JP6826396B2 - Engine control unit - Google Patents

Description

The present invention relates to an engine control device that controls an engine.

Abnormal combustion of the engine includes knocking and pre-ignition accompanied by shock waves. Since these abnormal combustions are factors that damage the engine, devices and methods for detecting and coping with the abnormal combustion have been proposed (see Patent Documents 1 and 2).

JP-A-2007-231948 Japanese Unexamined Patent Publication No. 10-321343

By the way, pre-ignition in which the air-fuel mixture self-ignites before ignition by the spark plug is more difficult to suppress than knocking, so that pre-ignition may continuously occur depending on the situation in the cylinder. The continuous occurrence of pre-ignition in this way is a factor that causes great damage to the engine.

An object of the present invention is to prevent the engine from being significantly damaged when pre-ignition occurs.

The engine control device of the present invention is an engine control device that controls an engine, and ignites an injector provided in the engine and injecting fuel into a cylinder and an air-fuel mixture provided in the engine and in the cylinder. As the fuel injection mode of the spark plug, the abnormal combustion detection unit that detects the abnormal combustion of the air-fuel mixture, and the injector, the normal mode used when the regeneration is not detected and the regeneration are detected. anda fuel injection control unit having at least a first and abnormal modes Ru is damaged, the said spark plug is used when the in the first abnormal mode, the fuel amount of fuel injection in the normal mode The amount is increased beyond the injection amount, the end timing of fuel injection is set later than the end timing of fuel injection in the normal mode, and the timing of fuel injection in the first abnormal mode is injected from the injector. This includes the timing at which the fuel changes direction at the piston in the cylinder and adheres to the spark plug.

According to the present invention, it is possible to prevent the engine from being significantly damaged when pre-ignition occurs.

It is a schematic diagram which shows the engine 11 controlled by the engine control device which is one Embodiment of this invention. (A) is a diagram showing an example of a change in cylinder internal pressure when pre-ignition occurs, and (b) is a diagram showing an example of a signal change of a knock sensor when pre-ignition occurs. It is explanatory drawing which shows the fuel injection mode of an injector. (A) to (c) are explanatory views which show the fuel injection state in order in the quenching injection mode. It is a diagram which shows the temperature transition of the spark plug in the quenching injection mode. It is a flowchart which shows an example of the procedure at the time of switching a fuel injection mode. It is explanatory drawing which shows another example of the fuel injection mode of an injector. It is a diagram which shows the temperature transition of the spark plug in the quenching injection mode.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing an engine 11 controlled by an engine control device 10 according to an embodiment of the present invention. As shown in FIG. 1, the engine 11, which is a direct injection type internal combustion engine, has a cylinder block 13 in which a piston 12 is slidably housed, and a cylinder head 14 attached to the cylinder block 13. .. The cylinder head 14 is formed with a combustion chamber 15, that is, an intake port 16 communicating with the inside of the cylinder, and an exhaust port 17 communicating with the inside of the cylinder. Further, the cylinder head 14 is assembled with an injector 18 for injecting fuel into the cylinder, and a spark plug 19 for igniting the air-fuel mixture in the cylinder.

The illustrated engine 11 is an engine in which the air-fuel mixture is stratified and burned by layered air supply. Therefore, the head portion 20 of the piston 12 is provided with a cavity 21 that functions as a so-called wall guide, that is, a cavity 21 that forms a stratified air-fuel mixture toward the spark plug 19. The fuel injected from the injector 18 toward the cavity 21 turns along the cavity 21 and is guided to the vicinity of the spark plug 19. Since the stratified air-fuel mixture can be supplied in the vicinity of the spark plug 19 in this way, lean burn of the engine 11 can be achieved, and the fuel efficiency of the engine 11 can be improved.

The engine control device 10 that controls the engine 11 has an engine controller 30 including a microcomputer or the like. The engine controller 30 controls the operating state of the engine 11 by executing fuel injection control, ignition timing control, and the like based on signals from various sensors that detect the operating state of the engine 11. As sensors connected to the engine controller 30, a crank angle sensor 31 that detects the rotation angle of the crankshaft, a cam angle sensor 32 that detects the rotation angle of the camshaft, a knock sensor 33 that detects the vibration of the cylinder block 13, and an intake air. There are an air flow meter 34 for detecting the amount, an O ₂ sensor 35 for detecting the oxygen concentration in the exhaust gas, an A / F sensor 36 for detecting the air fuel ratio in the exhaust gas, and the like.

