JPH078125U - Water droplet removal control device - Google Patents

Abstract

(57) [Summary] [Purpose] Even if the ultrasonic controller fails for some reason, the oscillator 30 is driven only for a predetermined time. A drive circuit 20 that operates according to a signal from an ultrasonic controller is provided with an operation limiting circuit 24 that operates simultaneously with the start of operation of the drive circuit 20, and the operation limiting circuit 2
4 limits the drive signal output from the drive circuit 20 to the vibrator 30 within a predetermined time. For details, operation restriction circuit 2
4, an integrating circuit 24a including a resistor 23a and a capacitor 23b is provided, and when the charging voltage of the capacitor 23b exceeds a predetermined voltage, the MOS transistors Q1 and Q2 are turned off and the primary input of the step-up transformer 22 is turned off.
Then, the operation of the vibrator 30 is stopped.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a water droplet removal control device for removing water droplets attached to a mirror of an automobile or the like.

[0002]

[Prior art]

 Conventionally, a water drop removing device has been proposed in which ultrasonic waves generated by a vibrator such as a piezoelectric element is applied to a mirror surface to remove water drops adhering to a mirror, and the water drops are repelled (actually, 2-126964; Kaihei 3-94359). As one example of control of this water drop removing device, one shown in FIG. 4 is known. In the figure, when the switch S2 is turned on while the switch S1 (ignition switch) is turned on, the control circuit in the ultrasonic controller 10 (controller) operates. By this control circuit, the transistor 11 becomes conductive, the relay 12 operates, and the relay contact 12a is closed. As a result, power is supplied to the drive circuit 20 and the vibrator starts vibrating. Since this oscillator emits ultrasonic waves to the mirror surface, the mirror surface vibrates and the attached water droplets are repelled.

[0003]

[Problems to be solved by the device]

 However, in the above configuration, if a failure occurs such that the transistor 11 remains conductive or the relay contact 12a is welded during the operation of the vibrator, the vibrator is irrespective of the closed state of the switch S2. Will continue to operate until switch S1 is turned off. In such a case, ultrasonic waves are continuously emitted for a long time, so that there are problems that the failure of the mirror is induced and a good visibility cannot be secured in rainy weather. Then, this invention aims at providing the water droplet removal control apparatus which solved the said problem.

[0004]

[Means for Solving the Problems]

 In order to achieve the above object, in a water droplet removal control device in which a drive circuit oscillates a vibrator in response to a signal from a controller, the drive circuit operates at the same time as the operation of the drive circuit is started, and the operation is a predetermined operation. There is provided an operation limiting means for stopping the output from the drive circuit when the time has elapsed. A MOS transistor whose operation is controlled by the operation limiting means is connected to the primary terminal side, and a booster transformer is provided on the secondary terminal side to which the vibrator is connected. Furthermore, a sweep frequency oscillation circuit for changing the frequency of the AC signal output to the vibrator is provided. For example, the operation limiting means outputs a "high level" signal when the output level of the integrating circuit or the timer circuit and the integrating circuit or the timer circuit is equal to or lower than a predetermined voltage, and when the output level is equal to or higher than the predetermined voltage. It has an IC that outputs a "low level" signal. Further, the sweep frequency oscillating circuit has a counter that outputs a pulse signal at a predetermined time interval, counts the pulse signal, and controls the MOS transistor when a predetermined count is reached. Become.

[0005]

[Action]

 Based on the above configuration, an integrating circuit or a timer circuit is provided to stop the output from the drive circuit when the continuous operation time of the drive circuit exceeds a predetermined time. Further, the integrating circuit is provided with a counter for counting the pulse signals output from the sweep frequency oscillating circuit instead of the timer circuit, and the output time from the drive circuit is controlled by the count number. Thus, even if the drive circuit operates for a predetermined time or longer due to a failure of the ultrasonic controller or the like, the output from the drive circuit is limited to prevent damage to the mirror or the like.

