| 摘要 |
On a region of a ring-shaped continuous decorative portion 15 formed of tops and bottoms in cross-section, protruding portions 17 higher than the decorative portion 15 and having a predetermined surface area are provided. A joined portion of the decorative portion 15 and each protruding portion 17 or of the protruding portions is set higher than the bottoms of the decorative portion 15, and a rigidity difference between the protruding portions 17 and the decorative portion 15 is resolved, thus restricting an occurrence of a stress concentration.
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