This document provides specifications and maintenance information for a Komatsu WA150-5H wheel loader. It includes: - Specifications for the machine including operating weight, engine details, dimensions, performance specs and more. - Assembly drawings showing views and key dimensions of the machine. - A parts list with weights of major components to aid in handling and transport. - Lubrication information including recommended oils and fluids for systems like the engine, hydraulics and axles. - Sections covering the engine mounting, cooling system, powertrain, hydraulic piping diagrams and maintenance of components like the HST pump and motors.

1. 00-1
MACHINE MODEL SERIAL NUMBER
WA150-5H H50051 and up
• This shop manual may contain attachments and optional equipment that are not available in your
area. Please consult your local Komatsu distributor for those items you may require.
Materials and specifications are subject to change without notice.
• WA150-5 mounts the SAA4D102E-2 engine.
For details of the engine, see the 102 Series Engine Shop Manual.
VEBM934100
© 2004
All Rights Reserved
Printed in Japan 09-04(02)
(2)

2. 00-2 WA150-5H
CONTENTS
No. of page
01 GENERAL ................................................................................................................01-1
10 STRUCTURE, FUNCTION AND
MAINTENANCE STANDARD......................................................................10-1
20 TESTING AND ADJUSTING .......................................................................20-1
30 DISASSEMBLY AND ASSEMBLY ..........................................................30-1
90 OTHERS ....................................................................................................................90-1
(2)

3. WA150-5H 01-1
GENERAL ASSEMBLY DRAWINGS......................................... 01-2
SPECIFICATIONS ..................................................................... 01-3
WEIGHT TABLE ........................................................................ 01-7
LIST OF LUBRICANT AND COOLANT..................................... 01-9
01 GENERAL

4. 01-2 WA150-5H
GENERAL GENERAL ASSEMBLY DRAWINGS
GENERAL ASSEMBLY DRAWINGS
Item Unit WA150-5H
Operating weight (With BOC) kg 7,425
Rated load kN {kg} 23.5 {2,400}
Bucket capacity (piled) (With BOC) m3 1.5
Engine model — KOMATSU SAA4D102E-2 Diesel engine
Flywheel horse power kW {HP} / rpm 71 {96} / 2,000
A Overall length (With BOC) mm 6,320
B Overall height mm 3,035
C Overall height when bucket is raised mm 4,630
D Overall width mm 2,250
E Min. ground clearance mm 400
F Bucket width mm 2,390
G Dumping clearance Tip of bucket/Tip of BOC mm 2,765 / 2,705
H Dumping reach Tip of bucket/Tip of BOC mm 940/ 970
I Bucket dump angle deg. 45
Min. turning radius
Tip of bucket/Tip of BOC mm 5,165 / 5,185
Center of outside wheel mm 4,470
Travel speed
F1 km / h 4.6 – 13.0
F2 km / h 13.0
F3 km / h 20.0
F4 km / h 38.0
R1 km / h 4.6 – 13.0
R2 km / h 13.0
R3 km / h 20.0
R4 km / h 38.0

5. WA150-5H 01-3
GENERAL
SPECIFICATIONS
Machine model WA150-5H
Serial No. H50051 and up
Weight
Operating weight (With BOC) kg 7,425
Distribution (front) SAE travel posture kg 2,975
Distribution (rear) SAE travel posture kg 4,450
Performance
Bucket capacity (piled) (With BOC) m³ 1.5
Rated load kN {kg} 23.5 {2,400}
Travel speed FORWARD 1st km / h 4.6 – 13.0
FORWARD 2nd km / h 13.0
FORWARD 3rd km / h 20.0
FORWARD 4th km / h 38.0
REVERSE 1st km / h 4.6 – 13.0
REVERSE 2nd km / h 13.0
REVERSE 3rd km / h 20.0
REVERSE 4th km / h 38.0
Max. rimpull FORWARD kN {kg} 63.7 {6,500}
REVERSE kN {kg} 63.7 {6,500}
Gradeability deg. 25
Min. turning radius
(Center of outside
wheel) mm 4,470
Min. turning radius [SAE travel posture]
(Tip of bucket/Tip of BOC) mm 5,165 / 5,185
Dimensions
Overall length (with BOC) mm 6,320
Overall width (chassis) mm 2,250
Bucket width (with BOC) mm 2,390
Overall height (top of cab) mm 3,035
Overall height (Bucket approx. raised to
max.) mm 4,630
Wheel base mm 2,600
Tread mm 1,780
Min. ground clearance mm 400
Max. height of bucket hinge pin mm 3,485
Dumping clearance (Tip of bucket/Tip of BOC) mm 2,765 / 2,705
Dumping reach (Tip of bucket/Tip of BOC) mm 940 / 970
Steering angle deg. 40
Bucket tilt angle (travel posture) deg. 46
Bucket tilt angle (max. height) deg. 66
Bucket dump angle (max. height) deg. 46
Digging depth (10° dump)
(Tip of bucket/Tip of BOC) mm 220 / 255
SPECIFICATIONS

