Hydraulic Pump

1. Structure and Functions

The main pump is a kind of energy conversion device, and it converts the mechanical energy
transmitted from the engine into the hydraulic energy, provides the hydraulic system with pressure
oil of certain flow rate, to drive the hydraulic cylinder and the hydraulic motor, as the power
source for the entire hydraulic system.
Variable Pump: It is a pump able for self adjustment of flow rate according to the load of the drive
device, and the flow of the variable pump is generally increased or decreased along with the load
of the drive device.
Pilot Pump: It is a fixed displacement gear pump, controls the signal oil circuit for operation of the
excavator, and at the same time plays the auxiliary function for control over the main oil circuit.

Pz2 Rear Pump Governor Control Port A2 Rear Pump Output Port
Pi1 Front Pump Negative Flow Control Port A1 Front Pump Output Port
Dr Oil Drain Outlet A3 Pilot Pump Output Port
B3 Pilot Pump Oil Inlet

10-H-1
2. Specification/Model

Main Pump Pilot Pump

Max. Displacement 97.6×2ml 15 ml
Rated Speed 2100 min-¹
Pressure 31.4 MPa 3.9 MPa
Max. Flow Rate 205×2 L/min 31.5 L/min
Max. Output Power 145 PS (including Pilot Pump 4.2)
Max. Output Torque 49.5 kgm (including Gear Pump 1.5)
Pump Model T5V112DP-11DR-HN9C

10-H-2
3. Main Pump
(1) External Structure

1 Swashplate Min. Angle Adjusting Screw 2 Piston 3 Swashplate 4 Drive Shaft 5 Piston Slipper
6 Front Pump Housing 7 Swashplate Max. Angle Adjusting Screw 8 Port Plate 9 Pilot Pump

10-H-3
Attached Table

S/N Name Qty S/N Name Qty

Drive Shaft 1 Oil Seal 1
111 774
Drive Shaft 1 Oil Seal 1
123 Roller Bearing 2 824 Snap Spring 2
127 Bearing Pad 2 808 Hexagonal Nut 2
Oil Seal Cover 1 886 Spring Pin 2
261
Oil Seal Cover 1 953 Set Screw 2
Hexagonal Socket
401 8 988 Support Subassembly 2
Bolt
Hexagonal Socket
406 4 251 Support Block 2
Bolt
710 O-Ring 2 409 Plug 8
717 O-Ring 2

10-H-4
10-H-5
Attached Table

S/N Name Qty S/N Name Qty

Spline Connecting
1 732 O-Ring 2
114 Sleeve
Gear 1 1 789 Support Ring 2
124 Needle Roller Bearing 2 792 Support Ring 2
153 9-Hole Plate 2 981 Piston Assembly 18
156 Spherical Bushing 2 151 Piston 18
157 Cylinder Block Spring 18 152 Slipper 18
211 Slipper Plate 2 982 Swashplate Assembly 2
271 Pump Housing 2 212 Swashplate 2
467 VP Plug 3 214 Swashplate Bushing 2
Swashplate Pin
532 Servo Piston 2 983 2
Subassembly
534 Baffle Block L 2 548 Feedback Pin 2

535 2 531 Swashplate Pin 2

Baffle Block S
Cylinder Block
702 O-Ring 2 984 1
Assembly
728 O-Ring 3 141 Cylinder Block 1
313 Port Plate 1

10-H-6
10-H-7
Attached Table

S/N Name Qty S/N Name Qty

113 Drive Shaft 1 885 Pin 2
124 Needle Roller Bearing 2 886 Spring Pin 2
271 Pump Housing 2 901 Suspension Ring Bolt 2
Valve Body 1 954 Limit Screw 2
312 Valve Body 1 41 One-Way Valve 2
Valve Body 1 42 One-Way Valve 2
Valve Block
325 1 541 Baffle Seat 2
(Electronic)
Hexagonal Socket
407 3 543 Baffle Block 1 2
Bolt
VP Plug 2 544 Baffle Block 2 2
466
VP Plug 2 545 Steel Ball 4
Electromagnetic
490 Plug 8 1
Proportional Valve
969
Electromagnetic
717 O-Ring 2 1
Proportional Valve
Cylinder Block
724 O-Ring 16 985 1
Assembly
O-Ring 2 141 Cylinder Block 1
725
O-Ring 2 314 Port Plate 1
808 Hexagonal Socket Nut 2

10-H-8
(2) Operating Principle The swashplate part is composed of swashplate
(212), slipper plate (211), swashplate seat
The structure of the main pump is the (251), swashplate bushing (214), swashplate
connection of the front pump and the rear pump pin (531), and servo piston (532), etc. The
through the spline joint (114), and the drive circular arc part on the reverse face of the
shaft of the gear pump is connected onto the slipper sliding face is supported on the
inner spline of the drive shaft (R) (113). The swashplate seat, to control the hydraulic oil
rotation of the engine output shaft is transmitted through throttle adjustment, and to guide the
onto the drive shaft (F) (111) of the front pump, pressure into the hydraulic oil cavities on the
for the two pumps and one gear pump to be two sides of the servo piston, able to left and
simultaneously driven. The suction and output right move the servo piston, to actuate the slide
ports of hydraulic oil are on the connecting part of swashplate on the swashplate seat through
of the two pumps, namely on the valve body the swashplate pin installed on the servo piston
(312), while the suction port is shared by the to change the tip angle (α).
front pump and the rear pump. The structure
and the operating principle of the front/rear The valve cover part is composed of valve body
pumps are the same, and only the front pump is (312), port plate (313), and port plate pin (885).
described below. The port plate for two circular arc oil ports are
installed on the valve body, and its function is
This pump is divided into three parts: the to provide and recover the hydraulic oil to and
rotating body part for rotating movement, the from the cylinder block, and the hydraulic oil
swashplate part for change in output flow rate, converted through port plate is connected to the
and the valve cover part for changeover of external pipeline through the valve body.
suction and output directions. Additionally, the drive shaft is driven by
The rotating body part is composed of drive engine, and the cylinder block connected
shaft (111), cylinder block (141), piston-slipper through the spline rotates at the same time. As
(151, 152), nine-hole plate (153), spherical the swashplate is inclined, at the same time
bushing (156), retainer ring (158), and cylinder when the piston inside the cylinder block
block spring (157). The two ends of the drive rotates together with the cylinder, it makes
shaft are supported by bearings (123, 124). The reciprocating linear movement relative to the
slipper is forged on the piston to for the cylinder block. If only one piston is taken into
spherical contact, to relieve the impact brought consideration, when the cylinder block rotates
by load pressure, and the slipper plate (211) is for one circle, the piston rotates for 180°from
able for steady slide to form the hydraulic the direction away from the port plate (stroke of
balance, designed with buffer zone-shaped the sucked hydraulic oil), and then rotates for
position. The spherical bushing is mounted 180° in the direction close to the port plate
between the piston-slipper assembly and the (stroke of the output hydraulic oil). If the
nine-hole plate, pressed on the slipper plate swashplate is not inclined (in the situation when
through cylinder block spring, thus to be able dip angle is located at 0°), then the piston has
for the piston-slipper assembly to steadily slide no stroke, and will not output the hydraulic oil.
on the slipper plate. Similarly the cylinder
block is also pressed on the port plate (314)
through the cylinder block spring.

10-H-9
 Swashplate Axial Piston Pump Operating Principle
1 -0 Swashplate 2- Cylinder Block 3 – Piston 4 – Port Plate 5 – Drive Shaft

10-H-10
4. Governor
(1) Structure

10-H-11
10-H-12
10-H-13
Attached Table

Part Part Part Part

Part Name Part Name Part Name Part Name
No No No No
Adjusting
925 734 O-Ring 646 Guide Spring 622 Piston Sleeve
Bolt (QI)
Hexagonal
Socket Adjusting Adjusting
924 733 O-Ring 645 621
Retaining Ring (Q) Piston
Screw
Spring Seat Adjusting
898 Pin 732 O-Ring 644 615
(Q) Plug
Negative
897 Pin 730 O-Ring 643 Flow Control 614 Center Plug
Valve Stem
Drive
887 Pin 728 O-Ring 641 Guide Cap 613 Connecting
Rod (2)

Pf Drive
875 Pin 725 O-Ring 631 612 Connecting
Slide Cover Rod (1)
Feedback
874 Pin 724 O-Ring 630 Lock Nut 611
Rod Block
858 Lock Ring 722 O-Ring 629 Cover (C) 601 Housing
Retainer Adjusting
836 708 O-Ring 628 496 Plug
Ring Bolt (C)
Hexagonal
Retainer Adjusting
814 656 Blind Plate 627 438 Socket Bleed
Ring Ring (C)
Screw
Hexagonal
Hexagonal
801 655 Spring 626 Inner Spring 436 Socket Bleed
Nut
Screw
Hexagonal
763 O-Ring 654 Return Spring 625 Outer Spring 413 Socket Bleed
Screw
Hexagonal
Spring Seat
756 O-Ring 653 Spring Seat 624 412 Socket Bleed
(C)
Screw
Adjusting
755 O-Ring 652 Busing 623
Lifter
735 O-Ring 651 Slide Block

10-H-14
(2) Position of Negative Flow Adjusting Device

Adjusting Device Installation Position

Negative Flow Governor Device

1. Front Pump 2. Rear Pump 3. Pilot Pump 4. p1 Governor Pump 5. p2 Governor Pump
6. EPPR Valve 7, 8 Min. Flow Adjusting Screw 9. Max. Flow Adjusting Screw
Pi1, or Pi2 governs the first-in oil circuit at the maximum or minimum flow rate (connected with
the main control valve).

10-H-15
(3) Governor Functions

The governor device is the device for changing

Main Pump Flow Rate Q

the swashplate tip angle to control the main pump Maximum
flow rate, and it includes the following three kinds
of operation:
Firstly. When operation is not actuated for the
excavator, as circulation of working oil is not
required, the main pump flow rate is governed to
the minimum to save the energy.
Secondly, after operation is actuated, in order to Minimum
get the quickest speed, the main pump flow rate is
governed to the maximum.
Thirdly, when operation is actuated, the main
pump flow rate is reduced after relatively large
Negative Flow Control Pressure pi
load is met, and the main pump flow rate is
increased after relatively small load is
encountered, to avoid engine from being
overloaded.
Negative Flow Control Mode
It is a mode not through the hydraulic actuating
device, with main pump – main valve – oil tank as
the circulating circuit, and it is also known as the
“negative flow rate control”, as the flow is small
when return oil pressure is high, and the flow is
large when the return oil pressure is low.

1) Negative Flow Control B-B

When the control valve is located on the median state, the main pump output flow is minimized,
while the output flow is maximized when operation is actuated.

Delivery Increase Delivery Decrease

Negative Flow Control B-B
10 Flow Conversion Characteristic 11 Lock Nut 31 Max. Flow Control Spring
20 Flow Max. Control Screw

10-H-16
Flow Changing Characteristic Adjustment

Main Pump Flow Rate Q

Adjusting Screw (10): Adjusting the inflection
point for increase or decrease in flow rate

Negative Flow Control Pressure pi

2) Power Control A-A:

Adjust the main pump flow rate, along with the size of the load for the actuating device, to avoid
the engine from being overloaded.

