Daewoo Solar 225LC-V, Shop Manual

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S0708320
Page 6 Main Pump (With Regulator)
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PUMP REGULATOR DESCRIPTION
A regulator control valve is integrally-mounted to
the housing of each of the two variable
displacement hydraulic pumps (Figure 1). The
regulator valves perform the task of controlling
the rate of pump discharge for the main pump
assembly. Pump output may need to be varied
as a result of increased or decreased work load
demand, operator-input changes to control lever
position and/or to maintain balanced output
between pumps, increasing or decreasing the
discharge rate at one pump to compensate for
the output of the other pump.
The two regulators work in conjunction, varying
pilot pressure (Pi) through three different control
functions - "Horsepower Control," "Powershift
Control," and "Negative Control."
HORSEPOWER CONTROL
This hydraulic system design feature provides balanced pump output, maintaining steady and consistent
power production through the hydraulic system.
If there is a momentary increase of outlet pressure (P1) at one pump, the tilt angle of the swash plate in the
remaining pump is automatically reduced - decreasing the other pump’s outlet pressure (P2) - to equalize
system output. The advantage of this design feature is that it keeps available horsepower through the
system constant, directly proportional to the input rotational speed (rpm) of the engine.
POWER SHIFT CONTROL
This design feature modifies the total available power output of the hydraulic system through
microprocessor-controlled application of electronic controls. Supplementary electronic control of the
hydraulic system provides increased operating flexibility.
The electronic proportional reducing valve through which the system operates is just upstream from the 2
pump regulators. It responds directly to signals from the EPOS-V microprocessor and relays control
signals to each of the 2 pump regulators to optimize each pump’s power output, according to changes in
secondary pressure, Pf ("Powershift pressure").
Pf pressure is monitored from interior pump passages, through the horsepower control part of each pump
regulator. It allows simultaneous control of horsepower output at both pumps, for optimum, efficient
response to changing workload demand.
NEGATIVE OIL DISCHARGE (PUMP BYPASS) CONTROL
The volume of main pump bypass oil is automatically controlled by pilot pressure, which is regulated by the
position of the spool in the control valve. When the control valve spool is in the neutral position (high pilot
pressure, high bypass), the tilt angle of the swash plate decreases, reducing the volume of bypass oil
through the main pump. When the control valve spool is at maximum stroke (low pilot pressure), the tilt
angle of the swash plate increases, boosting main pump bypass oil volume.
Figure 6