JPH1018888A - Fuel injection valve drive circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control open/close operation of a fuel injection valve with good responsiveness. SOLUTION: A capacitor 2 connected at its one end to a reference potential points is connected at the other end to a connecting point between high and low voltage power supply units and a solenoid 1 of a fuel injection valve. When an application of a voltage from the high voltage power supply unit or the low voltage power supply unit is cut off, the solenoid 1 is quickly discharged by accumulating a magnetic energy which remains in the solenoid 1 as a current in a capacitor C2. At the time of instruction for closing the fuel injection valve, a switching element Q3 disposed between one end of the capacitor C2 and the reference potential point is turn ON and a voltage is applied from the capacitor C2 to the solenoid 1 so as to make a current flow in the direction in which a force of closing the fuel injection valve act, whereby demagnetization of the solenoid 1 is accelerated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection valve driving circuit for supplying fuel to an engine, and more particularly to a fuel injection valve driving circuit for high-speed opening / closing control with excellent responsiveness.

[0002]

2. Description of the Related Art In recent years, in a fuel supply system of an automobile engine, it has been required to control the amount and timing of injected fuel with extremely high accuracy in order to improve fuel efficiency and drivability. In particular, in a direct injection type engine, the injection port of the fuel injection valve directly faces the cylinder, and basically, the fuel must be injected within a short time during the intake stroke.
In particular, accurate opening and closing control is required.

[0003] In an electromagnetically driven fuel injection valve using a solenoid generally used in an automobile engine, the response time of the solenoid required for opening and closing the valve is shortened as much as possible, and the valve opening time and the fuel injection with respect to the injection pulse signal are reduced. By allowing the amount to be taken as a proportional relationship, it becomes easy to accurately control the timing and amount of fuel injection.

Conventionally, as a fuel injection valve driving circuit for the purpose of improving such response, there is, for example, a circuit as shown in FIG. 9A (see Japanese Patent Application Laid-Open No. 57-49059). In this circuit, as shown in FIG. 9 (b), when the injection pulse signal IN becomes high level, the transistor 11 and the transistors 12 and 13 controlled by the signal Q are turned on, and the solenoid 15 To the solenoid 15 by applying a sufficiently high voltage (for example, several hundred volts).
The current ic flowing through is rapidly raised. When the current ic reaches a predetermined value, the signal Q changes to a low level, the transistors 12 and 13 are turned off, and a voltage VB (ten tens of volts) is applied to the solenoid 15 to hold the solenoid. Further, when the ejection pulse signal falls, the transistor 11 is turned off, and a current that tends to continue to flow through the solenoid 15 flows into the capacitor 14. In other words, the magnetic energy remaining in the solenoid 15 flows into the capacitor 14 as a current, and the capacitor 14 is charged to a high voltage, and at the same time, the current ic of the solenoid 15 falls.

[0005]

However, in such a conventional drive circuit, when the state shifts from the rising state where the high voltage is applied to the holding state where the voltage VB is applied, the current flowing through the solenoid is: It does not immediately decrease to a steady value determined by the voltage VB and the resistance of the solenoid coil, but gradually decreases due to the inductance component of the solenoid coil. That is, for a while (for example, several hundreds of microseconds) after the applied voltage is switched from the discharge voltage of the capacitor to VB, the current does not reach the above-mentioned steady value, and more current than necessary flows wastefully. However, there is a problem that heat generation of the fuel injection valve is increased.

In addition, since the current flowing through the solenoid continues to change from the time when the state is switched to the holding state until the steady value is obtained, if the injection pulse input is turned off during this period, the current is required to disappear. Time is no longer constant,
The time required for the solenoid to fall will vary. As a result, there is a problem that the proportional relationship between the length of the injection pulse and the injection amount of the fuel injection valve is not maintained, and accurate control becomes difficult.

Further, when the ejection pulse signal falls,
The magnetic energy remaining in the solenoid is absorbed as a current by the high-voltage application capacitor, and the current of the solenoid is rapidly extinguished.However, the change in the magnetic flux has a delay with respect to the change in the current. Even if it disappears, there is a problem that the suction force of the solenoid does not immediately become zero and the delay in falling cannot be completely eliminated.

