JPH0425908B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a wiper drive device, and more particularly to a wiper drive device having a structure in which a wiper blade is caused to perform a reciprocating wiping motion by reversing the rotational direction of a drive motor. .

[Technical background of the invention and its problems]

Most common wiper drives are configured to convert the continuous rotation of a drive motor in one direction into a reciprocating wiping motion of a wiper blade via a linkage. Also, by eliminating this link mechanism,
There is also known a device in which the direction of rotation of the drive motor is reversed every time the wiper blade reaches a predetermined position, thereby causing the wiper blade to perform a reciprocating wiping motion (for example, Japanese Patent Laid-Open No. 13240/1983).

Furthermore, Japanese Patent Application Laid-Open No. 59-92235 discloses the following technology for weakening the impact force and inertia force when the wiper blade's wiping direction is reversed in a wiper drive device using the above-mentioned link mechanism. There is. This is configured so that the rotational speed of the motor can be switched in three stages, and when the wiper blade reaches just before the direction reversal position, the rotational speed of the motor is automatically switched to the lowest speed.

However, this technique is intended only for devices in which the drive motor continuously rotates in one direction, and the impact force can only be reduced by lowering the motor speed by one step.

In a wiper device that eliminates the link mechanism described above and controls the drive motor in reverse, the motor torque is If the changes are sudden or discontinuous, the wiper blades and motor will generate significant noise and vibration. This noise and vibration not only cause discomfort to the driver, but also accelerate the wear and tear of wiper blades and the like.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a wiper drive device in which the rotation direction of the drive motor is reversely controlled to cause the wiper blade to perform a reciprocating wiping motion. The objective is to reduce the generation of noise and vibration by stopping the motor immediately and smoothly increasing the driving torque in the opposite direction.

[Summary of the invention]

In order to achieve the above object, the present invention includes a position detection means that generates a switching signal when the wiper blade reaches a predetermined position slightly before the two limit positions of the wiping movement range, and a When the switching signal is generated during reverse rotation), the forward (reverse) drive voltage to the motor is cut off, and the current due to the back electromotive force of the motor is absorbed by a closed loop circuit whose impedance gradually increases over time. a stop control means that gradually reduces the rotational speed of the motor and stops the motor; and a predetermined time after the switching signal is generated during forward rotation (reverse rotation) of the motor (after the time required for the motor to stop); Reverse start control means for applying a reverse (forward) drive voltage to the motor, gradually increasing the current flowing through the motor to a predetermined position over time, and gradually increasing the rotational speed of the motor to a steady value; The motor is stopped and started in reverse when the direction is reversed so that the torque changes smoothly and continuously.

[Embodiments of the invention]

FIG. 1 shows the overall structure of a wiper drive device according to an embodiment of the present invention. 600 is a motor that drives a wiper blade (not shown);
500 indicates a motor drive section. The motor drive unit 500 includes power MOS transistors TR1 to
This is a bridge-shaped circuit consisting of TR4 and motor current detection resistors RM1 and RM2. TR1 and TR2 are P-channel power MOS transistors,
TR3 and TR4 are N-channel power MOS transistors. When the transistors TR1 and TR3 are turned on, the motor 600 rotates in the forward direction, and when the transistors TR2 and TR4 are turned on, the motor 600 rotates in the reverse direction.

A position detector 100 is attached to the rotation system of the motor 600. The position detector 100 includes a contact plate 10 that rotates relatively with the wiper blade.
1 and two sliders 102 and 103.

When the wiper blade reaches a predetermined position just before the limit position in the reverse direction, the signal A of the position detector 100 changes from H level to L level. Conversely,
When the wiper blade reaches a predetermined position immediately before the limit position in the normal rotation direction, the signal B changes from the H level to the L level.