[Pre-ignition]
As abnormal combustion of the engine 11, there is early ignition, that is, pre-ignition, in which the air-fuel mixture self-ignites before ignition by the spark plug 19. In this pre-ignition, it is considered that the air-fuel mixture during the compression stroke self-ignites due to the heat source such as carbon sludge and oil existing in the cylinder. Since pre-ignition accompanied by a shock wave is a factor that seriously damages the engine 11, it is necessary to protect the engine 11 from pre-ignition by detecting the occurrence of pre-ignition and taking appropriate measures. Therefore, the engine controller 30 is provided with an abnormal combustion detection unit 37 that detects pre-ignition, and a fuel injection control unit 38 that switches the fuel injection mode of the injector 18 in order to protect the engine 11. Hereinafter, the fuel injection mode for protecting the engine 11 will be described after the pre-ignition detection method is described.

[Pre-ignition detection]
FIG. 2A is a diagram showing an example of a change in the cylinder internal pressure when a pre-ignition occurs, and FIG. 2B is a diagram showing an example of a signal change of the knock sensor 33 when a pre-ignition occurs. As shown by the characteristic line L1 in FIG. 2 (a), when the air-fuel mixture burns normally, the cylinder internal pressure, that is, the cylinder internal pressure changes slowly, whereas the characteristic line L2 is shown in FIG. 2 (a). As described above, when the pre-ignition of the air-fuel mixture occurs, the cylinder internal pressure changes abruptly due to the shock wave. Further, as shown by reference numeral X in FIG. 2B, when pre-ignition occurs, the cylinder block 13 vibrates due to the shock wave, so that pre-ignition is performed based on the pattern and timing of the detection signal of the knock sensor 33. It is possible to detect. That is, the abnormal combustion detection unit 37 of the engine controller 30 detects the occurrence of pre-ignition based on the detection signal of the knock sensor 33. The abnormal combustion detection unit 37 can identify the cylinder in which the pre-ignition has occurred among the plurality of cylinders included in the engine 11 based on the rotation angles of the crankshaft and the camshaft.

[Fuel injection mode]
FIG. 3 is an explanatory diagram showing a fuel injection mode of the injector 18. As shown in FIG. 3, three fuel injection modes of the injector 18, a normal injection mode, an increase injection mode, and a quenching injection mode are set. In the normal injection mode (normal mode), the control target value of the engine 11 is determined based on the driving conditions such as the vehicle speed and the accelerator operation, and the fuel injection amount and the fuel injection timing are controlled toward the control target value. It is an injection mode. During normal driving without pre-ignition, the normal injection mode is set as the fuel injection mode.

When pre-ignition occurs in this normal injection mode, an increased injection mode (second abnormal mode) is executed in order to suppress the continuous generation of pre-ignition. As shown in FIG. 3, the fuel injection time T2 in the increased injection mode is set longer than the fuel injection time T1 in the normal injection mode. That is, the fuel injection amount in the increased injection mode is set to be larger than the fuel injection amount in the normal injection mode. By executing this increased injection mode, the fuel injection amount can be increased and the temperature inside the cylinder can be lowered, and the occurrence of pre-ignition can be suppressed. The fuel increase in this increase injection mode is set so that, for example, the air-fuel ratio is near the misfire limit so that the maximum cooling effect can be obtained within a range that does not cause a misfire.

If the pre-ignition does not converge even when the fuel increase mode is executed, the quenching injection mode (first abnormal mode) that damages the spark plug 19 is executed. As shown in FIG. 3, the fuel injection end timing Te3 in the quenching injection mode is set later than the fuel injection end timing Te1 in the normal injection mode. Further, the fuel injection end timing Te3 in the quenching injection mode is set later than the fuel injection end timing Te2 in the increased injection mode. This quenching injection mode is a fuel injection mode in which it is not necessary to burn the air-fuel mixture. Therefore, in the quenching injection mode, the fuel injection end timing Te3 is set close to the top dead center (TDC) so as to interrupt the vaporization time Tg required for fuel vaporization.

Further, the fuel injection time T3 in the quenching injection mode is set longer than the fuel injection time T1 in the normal injection mode and further longer than the fuel injection time T2 in the increased injection mode. That is, the fuel injection amount in the quenching injection mode is set to be larger than the fuel injection amount in the normal injection mode and the increased injection mode. By executing this quenching injection mode, the fuel injection amount can be further increased and the temperature inside the cylinder can be lowered. In particular, the generation of pre-ignition can be suppressed more effectively than in the increased injection mode due to the temperature lowering effect in the cylinder due to the "heat of vaporization of the fuel not burned" that is excessively injected to damage the spark plug 19. ..

