JP4207010B2 - Fuel injection device - Google Patents

Description

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

[Conventional technology]
2. Description of the Related Art Conventionally, there has been known a pressure accumulation type fuel injection device that includes a common rail that receives supply of fuel so that fuel is accumulated at a target pressure corresponding to the state of the engine, and that injects fuel to the engine via the common rail. Yes.

  2. Description of the Related Art In recent years, in a pressure accumulation type fuel injection device, the pressure of fuel in the device has been increased for the purpose of improving injection response and promoting atomization of spray. As the pressure increases, there is an increasing demand for improved reliability for pressure reduction control for accurately reducing the actual pressure (actual rail pressure) of fuel accumulated in the common rail.

  The conventional fuel injection device relates to pressure reduction control of the actual rail pressure, and opens a valve to release fuel from the common rail, thereby reducing the actual rail pressure and a command value given to the pressure reduction valve using a predetermined pressure reduction characteristic. Is calculated and output to the pressure reducing valve to provide rail pressure control means for controlling the operation of the pressure reducing valve. This pressure reduction characteristic indicates, for example, the correlation between the amount of fuel escaped from the pressure reducing valve per unit time and the actual rail pressure. The rail pressure control means estimates the escape amount by applying the measured actual rail pressure to this pressure reduction characteristic, and calculates a command value based on this estimation.

[Problems with conventional technology]
By the way, the pressure reducing valve uses a magnetic attraction generated by energizing the solenoid to magnetically attract the mover toward the stator, thereby allowing the common rail to escape and open to the flow path. It is a type. For this reason, the abnormality determination of the valve opening operation has been conventionally performed, but the abnormality determination of the valve closing operation is hardly studied. In addition, even if an abnormality occurs in the valve closing operation, the state shifts to the safe side (that is, the engine is stopped by excessively releasing fuel from the common rail and reducing the actual rail pressure (ie, injection pressure)). Therefore, the demand for abnormality determination of the valve closing operation is small.

  However, if fuel is escaped excessively from the common rail and injection is performed in a state where the actual rail pressure is excessively lower than the target pressure, the spray is not sufficiently atomized and the risk of emission deterioration increases. With the recent increase in pressure, in situations where injection control is performed on the premise of atomization with a higher target pressure, the risk of worsening emissions due to excessive reduction of the actual rail pressure becomes even higher. It has become.

  Furthermore, due to the recent increase in interest in evacuation travel at the time of failure, there is an increasing demand for a determination method for switching the control mode for evacuation travel before the actual rail pressure decreases excessively and the engine stops. The abnormality determination of the valve closing operation of the pressure reducing valve can be used as one of the determination methods for switching to the retreat travel.

For the purpose of improving the performance of the pressure reducing valve, a pressure reducing valve including a solenoid for driving the mover in the valve opening direction and a solenoid for driving in the valve closing direction has been considered (for example, Patent Documents). 1). However, the purpose of improving the performance of the pressure reducing valve is to expand the controllable pressure range, and not to perform the abnormality determination of the valve closing operation as described above.
JP 2004-11448 A

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a fuel injection device capable of reducing the actual rail pressure by opening the pressure reducing valve and letting out the fuel. It is to be able to determine whether or not an abnormality has occurred in the valve closing operation.

[Means of Claim 1]
The fuel injection device according to claim 1 includes a common rail that receives the supply of fuel so that the fuel is accumulated at a target pressure corresponding to the state of the engine, and the fuel is injected and supplied to the engine via the common rail. . Moreover, the actual pressure is reduced by opening the valve and releasing the fuel from the common rail to reduce the actual pressure of the fuel accumulated in the common rail, and calculating the command value given to the pressure reducing valve and outputting it to the pressure reducing valve. Rail pressure control means that controls the operation of the pressure reducing valve so that it substantially matches the target pressure, and the maximum relief pressure reduction amount that indicates the maximum amount of actual pressure drop due to the opening of the pressure reducing valve, the fuel release from the pressure reducing valve The maximum relief pressure reduction amount estimation means that is estimated by assuming that the amount is at the upper limit of the performance specification of the pressure reduction valve, and the actual pressure reduction amount that indicates the amount of decrease in actual pressure due to the execution of the rail pressure control means A valve closing that determines that an abnormality has occurred in the valve closing operation of the pressure reducing valve when the pressure reducing amount is equal to or greater than the judgment pressure reducing amount that is the sum of the other pressure reducing amount estimated from the pressure reducing factors other than the valve and the maximum relief pressure reducing amount. An abnormality determination means.

  When an abnormality occurs in the valve closing operation of the pressure reducing valve, fuel is released through the pressure reducing valve with a relief amount that exceeds the upper limit of the performance standard of the pressure reducing valve. Therefore, as described above, the determination is made by adding the additional decompression amount estimated from the decompression factor other than the opening of the decompression valve to the maximum relief decompression amount when the relief amount is assumed to be the upper limit of the performance standard of the decompression valve. If the amount of reduced pressure is used as a threshold value, the abnormality determination of the valve closing operation can be performed with high accuracy.

  Note that physical quantities called decompression quantities, such as maximum relief decompression quantity, actual decompression quantity, other decompression quantity, and judgment decompression quantity, can be calculated as physical quantities having a pressure dimension, but physical quantities having fuel elastic modulus and viscosity dimensions. Can also be calculated as The same applies to the maximum leak pressure reduction amount and the estimated pressure reduction amount described later.

[Means of claim 2]
According to a second aspect of the present invention, the fuel injection device includes an injector that communicates with the common rail and injects fuel accumulated in the common rail into a cylinder of the engine. In addition, the actual pressure is reduced by fuel leaking from the injector, and the valve closing abnormality determining means determines the maximum leak pressure reduction amount indicating the maximum drop in actual pressure due to the fuel leak from the injector from the injector. Estimated by assuming that the amount of fuel leakage is at the upper limit of the performance standard of the injector, and set it as the other decompression amount.

