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178T-2-1

SECTION 2

SYSTEM

CONTENTS

Group 1 Control System

Outline .....................................................T2-1-1

Engine Control .........................................T2-1-2

Pump Control .........................................T2-1-23Valve Control..........................................T2-1-32

Other Controls........................................T2-1-46

Group 2 Hydraulic System

Outline .....................................................T2-2-1

Pilot Circuit...............................................T2-2-2

Main Circuit ............................................T2-2-12

Group 3 Electrical System

Outline .....................................................T2-3-1Main Circuit ..............................................T2-3-2

Electric Power Circuit ...............................T2-3-3

Indicator Light Check Circuit.....................T2-3-4

Accessory Circuit ......... .... .... ....... .... .... .... .T2-3-5

Preheat Circuit .........................................T2-3-6

Starting Circuit .........................................T2-3-8

Charging Circuit .....................................T2-3-10

Serge Voltage Prevention Circuit ............T2-3-14

Engine Stop Circuit.................................T2-3-16

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178T-2-2

(Blank)

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SYSTEM / Control System

T2-1-1

OUTLINE

The main controller (MC) is used to control machine

operations. Electronic signals from the engine control

dial, various sensors and switches are sent to the MC.

After processing the received signals in the logic circuit,

the MC sends out control signals to the EC motor,

solenoid valve units, torque control solenoid valve, and

other control circuits to regulate the engine, pumps,

motors and valves.

Input Signals Output Signals

EC Sensor Engine Control (EC Motor)

Engine Control Dial Engine Control Dial

Pump 1 Control Pressure Sensor HP Mode Control

Pump 2 Control Pressure Sensor E mode Control

Pump 1 Delivery Pressure Sensor Auto-Idle Control

Pump 2 Delivery Pressure Sensor Auto-Acceleration Control

Pump 3 Delivery Pressure Sensor Auto-Warming Up Control

(Oprtional) Idle Speed-Up Control

N sensor Engine Speed Automatic Increase Control at

Travel(Oniy ZAXIS270)

Pressure Switch (Travel) Attachment Operation Speed Increase Control

Pressure Switch (Front Attachment) Attachment Operation Speed Limit Control

Pressure Switch (Swing) Engine Learning Control

Pressure Switch (Boom Raise)

Pressure Switch (Arm Roll-In) Pump Control (Torque Control Solenoid Valve)

Pressure Switch (Auxiliary) MC Speed Sensing Control

Pressure Switch (Arm Roll-Out)

Slow Speed Torque Increase Control (Optional) Pump 1 Flow Rate Limit Control

Hydraulic Oil Temperature Sensor Pump 2 Flow Rate Limit Control

Auto-Idle/Acceleration Selector Pump 3 Torque Decrease Control

Power Digging Switch

Power Mode Switch (HP/E/P) Valve Control (Solenoid Valve Unit)

Travel Mode Switch (Fast/Slow) Power Digging Control

Work Mode Switch Arm Flow Rate Control

(Digging/Attachment) Arm Regenerative Control

Learning Switch Travel Motor Swash Angle Control

Key Switch Auto-Power Lift Control

Boom Angle Sensor (Only ZAXIS225US)

Auxi liary Flow Rate ControlAuxiliary Mode Switch (Optional)

Other Controls

Boom Electronic Cushion Control (Only

ZAXIS225US)

Work Mode Control

Travel Alarm Control

NOTE:

Only on the machines equipped with the

corresponding optional parts.

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T2-1-2

ENGINE CONTROL

The engine control system is grouped as follows:

Engine Control Dial Control HP Mode Control

E Mode Control

Auto-Idle Control

Auto-Acceleration Control

Auto-Warming Up Control

Idle Speed-Up Control Engine Speed Automatic Increase Control at

Travel (Only ZAXIS270)

Attachment Operation Speed Increase Control

Attachment Operation Speed Limit Control

Engine Learning Control

NOTE:

Only on the machines with the


Engine Control System Layout

T178-02-01-027

Auxiliary (Optional)

Arm Roll- In

Boom Raise

Swing

Front Attachment

Travel

EC Motor

EC Sensor

Pump 2Control

PressureSensor

Pump 2DeliveryPressureSensor

AttachmentMode

DiggingMode

Hydraulic OilTemperatureSensor

Auto-Idle /AccelerationSelector

Auto-Idle

Auto-Acceleration

EngineControl Dial

P Mode

E Mode

HP Mode

Key Switch

Learning Switch

Auxil iary ModeSwitch(Optional)

Work ModeSwitch

Power Mode Switch

Pressure Sensor


Pump 1ControlPressureSensor

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T2-1-3

(Blank)

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T2-1-4

Engine Control Dial Control

Function: Controls the engine speed in response to

the rotation angle of the engine control dial

and reduces the engine speed by 100 min-1

to reduce fuel consumption and noise level

when all control levers are in neutral.

Operation: The MC drives the governor lever in

response to the rotation angle of the engine

control dial to regulate the engine speed.

NOTE: Even if the control dial is rotated to the full

speed position, the governor lever doesnt

come in contact with the full speed stopper.

(Refer to the HP mode control.)

Approx. 1 second after all control levers are in neutral

(the travel and front attachment sensors are OFF), the

MC drives the EC motor so that the engine speed is

reduced from the maximum speed by 100 min-1

.

NOTE: The engine speed is reduced from the

maximum speed by 100 min-1

. Therefore,

when the engine speed set by the engine

control dial is already slower than the

maximum speed by 100 min

-1

, the enginespeed remains unchanged. This engine

speed reduction control is activated

regardless of whether the auto-idle and/or

auto-acceleration control is activated or not.

MinimumSpeed

Engine speed isreduced by 100min

-1when the

control levers arein neutral.

EngineControl DialPosition

EngineSpeed

Control Range

MaximumSpeed

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T2-1-5

T178-02-01-004

EngineControl Dial

Front Attachment

Travel

Pressure Sensor

EC Motor

ANIMATION

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T2-1-6

HP Mode Control

Function: Slightly increases digging power such as

arm roll-in operation while excavating

deeply.

Operation: The MC drives the EC motor to slightly

increase the engine speed set by the

engine control dial when all the following

conditions exist with the power mode

switch is in the HP position.

Engine Control Dial: Set at 1500 min-1

or faster.

Boom Raise and/or Arm Roll-In Control: In

Operation

Average Delivery Pressure of Pumps 1 and 2:High

NOTE: The engine governor stopper position is

adjusted in the HP mode. Accordingly, the

governor lever doesnt come in contact with

the stopper in the normal mode.

1500 min-

Minimum

Speed

Maximum

Speed

Engine

Speed1650 min

- Maximum speedincreases by200 min

-1except

ZAXIS230 and270 (by 100min

1).


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T2-1-7

T178-02-01-005

EngineControl Dial

HP Mode

EC Motor

Arm Roll -In

Boom Raise


Pressure Sensor


Power Mode Switch

ANIMATION

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T2-1-8

E Mode Control

Function: Reduce the engine speed by the constant

specified ratio.

Operation: The MC drives the EC motor to reduce the

engine speed set by the engine control dial

when the power mode switch is in the E

mode position. The engine speed is

reduced in proportion to the rotation angle

of the engine control dial.

