Danfoss Electrohydraulic Controls Series 51 Service guide

MAKING MODERN LIVING POSSIBLE

Service Manual

Electrohydraulic Controls Series 51

A7, D7, D8, DA, DC, EE, EP, EQ,

ER, ES, L1, L2, L7

powersolutions.danfoss.com

Service Manual	Series 51 Electrohydraulic Proportional Controls Service Manual

Revision history	Table of revisions
	Date	Changed	Rev
	July 2014	Danfoss layout	BA
	July 2009	First edition	AA

2	11009448 • Rev BA • July 2014

Service Manual	Series 51 Electrohydraulic Proportional Controls Service Manual
Contents
Introduction
	Safety Precautions............................................................................................................................................................................	5
	Unintended Machine Movement..........................................................................................................................................	5
	Flammable Cleaning Solvents................................................................................................................................................	5
	Fluid Under Pressure..................................................................................................................................................................	5
	Personal Safety.............................................................................................................................................................................	5
	Hazardous Material.....................................................................................................................................................................	5
	Symbols used in Danfoss literature............................................................................................................................................	6
	Overview..............................................................................................................................................................................................	6
	General Instructions........................................................................................................................................................................	7
	Keep it Clean.................................................................................................................................................................................	7
	Inspect for System Contamination.......................................................................................................................................	7
	Replace the O-rings and Gaskets...........................................................................................................................................	7
	Lubricate all Moving Parts........................................................................................................................................................	7
	Torque Procedure.......................................................................................................................................................................	7
	General Description.........................................................................................................................................................................	7
	Overview........................................................................................................................................................................................	7
	Multifunction Block....................................................................................................................................................................	7
	Pressure Compensating OverRide (PCOR) Option..........................................................................................................	8
	Brake Pressure Defeat (BPD) option.....................................................................................................................................	8
	Threshold and Ramp Springs...............................................................................................................................................	10
Pressure measurements
	Port Locations and Gauge Installation...................................................................................................................................	11
Adjustments
	Threshold Setting...........................................................................................................................................................................	12
	Checking Threshold Setting.................................................................................................................................................	12
	Adjusting Threshold Setting.................................................................................................................................................	12
	Pressure compensator Override (PCOR) setting.................................................................................................................	13
	PCOR Adjustment.....................................................................................................................................................................	13
	Checking PCOR Setting on a Test Stand..........................................................................................................................	14
	Adjusting the PCOR Setting..................................................................................................................................................	14
PCOR
	Optional PCOR Housing Repair.................................................................................................................................................	15
	Disassembly................................................................................................................................................................................	15
	Inspection....................................................................................................................................................................................	15
	Assembly......................................................................................................................................................................................	15
Multifunction block
	Optional Multifunction Block Repair.......................................................................................................................................	17
	Disassembly................................................................................................................................................................................	17
	Inspection....................................................................................................................................................................................	18
	Assembly......................................................................................................................................................................................	18
A7, L1, L2, L7 Controls
	Operation .........................................................................................................................................................................................	19
	General Description.................................................................................................................................................................	19
	Proportional Solenoid.............................................................................................................................................................	19
	Check Valve.................................................................................................................................................................................	19
	Schematic.........................................................................................................................................................................................	21
	Repair..................................................................................................................................................................................................	21
	Removing Solenoid..................................................................................................................................................................	21
	Disassembly................................................................................................................................................................................	21
	Inspection....................................................................................................................................................................................	23
	Assembly......................................................................................................................................................................................	23
	Solenoid Assembly...................................................................................................................................................................	23
D7, D8, DA, DC Controls
	Operation..........................................................................................................................................................................................	24
	General Description.................................................................................................................................................................	24

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Service Manual	Series 51 Electrohydraulic Proportional Controls Service Manual

