Analysis of internal structure of electric vehicles
Electric vehicles are mainly composed of three parts: electric drive system, energy system and auxiliary work system. The electric drive system is the "brain center" of electric vehicles and the most different from fuel vehicles. The function of the electric drive system is to convert the electric energy stored in the battery into driving kinetic energy and play the role of regenerative braking (that is, to recover the kinetic energy during the deceleration of the car and return it to the battery). The energy system is the "digestive system" in the car body. It converts the "food" (electric energy or other forms of energy) obtained from the outside into the battery energy for storage, providing a continuous source of energy for the car. The auxiliary work system carries the role of “car attendant”. She provides so-called “other” functions such as air conditioning, lighting, and auxiliary power source, which can improve the overall operability of the car and the driver's comfort. Similar to a normal fuel car.
Drive motor
The function of the drive motor is to convert the battery power into mechanical energy and drive the vehicle to operate through the transmission system. At the same time, most electric vehicles in the brake state, the motor will play the role of "generator", the excess mechanical energy is fed back to the battery for charging. In the market, motors can be divided into DC motors, asynchronous motors, permanent magnet synchronous motors and switched reluctance motors. For example, Tesla uses an asynchronous motor that accelerates faster and does not generate noise. The Beiqi EU260 uses a permanent magnet synchronous motor because it is light and easy to install.
2. Electric controller
The electric controller is provided for shifting and direction change of the electric vehicle, and functions to control the voltage or current of the motor to complete the control of the driving torque and the rotation direction of the motor. By uniformly changing the terminal voltage of the motor and controlling the current of the motor, the stepless speed regulation of the motor is realized. This process is called thyristor chopper speed regulation.
In the rotary direction control of an electric vehicle, the direct current motor changes the direction of the current of the armature or the magnetic field by the contactor to realize the direction change. When driven by an AC asynchronous motor, the change of the steering of the motor only needs to change the phase sequence of the three-phase current of the magnetic field, so that the control circuit can be simplified. In addition, the AC motor and its variable frequency speed control technology make the braking energy recovery control of the electric vehicle more convenient and the control circuit is simpler.
3. Transmission and travel equipment
The function of the electric vehicle transmission device is to transmit the driving torque of the electric motor to the driving shaft of the automobile, and then the driving device (wheel, tire and suspension, etc.) is converted into a force acting on the ground, thereby driving the wheel to travel. The motor can be started with a load, and the clutch on the general fuel car can be removed. Moreover, the drive motor can realize the direction change by circuit control, so the reverse gear in the fuel vehicle transmission can also be omitted. Compared with the fuel vehicle, it is more convenient to use the motor stepless speed control, the electric vehicle can ignore the transmission; when using the electric wheel drive, the differential can be omitted, so the electric vehicle greatly simplifies the internal structure.
4. Brake system
The brake system is also known as the “brake system”. However, there are electromagnetic brake devices on the electric vehicle, which can convert the excess kinetic energy during the braking process and leave it in the battery to effectively recycle energy.
5. Battery
The battery is the energy source for all work of electric vehicles. It not only converts electric energy into driving kinetic energy, but also the energy of other vehicle-mounted devices. On the market, there are a variety of batteries, including lead acid, nickel hydrogen, lithium iron phosphate, lithium manganate, lithium titanate, ternary materials, and multi-component composite materials. Among them, the pure electric passenger car ternary power battery is the mainstream, the installed capacity can reach 76%; in the electric bus, the lithium iron phosphate battery is more dominant, with more than 60% installed capacity. The basic considerations for installing batteries in electric vehicles are usually higher than energy, mature charging technology, short time, high continuous discharge rate, low self-discharge rate, suitable for vehicle operating environment, safe and reliable, long life and easy maintenance.
6. Energy Management System
The energy management system plays the role of “energy coordinator”. During the driving process of the car, the energy is effectively distributed and managed, and various parts of work management are coordinated to achieve the maximum utilization of energy. The energy management system also participates in the energy recovery during the braking process of the vehicle body, assisting the control device to work and improving the battery life. At the same time, it will also monitor the battery temperature, terminal voltage, discharge current and other parameters in real time, to avoid overcharging and overdischarging of the battery, and effectively improve the battery life.
7. Charger
The charger device stores the alternating current of the external power grid into a corresponding voltage and stores the direct current in the battery while controlling the charging current. In the three stages of the charging process, the constant current section, the constant voltage section and the floating charging section are all controlled thereby.
8. Power steering system
The steering device is provided for turning a car, and is composed of a steering wheel, a steering gear, a steering mechanism, and a steering wheel. In order to improve driver operability, an electronically controlled power steering system EPS can be employed.
