Conventional vehicle windshield wiper systems include wipers that move in an arcuate sweeping motion across the windshield in order to remove unwanted water from the windshield. The typical wipe pattern of a windshield wiper is a semicircular arc. The wiper begins at one end of the arc, travels across the windshield to the opposite end of the arc and reverses direction at that point and returns to the initial position. Such motion necessarily includes an acceleration of the windshield wiper from one end of the arc to the other end. The ends of the arc are commonly referred to as the reversal points of the wiper pattern.
Various shortcomings and drawbacks are associated with conventional windshield wiper systems. For example, the acceleration of the blade to the reversal point followed by an abrupt stop at the reversal point often produces undesirable noise. Further, the acceleration of the wiper up to the reversal point can result in wipe pattern growth or the deformation of a preselected wipe pattern due to wear on the components of the wiper system caused by the acceleration and abrupt stopping of the wiper at the reversal points. Further, at high wiper speeds, the amount of lateral expulsion of water from the vehicle can be increased to an undesirable amount.
These drawbacks are associated with windshield wiper systems that include a tandem symmetrical overlapping windshield wiper pattern or those that have a single extending arm with a single wiper blade.
This invention provides a windshield wiper system that overcomes the shortcomings and drawbacks discussed above. This invention reduces the effects that are typically considered undesirable by slowing the motor speed for a preselected portion of the wipe pattern just prior to the reversal points. This invention preferably includes a variable speed dc motor wherein the motor speed is changed as a function of wiper blade position relative to the reversal points of the wipe pattern.