| 摘要 |
PROBLEM TO BE SOLVED: To increase the number of thickness reduction parts while ensuring required rigidity even in the tone wheel of a small diameter and improve detection precision and stability of rotating speed by making width in the circumferential direction of each thickness reduction part larger than the minimum width in the circumferential direction of a solid part which exists between the adjacent thickness reduction parts in the circumferential direction. SOLUTION: A tone wheel 13a cylindrically forms a whole by a magnetic metal plate such as a steel plate, and forms a large number of through-holes 17a, 17a having a thickness reduction part in an axial intermediate part at a regular interval in the circumferential direction. These through-holes 17a, 17a is in the form of a slit in the axial direction respectively. The width in the circumferential direction of each through-holes 17a, 17a is larger than the minimum width in the circumferential direction of each column part, and the minimum width in the circumferential direction of each column part is smaller than a thickness T of a magnetic metal plate. The tone wheel 13a can be realized, without straining each column part by using a total type pierce and simultaneously punching each through-holes 17a, 17a. |
