JP2007255333A - Common rail fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a common rail fuel injection device in which power is savely fed to a drive circuit part prepared commonly for a fuel injection valve and a pressure reducing valve. <P>SOLUTION: A control circuit 50 switches on/off of a MOSFET 36 to supply power from a common power supply system to the fuel injection valve and the pressure reducing valve according to injection signals and pressure reduction signals. As a reference for switching on/off of the MOSFET 36, the control circuit 50 has a voltage dividing circuit in which resistors 51, 52 are connected in series between a constant-voltage source Vcc and the ground to provide a voltage Vp equivalent to a peak current threshold. The resistor 52 is formed by connecting the resistors 52a, 52b in series to each other. The intermediate part of the emitters and the intermediate part of the collectors of a transistor 53 are so connected to each other parallel with the resistor 52b that the pressure reduction signals are input into the base of the transistor 53. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a common rail fuel injection device having an electromagnetically driven pressure reducing valve.

  For example, in a diesel engine, there is a common rail fuel injection system in which fuel is stored in a common rail common to each cylinder in a high pressure state, and the stored fuel is injected into the engine using an electromagnetically driven injector (fuel injection valve). It is used. In such a common rail type fuel injection system, a high pressure pump that pressurizes and supplies fuel to the common rail is connected. A suction metering valve is provided in the suction part of the high-pressure pump. By adjusting the opening of the suction metering valve, the amount of fuel pumped to the common rail by the high-pressure pump is adjusted, and the fuel pressure in the common rail is adjusted. The desired pressure is maintained.

  In recent years, some common rails are provided with electromagnetically driven pressure reducing valves. In such a common rail type fuel injection system, when the fuel pressure in the common rail becomes larger than a desired pressure, the fuel in the common rail is discharged by opening the pressure reducing valve to reduce the fuel pressure in the common rail. It is possible to reduce.

However, in the common rail fuel injection system provided with such a pressure reducing valve, a drive circuit for driving the pressure reducing valve is required in addition to the injector and the intake metering valve. To solve this problem, for example, in Patent Document 1, power is supplied to a suction metering valve and a pressure reducing valve from a common drive circuit, and the suction metering valve and the pressure reducing valve are driven.
JP 2003-332067 A

  By the way, when the injector and the pressure reducing valve each have the same electromagnetic solenoid, a configuration in which the drive circuits of the injector and the pressure reducing valve are made common is conceivable. However, the injectors need to be driven at high speed in order to supply fuel at the desired injection timing and injection amount, while the pressure reducing valves need only be opened, so the magnitude of the drive current required by each injector Is different. For this reason, in a configuration in which power is simply supplied from a common drive circuit, excess current flows when the pressure reducing valve is driven.

  The main object of the present invention is to provide a common rail fuel injection device capable of supplying power without waste in a configuration in which the drive circuit unit of the fuel injection valve and the pressure reducing valve is shared.

  Hereinafter, means for solving the above-described problems and the effects thereof will be described.

  The common rail fuel injection device of the present invention is premised on a common rail that stores fuel in a high pressure state, a fuel pump that pressurizes and supplies the fuel to the common rail, and a fuel injection valve that injects and supplies fuel stored in the common rail to the engine. And a system including a pressure reducing valve for discharging fuel in the common rail.

  According to the first aspect of the present invention, the fuel injection valve is powered on the basis of an injection signal generated in accordance with the operating state of the engine to drive the fuel injection valve to open, and is generated when the fuel pressure is requested to be reduced. A drive circuit unit that feeds power to the pressure reducing valve based on the pressure reducing signal and opens the pressure reducing valve. Here, the drive circuit unit is configured such that the drive current when the decompression valve is driven to open is smaller than the drive current when the fuel injection valve is driven to open.

