| 摘要 |
A cylinder tube of a hydraulic cylinder includes a substantially cylindrical outer peripheral wall portion, a port hole, and a plurality of rigidity changing portions. The port hole is formed in a part of the outer peripheral wall portion to communicate with an interior space of the outer peripheral wall portion. The rigidity changing portions are arranged at positions spaced at about 90 degrees leftward and rightward away from the port hole in the circumferential direction as viewed in section, with each of the rigidity changing portions having cross-sectional rigidity larger than a part in proximity to the port hole.
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