GB2183730A

GB2183730A - Charging internal combustion reciprocating piston engine

Info

Publication number: GB2183730A
Application number: GB08625750A
Authority: GB
Inventors: Gordon Philip Hobday
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-11-26
Filing date: 1986-10-28
Publication date: 1987-06-10
Also published as: GB8625750D0; GB8529102D0

Abstract

A first piston 11 in a cylinder 10 compresses air admitted through a valve 16, a combustion chamber 12 receives the compressed air through a valve 17 and fuel from an injector 21 and a second piston 14 is driven in a cylinder 13 by expansion of the products of combustion supplied from the combustion chamber 12 through a valve 18, the exhaust gas passing out through a valve 20. The combustion chamber 12 may be provided in a slide valve 25 (Fig 4). The pistons 11, 14 may be connected to a common crankpin on a crankshaft 28 whose axis lies between the axes of the cylinders 10 and 13 (Figure 5). <IMAGE>

Description

SPECIFICATION Internal combustion reciprocating piston engine This invention relates to an internal combustion reciprocating piston engine and particularly to a compression ignition engine.

According to the present invention there is provided an internal combustion reciprocating piston engine comprising a first piston and cylinder for compressing gas admitted thereto, a combustion chamber for receiving gas compressed in said first piston and cylinder, meansforsupplying fuel to said combustion chamberfor combustion therein, a second piston and cylinderfor receiving the products of combustion from the combustion chamber and in which said products are expanded, and valve meansfor controlling theflow of gases into and out ofthe cylinders and the combustion chamber.

Preferably the piston of said first piston and cylinder is arranged to reach its top dead centre position in advance of the piston ofthesecond piston and cylinder.

The diameter of the second piston and cylinder is preferably largerthan that ofthe first piston and cylinder.

Some embodiments ofthe invention will now be described, by way of examples, with reference to the accompanying drawings, in which Figure 1 is a diagrammatic illustration of a first embodiment of an internal combustion engine according to the present invention, Figure2is a diagram showingtheopening and closing ofthevalves relativetothe position ofthe crankshaft angle, Figure3 illustrates diagrammatically one form of valve means, Figure 4illustrates diagrammatically a slide valve constituting the valve means, and FigureS illustrates one particular arrangement of the two pistons and cylinders connected to a common crankpin.

The internal combustion reciprocating piston engine consists of a first cylinder 10 in which is reciprocated a piston 11,a combustion chamber 12 and a second cylinder 13 in which is reciprocated a piston 14. Air is admitted to the cylinder 10 from an air intake duct 1 via a valve 16 and the cylinder 10 communicates with the combustion chamber 12 via a valve 17. The combustion chamber 12 communicates with the cylinder 13via a valve 18and the cylinder 13 communicates with an exhaust duct 19via avalve20.

The internal combustion engine may be provided with a plurality of pairs ofcylinders 10 and 13.

The combustion chamber 12 is provided with a fuel injector 21.

Figure 2 shows the opening and closing ofthe valves 16, 17, 18, 20 relative to the position of crankshaft angle. At the starting point 00 the piston 14 is at top dead centre.

During operation of the engine air is drawn into the cylinder 10thorough the open valve 16, with the valve 17 closed, as the piston 11 moves downwardly towards its bottom dead centre position. On the piston 11 reaching BDC the valve 16 is closed.

Upward movement of the piston 11 then compresses the change of air in the cylinder 10. The valve 17 is opened when the engine crankshaft has rotated 1800to allow the compressed airtoflow into the combustion chamber 12 and the valve 17 remains open until the piston 11 reaches its top dead centre position. The valve 18 is closed atthistime.

When the valves 17 and 18 are closed fuel is injected into the combustion chamber 12 bythe injector 21 and combustion takes place in the combustion chamber 12. The valve 18 is opened when the crankshaft has rotated 360" at which time the piston 14 is atTDC and the products of combustion are admitted into the cylinder 13. The piston 14 is driven down the cylinder 13 by the expanding gases, the valve 20 being closed at this time. When the piston 14 reaches its bottom dead centre position the valve 20 is opened so that the expanded gases are passed to the exhaust duct 19 as the piston 14 rises towards its top dead centre position. The opening and closing of the valves 16,17,18,20 relativetothecrankshaft angle and the position ofthe pistons 11 and 14is shown in figure 2.

Preferably the diameter of the cylinder 13 and piston 14 is greaterthan that of the cylinder 10 and piston 11.

The pistons 11 and 14 do not reach their top dead centre position at the same time. Piston 11 is in advance of piston 14. The amount of advance can be chosen to suit the particular application of use of the engine. This angle of advance is shown at 'A' in Figure 2. The timing of the fuel injection will depend upon the design and will be controlled in accordance with the desired engine speed.

The angle of advance 'A' allowsforignition and combustion time. It may be possible to have an angle of ignition advance greaterthan that of a conventional internal combustion piston engine and this is desirable to give a more complete combustion before admitting the products of combustion into the cylinder 13, buttheir is a limitation on the size of the angle. Valve 17 must remain closed until the power stroke isfinished and can only be openforthetime between the end of the power stroke of piston 14 and the end of the compression stroke of piston 11, that is 1800-A0.Thistime cannot betoo small and thusA cannotbetoo large.

