PC130-7

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MACHINE MODEL

SERIAL NUMBER

PC130-7

70001 and up

• This shop manual may contain attachiments and optional equipment that are not available in your area. Please consult your local Komatsu distributor for those items you may require.

Materials and specifications are subject to change without notice. • PC130-7 mounts the SAA4D95LE-3 engine.

For details of the engine, see the 95-3 Series Engine Shop Manual.

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No. of page

01 GENERAL

...01-1

10 STRUCTURE AND FUNCTION

...10-1

20 TESTING AND ADJUSTING

... To be issued next time

30 DISASSEMBLY AND ASSEMBLY

... To be issued next time

40 MAINTENANCE STANDARD

...40-1

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GENERAL ASSEMBLY DRAWING ... 01-2 SPECIFICATIONS ... 01-4 WEIGHT TABLE ... 01-7 LIST OF LUBRICANTS AND WATER ... 01-9

01 GENERAL

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GENERAL ASSEMBLY DRAWING

SPECIFICATION DIMENSIONAL DRAWING

Item Unit PC130-7

2.5 m arm, 500 mm shoe 3.0 m arm, 700 mm shoe

A Overall length mm 7,595 7,485

B Overall height mm 2,810 3,170

C Overall width mm 2,490 2,490

D Shoe width mm 500 700

E Cab height mm 2,810 2,810

F Trail swing radius mm 2,190 2,190

G Crawler overall length mm 3,610 3,610

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GENERAL

WORKING RANGE DRAWING

Working range (mm) PC130-7

2.5 m arm 3.0 m arm

A Maximum digging radius 8,290 8,785

B Maximum digging depth 5,520 6,015

C Maximum digging height 8,610 8,790

D Maximum vertical wall digging depth 4,940 5,360

E Maximum dumping height 6,170 6,535

F Minimum swing radius of work equipment 2,450 2,610

G Maximum reach at ground level 8,170 8,665

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SPECIFICATIONS

Machine model PC130-7

Serial No. 70001 and up

Bucket capacity (SAE) m3 0.5 0.5

Operating weight kg 12,200 13,050 P er for m ance W or ki ng r anges

Max. digging depth mm 5,520 6,015

Max. vertical wall depth mm 4,940 5,360

Max. digging reach mm 8,290 8,785

Max. reach st ground level mm 8,170 8,665

Max. digging height mm 8,610 8,970

Max. dumping height mm 6,170 6,535

Max. digging force (bucket) kN {kg} 93.2 {9,500} 93.2 {9,500}

Swing speed rpm 11.0 11.0

Swing max. slope angle deg. 2.0 2.0

Travel speed (Hi/Lo) km/h 2.7/5.5 2.7/5.5

Gradeability deg. 35 35

Ground pressure kPa {kg/cm2_} _{38 {0.39}} _{29 {0.30}}

Di

m

ensi

on

Overall length (for transport) mm 7,595 7,485

Overall width mm 2,490 2,490

Overall height (for transport) mm 2,810 3,170

Overall height to top of cab mm 2,730 2,730

Ground clearance of counterweight mm 855 855

Min. ground clearance mm 400 400

Tail swing radius mm 2,190 2,190

Min. swing radius of work euipment mm 2,450 2,450

Height of work equipment at min.

swing radius mm 6,455 6,455

Length of track on ground mm 3,610 3,610

Distance between tumbler center mm 3,880 3,880

Track gauge mm 1,990 1,990

Overall height of machine cab mm 1,885 1,885

Engi

ne

Model SAA4D95LE-3

Type _{direct injection, with turbochatger, after cooler}4-cycle, water-cooled, in-line, vertical,

No. of cylinders-bore x stroke mm 4 – 95 x 115

Piston displacement l {cc} 3.260 {3,260} Per for m ance Rated horsepower kW/rpm{HP/rpm} 66.2/2,200 {88.7/2,200} Max. torpue Nm/rpm{kgm/rpm} 353/1,500 {36.0/1,500}

High idling speed rpm 2,400

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GENERAL

Engi

ne

Starting motor 24V, 3.0 kw

Alternator 24V, 25A

Battery 12V, 64 Ah x 2

Radiator type Aluminum wave (4-line)

Under

car

riage

Carrier roller 1 on each side

Track roller 7 on each side

Track shoe (iron shoe) Asembly-type triple grouster, 43 on each side

(road liner) Road liner, 43 on each side

Hyd raul ic sys te m Hydr aul ic pum

p Type x no. Variable displacement piston type x 1

Discharge l /min 226 (at 2,200rpm)

Set pressure (at operation) MPa {kg/cm2_} _{31.9 {325}}

(at traveling) 34.8 {355} Co nt ro l va lv

e Type x no. 7-spool type x 1

Control method Hydraulic type

Hy dr au lic m ot or

Travel motor Variable displacement piston type_{(with brake valve, holding brake) x 2} Swing motor Fixed displacement piston type_{(with safety valve, holding brake) x 1}

Hydraulic tank Box-shaped, open

Hydraulic filter Tank return side

Hydraulic cooler Air cooled

Wor k eq uip m en t cyli nde r Bo om cyl ind er

Type Reciprocating piston tipe Reciprocating piston tipe

Cylinder inner diameter mm 105 105

Piston rod diameter mm 70 70

Stroke mm 990 990

Max. length betwiin pins mm 2,490 2,490

Min. length betwiin pins mm 1,500 1,500

Ar

m

cy

linde

r

Stroke mm 1,175 1,175

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H ydra ul ic sy st em Wo rk equ ipm en t cy lind er Buck et cyl inder

Stroke mm 885 885

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GENERAL

WEIGHT TABLE

k This weight table is a guide for use when transporting or handling component.

Unit: kg

Engine assembly (excl. water, oil) 449

• Engine (excl. water, oil) 345

• Engine mount 19.6

• PTO 4.1

• Hydraulic pump 80

Radiator, oil cooler assembly 83

Revolving frame 1,110

Operator's cab 279

Operator's seat 35

Fuel tank (excl. fuel) 101

Hydraulic tank (excl. hydraulic oil) 89

Control valve 116

Self pressure reducing valve 4.8

Counterweight 2,455

Swing motor (with brake valve) 26

Swing circle 155

Swing machinery 72.2

Center swivel joint 28.6

Track frame assembly 2,260

• Track frame 1,280

• Idler assembly 79 x 2

• Recoil spring assembly 69.5 x 2

• Carrier roller 16.5 x 2

• Track roller 21 x 14

• Travel motor, final drive assembly 144 x 2

• Sprocket 33.7 x 2

Track shoe assembly

• Triple grouser shoe (500mm) 725 x 2

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Unit: kg

Boom assembly 1,088

Arm assembly 392.4

Bucket link assembly 92.7

Bucket assembly 369

Boom cylinder assembly 92.7

Arm cylinder assembly 135

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GENERAL

LIST OF LUBRICANTS AND WATER

-22 -4 14 32 50 68 86 104°F -30 -20 -10 0 10 20 30 40°C

RESERVOIR

Engine oil pan

PTO case

Swing machinery case Final drive case (each)

Hydraulic system Idler (each) Hydraulic oil Diesel fuel Add antifreeze Cooling system Fuel tank Coolant Carrier roller (each)

Track roller (each)

