Direct-current wheel hub motor device

The invention discloses a direct-current wheel hub motor device. The rotary shaft of a motor is coaxial with a wheel shaft of a vehicle, and a shell and a wheel hub are fixed together; when the motor is powered on, electromagnetic acting force is produced between a stator magnet and a rotor armature; the stator magnet is motionless, so that the rotor armature and a transmission gear rotate anticlockwise under the action of the electromagnetic force; when the transmission gear is transmitted, a rotary part of a one-way fly wheel cannot rotate anticlockwise, and therefore, planetary gears rotate clockwise under the driving of the transmission gear to drive a gear ring and the shell to rotate clockwise, and then the wheels are driven to move forwards; when the motor is not powered on, wheels move forwards by virtue of inertia or under driving of manpower, so that the shell continuously rotates clockwise along with the wheels, each planetary gear synchronously revolves along with the shell under the driving of the gear ring, the rotary part of the one-way fly wheel is driven to rotate clockwise; the planetary gears automatically rotate while revolving, and the transmission gear does not rotate, and therefore, the stator magnet and the rotor armature are still without mutual acting force, and electromagnetic resistance for moving wheels when the motor is powered off is avoided.