Auxiliary chamber type internal combustion engine

Abstract

To provide an auxiliary chamber type internal combustion engine capable of suppressing shock caused by a jet flame.SOLUTION: An auxiliary chamber type internal combustion engine includes an ignition device, a main combustion chamber, and an auxiliary combustion chamber disposed to separate from the main combustion chamber via a first wall. The ignition device is disposed in the main combustion chamber, and the auxiliary combustion chamber includes: a second wall formed to surround the periphery of the ignition device and separating the main combustion chamber and the auxiliary combustion chamber from each other; and a communication passage formed on the second wall.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a prechamber internal combustion engine.

Background Art

[0002] Conventionally, a prechamber internal combustion engine has been known (see, for example, Patent Document 1). The prechamber internal combustion engine includes a main combustion chamber and a prechamber, and ignites the air-fuel mixture in the main combustion chamber by injecting a jet flame from the prechamber toward the main combustion chamber. In such a prechamber internal combustion engine, the column vibration generated by the flame propagation in the main combustion chamber may be amplified by the column vibration generated by the jet flame injected from the prechamber, resulting in a shock. Such a shock may also be referred to as a jet shock.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The air-fuel mixture in the main combustion chamber may have a difference in concentration due to the flow in the main combustion chamber. When a difference in concentration occurs in the main combustion chamber, a difference in the flame propagation speed in the main combustion chamber occurs according to the difference in concentration. When variations occur in the jet flame injected from the prechamber, the difference in the flame propagation speed in the main combustion chamber is more likely to increase. When the difference in the flame propagation speed increases, the shock caused by the jet flame is more likely to increase.

[0005] An object of the present disclosure is to provide a prechamber internal combustion engine capable of suppressing the shock caused by the jet flame.

Means for Solving the Problems

[0006] The auxiliary chamber type internal combustion engine according to the present disclosure includes an ignition device, a main combustion chamber, and an auxiliary combustion chamber disposed separately from the main combustion chamber with a first wall therebetween. The ignition device is disposed in the main combustion chamber, and the auxiliary combustion chamber is formed to surround the periphery of the ignition device. The auxiliary combustion chamber has a second wall separating the main combustion chamber and the auxiliary combustion chamber, and a communication passage formed in the second wall.

Advantages of the Invention

[0007] According to this configuration, the air-fuel mixture in the main combustion chamber around the ignition device is first ignited, and a flame is ejected from the main combustion chamber around the ignition device into the main combustion chamber. At the same time, the flame in the main combustion chamber around the ignition device is ejected into the auxiliary combustion chamber through the communication passage to ignite the air-fuel mixture in the auxiliary combustion chamber, and a jet flame is ejected from the auxiliary combustion chamber toward the main combustion chamber with a delay from the flame in the main combustion chamber around the ignition device. That is, an intentional phase difference can be provided between the flame in the main combustion chamber around the ignition device and the jet flame ejected from the auxiliary combustion chamber. As a result, for example, by arranging the auxiliary combustion chamber according to the air-fuel ratio of the air-fuel mixture in the main combustion chamber, the difference in flame propagation speed in the main combustion chamber can be reduced. Consequently, the shock caused by the jet flame can be suppressed.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0009] Hereinafter, a first embodiment of the present disclosure will be described with reference to the drawings.

[0010] As shown in Fig. 1, the auxiliary chamber type internal combustion engine 1 includes a main combustion chamber 2, an auxiliary combustion chamber 4, an ignition device 6, 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 in which two slopes are 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 to, for example, 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 to, for example, an exhaust passage (not shown).

[0012] The auxiliary combustion chamber 4 is disposed adjacent to the main combustion chamber 2 at the top of the pent-roof shape and has a space surrounded by an auxiliary combustion chamber wall (an example of the first wall) 4a. The auxiliary combustion chamber 4 protrudes from the cylinder head 12 toward the main combustion chamber 2 and is disposed with a space therebetween via the auxiliary combustion chamber wall 4a. The auxiliary combustion chamber wall 4a has a side wall 41, a bottom wall 42, and an upper wall 43. The side wall 41 is a wall that separates the cylinder 10a side of the auxiliary combustion chamber 4 from the main combustion chamber 2. The bottom wall 42 is a wall that separates the piston 8 side of the auxiliary combustion chamber 4 from the main combustion chamber 2. In this embodiment, the bottom wall 42 is formed in an arc shape or a linear shape in cross section. However, the shape of the bottom wall 42 is not limited to this and may be any shape. The upper wall 43 is a wall that separates the auxiliary combustion chamber 4 from the cylinder head 12. In this embodiment, the upper wall 43 is formed integrally with the lower surface of the cylinder head 12.

[0013] As shown in Figs. 2(a) and 2(b), the auxiliary combustion chamber 4 has an inner wall (an example of the second wall) 4b, an intake side space 4c, and an exhaust side space 4d. The inner wall 4b is formed surrounding the ignition plug 6a of the ignition device 6 and separates the main combustion chamber 2 from the auxiliary combustion chamber 4. The main combustion chamber 2 forms a space around the plug 2b by surrounding the ignition plug 6a with the inner wall 4b. The space around the plug 2b is a space that is open toward the piston 8 (see Fig. 1) side.