4 (a) to 4 (c) are explanatory views showing the fuel injection state in the quenching injection mode in order. Note that FIG. 4A shows the situation immediately before top dead center, FIG. 4B shows the situation at top dead center, and FIG. 4C shows immediately after top dead center. The situation is shown. As shown in FIGS. 4A to 4C, the fuel F injected from the injector 18 immediately before the top dead center is reflected by the cavity 21 of the piston 12 and is applied to the spark plug 19. That is, the fuel injected from the injector 18 reaches the spark plug 19 before the vaporization time elapses, and the fuel before vaporization, that is, the liquid fuel adheres to the spark plug 19. As a result, the spark plug 19 can be rapidly cooled, and the spark plug 19 can be damaged. As described above, the timing of fuel injection in the quenching injection mode includes the timing at which the fuel F injected from the injector 18 is reflected by the piston 12 and adheres to the spark plug 19.

Here, FIG. 5 is a diagram showing the temperature transition of the spark plug 19 in the quenching injection mode. As shown by reference numeral a1 in FIG. 5, the temperature of the spark plug 19 rises as the crank angle approaches the top dead center. That is, since the air-fuel mixture is adiabatically compressed as the crank angle approaches the top dead center, it is milder than the normal injection mode in which the fuel amount is not increased, but as the temperature of the air-fuel mixture rises, the spark plug 19 The temperature will also rise. Then, as described above, since the liquid fuel adheres to the spark plug 19 near the top dead center, the temperature of the spark plug 19 drops rapidly as shown by reference numeral a2. That is, as shown by the broken line X in FIG. 5, the temperature of the spark plug 19 is sharper when the liquid fuel is attached to the spark plug 19 than when the liquid fuel is not attached to the spark plug 19. Can be reduced to.

By quenching the spark plug 19 with the liquid fuel in this way, the spark plug 19 can be damaged as shown in the enlarged portion of FIG. 4C. That is, the spark plug 19 has a center electrode 40 arranged at the center, an insulating insulator 41 provided outside the center electrode 40, and a ground electrode 42 provided outside the insulating insulator 41. By applying liquid fuel to the spark plug 19, the ceramic insulator 41 can be rapidly cooled and cracked. When the insulator 41 of the spark plug 19 is broken, the ground electrode 42 and the center electrode 40 are short-circuited, so that the ignition function of the spark plug 19 is lost.

That is, the ignition plug 19 is intentionally damaged to cause a minor failure state as compared with the serious damage of the engine 11 that may occur due to the continuation of pre-ignition. This makes it possible to notify the driver (occupant) of the engine malfunction before causing serious damage to the engine 11. At this time, by suppressing the torque generated by the other cylinders (the cylinders in which pre-ignition is not generated) in which the spark plug 19 is not damaged and controlling the rotation speed to be lowered, the generation of pre-ignition is more reliable. It can be suppressed. In addition, by notifying the driver of the engine malfunction, it is possible to guide the driver so that the operation is such that the engine speed is lowered, which also leads to suppression of the occurrence of pre-ignition. Further, by cooling the spark plug 19, if the pre-ignition is caused by the high temperature of the spark plug 19, the generation of the pre-ignition can be suppressed more effectively.

In addition, since the quenching injection mode that damages the spark plug 19 is executed for the cylinder in which pre-ignition occurs, torque is limited for engine protection for other cylinders in which pre-ignition does not occur, but it is normal. It can be made to function and the minimum running performance can be ensured. Further, the engine controller 30 detects that the ignition function of the spark plug 19 has been lost, that is, that the inside of the cylinder has fallen into a misfire situation, based on the detection signals of the O ₂ sensor 35 and the A / F sensor 36. Is possible. As a result, the engine controller 30 can grasp the loss of function of the spark plug 19, and can turn on the warning light 43 to notify the driver of the engine malfunction. In addition, the warning light 43 can be turned on to urge the driver to enter the repair shop or the like.

[flowchart]
Subsequently, the above-mentioned switching of the fuel injection mode will be described with reference to the flowchart. FIG. 6 is a flowchart showing an example of a procedure for switching the fuel injection mode. The flowchart shown in FIG. 6 is executed by the engine controller 30 at a predetermined cycle for each cylinder.