6. 01-4 WA150-5H
GENERAL
*1: Battery capacity (Ah) shows the rate of 5 hours.
Machine model WA150-5H
Serial No. H50051 and up
Engine
Model SAA4D102E-2
Type 4-cycle, water-cooled, in-line, 4-cylinder,
direct injection with turbocharger, air-cooled after cooler
No. of cylinders - bore x stroke mm 4 – 102 x 120
Piston displacement l {cc} 3.92 {3,920}
Flywheel horsepower kW / rpm 71 / 2,000
{HP / rpm} {96 / 2,000}
Maximum torque Nm / rpm 402 / 1,300
{kgm / rpm} {41 / 1,300}
Min. fuel consumption ratio g / kWh {g / HPh} 219 {161}
High idling speed rpm 2,250
Low idling speed rpm 825
Starting motor 24 V 5.5 kW
Alternator 24 V 35 A
Battery (*1) 24 V 92 Ah x 2 pcs.
Powertrain
HST pump Variable displacement swash plate-type piston pump
HST motor 1 Variable displacement swash plate-type piston motor
HST motor 2 Variable displacement swash plate-type piston motor
Transfer
Multiple shaft planetary compound-type, spur gear
constant mesh-type, 2 alternative power systems
Reduction gear Spiral bevel gear, splash lubrication type
Differential Straight bevel gear type, torque portioning
Final drive Planetary gear 1-stage, splash lubrication type
Axle
Drive type Front and rear wheel drive
Front axle Fixed to frame, semi-floating type
Rear axle Center pin support, semi-floating type
Tire
Tire size 16.9–24–10PR (L2)
Rim size W15L × 24
Inflation pressure Front tire kPa {kg / cm²} 235 {2.4}
Rear tire kPa {kg / cm²} 235 {2.4}
Brakes
Main brake
Braking system
4 wheel braking, Front and rear wheel independent sys-
tem control
Brake type Enclosed wet multiple disc type
Operation method Hydraulically controlled
Control method Hydraulic power servo assisted brake
Parking brake
Braking system Speed change gear output shaft braking
Brake type Wet multiple disc type
Operation method Mechanical type
Control method Hand lever type
SPECIFICATIONS

7. WA150-5H 01-5
GENERAL
Machine model WA150-5H
Serial No. H50051 and up
Steering
control
Type Articulated steering
Control Hydraulic control
Hydraulicsystem
Hydraulicpump
Work equipment and Steering pump
• Type Gear type
• Theoretical capacity cm³/rev 63.1
Brake and cooling fan pump
• Type Gear type
• Theoretical capacity cm³/rev 10.5
Transfer lubrication pump
• Type Gear type
• Theoretical capacity cm³/rev 6.4
Cylinder
Steeringcylinder
Type Reciprocating piston type
Cylinder inner diameter mm 55
Piston rod diameter mm 30
Stroke mm 375
Max. length between pins mm 1,020
Min. length between pins mm 645
Liftcylinder
Type Reciprocating piston type
Cylinder inner diameter mm 110
Piston rod diameter mm 60
Stroke mm 628
Max. length between pins mm 1,659
Min. length between pins mm 1,031
Bucketcylinder
Type Reciprocating piston type
Cylinder inner diameter mm 110
Piston rod diameter mm 55
Stroke mm 452
Max. length between pins mm 1,367
Min. length between pins mm 915
SPECIFICATIONS

8. 01-6 WA150-5H
GENERAL
Machine model WA150-5H
Serial No. H50051 and up
Hydraulicsystem
Controlvalve
Work equipment control valve
• Type 2-spool type
• Set pressure MPa {kg / cm²} 20.6 {210}
Steering valve
• Type Orbit-roll type
• Set pressure MPa {kg / cm²} 18.6 {190}
Motor
Cooling fan motor
• Type Fixed displacement piston type
Work
equipment
Link type Single link
Bucket edge type Flat blade with top BOC
SPECIFICATIONS

