The motor is divided into two types: DC and AC, and in principle, both can be used as automotive motors. The DC motor is widely used, the technology is mature, and the reverse control of start-stop speed regulation is very convenient, which is especially suitable for the characteristics of low-voltage DC power supply of solar cars. The AC asynchronous motor has the characteristics of light weight, small size, high efficiency and low cost. If it is used for solar cars, an inverter must be installed. The AC variable frequency motor is convenient for speed regulation and energy saving, and is an important way of electric car transmission. The following are some of the most widely used automotive motors.
1. DC motor
(1) The construction principle and type of DC motor.
The structure of the DC motor consists of the magnetic pole (including the excitation coil) fixed on the casing and the rotor (including the armature coil) fixed on the central rotating shaft of the casing. It is a DC motor. According to different excitation methods, DC motors can be divided into 4 types, as shown in Figure 1.
(2) Characteristics and load characteristics of DC motors.
The characteristics and load characteristics of the DC motor are shown in Figure 2. It can be seen from the figure that there are considerable differences in the characteristics of different types of DC motors. The shape characteristics of a certain permanent magnet motor in the figure show the relationship between the output torque M, the output power P1 and P2 and the efficiency EFF when the input voltage U, current I and speed n are different. When the current I and the rotational speed n, a higher efficiency value can be obtained.
(3) The grades and parameters of commonly used DC motors.
It can be seen from Figure 3 that the grade of the motor can reflect its parameter type and main characteristics. There are two types of DC motors: servo motors (SZ) and permanent magnet DC motors (ZYT). The motor is mainly selected for power and speed. Generally, the geared motor is mostly used for cars. The model of the geared motor is added with J at the front and PX64A1 at the back.
2. Permanent magnet brushless motor
(1) Principle of permanent magnet brushless motor.
The difference between an uncontrolled motor and a general motor is that there is no brush. Brushless DC motors have stator coils and permanent magnet rotors without brushes and commutators inside. The stator coil is connected to the control electronic circuit, and the motor electronic circuit is similar to the commutator, which drives the appropriate coils; the stator coil is driven by the current rotating around the stator to cut the magnetic field lines of the hydromagnetic rotor to generate the torque direct output. No other motors are more efficient, run faster and quieter, cost less to manufacture, and are easier to maintain. Figure 4(a) for the appearance of the permanent magnet non-dramatic motor, and Figure 4(b) and (e) for its structure. The 9 coils fixed on the motor casing are divided into three groups, and the windings on the pole are divided into three groups to form a star. The shape connection method leads to 3 wires A, B and C as the stator; a flip-shaped permanent mag net iron core is used as the rotor, the concentric shafts at both ends of the iron core, one end is the drive shaft, the other end is the accessory shaft, and the accessories box is installed with Hall sensors and Hall sensor magnet. The lead wire of the stator coil is connected to the electronic control circuit, and its commutation process is shown in Figure 4(d) Time-sharing current flows through the stator coil to generate alternating magnetic lines of force to cut the magnetic lines of the permanent magnet rotor and make the rotor rotate. Its electrical control principle is shown in Figure 4(e), and the rotor position can also be estimated and adjusted through the back EMF voltage information. The position detection and current detection and adjustment results are compared and input to the coil in a time-sharing manner, and the rotating magnetic field is controlled by an electronic circuit to replace the brush commutation to make the motor run, which is called a non-auxiliary motor .
(2) The structure of a typical brushless motor.
The structure of a typical brushless motor is shown in Figure 5. Its power can reach 3~5kW and the maximum torque can reach 25.2N m. Now there are a series of brushless motor systems with control boxes for users to choose and use.
(3) Motor series and frame assembly.
The power of the rear axle motor products of a factory is 3~20kW. The overall assembly of the motor, the rear axle and the frame is shown in Figure 6.
(4) Representation method of brushless motor model.
The representation method of the brushless motor model and its example are shown in Figure 7. In the product name, X in SwX stands for rare earth permanent magnet, W stands for brushless, S stands for DC motor; T in SWT stands for ferrite permanent magnet magnet, and SXPX stands for rare earth permanent magnet wire wound disc DC motor. Brushless motors are mostly made into disc motors. The 5kW brushless motor in Figure 6 is 126mm long and 206mm in diameter, which is a disc motor.
3. disc type high torque motor
(1) The structure of the disc motor.
The principle of the disc motor is shown in Figure 8(a). The magnetic field lines generated by the permanent magnets fixed on the main end cover are rotated and cut by the coils fixed on the rotor to generate current, and the current is input or output by wires through the commutator and brush. If the power (wind turbine, water turbine, steam turbine, motor, etc.) drives the rotor to rotate, the output current becomes a generator; otherwise, the input current can make the rotor rotate and drive the load to rotate into a motor. The disc motor is a plane coil as shown in Figure 8(b), which is encapsulated in an insulator and pressed into a disc shape to form an ironless rotor structure, and is connected to the commutator as shown in Figure 8(c), the commutator is installed at the main end The brush on the cover is pressed tightly as shown in Figure 8(d). The final assembly is shown in Figure 8(e). The characteristics of the disc motor are: small size, light weight, compact structure and high efficiency. Disc motors can also be made into generators.
(2) Typical brushless disc motor structure and technical parameters.
The disc motor can also be made into a brushless disc motor. The typical structure and technical parameters of the brushless disc motor are shown in Figure 9. The power can be large or small, which is the basis of the electric wheel hub.
(3) Installation and application of disc motor.
