Bosch Rexroth 3 Series User manual

Axial piston variable pump
A4CSG
Series 3x
Instruction manual
RE 92105-01-B/06.2017
Replaces: –.–
English

© Bosch Rexroth AG 2017. All rights reserved,
also regarding any disposal, exploitation,
reproduction, editing, distribution, as well
as in the event of applications for industrial
property rights. The data specified within only
serves to describe the product. No statements
concerning a certain condition or suitability
for a certain application can be derived from
our information. The information given does
not release the user from the obligation of
own judgment and verification. It must be
remembered that our products are subject to a
natural process of wear and aging.
The cover shows an example application. The
product delivered may differ from the image on
the cover.
The original instruction manual was created in
the German language.

RE 92105-01-B/06.2017, A4CSG, Series 3x, Bosch Rexroth AG
3/68Contents
Contents
1 About this documentation 5
1.1 Validity of the documentation 5
1.2 Required and supplementary documentation 5
1.3 Representation of information 6
1.3.1 Safety instructions 6
1.3.2 Symbols 7
1.3.3 Designations 7
1.3.4 Abbreviations 7
2 Safety instructions 8
2.1 About this chapter 8
2.2 Intended use 8
2.3 Improper use 8
2.4 Personnel qualifications 9
2.5 General safety instructions 10
2.6 Product-specific safety instructions 11
2.7 Personal protective equipment 14
3 General instructions on damage to property and theproduct 15
3.1 Operator's obligations 17
4 Scope of delivery 18
5 About this product 19
5.1 Performance description 19
5.2 Product description 19
5.2.1 Layout of the axial piston unit 19
5.2.2 Functional description 20
5.3 Product identification 21
5.3.1 Name plate of the axial piston unit 21
6 Transport and storage 22
6.1 Transporting the axial piston unit 22
6.1.1 Transporting by hand 22
6.1.2 Transporting with a lifting device 23
6.2 Storing the axial piston unit 24
7 Installation 27
7.1 Unpacking 27
7.2 Installation conditions 27
7.3 Installation position 28
7.3.1 Below-reservoir installation (standard) 28
7.3.2 Above-reservoir installation 29
7.4 Installing the axial piston unit 32
7.4.1 Preparation 32
7.4.2 Dimensions 32
7.4.3 General instructions 32
7.4.4 Installation with coupling 33
7.4.5 Installation on a gearbox 34
7.4.6 Installation with cardan shaft 35
7.4.7 Completing installation 35
7.4.8 Hydraulically connecting the axial piston unit 37

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7.4.9 Electrically connecting the axial piston unit 42
7.5 Performing flushing cycle 43
8 Commissioning 44
8.1 Initial commissioning 44
8.1.1 Filling the axial piston unit 44
8.1.2 Testing the hydraulic fluid supply 45
8.1.3 Performing a functional test 46
8.2 Running-in phase 47
8.3 Recommissioning after standstill 47
9 Operation 48
9.1 Operating the optional auxiliary activation device 48
10 Maintenance and repair 49
10.1 Cleaning and care 49
10.2 Inspection 49
10.3 Maintenance 51
10.4 Repair 54
10.5 Spare parts 55
11 Removal and replacement 56
11.1 Required tools 56
11.2 Preparing for removal 56
11.3 Performing removal 56
11.4 Preparing the components for storage or further use 56
12 Disposal 57
13 Extension and conversion 58
14 Troubleshooting 59
14.1 How to proceed with troubleshooting 59
14.2 Malfunction table 60
15 Technical data 64
16 Alphabetical index 66
Contents

