JPH0947051A - Motor control circuit for motor housing mirror - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the service life of a motor even if an overcurrent is fed excessively by controlling the detection of driving current of motor for motor housing mirror through an FET. SOLUTION: A switch 6 is turned to L side in R side region 11 thus turning a motor M1 to the left or right and moving a motor housing door mirror. When the motor housing door mirror is moved to a fixed position, rotation of the motor M1 is stopped and a higher current flows through the motor M1 as compared with the rotating time. When a current flows through a resistor R1 and a FET, a potential difference is produced by the quantity of current. The potential difference is subjected to differential amplification by an operational amplifier OP1 at a potential difference detecting section 1 and fed to the input part of an operational amplifier 0P2. When the potential difference reaches a level corresponding to overcurrent flow, the operational amplifier OP2 turns the FET off to interrupt the current flowing through the motor M1 thus ending the rotation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to control of a bidirectionally rotating motor of an electric storage door mirror for an automobile,
In particular, the power supply to the motor is stopped when the motor is stopped by the external force of the electric storage door mirror for an automobile.

[0002]

2. Description of the Related Art In a conventional electric retractable door mirror, as shown in FIG. 3, a direct current power source applied from a battery 7 is applied to a control circuit 5 with its polarity reversed by a changeover switch 6, and the control circuit 5 The motor M1 is controlled to rotate the electric storage door mirror 4 left and right (in the direction of the arrow) depending on the direction of the applied current.

In an actual circuit diagram of a conventional electric retractable door mirror, when the switch 6 shown in FIG. 3 is switched and the polarity of the power supply circuit is reversed, a current is stored in the coil 9 of the relay 8 by the electric charge stored in the capacitor C4. Flows, the contact 10 of the relay 8 is switched, and the contact 1 of the relay 8 is switched.
A current was flowing through the normally open contact 0, and the motor M1 was rotating. Here, the relay 8 is self-held by the resistor R7 and the coil 9 and continues to supply power to the motor M1. The rotation of the motor M1 causes the electric storage door mirror 4 to move in the opening or closing direction to abut against a part of the vehicle body, and the external force of the abutment stops the rotation of the motor M1 to stop the motor.
When an overcurrent flows through M1, the temperature of the overcurrent detection element PTC12 rises and the electric resistance increases, so that no current flows, the current does not flow to the coil 9 of the relay 8, and the contact 10 of the relay 8 is normally kept. It was opened and no current was flowing to the motor M1.

[0004]

In the conventional circuit, since the relay 8 is used for bidirectional current switching, there is a problem of the physical life of the relay 8. Also,
Since the PTC 12, which is an overcurrent detection element, is an element that changes the electrical resistance depending on the temperature, the operation may be slow when the outside temperature is low, and an overcurrent may flow too much to shorten the life of the motor.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and a diode bridge composed of four diodes and an electric storage connected to the diode bridge. A motor control circuit for a motor for electric storage and a motor for electric storage mirror for controlling the detection of the drive current of the motor for electric storage mirror in the diode bridge by a field effect transistor. Is.

[0006]

In the motor control circuit of the present invention, the diode bridge and the field effect transistor F are provided in the switching section.
A non-contact circuit using ET, an operational amplifier is used to detect the overcurrent of the motor, and the power to the motor is turned on and off.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The control circuit of the present invention is used for a motor vehicle mirror, in particular, an electric retractable mirror, and the direction of the current in the four diode bridges of the detection current switching section is It is always set in the same direction regardless of the rotation direction of the motor.

[0008]

An embodiment of the present invention will be described with reference to the accompanying drawings. In the electric circuit diagram of the electric retractable door mirror shown in FIG. 1, by turning the switch 6 to the R side or the L side,
Rotate the motor M1 left or right to move the electric retractable door mirror. When the electric retractable door mirror moves to a fixed position, the door mirror comes into contact with a part of the vehicle body and does not move any further.

First, the switch 6 is a double throw switch connected to a DC power source. When the switch 6 is turned to the R side, the current flows in the R direction (solid arrow), the motor M1 and the diode D.
1, the resistor R1, the field effect transistor FET, and the diode D3 flow in this order, and the motor M1 rotates rightward. When the electric retractable door mirror moves to the fixed position and the rotation of the motor M1 is stopped, a larger current flows through the motor M1 than when it is rotating (overcurrent).
Since there is a resistor R1 and a field effect transistor FET between the potential measurement points A and B, when a current flows through the resistor R1 and the field effect transistor FET, a potential difference occurs due to the amount of the current. This potential difference is differentially amplified by the operational amplifier OP1 of the potential difference detection unit 1 and output to the input unit of the operational amplifier OP2. The operational amplifier OP2 operates as a comparator when the potential difference when a preset overcurrent flows becomes large, and when the potential difference becomes large, the current increases even though the motor M1 is not rotating, and the operational amplifier OP2 is a field effect transistor. The FET is turned off to cut off the electric current flowing through the motor M1 to end the rotation of the motor M1.