  Since the injector communicates with the common rail, the amount of fuel leakage from the injector greatly affects the actual decompression amount. Therefore, if the maximum leak pressure reduction amount when assuming that the fuel leak amount from the injector is at the upper limit of the performance standard of the injector is used as the other pressure reduction amount, the abnormality determination of the valve closing operation can be performed with higher accuracy. it can.

[Means of claim 3]
The valve closing abnormality determining means in the fuel injection device according to claim 3 is executed when the engine stops.
When the engine is stopped (so-called ignition off), it is sure that there is no injection and pressure reduction is being performed, and the amount of other pressure reduction due to a pressure reduction factor (for example, fuel leakage from the injector) other than the valve opening is Very easy to predict. Therefore, if the valve closing abnormality determining means is executed when the ignition is off, the abnormality of the valve closing operation can be determined with higher accuracy.

[Means of claim 4]
The maximum leak pressure reduction amount in the fuel injection device according to claim 4 indicates the maximum amount of actual pressure drop due to static leak in which fuel leaks through the sliding portion inside the injector.
When ignition is turned off, it is considered that fuel leaks from the injector due to static leaks, and dynamic leaks that are intentional leaks, such as fuel supply and discharge in back pressure control, are less likely to be considered as leak factors. it is conceivable that. Therefore, when performing an abnormal determination of the valve closing operation when the ignition is off, it is possible to improve the determination accuracy by taking static leaks as a leak factor and not to consider other leak factors such as dynamic leaks. The calculation load of a microcomputer or the like can be reduced.

[Means of claim 5]
The rail pressure control means in the fuel injection device according to claim 5 calculates the command value based on the pressure reduction characteristic indicating the correlation between the relief amount and the actual pressure.
Thus, the operation of the pressure reducing valve can be changed according to the actual rail pressure.

[Means of claim 6]
According to a sixth aspect of the present invention, the fuel injection device includes a pressure reduction characteristic correcting unit that corrects the pressure reduction characteristic in accordance with a difference between the actual pressure reduction amount and the estimated pressure reduction amount estimated from the pressure reduction characteristic. This is executed after the decompression characteristic is corrected by the execution of the decompression characteristic correcting means.
The decompression characteristics correction means corrects the decompression characteristics for each product in accordance with how the escape amount in each product of the decompression valve is biased, and changes it to one suitable for control of each product. As a result, the amount of relief that is at the upper limit of the performance specification of the pressure reducing valve can be corrected for each product, so that the maximum amount of relief pressure reduced for each product can be calculated.
As described above, when the abnormality determination of the valve closing operation is performed, a threshold value (determination decompression amount) suitable for each product can be set for each product of the pressure reducing valve.

[Means of Claim 7]
The command value in the fuel injection device according to claim 7 is an open command period that indicates a period during which the pressure reducing valve is open, and the valve closing abnormality determining means is configured such that the actual pressure reducing amount is equal to or greater than the determined pressure reducing amount. Determine whether there is an abnormality in the valve closing operation of the pressure reducing valve according to the actual pressure reducing amount generated by giving the pressure reducing valve a temporary opening command period shorter than the opening command period calculated based on the pressure reducing characteristics. To do.
As a result, it is possible to check the abnormality determination of the valve closing operation. That is, when the actual pressure reduction amount generated by the operation of the pressure reducing valve based on the temporary opening command period is larger than the expected pressure reduction amount, it can be reliably determined that an abnormality has occurred in the valve closing operation. Note that the expected amount of pressure reduction is, for example, the amount of pressure reduction predicted when the actual pressure reduction amount when the provisional opening command period is given to the pressure reducing valve is assumed that no valve closing abnormality has occurred.

[Means of Claim 8]
The fuel injection device according to claim 8 includes a fuel supply pump that pressurizes and supplies fuel to the common rail, and the valve closing abnormality determining means is configured such that the amount of fuel supplied by the fuel supply pump is equal to the valve closing operation of the pressure reducing valve. When it can be determined that the amount has increased by a predetermined amount or more than when it is normal, it is determined that an abnormality has occurred in the valve closing operation of the pressure reducing valve.
Even though the amount of fuel supplied by the fuel supply pump has increased by more than a predetermined amount compared to when the pressure-reducing valve is closed normally, a state where the actual pressure-reducing amount is large is closed by the pressure-reducing valve. It is very likely that an abnormal operation has occurred. Therefore, by adding the condition that “the amount of fuel supplied by the fuel supply pump is increased to a predetermined amount or more than when the valve closing operation of the pressure reducing valve is normal” to the determination condition, the condition is further closed. It is possible to improve the determination accuracy for abnormal valve operation.

The fuel injection device of the best mode 1 is provided with a common rail that receives the supply of fuel so that the fuel is accumulated at a target pressure corresponding to the state of the engine, and the fuel is injected and supplied to the engine via the common rail.
The fuel injection device opens the valve and releases the fuel from the common rail, thereby reducing the actual pressure of the fuel accumulated in the common rail, and calculating a command value to be given to the pressure reducing valve and outputting the command value to the pressure reducing valve. The rail pressure control means for controlling the operation of the pressure reducing valve so that the actual pressure substantially matches the target pressure, and the maximum relief pressure reducing amount indicating the maximum amount of actual pressure drop due to the opening of the pressure reducing valve The maximum relief pressure reduction amount estimation means that is estimated by assuming that the fuel escape amount from the upper limit of the performance specification of the pressure reducing valve and the actual pressure reduction amount that indicates the amount of decrease in the actual pressure due to the execution of the rail pressure control means are An abnormality has occurred in the closing operation of the pressure reducing valve when the pressure reducing amount exceeds the judgment pressure reducing amount that is the sum of the other pressure reducing amount estimated from the pressure reducing factors other than the opening of the pressure reducing valve and the maximum relief pressure reducing amount. And a valve closing abnormality determining means for determining.

