Page 338 of 444

0-20
RODIUS 2007.07
4892-01
ABS SYSTEM
Pressure Decreases in the Circuit when ABS is Operating ▶
Pressure Increases in the Circuit when ABS is Operating ▶
Even when the hydraulic pressure on each circuit is stable, the wheel can be locked as the
wheel speed decreases. This is when the ABS ECU detects the wheel speed and the vehicle
speed and gives the optimized braking without locking the wheels. In order to prevent from
hydraulic pressure increases, the inlet valve is closed and the outlet valve is opened. Also, the
oil is sent to the low pressure changer and the wheel speed increases again. The ABS ECU
operates the pump to circulate the oil in the low pressure chamber to the master cylinder. This
may make the driver to feel the brake pedal vibration and some noises.
As the wheel speed increases, the inlet valve opens and the wheel’s pressure increases
due to the master cylinder pressure. The oil in the low pressure chamber circulates to the wheel
by the pump and the wheel speed decreases as the hydraulic pressure at wheel increases. This
operation continues repetitively until there are no signs that the ECU is locking the wheels.
When the ABS hydraulic pressure control takes place, there may be some vibration and noises
at the brake pedal.
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POWER STEERING SYSTEM
RODIUS 2007.07
4610-00
4. OVERVIEW
The power steering system consists of pump, oil reservoir, rack and pinion gear. The power
steering pump is a vane type and delivers hydraulic pressure to operate the power steering
system. The pressure relief valve in pump controls the discharging pressure.
The rotary valve in rack and pinion gear directs the oil from the power steering pump to one
side of rack piston.
The integrated rack piston converts the hydraulic pressure to linear movement.
The operating force of rack moves the wheels through tie rod, tie rod end and steering knuckle.
Even though the hydraulic pressure cannot be generated, a driver can steer the vehicle without
power assist but it needs very high steering force.
In this case, the operating force of steering wheel is conveyed to pinion, and the movement o
f
pinion moves the rack through pinion gear combined to rack gear.
5. COMPONENTS
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0-8
RODIUS 2007.07
4610-00
POWER STEERING SYSTEM
3. POWER STEERING PUMP
The vane type pump that is connected to engine by belt is used for the power steering system.
This pump generates and controls a proper hydraulic pressure and flows by using the flow
control valve and pressure relief valve.
The flow control valve regulates the excessive amount of discharging oil. When the steering
wheel is stationary or the oil circuit is blocked, the pressure relief valve returns the ove
r
pressurized oil to the oil reservoir.
4. OIL RESERVOIR
The oil reservoir sends the oil to the power steering pump and receives the oil from the power
steering gear.
The oil level in the reservoir depends on the steering wheel positions. therefore, measure the oil
level when the steering wheel is positioned at straight ahead direction (neutral).
Steering pump Reservoir tank