Steering Gear: Description and Operation

DESCRIPTION
The steering gear box consists of two sections: one including a cylinder and the other a valve. Main components of the cylinder section are a gear box, a rack and a tube and those of the valve section are a valve case, a sleeve and a stub shaft. The sleeve is linked with the pinion through a pin and the valve and stub shaft are integrated into one unit. Then the pinion and the stub shaft are linked to each other by means of the torsion bar.
Thus, when the stub shaft moves, the valve changes its position, thereby switching the hydraulic passage from the pump to the cylinder to help steering operation.
When turning the steering wheel feels heavy due to Power Steering (P/S) fluid leakage or for some other reason (i.e., when in the manual steering mode), the stub shaft and pinion are in direct linkage and the force is output directly through the pinion and rack.





OPERATION
When Steering Wheel Held at Straight Position
When the steering wheel is not turned, the valve is held at the neutral position by the torsion bar and the fluid from the pump flow through the valve back to the tank.

When Steering Wheel Turned (to the right)
Turning the steering wheel clockwise will cause the stub shaft to turn clockwise, twisting the torsion bar.
Then the valve is switched to allow the fluid pressure to be applied to the cylinder which then pushes the rack.
As the rack moves, the pinion turns clockwise to actuate the torsion bar which then causes the valve to return to the neutral position. This is called the feed back operation of the power steering system.