  The fuel injection device includes an injector that communicates with the common rail and injects fuel accumulated in the common rail into a cylinder of the engine. In addition, the actual pressure is reduced by fuel leaking from the injector, and the valve closing abnormality determining means determines the maximum leak pressure reduction amount indicating the maximum drop in actual pressure due to the fuel leak from the injector from the injector. Estimated by assuming that the amount of fuel leakage is at the upper limit of the performance standard of the injector, and set it as the other decompression amount.

  The valve closing abnormality determining means is executed when the engine stops. The maximum leak pressure reduction amount indicates the maximum amount of actual pressure drop caused by static leak in which fuel leaks through the sliding portion inside the injector.

  Further, the rail pressure control means calculates a command value based on a pressure reduction characteristic indicating a correlation between the relief amount and the actual pressure. The fuel injection device includes a decompression characteristic correcting unit that corrects the decompression characteristic according to a difference between the actual decompression amount and the estimated decompression amount estimated by the decompression characteristic, and the valve closing abnormality determining unit includes the decompression characteristic correcting unit. This is executed after the decompression characteristic is corrected by the execution of.

  The command value is an open command period indicating a period during which the pressure reducing valve is open, and the valve closing abnormality determining means is calculated based on the pressure reducing characteristic when the actual pressure reducing amount is equal to or greater than the determined pressure reducing amount. It is determined whether an abnormality has occurred in the valve closing operation of the pressure reducing valve according to the actual pressure reducing amount generated by giving the pressure reducing valve a temporary opening command period shorter than the opening command period.

  In addition, the fuel injection device includes a fuel supply pump that pressurizes and supplies fuel to the common rail, and the valve closing abnormality determining means is configured to supply fuel by the fuel supply pump when the valve closing operation of the pressure reducing valve is normal. When it can be determined that the pressure has increased to a predetermined amount or more, it is determined that an abnormality has occurred in the valve closing operation of the pressure reducing valve.

[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 5.
As shown in FIG. 1, the fuel injection device 1 includes a common rail 3 that receives supply of fuel so that fuel is accumulated at a target pressure corresponding to a state of an engine (not shown). The fuel is injected and supplied.

  In addition to the common rail 3, this fuel injection device 1 is mounted on an engine, a fuel supply pump 5 that pumps fuel from a fuel tank 4, pressurizes and supplies the fuel to the common rail 3, and injects fuel accumulated in the common rail 3 into the cylinder. Injector 6 for reducing the actual pressure of the fuel accumulated in the common rail 3 (actual rail pressure), a pump command value to be supplied to the fuel supply pump 5 based on detection values input from various sensors, and the injector 6 The injector command value given to the pressure reducing valve 7, the pressure reducing valve command value given to the pressure reducing valve 7, etc. are calculated and output as a command signal, and the drive current and applied voltage are supplied to the fuel supply pump 5 according to the command signal output from the microcomputer 8 It is composed of various drive circuits and the like given to the injector 6, the pressure reducing valve 7, and the like.

  Here, the various drive circuits are: a pressure reducing valve driving circuit 12 for supplying a driving current to the pressure reducing valve 7, an injector driving circuit 13 for supplying a driving current and an applied voltage to the injector 6, and a pump driving for supplying a driving current to the fuel supply pump 5. Circuit 14 or the like.

  The common rail 3 is connected to the discharge port of the fuel supply pump 5 through a high-pressure pipe 15, receives the supply of high-pressure fuel, accumulates the fuel in a high-pressure state, and passes through the inlet of each injector 6 and the high-pressure pipe 16. The fuel of the actual rail pressure is connected and supplied to each injector 6. That is, the common rail 3 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 6. Further, the actual rail pressure is detected by a rail pressure sensor 17 attached to one end of the common rail 3, and the detected value is output to the microcomputer 8 as a rail pressure detection signal.

  The fuel supply pump 5 pressurizes the fuel pumped from the fuel tank 4 according to the target pressure (target rail pressure) of the common rail 3 and the fuel metered by the suction metering valve 19. And a high pressure pump (not shown) for discharging to the high pressure pipe 15. That is, a pump drive current as a pump command value is given to the intake metering valve 19 from the microcomputer 8 via the pump drive circuit 14. 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 suction metering valve 19 so that the valve opening degree of the suction metering valve 19 is adjusted, and according to the target rail pressure. Metering is performed.

  The injector 6 is connected to the common rail 3 through a high-pressure pipe 16 connected thereto, and includes an injection nozzle 21 for injecting fuel into the cylinder, an electromagnetic valve 22 for operating the injection nozzle 21, and the like. The number of injectors 6 is the same as the number of cylinders (only one is shown in FIG. 1).

  As shown in FIG. 2, the injection nozzle 21 has a needle-like valve body 25 (hereinafter referred to as an injection valve body 25) that opens and closes the injection hole 24. The injection valve body 25 opens the injection hole 24 in the direction (opening side) by the pressure of the fuel supplied from the common rail 3 to the accumulation portion 28 via the high pressure flow path 27 provided in the high pressure pipe 16 and the body 26. At the same time, the spring 29 disposed on the side opposite to the injection hole of the injection valve body 25 and the back pressure transmitted from the command piston 30 are urged in the direction of closing the injection hole 24 (closed side). .

  Here, the back pressure is the pressure of the fuel supplied to the back pressure chamber 31, and the back pressure chamber 31 is formed on the side opposite to the injection hole of the injection valve body 25 and closed downward by the command piston 30. ing. The back pressure chamber 31 communicates with the common rail 3 through the high-pressure pipe 16 and the orifice 32, and the back pressure increases by receiving fuel supply from the common rail 3. The fuel supply from the common rail 3 is restricted by the orifice 32. Further, the back pressure chamber 31 is opened by the valve body 36 of the electromagnetic valve 22, so that fuel is discharged through the orifice 37 and the back pressure is reduced. The orifices 32 and 37 are provided such that the discharge amount from the orifice 37 is larger than the supply amount from the orifice 32.

