INTERNAL COMBUSTION ENGINE

Abstract

An internal combustion engine having a prechamber with first and second sub-chambers. The first sub-chamber has a prechamber gas valve and an igniter. The second sub-chamber has a plurality of first orifices to couple with a main combustion chamber. The second sub-chamber is coupled to the first sub-chamber via a direct connection or an indirection connection. The direct connection includes at least one second orifice, such as a plurality of second orifices. The indirect connection includes a third sub-chamber, wherein the third sub-chamber is coupled to the first sub-chamber by at least one third orifice (e.g., a plurality of third orifices), and the third sub-chamber is coupled to the second sub-chamber by at least one second orifice (e.g., a plurality of second orifices).

Claims

1. An internal combustion engine having: at least one cylinder head; an intake manifold; a plurality of piston-cylinder-units each having a piston movably arranged in a cylinder; a plurality of main combustion chambers; a plurality of intake ports, wherein each intake port of the plurality of intake ports is connected to one of the plurality of main combustion chambers and to the intake manifold; a plurality of prechambers, wherein each prechamber of the plurality of prechambers is connected to one of the plurality of main combustion chambers and is provided with a prechamber gas valve and an ignition device; an electronic control unit configured to provide the prechamber gas valves with a mixture of fuel gas and air; wherein each prechamber of the plurality of prechambers has at least: a first sub-chamber having the prechamber gas valve and the ignition device; a second sub-chamber connected to the main combustion chamber by a plurality of first orifices, wherein the second sub-chamber is connected to the first sub-chamber either: directly by at least one second orifice; or indirectly by at least one third sub-chamber, wherein the at leach one third sub-chamber is connected to the first sub-chamber by at least one third orifice, and the at leach one third sub-chamber is connected to the second sub-chamber by at least one second orifice.

2. The engine of claim wherein a first volume of the first sub-chamber is smaller than a second volume of the second sub-chamber.

3. The engine of claim 1, comprising a plurality of sub-chambers including the at least one third sub-chamber disposed between the first and second sub-chambers, wherein following a fluid passage from the first pre-chamber to the main combustion chamber to which the prechamber is connected, each sub-chamber of the plurality of sub-chambers has a smaller volume than a next sub-chamber.

4. The engine of claim 3, wherein a ratio of the first volume of the first pre-chamber to the second volume of the second pre-chamber is about 1/3 to 1/7; or a ratio of the second volume of the second pre-chamber to a third volume of the at least one third pre-chamber is about 1/3 to 1/7; or a ratio of the first volume of the first pre-chamber to the third volume of the at least one third pre-chamber is about 1/3 to 1/7, or a combination thereof.

5. The engine of claim 1, wherein the prechamber gas valve is coupled to a source for a gas-air mixture which is formed by: the intake port of the main combustion chamber to which the prechamber is connected and a connection line provided between the intake port and the prechamber gas valve; or the intake manifold and a connection line provided between the intake manifold and the prechamber gas valve

6. The engine of claim 3, wherein at least one sub-chamber of the plurality of sub-chambers comprises a riser channel, wherein a first end of the riser channel is connected to the at least one sub-chamber and a second end of the riser channel is connected to an adjacent sub-chamber of the plurality of sub-chambers through a plurality of orifices.

7. The engine of claim 3, wherein the at least one second orifice comprises a plurality of second orifices, wherein the at least one third orifice comprises a plurality of third orifices, wherein the first sub-chamber, the second sub-chamber, and the at least one third sub-chamber are formed separately from each other and are connected only by the plurality of second and third orifices.

8. The engine of claim 1, wherein only the first sub-chamber is provided with the prechamber gas valve.

9. The engine of claim 1, wherein the electronic control unit configured to provide the intake manifold and/or the prechamber gas valves with a mixture of fuel gas, air, and exhaust gas with a lambda (λ) greater than 1.2.

10. The engine of claim 1, comprising an external exhaust gas re-circulation to the intake manifold, wherein the electronic control unit is configured to provide the intake manifold with a mixture of fuel gas, air, and exhaust gas with: a lambda (λ) of approximately 1; and an exhaust gas recirculation (EGR) content of about 10% to about 45%.