Contents
Pressure-Reducing Valve.......................................................................................................................................................	24
Schematic.........................................................................................................................................................................................	25
Repair..................................................................................................................................................................................................	26
Disassembly................................................................................................................................................................................	26
Inspection....................................................................................................................................................................................	27
Assembly......................................................................................................................................................................................	27
EE Control
Operation..........................................................................................................................................................................................	29
General Description.................................................................................................................................................................	29
Repair..................................................................................................................................................................................................	30
Disassembly................................................................................................................................................................................	30
Inspection....................................................................................................................................................................................	31
Assembly......................................................................................................................................................................................	31
EP, EQ, ER, ES Controls
Operation..........................................................................................................................................................................................	33
General Description.................................................................................................................................................................	33
Schematics........................................................................................................................................................................................	34
Definitions...................................................................................................................................................................................	35
Repair..................................................................................................................................................................................................	35
Control Housing Disassembly..............................................................................................................................................	35
PCOR Disassembly....................................................................................................................................................................	36
Multifunction Block Disassembly........................................................................................................................................	37
Control Orifices..........................................................................................................................................................................	38
Inspection....................................................................................................................................................................................	39
Multifunction Block Assembly.............................................................................................................................................	39
Inspection....................................................................................................................................................................................	40
PCOR Assembly.........................................................................................................................................................................	40
Control Housing Assembly....................................................................................................................................................	41

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Service Manual	Series 51 Electrohydraulic Proportional Controls Service Manual

Introduction

Safety Precautions

Always consider safety precautions before beginning a service procedure. Protect yourself and others from injury. Take the following general precautions whenever servicing a hydraulic system.

Unintended Machine Movement

W Warning

Unintended movement of the machine or mechanism may cause injury to the technician or bystanders. To protect against unintended movement, secure the machine or disable/disconnect the mechanism while servicing.

Flammable Cleaning Solvents

W Warning

Some cleaning solvents are flammable. To avoid possible fire, do not use cleaning solvents in an area where a source of ignition may be present.

Fluid Under Pressure

W Warning

Escaping hydraulic fluid under pressure can have sufficient force to penetrate your skin causing serious injury and/or infection. This fluid may also be hot enough to cause burns. Use caution when dealing with hydraulic fluid under pressure. Relieve pressure in the system before removing hoses, fittings, gauges, or components. Never use your hand or any other body part to check for leaks in a pressurized line. Seek medical attention immediately if you are cut by hydraulic fluid.

Personal Safety

W Warning

Protect yourself from injury. Use proper safety equipment, including safety glasses, at all times.

Hazardous Material

W Warning

Hydraulic fluid contains hazardous material. Avoid prolonged contact with hydraulic fluid. Always dispose of used hydraulic fluid according to state, and federal environmental regulations.

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Service Manual	Series 51 Electrohydraulic Proportional Controls Service Manual

Introduction

Symbols used in Danfoss literature

WARNING may result in injury	Tip, helpful suggestion
CAUTION may result in damage to product or	Lubricate with hydraulic fluid
property
Reusable part	Apply grease / petroleum jelly
Non-reusable part, use a new part	Apply locking compound
Non-removable item	Inspect for wear or damage
Option - either part may exist	Clean area or part
Superseded - parts are not interchangeable	Be careful not to scratch or damage
Measurement required	Note correct orientation
Flatness specification	Mark orientation for reinstallation
Parallelism specification	Torque specification
External hex head	Press in - press fit
Internal hex head	Pull out with tool – press fit
Torx head	Cover splines with installation sleeve
O-ring boss port	Pressure measurement/gauge location or
	specification

The symbols above appear in the illustrations and text of this manual. They are intended to communicate helpful information at the point where it is most useful to the reader. In most instances, the appearance of the symbol itself denotes its meaning. The legend above defines each symbol and explains its purpose.

Overview

This manual includes information for the installation, maintenance, and minor repair of Series 51 electrohydraulic proportional controls. It includes a description of the unit and its individual components, and minor repair procedures.

Performing minor repairs may require removal of the unit from the vehicle/machine. Thoroughly clean the unit before beginning maintenance, or repair activities. Since dirt and contamination are the greatest enemies of any type of hydraulic equipment, strictly follow cleanliness requirements. This is especially important when changing the system filter and when removing hoses or plumbing.

A worldwide network of Danfoss Global Service Partners is available for major repairs. Danfoss Global Service Partners are trained by the factory and certified on a regular basis. You can locate your nearest Global Service Partner using the distributor locator at www.powersolutionsdanfoss.com. Click on the

Sales and Service link.

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Service Manual	Series 51 Electrohydraulic Proportional Controls Service Manual

Introduction

General Instructions

Keep it Clean

You can complete many repairs or adjustments without removing the unit from the machine, if the unit is accessible and you can thoroughly clean it before beginning any procedures.

Cleanliness is a primary means of assuring satisfactory motor life on either new or repaired units. Clean the outside of the motor thoroughly before disassembly. Take care to avoid contamination of the system ports. Cleaning parts with a clean solvent wash and air drying is usually adequate.

