GB2482565A

GB2482565A - Crankless barrel-type internal combustion engine

Info

Publication number: GB2482565A
Application number: GB1013336.1A
Authority: GB
Inventors: William Fairney
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-08-07
Filing date: 2010-08-07
Publication date: 2012-02-08
Anticipated expiration: 2030-08-07
Also published as: GB201013336D0; GB2482565B

Abstract

An axial barrel-type spark-ignition or compression-ignition internal combustion engine may have at least two cylinders each containing two opposed pistons 13 with their heads facing each other. The piston rods may be coupled to the drive shaft 11 of the engine by opposed cams 12 each having a sinusoidal or non-sinusoidal profile. All the cylinders may be arranged on one side of the cam or in co-linear pairs on opposite sides of the cam. The engine may have roller bearings to support the piston side-loads. Modular cylinder assemblies may be arranged to be removable without excessive dismantling of the engine. Split cams may be used to enable removal without excessive dismantling of the engine. Sections of the engine casing may be removable to assist access.

Description

INTERNAL COMBUSTION ENGINE

This invention relates to an internal combustion (LC.) engine.

Background

Diesel engines have several advantages over carburetted petrol engines.

Spark-distributors, magnetos or sparking plugs are a source of unreliability in petrol engines. The higher specific energy content of diesel fuel means that a greater endurance can be experienced with a full fuel tank. Also, the higher combustion temperature and pressure of the diesel engine results in a higher efficiency, hence lower fuel cost and environmental impact.

This invention relates to an opposed-piston spark-ignition or compression-ignition diesel engine of the barrel type wherein the cylinders lie parallel to and concentric with the drive shaft and the drive from the pistons to the drive shaft are by means shaped cams.

In a conventional internal combustion engine with the cylinders arranged in-line or in a V-formation or in a radialy distributed arrangement, the combustion forces impose high levels of stress on the crankcase. These forces can be alleviated by matching the weights of the reciprocating masses such as pistons and connecting rods so that the inertia forces arising from the acceleration of these masses partly offsets the combustion forces. In such engines the offset of the crankshaft is usually small in relation to the stroke of the piston with the result that the mechanical advantage is low and the side-forces exerted on the pistons are moderate..

This factor also applies to an opposed piston engine having crankshafts.

Referring firstly to Figure 1, a Jumo-type diesel engine is diagrammatically illustrated. Manufactured by the German Junkers company during the 1930s and 1940s, the Jumo diesel engine was a two-stroke aero internal combustion engine with two opposed pistons per cylinder. The pistons came together in the centre of the cylinder at Top-Dead-Centre (TDC), 1, for fuel injection and combustion, and were furthest apart at Bottom-Dead-Centre (BDC), 2, for exhaust gas removal and fresh air charging of the cylinders. Each piston drove a crankshaft at opposite ends of the engine, 3 and 4. The two crankshafts were linked by a gear-train 5 to drive a single propeller shaft 6. The major advantages of the design were:- 1) The combustion forces acted equally on both pistons in opposite directions and the pistons moved with equal but opposite accelerations dunng the power stroke thereby eliminating the majority of unbalance forces. Because the piston stroke is long compared to the throw of the crankshaft the piston side-forces are moderate.

2) The air inlet 7 and exhaust gas exit 8 were effected through ports in the extremities of the cylinders which were uncovered as the pistons reached the end of the power stroke. Thus conventional poppet inlet and exhaust valves and their associated rocker-arm and tappet assemblies with the associated lubrication, wear and maintenance, were eliminated. Further advantage was gained from the fact that the inlet air was supplied under pressure from a shaft-driven or exhaust gas-driven turbo-charger, thus facilitating scavenging of exhaust gases.

Sections (a) to (f) of Figure 1 show the cylinder and pistons at different parts of the cycle.

