SECTION 2 STRUCTURE AND FUNCTION

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

Group 2 Main Control Valve - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2-21
Group 3 Swing Device - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2-46
Group 4 Travel Deviceb - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2-57
Group 5 RCV Lever - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2-64
Group 6 RCV Pedal - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2-71
 SECTION 2 STRUCTURE AND FUNCTION
GROUP 1 PUMP DEVICE(~#0463)
1. STRUCTURE
The pump device consists of main pump, regulator and gear pump.

45070MP00

Port Port name Port size

A1,A2 Delivery port SAE6000psi 1"
B1 Suction port SAE2500psi 3"
Dr1,Dr2 Drain port PF 3/4 - 20
Pb1,Pb2 Back pressure port PF 1/4 - 15
Pi1,Pi2 Pilot port PF 1/4 - 15
Pm1,Pm2 Qmax cut port PF 1/4 - 15
Psv Servo assist port PF 1/4 - 15
a1 ~ a3 Gauge port PF 1/4 - 14
Di Oil filling port PF 3/4 - 20
Do Outlet port PF 3/4 - 20
Pb Gauge port PT 1/8
A3 Gear pump delivery port PF 1/2 - 19
B3 Gear pump suction port PF 3/4 - 20.5
Dr3 Gear pump drain port PF 3/8 - 15
29073CD01
a4 Gauge port PF 1/4 - 14

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

45070MP03

2-2
 04 Gear pump 262 Cover 548 Feed back pin
080 Proportional reducing 271 Pump casing 702 O-ring
valve assy 312 Valve cover 709 O-ring
111 Drive shaft 313 Valve plate(R) 711 O-ring
113 Driven shaft 314 Valve plate(L) 712 O-ring
123 Roller bearing 405 Hexagon socket bolt 724 O-ring
124 Needle bearing 406 Hexagon socket bolt 725 O-ring
126 Spacer 408 Hexagon socket bolt 726 O-ring
127 Spacer 409 Hexagon socket bolt 728 O-ring
128 Bearing spacer 410 Hexagon socket bolt 732 O-ring
129 Bearing spacer 411 Hexagon socket bolt 752 Seat packing
130 Booster 412 Hexagon socket bolt 774 Oil seal
131 Booster cover 413 Hexagon socket bolt 789 Back up ring
141 Cylinder block 467 Plug 792 Back up ring
151 Piston 469 Plug 806 Nut
152 Shoe 490 Plug 807 Nut
153 Plate 491 Plug 823 Snap ring
156 Bushing 492 Restrictor 824 Snap ring
157 Cylinder spring 493 Plug 825 Snap ring
171 Front casing 531 Tilting pin 827 Snap ring
191 Drive gear 532 Servo piston 828 Snap ring
192 Driven gear 534 Stopper(L) 885 Valve plate pin
211 Shoe plate 535 Stopper(S) 886 Spring pin
212 Swash plate 536 Servo cover 888 Pin
214 Tilting bushing 541 Seat 901 Eye bolt
251 Swash plate support 543 Stopper 953 Set screw
261 Front cover 545 Steel ball 954 Set screw

2-3
MAIN PUMP(2/2)

45070MP04

079 Proportional reducing valve 408 Hexagon screw 724 O-ring

325 Valve casing 467 Plug 725 O-ring
407 Hexagon screw 490 Plug 732 O-ring

2-4
2) REGULATOR(1/2)

Port Port name port size

Pb Back pressuye port PF 1/4 - 15

Pi Pilot port PF 1/4 - 15

45070RG01
Pm Qmax cut port PF 1/4 - 15

2-5
REGULATOR(2/2)

