JP2001107784A - Injector driving circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently carry out pressure reduction of fuel pressure within a common rail while reducing processing load of a microcomputer. SOLUTION: In a common rail type fuel injection system, the microcomputer 151 generates drive signals of injectors 101 to 104 in response to an engine operation state, and determines whether pressure reduction of a common rail pressure is carried out or not. A drive circuit 100 turns ON transistors T10 to T40 and drives the injectors 101 to 104 based on the drive signals from the microcomputer 151. Upon request of cold blow from the microcomputer 151, the drive circuit 100 turns ON/OFF the transistors T10 to T40 in a small current region in which a fuel injection is not actually carried out, based on a current value flowing in a solenoids 101a to 104a of the injectors 101 to 104, and the cold blow by the injectors 101 to 104 is performed thereby reducing the common rail pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive circuit for an injector provided in an internal combustion engine, for example, in a common rail type fuel injection system, a pressure reduction control for appropriately reducing the fuel pressure in the common rail as required. And an injector driving circuit for performing the operation.

[0002]

2. Description of the Related Art In recent years, high-pressure fuel has been stored in a common rail,
A common rail fuel injection device that injects the stored high-pressure fuel from an injector is being embodied. In the fuel injection device, a high-pressure pump that is linked to the engine output shaft is provided. By driving the high-pressure pump, the fuel pressure in the common rail (common rail pressure) is increased to a target pressure required for fuel injection control. The common rail pressure is
Although the pressure is reduced by fuel injection by the injector, if the common rail pressure rises excessively, for example, noise due to abnormal combustion in the internal combustion engine or shift shock of the vehicle may occur, so it is necessary to solve such problems. It is necessary to reduce the common rail pressure.

[0003] Therefore, for example, a pressure reducing valve is provided on a common rail, and when the common rail pressure excessively rises, control such as opening the pressure reducing valve is performed. However, when the pressure reducing valve is provided, the cost increases and the common rail pressure (for example, 160 Mpa) becomes high, which may cause fuel leakage.

Therefore, conventionally, as a method of solving the above problem and reducing the common rail pressure by driving the injector, a microcomputer generates a continuous drive signal with a short time width so as not to perform fuel injection and drives the injector. Then, so-called idle driving control, in which high-pressure fuel in the common rail is returned to the fuel tank, has been proposed.
In other words, the injector is driven for idle driving by energizing the solenoid with a time width shorter than the delay time from when the solenoid of the injector is energized to when fuel injection is actually started.

[0005] In the above-mentioned idling control, it is necessary to generate a short pulse with high accuracy by a microcomputer in order to reliably perform an operation such as reducing the common rail pressure without performing fuel injection. In addition, since the pressure reduction due to the idle driving is small, the amount of pressure reduction per operation is small. Therefore, in order to reduce the common rail pressure (fuel pressure) with good responsiveness, it is necessary to perform many idle driving operations of the injector in a short period of time. However, in satisfying such accuracy requirements and performing idle driving control with higher responsiveness, if each control is processed by a microcomputer, the processing load increases, and other controls may be hindered.

Further, energy higher than a power supply voltage is stored in a capacitor by, for example, a DC-DC converter,
In the case of a device that energizes the solenoid by releasing the stored energy to increase the valve opening response of the injector, the amount of energy released is not constant, and if the amount of energy released is less than the required amount for idle driving, it is possible to perform appropriate pressure reduction Can not. Therefore, in order to carry out continuous blanking, the microcomputer monitors the charged amount of the capacitor at all times, waits until the charged amount is sufficiently secured, and generates and outputs a short pulse for subsequent blanking. must not. Therefore, it is difficult to reduce the common rail pressure efficiently in consideration of the arithmetic processing and the waiting time until each short pulse is output.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is an injector which can reduce the processing load on a microcomputer and reduce the fuel pressure in a common rail efficiently. It is an object to provide a driving circuit.

[0008]

The injector drive circuit according to the present invention is applied to a common rail type fuel injection system, and drives a injector in response to a drive signal from a microcomputer to perform fuel injection. Further, when a request to reduce the fuel pressure in the common rail (a request for idling) occurs, the drive circuit drives the injector to cause the fuel to leak from the common rail to the low pressure side of the fuel system,
The fuel pressure is preferably reduced without increasing the processing load on the microcomputer when the injector is driven.

The injector driving circuit according to the present invention is characterized in that the injector driving circuit includes a determination circuit which determines the end of one pressure reducing operation by driving the injector after the start of driving of the injector at the time of a pressure reducing request from the microcomputer. After the determination by the determination circuit, the injector driving for the next pressure reduction is restarted.

That is, at the time of the pressure reduction operation by driving the injector, the end of each pressure reduction operation is determined by the determination circuit in the injector drive circuit, and the injector drive for the next pressure reduction operation is prepared in accordance with the determination. Then, the subsequent injector drive is restarted. Then, this pressure reducing operation is repeatedly performed. Therefore, unlike the conventional device in which individual pressure reduction operations are performed after waiting for a drive signal (short pulse) transmitted from the microcomputer, the fuel pressure can be reduced efficiently. Also, unlike a conventional configuration in which a microcomputer generates a continuous drive signal with a short time width, the microcomputer determines only whether or not to reduce the fuel pressure in the common rail. Even if a large number of idle shots are required in a short period of time, the disadvantage that the processing load on the microcomputer increases is not caused.

Further, in the injector drive circuit according to the second aspect, when a pressure reduction request is issued from the microcomputer, the solenoid drive circuit operates in a current range small enough not to actually perform fuel injection based on a value detected by the current detection means. Of the switching means is turned on / off to drive the injector.

According to the present invention, during a pressure reducing operation by driving the injector, the current supplied to the solenoid is monitored in the injector drive circuit, and the injector is driven in a current range small enough not to actually perform fuel injection. Then, with the injector driving by such current control, the pressure reducing operation is repeatedly performed. Therefore, claim 1
Similarly to the invention of the third aspect, unlike the conventional apparatus in which individual pressure reducing operations are performed after waiting for a drive signal (short pulse) transmitted from the microcomputer, the fuel pressure can be reduced efficiently. Also, unlike a conventional configuration in which a microcomputer generates a continuous drive signal with a short time width, the microcomputer determines only whether or not to reduce the fuel pressure in the common rail. Even if a large number of idle shots are required in a short period of time, the disadvantage that the processing load on the microcomputer increases is not caused.

Further, in the case where the fuel pressure is reduced (idling) by driving the injector by time control as in the well-known technique, if the voltage level of the operating power source fluctuates, the controllability of the pressure reduction is deteriorated accordingly. However, good controllability can be ensured even when the operating power source fluctuates by driving the injector by current control and reducing the fuel pressure (idling) as in the present invention.

