Systems Operation.pdf

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peracin de Sistemas20 AND 320 L EXCAVATORS HYDRAULIC SYSTEM

ystems Operation

ntroduction

eference: For Electric And Electronic Systems Operation, see Form No. SENR5404.

eference: For Testing And Adjusting of the hydraulic and electronics systems, make reference to Testing Anddjusting for 320 And 320 L Excavators Hydraulic And Electronic Systems, Form No. SENR6044.

OTE: For Specifications with illustrations make reference to the Specifications For 320 And 320 L Excavatorsydraulic System, Form No. SENR6049. If the specifications in Form No. SENR6049 are not the same as in the Sysperation, look at the printing date on the front cover of each book. Use the specifications in the book with the latest

OTE: For Hydraulic schematics, make reference to the following: Hydraulic Schematic for 320 And 320 L Excavaorm No. SENR5457.

OTE: For Electrical schematics, make reference to Electrical Schematic for 320 And 320 L Excavators, Form No.ENR6015.

ydraulic Schematic

Cerrar S

Pantalla anterior

Producto: EXCAVATORModelo: 320 L EXCAVATOR 9KKConfiguracin: 320L SUPPLEMENT FOR TRACK-TYPE EXCAVATOR /MPUPPER FRAME PKG./ 9KK01359-UP (MACHINE)

mero de medio -SENR6043-00 Fecha de publicacin -01/12/1992 Fecha de actualizacin -12/10

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) Swing parking control valve.

) Travel motor (left).

) Travel motor (right).

) Stick cylinder.

) Swing motor.

) Travel brake valve (left).

) Travel brake valve (right).

) Bucket cylinder.

) Boom cylinders.

0) Stick drift reduction valve.

1) Swivel.

2) Pressure switch (implement/swing).

3) Pressure switch (travel).

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4) Main control valves.

5) Boom drift reduction valve.

6) Main relief valve.

7) Pressure switch (BOOM RAISE).

8) Pilot control valve.



1) Proportional reducing valve.

2) Pilot oil manifold.

3) Pilot relief valve.

4) Accumulator.


6) Shock reducing valve.

7) Solenoid valve (swing priority).

8) Solenoid valve (fine control).

9) Shock reducing valve.

0) Hydraulic activation control valve.

1) Upper pump.

2) Lower pump.

3) Solenoid valve (travel speed).

4) Automatic travel speed change valve.

5) Pilot filter.

6) Pilot pump.

7) Hydraulic tank.

8) Bypass check valve.

9) Slow return check valve.

0) Oil cooler.


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A) Return passage.

eference: For Hydraulic System Schematic 320 and 320 L see, Form No. SENR5457.

Pump Flow And Pressure Control

ntroduction

mp Compartment1) Upper pump. (32) Lower pump. (42) Outlet line (upper pump). (43) Housing. (44) Outlet line (lower pump).

his machine is driven and controlled by the following three systems:

1.The Main Hydraulic System (provides oil to the cylinders and motors of the machine).2.The Pilot Hydraulic System (provides oil to the control circuits).3.The Electronic Control System (controls outputs from the engine and pump).

he main hydraulic system is driven by main pumps (31) and (32). Pumps (31) and (32) are variable displacement annt axis piston type pumps. The pumps are identical in performance. Lower pump (32) is directly connected to thegine by a flexible coupling. Pumps (31) and (32) are mechanically connected in parallel through gears. Gear type p

ump (36), installed in housing (43) is directly connected to lower pump (32) and drives the pilot hydraulic system. A

gine output is used for driving these three pumps.

ach of the main pumps delivers approximately 185 liter/min (49 U.S. gpm) of hydraulic oil at no load. When a load aced on the machine, the hydraulic oil is forced into the hydraulic circuit. As the load increases, the main pumpscrease their output. The system is designed to keep the hydraulic horsepower approximately the same as the engine

orsepower during system pressure increase or decrease.

he pilot pump delivers approximately 22 liter/min (5.8 U.S. gpm) of hydraulic oil at 3450 kPa (500 psi) and 1800 rp

ain Control Valve Compartment6) Main relief valve. (42) Outlet line (upper pump). (44) Outlet line (lower pump). (45) Right control valve body (operated by upper pump6) Left control valve body (operated by lower pump oil).

he oil delivered from upper and lower pumps (31) and (32) respectively enters right and left valve bodies (45) and (main control valves (14). If no work is being performed, pump oil flows through the control valves and returns to

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ydraulic tank (37). Main control valves (14) now sends a signal (negative flow control) to each pump causing thespective pump to destroke to minimum output flow.

an operation is being performed, main control valves (14) direct pump oil to the respective cylinders (boom, buckeck) and/or motors (swing and travel). Main control valves (14) contain various valve stems, passages, check valvesifices which allow an operation to be done by itself or in combination with other operations. The maximum workinessure of the main hydraulic system is restricted to main relief valve (16) setting of 34 300 kPa (5000 psi) during tr

peration and 31 400 kPa (4500 psi) during implement/swing operation.

b7) Control lever (stick and swing). (48) Control lever (boom and bucket). (49) Travel pedal (left). (50) Travel pedal (right).

lot pump (36) delivers a constant flow of pressure oil to the pilot circuit. The operating pilot pressure increases to thlot relief valve setting of 3450 kPa (500 psi).

he pilot circuit has the following three functions:

1.To operate main control valves (14): When control levers (47) and (48) or travel pedals (49) and (50) areoperated, pilot oil flows to the main control valves through pilot control valves (20), (25), (18) and (19)respectively. This pilot pressure oil shifts the stems in the main control valves allowing the main pump oil to flto the required circuits of cylinders (4), (8) and (9) and motors (5), (2) and (3).2.To control pump output: Proportional reducing valve (21) receives an electronic signal and uses the pilot sysoil to develop a hydraulic signal pressure. The hydraulic signal pressure goes to the regulators in the main pum

and controls the pump output flow.3.To create pilot signal pressure in the pilot circuit so the following controls can be achieved:

A.Activate Automatic Engine Speed Control (AEC) system, causing functions to automatically reduce the engspeed when no, or very small hydraulic operation is called for.

B.Change the main relief valve pressure setting for travel or implement/swing operation.

C.Release the swing motor parking brake.

D.Automatically change travel speed to HIGH or LOW, depending on the machine load.

E.Operate the straight travel control valve to keep the machine traveling straight during a combined operation travel and implement.

F.Control operations of valves required for easier loading or trenching.

OTE: For details of the pilot control, see the section, "Pilot Circuit".

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b1) Switch panel. (52) Engine speed dial.

achine Left Side3) Controller.

he electronic control system controls the outputs from the engine and the pump through controller (53). Controller (nses the position of the engine governor lever selected by engine speed dial (52). Controller (53) also senses the poode position selected by the power mode switch located on switch panel (51). Controller (53) processes the informad sends a signal pressure to the pump so the pump can provide optimum output depending on the machine load andgine speed.

he electronic control system has the following major functions:

1.When a large load is placed on the machine, the system allows the pump to destroke, allowing the maximumhorsepower available from the engine.2.Depending on the load placed on the machine, the system controls the output of the pump at an optimum powmode from three different power mode setting. This allows the machine to operate at an optimum speed and heto reduce the fuel consumption.3.At a no or very small load condition, the system automatically decreases the engine speed to improve the fueconsumption and noise level.4.The system causes solenoid valves for fine control (28) and swing priority (27) to activate for easier groundsurface leveling or vertical finishing of ditch wall surfaces, respectively.

OTE: For details of the electronic control system, see the separate module "Electric And Electronic System, System

peration, Form No. SENR5454".

Main Pumps

Construction

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ain Pumps Port (upper pump negative flow control pressure). (2) Outlet port (pilot pump). (3) Upper pump. (4) Outlet port (upper pump). (5) Inlet p Port (power shift pressure). (7) Port (lower pump negative flow control pressure). (8) Lower pump. (9) Outlet port (lower pump). (10)

ousing. (11) Pilot pump.

he main pumps consist of upper pump (3) and lower pump (8), coupled in housing (10). The upper and lower pumpentical in construction, operation and control system.

il from the hydraulic tank enters inlet port (5) which is common to both pumps. Each pump delivers oil through itsspective outlet port (4) or (9). Pilot pump (11) draws oil through inlet port (5) and delivers oil through outlet port (2

he power shift pressure for the electronic controller enters the main pump through port (6). The negative flow contressure from the main control valves enters the main pumps through respective ports (1) and (7).

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ain Pumps Outlet port (upper pump). (5) Inlet port. (9) Outlet port (lower pump). (10) Housing. (11) Pilot pump. (12) Gear (pilot pump). (13) Plate.

n. (15) Line (pilot pump). (16) Inlet port (pilot pump oil). (17) Regulator. (18) Drive shaft (lower pump). (19) Center line. (20) Trunnion. (ousing. (22) Center line. (23) Gear (lower pump). (24) Piston. (25) Cylinder. (26) Valve plate. (27) Piston. (28) Gear (upper pump). (29) Shpper pump). (30) Cylinder passage. (31) Inlet passage. (32) Inlet passage. (33) Center hole. (34) Outlet passage. (35) Outlet passage.

he pump is a bent-axis piston type pump. The term bent-axis refers to the angular movement of the piston pumpsembly about the point of intersection of center lines (19) and (22). The pump changes its output depending on thegle of cylinder (25).

rive shaft (18) of the lower pump is coupled with the engine flywheel. Gear (23) of drive shaft (18) engages with ge8) of shaft (29). When drive shaft (18) is driven by the engine flywheel, shaft (29) of the upper pump is driven togerough the mechanical linkage of gears (23) and (28). Because the numbers of teeth of gears (23) and (28) are the sae upper and lower pumps rotate at the same rpm as the engine.

ecause gear (23) engages with gear (12) of pilot pump (11), pilot pump (11) rotates with the main pumps.

