JPH09105367A - Injector drive circuit - Google Patents

Abstract

(57) Abstract: An injector drive circuit capable of simplifying a booster circuit and reducing the capacitance of a capacitor to downsize the system and reduce the cost. An electronic control unit (ECU) inputs a pre-energization signal to a control signal generator at t0. Based on this signal, the control signal generation unit t0
At the same time, the switch SW2 is turned on. As a result, battery B
The pre-energized current Iα is supplied from the solenoid L to the solenoid L. Next, the ECU inputs the solenoid drive signal to the control signal generator at time t1, and the control signal generator 14
Based on this signal, the switch SW1 is turned on, and
The switch SW1 is kept on as it is, and the supply of the holding current Ih is delayed until the solenoid voltage becomes a negative voltage due to LCR resonance. As a result, the high voltage charged in the capacitor C by the booster circuit 11 is applied to the solenoid L to operate at high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injector drive circuit for driving an injector in an internal combustion engine, and more particularly to an injector drive circuit suitable for a high pressure injector.

[0002]

2. Description of the Related Art Conventionally, an injector (fuel injection valve) in a gasoline engine is generally arranged in an intake manifold, and gasoline fuel injected by the injector is used for combustion in the intake manifold. After being mixed with air at a desired mixing ratio, it was supplied into the cylinder. In addition, the fuel pressure (fuel pressure) of the gasoline fuel supplied to the injector is about several atmospheres, and the actuator that opens and closes the injector is not required to have high-speed response. A smooth injector drive was realized.

In recent years, in order to improve combustion efficiency, it has been attempted to arrange an injector in a cylinder and inject it into the cylinder. With this direct injection of fuel into the cylinder, all of the gasoline fuel supplied from the injector is supplied into the cylinder, making it possible to achieve combustion that is closer to the theoretical value, thus improving fuel efficiency and exhaust gas. It is possible to reduce NOx, HC and the like in the inside.

However, in such a case, the space into which gasoline fuel is injected is a space composed of a cylinder, a piston, and a cylinder, and considering injection during the compression stroke, it is compared with the case where it is injected into the intake manifold. Then, the injection must be performed under a very high pressure. There is no space or time to sufficiently diffuse the fuel after fuel injection. Therefore, under these conditions, in order to obtain the same combustion condition as the conventional one, the fuel pressure of the gasoline fuel supplied to the injector is increased, and the fuel is sufficiently diffused from the moment the fuel is injected into the cylinder. You can do it like this. If the fuel pressure is increased in this way, more gasoline fuel will be supplied to the cylinder within the same injector opening time, but the amount of gasoline fuel required by the engine will be the same as that for fuel injection in the conventional intake manifold. The amount of fuel injection must remain the same without change.

For that purpose, it is necessary to drive the injector at high speed against a high fuel pressure to accurately control the fuel injection time, and by applying a high voltage to the actuator,
A high-speed drive circuit for an actuator that turns the injector on and off (opens and closes the valve) at high speed is required.

Here, as a drive circuit of an actuator which has been conventionally used, for example, JP-A-57-49 is used.
There is an actuator drive circuit described in Japanese Patent No. 059. The actuator drive circuit described in this publication requires a large-capacity, high-voltage-resistant capacitor and a booster circuit for charging the capacitor.

The structure of a conventional injector drive circuit will be described with reference to FIG. A booster circuit 21 including a DC-DC converter is connected to both terminals of the battery B, and a switch SW4 and a capacitor C are connected to both output terminals of the booster circuit 21. A parallel circuit of the switches SW1 and SW3, a solenoid L, and a resistor R are connected in series between both terminals of the capacitor C. Between the positive terminal of the battery B and the connection point between the solenoid L and the switch SW1 (switch SW3), a switch SW2, a parallel circuit with the Zener diode ZD, and a diode D
A series circuit consisting of and is connected. The diode D is for preventing the reverse flow of the applied voltage for preventing the reverse flow of the voltage applied from the capacitor C to the solenoid L. Further, the primary side negative terminal of the booster circuit 21 and the secondary side negative terminal are grounded. Each of the switches SW1 to SW4 is composed of a switching circuit such as a transistor and a triac so as to be turned on and off by a control means (not shown). Also, switch S
W2 also includes a constant current circuit.

The drive control of the injector will be described using the injector drive circuit configured as described above.
First, the high voltage charged in the capacitor C by the booster circuit 21 is turned on (at time t1 in FIG. 10) by the switch SW1.
Apply to solenoid L to operate at high speed.

