Bosch rexroth A21VG 10 Series User manual

Instruction manual
RE 93223-01-B/09.2020
Replaces: -.-
English
Axial Piston Variable Double
Pump A21VG
Series 10

The data specied above serve to describe the
product. Should information be provided on
use, these are only examples of applications
and suggestions. Information from the catalog
are not assured properties. The information
given does not release the user from the
obligation of own judgment and verication.
Our products are subject to a natural wear and
aging process.
© This document, as well as the data,
specications and other information set forth in
it, are the exclusive property of Bosch Rexroth
AG. It may not be reproduced or given to third
parties without its consent.
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 English language.

RE 93223-01-B/09.2020, A21VG Series 10, Bosch Rexroth Corporation
3/56Inhalt
Inhalt
1 About this documentation 5
1.1 Validity of the documentation 5
1.2 Required and supplementary documentation 5
1.3 Display of information 6
1.3.1 Safety instructions 6
1.3.2 Symbols 6
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 qualications 9
2.5 General safety instructions 9
2.6 Product-specic safety instructions 11
2.7 Personal protection equipment 13
3 General instructions on damage to equipment and the product 14
4 Scope of supply 17
5 Product description 18
5.1 Performance description 18
5.2 Product description 18
5.2.1 Assembly of the axial piston unit 18
5.2.2 Functional description 19
5.3 Product identication 20
6 Transport and storage 21
6.1 Transporting the axial piston unit 21
6.1.1 Transporting by hand 21
6.1.2 Transporting with lifting device 21
6.2 Storing the axial piston unit 23
7 Installation 25
7.1 Unpacking 25
7.2 Installation conditions 25
7.3 Installation position 27
7.3.1 Below-reservoir installation (standard) 27
7.3.2 Above-reservoir installation 28
7.4 Installing the axial piston unit 29
7.4.1 Preparation 29
7.4.2 Dimensions 29
7.4.3 General instructions 29
7.4.4 Installation with coupling 31
7.4.5 Installation on a gearbox 31
7.4.6 Installation with cardan shaft 32
7.4.7 Completing installation 32
7.4.8 Hydraulically connecting the axial piston unit 34
7.4.9 Electrically connecting the axial piston unit 38
7.5 Performing ushing cycle 38

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4/56 Inhalt
8 Commissioning 39
8.1 Initial commissioning 39
8.1.1 Filling the axial piston unit 39
8.1.2 Testing the hydraulic uid supply 41
8.1.3 Performing functional test 41
8.2 Running-in phase 42
8.3 Recommissioning after standstill 42
9 Operation 43
10 Maintenance and repair 43
10.1 Cleaning and care 43
10.2 Inspection 44
10.3 Maintenance 44
10.4 Repair 45
10.5 Spare parts 45
11 Removal and replacement 46
11.1 Required tools 46
11.2 Preparing for removal 46
11.3 Removal of the axial piston unit 46
11.4 Preparing the components for storage or further use 46
12 Disposal 47
13 Extension and conversion 47
14 Troubleshooting 48
14.1 How toproceed for troubleshooting 48
14.2 Malfunction table 49
15 Technical data 51
16 Alphabetical index 53