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ump Operation

he upper and lower pumps are identical in operation. Description is given to the lower pump as a typical example.

rive shaft (18) is driven by the engine. Drive shaft (18) turns seven pistons (24), causing cylinder (25) to rotate.ylinder (25) is in contact with valve plate (26). Cylinder (25) rotates on valve plate (26). Cylinder (25) pivots on pin4). Gear (23) has plate (13) that retains heads of pistons (24), allowing them to swivel in their sockets.

mp Cover And Valve Plate Outlet port (upper pump). (5) Inlet port. (9) Outlet port (lower pump). (20) Trunnion. (21) Housing. (26) Valve plate. (31) Inlet passage. nter hole. (35) Outlet passage. (36) Grooves.

il from the hydraulic tank goes into housing (21) through inlet port (5). The oil goes through inlet passages (32) and1) in valve plate (26), respectively. The oil then enters cylinder passages (30) of cylinder (25) which are positionedlet passage (31). As the cylinder turns, openings of passages (30) in the cylinder rotate to the position of inlet passa1).

ston (24) changes its stroke (displacement), depending on the angle of cylinder (25). As the piston moves out of theore of cylinder (25), it draws oil behind it. As the piston moves in the bore, it pushes oil ahead of the piston. The oilpushed ahead of the piston goes through cylinder passage (30) and then through outlet passage (35) in valve plate (

he oil then leaves the lower pump through outlet port (9) and goes to the hydraulic circuit.

alve plate (26) moves on the machined grooves (36) of housing (21). Housing (21) has a circular contour. Center ho3) of valve plate (26) holds one end of trunnion (20). The other end of the trunnion is held to piston (27) of regulato7). As piston (27) moves in or out during regulator operation (described later), the cylinder changes its angle becaue mechanical linkage of trunnion (20) and valve plate (26). When valve plate (26) moves in radial direction (C), thelinder decreases its angle, decreasing the stroke of pistons (24), causing pump output to decrease. When valve plate6) moves in radial direction (D), the cylinder increases its angle, increasing the piston stroke for an increase in pum

utput.

let oil is sealed from the outlet oil by a metal-to-metal seal between the face of valve plate (26) and the face of cylin5). On the other side of valve plate (26), the seal is made with the face of the machined groove (36). The sealing fae made with precision. Protection must be given to these faces during disassembly and assembly.

alve plate (26) in the lower pump is not the same as valve plate (37) in the upper pump. Use extra care to install valates (26) and (37) in their correct position.

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alve Plates6) Valve plate (in lower pump). (37) Valve plate (in upper pump).

ump Regulator

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gulator (Upper Pump) Passage. (2) Passage. (3) Passage. (4) Shuttle valve. (5) Passage. (6) Passage. (7) Passage. (8) Housing. (9) Outlet port (upper pump). (10

utlet passage. (11) Line (upper pump Pn). (12) Passage. (13) Piston. (14) Control piston. (15) Passage. (16) Passage. (17) Passage. (18) Spr

9) Bushing. (20) Passage. (21) Pin. (22) Spring. (23) Line (PS). (24) Control piston. (25) Passage. (26) Spring chamber. (27) Spring. (28)

ring. (29) Spring spacer. (30) Spring. (31) Trunnion. (32) Piston. (33) Bolt. (34) Ring. (35) Passage. (36) Cover chamber. (37) Piston cham

8) Bolt. (PD) Main pump delivery pressure (upper pump). (PG) Pilot pump delivery pressure. (PN) Negative flow control pressure. (PS) Powift pressure.

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mp Compartment

1) Line (upper pump Pn). (23) Line (PS). (39) Outlet line (P

G). (40) Regulator (upper pump). (41) Port. (42) Regulator (lower pump). (43)

wer pump Pn).

he pump regulator functions as follows:

1.Using the electronic control system, the regulator receives the hydraulic signal pressure [power shift pressur(Ps)] and controls the pump output flow depending on the machine load and engine speed.

2.To keep the horsepower from the engine to the pump constant, the regulator receives the main pump delivery

pressure (PD). This is called the constant horsepower flow control.3.When the control levers are in NEUTRAL or in PARTIAL MOVEMENT position, the regulator receives thnegative flow control pressure (PN). Negative flow control pressure (PN) controls the pump output flow. This i

called the negative flow control.

he regulators of the upper and lower pumps are basically identical in construction and operation. Description is givee upper pump regulator.

il from the upper pump and pilot pump flows to regulator (40) as follows:

il from the upper pump goes through passages (10) and (7) in housing (8), passages (1) and (3), and shuttle valve (4

ssage (2). Oil from the pilot pump goes through passages (16) and (5) and shuttle valve (4) to passage (2). Only thegher pressure of main pump delivery pressure (PD) or pilot pump delivery pressure (PG) can go through passage (2

he pressure through passage (2) separates into the following three paths:

1.One path goes through passage (15) to control piston (14) in the regulator.2.Another path goes through passage (17) to control piston (24) in the regulator.3.The third path goes through passages (6) and (35) and cover chamber (36) to piston chamber (37).

ower shift pressure (PS) goes through line (23) to port (41) which is common to upper and lower pump regulators (4

d (42).

uring constant horsepower flow control, the higher pressure of main pump delivery pressure (PD) or pilot pump del

essure (PG) acts against the shoulder of control piston (14) while power shift pressure (PS) is acting against the top

ce of control piston (14). Control piston (14), pin (21) and control piston (24) now shift to control the pump output.

OTE: For further information, see the section, "Regulator Operation" in this module.

uring negative flow control, negative flow control pressure (PN) from line (11) acts against the top surface of piston

3). Control piston (14) shifts, allowing control piston (24) to move for pump flow control.

Regulator Operation

onstant Horsepower Flow Control (Before Pump Destroke)

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gulator Operation (Before Pump Destroke) Shuttle valve. (14) Control piston. (15) Passage. (17) Passage. (20) Passage. (21) Pin. (22) Spring. (24) Control piston. (25) Passage. (26)ring chamber. (27) Spring. (30) Spring. (31) Trunnion. (32) Piston. (33) Bolt. (34) Ring. (35) Passage. (37) Piston chamber. (38) Bolt. (44

mp. (45) Upper pump. (PD

) Main pump delivery pressure. (PG

) Pilot pump delivery pressure. (PS) Power shift pressure.

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gulator Operation (Partial)4) Control piston. (15) Passage. (17) Passage. (20) Passage. (21) Pin. (22) Spring. (24) Control piston. (25) Passage. (26) Spring chamber.

ring. (46) Shoulder. (47) Top surface. (48) Passage. (49) Passage. (PD


) Pilot pump delivery pressure. (

wer shift pressure.

hen the machine is operating with a low load, the higher main pump delivery pressure (PD) or pilot pump delivery

essure (PG) from passage (15) acts on shoulder (46) of control piston (14). Power shift pressure (PS) from passage

ts on top surface (47) of control piston (14). Control piston (14) pushes down against pin (21), trying to move contrston (24) down. Control piston (24) does not move down because the total forces of main pump delivery pressures

lot pump delivery pressure (PG) and power shift pressure (PS) are less than the combined forces of springs (22), (27

d (30). The force of spring (30) is less than that of spring (27). Spring (30) is compressed before spring (27) ismpressed. Passage (48) closes and passage (49) opens making an open connection between passage (25) and springamber (26). Tank pressure in spring chamber (26) acts on the bottom surface of ring (34). Main pump delivery pres

D) or main pump delivery (PG) in piston chamber (37) moves piston (32) and ring (34) down until bolt (33) comes

ntact with bolt (38). Because of the mechanical linkage of piston (32) and the cylinder through trunnion (31), thelinder is held at the maximum angle position, allowing the pump to maintain the maximum output flow.

onstant Horsepower Flow Control (After Start Of Pump Destroke)

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gulator Operation (After Start Of Pump Destroke) Shuttle valve. (14) Control piston. (15) Passage. (17) Passage. (20) Passage. (21) Pin. (22) Spring. (24) Control piston. (25) Passage. (26)ring chamber. (27) Spring. (28) Spring. (30) Spring. (31) Trunnion. (32) Piston. (34) Ring. (35) Passage. (37) Piston chamber. (44) Pilot p

5) Upper pump. (50) Set screw. (PD

) Main pump delivery pressure. (PS) Power shift pressure.

