SECTION 2 STRUCTURE AND FUNCTION

Group 1 Pump Device --------------------------------------------------------------------------------------------------- 2-1

Group 2 Main Control Valve ----------------------------------------------------------------------------------------- 2-22
Group 3 Swing Device -------------------------------------------------------------------------------------------------- 2-58
Group 4 Travel Device -------------------------------------------------------------------------------------------------- 2-69
Group 5 RCV Lever ------------------------------------------------------------------------------------------------------- 2-83
Group 6 RCV Pedal ------------------------------------------------------------------------------------------------------- 2-90
 SECTION 2 STRUCTURE AND FUNCTION
GROUP 1 PUMP DEVICE

1. STRUCTURE
The pump device consists of main pump, regulator and gear pump.
1) OUTLINE (1/2) - WITHOUT PTO TYPE
Pi1

A3

B3

Dr Psv Pi2

a4
Qmin adjusting screw Qmax adjusting screw Qmin adjusting screw

Regulator Regulator

Pi1 Pi2

a4
Dr1 Psv
B3

B1

a3

a1 a2
A2
Front pump Port block Rear pump Gear pump

A1 Psv a4 A2 Port Port name Port size

A1, 2 Delivery port SAE6000 psi 1"
a1 a2 B1 Suction port SAE2500 psi 3"
Dr Drain port PF 3/4 - 23
Pi1, i2 Pilot port PF 1/4 - 15
Pi1 Pi2 Psv Servo assist port PF 1/4 - 15
a1, 2, 4 Gauge port PF 1/4 - 15
Dr a3 Gauge port PF 1/4 - 14
M A3 Gear pump delivery port PF 1/2 - 19
a3
B1 B3 Dr3 A3 B3 Gear pump suction port PF 3/4 - 20.5
Dr3 Gear pump drain port PF 3/8 - 15
300S2MP01

2-1
 2) OUTLINE (2/2) - WITH PTO TYPE

Pi1

A3

B3

Dr Psv Pi2

a4
Qmin adjusting screw Qmax adjusting screw Qmin adjusting screw

Regulator Regulator

Pi1 Pi2

a4
Dr1 Psv
B3

B1

a3

a1 a2
A2
Front pump Port block Rear pump Gear pump
Port Port name Port size
A1 Psv a4 A2
A1, 2 Delivery port SAE6000 psi 1"
B1 Suction port SAE2500 psi 3"
a1 a2
Dr Drain port PF 3/4 - 23
Pi1, i2 Pilot port PF 1/4 - 15
Psv Servo assist port PF 1/4 - 15
Pi1 Pi2 a1, 2, 4 Gauge port PF 1/4 - 15
a3 Gauge port PF 1/4 - 14
Dr A3 Gear pump delivery port PF 1/2 - 19
M
a3 B3 Gear pump suction port PF 3/4 - 20.5
B1 B3 Dr3 A3 Dr3 Gear pump drain port PF 3/8 - 15
300S2MP02

2-2
 2) MAIN PUMP (1/3)
The main pump consists of two piston pumps (front & rear) and valve block.

953 535 789 732 532 214 548 531 724 702 792 534 808 901 954 719 151 152 211 113
A
808
886
717
406
261
04
774
111

127
123
710
824
251 497 212 153 156 468 157 714 885 314 981 141 271 401
728 313 124 312 116 983
466
725
300S2MP03

04 Gear pump 313 Valve plate (R) 717 O-ring

111 Drive shaft (F) 314 Valve plate (L) 719 O-ring
113 Drive shaft (R) 401 Hexagon socket bolt 723 O-ring
114 1st gear 406 Hexagon socket bolt 724 Square ring
123 Roller bearing 465 ROH plug 725 O-ring
124 Needle bearing 466 VP plug 728 O-ring
127 Bearing spacer 468 VP plug 732 O-ring
141 Cylinder block 497 MH plug 774 Oil seal
151 Piston 531 Tilting pin 789 Back up ring
152 Shoe 532 Servo piston 792 Back up ring
153 Set plate 534 Stopper (L) 806 Hexagon head nut
156 Spherical bushing 535 Stopper (S) 808 Hexagon head nut
157 Cylinder spring 541 Seat 824 Snap ring
211 Shoe plate 543 Stopper 1 885 Valve plate pin
212 Swash plate 544 Stopper 2 886 Spring pin
214 Tilting bushing 545 Steel ball 901 Eye bolt
251 Swash plate support 548 Feedback pin 953 Set screw
261 Seal cover (F) 702 O-ring 954 Set screw
271 Pump casing 710 O-ring
312 Valve block 714 O-ring

2-3
 MAIN PUMP (2/3)

414 326

544

545
541
543

079

VIEW A VIEW B-B

300S2MP04

079 Proportional reducing valve 541 Seat 544 Stopper 2

326 Cover 543 Stopper 1 545 Steel ball
414 Hexagon socket bolt

2-4
 MAIN PUMP (3/3, WITH PTO TYPE)
468 728 125 825 326
102
124
435
711

262
416

826
118
435
117
126 827
115
128

886

300S2MP05

102 Cover 262 Cover 724 O-ring

115 Idler shaft 326 Gear case 728 O-ring
117 2nd gear 414 Hex socket screw 825 Retainer ring
118 3rd gear 435 Hex socket screw 826 Retainer ring
125 Ball bearing 468 Plug 885 Spring pin
126 Roller bearing 711 O-ring 886 Pin
128 Bearing spacer

2-5
2) REGULATOR (1/2)

412 876 874 A

755
A 858
897 B P2
614
612 Pf

Pi

615
613

A 875
B 611
B

Port Port name Port size

A Delivery port SAE 6000 PSI 1"

B Suction port SAE 2500 PSI 3"
Pi Pilot port PF 1/4-15
Pf Power shift pressure -
P2 Companion delivery pressure -

Pi 412 Hexagon socket screw

438
413 Hexagon socket screw
436 Hexagon socket screw
801
438 Hexagon socket screw
497 Plug
924 611 Feed back lever
612 Lever (1)
730 643 708 644 645 646 728 613 Lever (2)
614 Fulcrum plug
SECTION B-B 615 Adjust plug
643 Pilot piston
644 Spring seat (Q)
413 438
645 Adjust stem (Q)
438 646 Pilot spring
656 Block cover
708 O-ring
656 722 O-ring
724 O-ring
735 Pi 725 O-ring
728 O-ring
722
730 O-ring
735 O-ring
755 O-ring
801 Nut
858 Snap ring
497 724 725 436 874 Pin
VIEW C 875 Pin
300S2MP06
876 Pin
897 Pin
924 Set screw

2-6
 REGULATOR (2/2)

SECTION A-A
300S2MP07

601 Casing 630 Lock nut 734 O-ring

621 Compensator piston 631 Sleeve, pf 753 O-ring
622 Piston case 641 Pilot cover 756 O-ring
623 Compensator rod 651 Sleeve 763 O-ring
624 Spring seat (C) 652 Spool 802 Nut
625 Outer spring 653 Spring seat 814 Snap ring
626 Inner spring 654 Return spring 836 Snap ring
627 Adjust stem (C) 655 Set spring 887 Pin
628 Adjust screw (C) 732 O-ring 898 Pin
629 Cover (C) 733 O-ring

2-7
3) GEAR PUMP

887 700 354 353 351

887 433

434

850

355
311

312
732

710 435 361 307 310 308 309 434 466 725

300S2MP08

307 Poppet 353 Drive gear 466 Plug

308 Seat 354 Driven gear 700 Ring
309 Ring 355 Filter 710 O-ring
310 Spring 361 Front case 725 O-ring
311 Screw 433 Flange socket 732 O-ring
312 Lock nut 434 Flange socket 850 Snap ring
351 Gear case 435 Flange socket 887 Pin

2-8
2. FUNCTION
1) MAIN PUMP
The pumps may classified roughly into the rotary group performing a rotary motion and working as
the major part of the whole pump function: the swash plate group that varies the delivery rates: and
the valve cover group that changes over oil suction and discharge.

(1) Rotary group

The rotary group consists of drive shaft
(F)(111), cylinder block (141), piston
shoes (151,152), set plate (153), spherical
bush (156), and cylinder spring (157).
The drive shaft is supported by bearing 124
313
(123,124) at its both ends. 141
157
The shoe is caulked to the piston to from 156
153
a spherical coupling. It has a pocket to 211
relieve thrust force generated by loading 151
pressure and the take hydraulic balance 111
152
so that it slides lightly over the shoe plate
(211). The sub group composed by a
piston and a shoe is pressed against the 123
shoe plate by the action of the cylinder
spring via a retainer and a spherical bush.
Similarly, the cylinder block is pressed
against valve plate (313) by the action of
the cylinder spring. 29092MP06

548
(2) Swash plate group
The swash plate group consists of swash 214 531
plate (212), shoe plate (211), swash plate
support (251), tilting bush (214), tilting pin 251 212
(531) and servo piston (532). 211
The swash plate is a cylindrical part
formed on the opposite side of the sliding 532
surface of the shoe and is supported by
the swash support.
If the servo piston moves to the right and 29092MP07

left as hydraulic force controlled by the

α
regulator is admitted to hydraulic chamber
located on both sides of the servo piston,
the swash plate slides over the swash
plate support via the spherical part of the α
tilting pin to change the tilting angle (α)

2-7

2-9
(3) Valve block group
The valve block group consists of valve
block (312), valve plate (313) and valve
plate pin (885).
The valve plate having two melon-shaped
ports is fixed to the valve block and feeds
and collects oil to and from the cylinder 312
block.
The oil changed over by the valve plate is 313
connected to an external pipeline by way
of the valve block.
885
Now, if the drive shaft is driven by a prime
mover (electric motor, engine, etc), it
rotates the cylinder block via a spline
linkage at the same time. If the swash 29092MP08

plate is tilted as in Fig (previous page) the

pistons arranged in the cylinder block
make a reciprocating motion with respect
to the cylinder block, while they revolve
with the cylinder block.
If you pay attention to a single piston, it
performs a motion away from the valve
plate (oil sucking process) within 180
degrees, and makes a motion towards the
valve plate (or oil discharging process) in
the rest of 180 degrees. When the swash
plate has a tilting angle of zero, the piston
makes no stroke and discharges no oil.

2-10
2) REGULATOR
Regulator consists of the negative flow control, total horse power control and power shift control
function.

(1) Negative flow control

By changing the pilot pressure Pi, the
pump tilting angle (delivery flow) is
regulated arbitrarily, as shown in the
figure.
This regulator is of the negative flow

Delivery flow, Q
control in which the delivery flow Q
decreases as the pilot pressure Pi rises.
With this mechanism, when the pilot
pressure corresponding to the flow
required for the work is commanded, the
pump discharges the required flow only,
and so it does not consume the power Pilot pressure, Pi
uselessly.

2-11
① Flow reducing function

643 654 651 652 613 646

P1 CL
B(E)
874
897
C
A

Pi(from MCV)

875
611

Small diameter
Large diameter Servo piston 548 chamber
chamber
D 531

300S2MP09

As the pilot pressure Pi rises, the pilot piston (643) moves to the right to a position where the
force of the pilot spring (646) balances with the hydraulic force.
The groove (A) in the pilot piston is fitted with the pin (875) that is fixed to lever 2 (613).
Therefore, when the pilot piston moves, lever 2 rotates around the fulcrum of point B [Fixed by
the fulcrum plug (614) and pin (875)]. Since the large hole section (C) of lever 2 contains a
protruding pin (897) fixed to the feedback lever (611), the pin (897) moves to the right as lever 2
rotates. Since the opposing-flat section (D) of the feedback lever is fitted with the pin (548) fixed
by the tilting pin (531) that swings the swash plate, the feedback lever rotates around the fulcrum
of point D, as the pin (897) moves.
Since the feedback lever is connected with the spool (652) via the pin (874), the spool moves to
the right.
The movement of the spool causes the delivery pressure P1 to connect to port CL through the
spool and to be admitted to the large diameter section of the servo piston. The delivery
pressure P1 that is constantly admitted to the small diameter section of the servo piston moves
the servo piston to the right due to the area difference, resulting in decrease of the tilting angle.
When the servo piston moves to the right, point D also moves to the right. The spool is fitted
with the return spring (654) and is tensioned to the left at all times, and so the pin (897) is
pressed against the large hole section (C) of lever 2.
Therefore, as point D moves, the feedback lever rotates around the fulcrum of point C, and the
spool is shifted to the left. This causes the opening between the sleeve (651) and spool (652) to
close slowly, and the servo piston comes to a complete stop when it closes completely.

