AU696914B2 - An internal combustion reciprocating engine - Google Patents

Description

P/0o/on Regulation 3.2

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT Name of Applicant: Address of Applicant: BRUCE WELLER 24 Watson Drive MANDURAH WA 6210 Actual Inventor: Address for Service: BRUCE WELLER Griffith Hack Co.

256 Adelaide Terrace (6 Floor) PERTH WA 6000 c es a os a a

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o e Standard Complete Specification for the invention entitled: AN INTERNAL COMBUSTION RECIPROCATLNG ENGINE Details of Associated Provisional Applications: Australian Provisional Patent Application No. PN3433 filed on 7 June 1995.

The following is a full description of this invention, including the best method of performing it known to me:-

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I i n~ III -R 2 2 AN INTERNAL COMBUSTION RECIPROCATING ENGINE The present invention relates generally to an internal combustion reciprocating engine of the type having a rotatable cam drum driven by one or more reciprocating pistons. This type of engine is referred to as a crankless engine.

European patent publication No. 0,566,072 describes a known crankless engine having a plurality of pistons each housed in separate cylinders disposed about a rotatable cam drum.

A sinusoidal-shaped cam extends about a circumferential surface of the cam drum. The pistons and corresponding cylinders may be arranged in pairs disposed about the cam drum so that each pair of pistons is interconnected by a common con-rod. The common con-rod, about mid-way along its length, engages the sinusoidal-shaped cam, typically via a pair of bearings rotatably coupled to the con-rod.

Reciprocation of the pistons in the cylinders, caused by combustion of fuel in each of the cylinders, effects rotation of the cam drum as the bearings run up and down the sinusoidal-shaped cam. Alternatively, a single piston, rather than a pair of piston, can be connected to each conrod for rotatably driving the cam drum.

In the known engine described above, the four-stroke combustion cycle is controlled by an intake and an exhaust valve in fluid communication with each of the engine cylinders. The intake and exhaust valves are stroked by a cam plate having a pair of lobes arranged so as to stroke the inlet and the exhaust valves, respectively. The cam plate is fixed axially to the cam drum and is thus rotatably driven by the cam drum at engine speed.

The combustion cycle of this known engine, is such that adjacent cylinders disposed about the cam drum fire consecutively. Because the power stroke for adjacent 3 cylinders occurs at about the same time, the engine has relatively high vibrational forces. To compensate for these relatively high forces heavy engine mountings with good vibration dampening ability are used. However, these relatively high vibrational forces can still lead to premature failure of engine components, and furthermore reduce overall engine efficiency.

With a view to reducing these high vibrational forces, European patent publication No. 0,566,072 describes another crankless engine which includes a pair of sinusoidal-shaped cams formed about a circumferential surface of the rotatable cam drum. This engine has pairs of pistons and corresponding cylinders disposed about the cam drum, each piston of the pair having its own con-rod designed to operatively engage one of the pair of cams. The other piston of the pair operatively engages the other of the cams. The pair of sinusoidal-shaped cams are r "-'ged on the cam drum so that axially opposite pistons and cylinders perform their power stroke at the same time, and axially 20 opposite pistons move in opposite directions. A cam plate, operatively coupled to each end of the cam drum, controls the combustion cycle of the engine. This known crankless engine is thus relatively well balanced throughout its combustion cycle.

25 However, as described above, the known crankless engine is restricted in that it must be designed with pairs of pistons and corresponding cylinders together with a pair of cam plates, and thus is relatively large and heavy.

An intention of the present invention is to provide an 30 internal combustion reciprocating engine which is relatively well balanced and runs efficiently.

According to the present invention there is provided an internal combustion reciprocating engine comprising: i c 4 an engine housing; a drive shaft coaxially connected to a cam drum having an endless cam of a predetermined profile extending around a circumferential surface of said cam drum, said cam drum being rotatably mounted in the engine housing; a plurality of cylinders formed in said engine housing and spaced circumferentially about an axis of rotation of the cam drum wherein each cylinder has a substantially radially opposite cylinder; and a piston housed within each of said plurality of cylinders, each piston coupled to a con-rod which is designed to operatively engage the endless cam so that, in use, reciprocating movement of said plurality of pistons between top dead centre and bottom dead centre rotatably drives the cam drum and thus imparts torque to the drive shaft, the combustion cycle of the engine being controlled wherein the power stroke of any one piston sequentially precedes the power stroke of another piston which, of the pistons approaching top dead centre, is the most radially distant piston relative to said one piston, and thus the S.engine is relatively well balanced.