The placing of the in let and exhaust ports was such that as the power stroke ended, the exhaust port opened first, allowing exhaust gases to rush out. (a). As the cylinder pressure fell to near atmospheric pressure, the inlet port opened, admitting air at turbo-charger pressure, to scavenge the cylinder of remaining exhaust gases, (b). After the pistons 13 reached Bottom-Dead-Centre (BDC), on the return stroke, the inlet port 7closed first, then the exhaust port 8, and the air was compressed to high pressure, (c, d). As the pistons 13 approached Top-Dead-Centre (TOC), (e), fuel was injected at high pressure into the space between the pistons and ignited spontaneously, causing the pistons to be driven back again with great force, to drive the crank-shafts, (f).

The Jumo design was produced with six cylinders in-line, to produce very smooth running, but it had three disadvantages; 1, The gear trains to the propeller shaft were expensive, caused transmission losses, wear and added weight.

2 In poppet valve diesel engines the valve opening and closing times can be altered by the shape of the cams which drive them, and the exhaust valve can be closed before the inlet valve, allowing gas at turbo-charger pressure to fill the cylinder before cutting off the inlet gases, thus enabling a concentrated charge of air, which can sustain a larger fuel charge and hence higher power output per stroke. In the Jumo engine the inlet port closes first, so the inlet cylinder pressure is close to atmospheric pressure, and power output per stroke is lower.

3, Whilst the piston acceleration forces of the opposed pistons are balanced, the forces acting on the pistons due to combustion are transferred via the crankshafts to the engine crankcase and as they act in opposite directions they require a very strong construction.

Figure 2 diagrammatically illustrates another known internal combustion engine, the barrel engine, in which the cylinders 10 lie parallel to the drive shaft 11 and impart rotary motion to the shaft 11 by means of an angled cam 12 mounted on it. The angle of slant of the cam 12 is such that the distance between the extremes of the face of the cam 12 as it rotates, is equal to the stroke of the piston 13. The position of the axial face of the cam 12 varies sinusoidaly or non-sin usoidaly with the shaft angle. The ends of the pistons 13 push against the angled face of the cam 12, causing it to rotate. Because the stroke of the piston drives the cam through a complete 180 degrees the mechanical advantage is high, and the side-forces on the pistons are high. This has proved to be a serious factor in the operation of such engines, resulting in high wear rates and breakdown of the lubricating oil film between the pistons and the cylinders. Such engines have been made in petrol-ignition or diesel form, with Iwo or four strokes to the firing cycle.

In the petrol-ignition manifestation barrel engines have been built with pistons at one end as in Figure 2, or both ends such as is illustrated in Figure 3.

The inlet and exhaust gases enter and leave via conventional poppet valves 14 in the cylinder head 15. The design has the advantage of a small frontal area, which is attractive for aero-engine, low-deck omnibus and marine applications. It also has the advantage of the fact that the drive is direct to the shaft 11, without gearing, and that a plain cylindrical shaft 11 is used, without expensive cranks. There are no connecting rods or big or little-end bearings, although there are bearing surfaces 13a required between the end of the pistons 13 and the cam 12. The pistons 13 engage with the cam 12 with ball-ended sockets, or with a shoe, or with roller bearings 26 as shown in Figure 6.

In addition the cam 12 does impart side forces to the pistons 13, and does require complex machining during manufacture. In practice the cam may have two or more cycles of axial variation per revolution as illustrated in Figures 4 and 6, in which case there may be two or more firing strokes per revolution of the shaft 11.

This design has the advantage in that the number of moving parts is kept to a minimum and provides improved reliability over internal combustion engines fitted with poppet valves and the associated camshafts, push-rods and rocker arms.

As diagrammatically shown in Figure 5 several cylinders 10 may also be arranged in a barrel arrangement around the shaft 11, rather like the chambers of a revolver firearm.