In the injector drive circuit according to the third aspect, when a request to reduce the fuel pressure is made, the switching means for driving the solenoid and the energy release are turned on to release the energy of the energy storage means to the solenoid, and thereafter, the current detection is performed. When the value detected by the means reaches a predetermined value in a current range in which fuel is not actually injected, the switching means for driving the solenoid is turned off. Further, thereafter, when it is determined by the boosting means that the energy amount of the energy storing means is equal to or more than the predetermined amount, the energy storing means causes the next energy release.

According to the third aspect, energy release, current monitoring, energization cutoff, and energy replenishment to the energy storage means by the energy storage means are repeatedly performed, and pressure reduction by the injector drive is continuously performed at an optimum short cycle. You. In this case, the step-up energy is released from the energy storage means, and the decompression is performed instantaneously, so that the number of times of decompression within a limited short period can be increased.

Further, in the injector driving circuit according to the present invention, a signal indicating a request to reduce the fuel pressure from the microcomputer and a signal indicating that the energy amount of the energy storage means exceeds a predetermined amount are input. A logic circuit is provided, and the logic circuit outputs a logical product of the two input signals as a signal that triggers energy release by energy storage means. Therefore, the energy is released from the energy storage unit after a sufficient amount of energy is secured by the energy storage unit, and at this time, the fuel pressure is appropriately reduced.

In the injector drive circuit according to the present invention, when a fuel pressure reduction request is made, switching means for driving the solenoid and power supply are turned on to apply a power supply voltage to the solenoid. When the detected value reaches a predetermined value in a current range in which fuel injection is not actually performed, the solenoid driving switching means is turned off to cut off the solenoid energization. Immediately after the power is cut off, the switching means for driving the solenoid is turned on again to apply the power supply voltage to the solenoid.

According to the fifth aspect, the application of the power supply voltage to the solenoid, the current monitoring, and the cutoff of the current supply are repeatedly performed, and the pressure reduction by the driving of the injector is continuously performed at an optimum short cycle. In this case, the next energization is started immediately after the energization of the solenoid is cut off, so that an efficient pressure reducing operation can be performed in a limited short period.

The injector drive circuit according to the present invention is provided with a logic circuit for inputting a signal indicating a request for reducing the fuel pressure from the microcomputer and a signal indicating that a current of a predetermined value or more has flowed through the solenoid. The logic circuit inputs a signal indicating a pressure reduction request and outputs a signal that triggers energization of the solenoid by the power supply voltage when a current value flowing through the solenoid is smaller than a predetermined value.

That is, since the energizing current of the solenoid is initially 0 when the signal indicating the pressure reduction request is transmitted from the microcomputer, the logic circuit outputs a signal for triggering the energizing of the solenoid. Is started. Also, after the solenoid is energized, when the energization is interrupted and the current value becomes 0 again, this triggers the next energization of the solenoid. By continuously energizing the solenoid in this way, the fuel pressure is properly reduced.

[0021] In the injector driving circuit according to the present invention, the distribution circuit inputs a signal for triggering the energization of the solenoid when the fuel pressure is reduced, and alternately distributes the signal to the plurality of injectors. According to the present invention, the same injector is not driven every time to reduce the fuel pressure, and the load on each injector can be made uniform.

In the injector driving circuit according to the present invention, when the fuel pressure is reduced, the injectors are simultaneously driven for a plurality of injection groups, so that the fuel pressure can be simultaneously reduced (blank firing) by the plurality of injectors. Therefore, the fuel pressure can be reduced quickly,
Responsiveness of decompression is further improved.

In the injector drive circuit according to the ninth aspect, a drive signal of an injector that is turned on in all cylinders when a request for reducing fuel pressure is received from a microcomputer, and the fuel pressure is reduced by the drive signal for turning on all cylinders. And a request signal generation circuit for generating a pressure reduction request signal. Therefore, even when the microcomputer and the injector drive circuit are connected only by the signal line for the injector drive signal, the fuel pressure can be appropriately reduced. In addition, there is no need to add a signal line for a pressure reduction request other than the signal line for the injector drive signal, and the configuration can be simplified.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. The present embodiment is embodied as a common rail fuel injection system for a vehicle-mounted four-cylinder diesel engine.

(First Embodiment) FIG. 1 is a configuration diagram showing an outline of the present fuel injection system. In this system, the high-pressure pump 11 has a well-known configuration in which the amount of discharged fuel is variable. The high-pressure pump 11 pressurizes the fuel pumped from the fuel tank 12 by reciprocating a piston interlocking with an engine output shaft (not shown) to increase the pressure. The pressurized fuel is supplied to the common rail 13. The common rail 13 stores the high-pressure fuel supplied from the high-pressure pump 11 at a predetermined fuel pressure. The common rail 13 is provided with a pressure sensor 14 for detecting the internal fuel pressure (common rail pressure). Electromagnetically driven injectors 101, 102, 103, 104
Is provided for each cylinder and injects high-pressure fuel supplied from the common rail 13.

The configuration of one injector 101 will be described. The injector 101 includes an injector body 16 and a solenoid valve 17. High-pressure fuel from the common rail 13 is supplied to the injector body 16 and the solenoid valve 1.
7 is supplied. In the injector body 16, a needle valve 19 is disposed in the fuel chamber 18. The needle valve 19 is connected to a piston 20 and is urged by a spring 21 in a direction to close the injection port.

The solenoid valve 17 includes a housing 22, a cylindrical outer valve 23 that slides in the housing 22 in the vertical direction in the drawing, and an inner valve 24 housed in the outer valve 23. The housing 22 is provided with a first port (fuel intake port) 25, a second port 26, and a drain port 27. The first port 25 is provided on the common rail 13, the second port 26 is provided on a space above the piston 20, The drain ports 27 are connected to the drain tanks 32, respectively. The outer valve 23 is provided with a port 28 corresponding to the first port 25 and a port 29 corresponding to the second port 26.

Here, the outer valve 23 is urged downward in the figure by a spring 31. When the solenoid 101a is not energized, the outer valve 23 is seated on the inner peripheral surface of the housing 22 and the space between the ports 26 and 27 is formed. While being shut off, the first port 25 and the second port 26 of the housing 22 are communicated via the ports 28 and 29 of the outer valve 23 (the state shown). Accordingly, high-pressure fuel from the common rail 13 is applied to the upper surface of the piston 20 through these ports 25, 28, 29, and 26, and the needle valve 19 is pressed downward by this pressure to keep the injection port closed. .

When the solenoid 101a is energized, the outer valve 23 is sucked and rises, and the inner peripheral surface of the outer valve 23 comes into contact with the outer peripheral surface of the inner valve 24.
The connection between ports 25 and 26 is shut off. At this time, since the ports 26 and 27 are communicated with each other, the pressure applied to the piston 20 is increased through the ports 26 and 27 to the drain tank 32.
Leaks to the side (low pressure side). Thereby, the needle valve 1
9 rises by the high-pressure fuel in the fuel chamber 18, and the injector 101 opens the injection port to inject the fuel. When the energization of the solenoid 101a is cut off, the outer valve 23 returns to the original position, and the fuel injection is stopped.

