JP7661920B2 - Engine Control Unit - Google Patents

Description

This invention relates to an engine control device.

Lean-burn engines have been proposed in the past, which burn a mixture with a leaner fuel ratio (excess air relative to fuel) than the theoretical air-fuel ratio. In order to better burn this lean mixture, a pre-chamber engine has been proposed, which has a main chamber and a pre-chamber as combustion chambers. In a pre-chamber engine, a communication passage is provided in the partition wall separating the main chamber and the pre-chamber, and the mixture formed by fuel injected into the main chamber is supplied to the pre-chamber through the communication passage, where it is ignited by a spark plug. When a flame is formed in the pre-chamber, the flame propagates through the communication passage to the main chamber and ignites the mixture in the main chamber. This allows operation with a leaner air-fuel ratio, which is said to improve fuel efficiency (see, for example, Patent Document 1 and Patent Document 2).

Patent No. 4389777 International Publication No. 2020/196206

In general engines, when knocking occurs under high load, the ignition timing is retarded to reduce the pressure inside the cylinder and prevent knocking. However, in the case of pre-chamber engines, retarding the ignition timing creates a lean environment in the pre-chamber, which can make ignition of the air-fuel mixture in the pre-chamber unstable. There is also a need for ways to avoid knocking and ensure good combustion under a variety of constantly changing operating conditions.

Therefore, the objective of this invention is to ensure good combustion under various operating conditions.

In order to solve the above problems, the present invention provides an engine including a combustion chamber having a main chamber surrounded by the inner circumferential surface of the cylinder, the inner surface of the cylinder head, and the top surface of the piston, a sub-chamber separated from the main chamber by a partition and formed at the end of the main chamber on the cylinder head side, a communication passage provided in the partition that connects the main chamber to the sub-chamber, an injection device that supplies fuel to the combustion chamber, and an ignition device facing the sub-chamber and igniting the mixture in the sub-chamber, a means for detecting or predicting the occurrence of knocking in the engine, and a control means for controlling to avoid the knocking, and the control means employs an engine control device that performs fuel injection reduction control to reduce the amount of fuel injection of the sub-chamber injection that supplies fuel to the sub-chamber by the injection device when the occurrence of knocking is detected or predicted, and performs ignition energy increase control to increase the ignition energy of the mixture by the ignition device.

Here, the control means may be configured to perform ignition timing retard control to retard the ignition timing of the ignition device to the air-fuel mixture when the occurrence of knocking is detected or predicted.

In this case, the ignition energy increase control can be configured to set a larger increase in ignition energy the greater the amount of retardation of the ignition timing in the ignition timing retard control.

When performing the ignition timing retard control, a configuration can be adopted in which injection timing retard control is performed to retard the injection timing of the pre-chamber injection by the injection device.

In each of these aspects, a means for detecting torque fluctuations or combustion fluctuations in the engine can be provided, and the ignition energy increase control can be performed only when the torque fluctuations or combustion fluctuations exceed a predetermined value.

In each of these aspects, an air-fuel ratio detection means is provided for detecting or estimating the air-fuel ratio in the main chamber, and the control means, if the occurrence of knocking is detected or predicted and the air-fuel ratio is richer than a predetermined value, performs the ignition timing retard control and does not perform the ignition energy increase control, but reduces the amount of fuel injection of the main chamber injection that supplies fuel from the injection device to the main chamber, and if the detection or prediction of the occurrence of knocking continues, further performs the ignition timing retard control and performs the ignition energy increase control.

This invention ensures good combustion under a variety of operating conditions.

