JPH09306732A - Actuator driving circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable miniaturization and simplification of a voltage booster circuit which is required to realize high-speed driving, and enable miniaturization and reduction in cost of a system. SOLUTION: When a switch SW1 is turned on, a capacitor C1 is discharged and the discharge current is supplied to a solenoid L. The switch SW1 is turned off after the capacitor C1 has a negative voltage. Consequently, the solenoid L is driven at a high speed. On the other hand, a switch SW4 is turned on at the time of charging a capacitor C2. This ON-operation causes a booster circuit 21 to charge the capacitor C2 up to a voltage Vb. When, a switch SW3 is turned on at the time of charging the capacitor C1, a discharge current is supplied from the capacitor C2 to charge the capacitor C1. As the capacitor C2 and a coil L are serially resonated at the time of charging the capacitor C1, the energy of the capacitor C1 which was a negative voltage is transformed to a positive voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an actuator drive circuit for driving an actuator.

[0002]

2. Description of the Related Art For example, an injector (fuel injection valve) as an actuator in a gasoline engine is generally arranged in an intake manifold,
Also, the gasoline fuel injected by the injector is
After being mixed with the combustion air in the intake manifold at a desired mixing ratio, it was supplied into the cylinder.
Further, 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 responsiveness either, and is satisfied by the power supply voltage of the vehicle battery. 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. In addition, spatially enough to diffuse the fuel after fuel injection,
I have no time. 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. When the fuel pressure is increased in this way, more gasoline fuel is supplied to the cylinder within the same injector opening time, but the amount of gasoline fuel required by the engine is the same as in the case of 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 actuator 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 SW1 and a capacitor C1 are connected to both output terminals of the booster circuit 21. A switch SW1, a solenoid L, and a resistor R are provided between both terminals of the capacitor C1.
Are connected in series. A snubber circuit including a resistor R1 and a capacitor C3 is connected between the switch SW1 and the negative terminal of the capacitor C1. Between the positive terminal of the battery B and the connection point between the solenoid L and the switch SW1, a step-down circuit 22, a constant current circuit 23, a switch S
A series circuit including W2, a parallel circuit with the Zener diode ZD, and a diode D 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 C1 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 SW3 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).

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 C1 by the booster circuit 21 is turned on (at time t1 in FIG. 5) 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 VSOL becomes a negative voltage due to the LCR resonance (holding delay system). After the end of the holding delay period (at t2 in FIG. 5), 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. 5, the holding current is adjusted by using the limiter or the switching of the switch SW2 (holding current control method). Then, the switch SW2 is turned off at the off timing (at t3) of the solenoid L. Next, at an appropriate timing, SW3 is turned on (t4
At the time), the booster circuit 21 charges the capacitor C1.
After charging is completed, the switch SW3 is turned off (at T5). In FIG. 5, VC1 is the capacitor voltage of the capacitor C1.

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

In order to produce the peak portion of this solenoid current ISOL, the voltage 12V of the vehicle-mounted battery B is insufficient, and the booster circuit 21 generates a voltage of about 180V to 250V, which is charged in the capacitor C1, 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. .

[0014]

As described above, in order to drive the injector efficiently, it is necessary to give as much peak current (ISOL) as possible. Therefore, for this purpose, it is indispensable to set the capacitor C1 to a negative voltage in the above t1 to t2.
That is, due to the relationship between the phases of ISOL and Vc1, Vc1 has already become Vc1≈0 (V) when ISOL has a peak,
In order to drive at high speed, ISOL is desired to be as large and long as possible, so the switch SW1 is kept on until Vc1 <0.

However, when the capacitor C1 is charged from the time t4, the capacitor voltage Vc1 needs to be boosted from a negative voltage, so the booster circuit 21 needs to boost more power. As a result, there is a problem that the conventional booster circuit needs to be upsized and its circuit configuration becomes complicated. Further, since the booster circuit needs to process a larger amount of electric power, the heat sink is increased in size as a measure against heat generation and an element having a large maximum rating is required, which causes a problem of high cost.

It is an object of the present invention to provide an actuator drive circuit which can miniaturize and simplify a booster circuit in an actuator drive circuit which is required to be driven at high speed, and can miniaturize the system to reduce the cost. I am trying.

