Gear backlash adjusting mechanism

Claim 1

A driving apparatus for use in a windshield wiper of a vehicle, comprising; a wiper motor having a motor shaft; a worm provided on the motor shaft, said worm having a gear tooth on its outer periphery; a worm wheel provided on an output shaft and adapted to be connected to a lever of a windshield wiper, said worm wheel having a gear tooth that engages with the gear tooth of the worm over a virtual contact area, the gear tooth of the worm wheel being curved or tapered radially outwards toward one end of the gear tooth of the worm wheel in an axial direction thereof; a gear casing for accommodating the worm and worm wheel therein and supporting rotatably the motor shaft and the output shaft which is slidably supported so that one end of the output shaft extends outside the gear casing; and an adjusting means including an initially coned disk spring disposed between the gear casing and the worm wheel with the output shaft of the worm wheel extending through an opening of the disk spring for providing a force that urges the worm wheel in a first direction and a stopper means for providing a force in opposition to the force of the disk spring in order to set the position of the worm wheel relative to the worm whereby a distance between the gear tooth of the worm and the gear tooth of the worm wheel can be adjusted.