The new Reiz passenger car is equipped with a newer type of electric steering device. Modern car power steering, there are two types of hydraulic and electric, the vast majority of cars using hydraulic power steering. As the electric power steering system has a series of advantages, so the use of modern cars growing. Electric power steering has two basic forms, namely electro-hydraulic steering system and electric power steering system. The power steering system is powered by the motor. The structure of the electric steering is more complex, the technical content is higher. This paper analyzes the structure and basic principles of the system and its common faults, hoping to help the peers.
    First, Rui Zhi passenger car electric power steering system of the basic composition
    The electric power steering system is a steering system that is operated by the steering control unit to control the steering motor (see Figure 1). The driver controls the steering wheel steering torque, through the steering gear and steering rod to the steering wheel of the car; at the same time, the electronic control unit and then according to the current steering wheel steering torque steering wheel, then travel speed and a certain design requirements, Calculate the required steering power. And the required steering power is achieved by adjusting the motor voltage and current, so the steering wheel on the final steering torque, is the driver steering torque and steering electric power and the sum (the latter is much larger than the former). Electric power steering system directly use the power, it does not consume the engine's mechanical power, it will not directly affect the operation of the engine, which than the traditional hydraulic power steering system to save fuel.
    Second, the main components of the steering system
    The electric power steering system mainly comprises a torque sensor directly driven by a steering wheel, a lower pinion drive rack, a steering motor mounted in the middle of the steering column, a decelerating device, and a recirculating ball Type reduction gear; corner sensor, reflecting the power of the motor rotation and steering; rack shaft shell and left and right bar. Its structure shown in Figure 2.
    1. Steering torque sensor structure and working principle
    The steering torque sensor consists of two parts, which are mounted on the input shaft of the steering wheel and the output shaft of the steering pinion.
    (1) The rotor part is composed of two layers, and are equipped with torque sensor (shown in Figure 2). The input shaft and output shaft are integrally connected by a fine metal pin with pin holes above the rotor section (see Figure 3). Both the input shaft and the output shaft are of the upper part and are driven by the input shaft of the steering wheel of the car. The lower rotor drives the pinion to push the translation of the rack, driving the steering wheel to turn left and right.
  The upper part of the steering torque sensor is driven directly by the steering wheel, and its rotation is fully synchronized with the steering wheel shaft because there is no load at the lower end. But the lower part of the torque sensor with a steering gear (with a certain resistance), the middle through the torsion bar drive, resulting in the lower rotor rotation is relatively small, which causes the upper and lower rotor in the mechanical will produce relative angular displacement difference. When the car turns, the two shafts of the input and output shafts produce an angle difference corresponding to the steering torque when different steering conditions are encountered in different road conditions.
    (2) stator part also has two upper and lower coils, respectively, corresponding to the upper and lower rotor. Stator coil part of the two coil distribution, respectively, is the excitation coil and the detection coil (shown in Figure 4), on which a total of seven different colors of thin wire and the outside world. The excitation coil of the rotor part of the coil through the electromagnetic induction excitation; detection coil will be input and output shaft of the upper and lower angle difference (steering torque) detected, the electrical control unit to send electrical signals, the electrical signal is the stator coil On the two sets of sine wave phase difference, reflecting the torque sensor at this time to detect the size of the torque.
    2. Structure and working principle of boost motor and reducer
    In the middle of the middle of the steering tube, install the auxiliary motor and reducer (shown in Figure 2).
    Power supply motor for the brushless three-phase AC motor, stator coil for the three-phase double star connection (shown in Figure 5), the motor rotor is strong permanent magnet type. This motor design of the inertia of the smaller inertia, easy to drive when the car flexible to the operation. The direction of the motor to change the rotation is very convenient, but the three-phase power supply between any two-phase change that can achieve rapid steering power operation. And this motor has a low noise, high torque characteristics, to overcome the road when driving a variety of road resistance, flexible steering operation.
    (2) The power supply to the booster motor is 27 ~ 34V three-phase AC voltage. This electric power steering control unit, but also specifically set up a voltage rise of the inverter and the inductor energy storage coil, similar to the three-phase bridge, the battery voltage can be converted to 27 ~ 34V circuit. When the driver controls the steering wheel, it will automatically according to the size of the steering resistance, the output of 27 ~ 34V between the variable voltage; when the driver did not hit the direction or the vehicle straight line, the motor does not run, then the motor voltage is 0.
    (3) control the power of the boost motor to control the size of the steering power. The control unit of the electric power steering unit receives the signal of the torque sensor and the vehicle speed sensor and determines the current vehicle running condition based on the data of the rotation angle sensor and determines the magnitude of the boost current applied to the steering motor (as shown in Fig. 6).
    Steering motor also has overheat protection function, when the temperature exceeds the specified value, in order to protect the power supply and the motor is not overloaded, this time should limit the motor boost current until the temperature drop the allowable value so far.
