PDF Service Manual Hyundai HX480L HX520L Excavator - 4 MB
This is the complete 2023 service manual for the Hyundai HX480L and HX520L hydraulic excavators.
It provides comprehensive, factory-authorized procedures for every aspect of repair and maintenance.
Inside you'll find detailed specifications, troubleshooting charts, and step-by-step instructions.
This manual is designed for professional technicians to perform everything from minor adjustments to a complete overhaul.
Rely on this guide to service your Hyundai excavator to the highest standards.
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--- Page 1 ---
CONTENTS
SECTION 1 GENERAL
Group 1 Safety Hints ------------------------------------------------------------------------------------------------------ 1-1
Group 2 Specifications --------------------------------------------------------------------------------------------------- 1-10
SECTION 2 STRUCTURE AND FUNCTION
Group 1 Pump Device ---------------------------------------------------------------------------------------------------- 2-1
Group 2 Main Control Valve ------------------------------------------------------------------------------------------- 2-20
Group 3 Swing Device ---------------------------------------------------------------------------------------------------- 2-60
Group 4 Travel Device ---------------------------------------------------------------------------------------------------- 2-71
Group 5 RCV Lever -------------------------------------------------------------------------------------------------------- 2-85
Group 6 RCV Pedal -------------------------------------------------------------------------------------------------------- 2-92
SECTION 3 HYDRAULIC SYSTEM
Group 1 Hydraulic Circuit ----------------------------------------------------------------------------------------------- 3-1
Group 2 Main Circuit ------------------------------------------------------------------------------------------------------- 3-2
Group 3 Pilot Circuit -------------------------------------------------------------------------------------------------------- 3-5
Group 4 Single Operation ---------------------------------------------------------------------------------------------- 3-14
Group 5 Combined Operation --------------------------------------------------------------------------------------- 3-24
SECTION 4 ELECTRICAL SYSTEM
Group 1 Component Location --------------------------------------------------------------------------------------- 4-1
Group 2 Electric Circuit -------------------------------------------------------------------------------------------------- 4-3
Group 3 Electrical Component Specification --------------------------------------------------------------- 4-23
Group 4 Connectors ------------------------------------------------------------------------------------------------------- 4-32
SECTION 5 MECHATRONICS SYSTEM
Group 1 Outline --------------------------------------------------------------------------------------------------------------- 5-1
Group 2 Mode selection System ----------------------------------------------------------------------------------- 5-3
Group 3 Automatic Deceleration System --------------------------------------------------------------------- 5-6
Group 4 Power Boost System --------------------------------------------------------------------------------------- 5-7
Group 5 Travel Speed Control System ------------------------------------------------------------------------- 5-8
Group 6 Automatic Warming Up Function -------------------------------------------------------------------- 5-9
Group 7 Engine Overheat Prevention Function ----------------------------------------------------------- 5-10
Group 8 Variable Power Control System ---------------------------------------------------------------------- 5-11
--- Page 3 ---
TEMPERATURE
Fahrenheit-Centigrade Conversion.
A simple way to convert a fahrenheit temperature reading into a centigrade temperature reading or vice verse
is to enter the accompanying table in the center or boldface column of figures.
These figures refer to the temperature in either Fahrenheit or Centigrade degrees.
If it is desired to convert from Fahrenheit to Centigrade degrees, consider the center column as a table of
Fahrenheit temperatures and read the corresponding Centigrade temperature in the column at the left.
If it is desired to convert from Centigrade to Fahrenheit degrees, consider the center column as a table of
Centigrade values, and read the corresponding Fahrenheit temperature on the right.