2-12
② Flow increasing function

643 654 651 652 613 646

P1 CL
B(E)
874
897
C

Pi

875
611

Small diameter
Large diameter Servo piston 548 chamber
chamber
D 531

300S2MP10

As the pilot pressure Pi decreases, the pilot piston (643) moves to the left by the action of the
pilot spring (646) and causes lever 2 (613) to rotate around the fulcrum of point B. Since the pin
(897) is pressed against the large hole section (C) of lever 2 by the action of the return spring
(654) via the spool (652), pin (874), and feedback lever (611), the feedback lever rotates around
the fulcrum of point D as lever 2 rotates, and shifts the spool to the left. Port CL opens a way to
the tank port as the spool moves. This deprives the large diameter section of the servo piston of
pressure, and shifts the servo piston to the left by the discharge pressure P1 in the small
diameter section, resulting in an increase in the flow rate.
As the servo piston moves, point D also moves to the left, the feedback lever rotates around the
fulcrum of point C, and the spool moves to the right till the opening between the spool and sleeve
is closed.

2-13
③ Adjustment of flow control characteristic
The flow control characteristic can be
adjusted with the adjusting screw.
Adjust it by loosening the hexagon nut 801
(801) and by tightening (or loosening) 924
the hexagonal socket head screw (924).
Tightening the screw shifts the control
chart to the right as shown in the figure.
※ Adjusting values are shown in table.
Adjustment of flow control
characteristic 2-12
Speed
Tightening Flow control Flow
amount of starting change
adjusting pressure amount
screw change

Delivery flow, Q
(924) amount

(min -1) (Turn) (kgf/cm2) (ℓ/min)

1800 +1/4 +0.7 +14.6

Pilot pressure, Pi

2-14
(2) Total horsepower control
The regulator decreases the pump tilting
angle (delivery flow) automatically to limit
the input torque within a certain value with

Delivery flow, Q
a rise in the delivery pressure P1 of the
self pump and the delivery pressure P2 of
the companion pump.
(The input horsepower is constant when
the speed is constant.)
Since the regulator is of the simultaneous
Delivery pressure, (P1+P2)
total horsepower type that operates by the
sum of load pressures of the two pumps
in the tandem double-pump system, the
prime mover is automatically prevented
from being overloaded, irrespective of the
load condition of the two pumps, when
horsepower control is under way.
Since this regulator is of the simultaneous
total horsepower type, it controls the tilting
angles (displacement volumes) of the two
pumps to the same value as represented
by the following equation :
Tin = P1×q / 2 π + P2×q / 2 π
= (P1+P2)×q / 2 π
The horsepower control function is the
same as the flow control function and is
summarized in the following. (for detailed
behaviors of respective parts, refer to the
section of flow control).

2-15
① Overload preventive function

621 651 652 623 612 601 625 626

P1 CL
B(E)
897
F

P2 P1
875

611

Large diameter Servo piston Small diameter

chamber chamber

300S2MP11

When the self pump delivery pressure P1 or the companion pump delivery pressure P2 rises, it
acts on the stepped part of the compensating piston (621). It presses the compensating rod
(623) to the right till the force of the outer spring (625) and inner spring (626) balances with the
hydraulic force. The movement of the compensating rod is transmitted to lever 1 (612) via pin
(875).
Lever 1 rotates around the pin (875) (E) fixed to the casing (601).
Since the large hole section (F) of lever 1 contains a protruding pin (897) fixed to the feedback
lever (611), the feedback lever rotates around the fulcrum of point D as lever 1 rotates, and then
the spool(652) is shifted to the right. As the spool moves, the delivery pressure P1 is admitted to
the large diameter section of the servo piston via port CL, causes the servo piston move to the
right, reduces the pump delivery, flow rate, and prevents the prime mover from being overloaded.
The movement of the servo piston is transmitted to the feedback lever via point D. Then the
feedback lever rotates around the fulcrum of point F and the spool is shifted to the left. The
spool moves till the opening between the spool (652) and sleeve (651) is closed.

2-16
② Flow reset function

621 651 652 623 612 601 625 626

P1 CL
B(E)
897
F

P2 P1
875

611

Large diameter Small diameter

chamber Servo piston chamber

300S2MP12

As the self pump delivery pressure P1 or the companion pump delivery pressure P2 decreases,
the compensating rod (623) is pushed back by the action of the springs (625 & 626) to rotate
lever 1 (612) around point E. Rotating of lever 1 causes the feedback lever (611) to rotate
around the fulcrum of point D and then the spool (652) to move to the left. As a result, port CL
opens a way to the tank port.
This causes the servo piston to move to the left and the pump's delivery rate to increase.
The movement of the servo piston is transmitted to the spool by the action of the feedback
mechanism to move it till the opening between the spool and sleeve is closed.

2-17
③ Low tilting angle (low flow) command preferential function
As mentioned above, flow control and horsepower control tilting angle commands are transmitted
to the feedback lever and spool via the large-hole sections (C & F) of levers 1 and 2. However,
since sections C and F have the pins (Ø4) protruding from the large hole (Ø8), only the lever
lessening the tilting angle contacts the pin (897) ; the hole (Ø8) in the lever of a larger tilting
angle command is freed without contacting the pin (897). Such a mechanical selection method
permits preference of the lower tilting angle command of the flow control and horsepower control.
④ Adjustment of input horsepower
Since the regulator is of total cumulative horsepower type, adjust the adjusting screws of both the
front and rear pumps, when changing the horsepower set values. The pressure change values
by adjustment are based on two pumps pressurized at the same time, and the values will be
doubled when only one pump is loaded.

a. Adjustment of outer spring

Adjust it by loosening the hexagon nut
625 626 630 628
(630) and by tightening (or loosening)
the adjusting screw C (628). Tightening
the screw shifts the control chart to the 802

right and increases the input horsepower

as shown in the figure. Since turning
the adjusting screw C by N turns
changes the setting of the inner spring
(626), return the adjusting screw QI
627
(627) by N×A turns at first. (A=1.59)
※ Adjusting values are shown in table.

Adjustment of outer spring 8007A2MP03

Speed
Tightening Compensating Input
amount of control torque
adjusting starting change
Delivery flow, Q

screw (C) pressure amount

(628) change
amount

(min -1) (Turn) (kgf/cm2) (kgf·m)

1800 +1/4 +19 +5.6

Delivery pressure, (P1+P2)

2-18
b. Adjustment of inner spring
Adjust it by loosening the hexagon nut
(802) and by tightening (or loosening) 626
802
the adjusting screw QI (627).
Tightening the screw increases the flow
and then the input horsepower as
shown in the figure.
※ Adjusting valves are shown in table.
627
Adjustment of inner spring
Speed
Tightening Flow change Input
amount of amount torque 8007A2MP04
adjusting change
screw (QI) amount
(627)

Delivery flow, Q
(min -1) (Turn) (kgf/cm2) (kgf·m)
1800 +1/4 +12.6 +5.7

Delivery pressure, (P1+P2)

2-19
(3) Power shift control

621 651 652 623 612 625 626

P1 CL
B(E)
897
898 F

Pf
P2 P1

611

Large diameter Small diameter

chamber Servo piston chamber

300S2MP13

The set horsepower valve is shifted by varying

the command current level of the proportional
pressure reducing valve attached to the pump.
Delivery flow, Q

Only one proportional pressure reducing valve is

provided. Pf=
MIN
However, the secondary pressure Pf (power shift .
Pf=
pressure) is admitted to the horsepower control M AX
.
section of each pump regulator through the
pump's internal path to shift it to the same set
horsepower level. Delivery pressure, (P1+P2)
This function permits arbitrary setting of the
pump output power, thereby providing the optimum power level according to the operating
condition.
The power shift pressure Pf controls the set horsepower of the pump to a desired level, as shown
in the figure.
As the power shift pressure Pf rises, the compensating rod (623) moves to the right via the pin
(898) and compensating piston (621).
This decreases the pump tilting angle and then the set horsepower in the same way as explained
in the overload preventive function of the horsepower control. On the contrary, the set
horsepower rises as the power shift pressure Pf falls.

2-20
(4) Adjustment of maximum and minimum flows
808
① Adjustment of maximum flow
Adjust it by loosening the hexagon nut 954
(808) and by tightening (or loosening)
the set screw (954).
The maximum flow only is adjusted
without changing other control
characteristics. 2-19(1)

Adjustment of max flow

Speed

Delivery flow, Q
Tightening Flow change
amount of amount
adjusting screw
(954)

(min -1) (Turn) (ℓ/min)

1800 +1/4 -5.6 Delivery pressure, Pi

② Adjustment of minimum flow

Adjust it by loosening the hexagon nut
(808) and by tightening (or loosening)
808
the hexagonal socket head set screw
(953). Similarly to the adjustment of the 953
maximum flow, other characteristics are
not changed.
However, remember that, if tightened too
much, the required horsepower during 2-19(2)

the maximum delivery pressure (or

during relieving) may increase.

Adjustment of min flow

Delivery flow, Q

Speed
Tightening Flow change
amount of amount
adjusting screw
(953)

(min -1) (Turn) (ℓ/min)

Delivery pressure, Pi
1800 +1/4 +4.5

2-21
 GROUP 2 MAIN CONTROL VALVE
1. STRUCTURE (1/8) Mark Port name
P02
Port size Tightening torque
A
Rs Make up for swing motor 20~25 kgf·m
DR6
PF1 (145~180 lbf·ft)
Patt Auto idle signal-attachment
Pu
PbL Lock valve pilot port (boom)
PCbc Bucket in confluence pilot port
CMR2 CMR1

(PDbc) Option confluence pilot port

X1 Btr
TRAVEL RIGHT Atr

LCb1
P2
T1
P01 Pilot signal port
P02 Pilot signal port
BOOM1 Ab Bb
P03 Swing logic pilot port
PbL DR2

LCbk P04 Bucket parallel orifice pilot port

Bbk (P05) Option B confluence pilot port 3.5~4.0 kgf·m
ARM REGEN LCar X6 V2
X7
PaL Lock valve pilot port (arm) PF1/4 (25.3~28.9 lbf·ft)
DR6
Ptr Auto idle signal-travel
P02
P1

ARM2 X8
Pu Power boost
DR1 Drain port
Ak
DR2 Drain port
DR3 Drain port
Bk
BUCKET DR5
LCk1 LCk2

RS DR4 Drain port

DR5 Drain port
P03 DR7 Drain port
DR9 Drain port
VIEW A
(P4) - PF1/2
10~12 kgf·m
(P5) - (72.3~86.8 lbf·ft)
PAtr Travel pilot port-RH (FW)
Ptr
PBtr Travel pilot port-RH (BW)
PCtl Travel pilot port-LH (BW)
X4 MR
Dr0
X8
BtR
P01
PDtl
PDtl Travel pilot port-LH (FW)
Ctr Dtl
TRAVEL LEFT
AtR
PAb1 Boom up pilot port
BbR
PBtr PCtl DR5 DR5 Patt PAtr PDb2 Boom up confluence pilot port
P03 P03 PBb1 Boom down pilot port
Ds
SWING
PCs Swing pilot port (LH)
Cs
PCs Dr3
PDs Swing pilot port (RH)
Dr1 PBb1 PDs PAb1
DaR AbR
PBrc SWING
PRIORITY
X5 PBa Arm in regen-cut signal selector port
BOOM2
PBa
Ccb PBa2 Arm in confluence pilot port
DR6
BbkR
PCsp PDb2 PAbk Dr6
PCsp Swing priority pilot port 7~8 kgf·m
CaR DR7 PaL PF3/8 (50.6~57.8 lbf·ft)
PAbk Option A pilot port (breaker)
LCa
P02 Ca Da ARM1 PD P02