According to another existing invention (Reference 1, Redrup and Redrup, March 1955) there is provided an internal combustion engine comprising at least two cylinders each with two opposed pistons therein, with piston heads of the pistons facing each other, piston rods of the pistons being coupled to a drive shaft of the engine through two opposed cams. The two opposed cams have sinusoidal cam profiles. And therefore the performance is similar to the earher Jumo engine, except that the forces on the cams due to combustion and the piston inertia forces are equal and opposite and cancel out. Thus a lightweight casing can be used, but the drive shaft must be dimensioned to carry these axial forces.

According to another existing invention (Reference 2, Renegar, October 1979) there is provided an internal combustion engine comprising at least two cylinders each with Iwo opposed pistons therein, with piston heads of the pistons facing each other, piston rods of the pistons being coupled to a drive shaft of the engine through two opposed cams. The two opposed cams have preferably non-sinusoidal cam profiles. The two opposed cams also preferably have different profiles near the bottom dead centre position to optimize inlet and exhaust gas flow. Furthermore the cams can be shaped to hold the pistons at or near the Top-Dead-Centre position for sufficient time to enable combustion to be completed at constant volume thereby improving the thermal efficiency of the engine by making the engine operate on the well-known Otto Cycle of the conventional internal combustion engine instead of the usual constant pressure cycle of a diesel engine. Engines of these types of arrangement may be made to operate on a two or four-stroke thermodynamic cycle.

This previous invention (Renegar) also has the advantage that the cams may be shaped so that the inlet and exhaust ports may be opened and closed at different times to enable the combustion cycle to be optimized, thereby ensuring that a higher thermal efficiency may be achieved than that by conventional sinusoidal profiles. However this and other previous inventions have two disadvantages.

One disadvantage of this type of barrel engine is the piston side-forces already referred to. Some prior art inventions sought to relieve these side-forces by attaching the pistons to slide rails or other compensating mechanisms. Whilst these arrangements de-coupled the high temperature duty of the pistons from the side-force supports, they retained the disadvantage of a high-friction sliding contact.

A further disadvantage of this type of engine is the difficulty of access to the engine internal mechanism for maintenance or repair purposes. With conventional in-line or V' or radial cylinder arrangements individual cylinder heads can be removed. In many designs the whole cylinder can be removed to give access to pistons, connecting rods and bearings. In previous manifestations of the barrel-type engine this has not been possible, except for small access hatches for minor maintenance. To access individual pistons or cylinders it was necessary to remove the engine from its fixing points and to dismantle it.

Statement of Invention

The present invention solves these two problems by using roller bearings to contain the piston side-forces, and by using a modular cartridge' approach whereby each cylinder plus pistons plus inlet and outlet ducts are individually attached to the engine casing by means of simple fixings and are individually rempvable.

Detailed Description

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to Figures 2, 3 and 6 to 15 of the accompanying drawings, in which: -Figures 2, 3 and 6 are diagrammatic illustrations of the generic types of engine to which the invention may be applied.

Figure 7 is a diagrammatic illustration showing a cross-section of one cylinder and cylinder liner and pistons and inlet duct and outlet duct assembly typical of the manifestation of the engine as shown in Figure 6.

Figure 8 is a diagrammatic illustration of an exploded view of the cylinder assembly shown in cross-section in Figure 7.

Figure 9 is a diagrammatic illustration of the engine inner casing which supports the cylinder assemblies shown in Figures 7 and 8.

Figure 10 shows a diagrammatic illustration of the end view of the inner engine casing shown in Figure 9.

Figure 11 shows three diagrammatic illustrations of successive stages of assembly of the engine.

Figure 12 shows diagrammatic illustrations of a cut-away section of the engine together with views of the central drive shaft and one cam.

Figure 13 shows diagrammatic illustrations of a cam split into two parts and joined together with mechanical fixtures and mounted on a splined shaft.

Figure 14 shows roller bearing assemblies for the location of pistons in the cylinder liners and to relieve side loads therefrom.

Figure 15 shows alternative configurations of roller bearings and the means of their operation.

