Patent ID: 8100422

Claim:
A central transmission device of a four-wheel steering system, which is connected between a front wheel turning mechanism and a rear wheel turning mechanism for moving the rear wheel turning mechanism in response to turning movements of the front wheel turning mechanism, the central transmission device comprising: a housing adapted to be disposed between said front and rear turning mechanisms and having front and rear walls; a turning output unit including an output shaft that extends rotatably through said rear wall and that has a rear end adapted for connection with the rear wheel turning mechanism, and a rotary disc that is coaxial and integral with a front end of said output shaft within said housing, said rotary disc including a radially extending slide groove that has an inner end proximate to a center of said rotary disc and an outer end proximate to a circumference of said rotary disc; and a turning input unit including an input shaft that extends rotatably through said front wall and that has a front end adapted for connection with the front wheel turning mechanism, and a cam protrusion that is disposed eccentrically at a rear end of said input shaft within said housing, said input shaft having an axis of rotation parallel to and offset from that of said output shaft, said cam protrusion extending slidably into said slide groove to turn said rotary disc within a limited angle; wherein, when said input shaft is not rotated by the front wheel turning mechanism, said cam protrusion is located at said inner end of said slide groove; and wherein, when said turning input unit is rotated by the front wheel turning mechanism, said cam protrusion slides to an intermediate position between said inner and outer ends of said slide groove to rotate said rotary disc in a direction opposite to that of said input shaft, and then to said outer end of said slide groove to rotate said rotary disc in the same direction as said input shaft, and thereafter moves back to said intermediate position to rotate said rotary disc in the same direction.