Abstract: A starter for an internal combustion engine includes a power transmission mechanism. The power transmission mechanism has an outer race plate fastened to a crankshaft, and a ring gear coupled to a rotational shaft of an electric motor for starting the engine. The power transmission mechanism further has a one-way clutch for permitting torque transmission only from the ring gear to the outer race plate, and two sealing members. Lubricant is supplied from the cylinder block to the interior of the power transmission mechanism for lubricating the power transmission mechanism. The outer race plate has a groove on its contact surface of a contact portion between the crankshaft and the outer race plate. The groove extends in the entire circumferential direction of the crankshaft. This maintains the coupling strength between the outer race plate and the crankshaft, while enhancing the sealing performance of the power transmission mechanism.

Abstract: The lubricant-return holes are provided in the intermediate portion of the ring gear. Thus, the lubricant stagnating above the first oil sealing member can be easily discharged to the oil pan side via the lubricant-return holes even when the ring gear has stopped rotating in response to the starter motor being turned off after completion of the start of the internal combustion engine. As such, the level of the surface of lubricant stagnating between the ring gear and the outer race member does not rise, and therefore the lubricant surface virtually does not reach the outer race and the one-way clutch that are rotating while the internal combustion engine is running. Thus, bubbling of lubricant and production of sludge, which may otherwise be caused by agitation of the lubricant surface, can be prevented.

Abstract: A ring gear is formed by joining a race side-region formed body, a gear side-region formed body and an intermediate region formed body. Accordingly, it is possible to perform processing of an inner race portion of the race side-region formed body with none of the gear side-region formed body and the intermediate region formed body present. By causing the gear side-region formed body and the intermediate region formed body to absorb changes in design depending on the type of internal combustion engine, it is possible to standardize the size and the shape of the race side-region formed body for various engine types. Because the inner race portion, as well as a disposition surface and a contact surface for the seal rings are formed on the same race side-region formed body, it is possible to finish the surfaces with precise positional relationship.

Abstract: A sliding bearing is constructed by an upper split bearing half and a lower split bearing half. The upper split bearing half has a sliding surface, in which an oil groove which allows a lubricating oil to flow therein is formed over the entire circumferential extent of the sliding surfaced. The oil groove extends through a crush relief to be open to a junction area, and the oil groove has a bottom which is formed so that a portion disposed toward the junction area as considered in the circumferential direction of the crush relief is located closer to the center of the upper split bearing half in comparison to a central portion. An ingress in large quantities of foreign particles within the oil groove onto the sliding surface of the sliding bearing and into a connecting rod bearing after passing through a lubricating oil feed passage is suppressed, and an oil leakage through the crush relief is reduced, allowing a lubricating oil pressure to be secured and augmented.

Abstract: The lubricant-return holes are provided in the intermediate portion of the ring gear. Thus, the lubricant stagnating above the first oil sealing member can be easily discharged to the oil pan side via the lubricant-return holes even when the ring gear has stopped rotating in response to the starter motor being turned off after completion of the start of the internal combustion engine. As such, the level of the surface of lubricant stagnating between the ring gear and the outer race member does not rise, and therefore the lubricant surface virtually does not reach the outer race and the one-way clutch that are rotating while the internal combustion engine is running. Thus, bubbling of lubricant and production of sludge, which may otherwise be caused by agitation of the lubricant surface, can be prevented.

Abstract: An outer race support plate to which torque of a pinion gear is transmitted from a ring gear via a one-way clutch and thus rotates a crankshaft is provided separately from a flywheel and is mounted to the crankshaft not via the flywheel. As a result, impact noise produced when the one-way clutch engages is not directly transmitted to the flywheel. Accordingly, noise radiation from the flywheel can be suppressed, thereby enabling noise to be reduced.

Abstract: A ring gear is formed by joining a race side-region formed body, a gear side-region formed body and an intermediate region formed body. Accordingly, it is possible to perform processing of an inner race portion of the race side-region formed body with none of the gear side-region formed body and the intermediate region formed body present. By causing the gear side-region formed body and the intermediate region formed body to absorb changes in design depending on the type of internal combustion engine, it is possible to standardize the size and the shape of the race side-region formed body for various engine types. Because the inner race portion, as well as a disposition surface and a contact surface for the seal rings are formed on the same race side-region formed body, it is possible to finish the surfaces with precise positional relationship.