T178-02-01-006

Minimum Speed Maximum Speed

EngineSpeed

Engine speed isreduced at theconstantspecified ratio.

EngineControl Dial

E Mode

EC Motor


Power Mode Switch

ANIMATION

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T2-1-9

(Blank)

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T2-1-10

Auto-Idle Control

Function: Reduces the engine speed when all control

levers are in neutral to reduce fuel

consumption and noise level.

Operation: Approx. 3.5 seconds after all control levers

are return to neutral, the MC drives the EC

motor so that the engine speed is reduced

to the auto-idle speed. As soon as a control

lever is operated (the travel and/or front

attachment pressure sensor is turned ON),

the MC drives the EC motor so that the

engine speed is increased to the original

engine speed (set by the engine control

dial).

Auto-Idle System Deactivation Requirements:

Control Levers: Being operated (either travel or

front attachment control levers with pilot sensor

ON)

Power Mode Switch: When the E mode is

changed to P mode or the P mode is changed to

the E mode.

Engine Control Dial: When engine speed is

changed.

Auto-IdleSpeed

MinimumSpeed

MaximumSpeed

Engine speed isreduced to theauto-idle speed3.5 seconds later.

EngineSpeed


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T2-1-11

T178-02-01-007

Auto-Idle

Auto-Idle/AccelerationSelector

EngineControl Dial

E Mode

Front Attachment

Travel

Pressure Sensor

EC Motor

Power Mode Switch

ANIMATION

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T2-1-12

Auto-Acceleration Control

Function: Automatically regulates the engine speed to

meet the machine operating conditions.

When all the control levers are in neutral,the engine speed is reduced to reduce fuel

consumption and noise level.

Operation: When a control lever is operated with the

auto-idle / acceleration selector in auto

acceleration position, the MC calculates the

most proper engine operating speed

corresponding to the signals from pressure

sensors (travel, swing, boom raise, and arm

roll-in), the pump control pressure sensors,

and the pump delivery pressure sensors.

Then, the MC drives the EC motor so thatthe engine speed is set to the rotation

speed calculated by the MC.

When all control levers are returned to

neutral, the engine speed is reduced by 400

min-1

from the maximum speed first. Then,

3.5 seconds later, the engine speed is

further reduced to the auto-idle speed.

NOTE: When all control levers are returned to

neutral, the engine speed is reduced by

400 min-1

from the maximum speed. In

case the engine speed is set by the enginecontrol dial and is running at a speed

slower than the maximum speed by 100

min-1

, the engine speed will be reduced by

300 min-1

.

Lever Stroke VS. Engine Speed Change

Operating Time Progress VS. Engine Speed Change

Engine

Speed

MinimumSpeed

MaximumSpeed

Engine speed isautomaticallycontrolled inresponse to thecontrol leveroperations.

Auto-IdleSpeed


Engine speed is reducedfrom the maximum speed by400 min

-1.

Engine speed is reducedto the auto-idle speed 3.5seconds later.

Control Lever Stroke

Full Stroke

NeutralPosition

Time

In response to the controllever stroke and the pumpdelivery pressure, theoptimum engine speed isselected.

Engine Speed

Max. EngineSpeed (P Mode) Auto

AccelerationControl

Auto-IdleEngine Speed

Time

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T2-1-13

T178-02-01-008

EngineControl Dial

Auto-Acceleration

Swing

Arm Roll- In

Boom Raise

Travel

Pump 1 ControlPressureSensor

Pump 2 ControlPressureSensor


Pressure Sensor

EC Motor


Auto-Idle/Accelerat ionSelector

ANIMATION

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T2-1-14

Auto-Warming Up Control

Function: Automatically warms up the hydraulic

system (similar to the auto choke on

automobiles).

Operation: When the hydraulic oil temperature is

below 0 C (32 F), the MC drives the EC

motor in response to signals from the key

switch and the hydraulic oil temperature

sensor to run the engine at the auto warm

up speed for 15 minutes after starting the

engine.

IMPORTANT: When adjusting the auto-idle speed

deactivate the auto warming upcontrol function using Dr. EX, or wait

to adjust until 15 minutes after

starting the engine.

T178-02-01-009

MinimumSpeed

MaximumSpeed

EngineSpeed

IncreasingSpeed

AutoWarm Up

Speed

Key Switch

EngineControl Dial

Hydraulic OilTemperatureSensor

EC Motor


ANIMATION

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T2-1-15

Idle Speed-Up Control

Function: Prevents the engine from hunting when

running the engine at slow speed.

Operation: When the travel or front attachment

function is operated while the engine is

running at a speed between the minimum

speed and the Idle Speed-Up Speed, the

MC drives the EC motor so that the engine

speed is increased to the Idle Speed-Up

Speed.

T178-02-01-010

IncreasingSpeed

EngineSpeed

MinimumSpeed

MaximumSpeed

Idle Speed-Up

Speed

EngineControl Dial

Front Attachment

Travel

Pressure Sensor

EC Motor


ANIMATION

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T2-1-16

Engine Speed Automatic Increase Control at

Travel (Only ZAXIS270)

Function: Increases the engine speed at travel single

operation to increase the travel speed.

Operation: MC drives EC motor to increase the engine

speed by 100 min1(rpm) when the power

mode switch is turned to P or HP and the

following conditions exist.

Consequently, the pump delivery flow rate

increases, so that the travel speed

increases.

Condition: Engine Control Dial: The speed is set to

maximum.

Travel Operation: OperatedFront Attachment Operation: Not operated

T1HG-02-01-001

TravelFrontAttachment

EC Motor

Pressure Sensor

EngineControl Dial

ANIMATION

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T2-1-17

(Blank)

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T2-1-18

Attachment Operation Speed Increase Control

(Only on the machines equipped with the

auxiliary mode switch (Optional).)

Function: Increases the maximum engine speed to

the attachment (hydraulic breaker,

secondary crusher, primary crusher or

vibrating hammer) operating engine speed

set by Dr. EX when the attachment is

operated.

Operation: When the following conditions exist, the MC

drives the EC motor so that the engine

maximum speed is increased to the

attachment operating speed set by Dr. EX

when the attachment is operated.

Operating Conditions:

Dr. EX: Resets the maximum engine speed to a faster

(+) attachment (hydraulic breaker, secondary crusher,

primary crusher, or vibrating hammer) operating speed

in the service mode.

Engine Control Dial: Maximum Speed Position

Power Mode Switch: HP Mode

Auxiliary: In Operation

Work Mode Switch: Attachment Mode

Auxiliary Mode Switch (Optional): Attachment position

(hydraulic breaker, secondary crusher, primary crusher,

or vibrating hammer) reset by Dr. EX.

NOTE: When the P mode engine speed is preset to

a slower speed in the Dr. EX service mode,

the maximum engine speed wont be

increased when operating the attachment.

MinimumSpeed

MaximumSpeed

EngineSpeed

When allconditions exist,the maximum

engine speed isincreased to thespeed set by Dr.EX.


