FRAME AS-SUSP 5658445 - Caterpillar

Introduction
Illustration 1 g01752493
(1) Main control valve (2) Main relief valve (3) Return passage (4) Parallel feeder passage (5) Valve for flow control (6) Passage (7) Orifice (8) Passage (9) Passage (10) Center bypass passage (11) Passage (12) Orifice (13) Drain passage (14) Drain line to tank (15) Signal line for flow control (16) Main pump pressure (17) Pilot line (18) Flow compensator valve (19) Swashplate (20) Main pump (21) Swashplate control piston (22) Pilot pump (23) Passage (24) Pilot manifold (25) Hydraulic tank (26) Passage (27) Orifice (28) Bucket control valve (29) Orifice (30) Check valve (31) Passage (32) OrificeMain pump (20) receives signal oil pressure through flow control valve (5) and line (15) . This signal pressure (pN) that is created in main control valve (1) is called flow control pressure. Flow control pressure flows to the regulator at main pump (20) in order to control the output flow. Flow control pressure is created during the following machine operating conditions.
All of the joysticks and travel levers/pedals are in the NEUTRAL position.
Any of the joysticks and/or travel levers/pedals are partially moved from the NEUTRAL position in order to perform a fine control operation.
A boom lower operation is performed alone.
Illustration 2 g01493680
Partial cross section of flow control valve (5) Valve for flow control (15) Signal line for flow control (26) Passage (31) PassageOil from main pump (20) , flows through line (16) , passage (26) , and flow control valve (5) . Flow control valve (5) shifts to the right and oil flow takes one of two paths. Part of the oil flows through orifice (12) , and return passage (14) to hydraulic tank (25) . The other part flows through flow control orifice (27) and line (15) . Because the full flow is restricted by orifice (12) , the signal pressure (pN) in line (15) becomes maximum. Signal pressure (pN) now flows to the pump regulator and flow compensator valve (18) . The operation of flow control to the regulator on main pump (20) , causes swashplate (19) to move to the minimum angle position. The output flow of main pump (20) is decreased due to the increased signal pressure for flow control that is created in line (15) .
Illustration 3 g03370851
Partial cross section of bucket control valve (4) Parallel feeder passage (29) Orifice (30) Check valve (31) Passage (33) Passage (34) Port (35) Spool (36) Pilot port (37) Load check valve (38) PassageWhen the control lever is moved partially for fine control, pilot pressure from port (36) starts to shift spool (35) to the right. The pilot pressure begins to open parallel feeder passage (4) to passage (38) . Part of the oil pressure at passage (38) flows through load check valve (37) , passage (33) , and port (34) to the bucket cylinder. The remainder of the main pressure flows from passage (38) through orifice (29) , check valve (30) , passage (31) , orifice (32) and flow control valve (5) . Oil pressure shifts flow control valve