Typically, the internal combustion reciprocating engine further comprises: a cam plate, having at least one cam lobe, 25 coaxially coupled to the cam drum; and each cylinder is provided with an intake valve and an exhaust valve so that, in use, the cam plate can be rotated by the cam drum in a predetermined direction and at a predetermined speed and said at least one cam lobe actuates the intake and/or the exhaust valves to Ssubstantially coincide with the combustion cycle of the engine.

Preferably, the cam plate is provided with an intake lobe and an exhaust lobe designed to actuate the intake valve and the exhaust valve, respectively, of each cylinder.

5 Typically, the cam plate is coaxially coupled to the cam drum via a planetary gear set designed so that the cam plate is rotated in the predetermined direction and at the predetermined rotational speed.

Typically, the predetermined profile of the endless cam is wave-shaped including at least four ramps corresponding to a four stroke combustion, exhaust, intake, and compression cycle, respectively, the ramp dedicated to the combustion stroke being shaped so that torque is maximised during this stroke of the cycle. Preferably, the cam has a relatively steep slope at this stage of the combustion cycle.

Accordingly, the piston movement to driveshaft rotation is designed so that maximum rotational force of the driveshaft is derived. Thus, the engine develops optimum torque and horsepower for a given charge of fuel. This profiling of the endless cam was developed through the realisation that in known crankless engines the con-rod and cam are in a mechanically disadvantaged position during the initial stages of a combustion stroke, that is within the first 300 of driveshaft rotation after the top dead centre.

*.*":Preferably, the profile of said endless cam is repeated about the circumferential surface of the cam drum depending on the number of combustion cycles and thus power stro,:es required for each revolution of the cam drum. For example, if each piston is to perform one combustion cycle and power stroke per revolution of the cam drum the sinusoidal-shaped cam from 0 to 3600 is to be repeated twice. Alternatively, if each piston is to perform two combustion cycles and power strokes per revolution of the cam drum the 30 sinusoidal-shaped cam is to be repeated four times.

In one example the internal combustion reciprocating engine comprises five pistons disposed in five cylinders, respectively, formed in said engine housing and equally

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6 spaced circumferentially about an axis of rotation of the cam drum.

In the five cylinder internal combustion reciprocating engine, where each of the cylinders is numbered one (1i) to five consecutively in a clockwise direction around the engine housing, the firing order of the engine is one four two five and three such that the power stroke of any one piston sequentially precedes the power stroke of another piston which, of the pistons approaching top dead centre, is the most radially distant piston relative to said one piston, and thus the engine is relatively well balanced.

In the five cylinder internal combustion reciprocating engine the cam plate has three intake lobes and three exhaust lobes, each of the intake and the exhaust lobes equally spaced circumferentially about an axis of rotation of the cam plate, the intake lobes radially spaced from the exhaust lobes so that, in use, the intake lobes actuate the intake valve of each cylinder and the exhaust lobes actuate 20 the exhaust valve of each cylinder to coincide with the combustion cycle of the engine.

In the five cylinder internal combustion reciprocating "engine the cam plate is rotated in an opposite direction and at substantially two thirds the rotational speed of the cam drum so that each of the intake valves and the exhaust **"valves are actuated by one of the intake lobes and the exhaust lobes, respectively, to substantially coincide with the combustion cycle of the engine.

In another example the internal combustion reciprocating engine comprises eight pistons disposed in eight cylinders, respectively, formed in said engine housing and equally spaced circumferentially about an axis of rotation of the cam drum.

