YOKE ARRANGEMENT FOR AN ELECTRIC MOTOR HAVING AN IMPROVED MECHANICAL STRENGTH

摘要

In a yoke arrangement for electric motors which are particularly suitable for use in electric power steering devices, the yoke comprises a first tubular portion, a second tubular portion which has a smaller diameter than the first tubular portion, and a tapered section connecting the two tubular portions. The length of the tapered sections is desired to be minimized so that the overall length of the electric motor may be minimized. Reducing the length of the tapered section and thereby increasing the taper angle of the tapered section leads to the reduction in the mechanical strength of the yoke against an axial force. To compensate for this reduction in mechanical strength, the wall thickness of the tapered section is made larger than that of the first portion. Thus, the overall mechanical strength of the yoke can be ensured with a minimum increase in the material cost and manufacturing cost. The yoke may be formed by plastic deformation such as swaging and expansion.