Steering control apparatus

A vehicle steering apparatus for automatic steering control to steerable wheels of a vehicle, said apparatus comprising:

• a rack disposed for lateral movement with respect to the vehicle, said rack including a housing;
• steering input means linked to said rack for providing lateral movement to said rack;
• a lateral shaft disposed for lateral movement with respect to said rack, said shaft including a piston disposed thereon and within said housing, said piston dividing said housing into first and second fluid chambers, said shaft having opposite ends linked to the steerable wheels of the vehicle;
• fluid pressure source means in communication with said fluid chambers for providing fluid pressure to said fluid chambers, lateral movement of said rack being transferred to said shaft through the fluid pressure in said fluid chambers;
• automatic steering control means for detecting an actual steering position of the vehicle and determining a desired steering position, said automatic steering control means comparing the actual steering position and the desired steering position to control communication between said fluid pressure source means and said fluid chambers to pressurize one fluid chamber with respect to the other fluid chamber and thereby cause said piston to move within said housing and further causing said shaft to move relative to said rack;
• and
• restraining means for restraining movement of at least one of said steering input means and said rack in relation to the vehicle when said automatic steering control means controls the communication between said fluid pressure source means and said fluid chambers.