Auxiliary chamber type internal combustion engine

Abstract

To provide an auxiliary chamber type internal combustion engine that easily forms a rich mixture around an auxiliary combustion chamber.SOLUTION: An auxiliary chamber type internal combustion engine comprises a piston that slides within a cylinder, a main combustion chamber, an auxiliary combustion chamber that is disposed separatedly from the main combustion chamber by a partition wall, a fuel injection valve that injects fuel toward the auxiliary combustion chamber, a first communication passage that connects the main combustion chamber and the auxiliary combustion chamber toward the fuel injection valve, and a second communication passage that connects the main combustion chamber and the auxiliary combustion chamber toward the piston. The spray injected from the fuel injection valve is directed between the first communication passage and the second communication passage and is inclined toward the first communication passage.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Conventionally, a pre-combustion chamber type internal combustion engine has been known (see, for example, Patent Document 1). The pre-combustion chamber type internal combustion engine of Patent Document 1 comprises a main combustion chamber and a pre-combustion chamber, with an ignition device and a fuel injection valve disposed in the pre-combustion chamber. The pre-combustion chamber type internal combustion engine of Patent Document 1 generates an air-fuel mixture in the pre-combustion chamber and ignites this air-fuel mixture to form a flame. The flame formed in the pre-combustion chamber is injected into the main combustion chamber via a communication passage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-85181 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, pre-combustion chamber internal combustion engines have been developed, in which a fuel injection valve is placed in the main combustion chamber or intake port, a mixture is supplied from the main combustion chamber to the pre-combustion chamber, and the mixture in the pre-combustion chamber is burned in the pre-combustion chamber. In such pre-combustion engines, a jet flame is injected toward the cylinder, so combustion progresses from the outside to the inside of the main combustion chamber. As a result, the mixture in the pre-combustion chamber (actually, around the wall of the pre-combustion chamber) tends to remain unburned. Therefore, it is desirable to form a mixture with a high fuel concentration around the pre-combustion chamber.

[0005] An object of the present disclosure is to provide an auxiliary combustion chamber type internal combustion engine that is easy to form a mixture with a high fuel concentration around the auxiliary combustion chamber. [Means for solving the problem]

[0006] The auxiliary combustion chamber type internal combustion engine according to the present disclosure includes a piston that slides within a cylinder, a main combustion chamber, an auxiliary combustion chamber that is separated from the main combustion chamber by a partition wall, a fuel injection valve that injects fuel toward the auxiliary combustion chamber, a first communication passage that connects the main combustion chamber and the auxiliary combustion chamber toward the fuel injection valve, and a second communication passage that connects the main combustion chamber and the auxiliary combustion chamber toward the piston. The spray injected from the fuel injection valve is directed between the first communication passage and the second communication passage and is inclined toward the first communication passage. [Effects of the Invention]

[0007] In this pre-combustion chamber internal combustion engine, the spray injected from the fuel injection valve collides between the first and second communication passages. Because the spray is tilted toward the first communication passage, the spray after collision flows toward the second communication passage. This makes it easier for a fuel-rich mixture to form around the pre-combustion chamber. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating an internal combustion engine with a pre-chamber according to an embodiment of the present disclosure; [Figure 2] FIG. 2 is a side view of a pre-combustion chamber wall according to an embodiment of the present disclosure. [Figure 3] FIG. 2 is a bottom view of the vicinity of the auxiliary combustion chamber according to an embodiment of the present disclosure. [Figure 4] FIG. 2 is an enlarged cross-sectional view of the vicinity of an auxiliary combustion chamber according to an embodiment of the present disclosure. [Figure 5] FIG. 10 is a side view of the auxiliary combustion chamber wall according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the sliding direction of the piston 8 is indicated as P, the side where the intake valve 14 is located is indicated as the intake side IN, and the side where the exhaust valve 16 is located is indicated as the exhaust side EX.

[0010] As shown in Figures 1 and 2, the auxiliary combustion chamber type internal combustion engine 1 includes a main combustion chamber 2, an auxiliary combustion chamber 3, a first communication passage 4, a second communication passage 6, an ignition device 7, a piston 8, and a fuel injection valve 9.

