980b wheel loader hydra

27/2/2014 980B WHEEL LOADER 89P04784-UP (MACHINE) POWERED BY 3306 ENGINE(SEBP1144 - 00) - Documentación

https://sis.cat.com/sisweb/sisweb/techdoc/techdoc_print_page.jsp?returnurl=/sisweb/sisweb/mediasearch/mediaheaderinfoframeset.jsp&calledpage=/sisweb/si… 1/13

Cerrar SIS

Pantalla anterior

Bienvenido: cr080lcazProducto: WHEEL LOADERModelo: 980B WHEEL LOADER 89PConfiguración: 980B WHEEL LOADER 89P04784-UP (MACHINE)POWERED BY 3306 ENGINE

Operación de Sistemas 980 WHEEL LOADER HYDRAULIC SYSTEMNúmero de medio -REG00801-03 Fecha de publicación -01/11/1978 Fecha de actualización -10/10/2001

Systems Operation

Introduction

NOTE: For Specifications with illustrations, make reference to the SPECIFICATIONS FOR 980B LOADER

HYDRAULIC SYSTEM, Form No. REG01413. If the Specifications given in Form REG01413 are not the same

as given in the Systems Operation and the Testing and Adjusting, look at the printing date on the back cover ofeach book. Use the Specifications given in the book with the latest date.

Loader Hydraulic System



HYDRAULIC SYSTEM (HOLD POSITION)

Tilt And Lift Control Valve

The tilt and lift circuits are arranged in a modified series. Pressure oil is available to the lift circuit only when the tiltvalve is in HOLD position.

The modified series arrangement allows the operator to control the raising and tilting of the bucket by placing the liftcontrol lever in RAISE (locked) position and operating the tilt lever only.

Hold



With both control valves in HOLD position, all cylinder ports are blocked. Oil from the pump flows past the valvesthrough the control valve body to the oil filter. Oil is filtered and returns to the tank. If the filter element becomes

blocked or the oil is extremely viscous due to cold weather, a bypass valve in the filter allows the oil to bypass theelement.

Tilt Back

When the tilt control lever is moved to TILT BACK position, the tilt valve moves into the valve body. Pump flow isdirected to and opens the tilt check valve. The oil is directed to the rod ends of the tilt cylinders, retracting the rods

and tilting the bucket. Oil in the head ends of the tilt cylinders returns through the control valve and filter to the tank.

Dump

When the tilt control lever is moved to the DUMP position, the tilt valve moves outward, and pressure oil isdirected to the head ends of the tilt cylinders. Rods extend out of the cylinders, and bucket dumps. Oil from the rod

ends of the tilt cylinders returns through the valve body, filter, and to the tank.

Raise

When the lift control lever is moved to RAISE position, lift valve is moved out of the valve body. Pressure oil is

directed through the lift check valve to the head ends of the lift cylinders, raising the lift arm and bucket. Oil in therod ends of the lift cylinders flows through the control valve and filter to the tank.

Lower

When the lift valve is moved to LOWER position, the oil flow is directed to the rod ends of the lift cylinders,retracting the rod. Oil from the head ends of the lift cylinders returns through the control valve and filter to the tank.

Float

When the lift valve is in FLOAT position and the tilt valve is in HOLD position, oil from the pump flows past the tiltvalve, but is restricted from flowing to the filter by the position of the lift valve. The rod and head ends of the liftcylinders are open to filter port and to each other; therefore, the pump flow can open the lift check valve and

furnish oil to either rod or head end of the cylinders. This arrangement equalizes the pressure in both ends of the liftcylinders and allows the pistons to operate in either direction, depending upon the external forces on the bucket. As

the pistons move, all excess oil flows to the filter and any make-up oil is supplied by the pump.

Oil Cooler

An air to oil cooler is mounted next to the engine coolant radiator. A portion of the total oil flow from the filter tothe return baffle is diverted through this cooler.