11. The engine of claim 10, wherein the electronic control unit is configured to provide the EGR content between about 15% and about 40%.

12. The engine of claim 10, comprising a three-way-catalysator arranged in an exhaust manifold of the internal combustion engine downstream or upstream of a turbine of a turbocharger.

13. The engine of claim 1, wherein the fuel gas is supplied either by a gas mixer upstream of a compressor of a turbocharger or by port fuel injection valves positioned downstream of the compressor of the turbocharger.

14. The engine of claim 5, wherein the internal combustion engine comprises at least one turbocharger and the connection lines branch off from the intake ports or the intake manifold between the turbocharger and inlet valves of the main combustion chambers.

15. The engine of claim 1, wherein the diameters of the cylinders are above 140 mm.

16. The engine of claim 1, wherein inlet and outlet valves of the plurality of main combustion chambers are actuated by a camshaft or an actuator controlled by the electronic control unit such that an inlet valve closes before the piston reaches a lower dead center position for each of the plurality of piston-cylinder-units.

17. The engine of claim 1, wherein a ratio of a volume of a prechamber to a compression volume of the main combustion chamber coupled to the prechamber in an upper dead center of a piston movement ranges from about 0.5% to about 4%.

18. The engine of claim 5, wherein the connection lines are formed as cavities in the cylinder head.

19. A system, comprising: a prechamber of an internal combustion engine, wherein the prechamber comprises: a body; a plurality of sub-chambers disposed in the body, wherein each pair of adjacent sub-chambers of the plurality of sub-chambers are fluidly coupled together via a plurality of orifices; and a fluid path through the plurality of sub-chambers in a sequence from a first sub-chamber toward a main combustion chamber of the internal combustion engine.

20. The system of claim 19, wherein the plurality of sub-chambers progressively decrease in volume from one sub-chamber to another in the sequence from the first sub-chamber toward the main combustion chamber.

21. A method, comprising: controlling operation of a prechamber of an internal combustion engine, wherein the prechamber comprises: a body; a plurality of sub-chambers disposed in the body, wherein each pair of adjacent sub-chambers of the plurality of sub-chambers are fluidly coupled together via a plurality of orifices; and a fluid path through the plurality of sub-chambers in a sequence from a first sub-chamber toward a main combustion chamber of the internal combustion engine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Embodiments of the invention are discussed with respect to the Figures:

[0050] FIG. 1 shows a detail of a first embodiment of the invention.

[0051] FIG. 2 shows a detail of a second embodiment of the invention.

[0052] FIG. 3a,b show a detail of a third and fourth embodiment of the invention.

[0053] FIG. 4 shows an internal combustion engine 1 according to the invention.

[0054] FIG. 4 shows a single piston-cylinder-unit of the internal combustion engine of FIG. 4.

[0055] FIG. 5 shows a single piston-cylinder-unit of the internal combustion engine of FIG. 4.

DETAILED DESCRIPTION

[0056] FIG. 1 shows a detail of a first embodiment of an internal combustion engine 1 according to the invention, namely one of the plurality of prechambers 7 which—in this embodiment—has a first sub-chamber 71 which is provided with the prechamber gas valve 8 and with an ignition device 9 (e.g., spark plug) and a second sub-chamber 72 which is connected to a main combustion chamber 5 of the internal combustion engine 1 (not shown here but see FIGS. 4 and 5) by a plurality of first orifices Oi and which is connected to the first sub-chamber 71 by a plurality of second orifices 02. In this embodiment, an optional riser channel 27 is provided in the second sub-chamber 72.

