Chery QQ Service Manual page 607

Opened vacuum
valve & control
valve
A is connected
with B
1. Brake Booster not in Braking
Piston
Passage A
Constant
pressure
chamber
Air valve
(closed)
Passage B
Variable pressure chamber
When not in braking
Vacuum valve (opened)
Control valve
Control valve spring
Valve body
Air filter element
Air valve return spring
Valve control lever