    (4) the use of circular ball-type reduction mechanism. In order to reduce the rotational speed of the steering motor to obtain a greater torque, a recirculating ball type reduction gear is provided with the motor rotor inner casing. The tiny ball is circulated in four very smooth slots (as shown in Figure 2). The power is transmitted to the rack shaft for linear motion, pushing the two steering wheels to swing around to drive the car. As the ball is very small, in the fine processing of the guide groove rolling, so the transmission noise is minimal.
    3. The structure and working principle of corner sensor
    The sensor is an electromagnetic induction sensor, can turn the steering angle of the motor signal output to the control unit. The rotor of the sensor is a salient pole, and the rotor is connected to the motor rotor. Stator coil was ring-shaped, set in the rotor, through the electromagnetic induction principle, to detect the rotor corner. In the demolition can not be removed alone this corner sensor, only through the disintegration of the steering gear assembly, to check. But can be detected by the circuit connector on the stator.
    The steering control unit is installed in the bottom of the battery, in addition to processing sensor signal function, the control unit also has to enhance the battery voltage, inverter into three-phase current function. Also shorten the control unit and the power steering machine assembly between the cable length, can reduce the line voltage drop.
    Third, the basic working principle of electric power steering system
    1. Steering the control signal flow
    The steering signal flow is shown in Fig.
    2. Turn to initialization function
    When you replace or check the steering wheel, steering column, steering control unit and other components, the steering of the electrical control system should be initialized set, available detector or manual settings, manual initialization method is:
    (1) short wire Tc and chassis ground wire CG terminal,
    (2) turn on the ignition switch;
    (3) and then short-circuit the Ts and CG terminals;
    (4) Disconnect / connect the Tc terminal 20 times within 20 s;
    (5) confirm that the P / S warning light is on;
    (6) turn off the ignition switch to complete the electrical initialization work.
    The electric steering initialization connector is shown in Figure 8.
    Fourth, the advantages of electric power steering system
    1. can effectively enhance the economy of the whole car
    Electric steering only in the driver to manipulate the car when the power consumption, and more than 90% of the vehicle driving process does not need to turn, do not turn when the power does not consume. The hydraulic power steering system of the pump directly from the engine belt drive, even if the car does not turn, the hydraulic pump is running, thus consuming the engine power. Data statistics, compared to the two, electric steering system than hydraulic steering system fuel economy 3%.
    2. Make the steering control more flexible
    Steering wheel steering characteristics, steering feel and the stability of the car characteristics, can be adjusted and optimized by software, without the impact of engine speed and power, its function is clearly superior to the traditional hydraulic power system; with the body stability control system, The optimum steering response and steering force can be achieved at different speeds.
    3. Strong sense of road, fast response control
    Low-speed driving, the electric system to provide greater help, help the degree of increase with the speed gradually reduced. In order to improve the comfort of driving, most modern cars are equipped with wide low-pressure tires, which increases the contact area between the tire and the road, and the greater the steering resistance when the running resistance becomes larger. Even if the engine flameout, electric power steering system can work as usual, it is suitable for electric vehicles or hybrid cars.
    4. Peripheral structure is simple
    The quality of the steering device is lightweight and the structure is more compact. Because there is no hydraulic system, can save oil, oil, change the belt and other maintenance work.
    Fifth, Reiz turned to a heavy case
    Fault phenomenon
    A 2006 paragraph Reiz passenger car, in the process of running, found abnormal turn heavy, while the P / S light (as shown in Figure 9).
    Troubleshooting and troubleshooting
    Read the fault code for C1525, C1526, C1528. Which means that the corner sensor is not initialized; and the motor rotation angle sensor is faulty. Maintenance data indicates that when the C1528 fault code appears, the system enters the fail-safe state and the power steering system stops working.
    With the Toyota-specific detector IT-II to clear the fault code, C1528 can be cleared, and C1525, C1526 can not be cleared. And then the corner sensor to initialize the results of the detector shows the initialization failed, indicating that the motor rotation angle sensor is indeed a fault. Unplug the corner sensor connector and found that there are traces of water inside, line plug has covered a layer of green copper rust, there is corrosion phenomenon. Plug the water into the sensor signal short circuit, the electric steering control unit can not receive the angle sensor signal, so that the electric power steering system into the protection state, turn to help stop the work, the control unit at the same time record the error code C1528. Troubleshooting is very simple, remove the plug of water and rust, and then IT-II motor angle sensor to initialize, the fault completely ruled out. P / S lights are no longer lit, the steering wheel is easy and flexible, troubleshooting.
    Maintenance summary
    The waterproofing of electrical connectors should be given sufficient attention. Reiz turned to the system using a full electric way, so that the steering system structure is greatly simplified, completely solve the hydraulic pump and the direction of the traditional system of oil leakage system defects. But the attendant is the waterproofing of the electrical system. The steering gear is installed at the very bottom of the vehicle, and on the rainy day or flooding the road may cause the steering gear to enter the water so that the system does not work properly. Although the plug has been made waterproof measures, but when it is completely immersed in water when there is still possible water. The car's failure is occurring in the rain, this phenomenon reminds our owners in the rainy days or wading to be particularly careful when driving, try to escape the deep water area, to prevent the steering system of electrical plug water caused by failure.