As shown in FIG. 5, in step S10, it is determined whether or not pre-ignition has occurred. If it is determined in step S10 that pre-ignition has not occurred, the process proceeds to step S11, and the injector 18 is controlled in the normal injection mode. If it is determined in step S10 that pre-ignition has occurred, the process proceeds to step S12, and the fuel injection mode is switched from the normal injection mode to the increased injection mode. By executing this increased injection mode, the fuel injection amount can be increased and the temperature inside the cylinder can be lowered, and pre-ignition can be suppressed.

When the increased injection mode for increasing the fuel injection amount is executed in this way, the process proceeds to step S13, and it is determined whether or not pre-ignition has occurred again. If it is determined in step S13 that pre-ignition has occurred, that is, if it is determined that the pre-ignition has not converged even by executing the increase injection mode, the process proceeds to step S14 and the fuel injection mode is increased. It is possible to switch from the injection mode to the quenching injection mode.

As described above, when the pre-ignition is not settled even by the increased injection mode, that is, when there is a possibility that the pre-ignition is continuously generated, the quenching injection mode for delaying the fuel injection end timing Te3 is executed. As a result, liquid fuel is applied to the spark plug 19 to positively damage the spark plug 19 while effectively suppressing the generation of pre-ignition. Then, when it is detected in step S15 that the spark plug 19 is damaged, the process proceeds to step S16, and the warning light 43 is turned on to notify the driver of the engine abnormality. When no damage to the spark plug 19 is detected in step S15, the process returns to step S13 to determine whether or not the pre-ignition continues.

As described above, when pre-ignition is detected, an increased injection mode for increasing the injected fuel is executed in order to suppress the pre-ignition. Then, when the pre-ignition is not settled even by the increased injection mode, that is, when there is a possibility that the pre-ignition is continuously generated, the quenching injection mode for delaying the fuel injection end timing Te3 is executed. This makes it possible to notify the driver of engine malfunction while effectively suppressing the continuous occurrence of pre-ignition.

As described above, when there is a possibility that pre-ignition may occur continuously, the spark plug 19 is positively damaged. That is, when there is a possibility that pre-ignition may occur continuously, the spark plug 19 functions as a fuse to protect the engine 11 from serious damage due to pre-ignition. Moreover, even when the quenching injection mode is executed, the engine 11 can be repaired by replacing the spark plug 19, so that the engine 11 can be repaired easily and inexpensively. Further, since the spark plug 19 is physically damaged by the quenching injection mode, the occurrence of pre-ignition can be easily verified. That is, it is possible to easily verify that the pre-ignition has occurred based on the execution status of the rapid injection mode recorded in the engine controller 30 and the physical damage status of the spark plug 19.

In the above description, the fuel injection mode is switched from the normal injection mode to the increased injection mode, and then the fuel injection mode is switched from the increased injection mode to the quenching injection mode, but the present invention is not limited to this. That is, depending on the state of occurrence of pre-ignition, the fuel injection mode may be switched from the normal injection mode to the quenching injection mode without executing the increase injection mode. Further, in the example shown in FIG. 3, the end timing Te3 of the fuel injection in the quenching injection mode is set before the ignition timing Ti, but the present invention is not limited to this, and as shown by the broken line α in FIG. The end timing Te3 may be set after the ignition timing Ti, or the end timing Te3 may be set after the top dead center as shown by the broken line β in FIG. Further, in the example shown in FIG. 3, the fuel injection start timings Ts1, Ts2, and Ts3 in each fuel injection mode are matched with each other, but the present invention is not limited to this, and the fuel injection start timings Ts1, Ts2, Ts3 May be staggered from each other.

[Other embodiments]
In the above description, fuel injection is started in the quenching injection mode at the same timing as in the normal injection mode and the increased injection mode, but the present invention is not limited to this, and the fuel injection start timing Ts3 in the quenching injection mode is not limited to this. May be delayed. Here, FIG. 7 is an explanatory diagram showing another example of the fuel injection mode of the injector 18. Further, FIG. 8 is a diagram showing a temperature transition of the spark plug 19 in the quenching injection mode. The normal injection mode and the increased injection mode shown in FIG. 7 are the same as the normal injection mode and the increased injection mode shown in FIG. Further, the broken line X shown in FIG. 8 is the same as the broken line X shown in FIG.

