Hyundai Excavator R450LC-7. Service and repair manual

2-58

TRAVEL MOTOR(1/2)

Rotary group

Hyd section rotary

Cylinder

Control lens

Center pin

Piston

Steel ring

Adjustment shim

Pressure spring

Retainer plate

Screw

Drive shaft

Shim

Back up plate

Retainer ring

Roller bearing

Housing

Retainer ring

Shaft seal ring

Back up plate

O-ring

Locking screw

O-ring

Threaded pin

Seal lock nut

O-ring

450A8TO02

2-59

TRAVEL MOTOR(2/2)

Control part

O-ring

Throttle pin

Valve

Poppet valve

Pressure spring

Seat poppet

Poppet valve

Pressure spring

Locking screw

O-ring

Locking screw

Valve screw

Bushing

Socket screw

Cylinder pin

Locking screw

Port plate

Position piston

Position turnnion

Control bushing

Control piston

Pressure spring

Locking screw

Throttle screw

Brake valve

Brake piston

Locking screw

Pressure spring

Washer

Throttle screw

Throttle pin

Locking screw

O-ring

Brake off pin

Ball

Locking screw

Brake off pin

Locking screw

Pressure control valve

Locking screw

Control piston

Control bushing

Pressure spring

O-ring

Shim

Relief pressure valve

Cap

312

450A8TO03

2-60

REDUCTION GEAR

Washer

Breather plug

Screw

Cover set

O-ring

Pad

Sun gear

Reduction assy(1st)

Sun gear

Reduction assy(2nd)

Screw

Reduction assy(3rd)

Bushing

Sun gear

Housing

Lifetime seal

Hub

Spacer

Brake shaft

O-ring

Brake disc

Steel ring

Back up ring

O-ring

Spiral ring

Piston

Spring

Spacer

Circlip

Flange

O-ring

Screw

Plug

Screw

O-ring

450A8TR01

2-61

2. FUNCTION

HYDRAULIC MOTOR(plug-in motor with intergrated counter balance valve)

The variable displacement motor has a rotary group in bent axis design.
The torque is generated directly at the drive shaft(12).
The cylinder barrel(3) is driven by a tapered piston(6) arrangement.
The change of displacement is generated by the control lens(4) via positioning piston(2). The control
lens(4) slides on a circular shaped surface.

In case of constant pump flow volume and high pressure
- The output speed is increased at smaller swivel angle, the torque is reduced
- The torque rises at swivel angle increase, the output speed is decreased.

The max. swivel angle is 25

。

, the min. swivel angle is 5

。.

The variable displacement motor with integrated counterbalance valve is designed to be operated in
open loop.

The min. displacement is limited by a threaded pin(25) in the housing(18). Min. displacement is set
according to requirement. Stepless adjustment to various higher values is possible.

※

eduction to smaller displacement may result in overspeeding the motor.

450A2TO02

2-62

PORT PLATE
With hydraulic two-speed control, integrated
counterbalance valve and secondary
pressure relief valves, gauge and boosting
ports, control pressure ports, brake release
pressure ports and service ports.

HYDRAULIC TWO-SPEED CONTROL
Operated by control pressure at port X a
4/2 directional valve guides high pressure to
the positioning piston to switch the motor
from min. to max. displacement and vice
versa.

At control pressure 0 bar at port X the motor
is at max. displacement.
At control pressure > 10bar at port X the
motor is at min. displacement.
Intermediate positions are not possible.

The necessary positioning energy is taken
from the respective high pressure side via
shuttle valve. For this an operating
pressure of at least 15bar is necessary.

Swivelling results in a change of the
displacement.
Swivel time is controlled by an orifice.

COUNTERBALANCE VALVE(for traveling)
Integrated into the port plate including a
brake release valve.
In case of downhill traveling or deceleration
of the vehicle a counterbalance valve
avoids overspeeding and cavitation of
hydraulic motors.

FUNCTION AS TO CIRCUIT DIAGRAM
Check valves in the inlet line A and B for by-passing of the counterbalance valve.
At traveling forward the return oil flow is controlled by a counterbalance spool. At drop in inlet
pressure the counterbalance spool throttles the return oil flow. The motor is locked. The oil flow
behind the spool is led to the low pressure side via an additional check valve. Same function for
traveling forward and backward. For limitation of the max. pressure during braking operation two
cross-over relief valves are installed. Cavitation can be prevented via cross-over relief valves
functioning as a check valve. A brake release valve pressurized by one of the inlet pressure sides
via shuttle valve builds up a maximum of 30-50bar to release parking brake. The brake release
valve delays the engagement of parking brake after travelling.

450A2TO03-1

450A2TO03-2

2-65

CROSS SECTION

The construction of the pilot valve is shown in the attached cross section drawing. The casing has
vertical holes in which reducing valves are assembled.
The pressure reducing section is composed of the spool(5), spring(7) for setting secondary pressure,
return spring(10), stopper(9), spring seat(8) and shim(6). The spring for setting the secondary
pressure has been generally so preset that the secondary pressure is 5 to 20.5kgf/cm

(Depending on

the type). The spool is pushed against the push rod(14) by the return spring.
When the push rod is pushed down by tilting the handle, the spring seat comes down simultaneously
and changes setting of the secondary pressure spring.

