TEE AS 3295474 - Caterpillar

Illustration 2 g06199890
(10) Main relief valve
(15) Pilot pressure reducing valve
(34) Main control valve
(38) Hydraulic lock solenoid
(55) Hydraulic tank
(56) Pump 1
(57) Pump 2
(58) Heavy lift solenoidPilot Oil Circuit
The pilot circuit pressure is limited by pilot pressure reducing valve (15).The oil flow from pump 2 (57) performs the main functions of providing pilot oil pressure to the control valves for implements, swing, and travel to perform machine operations.The pilot circuit is classified into the following circuits:
Pilot control valve circuit (main control valve)
Swing brake
Automatic travel speed change
Heavy Lift
Pump displacement actuation circuitPilot Control Valve Circuits
Illustration 3 g06235349
Ports and solenoids at the solenoid manifold
(1) Travel speed solenoid
(2) Swing brake solenoid
(4) Boom 2 cylinder extend solenoid
(5) Stick 1 cylinder retract solenoid
(6) Swing left solenoid
(7) Left travel backward solenoid
(8) Straight travel solenoid
(11) Right travel backward solenoid
(12) Bucket cylinder extend solenoid
(14) Boom cylinder retract solenoid
(35) Swing priority solenoid
(36) Stick unloading solenoid
(38) Hydraulic lock solenoid
(39) Stick 1 cylinder extend
(40) Swing right solenoid
(41) Left travel forward solenoid
(46) Right travel forward solenoid
(47) Bucket cylinder retract solenoid
(49) Boom 1 cylinder extend solenoid
(50) Stick 2 cylinder extend solenoid
(59) Drain port (Dr1)
(60) Travel speed control port (Pi5)
(61) Swing brake port (Pi4)
(62) PAC port (accumulator port)Oil from pump 2 (57) flows through main control valve (34). Within the main control valve, the oil flows to the various valve spools through center bypass passages (16) and (31) for use upon activation. The oil also flows to pilot pressure reducing valve (15). The pilot pressure reducing valve reduces the pressure of the oil for use in the pilot circuit. The pilot oil flows to hydraulic lock solenoid (38). When the hydraulic lock solenoid is energized, pilot oil flows to the control solenoids.When the hydraulic activation control lever is shifted to the UNLOCKED position, the machine ECM energizes the hydraulic lock solenoid. The pilot oil now flows through the solenoid valve to the control valves for the implements, swing, and travel. When the joysticks and/or travel levers/pedals are moved, the pilot oil flows within the main control valve to control the machine functions.
Illustration 4 g06200180
Control valves on main control valve
(17) Swing priority control valve
(18) Boom 2 control valve
(19) Stick unload control valve
(20) Stick 1 control valve with regeneration
(21) Swing control valve
(23) Travel left control valve
(24) Straight travel valve
(26) Travel right control valve
(27) Bucket control valve
(28) Boom 1 control valve with regeneration
(32) Stick 2 control valveWhen the joysticks are operated, the ECM controls the pilot control valves to send pilot oil through the main control valve to shift the spools. Refer to Illustration 1 for the location of the pilot lines and machine operations.The following example is given for lowering and raising the boom. Stick, bucket, travel, and swing operation are accomplished in the same manner as the boom.When the joystick for the boom is moved to the BOOM RAISE position, pilot oil from boom 1 cylinder extend solenoid (49) flows through passages in the main control valve to boom 1 control valve (28) and