JP2006291843A - Fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection device for reducing the possibility of breaking equipment such as a common rail while suppressing pressure rise of fuel in the device after ignition-off. <P>SOLUTION: The fuel injection device comprises a control means for stopping the suction of fuel by a fuel supply pump during ignition-off. The control means predicts the rising amount of actual rail pressure after ignition-off, compares possible reaching pressure calculated by using the predicted rising amount with equipment guaranteeing pressure, and determines whether the actual rail pressure is reduced or not, in accordance with the comparison result. Thus, the amount of the fuel flowing into the common rail is reduced after ignition-off, and processing for reducing the actual rail pressure is executed when the rising amount is predicted to be larger, reliably reducing the possibility of breaking the equipment such as the common rail while suppressing the rise of the actual rail pressure after ignition-off. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel injection device that injects and supplies fuel to an engine.

[Conventional technology]
Conventionally, a fuel supply pump that sucks in fuel from a fuel tank and pressurizes and discharges the fuel, a common rail that accumulates fuel discharged from the fuel supply pump, and a valve that opens the fuel accumulated in the common rail. 2. Description of the Related Art There is known a fuel injection device including an injector that injects into a cylinder and a control unit that controls operations of a fuel supply pump, an injector, and the like.

  Here, the injector includes a valve body that opens and closes the nozzle hole and an actuator that supplies and discharges fuel (back pressure fuel) that exerts a back pressure on the valve body in a direction of closing the nozzle hole. Then, the actuator is actuated by receiving power supply and discharges the back pressure fuel, so that the valve body is driven in a direction to open the injection hole, thereby opening the injector and injecting the fuel.

  In the conventional fuel injection device, after the ignition is turned off, the operation of the fuel supply pump is stopped after the operation of the injector is stopped in order to surely stop the engine ahead of other devices. That is, as shown in FIG. 6, in the control cycle immediately after the ignition is turned off, the operation state of the injector is shifted from the injection execution state to the injection stop state, and the fuel injection is stopped. In the next control cycle, the operating state of the fuel supply pump is shifted from the suction execution state to the suction stop state, and the fuel suction is stopped.

  For this reason, the fuel sucked by the fuel supply pump before the injection of the injector is stopped may be discharged after the injection is stopped. When the fuel sucked before the injection is stopped is discharged after the injection is stopped, the actual rail pressure rises even after the ignition is turned off. Even after the fuel supply pump stops discharging, the discharged fuel once flows into the common rail or the like due to inertia. Also, the actual rail pressure after ignition off increases due to the inflow of fuel accompanying such inertia.

[Problems with conventional technology]
In recent years, with respect to fuel injection devices, there is an increasing demand for high pressure fuel in the devices for the purpose of improving injection response and promoting atomization of sprays. In response to this requirement, if the pressure is increased with the conventional fuel injection device having the above-described characteristics, the actual rail pressure after ignition off exceeds the guaranteed pressure of the equipment such as the common rail, and the equipment may be damaged.

  In order to prevent the actual rail pressure from exceeding the guaranteed pressure in this way, a method of attaching a pressure limiter to the common rail is also conceivable. However, the pressure limiter may not operate normally due to a failure, and the actual rail pressure may exceed the guaranteed pressure due to performance variations of the pressure limiter. For this reason, even if a pressure limiter is attached, there is a risk of equipment damage.

In order to reduce the actual rail pressure, a technique for opening a pressure reducing valve attached to the common rail (see, for example, Patent Document 1), or multi-stage injection by an injector increases so-called dynamic leak amount. The technique (for example, refer patent document 2) to make is known. Here, the dynamic leak amount means the amount of fuel discharged from the common rail or the like through the injector by an intentional control operation such as discharge of back pressure fuel. However, these techniques execute the reduction of the actual rail pressure during the operation of the engine, and do not correspond to the suppression of the increase in the actual rail pressure after the ignition is turned off.
JP 2003-239823 A JP 2004-156578 A

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to suppress an increase in the pressure of fuel in the apparatus after the ignition is turned off in the fuel injection apparatus and reduce the possibility of damage to the equipment. There is.

[Means of Claim 1]
According to a first aspect of the present invention, there is provided a fuel injection device that sucks fuel from a fuel tank and pressurizes and discharges the fuel, a common rail that accumulates fuel discharged from the fuel supply pump, and a fuel that is accumulated in the common rail. And control means for controlling the operation of the fuel supply pump according to the actual rail pressure, which is a pressure, and injects and supplies the fuel accumulated in the common rail to the engine. The control means stops the discharge of fuel from the fuel supply pump to the common rail when the engine stops, and predicts the amount of increase in the actual rail pressure after the engine stops, and executes the actual operation according to the result of this prediction. Decide whether to reduce rail pressure.