Referring to Figures 7 and 8 which show one modular cylinder assembly of one manifestation of the engine shown in Figure 6, 21 is the inner cylinder liner of the assembly, 22 is the outer casing of the individual cylinder assembly, 23 are the end-liners of the cylinder assembly. 25 are the end caps of the cylinder and 25a are oil injection tubes. 26 are the cam rollers within the pistonsl3. 19 is the inlet air duct and 20 is the exhaust duct. 21 a is the location holder for the spark plug in the case of a spark-ignition engine or the fuel injector in the case of a diesel engine.

are water or other fluid cooling ducts in the case of a liquid-cooled engine. 29 are optional piston support bearings and 24 are recesses in the outer casing 22 into which the piston support bearings 29 seat. 13b are piston-sealing and oil-control rings. 27 are slots in the outer casing 22 into which locating spigots 31 attached to the pistons 13 may slide. 28 is the assembled cylinder module.

According to the present invention the assembly is created by first pressing the inner cylinder liner 21 into the outer casing 22 until it is located in place axially by the spark plug or fuel injector socket 21 a. Optional piston support bearings 29 are then pressed into place in the recesses 24.

The end-liners 23 are then pressed into place to abut their respective piston support bearings 29.

The pistons 13 complete with their cam rollers 26 and piston-sealing and oil-control rings I 3b are then each fitted axially through their respective end-liners 23, the piston support bearings 29 and into the inner cylinder liner 21. The locating spigots 31 are then attached to the pistons 13 through the slots 27.

The cylinder end caps 25 complete with their respective oil injector tubes 25a are then secured to the ends of the cylinder. The oil injector tubes 25a engage with holes in the pistons and conduct oil to lubrication passages (not shown) feeding oil to the rollers 26.

Referring to Figure 9 and Figure 10 there is in the construction of the present invention a strong engine inner casing 32 comprising end-plates 33 and inner-plates 34 held together by cross beams 35 and 35a. Cross beams 35 are located between the inner-plates 34. The cross beams 35a are located between the end-plates 33 and the inner-plates 34 at a diameter sufficient to allow the cams to fit between these plates. The components 33 and 34 and 35 and 35a are securely fixed together by means of welding and/or through bolts 36 or by other means to ensure a rigid structure of the inner-casing 32.

The end-plates 33 and inner-plates 34 have cut-outs 37 which closely engage the modular cylinder assemblies such as 28. The cross beams 35 and 35a are machined to fit the circular cross-section of the cylinder modules 28.

The cylinder modules 28 are held in place by shaped clamps 38 which are a tight fit into the end-plates and inner-plates 33 and 34. They are held in place by screws or similar fixings 39. The shaped clamps 38 and the end-plates and inner-plates 33 and 34 have machined grooves 40 and are fitted wIth 0' rings of a conformable material 41 to effect a seal between the outside surfaces of the inner engine casing 32 and its inner surfaces. Similarly the curved faces of the cross beams 35 and 35a have axial grooves which contain conformable material 42 to likewise effect a seal between the cylinder modules 28 and the inner and outer surfaces of the inner engine casing 32.

Referring to Figure 11, Figure 1 1A shows a diagrammatic illustration of the fully-assembled cylinder modules 28 onto the inner engine casing 32. Figure 11 B shows the inner casing with outer casing panels 43 fitted. These outer casing panels 43 have holes for the inlet air ducts 19 and exhaust ducts 20 and spark plug or fuel injector holders 21 and also for water-cooling lines and oil supply tines (not shown).

Figure 11 C shows the engine fitted with segmented inlet and exhaust ducts 44a, 44b, etc and 45a, 45b etc respectively and with ignition harness in the case of a spark-ignition engine or fuel tines in the case of a compression-ignition engine 46.

