A device for igniting a mixture of fuel and air

Abstract

To provide a device capable of further improving processes of ignition and combustion of a fuel-air mixture.SOLUTION: A device (1) for igniting a fuel-air mixture in a combustion chamber (3) of a cylinder (2) of an internal combustion engine (100) comprises: a first antechamber (12), which is arranged at least in part outside the combustion chamber (3), and has an ignition device (13) capable of igniting a flammable fuel-air mixture within the antechamber (12); and at least one second antechamber (15), which extends around a part of the first antechamber (12), and has a flow channel connected to the first antechamber (12), where the second antechamber (15) is arranged completely inside the combustion chamber (3), and in particular is shaped into a truncated cone and has a larger volume than the first antechamber (12).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a device for igniting a fuel-air mixture in a combustion chamber of a cylinder of an internal combustion engine according to the preamble of claim 1. Furthermore, the invention relates to an internal combustion engine equipped with such a device. [Background technology]

[0002] From the prior art, devices are known in completely different embodiments which are provided for igniting a fuel-air mixture in a combustion chamber of a cylinder of an internal combustion engine, such devices having a pre-chamber, in which an ignition device is accommodated and which allows the ignition of a combustible fuel-air mixture, whereby due to its relatively small volume fuel is not injected directly into the pre-chamber (passive pre-chamber).

[0003] In the case of so-called pre-chamber jet ignition, a part of the fuel-air mixture is pushed into a pre-chamber during the compression stroke of the internal combustion engine so that the fuel-air mixture ignites in the pre-chamber. This ignition then propagates to the combustion chamber of the internal combustion engine. As a result, the combustion of the fuel-air mixture in the combustion chamber is accelerated and the occurrence of knocking is reduced.

[0004] Typically, a passive prechamber has a relatively small volume, which corresponds to about 2-5% of the volume of the combustion chamber at the top dead center of the piston moving in the combustion chamber. This small volume of the prechamber limits the acceleration effect caused by the ignition of the fuel-air mixture in the prechamber to the first phase of the combustion stroke (about 0-10% of the total combustion time).

[0005] According to Patent Document 1, an internal combustion engine is known that has a number of pre-chambers, each of which is connected to a main combustion chamber. The pre-chambers are provided for receiving a mixture of fuel gas and air by means of a pre-chamber gas valve. Each pre-chamber further has up to three auxiliary chambers that are connected to each other through a flow opening and arranged in descending order of capacity. The first auxiliary chamber has a pre-chamber gas valve and an ignition device for igniting the mixture of fuel gas and air. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2022 / 011400 Summary of the Invention [Problem to be solved by the invention]

[0007] The object of the invention is to make it possible to use a device for igniting a fuel-air mixture of the type mentioned at the beginning, which makes it possible to further improve the ignition and combustion process of the fuel-air mixture. [Means for solving the problem]

[0008] The solution according to the invention provides such a device for igniting a fuel-air mixture in a combustion chamber of a cylinder of an internal combustion engine with the features set forth in claim 1. The dependent claims show advantageous developments of the invention.

[0009] The device according to the invention for igniting a fuel-air mixture in a combustion chamber of a cylinder of an internal combustion engine is characterized in that the second pre-chamber is arranged completely within the combustion chamber, is in particular frusto-conical in shape and has a larger volume than the first pre-chamber.

[0010] It is shown that the accelerating effect of the pre-chamber ignition can be significantly increased by providing a second pre-chamber, in particular frustoconical, which extends in the combustion chamber around a portion of the first pre-chamber and has a larger volume than the first pre-chamber. The combustion energy flowing out of the second pre-chamber and into the combustion chamber can thus be advantageously increased. The same effect cannot be achieved by simply increasing the volume of the first pre-chamber, since a constant ratio between the bore surface of the flow opening and the pre-chamber volume must be maintained.

[0011] In order to further enhance the above-mentioned effect, an advantageous embodiment is proposed in which the device has at least one third pre-chamber, in particular of truncated cone shape and extending around the second pre-chamber, so that the combustion energy leaving the third pre-chamber can be further increased. Preferably, the third pre-chamber is designed to have a larger volume than the second pre-chamber.

[0012] In another advantageous embodiment, the device has a number of pre-chambers k≧1, which are in particular frustoconical in shape and extend around the circumference of the respective pre-chamber mentioned above. For example, the pre-chamber system may be provided with four or five pre-chambers.