With the present invention the hot gases are expanded in the cylinder 13 having a largervolume than the cylinder 10 in which compression takes place and therefore they can be expanded almost to atmospheric pressure and the whole of the energy released on expansion of the gases acts on the piston 1 4thus giving good thermal efficiency and a quieter exhaust compared with conventional internal combustion reciprocating piston engines. Ignition can be timed to be before the top dead centre position of the piston 14without having to be before the top dead centre position ofthe compression piston 11. This has the advantage that the normal loss in power of conventional engines caused by back pressure due to ignition before top dead centre is eliminated and smoother operation results withoutthe "knock" of conventional compression ignition engines.

In conventional engines a slight loss of power at the end ofthe power stroke is tolerated in orderto achieve better scavenging of the gases when the exhaust valve is opened before bottom dead centre ofthe piston. This is unnecessary with an engine according to the present invention.

It is possible to advance the ignition furtherthan can be done in conventional engines so as to give a longer combustion time resulting in more complete combustion, a higherfuel efficiency and less pollution oftheatmosphere.

The engine according to the preset invention is a two cylinder basicunit having a powerstrokefor each revolution of the crankshaft and therefore is comparable with a two cylinderfour stroke engine of conventional design.

As each valve 16,17, 18 and 20 operates once each revolution of the crankshaftthere is no need fora separate camshaft. The cams operating the valves can be directly on the crankshaft. This will reduce the cost of the engine, give fewer working parts, produce less friction and less mechanical noise.

The inletand outlet manifolds or ducts 15 and 19 can be simple in design as only one inlet and one outletduct is required for a two cylinder unit. Only one fuel injector is required for two cylinders and the fuel injector pump can besimple.

Thevalves 17 and 18 may have valve stemswhich pass through the combustion chamber 12 and as shown in Figure 3 they may be provided with piston ring type seals 22 and be acted upon by springs 23, the stems having recesses 24 which can be contacted by forks provided on push rods. The valve stem may be hollow and cooled by oil flowing into the valve stems.

Alternatively, as shown in Figure 4, the valve means may consist of a slide valve member 25 which incorporates the combustion chamber 12, the cylinder 10 having a port 26 and the cylinder 13 having a port 27 which are controlled by the slide valve member25. Asimple lever system may be provided to drive the slide valve 25. Also, a simple injection pump may be driven from the same lever system.

The cylinders 10 and 13 may be disposed in-line one behind the other or they may be disposed side-by-side. When the cylinders 10 and 13 are disposed side-by-side the sideways force produced by the power piston 14 and the friction and wear produced by such force can be reduced if the axis of rotation ofthe crankshaft 28 is offset, as shown in Figure 5, so that during the power stroke ofthe piston 14the connecting rod 29 is nearly in line with the axis ofthe cylinder 13. As shown in Figure Sthe cylinders 11 and 14 are arranged in a V-shape and the connecting rods 29 and 30 are connected to the same crankpin which gives the required angle of advance, i.e. the angle of advance is the angle between the arms ofthe V-shape.

In a conventional V-engine the cylinder heads are far apart and if a narrow V-shape is chosen to bring the cylinder heads close togetherthen very long connecting rods are required if the axis ofthe crankshaft is located at the intersection of the axes of the cylinders. However with the design shown in Figure 5 shortening ofthe connecting rods and a reduction ofthe side loading on both pistons is achieved by offsetting the axes of the crankshaft 28 from the axes ofthe cylinders 11 and 14to a point withintheV-shapeformed bythe axes ofthe cylinders.

Claims

1. An internal combustion reciprocating piston engine comprising a first piston and cylinderfor compressing gas admitted thereto, a combustion chamber for receiving gas compressed in said first piston and cylinder, means for supplying fuel to said combustion chamberfor combustion therein, a second piston and cylinderfor receiving the products of combustion from the combustion chamber and in which the products are expanded, and valve means for controlling the flow of gases into and out of the cylinders and combustion chamber.

2. An internal combustion engine as claimed in claim 1, in which the piston of the first piston and cylinder is arranged to reach its top dead centre position in advance of the piston ofthe second piston and cylinder.

3. An internal combustion engine as claimed in claim 1 orclaim 2, in which the diameter ofthe second piston and cylinder is larger than that ofthe first piston and cylinder.

4. An internal combustion engine as claimed in any preceding claim in which said valve means comprise spring loaded valves having stems connected to push rods.

5. An internal combustion engine as claimed in any one of claims 1 to 3, in which said valve means comprises a slide valve in which said combustion chamber isformed.

6. An internal combustion engine as claimed in any preceding claim, in which the cylinders are disposed side-by-side in a V-shaped arrangement.

7. An internal combustion engine as claimed in claim 6, in which the connecting rods of both pistons are connected to a common crankpin.

8. An internal combustion engine as claimed in claim 6 or claim 7, in which the axis ofthecrankshaft is offset from the axes of the cylinders to a point within theV-shapeformed by the axes ofthe cylinders.

9. An internal combustion engine as claimed in any one of claims 1 to 5, in which the cylinders are disposed in-line one behind the other.

10. An internal combustion reciprocating piston engine substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.