Next, the switch SW1 is continuously turned on as it is, and the supply of the holding current is delayed until the solenoid voltage V _SOL becomes a negative voltage due to the LCR resonance (holding delay system). After the holding delay period ends (at t2 in FIG. 10), the switch SW2 is turned on to supply the holding current. At this time,
The switch SW1 is turned off.

During the period from t2 to t3 in FIG. 10, the holding current is adjusted by using the limiter or the switching of the switch SW2 (holding current control method). Then, solenoid L
The switch SW2 is turned off at the off timing (at t3). Slightly after this point, switch SW3
Is turned on (at t4), the reverse voltage of the capacitor C is applied to the solenoid L, and a reverse current is supplied (reverse voltage application method). Then, after this, the switch SW3 is turned off (at t5) at an appropriate timing.

Next, at an appropriate timing, SW4 is turned on (at t6), and the booster circuit 21 charges the capacitor C. After charging is completed, switch SW4 is turned off (T7
Time). In FIG. 10, V _C is the capacitor voltage.

As described above, in the injector drive circuit, it is necessary to drive the injector at high speed against the high fuel pressure to accurately control the fuel injection time. Therefore, the solenoid current of the injector between t1 and t2 in FIG. The peak part of I _SOL is required.

In order to generate the peak portion of this solenoid current I _SOL , the voltage of the on-vehicle battery B of 12 V is insufficient, and the booster circuit 21 generates a voltage of about 180 V to 250 V, which is charged in the capacitor C, As described above, the voltage is applied all at once at the injector ON timing.

That is, a battery voltage 1 which is a vehicle-mounted power source.
2V is boosted to several 100V by the booster circuit 21 such as a DC-DC converter to charge the capacitor C, and the capacitor C is discharged to apply a high voltage to the actuator, thereby driving the actuator at high speed. .

[0015]

However, the conventional injector drive circuit has a problem in that it is upsized due to the booster circuit and the large-capacity, high-voltage-resistant capacitor, and the circuit becomes complicated and the cost is high. .

An object of the present invention is to provide an injector drive circuit which can simplify the booster circuit, reduce the capacitance of the capacitor, and downsize the system to reduce the cost.

[0017]

In order to solve the above-mentioned problems, the invention of claim 1 is a solenoid for driving an injector, a first switch circuit for on / off controlling a holding current from a power source to the solenoid, and An injector drive circuit comprising: a capacitor charged by a booster circuit connected to a power supply; and a second switch circuit for controlling on / off of a discharge current from the capacitor to the solenoid in response to an injector drive signal. The gist of the injector drive circuit is a switch control means for turning on the first switch circuit in order to supply a pre-energized current to the solenoid prior to turning on the switch circuit _.

According to a second aspect of the present invention, in the first switch circuit, the pre-conduction current supplied before the generation of the injector drive signal is larger than the holding current supplied after that. The gist of the injector drive circuit according to claim 1 is that which includes a current control means for controlling _.

(Operation) In the invention of claim 1, the switch control means controls the first switch circuit to be turned on prior to turning on the second switch circuit. As a result, a pre-energized current is supplied from the power supply to the solenoid in advance. After that, the second switch circuit is turned on in response to the injector drive signal, and the exciting current is supplied from the capacitor to the solenoid. Therefore, the solenoid current I _SOL makes a peak due to the current supplied from the capacitor by the ON control of the second switch circuit later, and the solenoid current I _SOL is applied all at once at the injector ON timing.

As a result, in order to supply the solenoid L with the peak current value I _SOL-P required for the solenoid current, the energy supplied by the capacitor C to the solenoid is "(L · I _SOL-P ² ) / 2 ”or more was required, but in the invention of claim 1,“ (L · I _SOL-P ² ) / 2 ”
-(L · Iα ² ) / 2 ”or more. In the above formula, L is the inductance of the solenoid.

According to the second aspect of the present invention, the current control means controls the current so that the pre-energization current before the generation of the injector drive signal becomes larger than the holding current supplied after that. As a result, by increasing the pre-energization current that flows in advance by the first switch circuit, it is possible to realize a low cost with a simple configuration of the capacitor _{and the} booster circuit.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIGS. 1 to 4 and 7.