Next, when the switch 6 is turned on in the L direction, the current flows in the L direction (broken line arrow) through the diode D2, the resistor R1, the field effect transistor FET, the diode D4 and the motor M1 in this order. The basic operation is the same as in the R direction, but one difference is that the field effect transistor FET is behind the load (motor) when flowing in the R direction, Since it is in front, the voltage applied to the gate must be changed to turn on the field effect transistor FET.

Therefore, the reference voltage correction unit 2 corrects the measured current. The mechanism is that, when a current flows to the R side, the base voltage of the transistor TR1 rises via the resistor R6 of the reference voltage correction unit 2 and the transistor T1
The collector and emitter of R1 become conductive, and the potential at point A has a value determined by the voltage drop across the resistor R4, diode D5 and transistor TR1 from the rectifier circuit 11 and the dividing resistor formed by the resistor R5. When it flows to the L side, the base potential of the transistor 1 becomes 0 and the transistor T
R1 is turned off, and the potential at the point D is set to the voltage determined by the Zener diode D6 from the rectifier circuit 11 by the diode D
It becomes the value which added the voltage drop of 5. Since the operational amplifier OP2 performs the comparison based on the potential at the point D, it is possible to correct the difference in potential difference by selecting the characteristics of each element.

The stabilizing section 3 in FIG. 1 is for correcting the unstable operation of the operational amplifier immediately after the switch 6 is switched, and the capacitor C1 (C2) and the resistor R2 (R3) reverse the polarity when the switch 6 is switched. The transistor TR2 is turned on by differentiating the rising and falling waveforms of, and the field effect transistor FET is turned on. This operation will be described with reference to FIGS. 1 and 2. At the beginning,
When the changeover switch 6 is in the R side, the power source side F point of C1 becomes the power source voltage Vin, and the circuit side H point becomes the voltage Vref passing through the rectifier of the power source voltage. Here, when the changeover switch 6 is switched to the L side (J in FIG. 2), the power source side of the capacitor C1 becomes 0, and the circuit side transmits a negative potential due to the charge / discharge characteristics at the moment of switching. The circuit side of the capacitor C1 is charged through the resistor R2, but until the capacitor C1 is sufficiently charged (time t), the potentials at the H point and the C point become LOW, and the transistor TR2 is turned on. Therefore, the potential at point D is HIGH
And the field effect transistor FET is turned on, so that a current flows through the motor M1. Changeover switch 6
When L switches from L to R, the capacitors C2 and R3 act in the same manner in place of the capacitor C1 and the resistor R2, and a current flows through the motor M1. Therefore, even if the operational amplifier of the overcurrent detection circuit causes an unstable operation immediately after the changeover switch 6 is switched, electric power can be stably supplied to the motor M1.

[0013]

Since the present invention has the above-described structure, it becomes easy and sure to detect the overcurrent of the motor in driving the electric retractable mirror, and the life of the control circuit and the motor is long. It enables stable motor control.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram of an electric retractable mirror.

[Figure 2] Waveform diagram

FIG. 3 is a schematic diagram of an electric retractable mirror

FIG. 4 is a circuit diagram of a conventional electric retractable mirror.

[Explanation of symbols]

 1 Potential Difference Detection Section 2 Reference Voltage Correction Section 3 Stabilization Section 4 Electric Retractable Door Mirror 5 Control Circuit 6 Changeover Switch 7 Power Supply 8 Relay 9 Coil 10 Contact 11 Rectifier Circuit 12 Overcurrent Detection Element M1 Motor R1 Resistance R2 Resistance R3 Resistance R4 Resistance R5 resistance R6 resistance R7 resistance R8 resistance D1 diode D2 diode D3 diode D4 diode D5 diode D6 Zener diode C1 capacitor C2 capacitor C3 capacitor FET FET field effect transistor TR1 transistor TR2 transistor OP1 operational amplifier OP2 operational amplifier

Claims (3)

[Claims] 1. A diode bridge composed of four diodes, a motor for an electric storage mirror connected to the diode bridge, and a motor for the electric storage mirror in the diode bridge. A motor control circuit for an electric storage mirror, characterized in that the detection of a drive current of a motor is controlled by a field effect transistor. 2. The motor control circuit for an electric storage mirror according to claim 1, wherein an operational amplifier for measuring a potential difference of an output current in the diode bridge is used. 3. The polarity of the detection current of the drive power source of the mirror motor is the same regardless of the rotation direction of the motor due to the switch using the diode bridge. The motor control circuit for the electric storage mirror according to claim 1.