US 5,857,380 AGranted

Starter having planetary gear reduction device

AssigneeDenso Corporation

InventorsSadayoshi Kajino, Tsutomu Shiga, Keiichi Matsushima, Akifumi Hosoya, Masanori Ohmi

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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.

Claims26

Dependent claims

A starter comprising:

a housing;
a motor for generating a rotational torque to start an engine;
and
a planetary gear reduction device connected to the motor and disposed in the housing, which comprises a sun gear driven by the motor, a plurality of planetary gears engaging with the sun gear to be driven thereby, an internal gear disposed in the housing and engaged with the planetary gears, a drive shaft, connected to the planetary gears to be driven by an orbital rotation thereof around the sun gear, having a pinion operably connected thereto for rotating a ring gear of the engine, and coupling means connecting the internal gear to the housing, wherein:
a gear Module of the planetary gear reduction device is less than 1.0;
and
a reduction ratio of the planetary gear reduction device is higher than 6.0, and wherein:
under a condition where a rotational torque imposed on the internal gear is smaller than a predetermined value, the coupling means fixedly connects the internal gear to the housing;
under a condition where a rotational torque imposed on the internal gear is larger than the predetermined value, the coupling means loosens a connection between the internal gear and the housing for permitting a rotation of the internal gear relative to the housing, thereby relieving an excessive impact imposed on the reduction device at an instant the pinion engages with the ring gear of the engine;
and
under a condition where a varying rotational torque is imposed on the internal gear, the coupling means permits the internal gear to rotate back and forth relative to the housing within a small angle, thereby absorbing an impact force imposed on the reduction device and reducing a noise during a cranking period of the engine.

8 more elements

A starter comprising:

a housing;
a motor for generating a rotational torque to start an engine;
and
a planetary gear reduction device coupled to the motor and disposed within the housing, the planetary gear reduction device comprising:
a sun gear driven by the motor;
a plurality of planetary gears engaged with the sun gear to be driven thereby;
an internal gear disposed within the housing and engaged with the planetary gears;
a drive shaft coupled to the planetary gears to be driven by an orbital rotation of the planetary gears around the sun gear;
a pinion operably connected to the drive shaft for rotating a ring gear of the engine;
and
coupling structure connecting the internal gear to the housing,
wherein, a gear Module of the planetary gear reduction device is less than 1.0 and a reduction ratio of the planetary gear reduction device is higher than 6.0, and
wherein the coupling structure is constructed and arranged to (1) fixedly connect the internal gear to the housing to prevent relative rotation therebetween when a rotational torque imposed on the internal gear by the plurality of planetary gears is smaller than a predetermined value, (2) to permit rotation of the internal gear relative to the housing when the rotational torque imposed on the internal gear by the plurality of planetary gears is larger than the predetermined value, thereby relieving excessive impact imposed on the reduction device at an instant the pinion engages with the ring gear of the engine, and (3) permit the internal gear to rotate back and forth relative to the housing when a varying rotational torque is imposed on the internal gear by the plurality of planetary gears, thereby absorbing an impact imposed on the reduction device and reducing noise during a cranking period of the engine.

10 more elements

Dependencies are inferred from the claim text.