Engine oil 17.5 16 0.75 0.75 2.5 2.5 2.5 140 90 240 18.2 2.5 0.090 ---0.105 0.090 ---0.105 0.075 ---0.085 0.075 ---0.085 0.068 ---0.076 0.068 ---0.076 KIND OF FLUID

AMBIENT TEMPERATURE CAPACITY ( )

SAE 30 SAE 10W SAE 10W-30 SAE 15W-40 SAE 30 SAE 30 SAE 10W SAE 10W-30 HD46-HM (a) ASTM D975 No.2 SAE 15W-40 ASTM D975 No. 1 Specified Refill

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PTO ...10- 2 COOLING SYSTEM ...10- 3 POWER TRAIN ...10- 5 SWING CIRCLE ...10- 6 SWING MACHINERY...10- 7 TRACK FRAME...10- 8 IDLER CUSHION ...10- 9 HYDRAULIC COMPONENT LAYOUT ...10- 10 VALVE CONTROL...10- 12 HYDRAULIC TANK AND FILTER...10- 14 HYDRAULIC PUMP (PISTON PUMP) ...10- 15 CONTROL VALVE ...10- 36 SUCTION SAFETY VALVE ...10- 46 CLSS ...10- 47 SELF PRESSURE REDUCING VALVE ...10- 79 CENTER SWIVEL JOINT...10- 86 TRAVEL MOTOR (FINAL DRIVE)...10- 87 SWING MOTOR ...10- 96 SOLENOID VALVE...10-102 PPC ACCUMULATOR...10-104 PPC VALVE ...10-105 WORK EQUIPMENT ...10-116 AIR CONDITIONER PIPING ...10-117 ENGINE CONTROL ...10-118 ELECTRIC CONTROL SYSTEM ...10-123 MONITOR SYSTEM...10-150

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PTO

1. Coupling 2. Shaft 3. Cage 4. Hydraulic pump 5. Level plug 6. Oil filler plug 7. Breather

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STRUCTURE AND FUNCTION

COOLING SYSTEM

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1. Reservoir tank 2. Shroud 3. Oil cooler 4. Fan 5. Radiator 6. Fan guard 7. Oil cooler 8. Radiator cap

9. Charge air inlet hose 10. Radiator inlet hose 11. Charge air outlet hose 12. Oil cooler outlet 13. Drain valve

14. Radiator outlet hose 15. Air condenser 16. Oil cooler inlet SPECIFICATION

Radiator Oil cooler Charge air cooler

Core type Aluminum wave_(4-line) CF40 Aluminum wave

Fin pitch (mm) 3.5/2 3.5/2 4.0/2

Total heat dissipation surfase (m2₎ _25.58 _11.60 _9.54

Pressure valve cracking pressure

(kPa {kg/cm2_}) 49.0 ± 14.7_{{0.5 ± 0.15}} — —

Vacuum valve cracking pressure

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POWER TRAIN

1. Idler

2. Control valve

3. Self pressure reducing valve 4. Travel motor

5. Hydraulic pump 6. Engine

7. 2-stage relief solenoid valve

8. Swing hold brake solenoid valve

9. 2-speed travel changeover solenoid valve 10. PPC lock solenoid valve

11. Swing motor 12. Center swivel joint 13. Swing machinery 14. Swing circle

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SWING CIRCLE

1. Outer race 2. Ball 3. Inner race

a. Inner race soft zone "S" position b. Outer race soft zone "S" position

SPECIFICATIONS

Reduction ratio: – = – 8.182

Amount of grease: 6.5 l (Grease: G2-LI)

90 11

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SWING MACHINERY

1. Swing pinion (No. of teeth: 11) 2. Case

3. No. 2 sun gear (No. of teeth: 17) 4. No. 2 planetary carrier (No. of teeth: 17) 5. Ring gear (No. of teeth: 61)

6. No. 1 planetary carrier (No. of teeth: 17) 7. No. 1 sun gear (No. of teeth: 14) 8. Oil level gauge/ oil filler port 9. Swing motor

10. No. 1 planetary gear (No. of teeth: 24) 11. No. 2 planetary gear (No. of teeth: 22) 12. Drain plug

13. Swing circle SPECIFICATION

Reduction ratio:14 + 61₁₄ x 17 + 61₁₇ = 24.58

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TRACK FRAME

1. Idler 2. Track frame 3. Carrier roller 4. Travel motor 5. Sprocket 6. Track roller 7. Idler cushion 8. Track shoe

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IDLER CUSHION

1. Idler 2. Support 3. Yoke 4. Cylinder 5. Recoil spring 6. U-packing 7. Pilot 8. Nut 9. Valve SPECIFICATION Grease : G2-LI

Amount of filled grease : 140 ml

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HYDRAULIC COMPONENT LAYOUT

1. Bucket cylinder 2. Arm cylinder 3. Boom cylinder 4. Hydraulic tank 5. Swing motor 6. Hydraulic pump 7. Oil cooler 8. L.H. travel motor 9. Control valve

10. 4-spool solenoid valve • PPC lock

• 2-speed travel speed selection • Swing holding brake

• 2-stage relief 11. L.H. PPC valve 12. R.H. PPC valve 13. Travel PPC valve 14. Center swivel joint

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1. R.H. work equipment PPC valve 2. R.H. work equipment control lever

(for boom and bucket operation) 3. Main pump

4. Control valve

5. 4-spool solenoid valve

6. L.H. work equipment control lever (for arm, swing operation)

7. L.H. work equipment PPC valve 8. Safety lock lever

9. L.H. travel pedal 10. R.H. travel pedal 11. L.H. travel lever 12. R.H. travel lever 13. Travel PPC valve 14. Attachment PPC valve

(Attachment installable machine) 15. Attachment pedal

(Attachment installable machine) Lever and Pedal Positions

(A) HOLD

(B) Boom LOWER (C) Boom RAISE (D) Bucket CURL (E) Bucket DUMP (F) HOLD (G) Arm OUT (H) Arm IN (J) Swing LEFT (K) Swing RIGHT (L) L.H. travel FORWARD (M) L.H. travel REVERSE (N) R.H. travel FORWARD (P) R.H. travel REVERSE (Q) PPC FREE (R) PPC LOCK VALVE CONTROL

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HYDRAULIC TANK AND FILTER

1. Hydraulic tank 2. Drain plug 3. Oil filler cap 4. Pressure valve 5. Vacuum valve 6. Sight gauge 7. Suction strainer 8. Filter element 9. Bypass strainer 10. Bypass valve SPECIFICATION Tank capacity : 130 l

Hydraulic oil amount in tank : 90 l Pressure valve cracking pressure :

16.7 ± 6.9 kPa {0.17 ± 0.07 kg/cm2_}

Vacuum valve cracking pressure :

-0.49 – 0 kPa {-0.005 – 0 kg/cm2_}

Bypass valve set pressure :

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HYDRAULIC PUMP (PISTON PUMP)

MAIN PUMP

Type : HPV95 (for 105cc/rev.)

1. Main pump 2. LS valve 3. PC valve

4. Fixed choke valve

5. PC-EPC valve (for PC mode selection) 6. LS-EPC valve (for LS set selection)

IM : PC mode change current PA : Main pump delivery PB : Main pump pressure input PS : Main pump absorption PD1 : Case drain

PLS : Control valve LS pressure inlet

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1. Shaft 2. Cradle 3. Case 4. Rocker cam 5. Shoe 6. Piston 7. Cylinder block 8. Valve plate 9. End cap 10. Spring

11. Servo last chance filter 12. Servo piston

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FUNCTION

• This pump converts engine rotation and torque transmitted to the pump shaft into hydraulic energy and discharges pressurized oil according to load.