It will be appreciated that this segmented arrangement of the engine casings and cylinder modules and auxiliary pipework will enable access to the individual cylinder modules to be effected without the need to totally dismantle the engine and that this is a significant advantage over the prior art of axial barrel engines.

Referring to Figure 12 Figure 1 2A shows a cut-away section of one manifestation of the engine shown illustratively in Figure 6. The engine casing is divided into three sections by the inner-plates 34 comprising a central section 47 and two cam chamber sections 48 containing the cams 12. The sections are separated by the inner-plates 35a and the sealing 0' rings 41 around the cylinder modules 28 and the conformable material 42 between the cylinder modules 28 and the cross beams 35 and 35a as described in Figure 10. The drive shaft 11 is supported on typically four roller or ball or spherical roller bearings 17 or a combination of these types (not shown) mounted in the inner-plates and the end-plates. A thrust bearing 49 is typically installed in one of the end-plates.

Figure 1 2B shows an end view if the inner engine casing with the outline of the installed cams 12 which are mounted on the drive shaft 11. The cam chambers 48 are enclosed by the cylinder modules 28 and the cross beams 35a.

According to one version of the present invention shown in Figure 12C there is a means to enable the cams 12 to be installed or replaced in the cam chambers 48. One or more of the cross beams 35a are removable and are located onto the end-plates and inner-plates by means of fitted high-tensile bolts, screws or other such secure fixing 50. This feature of the present invention requires the drive shaft 11 to be withdrawn axially which in most manifestations of the barrel type of engine requires considerable dismantling of the engine.

According to an alternative version of the present invention Figure 13 shows one of the cams 12 which is composed of two not necessarily but preferably identical halves which are joined together by fitted bolts and nuts 51 and 52 respectively through attached lugs 53. According to the present invention the cams 12 can be accessed by removal of a number of the modular cylinder assemblies 28 and a small number of the cross beams 35a without the need to remove the drive shaft 11. The cams 12 are mounted preferably but not necessarily on splines 54 on the shaft 11 which engage with sphnes 55 on the cams 12. The cams sit between faces 56 and 57 of the drive shaft 11 which cany any axial thrust from the cams 12. According to the present invention the cut between the two halves of each cam is made at or near the bottom dead centre position of the cam profile at a point where the axial force on the cam is low or zero thereby avoiding any excess wear on the cam faces 58 where the two halves join.

According to the present invention and refemng to Figure 14 there are roller bearing assemblies 29 fitted into the cylinder modules 28 whose dimensions are such as to carry the side thrust loads transferred to the pistons 13 via cam rollers 26 as depicted in Figure 14A. The roller bearing assemblies 29 consist of a cylindrical housing 59 containing bearing rollers 60 which are of a part-cylindrical cross-section having a radius of curvature 61 equal to the radius of the pistons 13.

as shown in 14B. The bearing rollers are mounted to freely rotate on spindles 62 which are a tight fit in the housing 59. The rollers may be located in a variety of numbers and orientations as shown in 14C and 14D and 14E. In the present application of the invention the side loads from the pistons 13 are exerted tangentially to the axis of the engine and so the bearing rollers 60 are preferably orientated to provide maximum support to the pistons 13. There are also radial loads on the pistons arising from mis-alignment and dimensional tolerance errors in the engine construction so an arrangement such as those shown in Figures 140 or 1 4E is preferred. To carry the loads from the pistons 13 to the cylinder modules 28 and to ensure accurate alignment of the pistons 13 in the inner cylinder liners 21 and the end-liners 23 it will be appreciated that two or more roller bearing assemblies 29 are required as shown in Figures 7 and 14. To ensure accurate location of the roller bearing assemblies 29 in the cylinder modules 28 they may be installed with a shrink fit thereby ensuring a compressive stress in the material of the said roller bearings and furthermore they may be located by a dowel or dowels 63 to prevent movement.

According to the present invention and with reference to Figure 15 there is an optimum design for roller bearings as described in accordance with Figure 14.

