JP2000205437A - Solenoid valve drive circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve responsibility of a solenoid valve at the time of breaking an electric current to a solenoid coil. SOLUTION: A control circuit IC101, a rush current supply circuit 110, a holding current supply circuit 130 and an electrifying circuit 140 apply charging voltage of a condenser 116 or battery voltage VB to a solenoid coil 42 in response to a driving signal to drive a solenoid valve and flow a driving electric current in a specified direction to the solenoid coil 42 in a solenoid valve driving circuit 100. A condensing circuit 180 condenses energy in the coil 42 in a condenser 182 when the solenoid coil 42 comes to be in a non-working state. A backward current supply circuit 150 applies charging voltage of the condenser 182 to the solenoid coil 42 at the time when the driving signal of the solenoid valve 36 becomes off and flows an electric current to the solenoid coil 42 in the opposite direction of the normal driving electric current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solenoid valve driving circuit for opening and closing a solenoid valve in accordance with energization of a solenoid coil, and more particularly to a solenoid valve driving circuit used for a fuel injection device of an engine.

[0002]

2. Description of the Related Art In a fuel injection device of an engine, there is known an electromagnetic valve which overflows (spills) high-pressure fuel in response to a drive signal at a predetermined timing from a control computer. Such an electromagnetic valve generally has a valve element for opening or closing a fuel passage, a solenoid coil for driving the valve element, an armature integrated with the valve element, and a stator for accommodating the solenoid coil. When a drive signal to the solenoid coil is turned on, the armature is attracted to the stator, and the valve body moves to a predetermined valve opening position or a predetermined valve closing position.

As one method of driving the solenoid valve, a voltage equal to or higher than a battery voltage (power supply voltage) is stored in a capacitor in advance, and a high voltage is discharged from the capacitor to the solenoid coil at once in the initial stage of driving the solenoid valve. (Inrush current is supplied), and then a constant current (holding current) generated from the battery voltage is supplied. According to such a method, the magnetic flux in the solenoid coil of the solenoid valve rises sharply, and a high-speed valve opening or closing operation can be realized.
The subsequent valve opening or valve closing state can be maintained for a desired period.

Japanese Patent Laid-Open Publication No. 8-14091 discloses an electromagnetic valve driving circuit in which energy in a solenoid coil is stored in a power storage circuit (capacitor) when the solenoid coil is inoperative. I have. In such an electromagnetic valve drive circuit, when the storage voltage of the storage circuit is applied to the solenoid coil, the operation ends when the storage voltage decreases to a predetermined voltage higher than the DC power supply voltage,
Thereafter, when the solenoid coil is deactivated and energy in the solenoid coil is recovered, energy recovery is performed using a voltage higher than the DC power supply voltage. Thereby, the fall of the current in the solenoid coil is made to be steep. The storage voltage of the storage circuit is configured to be applied to the solenoid coil in the same direction as the DC power supply voltage.

[0005]

In recent diesel engines, a so-called pilot injection, which injects a very small amount of fuel prior to the main injection in each cylinder, is performed to improve fuel efficiency, reduce exhaust gas, and reduce noise. A fuel injection control system designed to take measures and the like has been proposed and put into practical use.

However, when performing pilot injection with an existing solenoid valve drive circuit including the above-mentioned conventional publication, there are the following problems. That is, the valve opening operation of the valve body at the time of de-energization is delayed due to residual magnetic flux remaining after the energization of the stator and the armature of the solenoid valve is completed.・ The minimum injection amount of the main injection cannot be reduced. Such a problem arises.

In such a case, there is a demand for reducing the pilot interval or reducing the minimum injection amount of the main injection in accordance with the engine operating state in order to reduce noise and emission, but the existing drive circuit meets the demand. Not be able to shorten the pilot interval sufficiently,
Alternatively, the minimum injection amount of the main injection cannot be reduced.

[0008] On the other hand, the need for so-called pre-stroke injection, which changes the fuel injection rate in accordance with the operating state of the engine by changing the use range of the cam, has also been increasing. Due to the residual magnetic flux of
The injection quantity cannot be reduced as required according to the engine operating condition.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a solenoid valve driving circuit capable of improving the responsiveness of a solenoid valve when current is interrupted to a solenoid coil. It is to provide.

[0010]

According to the first aspect of the present invention, a DC power supply voltage is applied to a solenoid coil in response to a drive signal for driving an electromagnetic valve. A first current supply circuit for supplying a drive current in a predetermined direction to the solenoid coil, a power storage circuit for storing energy in the solenoid coil when the solenoid coil is in a non-operation state, and after a drive signal of the solenoid valve is turned off. A second current supply circuit that applies a charging voltage from the power storage circuit to a solenoid coil and supplies a current to the solenoid coil in a direction opposite to a drive current from the first current supply circuit.

According to the above configuration, the solenoid valve is driven by the supply of the drive current to the solenoid coil by the first current supply circuit. That is, the armature is sucked by the stator, and the valve body moves to a predetermined operating position accordingly. Further, when the solenoid coil changes from the operating state to the non-operating state, the energy in the solenoid coil is quickly stored as electric charge in the electric storage circuit. The second current supply circuit includes:
After the drive signal of the solenoid valve is turned off and the energization of the solenoid coil is temporarily interrupted, the charging voltage of the power storage circuit is applied to the solenoid coil, and the current is applied to the solenoid coil in a direction opposite to the drive current by the first current supply circuit. Flow. When the energization of the solenoid coil is cut off, the followability of the valve body operation tends to decrease due to the residual magnetic flux of the stator and the armature, but as described above, the followability of the valve body operation is improved by flowing the reverse current through the solenoid coil. It will be good. As a result, the responsiveness of the solenoid valve at the time of interrupting the current to the solenoid coil can be improved.