SCHEMATIC OF OIL COOLER CIRCUIT

The baffle contains an orifice valve and spring. Relatively low back pressure of approximately 30 to 60 psi (205 to415 kPa), created by the orifice valve, forces a portion of oil to the cooler.

Maximum cooling will occur at higher engine speeds because of higher oil flow and air flow through the cooler.

Component Location

HYDRAULIC PUMPS



HYDRAULIC TANK

LINE CONNECTIONS TO HYDRAULIC TANK

Main Pressure Relief Valve

The main pressure relief valve limits the pressure imposed on the hydraulic pump and the loader hydraulic circuitwhen a control valve is in an operating position.

The dump valve and the pilot valve are held seated by springs. Pump flow pressure is sensed in the dump valvechambers and at the pilot valve.



MAIN PRESSURE RELIEF VALVE

When the pump flow pressure exceeds the main pressure relief valve setting, the pressure unseats the pilot valve,

and oil flows through the orifice and joins the supply oil in the tank. As the pressure behind the dump valve lowers,the pressure in front of the dump valve forces the dump valve to compress the dump valve spring, allowing fullpump flow through the valve to the tank.

Shims are provided to control the force of the spring on the pilot valve. Adding shims decreases the main pressurerelief valve setting.

Make-up Valves

Make-up valves are held seated by springs and the pressure of the oil in their corresponding cylinder ends. If the

pressure of the oil in any of the hydraulic circuits drops below tank oil pressure, the pressure of the oil in the tankopens the corresponding make-up valve allowing supply oil in the tank to enter the lines and cylinders. When thepressure in the line is approximately equal to the tank oil pressure, a spring reseats the make-up valve.

The make-up valves open to supplement pump flow in the event the cylinders are returning oil to the tank faster

than the pump can supply oil to the cylinders. This prevents a void of oil.

A tilt circuit make-up valve will open when either of the tilt relief valves are opened by excessive pressure and the

tilt control valve is in HOLD position.

Check Valves

The lift and tilt check valves prevent reverse oil flow and resulting cylinder drift. When a control valve is placed inan operating position, the check valve remains seated until the pressure of pump flow is sufficient to overcome the

combined force of the check valve return spring and the pressure of the oil in the selected cylinder ends.

Tilt Circuit Relief Valves

Earlier Machines

The tilt circuit relief valves limit the external pressure imposed on the rod ends and head ends of the tilt hydraulic

cylinders when the tilt valve spool is in HOLD position. Both relief valves operate in the same manner; the reliefvalve on the rod ends will be discussed.



TILT CIRCUIT RELIEF VALVE 1. Shims. 2. Dump valve return springs. 3. Chamber. 4. Piston. 5. Block. 6. Spacer. 7. Return port. 8. Orifices. 9. Port from rod end ofcylinders. 10. Dump valve.

Normally, valve (10) and spacer (6) are held against block (5) by springs (2). The pressure in the rod ends of the

tilt cylinders is sensed in chamber (3) and on piston (4).

When the pressure of the oil in chamber (3) exceeds the tilt circuit relief valve setting, piston (4) and spacer (6) are

forced against dump valve (10). The dump valve compresses springs (12) and opens port (9) to port (7). The oilfrom the rod ends of the tilt cylinders flows through orifices (8), port (7), and joins the supply oil in the tank. This

allows the tilt cylinder pistons to be moved by the external force, preventing damage to the machine components.Orifices (8) are patterned to allow a gradual pressure reduction.

Shims (1) are provided to control the force of springs (2) on dump valve (10). Adding or removing shims adjuststhe tilt circuit relief valve setting.

Later Machines

The tilt circuit relief valves limit the pressure of the oil in the ends of the tilt cylinders when the tilt valve spool is inHOLD position.



TILT CIRCUIT RELIEF VALVE (Valve for Rod Ends Shown) 1. Shims. 2. Springs. 3. Valve. 4. Passage to tank. 5. Shim (not used in valve for head ends). 6. Passage to tank. 7. Passage with tiltcylinder oil pressure.