Abstract: A torque transmitting mechanism, including a ring gear; a crankshaft side member which rotates in conjunction with a crankshaft; a one-way clutch arranged between the ring gear and the crankshaft; a bearing arranged between the crankshaft or the crankshaft side member and a surface of the ring gear that faces in the opposite direction from the side of the ring gear on which the one-way clutch is arranged; a first oil seal member arranged together with the bearing between the crankshaft or the crankshaft side member and the surface of the ring gear that faces in the opposite direction from the side of the ring gear on which the one-way clutch is arranged, and is arranged on the opposite side of the bearing from the internal combustion engine main body; and a second oil seal arranged between the ring gear and the internal combustion engine main body.

Abstract: A starter for an internal combustion engine includes a power transmission mechanism. The power transmission mechanism has an outer race plate fastened to a crankshaft, and a ring gear coupled to a rotational shaft of an electric motor for starting the engine. The power transmission mechanism further has a one-way clutch for permitting torque transmission only from the ring gear to the outer race plate, and two sealing members. Lubricant is supplied from the cylinder block to the interior of the power transmission mechanism for lubricating the power transmission mechanism. The outer race plate has a groove on its contact surface of a contact portion between the crankshaft and the outer race plate. The groove extends in the entire circumferential direction of the crankshaft. This maintains the coupling strength between the outer race plate and the crankshaft, while enhancing the sealing performance of the power transmission mechanism.

Abstract: The lubricant-return holes (12d) are provided in the intermediate portion (12c) of the ring gear (12). Thus, the lubricant stagnating above the first oil sealing member (32) can be easily discharged to the oil pan (36) side via the lubricant-return holes (12d) even when the ring gear (12) has stopped rotating in response to the starter motor being turned off after completion of the start of the internal combustion engine. As such, the level of the surface of lubricant stagnating between the ring gear (12) and the outer race member (14) does not rise, and therefore the lubricant surface virtually does not reach the outer race (30) and the one-way clutch (20) that are rotating while the internal combustion engine is running. Thus, bubbling of lubricant and production of sludge, which may otherwise be caused by agitation of the lubricant surface, can be prevented.

Abstract: An outer race support plate to which torque of a pinion gear is transmitted from a ring gear via a one-way clutch and thus rotates a crankshaft is provided separately from a flywheel and is mounted to the crankshaft not via the flywheel. As a result, impact noise produced when the one-way clutch engages is not directly transmitted to the flywheel. Accordingly, noise radiation from the flywheel can be suppressed, thereby enabling noise to be reduced.

Abstract: A one-way clutch and a bearing are both grease-filled so even if an oil seal member prevents engine oil from flowing thereto, it will cause no problems in terms of lubrication of the one-way clutch and the bearing. Therefore, the oil seal member 18 need only seal between a main body side of an internal combustion engine and a crankshaft and so does not need to have a large diameter. As a result, even when the crankshaft rotates while the internal combustion engine is operating, the small diameter oil seal member will not slide at a high rate of speed against an outer peripheral surface of the crankshaft and so will not degrade quickly.

Abstract: A construction width region Aowc of a one-way clutch overlaps with a mesh width region Agg where torque is transferred from a pinion to a ring gear at the time of startup of the engine, so that the center positions of the two regions coincide with each other in the direction of the rotation axis. Due to this overlap, the reaction force that occurs on a one-way clutch when torque is transferred from the pinion to the ring gear can be sufficiently restrained from becoming, together with the torque, a force that inclines the rotation axis of the ring gear. Therefore, it is possible to restrain the direction of engagement force from tilting from a normal position relative to a sprag or the like of the one-way clutch, and to sufficiently prevent occurrence of bad engagement. Furthermore, damages, such as impressions inside a bearing and the like, and deformations of oil seal portions can be prevented.

Abstract: A sliding bearing 4 is constructed by an upper split bearing half 8 and a lower split bearing half 9. The upper split bearing half 8 has a sliding surface 8a, in which an oil groove 10 which allows an lubricating oil to flow therein is formed over the entire circumferential extent of the sliding surface 8a. The oil groove extends through a crush relief 8c to be open to a junction area 8b, and the oil groove has a bottom 10a which is formed so that a portion disposed toward the junction area as considered in the circumferential direction of the crush relief is located closer to the center of the upper split bearing half in comparison to a central portion. An ingress in large quantities of foreign particles within the oil groove onto the sliding surface of the sliding bearing and into a connecting rod bearing after passing through a lubricating oil feed passage is suppressed, and an oil leakage through the crush relief is reduced, allowing a lubricating oil pressure to be secured and augmented.