˚C ˚F ˚C ˚F ˚C ˚F ˚C ˚F
-40.4 -40 -40.0 -11.7 11 51.8 7.8 46 114.8 27.2 81 117.8
-37.2 -35 -31.0 -11.1 12 53.6 8.3 47 116.6 27.8 82 179.6
-34.4 -30 -22.0 -10.6 13 55.4 8.9 48 118.4 28.3 83 181.4
-31.7 -25 -13.0 -10.0 14 57.2 9.4 49 120.2 28.9 84 183.2
-28.9 -20 -4.0 -9.4 15 59.0 10.0 50 122.0 29.4 85 185.0
-28.3 -19 -2.2 -8.9 16 60.8 10.6 51 123.8 30.0 86 186.8
-27.8 -18 -0.4 -8.3 17 62.6 11.1 52 125.6 30.6 87 188.6
-27.2 -17 1.4 -7.8 18 64.4 11.7 53 127.4 31.1 88 190.4
-26.7 -16 3.2 -6.7 20 68.0 12.8 55 131.0 32.2 90 194.0
-26.1 -15 5.0 -6.7 20 68.0 12.8 55 131.0 32.2 90 194.0
-25.6 -14 6.8 -6.1 21 69.8 13.3 56 132.8 32.8 91 195.8
-25.0 -13 8.6 -5.6 22 71.6 13.9 57 134.6 33.3 92 197.6
-24.4 -12 10.4 -5.0 23 73.4 14.4 58 136.4 33.9 93 199.4
-23.9 -11 12.2 -4.4 24 75.2 15.0 59 138.2 34.4 94 201.2
-23.3 -10 14.0 -3.9 25 77.0 15.6 60 140.0 35.0 95 203.0
-22.8 -9 15.8 -3.3 26 78.8 16.1 61 141.8 35.6 96 204.8
-22.2 -8 17.6 -2.8 27 80.6 16.7 62 143.6 36.1 97 206.6
-21.7 -7 19.4 -2.2 28 82.4 17.2 63 145.4 36.7 98 208.4
-21.1 -6 21.2 -1.7 29 84.2 17.8 64 147.2 37.2 99 210.2
-20.6 -5 23.0 -1.1 35 95.0 21.1 70 158.0 51.7 125 257.0
-20.0 -4 24.8 -0.6 31 87.8 18.9 66 150.8 40.6 105 221.0
-19.4 -3 26.6 0 32 89.6 19.4 67 152.6 43.3 110 230.0
-18.9 -2 28.4 0.6 33 91.4 20.0 68 154.4 46.1 115 239.0
-18.3 -1 30.2 1.1 34 93.2 20.6 69 156.2 48.9 120 248.0
-17.8 0 32.0 1.7 35 95.0 21.1 70 158.0 51.7 125 257.0
-17.2 1 33.8 2.2 36 96.8 21.7 71 159.8 54.4 130 266.0
-16.7 2 35.6 2.8 37 98.6 22.2 72 161.6 57.2 135 275.0
-16.1 3 37.4 3.3 38 100.4 22.8 73 163.4 60.0 140 284.0
-15.6 4 39.2 3.9 39 102.2 23.3 74 165.2 62.7 145 293.0
-15.0 5 41.0 4.4 40 104.0 23.9 75 167.0 65.6 150 302.0
-14.4 6 42.8 5.0 41 105.8 24.4 76 168.8 68.3 155 311.0
-13.9 7 44.6 5.6 42 107.6 25.0 77 170.6 71.1 160 320.0
-13.3 8 46.4 6.1 43 109.4 25.6 78 172.4 73.9 165 329.0
-12.8 9 48.2 6.7 44 111.2 26.1 79 174.2 76.7 170 338.0
-12.2 10 50.0 7.2 45 113.0 26.7 80 176.0 79.4 172 347.0
0-8
--- Page 4 ---
DISPOSE OF FLUIDS PROPERLY
Improperly disposing of fluids can harm the
environment and ecology. Before draining any
fluids, find out the proper way to dispose of
waste from your local environmental agency.
Use proper containers when draining fluids. Do
not use food or beverage containers that may
mislead someone into drinking from them.
DO NOT pour oil into the ground, down a drain,
or into a stream, pond, or lake. Observe 13031GE24
relevant environmental protection regulations
when disposing of oil, fuel, coolant, brake fluid,
filters, batteries, and other harmful waste.
REPLACE SAFETY SIGNS
Replace missing or damaged safety signs.
See the machine operator's manual for correct
safety sign placement.
13031GE25
LIVE WITH SAFETY
Before returning machine to customer, make
sure machine is functioning properly, especially
the safety systems. Install all guards and
shields.
