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Takeuchi compact excavator TB125, TB135, TB145 / diesel TNE / diesel Yanmar. Service Manual - page 20

IV-44

HYDRAULIC UNITS

HYDRAULIC PUMP

TB125, 135, 145

15. Install the gear pump by using two cap screws and

washers.

Cap Screw:
<TB125> S/N 12512126~: 9.8~14.2 N·m
<TB135>
S/N 13510004~13512532: 9.8~14.2 N·m
S/N 13512533~: 19.6~23.5 N·m

16. Fit the O-rings to the solenoid valves and secure

the solenoid valves to the pump using the cap
screws and washers.

Cap Screw: 20~25.5 N·m

17. To check if the assembly is complete, lightly

clamp the pump shaft in a vise and turn the pump.
If the pump does not turn smoothly, reassemble it
again.

G4D105

G4D104

IV-45

HYDRAULIC UNITS

HYDRAULIC PUMP

TB125, 135, 145

Parts

Judgment Criteria

Treatment

• A clearance S of 0.05 mm or more

between the piston and the cylinder
block

• Occurrence of scratches, scoring,

abnormal wear, etc. on sliding parts

Piston and cylinder
block assembly

Slack of the piston
shoe

Shaft and oil seal
installation part

Valve plate

• A slack S of 0.2 mm or more for the

piston shoe

• A wear amount of 0.025 mm at the

installation part of shaft and oil seal

• No abnormal scratches (0.02 mm or

more), wear, or sticking for the slid-
ing surfaces

• Exchange

• Exchange.

• Exchange

• Correct by lapping

or exchange.

• No abnormal wear or harmful

scratches of the sliding surfaces

• At the time of reassembly after dis-

assembly

• No abnormal scratches, wear, or

flaking of the tooth surfaces

• No abnormal scratches, wear, or

flaking of the rolling surfaces

• Exchange

• Exchange the shaft

and the assembly.

Bushing

Seals and O-rings

Drive gear and
driven gear

Ball bearings and
needle bearings

OIL SEAL MOUNT

STANDARD DIMENSION

INSPECTION AND ADJUSTMENT

Checking the Parts

IV-46

HYDRAULIC UNITS

HYDRAULIC PUMP

TB125, 135, 145

TROUBLESHOOTING

Symptom

Probable Causes

Remedy

• Remove the dirt or eliminate the pinched

condition of the hose.

• Retighten each joint.

• Replace the hydraulic oil with oil of the

proper viscosity.

• Center the pump with respect to the

engine.

• Investigate the cause of the bubbles and

repair it.

• Operate the engine at the specified speed.

• Check and replace the drain piping.

• Replace the damaged parts or replace

the pump.

Noise is loud. Abnormal
noise is generated.

• The suction hose is pinched or the suc-

tion filter is clogged.

• The suction side joint is loose and air is

being sucked in.

• The hydraulic oil’s viscosity is too high

and cavitation is occurring.

• The pump is off center with respect to

the engine.

• There are bubbles in the hydraulic oil.

• The engine’s speed is higher than the

specified speed.

• The drain back pressure is higher than

the specified pressure.

• The bearing, etc. is mechanically dam-

aged.

• The engine’s speed is too low.
• The oil temperature is abnormally high.

• The hydraulic oil’s viscosity is too high.

• The pump’s volumetric efficiency has

dropped.

• The horsepower setting adjustment

screw is loose.

• The oil level in the tank is low.

• The suction side pipe or the suction

filter is clogged.

• The amount of leakage from hydraulic

devices other than the pump is increasing.

• Operate the engine at the specified speed.
• Stop the machine and let the oil cool off,

then check again.

• Replace the hydraulic oil with oil of the

proper viscosity.

• Replace the pump.

• Reset the screw and lock it.

• Replenish the tank with hydraulic oil to

the specified level.

• Clean the piping.

• Repair the hydraulic device or replace

it.

• The relief valve setting has dropped.
• The amount of leakage from hydraulic

devices other than the pump is increasing.

• The pump’s volumetric efficiency has

dropped.

• The peak pressure is generated due to a

drop in the relief valve’s response.

• There is foreign matter trapped in the

pilot line or foreign matter is caught in
the sliding parts of the control equip-
ment.

