Internal combustion engine

Abstract

An internal combustion engine, in particular a gas Otto-cycle engine, is provided. The internal combustion engine comprises a plurality of cylinders. Each cylinder is provided with a pre-chamber, and a pre-chamber gas supply conduit through which the pre-chamber can be supplied with fuel gas. The fuel gas is supplied to the pre-chambers by way of a pre-chamber gas valve associated with the respective pre-chamber. Also, an aperture is arranged between the pre-chamber gas supply conduit and the pre-chamber gas valve. At least one aperture associated with a pre-chamber gas valve has a through-flow coefficient such that pressure occurring at a maximum between combustion cycles in a volume between the pre-chamber gas valve and the aperture does not reach a pressure prevailing in the pre-chamber gas supply conduit.

Claims

1. An internal combustion engine comprising: a plurality of cylinders; a plurality of pre-chambers, wherein each cylinder of the plurality of cylinders is provided with a respective pre-chamber of the plurality of pre-chambers; a pre-chamber gas supply conduit configured to supply a fuel gas; a plurality of conduits, wherein each conduit of the plurality of conduits extends from the pre-chamber gas supply conduit to a respective pre-chamber of the plurality of pre-chambers; a plurality of pre-chamber gas valves, wherein each conduit of the plurality of conduits has only one pre-chamber gas valve located therein between the pre-chamber gas supply conduit and the respective pre-chamber of the plurality of pre-chambers, wherein each of the plurality of pre-chamber gas valves comprises a non-return valve configured to open at a given pressure difference between a first pressure upstream of the non-return valve and a second pressure downstream of the non-return valve in fluid communication with the respective pre-chamber of the plurality of pre-chambers; a plurality of apertures, wherein each conduit of the plurality of conduits has only one aperture located therein upstream of the only one pre-chamber gas valve, wherein each of the plurality of apertures is always open; a central aperture arranged between the pre-chamber gas supply conduit and a pressure regulating valve associated with a gas supply; and wherein the only one aperture located in each conduit of the plurality of conduits has an opening sized with a through-flow coefficient limiting the first pressure within a volume between the only one pre-chamber gas valve and the only one aperture to a maximum pressure that remains below a supply pressure prevailing in the pre-chamber gas supply conduit during a combustion cycle, to meter an amount of the fuel gas being supplied without being skewed by the supply pressure and a starting pressure in the cylinder immediately before opening the only one pre-chamber gas valve.

2. The internal combustion engine as set forth in claim 1, wherein the through-flow coefficient of the only one aperture of at least two conduits of the plurality of conduits is different between the at least two conduits.

3. The internal combustion engine as set forth in claim 1, wherein the plurality of apertures limits the first pressures in the volumes of the plurality of conduits to substantially equalize amounts of the fuel gas being supplied by the plurality of pre-chambers to the plurality of cylinders.

4. The internal combustion engine as set forth in claim 1, wherein, when the plurality of cylinders have different pressures immediately before opening of the respective plurality of pre-chamber gas valves during the combustion cycle, the plurality of apertures limits the first pressures in the volumes to remain below the supply pressure during the combustion cycle to substantially equalize amounts of the fuel gas being supplied by the plurality of pre-chambers to the plurality of cylinders.

5. The internal combustion engine as set forth in claim 1, wherein, when the plurality of pre-chamber gas valves open and close to supply the amounts of the fuel gas during the combustion cycle, the plurality of apertures limits the first pressures in the volumes to remain below the supply pressure during the combustion cycle to substantially match maximum pressure variations in fuel pressures of the fuel gas supplied to the plurality of cylinders, wherein the maximum pressure variation in the fuel gas supplied in each of the plurality of cylinders corresponds to a maximum difference in the fuel pressure of the fuel gas between a starting value and an ending value.

6. The internal combustion engine as set forth in claim 5, wherein the starting and ending values of the fuel pressure are different in the plurality of cylinders.

7. The internal combustion engine as set forth in claim 1, wherein each of the plurality of apertures limits the first pressure to remain below 99 percent of the supply pressure of the fuel gas during the combustion cycle.

8. The internal combustion engine as set forth in claim 1, wherein each of the plurality of apertures limits the first pressure to remain below 95 percent of the supply pressure of the fuel gas during the combustion cycle.

