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Service Manual
H1P 045/053/060/068
Axial Piston Single Pumps
www.danfoss.com
Service Manual
H1P 045/053/060/068 Axial Piston Single Pumps
Revision history |
Table of revisions |
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Date |
Changed |
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December 2021 |
Added HDC control |
0501 |
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April 2021 |
Corrected mounting screw information |
0406 |
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June 2020 |
Changed document number from 'AX00000104' to 'AX152886481964' and added |
0405 |
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caution note to start-up procedures |
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November 2018 |
Major layout update. |
0401 |
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April 2018 |
add EDC with angle sensor |
0303 |
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March 2010 |
Fix Osaka address |
AC |
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Nov. 2008 - Sep 2014 |
Various changes. |
AB-CB |
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Jun 2007 |
First edition |
AA |
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2 | © Danfoss | December 2021 |
AX152886481964en-000501 |
Service Manual |
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H1P 045/053/060/068 Axial Piston Single Pumps |
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Contents |
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Introduction |
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Hydrostatics Servicing Overview................................................................................................................................................ |
5 |
General Servicing Instructions..................................................................................................................................................... |
5 |
Safety Precautions............................................................................................................................................................................ |
6 |
General description of H1 family hydrostatic pumps.......................................................................................................... |
7 |
Design................................................................................................................................................................................................... |
8 |
H1 Single Pumps Closed Circuit Pictorial Diagram.............................................................................................................. |
9 |
H1 system schematic.................................................................................................................................................................... |
10 |
Operation |
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Pressure Limiter Valves................................................................................................................................................................ |
11 |
Pressure Limiter Sectional View.......................................................................................................................................... |
11 |
High Pressure Relief Valve (HPRV) and Charge Check Valve.......................................................................................... |
12 |
HPRV/Charge Check Valve Sectional View...................................................................................................................... |
12 |
Charge Pressure Relief Valve (CPRV)....................................................................................................................................... |
13 |
Bypass function............................................................................................................................................................................... |
14 |
System Schematic for Single Pump................................................................................................................................... |
14 |
Electrical Displacement Control (EDC)................................................................................................................................... |
15 |
EDC Operation........................................................................................................................................................................... |
16 |
Hydraulic Displacement Control (HDC)................................................................................................................................. |
17 |
HDC principle............................................................................................................................................................................. |
17 |
HDC operation........................................................................................................................................................................... |
17 |
Manual Override (MOR)............................................................................................................................................................... |
19 |
Manual Displacement Control (MDC) .................................................................................................................................... |
20 |
MDC operation.......................................................................................................................................................................... |
20 |
MDC Torque................................................................................................................................................................................ |
21 |
Neutral start switch (NSS)...................................................................................................................................................... |
21 |
Case Gauge Port M14.............................................................................................................................................................. |
22 |
Operating Parameters |
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Input Speed...................................................................................................................................................................................... |
23 |
System Pressure.............................................................................................................................................................................. |
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Servo Pressure................................................................................................................................................................................. |
24 |
Charge Pressure.............................................................................................................................................................................. |
24 |
Charge Pump Inlet Pressure....................................................................................................................................................... |
24 |
Case Pressure................................................................................................................................................................................... |
25 |
External Shaft Seal Pressure....................................................................................................................................................... |
25 |
Temperature.................................................................................................................................................................................... |
25 |
Viscosity............................................................................................................................................................................................. |
25 |
Technical Specifications |
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H1 Pumps General Specification.............................................................................................................................................. |
26 |
H1 Pumps Physical Properties .................................................................................................................................................. |
26 |
Fluid Specification......................................................................................................................................................................... |
27 |
Fluid and Filter Maintenance Recommendations |
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Filtration System............................................................................................................................................................................. |
29 |
Pressure Measurements |