1-9
--- Page 5 ---
9) HX520 L
余7.06 m (23' 2") BOOM, 2.40 m (7' 10") ARM
480F2SP03
Description Unit Specification
Operating weight kg (lb) 52160 (114990)
Bucket capacity (SAE heaped), standard m3 (yd3) 2.20 (2.88)
Overall length A 12510 (41' 1")
Overall width, with 600 mm shoe
B 2980/3540 (9' 10"/11' 7")
(transport position / working position)
Overall height C 4070 (13' 4")
Superstructure width D 2980 ( 9' 9")
Overall height of cab E 3340 (10' 11")
Ground clearance of counterweight F 1445 ( 4' 9")
Engine cover height G 3030 ( 9' 11")
Overall height of handrail G' 3595 (11' 8")
Minimum ground clearance H mm (ft-in) 770 ( 2' 6")
Rear-end distance I 3885 (12' 9")
Rear-end swing radius I' 3940 (12' 11")
Distance between tumblers J 4470 (14' 8")
Undercarriage length K 5405 (17' 7")
Undercarriage width
L 2990/3540 (9' 10"/11' 7")
(transport position / working position)
Track gauge
M 2380/2940 (7' 10"/9' 8")
(transport position / working position)
Track shoe width, standard N 600 (24")
Travel speed (low/high) km/hr (mph) 3.3/5.3 (2.1/3.3)
Swing speed rpm 8.6
Gradeability Degree (%) 35 (70)
Ground pressure (600 mm shoe) kgf/cm2 (psi) 0.91 (12.94)
Max traction force kg (lb) 34100 (75180)
1-19
--- Page 6 ---
5) HX520 L
余6.55 m (21' 6") BOOM
A
A'
F
D
B' E
C
B
8ft
480F2SP05
Description 2.40 m (7' 10") Arm 2.90 m (9' 6") Arm
Max digging reach A 10690 mm (35' 1") 11130 mm (36' 6")
Max digging reach on ground A' 10430 mm (34' 3") 10870 mm (35' 8")
Max digging depth B 6240 mm (20' 6") 6740 mm (22' 1")
Max digging depth (8ft level) B' 6060 mm (19'11") 6580 mm (21' 7")
Max vertical wall digging depth C 4370 mm (14' 4") 5420 mm (17' 9")
Max digging height D 10390 mm (34' 1") 10660 mm (35' 0")
Max dumping height E 7040 mm (23' 1") 7210 mm (23' 8")
Min swing radius F 4870 mm (16' 0") 4540 mm (14'11")
241.2 [263.2] kN 241.2 [263.2] kN
SAE 24600 [26840] kgf 24600 [26840] kgf
54230 [59170] lbf 54230 [59170] lbf
Bucket digging force
280.5 [306.0] kN 280.5 [306.0] kN
ISO 28600 [31200] kgf 28600 [31200] kgf
63050 [68780] lbf 63050 [68780] lbf
278.5 [303.8] kN 225.6 [246.1] kN
SAE 28400 [30980] kgf 23000 [25090] kgf
62610 [68300] lbf 50710 [55310] lbf
Arm crowd force
291.3 [317.7] kN 235.4 [256.7] kN
ISO 29700 [32400] kgf 24000 [26180] kgf
65480 [71430] lbf 52910 [57720] lbf
[ ] : Power boost
1-29
--- Page 7 ---
(4) 7.06 m (23' 2") boom, 2.90 m (9' 6") arm equipped with 2.20 m3 (SAE heaped) bucket and 600 mm
(24") triple grouser shoe and 10,200 kg (22,490 lb) counterweight.
余 : Rating over-front 余 : Rating over-side or 360 degree
Load radius At max. reach
Load point 3.0 m (9.8 ft) 4.5 m (14.7 ft) 6.0 m (19.6 ft) 7.5 m (24.5 ft) 9.0 m (29.4 ft) Capacity Reach
height
m (ft)
7.5 m kg *11360 *11360 *9210 7190 10.11
(24.5 ft) lb *25050 *25050 *20310 15860 33.03
6.0 m kg *12120 11520 *9220 6250 10.76
(19.6 ft) lb *26730 25400 *20340 13770 35.15
4.5 m kg *19010 *19010 *15110 *15110 *13300 11010 *12330 8060 9050 5720 11.13
(14.7 ft) lb *41900 *41900 *33310 *33310 *29320 24270 *27180 17770 19940 12600 36.37
3.0 m kg *23620 23090 *17420 14840 *14570 10470 12350 7770 8730 5470 11.26
(9.8 ft) lb *52060 50900 *38400 32710 *32120 23090 27230 17130 19250 12050 36.80
1.5 m kg *21570 *21570 *19080 14100 *15610 10020 12070 7510 8770 5460 11.16
(4.9 ft) lb *47560 *47560 *42070 31080 *34410 22090 26600 16560 19320 12040 36.45
Ground kg *25090 21760 *19800 13690 15860 9730 11880 7340 9180 5720 10.81
Line lb *55310 47970 *43660 30190 34960 21440 26180 16170 20230 12610 35.32
-1.5 m kg *20350 *20350 *24810 21780 *19640 13570 15730 9610 10110 6330 10.19
(-4.9 ft) lb *44860 *44860 *54690 48020 *43300 29910 34670 21180 22280 13950 33.30
-3.0 m kg *28610 *28610 *23130 22020 *18630 13670 *15310 9690 *11360 7540 9.23
(-9.8 ft) lb *63060 *63060 *50990 48550 *41080 30140 *33750 21360 *25040 16620 30.17
-4.5 m kg *20370 *20370 *16510 14020 *10730 10170 7.79
(-14.7 ft) lb *44910 *44910 *36390 30910 *23650 22430 25.43
(5) 7.06 m (23' 2") boom, 3.38 m (11' 1") arm equipped with 2.20 m3 (SAE heaped) bucket and 600
mm (24") triple grouser shoe and 10,200 kg (22,490 lb) counterweight.
