JPH0771639A - Solenoid valve driving circuit - Google Patents

Abstract

PURPOSE:To provide a solenoid valve driving circuit capable of reducing an energy burden in an auxiliary power supply part. CONSTITUTION:A battery 1, power transistor 5 and a solenoid valve 4 are connected in series. A capacitor 11 in a DC-DC converter part 14 supplies a large current to the solenoid valve 4 when the power transistor 5 is closed. In a control circuit 12, the power transistor 5, in the beginning of electrifying the solenoid valve 4 according to inputting an injection signal, is actuated to close a circuit for a fixed time in a saturated region, to supply a current by the DC-DC converter part 14 and a current by the battery 1 to the solenoid valve 4. This fixed time is that a time for bounding a needle is added to a time for fully lifting the needle of the solenoid valve 4. Thereafter, the control circuit 12 performs constant current action by using an active region of the power transistor 5, to hold the solenoid valve 4 opened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solenoid valve drive circuit.

[0002]

2. Description of the Related Art Conventionally, in a drive device for a fuel injection solenoid valve used in an internal combustion engine, in order to drive the solenoid valve at high speed,
It is necessary to form the magnetic flux in the core inside the solenoid valve in a short time. Therefore, for example, as shown in FIG.
1, a DC-DC converter unit 33 and a constant current supply unit 34 are connected via an ignition key 32. Then, the DC-DC of the DC-DC converter unit 33
The converter 35 is charged in advance to a high voltage by the converter 38, the high voltage is applied to the solenoid valve (electromagnetic coil) 36 at the injection start timing, and a constant current is supplied from the constant current supply unit 34 to the solenoid valve 36. Open the solenoid valve 36,
After that, the constant current control was performed by the constant current supply unit 34 to keep the valve open. That is, a high voltage is generated in the DC-DC converter 38, the voltage is stored in the capacitor 35, an inrush current is supplied to the solenoid valve 36, and a constant current is supplied to the solenoid valve 36 by the constant current supply unit 34. . Further, the electromagnetic valve cutoff unit 37 cuts off the current flowing through the electromagnetic valve 36 in accordance with the injection signal.

[0003]

However, in this method, most of the energy required to open the solenoid valve 36 is covered by the energy stored in the capacitor 35, so that the DC-
There is a problem in that the energy generated in the DC converter unit 33 becomes very large and the cost of the drive device increases.

Therefore, an object of the present invention is to provide an electromagnetic valve drive circuit capable of reducing the energy burden on the auxiliary power source section composed of the DC-DC converter section.

[0005]

According to the present invention, a power source, an energization control transistor and a solenoid valve are connected in series, and an auxiliary power supply for supplying a large current to the solenoid valve when the energization control transistor is closed is provided. Furthermore, the energization control transistor is closed in a saturation region for a certain period of time at the initial stage of energization of the solenoid valve to supply a current from the auxiliary power source and a current from the power source to the solenoid valve, and then the energization control transistor. The gist of the invention is a solenoid valve drive circuit provided with a drive control circuit for performing a constant current operation using the active region.

[0006]

[Operation] The drive control circuit closes the energization control transistor in the saturation region for a certain period of time at the initial stage of energization of the solenoid valve to supply the current from the auxiliary power source and the current from the power source to the solenoid valve,
After that, a constant current operation is performed using the active region of the conduction control transistor. That is, in the initial stage of energization of the solenoid valve, the current from the auxiliary power source and the current from the power source are supplied to the solenoid valve. Therefore, in the initial stage of energization of the solenoid valve, the present invention reduces the energy load for valve operation in the auxiliary power source, as compared with the conventional case where the current from the auxiliary power source and the current from the constant current source are supplied to the solenoid valve. it can.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a drive device for a fuel injection solenoid valve used in an internal combustion engine will be described below with reference to the drawings.

FIG. 1 shows the overall structure. For a battery 1 as a power source, an ignition switch 2, a diode 3, an injection solenoid valve (electromagnetic coil) 4, and a power transistor (NP) as a conduction control transistor.
An N bipolar transistor 5 and a current detecting resistor 6 are connected in series. Ignition switch 2
A primary winding 7a of the step-up transformer 7, a power transistor (NPN bipolar transistor) 8 and a current detecting resistor 9 are connected in series at a connection point a between the diode 3 and the diode 3. Further, the secondary winding 7b of the step-up transformer 7, the diode 10 and the capacitor 11 are connected in series.
A connection point b between the diode 10 and the capacitor 11 is connected to a connection point c between the diode 3 and the solenoid valve 4.