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Port Locations and Gauge Installation................................................................................................................................... |
30 |
H1P Ports Information............................................................................................................................................................. |
30 |
Initial Startup Procedures |
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Unintended machine movement............................................................................................................................................. |
31 |
Start-Up Procedure........................................................................................................................................................................ |
31 |
Troubleshooting |
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High Inlet Vacuum......................................................................................................................................................................... |
33 |
Unintended machine movement....................................................................................................................................... |
33 |
Fluid Under Pressure............................................................................................................................................................... |
33 |
Electrical Troubleshooting.......................................................................................................................................................... |
33 |
Neutral Difficult or Impossible to Find................................................................................................................................... |
34 |
© Danfoss | December 2021 |
AX152886481964en-000501 | 3 |
Service Manual |
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H1P 045/053/060/068 Axial Piston Single Pumps |
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Contents |
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Transmission Operates Normally in One Direction Only................................................................................................. |
34 |
System Operating Hot.................................................................................................................................................................. |
34 |
System Will Not Operate in Either Direction........................................................................................................................ |
35 |
System Noise or Vibration........................................................................................................................................................... |
35 |
Sluggish System Response......................................................................................................................................................... |
35 |
Adjustments |
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Standard Procedures.................................................................................................................................................................... |
37 |
Charge Pressure Relief Valve Adjustments........................................................................................................................... |
38 |
Pressure Limiter Adjustment..................................................................................................................................................... |
39 |
Engaging the Bypass Function.................................................................................................................................................. |
40 |
Displacement Limiter Adjustment for Single Pumps........................................................................................................ |
42 |
Control Neutral Adjustment....................................................................................................................................................... |
43 |
Mechanical Neutral Adjustment............................................................................................................................................... |
45 |
Pump Setup...................................................................................................................................................................................... |
46 |
Servo Adjustment.......................................................................................................................................................................... |
47 |
Minor Repair |
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Standard Procedures at Removing Pump............................................................................................................................. |
48 |
EDC/HDC Control Repair............................................................................................................................................................. |
49 |
EDC/HDC Control Installation.............................................................................................................................................. |
50 |
Control Solenoids Repair............................................................................................................................................................. |
50 |
MDC Control Repair....................................................................................................................................................................... |
51 |
MDC Control Assembly........................................................................................................................................................... |
52 |
Angle sensor on EDC Repair....................................................................................................................................................... |
53 |
EDC with Angle Sensor Repair................................................................................................................................................... |
54 |
Automotive Control Repair........................................................................................................................................................ |
56 |
AC Control Installation............................................................................................................................................................ |
58 |
Shaft Seal, Roller Bearing and Shaft Repair........................................................................................................................... |
59 |
Charge Pump Repair..................................................................................................................................................................... |
61 |
High Pressure Relief Valve Repair............................................................................................................................................. |
64 |
Charge Pressure Relief Valve Repair........................................................................................................................................ |
65 |
Pressure Limiter Repair................................................................................................................................................................ |
66 |
Torque Chart |
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Fasteners and Plugs...................................................................................................................................................................... |
67 |
Fastener Size and Torque Chart................................................................................................................................................ |
69 |
Plug Size and Torque Chart........................................................................................................................................................ |
69 |
4 | © Danfoss | December 2021 |
AX152886481964en-000501 |
Service Manual
H1P 045/053/060/068 Axial Piston Single Pumps
Introduction
Hydrostatics Servicing Overview
This manual includes information on installation, maintenance, and minor repair of the . It includes a description of the unit and its individual components, troubleshooting information, and minor repair procedures.
Performing minor repairs may require the unit to be removed 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, follow cleanliness requirements strictly. 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 trains and certifies Global Service Partners on a regular basis. You can locate your nearest Global Service Partner using the distributor locator at http://www.danfoss.com.
For detailed technical information about the , please see the relevant technical information document.
Attention
Major repairs requiring the removal of a unit’s center section, servo sleeves, or front flange voids the warranty unless a Danfoss Authorized Service Center performs them.
