2012 SSANGYONG RODIUS brake sensor

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3) HBA (Hydraulic Brake Assist System)
(1) Purpose
HBA (Hydraulic Brake Assist) system helps in an emergency braking situation when the driver
applies the brake fast, but not with sufficient pressure, which leads to dangerously long braking
distance. ECU recognizes the attempt at full braking and transmits the signal calling for full brake
pressure from the hydraulic booster. An inexperienced, elderly or physically weak driver may
suffer from the accident by not fully pressing the brake pedal when hard braking is required
under emergency. The HBA System increases the braking force under urgent situations to
enhance the inputted braking force from the driver.
Based on the fact that some drivers depress the brake pedal too soft even under when hard
braking is necessary, the HECU system is a safety supplementary system that builds high braking
force during initial braking according to pressure value of the brake pressure sensor and the
pressure changes of the pressure sensor intervals.
When the system is designed to apply high braking force when brake pedal is depressed softly by
an elderly or physically weak driver, the vehicle will make abrupt stopping under normal braking
situation due to high braking pressure at each wheels.

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(2) Operation
The brake pressure value and the changed value of the pressure sensor are the conditions in
which the HBA System operates. There are 2 pressure sensors under the master cylinder. When
the ESP ECU system determines that emergency braking is present, the pump operates, the
brake fluid in the master cylinder is sent to the pump and the braking pressure is delivered to the
wheels via the inlet valves.
If the drive depress the brake pedal slowly, the pressure change is not high. In this case, only the
conventional brake system with booster is activated.

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4. SCHEMATIC DIAGRAM
When equipped with ABS, the braking force at each wheel will be controlled with 3-channel 4-
sensor method. And when equipped with ESP, 4 wheels will be controlled independently with 4-
channel method. (When controlling ABS system only, it will be operated with 3-channel method.)
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 increase, decrease or unchanged conditions.
▶The warning lamp comes on and warning beep sounds when the ESP is operating
Driving feeling when the ESP is operating ▶
▶Noise and vibration that driver senses when the ESP is operating
1) Hydraulic Circuit Diagram
When the ESP operates during vehicle movement, the ESP warning lamp on the instrument
panel flickers and beep comes on every 0.1 seconds. The ESP operation shows that the vehicle
stability is extremely unstable and it is used to warn the driver. The ESP system is just a
supplementary system for the vehicle motion and it cannot control the vehicle when it exceeds
the physical limits. Do not solely rely on the system but be advised to drive the vehicle safely.
When the ESP system activates, the driving feeling can be different depending on vehicle
driving conditions. For example, you will feel differently when the ESP system is activated during
when ABS is operating with the brakes applied and when brakes are not applied on a curve.
Thus, the ESP system would make the driver feel more abruptly when the brakes are applied
during the ESP system activation.
The ESP system may transfer noise and vibration to the 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 feel noise and vibration due to sudden
brake application. Also, the ESP system controls the engine output. So, the driver may notice
the engine output decrease even when the accelerator pedal is being applied.

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(2) 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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Brake Pressure Sensor, ESP Sensor, Sensor Cluster, ESP OFF Switch ▶

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2) EBD (Electronic Brake Force Distribution) System
▶System description
As an add-on logic to the ABS base algorithm, EBD works in a range in which the intervention
thresholds for ABS control are not reached yet.
EBD ensures that the rear wheels are sensitively monitored for slip with respect to the front axle. If slip is
detected, the inlet valves for the rear wheels are switched to pressure hold to prevent a further increase
in pressure at the rear-wheel breaks, thus electronically reproducing
a pressure-reduction function at the rear-wheel brakes.
ABS features an enhanced algorithm which includes control of the brake force distribution between the
front and rear axles. This is called Electronic Brake Distribution. In an unloading car condition the brake
efficiency is comparable to the conventional system but for a fully loaded vehicle the efficiency of the
EBD system is higher due to the better use of rear axle braking capability.
▶Advantages
Elimination of conventional proportioning valve EBD utilizes the existing rear axle wheel speed
sensor to monitor rear wheel slip.
Based on many variables in algorithm a pressure hold, increase and/or decrease pulsetrain may be
triggered at the rear wheels insuring vehicle stability.
Vehicle approaches the ideal brake force distribution (front to rear).
Constant brake force distribution during vehicle lifetime.
EBD function is monitored via ABS safety logic (conventional proportioning valves are not
monitorable). ·
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3) Important Notice
The modulators for production line are not filled with the brake fluid (dry type). But, for after service, they
are filled with the brake fluid (wet type).
Make sure to keep the procedures in service manual when bleeding the air from the brake lines.
Be familiar with the lamp ON conditions to provide the correct information and reliability to customers.
ECU monitors the valve and motor for ABS when the vehicle speed approaches 5 km/h. At this time, you
can hear the clattering noise. 1.
2.
3.

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4. HYDRAULIC CIRCUIT DIAGRAM
1) Hydraulic Circuit of ABS
The vehicle equipped only with the ABS controls the wheel’s braking force using three 3-channel
4-sensor method. The front wheels that are the primary circuit of the brake system is composed of two
wheel speed sensors and two channel valves system with two inlet valves and two outlet valves. The
rear wheels that are the secondary circuit of the brake system is composed of two wheel speed sensors,
one inlet valve and one outlet valve. This system is similar to the one from the previous model.