Hydraulic Schematic Of Main Control Valve

Illustration 1 g03207376
(1) Return port
(2) Line relief valve (stick cylinder rod end)
(3) Stick drift reduction valve
(4) Left body
(5) Main control valve
(6) Right body
(7) Line relief valve (boom cylinder head end)
(8) Boom drift reduction valve
(9) Relief valve (negative flow control)
(10) Negative flow control orifice
(11) Boom II control valve
(12) Center bypass passage
(13) Stick regeneration valve
(14) Parallel feeder passage
(15) Load check valve
(16) Stick I control valve
(17) Swing control valve
(18) Left travel control valve
(19) Straight travel control valve
(20) Main relief valve
(21) Right travel control valve
(22) Load check valve
(23) Attachment control valve
(24) Bucket control valve
(25) Line relief valve (bucket cylinder rod end)
(26) Line relief valve (bucket cylinder head end)
(27) Boom I control valve
(28) Center bypass passage
(29) Boom regeneration valve
(30) Line relief valve (boom cylinder rod end)
(31) Stick II control valve
(32) Negative flow control orifice
(33) Relief valve (negative flow control)
(34) Negative flow control line
(35) Line relief valve (stick cylinder head end)
(36) Swing priority solenoid
(37) Inlet port (idler pump)
(38) Inlet port (drive pump)
(39) Parallel feeder passage
(40) Negative flow control line
(41) Hydraulic tank
(42) Pilot pump
(43) Drive pump
(44) Idler pump

Main control valve ports

Illustration 2 g02120493
Main control valve ports (top side view and front side view)
(BL3) Stick I control valve (STICK IN)
(BL2) Swing control valve (SWING RIGHT)
(BL1) Left travel control valve (FORWARD TRAVEL)
(BR1) Right travel control valve (FORWARD TRAVEL)
(BR2) Attachment control valve (EXTEND)
(BR3) Bucket control valve (BUCKET OPEN)
(BR4) Boom I control valve (BOOM LOWER)
(BR5) Stick II control valve (STICK IN)
(MU) Return port (SWING MOTOR)
(AR5) Stick II control valve (STICK OUT)
(AR4) Boom I control valve (BOOM RAISE)
(AR3) Bucket control valve (BUCKET CLOSE)
(AR2) Attachment control valve (RETRACT)
(AR1) Right travel control valve (REVERSE TRAVEL)
(AL1) Left travel control valve (REVERSE TRAVEL)
(AL2) Swing control valve (SWING LEFT)
(AL3) Stick I control valve (STICK OUT)
(AL4) Boom II control valve (BOOM RAISE)
(HL) Negative flow signal pressure port (idler pump)
(HR) Negative flow signal pressure port (drive pump)
(STDr) Drain port (solenoid for straight travel control)
(R1) Return port (tank)
(PUMP-S1) Pressure port (idler pump)
(PUMP-S2) Pressure port (drive pump)

Illustration 3 g02122318
Main control valve ports (bottom side view and rear side view)
(P1) Inlet port (drive pump)
(P2) Inlet port (idler pump)
(T) Return port (tank)
(STPi) Pilot port (straight travel solenoid valve)
(aL4) Pilot port at boom II control valve (BOOM RAISE)
(aL3) Pilot port at stick I control valve (STICK OUT)
(aL2) Pilot port at swing control valve (SWING LEFT)
(aL1) Pilot port at left travel control valve (REVERSE TRAVEL)
(aR1) Pilot port at right travel control valve (REVERSE TRAVEL)
(aR2) Pilot port at attachment control valve (RETRACT)
(aR3) Pilot port at bucket control valve (BUCKET CLOSE)
(aR4) Pilot port at boom I control valve (BOOM RAISE)
(aR5) Pilot port at stick II control valve (STICK OUT)
(bR5) Pilot port at stick II control valve (STICK IN)
(bR4) Pilot port at boom I control valve (BOOM LOWER)
(bR3) Pilot port at bucket control valve (BUCKET OPEN)
(bR2) Pilot port at attachment control valve (EXTEND)
(bR1) Pilot port at right travel control valve (FORWARD TRAVEL)
(dST) Drain port (straight travel control valve)
(bL1) Pilot port at left travel control valve (FORWARD TRAVEL)
(bL2) Pilot port at swing control valve (SWING RIGHT)
(bL3) Pilot port at stick I control valve (STICK IN)
(bL4) Pilot port at boom II control valve (STICK IN)
(SRPi) Pilot Port (Stick Regeneration valve)
(SRDr) Drain Port (Stick Regeneration valve)
(BRPi) Pilot Port (Boom Regeneration valve)
(BRDr1) Drain Port (Boom Regeneration valve)
(BRDr2) Drain Port (Boom Regeneration valve)
(SWDr) Drain port at swing priority solenoid

Introduction

Illustration 4 g02137133
Main control valve (front view)
(3) Stick drift reduction valve
(4) Left body
(6) Right body
(8) Boom drift reduction valve
(11) Boom II control valve
(16) Stick I control valve
(17) Swing control valve
(18) Left travel control valve
(19) Straight travel control valve
(20) Main relief valve
(21) Right travel control valve
(23) Attachment control valve
(24) Bucket control valve
(27) Boom I control valve
(31) Stick II control valve

Main control valve (5) is located in the hydraulic system between the pumps and actuators (cylinders and
motors). Depending on the machine operation, components and passages in the valve control oil flow and
pressure in the circuits from the pumps to actuators.