General Servicing Instructions
Follow these general procedures when repairing this product:
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Description |
Instructions |
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• If necessary, remove the unit from the vehicle/machine. |
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• Chock the wheels on the vehicle or lock the mechanism to inhibit movement. |
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Remove the unit |
• Be aware that hydraulic fluid may be under high pressure and/or hot. |
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• Inspect the outside of the pump and fittings for damage. |
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• Cap hoses after removal to prevent contamination. |
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• Cleanliness is a primary means of assuring satisfactory pump life, on either |
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new or repaired units. |
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• Clean the outside of the pump thoroughly before disassembly. |
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• Take care to avoid contamination of the system ports. |
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Keep it clean |
• Cleaning parts by using a clean solvent wash and air drying is usually |
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adequate. |
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• As with any precision equipment, keep all parts free of foreign materials and |
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chemicals. |
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• Protect all exposed sealing surfaces and open cavities from damage and |
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foreign material. |
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• If left unattended, cover the pump with a protective layer of plastic. |
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Replace O-ring, |
• Danfoss recommends that you replace all O-rings, seals and gaskets. |
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gasket |
• Lightly lubricate all O-rings with clean petroleum jelly prior to assembly. |
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• For repair, place the unit in a stable position with the shaft pointing |
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Secure the unit |
downward. |
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• It will be necessary to secure the pump while removing and torquing end |
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covers, controls, and valves. |
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© Danfoss | December 2021 |
AX152886481964en-000501 | 5 |
Service Manual
H1P 045/053/060/068 Axial Piston Single Pumps
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
Unintended movement of the machine or mechanism may cause injury to the technician or bystanders. Secure the machine or disable/disconnect the mechanism while servicing to protect against unintended movement.
Independent Braking System
Unintended vehicle or machine movement hazard. Exceeding maximum speed may cause a loss of hydrostatic drive line power and braking capacity.
Machine manufacturer is responsible to provide a braking system, redundant to the hydrostatic transmission, sufficient to stop and hold the vehicle or machine in the event of hydrostatic drive power loss. The braking system must also be sufficient to hold the machine in place when full power is applied.
High Inlet Vacuum
High inlet vacuum causes cavitation which can damage internal pump components.
Manufacturer’s Warranty
Contamination can damage internal components and void the manufacturer’s warranty.
Take precautions to ensure system cleanliness when removing and installing system lines.
Fluid Under Pressure
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.
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. Use caution when dealing with hydraulic fluid under pressure. Seek medical attention immediately if you are cut by hydraulic fluid.
Flammable cleaning solvents
Some cleaning solvents are flammable.
Do not use cleaning solvents in an area where a source of ignition may be present to avoid possible fire.
Personal safety
Protect yourself from injury whenever servicing a hydraulic system.
Use proper safety equipment, including safety glasses, at all times.
Hazardous material
Hydraulic fluid contains hazardous material.
Avoid prolonged contact with hydraulic fluid. Always dispose of used hydraulic fluid according to state, and federal environmental regulations.
6 | © Danfoss | December 2021 |
AX152886481964en-000501 |
Service Manual
H1P 045/053/060/068 Axial Piston Single Pumps
Introduction
General description of H1 family hydrostatic pumps
The H1 family of closed circuit variable displacement axial piston pumps is designed for use with all existing Danfoss hydraulic motors for the control and transfer of hydraulic power. The H1 axial piston variable displacement pumps are of cradle swash-plate design and are intended for closed circuit applications.
Flow direction is reversed by tilting the swash-plate to the opposite side of the neutral (zero displacement) position. The flow rate is proportional to the pump input speed and displacement. The latter is infinitely adjustable between zero and maximum displacement.
H1 pumps can be used together in combination with other Danfoss pumps and motors in the overall hydraulic system.
•Danfoss hydrostatic products are designed with 15 different displacements (cm³ [in³]):
045 |
053 |
060 |
068 |
069 |
078 |
089 |
100 |
115 |
130 |
147 |
165 |
210 |
250 |
280 |
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45.0 |
53.8 |
60.4 |
68.0 |
69.0 |
78.0 |
89.2 |
101.7 |
115.8 |
130.8 |
147.0 |
165.0 |
211.5 |
251.7 |
280.2 |
[2.75] |
[3.28] |
[3.69] |
[4.15] |
[4.22] |
[4.76] |
[5.44] |
[6.21] |
[7.07] |
[7.98] |
[8.97] |
[10.07] |
[12.91] |
[15.36] |
[17.10] |
•Danfoss hydrostatic products are designed with many different pressure, load-life and control capabilities:
‒Electric Displacement Control (EDC)
‒Forward-Neutral-Reverse control (FNR)
‒Non-Feedback Proportional Electric control (NFPE)
‒Automotive Control (AC)
‒Fan Drive Control (FDC)
‒Manual Displacement Control (MDC)
‒Hydraulic Displacement Control (HDC)
‒Control-Cut-Off valve (CCO)
•High power density where all units utilize an integral electro-hydraulic servo piston assembly that controls the rate (speed) and direction of the hydraulic flow.
