Power transmission device
A power transmission device includes a first one-way clutch that transmits a rotational power of a pulley to a rotating shaft, and a second one-way clutch that transmits a rotational power of a rotor of a motor to the rotating shaft. The first one-way clutch is of inner cam type in which an engagement cam-surface is formed in an outer periphery of a first inner ring, while the second one-way clutch is of outer cam type in which an engagement cam-surface is formed in an inner periphery of a second outer ring. This arrangement improves engagement performance of the first one-way clutch as well as reducing heat generation of the second one-way clutch, so that the lifetime of grease is prolonged.
1. A power transmission device comprising:
a pulley to which a rotational power is transmitted via a belt;
a motor having a rotor;
a shaft to which a rotational power of the pulley and a rotational power of the rotor are transmitted;
a first one-way clutch including an inner ring, an outer ring, and engagement members disposed between the inner ring and the outer ring, the first one-way clutch transmitting the rotational power of the pulley to the shaft when a rotational speed of the pulley is relatively higher than that of the rotating shaft; and
a second one-way clutch including an inner ring, an outer ring, and engagement members disposed between the inner ring and the outer ring, the second one-way clutch transmitting the rotational power of the rotor to the shaft when the rotational speed of the rotor is relatively higher than that of the shaft;
wherein, in the second one-way clutch,
the inner ring has an engagement cylindrical surface in an outer periphery thereof and is rotatable together with the shaft;
the outer ring has an engagement cam-surface in an inner periphery thereof and is rotatable together with the rotor; and
the engagement members are engagement rollers disposed between the engagement cylindrical surface of the inner ring and the engagement cam-surface of the outer ring;
wherein,in the first one-way clutch,
the inner ring has an engagement cam-surface in an outer periphery thereof and is rotatable together with a shaft;
the outer ring has an engagement cylindrical surface in an inner periphery thereof and is rotatable together with the pulley; and
the engagement members are engagement rollers disposed between the engagement cam-surface of the inner ring and the engagement cylindrical surface of the outer ring.
2. The power transmission device according to claim 1 , wherein, in at least one of the first one-way clutch and the second one-way clutch, the inner ring and the outer ring are provided with raceway surfaces adjacent the engagement surfaces of the inner ring and the outer ring and balls are disposed between these raceway surfaces so that a ball bearing portion is provided.
3. The power transmission device according to claim 1 , wherein, in at least one of the first one-way clutch and the second one-way clutch, the inner ring and the outer ring are provided with raceway surfaces adjacent the engagement surfaces of the inner ring and the outer ring and balls are disposed between these raceway surfaces so that a ball bearing portion is provided.