The relief valve for the head end circuit of the tilt cylinders is set at a lower pressure than the relief valve for the rod

end. Both of the relief valves are the same except shim (5) is used in the relief valve for the rod end and the reliefvalve for the head ends has one spring.

Pressure oil in the circuit for the tilt cylinders is in passage (7) of the relief valve. Pressure oil in the circuit which hasa higher force than springs (2) moves valve (3). Now the oil in passage (7) goes through passages (4) and (6) to

the tank.

Add or remove shims (1) to adjust the relief valve.

Head End (Differential) Relief Valve Operation (6J2782) (Earlier Machines)

This relief valve is similar to the rod end relief valve. The only difference between the two valves is the head end

relief valve has two pistons where the rod end valve has one.



HEAD END (DIFFERENTIAL) RELIEF VALVE

The dump valve and spacer are held against the block by springs. The pressure in the head ends of the tilt cylinders

is sensed in the piston chamber and on the tilt piston. Pressure in the head ends of the lift cylinders is sensedthrough a separate line, connected to a port in the block to the lift piston. Both pistons are the same diameter.

When the sum pressure of oil in the two piston chambers exceeds the valve setting, both pistons and spacer are

forced against the dump valve. The dump valve springs compress and the tilt cylinder port is opened to the returnport. Oil from the head ends of the tilt cylinders flows through the valve orifices and back to the tank. This allows

the lift arm linkage to force the tilt cylinder piston rods into their cylinders as the lift arm is raised.

The relief valve can also be opened by the pressure in the head ends of the tilt cylinders alone if the pressure is

greater than the relief valve setting.

Since the pressure setting of this relief valve is lower than the main pressure relief valve, the tilt circuit relief valve

limits the pressure that can be imposed on the head ends of the tilt circuit when the tilt valve spool is in DUMP

position.

Shims are provided to control the force of the springs on the dump valve. Adding shims decreases the tilt circuit

relief valve setting.

Oil Filter

The hydraulic oil filter is mounted horizontally inside the hydraulic oil supply tank. Oil enters port (15), encircles theelements and is forced through elements (3). The filtered oil then leaves the housing (1) through port (13).

If the filter elements become blocked, or the oil becomes extremely viscous due to cold weather, the oil will bypass

the filter elements by flowing through passages (8) and forcing bypass valve (7) off seat (9).

HYDRAULIC OIL FILTER CONSTRUCTION (6J1443)


https://sis.cat.com/sisweb/sisweb/techdoc/techdoc_print_page.jsp?returnurl=/sisweb/sisweb/mediasearch/mediaheaderinfoframeset.jsp&calledpage=/sisweb/… 10/13

1. Filter housing. 2. Pin. 3. Filter elements. 4. Cotter pin. 5. Retainer. 6. Bypass valve return spring. 7. Bypass valve. 8. Passage(two). 9. Seat. 10. Seat retaining spring. 11. Cover. 12. Bleed plug. 13. Outlet port. 14. Cover and O-ring seal. 15. Inlet port (fromloader hydraulic system). 16. Washer. 17. Cover-to-housing bolt. 18. Gasket. 19. Drain plug. A. Port (inlet pressure). B. Port (outletpressure).

FILTER CHANGE INDICATOR

The filter change indicator assembly is located at the right of the lift and tilt control levers. The ports (C) and (D) of

the indicator assembly are connected to filter housing ports (B) and (A), respectively.

The indicator (21) and piston (25) are magnets which are assembled in body (20) so their north (N) poles are

facing each other. As the filter elements (3) become dirty or blocked, the pressure in the inlet port becomes greaterthan the pressure in the outlet port. When the difference in the two pressures becomes greater than 12 to 15 psi

(85 to 105 kPa), piston (25) moves toward indicator (21). Since like poles repel; the indicator rises.

If the indicator (21) remains up when the engine is running and the oil in the hydraulic tank is at normal operating

temperature, new elements should be installed.