•Compatible with the Danfoss family of PLUS+1® micro-controllers for easy Plug-and-Perform installation.
•More compact and lightweight
•Improved reliability and performance
Go to the Danfoss website or applicable product catalog to choose the components that are right for your complete closed circuit hydraulic system.
© Danfoss | December 2021 |
AX152886481964en-000501 | 7 |
Service Manual
H1P 045/053/060/068 Axial Piston Single Pumps
Introduction
Design
The H1 axial piston variable displacement pumps are of cradle swashplate design and are intended for closed circuit applications.
The flow rate is proportional to the pump input speed and displacement. The latter is infinitely adjustable between zero and maximum displacement.
Flow direction is reversed by tilting the swashplate to the opposite side of the neutral (zero displacement) position.
The H1 family of closed circuit variable displacement axial piston pumps is designed for use with all existing Danfoss hydraulic motors for the control and transfer of hydraulic power. H1 pumps are compact and high power density where all units utilize an integral electro-hydraulic servo piston assembly that controls the rate (speed) and direction of the hydraulic flow. H1 pumps are specifically compatible with the Danfoss family of PLUS+1™ microcontrollers for easy Plug-and-Perform™ installation.
H1 pumps can be used together in combination with other Danfoss pumps and motors in the overall hydraulic system. Danfoss hydrostatic products are designed with many different displacement, pressure and load-life capabilities. Go to the Danfoss website or applicable product catalog to choose the components that are right for your complete closed circuit hydraulic system.
Cross section view
Electric displacement control
Swashplate feedback pin
Piston
Slipper
Shaft seal
Shaft 
Front bearing 
Swashplate bearing 
Swashplat e |
Cylinder block |
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Servo piston
Valve plate
Rear bearing
Charge Pump
P106 337E
8 | © Danfoss | December 2021 |
AX152886481964en-000501 |
Service Manual
H1P 045/053/060/068 Axial Piston Single Pumps
Introduction
The Basic Closed Circuit
Hydraulic lines connect the main ports of the pump to the main ports of the motor. Fluid flows in either direction from the pump to the motor and back. Either of the hydraulic lines can be under high pressure. In pumping mode the position of the pump swashplate determines which line is high pressure as well as the direction of fluid flow.
Case Drain and Heat Exchanger
The pump and motor require case drain lines to remove hot fluid from the system. The pump and motor drain from the topmost port to ensure the cases remain full of fluid.
The motor case drain can connect to the lower drain port on the pump housing or it can tee into the case drain line upstream of the heat exchanger. A heat exchanger with bypass valve cools the case drain fluid before it returns to the reservoir.
