WO1999037899A1

WO1999037899A1 - Internal combustion engine

Info

Publication number: WO1999037899A1
Application number: PCT/CA1998/000045
Authority: WO
Inventors: Fran�ois T. DORNEZ
Original assignee: Dornez Francois T
Priority date: 1998-01-27
Filing date: 1998-01-27
Publication date: 1999-07-29
Also published as: AU5744498A

Abstract

A reciprocating piston rotary apparatus (10) uses a cam drive (26). To minimize side loadings on the pistons (36) and cylinders (34), the mechanism coupling the pistons (36) to the cam followers (70) includes a laterally constrained element (54) that will not transmit lateral loads but only loads parallel to the piston reciprocation. In the illustrated embodiment, this mechanism is a pinion (52), two racks (42, 54) on the piston and cam follower and constraining rollers (64, 66) engaging the cam follower rack (54). The invention is applicable to internal combustion engines or piston pumps.

Description

I N T E R N A L C O M B U S T I O N E N G I N E FIELD OF THE INVENTION

The present invention relates to reciprocating piston machinery, especially internal combustion engines, although it is also applicable to reciprocating piston pumps. BACKGROUND

Conventional reciprocating piston machines, for example internal combustion engines, have been constrained to certain operating cycles by the crankshaft and connecting rod mechanism used for converting the reciprocating motion of the pistons into a rotary output or a rotary input to reciprocating motion of the pistons. For greater efficiency, efforts have been made to use operating cycles that are incompatible with this conventional crankshaft and connecting rod mechanism. These usually involve the use of cams acting on fixed piston rods or the equivalent to control piston motion. With the cam system, considerable side loads are exerted on the piston and transferred to the cylinder wall. This produces high friction areas, asymmetric piston and cylinder wear and sealing problems.

The present invention is concerned with an arrangement for mitigating this problem with reciprocating piston machines. SUMMARY

According to the present invention there is provided a reciprocating piston apparatus comprising: a cylinder; a first reciprocating assembly including a piston reciprocable in the cylinder; a second reciprocating assembly reciprocable independently of the first reciprocating assembly and including a cam follower; oscillating linkage means joining the first and second reciprocating assemblies to transmit therebetween forces in the direction of reciprocation of the piston, and side load restraint means engaging the second reciprocating assembly for resisting forces exerted on the linkage means in a direction perpendicular to the direction of reciprocation of the piston; and a cam engaging the cam follower and rotatable about a cam axis with reciprocation of the cam follower.

This effectively isolates side loadings from the piston and cylinder to minimize the wear and sealing problems at this point.

In preferred embodiments, a mechanical linkage couples the piston assembly to the cam follower and the cam follower is constrained to move in a linear, oscillating manner by appropriate bearings that take up the side loadings.

One preferred mechanical linkage is a pinion engaged with racks on the piston assembly and on the cam follower. Side loads are taken up by bearings, preferably rollers engaging the rack on the cam follower.

The apparatus may be a multi-cylinder engine with the cylinders arranged in an annular array and operating on a common cam. The engine may be an opposed piston engine with two, opposed pistons reciprocating in each cylinder and driving respective cams.

A preferred engine design has a rotor containing the annular array of cylinders set inside a hollow cylindrical stator. The stator encompasses two cylindrical or crown cam drives at respective ends of the stator. An engine of this design is balanced to reduce vibration because the rotor and stator are symmetrical or quasi-symmetrical about the center of the engine with each piston being driven opposite to its mirror image so that the opposed pistons balance each other and annul each other's loads. Reduced vibration raises the possibility of constructing these engines out of materials such as ceramics and plastics.

Also of importance is how readily a cycle can be selected to optimize an engine's performance for a given application by altering the cam profiles. It is possible to use an engine cycle with a prolonged expansion stroke, allowing more time for complete combustion and delivery of a more effective energy transfer.

