Brake System chery qq
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Transcript of Brake System chery qq
S11 Brake System
S11 Brake System Introduction
ABS warning lampRight brake lamp
Left brake lamp
Brake switch
Left rear wheel speed sensor
ABS wheel speed sensor
ABS control moduleABS master
cylinder
Brake lamp switchVacuum booster
ABS electronic control module
ABS hydraulic control unit
Composition of Ordinary Brake System
Brake booster
Parking brake control lever
Disc brake
Brake master cylinder
Disc brakeBrake pedal
Proportioning valveParking brake cable
Brake Booster
1. Usually, the brake booster can increase the braking force two to
four times.
2. Brake booster's performance varies with the actual atmospheric
pressure, vacuum degree and its active area. The bigger its active
area is, the stronger its boosting force is.
Brake Booster not in Braking
Variable-pressure chamber- chamber A
Relationship between Fb + Fsand Fa
Fb=FaFs pushes the piston to the right.
Brake master cylinder
SpringPiston
Valve
Cylinder sleeve
Vacuum
To brake wheel
cylinder
Constant-pressure chamber- chamber B
Relationship between Fb + Fsand Fa
Fb + Fs < FaFa pushes the piston to the right
Vacuum
Brake master cylinder
Hydraulic pressure
Air
Valve
Brake Booster in Braking
Brake Booster Structure
Vacuum Check valve
Constant-pressure chamber
Diaphragm
Power piston
Reaction disc
Valve body
Air
Variable-pressure chamberBooster housing
Push rod
Brake master cylinder
Diaphragm spring
Booster housing sealing member
Booster housing sealing member
Air filter
Valve control lever
Opened vacuum valve & control valve
A is connected with B
1. Brake Booster not in Braking
Piston
Passage A
Passage B
Constant pressure chamber
Variable pressure chamber
Air valve (closed)
Air valve return spring
Air filter element
Valve control lever
Valve body
Control valve spring
Control valve
Vacuum valve (opened)
When not in braking
2. Brake Booster in Braking
C
Closed vacuum valve & control valve
A is not connected with BB is connected with C
Piston
Passage B
Constant pressure chamber
Variable pressure chamber
Air valve (opened)
Air filter element
Control valve
When not in braking
Air
Reaction disc
Booster push rod
3. Brake Booster in the Retained Position
Closed vacuum valve & control valve
A is not connected with B or C
Piston
Constant pressure chamber
Air valve (closed)
Control valve
When in the retained position (brake force)
Valve control lever
Control valve spring
Vacuum valve (closed)
Stop
Variable pressure chamber
4. Brake Booster in the Released Position
Opened vacuum valve & control valve
A is connected with B and C
Piston
Air valve (closed)
Control valve
When in the released position (brake)
Valve control lever
Vacuum valve (opened)
Variable pressure chamber
Air valve return springPassage B
Passage A
Purpose of Brake Master Cylinder
Brake master cylinder
Drum brake
Brake pedalFront/rear brakes
Brake Master Cylinder Structure
Tandem brake master cylinderPrimary pistonSecond pistonRubber piston cup
Reservoir
Liquid lever sensor
RR/LF brake cylinders
RF/LR brake cylinders
Piston cup is located between inlet port and compensating port
1. Brake Master Cylinder not in Braking
Secondary return springPrimary return spring
Compensating port
Inlet port
Primary piston cup
Secondary piston cup
Stopper bolt
When not in braking
进油孔
Secondary piston
Both inlet port
and
compensating
port are closed
with the oil
pressure
increased
2. Brake Master Cylinder in Braking
When in braking
Primary piston
Inlet port
Compensating port
Piston cup
3. Brake Master Cylinder when Released (1)
Inlet portOrifice
Piston cup
When brake pedal is released (1)
The orifice in the
piston is opened
and the brake
fluid flows back
to the piston-cup
side
4. Brake Master Cylinder when Released (2)
The
compensating
port allows
surplus fluid to
flow back to
the reservoir
Compensating port
When brake pedal is released (2)
5. Rear-end Leakage
In contact
Primary pistonSecondary piston
Rear-end leakage
6. Front-end Leakage
Piston contacts cylinder wall
Primary pistonSecondary piston
Front-end leakage
Proportioning valve
Proportioning Valve
Importance of Proportioning Valve
1. Loads on front and rear wheels are differentThe front wheels of the vehicle bear more of the vehicle weight than its rear wheels. In addition, its center of gravity will move forward when in braking, resulting in increased load on front wheels and reduced load on rear wheels. The bigger the braking force is, the more obvious this change is.
2. The risk of too early locking of rear wheelsWhen in braking, the load on rear wheels is light, and this causes them to be easily locked too early, thereby resulting in lateral sway of the vehicle body's rear half.
3. Measure to prevent the above problem from happeningProportioning valve: to automatically reduce hydraulic pressures delivered from brake master cylinder to rear-wheel brake wheel cylinders. Pressure reduction is in proportion to the stepping force on the brake pedal.
Bifurcation point
Pressure in brake master cylinder
Pres
sure
in re
ar b
rake
whe
el c
ylin
der
Requirements on Rear-wheel Brake Force
LF wheel
Proportioning Valve
RR wheel
RF wheel
RF wheel
Working Principle of Proportioning Valve—When the Pressure is zero
Spring
Control valve
Proportioning valve
Rear
Piston
Working Principle of Proportioning Valve—When the Pressure is Low
Spring
Piston
Cha
mbe
r A si
de
Cha
mbe
r B si
de
Piston
Small area Large areaFa+Fs=Fb
Working Principle of Proportioning Valve—When the Pressure is high
Fa+Fs<Fb
When the pressure is higher than some point, the difference between chambers A and B will overcome the spring's elastic force to make the piston move until the port C is closed.
1.When the Braking Pressure is Low
Cylinder cup
Spring To rear-wheel brake wheel cylinders
Piston
From brake master cylinder
2.When the Braking Pressure is High
In contact
Piston
3.When the Brake Pedal is Released
Cylinder cup
Piston
Spring
When the brake pedal is released, the pressure drop in the left chamber will cause the piston to move to the left.
Floating caliper
Disc Brake
Fixed caliper
Brake disc
Motion
Rotor disc
Brake lining
Floating-caliper type
Hyd
raul
ic p
ress
ure
Piston
Friction disc thickness sensor
Stee
ring
knuc
kle
Front-wheel Brake
Rear-wheel Brake