FIG. 2 is a vertical cross-sectional view of a pre-combustion chamber engine. This is a cross-sectional view of FIG. FIG. 2 is a vertical cross-sectional view showing the combustion state of a pre-combustion chamber engine. FIG. 2 is a vertical cross-sectional view showing the combustion state of a pre-combustion chamber engine. FIG. 2 is a vertical cross-sectional view showing the combustion state of a pre-combustion chamber engine. FIG. 4 is a graph showing control under normal operating conditions. FIG. 4 is a graph showing the control of the present invention. FIG. 4 is a graph showing the control of the present invention. 1 is a schematic diagram showing an example of a vehicle according to the present invention;

An embodiment of the present invention will be described with reference to the drawings. This embodiment is a hybrid vehicle 60 (hereinafter simply referred to as vehicle 60), and the main parts of the engine 10 mounted on the vehicle 60 are shown in Figures 1 and 2.

The vehicle 60 is equipped with a battery 50 that is used primarily as a power source for traveling, and two rotating electric machines 30, 40. One rotating electric machine 30 (hereinafter referred to as the first rotating electric machine 30) functions as a starter, and the engine 10 starts when the first rotating electric machine 30 operates. The other rotating electric machine 40 (hereinafter referred to as the second rotating electric machine 40) is a motor that supplies driving force for traveling. The first rotating electric machine 30 also functions as a generator that generates electricity using the driving force of the engine 10 (see FIG. 7).

The vehicle 60 is a hybrid vehicle that has three drive modes: an electric drive mode (EV mode), a series drive mode, and a parallel drive mode. An electronic control unit (Electronic Control Unit) 20 provided in the vehicle 60 selects the optimal drive mode depending on the state and drive state of the vehicle 60 at that time, the driver's request, etc. The engine 10, the first rotating electric machine 30, the second rotating electric machine 40, etc. are controlled depending on the selected drive mode. In the embodiment, the vehicle 60 is assumed to be a plug-in hybrid car (PHEV vehicle) that can charge the battery 50 directly using a plug from a household outlet, etc.

The first rotating electric machine 30 is a motor-generator that functions both as an electric motor (motor) and as a generator. When starting the engine 10, the first rotating electric machine 30 functions as a starter motor. At this time, it uses power from the battery 50 or a separately installed auxiliary battery. In addition, when the engine 10 is running, it performs the function of generating power using the driving force of the engine 10. The power generated by the first rotating electric machine 30 is supplied to the second rotating electric machine 40 and the battery 50, etc. The rotating shaft of the first rotating electric machine 30 is connected to the crankshaft of the engine 10 via an endless member such as a belt or a gear. When the engine 10 is running, the first rotating electric machine 30 is usually rotated along with the rotation of the crankshaft.

The second rotating electric machine 40 is provided as a drive source for driving the vehicle 60. The second rotating electric machine 40 is driven using the electric power stored in the battery 50 and the electric power generated by the first rotating electric machine 30. As shown in FIG. 6, there are examples where only one second rotating electric machine 40 is provided on the front side, and examples where one is provided on the front side and one on the rear side, and the number and locations of the second rotating electric machines 40 vary. The second rotating electric machine 40 also functions as a generator that generates regenerative electric power mainly during coasting.

A control unit (not shown) equipped with an inverter that converts DC and AC currents is provided between the first rotating electric machine 30 and the second rotating electric machine 40 and the electronic control unit 20. The rotational speeds of the first rotating electric machine 30 and the second rotating electric machine 40 when they are driven are controlled by the electronic control unit 20 via the inverter.

Engine 10 is a gasoline engine. Depending on the driving mode, the rotation of the crankshaft of engine 10 is switched between a state in which it is transmitted to the drive wheels via a torque converter, a continuously variable transmission, a clutch, a differential, etc., and a state in which the transmission is cut off.

The battery 50 is a high-voltage power source that can store (charge) the power generated by the first rotating electric machine 30 and the regenerated power by the second rotating electric machine 40, and can discharge the stored power. The battery 50 is mainly used as a power source that supplies power for driving. In this embodiment, the battery 50 is compatible with a plug-in hybrid car (PHEV vehicle) and can be externally charged, such as from a power source outside the vehicle, for example, a household AC power source (normal charging) or from a high-voltage DC power source (fast charging).

