Futhermore, the tapered nature- of the gap provided between the split floating seal 17 and the rotor 19, as illustrated in Figure 4, causes the lubricating oil to flow to the ends of the split floating seal 17 to the drainage area. The pressure of the gases in the cylinder 11 during compression and expansion also helps prevent migration of oil into the central portion of the split seal 17. Thus very little lubricating oil is carried into the combustion chamber 11 by the rotor 19 to be burnt.

The pressure of the gas in the chamber 11 also acts directly on the split seal 17, forcing it into engagement with the rotor 19 and decreasing clearances between the split seal 17 and the rotor 19 to provide effluent sealing when most required (ie. sealing increases with increased gas pressures). The oil films in the lubricated zones of the split seal 17 bear the loading in the split seal and compresses to reduce clearances. The forces on the split seal 17 tend to ' force the oil of the oil films into drainage areas due to the tapered clearance shown in Figure 4.

As mentioned previously radial slots 43 and 44 in the split seal 17 are provided in the split floating seal 17 which engage with ring pegs provided on the split housing 16. The ring pegs prevent rotation of the split floating seal 17 and also prevent leakage of air from the port 30 into the lubricated bearing areas of the split seal housing 17.

In the figures so far described, the system provides a radial fuel/air feed system for an internal combustion engine. This differs from the system described in the Gabelish patent US 4597321, wherein gases are fed axially along the rotor. Use of radial feed has advantages in certain instances. For instance, the rotor of the radial feed system of the preferred embodiment can run at half the rotational speed of the rotor of the Gabelish system since it only has to turn through only 1800 for a rotor ports to align with the cylinder port whilst the rotor of Gabelish must rotate through 3600. To reduce frictional loads in an engine and to minimise loading in a rotor and limit noise and vibration it is beneficial to have a rotor running at as slow a rotational speed as possible.This is particularly important when the arrangement isused in a two-stroke engine, in which application the Gabelish rotor would have to rotate at engine speed whilst the radial arrangement of the present invention operates at half engine speed. The Gabelish rotor would also suffer problems of thermal distortion since the heat input to the rotor would always be directed to the same point, whilst in the present invention two diametrically opposite ports of the rotor receive successive heat inputs.

The use of an axial feed system as described in the Gabelish patent is also not particularly suited to use in "in line" multi-cylinder engines. No more than two cylinders could be fed from one axial rotor due to the practical reason of localised change depletions along the rotor. Obviously, such depletion is not a problem with radial feed arrangements.

If the system of the invention were to be used in the preferred embodiment of WO91/19889, the stator 20 could be provided with a central dividing number 50 as shown in Figure 7. It will also be seen that the retaining cover 50 is provided with a divider 51 and the two portions 16a and 16b of the split housing 16 are each provided with members 53 and 54 which together define a divider. Fuel/air mixture would be supplied in the passages 56a and 56b on one side of the dividers and air under pressure would be provided through the passages 55a and 55b on the other side of the dividers. The rotary valve arrangement would then be used for the two-stroke engine to provide a stratified charge of fuel/air and would ensure good scavenging by the use of pressurised air.The pressurised air would be introduced first nto the chamber 11 since the rotor 19 uncovers the passage 55b first in its rotation (anti-clockwise as shown in the figure). This has been fully described in WO91/19889.

Whilst in the above embodiments radial feed designs are discussed and are advantageous in certain applications, the rotary valve arrangement of the invention could equally well be used with an axial feed design as described in WO91/19889. Such an embodiment is shown in the Figure 8, where the stator 20 is divided into two chambers 60 and 61, fuel/air mixture being provided to the chamber 61 and air under pressure being supplied to the chamber 60. Again, the advantages of stratified charging and improved scavenging are provided. The use of axial feeding would be preferable in engines which do not have many in line cylinders since the air under pressure and fuel/air mixture can be supplied completely separately to the combustion chamber 11.The arrangement shown in the Figure 7 using radial feed cannot divide the fuel/air mixture from the pressurised air completely throughout the flow path of both, since this is not possible due to the presence of the rotor 19. The embodiment of Figure 8 would be rotated at engine speed in a two-stroke application since the rotor and split seal each have only one port. However, two parts could be provided in the rotor and the rotary valve could then be rotated at half engine speed.

