Prechamber internal combustion engine

Abstract

A prechamber internal combustion engine comprising: a cylinder head that has an attachment hole; a main combustion chamber that is formed between the cylinder head and a piston; an auxiliary combustion chamber that is positioned so that a partition wall is interposed between the auxiliary combustion chamber and the main combustion chamber, said auxiliary combustion chamber extending from the cylinder head toward the side where the piston is positioned, and being attached to the attachment hole; a communication passage that communicates the main combustion chamber and the auxiliary combustion chamber; and an expansion part that is positioned at the edge of the attachment hole in the cylinder head, expands from the cylinder head toward the side where the piston is positioned, and contacts the partition wall, wherein the expansion part has a main portion, and the main portion extends to the side of the communication passage where the cylinder head is positioned.

Description

Pre-chamber internal combustion engine

[0001] The present disclosure relates to a pre-chamber internal combustion engine.

[0002] Conventionally, pre-chamber internal combustion engines are known (see, for example, Patent Document 1). The pre-chamber internal combustion engine of Patent Document 1 includes a main combustion chamber and a pre-combustion chamber, wherein an ignition device is disposed in the pre-combustion chamber, and a fuel injection device is disposed in the main combustion chamber. The pre-chamber internal combustion engine of Patent Document 1 is a passive-type pre-chamber internal combustion engine that forms an air-fuel mixture in the pre-combustion chamber by supplying fuel injected from the main combustion chamber to the pre-combustion chamber. The air-fuel mixture formed in the pre-combustion chamber is ignited by the ignition device to form a flame. The flame formed in the pre-combustion chamber is injected as a jet flame into the main combustion chamber through a communication passage.

[0003] Japanese Unexamined Patent Application Publication No. 2023-84004

[0004] In such a pre-chamber internal combustion engine, the pre-combustion chamber may become high temperature in a high rotation speed or high load region. When the pre-combustion chamber becomes high temperature, knocking may occur.

[0005] An object of the present disclosure is to provide a pre-chamber internal combustion engine capable of cooling the pre-combustion chamber.

[0006] A pre-chamber internal combustion engine according to the present disclosure includes: a cylinder head having a mounting hole; a main combustion chamber formed between the cylinder head and a piston; a pre-combustion chamber disposed between the main combustion chamber via a partition wall, extending from the cylinder head toward a side where the piston is disposed, and mounted in the mounting hole; a communication passage that communicates the main combustion chamber and the pre-combustion chamber; and an expansion portion disposed at an edge of the mounting hole of the cylinder head, expanding from the cylinder head toward the side where the piston is disposed, and contacting the partition wall, wherein the expansion portion has a main portion, and the main portion extends to a side of the communication passage where the cylinder head is disposed.

[0007] In this pre-chamber internal combustion engine, the expansion portion contacts the partition wall, and heat of the pre-combustion chamber flows to the expansion portion through the partition wall. The expansion portion dissipates heat to the cylinder head. Thereby, the pre-combustion chamber is cooled.

[0008] According to this disclosure, a sub-chamber type internal combustion engine capable of cooling the sub-combustion chamber can be provided.

[0009] A diagram showing a sub-chamber internal combustion engine according to one embodiment of the present disclosure. An enlarged view of the sub-combustion chamber portion according to one embodiment of the present disclosure. A bottom view of the main combustion chamber and sub-combustion chamber portions of the sub-chamber internal combustion engine according to one embodiment of the present disclosure in a cold state. A bottom view of the sub-combustion chamber portion of the sub-chamber internal combustion engine according to one embodiment of the present disclosure in a cold state.

[0010] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. In the drawings, the sliding direction of the piston 7 is denoted as Z. In the specification, the side of the sliding direction Z where the piston 7 is located is denoted as the piston side PS, and the side where the cylinder head 2 is located is denoted as the cylinder head side CS. In the drawings, the side where the intake valve 14 is located is denoted as the intake side IN, the side where the exhaust valve 16 is located is denoted as the exhaust side EX, and the direction connecting the intake side IN and the exhaust side EX is denoted as the intake / exhaust direction Y. Furthermore, in the drawings, the direction perpendicular to the sliding direction Z and the intake / exhaust direction Y is denoted as the ridge direction X. In this embodiment, the ridge X1 of the pent roof extends in the ridge direction X.