As with any precision equipment, keep all parts free of foreign materials and chemicals. Protect all exposed sealing surfaces and open cavities from damage and foreign material. Cap all hoses after removal, and plug all open ports. Cover any unattended parts with a protective layer of plastic.

Inspect for System Contamination

Inspect the motor for signs of system contamination. If you find contamination, fully disassemble, clean and inspect all components of the motor.

Replace the O-rings and Gaskets

Replace all O-rings and gaskets. Discard them only after you make certain that you have the correct replacement parts. Lightly lubricate all O-rings with clean petroleum jelly before assembly.

Lubricate all Moving Parts

During reassembly, coat all moving parts with a film of clean hydraulic oil. This helps lubricate the surfaces during start-up.

For fluid quality requirements, refer to Hydraulic Fluids and Lubricants, Technical Information 520L0463.

Torque Procedure

During reassembly, cross torque all retaining screws to the given value. Do not overtorque.

General Description

Overview

Electrohydraulic proportional controls infinitely vary motor displacement between maximum and minimum. They do this by shifting the 4-way valve. The spool position shifts with an

•electric pressure-reducing valve. It varies signal pressure on the end of the 4-way valve (D7, D8 controls), or

•electrically varied differential pressure on the ends of a piston connected to the 4 way valve (EP, EQ, ER, ES, ED, EE controls), or

•electric proportional solenoid acting directly on the 4-way valve (A7, L1, L2, L7 controls).

Multifunction Block

Some of the electrohydraulic proportional controls are used in conjunction with the multifunction block. The multifunction block is a manifold with a shuttle valve that routes high loop (system pressure) from port A or B to the 4-way valve while routing the low loop (stystem pressure) to the PCOR valve. The 4-way valve directs this pressure to the ends of the servo piston to change displacement. The multifunction block may also provides the pressure compensating override (PCOR) option that regulates system pressure.

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Service Manual	Series 51 Electrohydraulic Proportional Controls Service Manual

Introduction

Pressure Compensating OverRide (PCOR) Option

The PCOR function allows the motor to match its displacement to the system load. The PCOR overrides the control command allowing the motor to increase displacement when system pressure reaches a set level due to load. This permits the motor to regulate system pressure by modulating the displacement of the rotating group. As displacement increases, so does available torque while output speed decreases and system pressure remains nearly constant at the PCOR setting.

The PCOR setting pressure is adjustable from 110 to 370 bar [1595 to 5365 psi]. Optional orifices at locations T4, T5, T6, U6, and U7 regulate the speed of the PCOR operation.

PCOR

	N18
N20	N14
	N16

N27

N29

N23

N23	N27	P101 906

Brake Pressure Defeat (BPD) option

The PCOR function can be equipped with a brake pressure defeat (BPD) option that defeats the PCOR operation during dynamic braking. A shuttle spool in the multifunction block in front of the PCOR valve directs only acceleration system pressure to the PCOR. During deceleration, the high dynamic braking pressure is blocked from the PCOR. This limits rapid and uncontrolled pressures or engine over-speeding while the vehicle/machine is slowing down. External hydraulic signal pressures fed to ports XA or XB are essential to operate the BPD spool. PCOR operation on one-system pressure side is also an option.

EP, EQ Electrohydraulic Proportional Control with Pressure Compensator and Hydraulic Brake Pressure Defeat.

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Service Manual	Series 51 Electrohydraulic Proportional Controls Service Manual

Introduction

BPD
XB	XA	A
BPD
	PCOR
Multifunction Block		B

M4	M3
	M1
	L1
Max.
displ.
	L2
	M5
	M2
M7	M8
	P101 907
X1	Control

BPD option

Brake defeat spool

Shuttle valve

PCOR adjuster

PCOR spool

P106 431E

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Service Manual	Series 51 Electrohydraulic Proportional Controls Service Manual

Introduction

Threshold and Ramp Springs

A threshold spring and ramp spring(s) act on the opposite end of the 4-way valve. The threshold adjustment screw (S100) varies the threshold spring force. This changes the signal current required to move the 4-way valve and start the change in displacement. The S10* ramp spring(s)—two used in 160 cc and 250 cc motors and one used in 80 cc and 110 cc motors—increase the force on the 4-way valve as the servo piston moves toward minimum displacement. This provides a motor displacement proportional to the variable input signal current.

The control-operating threshold (the signal current or force when the motor starts to shift) is adjustable. Adjust it using the S100 adjusting screw in the motor’s end cap.