The vehicle 60 is equipped with a steering wheel, a brake pedal, an accelerator pedal, and the like that are operated by the driver. The brake pedal is provided with a brake sensor that detects the force with which the driver presses the brake pedal. The accelerator pedal is provided with an accelerator position sensor that detects the amount of depression of the accelerator pedal by the driver. Brake information detected by the brake sensor and accelerator information detected by the accelerator position sensor are sent to the electronic control unit 20. The vehicle 60 is also equipped with a vehicle speed sensor that is provided on the axle or the like and detects the traveling speed of the vehicle 60. Vehicle speed information detected by the vehicle speed sensor is also sent to the electronic control unit 20.

The vehicle 60 is also provided with an engine speed sensor that detects the speed of the engine 10, speed sensors that detect the speeds of the first rotating electric machine 30 and the second rotating electric machine 40, a voltage sensor that detects the cell voltage of the battery 50, and a current sensor that detects the current of the battery 50. The vehicle 60 is also provided with a water temperature sensor that detects the temperature of the cooling water for the engine 10, and an oil temperature sensor that detects the temperature of the engine oil. Information from these sensors is also sent to the electronic control unit 20.

The electronic control unit 20 comprises an engine control unit 21 that mainly controls the engine 10, and a vehicle control unit 22 that controls the operation of the entire hybrid vehicle. The electronic control unit 20 is a collection of electronic control devices (computers) that control various devices equipped in the vehicle 60. Inside it are built-in interfaces, processors, memories, etc. that are connected to each other via a bus. The contents of the controls executed by the engine control unit 21 and the vehicle control unit 22 are stored in advance in memory, and new data is stored as the control progresses, and this data is used for future control. The electronic control unit 20 selects and switches between driving modes such as electric driving mode (a mode in which the vehicle runs only on the driving force of the second rotating electric machine 40), series driving mode (a mode in which the vehicle runs only on the driving force of the second rotating electric machine 40 using the driving force of the engine 10 to operate the first rotating electric machine 30 to generate electricity, and a parallel driving mode (a mode in which the vehicle 60 runs on the driving force of the engine 10 and, as necessary, the driving force of the second rotating electric machine 40 assists the vehicle 60 in running).

The engine 10 is a sub-chamber type engine. Figures 1 and 2 show the main parts of one cylinder 2 of the engine 10. The engine 10 is equipped with an intake passage (intake port) 5 that feeds air into the combustion chamber C, an exhaust passage (exhaust port) 6 drawn from the combustion chamber C, an injection device 9 that supplies fuel to the combustion chamber C, and the like. The opening 5a of the intake passage 5 to the combustion chamber C is opened and closed by an intake valve 7. The opening 6a of the exhaust passage 6 to the combustion chamber C is opened and closed by an exhaust valve 8. In the embodiment, the injection device 9 is equipped with both a direct injection type fuel injection device 9a that directly injects fuel into the combustion chamber C and a port injection type fuel injection device 9b that injects fuel into the intake passage 5. In the figures, only the members and means directly related to this invention are shown, and other members, etc. are omitted. The number of cylinders that the engine 10 has can be freely set according to the specifications of the vehicle 60 and the engine 10, and may be, for example, three cylinders, four cylinders, or any other number of cylinders.

As shown in FIG. 1, the combustion chamber C includes a main chamber 1 surrounded by the inner peripheral surface 2a of the cylinder (cylinder block) 2, the inner surface (lower surface) of the cylinder head 13, and the top surface 3a of the piston 3, and an auxiliary chamber 11 separated from the main chamber 1 and formed at the end of the main chamber 1 on the cylinder head 13 side. The combustion chamber C also includes a partition wall 14 separating the main chamber 1 from the auxiliary chamber 11, and a communication passage 12 consisting of a small hole penetrating the partition wall 14. The communication passage 12 connects the space of the main chamber 1 to the space of the auxiliary chamber 11. The auxiliary chamber 11 is also provided with an ignition device 4 that ignites the mixture in the auxiliary chamber 11 by producing an electric spark.