45070RG02

412 Hexagon socket screw 631 Sleeve, pf 730 O-ring

413 Hexagon socket screw 641 Pilot cover 732 O-ring
436 Hexagon socket screw 642 Adjust screw(QMC) 733 O-ring
438 Hexagon socket screw 643 Pilot piston 734 O-ring
496 Plug 644 Spring seat(Q) 735 O-ring
601 Casing 645 Adjust stem(Q) 755 O-ring
611 Feed back lever 646 Pilot spring 756 O-ring
612 Lever(1) 647 Stopper 763 O-ring
613 Lever(2) 648 Piston(QMC) 801 Nut
614 Center plug 651 Sleeve 814 Snap ring
615 Adjust plug 652 Spool 836 Snap ring
621 Compensator piston 653 Spring seat 858 Snap ring
622 Piston case 654 Return spring 874 Spring pin
623 Compensator rod 655 Set spring 875 Pin
624 Spring seat(C) 656 Block cover 887 Pin
625 Outer spring 708 O-ring 897 Pin
626 Inner spring 722 O-ring 898 Pin
627 Adjust stem(C) 723 O-ring 924 Set screw
628 Adjust screw(C) 724 O-ring 925 Adjust screw(QI)
629 Cover(C) 725 O-ring
630 Lock nut 728 O-ring

2-6
3) GEAR PUMP

45070RG03

307 Poppet 353 Drive gear 466 Plug

308 Seat 354 Driven gear 700 Ring
309 Spring seat 355 Filter 709 O-ring
310 Spring 361 Front case 725 O-ring
311 Adjusting screw 433 Flange socket 732 O-ring
312 Lock nut 434 Flange socket 850 Snap ring
351 Gear case 435 Flange socket

2-7
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(123,124) at its both ends.
The shoe is caulked to the piston to from
a spherical coupling. It has a pocket to
relieve thrust force generated by loading
pressure and the take hydraulic balance
so that it slides lightly over the shoe
plate(211). The sub group composed by
a piston and a shoe is pressed against the
shoe plate by the action of the cylinder 45070RG04
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.
Swash plate group
(2) The swash plate group consists of swash
plate(212), shoe plate(211), swash plate
support(251), tilting bush(214), tilting
pin(531) and servo piston(532).
The swash plate is a cylindrical part
formed on the opposite side of the sliding
surface of the shoe and is supported by
the swash support.
If the servo piston moves to the right and
left as hydraulic force controlled by the
45070RG05
regulator is admitted to hydraulic chamber α
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 (210-7)

2-8
(3) Valve cover group
The valve cover group consists of valve
cover(312), valve plate(313, 314),
booster(130), boost cover(131) and valve
plate pin(885).
The valve plate having two melon-shaped
ports is fixed to the valve cover and feeds
and collects oil to and from the cylinder
cover.
The oil changed over by the valve plate is
connected to an external pipeline by way
of the valve cover.
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
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
45070RG06
makes no stroke and discharges no oil.

2-9
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.

2-10
① Flow reducing function

45070RG07

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.

2-11
② Flow increasing function

45070RG08

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.

2-12
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) the 924
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 (210-7)
Speed
Tightening Flow control Flow
amount of starting change
adjusting pressure amount
screw(924) change

Delivery flow, Q
amount

(min -1) (Turn) (kgf/cm2) (ℓ/min)

1900 +1/4 +1.7 +22.7

Pilot pressure, Pi

2-13
(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/2Л + P2×q/2Л
= (P1+P2)×q/2Л
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).

2-14
① Overload preventive function

45070RG09

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.

2-15
② Flow reset function

45070RG10

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.

2-16
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 625 626 630 628
nut(630) and by tightening(or loosening)
the adjusting screw C(628). Tightening
the screw shifts the control chart to the 801
right and increases the input
925
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
CI(925) by N×A turns at first.(A=1.9)
※ Adjusting values are shown in table.

Adjustment of outer spring 2-16 (210-7)

Speed
Tightening Compens- Input torque
amount of ating control change
adjusting starting amount
Delivery flow, Q

screw(C) pressure
(628) change
amount

(min -1) (Turn) (kgf/cm2) (kgf·m)

1900 +1/4 +19.2 +4.9

Delivery pressure, (P1+P2)

2-17
b. Adjustment of inner spring
626
Adjust it by loosening the hexagon nut
(801) and by tightening(or loosening)
the adjusting screw QI(925).
Tightening the screw increases the flow 801
and then the input horsepower as
925
shown in the figure.
※ Adjusting valves are shown in table.