[0057] It is important that according to embodiments of the invention, an electronic control unit 19 of the internal combustion engine 1 (see FIG. 4) is configured to provide the prechamber gas valve 8 with a mixture of fuel gas and air not with either pure fuel gas or pure air. It is preferred, although not essential for embodiments of the invention, that only the first sub-chamber 71 (the one provided with the ignition device 9) is provided with a prechamber gas valve 8 such that the first sub-chamber 71 forms the only source for the second sub-chamber 72. It is also preferred, in certain embodiments, that—as shown—the first sub-chamber 71 and the second sub-chamber 72 are formed separately from each other and are connected only by the plurality of orifices O.sub.1, O.sub.2. In other words, the sub-chambers 71, 72 are not nested.

[0058] The prechamber 7 shown in FIG. 2 differs from the one shown in FIG. 1 only in that a third sub-chamber 73 is provided between the first sub-chamber 71 and the second sub-chamber 73. is the third sub-chamber 73 is connected to the first sub-chamber 71 by a plurality of third orifices O.sub.3 and to the second sub-chamber 72 by a plurality of second orifices O.sub.2. All other information given above with respect to FIG. 1 can also be applied to FIG. 2 with the understanding that the third sub-chamber 73 is present.

[0059] FIG. 3a shows a third embodiment of the invention in a detailed view of a prechamber 7, which has a first sub-chamber 71 and a second sub-chamber 72, which are both formed in a single component. The gas valve 8 and the ignition device 9 are not shown, but openings for partially receiving these devices can be seen.

[0060] The fourth embodiment of FIG. 3b differs from the third embodiment of FIG. 3a only in that here the component in which the first sub-chamber 71 and the second sub-chamber 72 are formed is made of two pieces P.sub.1 and P.sub.2, which are easier to manufacture. In this example, in the first piece P.sub.1 the first sub-chamber 71 and the plurality of second orifices O.sub.2 are formed; in the second piece P.sub.2 the second sub-chamber 72 and the plurality of first orifices O.sub.1 are formed

[0061] FIG. 4 shows an embodiment of the internal combustion engine 1:

[0062] The internal combustion engine 1 has a cylinder head 2 (in reality two cylinder heads 2 in V configuration but only one is shown), a plurality of piston-cylinder-units 3 in which pistons 4 are movably arranged, and a plurality of main combustion chambers 5, wherein each main combustion chamber 5 is formed in a cylinder 6 by a piston 4 (cf. FIG. 5) and the cylinder head 2.

[0063] A plurality of intake ports 10 is provided wherein each intake port 10 is connected to one of the main combustion chambers 5.

[0064] A plurality of prechambers 7 is provided wherein each prechamber 7 is connected to one of the main combustion chambers 5 and is provided with a prechamber gas valve 8, an ignition device 9 (the ignition timing of which can be controlled by an electronic control unit 19), and a source for a mixture of fuel gas, air and exhaust gas. The prechambers 7 are designed according to embodiments of the invention with at least two sub-chambers 71, 72, in particular, as shown in the embodiments of FIGS. 1 to 3.

[0065] The source for a mixture of fuel gas, air and exhaust gas is formed by the intake port 10 of the main combustion chamber 5 to which the prechamber 7 is connected (shown as an example for all of the prechambers 7 but one) or the intake manifold 12 (shown as an example with respect to the prechamber 7 which is situated second from left in the upper region of FIG. 4) and a connection line 11 provided between the intake port 10 or the intake manifold 12 and the prechamber gas valve 9. Of course, other than shown in FIG. 1, it will be preferred, in certain embodiments, to connect the connection lines 11 of all prechambers 7 either to the intake port 10 or the intake manifold 12.

[0066] In FIG. 4, a mixing device 23 for air and fuel gas and port fuel injection valves 26 are shown together. It is of course preferred, in certain embodiments, to use either a mixing device 23 or port fuel injection valves 26.

[0067] The electronic control unit 19 (dashed command lines are shown only with respect to a single piston-cylinder-unit 3 but are of course provided with respect to all of them) is configured to provide the intake manifold 12 with a mixture of fuel gas, air and exhaust gas via a fuel gas-air mixing device 23 with a lambda λ of at approximately 1 and via an external exhaust gas re-circulation (external EGR) mixing device (having an EGR control device 24 controlled by the electronic control unit 19 and an EGR cooler 25) with x.sub.EGR of approximately 10% to 45%. Provision of EGR is of course optional, because embodiments of the invention work with all types of combustion control provided there are prechambers 7 flushed with a mixture of fuel gas and air and having at least two sub-chambers 71, 72.

