Electricity: motive power systems – Automatic and/or with time-delay means – Moisture content or wetness
Patent
1997-10-02
1999-10-19
Ro, Bentsu
Electricity: motive power systems
Automatic and/or with time-delay means
Moisture content or wetness
318444, 318DIG2, B60S 108
Patent
active
059694939
DESCRIPTION:
BRIEF SUMMARY
STATE OF THE ART
The invention relates to an apparatus for operating a windshield wiper that has a sensor device for detecting the state of wetness of a windshield, an evaluation device that receives the sensor signal and has a signal-processing stage, a difference-initiating stage and a control-signal-generation stage, and an actuating unit for the windshield wiper, which can be actuated by the evaluation device to effect wiping operation.
This type of apparatus is known from DE 33 14 770 A1. In this known apparatus, wiping operation is initiated if a difference between a reference value and a current measured value of the sensor signal exceeds a predetermined threshold value. A difference of this type is formed, for example, if a certain number of raindrops reduces the intensity of the signal and it drops below the predetermined threshold value. In this case, wiping operation is frequently not initiated if only a few raindrops impact the windshield, although such occurrences of wetness on the windshield can be disturbing.
ADVANTAGES OF THE INVENTION
It is the object of the invention to refine an apparatus of the type mentioned at the outset such that wiping operation is better adapted to external conditions, increasing safety.
This object is accomplished with a generic apparatus having the features of claim 1.
Accordingly, it is provided that current measured values of the sensor signal can be supplied to both the difference-initiating stage and a drop-recognition device in the evaluation device, in which the sensor signal can be evaluated with respect to individual drops using signal breaks, and that when a minimum signal break is recognized, an adapted control signal can be generated by the control-signal-generation stage, with which signal a corresponding wiping operation can be initiated by way of the actuating unit.
With the additional drop-recognition device, occurrences of wetness on the windshield can also be detected that can be attributed to individual, larger drops, and the disturbing wetness can be eliminated by the windshield wiper.
The apparatus is advantageously configured such that the drop-recognition device operates even during periods during which the difference-initiating stage is switched to be inactive. An example of a case in which the difference-initiating stage is switched to be inactive is when the windshield is not completely clean after wiping, and the signal shows an increasing tendency due to residual moisture that is still present, or streaks caused by the relatively rapid drying process. In a normal case, no wiping process should be initiated. If drops impact the windshield during this time, they can be recognized by the drop-recognition device over the course of the sensor signal, because the drops cause a visible signal break, and a necessary wiping process can be initiated immediately in this situation.
A further advantageous embodiment of the apparatus provides that the signal breaks can be detected in the drop-recognition device through the determination of the difference between a current measured value and a reference value. Existing signal breaks can consequently be ascertained, and the drop-recognition device can be activated for analysis of the cause of the signal break to distinguish between wetness and disturbance.
A reliable reference variable that also takes into consideration an increasing tendency of the sensor signal, for example, and is insensitive to instantaneous disturbances, is advantageously obtained through the formation of the reference variable from the mean value of a plurality of the last measured values preceding the current measured value. For example, the last four measured values can be used to form the mean value.
In the event that a signal break has been detected, a reliable evaluation with respect to the presence of drops can be effected in that the drop-recognition device has a surface-calculation stage, with which the surface between the reference variable and a plurality of sequential, current measured values (MW) can be determined
REFERENCES:
patent: 5140233 (1992-08-01), Wallrafen
patent: 5319293 (1994-06-01), Levers
patent: 5684464 (1997-11-01), Egger
patent: 5760559 (1998-06-01), Pientka et al.
Blitzke Henry
Buerkle Joerg
Pientka Rainer
Ro Bentsu
Robert & Bosch GmbH
Spencer George H.
Wells Ashley J.
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