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T2-1-19

T178-02-01-011

Auxil iary(Optional)

Pressure Sensor

Power Mode Switch

HP Mode

EC Motor


AttachmentMode

Work ModeSwitch

EngineControl Dial

ANIMATION

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T2-1-20

Attachment Operation Speed Limit Control (Only

on the machines equipped with the auxiliary

mode switch (Optional).)

Function: Decreases the maximum engine speed to

the attachment (hydraulic breaker,

secondary crusher, primary crusher or

vibrating hammer) operating engine speed

set by Dr. EX when the attachment mode is

selected.

Operation: When the following conditions exists, the

MC drives the EC motor so that the engine

maximum speed is reduced to the

attachment operating speed set by Dr. EX

when the attachment mode is selected.


Dr. EX: Resets the maximum engine speed to a slower

() attachment (hydraulic breaker, secondary crusher,

primary crusher, or vibrator) operating speed in the

service mode.

Work Mode Switch: Attachment Mode

Auxiliary Mode Switch (Optional): Attachment position

(hydraulic breaker, secondary crusher, primary crusher,

or vibrating hammer) set by Dr. EX.

T178-02-01-012

MinimumSpeed

MaximumSpeed

EngineSpeed

When all

conditions exist,the maximumengine speed isreduced to thespeed set by Dr.EX.

AttachmentMode

Work ModeSwitch

EC Motor



ANIMATION

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T2-1-21

Engine Learning Control

Function: Inputs the governor lever stopper positions

on both the STOP and FULL sides as the

standard data to control the engine.

Operation:When the learning switch in the rear

console is turned to the engine learning

position, the EC motor is driven by the

signals from the MC. The EC motor moves

the governor lever from the IDLE to FULL

and to STOP positions in this order. The EC

sensor detects the stopper positions of the

governor lever on both the FULL and STOP

sides and sends each stopper position

signal to the MC. The MC stores these

signals in its memory.

IMPORTANT: Be sure to perform the engine

learning if the following repair work

is done. (Refer to the

Troubleshooting Section in T/M.)

After performing the engine learning,

check that the engine learning has

been performed correctly using Dr.

EX.

After the engine, engine control

cable, or EC motor has been

removed or replaced.

After the MC has been replaced.

NOTE: The engine learning is not required whenthe batteries are replaced.

T178-02-01-014

EC Motor

Learning Switch

Key Switch

EC Sensor

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T2-1-22

(Blank)

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T2-1-23

PUMP CONTROL

The pump control system has the following functions:

Speed Sensing Control

Slow Speed Torque Increase Control

Pump 1 Flow Rate Limit Control

Pump 2 Flow Rate Limit Control

Pump 3 Flow Torque Decrease Control

NOTE:



Pump Control System Layout

T178-02-01-002

Auxiliary(Optional)

Travel


Torque Control Solenoid Valve

EngineControl Dial

N SensorPressure Sensor


Max. Pump 1 Flow Rate LimitSolenoid Valve (Optional)

Max. Pump 2 Flow RateLimit Solenoid Valve

Pump 3DeliveryPressureSensor(Optional)

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T2-1-24

Speed Sensing Control

Function: Controls the pump flow rate in response to

engine speed changes due to variations in

load so that the engine output can be utilized

more efficiently. (Engine stall is prevented

when the machine operates under adverse

conditions such as operating at high

altitude.)

Operation:

1. The target engine operating speed is set by

controlling the engine control dial.

2. The MC calculates the difference in speed

between the target operating speed and the actual

operating speed monitored by the N sensor. Then,

the MC sends signals to the torque control

solenoid valve.

3. The torque control solenoid valve delivers pilot

pressure oil in response to the signals received

from the MC to the pump regulator, controlling the

pump flow rate.

4. If the engine load increases and the actual engine

operating speed becomes slower than the target

operating speed, the pump swash angle is

reduced so that pump flow rate will be reduced.

Therefore, the engine load is reduced, preventing

engine stall.

5. If the actual engine operating speed becomesfaster than the target operating speed, the pump

swash angle is increased so that the pump flow

rate will increase, by which the engine output can

be utilized more efficiently.

Flow Rate

Q

PPressure

Pump P-Q Curve

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T2-1-25

T178-02-01-015


N Sensor

EngineControl Dial

ANIMATION

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T2-1-26

Slow Speed Torque Increase Control

Function: Allows the machine to travel at the maximum

pump flow rate when the engine is running at

slow speed. When travel operation is madewith the engine running at slow speed,

normally, the hydraulic pump delivers

pressure oil at the flow rate corresponding to

point A on the P-Q curve illustrated to the

right. Therefore, if any difference exists

between pump 1 and pump 2 flow rate, the

machine will mistrack. To prevent

mistracking, the pump P-Q curve is raised so

that, when traveling the machine with the

engine running at slow speed, the pump

delivers pressure oil at the flow rate

corresponding to point B (maximum flowrate).

Operation:

1. When the engine speed set by the engine control

dial is slow, the MC processes signals from the

travel pressure sensor, and pump 1 and 2 delivery

pressure sensors and sends control signals to the

torque control solenoid valve.

2. The torque control solenoid valve delivers the pilot

pressure oil corresponding to the signals received

from the MC to the regulator, increasing the pump

flow rate.

NOTE: If the MC stops the slow speed torque

increase control when the front attachment

is operated while traveling, the pump flow

rate will be reduced quickly, developing a

shock load to the machine. Therefore, the

MC maintains the slow speed torque

increase control even if the front

attachment is simultaneously operated

while traveling.

Flow Rate

Q

PPressure

Increased TorqueP-Q Curve

Normal P-Q Curve

A

B

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T2-1-27

T178-02-01-016


EngineControl Dial



Travel

Pressure Sensor

ANIMATION

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T2-1-28

Pump 1 Flow Rate Limit Control (Only on the

machines with the auxiliary sensor (Optional).)

Function: Limits the maximum pump 1 flow rate when

a front attachment (mainly a vibratinghammer) is used.

Operation:

1. When a front attachment is used, the MC receives

signals from the pressure sensor (auxiliary).

2. In response to the signals arriving from the

pressure sensor, the MC drives the maximum

pump 1 flow rate limit solenoid valve (optional) to

reduce the maximum pump flow rate.

NOTE: In proportion to the attachment control

pedal stroke, the maximum pump flow ratedis reduced. The minimum pump swash set-

angle for a front attachment (hydraulic

breaker, secondary crusher, primary

crusher or vibrating hammer) can be set in

the service mode of Dr. EX.

Pump 2 Flow Rate Limit Control (Only on the

machines with the auxiliary sensor (Optional).)

Function: Limits the maximum pump 2 flow rate when

a front attachment (mainly a hydraulicbreaker) is used.

Operation:

1. When a front attachment is used, the MC receives

signals from the pressure sensor (auxiliary).

2. In response to the signals arriving from the

pressure sensor, the MC drives the maximum

pump 2 flow rate limit solenoid valve (optional) to

reduce the maximum pump flow rate.

NOTE: In proportion to the attachment control pedal

stroke, the maximum pump flow rated isreduced. The minimum pump swash set-

angle for a front attachment (hydraulic

breaker, secondary crusher, primary

crusher or vibrating hammer) can be set in

the service mode of Dr. EX.