• This pump can change delivery when the swash plate angle is changed.

STRUCTURE

• The cylinder block (7) is supported to the shaft (1) with the spline a, and the shaft (1) is sup-ported with the front and rear bearings.

• The shoe (5) is punched to the tip of the piston (6) with a concave ball so that the piston (6) and the shoe (5) form a spherical bearing.

• The shoe (5) is always pressed to the plane A of the rocker cam (4) and slides in a circle.

The rocker cam (4) leads highly pressurized oil together with the cylindrical plane B with the cra-dle (2) fixed to the case, forms a static pressure bearing and slides.

• The piston (6) moves in the axial direction rela-tively in each cylinder of the cylinder block (7). • The cylinder block (7) rotates relatively while

sealing pressurized oil against the valve plate (8), and the plane is designed to balance the oil pressure properly.

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OPERATION

1. Pump Operation

• The shaft (1) rotates together with the cylinder block (7), and the shoe (5) slides on the plate A. When the rocker arm (4) moves along the cylin-drical plane B, the inclination to the centerline X of the rocker cam (4) and the axial direction of the cylinder block (7) changes. The inclination

is called "swash plate angle."

• When the swash plate angle of the center line X of the rocker cam (4) is to the axial direction of the cylinder block (7), the plane A works like the cam against the shoe (5).

• Therefore, the piston (6) slides inside the cylin-der block (7), and the capacities E and F of the cylinder block (7) come to change differently. Then, the pump absorbs and discharges the dif-ference E-F.

• When the capacity in the E chamber contracts as the cylinder block (7) rotates, the pump dis-charges oil during the process. On the other hand, when the capacity in the F chamber increases, the pump absorbs oil during the pro-cess. (The figure shows the end of the absorbing process in the Chamber F and the end of the dis-charging process in the Chamber E.

• When the centerline X of the rocker cam (4) comes to the axial direction of the cylinder block (7) (when the swash plate angle is 0), the differ-ence between the capacities E and F in the cylin-der block (7) comes to 0. And the pump comes to stop absorbing or discharging oil, i.e., the pump stops. (However, the swash plate angle never comes to 0 practically.)

• In the other words, the swash plate angle and the pump delivery are in the proportional rela-tions.

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2. Delivery Control

• When the swash plate angle increases, the difference between the capacities E and F becomes larger and the delivery Q increases. The servo piston (12) changes the swash plate angle .

• The servo piston moves in the direction of straight reciprocation according to signal pres-sures of the PC and LS valves. This straight motion is transmitted to the rocker arm (4) through the slider (13), and the rocker cam (4), which is supported with the cylindrical plane to the cradle (2), slides in the direction of rotation.

• The servo piston's (12) area receiving the pres-sure is different on the right and left sides, and the discharge (self) pressure PP from the main pump is always led to the pressure chamber of the small diameter piston.

• The output pressure Pen of the LS valve is led to the pressure chamber of the large diameter pis-ton.

• Motions of the servo piston are controlled according to the relations between the small diameter piston pressure PP and the large diam-eter piston pressure Pen and the rate of area receiving pressure of the small diameter piston to that of the large diameter piston.

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LS AND PC VALVE

LS valve 1. Sleeve 2. Piston 3. Spool 4. Seat 5. Plug 6. Spring 7. Sleeve 8. Nut 9. O-ring 10. Nut

PA : Pump pressure inlet PB : Pump pressure inlet PDP : Drain

PLP : Control pressure outlet PLS : Over load pressure inlet PPL : Control pressure intle

PSIG : LS mode switching pressure inlet

PC Valve 1. Piston 2. Spring 3. Seat 4. Spring 5. Seat 6. Spool 7. Piston 10. Plug 11. Lock nut

PA : Pump discharge pressure inlet PA2 : Pump discharge pressure inlet PD : Drain pressure outlet

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FIXED THROTTLE VALVE

1. Plug 2. Plug

PA : Drain pressure outlet POUT : Control pressure outlet PIN : LS valve signal pressure inlet

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FUNCTION 1. LS Valve

• The LS valve detects loads and controls delivery. • This valve controls the main pump delivery Q with the differential pressure PLS (PP – PLS) [that is called LS Differential Pressure] between the main pump pressure PP and the control valve outlet pressure PLS.

• This valve is applied with the main pump pres-sure PP, the prespres-sure PLS that is obtained from the control valve output [that is called LS Pres-sure] and the pressure PSIG from the LS-EPC valve [that is called LS Selection Pressure]. • The relations of the differential pressure PLS

(= PP – PLS) between the main pump pressure PP and the LS pressure PLS with the delivery Q vary with the LS selection current ISIG of the LS-EPC valve as shown in the right figure.

• As ISIG changes from 0 to 1A, the spring set force changes accordingly, and the selector point for pump discharge amount changes from 0.64 to 2.1 MPa {6.5 to 21.5 kg/cm2} at the standard median.

2. PC Valve

• When the pump discharge pressure PP rises, the control valve spool stroke will increase and the opening area will enlarge. So, the PC valve controls the pump delivery Q so that the delivery Q does not increase above a certain level depending on the discharge pressure PP. The valve also controls the pump absorbing hydraulic horsepower to approximately equal horsepower so that the pump absorbing horse-power does not exceed the engine horsehorse-power. • This means that, when a load to the actuator

increases during operation and the pump dis-charge pressure PP rises, this valve will reduce the pump delivery Q, or when the pump dis-charge pressure PP drops, this valve will increase the delivery Q.

• In this case, the relations between the pump dis-charge pressure PP and the pump delivery Q change as shown in the right figure since the cur-rent value given to the PC-EPC valve solenoid is regarded as a parameter.

• However, some PC valves have the function to sense actual engine speeds in the heavy-duty operation mode and to reduce the pump delivery and recover the speed when the speed reduces due to increase of load.

• In the other words, when an increase of load reduces the engine speed below the set value, the command current from the controller to the PC-EPC valve solenoid will increase as the engine speed reduces and will reduce the pump swash plate angle.

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OPERATION

1. LS Valve

1) When the control valve is at the center value position

• The LS valve is a 3-way selector valve, and the pressure PLS (LS pressure) from the control valve inlet is being led to the spring chamber B and the pump discharge pres-sure PP is being led to the H port of the sleeve (8).

• The spool (6) position is determined depend-ing on the force of the LS pressure PLS + the force of spring (4) Z and the force of the pump discharge pressure (self-pressure) PP.

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• Before the engine starts, the servo piston (12) is pressed to the right side. (See the right figure.)

• If the control lever is at the "center value" position when the engine starts, the LS pres-sure PLS will be 0 MPa (0 kg/cm2_{). (The LS}

valve interconnects to the drain circuit through the control valve spool.)

• At the time, the spool (6) is pressed to the left side and the C port is connected to the D port. The pump discharge pressure enters from the K port to the piston large diameter side and from the J port to the piston small diameter side respectively. So, the area dif-ference of the servo piston (12) minimizes the swash plate angle.