ECU (Electric Control Unit) 150
Includes a well-known microcomputer (microcomputer) 151 including a CPU, various memories, and the like. Microcomputer 151
Generates an injection signal for each cylinder based on engine operation information detected by various sensors such as an engine speed Ne, an accelerator opening ACC, an engine coolant temperature THW, and outputs the injection signal to a drive circuit (EDU: Electric Driver Unit) 100. I do.
Further, the microcomputer 151 controls the driving of the high-pressure pump 11 based on the detection result of the pressure sensor 14 so that the common rail pressure is maintained at a predetermined target value. Furthermore, microcomputer 1
Reference numeral 51 denotes a predetermined pressure reducing condition (idling condition) for outputting an idling request signal Qe indicating whether or not to execute the idling to the drive circuit 100 to reduce the common rail pressure.
Is established, a Qe signal for executing the idle driving is output to the drive circuit 100.

The drive circuit 100 receives the injection signal from the ECU 150 and energizes the solenoid of each injector.
The injectors 101 to 104 are driven. According to the drive circuit 100, the injector 101 is used for fuel injection.
To 104 are driven with a large current at the beginning of the injection, and thereafter,
Driven by constant current. The drive circuit 100 includes the ECU 1
In response to the idling request signal Qe from the controller 50, the common rail pressure is reduced.

Next, the basic configuration of the drive circuit 100 will be described with reference to the electric circuit diagram of FIG. 2, and the basic operation of the drive circuit 100 will be described with reference to the time chart of FIG. However, FIG. 2 does not disclose the configuration of the idle driving control which is the gist of the present invention, and shows only the other basic configuration.

The drive circuit 100 shown in FIG. 2 is based on the premise that fuel injection of two cylinders is overlapped and injectors of each cylinder are simultaneously driven, that is, so-called multiple injection is performed. Each of 101 to 104 is driven by being divided into two cylinders. In this case, the injector 10
1 and 103 are connected to the common terminal COM1 of the drive circuit 100 as the same injection group, and the injectors 102 and 10
4 are connected to the common terminal COM2 of the drive circuit 100 as the same injection group. Each injection group may be constituted by injectors that are not driven at the same time, and the grouping is determined by the design specifications of the engine, such as which cylinder is to perform multiple injection. In the case of a six-cylinder engine other than the four-cylinder engine, for example, the injector of each cylinder may be divided into three cylinder injection groups.

A series circuit including an inductor L11, a transistor T13, and a current detection resistor R00 is provided between the battery power supply line (+ B) and GND.
A self-excited oscillation circuit 110 is connected to the gate terminal of the transistor T13.
The drive is controlled by 0. A diode D1 for backflow prevention is provided between the inductor L11 and the transistor T13.
3, one end of the capacitor C10 is connected, and one end of the capacitor C20 is connected via a diode D23 for preventing backflow. These capacitors C1
The other ends of 0 and C20 are connected to a connection point between the transistor T13 and the current detection resistor R00. These inductor L11, transistor T13, current detection resistor R00, oscillation circuit 110, diodes D13, D23, and capacitors C10, C20 constitute a DC-DC converter circuit. Among them, the inductor L11, the transistor T13, the current detection resistor R00, and the oscillation circuit 110 correspond to the booster, and the capacitors C10 and C20 correspond to the energy storage.

The capacitor C10 is an energy storage capacitor dedicated to the injectors 101 and 103 which are the injection group on the COM1 side.
Is an injector 10 which is an injection group on the COM2 side.
It is an energy storage capacitor dedicated to 2,104.

When the transistor T13 is turned on / off, the capacitor C1 is connected through the diodes D13 and D23.
0 and C20 are charged. Thereby, each capacitor C
10, C20 is charged to a voltage higher than the battery voltage + B. In such a case, the transistor T13 is turned on / off by the oscillation circuit 110 while the charging current is monitored by the current detection resistor R00, so that the capacitor C1
0 and C20 are charged in an efficient cycle. The charging voltage of the capacitors C10 and C20 is, for example, 100V.

The drive IC 120 is connected to input terminals # 1 to # 4, and the drive IC 120 receives signals from the microcomputer 151 through the terminals to the first cylinder (# 1) to the fourth cylinder (#).
Each injection signal of 4) is taken in.

The transistors T12 and T22 are # 1 to #
4 is turned on temporarily at the timing when the injection signal of No. 4 is inverted from L level (logic low level) to H level (logic high level), and is a transistor for supplying the energy stored in the capacitors C10 and C20 to the injectors 101 to 104. is there. More specifically, the transistor T12 is provided between the capacitor C10 and the common terminal COM1, and when the transistor T12 is turned on by the driving IC 120, the energy stored in the capacitor C10 becomes COM.
It is supplied to the injectors 101 and 103 on one side. The transistor T22 is provided between the capacitor C20 and the common terminal COM2, and when the transistor T22 is turned on by the driving IC 120, the energy stored in the capacitor C20 is reduced by the injectors 102, 1 on the COM2 side.
04. Such capacitors C10 and C20
With this energy supply, a large current flows as a driving current for the injector, and accordingly, the valve opening response of the injector is improved.

On the low side of each of the injectors 101 to 104, terminals INJ1, INJ2, I
Transistors T10 and T2 via NJ3 and INJ4
0, T30 and T40 are connected, and the driving IC 12
When the injection signals from # 0 to # 1 to # 4 are respectively supplied, the transistors T10 to T
40 turns on. The transistors T10 and T30 and the transistors T20 and T40 form the same injection group, and each of the transistors is grounded via a current detection resistor R10 and R20 for each group. The drive current flowing through the injectors 101 to 104 is detected by the current detection resistors R10 and R20, and the detection result is taken into the drive IC 120.

The terminals COM1 and COM2 are connected to a battery power line (+ B) via diodes D11 and D21 and transistors T11 and T21, respectively. In such a case, the driving IC 120 is connected to the injector 1
01 to 104 according to the drive current flowing through the transistor T
11, ON / OFF control of T21. Thereby, + B
Supplies a constant current to the injectors 101-104. The diodes D12 and D22 are feedback diodes for constant current control, and the current flowing through the injectors 101 to 104 when the transistors T11 and T21 are turned off is returned via the diodes D12 and D22.

In the actual operation, the transistor T12 or T22 is first turned on at the same time as the rise of the injection signal which is the drive command, and after a large current flows as the drive current for the injectors 101 to 104 by the energy supply of the capacitors C10 and C20. , Followed by the transistor T
A constant current flows through 11 or T21, and the driving current is cut off as the injection signal falls. Note that when supplying energy to the capacitors C10 and C20, the diodes D11 and D21 prevent sneak from the high potential COM1 and COM2 terminals to the + B side.