The current detecting resistor 9 is a power transistor 8
It is for detecting the electric current flowing through. Further, the diode 10 rectifies the current generated in the secondary winding 7b of the step-up transformer 7. The capacitor 11 is for storing a high voltage. The diode 3 is for preventing current from flowing back to the battery 1 when the capacitor 11 has a high voltage. The current detection resistor 6 is a resistor for detecting a current flowing through the emitter of the power transistor 5 necessary for controlling the power transistor 5.

The base terminal of the power transistor 5 is connected to the control circuit 12 as a drive control circuit. Then, the control circuit 12 controls the base current of the power transistor 5 to interrupt and limit the current flowing through the injection solenoid valve 4. The base terminal of the power transistor 8 is connected to the control circuit 12. Then, the control circuit 12 turns on / off the power transistor 8 to interrupt the current flowing through the primary winding 7a of the step-up transformer 7 to generate a high voltage in the secondary winding 7b. The emitter terminal of the power transistor 5 (one end of the current detecting resistor 6) is connected to the control circuit 12. Similarly, the emitter terminal of the power transistor 8 (one end of the current detection resistor 9) is connected to the control circuit 12.

The control circuit 12 is an engine control E.
ECU1 for engine control, connected to CU13
An injection signal is output from the control circuit 12 to the control circuit 12.

In the present embodiment, the step-up transformer 7, the power transistor 8, the current detecting resistor 9, the diode 10 and the capacitor 11 constitute a DC-DC converter section 14 as an auxiliary power source. The DC-DC converter unit 14 turns on (closes) the power transistor 5.
A large current is sometimes supplied to the solenoid valve 4. Also, diode 3
And solenoid valve 4, power transistor 5 and current detection resistor 6
The solenoid valve drive unit 14 is configured by the above.

Then, the control circuit 12 inputs the injection signal and receives the DC-DC converter section 14 and the solenoid valve drive section 15.
Is designed to control the operation of. FIG. 2 shows a specific configuration of the control circuit 12.

The control circuit 12 includes a waveform shaping circuit 16, a rising monostable generator circuit 17, a drive circuit 18, a constant current control circuit 19, a falling monostable generator circuit 20, and a drive circuit 2.
1 and a comparator 22. The injection signal from the engine control ECU 13 is input to the waveform shaping circuit 16, and the waveform shaping circuit 16 removes noise in the injection signal. The output signal of the waveform shaping circuit 16 is sent to the rising monostable generator circuit 17, the drive circuit 18, and the falling monostable generator circuit 20. The rising monostable generation circuit 17 detects the rising edge of the output signal (ejection signal) of the waveform shaping circuit 16 and outputs a one-shot signal to the drive circuit 18. The drive circuit 18 is connected to the base terminal of the power transistor 5 of the solenoid valve drive unit 15. Further, the drive circuit 18 includes a constant current control circuit 19
The constant current control circuit 19 is connected to the emitter terminal of the power transistor 5 of the solenoid valve drive unit 15 (one end of the current detection resistor 6). Then, when the rising monostable generation circuit 17 detects the rising edge of the ejection signal, the power transistor 5 is turned on in the saturation region via the drive circuit 18. Further, during constant current control, the constant current control circuit 19 adjusts the base current using the active region of the power transistor 5 via the drive circuit 18 in order to keep the current flowing through the current detection resistor 6 constant. There is.

A drive circuit 21 is connected to the falling monostable generation circuit 20, and the drive circuit 21 has a DC-D.
The base terminal of the power transistor 8 of the C converter unit 14 is connected. The non-inverting input terminal of the comparator 22 is connected to the emitter terminal (one end of the current detecting resistor 9) of the power transistor 8 of the DC-DC converter unit 14, and the inverting input terminal of the comparator 22 is connected to the comparison voltage V.
ref is being applied. Then, when the falling monostable generation circuit 20 detects the falling edge of the injection signal, the power transistor 8 is turned on via the drive circuit 21, and the voltage value corresponding to the current flowing through the current detection resistor 9 is changed to the comparator 22. Is compared with the comparison voltage Vref at
When the current flowing through the current detection resistor 9 becomes the cutoff current of the primary winding 7a of the booster transistor 7 required to charge the capacitor 11 to the set voltage, the falling monostable generator circuit 20
Turns off the power transistor 8 via the drive circuit 21.