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gulator Operation (Partial)4) Control piston. (15) Passage. (17) Passage. (20) Passage. (22) Spring. (24) Control piston. (25) Passage. (26) Spring chamber. (27) Sprin

6) Shoulder. (47) Top surface. (48) Passage. (49) Passage. (50) Set screw. (PD

) Main pump delivery pressure. (PS) Power shift pressure.

n increased load on the main pump increases power shift pressures (PS) and main pump delivery pressure (PD). (PDld more than (PG)

he combined forces of increased power shift pressure (PS) and main pump delivery pressure (PD) act on top surface

d shoulder (46) of control piston (14) to overcome the total forces of springs (22) and (30). Control piston (14) pus

own on control piston (24) through pin (21). Passage (49) closes and passage (48) opens, allowing main pump delivessure (PD) from passage (17) to go through passage (25) to the bottom surface of ring (34).

ain pump delivery pressure (PD) acting on the top surfaces of ring (34), is now supplied to piston chamber (37) thro

ssage (35). Main pump delivery pressure (PD) is common to both top and bottom surfaces of ring (34). Because the

ea of ring (34) bottom surface is larger than that of its top surface, ring (34) pushes piston (32) up against the forcesrings (30) and (28). The mechanical linkage of piston (32) and the cylinder through trunnion (31), causes the cylindove in its smaller angular direction for pump destroke.

s control piston (32) moves up, spring (30) compresses and pushes piston (24) up. Passage (48) closes and passage

rtially opens, allowing oil to flow from passage (25) to spring chamber (26). Because spring chamber (26) is open

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nk pressure, the pressure on the bottom surface of ring (34) becomes less than main pump delivery pressure (PD). P

2) starts to stop upward movement. When the force of main pump delivery pressure (PD) on the top surface of the r

comes more than the force on its bottom surface, piston (32) starts to move down. Because of the decreasedmpression force of spring (30), control piston (24) also starts to move down. Passage (49) now closes and passage rtially opens. Piston (32) now starts to move up again because of main pump delivery pressure (PD) through passag

5) to the bottom surface of the ring.

s main pump delivery pressure (PD) further increases and compresses spring (27), pistons (24) and (32) operate in t

me operating manner as that described above.

hen main pump delivery pressure (PD) is equal to the combined force of springs (27), (28) and (30), piston (32) is i

lanced position and the angle of the cylinder is held at this point. Control piston (24) is now also held at a balancedosition by keeping the openings of both passages (48) and (49) slightly opened.

urning set screw (50) changes the compression force of spring (22) which changes the pump output flow. An increampression force of the spring increases the pump output flow.

egative Flow Control

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egative Flow Control Operation (Partial)

1) Line [negative flow control pressure (PN

)]. (12) Port. (13) Piston. (14) Control piston. (17) Passage. (18) Spring. (19) Bushing. (21) Pin

ring. (24) Control piston. (25) Passage. (26) Spring chamber. (27) Spring. (28) Spring. (30) Spring. (32) Piston. (45) Upper pump. (46)oulder. (47) Top surface. (48) Passage. (49) Passage. (51) Passage. (52) Center bypass passage. (53) Negative flow control orifice. (54) M

ntrol valves. (55) Spring spacer. (56) Spring spacer. (PD


) Pilot pump delivery pressure. (PN

) Negative

ntrol pressure. (PS) Power shift pressure.

hen all control levers are in NEUTRAL position, oil flow through the center passage (52) of main control valve (54stricted by orifice (53). This results in an increase in negative flow pressure (PN) in line (11). Negative flow pressur

N) enters port (12) and acts on pin (13).

hen negative flow pressure (PN) acting on pin (13) is greater than the combined forces acting on bushings (19), pin

oves down. As pin (13) moves down, bushing (19) is pushed down, pushing control piston (14) down against pin (2oving control piston (24) down, opening passage (48). Now main pump delivery pressure (PD) or pilot pump delive

essure (PG

) in passage (17) pushes piston (32) up compressing springs (27), (28), and (30). When the top surface of

ring spacer (56) comes in contact with spring spacer (55), control piston (24) is pushed up with piston (32) by the f

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main pump delivery pressure (PD) or pilot pump delivery pressure (PG) until a balancing condition occurs. Contro

ston (24) remains in the new balancing position to keep both openings of passages (48) and (49) slightly opened in me manner as that described for the constant horsepower flow control. The cylinder is now held at the minimum an

osition for minimum pump output flow.

hen the control levers are partially moved, oil flow through center passage (52) flows to implement and return to thydraulic tank. This decreases the flow through orifice (53) causing the negative flow pressure to become lower. Thegative flow pressure (PN) gradually decreases its force on pin (13). As the forces of compressed springs (27) and (3

vercome the force of the decreased negative flow pressure (PN), control piston (24) moves up before spring spacer (

mes in contact with spring spacer (55).

uring a leveling operation, the pump output flow is controlled at any rate between minimum and maximum dependin negative flow pressure (PN).

OTE: For more information on the negative flow control pressure (PN), see "Control Valve" in this module.

hen main pump delivery pressure (PD) is very low [less than 3450 kPa (500 psi)] during a fine control operation, p

2) remains stationary because the low main pump delivery pressure (PD) cannot overcome the resistance of the

linder. Now passage (17) and piston chamber (37) are supplied pilot pump delivery pressure (PG

) so that piston (32

n shift.

ressure/Flow (P-Q) Characteristic Curves

Q Characteristic Curves Point (start of pump destroke). (2) Horsepower characteristics.

he output characteristics of each pump depends on two pressures:

1.Pump output circuit pressure.

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2.Power shift pressure.

fter a pump starts to operate, each pump has a set of pressure/flow (P-Q) characteristic curves. The P-Q curve represet of flow rates for different pump circuit pressures. Each point on curve (2) represents the respective flow rate andessure to maintain pump output horsepower constant.

ydraulic Schematic Of Main Control Valves

) Line relief valve (stick cylinder rod end).

) Stick drift reduction valve.

) Return passage.

) Check valve.

) Boom II control valve.

) Line relief valve (stick cylinder head end).

) Stick I control valve.

) Load check valve.

) Logic valve.

0) Swing control valve.

1) Parallel feeder passage.

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2) Left travel control valve.

3) Center bypass passage.

4) Straight travel control valve.

5) Pilot passage.


7) Pressure control valve.

8) Pilot passage.

9) Pilot passage.

0) Pressure switch (implement/swing).


2) Pilot passage.

3) Right travel control valve.


5) Attachment control valve.

6) Load check valve.

7) Bucket control valve.

8) Boom I control valve.

9) Check valve.

0) Stick II control valve.

1) Passage.

2) Passage (lower pump negative flow control).

3) Orifice (lower pump negative flow control)

4) Negative flow control relief valve (lower pump).

5) Negative flow control line (lower pump).

6) Return line.

7) Passage (upper pump negative control).

8) Orifice (upper pump negative flow control).

9) Negative flow control line (upper pump).

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0) Line.

1) Negative flow control relief valve (upper pump).


3) Line relief valve (boom cylinder head end).

4) Return passage.

5) Passage.

6) Passage.




0) Line relief valve (bucket cylinder head end).

1) Line relief valve (bucket cylinder rod end).

2) Pilot passage.

3) Line relief valve (boom cylinder rod end).

4) Selector valve.

5) Check valve.

6) Return line.

7) Upper pump.

8) Lower pump.

9) Pilot pump.

Main Control Valves

ntroduction

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rcuit Flow Illustration (Main Control Valves In Neutral Position) Return passage. (5) Boom II control valve. (13) Center bypass passage. (14) Straight travel control valve. (16) Main control valves. (23) Rvel control valve. (24) Center bypass passage. (30) Stick II control valve. (36) Return line. (44) Return passage. (56) Return line. (57) Uppmp. (58) Lower pump.

ain control valves (16) are located in the hydraulic system between the pumps and actuators (cylinders and motors)epending on the machine operation, components and passages in the valves control oil flow and pressure in the circom the pumps to actuators.

this section, a general circuit and component description is given for the following control valve operations:

1.Main Control Valves In NEUTRAL position.2.Individual Control Valve.3.Negative flow control.4.Pilot Control.

5.Combined Implements/Motors and combined pump flow of boom and stick circuits.

OTE: Detailed information on the previous items 1, 2 and 3 is given in this section.

OTE: For detailed information on items 4 and 5, see separate "Operation" sections involved.

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rcuit Flow Illustration (Individual Control Valve Operation) (Bucket Cylinder Operation As A Typical Example)6) Main control valves. (24) Center bypass passage. (26) Load check valve. (27) Bucket control valve. (36) Return line. (48) Main relief va9) Parallel feeder passage. (50) Line relief valve. (51) Line relief valve. (56) Return line. (57) Upper pump. (58) Lower pump.

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rcuit Flow Illustration (Negative Flow Control Operation)3) Center bypass passage. (16) Main control valves. (24) Center bypass passage. (32) Passage. (33) Orifice. (34) Negative flow control relilve. (35) Negative flow control line. (37) Passage. (38) Orifice. (39) Negative flow control line. (41) Negative flow control relief valve. (5pper pump. (58) Lower pump.

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rcuit Flow Illustration (Pilot Control Operation) Logic valve. (14) Straight travel control valve. (15) Pilot passage. (16) Main control valves. (17) Pressure control valve. (18) Pilot passag

9) Pilot passage. (20) Pressure switch. (21) Pressure switch. (22) Pilot passage. (28) Boom I control valve. (47) Pressure control valve. (48)ain relief valve. (52) Pilot passage. (59) Pilot pump. (60) Swing parking brake control valve. (61) Pilot passage. (62) Pilot control valve.