Adjustment of inner spring

Speed
Tightening Compens- Input torque
amount of ating control change 2-17 (210-7)

adjusting starting amount

screw(QI) pressure
(925) change
amount

Delivery flow, Q
(min -1) (Turn) (kgf/cm2) (kgf·m)

1900 +1/4 +16.3 +4.2

Delivery pressure, (P1+P2)

2-18
(3) Power shift control

45070RG11

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. However, the secondary pressure Pf Pf=
MIN
(power shift pressure) is admitted to the Pf= .
MA
horsepower control section of each pump X.
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.

2-19
(4) Adjustment of maximum and minimum flows
① Adjustment of maximum flow
Adjust it by loosening the hexagon
nut(806) and by tightening(or loosening)
the set screw(953).
The maximum flow only is adjusted without
changing other control characteristics.
45070RG12

Adjustment of max flow

Speed
Tightening Flow change

Delivery flow, Q
amount of amount
adjusting screw
(953)

(min -1) (Turn) (ℓ/min)

1900 +1/4 -7.6

Pilot pressure, Pi

② Adjustment of minimum flow

Adjust it by loosening the hexagon
nut(807) and by tightening(or loosening)
the hexagonal socket head set screw
(954). Similarly to the adjustment of the
maximum flow, other characteristics are
not changed.
However, remember that, if tightened too
45070RG13
much, the required horsepower during
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
(954)

(min -1) (Turn) (ℓ/min)

Pilot pressure, Pi
1900 +1/4 +7.6

2-20
 GROUP 1 PUMP DEVICE(#0464~)
1. STRUCTURE
The pump device consists of main pump, regulator.
Pi1 Pm1 Psv2
a5
(a1) (a2)

a1

a4

Psv1 PB Pi2

Qmin adjusting screw Qmax adjusting screw Qmin adjusting screw

Regulator Regulator
Psv1
Pm1 Pm2
a1 Pi2

(a1)

Dr3
Dr1 PB

Dr2 A1 A2
Dr4

(a2)

a2
B1
Front pump Port block Rear pump

470072MP01

a4 Psv1 A1 a1 a2 A2 Psv2 a5

Port Port name Port size

Front Rear
A1,A2 Delivery port SAE6000psi 1"
B1 Suction port SAE2500psi 3"
Dr1~Dr4 Drain port PF 3/4 - 23
Pm1 Pm2 Pi1,Pi2 Pilot port PF 1/4 - 15
Pi1 Pi2
Pm1,Pm2 Qmax cut port PF 1/4 - 15
Engine Psv1, Psv2 Servo assist port PF 1/4 - 15
a1, a2, a4, a5 Gauge port PF 1/4 - 15
Dr1,r2 B1 Dr3,r4
Pb Gauge port RC 1/8
Hydraulic circuit

2-20-1
 1) MAIN PUMP(1/2)
The main pump consists of two piston pumps(front & rear) and valve block.

789 732 532 214 531,548 724 702 792 534 719 901 492 130 706 954 468,728 151 152 113 263 406
535
808
953
886
717
251
406
824
111

774
261
127
710
123

401 490 212 211 153 156 157 490 313 311 124 114 719 466,725 312 885 314 012 271 402
492

470072MP02

012 Cylinder block 271 Pump casing 710 O-ring

111 Drive shaft(F) 311 Valve cover(F) 717 O-ring
113 Driven shaft(R) 312 Valve cover(R) 719 O-ring
114 Coupling 313 Valve plate(R) 724 O-ring
123 Roller bearing 314 Valve plate(L) 725 O-ring
124 Needle bearing 401 Hexagon socket bolt 728 O-ring
127 Spacer 402 Hexagon socket bolt 732 O-ring
130 Booster 406 Hexagon socket bolt 774 Oil seal
151 Piston 466 VP Plug 789 Back up ring
152 Shoe 468 VP Plug 792 Back up ring
153 Plate 490 VP Plug 808 Hexagon head nut
156 Bushing 492 VP Plug 824 Snap ring
157 Cylinder spring 531 Tilting pin 885 Pin
211 Shoe plate 532 Servo piston 886 Spring pin
212 Swash plate 534 Stopper(L) 901 Eye bolt
214 Bushing 535 Stopper(S) 953 Set screw
251 Support plate 548 Feed back pin 954 Set screw
261 Seal cover(F) 702 O-ring
263 Seal cover(R) 706 O-ring