Engines according to the present invention can be used with various fuels, including liquid fuels, for example gasoline and diesel fuels, or with gaseous fuels, for example propane, natural gas and hydrogen. The engine may be designed as a compression ignition engine or a spark ignition engine. The engine is constructed as a two-stroke, valveless engine, which is particularly suitable for hydrogen fuel as it eliminates the incompatibility of hydrogen fuel with a valved engine. BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, which illustrate an exemplary embodiment of the present invention:

Figure 1 is a longitudinal cross-section of an engine constructed according to the present invention;

Figure 2 is a side view, partially broken away of the engine of Figure 1 ;

Figure 3 is a view along line 3-3 of Figure 1 ;

Figure 4 is a view along line 4-4 of Figure 1 ;

Figure 5 is a view along line 5-5 of Figure 1 ;

Figure 6 is a view along line 6-6 of Figure 1 ;

Figures 7a, 7b and 7c are schematic illustrations showing the operating linkage; Figure 8 is a top view of the schematic of Figure 7c;

Figure 9 is a view along line 9-9 of Figure 8; and

Figure 10 is a schematic developed view showing the operating cycle of an engine. DETAILED DESCRIPTION

Referring to the accompanying drawings, there is illustrated an elongate cylindrical engine 10. The engine has an external stator 12 enclosing a rotor 14. At each end of the engine the stator includes a stator housing 16 including a flat, annular end panel 18 and a cylindrical side wall 20. The end panel 18 has a central end opening 22. The two housings 16 are mounted on opposite ends of a stator core 24 having two annular cam tracks 26 formed on its inner surface adjacent the opposite ends of the stator. The stator core has a set of air intake slots 28 extending partially around the core and a set of exhaust slots 30 spaced partially around the core. The intake and exhaust slots are positioned between the two stator housings 16. At the centre of the stator core 24, on its inner surface, is an annular fuel injector actuating track 32.

Mounted on the stator core 24 are five cylinders 34. These are spaced around the stator core in an annular array with the cylinders parallel to the longitudinal axis X-X of the engine.

Each cylinder accommodates two confronting pistons 36. Each piston has a crown 38 extending across the cylinder and a skirt 40 extending along the cylinder. The skirt is equipped with the usual piston rings 41 for maintaining pressure and distributing oil. The piston also includes a piston rod 42 fixed to the piston.

At each end of the rotor is a series of end plates 44. These are mounted on the rotor core 24 and carry support flanges 46 parallel to the axis of the engine. The support flanges carry rollers 48 that engage sides of each piston rod 42 to guide the piston rod for linear reciprocating movement along the associated cylinder. One side of the piston rod carries a rack 50 that engages a pinion 52 also mounted on the support flanges 46.

On the side of each pinion 52 opposite its engagement with the respective rack 50 is a rack 54. The teeth of rack 54 are on a bevelled face 56 of the rack parallel to the rack 50 on the piston rod. The rack also has an outer face 58 tangential to the rotor and two side faces 60 and 62 perpendicular to the outer face. The rotor carries guide rollers 64 which engage the side faces 60 and 62 of the rotor. Additional guide rollers 66 are mounted on the rack adjacent its inner end to run on the inner faces of two guide plates 68 of the stator parallel to the side faces 60 and 62 of the rack. The guide rollers 64 and 66 guide the rack for linear movement parallel to the engine axis X-X.

A cam follower roller 70 is mounted on the rack 54 and engages in the adjacent cam track 26 of the stator so that movement of the rack 54 will be controlled by movement of the cam follower roller 70 along the cam track.

Each of the cylinders 34 has a series of intake ports 72 spaced around the cylinder at a position just inside the bottom dead center position of one of the piston crowns 38 to be opened when the piston crown reaches this bottom dead center position. A similar set of scavenging ports 74 is also formed in the cylinder to be opened by the opposite piston when its crown 38 reaches its bottom dead center position.

The intake ports 72 receive fresh combustion air from two sources. One of these is a core air intake tube 76 with a flared end 78 leading from the end opening 22 of one of the stator end panels 18. Air entering this tube is deflected by the convergent end 80 of the intake tube 76 into an annular chamber 82 surrounding the cylinder at the level of the intake ports 72. The second air intake is through the intake slots 28 in the side of the stator core 24. Vanes 88 mounted on the rotor and sweeping past the intake slots 28 pump air into the cylinder intake ports 72 as the rotor rotates.