[0017]

In order to solve the above problems, the invention of claim 1 is directed to a solenoid for driving an actuator, a first capacitor for supplying a discharge current to the solenoid, and an actuator drive signal. In response to the above, in an actuator drive circuit that is turned on and includes a first switch means that supplies the discharge current from the first capacitor to the solenoid, the actuator drive circuit is charged by a booster circuit connected to a power source. A second resonance circuit connected to the first capacitor via a coil and forming a series resonance circuit with the coil when the first capacitor is charged
Connected between the first capacitor and the second capacitor, the second switch means connected between the second capacitor and the booster circuit and turned on when the second capacitor is charged, and the second switch means connected between the first capacitor and the second capacitor. The gist is an actuator drive circuit including a third switch means that is turned on when the first capacitor is charged.

According to the first aspect of the invention, when the first switch means is turned on in response to the actuator drive signal, the first capacitor is discharged and the discharge current is supplied to the solenoid. The first switch means is
After the first capacitor has a negative voltage (Vc shown in FIG. 3), it is turned off. Therefore, the solenoid is driven at high speed by this discharge current.

On the other hand, the second switch means is turned on when the second capacitor is charged. By this ON operation, the booster circuit connected to the power supply charges the second capacitor to the voltage Vb shown in FIG.

When charging the first capacitor, the third capacitor is charged.
When the switch means is turned on, the discharge current is supplied from the second capacitor, so that the first capacitor is charged. When charging the first capacitor, the second
The capacitor and the coil are resonated in series, and the resonance causes the energy of the first capacitor, which has been a negative voltage, to be converted into a positive voltage (Va).

This means that unlike the conventional case, the second capacitor is charged with less energy than in the case of directly charging the capacitor in the negative voltage state by the booster circuit. That is, conventionally, the booster circuit needs energy of (1/2) C1 (Va + Vc) ² in order to bring the voltage Vc1 of the first capacitor to Va as shown in FIG. In the present invention, the booster circuit is (1/2) C1 (Va ²
The energy of −Vc ² ) improves. If the voltage after discharging the second capacitor is Vd, then (1/2) C2V
d ² = and has a ^{(1/2) C1 (Va 2 -Vc} 2).

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a drive circuit for an injector of an engine will be described below with reference to FIGS.

FIG. 1 shows an injector drive circuit 10 for one cylinder according to the present invention. FIG. 2 shows a control circuit 12 as a switch control means for controlling the injector drive circuit 10. FIG. 3 shows solenoid drive signals, switches SW1 to SW4, capacitor voltage, solenoid voltage,
The time chart of the solenoid current and the current of the switch SW2 is shown. Among the configurations of the injector drive circuit 10 of FIG. 1, the same configurations as the configurations of the conventional injector drive circuit of FIG. 4 and corresponding configurations are denoted by the same reference numerals, and description thereof will be omitted.

The booster circuit 21 of the injector drive circuit 10 of FIG. 1 is configured 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.

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 biasing force of the needle valve in the valve closing direction. It has a spring. 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 switch SW4 and a coil L1 are connected between the positive terminal on the secondary output side of the booster circuit 21 and the switch SW3. A capacitor C2 is connected between the connection point between the switch SW4 and the coil L1 and the negative terminal on the secondary output side of the booster circuit 21.

The inductive reactance and the capacitive reactance of the coil L1 and the capacitor C2 are set so that the coil L1 and the capacitor C2 become a series resonance circuit at the transition of charging of the capacitor C1. Since the coil L1 also has a substantial resistance component, the series resonance circuit is an LCR series resonance circuit.

When the capacitor C2 charged by the booster circuit 21 charges the capacitor C1,
To prevent the voltage Vc1 from becoming a negative voltage, the capacitor C
The capacitances of 1 and the capacitor C2 are C1 >> C2.

In this embodiment, the capacitor C1 is the first
And a capacitor C2 constitutes a second capacitor. The switch SW1 constitutes the first switch means in the present invention, the switch SW4 constitutes the second switch means, and the switch SW3 constitutes the third switch means. The switches SW1 to SW4 are composed of switching circuits such as transistors and triacs so as to be driven by the control circuit 12 described later.

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.
It is equipped with 4. 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 a communication line 15. ECU
Reference numeral 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 the communication line 15. Enter through. The control signal generator 14 has switches S
It is connected to W1 to SW4 via each signal line. Based on the control signal input from the ECU 13, the control signal generation unit 14 switches SW1 to SW each time some predetermined time elapses after the control signal is input.
It is possible to control ON / OFF of W4 separately.

Next, the operation of the injector drive circuit 10 will be described with reference to FIG. The ECU 13 determines the drive start timing t1 and the drive off timing t3 (that is, the on-time time of the solenoid drive signal as the actuator drive signal) based on the input signals from the various sensors according to the fuel injection control program. Next ECU
A solenoid drive signal 13 is input to the control signal generator 14 via the communication line 15 at t1. The control signal generator 14 turns on the switch SW1 based on the rising edge of the solenoid drive signal and continues to turn on the switch SW1 as it is until the solenoid current VSOL becomes a negative voltage due to the LCR resonance.
Delay the supply of h (hold delay method).

