Daewoo Solar 300LC-V, Manual

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S0708315K
Page 33
Main Pump (Kawasaki)
Negative Flow Control
By changing the pilot pressure Pi, the pump
tilting angle (delivery flow) is regulated
arbitrarily, as shown in Figure 24.
This regulator is a negative flow control in which
the delivery flow Q decreases as the pilot
pressure Pi rises. With this mechanism, when
the pilot pressure corresponding to the flow
required for the work is commanded, the pump
discharges the required flow only, so it does not
consume unnecessary power.
1. Functional Explanation
A. Flow reducing Function
As the pilot pressure Pi rises, the
pilot piston (643) moves to the right to a position where the force of the pilot spring (646)
balances with the hydraulic force.
The groove (A) in the pilot piston is attached with pin (875) that is fixed to lever 2 (613).
Therefore, when the pilot piston moves, lever 2 rotates around the fulcrum of point B (fixed by
the fulcrum plug (614) and pin (875). Since the large-hole section (C, Figure 23) of lever 2
contains a protruding pin (897) fixed to the feedback lever(611), the pin (897) moves to the right
as lever 2 rotates. Since the opposing-flat section (D) of the feedback lever is attached with the
pin (548) fixed by the tilting pin (531) that swings the swash plate, the feedback lever rotates
around the fulcrum of point D, as the pin (897) moves. Since the feedback lever is connected
with the spool (652) via the pin (874), the spool moves to the right.
The movement of the spool causes the delivery pressure P1 to connect to port C liter through
the spool and to be admitted to the large-diameter section of the servo position. The delivery
pressure P1 that is constantly admitted to the small-diameter section of the servo piston moves
the servo piston to the right due to the area difference, resulting in decrease of the tilting angle.
When the servo piston moves to the right, point D also moves to the right. The spool is fitted
with the return spring (654) and is tensioned to the left at all times, and so the pin (897) is
pressed against the large-hole section (C) of lever2. Therefore, as point D moves, the feedback
lever rotates around the fulcrum of point C, and the spool is shifted to the left. This causes the
opening between the sleeve (651) and spool (652) to close slowly, and the servo piston comes
to a complete stop when it closes completely.
B. Flow Increasing Function
As the pilot pressure Pi decreases, the pilot piston (643) moves to the left by the action of the
pilot spring (646) and causes lever 2 (613) to rotate around the fulcrum of point B. Since the pin
(897) is pressed against the large-hole section (C) of lever 2 by the action of the return spring
(654) via the spool (652), pin (874), and feedback lever (611), the feedback lever rotates around
the fulcrum of point D as lever 2 rotates, and shifts the spool to the left. Port C liter opens a way
to the tank port as the spool moves. This deprives the large-diameter section of the servo piston
of pressure, and shifts the servo piston to the left by the discharge pressure P1 in the small-
diameter section, resulting in an increase in the flow rate.
As the servo piston moves, point D also moves to the left, the feedback lever rotates around the
fulcrum of point C, and the spool moves to the right till the opening between the spool and
sleeve is closed.
Figure 24