Electricity: motive power systems – Automatic and/or with time-delay means
Reexamination Certificate
2000-03-28
2001-10-16
Nappi, Robert E. (Department: 2837)
Electricity: motive power systems
Automatic and/or with time-delay means
C318SDIG002, C015S250120
Reexamination Certificate
active
06304047
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a motor control apparatus for a wiper motor. The motor control apparatus includes a switch mechanism for carrying out switching operation in cooperation with an output shaft of the motor.
2. Description of the Related Art
In a wiper control apparatus for a vehicle, when a driver turns off a operator switch, wiper blades move to a predetermined position wherever a position of the wiper blades are at that time because of an automatic stopping mechanism.
A wiper apparatus is usually constituted of a direct current motor and a speed reduction mechanism having an output shaft, a motor control apparatus having an operator switch for operating the motor and a link mechanism for converting rotational motion of the output shaft of the motor into swinging motion of wiper arms.
However, when the wiper apparatus is operated at a low speed or a high speed, an electromagnetic noise is generated from the motor control apparatus. For example, such noise includes a frequency range of 20 through 200 MHz, which may bring trouble on a radio set, a TV set or other electronic devices.
SUMMARY OF THE INVENTION
A main object of the present invention is to provide a motor control apparatus capable of restraining electromagnetic wave generated by a switch mechanism for controlling a motor when the motor is continuously operated.
It has been recognized that there are produced contact potential differences between a power feeding side and a rotary electrode and between the rotary electrode and a fixed terminal of the rotary switch. As switching operation is repeated, accumulation and discharge of electric charge are repeatedly carried out therebetween.
Therefore, another object of the present invention is to reduce or eliminate the electric potential difference in the rotary switch.
According to an aspect of the invention, the rotary switch is not applied with voltage of the battery while the motor is continuously operated, but is brought into the ground potential. Accordingly, the contact potential differences between the power-side terminal and the rotary electrode and between the rotary electrode and the switch-side terminal are restrained. Further, electric charge accumulated in the power-side terminal, the rotary electrode and switch-side terminal is reduced.
If the power-side terminal is connected to the battery or to the ground line, the battery voltage is prevented from being applied to the rotary switch when the motor is continuously operated. This can be attained by a switching relay.
The power-side terminal is connected by the switching relay to the ground line when the operator switch is shifted to a low speed wiping position or a high speed wiping position. While the motor is continuously operated, the power-side terminal, the rotary electrode and the switch-side terminal are brought into the ground potential and accordingly, the contact potential differences are eliminated, and electric charge is not accumulated.
According to another aspect of the invention, when the operator switch is shifted to the low speed position or the high speed position, the power-side terminal is connected to the low potential point formed by a voltage dividing circuit.
According to another aspect of the invention, the battery is connected to the ground line via a resistor even if the switching relay is short-circuited. Therefore, short-circuit of the battery can be prevented.
According to further aspect of the invention, a movable piece of the switching relay is fixed while it is operated. When the operator switch is brought into the OFF position, the battery is connected to the power-side terminal. Therefore, even if the switching relay fails in the operational state, the respective terminals and the rotary electrode of the rotary switch are connected to the low potential point.
According to another aspect of the present invention, a number of parts is not increased.
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Nakata Masahi
Uchida Yasuaki
Asmo Co. Ltd.
Duda Rina I.
Law Offices of David G. Posz
Nappi Robert E.
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