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1 About this documentation
1.1 Validity of the documentation
This documentation applies to the following products:
• Axial piston variable double pump A21VG series 10
This documentation is intended for machine/system manufacturers, tters and
service technicians.
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
equipment and the product” on page 14 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 conrmation
Contains the order-related technical data of your A21VG axial piston variable
double pump.
–Order conrmation
Installation drawing
Contains the outer dimensions, all ports and the hydraulic schematic
for your axial piston variable double pump A21VG.
Please request the
installation drawing
via your contact
person at Bosch
Rexroth.
Installation drawing
Axial piston variable double pumpA21VG
Contains the permissible technical data, ports, main dimensions and
circuitdiagrams.
93223 Data sheet
Mineral-oil based hydraulic uids and related hydrocarbons
Describes the requirements on a mineral-oil based hydraulic uid and related
hydrocarbons for the operation with Rexroth hydraulic components, and assists
you in selecting a hydraulic uid for your hydraulic system.
90220 Data sheet
Environmentally acceptable hydraulic uids
Describes the requirements on an environmentally acceptable hydraulic uid
for operation with Rexroth hydraulic components and assists you in selecting a
hydraulic uid for your hydraulic system.
90221 Data sheet
Fire-resistant, water-free hydraulic uids (HFDU/HFDR)
Describes the requirements on re-resistant, water-free hydraulic uids for
operation with Rexroth hydraulic components and assists you in selecting a
hydraulic uid for your hydraulic system.
90222 Data sheet
Notes 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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Bosch Rexroth Corporation, A21VG Series 10, RE 93223-01-B/09.2020
1.3 Display of information
Standardized safety instructions, symbols, terms and abbreviations are used so
that you can use this documentation to 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-specic
safety instructions” on page 11 and in chapter 3 “General instructions on
damage to equipment and the product” on page 14 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 in case of noncompliance
▶Measure for danger prevention
▶<List>
•Warning sign: draws attention to the danger
•Signal word: identies the degree of the danger
•Type and source of danger: identies 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: Danger classes in accordance with ANSI Z535.6-2006
Warning sign, signal word Meaning
DANGER Identies a dangerous situation that will result in death
or serious injuries if it is not avoided.
WARNING Identies a dangerous situation that may result in death
or serious injuries if it is not avoided.
CAUTION Identies a dangerous situation that may result in minor
to moderate injuries if it is not avoided.
NOTICE Damage to equipment: the product or the environment
may be damaged.
1.3.2 Symbols
The following symbols mark notes that are not safety-relevant but which increase
the understanding of the documentation.

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Table 3: Meaning of the symbols
Symbol Meaning
If this information is disregarded, the product can not be used
and/or operated to the optimum extent.
▶Single, independent step
1.
2.
3.
Numbered instruction:
The numbers specify that the steps are completed one after the other.
1.3.3 Designations
This documentation uses the following designations:
Table 4: Designations
Designation Meaning
A21VG Axial piston variable double pump, closed circuit
Threaded plug Metal screw, pressure-resistant
Protection plug Made out of plastic, not pressure-resistant, only for transportation
As umbrella term for “A21VG axial piston variable double pump” 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
ATE X EU directive for explosion protection (Atmosphère explosible)
DIN Deutsche Industrie Norm (German Institute for Standardization)
EP Proportional control electric
ET Electric control, direct controlled
HT Hydraulic control, direct controlled
HW Proportional control, hydraulic, mechanical servo
ISO International Organization for Standardization
JIS Japan Industrial Standard
RE Rexroth document in the English language
VDI2230 Directive for the systematic calculation of high duty bolted joints and
joints with one cylindrical bolt from the VDI (VereinDeutscherIngenieure
– Association of German Engineers)

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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 damage to equipment 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 classied neither as complete nor as incomplete machines in the sense
of the EU machine directive 2006/42/EC. A component is exclusively intended to
form an incomplete or a complete machine 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 machine directive.
The 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, application and operating conditions and
performance limits as specied in data sheet 93223 and in the order
conrmation. Information about approved hydraulic uids can be found in data
sheet93223.
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 the 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 shall accept no liability
whatsoever for damage resulting from improper use. The user shall bear all risks
arising from improper use.
Similarly, the following foreseeable faulty usages are also considered to be
improper:
• Use outside the operating parameters approved in the data sheet or in the order
conrmation (unless customer-specic approval has been granted)
• Use for non-approved uids, e.g.water or polyurethane components
• Modication of factory settings by non-authorized persons

