Electricity: motive power systems – Periodic – repetitious or successive operations control of... – Variable periods or intervals between controlling operations
Patent
1996-08-01
1997-12-02
Ro, Bentsu
Electricity: motive power systems
Periodic, repetitious or successive operations control of...
Variable periods or intervals between controlling operations
318483, B60S 108
Patent
active
056940122
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention concerns a device for operating a windshield wiper in intermittent and continuous modes, and more particularly to a windshield wiper of the type with at least one sensor that emits signals depending on the moisture coating or amount of rain on the windshield to be cleaned, and with an electronic control for controlling the windshield wiper operation in dependence on the sensor signals.
During constantly changing rain density, for example, it is bothersome and complicated for the driver of a motor vehicle to actuate time and again a changeover device, in order to adapt the windshield wiper operation to the actual rain density. An automatic changeover device was therefore proposed in DE 40 18 903 C2 already, for which the interval between sequential wiping operations is influenced in dependance on the number of signals emitted by the sensor, for example relative to the signals that occur within a given time segment. Above a certain number of signals, the windshield wiper is switched to the continuous mode.
Thus, no direct changeover between intermittent and continuous mode takes place, but an indirect changeover via the control of the interval between the various wiping operations. This leads to a relatively involved control and a relatively inexact changeover between intermittent and continuous mode. Another problem is that no calculated "interval time" exists in the continuous mode, which can be used as criterium for the transition between continuous/intermittent mode.
SUMMARY OF THE INVENTION
The device according to the invention, with the essential characteristics, has the advantage of recording the rain density very accurately and that a simple and precise evaluating device as well as a changeover device between intermittent and continuous mode can be realized.
In accordance with the invention, this advantage can be attained by providing a windshield wiper which is characterized in that it has an evaluation mechanism, which records the number of sensor signals per wiping interval as a control signal, and a changeover device that switches between intermittent and continuous modes depending on whether at least one threshold valve is exceeded or not reached by the control signal or a signal that is derived from control signals.
It is preferable if the wiping intervals provided for the generating of control signals are wiping cycles, so that on the one hand, the rain density is recorded over a relatively long period of time and, on the other, the synchronizing signals for such wiping cycles already exist in the form of control signals for the motor control.
It is advantageous if water-induced signal breaks of the sensor output signal are used as sensor signals for further evaluation. Such signal breaks can develop as a result of rain drops hitting, of the wet wiper blade gliding across the sensor surface, or rapidly changing surface textures, e.g. very heavy streaking.
The individual signal breaks are no longer as distinctive at higher rain density, but the sensor output signal is essentially weakened continuously because of the high number of these breaks. Thus, in order to form the control signal during higher rain density, means for recording the sensor output signal decline are provided, which divide especially the declining sensor output signal into small time intervals, wherein the respective signal decline during one such small time interval is rated as at least one signal break.
Appropriately, a counting device for recording the sensor signal per evaluation interval is provided.
The number of signal breaks per wiping cycle may fluctuate considerably. In order to prevent a constant changeover between continuous and intermittent mode, the evaluating device has a mechanism for taking the mean of a fixed number of successive control signals, wherein the mean values form the actual control signals. It makes sense to take the mean after each wiping cycle, e.g. a mean is taken for the preceding five wiping cycles.
However, so that the evaluating device does no
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patent: 4916374 (1990-04-01), Schierbeek et al.
patent: 5059877 (1991-10-01), Teder
Blitzke Henry
Pientka Rainer
Ro Bentsu
Robert & Bosch GmbH
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