In addition, of the injectors 101 to 104, the injectors 10 constituting one injection group
1 and 103 are connected to the capacitor C10 via the diodes D10 and D30, and the back electromotive force energy generated in the injectors 101 and 103 due to the cutoff of the current is supplied to the capacitor C1 via the diodes D10 and D30.
Collected to 0. Further, the injectors 102 and 104 constituting the other injection group include diodes D20 and D20.
The counter electromotive energy generated in the injectors 102 and 104 due to the cutoff of the current is recovered to the capacitor C20 through the diodes D20 and D40.

Next, the operation of the drive circuit 100 of FIG. 2 will be described with reference to the time chart of FIG. FIG. 3 shows an example in which pilot injection and subsequent main injection are performed in the first cylinder (# 1).

Before the pilot injection shown in FIG. 3, the capacitor C10 is fully charged, and when the injection signal of # 1 rises to the H level, the transistor T10
10 turns on and at the same time, the transistor T1
2 is turned on for a predetermined time ta, and the energy stored in the capacitor C10 is changed to the solenoid 101a of the injector 101.
Supplied to Accordingly, a large current flows through the solenoid 101a at the beginning of the pilot injection, and the valve opening response of the injector 101 is accelerated.

After the energy is supplied by the capacitor C10, the transistor T1 is subsequently turned on in accordance with the drive current (INJ1 current) detected by the current detection resistor R10.
1 is turned on / off, and a constant current is supplied to the solenoid 101a via the diode D11. This allows
The injector 101 is held in a valve-open state.

When a predetermined time tb has elapsed from the start of the pilot injection, the on / off of the transistor T13 starts, and the capacitor C10 of the DC-DC converter circuit is started.
Is started.

Thereafter, when the # 1 injection signal falls to the L level, the transistor T10 is turned off, and the solenoid 1
01a is shut off. The back electromotive force energy generated when the power is cut off is recovered through the diode D10 and stored in the capacitor C10.

After the solenoid 101a is de-energized, when the drive current of the injector (INJ1 current) attenuates to a predetermined valve-closing level that can overcome the urging force of the return spring, the injector 101 closes and the injector 10 closes.
1 ends the pilot injection. And then
When the capacitor C10 reaches a fully charged state, the on / off of the transistor T13 is stopped.

Thereafter, the same operation is performed in the main injection. That is, the energy stored in the capacitor C10 is supplied to the solenoid 101a at the beginning of the main injection when the injection signal of # 1 is turned on, and subsequently, the solenoid 101a is driven with a constant current. Thereafter, when the # 1 injection signal is turned off and the INJ1 current is attenuated, the main injection by the injector 101 is terminated. The capacitor C10 is charged by the DC-DC converter circuit, and supplies the back electromotive force energy generated when the solenoid 101a is turned off to the diode D10.
Collect through.

On the other hand, in the present fuel injection system, when performing idle driving for reducing the common rail pressure, the current supplied to the solenoid is controlled. The principle of the operation is described in the structure of the injector 101 in FIG. This will be described with reference to FIG. 4 and the injector operating characteristics.

That is, in the current rising process in the minute current range, the outer valve 23 on the solenoid valve 17 side starts lifting at the current value i1 and reaches the predetermined valve opening position when the current value becomes i2. . At this time, as the outer valve 23 is lifted, the high-pressure fuel acting on the upper surface of the piston 20 is moved to the low-pressure side (the drain tank 3 in FIG. 1).
The leak occurs in 2), and the common rail pressure is reduced accordingly. However, at the current values i2 to i3, the needle valve 19 on the injector body 16 side still does not lift and the injector 1
01 is not performed.

When the energizing current reaches the current value i3,
The needle valve 19 starts lifting. Thereby, fuel is injected from the injector 101. Normally, fuel injection by the injector 101 is performed in a current range of i4 or more in the drawing.

In short, in the present embodiment, the needle valve 19 is opened by controlling the current supplied to the injector 101 in the range of i4 or more, so that the injector 1
The fuel injection of 01 to 104 is performed. In addition, the i
By controlling within the range of 2-3, the needle valve 1
The injector 101 is driven for idling without opening the valve 9.

Next, the configuration of the drive circuit 100 for realizing the current control for the above-mentioned idling will be described with reference to FIG. However, FIG. 5 shows only the configuration of the injectors 101 and 103 among the two injection groups.

In FIG. 5, the positive terminal of the comparator 201 receives the charging voltage of the capacitor C10, and the negative terminal receives the constant voltage Vcc and the threshold voltage Vf1 generated by the voltage dividing resistors R1 and R2. . Comparator 2
01 indicates that the charging voltage of the capacitor C10 is equal to the threshold voltage V
If f1 or more, an H-level signal is output. here,
Threshold voltage Vf1 is set to a value near full charge of capacitor C10.

A voltage corresponding to the current flowing through the injector 101 or 103 is input to the + terminal of the comparator 202, and the constant voltage Vcc and the voltage dividing resistor R are input to the-terminal.
3, a threshold voltage Vf2 generated by R4 is input. The comparator 202 outputs an H-level signal when the voltage value corresponding to the current supplied to the injector 101 or 103 is equal to or higher than the threshold voltage Vf2. Here, the threshold voltage Vf2 may be a value corresponding to the current range of i2 to i3 in FIG. 4 (however, the current range of i1 to i2 can be used).

The output of the comparator 201 is input to the flip-flop 203 as a set (S) input, and the output of the comparator 202 is input as a reset (R) input. That is, the flip-flop 203
When the output of the comparator 201 becomes H level, the output Q
Is at the H level, and when the output of the comparator 202 is at the H level, the output Q is at the L level.

The AND circuit 204 receives the idle request signal Qe transmitted from the microcomputer 151 and the Q output of the flip-flop 203, and outputs the output to the frequency dividing circuit 2.
05 is input. The frequency dividing circuit 205 is configured by a D flip-flop, and AND
The output of the circuit 204 is input, and / Q is input as the data input D.
An output (an inverted signal of the Q output) is input.

The AND circuit 206 includes an AND circuit 204
And the Q output of the frequency dividing circuit 205 are input to the OR circuit 207 together with the # 1 injection signal. The output of the AND circuit 204 and the / Q output of the frequency dividing circuit 205 are input to the AND circuit 208, and the output is input to the OR circuit 209 together with the # 3 injection signal. Then, the output of the OR circuit 207 drives the transistor T10, and the output of the OR circuit 209 drives the transistor T30.

The T12 driving IC 210 is connected to the OR circuit 20.
7 and 209, the transistor T12 is turned on for a predetermined time ta after the rise of the output. However, the T12 driving IC 210 may be the driving IC 120 of FIG. 2 itself, and the configuration for turning on the transistor T12 for a predetermined time ta is the same as the driving IC 120.

