Control system for prechamber internal combustion engine

Abstract

A control system for a prechamber internal combustion engine according to the present disclosure is for a prechamber internal combustion engine comprising: a cylinder head; a main combustion chamber that is formed between the cylinder head and a piston; an auxiliary combustion chamber 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 piston side; and a fuel injection valve that is positioned facing the main combustion chamber and injects fuel toward the auxiliary combustion chamber, said control system comprising a first warming unit that warms the surface of the partition wall on the side facing the side of the main combustion chamber where the fuel injection valve is disposed, and a control device that controls the first warming unit, wherein the control device activates the first warming unit when the prechamber internal combustion engine is in a cold state.

Description

Control system for an auxiliary-chamber internal combustion engine

[0001] The present disclosure relates to a control system for an auxiliary-chamber internal combustion engine.

[0002] Conventionally, auxiliary-chamber internal combustion engines are known (see, for example, Patent Document 1). The auxiliary-chamber internal combustion engine disclosed in Patent Document 1 comprises a main combustion chamber and an auxiliary combustion chamber, wherein an ignition device is disposed in the auxiliary combustion chamber, and a fuel injection device is disposed in the main combustion chamber. The auxiliary-chamber internal combustion engine of Patent Document 1 is a passive-type auxiliary-chamber internal combustion engine that forms an air-fuel mixture in the auxiliary combustion chamber by supplying fuel injected from the main combustion chamber into the auxiliary combustion chamber. The air-fuel mixture formed in the auxiliary combustion chamber is ignited by the ignition device to form a flame. The flame formed in the auxiliary 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 an auxiliary-chamber internal combustion engine, fuel is injected toward the auxiliary combustion chamber. This allows a larger amount of fuel to be supplied to the auxiliary combustion chamber. However, when the cylinder head and the auxiliary combustion chamber are in a low-temperature state, such as when the auxiliary-chamber internal combustion engine is cold-started, the amount of fuel adhering to the cylinder head and the auxiliary combustion chamber increases. As a result, there is a risk that emissions will deteriorate.

[0005] An object of the present disclosure is to provide a control system for an auxiliary-chamber internal combustion engine that can improve emissions.

[0006] A control system for an auxiliary-chamber internal combustion engine according to the present disclosure is a control system for an auxiliary-chamber internal combustion engine, comprising: a cylinder head; a main combustion chamber formed between the cylinder head and a piston; an auxiliary combustion chamber disposed via a partition wall from the main combustion chamber and extending from the cylinder head toward the piston side; and a fuel injection valve disposed facing the main combustion chamber and injecting fuel toward the auxiliary combustion chamber, the control system comprising: a first warm-up unit that warms up a surface of the partition wall on a side where the fuel injection valve is disposed, the surface facing the main combustion chamber; and a control device that controls the first warm-up unit, wherein the control device activates the first warm-up unit when the auxiliary-chamber internal combustion engine is in a cold state.

[0007] According to this disclosure, when a pre-chamber internal combustion engine is in a cold state, the first warm-up unit can reduce the amount of fuel adhering to the pre-combustion chamber.

[0008] This disclosure provides a control system for a sub-chamber internal combustion engine that can improve emissions.

[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 flowchart showing the control procedure performed by the control device according to one embodiment of the present disclosure.

[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 11 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 control system 1 for the pre-chamber internal combustion engine 2 comprises the pre-chamber internal combustion engine 2, a first warm-up unit 20, a second warm-up unit 30, and a control device 40. The control system 1 for the pre-chamber internal combustion engine of this embodiment is installed in a plug-in hybrid vehicle (PHEV) equipped with external charging, which allows power from an external power source to be stored in the drive battery by a charger, and external power supply, which allows power from the drive battery to be supplied to external devices by an external power supply device.

[0012] The pre-chamber internal combustion engine 2 includes 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, an expansion section 9, a cylinder block 10, a cylinder head 11, an intake port 12, and an exhaust port 13. In this embodiment, the pre-chamber internal combustion engine 2 is a gasoline engine that ignites the fuel-air mixture in the sub-combustion chamber 4 by the ignition device 6.

[0013] The main combustion chamber 3 is the space enclosed by the cylinder 10a of the cylinder block 10, the cylinder head 11, 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 12 side and the exhaust port 13 side of the cylinder head 11. The main combustion chamber 3 is connected to the intake port 12 via the intake valve 14. The intake port 12 is connected to, for example, an intake passage (not shown). The main combustion chamber 3 is connected to the exhaust port 13 via the exhaust valve 16. The exhaust port 13 is connected to, for example, an exhaust passage (not shown).

[0014] 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 11 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.

[0015] 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. 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.

[0016] 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).

[0017] 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.

[0018] 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 hole 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. The fuel injector 8 is connected to a high-pressure pump 8b, and the fuel pressure is adjustable. In this embodiment, the sub-chamber type internal combustion engine 2 further has an intake port fuel injector 8a that injects fuel into the intake port 12. However, the intake port fuel injector 8a that injects fuel into the intake port 12 is not necessarily required.

