JP6764131B2 - Internal combustion engine fuel injection system - Google Patents

Description

The present invention relates to a failure diagnosis technique for a high-pressure fuel supply device that supplies fuel to an in-cylinder fuel injection valve of an internal combustion engine.

An internal combustion engine equipped with an in-cylinder fuel injection valve that injects fuel into a combustion chamber is known. The in-cylinder fuel injection valve is supplied with high-pressure fuel from the fuel tank by a high-pressure fuel supply device, so that fuel can be injected into the high-pressure combustion chamber. The high-pressure fuel supply device includes, for example, a high-pressure fuel pump (plunger pump) driven by an internal combustion engine and a flow control valve (spill valve), and the discharge pressure from the high-pressure fuel pump, that is, the fuel supplied to the in-cylinder fuel injection valve. The pressure (delivery fuel pressure) is detected by the fuel pressure sensor, and the flow control valve is driven and controlled so that the delivery fuel pressure reaches the target fuel pressure. Further, many of the high-pressure fuel supply devices are provided with a relief valve, which opens when the delivery fuel pressure becomes equal to or higher than a predetermined pressure to reduce the delivery fuel pressure.

Further, Patent Document 1 proposes a failure diagnosis device that raises the target fuel pressure above the relief pressure and determines that the relief valve has failed when the delivery fuel pressure detected by the fuel pressure sensor exceeds the relief pressure. ..

Japanese Patent No. 5370635

However, controlling the delivery fuel pressure to be higher than the relief pressure as in Patent Document 1 increases the frequency of valve opening operation of the relief valve, and may shorten the life of the relief valve. Therefore, a method of lowering the delivery fuel pressure and determining the failure of the relief valve or the fuel pressure sensor based on the change in the detected value of the fuel pressure sensor can be considered. However, if the delivery fuel pressure is lowered in order to perform a failure diagnosis when the engine is started, the engine may be stopped.

The present invention has been made to solve the above-mentioned problems, and an object thereof is
It is an object of the present invention to provide a fuel injection device for an internal combustion engine capable of determining a failure of a relief valve and a fuel pressure sensor while suppressing an engine stop when the engine is started.

In order to achieve the above object, the fuel injection device of the internal combustion engine of the present invention is supplied with a high-pressure fuel supply device that pressurizes the fuel stored in the fuel tank and the fuel that is pressurized by the high-pressure fuel supply device. An in-cylinder fuel injection valve that injects into the combustion chamber of the engine, an intake passage fuel injection valve that injects fuel into the intake passage of the internal combustion engine, the in-cylinder fuel injection valve and the above based on the operating state of the internal combustion engine. A fuel injection control unit that supplies fuel to the internal combustion engine by at least one of the intake passage fuel injection valves, and fuel that is opened at a predetermined relief pressure and supplied from the high-pressure fuel supply device to the in-cylinder fuel injection valve. A relief valve that suppresses pressure, a pressure detector that detects the pressure of fuel supplied from the high-pressure fuel supply device to the in-cylinder fuel injection valve, and pressure detection by the pressure detector when the internal combustion engine is started. A fuel injection device for an internal combustion engine including a failure determination unit for determining a failure of the pressure detector and the relief valve based on a value, and the failure determination unit is when the internal combustion engine is instructed to start. When the pressure detection value exceeds the relief pressure, the injection of fuel by the in-cylinder fuel injection valve is stopped until a predetermined period elapses from the start of the internal combustion engine, and the intake passage fuel injection valve alone is used. It is characterized in that fuel is supplied to the internal combustion engine, and after a lapse of the predetermined period, fuel pressure lowering control for lowering the pressure of the fuel supplied to the in-cylinder fuel injection valve is executed to identify a failure location.

Further, preferably, the failure determination unit may change the predetermined period based on the soak state until the internal combustion engine starts.
Further, preferably, the soak state is the cooling water temperature or the lubricating oil temperature of the internal combustion engine at the start of stopping before starting the internal combustion engine, and the time from the start of stopping of the internal combustion engine to the start instruction of the internal combustion engine. It should be set based on.

