TUBE AS 1782621 - Caterpillar

Illustration 10 g03871238
Bucket IMV section
(48) Bucket compensator valve
(49) Inverse shuttle valve
(50) Load check valve
(52) Bucket RE P-C spool
(53) Bucket HE P-C spool
(73) Return passage
(74) Return passage
(75) Supply passage An independent metering valve (IMV) controls one hydraulic function using four electronically controlled spools. Independent control means that software can adjust openings on the pump-to-cylinder (P-C) and cylinder-to-tank (C-T) ports to provide optimum efficiency and control for different front linkage weights and operating conditions. The main control valve is a closed center compensated valve with separate pump-to-tank bypass valves. To actuate a hydraulic function, an electrical current is applied to at least two IMV solenoids, typically controlling one pump-to-cylinder (P-C) spool and one cylinder-to-tank (C-T) spool. The IMV solenoids control small pilot valves that reduce pilot supply pressure to a control pressure that pushes the metering spool against a spring.In the bucket IMV section, the front pump supplies oil through passage (75). The oil then flows through a series of drilled holes, located in compensator valve (48). Once oil flows through compensator valve (48), oil pressure opens load check valve (50). Once load check valve (50) opens, oil flows to bucket HE P-C spool (53) and bucket RE P-C spool (52). Oil flow is blocked at spool (53) and spool (52), since no work is being performed and the hydraulic system is in the NEUTRAL position. When all of the joysticks and/or travel levers/pedals are in the NEUTRAL position, or when no work is being performed, pump oil flows to the main control valve and through the bypass cut spool (40) and bypass cut spool (38). From the bypass cut spools the pump oil returns to the hydraulic tank, through return passages (73) and (74).Individual Valve Operation
Illustration 11 g03871239
Bucket IMV section (bucket CLOSE)
(42) Bucket RE C-T PHMV
(44) Bucket HE P-C PHMV
(46) Bucket RE pressure sensor
(48) Bucket compensator valve
(49) Inverse shuttle valve
(50) Load check valve
(51) Bucket RE C-T spool
(52) Bucket RE P-C spool
(53) Bucket HE P-C spool
(56) Bucket HE pressure sensor
(74) Return passage
(75) Supply passage The bucket control valve is used as a typical example for describing the operation of individual control valves.When the joystick for the bucket is moved to the BUCKET CLOSE position, an electrical current is applied to bucket HE P-C PHMV (44) and bucket RE C-T PHMV (42). The idler pump supplies oil through passage (75). The oil then flows through compensator valve (48). Once oil flows through compensator valve (48), oil pressure opens load check valve (50). Once load check valve (50) opens, oil flows past bucket HE P-C spool (53) to the head end of the bucket cylinder. Return oil from the rod end of the bucket cylinder flows past bucket RE C-T spool (51) to return passage (74).Inverse shuttle valve (49) shifts to the left, directing the lower signal pressure from pump-to-cylinder (P-C) spool (52) to the spring side of compensator valve (48).Individual component functions
Illustration 12 g03871240
(48) Compensator valve
(49) Inverse shuttle valve
(53) P-C spool
(76) Orifice
(77) Passage
(78) Orifice
(79) Passage The compensator valve is a hydromechanical device that prevents