About this documentation 5/68
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1 About this documentation
1.1 Validity of the documentation
This documentation is valid for the following product:
•Axial piston variable pump A4CSG Series 3x (standard version).
This documentation is intended for machine/system manufacturers, assemblers and
service engineers.
This documentation contains important information on the safe and appropriate
transport, installation, commissioning, operation, maintenance, removal and simple
troubleshooting of the axial piston unit.
▶ Read this documentation completely and in particular the chapter 2 “Safety
instructions” on page 8 and chapter 3 “General instructions on damage to
property and theproduct” on page 15 before you start work with the axial
piston unit.
1.2 Required and supplementary documentation
▶ Only commission the axial piston unit if the documentation marked with the book
symbol is available to you and you have understood and observed it.
Table 1: Required and supplementary documentation
Title Document number Document type
Order confirmation
Contains the technical data relevant to the Axial piston variable pump A4CSG
ordered.
– Order confirmation
Installation drawing
Contains the outer dimensions, all ports and the hydraulic circuit diagram for your
Axial piston variable pump A4CSG.
Please request the
installation drawing
from your contact at
Bosch Rexroth.
Installation drawing
Axial piston variable pump A4CSG
Contains the permissible technical data.
92105 Data sheet
Mineral oil-based hydraulic fluids and related hydrocarbons
Describes the requirements on a mineral oil-based hydraulic fluid and related
hydrocarbons for operation with Rexroth hydraulic components, and assists you in
selecting a hydraulic fluid for your hydraulic system.
90220 Data sheet
Information on the use of hydrostatic drives at low temperatures
Contains additional information on the use of Rexroth axial piston units at low
temperatures.
90300-03-B Manual
Storage and preservation of axial piston units
Contains additional information on storage and preservation.
90312 Data sheet

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1.3 Representation of information
Standardized safety instructions, symbols, terms and abbreviations are used
throughout this documentation so that you can work quickly and safely with your
product. To give you a better understanding they are explained in the sections below.
1.3.1 Safety instructions
This documentation includes safety instructions in chapter 2.6 “Product-specific
safety instructions” on page 11 and in chapter 3 “Alphabetical index” on
page15 and before a sequence of actions or an instruction for action involving a
risk of personal injury or damage to equipment. The described danger prevention
measures must be observed.
Safety instructions are set out as follows:
SIGNAL WORD
Type and source of danger!
Consequences of noncompliance
▶ Measures to prevent danger
▶ <List>
•Warning sign: draws attention to the danger
•Signal word: identifies the degree of the danger
•Type and source of danger: indicates the type and source of the danger
•Consequences: describes what occurs if the safety instructions are not complied
with
•Precautions: states how the danger can be avoided
Table 2: Hazard classes as defined in ANSI Z535.6-2006
Warning sign, signal word Meaning
DANGER Identifies a dangerous situation that will result in death or
serious injuries if it is not avoided.
WARNING Identifies a dangerous situation that may result in death or
serious injuries if it is not avoided.
CAUTION Identifies a dangerous situation that may result in minor to
moderate injuries if it is not avoided.
NOTICE Property damage: The product or the environment may get
damaged.

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1.3.2 Symbols
The following symbols indicate information that is not safety-relevant but increases
understanding of the documentation.
Table 3: Meaning of the symbols
Symbol Meaning
If this information is disregarded, the product cannot be used and/or
operated to the optimum extent.
▶ Single, independent action
1.
2.
3.
Numbered instruction:
The numbers indicate that the actions must be completed one after the
other.
1.3.3 Designations
This documentation uses the following designations:
Table 4: Designations
Designation Meaning
A4CSG Axial piston variable pumpClosed circuit
Threaded plug Metal screw, pressure-resistant
Protective plug Made out of plastic, not pressure-resistant, only for transportation
As an umbrella term for “Axial piston variable pump A4CSG”, the designation “axial
piston unit” will be used in the following.
1.3.4 Abbreviations
This documentation uses the following abbreviations:
Table 5: Abbreviations
Abbreviation Meaning
ATEX EC directive on explosion protection (Atmosphère explosible)
DIN Deutsche Industrie Norm (German Institute for Standardization)
EP Electrohydraulic control with Proportional solenoid and pressure control
ISO International Organization for Standardization
JIS Japan Industrial Standard
RD Rexroth document in the Deutsch (German) language
VDI 2230 Directive for the systematic calculation of high duty screwed joints and
cylindrical screw joints from the VDI (Verein Deutscher Ingenieure -
Association of German Engineers)