  The drive current required for the valve opening drive differs between the fuel injection valve and the pressure reducing valve due to the difference in response required. In particular, a pressure reducing valve that only needs to be in an open state requires a smaller driving current for driving than a fuel injection valve. That is, according to the present invention, since the drive current when the pressure reducing valve is driven to open is smaller than the drive current when the fuel injection valve is driven to open, excessive power feeding is avoided. Therefore, power can be supplied without waste, and the driving current can be reduced and the heat generation of the pressure reducing valve can be reduced.

  According to a second aspect of the present invention, there is provided detection means for detecting the magnitude of the drive current, and comparison means for comparing the magnitude of the drive current detected by the detection means with a predetermined current threshold value. In the configuration in which the current path through which the drive current flows is interrupted according to the comparison result, the current threshold is changed so that the drive current is smaller when the pressure reducing valve is opened, compared to when the fuel injector is opened. That is, in a configuration in which power supply is intermittently performed based on a predetermined current threshold, the magnitude of the drive current can be changed by changing the current threshold.

  According to a third aspect of the present invention, in a configuration including a voltage dividing circuit including a first voltage dividing resistor and a second voltage dividing resistor, the output voltage of the voltage dividing circuit is used as a current threshold value. The voltage dividing resistor or the second voltage dividing resistor is configured by connecting two voltage dividing resistors in series, and a voltage dividing circuit switching element is provided in parallel with one of the two resistors. When the pressure reducing valve is driven to open, the voltage dividing circuit switch element is turned on or off so that the current threshold value becomes smaller than when the fuel injection valve is driven to open.

  According to the above configuration, with the conduction / cutoff of the voltage divider circuit switch element, the voltage dividing ratio of the voltage dividing circuit changes, the output voltage of the voltage dividing circuit changes, and the current threshold value changes. Accordingly, when the pressure reducing valve is driven to open, the voltage dividing circuit switch element is turned on or off so that the current threshold is smaller than when the fuel injection valve is driven to open. It becomes smaller than the drive current of the injection valve. Here, the voltage dividing circuit capable of changing the current threshold is realized by a simple configuration including three resistors and one switch element, which is advantageous in terms of cost.

  In the fourth aspect of the invention, when the pressure reducing valve is driven to open, the magnitude of the drive current is changed according to the operating state of the engine. That is, the responsiveness required for the pressure reducing valve and the magnitude of the required drive current vary depending on the engine speed, the fuel pressure in the common rail, the amount of pressure reduction, and the like. Therefore, the drive current can be made appropriate by changing the magnitude of the drive current in accordance with the operating state of the engines.

  In particular, in a configuration including three types of pressure reducing valves, the drive current is preferably decreased as the fuel pressure in the common rail increases. In the three-type pressure reducing valve, the valve member is closed by high-pressure fuel in the back pressure chamber, and the valve member is opened as the fuel in the back pressure chamber leaks. For this reason, when the magnitude of the drive current is the same, the higher the fuel pressure in the common rail, the faster the valve is opened. Therefore, if the responsiveness required for the pressure reducing valve is constant, the drive current can be reduced as the fuel pressure increases. Thereby, the drive current required for the pressure reducing valve is supplied more appropriately, and the drive current can be further reduced.

  According to the fifth aspect of the present invention, in the configuration in which a predetermined opening-time drive current is supplied at the beginning of opening of the fuel injection valve and the pressure reducing valve, when the pressure reducing valve is driven to open, the fuel injection valve is driven to open. Reduce the drive current when opening the valve.

  When the fuel injection valve or the pressure reducing valve is opened, a relatively large drive current (so-called peak current) is supplied as a predetermined valve-opening drive current in order to quickly open the valve at the beginning. For this reason, if the valve-opening drive current when the pressure reducing valve is driven to open is smaller than the valve-opening drive current when the fuel injection valve is driven to open, the reduction in the drive current is large. The effect of reducing is great.

  According to the sixth aspect of the present invention, in the configuration in which the valve opening maintaining current for maintaining the valve open state of the fuel injection valve and the pressure reducing valve is supplied, the valve opening drive of the pressure reducing valve is compared with the time of the fuel injection valve opening driving. To reduce the valve opening maintenance current.