• Leakage from the pump is increasing.
• The bearings, etc. are mechanically dam-

aged.

• There is seizing of sliding parts.

• Seals are damaged.
• The shaft surface which slides against

the oil seal is worn.

• The plug or bolts are loose.

• Reset the relief valve setting.
• Repair the hydraulic device or replace

it.

• Replace the pump.
• Repair the relief valve or replace it.

• Remove the foreign matter and repair or

replace the scratched parts.

• Replace the pump.
• Replace the damaged parts or replace

the pump.

• Replace the damaged parts or replace

the pump.

• Replace the seals.
• Replace the shaft or replace the pump.

• Tighten them or replace the seals.

Discharge is insufficient.

Pressure doesn’t rise.

The rotational speed drops
when there is a dynamic
load.

Abnormal heat is gener-
ated.

Hydraulic oil is leaking.

IV-47

HYDRAULIC UNITS

CONTROL VALVE

TB125, 135, 145

CONTROL VALVE (TB125, TB135)

CONSTRUCTION

1. End Cover
2. Boom Block Assembly
3. Bucket Block Assembly
4. Left Travel Block Assembly
5. Auxiliary Block Assembly
6. Right Travel Block Assembly
7. Swing Block Assembly
8. Arm Block Assembly
9. Outlet Housing
10. Dozer Blade Block Assembly

11. Slew Block Assembly
12. Inlet Housing
13. Port Relief Valve
14. Main Relief Valve
15. Anti Cavitation Valve
16. Port Relief Valve
17. Main Relief Valve
18. Tie Rod
19. Nut
20. Switch Valve

G4D200

18
19

IV-48

HYDRAULIC UNITS

CONTROL VALVE

TB125, 135, 145

Left Travel Block

Right Travel Block

Swing Block

1. Screw
2. Spring Holder
3. Spring
4. Cover
5. Seal Holder
6. Backup Ring
7. O-ring
8. Poppet

1. O-ring
2. Screw
3. Spring Holder
4. Spring
5. Cover
6. Seal Holder
7. Poppet
8. Spring
9. Backup Ring

G4D201

G4D202

G4D203

IV-49

HYDRAULIC UNITS

CONTROL VALVE

TB125, 135, 145

Boom Block, Bucket Block

Slew Block

Arm Block

1. Cover
2. Screw
3. Spring Holder
4. Spring
5. Cover
6. Poppet
7. Spring
8. O-ring

1. Cover
2. Screw
3. Spring Holder
4. Spring
5. Cover
6. Poppet
7. Spring
8. Poppet
9. Spring

G4D204

G4D205

G4D206

IV-50

HYDRAULIC UNITS

CONTROL VALVE

TB125, 135, 145

Dozer Blade Block

Switch Valve

Auxiliary Block

1. O-ring
2. Screw
3. Spring Holder
4. Spring
5. Cover
6. Seal Holder
7. Poppet
8. Spring
9. Backup Ring

1. Poppet
2. Spring Holder
3. Spring
4. Cover
5. Spring
6. Filter
7. Snap Ring
8. Cover

1. Cover
2. Screw
3. Spring Holder
4. Spring
5. Cover
6. Poppet
7. Spring
8. O-ring

G4D207

G4D208

SECTION "X-X"

DETAIL "Y"

G4D209

IV-51

HYDRAULIC UNITS

CONTROL VALVE

TB125, 135, 145

Outlet Housing

Main Relief Valve, Port Relief Valve

Anti-Cavitation Valve

1. Housing
2. Poppet
3. Spring

1. Housing
2. Plug
3. Sleeve
4. Main Poppet
5. Piston
6. Needle Valve
7. Set Screw
8. O-ring

9. Lock Nut
10. Spring
11. Spring
12. O-ring
13. Backup Ring
14. O-ring
15. O-ring

1. Sleeve
2. Poppet
3. Spring
4. O-ring
5. Plug
6. Backup Ring
7. O-ring
8. O-ring

G4D210

G4D212

IV-52

HYDRAULIC UNITS

CONTROL VALVE

TB125, 135, 145

OPERATION

When the Spool is in the Neutral Position
When the control valve spool is not moving, hydrau-
lic oil flows through the center bypass passage (1) and
then through the tank passage (T) in the arrow direc-
tion, returning to the tank.