H1 Single Pumps Closed Circuit Pictorial Diagram
Heat Exchanger
Bypass Valve
Reservoir
Displacement Control
Heat Exchanger
System Pressure
Servo Pressure
Charge/Low Loop Pressure
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Suction/Case Drain/ |
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Charge Pump |
System Return |
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Bent Axis Variable |
Servo Control |
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Displacement Motor |
Cylinder |
Charge Filter |
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Check/ |
Motor Swashplate |
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Variable |
Pressure Relief Valve |
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Displacement |
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Output |
Pump |
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Shaft |
Input |
Synchronizing |
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Shaft |
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Shaft |
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Pump Swashplate |
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Charge Check/High Pressure Relief Valve |
P104 464E |
© Danfoss | December 2021 |
AX152886481964en-000501 | 9 |
Service Manual
H1P 045/053/060/068 Axial Piston Single Pumps
Introduction
H1 system schematic
System schematic H1 pump and H1 motor with EDC
M14 |
M6 |
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<![if ! IE]> <![endif]>R2 |
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C2 |
C1 |
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M3 L1 |
L2 MA |
L2 |
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F00B |
F00A |
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M5 |
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CW |
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max. |
min. |
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L1 |
M4 |
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B |
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S L3 |
L4 |
MB |
M4 |
M5 |
MB |
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max. 3 bar |
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[43.5 psi] |
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P003 424 |
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The schematic above shows the function of a hydrostatic transmission using an H1 axial variable displacement pump with electric proportional displacement control (EDC) and an H1 bent axis variable displacement motor with electric proportional control (L*) and integrated loop flushing device.
10 | © Danfoss | December 2021 |
AX152886481964en-000501 |
Service Manual
H1P 045/053/060/068 Axial Piston Single Pumps
Operation
Pressure Limiter Valves
Pressure limiter valves provide system pressure protection by compensating the pump swash plate position when the set pressure of the valve is reached. A pressure limiter is a non-dissipative (non heat generating) pressure regulating system.
Each side of the transmission loop has a dedicated pressure limiter valve that is set independently. A pump configured with pressure limiter must have pressure limiters on both sides of the system pressure loop. The pump order code allows for different pressure settings to be used at each system port.
The pressure limiter setting is the maximum differential pressure between the high and low loops. When the pressure limiter setting is reached, the valve ports oil to the low-pressure side of the servo piston. The change in servo differential pressure rapidly reduces pump displacement. Fluid flow from the valve continues until the resulting drop in pump displacement causes system pressure to fall below the pressure limiter setting.
An active pressure limiter destrokes a pump to near neutral when the load is in a stalled condition. The pump swash-plate moves in either direction necessary to regulate the system pressure, including into stroke (overrunning) or over-center (winch payout).
The pressure limiter is optional on H1 pumps (except H1T 045/053 tandem pumps).
Pressure Limiter Sectional View
© Danfoss | December 2021 |
AX152886481964en-000501 | 11 |
Service Manual
H1P 045/053/060/068 Axial Piston Single Pumps
Operation
High Pressure Relief Valve (HPRV) and Charge Check Valve
All H1 pumps have a combination high pressure relief and charge check valve. The high pressure relief function is a dissipative (heat generating) pressure control valve for the purpose of limiting excessive system pressures. The charge check function replenishes the low pressure side of the working loop with charge oil.
Each side of the transmission loop has a dedicated HPRV valve that is non-adjustable with a factory set pressure. When system pressure exceeds the factory setting of the valve, oil is passed from the high pressure system loop, into the charge gallery, and into the low pressure system loop via the charge check.
The pump may have different pressure settings to be used at each system port. When an HPRV valve is used in conjunction with a pressure limiter, the HPRV valve is always factory set above the setting of the pressure limiter. The system pressure shown in the order code for pumps with only HPRV is the HPRV setting.
The system pressure shown in the order code for pumps with pressure limiter and HPRV is a reflection of the pressure limiter setting:
HPRVs are set at low flow condition. Any application or operating condition which leads to elevated HPRV flow will cause a pressure rise with flow above the valve setting. Consult factory for application review.
Excessive operation of the HPRV will generate heat in the closed loop and may cause damage to the internal components of the pump.
HPRV/Charge Check Valve Sectional View
HPRV and Charge Check Valve with Bypass Function (except 045/053)
Relief mode
P003 268
12 | © Danfoss | December 2021 |
AX152886481964en-000501 |
Service Manual
H1P 045/053/060/068 Axial Piston Single Pumps
Operation
Charge Pressure Relief Valve (CPRV)
The charge pressure relief valve is a direct acting poppet valve that opens and discharges fluid to the pump case when pressure exceeds a designated level. The charge pressure relief valve maintains charge pressure at a designated level above case pressure.