Delivery Increase Delivery Decrease

Negative Flow Control A-A
1, 2 Power Adjusting Screw 3. Power Adjusting Spring 4. Power Adjusting Spring
5, 6 Lock Nut

10-H-17
When cylinder or motor and other hydraulic devices are under the load effect, the methods for
adjusting the inflection point for change in main pump pressure are as follows:
Main Pump Flow Q

Main Pump Flow Q

Main Pump Pressure Main Pump Pressure

Power Adjusting Screw (2) Power Adjusting Screw (1)

3) Operating Principle for Negative Flow Control Governor Device:

Mid-Position State Adjusting Device Flow Decrease

1. Negative Flow Control Valve Step 2. Servo Piston 3. Power Control Valve Stem
4. Servo Valve Core 5, 6 One-Way Valve 7 Swashplate
8. Electromagnetic Proportional Pressure Relief Valve
① Operation for Decrease in Flow Rate
When all the control valves are under the median state, the working oil of the main pump P1 flows
to the main control valve, at the same time the one-way valve (5) is opened, and the working oil
enters into the oil circuit connected with this.
The working oil pressure on the PR side at the right side of the servo piston pushes the servo
piston leftwards, and the swashplate dip angle (7) is increased.

10-H-18
The working oil pressure transmitted to the servo valve core (4) is disconnected here as the oil
circuit is not through.
The pressure entering into the power control valve stem (3) pushes the servo valve core (4)
rightwards, however, as the main pump P1 pressure is low, the acting area of the power control
valve stem is small, the thrust force is relatively small, and there is no way to push the servo valve
core (4). On that account, the output flow is the largest under the acting force of the main pump at
PR. However, when the main control valve transmits the pressure signal to pi1, and the pressure of
pi1 is acted on the negative flow control valve (1), it pushes the servo valve core (4) rightwards,
and the pressure disconnected on the servo valve core (4) is transmitted onto the PL side of the
servo piston (2).
PR and PL pressures exist on the both sides of the servo piston (2), and the pressure values are the
same, but the acting area of PL is larger than the acting area of PR, and therefore the servo piston
moves rightwards. Consequently the servo piston (2) will decrease the dip angle of the swashplate
(7), and reduce the flow rate of the main pump. When all the control valves are under the median
state, the pressure of pi1 is the largest, and the main pump P1 outputs the minimum flow rate.
When governor device is under the median state, the main pump flow rate is reduced according to
the following ways.

Reduce the inclination

When pi pressure is transmitted
The pi pressure pushes the negative flow control valve stem (1) rightwards, and at this point the
pin D connected with the negative flow control valve stem is also pushed rightwards, while the
link L1 fixed by the pin turns rightwards with A as the axle center.
After the link L1 turns rightwards, the pin C in contact with the hole H1 also moves rightwards,
while the feedback link connected with the pin C moves rightwards.
The feedback link L2 turns with the pin E as the axle center, and therefore after L2 turns
rightwards, the servo valve core (3) connected with the pin B is also pulled rightwards.
After the servo valve core (3) is moved rightwards, the working oil pressure of the P1 pump may
be transmitted to the PL side of the servo piston.

10-H-19
When the action of the P1 pump working oil pressure exists on the PL side, the servo piston turns
the dip angle of the swashplate to be small, and therefore the flow rate of the main pump is
decreased. When pi pressure is the largest, the corresponding flow rate of the main pump is the
smallest.
② Operation for Increase in Flow Rate

Swashplate Dip Angle Decrease

When it is on mid-position state Governor Device Flow Rate Increase
When operation is actuated for the excavator, the working oil of the main pump is distributed by
the main control valve to the hydraulic drive device, and therefore the oil return pressure pi of the
central bypass oil circuit disappears. Consequently, the pressure to push the negative flow control
valve stem (1) vanishes, while the servo valve core (4) is pushed to move leftwards by the return
spring, and the working oil of PL flows to the oil tank. However, the supply of the working oil for
PR is continued, the servo piston (2) moves leftwards, the dip angle of the swashplate (7) is
increased, and the flow rate of P1 is enlarged.

The output flow of the main pump may change

Main Pump Flow Rate Q

within the changing range of the swashplate dip

angle, and the changing rule is in inverse
proportion to the pi pressure as indicated in the
right figure. After the pi pressure is increased to
the set value, the main pump flow rate will
maintain a maximum value.

Pressure pi

10-H-20
When there is no pi pressure or the pressure is reduced (when pi pressure is smaller than the force
of the spring S1), the governor device achieves the increase in flow rate for the main pump as
follows.
The working oil of the main pump is fully or partly supplied to the hydraulic devices, the pi
pressure is small enough for the spring S1 to push the negative flow control valve stem (1)
leftwards, while the pin D connected with the negative flow control valve stem (1) pushes the link
L1 leftwards, and the link L1 rotates leftwards as indicated by the arrow in the figure below, with
pin A as the axle center.

Max. inclination

Flow Rate Increase Operation of Governor Device: Pi Pressure Decrease

No more acting force will be generated for the pin C in contact with the hole H1 wall face after the
link L1 turns leftwards. The pin C is connected with the link L2, and therefore the link L2 is no
longer subjected to the leftward thrust force, while the servo valve core (3) is not be pulled any
longer. The valve core (3) is pulled leftwards by the spring S2, the working oil of the main pump
P1 is no longer connected with the servo piston PL, and the working oil on the PL side flows back
to the oil tank.
Though the pressure on the PL side disappears, the action of the P1 pressure still exists on the PR
side. On that account, the servo piston moves leftwards, and the pin (6) pulls the swashplate (7)
leftwards, for the dip angle to be increased, and the flow rate of the main pump to be enlarged.

10-H-21
③Operation for Decrease in Flow when
Overloaded
The force stressed when the output flow rate
of the main pump is the largest is transmitted
to all the oil circuits through A1.
The working oil through A1 opens the
one-way valve (5) to transmit the pressure to
the power control valve stem (3), and the
power control valve step (3) pushes the servo
valve core (4) rightwards after the spring is
compressed, to open the oil circuit to the PL
side, so that the working oil enters into the PL
side, to push the servo piston rightwards.
At this point, the pressures of PL and PR are
the same, but the acting area on the PL side is
larger than the acting area on the PR side, and
on that account the servo piston (2) moves
rightwards, for the swashplate dip angle to be
diminished, and the flow rate of the main
pump P1 to be decreased.

When the main pump outputs the maximum flow Flow Rate Decreased under Load Effect

10-H-22
The governor device achieves decrease in flow rate under the overloaded state in the following
modes.

Operation for Achieving Decrease in Flow Rate, when Overloaded

Under the overloaded state, the pressures of the main pumps P1 and P2 rise, the pressure is
transmitted to the power control valve stem (1) to push the piston (2) rightwards, to compress the
springs S1 and S2.
After the piston (2) is moved, the pin D installed on the piston hole moves rightwards, and as the
piston D is connected with the link L1, the link L1 turns rightwards with pin A as the axle center.
After the link L1 turns rightwards, the pin C connected with the hole H1 on the link L1 also moves
rightwards.
The link L2 rotates with the pin E as the axle center, and therefore the servo valve core (3)
connected with the pin B is also pulled rightwards after L2 turns rightwards.
After the servo valve core (3) moves rightwards, the working oil pressure of the P1 pump may be
transmitted to the PL side of the servo piston. At this point, the pressures of PL and PR are the
same, but the acting area of the PL side is larger than the acting area of the PR side, and therefore
the servo piston (2) moves rightwards, for the swashplate dip angle to be diminished, and the flow
rate of the main pump P1 to be decreased.

10-H-23
The operation of governor device for increase in flow rate after load relief is given as follows.

Increase Dip
Angle
Operation for Achieving Increase in Flow Rate after Overload Relief
When the loaded state for the main pumps P1 and P2 is relieved, the pressure is reduced and
transmitted to the power control valve stem (1). As there is no pressure acting on the piston (2),
the springs S1 and S2 push the piston (2) leftwards. At this point, the pin D embedded on the
piston (2) moves leftwards as well. Further because the pin D is connected with the link L1, the
link L1 turns leftwards around the pin A.
After the link L1 turns leftwards, the acting force for pushing the pin C disappears, thus the acting
force for pushing the link L2 vanishes as well, and the servo valve core (4) connected with the link
L2 and the pin B is no more subjected to the rightward pulling force. At this point, the servo valve
core (4) is pulled leftwards by the spring S3. After the servo valve core (4) moves leftwards, the
oil circuit between the PL side of the servo piston and the main pump P1 is shut off, the working
oil of PL flows back to the oil tank, but oil supply from the main pump P1 is still lasting. On that
account the servo piston moves leftwards, for the swashplate dip angle to be diminished, and the
flow rate of the main pump is enlarged.

10-H-24
④ Flow Rate Adjustment for Electromagnetic Proportional Pressure Relief Valve

When ERRP valve is closed When EPPR valve is opened

After the electromagnetic proportional pressure relief valve works, the pilot oil pressure of PSV
enters into the power control valve stem (3), and pushes the servo valve core (4) after the spring is
compressed, while the oil circuit on the PL side is connected with the oil circuit of the main pump
P1. The pressure of the main pump P1 is transmitted to the PL side, and pushes the servo piston (2)
rightwards, for the dip angle of the swashplate (7) to be diminished, and the flow rate of the main
pump to be decreased.
Main Pump Governor Operating Schematic Diagram

1. Power Control Valve Stem 2. Servo Valve Core 3. Negative Flow Control Valve Stem
4. Drive Connecting Rod 5. Servo Piston

10-H-25
(4) Adjustment of Governor

This governor is able to adjust the maximum flow

Flow Rate Q
rate, minimum flow rate, power control
characteristic, flow control characteristic, and
maximum flow rate stage 2 control characteristic.
1) Adjustment of Maximum Flow Rate
Loosen the hexagonal nut (808), to make
adjustment in the mode of tightening (or
loosening the adjusting screw (954). Tighten the
adjusting screw, and then the output flow rate is
decreased. Other control characteristics remain
unchanged, while only the maximum flow rate is
changed.
Negative Feedback Pressure Pi

Flow Rate Q
2) Adjustment of Minimum Flow Rate
Loosen the hexagonal nut (808), and make
adjustment in the mode of tightening (or
loosening the hexagonal bleed screw (953).
Tighten the hexagonal bleed screw, and then the
flow rate is increased. Similar to the adjustment of
the maximum flow rate, the other characteristics
remain unchanged. If it is tightened too much,
then during the maximum output pressure
(pressure relief), the required power will be
increased, to which attention shall be paid.

Negative Feedback Pressure Pi

3) Adjustment of Output Power

This governor has the full power control mode,
and therefore when power setup is changed, it is
required to make adjustment for the same amounts
to the adjusting screws of the front pump and the
rear pump. The pressure changing value of the
adjustment is the value when the pressure of the
two pumps is raised simultaneously. If only one
pump is subjected to the load, then the adjusted
pressure changing value is two times that of the
load changing value.