In Figure 1 5A, 64 is the radius r of the bearing roller 60 at the narrowest section and 65 is the radius R at the ends of the bearing roller 60. The bearing roller 60 rotates at an angular velocity wand the velocity of the surface of the roller at the narrowest section is therefore wx r.

Similarly the velocity of the ends of the bearing roller 45 is wx R. As the piston 13 at any instant is travelling at the same axial velocity at all points around its periphery there must be some slippage between the bearing roller 60 and the piston 13.

The degree of this slippage is determined by the ratio R/r and the degree of slippage is minimised with a lower value of this ratio. Figure 15B shows one implementation of a roller bearing having two slim rollers with a high RIr ratio..

Figure 1 5C shows a comparison of the roller bearing assembty of Figure 1 5B and another implementation of the same configuration but having fatter rollers with a lower R/r ratio. The dimension t, 50 in Figure 1 5C determines the strength of the roller bearing assembly 29 and to make this the same for both implementations shown in Figure 1 5C it is necessary to increase the overall dimension of the roller bearing assembly 29. The overall diameter of the roller bearing assembly 29 can be maintained at a smaller value by reducing the length of the bearing rollers 60 and using more of them as shown in Figures 15D and 15E. The choice of roller length and width will depend on the particular engine configuration. By the means described with reference to Figures 14 and 14 an optimum configuration may be achieved.

It will be appreciated that the present construction has considerably fewer moving parts than a conventional petrol engine, previous cam engines or the Jumo diesel engine. This makes for easier construction, improved reliability, lower weight and lower maintenance costs.

It will be appreciated that the present construction is intended to provide an engine with high performance, greater economy and a reduced number of moving parts with a consequential reduced cost and weight and potential high reliability It will be appreciated that the combination of the two opposed-pistons per cylinder, two-stroke diesel design with the cam-driven barrel-engine design to minimize moving parts, should reduce cost and weight and improve efficiency.

It will be appreciated that the use of non-sinusoidal cam profiles can optimize cylinder charging, combustion, and power per firing stroke.

It will be appreciated that the use of multiple cam profiles around the cam periphery can optimize the number of firing strokes and engine revolutions and improve engine balance particularly but not exclusively for aero engine or marine engine applications.

It will be appreciated that the use of a modular assembly of cylinder components can assist engine access and maintenance.

It will be appreciated that the use of a fabricated engine casing to which cylinder modules can be attached without the need for major engine dis-assembly can assist engine access and maintenance.

It will be appreciated that by the use of split cams in an axial barrel type engine cam maintenance and replacement can be achieved without the need to undertake major engine dis-assembly.

It will be appreciated that the use of roller bearing assemblies to locate the pistons in the cylinder modules will ensure accurate alignment and remove side loads from the cylinder liner walls thereby reducing friction.

It will be appreciated that any of the above advantages can be applied to engines of the configurations shown in Figures 2, 4 and 6 and that they can be achieved with internal combustion engines of the spark-ignition or compression -ignition type.

References (1) UK Patent No. 726,64; Redrup and Redrup, March 1955.

(2) UK Patent No. 2,019,487; Renegar, October 1979.

