Automatic windshield wiper speed control with piezoelectric sensor

• US 4,527,105 A
• Filed: 08/30/1983
• Issued: 07/02/1985
• Est. Priority Date: 09/02/1982
• Status: Expired

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Shiraishi, Yasuhiro
• Primary Examiner(s): Shoop, William M.
• Assistant Examiner(s): Ro, Bentsu
• Application Number:
  US06/527,776
• Time in Patent Office: 672 Days
• Field of Search: 318/443, 318/444, 318/DIG. 2, 318/483, 15/250 C, 15/250 B, 15/250.13
• US Class Current: 318/444
• CPC Class Codes: B60S 1/0822 characterized by the arrangement or type of detection means
• CPC Class Codes: B60S 1/0859 Other types of detection of rain, e.g. by measuring friction or rain drop impact
• CPC Class Codes: Y10S 15/15 Moisture responsive
• CPC Class Codes: Y10S 318/02 Windshield wiper controls

Abstract

A wiper speed control system for an automotive wiper controls the operational speed of a wiper in accordance with rain conditions. The control system includes a rain sensor detecting rain conditions to produce an analog signal having an amplitude depending upon the detected rain conditions. The analog sensor signal is converted into a digital pulse signal by a converter for application to a digital circuit system. A control signal is produced by digitally processing the pulse signal. The control signal is applied to a wiper driver circuit to adjust the operational speed or timing in accordance with the control signal.

Claims

1. A control system for controlling a windshield wiper comprising:

rain sensor means for sensing the rate of rain and generating sensor signals indicative of the sensed rain rate;

means responsively connected to the rain sensor means for generating digital pulses having a frequency corresponding to the sensed rain rate in response to the sensor signals;

means responsively connected to the means for generating digital pulses for counting the digital pulses and generating a wiper control signal every time a predetermined number of the digital pulses has been counted;

a signal generator for outputting a constant-frequency digital signal to said counting means, said counting means being responsive to both the number of the digital pulses and the number of pulses in the digital signal in generating said wiper control signal; and

means responsively connected to the counting means for driving the windshield wiper through one cycle whenever the wiper control signal is generated.

2. A control system for controlling a windshield wiper comprising:

a driver motor associated with the windshield wiper for driving the windshield wiper at a variable rate;

a rain sensor including a vibrator with a sensor surface exposed to rain and vibrating in accordance with the rate of rain, said rain sensor producing a sensor signal having an amplitude which varies in accordance with the magnitude of vibration of said vibrator;

means for converting the sensor signal into a train of digital pulses having a frequency corresponding to the sensed rain rate in response to the sensor signal; and

a drive signal generator receiving the train of digital pulses and including counting means for counting the number of pulses in said train of digital pulses, generating a drive signal for driving the driver motor for one cycle of wiper operation whenever a given number of pulses are received.

3. The control system as set forth in claim 2, wherein said rain sensor further includes a piezoelectric element detecting the magnitude of vibration of said vibrator and producing said sensor signal with an amplitude corresponding to the vibration magnitude of said vibrator.

4. The control system as set forth in claim 3, wherein said converter means comprises means for shaping said sensor signal into a train of digital pulses.

5. The control system as set forth in claim 4, wherein said drive signal generator comprises a counter which counts the pulses of said pulse train and produces said driver signal whenever the counter value reaches a predetermined value.

6. The control system as set forth in claim 5, wherein said driver motor is responsive to said driver signal to drive said windshield wiper through one cycle so as to control the timing between intermittent strokes of the wiper in dependence upon said driver signal.

7. The control system as set forth in claim 6, wherein said sensor surface has an area of more than 100 mm².

8. The control system as set forth in claim 3, wherein said vibrator of said rain sensor is provided the natural resonant frequency in a range of from approximately 10 KHz to approximately 25 KHz.

9. The control system as set forth in claim 3, wherein said rain sensor is mounted on a cowl top panel of the vehicle and said sensor surface is inclined approximately parallel to a windshield.

10. The control system as set forth in claim 3, wherein said rain sensor is mounted on a cowl top panel of the vehicle and said sensor surface is inclined facing forward at an angle of about 5°

to 25°

.

11. A control system for controlling a windshield wiper comprising:

rain sensor means for sensing the rate of rain and generating sensor signals indicative of the sensed rain rate;

means responsively connected to the rain sensor means for generating digital pulses having a frequency corresponding to the sensed rain rate in response to the sensor signals;

means responsively connected to the means for generating digital pulses for counting the digital pulses and generating a wiper control signal every time a predetermined number of the digital pulses has been counted; and

means responsively connected to the counting means for driving the windshield wiper through one cycle whenever the wiper control signal is generated;

wherein said rain sensor means comprises a vibration sensor which detects the rain conditions by detecting vibrations created by the impact of a raindrop onto a sensor surface thereof, said vibration sensor comprising a vibrator having said sensor surface and a piezoelectric element for detecting magnitude of vibration of said vibrator to produce said sensor signals.

12. The control system as set forth in claim 11, wherein said sensor surface of said rain sensor means has an area greater than 100 mm².

13. The control system as set forth in claim 11, wherein said vibrator of said rain sensor has a natural resonant frequency in a range of from approximately 10 KHz to approximately 25 KHz.