Based on the signals A and B from the position detector 100, the rotation direction determining section 200 determines whether the rotation is normal or reverse. That is, when the wiper blade reaches just before the reverse rotation limit, the signal A causes the output of the rotation direction determining section 200 to go to H level. On the other hand, when the wiper blade reaches just before the normal rotation limit, the signal B causes the output of the rotation direction determining section 200 to go to L level.

The output of the rotation direction determining section 200 is input as a switching signal to the forward rotation control section 300 and the reverse rotation control section 400, and the transistor of the motor drive section 500 is
TR1 to TR4 are controlled.

The internal configurations of the forward rotation control section 300 and the reverse rotation control section 400 are completely the same, and the connection relationship with the motor drive section 500 is symmetrical with respect to the rotation direction of the motor 600. Both control units 300, 4
00 are the wiping command signal generating units 320 and 4, respectively.
20, reverse start control section 340, 440, stop control section 360, 460, and motor current detection section 38
0,480. The forward rotation control section 300 will be mainly described below.

The specific configuration and operation of this embodiment will be explained in order based on the circuit diagram in FIG. 2 and the waveform diagram in FIG. 5.

Signal A of the position detector 100 becomes L level,
Assume that the output Q of the rotation direction determining section 200 changes to H level at time t0. As will become clear from the following description, at this time the wiper blade is decelerating toward the reverse rotation limit position, and the motor 600 is under stop control.

Buffer BUF 321, resistor 321, and diode D3 in the wiping command signal generating section 320 in FIG.
21. The capacitor C321 constitutes an on-delay circuit, and causes the rising edge of the output Q of the rotation direction determining section 200 to be sent by ΔT, like the signal S in FIG. This signal S is the inverter INV321
is inverted and becomes VG (TR1), and the transistor
Applied to the gate of TR1. In other words, the output Q is H
At time t1, which is a time ΔT after the time t0 when the level changes, the transistor TR1 is turned on.

The above signal S is applied to the integrator circuit (operational amplifier OP341, resistor R341,
R342, capacitor C341, and analog switch SW341), the voltage VG gradually increases from time t1 and reaches the power supply voltage.
(TR3) is created. This voltage VG (TR3) is applied to the gate of the transistor TR3, and the transistor TR3 starts to conduct from time t1, its impedance gradually decreases, and becomes completely turned on at time t3. Note that the rate of increase in the voltage VG (TR3) at this time is relatively large until time t2, and becomes relatively small from time t2 to t3. This rate of change is switched by analog switch SW341, which determines the time constant in the integration circuit, by flip-flop FF3.
This is done by switching from on to off at the output of 41.

Details up to the above time point t3 are shown in FIG. Transistor TR1 turns on at time t1, and transistor TR3 gradually becomes conductive at the larger rate of change from time t1 to time t2. Therefore, the motor current gradually increases as shown by the solid line in the figure.
Motor 600 gradually begins to rotate forward. When the wiper blade overcomes the static friction force and starts moving,
The motor current stops increasing and starts decreasing. The point at which the motor current changes from increasing to decreasing is time t2, and at this time t2, the motor current detection section 380 and the falling detection circuit of the inversion start control section 340 (op-amp OP342, resistors R343 to R346, capacitor C342, diode D341 (consisting of).

In other words, the motor current detection unit 380 includes a differential amplifier (op-amp OP38) that detects the voltage across the current detection resistor RM1 connected in series with the transistor TR3.
1. consists of resistors R381 to R384) and is a voltage proportional to the motor current to be output (this is referred to as the motor current value for convenience) V
(RM1) is input to a falling detection circuit composed of an operational amplifier OP342 and the like. And V
When (RM1) changes from increasing to decreasing, the flip-flop 341 is set by the output of the operational amplifier OP342, and the analog switch SW341 is turned off. Therefore, the rate of increase of voltage VG (TR3) is switched to a smaller value from time t2, and gradually increases until time t3, when it reaches the power supply voltage.