The scavenging system for exhaust gases is similar to the intake, with the vanes 90 operating to pump air out of the scavenging ports 74. The system includes an exhaust core tube 92 with a flared end 94.

Along the axis X-X of the engine is a rotor shaft 100. This is fixed to the rotor and serves as the output shaft of the engine. Extending along the shaft 100 from one end is a fuel line 102. At the centre of the engine, this is branched off into independent fuel lines 104 for each cylinder. The lines 104 deliver fuel to injectors 106. Each injector includes a cylinder 108 with an injector nozzle 110. The nozzle discharges fuel into a respective one of the cylinders. Fuel is drawn into the cylinder from line 104 by a piston 112. riding in the cylinder. Movement of the piston towards the nozzle ejects fuel from the nozzle into the cylinder. The piston carries a follower roller 114 that rides in the actuator track 32 on the stator. At the injection point is an injector actuator 116. The actuator has a first, loading section 118 pivotally mounted on the stator to move outwardly to form a ramp section of the track 32. This allows the injector piston to move outwardly in the cylinder as follower roller 114 moves along the loading section of the actuator. This draws fuel into the cylinder. The follower has a second injection section 120 pivotally mounted at one end on the stator and having its opposite end pinned to a slot 122 in the first section, so that the two sections will pivot outwardly together. The degree of movement is governed by the engine throttle. With maximum movement, the piston will be drawn outwardly as far as possible, and the maximum amount of fuel will be drawn into the injector for injection into the cylinder. Smaller injector displacements will result in correspondingly smaller amounts of injected fuel. As illustrated most particularly in Figures 7a, 7b and 7c, the guide rollers 64 and 66 for each rack 54 act to take up any lateral loads on the rack tangential to the rotor. The only load applied to the piston assembly, consisting of the piston itself and the piston rod, are parallel to the engine axis and parallel to the walls of the cylinder. Figures 7a, 7b and 7c illustrate the different loadings that can be applied to the laterally constrained rack 54 at different cam orientations.

Figure 10 illustrates an operating cycle for one cylinder of an engine that is described in the foregoing. At A, the pistons are both at bottom dead centre and the intake and scavenging ports are open. Intake air is drawn in through the intake ports and exhaust gases are drawn out of the exhaust ports. After a short dwell time, the cam follower engages a steep cam section at B to advance the pistons rapidly towards the top dead centre position shown at C. At this point, the injector injects fuel into the cylinder between the two pistons. The illustrated engine is an auto-ignition engine and the injection of fuel is followed by combustion which drives the pistons apart. Because the cam slope is much shallower in this power stroke, the power stroke is much longer in duration than the compression stroke, and combustion is more complete than would be the case with a symmetrical compression and power stroke system. At the end of the power stroke, at D, the pistons are rapidly withdrawn beyond the inlet and exhaust ports and the intake and scavenging dwell period begins once more.

While one particular embodiment of the present invention has been described in the foregoing, it is to be understood that other embodiments are possible within the scope of the invention. The invention is applicable to various different types of reciprocating piston machines operating on various different cycles. Appropriate configuration of the cams will allow almost any desired sequence or duration of expansion and compression sequences. Where desired, the fuel may be carburetted rather than injected. Spark ignition rather than auto-ignition may be employed as well.

The mechanical control of the injectors may be replaced with an electronic control, for example the type of injector control now used in many automotive applications.

The engine is preferably operated with the cylinders horizontal. For lubrication, the illustrated embodiment uses a splash feed system, with the maximum compression positions of the pistons at the bottom of the rotor's rotation to facilitate the splash feed of oil to the cylinder walls behind the piston. It is, in other embodiments, possible to use a pressure feed lubrication system.

The linkage used to transmit power between the pistons and the cam may take various forms. The oscillating coupling between the piston and cam follower may be a rocker arm for shorter strokes. A flexible linkage, for example a chain or cable, is another possibility.

