GB1579373A

GB1579373A - Internal combustion engine

Info

Publication number: GB1579373A
Application number: GB1399977A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-04-02
Filing date: 1977-04-02
Publication date: 1980-11-19

Description

(54) AN INTERNAL COMBUSTION ENGINE (71) I, AUGUSTE MOIROUX, a French Citizen of 28 route de Dardilly, Ecully (Rhone) France, do hereby declare the invention, for which I pray that a Patent may be granted to me, and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to an internal combustion engine.

In an internal combustion engine, it is known that the volume of the combustion chamber at top dead centre is defined by the position of the piston. During combustion, the pressure attained in the combustion chamber increases to about twice that which exists, due to compression, at the end of the compression stroke. Thus the pressure attained during combustion can be very high. However an engine cannot withstand application of pressure in the combustion camber, beyond a certain maximum pressure value. In order to ensure this maximum value is not exceeded, it is necessary to ensure that the compression pressure attained at the end of the compression stroke is only moderate. But limiting the maximum compression pressure to a moderate value can adversely affect the efficiency of the engine.

According to the invention there is provided an internal combustion engine comprising a combustion chamber, an accumulator, a bore extending between the combustion chamber and accumulator and opening into each, a plunger comprising a guided stem provided with an enlarged part or head exposed to said combustion chamber and slidable along said bore with very slight clearance between the head and the wall of the bore, said head being arranged for abutment against a seat associated with the bore, and means to fill the accumulator with gas at pre-determined pressure which is applied to the plunger to provide a force acting in a direction along the bore to urge the head towards the seat in opposition to force acting on the plunger along the opposite direction due to pressure applied to said plunger by gas in the combustion chamber, the pre-determined gas pressure in the accumulator determining the maximum combustion pressure in said combustion chamber.

Thus an engine can be constructed in accordance with the invention, in which the combustion pressure acting on the plunger head pushes it along the bore to effectively increase the overall volume of the region in which combustion is taking place. This increase in volume has the effect of reducing the maximum value of the combustion pressure attained, when compared with the maximum combustion pressure which could have been attained if the engine had been of conventional design. Accordingly, in an engine constructed in accordance with the invention, it is possible to use a higher compression pressure than that used in a conventional engine. This facilitates a reduction of the time required for ignition and of combustion noise.It also facilitates an improvement in engine efficiency and gives the engine a suitability for supercharging since the maximum combustion pressure is less than that developed in a supercharged conventional engine.

The stem can be mounted on a side of the plunger head remote from the combustion chamber. Therefore the stem which can slide in a guide is protected from the hot gases workmg in the combustion chamber.

Preferably the plunger head and seat are so arranged that when the head sits on the seat, the bore is hermetically sealed from the combustion chamber.

The plunger can be provided with a damping device which comes into operation just before the plunger head contacts the seat during movement of the head towards the seat. This speed damping device reduces the chance of the plunger head striking the seat with excessive force, whilst allowing the head to move at high speed towards the seat prior to the damping device operating.

The gas filling the accumulator can be compressed air from a supply coming from the engine cylinder itself, or from an auxiliary compressor, or from an independent pressurised circuit.

The air pressure in the accumulator may either be kept constant, or be varied, or may be governed by an operating parameter of the engine.

The combustion chamber may be provided with either a fuel injector in the case of a diesel engine, or with a spark-plug in the case of a carburation or petrol injection engme.

invention will now be further described, by way of example, with reference to the accompanying drawings in which: Fig. 1 is a diagrammatic cross-sectional view of a four-stroke internal combustion engine formed according to the invention which can also be applied to two-stroke engines; Fig. 2 is a view partly in cross-section of a plunger which can be used in an engine formed according to the invention; Figs. 3 to 5 show, partly in cross-section, fragments of three variations of the supply device of the means for filling the accumulator with compressed air, and Fig. 6 is a diagram showing, in relation to angular position of the crankshaft of the engine, variation in pressure in the combustion chamber and operation of the plunger in an engine formed according to the invention, and operation of a fuel injector.

The engme in Fig. 1 compnses a casing 1 in which a piston 2 and a connecting rod 3 connected to a crank moves. It also comprises inlet and outlet valves 4 and 5 respectively, and a cylinder head 6.

