Electricity: motive power systems – Automatic and/or with time-delay means – Moisture content or wetness
Patent
1996-04-04
1998-03-17
Wysocki, Jonathan
Electricity: motive power systems
Automatic and/or with time-delay means
Moisture content or wetness
318DIG2, 318443, 15DIG15, 307 101, H02P 700
Patent
active
057291055
DESCRIPTION:
BRIEF SUMMARY
SPECIFICATION
The invention relates to a device according to the Preamble of Patent claim 1.
In order to maintain good visibility of the driving lane while driving in rain it has been customary for a long time to provide windshield wipers which, at least for a given length of time, clear the windshield. These windshield wipers are activated through a manually actuatable windshield wiper switch or lever, where some times three switch positions are provided: one for slow wiping, one for fast wiping and one for intermittent wiping. In addition, a wipe-wash switching mechanism can be provided, upon the actuation of which water is sprayed from a container onto the windshield in order to clean it.
Since, in particular under rapidly changing weather conditions, the manual actuation of the windshield wiper is tiresome, windshield wiper controls have previously been suggested which comprise a sensor which detects the moisture on the windshield and automatically drives the windshield wiper as a function of the moisture.
In the simplest form of the automatic windshield wiper only the occurrence of moisture on the windshield is detected and, subsequently, the windshield wiper actuated. However, this has the disadvantage that in the presence of extremely low moisture which is not perceptible to the driver, the windshield wiper is already activated. In order to remedy this disadvantage, it is possible to define a moisture threshold value and the windshield wiper is only activated when this value is exceeded.
Such windshield wiper control, however, has the disadvantage that the wiping is continued even after it has stopped raining because under these conditions the set threshold value can still be exceeded. Consequently, the windshield wiper would be switched off too late and would continue wiping a dry windshield.
In order to be able to differentiate between rain proper and mere water streaks, it has already been suggested to provide, in addition to said threshold value switch, an arrangement which detects whether or not the moisture increases or decreases (DE-A-37 22 510). Only when both conditions are present--the given moisture threshold is exceeded and the moisture increases--is the windshield wiper activated. Of disadvantage in this arrangement is that it already triggers the windshield wiper motor following extremely small moisture increases on the windshield.
So that the windshield wiper is not actuated after every insignificant moisture increase, it has been suggested to carry out the triggering if the magnitude of the moisture increase exceeds a given value (WO 90/08680).
In another known arrangement a sensor is used which differentiates the water drops impinging on the windshield according to their size (EP-A-0 549 010). This sensor comprises two electrodes between which gaps are disposed which change with respect to size. Hereby large gaps are only bridged by large drops.
Furthermore is known an optical rain sensor for a windshield wiper control which comprises several light transmitters and receivers and the light signals received by a light receiver are compared with a reference level. If the reference level is exceeded, the sensor outputs a signal. On the basis of the count of rises above the level conclusions are drawn about the conditions on the outside of the windshield (U.S. Pat. No. 4,867,561). Of disadvantage is here that approximately 15 light transmitters and receivers must be used.
In the not previously published German Patent Application (unexamined) 42 17 391, furthermore, a device for the automatic control of a windshield wiper motor is suggested, which is equipped with a moisture sensor which outputs a signal as a function of the moisture (DE-A-4 217 391). This device also comprises an evaluation device which evaluates the signal of the moisture sensor with the sensor output signal varying over time. Moreover, a circuit configuration is provided which is provided with a switch-on threshold dependent on the sensor signal.
Lastly, an automatic control of motor vehicle windshield wiper systems i
REFERENCES:
patent: 4495452 (1985-01-01), Boegh-Paterson
patent: 4867561 (1989-09-01), Fuji et al.
patent: 4916374 (1990-04-01), Schierbeek et al.
patent: 5057754 (1991-10-01), Bell
patent: 5059877 (1991-10-01), Teder
patent: 5216341 (1993-06-01), Nomura et al.
patent: 5319293 (1994-06-01), Levers
patent: 5508595 (1996-04-01), Schaefer
patent: 5568027 (1996-10-01), Teder
patent: 5600254 (1997-02-01), Berberich
Etablissement Voralp
Wysocki Jonathan
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