Control system for divided-chamber type internal combustion engine

Abstract

This control system for a divided-chamber type internal combustion engine comprises: a main combustion chamber; a sub-combustion chamber that is disposed to be separated from the main combustion chamber by a partition wall; a fuel injection valve that is disposed in the main combustion chamber and injects fuel toward the sub-combustion chamber; a knocking detection device that detects knocking; and a control device that executes compression stroke injection for causing the fuel injection valve to inject the fuel in a compression stroke. The control device changes the injection timing of the compression stroke injection when knocking is detected.

Description

Control system for pre-chamber internal combustion engines

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

[0002] Conventionally, a pre-combustion chamber type internal combustion engine is known (see, for example, Patent Document 1). The pre-combustion chamber type internal combustion engine of Patent Document 1 includes a main combustion chamber and a pre-combustion chamber, with an ignition device disposed in the pre-combustion chamber and a fuel injection valve disposed in the main combustion chamber. The pre-combustion chamber type internal combustion engine of Patent Document 1 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 into the main combustion chamber via a communication passage.

[0003] International Publication No. 2022 / 208575

[0004] In such a pre-chamber type internal combustion engine, knocking may occur due to an increase in the temperature of the pre-chamber or the spark plug during high load operation or high speed operation.

[0005] An object of the present disclosure is to provide a control system for a pre-chamber internal combustion engine that can suppress knocking.

[0006] The control system for an auxiliary combustion engine according to the present disclosure includes a main combustion chamber, an auxiliary combustion chamber separated from the main combustion chamber by a partition wall, a fuel injection valve disposed in the main combustion chamber and injecting fuel toward the auxiliary combustion chamber, a knocking detection device that detects knocking, and a control device that performs compression stroke injection, causing the fuel injection valve to inject fuel during the compression stroke, and when knocking is detected, the control device changes the injection timing of the compression stroke injection.

[0007] According to this control system for an auxiliary combustion chamber internal combustion engine, the injection timing of the compression stroke injection is changed, thereby reducing the amount of fuel supplied to the auxiliary combustion chamber 3. This weakens the power of the jet flame. As a result, this control system for an auxiliary combustion chamber internal combustion engine can suppress knocking.

[0008] Fig. 1 is a system diagram of a control system for a pre-combustion engine according to an embodiment of the present disclosure; Fig. 2 is a flowchart showing a control procedure executed by a control device according to an embodiment of the present disclosure; Fig. 3 is a diagram showing injection timing for a pre-combustion engine according to an embodiment of the present disclosure; Fig. 4 is a system diagram (1) of a control system for a pre-combustion engine according to another embodiment; Fig. 5 is a system diagram (2) of a control system for a pre-combustion engine according to another embodiment.

[0009] First Embodiment A first embodiment of the present disclosure will now be described with reference to the drawings. In the drawings, the sliding direction of the piston 8 is indicated as P, the side on which the intake valve 14 is disposed is indicated as the intake side IN, and the side on which the exhaust valve 16 is disposed is indicated as the exhaust side EX.

[0010] As shown in FIG. 1 , the control system 1 for the auxiliary combustion chamber type internal combustion engine E includes a main combustion chamber 2, an auxiliary combustion chamber 3, a communication passage 4, an ignition device 6, a piston 8, a first fuel injection valve 9, a second fuel injection valve 10, a fuel pressure adjustment device 13, a knocking detection device 15, a water temperature detection device 17, and a control device 20.

[0011] The main combustion chamber 2 is a space surrounded by the cylinder 11a of the cylinder block 11, 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 and is 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 of this embodiment is located adjacent to the main combustion chamber 2 at the top of the pent roof shape, and has a space surrounded by the auxiliary combustion chamber wall 5.

[0013] 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 communication passages 4 are provided in the auxiliary combustion chamber wall 5. The communication passages 4 communicate between the main combustion chamber 2 and the auxiliary combustion chamber 3. In this embodiment, a total of six communication passages 4 are provided, three toward the intake side and three toward the exhaust side.

[0015] 1, the ignition device 6 is disposed in the auxiliary combustion chamber 3. The ignition device 6 discharges the current flowing through the ignition coil using the center electrode and the side electrode, igniting the air-fuel mixture in the auxiliary combustion chamber 3. The ignition device 6 is electrically connected to the control device 20, and the ignition timing is controlled by the control device 20.

[0016] The piston 8 is housed in the cylinder 11a and slides within the cylinder 11a. The piston 8 surrounds the main combustion chamber 2 from below.