When the Spool is Actuated
Explanation is given for the case where the spool is
moved to the right.
When the spool (2) is moved to the right, the center
bypass passage (3) is closed and hydraulic oil entering
from the pump passes through the load check valve
(5) from the parallel passage (4), flowing from the A
port to the actuator. On the other hand, oil returning
from the B port flows through the tank circuit (T) and
returns to the tank.

Load Check Valve
This valve prevents oil from flowing backward due to
the load pressure (C) from the actuator port during
switching of the spool.

IV-53

HYDRAULIC UNITS

CONTROL VALVE

TB125, 135, 145

Main Relief Valve, Port Relief Valve

A main relief valve is mounted between the pump
circuit and tank circuit of each inlet housing and
serves to maintain the circuit pressure at the set value.

A port relief valve is located between the actuator port
and the tank circuit and when abnormal pressure due
to shock pressure or external pressure generated when
the actuator port is suddenly blocked by the spool or
when there is an overload occurs, these valves act to
protect the actuator.

Relieving Operation
When the pressure in the circuit is low with respect to
the set value, the relief valve is maintained at equilib-
rium. Pressure from the pump passes from chamber B
to the orifice in piston (4), then reaches chamber C and
the needle valve (5). On the other hand, forces F and
F1 are acting in the arrow directions on both sides of
the main poppet (6).

F = P

F1 = P

P: Pressure A,A1: Sectional Area

Since the sectional area of A is less than that of A1, the
main poppet (6) is pushed by the force “F1-F” to the
seat surface on the left side.

If the pressure in the circuit becomes higher than the
force of the spring (7), the needle valve (5) is pushed
to the right by hydraulic pressure, opening. Oil then
flows around the circumference of the needle valve
(5) and passes through the slits, flowing into the tank
passage (T).

Compared to the chamber B side, the pressure in
chamber C is low and there is no equilibrium in
pressure. For this reason, the main poppet (6) opens
and pressurized oil flows to the tank passage (T).

G4D214

G4D215

G4D216

IV-54

HYDRAULIC UNITS

CONTROL VALVE

TB125, 135, 145

Suction Operation
When the cylinder is operated at high speed, and the
supply of oil cannot keep up with it, creating a vacuum
in chamber B, oil is supplied from the tank side,
preventing the occurrence of cavitation.
When the pressure in chamber B is lower than the
pressure in the tank passage (T), the differences in the
sectional areas A and A1 cause the main poppet (8) to
open. Thus, sufficient oil from the tank passage (T)
enters chamber B, filling the empty space.

Anti-Cavitation Valve

When a cylinder is operated at high speed and when
the supply of hydraulic oil can't keep up with it,
causing a vacuum to form at the cylinder port, this
valve supplies oil from the tank, preventing cavitation
from occurring. Normally in the cylinder port, pres-
sure is brought to bear, so the poppet (1) is closed. If
a vacuum is generated at the cylinder port (P), the oil
in the tank passage (T) pushes on the poppet (1) and
flows from the tank passage to the cylinder port.

G4D217

G4D218

IV-55

HYDRAULIC UNITS

CONTROL VALVE

TB125, 135, 145

Switch Valve

The switch valve is actuated only when the travel
motor and hoe attachment are operated simultaneously.
When the Switch Valve is Actuated
When the spool of the hoe attachment is switched to
block the pilot passage (1) connected to the tank
passage, the pressure in the pilot chamber (2) is
preserved.
This switches the spool (3) to let the oil from the pump
P3 flow into the passages (4) and (5) through the notch
and hole provided on the spool (3). As the passage (4)
is connected to the boom and bucket block while the
passage (5) is connected to the arm block and swing
block, the hoe attachment can be operated while the
machine is traveling.

When the Switch Valve is NOT Actuated
The pilot passage (1) is opened to the tank passage,
making the pressure in the pilot chamber (2) equal to
that in the tank, and the spool (3) is not switched.
Therefore, the oil that has flowed into the switch valve
from the pump P3 returns to the tank from the passage
(6) through the center bypass passage of the auxiliary
block.

