7.2.3 System Working Principle
7.2.3.1 Hydraulic Power Rack and Pinion
Steering Working Principle
Intermediate Shaft
Pinion
Steering Tie Rod
Rack
Steering
Tie Rod
Pinion Rotation
Rack Movement
FE07-1001b
When there is no hydraulic pressure assistance, the steering
working principle is as shown in the graphic. The torque applied
on the steering wheel, passes through the intermediate shaft
to the steering drive gear (steering control valve gear), because
the drive gear tooth (steering control valve gear tooth) and the
rack teeth are in meshing state, it will convert the torque to rack
linear force, move the rack. Linear force passes through the
inner and outer steering tie rod, to the steering knuckle, which
steers the wheel.
PAS
Pump
Power Assisted Steering
(PAS) Fluid Reservoir
Return Hose
Pressure
Hose
Valve
Assembly
Steering System Assembly
FE07-1002b
Rack and pinion with hydraulic pressure assistance steering
system is as shown in the graphic. The mechanical rack and
pinion steering, steering cylinder and steering control valve are
designed to be integrated to form the integral power steering
system. Power cylinder piston and the rack is made as a whole,
the power cylinder is divided into about two chambers.
Steering Control
Valve Gear
Shaft
Valve Core
FE07-1003b
When the steering wheel is not turned, the steering control
valve is in the middle position, fluid the master cylinder flows
through the steering control valve inlet into the valve cavity. As
the steering control valve is in the middle position, so that
power cylinder two chamber are connected. The fluid flows
from the steering control valve outlet to to the fluid reservoir, so
the hydraulic power does not work.
7-6
Hydraulic Power Steering System
Steering System
EC718/EC718RV EC715/EC715RV 10/2009
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