Central transmission device for a four-wheel steering system

A central transmission device of a four-wheel steering system, comprising:

• a housing having front and rear walls;
• 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 a front wheel turning mechanism, and an input rotary disc disposed at a rear end of said input shaft within said housing, said input rotary disc having a rear end face formed with a first slide groove extending diametrically;
• 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 a rear wheel turning mechanism, and an output rotary disc disposed at a front end of said output shaft within said housing and having a front end face formed with a second slide groove extending diametrically;
• and
• a transmission unit disposed between said input and output rotary discs, and including a hollow adjustment block that is disposed movably within said housing to move leftwards or rightwards, and a transmission member that has a moving body movable within and relative to said hollow adjustment block, and two slide pieces projecting oppositely from said moving body and inserted respectively into said first and second slide grooves, each of said slide pieces being slidable along a respective one of said first and second slide grooves,
• wherein, when said hollow adjustment block is moved and adjusted in position within said housing, each of said slide pieces can be set at a predetermined position within the respective one of said first and second slide grooves to vary a relationship between turning angles of said input and output shafts,
• wherein said hollow adjustment block has front and rear sides respectively facing said input and output rotary discs, and a receiving space that opens at said front and rear sides, said moving body being movable in said receiving space, said slide pieces being in line with each other and parallel to said input and output shafts, and
• wherein said receiving space extends curvedly in a top-bottom direction, said moving body being formed as a cylindrical rod extending through said receiving space, said moving body moving upward and downward along said receiving space, two opposite ends of said cylindrical rod being formed as said slide pieces, respectively.