According to the second aspect of the present invention, the second current supply circuit discharges only a part of the stored electric charge when discharging the electric storage circuit, so that a part of the electric charge is stored in the electric storage circuit. It remains without being discharged, and its voltage is always relatively high (for example, 60 to 10 higher than the DC power supply voltage).
(About 0 V). Therefore, when the energy in the solenoid coil is recovered to the power storage circuit while the solenoid coil is not operated, the energy is recovered using a relatively high voltage, so that the time for the current to flow from the solenoid coil to the power storage circuit is short. As a result, the current of the solenoid coil falls earlier.

According to the third aspect of the present invention, the second current supply circuit supplies the power to the power storage circuit at a timing at which the drive current flowing through the solenoid coil becomes substantially zero after the drive signal of the solenoid valve is turned off. The stored electric charge is discharged to cause a reverse current to flow through the solenoid coil. Therefore, when discharging the power storage circuit, the discharged charge can be effectively used as a reverse current.

According to the fourth aspect of the present invention, in the first current supply circuit, the transistor connected to the solenoid coil is turned on / off in response to a drive signal of the solenoid valve.
Further, the Zener diode connected to the transistor absorbs a high voltage generated when current is cut off to the solenoid coil. Since the charging voltage of the power storage circuit is regulated by a value lower than the Zener voltage of the Zener diode in the first current supply circuit, the discharge voltage of the power storage circuit causes the Zener diode in the first current supply circuit to discharge. The inconvenience that the transistor is inadvertently turned on via the switch does not occur.

According to a fifth aspect of the present invention, the first current supply circuit includes a high voltage circuit for storing a voltage higher than the DC power supply voltage, and a predetermined constant current supplied to the solenoid coil upon receiving the DC power supply voltage. A constant current supply circuit for supplying
At the beginning of the operation of the solenoid valve, the high voltage of the high voltage circuit is discharged at a stretch, and the solenoid valve is kept on by the constant current of the constant current supply circuit.

According to this configuration, a steep rise of the current is obtained at the beginning of the operation of the solenoid valve, and the valve body quickly moves to the predetermined operating position. Further, the state can be maintained for a desired period after the operation of the solenoid valve. By having such an electromagnetic valve driving method, the electromagnetic valve driving circuit of the present invention can realize high-speed driving of the electromagnetic valve both when the drive signal is on and when it is off.

According to the invention described in claim 6, in the second current supply circuit, the transistor connected to the solenoid coil is turned on / off when the power storage circuit is discharged.
Further, the Zener diode connected to the transistor absorbs a high voltage generated at the end of discharging of the power storage circuit. Since the charging voltage of the high voltage circuit is regulated by a value lower than the Zener voltage of the Zener diode in the second current supply circuit, when discharging the high voltage circuit, the discharge voltage in the second current supply circuit There is no inconvenience that the transistor is inadvertently turned on via the Zener diode.

According to a seventh aspect of the present invention, the fuel injection device is applied to a fuel injection device for increasing the pressure of fuel as the plunger reciprocates and controlling the injection amount when the high-pressure fuel is supplied to the internal combustion engine. The solenoid coil is energized to perform pre-stroke injection in which fuel injection is started during the pressurization of fuel by the plunger at the beginning of fuel pressurization by the plunger.

For example, in the case of performing pilot injection, the valve body operation at the time of energization cutoff is delayed due to residual magnetic flux of the stator and armature of the solenoid valve, and the interval between the pilot injection and the main injection (pilot interval) cannot be shortened. .・ The minimum injection amount of the main injection cannot be reduced. However, according to the present invention, the above-described conventional problems can be solved by improving the responsiveness of the solenoid valve at the time of current interruption to the solenoid coil as described above. Therefore, it is possible to sufficiently meet the demands of reducing the pilot interval or reducing the minimum injection amount of the main injection in accordance with the engine operating state in order to reduce noise and emission.

Also in the case of performing the pre-stroke injection, the responsiveness of the solenoid valve at the time of interrupting the current to the solenoid coil is improved, so that the injection amount can be appropriately reduced according to the engine operating state. Become.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of a solenoid valve drive circuit according to the present invention will be described below with reference to the drawings. In the present embodiment, a fuel injection device of a multi-cylinder diesel engine for a vehicle is taken as an example, and an electromagnetic fuel spill valve of a distribution type fuel injection pump in the device is driven to optimally control a fuel injection amount to the engine. The solenoid valve driving circuit will be described in detail.

