Patent ID: 7311633
Filing Date: 2007-12-25
Classification: B60K,F16H

Abstract:
1. A vehicular four-wheel drive unit comprising a central differential mechanism and an axle-differential mechanism in a housing, said central differential mechanism dividing and transmitting a rotational driving force of a drive source to a front-wheel side and to a rear-wheel side, and said axle-differential mechanism further dividing and transmitting said rotational driving force that has been divided by said central differential mechanism to a right wheel and to a left wheel of one of said front-wheel side and said rear-wheel side; wherein: said central differential mechanism comprises a single pinion type first planetary gear train that includes an input gear member, which receives said rotational driving force of said drive source and is thereby driven rotationally, a first carrier member, which is provided in a one-piece body with said input gear member, a first sun gear member, a first ring gear member and an output gear member, which is provided in a one-piece body with and around said first ring gear member and which transmits said rotational driving force to another of said front-wheel side and said rear-wheel side; said axle-differential mechanism comprises a double pinion type second planetary gear train that includes a second ring gear member, which is provided in a one-piece body with said first sun gear member, a second sun gear member, which is connected to one of said right and left wheels, and a second carrier member, which is connected to another of said right and left wheels; a cylindrical retaining member is connected fittingly to said first carrier member, which is provided in a one-piece body with said input gear member, together constituting an input rotating member, in which said second planetary gear train is disposed; said first ring gear member and said output gear member constitute a cylindrical output rotating member in a one-piece body, which is disposed radially surrounding said retaining member; a differential limiter is provided between an inner circumferential surface of said input gear member and an outer circumferential surface of said output rotating member; and said differential limiter generates a rotational resistance, which acts to reduce a rotational difference between said input rotating member and said output rotating member.