The impedance reduction of transistor TR3 is
Corresponding to the change in voltage VG (TR3), it is completely turned on at time t3. Therefore, the speed of motor 600
VSP is at time t1, as shown by the solid line in FIG.
It increases slowly to a steady value from to time t3.

Note that the dotted line shown in FIG. 3 is that of a conventional example shown for comparison with the present invention. That is, at time t1, transistor TR3 is also completely turned on. Immediately after that, a very large current close to the lock current IL flows through the motor 600, and at the same time the wiper blade starts moving, the rated current IN
It settles to a value close to . Correspondingly, motor 600
begins to rotate rapidly, and its speed rapidly increases. This caused large shocks and noise to be generated from the motor and wiper blades. According to the present invention, since the motor speed increases smoothly and continuously as shown by the solid line in FIG. 3, it is possible to significantly reduce impact and noise.

Next, stop control of the motor 600 will be explained. When the wiper blade reaches the limit point in the forward rotation direction due to the forward rotation of the motor 600, the signal B of the position detector 100 goes to L level at time t4, and the output Q of the rotation direction determination unit 200 goes to L level. Invert. Then, the wiping command signal generating section 320
The signal S becomes L level, and the inverted signal
VG (TR1) becomes H level. Therefore, transistor TR1 is turned off, cutting off the normal rotation drive voltage to motor 600.

Inverter INV3 in stop control unit 360
63, resistor R363, and capacitor C363 are constant pulse generation circuits, which are triggered at the rising point of signal VG (TR1) and output an H level pulse with a constant width, as shown in V _G (TR4) in Figure 5. . This pulse is applied as signal VG (TR4) to the gate of transistor TR4, turning it on. At this time, the transistor TR3 is also turned on (conducting), so that a series closed loop circuit including the transistor TR3, the resistor RM1, the resistor RM2, and the transistor TR4 is connected to both ends of the motor 600. This closed loop circuit gradually absorbs the current caused by the back electromotive force of the motor 600, and the motor 60
0 and bring it to a smooth stop.

The control for smoothly stopping the motor 600 is based on the voltage
This is done by gradually decreasing VG (TR3) to zero from time t4 to time t5, and gradually increasing the impedance of transistor TR3.

Voltage VG decreasing from time t4 to time t5
(TR3) is generated by the operational amplifier OP361 in the stop control section 360. Above signal S
When becomes L level at time t4, the analog switch SW361 is turned on with the signal inverted by the inverter INV361, and from this point on, the operational amplifier
The output of OP361 is applied as VG (TR3) to the gate of transistor TR3.

The operational amplifier OP361 is for impedance conversion, and its input side has a motor current detection section 38.
Capacitor C charged with output V (RM1) of 0
362, a resistor R362 which serves as a discharge path for this capacitor C362, and a transistor TR361 are connected. The above-mentioned signal S is applied to the gate of this transistor TR361 via a circuit consisting of a capacitor C361 and a resistor R361.

Until just before time t4, capacitor C362 is charged with a voltage approximately equal to the motor current value V (RM1) during forward rotation. Furthermore, the capacitor C361 is charged via the resistor R361 by the signal S which has been at the H level just before time t4, and this charging voltage is applied to the transistor TR361.
The transistor TR361 is conductive with an impedance approximately inversely proportional to the charging voltage of the capacitor C361.

When the signal S becomes L level at time t4, the capacitor C362 connects the resistor R362 and the transistor TR.
361, and its voltage gradually decreases. This gradually decreasing voltage is passed through the operational amplifier OP361 and the analog switch SW361 to the transistor TR as voltage VG (TR3).
Applied to the gate of 3. The discharge time constant during this discharge differs depending on the conduction impedance of the transistor TR361. This impedance becomes smaller as the charging voltage of the capacitor C361 becomes larger. The charging voltage of the capacitor C361 increases as the time that the signal S remains at the H level increases. The H level time width of the signal S is the normal rotation period of the motor 600, and becomes shorter as the steady speed of the motor 600 (which can be switched to multiple stages) increases. Further, the higher the steady speed of the motor 600, the greater the motor back electromotive force when stopped.

