Patent ID: 8091873

Claim:
A coned disc spring, arranged between a second component and a third component provided inside a tubular first component and movable in an axial direction, comprising: a body having a circular dish shape; teeth closely fitting into spline grooves which are formed on an inner peripheral surface of the first component and extend in the axial direction and projecting to a radial outer side on an outer periphery of the body, the teeth preventing the body from relative rotation with respect to the tubular first component; and a stress relaxation portion formed at a base of a tooth of the teeth, wherein the stress relaxation portion having: a first circular arc portion formed by notching the base of the tooth in an approximately circular arc shape in a radial direction of the body and having opposite first and second ends, wherein the first end of the first circular arc portion is smoothly connected to the outer periphery of the body; a second circular arc portion formed by notching the base of the tooth in an approximately circular arc shape in a circumferential direction of the body and having opposite first and second ends, wherein the first end of the second circular arc portion is smoothly connected to the second end of the first circular arc portion, and the second end of the second circular arc portion is smoothly connected to a side of the tooth; and the second circular arc portion being configured such that a width of the base of each of the teeth, in the circumferential direction, is smaller than a width of a distal end of each of the teeth in the circumferential direction.