余 : Rating over-front 余 : Rating over-side or 360 degree
Load radius At max. reach
Load point 3.0 m (9.8 ft) 4.5 m (14.7 ft) 6.0 m (19.6 ft) 7.5 m (24.5 ft) 9.0 m (29.4 ft) Capacity Reach
height
m (ft)
6.0 m kg *11640 *11640 *11410 8380 *7750 5820 11.18
(19.6 ft) lb *25650 *25650 *25160 18480 *17080 12840 36.53
4.5 m kg *17410 *17410 *14350 *14350 *12860 11130 *12030 8110 *7860 5340 11.54
(14.7 ft) lb *38390 *38390 *31640 *31640 *28360 24540 *26530 17890 *17330 11780 37.70
3.0 m kg *22210 *22210 *16770 15090 *14210 10580 12390 7800 *8060 5120 11.67
(9.8 ft) lb *48960 *48960 *36960 33280 *31330 23320 27320 17200 *17760 11280 38.11
1.5 m kg *25070 22400 *18660 14280 *15370 10100 12080 7520 8240 5100 11.57
(4.9 ft) lb *55270 49380 *41150 31490 *33880 22260 26630 16570 18160 11250 37.78
Ground kg *25800 21880 *19670 13790 15900 9760 11850 7310 8590 5320 11.23
Line lb *56880 48230 *43370 30400 35040 21510 26120 16110 18930 11730 36.69
-1.5 m kg *19680 *19680 *25300 21780 *19800 13580 15700 9580 11750 7210 9370 5830 10.64
(-4.9 ft) lb *43390 *43390 *55780 48010 *43640 29940 34620 21130 25890 15900 20660 12860 34.77
-3.0 m kg *25950 *25950 *23920 21930 *19080 13600 15710 9590 *10510 6840 9.74
(-9.8 ft) lb *57200 *57200 *52740 48350 *42069 29990 34630 21140 *23180 15080 31.82
-4.5 m kg *27870 *27870 *21540 *21540 *17390 13850 *10990 8910 8.39
(-14.7 ft) lb *61430 *61430 *47480 *47480 *38330 30530 *24230 19640 27.41
1-39
--- Page 8 ---
8. SPECIFICATIONS FOR MAJOR COMPONENTS
1) ENGINE
Item Specification
Model Scania DC13
Type 4-cycle turbocharged charger air cooled diesel engine
Cooling method Water cooling
Number of cylinders and arrangement 6 cylinders, in-line
Firing order 1-5-3-6-2-4
Combustion chamber type Direct injection type
Cylinder bore佴stroke 130佴160 mm (5.12"佴6.3")
Piston displacement 12700 cc (775 cu in)
Compression ratio 17.5 : 1
Rated net horse power (SAE J1349) 424 Hp at 1900 rpm (316 kW at 1900 rpm)
Rated gross horse power (SAE J1995) 444 Hp at 1900 rpm (331 kW at 1900 rpm)
Maximum torque 232 kgf余m (1678 lbf余ft) at 1300 rpm
Engine oil quantity 38再(10 U.S. gal)
Dry weight 1075 kg (2370 lb)
Low idling speed 800佳50 rpm
High idling speed 1900.50 rpm
Rated fuel consumption 152.8 g/Hp余hr at 1900 rpm
Starting motor 24V-5.5kW
Alternator 24V-100A
Battery 2佴12V佴200Ah
2) MAIN PUMP
Item Specification
Type Variable displacement tandem axis piston pumps
Capacity 2佴200 cc/rev
Maximum pressure 330 kgf/cm2 (4690 psi) [360 kgf/cm2 (5120 psi)]
Rated oil flow 2佴380再/min (100.4 U.S. gpm / 83.6 U.K. gpm)
Rated speed 1750 rpm
[ ] : Power boost
1-49
--- Page 9 ---
3) REAR REGULATOR (1/2)
728 438
Pi
730 643 708 644 645 646 801 924
SECTION B-B
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 -
480F2RG03
2-5
--- Page 10 ---
(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
--- Page 11 ---
2. HYDRAULIC CIRCUIT
ps1 T3 T1 T2 T4 ps2
pa10
pa11
DR1'
DR1
pc1
B5
B9
A5
A9
pb5
ARM1
pa5 pb9
ARM2
B4 pa9
B8
A4 A8
pb4
pb8
OPTION BUCKET
pa8
pa4 DR2'
DR2
A3 pc2
B3 A7
B7
pb3
pa3
BOOM2
pb7
B2 BOOM1
A2
pa7
pb2 B6
DR3 SWING A6
pb6
pa2 TRAVEL-LH
pc6 pa6
B1
A1
pb1