FILTER CHANGE INDICATOR CONSTRUCTION 20. Body. 21. Indicator (magnet). 22. Base. 23. O-ring seal. 24. Piston return spring. 25. Piston. 26. Retaining ring. C. Port (outletpressure). D. Port (inlet pressure).

Bucket Positioner Hydraulic Circuit



BUCKET POSITIONER HYDRAULIC CIRCUIT (SCHEMATIC) (Control valve in HOLD position, bucket slightly dumped frompreselected angle)

The bucket positioner hydraulic circuit automatically returns the tilt circuit valve spool from TILT BACK (locked)

position to HOLD position when the bucket reaches a predetermined digging angle.

Bucket Positioner Circuit Operation

When the bucket is in a dumped position and the tilt control lever is placed in TILT BACK (locked) position the

following events occur:

The cam lever is rotated, moving the tilt control valve into the valve body. At the same time, the cam surface of thelever is moved along the roller until the spring pulls the roller down, locking the tilt control valve in TILT BACK

position. The slave cylinder spool is moved into the slave cylinder body.

In TILT BACK position, pump flow is directed to the rod ends of the tilt cylinders. An oil line joins the oil in the

rod ends of the tilt cylinders to the bucket positioner master valve and is blocked by the position of the mastervalve spool.

As the tilt cylinder rods retract, the cam on the right side tilt cylinder contacts the roller on the master valve. The

master valve spool is moved inward which opens the oil from the rod end of the tilt cylinders to the bucketpositioner slave cylinder in the tank. The oil flows through the passage in the slave cylinder spool to the chamber

behind the slave cylinder spool. The spool is forced outward which raises the roller, unlocking the cam lever. Thetilt control valve centering spring returns the control valve to HOLD position, stopping the bucket at a preset angle.

As the cam lever rotates, the slave cylinder spool is positioned and blocks the flow from the rod ends of the tilt

cylinder.

In DUMP position, the control valve must be held in position by the operator.



Lift Kickout Hydraulic Circuit

LIFT KICKOUT HYDRAULIC CIRCUIT (SCHEMATIC) (Control Valve in HOLD position, bucket slightly lowered frompreselected height)

The lift kickout hydraulic circuit automatically returns the lift circuit valve spool from RAISE (locked) position to

HOLD position when the bucket reaches a predetermined height.

Lift Kickout Circuit Operation

When the lift control lever is pulled back to RAISE (locked) position, the following events occur:

The cam lever is rotated, moving the lift control valve outward. At the same time, the cam surface of the cam lever

is moved along the roller until the spring pulls the roller up, which locks the lift control valve in RAISE position. The

slave cylinder spool is moved into the slave cylinder body.

In RAISE position, pump flow is directed to the head ends of the lift cylinders. An oil line joins the oil in the head

ends of the lift cylinders to the lift kickout master valve and is blocked by the position of the master valve spool.

As the lift cylinder rods extend, the cam connected to the lift arm rotates upward. The cam contacts the roller on

the lift kickout master valve, moving the spool inward. The oil flow from the head ends of the lift cylinders is

directed to the chamber behind the slave cylinder spool. The spool is forced outward, which moves the rollerdown, unlocking the cam lever. The lift control valve centering springs return the control valve to HOLD position,

thereby stopping the lift arms at a preset height. As the cam lever rotates, the slave cylinder spool is positioned so it

blocks the flow from the head ends of the lift cylinders.

The cam assembly can be adjusted to increase or decrease the bucket height position.

In LOWER position, the lift control valve must be held in position.



In FLOAT position, the lift control valve spool is moved into the control valve body and the roller locks the cam

lever and lift valve spool in FLOAT position. However, the control valve must be manually returned to HOLDposition.

Copyright 1993 - 2014 Caterpillar Inc.Todos los derechos reservados.Red privada para licenciados del SIS.

Thu Feb 27 2014 20:43:31 GMT-0500 (Eastern Standard Time)

cr080lcaz