  The electromagnetic valve 22 receives a magnetic attraction force and is displaced in a direction (opening side) to open the back pressure chamber 31, and receives a high voltage and a constant current to open the valve body 36 on the opening side. And a solenoid 38 that generates a magnetic attractive force that is held on the opening side and a spring 39 that biases the valve body 36 in a direction in which the back pressure chamber 31 is closed (closed side).

  The electromagnetic valve 22 is given an injection start time and an injection period as an injector command value from the microcomputer 8 via the injector drive circuit 13. These injector command values are calculated so that an amount of fuel corresponding to the state of the engine is injected at a time corresponding to the state of the engine. A command signal is output from the microcomputer 8 to the injector drive circuit 13 based on the injection start timing and the injection period. In response to this command signal, the injector drive circuit 13 applies a high voltage to the solenoid 38 and a predetermined constant value. Current is passed through solenoid 38. Thus, an amount of fuel corresponding to the engine state is injected at a time according to the engine state.

  That is, when a high voltage is applied to the solenoid 38 and a constant current is continuously applied, the valve body 36 is displaced to the open side and the back pressure chamber 31 is opened, and this open state continues. The discharge amount from 31 becomes larger than the supply amount to the back pressure chamber 31, and the back pressure decreases. As a result, the biasing force acting on the opening side with respect to the injection valve body 25 (the biasing force due to the fuel pressure of the reservoir portion 28) is applied to the biasing force acting on the closing hole side (the biasing force due to the back pressure and the spring 29). It becomes stronger than the urging force. As a result, the injection valve body 25 is displaced to the opening side, the injection hole 24 is opened, and injection is performed.

  When the energization of the solenoid 38 is eventually stopped, the valve body 36 is displaced toward the closed chamber side, the back pressure chamber 31 is closed, and the discharge from the back pressure chamber 31 is stopped. Pressure rises. Thereby, the urging force acting on the closed hole side with respect to the injection valve body 25 becomes stronger than the urging force acting on the opening side. As a result, the injection valve body 25 is displaced to the closed hole side, the injection hole 24 is closed, and the injection is stopped.

  In addition, the solenoid valve 22 is provided with a leak port 42 for leaking excess fuel in the injector 6 that has not been used for injection into the low-pressure pipe 41. 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 6. For example, the fuel in the reservoir portion 28 leaks from the sliding portion between the body 26 and the injection valve body 25 or the back. The fuel in the pressure chamber 31 leaks from the sliding portion between the body 26 and the command piston 30. The fuel leaking from the reservoir 28 and the back pressure chamber 31 flows into a spring chamber 43 formed between the injection valve body 25 and the command piston 30 and containing the spring 29, and is provided in the low pressure passage provided in the body 26. 44, leaks from the leak port 42 to the low-pressure pipe 41 through the low-pressure channel 45 provided in the electromagnetic valve 22.

  The dynamic leak is a fuel leak caused by an intentional operation such as giving an injector command value to the electromagnetic valve 22 as in the case of discharging the fuel from the back pressure chamber 31 in order to reduce the back pressure. is there. Then, the fuel discharged from the back pressure chamber 31 through the orifice 37 merges with the fuel due to static leak in the low pressure channel 45 and leaks from the leak port 42 to the low pressure pipe 41.

  The pressure reducing valve 7 is attached to the other end of the common rail 3 and is opened to release the fuel from the common rail 3 to the low pressure pipe 48 to reduce the actual rail pressure. As shown in FIG. 3, the pressure reducing valve 7 is in contact with a ball-shaped valve body 49 and a valve body 49 that are opened or closed by communicating or blocking between the common rail 3 and the low-pressure pipe 48. The movable element 50 that contacts and displaces to the valve opening side upon receiving a magnetic attraction force, the solenoid 51 that generates a magnetic attraction force that receives the energization of the driving current and displaces the movable element 50 to the valve opening side, and the energization of the solenoid 51 A stator 52 that is excited and magnetically attracts the mover 50, a spring 53 that is disposed between the mover 50 and the stator 52, and biases the mover 50 toward the valve closing side, and the like.

  A pressure reducing valve command value is given to the pressure reducing valve 7 via the pressure reducing valve drive circuit 12 from the microcomputer 8. The pressure reducing valve command value is an open command period indicating a period during which the pressure reducing valve 7 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 12, and the pressure reducing valve drive circuit 12 energizes the solenoid 51 in accordance with this command signal. As a result, the pressure reducing valve 7 is opened, fuel is released from the common rail 3 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 41 into which the fuel leaked from the injector 6 flows, and the fuel released from the common rail 3 returns to the fuel tank 4 together with the fuel leaked from the injector 6.

  The microcomputer 8 is a computer having a known structure including a CPU that performs control processing and arithmetic processing, storage means such as a ROM, RAM, EEPROM, and backup RAM that store various programs and data, an input circuit, an output circuit, and the like. Then, based on detection values input from various sensors such as the rail pressure sensor 17, a pump command value, an injector command value, a pressure reducing valve command value, and the like are calculated and output to the respective drive circuits as command signals.

  With the above configuration, in the fuel injection device 1, the amount of fuel supplied from the fuel supply pump 5 and the amount of fuel from the pressure reducing valve 7 are adjusted so that the actual rail pressure substantially matches the target rail pressure corresponding to the 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 6 are controlled so that an amount of fuel according to the engine state is injected at a time according to the engine state. As a result, the actual rail pressure substantially coincides with the target rail pressure, and fuel is injected into each cylinder at an injection pressure corresponding to the actual rail pressure, and an operation corresponding to the state of the engine is performed.