Flow Rate

Q

PPressure

Maximum flow rate is reduced.

Pump P-Q Curve

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T2-1-29

T178-02-01-017

Maximum Pump 1 Flow RateLimit Solenoid Valve

Maximum Pump 2 FlowRate Limit SolenoidValve(Optional)

Auxiliary(Optional)

Pressure Sensor

ANIMATION

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T2-1-30

Pump 3 Torque Decrease Control (Only on the

machines equipped with pump 3 (Optional).)

Function: Reduces pump 1 and pump 2 driving

torque to prevent the engine from stalling,utilizing the engine output efficiently when

the pump 3 driving torque increases.

Operation: When the MC receives signals from pump

3 delivery pressure sensor (optional), the

MC drives the torque control solenoid valve

so that pump 1 and pump 2 flow rates are

reduced. Thereby, the total pump 1, 2, and

3 driving torque is maintained not to exceed

the engine output, utilizing the engine

output efficiently.

T178-02-01-018

Flow Rate

Q

PPressure

P-Q curve is controlled in

proportion to pump 3 deliverypressure.

Normal P-Q Curve



ANIMATION

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T2-1-31

(Blank)

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T2-1-32

VALVE CONTROL

The valve control system functions as follows:

Power Digging Control Auto-Power Lift Control

Arm Flow Rate Control

Arm Regenerative Control

Travel Motor Swash Angle Control

Auxiliary Flow Rate Control

NOTE:



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T2-1-33

Valve Control System Layout

T178-02-01-003

SI

SE

EngineControl Dial

PowerDiggingSwitch

Slow

Fast

Key Switch

Learning

Switch

SC

SG

Hydraulic Oil

Temperature Sensor

Auxiliary(Optional)

Arm Roll- In

Boom Raise

Swing

Pump 1 ControlPressure Sensor



Pressure Sensor

Main Relief Valve

Travel Motor

Swash AngleControl Valve

Arm RegenerativeValve

Auxil iary Flow RateControl Valve

Arm Flow Rate ControlValve

Auxil iary FlowRate ControlSolenoid Valve(Optional)

Solenoid Valve Unit

Travel Mode Switch


ANIMATION

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T2-1-34

Power Digging Control

Function: Increases digging force by temporarily

increasing relief pressure.

Operation: For maximum 8 seconds after the power

digging switch is turned ON, the MC

continuously activates solenoid valve

unit(SG). Solenoid valve unit (SG) delivers

the pilot oil pressure to the relief valve,

increasing the relief set-pressure. (Refer to

the COMPONENT OPERATION / Control

Valve group.)

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T2-1-35

T178-02-01-019

PowerDiggingSwitch

SG

Main Relief ValveSolenoid Valve Unit

ANIMATION

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T2-1-36

Auto-Power Lift Control

Function: Increases oil pressure when raising the

boom.

Operation: The MC activates solenoid valve unit (SG)

when signals from pressure sensor (boom

raise) and pump 1 delivery pressure sensor

meet the following conditions. Solenoid

valve (SG) delivers the pilot pressure oil to

the relief valve, increasing the relief set-

pressure. (Refer to the COMPONENT

OPERATION / Control Valve group.)


Boom Raise Pressure Sensor: Outputting signals.

(The boom must be raised to a certain extent.)Pump 1 delivery Pressure Sensor: High pressure.

Arm Roll-In Pressure Sensor: Output zero. (The

control lever is in neutral.)

NOTE: This control system is activated during

combined operations (except for the arm

roll-in combined operation).

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T2-1-37

T178-02-01-020

SG

Boom Raise

Pressure Sensor

Main Relief Valve

Solenoid Valve Unit

Arm Roll- In

Pump 1 DeliveryPressure Sensor

ANIMATION

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T2-1-38

Arm Flow Rate Control

Function: Gives pressure oil from pump 2 priority to

flow to the swing motor spool over the arm

1 spool to ensure swing power.

Operation: The MC activates solenoid valve unit (SE)

when signals from the pump 2 delivery

pressure sensor and pressure sensors

(swing and arm roll-in) meet the following

conditions. Solenoid valve unit (SE)

delivers the pilot pressure oil to the arm

flow rate control so that the parallel oil

passage to the arm 1 spool is restricted.

Thereby, the swing spool has priority,

ensuring swing motor power, preventing the

upperstructure from being rotated by thearm reaction force when the arm is rolled in.

(Refer to the COMPONENT

OPERATION/Control Valve group.)


Pump 2 Delivery Pressure Sensor: High pressure.

Swing Pressure Sensor: Must have some output. (The

swing control lever is stroked to a certain extent.)

Arm Pressure Sensor: Outputting signals.

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T2-1-39

T178-02-01-021

SE

Arm Roll- In

SwingPump 2DeliveryPressureSensor

Pressure Sensor

Arm Flow Rate Control Valve

Solenoid Valve Unit

ANIMATION

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T2-1-40

Arm Regenerative Control

Function: Accelerates the arm roll-in speed to prevent

arm hesitation during arm roll-in operation.

Operation: The MC activates the solenoid valve unit

(SC) so that solenoid valve delivers the

pilot pressure oil to shift the arm

regenerative valve when signals from the

pump 2 delivery pressure sensor, swing

pressure sensor, arm roll-in pressure

sensor, and boom raise pressure sensor

meet the following conditions. When the

arm regenerative valve is shifted, the return

circuit from the arm cylinder rod side to the

hydraulic oil tank is closed. Then, the return

oil from the cylinder rod side is combinedwith the pressure oil from the pump and is

routed to the cylinder bottom, accelerating

the arm roll-in speed and preventing arm

hesitation. (Refer to the COMPONENT

OPERATION / Control Valve group.)


Pump 2 Delivery Pressure Sensor: Low pressure. (The

arm doesnt need much power.)

Arm Roll-In Pressure Sensor: High output. (The arm

control lever stroke is large.)

Swing or Boom raise Sensor: Outputting signal.

NOTE: To improve arm leveling performance, the

MC gradually activates solenoid valve unit

(SC) when the hydraulic oil temperature is

at 0 to 10 C (32 to 50 F).

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T2-1-41

T178-02-01-022

SC

Hydraulic OilTemperature Sensor

Arm Roll- In

Boom Raise

SwingPump 2DeliveryPressureSensor

Pressure Sensor

Solenoid Valve Unit

Arm Regenerat ive Valve

ANIMATION

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T2-1-42

Travel Motor Swash Angle Control

Function: Controls the travel mode.

Operation: When the travel mode switch is in theSLOW position, the travel motor swash

angle is kept in the maximum angle so that

the travel speed is slow.

When the MC receives the signals from the

travel pressure sensor, pump 1 and 2

delivery pressure sensors, pump 1 and 2

control pressure sensors under the

following conditions with the travel mode

switch in the FAST position, the MC

activates the solenoid valve unit (SI). Then,

the solenoid valve (SI) delivers the pilot

pressure oil to the travel motor swash anglecontrol valve, reducing the swash angle to

the minimum so that the travel speed

increases.