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Bosch Rexroth AG, A4CSG, Series 3x, RE 92105-01-B/06.2017
2 Safety instructions
2.1 About this chapter
The axial piston unit has been manufactured according to the generally accepted
rules of current technology. There is, however, still a danger of personal injury or
property damage if this chapter and the safety instructions in this documentation are
not complied with.
▶ Read this documentation completely and thoroughly before working with the axial
piston unit.
▶ Keep this documentation in a location where it is accessible to all users at all
times.
▶ Always include the required documentation when you pass the axial piston unit
on to third parties.
2.2 Intended use
Axial piston units are hydraulic components, meaning that in their application area
they are classified neither as complete nor as partly completed machinery in the
sense of the EC Machinery Directive 2006/42/EC. The component is exclusively
intended to form partly completed machinery or complete machinery together with
other components. The component may only be commissioned after it has been
installed in the machine/system for which it is intended and the safety of the entire
system has been established in accordance with the Machinery Directive.
This product is intended for the following use:
The axial piston unit is only approved as a pump for hydrostatic drives in closed
circuit.
▶ Observe the technical data, the application and operating conditions and
the performance limits as specified in data sheet 92105 and in the order
confirmation. Information about approved hydraulic fluids can be found in data
sheet 92105.
The axial piston unit is only intended for professional use and not for private use.
Intended use includes having read and understood the complete documentation,
especially chapter 2 “Safety instructions” on page 8.
2.3 Improper use
Any use other than that described as intended use shall be considered as improper
and is therefore impermissible.
Bosch Rexroth AG is not liable for damages resulting from improper use. The user
shall bear all risks arising from improper use.
Similarly, the following foreseeable forms of misuse are deemed faulty usage:
•Use outside the operating parameters approved in the data sheet 92105 or in the
order confirmation (unless customer-specific approval has been granted)
•The axial piston variable pump A4CSG is, except for momentary pressure
reduction, not approved for motor/reversing operation.
•Use of non-approved fluids, for example, water or polyurethane components
•Changes to factory settings by unauthorized persons
•Use of assembled parts (e.g. attachment filter, control unit, valves) other than the
specified Rexroth components

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•Use of the axial piston unit with assembled parts under water at a depth of
more than 10 meters without the necessary additional measures, e.g., pressure
equalization. Units with electrical components (for example, sensors) generally
cannot come into contact with water.
•Use of the axial piston unit under a continuous pressure differential between case
to ambient pressure greater than 2bar, whereby the ambient pressure must always
be lower than the case pressure. Momentary (t < 0.1 s) pressure peaks of up to
10bar are permitted. Beyond this, the maximum case pressure specified on the
data sheet cannot be exceeded.
•Use of the axial piston unit in explosive environments unless the component or
machine/system has been certified as compliant with the ATEX directive 2014/34/EC
•Use of the axial piston unit in a corrosive atmosphere
•Use of the axial piston unit in aircraft or spacecraft
2.4 Personnel qualifications
The activities described in this documentation require basic knowledge of
mechanics, electrics, hydraulics and ATEX, as well as knowledge of the associated
technical terms. For transporting and handling the product, additional knowledge
is necessary with regard to working with lifting devices and their slings. In order to
ensure safe use, these activities should only be performed by skilled personnel or an
instructed person under the direction and supervision of skilled personnel.
Skilled persons are those who can recognize possible dangers and take the
appropriate safety measures due to their professional training, knowledge, and
experience, as well as their understanding of the relevant regulations pertaining to
the work to be done. Skilled personnel must follow the rules relevant to their field
and have the necessary hydraulics expert knowledge.
Hydraulic expert knowledge includes:
•Reading and fully understanding hydraulic circuit diagrams,
•especially fully understanding the relationships with regard to safety devices
•and understanding how hydraulic components work and are put together.
Bosch Rexroth offers training support for specialized fields. An overview of the training
contents can be found online at: http://www.boschrexroth.com/training.

