Power steering system
The power steering system is a steering system that uses both the driver’s physical strength and the engine power as the steering energy. Under normal circumstances, only a small part of the energy required for the steering of the car 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 generally be able to independently undertake the task of steering the vehicle. Therefore, the power steering system is formed by adding a set of power steering devices on the basis of the mechanical steering system.
For a heavy-duty vehicle with a maximum total mass of more than 50t, once the power steering device fails, the force applied by the driver to the steering knuckle through the mechanical drive train is far from enough to deflect the steering wheel to achieve steering. Therefore, the power steering of such vehicles should be particularly reliable.
The components belonging to the power steering device are: steering oil tank, steering oil pump, steering control valve and steering power cylinder. When the driver turns the steering wheel counterclockwise (left steering), the steering rocker arm moves the steering straight rod forward. The pulling force of the straight tie rod acts on the steering knuckle arm, and is transmitted to the trapezoidal arm and the steering tie rod in turn to move it to the right. At the same time, the steering straight rod also drives the spool valve in the steering control valve, so that the right chamber of the steering power cylinder is connected to the steering oil tank with zero liquid surface pressure. The high-pressure oil of the oil pump enters the left cavity of the steering power cylinder, so the hydraulic force to the right on the piston of the steering power cylinder is applied to the tie rod through the push rod, and it also moves to the right. In this way, a small steering torque applied by the driver to the steering wheel can overcome the steering resistance torque acting on the steering wheel by the ground.