Further, preferably, the soak state includes the cooling water temperature or lubricating oil temperature of the internal combustion engine at the start of stopping before starting the internal combustion engine, and the cooling water temperature or lubricating oil of the internal combustion engine at the time of instructing the start of the internal combustion engine. It should be set based on the temperature.
Further, preferably, the failure determination unit executes the fuel pressure lowering control by fuel injection by the in-cylinder fuel injection valve after the elapse of the predetermined period, and based on the degree of change in the pressure detection value, the relief valve and the above. It is advisable to identify which of the pressure detectors is defective.

According to the fuel injection device of the internal combustion engine of the present invention, if the pressure detection value exceeds the relief pressure when the internal combustion engine is instructed to start, it is estimated that the relief valve or the pressure detector is out of order. be able to. Then, the fuel pressure can be secured by stopping the fuel injection by the in-cylinder fuel injection valve from the start of the internal combustion engine until a predetermined period of time elapses and supplying the fuel to the internal combustion engine only by the intake passage fuel injection valve. It is possible to suppress the stoppage of the internal combustion engine due to the decrease in fuel pressure when the fuel pressure decrease control is executed to identify the failure location.

It is a schematic block diagram of the fuel injection device of the internal combustion engine of one Embodiment of this invention. It is a flowchart which shows the failure determination procedure at the time of starting an engine of this embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a fuel injection device for an internal combustion engine according to an embodiment of the present invention.
The engine (internal combustion engine) provided with the fuel injection device according to the embodiment of the present invention is, for example, an automobile driving drive engine and a 4-cylinder gasoline engine. The engine has an intake passage fuel injection valve 10 (10a to 10d) for injecting fuel into the intake passage and an in-cylinder fuel injection valve 11 (11a to 11d) for injecting fuel into the combustion chamber, one for each cylinder. It is provided one by one.

The intake passage fuel injection valve 10 has an injection port arranged at an intake port of an internal combustion engine. As shown in FIG. 1, the intake passage fuel injection valve 10 is supplied with fuel from the fuel tank 12 by the feed pump 13 and injects low-pressure fuel into the intake port. The discharge pressure of the feed pump 13 is regulated by the regulator 14. The fuel injection by the intake passage fuel injection valve 10 is referred to as intake passage fuel injection (MPI).

The in-cylinder fuel injection valve 11 has an injection port arranged in the combustion chamber of the engine. The in-cylinder fuel injection valve 11 injects high-pressure fuel supplied from the high-pressure fuel supply device 20 into the combustion chamber. The high-pressure fuel supply device 20 pressurizes the low-pressure fuel supplied from the fuel tank 12 by the feed pump 13 and supplies it to the in-cylinder fuel injection valve 11. The fuel injection by the in-cylinder fuel injection valve 11 is referred to as in-cylinder fuel injection (DI).

Orifices 21a and 21b are provided in the fuel supply path between the feed pump 13 and the intake passage fuel injection valve 10, and the orifice 22 is provided in the fuel supply path between the high pressure fuel supply device 20 and the in-cylinder fuel injection valve 11. Are provided to adjust the fuel flow rate respectively.
Further, the delivery pipe 23, which is a fuel supply path from the high-pressure fuel supply device 20 to the in-cylinder fuel injection valves 11a to 11d, has a delivery fuel pressure Pd (pressure detection value) which is the discharge pressure of the fuel from the high-pressure fuel supply device 20. ) Is provided as a fuel pressure sensor 24 (pressure detector).

The high-pressure fuel supply device 20 includes a filter 30, a pulsation damper chamber 31, a spill valve 32, a plunger pump 33, a discharge valve 34, and a relief valve 35.
The plunger pump 33 is provided so that the plunger 37 can reciprocate in the cylindrical cylinder 36. The plunger 37 is moved by a cam provided on a drive shaft of an engine (not shown). The drive shaft is connected to, for example, the exhaust camshaft of the engine, so that the plunger 37 reciprocates in the cylinder 36 by driving the engine, and the volume of the pressurizing chamber 38 in the cylinder 36 is increased or decreased.

The high-pressure fuel supply device 20 is provided with a supply path 39 for supplying fuel from the feed pump 13 to the pressurizing chamber 38 and a discharge path 40 for discharging fuel from the pressurizing chamber 38.
A filter 30, a pulsation damper chamber 31, and a spill valve 32 are arranged in order from the upstream side in the supply path 39.
The filter 30 has a function of filtering the fuel supplied from the fuel tank 12 by the feed pump 13. The pulsation damper chamber 31 has a function of suppressing fluctuations in fuel pressure in the supply path 39.