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Bosch Rexroth AG, A4CSG, Series 3x, RE 92105-01-B/06.2017
2.5 General safety instructions
•Observe the applicable accident prevention and environmental protection
regulations.
•Observe the safety regulations and provisions of the country in which the product
is used/operated.
•Use Rexroth products only when they are in good working order.
•Observe all notices on the product.
•Persons who install, operate, remove or maintain Rexroth products may not be
under the influence of alcohol, drugs or medication that may affect their reaction
time.
•Only use genuine Rexroth accessories and spare parts to ensure there is no hazard
to persons due to unsuitable spare parts.
•Observe the technical data and ambient conditions specified in the product
documentation.
•If unsuitable products are installed or used in applications that are of relevance
to safety, unexpected operating conditions may occur in the application, which
could result in injury to personnel or property damage. For this reason, only use
the product in safety-relevant applications if this use is expressly specified and
permitted in the product documentation, for example in explosion protection
applications or in safety-related parts of a control system (functional safety).
•You may only commission the product if it has been determined that the end
product (for example, machinery or system) in which the Rexroth products are
installed complies with the country-specific provisions, safety regulations and
standards for the application.
•Use tools appropriate for the work being performed and wear appropriate
protective clothing to prevent punctures and cuts (for example, when removing
protective covers, disassembly).
•There is a risk of entanglement when operating the axial piston unit with a bare
shaft end. Check whether or not your machine requires additional safety measures
for your application. If necessary, make sure that these are properly implemented.
•Depending on the type of control used, electromagnetic effects can be produced
when using solenoids. When a direct current is applied, solenoids do not cause
electromagnetic interference nor is their operation impaired by electromagnetic
interference. Other behavior can result when a modulated direct current
(e.g.PWMsignal) is applied. Potential electromagnetic interference for persons
(e.g. persons with a pacemaker) and other components must be tested by the
machine manufacturer.

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2.6 Product-specific safety instructions
The following safety instructions apply to chapters 6 to 14.
WARNING
Danger from excessively high pressure!
Risk of death or injury, or property damage!
Improperly changing the factory pressure settings can result in a pressure increase
beyond the permissible maximum pressure.
Operating the unit above the permissible maximum pressure can cause
components to burst and hydraulic fluid to escape under high pressure.
▶ Changes to the factory settings must only be made by Bosch Rexroth specialists.
▶ If the axial piston unit is equipped with a pressure cut-off and/or a pressure
controller, this is not an adequate back-up against pressure overload.
▶ Set the external pressure relief valve so that the permissible maximum pressure
cannot be exceeded, see data sheet 92105.
▶ Set the cracking pressure of the high-pressure relief valve to a value not lower
than 30 bar above the setting of the pressure controller.
Danger from suspended loads!
Risk of death or injury, or property damage!
Improper transportation may cause the axial piston unit to fall down and lead to
injuries, for example, crushing or broken bones or damage to the product.
▶ Make sure that the forklift truck or lifting device has adequate lifting capacity.
▶ Never stand or put your hands under a suspended load.
▶ Make sure the unit remains stable during transport.
▶ Wear your personal protective equipment (e.g. safety goggles, safety gloves,
suitable working clothes, safety shoes).
▶ Use suitable lifting devices for transportation.
▶ Observe the prescribed position of the lifting strap.
▶ Observe the national laws and regulations on work and health protection and
transportation.
System/machine under pressure!
Danger to life or risk of injury, serious injuries when working on machines/systems
not secured! Risk of property damage!
▶ Switch off the entire system and secure it against reconnection according to the
parameters provided by the machine/system manufacturer.
▶ Make sure that all relevant components of the hydraulic system are
depressurized. Follow the parameters given by the machine/system
manufacturer.
▶ Note that the hydraulic system may still may be under pressure even after the
pressure supply itself has been disconnected.
▶ Do not disconnect any line connections, ports and components as long as the
hydraulic system is under pressure.

