| 摘要 |
<p>A rear frame (20) is a casting of magnesium-based material. The rear frame (20) includes a side portion (21A) and a fastening portion (80) having a through hole (23) formed therein, the through hole (23) having a bolt passed therethrough. The fastening portion (80) has contact surfaces (81) formed around one end side and the other end side of the through hole (23), the contact surfaces (81) being to be placed on a main frame. The fastening portion (80) has a recessed portion (82) formed in a portion that is located outside in the radial direction of the through hole (23) and in the middle in an axial direction of the through hole (23), the recessed portion (82) being recessed towards the through hole (23).</p> |
