JPH03177668A - Solenoid drive unit - Google Patents

Abstract

PURPOSE:To save the power consumption and prevent the exothermicity of a solenoid and the thermal destruction of a driving transistor by providing a control means for controlling a switching means to be turned off at the time of an exciting current detected by a current detecting means being larger than the specified value and to be turned on at the time of the detected exciting current being smaller than the specified value. CONSTITUTION:When a signal A reaches a high level, the output side of a reversing buffer 110 is on a low level. At this time, a signal B is on a low level, the output side of a reversing buffer 111 is on a high level, and a transistor 103 is turned on. The base current of a transistor 102 rises by a resistance 114, and the transistor 102 is turned on. Voltage VL therefore rises and an exciting current IL flowing in a solenoid 401 rises moderately, and when the output voltage of a current detecting circuit 107 becomes higher than the reference voltage VREF, the output of a comparator 109 is on a low level. The transistors 102, 103 are then turned off.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a solenoid drive device, and in particular to a solenoid that controls an excitation current to be supplied to a solenoid used in a solenoid valve for hydraulic control of various parts of an automatic vehicle such as a transmission gear of an automatic vehicle. It relates to a drive device.

Prior Art Conventionally, solenoid valves for automobile electrical equipment have had hysteresis characteristics as shown in FIG. In other words, the solenoid valve is located at the bottom of the tank and includes an electromagnetic solenoid (described later), and when the excitation current to the solenoid exceeds a certain level, the solenoid valve turns on, and after that it remains on even if the excitation current decreases a little. It is about maintaining the state.

Therefore, in conventional solenoid drive devices, the hysteresis characteristic is used to first apply an excitation current to the solenoid to turn on the solenoid valve, and then reduce the excitation current to the minimum current value required to maintain the on state. By this,
Efforts are being made to save power and prevent the solenoid from overheating.

The operation of the conventional solenoid drive device will be explained using FIGS. 4 and 5. FIG. 4 is a circuit diagram of the main parts of a conventional solenoid drive device, and FIG. 5 is a waveform diagram showing the operation of each part of the circuit shown in FIG.

In FIG. 4, reference numeral 401 is the above-mentioned electromagnetic solenoid, and by passing an excitation current through this solenoid, a solenoid valve (not shown) is turned on.

Therefore, in order to control the excitation current given to this solenoid 401, the electric current i! is applied via the drive transistor 402. 1W
VB is supplied. Further, in order to control the operating state of the transistor 402, that is, to change the base current, the logic circuit 407 and the transistor 4,
D3 is further provided with a differential amplifier 404. Note that 408 is a Zener diode for surge voltage countermeasures.

Differential amplifier 404 connects reference voltage 'VREF and solenoid 4
01 terminal voltage V L and sends out a voltage corresponding to the voltage difference between the terminal voltage V L and the reference voltage V REP. Note that 413 is a filter capacitor.

A logic circuit 407 transfers a signal to be described later to an inversion buffer 40.
5 and 406, and the inversion buffer 40
5.40Ei respectively sends signals of the inverted values.

In the circuit having such a configuration, it is assumed that signals A and B shown in FIG. 5 are sent out from the logic circuit 407. Signal A is a signal that defines overexcitation time TK, and overexcitation time TK is set to the time required for the solenoid valve to be driven and turned on. Further, the signal B is set to the time when the solenoid valve shifts from the on state to the off state. That is, when the signal A is at a high level, the transistor 402 is turned on, and when the signal B is at a high level, the transistor 402 is turned off.

First, when the signal A becomes high level, the inverting buffer 40
The output side of 5 becomes low level. At this time, the output side of the inverting buffer 40B is at a high level, and the transistor 4
03 is turned on.

Then, the base current of the transistor 402 increases due to the resistor 409, and the transistor 402 is turned on. Therefore, the voltage VL increases as shown in FIG. 5C, and the excitation current IL flowing through the solenoid 401 gradually increases as shown in the same figure.

Here, when the signal A changes from high level to low level, the output side of the inversion buffer 405 becomes high level.

At this time, since the output side of the inversion buffer 40B is also at a high level, the transistor 403 operates in the active region. As a result, the IC becomes smaller and the voltage VL becomes the fifth
The level becomes low as shown in C in the figure. Therefore, the current value flowing through the solenoid 401 gradually decreases,
As shown in the figure, it becomes smaller.