[0068] In this embodiment, the main chamber and prechamber charge is controlled to have a lambda λ of approximately 1 (preferably between about 0.95 and 1.05) and a recirculated exhaust gas content x.sub.EGR of about 10% to about 45%, preferably between about 10% and about 45%, more preferably about 15% and 40%. It should be noted that, in certain embodiments, the concept of prechambers 7 flushed with a mixture of fuel gas and air and having at least two sub-chambers 71, 72 can be used irrespective of the question of the value of lambda λ.

[0069] If a turbocharger 20 is provided, exhaust gas is provided upstream of a compressor C of the turbocharger 20.

[0070] In this embodiment, the internal combustion engine 1 is provided with at least one turbocharger 20 (having a compressor C and a turbine T) to provide pressurized mixture (air-EGR or air-fuel gas-EGR) to the intake manifold 12. The connection lines 11 branch off from the intake manifold 12 or the intake ports 10 between the turbocharger 20 and inlet valves 15 of the main combustion chambers 5.

[0071] Inlet and outlet valves 15, 16 of the main combustion chambers 5 are actuated by an actuator 22 (which might optionally be controlled by the electronic control unit 19), such that an inlet valve 15 closes before the piston 4 reaches a lower dead center position. It is however preferred, in certain embodiments, to control this motion of the inlet and outlet valves 15, 16 without the electronic control unit 19 via a camshaft.

[0072] A three-way-catalysator 14 is arranged preferably downstream of the turbocharger turbine T in the exhaust manifold 13.

[0073] As an example, a ratio of a volume of a prechamber 7 to a compression volume of the main combustion chamber 5 to which the prechamber 7 is connected in an upper dead center of a piston movement ranges from about 0.5% to about 4%.

[0074] As an example, the connection lines 11 are formed as cavities in the cylinder head 2.

[0075] A tempering device 17 and a throttle 21 can be provided for each connection line 11.

[0076] An aperture 18 can be provided for each connection line 11 in order to decouple the prechambers 7 from pressure pulsations in the intake ports 10 or the intake manifold 12.

[0077] Although FIG. 4 shows an embodiment of the invention using EGR, this is not an essential feature of the invention and it would be possible to either run the embodiment shown in FIG. 4 with x.sub.EGR of 0% or to use an embodiment without an exhaust gas re-circulation device. If no EGR is used, a lean operation mode of the internal combustion engine 1 is preferred in certain embodiments.

LIST OF REFERENCE SIGNS

[0078] 1 internal combustion engine [0079] 2 cylinder head [0080] 3 piston-cylinder-unit [0081] 4 piston [0082] 5 main-combustion chamber [0083] 6 cylinder [0084] 7 prechamber [0085] 71 first sub-chamber [0086] 72 second sub-chamber [0087] 73 third sub-chamber [0088] 8 gas valve [0089] 9 ignition device [0090] 10 intake port [0091] 11 connection line [0092] 12 intake manifold [0093] 13 exhaust manifold [0094] 14 three-way-catalysator [0095] 15 inlet valve [0096] 16 outlet valve [0097] 17 tempering device [0098] 18 aperture [0099] 19 electronic control unit [0100] 20 turbocharger [0101] 21 throttle [0102] 22 actuator [0103] 23 mixing device [0104] 24 EGR control device of external exhaust gas re-circulation [0105] 25 EGR cooler of external exhaust gas re-circulation [0106] 26 port fuel injection valve [0107] 27 riser channel [0108] 28 [0109] O.sub.1 first plurality of orifices [0110] O.sub.2 second plurality of orifices [0111] O.sub.3 third plurality of orifices [0112] P.sub.1 first part [0113] P.sub.2 second part [0114] C compressor of turbocharger [0115] T turbine of turbocharger