Next, the actual rail pressure reduction control by the microcomputer 8 and the pressure reducing valve drive circuit 12 and the abnormality determination of the valve closing operation of the pressure reducing valve 7 will be described.
The microcomputer 8 and the pressure reducing valve drive circuit 12 function as rail pressure control means for controlling the operation of the pressure reducing valve 7 so that the actual rail substantially matches the target rail pressure. This control calculates the open command period as the pressure reducing valve command value based on the pressure reducing characteristic indicating the correlation between the amount of fuel escaped from the pressure reducing valve 7 (hereinafter referred to as the amount of escape) and the actual rail pressure. It is executed by outputting to.

  That is, the microcomputer 8 stores a decompression characteristic indicating a correlation between the relief amount and the actual rail pressure, and calculates an open command period based on the decompression characteristic. That is, as shown in FIG. 4, the pressure reduction characteristic is a correlation between the opening command period and the actual rail pressure. Further, the opening command period is, for example, a pressure reduction required for the actual rail pressure to be reduced by a unit pressure. This corresponds to the valve opening time of the valve 7 and corresponds to the amount of escape per unit time. Then, the microcomputer 8 synthesizes a command signal based on the calculated opening command period and outputs it to the pressure reducing valve drive circuit 12, and the pressure reducing valve drive circuit 12 supplies a drive current to the solenoid 51 in accordance with this command signal. The pressure reducing valve 7 is opened.

  Further, the microcomputer 8 functions as a maximum relief pressure reduction amount estimating means for estimating a maximum relief pressure reduction amount indicating the maximum drop amount of the actual rail pressure due to the opening of the pressure reduction valve 7. The maximum relief decompression amount estimation means estimates the maximum relief decompression amount on the assumption that the relief amount from the decompression valve 7 is at the upper limit of the performance standard of the decompression valve 7. That is, when the fuel is released from the pressure reducing valve 7 with the amount of relief of the upper limit of the performance standard, the maximum relief pressure reducing amount estimating means calculates a physical quantity corresponding to the amount of decrease in the actual rail pressure due to the opening of the pressure reducing valve 7 This is calculated as the maximum relief pressure reduction amount. Here, since the performance standard upper limit of the escape amount changes according to the actual rail pressure, it is calculated based on the detection value from the rail pressure sensor 17.

  Note that a physical quantity called a decompression amount such as a maximum relief decompression amount can be calculated as a physical quantity having a pressure dimension, but can also be calculated as a physical quantity having a fuel elastic modulus or viscosity dimension. The same applies to the actual decompression amount, other decompression amount, determination decompression amount, maximum leak decompression amount, and estimated decompression amount, which will be described later.

  Further, the microcomputer 8 functions as a valve closing abnormality determining means for determining whether or not an abnormality has occurred in the valve closing operation of the pressure reducing valve 7 (hereinafter, “abnormality of the valve closing operation” is referred to as “valve closing abnormality”). Call). The valve closing abnormality determining means has a valve closing abnormality in the pressure reducing valve 7 when the actual pressure reducing amount indicating the amount of decrease in the actual rail pressure due to the execution of the rail pressure control means becomes equal to or greater than the determined pressure reducing amount. Judge. Here, the determined pressure reduction amount is the sum of the maximum relief pressure reduction amount and the other pressure reduction amount, and serves as a threshold value for the valve closing abnormality determination. The other decompression amount is a decompression amount estimated from a decompression factor other than the opening of the decompression valve 7.

  The microcomputer 8 also functions as a decompression characteristic correcting unit that corrects the decompression characteristic in accordance with the difference between the actual decompression amount and the estimated decompression amount estimated from the decompression characteristic. Then, the valve closing abnormality determining means is executed after the pressure reducing characteristic is corrected by the execution of the pressure reducing characteristic correcting means. That is, the valve closing abnormality determining means determines whether or not the valve closing abnormality has occurred after confirming that the pressure reducing characteristic has been corrected.

  Further, the microcomputer 8 estimates the maximum leak pressure reduction amount indicating the maximum drop amount of the actual rail pressure due to the fuel leak of the injector 6 as the other pressure reduction amount. The maximum leak pressure reduction amount is estimated by assuming that the fuel leak amount from the injector 6 is at the upper limit of the performance standard of the injector 6. Further, the estimation of the maximum leak pressure reduction amount is performed based on the fuel balance in the fuel injection device 1 with the actual rail pressure, the engine speed, etc. as the variable factors.

  In addition, since the valve closing abnormality determination means of this embodiment is executed when the engine stops (when the ignition is off), the maximum leak pressure reduction amount corresponds to the amount of decrease in the actual rail pressure caused by static leak. Calculated as the amount of pressure reduction.

  Further, the valve closing abnormality determining means is further provided with an additional condition for determining that the valve closing abnormality has occurred in the pressure reducing valve 7. It is determined whether or not the amount has increased by a predetermined amount or more than when it is normal. When this additional condition is satisfied, it is determined that a valve closing abnormality has occurred in the pressure reducing valve 7.

  Further, the valve closing abnormality determining means, as a confirmation process for determining that the valve closing abnormality has occurred in the pressure reducing valve 7, according to the actual pressure reducing amount generated by giving the temporary opening command period to the pressure reducing valve 7, It is determined whether or not a valve closing abnormality has occurred in the pressure reducing valve 7. The temporary opening command period is an opening command period that is shorter than the normal opening command period calculated based on the pressure reduction characteristics. Since this process is confirmation that a valve closing abnormality has occurred, it is executed when the actual pressure reduction amount is greater than or equal to the determined pressure reduction amount.