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• Use of add-on parts (e.g. control unit, valves) that are not specied Rexroth
components
• Using the axial piston unit under water at a depth of more than 10 meters
without necessary additional measures, e.g. pressure equalization
• Using the axial piston unit when the exterior pressure is greater than the interior
pressure (case pressure)
• Using the axial piston unit in explosive environments unless the component or
machine/system has been certied as compliant with the ATEX directive 94/9/EC
• Using the axial piston unit in an aggressive atmosphere
• Using the axial piston unit in aircraft or space craft
2.4 Personnel qualications
The activities described in this documentation require basic mechanical, electrical
and hydraulic knowledge, as well as knowledge of the associated technical terms.
For transporting and handling the product, additional knowledge is necessary
with regard to working with a lifting device and the corresponding attachment
equipment. In order to ensure safe use, these activities may therefore only be
carried out by appropriate qualied personnel or an instructed person under the
direction and supervision of qualied personnel. Qualied personnel are those
who can recognize possible hazards and institute 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.
Qualied personnel must observe the rules relevant to the subject area and have
the necessary hydraulic knowledge.
Hydraulic knowledge means, for instance:
• reading and fully understanding hydraulic plans,
• fully understanding in particular the interrelationships regarding safety devices,
and
• having knowledge on the function and assembly of hydraulic components.
Bosch Rexroth offers training support for special elds. You can nd an
overview of the training contents on the internet at:
http://www.boschrexroth.com/didactic.
2.5 General safety instructions
• Observe applicable accident prevention and environmental protection
regulations.
• Observe the safety regulations 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.
• Do not install, operate, remove ormaintain Rexroth products if under
theinuence of alcohol, drugs ormedication that may affect your reaction time.
• Only use genuine Rexroth accessories and spare parts toensure there isno
hazard to persons from unsuitable spare parts.
• Observe the technical data and ambient conditions specied inthe product
documentation.

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Bosch Rexroth Corporation, A21VG Series 10, RE 93223-01-B/09.2020
• 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 personal injury or property damage. For this reason, only use
theproduct in safety-relevant applications if this use isexpressly indicated
and approved in the product documentation, e.g. inexplosion protection areas
orinsafety-related parts of a control system (functional safety).
• Only commission theproduct if it has been determined that theend product (e.g.
machinery/system) in which the Rexroth products are installed complies with the
country-specic 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 (e.g. 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 these are appropriately
implemented.
• Depending on the type of control used, electromagnetic effects can beproduced
when using solenoids. Applying a direct voltage signal (DC) to solenoids does not
create electromagnetic interference (EMI) nor is the solenoid affected byEMI.
Potential electromagnetic interference (EMI) exists if the solenoid isenergized
with a modulated direct current (e.g. PWMsignal). Appropriate testing and
measures should be taken by the machine manufacturer toensure other
components oroperators (e.g. with pacemaker) are not affected bythis potential.

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2.6 Product-specic safety instructions
The following safety instructions apply for chapters 6 to 14.
WARNING
Danger from excessive pressure!
Danger tolife, risk ofinjury orproperty damage!
Improperly changing thefactory pressure settings can result inapressure
increase beyond themaximum permissible pressure.
Operating theunit above themaximum permissible pressure can cause
components toburst and hydraulic uid toescape under high pressure.
▶Changes tothe factory settings may only bemade byBoschRexroth
specialists.
▶Inaddition, apressure relief valve isrequired inthe hydraulic system
asback-up. If theaxial piston unit isequipped with apressure cut-off and/
or pressure controller, this isnot anadequate safeguard against pressure
overload.
Danger due tosuspended loads!
Danger tolife, risk ofinjury orproperty damage!
Improper transportation may cause theaxial piston unit tofall down and lead
toinjury, e.g. crushing orfracture, ordamage tothe product.
▶Make sure that theload bearing capacity ofthelifting device issufcient
tosafely bear theweight oftheaxial piston unit.
▶Never step orgrip under suspended loads.
▶Ensure astable transport position.
▶Use your personal protective equipment (e.g. safety goggles, safety gloves,
suitable working clothes, safety shoes).
▶Use suitable lifting devices for transport.
▶Observe theprescribed position ofthelifting strap.
▶Observe thenational laws and specications ofoccupational safety and health
and transport.
System/machine under pressure!
Risk ofdeath orserious injury when working onunsecured machines/systems!
Property damage!
▶Switch off theentire system and secure itagainst reactivation according tothe
parameters provided bythemachine/system manufacturer.
▶Ensure that all relevant components ofthehydraulic system are depressurized.
For this purpose, observe theparameters indicated bythemachine/system
manufacturer.
▶Please note that thehydraulic system might still bepressurized even after
separation from theactual pressure supply.
▶Do not disconnect any line connections, ports andcomponents aslong
asthehydraulic system isunder pressure.

