| 摘要 |
An engagement structure for cylindrical members includes a first cylindrical member including a plurality of engagement projection portions of different shapes having the same projecting length in the radial direction, and a second cylindrical member including a plurality of groove portions corresponding to the engagement projection portions, each the groove portions having at least one groove, wherein one of the first and second cylindrical members is accommodated inside the other of the first and second cylindrical members. The engagement projection portions and the corresponding groove portions can be engaged and disengaged only at one relative circumferential position of the first and second cylindrical members, and at a relative circumferential position other than the one relative circumferential position, the engagement projection portions of the first cylindrical member are always engaged with at least a portion of the groove portions other than the grooves thereof.
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