| 摘要 |
A contact member (7) is configured such that a contour (70) of a cross section (75) includes a second contour segment (71) in the form of a straight line, a first contour segment (72) in the form of a curve swelling radially, and third contour segments (73) in the form of curves connecting the second contour segment (71) and the first contour segment (72). When the contact member (7) is pressed, for disposition, into a space between a connection base portion 37 of a center shaft (3) and the inner circumferential surface of an axial bore (43) of a metallic shell (4), the straight second contour segment (71) functions as a core, whereby the contact member (7) is free from inward drag or bending. Since the first contour segment (72) is curved, deformation of reducing radial thickness is smoothly performed; thus, a deformed portion having high internal stress does not arise locally. Since the inside diameter of the contact member (7) is expanded by a shoulder portion (38) of the center shaft (3), and, then, the outside diameter of the contact member (7) is narrowed by a taper portion (47) of the metallic shell (4), the contact member (7) is free from twist and wrinkling. |