ZAXIS200,225USR,225US,230


Travel Pressure Sensor: ON

Front Attachment Pressure Sensor: OFF

Pump 1 and 2 Delivery Pressure Sensor: Either pump

delivery pressures are low.

Pump 1 and 2 Control Pressure Sensor: Either pump

control pressures are high.

NOTE: When one side track is raise off the ground

using the front attachment and is rotated,

the one side pump control pressure

increases, allowing the raised track to

rotate at fast speed.

When the machine is traveling in the fast

mode, even if the front attachment is

operated (the front attachment pressure

sensor is turned ON), the travel mode is

kept unchanged in the fast mode.

ZAXIS270


Travel Pressure Sensor: ON

Front Attachment Pressure Sensor: OFF

Pump 1 and 2 Delivery Pressure sensor: Both of pump

1 and 2 delivery pressure are low.

Pump 1 and 2 Control Pressure Sensor: Both of pump

1 and 2 control pressures are high.

NOTE: When one side track is raise off the ground

using the front attachment and is rotated,

the one side pump displacement target

angle remains small so that the travel motor

speed does not increase.

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T2-1-43

T178-02-01-023

Travel

Pressure Sensor

Travel Mode Switch

FastMode

SI


Swash Angle Control Valve

Travel Motor

Solenoid Valve Unit




ANIMATION

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T2-1-44

Auxiliary Flow Rate Control (Only on the

machines equipped with the auxiliary pressure

sensor and auxiliary flow rate control solenoid

valve)

Function: Restricts the oil flow to the auxiliary spool

when the combined operation of the swing,

boom raise, and arm roll-in is made while

operating a front attachment using the

auxiliary spool to maintain controllability of

the combined operation.

Operation: The MC activates the auxiliary flow rate

control solenoid valve (optional) so that the

oil flow to the auxiliary spool is restricted

under the following conditions.


Auxiliary Pressure Sensor: ON

Swing, Boom Raise, Arm Roll-In Pressure Sensors:

ON

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T2-1-45

T178-02-01-024

Arm Roll- In

Boom Raise

Swing

Auxil iary(Optional)

Pressure Sensor

Auxil iary FlowRate Control Valve

Auxil iary FlowRate ControlSolenoid Valve(Optional)

ANIMATION

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T2-1-46

OTHER CONTROLS

Boom Electronic Cushion Control (ZAXIS225US)

Function: Reduces the shock which may occur whenthe boom reaches to its full stroke position

at boom raise operation by functioning the

electronic cushion in the speed reduction

area.

Operation:The signal from the boom angle sensor

comes into MC at boom raise operation.

MC calculates the boom angle by this

signal. When the boom angle reaches to

the speed reduction area, MC controls the

boom electronic cushion solenoid valve to

decrease the boom raise pilot pressure.

T1GF-02-01-001

Boom Full Stroke Position

Position where speedreduction begins

Speed Reduction Area

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T2-1-47

T1GF-02-01-002

Boom ElectronicCushion SolenoidValve

Boom Raise

Boom Angle Sensor

1

1

1

Boom 1Boom 2

Control Valve

Signal Control Valve

ANIMATION

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T2-1-48

Work Mode Control

Two work modes, digging and front attachment, are

available by operating the work mode switch.

Digging Mode: Normal control is performed.

Front Attachment Mode:

Functions only when a front attachment in the

optional kit is operated. The engine speed (see

T2-1-18 and 20) and pump flow rate (see T2-1-

28) are controlled so as to match the installed

front attachment operation in response to the

movement of the auxiliary valve spool. The engine

speed and pump flow rate control settings are

made by using Dr. EX.

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T2-1-49

Travel Alarm Control (Only on the machines

equipped with the travel alarm device)

Function: Sounds the buzzer while traveling.

Operation: As long as the MC receives signals from

the travel pressure sensor when travel

operation is made, the MC sends out

signals to the travel alarm device to sound

the buzzer.

NOTE: After traveling continuously for more than

13 seconds, the buzzer can be stopped

with the buzzer deactivation switch.

T178-02-01-025

Buzzer DeactivationSwitch (Optional)

Travel AlarmDevice (Optional)

Buzzer(Optional)

Travel

Pressure Switch

ANIMATION

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T2-1-50

(Blank)

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SYSTEM / Hydraulic System

T2-2-1

OUTLINE

The hydraulic system is broadly divided into two cir-

cuits, the main circuit and the pilot circuit.

Main Circuit:

Power Source Controller Actuator

Main Pumps Control Valves Motors

Cylinders

Front Attachmens (Optional)

Pilot Circuit:

Power Source Controller Pilot Circuit

Pilot Pumps Pilot Valves Operation Control Circuit

Pump Regulator Pump Control Circuit

Solenoid Valve Unit Valve Control Circuit

Signal Control Valve Swing Parking Brake Release Circuit

Boom Electronic Cushion Travel Motor Swash Angle Control Circuit

Solenoid Valve Hydraulic Oil Heat Circuit

(Only ZAXIS225US)

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T2-2-2

PILOT CIRCUIT

Outline:

Pressure oil from the pilot pump is used to oper-

ate the operation control circuit, pump control cir-

cuit, valve control circuit, swing parking brake re-

lease circuit, travel motor swash angle control cir-

cuit, and hydraulic oil heat circuit.

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T2-2-3

NOTE: *Boom Electronic Cushion Solenoid Valve

is ZAXIS225US Only.

Left Pilot

Valve

Travel Pilot

Valve

Boom Electronic CushionSolenoid Valve

Right Pilot

Valve

Pilot Shut-

Off ValveSignal Control Valve

Swing Motor

Relief Valve

Travel Motor Travel Motor

Bucket FlowRate ControlValve

FlowCombinerValve

Boom Anti-Drift Valve

Arm Anti-Drif t Valve

Control Valve

To Control Valve

Spools

Auxil iary Flow Rate ControlSolenoid Valve (When theauxiliary spool is used.)

Auxil iary Flow CombiningSolenoid Valve (When theauxiliary spool is used.)

TorqueControl Sole-noid Valve

Maximum Pump 2

Flow Rate Control

Solenoid Valve

Maximum Pump 1 FlowRate Control SolenoidValve (Optional)

Regulator

Operation Control Circuit

Hydraulic OilHeat Circuit

Pump

Control Circuit

Travel Motor Swash

Angle Control Circuit

Swing Parking Brake

Release Circuit

Pilot Filter

Pilot Pump

Hydraulic

Oil Tank

Suction

Filter

Arm Flow Rate Control Valve

Arm Regenerat ive Valve

Main Relief Valve

VC Solenoid

Valve Unit

ValveControlCircuit

Auxil iary Flow Combiner Valve

Auxil iary Flow Control Valve

Bypass Cut Valve

Auxiliary Pilot

Valve

ANIMATION

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T2-2-4

Operation Control Circuit

The pilot valves control the pressure oil from the

pilot pump to operate the control valve spools.

The signal control valve is provided between the

pilot valves and the control valve. The shockless

valve (in the boom lower circuit) built in the signal

control valve dampens quick spool movement in

the control valve. (Refer to the COMPONENT

OPERATION / Signal Control Valve group.)

The boom electronic cushion solenoid valve is

provided between the pilot valve (right) and the

signal control valve on ZAXIS225US.