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2) Operation in direction for maximum pump delivery

• When the LS differential pressure PLS between the pump discharge pressure PP and the LS pressure PLS reduces (when the control valve is large and the discharge pres-sure PP drops, for example), the combined force of the LS pressure PLS and the spring (4) pushes the spool (6) to the right side. • When the spool (6) moves, port D is

con-nected to port E to bring the PC valve in line. At the time, the PC valve is connected to the drain port, and the circuit D – K is applied with the drain pressure PT. (The operation of

• Therefore, the pressure on the piston large diameter side of the servo piston (12) comes to the drain pressure PT, and since the pump dischargepressure PP is applied to port J on the small diameter side, the servo piston (12) is pushed to the right side and the swash plate is moved to the delivery increasing direction.

• When port G is applied with the output pres-sure of the EPC valve for the LS valve, the piston (7) is pushed to the left side.

• This is effective to reduce the spring (4) set force, and the differential pressure between the oil pressure PP when ports D and E of HYDRAULIC PUMP

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3) Operation in direction for minimum pump delivery

• The following explains move of the servo pis-ton (12) to the left side (in the direction for minimum pump delivery). When the LS dif-ferential pressure PLS increases (when the control valve opening area becomes small and the pump discharge pressure PP increases, for example), the force of the dis-charge pressure PP pushes the spool (6) to the left side.

• As the spool (6) moves, the pump discharge pressure PP flows from port C to port D and comes from port K to the piston large diame-ter side.

• Though the pump discharge pressure PP comes to port J of the piston small diameter side, the servo piston (12) is pushed to the left side due to the area difference between the piston large diameter side and the piston small diameter side of the servo piston (12) and the swash plate is moved in the delivery reducing direction.

• When port G is applied with the LS selection pressure, it is effective to reduce the spring (4) set force.

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4) When the servo piston balances

• The area receiving the pressure on the pis-ton large diameter side is supposed to be A1, the one on the small diameter side is supposed to be A0 and the pressure flowing to the piston large diameter side is supposed to be PEN.

• When the pump discharge pressure PP of the LS valve balances with the combined force of the LS pressure PLS and the spring (4) force Z and the relations of A0 x PP = A1 x PEN are satisfied, the servo piston (12) stops at the position and the swash plate is held at the intermediate position (stops

• At the time, the relations of areas receiving the pressure on the both ends of the servo piston (12) are A0 : A1 = 1 : 1.75, and the ones of pressures applied on the piston both ends at the balancing time are PP : PEN = 1.75 : 1 approximately.

• The spring (4) force has been adjusted so that the balance stop position of the spool (6) is determined when PP – PLS = 2.21 MPa {22.5 kg/cm2} is satisfied at the standard center.

• When port G is applied with PSIG (EPC valve output pressure for LS valve of 0 – 2.9 MPa {10 – 30 kg/cm2}), however, the bal-HYDRAULIC PUMP

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2. PC Valve

(1) When the pump controller is normal, the load to the actuator is small and the pump discharge pressure PP is low

1) Function of PC-EPC Valve Solenoid (1)

• The pump controller provides a com-mand current to the PC-EPC valve sole-noid (1). This command current actuates the PC-EPC valve and outputs a signal pressure. When receiving the signal pressure, the PC valve changes the force given to the piston (2).

• The spool (3) stops where the force to the piston (2) balances with the com-bined force of the spring setting force of the springs (4) and (6) on the opposite

And the pressure output from the PC valve (the pressure at the C port) varies with the spool position.

• The value of the command current X is determined depending on type of work (lever control), selection of working mode, set point of engine speed and actual speed.

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2) Function of Spring

• The loads to the springs (4) and (6) of the PC valve are determined depending on swash plate position.

• As the servo piston (9) moves, the piston (7) connected to the slider (8) moves to the right or the left.

• When the piston (7) moves to the left, the spring (6) will be contracted. If the piston moves further to the left, the spring will be brought to the seat (5) and be fixed there. Thereafter, the spring (4) will only move. This means that the spring load changes as the piston (7) extends or contracts the springs (4) and (6).

• Also, since the pressing force of the pis-ton (2) changes as the command current input to the PC-EPC valve solenoid (1) changes, the load to the springs (4) and (6) changes depending on the value of the command current.

• The C port of the PC valve is connected to the E port of the LS valve. The self pressure PP is provided to the A port, the small diameter side of the servo piston (9) and the B port.

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• When the pump discharge pressure PP is small, the spool is located at a position in the left direction. At the time, the C port is connected to the D port, and the pressure to the LS valve becomes the drain pressure PT. If the E port of the LS valve is connected to the G port at the time, the pressure from the J port to the large diameter side of the piston will become the drain pressure PT. And the servo piston will moves to the right side. Then, the pump delivery will come to increase.

• Also, as the servo piston (9) operates, the slider (8) moves the piston (7) to the right side, and the spring force becomes weak because the springs (4) and (6) expand. As the spring force becomes weak, the spool (3) moves to the right side to disconnect the C port from the D port. Then, the pump discharge pres-sure ports B and C are connected. • As a result, the pressure at the C port

rises and the pressure on the large diam-eter side of the piston rises as well, and the servo piston (9) stops moving to the right side. This means that the stop posi-tion of the servo piston (9) (= pump deliv-ery) is determined where the pressing force caused the pressure PP to the spool (3), the pressing force of the PC-EPC valve solenoid and the forces of the springs (4) and (6) balance with each other.

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(2) When the pump controller is normal, the load to actuator is large and the pump discharge pressure PP is high

• When the load is large and the pump dis-charge pressure is high, the force pushing the spool (3) to the left side increases and the spool (3) comes to the position shown in the above figure.

• Then, the pressure flowing from the C port to the LS valve becomes about 3/5 of the pump discharge pressure PP because the pres-sure from the A port partly flows from the C port to the D port through the LS valve as shown in the above figure.

• When the E port of the LS valve is connected to the G port, this pressure is led from the J port to the large diameter side of the servo piston (9) and the servo piston comes to stop.

• When the pump discharge pressure PP increase and the spool (3) moves further to the left side, the discharge pressure PP will flow to the C port so as to minimize the pump delivery.

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• When the servo piston (9) moves to the left side, the piston (7) will move to the left. Then, the springs (4) and (6) will be com-pressed and will push the spool (3) back. If the piston (7) moves further to the left, the ports C and D will open wide.

• As a result, the pressure at the port C (= J) will drop, and the servo piston (9) will move to the left and will stop.

At the time, the servo piston (9) is located further to the left than where it is when the pump discharge pressure PP is low.

• The positional relations between the pump discharge pressure PP and the servo piston (9) are shown by a broken line because the springs (4) and (6) are 2-stage ones. And the relations between the discharge pressure PP and the pump delivery Q are as shown in the right figure.

• Also, when the command current X to the PC-EPC valve solenoid increases, the rela-tions between the pump discharge pressure PP and the pump delivery Q will move in par-allel in relation to the pushing force of the PC-EPC valve solenoid. Therefore, the force of the PC-EPC valve solenoid (1) will be added to the leftward pressing force of the discharge pressure PP to the spool (3), and the relations between PP and Q will move from to as X increases.

(45)

3) When the pump controller is out of order and the PC redundant switch is set to ON 1) In case of light load to main pump • When the pump controller is out of order,

set the PC redundant switch to ON to change the circuit to the resistor side. In this case, since the current is too large when the power is directly taken from the battery, the resistor is connected to con-trol the current to the PC-EPC valve sole-noid.

• At the time, the current becomes con-stant and the piston (2) pressing force becomes constant as well.