2-20-2
 2) FRONT REGULATOR(1/2)

412 876 874 a Psv

A 755
897 B 858
614 A
612
FRONT
615
613
Pf
611
P2
875 Pi
Pm
A
B

Hydraulic circuit
B

647 728 438

648
723
642 Pi

Pm
801
641

730 643 708 644 645 646 801 924

SECTION B-B

408 755 541 545 543 722 496 438 413

Psv

470072RG01

466 Pi
755 Pm Port Port name Port size

Pi Pilot port PF 1/4 - 15

Psv Servo assist port PF 1/4 - 15
696 697 735 755 724 725 436 P2 Companion delivery port -
Pf Powershift port -
VIEW C
a Gauge port PF 1/4 - 15

2-20-3
 FRONT REGULATOR(2/2)

655 734 653 654 836 651 652 601 624 629 630 628

641
814

801
C
925
898

631
627
732
732
733

622

621 623 625 626 887 763 756

SECTION A-A
470072RG02

408 Hexagon socket screw 628 Adjust screw(C) 725 O-ring

412 Hexagon socket screw 629 Cover(C) 728 O-ring
413 Hexagon socket screw 630 Lock nut 730 O-ring
436 Hexagon socket screw 631 Sleeve, pf 732 O-ring
438 Hexagon socket screw 641 Pilot cover 733 O-ring
466 Plug 642 Adjust screw(QMC) 734 O-ring
496 Plug 643 Pilot piston 735 O-ring
541 Seat 644 Spring seat(Q) 755 O-ring
543 Stopper 645 Adjust stem(Q) 756 O-ring
545 Steel ball 646 Pilot spring 763 O-ring
601 Casing 647 Stopper 801 Nut
611 Feed back lever 648 Piston(QMC) 814 Snap ring
612 Lever(1) 651 Sleeve 836 Snap ring
613 Lever(2) 652 Spool(A) 858 Snap ring
614 Center plug 653 Spring seat 874 Spring pin
615 Adjust plug 654 Return spring 875 Pin
621 Compensator piston 655 Set spring 876 Pin
622 Piston case 696 Port cover 878 Pin
623 Compensator rod 697 Check valve plate 887 Pin
624 Spring seat(C) 708 O-ring 897 Pin
625 Outer spring 722 O-ring 898 Pin
626 Inner spring 723 O-ring 924 Set screw
627 Adjust stem(C) 724 O-ring 925 Adjust screw(QI)

2-20-4
3) REAR REGULATOR(1/2)

470072RG03

Port Port name Port size

Pi Pilot port PF 1/4 - 15

Psv Servo assist port PF 1/4 - 15
P2 Companion delivery port -
Pf Powershift port -
a Gauge port PF 1/4 - 15

2-20-5
 REAR REGULATOR(2/2)