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WARNING
Escaping hydraulic uid mist!
Risk ofexplosion and re hazard, health hazard, risk ofenvironmental pollution!
▶Depressurize therelevant machine/system component and repair theleak.
▶Only perform welding work when themachine/system isdepressurized.
▶Keep open ames 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 any escaping hydraulic
uid 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 disconnect thevoltage supply tothe relevant machine/system
part before installing theproduct and/or connecting ordisconnecting
theconnector. Protect themachine/system against being re-energized.
Danger from unexpected machine movement!
Danger tolife orrisk ofinjury! Unintentional orcareless actuation ofthemanual
override ofthesolenoids can cause unexpected machine movements.
▶Use themanual override only for functional testing orinthe event oftechnical
malfunctions.
▶Using themanual override ona permanent basis (e.g. bywedging, blocking)
isnot permitted.
▶The use ofthemanual override isonly permitted with limited technical data
(e.g. 0.25×maximum data).
▶Check whether ornot your machine requires additional safety measures for
your application toavoid unintentional actuation. Ifnecessary, make sure
these are appropriately implemented.
▶Wear suitable protective clothing.
Limitation oftheclosed loop control and/or open loop control function!
Risk ofinjury orproperty damage!
Under certain circumstances, moving parts incontrol equipment
(e.g.,valvespools) can get stuck inan undened position due tocontamination
(e.g.,impure hydraulicuid, abrasion orresidual dirt from components).
Asaresult, the hydraulic uid ow and the build-up oftorque inthe axial piston
unit can nolonger respond correctly tothe operator’s specications. Even theuse
ofvarious lter elements (external orinternal ow ltration) will not rule out
afault but merely reduce therisk.
▶Check whether your application requires remedial measures onyour machine
inorder tobring thedriven consumer toasafe position (e.g. safe stop).
▶Ifnecessary, make sure these are appropriately implemented.

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CAUTION
High noise development during operation!
Danger ofhearing damage, hearing loss!
The noise emission ofaxial piston units depends onrotational speed, working
pressure and installation conditions, among other factors. The sound pressure
level may rise above 70 dB (A) incertain application conditions.
▶Always wear hearing protection near arunning axial piston unit.
Hot surfaces onaxial piston unit!
Risk ofburning!
▶Allow theaxial piston unit tocool down sufciently before touching it.
▶Protect yourself with heat-resistant protective clothing, e.g. gloves.
Inappropriate 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,
e.g.due tolines and connectors being torn off.
▶Always install cables and lines inaway that nobody can fall over them, that
they are not bend ortwisted, do not chafe onedges and are not guided
through ducts with sharp edges without sufcient protection.
Contact with hydraulic uid!
Danger tohealth / damage tohealth, e.g. eye injury, skin damage, toxication
inthe event ofinhalation!
▶Avoid any contact with hydraulic uids.
▶When handling hydraulic uids, thesafety instructions ofthelubricant
manufacturer need tobe observed atall times.
▶Use your personal protective equipment (e.g. safety goggles, safety gloves,
suitable working clothes, safety shoes).
▶Immediately seek medical attention, however, ifhydraulic uid gets into your
eyes orblood circuit orif you swallow itaccidentally.
Escaping hydraulic uid through leaking machine/system components!
Risk ofburning and risk ofinjury due toescaping hydraulic uid jet!
▶Depressurize therelevant machine/system component and repair theleak.
▶Never attempt toblock orseal theleak orhydraulic uid jet with acloth.
Danger from improper handling!
Slip hazard! 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.
2.7 Personal protection equipment
The personal protection equipment is the responsibility of the user of the axial
piston unit. Observe the safety regulations and provisions of your country.
All components of the personal protection equipment must be intact.

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3 General instructions on damage to
equipment and the product
The following instructions apply for chapters 6 to 14.
NOTICE
Danger from improper handling!
Product can bedamaged!
▶Do not subject theproduct toimproper mechanical loads.
▶Never use theproduct ashandle orstep.
▶Do not put/place 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 (e.g. sensors orvalves).
▶Do not hit sealing surfaces (e.g. onthe work connections).
▶Leave theprotective covers onthe axial piston unit until you connect thelines.
▶Disconnect all electrical connectors before arc welding andpainting
operations.
▶Ensure that theelectronic components (e.g. sensors) are not electro-statically
charged (e.g. during painting operations).
Risk ofproperty damage due toinadequate lubrication!
Product can bedamaged ordestroyed!
▶Never operate theaxial piston unit with insufcient hydraulic uid.
Specically, make sure that therotary group has sufcient lubrication.
▶When commissioning amachine/system, make sure that thehousing area and
theworking lines oftheaxial piston unit are lled with hydraulic uid and
remain lled during operation.
▶Check thehydraulic uid level inthe housing area regularly and recommission,
ifnecessary. For above-reservoir installation, thehousing area may drain
out through thedrain line after prolonged standstill periods (air enters
through theshaft seal) orthrough theworking line (gap leakage). This means
thebearings are insufciently lubricated when thesystem isturned on.
▶Make sure thesuction line isalways lled with hydraulic uid during
commissioning and operation.
Mixing hydraulic uids!
Product can bedamaged!
▶Before installation, remove all uids from theaxial piston unit toprevent
mixing with thehydraulic uid used inthe machine/system.
▶Any mixture ofhydraulic uids ofdifferent manufacturers and/or different
types ofthesame manufacturer isgenerally not permissible.

