tractors and presents components and system solutions. These solutions – when engineeredto the speciﬁc application – are also deployable to other mobile machines. The reader of thisbook should have a good knowledge of hydraulics and be familiar with the symbols used inhydraulic schematics to fully grasp and enjoy the information conveyed.

Knowledge in Detail

Hydraulics in Tractors

Hydraulics in Tractors

This book provides an overview of the most important hydraulic functions of agricultural

Knowledge in DetailBosch Rexroth AG
Drive & Control Academy
Bahnhofplatz 297070 Würzburg, Germany
Phone: +49 9352 18-1920
Fax: +49 9352 18-1040
media@boschrexroth.dewww.boschrexroth.com/academy© Bosch Rexroth AG 2014
Material number: R961009447

Umschlag_Traktorbuch_2014-07_Hardcover_.indd 1

05.08.2014 14:29:54

Bosch Rexroth AG

Contents | Hydraulics in tractors

Contents
Section I – General introduction
1

With hydraulics to a universal working machine

92

Design and characteristics of hydraulic systems

15

3

Basic schematics and system variants

17

3.1

Basic schematics of hydraulic systems

17

3.2

Systems for diﬀerent power classes

20

3.2.1

Lower power range (< 70 kW)

20

3.2.2

Medium power range (70 – 125 kW)

20

3.2.3

Upper power range (> 125 kW)

21

Section II – Hydraulic and electronic components
4

Pumps and motors

23

4.1

Gear units

24

4.1.1

Gear pumps

24

4.1.2

Gear motors

27

4.2

Axial piston units

28

4.2.1

Designs of axial piston units

28

4.2.2

Swashplate pumps for open circuit

30

4.2.3

Swashplate pumps for closed circuit

35

4.2.4

Axial piston motors

36

5

Directional and priority valves

37

5.1

Design and characteristics of directional valves

38

5.2

Directional valves with mechanical actuation

41

5.2.1

Directional valve series SB23-M (OC)

41

5.2.2

Directional valve series SM12-M (OC)

46

5.2.3

Directional valve series SB23-M (LS)