[0017] The first fuel injection valve 9 injects fuel toward the auxiliary combustion chamber 3 to form an air-fuel mixture in the auxiliary combustion chamber 3. As shown in the normal injection timing in Figure 3, the first fuel injection valve 9 performs compression stroke injection F1, which injects fuel during the compression stroke, thereby supplying fuel to the auxiliary combustion chamber 3 via the communication passage 4. As shown in Figure 1, in this embodiment, the first fuel injection valve 9 is disposed on the intake side IN. The first fuel injection valve 9 is an in-cylinder injection valve that injects fuel directly into the main combustion chamber 2. The first fuel injection valve 9 is electrically connected to a control device 20, and the fuel injection timing and injection amount are controlled by the control device 20.

[0018] The second fuel injection valve 10 injects fuel into the intake port 12a. The second fuel injection valve 10 is a port injection valve disposed in the intake port 12a. As shown in the normal injection timing in Figure 3, the second fuel injection valve 10 performs port injection F2 mainly between the exhaust stroke and the intake stroke, so that the fuel mixes with air in the intake port 12a and flows into the main combustion chamber 2 to form an air-fuel mixture. As shown in Figure 1, the second fuel injection valve 10 is electrically connected to a control device 20, and the control device 20 controls the fuel injection timing and injection amount.

[0019] The fuel pressure regulating device 13 regulates the pressure of fuel supplied to the first fuel injection valve 9. In this embodiment, the fuel pressure regulating device 13 is a mechanical pump driven by an intake cam (not shown) that drives the intake valve 14 or an exhaust cam (not shown) that drives the exhaust valve 16. However, the fuel pressure regulating device 13 may also be an electric pump. The fuel pressure regulating device 13 is supplied with fuel from a fuel tank (not shown). The fuel pressure regulating device 13 is electrically connected to a control device 20, and the control device 20 controls a valve that regulates the fuel pressure, thereby regulating the pressure of fuel supplied to the first fuel injection valve 9.

[0020] The knocking detection device 15 detects knocking that occurs in the main combustion chamber 2. In this embodiment, the knocking detection device 15 is a knocking sensor disposed in the cylinder block 11. The knocking sensor detects knocking that occurs in the main combustion chamber 2 by detecting vibrations of the cylinder block 11. However, the knocking detection device 15 may also be an in-cylinder pressure sensor that detects the in-cylinder pressure of the main combustion chamber 2. The knocking detection device 15 is electrically connected to the control device 20, converts the detected vibrations, etc. into an electrical signal, and transmits it to the control device 20.

[0021] The water temperature detection device 17 is a device that detects the temperature of the cooling water flowing through the cylinder block 11 and the cylinder head 12. In this embodiment, the cooling water passes through a cooling water passage (not shown) in the cylinder head 12 and enters the water jacket 11b of the cylinder block 11. The water temperature detection device 17 is a water temperature sensor that detects the temperature of the cooling water that leaves the water jacket 11b.

[0022] The control device 20 receives a signal from the knocking detection device 15 and controls the first fuel injection valve 9, the second fuel injection valve 10, and the fuel pressure adjustment device 13. The control device 20 is actually an ECU (Electronic Control Unit) configured by a microcomputer including an arithmetic unit, a memory, an input / output buffer, etc. The control device 20 controls the first fuel injection valve 9, the second fuel injection valve 10, and the fuel pressure adjustment device 13 based on maps and programs stored in the memory.

[0023] Next, a control procedure executed by the control device 20 will be described with reference to the flowchart of Fig. 2 and Fig. 3. The control device 20 starts the control procedure when an ignition switch (not shown) is turned on.

[0024] In step S1, the control device 20 acquires a signal from the knock detection device 15 and determines whether knocking has occurred (detected). In this embodiment, the control device 20 determines that knocking has occurred if the amplitude and frequency of the vibration acquired by the knock sensor are equal to or greater than a predetermined amplitude or frequency. When knocking occurs, combustion becomes unstable and pressure fluctuations within the cylinder increase. The knock sensor detects the sound caused by this pressure fluctuation within the cylinder as vibration. The in-cylinder pressure sensor directly detects this pressure change. If the control device 20 determines that knocking has occurred (YES in step S1), the control device 20 proceeds to step S2.

[0025] In step S2, the control device 20 reduces the injection quantity Q1 of the compression stroke injection F1 of the first fuel injector 9. Reducing the injection quantity Q1 of the compression stroke injection F1 weakens the momentum of the jet flame injected from the auxiliary combustion chamber 3 through the communication passage 4 into the main combustion chamber 2, thereby suppressing knocking. The control device 20 gradually reduces the injection quantity Q1 of the compression stroke injection F1 as long as knocking occurs. At this time, the control device 20 may increase the injection quantity of the intake stroke injection F1a. This causes fuel to collide with the auxiliary combustion chamber wall 5, cooling the auxiliary combustion chamber. After reducing the injection quantity Q1 of the compression stroke injection F1, the control device 20 proceeds to step S3.

