| 摘要 |
PROBLEM TO BE SOLVED: To surely prevent a harmful moment load from being applied to the push rod of an actuator by setting the sectional profile of a recessed hole to a noncircular form, and setting the diameter of the maximum inscribed circle concerning the inside surface of the recessed hole in the state prior to the press-in of a steel ball smaller than the outer diameter of the steel ball. SOLUTION: In this auto-tensioner for imparting a regularly proper tension to a belt such as the timing belt of an automotive engine, an elastic force is imparted to a rocking frame 4 by butting the top end surface of a bush rod protruded from a cylinder against a receiving piece 13a fixed to a part of the rocking frame 4. A recessed hole 21a having a regular hexagonal sectional profile is formed on the top end surface of a rocking arm part 20, and the receiving piece 13a that is a bearing steel-made steel ball is pressed and fixed into the recessed hole 21a. The outer diameter dimension D of the receiving piece 13a is set slightly larger than the diameter r21a of the maximum inscribed circle of the recessed hole 21a prior to the press-in of the receiving piece 13a and smaller than the diameter R21a of the circumscribed circle of the recessed hole 21a.
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