Here, the idling determination processing performed by the microcomputer 151 will be described with reference to the flowchart of FIG. In FIG. 6, first, in step 110, it is determined whether or not the fuel is cut off.
At 20, it is determined whether the common rail pressure is greater than the control target pressure. Steps 110 and 120 are both YES
In step 130, the process proceeds to step 130, in which the high-pressure pump 11 stops fuel pumping, and in step 140, the idling request signal Qe is set to "H". Step 11
If any of 0 and 120 is NO, the routine proceeds to step 150, where the idling request signal Qe is set to "L".

That is, the microcomputer 151 determines whether or not the pressure-reducing condition (steps 110 and 120) by idling is satisfied. When the pressure-reducing condition is satisfied, Qe = H is set.
The driving circuit 100 is instructed to perform the idle driving. When the pressure reduction condition is not satisfied, Qe = L is set, and the injector 101
The common rail pressure is controlled to the target pressure by reducing the common rail pressure by the fuel injection of ~ 104 or by adjusting the fuel pumping amount of the high pressure pump 11.

FIG. 7 is a time chart for explaining the operation of the idle driving control by the drive circuit 100. FIG. 7
At time t1, the predetermined pressure reduction condition is satisfied, and the microcomputer 151 raises the idle hit request signal Qe to the H level.

Before time t1, the capacitor C10 is almost fully charged, so that the comparator 20
1 is at the H level and the flip-flop 2
The Q output of 03 goes to the H level. At this time, the output of the AND circuit 204 remains at the L level.

When the idling request signal Qe rises to H level at time t1, the output of the AND circuit 204 goes to H level, and the H level signal is input to the C terminal of the frequency dividing circuit 205. At this time, the / Q signal of the frequency dividing circuit 205 becomes H
If so, the Q signal of the same frequency dividing circuit 205 rises to H level. Then, the two inputs of the AND circuit 206 both become H level, the output thereof becomes H level, and the output of the OR circuit 207 also becomes H level. Therefore,
The transistor T1 is output by the H level signal of the OR circuit 207.
0 turns on. Also, the T12 driving IC 210 is
Upon receiving the H level output of the R circuit 207, the transistor T12 is turned on for a predetermined time ta. As a result, the capacitor C10 is discharged during the period ta during which the transistor T12 is turned on, and the solenoid 101a of the injector 101 is energized.

At time t2 when the current flowing through the solenoid 101a (R10 detection current) reaches a current value corresponding to the threshold voltage Vf2 of the comparator 202, the comparator 202
Goes high, and the flip-flop 203 is reset. Thereby, the flip-flop 203
The output of the AND circuit 204 and the output of the AND circuit 204 become L level, and accordingly, the AND circuit 206 and the OR circuit 20
7 is also at the L level. Therefore, at this time t2, the transistor T10 is turned off and the solenoid 10
1a is shut off.

During the period from time t1 to t2, the solenoid 1
Since 01a is energized in a current range in which fuel injection is not actually performed (current range of i2 to i3 in FIG. 4), the injector 101 is driven to idle, and the common rail pressure is reduced.

After discharging the capacitor C10, the DC-D
Charging by the C converter is performed. And at time t3
When the capacitor C10 is almost fully charged and the charged voltage reaches the threshold voltage Vf1, the flip-flop 203 is set, and the AND circuit 204 is set.
Output goes high again. At time t3, the Q signal of the frequency divider 205 is at the L level, and the / Q signal is at the H level.
The output of the AND circuit 208 and the output of the OR circuit 209 go high accordingly. Therefore, the transistor T30 is turned on.

At time t3 to t4, time t1
Similarly to t2, the transistor T12 is turned on, the capacitor C10 is discharged, and the solenoid 103a is energized until the energizing current of the solenoid 103a reaches a current value corresponding to the threshold voltage Vf2 of the comparator 202. That is, the energization is started in a state where the capacitor C10 is almost fully charged (time t3), and the energization is terminated when the current required for idling flows (time t4).

In the period from time t3 to t4, similarly to t1 and t2, the solenoid 103a is energized in a current range where fuel is not actually injected (current range of i2 to i3 in FIG. 4). 103 is driven for idle driving, and the common rail pressure is reduced.

Thereafter, energization is started in a state where the capacitor C10 is almost fully charged (the flip-flop 203 is set). After the energization is started, energization is terminated when a current required for idling flows (flip-flop). Are reset by the injectors 101 and 103 alternately.

Although not shown, the injector 1
The same circuit as that shown in FIG. 5 is also provided in the injection groups 02 and 104, and as described in the time chart of FIG. 7, when Qe = H, the capacitor C20 is discharged for a predetermined time, and the solenoid 102a or 104a is discharged. It is energized. In this energization, the energization current is i2 in FIG.
To i3, the injector 102
Or, 104 is driven for idle driving, and the common rail pressure is reduced. After the capacitor C20 is discharged, charging is performed by the DC-DC converter. When the capacitor C20 is charged to a substantially fully charged state, the capacitor C20 is discharged again. Thereafter, the injectors 102 and 104 are alternately driven, and the idling is continuously repeated.

FIG. 8 shows injectors 10 for all four cylinders.
The state of idle driving by 1 to 104 is shown. Although not shown, in FIG. 8, during the period of Qe = H, the injection signals # 1 to # 4 are all held at the L level.

During the period when Qe = H, # 1 and #
In the third injection group, the transistors T10 and T30 are alternately turned on, the capacitor C10 is discharged in synchronization with this, and the solenoids 101a and 103a are alternately energized. Then, with each energization, the high-pressure fuel leaks to the low-pressure side, and the common rail pressure is reduced. On the other hand,
Similarly, in the injection groups of # 2 and # 4, similarly, the transistors T20 and T40 are alternately turned on, and the capacitor C20 is discharged in synchronization therewith, and the solenoids 102a and 102
4a are alternately energized. Then, with each energization, the high-pressure fuel leaks to the low-pressure side, and the common rail pressure is reduced.

After the idle request signal Qe goes low, the output of the AND circuit 204 falls to the low level.
To T40 are stopped.

In this embodiment, the transistor T1
0 to T40 correspond to switching means for driving the solenoid, and the transistors T12 and T22 correspond to switching means for discharging energy. Also, comparator 2
02 corresponds to the current detection means and the determination circuit, and the comparator 201 corresponds to the energy amount determination means. Furthermore,
The frequency dividing circuit 205 corresponds to the distribution circuit.

According to the present embodiment described in detail above, the following effects can be obtained. (A) The microcomputer 151 outputs the idle driving request signal Qe indicating whether or not to execute the idle driving to the drive circuit 100,
The drive circuit 100 turns on / off the transistors T10 to T40 in a current range small enough not to actually perform the fuel injection based on the current flowing through the solenoids 101a to 104a, and drives the injectors 101 to 104. Therefore,
Unlike a conventional device that performs a number of idle shots after waiting for a drive signal transmitted from a microcomputer, the common rail pressure can be reduced efficiently. Further, unlike the conventional configuration in which the microcomputer generates a continuous drive signal having a short time width, the microcomputer determines only whether or not to execute the blanking, so that a large number of blanking is required in a short period of time. In such a case, there is no inconvenience that the processing load on the microcomputer increases.

