Electricity: motive power systems – Periodic – repetitious or successive operations control of... – Variable periods or intervals between controlling operations
Patent
1997-06-11
1998-12-01
Ro, Bentsu
Electricity: motive power systems
Periodic, repetitious or successive operations control of...
Variable periods or intervals between controlling operations
318483, 318DIG2, B60S 108
Patent
active
058443894
DESCRIPTION:
BRIEF SUMMARY
This application was filed under the Patent Cooperation Treaty on Apr. 17, 1996, and assigned Ser. No. PCT/DE96/00673.
BACKGROUND OF THE INVENTION
The invention relates to an apparatus for operating a windshield wiper, having a sensor device for detecting the state of wetness of a windshield, an evaluating device that receives the sensor signal, and in which an adjusting device is provided for generating a reference value, and an actuator unit for the windshield wiper that is actuated by the evaluating device for initiating a wiping process if the difference between the reference value and a current measured value exceeds a predetermined threshold.
An apparatus of this type is known from DE 33 14 770 A1. In this known apparatus, a reference value is adjusted to the maximum sensor signal value following an initial wiping process, and, if the sensor signal is reduced due to soiling or cloudiness of the windshield that cannot be eliminated by the wiper, the reference value can be followed by the reduced signal amplitude in an order of magnitude of a few minutes. It has been seen, however, that this type of following does not adequately take into account influences that can be attributed to wetness or soiling of the windshield that can be eliminated by the wiper.
Similar difficulties affect the apparatus disclosed in DE 41 12 847 A1, whose objective is to adapt the steady-state level of a sensor signal to a long-time drift, a temperature drift and/or to structural conditions in the region of the sensor device.
SUMMARY OF THE INVENTION
It is the object of the invention to refine an apparatus of the type mentioned at the outset in such a way that events that should trigger a wiping process can be better recognized.
This object is accomplished by an apparatus of the type mentioned at the outset which is characterized in that the wiping process is initiated if a difference between the reference value and the current measured value exceeds a threshold value; in that the time constant of the adjusting stage is on the order of magnitude of one second to a few seconds for following the reference value during the wiping operation; and in that the reference value is followed step-wise with consideration of all current measured values received at intervals of fractions of a second.
Accordingly, it is provided that the adjusting device has at least one adjusting stage, whose time constant is on the order of magnitude of one second to a few seconds, and that the reference value can be followed step-wise, taking into consideration all of the current measured values received at intervals of fractions of a second. Consequently, the reference value, with respect to which the difference from the current measured value is determined for triggering the wiping operation if a predetermined threshold value is exceeded, is followed by the sensor signal, for example with a slow buildup on the windshield due to fine raindrops, such that the type of event that may trigger a wiping operation can be better detected and analyzed than in apparatuses of this type that have been used up to this point, and a wiping operation that is optimally matched to the event can be selected.
The wiping operation is adapted well to the external conditions because the one time constant can be selected to be between one second and six seconds, and the current measured values are received at intervals of a few milliseconds.
For reliable detection of the current measured values of the sensor device, and simple, selectable adjustment of the reference value, for example through corresponding programming, it is possible for the reference value to be updated by one increment in the direction of a reference source value generated in an upstream, first adjusting stage after the time corresponding to a time constant has expired, and for the first time constant of the first adjusting stage to amount to a fraction of the one time constant, and for the reference source value to be altered by one increment in the direction of the then-present, current measured valu
REFERENCES:
patent: 4495452 (1985-01-01), Boegh-Peterson
patent: 4916374 (1990-04-01), Schierbeek et al.
patent: 5568027 (1996-10-01), Teder
Blitzke Henry
Buerkle Joerg
Pientka Rainer
Ro Bentsu
Robert & Bosch GmbH
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