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Circuit description ▶
When compared to the vehicle equipped with ABS/EBD only, the internal hydraulic circuit has a
normally-open separation valve and a shuttle valve in primary circuit and in secondary circuit.
When the vehicle brakes are not applied during engine running or when applying the non-ABS operating
brakes, the normally-open separation valve and the inlet valve are open, whereas the normally-closed
shuttle valve and the outlet valve are closed.
When the ESP system is operating, the normally-open separation valve will be closed by the solenoid
valve operation and the hydraulic circuit will be established by the shuttle valve. Then, the inlet and outlet
valves will be closed or open depending on the braking pressure RISE, HOLD or DUMP conditions.
Flashing warning lamp and warning sound during ESP operation ▶
When the ESP operates while the vehicle is moving, the ESP warning lamp on the instrument panel
flickers and the buzzer sounds at every 0.1 second. The ESP lamp operation is to inform a driver that the
vehicle is extremely unstable.
The ESP system is just a supplementary system for the vehicle and it cannot control the vehicle over the
physical limit. Do not solely rely on the system but be advised to drive the vehicle safely.
Drive feeling during ESP operation ▶
When the ESP system activates, the driving feeling can be different depending on vehicle driving
conditions. For example, it will feel different when the ESP system is activated while the ABS is operated
by depressing the brake pedal and when the ESP system is in control without the brake pedal
depressed on the same curve.
If the ESP system operates with the brake applied, the brake pressure will be increased on the
corresponding wheel which already has braking pressure for the ESP controls. In other words, the ESP
system would make the driver feel more abruptly braked compared to the situation that the braking
pressure is applied to wheel which had no braking force.
Noise and vibration that driver senses during ESP operation ▶
The ESP system may transfer noise and vibration to a driver due to the pressure changes caused by the
motor and valve operations in a very short period of time.
Extreme cornering will trigger the ESP operation and this will make the driver sense noise and vibration
due to sudden brake application.
Also, the ESP system controls the engine power. Therefore, the driver may notice the engine power
decreases even when the accelerator pedal is depressed.
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11-234890-10
1) Idling and Normal Braking Condition
In this position, the separation valve and the inlet valve are open (normal open), the electrically operated
shuttle valve and the outlet valve are closed.
When the brake is applied under these conditions, the brake fluid will be sent to each wheel via the
separation valve and inlet valve.
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2) DUMP (ESP is working) Mode
The pressure decreases just before the wheel speed drops and the wheels are locked.
The inlet valve closes and the outlet valve opens as in the ABS HECU and the oil is gathered at the low
pressure chamber while no additional oil is being supplied. Then the pump operates to allow fast oil
drainage. The shuttle valve and the separation valve do not operate while decompression.
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3) HOLD (ESP is working) Mode
The Inlet valve and outlet valve will be closed to maintain the pressure in the hydraulic circuit applied at
the wheels. By closing the valves, the hydraulic pressure at the wheels will not be lost or supplied any
more. During ESP operation, the separation valve closes and only the shuttle valve at the pump opens.
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4) RISE (ESP is working) Mode
The shuttle valve and inlet valve will be open and the separation valve and outlet valve will be closed.
Then, the pump is operated. When ESP operates while the ABS is operating, the pressure will be
increased continuously until just before the corresponding wheel gets locked.
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5) Hydraulic Circuit of HBA
The above figure shows one front and one rear wheel and the same hydraulic circuit forms as in the
ESP operation. When HECU recognizes that it is an emergency and it is required for hard braking,
depending on the pressure value of the brake pressure sensor and pressure changes caused by the
pressure sensor timing, it operates the pump immediately to apply the brake pressure at the wheels.
Then, the pressure in the pump increases until just before the corresponding wheel gets locked. The
motor still keeps rotating and the outlet valve and the separation valve will stay closed. When the wheel
starts to lock, the HBA function cancels and switches to ABS operation.
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12-34610-01
1. SPECIFICATIONS
Description Specification
Steering wheel Type 4-spoke type
Gear box
(HPS)Type Rack and pinion type
Gear ratio 40.245
Steering angle Inner36.2˚
Outer32.4˚
Oil pump
(HPS)Type Vane type
Maximum pressure (kgf/cm2)90 ± 3
Pulley size (mm)Ø115
Operating temperature-40℃~150℃
Minimum turning radius (m) 5.8
Steering oil Type S-PSF-3
Capacity (L) Approx. 1.0
Service interval Daily check and add if necessary.
Steering column shaft Tilting angle-4.0/ 0° /+4.0° / +8.0°
This section describes the power steering pump and gear box based on the HPS (Hydraulic Power
Steering) system. For the information of the SSPS (Speed Sensing Power Steering) system, refer to
SSPS section under CHASSIS.
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Steering Wheel Body & Heated Wire Controller
Heated pad and controller added to steering wheel body
Heated Steering Wheel Adopted ▶
HEATED STEERING WHEEL SWITCH
Heated steering wheel switch added to cluster fascia panel switch assembly
Heated pad (inside)
controller