9. WA150-5H 01-7
GENERAL
WEIGHT TABLE
This weight table is a guide for use when transporting or handling components.
Unit: kg
Machine model WA150-5H
Serial Numbers H50051 and up
Engine (without coolant and oil)
Cooling assembly (without coolant)
Cooling fan motor
Damper
450
71
6
3
HST pump
HST motor 1
HST motor 2
56
26
26
Transfer
Front drive shaft
Rear drive shaft
Front axle
Rear axle
Axle pivot (rear axle)
158
14
4
410
380
66
Wheel (each)
Tire (each)
Orbit-roll valve
Priority valve
Steering cylinder assembly (each)
Brake valve
53
91
7
6
13
10
Hydraulic tank (without hydraulic oil)
3-gear pump unit
Work equipment PPC valve
Work equipment control valve
Lift cylinder assembly (each)
Bucket cylinder assembly
Engine hood (with side panel)
Front frame
Rear frame
59
20
3
19
64
50
140
593
573
WEIGHT TABLE

10. 01-8 WA150-5H
GENERAL
Unit: kg
Machine model WA150-5H
Serial Numbers H50051 and up
Lift arm (including bushing)
Bucket (1.5m2, including BOC)
Bell crank
Bucket link
Counterweight
Additional counterweight (1 piece)
Fuel tank (without fuel)
Battery (each)
Operator’s Cab (including air conditioner and interior parts)
Operator’s seat
447
595
108
17
660
100
70
33
755
41
WEIGHT TABLE

11. WA150-5H 01-9
GENERAL
LIST OF LUBRICANT AND COOLANT
WA150-5H
LUBRICANTS, FUELS AND FILLING CAPACITIES
Lubricant and
operating
medium
Short code /
cask lettering
Quality grade
Temperature
range
Viscosity
range
Filling
capacity in
litres
Engine Engine oil
EO 0030A
EO 0540A
EO 10
EO 30
EO 1030A
EO 1540A
CCMC D4
or, if not available:
API CD or
API CE or
API CF -4
-30° up to 40° C
-25° up to 40° C
-20° up to 10° C
0° up to 40° C
-20° up to 40° C
- 15° up to 50° C
SAE 0W-30
SAE 5W-40
SAE 10
SAE 30
SAE 10W-30
SAE 15W-40 *)
14
(12.5 **)
Transfer case Engine oil EO 10
CCMC D4
or, if not available:
API CD or API CE or
API CF -4
-30° up to 40° C SAE 10W*)
4.9
(4.4 **)
Hydraulic system Hydraulic oil
HYD 0530
HYD1030
HVLP, HVLP D
-30° up to 40° C
-20° up to 30°
ISO VG46 *)
ISO VG68
104
(47**)
Axle with
standard
differential
Axle oil
AXO 80
AXO Shell: DONAX TD5W30***
80W
SAE 5W-30 *)
front 14
rear 14.5
or Engine oil EO 30
CCMC D4
or, if not available:
API CD or API CE or
API CF -4
0° up to 40° C SAE 30
Axle with
limited-slip
differential (*3)
Axle oil (*4) AXO
Shell: DONAX TD5W30***
Esso: TORQUE FLUID56****
Mobil: MOBILFLUID 424
Fuchs: TITAN HYDRA ZF20W-40
SAE 5W-30 *)
SAE 20W-40
Fuel tank Diesel fuel
ASTM D975 No.1
ASTM D975 No.2
DIN-EN 590
CFPP class B
CFPP class D
CFPP class F
-30° up to -10° C
-10° up to 40° C
0° up to 40° C
-10° up to 40° C -
20° up to 40° C
133
Grease nippels
Multi purpose
grease on a lith-
ium base
MPG-A KP2N-20 -30° up to 40° C NLGI-No. 2 –
Grease box of
centrallubrication
unit
Multi purpose
grease on a lith-
ium base
MPG-A KP2N-20 -30° up to 40° C NLGI-No. 2 –
Cooling system
Water and
coolant
SP-C Add antifreeze with corrosion resistor 17
Air conditioner Coolant NRS R134a (CFC-free) 860 g
*) Work filling
** Top-up quantity
*** North American manufacted DONAX TD 20W-40 must not be used.
**** North American manufacted TORQUE FLUID 56 must not be used.
LIST OF LUBRICANT AND COOLANT

