JPH0362575B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wiper drive device that continuously and intermittently drives a wiper for a window glass of a vehicle such as an automobile.

As a wiper drive device that drives a wiper continuously and intermittently, there is a wiper speed control system disclosed in Japanese Patent Application Laid-open No. 58-67543. The wiper speed control system includes an INT switch for intermittent operation, a CONT switch for continuous operation, a FAST switch and a SLOW switch for controlling intermittent time and wiper speed. It consists of a control memory and a control section that drives the wiper motor on a duty basis according to the contents of the speed control memory. Also, above
The states of the INT switch, CONT switch, SLOW switch, and FAST switch are transmitted from the switches to the control device by multiplexed transmission signals. In the above wiper speed control system, the wiper control section is configured with a digital circuit,
Turn on/off the FAST switch or SLOW switch
By operating the controller, the contents of the speed control memory are increased or decreased, and the wiper motor is duty-controlled in accordance with the contents of the speed control memory, thereby variably controlling the wiper speed.

However, as in the wiper speed control system described above, the accuracy of the speed control of the wiper motor by an open circuit in which the control signal flow is unidirectional is solely dependent on the accuracy of the clock pulse input to the speed counter and the pulse of a predetermined period. It turns out. Therefore, not only a high-precision clock pulse oscillator and a pulse generation circuit are required, but also peripheral control means such as means for reading out the contents of the speed control memory and multiplex transmission control means for multiplex transmission of signals are required. There is a problem that the configuration becomes complicated and expensive.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a wiper drive device that is simple in construction and inexpensive and can drive the wiper continuously or intermittently at an appropriate speed depending on the amount of rain and the vehicle speed. be. According to the present invention, as shown in FIG. 2, there is provided a bridge circuit including a DC motor on one side, and a differential amplifier circuit that differentially amplifies the back electromotive force of the DC motor from the bridge circuit. , an amplifier circuit for amplifying the current flowing through the DC motor, a rotation speed setting means for setting the rotation speed of the DC motor, and a signal from the differential amplifier circuit and the rotation speed setting means being added or subtracted to control the DC motor. A wiper driving device is provided which is mainly equipped with an operational amplifier circuit that generates a signal to set a set speed, and a comparison circuit that compares the signal from the operational amplifier circuit with the signal from the amplifier circuit. Based on this, by intermittent operation of the bridge circuit drive switching means, the wiper drive speed can be freely set over a range from low speed to high speed. Furthermore,
In addition to the above configuration, there is also a timer circuit that sets the intermittent operation time of the wiper, and a continuous wiper
The wiper set as described above is provided with an intermittent operation changeover switch means and a logic circuit that conducts or deconducts the bridge circuit drive switching means based on the operation changeover switch means and a signal from the comparison circuit. A wiper drive device is provided that is capable of intermittent drive at speed levels.

The invention will be explained below with reference to embodiments shown in the drawings. FIG. 3 is a circuit diagram showing the entire wiper drive device showing one embodiment of the present invention, and FIG.
FIG. 5 is a specific circuit diagram for continuous wiper drive of the wiper drive device shown in the figure, and FIG. 5 is a specific circuit diagram for intermittent wiper drive.

In FIGS. 3 and 4, 1 is a DC motor for driving a wiper (wiper blade), 2 is a bridge circuit including the DC motor 1, and a series circuit of the DC motor 1 and a resistor 3, and a resistor. 4 and resistance 5
It is constructed by connecting series circuits in parallel. Reference numeral 6 designates a main power switch. Normally (when in the open state), the movable contact 6a is in contact with the fixed contact 6b as shown by the solid line, and is open. When the main power switch 6 is turned on, the movable contact 6a is in contact with the fixed contact 6b as shown by the dotted line. The movable contact 6a contacts the fixed contact 6c and closes. The fixed contact 6c is connected to the positive electrode of the power supply.

7 is the main power switch 6 and the bridge circuit 2
Switching means for driving the bridge circuit provided between the two terminals is composed of a PNP type transistor 8. The emitter of this transistor 8 is connected to the movable contact 6a side, and the collector thereof is connected to the DC motor 1 side.

9 is a flywheel diode (product name) connected in antiparallel to the series circuit of the DC motor 1 and the resistor 3; its anode is grounded, and its cathode is connected to the power supply side of the DC motor 1; The DC motor 1 functions to feed back the back electromotive force of the motor 1 so that the DC motor 1 rotates smoothly without pulsation.

10 is a differential amplifier circuit for differentially amplifying the back electromotive voltage of the DC motor 1 from the bridge circuit 2. For this purpose, the voltage generated at the connection point P between the DC motor 1 and the resistor 3 is input to the inverting input side of the differential amplifier circuit 10, and the divided voltage is applied to the connection point Q between the resistor 4 and the resistor 5. It is arranged to be input to the non-inverting input side of the amplifier circuit 10.