In all embodiments, it is possible to provide a stator 20 which is moveable by suitable control apparatus. This control apparatus is described in WO91/19889, where it is shown that the stator of a rotary valve can be rotated to provide optimum operating conditions for different engine speeds and loads and temperatures. In all of the embodiments, the area through which fuel/air mixture can be admitted to the chamber 11 can be varied by rotating the stator. In all -engines it is beneficial to vary the angle-area (integral of port area with degrees of engine rotation) to meet the engine the time-area (integral of port area with time) requirements throughout the speed and load range.

Therefore the stator typically allows a small flow area at low engine speeds and a larger flow area at higher engine speeds.

From the above, it can be seen that the present invention provides in all embodiments a rotary valve housing arrangement which enables use of an optimum shape cylinder head, since it does not require any specialised cylinder head. Furthermore, the static sealing grid used in the invention provides a very efficient sealing mechanism and the arrangement can be used in both radial half and full speed and axial feed configurations. In both configurations in a two-stroke applications the rotary valve could rotate at half engine speed or at full engine speed if so desired. Lastly, the system is very efficient at ensuring that the lubricating oil used for hydrodynamic sealing is not combusted in the combustion chamber.

The arrangement of the present invention also has the advantage over the Gabelish system that the gas pressure in the combustion chamber is applied directly to the split floating seal 17 which is forced towards the rotor 20, thereby ensuring good sealing properties. Gas pressure is also used to ensure a good seal between the cylinder head and the floating seal.

Of course, the system has the usual advantages of a rotary valve when compared with equivalent poppet valve system, ie. simplicity, improved thermal efficiency and mechanical quietness. A rotary valve is particularly suited for use in a two-stroke engine, because it is able to provide a greater time-area for delivery of gases to the combustion chamber than equivalent poppet valve systems and also provides better scavenging.

Claims (16)

1. An internal combustion engine or compressor having at least one working chamber and a rotary valve arrangement for controlling the flow of fluid into and/or out of the working chamber through a port in the working chamber comprising; a rotary valve and means to rotate the rotary valve in timed relationship with the operation of the engine or compressor, a resiliently deformable sleeve member which surrounds the rotary valve and which has a slit which extends along the entire axial length thereof whereby the sleeve member can deform to allow deformation of the rotary valve, the sleeve member having a port therein to allow fluid flow from the rotary valve to the working chamber and/or vice versa, biasing means for applying a biasing force on the sleeve member to bias the sleeve member towards the rotary valve, which biasing means comprises abutment means biased into abutment with the exterior surface of the sleeve member and moveable relative to the sleeve member to allow deformation of the sleeve member, wherein the rotary valve, the sleeve member and the biasing means are located in a rotary valve cavity provided in the engine or compressor, which rotary valve cavity communicates with the working chamber via the port of the working chamber, characterised in that the abutment means of the biasing means is moveable in two dimensions against the biasing force.

2. An internal combustion engine or compressor having at least one working chamber and a rotary valve arrangement for controlling the flow of fluid into and/or out of the working chamber through a port of the working chamber comprising: a rotary valve and means to rotate the rotary valve in timed relationship with the operation of the engine or compressor, a resiliently deformable sleeve member which surrounds the rotary valve and which has a slit which extends along the entire axial length thereof whereby the sleeve member can deform to allow deformation of the rotary valve, the sleeve member having a port therein to allow fluid flow from the rotary valve to the working chamber and/or vice versa, biasing means for applying a biasing force on the sleeve member to bias the sleeve member towards the rotary valve, which biasing means comprises abutment means biased into abutment with the exterior surface of the sleeve member and moveable relative to the sleeve member to allow deformation of the sleeve member, wherein the rotary valve, the sleeve member and the biasing means are located in a rotary valve cavity provided in the engine or compressor, which rotary valve cavity communicates with the working chamber via the port of the working chamber, characterised in that the abutment means of the biasing means is biased into direct abutment with the surface of the rotary valve cavity to establish a seal between the rotary valve and the surface of the rotary valve cavity.

