JPH0741822B2 - Wiper control circuit - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiper control circuit having a function of intermittently operating a wiper of a vehicle at regular intervals when the amount of rainfall is small.

(Prior Art and its Problems) Conventionally, a control circuit for controlling intermittent operation of a wiper generally uses a relay as a means for connecting and disconnecting electricity to a wiper motor. Therefore, not only the noise of the relay is generated during the intermittent operation, but also the contact is opened and closed, which causes a problem in the durability. Therefore, as disclosed in Japanese Utility Model Application Laid-Open No. 53-160143, the energization is controlled by turning on / off a transistor connected in series with the wiper motor to make a contactless state. There is a type in which the transistor is turned on to perform dynamic braking in which the current generated by the wiper motor that is rotating inertially escapes.

However, in the case of controlling the operation of the wiper motor using the transistor as in the above publication, when the power source is once disconnected from the circuit due to maintenance or the like and then reconnected,
If the positive potential side and the negative potential side of the power supply are connected in reverse, there is a problem that the transistor is destroyed. Even if a circuit (for example, a diode) that protects a transistor is provided in order to cope with such a reverse connection, a diode of high power must be used depending on the installation position, and the circuit becomes large as a whole.

(Object of the Invention) In order to solve the above-mentioned drawbacks, the present invention aims to prevent noise and improve durability by making the circuit non-contact during intermittent operation of the wiper, and to increase the size of the circuit while coping with reverse connection of the power supply. It is an object of the present invention to provide a wiper control circuit that also has a prevention function.

[Means for Solving the Problems]

Therefore, the present invention provides a wiper motor for driving a wiper of a vehicle, a power supply unit connected in series to the wiper motor to supply power to the wiper motor, and a first electric field for driving the wiper motor connected in series to the wiper motor. An effect type power element, a second field effect type power element connected in parallel to the wiper motor for stopping the wiper motor, and ON / OFF control of the first and second field effect type power elements in a constant cycle. A control circuit; a booster circuit that sets a voltage higher than the power supply voltage and applies the set voltage to the gate of the first field effect power element based on ON / OFF control of the control circuit; Is provided in a parallel connection circuit to which the field effect type power element is connected, and when the power supply means is reversely connected, the first and second field effect type It employs a wiper control circuit including a protection means for preventing reverse connection current from flowing into the power element.

[Action effect]

With the above configuration, in the present invention, the power supply control to the wiper motor is performed by turning on and off the field-effect power element, so that the mechanical contact is eliminated and the problems of noise and durability during operation are solved. There is an excellent effect.

Further, by providing the protection means, even if the power supply means is erroneously reversely connected after maintenance, etc., the reverse connection current is prevented from flowing into the first and second field effect power elements. It is possible to prevent the first and second field effect power elements from being destroyed, and moreover, this protection means is provided in the parallel connection circuit to which the second field effect power element is connected. Therefore, since a small current flows through the protection means by providing the protection means in the path for releasing the current generated by the wiper motor, the protection means itself is downsized by using the small power protection means. Therefore, there is an excellent effect that the size of the circuit can be prevented.

(Embodiment) An embodiment of the present invention shown in FIG. 1 will be described below.
Reference numeral 1 is an on-vehicle battery, 2 is a power switch interlocked with a key switch, 3 is a wiper motor, and there are contacts 3a and 3b as rotation detection means on a cam plate for decelerating the rotation of the motor 3d, and normally closed on the contact 3b side. ing. It should be noted that one rotation of the cam plate corresponds to one stroke of the wiper blade. 4,5 are N-channel type power MOS field effect transistors (hereinafter referred to as FETs), which are switching semiconductors F
ET4 is connected in series with motor 3d, while FET5 is connected to motor 3d
Are connected in parallel to short-circuit. 6 is a current detection resistor for detecting the current flowing in the FET 4, 7 is a comparator of the judging means which outputs L when the current flowing through the current detection resistor 6 increases and the voltage drop increases, and 8 uses an astable multivibrator. The oscillation circuit oscillates at a frequency of about 40 KHz to boost the inductance 9. Reference numeral 10 is a capacitor for accumulating the electric charge pumped by the action of the inductance 9, and the terminal voltage V _DH is set to about 36V, which is three times the battery voltage V _B = 12V. 11 is a zener diode for limiting the voltage of the capacitor 10, and 12 is as shown in FIG.
An IC that generates an ON signal for FET4 at a fixed cycle when the wiper operates intermittently, and also indicates the timing of the washer operation. 13 is off, intermittent (iNT), Lo, and Hi and wiper operation mode setting of 4 steps and washer operation, 20 to 23 are inverters, 24 and 25 are AND gates, 26,
27 and 28 are transistors that turn on when the output of the inverter 22 is H. At this time, FET4 turns on, FET5 turns off, and if the output is L, FE
T4 turns off and FET5 turns on. The diode 30 is provided in the parallel connection circuit to which the FET 5 is connected, and has a function of protecting the FETs 4 and 5 from the reverse connection current when the vehicle-mounted battery 1 is reversely connected.