OTE: For further information, go to the referenced section.

rcuit Flow Illustration (Combined Operation And Pump Flow Combined Operation) Check valve. (5) Boom II control valve. (7) Stick I control valve. (9) Logic valve. (13) Center bypass passage. (14) Straight travel controllve. (16) Main control valves. (24) Center bypass passage. (29) Check valve. (30) Stick II control valve. (31) Passage. (40) Line. (46) Pass

7) Pressure control valve. (49) Parallel feeder passage. (54) Selector valve. (55) Check valve. (57) Upper pump. (58) Lower pump.

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OTE: For further information, go to the referenced section.

Control Valve Bodies

ain Control Valve (Outside View)

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Stick II control valve. (2) Boom I control valve. (3) Bucket control valve. (4) Attachment control valve. (5) Right travel control valve. (6ain relief valve. (7) Left travel control valve. (8) Swing control valve. (9) Stick I control valve. (10) Boom II control valve. (11) Line relielve (bucket cylinder head end). (12) Right body. (13) Line relief valve (stick cylinder head end). (14) Left body. (15) Return port (see NOT6) Line relief valve (boom cylinder rod end). (17) Line relief valve (bucket cylinder rod end). (18) Inlet port (upper pump). (19) Inlet portwer pump). (20) Line relief valve (stick cylinder rod end). (21) Stick drift reduction valve. (22) Return port. (23) Straight control travel va

he main control valves consist of right and left bodies (12) and (14). In right body (12), the following control valvesparallel:

ick II control valve (1)Boom I control valve (2).Bucket control valve (3)Attachment control valve (4).Right travel

ntrol valve (5).

left body (14), the following control valves are in parallel:

raight travel control valve (23).Left travel control valve (7).Swing control valve (8).Stick I control valve (9).Boom ntrol valve (10).

hese two bodies are coupled with bolts to make one assembly.

he right body has return port (15). The left body has inlet ports (18) and (19) and return port (22). Upper pump oil fport (18). Lower pump oil flows to port (19). Both pump oil flows are controlled by the control valves and supplie

linder(s) and/or motor(s) selected for operation.

eturn oil from cylinder(s) and/or motor(s) enters the control valves and flows out ports (15) and back to the hydraulnk through the return line.

he right body is provided with line relief valves (11), (16) and (17). The left body is provided with main relief valvene relief valves (13) and (20) and stick drift reduction valve (21). The line relief valve on the stick cylinder rod end stalled on the stick drift reduction valve.

wing Motor (Right Front)4) Boom drift reduction valve. (25) Line relief valve.

ne relief valve (25) on the boom cylinder head end is installed on boom drift reduction valve (24). Boom drift redulve (24) is located between the main control valve and the boom cylinders.

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ain Control Valves Stick II control valve. (2) Boom I control valve. (3) Bucket control valve. (4) Attachment control valve. (5) Right travel control valve. (7vel control valve. (8) Swing control valve. (9) Stick I control valve. (10) Boom II control valve. (12) Right body. (14) Left body. (15) Returt. (18) Inlet port. (19) Inlet port. (22) Return port. (23) Straight control travel valve. (26) Parallel feeder passage. (27) Parallel feeder pass8) Return passage. (29) Negative flow control orifice. (30) Center bypass passage. (31) Center bypass passage. (32) Negative flow controlfice. (33) Return passage.

he upper pump supplies oil to right body (12) through inlet port (18), center bypass passage (30) and parallel feederssage (26). The lower pump supplies oil to left body (14) through inlet port (19), center bypass passage (31) andrallel feeder passage (27).

ith the control levers in the NEUTRAL position (no load placed on the machine), upper pump oil flows through ceypass passage (30), negative flow control orifice (29), return passage (28) and out through return port (15).

ith the control levers in the NEUTRAL position (no load placed on the machine), the upper pump oil flows throughnter bypass passage (30), negative flow control orifice (29), return passage (28) and out through return port (22).

he oil then flows back to the hydraulic tank. Lower pump oil flows through center bypass passage (31), negative flontrol orifice (32), return passage (33), return port (22) and back to the hydraulic tank. Oil in parallel feeder passage6) and (27) supplied from both pumps remains blocked.

ctivation of any control levers provides two paths for upper pump oil. One path is from center bypass passage (30) t

ght travel control valve (5). The other path is from parallel feeder passage (26) to attachment control valve (4), buckntrol valve (3) and boom I control valve (2). Activation of any control lever also provides two paths for lower pumne path is from center bypass passage (31) to left travel control valve (7) and stick I control valve (9). The other patom parallel feeder passage (27) to swing control valve (8).

ndividual Valve Operation

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ucket Control Valve (Neutral Position) Bucket control valve. (2) Spring. (3) Port. (4) Port. (5) Pilot port. (6) Pilot port. (7) Passage. (8) Center bypass passage. (9) Load check va

0) Return passage. (11) Parallel feeder passage. (12) Line relief valve (bucket cylinder rod end). (13) Line relief valve (bucket cylinder head). (14) Stem.

he bucket control valve is used as a typical example for describing the operation of individual control valves.

hen all controls are in NEUTRAL position, there is no pilot oil sent to pilot ports (5) and (6) from the pilot controllve. Stem (14) is centered in the NEUTRAL position by the force of spring (2). The upper pump oil goes through c

ypass passage (8) to the hydraulic tank.

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ucket Control Valve (Bucket Close Position) Port. (4) Port. (6) Pilot port. (7) Passage. (8) Center bypass passage. (9) Load check valve. (10) Return passage. (11) Parallel feeder passa

4) Stem. (15) Passage. (16) Passage.

hen the bucket control valve is operated to the bucket close position, pilot oil is supplied to pilot port (6) moving st4) to the left. This closes center bypass passage (8) and opens passage (16). Passage (15) is now connected to returnssage (10).

pper pump oil in parallel feeder passage (11) flows through load check valve (9), passages (7) and (16) to port (3). Tucket cylinder rod extends, allowing the displaced oil in the rod end to flow to port (4).

il from port (4) flows through passage (15) to return passage (10) and back to the hydraulic tank.

Negative Flow Control Signal

ydraulic Schematic (Partial) (Negative Flow Control)

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Center bypass passage. (2) Center bypass passage. (3) Passage. (4) Passage. (5) Orifice. (6) Negative flow control relief valve. (7) negativw control line. (8) Orifice. (9) Negative flow control line. (10) Negative flow control relief valve. (11) Return passage. (12) Upper pump. wer pump.

ain Control Valves (Viewed From Rear) Negative flow control line. (9) Negative flow control line.

negative flow control pressure signal from center bypass passages (1) and (2) occurs during the following instance

A.When cylinders or motors are not in operation.B.When fine control of the pilot control valves is needed.

oss Section Of Stick II Control Valve (Partial) (Negative Flow Control Relief Valve) Passage. (4) Passage. (8) Orifice. (10) Negative flow control relief valve. (11) Return passage. (14) Plug. (15) Spring. (16) Body. (17) Va

N) Negative flow control signal pressure.

il from upper pump (12) flows through center bypass passage (2), passage (3) and orifice (8) to return passage (11).ow through orifice (8) is restricted causing the pressure in passage (3) to increase. A negative flow control signal

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essure (PN) now goes through passage (4) and negative flow control line (9) to the pump regulator. The negative fl

ntrol of the regulator causes the pump to destroke.

egative flow control relief valve (10) consists of body (16), plug (14), valve (17) and spring (15).

hen the oil flow in a center bypass passage suddenly changes, there will be a sudden rise in the negative flow contressure. To prevent pressure shock to machine implements, negative flow control relief valve (10) gives a cushion e

y allowing part of the oil to flow by valve (17) and through return passage (11).

hen all controls are in NEUTRAL position, all of the upper pump oil goes through center bypass passage (2). The oen goes through orifice (8), return passage (11), and back to the hydraulic tank. Maximum negative flow controlessure (PN) in passage (3) now goes to the upper pump. The pump cylinder rotates to its minimum angle, causing th

pper pump to destroke to provide minimum oil flow.

pical Cross Section Of Bucket Control Valve (Fine Control Operation) Center bypass passage. (18) Parallel feeder passage. (19) Port. (20) Stem. (21) Passage. (P) Pilot pressure.

hen partial implement operation is started, pilot pressure (P) shifts stem (20) slightly to the left. Pilot pressure (P)rtially opens passage (21) and partially closes center bypass passage (2). Part of the upper pump oil from center byssage (2) goes to orifice (8). The remainder of the oil goes through parallel feeder passage (18) and passage (21) to9). The oil flow in center bypass passage (2) now decreases. The resistance to oil flow through orifice (8) decreasese negative flow control pressure (PN) in passage (3) decreases. The pump cylinder rotates to a larger angle, causing

pper pump to upstroke increasing the oil flow.

ontinuing to full operation moves stem (20) to the left closing center bypass passage (2). There is no oil flow goingrough passage (3), causing no negative flow control pressure (PN). The upper pump output is held maximum.

odulation (increase or decrease) of exact pump output needed is done by inching the control levers. This allows finntrol operation of implements for precision work.

he negative flow control works in the same way for lower pump oil through orifice (5).