In this regard, it is possible to improve the responsiveness of the needle valve by disposing the switching element in an H-bridge structure with respect to the solenoid, and causing the current to flow in the opposite direction to the coil at the time of the fall to rapidly demagnetize the solenoid. It is. However, a charging unit is required for each of the valve opening and valve closing capacitors,
In addition, since five or more switching elements are required for each cylinder, and the circuit scale is large and control is complicated, a drive circuit having a simpler configuration has been desired.

The present invention has been made in view of such conventional problems,
It is an object of the present invention to provide a fuel injection valve drive circuit that is excellent in responsiveness and energy efficiency of a solenoid.

[0010]

According to the present invention, there is provided a driving circuit for an electromagnetically driven fuel injection valve, comprising a high voltage power supply and a low voltage power supply, and a command to open the fuel injection valve. Occasionally, one end of the solenoid for driving the fuel injection valve, one end of which is connected to a reference potential point via a resistance for current detection, is connected to the high voltage power supply, and the solenoid is opened by the solenoid. As a configuration having valve-opening switching means for applying a high voltage in a direction in which a force acts, the current flowing through the solenoid is rapidly raised.

Further, after a predetermined time has passed from the time of the valve opening command, while the low voltage power supply and the solenoid are shut off, the connection between the high voltage power supply and the solenoid is cut off to apply a high voltage. And a rapid discharging means for rapidly discharging the current flowing through the solenoid until the current drops to a predetermined current value capable of maintaining the open state of the fuel injection valve. Move to

After the rapid discharge by the rapid discharge means, the application of a low voltage by connecting the low voltage power supply to the other end of the solenoid and the discharge by interruption are controlled so that the current flowing through the solenoid is controlled to the predetermined level. Is provided so that the current flowing through the solenoid is always constant when the solenoid current is turned off when the valve is closed.

Further, magnetic energy remaining in the solenoid is stored as a current when the high-voltage power supply and the solenoid are cut off by the rapid discharge means and when the low-voltage power supply and the solenoid are cut off by the current holding means. Power storage means, and the power storage means and the solenoid for a predetermined period of time such that a current flows in a direction in which the valve closing force of the fuel injection valve acts on the solenoid in synchronization with a valve closing command of the fuel injection valve. A valve closing switching means is provided for connection, and the electric charge accumulated in the power storage means is used to flow a current in the solenoid opposite to the valve opening state and the holding state at the time of valve closing.

[0014] The power storage means is interposed between a capacitor having one end connected to the other end of the solenoid and a reference potential point, for example, as in the second aspect of the present invention. A simple configuration including a diode. Further, in the invention according to claim 3, the power storage device includes a constant voltage diode connected in parallel to the capacitor, and limits the amount of charge stored in the capacitor to a constant value.

The valve-closing switching means may include a switching element provided in parallel with the diode interposed between the other end of the capacitor and a reference potential point. With this configuration, the electric charge accumulated in the capacitor can be made to flow through the solenoid as a current in a direction opposite to that in the valve opening state and the holding state.

Further, in the invention according to claim 5, the current holding means controls connection and disconnection between the low-voltage power supply and the other end of the solenoid based on a value of a current flowing through the current detecting resistor. Then, control is performed so that the current flowing through the solenoid in the holding state is stabilized at a predetermined value.

[0017]

According to the first aspect of the present invention, the current flowing through the solenoid coil at the time of the valve opening command is rapidly raised, while the state is rapidly shifted from the high voltage application state to the holding state, and the extra current is reduced. This has the effect of reducing heat generation of the fuel injection valve. When the valve is closed, the current flowing through the solenoid is always constant, and when the valve is opened and the current flowing in the opposite direction to the holding state is passed through the solenoid to demagnetize, the valve closing operation can be performed smoothly and quickly. There is also an effect that accurate opening / closing valve control corresponding to the timing and length of the injection pulse signal can be performed.

