Electricity: motive power systems – Periodic – repetitious or successive operations control of... – Variable periods or intervals between controlling operations
Reexamination Certificate
1999-12-20
2001-01-16
Ip, Paul (Department: 2837)
Electricity: motive power systems
Periodic, repetitious or successive operations control of...
Variable periods or intervals between controlling operations
C318S466000, C318S483000, C318SDIG002
Reexamination Certificate
active
06175205
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention is based on a device for operating a windshield wiper.
A device for controlling a windshield wiper system is already known (from German Patent Disclosure DE 41 41 348 A1), which automatically adapts the wiping cycle frequency to qualitatively and/or quantitatively varying states of the precipitation on the window. To that end, the signals of an optical rain sensor are evaluated by a circuit arrangement. A wiping cycle is initiated when the signals undershoot a particular switching threshold. Each time the wiper sweeps over the rain sensor, the signal increases again, up to a maximum signal value, which is then stored in memory as a reference value for the next wiping cycle. The switching threshold is defined at 95%, as a function of this reference value.
A substantial disadvantage of this control arrangement is that after a defined period of time has elapsed, a new wiping cycle is tripped if during this time period no new precipitation has formed to a sufficient extent, and if the signal value of the sensor device does not undershoot the switching threshold. A new reference value is thus formed, because the old one in the meantime may no longer be usable, because of the temperature drift of the sensor signal. Yet this means that the wiper will be wiping a dry or nearly dry window.
Another resultant disadvantage is that signals generated by fog or drizzle cannot be distinguished from the signal change caused by an increase in temperature of the sensor: Both effects cause the signal value to undershoot the switching threshold.
Still another disadvantage is that the reference value is written in anew for each wiping operation and used to determine the switching threshold for the next wiping cycle. Heavy soiling of the window, for instance, leads to a lower reference value and thus a lower switching threshold, so that the wiping operation is not tripped until there is a heavier total coating of both soil and moisture on the window. This heavier coating impairs the driver's vision and is a safety risk.
It is therefore an object of the present invention to provide a device for operating a windshield wiper, which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in a device for operating a windshield wiper, in which incremental values are allocated to the measured values by a control unit, and a mean value of at least two successive measured values is formed as the incremental value, and the respective difference between two successive incremental values is to be added with a sign + or − in the memory to a sum of differences formed previously in the same way, and finally when the threshold is reached by the sum stored in the memory, the control unit trips a wiper operating mode.
SUMMARY OF THE INVENTION
The device of the invention has the advantage that in addition to detecting rain and droplets, it also detects fog and drizzle. The moisture on the window is detected, and a wiper operating mode appropriate for the incident precipitation is tripped.
The allocation of the maximum measured value to a predetermined limit value when the wiper is put into operation is especially advantageous. After that, the allocation is corrected only if maximum values rise, for instance because the window has then been cleaned better.
The advantage of forming a mean value from the measured values resides in the quieter response of the device, because individual measured values do not lead to tripping of the wiper activity; only the measured values averaged over a short period of time, or from a predetermined number of values, does so.
Another advantage resides in the signal evaluation, which because of the device of the invention is independent of the signal amplification in the control unit, or its increase.
Along with program-controlled compensation for the temperature drift of the moisture sensor signals, measuring the temperature and taking it into account in the signal evaluation is also advantageous.
REFERENCES:
patent: 5453670 (1995-09-01), Schaefer
patent: 5508585 (1996-04-01), Schaefer
patent: 5568027 (1996-10-01), Teder
patent: 5694012 (1997-12-01), Pientka et al.
patent: 5969493 (1999-10-01), Pientka et al.
patent: 41 41 348 A1 (1993-06-01), None
Blitzke Henry
Buehren Harald
Kroeninger Mario
Michenfelder Gebhard
Ip Paul
Robert & Bosch GmbH
Striker Michael J.
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