Patent ID: 8037984

Claim:
A four-wheel-drive-vehicle driving force distribution apparatus comprising: an input shaft; a main output shaft; an auxiliary output shaft; an auxiliary transmission mechanism for switching motive power transmitted to said input shaft at least between a high speed and a low speed, and transmitting the motive power to said main output shaft; a friction clutch for selectively transmitting the motive power of said main output shaft to said auxiliary output shaft; a motor having an output shaft with a pinion gear rotatably and coaxially disposed on said output shaft of said motor, and having a shifting cylindrical cam rotatably and coaxially disposed on said output shaft of said motor; a ball cam mechanism for changing a pressing force of said friction clutch in a non-step manner corresponding to rotation of said pinion gear which is rotatably and coaxially disposed on said output shaft of said motor; a shift mechanism for converting rotation of said shifting cylindrical cam which is rotatably and coaxially disposed on said output shaft of said motor into linear shift motion and shifting said auxiliary transmission mechanism; a drive member which is fixed to said output shaft of said motor, and configured to be rotated in one of a first direction and a second direction from a control starting point of a rotational direction by said motor; a clutch control mechanism disposed between said drive member and said pinion gear for changing a clutch pressing force caused by said ball cam mechanism corresponding to rotation of said drive member in the first direction caused by said motor starting from said control starting point; and a shift control mechanism, disposed between said drive member and said shifting cylindrical cam, configured to shift said auxiliary transmission mechanism to a predetermined shift position, wherein shifting of said auxiliary transmission mechanism only occurs when said drive member is rotated from said control starting point in the second direction, after which, said drive member is rotated in the first direction to return to said control starting point, and the shifting is capable of occurring an unlimited number of times without changing the clutch pressing force.