The disc motor can be installed vertically or horizontally, and can also be integrated with an electric wheel or bicycle wheel as an electric wheel, and can also be installed together with a planetary reducer to form a disc gear motor, as shown in Figure 10. The disc motor can also be used as a wheel for a higher-power electric car, and the drive mechanism and electronic devices can be installed inside it, which is isolated from the external environment by a layer of impregnating compound. The motor is completely sealed with other auxiliary devices through insulating substances, which is a mechatronic in-wheel motor.
4. hub motors
(1) Characteristics and development of in-wheel motor technology.
In-wheel motor technology is also known as in-wheel motor technology. Its biggest feature is that power, transmission and braking devices are integrated into the wheel hub, thus greatly simplifying the mechanical part of electric cars. As early as 1900, Porsche first produced electric cars with in-wheel motors in the front wheels. In the 1970s, in-wheel motors were used in mining transport cars and other fields. For in-wheel motors used in passenger cars, Japanese manufacturers have carried out research and development earlier . The overall structure and internal structure of in-wheel motors are shown in Figure 11. (a) It is a relatively simple in-wheel motor for low-power cars. Several solar electric trolleys we have developed use this in-wheel motor with a power of 0.25kW. (b) It is a 30kW in-wheel motor for large cars, which incorporates springs, brake discs, suspensions, etc. into the hub. (c) Structure diagram of the drive/suspension system developed for Michelin that integrates in -wheel motors, electronic systems, and active suspension into the wheel.
(2) In-wheel motor type.
Now in-wheel motors basically use brushless disc motors. The in-wheel motor drive system is divided into inner rotor type and outer rotor type according to the rotor form of the motor. Among them, the outer rotor type adopts a low-speed outer transmission sub-motor, the maximum speed of the motor is 1000~1500r/min, there is no reduction device, and the speed of the wheel is the same as that of the motor; the inner rotor type adopts a high-speed inner rotor motor, and a reducer with a fixed transmission ratio is required. , In order to obtain higher power density, the speed of the motor can be as high as 10000r/min. Due to the advent of planetary gear reducers, the inner-rotor in -wheel motors are more competitive in terms of power density. The typical inner-rotor in-wheel motor drive structure is shown in Figure 12(a). Figure 12(b) shows that the in-wheel motor designed by GM for a 150t heavy-duty truck is driven by an inner rotor and has a large motor speed. It can be seen from the fig ure that there are corresponding gears inside. deceleration system.
(3) Advantages and disadvantages of in-wheel motor transmission.
Its advantages are: 1. It saves a lot of mechanical transmission components such as clutches, transmissions, differentials and transmission shafts, which can reduce the weight of the car, expand the use space, improve the transmission efficiency, simplify the structure of the car body, and be easy to operate and maintain; 2. No axles, Two-wheel, four-wheel, and eight-wheel can be operated independently or in combination, which is convenient for electronic control of energy increase and decrease and differential steering, which is conducive to starting and regenerative braking; ③It is easy to match with a variety of new energy cars. The disadvantages are: ① the increase of the unsprung mass and the moment of inertia of the wheel has a certain influence on the operation; ② the electric braking capacity is limited, and the braking energy consumption is more; ③ the requirements for waterproof, dustproof and cooling are high.
(4) Application of in-wheel motors.
The in-wheel motor is easy to match with a variety of new energy cars. As shown in Figure 13, the structure of the car can be simplified and the efficiency can be improved. At the same time, the chassis and floor at the front and rear axles of the car have no protruding parts, and can be made into a flat chassis and floor. . Among them, the use of pure electric cars is the most simple, and can be designed into two-wheel drive, four-wheel drive, eight-wheel drive and more double-wheel drive. Differential steering can be electronically controlled, and power requirements can also be adjusted according to operating conditions.
5. Comparison of transmission combinations of various cars
(1) Fuel cars.
The power and transmission system of the fuel car is shown in Figure 14(a). For traditional fuel cars, the structure of the internal combustion engine in the power part is very complex, with low energy efficiency, large exhaust emissions, and difficult control and maintenance. Mechanical parts clutches, transmissions, drive shafts, differentials and even transfer cases are all essential, and these components not only have high mass, but also make the structure of the car more complex, and there are also problems that require regular maintenance and have a high failure rate. problem.
(2) Pure electric cars.
The power and transmission system of the pure electric car is shown in Figure 14(b). The battery pack is used instead of the internal combustion engine to drive the motor to make the car run, which simplifies the structure of the energy equipment and improves the energy utilization efficiency. The motor reducer and differential steering mechanism can also be integrated with the rear axle, which greatly simplifies the mechanical transmission structure, and has a dedicated controller, which makes the structural production of the car simpler and more standardized. At present , pure electric cars still have the following problems: First, the continuation mileage is short and the charging time is long, which can be solved by adding a supercapacitor battery or using a hybrid supercapacitor lithium battery on the basis of the lithium battery. The second is the difficulty of charging. In addition to vigorously promoting new charging piles, another solution is to replace the bulbs of solar stree t lamps with LED bulbs, install charging piles scattered along the way at the base of street lamps, and use the surplus solar energy to charge electric cars. It is a good way to save more and more quickly, but it will also use mains power to charge.
(3) Solar electric wheel car.
The further development of electric cars is the electric hub car. The solar electric car in Figure 14(c) uses four electric hubs that are not connected by axles and directly mounted on the chassis (refer to Figure 13), which is directly driven by the battery through the controller. The electric wheel travels further simplifies the mechanical structure, and it is easy to carry out energy combination and electronically controlled differential steering. At the same time, it is easy to combine with battery and solar energy to form a solar electric car, and the battery can be floated by its own solar power supply.