655 734 653 654 836 651 652 601 624 629 630 628

641
814

801
C
925
898

631
627
732
732
733

622

621 623 625 626 887 763 756

SECTION A-A
470072RG02

079 EPPR valve 627 Adjust stem(C) 724 O-ring

407 Hexagon socket screw 628 Adjust screw(C) 725 O-ring
412 Hexagon socket screw 629 Cover(C) 728 O-ring
413 Hexagon socket screw 630 Lock nut 730 O-ring
436 Hexagon socket screw 631 Sleeve, pf 732 O-ring
438 Hexagon socket screw 641 Pilot cover 733 O-ring
482 Plug 642 Adjust screw(QMC) 734 O-ring
496 Plug 643 Pilot piston 735 O-ring
541 Seat 644 Spring seat(Q) 755 O-ring
543 Stopper 645 Adjust stem(Q) 756 O-ring
545 Steel ball 646 Pilot spring 763 O-ring
601 Casing 647 Stopper 801 Nut
611 Feed back lever 648 Piston(QMC) 814 Snap ring
612 Lever(1) 651 Sleeve 836 Snap ring
613 Lever(2) 652 Spool(A) 858 Snap ring
614 Center plug 653 Spring seat 874 Spring pin
615 Adjust plug 654 Return spring 875 Pin
621 Compensator piston 655 Set spring 876 Pin
622 Piston case 697 Check valve plate 887 Pin
623 Compensator rod 699 Port cover 897 Pin
624 Spring seat(C) 708 O-ring 898 Pin
625 Outer spring 722 O-ring 924 Set screw
626 Inner spring 723 O-ring 925 Adjust screw(QI)

2-20-6
 4) GEAR PUMP

Dr Dr
B A
G G

12 7 6 8,9

16
Dr
3

A 5
B
10,11

14,15
G
Hydraulic circuit
2 4 13
470072GP01

Port Port name Port size

1 Gear shaft 9 Back up seal
A Delivery port PF 1/2 2 Drive gear 10 Retainer seal
B Suction port PF 1 3 Cover(F) 11 Snap ring
G Gauge port PF 1/4 4 Gear housing 12 Dowel pin
Dr Drain port PF 3/8 5 Cover(R) 13 O-ring
6 Block 14 Hexagon bolt
7 Bushing 15 Washer
8 Seal 16 Relief valve

2-20-7
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(012), piston
shoes(151,152), set plate(153), spherical 313
bush(156), and cylinder spring(157). 012
157
The drive shaft is supported by 156
bearing(123,124) at its both ends. 153
151
The shoe is caulked to the piston to from 152
a spherical coupling. It has a pocket to
111
relieve thrust force generated by loading 211
pressure and the take hydraulic balance 123
so that it slides lightly over the shoe
plate(211). The sub group composed by
a piston and a shoe is pressed against the
shoe plate by the action of the cylinder 50072MP01
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.
(2) Swash plate group
The swash plate group consists of swash 531
548
plate(212), shoe plate(211), swash plate
214
support(251), tilting bush(214), tilting
pin(531) and servo piston(532). 212
The swash plate is a cylindrical part
251 211
formed on the opposite side of the sliding
surface of the shoe and is supported by
the swash support.
If the servo piston moves to the right and
left as hydraulic force controlled by the 532 α
regulator is admitted to hydraulic chamber
located on both sides of the servo piston,
the swash plate slides over the swash α
plate support via the spherical part of the
tilting pin to change the tilting angle(α)

2-7 (210-7)

2-20-8
(3) Valve cover group
The valve cover group consists of valve
cover(F, 311), valve cover(R, 312), valve
plate(313, 314), spline coupling(114),
booster(130) and valve plate pin(885).
The valve plate having two melon-shaped
ports is fixed to the valve cover and feeds
and collects oil to and from the cylinder
cover.
314
The oil changed over by the valve plate is 312
connected to an external pipeline by way
of the valve cover. 130
Now, if the drive shaft is driven by a prime 114
885
mover(electric motor, engine, etc), it 311
rotates the cylinder block via a spline
linkage at the same time. If the swash
plate is tilted as in Fig(previous page) the
pistons arranged in the cylinder block
make a reciprocating motion with respect
885
to the cylinder block, while they revolve 313
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
36072MP03
makes no stroke and discharges no oil.

2-20-9
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.

2-20-10
① Flow reducing function

643 654 651 652 613 646

P1 CL
B(E)
874
897
C
A

875

611

Servo piston Small diameter

Large diameter D
548 chamber
chamber
531

2-10

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.

2-20-11
② Flow increasing function

643 654 651 652 613 646

P1 CL
B(E)
874
897
C

875
611

Small diameter
Servo piston D 548 chamber
Large diameter
chamber
531

2-11

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.