[0026] In step S3, the control device 20 determines whether the injection quantity Q1 of the compression stroke injection F1 is equal to or less than the minimum injection quantity Q1min (an example of a predetermined injection quantity). The minimum injection quantity Q1min is the smallest value of the injection quantity that the first fuel injection valve 9 can inject. Therefore, the first fuel injection valve 9 cannot execute injection of less than the minimum injection quantity Q1min. The minimum injection quantity Q1min may be a value that allows for a margin with respect to the minimum value of the injection quantity that the actual first fuel injection valve 9 can inject. If the control device 20 determines that the injection quantity Q1 is equal to or less than the minimum injection quantity Q1min (YES in step S3), the control device 20 proceeds to step S4.

[0027] In step S4, the control device 20 determines whether an advance condition is met. The advance condition is a condition under which the injection timing of the compression stroke injection F1 can be advanced. For example, when the pre-combustion chamber internal combustion engine E has completed warming up, if a fuel-rich mixture remains around the pre-combustion chamber wall 5, the jet flame injected from the communication passage 4 is likely to ignite. Therefore, even if the jet flame's intensity is weakened, it is difficult to suppress knocking. On the other hand, when the pre-combustion chamber internal combustion engine E is cold, even if a fuel-rich mixture remains around the pre-combustion chamber wall 5, the jet flame is unlikely to ignite. In fact, the fuel-rich mixture around the pre-combustion chamber wall 5 stabilizes combustion. Therefore, the advance condition is a condition under which it is better to advance the compression stroke injection F1 due to the temperature of the pre-combustion chamber internal combustion engine E.

[0028] In this embodiment, the control device 20 obtains the coolant temperature Wt from the water temperature detection device 17, and determines that the advance angle condition is met if the temperature Wt is equal to or higher than a predetermined temperature TWt. The predetermined temperature TWt is, for example, 80° C., at which the pre-combustion chamber type internal combustion engine E completes warm-up. If the advance angle condition is met, the control device 20 proceeds to step S5.

[0029] In step S5, the control device 20 advances the injection timing of the compression stroke injection F1. As shown in the graph in FIG. 3 where the injection quantity Q1 is equal to or less than the minimum injection quantity Q1 min and the advance condition is met, in this embodiment, the control device 20 maintains the injection quantity Q1 of the first fuel injector 9 at the minimum injection quantity Q1 min while advancing the injection timing of the compression stroke injection F1 relative to the injection timing when the first fuel injector 9 (DI in FIG. 3) injected the minimum injection quantity Q1 min. This reduces the amount of fuel entering the auxiliary combustion chamber 3 and weakens the momentum of the jet flame. Furthermore, advancing the injection timing of the compression stroke injection F1 makes it difficult for a fuel-rich mixture to be generated around the auxiliary combustion chamber wall 5. As a result, the combustion speed in the main combustion chamber 2 is slowed, and knocking is suppressed. As shown in FIG. 2, once the control device 20 advances the injection timing of the compression stroke injection F1, the process proceeds to step S1.

[0030] If the control device 20 determines in step S1 that knocking has not occurred (step S1 NO), this control will not be executed until knocking occurs. If in step S3 the injection amount Q1 of the compression stroke injection F1 is greater than the minimum injection amount Q1min (step S3 NO), the control device 20 proceeds to step S2, where the control device 20 reduces the injection amount Q1 of the compression stroke injection F1 until the injection amount Q1 of the compression stroke injection F1 becomes the minimum injection amount Q1min.

[0031] If the control device 20 determines in step S4 that the advance condition is not satisfied (NO in step S4), the control device 20 proceeds to step S6. In this embodiment, if the temperature Wt acquired by the water temperature detection device 17 is lower than the predetermined temperature TWt, the control device 20 determines that the advance condition is not satisfied.

[0032] In step S6, the control device 20 retards the injection timing of the compression stroke injection F1. As shown in the graph in FIG. 3 where the injection amount Q1 is equal to or less than the minimum injection amount Q1 min and the advance condition is not satisfied, in this embodiment, the control device 20 maintains the injection amount Q1 of the first fuel injector 9 at the minimum injection amount Q1 min, while retarding the injection timing of the compression stroke injection F1 relative to the injection timing when the first fuel injector 9 injected the minimum injection amount Q1 min. This reduces the amount of fuel entering the auxiliary combustion chamber 3, weakening the momentum of the jet flame. As a result, the combustion speed in the main combustion chamber 2 slows, and knocking is suppressed. As shown in FIG. 2, once the control device 20 retards the injection timing of the compression stroke injection F1, the process proceeds to step S7.