The current for degaussing the solenoid when the valve is closed is a current accumulated from the solenoid when the valve shifts from the high voltage application state to the holding state when the valve is opened or when the valve is controlled to a fixed holding state. Is used, energy can be used effectively, and there is an effect that unnecessary heat generation can be suppressed. According to the second aspect of the present invention,
Since the structure is simpler than that of the conventional driving circuit, the number of parts, the number of manufacturing steps, and the cost can be reduced, and there is an effect that it can be easily implemented.

According to the third aspect of the present invention, the amount of electric charge stored in the capacitor due to the discharge from the solenoid is limited to a predetermined value regardless of the length of the injection pulse signal. There is an effect that the current for demagnetization flowing through the solenoid is made constant and a stable valve closing operation can be obtained. According to the invention of claim 4, the supply of the current for demagnetizing the solenoid can be controlled only by adding one switching element, so that the manufacturing process and the cost can be reduced. In addition, there is an effect that control is simplified because the number of switching elements is small.

According to the invention of claim 5, since the application of the low voltage is controlled based on the current value actually flowing through the solenoid, accurate control corresponding to the change can be performed.
There is an effect that the current of the solenoid can be maintained at a predetermined value.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of a fuel injection valve drive circuit according to one embodiment of the present invention. The solenoid 1 of the fuel injection valve is electrically composed of an inductance component L1 and a resistance component R1. One end of the solenoid 1 is connected (grounded) to a reference potential point via a current detection resistor R2.

The other end of the solenoid 1 is connected to a high voltage charging section 2 via a switching element Q1 (transistor in FIG. 1).
Is connected. The other end of the capacitor C1 having one end connected to the reference potential point is connected to a connection point between the switching element Q1 and the high-voltage charging unit 2. When the switching element Q1 is turned on, a high voltage is applied. A high voltage is applied to the solenoid 1 from the capacitor C1 charged to a predetermined voltage (for example, 200 V) by the charging unit 2. The high-voltage charging unit 2 and the capacitor 1 correspond to a high-voltage power supply, and the switching element Q1 corresponds to a valve-opening switching unit.

A connection point between the switching element Q1 and the solenoid 1 has a diode D
1 and a battery 3 (for example, 12 V) as a low-voltage power supply via a switching element Q2,
By controlling ON / OFF of the switching element Q2, application of the low voltage VB to the solenoid 1 is controlled. Further, the connection point between the switching element Q1 and the solenoid 1 is connected to the other end of a capacitor C2 having one end connected to a reference potential point via a diode D2. When the switching element Q1 (or Q2) is turned off and the application of voltage to the solenoid is stopped, the diode D2 allows energization only in a direction in which magnetic energy remaining in the solenoid regenerates as a current to the capacitor C2. To enable rapid discharge of the solenoid. In addition, a constant voltage diode ZD1 is connected in parallel with the capacitor C2, so that the capacitor C2 is limited so as not to store more than a predetermined value. This diode D2, constant voltage diode Z
D1 and capacitor C2 correspond to power storage means. The switching element Q1 also plays a role as a rapid discharge unit in addition to the valve-opening switching unit described above.

A switching element Q3 as valve closing switching means is connected between the other end of the capacitor C2 and the reference potential point in parallel with the diode D2.
At the time of the valve closing command, by turning on the switching element Q3, a demagnetizing current is supplied from the capacitor C2 to the solenoid 1 in a direction opposite to that in the valve opening state and the holding state.

The switching elements Q1 and Q3 are on / off controlled based on signals P1 and P3 synchronized with an ejection pulse signal IN generated from a logic circuit (not shown). On the other hand, the switching element Q2 is subjected to PWM (Pulse Width Modulation) control in order to set the current flowing through the solenoid 1 to a predetermined value in the holding state. This is controlled on / off by the output signal of the AND element 4. On the input side of the AND element 4, the current control unit 5 compares the terminal voltage V1 of the current detection resistor R2 with a predetermined reference voltage. , And a signal P2 synchronized with the ejection pulse signal IN. This switching element Q2,
The current control unit 5 and the AND element 4 correspond to a current holding unit.

