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HYDRAULIC CIRCUIT
CASE TRAINING CENTER
AUGUST 2000
Pump engine running, two controls operated
There are 3 possibilities
1. The negative flow control signals PZ1 & PZ2 are low and slighltly equal
1. The negative flow control signals PZ1 & PZ2 are different
1. The regulation torque pressure is reached
1. If PZ1 equals PZ2 (travel motor fully supply) the negative control signal is very low and the negative control
valves E & E' are fully pushed back to the right side by the springs. The piston B and B' are connected to
the tank through E & E' valves. The two pumps deliver the same maximum flow.
A difference of pressure between the RH and LH side doesn't affect the outputs because the pistons A & A'
receives the same pressure from the compensation valve C.
1. If PZ1 > PZ2 (current usage for boom and dipper) the dynamic balance of the piston A & B is obtained
before the balance of the spool A' & B'. For this reason the swash plate angle is smaller on PZ1 side and the
flow is smaller.
(PZ2> PZ1 respectively)
If PA1 + PA2 reaches the pressure of the torque regulation value, the compensated pressure from the
valve C acts identically on the lever L & L'. L & L' levers push on the torque regulations valves D & D' to reduce
proportionally the swash plate angle of the two pumps.
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