Transmission structure of mid-drive motor

A transmission structure of a mid-drive motor, the transmission structure comprising:

• a shell having two opposite surfaces;
• an output axle disposed through the two opposite surfaces of the shell, and the output axle having:
• a transmission toothed portion protruding from an outer annular surface of the output axle;
• a motor unit mounted in the shell;
• and
• a clutch assembly mounted in the shell, and the clutch assembly connecting with the output axle and the motor unit, the clutch assembly including:
• a driving ring connected to the motor unit, thereby the driving ring driven to rotate by the motor unit;
• the driving ring having:
• an outer annular toothed portion formed on an outer annular surface of the driving ring, and the motor unit connected to the outer annular toothed portion;
• and
• an inner annular toothed portion formed on an inner annular surface of the driving ring;
• a clutch gear disposed in the driving ring and being movable along an axial direction of the driving ring, the clutch gear being magnetically attractable;
• the clutch gear having:
• a clutch annular toothed portion formed on an outer annular surface of the clutch gear, and the clutch annular toothed portion engaging with the inner annular toothed portion of the driving ring;
• multiple first engaging portions formed on an end surface of the clutch gear, the first engaging portions surrounding a center of rotation of the clutch gear, and the first engaging portions connected to each other;
• and
• a first abutting portion formed on another end surface of the clutch gear;
• an output gear connected to the output axle, and the output gear capable of driving the output axle to rotate, the output gear and the clutch gear detachably connected to each other;
• the output gear having:
• an output annular toothed portion formed on an outer annular surface of the output gear, and engaging with the transmission toothed portion of the output axle;
• multiple second engaging portions formed on an end surface of the output gear, said end surface of the output gear facing towards the clutch gear, the second engaging portions surrounding a center of rotation of the output gear, and the second engaging portions connected to each other;
• the second engaging portions selectively engaging with the first engaging portions;
• and
• a pressing device located at a side of the clutch gear away from the output gear, the pressing device being magnetic and having:
• a base casing being annular to form a mounting space, and an opening formed on the base casing;
• the opening spatially communicating with the mounting space, and the opening facing towards the clutch gear, the base casing having:
• an inner bottom surface located in the mounting space and facing towards the opening;
• and
• a first sliding portion formed on the inner bottom surface;
• a pressing disc located in the mounting space and being movable along an axial direction of the base casing;
• the pressing disc having:
• a second abutting portion formed on a surface of the pressing disc, and said surface of the pressing disc facing towards the opening, the second abutting portion and the first abutting portion detachably abutting each other, thereby the clutch gear driving the pressing disc to rotate;
• and
• a second sliding portion formed on a surface of the pressing disc, and said surface of the pressing disc facing towards the inner bottom surface, and the second sliding portion capable of sliding with respect to the first sliding portion;
• and
• an elastic unit located in the mounting space, and the elastic unit abutting the pressing disc and a part of the base casing surrounding the opening.