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1~BIY"rrVllrau ep- C 7 In the eight cylinder internal combustion reciprocating engine, where each of the cylinders is numbered one to eight consecutively in a clockwise direction around the engine housing, the firing order of the engine is one six three eight five two seven and four such that the power stroke of any one piston sequentially precedes the power stroke of another piston which, of the pistons approaching top dead centre, is the most radially distant piston relative to said one piston, and thus the engine is well balanced.

In the eight cylinder internal combustion reciprocating engine the cam plate has three intake lobes and three exhaust lobes, each of the intake and the exhaust lobes equally spaced circumferentially about an axis of rotation of the cam plate, the intake lobes radially spaced from the exhaust lobes so that, in use, the intake lobes actuate the intake valve of each cylinder and the exhaust lobes actuate the exhaust valve of each cylinder to coincide with the combustion cycle of the engine.

20 In the eight cylinder internal combustion reciprocating engine the cam plate is rotated in an opposite direction and at substantially one third the rotational speed of the cam drum so that each of the intake valves and the exhaust valves actuated by one of the intake lobes and the exhaust 25 lobes, respectively, to substantially coincide with the combustion cycle of the engine.

Typically, the internal combustion reciprocating engine further comprises a plurality of thrust bearing means each connected to the engine housing and operatively cooperating with each of the plurality of con-rods whereby, in use, forces acting substantially tangential to said cam drum, between each of the plurality of con-rods and the endless cam, are transmitted to the engine housing by the thrust bearing means, thereby reducing tangential forces P _l M 8 transmitted through the plurality of con-rods to the plurality of pistons.

In one embodiment each of the plurality of thrust bearing means consists of a rigid link extending tangential to the circumferential surface of the cam drum, said link at one end being pivotally coupled to one of the plurality of conrods and at an opposite end being pivotally coupled to said engine housing.

Alternatively, each of the plurality of thrust bearing means consists of a thrust block connected to the engine housing the thrust block having two opposing pairs of friction plates designed to operatively engage one of the plurality of con-rods and thus transmit the tangential forces to the engine housing through the opposing friction plates.

An endless cam includes either a protrusion on or a recess in the cam drum.

S.In order to achieve a better understanding of the nature of the present invention a preferred embodiment of an internal 20 combustion reciprocating engine will now be described in some detail, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a cross-sectional view taken axially through an internal combustion reciprocating engine; 25 Figure 2 is a schematic side view of the endless cam shown in Figure 1 developed with the five pistons and con-rods superimposed on the developed cam; and Figure 3 is a schematic plan view of intake and exhaust lobes of a cam plate superimposed on the five cylinder internal combustion reciprocating engine shown in Figure 1.

~I I~_ As illustrated in Figure i, there is an internal combustion reciprocating engine shown generally as 10 comprising a drive shaft 12 coaxially connected to a cam drum 14, and an engine housing 16 having five cylinders 18 equally spaced circumferentially around the drive shaft 12. A cylinder head 20 is located above the cylinders 18. A cam plate 22 is coaxially coupled to the cam drum 14 via a planetary gear set 24. Each cylinder 18 houses a piston 26 which is connected to one end of a con-rod 28 via a wrist pin 30. In this example, the con-rod 28 is substantially rectangular in cross-section and at an opposite end has a pair of spaced apart tapered rollers 32.

An endless cam 34 extends around and, in this example, protrudes from a circumferential surface of the cam drum 14. The cam 34 has a pair of opposing cam surfaces 36, and in this example the predetermined profile of the endless cam 34 is shaped sinusoidal. As best shown in figure 2 the sinusoidal-shaped cam 34 from 0 to 3600 is repeated twice about the circumferential surface of the cam drum 14. Each S. 20 ramp of the sinusoidal-shaped cam 34 corresponds to a a. combustion, exhaust, intake, and compression stroke for each piston 26, in a conventional four-stroke cycle.

