A power unit includes a drive unit and a power sprocket for engaging the transmission band of a bicycle. The power unit includes a first free-wheeling sprocket arranged on a first side of the power sprocket and a second free-wheeling sprocket arranged on a second side of the power sprocket. The power sprocket receives the transmission band from the first free-wheeling sprocket on the first side and passes the transmission band to the second free-wheeling sprocket.

A vehicle that is operable by motor power and/or by muscular power, in particular an electric bicycle, including a crankshaft drive having a bottom bracket bearing shaft, a front sprocket that transmits a drive torque for the vehicle to a chain, an electric drive and a friction gear for continuously varying a transmission ratio, the friction gear and the electric drive being configured on the crankshaft drive, and the friction gear being coupled to the crankshaft drive and adapted for transmitting a rider-produced torque to the front sprocket.

A vehicle that is operable by motor power and/or by muscular power, in particular an electric bicycle, including a crankshaft drive having a bottom bracket bearing shaft, a front sprocket that transmits a drive torque for the vehicle to a chain, an electric drive and a friction gear for continuously varying a transmission ratio, the friction gear and the electric drive being configured on the crankshaft drive, and the friction gear being coupled to the crankshaft drive and adapted for transmitting a rider-produced torque to the front sprocket.

A compound power mechanism and an electric bicycle are provided. The compound power mechanism includes a motor casing fixed to the bicycle, a motor drive shaft coupled with a rotor, and a stator provided in the motor casing. A crank drive shaft is disposed in the motor drive shaft. Two ends of the crank drive shaft extend out of the two ends of the motor drive shaft and are coupled with pedal cranks. A freewheel is coupled to a respective end of the motor drive shaft and the crank drive shaft. A drive sprocket is located between and coupled to the two freewheels and adapted to bring a bicycle chain to turn. The drive sprocket can be driven by the motor drive shaft or by the crank drive shaft when pedaled. The size of the motor is reduced and the cost of manufacture is lowered.

A compound power mechanism and an electric bicycle are provided. The compound power mechanism includes a motor casing fixed to the bicycle, a motor drive shaft coupled with a rotor, and a stator provided in the motor casing. A crank drive shaft is disposed in the motor drive shaft. Two ends of the crank drive shaft extend out of the two ends of the motor drive shaft and are coupled with pedal cranks. A freewheel is coupled to a respective end of the motor drive shaft and the crank drive shaft. A drive sprocket is located between and coupled to the two freewheels and adapted to bring a bicycle chain to turn. The drive sprocket can be driven by the motor drive shaft or by the crank drive shaft when pedaled. The size of the motor is reduced and the cost of manufacture is lowered.

A bicycle drive unit includes a planetary gear mechanism, a first motor and a second motor. The planetary gear mechanism includes a sun gear, a ring gear, a plurality of planetary gears and a carrier. The ring gear is disposed around the sun gear on the same axis as the sun gear. The planetary gears are disposed between the sun gear and the ring gear. The carrier rotatably holds the planetary gears and receives an input rotation of a crankshaft. The first motor is configured to transmit torque to the carrier. The second motor is configured to transmit torque to the sun gear and control the rotation of the sun gear.

A bicycle drive unit includes a planetary gear mechanism, a first motor and a second motor. The planetary gear mechanism includes a sun gear, a ring gear, a plurality of planetary gears and a carrier. The ring gear is disposed around the sun gear on the same axis as the sun gear. The planetary gears are disposed between the sun gear and the ring gear. The carrier rotatably holds the planetary gears and receives an input rotation of a crankshaft. The first motor is configured to transmit torque to the carrier. The second motor is configured to transmit torque to the sun gear and control the rotation of the sun gear.

Provided is an electric assist bicycle that can apply a sufficient auxiliary driving force with a satisfactory gear change, preclude problems caused by interference between a mount or a battery and a front derailleur, and prevent a reduction in torque transmission efficiency. A cylindrical human-power transmission member that receives a transmitted human driving force is disposed on the outer periphery of a crank shaft, and a combined-force transmission member that receives the combined force of a human driving force and an auxiliary driving force from a motor is disposed on the outer periphery of the crank shaft. The electric assist bicycle includes a speed reduction mechanism that has pairs of reduction gears and a selection clutch engageable with the reduction gears, combines the human driving force and the auxiliary driving force, and changes gears for the combined force of the human driving force and the auxiliary driving force.

Provided is an electric assist bicycle that can apply a sufficient auxiliary driving force with a satisfactory gear change, preclude problems caused by interference between a mount or a battery and a front derailleur, and prevent a reduction in torque transmission efficiency. A cylindrical human-power transmission member that receives a transmitted human driving force is disposed on the outer periphery of a crank shaft, and a combined-force transmission member that receives the combined force of a human driving force and an auxiliary driving force from a motor is disposed on the outer periphery of the crank shaft. The electric assist bicycle includes a speed reduction mechanism that has pairs of reduction gears and a selection clutch engageable with the reduction gears, combines the human driving force and the auxiliary driving force, and changes gears for the combined force of the human driving force and the auxiliary driving force.

A bicycle propulsion system including a concentric rotor assembly and a chassis assembly. The concentric rotor assembly: defines an outer drive surface; defines an inner retention surface; includes a set of sprocket brackets arranged about the inner retention surface of the concentric rotor assembly and configured to engage with teeth of a bicycle sprocket; and is configured to engage around the bicycle sprocket, wherein a center axis of the outer drive surface is concentric with a rotational axis of the bicycle sprocket. The chassis assembly: is configured to secure to a stay of the bicycle; includes a retention subassembly configured to translationally constrain the concentric rotor assembly relative to the chassis assembly; includes a drive subassembly configured to engage the outer drive surface of the concentric rotor assembly; and includes a motor configured to rotate the concentric rotor assembly via the drive subassembly.