As a result, the high voltage charged in the capacitor C1 is applied to the solenoid L to operate at high speed. Further, the control signal generator 14 turns on SW2 after a predetermined time (delay time) τ1 has passed from t1, that is, at t2, supplies a holding current and turns off SW1. The constant current circuit 23 supplies a constant current of about 0.5 A to 1.5 A to the solenoid L as the holding current Ih during the period of t2 to t3 in FIG. (Holding current control method).

Between t2 and t3, that is, when SW3 is off, the control signal generator 14 turns on the switch SW4 at t6 to charge the capacitor C2. Then, between t2 and t3, that is, at time t7 after the charging of the capacitor C2 is completed when SW3 is in the off state, the control signal generator 14 turns off the switch SW4.

After that, at time t3 when the solenoid drive signal falls, the control signal generator 14 turns off the switch SW2. After that, the control signal generator 14 turns on the switch SW3 at time t4 when a predetermined time τ2 has elapsed from the time t3 when the solenoid drive signal falls, and the capacitor C2 charges the capacitor C1. Then, the switch SW3 is turned off at the time t5 after the charging of the capacitor C1 is completed. (A) According to this embodiment, since the capacitor C1 is not directly charged, large energy is not required,
It suffices to charge the capacitor C2 with a small amount of energy. For this reason, the structure of the booster circuit 21 can be simplified, and since heat generation measures can be taken as a small booster circuit, the entire system can be downsized and the cost can be reduced. (B) Further, by properly selecting the combination of the ratings of the capacitor C2 and the coil L1, Va> Vb in FIG.
Furthermore, the withstand voltage of each element required for the booster circuit can be reduced, and the booster circuit and the entire system can be downsized and the cost can be reduced.

The present invention is not limited to the above-mentioned embodiment, but can be modified as follows. (A) Although the booster circuit is configured by the D / D converter in the above embodiment, it may be configured by a transformer.

From the matters described in this specification, technical ideas understood from the claims other than the claims will be described together with their effects. (1) The actuator drive circuit according to claim 1, wherein the actuator is an injector of an internal combustion engine. With this configuration, the booster circuit can be simplified and the cost can be reduced even in the injector drive circuit in the internal combustion engine that requires high-speed driving.

[0038]

As described in detail above, according to the present invention, in the drive circuit of the actuator which is required to be driven at high speed, the booster circuit can be downsized and simplified, and the system can be downsized and the cost can be reduced. In addition, since the booster circuit can be downsized and simplified, the degree of freedom in space is increased, which facilitates the design layout.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram of an injector drive circuit according to an embodiment.

FIG. 2 is an electric circuit diagram of the control circuit of the same.

FIG. 3 Solenoid drive signal, switches SW1 to SW
4, time chart of capacitor voltage, solenoid voltage, solenoid current.

FIG. 4 is an electrical circuit diagram of a conventional injector drive circuit.

[FIG. 5] Similarly, a solenoid drive signal and a switch SW1,
SW3, capacitor voltage, solenoid voltage, solenoid current time chart.

[Explanation of symbols]

Reference numeral 10 ... Injector drive circuit, 12 ... Control circuit (switch control means), 13 ... ECU, 14 ... Control signal generator, 15 ... Communication line, 21 ... Booster circuit, 22 ... Step-down circuit, 23 ... Constant current output circuit, B ... Battery, C1 ... Capacitor (first capacitor), C2 ... Capacitor (second capacitor)
Capacitor), L ... Solenoid, L1 ... Coil, SW
1 ... Switch (first switch means), SW2 ... Switch, SW3 ... Switch (third switch means), SW4
... Switch (second switch means)

Claims (1)

[Claims] 1. A solenoid for driving an actuator, a first capacitor for supplying a discharge current to the solenoid, and an ON operation in response to an actuator drive signal for discharging a discharge current from the first capacitor. In an actuator drive circuit provided with a first switch means for supplying to the solenoid, while being charged by a booster circuit connected to a power source,
A second capacitor connected to the first capacitor via a coil and forming a series resonance circuit with the coil when the first capacitor is charged; and a second capacitor connected between the second capacitor and a booster circuit, A second switch means that is turned on when the second capacitor is charged; and a third switch means that is connected between the first capacitor and the second capacitor and that is turned on when the first capacitor is charged. Actuator drive circuit equipped.