10-H-26
① Adjustment of Outer Spring

Loosen the fastening nut (630), and make

Flow Rate Q
adjustment through the mode of tightening (or
loosening) the adjusting screw (628). If the
adjusting screw is tightened, as indicated in the
figure below, for getting away from the control line
graph, the input power is increased. If the adjusting
screw is tightened, then the control pressure is
increased, while the input power will be increased.
If the adjusting screw (628) is rotated for N circles,
then the set value of the inner spring will be
changed as well, and therefore the adjusting screw
(925) shall be rotated in the reverse direction.

Outlet Pressure P1+P2

② Adjustment of Inner Spring

Loosen the hexagonal nut (801), and make Flow Rate Q
adjustment through the mode of tightening (or
loosening) the adjusting screw (925). If the
adjusting screw is tightened, as indicated in the
figure below, the flow rate is increased, and the
power required by the pump is increased as well.
Therefore, if the adjusting screw (925) is tightened,
the output flow rate is increased, and then the
output power is increased likewise.

Outlet Pressure P1+P2

4-4. Adjustment of Flow Control Characteristic

Flow Rate Q

Loosen the hexagonal nut (801), and make

adjustment through the mode of tightening (or
loosening) the hexagonal socket adjusting screw
(924). The hexagonal screw is tightened as
indicated in the figure below. The control
characteristic curve moves rightwards, and the
output flow rate is then increased.

Outlet Pressure P1+P2

10-H-27
4. Pilot Pump
(1) Structure and Function
The pilot pump is the fixed displacement gear pump. It controls the signal oil circuit for the
operation of the excavator, and at the same time plays the auxiliary function for control over the
main oil circuit.

Attached Table

S/N Name S/N Name S/N Name

307 Ejector Pin 353 Drive Gear 466 Plug
308 Block Seat 354 Driven Gear 700 Washer
309 Retainer Ring 355 Filter Gauze 710 O-Ring
310 Spring 361 Front Housing 725 O-Ring
Hexagonal Socket
311 Tightening Bolt 433 732 O-Ring
Bolt
Hexagonal Socket
312 Lock Nut 434 850 Snap Spring
Bolt
Hexagonal Socket
351 Gear Housing 435
Bolt

10-H-28
Operating Principle

The operating principle of the gear pump is

shown in the right figure. When gear rotates
according to the graphic direction, the gear of
the right-side oil suction chamber is gradually
disengaged, and the sealed working chamber
is gradually enlarged, to form the vacuum. On
that account, the oil fluid in the oil tank enters
into the oil suction chamber through the oil
suction pipe, under the effect of the
atmospheric pressure, to fill up the tooth
grooves, and rotates along with the gear, to
bring the oil fluid into the left-side pressure oil
chamber. As the gears in the left-side pressure
oil chamber are engaged, the sealed working
chamber is gradually diminished, the oil fluid
between the teeth are extruded out, to output
through the oil outlet of the pump. The oil Pilot Pump Operating Principle Sketch
suction chamber and the pressure oil chamber
are separated by the mutually engaged gears
and the end covers on the two sides.

10-H-29
Main Control Valve
1. Structure and Function
The main control valve is to divert the high-pressure oil exported from the main pump, as required
by the action of the working device, thus to achieve different operations of the working device.
The excavator generally has six basic operations including the movable arm operation, bucket rod
operation, bucket operation, rotary operation, left travel operation, and right travel operation. The
abovementioned six types of basic operation all have their corresponding control valves, and the
main control valve is the part used to pool these control valves together.
Additionally, the main control valve has the standby valve, and therefore the conventional
excavator main control valve has totally seven kinds of control valves. (Generally the movable
arm operation and the bucket rod operation are of the confluent control, and on that account there
will be two more control valves, and one main control vale has totally nine valve stems in
general.).
Bucket Movable Right
Rod 2 Arm 1 Bucket Standby Travel

Bucket Movable Rotary Left Linear

Rod 1 Arm 2 Travel Travel

10-H-30
Main Valve Left Side:
Main Valve Oil Inlet
One-Way Valve
Linear Travel
Isolating Valve
Linear Travel
Valve
One-Way
Throttle Valve
One-Way
Valve
One-Way
Main Valve
Pressure One-Way
Relief Valve
Valve

Bucket Rod
Holding Valve
Bottom Pressure
Bucket Confluent
Relief Valve
Isolating Valve

10-H-31
Right Side

One-Way Valve
Pg Port

One-Way
Valve

One-Way
Valve
One-Way
Movable Arm Valve
Retention
One-Way
Valve

Throttle
Orifice
Bottom
Pressure
Relief Valve

10-H-32
Code Name Code Name
Pat2 Control Right Travel Valve Stem PAo Control Standby Valve Stem
Control Movable Arm 1 Valve
Pak Control Bucket Valve Stem PAb1
Stem
PAa2 Control Bucket Rod 2 Valve Stem PAa1 Control Bucket Rod 1 Valve Stem
pAb2 Control Movable Arm 2 Valve Stem PAs Control Rotary Valve Stem
PAtl Control Left Travel Valve Stem Pg Port Connected to Py Pressure Switch
p1, p2 Main Valve Oil Inlet Pg Port Connected to Px Pressure Switch

10-H-33
Internal Structure

1. Return Oil Circuit 2. Parallel Oil Circuit 3. Central Bypass Oil Circuit
4. Return Oil Circuit 5. Signal Oil Circuit

10-H-34
2. Main Valve Specification/Model AV280

1 Rated Pressure 34.3MPa (360kg/cm2)

2 Rate Flow Rate 280 L/min
3 Safety Valve Adjusting Range 5.88 ~ 35.3MPa (60～360kg/cm2)
4 Overload Valve Adjusting Range 5.88 ~ 39.2MPa (60～400kg/cm2)
5 Pilot Pressure 4.9MPa (50kg/cm2) MAX.
6 Back Pressure 0.98MPa (10kg/cm2) /PEAK 1.47MPa (15kg/cm2)
7 Valve Core Stroke 10mm
8 Valve Stem Leakage 60 ml/min Max. at 14.7MPa (150kg/cm2)
9 Holding Leakage 3.0ml/min Max. at 14.7MPa (150kg/cm2)
10 Hydraulic Oil Type Mineral Oil
11 Hydraulic Oil Temperature Range -20 ~ +90℃
12 Weight 180 kg

10-H-35
3. Bucket Circuit
(1) Mid-Position State

2. One-Way Valve 3,4. Oil Port Pressure Relief Valve 5. Valve Core 6. Valve Body 7,8. Cover
9. Spring Holder 10,11. Spring 12. Spring Limit

The working oil of the bucket oil circuit is independently supplied by the P2 pump of the main
pumps P1 and P2 during outward tipping operation, and supplied in confluence by P1 and P2
during inward retraction. When the bucket pilot control valve is located under the median state,
the working oil of the P2 pump returns to the oil tank through the central bypass oil circuit of the
bucket valve core (3).

10-H-36
(2) Excavation Circuit

Pull the pilot control valve according to the graphic direction as indicated in the above figure, the
pilot oil pushes the bucket valve core (3) leftwards, after entering into the b oil circuit, and the
working oil of the main pump P2 and the oil circuit B are connected. The working oil of the main
pump P2 enters into the cylinder Bc-side chamber after the one-way valve (2) is ejected open, to
push the piston rod to stretch out, so as to achieve the bucket inward retracting action, and the
corresponding Ac-side working oil returns to the oil tank after it flows out through the channel of
the valve core (3). At this point the maximum acting force able to be played during bucket inward
retraction is the bucket digging force, and the size of the bucket digging force depends on the
setting of the pressure spring for the main pressure relief valve (20). When the stressed load
during bucket excavation is larger than the set spring force of the main pressure relief valve (20),
there is no way for bucket to retract inwards, and the working oil of the P2 pump returns to the oil
tank after the main pressure relief valve (20) is opened, to protect the hydraulic system, while the
rising pressure signal is transmitted to the main pump governor device to reduce the main pump
flow rate.

10-H-37
(3) Outward Tip Circuit

Pull the bucket pilot control valve in the direction as indicated in the above figure, the pilot oil
pushes the bucket valve core (3), after entering into the a oil circuit, and the working oil of the
main pump P2 and the oil circuit A are connected. The working oil of the main pump P2 enters
into the Ac-side piston rod chamber after the one-way valve (2) is ejected open, for the piston rod
to retract, to achieve the bucket outward tipping action, and the corresponding Bc-side working oil
returns to the oil tank, through the channel of the valve core (3). When the stressed load during
bucket outward tipping operation is larger than the set pressure of the main pressure relief valve
(20), there is no way for bucket to act, and the working oil of the P2 pump returns to the oil tank
after the main pressure relief valve (20) is opened, to protect the hydraulic system, while the rising
pressure signal is transmitted to the main pump governor device to reduce the main pump flow
rate.

10-H-38
4. Bucket Rod Oil Circuit
(1) Mid-Position State

Bucket Rod Holding Valve: 1. Valve Core 2.Spring 3. Slide Block

4. Housing 5. Cone Valve
Bucket Selector Valve: 6. One-Way Valve 7. Valve Core 8,9 Return Oil Channel
10. Housing 11,13. Oil Port Pressure Relief Valve
12,14. Makeup Valve
If the control handle is maintained on the mid position, and the placement position of the bucket
rod is suspended half in the air, as indicated in the above figure, the bucket rod is stressed to the
action of the force in descending direction, due to the gravity influence of the working device.
At this point the working oil of the cylinder Bc is subjected to the gravity action, the pressure
keeps rising, and this pressure:
Is transmitted to the pressure relief valve (11), to be disconnected.
Is transmitted to the makeup valve (12), to be disconnected.
At the same time the P1-side working oil is connected with the channel of the slide block (3) and
the valve core (1) to be transmitted to PU, to push the cone valve (5A) downwards, to keep closed.
(Under the condition when pressures are the same, the side of larger area has bigger acting force.).
At the same time the working oil of Bc is cut off by the return oil circuit, the cylinder has no way
to move, and the bucket rod remains under the suspended state.

10-H-39
10-H-40
(2) Inward Retraction Circuit

Bucket Rod Holding Valve: 1. Valve Core 2. Spring 3. Slide Block 4. Housing
5. Cone Valve
Bucket Rod Selector Valve: 6. One-Way Valve 7. Valve Core 8, 9 Oil Return Channel
10. Housing 11,13. Oil Port Pressure Relief Valve
12,14. Makeup Valve
Operate the control handle, to perform the bucket rod retracting action, the pilot working oil flows
to al, and takes the following actions:
Push the bucket rod valve core (7) rightwards, to connect the channel of the main pump and the
circuit A. The main pump working oil (P) enters into Ac, through the channel A, the bucket rod
cylinder stretches out, to take the retracting action.
The al working oil pushes the bucket rod holding valve core (1) leftwards at the same time, to
connect the PU circuit and the return oil circuit, and the PU working oil returns to the oil tank,
thereby to close the cone valve (5) for the pressure to be relieved. The bucket rod cylinder begins
to act, the working oil flows to PL, to open the cone valve (5), and flows to the oil tank through
the bucket rod selector valve core (7).