Changing ramp spring force requires replacing the springs. There are several spring rates available.

Optional orifices may be installed at several locations to regulate shift speed. Refer to the Model Code for your motor for details.

Ramp Springs

J50

S100

(includes J30)

P101 909

S20

S10*

S10

160cc and 250cc

80cc and 110cc	S10*

J30

J10*

J20

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Service Manual	Series 51 Electrohydraulic Proportional Controls Service Manual

Pressure measurements

Port Locations and Gauge Installation

Series 51 Motors

M3

M3

L1

Y

Main ports A+B

Y side port

M1

M5

M5

W M2 M4

W

L2	M1	P101 204E
	M7

Axial port

Y

System pressure A+B

Guage port M1+M2

M3

Y

Axial port

Main port B

W

M5

	M4
	M5
Main
port A	P101 204E

Legend

Abbreviation	Definition
L1	Case drain; (1-5/16-12UNF)
L2	Alternate case drain: (1-5/16-12UNF)
M1	Gauge port: system pressure A (9/16-18UNF)
M2	Gauge port: system pressure B (9/16-18UNF)
M3	Gauge port: servo pressure min. angle (9/16-18UNF)
M4,	Gauge port: servo pressure max. angle (9/16-18UNF)
M5	Gauge port: servo supply pressure (9/16-18UNF)
M7	Control pressure port (9/16-18UNF)

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Service Manual	Series 51 Electrohydraulic Proportional Controls Service Manual

Adjustments

Threshold Setting

Checking Threshold Setting

1.Install a 50 bar [600 psi] gauge at port M3 to read minimum servo pressure.

2.Install a 50 bar [600 psi] gauge at port M4 to read maximum servo pressure.

3.Install meter to read signal current.

4.Increase the signal current to the proper setting.

The pressure at port M3 should rise to about 100 psi [6.89 bar] higher than the pressure at port M4. This causes the servo piston to start to move toward minimum position. Signal current at this point is the threshold setting.

On a test stand, increase signal current until the flow from the motor begins to decrease. The signal current at this point is the threshold setting.

Adjusting Threshold Setting

1.Using a 10 mm wrench, loosen the locknut on the adjusting screw.

2.Using a 3 mm internal hex wrench turn the adjusting screw:

•Clockwise (cw) to increase the setting

•Counterclockwise (ccw) to decrease the setting.

3.While holding the position of the adjustment screw:

•tighten the locknut

•using a 10 mm wrench torque the locknut to 9 N•m [6.6 lbf•ft].

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Service Manual	Series 51 Electrohydraulic Proportional Controls Service Manual

Adjustments

Locknut and Threshold

Locknut

10 mm

9 Nm [6.6 lbf•ft]

Spring seat

P101 911

Pressure compensator Override (PCOR) setting

PCOR Adjustment

In order to measure and adjust the start pressure setting for the PCOR function:

1.Install a 600 bar [10000 psi] gauge at port M1 or M2 or M5 to read high system pressure.

2.Install a 600 bar [10000 psi] gauge at port M3 to read minimum servo pressure.

3.Lock the motor shaft from moving by:

•Applying the park brake, apply an extreme load, or

•Position the machine against an immovable object, or

•Other means to hold the machine.

4.Start the prime mover. Operate at medium RPM.

5.Stroke the pump very slowly to gradually increase the system pressure.

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Service Manual	Series 51 Electrohydraulic Proportional Controls Service Manual

Adjustments

An alternate method to slowly increase the system pressure is to use the pump’s pressure limiter (PL) valve. Lower the PL setting below the PCOR setting. Stroke the pump to about one-fourth displacement. Raise the PL setting slowly to increase system pressure until pressure at the M3 port drops down. System pressure at this point is the PCOR setting. Adjust the PL back to its proper setting after checking the PCOR setting.

6.Increase system pressure until pressure at port M3 drops down, system pressure at this point is the PCOR setting.

Checking PCOR Setting on a Test Stand

Increase system pressure until the system flow begins to increase. System pressure at this point is the PCOR setting.

W Warning

System pressure may increase rapidly when flow increases.

Adjusting the PCOR Setting

For PCOR valves mounted on a Multiblock; use a 1-1/16 in. wrench to loosen the lock nut on the adjusting screw. Using a large screw driver or a 13 mm wrench turn the adjusting screw clockwise to increase pressure setting or counter clockwise to lower pressure setting. One turn of the adjusting screw changes the setting approximately 69 bar [1000 psi].

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