Patent ID: 8267060

Claim:
A lubrication structure of a cranking rotational force transmission mechanism for an internal combustion engine, the cranking rotational force transmission mechanism having an outer race member that is coupled with a rotational output shaft of the internal combustion engine; a ring gear to which a rotational drive force is transmitted from a starter motor and a portion of which faces the outer race member from the side of the internal combustion engine; and a one-way clutch that is provided in a position across which the portion of the ring gear faces the outer race member and that transmits a rotational force of the starter motor in one rotational direction from the ring gear to the outer race member and interrupts transmission of a rotational force of the starter motor in the other rotational direction from the ring gear to the outer race member, the lubrication structure comprising: a sealing member that is provided to oil-seal a gap between the ring gear and the outer race member so that the one-way clutch is in an oil-sealed area in the internal combustion engine side; and a lubricant-return hole that is formed in a portion of the ring gear between a portion of the ring gear at which the one-way clutch is provided and a portion of the ring gear at which the sealing member is provided, the lubricant-return hole penetrating the ring gear from one side to the other side; and wherein the lubricant-return hole is provided in plurality and the lubricant-return holes are formed around a rotational axis of the ring gear, such that, at any rotational phase of the ring gear, at least a part of one of the lubricant-return holes is present below a horizontal line that is drawn tangent to a lower side of an outer periphery of the outer race member.