10-H-41
10-H-42
(3) Outward Tip Circuit

Bucket Rod Holding Valve: 1. Valve Core 2. Spring 3. Slide Block 4. Housing
5. Cone Valve
Bucket Rod Selector Valve: 6. One-Way Valve 7. Valve Core 8, 9 Oil Return Channel
10. Housing 11, 13. Oil Port Pressure Relief Valve
12, 14. Makeup Valve
Operate the control handle, to perform the bucket rod outward swinging action, the pilot working
oil flows to b2, and takes the following actions:
Push the bucket rod valve core (7) leftwards, and open the channel for entry of the main pump (P)
working oil.
The working oil passing through the bucket rod valve core (7) ejects open the cone valve (5), and
flows to B through PL. When the cone valve (5) is opened, the PU-end working oil takes
confluent action with the circuit B through the cone valve (5) and the slide block (3).
The working oil passing through B enters into the cylinder pipe chamber Bc, to push the piston
downwards, the cylinder retracts, and the bucket rod takes the outward swinging action.
The bucket rod cylinder begins to act, and the working oil flowing from the pipe-free chamber
returns to the oil tank through the bucket rod valve core (7).

10-H-43
10-H-44
(4) Bucket Rod Regeneration Circuit

1) Function of Bucket Rod Regeneration

When oil enters into the pipe-free chamber of the bucket rod cylinder, if insufficient oil supply is
caused by too quick oil entry in pipe-free chamber, the oil of the pipe chamber may be directly
supplied to the pipe-free chamber through the one-way valve, to prevent generation of cavitation
in the digging process for the bucket rod, and at the same time quicken up the excavating speed of
the bucket rod cylinder, so as to improve working efficiency.
2) Principle of Regeneration

When bucket rod digging action is taken, the

oil circuit of main oil inlet is connected with
the bucket rod cylinder pipe-free chamber. In
the meantime, the pressure of the main inlet
oil circuit connected with the cylinder
pipe-free chamber is applied onto the isolating
valve at the A point through the oil circuit. If
the pressure of the bucket rod cylinder
pipe-free chamber is larger than the pressure
of the spring for the isolating valve, the
compression spring of the isolating valve
moves leftwards, and the hydraulic oil of the
bucket rod cylinder pipe chamber is smoothly
connected to the return oil pipeline through the
return oil pipeline.

10-H-45
If the bucket rod retraction is relatively quick,
the main inlet oil is insufficient, and the main
pressure oil port of the bucket rod cylinder
pipe-free chamber will turn to be relatively
low, while the pressure applied onto the
isolating valve of the main valve core will be
reduced, the isolating valve moves rightwards
under the effect of the spring, and the bucket
rod cylinder pipe chamber and the return oil
circuit are disconnected. The hydraulic oil of
the bucket rod cylinder pipe chamber is forced
to pass through the one-way valve inside the
main valve core to flow to the bucket rod
cylinder pipe-free chamber, to prevent the
occurrence of the empty suction with the
bucket rod cylinder pipe-free chamber. This is
namely the principle for bucket rod
regeneration.

5. Movable Arm Circuit

The basic structure and the operating principle of the movable arm circuit are the same as those of
the bucket circuit, but the working oil of the P1 and P2 double pump is used by the movable arm
in combination with the two valve cores at the same time, and the movable arm holding valve is
additionally attached.
(1) Mid-Position State

The movable arm keeps the suspended posture under the median state, and the oil circuit of the
cylinder is shut off by the valve core. The working device and the bucket6 load act on the piston,
and the pressure in the lower part of the piston inside the cylinder rises. The working oil with
pressure raised inside the cylinder will leak from the gap between the movable arm valve core (7)
and the valve body (10) due to the pressure difference, the movable arm will drop slowly.

10-H-46
The movable arm holding valve is located between the cylinder (A) and the movable arm valve
core (7), and it cuts off the oil circuit between the two, to prevent leakage of the working oil on the
cylinder from the area of the valve core.
It may be found when the structure drawing of the movable arm holding valve is carefully
observed that, as the working device and the bucket are under the effect of the gravity, the
working oil pressure generated inside the movable arm cylinder (A) will be transmitted to the
following two oil circuits:
One circuit is to enter into the PL side, to apply upward thrust to the cone valve (5).
The other circuit pushed open the channel between the slide block (3) through the valve core (1)
after entering into the holding valve, and ultimately enters into the PU side in the upper part of the
cone valve (5), to apply the downward thrust to the cone valve (5).
The pressures of PL and PU are the same, and therefore the overall stress direction is from the PU
side with relatively large stressed area, and therefore the oil circuit is closed as pushed downwards
by the cone valve. The oil circuit between the cylinder (A) and the movable arm valve core (7) is
shut off, leakage will no longer happen to the working oil, and the movable arm may remain in the
suspended posture.

10-H-47
(2) Movable Arm Drop

Operate the pilot control valve, to actuate the movable arm dropping action. Pilot Oil of Pilot
Control Valve:
Supplied to the b1 control port, to push the movable arm valve core (7) leftwards, and the working
oil of the main pump P is led to the cylinder piston rod chamber.
The pilot oil supplied to the b2 oil inlet at the same time pushes the movable arm holding valve
core (1) rightwards, to disconnect the channel between PL and PU. The working oil on the PU
side returns to the oil tank, and the pressure drops.
The downward thrust does not exist any longer on the PU side in the upper part of the cone valve
(5), the cone valve is ejected upwards, and the working oil of the cylinder A returns to the oil tank
through the channel of the selector valve.
The symbol represents: Movable Arm Drop
Use the symbol to indicate that the working oil on the PU Side returns, after the pilot oil supplied
by the b2 oil circuit has pushed open the valve core.
The thrust for PU to push the cone valve disappears, and the cone valve opens the oil circuit from
Ac to P.

10-H-48
(3) Movable Arm Lift

Operate the pilot control valve, and actuate the movable arm lifting action. The working oil of the
pilot control valve enters into the left side of the control port for the movable arm selector valve,
and pushes the movable arm valve core (2) rightwards. The working oil of the main pump P opens
the oil circuit of the one-way valve (8) through the movable arm valve core (2) and enters into the
cylinder B chamber through the oil circuit of the movable arm valve core (2).

Movable Arm Priority Valve

It is a device to supply relatively more working oil to the movable arm circuit, when compound
action is taken for arm movement and rotation.
When digging operation is performed, in order to improve operating efficiency, it performs
rotation while the movable arm is lifted, rather than an operation of lifting the movable arm before
rotation. Therefore in order to avoid excessive rotation to touch the edge of the digging pit under
the state when movable arm is not yet highly lifted, it is required to correspondingly increase the
movable arm lifting speed, to supply the movable arm cylinder with relatively more working oil.
When the compound action is taken for the two kinds of actions simultaneously, the device
providing relatively more working oil to one circuit is called the priority valve.
The priority valve for the movable arm speed to be relatively quick is called the movable arm
priority valve.

10-H-49
6. Travel Circuit
The working fluid from respective pumps is supplied to respective travel motors.
Working State
Left Travel Motor

Right Travel Motor

Travel Compound Action

Left Travel Motor

Working State

Right Travel Motor

Function
During the traveling process of the excavator, any one action of either the rotary or the working
device is operated simultaneously, the liner travel valve will play function in either case, to keep
the linear travel of the excavator, or to keep the relative flow rates entering into the two travel
motors remain constant.
Basic Principle:
The working fluid of one pump is supplied to two travel motors. The working fluid of the other
pump is supplied to other actions.

10-H-50
7. Main Pressure Relief Valve
(1) Structure and Function

Main Pressure
Relief Valve

The maximum pressure is set by the main pressure relief valve for the entire hydraulic system
when it is working. When system pressure exceeds the main pressure relief valve set pressure, the
main pressure relief valve is opened, for the hydraulic oil to flow back to the oil tank, to avoid too
high pressure of the oil circuit, so as to protect the entire hydraulic system.

Functional Symbol

Spring
2. Poppet 1. Spr9ing
Poppet

3. Relief Piston

Relief
Piston

10-H-51
(2) Operating Principle
1) Standard State

1. Spring (1) 2. Poppet 3. Relief Piston 4. Oil Return Channel

The main pressure relief valve is installed between the pump port site (P) and the return oil
channel (4). When system pressure P is lower than 31.9MPa (325kg/cm2): the poppet (2) is closed
under the pressure of the spring (1), there is no oil flow in the mini-pore of the relief piston (3),
and the poppet (2) is firmly motionless under the effect of the spring force. At this point the
pressure oils of the system and the channel of the oil tank are cut off, and the system pressure may
be maintained.

2) Pressure Relief State

Oil Return Channel (4)

When system pressure P is higher than 31.9MPa (325kgt/cm2): The poppet (2) overcomes the
force of the spring (1) to be pushed leftwards, oil begins to flow in the mini-pore inside the relief
piston (3). Due to the front and back pressure difference the relief piston (3) is presently pushed
leftwards, the pressure oil returns to the oil tank through the return oil channel, and the system
pressure drops to 31.9MPa (325kg/cm2).

10-H-52
3) Pressure Rise State

Excavating Boost
Signal Oil

Oil Return Channel (4)

When system pressure P is higher than 31.9MPa (325kg/cm²): the poppet (2) overcomes the force
of the spring (1), to be pushed leftwards, oil begins to flow in the mini-pore inside the relief piston
(3). Due to the front and back pressure difference, the relief piston (3) is presently pushed
leftwards, the pressure oil returns to the oil tank through the return oil channel, and the system
pressure drops to 31.9MPa(325kg/ cm²).

10-H-53
8. Secondary Pressure Relief
(1) Structure and Function
It increases the pressure of the hydraulic system within a short time, lasting for about 5-8s. This
function may be used, when large stone or tree root is met during the digging process.
(2) Operating Principle
There is a control push button on the operating handle, and press it to be able to control the
digging boost solenoid valve for the pilot control oil to be connected, as indicated in the figure
below:
Pilot Control Oil

Power
Supply
Excavating Boost Electromagnetic Valve

Control Button

Pilot Oil Pump

10-H-54
9. Safety Suction Valve
(1) Structure and Function
The safety suction valve is installed on each branch oil circuit of the hydraulic actuating devices
(cylinder, or motor).
When cylinder or motor is subjected to the anomalous impact for from the external environment,
anomalously high pressure will be generated inside the cylinder, the safety suction valve is opened,
{assuming that the set pressure is generally 34.3MPa (350kg/cm²)} to relieve the anomalously
high pressure back to the oil tank. In such case, this valve plays the function as a safety valve, to
protect the related hydraulic cylinder and the hydraulic oil pipe.
When negative pressure is generated inside the cylinder, this valve will play the function as an oil
suction valve, to make up the oil from the oil tank pipeline into the negative pressure area, to
avoid formation of vacuum, and generation of cavitation.