To explain the operating state of the engine 10, first, as shown in FIG. 3A, air is introduced into the main chamber 1 from the intake passage 5, and a lean mixture is formed in the main chamber 1 by the injection of fuel from the injector 9. The lean mixture is pushed from the main chamber 1 into the auxiliary chamber 11 during the compression stroke when the piston 3 rises, as shown in FIG. 3B. Here, as shown in FIG. 3C, a spark is generated at the electrode 4a of the ignition device 4, and the mixture introduced into the auxiliary chamber 11 is ignited. When the mixture is ignited in the auxiliary chamber 11, the flame is injected to the main chamber 1 side through the connecting passage 12, becoming a high-speed jet flame. This jet flame promotes the combustion of the mixture even when it is lean (including when a large amount of exhaust gas is introduced). The gas after combustion is discharged to the outside through the exhaust passage 6. In the embodiment, fuel is injected twice during one combustion cycle. That is, a first injection is performed to supply fuel mainly to the main chamber 1, and a second injection is performed to supply fuel mainly to the auxiliary chamber 11. The first fuel injection is performed during the intake stroke, which will be referred to as the main chamber injection below. The second fuel injection is performed during the compression stroke, which will be referred to as the auxiliary chamber injection below. In this embodiment, the main chamber injection is mainly performed by the port injection type fuel injection device 9b, and the auxiliary chamber injection is mainly performed by the direct injection type fuel injection device 9a.

As mentioned above, in a typical engine, when knocking occurs under high load, the ignition timing is retarded to reduce the pressure inside the cylinder, thereby preventing knocking. However, in a pre-chamber engine, the flame propagates quickly in the combustion chamber C, so the occurrence of knocking is not affected much by the engine speed, but is affected more by the engine load. For example, in a region where the engine load is low, the combustion cycle fluctuations tend to be large regardless of the engine speed. For this reason, the amount of fuel injected (in the embodiment, both the direct fuel injection device 9a and the port fuel injection device 9b are provided, so the amount of fuel injected by the direct fuel injection device 9a in particular) is increased. Also, for example, in a region where the engine load is high, knocking tends to occur more prominently regardless of the engine speed. For this reason, the amount of fuel injected (in the embodiment, both the direct fuel injection device 9a and the port fuel injection device 9b are provided, so the amount of fuel injected by the direct fuel injection device 9a in particular) is reduced.

The electronic control unit 20 is provided with a means for detecting or predicting the occurrence of knocking based on the relationship between the engine 10 speed and engine load at that time. Such a means for detecting or predicting the occurrence of knocking is hereinafter referred to as a knocking detection and prediction means. As the knocking detection and prediction means, a device that detects or predicts the occurrence of knocking by detecting torque fluctuations or combustion fluctuations due to vibrations of the engine 10, changes in cylinder pressure, or changes in the rotational angular velocity of the crankshaft, etc., may also be used. The operating region in which the occurrence of knocking is detected or predicted is hereinafter referred to as a knocking occurrence region.

The engine 10 of this embodiment is based on a lean mixture with a lower fuel ratio (lean fuel) than the theoretical air-fuel ratio (A/F = 14.7). The air-fuel ratio of this lean mixture is the initial value. The air-fuel ratio is the air/fuel ratio, which is a dimensionless quantity obtained by dividing the air mass by the fuel mass. The electronic control unit 20 has the function of estimating the air-fuel ratio in the auxiliary chamber 11 and the air-fuel ratio of the entire combustion chamber C, etc., based on information from sensors around the engine 10.

In the knocking occurrence region, the control means provided in the electronic control unit 20 performs control to avoid knocking. The control means first performs fuel injection reduction control to reduce the amount of fuel injected by the direct fuel injection device 9a in the auxiliary chamber when the knocking occurrence region is entered (when the occurrence of knocking is detected or predicted), thereby avoiding knocking. However, reducing the amount of fuel injected creates a lean environment in the combustion chamber C and the auxiliary chamber 11, and the period during which the ignition timing can be set is extremely limited.