This level is nominally set with the pump running at 1800 min-1(rpm), and with a fluid viscosity of 32 mm²/s [150 SUS]. In forward or reverse, charge pressure will be slightly lower than in neutral position. The model code of the pump specifies the charge pressure relief valve setting. Typical charge pressure increase from 1.2-1.5 bar per 10 l/min [17.4-21.8 psi per 2.64 US gal/min]. For external charge flow the CPRV is set according to the table below:
CPRV flow setting for external charge supply
Tandem 045/053 |
Single 045/053 |
Single 060—165 |
Single 210/250/280 |
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30 l/min [7.9 US gal/min] |
15 l/min [3.9 US gal/min] |
22.7 l/min [6.0 US gal/min] |
40.0 l/min [10.6 US gal/min] |
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Charge pressure relief valve
© Danfoss | December 2021 |
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Service Manual
H1P 045/053/060/068 Axial Piston Single Pumps
Operation
Bypass function
The bypass function allows a machine or load to be moved without rotating the pump shaft or prime mover. The single pump HPRV valve also provides a loop bypass function when each of the two HPRV hex plugs are mechanically backed out three full turns.
Engaging the bypass function mechanically connects both A & B sides of the working loop to the common charge gallery.
Possible damage to hydromotor(s).
Excessive speeds and extended load/vehicle movement must be avoided. The load or vehicle should be moved not more than 20% of maximum speed and for a duration not exceeding 3 minutes. When the bypass function is no longer needed, care should be taken to re-seat the HPRV hex plugs to the normal operating position.
Bypass function not available for tandem pumps.
System Schematic for Single Pump
The schematic below shows the function of an H1P axial piston variable displacement pump with electric displacement control (EDC).
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M14 |
M6 |
1 |
2 |
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R1 |
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<![if ! IE]> <![endif]>R2 |
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C1 |
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C2 |
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M3 L2 |
MA |
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F00B |
F00A |
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A |
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M4 |
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CW |
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M5 |
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B |
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S |
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L4 |
MB |
P003 418E |
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14 | © Danfoss | December 2021 |
AX152886481964en-000501 |
Service Manual
H1P 045/053/060/068 Axial Piston Single Pumps
Operation
Electrical Displacement Control (EDC)
An EDC is a displacement (flow) control. Pump swash plate position is proportional to the input command and therefore vehicle or load speed (excluding influence of efficiency), is dependent only on the prime mover speed or motor displacement.
The Electrical Displacement Control (EDC) consists of a pair of proportional solenoids on each side of a three-position, four-way porting spool. The proportional solenoid applies a force input to the spool, which ports hydraulic pressure to either side of a double acting servo piston. Differential pressure across the servo piston rotates the swash plate, changing the pump‘s displacement from full displacement in one direction to full displacement in the opposite direction.
A serviceable 170 μm screen is located in the supply line immediately before the control porting spool.
Under some circumstances, such as contamination, the control spool could stick and cause the pump to stay at some displacement.
Electrical Displacement Control |
EDC schematic, feedback from swash plate |
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C1 |
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C2 |
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F00B |
F00A |
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Feedback from |
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Swash plate |
P003 478E |
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P003 191
© Danfoss | December 2021 |
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Service Manual
H1P 045/053/060/068 Axial Piston Single Pumps
Operation
EDC Operation
H1 EDC’s are current driven controls requiring a Pulse Width Modulated (PWM) signal. Pulse width modulation allows more precise control of current to the solenoids.
The PWM signal causes the solenoid pin to push against the porting spool, which pressurizes one end of the servo piston, while draining the other. Pressure differential across the servo piston moves the swashplate.
A swashplate feedback link, opposing control links, and a linear spring provide swashplate position force feedback to the solenoid. The control system reaches equilibrium when the position of the swashplate spring feedback force exactly balances the input command solenoid force from the operator. As hydraulic pressures in the operating loop change with load, the control assembly and servo/swashplate system work constantly to maintain the commanded position of the swashplate.
The EDC incorporates a positive neutral deadband as a result of the control spool porting, preloads from the servo piston assembly, and the linear control spring. Once the neutral threshold current is reached, the swashplate is positioned directly proportional to the control current. To minimize the effect of the control neutral deadband, we recommend the transmission controller or operator input device incorporate a jump up current to offset a portion of the neutral deadband.