  Thereby, after the ignition is turned off, first, the fuel supply pump stops discharging the fuel, so that the amount of fuel flowing into the common rail or the like after the ignition is turned off is reduced as compared with the prior art. In addition, even if fuel flows into the common rail or the like due to inertia after the ignition is turned off, the amount of increase in the actual rail pressure is predicted in advance, and whether to reduce the actual rail pressure is determined according to the prediction result. Yes. For this reason, when the amount of increase is predicted to be large, a process for reducing the actual rail pressure is executed.

  As described above, after reducing the amount of fuel flowing into the common rail and the like after the ignition is turned off, and when the amount of increase is predicted to be large, the processing for reducing the actual rail pressure is executed, so that after the ignition is turned off. The increase in the actual rail pressure can be suppressed, and the possibility of equipment damage can be reliably reduced.

  In addition, the fuel supply pump adjusts the amount of fuel drawn from the fuel tank so that the amount of fuel discharged to the common rail substantially matches the target amount of discharge, and the amount of fuel drawn from the fuel tank. By adjusting the discharge amount at the time of discharge, it is possible to adopt a discharge metering method in which the discharge amount of fuel to the common rail substantially matches the target discharge amount. In any of the fuel supply pumps of the intake metering method and the discharge metering method, “stopping the discharge of fuel from the fuel supply pump to the common rail” means a discharge stop command given from the control means to the fuel supply pump. On the other hand, it means that the discharge of fuel is stopped immediately.

[Means of claim 2]
The fuel injection device according to claim 2 is mounted in each cylinder of the engine, the operation is controlled according to the operating state of the engine by the control unit, and the fuel accumulated in the common rail is opened by opening the valve. An injector for injecting into the cylinder is provided. And if a control means determines to reduce an actual rail pressure, it will open all the injectors.
As a result, the actual rail pressure can be quickly reduced.

[Means of claim 3]
According to a third aspect of the present invention, the fuel injection device includes a pressure reducing valve that is attached to the common rail, and whose operation is controlled in accordance with the actual rail pressure by the control means, and the actual rail pressure is reduced by opening the valve. Then, when it is determined that the actual rail pressure is reduced, the control means opens the pressure reducing valve.
As a result, the actual rail pressure can be quickly reduced.

[Means of claim 4]
The fuel injection device according to claim 4 is mounted in each cylinder of the engine, and the operation is controlled according to the operating state of the engine by the control means, and the valve stores the fuel accumulated in the common rail by opening the valve. An injector for injecting into the cylinder is provided. The injector has a valve body that opens and closes the nozzle hole, and an actuator that supplies and discharges fuel that applies back pressure to the valve body in the direction of closing the nozzle hole. By discharging the fuel, the valve element is driven in the direction to open the nozzle hole to open the valve. Then, when it is determined that the actual rail pressure is to be reduced, the control means selects an injector to be opened according to the upper limit of the power supply capability to the actuator, and opens the selected injector.
Thereby, according to the electric power feeding capability to an actuator, a valve body can be driven reliably and an injection hole can be opened.

  The fuel injection device of the best mode 1 includes a fuel supply pump that sucks and pressurizes fuel from a fuel tank, a common rail that accumulates fuel discharged from the fuel supply pump, and a pressure of fuel accumulated in the common rail Control means for controlling the operation of the fuel supply pump according to the actual rail pressure, and the fuel accumulated in the common rail is supplied to the engine by injection. The control means stops the discharge of fuel from the fuel supply pump to the common rail when the engine stops, and predicts the amount of increase in the actual rail pressure after the engine stops, and executes the actual operation according to the result of this prediction. Decide whether to reduce rail pressure.

  The fuel injection device is mounted in each cylinder of the engine, and the operation is controlled by the control means according to the operating state of the engine, and the fuel accumulated in the common rail is injected into the engine cylinder by opening the valve. An injector is provided. And if a control means determines to reduce an actual rail pressure, it will open all the injectors.

  The fuel injection device of the best mode 2 is provided with a pressure reducing valve that is attached to the common rail and whose operation is controlled by the control means in accordance with the actual rail pressure and opens the valve to reduce the actual rail pressure. Then, when it is determined that the actual rail pressure is reduced, the control means opens the pressure reducing valve.