First, the configuration of the fuel injection pump and its solenoid valve will be described with reference to FIG. Fuel injection pump 20
A drive shaft 22 is rotatably arranged in the casing 21 of the first embodiment, and a cam plate 23 is coupled to the drive shaft 22 via a known coupling.
A cam surface 23a formed on the cam plate 23 is in contact with a plurality of rollers 25 supported by a roller ring 24, and the cam plate 23 is periodically moved back and forth in the axial direction as the drive shaft 22 rotates (see FIG. Reciprocating in the left-right direction). Thereby, the plunger 27 in the cylinder 26
Reciprocates back and forth together with the cam plate 23, and at the time of forward movement, compresses the fuel in the pressure chamber 28 formed at the tip of the plunger 27 and supplies it to the injection valve 31 through the distribution port 29 and the distribution flow path 30, and then retreats. Sometimes, the fuel in the low-pressure chamber 34 is transferred to the pressure chamber 2 through the suction passage 32 and the suction group 33.
Introduce to 8. A normally-open solenoid valve (electromagnetic fuel spill valve) 36 is disposed downstream of the pressure chamber passage 35 extending upward from the pressure chamber 28 in the figure. A low pressure chamber 34 communicates with a low pressure chamber 34 through a flow path 37 in a solenoid valve 36 and a low pressure flow path 38.

A signal rotor 40 is provided on the drive shaft 22, and a rotation sensor 41 composed of a pickup coil detects passage of the teeth of the signal rotor 40 and outputs a cylinder discrimination signal and an engine speed signal.

A microcomputer (hereinafter, referred to as a microcomputer) 50 for executing a known fuel injection control receives a cylinder discrimination signal of the rotation sensor 41 and an engine speed signal, and receives an accelerator opening degree from various sensors (not shown). Each state signal for fuel injection control, such as a signal and an engine cooling water temperature signal, is input. The microcomputer 50 determines the optimum fuel injection timing and fuel injection amount based on each of the state signals, and supplies a drive signal to the solenoid valve drive circuit 100. When the solenoid coil 42 in the solenoid valve 36 is operated by this drive signal, the valve opening / closing operation of the needle valve 43 as a valve body in the solenoid valve 36 is controlled, and an appropriate fuel according to the engine operating state is obtained. The injection amount is given from the injection valve 31 to each cylinder of the engine.

When the solenoid valve 42 is energized when the solenoid valve driving circuit 100 drives the solenoid valve 36, the armature 45 is attracted to the stator 44 side, and the push rod 46 integrated with the armature 45 is moved by the spring 47. The needle valve 43 is moved downward against the urging force. As a result, the needle valve 43 moves to the valve closing position, and the flow (spill) of the fuel from the pressure chamber 28 to the low-pressure chamber 34 is stopped. Then, with the lift of the plunger 27, high-pressure fuel in the pressure chamber 28 is injected from the injection valve 31.

When the power supply to the solenoid coil 42 is cut off, the needle valve 43 returns to the valve-opening position by the urging force of the spring 47 (the state shown in the figure). Thereby, the high-pressure fuel in the pressure chamber 28 is spilled to the low-pressure chamber 34, and the fuel injection by the injection valve 31 is stopped.

In this embodiment, the fuel injection pump 2
At the time of fuel injection from 0 to a diesel engine, a main injection and a pilot injection preceding the main injection are performed. That is, the microcomputer 50 generates a drive signal for pilot injection and a drive signal for main injection as drive signals for the solenoid valve, and outputs these signals to the solenoid valve drive circuit 10.
By sequentially outputting 0, both injections are realized.

Next, the configuration of the solenoid valve driving circuit 100 is shown in FIG.
This will be described with reference to FIG. In FIGS. 1 and 2,
For ease of explanation, the solenoid valve driving circuit 100 including the solenoid coil 42 in the solenoid valve 36 is shown.

The solenoid valve drive circuit 100 has a control circuit IC 101 and an inrush current supply circuit 110 as main components.
, A holding current supply circuit 130, an energization circuit 140, a reverse current supply circuit 150, and a power storage circuit 180. Briefly describing them, the control circuit IC101 includes the microcomputer 5
0, and each circuit 110,
Signals are output to 130 and 140. The inrush current supply circuit 110 stores a voltage higher than the battery voltage VB, applies the high voltage to the solenoid coil 42, and supplies an inrush current (approximately 10A) at the initial drive of the solenoid valve 36. The holding current supply circuit 130 supplies a predetermined holding current (about 3 A) smaller than the rush current to the solenoid coil 42 following the rush current. The energization circuit 140 allows energization of the solenoid coil 42 during the ON period of the drive signal from the microcomputer 50. Reverse current supply circuit 15
A value of 0 causes a reverse current to flow through the solenoid coil 42 for a predetermined short time when the drive signal from the microcomputer 50 is turned off. Further, the electric storage circuit 180 includes the solenoid coil 4
2 stores energy in the solenoid coil 42 when it becomes inactive.

In this embodiment, the control circuit IC10
1. Inrush current supply circuit 110, holding current supply circuit 130
And the energizing circuit 140 is the “first current supply circuit” of the present invention.
And the control circuit IC101 and the reverse current supply circuit 15
0 corresponds to the “second current supply circuit” of the present invention. Further, the inrush current supply circuit 110 corresponds to a “high voltage circuit”, and the holding current supply circuit 130 corresponds to a “constant current supply circuit”.

More specifically, in the control circuit IC101,
A drive signal from the microcomputer 50 is input to the terminal A.
The control circuit IC101 outputs either an ON signal (5V) or an OFF signal (0V) from the terminals C, E, F, and G based on the drive signal and the voltage signals input to the terminals D and H. Note that 5 V is input to the terminal B of the control circuit IC101, and the terminal I is connected to the ground potential terminal.