9. The internal combustion engine as set forth in claim 1, wherein each of the plurality of apertures limits the first pressure to remain below 85 percent of the supply pressure of the fuel gas during the combustion cycle.

10. The internal combustion engine as set forth in claim 1, comprising a pressure sensor coupled to the volume between the only one pre-chamber gas valve and the only one aperture of each conduit of the plurality of conduits.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawing:

(2) FIG. 1 shows a diagrammatic view of an internal combustion engine with pre-chamber gas supply;

(3) FIG. 2 shows a graph with pressure variations before the pre-chamber gas valve in accordance with the state of the art; and

(4) FIG. 3 shows a graph with pressure variations before the pre-chamber gas valve (according to the disclosure).

DETAILED DESCRIPTION

(5) FIG. 1 is a diagrammatic view showing an internal combustion engine 1 having a plurality of cylinders Z. For the sake of clarity only two cylinders Z are shown. The combustion chambers of the cylinder Z receive combustible mixture by way of the induction manifold 10. A configuration which is not shown but which can equally be envisaged is one in which compressed air is fed to the combustion chambers by way of the induction manifold 10 and fuel gas is fed thereto separately by way of dedicated valves, for example port injection valves.

(6) Ignition for the combustion chambers in the cylinders Z is effected by pre-chambers 2 (for the sake of clarity only one pre-chamber 2 is shown), from which ignition flares pass into the combustion chamber of the cylinders Z, as is known per se from the state of the art. For that purpose an ignition device is arranged in the pre-chambers 2 (this is not shown).

(7) Associated with the individual pre-chambers and thus the individual cylinders Z is a respective pre-chamber gas valve 3, by way of which fuel gas can be fed to the pre-chambers from the pre-chamber gas supply conduit 4. For the sake of clarity the association of the pre-chamber 2 and the pre-chamber gas valve 3 is shown only on one cylinder Z.

(8) The pre-chamber gas valves 3 are mostly in the form of passive non-return valves which open at a given positive pressure between the pressure in the conduit 6 and the pressure prevailing in the pre-chamber 2 and thus meteredly feed a given amount of gas to the pre-chamber 2. If the pressure is below the opening differential pressure the pre-chamber gas valve remains closed. The pressure in the pre-chambers approximately corresponds to the combustion chamber pressure of the associated cylinders Z.

(9) The pre-chamber gas supply conduit 4 is fed by a main gas supply 9 by way of a pressure regulating valve 8 and a central aperture 7. The pressure regulating valve 8 regulates the pressure in the pre-chamber gas supply conduit 4 to a constant ratio to the charge pressure of the internal combustion engine. Besides setting the pre-chamber gas volume flow, the central aperture 7 provides that no pressure pulsations are transmitted from the main gas supply 9 to the pre-chamber gas supply conduit 4.

(10) Decentral apertures 5 are associated with the pre-chamber gas supply conduit 4, wherein a respective decentral aperture 5 is arranged in that conduit portion 6 of the pre-chamber gas supply, that leads from the pre-chamber gas supply conduit 4 to the individual pre-chambers 2 of the internal combustion engine 1. This means that a decentral aperture 5 is associated with each pre-chamber valve 3.

(11) Upon opening of the pre-chamber gas valves 3 fuel gas flows out of the conduit portion 6 into the pre-chamber. Fuel gas is delayed by the decentral aperture 5 in its flow out of the pre-chamber gas supply conduit 4 into the conduit portion 6. In the state of the art the decentral apertures 5 are of such dimensions that they throttle pressure fluctuations and that the pressure of the pre-chamber gas supply conduit 4 prevails prior to opening of the pre-chamber gas valve 3 in the conduit portion 6.

(12) In the configuration according to the invention of the decentral apertures 5, the pressure prevailing in the pre-chamber gas supply conduit 4 is not achieved in the conduit portion 6 during a working cycle of the internal combustion engine 1.

(13) FIG. 2 shows various variations in the pressure in the volume between the decentral aperture 5 and the pre-chamber gas valve 3 during a working cycle (corresponding to 720 in the case of a 4-stroke engine) for a decentral aperture 5 having a diameter or through-flow coefficient in accordance with the state of the art. The Figure shows the pressure variations for cylinder A and cylinder B of an internal combustion engine 1. The pressure in the volume between the pre-chamber gas valve 3 and the aperture 5 is plotted on the ordinate and the crank angle on the abscissa.