Functional Symbol:

Safety Oil Suction Valve

Oil Tank

High-Pressure Oil Area

1. Suction Valve 2. Relief Piston

3. Piston 4. Piston Spring
5. Cone Valve 6. Cone Valve Spring
7. Suction Valve Spring 8. Valve Body
9. Adjusting Screw 10. Lock Nut

10-H-55
(2) Operating Principle
1) Safety Part
When oil pressure in the high-pressure oil area rises to 34.3MPa (350kg/cm²), the cone valve (5)
overcomes the force of the spring (6) to be opened upwards, and the oil of the channel in the
piston (3) begins to flow in a small amount. The front and back pressure difference is generated
with the piston (3) under the effect of throttle orifice, and the relief piston (2), as subjected to the
effect of this pressure difference, overcomes the force of the spring (4) to be opened upwards, for
a large amount of high-pressure oil to be relieved back to the oil tank, to protect the hydraulic
components.
2) Suction Part:
To prevent the generation of cavitation in the hydraulic oil circuit namely the oil pressure in the
negative pressure oil are lower than the pressure of the oil tank, the suction valve (1) above and
below moves upwards due to the difference value of this negative pressure, for the oil of the oil
tank to be made up into this negative pressure area.

3) Normal State

Return Oil

4) Safety Pressure Relief State

Return Oil 1 Suction Valve

2 Relief Piston
3 Piston
4 Piston Spring
5 Cone Valve
6 Cone Valve Spring
7 Oil Suction Valve
Spring
8 Valve Body
9 Adjusting Screw
10 Lock Nut

10-H-56
5) Makeup State

Reverse Direction Load

Return Oil

10-H-57
10. Bottom Pressure Relief Valve

(1) Structure and Function

After engine is started, the pressure oil
exported from the main pump generates
pressure through the throttle orifice of the
bottom pressure relief valve when respective
valve cores are on the mid positions, and the
pressure oil acts onto the flow governor of
each pump when respective valve cores are on
different positions to achieve the appropriate
flow rates.

Bottom Pressure
Relief Valve

(2) Operating Principle

When all the valve cores are on the mid positions, the hydraulic oil of the left pump and the right
pump returns to the oil tank (negative flow control valve) through the bottom pressure relief valve.
At the same time throttle orifice exists on the return oil circuit, and the oil generates pressure
difference through this throttle orifice, and guide the pressure before the throttle orifice to the
pump governor to control the displacement of the pump.

10-H-58
11. Movable Arm Holding Valve
(1) Structure and Function
The movable arm holding valve is used to prevent happening of hydraulic slippage, for it to be
able to still stay in the original place for a relatively long time.

Movable Arm
Holding Valve

When movable arm valve core is under the median state, P has no working oil pressure. However,
pressure is generated after the working oil on the cylinder AC side is subjected to the weight of the
working device and is respectively transmitted to the PL side and the PU side. The PU-side
stressed area is larger than the PL-side stressed area for the cone valve (5), and therefore the cone
valve is wholly stressed rightwards, to disconnect the P and AC oil circuits.

Two-Position Selector Valve: 1-4

1. Valve Core 2. Spring
3. Slide Block 4. Valve Body
5. Cone Valve: Areas of PL Side and PU Side Different
P. Connected with Movable Arm Valve Core
AC. To Oil Circuit of Cylinder
b2. Pilot Oil Circuit: Movable Arm Drop Signal of Pilot Control Valve

10-H-59
(2) Operating Principle
1) Mid-Position State
Under the median state, as the weight of the working device acts onto the upper side of the
one-way valve through valve core, the one-way valve is closed, and the oil inside the cylinder has
no way to flow out, thus the movable arm remains motionless.

10-H-60
2) Drop State
Operate the pilot control valve, and actuate the movable arm dropping action. After the pilot oil of
the pilot control valve opens the valve core, the one-way valve is opened, as the working oil in the
upper part of the one-way valve is sent to the oil tank, and on that account the working oil inside
the cylinder flows out, thus to enable the movable arm to achieve the dropping action.

10-H-61
12. Bucket Rod Holding Valve
(1) Structure and Function
The bucket rod holding valve is installed in the area of the oil port from the main valve to the
bucket rod cylinder small chamber. When the bucket rod control lever is located on the mid
position, this valve prevents the oil of the bucket rod cylinder small chamber from returning to the
oil tank through the bucket rod main valve core, under the effect of the bucket rod deadweight,
and prevents the bucket rod from natural fall.

Bucket Rod
Holding Valve

The bucket valve core is under the median state, and P has no working oil pressure. However, the
working oil on the cylinder AC side generates pressure after it is subjected to the weight of the
working device and is respectively transmitted to the PL side and the PU side. The PU-side
stressed area is larger than the PL-side stressed area for the cone valve (5), and therefore the cone
valve is wholly stressed rightwards, to disconnect the P and AC oil circuits.

Two-Position Selector Valve 1-4

1. Valve Core 2. Spring
3. Slide Block 4. Valve Body
5. Cone Valve: Areas of PL Side and PU Side Different
P. Connected with Bucket Rod Valve Core
AC. To Oil Circuit of Cylinder
b2. Pilot Oil Circuit: Bucket Rod Inward Retraction Signal of Pilot Control Valve
(2) Operating Principle
The operating principle of the bucket rod holding valve is the same as the operating principle of
the movable arm holding valve.

10-H-62
Rotary Motor
1. Structure and Function
Rotary operating handle acts, the high-pressure oil exported from the main pump enters into the A
port or B port of the rotary motor through the rotary main valve core to push the rotation of the
rotary motor, and the rotary movement is made for the rotation of the rotary motor by driving the
top frame of the excavator through the planetary gear speed reduction mechanism.

Oil Inlet B Oil Inlet A Gear Oil Filler

Makeup
Filler

One-Way
Oil Drain Valve

Oil Level
Indicator
Safety
Valve

Time-Delay
Valve

10-H-63
S/N Name S/N Name S/N Name
1 Rotary Motor Housing 17 Brake Piston 35 Time-Delay Valve
2 Oil Seal 18 O-Ring 36 Hexagonal Bolt
3 Roller Bearing 19 O-Ring 37 Pipe Plug
4 Snap Ring 20 Spring 38 O-Ring
5 Drive Shaft 21 Rear Cover 39 Plug
6 Bushing 22 Needle Roller Bearing 40 Plug
7 Brake Ring 23 Valve Needle 41 Plug
8 Valve Needle 24 Port Plate 42 Nameplate
9 Support Plate 27 Hexagonal Bolt 43 Rivet
10 Cylinder Block 28 Plug 44 Vernier Gauge
11 Spring 29 Washer 45 Flange
12 Ball Groove 30 O-Ring 46 O-Ring
13 Returner Plate 31 Spring 47 Plug
14 Piston Assembly 32 One-Way Valve 48 O-Ring
15 Friction Plate 33 Safety Valve 49 O-Ring
16 Clutch Disc 34 Anti-Swing Valve 50 Washer

10-H-64
2. Specification/Model

Model HMFG151-01-VBR
Displacement 151 cc\rev
Rated Flow Rate 215 L/min
Service Pressure 24.5MPa
Output Torque 57.67 N·m
Brake Torque 59 N·m
Brake Release
Min 3.37～Max5.61Mpa
Pressure
Port A Connected with Oil Counterclockwise Rotation
Rotational Direction
Port B Connected with Oil Clockwise Rotation

3. Operating Principle
As indicated in the figure below, the high-pressure oil flows into the cylinder block through the oil
inlet of the port plate (1), to push the movement of the piston from right to left, and at this point
force is generated axially. The force (F) generates the component force F1 vertical to the
swashplate surface to the swashplate (3) through the slipper (2) and the component force F2
vertical to the main shaft. The component force F2 actuates the slipper to move on the swashplate
surface thus to actuate the piston to make the piston movement, and at this point the cylinder block
rotates together with the piston and the guide slipper. Totally nine piston assemblies are installed
inside the cylinder block, and as indicated in the figure below, the high-pressure oil passes through
the nine piston assemblies for a single time through the A oil inlet, and the high-pressure oil
begins to enter into the piston assemblies counterclockwise from the lowest point to push the
cylinder block to work. When the piston assembly rotates to the highest point, it reaches the stroke
limit and the work is completed. However, as pushed by other pistons, it continues to rotate to the
lowest point, to push out the oil from the B port. On this account, rotation of piston for once circle
may be divided into two parts: the work doing stage and the oil returning stage. The flowing
directions of the high-pressure oil are contrary, and the rotating directions of the piston and the
cylinder block are reverse as well.

10-H-65
10-H-66
4. Safety Valve
(1) Structure and Function
The port of oil flowing from the main control valve into the rotary motor is disconnected. When
rotary operation is stopped, due to the rotary inertia with the top frame of the excavator, the oil
pressure at the outlet of the rotary motor is abruptly raised. The high-pressure oil at the outlet
relieves part of the pressure through the safety valve back to the oil tank, to prevent damage of the
motor.

Safety Valve Sectional Schematic Drawing

1. Cone Valve 2. Spring 3. Shim for Adjusting Pressure 4. Spring Seat

5. Piston 6. Bushing 7. Plug 8. Valve Body
O1. Throttle Orifice O2. Throttle Orifice A1, A2, and A3 Pressure Acting Area

(2) Operating Principle

1 Stage 1: When it is on the mid position:
As rotary operation is not started, the cone
valve 1 of the safety valve keeps under the
closed state under the tension of the spring 2.
It may be taken as P=P, not subjected to the
influence of the external force on the flat
ground.

10-H-67
2 Stage 2: When rotary operation is just
begun:
It is required to overcome the rotary torque of
the top frame of the excavator, and the
pressure keeps rising. When the P working oil
pressure rises to the “Spring Force + Pressure
Acted to A2”, the cone valve moves
rightwards, and the working oil returns to the
oil tank through the oil port R. As the pressure
acted on A2 has passed through the throttle
orifice O1, it is smaller than the P pressure.

3 Stage 3: When rotation is continued:

Operate the rotary pilot control valve, and the
pressure at the P oil port rises along with the
operation, while the circuit pressure
overcomes the force of the spring 2 to push the
cone valve 1 rightwards. The high-pressure oil
flows to the R oil port from the P oil port. In
the meantime the pressure acted on A2
through the throttle orifice O1 actuates the
cone valve to move slowly.
At the same time the high-pressure flowing
into the chamber C flows to the right side of
the piston 6 through the throttle orifice 2, and
the acting area is A3, to push the valve core
leftwards, while the spring 2 is compressed in
the meantime, to push the piston 1 leftwards to
close the safety valve. At this point the
pressure in the area of the P port rises, the
rotary motor is under the accelerated state, the
circuit of the return oil tank is shut off, and all
the flows are fully applied to the rotary action.

4 Stage 4: When rotary operation is stopped:

When rotary operation is stopped, the port of
oil flowing from the main control valve into
the rotary motor is disconnected. Due to the
rotary inertia with the top frame of the
excavator, the oil pressure at the outlet of the
rotary motor is abruptly raised. At this point
the pressure P at the corresponding inlet of the
safety valve on the oil circuit rises, and for the
same reason, the P pressure acts on the A1
face, push the cone valve (1) rightwards, while
the working oil inside the gap C is extruded
out through O1, the cone valve moves
rightwards, and the high-pressure oil of the
return oil circuit returns to the oil tank through
the return oil circuit R.

10-H-68
5. Brake Device
(1) Structure and Function
The rotary brake is composed of the friction plate (11), separator plate (12), brake piston (13),
piston seal (14, 15), and spring (16). As all the parts are working in the working oil, the heat
generated by friction may be reduced, known as the wet-type disc brake. In the cylinder block (2)
and the motor housing (1), spline, cylinder block and friction plate (11) are respectively process,
to be connected together, while the motor housing and the separator plate (12) are connected
together. The brake piston presses the separator plate and the friction plate downwards, for the
cylinder block and the motor housing to become as a whole, so that the cylinder block has no way
to rotate.