Next, the operation of the drive device for the solenoid valve for fuel injection configured as described above will be described with reference to FIG. When a pulsed injection signal is output from the engine control ECU 13 to the control circuit 12 (timing t1 in FIG. 3), the rising monostable generation circuit 17 of the control circuit 12 in FIG.
Detects the rising edge of the injection signal and opens the solenoid valve 4 via the drive circuit 18 so that the power transistor 5
Is turned on in the saturation region. As a result, the high voltage already stored in the capacitor 11 is discharged through the solenoid valve 4. Then, when the voltage of the capacitor 11 becomes lower than the voltage of the battery 1, a current flows from the battery 1 through the diode 3 to the solenoid valve 4. At this time, the control circuit 12
Causes the power transistor 5 to be continuously turned on (closed) in the saturation region for a certain period (T1) from the rising edge of the injection signal (timing t1 to t3 in FIG. 3). This time T1 is called voltage drive time.

Here, the voltage driving time T1 is a time T3 (for example, when the needle of the solenoid valve 4 bounces with respect to a time T2 (timing of t1 to t2 in FIG. 3) when the needle of the solenoid valve 4 is fully lifted (fully opened)). (0.1 to 0.3 ms) is added.

When the power transistor 5 is turned on for T1 in the initial stage of energization of the solenoid valve 4 (after the voltage driving is completed at the timing of t3) and there is still an injection time, the power transistor 5 holds the valve open. Performs constant current operation. That is, in FIG. 2, the constant current control circuit 19 adjusts the base current using the active region of the power transistor 5 via the drive circuit 18 in order to keep the current flowing through the solenoid valve 4 constant (t3 to t4 in FIG. 3). Timing).

When the injection signal falls (timing t4 in FIG. 3), the drive circuit 18 of the control circuit 12
Turns off the power transistor 5 and closes the solenoid valve 4 to end the injection.

At the falling edge of the injection signal, the control circuit 12 detects the falling edge of the falling monostable generator circuit 20 shown in FIG. 2 to turn on the power transistor 8 via the drive circuit 21, and the capacitor 11 When the primary winding cutoff current value of the step-up transformer 7 required to charge up to the set voltage is reached, the power transistor 8 is turned off. That is, the current flowing through the primary winding 7a of the step-up transformer 7 is detected by the current detecting resistor 9, and the comparator 2 of the control circuit 12 is detected.
In step 2, the comparison voltage Vref is compared, and when the set current is reached based on the comparison result, the falling monostable generation circuit 20 turns off the power transistor 8 via the drive circuit 21. In this way, the capacitor 11 is charged again.

Thereafter, this operation is repeated. Next, the difference between the conventional apparatus shown in FIG. 9 and the apparatus of this embodiment will be described with reference to FIG.

FIG. 4 shows the solenoid valve drive current a of the conventional device.
And a comparison with the solenoid valve drive current b according to the present embodiment.
However, the valve opening time shall be the same. Here, the hatched portion in the figure indicates the current supplied from the battery until the valve is opened. However, the return current of the solenoid valve inrush current due to capacitor discharge is excluded.

Comparing the hatched portions of the solenoid valve drive current a of the conventional device and the solenoid valve drive current b of this embodiment, the solenoid valve drive current a of the conventional device is limited by the constant current control. It is smaller than the solenoid valve drive current b according to the embodiment. That is, the insufficient current must be compensated by the current supplied from the capacitor, and DC-DC
The burden on the converter increases. However, in this embodiment, the load on the DC-DC converter can be reduced, which is advantageous for downsizing and cost reduction.