This valve reduces the shock which may occur

when the boom reaches to its full stroke position.

(Refer to SYSTEM / Control System group.)

ZAXIS225US:

T1GF-02-02-001Signal Control Valve

Pilot Valve (Right)

Boom ElectronicCushion SolenoidValve

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T2-2-5

ZAXIS200,225USR,230,270

T178-02-02-005

1 - Boom Raise 4 - Arm Roll-In 7 - Bucket Roll-In 10 - Left Travel Reverse

2 - Boom Lower 5 - Left Swing 8 - Bucket Roll-Out 11 - Right Travel Forward3 - Arm Roll-Out 6 - Right Swing 9 - Left Travel Forward 12 - Right Travel Reverse

Pilot Valve (Right)Pilot Valve (Left)Travel Pilot Valve

Signal Control Valve

Shockless Valve

56

7

7

8

8

4

2

6

PilotPump

Control Valve

5

3

1

3

1

123

412

1211

11

10

10

9

9

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T2-2-6

Pump Control Circuit (Refer to the COMPOMENT

OPERATION / Pump Device group.)

Pump Flow Rate Control by Flow Rate Control Pres-

sure Pi

Pressure oil from the pilot valve is selected by the

shuttle valves in the signal control valve. Then, the

selected pressure oil is routed further to either the

pump 1 flow rate control valve or the pump 2 flow

rate control valve in the same signal control valve,

shifting either of the flow rate control valves.

When either the pump 1 flow rate control valve or

the pump 2 flow rate control valve is shifted, the

pilot pressure oil from the pilot pump is routed to

either main pump 1 or main pump 2 as flow rate

control pressure Pi.

NOTE: When the boom (raise/lower), arm (roll-

in/out), bucket (roll-in/out), auxiliary, and/or

travel (right) function is operated, flow rate

control pressure Pi is routed to main pump

1. When the boom (raise/lower), arm (roll-

in/out), swing (right/left), and/or travel (left)

function is operated, flow rate control pres-

sure Pi is routed to main pump 2.

Torque Control (Speed Sensing) by Torque Control

Solenoid Valve After the pilot oil pressure from the pilot pump is

regulated by the torque control solenoid valve, the

regulated pilot oil pressure is routed to main pump

1 and 2 as speed sensing pressure Ppc.

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T2-2-7

T178-02-02-006

SignalcontrolValve

BucketBoomArmSwingTravel (Right)Travel (Left)

Pump 2 Flow RateControl Valve

Pump 1

Control Valve

Pump 2

TorqueControlSolenoidValve

Pilot Pump

Pump 1 Flow RateControl Valve

ANIMATION

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T2-2-8

Valve Control Circuit (Refer to the COMPONENT

OPERATION / Control Valve and Travel Device

groups.)

The following valves are controlled by pressure oil

from the pilot valves, solenoid valve unit (SC, SE,

and SG), the flow combiner valve control spool in the

signal control valve, and the bucket flow rate control

valve control spool.

Boom Lower Pilot Pressure: Boom Anti-Drift Valve

Arm Roll-In Pilot Pressure: Arm Anti-Drift Valve

Auxiliary Pilot Pressure: Auxiliary Flow Combiner

Valve, Bypass Shut-Out Valve (When the auxiliary

spool is used.)

Solenoid Valve SC: Arm Regenerative Valve

Solenoid Valve SE: Arm Flow Rate Control Valve

Solenoid Valve SG: Main Relief Valve (increasing

the set-pressure)

Auxiliary Flow Rate Control Solenoid Valve: Auxil-

iary Flow Rate Control Valve (When the auxiliary

spool is used.)

Auxiliary Flow Combining Solenoid Valve: Boom,Arm, and Bucket Pilot Pressure

Flow Combiner Valve Control Spool: Flow Com-

biner Valve

Bucket Flow Rate Control Valve Control Spool:

Bucket Flow Rate Control Valve

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T2-2-9

T178-02-02-007

Auxil iary

SolenoidValve Unit

Bypass Shut-OutValve

Boom Anti-Drift Valve

Bucket Flow RateControl Valve

Flow Combiner Valve

Auxil iary Flow CombinerValve

Arm Anti -Drif tValve

Auxil iary FlowRate ControlSolenoid Valve

Arm F low RateControl Valve

ArmRegenerativeValve

Pilot Pump

Auxil iary FlowRate ControlValve

Main Relief Valve

Auxil iary FlowCombiningSolenoid Valve

Boom LowerArm Roll- In

2

SE

SC

SG4

2

4

Travel (Right)

Bucket Flow Rate

Control Valve ControlSpool

Flow Combiner ValveControl Spool

SignalControlValve

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T2-2-10

Swing Parking Brake Release Circuit (Refer to the

COMPONENTS OPERATION / Swing Device

group.)

When the front attachment and/or swing function

is operated, the pilot oil pressure selected by the

shuttle valves in the signal control valve shifts the

swing parking brake release spool.

Consequently, the release signal oil pressure is

routed to the swing motor, releasing the swing

parking brake.

Travel Motor Swash Angle Control Circuit (Refer

to the COMPONENTS OPERATION / Travel Device

group.)

The pilot oil pressure from solenoid valve SI regu-

lates the travel motor swash angle control valve.

Hydraulic Oil Heat Circuit (Refer to the COMPO-

NENTS OPERATION / Others (Upperstructure)

group.)

When the pilot shut-off valve is closed, the pilot oil

pressure is routed to the signal control valve so

that hydraulic oil is warmed while passing through

the orifice in the signal control valve.

The warmed pilot pressure oil flows to the signal

control valve and pilot valves so that the pilot sys-

tem components are warmed.

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T2-2-11

T178-02-02-008

BucketBoom

SignalControlValve

SolenoidValve Unit

SI

Swash Angle Control Valve

Travel Motor

Control Valve

Swing Motor

ArmSwing

Swing Parking BrakeRelease Spool

Orifice

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T2-2-12

MAIN CIRCUIT

Outline

Main pumps (1 and 2) draw hydraulic oil from the

hydraulic oil tank. Main pump 1 and main pump 2

deliver pressure oil to the 4-spool control valve

and the 5-spool control valve respectively.

Delivered pressure oil is routed to the motor(s) or

cylinder(s) in response to operation(s) of the

spool(s) in the control valve(s).

The return oil from the motor(s) and/or cylinder(s)

flows back to the hydraulic oil tank via the control

valve and/or the oil cooler.

When the oil temperature is low (high viscosity),the oil flow resistance increases in the oil cooler,

which opens the bypass check valve, allowing hy-

draulic oil to return directly to the hydraulic oil tank

without passing through the oil cooler.

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T2-2-13

Main

Pump 2

Main

Pump 1

Hydraulic

Oil Tank

Suction

Filter

Arm 2

Boom 1

Travel (Right)

Swing

Arm 1

Boom 2

Travel (Left)

BucketAuxil iary

Control Valve

Travel Motor (Lef t) Travel Motor (Right )

Bucket Cylinder

Boom Cylinder

OilCooler

Swing Motor

Front Attachment (s)

Bypass CheckValve

5-Spool Side

4-SpoolSideArm Cylinder

ANIMATION

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T2-2-14

Neutral Circuit

When the control lever is in neutral, pressure oil

from the main pump passes through the control

valve and returns to the hydraulic oil tank.