[Control Method of Example 1]
A control method according to the first embodiment will be described with reference to a flowchart shown in FIG.
First, in step S <b> 1, it is determined whether or not a condition (determination condition) that can determine whether the pressure reducing valve 7 is closed is satisfied. The determination condition is that the microcomputer 8 confirms that the engine is surely in the non-injection and decompression execution state as when the ignition is off, and that the decompression characteristic is corrected by the execution of the decompression characteristic correcting means. And so on. If the determination condition is satisfied (YES), the process proceeds to step S2. If the determination condition is not satisfied (NO), the process is terminated.

  Next, in step S2, the initial value of the actual rail pressure is measured. This measurement is performed by the microcomputer 8 using a rail pressure detection signal input from the rail pressure sensor 17 to the microcomputer 8. In step S3, it is determined whether or not a predetermined time has elapsed. If the predetermined time has elapsed (YES), the process proceeds to step S4, and the final value of the actual rail pressure is measured in the same manner as the initial value. In step S3, the process does not proceed while the predetermined time has not elapsed (NO). Note that this predetermined time is at least longer than the time required for the processing by the rail pressure control means to be executed to calculate a new opening command period and to perform valve opening based on the new opening command period. Is set.

  Next, in step S5, the difference between the initial value of the actual rail pressure and the final value of the actual rail pressure, that is, the amount of decrease in the actual rail pressure associated with the execution of the rail pressure control means is obtained. Calculate the amount. In step S6, the maximum escape pressure reduction amount is estimated. This estimation is performed on the assumption that the escape amount from the pressure reducing valve 7 is at the upper limit of the performance standard of the pressure reducing valve 7. Here, since the performance standard upper limit of the escape amount changes according to the actual rail pressure while exhibiting the same tendency as the decompression characteristic, it can be calculated using the initial value of the actual rail pressure and the decompression characteristic.

  In step S7, the maximum leak pressure reduction amount is estimated. This estimation is performed on the assumption that the amount of fuel leakage from the injector 6 is at the upper limit of the performance standard of the injector 6. Here, the performance specification upper limit of the leak amount can be calculated based on the fuel balance in the fuel injection device 1 with the actual rail pressure, the engine speed, and the like as the variation factors. That is, by applying the initial value of the actual rail pressure or the like to various correlation equations determined from the fuel balance, the upper limit of the performance standard for the leak amount can be calculated. In step S8, the sum of the maximum relief pressure reduction amount and the maximum leak pressure reduction amount is calculated, and the sum is set as the determination pressure reduction amount.

  Next, in step S9, it is determined whether or not the actual reduced pressure amount is greater than or equal to the determined reduced pressure amount. If the actual decompression amount is equal to or greater than the determination decompression amount (YES), the process proceeds to step S10. If the actual decompression amount is less than the determination decompression amount (NO), the process ends.

  Next, in step S10, it is determined whether or not the amount of fuel supplied by the fuel supply pump 5 is increased by a predetermined amount or more than when the valve closing operation of the pressure reducing valve 7 is normal. This condition is an additional condition for determining that a valve closing abnormality has occurred in the pressure reducing valve 7.

  The determination as to whether or not this additional condition is satisfied can be made by setting a threshold value for the pump command value and comparing the pump command value with the threshold value. For example, when the intake metering valve 19 is a normally closed type that is fully closed when the solenoid is not energized, the additional condition is satisfied if the pump command value is equal to or greater than the threshold value. Can be judged. Further, when the suction metering valve 19 is a normally open type that is fully opened when the solenoid is not energized, it is determined that the additional condition is satisfied if the pump command value is equal to or less than the threshold value. it can.

  Further, the determination as to whether or not the additional condition is satisfied can be made, for example, by determining whether or not the pump command value is fixed at the limit value or whether or not the pump command value is changing near the limit value. For example, when the intake metering valve 19 is a normally closed type, the pump command value is fixed to a value (command upper limit value) such that the valve opening degree of the intake metering valve 19 becomes the upper limit, or the command When transitioning in the vicinity of the upper limit value, it can be determined that the additional condition is satisfied. When the intake metering valve 19 is a normally open type, the pump command value is fixed to a value (command lower limit value) such that the valve opening degree of the intake metering valve 19 becomes the lower limit, or the command When transitioning near the lower limit value, it can be determined that the additional condition is satisfied.

  If it is determined that the amount of fuel supplied by the fuel supply pump 5 has increased by a predetermined amount or more compared to when the valve closing operation of the pressure reducing valve 7 is normal (YES), the process proceeds to step S11, and the pressure reducing valve If it is determined that the valve closing operation 7 has not increased more than a predetermined amount as compared with the normal time (NO), the process is terminated.

  Next, in step S <b> 11, it is determined whether a valve closing abnormality has occurred in the pressure reducing valve 7 according to the actual pressure reducing amount generated by giving the temporary opening command period to the pressure reducing valve 7. This process is a confirmation process for determining that a valve closing abnormality has occurred in the pressure reducing valve 7. This confirmation process can be executed, for example, by giving the temporary opening command period to the pressure reducing valve 7 as zero. That is, by giving the provisional opening command period to zero to the pressure reducing valve 7, if the generation of the actual pressure reducing amount is confirmed even though the command to be opened is not substantially given, the valve closing abnormality is It can be confirmed that it has occurred. If the occurrence of the valve closing abnormality can be confirmed (YES), the process proceeds to step S12, and the occurrence of the valve closing abnormality is confirmed. If the occurrence of valve closing abnormality cannot be confirmed (NO), the process is terminated.