Rotary Motor Profile Rotary Brake 10 Profile

1. Motor Housing 2. Cylinder Block 3. Piston 5. Time-Delay Valve 17. Rear Cover
18. Pressure Relief Valve 10. Rotary Brake Device 11. Friction Plate 12. Separator Plate
13. Brake Piston 14. Piston Seal 15. Piston Seal 16. Spring

(2) Operating Principle

1) Release Brake
Operate the rotary brake handle, the working
oil of the pilot pump flows to the Pg port, to
eject the brake piston (13) upwards, and at the
same time the spring (16) is compressed, for
the friction plate (11) and the separator plate
(12) to be no more tightly jointed, so that the
cylinder block (3) is able to rotate.

10-H-69
2) Actuate Brake
When the rotary control handle is located on
the mid position, the pilot oil flowing to the Pg
port is cut off, and the spring (16) pushes the
brake piston (13) downwards, to press on the
friction plate (11) and the separator plate (12).
At this point the cylinder block (3) and the
motor housing (1) becomes a whole, and
motor has no way to rotate. The function of
the rotary brake is to absorb the impact when
rotary action is stopped, rather than to control
the stop of rotary action, to mainly play the
function for protecting the motor.
The spring (16) is reset, and pushes the brake
piston, for the working oil that ejects open the
brake piston to return to the oil tank slowly
through the throttle orifice, so that the brake
piston is slowly compacted as well, to be only
able to achieve parking brake in about 5s after
rotation has been stopped. This valve is known
as the time-delay valve.

5. Time-Delay Valve
(1) Structure and Function

Brake Brake
Piston Piston

a. When Brake is Released b. When Brake is Actuated

Time-Delay Valve Profile
1. Valve Seat 2. Valve Core 3. Spring 4. Spring Seat 5. Piston 6. Spring
7. Throttle Valve 8, 9 Plug Pg. Pilot Oil Sh. Working Oil from Shuttle Valve

10-H-70
(2) Operating Principle
1) When Brake is released
Operate the operating control handle, the pilot working oil enters into the sh, to provide the signal
pressure for releasing brake. At this point the spring is compressed, the valve core (2) moves
leftwards, to open the channel of the oil circuit, and the Pg working oil under the cut-off state
flows to the brake piston and release the brake through the opened oil circuit.
2) When Brake is actuated
When the operation control handle is on the mid position, the signal pressure flowing to the sh is
disconnected, the force for pushing open the valve core (2) disappears, the valve core is reset
under the effect of the force of the spring (3), and the Pg return oil circuit of the brake piston is
shut off. At this point, the brake spring compressed by the Pg pressure is reset, to push the brake
piston downwards, the oil fluid slowly returns to the oil tank through the throttle orifice (7) of the
piston (5), and the brake piston is slowly reset.
6. Makeup Valve
(1) Structure and Function
The makeup valve is the one-way valve composed of the cone valve, spring, and other parts. It is
functionally observed that it plays the function for making up the flow rate.

1. Cone Valve 2. Spring 3. Plug

P. Main Pump Flowing to Rotary Motor R. Return Oil Tank

(2) Operating Principle

1) When it is under the median state or the
rotary operation is performed, the
working oil flow to the A side, while the
rotary motor rotates rightwards, and
returns to the oil tank from the B side.
The one-way valve 1A keeps under the
closed state by the pressure A, and the
one-way valve 1B keeps under the closed
state by the pressure B. The safety valves
4A and 4B keep under the closed state
simultaneously.

10-H-71
2) When rotary action is stopped
When rotary control handle is operated back to the mid position, the working oil flowing to A and
the working oil returning to the oil tank from B are cut off by the valve stem of the rotary selector
valve. However, the rotary motor is still able to continue rotation, as indicated in the above figure,
due to the action of the inertia force, the rotary action will continue rotate for 45-60°before it
stops.
During this process the motor turns under the condition when no working oil is supplied on the A
side, and cavitation will appear inside. At this point the working oil inside the return oil circuit R
opens the one-way valve to make up the oil, to eliminate the effect of cavitation.
7. Anti-Swing Valve
(1) Structure and Function
Reverse rotating force exists when rotary motor is stopped, and the function of the anti-swing
valve is to eliminate the reverse force.

2 Anti-Swing Valve (1 Left Side 2 Right Side a Piston b Throttle Valve c Valve Core
d Inside of Valve Core 3 Pressure Relief Valve 4 Makeup Valve

10-H-72
(2) Operating Principle
1) Under the median state, as indicated in the above figure, the pressures of A and B circuits are
the same, and when valve core (d) keeps under the median state, the A-B working oils are
mutually connected.
2) When rotary operation is begun:

The working oil flowing to the circuit A circulates from A to B, and the working oil of the circuit
A pushes the valve core d leftwards through the throttle pore (b1) of the piston (al), to shut off the
circuit between A-B inside the anti-swing valve.
3) When rotary action is stopped: Stage 1:

Operate the pilot control handle back to the mid position, and the circuit A side flowing to the
rotary motor and the circuit B of the return oil tank are both shut off. The motor is still able to
continue rotation due to the inertia.
At this point the working oil on the B side is compressed, and the pressure rises.
The motor rotates under the situation when no working oil is supplied, and cavitation occurs on
the A side. At this point the working oil on the R side opens the makeup valve (41), to make up
the oil. (pressure on circuit A side dropped, and suction force generated)
At this point the high-pressure oil on the circuit B side generates reverse rotary force to the circuit
A side with relatively lower pressure.

10-H-73
The high-pressure state is still kept inside the working oil entering into the anti-swing valve C1 for
failure of timely oil return from the throttle orifice b1, while the low-pressure state is maintained
for the working oil on the other side for failure of timely flow to the cr chamber from the throttle
orifice br.

The pressure of the anti-swing valve cl chamber drops, the working oil of the circuit B flow to the
cr chamber, the pressure rises to push the piston d leftwards, and the working oil of the circuit B
flow to the circuit A.
Presently the pressure difference between the circuit A and the circuit B is reduced, and the acting
force of the motor reverse rotation is eliminated.
5) When rotary action is stopped: Stage 3

The working oil of the circuit B fully flows into the cr chamber, the pressure rises, and at the same
time the pressure of the cl chamber drops, the piston d moves leftwards, to reach the stroke limit.
At this point the circuit B and the circuit A are disconnected. 1-3 process is repeated for 4-5 times,
and the rotary action ends.

10-H-74
Effect of Anti-Swing Valve

10-H-75
2. Rotary Reducer
(1) Structure and Function
The rotary movement is made for the speed reduction mechanism by actuating the planetary gear
through the rotary motor and by driving the top frame of the excavator through its speed reduction
mechanism.

Structure Drawing

10-H-76
Attached Table for Structure Drawing

S/N Name S/N Name S/N Name

1 Motor Assembly 14 Washer 27 Central Gear 1#
2 Gear Motor Housing 15 Planetary Gear 2# 29 Plug
3 Drive Shaft 16 Pin 2# 30 Oil Drain
4 Gasket 17 Spring Pin 31 Oil Filler
5 Bearing 18 Central Gear 2# 32 Vernier Gauge Holder
6 Oil Seal 19 Planetary Gear Carrier 1# 33 Vernier Gauge
7 Bearing 20 Side Plate 1# 34 Protective Cover
8 Thrust Plate 2# 21 Pin 1# 35 Screw Iron Plug
9 Planetary Gear Carrier 22 Needle Roller Bearing 36 Lock Plate
10 Brake Ring 23 Bushing 2# 37 Screw Bolt
11 Gear Ring 24 Planetary Gear 1# 38 Brake Ring
12 Locating Pin 25 Lock Washer 39 Side Plate 2#
13 Planetary Gear 26 Side Plate 3#

(2) Operating Principle

The planetary secondary speed reduction mechanism is applied to the rotary reducer. The
planetary gear is configured in the way of direct transmission, to be exported after the secondary
speed reduction. The operating principle of the planetary gear reducer is firstly described. The
planetary gear reducer is composed of the central gear, planetary gear, cog gear, and the planetary
gear carrier. The planetary gears (24), and (25) are engaged together with the central gears (27),
and (28) and the gear ring (11) as respectively retained by the planetary gear carriers (9) and (29).
The rotation of the central gear (27) is transmitted to the planetary gear (24), and the planetary
gear (24) and the gear ring (11) are engaged together, while the central gear (27) is fixed on the
original position, unable to rotate. Therefore, the planetary gear performs rotation at the same time
during revolution around the central gear, and transmits the torque to the central gear (27) to the
planetary gear carrier (19), thus to achieve the primary speed reduction. The rotation of the
planetary gear (24) is transmitted to the central gear (18), and central gear (18) and the planetary
gear (15) are engaged together, while the gear ring (11) and the planetary gear (15) are engaged
together and transmit the torque of the planetary gear (24) of the central gear to the planetary gear
carrier (9), thus to achieve the secondary speed reduction. The torque direction of the planetary
gear is the same as the direction of the central gear.

10-H-77
Central Rotary Joint
1) Structure and Function
When the main pump located on the top frame of the excavator supplies the oil to the travel motor
located on the bottom frame of the excavator, as the top and the bottom frames take the relative
rotations, it will cause distortion to the hydraulic hose. In order to prevent the occurrence of such
thing, the central rotary joint is installed at the center of the top frame. The central rotary joint is
composed of the housing and the core shaft. The housing is installed on the top frame of the
excavator, while the core shaft is mounted on the bottom frame of the excavator.

Central Rotary Joint

Annular grooves in equal number of the pipelines are opened out on the core shaft, and the
hydraulic oil from the inlet of the housing is supplied to the travel motors on the two sides from
the vertical holes through these oil grooves.
Even if the housing is continuously rotating along with the top frame of the excavator, the grooves
on the core shaft keep unobstructed with the oil ports on the housing, for the hydraulic oil to be
able for entry and exit freely.

10-H-78
 J-Direction Rotation

J-Direction

S/N Name
A Right Side Backward
B Left Side Backward
C Right Side Forward
D Left Side Forward
F Travel Double Speed
G Return Oil Port

10-H-79
Travel Motor
1. Structure and Function
The travel device is composed of the valve unit 1, travel motor 2, and travel reducer 3, and then
for the machine to be able to move forwards or backwards, and to take turn by driving the crawler
belt through the driving wheel.