The neutral position of the control spool does provide a positive preload pressure to each end of the servo piston assembly.
When the control input signal is either lost or removed, or if there is a loss of charge pressure, the springloaded servo piston will automatically return the pump to the neutral position.
16 | © Danfoss | December 2021 |
AX152886481964en-000501 |
Service Manual
H1P 045/053/060/068 Axial Piston Single Pumps
Operation
Hydraulic Displacement Control (HDC)
HDC principle
An HDC is a Hydraulic Displacement Control. Pump swashplate position is proportional to the input command and therefore vehicle speed or load speed (excluding influence of efficiency), is dependent only on the prime mover speed or motor displacement.
The HDC control uses a hydraulic input signal to operate a porting spool, which ports hydraulic pressure to either side of a double acting servo piston. The hydraulic signal applies a force input to the spool which ports hydraulic pressure to either side of a double acting servo piston. Differential pressure across the servo piston rotates the swashplate, changing the pump’s displacement from full displacement in one direction to full displacement in the opposite direction. Under some circumstances, such as contamination, the porting spool could stick and cause the pump to stay at some displacement.
A serviceable 175 μm screen is located in the supply line immediately before the control porting spool.
HDC control
P400520
HDC schematic
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M14 |
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X2 |
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F00B |
Feedback from |
F00A |
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Swashplate |
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P400519 |
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HDC operation
HDC’s are hydraulically driven control which ports hydraulic pressure to either side of a porting spool, which pressurizes one end of the servo piston, while draining the other end to case. Pressure differential across the servo piston moves the swashplate.
A swashplate feedback link, opposing control linkage, and a linear spring provide swashplate position force feedback to the hydraulic pressure. As hydraulic pressures in the operating loop change with load, the control assembly and servo/swashplate system work constantly to maintain the commanded position of the swashplate.
© Danfoss | December 2021 |
AX152886481964en-000501 | 17 |
Service Manual
H1P 045/053/060/068 Axial Piston Single Pumps
Operation
The HDC incorporates a positive neutral dead band as a result of the control spool porting, preloads from the servo piston assembly, and the linear control spring. Once the neutral threshold point is reached, the swashplate is positioned directly proportional to the control pressure.
When the control input is either lost or removed, or if there is a loss of charge pressure, the spring loaded servo piston will automatically return the pump to the neutral position.
Pump displacement vs signal pressure
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100 % |
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-b |
<![if ! IE]> <![endif]>Displacement |
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-a |
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Signal pressure |
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"0" |
a |
b |
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100 % |
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P102 031E |
18 | © Danfoss | December 2021 |
AX152886481964en-000501 |
Service Manual
H1P 045/053/060/068 Axial Piston Single Pumps
Operation
Manual Override (MOR)
All controls are available with a manual override functionality, either as a standard or as an option for temporary actuation of the control to aid in diagnostics.
Control with manual override
P003 204 |
MOR schematic (EDC control shown)
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M14 |
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C1 |
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C2 |
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F00B |
F00A |
T |
P |
Feedback from swash plate.
The MOR plunger has a 4 mm diameter and must be manually depressed to be engaged. Depressing the plunger mechanically moves the control spool which allows the pump to go on stroke. The MOR should be engaged anticipating a full stroke response from the pump.
An o-ring seal is used to seal the MOR plunger where initial actuation of the function will require a force of 45 N to engage the plunger. Additional actuation typically require less force to engage the MOR plunger.
Proportional control of the pump using the MOR should not be expected.
W Warning
Unintended MOR operation will cause the pump to go into stroke; example: vehicle lifted off the ground. The vehicle or device must always be in a safe condition when using the MOR function.
Refer to control flow table for the relationship of solenoid to direction of flow.
