Components of power transmission system of electric vehicle

The components of electric vehicle power transmission system include motor, transmission, transmission shaft, differential, half shaft and wheel. The motor can run from a stationary state and can work effectively in a wide speed range. This capability allows it to eliminate the clutch, which is required in traditional internal combustion engine vehicles. A single transmission ratio can meet the matching of motor speed and wheel speed. Electric vehicles can be designed without gears, but the use of reducer makes the motor run at high speed at a certain speed. This demand characteristic of high speed and low torque can reduce the size of the motor.
In the case of front wheel drive, the schematic diagram of the motor driving the transmission installed on the front axle is shown in Figure 1. This is the structural form of electric vehicle using a single drive motor. The single motor drives the drive axle on the coaxial, and transmits power to the two wheels through the hollow motor shaft. The structure of the transmission system in the rear wheel drive is more complex, and it needs a differential to control the turning of the vehicle. Figure 2 shows the structural form of the power transmission system of a typical rear wheel drive electric vehicle.
Typical front wheel drive
Typical rear wheel drive
Using dual motors to drive the front wheels independently simplifies the powertrain and eliminates the need for a differential. Using two driving motors to drive two wheels can realize a variety of structural forms. In one arrangement, the motor suspended from the chassis can be connected to the wheels through two short half shafts. ddc. greenwheel. com. Cn in order to make the vehicle easy to operate under different road conditions, the suspension system isolates the wheels and their related components from other mechanisms of the vehicle: when the motor is suspended on the vehicle chassis, the wheels can move freely without the weight of the motor.
In another arrangement, the motor is mounted on the motor drive shaft as part of the half shaft. On one side, the half axle is connected with the wheel, while on the other side, the chassis is connected through a fulcrum. Another arrangement of motor on electric vehicle is hub motor. The problem with this arrangement is that the unsprung mass of the vehicle increases due to the installation of motors in the wheels, which makes the traction control more complex. In order to reduce the unsprung mass of the vehicle, and due to the limited available space, the hub motor must have high power density. As mentioned above, the use of reducer is necessary, but it will aggravate the limitations of available space. The high cost of high-power and high torque motor is the biggest obstacle to the use of hub motor in electric vehicles. Another problem of hub motor is whether the heat generated during braking can be lost by the limited cooling capacity of narrow space. However, this simple transmission system has led to many engineering problems about the development of electric vehicle hub motor.

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