The energy required for the steering of a car using a power steering system, under normal circumstances, only a small part is the physical energy provided by the driver, and most of it is the hydraulic energy provided by the oil pump (or air compressor) driven by the engine (or motor) (Or air pressure energy).

It is used to convert part of the mechanical energy output by the engine (or motor) into pressure energy, and under the control of the driver, apply hydraulic or pneumatic forces in different directions to the steering gear or a transmission member in the steering gear to help the driver A series of parts with insufficient force are collectively referred to as power steering gears. The following describes the types and working principles of power steering gears.

(1) Type of power steering gear

According to the different energy transmission media, the power steering gear has two types: pneumatic and hydraulic. Pneumatic power steering gear should not be used for trucks with extremely heavy loading, because the working pressure of the pneumatic system is low (generally not higher than 0.7MPa), and when used in heavy vehicles, the size of its components will be too large. The working pressure of hydraulic power steering gear can be as high as 10MPa or more, so the size of its components is small. The hydraulic system works without noise, has a short working lag time, and can absorb the impact from uneven roads. Therefore, hydraulic power steering gears have been widely used in various types of automobiles.

According to the different arrangement and connection relationship of the mechanical steering gear, the steering power cylinder and the steering control valve in the steering device, the hydraulic power steering device is divided into an integral type (mechanical steering gear, steering power cylinder and steering control valve) Designed as one), combined type (the mechanical steering gear and the steering control valve are designed together, the steering power cylinder is independent) and the separated type (the mechanical steering gear is independent, the steering control valve and the steering power cylinder are designed as one) Structure type.

Only the hydraulic integral power steering gear will be introduced here.

(2) The working principle of the power steering system

The power steering system is composed of a set of power assist devices on the basis of the mechanical steering system. As shown in the figure below, the steering oil pump 6 is installed on the engine, driven by the crankshaft through a belt and outputting hydraulic oil. The steering oil tank 5 has oil inlet and outlet pipe joints, which are respectively connected with the steering oil pump and the steering control valve 2 through oil pipes. The steering control valve is used to change the oil circuit. The mechanical steering gear and the cylinder block form two left and right working chambers, which are respectively connected by an oil passage and a steering control valve.

When the car is traveling in a straight line, the steering control valve 2 connects the working fluid pumped by the steering oil pump 6 with the oil tank, the steering oil pump is in an unloading state, and the power steering does not have a boosting effect. When the car needs to turn to the right, the driver turns the steering wheel to the right, and the steering control valve connects the working fluid pumped by the steering oil pump to the R cavity, and connects the L cavity to the oil tank. Under the action of oil pressure, The piston moves downwards, and the left and right wheels are deflected to the right through the transmission structure, thereby realizing right steering. When turning to the left, the situation is reversed.