4 shows an air-fuel ratio curve G showing the change in the air-fuel ratio before the fuel injection amount is reduced, a post-reduction air-fuel ratio curve F showing the change in the air-fuel ratio after the fuel injection amount is reduced, a fuel injection timing C (by direct injection), and an optimal ignition timing D. The air-fuel ratio curve G shows that the air-fuel ratio in the auxiliary chamber 11 starts to decrease (the amount of fuel increases) from the injection timing C during one combustion cycle, and the air-fuel ratio becomes minimum (the amount of fuel becomes maximum) at approximately the optimal ignition timing D. As the piston 3 approaches the top dead center E, the air-fuel ratio increases (the amount of fuel decreases). Here, the point where the air-fuel ratio in the auxiliary chamber 11 becomes minimum (richest) is the optimal ignition timing D. Stable ignition is ensured only in the range surrounded by the upper limit line A of the amount of fuel in the auxiliary chamber that can be ignited and the air-fuel ratio curve G in the auxiliary chamber 11, that is, the range L _A from point s to point a. However, when the amount of fuel injection is reduced and the air-fuel ratio curve G shifts to the post-reduced air-fuel ratio curve F, the range of appropriate ignition timing for achieving good combustion, i.e., the range _LA from point s to point a, becomes increasingly narrow, making it more likely that the combustion will become unstable.

Therefore, when the knocking occurrence region is entered (when the occurrence of knocking is detected or predicted), the control means performs the fuel injection reduction control as well as the ignition energy increase control for increasing the ignition energy to the mixture by the ignition device 4. When the ignition energy is increased, the upper limit line A of the pre-chamber air-fuel ratio at which ignition is possible shifts to the modified upper limit line B which is on the leaner side (lower side) than the upper limit line A on the graph. Therefore, the range of appropriate ignition timing at which good combustion is realized can be expanded to the range surrounded by the modified upper limit line B and the reduced air-fuel ratio curve F, that is, the range L _B from point s' to point a', and the stability of ignition can be ensured. In addition, the range in which the ignition timing can be set is also expanded.

Conventionally, ignition energy was constant regardless of the ignition timing (crank angle). However, with this invention, when the amount of fuel injected is reduced to avoid knocking, the ignition energy is increased, making it possible to ensure good and stable combustion. However, constantly increasing the ignition energy may cause the ignition device 4 (spark plug) to melt, or may use too much electricity, reducing the thermal efficiency of the engine 10. For this reason, when increasing the ignition energy, it is necessary to limit the increase in energy to the minimum necessary.

In the ignition energy increase control, an ignition energy C2 (referred to as a second ignition energy C2) corresponding to the start of the control is set to be relatively large compared to an ignition energy C1 (referred to as a first ignition energy C1) in a steady state before the start of the control. Here,
(Second ignition energy C2)=(First ignition energy C1)×α
In this case, α>1, and the value of α can be set to, for example, 1.1, 1.2, 1.3, 1.4, . . . , or the like, which is the minimum required value according to the operating state.

Here, since the range in which the ignition timing can be set is expanded to the range L _B from point s' to point a', the control means can perform ignition timing retard control to retard the timing of ignition of the air-fuel mixture by the ignition device 4. By performing ignition timing retard control, knocking can be avoided more reliably.

In the ignition timing retard control, the ignition timing is retarded from the ignition timing B1 (referred to as the first ignition timing B1) in the steady state before the start of the control to the ignition timing B2 (referred to as the second ignition timing B2) corresponding to the start of the control. The first ignition timing B1 may be between points s and a shown in FIG. 5, that is, a timing when the air-fuel ratio in the auxiliary chamber 11 is below the numerical value of the upper limit line A (richer side (upper side) than line A on the graph) and the mixture is smoothly ignited. Usually, the first ignition timing B1 is set to coincide with the timing D (optimum ignition timing D) when the air-fuel ratio in the auxiliary chamber 11 is the richest, improving the thermal efficiency. It is desirable that the first ignition timing B1 is as close to the optimal ignition timing D as possible. The second ignition timing B2 may be between points s' and a' shown in FIG. 5, that is, a timing when the air-fuel ratio in the auxiliary chamber 11 falls below the value of the modified upper limit line B (is on the richer side (above) line B on the graph) and the mixture is smoothly ignited.