[0006]

【Example】

 An embodiment of the present invention will be described with reference to the drawings. It should be noted that the same parts as those of the conventional technique are designated by the same reference numerals and the description thereof will be omitted. FIG. 1 is a circuit diagram showing a drive circuit according to the present invention, which includes a sweep frequency oscillation circuit 21, MOS transistors Q1 and Q2, a step-up transformer 22 and an operation limiting means 24. The operation limiting means 24 is composed of an integrating circuit 24a, an IC 24b, and diodes D1, D2, D3. When power is supplied from the ultrasonic controller 10 (that is, when power is supplied), the sweep frequency oscillation circuit 21 starts transmitting, and the capacitor 23b starts charging via the resistor 23a. Will rise. The integrating circuit 24a is set so that, when the drive circuit 20 is operating normally, it takes 5 seconds or more before the voltage at the point A becomes 1/2 VDD. Further, the IC 24b is set so as to output a "high level" signal when the voltage at the point A is 1/2 VDD or lower, and to output a "low level" signal when the voltage at the point A is 1/2 VDD or higher. . Therefore, the voltage at point A immediately after the drive circuit 20 starts operating is less than 1/2 VDD because the capacitor 23b is not charged, and the output from the IC 24b is "high level". Whereas, the diodes D1 and D2 are connected to the output terminal of the IC 24b so that current flows into the output terminal of the IC 24b (in the forward direction), and the other ends thereof are connected to the gates of the MOS transistors Q1 and Q2. . Therefore, immediately after the drive circuit 20, the operation of the MOS transistor is controlled by the signal from the sweep frequency oscillation circuit 21.

Therefore, even if a predetermined time (5 seconds or more) has elapsed from the start of the operation of the drive circuit 20, if the ultrasonic controller 10 continues to be energized, the potential at the point A exceeds 1/2 VDD. Therefore, the output of the IC 24b becomes "low level". Then, the signal current from the sweep frequency oscillating circuit 21 begins to flow into the IC 24b, and the MOS transistors Q1 and Q2 are in the non-conducting state regardless of the signal of the sweep frequency oscillating circuit 21 and the primary input of the step-up transformer 22. Is turned off. Therefore, the vibrator 30 stops operating. The diode D1 is provided in order to promptly discharge the electric charge of the capacitor 23b to prepare for the next operation when VDD drops during normal operation. FIG. 2 is a graph showing the voltage rise at the point A against the energization time. It is desirable that t 1 (that is, the time until the voltage at the point A becomes 1/2 VDD) in the figure is about 2 to 3 times the normal operation time.

In the above description, the integrating circuit 23 is composed of the resistor 23a and the capacitor 23b, but a timer IC or the like may be used. Further, as shown in FIG. 3, a counter 25 is used, and when a pulse signal from the sweep frequency oscillation circuit 21 is input to the counter 25 and a predetermined pulse is counted (that is, when a predetermined time elapses), the MOS transistor Q1. , Q2 may be controlled to be inoperative.

[0009]

[Effect of device]

 As described above, even if the ultrasonic controller keeps outputting due to some abnormality and the operating time of the driving circuit becomes longer than the predetermined time, the output from the driving circuit is output by the operation limiting means such as an integrating circuit. Since it was stopped, it was possible to prevent the failure from spreading to the mirror etc. due to the continuous operation of the oscillator. This also prevented unnecessary power consumption.

[Brief description of drawings]

FIG. 1 is a circuit diagram applied to a description of an embodiment.

FIG. 2 is a diagram illustrating a voltage rise of an integrating circuit in FIG.

3 is a circuit diagram in which a counter is used instead of the integrating circuit in FIG.

FIG. 4 is a circuit diagram of a water droplet removal control device applied to the description of the conventional technique.

[Explanation of symbols]

 10 Ultrasonic Controller (Controller) 20 Drive Circuit 21 Sweep Frequency Oscillation Circuit 22 Step-up Transformer 24a Integration Circuit (Operation Limiting Means) 24b Operation Limiting Means 25 Counter 30 Transducers D1, D2 Diodes Q1, Q2 MOS Transistors

Claims (3)

[Scope of utility model registration request] 1. A water droplet removal control device in which a drive circuit oscillates a vibrator in response to a signal from a controller, wherein the drive circuit operates simultaneously with the start of operation of the drive circuit, and the operation has passed a predetermined time. When the output voltage from the drive circuit is stopped, an operation limiting unit and a MOS transistor whose operation is controlled by the operation limiting unit are connected to the primary terminal side and the oscillator is connected to the secondary terminal side. A water droplet removal control device comprising a transformer and a sweep frequency oscillation circuit that changes the frequency of an AC signal output to the vibrator. 2. The operation limiting means outputs an "integrated circuit or timer circuit" and a "high level" signal when the output level of the integrated circuit or timer circuit is below a predetermined voltage, and when the output level is above a predetermined voltage. The water droplet removal control device according to claim 1, further comprising an IC that outputs a "low level" signal. 3. The sweep frequency oscillating circuit outputs a pulse signal at a predetermined time interval, counts the pulse signal, and when the predetermined count is reached, the M
The water droplet removal control device according to claim 1, further comprising a counter that controls the OS transistor.