(14) Two markedly different cylinders were selected in order to demonstrate the unintended differences in the metered feed of pre-chamber gas for those two cylinders. The pressure variation for cylinder A is shown as a dashed line, that for cylinder B is shown as a solid line, while the pressure in the pre-chamber gas supply conduit 4 (rail pressure) is shown as a dotted line.

(15) For both cylinders A and B the starting pressure corresponds to the pressure in the pre-chamber gas supply conduit 4. The pre-chamber gas valve 3 opens when a given positive pressure difference is reached between the pressure in the pre-chamber gas supply conduit 4 and the pressure in the pre-chamber 2.

(16) It will be seen that the pressure drop p.sub.A for the cylinder A is much more heavily pronounced than for the pressure drop p.sub.B for the cylinder B. On the simplified assumption that the difference between the minimum and the maximum pressure in the volume 6 is proportional to the amount of gas which is flowing across, it can be seen that the cylinder A receives substantially more pre-chamber gas than the cylinder B.

(17) Expressed in other words, in the opening phase of the pre-chamber gas valve 3, the cylinder A, because of the lower pressure in the cylinder, can suck in more gas from the pre-chamber gas supply conduit 4 than the cylinder B.

(18) After closure of the valves the pressures in the volumes 6 for both cylinders A and B regain the starting pressure, that is to say the pressure in the pre-chamber gas supply conduit 4. If the pressure in the pre-chamber gas supply conduit 4 is established as 100% therefore the pressures in the volumes 6 achieve that 100% during a combustion cycle.

(19) Reference will now be made to FIG. 3 to discuss the pressure variations described with reference to FIG. 2, for an embodiment in which the through-flow coefficient of the decentral aperture 5 has been reduced to an unusual extent.

(20) The first evident alteration concerns the different pressure levels before opening of the valve. It will be seen that cylinder B, again shown as a solid line, starts at a higher pressure level than the cylinder A, shown as a dashed line.

(21) The two cylinders A and B do not reach the pressure level of the pre-chamber gas supply conduit 4 (rail, shown as a dotted line). If the pressure in the pre-chamber gas supply conduit 4 is again established at 100% then the pressures in the volumes 6 do not reach the 100% within a cycle.

(22) It can be clearly seen that the pressure variations, p.sub.A for the cylinder A and p.sub.B for the cylinder B, which is the maximum difference between the starting value and the lowest value reached, were matched for the two cylinders. The curves cylinder A and cylinder B now extend parallel.

(23) This therefore provides approximate equalization of the cylinders A and B in regard to the pre-chamber gas supplied. They therefore receive approximately the same amount of pre-chamber gas.

(24) It is also to be seen that the pressures do not reach the pressure level of the pre-chamber gas supply, but, upon opening of the pre-chamber gas valves, are still in a rising trend, that is to say at that moment in time gas is still flowing out of the pre-chamber gas supply conduit 4 through the decentral aperture 5 into the volume 6 between the decentral aperture 5 and the pre-chamber gas valve 3.

(25) Whether a decentral aperture 5 is designed in accordance with the invention can be very easily checked by measuring the pressure in the volume 6 between the decentral aperture 5 upstream of the pre-chamber gas valve 3 and the pressure in the pre-chamber gas supply conduit 4. Instrumentation with pressure sensors is effected in a way familiar to the man skilled in the art. If the pressure prevailing in the pre-chamber gas supply conduit 4 is not reached in the volume 6 between the combustion cycles (this mean the pressure which occurs at a maximum in the volume 6), then decentral apertures 5 are designed in accordance with the invention and the described equalization of the cylinders in respect of the amount of pre-chamber gas is achieved.

LIST OF REFERENCES USED

(26) 1 internal combustion engine 2 pre-chamber 3 pre-chamber gas valve 4 pre-chamber gas supply conduit 5 decentral aperture 6 volume between pre-chamber gas valve 3 and aperture 5 7 central aperture 8 pressure regulating valve 9 main gas supply conduit 10 induction manifold Z cylinder p.sub.i pressure drop, pressure variation