  When the fuel injection valve or the pressure reducing valve is driven to open, a valve opening maintaining current (so-called hold current) is supplied over a relatively long period of time in order to maintain fuel injection by the fuel injection valve and fuel discharge by the pressure reducing valve. For this reason, if the valve opening maintenance current when the pressure reducing valve is driven to open is made smaller than the valve opening maintenance current when the fuel injection valve is driven to open, the drive current is reduced over a long period of time, and the drive current is reduced. The effect is great.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings. This embodiment embodies the present invention as a common rail fuel injection system for an on-vehicle multi-cylinder diesel engine. First, the overall schematic configuration of the common rail fuel injection system will be described with reference to FIG.

  In FIG. 1, a four-cylinder diesel engine (hereinafter referred to as an engine) 10 is provided with an electromagnetically driven injector 11 for each cylinder, and these injectors 11 are connected to a common rail 12 common to each cylinder. A high pressure pump 13 is connected to the common rail 12. The high-pressure pump 13 is provided with an intake metering valve 14 at its suction portion, and the intake metering valve 14 is connected to a fuel tank 16 via a feed pump 15. With this configuration, the fuel in the fuel tank 16 is pumped up by the feed pump 15, metered by the suction metering valve 14, and sucked into the high-pressure pump 13. Then, the fuel sucked into the high-pressure pump 13 is pressurized and supplied to the common rail 12 and accumulated in a high-pressure state. The common rail 12 is provided with an electromagnetically driven pressure reducing valve 17, and the fuel in the common rail 12 is discharged to the fuel tank 16 by opening the pressure reducing valve 17. The common rail 12 is provided with a fuel pressure sensor 18 that detects the fuel pressure in the common rail 12.

  As is well known, the electronic control unit 20 is mainly composed of a microcomputer including a CPU, a ROM, a RAM, and the like. The electronic control unit 20 is sequentially inputted with operation information such as a detection signal of the fuel pressure sensor 18, an engine speed and an accelerator operation amount. The electronic control unit 20 executes various control programs stored in the ROM, thereby performing various controls related to the operation of the engine 10 such as fuel pressure control and fuel injection control based on the inputted operation information.

  That is, in the fuel pressure control, operation information such as the engine rotation speed and the accelerator operation amount is acquired, and the target fuel pressure in the common rail 12 is calculated based on the operation information. Then, the actual fuel pressure in the common rail 12 is acquired from the fuel pressure sensor 18, the opening amount of the intake metering valve 14 is calculated from the difference between the target fuel pressure and the actual fuel pressure, and the intake adjustment is performed according to the opening amount. The quantity valve 14 is opened. In the fuel injection control, the operation information such as the engine speed and the accelerator operation amount is acquired, and the optimum fuel injection timing and injection amount are calculated based on the operation information, and the fuel injection control is performed according to the injection timing and the injection amount. Outputs an injection signal. Here, the injection signal is a pulse-like signal which is given to each injector 11 provided in each cylinder and becomes H level during a period in which fuel injection is performed by opening the injector 11.

  In addition, when the actual fuel pressure in the common rail 12 becomes higher than the target fuel pressure, the electronic control unit 20 performs pressure reducing valve control for opening the pressure reducing valve 17 and discharging the fuel in the common rail 12. In the pressure reducing valve control, the target fuel pressure calculated by the fuel pressure control is acquired, and the actual fuel pressure in the common rail 12 is acquired from the fuel pressure sensor 18. When the actual fuel pressure is higher than the target fuel pressure by a predetermined amount or more, the pressure reducing valve 17 is opened for a period corresponding to the discharge amount in order to open the pressure reducing valve 17 and discharge the fuel in the common rail 12. The decompression signal is output. Here, the decompression signal is a pulse-like signal that becomes H level during the period in which fuel is discharged by opening the decompression valve 17.