PBrc Arm in regeneration cut port

PBa2 PCa PAa2
BkR LCo
PCa Arm in pilot port
CoR (Do) DoR
(Co) AkR

PBk
OPTION
PAk PDa Arm out pilot port
P04
(PCo)
BYPASS CUT1
(PDo)
PAa2 Arm out confluence pilot port
(BUCKET)
BYPASS CUT2 PAk Bucket in pilot port
NRV2 PCbc (OPTION) PDbc NRV1
PBk Bucket out pilot port
(PCo) Option B pilot port
(PDo) Option B pilot port
Pn1 Negative control signal port (A2 port side)
Pn2 Negative control signal port (A1 port side)
P03
V2 Carry-over port
Atr Travel motor port-LH (FW)
Btr Travel motor port-LH (BW)
Ctl Travel motor port-RH (BW)
Dtl Travel motor port-RH (FW)
(P05) Ab Boom up port
P5 CCo
Bb Boom down port
Cs Swing motor port (LH)
DR9 Ds Swing motor port (RH)
Bbk Option A port (breaker) M10 5.0~6.5 kgf·m
Ca Arm in port (36.2~47.0 lbf·ft)
Da Arm out port
X3 Pn2 Pn1 X2

Ak Bucket in port
Bk Bucket out port
CCk
P4
(Co) Option B port
(Do) Option B port
P1 Pump port (A2 side)
P2 Pump port (A1 side)

T1 Return port 8.0~11.0 kgf·m

P02
M12 (57.9~79.6 lbf·ft)
300S2MC01

2-22
 STRUCTURE (2/8)

P1 P1

P2 P2

32 31

TOP VIEW

1 64 66

A A' 1 Housing P1
31 Plug
B B' 32 Plug
64 Hex socket head bolt
C C' 66 Spring washer

D D'

E E'

F F'

G G'

P1 BLOCK SPOOL SECTION 220S2MC02

2-23
 STRUCTURE (3/8)

52 53
2

A A'

Y
W W W W W

W W
51
B B'

Y
W W W WV V

C C' V V

54

D D' U U
X X

W W W W 56
V V

E E' X X

X X X X

F F'
W W W W V V
V V

G G'
W W W W W WW W

64 66
52
P2 BLOCK SPOOL SECTION
CONTACT FACE

33 2 Housing 2
33 Plug
51 O-ring
52 O-ring
53 O-ring
54 O-ring
56 O-ring
64 Hex socket head bolt
66 Spring washer

BOTTOM VIEW 300S2MC03

2-24
 STRUCTURE (4/8)

28 40 39 24 10 Travel straight spool kit

24 Main relief valve
28 Plug
30 Plug
P2 32 Plug
34 Pilot cover A
35 Pilot cover B
34 39 Check valve poppet 2
40 Check valve spring 2
55 O-ring
57 Hex socket head bolt

57 55 30 55 57 10 35 32

A-A' (STRAIGHT TRAVEL AND SUPPLY) 220S2MC04

27 28 27 3 Travel spool kit

26 Orifice signal plug
3
27 ORV plug
28 Plug
34 Pilot cover A
35 Pilot cover B
55 O-ring
57 Hex socket head bolt
34

57

55 26 55 57 35

B-B' (TRAVEL RIGHT AND LEFT) 220S2MC05

2-25
STRUCTURE (5/8)
18 30 38 37 5 16 58 65

34

57 55 71 7 55 57
70 22 35

C-C' (SWING AND BOOM1)

16

3 4 5 6 7 8 9 10 11 12 13 14 15 16
2 17

HOLDING VALVE 300S2MC06

5 Boom 1 spool kit 16-9 Back up ring 30 Plug

7 Swing spool kit 16-10 O-ring 34 Pilot cover A
16 Holding valve assy 16-11 Plug 35 Pilot cover B
16-1 Main poppet 16-12 Pilot piston 37 Check valve poppet 1
16-2 Restrictor 16-13 Piston guide 38 Check valve spring 1
16-3 Pilot spring 16-14 Spring 55 O-ring
16-4 C-ring 16-15 Main piston 57 Hex socket head bolt
16-5 Pilot poppet 16-16 Plug 58 Hex socket head bolt
16-6 Poppet guide 16-17 Block 65 Spring washer
16-7 O-ring 18 Overload relief valve 70 O-ring
16-8 Poppet seat 22 Swing logic valve 71 Hex socket head bolt

2-26
 STRUCTURE (6/8)

65 58 17 46 56 61 30 38 37 28 40 39 18 12 35 9 Boom 2 spool kit

12 Arm regen spool kit
13 Swing priority spool kit
17 Regen valve
18 Overload relief valve
28 Plug
29 Plug
30 Plug
35 Pilot cover B
37 Check valve poppet 1
38 Check valve spring 1
39 Check valve poppet 2
40 Check valve spring 2
35
41 Check valve poppet 3
35 57 55 13 30 29 42 41 9 18 50 57
300S2MC07
42 Check valve spring 3
46 Flange
D-D' (SWING PRI, BOOM 2 & ARM REGEN) 50 Gasket 3
55 O-ring
56 O-ring
57 Hex socket head bolt
58 Hex socket head bolt
61 Hex socket head bolt
65 Spring washer

25 25 14 Bypass cut 1 spool kit (bucket)

15 Bypass cut 1 spool kit (option)
25 Negacon valve
43 29 Plug
42 42 Check valve spring 3
Z Z
29 43 Check valve poppet 4
SECTION Z-Z 67 BC plug

Z Z
67 14 15 67

220S2MC08

G-G' (BYPASS CUT & NEGATIVE CONTROL)

2-27
STRUCTURE (7/8)

75 12 70 22 71 55 77 8 35

55

34

57 18 30 38 37 4 16 58 65 77

E-E' (ARM 1 & ARM 2)

16

3 4 5 6 7 8 9 10 11 12 13 14 15 16
2 17

HOLDING VALVE 300S2MC09

4 Arm 1 spool kit 16-9 Back up ring 34 Pilot cover A

8 Arm 2 spool kit 16-10 O-ring 35 Pilot cover B
12 Arm regen spool kit 16-11 Plug 37 Check valve poppet 1
16 Holding valve assy 16-12 Pilot piston 38 Check valve spring 1
16-1 Main poppet 16-13 Piston guide 55 O-ring
16-2 Restrictor 16-14 Spring 57 Hex socket head bolt
16-3 Pilot spring 16-15 Main piston 58 Hex socket head bolt
16-4 C-ring 16-16 Plug 65 Spring washer
16-5 Pilot poppet 16-17 Block 70 O-ring
16-6 Poppet guide 18 Overload relief valve 71 Hex socket head bolt
16-7 O-ring 22 Swing logic valve 75 Plug
16-8 Poppet seat 30 Plug 77 Orifice plug

2-28
 STRUCTURE (8/8)

36 18 28 40 39 18 6 35 6 Bucket spool kit

11 Option spool kit
18 Overload relief valve
20 Overload relief valve
21 Overload relief valve
28 Plug
30 Plug
55
34 Pilot cover A
57 35 Pilot cover B
34
36 Pilot cover (stroke limit)
37 Check valve poppet 1
38 Check valve spring 1
39 Check valve poppet 2
69 57 20 30 38 37 11 21 50 57 35 68 40 Check valve spring 2
46 56 61
300S2MC10
46 Flange
50 Gasket 3
F-F' (OPTION & BUCKET)
55 O-ring
56 O-ring
57 Hex socket head bolt
61 Hex socket head bolt
68 Plug kit 1
69 Plug kit 2

2-29
2. HYDRAULIC CIRCUIT

[MAKE UP]

P5 Rs P4 Pn1 Pn2

[BUCKET CONF.] PCbc

BC1

NRV2 Cck
[OPTION CONF.] PDbc

DR9
BC2

NRV1
Cco

BkR
CoR Bk
Co
Ak
P05
AkR
Do
DoR P04 [BOOM UP]
PCo PBk [BUCKET OUT]
PDo PAk [BUCKET IN]
OPTION BUCKET
LCo LCk1
LCk2
CaR
Ca

DaR BbkR
Da
DR7 CRa

[UNLOCK SIGNAL] PaL

PBa2 [ARM IN]
[ARM IN] PCa PAa2 (ARM OUT)

[ARM OUT] PDa ARM LCa ARM2

LCa2
DR6
P02
PBa (ARM IN)
Ccb
LCar Abk
PCsp PBrc (ARM REGEN CUT)
[SWING PRIORITY]

[BOOM UP PILOT] PDb2 PAbk (BREAKER)

SWING P/R ARM REGEN
BOOM2
LCbk DR4
BbR
Bb

Cs Ab
AbR CRb DR2
Ds
PbL (UNLOCK SIGNAL)
[SWING CCW] PCs PBb1 (BOOM DOWN)

[SWING CW] PDs PAb1 (BOOM UP)

SWING BOOM
DR5
LCs LCb
(BOOM PRI.) P03
DR3
Btr
Ctl BtR
Dtl Atr
AtR
[RH-BW] PCtl PBtr [LH-BW]

[RH-FW] PDtl PAtr [LH-FW]

(RIGHT) (LEFT)
Patt PS TRAVEL TRAVEL
DR1
V2
P01
Ptr PS MRV
TS T1

P1 P2 Pu 300S2MC11

2-30
3. FUNCTION

1) CONTROL IN NEUTRAL POSITION

(1) P1 housing side
The pressurized oil discharged from hydraulic pump flows into the main control valve through the
inlet port P1 and pass the land of the straight travel spool into the P1 bypass passage and P1
parallel passage.
When the straight travel spool is neutral, the P1 side bypass passage is not cut-off and the
pressurized oil is directed to the tank port T1 through the bypass passage of spools (travel right
-> boom 1 -> arm regeneration -> arm 2 -> bucket), the negative control valve of P1 and tank
passage.

P1 parallel passage Tank port T1

Housing P2
P1 bypass
passage

Flow into P1
housing side

Travel straight spool P1 port

Housing P2

220S2MC13
TOP VIEW A-A' (STRAIGHT TRAVEL AND SUPPLY)
Tank port T1

Travel right

Boom 1

Arm regen

Arm 2

Bucket

P2 side negative P2 side negative

control valve control valve
P1 BLOCK SPOOL SECTION 220S2MC14

2-31
 P1 side negative control valve

G-G' (BYPASS CUT & NEGATIVE CONTROL) 220S2MC15

2-32
(2) P2 housing side
The pressurized oil discharged from hydraulic pump flows into the main control valve through the
inlet port P2 and pass the land of the straight travel spool into the P2 bypass passage and P2
parallel passage.
When the straight travel spool is neutral, the P2 side bypass passage is not cut-off and the
pressurized oil is directed to the tank port T1 through the bypass passage of spools (travel left ->
swing -> boom 2 and swing priority -> arm 1 -> option), the negative control valve of P2 and tank
passage.

P2 port Tank port T1

P1 bypass
passage

Flow into P2
housing side

P2 bypass passage
Return from P2 P2 parallel passage
negative control valve

A-A' (STRAIGHT TRAVEL AND SUPPLY) 220S2MC16

Straight travel

Travel left

Swing

Boom 2 and
swing priority

Arm 1

Option

BC1 spool (BKT) BC1 spool (OPT)

Discharge to P2 negative control valve

P2 BLOCK SPOOL SECTION 220S2MC17

2-33
2) TRAVEL OPERATION
(1) Travel forward operation
During the travel forward operation, the pilot secondary pressure from the remote control valve is
supplied to the spring side of pilot port and it shifts travel spools to the left direction.
The pressurized oil from the pump flows into the bypass passage of the travel spools through the
land of the straight travel spool.
When the travel spools is shifted and the bypass passage is shut-off. The pressurized oil flowed
into bypass passage is supplied to the travel motors through opened port Atr and Dtl.
On the other hand, the return oil from the travel motors flows into main control valve inside
through the port Btr and Ctl and return to the tank passage.