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NOTICE
Contamination ofhydraulic uid!
The cleanliness ofthe hydraulic uid impacts the service life ofthe axial piston
unit. Contamination ofthe hydraulic uid may lead topremature wear and
malfunctions!
▶Always ensure awork environment inthe assembly location that isfree from
dust and foreign particles toprevent foreign particles, e.g. welding beads
ormetal cuttings, from entering thehydraulic lines and lead towear and
malfunctions inthe product. The axial piston unit should beclean when
installed.
▶Only use clean ports, hydraulic lines and assembled parts (e.g. measuring
devices).
▶When plugging theports, nocontamination may ingress.
▶Before commissioning, ensure that all hydraulic connections are tight and
that all seals and plugs oftheplug-in connection are correctly installed and
undamaged toprevent uids and foreign particles from entering theproduct.
▶Filter the hydraulic uid when lling the system with asuitable lter system
tominimize the solid particle contamination and water inthe hydraulic system
and to achieve the required cleanliness level.
Improper cleaning
Product can bedamaged!
▶Plug all openings with appropriate protective covers inorder toprevent
cleaning agents from entering thehydraulic system.
▶Never use solvents oraggressive cleaning agents. Use only water and,
ifnecessary, amild cleaning agent toclean theaxial piston unit.
▶Do not point ahigh-pressure cleaner atsensitive components, e.g. shaft seal,
electrical connections and components.
▶Use ber-free cleaning cloths for cleaning.
Environmental pollution due toincorrect disposal!
Careless disposal oftheaxial piston unit and its assembled parts,
thehydraulicuid and thepackaging material can cause environmental pollution!
▶Dispose oftheaxial piston unit, hydraulic uid and packaging inaccordance
with theregulations inyour country.
▶Dispose ofthehydraulic uid inaccordance with theapplicable
safetydatasheet ofthehydraulic uid.
Danger due tochemical oraggressive environmental conditions!
Product can be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. Leaks may lead
toaleakage ofhydraulic uid.
▶Take appropriate measures toprotect theaxial piston unit from chemical
orcorrosive environmental conditions.

16/56 General instructions on damage to equipment and the product
Bosch Rexroth Corporation, A21VG Series 10, RE 93223-01-B/09.2020
NOTICE
Leakage orspilling ofhydraulic uid!
Environmental pollution and contamination oftheground water!
▶Always place adrip tray under theaxial piston unit when adding and draining
thehydraulic uid.
▶Use asuitable binding agent ifhydraulic uid isspilled.
▶Observe thesafety data sheet for thehydraulic uid and thespecications
provided bythesystem manufacturer.
Danger due toheat development incomponents!
Adjacent products may bedamaged! Due toaheat development incomponents
(e.g. solenoids), adjacent products may bedamaged during assembly ifno
sufcient safety distance iscomplied with.
▶When installing theaxial piston unit, check thesafety distances tonearby
products toensure that they are not damaged.
The warranty applies only to the delivered conguration.
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.