(B) In the case where the injector is driven by time control to perform idle driving as in the known technique, if the energy stored in the capacitors C10 and C20 fluctuates, there is a concern that the controllability of idle driving may be deteriorated accordingly. But
By driving the injector by current control and performing idle driving, even if the energy stored in the capacitors C10 and C20 fluctuates, the idle driving is reliably performed, and the controllability is improved.

(C) In response to a request for idling, the capacitor C1
Since charging and discharging are repeatedly performed while monitoring the charging voltages of 0 and C20, a large number of idle shots can be continuously performed at an optimal short cycle, and the pressure reduction response of the common rail pressure can be improved. In addition, since the energy obtained by boosting + B is released from the capacitors C10 and C20, and the pressure is reduced instantaneously, the number of pressure reductions in a limited short period can be increased.

(D) An AND circuit 204 for inputting the idling request signal Qe from the microcomputer 151 and a signal indicating completion of charging of the capacitors C10 and C20 is provided. To give permission. Therefore, after the capacitors C10 and C20 are sufficiently charged, the capacitors C10 and C20 are not charged.
Is discharged, and the common rail pressure is properly reduced.

(E) A frequency dividing circuit 205 is provided to alternately distribute signals for triggering solenoid energization to injectors of the same injection group.
The same injector will not be driven idle every time,
The load on each injector can be made uniform.

(F) Since the injectors are simultaneously driven for a plurality of injection groups upon a request for an idle shot, an idle shot can be simultaneously performed by a plurality of injectors. Therefore, the common rail pressure can be quickly reduced, and the responsiveness of the reduced pressure is further improved.

(Second Embodiment) Next, a second embodiment of the present invention will be described. In the above-described first embodiment, the injector is idled by using the energy stored in the capacitors C10 and C20. In the present embodiment, the injector is idled without using the energy stored in the capacitors C10 and C20. Other techniques for implementing are disclosed. Hereinafter, a description will be given focusing on differences from the above-described first embodiment.

FIG. 9 is a circuit diagram showing a main configuration of drive circuit 100. In FIG. 9, a gate circuit 301 includes:
The gate request signal Qe and an inverted signal of the output of the comparator 202 are input, and the gate circuit 301 outputs an H level signal when the idle request signal Qe is at the H level and the output of the comparator 202 is at the L level. I do. The frequency dividing circuit 205 uses the output of the gate circuit 301 as a clock input C. Configuration of frequency divider circuit 205 and logic circuits 206 to
The configuration of 209 is the same as that of FIG. Comparator 2
02 is the injector 101 or 10 as in FIG.
If the energizing current of No. 3 is equal to or higher than the threshold voltage Vf2 corresponding to the current range of i2 to i3 in FIG. 4, an H level signal is output.

The T11 drive IC 302 may be the drive IC 120 of FIG. 2 itself, and is a circuit for turning on / off the transistor T11 and driving the injector at a constant current during normal fuel injection, following the discharge of the capacitor C10. . Further, the T11 driving IC 302 captures the idle hit request signal Qe, and when Qe = H, outputs an H level signal to turn on the transistor T11.

FIG. 10 is a time chart for explaining the operation of the idling control by the drive circuit 100 shown in FIG. When the idling request signal Qe rises to the H level at time t11, the transistor T11 is turned on by the T11 driving IC 302, and the on state is maintained thereafter.

At time t11, since the output of the comparator 202 is at L level, the gate circuit 3
01 is at the H level, and the H level signal is
05 is input to the C terminal. At this time, if the / Q signal of the frequency dividing circuit 205 is at the H level, the Q signal of the frequency dividing circuit 205 is raised to the H level. Then, the AND circuit 2
06 are both at the H level and the output is at the H level.
Level, and the output of the OR circuit 207 also becomes H level. Accordingly, the transistor T10 is turned on, and the solenoid 101a is energized by power supply from + B.

Thereafter, the energizing current (R10 detection current) of the solenoid 101a rises, and at time t12 when the current reaches a current value equivalent to the threshold voltage Vf2 of the comparator 202, the output of the comparator 202 becomes H level, The output of gate circuit 301 falls to L level.
Therefore, at this time t12, the AND circuit 206 and the O
The output of the R circuit 207 also becomes L level, and the transistor T
10 is turned off, and the energization of the solenoid 101a is cut off.

When the solenoid is energized during the period from time t11 to time t12, the energizing current is controlled in a current region in which fuel injection is not actually performed (i3 or less in FIG. 4). It is driven and the common rail pressure is reduced.

When the power supply is cut off at time t12, R1
Since the detection current of 0 becomes 0 and the output of the comparator 202 goes to L level, the output of the gate circuit 301 instantaneously returns to H level, the Q signal of the frequency dividing circuit 205 goes to L level, and the / Q signal goes to H level. Invert to level. Then, the two inputs of the AND circuit 208 both become H level, the output thereof becomes H level, and the output of the OR circuit 209 also becomes H level. Therefore, the transistor T30 is turned on, and + B
, The solenoid 103a is energized.

Thereafter, at time t13 when the current supplied to the solenoid 103a (R10 detection current) reaches a current value equivalent to the threshold voltage Vf2 of the comparator 202, the output of the gate circuit 301 goes low for a short period of time, and the solenoid 103a The energization is cut off, and immediately thereafter, the transistor T10 is turned on again.

Thereafter, the transistors T10 and T30
Are alternately turned on, and the solenoid 101a or 103a is energized by + B.

FIG. 11 shows an injector 1 for all four cylinders.
The state of the idle driving by 01 to 104 is shown. Although illustration is omitted, in the period of Qe = H in FIG.
Each of the injection signals of No. 4 is held at the L level.

During the period when Qe = H, # 1 and #
In the third injection group, the transistors T10 and T30 are alternately turned on, and in synchronization with this, the solenoids 101a and 103a are alternately energized by + B. Then, with each energization, the high-pressure fuel leaks to the low-pressure side, and the common rail pressure is reduced. On the other hand, in the injection groups # 2 and # 4, similarly, the transistors T20 and T40 are alternately turned on, and in synchronism therewith, the solenoids 102a and 104a are alternately energized by + B. Then, with each energization, the high-pressure fuel leaks to the low-pressure side, and the common rail pressure is reduced.

After the idle request signal Qe goes to L level, the output of the gate circuit 301 falls to L level.
To T40 are stopped.

As described above, according to the second embodiment, the first
Similarly to the third embodiment, the common rail pressure can be reduced efficiently, and even when a large number of idle shots are required in a short period of time, the disadvantage that the processing load of the microcomputer is increased does not occur. In addition, since the energizing current is controlled in a current range small enough not to actually perform the fuel injection and the injectors 101 to 104 are idled, the power supply voltage +
Even if B fluctuates, the blanking is reliably performed, and the controllability is improved.

