Page 1206 - Foton Workshop Manual - Auman EST-M

BR-74 Brake system – service brake (air pressure)

Working principle:
Exhaust braking refers to the process of using the engine exhaust as an auxiliary braking approach to alleviate
the thermal deterioration of the brake incurred by the frequent foot braking. To a certain degree, it can prevent
the engine from running at too high speed in a passive way and extend the service life of the friction discs.
The exhaust brake consists mainly of pneumatic circuit opening/closing solenoid valve, exhaust brake valve,
cylinder, etc. The exhaust brake has a simple structure and is easy to repair.

The operation of the exhaust brake is controlled by the pneumatic circuit's solenoid valve, the operation
of which is controlled by three switches in series (for the clutch, accelerator pedal, and exhaust brake). The
exhaust brake can work only when all of the three switches are in the turned-on position. In order to carry out
exhaust braking, the driver operates the exhaust brake switch to allow the solenoid valve to fill air into the
exhaust brake valve, the butterfly valve on which closes the exhaust pipe to increase the running resistance of
the engine. There are an acceleration switch and a clutch switch in the control circuit, which can allow the
exhaust braking to be automatically disabled when the driver depresses the accelerator pedal and clutch pedal.

The clearance between the body of the exhaust brake valve and the valve itself shall be adjusted into the
0.4~0.6mm range during the maintenance.

BR-074