Bicycle drive unit
A bicycle drive unit has a transmission and a motor that transmits torque to the transmission. The transmission includes first and second input side rotating bodies, first and second output side rotating bodies, an output unit and a switching mechanism. The first and second output side rotating bodies are coupled to the first and second input side rotating bodies, respectively. The switching mechanism switches between a first state in which rotation of the first input side rotating body is transmitted to the output unit, and a second state in which rotation of the second input side rotating body is transmitted to the output unit. Only torque of the motor is transmitted from the first and second input side rotating bodies to the output unit, while torque outputted from the output unit merges with a manual drive force in a drive force transmission path from the output unit to a wheel.
1. A bicycle drive unit comprising:
a transmission having a plurality of gear shift stages; and
a motor configured to transmit torque to the transmission,
the transmission comprises
a first input side rotating body and a second input side rotating body rotatably disposed around a first rotational axis;
a first output side rotating body rotatably disposed around a second rotational axis that is parallel to the first rotational axis, and coupled to the first input side rotating body;
a second output side rotating body rotatably disposed around the second rotational axis and coupled to the second input side rotating body;
an output unit configured to receive rotation of the first output side rotating body and the second output side rotating body; and
a switching mechanism configured to switch between a first state in which the rotation of the first input side rotating body is transmitted to the output unit, and a second state in which the rotation of the second input side rotating body is transmitted to the output unit;
the output unit being configured to receive only torque from the motor via the first input side rotating body and the second input side rotating body, and
the output unit being configured such that torque outputted from the output unit merges with a manual drive force in a drive force transmission path from the output unit to a wheel.
2. The bicycle drive unit according to claim 1 , wherein
the output unit includes a crankshaft.
3. The bicycle drive unit according to claim 1 , wherein
the output unit includes a hollow shaft configured to receive a crankshaft therein.
4. The bicycle drive unit according to claim 3 , further comprising
the crankshaft being coupled to the hollow shaft of the output unit.
5. The bicycle drive unit according to claim 1 , wherein
the first input side rotating body and the second input side rotating body are gears having different diameters;
the first output side rotating body is a gear that is engaged with the first input side rotating body; and
the second output side rotating body is a gear that is engaged with the second input side rotating body.
6. The bicycle drive unit according to claim 1 , further comprising
a first rotational shaft that rotates on the first rotational axis, the first output side rotating body and the second output side rotating body being fixed to the output unit; and
the switching mechanism integrally rotating the first rotational shaft and the first input side rotating body together as a unit and rotating the first rotational shaft relative to the second input side rotating body while the switching mechanism is in the first state, and
the switching mechanism integrally rotates the first rotational shaft and the second input side rotating body together as a unit and rotating the first rotational shaft relative to the first input side rotating body while the switching mechanism is in the second state.
7. The bicycle drive unit according to claim 6 , wherein
a rotational speed ratio of the first output side rotating body with respect to a rotational speed of the first input side rotating body is configured to be smaller than a rotational speed ratio of the second output side rotating body with respect to a rotational speed of the second input side rotating body; and
the switching mechanism comprises:
a connection switching unit configured to couple the first rotational shaft and the second input side rotating body while the switching mechanism is in the first state and allow a relative rotation between the first rotational shaft and the second input side rotating body while the switching mechanism is in the second state, and
a one-way clutch disposed between the first rotational shaft and the first input side rotating body.
8. The bicycle drive unit according to claim 7 , wherein
the one-way clutch is configured to integrally rotate the first rotational shaft and the first input side rotating body while the rotational speed of the first input side rotating body in a first rotational direction is equal to the rotational speed of the first rotational shaft, and
the one-way clutch is configured to rotate the first rotational shaft relative to the first input side rotating body while the rotational speed of the first input side rotating body in the first rotational direction is greater than the rotational speed of the first rotational shaft.
9. The bicycle drive unit according to claim 7 , wherein
the connection switching unit comprises a pawl provided on and protruding from one of the first rotational shaft and the second input side rotating body, and an engagement portion provided to the other of the first rotational shaft and the second input side rotating body so that the pawl is configured to selectively engage the engagement portion, and
the first rotational shaft and the second input side rotating body are coupled by the pawl engaging the engagement portion, and permitting rotation of the first rotational shaft with respect to the second input side rotating body by disengaging the pawl from the engagement portion.
10. The bicycle drive unit according to claim 7 , wherein
the switching mechanism further comprises an actuator configured to control the connection switching unit.
11. The bicycle drive unit according to claim 10 , wherein
the connection switching unit comprises a pawl provided on and protruding from one of the first rotational shaft and the second input side rotating body, and an engagement portion provided to the other of the first rotational shaft and the second input side rotating body so that the pawl is configured to selectively engage the engagement portion,
the first rotational shaft and the second input side rotating body are coupled by the pawl engaging the engagement portion, and permitting rotation of the first rotational shaft with respect to the second input side rotating body by disengaging the pawl from the engagement portion, and
the actuator comprises a biasing member that applies force to the pawl so that the pawl projects from one of the first rotational shaft and the second input side rotating body; a movable member that is configured to cause the pawl to operate with respect to the other of the first rotational shaft and the second input side rotating body so that the pawl moves away from the engagement portion; and a drive unit that switches between the first state arid the second state by moving the movable member.
12. The bicycle drive unit according to claim 6 , wherein
the first rotational shaft is inserted in holes provided in each of the first input side rotating body and the second input side rotating body.
13. The bicycle drive unit according to claim 12 , wherein
the connection switching unit comprises a pawl provided on and protruding from one of the first rotational shaft and the second input side rotating body, and an engagement portion provided to the other of the first rotational shaft and the second input side rotating body so that the pawl is configured to selectively engage the engagement portion,
the first rotational shaft and the second input side rotating body are coupled by the pawl engaging the engagement portion, and permitting rotation of the first rotational shaft with respect to the second input side rotating body by disengaging the pawl from the engagement portion, and
the pawl is disposed between an outer perimeter of the first rotational shaft and an inner perimeter of the second input side rotating body.
14. The bicycle drive unit according to claim 1 , further comprising
a speed reducer configured to reduce a rotational speed of the motor and transmit a rotation of the motor to the transmission.
15. The bicycle drive unit according to claim 1 , wherein
the motor is partially disposed on a plane that includes at least one of the first input side rotating body and the second input side rotating body, the plane being perpendicular to the first rotational axis and the second rotational axis.
16. The bicycle drive unit according to claim 1 , wherein
the first output side rotating body and the second output side rotating body are integrally fanned together as a unit.