  In the fuel injection device of the best mode 3, the injector has a valve body that opens and closes the injection hole, and an actuator that supplies and discharges fuel that applies back pressure to the valve body in the direction of closing the injection hole. The valve body is driven in the direction to open the nozzle hole by opening the valve body by discharging the fuel that operates by receiving power supply and exerts back pressure. Then, when it is determined that the actual rail pressure is to be reduced, the control means selects an injector to be opened according to the upper limit of the power supply capability to the actuator, and opens the selected injector.

[Configuration of Example 1]
A configuration of the fuel injection device 1 according to the first embodiment will be described with reference to FIGS. 1 to 3.
As shown in FIG. 1, the fuel injection device 1 includes a fuel supply pump 3 that sucks fuel from a fuel tank 2 and pressurizes and discharges the fuel, a common rail 4 that accumulates fuel discharged from the fuel supply pump 3, an engine It is mounted on each cylinder (not shown), and the injector 5 that injects fuel accumulated in the common rail 4 into the cylinder of the engine by opening the valve and the common rail 4 are mounted and opened. A pressure reducing valve 6 for reducing the pressure of the fuel accumulated in the common rail 4 (actual rail pressure) and a control means 7 for controlling the operation of the fuel supply pump 3 and the injector 5, etc., and a direct injection type such as a diesel engine. The fuel is injected and supplied to the engine.

  Further, the control means 7 calculates various command values to be given to each device such as the injector 5 based on detection values input from various sensors, and outputs from the microcomputer 8 as a command signal. It is composed of various drive circuits that feed power from a vehicle-mounted power source (not shown) to each device in response to a command signal.

  Here, the command values are, for example, a pump command value given to the fuel supply pump 3, an injector command value given to the injector 5, a pressure reducing valve command value given to the pressure reducing valve 6, and the like. A pump drive circuit 9 that supplies power to the pump 3, an injector drive circuit 10 that supplies power to the injector 5, a pressure reducing valve drive circuit 11 that supplies power to the pressure reducing valve 6, and the like.

  The fuel supply pump 3 sucks the fuel pumped up from the fuel tank 2 in accordance with the target pressure (target rail pressure) of the fuel accumulated in the common rail 4 and measures the amount by the intake metering valve 12 and the intake metering valve 12. A high pressure pump (not shown) that pressurizes the fuel sucked in and discharges the fuel to the high pressure pipe 16.

  Here, the intake metering valve 12 is supplied with a pump drive current as a pump command value from the microcomputer 8 via the pump drive circuit 9. The pump command value is calculated so that the actual rail pressure substantially matches the target rail pressure. Then, a current having a magnitude based on the pump command value is energized to a solenoid (not shown) of the intake metering valve 12, so that the valve opening degree of the intake metering valve 12 is adjusted, and according to the target rail pressure. Metering is performed. The intake metering valve 12 employs a normally closed type in which the valve opening is zero when the energized current is zero. Further, the fuel pumped up from the fuel tank 2 is sucked in by the suction metering valve 12 after foreign matters are removed by the filter 17.

  The common rail 4 is connected to the discharge port of the fuel supply pump 3 via a high-pressure pipe 16, receives the supply of pressurized fuel, accumulates fuel in a high-pressure state, and passes through each injector 5 and the high-pressure pipe 18. The fuel of the actual rail pressure is connected and supplied to each injector 5. That is, the common rail 4 functions as a pressure accumulation container that accumulates high-pressure fuel, and also functions as a distribution container that distributes high-pressure fuel to the injectors 5.

  A rail pressure sensor 19 that detects the actual rail pressure and outputs the detected value to the microcomputer 8 as a detection signal is attached to one end of the common rail 4. Further, a pressure limiter 20 is attached to the other end, which opens when the actual rail pressure exceeds the limit value and suppresses the actual rail pressure to be equal to or less than the limit value. Note that the pressure at which the pressure limiter 20 opens, that is, the above limit value is set to be approximately the same as the guaranteed pressure of the equipment such as the common rail 4.

  As shown in FIG. 2, the injector 5 is connected to the common rail 4 through a high-pressure pipe 18 and is composed of an injection nozzle 23 for injecting fuel into the cylinder, an electromagnetic valve 24 for operating the injection nozzle 23, and the like. Yes. The number of injectors 5 is the same as the number of cylinders.

