Patent ID: 6848536

Claim:
A rack assist type electric power steering system, comprising: a rack bar which includes a screw hole for connecting an inner ball joint at left and right ends in an end surface and a ball screw provided in an intermediate portion, a rack gear provided on one side of the same, and a straight line section provided on the other side of the same, said straight line section having a first diameter, said intermediate portion having a second diameter, said first diameter being smaller than said second diameter; an input shaft which is engaged with a pinion of a lower portion in a rack gear portion of the rack bar; a first rack housing which is formed in such a manner that a rack gear portion of the rack bar and the input shaft are concurrently surrounded and which has a support yoke for supporting a rear portion of the rack gear; a torque sensor which surrounds an upper surrounding portion of the input shaft and is fixed to an upper portion of the first rack housing; a second rack housing which surrounds the straight line section of the rack bar and contacts by a bush inserted into an inner diameter portion of the same; and a motor assembly which includes: a cylindrical motor housing which connects both end portions to the first rack housing and the second rack housing, respectively, between the first rack housing and the second rack housing; a stator which is fixed to an inner diameter portion of the motor housing; a hollow motor shaft which is inserted into a surrounding portion of the ball screw of the rack bar in the interior of the motor housing; a rotor which includes a plurality of magnets attached along an outer surrounding surface of the motor shaft; a ball nut which is fixed to an inner diameter of the motor shaft and includes a plurality of balls, said motor shaft including an expanded portion at one end for fixing the ball nut on the inner diameter of the motor shaft; and a motor assembly which includes a plurality of bearings interposed between the motor shaft and the motor housing; and a connector which includes a through hole in one side of the motor housing and extends a power coil of the stator through the through hole and connects the same.