Scope of supply 17/56
RE 93223-01-B/09.2020, A21VG Series 10, Bosch Rexroth Corporation
4 Scope of supply
Included in the scope of supply are:
• Axial piston unit as per order conrmation
The following parts are also installed on delivery:
• Protection plug/threaded plug(1)
• For version with through drive, metallic protection cover and mounting bolts (2)
1
2
Fig. 1: Axial piston unit

18/56 Product description
Bosch Rexroth Corporation, A21VG Series 10, RE 93223-01-B/09.2020
5 Product description
5.1 Performance description
The axial piston variable double pump generates, controls and regulates a
hydraulic-uid ow. It is designed for mobile applications such as construction
machinery.
Refer to data sheet 93223 and the order conrmation for the technical data,
operating conditions and operating limits of the axial piston unit.
5.2 Product description
The A21VG is a variable double pump with two axial piston rotary groups in
swashplate design for hydrostatic drives in closed circuits. The two ows are
proportional to the drive speed and the displacement. The ow can be steplessly
changed by controlling the cradle (11). Both circuits can be adjusted independent
of one another. For axial piston units with swashplate design, the pistons are
arranged axially with respect to the drive shaft.
In the closed circuit, the hydraulic uid ows from the hydraulic pump to the
consumer (e.g. the hydraulic motor) and from there directly back to the hydraulic
pump.
There is a high-pressure side and a low-pressure side which alternate depending
on which side is under load.
5.2.1 Assembly of the axial piston unit
1
4
5
4
3
2
10
12
11
8
9 6 8 96
7
3
2
10
12
11
Fig. 2: Assembly of the A21VG
1 Drive shaft
2 Retainer plate
3 Controller (using the ET
as an example here)
4 Stroking piston
5 High-pressure side
6 Low-pressure side
7 Control plate
8 Cylinder
9 Piston
10 Slipper pad
11 Cradle
12 Angle Sensor
(optional)
Closed circuit

Product description 19/56
RE 93223-01-B/09.2020, A21VG Series 10, Bosch Rexroth Corporation
5.2.2 Functional description
Torque and rotational speed are applied to the drive shaft (1) by an diesel engine.
The drive shaft is connected by splines to the cylinder(8) to set this in motion.
With every revolution, the pistons (9) in the cylinder bores execute one stroke
whose magnitude depends on the setting of the cradle(11). The pistons hold the
slipper pads (10) onto the glide surface of the cradle with the retainer plate (2)
and guide them along. The swashplate setting during a rotation causes each piston
to move over the bottom and top dead centers and back to its initial position.
Here, hydraulic uid is fed in and drained out through the two control slots in the
control plate(7) according to the stroke displacement. On the high-pressure side
(5) the hydraulic uid is pushed out of the cylinder chamber and into the hydraulic
system by the pistons. At the same time, hydraulic uid ows into the growing
piston chamber on the low-pressure side(6). In a closed circuit, supported by the
return and boost pressure.
The four high-pressure relief valves protect the hydrostatic transmission (pump and
engine) against overloading. They limit the maximum pressure in the relevant
high-pressure line and at the same time act as boost valves. High-pressure relief
valves are not working valves and are only suitable for pressure spikes or high rates
of pressure change.
In order to replenish internal leakage in the variable double pump and consumers,
portG must be connected to an external source of boost pressure. The boost
pressure-relief valve is integrated.
The swivel angle of the cradle (11) is steplessly varied. Controlling the swivel
angle of the swashplate changes the piston stroke and therefore the displacement.
Adjusting the swashplate through the neutral position will change the direction of
ow (making reversing operation possible). The swivel angle is controlled
hydraulically by means of the stroking piston. 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 93223.
Pump
High-pressure
safeguarding
Version without boost
pump
Control

20/56 Product description
Bosch Rexroth Corporation, A21VG Series 10, RE 93223-01-B/09.2020
5.3 Product identication
The axial piston unit can be identied from the name plate. The following example
shows an A21VG name plate:
CNR:
MNR:
SN:
FD: Rotation:
DE - 89275 Elchingen
Made in Germany
X1234567890Y
R90XXXXXXX SC: X
12345678
2013W28
n XXXX min-1 P XXX kW m XXX kg
7202
Typ: A21VG45ET1PD0/10ARNB2S73UB2S4-0
1
2
8
3
4
5
6
7
14
9
13
12
11
10
Fig. 3: Name plate A21VG
1 Manufacturer
2 Sample category (optional)
3 Internal plant designation
4 Specied area for inspection stamp
5 Direction of rotation (viewed on
drive shaft) – here: clockwise
6 Weight (optional)
7 Power
8 Bar code
9 Rotational speed
10 Manufacturing date
11 Serial number
12 Material number of the axial piston
unit
13 Ordering code
14 Customer material number