In addition, the solenoids 101a-104
a while the current flowing through the injector 101 is monitored.
Since the idle driving of 104 is continuously performed at an optimum short cycle, an efficient pressure reducing operation can be performed in a limited short period. In particular, when the idling request signal Qe is turned on and the output of the comparator 201 is turned off, the gate circuit 3 outputs a signal that triggers energization of the solenoid by the power supply voltage.
Since 01 is provided, the solenoid is continuously energized, and the fuel pressure is properly reduced. Unlike the first embodiment, when the solenoid is energized, the capacitor C
Since there is no need to wait for the completion of charging of C10 and C20, there is an advantage that a circuit for monitoring the charging voltage (comparator 201 in FIG. 5) is not required and the solenoids 101a to 104a can be energized continuously without interruption. .

(Third Embodiment) In the present embodiment,
Of the various signal lines between the ECU 150 and the drive circuit 100, the signal line for the idling request signal Qe is eliminated, and the idling request signal Qe is generated in the drive circuit 100 from the injection signals # 1 to # 4. A configuration example will be described.

FIG. 12 shows the configuration of a signal input circuit 400 provided at the input section of the drive circuit 100. The signal input circuit 400 corresponds to the request signal generation circuit of the present invention. # Sent from the ECU 150 side to the gate circuit 401
All the injection signals of # 1 to # 4 are input and the gate circuit 4
01 outputs an H level signal when all the inputs are at H level. In this case, when the microcomputer 151 requests idle driving for reducing the common rail pressure, the microcomputer 151 performs # 1 to # 4.
Are set to the H level. As a result, the signal input circuit 400 (gate circuit 401) outputs an H level signal as the idling request signal Qe.

Gate circuits 411, 412, 413, 41
4 receives the inverted signal of the gate circuit 401 and the injection signals of # 1 to # 4, respectively. When the output of the gate circuit 401 is at the L level, that is, when the idle firing request is not made, these gate circuits 411 to 414 are input. Directly outputs the injection signals # 1 to # 4 as the injection signals # 1 ′ to # 4 ′.
Further, when the output of the gate circuit 401 is at the H level, that is, at the time of the idle driving request, the gate circuits 411 to 414 operate as # 1 ′.
噴射 # 4 ′ are all output as L level. The idling request signals Qe and # 1 ′ to # thus generated
The 4 ′ injection signal is applied to the idling or fuel injection control in the drive circuit 100 described above.

As described above, according to the third embodiment, # 1 to #
4 other than the signal line for the drive signal,
There is no need to add a signal line for e, and the configuration can be simplified. Further, even in the drive circuit 100 having such a simplified configuration, the common rail pressure can be appropriately reduced.

The present invention can be embodied in the following modes other than the above. In each of the above embodiments, the configuration in which the injector is driven by current control to perform idle driving is described. Instead, the configuration may be such that the injector is driven by time control to perform idle driving. For example, the drive circuit 100 is configured as shown in FIG. FIG.
5 is a modification of the above-described FIG. 5 except that the comparator 202 is eliminated as a different point, and a timer circuit 501 is provided instead. In this case, the timer circuit 501
Takes the outputs of the OR circuits 207 and 209, and after the outputs go to the H level, when a predetermined time tx shorter than the delay time (for example, about 0.2 to 0.4 msec) of the injector elapses. The output is set to H level.
That is, when the time tx has elapsed from the start of energization of the solenoid, the flip-flop 203 is reset, and the energization of the solenoid is cut off. At this time, the injector is driven for idle driving while the predetermined time tx has elapsed, and the common rail pressure is reduced. In this configuration, the timer circuit 501 corresponds to the determination circuit of the present invention.

Also, the configuration shown in FIG. 9 can be changed to a configuration in which idle driving is performed by controlling the injector driving time. That is, the comparator 202 in FIG.
, A timer circuit is provided, and the output of the timer circuit is input to the gate circuit 301. In this case, after + B is supplied to the solenoid, the output of the gate circuit 301 is set to L level when a predetermined time shorter than the delay time of the injector elapses after the supply of + B to the solenoid, and the energization of the solenoid is cut off.

Also in the case of performing idle control by time control as shown in FIG. 13 and the like, the drive circuit 100 receives the idle control request signal Qe from the microcomputer 151 and causes the injectors 101 to 101 to operate.
Since the idle driving of the 104 is performed, the common rail pressure can be reduced efficiently. Further, even when a large number of blank shots are required in a short period of time to reduce the common rail pressure, the disadvantage that the processing load of the microcomputer 151 increases does not occur.

In the configurations of FIGS. 5 and 9, the signal for triggering the energization of the solenoid at the time of the idling request is alternately distributed to a plurality of injectors in the same injection group. good. That is,
The frequency divider 205 and the logic circuits 206-2 of FIGS.
09 is excluded. Alternatively, instead of alternately switching the injectors to be driven each time the injectors are driven during idling, the injectors to be driven may be alternately switched each time an idling request occurs.

In the configuration of FIG. 2, the solenoid 101a
-Electrical energy generated at the time of shutting off the power supply to the capacitors 104a to 104a is collected by the diodes D10 to D40 and
The configuration of storing data in 0 and C20 may be omitted.
In addition, after supplying energy from the capacitors C10 and C20, the configuration is changed such that the transistors T11 and T21 are turned on / off to drive the solenoids 101a to 104a at a constant current.
4a may be directly driven.

Next, technical ideas other than the inventions described in the claims, which can be understood from the above embodiments, will be described below together with their effects. (A) Applied to a common rail fuel injection system including a common rail for storing high pressure fuel and an electromagnetically driven injector that injects high pressure fuel in the common rail to a cylinder of an internal combustion engine, and reduces the fuel pressure in the common rail. An injector drive circuit for driving an injector to cause fuel to leak from the common rail to the low pressure side of the fuel system when a request is made, the solenoid drive circuit being connected to the solenoid of the injector to turn on / off the energization of the solenoid. Switching means, and current detecting means for detecting a current flowing through the solenoid of the injector, and when the fuel pressure in the common rail is reduced, based on the value detected by the current detecting means, fuel injection is not actually performed. Switching means for solenoid drive is turned on in a very small current range Off, and the injector driving circuit and drives the injector.

As is well known in the art, when the fuel pressure is reduced (blank firing) by time control, such as driving the injector with a time interval short enough not to perform fuel injection, when the voltage level of the operating power supply fluctuates. Therefore, there is a concern that the controllability of the pressure reduction may be deteriorated accordingly. In contrast,
By driving the injector by current control and reducing the fuel pressure (idling) as described above, good controllability can be ensured even when the operating power supply fluctuates.