2. Specification/Model

Model JMV-147/95-01-VBC-R-51
Description Item Unit Spec
Flow Rate L/min 220
Safety Valve Set Pressure (Opening Pressure) Kg/cm2 360(330)
Motor Displacement cc/rev 146.5/95
Motor Output Torque Kgm 76.94/49.9
Motor Speed rpm 1501/2316
Brake Torque Kgm Min. 49
Release Brake Torque Kg/cm 2 11
Back Pressure Kg/cm 2 2
Double Speed Switching Control Pressure Range Kg/cm 2 20～70
Automatic Switching Pressure Kg/cm 2 250～260
Net Weight Kg 335

10-H-80
Reference Items:
1. The abovementioned output torques and the rotating speeds are all the theoretical calculation
values.
2. The displacement of this style of JMV-147/95 series travel speed reduction mechanism may
be adjusted as 98ml (high speed)/170ml (low speed).
3. Exploded View of Parts
(1) Travel Motor
Travel Motor Exploded View 1

10-H-81
Travel Motor Exploded View 2

1 Housing 22 O-Ring 43 Spring Seat 64 Plug

2 Screw Plug 23 Support Ring 44 O-Ring 65 Pin
3 Oil Seal 24 O-Ring 45 Torsional Bolt 66 Pin
Swashplate Pressure Relief
4 25 Support Ring 46 67 Spring
Piston Valve Assembly
5 Piston Seal Ring 26 Throttle (Orifice) 47 Valve Core 68 Spring
6 Shaft 27 O-Ring 48 Guide Sleeve 69 Bearing
7 Bearing 28 O-Ring 49 O-Ring 70 (Port Plate)
Valve Housing
8 Steel Ball 29 50 Support Ring 71 Torsional Bolt
(Motor End Cover)
9 Swashplate 30 Main Valve Stem 51 O-Ring 72 Plug
Piston Cylinder
10 31 One-Way Valve 52 Support Ring 73 Nameplate
Block
11 Spring Seat 32 Spring 53 Retainer Ring 74 Rivet
Sealing
12 Spring 33 Plug 54 Plug 75
Subassembly
13 Limit Plate 34 O-Ring 55 O-Ring 76 Throttle (Orifice)
14 Retainer Ring 35 Spring Seat 56 Spring 77 Gasket
15 Pin 36 Spring 57 Spring Seat
Ball Guide
I16 37 Cover 58 Plug
Holder
17 Installation Plate 38 Spring 59 Valve Stem
18 Piston Assembly 39 Valve Core 60 Throttle (Orifice)
19 Friction Plate 40 Steel Ball 61 Throttle (Orifice)
20 Brake Disc 41 Spring 62 Plug
21 Brake Piston 42 Plug 63 O-Ring

10-H-82
(2) Travel Reducer

1 Motor Assembly 10 Thrust Washer 2 19 Rear Pad 28 Central Gear 2

2 Floating Oil Seal 11 Pin 2 20 Pad 29 Gear
3 Bearing 12 Spring Pin 21 O-Ring 30 Parallel Pin
4 Wheel Hub 13 Planetary Gear 1 22 Plug 31 Coupling
5 Fixed Mount 14 Torsional Bolt 23 Installation Screw
6 Torsional Bolt 15 Thrust Washer 1 24 Planet Carrier 1
7 Spring Pin 16 Needle Roller 1 25 Central Gear 1
8 Planetary Gear 2 17 Pin 1 26 Thrust Ring
9 Needle Roller 2 18 Limit Ring 27 Planet Carrier 2

10-H-83
4. Operating Principle
(1) Rotating Part
As indicated in the figure below: The high-pressure oil flows into the cylinder block through the
oil inlet of the port plate (1), to push the piston to move from right to left, and at this point the
force (F) is generated axially. The force (F) generates the component F1 vertical to the swashplate
surface to the swashplate (3) through the slipper (2) and the component force F2 vertical to the
main shaft. The component force F2 actuates the slipper to move on the swashplate surface thus to
drive the piston to make piston movement, and at this point the cylinder block rotates together
with the piston-guide slipper. Totally nine piston assemblies are installed inside the cylinder
block.
As indicated in the figure below: The high-pressure oil passes through the nine piston assemblies
successively through the A oil inlet, the high-pressure oil begins to enter into the piston assembly
from the highest point clockwise to push the cylinder block to work, and it reaches the stroke limit
when the piston assembly rotates to the lowest point and the work is completed. However, it
continues to rotate to the highest point, as pushed by other pistons, to discharge the oil from the B
port.
It is known from this that the rotation of the piston for one circle is divided into two stages: the
work doing stage and the oil returning stage. The flowing directions of the high-pressure oil are
contrary, and the rotating directions of the piston and the cylinder block are reverse as well.

10-H-84
(2) Operation of Service brake
The Service brake is composed of multi-group friction plates and brake discs, depending on brake
spring to press on the friction plate, thus to play the function of brake. Release of mechanical
brake can only be achieved through motor operating oil pressure.
1) Service brake Releasing Operation
When travel device is operated, the high-pressure oil at the inlet enters into the chamber on the
side of the valve stem through the throttle orifice on the balance valve. After the chamber is filled
up with high-pressure oil, the pressure pushes the balance valve to the other side, so that the
opening on the valve stem allows the high-pressure oil circuit and the brake release oil circuit to
be mutually connected. The high-pressure oil enters into the chamber on the left side of the brake
piston, thus to move the brake piston rightwards to release brake.

10-H-85
2) Service brake Operation
The travel operating lever returns to the median state, and the high-pressure oil at the inlet is cut
off. The high-pressure oil on the side of the balance valve is relieved through the throttle orifice
along with, and the balance valve return to the median state again under the effect is the spring
force, to shut off the brake release oil circuit.
At the same time the brake release chamber is connected with the motor housing through c oil
circuit, and the high-pressure oil is discharged through the housing, thus for the brake piston to
move leftwards to press on the brake disc and friction plate brake motor.

10-H-86
(3) Safety Valve
1) Function of Safety Valve
When the travel operating lever returns to the median state, it shut off the travel oil circuit on the
main control valve, the high-pressure oil on the inlet side is cut off to begin parking, but the motor
continues rotation due to inertia. At this point the pressure of hydraulic oil on the locked outlet
side rises abruptly, for motor to be injured. The function of the safety valve is for the too high
pressure oil to pass the safety valve and flow to the low-pressure side, for motor to be free from
injury.

Safety Valve Set Pressure 360 Kg/cm2

Back Pressure 5 Kg/ cm2
Opening Pressure 330 Kg/c ㎡ (Closing Pressure)

2) During Traveling Start

Safety Valve A
Step 1: Operate the travel control lever, and the RA oil port pressure begins to rise. After the RA
pressure reaches P1³A (the acting face on the left side of the plug) = spring force, the plug
rightward movement is started. The high-pressure oil flows to the RB oil port from the RA
oil port. At the same time the high-pressure oil flows into the chamber 1, through the
throttle orifice 1.

10-H-87
Step 2: The high-pressure oil flowing into the chamber flows into the chamber 2 through the
throttle orifice 2, for the buffer block to move leftwards. When buffer block reaches the
stroke limit, the pressures of the chamber 1 and the chamber 2 rise, and the raised
pressures act on the right-side end face B of the plug. This acting force plus the spring
force will exceed the pressure on the left side of the plug, and the plug is re-plugged.
The pressures of the chamber 1 and the chamber 2 rise along with the pressure at the RA
port, and when the RA port pressure reaches P2³(A－B)=spring force, the plug is
re-pushed open. P2 is also the set pressure of the safety valve.
In summary about the above, the start of the safety valve is divided into two steps. After it
is firstly started for the time being to work at low pressure P1 at the beginning, it is
re-opened at the set pressure, to minimize the stressed impact.

3) During Traveling Operation

Safety Valve B
During travel operation, the RA oil port pressure is high, while the RB oil port pressure is low.
The high-pressure oil at the RA oil port flows into the chamber to be superposed with the spring
force, to push the plug leftwards, to maintain the pressure.

10-H-88
4) During Service brake
Safety Valve B
When travel operation is stopped or it is operated in reverse direction, as RA stops supply of the
high-pressure oil, the RA oil port pressure drops abruptly caused by the inertia force of the frame
of the excavator, and the RB oil port is locked at the same time, for the pressure at the RB oil port
to rise abruptly. At this point the safety valve B is opened, and the high-pressure oil of the RB oil
port flows into the low-pressure RA oil port. (The principle is the same as the opening principle of
the safety valve A during traveling start.)

(4) Balance Valve

Functions of Balance Valve:
It is used to release brake or re-brake the motor.
During downgrade of the complete excavator, it is used to control the flow rate to prevent sudden
downslide.
When the complete excavator is parked on a slope or begins for upgrade, it is used to prevent
slide.
When motor is stopped, it plays the function for making up the oil.

10-H-89
1) During Traveling Start

Operate the travel control lever, for the high-pressure oil to enter into the motor from the A oil
port. The high-pressure oil enters into the left-side chamber through the throttle orifice on the
balance valve. When the pressure inside the chamber rises to high enough, it pushes the balance
valve to move rightwards.
After the balance valve moves rightwards, the opening on the valve core allows the brake release
oil circuit and the high-pressure oil to be mutually connected, to release the mechanical brake of
the motor.
At the same time, the opening b on the balance valve core allows the oil port B and the oil outlet
of the piston cylinder block to be mutually connected.
Under this state, the high-pressure oil from the A port pushes open the one-way valve and turn the
piston cylinder block after entering into the piston cylinder block.
For the same reason, when the control lever is operated in reverse direction, the high-pressure oil
enters from the B port, and oil returns from the A port, while the rotating direction is contrary.

10-H-90
2) During Parking

The travel control lever is reset, and the high-pressure oil entering into the motor A port is cut off.
Though high-pressure oil is not supplied to the motor, the motor will still continue rotation due to
inertia.
At this point the pressure at the A oil inlet drops abruptly, the left-side chamber of the balance
valve is relieved through the throttle orifice, and the balance valve returns to the median state. The
b oil circuit is therefore shut off, and the oil outlet of the piston cylinder block is locked thus to
brake the motor.
In the meantime, the balance valve that has returned to the median state shuts off the a oil circuit,
for the mechanical brake to take action at the same time.
At parking the balance valve activates the mechanical brake while shutting off the oil circuit, thus
to brake the travel motor.

10-H-91
(5) Operation of Motor Speed Regulation
1) At Low Speed (when the angle of the motor swashplate is the largest):
When the double-speed switch electromagnetic valve is not operated, the pilot pressure will not
enter into the motor, and therefore the double-speed switch electromagnetic valve core (47) is
withstood on the right end under the effect of the spring (56).
At the same time, the double-speed switch electromagnetic valve core (47) shuts off the
high-pressure oil from the oil circuit a or b.
The right-side chamber B of the swashplate piston is relieved through the double-speed switch
electromagnetic valve core.

Under the abovementioned condition, it is ensured that motor rotates at low speed under the state
of the maximum swashplate dip angle θ 1

10-H-92
2) At High Speed (when motor swashplate angle is the smallest):
Open the double-speed switch electromagnetic valve, the pilot pressure enters through A, and is
then led to the right side of the valve core through the oil circuit on the double-speed switch
electromagnetic valve core, to push the valve core to move leftwards.
After leftward movement, the opening on the double-speed switch electromagnetic valve (47)
allows the high-pressure oil from a or b to be mutually connected with the chamber B on the right
side of the swashplate piston. The high-pressure oil enters from a during left rotation, while the
high-pressure oil enters from b during right rotation.
After the pressure of the chamber B on the right side of the swashplate piston rises, it passes
through the swashplate piston to push the lower part of the swashplate to move leftwards, for the
swashplate dip angle to be diminished.

