Komatsu PC58UU-3, Руководство по ремонту

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STRUCTURE, FUNCTION AND MAINTENANCE STANDARD SWING MOTOR
10-76
PC58UU-3
12
MODULATING RELIEF VALVE
Function
• The characteristic of the swing motor relief
valve is to restrain sharp rise of relief valve
(as shown in the right figure) and to reduce
shocks when starting and stopping swing.
Operation
1. When circuit pressure is PO
• The relief valve does not work.
2. When circuit pressure rises sharply
• When the circuit pressure reaches P1 , the oil
pressure will push the spring (4) due to the
area difference (
D1>D3 ) of the valve (3).
Then, the valve (3) will start opening.
• At this time, the oil pressure will work on the
seat (1) due to the area difference (
D2>D1 ),
and the seat will be apt to follow the valve (3).
• But the seat is going to compress the oil in
the
a chamber and moves more slowly than
the valve (3) because the passage through
which the oil escapes to the
S port is throttled
with the ball (2).
• So, the relief pressure will rise slowly from
P1 to P2 until the seat (1) comes to the sleeve
(5).
(5)