  An electronic driver unit (hereinafter referred to as EDU) 30 inputs an injection signal and a pressure reduction signal from the electronic control unit 20, and drives the injector 11 and the pressure reduction valve 17 by supplying power in accordance with these various signals. The injector 11 and the pressure reducing valve 17 of the present embodiment each have the same electromagnetic solenoid, and when the electromagnetic solenoid of the injector 11 is energized, fuel is injected from the injector 11 and the electromagnetic solenoid of the pressure reducing valve 17 is energized. As a result, the fuel is discharged from the common rail 12. For this reason, power is supplied by a common EDU 30. Further, the EDU 30 is configured to output a fail signal for informing the presence or absence of an abnormality in the EDU 30.

  FIG. 2 is a circuit diagram showing an electrical configuration of the EDU 30 that drives the injector 11 and the pressure reducing valve 17. As shown in FIG. 2, the electromagnetic solenoids 11 a, 11 b, 11 c, and 11 d of the injector 11 are connected to the EDU 30, and the electromagnetic solenoid 17 a of the pressure reducing valve 17 is connected to the EDU 30. Further, the EDU 30 is connected to the electronic control unit 20 as described above, and inputs injection signals # 1 to # 4 and a decompression signal for each cylinder from the electronic control unit 20. On the other hand, the EDU 30 outputs a fail signal that notifies the electronic control unit 20 of the presence or absence of an abnormality in the EDU 30. The EDU 30 is connected to the battery 21 and receives power supply from the battery 21.

  In the present embodiment, the EDU 30 has a plurality of drive systems so that the injector 11 of any cylinder can be driven even when an abnormality occurs in the EDU 30. That is, the first drive system that combines the electromagnetic solenoids 11a and 11d of the injector 11 in the first and fourth cylinders and the second drive system that combines the electromagnetic solenoids 11b and 11c of the injector 11 in the second and third cylinders. Drive system. The electromagnetic solenoid 17a of the pressure reducing valve 17 is connected to the second drive system.

  The EDU 30 includes a high voltage generation circuit 31 that inputs a battery voltage (for example, 12 volts) and outputs a predetermined high voltage (for example, about 100 volts). The high voltage generation circuit 31 is connected to the high side of the electromagnetic solenoids 11a and 11d via the MOSFET 32 as a first drive system. The high side of the electromagnetic solenoids 11 a and 11 d is connected to the battery 21 through the MOSFET 33 and the diode 34 and is grounded through the diode 35. Here, the diodes 34 and 35 are connected with the direction in which the current flows toward the high side of the electromagnetic solenoids 11a and 11d as the forward direction. On the other hand, the low sides of the electromagnetic solenoids 11a and 11d are connected to MOSFETs 41a and 41d, respectively, and the MOSFETs 41a and 41d are grounded via a resistance 43 for detecting an energization current.

  Next, as a second drive system, the high voltage generation circuit 31 is connected to the high side of the electromagnetic solenoids 11b, 11c, and 17a via the MOSFET 36. The high side of the electromagnetic solenoids 11 b, 11 c, and 17 a is connected to the battery 21 via the MOSFET 37 and the diode 38 and is grounded via the diode 39. Here, the diodes 38 and 39 are connected with the direction of current flowing toward the high side of the electromagnetic solenoids 11b, 11c and 17a as the forward direction. On the other hand, the low sides of the electromagnetic solenoids 11b, 11c, and 17a are connected to MOSFETs 41b, 41c, and 42a, respectively, and the MOSFETs 41b, 41c, and 42a are grounded through a resistance 44 for detecting an energization current.