The cylinder-head 6 comprises a combustion chamber 7 surmounted by a plunger 8 having a stem sliding in a guide 9. The stem of plunger 8 is mounted on an enlarged part or head resting on a seat 10. This plunger head slides with very slight clearance in a bore 11 which communicates with an accumulator reservoir 12 supplied with air at high pressure by a supply 13. In the case of a diesel engine a fuel injector is located at position 14, whilst in the case of a petrol engine a spark-plug is located at position 14.

The plunger 8 shown in Fig. 2 comprises a damping piston 15 at the end of the stem. At the end of its downward travel, the piston 15 enters a bore 16 with very slight clearance.

This bore defines a chamber which is supplied with lubricating oil in a metered quantity through an orifice 17.

The supply 13 to the accumulator 12 may be ensured in several ways: for example, it is ensured in arrangement shown in Fig. 3 by means of a compressed air circuit, regulated by a conventionalpres- sure relief valve such as that shown in Fig. 3 having a diaphragm 18, a regulating needle valve 19 and an opposing spring 20 acting on the diaphragm. This spring can be variably stressed by regulating parameters 21, such as, for example, the supercharging pressure. The compressed air arrives through pipe 22.

In the arrangement in Fig. 4, the supply 13 of the accumulator 12 is ensured by means of a counter-balanced piston 23, supplied by the combustion chamber 7 of the engine through an orifice 24. The piston 23 is subject to the action of an opposing spring 25 controlled by external parameters represented in Fig. 4 by the double headed arrow. These parameters can be operating parameters of the engine. The piston 23 has a connecting groove 27 which, via the nonreturn valve 28, supplies the inlet to the accumulator 12 when in response to said external parameters the piston 23 moves to bring the groove 27 into alignment with the orifice 24.

In the arrangement in Fig. 5, the supply 13 of the accumulator is ensured by means of a valve 29 which co-operates with a valve seat provided in the wall of the combustion chamber of the engine or in an auxiliary compressor. The valve 29 is actuated by a cam 30 controlled by a cam-shaft of the engine. The valve 29 is urged towards its closed position by a spring 31. The cam 31 may have an angular position, relative to cam shaft 32, which is variable owing to oblique grooves located on the cam-shaft 32 and the cam 30, the cam being pushed by the action of regulating parameters 33 acting through the intermediary of an abutment 34, the cam also being pushed by an opposing spring 35.

The operation of the engine is as follows: After closure of the inlet valve 4, the piston 2 begins its compression stroke and the air is thus progressively compressed in the combustion chamber 7. When the desired maximum compression pressure is reached, as determined by means of the pressure prevailing in the accumulator 12 before the piston 2 reaches upper dead centre, the compression pressure then exerts a force on the plunger 8 in an upwards direction which raises the plunger because the upward force exerted on the plunger is greater than that exerted in a downwards direction on the plunger by the air in the accumulator. At a chosen instant, the fuel injector injects fuel or the spark-plug produces the spark and after the time required for ignition in the vicinity of the upper dead centre position, combustion begins.The pressure in the combustion chamber 7 increases but, immediately, the force exerted on the plunger 8 in the upwards direction increases and the plunger, already having an ascending speed, accelerates in the upwards direction, thus further increasing the volume of the combustion chamber and so limiting the maximum pressure developed in the combustion chamber. When the piston now moves down towards the bottom dead centre position, this tends to increase the volume of the combustion chamber 7 and decrease the pressure therein. However the plunger 8 also descends in response, and reduces the volume of the bore 11 open to the combustion chamber 7. This provides a compensation for the increase in the volume of the chamber 7, so that for a period the overall volume occupied by the burning gases remains substantially constant.Thus pressure and temperature conditions favourable to combustion and driving force exerted on the piston are maintained for the period.

When the head of the plunger 8 descends to its seat 10 the plunger head makes a completely air-tight contact with the seat thus isolating the pressurised air in the accumulator 12 from the combustion chamber. Towards the end of the downwards movement of the plunger 8, the damping piston 15 (Fig. 2) of the plunger enters the bore 16 and substantially slows down the speed of the plunger before the plunger head reaches the seat 10. Accordingly the earlier part of the downward movement of the plunger 8 can be carried out at high speed, because the damping at the end of that movement reduces the risk of the plunger head hitting the seat with excessive force.

The supply of the accumulator 12 may take place in various ways as indicated above. In the case of the arrangement in Fig.

3, the air circuit 22 may be established before starting the engine, which makes it possible to start under normal conditions from the first revolution of the crankshaft.