Btr Atr
Tank passage

RCV signal

Travel left

Travel right

RCV signal

Ctl Dtl

B-B' (TRAVEL RIGHT AND LEFT) 220S2MC18

(2) Travel backward operation

During the travel backward operation, the pilot secondary pressure from the remote control valve
is supplied to the against pilot port of the spring side and it shifts travel spools to the right
direction.
The pressurized oil from the pump flows into the bypass passage of the travel spools through the
land of the straight travel spool.
When the travel spools are shifted and the bypass passage is shut-off. The pressurized oil flowed
into bypass passage is supplied to the travel motors through opened port Btr and Ctl.
On the other hand, the return oil from the travel motors flows into main control valve inside
through the port Atr and Dtl and return to the tank passage.

2-34
 Btr Atr
Tank passage

RCV signal

Travel left

Travel right

RCV signal

Ctl Dtl

B-B' (TRAVEL RIGHT AND LEFT) 220S2MC19

2-35
(3) Travel straight function
This function keeps straight travel in case of simultaneous operation of other actuators (boom,
arm, bucket, swing etc) during a straight travel.
In normal conditions, travel straight spool keeps neutral conditions, the pressurized oil of the P1
and P2 pumps is supplied to each passage independently.
When the attachment spool is operated under the travel operation of both sides, the pilot
pressure is supplied to the spring side port of the travel straight spool and then the travel straight
spool is shifted to the left direction.

P1 parallel passage Tank port T1

P2 port
P1 bypass passage P1 bypass passage

Some of attachment
oil is supplied to rravel

Signal by the combined operating

Travel straight spool of travel and attachment
P1 port
P2 bypass passage
P2 parallel passage

A-A' (STRAIGHT TRAVEL AND SUPPLY) 220S2MC20

After changeover of the travel straight spool, the pressurized oil discharged from the P1 pump is
connected with P2 port oil and is supplied to the attachment line through both parallel passage of
the P1 and P2.
Also, some of the pressurized oil open the check valve of the spool inside through side of the
travel straight spool and is connected with the bypass passage of the P2 side.
On the other hand, the pressurized oil discharged from the P2 pump is connected with P1 port oil
and is supplied to the travel line through both parallel passage of the P1 and P2.
Accordingly the attachment spool is operated under the travel operation of both sides, the
pressurized oil discharged from P2 pump is mainly supplied to left and right travel line and the
pressurized oil discharged from P1 pump is mainly supplied to attachment line.
As a result, simultaneous operation of both travel spools and attachment is not influenced to the
travel operation of the both sides and the machine keeps straight travel.

2-36
3) BOOM OPERATION
(1) Boom up operation
During the boom up operation, the pilot secondary pressure from the RCV is supplied to the port
of the spring side and shifts the boom 1 spool to the left direction. The P1 bypass passage is shut
off by the movement of the boom 1 spool and the pressurized oil from P2 port is entered P1
parallel passage and then passes through the load check valve, bridge passage and boom
holding valve then flows into the head side of the boom cylinder via Ab port. (In this case, the
boom holding valve is free flow condition)
At the same time, the pilot secondary pressure from RCV is supplied to the port of the spring side
of boom 2 and shifts the boom 2 spool. The bypass passage is shut off by the movement of the
boom 2 spool and the pressurized oil from P2 port entered boom summation passage via the P2
parallel passage, notch of the boom 2 spool, the check valve.
The oil from boom 2 spool combined with the boom 1 spool oil and is supplied Ab port.
At the same time, the return oil from rod side of the boom cylinders flows the boom 1 spool
through the Bb port and return to the hydraulic oil tank through the tank passage.

Cylinder rod side Cylinder head side

Tank passage Bb Ab

RCV signal

Boom 1

Swing

C-C' (SWING AND BOOM1) 220S2MC21

2-37
 Boom 1

Swing

Area of oil summation

C-C' (SWING AND BOOM1)

Open check valve and pass out
to housing mating side
Housing mating side

Arm regen

RCV signal

Swing priority Boom 2

D-D' (SWING PRI, BOOM 2 & ARM REGEN) 220S2MC22

2-38
(2) Boom down operation
During the boom down operation, the pilot secondary pressure from the RCV is supplied to the
against port of the spring side and shifts the boom 1 spool to the right direction. The P1 bypass
passage is shut off by the movement of the boom 1 spool and the pressurized oil from P1 port is
entered P1 parallel passage and then passes through the load check valve and bridge passage
then flows into the rod side of the boom cylinder via Bb port.
At the same time, the return oil from head side of the boom cylinders flows the boom 1 spool
through the Ab port and the boom holding valve and return to the hydraulic oil tank through the
tank passage.
At this time, some of the return oil from the boom head side passes to the connected passage of
the boom 1 spool inside and flows into the P1 parallel passage. (Boom spool inside regeneration
function). At this time, the boom holding valve is open status and the operation principles are
described following page.
During the boom down operation, the flow is not combined.

Cylinder rod side Cylinder head side

RCV signal
Bb Ab Holding valve
release signal
RCV signal Tank passage

Boom 1

Swing

C-C' (SWING AND BOOM1) 220S2MC23

2-39
4) HOLDING VALVE OPERATION
(1) Holding operation
At neutral condition, the pilot piston chamber is connected to drain port through the pilot port.
And the main piston is seated by the spring B.
Also, the pressurized oil from the actuator entered to inside of the holding valve through the
periphery hole of the main poppet, crevice of the main poppet and the restrictor and the
periphery hole of the restrictor.
Then, this pressured oil pushed the pilot poppet to the poppet seat and the main poppet to the
seat of body.
So the pressurized oil from the holding side of the actuator is not escaped and the actuator is not
moved.

Pilot poppet
Spring Pilot piston Pilot port for
Actuator port holding valve releasing
Drain port
Main poppet
Piston guide

Pilot piston chamber

Main piston
Restrictor Poppet seat Spring B

HOLDING VALVE BLOCK SECTION 220S2MC24

2-40
(2) Releasing holding operation
The pilot pressure is supplied to the pilot port for releasing holding valve and shifts the main
piston to the left direction against the spring B and shifts the pilot poppet to the left direction
through the pilot piston and open the passage for the drain.
At same time, the return oil from actuator returns to the drain port through the periphery hole of
main poppet, crevice of the main poppet and the restrictor, the periphery hole of the restrictor,
inside of holding valve, crevice of the pilot poppet and the drain passage of the holding valve.
After above operation, pressure of inside of holding valve is decreased and the main poppet is
opened by the return oil of the actuator and the return oil from actuator returns to the tank
passage through the notch of spool.

Pilot poppet
Spring Pilot piston Pilot port for
Actuator port holding valve releasing
Drain port
Main poppet
Piston guide

Pilot piston chamber

Open the main poppet and

pressurized oil passes through
actuator port
Main piston
Restrictor Poppet seat Spring B

HOLDING VALVE BLOCK SECTION 220S2MC25

2-41
5) BUCKET OPERATION
(1) Bucket in operation
① Bucket operation only
During the bucket in operation, the pilot secondary pressure from the RCV is supplied to port of
the spring side and shifts the bucket spool to the left direction.
The P1 bypass passage is shut off by the movement of the bucket spool and the pressurized oil
from P1 port entered P1 parallel passage and is directed to the Ak port through the check valve 2.
At the same time, the pressurized oil from P1 bypass passage is directed to the AK port through
the check valve 1.
The return oil from the rod side of the bucket cylinder (Bk port) returns to the hydraulic oil tank
through the tank passage.
② Combined operation
When combined operation of the bucket and other actuators, mostly same as above operation
but the fluid from P1 bypass passage is empty by the upstream operation such as the arm or
boom operation.
So only the fluid from P1 parallel passage is supplied to the Ak port.

Cylinder rod side Cylinder head side

Check Check
P1 bypass passage valve 1 valve 2 P1 parallel passage
Bk Ak
Tank passage

RCV signal

Bucket

Option

F-F' (OPTION AND BUCKET) 220S2MC26

2-42
(2) Bucket slow operation (incase bucket in)
This function is used to speed up of the boom or arm by reducing the bucket speed when the
bucket operation with boom or arm operation simultaneously.
The bucket slow pilot pressure is supplied the pilot port of the BC1 spool and the piston is shifted
to the right and then the bucket spool stroke is limited and the oil passage from P1 to the bucket
cylinder is reduced and the oil flow of the bucket spool is reduced.

Bucket flow summation function, bypass cut-off 1 spool

During the bucket in operation, the pilot secondary pressure from the RCV is supplied to port of
the spring side and shifts the BC1 (bucket) spool to the right direction.
The P2 parallel passage is shut off by the movement of the BC1 spool and the pressurized oil
from P2 port opens the check poppet and combined with the flow of the bucket spool.
(Only bucket in operation)

RCV signal Bucket

Bucket flow
summation passage
Option

Open check poppet and

combined with oil flow of
bucket spool

F-F' (OPTION AND BUCKET)

Z
Z

SECTION Z-Z

Bucket in
RCV signal

BC1 spool (bucket) Z Z

P2 parallel passage
G-G' (BYPASS CUT & NEGATIVE CONTROL)

FLOW SUMMATION BY THE SHIFTING OF THE BC1 SPOOL

220S2MC27

2-43
(3) Bucket out operation
① Bucket operation only
During the bucket out operation, the pilot secondary pressure from the RCV is supplied to
against port of the spring side and shifts the bucket spool to the right direction.
The P1 bypass passage is shut off by the movement of the bucket spool and the pressurized oil
from P1 port entered P1 parallel passage and is directed to the Bk port through the check valve 2.
At the same time, the pressurized oil from P1 bypass passage is directed to the Bk port through
the check valve 1.
The return oil from the head side of the bucket cylinder (Ak port) returns to the hydraulic oil tank
through the tank passage.
② Combined operation
When combined operation of the bucket and other actuators, exactly same as above operation.

Cylinder rod side Cylinder head side

Check Check
Bk valve 1 valve 2
Ak
Tank passage

RCV signal Bucket

Option

F-F' (OPTION AND BUCKET) 220S2MC28

2-44
6) SWING OPERATION
(1) Swing left and right operation
During the swing left operation, the pilot secondary pressure from the RCV is supplied to the port
of the spring side and shifts the swing spool in left direction. The P2 bypass passage is shut off by
the movement of the swing spool and the pressurized oil from P2 port flows into the P2 parallel
passage and open the load check valve and is supplied to swing motor through the Ds port.
As the result, the return oil from the swing motor flows into the main control inside through Cs
port and returns to the hydraulic oil tank through the swing spool and the tank passage.
In case of swing right operation, the operation is similar to swing left operation but the pilot
secondary pressure from the RCV is supplied to the port of the spring opposite side.
Accordingly, the pressurized oil from P2 parallel passage flows into swing motor through the Cs
port and returns to the hydraulic oil tank through the Ds port and the tank passage.

Tank passage

Boom 1
RCV signal

Swing

Cs Ds

C-C' (SWING AND BOOM1) 220S2MC29

2-45
(2) Boom priority function
This function is used to speed up of the boom by reducing the swing speed when the swing
operation with boom operation simultaneously.
The boom priority signal is supplied the pilot port and the poppet of the swing logic valve is closed
and then the pressurized oil from P2 port is reduced by the oil leaking through the orifice.
As a result, the swing speed is slowed.