  The control circuit 50 switches on / off (conduction / cutoff) of each MOSFET according to the injection signals # 1 to # 4 and the pressure reduction signal. Hereinafter, the on / off switching operation of each MOSFET by the control circuit 50 will be described with reference to FIG. 3 for the drive of the injector 11 of the first cylinder. That is, as shown in FIG. 3, when the injection signal # 1 becomes H level at timing t1, the control circuit 50 turns on the low-side MOSFET 41a of the electromagnetic solenoid 11a and turns on the high-side MOSFET 32 of the electromagnetic solenoid 11a. To do. Then, since the high output voltage of the high voltage generation circuit 31 is applied to the electromagnetic solenoid 11a, the energization current of the electromagnetic solenoid 11a increases rapidly. When the energizing current of the electromagnetic solenoid 11a reaches a predetermined peak current threshold Ith at timing t2, the control circuit 50 turns off the MOSFET 32. Thereafter, the MOSFET 33 is repeatedly turned on / off so that the energization current of the electromagnetic solenoid 11a is maintained at a predetermined hold current threshold value or more during the period when the injection signal # 1 is at the H level. At timing t3, when the injection signal # 1 becomes L level, the MOSFET 41a is turned off.

  By turning on / off the MOSFETs 32, 33, 41a as described above, a relatively large current (peak current) is supplied to the electromagnetic solenoid 11a when the injection signal # 1 rises, and the injector 11 is quickly opened to provide fuel. Injection starts. Thereafter, during a period when the injection signal # 1 is at the H level, the electromagnetic solenoid 11a is energized with a constant current (hold current) to maintain the fuel injection, the injector 11 is kept open, and the fuel injection continues. Done. Similarly, the control circuit 50 switches each MOSFET on / off when supplying power to the electromagnetic solenoids 11b, c, d of the injectors 11 of the other cylinders and the electromagnetic solenoid 17a of the pressure reducing valve 17.

  By the way, when the injector 11 is driven, responsiveness is required to inject and supply fuel according to the injection timing and the injection amount. Therefore, it is necessary to flow a relatively large current of about 16 amperes as a peak current to the electromagnetic solenoids 11a to 11d. There is. On the other hand, when the pressure reducing valve 17 is driven, it is only necessary to open the valve, and a relatively small current of about 10 amperes as a peak current may flow through the electromagnetic solenoid 17a. For this reason, if the control circuit 50 having the above-described configuration is used to similarly switch the MOSFETs on and off when the injector 11 is driven and when the pressure reducing valve 17 is driven, an excessive current flows in the electromagnetic solenoid 17 a of the pressure reducing valve 17. Will flow. Therefore, in the present embodiment, the control circuit 50 is configured such that the peak current threshold value Ith can be changed between when the injector 11 is driven and when the pressure reducing valve 17 is driven.

  FIG. 4 shows an electrical configuration of the control circuit 50 that can change the peak current threshold Ith when the electromagnetic solenoids 11b and 11c of the injector 11 are energized and when the electromagnetic solenoid 17a of the pressure reducing valve 17 is energized. It is a circuit diagram. In FIG. 4, as a circuit diagram of the control circuit 50, only a circuit of a part for switching on / off of the MOSFET 36 is shown.

  As shown in FIG. 4, the control circuit 50 has a voltage dividing circuit in which resistors 51 and 52 are connected in series between the constant voltage source Vcc of the EDU internal circuit and the ground. Here, the resistor 52 has resistors 52a and 52b connected in series, and the emitter and collector of the transistor 53 are connected in parallel with the resistor 52b. A decompression signal is inputted to the base of the transistor 53, and the transistor 53 is turned on when the decompression signal is at the H level.

  The control circuit 50 also includes a comparator 54 for comparing the magnitudes of the energization current values of the electromagnetic solenoids 11b, 11c, and 17a with the peak current threshold value Ith. The negative terminal of the comparator 54 is connected between the resistors 51 and 52, and the voltage Vp divided by the resistors 51 and 52 is input to the negative terminal. Such voltage Vp corresponds to the peak current threshold Ith. On the other hand, the + terminal of the comparator 54 is connected to the high side of the resistor 44 for current detection, and the voltage Vi corresponding to the energization current value of the electromagnetic solenoids 11b, 11c, and 17a is input to the + terminal. The output terminal of the comparator 54 is connected to the MOS drive circuit 55, and this MOS drive circuit 55 is connected to the gate terminal of the MOSFET 36. The MOS drive circuit 55 switches on / off of the MOSFET 36 in accordance with the injection signals # 2 and # 3, the decompression signal, and the output of the comparator 54. Specifically, the MOSFET 36 is turned on when the injection signals # 2 and # 3 and the decompression signal rise to H level. Thereafter, when the voltage Vi corresponding to the energization current value becomes larger than the voltage Vp corresponding to the peak current threshold Ith and the output of the comparator 54 is inverted, the MOSFET 36 is turned off.

