Takeuchi TB175W, Руководство по ремонту

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HYDRAULIC UNITS
CONTROL VALVE
IV-39
TB175W
Main Relief Valve
Relieving Operation
When the pressure in the circuit is low with respect to
the set value, the relief valve is maintained at equilib-
rium. Hydraulic oil from the pump passes through the
orifice from chamber B and arrives at the spring
chamber C and the needle valve (5). On the other
hand, forces F and F1 are acting in the arrow direc-
tions on both sides of the main poppet (6).
F = P
×
A F1 = P
×
A1
P: Pressure A,A1: Sectional Area
Since the sectional area of A is less than that of A1, the
main poppet (6) is pushed by the force “F1-F” to the
seat surface on the left side.
If the pressure in the circuit becomes higher than the
force of the spring (7), the needle valve (5) is pushed
to the right by hydraulic pressure, opening. Oil then
flows around the circumference of the needle valve
(5) and passes through the slits, flowing into the tank
passage (T).
Compared to the chamber B side, the pressure in
chamber C is low and there is no equilibrium in
pressure. For this reason, the main poppet (6) opens
and pressurized oil flows to the tank passage (T).
Pressure Increase Operation
When the pressure is applied to the pilot port PH, the
piston (8) is pushed to the left to hit the plug (9). Then,
the spring force of the spring (7) becomes larger,
increasing the pressure in chamber B.
W2D207
B A
6 C 5 A1
F
F1
W2D208
T
7
5
W2D209
T B
6 C
W2D210
B 7
8 9
PH