Orifice shape

Boom priority signal

SWING LOGIC VALVE

220S2MC30

2-46
7) ARM OPERATION
(1) Arm in operation
During the arm in operation, the pilot secondary pressure from the RCV is supplied to the port of
the spring opposite side and shifts the arm 1 spool in the right direction.
The P2 bypass passage is shut off by the movement of the arm 1 spool and the pressurized oil
from the P2 port flows into the arm cylinder head side through P2 parallel passage, the load
check valve, bridge passage and the Ca port.
At the same time, the pilot secondary pressure from the RCV is supplied to the port of spring
opposite side and shifts the arm 2 spool in the right direction. The P2 bypass passage is shut off
by the movement of the arm 2 spool and the pressurized oil from the P1 port flows into the arm
summation passage through P1 parallel passage, the check valve and the notch of the arm 2
spool.

Tank passage

RCV signal

Arm 2

Arm 1

Ca Da

Cylinder head side Cylinder rod side

E-E' (ARM 1 AND ARM 2) 300S2MC31

ARM REGENERATION
The return oil from the arm cylinder rod side passes the arm holding valve (open condition)
through the Da port and the notch of the arm 1 and arm 2, and swing priority spool. And some of
the oil return to the tank passage through the notch of the arm regeneration spool and most of
the oil is supplied to the head side of the arm cylinder through internal summation passage.
This is called the arm regeneration function.

2-47
 The amount of regeneration fluid is changed by movement of the arm regeneration spool. A few
fluids of the oil that is supplied to the head side of the arm cylinder passes the selector spool ( in
this case, the selector spool is opened by the arm in pilot pressure) built in the arm regeneration
block through internal passage and is pushed the piston C.
The amount of the regeneration oil from the rod side of the arm cylinder to the tank passage is
increased by the movement of the piston C and the arm regeneration spool to the right direction
and the arm regeneration flow is decreased as much increased oil.
The pressure of the arm cylinder head increases, then, the arm regeneration flow decreases.
Furthermore, the arm regeneration cut-off pressure is supplied to the port of the spring opposite
side and the arm regeneration spool is moved to the right direction fully. The flow from the arm
cylinder rod to the tank passage is maximum condition.

Arm regen cut-off valve

internal passage
Arm regen cut-off block
Selector spool
RCV signal
Arm regen
cut-off pressure Arm regeneration

Piston C

Boom 2 and swing priority

D-D' (SW PRI, BM 2 & ARM REGEN) Boom 1

Arm regen

Arm 2

P1 BLOCK SPOOL SECTION

RCV signal

Arm 2

Arm 1

Ca Da

Cylinder head side Cylinder rod side

E-E' (ARM 1 AND ARM 2)
ARM REGENERATION PASSAGE 300S2MC32

2-48
(2) Arm out operation
During arm out operation, the pilot secondary pressure from the RCV is supplied to the port of
the spring side and shifts the arm 1 spool to the left direction.
The bypass passage is shut off by the movement of the arm 1 spool and the pressurized oil from
the P2 port flows into arm 1 spool through the P2 parallel passage. Then it enters into the arm
cylinder rod side through the load check, bridge passage, arm holding valve (oped status) and
the port Da.
Also, the pilot secondary pressure from the RCV is supplied to the port of the spring side and
shifts the arm 2 spool to the left direction.
The bypass passage is shut off by the movement of the arm 2 spool and the pressurized oil from
the P2 port through the P2 parallel passage. Then it combined with the flow of the arm 1 passage
through P1 parallel passage, the check valve, bridge passage, the notch of the arm 1 and the
arm holding valve (open status).
On the other hand, the return flow from the arm cylinder head side returns to the hydraulic tank
through the port Ca, the notch of the arm 1 spool and tank passage.

RCV signal

Arm 2

Arm 1

Ca Da
Tank passage

Cylinder head side Cylinder rod side

E-E' (ARM 1 AND ARM 2) 300S2MC33

2-49
8) OPERATION OF SWING PRIORITY SPOOL
During swing priority operation, the pilot secondary pressure is supplied to the port of the spring
side of the swing priority spool and shift swing priority spool to the right direction.
The pressurized oil from the P2 port flows into the P2 parallel passage through the notch of the
swing priority spool.
When the swing priority spool is neutral condition, the passage is same as normal condition. But
due to shifting of the swing priority spool, the orifice is formed between the notch of the swing
priority spool and the land of the block housing and then the fluid to the swing side more then the
downstream of the swing spool such as the arm 1 and option spool.
As a result, the flow is supplied to the swing operation most preferential.

Swing priority Arm regeneration

pilot pressure

Boom 2 and swing priority

Swing priority

Orifice
P2 parallel passage
P2 parallel passage

D-D' (SWING PRI, BOOM 2 & ARM REGENERATION) 220S2MC34

2-50
9) OPERATION OF OPTION SPOOL
(1) 1-way operation
※ The pilot pressure is supplied to the port of the spring side and shifts spool to the left direction.
The pilot secondary pressure from the RCV is supplied to the port of the spring opposite side of
the option spool, the P2 bypass passage is shut off by the movement of the option spool and the
pressurized oil from the P2 port flows into the actuator through the P2 parallel passage, the
check valve, bridge passage and the Do port.
(2) 2-way operation
※ Shifts spool to the left and right direction.
- When the spool shifts to the left, same as 1-way operation.
- When the spool shifts to the right, the pressurized oil from the P2 port flows into the actuator
through the P2 parallel passage, the check valve, bridge passage and the Co port.

Bucket

RCV signal

Option

P2 parallel passage
Poppet check
Co Do

Cylinder head side Cylinder rod side

F-F' (OPTION AND BUCKET) 300S2MC35

2-51
 Option flow summation function, bypass cut-off 2 spool
During the 2-way option operation, the pilot secondary pressure from the RCV is supplied to port
of the spring side and shifts the BC2 (option) spool.
The P1 parallel passage is shut off by the movement of the BC2 spool and the pressurized oil
from P1 port opens the check poppet and combined with flow of the option spool.
(Only bucket in operation)

Bucket

RCV signal RCV signal

Option
Bucket flow
summation passage

Open check poppet and

combined with oil flow of
bucket spool F-F' (OPTION AND BUCKET)

P1 parallel passage

Z
Z

SECTION Z-Z

Option spool RCV signal

(when left and right shift)

Z Z

BC1 spool (bucket)

G-G' (BYPASS CUT & NEGATIVE CONTROL)

FLOW SUMMATION BY THE SHIFTING OF THE BC2 SPOOL 300S2MC36

2-52
10) OPERATION OF NEGATIVE CONTROL VALVE
When no function is being actuated on P1 side, the hydraulic fluid from the P2 port, flows into the
tank passage through the P1 bypass passage and the orifice of the negative control valve.
The negative control pressure caused by this operation is transferred to the regulator of the piston
pump through the Pn1 port.
This pressure controls the swash plate angle of the pump to the minimum and minimize the flow of
the P1 side.
When one or more spools are shifted, the P1 bypass passage is shut-off and the flow is almost
zero.
Accordingly, the negative control pressure that is supplied to the pump through Pn1 port is
lowered and the swash plate angle becomes maximum and the flow of the P1 side becomes
maximum.
On the other hand, the negative control pressure is increased and high than the setting pressure
of the spring, the negative control valve is opened and the flow passes to the hydraulic tank and
functions as a relief valve.
The operation of the negative control valve of the P2 side is same as that of the P1 side.

Pn2 port Adjust swash plate angle of pump

by orifice pressure

Pn1 port

P2 negative control valve Orifice

Z Spring
Z

P1 negative control valve

Z Z Tank passage

P1 parallel passage

OPERATION OF NEGATIVE CONTROL VALVE 220S2MC37

2-53
11) OPERATION OF MAIN RELIEF VALVE

(1) Neutral
The pressurized oil passes through the internal passage of the piston A, fitted in the main poppet
and the orifice A and is filled up in the chamber A of the inside and seats the main poppet against
socket and socket against the housing securely.
(2) When operation (relief)
① When the pressurized oil flowed in the chamber A through the orifice becomes equal to the set
pressure of the spring, the hydraulic oil apply to the main poppet through the piston and pushes
open the pilot poppet and flows to tank passage through the piston A internal passage, orifice A,
chamber A, periphery orifice B and the hole E.

Piston A Hole E Hole A Piston B

Spring
Socket Chamber A

Housing Passage T Pilot poppet

Main poppet Orifice Periphery orifice B 220S2MC40

OPERATION 1 OF MAIN RELIEF VALVE

② The pressure in chamber A is lowered by moving of the pilot poppet and the main poppet is
opened. As a result, the pressurized oil flows out to the tank passage through the hole of the
socket side.

Piston A
Socket Chamber A

Housing Passage T Pilot poppet

Main poppet Orifice Periphery orifice B 220S2MC41

OPERATION 2 OF MAIN RELIEF VALVE

2-54
(3) When retraction (return)
On the other hand, the pressure of the pressurized oil becomes lower than set pressure of the
spring, the main poppet is seated by spring force. Then the pressure of the chamber A becomes
equal to the pressure of the P port and the main poppet is seated to the seat of the socket. The
valve returns to the initial condition.
Power boost function
During power boost operation, the pilot pressure for the power boost enters inside of the piston B
through the hole A, the crevice passage and the side hole of the piston B.
It pushes the piston to the left direction and the set pressure of the spring is increased.

Piston A Hole A Piston B

Spring
Socket Chamber A

Housing 220S2MC42

OPERATION 3 OF MAIN RELIEF VALVE

2-55
12) OPERATION OF PORT RELIEF VALVE

(1) Function as relief valve

① The pressurized oil passes through the internal passage of the piston A, fitted in the main
poppet and the orifice A and is filled up in the chamber A of the inside and seats the main
poppet against socket and socket against the housing securely.

Socket
Chamber A
Pilot poppet

Spring

Parallel passage

Housing Tank passage Piston A Main poppet Orifice A

PORT RELIEF VALVE 220S2MC43

② When the pressurized oil from the actuators becomes equal to the set pressure of the spring,
the hydraulic oil apply to the pilot poppet and pushes the pilot poppet to the right direction and
flows to tank passage through the piston A internal passage, orifice A, chamber A, periphery
orifice B and the hole E.

Periphery orifice B

Hole E

Parallel passage

Housing Tank passage

OPERATION 1 OF PORT RELIEF VALVE 220S2MC44

2-56
 ③ The pressure in chamber A is lowered by moving of the pilot poppet and the main poppet is
opened. As a result, the pressurized oil from the actuator port flows out to the tank passage
through the hole of the socket side.

Parallel passage

Housing Tank passage

OPERATION 2 OF PORT RELIEF VALVE 220S2MC45

④ On the other hand, the pressure of the actuator becomes lower than set pressure of the spring,
the pilot poppet is seated by spring force. Then the pressure of the chamber A becomes equal to
the pressure of the actuator port and the main poppet is seated to the seat of the socket. The
valve returns to the initial condition.
Make up function
When negative pressure exists at the actuator port, the oil is supplied through tank passage. When
the pressure at tank passage becomes higher than that of at the actuator port, it pushed the socket
moves in the right direction. Then, the gap between the housing and socket is opened and
pressurized oil from the tank passage flows into parallel passage side.

Socket

Parallel passage

Housing Tank passage

MAKE UP FUNCTION OF PORT RELIEF VALVE 220S2MC46

2-57
GROUP 3 SWING DEVICE

1. STRUCTURE
Swing device consists swing motor, swing reduction gear.
Swing motor include mechanical parking valve, relief valve, make up valve and time delay valve.

MU SH PG
Time delay valve Relief valve AU
Oil level & DR
SH
air vent port
PG
(PT 1/4)

HEAVY INDUSTRIES CO.,LTD.