In the rush current supply circuit 110,
One end on the primary side of the transformer 111 is connected to a battery power supply (VB) as a DC power supply, and the other end is also connected to the collector of an NPN transistor 112. The emitter of the transistor 112 is connected to the ground potential terminal. The base of the transistor 112 is connected to the ground potential terminal via the resistor 113 and to the terminal C of the control circuit IC 101 via the resistor 114.

One end on the secondary side of the transformer 111 is connected to a capacitor 116 via a diode 115, and the other end is also connected to a ground potential terminal. Capacitor 1
16 high potential terminals are connected to ground potential terminals through resistors 117 and 118, and these resistors enable the capacitor 1
The 16 voltages are divided and detected. Resistance 117, 11
The connection point between 8 is connected to the terminal D of the control circuit IC101. Here, in order to reduce the amount of charge stored in the capacitor 116 flowing to the ground potential terminal via the resistors 117 and 118, it is desirable to set the resistance values of the resistors 117 and 118 to relatively large values. In form 1
17 is 3 MΩ, and the resistor 118 is 1 MΩ.

The capacitance of the capacitor 116 is 10 μF, and the capacitor 116 is charged until the charging voltage becomes 150V. That is, the control circuit IC101 detects the charging voltage of the capacitor 116 at the connection point between the resistors 117 and 118, and when the voltage is lower than 150V, switches the transistor 112 to 150V to charge the capacitor 116.

The high potential terminal of the capacitor 116 is
It is connected to the emitter of a PNP transistor 119 and to the base of the transistor 119 via a resistor 120. The collector of the transistor 119 is connected to the solenoid coil 4 via the diode 125.
2 and the base is also connected to the N
It is connected to the collector of a PN transistor 122. The emitter of the transistor 122 is connected to the ground potential terminal, the base is connected to the ground potential terminal via the resistor 123, and the control circuit I
It is connected to terminal E of C101.

The control circuit IC101 turns on the output of the terminal E for a predetermined time (for 0.7 ms in this embodiment) from when the drive signal from the microcomputer 50 input to the terminal A is turned on from off. A signal (5 V) is applied, and the transistors 119 and 122 are turned on. At this time, the peak is about 10 due to the high voltage charge stored in the capacitor 116.
An inrush current of A is supplied to the solenoid coil 42.

In the holding current supply circuit 130,
The emitter of the PNP transistor 131 is connected to a battery power supply (VB). The base of the transistor 131 is connected to a battery power supply (VB) via a resistor 132 and the control circuit IC10 via a resistor 133.
1 terminal F. The collector of the transistor 131 is connected to the solenoid coil 42 via the diode 134. The anode of the diode 135 is connected to the ground potential terminal, and the cathode is connected to the solenoid coil 42.

While the drive signal from the microcomputer 50 is ON (5 V), the control circuit IC 101 outputs a predetermined holding current (about 3 V).
The output signal of the terminal F is turned on / off while monitoring the drive current of the coil 42 so that A) is supplied to the solenoid coil 42.

Further, in the energizing circuit 140, the collector of the NPN transistor 141 is connected to the solenoid coil 4
2 and the emitter is connected via a resistor 142 to a ground potential terminal. As shown, a Zener diode 14 is provided between the base and collector of the transistor 141.
3 and the diode 144 are connected. The Zener diode 143 plays a role for absorbing a high voltage generated when the current to the solenoid coil 42 is cut off. The base of the transistor 141 is connected to the terminal G of the control circuit IC 101 via the resistor 145 and to the ground potential terminal via the resistor 146.

Here, the resistance value of the resistor 142 is set sufficiently smaller than the resistance value of the solenoid coil 42, so that the amount of current flowing through the solenoid coil 42 is not significantly affected. Actually, while the resistance value of the solenoid coil 42 is 1.5Ω, the resistance 142
Is 0.05Ω. In the figure, the voltage at point a is determined by the current flowing through the resistor 142, and the voltage is input to the terminal H of the control circuit IC101. That is, a voltage corresponding to a current value flowing through the solenoid coil 42, the transistor 141, and the resistor 142 is input to the terminal H of the control circuit IC101.

The above configuration (the control circuit IC 101 and the circuits 110, 130, 140 in FIG. 1) corresponds to a basic configuration for driving the solenoid valve 36, and its operation will be described next with reference to a time chart in FIG. explain.

The output of the terminal G of the control circuit IC101 is turned on / off in response to a drive signal from the microcomputer 50. When the output of the terminal G is on, the transistor 141 is turned on, and the output of the terminal G is also turned off. During the period, the transistor 141 is turned off. When the drive signal from the microcomputer 50 is turned on, the output from the terminal E of the control circuit IC 101 is turned on for 0.7 ms. This allows
The transistors 122 and 119 are turned on, and an inrush current is supplied to the solenoid coil 42 by the high voltage charge stored in the capacitor 116. Note that the charging voltage of the capacitor 116 temporarily drops, but is recharged until it becomes 150 V by turning on / off the transistor 112.

A resistor 14 is connected to a terminal H of the control circuit IC101.
2 (voltage at point a in FIG. 1) is input, and the control circuit IC101 outputs the current value through the resistor F from the terminal F so that the current value flowing through the resistor 142 becomes about 3 A while the drive signal from the microcomputer 50 is on. Turn on / off the output of Specifically, when the current value becomes equal to or more than 3.1 A, the output is turned off and 2.9 A
A hysteresis of about 0.2 A is provided so that the output is turned on when the voltage becomes below.