47

5.3

Directional valves with electronic actuation

50

5.3.1

SB23-EHS directional valves

51

5.3.2

SB23-EHS1 directional valves

56

5.3.3

SB33-EHS2 directional valves

56

5.4

Joysticks – mechanical-electronic control levers

62

5.5

Priority valves

64

5.6

Valve blocks

66

5

6

Hydraulics in tractors | Contents

Bosch Rexroth AG

6

Electronic controllers and bus systems

69

6.1

Digital electronic controllers

69

6.1.1

The basic functions

69

6.1.2

Hardware

70

6.1.3

Software76

6.2

Electronic bus systems

77

6.2.1

Operating mode of CAN bus systems

78

6.2.2

Bus systems for agricultural engineering

79

6.2.3

The ISOBUS system

80

6.2.4

Advantages of bus systems for mobile working machines

84

Section III – Hydraulic systems
7

Steering systems

85

7.1

Design and function of hydrostatic steering systems

85

7.2

Design and function of hydrostatic steering units

86

7.3

System related variants

88

7.3.1

Steering systems for OC systems

88

7.3.2

CC steering systems for LS systems

89

7.4

Emergency steering function

90

7.4.1

Steering units with two gerotor sets

92

7.4.2

Steering unit with chamber cut-oﬀ

93

7.4.3

Steering unit with ﬂow increase

95

7.5

Electronic-hydraulic steering systems

96

8

Travel drives and PTO drives

101

8.1

Hydraulically controlled gear transmissions

102

8.1.1

Controlled switching activation of PTO's

105

8.2

Hydrostatic continuously variable transmissions

106

8.2.1

Function and design principles

106

8.2.2

The Fendt Vario transmission

110

8.2.3

The ZF Eccom transmission

114

Bosch Rexroth AG

Contents | Hydraulics in tractors

9Braking systems

119

9.1

Remotely powered brake systems for tractors

119

9.1.1

Design of hydraulic remotely powered brake systems

120

9.1.2

Hydraulic remotely powered brake system with ABS

121

9.1.3

Summary

125

9.2

Trailer brake

126

9.2.1

Design and function of trailer brake systems

126

9.2.2

Brake valves

129

9.2.3

Schematics of trailer brakes in hydraulic systems

134

9.2.4

Outlook for future developments

135

10

Suspension systems

137

10.1

Hydro-pneumatic suspension for front axles

138

10.1.1

Front axles and their suspension

139

10.1.2

Electronic-hydraulic control

140

10.1.3

Improvement through front axle suspension

141

10.2

Cab and seat suspensions

141

10.2.1

Cab suspensions

141

10.2.2Seat suspensions

144

10.3

Summary

145

11Electrohydraulic Hitch Control EHC

147

11.1

History147

11.2

Components of the EHC

150

11.2.1

Control valves

150

11.2.2

Electronic controllers

160

11.2.3

Electronic sensors

163

11.2.4Control panel for the EHC

169

11.3

EHC functions

170

11.3.1

Position control

170

11.3.2

Tractive force and mixed control

171

11.3.3

Slip control

171

11.3.4

Active vibration damping

172

11.3.5Pressure control

174

11.3.6Weighing

176

11.3.7External control

177

7

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Hydraulics in tractors | Contents

Bosch Rexroth AG

12

Fan drives

179

12.1

Introduction

179

12.2

System layout of hydraulic fan drives

180

12.3

Systems with hydro-mechanical control

180

12.4

Systems with electronic-hydraulic control

181

12.5

Systems with reversing function

183

12.6

Separate coolant circuits

184

12.7

Components of hydraulic fan drive systems

184

12.7.1

Thermal pressure valves and pressure control valves

185

12.7.2Temperature sensors

186

12.7.3

Electronic controllers

186

13

Control of implements

189

13.1

The hydraulic interfaces between tractor and implements

189

13.2

Changeover between on-road driving and ﬁeld operations

191

13.3

Control of a seedbed combination at the headland

192

13.4

Hydraulic settings and additional functions for plowing

193

13.4.1

Turning large plows

193

13.4.2Adjusting plows

194

13.4.3

Additional functions for saddle plows

195

13.5

Drive and control of centrifugal fertilizer spreaders

196

13.6

Control of front loaders

198

13.7

Conclusion

198

Literature

199

56

Hydraulics in tractors | Directional and priority valves

5.3.2

SB23-EHS1 directional valves

Bosch Rexroth AG

Pilotventil
Pilot
valve

The directional valve SB23-EHS1 is afurther development of the SB23-EHS,

Check valves
Sperrventil

Housing
GehäusePosition
sensorWegaufnehmerfeaturing the same essential performancedata.
Figure 5.35 shows a sectional view ofthe valve slice. The diﬀerence is thatthe ﬂanged EHS actuator unit has been
replaced by an integrated pilot system.
The 4/3-way pilot valve is integrated
in the valve housing and instead of aseparate stroking cylinder, the end facesof the piston spool are used as its control
as is common with pilot operated valves.
Mechanical control is no longer available.
Emergency manual actuation can be

Elektronik
Electronics
Pilot spool
Steuerschieber

Individualdruckwaage
Individualpressure compensator

Fig. 5.35: Sectional view of a Rexroth SB23-EHS1 valve slice

ﬁtted on request.
5.3.3

SB33-EHS2 directional valves

Figure 5.36 shows a sectional view of avalve slice SB23-EHS1 and a valve blockof the series SB33-EHS2 with four slices.
In 2006, Bosch Rexroth realized a new
basic valve concept whose performancedata can also satisfy future requirements.
The most important features are:
▶ Increased ﬂow range▶ Lower ﬂow resistance▶ Load-compensated input and output
ﬂows▶ Hydraulically controlled check valves▶ Integrated pressure sensors▶ Higher dynamics▶ Suitable for use as control valve for
EHC hitch control

Fig. 5.36: Rexroth SB33-EHS2 valve block and sectional view of a SB23-EHS1 valve slices

Bosch Rexroth AG

Directional and priority valves | Hydraulics in tractors

Like on the EHS1, the main spool is

Check valves

Sperrventil

controlled via a 4/3-pilot valve, which

Work ports
Verbraucheranschlüsse

is integrated in the valve slice and uses
the end faces of the main spool for its
control.