[0011] The main combustion chamber 2 is a space surrounded by the cylinder 10a of the cylinder block 10, the cylinder head 12, and the piston 8. In this embodiment, the main combustion chamber 2 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 12. The main combustion chamber 2 is connected to the intake port 12a via an intake valve 14. The intake port 12a is connected, for example, to an intake passage (not shown). The main combustion chamber 2 is connected to the exhaust port 12b via an exhaust valve 16. The exhaust port 12b is connected, for example, to an exhaust passage (not shown).

[0012] The auxiliary combustion chamber 3 protrudes from the cylinder head 12 toward the main combustion chamber 2, straddling a ridgeline X (see FIG. 3) formed at the top of the pent roof shape. The auxiliary combustion chamber 3 is disposed separated from the main combustion chamber 2 by an auxiliary combustion chamber wall (an example of a partition wall) 5. The auxiliary combustion chamber 3 is disposed adjacent to the main combustion chamber 2, and has a space surrounded by the auxiliary combustion chamber wall 5.

[0013] 2 and 3, in this embodiment, the auxiliary combustion chamber wall 5 has a side wall 51 and a bottom wall 52. In this embodiment, the side wall 51 is formed in a cylindrical shape, and the bottom wall 52 is formed in a hollow hemispherical shape.

[0014] The bottom wall 52 has a first protrusion 52a and a second protrusion 52b. The first protrusion 52a is disposed on the exhaust side of the second communication passage 6 and extends closer to the piston 8 (see FIG. 1) than the second communication passage 6 formed in the bottom wall 52. The second protrusion 52b is disposed closer to the cylinder head 12 than the first communication passage 4 and extends closer to the fuel injection valve 9 (intake side) than the first communication passage 4.

[0015] In this embodiment, the bottom wall 52 has a thin portion 52c and a thick portion 52d. The thin portion 52c is disposed on the intake side of the bottom wall 52. The thick portion 52d is disposed on the exhaust side of the bottom wall 52. A step surface 52e is formed at the boundary between the thin portion 52c and the thick portion 52d. This step surface 52e connects the first protrusion 52a and the second protrusion 52b, and the first protrusion 52a and the second protrusion 52b are continuous with each other.

[0016] The first communication passage 4 and the second communication passage 6 are arranged in the auxiliary combustion chamber wall 5. The first communication passage 4 connects the main combustion chamber 2 and the auxiliary combustion chamber 3 toward the fuel injection valve 9. In this embodiment, the first communication passage 4 is arranged in the thin-walled portion 52c. Four first communication passages 4 are provided, and each of the four first communication passages 4 is formed facing a different direction toward the intake side. However, as shown in FIG. 3 , no first communication passage 4 is arranged in a position opposite the fuel injection valve 9 when viewed in the direction from the intake side toward the exhaust side. By arranging the first communication passage 4 in this way, the jet flame injected from the first communication passage 4 is prevented from directly impinging on the fuel injection valve 9.

[0017] As shown in FIGS. 2 and 3, the second communication passage 6 connects the main combustion chamber 2 and the auxiliary combustion chamber 3 toward the piston 8. In this embodiment, the second communication passage 6 is disposed in the thin-walled portion 52c. The second communication passage 6 is disposed so that the center line C2 of the second communication passage 6 overlaps with the center line Cs of the auxiliary combustion chamber 3. As shown in FIG. 1, in this embodiment, the center line Cs of the auxiliary combustion chamber 3 coincides with the center line Cc of the cylinder 10a (the center line of the main combustion chamber 2). Therefore, as shown in FIG. 2, the center line C2 of the second communication passage 6 is formed along the center line Cc of the cylinder 10a toward the bottom dead center side (toward the piston 8) in the sliding direction P.

[0018] Furthermore, in this embodiment, a third communication passage 17 is disposed on the exhaust side of the auxiliary combustion chamber wall 5. The third communication passage 17 connects the main combustion chamber 2 and the auxiliary combustion chamber 3 toward the exhaust side. In this embodiment, the third communication passage 17 is disposed in the thick-walled portion 52d. Four third communication passages 17 are provided, and each of the four third communication passages 17 is formed facing a different direction toward the exhaust side. Because the third communication passage 17 is formed in the thick-walled portion 52d, the overall length of the passage is longer than that of the first communication passage 4 formed in the thin-walled portion 52c. For this reason, a counterbore portion 18 is provided around the opening on the exhaust side of the third communication passage 17 (see FIG. 4). This allows the contact length of the jet flame of the third communication passage 17 to be matched with that of the first communication passage 4. As a result, the jet flame ejected from the first communication passage 4 and the jet flame ejected from the third communication passage 17 can have the same momentum and spread.

