Motorized reduction gear unit, in particular for driving a screen wiper in a motor vehicle

摘要

A motor vehicle screen wiper drive unit is a motorized reduction gear unit comprising a reduction gear train between a driving shaft, driven by a motor, and a driven shaft. The gear train comprises at least one worm fixed to the driving shaft and meshing with a first set of teeth of an intermediate gear wheel. The latter also has a second set of teeth meshing with a driven gear wheel which is carried by the driven shaft. The second teeth of the intermediate gear wheel, and the teeth of the driven wheel, are generally helical, being so oriented that the driven wheel exerts an axial force urging the intermediate gear wheel in a direction opposite to that in which the worm is urged by an axial force exerted on the intermediate wheel by the worm. The need for rigid abutment means for the intermediate wheel is thereby avoided.