Patent claim: An electric power steering apparatus comprising an electric motor that generates a rotation assist force in accordance with a steering operation of a driver a shaft coupling that has a first end coupled to an output shaft of the electric motor and a speed reduction mechanism coupled to a second end of the shaft coupling to reduce a rotation speed of the output shaft of the electric motor to transmit a reduced rotation speed to a steering mechanism wherein the shaft coupling includes a first yoke having the first end a second yoke having the second end and an intermediate member provided between the first yoke and the second yoke wherein the intermediate member includes a cylindrical intermediate boss portion a plurality of arm portions extending radially from the intermediate boss portion and an engagement space defined by a pair of the adjacent arm portions wherein the intermediate member includes a center portion a first cover portion disposed on an electric motor side with respect to the center portion and a second cover portion disposed on a speed reduction mechanism side with respect to the center portion wherein the center portion includes a center boss portion that configures a part of the intermediate boss portion a center arm portion that configures a part of the arm portion and a center engagement space that configures a part of the engagement space the first cover portion includes a first cover boss portion that configures a part of the intermediate boss portion a first cover arm portion that configures a part of the arm portion and a first cover engagement space that configures a part of the engagement space the second cover portion includes a second cover boss portion that configures a part of the intermediate boss portion a second cover arm portion that configures a part of the arm portion and a second cover engagement space that configures a part of the engagement space andthe center portion is configured to protrude toward an engagement space side with respect to the first cover portion and the second cover portion.

Related passage: As particularly shown in Fig.9 in the same way as the rotation transmitting member 6 the rotation transmitting member 7 which is formed integrally from a polyacetal resin a polyamide resin or the like and is rigid includes an annular base portion 51 disposed concentrically with the base portion 16 four pairs of projecting portions 53 which are provided integrally with the base portion 51 in such a manner as to extend radially from a cylindrical outer peripheral edge 52 of the base portion 51 and are disposed in such a manner as to be spaced apart from each other at equiangularintervals of 45 in the R direction four grooves 55 provided in a cylindrical inner peripheral edge 54 of the base portion 51 in such a manner as to extend in the A direction and to be spaced apart from each other at equiangular intervals of 90 in the R direction and four retaining grooves 57 which are each connected to one end of each groove 55 and are provided at the inner peripheral edge 54 of the base portion 51 and in a surface 56 of the base portion 51 opposing the annular surface 17.The rotation transmitting member 7 is thus constructed identically to the rotation transmitting member 6.