[0019] The ignition device 7 is disposed in the auxiliary combustion chamber 3. As shown in FIG. 4, the ignition device 7 has an ignition coil (not shown) and an ignition plug 7a. A center electrode 7b and a side electrode 7c of the ignition plug 7a protrude into the auxiliary combustion chamber 3. In this embodiment, the center electrode 7b is disposed on the center line Cs of the auxiliary combustion chamber 3. However, the center electrode 7b may be disposed offset from approximately the center of the auxiliary combustion chamber 3 toward the cylinder 10a.

[0020] As shown in FIG. 1 , a piston 8 is housed in a cylinder 10a and slides within the cylinder 10a. The cylinder 10a surrounds the periphery of the main combustion chamber 2. The piston 8 surrounds the main combustion chamber 2 from below. A fuel injection valve 9 injects fuel toward the auxiliary combustion chamber 3 and forms an air-fuel mixture in the main combustion chamber 2 and the auxiliary combustion chamber 3. In this embodiment, the fuel injection valve 9 is a direct injection type that injects fuel directly into the main combustion chamber 2. In this embodiment, the auxiliary combustion chamber internal combustion engine 1 further includes a port injection valve 19. The port injection valve 19 injects fuel into the intake port 12a and forms an air-fuel mixture in the main combustion chamber 2. However, the auxiliary combustion chamber internal combustion engine 1 may include an in-cylinder injection valve that injects fuel into the cylinder instead of the port injection valve 19. Furthermore, the auxiliary combustion chamber internal combustion engine 1 may inject fuel into the main combustion chamber 2 using the fuel injection valve 9.

[0021] The cross section of the auxiliary combustion chamber wall 5 in FIG. 4 is cross section II in FIG. 3. As shown in FIG. 4, the auxiliary combustion chamber internal combustion engine 1 configured as described above injects fuel using a fuel injection valve 9 to form an air-fuel mixture in the main combustion chamber 2 and the auxiliary combustion chamber 3. At this time, the fuel spray injected from the fuel injection valve 9 (an example of the spray, see the dotted hatching in FIG. 4) is directed between the first communication passage 4 and the second communication passage 6 and is inclined toward the first communication passage 4. More specifically, the spray axis F of the fuel spray is located between the center line C1 of the first communication passage 4 and the center line C2 of the second communication passage, and intersects with the outer peripheral surface of the thin-walled portion 52c between the first communication passage 4 and the second communication passage 6. The spray axis F is an axis located at the center of the fuel spray injected from the fuel injection valve 9. The spray axis F of the fuel spray is formed so as to be inclined toward the center line C1 of the first communication passage 4 and intersects with the center line C1 of the first communication passage 4 on the intake side. That is, the fuel injection valve 9 injects fuel so that the angle α formed by the spray axis F and the tangent line S1 at the position of the center line C1 of the first communication passage 4 is within 90 degrees.

[0022] Furthermore, the fuel spray is closer to the first communication passage 4 than to the second communication passage 6. More specifically, the spray axis F of the fuel spray intersects with the outer peripheral surface of the thin-walled portion 52c between the first communication passage 4 and the second communication passage 6 at a position closer to the center line C1 of the first communication passage 4 than to the center line C2 of the second communication passage 6.

[0023] By forming the fuel spray in this manner, the fuel spray collides with the thin portion 52c of the auxiliary combustion chamber wall 5 and diffuses. The diffused fuel spray flows toward the second communication passage 6. The fuel spray that flows into the second communication passage 6 collides with the first protrusion 52a and forms an air-fuel mixture around the second communication passage 6. In conventional auxiliary combustion chamber internal combustion engines, the fuel concentration of the air-fuel mixture on the piston side of the auxiliary combustion chamber wall tends to be low. However, the auxiliary combustion chamber internal combustion engine 1 of this embodiment can form a mixture with a high fuel concentration around the second communication passage 6.

[0024] On the other hand, part of the fuel spray that collides with the thin-walled portion 52c flows toward the first communication passage 4. The fuel spray that flows into the first communication passage 4 collides with the second protrusion 52b and diffuses. As a result, an air-fuel mixture is also formed around the first communication passage 4. In this way, the fuel diffuses over the entire thin-walled portion 52c of the auxiliary combustion chamber wall 5.

