Chery QQ6 (S21) / S12LHD. Manual — part 120

Page 5 of 38

2． System Structure

Including:

Electronic Control Unit

The sensor will calculate the speed and acceleration/deceleration
of four wheels and judge the skid status of the wheels and
therefore drive the electromagnetic valve and motor, control the
pressure increment and pressure reduction, maintain the status,
and etc.

Hydraulic Unit

The basic hydraulic circuit is comprised of the 1

st

circuit and the

2

nd

circuit that is active only when the ABS is functioning and is

the integral part that controls the hydraulic parts transmitted to
various wheels.
Depending on the transmitted signal output of the sensor, the
ECU performs the calculation and judges the skid status to
determine if it’s necessary to run the ABS. Therefore, depending
on the control procedure of the ECU, the electromagnetic valve
and the motor will be started to control the pressure increment
and pressure reduction, maintain the status, and etc.

Sensor

In order to make the ECU to calculate the speed and acceleration/
deceleration of the four wheels, it always transmits the revolution
measurement of the gear ring to the ECU.

Motor

When the ABS is functioning, the motor will rotate following the
ECU signal and convert the rotation movement into linear
reciprocated movement via the bearing to circulate the brake oil.

Motor

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3． System Functioning Theory

3.1 ABS Control Theory

3.2 ABS Control Mode

①

Functioning Status of General Brake

For the vehicles equipped with ABS, if the braking pressure applied onto the wheels is not enough
to lock the wheels, the pressure generated by the general pump will transmit to the wheel branch
pump via the normal open valve to obtain the braking effects. When it’s unnecessary for further
braking, the driver will reduce the pressure on the brake pedal and then the brake liquid of various
wheels will return to the general pump to reduce the braking pressure.

Solenoid Valve

Power Status

Solenoid Valve Status

Normal Open Valve (NO Valve)

OFF

Open

Normal Close Valve (NC Valve)

OFF

Close

ABS Control Range

Slip Ratio

Start

Pressure

Reduction

Start
Pressure
Increment

Tire braking force (μs)

Body Speed – Wheel Speed

Body Speed

Skid Ratio

Tire transversal friction force (μs)

λ= 0%: The status that the brake is

not functioning

λ= 100%: The status that the wheels

are locked

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ABS

②

Functioning (Pressure Reduction) Status

For the vehicles equipped with ABS, if the applied braking pressure is too big, the wheels will
have rapider deceleration than that of vehicle body, which will be ready to result the lock of the
wheels. Under such case, the ECU will transmit the code for wheel pressure reduction to the HCU,
namely turn off the normal open valve and turn on the normal close valve to reduce the pressure of
wheel branch pump. In such case, the brake oil released by the wheel branch pump is temporarily
stored in the low pressure accumulator (LPA). The brake oil stored in the LPA will be sucked
back to the general pump by the oil pump started following the rotation of the motor. The brake
liquid will return to the high pressure accumulator (HPA) in the pipeline and reduce the high
pressure pulse generated by the running of the oil pump by means of the orifice hydraulic
resistance.

Solenoid Valve

Power Status

Solenoid Valve Status

Normal Open Valve (NO Valve)

ON

Close

Normal Close Valve (NC Valve)

ON

Open

ABS

③

Functioning (Maintaining) Status

When the branch pumps of the wheels are applied with proper pressure via the pressure reduction
or pressure increment, the normal open valve and the normal close valve will be turned off to
maintain the pressure of the wheel branch pumps. For the operations mentioned in above

~

②

④,

depending on that wheels are locked or not, the ABS will function till the vehicle is fully stopped
and therefore the safety and steering capability of the vehicle are guaranteed.

Solenoid Valve

Power Status

Solenoid Valve Status

Normal Open Valve (NO Valve)

ON

Close

Normal Close Valve (NC Valve)

OFF

Close

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ABS

④

Functioning (Pressure Increment) Status

During the implementation of the pressure reduction, if the excessive brake liquid is drained or the
friction coefficient between the wheels and the road is increased, it’s necessary to increase the
pressure of various wheels. Under such case, the ECU will transmit the code for wheel pressure
increment to the HCU, namely turn on the normal open valve and turn off the normal close valve to
increase the pressure of wheel branch pump. During the implementation of the pressure reduction,
the brake liquid stored in the low pressure accumulator (LPA) will continue to rotate the motor to
drain the brake liquid under the pressure increment status. In such case, the brake liquid is supplied
to branch pump of various wheels via the general pump and normal open valve. The brake liquid
will return to the high pressure accumulator (HPA) in the pipeline and reduce the high pressure pulse
generated by the running of the oil pump by means of the orifice hydraulic resistance.

Solenoid Valve

Power Status

Solenoid Valve Status

Normal Open Valve (NO Valve)

OFF

Open

Normal Close Valve (NC Valve)

OFF

Close