11 is an amplifier circuit that amplifies the current flowing through the DC motor 1.

12 is a rotational speed setting means (variable resistor) of the DC motor 1.

Reference numeral 13 denotes an operational amplifier circuit for adding the input signal from the differential amplifier circuit 10 and the speed command input signal from the rotational speed setting means 12 to set the DC motor 1 at a set speed. Therefore, when the rotational speed of DC motor 1 is faster than the set value, a signal is output that causes DC motor 1 to rotate at a low speed, and when the rotational speed of DC motor 1 is slower than the set value, a signal that causes DC motor 1 to rotate at high speed is output. It has a function to output the DC motor 1 to the set speed.

14 and 15 are resistors, 16 is an operational amplifier circuit 13
This is a comparison circuit that compares the input signal from the amplifier circuit 11 with the input signal from the amplifier circuit 11.

17 is a PNP type transistor 8 based on the input signal from the comparator circuit 16 and the input signal from the wiper continuous/intermittent operation switch 18, which will be described later.
This logic circuit 17 is constituted by a NAND circuit 17a in this example, and the output of the NAND circuit 17a is connected to the base of the PNP transistor 8.

The above components constitute the wiper continuously variable speed circuit.

In FIGS. 3 and 4, 20 is a mechanical switch connected in parallel with the main power switch 6, and is provided inside the DC motor 1 for self-holding purposes. In this mechanical switch 20, when the wiper blade (not shown) is stored at a predetermined home position, the movable contact 20a is in the position shown by the solid line and is open, and when the wiper blade rotates, the movable contact 20a is opened as shown by the dotted line. As shown, it contacts and closes a fixed contact 20b, and this fixed contact 20b is connected to the positive electrode of the power supply. The reason for this self-protection measure is that
This is to allow the wiper blade to be stored at a predetermined original position so as not to obstruct visibility.

21 is a dynamic brake circuit that short-circuits the armature coil inside the DC motor 1 to stop the DC motor 1 after the main power switch 6 is opened. 21a, 21
b, 21c, and 21d are resistors, 21e is PNP
The transistors 21f and 21g are NPN type transistors.

19 is a sub power switch that closes or opens in conjunction with the main power switch 6, and has a fixed contact 19.
b is connected to the base of the NPN transistor 21g. This NPN type transistor 21g,
With the sub power switch 19, the mechanical switch 20 remains open for a certain period of time even after the main power switch 6 is opened.
This constitutes a dynamic brake control means for closing the wiper blade and driving the DC motor 1 for a certain period of time to house the wiper blade at a predetermined origin position.

The reason for providing this dynamic brake control means is that when the mechanical switch 20 is in the open state (at this time, the main power switch 6 and the sub power switch 19 are closed), the brake circuit 21 is activated, and the DC motor 1 is stopped. However, while the wiper is in continuous operation, it would be a problem if the wiper blade just continues to rotate back and forth and stops, so the sub power switch 19 is closed. This is to prevent the dynamic brake circuit 21 from operating.

In FIGS. 3 and 5, 22 is a waveform shaping circuit for shaping the rectangular signal waveform obtained from the connection point between the resistor 21b and the resistor 21c into a pulse waveform.

23 is a timer circuit which, based on the signal from the waveform shaping circuit 22, sends high and low signals in accordance with the intermittent operation of the wiper to the wiper continuous/intermittent operation changeover switch 1.
8 to the NAND circuit 17a.

In the wiper continuous/intermittent operation changeover switch 18, the movable contact 18a is normally brought into contact with a fixed contact 18b connected to the positive electrode of the power supply, so that the wiper can perform continuous variable operation. When the fixed contact 18c is switched to the fixed contact 18c, the wiper is selected to operate intermittently.

Next, the operation of the apparatus of the present invention having the above configuration will be explained.

First, the case of continuous variable speed wiper operation will be described.

When the main power switch 6 is closed (with the movable contact 6a switched to the fixed contact 6c), the sub power switch 19 is closed as the movable contact 19a contacts the fixed contact 19b.

Since the motor 1 rotates when the main power switch 6 is closed, the mechanical switch 20 switches the movable contact 20a to the fixed contact 20b after a short period of time and is closed for a certain period of time. However, since the sub power switch 19 is closed, the base current is supplied from the positive electrode of the power supply to the transistor 21g via the wiper continuous/intermittent operation selector switch 18 and the sub power switch 19, and this transistor 21g becomes conductive. Since the base and emitter of the NPN transistor 21f are short-circuited and the transistor 21f is non-conductive, the brake circuit 21 does not operate.