Under the abovementioned condition, it is ensured that motor rotates at high speed under the state
of the minimum swashplate dip angle θ 2.

10-H-93
Control Valve
(1) Structure and Function
The control valve is a kind of proportional pressure control valve, installed under the respective
operating handles in the cab. It is able to output pressure oil of corresponding pressure, according
to the stroke size of the handle operated by driver, for the main control valve core to be provided
with corresponding movement, thus to control the action and speed of the working device.

Standard
Oil Port
Right Control Lever Left Control Lever
P From Pilot Pump From Pilot Pump
T To Oil Tank To Oil Tank
1 Bucket Digging Right Rotation
2 Movable Arm Lift Bucket Rod Retraction
3 Bucket Outward Tip Left Rotation
4 Movable Arm Drop Bucket Rod Outward Tip

10-H-94
Drawing of Parts

S/N Part Name S/N Part Name S/N Part Name

1 Housing 12 Limit Block 23 Joint Assembly
2 Screw Plug 13 Spring 24 Swashplate
3 Screw Plug 14 Push Rod 25 Hexagonal Nut
4 O-Ring 15 Spring 26 Push Rod
5 O-Ring 16 Spring Seat 27 Nut
6 Valve Core 17 Limit Block 28 Screw Leather Sleeve
7 Gasket 18 Plug 29 Nut
8 Spring 19 O-Ring 30 Switch Assembly
9 Spring Seat 20 Push Rod Sealing Part 31 Embedded Block
10 Spring 21 Fixed Disk 32 Handle Assembly
11 Retainer Ring 22 Shaft Sleeve 33 Screw

10-H-95
(2) Operating Principle

1) When operating handle is on the mid

position:
The handle is located on the mid position, and
the oil of the main valve pilot oil port A and
Port B is reset through the valve stem 1 and
connected with the oil tank.
The main valve core remains on the mid
position under the effect of the internal spring,
and the working device takes no action.
2) When operating handle acts:
Operate the handle, for the disc (7) to push the
push rod (6) to move downwards, and for the
push rod (6) and the spacer washer (5) as well
as the spring seat (3) as a whole to move
downwards, so that the return spring (4) is
compressed.
The valve stem (1) moves downwards together
with the spacer washer (5), based on the set
force of the balance spring (2).
When the push rod (6) is further pushed down,
the valve stem (1) moves downwards as well
to open the groove area (bA), while the
pressure oil of the oil port P pushes the valve
stem (1) upwards.

When the force of the P port oil pressure reaches the set force of the balance spring (2), the spring
(2) is not compressed, and consequently the valve stem (1) will not move upwards, thus to close
the gap of the area (a), for the groove of the area (b) to remain open, while the pressure oil
exported from the pilot control valve is connected with the pilot oil port A (B) of the main valve.
The main valve core moves rightwards (leftwards).
The oil from the main pump flows to the working device through this valve core, and the working
device begins to act.

3) Control Handle Global Control:

When the control handle is further moved, it then pushes the push rod (6) downwards, and the
valve stem (1) is pushed downwards, for the oil pressure at the oil outlet to rise.
Therefore, when the balance spring (2) is compressed by the push rod (6), its spring force will
increase proportionally along with the increase in the stroke of the push rod.
Thus the pressure at the P port is increased, and the increase in the P port oil pressure offsets the
spring force.
The movement of the main valve core is increased, the flow rate flowing to the working device is
increased, and the working speed of the working device is quickened.

10-H-96
Travel Control Valve
(1) Structure and Function
The travel control valve is also a kind of proportional pressure control valve, and it is able to
output pressure oil of corresponding pressure, according to the stroke size of the travel control
valve operated by driver, for the travel valve core of the main control valve to be provided with
corresponding movement, thus to control the action and the speed of the travel motor.

Oil Port Standard

P From Pilot Pump
T To Oil Tank
1 Left Side Backward
2 Left Side Forward
3 Right Side Backward
4 Right Side Forward

10-H-97
Exploded View of Parts

S/N Name S/N Name S/N Name S/N Name

Valve Core Adjusting
1 Housing III IV-15 O-Ring II-24
Subassembly Screw
2 pedal III-8 Valve Core IV-16 Dust Ring 25 Torsional Bolt
Push Rod
3 Pedal Cover III-9 Gasket IV-17 26 Screw Plug
Sealing Part
Cover Connecting
I III-10 Spring Seat 18 Spring 27
Subassembly Block
Sealing
I-4 Cover III-11 Spring IV-19 Push Rod V
Subassembly
I-5 Bushing III-12 Spring Seat 20 Torsional Bolt V-28 O-Ring
Cam
II III-13 Retainer Ring II-21 Adjusting Screw 29 Torsional Bolt
Subassembly
Push Rod
II-6 Cam IV II-22 Nut 30 Screw Plug
Subassembly
Corrugated
7 IV-14 Plug 23 Camshaft
Leather Sleeve

10-H-98
(2) Operating Principle
1) At Neutral Gear (Corresponding to the A-B Part of the Output Curve Graph)
At the neutral gear, the valve stem (6) shuts the oil port P (input oil port), while the oil port T of
the oil tank is connected to the oil outlet. Thus, the pressure of the oil outlet is the same as the
pressure of the oil tank oil port T.
When control lever is slightly moved from A to B, the push rod (2) and the spring seat (3) move
downwards together, to withstand the return spring (5) and the balance spring (4). At this point, as
the oil pressures in the upper part and the lower part of the valve stem (6) are the same, the valve
stem (6) and the spring seat (3) move downwards together, until the gap (A) is 0.

Output Curve Diagram

10-H-99
2) Operation Corresponding to the C-D Part on the Output Curve Graph
When control lever further moves and pushes the push rod (2) downwards, the lower end of the
valve stem gap is then opened together with the oil port P, and the pilot pump pressure is
connected.
When the pressure applied to the valve stem reaches the set pressure (C), the valve stem (6) will
move upwards, to shut the oil port P. At this point, as the oil port T of the oil tank to the upper part
of the valve stem gap is shut as well, even if the push rod further moves downwards, for the return
spring (5) and the balance spring (4) to be compressed, the valve stem (6) is still unable to move.
The more the balance spring (4) is compressed, the larger the force of the balance spring will be,
and therefore, the output pressure will is increased proportionally according to the increase in the
balance spring force.
When the control lever moves in whole range, the push rod (2) moves downwards, until the spring
seat (3) is in contact with the shoulder of the housing (the terminal end for the stroke of the push
rod), for the valve stem gap to be further opened to the oil port P. The output pressure (pilot
pressure to the control valve) remains at the pilot system pressure (pressure of oil port P).

Output Curve Diagram

10-H-100
Operating Control System

1．Travel Control Lever 2. Foot Valve Pedal 3. Control Handle

4. Boarding Stand 5. Main Control Valve 6. Control Valve 7. Foot Valve

10-H-101
Pilot Valve Unit
(Safety Locking Electromagnetic Valve, Travel Double-Speed Electromagnetic Valve, Pilot Filter
Core, and Accumulator)

1. To Main Valve PG Port 2. To Control Pump Oil Outlet

3. To Oil Return Block on Oil Tank 4. Screw
5. Valve Body 6. To Control Oil Inlet Cross Joint
7. Safety Locking Electromagnetic Valve 8. Travel Double-Speed Electromagnetic Valve
9. To Rotary Joint F Port (Travel Double Speed)

10-H-102
Accumulator

1. Structure and Function

Accumulator is a kind of device for storing the
control oil circuit pressure, installed between
the pilot pump and the control valve. Its
function is to maintain the stability of the
pressure with the control oil circuit, and when
engine is turned off, the working device can
still be put down under the effect of the
gravity, to ensure the machine safety.

Accumulator

There is a bag inside the accumulator, and the

bag is used to isolate the gas charged from the
air plug from the hydraulic oil fluid.
Notice: High-pressure nitrogen is charged
inside the accumulator, and it is quite
dangerous if a wrong method is used for
disposal.
It is not allowable to punch hole or burn with
flame on the accumulator.
It is not allowable to weld any boss on the
accumulator.
When accumulator is disposed, and when it is
required to bleed gas from the accumulator,
please contact the dealers of Strong
Construction Machinery.

2. Operating Principle

After engine is started, the gas in the A

chamber of the bag is subjected to the action
from the pilot pump oil pressure and is under
the compressed state. After engine is stopped,
the gas inside the bag is still located under the
compressed state.
Operate the control valve at this point, the air
bag dilates, depending upon the pressure of
the gas inside the A chamber, the oil in the B
chamber serves as the control pressure oil and
pushes the valve core of the main control
valve, and the working device may be put
down under the effect of its deadweight.

10-H-103
Hydraulic Oil Tank
1 Structure and Function
Hydraulic Oil Tank Assembly

10-H-104
S/N Name Qty S/N Name Qty S/N Name Qty
Hydraulic Oil Fluid Level
1 1 2 1 3 Gasket 2
Tank Gauge
Permanent
4 Hollow Bolt 2 5 3 6 Oil Drain Cap 1
Magnet
7 Washer 12 8 Bolt 12 9 O-Ring 1
Return Oil Filter
10 O-Ring 1 11 Screw Plug 1 12 1
Core
Bypass Filter
13 1 14 Core Shaft 1 15 Valve Seat 1
Gauze
16 Valve Core 1 17 Spring 1 18 Spring Seat 1
19 Nut 1 20 Pin 1 21 Oil Return Spring 1
Return Oil Port Oil Suction Filter
22 O-Ring 1 23 2 24 1
Cap Gauze
Filter Core Oil Suction Oil Suction Port
25 1 26 1 27 1
Pressure Bar Spring Seat

2. Technical Parameters
Hydraulic Oil Tank Oil Capacity: About 250L
Net Weight: 172.67kg

10-H-105
Hydraulic Cylinder
Bucket Cylinder

Tightening Torque:

B-B
Tightening Torque: Direction – C
(Remove Protective Cover)

Tightening Torque:

Cylinder Parameters

Designation Size
Cylinder Bore Ф 115 mm
Pipe Diameter Ф 80 mm
Stroke 1120 mm
Installation Size 1680 mm
Operating Pressure 34.3 Mpa

10-H-106
Bucket Rod Cylinder

Tightening Torque:
Tightening Torque:

Tightening Torque:

Tightening Torque: Tightening Torque:

Cylinder Parameters

Designation Size
Cylinder Bore Ф 135 mm
Pipe Diameter Ф 95 mm
Stroke 1490 mm
Installation Size 2075 mm
Operating Pressure 34.3 Mpa

10-H-107
Movable Arm Cylinder

Left Movable Arm Cylinder

Tightening Torque:

Tightening Torque:

Cylinder Parameters

Designation Size
Cylinder Bore Ф 120 mm
Pipe Diameter Ф 85 mm
Stroke 1285 mm
Installation Size 1875 mm
Operating Pressure 34.3 Mpa

10-H-108
Right Movable Arm Cylinder

Tightening Torque:

Tightening Torque:

Cylinder Parameters

Designation Size
Cylinder Bore Ф 120 mm
Pipe Diameter Ф 85 mm
Stroke 1285 mm
Installation Size 1875 mm
Operating Pressure 34.3 Mpa

10-H-109