  The injection nozzle 23 has a needle-like valve element (hereinafter referred to as an injection valve element) 26 that opens and closes the injection hole 25. The injection valve body 26 opens the injection hole 25 in the direction (opening side) by the pressure of the fuel supplied from the common rail 4 to the accumulation part 29 via the high-pressure flow path 28 provided in the high-pressure pipe 18 and the body 27. In addition to being biased, the spring 30 disposed on the side opposite to the injection hole of the injection valve body 26 and the back pressure transmitted from the command piston 31 are biased in the direction of closing the injection hole 25 (closed side). .

  Here, the back pressure is the pressure of the fuel supplied to the back pressure chamber 32, and the back pressure chamber 32 is formed on the side opposite to the injection hole of the injection valve body 26 and closed downward by the command piston 31. ing. The back pressure chamber 32 communicates with the common rail 4 through the high-pressure pipe 18 and the orifice 33, and the back pressure rises when fuel is supplied from the common rail 4. The supply of fuel from the common rail 4 is restricted by the orifice 33. Further, the back pressure chamber 32 is opened by the valve body 34 of the electromagnetic valve 24, so that the fuel is discharged through the orifice 35 and the back pressure is reduced. The orifices 33 and 35 are provided so that the amount of fuel discharged from the orifice 35 is larger than the amount of fuel supplied from the orifice 33.

  The electromagnetic valve 24 operates as an actuator of the injector 5 by supplying and discharging fuel that exerts a back pressure on the closed hole side with respect to the injection valve body 26 (that is, fuel in the back pressure chamber 32). That is, the solenoid valve 24 operates by receiving power supply, and the fuel in the back pressure chamber 32 is discharged, whereby the injection valve body 26 is driven to the opening side and the injector 5 is opened.

  The electromagnetic valve 24 receives a magnetic attraction force and is displaced in a direction (opening side) to open the back pressure chamber 32. The electromagnetic valve 24 receives a high voltage and a constant current to open the valve body 34. A solenoid 36 that generates a magnetic attractive force that is displaced to the side and that is held on the opening side, and a spring 37 that urges the valve body 34 in the direction of closing the back pressure chamber 32 (closing side).

  The electromagnetic valve 24 is given an injection start time and an injection period as an injector command value from the microcomputer 8 via the injector drive circuit 10. These injector command values are calculated such that an amount of fuel corresponding to the engine operating state is injected at a time corresponding to the engine operating state. Based on the injection start timing and the injection period, a command signal is output from the microcomputer 8 to the injector drive circuit 10. In response to this command signal, the injector drive circuit 10 applies a high voltage to the solenoid 36 and a predetermined constant value. A current is passed through the solenoid 36. Thus, an amount of fuel corresponding to the operating state of the engine is injected at a time corresponding to the operating state of the engine.

  That is, when a high voltage is applied to the solenoid 36 and a constant current is continuously applied, the valve body 34 is displaced to the open side and the back pressure chamber 32 is opened, and this open state continues. The amount of fuel discharged from 32 becomes larger than the amount of fuel supplied to the back pressure chamber 32, and the back pressure decreases. As a result, the biasing force acting on the opening side of the injection valve body 26 (the biasing force due to the fuel pressure of the reservoir portion 29) is the biasing force acting on the closing hole side (the biasing force due to the back pressure and the spring 30). It becomes stronger than the urging force. As a result, the injection valve body 26 is displaced to the opening side, the injection hole 25 is opened, and injection is performed.

  When the energization of the solenoid 36 is eventually stopped, the valve element 34 is displaced to the closed chamber side, the back pressure chamber 32 is closed, and the discharge of fuel from the back pressure chamber 32 is stopped. As a result, the back pressure increases. Thereby, the urging force acting on the closed hole side with respect to the injection valve body 26 becomes stronger than the urging force acting on the opening side. As a result, the injection valve body 26 is displaced to the closed hole side, the injection hole 25 is closed, and the injection is stopped.

  In addition, the solenoid valve 24 is provided with a leak port 39 for leaking excess fuel in the injector 5 that has not been used for injection into the low-pressure pipe 38. Here, the leaking fuel includes a fuel caused by a static leak and a fuel caused by a dynamic leak.

  The static leak means that the fuel leaks through the sliding portion inside the injector 5. For example, the fuel in the reservoir 29 leaks from the sliding portion between the body 27 and the injection valve body 26, or the back. The fuel in the pressure chamber 32 leaks from the sliding portion between the body 27 and the command piston 31. The fuel leaking from the reservoir 29 and the back pressure chamber 32 flows into the spring chamber 40 formed between the injection valve body 26 and the command piston 31 and containing the spring 30, and is provided in the body 27. 41, leaks from the leak port 39 to the low pressure pipe 38 via the low pressure flow path 42 provided in the electromagnetic valve 24.