[0019] The sub-combustion chamber 4 is attached to a mounting hole 2c provided in the cylinder head 11. In this embodiment, the mounting hole 2c is provided through the upper surface of the cylinder head 11, and the sub-combustion chamber 4 is inserted into the mounting hole 2c from above the cylinder head 11 and attached.

[0020] As shown in Figure 2, the expansion portion 9 is positioned on the edge 2a of the mounting hole 2c provided in the cylinder head 11. The expansion portion 9 expands from the cylinder head 11 toward the piston side PS. As shown in Figure 3, the expansion portion 9 is positioned around the entire circumference of the cylindrical cross-section sub-combustion chamber wall 41.

[0021] The intake port 12 is located in the cylinder head 11 and connected to the main combustion chamber 3. As shown in Figure 3, in this embodiment, the sub-chamber internal combustion engine 2 is a double overhead cam type internal combustion engine in which two intake ports 12 are opened and closed by two intake valves 14. The intake port 12 includes a first intake port (an example of a first intake passage) 12a and a second intake port (an example of a second intake passage) 12b. The first intake port 12a is opened and closed by an intake valve 14a. The second intake port 12b is opened and closed by an intake valve 14b. The second intake port 12b is located next to the first intake port 12a with a gap in the ridge direction X. The fuel injection valve 8 is located between the first intake port 12a and the second intake port 12b. The first intake port 12a has an opening 12c. When the intake valve 14a is closed, the umbrella portion 14c (see Figure 2) of the intake valve 14a abuts against the opening 12c. This causes the intake valve 14a to close the first intake port 12a. The second intake port 12b has an opening 12d. When the intake valve 14b is closed, the umbrella portion 14d (see Figure 2) of the intake valve 14 abuts against the opening 12d. This causes the intake valve 14b to close the second intake port 12b.

[0022] The surface roughness of the surface (ignition surface) forming the main combustion chamber 3 of the cylinder head 11 in the portion 11a between the opening 12c of the first intake port 12a and the opening 12d of the second intake port 12b is lower than the surface roughness of the surface forming the main combustion chamber 3 in a portion other than the portion 11a in between. In this embodiment, the surface forming the main combustion chamber 3 of the cylinder head 11 in the portion 11a in between is formed by mirror polishing. Fuel injected from the fuel injector 8 tends to adhere to the portion 11a in between. However, if the surface roughness of the portion 11a in between is low, fuel is less likely to adhere. As a result, hydrocarbon emissions can be suppressed and emissions can be improved.

[0023] The first warm-up unit 20 is located on the side of the sub-combustion chamber wall 41 (see Figure 2) where the fuel injection valve 8 is located, and warms the side of the sub-combustion chamber wall 41 facing the main combustion chamber 3 on the side where the fuel injection valve 8 is located. The first warm-up unit 20 is an electric heater located in the expansion unit 9. In this embodiment, the first warm-up unit 20 is an electric heating wire embedded in the intake side IN of the expansion unit 9. The first warm-up unit 20 is electrically connected to the control device 40 and controlled by the control device 40.

[0024] The second warming unit 30 is positioned on the surface of the cylinder head 11 of the main combustion chamber 3 and warms up the main combustion chamber 3. The second warming unit 30 is an electric heater positioned between the opening 12c of the first intake port 12a and the opening 12d of the second intake port 12b. The second warming unit 30 is positioned along the opening 12c of the first intake port 12a and the opening 12d of the second intake port 12b. In this embodiment, the second warming unit 30 is an electric heating wire embedded in the portion 11a between the cylinder heads 11.

[0025] Returning to Figure 1, the control device 40 controls the injection timing and injection amount of fuel injected from the fuel injector 8. The control device 40 is actually an ECU (Electronic Control Unit) composed of a microcomputer including an arithmetic unit, memory, and input / output buffers. Based on maps and programs stored in memory, the control device 40 controls the first warm-up unit 20, the second warm-up unit 30, and the fuel injector 8.

[0026] Next, the control procedure performed by the control device 40 will be explained using the flowchart in Figure 4. The control device 40 starts the control procedure when an ignition switch (not shown) is turned on.

[0027] In step S1, the control device 40 determines whether the pre-chamber internal combustion engine 2 is being started in a cold state. The control device 40 may determine that the pre-chamber internal combustion engine 2 is being started in a cold state if, for example, the water temperature detected by the water temperature sensor 40a (see Figure 1), which detects the temperature of the cooling water of the pre-chamber internal combustion engine 2, is 40°C or lower. If the control device 40 determines that the pre-chamber internal combustion engine 2 is being started in a cold state (step S1 YES), it proceeds to step S2. If the control device 40 determines that the pre-chamber internal combustion engine 2 is not being started in a cold state (step S1 NO), it returns.