The spill valve 32 is urged to open by a spring 41 and is configured to close by energizing the solenoid 42. The solenoid 42 closes the spill valve 32 by supplying electric power as a spill valve drive signal from the control unit 50 (fuel injection control unit).
A discharge valve 34 is arranged in the discharge path 40. The discharge valve 34 is urged to be closed by a spring, and the front-rear differential pressure rises above a predetermined value, that is, the pressure inside the pressurizing chamber 38 rises above the set supply pressure to the in-cylinder fuel injection valve 11. It is set to open the valve when it is used.

Further, the relief valve 35 is arranged in parallel with the discharge valve 34. The relief valve 35 is set so that the pressure on the downstream side of the discharge valve 34 is equal to or higher than the relief pressure Pr.
In the high-pressure fuel supply device 20, the spill valve 32 is opened when the plunger 37 is moved downward, that is, when the volume of the pressurizing chamber 38 is expanded, and fuel is supplied into the pressurizing chamber 38 from the supply path 39. .. When moving upward of the plunger 37, that is, when the volume of the pressurizing chamber 38 is reduced, a spill valve drive signal is temporarily supplied to the solenoid 42 to close the spill valve 32, thereby closing the plunger valve 37 thereafter. The closed state of the spill valve 32 is maintained at the time of movement to, and the fuel in the pressurizing chamber 38 is pressurized.

Therefore, in the high-pressure fuel supply device 20, the spill valve drive signal for closing and operating the spill valve 32 is input to the solenoid 42 at each start of movement upward from the bottom dead center of the plunger 37, so that the plunger 37 moves up and down. Correspondingly, the spill valve 32 repeatedly opens and closes, the fuel is repeatedly pressurized, and the high-pressure fuel can be discharged.
In the high-pressure fuel supply device 20 of the present embodiment, fuel is supplied from the pulsation damper chamber 31 and stored in a sub chamber opposite to the pressurizing chamber 38 with respect to the plunger 37 in the cylinder 36. It is configured as follows.

The control unit 50 includes an input / output device, a storage device (ROM, RAM, non-volatile RAM, etc.), a central processing unit (CPU), and the like. The control unit 50 controls the intake passage fuel injection valve 10 and the in-cylinder fuel injection valve 11 based on the accelerator operation, the engine rotation speed, and the like to control the fuel injection amount and operate spark plugs and the like (not shown). Control is performed to control the operation of the engine.

Further, the control unit 50 determines the fuel injection mode based on the rotation speed and the load of the engine. The fuel injection mode is determined using the fuel injection mode map. For example, the MPI mode is determined during low load and low rotation, and the DI + MPI mode is determined during medium and high load operation. The MPI mode is a mode in which fuel injection is performed only by the intake passage fuel injection valve 10 without fuel injection by the in-cylinder fuel injection valve 11, and in the DI + MPI mode, the in-cylinder fuel injection valve 11 and the intake passage fuel injection are performed. Fuel is injected from both valves 10.

Further, the control unit 50 has a function of inputting the delivery fuel pressure Pd from the fuel pressure sensor 24 and feedback-controlling the high-pressure fuel supply device 20 so that the delivery fuel pressure Pd becomes a predetermined target fuel pressure Pdt when the engine is operated. There is. The target fuel pressure Pdt is set to the basic target fuel pressure Pdta that is set based on the fuel injection mode during engine operation. Further, the control unit 50 also has a function of injecting fuel from the in-cylinder fuel injection valve 11 to reduce the delivery fuel pressure Pd to the target fuel pressure Pdt when the delivery fuel pressure Pd is higher than the target fuel pressure Pdt.

Further, the control unit 50 of the present embodiment includes a failure diagnosis unit 51 for failure diagnosis of the high-pressure fuel supply device 20, specifically, a failure determination unit 51 for detecting a failure of the fuel pressure sensor 24 and the relief valve 35 and identifying which one is failed. I have. The failure diagnosis of the fuel pressure sensor 24 and the relief valve 35 by the failure determination unit 51 when the engine is started will be described below with reference to FIG.

