Patent ID: 8074531
Filing Date: 2011-12-13
Classification: B62D,F16C,F16H,Y10T

Abstract:
1. An electric power steering apparatus, comprising: a transmission mechanism for transmitting power of an electric motor for steering assist to a steering mechanism, the transmission mechanism comprising a drive gear and a driven gear meshed with the drive gear; a bearing for rotatably supporting one end in an axial direction of the drive gear; a housing accommodating the transmission mechanism, the housing having a bearing hole formed therein for supporting the bearing so that the bearing can be biased in a direction in which a center-to-center distance between the drive gear and the driven gear is changed; and a curved plate spring for elastically urging the drive gear through the bearing in a direction in which the center-to-center distance is shortened, the curved plate spring including an annular main body surrounding the bearing, a pair of ends extending in a circumferential direction of the main body, and at least one elastic tongue supported in a cantilevered shape by at least one of the pair of ends of the main body, wherein a recess is formed on a first part of an inner peripheral surface of the bearing hole in the housing, the recess has a bottom and a pair of inner wall surfaces opposed to each other in a circumferential direction of the bearing hole, the elastic tongue has a base end connected to the main body, a pressing portion for elastically pressing the bottom of the recess, and a connection portion for connecting the base end and the pressing portion to each other, to have a crank shape, a relief portion, which avoids contact with the connection portion of the elastic tongue and the annular main body of the curved plate spring, is formed between at least one of the inner wall surfaces of the recess and the first part of the inner peripheral surface of the bearing hole, and includes a chamfer connecting the at least one of the inner wall surfaces of the recess and the first part of the inner peripheral surface of the bearing hole to each other, a boundary between the relief portion and the inner peripheral surface of the bearing hole is engaged with the main body of the curved plate spring, to substantially prevent the movement of the main body in a circumferential direction thereof, a surface of the relief portion, and the inner peripheral surface of the bearing hole at the boundary intersect each other to form a second recess adjacent to the recess, a gap is formed between the annular main body of the curved plate spring and a second part of the inner peripheral surface of the bearing hole, and the second part is substantially opposed to the first part, the connection portion of the elastic tongue is spaced apart from the at least one of the inner wall surfaces of the recess in a circumferential direction of the bearing hole, and the boundary is engaged with an engaged portion of the main body, the engaged portion being located at an end of the chamfer and spaced apart from the base end of the elastic tongue in the circumferential direction so as to substantially prevent the movement of the main body in the circumferential direction thereof.