Doosan DX60R Shop Manual page 525

Valve Casing Part
1. Anticavitation Check Valve
The motor can be rotated faster than supplied oil flow
because there is no counter-balancing valve to prevent
over speed ; in order to prevent cavitation of the motor, oil
compensation insufficient flow is drawn through the anti-
cavitation check valve.
2. Relief Valve: TSR25A (Figure 3)
We consider that port P is applied pressure by tank
pressure.
Port P, R are affected by tank pressure at first, as shown
(1, Figure 3). The relief valve starts operating when the
force that is determined by multiply the pressure area (A1)
of plunger (301) by pressure P1 is equal to the sum spring
(321) force (Fsp) and the force that is determined by
multiply the pressure area (A2) by pressure Pg of room 'g'
in the plunger (301).
Here, Pg is the pressure of room 'g' applied pressure by
passing oil through orifice m. If Pg arrives at the pressure
which is determined by spring (321) pushing the piston
(302), the piston move to left side. when piston (302) move
left side, room 'h' operates as damping room which is
designed at the side of adjustment plug (401) and piston
(302).
Because of this mechanism, the pressure of room 'g'
increases smoothly while the piston (302) reaches end of
adjustment plug (401) (2, Figure 3).
×
P1
P1
If the piston (302) reaches end of adjustment plug (401), it
doesn't move left side anymore. So, the pressure of room
'g' is Ps and spring (321) force is Fsp (3, Figure 3).
Therefore, the pressure P changes as shown (4, Figure 3).
The pressure (Ps) of last state is following equation.
×
Ps A1
Swing Motor
×
A1 = Fsp + Pg A2
×
Fsp + Pg A2
--------------------------------------
=
A1
×
= Fsp' + Ps A2
Fsp'
-------------------- -
Ps =
A1 A2 –
Control Valve
Figure 3
C Port
FG013320
SP001630
Page 11