• When the pump discharge pressure is low, the combined force of the force of the PC-EPC valve solenoid (1) and the discharge pressure PP is smaller than the spring set force. So, the spool (3) balances at a position in the left side. • At the time, the C port has the same

pressure as the drain pressure at the D port, and the drain pressure PT is led to the large diameter side of the servo pis-ton (9) through the LS valve. Then, the servo piston (9) moves in the diction where the delivery increases because the pressure on the small diameter side of the piston is large.

(46)

2) In case of heavy load to main pump • When the PC redundant switch is set to

ON just like in the previous paragraph, a constant command current is sent to the PC-EPC valve solenoid (1). So, the pis-ton (2) pushes the spool (3) with a con-stant force.

• When the pump discharge pressure PP rises, the spool will moves further to the left side than when the main pump is lightly loaded and will balance at the position shown in the above figure. • In this case, since the pressure from the

A port is led to the C port, the servo pis-ton (9) will move to the left side (small delivery) and will stop at a position fur-ther to the left than when the pump is

(47)

• This means that the current, which is sent to the PC-EPC valve solenoid through the resistor when the PC redun-dant switch is set to On, determines the curve between the pump discharge pres-sure PP and the delivery Q as shown in the figure.

• When the PC redundant switch is set to ON, the curve is further to the left than the curve drawn when the pump controller is normal.

(48)

CONTROL VALVE

OUTLINE

There are the following 2 types of contral valve. • 6-spool valve (without service valve) • 7-spool valve (with service valve) • 7-spool valve (with blade)

• 8-spool valve (with blade and service valve) a Each service valve is a single add-on type, so it

is possible to add or remove the extra valve at any time.

Extermal oppearance and cross section is given only for the 7 spool valve.

AA : Pressure sensor port (pressure sensor is intalled) A1 : To swing motor MB

A2 : To L.H. travel motor A A3 : To R.H. travel motor A A4 : To boom cylinder bottom A5 : To arm cylinder head A6 : To bucket cylinder head A7 : To attachment 1

B1 : To swing motor MA B2 : To L.H. travel motor B B3 : To R.H. travel motor B B4 : To boom cylinder head B5 : To arm cylinder bottom B6 : To bucket cylinder bottom B7 : To attachment 1

BP : From boom RAISE PPC/EPC valve LS : To pump LS valve

PA1 : From swing L.H. PPC/EPC valve PA2 : From L.H. travel forward PPC valve PA3 : From R.H. travel reverse PPC valve PA4 : From boom RAISE PPC/EPC valve PA5 : From arm OUT PPC/EPC valve PA6 : From bucket DUMP PPC/EPC valve PA7 : From service 1 PPC valve

PB1 : From swing R.H. PPC/EPC valve PB2 : From L.H. travel reverse PPC valve PB3 : From R.H. travel forward PPC valve PB4 : From boom LOWER PPC/EPC valve PB5 : From arm IN PPC/EPC valve

PB6 : From bucket CURL PPC/EPC valve PB7 : From service 1 PPC valve

P : From main pump PP : To main pump

PX : From 2-stage relief solenoid valve SA : From swing stroke contral solenoid valve SB : From swing stroke contral solenoid valve TS1 : To tank TS2 : To tank TB : To tank TC : To oil cooler TSW : To swing motor

1. Swing bleed valve 2. Travel junction valve 3. Arm regeneration valve 4. Cover 5. Service valve 6. Bucket valve 7. Arm valve 8. Boom valve 9. R.H. travel valve 10. L.H. travel valve 11. Swing valve 12. PT port block 13. Safety-suction valve

(49)

7 spool valve

(6 spool valve + service valve)

(50)

CROSS-SECTIONAL DRAWING

a Cross-sectional drawing shows 7-spool valve (6-spool + service valve). (1/8)

1. Safety-suction valve

2. Suction valve (L.H. travel A) 3. Suction valve (R.H. travel A) 4. Suction valve (Boom bottom) 5. Suction valve (Arm head) 6. Suction valve (Bucket head)

7. Safety-suction valve mount (service A)

8 Safety-suction valve mount (service B) 9. Suction valve (Bucket bottom)

10. Suction valve (Arm bottom) 11. Suction valve (Boom head) 12. Suction valve (R.H. travel B) 13. Suction valve (L.H. travel B) 14. Lift check valve

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(2/8)

1. Main relief valve 2. Spool (swing) 3. Spool (L.H. travel) 4. Spool (R.H. ravel) 5. Spool (boom) 6. Spool (arm) 7. Spool (bucket) 8. Spool (service) CONTROL VALVE

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(3/8)

1. Pressure compensation valve F (swing) 2. Pressure compensation valve F (L.H. travel) 3. Pressure compensation valve F (R.H. travel) 4. Pressure compensation valve F (boom) 5. Pressure compensation valve F (arm) 6. Pressure compensation valve F (bucket) 7. Pressure compensation valve F (service) 8. Unload valve

9. Pressure compensation valve R (service) 10. Pressure compensation valve R (bucket) 11. Pressure compensation valve R (arm) 12. Pressure compensation valve R (boom) 13. Pressure compensation valve R (R.H. travel) 14. Pressure compensation valve R (L.H. travel) 15. Pressure compensation valve R (swing)

a The above F and R means the following valves : F : Flow control valve

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(4/8)

1. LS pressure detection plug 2. LS bypass plug

3. Pump pressure detection plug 4. Check valve (bucket head) 5. Check valve (arm head) 6. LS selection valve

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(5/8)

1. Main relief valve 2. Cooler bypass valve 3. Lift check valve 4. LS selection valve 5. Spool (swing)

6. Pressure compensation valve R

7. Swing bleed valve

8. Pressure compensation valve F F : Flow control valve

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(6/8)

1. Suction valve (A) 2. Suction valve (B) 3. Spool (L.H. travel)

4. Pressure compensation valve R 5. Travel junction valve

6. Pressure compensation valve F 7. Suction valve (A)

8. Suction valve (B) 9. Spool (R.H. travel)

10. Pressure compensation valve R 11. Pressure compensation valve F F : Flow control valve

R : Pressure reducing valve

(56)

(7/8)

1. Suction valve (A) 2. Suction valve (B) 3. Spool

4. Pressure compensation valve R 5. Pressure compensation valve F 6. Suction valve (A)

7. Suction valve (B)

8. Spool

9. Pressure compensation valve R 10. Arm regemeration valve

11. Pressure compensation valve F F : Flow control valve

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(8/8)

1. Suction valve (A) 2. Suction valve (B) 3. Spool

4. Pressure compensation valve R 5. Pressure compensation valve F 6. Safty-suction valve mount (A) 7. Safty-suction valve mount (B) 8. Spool

9. Pressure compensation valve R 10. Pressure compensation valve F 11. Pressure relief plug

12. Unload valve F : Flow control valve R : Pressure reducing valve

(58)

SUCTION SAFETY VALVE

(SAFETY VALVE WITH SUCTION FOR SERVICE PORT)

1. Suction valve 2. Main valve 3. Piston 4. Piston spring 5. Poppet 6. Poppet spring 7. Suction valve 8. Sleeve 9. Adjustment screw 10. Lock nut SPECIFICATION

Part No. (Reference) Set pressure Use

709-70-74600 24.5 MPa {250 kg/cm_{(at the time of 5}_l/min.)2} For crusher 709-70-74700 17.2 MPa {175 kg/cm_{(at the time of 5}_l/min.)2}

(59)

CLSS

OUTLINE OF CLSS

Features

CLSS stands for Closed Center Load Sensing Sys-tem and is featured as follows :

• Fine controllability without affect of load

• Controllability that allows digging even in the fine control mode.