Pressure
Drucksensor
sensorReturnspringRückstellfeder

Pilot
valve
Vorsteuerventil

The hydraulically controlled check valves
in both of the consumer ports are new.
They have the function of hydraulicallyunlockable check valves, working as loadcompensating pressure compensators,
like lowering valves, for lowering or

Position
sensorWegaufnehmer

Drucksensor
Pressure
sensorCircuitboard
Leiterplatte

driving loads.
Another new feature is that the valve
can be optionally equipped with up to

Stellraum
Chamber
Shuttle valve
Wechselventil

Stellraum
Chamber

Hauptschieber
Main
spool

Fig. 5.37: Design of a Rexroth SB33-EHS2 directional valve

three pressure sensors, which, as shownin Figure 5.37, can be assigned to ﬁve

This requires minimal ﬂow resistancediﬀerent measuring points.

in the connected cylinder lines. Thisis achieved through large ﬂow cross-

The maximum intake ﬂow can amount tosections of the check valves, which are

170 l/min and in the return ﬂow channels

hydraulically fully opened.

250 l/min. The ﬂow resistances and thus
the power dissipation compared to the

As described for EHS valves, the operator

SB23-EHS1 are reduced at the samecan conveniently change the ﬂow char-time.

acteristics and the time response of thevalves electronically and adapt to the rela-

The electronically controllable valves aretive work task. The valves are parameter-

increasingly used for automatic control

ized via the CAN interface. With the aid ofof working processes. The dynamic

software tools, the tractor manufacturer

behavior has therefore been reduced

can develop and test an optimal operat-

from 70 ms to 50 ms for a full stroke froming concept for the machine. The tractor

the center position.

driver is oﬀered an operating conceptthat does not place high demands andAt the same time the resolution of the ﬂow

that allows to adapt the controls to thecurve in the ﬁne control range has been

special work tasks of the attached ma-

improved to approx. 0.2 l/min. The ﬂoat

chines in a simple manner.

position of the valves is often used forlight implements which lie on the groundA diagnosis memory is integrated in theand are to follow the ground proﬁle.

valve electronics. The operating conditions are saved here and can be readand evaluated with an easy to operate
software tool.

Individualdruckwaage
Individual pressure compensator

57

58

Bosch Rexroth AG

Hydraulics in tractors | Directional and priority valves

5.3.3.1

Valve operating positions
Consumer

Position “0” – neutralA

The valve's functional range is compre-

B

Check valveshensive and complex. The functions of

Rx X

the individual components for the four

Thruster spool

valve spool positions are described
below. The transitions between thepositions are stepless, each main spool

R

Pilot valve

position is set in a position controlledmanner, relevant to the setpoint value.
Y

Figure 5.38 shows the valve in neutral
position, with a signal-free pilot valve.

Main spoolP

Shuttle valve

The pressure chambers at the end of themain spool are unloaded via the pilot
valve to the pilot return line Rx, and themain spool is centered in neutral positionby the return spring, see Figure 5.37.

Individual pressure compensator
Fig. 5.38: Neutral position of the Rexroth SB33-EHS2 valve

The spool for opening the check valves
and the spring chamber in the pressurecompensator are unloaded to the returnline R.
Position "1" – Operating the cylinder
via port B
In position "1" the centering-springchamber at the spool end to the rightis pressurized via the pilot valve. The
pressure chamber at the left side of themain spool is unloaded to the pilot ﬂow
return line. Against the return springforce the main spool is shifted to the left.
At the main spool, the control edges P2-B
and A-R are opened, port B is connectedto the pump ﬂow and port A to the returnﬂow.
The spool for opening the check valve
in A is connected to the pilot pressure X
and pushed open hydraulically, so thatthe return oil ﬂow from port A can ﬂow
unrestricted to the return line

Fig. 5.39: Rexroth SB33-EHS2 valve in position"1" – cylinder drive via port B

Bosch Rexroth AG

Directional and priority valves | Hydraulics in tractors

The check valve B is not piloted, as it
functions as a check valve and opens
itself through the ﬂow to the load. The
connection between the spring chamberof the pressure compensator and thereturn line is closed and connected via ashuttle valve to the load pressure in the
B-channel.
Position "2" – Operating the cylinder
via port A
In position "2", see Figure 5.40, thepressure chamber at the left spool sideis pressurized via the pilot valve and thespring cap chamber is unloaded to thepilot oil return line. Against the return
spring force the main spool is shifted to
the right. The further control operations
take place in a similar way as in position
1.

