Tab010 - 3W_AC_MIT_Hydraulic Schematic Animation

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Hydraulic Schematic AnimationHydraulic Schematic Animation

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Learning objectiveLearning objective

Learning Objectives:At the completion of this lesson, the student will be able to:

• Given a truck, operate all truck functions using correct safety procedures.

• Identify and explain the function of each hydraulic component.

• Given schematics and training materials, describe the hydraulic system and trace the functional circuits on the truck.

• Using schematics and training materials, find and test all hydraulic test points on the truck.

• Troubleshoot electrical and hydraulic problems in a logical manner

All Registered trademarks herein are the property of their respeAll Registered trademarks herein are the property of their respective owners.ctive owners.The information set forth herein is confidential and is not for The information set forth herein is confidential and is not for distribution beyond MCFS and its distribution beyond MCFS and its authorisedauthorised Mitsubishi Forklift Trucks andMitsubishi Forklift Trucks andMIT MIT ®® Forklift Trucks dealer network.Forklift Trucks dealer network.Copyright Copyright ©© by MCFS. All rights reserved. Reproduction of this material in by MCFS. All rights reserved. Reproduction of this material in any form is Prohibited without written permission of MCFS.any form is Prohibited without written permission of MCFS.

Learning Objectives:At the completion of this lesson, the student will be able to:

Given a truck, operate all truck functions using correct safety procedures.• Identify and explain the function of each hydraulic component.• Given schematics and training materials, describe the hydraulic

system and trace the functional circuits on the truck.• Using schematics and training materials, find and test all hydraulic

test points on the truck.• Troubleshoot electrical and hydraulic problems in a logical manner.

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System Layout for MC typeSystem Layout for MC type

Block Diagram showing all hydraulic components and controls.

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Hydraulic component locationsHydraulic component locations

Pressure Switch

Priority Valve

This valve is located under the LH step.Because this model is a so called “2-motor system” , the traction system is one and the hydraulic system is the other one. The hydraulic system only has one motor and one pump. In the pump has no priority valve. Therefore, an external priority valve is used to give steering priority over mast operation for safety reasons.

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Identifying Hydraulic ComponentsIdentifying Hydraulic Components

Hydraulic Tank

Gear Pump

Control Valve

Flow Regulator

Valve

Down Safety Valve

Lift Cylinders Tilt

Cylinder

Component view from the operator seat1.Hydraulic tank2.Gear pump3.Control valve4.Flow regulator valve5.Down safety valve6.Lift cylinder7.Tilt cylinder8.First lift cylinder (3-stage and 2-stage full-free panorama mast system)

When the lifts lever or Tilt lever is operated, the micro-switches located in the spool of the control valve send signals to the logic card in the main controller. Based on received signals, the logic card drives the pump motor and operates the oil pump.The oil flows from the oil pump to the hydraulic system is the same way as in the engine powered models.

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Identifying Identifying HydHyd. Control Valve Components. Control Valve Components

Lift Valve Ass

Tilt Valve Ass

Att. Valve Ass

End Cover

Pump Port

From Steering Control valve

To Tank

Main Relief Valve

Unload Solenoid Valve

Lift Lock Solenoid Valve

Lift Micro-Switches 1, 2

Tilt Micro-Switches

Att. Micro-Switches

1. Lift valve assembly 9. Unload solenoid valve2. Tilt valve assembly 10. Lift lock solenoid valve3. Attachment valve assembly 11. Tie bolt4. End cover 12. Nut5. Pump port 13. Lift switch 1, 2 (Micro-switch)6. From steering control valve 14. Tilt switch (Micro-switch)7. To tank 15. Att. switch (Micro-switch)8. Main relief valve

The lift valve assembly contains the main relief valve, lift lock solenoid valve and unload solenoid valve. The tilt valve spool contains the tilt lock valve.The micro-switch located on top of the control valve turn ON and OFF according to the spool movement and send lift and tilt signals to the logic card.The lift valve is equipped with two micro-switch for two-step lift speed selection.

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Flow Regulator ValveFlow Regulator Valve

• The flow regulator valve is located between each lift cylinder and control valve.

• It limits the flow of oil forced out of the cylinder to keep a constant safe lowering speed regardless of load when the loaded forks arelowered.

The flow regulator valve is located between each lift cylinder and control valve.It limits the flow of oil forced out of the cylinder to keep a constant safe lowering speed regardless of load when the loaded forks are lowered.

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Down Safety ValveDown Safety Valve

The down safety valve is located at the bottom left of second lift cylinder.

This safety valve regulates the flow of oil to prevent the fork from moving down too quickly in the following situations:

• Hose burnt• Maladjusted of regulator valve• A fault of another component.

