Patent ID: 7152704

Claim:
A four-wheel drive work vehicle comprising: an engine; a pair of right and left steerable wheels rotatably driven by receiving power from the engine via a differential mechanism; a pair of right and left non-steerable wheels rotatably driven by receiving power from the engine via right and left side clutches; a displacement converter mechanism for converting a steered displacement of the steerable wheels into a different mode of displacement; and a clutch operating member for operating one of the side clutches based on said different mode displacement converted by the displacement converter mechanism; wherein said displacement converter mechanism comprises a pivotal cam mechanism including a cam member which is displaced based on said steered displacement and a cam follower member operably associated with said cam member; and for a vehicle turn, said clutch operating member is displaced via said pivotal cam mechanism by a predetermined amount in response to a steering operation of the steerable wheels by an angle exceeding a predetermined angle from a straight traveling condition and wherein, in association with said displacement of the clutch operating member by said predetermined amount, said one side clutch for one of the non-steerable wheels located on the inner side of said vehicle turn is automatically disengaged against an engaging urging force, wherein the cam follower has an operative cam face portion for contacting the cam member to move the cam follower in order to disengage said one side clutch and a stable cam face portion for maintaining the side clutch at a predetermined clutch disengaging condition during a further steering operation of the steerable wheels after the clutch disengagement.