[0028] In step S2, the control device 40 determines whether the rotational speed R of the pre-chamber internal combustion engine 2 is equal to or greater than a predetermined rotational speed Rt. The rotational speed R may be the actual rotational speed of the pre-chamber internal combustion engine 2, or it may be the rotational speed of the pre-chamber internal combustion engine 2 (requested rotational speed) calculated based on the accelerator opening obtained from an accelerator position sensor (not shown). The predetermined rotational speed Rt may be, for example, about half of the maximum rotational speed. When the rotational speed R becomes equal to or greater than the predetermined rotational speed Rt, the amount of fuel injected from the fuel injector 8 increases. As a result, the amount of fuel adhering to the cylinder head 11 also increases. If the control device 40 determines that the rotational speed R is equal to or greater than the predetermined rotational speed Rt (step S2 YES), it proceeds to step S3.

[0029] In step S3, the control device 40 activates both the first warm-up unit 20 and the second warm-up unit 30. This prevents fuel from adhering to the portion 11a (see Figure 3) between the sub-combustion chamber 4 and the cylinder head 11. As a result, hydrocarbon emissions are suppressed, and emissions are improved. Once both the first warm-up unit 20 and the second warm-up unit 30 are activated, the control device 40 proceeds to step S4.

[0030] In step S4, the control device 40 controls the high-pressure pump 8b to increase the injection pressure of the fuel injected from the fuel injector 8 (injection pressure increase). This allows the control device 40 to atomize the fuel injected from the fuel injector 8 and reduce the amount that adheres to the cylinder head 11. The control device 40 returns after increasing the injection pressure.

[0031] On the other hand, in step S2, if the control device 40 determines that the rotational speed R of the pre-chamber internal combustion engine 2 is less than a predetermined rotational speed Rt (step S2 NO), it proceeds to step S5. In step S5, the control device 40 activates the first warm-up unit 20. In this embodiment, the second warm-up unit 30 is not activated. This reduces the amount of fuel adhering to the pre-combustion chamber wall 41. As a result, emissions can be improved. The control device 40 returns after activating the first warm-up unit 20.

[0032] As described above, this disclosure provides a control system 1 for a pre-chamber type internal combustion engine 2 that can improve emissions.

[0033] <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.

[0034] 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.

[0035] 1: Control system, 2: Pre-chamber internal combustion engine, 3: Main combustion chamber, 4: Sub-combustion chamber, 7: Piston, 8: Fuel injector, 9: Expansion section, 11: Cylinder head, 110: First warm-up section, 30: Second warm-up section, 40: Control device

Claims

1. A control system for a sub-chamber internal combustion engine having a cylinder head, 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 and extending from the cylinder head toward the piston, and a fuel injector valve disposed facing the main combustion chamber and injecting fuel toward the sub-combustion chamber, comprising: a first warm-up section that warms the side of the partition wall facing the main combustion chamber on the side where the fuel injector valve is located, and a control device that controls the first warm-up section, wherein the control device activates the first warm-up section when the sub-chamber internal combustion engine is in a cold state.

2. The control system for a pre-chamber type internal combustion engine according to claim 1, wherein the pre-chamber type internal combustion engine has an expansion portion at the edge of the mounting hole of the cylinder head that expands toward the side in which the piston is positioned and contacts the partition wall, and the first warm-up unit is positioned in the expansion portion.

3. A control system for a sub-chamber type internal combustion engine according to claim 1, further comprising a second warming unit disposed on the surface of the cylinder head of the main combustion chamber for warming up the main combustion chamber.

4. A control system for a pre-chamber type internal combustion engine according to claim 3, wherein the pre-chamber type internal combustion engine comprises: a first intake passage located in the cylinder head and connected to the main combustion chamber; a second intake passage located in the cylinder head and connected to the main combustion chamber and spaced apart from the first intake passage; a fuel injection valve located between the first intake passage and the second intake passage; and a second warm-up unit located between the opening of the first intake passage and the opening of the second intake passage.

5. The control system for a pre-chamber internal combustion engine according to claim 3, wherein the pre-chamber internal combustion engine has an intake passage located in the cylinder head and connected to the main combustion chamber, and the second warm-up unit is located along the opening of the intake passage.

6. The control system for a pre-chamber internal combustion engine according to claim 3, wherein the pre-chamber internal combustion engine comprises: a first intake passage located in the cylinder head and connected to the main combustion chamber; a second intake passage located in the cylinder head and connected to the main combustion chamber and spaced apart from the first intake passage; and a fuel injection valve located between the first intake passage and the second intake passage, wherein the surface roughness of the portion between the opening of the first intake passage and the opening of the second intake passage is lower than the surface roughness of the portion different from the portion in between.

7. The control device, when the pre-chamber internal combustion engine is cold-started, activates both the first warm-up unit and the second warm-up unit if the rotational speed of the pre-chamber internal combustion engine is above a predetermined rotational speed, and activates the first warm-up unit if the rotational speed is below a predetermined rotational speed, as described in claim 3.

8. The control device increases the pressure of the fuel injected from the fuel injection valve when the pre-chamber internal combustion engine is cold-started and the rotational speed of the pre-chamber internal combustion engine is above a predetermined rotational speed, according to any one of claims 1 to 7.

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