P A R T NO. :

MA
39Q6-11100
SERIAL NO. :

AU DR

MU

MA MB

VA VB

Oil level gauge

& oil supply port
MB
Reduction gear oil
drain port (PT 1/2) VA VB
Reduction gear Swing motor

SH

AU PG

DR
Port Port name Port size
VA Main port 凱20
VB Main port 凱20
DR Drain port PF 1/2
MB MA
MU
MU Make up port PF 1 1/4
PG Brake release stand by port PF 1/4
SH Brake release pilot port PF 1/4
MA, MB Gauge port PF 1/4
AU Air vent port PF 1/4

VB VA

Hydraulic circuit
300L2SM01

2-58
 1) SWING MOTOR

3 2 11 10 1 35 42 19 18 22 17 21 20 29 28 39 27 26 25 38 24 41 30 40 24 38 25 26 27

4 5 7 8 9 12 13 14 15 16 6 23 28 29 37 36 38 34 32 33 31 33 32 34 38 37

300L2SM02

1 Casing 15 Parking piston 29 O-ring

2 Oil seal 16 Brake spring 30 Relief valve assy
3 Shaft 17 Spring pin 31 Reactionless valve assy
4 Snap ring 18 O-ring 32 Plug
5 Roller bearing 19 O-ring 33 O-ring
6 Needle bearing 20 Valve plate 34 O-ring
7 Swash plate 21 Spring pin 35 Time delay valve assy
8 Cylinder block 22 O-ring 36 Level gauge
9 Spring 23 Valve casing 37 Socket bolt
10 Ball guide 24 Check valve 38 Socket bolt
11 Retainer plate 25 Spring 39 Plug
12 Piston assy 26 Plug 40 Name plate
13 Friction plate 27 O-ring 41 Rivet
14 Separate plate 28 Plug 42 Socket bolt

2-59
 2) REDUCTION GEAR

29 28 30 7 19 18 17 15 13 32 14 16 15 25 23

21

22

23

24

26

27

34
33

35

8 10 3 9 2 4 5 6 31 12 1 20 11
300L2SM03

1 Ring gear 13 Planetary gear 2 25 Spring pin 1

2 Drive shaft 14 Needle bearing 2 26 Sun gear 1
3 Bearing 15 Thrust washer 2 27 Thrust plate 1
4 Bearing 16 Carrier pin 2 28 Sleeve
5 Thrust plate 17 Spring pin 2 29 O-ring
6 Snap ring 18 Sun gear 2 30 Oil seal
7 Cover 19 Thrust plate 2 31 Parallel pin
8 Hex head bolt 20 Carrier 1 32 Hex socket head bolt
9 Casing 21 Planetary gear 1 33 Name plate
10 O-ring 22 Needle bearing 1 34 Rivet
11 Hex socket head bolt 23 Thrust washer 1 35 Plug
12 Carrier 2 24 Carrier pin 1

2-60
2. PRINCIPLE OF DRIVING
2.1 Generating the turning force
The high hydraulic supplied from a hydraulic pump flows into a cylinder block (8) through valve casing
of motor (1), and valve plate (20).
The high hydraulic is built as flowing on one side of Y-Y line connected by the upper and lower sides
of piston (12).
The high hydraulic can generate the force, F1=P×A (P : supplied pressure, A : water pressure area),
like following pictures, working on a piston.
This force, F1, is divided as N1 thrust partial pressure and W1 radial partial pressure, in case of the
plate of a tilt angle, α.
W1 generates torque, T=W1×R1, for Y-Y line connected by the upper and lower sides of the piston
as following pictures.
The sum of torque (ΣW1×R1), generated from each piston (4~5 pieces) on the side of a high
hydraulic, generates the turning force.
This torque transfers the turning force to a cylinder (8) through a piston; because a cylinder is
combined with a turning axis and spline, a turning axis rotates and a turning force is sent.

W1 Pistion
Cylinder

W1
R1
N1
O A
f1 F1 P

High Y Low
pressure pressure

21078TM05

2-61
2) MAKE UP VALVE
In the system using this type of motor, there is no counter balance functioning valve and there
happens the case of revolution exceeding hydraulic supply of motor. To prevent the cavitation
caused by insufficient oil flow there is a make up valve to fill up the oil insufficiency.
A make up valve is provided immediately before the port leading to the hydraulic oil tank to secure
feed pressure required when the hydraulic motor makes a pumping action. The boost pressure
acts on the hydraulic motor's feed port via the make up valve.
Pressurized oil into the port B, the motor rotate counterclockwise.
If the plunger of MCV moves neutral position, the oil in the motor is drain via left relief valve, the
drain oil run into motor via right make up valve, which prevent the cavitation of motor.

Relief valve

Make up check valve Make up check valve

A B

21092SM04

2-62
3) RELIEF VALVE

11 1 Body
2 Seat
10
5 3 Plunger
4 Spring
6 5 Adjusting screw
7
6 Piston
7 Bushing
8
8 Spring seat
9
9 Shim
12
10 O-ring
1 11 Back up ring
3 12 O-ring
4

2
14007A2SM05

(1) Construction of relief valve

The valve casing contains two cartridge type relief valves that stop the regular and reverse
rotations of the hydraulic motor. The relief valves relieve high pressure at start or at stop of swing
motion and can control the relief pressure in two steps, high and low, in order to insure smooth
operation.

(2) Function of relief valve

Figure illustrates how the pressure acting
on the relief valve is related to its rising P P=pressure, T=time
process. Here is given the function, Ps
referring to the figure following page.
4
P2

3
P1

T
1
2-48(2)

2-63
① Ports (P,R) at tank pressure.

A2 m h n g

A1
P

14007A2SM06

② When hydraulic oil pressure (P×A1) reaches the preset force (FSP) of spring (4), the plunger (3)
moves to the right as shown.
P1×A1=Fsp+Pg×A2

Fsp+Pg×A2
P1=
A1

4 g

P=P1

14007A2SM07

2-64
③ The oil flow chamber g via orifice m and n. When the pressure of chamber g reaches the preset
force (FSP) of spring (4), the piston (6) moves left and stop the piston (6) hits the bottom of bushing
(7).

4 m n g

P=P2

7 6
14007A2SM08

④ When piston (6) hits the bottom of bushing (7), it stops moving to the left any further. As the
result, the pressure in chamber (g) equals (Ps).
Ps×A1=Fsp+Ps×A2

Fsp
Ps=
A1-A2

P=Ps

7 6 g
14007A2SM09

2-65
4) BRAKE SYSTEM
(1) Control valve swing brake system
This is the brake system to stop the swing motion of the excavator during operation.
In this system, the hydraulic circuit is throttled by the swing control valve, and the resistance
created by this throttling works as a brake force to slow down the swing motion.

Work Deceleration Stop

A B A B A B

MCV MCV MCV

MCV A, B opened MCV A, B throttled MCV A, B closed

2-48(1)

(2) Mechanical swing parking brake system

This is function as a parking brake only when all of the RCV lever (except swing, arm in) are not
operated.

① Brake assembly
Circumferential rotation of separate plate
(16) is constrained by the groove located
at housing (1). When housing is
pressed down by brake spring (20) 20
through friction plate (15), separate plate 10
(16) and brake piston (17), friction force 17
occurs there. 16
Cylinder block (10) is constrained by this 15
friction force and brake acts, while brake 1
Groove
releases when hydraulic force exceeds
spring force.

21092SM15

1 Housing 16 Separate plate

10 Cylinder block 17 Brake piston
15 Friction plate 20 Spring

2-66
② Operating principle
a. When the RCV lever (1) is set to the swing or arm in operating position, the pilot oil go to SH of
the time delay valve (35).
This pressure moves spool (5) to the leftward against the force of the spring(8), so pilot pump
charged oil (P3) goes to the chamber G through port PG.
This pressure is applied to move the piston (17) to the upward against the force of the spring
(20). Thus, it releases the brake force.

35

SH

5
PG
20

17 G

1 RCV lever
2 Shuttle valve
5 Spool
8 Spring
17 Brake piston
20 Brake spring P3
35 Time delay valve

300L2SM04

2-67
b. When all of the RCV lever (1) are set the neutral position, the spool (5) returns to the top.
Then, the brake piston (17) is moved lower by spring force and the return oil from the chamber
G flows back to tank port.
At this time, the brake works.

35

SH

20

17 G PG

1 RCV lever
2 Shuttle valve
5 Spool
8 Spring
17 Brake piston
20 Brake spring P3
35 Time delay valve

300L2SM05

2-68
 GROUP 4 TRAVEL DEVICE (TYPE 1 & 2)

1. CONSTRUCTION
Travel device consists travel motor and gear box.
Travel motor includes brake valve, parking brake and high/low speed changeover mechanism.

Ps
PS

PS

A DR DR
MB MA

VB VA

DR DR

MB MA

VB VA

Ps
DR
R/G
MB MA

VB VA

HYDRAULIC CIRCUIT VIEW A

300L2TM01

Port Port name Port size

VA, VB Valve port PF 1
Ps Pilot port PF 1/4
DR Drain port PF 1/2
MA, MB Gauge port PF 1/4

2-69
 2. SPECIFICATION
1) TRAVEL MOTOR

59
6 2 8 7 15 21 22 20 23 24 1 30 60 31 32 29 33 2 37 38 39 36 47 53 54 48 51 50 52 54 49 47 35 36 38 39 37

34
56
57
43
63

58
44
62
61

46 59 45 60

3 4 5 12 14 10 16 17 19 27 26 25 9 18 28 11 13 64 65 55 40 41 43 42 65 64
300L2TM02

1 Casing 23 Friction plate 45 O-ring

2 Plug 24 Separate plate 46 O-ring
3 Oil seal 25 Parking piston 47 Relief valve assy
4 Thrust block 26 D-ring 48 Spool
5 O-ring 27 D-ring 49 Plug
6 Snap ring 28 Valve plate 50 Spring seat
7 Piston 29 Parallel pin 51 Parallel pin
8 Piston seal 30 Spring 52 Spring
9 Shaft 31 O-ring 53 Connector
10 Cylinder roller bearing 32 Spring pin 54 O-ring
11 Needle bearing 33 Parallel pin 55 Hexagon socket head bolt
12 Snap ring 34 Rear cover 56 Check valve
13 Snap ring 35 Main spool assy 57 Spring
14 Thrust plate 36 Spring seat 58 Plug
15 Steel ball 37 Plug 59 Restrictor
16 Pivot 38 Spring 60 Restrictor
17 Swash plate 39 O-ring 61 Name plate
18 Cylinder block 40 Restrictor 62 Rivet
19 Spring 41 Spring 63 Plug
20 Ball guide 42 Plug 64 Plug
21 Retainer plate 43 O-ring 65 O-ring
22 Piston assy 44 O-ring

2-70
2) TRAVEL REDUCTION GEAR

8,34 21 22 19 20 23 13 11 12 14 15 16 9 4 28

31,32

25 29,35 33 27 18 1 24 17 10 26 30 5 6 2 7 3

300S2TM03

1 Gear ring 13 Thrust washer 2 25 Thrust plate

2 Ball bearing 14 Carrier pin 2 26 Thrust plate
3 Floating seal assy 15 Spring pin 2 27 Cover
4 Nut ring 16 Solid pin 2 28 Hexagon socket head bolt
5 Lock plate 17 Sun gear 2 29 Plug
6 Hexagon socket head bolt 18 Carrier 1 30 Snap ring
7 Housing 19 Planetary gear 1 31 Name plate
8 Hexagon socket head bolt 20 Needle bearing 1 32 Rivet
9 Coupling 21 Thrust washer 1 33 O-ring
10 Carrier 2 22 Carrier pin 1 34 Rubber cap
11 Planetary gear 2 23 Spring pin 1 35 Rubber cap
12 Needle bearing 2 24 Sun gear 1

2-71
3. OPERATION
1) MOTOR
High pressure oil delivered form hydraulic pump is led to inlet port that is provided in the brake
valve portion and, through the rear cover (34) and valve plate (28), led to cylinder block (18).
The oil flow and direction of shaft rotation are indicated in table.