The pair of tapered rollers 32 operatively engage the opposing cam surfaces 36, respectively. The axis of 25 rotation of the tapered rollers 32 converge in a direction substantially perpendicular toward the axis of rotation of the drive shaft 12. The axis of rotation of the tapered rollers 32 in this example is at an angle eo to the axis of the drive shaft 12, where 30 0 9 0 0 r and Po is equal to the included angle of the tapered rollers 32. A contact face of the rollers 32 may be pivoted away from perpendicular to the drive shaft 12 to ease thrust pressure on the cam surface 36. The distance between the rollers 32 in each pair depends on the distance -Cl- l I II 10 between opposing cam surfaces 36 and the predetermined profile of the endless cam 34. The taper of the pair of rollers 32 depends on the circumferential distance of the cam drum 14 at the innermost and outermost sections of the opposing cam surfaces 36. The largest and smallest diameter sections of the tapered rollers 32 are designed to allow for this difference in the circumferential distance around the opposing cam surfaces 36. This reduces unnecessary friction which may be caused by differential skidding of thI- tapered rollers 32 on the cpposing cam surfaces 36.

During operation each of the pistons 26 reciprocates, between top dead centre and bottom dead centre, in its corresponding cylinder 18 and thus the corresponding conrod 28 drives the pair of tapered rollers 32 up and down in a direction parallel to the axis of rotation of the drive shaft 12. The rollers 32, which operatively engage the opposing cam surfaces 36, bear on the cam surfaces and thus force the cam drum 14 and the drive shaft 12 to rotate.

I. The internal combustion reciprocating engine 10 further 20 comprises thrust bearing means, in this example a link 38 arranged substantially tangential to the cam drum 14 and pivotally connected at each end to the con-rod 28 and the engine housing 16, respectively. The con-rod 28 at an end opposite its connection to the piston 26 has a machined 25 section adapted to receive a pin 40. An opposite end of the link 38 has a second pin 42 used to pivotally connect the link 38 to the engine housing 16. The link 38 is designed to transmit any forces acting substantially tangential to the cam drum 14 through to the engine housing 16 from the con-rod 28. The link 38 interconnected between S 0 the cylinder housing 16 and the con-rod 28 causes the conrod 28 and the corresponding pair of rollers 32 to move in an arc. This movement must be allowed for when designing the predetermined profile of the endless cam 34 to avoid -~clc- L~As~urarrunmr*-au 11 the likelihood of jamming of the tapered rollers 32 on the endless cam 34.

By extending the distance between the tapered rollers 32 and the machined section of the con-rod 28, designed to receive the pin 40, the likelihood of jamming is decreased.

During reciprocation of the pistons 26 movement of the conrod 28 sideways, at the tapered rollers 32, is decreased by extending this distance. Ideally each of the pair of tapered rollers 32 should contact the corresponding cam surface 36 during the entire engine 10 combustion cycle.

Typically a nominal clearance provides for a surface lubricant between each of the rollers 32 and the cam surface 36.

In this embodiment the internal combustion reciprocating engine 10 further comprises a second drive shaft 44 coaxially connected to the cam drum 14. The second drive shaft 44 runs in tapered roller bearings 46 located between the cylinder housing 16 and the second drive shaft 44. The drive shaft 12 adjacent the cam drum 14 is likewise run in 20 tapered roller bearings 48 located between the cylinder housing 16 and the drive shaft 12. Ball bearings 50 are located further along the drive shaft 12 to carry radial forces in the vicinity of the cylinder head 20. The planetary gear set 24 is connected to the drive shaft 12 25 and operatively rotates the cam plate 22.

As illustrated in Figure 3 the cam plate 22 has three intake lobes 52A, 52B, 52C and three exhaust lobes 54A, 54B, 54C, (depicted by black dots), each of the intake and exhaust lobes 52, 54, respectively, equally spaced 30 circumferentially about an axis of rotation of the cam plate 22. Adjacent intake and exhaust lobes 52, 54, respectively, are displaced 1200 relative to each other.

The exhaust lobes 54 are offset 600 in an anti-clockwise direction relative to the intake lobes 52. In this i i 12 example, the intake lobes 52 are 2ated radially inside the exhaust lobes 54 to coincide with radial positions of intake valves 56A, 56B, 56C, 56D, 56E and exhaust valves 58A, 58B, 58C, 58D, 58E located in each of the cylinder heads Lubrication of the internal combustion reciprocating engine is achieved by an oil pump (not shown) which is driven by the drive shaft 12. Oil is pumped to the tapered rollers 32, the opposing cam surfaces 36, and additional lubricant to the wrist pins 40, 42, of the rigid link 38.