Load Check Valve

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om I Control Valve (Boom Raise Position, Load Check Valve Open) Load check valve. (2) Center bypass passage.

oad check valve (1) performs two jobs. First, load check valve (1) prevents a high pressure circuit that is in parallel operation at the same time with a lower pressure circuit, from losing oil to the lower pressure circuit. For example,e bucket cylinder, whose load is light, is moved while the boom cylinders are going up, the high pressure oil of the

oom cylinders would want to flow toward the low pressure oil side of the bucket cylinder. If load check valve (1) wot in the circuit, the boom would lower.

econd, load check valve (1) prevents the boom from coming down when started at a slow speed. When the boom staoing up at a slow speed, center bypass passage (2) of the boom control valve has partial flow to the hydraulic tank.ithout load check valve (1), the pressure oil in the boom cylinders would flow through center bypass passage (2) to

ydraulic tank, causing the boom to come down. Load check valve (1) prevents flow of pressure oil from the head ene boom cylinders to the tank.

he stick and bucket cylinders also have a load check valve to prevent similar reverse oil flow.

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oss Section Of Straight Travel Control Valve And Main Relief Valve Straight travel control valve. (2) Main control valve. (3) Drain passage. (4) Pressure control valve. (5) Passage. (6) Passage. (7) Right travntrol valve. (8) Check valve. (9) Check valve. (10) Pilot passage. (11) Passage. (12) Main relief valve. (13) Piston. (14) Line. (15) Line. (1ne. (17) Upper pump. (18) Lower pump. (19) Pilot pump. (20) Spring. (21) Passage. (22) Passage. (23) Passage. (24) Valve.

il from upper and lower pumps (17) and (18) enters main control valves (2) through lines (14) and (15), respectivelypper and lower pump oil then goes through check valves (8) and (9) to passage (11).

nly the higher oil pressure from either the upper or lower pump can go through passage (11) to main relief valve (12

il from pilot pump (19) goes through line (16) to pilot passages (5) and (6). Activation of travel control causes theessure in passage (6) to increase. Activation of any of implements or swing controls causes the pressure in passage increase. When travel control is operated alone, pilot oil in passage (6) goes through pressure control valve (4) andlot passage (10) to piston (13) of main relief valve (12). When implement or swing controls are activated, valve (24ifted by the increased pressure in passage (5). The oil acting on piston (13) goes through passage (10) to drain pass) and becomes low pressure oil. Now, piston (13) can activate to limit the main relief pressure to 34 300 kPa (4975hen travel control is activated alone. When piston (13) is not activated (during implement or swing operation), the mlief pressure is limited to 31 400 kPa (4550 psi) for any implement operation.

essure control valve (4) is located on right travel control valve (7). During travel operation, the oil pressure in passa) is less than the force of spring (20), causing valve (24) to move to the right opening passage (23). This allows the

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l from passage (6) to flow through passages (23) and (22) to pilot passage (10). When implements and swing controe activated, the pressure in passage (5) increases and moves valve (24) to the left. Passage (23) now closes and pass1) opens. Oil in pilot passage (10) now goes through passage (21), drain passage (3) to the pump suction line andcomes low pressure oil.

ain Relief Valve (In Closed Position)1) Passage. (25) Valve. (26) Spring chamber. (27) Spring. (28) Valve. (29) Spring. (30) Passage. (31) Orifice. (32) Return passage.

hen main pump oil pressure in passage (11) is less than the main relief valve pressure setting, valve (28) is closed be force of spring (29). The oil in passage (11) goes through orifice (31) and enters spring chamber (26). Because theessures in passage (11) and spring chamber (26) are equal, valve (25) shifts to the left by the force of spring (27) anoses passage (30). There is no oil flow from passage (11) to return passage (32).

ain Relief Valve (During Travel Operation With Valve In Open Position)0) Pilot passage. (11) Passage. (13) Piston. (25) Valve. (26) Spring chamber. (27) Spring. (28) Valve. (29) Spring. (30) Passage. (31) Orific2) Return passage. (33) Passage. (34) Piston chamber. (35) Adjuster. (36) Passage. (37) Valve chamber.

uring travel operation, oil from pilot passage (10) goes through passage (33) to piston chamber (34). Piston (13) mothe left compressing spring (29). A higher system pressure is now required to open valve (28).

s the oil pressure in passage (11) increases to the relief valve pressure setting for the travel circuit, the oil pressure i

ssage (11) overcomes the force of spring (29) and opens valve (28). The oil in valve chamber (37) goes through

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ssage (36) to return passage (32) and becomes low pressure oil. Now, the oil pressure from passage (11) is decreasifice (31). The oil then goes through spring chamber (26) to valve chamber (37). Because of decreased oil pressure ring chamber (26), the pressure oil from passage (11) pushes valve (25) to the right against the force of spring (27)

assage (30) now opens, allowing the high pressure oil flow from passage (11) to return passage (32). Pressuredjustment can be made by turning adjuster (35).

ain Relief Valve (During Implement Or Swing Operation With Valve In Open Position)0) Pilot passage. (11) Passage. (13) Piston. (25) Valve. (28) Valve. (29) Spring. (32) Return passage. (34) Piston chamber. (38) Plunger.

uring an implement or swing operation, there is no oil flow from pilot passage (10) to piston chamber (34). The oilessure in piston chamber (34) is low. The low oil pressure in piston chamber (34) allows spring (29) to move piston3) to the right against plunger (38). As piston (13) moves to the right during an implement operation, the force of sp9) acting on valve (28) decreases. The relief valve pressure for implements and swing circuits is now lower than thaavel circuit.

s the oil pressure in passage (11) increases to the relief valve pressure setting for implement or swing circuit, valvesd (25) shift to the right allowing oil flow from passage (11) to return passage (32). Pressure adjustments can be ma

y turning plunger (38).

Line Relief And Makeup Valves (Built in)

ne relief valve and makeup valves are in the passage between each cylinder and its control valve. With an outside fting against a cylinder (with the control valve in the NEUTRAL position), the pressure in the cylinder and the circue control valve increases. The line relief valve limits the pressure to 33 300 kPa (4850 psi). The line relief valve als

perates as a makeup valve.

hen an outside force acts on the implement cylinder (with the control valve in the NEUTRAL position), the implemlinder piston will try to move. A vacuum will occur in the cylinder. The makeup part of the valve sends part of theturn oil to the cylinder, removing the vacuum condition.

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ne Relief Valve (Closed Position) Passage. (2) Valve. (3) Valve. (4) Spring chamber. (5) Valve. (6) Spring. (7) Piston. (8) Return passage. (9) Passage.

igh pressure oil from the line between each cylinder and its control valve goes through passage (1) and enters the linlief valve. The oil then goes through passage (9) in piston (7), and into spring chamber (4). As long as the oil pressu

oes not exceed the line relief valve pressure setting, valve (5) is kept closed by the force of spring (6). This equalizesessure in passage (1) and spring chamber (4). Because there is more surface area on the spring chamber side of valv) and (3) than on the cylinder passage side, both valves are shifted all the way to the left and held in position. The oow from passage (1) remains blocked to return passage (8).

ne Relief Valve (Open Position) Passage. (3) Valve. (4) Spring chamber. (5) Valve. (6) Spring. (7) Piston. (8) Return passage. (9) Passage. (10) Valve chamber. (11) Passa

2) Passage.

s oil pressure in passage (1) increases to the relief valve setting, valve (5) shifts to the right (open position) against t

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rce of spring (6). The oil from valve chamber (10) now goes through passage (12) to return passage (8). The oilessure in valve chamber (10) decreases. Oil pressure from passage (1) moves piston (7) to the right coming in contaith the left end face of valve (5). The oil from passage (1) now goes around piston (7), and through passage (9). Theen goes through spring chamber (4) and into valve chamber (10). Because the oil flow is restricted at the outerrcumference of piston (7), the oil pressure in spring chamber (4) is decreased. Valve (3) now moves to the right opessage (11). The oil will now flow from passage (1) to return passage (8).

ne Relief Valve (Make-up Valve In Operation) Passage. (2) Valve. (3) Valve. (4) Spring chamber. (8) Return passage. (9) Passage. (13) Shoulder.

hen oil is lost through operation of the line relief valve for the rod end of a cylinder, the oil has to be made up

eplaced) in the head end to prevent a vacuum condition.

ecause passage (1) is connected to spring chamber (4) through passage (9), a vacuum can occur in passage (1) andring chamber (4). With oil pressure from return passage (8) acting on shoulder (13) and negative pressure from spriamber (4) acting on its backside of shoulder (13), valve (2) moves to the right. Oil then goes from return passage (8ssage (1) as makeup oil which removes the vacuum condition in passage (1).

ydraulic Schematic For Pilot Oil

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) Swing parking brake control valve.

) Swing parking brake.

) Displacement change valve (left travel).

) Displacement change valve (right travel).

) Pilot line.

) Pilot line.

) Stick drift reduction valve.

) Pilot line.

) Pressure switch (implement/swing).




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3) Pilot line.


5) Logic valve.

6) Straight travel control valve.



9) Line.

0) Pilot line.

1) Pilot line.

2) Pilot line.

3) Pilot line.

4) Pilot line.

5) Pilot line.

6) Pilot line.

7) Pilot line.

8) Pressure switch (boom raise).

9) Pilot line.

0) Pilot line.

1) Pilot control valve (left travel).