  The dynamic leak is that the fuel leaks by an intentional control operation, such as when the fuel is discharged from the back pressure chamber 32 in order to reduce the back pressure. Then, the fuel discharged from the back pressure chamber 32 through the orifice 35 merges with the fuel due to static leak in the low pressure channel 42 and leaks from the leak port 39 to the low pressure pipe 38.

  The pressure reducing valve 6 is attached to the common rail 4 and is opened to reduce the actual rail pressure by allowing fuel to escape from the common rail 4 to the low pressure pipe 48. As shown in FIG. 3, the pressure reducing valve 6 contacts a ball-shaped valve body 49 and a valve body 49 that open or close by communicating or blocking between the common rail 4 and the low-pressure pipe 48. At the same time, the movable element 50 that receives the magnetic attraction force and moves to the valve opening side is energized. The solenoid 51 that receives the energization of the drive current and generates the magnetic attraction force that displaces the mover 50 to the valve opening side, and the energization to the solenoid 51 The stator 52 includes a stator 52 that magnetically attracts the mover 50, a spring 53 that is disposed between the mover 50 and the stator 51, and biases the mover 50 toward the valve closing side.

  A pressure reducing valve command value is given to the pressure reducing valve 6 from the microcomputer 8 via the pressure reducing valve drive circuit 11. The pressure reducing valve command value is an open command period indicating a period during which the pressure reducing valve 6 is open, and indicates a period during which the solenoid 51 is energized. This pressure reducing valve command value (open command period) is calculated according to the difference between the actual rail pressure and the target rail pressure. Then, based on the open command period, a command signal is output from the microcomputer 8 to the pressure reducing valve drive circuit 11, and the pressure reducing valve drive circuit 11 energizes the solenoid 51 in accordance with this command signal. As a result, the pressure reducing valve 6 is opened, fuel is released from the common rail 4 to the low pressure pipe 48, and the actual rail pressure is reduced.

  The low pressure pipe 48 is connected to a low pressure pipe 38 into which the fuel leaked from the injector 5 flows, and the fuel released from the common rail 4 returns to the fuel tank 2 together with the fuel leaked from the injector 5.

  The microcomputer 8 is a computer having a known structure including a CPU that performs control processing and arithmetic processing, ROM, RAM, and other storage means that store various programs and data, an input circuit, an output circuit, and the like. Based on detection values input from various sensors such as the rail pressure sensor 19, the rotation speed sensor 56 for detecting the engine rotation speed, and the accelerator opening degree sensor 57 for detecting the accelerator opening degree, a pump command value and an injector command value are set. The pressure reducing valve command value and the like are calculated and output to each drive circuit as a command signal.

  Each drive circuit incorporates a switching element that operates or stops operating in response to a command signal. Then, when the switching element is activated or deactivated, power supply corresponding to each command value is performed from the in-vehicle power source to each device such as the injector 5.

  With the above configuration, in the fuel injection device 1, the amount of fuel supplied from the fuel supply pump 3 and the fuel from the pressure reducing valve 6 are adjusted so that the actual rail pressure substantially matches the target rail pressure corresponding to the operating state of the engine. The amount of escape is controlled. Further, in the fuel injection device 1, the injection start timing and the injection period by the injector 5 are controlled so that an amount of fuel corresponding to the engine operating state is injected at a time corresponding to the engine operating state. As a result, the actual rail pressure substantially coincides with the target rail pressure, and fuel at a pressure corresponding to the actual rail pressure is injected into each cylinder, and an operation corresponding to the state of the engine is performed.

[Features of Example 1]
The characteristics of the fuel injection device 1 according to the first embodiment will be described.
The microcomputer 8 according to the first embodiment stops the intake of fuel by the fuel supply pump 3 when the engine is stopped (when the ignition is off: hereinafter, the engine is stopped), and after the ignition is turned off. The amount of increase in rail pressure is predicted, and whether or not the actual rail pressure is reduced is determined according to the result of the prediction.

  First, the microcomputer 8 stops outputting the command signal based on the pump command value when the ignition is off, and stops energization of the solenoid of the intake metering valve 12. Thereby, the valve opening degree of the intake metering valve 12 becomes zero, and the amount of fuel sucked by the intake metering valve 12 becomes zero. As a result, the intake of fuel by the fuel supply pump 3 is stopped.