The down safety valve is located at the bottom left of second lift cylinder.

This safety valve regulates the flow of oil to prevent the fork from moving down too quickly in the following situations:

• If the piping between the lift cylinder and flow regulator valve is broken, or

• If the flow of return oil from the lift cylinder because excessive due to a maladjusted regulator valve or

• a fault of another component.

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Component Identification

Hydraulic System AnimationHydraulic System Animation

Component IdentificationLeft click mouse• Hydraulic tank and filtersLeft click mouse• Pump motor and hydraulic pumpLeft click mouse• Steering Priority ValveLeft click mouse• Steer Orbitrol UnitLeft click mouse• Steer CylinderLeft click mouse• Steering Pressure Sensing SwitchLeft click mouse• Main Hydraulic Control ValveLeft click mouse• Tilt Cylinders

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Component IdentificationLeft click mouse• Mast Lift Cylinders and Down Safety ValveLeft click mouse• Flow Regulator ValveLeft click mouse• Overload Valves (auxiliary relief cartridges)Standard with truck• Qty 2, P/N 91273-04700 18.1 MPa 2625 PSIOption• Qty 2, P/N 05461-23050 4.9 MPa 710 PSI• Qty 2, P/N 05461-23070 6.9 MPa 1,001 PSI• Qty 2, P/N 05461-23080 7.8 MPa 1,031 PSI• Qty 2, P/N 05461-23100 9.8 MPa 1,421 PSI• Qty 2, P/N 05461-23120 11.8 MPa 1,711 PSI• Qty 2, P/N 05461-23140 13.7 MPa 1,987 PSI• Qty 2, P/N 05461-23160 15.7 MPa 2,277 PSI

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Component IdentificationLeft click mouse• Mast Lift Cylinders and Down Safety ValveLeft click mouse• Flow Regulator Valve

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Pump Running (No Operator Request)

Suction

Pressure

Return


Pump Running (No Operator Request)Left click mouse• Pump Motor is started and oil is drawn from the hydraulic tank. Pressurized oil

is sent to the steering orbitrol but it is at rest and oil flow is stopped. Pilot oil now shifts the steering priority valve envelopes letting oil go the hydraulic valve.

Left click mouse• Oil flows then to the open centered valve, all spools and back to tank.Left click mouse• Note: See circle. The next lines identified are connected to return to tank.Left click mouse• All low pressure lines connected to tank are identified.

Steering Theory will be addressed in Steering Section (Tab 6) in student work book.

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(Lift Request)

Suction

Pressure

Return

(Unloader Solenoid Disabled)


Operator Requests Lift (Unloader Solenoid Disabled)Left click mouse• Operator pulls lift lever back and shifts the envelopes in the lift spool.Left click mouse• Lift switch 1 closes and if the pump motor is turned on. At this moment oil is

being pumped to the lift spool. Then to the lift cylinders.Left click mouse• Seat switch is open. Unloader Solenoid is not enabled and N/O normally open.

This allows the poppet to be pushed open and allows oil to return to tank and no active hydraulic functions.

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(Lift Request)

Suction

Pressure

Return

(Unloader Solenoid Enabled)


Operator Requests LiftLeft click mouse• Operator is in the seat and seat switch is closed the Unloader Solenoid is

enabled and closed. No oil can return to the hydraulic tank through it.Left click mouse• Operator pulls lift lever back and shifts the envelopes in the lift spool.Left click mouse• Lift switch 1 closes and the Pump motor is turned on or if direction switch is

closed pump motor speed is increased to lift speed 1. At this moment oil is being pumped to the lift spool. Then to the lift cylinders.

Note: Pulling the lift lever back further closes lift switch 2 and increases the oil flow to the lift cylinders by increasing pump motor speed. Results are increased lift speed.

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(Lower Request)

Suction

Pressure

Return

(Lift Lock Solenoid Enabled)


Operator Requests LowerLeft click mouse• Operator pushes lift lever forward and shifts the envelopes in the lift spool.• Seat switch is open. Mast Interlock Solenoid is not enabled and N/C normally

closed. This stops the poppet from being pushed open and does not allow oil to return to tank and the mast will lower.

• Seat switch is closed the solenoid is open. This allows the poppet to be pushed open and allows oil to return to tank and the mast will lower.

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(Tilt Forward Request)

Suction

Pressure

Return



Operator Requests Tilt ForwardLeft click mouse• Operator is in the seat and seat switch is closed the operator pushes tilt lever

forward and shifts the envelopes in the tilt spool.Left click mouse• Tilt switch closes and the Pump motor is turned on or if direction switch is

closed pump motor speed is increased to tilt speed. At this moment oil is being pumped to the tilt spool. Then to the piston side of the tilt cylinders. Then back to the “Anticavitation Valve” in the tilt spool.

