| 摘要 |
A partial groove 14 is formed in an inner circumferential surface of an upper side bearing member 11 of a main bearing 5 which pivotally supports a main shaft 3A of a crankshaft 3, and a space D between an end portion of the partial groove 14 and each of crush reliefs 11b formed at both ends in a circumferential direction of the upper side bearing member 11 is provided within a range of 2 mm ‰¤ D ‰¤ main shaft diameter/3. Further, a depth gradually decreasing portion 14b having an arc-shaped section is formed at an end portion of the partial groove 14, and a radius r of the depth gradually decreasing portion 14b is provided within a range of 0 ‰¤ r ‰¤ main bearing inner circumferential surface radius x 0.5. Further, in a connecting rod bearing 6, a lubricating oil discharge passage 23, which discharges a lubricating oil outside a connecting rod 4 when communicating with an internal passage 3C formed in the crankshaft 3, is provided. An amount of the lubricating oil which is discharged from a sliding portion of the main bearing is suppressed, and damage to the main bearing and the connecting rod bearing due to a foreign substance in the lubricating oil can be prevented as much as possible.
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