Claims

CLAIMS1. An internal combustion engine comprising at least two cylinders each with two opposed pistons therein, with piston heads of the pistons facing each other, piston rods of the pistons being coupled to a drive shaft of the engine through two opposed cams, each cam having a sinusoidal profile.
2. An internal combustion engine comprising at least two cylinders each with two opposed pistons therein, with piston heads of the pistons facing each other, piston rods of the pistons being coupled to a drive shaft of the engine through two opposed cams, each cam having a non-sinusoidal profile and the two opposing cams having different profiles to optimise the inlet and exhaust gas flow.
3. An internal combustion engine comprising at least two cylinders each with a piston therein, piston rods of the pistons being coupled to a drive shaft of the engine through a cam having a sinusoidal profile and the cylinders all being on one side of the cam.
4. An internal combustion engine comprising at least two cylinders each with a piston therein, piston rods of the pistons being coupled to a drive shaft of the engine through a cam having a non-sinusoidal profile and the cylinders all being on one side of the cam.
5. An internal combustion engine comprising at least two cylinders each with a piston therein, piston rods of the pistons being coupled to a drive shaft of the engine through a cam having a sinusoidal profile and the cylinders being arranged in co-linear pairs on opposite sides of the cam.
6. An internal combustion engine comprising at least two cylinders each with a piston therein, piston rods of the pistons being coupled to a drive shaft of the engine through a cam having a non-sinusoidal profile and the cylinders being arranged in co-linear pairs on opposite sides of the cam.
7. An engine according to any one of the preceding claims wherein the bearing surfaces between each of the pistons and the cylinder walls and of the cam or cams and their associated pistons are cooled and lubricated by channels in each piston which direct oil onto the bearing faces of the cylinders, cams and pistons.
8. An engine according to any one of the preceding claims, and having multiples of two cylinders and associated pistons and cams.
9. An engine according to any one of the preceding claims wherein the cylinders are arranged in a barrel formation around the drive shaft.
10. An engine according to any one of the preceding claims and being a two-stroke engine.
11. An engine according to any one of the preceding claims and being a four-stroke engine.
12. An engine according to any one of the preceding claims and being a diesel engine.
13. An engine according to any one of the preceding claims and being a spark-ignition engine.
14. An engine according to any one of the preceding claims and having modular cylinder assemblies containing cylinder liners and water cooling channels and lubricating oil channels and pistons.
15. An engine according to any one of the preceding claims and having modular cylinder assemblies containing piston roller bearing assemblies.
16. An engine according to any one of the preceding claims and having an engine frame with cut-away sections to accommodate modular cylinder assemblies as described in Claims 14 and 15.
17. An engine according to any one of the preceding claims and having removable engine frame sections to provide access to and/or removal of the cam or cams.
18. An engine according to any one of the preceding claims and having cam or cams which are divided into two or more sections to assist ease of removal in accordance with Claim 17.
19. An engine according to any one of the preceding claims and having roller bearing assemblies to support the pistons and carry side loads.
20. An engine according to Claim 19 and having roller bearings whose wherein the rollers have a cross-section conforming to the piston cross-section.
21. An internal combustion engine, substantially as hereinbefore described, with reference to Figures 6 to 15 of the accompanying drawings.Amendments to the claims have been filed as follows:CLAIMS1. An internal combustion engine of the barrel-engine type in which the cylinders comprise two or more removable modular assemblies which lie parallel to the drive shaft and contain one or more pistons incorporating driving rollers or other means of imparting rotary motion to a cam or cams having sinusoidal or non-sinusoidal profiles comprised of one or more sections which are mounted on the drive shaft and impart rotary motion thereto.2. An engine according Claim I and having an engine frame with cut-away sections and clamps or other means of fixing to facilitate the easy assembly and disassembly of the modular cylinder assemblies.3. An engine according to any one of the preceding claims and having a cam or cams which are divided into two or more sections which are held rigidly together by removable clamps or other means of fixing to assist ease of removal of the cam sections.4. An engine according to any one of the preceding claims and having removable engine frame sections to provide access to the cam or cams to facilitate the removal of the cam or cams.5. An engine according to any one of the preceding claims, and having multiples of two cylinders and associated pistons and cams.6. An engine according to any one of the preceding claims and being a two-stroke engine.:4' An engine according to any one of the preceding claims and being a four-stroke engine.S*S*S..* 8. An engine according to any one of the preceding claims and being a diesel engine. S. * .* 9. An engine according to any one of the preceding claims and being a spark-ignition engine. * S.:.: *10 An internal combustion engine, substantially as hereinbefore described, with reference to :.:Figures 6 to 13 of the accompanying drawings.