In the case of the arrangement in Fig. 4, from the time of starting of the engine, the combustion chamber 7 or auxiliary compressor supplies the orifice 24 which remains connected to the supply 13 of the accumulator 12 because the groove 27 is aligned with the orifice 24, as long as the pressure prevailing in the accumulator and acting on the piston 23 against the opposing spring 25 does not push this piston 23 down.

As soon as the pressure in the accumulator 12 is sufficient, the piston 23 is pushed downwards and the groove 27 descends, from alignment with the orifice 24, into the attitude shown in Fig. 4, thus cutting the connection between the orifice and the supply 13.

The Fig. 4 arrangement makes it possible to fill the accumulator 12 through the nonreturn valve 28, whereas the accumulator may empty slightly through leakages between the bore 11 and the head of the plunger 8.

Any action of the regulation parameters represented by the double headed arrow in Fig. 4 introduces modulation of the pressure attained in the accumulator 12.

In the arrangement in Fig. 5, the valve 29 establishes a connection between the accumulator 12 and combustion chamber 7 or auxiliary compressor when the crankshaft attains anv desired pre-determined angle. The accumulator 12 is thus charged at the pressure prevailing in the combustion chamber or the auxiliary compressor, at that time. As soon as the pressure in the accumulator 12 corresponds to that prevailing in the combustion chamber 7 or auxiliary compressor, the transfer of air to the accumulator stops.

In view of the fact that the opening and closing of the valve 29 is controlled by the cam 30, the cam can be arranged only to hold the valve 29 open during the compression stroke of the piston 2 so that the accumulator is filled with pure compressed air, which is not the case when the arrangment in Fig. 4 is used.

Action of regulating parameters 33 can vary the angular position of the cam 38 relative to the cam shaft 32 and thus alter the timing of the opening and closing of the valve 29, making it possible to vary the pressure in the accumulator and thus the maximum combustion pressure.

In Fig. 6 the abscissa represents crankshaft angle during a reciprocating cycle of the piston 2, PMB being bottom dead centre and PMH top dead centre. Curve 36 indicates variation in pressure in the combustion chamber during the compression stroke and succeeding power stroke of a supercharged engine, and curve 37 represents the same for an engine having natural induction. The two curves at 38 represent the lift of the plunger 8 in relation to crank-shaft angle, the upper curve of the two corresponding to the supercharged engine and the lower curve corresponding to the natural induction engine. The two curves at 39 represent operation of a fuel injector in relation to crank-shaft angle, the upper curve relating to the supercharged engine and the lower curve relating to the engine with natural induction.

WHAT I CLAIM IS: 1. An internal combustion engine comprising a combustion chamber, an accumulator, a bore extending between the combustion chamber and accumulator and opening into each, a plunger comprising a