Oil galleries (not shown) are provided for lubricating the drive shaft roller bearings 46, 48, cam plate bearings the planetary gear set 24, cam lobes 52, 54, and the intake and exhaust valves 56, 58, respectively. The engine oil then returns to a sump (not shown) where it may be pumped to the internal combustion engine 10 for further lubrication. The engine oil sump is located at the lowest o*opoint of the engine 10 adjacent the cam drum 14.

Operation of the internal combustion reciprocating engine 10 described above will now be explained. In this example, the engine 10 cycle is a four-stroke cycle but it should be appreciated that the scope of the present invention also extends to a two-stroke cycle.

The four-stroke cycle comprises the conventional steps of combustion, exhaust, intake, and compression. With the cam 34 and cam drum 14 rotating clockwise or moving in the direction indicated by the arrow shown in figure 2 the combustion stroke, also known as the power stroke, is performed in the following order (where each of the cylinders 18A, 18B, 18C, 18D, 18E is numbered one to five consecutively in a clockwise direction around the cylinder housing 16): one four two five and three In this way the power stroke performed by, for example piston 26A precedes the power stroke of another ci I BP49~ F~VP~a~-~lrr~- 13 piston 26D which, of the pistons 26B or 26D approaching top dead centre, is the most radially distant piston 26D relative to piston 26A. The force exerted on the engine by the power stroke of one piston 26 is thus substantially compensated by the force exerted by another piston 26 and the engine is relatively well balanced.

In the five cylinder internal combustion reciprocating engine 10 described the cam plate 22 is rotated at twothirds the rotational speed of the cam drum 14 or drive shaft 12. The planetary gear set 24 is designed so that this rotational speed is achieved. As viewed in Figure 3, the cam plate 22 is rotated in an anti-clockwise direction.

The first exhaust lobe 54A strokes the exhaust valve 58A of cylinder number one and when the cam plate is rotated 240 in an anti-clockwise direction the second exhaust lobe 54B strokes the exhaust valve 58D of cylinder number four The cam plate 22 is then rotated a further 240 wherein the third exhaust lobe 54C strokes the exhaust valve 58B of cylinder number two The exhaust valves 58 of each cylinder 18 are thus stroked according to the firing order of the engine 10 as described above.

Likewise, each of the intake lobes 52 stroke each of the intake valves 56 so as to coincide with the combustion cycle of the engine 10. In this example, where the cam 25 plate 22 is, rotated at two-thirds the rotational speed of the cam drum 14 or drive shaft 12, the exhaust lobes 54 are offset 600 in an anti-clockwise direction relative to the intake lobes 52. It should be appreciated that the intake 0°.0 lobes 52 and exhaust lobes 54 may be further offset relative to each other depending on the relative positions of the intake and exhaust valves 56, 58, respectively, in.

the cylinder head Generally the length of each of the exhaust or intake lobes 54, 52 is sufficient to hold the exhaust or intake valves 58, 56, respectively, open until the corresponding piston i-i 5 i 14 26 has travelled substantially its full stroke. The exhaust or intake lobes 54, 52, in this example, hold the exhaust or intake valves 58, 56, respectively, open for approximately 600 of cam plate 22 rotation. However, the .cam lobe length and relationship in timing between intake and exhaust lobes may vary according to the engine 10 fuel economy/power requirements.

In this example the predetermined profile of the endless cam 34 is substantially sinusoidal in shape and is repeated twice about the circumferential surface of the cam drum 14.

For 3600 of cam drum 14 or drive shaft 12 rotation each piston 26 or corresponding cylinder 18 will perform four strokes, namely: combustion, exhaust, intake, and compression and the five cylinder engine 10 will thus perform five power .strokes for each revolution of the cam drum 14. By repeating the number of times the sinusoidalshaped cam occurs on the circumferential surface of the cam drum 14 the number of power strokes for each revolution of the cam drum 14 can be varied. This will be dictated largely by the diameter of the cam drum 14. Accordingly, the rotational speed of the cam plate 22 will be varied to stroke the intake valve 56 and exhaust valve 58 of each cylinder head 20 at the appropriate time. If, for example, each piston 26 performs two power strokes for each 25 revolution of the cam drum 14 the endless sinusoidal-shaped cam 34 is repeated four times around the circumferential surface of the cam drum 14. In this example, the cam plate 22 will again rotate at two-thirds the cam drum 14 or drive shaft 12 speed.

