SECTION 2 STRUCTURE AND FUNCTION

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

Group 2 Main Control Valve -------------------------------------------------------------------------------------------- 2-20
Group 3 Swing Device ---------------------------------------------------------------------------------------------------- 2-46
Group 4 Travel Device ----------------------------------------------------------------------------------------------------- 2-58
Group 5 RCV Lever --------------------------------------------------------------------------------------------------------- 2-72
Group 6 RCV Pedal --------------------------------------------------------------------------------------------------------- 2-79
 SECTION 2 STRUCTURE AND FUNCTION
GROUP 1 PUMP DEVICE

1. STRUCTURE
The pump device consists of main pump, regulator and gear pump.
Pi1 Psv2
a5
(a1) (a2) A3

a1 B3

a4

Psv1 Pi2

Qmin adjusting screw Qmax adjusting screw Qmin adjusting screw

Regulator Regulator
Psv1

a1 Pi2

(a1)

Dr3 B3
Dr1

Dr2 A1 A2
Dr4
a3
(a2)

a2
B1
Front pump Port block Rear pump Gear pump

Port Port name Port size

A1, 2 Delivery port SAE6000 psi 1"
a4 Psv1 A1 a1 a2 A2 Psv2 a5
B1 Suction port SAE2500 psi 3"
Dr Drain port PF 3/4 - 23
Front Rear
Pi1, i2 Pilot port PF 1/4 - 15
Psv1 Servo assist port PF 1/4 - 15
Psv2 Servo assist port PF 1/4 - 13
a1, 2, 4 Gauge port PF 1/4 - 15
a3 Gauge port PF 1/4 - 14
Pi1 Engine Pi2 a5 Gauge port PF 1/4 - 13
a3 A3 Gear pump delivery port PF 1/2 - 19
Dr1,r2 B1 Dr3,r4 B3 A3
38092MP01
B3 Gear pump suction port PF 3/4 - 20.5
Hydraulic circuit

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

4309A2MP01

04 Gear pump 271 Pump casing 710 O-ring

111 Drive shaft (F) 311 Valve cove r(F) 717 O-ring
113 Drive shaft (R) 312 Valve cover (R) 719 O-ring
114 Spline 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 Bearing spacer 402 Hexagon socket bolt 732 O-ring
130 Booster 406 Hexagon socket bolt 774 Oil seal
012 Cylinder block 466 VP Plug 789 Back up ring
151 Piston 468 VP Plug 792 Back up ring
152 Shoe 490 Plug 808 Hexagon head nut
153 Set plate 492 Plug 824 Snap ring
156 Bushing 531 Tilting pin 885 Pin
157 Cylinder spring 532 Servo piston 886 Spring pin
211 Shoe plate 534 Stopper (L) 901 Eye bolt
212 Swash plate 535 Stopper (S) 953 Set screw
214 Bushing 548 Feedback pin 954 Adjust screw
251 Support plate 702 O-ring 956 Set screw
261 Seal cover (F) 706 O-ring

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

412 876 874 Psv1 A

755
A 858
897 B 614
612 FRONT

P2

615 Pf
613 Pi1
A 875
B 611

B
Hydraulic circuit

641

438

801

924

730 643 708 644 645 646 728

SECTION B-B

408 755 541 545 543 722 496 438 413

466 Pi
755

Port Port name Port size

696 697 735 755 724 725 436 Pi1 Pilot port PF 1/4-15

VIEW C Psv1 Servo assist port PF 1/4-15

38092RG01

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

412 876 874

755
A REAR
A 858
897 B 614 P2
612
Pf

Pi2
615
613
A 875
B Psv2
611

B
Hydraulic circuit

438

801

924

730 643 708 644 645 646 728

SECTION B-B

Port Port name Port size

Pi2 Pilot port PF 1/4-15
Psv2 Servo assist port PF 1/4-13

38092RG02

2-4
 REGULATOR (2/2)

SECTION A-A 38092RG03

407 Hexagon socket bolt 626 Inner spring 728 O-ring

408 Hexagon socket bolt 627 Adjust stem (C) 730 O-ring
412 Hexagon socket bolt 628 Adjust screw (C) 732 O-ring
413 Hexagon socket bolt 629 Cover (C) 733 O-ring
436 Hexagon socket bolt 630 Lock nut 734 O-ring
438 Hexagon socket bolt 631 Sleeve, pf 735 O-ring
466 Plug 641 Pilot cover 753 O-ring
482 Plug 643 Pilot piston 755 O-ring
496 Plug 644 Spring seat (Q) 756 O-ring
541 Seat 645 Adjust stem (Q) 763 O-ring
543 Stopper 646 Pilot spring 801 Hexagon nut
545 Steel ball 651 Sleeve 802 Nut
601 Casing 652 Spool 814 Snap ring
611 Feedback lever 653 Spring seat 836 Stop ring
612 Lever(1) 654 Return spring 858 Snap ring
613 Lever(2) 655 Set spring 874 Pin
614 Center plug 696 Port cover 875 Pin
615 Adjust plug 697 Check valve plate 876 Pin
621 Compensator piston 699 Valve casing 887 Pin
622 Piston case 708 O-ring 897 Pin
623 Compensator rod 722 O-ring 898 Pin
624 Spring seat (C) 724 O-ring 924 Set screw
625 Outer spring 725 O-ring