Left click mouse• Next slide

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(Tilt Forward Request)(Anti Cavitation Valve Enabled)


Tilt Anti Cavitation Valve in Tilt SpoolLeft click mouse• When tilt forward is requested by the operator the tilt lever is pushed forward.

The oil flows through the top envelop tilt spool port.• The pressurized oil comes back into the spool from the ram side of the tilt

cylinders. Since the oil is blocked pressure is applied to a pilot port in the spool.Left click mouse• Pressurized hydraulic oil is forced against the “Anti Cavitation Valve” in the tilt

spool. Because the valve is not open, pressure is applied to the bottom of the moveable anti cavitation spool and against the spring tension. This opens the port to let pressurized oil from the rod side of the tilt cylinders return to tank.

Left click mouse• The rod side oil flow is controlled returning to tank as the restriction will vary

as the pressure to the piston side of the tilt cylinders changes.• This prevents the tilt cylinders from moving faster than the quantity of oil

supplied to the piston end. If this valve is stuck open, the cylinders will acquire an air pocket between the piston and cylinder tube from lack of oil. If this occurs the mast will free fall backwards after tilting back past mast vertical.

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(Tilt Forward Request)

Suction

Pressure

Return



Operator Requests Tilt ForwardLeft click mouse• As the position of the spool and the position of the anticavitation gives the

operator the ability to control tilt speed.• Oil from the ram side of the tilt cylinders returns to tank.

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(Tilt Back Request)

Suction

Pressure

Return


(Tilt Backward Request)(Unloader Solenoid Enabled)


Operator Requests Tilt BackwardLeft click mouse• Operator is in the seat and seat switch is closed the operator pushes tilt lever

forward and shifts the envelopes in the tilt spool.Left click mouse• Tilt switch closes and the Pump motor is turned on or if direction switch is

closed pump motor speed is increased to tilt speed. At this moment oil is being pumped to the tilt spool. Then to the rod side of the tilt cylinders. The oil on the piston side of the tilt cylinder is now returned to tank.

Note: The anticavitation valve is not needed for this function. The amount of oil available at the piston side is much more than the rod side. No possible vacuum bubbles are created during this function do to hydraulic port size..

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(Tilt Back Request)

Suction

Pressure

Return


(1st Aux Request)(Unloader Solenoid Enabled)


Operator Requests 1st Aux FunctionLeft click mouse• Operator is in the seat and seat switch is closed the operator pulls aux lever back

and shifts the envelopes in the 1st aux spool.Left click mouse• 1st aux switch closes and the pump motor is turned on or if direction switch is

closed pump motor speed is increased to 1st aux speed. At this moment oil is being pumped to the 1st aux spool. Then to the attachment cylinders. The oil on the other side of the attachment cylinder is now returned to tank.

Note: This works for the lever pushed forward and the same for the 2nd aux function.

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Hydraulic Control Valve Oil Flow Capabilities

Oil flow is controlled by availability from the Hydraulic Pump and the smallest restriction between the valve and the mechanism to be operated.

Most likely on a Forklift this restriction will be located in the fittings or hose size used to operate a hydraulic device.

The following maximum efficient oil flows are as follows:1/4 “ # 4 hose at 2000 PSI at 20 ft per second = 5.0 GPM3/8 “ # 6 hose at 2000 PSI at 20 ft per second = 10.0 GPM1/2 “ # 8 hose at 2000 PSI at 20 ft per second = 15.0 GPM

Hydraulic Control Valve Oil Flow Capabilities

• Oil flow is controlled by availability from the hydraulic pump and the smallest restriction between the valve and the mechanism to be operated.

• Most likely on a forklift this restriction will be located in the fittings or hose size used to operate a hydraulic device.

The following maximum oil flows are as follows:

• 1/4 “ # 4 hose at 2000 PSI at 20 ft per second = 5.0 GPM



Attachments that are sometimes used require the following oil supply GPM.

• Paper Roll Clamp Arm pressure: Max. 2300 PSI at 10 GPM

• Paper Roll Clamp Rotator pressure: Max 2300 PSI at 15 GPM

• Side Shifter Pressure: Max 2100 PSI at 5 GPM

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Any Questions?Any Questions?

Tab010 - 3W_AC_MIT_Hydraulic Schematic Animation

Documents

hydraulic system

hydraulic problems

hydraulic tank2

hydraulic test points

motor system

truck functions

traction system

oil pump