12. 01-10 WA150-5H
GENERAL
*1: ASTM D975 No. 1
*2: Use only diesel fuel.
*3: For the standard differential, except for "AX080", the oil for machines equipped with the anti-slip differential
in the table below and EO30 can be used. However, in the case of "EO30", depending on conditions such
as the brakes are used and the oil temperature, the brakes may squeal just before the machine stops, but
there is no problem with the brake performance or durability.
*4: The letters "ASD" are stamped on the name plate of machines equipped with the anti-slip differential axle.
*5: For machines equipped with the limited-slip differential axle, select from the oil given in the table below.
Maker Brand Remarks
SHELL DONAX TD 5W-30 North American manufactured DONAX TD
20W–40 must not be used
ESSO TORQUE FLUID 56
North American manufactured must not
be used
MOBIL MOBILFLUID 424
FUCHS RENOGEAR HYDRA ZF 20W–40
LIST OF LUBRICANT AND COOLANT

13. WA150-5H 10-1
ENGINE MOUNT AND TRANSFER MOUNT 10- 2
DAMPER........................................................ 10- 3
COOLING SYSTEM....................................... 10- 4
POWER TRAIN.............................................. 10- 5
POWER TRAIN SYSTEM DIAGRAM ............ 10- 6
DRIVE SHAFT (PROPELLER SHAFT) ......... 10- 8
HST HYDRAULIC PIPING DIAGRAM ........... 10- 9
HST PUMP .................................................... 10-10
HIGH-PRESSURE RELIEF VALVE............... 10-12
LOW-PRESSURE RELIEF VALVE................ 10-14
HST CHARGE PUMP .................................... 10-15
SPEED-RELATED VALVE (DA VALVE) ....... 10-16
HIGH-PRESSURE CUT-OFF VALVE............ 10-17
HST MOTOR ................................................. 10-18
EP SERVO VALVE ........................................ 10-21
HA SERVO VALVE........................................ 10-22
FORWARD-REVERSE SHUTTLE VALVE .... 10-23
TRANSFER.................................................... 10-24
CLUTCH SOLENOID VALVE ........................ 10-35
AXLE.............................................................. 10-36
DIFFERENTIAL ............................................. 10-38
LIMITED-SLIP DIFFERENTIAL ..................... 10-44
FINAL DRIVE................................................. 10-48
AXLE MOUNTING AND
CENTER HINGE PIN .............................. 10-50
STEERING PIPING ....................................... 10-55
STEERING COLUMN .................................... 10-56
PRIORITY VALVE ......................................... 10-57
ORBIT-ROLL VALVE..................................... 10-60
STEERING CYLINDER ................................. 10-68
EMERGENCY STEERING PIPING ............... 10-70
EMERGENCY STEERING VALVE................ 10-71
BRAKE PIPING.............................................. 10-74
BRAKE VALVE .............................................. 10-75
INCHING VALVE ........................................... 10-79
CHARGE VALVE ........................................... 10-80
ACCUMULATOR (FOR BRAKE) ................... 10-84
SLACK ADJUSTER ....................................... 10-85
BRAKE........................................................... 10-88
PARKING BRAKE CONTROL ....................... 10-91
PARKING BRAKE.......................................... 10-92
HYDRAULIC PIPING ..................................... 10-94
WORK EQUIPMENT LEVER LINKAGE ........ 10-96
HYDRAULIC TANK........................................ 10-97
3-GEAR PUMP UNIT....................................10-100
ACCUMULATOR (FOR PPC CIRCUIT).......10-102
LOCK VALVE ...............................................10-103
E.C.S.S. VALVE ...........................................10-104
ACCUMULATOR (FOR E.C.S.S.) ................10-107
HYDRAULIC PIPING OF
COOLING SYSTEM...............................10-108
COOLING FAN MOTOR...............................10-109
WORK EQUIPMENT CONTROL VALVE.....10-110
WORK EQUIPMENT PPC VALVE ...............10-123
WORK EQUIPMENT LINKAGE....................10-130
BUCKET .......................................................10-132
BUCKET POSITIONER AND
BOOM KICK-OUT..................................10-133
WORK EQUIPMENT CYLINDER.................10-139
AIR CONDITIONER......................................10-140
MACHINE MONITORING SYSTEM.............10-141
MACHINE MONITOR ...................................10-151
LIST OF ITEMS DISPLAYED
ON MONITOR........................................10-152
ELECTRICAL SYSTEM
(HST CONTROLLER SYSTEM) ............10-178
HST CONTROLLER.....................................10-182
ENGINE START CIRCUIT............................10-183
ENGINE STOP CIRCUIT..............................10-185
PREHEATING CIRCUIT...............................10-186
PARKING BRAKE CIRCUIT.........................10-187
ELECTRONICALLY CONTROLLED
SUSPENSION SYSTEM........................10-190
SENSORS ....................................................10-191
10 STRUCTURE, FUNCTION AND
MAINTENANCE STANDARD