• Ease of compound operation in which the flow distribution performance depends on spool opening area during compound operation. • Saving of energy by variable pump control

Configuration

• The CLSS consists of a variable displacement piston pump, a control valve and actuators. • The pump body consists of a main pump, a PC

valve and an LS valve.

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Basic principle

1. Control of pump swash plate angle

• The pump swash plate angle (pump delivery) is controlled so that the LS differential pressure PLS, which is the difference between the pump discharge pressure PP and the LS pressure PLS (actuator load pressure) at the control valve out-let, becomes constant.

(LS differential pressure PLS = Pump pressure PP - LS pressure PLS)

• When the LS differential pressure PLS reduces below the set pressure of the LS valve (when the actuator load pressure is high), the pump swash plate angle will move in the direction of maxi-mum. When the set pressure is raised (when the actuator load pressure is low), the pump swash plate angle will move in the direction of mini-mum.

a For the detail of the operation, see the paragraph of "Hydraulic Pump."

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2. Pressure compensation control

• A valve (pressure compensation valve) is mounted on the outlet side of the control valve. In case of compound operation of the actuator with this valve, the differential pressure P between the spool upstream (inlet) and the downstream (outlet) of each valve becomes con-stant irrespective of load (pressure). So, the flow from the pump is distributed (compensated) in proportion to the opening areas S1 and S2 of each valve being operated.

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EACH FUNCTION AND OPERATION OF EACH VALVE

(63)

1. Unload valve

Set pressure : 3.38 MPa {34.5 kg/cm2} 2. Safety-suction valve

Set pressure : 35.8 MPa {365 kg/cm2} 3. Pressure compensation valve

4. Suction valve 5. Main relief valve

Set pressure : normal: 31.9 MPa {325 kg/cm2_}

High pressure : 34.8 MPa {355 kg/cm2_}

6. Lift check valve 7. Cooler bypass valve 8. LS selection valve 9. Swing bleeding valve 10. Travel junction valve 11. Arm regeneration valve

(64)

UNLOAD VALVE

1. When the control valve is neutral FUNCTION

• When the control valve is neutral, the delivery Q equivalent to the pump minimum swash plate angle is released to the tank circuit. At the time, the pump discharge pressure PP is set to 2.45 MPa {25.0kg/cm2} with the spring (3) inside the vale. (The LS pressure PLS is 0 MPa {0kg/cm2_}.)

OPERATION

• The pump discharge pressure PP is applied to the left end face of the spool (4) and the LS pres-sure PLS is applied to the right end face.

• Since the LS pressure PLS is 0 when the control valve is neutral, the pump discharge pressure PP is only applied and is set with the lead to the spring (3).

• When the pump discharge pressure PP rises to the spring (3) load (2.45 MPa {25.0 kg/cm2_{}), the}

spool (4) will move toward the right side and the pump circuit PP will interconnect to the tank cir-cuit T through the drill hole.

• Therefore, the pump discharge pressure PP is set to 2.45 MPa {25.0 kg/cm2}. 1. Unload valve 2. Sleeve 3. Spring 4. Spool PLS : LS circuit (pressure)

PP : Pump circuit (pressure) T : Tank circuit

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2. When the control valve is in the fine control mode

FUNCTION

• When the control valve is in the fine control mode and the requested flow of the actuator is less than the pump minimum swash plate angle, the pump discharge pressure PP is set to the LS pressure PLS + 2.45 MPa {25.0 kg/cm2}.

When the differential pressure between the dis-charge pressure PP and the LS pressure PLS comes to the spring (3) load (2.45 MPa {25.0 kg/ cm2}), the unload valve will open and the LS dif-ferential pressure PLS will come to 2.45 MPa {25.0 kg/cm2_}.

OPERATION

• When the control valve is operated in the fine control mode, the LS pressure PLS will occur and will be applied to the right end face of the spool (4). At the time the differential pressure between the LS pressure PLS and the pump dis-charge pressure PP increases because the opening area of the control valve spool is small. • When the differential pressure between the

pump discharge pressure PP and the LS pres-sure PLS comes to the spring (3) load (2.45 MPa {25.0 kg/cm2}), the spool (4) will move to the right side and the pump circuit PP will intercon-nect to the tank circuit T.

• This means that the pump discharge pressure PP is set to the spring force (2.45 MPa {25.0 kg/ cm2_{} + LS pressure PLS, and the LS differential}

1. Unload valve 2. Sleeve 3. Spring 4. Spool

PLS : LS circuit (pressure) PP : Pump circuit (pressure) T : Tank circuit

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3. When the control valve is operated FUNCTION

• If the required flow of the actuator increases over the pump minimum swash plate angle when the control valve is operated, the flow to the tank cir-cuit T will be interrupted and the pump delivery Q will be completely flown to the actuator circuit.

OPERATION

• When the control valve is operated with large stroke, the LS pressure PLS will occur and will be applied to the right end face of the spool (4). At the time, the opening areas of the control valve spool is large and the difference between the LS pressure PLS and the pump discharge pressure PP is small.

• So, the differential pressure between the pump discharge pressure PP and the LS pressure PLS does not reach the spring (3) load (2.45 MPa {25.0 kg/cm2}) and the spring (3) pushes the spool (4) to the left side.

• Then, the pump circuit PP and the tank circuit T are interrupted, and the pump delivery Q is com-pletely flown to the actuator circuit.

1. Unload valve 2. Sleeve 3. Spring 4. Spool

PLS : LS circuit (pressure) PP : Pump circuit (pressure) T : Tank circuit

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LEADING OF LS PRESSURE

FUNCTION

• The LS pressure is load pressure to the actuator on the outlet side of the control valve.

• In case of a work equipment valve, the pressure reducing valve (3) of the pressure compensation valve reduces the pump discharge pressure PP to the same level as the actuator circuit pressure A and leads the pressure to the LS circuit PLS.

Also, the orifice C is mounted on the piston (5) halfway from the pump circuit PP to the pressure reducing valve (3), and the orifice has the damper function.

• The travel valves leads the actuator circuit pres-sure A directly to the LS circuit PLS.

1. Work equipment valve (boom, arm, bucket, swing)

OPERATION

• When the spool (1) is operated, the pump dis-charge pressure PP will be led to the actuator circuit A through the bridge passage b from the flow control valve (2) and the spool notch a. • Since the pressure reducing valve (3) moves to

the right at the same time, the pump discharge pressure PP led from the orifice c is reduced due to pressure loss at the notch d and is led to the LS circuit PLS and to the spring chamber PLS1. • At the time, the LS circuit PLS is connected to

the tank circuit T from the LS bypass plug (4).

• The both end face areas of the pressure reduc-ing valve (3) are the same (SA = SLS), and the actuator circuit pressure PA (= A) is applied to the SA side and the reduced pump discharge pressure PP is applied to the SLS side on the opposite side.

• Therefore, the pressure reducing valve (3) bal-ances at the position where the actuator circuit pressure PA becomes equal to the pressure of the spring chamber PLS1. The pump discharge pressure PP reduced at the notch d comes to the actuator circuit pressure A and is led to the LS circuit PLS.

