Starter having planetary gear reduction device

Abstract

To reduce the size of a starter for installing it in a smaller engine compartment, the rotational speed of the starter motor has to be high and it is reduced to a certain speed through a reduction device to obtain a higher torque. To realize a high reduction ratio in a small planetary gear reduction device, an impact force imposed on the device at an instant a starter pinion engages with a engine ring gear and repeating impacts during a cranking period must be reduced. As a coupling between an internal gear and a housing of the reduction device, a flexible or a resilient coupling is disclosed herein. The flexible or resilient coupling relieves an excessive impact force at the engagement by permitting rotation of the internal gear relative to the housing, and reduces noise caused by the cranking impacts by permitting a small vibrating move of the internal gear. The flexible coupling is realized by a combination of a bumpy surface and projections coupled thereto. The resilient coupling is realized by pushing a spring against the bumpy surface.