  In addition, the microcomputer 8 detects the engine rotational speed immediately before the ignition is turned off, the fuel injection by the injector 5 immediately before the ignition is turned off and immediately after the ignition is turned off, or the fuel inflow / outflow amount in the common rail 4 due to the fuel discharge by the fuel supply pump 3. Based on the above, the increase amount of the actual rail pressure after the ignition is turned off is predicted.

  In this prediction, the microcomputer 8 first stores the detected value of the engine speed immediately before the ignition is turned off, calculates the fuel inflow / outflow amount in the common rail 4 immediately before the ignition is turned off, and stores the calculated value (hereinafter referred to as the common rail). The amount of fuel flowing out from 4 is referred to as the rail outflow amount, the amount of fuel flowing in from the fuel supply pump 3 is referred to as the rail inflow amount, and the amount of fuel flowing into and out of the common rail 4 is referred to as the rail outflow amount. The rail inflow / outflow amount immediately before the ignition is turned off can be calculated from the change rate of the actual rail pressure and the bulk modulus of the fuel immediately before the ignition is turned off.

  Here, when the change rate of the actual rail pressure is a positive value, the rail inflow / outflow amount is calculated as a positive value because the rail inflow amount is larger than the rail outflow amount. The rail inflow / outflow amount is calculated as a negative value when the rate of change in the actual rail pressure is a negative value, the rail outflow amount is greater than the rail inflow amount.

  Next, the microcomputer 8 is predicted to flow out of the common rail 4 immediately after the ignition is turned off based on the engine operating state such as the engine speed and the accelerator opening degree immediately before the ignition is turned off, that is, the target value of the fuel injection amount by the injector 5. The amount of fuel flow out (that is, the rail outflow immediately after the ignition is turned off) is calculated.

  Then, the microcomputer 8 is based on the stored detected value of the engine speed immediately before the ignition off, the stored calculated value of the rail inflow / outflow immediately before the ignition off, the calculated value of the rail outflow immediately after the ignition off, etc. Predict the amount of increase in actual rail pressure after ignition off.

  Note that the rail inflow / outflow amount immediately before the ignition is turned off is a target value calculated based on the operating state of the engine (that is, a target value of the fuel discharge amount by the fuel supply pump 3 and a target value of the fuel injection amount by the injector 5). ).

  By adding the predicted value of the increase amount of the actual rail pressure calculated as described above to the detected value of the actual rail pressure immediately before the ignition is turned off, the possible reach pressure of the actual rail pressure after the ignition is turned off is calculated. And when the possible reach | attainment pressure of an actual rail pressure exceeds the value of the guarantee pressure of apparatuses, such as the common rail 4, the process (pressure reduction process) for reducing an actual rail pressure is performed.

  The decompression process of the first embodiment is to open all the injectors 5. That is, when the microcomputer 8 determines to reduce the actual rail pressure, the microcomputer 8 calculates the injector command value so that all the injectors 5 are opened, synthesizes the command signal in accordance with the calculated injector command value, and the injector drive circuit. 10 is output. Thereby, all the injectors 5 open.

[Control Method of Example 1]
The control method of Example 1 is demonstrated using the flowchart shown in FIG.
First, in step S1, it is determined whether or not the ignition is off. If the ignition is off (YES), the process proceeds to steps S2 and S3. If the ignition is not off (NO), the process waits until the ignition is off.

  First, in step S2, the intake of fuel by the fuel supply pump 3 is stopped. This process is executed by stopping the output of the command signal based on the pump command value and stopping the energization of the solenoid of the intake metering valve 12.

  Further, in step S3, an increase amount of the actual rail pressure after the ignition is turned off is predicted. This process is executed by calculating the increase amount of the actual rail pressure based on the engine speed immediately before the ignition is turned off, the rail inflow / outflow amount immediately before the ignition is turned off, the rail outflow amount immediately after the ignition is turned off, and the like. In step S4, a possible reach pressure of the actual rail pressure after the ignition is turned off is calculated. This process is executed by adding the predicted value of the increase amount of the actual rail pressure to the detected value of the actual rail pressure immediately before the ignition is turned off.

  In step S5, it is determined whether or not the possible reach pressure of the actual rail pressure is smaller than the guaranteed pressure of the equipment such as the common rail 4. If the possible reach pressure is smaller than the guaranteed pressure (YES), the process proceeds to step S8. If the possible reach pressure is equal to or greater than the ensure pressure (NO), the process proceeds to step S6.