FIG. 1 shows an injector drive circuit 10 for one cylinder according to the present invention. 2 is a time chart of a pre-energization signal and a solenoid drive signal, and FIG. 3 is a solenoid drive signal, switches SW1 to SW4, capacitor voltage, solenoid voltage, solenoid current, switch SW2.
FIG. 4 shows a control circuit 12 for controlling the injector drive circuit 10 in the current chart of FIG.
The configuration of the injector drive circuit 10 of FIG. 1 is different from the configuration of the conventional injector drive circuit of FIG. 9 only in the booster circuit and the capacitor, and the configuration of the switch SW2 is different, and the other configurations are the same. , The same reference numerals are given and the description thereof is omitted.

The booster circuit 11 of the injector drive circuit 10 of FIG. 1 is constructed so that the output voltage on the secondary side becomes smaller than that of the booster circuit 21 of the conventional injector drive circuit of FIG. In addition, the injector drive circuit 1 of FIG.
The capacitor C1 of 0 corresponds to the conventional injector drive circuit 2
The capacitor C of No. 1 has a small capacity and a small withstand voltage. Further, the solenoid L is a solenoid type actuator incorporated in the fuel injection valve, and includes a plunger sliding in the solenoid L, a needle valve fixed to the plunger, and a spring for urging the needle valve in the valve closing direction. Is equipped with. When a voltage is applied to the solenoid L, the plunger moves in the valve opening direction against the spring elastic force and the fuel pressure applied to the needle valve, and the injection hole closed at the tip of the needle valve opens. To be done.

A control circuit 12 as a switch control means for controlling the injector drive circuit 10 will be described with reference to FIG. The control circuit 12 includes an electronic control unit (hereinafter referred to as “ECU”) 13, a control signal generator 1.
4 is provided. The ECU 13 includes a central processing unit (CPU) not shown. Various sensors (not shown) are connected to the ECU 13 in order to detect the operating state of the engine as an internal combustion engine. That is, E
An air flow meter, an intake air temperature sensor, a throttle sensor, a water temperature sensor, an oxygen sensor, an engine speed sensor, and the like are connected to the CU 13 via communication lines. The air flow meter measures the amount of intake air taken in by the engine, and the intake air temperature sensor detects changes in the temperature of intake air flowing through the intake passage. The intake air temperature corresponds to the ambient temperature around the tip of the injector. The throttle sensor detects the opening (throttle opening) of a throttle valve provided in the intake passage. The water temperature sensor is attached to the water outlet of the engine and detects the temperature of the engine cooling water (cooling water temperature). The oxygen sensor detects the oxygen concentration in the exhaust gas in the exhaust manifold.

A control signal generator 14 is connected to the ECU 13 via communication lines 15 and 16.
The communication line 15 is a dedicated line for the pre-energization signal, and the communication line 16
Is a dedicated line for solenoid drive signals. The ECU 13 determines the operating state of the engine based on the detection signal from each sensor according to a control program stored in a ROM (not shown), and generates a first control signal and a second control signal corresponding to the operating state. Input to the section 14 via the respective communication lines 15 and 16. The control signal generator 14 is connected to each of the switches SW1 to SW4 via each signal line. Control signal generator 1
Reference numeral 4 denotes switches SW1 to SW4 based on the first control signal and the second control signal input from the ECU 13 every time a predetermined period of time elapses after the control signal is input.
It is possible to control ON / OFF separately. The switch SW1 constitutes a second switch circuit.

Next, the configuration of the switch SW2 as the first switch circuit will be described with reference to FIG. FIG. 7 shows a circuit configuration of the switch SW2. In the figure, an input signal timing distribution circuit 22 is connected to the control signal generator 14. The solenoid drive signal is input to the input signal timing distribution circuit 22 via the signal line 16 of the ECU 13. The input signal timing distribution circuit 22 has a switching transistor Tr.
The base terminal of is connected. The emitter terminal of the switching transistor Tr is connected to the battery B, and the collector terminal is connected to the anode of the diode D via the diode D1. The switching transistor Tr is turned on based on an input signal from the input signal timing distribution circuit 22, and is capable of supplying the pre-energized current Iα to the solenoid L. The switching transistor Tr is set so that the pre-energized current Iα has a larger value at the time t1 than the holding current Ih described later.

A constant current output circuit 23 is connected to the input signal timing distribution circuit 22, and the identification current output circuit 23 is connected.
Is connected to the anode of the diode D via the diode D2. Further, the constant current output circuit 23 is connected to the battery B, and a constant current (holding current) Ih is received by the input signal from the input signal timing distribution circuit 22.
Can be supplied to the solenoid L. This holding current Ih is set to the minimum value capable of holding the valve open state by exciting the solenoid L and moving the plunger of the injector in the valve opening direction against the spring elastic force and the fuel pressure applied to the needle valve. There is.

