Electricity: motive power systems – Periodic – repetitious or successive operations control of...
Patent
1992-09-25
1994-03-01
Ro, Bentsu
Electricity: motive power systems
Periodic, repetitious or successive operations control of...
318268, 318432, 318DIG2, 388819, B60S 108
Patent
active
052911098
DESCRIPTION:
BRIEF SUMMARY
STATE OF THE ART
The invention is based on a windshield wiper system of the type including at least one electrical drive motor that makes available a driving moment for at least one windshield wiper performing a back and forth movement on a pane to be cleaned. A windshield wiper driven by an electric motor and performing a back and forth movement on a pane to be cleaned has a varying requirement for torque during a wiping cycle, for example, with this requirement being a function of the state of the pane to be cleaned and of the position of the windshield wiper. A great change in the torque requirement occurs in the reversal positions of the windshield wiper since there the required driving moment temporarily takes on the value of zero. The different torque requirement during a wiping cycle leads to differences in load on the drive motor which influence the noise development of the motor. The short-term absence of driving torque in the reversal positions, particularly in the increasingly employed small, high speed electric motors, leads to a temporary increase in the rate of rotation which is considered to be particularly annoying.
It is the object of the invention to reduce the noise development of such windshield wiper systems.
SUMMARY OF THE INVENTION
The above object is generally achieved according to the present invention by a windshield wiper system including at least one electrical drive motor that makes available a driving moment for at least one windshield wiper performing a back and forth movement on a pane to be cleaned, and a signal processing arrangement which, via an electrical switching stage, controls the rotation rate of the motor to a constant value, with the switching stage determining the operating voltage (U.sub.+) of the motor as a function of the current (I.sub.M) flowing through the motor.
ADVANTAGES OF THE INVENTION
Regulation of the rotation rate as well as the control of the rotation rate of the electric windshield wiper drive motor according to the invention reduce the noise development of the drive. The difference between control and regulation of the rotation rate lies in that regulation includes means for detecting the rate of rotation of the motor so as to put out a signal to a signal processing arrangement. A control is able to operate without this report of the rate of rotation and can therefore be realized more economically. The regulation of the rate of rotation of the motor permits the input of a desired rotation rate value while the control keeps the rate of rotation essentially constant, with the precise value of the rate of rotation being of subordinate significance. Significant for the invention is the avoidance of greater changes in the rate of rotation during wiping operation.
Keeping the rate of rotation of the drive motor constant reduces, particularly in the reversal positions of the windshield wiper, the noise from the drive. A change in the noise, to which the human ear reacts with particular sensitivity, is substantially avoided.
Another advantage of regulation or control of the rate of rotation of the electric drive motor results from the possibility of providing different wiping speeds which are set electronically with the aid of the signal processing arrangement. The action on the motor practiced in the past, for example, the use of a collector direct current motor having three instead of two brushes, is no longer required. The omission of the third brush further reduces noise development and increases the efficiency of the drive. The electronic control reduces the costs for interference suppression for the electric motor which might have to be implemented.
Advantageous modifications and improvements of the basic system according to the inventor are disclosed.
A first advantageous modification provides for the derivation of a value that is proportional to the rate of rotation of the electric motor from the electromotor countervoltage of the motor. This voltage can be measured at a motor that is operated as a generator. Generator operation during wi
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Ro Bentsu
Robert & Bosch GmbH
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