[0011] As shown in Figure 1, the pre-chamber internal combustion engine 1 comprises a cylinder head 2, a main combustion chamber 3, a sub-combustion chamber 4, a communication passage 5, an ignition device 6, a piston 7, a fuel injection valve 8, and an expansion section 9. In this embodiment, the pre-chamber internal combustion engine 1 is a gasoline engine in which the fuel-air mixture in the sub-combustion chamber 4 is ignited by the ignition device 6. The pre-chamber internal combustion engine 1 of this embodiment is mounted on a vehicle such as an automobile.

[0012] The main combustion chamber 3 is the space enclosed by the cylinder 10a of the cylinder block 10, the cylinder head 2, and the piston 7. In this embodiment, the main combustion chamber 3 has a pent-roof shape with two slopes formed toward the intake port 12a side and the exhaust port 12b side of the cylinder head 2. The main combustion chamber 3 is connected to the intake port 12a via the intake valve 14. The intake port 12a is connected to, for example, an intake passage (not shown). The main combustion chamber 3 is connected to the exhaust port 12b via the exhaust valve 16. The exhaust port 12b is connected to, for example, an exhaust passage (not shown).

[0013] As shown in Figure 2, the sub-combustion chamber 4 is a space surrounded by a sub-combustion chamber wall (an example of a partition wall) 41. The sub-combustion chamber 4 protrudes from the cylinder head 2 toward the main combustion chamber 3 and is separated from the main combustion chamber 3 via the sub-combustion chamber wall 41. In this embodiment, the sub-combustion chamber 4 is positioned adjacent to the main combustion chamber 3 at the top of the pent-roof shape of the main combustion chamber 3, and the central axis C2 of the sub-combustion chamber 4 in this embodiment, which extends in the sliding direction Z, coincides with the central axis C1 of the main combustion chamber 3, which extends in the sliding direction Z.

[0014] The sub-combustion chamber wall 41 has a side wall 41a and a bottom wall 41b. In this embodiment, the side wall 41a is formed in a cylindrical shape. In this embodiment, the side wall 41a is inserted along the mounting hole 2c of the cylinder head 2. The bottom wall 41b is formed in a hollow hemispherical shape. In this embodiment, the sub-combustion chamber wall 41 (side wall 41a and bottom wall 41b) is formed from sheet metal.

[0015] As shown in Figure 3, the communication passage 5 is provided in the sub-combustion chamber wall 41 and connects the main combustion chamber 3 and the sub-combustion chamber 4. There may be multiple communication passages 5. In this embodiment, there are a total of eight communication passages 5: two along the pent-roof ridge line X1 of the main combustion chamber 3, three facing the intake side (IN), and three facing the exhaust side (EX).

[0016] As shown in Figure 2, the ignition device 6 is located inside the sub-combustion chamber 4. The ignition device 6 discharges the current flowing through the ignition coil using the central electrode and side electrodes, igniting the fuel-air mixture in the sub-combustion chamber 4.

[0017] As shown in Figures 1 and 3, the fuel injector 8 is located in the main combustion chamber 3 and injects fuel toward the sub-combustion chamber 4, forming a fuel-air mixture in the main combustion chamber 3 and the sub-combustion chamber 4. In this embodiment, the fuel injector 8 is located on the intake side IN. The fuel injector 8 is a direct injection type with its injection port facing the main combustion chamber 3. The fuel injector 8 injects fuel F1 toward the sub-combustion chamber 4, supplying fuel to the sub-combustion chamber 4 via the communication passage 5 of the sub-combustion chamber 4, and forming a fuel-air mixture in the sub-combustion chamber 4.

[0018] The sub-combustion chamber 4 is attached to a mounting hole 2c provided in the cylinder head 2. In this embodiment, the mounting hole 2c is provided through the upper surface of the cylinder head 2, and the sub-combustion chamber 4 is inserted into the mounting hole 2c from above the cylinder head 2 and attached.

[0019] As shown in Figure 2, the expansion portion 9 is positioned on the edge 2a of the mounting hole provided in the cylinder head 2. The expansion portion 9 expands from the cylinder head 2 toward the piston side PS. The expansion portion 9 has a main portion 9a and a protruding portion 9b.

