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; an expansion part that is positioned at the edge of the attachment hole in the cylinder head, expands toward the side where the piston is positioned, and contacts the partition wall; and a fuel injection valve that is disposed facing the main combustion chamber and injects fuel toward the auxiliary combustion chamber, wherein the expansion portion has an inclined surface that extends to the side of the communication passage where the cylinder head is positioned, and is inclined from the side where the cylinder head is positioned toward the side where the piston is positioned.

Description

Pre-chamber internal combustion engine

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

[0002] Pre-chamber internal combustion engines have been conventionally 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 via the communication passage.

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

[0004] In such a pre-chamber internal combustion engine, the temperature of the pre-combustion chamber may rise in high-speed or high-load operating regions. When the pre-combustion chamber becomes high in temperature, knocking may occur.

[0005] An object of the present disclosure is to provide a pre-chamber internal combustion engine capable of cooling a 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 to communicate with 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 with the pre-combustion chamber; an expanded portion disposed at an edge of the mounting hole of the cylinder head, expanding toward the side where the piston is disposed, and coming into contact with the partition wall; and a fuel injection valve disposed facing the main combustion chamber and injecting fuel toward the pre-combustion chamber, wherein the expanded portion has an inclined surface that extends toward a side where the cylinder head is located of the communication passage while inclining from a side where the cylinder head is disposed toward a side where the piston is disposed.

[0007] According to this disclosure, the expansion section comes into contact with the partition wall, and heat from the sub-combustion chamber flows through the partition wall to the expansion section. The expansion section dissipates heat to the cylinder head. This cools the sub-combustion chamber. Furthermore, the inclined surface guides any fuel that did not enter the sub-combustion chamber to the vicinity of the sub-combustion chamber in the main combustion chamber via the expansion section, thereby increasing the air-fuel ratio in the vicinity of the sub-combustion chamber in the main combustion chamber. This prevents the air-fuel mixture from entering the gap between the expansion section and the sub-combustion chamber wall.

[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 includes 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 (see Figure 1 for both).

[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 into 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. By injecting fuel toward the sub-combustion chamber 4, the fuel injector 8 supplies fuel to the sub-combustion chamber 4 via the communication passage 5 of the sub-combustion chamber 4, forming a fuel-air mixture.

[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 is positioned adjacent to the sub-combustion chamber wall 41 in at least a direction perpendicular to the direction connecting the sub-combustion chamber 4 and the fuel injection valve 8 (in this embodiment, the ridge direction X).

[0020] As shown in Figures 2, 3, and 4, the expansion section 9 has a first expansion section 9a and a second expansion section 9b. The first expansion section 9a is adjacent to the sub-combustion chamber wall 41 on the side where the fuel injector 8 is located, when viewed in the direction connecting the sub-combustion chamber 4 and the fuel injector 8. In this embodiment, the first expansion section 9a is adjacent to the intake side IN of the sub-combustion chamber wall 41. The second expansion section 9b is adjacent to the sub-combustion chamber wall 41 on the side opposite to where the fuel injector 8 is located. In this embodiment, the second expansion section 9b is adjacent to the exhaust side EX of the sub-combustion chamber wall 41.

[0021] The thickness H of the second expansion section 9b in the direction perpendicular to the cylinder (the direction perpendicular to the sliding direction Z, i.e., the radial direction of the sub-combustion chamber wall 41 as viewed from the sliding direction Z, in this embodiment the intake / exhaust direction Y) is greater than the thickness of the first expansion section 9a. Furthermore, the thickness of the second expansion section 9b in the direction perpendicular to the cylinder increases as it moves away from the fuel injection valve 8. In other words, the thickness of the second expansion section 9b gradually increases in the circumferential direction of the cylinder 10a as it moves toward the exhaust side EX with respect to the central axis C2 of the sub-combustion chamber 4. As shown in Figure 4, the second expansion section 9b is approximately triangular when viewed from the piston side PS.

[0022] The sub-combustion chamber wall 41 on the exhaust side EX is not exposed to fuel and therefore does not cool easily. In this way, the volume of the second expansion section 9b on the opposite side of the fuel injection valve 8 is increased, making it easier to cool the exhaust side EX of the sub-combustion chamber wall 41 while also regulating the flow of the air-fuel mixture on the exhaust side EX.