The injector drive circuit described in (a) discharges the energy stored in the energy storage means to drive the injector to reduce the fuel pressure (idling). Invention, Claim 5,
As described in 6, the invention can be embodied as an invention in which a power supply voltage is applied to a solenoid to drive an injector to reduce fuel pressure (idling). For example,
In the case where the idle driving is performed using the stored energy of the energy storage means, the idle driving is reliably performed even if the stored energy fluctuates, and the controllability thereof is improved. Further, in the case where the idle driving is performed using the power supply voltage, the idle driving is reliably performed even if the power supply voltage fluctuates, and the controllability thereof is improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an outline of a common rail fuel injection system for a diesel engine.

FIG. 2 is a circuit diagram showing a basic configuration of a driving circuit.

FIG. 3 is a time chart for explaining a basic operation of a driving circuit.

FIG. 4 is a diagram for explaining operating characteristics of the injector.

FIG. 5 is a circuit diagram illustrating a main configuration of a driving circuit.

FIG. 6 is a flowchart illustrating a blank hit determination process performed by the microcomputer.

FIG. 7 is a time chart for explaining idling control by the injector.

FIG. 8 is a time chart for explaining idling control by the injector.

FIG. 9 is a circuit diagram showing a configuration of a main part of a drive circuit in a second embodiment.

FIG. 10 is a time chart for explaining idling control by the injector.

FIG. 11 is a time chart for explaining idling control by the injector.

FIG. 12 is a circuit diagram showing a configuration of a signal input unit of a drive circuit in a third embodiment.

FIG. 13 is a circuit diagram illustrating a main part configuration of a drive circuit in another embodiment.

[Explanation of symbols]

13: common rail, 100: drive circuit (EDU), 1
01 to 104: injector, 101a to 104a: solenoid, 110: oscillation circuit, 150: ECU, 151
... Microcomputer, 201... Comparator as energy amount determining means, 202... Comparator as current detecting means, 204. AND circuit, 205... Frequency dividing circuit as distribution circuit, 301 gate circuit, 400. A signal input circuit as a generation circuit; 501, a timer circuit as a determination circuit; C10, C20, capacitors as energy storage means; T10 to T40, transistors as switching means for driving a solenoid;
1, T21: transistors as switching means for supplying power, T12, T22: transistors as switching means for energy release, R10, R20 ...
Current detection resistor, L11: inductor forming a boost circuit, T13: transistor forming a boost circuit, R00
... Current detection resistors that constitute the booster circuit.

Claims (9)

[Claims] A common rail for storing high-pressure fuel, an electromagnetically driven injector for injecting high-pressure fuel in the common rail to a cylinder of an internal combustion engine, and a drive signal for the injector are generated in accordance with an engine operating state and the like. Is applied to a common rail fuel injection system including a microcomputer that determines whether or not to reduce the fuel pressure in the common rail. When a request to reduce the fuel pressure in the common rail occurs, the low pressure side of the fuel system from the common rail An injector drive circuit for driving the injector to cause fuel to leak to the fuel cell, comprising: a determination circuit for determining the end of one pressure reduction operation by driving the injector after the start of driving of the injector at the time of a pressure reduction request from the microcomputer; After the determination by the determination circuit, the injector drive for the next pressure reduction is performed. An injector drive circuit characterized by restarting operation. 2. A common rail for storing high-pressure fuel, an electromagnetically driven injector for injecting high-pressure fuel in the common rail to a cylinder of an internal combustion engine, and a drive signal for the injector according to an engine operating state and the like. Is applied to a common rail fuel injection system including a microcomputer that determines whether or not to reduce the fuel pressure in the common rail. When a request to reduce the fuel pressure in the common rail occurs, the low pressure side of the fuel system from the common rail An injector drive circuit for driving an injector to cause fuel to leak from the injector, the solenoid driving circuit being connected to a solenoid of the injector for turning on / off the energization of the solenoid, and detecting a current flowing through the solenoid of the injector. And a current detection means. In response to a pressure reduction request from the motor, based on the value detected by the current detecting means, the solenoid driving switching means is turned on / off in a current range small enough not to actually perform fuel injection to drive the injector. Characteristic injector drive circuit. 3. An injector driving circuit according to claim 2, wherein said boosting means boosts a power supply voltage, energy storing means stores high energy boosted by said boosting means, and said energy storing means and a solenoid. Switching means for discharging energy provided between the fuel cell and an energy amount determining means for determining that the energy amount of the energy storing means is equal to or more than a predetermined amount; Turn on the switching means for release to release the energy of the energy storage means to the solenoid, and then
When the value detected by the current detecting means reaches a predetermined value in a current range in which fuel injection is not actually performed, the switching means for driving the solenoid is turned off, and then the energy amount of the energy storage means is increased by a predetermined amount by the boosting means. The injector drive circuit causes the energy storage means to release the next energy when the energy amount determination means determines that 4. The injector driving circuit according to claim 3, wherein a signal indicating a request for reducing the fuel pressure from the microcomputer and a signal indicating that the energy amount of the energy storage means exceeds a predetermined amount are input. An injector drive circuit comprising a logic circuit, wherein the logic circuit outputs a logical product of the two input signals as a signal that triggers energy release by energy storage means. 5. The injector driving circuit according to claim 2, further comprising a power supply switching means provided between the power supply and the solenoid, wherein the switching means for driving the solenoid and supplying power to the power supply when the fuel pressure is required to be reduced. The switching means is turned on to apply a power supply voltage to the solenoid, and thereafter, when the value detected by the current detection means reaches a predetermined value in a current range where fuel injection is not actually performed, the switching means for solenoid driving is turned off. An injector drive circuit that shuts off solenoid energization and immediately turns on the solenoid drive switching means to apply a power supply voltage to the solenoid immediately after the energization cutoff. 6. The injector drive circuit according to claim 5, wherein a signal indicating a request for reducing fuel pressure from the microcomputer and a signal indicating that a current equal to or more than a predetermined value has flowed through the solenoid are input. And the logic circuit comprises:
An injector drive circuit that inputs a signal indicating a pressure reduction request and outputs a signal that triggers energization of the solenoid by a power supply voltage when a current value flowing through the solenoid is smaller than a predetermined value. 7. The injector driving circuit according to claim 2, wherein a signal for triggering solenoid energization when the fuel pressure is reduced is input, and the signal is alternately distributed to a plurality of injectors. An injector drive circuit including a distribution circuit. 8. The fuel injection system according to claim 1, wherein a plurality of injection groups are formed by combining injectors that cannot be driven simultaneously, and the injectors are simultaneously driven for the plurality of injection groups when a fuel pressure reduction request is made. An injector drive circuit according to any one of claims 1 to 3. 9. An injector drive circuit connected to a microcomputer by a signal line for receiving a drive signal of an injector for each cylinder, wherein a drive signal of an injector that is turned on for all cylinders when a fuel pressure reduction is requested is received from the microcomputer. And a request signal generation circuit for generating a pressure reduction request signal for reducing the fuel pressure based on the drive signal for turning on all the cylinders.
9. The injector drive circuit according to any one of claims 1 to 8.