PURPOSE: To simplify the reduction gear mechanism and to improve the performance, reduce the transmission loss and tone capacity of a motor, and smoothly move a rack shaft with a slight force.
CONSTITUTION: A rotary external rotary shaft 21 which is rotated by a motor 12 is installed within a housing 1 to support a rack shaft 2. A cylindrical internal rotary shaft 21 is arranged inside the external rotary shaft 13. The rack shaft 2 is passed inside the internal rotary shaft 21. The respective rotary shafts 13, 21 are connected to each other through a spline 27 though these rotary shafts can be moved in the axial direction. The internal rotary shaft 21 is connected to the housing 1 through a first ball screw 28. The rack shaft 2 is connected to the internal rotary shaft 21 through a second ball screw 32. The internal rotary shaft 21 consists of a first component member 22 to be connected to the external rotary shaft 13 through the spline 27, and a second component member 23 to be connected to the housing 1 through the first ball screw 28 and at the same time, to the rack shaft 2 through the second ball screw 32. The respective component members are connected to each other through a flexible shaft coupling means.
MATSUSHITA SHIGEHISA
TOKUMOTO YOSHITOMO