  In step S6, a decompression process is executed. The decompression process of the first embodiment is to open all the injectors 5. This decompression process is executed by calculating injector command values so that all the injectors 5 are opened, synthesizing command signals according to the calculated injector command values, and outputting them to the injector drive circuit 10. .

Next, in step S7, it is determined whether or not the actual rail pressure after execution of the pressure reduction process is smaller than the reference pressure. Here, the reference pressure is a threshold value calculated based on the guaranteed pressure. If the actual rail pressure is smaller than the reference pressure (YES), the process proceeds to step S8. If the actual rail pressure is equal to or higher than the reference pressure (NO), the process returns to step S6, and the decompression process is executed again.
In step S8, the injection by the injector 5 is stopped. This process is executed by stopping the output of the command signal based on the injector command value and stopping the energization of the solenoid 36 of the solenoid valve 24.

[Operation of Example 1]
The operation of the fuel injection device 1 according to the first embodiment will be described with reference to FIG.
First, at the time t0, when the ignition is turned off, the engine speed starts to decrease, the energization to the solenoid of the intake metering valve 12 of the fuel supply pump 3 is stopped, and the intake of fuel to the fuel supply pump 3 is stopped. To do. Further, the amount of increase in the actual rail pressure is predicted, and the possible reach pressure of the actual rail pressure is calculated. Then, if it is determined that the possible reach pressure is equal to or higher than the guaranteed pressure, the decompression process is executed. As a result, the actual rail pressure predicted to exceed the guaranteed pressure as indicated by the broken line A changes without exceeding the guaranteed pressure as indicated by the solid line B. As a result, since the actual rail pressure is equal to or higher than the guaranteed pressure, the possibility that the equipment such as the common rail 4 is damaged is reduced.

[Effect of Example 1]
The control means 7 of the fuel injection device 1 according to the first embodiment stops the intake of fuel by the fuel supply pump 3 when the ignition is off. Further, the control means 7 predicts the increase amount of the actual rail pressure after the ignition is turned off, compares the possible reach pressure calculated using the predicted increase amount and the guaranteed pressure, and according to the result of this comparison. Decide whether to reduce the actual rail pressure.

  Thereby, after the ignition is turned off, first, the fuel intake by the fuel supply pump 3 is stopped. For this reason, the amount of fuel flowing into the common rail 4 and the like after the ignition is turned off is more reliable than in the case where the fuel injection by the injector 5 is stopped before the fuel intake by the fuel supply pump 3 as in the prior art. Decrease. Even if fuel flows into the common rail 4 or the like after the ignition is turned off, the amount of increase in the actual rail pressure is predicted in advance, and whether or not the actual rail pressure is reduced according to the result of comparison between the possible reach pressure and the guaranteed pressure. Has been decided. For this reason, when the amount of increase is large and the possible ultimate pressure is predicted to be equal to or higher than the guaranteed pressure, a process for reducing the actual rail pressure is executed.

  As described above, when the fuel injection device 1 is used, the amount of fuel flowing into the common rail 4 and the like after the ignition is turned off is reduced, and when the amount of increase is predicted to be large, the process for reducing the actual rail pressure is performed. By executing the above, it is possible to suppress an increase in the actual rail pressure after the ignition is turned off, and to reliably reduce the possibility of damage to equipment such as the common rail 4.

  Further, when it is determined that the actual rail pressure is reduced, the control means 7 opens all the injectors 5. As a result, the actual rail pressure can be quickly reduced.

  When the control means 7 of the fuel injection device 1 according to the second embodiment determines to reduce the actual rail pressure, the control means 7 opens the pressure reducing valve 6. That is, the decompression process of the second embodiment is to open the decompression valve 6. That is, if the microcomputer 8 determines to reduce the actual rail pressure, the microcomputer 8 calculates the pressure reducing valve command value so that the possible reach pressure becomes smaller than the guaranteed pressure, and synthesizes the command signal according to the calculated pressure reducing valve command value. At the same time, it is output to the pressure reducing valve drive circuit 11. As a result, the pressure reducing valve 6 can be opened, and the actual rail pressure can be quickly reduced. Further, since the decompression process is executed without performing the fuel injection by the injector 5, the engine speed can be quickly reduced.

  When it is determined that the actual rail pressure is reduced, the control means 7 of the fuel injection device 1 according to the third embodiment selects the injector 5 to be opened according to the upper limit of the power supply capability to the solenoid 36 of the injector 5 and is selected. The injector 5 is opened. That is, the decompression process of the third embodiment is to select the injector 5 to be opened according to the upper limit of the power supply capability by the in-vehicle power supply, the injector drive circuit 10 or the like, and to open the selected injector 5.