Now that a preferred embodiment of an internal combustion reciprocating engine has been described in some detail, it will be apparent to those skilled in the art that the engine has at least the following advantages over the admitted prior art: I L la li~Esllllll~~l-- I; 15 (i) (ii) (iii) (iv) a relatively well balanced and thus efficient engine can be designed by controlling the combustion cycle of an engine in accordance with the present invention; an engine according to the present invention provides a low friction, low vibration engine resulting in improved fuel economy; the overall weight of the engine is reduced due to the improved vibration characteristics exhibited by the engine largely due to the controlled combustion cycle and constant torque supplied to the driveshaft; the combustion cycle of the engine can be varied according to the predetermined profile of the endless cam located on the cam drum; the profile of the cam can be designed so that torque is optimised during the combustion stroke thereby reducing the flywheel weight, requiring less fuel per kilowatt of power produced, lowering combustion pressure thus reducing piston, ring, and bearing wear, and permitting lower compression ratios which is particularly suitable for low octane fuels; the engine lends itself to more efficient combustion thus being relatively economical with redueduced NOX emissions; and the engine is relatively cool and quiet when running, requiring reduced exhaust sound suppression.

9999 .9,9 a *9 9 99* 99 9 9 *9 a *O o (vi) (vii) It will be apparent to persons skilled in the relevant arts that numerous variations and modifications can be made to the internal combustion reciprocating engine in addition to those already mentioned above, without departing from the basic inventive concepts of the present invention. For example, the engine may operate in a two-stroke cycle rather than a four-stroke cycle as described in the above n I- 16 embodiments. The endless cam may be shaped in practically any form and is not limited to the sinusoidal shape described. Preferably, the cam is shaped so that torque to the drive shaft is maximised during the combustion stroke of the engine, the cam having a relatively steep slope during this stage of the combustion cycle. The engine may be oriented horizontally rather than vertically as herein described.

The internal combustion reciprocating engine is not limited to a five cylinder engine but may include any number of cylinders where the combustion cycle is staggered so that the engine during operation is relatively well balanced.

For example the present invention would include an eight cylinder engine having a firing order of one six three eight five two seven and four with a cam plate having three lobes equally spaced circumferentially about the cam plate. The cam plate in this instance rotates in an opposite direction to- and at S" one-third the engine speed. With a sinusoidal-shaped cam repeated twice about the cam drum each cylinder or ))iston will perform a single power stroke for each revolution of the engine. In this example, the engine will, therefore, perform eight power strokes for each revolution of the engine and this may be varied by repeating the sinusoidal- 25 shaped cam around the circumferential surface of the cam drum. For example, by repeating the sinusoidal-shaped wave form four times around the cam drum there would be sixteen power strokes performed for each revolution of the eight cylinder engine.

A nine cylinder engine would have a firing order of one five nine four eight three seven two and six with a cam plate having two lobes equally spaced circumferentially about the cam plate.

A seven cylinder engine wouid have a firing order of one three five seven two four and i- -7 ii i i i I 4 17 six with a cam plate having three equally spaced lobes.

Alternatively the firing order in the seven cylinder engine could be one four seven three six two and five with a cam plate having two equally spaced lobes. ten cylinder engine would have a firing order of one four seven ten three six nine two five and eight with a cam plate having three equally spaced lobes. A sixteen cylinder engine would have a firing order of one six eleven sixteen five ten fifteen four nine fourteen three eight thirteen two seven and twelve (12) with a cam plate having three equally spaced lobes.

The engine may be fuelled by a choice of either gasoline, methanol, diesel, LPG, any other combustible fuel, or any combination thereof.

.All such variations and modifications are to be considered within the scope of the present invention, the nature of which is to be determined from the foregoing description.