14. 10-2 WA150-5H
STRUCTURE, FUNCTION AND MAINTENANCE STANDARD
ENGINE MOUNT AND TRANSFER MOUNT
ENGINE MOUNT AND TRANSFER MOUNT

15. WA150-5H 10-3
STRUCTURE, FUNCTION AND MAINTENANCE STANDARD
DAMPER
Unit: mm
3. Flange
4. HST pump input shaft
5. Hub
6. Cover
7. Flywheel
8. Insert
Outline
• The damper reduces the torsional vibration
caused by fluctuation of the engine torque to pro-
tect the drive system after the engine from the
torsional vibration.
• The power from the engine is transmitted through
flywheel (7) to flange (3), which absorbs the tor-
sional vibration, and then transmitted through
hub (5) to the HST pump.
No. Check item Criteria Remedy
1
Distance between HST pump
mounting face and end of hub
Standard size Repair limit
Adjust
61.2 ± 0.8
2 Wear of flange and insert Repair limit: 1.0 Replace
DAMPER

16. 10-4 WA150-5H
STRUCTURE, FUNCTION AND MAINTENANCE STANDARD
COOLING SYSTEM
1. Oil cooler
2. After cooler
3. Radiator
4. Reservoir tank
5. Cooling fan
6. Cooling fan motor
Specification
Radiator Oil cooler After cooler
Core type AL WAVE–4 CF40–1 AL WAVE
Fin pitch (mm) 3.5 / 2 3.5 / 2 4.0 / 2
Total heat radiating area (m2) 22.0 5.72 5.75
Pressure valve opening pressure
(kPa {kg/cm2
})
68.6
{0.7}
— —
Vacuum valve opening pressure
(kPa {kg/cm2
})
0 – 4.9
{0 – 0.05}
— —
COOLING SYSTEM

17. WA150-5H 10-5
STRUCTURE, FUNCTION AND MAINTENANCE STANDARD
POWER TRAIN
1. Engine
2. Damper
3. HST pump
4. 3-gear pump unit
5. High-pressure hose
6. HST motor 1
7. HST motor 2
8. Transfer
9. Front drive shaft
10. Front axle
11. Rear drive shaft
12. Rear axle
POWER TRAIN

18. 10-6 WA150-5H
STRUCTURE, FUNCTION AND MAINTENANCE STANDARD
POWER TRAIN SYSTEM DIAGRAM
POWER TRAIN SYSTEM DIAGRAM

19. WA150-5H 10-7
STRUCTURE, FUNCTION AND MAINTENANCE STANDARD
1. Engine
2. Damper
3. HST pump
4. Work equipment and Steering pump
5. Brake and cooling fan pump
6. Transfer lubricating oil pump
7. High-pressure hose
8. HST motor 1
9. HST motor 2
10. Emergency steering valve (If equipped)
11. Transfer
12. Transfer clutch
13. Parking brake
14. Front drive shaft
15. Front axle
16. Differential
17. Wet multiple disc brake
18. Final drive
19. Front tire
20. Rear drive shaft
21. Rear axle
22. Differential
23. Wet multiple disc brake
24. Final drive
25. Rear tire
Outline
• The power of engine (1) is transmitted to HST
pump (3) through damper (2) which is installed to
the flywheel and which absorbs the torsional vi-
bration of the power,
• The power of engine (1) is also transmitted to
HST pump (3), HST charge pump built in HST
pump (3), work equipment and steering pump (4)
connected to HST pump (3), brake and cooling
fan pump (5), and transfer lubricating oil pump
(6).
• HST pump (3) is equipped with the forward-re-
verse shifting valve and servo piston, which
changes the discharge direction and discharge
rate of HST pump (3) continuously by changing
the swash plate angle.
• HST motors (8) and (9) are installed to transfer
(11) and connected to HST pump (3) by high-
pressure hose (7).
• The turning direction and speed of HST motors
(8) and (9) are changed by the hydraulic power of
HST pump (3) to control the travel direction and
travel speed of the machine.
• The power of HST motor 1 (8) is transmitted
through transfer clutch (12) in transfer (11) to the
output shaft.
The power of HST motor 2 (9) is transmitted
through the gear in transfer (11) to the output
shaft.
• Parking brake (13) is installed on the rear side in
transfer (11). It operates the wet multiple disc
brake to stop the machine according to the oper-
ation of the parking brake lever.
• The power for the front side is transmitted
through front drive shaft (14) to front axle (15).
The power for the rear side is transmitted
through rear drive shaft (20) to rear axle (21).
• The power transmitted to axles (15) and (21) is
reduced in speed by the pinion gears of differen-
tials (16) and (22), and then transmitted through
the sun gear shaft to the sun gear.
• The power of the sun gear is reduced in speed by
the planetary mechanisms of final drives (18) and
(24), and then transmitted through the axle shaft
and wheels to tires (19) and (25).
POWER TRAIN SYSTEM DIAGRAM