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. combustion begins. The pressure in the combustion chamber 7 increases but, immediately, the force exerted on the plunger 8 in the upwards direction increases and the plunger, already having an ascending speed, accelerates in the upwards direction, thus further increasing the volume of the combustion chamber and so limiting the maximum pressure developed in the combustion chamber. When the piston now moves down towards the bottom dead centre position, this tends to increase the volume of the combustion chamber 7 and decrease the pressure therein. However the plunger 8 also descends in response, and reduces the volume of the bore 11 open to the combustion chamber 7.This provides a compensation for the increase in the volume of the chamber 7, so that for a period the overall volume occupied by the burning gases remains substantially constant. Thus pressure and temperature conditions favourable to combustion and driving force exerted on the piston are maintained for the period. When the head of the plunger 8 descends to its seat 10 the plunger head makes a completely air-tight contact with the seat thus isolating the pressurised air in the accumulator 12 from the combustion chamber. Towards the end of the downwards movement of the plunger 8, the damping piston 15 (Fig. 2) of the plunger enters the bore 16 and substantially slows down the speed of the plunger before the plunger head reaches the seat 10. Accordingly the earlier part of the downward movement of the plunger 8 can be carried out at high speed, because the damping at the end of that movement reduces the risk of the plunger head hitting the seat with excessive force. The supply of the accumulator 12 may take place in various ways as indicated above. In the case of the arrangement in Fig. 3, the air circuit 22 may be established before starting the engine, which makes it possible to start under normal conditions from the first revolution of the crankshaft. In the case of the arrangement in Fig. 4, from the time of starting of the engine, the combustion chamber 7 or auxiliary compressor supplies the orifice 24 which remains connected to the supply 13 of the accumulator 12 because the groove 27 is aligned with the orifice 24, as long as the pressure prevailing in the accumulator and acting on the piston 23 against the opposing spring 25 does not push this piston 23 down. As soon as the pressure in the accumulator 12 is sufficient, the piston 23 is pushed downwards and the groove 27 descends, from alignment with the orifice 24, into the attitude shown in Fig. 4, thus cutting the connection between the orifice and the supply 13. The Fig. 4 arrangement makes it possible to fill the accumulator 12 through the nonreturn valve 28, whereas the accumulator may empty slightly through leakages between the bore 11 and the head of the plunger 8. Any action of the regulation parameters represented by the double headed arrow in Fig. 4 introduces modulation of the pressure attained in the accumulator 12. In the arrangement in Fig. 5, the valve 29 establishes a connection between the accumulator 12 and combustion chamber 7 or auxiliary compressor when the crankshaft attains anv desired pre-determined angle. The accumulator 12 is thus charged at the pressure prevailing in the combustion chamber or the auxiliary compressor, at that time. As soon as the pressure in the accumulator 12 corresponds to that prevailing in the combustion chamber 7 or auxiliary compressor, the transfer of air to the accumulator stops. In view of the fact that the opening and closing of the valve 29 is controlled by the cam 30, the cam can be arranged only to hold the valve 29 open during the compression stroke of the piston 2 so that the accumulator is filled with pure compressed air, which is not the case when the arrangment in Fig. 4 is used. Action of regulating parameters 33 can vary the angular position of the cam 38 relative to the cam shaft 32 and thus alter the timing of the opening and closing of the valve 29, making it possible to vary the pressure in the accumulator and thus the maximum combustion pressure. In Fig. 6 the abscissa represents crankshaft angle during a reciprocating cycle of the piston 2, PMB being bottom dead centre and PMH top dead centre. Curve 36 indicates variation in pressure in the combustion chamber during the compression stroke and succeeding power stroke of a supercharged engine, and curve 37 represents the same for an engine having natural induction. The two curves at 38 represent the lift of the plunger 8 in relation to crank-shaft angle, the upper curve of the two corresponding to the supercharged engine and the lower curve corresponding to the natural induction engine. The two curves at 39 represent operation of a fuel injector in relation to crank-shaft angle, the upper curve relating to the supercharged engine and the lower curve relating to the engine with natural induction. WHAT I CLAIM IS:

1. An internal combustion engine comprising a combustion chamber, an accumulator, a bore extending between the combustion chamber and accumulator and opening into each, a plunger comprising a

guided stem provided with an enlarged part or head exposed to said combustion chamber and slidable along said bore with very slight clearance between the head and the wall of the bore, said head being arranged for abutment against a seat associated with the bore, and means to fill the accumulator with gas at pre-determined pressure which is applied to the plunger to provide a force acting in a direction along the bore to urge the head towards the seat in opposition to force acting on the plunger along the opposite direction due to pressure applied to said plunger by gas in the combustion chamber, the pre-determined gas pressure in the accumulator determining the maximum combustion pressure in said combustion chamber.

2. An engine as claimed in claim 1, in which the gas which fills the accumulator is compressed air.

3. An engine as claimed in claim 2, in which the air pressure in the accumulator is kept constant by means of a compressed air circuit provided with a pressure relief valve.

4. An engine as claimed in claim 2, in which the air pressure in the accumulator is regulated by a device responsive to operating parameters of the engine.

5. An engine as claimed in claim 4, in which an air supply pipe opens into the interior of the combustion chamber in order to supply the accumulator with air through the intermediary of the regulating device.

6. An engine as claimed in any preceding claim, so arranged that the plunger head is applied against the seat to seal the bore hermetically from the combustion chamber when the pressure of the combustion chamber is less than a predetermined value.

7. An engine as claimed in any preceding claim, in which the plunger head is mounted on the stem located on a side of the valve head remote from the combustion chamber.

8. An engine as claimed in any preceding claim, in which the plunger is connected to a damping device comprising a piston integral with said plunger and able to close off a second chamber containing a measured quantity of oil by sliding with slight clearance in a bore defining said second chamber, the arrangement being such that this closure of the second chamber takes place towards the end of movement of the plunger head into contact with the seat.

9. A diesel engine as claimed in any preceding claim, having a fuel injector provided in the combustion chamber.

10. A carburation or petrol injection engine as claim in any of claims 1 to 8, having a spark-plug located in the combustion chamber.

11. An internal combustion engine substantially as hereinbefore described with reference to the accompanving drawings.