When the drive signal from the microcomputer 50 is turned off, the control circuit IC 101 turns off the outputs of the terminals F and G, and stops the supply of the current to the solenoid coil 42. When the outputs of the terminals F and G are turned off, the voltage at the point b in FIG. 1 temporarily becomes the Zener voltage Vz (= 170 V) of the Zener diode 143, and the transistor 141 operates in the active region. At this time, assuming that the inductance of the solenoid coil 42 is L, the current rapidly decreases with the gradient of the current, di / dt = −Vz / L, and the current value becomes 0A. When the solenoid coil 42 shifts to the non-operating state (when the coil current decreases to 0 A), the current flows through the path of the ground potential terminal → the diode 135 → the solenoid coil 42 → the transistor 141 → the resistor 142. However, this is an operation when the reverse current supply circuit 150 described later is not provided, and the operation is slightly changed when the circuit 150 is provided.

On the other hand, in the reverse current supply circuit 150 of FIG. 2, the monostable multivibrator 151
Is detected, and the output is turned on for a predetermined time determined by the resistor 152 and the capacitor 153. Also, the monostable multivibrator 154
The falling of the output signal of the monostable multivibrator 151 is detected, and the output is turned on for a predetermined time determined by the resistor 155 and the capacitor 156. The output of the monostable multivibrator 154 is an NPN transistor 1
57 and 165 are respectively input to the bases.

The base of the transistor 157 is further connected to a ground potential terminal via a resistor 158, and the emitter is connected to the ground potential terminal. Also, the transistor 15
7 is connected to the base of a PNP transistor 160 via a resistor 159. A resistor 161 is connected between the base and the emitter of the transistor 160, and the collector of the transistor 160 is connected to the diode 1
It is connected to the solenoid coil 42 via 62.
The anode of the diode 163 is connected to the ground potential terminal, and the cathode is connected to the solenoid coil 42.

The base of the transistor 165 is further connected to a ground potential terminal via a resistor 166, and the emitter is connected to the ground potential terminal. Also, the transistor 16
5 is connected to the solenoid coil 42. As shown, a diode 167 and a Zener diode 16 are connected between the base and collector of the transistor 165.
8 are connected.

The power storage circuit 180 includes the diode 18
1 and a capacitor 182,
One end of 2 is connected to the solenoid coil 42 via the diode 181 and to the emitter of the transistor 160, and the other end of the capacitor 182 is connected to the ground potential terminal.

Here, energy in the solenoid coil 42 is stored in the capacitor 182 when the solenoid coil 42 is in a non-operation state. In practice, the capacitance of the capacitor 182 is 1 μF, and the capacitor 182 is charged to about 150V. Then, the high-voltage charge of the capacitor 182 is discharged during a period in which a signal output via the monostable multivibrators 151 and 154 is on. However, the discharging of the capacitor 182 is for discharging only a part of the stored electric charge.
During the discharging period, the charging voltage is about 150 V to about 100 V
It is regulated in a relatively short time until it drops to Therefore, the charging voltage is always maintained at 100 V or more.

Next, the characteristic operation of the present embodiment will be described with reference to the time chart of FIG. 5, focusing on the operation of the reverse current supply circuit 150 and the power storage circuit 180. When the drive signal for pilot injection is turned on at time t1, an inrush current of about 10A is supplied to the solenoid coil 42 by the high voltage charge stored in the capacitor 116 as described above, and the needle valve 43 closes promptly. Move to valve position. After the inrush current is supplied, a holding current of about 3 A flows through the solenoid coil 42, and the closed state of the needle valve 43 is maintained. At time t1, the solenoid valve 36
The magnetic flux generated in the stator 44 and the armature 45 increases.

Thereafter, at time t2, the lift of the plunger 27 starts, and the injection of fuel from the injection valve 31 is started. Then, when the drive signal from the microcomputer 50 is turned off at time t3, the fuel injection by the injection valve 31 is temporarily stopped. During the period from time t2 to t3, fuel injection corresponding to pilot injection is performed.

At time t3, a current that is to continue flowing through the solenoid coil 42 flows from the ground potential terminal to the capacitor 182 through the diode 135 in the holding current supply circuit 130, the solenoid coil 42, and the diode 181 in the power storage circuit 180. Inflow, and as a result, capacitor 1
82 is charged to about 150V.

At this time, the gradient “di / dt” of the current flowing to the capacitor 182 is
Since 2 is charged to about 100 V, a large value is achieved from the relationship of di / dt = -Vc (t) / L (L is the inductance of the solenoid coil 42, and Vc is the voltage of the capacitor 182). That is, since the capacitor 182 is always kept at 100 V or more, the time during which the current flows from the solenoid coil 42 to the capacitor 182 is short, and the fall of the current flowing through the solenoid coil 42 can be prevented from becoming long.

At time t3, during T1 [ms],
The output of the monostable multivibrator 151 is turned on.
T1 [ms] is a time determined by the resistor 152 and the capacitor 153, and is set to substantially coincide with the time when the current flowing through the solenoid coil 42 decreases to 0 mA.

Thereafter, when T1 [ms] elapses, the output of the monostable multivibrator 151 turns off, and subsequently, for T2 [ms], the output of the monostable multivibrator 151 turns on. T2 [ms] is the resistance 15
5 and the time determined by the capacitor 156,
The time is set until the voltage of the capacitor 182 decreases from about 150V to about 100V.