[0025] The air-fuel mixture passes through the first communication passage 4 and the second communication passage 6 and is supplied to the auxiliary combustion chamber 3. As described above, in the auxiliary combustion chamber internal combustion engine 1, fuel diffuses over the entire thin-walled portion 52c of the auxiliary combustion chamber wall 5, making it easy to form a fuel-rich mixture on the intake side and piston 8 side of the auxiliary combustion chamber wall 5. This allows a fuel-rich mixture to be supplied to the auxiliary combustion chamber 3 from the first communication passage 4 and the second communication passage 6. The mixture supplied to the auxiliary combustion chamber 3 is ignited by the ignition device 7 to form a flame. The flame in the auxiliary combustion chamber 3 passes through the first communication passage 4, the second communication passage 6, and the third communication passage 17, becoming a jet flame and being injected into the main combustion chamber 2. In this embodiment, because a fuel-rich mixture is supplied to the auxiliary combustion chamber 3, the jet flame also becomes stronger. It should be noted that the rich mixture around the auxiliary combustion chamber 3 does not necessarily mean only a rich mixture that is richer than the stoichiometric air-fuel ratio, but it may be a mixture with a stoichiometric air-fuel ratio or a lean mixture that is leaner than the stoichiometric air-fuel ratio as long as it is a mixture richer than the air-fuel ratio of the main combustion chamber 2.

[0026] As described above, according to the present disclosure, it is possible to provide an auxiliary combustion chamber type internal combustion engine 1 that is likely to form a rich mixture around the auxiliary combustion chamber 3.

[0027] <Other embodiments> Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments, and various modifications are possible within the scope of the gist of the invention. In particular, the multiple modifications described in this specification can be arbitrarily combined as necessary.

[0028] (a) In the above embodiment, an example was described in which the side wall 51 was provided on the auxiliary combustion chamber wall 5, but the present disclosure is not limited to this. For example, the side wall 51 may be formed integrally with the cylinder head 12.

[0029] (b) In the above embodiment, the side wall 51 is cylindrical, but the present disclosure is not limited to this. The side wall 51 may have another cylindrical shape.

[0030] (c) In the above embodiment, the auxiliary combustion chamber wall 5 has been described as having a thin portion 52c and a thick portion 52d, but the present disclosure is not limited to this. For example, as shown in FIG. 5, a first protrusion 52a and a second protrusion 52b may be disposed on a portion of the auxiliary combustion chamber wall 5. [Explanation of symbols]

[0031] 1: Pre-chamber internal combustion engine, 2: Main combustion chamber, 3: Pre-combustion chamber, 4: First communication passage 5: Pre-combustion chamber wall, 6: Second communication passage, 8: Piston, 9: Fuel injection valve 10a: Cylinder, 12: Cylinder head 51: side wall, 52: bottom wall, 52a: first convex portion, 52b: second convex portion EX: Exhaust side, IN: Intake side F: Spray axis

Claims

1. A piston that slides in a cylinder; A main combustion chamber; an auxiliary combustion chamber arranged separated from the main combustion chamber via a partition wall; a fuel injection valve that injects fuel toward the auxiliary combustion chamber; a first communication passage that communicates the main combustion chamber with the auxiliary combustion chamber toward the fuel injection valve; a second communication passage that communicates the main combustion chamber with the auxiliary combustion chamber toward the piston; Equipped with a spray injected from the fuel injection valve is directed between the first communication passage and the second communication passage and is inclined toward the first communication passage; Pre-chamber internal combustion engine.

2. the spray is sprayed at a closer distance from the first communication passage than from the second communication passage; 2. The pre-combustion chamber type internal combustion engine according to claim 1.

3. a first protrusion disposed on an exhaust side of the second communication passage and extending closer to the piston than the second communication passage; 2. The pre-combustion chamber type internal combustion engine according to claim 1.

4. a second protrusion disposed on a cylinder head side of the first communication passage and extending toward the fuel injection valve beyond the first communication passage; 2. The pre-combustion chamber type internal combustion engine according to claim 1.

5. a first protrusion disposed on an exhaust side of the second communication passage and extending closer to the piston than the second communication passage; a second protrusion disposed on a cylinder head side of the first communication passage and extending toward the fuel injection valve side relative to the first communication passage; Furthermore, The first convex portion and the second convex portion are formed on the auxiliary combustion chamber wall, and the first convex portion and the second convex portion are continuous with each other.

5. The pre-combustion chamber type internal combustion engine according to claim 1.

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