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Bosch Rexroth AG, A4CSG, Series 3x, RE 92105-01-B/06.2017
WARNING
Escaping oil mist!
Risk of explosion and fire, health hazard, risk of environmental pollution!
▶ Depressurize the relevant machine/system part and repair the leak.
▶ Only perform welding work when the machine/system is depressurized.
▶ Keep open flames and ignition sources away from the axial piston unit.
▶ If axial piston units are located in the vicinity of ignition sources or powerful
thermal radiators, a shield must be erected to ensure that any escaped hydraulic
fluid cannot be ignited, and to protect hose lines from premature aging.
Electrical voltage!
Risk of injury from electric shock or risk of property damage!
▶ Always set up the relevant part of the machine/system so that it is free of
electrical voltage before you install the product or when connecting and
disconnecting connectors. Protect the machine/system against being re-
energized.
Restriction of the control function!
Risk of injury or property damage!
Moving parts in control equipment (e.g.valve spools) can, under certain
circumstances, get stuck in position as a result of contamination (e.g.impure
hydraulic fluid, abrasion, or residual dirt from components). As a result, the
hydraulic fluid flow and the build-up of torque in the axial piston unit can no longer
respond correctly to the operator's specifications. Even the use of various filter
elements (external or internal flow filtration) will not rule out a fault but merely
reduce the risk.
▶ Check whether your application requires that remedial measures be taken
on your machine in order to bring the driven consumer into a safe position
(e.g.safe stop).
▶ If necessary, make sure that these are properly implemented.

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CAUTION
High noise development during operation!
Risk of hearing damage or hearing loss!
The noise emission of axial piston units depends on, among other factors,
rotational speed, working pressure and installation conditions. The sound pressure
level may rise above 70 dB (A) during normal application conditions.
▶ Always wear hearing protection when in the vicinity of the operating axial piston
unit.
Hot surfaces on the axial piston unit!
Risk of burning!
▶ Allow the axial piston unit to cool down sufficiently before touching it.
▶ Wear heat-resistant protective clothing, for example, gloves.
Improper routing of cables and lines!
Risk of stumbling and property damage! Improper routing of cables and lines can
cause a risk of stumbling as well as damage to equipment and components, for
example, tearing of lines and connectors.
▶ Always lay cables and lines in such a way that no one can trip over them, that
they do not become kinked or twisted, do not rub on edges and do not run
without adequate protection through sharp-edged ducts.
Contact with hydraulic fluid!
Risk of adverse health effects, e.g. eye injury, skin irritation, poisoning from
inhalation!
▶ Avoid contact with hydraulic fluids.
▶ When working with hydraulic fluids, strictly observe the safety instructions
provided by the lubricant manufacturer.
▶ Wear your personal protective equipment (e.g. safety goggles, safety gloves,
suitable working clothes, safety shoes).
▶ Consult a doctor immediately if hydraulic fluid gets in your eyes or bloodstream,
or is swallowed.
Escaping hydraulic fluid due to machine/system leakage!
Risk of burns and risk of injury due to escaping oil jet!
▶ Depressurize the relevant machine/system part and repair the leak.
▶ Never attempt to block or seal the leak or oil jet with a cloth.
Danger from improper handling!
Risk of slipping! Risk of slipping on wet surfaces when climbing on the axial piston
unit.
▶ Never grab or climb onto the axial piston unit.
▶ Check how to safely get on top of the machine/system.

14/68 Safety instructions
Bosch Rexroth AG, A4CSG, Series 3x, RE 92105-01-B/06.2017
2.7 Personal protective equipment
Personal protective equipment is the responsibility of the user of the axial piston
unit. Observe the safety regulations and provisions in your country.
All pieces of personal protective equipment must be intact.