14. The control system as set forth in claim 11, wherein said sensor surface is inclined to be approximately parallel with the windshield.

15. The control system as set forth in claim 11, wherein said sensor surface is inclined upward front-to-rear with respect to vehicle travel at an angle of 5°

to 25°

to the horizontal.

16. A control system for controlling a windshield wiper comprising:

rain sensor means comprising a vibration sensor which detects rain conditions by detecting vibrations created by the impact of a raindrop onto a sensor surface thereof, said vibration sensor comprising a vibrator having said sensor surface inclined to be approximately parallel with the windshield and a piezoelectric element for detecting magnitude of vibration of said vibrator to generate sensor signals indicative of the sensed rain rate

means responsively connected to the rain sensor means for generating digital pulses having a frequency corresponding to the sensed rain rate in response to the sensor signals;

means responsively connected to the means for generating digital pulses for counting the digital pulses and generating a wiper control signal every time a predetermined number of the digital pulses has been counted;

a signal generator for outputting a constant-frequency digital signal to said counting means, said counting means being responsive to both the number of digital pulses and the number of pulses in said digital signal in generating said wiper control signal; and

means responsively connected to the counting means for driving the windshield wiper through one cycle whenever the wiper control signal is generated.

17. A control system for controlling a windshield wiper comprising:

rain sensor means comprising a vibration sensor which detects rain conditions by detecting vibrations created by the impact of a raindrop onto a sensor surface thereof, said vibration sensor comprising a vibrator having said sensor surface inclined upward front-to-rear with respect to the direction of vehicle travel at an angle of 5°

to 25°

to the horizontal and a piezoelectric element for detecting magnitude of vibration of said vibrator to generate sensor signals indicative of the sensed rain rate

means responsively connected to the rain sensor means for generating digital pulses having a frequency corresponding to the sensed rain rate in response to the sensor signals;

means responsively connected to the means for generating digital pulses for counting the digital pulses and generating a wiper control signal every time a predetermined number of the digital pulses has been counted;

a signal generator for outputting a constant-frequency digital signal to said counting means, said counting means being responsive to both the number of digital pulses and the number of pulses in said digital signal in generating said wiper control signal; and

means responsively connected to the counting means for driving the windshield wiper through one cycle whenever the wiper control signal is generated.

18. A control system for controlling a windshield wiper comprising:

a rain sensor including a vibrator with a sensor surface exposed to rain and vibrating in accordance with the rate of rain, and further including a piezoelectric element detecting the magnitude of vibration of said vibrator and producing a sensor signal having an amplitude which varies in accordance with the magnitude of vibration of said vibrator;

means for converting the sensor signal into a train of digital pulses having a frequency corresponding to the sensed rain rate, said converting means comprising means for shaping said sensor signal into a train of digital pulses;

a driver signal generator receiving the train of digital pulses and comprises a counter which counts the number of pulses in said pulse train and produces a driver signal whenever the counted number of pulses reaches a predetermined value;

a pulse generator adapted to output a constant-frequency pulse signal to said counter, said counter counting the pulses from both said constant-frequency pulse signal and said digital signal to produce said driver signal whenever the sum of the pulses from said converter means and the pulses from said pulse generator reaches the predetermined value; and

a driver motor associated with said windshield wiper and responsive to said driver signal for driving said windshield wiper through one cycle so as to control the timing between intermittent strokes of the wiper in dependence on the driver signal.

19. An intermittent timing control system for an automotive wiper system comprising:

a windshield wiper;

a wiper motor for driving said wiper, said wiper motor being controllable to drive said wiper at a variable sweep speed and operative for driving said wiper at variable intervals in an intermittent mode of operation;

a rain sensor having a sensor surface exposed to rain for detecting the rate of rain, vibrating in response to an impact of raindrops on said sensor surface at a magnitude and frequency depending upon the rate of rain, and producing a sensor signal having an amplitude and frequency corresponding to the magnitude and frequency of vibration of said sensor surface;

a pulse generator for producing a train of pulses corresponding to said sensor signals and having a frequency depending upon the rate of rain; and

counting means receiving said train of pulses and producing a drive signal for operating said driver motor for one cycle of wiper operation whenever a given number of pulses are received.

20. An intermittent timing control system for an automotive wiper system comprising:

a windshield wiper;

a wiper motor for driving said wiper, said wiper motor being controllable to drive said wiper at a variable sweep speed and operative for driving said wiper at variable intervals in an intermittent mode of operation;

a rain sensor having a vibrator adapted to oscillate at an amplitude and frequency depending upon the rate of rain, said vibrator having one surface exposed outwardly and inclined to be approximately parallel with the windshield so that raindrops directly collide with said one surface for causing oscillation of said vibrator, and said vibrator producing a sensor signal having an amplitude and frequency corresponding to the magnitude of vibration and frequency thereof;

means responsively connected to the rain sensor for generating digital pulses at a frequency corresponding to the frequency of said sensor signals;

means, responsively connected to said generating means, for counting the number of digital pulses;

a signal generator for outputting a constant-frequency digital signal to said counting means, and said counting means being responsive to both the number of digital pulses and the number of pulses in said digital signal in generating said wiper control signal; and

means responsive to said sensor signal indicative of the magnitude and frequency of vibration of said vibrator for deriving an intermittent timing signal for wiper intermittent operation based on the sensor signal value.