Automatic windshield wiper speed control with piezoelectric sensor

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.

What is claimed is: 
     
       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.]. .Iadd.converting means .Iaddend.comprises means for shaping said sensor signal into .[.a train.]. .Iadd.said train .Iaddend.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.]. .Iadd.counted value .Iaddend.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 mm 2 . 
     
     
       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.]. .Iadd.the cowl top of a vehicle .Iaddend.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.]. .Iadd.the cowl top of a vehicle .Iaddend.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 mm 2 . 
     
     
       13. The control system as set forth in claim 11, wherein said vibrator of said rain sensor .Iadd.means .Iaddend.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.]. .Iadd.said train .Iaddend.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.]. .Iadd.said converting means .Iaddend.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 generation 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.]. .Iadd.said wiper motor .Iaddend.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.]. .Iadd.a wiper control signal.Iaddend.; 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. .Iadd.   
     
     
       21.  An intermittent timing control system for a wiper system of a vehicle, 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 of said vehicle so that raindrops directly collide with said one surface for causing oscillation of said vibrator, said one surface of said sensor being mounted on a point on the body of said vehicle subject to positive pressure from an air stream travelling over said vehicle and said vibrator producing a sensor signal having an amplitude and frequency corresponding to the magnitude of vibration and frequency of said one surface; 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. .Iaddend. .Iadd.22. The control system as set forth in claim 21 wherein said one surface of said rain sensor has an area greater than 100 mm 2 . .Iaddend. .Iadd.23. The control system as set forth in claim 21 wherein said one surface of said rain sensor is inclined at an angle relative to the horizontal. .Iaddend. .Iadd.24. The control system as set forth in claim 23 wherein said angle is in the range of 5 degrees to 25 degrees. .Iaddend. .Iadd.25. The control system as set forth in claim 24 wherein said angle is variable in dependence on raid drop speed. .Iaddend. .Iadd.26. The control system as set forth in claim 21 wherein said one surface is mounted on a cowl top panel of said vehicle. .Iaddend.   
     
     
        .Iadd.     A control system for controlling a windshield wiper of a vehicle, comprising: a driver motor associated with the windshield wiper for driving the windshield wiper;   a rain sensor for sensing rain and producing sensor signals indicative of the sensed rain, said rain sensor including a sensor surface having a variable angle of inclination with respect to the horizontal which is mounted on an external surface of said vehicle body at an orientation in front of a front windshield, which orientation subjects said sensor surface to positive pressure from an air stream travelling over said vehicle; and   means responsive to said sensor signal for deriving a driving signal for   
     
     
        said driver motor. .Iaddend. .Iadd.28.  A control system as set forth in claim 27 wherein said sensor surface is mounted on a cowl top panel of 
     
     
        said vehicle. .Iaddend. .Iadd.29.  A control system for controlling a windshield wiper of a vehicle comprising: a variable inclination rain sensor for sensing the rate of rain and generating sensor signals indicative of the sensed rain date, said sensor being mounted on an external portion of the vehicle body at an orientation in front of a front windshield, which orientation subjects said sensor to positive pressure from an air stream passing over said vehicle;   means responsively connected to the rain sensor 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. .Iaddend. .Iadd.30.  A rain sensor for use in an intermittent timing control system for a wiper system of a vehicle, which wiper system includes 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, and a wiper control circuit associated with said wiper motor for operating the latter at a controlled timing, said wiper control circuit being responsive to a rain condition indicative sensor signal for deriving said timing, wherein said rain sensor comprises: a sensor housing mounted on an external surface of an vehicle body adjacent a front windshield;   a vibrator supported on said sensor housing and adapted to oscillate at an amplitude frequency depending upon the rate of rain, said vibrator having one surface exposed outwardly to the atmosphere so that raindrops directly collide with said one surface for causing oscillation of said vibrator, said one surface of said vibrator being inclined at a given angle determined in relation to the inclination of the front windshield, and said vibrator producing said rain condition indicative sensor signal having an amplitude and frequency corresponding to the magnitude of   
     
     
        vibration and frequency of said one surface. .Iaddend. .Iadd.31.  A rain sensor as set forth in claim 30 wherein said inclination angle is in the range of 5 degrees to 25 degrees. .Iaddend. .Iadd.32. A rain sensor as set forth in claim 30 wherein said one surface is mounted on a cowl top panel of said vehicle. .Iaddend. .Iadd.33. A rain sensor for use in an intermittent timing control system for a wiper system of a vehicle, which wiper system includes 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, and a wiper control circuit associated with said wiper motor for operating the latter at a controlled timing, said wiper control circuit being responsive to a rain condition indicative sensor signal for deriving said timing, wherein said rain sensor comprises: a sensor housing mounted on an external surface of an vehicle body adjacent a front windshield;   a vibrator supported on said sensor housing and adapted to oscillate at an amplitude and frequency depending upon the rate of rain, said vibrator having one surface exposed outwardly to the atmosphere so that raindrops directly collide with said one surface for causing oscillation of said vibrator, said one surface of said vibrator having an area greater than or equal to 100 mm2, and said vibrator producing said rain condition indicative sensor signal having an amplitude and frequency corresponding to the magnitude of vibration and frequency of said one surface. .Iaddend.   
     
     
        .Iadd.34.  A rain sensor as set forth in claim 33, wherein said vibrator one surface being inclined at an angle in the range of 5 degrees to 25 degrees in relation to the inclination of the front windshield. .Iaddend. .Iadd.35. A rain sensor as set forth in claim 33 wherein said one surface is mounted on a cowl top panel of said vehicle. .Iaddend. .Iadd.36. A rain sensor for use in an intermittent timing control system for a wiper system of a vehicle, which wiper system includes 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, and a wiper control circuit associated with said wiper motor for operating the latter at a controlled timing, said wiper control circuit being responsive to a rain condition indicative sensor signal for deriving said timing, wherein said rain sensor comprises: a sensor housing mounted on an external surface of a vehicle body adjacent a front windshield;   a vibrator supported on said sensor housing and adapted to oscillate at an amplitude and frequency depending upon the rate of rain, said vibrator having one surface exposed outwardly to the atmosphere so that raindrops directly collide with said one surface for causing oscillation of said vibrator, said one surface of said vibrator being inclined at a given angle determined in relation to the inclination of the front windshield, and said vibrator producing said rain condition indicative sensor signal having an amplitude and frequency corresponding to the magnitude of   
     
     
        vibration and frequency of said one surface. .Iaddend. .Iadd.37.  A rain sensor as set forth in claim 36 wherein said inclination angle is in the range of 5 degrees to 25 degrees. .Iaddend. .Iadd.38. A rain sensor as set forth in claim 36 wherein said one surface is mounted on a cowl top panel of said vehicle. .Iaddend.