Electricity: motive power systems – Automatic and/or with time-delay means – Moisture content or wetness
Patent
1997-01-16
1998-08-04
Ip, Paul
Electricity: motive power systems
Automatic and/or with time-delay means
Moisture content or wetness
318443, 318483, 318DIG2, 15250C, B60S 108, H02P 104
Patent
active
057898898
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to an arrangement for operating a windshield wiper, having a sensor device for detecting the degree of moisture on a windshield with an evaluation device receiving the sensor signal, which evaluation device is provided with a signal processing device, a triggering stage for the wiping operation and a control signal generating device, and having an actuation unit for the windshield wiper which can be actuated by the evaluation device to produce a wiping action.
An arrangement of this type has been revealed as being known in EP 360 832 B1. Here, a suitable wiping operation is triggered automatically if certain triggering criteria are recognized in the sensor signal. Fast-drying water streaks on the windshield stemming, for example, from damaged wiper blades and for which a wiping operation is inappropriate are not recognized reliably, if at all, which may result in undesired wiping actions.
SUMMARY OF THE INVENTION
It is the object of the invention to modify an arrangement of the type mentioned at the outset in such a way that unnecessary wiping actions are reliably prevented.
This object is solved an arrangement of the generic type by the features listed in patent claim 1.
In order to attain this object, the evaluation device is provided with a recognition stage for drying moisture that is present on the windshield; by means of the recognition stage a level of the measured values that is rising as a result of the drying process can be determined from a time sequence of measured values derived from the sensor signal.
By way of these measures, a phase of drying moisture on the windshield, as it occurs, for example, when streaks are formed due to worn-out windshield wipers, is recognized reliably so that during this phase a wiping action can be suppressed by the evaluation device. Unnecessary dry wiping is therewith prevented since such moisture residues usually quickly dry by themselves.
A simple, reliably functioning embodiment of the arrangement is comprised in that the recognition stage has a difference generator for detecting the difference between the actual measured value and a preceding measured value as well as an adding stage for generating the sums of the successive, signed differences and in that the drying moisture can be recognized by determining whether the sum exceeds a preset threshold.
Here, a simple design is such that the summing stage is formed by way of a summation register having an upper and a lower limit value which are not exceeded or undershot in the addition, such that the threshold lies within the limit values, and such that the sum is set to be in the proximity of the threshold as starting value when the arrangement is started.
If the threshold has a hysteresis, interferences which can cause fluctuations around the threshold range are suppressed reliably.
If it is provided that the triggering stage has a differential trigger which can be switched so as to be inactive when a phase of drying moisture is recognized, a wiping operation during such a phase is reliably prevented, even though the triggering threshold is exceeded during the differential operation, that is, when the difference of the signal level compared to a predetermined reference value exceeds a preset magnitude.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is described below in greater detail by way of an embodiment with reference to the drawings. These show:
FIG. 1 is a schematic block illustration of an arrangement for the automatic operation of a windshield wiper,
FIG. 2 is a graph showing the course of a sensor signal plotted over time during a drying phase, and
FIG. 3 is a schematic block illustration showing the composition of an evaluation device of shown in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 shows an arrangement for the automatic operation of a windshield wiper having a sensor device 10 which emits a sensor signal S to an evaluation device 20. The sensor signal S may already be processed and can be processed further in the evalu
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Blitzke Henry
Buerkle Joerg
Pientka Rainer
Ip Paul
Robert & Bosch GmbH
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