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Claims (18)

1. An internal combustion reciprocating engine comprising: an engine housing; a drive shaft coaxially connected to a cam drum having an endless cam of a predetermined profile extending around a circumferential surface of said cam drum, said cam drum being rotatably mounted in the engine housing; a plurality of cylinders formed in said engine housing and spaced circumferentially about an axis of rotation of the cam drum wherein each cylinder has a substantially radially opposite cylinder; and a piston housed within each of said plurality of cylinders, each piston coupled to a con-rod which is designed to operatively engage the endless cam so that, in use, reciprocating movement of said plurality of pistons between top dead centre and bottom dead centre rotatably drives the cam drum and thus imparts torque to the drive shaft, the combustion cycle of the engine being controlled 20 wherein the power stroke of any one piston sequentially precedes the power stroke of another piston which, of the pistons approaching top dead centre, is the most radially distant piston relative to said one piston, and thus the engine is relatively well balanced.

2. An internal combustion reciprocating engine as defined in claim 1 further comprising: a cam plate, having at least one cam lobe, *to* 'coaxially coupled to the cam drum; and each cylinder is provided with an intake valve and an exhaust valve so that, in use, the cam plate can be rotated by the cam drum in a predetermined direction and at a predetermined speed and said at least one cam lobe actuates the intake and/or the exhaust valves to subs-antially coincide with the combustion cycle of the engine. I p p-%ar ~LILI~P-C~-BsF I- 19

3. An internal combustion reciprocating engine as defined in claim 2 wherein the cam plate is provided with an intake lobe and an exhaust lobe designed to actuate the intake valve and the exhaust valve, respectively, of each cylinder.

4. An internal combustion reciprocating engine as defined in either claim 2 or 3 wherein the cam plate is coaxially coupled to the cam drum via a planetary gear set designed so that the cam plate is rotated in the predetermined direction and at the predetermined rotational speed.

An internal combustion reciprocating engine as defined in any one of the preceding claims wherein the predetermined profile of the endless cam is wave-shaped 15 including at least four ramps corresponding to a four .stroke combustion, exhaust, intake, and compression cycle, •..[.respectively, the ramp dedicated to the combustion stroke being shaped so that torque is maximised during this stroke of the cycle. 20

6. An internal combustion reciprocating engine as 999, defined in any one of the preceding claims wherein the profile of said endless cam is repeated about the .9 circumferential surface of the cail drum depending on the number of combustion cycles and thus power strokes required for each revolution of the cam drum.

7. An internal combustion reciprocating engine as defined in any one of the preceding claims comprising five pistons disposed in five cylinders, respectively, formed in said engine housing and equally spaced circumferentially about an axis of rotation of the cam drum.

8. An internal combustion reciprocating engine as defined in claim 7 wherein where each of the cylinders is ~sprg-- l I rrslrrarspqp 20 numbered one to five consecutively in a clockwise direction around the engine housing, and the firing order of the engine is one four two five and three such that the power stroke of any one piston sequentially precedes the power stroke of another piston which, of the pistons approaching top dead centre, is the most radially distant piston relative to said one piston, and thus the engine is relatively well balanced.

9. An internal combustion reciprocating engine as defined in either claim 7 or 8 wherein the cam plate has three intake lobes and three exhaust lobes, each of the intake and the exhaust lobes equally spaced circumferentially about an axis of rotation of the cam plate, the intake lobes radially spaced from the exhaust lobes so that, in use, the intake lobes actuate the intake valve of each cylinder and the exhaust lobes actuate the exhaust valve of each cylinder to coincide with the combustion cycle of the engine.

An internal combustion reciprocating engine as defined in claim 9 wherein the cam plate is rotated in an opposite direction and at substantially two thirds the rotational speed of the cam drum so that each of the intake valves and the exhaust valves are actuated by one of the intake lobes and the exhaust lobes, respectively, to "s 25 substantially coincide with the combustion cycle of the engine.

11. An internal combustion reciprocating engine !s defined in any one of claims 1 to 6 comprising eight pistons disposed in eight cylinders, respectively, formed in said engine housing and equally spaced circumferentially about an axis of rotation of the cam drum.