Single Operation Circuit

Pressure oil from main pump 1 is routed to the 4-

spool control valve and is further routed to each

spool of the travel (right), bucket, boom 1, and

arm 2.

Pressure oil from main pump 2 is routed to the 5-

spool control valve and is further routed to each

spool of the swing, arm 1, boom 2, and travel

(left).

The boom and arm are actuated by pressure oilfrom two main pumps. Pressure oil from each

main pump is combined and supplied together.

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T2-2-15

T178-02-02-001

Boom Cylinder

Bucket Cylinder

Travel Motor (Right)

Swing Motor

Arm Cylinder

Travel(Right)

Bucket

5-Spool Side

4-Spool Side

Pump 2 Pump 1

Boom 1

Arm 1

Arm 2

Swing

Boom 2

Auxil iary

Travel(Left)

Front Attachment

Control Valve

Travel Motor (Left)

ANIMATION

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T2-2-16

Combined Operation Circuit

Swing and Boom Raise Operation

When the boom is raised while swinging, the pilot

oil pressure shifts the swing, boom 1, and boom 2

spools.

Pressure oil from pump 1 flows into the boom cyl-

inders via the parallel circuit and the boom 1 spool,

raising the boom.

Pressure oil from pump 2 flows into the swing mo-

tor via the swing spool.

At the same time, pressure oil from pump 2 flows

through the parallel circuit and after being com-

bined with pressure oil from pump 1, f lows into the

boom cylinders, raising the boom together withpressure oil from pump 1.

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T2-2-17

T178-02-02-002

Swing Motor

Boom Cylinder

ParallelCircuit

Boom 1

Swing

Pump 2 Pump 1

Boom 2

Parallel Circuit

ANIMATION

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T2-2-18

Travel and Arm Roll-In Operation

When the arm is rolled in while traveling, the pilot

oil pressure shifts the travel, arm 1 and 2 spools.

At the same time, the right travel pilot oil pressure

shifts the flow combiner valve control spool in the

signal control valve. Pressure oil from the flow

combiner valve control spoolis routed to the flow

combiner valve, shifting the flow combiner valve.

Pressure oil from pump 1 drives the right travel

motor via the right travel spool.

At the same time,pressure oil from pump 1

passes through the flow combiner valve and the

left travel spool and drives the left travel motor.

Pressure oil from pump 2 flows into the arm cylin-

der via the arm 1 spool, moving the arm.

Consequently, pressure oil from pump 2 is used

only to operate the arm. Pressure oil pump 1 is

equally routed to both the right and left travel mo-

tors, ensuring that the machine can travel straight.

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T2-2-19

T178-02-02-003

Travel Motor (Right)Pilot Pressure

Oil from FlowCombiner ValveControl Spool inSignal ControlValve

RightTravel

4-Spool Side5-Spool Side

Pump 2 Pump 1

Arm 1

LeftTravel

Arm Cylinder

Travel Motor (Left)

ANIMATION

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T2-2-20

Auxiliary Circuit

When a front attachment such as a hydraulic

breaker is operated, the pilot pressure oil from the

hydraulic breaker pilot valve shifts the auxiliary

flow combiner valve and bypass shut-out valve.

Therefore, the neutral circuit in the 4-spool control

valve is blocked so that pressure oil from pump1

is routed to the auxiliary spool via the auxiliary

flow combiner valve.

NOTE: During boom (raise or lower), arm (roll-in or

rollout), bucket (roll-in or rollout), and/or

right travel operation, pilot pressure oil isrouted to port SN from the signal pilot pres-

sure control valve so that the aux. flow

combiner valve is not shifted. (Refer to the

SYSTEM / Control System group.)

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T2-2-21

T178-02-02-004

Pilot Oil Pressurefrom HydraulicBreaker Pilot Valve

Auxil iary Flow Com-bining Solenoid Valve

Auxil iary

Pump 2 Pump 1

FrontAttachment

BypassCut Valve

NeutralCircuit

Pilot Pressure fromSignal Control Valve

SMSN

Auxil iary FlowCombiner Valve

ANIMATION

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T2-2-22

(Blank)

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SYSTEM / Electrical System

T2-3-1

OUTLINE

The electrical circuit is broadly divided into the main

circuit, monitor circuit, and control circuit.

Main Circuit The engine and accessory operation related circuit.

Monitor Circuit The electrical circuit group consists of the monitors,

sensors, and switches, and displays the machine

operation status.

Control Circuit (Refer to the SYSTEM / ControlSystem group.)

The control circuit is categorized into the engine,

pump, and valve control circuits. Each circuitconsists of the actuators such as solenoid valves,

MC (main controller), switch boxes, sensors and

pressure switches.

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T2-3-2

MAIN CIRCUIT

The major functions and circuits in the main circuit are

as follows.

Electric Power Circuit: Supplies all electric power

to all electrical systems on this machine. [Key

Switch, Batteries, Fuses (Fuse Boxes, Fusible

Links), Battery Relay]

Indicator Light Check Circuit

Checks all indicator bulbs for burning.

Accessory Circuit

Becomes operative when the key switch is turned

to the ACC position.

Preheat Circuit

Assists the engine to start in cold weather. [Key

Switch, QOS Controller, Coolant Switch, Glow

Plug Relay, Glow Plugs]

Starting Circuit

Starts the engine. [Key Switch, Starter, Starter

Relay]

Charging Circuit

Charges the batteries. [Alternator, Regulator]

Serge Voltage Prevention Circuit

Prevents the occurrence of serge voltage

developed when stopping the engine. [Load

Damp Relay]

Engine Stop Circuit

Stops the engine using the EC motor. [MC, EC

Motor]

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T2-3-3

ELECTRIC POWER CIRCUIT (KEYSWITCH: OFF)

The battery ground terminal is connected to the vehicle

frame. Current from the battery plus terminal flows asshown below when the key switch is OFF.

T178-02-03-001

Battery

Glow Plug Relay

Power

Key Switch (B)

Load Damp Relay

Fuse Box

Fusible Link

Terminal #1: Radio (Backup Power)

Monitor (Backup Power)

ICX Controller (Backup Power)

Terminal #2: MC (Power)

Terminal #3: MC (EC Motor Power)Terminal #10: Optional

LoadDampRelay

MC

MC

Radio, Monitor,ICX Controller

Optional

GlowPlugRelay

Battery

Key Switch

ANIMATION

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T2-3-4

INDICATOR LIGHT CHECK CIRCUIT (KEYSWITCH: ON)

When the key switch is turned ON, terminal B is

connected to terminals ACC and M in the keyswitch.

Current from key switch terminal M excites the

battery relay.

Therefore, the battery current enters the monitor

controller via the battery relay and fuse #6 and

checks the indicator bulbs.

T178-02-03-002

FuseBox

Battery

Relay

Key Switch

Battery

MonitorController

ANIMATION

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T2-3-5

ACCESSORY CIRCUIT

When the key switch is turned to the ACC position,

terminal B is connected to terminal ACC in the key

switch.