While the output of the monostable multivibrator 154 is on, the transistors 157, 160, and 165 are on, and the high voltage charge stored in the capacitor 182 passes through the transistor 160, the diode 162, the solenoid coil 42, and the transistor 165. Flow into the ground potential terminal. At this time, a current flows in the solenoid coil 42 in a direction opposite to that when battery power (VB) is applied to the solenoid coil 42 (a current in a direction opposite to the period from t1 to t3). In other words, assuming that the current during the period from t1 to t3 is a positive current, a negative current flows when the capacitor 182 is discharged. Therefore, the magnetic flux in the stator 44 and the armature 45 is quickly eliminated. Therefore, the valve opening operation of the needle valve 43 is faster than in the conventional device without the reverse current supply circuit 150 and the power storage circuit 180, and the interval between the pilot injection and the subsequent main injection (pilot interval) can be reduced. Becomes

According to the inventor of the present invention, for example, when the engine rotation speed is 800 rpm, in the conventional device, if the pilot interval is shorter than 1.5 ms, the variation in the main injection amount per cycle becomes large. It has been confirmed that in the device of the form (1), stable fuel injection can be performed even if the time is shortened to 1.2 ms, which is 0.3 ms shorter than the conventional device.

Note that the Zener voltage Vz of the Zener diode 143 in the energizing circuit 140 is Vz = 170 V, which is higher than the maximum charging voltage 150 V of the capacitor 182. When the charge stored in the capacitor 182 is discharged, the transistor 141 It is configured not to be turned on carelessly.

When the output of the monostable multivibrator 154 is turned off after the lapse of T2 [ms], the transistor 1
57, 160 are turned off, and the reverse current which tries to keep flowing through the solenoid coil 42 is supplied from the ground potential terminal to the diode 163, the solenoid coil 42, and the transistor 165.
Through to the ground potential terminal. At this time, c in FIG.
The voltage at the point is the Zener voltage V of the Zener diode 168.
When z ′ is reached, the transistor 165 operates in the active region, and the reverse current rapidly decreases with the current gradient “di / dt = −Vz ′ / L”. The Zener diode 1
The zener voltage Vz ′ of 68 is the inrush current supply circuit 110
Vz ′ = 170 V, which is higher than the maximum charging voltage 150 V of the internal capacitor 116, so that the transistor 165 is prevented from being inadvertently turned on when an inrush current flows through the solenoid coil 42.

Thereafter, when the drive signal for main injection is turned on at time t4, an inrush current of about 10 A is again supplied to the solenoid coil 42, and the needle valve 43 moves to the valve closing position again. After the inrush current is supplied, a current of about 3 A flows through the solenoid coil 42 and the needle valve 4
The closed state of No. 3 is maintained. Then, when the drive signal from the microcomputer 50 is turned off at time t5, the fuel injection by the injection valve 31 ends. During the period from time t4 to t5, fuel injection corresponding to main injection is performed.

At time t5, similarly to time t3 at which the pilot injection ends, the current flowing through the solenoid coil 42 causes the capacitor 18 in the power storage circuit 180 to continue flowing.
2 is charged to about 150V. After a lapse of T1 [ms], a reverse current flows through the solenoid coil 42 due to the discharge of the high-voltage charge of the capacitor 182, and the stator 4
4 and the magnetic flux in the armature 45 are quickly eliminated.
Therefore, the valve opening operation of the needle valve 43 is performed promptly,
It becomes possible to make the minimum injection amount of the main injection smaller than that of the conventional device.

According to the present inventor, for example, when the main injection amount is smaller than 15 mm ^ 3 when the engine speed is 800 rpm, the variation of the main injection amount in each cycle increases, It has been confirmed that in the apparatus of the embodiment, stable fuel injection can be achieved even if the fuel injection amount is reduced to 10 mm ^ 3, which is 5 mm ^ 3 less than that of the conventional apparatus.

According to this embodiment described in detail above, the following effects can be obtained. (A) When the solenoid coil 42 is deactivated, the energy in the coil 42 is stored in the capacitor 182;
After the drive signal of the solenoid valve 36 is turned off, the charging voltage of the capacitor 182 is applied to the solenoid coil 42, and the current is caused to flow through the solenoid coil 42 in a direction opposite to the normal drive current. When the power supply to the solenoid coil 42 is interrupted, the followability of the operation of the needle valve 43 tends to decrease due to the residual magnetic flux of the stator 44 and the armature 45. However, by supplying the reverse current to the solenoid coil 42 as described above, the solenoid The responsiveness of the solenoid valve 36 when the current to the coil 42 is interrupted can be improved.

(B) When discharging the capacitor 182, only a part of the stored charge is discharged. Therefore, a part of the charge remains in the capacitor 182 without being discharged, and the voltage is always maintained at about 100V. You. Therefore, when the solenoid coil 42 is deactivated and the energy in the coil 42 is recovered by the capacitor 182, energy is recovered using a relatively high voltage, so that current flows from the solenoid coil 42 into the capacitor 182. The time is short, and the current of the solenoid coil 42 falls earlier.

(C) After the drive signal of the solenoid valve 36 is turned off, the electric charge stored in the capacitor 182 is discharged at the timing when the drive current flowing through the solenoid coil 42 becomes almost zero, and a reverse current is supplied to the solenoid coil 42. Since the current flows, the discharge charge of the capacitor 182 can be effectively used as a reverse current.