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2. Travel valve

OPERATION

• When the spool (1) is operated, the pump dis-charge pressure PP will be led to the actuator circuit A through the bridge passage b from the flow control valve (2) and the spool notch a. • At the same time, the actuator circuit pressure

PA moves the pressure reducing valve (3) to the right side, and the notches c and d interconnect to the travel junction circuit e and the LS circuit PLS respectively.

• So, the actuator circuit pressure PA (= A) is led from the notch c to the LS circuit PLS through the notch d.

a The travel circuit is different from the work equip-ment circuit, the actuator circuit pressure PA is directly led to the LS circui PLS.

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LS BYPASS PLUG

FUNCTION

• This plug released residual pressure of the LS pressure PLS.

• This plug slows the rising speed of the LS pres-sure PLS, causes prespres-sure losses at the spool and the throttle of the shuttle valve by the dis-carded throttled flow and reduces the effective LS differential pressure for higher safety.

OPERATION

• Pressurized oil in the LS circuit PLS flows from the clearance filter a in the space between the LS bypass plug (1) and the valve body to the tank circuit T through the orifice b.

1. LS bypass plug PLS : LS circuit (pressure) T : Tank circuit (pressure)

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PRESSURE COMPENSATION VALVE

FUNCTION

• When the load pressure becomes lower than another actuator and the flow is going to increase during a compound operation, this valve compensates the load pressure. (At the time, the load pressure of another actuator under compound operation (the upper side) is higher than that of the actuator on this side (the lower side).

(71)

OPERATION

• When the load pressure of another actuator side (the upper side) rises during a compound opera-tion, the flow in the actuator circuit A on this side (the lower side) is apt to increase.

• In this case, the LS pressure PLS of another actuator is applied to the spring chamber PLS1 and pushes the pressure reducing valve (1) and the flow control valve (2) to the left side.

• The flow control valve (2) throttles the opening area between the pump circuit PP and the spool upstream PPA and causes a pressure loss between PP and PPA.

• The flow control valve (2) and the pressure reducing valve (1) balance each other where the pressure difference between PA applied to the both end faces of the pressure reducing valve (1) and PLS becomes the same as the pressure loss between PP before and after the flow control valve and PPA.

• So, the pressure differences between the upstream pressures PPA and the downstream pressures PA of the both spools under com-pound operation become the same, and the pump flow is distributed in proportion to the opening area of each spool notch a.

(72)

AREA RATIO OF PRESSURE COMPENSATION VALVE

FUNCTION

• The pressure compensation valve slightly adjust the ratio (S2/S1) of the area S1 on the left side of the flow control valve (2) and the area S2 on the right side of the pressure reducing valve (1) to suite the character-istics of each actuator and determines the compensation charactercharacter-istics.

S1 : Area of the flow control valve (2) - area of the piston (3) S2 : Area of the pressure reducing valve (1) - area of the piston (3)

Area ratio (S1:S2) and compensation characteristics

• When the ratio is 1.00 : The expression [Pump (discharge) pressure PP - Spool notch upstream pressure PPB] [LS circuit pressure PLS - Actuator circuit pressure PA (= A)] can be held, and the flow is distributed as per the spool opening area ratio.

• When the ratio is more than 1.00 : The expression PP - PPB > PLS - PA (= A) can be held, and the flow is distributed less than the spool opening area ratio.

• When the ratio is less than 1.00 : The expression PP - PPB < PLS - PA (= A) can be held, and the flow is distributed more than the spool opening area ratio.

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ARM REGENERATION CIRCUIT

1. At arm in and own weight fall FUNCTION

• When the arm falls due to its own weight because the head pressure A in the arm cylinder (1) is higher than the bottom pressure B during arm digging, this circuit brings the return flow on the head side to the bottom side to increase the cylinder speed.

OPERATION

• When the arm falls for digging due to its own weight, the head side pressure A in the arm cyl-inder (1) will rise above the bottom side pressure B.

• At the time, part of the return flow on the head side passes through the regeneration passage a of the arm spool (2), pushes the check valve (3) to open it and flows to the bottom side.

1. Arm cylinder 2. Arm spool 3. Check valve

A : Head circuit (pressure) B : Bottom circuit (pressure) PP : Pump circuit (pressure)

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2. At arm in process FUNCTION

• When the bottom pressure B of the cylinder (1) rises above the head pressure A and the arm enters the digging process, the check valve (3) will be closed and the circuits on the head side and the bottom side will be interrupted.

OPERATION

• When the arm is in the digging process, the bot-tom side pressure B of the arm cylinder (1) will rise, close the check valve (3) and interrupt the circuits on the head side and the bottom side.

1. Arm cylinder 2. Arm spool 3. Check valve

A : Head circuit (pressure) B : Bottom circuit (pressure) PP : Pump circuit (pressure)

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(76)

TRAVEL JUNCTION VALVE

(L.H. and R.H. travel junction circuit) 1. When traveling straight

(77)

FUNCTION

• When the L.H. and R.H. travel spool is operated to compensate flow errors in the L.H. and R.H. travel circuits during straight travel, the junction circuit will open.

• Then, the flows to the L.H. and R.H. travel motors will become the same during the straight travel, and travel deviation will decrease.

• At the time of steering, load pressure difference brings back the pressure reducing valve of the travel valve inside the steering and closes the spool notch opening of the travel junction valve to close the junction circuit for steering.

OPERATION

• When the L.H. and R.H. travel spool (1) is oper-ated, the pump delivery will flow from the pump circuit PP to A through the actuator circuit PA. • When traveling straight, the actuator circuit PA

will be equalized and the L.H. and R.H. pressure reducing valves (2) will be pressed the same stroke to the right. Then, the notch a and the junction circuit will open.

• The L.H. travel forward oil pressure P1 and the R.H. travel forward oil pressure P2 are led to the spring chamber on the both end of the travel junction valve spool (4) through the respective shuttle valves (5). So, P1 = P2, and the spool is at the neutral position, and the notch d is ?open?.

• Then, the L.H. and R.H. travel actuator circuits are interconnected with the junction circuit. When any difference occurs in the flows to the L.H and R.H. travel motors, this valve will com-pensate them and will reduce occurrence of travel deviations.

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(79)

OPERATION

• When the L.H. travel spool (L.H. 1) is returned to the neutral side from the straight traveling state and the steering is operated, there will occur any difference in the load pressures in the L.H. and R.H. travel actuator circuits PA (R.H. A > L.H. A). The LS pressure PLS will become the same as the R.H. A on the higher load pressure side. • Therefore, the flow control valve on the L.H.

travel side is pressed to the left side with the LS pressure PLS, i.e., the load pressure on the R.H. travel side, and the notch a closes to interrupt the L.H. and R.H. travel circuits. Also, since the pressures in the spring chambers on the both ends of the travel junction valve spool (4) become different and P1 becomes higher than P2, the spool (4) moves to the P1 side and the notch d closes. Then, the steering can be oper-ated.

• The damper is provided to relax the transition characteristics of the junction circuit at the time of abrupt operation.

(80)

TRAVEL LS BYPASS CIRCUIT

(81)

FUNCTION

• When an actuator is operated during travel, this circuit will increase the discarded throttled flow of the LS circuit PLS, loosen the pressure compen-sation accuracy of the travel circuit and limits reduction of the travel speed to small extent. • The bypass circuit is closed in case of

indepen-dent travel or indepenindepen-dent operation of an actua-tor.