2) Pilot control valve (right travel).

3) Pilot control valve (swing and stick).

4) Line.

5) Proportional reducing valve.

6) Pilot relief valve.

7) Passage.

8) Pilot control valve (bucket and boom).

9) Pilot line.

0) Passage.

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1) Passage.

2) Solenoid valve (swing priority).

3) Pilot oil manifold.

4) Solenoid valve (fine control).

5) Upper pump.

6) Lower pump.

7) Line.

8) Line.

9) Hydraulic activation control valve.

0) Line.

1) Line.

2) Solenoid valve (travel speed).

3) Automatic travel speed change valve.

4) Passage.

5) Outlet line.

6) Pilot filter.

7) Pilot pump.

Pilot Oil Supply Circuit

ntroduction

mp Compartment5) Proportional reducing valve. (36) Pilot relief valve. (43) Pilot oil manifold. (55) Outlet line (pilot pump). (56) Pilot filter.

lot system oil output from pilot pump (57) goes through outlet line (55). The pilot system oil flows through pilot fil6) and enters pilot oil manifold (43). The pressure of pilot system oil is limited to 3450 kPa (500 psi) by pilot relief

lve (36). The oil then goes through passage (37) and separates into the following circuits:

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1.Pilot control valves (31), (32), (33) and (38).2.Proportional reducing valve (35).3.Automatic travel speed change valve (53) [with travel speed solenoid valve (52) activated].4.Logic valve (15) [with pressure control valve (18) and swing priority solenoid valve (42) activated].5.Swing parking brake (2).6.Pilot circuits in main control valves (12).

ilot Control Valve Circuits

b (Pilot Control Valves)1) Pilot control valve (left travel). (32) Pilot control valve (right travel). (33) Pilot control valve (swing and stick). (38) Pilot control valve

oom and bucket).

ewed From Under Cab Floor9) Hydraulic activation control valve.

he pilot control valve is the main component in the pilot system. The pilot oil in passage (37) goes through line (34)ydraulic activation control valve (49). The pilot oil then goes through lines (47), (48), (50) and (51) to pilot controllves (31), (32), (33) and (38), respectively. When any of pilot control valves (31), (32), (33) and (38) are operated, l goes to the main control valves selected. The pilot oil shifts the stem in the pilot control valve to operate a cylinded/or motor. This provides easier operation of the control levers.

ydraulic Activation Control Lever (LOCK Position)8) Lever.

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lve (7) in the same manner as that described for boom drift reduction valve (14). Now the stick cylinder operates foTICK IN.

or more information on boom and stick drift reduction valves, see the section "Boom And Stick Control".

ain Control Valve Compartment8) Pressure switch (boom raise)

hen the control lever is fully moved to BOOM RAISE position with the work mode switch at BOOM PRIORITYODE position, there is a pilot oil flow from pilot line (27) to pressure switch (boom raise) (28). Pressure switch (boise) (28) activates causing fine control solenoid valve (44) to energize. During a combined operation of the boom a

ck, there is no upper pump oil sent to the stick circuit but all of the upper pump oil is used for the boom circuit. Noe boom increases its speed.

roportional Reducing Valve Circuit

ot Oil Manifold Compartment5) Proportional reducing valve. (39) Pilot line (power shift pressure).

art of the pilot pump oil in passage (37) goes through passage (40) to proportional reducing valve (35). Proportionalducing valve (35) continuously receives an electrical signal from the electronic controller. Proportional reducing va5) changes the pilot oil sent from passage (40) into a hydraulic signal (power shift pressure). The hydraulic signal grough pilot line (39) to the regulator of the main pump, controlling the pump output flow.

OTE: For more information, see the separate Systems Operation module, "Electric and Electronic Systems, Form NENR6048".

Automatic Travel Speed Change Valve Circuit

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ot Oil Manifold Compartment2) Solenoid valve (travel speed). (53) Automatic travel speed change valve.

ght Console9) Travel speed switch.

he automatic travel speed change valve circuit activates only when travel speed switch (59) is in the AUTOMATICRAVEL SPEED MODE [HIGH (rabbit sign)] position. Moving travel speed switch (59) to AUTOMATIC TRAVEPEED position energizes travel speed solenoid valve (52). Part of the pilot oil in passage (37) goes through passage travel speed solenoid valve (52). With a smaller travel load placed on the machine, automatic travel speed change v3) remains open. The pilot oil now flows through automatic travel speed change valve (53) and pilot line (5) tosplacement change valves (3) and (4) in the left and right travel motors. The travel motors now operate at HIGH sps the travel load increases to a certain range, automatic travel speed change valve (53) automatically changes the traeed to LOW.

OTE: For more information, see the section, "Travel Control".

Logic Valve Circuit

ain Control Valve Compartment8) Pressure control valve. (22) Pilot line.

he logic valve circuit operates during combined loading operation involving boom, stick and swing.

art of the pilot oil from passage (37) goes through passage (41), swing priority solenoid valve (42) and pilot line (22essure control valve (18). This opens logic valve (15), allowing the swing and stick circuits to share the lower pum

om parallel feeder passage (11) for adequate swing and stick movements relative to boom movement.

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OTE: For more information, see the section, "Loading Operation".

wing Parking Brake Release Circuit

wing Motor Swing parking brake control valve. (8) Pilot line. (19) Line.

he swing parking brake release circuit functions to release the swing parking brake during implements and/or swingperation. Part of the pilot oil in passage (37) goes through line (19) to swing parking brake control valve (1). Duringperation, the pilot pressure oil in pilot line (8) keeps swing parking brake control valve (1) open. The pilot pressure oes to swing parking brake (2) an releases the parking brake.

OTE: For more information, see the section, "Swing Control".

ilot Oil Circuits In Main Control Valves

ydraulic Schematic (Partial) (Pilot Oil Circuit in Main Control Valves) Swing control valve. (2) Left travel control valve. (3) Swing parking brake control valve. (4) Straight travel control valve. (5) Main relieflve. (6) Pilot passage. (7) Pressure control valve. (8) Pressure switch (implement/swing). (9) Pilot passage. (10) Pressure switch (travel). (ot passage. (12) Right travel control valve. (13) Main control valves. (14) Boom I control valve. (15) Drain passage. (16) Orifice. (17) Or

8) Passage. (19) Passage. (20) Passage. (21) Pilot oil manifold. (22) Line. (23) Upper pump. (24) Pilot pump. (25) Suction line.

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oss Section Of Right Travel Control Valve Pressure control valve. (8) Pressure switch (implement/swing). (9) Pilot passage. (10) Pressure switch (travel). (11) Pilot passage. (16) O

7) Orifice. (22) Line.

ain Control Valve Compartment Straight travel control valve. (8) Pressure switch (implement/swing). (10) Pressure switch (travel). (12) Right travel control valve. (21) L

lot oil from pump (24) goes through pilot oil manifold (21) and enters main control valves (13) through line (22). Tl flow then divides into tow paths. One path goes through orifice (17) to pilot passage (11) which is connected to traessure switch (10) and pressure control valve (7). Depending on operation (travel or implement) the oil can passrough pressure control valve (7) to main relief valve (5).

he other path goes through orifice (16) and then divides into two paths. One path goes through passage (9) to pressuntrol valve (7), to swing and implement pressure switch (8) and to the swing parking brake control valve. The otheth flows to passage (18). From there it goes through the swing control valve (1) and stick I control valve to passage9). From passage (19) the oil flows to the attachment, bucket and boom I control valves (14) returning to pump suc

ne (25). Operating travel valves (2) and/or (12) directs pilot oil in passage (18) to passage (6) to shift straight travellve (4) whenever travel and an implement are operated at the same time.

lot pressure oil is supplied to the following circuits in the main control valves as follows:

1.Operating travel valve (2) and/or (12) closes passage (20) to drain causing an increase in oil pressure in pass(11). This closes switch (10) signaling the controller to increase engine speed and to also activate the travel alaThe increased pressure in passage (11) also goes through pressure control valve (7) to main relief valve (5) cauit to increase to travel system pressure.2.When any valve other than travel is operated, pilot oil in passage (18) is closed to drain causing oil pressure increase in passage (9). This closes switch (8) signaling the controller to increase engine speed. This increasedpressure in passage (9) also goes to swing parking brake (3) to release it. The pilot oil pressure in passage (9) spressure control valve (7) preventing pilot pressure in passage (11) from going to main relief valve (5). The ma

relief vale now remains at the lower implement system pressure.

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ot Filter Pilot filter. (2) Bypass relief valve. (3) Filter element.

lter element (3) in pilot filter (1) removes contaminants from the pilot oil.

the oil flow through filter element (3) becomes restricted due to the oil being too cold or too contaminated, the oilypasses the filter through bypass relief valve (2).

ilot Manifold Components

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ot Oil Manifold Compartment Accumulator. (2) Line (to hydraulic activation control valve). (3) Solenoid valve (swing priority). (4) Solenoid valve (travel speed). (5)

utomatic travel speed change valve. (6) Line (from pilot filter). (7) Pilot filter. (8) Pilot relief valve. (9) Proportional reducing valve. (10)lenoid valve (fine control). (11) Pilot oil manifold.

ot Oil Manifold (Partial) Accumulator. (2) Line (to hydraulic activation control valve). (6) Line (from pilot filter). (8) Pilot relief valve. (11) Pilot oil manifold. (12ssage. (13) Check valve. (14) Passage.

lot oil flowing through pilot filter (7) and line (6) enters pilot oil manifold (11) and flows through passage (14). Aortion of the pilot oil in passage (14) then flows through check valve (13), passage (12) and line (2) to the hydraulictivation control valve. Pilot oil in passage (14) is supplied at both inlets of pilot relief valve (8) and accumulator (1

ilot Relief Valve

lot relief valve (8) limits the pressure in the pilot circuit to 3450 kPa (500 psi). Since the flow of oil in the pilot systa minimal, most of the output from the pilot pump goes through the pilot relief valve. Most of the oil needed by the

lot system is used to shift one or more of the stems in the main control valves.