When the main power switch 6 is initially closed, the PNP transistor 8 is non-conductive, so the DC motor 1 does not rotate and the back electromotive voltage is low.

The back electromotive voltage signals at the connection points P and Q are differentially amplified by the differential amplifier circuit 10. Since the differentially amplified signal has a lower value than the signal from the rotation speed setting means 12, it is calculated by the operational amplifier circuit 13 and the DC motor 1 is set by the rotation speed setting means 12. A signal set to rotate at the same speed is output from the operational amplifier circuit 13 and input to the comparison circuit 16 via the resistor 14.

The signal corresponding to the current flowing through the armature coil of the DC motor 1 appearing at the connection point P is also low,
It is amplified by the amplifier circuit 11.

The comparison circuit 16 compares the signals (analog signals) from the operational amplifier circuit 13 and the amplifier circuit 11,
Since it outputs a “high” signal (digital signal),
The signal level input from the comparison circuit 16 to the logic circuit 17 is "high", and the signal level input from the continuous/intermittent operation changeover switch 18 to the logic circuit 17 (NAND circuit 17a) is also "high".
Therefore, the output of the logic circuit 17 is "low". Therefore, the base of the PNP transistor 8 becomes lower than the emitter by, for example, 0.6V, and the transistor 8 becomes conductive.

The conduction of the transistor 8 causes the DC motor 1 to rotate and the wiper to operate at a continuously variable speed, causing the wiper blade to reciprocate and slide on the window glass of the vehicle.

By adjusting and setting the wiper speed using the rotational speed setting means 12, the wiper can be operated at a continuously variable speed at a predetermined speed.

As the DC motor 1 rotates, the back electromotive force between the connection points P and Q begins to increase, and when a signal indicating that the DC motor 1 is rotating at a higher speed than the set speed appears at the output of the differential amplifier circuit 10, A signal for slowing down the DC motor 1 appears from the operational amplifier circuit 13, and the output of the comparison circuit 16 becomes a "low" level. Since the input from the continuous/intermittent operation selector switch 18 is "high", the output of the logic circuit 17 becomes "high", and the PNP transistor 8 becomes non-conductive, so no current is supplied to the DC motor 1. The rotational speed of the DC motor 1 decreases.

When the rotational speed of the DC motor 1 decreases, the PNP transistor 8 becomes conductive and current is supplied to the DC motor 1 in the same manner as described above, so that the DC motor 1 rotates at high speed again.

By repeating the above operations, the DC motor 1 continues to rotate at the set speed, so that the wiper can be operated continuously (variable speed) at the selected and set speed.

When the main power switch 6 is opened and the mechanical switch 20 is turned off, the base potential of the transistor 21e is pulled to the ground potential by the open signal, so the transistor 21e becomes conductive, and the transistor 21f also becomes conductive. conduction and short-circuit the armature coil of the DC motor 1. This short circuit activates the dynamic brake, and the DC motor 1 stops rotating.

Furthermore, when the main power switch 6 is opened, the sub power switch 19 is also opened, so
Since the transistor 21g is non-conductive,
The brake circuit 21 is made operable.

In this case, even if the main power switch 6 is opened, the mechanical switch 20 connected to the motor 1 is closed and self-maintained for a certain period of time, so the current from the positive electrode of the power source is transferred to the mechanical switch 20 and the fixed contact. 6b and the transistor 8 via the movable contact 6a.
Since the wiper blade continues to be electrically conductive, the DC motor 1 can continue to drive and store the wiper blade in the home position until the wiper blade is stored in the home position and the mechanical switch 20 is released.

The case of intermittent variable speed wiper operation will be explained.

3 and 5, the main power switch 6 is closed, and the movable contact 18a of the wiper continuous/intermittent operation changeover switch 18 is switched to the fixed contact 18c.

As a result, the input from the movable contact 18a to the NAND circuit 17a temporarily becomes a "low" level.

When the motor 1 is stopped, the input from the comparator circuit 16 to the NAND circuit 17a is at a "high" level. Therefore, the input to the NAND circuit 17a becomes "low" and "high", the output of the circuit 17a becomes "high", and the PNP transistor 8 becomes non-conductive.

The timer circuit 23 alternately generates "high" and "low" signals at intervals determined by the time constant of the time constant circuit. This signal is applied to the base of the NPN transistor 21g through the sub power switch 19 which is closed in conjunction with the main power switch 6, so when the signal from the timer circuit 23 is "low", the NPN transistor 21g is turned on. It is non-conductive (at this time, as described above, the PNP transistor 8 whose inputs to the NAND circuit 17a are "high" and "low" is in a non-conductive state), and the dynamic brake circuit 21 is activated. When the mechanical switch 20 is opened, the brake circuit 21 is activated and the DC motor 1 is stopped for the time period of the "low" signal set by the timer circuit 23.