Next, the operation of the above configuration will be described. Switch 2
When the wiper switch 13 is set to intermittent (iNT) with the switch closed (Fig. 3 (a)), the terminal 14 is grounded and the IC12
Is given an ON signal generation instruction for intermittent operation. And IC
L is output from the 12th terminal 6 at a constant cycle. As shown in FIG. 3 (b), the output of the inverter 20 is H. At this time, the output of the comparator 7 is H and the output of the inverter 23 is also H. Therefore, the output passing through the gate 25 and the inverter 22 becomes H. . (FIG. 3 (c)) As a result, the transistors 26 and 27 are sequentially turned on and, at the same time, the transistor 28 is also turned on. When the transistor 27 is turned on, the voltage V _DH of the capacitor 10 charged by the oscillation circuit 8 and the inductance 9 is F
Applying to the gate of ET4, energization of the motor 3d by the FET4 is started. (Fig. 3 (d)) The gate voltage of this FET4 is V _DH -V _B , which is about 24V, but it is clamped below 20V by the action of the Zener diode. When the motor 3d rotates, the contact on the cam plate switches from 3b to 3a.
(FIG. 3 (e)) As a result, the output of the inverter 21 is held at L. The output of the 6th terminal of IC12 is the motor.
It is already H during 3d rotation.

When one revolution of the cam plate (not shown) corresponding to one stroke of the wiper blade is completed in this way, the contact closes to the side 3b again, and the output of the inverter 21 becomes H, and therefore the inverter
The output of 22 is L and the transistors 26, 27 and 28 are turned off.
Therefore, instead of turning off the FET 4 to cut off the energization to the motor 3d, the FET 5 is turned on to perform the dynamic braking to release the generated current generated by the inertial rotation of the motor 3d to quickly stop the motor 3d. Similarly to the above, after a certain period of time, the start signal L of the motor 3d is output from the 6th terminal of the IC12, the motor 3d rotates, and the intermittent operation of stopping the energization by switching the contacts 3a to 3b is repeated. .

In this way, since FETs 4 and 5 are used to control the energization of the motor 3d, there is no mechanically actuated contact like a relay to prevent unpleasant noise, and the FET 5 stops energization of the motor 3d. Since the braking time is shortened by sometimes short-circuiting, unnecessary force due to inertial force can be reduced and the durability of the device can be improved. Furthermore, the FETs 4 and 5 can be directly controlled by the low level output of IC12, so the structure is simple and there is little risk of thermal runaway.

Next, when the motor 3d is locked, the voltage drop of the current detection resistor 6 becomes large, the output of the comparator 7 becomes L, and the inverter 23 becomes L, after which the FET 4 is turned off and the energization is cut off.

When the wiper operation mode is set to Lo and Hi, electricity is supplied without passing through FET4. Then, if the instruction to inject the washer fluid is issued during the intermittent operation or the off mode, the motor 3
d is driven and washer fluid is ejected, and after turning off the switch, it moves 2-3 times and returns to its original state.

Further, by providing the diode 30, even when the vehicle-mounted battery 1 is erroneously reverse-connected after maintenance or the like, the reverse connection current is prevented from flowing into the FETs 4 and 5, and
Can be prevented from being destroyed.

Moreover, since this diode 30 is provided in the parallel connection circuit to which the FET 5 is connected, by providing the diode 30 in the path for releasing the current generated by the motor 3d, a small current flows in the diode. By using the low power diode 30, it is possible to reduce the size of the diode itself, thereby preventing an increase in the size of the circuit.

Further, the motor lock prevention may be used at times other than the intermittent operation.

The switching semiconductor may be a P-channel type FET and an N-channel type FET, and may be a general power transistor other than the FET.

[Brief description of drawings]

FIG. 1 is an embodiment diagram of a control circuit of the present invention, FIG. 2 is a block diagram showing the structure of an IC, and FIG. 3 is a time chart showing the operation. 3 ... Wiper motor, 3a, 3b ... Contact, 4,5 ... FET, 6 ...
Current detection resistor, 7 …… Comparator, 12 …… IC, 13 …… Wiper switch.

Claims (1)

[Claims] 1. A wiper motor for driving a wiper of a vehicle, a power supply unit connected in series to the wiper motor to supply power to the wiper motor, and a first electric field for driving the wiper motor connected in series to the wiper motor. An effect type power element, a second field effect type power element connected in parallel to the wiper motor for stopping the wiper motor, and ON / OFF control of the first and second field effect type power elements in a constant cycle. A control circuit; a booster circuit that sets a voltage higher than the power supply voltage and applies the regulated voltage to the gate of the first field effect power element based on ON / OFF control of the control circuit; Is provided in a parallel connection circuit to which the field effect type power element is connected, and when the power supply means is reversely connected, the first and second field effect type power elements are provided. The control circuit of the wiper with a protection means for preventing the flow of reverse connection current to the child, the.