The input signal timing distribution circuit 22 switches when the drive signal from the control signal generator 14 is input before time t1, that is, before the ON signal of the solenoid drive signal from the ECU 13 is input. The transistor Tr is turned on. In addition, the input signal timing distribution circuit 22 sends the drive signal from the control signal generator 14 after the time t1, that is, the ECU 1
When the solenoid drive signal from 3 is input after the input of the ON signal, the constant current output circuit 23 is activated.

The input signal timing distribution circuit 22, the switching transistor Tr and the constant current output circuit 23 constitute a current control means. Next, the operation of the injector drive circuit 10 will be described with reference to FIGS.

The ECU 13 controls fuel injection timing t1 and drive off timing t3 (that is, the on time of the solenoid drive signal) based on input signals from various sensors, and pre-energization timing t0 for switching SW2. It is determined according to the program, and at the same time as the determination, the first control signal (preliminary Input signal). As shown in FIG. 3, the control signal generator 14 turns on the switch SW2 at t0 based on the rise of the first control signal (pre-energization signal) input from the communication line 15. That is, the input signal timing distribution circuit 22 shown in FIG. 7 turns on the switching transistor Tr on the basis of the drive signal from the control signal generation unit 14 to flow the pre-energized current Iα.

As a result, as shown in FIG. 3, the pre-energized current Iα is supplied from the battery B to the solenoid L. Therefore, from t0 to t1, as shown in FIG.
α is a current of (battery voltage / solenoid resistance), which is about 4 to 5 A in this embodiment.

Next, the ECU 13 inputs the second control signal (solenoid drive signal) to the control signal generator 14 via the communication line 16 at t1. The control signal generator 14 turns on the switch SW1 based on the rise of the solenoid drive signal, keeps turning on the switch SW1 as it is, and delays the supply of the holding current Ih until the solenoid voltage becomes a negative voltage due to LCR resonance ( Hold delay method).

As a result, the high voltage charged in the capacitor C1 by the booster circuit 11 is applied to the solenoid L to operate at high speed. Then, the control signal generator 14
SW2 is turned off based on the fall of the first control signal (pre-energization signal) input from the ECU 13 at t1a. That is, the input signal timing distribution circuit 22
Turns off the switching transistor Tr based on the input signal from the control signal generator 14. In addition,
When the pre-energization signal falls, the switch SW2
It may be at the same time as or slightly after the turning on at t1 and before the time when the capacitor voltage Vc becomes a negative voltage. The switch SW2 is turned off at the same time as the switch SW1 or thereafter, because a high voltage current flows from the capacitor C1 to the solenoid L when the switch SW1 is turned on, so that the circuit of the switch SW2 receives the current I _SW2 (see FIG. 3). To prevent the current from the switch SW2 from being charged to the capacitor C1 via the switch SW1 when the discharge current of the capacitor C1 flows and the capacitor voltage Vc becomes a negative voltage later. Is.

Further, the control signal generator 14 turns on SW2 again after a predetermined time (delay time) τ1 from t1, that is, at t2, supplies the holding current Ih, and turns off SW1. That is, the input signal timing distribution circuit 22 turns on the constant current output circuit 23 based on the drive signal from the control signal generator 14. As a result, the constant current output circuit 23 becomes t2 in FIG.
During the period from t3 to t3, the holding current Ih is supplied to the solenoid L as a constant current of about 0.5 A to 1.5 A. (Holding current control method).

Then, at time t3 when the solenoid drive signal falls, the control signal generator 14 turns off the constant current output circuit 23 via the input signal timing distribution circuit 22, and after a short time τ2, that is, , T4
At the same time, the switch SW3 is turned on. As a result, the reverse voltage of the capacitor C1 is applied to the solenoid L, and a reverse current flows (reverse voltage application method). After that, the control signal generator 14 turns off the switch SW3 at t5.