2-5
4) GEAR PUMP

700 354 351

887 433

B3

434 A3

311
850
312 a3 355
732
710 435 361 353 307 310 308 309 434 466, 725

29092MP05

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 Nut 434 Flange socket 850 Snap ring
351 Gear case 435 Flange socket 887 Pin

2-6
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
bush (156) and cylinder spring (157). The
drive shaft is supported by bearing 124
313
(123,124) at its both ends. 012
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. 32092MP03

(2) Swash plate group 531

The swash plate group consists of swash 548
plate (212), shoe plate (211), swash plate 214
support (251), tilting bush (214), tilting pin
(531) and servo piston (532). 251
The swash plate is a cylindrical part 211
formed on the opposite side of the sliding 212
surface of the shoe and is supported by
the swash support.
If the servo piston moves to the right and 532 ɷ
left as hydraulic force controlled by the
regulator is admitted to hydraulic chamber
located on both sides of the servo piston, ɷ
the swash plate slides over the swash
plate support via the spherical part of the
tilting pin to change the tilting angle (ɷ)

3607A2MP10

2-7
(3) Valve block group
The valve block group consists of valve
cover (F, 311), valve cover (F, 312), valve 314
312
plate (313, 314), spline coupling (114),
booster (130) and valve plate pin (885).
130
The valve plate having two melon-shaped 114
ports is fixed to the valve block and feeds 885
311
and collects oil to and from the cylinder
block.
The oil changed over by the valve plate is
connected to an external pipeline by way
of the valve block.
885
Now, if the drive shaft is driven by a prime 313
mover (electric motor, engine, etc), it
rotates the cylinder block via a spline 38092MP04

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
makes no stroke and discharges no oil.

2-8
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.

2-9
Η 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 D 548 chamber
chamber
531

29092MP09A

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.

2-10
Θ 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 D 548 chamber
chamber
531

29092MP10

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.

2-11
Ι Adjustment of flow control characteristic
The flow control characteristic can be
adjusted with the adjusting screw.
Adjust it by loosening the hexagon nut 801
924
(801) and by tightening (or loosening)
the hexagonal socket head screw (924).
Tightening the screw shifts the control
chart to the right as shown in the figure.
ö Adjusting values are shown in table.
Adjustment of flow control
characteristic
Speed R290RE08(1)

Tightening Flow Flow

amount of control change
adjusting starting amount
screw pressure

Delivery flow, Q
(924) change
amount
(min -1) (Turn) (kgf/cm2) (˶/min)
1750 +1/4 +1.6 +18.3

Pilot pressure, Pi

2-12
(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 = P1Ýq / 2 ʆ + P2Ýq / 2 ʆ
= (P1+P2)Ýq / 2 ʆ
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).

2-13
Η Overload preventive function

621 651 652 623 612 601 625 626

P1 CL
898
B(E)
897

Pf
P2 P1
875

611

Large diameter Servo piston

chamber Small diameter
D chamber

R130RE01

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 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.

2-14
Θ Flow reset function

621 651 652 623 612 601 625 626

P1 CL
B(E)
897

P2 P1
875

Large diameter
chamber Small diameter
D chamber
Servo piston

R130RE11

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.

2-15
Ι 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 (͚4) protruding from the large hole (͚8), only the lever
lessening the tilting angle contacts the pin (897) ; the hole (͚8) 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.
Κ 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 NÝA turns at first. (A=1.85)
ö Adjusting values are shown in table.

8007A2MP03
Adjustment of outer spring
Speed
Tightening Compensating Input torque
amount of control change
adjusting starting amount
Delivery flow, Q

screw (C) pressure

(628) change
amount
(min -1) (Turn) (kgf/cm2) (kgfÂm)

1750 +1/4 +17.7 +8.5

Delivery pressure, (P1+P2)

2-16
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.
ö Adjusting valves are shown in table.
627
Adjustment of inner spring
Speed
Tightening Flow change Input torque
amount of amount change 8007A2MP04
adjusting (lpm) amount
screw (QI)
(627)

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

1750 +1/4 +16.7 +9.2

Delivery pressure, (P1+P2)

2-17
(3) Power shift control

621 651 652 623 612 601 625 626

P1 CL
898
B(E)
897

Pf
P2 P1
875

611

Large diameter
chamber Small diameter
D chamber
Servo piston

R130RE13

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.

2-18
(4) Adjustment of maximum and minimum flows
Η Adjustment of maximum flow 808
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. R290RE08(5)

Speed Adjustment of max flow spring

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

(min -1) (Turn) (˶/min)

1750 +1/4 -6.7
Delivery pressure, Pi

Θ 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
much, the required horsepower during 3607A2MP02

the maximum delivery pressure (or

during relieving) may increase.

Speed Adjustment of min flow spring

Delivery flow, Q

Tightening Flow change

amount of adjusting amount
screw
(953)

(min -1) (Turn) (˶/min)

1750 +1/4 +6.7 Delivery pressure, Pi

2-19