[0020] As shown in Figure 3, the main portion 9a is arranged around the entire circumference of the cylindrical cross-section sub-combustion chamber wall 41. As shown in Figure 2, the expansion amount of the main portion 9a of the expansion portion 9 is smaller on the side where the fuel injector 8 is located than on the side opposite to where the fuel injector 8 is located. In this embodiment, the expansion amount of the intake side IN is smaller than the expansion amount of the exhaust side EX. More specifically, the height H1 of the main portion 9a of the exhaust side EX facing the piston side PS is higher than the height H2 of the main portion 9a of the intake side IN. The intake side IN is cooled by the fuel F1 (see Figure 1 or Figure 3) injected from the fuel injector 8. The exhaust side EX, which is on the opposite side of the fuel injector 8, is not cooled by fuel, so it is preferable to increase the area in contact with the sub-combustion chamber 4 and increase the amount of heat transferred from the sub-combustion chamber wall 41 to the expansion portion 9. On the other hand, if the expansion portion 9 of the intake side IN is made too large, it becomes difficult for fuel to enter the sub-combustion chamber 4.

[0021] The protrusion 9b extends from the main portion 9a toward the piston side PS between the multiple communication passages 5. In this embodiment, the protrusion 9b is positioned between all eight communication passages 5. This increases the contact area between the expansion portion 9 and the sub-combustion chamber 4, while preventing the expansion portion 9 from obstructing the jet flame injected from the communication passages 5. Furthermore, the protrusion 9b on the intake side IN facilitates the guidance of fuel into the communication passages 5.

[0022] As shown in Figures 3 and 4, the expansion section 9 is positioned with a gap S between it and the sub-combustion chamber wall 41 when the sub-chamber internal combustion engine 1 is cold. When the sub-chamber internal combustion engine 1 is cold, the temperature of the sub-combustion chamber 4 is low, so there is no need to cool the sub-combustion chamber 4. Therefore, the sub-chamber internal combustion engine 1 is designed so that heat transfer between the sub-combustion chamber wall 41 and the expansion section 9 is prevented by the gap S. In this embodiment, the cylinder head 2 is made of an aluminum material, and the expansion section 9 is made of the same material as the cylinder head 2. The sub-combustion chamber 4 expands as its temperature increases. When the sub-combustion chamber 4 expands, the gap S between the sub-combustion chamber wall 41 and the expansion section 9 is filled, and the contact area between the sub-combustion chamber wall 41 and the expansion section 9 increases. As a result, the amount of heat transferred from the expansion section 9 to the sub-combustion chamber wall 41 increases as the temperature of the sub-chamber internal combustion engine 1 increases.

[0023] As described above, this disclosure provides a sub-chamber type internal combustion engine 1 capable of cooling the sub-combustion chamber 4.

[0024] <Other Embodiments> Although embodiments of the present disclosure have been described above, the present disclosure is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. In particular, the various modifications described herein can be combined as needed.

[0025] In the above embodiment, an example in which eight connecting passages 5 are arranged was described, but this disclosure is not limited to this. There is no limit to the number of connecting passages 5, as long as there are multiple.

[0026] 1: Pre-chamber internal combustion engine, 2: Cylinder head, 2a: Edge, 2c: Mounting hole, 3: Main combustion chamber, 4: Sub-combustion chamber, 5: Connecting passage, 7: Piston, 8: Fuel injector, 9: Expansion section, 9a: Main section, 9b: Protruding section, 10a: Cylinder, S: Gap

Claims

1. A sub-chamber internal combustion engine comprising: a cylinder head having a mounting hole; a main combustion chamber formed between the cylinder head and a piston; a sub-combustion chamber disposed from the main combustion chamber via a partition wall, extending from the cylinder head toward the side where the piston is positioned, and attached to the mounting hole; a communication passage connecting the main combustion chamber and the sub-combustion chamber; and an expansion portion disposed at the edge of the mounting hole of the cylinder head, expanding toward the side where the piston is positioned from the cylinder head, and contacting the partition wall, wherein the expansion portion has a main portion, and the main portion extends to the side of the communication passage where the cylinder head is positioned.

2. The amount of heat transferred from the partition wall to the expansion section increases as the temperature of the sub-combustion chamber increases, according to claim 1.

3. The sub-chamber type internal combustion engine according to claim 2, wherein the expansion portion is arranged with a gap between it and the partition wall when the sub-combustion chamber is in a cold state.

4. The expansion section has a main section and a protruding section, and there are a plurality of connecting passages, the protruding section extending from the main section to the space between the plurality of connecting passages, the sub-chamber type internal combustion engine according to claim 1.

5. A sub-chamber internal combustion engine according to any one of claims 1 to 4, further comprising a fuel injector positioned facing the main combustion chamber and injecting fuel toward the sub-combustion chamber, wherein the expansion portion has an expansion amount on the side where the fuel injector is positioned that is smaller than the expansion amount on the side opposite to where the fuel injector is positioned.

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