SR-11Steering SystemPower Steering (General Introduction)
power steering oil pump
power steering gear steering drive shaft
oil cup
Power steering
Introduction
Principal of Power Steering
The power steering is a kind of hydraulic device that use
the engine power to steer. The engine drive the power
steering oil pump to generate the hydraulic pressure, which
actuates the piston in steering gear, so that the worm shaft
can provide to the piston with a supplementary force, which
has relation with the pressure actuated on the piston.
Therefore, pressure increase is required if larger steering
force is needed, and the pressure variation is accomplished
through the control valve.
Intermediate position (forward straightly)
The liquid from the power steering oil pump is sent to
the control valve, which, if locates at the intermediate, will
allow the liquid to pass and enter into the drain outlet, finally
return the pump. At this time, it is difficult to increase the
pressure; meanwhile, due to the equal pressures at the both
sides of the power piston, it cannot move toward either side.
Steering time
When the steering drive shaft move toward either side,
the control valve will move together with it, in case one oil
passage is shut off, meanwhile open the other larger, the
liquid flow variation will increase the pressure, as result, the
unequal pressure at both sides of piston will make the piston
move toward the side of smaller pressure, therefore, the
liquid is pressed in the pump through the control valve.
pump control valve
drain outlet
power cylinde
power piston
segmental gear shaft worm shaftsteering gear
Pump
SR-12Steering SystemPower Steering (Introduction)
Suggestion on maintenance
The failure of power steering system usually relates to the
steering difficulty due to lack of supplementary force. In such
case, it is the first to verify the problem is produced by the pump
or steering gear when repairing. In doing so, the problem can be
checked on vehicle with the pressure meter.
On-vehicle Inspection
As the power steering is a hydraulic pressure device, its
trouble usually caused by the lack of specified hydraulic
pressure or the abnormal work of control valve. As a result, it
cannot acquire the moderate hydraulic pressure.
In case the problem is caused by the pump, the steering
wheel will deflect toward right or left. On the other side, if the
problem is caused by control valve, when the steering wheel
rotates to left or right, the steering will become more difficult
due to the unequal supplementary force. However, when there
is wear on the piston sealing ring of power cylinder, it also cause
the hydraulic pressure loss that may lead into steering difficulty
toward right or left.
Before making inspection on vehicle, verify the power
steering system firstly to see whether there is air. If any, the air
volume will increase with the variation of hydraulic pressure,
which will cause the hydraulic pressure fluctuation that makes
the power steering work abnormally. In order to verify whether
there is any air in the system, check whether the liquid level
varies or not when the steering wheel rotates completely toward
the right or left. For instance, if there is air in the system, the air
will be compressed, which will reduce the liquid level
remarkably, when the steering wheel rotating. If there is no air
in system, the liquid level variation is very small even though
the hydraulic pressure increases. This is because the liquid
volume will not varies when being compressed. And the small
liquid level variation is caused by the expansion of hose
between the pump and steering gear when the hydraulic pres-
sure increasing.
Meanwhile, the air in system sometimes will cause the
pump or steering gear produce noise when the steering wheel
rotating completely toward a certain direction. After checking
or exchanging the pump or steering gear, the on-vehicle inspec-
tion should be often conducted to guarantee the normal work of
power steering system.