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3 General instructions on damage to
property and theproduct
The following instructions apply to chapters 6 to 14.
NOTICE
Danger from improper handling!
Product can get damaged!
▶ Do not expose the product to excessive mechanical loads.
▶ Never grab or climb onto the product.
▶ Do not place/lay any objects on the product.
▶ Do not strike the drive shaft of the axial piston unit.
▶ Do not set/place the axial piston unit on the drive shaft or assembled parts.
▶ Do not strike assembled parts (for example, sensors or valves).
▶ Do not strike sealing surfaces (for example, at working ports).
▶ Leave the protective covers on the axial piston unit until you connect the lines.
▶ Disconnect all electrical connectors before electro-welding or painting
operations.
▶ Make sure that the electronic components (for example, sensors) do not
become electrostatically charged (for example, during painting operations).
Risk of property damage due to inadequate lubrication!
Damage or destruction of product possible!
▶ Never operate the axial piston unit with insufficient hydraulic fluid. Specifically,
make sure that the rotary group has sufficient lubrication.
▶ When commissioning a machine/system, make sure that the housing area and
the working lines of the axial piston unit are filled with hydraulic fluid and
remain filled during operation. Air inclusions in the forward drive shaft bearing
are to be prevented, especially with the installation position “drive shaft
upwards”.
▶ Check the hydraulic fluid level in the housing area regularly; if necessary,
recommission. With above-reservoir installation, the housing area may drain
via the drain line after longer periods of disuse (air enters via the shaft seal)
or via the working line (gap leakage). This means the bearings are insufficiently
lubricated when the system is turned on.

16/68 General instructions on damage to property and theproduct
Bosch Rexroth AG, A4CSG, Series 3x, RE 92105-01-B/06.2017
NOTICE
Mixing of hydraulic fluids!
Product can get damaged!
▶ Before installation, remove all fluids from the axial piston unit to prevent mixing
with the hydraulic fluid used in the machine/system.
▶ Any mixing of hydraulic fluids from different manufacturers or different types
from the same manufacturer is generally not permitted.
Contamination of the hydraulic fluid!
The cleanliness of the hydraulic fluid has a considerable impact on the cleanliness
and service life of the hydraulic system. Contamination of the hydraulic fluid can
cause premature wear and malfunctions.
▶ Make sure that the working environment at the installation site is fully free
of dust and foreign substances in order to prevent foreign particles, such as
welding beads or metal cuttings, from getting into the hydraulic lines and
causing product wear or malfunctions. The axial piston unit must be installed in
clean condition.
▶ Use only clean connections, hydraulic lines and assembled parts (e.g. measuring
devices).
▶ No contamination may enter the ports when they are plugged.
▶ Before commissioning, make sure that all hydraulic connections are tight and
that all of the seals and plug-in connections are installed correctly to ensure
that they are leak proof and fluids and foreign particles are prevented from
penetrating the product.
▶ Use a suitable filter system to filter hydraulic fluid during filling to minimize solid
particle contamination and water in the hydraulic system.
Improper cleaning!
Product can get damaged!
▶ Plug all openings with the appropriate protection equipment in order to prevent
cleaning agents from entering the hydraulic system.
▶ Never use solvents or corrosive cleaning agents. Use only water and, if necessary,
a mild cleaning agent to clean the axial piston unit.
▶ Do not point the high-pressure cleaner on sensitive components, for example,
shaft seal, electrical connections and components.
▶ Use fiber-free cloths for cleaning.
Environmental pollution due to improper disposal!
Careless disposal of the axial piston unit and its assembled parts, the hydraulic
fluid and the packaging material can result in environmental pollution.
▶ Dispose of the axial piston unit, hydraulic fluid and packaging in accordance
with the national regulations in your country.
▶ Dispose of the hydraulic fluid in accordance with the applicable safety data
sheet for the hydraulic fluid.

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NOTICE
Danger from chemical or corrosive environmental conditions!
Product can get damaged! If the axial piston unit is exposed to chemical or
corrosive environmental conditions, such as sea water, fertilizer or road salt, it can
result in corrosion or, in extreme cases, malfunction. Hydraulic fluid can escape if
leaks occur.
▶ Take appropriate steps to protect the axial piston unit from chemical or
corrosive environmental conditions.
Escaping or spilling hydraulic fluid!
Risk of environmental pollution and contamination of ground water!
▶ Always place a drip tray under the axial piston unit when filling and draining the
hydraulic fluid.
▶ Use an oil binding agent if hydraulic fluid is spilled.
▶ Observe the parameters in the safety data sheet for the hydraulic fluid and the
specifications provided by the system manufacturer.
Danger from hot components!
Nearby products can become damaged! Components which heat up (for example,
solenoids) can cause damage to nearby products if they are too close.
▶ When installing the axial piston unit, check the distances to nearby products to
ensure that they do not get damaged.
The warranty only applies to the delivered configuration.
The entitlement to warranty cover will be rendered void if the product is incorrectly
installed, commissioned or operated, or if it is used or handled improperly.
3.1 Operator's obligations
The operator has the obligation to check in the order confirmation that the axial
piston unit supplied corresponds to the ordering details.