[Effect of Example 1]
In the fuel injection device 1 according to the first embodiment, the microcomputer 8 sets the maximum relief pressure reduction amount indicating the maximum drop amount of the actual rail pressure due to the opening of the pressure reducing valve 7 to the upper limit of the performance standard of the pressure reducing valve 7. The actual pressure reduction amount indicating the amount of decrease in the actual rail pressure due to the execution of the maximum relief pressure reduction amount estimating means and the rail pressure control means estimated by assuming that there is an estimated pressure reduction factor other than the opening of the pressure reducing valve 7 is estimated. It functions as a valve closing abnormality determining means for determining that a valve closing abnormality has occurred in the pressure reducing valve 7 when the pressure reducing amount is equal to or greater than the determined pressure reducing amount which is the sum of the other pressure reducing amount and the maximum relief pressure reducing amount.

  When the valve closing abnormality occurs in the pressure reducing valve 7, the fuel is released through the pressure reducing valve 7 with a release amount that is equal to or greater than the upper limit of the performance standard of the pressure reducing valve 7. Therefore, as described above, the other decompression amount estimated from the decompression factor other than the opening of the decompression valve 7 is added to the maximum relief decompression amount when the relief amount is assumed to be the upper limit of the performance standard of the decompression valve 7. If the determined pressure reduction amount is used as a threshold value, it is possible to determine the valve closing abnormality with high accuracy.

Further, the valve closing abnormality determining means estimates the maximum leak pressure reduction amount indicating the maximum drop amount of the actual rail pressure due to the fuel leak of the injector 6 by assuming that the leak amount is at the upper limit of the performance standard of the injector 6, Other reduced pressure amount.
Since the injector 6 communicates with the common rail 3, the amount of fuel leakage from the injector 6 greatly affects the actual amount of pressure reduction. Therefore, if the maximum leak pressure reduction amount when assuming that the fuel leak amount from the injector 6 is at the upper limit of the performance standard of the injector 6 is used as the other pressure reduction amount, the valve closing abnormality can be determined with higher accuracy. Can do.

The valve closing abnormality determining means is executed when the ignition is off.
When the ignition is turned off, there is no injection and the pressure is reduced. The other pressure reduction due to a pressure reduction factor (for example, fuel leakage from the injector 6) other than the opening of the pressure reducing valve 7 is extremely predictable. Therefore, if the valve closing abnormality determining means is executed when the ignition is off, the valve closing abnormality can be determined with higher accuracy.

The maximum leak pressure reduction amount indicates the maximum amount of actual rail pressure drop caused by static leak in which fuel leaks through the sliding portion inside the injector 6.
When the ignition is off, it is considered that the fuel leaks from the injector 6 due to static leak, and the dynamic leak is considered to be less necessary to be considered as a leak factor. Therefore, when determining the valve closing abnormality at the time of ignition off, by taking up static leak as a leak factor, it is possible to improve the determination accuracy and not considering other leak factors such as dynamic leak, The calculation load of the microcomputer 8 can be reduced.

Further, the rail pressure control means calculates a pressure reducing valve command value to be given to the pressure reducing valve 7 based on a pressure reducing characteristic indicating a correlation between the relief amount and the actual rail pressure.
Thus, the operation of the pressure reducing valve 7 can be changed according to the actual rail pressure.

The valve closing abnormality determining means is executed after the decompression characteristic is corrected by the execution of the decompression characteristic correcting means.
The pressure reduction characteristic is corrected for each product by the pressure reduction characteristic correcting means, and is changed to one suitable for control of each product according to the bias of the individual release amount of the pressure reducing valve 7. As a result, since the upper limit escape amount of the performance standard of the pressure reducing valve 7 can be corrected for each product, the maximum escape pressure reduction amount suitable for each product can be calculated.
As described above, when determining whether the pressure reducing valve 7 is closed abnormally, it is possible to set a performance standard upper limit of the escape amount suitable for each product.

In addition, the valve closing abnormality determining means provides the actual pressure reduction caused by giving the pressure reducing valve 7 a temporary opening command period shorter than the opening command period calculated based on the pressure reducing characteristic when the actual pressure reducing amount is equal to or larger than the determined pressure reducing amount. It is determined whether or not an abnormality has occurred in the valve closing operation of the pressure reducing valve 7 according to the amount.
Thereby, it is possible to confirm the occurrence of the valve closing abnormality. That is, when the actual pressure reduction amount generated by the operation of the pressure reducing valve 7 based on the temporary opening command period is larger than the expected pressure reduction amount, it can be determined that the valve closing abnormality has surely occurred.

Further, the valve closing abnormality determining means determines that the amount of fuel supplied by the fuel supply pump 5 has increased to a predetermined amount or more than when the valve closing operation of the pressure reducing valve 7 is normal. 7 determines that a valve closing abnormality has occurred.
A state in which the actual pressure reduction amount is large although the fuel supply amount by the fuel supply pump 5 is increased by a predetermined amount or more than when the valve closing operation of the pressure reducing valve 7 is normal is indicated in the pressure reducing valve 7. The possibility that a valve closing abnormality has occurred is extremely high. Therefore, by adding a condition that “the amount of fuel supplied by the fuel supply pump 5 can be determined to be greater than or equal to a predetermined amount compared to when the valve closing operation of the pressure reducing valve 7 is normal” to the determination condition, Furthermore, it is possible to improve the accuracy of the determination of the valve closing abnormality.

[Modification]
In this embodiment, only static leak is considered when estimating the maximum leak pressure reduction amount. However, when the actual rail pressure is reduced by causing the injector 6 to perform so-called “blank driving”, dynamic Leakage may be considered. The idle driving means that the injector 6 is given an injection period shorter than the time from the opening of the back pressure chamber 31 by the electromagnetic valve 22 to the opening of the injection hole 24 by the injection valve body 25 (injection delay time). Thus, the actual rail pressure is lowered by causing only the back pressure to be supplied and discharged without substantially performing injection.