Shaft rotation Left Shaft rotation Right

(Counterclockwise) (Clockwise)

Inlet Outlet Direction of shaft rotation

port port (viewing from rear cover)
VB VA Right (clockwise)
VA VB Left (counterclock wise)

300L2TM04

As shown in below figure, high pressure oil is supplied to the pistons which are on one side of the
line Y-Y that connects upper and lower dead points and produces force F1.
F1 = P×A (P : pressure, A : area of piston section)
The swash plate (17) with inclined angle of divides this force F1 into thrust force F2 and radial
force F31-34.
This radial force is applied to axis Y-Y as turning force and generate drive torque of T.
T = r1·F31+r2·F32+r3·F33+r4·F34
This drive torque is transmitted via cylinder block (18) to driving shaft (9).

Y
F31
P F1
r1 F31
F32 P F2

F32
r2
F33 P
r3
F33
P
F34 F34
Y
r4
29092TM07

2-72
2) PARKING BRAKE
Parking brake is released when high pressure oil selected by the brake valve portion that is
connected directly to the rear cover (34), is applied to the parking piston (25).
Otherwise the braking torque is always applied.
This braking torque is generated by the friction between the separated plates (24), inserted into the
casing (1), and friction plates (23), coupled to cylinder block (18) by the outer splines.
When no pressure is activated on the parking piston (25), it is pushed by the brake springs (30)
and it pushes friction plates (23) and separated plates (24) towards casing (1) and generates the
friction force which brakes the rotation of cylinder block (18) and hence the shaft (9).

9 23 24 1 25 18 30 34

2609A2TM05

2-73
 3) CAPACITY CONTROL MECHANISM
Figure typically shows the capacity control mechanism.
When high speed pilot line is charged with the pressure PA that overcome the spring (52), the
spring (52) is compressed and spool (48) shifts to the right to connect the port P and port C.
Then, the highest pressure is selected by the check valve (56) from inlet and outlet pressure of the
motor and high speed pilot line pressure and pushes shifter piston (7). As a result, swash plate (17)
turns around the line L which connect the two pivots (16) as shown by dotted lines. The turn stops
at the stopper (1-1) of casing and swash plate (17) keeps the position.
In this case, the piston stroke become shorter and motor capacity become smaller and motor
rotates faster, around 1.60 times, by the same volume of oil.
When no pressure is in the high speed pilot line PA, spool (35) is pushed back by the spring (52)
and pressure that pressed the shifter piston (7) is released to the hydraulic tank through restrictor
(60).
Here, nine pistons are there and they equally spaced on the swash plate (17). The force that
summed up those of pistons comes to almost the center of the swash plate (17) as shown. Since
the pivots (16) are off-set by S from the center, the rotating force of product S and the force moves
swash plate (17) to the former position and the speed returns to low.
When the power demand exceeds the engine power, such as in steep slope climbing or turning at
high speed mode, the system step down to the low speed automatically. The mechanism is that:
pump pressure is led to the port PB and this pressure activate on pin (51). When the pressure at PB
exceeds predetermined value, spool (48) returns to the left by the counter-pressure against pin (51)
and the pressure on the shifter piston (7) through port C is released to the tank and the motor
comes to low speed.
When PB goes down, the spool (48) moves to the right and the speed become high.

To counterbalance valve
(Brake valve)

MA MB
High speed pilot line
(External Pilot)
56 56 56

8 7 1-1 22
T
PA

48
S

L L VA or VB

PB P C
Load
16 16 17 application point 60 52 51

2609A2TM06

2-74
4) OVERLOAD RELIEF VALVE
(1) Structure
This valve is screwed in the motor rear cover (34) and consists of : plug (47-1) that is screwed and
fixed in the rear cover (34), poppet (47-10) and supports the poppet seat (47-11), spring (47-4)
that is operating relief valve setting pressure and supports the spring seat (47-5), that is inserted
in the sleeve (47-6), screw (47-14) that is adjust the spring force, nut (47-15) that fix screw (47-
14), piston (47-7) that reduce the shock.

47-15 47-1 47-2 47-4 47-9 47-8 47-5 47-6 47-13 47-12

47-14 47-3 47-16 47-7 47-10 47-11

2609A2TM07

47-1 Plug 47-7 Piston 47-12 O-ring

47-2 Guide 47-8 O-ring 47-13 Back-up ring
47-3 O-ring 47-9 Back-up ring 47-14 Socket screw
47-4 Spring 47-10 Poppet 47-15 Hexagon nut
47-5 Spring seat 47-11 Poppet seat 47-16 O-ring
47-6 Sleeve

2-75
(2) Operation
Two pieces of overload valves are located at cross-over position in the counterbalance circuit of
brake valve and have the following functions:
① When hydraulic motor starts, keep the driving pressure below predetermined value and while
accelerating, bypasses surplus oil to return line.
② When stopping the motor, keep the brake pressure, that develops on the outlet side of motor,
under the predetermined value to stop the inertial force.
③ To accelerate sharply while starting, and to mitigate the braking shock while stopping. For these
purposes, the developed pressure is kept comparatively low for a short period, then keep the line
pressure as normal value. While the pressure is low, meshing of reduction gears, crawler and
sprocket etc. can be smoothly done and the shock are absorbed.
When starting, "A" port pressure of overload valve increases, this pressure is applied to the
effective diameter of poppet (47-10) which seats on the poppet seat (47-11) and, at the same
time, is delivered, via small hole, to the spring seat (47-5) located inside the sleeve (47-6) and the
seat bore pressure increases up to "A" port pressure. The poppet (47-10) opposes to spring (47-
4) by the force of the pressure exerted on the area difference between poppet seat's effective
diameter and spring seat bore and keep the predetermined pressure.
When hydraulically braking, the piston (47-7) is at the left position by the driving pressure, and
when "A" port pressure increases, the pressure is applied also to the piston (47-7) through the
small hole in the poppet (47-10) and piston (47-7) moves rightward until it touches the stopper in
rear cover. In this while, the poppet (47-10) maintains "A" port pressure at comparatively low
against the spring (47-4) force and exhaust oil to "B" port side. After the piston reached to the
plug, the valve acts the same as at starting.

Spring(47-4) Piston(47-7) Spring seat(47-5) Poppet seat(47-11)

Port B

Port A

Poppet(47-10) Sleeve(47-6) Small hole

2609A2TM08

2-76
5) BRAKE VALVE
(1) Structure
The brake valve portion mainly consists of the following parts:
① Spool
By shifting the spool (35), the discharged oil from hydraulic motor is automatically shut off or
restricted according to the condition and give the effect of holding, accelerating, stopping and
counterbalance operations.
(See page 2-74, (2) Operation)
② Check valve (built in the spool)
This valve is located in the oil supplying passage to hydraulic motor, and at the same time
functions to lock oil displacement. Therefore, this valve serves as not only a suction valve but
also a holding valve for hydraulic motor.

37 40 41 35 38 43 46 44
2609A2TM09

35 Main spool 40 O-ring 44 O-ring

37 Spring 41 Spring seat 46 Plug
38 Restrictor 43 Restrictor spring

2-77
(2) Operation
① Holding operation
When the control valve is at neutral position, VA and VB ports are connected to the tank, and the
spring (38) located on both spool ends holds the spool (35) at central position.
Therefore, the passages from VA to MA and VB to MB are closed, which result in closing MA
and MB ports connected to hydraulic motor.
Since the passage to parking brake is connected to the tank line, the brake cylinder pressure is
equal to the tank pressure and the brake is applied by the springs. Thus, the rotation of the motor
is mechanically prevented.
If external torque is exerted on the motor shaft, the motor would not rotate as usual by this
negative parking brake.
In case the brake should be released for some reason, pressure is built on MA or MB port. But,
due to oil leakage inside hydraulic motor or so, high-pressure oil escapes from the closed circuit
and motor rotates a bit. So, the cavitation tends to occur in the lower pressure side of the closed
circuit. Then, the check valve, built in the spool (35), operates to avoid the cavitation and opens
the passage from VA to MA or from VB to MB. Then the oil equivalent to the leakage is sucked
from the tank line to the closed circuit.

DR

T
MB MA

MB MA

VB VA VB VA

25092TM29

2-78
② Accelerating operation
When VA and VB ports are connected respectively to pump and tank by operating the control
valve, hydraulic oil from pump is forwarded through VA port to push open the check valve
provided inside spool (35), and oil flows to motor via MA port to rotate the motor.
Therefore, the pressure increases and negative brake is released by the pressure supplied from
pump. At the same time, the pressure of pilot chamber increases to push and move the spool
(35) leftwards, overcoming the spring (38) force. Thus, the return line from MB to VB opens to
rotate the motor.
In case inertia load is too big to start rotation, accelerating pressure reaches the set pressure of
relief valve and high pressure oil is being relieved while the motor gains the rotational speed.
As the rotational speed goes up, the relieved volume decreases, and finally the motor rotates at
a fixed speed.

DR

T
MB MA

MB MA

VB VA
VB VA

25092TM30

2-79
③ Stopping operation
Returning the control valve to neutral position while running the motor, the oil supply is cut off
and VA and VB ports are connected to the tank line. Then the pressure of the pilot chamber
located on both spool ends become equal, and the spool (35) returns to the neutral position by
spring (38) force. Thus, the passage from MA to VA is closed.
Owing to the inertia force of the load, the hydraulic motor tends to continue the rotation. Here,
the motor functions as a pump and forwards the oil to MB port but the passage is blocked and
MB port pressure increases. Then the relief valve opens to relieve the pressure and rotational
speed decelerates and at last the motor stops.
Negative brake release pressure is gradually lowered due to the restrictor and finally the brake
works and the motor is mechanically stopped.

DR

T
MB MA

MB MA

VB VA
VB VA

25092TM31

2-80
④ Counterbalance operation
Counterbalance operation is required to decelerate slowly the hydraulic motor while absorbing
inertia force.
In case the hydraulic oil is gradually decreased from pump to VB port, the drive shaft of hydraulic
motor tends to rotate faster than that matched to the volume of oil supply.
Consequently, the pilot chamber pressure on MB to VB side decreases and the spring (38) force
moves the spool (35) leftwards towards neutral position.
Therefore, the area of passage from MA to VA becomes smaller and the pressure on MA side
rises due to increased resistance in the passage and the motor receives hydraulic braking effect.
If the motor rotates slower than that matched to the volume of supplied oil, the pilot chamber
pressure on VB port increases, and spool (35) moves rightwards to enlarge the area of passage
from MA to VA. Therefore the braking effect becomes smaller and the rotational speed of motor
is controlled to correspond to the volume of supplied oil.
In order to give stable counterbalance operation, the restrictors (40) are set in the pilot chamber
to damp the spool (35) movement.
The parking brake is released during pressure adjusting action of the spool (35).

DR

T
MB MA

MB MA

VB VA
VB VA

25092TM32

2-81
 6) REDUCTION GEAR
Reduction unit slows down the rotating speed of motor and converts motor torque to strong rotating
force.
This reduction unit utilizes two stages, planetary reduction system.
Planetary reduction system consists of sun gear, planetary gears, (planetary) carriers, and ring
gear.
When the sun gear (s) is driven through input shaft, planetary pinions (b), rotating on their center,
also move, meshing with fixed ring gear (a), around sun gear (s).
This movement is transferred to carrier (k) and deliver the torque.
This mechanism is called planetary gear mechanism.

Fixed ring gear(a)

Ring gear(a)
Carrier(k)
Planetary pinions(b) Carrier(k)
Sun gear(s)

Input Output
Sun gear(s)
Planetary pinions(b)

29072TM10 29072TM11

When the sun gear S1 is driven by input shaft, planetary action occurs among gears S1, a and b
and revolution of gear b transfers the rotation of carrier K1 to second sun gear S2, and also evokes
planetary action between gear S2, a and d.
This time, because carrier K2 is fixed to frame, gear d drives ring gear a and then ring gear a
rotates to drive sprocket.

b d

S1 S2

K1 K2

29072TM12

2-82
GROUP 5 RCV LEVER

1. STRUCTURE
The casing has the oil inlet port P (primary pressure) and the oil outlet port T (tank). In addition the
secondary pressure is taken out through ports 1, 2, 3 and 4 provided at the bottom face.
侍 Refer to the parts manual for the types of the RCV lever.