Here, the terminal voltage VL of the solenoid 401 and the current I L
is a constant value as shown in FIG. 5 because of the differential amplifier 40.
4 and transistors 403 and 402 so that the reference voltage VREP becomes the one-terminal voltage VL.

Next, when the signal B changes from low level to high level, the output side of the inversion buffer 406 becomes low level, and the transistor 403 is turned off. At this time, buffer 4
Since the output side of transistor 05 is at a high level, the base current of transistor 402 decreases, and thereafter transistor 402 is completely turned off.

As a result, the value of the current flowing through the solenoid 401 gradually decreases and finally reaches zero.

In other words, the feedback system of differential amplifier 404→transistor 403→transistor 402→differential amplifier 404 causes current to flow through solenoid 401 to keep the solenoid valve in the ON state, and the signal A is output regardless of this.

B forcibly controls the solenoid valve on and off. In this way, this device controls the solenoid valve to remain on by lowering the excitation current after a certain overexcitation time, which saves power and prevents the solenoid from generating heat. .

However, in the conventional solenoid drive device described above, when the excitation current is lowered to maintain the on state of the solenoid valve,
The drive transistor will be used in the active region,
The loss in the drive transistor is as large as PV-ICIVCE-IL (VB-VL), and the amount of heat generated is also large, which has the disadvantage that the drive transistor may be destroyed by heat.

OBJECTS OF THE INVENTION The present invention has been made to solve the above-mentioned conventional drawbacks, and its purpose is to provide a solenoid drive device that does not cause thermal damage to the drive transistor.

Structure of the Invention A solenoid drive device according to the present invention is a solenoid drive device that controls an excitation current to be supplied to a solenoid, and includes a switching device that controls on/off the excitation current to be supplied to the solenoid, and an excitation current flowing through the solenoid. current detection means for detecting the current, and control means for controlling the switching means to turn off when the excitation current detected by the current detection means is greater than a predetermined value, and to turn on the switching means when the excitation current is smaller than the predetermined value. It is characterized by having the following.

Example Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a circuit diagram of the main parts of an embodiment of the solenoid drive device according to the present invention, and FIG. 2 is a waveform diagram showing the operation of each part of the circuit shown in FIG.

The circuit of this embodiment is characterized in that a chopping circuit 108 and a current detection circuit 107 are provided in place of the conventional circuit, that is, the differential amplifier 404 in FIG. That is, the current detection circuit 107 converts the solenoid excitation current IL into a voltage value, and the chopping circuit 10 converts the solenoid excitation current IL into a voltage value.
Reference voltage V REP at comparator 109 in 8
Chopping is performed by comparing it to .

In the figure, 101 is an electromagnetic solenoid, and by passing an exciting current through this solenoid, a solenoid valve (not shown) is turned on. In order to control the excitation current applied to this solenoid 101, drive transistor 102. Excitation circuit 10 including h transistor 103 etc.
4 are provided.

A power supply VB is supplied to the solenoid 101 via a drive transistor 102 in this excitation circuit 104, and a transistor 103 and a logic circuit 112 are provided to control the on/off state of the transistor 102.

Logic circuit 112 applies a signal similar to that shown in FIG. 4 to inverting buffers 110 and 111, and inverting buffers 110 and 111 send out signals of their inverted values, respectively.

Further, the comparator 109 compares the output voltage of the current detection circuit 107 and the reference voltage VREF, and when the output voltage of the current detection circuit 107 is lower than the reference voltage VREF, its output becomes a high level and the reference voltage V R
When it is higher than EF, its output becomes low level. Therefore, when the output voltage of the current detection circuit 107 is lower than the reference voltage V REF, the transistor 103 is turned on, the transistor 102 is turned on, and the solenoid 1 is turned on.
Apply excitation current to 01.

On the other hand, the output voltage of the current detection circuit 107 is the reference voltage VRE.
When the voltage is higher than P, transistor +03 is turned off, transistor 102 is turned off, and the supply of excitation current to solenoid +01 is stopped. In other words, this chopping circuit 10
8, the excitation circuit 104 is intermittently controlled, and the excitation current is feedback-controlled to a value that corresponds to the reference voltage V REF.