That is, when the microcomputer 8 determines to reduce the actual rail pressure, the microcomputer 8 calculates the upper limit of the power supply capacity and selects the injector 5 to be opened according to the calculated upper limit. Then, the microcomputer 8 calculates an injector command value so that the selected injector 5 opens, synthesizes a command signal according to the calculated injector command value, and outputs it to the injector drive circuit 10. As a result, the selected injector 5 is opened.
Thereby, the injection valve body 26 can be reliably driven and the injection hole 25 can be opened according to the power supply capability to the solenoid 36 such as an in-vehicle power source.

[Modification]
The decompression process of the first and third embodiments is performed by causing the injector 5 to inject fuel, but can also be performed by causing the injector 5 to perform “idle driving”. The idle driving is to give the injector 5 an injection period shorter than the time (injection delay time) from the opening of the back pressure chamber 32 by the electromagnetic valve 24 to the opening of the injection hole 25 by the injection valve body 26, It is to perform only opening and closing of the back pressure chamber 32 without substantially performing injection. According to this idle driving, the actual rail pressure can be reduced via the injector 5 by dynamic leak or static leak regardless of fuel injection, so that the engine speed can be quickly reduced. .

  The fuel supply pump 3 of the present embodiment employs an intake metering system in which the amount of fuel discharged from the fuel tank 2 is adjusted so that the amount of fuel discharged to the common rail 4 substantially matches the target discharge amount. However, it is also possible to employ a discharge metering method in which the discharge amount of fuel to the common rail 4 is substantially matched with the target discharge amount by adjusting the discharge amount when discharging the fuel sucked from the fuel tank 2.

It is a whole lineblock diagram of a fuel injection device (example). It is a block diagram of an injector (Example). It is a block diagram of a pressure-reduction valve (Example). It is a flowchart which shows the process by a fuel-injection apparatus (Example). (A) is a time chart which shows transition of an engine speed, (b) is a time chart which shows execution of prediction of an actual rail pressure rise amount, (c) is a time chart which shows execution of pressure reduction processing. (D) is a time chart which shows transition of an actual rail pressure (Example). (A) is a time chart which shows the operating state of an injector, (b) is a time chart which shows the operating state of a fuel supply pump, (c) is a time chart which shows transition of an actual rail pressure (conventional example) ).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel injection apparatus 2 Fuel tank 3 Fuel supply pump 4 Common rail 5 Injector 6 Pressure reducing valve 7 Control means 24 Electromagnetic valve (actuator)
25 Injection hole 26 Injection valve element (valve element)

Claims (4)

A fuel supply pump that sucks fuel from the fuel tank and pressurizes and discharges the fuel;
A common rail for accumulating fuel discharged from the fuel supply pump;
A fuel injection device that controls the operation of the fuel supply pump according to an actual rail pressure that is a pressure of the fuel accumulated in the common rail, and that injects the fuel accumulated in the common rail to the engine. ,
The control means predicts the amount of increase in the actual rail pressure after the engine stops, and stops the discharge of fuel from the fuel supply pump to the common rail when the engine stops. In accordance with the fuel injection device, it is determined whether or not to reduce the actual rail pressure. The fuel injection device according to claim 1,
An injector which is mounted in each cylinder of the engine and whose operation is controlled by the control means in accordance with the operating state of the engine and opens the valve to inject fuel accumulated in the common rail into the cylinder of the engine With
When the control means determines to reduce the actual rail pressure, all the injectors are opened. The fuel injection device according to claim 1,
A pressure reducing valve that is attached to the common rail, controlled in operation according to the actual rail pressure by the control means, and reduces the actual rail pressure by opening the valve,
If the control means determines to reduce the actual rail pressure, the control means opens the pressure reducing valve. The fuel injection device according to claim 1,
An injector which is mounted in each cylinder of the engine and whose operation is controlled by the control means in accordance with the operating state of the engine and opens the valve to inject fuel accumulated in the common rail into the cylinder of the engine With
The injector includes a valve body that opens and closes a nozzle hole, and an actuator that supplies and discharges fuel that exerts a back pressure on the valve body in a direction in which the nozzle hole is closed. By discharging the fuel that exerts back pressure, the valve element is driven in the direction to open the nozzle hole, and the valve is opened,
When it is determined that the actual rail pressure is reduced, the control means selects an injector to be opened according to the upper limit of the power supply capacity to the actuator, and opens the selected injector. .

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