pa1 TRAVEL-RH
STRAIGHT
TRAVEL
pr1
P3
P1 PS PT PP PA PH P2
480F2MC05
2-25
--- Page 12 ---
(2) Arm in (flow summation)
When the arm 1 spool is pushed to the left by the pilot pressure of port Pa5, the oil discharged
from pump P1 flow into the port A5 via neutral passage (L1), the load check valve (S5-1) and
passage (S5-2).
When the arm 2 spool is pushed to the left by the pilot pressure of port Pa9, the oil discharged
from pump P2 flows together into the port A5 via neutral passage (R1), the load check valve
(S9-1) and passage (S9-2).
At the same time, as the port pc1 is pressurizing and the spool (AD3) of anti-drift valve is pushed
down, the pressure of spring chamber (AD5) is released and the poppet (AD1) is opened and
then the oil returned from port B5 flows into the tank passage (Ta) through the passage (S5-4)
inside arm 1 spool to open and is connected to the passage (S5-2) and flows together into the
port A5, the cylinder speed is raised and also is prevents the cavitation of bottom side.
45071MC11
2-35
--- Page 13 ---
(4) The oil flow from the high pressure passage (HP) to the poppet (D) behind is only around poppet
and orifice (F); then the high pressure passage (HP) is higher than the poppet (D)behind
pressure.
Thus the poppet (D) is pushed open and the oil directly flows into low pressure passage (LP).
45071MC18-3
(5) Make up operation
This relief valve is built-in the cylinder port (HP) and the low pressure passage (LP), and the
pressure oil fills up camber (G) inside via hole of piston (C).
Thus the sleeve (K) and the main poppet (D) are securely seated by difference area of A and B.
45071MC18-4
2-45
--- Page 14 ---
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 travel pedal) are not
operated.
① Brake assembly
Circumferential rotation of separate plate
(16) is constrained by the groove located
at housing (1). When housing is
20
pressed down by brake spring (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
2-55
--- Page 15 ---
(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 (45-9) which seats on the poppet seat (45-10) and, at the same time,
is delivered, via small hole, to the spring seat (45-5) located inside the sleeve (45-6) and the seat
bore pressure increases up to "A" port pressure. The poppet (45-9) opposes to spring (45-4) 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 (45-7) is at the left position by the driving pressure, and
when "A" port pressure increases, the pressure is applied also to the piston (45-7) through the
small hole in the poppet (45-9) and piston (45-7) moves rightward until it touches the stopper in
rear cover. In this while, the poppet (45-9) maintains "A" port pressure at comparatively low
against the spring (45-4) force and exhaust oil to "B" port side. After the piston reached to the
plug, the valve acts the same as at starting.
Poppet seat(45-10) Piston(45-7) Spring seat(45-5) Spring(45-4)
Port B
Port A
Small hole Poppet(45-9) Sleeve(45-6)
480F2TM08
2-65
--- Page 16 ---
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 L1.
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