WINDSHIELD WIPER SYSTEM HAVING REDUCED WIPE SPEED AT REVERSAL POINTS USING VARIABLE FREQUENCY INDUCTION MOTOR CONTROL

摘要

A windshield wiper system (10) having variable frequency induction motor control for reducing wipe speed at reversal points includes an induction motor (12), a wiper and blade assembly (14) operatively connected to the motor (12), a sensing means (22) for detecting when the position of the wiper and blade assembly (14) is within a preselected range of one of the reversal points, and a motor control (18) responsive to the control signal (S2) generated by the sensing means for causing the motor (12) to reduce wipe speed during the preselected range prior to the reversal point to reduce pattern growth, noise, and water expulsion. The sensing means (22) takes the form of a cam or plate operated switch driven by the induction motor. The control signal (S2) derived from the cam operated switch is provided as an input to a voltage controlled oscillator (18), whose variable frequency output is used to vary the frequency of the excitation voltage applied to the windings of the three phase induction motor (12).