FIG. 2 is a timing chart showing the transition of the current flowing through the solenoid corresponding to the change of the ejection pulse signal IN and the signals P1 to P3 for controlling each switching element. 3 to 7 show the current flow of the drive circuit of the present invention. Next, the operation will be described with reference to FIG. 2 and FIGS. The injection pulse signal IN is
This is a signal having a pulse width ti generated by a logic circuit (not shown). The signal P1 is a signal that rises to a high level by a predetermined pulse width t1 (for example, several 100 μs) from the rising of the ejection pulse signal IN, and the signal P2 is the ejection pulse signal IN.
This signal is at a high level during the same pulse width ti.
Further, the signal P3 is a signal that becomes high level during a predetermined pulse width t2 (for example, several 100 μs) from the fall of the ejection pulse signal IN.

First, when the injection pulse signal IN changes from the low level to the high level, the signal P1 also changes to the high level, the switching element Q1 is turned on, and the high voltage previously charged in the capacitor C1 is immediately applied to the solenoid 1. Is done. FIG. 3 shows a path through which current flows at this time. next,
When the time t1 has elapsed, the signal P1 goes low, the switching element Q1 is turned off, and the application of the high voltage to the solenoid 1 is cut off. At this time, the switching element Q2 remains off, and the voltage VB from the battery 3 is not applied to the solenoid 1. Then, as shown in FIG. 4, a current that is going to continue to flow through the solenoid 1 flows into the capacitor C2. That is, the magnetic energy remaining in the solenoid 1 is absorbed and stored as a current in the capacitor C2 via the current detection resistor R2 and the diode D2. In this way, the current flowing through the solenoid 1 decreases more rapidly than in a conventional drive circuit.

Then, the current control unit 5 controls the current detection resistor R
When it is determined that the current has decreased to a predetermined value for maintaining the valve-open state based on a comparison between the terminal voltage V1 of the second terminal and the predetermined reference voltage, the current control signal Pm goes high. At this time, since the signal P2 is at the high level together with the ejection pulse signal IN, the output signal of the AND element 4 is also at the high level, and the switching element Q2 is turned on. Thus, as shown in FIG. 5, the voltage VB is applied to the solenoid 1 via the diode D1, and the current flowing through the solenoid 1 starts to increase.

Thereafter, when the value of the current flowing through the solenoid 1 exceeds a predetermined value, the terminal voltage V1
Exceeds a predetermined reference voltage, and the current control signal Pm output from the current control unit 5 goes low. Thus, A
The output of the ND element 4 also changes to a low level, and the switching element Q2 is turned off, whereby the application of the voltage VB to the solenoid 1 is cut off.

As described above, based on the terminal voltage V1 of the current detection resistor R2 detected by the current control unit 5, the current flowing through the solenoid 1 is changed by the PWM control in which the switching element Q2 is repeatedly turned on / off. Is kept substantially constant at a current value sufficient to keep the valve open. Also, in this PWM control, the switching element Q
At the moment when the capacitor 2 is turned off, as shown in FIG. 6, the power storage action on the capacitor C2 occurs along the same path as described above.
The charge stored in the capacitor C2 is stored in the switching element Q2.
Is turned off each time the capacitor C2 is turned off.
Is limited by the constant voltage diode ZD1 connected in parallel to the power supply. Therefore, the voltage finally charged in the capacitor C2 does not change depending on the length of the ejection pulse width ti, and is always constant.

When the time ti has elapsed and the injection pulse signal IN has turned to a low level, the signal P2 also has a low level, and
Since the output signal of the D element 4 also becomes low level, the switching element Q2 is turned off. In synchronization with this, the signal P3 goes high, and the switching element Q3 is turned on for a predetermined time t2.
Turns on only during Then, the stored capacitor C
2 applies a voltage to the solenoid 1 in the direction in which current flows in the path shown in FIG. This is the direction opposite to the direction of the current when the solenoid 1 is in the holding state, and the reverse current can cause the magnetic flux remaining in the solenoid 1 to disappear very steeply. As described above, the storage amount of the capacitor C2 is determined by the constant voltage diode ZD1.
, The voltage is limited to a constant value, so that an excessive voltage is not applied, and a stable demagnetizing action can be obtained.

