Mechanical hydraulic power steering system
The mechanical hydraulic power steering system is generally composed of hydraulic pump, oil pipe, pressure and flow control valve body, V-shaped transmission belt, oil storage tank and other components, as shown in Figure 1.
This system must work regardless of whether it is steering or not, and when the speed of the vehicle is low in large steering, the hydraulic pump needs to output more power to obtain a larger boost. Therefore, resources were wasted to a certain extent. You can recall: driving such a car, especially when turning at low speeds, feels that the direction is heavier and the engine is more laborious. Also, due to the high pressure of the hydraulic pump, it is easier to damage the booster system. In addition, the mechanical hydraulic power steering system is composed of hydraulic pumps, pipelines and cylinders. In order to maintain pressure, the system must be in working condition regardless of whether steering assistance is required, and the energy consumption is high. This is also one of the reasons for resource consumption. Generally, economical cars use mechanical hydraulic power assist systems.
Electronic hydraulic power steering system
Since mechanical hydraulic power assistance requires a significant consumption of engine power, people have made improvements on the basis of mechanical hydraulic power assistance and developed an electronic hydraulic power steering system that saves energy. The steering oil pump of this system is no longer directly driven by the engine, but by an electric motor, and an electronic control system is installed on the previous basis, so that the steering assist force is not only related to the steering angle, but also related to the vehicle speed.
A hydraulic reaction device and a liquid flow distribution valve are added to the mechanical structure, and the new electronic control system includes a vehicle speed sensor, solenoid valve, steering ECU, etc.
Electric Power Steering System (EPS)
The electric power steering system uses the power generated by the electric motor to assist the driver in power steering. The composition of EPS, although the structural components of different cars are not the same, but generally the same. It is generally composed of torque (steering) sensor, electronic control unit, electric motor, reducer, mechanical steering gear, and battery power supply.
When the car is turning, the torque sensor will "feel" the torque of the steering wheel and the direction to be rotated. These signals will be sent to the electronic control unit through the data bus, and the electronic control unit will use data signals such as the transmission torque and the direction to be turned. , To issue an action command to the motor controller, so that the motor will output a corresponding amount of torque according to specific needs, thereby generating power steering. If it does not turn, the system will not work, and it will be in a sleep state waiting to be called. Due to the working characteristics of electric power steering, you will feel that driving such a car has a better sense of direction and is more stable at high speeds. As the saying goes, the direction is not "floating". And because it does not work when it is not turning, it also saves energy to some extent. Generally, high-end cars use such power steering systems.