[0014] The intake-side space 4c is the space located on the intake side among the spaces of the sub-combustion chamber 4 surrounded by the inner wall 4b, the side wall 41, the bottom wall 42, and the upper wall 43. The exhaust-side space 4d is the space located on the exhaust side among the spaces surrounded by the inner wall 4b, the side wall 41, the bottom wall 42, and the upper wall 43.

[0015] As shown in FIG. 2(b), in the present embodiment, the sub-combustion chamber 4 has an inner wall 4b with a circular cross-section and a side wall 41 with an elliptical cross-section. The side wall 41 is arranged with its center offset toward the intake side from the center of the inner wall 4b.

[0016] As shown in FIG. 2(a), the sub-combustion chamber 4 has a first communication passage 4e opening toward the piston 8 side and a second communication passage 4f opening toward the ignition device 6 side. The first communication passage 4e is arranged on the side wall 41 and communicates the sub-combustion chamber 4 with the main combustion chamber 2. The first communication passage 4e is arranged to be inclined toward the piston 8 side with respect to a plane orthogonal to the sliding direction (the central axis direction of the cylinder 10a) on the piston 8 side (see FIG. 1). As shown in FIG. 2(b), in the present embodiment, the first communication passage 4e has an intake-side first communication passage 4h arranged in the intake-side space 4c and an exhaust-side first communication passage 4i arranged in the exhaust-side space 4d. Three intake-side first communication passages 4h are arranged on the intake-side side wall 41 in different directions. However, the number of the intake-side first communication passages 4h may be changed as appropriate. Three exhaust-side first communication passages 4i are arranged on the exhaust-side side wall 41 in different directions. However, the number of the exhaust-side first communication passages 4i may be changed as appropriate.

[0017] As shown in FIG. 2(a), the second communication passage 4f is formed by the lower surface of the cylinder head 12 and the end portion 4g of the inner wall 4b. In the present embodiment, further, the auxiliary combustion chamber 4 has a gas pocket wall (an example of the third wall) 4j that separates the main combustion chamber 2 and the auxiliary combustion chamber 4 on the cylinder head 12 side of the second communication passage 4f. The gas pocket space surrounded by the gas pocket wall 4j, the side wall 41, and the upper wall 43 is difficult for the air-fuel mixture to enter. For this reason, the air-fuel mixture flows on the piston 8 side from the gas pocket space. As a result, the gas pocket space retains the un-scavenged burned gas from the previous cycle and promotes the induction of the air-fuel mixture toward the vicinity of the spark plug.

[0018] The ignition device 6 is disposed in the plug surrounding space 2b of the main combustion chamber 2. The ignition device 6 has an ignition coil (not shown) and a spark plug 6a. The center electrode 6b and the side electrode 6c of the spark plug 6a project into the plug surrounding space 2b. In the present embodiment, the center electrode 6b is disposed substantially at the center of the plug surrounding space 2b. However, the center electrode 6b may be disposed offset from the approximate center of the plug surrounding space 2b.

[0019] The end portion 4g of the inner wall 4b on the cylinder head 12 side is located closer to the cylinder head 12 side than the side electrode 6c of the ignition device 6. Thereby, after the air-fuel mixture in the plug surrounding space 2b is ignited, the flame easily propagates to the second communication passage 4f.

[0020] As shown in FIG. 1, the piston 8 is accommodated in the cylinder 10a and slides within the cylinder 10a. The piston 8 surrounds the main combustion chamber 2 from below. The fuel injection valve 9 injects fuel toward the main combustion chamber 2 and the auxiliary combustion chamber 4, and forms an air-fuel mixture of air and fuel in the main combustion chamber 2 and the auxiliary combustion chamber 4. In the present embodiment, the fuel injection valve 9 is a direct injection type that directly injects fuel into the cylinder 10a. However, the fuel injection valve 9 may be of a port injection type.

[0021] The sub-chamber type internal combustion engine 1 configured as described above injects fuel by the fuel injection valve 9 and forms an air-fuel mixture in the main combustion chamber 2 and the auxiliary combustion chamber 4. At this time, the fuel is injected toward the exhaust side, and the air-fuel ratio of the air-fuel mixture on the exhaust side tends to become rich due to the in-cylinder flow.

[0022] As shown in FIG. 3(a), when the ignition device 6 ignites the spark plug 6a, first, the air-fuel mixture in the space 2b around the plug ignites, and the flame propagates. Further, the flame in the space 2b around the plug injects a jet flame into the sub-combustion chamber 4 through the second communication passage 4f.

[0023] As shown in FIG. 3(b), when the air-fuel mixture in the sub-combustion chamber 4 ignites, first, the flame in the intake-side space 4c with a small volume propagates to the intake-side first communication passage 4h, and a jet flame is injected from the intake-side first communication passage 4h.