12. An internal combustion reciprocating engine as defined in claim 11 where each of the cylinders is numbered 1 21 one to eight consecutively in a clockwise direction around the engine housing, and the firing order of the engine is one six three eight five two seven and four such that the power stroke of any one piston sequentially precedes the power stroke of another piston which, of the pistons approaching top dead centre, is the most radially distant piston relative to said one piston, and thus the engine is well balanced.

13. An internal combustion reciprocating engine as defined in either claim 11 or 12 wherein the cam plate has three intake lobes and three exhaust lobes, each of the intake and the exhaust lobes equally spaced circumferentially about an axis of rotation of the cam plate, the intake lobes radially spaced from the exhaust lobes so that, in use, the intake lobes actuate the intake valve of each cylinder and the exhaust lobes actuate the exhaust valve of each cylinder to coincide with the combustion cycle of the engine.

14. An internal combustion reciprocating engine as defined in claim 13 wherein the cam plate is rotated in an opposite direction and at substantially one third the rotational speed of the cam drum so that each of the intake valves and the exhaust valves actuated by one of the intake 25 lobes and the exhaust lobes, respectively, to substantially coincide with the combustion cycle of the engine.

An internal combustion reciprocating engine as defined in any one of the preceding claims further comprising a plurality of thrust bearing means each connected to the engine housing and operatively cooperating with each of the plurality of con-rods whereby, in use, forces acting substantially tangential to said cam drum, between each of the plurality of con-rods and the endless cam, are transmitted to the engine housing by the thrust I- 22 bearing means, thereby reducing tangential forces transmitted through the plurality of con-rods to the plurality of pistons.

16. An internal combustion reciprocating engine as defined in claim 15 wherein each of the plurality of thrust bearing means consists of a rigid link extending tangential to the circumferential surface of the cam drum, said link at one end being pivotally coupled to one of the plurality of con-rods and at an opposite end being pivotally coupled to said engine housing.

17. An internal combustion reciprocating engine as defined in claim 15 wherein each of the plurality of thrust bearing means consists of a thrust block connected to the engine housing the thrust block having two opposing pairs of friction plates designed to operatively engage one of [.the plurality of con-rods and thus transmit the tangential forces to the engine housing through the opposing friction plates. o

18. An internal combustion reciprocating engine 20 substantially as herein described with reference to and as illustrated in the accompanying drawings. DATED THIS 5TH DAY OF JUNE 1996 oo BRUCE WELLER By His Patent Attorneys: 25 GRIFFITH HACK CO. Fellows Institute of Patent Attorneys of Australia. I ABSTRACT The present invention relates generally to an internal combustion reciprocating engine (10) comprising a drive shaft (12) coaxially connected to a cam drum and an engine housing (16) having five cylinders (18) equally spaced circumferentially about the drive shaft A cam plate (22) is coaxially coupled to the cam drum'(14) via a planetary gear set Each cylinder (18) houses a piston (26) which is connected to one end of a con rod The con rod at an opposite end has a pair of spaced apart tapered rollers (32) designed to engage an endless cam (34) extending around a circumferential surface of the cam drum In operation, the pistons (26) reciprocate between top dead centre and bottom dead centre and thus the 15 corresponding con rod (28) drives the pair of tapered rollers (32) up and down in a direction parallel to the axis of rotation of the drive shaft The rollers (32) bear on the endless cam (34) and thus force the cam drum (14) and the drive shaft (12) to rotate. In one example, 20 the combustion stroke or power stroke is performed in the following order (where each of the cylinders is numbered 1 to 5 consecutively): 1, 4, 2, 5, and 3. In this way the power stroke formed by one piston (26A) precedes the power stroke of another piston (26D) which, of the pistons (26B or 26D) approaching top dead centre, is the most radially distant (26D) relative to piston (26A). The force exerted on the engine (10) by the power stroke of piston (26) is thus substantially compensated by the force exerted by another piston (26) and the engine is relatively well balanced. Preferably, the cam is shaped so that torque to the drive shaft is maximised during the combustion stroke of the engine, the cam having a relatively steep slope during this stage of the combustion cycle.