18/68 Scope of delivery
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4 Scope of delivery
2
2
1
1
2
1
Fig. 1: Axial piston unit
The following is included in the scope of delivery:
•Axial piston unit as per order confirmation
The following parts are also assembled prior to delivery:
•Protective covers (1)
•Protective plug/threaded plug(2)
•For version with through drive, metallic protection cover and mounting bolts

About this product 19/68
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5 About this product
5.1 Performance description
The Axial piston variable pump generates, controls and regulates a hydraulic fluid
flow. It is designed for stationary applications.
Refer to data sheet 92105 and the order confirmation for the technical data,
operating conditions and operating limits of the axial piston unit.
5.2 Product description
The A4CSG is a variable pump with axial piston rotary group in swashplate design for
hydrostatic drives in closed circuits. The flow is proportional to the drive speed and
displacement.
The flow can be changed steplessly by controlling the swashplate (cradle) (14). For
axial piston units in swashplate design, the cylinder (11) with pistons (12) is to be
aligned axially to the drive shaft (1).
In the closed circuit, the hydraulic fluid flows from the hydraulic pump to the
consumer, e.g. hydraulic motor and from there directly back to the hydraulic pump.
There is then a high-pressure side (7) and a low-pressure side(9), which can change
according to loading. The integrated boost pump (8) feeds into the low pressure side
and compensates for volumetric losses.
5.2.1 Layout of the axial piston unit
1
3
2
4
10
5
6
8
111314 12
7
9
5.1
5.1
5
Fig. 2: Layout of A4CSG ; example NG 500 left, NG 355 right
1 Drive shaft
2 Ground terminal
(2 additional ground
terminals are located
on the solenoids)
3 Retaining plate
4 Stroking piston
5 EP control module
5.1Pressure control
6 Control plate
(distributor plate)
7 High-pressure side
8 Boost pump
9 Low-pressure side
10 Suction port
11 Cylinder
12 Piston
13 Slipper pad
14 Swashplate
(cradle)
Closed circuit

20/68 About this product
Bosch Rexroth AG, A4CSG, Series 3x, RE 92105-01-B/06.2017
5.2.2 Functional description
Torque and rotational speed are applied to the drive shaft(1) by a drive motor. The
drive shaft is connected by splines to the cylinder(11) to set this in motion. With
every revolution, the pistons(12) execute a stroke in the cylinder bores, the size of
which depends on the pitch of the cradle(14). The slipper pads (13) are held on
with the pistons and guided along the glide surface of the cradle by the retaining
plate (3). The pitch of the swashplate during a rotation causes each piston to move
over the bottom and top dead centers and back to its initial position. Here, hydraulic
fluid is fed in and drained out through the two control slots in the control plate(6)
according to the stroke displacement. On the high-pressure side (7) the hydraulic
fluid is pushed out of the cylinder chamber and into the hydraulic system by the
pistons. At the same time, hydraulic fluid flows into the growing piston chamber on
the low-pressure side(9). In a closed circuit, supported by the return flow and boost
pressure.
The swivel angle of the cradle (14) is infinitely variable. Controlling the swashplate
swivel angle changes the piston stroke and, therefore, the displacement. Controlling
the swashplate through the neutral position will change the direction of flow (making
reversing operation possible). The swivel angle is controlled hydraulically via the
stroke piston(4). The cradle is mounted in swivel bearings for easy motion and the
neutral position is spring-centered. Increasing the swivel angle increases the
displacement; reducing the angle results in a corresponding reduction in
displacement.
Various control devices are available depending on requirements. Information
about this can be found in data sheet 92105.
Pump
Control