  Further, in the flowchart of the present embodiment, it is determined whether or not the amount of fuel supplied by the fuel supply pump 5 has increased by a predetermined amount or more than when the valve closing operation of the pressure reducing valve 7 is normal (hereinafter referred to as fuel). The confirmation of the supply amount from the supply pump 5 and the confirmation by the temporary opening command period were performed after the actual pressure reduction amount and the determination pressure reduction amount were determined to be large or small. You may make it perform. That is, the order in which the supply amount from the fuel supply pump 5 is confirmed, the confirmation during the temporary opening command period, and the actual pressure reduction amount and the determination pressure reduction amount are determined can be changed as needed. Further, the confirmation of the supply amount from the fuel supply pump 5 and the confirmation during the temporary opening command period may be omitted as necessary.

  Although the pressure reducing valve 7 of the present embodiment opens or closes by an on / off method according to energization or non-energization of the solenoid 51, it is not limited to such a form. For example, the pressure reducing valve 7 may be a variable opening type that can adjust the valve opening degree by duty control, and the present invention can be applied to this variable opening type pressure reducing valve. In this case, the valve opening degree can be added as a variation factor to the decompression characteristics.

  Further, the pressure reducing valve 7 of this embodiment is opened by the pressure reducing valve drive circuit 12 energizing the solenoid 51 in accordance with a command signal output from the microcomputer 8. It is not limited to such a form. For example, the drive current may be directly applied to the solenoid 51 from a predetermined power source without providing the pressure reducing valve drive circuit 12.

  In the flowchart of the present embodiment, the actual rail pressure is measured before and after the elapse of a predetermined time, and the actual pressure reduction amount is calculated based on the difference (the amount of descent). However, the actual rail pressure is reduced by a predetermined amount. It is also possible to measure the time required to calculate the actual decompression amount using this time measurement value.

1 is an overall configuration diagram of a fuel injection device. It is a block diagram of an injector. It is explanatory drawing explaining pressure reduction control. It is a characteristic view which shows a pressure reduction characteristic. It is a flowchart which shows the process by a valve closing abnormality determination means, the maximum relief pressure reduction amount estimation means, and the maximum leak pressure reduction amount estimation means.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel injection apparatus 3 Common rail 5 Fuel supply pump 6 Injector 7 Pressure reducing valve 8 Microcomputer (Rail pressure control means, maximum relief pressure reducing amount estimating means, valve closing abnormality determining means, pressure reducing characteristic correcting means)
12 Pressure reducing valve drive circuit (rail pressure control means)

Claims (8)

In a fuel injection device that includes a common rail that receives supply of fuel so that fuel is accumulated at a target pressure corresponding to the state of the engine, and that supplies fuel to the engine through the common rail,
A pressure reducing valve for reducing the actual pressure of the fuel accumulated in the common rail by opening the valve and releasing the fuel from the common rail;
Rail pressure control means for controlling the operation of the pressure reducing valve so that the actual pressure substantially matches the target pressure by calculating a command value to be given to the pressure reducing valve and outputting the command value to the pressure reducing valve;
Estimating the maximum relief pressure reduction amount indicating the maximum pressure drop due to the opening of the pressure reducing valve by assuming that the fuel escape amount from the pressure reducing valve is at the upper limit of the performance standard of the pressure reducing valve Means for estimating the maximum relief pressure reduction amount,
The actual pressure reduction amount indicating the amount of decrease in the actual pressure accompanying the execution of the rail pressure control means is the sum of the other pressure reduction amount estimated from a pressure reduction factor other than the opening of the pressure reducing valve and the maximum relief pressure reduction amount. A fuel injection device comprising: a valve closing abnormality determining unit that determines that an abnormality has occurred in the valve closing operation of the pressure reducing valve when the determination pressure reducing amount is exceeded. The fuel injection device according to claim 1,
An injector that communicates with the common rail and injects fuel accumulated in the common rail into a cylinder of the engine;
The actual pressure is also reduced by fuel leaking from the injector,
The valve closing abnormality determining means sets a maximum leak pressure reduction amount indicating a maximum drop amount of the actual pressure due to a fuel leak from the injector, and a fuel leak amount from the injector as an upper limit of the performance standard of the injector. A fuel injection device characterized in that it is estimated by assuming that it is present, and the other decompression amount is set. The fuel injection device according to claim 2, wherein
The fuel injection device, wherein the valve closing abnormality determining means is executed when the engine is stopped. The fuel injection device according to claim 3, wherein
The maximum leak pressure reduction amount indicates a maximum drop amount of the actual pressure caused by a static leak in which fuel leaks through a sliding portion inside the injector. The fuel injection device according to claim 1,
The rail pressure control means calculates the command value based on a pressure reduction characteristic indicating a correlation between the relief amount and the actual pressure. The fuel injection device according to claim 5, wherein
In accordance with a difference between the actual decompression amount and the estimated decompression amount estimated by the decompression characteristic, the decompression characteristic correcting means for correcting the decompression characteristic is provided,
The fuel injection device according to claim 1, wherein the valve closing abnormality determining means is executed after the pressure reducing characteristic is corrected by execution of the pressure reducing characteristic correcting means. The fuel injection device according to claim 5, wherein
The command value is an open command period indicating a period during which the pressure reducing valve is open,
The valve closing abnormality determining means is generated by giving the pressure reducing valve a temporary opening command period shorter than the opening command period calculated based on the pressure reducing characteristic when the actual pressure reducing amount is equal to or larger than the determined pressure reducing amount. According to the actual pressure reduction amount, it is determined whether or not an abnormality has occurred in the valve closing operation of the pressure reducing valve. The fuel injection device according to any one of claims 1 to 7,
A fuel supply pump that pressurizes and supplies fuel to the common rail;
When the valve closing abnormality determining means can determine that the amount of fuel supplied by the fuel supply pump has increased to a predetermined amount or more than when the valve closing operation of the pressure reducing valve is normal, the pressure reducing valve It is determined that an abnormality has occurred in the valve closing operation of the fuel injection device.

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