4-17
OPERATION
OPERATION
The unloading valve (4) controls the minimum and maximum pressure of the braking system.
When the service brake pressure is below the maximum pressure (125
±
5 bar), the unloading
valve (4) is blocked and PS pilot pressure (brake priority pressure) increases.
As soon as PS pilot pressure raises up above 15 bar, pump controller current is reduced by MCU
(pressure sensor detects brake priority pressure, and pump supply flow and pressure in order to
meet the brake system).
The pressure sensor at PS port detect whether brake system needs to be charged.
Priority valve spring and pilot pressure (brake priority pressure) pushed priority spool to the
upward.
Therefore, full pump flow directly goes to the brake system in order to satisfy the demand of the
brake system.
Pump flow goes through the following components : orifice (7), check valve (2), shuttle valve (8).
Brake failure pressure sensor at G1 port detects pressure in the brake accumulators.
When the pressure is lower than 100 bar, the sensor activates warning lamp on the cluster in order
to check brake system.
When brake system pressure reaches the maximum brake system pressure (150 bar
±
5 bar),
unloading valve (4) opens, pilot pressure (brake priority pressure) of priority valve is low by draining
the spring side of priority valve (3) to hydraulic tank through unloading valve (4).
2)
2)
Summary of Contents for HL955
Page 557: ...7 6 MEMORANDUM MEMORANDUM ...