As described above, in the solenoid valve drive circuit of this embodiment, the battery 1 (power source), the power transistor 5 (transmission control transistor), and the solenoid valve 4 are connected in series, and when the power transistor 5 is closed, it is large. A DC-DC converter unit 14 (auxiliary power supply) for supplying a current to the solenoid valve 4 is provided, and the power transistor 5 is kept in a saturation region for a certain period of time T1 (= full lift time of the needle of the solenoid valve 4) at the beginning of energization of the solenoid valve 4. + Bounding time of the needle) A control circuit 12 (driving) for closing the circuit to supply a current from the DC-DC converter unit 14 and a current from the battery 1 to the solenoid valve 4 and then performing a constant current operation using the active region of the power transistor 5 Control circuit). That is, in the initial stage of energization of the solenoid valve 4, the DC-DC converter unit 14
Is supplied to the solenoid valve 4. Therefore, in the present embodiment, compared with the case where the current by the DC-DC converter unit 33 and the current by the constant current supply unit 34 are supplied to the solenoid valve 36 as in the conventional case of FIG. The energy load for opening the valve in the DC-DC converter unit 14 can be reduced, and downsizing and cost reduction can be achieved.

Further, in the present embodiment, the constant current element used in the conventional device of FIG. 9 is not required, so that the cost can be further reduced. The present invention is not limited to the above-described embodiment, and for example, the embodiment has been embodied in a drive device for a fuel injection solenoid valve used in an internal combustion engine. The type is not limited as long as it is a solenoid valve that opens and closes by the magnetic flux. Further, the solenoid valve may be a solenoid valve of a type that closes when an electric current is applied.

As shown in FIG. 5, when the solenoid valve 4 provided in the multi-cylinder engine is driven, the solenoid valve 4
If a circuit (power transistor 5) that connects and disconnects the energizing current is provided in parallel, when the currents to the solenoid valves 4 of the respective cylinders overlap, high voltage cannot be stored in the capacitor 11, so that the capacitor 11 shifts to the solenoid valve 4. A switch using the power transistor 23 or the like may be provided in the path to reach the switch and the switch may be turned on (closed) only when the current is discharged from the capacitor 11 to the solenoid valve 4.

Further, in the circuit shown in FIG. 5, even if the injection signals do not overlap with each other as shown in FIG. 6, the power transistor 23 is used even when the injection timing approaches and the capacitor 11 by the DC-DC converter cannot be charged in time. May be used.

When the power transistor 23 of FIG. 5 is used, as shown in FIG. 7, the DC-DC converter starts its operation immediately after the power transistor 23 is turned off.

Further, as shown in FIG. 8, only the solenoid valves 4 of the cylinders, in which the injection signals never overlap with each other and the charging time of the capacitor by the DC-DC converter can be secured, are connected in parallel to each other. A structure in which one DC-DC converter and the capacitor 11 are provided may be used.

Further, as the conduction control transistor, an FET may be used in addition to the bipolar transistor (power transistor 5).

[0031]

As described above in detail, according to the present invention,
The excellent effect that the energy burden of the auxiliary power supply unit can be reduced is exhibited.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a solenoid valve drive circuit according to an embodiment.

FIG. 2 is an electrical configuration diagram showing details of a control circuit.

FIG. 3 is a time chart showing various signals and operations.

FIG. 4 is a time chart showing various signals and operations.

FIG. 5 is an overall configuration diagram of a solenoid valve drive circuit of another example.

FIG. 6 is a time chart showing various signals and operations of a solenoid valve drive circuit of another example.

FIG. 7 is a time chart showing various signals and operations of a solenoid valve drive circuit of another example.

FIG. 8 is an overall configuration diagram of a solenoid valve drive circuit of another example.

FIG. 9 is an overall configuration diagram of a conventional solenoid valve drive circuit.

[Explanation of symbols]

1 Battery as Power Source 4 Solenoid Valve 5 Power Transistor as Energization Control Transistor 12 Control Circuit as Drive Control Circuit 14 DC-DC Converter Section as Auxiliary Power Source

Claims (1)

[Claims] 1. A power supply, an energization control transistor, and a solenoid valve are connected in series, and an auxiliary power supply for supplying a large current to the solenoid valve when the energization control transistor is closed is provided. At the beginning of energization, the energization control transistor is closed for a certain time in a saturation region to supply the current from the auxiliary power source and the current from the power source to the solenoid valve, and then a constant current using the active region of the energization control transistor. An electromagnetic valve drive circuit comprising a drive control circuit for operating the solenoid valve drive circuit.