In other embodiments, the stator and rotor may be reversed, with the part referred to as the "stator" in the foregoing being the rotating part, while the part referred to as the "rotor" is held stationary. This may lower the inertia of the rotating part in some cases. It is also possible to use an internal stator, inside the piston and cylinder assembly.

For internal combustion engines, the operating cycle is dictated primarily by the cam configuration, and may vary widely. The cycle shown is believed to be particularly effective. In other embodiments, the cams may not be symmetrical, so that the movements of two opposed pistons will not be mirror images of one another.

This invention is therefore to be construed as limited solely by the scope of the appended claims.

Claims

1. A reciprocating piston apparatus comprising: a cylinder; a first reciprocating assembly including a piston reciprocable in the cylinder; a second reciprocating assembly reciprocable independently of the first reciprocating assembly and including a cam follower; oscillating linkage means joining the first and second reciprocating assemblies to transmit therebetween forces in the direction of reciprocation of the piston, and side load restraint means engaging the second reciprocating assembly for resisting forces exerted on the linkage means in a direction perpendicular to the direction of reciprocation of the piston; and a cam engaging the cam follower and rotatable about a cam axis with reciprocation of the cam follower.

2. An apparatus according to Claim 1 wherein the second reciprocating assembly comprises a laterally constrained member connected to the cam follower and engaged by the side load restraint means for constraining the laterally constrained member to reciprocate linearly, parallel to the piston.

3. An apparatus according to Claim 2 wherein the first reciprocating assembly comprises a piston rod fixed to the piston and the oscillating linkage means comprise an oscillating member engaged with the piston rod and the laterally constrained member to transmit reciprocating motion therebetween.

4. An apparatus according to Claim 3 wherein the first reciprocating assembly comprises a first rack on the piston rod, the second reciprocating assembly comprises a second rack on the laterally constrained member and the oscillating member is a pinion engaging the two racks.

5. An apparatus according to Claim 2, 3 or 4 wherein the cam follower comprises a roller mounted on the laterally constrained member.

6. An apparatus according to any preceding Claim comprising an engine including a plurality of substantially parallel cylinders arranged in an annular array, a plurality of first reciprocating assemblies, second reciprocating assemblies, oscillating linkage means and side load restraint means associated with the respective cylinders.

7. An apparatus according to Claim 6 comprising two pistons reciprocable in each cylinder and means for reciprocating the pistons of each cylinder simultaneously in opposite directions.

8. An apparatus according to any preceding Claim comprising an internal combustion engine.

9. An internal combustion engine comprising: a stator including an annular cam; a rotor rotatable with respect to the stator about a rotor axis positioned centrally of the cam, the rotor including: a plurality of parallel cylinders, a plurality of first reciprocating assemblies including pistons reciprocable with respect to the respective cylinders; a plurality of second reciprocating assemblies reciprocable independently of the first reciprocating assemblies and including cam followers engaged with the cam, oscillating linkage means joining each first reciprocating assembly and a respective second reciprocating assembly to transmit therebetween forces in the direction of reciprocation of the piston, and side load restraint means engaging the linkage means for resisting forces exerted on the linkage means by the cam in a direction perpendicular to the direction of reciprocation of the piston.

10. An engine according to Claim 9 wherein the stator comprises two cams and the rotor comprises two opposed pistons reciprocable in each cylinder, with cam followers engaging respective ones of the cams for reciprocating the pistons of each cylinder simultaneously in opposite directions.

11. An engine according to Claim 6, 7, 9 or 10 wherein the cylinders include intake ports and scavenging ports opened and closed by the pistons reciprocating along the cylinders.

12. An engine according to Claim 11 including vanes mounted on the rotor for impelling ambient air into the intake ports in response to rotation of the rotor.

13. An engine according to Claim 11 or 12 including vanes mounted on the rotor for drawing exhaust gases from the scavenging ports in response to rotation of the rotor.

14. An engine according to any one of Claims 6 to 13 including injector means for injecting fuel into each cylinder, and injector actuator means comprising a cam track on the stator, around the rotor for engaging the injector means.