FIG. 2 is a flowchart showing a failure diagnosis control procedure of the high-pressure fuel supply device 20 executed by the failure determination unit 51 when the engine is started.
The failure diagnosis control shown in FIG. 2 is started when an engine start instruction (for example, a key switch is turned on) is given as step S10. Then, the process proceeds to step S20.
In step S20, the delivery fuel pressure Pd detected by the fuel pressure sensor 24 is input, and it is determined whether or not the delivery fuel pressure Pd is larger than the value obtained by adding the predetermined value α appropriately set to the relief pressure Pr of the relief valve 35. When the delivery fuel pressure Pd is larger than the value obtained by adding the predetermined value α to the relief pressure Pr (Pd> Pr + α), the process proceeds to step S30. When the delivery fuel pressure Pd is equal to or less than the value obtained by adding the predetermined value α to the relief pressure Pr (Pd ≦ Pr + α), this routine ends.

In step S30, a high-pressure failure determination is established in which the high-pressure fuel supply device 20 is out of order, specifically, any one of the fuel pressure sensor 24 and the relief valve 35 is out of order. Then, the process proceeds to step S40.
In step S40, the engine is started. The fuel injection mode at this time is the MPI mode. Then, the process proceeds to step S50.

In step S50, fuel injection by the in-cylinder fuel injection valve 11 is prohibited for a predetermined period ta after the engine is started, the MPI mode is set, and the high-pressure fuel supply device 20 is open-loop controlled to increase the delivery fuel pressure Pd by a predetermined amount. Then, the process proceeds to step S60.
In step S60, it is determined whether or not the fuel pressure lowering control execution condition is being satisfied. If the fuel pressure lowering control execution condition is being satisfied, the process proceeds to step S70. If the fuel pressure lowering control execution condition is not satisfied, step S60 is repeated. The fuel pressure drop control execution conditions are, for example, that the vehicle power is ON, that the engine is not in the engine stall mode or the start mode, that the in-cylinder fuel injection valve 11 is not a disconnection failure, and that the solenoid 42 of the high-pressure fuel supply device 20 is a ceiling fault or a ground fault. The conditions are that the fuel pressure sensor 24 is not a solenoid fault, a ground fault, or a wire break failure.

In step S70, fuel pressure lowering control is executed. Then, the process proceeds to step S80. The fuel pressure lowering control is a control for lowering the delivery fuel pressure Pd by injecting fuel through the in-cylinder fuel injection valve 11. The fuel pressure sensor sticking determination timer is set to the initial value Xd as the fuel pressure lowering control is started. The fuel pressure sensor sticking determination timer is a timer that measures the period (time or the number of ignitions) during which the fuel pressure lowering control is executed, and the initial value thereof may be set to, for example, a time corresponding to the number of ignitions 100 times.

In step S80, it is determined whether or not the fuel pressure lowering control is being executed. If the fuel pressure lowering control is being executed, the process proceeds to step S90. If the fuel pressure lowering control is not being executed, the process returns to step S60. The fuel pressure lowering control is stopped when the engine is stopped.
In step S90, the fuel pressure sensor sticking determination timer is subtracted by the elapsed time of the fuel pressure lowering control. Then, the process proceeds to step S100.

In step S100, the delivery fuel pressure Pd is detected by the fuel pressure sensor 24, and it is determined whether or not the change amount ΔPd of the delivery fuel pressure Pd after the start of the fuel pressure lowering control is equal to or greater than the determination value P1. If the amount of change ΔPd is the determination value P1 or more, the process proceeds to step S130. If the amount of change ΔPd is less than the determination value P1, the process proceeds to step S110. The determination value P1 is the amount of change in the delivery fuel pressure Pd until the fuel pressure sensor sticking determination timer becomes 0 from the initial value when the fuel pressure lowering control is performed while the fuel pressure sensor 24 and the relief valve 35 are normal. It may be set to the lower limit value.