OPERATION

• When the boom spool (1) is operated, the LS cir-cuit PLS will come to the same pressure as the boom circuit pressure A1.

• At the same time, the LS circuit pressure PLS is led to the spring chamber PLS1 of the pressure reducing valve (2) of the travel valve.

• Since the travel spool is not operated, the travel actuator circuit PA is closed and the check valve (4) inside the flow control valve (3) is also closed. • Therefore, the travel LS bypass circuit is closed

in case of independent operation of the boom.

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(83)

OPERATION

• When the boom spool (1) is operated, the LS cir-cuit PLS will come to the same pressure as the boom circuit pressure A1.

• Since the actuator circuit pressure is generally higher at boom RAISE than during travel (A1 > A2), the pressure in the spring chamber PLS1 of the flow control valve (3) on the travel side is higher than the travel circuit pressure PA. • So, the pressure reducing valve (2) moves to the

left side, and the LS pressure of the spring chamber PLS1 pushes the check valve (4) from the orifice a to open it and flows to the travel cir-cuit PA through the passages b and c.

• Therefore, when the LS circuit pressure PLS, which has been as high as the boom circuit sure A1, flows to the travel circuit A2, the pres-sure will drop.

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3. At simultaneous operation of boom + swing FUNCTION

• When the boom is raised at the time of swinging, the swing pool stroke will be controlled and the flow to the boom will be distributed more to raise the boom more.

1) When the boom is not raised

OPERATION

• Since the SA and SB ports are interconnected to the drain and no force is given to the piston (2), the stroke of the spool (1) is not controlled. So, the spool (1) comes to the cases (4) and (5) and the stroke increases by ST1. This increases the filtering oil flow.

1. Spool (swing) 2. Piston 3. Plug 4. Case 5. Case ST1 : Spool stroke

(85)

2) At simultaneous operation of boom RAISE

OPERATION

• When the boom RAISE PPC pressure is led to the piston (2) as the stroke control pilot pressure PS through the SA and SB ports, the piston (2) will be pressed in the inner direction.

• At the time, the maximum stroke of the spool (1) will shorten (by ST0) due to control of the piston (2). Boom RAISE OFF ST1 > Boom RAISE ON ST0

• The spool (1) stroke is controlled and shortens. If the boom is raised at the time of swing (hoist swing), the notch a opening area will decrease. So, the flow distribution to the boom will increase and the boom will rise higher at the time of hoist swing.

(86)

SWING BLEED VALVE

FUNCTION

• For swing operation, a bleed valve is provided to the pressure reducing valve to raise the LS pres-sure slowly and to smooth the swing operation. 1. Swing at neutral position

OPERATION

• Since the notch a of the pressure reducing valve (1) and the LS circuit are closed and the bleed-off circuit and the LS circuit are also closed, the LS pressure PLS is not affected by operation of other work equipment.

• The pump discharge pressure PP is also inter-rupted from the bleed-off circuit with the piston (2) and is not affected.

• The notch b of the bleed spool (3) and the bleed-off circuit are interconnected each other.

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2. At swing fine control

OPERATION

• The pressure reducing valve moves in the right direction, and the notch a and the LS circuit inter-connect each other. Also, the pump circuit PP, the bleed-off circuit and the LS circuit intercon-nect each other through the piston (2).

• The bleed spool (3) moves in the left direction in proportion to raise of the swing PPC pressure PA. But the notch b throttles and interconnect to the bleed-off circuit in the fine control region and determines the intermediate pressure before the pump discharge pressure PP is reduced and applied to the LS pressure PLS.

• Therefore, the intermediate pressure is set lower than the pump discharge pressure PP and rises as the bleed spool (3) moves . So, the LS pres-sure PLS rises slowly.

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3. At full swing operation

OPERATION

• When the swing PPC pressure PA comes to the maximum, the notch b of the bleed spool (3) interrupt the bleed-off circuit. The intermediate pressure becomes equal to the pump discharge pressure PP, and the LS pressure PLS becomes equal to the actuator circuit pressure.

(89)

LS SELECT VALVE

FUNCTION

• At the time of simultaneous operation of swing + boom RAISE, this valve prevents high swing LS pressure from entering the LS circuit PLS and also prevents the boom RAISE speed from reducing by securing the pump flow at the time of swing drive.

1. During normal operation

OPERATION

• The pilot pressure is not generally applied to the pilot port BP except for boom RAISE operation. • In this state, the pump discharge pressure PP

pushes the valve (1) to open it and is led to the pressure reducing valve (4) of the swing valve. At the time of swing operation, there occurs the LS pressure PLS suitable for the load pressure, and the pressure is led to the pump LS valve.

(90)

2. At simultaneous operation of swing + boom RAISE

OPERATION

• At the simultaneous operation of swing + boom RAISE, the signal pressure of the PPC circuit is led to the pilot port BP.

• When this pilot pressure BP is applied to the pis-ton (2) and reaches a pressure that is stronger than the spring (3), the piston (2) will be pushed to the left side, the valve (1) will close and the pump discharge pressure PP will not come to flow to the pressure reducing valve (4) of the swing valve.

• Then, the swing pressure does not cause LS pressure PLS, but the LS pressure PLS cause the boom RAISE pressure is led to the pump LS valve, and the pump delivery is controlled with the boom RAISE LS pressure.

• The pilot pressure BP depends on the control lever stroke.

(91)

SELF PRESSURE REDUCING VALVE

P1 : From pump

PR : Supply to solenoid valve, PPC valve and EPC valve. T : To hydraulic tank

(92)

1. Control valve block 2. Valve (sequence valve) 3. Spring

4. Screw 5. Poppet

6. Spring (pressure reducing valve pilot)

7. Spring (pressure reducing valve main) 8. Valve (pressure reducing valve) 9. Spring (safety valve)

10. Ball 11. Filter

(93)

FUNCTION

• The self pressure reducing valves reduces the discharge pressure of the main pump and sup-plies it to the solenoid valve, the PPC valve, etc. as the control pressure.

(94)

1. At engine stop (total low pressure)

OPERATION

• The spring (6) pushes the poppet (5) t the seat, and the circuit between the ports PR and T is closed.

• The spring (7) pushes the valve (8) to the left side, and the circuit between the ports P1 and PR is open.

• The spring (3) pushes the valve (2) to the left side, and the circuit between the ports P1 and P2 is closed.

(95)

2. At neutral and reduction of load pressure P2 (at own weight fall in boom LOWER and arm IN)

Note : When the load pressure P2 is lower than the output pressure PR of the self pressure reducing valve.

OPERATION

• The spring (3) and the PR pressure (0 MPa {0 kg/cm2} at the time of engine stop) pushes the valve (2) in the direction to close the circuit between the ports P1 and P2. When the hydraulic oil enters the P1 port, the expression (P1 pressure Spring (7) force + ( d area x PR pressure)) holds, and the self pressure reducing valve will adjust the openings of the ports P1 and P2 so that the P1 pressure can be maintained higher than the PR pressure.

• When the PR pressure rises above the set pres-sure, the poppet (5) will open and the hydraulic oil flows through the route from the PR port, the hole a in the spool (8), the poppet (5) opening to the tank port T.

• Therefore, there will occur a differential pressure around the hold a in the spool (8) and the spool will move in the direction to close the port P1 and the PR opening. Then, the P1 pressure is reduced and adjusted to a certain pressure (set pressure) with the opening and is supplied as the PR pressure.