1) TYPE M1, M3, M5

8
7
Null 5 5
Null

6 6

TYPEM1,
TYPE L1, M3
L3 TYPE
TYPE L5
M5
Switches
Type No. LH RH
5 One touch decel Horn
25 19 M1, M3
Simultaneous Single 6 Power boost Breaker
operation operation
5 One touch decel Horn
6 Power boost Null
M5
7 CCW rotation Close
8 CW rotation Open
侍 Number 7 and 8 : Option attachment

P T

A A

1 3 2 4
Hydraulic circuit

Pilot ports
4 Port LH RH Port size
2 3 P 1 P Pilot oil inlet port Pilot oil inlet port
T T
T Pilot oil return port Pilot oil return port
1 P 3 2
1 Left swing port Bucket out port
4 PF 3/8
2 Arm out port Boom up port
LH RH
VIEW A-A 3 Right swing port Bucket in port
4 Arm in port Boom down port
300L2RL01

2-83
 2) TYPE M2, M4, M6

8
7
Null 5
5 Null

6 6

TYPEM2,
TYPE L2, M4
L4 TYPEM6
TYPE L6

Switches
Type No. LH RH
25 19
Single 5 One touch decel Horn
Simultaneous M2, M4
operation
operation 6 Power boost Breaker
5 One touch decel Horn
6 Power boost Null
M6
7 CCW rotation Close
8 CW rotation Open
※ Number 7 and 8 : Option attachment
P T

A A

1 3 2 4
Hydraulic circuit

Pilot ports
2 4
T 1 Port LH RH Port size
3 P
1 T P Pilot oil inlet port Pilot oil inlet port
P 3 T Pilot oil return port Pilot oil return port
4 2
1 Left swing port Bucket out port
LH RH PF 3/8
2 Arm out port Boom up port
VIEW A-A
3 Right swing port Bucket in port
4 Arm in port Boom down port

300L2RL05

2-84
3) CROSS SECTION

1 Case
2 Bushing
3 Spool
No. Port
4 Shim
24 P
5 Spring
25 1, 2, 3, 4 (RH) 6 Spring seat
25 2, 4 (LH) 7 Spring
26 T (RH) 8 Plug
26 1, 3, T (LH) 9 Push rod
10 O-ring
11 Rod seal
20
12 Plate
13 Spacer
14 Boot
21
15 Joint assembly
22 16 Swash plate
17 17 Adjusting nut
13 18 Bushing
15
19 Plug
20 Handle assembly
23
16 21 Handle bar
22 Nut
9
23 Boot
14 11
24 Last guard filter
12
25 Connector
18 8 26 Connector
27~34
10 27 Connector
6 28 Connector
7 29 Connector
5 30 Connector
4 31 Small guide
2 3 32 Connector
19 33 Big guide
1 34 Connector
24
25
210S2RL06
26

Item numbers are based on the type M1.

The construction of the pilot valve is shown in the attached cross section drawing. The casing has
vertical holes in which reducing valves are assembled.
The pressure reducing section is composed of the spool (3), spring (5) for setting secondary pres-
sure, return spring (7), spring seat (6) and shim (4). The spring for setting the secondary pressure
has been generally so preset that the secondary pressure is 5 to 20.5 kgf/cm2 (depending on the
type). The spool is pushed against the push rod (9) by the return spring.
When the push rod is pushed down by tilting the handle, the spring seat comes down simultaneously
and changes setting of the secondary pressure spring.
2-85
2. FUNCTIONS
1) FUNDAMENTAL FUNCTIONS
The pilot valve is a valve that controls the spool stroke, direction, etc of a main control valve. This
function is carried out by providing the spring at one end of the main control valve spool and apply-
ing the output pressure (secondary pressure) of the pilot valve to the other end.
For this function to be carried out satisfactorily, the pilot valve is composed of the following ele-
ments.
(1) Inlet port (P) where oil is supplied from hydraulic pump.
(2) Output ports (1, 2, 3 & 4) to apply pressure supplied from inlet port to ends of control valve spools.
(3) Tank port (T) necessary to control the above output pressure.
(4) Spool to connect output port to inlet port or tank port.
(5) Mechanical means to control output pressure, including springs that work on the above spools.
2) FUNCTIONS OF MAJOR SECTIONS
Item numbers are based on the type M1.
The functions of the spool (3) are to receive the supply oil pressure from the hydraulic pump at its
port P, and to change over oil paths to determine whether the pressure oil of port P is led to output
ports 1, 2, 3 & 4 or the output port pressure oil to tank port T.
The spring (5) works on this spool to determine the output pressure.
The change the deflection of this spring, the push rod (9) is inserted and can slide in the plug (8).
For the purpose of changing the displacement of the push rod through the swash plate (16) and
adjusting nut (17) are provided the handle assy (20) that can be tilted in any direction around the
fulcrum of the universal joint (15) center.
The spring (7) works on the case (1) and spring seat (6) and tries to return the push rod (9) to the
zero-displacement position irrespective of the output pressure, securing its resetting to the center
position.
This also has the effect of a reaction spring to give appropriate control feeling to the operator.

2-86
3) OPERATION
The operation of the pilot valve will be described on the basis of the hydraulic circuit diagram
shown below and the attached operation explanation drawing.
The diagram shown below is the typical application example of the pilot valve.

5 6

3
1
3
P T

2 4

2-70

1 Pilot valve 3 Main pump 5 Hydraulic motor

2 Pilot pump 4 Main control valve 6 Hydraulic cylinder

2-87
(1) Case where handle is in neutral position

T
5

P
3

Port 1 Port 3

300L2RL03

The force of the spring (5) that determines the output pressure of the pilot valve is not applied to
the spool (3). Therefore, the spool is pushed up by the spring (7) to the position of port (1, 3) in
the operation explanation drawing. Then, since the output port is connected to tank port T only,
the output port pressure becomes equal to tank pressure.

2-88
(2) Case where handle is tilted

Port 1 Port 3

300L2RL04

When the push rod (9) is stroked, the spool (3) moves downwards.
Then port P is connected with port (1) and the oil supplied from the pilot pump flows through port
(1) to generate the pressure.
When the pressure at port (1) increases to the value corresponding to the spring force set by tilt-
ing the handle, the hydraulic pressure force balances with the spring force. If the pressure at port
(1) increases higher than the set pressure, port P is disconnected from port (1) and port T is con-
nected with port (1). If it decreases lower than the set pressure, port P is connected with port (1)
and port T is disconnected from port 1.
In this manner the secondary pressure is kept at the constant value.
Besides, in some type, when the handle is tilted more than a certain angle, the upper end of the
spool contacts with the inside bottom of the push rod and the output pressure is left to be con-
nected with port P.

2-89
GROUP 6 RCV PEDAL

1. STRUCTURE
The casing (spacer) has the oil inlet port P (primary pressure), and the oil outlet port T (tank). In
addition the secondary pressure is taken out through ports 1,2, 3 and 4 provided at the bottom face.

12.4 12.4

1 3

2 1

4 3

Port Port Port size

P T P Pilot oil inlet port
T Pilot oil return port
1 Travel (LH, Forward)
PF 1/4
2 Travel (LH, Backward)
3 Travel (RH, Forward)
1 2 3 4 4 Travel (RH, Backward)
Hydraulic circuit

130ZF2RP01

2-90
CROSS SECTION
The construction of the RCV pedal is shown in the below drawing. The casing has vertical holes in
which reducing valves are assembled.
The pressure reducing section is composed of the spool (7), spring (5) for setting secondary
pressure, return spring (9), stopper (8), and spring seat (6). The spring for setting the secondary
pressure has been generally so preset that the secondary pressure is 6.3±1 to 24.9±1.5 kgf/cm2
(depending on the type). The spool is pushed against the push rod (13) by the return spring.
When the push rod is pushed down by tilting pedal, the spring seat comes down simultaneously and
changes setting of the secondary pressure spring.

27 31 30 29 28 33

32
23
22 25,26
21 2

15
20 13
34
24 16
14 17
12
18
11 19
10
8 3
4
2
1 9
5 2
6
7

130ZF2RP02

1 Body 13 Push rod 25 Cover

2 Plug 14 Spring pin 26 Wrench bolt
3 Plug 15 Seal 27 Cam
4 Spring seat 16 Steel ball 28 Bushing
5 Spring 17 Spring 29 Cam shaft
6 Spring seat 18 Plate 30 Set screw
7 Spool 19 Snap ring 31 Set screw
8 Stopper 20 Plug 32 Hex nut
9 Spring 21 O-ring 33 Bellows
10 Rod guide 22 Rod seal 34 Expand
11 O-ring 23 Dust seal 35 Name plate
12 Snap ring 24 Piston

2-91
2. FUNCTION
1) FUNDAMENTAL FUNCTIONS
The pilot valve is a valve controls the spool stroke, direction, etc of a main control valve. This
function is carried out by providing the spring at one end of the main control valve spool and
applying the output pressure (secondary pressure) of the pilot valve to the other end.
For this function to be carried out satisfactorily, the pilot valve is composed of the following
elements.
(1) Inlet port (P) where oil is supplied from hydraulic pump.
(2) Output port (1, 2, 3 & 4) to apply pressure supplied from inlet port to ends of control valve spools.
(3) Tank port (T) necessary to control the above output pressure.
(4) Spool to connect output port to inlet port tank port.
(5) Mechanical means to control output pressure, including springs that work on the above spools.
2) FUNCTIONS OF MAJOR SECTIONS
The functions of the spool (7) are to receive the supply oil pressure from the hydraulic pump at its
port P, and to change over oil paths to determine whether the pressure oil of port P is led to output
ports 1, 2, 3 & 4 or the output spool to determine the output pressure.
The spring (5) works on this spool to determine the output pressure.
The change the deflection of this spring, the push rod (13) is inserted and can slide in the plug (20).
For the purpose of changing th displacement of the push rod through the cam (27) and adjusting
nut (32) are provided the pedal that can be tilted in any direction around the fulcrum of the cam (27)
center.
The spring (9) works on the body (1) and spring seat (6) and tries to return the push rod (13) to the
zero-displacement position irrespective of the output pressure, securing its resetting to the center
position.
This also has the effect of a reaction spring to give appropriate control feeling to the operator.

2-92
3) OPERATION
The operation of the pilot valve will be described on the basis of the hydraulic circuit diagram shown
below and the attached operation explanation drawing.
The diagram shown below is the typical application example of the pilot valve.

36072SF01

1 Pilot valve 3 Main pump 5 Hydraulic motor

2 Pilot pump 4 Main control valve 6 Hydraulic cylinder

2-93
(1) Case where pedal is in neutral position

7 T

9 P

130ZF2RP03

The force of the spring (5) that determines the output pressure of the pilot valve is not applied to
the spool (7). Therefore, the spool is pushed up by the spring (9) to the position of 1 and port 2.
Then, since the output port is connected to tank port T only, the output port pressure becomes
equal to tank pressure.

2-94
(2) Case where pedal is tilted

13

7 T

PORT 1 PORT 2
220F2RP04

When the push rod (13) is stroked, the spool (7) moves downwards.
Then port P is connected with port 1, and the oil supplied from the pilot pump flows through port
1 to generate the pressure.
When the pressure at port 1 increases to the value corresponding to the spring force set by tilting
the handle, the hydraulic pressure force balances with the spring force. If the pressure at port 1
increases higher than the set pressure, port P is disconnected from port 1 and port T is
connected with port 1. If it decreases lower than the set pressure, port P is connected with port
1 and port T is disconnected from port 1.
In this manner the secondary pressure is kept at the constant value.
Besides, in some type, when the handle is tilted more than a certain angle, the upper end of the
spool contacts with inside bottom of the push rod and the output pressure is left to be connected
with port P.

2-95