Incidentally, as a matter of course, the brake circuit 21
is activated when the wiper blade is in the home position and the mechanical switch 20 is open.

Since the timer circuit 23 repeats charging and discharging using a time constant circuit, the output becomes a "high" level after a period of time determined by the time constant has elapsed. nand circuit 1
Since both inputs of 7a become "high", its output becomes "low", PNP type transistor 8 becomes conductive, and DC motor 1 rotates. At this time, mechanical switch 20 is closed.

Furthermore, when the inputs of the NAND circuit 17a are "low" and "high", and when both inputs are "low",
The output of the NAND circuit 17a becomes "high"
Since the PNP transistor 8 becomes non-conductive, no current is applied to the DC motor 1, but once the motor 1 has started moving, it continues to rotate due to the action of the flywheel diode 9, so the wiper is in operation and the wiper blade is at the home position. Only when the mechanical switch 20 is opened by reaching the motor 1, the DC motor 1 is forcibly braked by the brake circuit 21.

By repeating the above operations, intermittent wiper operations can be performed continuously.

Incidentally, the intermittent operation time t ₂ (the time during which the wiper blade is at the home position) can be freely selected and set by adjusting the set time of the timer circuit 23 (see FIG. 1).
Since the details of FIGS. 4 and 5 are not the purpose of the present invention, a detailed explanation thereof will be omitted.

Symbols A to D in FIG. 4 and symbols A to D in FIG. 5 represent mutual connection points.

As described above, since the device of the present invention has the above configuration, it is possible to perform continuous variable control of the wiper over a wide range from low speed to high speed as shown in FIG. 1, and maintain the set speed constant at all times. Intermittent driving can be reliably performed at the set wiper speed level. Furthermore, the structure is simple and can be mass-produced at low cost.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the operating range of the device of the present invention;
FIG. 2 is a block diagram showing the configuration of the device of the present invention;
FIG. 3 is a circuit diagram of a wiper drive device showing an embodiment of the present invention, FIG. 4 is a specific circuit diagram for continuous wiper drive of the device shown in FIG. 3, and FIG. 5 is a specific circuit diagram for intermittent wiper drive. This is a typical circuit diagram. 1...DC motor, 2...Bridge circuit, 6...
... Main power switch, 7 ... Switching means for bridge circuit drive, 8 ... PNP type transistor, 10 ... Differential amplifier circuit, 11 ... Amplifier circuit, 12 ... Rotation speed setting means, 13 ... Operational amplifier circuit , 16... Comparison circuit, 17... Logic circuit, 18... Continuous/intermittent operation changeover switch, 19
...Sub power switch, 20...Mechanical switch, 21...Dynamic brake circuit, 21
f, 21g...NPN type transistor, 22...
Waveform shaping circuit, 23...timer circuit.

Claims (1)

[Scope of Claims] 1. A DC motor for driving a wiper, a bridge circuit including the DC motor on one side, and switching means for driving the bridge circuit provided in a path from a power source to the bridge circuit. and a differential amplifier circuit that differentially amplifies the back electromotive force of the DC motor from the bridge circuit, an amplifier circuit that amplifies the current flowing to the DC motor, and a rotation speed setting that sets the rotation speed of the DC motor. means and
an operational amplifier circuit that adds or subtracts signals from the differential amplifier circuit and the rotational speed setting means to generate a signal to set the DC motor at a set speed; and a comparison between the operational amplifier circuit and the signals from the amplifier circuit. What is claimed is: 1. A wiper drive device comprising: a comparison circuit, the switching means for driving the bridge circuit being made conductive or non-conductive based on a signal from the comparison circuit. 2. A DC motor for driving the wiper, a bridge circuit including the DC motor on one side, switching means for driving the bridge circuit provided in a path from the power supply to the bridge circuit, and a switch from the bridge circuit to the bridge circuit. a differential amplifier circuit that differentially amplifies the back electromotive force of the DC motor, an amplifier circuit that amplifies the current flowing through the DC motor, and a rotation speed setting means that sets the rotation speed of the DC motor;
an operational amplifier circuit that adds or subtracts signals from the differential amplifier circuit and the rotational speed setting means to generate a signal to set the DC motor at a set speed; and a comparison between the operational amplifier circuit and the signals from the amplifier circuit. a comparison circuit, a timer circuit for setting the intermittent operation time of the wiper, a wiper continuous/intermittent operation switching means for switching between the signal from the timer circuit and the signal from the constant voltage source, the comparison circuit and the operation selection switch. A wiper drive device comprising: a logic circuit that makes the bridge circuit drive switching means conductive or non-conductive based on a signal from the means.