Electricity: motive power systems – Periodic – repetitious or successive operations control of... – Variable periods or intervals between controlling operations
Patent
1983-08-08
1985-01-22
Witkowski, Stanley J.
Electricity: motive power systems
Periodic, repetitious or successive operations control of...
Variable periods or intervals between controlling operations
318DIG2, 15250C, H02P 104
Patent
active
044954522
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
A windshield wiper control receives information as to the amount of moisture on the windshield through a sensor which is arranged within the area which is swept by the windshield wipers.
In practice it has turned out that merely when driving in definitely rainy weather there is a need for continuous operation of the windshield wipers. In drizzle or humid weather it is often necessary to intervene manually in the wiping frequency in order to avoid that the wipers are operated on a too dry windshield, which may result in a reduced view and unnecessary wear of both the wiper motor and the wiper blade. It is known that by means of a conventional windshield wiper control, fixed intervals between the individual activation of the wipers may be obtained. However, manual intervention is still needed for adaption of the length of the intervals in relation to changing weather conditions.
SUMMARY OF THE INVENTION
The windshield wiper control according to the invention is of a kind which receives information as to the amount of moisture on the windshield through a sensor which is arranged on the windshield within the area which is swept by the windshield wipers. From this the wiper frequency is adjusted in relation to the current conditions so that, depending on the rain intensity, adequate intervals are inserted in the activation of the wipers. The active area of the sensor has to be so large that the signal which is generated is representative of the condition of the windshield in its entity. In practice, it has turned out that approximately 25 cm.sup.2 is sufficient. The sensor may be of the capacitive type and may generate an AC-signal the frequency of which is indicative of the relative humidity of the windshield. It is known to compare the signal which is received from the sensor with a fixed reference and to activate the windshield wipers when exceeding this reference. In practice it is, however, very difficult to make this principle provide a stable activation of the wipers. Partly, it is difficult to obtain sufficient temperature stability of especially the sensor and partly, impurities which do not normally disturb the view may affect the sensor and turn on the wipers unintentionally. In case a sufficient amount of water is not present for washing away these impurities, the view is impaired by wiping. Thus, it may be necessary to clean the windshield manually in order to stop the activation of the windshield wipers.
BRIEF DESCRIPTION OF THE DRAWING
The principle of the invention will be more clearly understood by reference to the description of the preferred embodiment taken in conjunction with the sole drawing in which:
FIG. 1 shows the block diagram of the repeatedly renewed offset windshield wiper control.
THE INVENTION
The windshield wiper control according to the invention is characterized in that the reference store (2) is connected to the output of the sensor (1) so that each time the wiper has just passed the sensor, the sensor signal is written in the store (2) and is used as reference at the next comparison. Thereby it is obtained thta the reference is always an expression for the cleanest windshield possible under the given circumstances. The wipers are not activated until a certain change of the signal from the sensor relative to the reference has been detected. In other words when a certain reduction of the view has taken place in relation to the view obtained at the last passage of the wipers. Therefore, the activation time is automatically adjusted in relation to the working conditions. Impurities which are not immediately removable by means of the wipers will e.g. not disturb the function. Neither will a worn wiper blade which is not capable of completely removing the water disturb, as these new working conditions are merely entered into the reference. If, on the other hand, a fixed reference had been employed, the wipers would be activated constantly in an attempt to remove the condition which influenced the sensor. This new principle implies that the win
REFERENCES:
patent: 3594563 (1971-07-01), Bishop
patent: 3786330 (1974-01-01), Inoue et al.
patent: 3826979 (1974-07-01), Steinmann
patent: 4131834 (1978-12-01), Blaszkowski
patent: 4388574 (1983-06-01), Bois et al.
Ro Bentsu
Witkowski Stanley J.
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