Thereafter, the control signal generator 14 turns on the switch SW4 at t6 when a predetermined time τ3 has elapsed from the time t3 when the solenoid drive signal falls,
The booster circuit 21 charges the capacitor C1. Then, the switch SW4 is turned off at time t7 after the capacitor C1 is completely charged. (A) Now, in the embodiment configured as described above, the ECU 13 controls the drive start timing t1 and the drive off timing t7 based on input signals from various sensors.
In addition, the pre-energization timing t0 is determined according to the fuel injection control program for switching SW2, and at the same time as this determination, the switch SW2 is turned on at a timing t0 ahead of a predetermined time. Therefore, t0 can be set easily and accurately on software. (B) Further, in this embodiment, it is only necessary to add the communication line 15 as compared with the conventional case, and it can be realized by adding a simple circuit. (C) Further, as compared with the booster circuit 21 of the conventional injector drive circuit, the output voltage on the secondary side is configured to be smaller, and the capacitor C1 is different from the capacitor C of the conventional injector drive circuit in capacitance. Is small and the withstand voltage is also small, so that the electric circuit can be simplified. (D) Further, in this embodiment, when the switching transistor Tr forming the switch SW2 is turned on,
At t1, the pre-energization current I that is larger than the holding current Ih
When α is supplied and the constant current seed circuit 23 is turned on, the holding current Ih is supplied so that the two-stage current supply system is adopted. Therefore, since the pre-energization current Iα can be made larger than the holding current Ih, the larger the pre-energization current Iα is, the more “(L · I _SOL-P ² ) / 2- (L
・ Iα ² ) / 2 ”or more can be further reduced, and the effect of the above (c) can be further enhanced.

Next, a second embodiment will be described with reference to FIGS. 3, 5 and 8. FIG. 5 shows the control circuit 12,
As shown in the figure, in this embodiment, the signal line 16 is omitted in the configuration of the control circuit 12 of the first embodiment,
The difference is that a timing generation circuit 17 is provided in the circuit between the control signal generation unit 14 and the switch SW2 _.

The control signal generator 14 is an ECU
Based on the solenoid drive signal from the switch 13, the switch S is operated at the times t1 to t7 every time some predetermined time elapses after the signal is input, as in the first embodiment.
On / off control of each of W1 to SW4 is possible.

[0040] Further, the timing generating circuit 17 constitutes a predictive control _unit, and is to perform predictive control of the switch SW2. That is, the timing generation circuit 1
The control signal generator 14 stores the cycle of the control drive signal for the switch SW2 input at t2 based on the solenoid drive signal. And this period, (for example in Fig. 8, t2 _n-1) t2 times according to the control of one control cycle before (in Fig. 8, t2 _n) t2 at which according to the current control from means a time until. Then, in the control, the timing generation circuit 17 inputs the ON signal to the switch SW2 at 0.9 W (t0 _n ) of the previous cycle W, and inputs the OFF signal to the switch SW2 at t1 a _n. . The switch SW2 is turned on / off based on these both signals. Then, in the control, the timing generation circuit 17 inputs the ON signal to the switch SW2 at t2 and inputs the OFF signal to the switch SW2 at t3.

Therefore, in the second embodiment, in addition to the effect (c) of the first embodiment, the solenoid drive signal as shown in FIG. 3 is obtained by the predictive control of the control signal generator 17. , The switch SW2 is turned on prior to the switch SW1 being turned on at t1.
As a result, the solenoid L can be pre-energized. Further, as compared with the first embodiment, the signal line 15
Can be omitted, and the circuit configuration becomes simple.

Next, the third embodiment will be described with reference to FIGS. 3 and 6 focusing on the points different from the first embodiment. FIG. 6 shows a control circuit 12, and as shown in the figure, in this embodiment, the control circuit 1 of the first embodiment is used.
In the configuration of 2, the signal line 15 is omitted.
Further, the ECU 13 determines the operating state of the engine based on the detection signals from the respective sensors according to a control program stored in a ROM (not shown), and sends a control signal corresponding to the operating state to the control signal generator 14 via a communication line. 1
Enter via 5. In more detail, EC
U13 determines the pre-energization timing t0 according to the pre-energization control program stored in the ROM, and at t0, the first control signal (to generate the ON signal of the switch SW2 via the communication line 15 to the control signal generator 14). Input the pre-energization signal). The control signal generator 14 turns on the switch SW2 at t0 based on the rising edge of the first control signal (pre-energization signal) input from the communication line 15. Then, the control signal generator 1
4 is based on the first control signal (pre-energization signal), every time some predetermined time after the signal is input, that is, t1 to t7 (including t1a) shown in FIG. At this time, the switches SW1 to SW4 are individually turned on.
It can be controlled off.

In this embodiment, the pre-energization signal makes it possible to secure a sufficient pre-energization time for the switch SW2. Further, unlike the second embodiment, it suffices to delay the on-timing of the switch SW1 later than the on-timing of the pre-energization signal, and there is an effect that can be realized only by replacing the connection of the conventional circuit.