Furthermore, when performing ignition timing retard control, injection timing retard control may also be performed to retard the fuel injection timing by the injector 9 (particularly the direct injection fuel injector 9a). For example, when retarding the ignition timing by 5 degrees of crank angle, there is a method of retarding the fuel injection timing by the same angle as the amount of retardation of the ignition timing, such as retarding the fuel injection timing by 5 degrees of crank angle. There is also a method of retarding the fuel injection timing by an angle smaller than the amount of retardation of the ignition timing, or a method of retarding the fuel injection timing by an angle larger than the amount of retardation of the ignition timing. This makes it possible to increase the amount of fuel remaining around the ignition device 4 at the ignition timing.

In addition, when performing ignition timing retard control, a method may be adopted in which the increase in ignition energy in ignition energy increase control is set to a larger amount as the retard amount of the ignition timing increases. Figure 6 shows the set ignition timing and the magnitude of ignition energy set corresponding to the ignition timing. Graph H showing the magnitude of ignition energy is set to a minimum value at reference point c located near or on the retard side of the apex b (optimum ignition timing D) of the air-fuel ratio curve G, and is set so that the ignition energy increases as the ignition timing is shifted further toward the retard side or advance side. Also, for example, if the ignition timing is retarded by 5 (deg) of crank angle, the coefficient of increase in ignition energy α is set to 1.05, and if the ignition timing is retarded by 7.5 (deg) of crank angle, the coefficient of increase in ignition energy α is set to 1.075. A method may be adopted in which the ratio (%) of the increase in ignition energy to the original ignition energy is proportional to the retard amount (deg) of the crank angle.

Furthermore, if the vehicle 60 is equipped with a means for detecting torque fluctuation or combustion fluctuation in the engine 10 (if the knocking detection and prediction means described above detects torque fluctuation or combustion fluctuation, it may be used), a method may be adopted in which the information on the torque fluctuation or combustion fluctuation is used to determine whether or not to perform ignition energy increase control, and if so, the degree of increase. For example, a method may be considered in which ignition energy increase control is performed only when the torque fluctuation or combustion fluctuation exceeds a predetermined value. Here, the predetermined value is the lower limit of the torque fluctuation or combustion fluctuation value at which it is possible to recognize that the combustion of the mixture in the combustion chamber C is unstable, and this value is obtained in advance by a simulation or the like. Another method is to increase the coefficient α of the increase in ignition energy based on the difference between each value and a predetermined value (each value > predetermined value) based on the torque fluctuation or combustion fluctuation value at that time, and the larger the difference, the larger the coefficient α of the increase in ignition energy.

In addition, a method of preventing misfires at the ignition timing after retarding by changing the ignition pattern during ignition timing retard control is also conceivable. Examples of changing the ignition pattern include a method of promoting ignition by performing multiple ignitions during one combustion cycle, a method of overlapping sparks by performing another discharge using a different coil after one discharge during one combustion cycle (boost), and a method of creating a state with a higher current value by shortening the discharge time in the ignition device 4 to promote ignition, and other methods that increase the total ignition energy during one combustion cycle.

In addition, when the knocking region is entered (when the occurrence of knocking is detected or predicted), if the air-fuel ratio in the main chamber 1 is richer than a predetermined value, the control means performs ignition timing retard control and does not perform ignition energy increase control, but reduces the amount of fuel injected from the port injection type fuel injection device 9b to the main chamber 1, and if the detection or prediction of the occurrence of knocking continues, performs further ignition timing retard control and ignition energy increase control. Here, the predetermined value may be any value that can determine that the main chamber 1 is rich, but may also be the theoretical air-fuel ratio value, for example. When the environment in the main chamber 1 is relatively rich, the control means first observes whether knocking can be avoided by limiting the ignition timing retard control and reducing the amount of fuel injected from the main chamber, thereby minimizing the opportunity for ignition energy increase control.

