Doosan 50001, Shop Manual

Page: 692 / 898

SP001488 Main Pump
Page 12
2. Control Function
• Exhaust pressure P1 and P2 are determined by
movement of tilting plate and piston.
• Spring works in direction against discharge
pressure.
• The set load of spring A (outer spring) decreases
and tilting plate becomes fixed at maximum tilt
position, when hydraulic pressure is applied to
piston.
• The tilting plate begins to incline when hydraulic
pressure is applied to piston and spring A exceeds
its set load, and keeps its tilting face at point where
hydraulic pressure is in equilibrium with strength of
spring. (Refer to "A" in middle part of Figure 6).
• Tilt angle begins to decrease when hydraulic
pressure is applied to piston, and then spring B that
so far has not worked begins to operate.
• The two springs become to revive their spring
tension when hydraulic pressure reaches highest
lower tilting point. (Refer to (A + B) domain in middle
part of Figure 6).
• The control changeover curve begins to change
when hydraulic pressure P3 that presses piston is
applied.
Figure 5