As shown in FIG. 7, the fuel injection start timing Ts3 in the quenching injection mode is set later than the fuel injection start timing Ts1 in the normal injection mode. Further, the fuel injection start timing Ts3 in the quenching injection mode is set later than the fuel injection start timing Ts2 in the increase injection mode. In this way, by delaying the start timing Ts3 of fuel injection in the quenching injection mode, the temperature after adiabatic compression is increased, and the spark plug 19 is supplied with heat.

As a result, as shown by reference numeral b1 in FIG. 8, the temperature of the spark plug 19 can be raised as compared with the quenching injection mode shown in FIG. Then, even in the quenching injection mode shown in FIG. 8, since the liquid fuel adheres to the spark plug 19 near the top dead center, the spark plug 19 is rapidly cooled. That is, since the temperature of the spark plug 19 has risen significantly as shown by reference numeral b1 in FIG. 8, a large temperature change is given to the spark plug 19 in the subsequent quenching process as shown by reference numeral b2 in FIG. be able to. By greatly changing the temperature of the spark plug 19 in this way, the insulating insulator 41 of the spark plug 19 can be cracked more reliably.

Also in the example shown in FIG. 7, the fuel injection time T3 in the quenching injection mode is made longer than the fuel injection time T1 in the normal injection mode to increase the fuel injection amount, and the spark plug 19 is used while controlling the in-cylinder temperature. It is preferable to give a sufficient temperature change. Further, the quenching injection mode shown in FIG. 7 is not continuously executed, but is executed once or a predetermined number of times immediately after shifting from the increase injection mode to the quenching injection mode, and then the quenching injection mode shown in FIG. 3 is performed. It may be carried out, or if the spark plug 19 is not damaged even if the quenching injection mode shown in FIG. 3 is executed, the quenching injection mode shown in FIG. 7 may be performed once or a predetermined number of times. good.

It goes without saying that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist thereof. For example, the engine 11 shown in the figure is a horizontally opposed engine, but the engine is not limited to this, and may be an engine of another type such as an in-line type or a V type. Further, in the above description, the insulating insulator 41 of the spark plug 19 is damaged by the quenching injection mode, but the present invention is not limited to this, and if it is possible to lose the ignition function of the spark plug 19. Other parts of the spark plug 19 may be damaged.

In the above description, the knock sensor 33 is used to detect the pre-ignition based on the vibration of the cylinder block 13, but the present invention is not limited to this. For example, by providing a pressure sensor that detects the pressure inside the cylinder, the occurrence of pre-ignition may be detected based on the pressure inside the cylinder. Further, by providing an ion current sensor that detects ions generated during combustion, the generation of pre-ignition may be detected based on the ion detection timing, that is, the combustion timing.

10 Engine control device 11 Engine 12 Piston 18 Injector 19 Spark plug 30 Engine controller 37 Abnormal combustion detection unit 38 Fuel injection control unit Ts1, Ts2, Ts3 Start timing Te1, Te2, Te3 End timing

Claims (3)

An engine control device that controls the engine
An injector provided in the engine and injecting fuel into the cylinder,
An ignition plug provided in the engine and igniting the air-fuel mixture in the cylinder,
An abnormal combustion detector that detects pre-ignition, which is abnormal combustion of the air-fuel mixture,
As the fuel injection mode of the injector has a normal mode that is used when the pre-ignition is not detected, and a first abnormal mode of Ru to damage the spark plug is used when the pre-ignition is detected at least Fuel injection control unit and
Have,
In the first abnormal mode, the fuel injection amount is increased more than the fuel injection amount in the normal mode, and the fuel injection end timing is set later than the fuel injection end timing in the normal mode .
The timing of fuel injection in the first abnormal mode includes the timing at which the fuel injected from the injector changes its direction by the piston in the cylinder and adheres to the spark plug.
Engine control device. In the engine control device according to claim 1,
The start timing of fuel injection in the first abnormal mode is later than the start timing of fuel injection in the normal mode.
Engine control device. In the engine control device according to claim 1 or 2 .
The fuel injection control unit
When the pre-ignition is detected during the normal mode, the fuel injection mode of the injector is switched to the second abnormal mode in which the fuel injection amount is larger than that of the normal mode.
When the pre-ignition is detected during the second abnormal mode, the fuel injection mode of the injector is switched to the first abnormal mode.
The end timing of fuel injection in the first abnormal mode is later than the end timing of fuel injection in the second abnormal mode.
Engine control device.

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