Hyundai HX140L, Manual

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NEGATIVE RELIEF VALVE OPERATION (TYPE 1)
When no function is being actuated on P1 side, the hydraulic fluid from the pump A2, flows into the
tank passage through the P1 bypass passage and orifice. The restriction caused by this orifice
thereby pressurizes. This pressure is transferred as the negative control signal pressure Pn1 to the
pump A2 regulator.
It controls the pump regulator so as to minimize the discharge of the pump A2.
The bypass passage is shut off when the shifting of one or more spools and the flow through
bypass passage became zero. The pressure of negative control signal becomes zero and the
discharge of the pump A2 becomes maximum.
The negative control pressure reaches to the set level, the hydraulic fluid in the passage pushes
open negative control valve and escapes into the return passage.
For the pump A1 the same negative control principle.
10)
Bucket spool
Tank passage
P2 Bypass passage P1 Bypass passage
P2 negative
relief valve
P1 negative
relief valve
Negative
control spring
Orifice
Tank passage
Pn1 port Pn2 port
140L2MC28