G4D219

G4D220

IV-56

HYDRAULIC UNITS

CONTROL VALVE

TB125, 135, 145

Arm Pulling Reclamation Function

At the time of arm pulling operation, the cylinder
speed increases because of the increasing oil flow to
the arm cylinder.
When the spool (1) of the arm section moves, the
pressure oil from the pump P2 enters on the head side
of the arm cylinder. On the other hand, the pressure oil
discharged from the rod side enters into the spool (1),
and a small quantity flows through the orifice (2) to
the tank port (T). The remaining pressure oil opens the
reclamation check valve (3) and is supplied (re-
claimed) to the head side of the arm cylinder, so that
the oil flow to the arm cylinder is increased.

/",

IV-57

HYDRAULIC UNITS

CONTROL VALVE

TB125, 135, 145

DISASSEMBLY AND ASSEMBLY

General Cautions

• Since all parts in control valves are precision

machined, carry out disassembly and assembly
operations in a clean place.

• Before disassembly, clean the outside surfaces

around the valves.

• Clean each of the disassembled parts and apply

clean hydraulic oil to them.

• Apply hydraulic oil to sliding surfaces and apply a

thin coating of grease to seals when assembling
them.

• Replace all seals with new ones each time the

valves are disassembled.

• Spools and section bodies are specially selected for

a precise fit. Therefore, if any damage is found in
either of these parts, replace the section assembly
as a unit.

• Be sure to number each section and spool to avoid

mistakes during assembly.

Following is an explanation of the control valve
disassembly procedure.
Follow the procedure used to disassemble the control
valve in reverse order when reassembling it.
• Before disassembly, number each section and spool.

Disassembly

Valve Assembly

1. Loosen the nuts and remove the tie rods, then

remove the sections.
• Nut tightening torque:

16.6~17.6 N·m (1.7~1.8 kgf·m)

2. Remove the O-ring.

• The mating surfaces are metal seals, so be

careful not to scratch, bruise or otherwise dam-
age them.

• When assembling, do not apply any oil or

grease to the O-rings used on the mating sur-
faces.

3. Remove the main relief valves and the port relief

valves, then remove the O-rings from the relief
valves.
• Do not disassemble the relief valves unless it is

necessary.

• When using a spanner or adjustable wrench, be

sure to attach it in the place shown in the figure
at right.

• Relief valve tightening torque:

39 N·m (4 kgf·m)

G4D223

IV-58

HYDRAULIC UNITS

CONTROL VALVE

TB125, 135, 145

4. Remove the anti-cavitation valve (1) and remove

the O-ring (2) from the valve.
• Plug tightening torque: 39 N·m (4 kgf·m)

5. Remove the load check valve.

a. Remove the plug (3) and the spring (4), then

remove the poppet (5).
• Plug tightening torque: 39 N·m (4 kgf·m)

b. Remove the O-ring (6) from the poppet.

Manually Operated Section

1. Remove the cap screws, the cover (1) and the

spool assembly (2).
• Cap screw tightening torque:

5.8~6.8 N·m (0.6~0.7 kgf·m)

2. Remove the seal holder, backup ring and O-ring.

3. Remove the cap screws on the spool yoke end

side of the section, then remove the seal holder,
backup ring and O-ring.
• Cap screw tightening torque:

5.8~6.8 N·m (0.6~0.7 kgf·m)

G4D224

G4D225

G4D226

IV-59

HYDRAULIC UNITS

CONTROL VALVE

TB125, 135, 145

Pilot Operated Section

1. Take out the cap screws and remove the cover.

• Cap screws tightening torque:

5.8~6.8 N·m (0.6~0.7 kgf·m)

2. Remove the O-ring from the section.

3. Remove the spool from the section.

4. Take out the cap screws and remove the cover.

• Cap screw tightening torque:

5.8~6.8 N·m (0.6~0.7 kgf·m)

5. Remove the O-ring from the section.

Switch Valve

1. Take out the cap screws and remove the cover.

• Cap screw tightening torque:

5.8~6.8 N·m (0.6~0.7 kgf·m)

2. Remove the O-ring from the section.

G4D227

G4D228

G4D229

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