© Danfoss | December 2021 |
AX152886481964en-000501 | 19 |
Service Manual
H1P 045/053/060/068 Axial Piston Single Pumps
Operation
Manual Displacement Control (MDC)
A Manual proportional Displacement Control (MDC) consists of a handle on top of a rotary input shaft. The shaft provides an eccentric connection to a feedback link. This link is connected on its one end with a porting spool. On its other end the link is connected the pumps swashplate.
This design provides a travel feedback without spring. When turning the shaft the spool moves thus providing hydraulic pressure to either side of a double acting servo piston of the pump.
Differential pressure across the servo piston rotates the swash plate, changing the pump’s displacement. Simultaneously the swashplate movement is fed back to the control spool providing proportionality between shaft rotation on the control and swash-plate rotation. The MDC changes the pump displacement between no flow and full flow into opposite directions.
Under some circumstances, such as contamination, the control spool could stick and cause the pump to stay at some displacement.
For the MDC with CCO option the brake port (X7) provides charge pressure when the coil is energized to activate static function such as a brake release. The X7 port must not be used for any continuous oil consumption.
The MDC is sealed by means of a static O-ring between the actuation system and the control block. Its shaft is sealed by means of a special O-ring which is applied for low friction. The special O-ring is protected from dust, water and aggressive liquids or gases by means of a special lip seal.
Manual Displacement Control |
Pump displacement vs. control lever rotation |
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100 % |
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<![if ! IE]> <![endif]>Displacement |
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"A" |
-d -b |
-a |
"0" |
Lever rotation |
d |
"B" |
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a |
b c |
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100 % |
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P301 752 |
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Deadband on B side: a = 3° ±1° |
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Maximum pump stroke: b = 30° +2/-1° |
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Required customer end stop: c = 36° ±3° |
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Internal end stop: d = 40° |
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MDC operation
The MDC provides a mechanical dead-band required to overcome the tolerances in the mechanical actuation. The MDC contains an internal end stop to prevent turning the handle into any inappropriate position.
The MDC provides a permanent restoring moment appropriate for turning the MDC input shaft back to neutral position only. This is required to take the backlash out of the mechanical connections between the Bowden cable and the control.
High case pressure may cause excessive wear and the NSS to indicate that the control is not in neutral position. In addition, if the case pressure exceeds 5 bar there is a risk of an insufficient restoring moment. The MDC is designed for a maximum case pressure of 5 bar and a rated case pressure of 3 bar.
20 | © Danfoss | December 2021 |
AX152886481964en-000501 |
Service Manual
H1P 045/053/060/068 Axial Piston Single Pumps
Operation
•Customers must install some support to limit the setting range of their Bowden cable to avoid an overload of the MDC.
•Customers can apply their own handle design but they must care about a robust clamping connection between their handle and the control shaft and avoid overload of the shaft.
•Customers can connect two MDC’s on a tandem unit in such a way that the actuation force will be transferred from the pilot control to the second control. The kinematic of the linkages must ensure that either control shaft is protected from torque overload.
C Caution
Using the internal spring force on the input shaft is not an appropriate way to return the customer connection linkage to neutral, or to force a Bowden cable or a joystick back to neutral position. It is not applicable for any limitation of the Bowden cable stroke, except the applied torque to the shaft will never exceed 20 N•m.
MDC Torque
Description |
Value |
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Torque required to move handle to maximum displacement |
1.4 N•m [12.39 lbf•in ] |
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Torque required to hold handle at given displacement |
0.6 N•m [5.31 lbf•in] |
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Maximum allowable input torque |
20 N•m [177 lbf•in] |
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C Caution
Volumetric efficiencies of the system will have impacts on the start and end input commands.
Neutral start switch (NSS)
The Neutral Start Switch (NSS) contains an electrical switch that provides a signal of whether the control is in neutral. The signal in neutral is Normally Closed (NC).
Neutral start switch schematic
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M14 |
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M5 |
M4 |
M3 |
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P005 702 |
Neutral start switch data
Max. continuous current with switching |
8.4 A |
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Max. continuous current without switching |
20 A |
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Max. voltage |
36 VDC |
Electrical protection class |
IP67 / IP69K with mating connector |
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© Danfoss | December 2021 |
AX152886481964en-000501 | 21 |
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