[0013] Preferably, the kth pre-chamber is formed to have a larger volume than the k-1th pre-chamber, and thus the volume of the pre-chambers arranged in the combustion chamber of the internal combustion engine preferably expands from the inside to the outside.

[0014] In conventional internal combustion engines, in order to control the air-fuel ratio in the first pre-chamber (so-called lambda control), the dimensions of the first pre-chamber are very small. In an advantageous development, it is therefore proposed that the device has a fuel injection means, in particular a fuel injection nozzle, which is arranged so as to extend into one of the pre-chambers having a larger volume than the first pre-chamber. By introducing a multi-stage pre-chamber system, the fuel injection means, in particular the fuel injection nozzle of the device, can be positioned in a large pre-chamber, which advantageously allows for an efficient control of the local air-fuel ratio.

[0015] Various combinations of fuel injection means, in particular fuel injection nozzles, and different numbers of pre-chambers are fundamentally conceivable.

[0016] In a further advantageous embodiment, the first pre-chamber is at least partially conically shaped and at least partially tapered - in the direction of the combustion chamber - from the inside to the outside.

[0017] Preferably, the second pre-chamber and possibly other existing pre-chambers can be extended into the combustion chamber.

[0018] Instead of being frustoconical, the pre-chamber can have another shape.

[0019] An internal combustion engine according to the invention is characterised by claim 8 in that it comprises a device according to any one of claims 1 to 7. [Brief description of the drawings]

[0020] [Figure 1] 1 shows a longitudinal section through a portion of a combustion cylinder of an internal combustion engine. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Other features and advantages of the present invention will become apparent from the following description of a preferred embodiment, with reference to the accompanying Figure 1, which shows a longitudinal section through a portion of a combustion cylinder 2 of an internal combustion engine 100. Although only one combustion cylinder 2 of the internal combustion engine 100 is shown in Figure 1, it is usual for the engine to be equipped with several such combustion cylinders 2.

[0022] Combustion cylinder 2 defines a combustion chamber 3 in which a piston 4 is axially movable from first (bottom) dead center to second (top) dead center, as shown in Figure 1, and vice versa. Combustion cylinder 2 is fluidly connected to an intake manifold 5 having an intake valve 7 disposed therein, and an exhaust manifold 6 having an exhaust valve 8 disposed therein.

[0023] The combustion cylinder 2 has a cylinder head 9 in which a first receiving portion 90 and a second receiving portion 91 are formed. In the first receiving portion 90 a first fuel injection means 10, in particular a fuel injection nozzle, is mounted, by means of which fuel can be injected into the combustion chamber 3 during operation of the internal combustion engine 100. When the intake valve 7 is in the open state, a flammable fuel-air mixture is generated in the combustion chamber 3.

[0024] The internal combustion engine 100 further comprises a device 1 for igniting a fuel-air mixture, capable of igniting a combustible fuel-air mixture in the combustion chamber 3 of the combustion cylinder 2. The combustion exhaust gases generated during the combustion of the fuel-air mixture flow into the exhaust manifold 6 when the exhaust valve 8 is open.

[0025] In the following, the details of the device 1 for igniting a fuel-air mixture shall be explained in detail. The device 1 has a pre-chamber housing 11 in which a first pre-chamber 12 is formed. Furthermore, the device 1 has an ignition device 13, in particular a spark plug, which is mounted in the pre-chamber housing 11 and leads to the first pre-chamber 12. The first pre-chamber 12 is partially conically shaped and partially tapered from the inside to the outside - thus in the direction of the combustion chamber 3. A cylinder-connecting part 14 of the pre-chamber housing 11 is mounted in the second receiving part 91 of the cylinder head 9 and extends partially into the combustion chamber 3. The volume enclosed by the cylinder-connecting part 14 of the pre-chamber housing 11 then forms part of the total volume of the pre-chamber 12.

[0026] The device 1 further comprises a second pre-chamber 15 in the combustion chamber 3, extending around the cylinder connection part 14 of the pre-chamber housing 11 and therefore around the first pre-chamber 12. The second pre-chamber 15 is in this embodiment frustoconical and shaped to extend starting from the cylinder head 9 into the combustion chamber 3. Preferably, the second pre-chamber 15 has a larger volume than the first pre-chamber 12. In this embodiment, the device 1 further comprises a third pre-chamber 16, extending around the second pre-chamber 15. The third pre-chamber 16 is in this embodiment likewise frustoconical and shaped to extend starting from the second pre-chamber 15 further into the combustion chamber 3.

