Electricity: motive power systems – Periodic – repetitious or successive operations control of... – Variable periods or intervals between controlling operations
Patent
1997-01-09
1999-04-06
Ip, Paul
Electricity: motive power systems
Periodic, repetitious or successive operations control of...
Variable periods or intervals between controlling operations
318443, 318282, 318283, 318DIG2, 1525017, 1525013, H02P 300, B60S 108
Patent
active
058923438
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is based on a windshield wiping arrangement, and more particularly to a windshield wiping arrangement that includes at least one wiper arm which is operated between stop positions by an electromotor with reversible rotational direction, having a time determination device which determines a time following the triggering of a wiping operation, a time presetting device for presetting a maximum allowable time, and a comparator which compares the maximum preset time with the determined time and which triggers a wiping operation in the opposite direction if a maximum allowable time is exceeded of the generic type. From DE-OS 40 32 922, an arrangement for wiping a windshield is known, for which the positions of the wiper arms in dependence on the predetermined desired positions are respectively controlled with a regulator. An overload or a blocking of a wiper arm is detected if a predetermined limit for a regulated condition is exceeded. Once an overload condition is detected, varied measures can be provided with the goal of maintaining a limited wiping operation. Such an overload condition can occur, for example, as a result of a snow load. The known device includes a position measuring device for each wiper arm. A limited wiping operation can be determined through wiping experiments, wherein the positions for the wiping limits are known from the position measuring devices.
SUMMARY OF THE INVENTION
It is the object of the invention to provide a windshield wiping arrangement, which permits a limited wiping operation with simple means in the case of a location-dependent overload.
The object is achieved, in a windshield wiping arrangement of the generic type identified above, by providing that the time determination device determines the time until one of the stop positions is reached and that the maximum allowable time is fixed in dependence on the determined time.
The windshield wiping arrangement according to the invention is tailored to a wiping mechanisms powered by an electromotor, for which the rotational direction can be reversed. The windshield wiping arrangement according to the invention has the advantage that no expensive instruments are needed to measure the wiper position if a limited wiping operation is performed as a result of a locality-dependent overload. In accordance with the invention, a time-determination unit is provided, which determines the time following the triggering of a wiping operation. Furthermore, a time setting unit exists, which presets a maximum allowable time for half a wiping cycle from stop position to stop position. A comparator, which compares the maximum allowable time with the determined time, triggers a wiping operation in the direction opposite to the preceding wiping operation if a time overrun has been detected. These measures permit a limited wiping operation during an overload, caused for example by snow, wherein an electromotor driving the wiper is always reversed following completion of the preset maximum time interval. The stop positions no longer have to be reached. If the overload condition is eliminated, a return to the normal wiping operation from stop position to stop position is ensured without requiring further measures.
One particularly advantageous embodiment provides that following a reversal triggered by the comparator, the time determination unit determines the time until the wiper has again reached a stop position, insofar as it can reach the stop position. The determined time is advantageously used for fixing the new maximum allowable time for the following wiping operation. The reduction of the maximum allowable time shortens the waiting time until the reversal of the wiper at the blocking position.
One advantageous improvement provides for the presetting of additional time segments whenever an incomplete wiping cycle without reaching a stop position has occurred. This measure takes into account those cases where either a previously occurring blocking has completely disappeared or where both stop positio
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Koch Stefan
Mack Rolf
Ip Paul
Robert & Bosch GmbH
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