The change in the current flowing through the solenoid 1 and the operation of the solenoid, that is, the needle valve displacement of the fuel injection valve are shown in FIG.
Shown in Compared to a conventional drive circuit, the current drops sharply when transitioning from the rising operation to the holding state, and the amount of excess current is small, so that the heat generation of the fuel injection valve can be suppressed. At the end of the injection period, the degaussing of the solenoid 1 is promoted by the reverse current, so that the needle valve returns more quickly.

According to the fuel injection valve driving circuit of the present invention described above, it is possible to control the fuel injection valve having a good response to the injection pulse signal IN by turning on / off the three switching elements. Also, since the extra current can be reduced,
It is possible to drive the fuel injection valve with high energy efficiency.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a fuel injection valve drive circuit according to one embodiment of the present invention.

FIG. 2 is a timing chart showing transition of each control signal and a current flowing through a solenoid.

FIG. 3 is a diagram showing a current flow of the drive circuit of the present invention.

FIG. 4 is a diagram showing a current flow of the drive circuit of the present invention.

FIG. 5 is a diagram showing a current flow of the drive circuit of the present invention.

FIG. 6 is a diagram showing a current flow of the drive circuit of the present invention.

FIG. 7 is a diagram showing a current flow of the drive circuit of the present invention.

FIG. 8 is a diagram showing solenoid current and needle valve displacement of a fuel injection valve.

FIG. 9 is a diagram showing a conventional fuel injection valve drive circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Solenoid 2 High voltage charging part 3 Battery 4 AND element 5 Current control part C1, C2 Capacitor D1, D2 Diode L1 Solenoid inductance component Q1-Q3 Switching element R1 Solenoid resistance component R2 Current detection resistance ZD1 Constant voltage diode

Claims (5)

[Claims] 1. A drive circuit for an electromagnetically driven fuel injection valve, comprising: a high-voltage power supply and a low-voltage power supply; one end of which is connected to a reference potential point via a current detection resistor when a command to open the fuel injection valve is provided. Valve opening switching means for connecting the other end of the connected solenoid for driving the fuel injection valve to the high voltage power supply and applying a high voltage to the solenoid in a direction in which the valve opening force of the fuel injection valve acts. After a lapse of a predetermined time from the valve opening command, while the low voltage power supply and the solenoid are kept shut off, the connection between the high voltage power supply and the solenoid is cut off to stop the application of the high voltage. A rapid discharge means for rapidly discharging a current flowing through the solenoid until the current decreases to a predetermined current value capable of holding the valve opening state of the fuel injection valve; and after the rapid discharge by the rapid discharge means, the low-voltage power supply And before Current holding means for controlling the application of a low voltage by connection with the other end of the solenoid and the discharge by interruption to hold the current flowing through the solenoid at the predetermined value; and the high voltage by the rapid discharge means. Power storage means for storing magnetic energy remaining in the solenoid as a current when the power supply and the solenoid are cut off and when the low voltage power supply and the solenoid are cut off by the current holding means, and a valve closing command for the fuel injection valve; Valve closing switching means for connecting the power storage means and the solenoid for a predetermined period so that a current flows in a direction in which the valve closing force of the fuel injection valve acts on the solenoid in synchronization with the solenoid. And a fuel injection valve drive circuit. 2. The power storage means includes: a capacitor having one end connected to the other end of the solenoid; and a diode interposed between the other end of the capacitor and a reference potential point. The fuel injection valve drive circuit according to claim 1, wherein: 3. The fuel injection valve drive circuit according to claim 2, wherein said power storage means includes a constant voltage diode connected in parallel to said capacitor. 4. The valve closing switching means comprises a switching element provided in parallel with the diode interposed between the other end of the capacitor and a reference potential point. The fuel injection valve drive circuit according to claim 2 or 3. 5. The apparatus according to claim 1, wherein the current holding means controls connection and disconnection between the low-voltage power supply and the other end of the solenoid based on a value of a current flowing through the current detection resistor. The fuel injection valve drive circuit according to any one of claims 1 to 4.