In step S110, it is determined whether or not the fuel pressure sensor sticking determination timer has become 0 or less. When the fuel pressure sensor sticking determination timer becomes 0 or less, the process proceeds to step S120. If the fuel pressure sensor sticking determination timer is greater than 0, the process returns to step S60.
In step S120, it is determined that the fuel pressure sensor 24 is in a stuck state, and the relief valve 35 is determined to be in a normal state in which the relief valve 35 is not closed and stuck. Then, this routine is terminated.

In step S130, it is determined that the fuel pressure sensor 24 is not stuck in a normal state, and the relief valve 35 is determined to be in a closed and stuck failure state. Then, this routine is terminated.
Further, in the present embodiment, when fuel injection by the in-cylinder fuel injection valve 11 is prohibited and the high-pressure fuel supply device 20 is open-loop controlled for a predetermined period ta after the engine is started in step S50, the predetermined period ta. Alternatively, the control amount Pa (discharge amount per unit time by the high-pressure fuel supply device 20) of the open loop control is changed based on the soak state of the vehicle until the engine is started. For example, after fixing ta for a predetermined period, when the engine temperature is high and the fuel pressure is likely to rise, the control amount Pa is reduced. Alternatively, after fixing the control amount Pa, if the engine temperature is high and the fuel pressure is likely to rise, the ta is shortened for a predetermined period. Regarding the soak state of the vehicle where the fuel pressure tends to rise, the engine water temperature (cooling water temperature) or oil temperature (lubricating oil temperature) when the engine is stopped (key switch off) is detected and stored, and when the engine is stopped. It is set based on the water temperature or oil temperature and the time from the engine stop to the engine start instruction (key switch on), or estimated by the engine water temperature or oil temperature when the engine is stopped and the engine water temperature or oil temperature when the engine start instruction is given. You can do it. When the setting is based on the engine water temperature or oil temperature when the engine is stopped and the time from the engine stop to the engine start instruction, as the engine water temperature or oil temperature when the engine is stopped increases, and from the engine stop to the engine. As the time until the start instruction is shortened, the engine temperature is high and the fuel pressure is likely to rise, and the control amount Pa is reduced or the ta is shortened for a predetermined period. When setting based on the engine water temperature or oil temperature when the engine is stopped and the engine water temperature or oil temperature when the engine start instruction is given, the higher the engine water temperature or oil temperature when the engine start instruction is given, and when the engine start instruction is given. The smaller the difference between the engine water temperature or oil temperature and the engine water temperature or oil temperature when the engine is stopped, the easier it is for the fuel pressure to rise. The control amount Pa may be reduced or the ta may be shortened for a predetermined period.

As described above, in the present embodiment, when the delivery fuel pressure Pd is detected before the engine is started and the delivery fuel pressure Pd is higher than the value (Pr + α) obtained by adding the predetermined value α to the relief pressure Pr of the relief valve 35. It is determined that the fuel pressure sensor 24 or the relief valve 35 is out of order.
Then, after the engine is started, the fuel injection by the in-cylinder fuel injection valve 11 is prohibited for a predetermined period of time, and then the fuel pressure lowering control is executed, and the detection value of the fuel pressure sensor 24 is reached by the time when a predetermined period (a predetermined time or a predetermined number of ignitions) elapses. Which of the fuel pressure sensor 24 and the relief valve 35 is defective can be identified by whether or not the delivery fuel pressure Pd drops by the determination value P1 or more.

In the present embodiment, the fuel injection by the in-cylinder fuel injection valve 11 is prohibited for a predetermined period after the engine is started, and the fuel pressure lowering control is executed after the open-loop control of the plunger pump 33 is performed. Therefore, for example, the fuel pressure sensor 24 is out of order. Even if the actual delivery fuel pressure Pd is lowered, the delivery fuel pressure Pd can be increased before the fuel pressure lowering control is started. Therefore, when the fuel pressure lowering control is performed, it is possible to prevent the engine from stopping due to the decrease in the delivery fuel pressure Pd.

Further, regarding the open-loop control of the high-pressure fuel supply device 20 when the fuel injection by the in-cylinder fuel injection valve 11 is prohibited for a predetermined period of time, when the engine temperature is rising and the fuel pressure is likely to rise. By reducing the control amount Pa or shortening the ta for a predetermined period, it is possible to suppress an excessive increase in the delivery fuel pressure Pd. When the control amount Pa is reduced, it is possible to suppress a rapid increase in the delivery fuel pressure Pd and protect various devices on the downstream side of the plunger pump 33 such as the relief valve 35. When the ta is shortened for a predetermined period, the fuel pressure decrease control is performed. Can be started promptly to shorten the time from the engine start to the end of the failure diagnosis.