  Here, since the voltage dividing circuit is configured as described above, it corresponds to the peak current threshold value when power is supplied to the electromagnetic solenoids 11b and 11c of the injector 11 and when power is supplied to the electromagnetic solenoid 17a of the pressure reducing valve 17. The voltage Vp to be changed changes. That is, when the electromagnetic solenoids 11b and 11c are energized to drive the injector 11, the transistor 53 is turned off, and the voltage Vp corresponding to the peak current threshold value Ith is applied to the resistors 52, 53a, and 53b. Determined by the resistance ratio (equivalent to 16 amps). On the other hand, when the electromagnetic solenoid 17a is energized to drive the pressure reducing valve 17, the transistor 53 is turned on, and the voltage Vp corresponding to the peak current threshold value Ith is the resistance ratio of the resistors 51 and 52a. (Corresponding to 10 amps).

  As described above, according to the embodiment described in detail, the following excellent effects can be obtained.

  When the pressure reducing valve 17 is driven, the control circuit 50 is configured to change the peak current threshold Ith. In the present embodiment, since the MOSFET 36 is switched on / off based on the peak current threshold value Ith, the peak current threshold value Ith is changed so that the energization current of the electromagnetic solenoid 17a is reduced. Thereby, the magnitude of the peak current flowing through the electromagnetic solenoid 17a of the pressure reducing valve 17 becomes smaller than the magnitude of the peak current flowing through the electromagnetic solenoids 11a to 11d of the injector 11. That is, it is possible to avoid an excessive current from flowing through the electromagnetic solenoid 17a. As a result, the drive current is reduced and the heat generation in the electromagnetic solenoid 17a is reduced.

  Particularly, in order to change the peak current threshold value Ith, two resistors 52a and 52b are connected in series in a voltage dividing circuit that includes resistors 51 and 52 and outputs a voltage Vp corresponding to the peak current threshold value Ith. The resistor 52 is connected to the transistor 52, the transistor 53 is connected in parallel with the resistor 52b, and a decompression signal is input to the base of the transistor 53. With this configuration, the transistor 53 is turned on / off when the injector 11 is driven and when the pressure reducing valve 17 is driven, the voltage dividing ratio of the voltage dividing circuit is changed, and the peak current threshold value Ith is changed. Further, according to the configuration described above, the peak current threshold value Ith is changed by the voltage dividing circuit including three resistors (resistors 51, 52a, 52b) and one switch element (transistor 53). Is advantageous.

  Further, by changing the peak current threshold Ith, the 16 ampere current required by the injector 11 as the peak current and the 10 ampere current required by the pressure reducing valve 17 are supplied appropriately. The That is, the driving current for 6 amperes is reduced, and the effect is great.

  The present invention is not limited to the embodiment described above, and may be implemented as follows.

  In the above embodiment, the peak current threshold value Ith is changed between when the injector 11 is driven and when the pressure reducing valve 17 is driven. FIG. 5 shows a change in the amount of opening of the pressure reducing valve 17 when a pressure reducing signal is raised to drive the pressure reducing valve 17. As shown in FIG. 5, the pressure reducing valve 17 is quickly opened as the fuel pressure in the common rail 12 increases. Therefore, when the pressure reducing valve 17 is driven, the peak current threshold value Ith is set smaller than when the injector 11 is driven, and the peak current threshold value Ith is further reduced as the fuel pressure in the common rail 12 increases. It is also good. As a result, it is possible to further reduce the drive current while ensuring the desired response.