(D) The charging voltage of the capacitor 182 is regulated at a value lower than the Zener voltage Vz of the Zener diode 143 in the energizing circuit 140.
At the time of discharging of the transistor 82, there is no inconvenience that the transistor 141 is inadvertently turned on via the Zener diode 143 by the discharging voltage.

(E) At the beginning of the operation of the solenoid valve 36, the high voltage of the capacitor 116 is discharged at once, and the solenoid valve 36 is kept on by a predetermined holding current. The steep rise of the current is obtained, and the needle valve 43 is quickly moved to the predetermined closing position. Further, after the operation of the solenoid valve 36, the closed state can be maintained for a desired period. By having such an electromagnetic valve drive system, the electromagnetic valve drive circuit 100 can realize high-speed driving of the electromagnetic valve 36 both when the drive signal is turned on and when the drive signal is turned off (when the valve is opened and when the valve is closed).

(F) Since the charging voltage of the capacitor 116 is regulated at a value lower than the Zener voltage Vz ′ of the Zener diode 168 in the reverse current supply circuit 150, the Zener diode is discharged by the discharging voltage when the capacitor 116 is discharged. There is no inconvenience that the transistor 165 is inadvertently turned on via 168.

(G) Due to the residual magnetic flux of the stator 44 and the armature 45 of the solenoid valve 36, the operation of the needle valve 43 at the time of energization cutoff becomes slow, and the interval (pilot interval) between the pilot injection and the main injection is short. Can not.
・ The minimum injection amount of the main injection cannot be reduced. Such a conventional problem can be solved, and it is possible to sufficiently meet the demands of reducing the pilot interval or reducing the minimum injection amount of the main injection in accordance with the engine operating state in order to reduce noise and emission.

(Second Embodiment) Next, a second embodiment of the present invention will be described. However, in the configuration of the second embodiment, the same components as those of the above-described first embodiment are denoted by the same reference numerals and the description thereof is simplified. The following description focuses on differences from the first embodiment.

In the first embodiment, the present invention is embodied by an apparatus for performing pilot injection and main injection. However, in this embodiment, the present invention is embodied by an apparatus for performing pre-stroke injection. . By the way, the pre-stroke injection means that the plunger 27 is changed by changing the use area of the cam.
This is an injection method in which the needle valve 43 is closed during the pressure feeding.

FIG. 6 is a time chart when the pre-stroke control is performed. In FIG. 6, when a drive signal from the microcomputer 50 is turned on at time t11 after a predetermined pre-stroke period has elapsed, the solenoid coil 42
A rush current of 0 A and a holding current of about 3 A subsequently flow, and fuel injection by the injection valve 31 is started. Then, when the drive signal from the microcomputer 50 is turned off at time t12, the fuel injection by the injection valve 31 ends.

Particularly at time t12, at time t12 in FIG.
3 and t5, the capacitor 18 in the electric storage circuit 180
2 is charged to about 150V. After a lapse of T1 [ms], a reverse current flows through the solenoid coil 42 due to the discharge of the high-voltage charge of the capacitor 182, and the stator 4
4 and the magnetic flux in the armature 45 are quickly eliminated.
Therefore, the valve opening operation of the needle valve 43 when the current to the solenoid coil 42 is interrupted is quickly performed, and the minimum injection amount of the pre-stroke injection can be reduced as compared with the conventional device.

According to the inventor of the present invention, for example, when the engine speed is 800 rpm, the injection amount is reduced by 15 in the conventional device.
If it is smaller than 3 mm ^ 3, the variation of the injection amount in each cycle will be large. On the other hand, in the device of this embodiment, stable fuel injection is possible even if it is reduced to 10 mm ^ 3 which is 5 mm3 less than the conventional device. It has been confirmed that

The embodiment of the present invention can be embodied in the following forms other than the above. In the above embodiment, when discharging the capacitor 182 of the power storage circuit 180, the discharging time is set to T2 [ms] by the monostable multivibrator 154, but this configuration is changed. For example, the capacitor 18
2 may be constantly monitored, and if the capacitor voltage decreases to a predetermined value (about 100 V) during discharging, the discharging may be terminated at that time. Also in such a case, only a part of the electric charge stored in the capacitor 182 is discharged, and as described above, the energy in the solenoid coil 42 is promptly recovered when the power supply is cut off.

In the inrush current supply circuit 110 of FIG. 1, the charging of the capacitor 116 is performed by boosting the transformer 111, but this configuration is changed. For example, transformer 111
And the capacitor 116 is charged by a high voltage generated when the solenoid coil 42 is de-energized (same as in JP-A-8-14091). In this case, if the discharge of the capacitor 116 is limited to a short time at the start of the operation of the solenoid valve and a part of the charge voltage is left, the charge voltage of the capacitor 116 is always maintained at a relatively high voltage. As a result, the fall of the current in the solenoid coil 42 can be made steep. In addition, cost reduction can be achieved.

Each of the transistors in the above embodiment may be any switch means that turns on / off in response to a drive signal of the solenoid valve 36. For example, an FET (field effect transistor) may be used instead of a bipolar transistor. Is also good.