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ccumulator

cumulator5) Gas chamber. (16) Bladder. (17) Bowl. (18) Oil chamber. (19) Inlet port.

he accumulator provides oil to the pilot circuit as makeup oil. During combined operations, the pilot system needs ml because there is not enough pilot pump flow. When lowering implements immediately after the engine has beenopped, pilot system makeup oil is provided by the accumulator.

he accumulator stores hydraulic pressure oil by taking advantage of the compressibility of nitrogen gas put in gasamber (15).

he pilot pump oil goes through inlet port (19) and in oil chamber (18). The pilot pressure oil pushes against bladder mpressing the nitrogen gas in gas chamber (15).

heck valve (13), located in the passage connected to inlet port (19), prevents pressure oil from the accumulator fromowing back to line (6). Accumulator oil goes through line (2) and is used only to shift the main control valve stems.

roportional Reducing Valve

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oportional Reducing Valve Proportional reducing valve. (20) Solenoid. (21) Valve.

oportional reducing valve (9) consists of solenoid (20) and valve (21). While the engine is operating, an electricalgnal from the electronic controller energizes the solenoid.

he solenoid controls valve (21). Valve (21) allows a certain amount of pilot pressure oil through to the pump regulantrol pump output. This pilot pressure to the regulator is called power shift pressure. A decrease in engine speedcreases the power shift pressure for a decrease in pump output.

n increase in engine speed decreases the power shift pressure for an increase in pump output.

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oss Section Of Proportional Reducing Valve (Partial) (Signal Current Increase)2) Rod. (23) Spool. (24) Passage (power shift pressure). (25) Spring. (26) Passage. (27) Passage (pilot pressure).

decrease in engine speed increases the signal current to solenoid (20), and increases the magnetic force to rod (22)2) pushes spool (23) down, overcoming the force of spring (25). Now passage (26) opens, allowing oil flow fromssage (27) through passage (26). The oil then goes through passage (24) to the pump regulator as power shift press

hen power shift pressure increases, it destrokes the pump.

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oss Section Of Proportional Reducing Valve (Partial) (Signal Current Decrease)2) Rod. (23) Spool. (24) Passage. (25) Spring. (26) Passage. (28) Passage (to pump suction line). (29) Passage.

n increase in engine speed decreases the signal current to solenoid (20). The magnetic force given to rod (22) is smaan the force of spring (25), causing rod (22) to move up. Spool (23) follows rod (22) up opening passage (29) andosing passage (26). The power shift pressure in passage (24) then vents through passage (29) and out through passa8) to the pump suction line. The power shift pressure decreases, allowing the pump to upstroke.

he power shift pressure is determined by the relationship between the force given to rod (22) and the force of spring5).

he power shift pressure decreases if the force on the rod is smaller than the force of the spring (smaller signal currenow to the solenoid).

he power shift pressure increases if the force on the rod is larger than the force of the spring (greater signal current fthe solenoid).

olenoid Operated Valves

here are three solenoid valves mounted on the pilot oil manifold.

hen the solenoid of a valve receives an electrical signal, it energizes and operates the valve section. For descriptionperation of each valve, see the section given separately.

wing priority solenoid valve

wing priority solenoid valve (3) activates for easier trenching operation.

OTE: For more information, see the section in this module "Trenching Operation".

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ction A-A Of Hydraulic Activation Control Valve (4) Port. (3) Limit switch. (9) Passage. (10) Passage. (11) Spool. (14) Plunger. (15) Notch.

hen hydraulic activation control valve (4) is placed in the unlock position, port (2) is open to passage (9) throughssage (10) of spool (11). Pilot pump oil enters hydraulic activation control valve (4) through port (2). The oil then grough passage (9) and out through ports (5), (6), (7) and (8) to the pilot control valves. The pilot control valves opee main control valves.

mit switch (3) is located in hydraulic activation control valve (4). When hydraulic activation control valve (4) is in

nlock position, spool (11) in hydraulic activation control valve (4) is held at the position in the previous illustration de). In this position, plunger (14) of limit switch (3) moves out to the left until its end seats in notch (15). Limit swi) is now in the OFF position.

hen hydraulic activation control valve (4) is in the lock position, spool (11) turns to move plunger (14) to the right,rning limit switch (3) ON. Now the pilot pump oil is blocked (held) between port (2) and passage (10), and passageconnected to return passage (13) of spool (11). With the flow of pilot pump oil blocked to passage (9), return oil frch pilot control valve goes through passages (9), (12) and (13), and out through return port (1) to the pump suction ow any activation of the pilot control valve levers will not activate the main control valves.

he start switch can operate only when switch (3) is turned ON and hydraulic activation control valve (4) is in the locosition.

ilot Control Valves

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ot Control Valve (Implements And Swing) Control lever. (2) Plate. (3) Rod. (4) Rod. (5) Seat. (6) Metering spring. (7) Spring. (8) Return chamber. (9) Return passage. (10) Returnssage. (11) Passage. (12) Passage. (13) Spool. (14) Spool. (15) Port. (16) Passage. (17) Port. (18) Line (from control valve). (19) Line (tontrol valve). (20) Pilot pump.

ach pilot control valve has four valves that control two operations. For example, the left pilot control valve has fourlves, two for stick and two for swing.

hen control lever (1) is moved to the left, plate (2) tilts to the left. Plate (2) pushes down on rod (3) and seat (5) pusainst the force of metering spring (6) and spring (7). The force of metering spring (6) moves spool (14) down, openssage (11). The oil can now go through passages (16) and (11), and out port (15) through line (19) to the main contlve. The pressure of the oil on the end of the main control valve stem causes it to move for implement or swing

peration.

he oil at the opposite end of the main control valve stem (for the operation) flows back through port (17), through ressage (10) and into return chamber (8) back to the hydraulic tank.

s long as rod (4) is not pushed down, return passage (10) is open and passage (12) is closed.

pring (7) provides the necessary force to allow the control levers to return to the NEUTRAL position when released

Modulated Pilot Pressure

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rtial Cross Section of Pilot Control Valve Rod. (5) Seat. (6) Metering spring. (9) Return passage. (11) Passage. (14) Spool. (16) Passage. (21) Passage. (D) Diameter [of spool (14) urn passage (9)]. (d) Diameter [of spool (14) for passage (11)]. (E) Shoulder [of spool (14)]. (F) Shoulder [of spool (14)]. (L) Length [of

etering spring (6) under compression].

hen the pilot control lever is moved to the left, rod (3) compresses metering spring (6) through seat (5), moving spo4) down. Any movement of spool (14), under this condition, controls the pressure of the pilot oil that goes throughssage (11) to the main control valves. This allows modulation (up and down) of the pilot pressure to the stem of mntrol valve for inching operation of the implement or swing.

ee Fig. A) When the force of metering spring (6) moves spool (14) down, passage (11) opens. Part of the pilot oil co through passage (21) and out to the main control valve, moving the stem only part of its travel distance against therce of its spring. This causes a slight increase in pressure which works against shoulders (E) and (F) of spool (14).

ecause the area of shoulder (E) is larger than that of shoulder (F), spool (14) moves up a small amount of its travelstance against the force of metering spring (6). Return passage (9) partially opens and passage (11) is closed (see Fi).

art of the oil in passage (21) goes out through return passage (9) causing a slight decrease in pressure in passage (21

hen the oil pressure acting on spool (14) is less than the force of metering spring (6), spool (14) returns to its positig. A.

pool (14) modulates (shifts up and down) in a balanced condition between the pressure in passage (21) and the forceetering spring (6).

uring modulation (up-and-down movement) of spool (14), a condition can occur that both return passage (9) andssage (11) are closed at the same time (see Fig. C). This condition provides a certain length (L) of metering spring t this point, the pressure in passage (21) and the force of metering spring (6) are equal.

urther downward movement of rod (3) decreases length (L) of metering spring (6) and establishes a new balancetween the force of metering spring (6) and the pressure in passage (21). The pressure in passage (21) increases withcrease in the force of metering spring (6).

lot oil pressure sent to the main control valves from the pilot control valves increases, directly proportionally to theavel distance of the pilot control lever. Movement of the main control valve stem causes an increased oil flow tolinders and/or motors, proportional to an increased pilot pressure. Fine movement of the pilot control valve lever al

ne control of operation of the cylinders and/or motors.

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he pilot valves for travel operate similar to the pilot valves for the implements and swing. There is a combination coever/foot pedal" for each of the left and right travel pilot control valves.

OTE: For more information on travel pilot control valve operation, see the section, "Travel Control".

ydraulic Schematic For Return Circuit

) Swing motor.