2-20-12
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) the 924
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 (210-7)
Speed
Tightening Flow Flow
amount of control change
adjusting starting amount
screw(924) pressure

Delivery flow, Q
change
amount

(min -1) (Turn) (kgf/cm2) (ℓ/min)

1900 +1/4 +1.73 +22.2

Pilot pressure, Pi

2-20-13
(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/2Л + P2×q/2Л
= (P1+P2)×q/2Л
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).

2-20-14
① Overload preventive function

45070RG09

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.

2-20-15
② Flow reset function

45070RG10

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.

2-20-16
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 625 626 630 628
nut(630) and by tightening(or loosening)
the adjusting screw C(628). Tightening
the screw shifts the control chart to the 801
right and increases the input horse-
925
power 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
CI(925) by N×A turns at first.(A=1.85)
※ Adjusting values are shown in table.

Adjustment of outer spring 2-16 (210-7)

Speed
Tightening Compens- Input torque
amount of ating control change
adjusting starting amount
Delivery flow, Q

screw(C) pressure
(628) change
amount

(min -1) (Turn) (kgf/cm2) (kgf·m)

1900 +1/4 +17.85 +9.7

Delivery pressure, (P1+P2)

2-20-17
b. Adjustment of inner spring
626
Adjust it by loosening the hexagon nut
(801) and by tightening(or loosening)
the adjusting screw QI(925).
Tightening the screw increases the flow 801
and then the input horsepower as
925
shown in the figure.
※ Adjusting valves are shown in table.

Adjustment of inner spring

Speed
Tightening Flow Input torque
amount of change change 2-17 (210-7)

adjusting amount amount

screw(QI)
(925)

Delivery flow, Q
(min -1) (Turn) (lpm) (kgf·m)

1900 +1/4 +16.4 +8.6

Delivery pressure, (P1+P2)

2-20-18
(3) Power shift control

45070RG11

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. However, the secondary pressure Pf Pf=
MIN
(power shift pressure) is admitted to the Pf= .
MA
horsepower control section of each pump X.
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.

2-20-19
(4) Adjustment of maximum and minimum flows
808
① Adjustment of maximum flow
Adjust it by loosening the hexagon 954
nut(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
Tightening Flow change

Delivery flow, Q
amount of amount
adjusting screw
(954)

(min -1) (Turn) (ℓ/min)

1900 +1/4 -7.6

Pilot 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
(953). Similarly to the adjustment of the
maximum flow, other characteristics are
not changed.
However, remember that, if tightened too
2-19(2)
much, the required horsepower during
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)

Pilot pressure, Pi
1900 +1/4 +7.6

2-20-20
(5) Qmax cut control 647
The regulator regulates the maximum 648
delivery flow by inputting the pilot pressure 723
Pm. Since this is a 2-position control 642 438
method, the maximum delivery flow may 801
be switched in two steps by turning on/off 801
924
the pilot pressure Pm.(The maximum
control flow cannot be controlled in 641 730 643 708 644 645 646 728
intermediate level.)
① Functional explanation 2-4

As shown in the figure, the pilot pressure

Pm switches the maximum flow in two
steps.
When the pilot pressure Pm is given, it is

Delivery flow, Q
admitted to the lefthand side of the piston Pm
QMC(648). The piston QMC moves the
stopper(647) and pilot piston(643) to the
right, overcoming the force of the pilot
spring(646), thereby reducing the
delivery flow of the pump.
Pilot pressure, Pi
Since the adjusting screw QMC(642) is
provided with a flange, the piston QMC
stops upon contact with the flange, and
the position of the pilot piston at this time
determines the maximum flow of the
pump.
② Adjustment of Qmax cut flow
Adjust it by loosening the hexagon
nut(801) and by tightening(or loosening)
Delivery flow, Q

the adjusting screw QMC(642).

Tightening the screw decreases the
Qmax cut flow as shown in the figure.

Pilot pressure, Pi

2-20-21