[0023] As shown in Figure 2, the expansion section 9 has an inclined surface 9c. The inclined surface 9c is the part that connects the first expansion section 9a and the second expansion section 9b, and extends to the cylinder head side of the communication passage 5, inclining from the cylinder head side CS towards the piston side PS as it moves from the first expansion section 9a to the second expansion section 9b.

[0024] In this embodiment, the lower end 9d of the inclined surface 9c is located on the cylinder head side CS of the connecting passage 5a (see Figures 3 and 4) that extends in the ridge direction X. The inclined surface 9c guides the fuel that did not enter the sub-combustion chamber 4 to the piston side PS and to the vicinity of the connecting passage 5a that extends in the ridge direction X. As a result, the air-fuel ratio of the connecting passage 5a of the main combustion chamber 3 that extends in the ridge direction X becomes richer. In addition, a gap S may occur between the expansion portion 9 (second expansion portion 9b) of the exhaust side EX and the sub-combustion chamber wall 41 due to the difference in expansion. However, by guiding the fuel to the vicinity of the connecting passage 5 that extends in the ridge direction X, it is possible to suppress fuel from flowing back into the exhaust side EX of the sub-combustion chamber 4 and to suppress fuel from entering this gap S.

[0025] The inclined surface 9c is sloped such that it becomes higher toward the piston side PS as it moves from the side where the fuel injector 8 is located toward the central axis C2 of the sub-combustion chamber 4. In this embodiment, the inclined surface 9c becomes higher toward the piston side PS as it moves from the intake side IN toward the exhaust side EX of the sub-combustion chamber 4. The inclined surface 9c is highest on the exhaust side EX of the connecting passage 5a that extends in the ridge direction X. This allows the inclined surface 9c to guide the fuel directly below the sub-combustion chamber 4 in the main combustion chamber 3.

[0026] The inclined surface 9c becomes steeper toward the piston side PS as it approaches the central axis C2 of the sub-combustion chamber 4. The inclined surface 9c ultimately extends in the sliding direction Z toward the piston side PS. This allows for more stable fuel guidance directly below the sub-combustion chamber 4 within the main combustion chamber 3.

[0027] As described above, this disclosure provides a sub-chamber type internal combustion engine 1 capable of cooling the sub-combustion chamber 4.

[0028] <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.

[0029] 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.

[0030] 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: First expansion section, 9b: Second expansion section, 9c: Inclined surface, 10a: Cylinder

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; an expansion portion disposed at the edge of the mounting hole of the cylinder head, expanding toward the side where the piston is positioned, and contacting the partition wall; and a fuel injection valve positioned facing the main combustion chamber and injecting fuel toward the sub-combustion chamber, wherein the expansion portion has an inclined surface that extends from the side where the cylinder head is positioned toward the side where the piston is positioned, to the side of the communication passage where the cylinder head is positioned.

2. The pre-chamber type internal combustion engine according to claim 1, wherein the expansion section is arranged adjacent to the partition wall in a direction perpendicular to the direction connecting the pre-combustion chamber and the fuel injection valve.

3. The inclined surface rises toward the side where the piston is located, from the side where the fuel injector is located toward the center of the sub-combustion chamber, according to claim 1.

4. The inclined surface becomes steeper toward the side where the piston is located as it approaches the center of the sub-combustion chamber, according to claim 3.

5. The pre-chamber type internal combustion engine according to any one of claims 1 to 4, wherein the expansion portion includes, when viewed in the direction connecting the pre-combustion chamber and the fuel injector, a first expansion portion adjacent to the partition wall on the side where the fuel injector is located, and a second expansion portion adjacent to the partition wall on the opposite side from where the fuel injector is located, wherein the thickness of the second expansion portion in the direction perpendicular to the cylinder is greater than the thickness of the first expansion portion.

6. The thickness of the second expansion section in the direction perpendicular to the cylinder increases with increasing distance from the sub-combustion chamber, as described in claim 5.

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