) Travel motor.

) Drain line.

) Makeup line.

) Drain line.

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) Center bypass passage.

) Return passage.

) Main control valves.

) Center bypass passage.

0) Orifice.

1) Drain line.

2) Return line.

3) Orifice.

4) Upper pump.

5) Return line.

6) Lower pump.


8) Return line.

9) Oil cooler.


1) Hydraulic tank.

2) Slow return check valve.

3) Suction line.

Return Circuit

ntroduction

he oil from upper and lower pumps (14) and (16) enters main control valves (8) and then flows as follows.

1.With no load placed on the machine;a.The upper pump oil goes through center bypass passage (9) and orifice (10) to return passage (7).b.The lower pump oil goes through center bypass passage (6) and orifice (13) to return passage (7).

2.With a load placed on the machine;a.Return oil from each control valve for travel, swing and implements goes to return passage (7).

he oil in passage (7) then flows as follows:

1.When the oil temperature is very low, most of the return oil goes through return line (15), bypass check valv(17) and (20) and back to hydraulic tank (21). The remainder of the oil goes through return line (12), slow retur

check valve (22) and oil cooler (19) to hydraulic tank (21).2.As the oil temperature increases, the rate of oil flow through return line (15) decreases and the rate of oil flow

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through return line (12) increases.

ase drain oil from swing motor (1) and travel motors (2) goes through respective drain lines (3) and (5), and combinain line (11). The oil then returns to hydraulic tank (21).

a vacuum occurs in the swing motor, makeup line (4) routes part of the oil from makeup line (4) to the motor,iminating the vacuum condition.

low Return Check Valve And Oil Cooler Circuit

ain Control Valve Compartment (Return Circuit)

Makeup line. (8) Main control valves. (12) Return line. (22) Slow return check valve.

ow return check valve (22) is provided in the downstream side of return line (12). Slow return check valve (22) resl flow, keeping the circuit pressure in return line (12) at approximately 290 kPa (43 psi). This causes part of oil in rene (12) to go to makeup line (4) to remove the vacuum in the swing motor.

OTE: For more information on the makeup operation, see the section, "Swing Control".

l Cooler (Engine Viewed From Left Side) (Return Circuit)9) Oil cooler. (24) Line (inlet). (25) Return line (outlet).

eturn oil flow from slow return check valve (22) goes through line (24) to oil cooler (19). The oil cooler is bolted togine radiator. The oil is cooled and returns to hydraulic tank (21) through return line (25).

Bypass Return Circuit

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ar Of Hydraulic Tank (Return Circuit)1) Drain line. (17) Bypass check valve. (18) Return line. (20) Bypass check valve. (21) Hydraulic tank. (25) Return line. (26) Air breather.

ypass Check Valve5) Return line. (17) Bypass check valve.

hen return oil temperature is very low, resistance to oil flow in return line (15) is high and causes an increase in oilessure. When the pressure increases to approximately 490 kPa (72 psi), bypass check valves (17) and (20) open.

ost of the return oil flows through return line (15) and bypass check valves (17) and (20) to hydraulic tank (21). Thmaining oil goes through return line (12), slow return check valve (22), oil cooler (19) and return line (25) to hydrank (21). This causes the oil temperature to increase, minimizing the pressure loss.

s the oil temperature increases, the oil pressure decreases. Bypass check valves (17) and (20) begin to close. Now th

less oil flow through return line (15) and more oil flow through return line (12). When bypass check valve (17) clol of the return oil goes through return line (12).

Hydraulic Tank

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) Boom cylinders.

) Line.

) Boom drift reduction valve.

) Line.

) Valve.

) Parallel feeder passage.

) Line.

) Main control valves.

) Port.

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0) Line.

1) Check valve.



4) Port.

5) Boom II control valve.


7) Return passage.

8) Port.

9) Port.

0) Return line.

1) Pilot line.

2) Return line.

3) Pilot line.


5) Pilot line.

6) Shock reducing valve (boom raise).

7) Upper pump.

8) Lower pump.

9) Pilot pump.

Boom, Bucket And Stick Control

Boom Raise Control

oom raise operation uses boom I control valve (13) and boom II control valve (15). The boom moves up in High sphen the oil is supplied to the head end of boom cylinders (1) from both upper pump (27) and lower pump (28). Theoom moves up in Low speed when oil is supplied only from the upper pump.

hock reducing valve (26) is provided to prevent sudden stopping of the boom by slowing down the stem returning toutral position when the boom pilot control valve is returned to the HOLD or NEUTRAL position.

OTE: The operation of the shock reducing valves is described in the section of this module "Components In Cylind

rcuits (Shock Reducing Valve)".

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oom drift reduction valve (3) is provided in the line between main control valves (8) and boom cylinders (1). Whenntrol levers are in the NEUTRAL position, boom drift reduction valve (3) stops reverse oil flow from the head end

oom cylinders (1) to prevent a boom drift.

Boom Raise (High Speed)

ain Control Valve Compartment3) Boom I control valve. (15) Boom II control valve.

il from upper pump (27) flows through parallel feeder passage (16). Parallel feeder passage (16) supplies oil to boontrol valve (13).

il from lower pump (28) flows through parallel feeder passage (6). Parallel feeder passage (6) supplies oil to boom Introl valve (15).

hen the boom control lever is moved to FULL RAISE position, the pilot oil in pilot control valve (24) goes throughlot line (25) and shock reducing valve (26) to pilot line (23). The pilot oil flow then divides into two paths. One oilows through port (19) into boom I control valve (13). The other is through pilot line (21) to port (18) of boom II conlve (15).

om I Control Valve (Boom Raise Position) Port. (12) Load check valve. (16) Parallel feeder passage. (17) Return passage. (19) Port. (30) Passage. (31) Passage. (32) Stem. (33) Pass

4) Passage. (35) Passage. (36) Spring.

he pilot oil flow from port (19) moves stem (32) of boom I control valve (13) to the left against the force of spring (he upper pump oil in parallel feeder passage (16) goes through load check valve (12), passage (31) and (35), and ourough port (9). The oil then goes through line (10), valve (5) of boom drift reduction valve (3) and line (2) to the he

d of boom cylinders (1).

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) Boom cylinders.

) Line.

) Pilot line.

) Spool.

) Line.

) Passage.

) Valve.

) Boom drift reduction valve.

) Pilot line.

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0) Line.

1) Pilot line.

2) Port.

3) Port.




7) Check valve (regeneration circuit).


9) Orifice.


1) Return passage.


3) Line.

4) Drain line.

5) Upper pump.

6) Pilot pump.

7) Lower pump.

Boom Lower Control

ntroduction

hen the boom is lowered, only the oil from upper pump (25) is supplied to boom cylinders (1) through boom I cont

lve (16).

oom I control valve (16) contains a regeneration circuit for check valve (17). When the control lever is moved to thOOM LOWER position, check valve (17) causes the displaced oil from the head end of boom cylinders (1) to go tod end of boom cylinders (1). During boom lower operation the regeneration circuit allows the oil flow from upper p5) to be shared in other implement functions.

enter bypass passage (15) in boom I control valve (16) partially opens, allowing upper pump oil to go through centeypass passage (15) to center bypass passage (18). The oil then goes through line (23) to the upper pump regulator. Tgative flow control of upper pump (25) is activated for destroking.

Boom Lower

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hen the control lever is moved to the BOOM LOWER position, pilot oil in pilot control valve (22) goes through pilne (9) and then separates into two paths. One path goes through pilot line (11) and enters boom I control valve (16)rough port (12). The other path goes through pilot line (3) to spool (4) in boom drift reduction valve (8).

he force of spring (48) on stem (41) is greater than the spring force of spool (4) in boom drift reduction valve (8). Thlows spool (4) to shift and valve (7) to open before stem (41) has shifted to boom lower.

om I Control Valve (Boom Lower Position)2) Port. (13) Port. (14) Load check valve. (15) Center bypass passage. (17) Check valve. (18) Center bypass passage. (20) Parallel feederssage. (21) Return passage. (28) Passage. (29) Passage. (30) Passage. (31) Passage. (32) Spring. (33) Spring chamber. (34) Passage. (35) V6) Spring. (37) Passage. (38) Passage. (39) Passage. (40) Passage. (41) Stem. (42) Passage. (43) Passage. (44) Passage. (45) Passage. (46)turn check valve. (47) Spring. (48) Spring.

he pilot oil from port (12) moves stem (41) to the right. Upper pump oil in parallel feeder passage (20) now goesrough load check valve (14), passage (30), and out through port (13). The oil then goes to the rod end of boom cylin) through line (5).

he return oil from the head end of boom cylinders (1) goes through line (2) and into boom drift reduction valve (8).ecause spool (4) is shifted by the pilot pressure from pilot line (3), passage (6) is open to drain line (24). The oilessure acting on the top of valve (7) becomes lower than the circuit pressure in line (2). The lower circuit pressureuses valve (7) to move up, allowing the oil in line (2) to go through line (10) and into boom I control valve (16). Pae return oil goes through passages (43) and (44) and back to the hydraulic tank through return passage (21). Now th

oom starts lowering.

ecause the return oil flow is restricted at passage (44), movement of the boom cylinder rod is slowed down.

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Systems Operation.pdf