[0024] As shown in FIG. 3(c), thereafter, the flame in the exhaust-side space 4d propagates to the exhaust-side first communication passage 4i, and a jet flame is injected from the exhaust-side first communication passage 4i.

[0025] In this way, in the auxiliary-chamber type internal combustion engine 1, with respect to the flame injected from the space 2b around the plug, the jet flame injected from the sub-combustion chamber 4 is injected with a phase delay. The jet flame is injected in the order of the space 2b around the plug on the piston side, the intake-side first communication passage 4h, and the exhaust-side first communication passage 4i, whereby the difference in the flame propagation speed in the main combustion chamber 2 can be suppressed.

[0026] Furthermore, in this embodiment, since the air-fuel ratio on the intake side is lean, the flame propagation speed is slower on the intake side than on the exhaust side. However, in this auxiliary-chamber type internal combustion engine 1, the air-fuel mixture on the intake side receives the jet flame for a longer time than the air-fuel mixture on the exhaust side, whereby the flame propagation speed on the intake side is promoted. On the other hand, since the air-fuel ratio on the exhaust side is rich, the flame propagation speed is suppressed by receiving the jet flame later than on the intake side. Thereby, the difference in the flame propagation speed between the intake side and the exhaust side can be reduced. As a result, the jet shock is suppressed.

[0027] Furthermore, in the present embodiment, the flame propagation distance in the exhaust-side space 4d is shorter than that in the intake-side space 4c. In other words, the distance from the second communication passage 4f to the exhaust-side first communication passage 4i is shorter than the distance from the second communication passage 4f to the intake-side first communication passage 4h. For this reason, in the intake-side space 4c, the internal pressure of the intake-side space 4c increases before the flame reaches the intake-side first communication passage 4h, and the momentum of the jet flame injected from the intake-side first communication passage 4h into the main combustion chamber 2 becomes stronger. As a result, the momentum of the jet flame injected from the intake-side first communication passage 4h is stronger than that from the exhaust-side first communication passage 4i. As a result, the flame propagation speed on the exhaust side with a rich air-fuel ratio can be further suppressed.

[0028] As described above, according to the present disclosure, it is possible to provide the auxiliary chamber type internal combustion engine 1 that can suppress the shock caused by the jet flame.

[0029] <Other Embodiments> As described above, the embodiments of the present disclosure have been described. However, the present disclosure is not limited to the above embodiments, and various modifications can be made without departing from the gist of the invention. In particular, a plurality of modifications described in this specification can be arbitrarily combined as needed.

[0030] (a) In the above embodiment, an example of the auxiliary combustion chamber 4 in one room has been described. However, the present disclosure is not limited to this. For example, the auxiliary combustion chamber 4 may be further divided into finer rooms.

[0031] (b) In the above embodiment, the auxiliary combustion chamber 4 has been described using an example in which the inner wall 4b has a circular cross-section and the side wall 41 has an elliptical cross-section. However, the present disclosure is not limited to this. The cross-sectional shape of the auxiliary combustion chamber 4 may be changed as appropriate.

Explanation of Reference Numerals

[0032] 1: Auxiliary chamber type internal combustion engine, 2: Main combustion chamber, 2b: Space around the plug 4: Auxiliary combustion chamber, 4a: Auxiliary combustion chamber wall, 4b: Inner wall 4e: First communication passage, 4f: Second communication passage 4g: End 4h: Intake-side first communication passage, 4i: Exhaust-side first communication passage 4j: Gas pocket wall 6: Ignition device 6a: Spark plug, 6b: Center electrode, 6c: Side electrode 8: Piston

Claims

1. An ignition device, a main combustion chamber, a sub-combustion chamber disposed at a distance from the main combustion chamber via a first wall, comprising, the ignition device is disposed in the main combustion chamber, the sub-combustion chamber is formed surrounding the periphery of the ignition device, and has a second wall separating the main combustion chamber and the sub-combustion chamber, and a communication passage formed in the second wall, a sub-chamber type internal combustion engine.

2. further comprising a piston accommodated in the main combustion chamber, the communication passage has a first communication passage opening towards the piston side and a second communication passage opening towards the ignition device side, the sub-chamber type internal combustion engine according to Claim 1.

3. further comprising a cylinder head, the lower surface of the cylinder head and the end of the second wall form the second communication passage, the sub-chamber type internal combustion engine according to Claim 2.

4. the sub-combustion chamber has a third wall separating the main combustion chamber and the sub-combustion chamber on the cylinder head side of the second communication passage, the sub-chamber type internal combustion engine according to Claim 3.

5. further comprising a piston accommodated in the main combustion chamber, the main combustion chamber surrounded by the second wall is open towards the piston, the sub-chamber type internal combustion engine according to Claim 1.

6. further comprising a cylinder head, the end of the second wall on the cylinder head side is located on the cylinder head side of the side electrode of the ignition device, the sub-chamber type internal combustion engine according to any one of Claims 1 to 5.

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