Case

Plug

O-ring

Spool

Shim

Spring

Spring seat

Stopper

Spring

Plug

Rod seal

O-ring

Push rod

Plate

Bushing

Joint assembly

Swash plate

Adjusting nut

Lock nut

O-ring

Handle connector

Nut

Insert

Boot

Handle

Switch assembly

Screw

Switch assembly

Switch cover

2-67

2. FUNCTIONS

FUNDAMENTAL FUNCTIONS
The pilot valve is a valve that controls the spool stroke, direction, etc of a main control valve. This
function is carried out by providing the spring at one end of the main control valve spool and
applying the output pressure(Secondary pressure) of the pilot valve to the other end.
For this function to be carried out satisfactorily, the pilot valve is composed of the following
elements.

Inlet port(P) where oil is supplied from hydraulic pump.

Output ports(1, 2, 3 & 4) to apply pressure supplied from inlet port to ends of control valve spools.

Tank port(T) necessary to control the above output pressure.

Spool to connect output port to inlet port or tank port.

Mechanical means to control output pressure, including springs that work on the above spools.

FUNCTIONS OF MAJOR SECTIONS
The functions of the spool(5) are to receive the supply oil pressure from the hydraulic pump at its
port P, and to change over oil paths to determine whether the pressure oil of port P is led to output
ports 1, 2, 3 & 4 or the output port pressure oil to tank port T.
The spring(7) works on this spool to determine the output pressure.
The change the deflection of this spring, the push rod(14) is inserted and can slide in the plug(11).
For the purpose of changing the displacement of the push rod through the switch plate(19) and
adjusting nut(20) are provided the handle(27) that can be tilted in any direction around the fulcrum
of the universal joint(18) center.
The spring(10) works on the case(1) and spring seat(8) and tries to return the push rod(14) to the
zero-displacement position irrespective of the output pressure, securing its resetting to the center
position.
This also has the effect of a reaction spring to give appropriate control feeling to the operator.

(1)

(2)

(3)

(4)

(5)

2-72

CROSS SECTION

The construction of the RCV pedal is shown in the below drawing. The casing has vertical holes in
which reducing valves are assembled.
The pressure reducing section is composed of the spool(8), spring(11) for setting secondary
pressure, return spring(18), stopper(13), spring seat(12) and shim(9). The spring for setting the
secondary pressure has been generally so preset that the secondary pressure is 5 to 19 kgf/cm

(depending on the type). The spool is pushed against the push rod(19) by the return spring.
When the push rod is pushed down by tilting pedal, the spring seat comes down simultaneously
and changes setting of the secondary pressure spring.

Casing

Pedal

Pedal cover

Cover

Bushing

Cam

Bellows

Spool

Shim

Spring seat

Spring

Spring seat

Stopper

Plug

O-ring

Dust seal

Rod seal

Spring

Push rod

Hexagon socket bolt

Set screw

Nut

Cam shaft

Set screw

Hexagon socket bolt

Plug

Spacer

O-ring

Hexagon socket bolt

Plug

9, 10

2-74 (210-7)

2-73

2. FUNCTION

FUNDAMENTAL FUNCTIONS
The pilot valve is a valve controls the spool stroke, direction, etc of a main control valve. This
function is carried out by providing the spring at one end of the main control valve spool and
applying the output pressure(Secondary pressure) of the pilot valve to the other end.
For this function to be carried out satisfactorily, the pilot valve is composed of the following
elements.

Inlet port(P) where oil is supplied from hydraulic pump.

Output port(1, 2, 3 & 4) to apply pressure supplied from inlet port to ends of control valve spools.

Tank port(T) necessary to control the above output pressure.

Spool to connect output port to inlet port tank port.

Mechanical means to control output pressure, including springs that work on the above spools.

FUNCTIONS OF MAJOR SECTIONS
The functions of the spool(8) are to receive the supply oil pressure from the hydraulic pump at its
port P, and to change over oil paths to determine whether the pressure oil of port P is led to output
ports 1, 2, 3 & 4 or the output spool to determine the output pressure.
The spring(11) works on this spool to determine the output pressure.
The change the deflection of this spring, the push rod(19) is inserted and can slide in the plug(14).
For the purpose of changing th displacement of the push rod through the cam(6) and adjusting
nut(22) are provided the pedal(2) that can be tilted in any direction around the fulcrum of the cam(6)
center.
The spring(18) works on the casing(1) and spring seat(12) and tries to return the push rod(19) to
the zero-displacement position irrespective of the output pressure, securing its resetting to the
center position.
This also has the effect of a reaction spring to give appropriate control feeling to the operator.

(1)

(2)

(3)

(4)

(5)

Hyundai Excavator R450LC-7. Service and repair manual - page 9