20. 10-8 WA150-5H
STRUCTURE, FUNCTION AND MAINTENANCE STANDARD
DRIVE SHAFT
1. Front axle
2. Front drive shaft
3. Transfer
4. Rear drive shaft
5. Rear axle
Outline
• The power from the output shaft of the transfer is
transmitted through front drive shaft (2) and rear
drive shaft (4) to front axle (1) and rear axle (5).
• When the machine is articulated or it receives an
impact from the road during travel or a working
impact, the positions of the transfer and front and
rear axles change. The drive shafts can change
their angles and lengths by means of the univer-
sal joints and sliding joints so that the power will
be transmitted without damaging any part even
when the positions of the components change
because of the impacts.
DRIVE SHAFT

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22. WA150-5H 10-9
STRUCTURE, FUNCTION AND MAINTENANCE STANDARD
HST HYDRAULIC PIPING DIAGRAM
1. Hydraulic tank
2. HST pump
3. Clutch solenoid valve
4. HST oil filter
5. HST motor 1
6. HST motor 2
HST HYDRAULIC PIPING DIAGRAM

23. 10-10 WA150-5H
STRUCTURE, FUNCTION AND MAINTENANCE STANDARD
HST PUMP
a HST: Abbreviation for Hydro Static Transmission
1. Forward-reverse shifting solenoid valve
2. High-pressure cut-off valve
3. Speed-related valve (DA valve)
4. Charge pump
5. Low-pressure relief valve
6. Servo cylinder
7. High-pressure relief valve
8. Control plate
9. Cylinder block
10. Piston
11. Swash plate
Specifications
Model A4VG71DA
Type
Variable displacement swash
plate-type piston pump
Theoretical capacity
(cc / rev)
0 – 71
Set pressure of high-pressure
relief valve (MPa {kg/cm2
})
43.2 {441}
Set pressure of high-pressure
cut-off valve (MPa {kg/cm2
})
Effective differential pressure
40.2 {410}
Set pressure of low-pressure
relief valve (MPa {kg/cm2
})
2.5 {25}
HST PUMP

24. WA150-5H 10-11
STRUCTURE, FUNCTION AND MAINTENANCE STANDARD
Operation
Flow of power
• The HST pump is installed to the coupling which
is installed to the engine flywheel.
• The power of the engine is transmitted from the
flywheel through the coupling to the HST pump.
• The HST pump is equipped with forward-reverse
shifting solenoid valve (1) and servo cylinder (6).
If the operator operates for forward or reverse
travel, forward-reverse shifting solenoid valve (1)
operates and swash plate (11) in the HST pump
slants to reverse the oil flow.
• Cylinder block (9) and pistons (10) in it rotate to-
gether with drive shaft (12) and the tips of pistons
(10) slide on swash plate (11) which does not ro-
tate. The pump has 9 pistons (10) in it.
Flow of oil
• As swash plate (11) of the HST pump slants, pis-
tons (10) in contact with its surface reciprocate
and work as pumps to suck and discharge the oil
in cylinder block (9).
• As a result, high-pressure oil flows in a constant
direction into the HST motor.
• If swash plate (11) slants in the opposite direc-
tion, the sucking and discharging directions of the
oil are reversed, that is, the oil flows in the oppo-
site direction. While swash plate (11) is in neu-
tral, pistons (10) do not reciprocate, thus they do
not discharge any oil.
• The strokes of pistons (10) are changed to con-
trol the travel speed by increasing or decreasing
inclination (angle) of swash plate (11).
• If the quantity of the oil in the low-pressure circuit
(the return circuit from the motor to the pump) be-
comes insufficient because of leakage from the
HST pump, HST motor, and control valve, the
charge pump adds oil through speed-related
valve (3) and check valve of high-pressure relief
valve (7).
HST PUMP