Importance

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Abstract

A power-assisting device for use with a bicycle includes a hollow shaft which is adapted to be rotatably supported in a hanger lug of the bicycle. The hollow shaft is restricted to movement along a rotation center line thereof, and has (i) a first end portion adapted to be projected out of the hanger lug and detachably attached to a rear wheel drive gear, and (ii) a second end portion adapted to be projected out of the hanger lug and detachably attached to an input gear. A crank shaft is rotatably supported in a center hole of the hollow shaft. The crank shaft is restricted to movement along a rotation center line thereof, and has first and second end portions extending out of the hollow shaft and adapted to be detachably attached to a first and second ones of a pair of pedal-equipped crank arms. A power-assisting unit is adapted to be detachably attached to a body of the bicycle, and includes a motor and a rotation force transmission mechanism adapted to transmit a motor rotation force from the motor to the input gear. The rotation force transmission mechanism has a one-way clutch for transmitting the motor rotation force to the input gear only in a direction for driving the bicycle forward. A rotation force control unit, interposed between the crank shaft and the hollow shaft outside the hanger lug, transmits a rotation force of the crank shaft to the hollow shaft and controls the motor to generate the motor rotation force when a value of the rotation force of the crank shaft becomes larger than a predetermined value.

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First Claim