3. An internal combustion engine or compressor as claimed in Claim 1 or Claim 2 wherein the abutment means comprises a plurality of abutment members each having a tapered surface and wherein the rotary valve cavity has matched tapered surfaces, the tapered surface of each abutment member being biased into abutment with a tapered surface of the cavity, the matched tapered surfaces allowing two dimensional motion.

4. An internal combustion engine or compressor as claimed in Claim 3 or Claim 4 wherein each abutment member has an abutment surface for abutting the exterior of the sleeve member which is shaped to match the exterior surface of the sleeve member.

5. An internal combustion engine or compressor as claimed in Claim 3 or Claim 4 wherein the abutment members abut only the exterior surface of the half of the sleeve member furthest from the port of the working chamber.

6. An internal combustion engine as claimed in Claim 5 wherein the majority of the exterior surface of the half the sleeve member furthest from the port of the working chamber is abutted by the abutment means.

7. An internal combustion engine or compressor as claimed in Claim 5 or Claim 6 wherein sealing means is provided between the half of the sleeve member nearest the port of the working chamber and the cavity, which sealing means surrounds the port of the working chamber and the port in the sleeve member to inhibit flow of fluid from the working chamber between the sleeve member and the surface of the rotary valve cavity.

8. An internal combustion engine or compressor as claimed in Claim 7 wherein the sealing means comprises one or more members moveable in recesses machined in the surface of the rotary valve cavity and biased into engagement with the sleeve member.

9. An internal combustion engine or compressor as claimed in Claim 8, wherein a clearance is provided between the sleeve member and the surface of the rotary valve cavity in the region between the port of the working chamber and the sealing members, whereby the pressure of the fluid in the working chamber is communicated to the sealing members and forces the sealing members into abutment with the walls of the recesses and the sleeve member.

10. An internal combustion engine or compressor as claimed in any one of the preceding claims wherein a clearance is provided between the exterior surface of at least part of the sleeve member and the surface of rotary valve cavity through which fluid from the working chamber passes between the exterior surface of the sleeve member and the surface of the rotary valve cavity, whereby fluid pressure can be applied directly on the sleeve member to force the sleeve member into abutment with the exterior surface of the rotary valve.

11. An internal combustion engine or compressor as claimed in any one of the preceding claims wherein there is provided means to supply oil to form a lubricating film between the sleeve member and the rotary valve in two zones spaced axially apart on the sleeve member, each zone being axially spaced from the part of the sleeve aligned with the port of the working chamber and clearances being provided between the sleeve member and the rotary valve in the lubricated zones which are tapered to increase in depth towards the ends of the sleeve member.

12. An internal combustion engine or compressor as claimed in any one of the preceding claims wherein a second port is provided in the sleeve member and conduit means is provided which communicate with the second port, the rotary valve being adapted to allow radial flow of fluid from the conduit means to the working chamber during a range of rotational positions thereof.

13. An internal combustion engine as claimed in Claim 12 wherein the conduit means is divided into two passages and air under pressure is supplied through one passage and fuel/air mixture through the other passage, the rotary valve having two corresponding passages whereby air under pressure can be delivered to the working chamber separately from fuel/air mixture.

14. An internal combustion engine as claimed in any one of the preceding claims or a compressor as claimed in any one of claims 1 to 12 wherein the rotary valve comprises a rotor which is rotated about a stator in timed relationship to the operation of the engine or compressor, the rotor being a sleeve surrounding the stator and having at least one port therein, the stator having at least one fluid passage and the rotary valve allowing flow of fluid to or from the working chamber when the port of the rotor aligns with the passage of the stator.

15. An internal combustion engine or compressor as claimed in Claim 14 wherein a control system is provided to rotate the stator with changes in operational speed of the engine or compressor, thereby varying the rate of flow of fluid to or from the working chamber in each working cycle.

16. An internal combustion engine or compressor having a rotary valve arrangement substantially as hereinbefore described with reference to the and as shown in the accompanying drawings.