As is clear from the above relationship, the motor 600
When the steady rotation speed of the capacitor C361 is set high, the charging voltage of the capacitor C361 is relatively low, the impedance of the transistor TR361 during discharging is high, and the discharge curve of the capacitor C362 becomes gentle. On the other hand, if the steady rotation speed of motor 600 is set low, the discharge curve of capacitor C362 will be relatively steep.

In this way, the transistor when the motor is stopped
Gradually increase the impedance of TR3 at a rate of change depending on the steady rotation speed of the motor. As a result, irrespective of the magnitude of the motor steady speed, the motor 600 starts to be braked from time t4 and is stopped at time t5.

The details of the operation from time t4 to t5 described above are shown in FIG. In this figure, the solid line indicates the case where the steady motor speed is relatively low, and the dashed line indicates the case where the steady motor speed is high. Since priority is given to keeping the wiper blade at the same stopping position even when the speed is high, the gate voltage VG (TR3 ) is changing the attenuation curve.

Note that the characteristics indicated by the dotted line in FIG. 4 are those of the conventional device. In the conventional device, the motor 6 at time t4
00 terminals were short-circuited, the current due to the back electromotive force was consumed instantaneously, and the motor was stopped as quickly as possible. Therefore, although the distance required to stop is short, the rapid torque changes generate large shocks and noise. In contrast, according to the present invention, the torque change when the motor is stopped is extremely smooth and continuous, and vibrations and noise when the direction is reversed can be extremely reduced. Further, in FIG. 5, the operation by the reverse rotation control section 400 is shown by dotted lines.

By the way, the time t for the forward rotation control unit 300
0 is equivalent to time t4 for the reverse rotation control unit 400, and the same operation as the operation in the forward rotation control unit 300 after time t0 is performed in the reverse rotation control unit 400 after time t4, causing the motor 600 to reverse. .

〔Effect of the invention〕

As explained in detail above, according to the present invention, in a wiper drive device that reverses the rotational direction of the motor to cause the wiper to perform a reciprocating wiping motion, torque fluctuations caused by stopping when the direction is reversed and restarting in the opposite direction are reduced. It is extremely smooth and continuous, and vibrations and noise generated by the motor and wiper blades are extremely low.

[Brief explanation of drawings]

FIG. 1 is an overall block diagram of a device according to an embodiment of the present invention, and FIG. 2 is a forward rotation control section 3 in FIG. 1.
Detailed circuit diagram centered on 00, Figure 3 is a waveform diagram showing the operating state of the same device at reverse startup,
FIG. 4 is a waveform diagram showing the operating state when the motor is stopped in the same device, and FIG. 5 is a waveform chart showing the timing relationship of each circuit part in the same device. 100...position detector, 300...forward rotation control section,
400... Reverse rotation control section, 500... Motor drive section,
600...Drive motor.

Claims (1)

[Scope of Claims] 1. A wiper drive device that reverses the rotational direction of a drive motor every time the wiper blade reaches a predetermined position to cause the wiper blade to perform reciprocating wiping motion; a position detection means that generates a switching signal when the motor reaches a predetermined position slightly before the motor; and a position detection means that generates a switching signal when the motor reaches a predetermined position slightly before the motor; a stop control means that interrupts the rotational speed of the motor and absorbs the current due to the back electromotive force of the motor in a closed loop circuit whose impedance gradually increases with time, thereby gradually decreasing the rotational speed of the motor and stopping the motor; After a predetermined period of time has elapsed since the switching signal is generated in the motor, a reverse (forward) drive voltage is applied to the motor, and the drive current flowing through the motor is gradually increased to a predetermined value over time, thereby changing the rotational speed of the motor. A wiper drive device comprising: a reversal start control means for gradually increasing and leading to a steady value; and;