① Brush disc winding motor. Brush disc winding motor is bonded to a cylinder with rare earth materials, and the disc winding wound with enameled copper wire is placed in the cylinder to form a rotor. The phase of the motor is adjusted by a mechanical inverter. The mechanical inverter adjusts the voltage phase by the friction between the fixed carbon brush and the rotating copper inverter. The brush of this kind of motor has been worn in use, and the life of the motor is hard to exceed 2000 h. At the same time, because of the high speed of the motor, it is necessary to use two-stage gears to slow down, which brings two problems, one is loud noise, the other is high efficiency loss, and the rated efficiency of the motor can only reach 68% ~ 72% after deceleration. However, the battery capacity used in electric bicycles is limited, generally 36V/ 12Ah. If the motor efficiency is not high, it will increase the power consumption and affect the driving range.
② Brush printed winding motor. Brush printed winding motor uses printed copper foil as winding, which reduces the weight of the motor. Because this kind of motor is all produced on the automatic production line, the technology is reliably guaranteed, the life of the motor is extended to 3000h, the noise is greatly reduced and the efficiency is improved to 72% ~ 76%. However, this kind of motor has "buzzing" high-frequency noise, and the efficiency is still not ideal after gear deceleration. The use of brush commutation can not improve the life of the motor.
③ Brushed winding motor. The efficiency of this motor can be improved to 74% ~ 78% by pressing the wound copper wire into a new winding. This kind of motor is still adopted by many electric bicycle manufacturers, but its efficiency, noise and life defects are still problems that must be improved.
Gear-driven hub-type brush DC motor is composed of disk armature brush motor and gear reduction drive system. Disc armature is a kind of high-speed rotating rotor. The structure of wheel-driven gear-driven brushed DC motor is shown in Figure 2-2. The torque of the motor is transmitted to the primary gear through the shaft, and the hub shell is driven to rotate through gear deceleration.
The disk armature of the motor with brush and toothed hub is thin, small in size, extremely light in weight and convenient to install. After winding, put the resin and glass fiber into the mold for hot pressing. In operation, the running sound of brush motor is louder than that of brushless motor because of the friction between brush and commutator and the deceleration of gear meshing.
In order to adapt to the hub structure, the brush motor is designed as a low-speed motor, with a rotor outside the armature, a stator with multiple pieces of magnetic steel and multiple windings inside the motor, and the design speed is about 180r/min. Fig. 2-3(a) shows the armature winding in the outer rotor of the motor, which is not formed by pressure, and the inside of the winding is a plane annular arrangement of commutator segments. Figure 2-3(b) shows the stator with 10 pieces of magnetic steel, which are arranged in the outer rotor at intervals. There are two holes in the hub plate in the middle, and the brush holder is located at the back side of the hole, and the brush is ejected from the brush holder by the spring wire.
The end of the stator shaft of the brush motor is sheathed with a nut to prevent the thread on the shaft from being damaged during processing. Put the brush into the brush holder, and then send this end into the hole shown in Figure 2-3(a) to make the brush contact with the commutator plane, and press the commutator with the elastic force of the spring. The magnetic steel just enters the outer rotor winding, leaving only a small annular air gap. The larger the diameter of this annular air gap, the greater the torque generated by the motor.
Due to the improvement in the design of the brush motor, there is no need for gear reduction, which can achieve low noise and low cost. This kind of motor is widely used in many low-cost electric bicycles. But the advantages of this kind of motor are small torque, small load, poor climbing ability and high power consumption. The mechanical brush commutator is still in use, and the problem of motor life has not been solved. Therefore, high-end electric bicycles do not use this kind of motor.