The main control valve consists of right body (6) and left body (4). The main control valve is coupled together
with bolts in order to make one assembly. The following control valves are in parallel in right body (6) .

 Right travel control valve (21) .

The following control valves are in parallel in left body (4) .

 Straight travel control valve (19) .

The left body has inlet ports (37) and (38) and return port (1). The drive pump oil flows into inlet port (38). The
idler pump oil flows into inlet port (37). The oil flow of the drive pump and the oil flow of the idler pump is
controlled by the main control valve. The oil flow is supplied to cylinders and/or motors that are selected for
operation. Return oil from cylinders and/or motors enters the main control valve. The oil then flows out of
return port (1) and back to hydraulic tank (41) through return line.

Right Body (6)

 Line relief valves (25) and (30) limit the circuit pressure.
 When the control levers are in the NEUTRAL position or when the control levers are moved partially,
relief valve (33) and negative flow control orifice (32) destroke the main pump.
 When the control levers are in the NEUTRAL position, boom drift reduction valve (8) prevents boom
cylinder drift.
 Load check valve (22) .

Left Body (4)

 Stick cylinder relief valves (2) and (35) .

The following five configurations are the functions of the main control valves.

 When the main control valves are in the NEUTRAL position, no pump oil flows to the cylinders and the
motors.
 Individual valve operation
 The main control valve controls the negative flow control signal when the control levers are in the
NEUTRAL position or when the control levers are moved partially.
 Prevention of cylinder drift with the load check valve.
 Limit the circuit pressure with the relief valve operation.

The description of some components that are installed on the main control valve or in the main control valves
will be listed separately. Refer to the appropriate sections that are in this module for further information on the
components.
  For more information on boom drift reduction valve (8), refer to Systems Operation, "Boom Hydraulic
System".
 For more information on straight travel control valve (19), refer to Systems Operation, "Control Valve
(Straight Travel)".

Main Control Valve Operation In The NEUTRAL Position

Illustration 5 g02116934
Main control valves (NEUTRAL position)
(1) Return port
(4) Left body
(6) Right body
(11) Boom II control valve
(12) Center bypass passage
(14) Parallel feeder passage
(16) Stick I control valve
(17) Swing control valve
(18) Left travel control valve
(19) Straight travel control valve
(21) Right travel control valve
(23) Attachment control valve
(24) Bucket control valve
(27) Boom I control valve
(28) Center bypass passage
(31) Stick II control valve
(37) Inlet port (idler pump)
(38) Inlet port (drive pump)
(39) Parallel feeder passage

The drive pump supplies oil to right body (6). Oil from the drive pump goes to the right body through inlet port
(38). The oil then goes through center bypass passage (28) and parallel feeder passage (39). The idler pump
supplies oil to left body (4). Oil from the idler pump goes to the left body through inlet port (37). The oil then
goes through center bypass passage (12) and parallel feeder passage (14) .

When all the control levers are in the NEUTRAL position, drive pump oil flows through center bypass passage
(28) and return port (1). The oil returns to the hydraulic tank. Idler pump oil from inlet port (37) flows through
center bypass passage (12) and out return port (1). The oil returns to the hydraulic tank. Oil in parallel feeder
passages (14) and (39) remains blocked by each control valve spool.

Activation of any control lever provides two paths for drive pump oil. One path is from center bypass passage
(28) to right travel control valve (21). The other path is from parallel feeder passage (39) to attachment control
valve (23), bucket control valve (24), and boom I control valve (27). Activation of any control lever also
provides two paths for idler pump oil. One path is from center bypass passage (12) to left travel control valve
(18) and stick I control valve (16). The other path is from parallel feeder passage (14) to swing control valve
(17) .

Individual Valve Operation

Illustration 6 g02125752
Bucket control valve (NEUTRAL position)
(1) Line relief valve (bucket cylinder rod end)
(2) Port
(3) Parallel feeder passage
(4) Load check valve
(5) Passage
(6) Port
(7) Line relief valve (bucket cylinder head end)
(8) Pilot port
(9) Return passage
(10) Spool
(11) Center bypass passage
(12) Spring
(13) Pilot port

The bucket control valve is used as a typical example for describing the operation of individual control valves.
When all pilot control valve levers are in the NEUTRAL position, pilot oil does not flow to port (8) and port
(13) from the pilot control valve. Spool (10) is centered in the NEUTRAL position by the force of spring (12).
The drive pump oil goes through center bypass passage (11) to the hydraulic tank.

Illustration 7 g02125792
Bucket control valve (BUCKET CLOSE)
(2) Port
(3) Parallel feeder passage
(4) Load check valve
(5) Passage
(6) Port
(9) Return passage
(10) Spool
(11) Center bypass passage
(13) Pilot port
(14) Passage
(15) Passage

When the bucket control valve is moved to the BUCKET CLOSE position, pilot oil is supplied to pilot port
(13). When pilot oil is supplied to pilot port (13), spool (10) shifts downward. Center bypass passage (11) is
closed and passage (15) becomes opened. Passage (14) is now connected to return passage (9) .

Oil that is in parallel feeder passage (3) goes through load check valve (4), passage (5) and passage (15). The oil
then goes to port (6). The bucket cylinder rod extends. When the bucket cylinder rod extends, the displaced oil
in the rod end flows to port (2) .

Oil from port (2) flows through passage (14) to return passage (9) and back to the hydraulic tank.