Construction principle of power steering system

Power steering system is a steering system that uses both driver's physical strength and engine power as steering energy. Under normal circumstances, only a small part of the energy required for vehicle steering is provided by the driver, and most of it is provided by the engine through the power steering device. However, when the power steering device fails, the driver should be able to undertake the vehicle steering task independently. Therefore, the power steering system is formed by adding a set of power steering device on the basis of mechanical steering system.

For heavy-duty vehicles with a total mass of more than 50t, once the power steering device fails, the force applied to the steering knuckle by the driver through the mechanical transmission system is far from enough to deflect the steering wheel and realize steering. Therefore, the power steering device of this vehicle should be particularly reliable.

Fig. 2 is a schematic diagram of the composition of a hydraulic power steering system and the pipeline layout of the hydraulic power steering device. The components belonging to the power steering device are: steering oil tank 9, steering oil pump 10, steering control valve 5 and steering power cylinder 12. When the driver rotates the steering wheel 1 (left steering) counterclockwise, the steering rocker arm 7 drives the steering tie rod 6 forward. The tension of the tie rod acts on the steering knuckle arm 4 and is successively transmitted to the trapezoidal arm 3 and the tie rod 11 to move it to the right. At the same time, the steering tie rod also drives the spool valve in steering control valve 5 to connect the right chamber of steering power cylinder 12 to the steering oil tank with zero liquid level pressure. The high-pressure oil of oil pump 10 enters the left chamber of the steering power cylinder, so the piston of the steering power cylinder receives a hydraulic force to the right, which is applied to tie rod 11 through the push rod to move it to the right. In this way, the small steering torque applied by the driver to the steering wheel can overcome the steering resistance torque acting on the steering wheel on the ground.