Note that the pull-up resistor 12 in the chopping circuit 108
4 is necessary when the output stage of the comparator 109 has a collector-object circuit configuration, and the resistor 123 is provided to give the output of the comparator 109 a hysteresis characteristic.

The current detection circuit 107 has internal resistors 105 and 119.
The current IL is converted into a voltage by the differential amplifier 1.
A non-inverting amplifier consisting of 0B and resistors 118 and 120 is used for amplification.

In the circuit having such a configuration, it is assumed that signals A and B shown in FIG. 2 are sent out from the logic circuit 112. Here, signals A and B are the same signals as in FIG.

Therefore, when signal A is at high level, transistor 10
2 is on and saturation region) When signal B is high level, the transistor! 02 will be turned off.

First, when the signal A becomes high level, the inverting buffer 11
The output side of 0 becomes low level. At this time, the signal B is at a low level, the output side of the inversion buffer Ill is at a high level, and the transistor +03 is turned on.

Then, the base current of the transistor 102 increases due to the resistor 114, and the transistor 102 is turned on. Therefore, the voltage VL increases as shown in FIG. 2C, and the excitation current IL flowing through the solenoid 401 gradually increases as shown in the same figure.

When the excitation current IL increases and the output voltage of the current detection circuit 107 becomes higher than the reference voltage V REF, the comparator 1
The output of 09 becomes low level. Then, the transistor 103 is turned off and the transistor 102 is turned off.

On the other hand, when the transistor 1G2 is turned off, the exciting current 11
falls, the output voltage of the current detection circuit 107 becomes lower than the reference voltage V REF, and the output of the comparator 109 becomes high level. Then, the transistor 103 is turned on, the transistor 102 is turned on, and the excitation current IL rises again.

Thereafter, the transistor 102 is repeatedly turned on and off, and the voltage VL is chopped as shown at C in FIG. In addition, with this chopping state, the exciting current IL repeats slight fluctuations as shown in FIG. 2C.

This chopped state stops when signal B becomes high level. That is, when the signal B becomes high level, the output side of the inversion buffer 111 becomes low level. Then, transistor 103 is turned off. As a result, the excitation current IL gradually decreases as shown in the second diagram. Furthermore, since the output side of the inversion buffer 110 is at a high level, the transistor 102 is turned off.

After that, signal B is at high level, that is, inversion buffer H1
As long as the output side of the transistor 102 is at a low level, the transistor 102 remains off. This off state continues until the signal A becomes high level and the signal B becomes low level again.

That is, in the present invention, the voltage VL is chopped by repeatedly turning on and off the transistor 102 only during the on-state period of the electromagnetic valve using the signals A and B, so that the loss in the transistor 102 can be reduced.

That is, the loss is PW -IC-VCE-K -IL -VCE(Sat
, ). Note that V CE (sat, ) is saturated (Sa
turatlOrl) voltage, K is the chopping duty rate.

Therefore, according to the present invention, it is possible to prevent the drive transistor 102 from generating heat.

Moreover, although the control of a solenoid valve including a solenoid has been described above, it is clear that the present invention can be widely applied to excitation control of a solenoid having hysteresis characteristics as shown in FIG.

As described in detail, according to the present invention, it is possible to save power, prevent the electromagnetic solenoid from generating heat, and also prevent the drive transistor from being damaged by heat.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of the main parts of a solenoid drive device according to an embodiment of the present invention, Fig. 2 is a waveform diagram showing the operation of each part of the circuit in Fig. 1, Fig. 3 is an on-off characteristic diagram of a solenoid valve, and Fig. 4 is a diagram showing the operation of each part of the circuit of Fig. 1. The figure is a circuit diagram of the main parts of a conventional solenoid drive device, and FIG. 5 is a waveform diagram showing the operation of each part of the circuit of FIG. 4. Explanation of symbols of main parts 101... Solenoid 102, 103... Transistor 107...
...Current detection circuit 108...Chopping circuit

Claims (1)

[Claims] (1) A solenoid drive device that controls an excitation current to be supplied to a solenoid, comprising a switching means for controlling on/off the excitation current to be supplied to the solenoid, and a current detection means for detecting an excitation current flowing through the solenoid; When the excitation current detected by the current detection means is larger than a predetermined value, the switching means is turned off;
A solenoid drive device comprising: control means for turning on the switching means when the predetermined value is smaller than the predetermined value.