In the above embodiment, the characteristic operation and effect of the fuel injection device for performing the pilot injection or the pre-stroke injection have been described.
(C component) is used as a catalyst reducing agent in other injection forms such as post-injection performed after the main injection or multi-stage split injection performed before the main injection at the time of low temperature start of the engine. It may be embodied. Also in such a case, excellent effects such as a reduction in injection interval or a reduction in injection amount when performing intermittent injection can be obtained.

As another application of the solenoid valve driving circuit according to the present invention, a common rail type fuel injection device may be embodied. Similarly, in the common rail type fuel injection device, excellent effects such as shortening the injection interval or reducing the injection amount when performing pilot injection, pre-stroke injection, and the like can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a solenoid valve driving circuit.

FIG. 2 is a circuit diagram showing a configuration of a solenoid valve driving circuit.

FIG. 3 is a sectional view showing a configuration of a fuel injection pump.

FIG. 4 is a time chart showing the operation of the solenoid valve drive circuit.

FIG. 5 is a time chart showing the operation of the solenoid valve drive circuit.

FIG. 6 is a time chart showing the operation of the solenoid valve driving circuit according to the second embodiment.

[Explanation of symbols]

Reference Signs List 20: fuel injection pump, 27: plunger, 36: solenoid valve, 42: solenoid coil, 43: needle valve as a valve element, 44: stator, 45: armature, 50: microcomputer, 100: solenoid valve driving circuit, 101: Control circuit I
C, 110: inrush current supply circuit as high voltage circuit, 1
30 ... a holding current supply circuit as a constant current supply circuit, 14
0 ... energizing circuit, 141 ... transistor, 143 ... Zener diode, 150 ... reverse current supply circuit, 165 ... transistor, 168 ... Zener diode, 180 ... electricity storage circuit, 182 ... capacitor.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) F02M 51/00 F02M 51 / 00F // F02M 51/06 51/06 M (72) Inventor Yoshifumi Katsuraya Aichi 14 Iwatani, Shimohanomachi, Nishio, Japan Pref. (72) Inventor Yasuhiro Takeuchi 1-1-1, Showa-cho, Kariya, Aichi F-term (reference) 3G066 AA07 AB02 AC04 AD12 BA19 BA22 BA23 CA01S CA08 CA09 CA20U CA32U CD26 CD28 CE02 CE22 CE24 CE25 CE29 DA10 DC04 DC05 DC09 DC14 3G301 HA02 JA14 LB16 LC10 MA11 MA18 MA23 PE01Z PE05Z PE08Z PF03Z 3H106 DA07 DA23 DB02 DB12 DB26 DB32 DC02 DD03 EE04 FA07 FA07

Claims (7)

[Claims] An electromagnetic valve driving circuit for driving an electromagnetic valve that attracts an armature to a stator when energizing a solenoid coil and moves a valve body to a predetermined operating position accordingly. A first current supply circuit for applying a DC power supply voltage to the solenoid coil in response to a drive signal for supplying a drive current in a predetermined direction to the solenoid coil, and a solenoid coil when the solenoid coil is deactivated. After the drive signal of the solenoid valve is turned off, the charging voltage by the power storage circuit is applied to a solenoid coil, and the solenoid is driven in the opposite direction to the drive current by the first current supply circuit. And a second current supply circuit for supplying a current to the coil. 2. The solenoid valve drive circuit according to claim 1, wherein the second current supply circuit discharges only a part of the stored electric charge when discharging the electric storage circuit. 3. The second current supply circuit discharges the charge stored in the power storage circuit at a timing when the drive current flowing through the solenoid coil becomes substantially zero after the drive signal of the solenoid valve is turned off. 3. The solenoid valve drive circuit according to claim 1, wherein a reverse current flows through the solenoid coil. 4. The first current supply circuit is connected to a solenoid coil and is turned on / off in response to a drive signal of a solenoid valve.
A transistor to be turned off, and a Zener diode connected to the transistor for absorbing a high voltage generated when current is interrupted to the solenoid coil, wherein the Zener diode is lower than a Zener voltage of the Zener diode in the first current supply circuit. The solenoid valve drive circuit according to claim 1, wherein a charging voltage of the power storage circuit is regulated by a value. 5. A first current supply circuit comprising: a high voltage circuit for storing a voltage higher than the DC power supply voltage; and a constant current supply circuit for receiving a DC power supply voltage and supplying a predetermined constant current to a solenoid coil. Wherein the high voltage of the high voltage circuit is discharged at once at the beginning of driving of the solenoid valve, and the solenoid valve is kept on by the constant current of the constant current supply circuit.
An electromagnetic valve driving device according to claim 4. 6. The solenoid valve drive circuit according to claim 5, wherein the second current supply circuit is connected to a solenoid coil and turned on / off when discharging the power storage circuit, and connected to the transistor. And a Zener diode for absorbing a high voltage generated at the end of discharging of the power storage circuit, wherein the charging voltage of the high voltage circuit is lower than the Zener voltage of the Zener diode in the second current supply circuit. The solenoid valve drive circuit is regulated. 7. A fuel injection device for increasing the pressure of fuel as the plunger reciprocates and controlling the injection amount when the high-pressure fuel is supplied to the internal combustion engine. The fuel injection device includes a main injection and a pilot injection preceding the main injection. To energize the solenoid coil to perform, or at the beginning of fuel pressurization by the plunger,
The solenoid valve driving circuit according to any one of claims 1 to 6, wherein the solenoid coil is energized to perform pre-stroke injection for starting fuel injection during the pressurization.