  In the above embodiment, the peak current threshold Ith is changed between when the injector 11 is driven and when the pressure reducing valve 17 is driven. However, the configuration is not limited to this, and the hold current threshold is changed. May be. The magnitudes of the hold current for maintaining the open state of the injector 11 and the hold current for maintaining the open state of the pressure reducing valve 17 are different. For this reason, when the pressure reducing valve 17 is driven to open, it is preferable to change the hold current threshold value so that the hold current becomes smaller than when the injector 11 is driven to open. Here, since the hold current is supplied over a relatively long period in order to maintain the open state of the injector 11 and the pressure reducing valve 17, the effect of reducing the hold current is great.

It is a block diagram which shows schematic structure of a common rail type fuel injection system. It is a circuit diagram which shows the electric constitution of EDU. It is a figure for demonstrating switching operation | movement of MOSFET on / off. It is a circuit diagram which shows the electrical constitution of the control circuit of EDU. It is a figure which shows the change of the opening amount of a pressure-reduction valve.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Injector as fuel injection valve, 12 ... Common rail, 13 ... High pressure pump as fuel pump, 17 ... Pressure reducing valve, 20 ... Electronic control unit, 30 ... EDU, 44 ... Resistance as detection means, 50 ... Control circuit, 51, 52... Voltage dividing resistors, 53... Transistors as voltage dividing circuit switch elements, 54.

Claims (6)

A common rail that stores fuel in a high-pressure state, a fuel pump that pressurizes and supplies fuel to the common rail, an electromagnetically driven fuel injection valve that injects fuel stored in the common rail to the engine, and fuel in the common rail. Applied to a system comprising an electromagnetically driven pressure reducing valve for discharging,
The fuel injection valve is powered based on an injection signal generated according to the operating state of the engine to drive the fuel injection valve to open, and based on a pressure reduction signal generated when a fuel pressure reduction request is made. Provided with a drive circuit unit that feeds power to the pressure reducing valve and drives the pressure reducing valve to open,
The common rail type fuel injection device, wherein the drive circuit unit is configured such that a drive current when the pressure reducing valve is driven to open is smaller than a drive current when the fuel injection valve is driven to open. Detection means for detecting the magnitude of the drive current flowing through the fuel injection valve and the pressure reducing valve, and comparison means for comparing the magnitude of the drive current detected by the detection means with a predetermined current threshold, In the common rail fuel injection device configured to intermittently pass a current path through which the drive current flows according to a comparison result by the comparison unit,
2. The common rail fuel according to claim 1, wherein when the pressure reducing valve is driven to open, the current threshold is changed so that the driving current is smaller than when the fuel injection valve is driven to open. Injection device. In a common rail fuel injection device comprising a voltage dividing circuit comprising a first voltage dividing resistor and a second voltage dividing resistor, and using an output voltage of the voltage dividing circuit as the current threshold value,
The voltage dividing resistor of either the first voltage dividing resistor or the second voltage dividing resistor is configured by connecting two resistors in series, and is divided in parallel with one of the two resistors. A pressure circuit switch element is connected, and when the pressure reducing valve is driven to open, the voltage divider circuit switch element is turned on or off so that the current threshold value is smaller than when the fuel injection valve is driven to open. The common rail fuel injection device according to claim 2, wherein   3. The common rail fuel according to claim 1, wherein the drive circuit is configured to change a magnitude of the drive current in accordance with an operating state of the engine when the pressure reducing valve is driven to open. 4. Injection device. In the common rail fuel injection device configured to supply a predetermined opening-time drive current at the beginning of opening of the fuel injection valve and the pressure reducing valve,
5. The common rail system according to claim 1, wherein, when the pressure reducing valve is driven to open, the valve opening drive current is made smaller than when the fuel injection valve is driven to open. Fuel injection device. In the common rail fuel injection device configured to supply a valve opening maintaining current for maintaining the valve opening state of the fuel injection valve and the pressure reducing valve,
6. The common rail fuel according to claim 1, wherein when the pressure reducing valve is driven to open, the valve maintenance current is made smaller than when the fuel injection valve is driven to open. Injection device.

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