Further, when the engine water temperature or the oil temperature at the time of the engine start instruction is equal to or higher than a predetermined value, the predetermined period ta or the control amount Pa may be set to 0. As a result, it is possible to suppress an unnecessary increase in the delivery fuel pressure Pd due to open loop control after the engine is started. Further, when the time from the engine stop to the engine start instruction elapses for a predetermined time, the actual delivery fuel pressure has dropped to the vicinity of the atmospheric pressure. Therefore, the above-mentioned delivery fuel pressure is not set to 0 for the predetermined period ta or the control amount Pa. As described above, the control amount Pa and the predetermined period ta may be set to appropriate values of 0 or more. As a result, it is possible to execute the fuel pressure lowering control and enable the failure diagnosis.

The present invention is widely used in an internal combustion engine that includes a high-pressure fuel supply device that supplies high-pressure fuel to an in-cylinder fuel injection valve, detects the pressure of the fuel supplied to the in-cylinder fuel injection valve, and controls the high-pressure fuel supply device. Can be applied.

1 Engine 11 In-cylinder fuel injection valve 20 High-pressure fuel supply device 24 Fuel pressure sensor 50 Control unit (fuel injection control unit)
51 Failure judgment unit

Claims (5)

A high-pressure fuel supply device that pressurizes the fuel stored in the fuel tank,
An in-cylinder fuel injection valve that is supplied with fuel pressurized by the high-pressure fuel supply device and is injected into the combustion chamber of an internal combustion engine.
An intake passage fuel injection valve that injects fuel into the intake passage of the internal combustion engine,
A fuel injection control unit that supplies fuel to the internal combustion engine by at least one of the in-cylinder fuel injection valve and the intake passage fuel injection valve based on the operating state of the internal combustion engine.
A relief valve that opens at a predetermined relief pressure and suppresses the pressure of the fuel supplied from the high-pressure fuel supply device to the in-cylinder fuel injection valve.
A pressure detector that detects the pressure of the fuel supplied from the high-pressure fuel supply device to the in-cylinder fuel injection valve, and
A failure determination unit that determines a failure of the pressure detector and the relief valve based on a pressure detection value by the pressure detector when starting the internal combustion engine.
It is a fuel injection device of an internal combustion engine equipped with
When the pressure detection value when the internal combustion engine is instructed to start exceeds the relief pressure, the failure determination unit uses the in-cylinder fuel injection valve until a predetermined period elapses from the start of the internal combustion engine. Fuel pressure reduction control is executed in which the injection of the fuel is stopped and fuel is supplied to the internal combustion engine only by the intake passage fuel injection valve, and the pressure of the fuel supplied to the in-cylinder fuel injection valve is reduced after the lapse of the predetermined period. A fuel injection device for an internal combustion engine, which is characterized by identifying a faulty part. The fuel injection device for an internal combustion engine according to claim 1, wherein the failure determination unit changes the predetermined period based on the soak state until the internal combustion engine starts. The soak state is set based on the cooling water temperature or lubricating oil temperature of the internal combustion engine at the start of stopping before starting the internal combustion engine, and the time from the start of stopping of the internal combustion engine to the start instruction of the internal combustion engine. The fuel injection device for an internal combustion engine according to claim 2. The soak state is based on the cooling water temperature or lubricating oil temperature of the internal combustion engine at the start of stopping before starting the internal combustion engine and the cooling water temperature or lubricating oil temperature of the internal combustion engine at the time of instructing the start of the internal combustion engine. The fuel injection device for an internal combustion engine according to claim 2, wherein the fuel injection device is set. After the lapse of the predetermined period, the failure determination unit executes the fuel pressure lowering control by fuel injection by the in-cylinder fuel injection valve, and based on the degree of change in the pressure detection value, either the relief valve or the pressure detector. The fuel injection device for an internal combustion engine according to any one of claims 1 to 4, wherein the fuel injection device is characterized in that the fuel injection device is a failure.

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