[0027] In the lower region of the cylinder connection part 14, a number of flow channels 140 are formed, which can serve as a flow connection between the first pre-chamber 12 and the second pre-chamber 15 in the combustion chamber 3. The second pre-chamber 15 has in its lower region a number of flow openings 150, which can serve as a flow connection between the second pre-chamber 15 and the third pre-chamber 16. Furthermore, the third pre-chamber 16 has in its lower region a number of flow openings 160, which can serve as a flow connection between the third pre-chamber 16 and the combustion chamber 3.

[0028] Depending on the installation purpose and intended use, a fourth pre-chamber and possibly further pre-chambers, preferably also frusto-conical in shape and each having a larger volume than the pre-chambers mentioned above, may be connected in a similar manner to the third pre-chamber 16.

[0029] The pre-chamber system of the device 1 with the three pre-chambers 12, 15, 16 described above operates passively, which means that no direct fuel injection takes place in any of the three pre-chambers 12, 15, 16.

[0030] In a further development not explicitly mentioned here, the device 1 itself can likewise comprise fuel injection means, in particular a fuel injection nozzle, which is arranged to lead into the respective pre-chamber 15, 16 having a larger volume than the first pre-chamber 12. In particular, the fuel injection means, in particular the fuel injection nozzle, is arranged to lead into the second pre-chamber 15.

[0031] During operation of the internal combustion engine 100, the fuel injection means, in particular the fuel injection nozzle, are able to inject fuel into the respective pre-chambers 15, 16. In this variant, the device 1 therefore operates by active fuel injection in the pre-chambers 15, 16 which have a larger volume than the first pre-chamber 12. This advantageously makes it possible to obtain a richer mixture in the respective pre-chambers 15, 16 than in the combustion chamber 3.

[0032] In conventional internal combustion engines, in order to control the air-fuel ratio in the first pre-chamber 12 (so-called lambda control), the dimensions of the first pre-chamber 12 are very small. A multi-stage pre-chamber system, preferably with a plurality of series-connected pre-chambers 12, 15, 16 with increased capacity, allows the fuel injection means, in particular the fuel injection nozzles assigned to the device 1, to be positioned in the larger pre-chambers 15, 16 and to efficiently control the local lambda control values.

[0033] Finally, it will be seen that - depending on the specific application - entirely different combinations of fuel injection means and multiple pre-chambers 12, 15, 16 are possible.

Claims

1. A device (1) for igniting a mixture of fuel and air in a combustion chamber (3) of a cylinder (2) of an internal combustion engine (100), comprising: a first pre-combustion chamber (12) arranged at least partially outside said combustion chamber (3) and having an ignition device (13) capable of igniting a combustible fuel-air mixture in said pre-combustion chamber (12); at least one second pre-chamber (15) extending around a portion of the first pre-chamber (12) and connected by a flow passage to said first pre-chamber (12), the second pre-chamber (15) is completely disposed within the combustion chamber (3), is frustoconical in shape, is shaped to extend starting from the cylinder head (9) of the cylinder (2) into the combustion chamber (3) and has a larger volume than the first pre-chamber (12); The device (1) is characterized in that it comprises at least one third pre-chamber (16) extending around the second pre-chamber (15).

2. 2. The device (1) according to claim 1, characterized in that the third pre-chamber (16) is formed to have a larger volume than the second pre-chamber (15).

3. 3. The device (1) according to claim 2, characterized in that the device (1) has a number k of further pre-chambers, where k ≥ 1, said pre-chambers extending around the periphery of each of the pre-chambers mentioned above.

4. 4. The device (1) according to claim 3, characterized in that the kth pre-chamber is formed to have a larger volume than the k-1th pre-chamber.

5. 5. The device (1) according to claim 1, characterized in that the device (1) comprises fuel injection means arranged so as to extend into one of the pre-combustion chambers (15, 16) having a larger volume than the first pre-combustion chamber (12).

6. 2. The device (1) according to claim 1, characterized in that the first pre-chamber (12) is at least partially conically shaped and at least partially tapered from the inside to the outside in the direction of the combustion chamber (3).

7. An internal combustion engine (100) comprising a device (1) for igniting a mixture of fuel and air in a combustion chamber (3) of a cylinder (2) of said internal combustion engine (100), characterized in that the device (1) according to claim 1 is formed.

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