Current from key switch terminal ACC flows to

horn (fuse #14), radio (fuse #15), lighter (fuse

#16), cab light (fuse #17) and auxiliary (fuse #18)

through the fuse box, making each accessory

operable.

T178-02-03-003

Cab Light

Lighter

Auxil iary

Radio

Horn

FuseBox

ANIMATION

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T2-3-6

PREHEAT CIRCUIT (KEY SWITCH: ON /START)

When the key switch is turned ON or to the

START position, terminal B is connected toterminal M in the key switch. Current from

terminal M is routed to QOS controller terminal #1

through fuse #19.

When the key switch is ON or in the START

position with the coolant switch OFF (when the

coolant temperature is 10 C (50 F) or below),

QOS controller terminal #4 is connected to

terminal #5 (ground).

Accordingly, the glow plug relay is turned ON,

routing current to the glow plugs so thatpreheating begins.

When preheating begins, QOS controller terminal

#6 is connected to terminal #5 for 8 seconds,

turning the preheat indicator ON. (When

preheating is not performed, the preheat indicator

comes ON for 2 seconds for indicator light check.)

NOTE: After preheating has been performed,

heating will continue for approx. 30

seconds after the engine starts.

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T2-3-7

T178-02-03-004

QOSController

Glow Plug

FuseBox

GlowPlugRelay

Preheat Indicator

Monitor

Key Switch

Coolant Temperature Switch

ANIMATION

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T2-3-8

STARTING CIRCUIT (KEY SWITCH:START)

When the key switch is turned to the START

position, terminal B is connected to terminals Mand ST in the key switch.

As current from terminal M excites the battery

relay, battery current is routed to starter terminal B

and starter relay terminal B via the battery relay.

Key switch terminal ST is connected to starter

relay terminal S so that current flows through the

starter relay coil.

Then, the starter relay is turned ON, allowing

current to flow from starter relay terminal C tostarter terminal C.

Consequently, the relay in the starter is turned ON

so that the starter begins rotating.

On the other hand, current from key switch

terminal M flows to the MC via fuse #6 as a signal

indicating that the key switch is in the ON or

START position.

As soon as the MC receives this signal, the MC

drives the EC motor, moving the governor lever to

the engine start position.

Starter Relay Operation

When the key switch is turned to the STARTposition, key switch terminal B is connected to

terminal ST so that current is routed to the base in

transistor (Q2) through resistance R4 in the

starter relay. Then, transistor (Q2) is turned ON,

allowing current to flow to coil (L) in the starter

relay. Therefore, starter terminal B is connected to

terminal C, rotating the starter.

After the engine starts, the alternator starts

generating electricity, increasing voltage at starter

relay terminal R.

When this voltage increases up to 21 to 22 V,

Zener diode (Z) is turned ON so that transistor

(Q1) is turned ON. Then, current to the base of

transistor (Q2) is not routed, turning transistor

(Q2) OFF. At this moment, starter terminal B is

disconnected from terminal C, stopping the

starter.

Condenser C1 is used to stabilize the operating

voltage and diode D4 protects the circuit in case the

battery terminals are reversely connected.

T107-04-04-003

To AlternatorTerminal L

Starter Relay

Starter

Key Switch

Battery

ANIMATION

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T2-3-9

T178-02-03-005

FuseBox

BatteryRelay

MC

EC Motor

Starter Relay

C

C

Starter

Battery

Key Switch

ANIMATION

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T2-3-10

CHARGING CIRCUIT (KEY SWITCH: ON)

After the engine starts and the key switch is

released, the key switch moves to the ON

position.

Then, key switch terminal B is connected to

terminals ACC and M in the key switch.

When the alternator starts generating electricity,

current flows from alternator terminal B to the

batteries via the battery relay, charging the

batteries.

Current from alternator terminal L flows to the

monitor controller and the ICX controller, turning

the alternator indicator OFF.

T178-02-03-006

MonitorController

ICXControllerBattery

Relay

Alternator

Battery

Key Switch

ANIMATION

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T2-3-11

(Blank)

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T2-3-12

Alternator Operation

The alternator consists of field coil FC, stator coil

SC, and diodes D. The regulator consists of

transistors (T1 and T2), Zener diode ZD, and

resistances (R1 and R2).

Alternator terminal B is connected to base B of

transistor T1 through the circuit [B R RF

( R ) (R1)].

When battery relay BS is ON, the battery voltage

is applied to base B of transistor T1 so that

collector C is connected to emitter E. Therefore,

field coil FC is grounded via transistor T1.

At the beginning, no current is flowing through

field coil FC. When the rotor starts turning,

alternate current is generated in stator coil SC by

the rotor remanent magnetism.

When current starts to flow through field coil FC,

the rotor is further magnetized so that the

generating voltage increases. Thereby, current

flowing through field coil FC increases and

generating voltage is increased further, to charge

the batteries.

T157-04-02-008

Regulator

Alternator

Battery

ANIMATION

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T2-3-13

Regulator Operation

When generating voltage increases more than the

set-voltage of Zener diode ZD, current is routed to

base B of transistor T2, connecting collector C to

emitter E.

Then, current which was routed to base B of

transistor disappears, turning transistor T1 OFF.

Therefore, no current flows through filed coil FC,

reducing generating voltage at stator coil SC.

When generating voltage decreases lower than

the set-voltage of Zener diode ZD, transistor T2 is

turned OFF, causing transistor T1 to turn ON

again.

Then, current flows through field coil FC,

increasing generating voltage at the stator coil.

The above operation is repeated so that the

alternator generating voltage is kept constant.

T157-04-02-009

Battery

ANIMATION

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T2-3-14

SERGE VOLTAGE PREVENTION CIRCUIT

When the engine is stopped (key switch: OFF),

current from key switch terminal M is

disconnected, turning the battery relay OFF.

The engine continues to rotate due to inertia force

just after the key switch is turned OFF so that the

alternator continues to generate electricity.

As the generating current cannot flow to the

battery, surge voltage arises in the circuit, possibly

causing failures of the electronic components,

such as the controller. To prevent the occurrence

of surge voltage, the surge voltage prevention

circuit is provided.

When the alternator is generating electricity,

generating current from alternator terminal L flows

to monitor controller terminal #A-2 so that themonitor controller connects terminal #C-3 to

ground.

Then, current flows through the load damp relay

exciting circuit, turning the load damp relay ON.

Accordingly, even if the key switch is turned OFF

while the engine is rotating, the battery current

continues to excite the battery relay via the load

damp relay until the alternator stops generating.

Therefore, the battery relay is kept ON, allowing

the generating current to flow to the batteries.

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T2-3-15

T178-02-03-007

LoadDampRelay

Battery

Relay

Alternator

Battery

Monitor Controller

Key Switch

ANIMATION

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ENGINE STOP CIRCUIT

When the key switch is turned from the ON

position to the OFF position, the signal current

indicating that the key switch is ON stops flowingfrom terminal M to MC terminal C-31.

Then, the MC drives the EC motor to the engine

stop position.

Key Switch

ANIMATION

Date post:	24-Feb-2018
Category:	Documents
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