The reason why the reduction in fuel injection amount is limited to main chamber injection (mainly by port injection fuel injection device 9b) is that when both direct injection fuel injection device 9a and port injection fuel injection device 9b are installed, the proportion of fuel injected from direct injection fuel injection device 9a is about 5-10% of the total, and direct injection fuel injection device 9a does not contribute much to creating a rich environment in the main chamber 1. If the detection or prediction of the occurrence of knocking continues, further ignition timing retard control is performed and ignition energy increase control is performed to reliably avoid knocking.

In the above embodiment, the injection device 9 is configured to include both the direct injection fuel injection device 9a and the port injection fuel injection device 9b, but the present invention is not limited to this embodiment, and the injection device 9 may be configured to include only the direct injection fuel injection device 9a. In addition, when the injection device 9 is configured to include both the direct injection fuel injection device 9a and the port injection fuel injection device 9b, the direct injection fuel injection device 9a may be disposed in either the main chamber 1 or the auxiliary chamber 11. In addition, in the above embodiment, a plug-in hybrid vehicle having at least three types of driving modes, namely, an electric driving mode, a series driving mode, and a parallel driving mode, is used as the vehicle 60, but the present invention can also be applied to other types of hybrid vehicles and general engine-equipped vehicles other than hybrid vehicles.

Reference Signs List 1 Main chamber 2 Cylinder 3 Piston 4 Ignition device 9 Injection device 10 Engine 11 Sub-chamber 12 Communication passage 20 Electronic control unit 30 First rotating electric machine 40 Second rotating electric machine 50 Battery 60 Hybrid vehicle (vehicle)
C. Combustion chamber

Claims (6)

a combustion chamber including: a main chamber defined by an inner peripheral surface of a cylinder, an inner surface of a cylinder head, and a top surface of a piston; an auxiliary chamber defined at an end of the main chamber on the cylinder head side and separated from the main chamber by a partition; and a communication passage defined in the partition for communicating the main chamber with the auxiliary chamber;
an injector for supplying fuel to the main chamber;
an engine having an ignition device facing the pre-chamber and igniting the air-fuel mixture in the pre-chamber;
A means for detecting or predicting the occurrence of knocking in the engine;
A control means for performing control to avoid the knocking;
Equipped with
The fuel supplied to the main chamber is forced into the auxiliary chamber by the compression stroke, and the control means, when the occurrence of knocking is detected or predicted, performs fuel injection reduction control to reduce the amount of fuel injection of the auxiliary chamber injection that supplies fuel to the auxiliary chamber by the injection device, and performs ignition energy increase control to increase ignition energy to the mixture by the ignition device. The engine control device according to claim 1, wherein the control means performs ignition timing retard control to retard the ignition timing of the ignition device to the mixture when the occurrence of knocking is detected or predicted. The engine control device according to claim 2, wherein the ignition energy increase control sets the increase in ignition energy to a larger amount the greater the amount of retardation of the ignition timing in the ignition timing retard control. The engine control device according to claim 2 or 3, wherein when the ignition timing retard control is performed, an injection timing retard control is performed to retard the injection timing of the pre-chamber injection by the injection device. means for detecting torque fluctuations or combustion fluctuations in the engine;
5. The engine control device according to claim 1, wherein the ignition energy increase control is performed when the torque fluctuation or the combustion fluctuation exceeds a predetermined value. an air-fuel ratio detection means for detecting or estimating an air-fuel ratio in the main chamber;
5. The engine control device according to claim 2, wherein, when the occurrence of knocking is detected or predicted, if the air-fuel ratio is richer than a predetermined value, the control means performs the ignition timing retard control and does not perform the ignition energy increase control, but reduces the fuel injection amount of main chamber injection that supplies fuel from the injection device to the main chamber, and if the detection or prediction of the occurrence of knocking continues, further performs the ignition timing retard control and performs the ignition energy increase control.

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