[0033] In step S7, the control device 20 executes port injection F2 during the intake stroke using the second fuel injection valve 10 (PFI in FIG. 3). Retarding the injection timing of the compression stroke injection F1 can result in an area where the fuel and air are not sufficiently mixed, potentially increasing nitrogen oxides. As shown in FIG. 3, in such a case, by executing intake stroke injection F1a, in which port injection F2 is injected during the intake stroke, the temperature of the air-fuel mixture in the main combustion chamber 2 can be lowered, thereby reducing nitrogen oxides. After executing port injection F2, the control device 20 proceeds to step S1.

[0034] As described above, according to the present disclosure, it is possible to provide a control system 1 for a pre-combustion chamber type internal combustion engine E that can reduce the amount of fuel entering the pre-combustion chamber 3, weaken the momentum of the jet flame, and suppress knocking by changing the injection timing of the compression stroke injection.

[0035] 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 without departing from the spirit of the invention. In particular, the multiple modifications described in this specification can be combined as needed.

[0036] (a) In the above embodiment, the second fuel injection valve 10 is described as a port injection valve arranged in the intake port 12a, but the present disclosure is not limited to this. As shown in FIG. 4 , the control system 1 for the pre-combustion chamber type internal combustion engine E may configure the second fuel injection valve 10 as an in-cylinder injection valve arranged in the main combustion chamber 2. The second fuel injection valve 10 may form an air-fuel mixture in the main combustion chamber 2. In this case, in step S7, the control device 20 may perform intake stroke injection F1a using the second fuel injection valve 10, which is an in-cylinder injection valve.

[0037] (b) In the above embodiment, an example using the first fuel injection valve 9 and the second fuel injection valve 10 has been described, but the present disclosure is not limited to this. As shown in Fig. 5, the control system 1 for the auxiliary combustion chamber type internal combustion engine E may execute multiple injection modes using one first fuel injection valve 9 arranged in the main combustion chamber 2. The first fuel injection valve 9 may execute compression stroke injection F1, which injects fuel toward the auxiliary combustion chamber 3 during the compression stroke, and may execute intake stroke injection F1a, which injects fuel into the main combustion chamber 2 during the intake stroke.

[0038] 1: Control system, 2: Main combustion chamber, 3: Auxiliary combustion chamber, 9: First fuel injection valve, 10: Second fuel injection valve, 15: Knocking detection device, 17: Water temperature detection device, 20: Control device, E: Auxiliary combustion chamber type internal combustion engine, F1: Compression stroke injection, F1a: Intake stroke injection

Claims

1. A control system for an auxiliary combustion chamber internal combustion engine comprising: a main combustion chamber; an auxiliary combustion chamber separated from the main combustion chamber by a partition wall; a first fuel injection valve disposed in the main combustion chamber and injecting fuel toward the auxiliary combustion chamber; a knocking detection device that detects knocking; and a control device that performs compression stroke injection by causing the first fuel injection valve to inject fuel during the compression stroke, wherein the control device changes the injection timing of the compression stroke injection when knocking is detected.

2. A control system for an internal combustion engine with a pre-compression chamber according to claim 1, wherein the control device changes the injection timing of the compression stroke injection when the injection amount of the compression stroke injection becomes equal to or less than a predetermined injection amount.

3. The control system for a pre-chamber internal combustion engine according to claim 1, wherein the control device advances the injection timing of the compression stroke injection if an advance condition is met when knocking is detected.

4. The control system for a pre-chamber internal combustion engine according to claim 3, wherein the control device retards the injection timing of the compression stroke injection when knocking is detected when the advance condition is not met.

5. A control system for an internal combustion engine with a pre-combustion chamber according to claim 4, further comprising a second fuel injection valve that injects fuel during the intake stroke, wherein the control device executes intake stroke injection by the second fuel injection valve when the injection timing of the compression stroke injection is retarded.

6. A control system for an intra-combustion engine with a pre-chamber as claimed in any one of claims 1 to 5, further comprising a water temperature detection device that detects the temperature of the cooling water of the intra-combustion engine, wherein the control device, when detecting knocking, advances the injection timing of the compression stroke injection if the temperature is equal to or higher than a predetermined temperature, and retards the injection timing of the compression stroke injection if the temperature is lower than the predetermined temperature.

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