The present invention is not limited to the above-mentioned embodiment, but can be modified as follows. (A) In the first embodiment, the two-stage current supply system is adopted. However, when it is desired to limit the pre-energized current Iα, the same constant current output circuit 23 as the constant current output circuit 23 is provided to the collector terminal side of the switching transistor Tr. A current output circuit may be provided.

(B) Further, in the first embodiment,
Although the current value of the current Iα is different from the holding current Ih, the switching transistor Tr and the input signal timing distribution circuit 22 are omitted so that the pre-energized current Iα has the same current value as the holding current Ih. The switch SW2 may be configured by a circuit including the circuit 23.

In this way, the current Iα and the holding current I
A separate configuration for outputting h at different current values is not required, and the circuit configuration is simple and
Since a large current does not flow to the solenoid L, heat generation of _the injector can be suppressed.

(C) Further, in the configuration of (b) above,
The constant current output circuit 23 may be configured to automatically change over time. From the matters described in this specification, technical ideas grasped other than the claims described in the scope of claims will be described together with their effects.

(1) The first switch circuit has a pre-energization current supplied before the generation of the injector drive signal,
The injector drive circuit according to claim 1, wherein the holding current supplied after that is supplied at the same current value. With this _{configuration,} the configuration of the first switch circuit is as simple, since a large current does not flow in the solenoid _L, it is possible to suppress the heat generation of the injector.

(2) The switch control means turns on / off the first switch circuit to supply the holding current.
A cycle prediction control means for storing the cycle before the control cycle and for turning on the first switch circuit so as to supply the pre-energized current to the solenoid for a preset time before the cycle. The injector drive circuit according to claim 1, wherein: With the above configuration, the signal line 15 can be omitted and the circuit configuration can be simplified as compared with the first embodiment.

[0050]

As described in detail above, according to the invention of claim 1, the voltage and current values generated in the booster circuit can be reduced.
_{In addition, the} booster circuit can be simplified and the capacitance of the capacitor can be reduced, so that the system can be downsized and the cost can be reduced _.

According to the second aspect of the present invention, by increasing the pre-energized current flowing in advance by the first switch circuit, the capacitance of the capacitor can be further reduced and _the booster circuit can be simplified, so that low cost is realized. it can.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram of an injector drive circuit according to a first embodiment of the present invention.

FIG. 2 is a time chart of a pre-energization signal and a solenoid drive signal.

FIG. 3 Solenoid drive signal, switches SW1 to SW
4. Time chart of capacitor voltage, solenoid voltage, solenoid current, and switch SW2 current.

FIG. 4 is an electric circuit diagram of the control circuit according to the first embodiment.

FIG. 5 is an electric circuit diagram of a control circuit according to a second embodiment.

FIG. 6 is an electric circuit diagram of a control circuit according to a third embodiment.

FIG. 7 is an electric circuit diagram of the switch SW2 according to the first embodiment.

FIG. 8 is a time chart of a control drive signal according to the switch SW2 of the second embodiment.

FIG. 9 is an electric circuit diagram of a conventional injector drive circuit.

[FIG. 10] Similarly, a solenoid drive signal and a switch SW1
~ SW4, capacitor voltage, solenoid voltage, solenoid current time chart.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Injector drive circuit, 12 ... Control circuit (switch control means), 13 ... ECU, 14 ... Control signal generation part, 15 ... Communication line (pre-energization signal dedicated line), 16
... communication line (solenoid drive signal dedicated line), 17 ... timing generation circuit, 21 ... boosting circuit, 22 ... input signal timing distribution circuit, 23 ... constant current output circuit, Tr ... switching transistor, B ... battery, C1 ... capacitor, L ... Solenoid. SW1 ... First switch (second switch circuit), SW2 ... Second switch (first switch circuit)

Claims (2)

[Claims] 1. A solenoid for driving an injector, a first switch circuit for on / off controlling a holding current from a power supply to the solenoid, a capacitor charged by a booster circuit connected to the power supply, and a response to an injector drive signal. And a second switch circuit for controlling on / off of a discharge current from the capacitor to the solenoid, in order to supply a pre-energized current to the solenoid prior to turning on the second switch circuit. An injector drive circuit comprising switch control means for turning on the first switch circuit. 2. The first switch circuit controls the current so that the pre-energized current supplied before the generation of the injector drive signal becomes larger than the holding current supplied after that. An injector drive circuit according to claim 1 including means.