Fig. 5.40: Rexroth SB33-EHS2 valve in position"2" – cylinder drive via port A

Position "F" (ﬂoat)
In the position "F" (ﬂoat), see Figure 5.41,
the main spool is shifted beyond position
2 against the stroke stop in the spring
cap.
Both service line ports A and B areconnected to the return line (A-R, B-R)
and therefore also with each other. In thisposition, the connections from the pumpto the load are closed and the springchamber in the pressure compensatoris unloaded to the return line R.
The control chambers of both check valve
pilot spools are connected to the pilotpressure X and are hydraulically pushed
open.
Both cylinder ports are therefore connected with each other and a connectedcylinder can move freely.

Fig. 5.41: Rexroth SB33-EHS2 valve in position "F" (ﬂoat)

59

60

Bosch Rexroth AG

Hydraulics in tractors | Directional and priority valves

5.3.3.2

Special valve functions
UnactuatedLoad compensated return ﬂow with apulling load
With the throttle control systems commonly used to date and operation with

Control edges fordownstream ﬂow at
the main spoolRpulling loads, a compromise between thecontrollability of heavy and light loads isalways necessary.

+
18 bar

The resulting speeds are always too highFloads.

and heavy loads, the oil ﬂow to the inlet

2

0

1

R

Fig. 5.42: Function of the check valves with load compensation for the return ﬂow

side is too low, resulting in a cavity whichneeds reﬁlling upon switching to theWith these features, the valve can control

other direction. With low load pressuresloads going from positive to negativeon the other hand, the pump must evenpressures without delay.

generate pressure when lowering theload, which results in energy losses.

Pilot pressure
switched on

Δp = 17 bar = constantwith heavy loads and too low with light

In the case of double-action cylinders

Actuated

1 bar

SPV control bycontrol edges
on main spool

This is a necessary precondition for a

These problems are prevented with the

double-action EHC hitch function, which

new control of the check valves.

will be dealt with in Chapter 6 "Electronic
controllers and bus systems".

These check valves control the oil ﬂow
from the cylinder to the return line, in

Figure 5.42 shows the working principle

principle like the individual pressureof the check valve. The pilot pressure iscompensators control the ﬂow fromused to keep the pressure drop and thus

pump to valve. The cylinder speed isthe ﬂow at the return ﬂow control edges

now independent of the load pressure.

in the valve constant, regardlessThrough the new "active ﬁlling" function,of the load pressure.

the pressure in the ﬂow to the cylinder
remains at a constant low level at highAs the schematic in Figure 5.42 shows,or low load pressure, without a vacuum

the check valve controls the pressure

or pressure increase.

drop at the return ﬂow edge of the mainspool to 17 bar, when the pilot pressure

A special LS circuit concept with an AB

is 18 bar and the equivalent check valve

shuttle valve automatically detects anspring pressure amounts to 1 bar. Since

insuﬃcient ﬁlling of the cylinder inlet

the pilot pressure is switched onto theside and controls the pump or pressure

return line, a tuning with the return line

compensator in such a manner thatpressure of the respective machine ispartial vacuum is prevented.

necessary.

Bosch Rexroth AG

Integrated pressure sensors

Dais-chain plugconnector

UBat

valve. These sensors enable a lot of new,especially automatic functions.
A maximum of three pressure sensors
can alternatively measure the pump pressure, the LS pressure at the valve outlet
and in the valve, and the load pressuresin the service line ports.

Stabi

Ground

4.2

Signalprocessing

3.1of the SB33-EHS2 valve.
The pressure signals can be processedinternally in the valve or externally, since
they are available in the CAN bus. Typical internal valve functions are a freely
programmable kickout or the automatic

5V

Reset PWM
AD

Potentiometer
PWM
3.2
CAN HI
RS232-RXD

AD

PWM

Timer

CAN LO
RS232-TXD
FA

CAN
CAN driverAD

Microprocessor withintegrated EEPROM

Relay driver for external
error deactivation withpotentiometer and PWM

EHC control panel
CAN busPressure sensor
PositionTurntransducer

EHS valves

EHR
valve
Force sensor

Widthadjustment

EHS2 valve only has to be actuated once.
The next sequence follows automatically,
since the pressure-controlled valve reverses the turning cylinder automaticallyin dead center.
Upon reaching the stop, the kickout
function switches the valve back into
neutral position, see Figure 5.44.
Typical functions with external processing of the pressure signals are pressure
dependent controls and pressure
controls as well as system monitoringand diagnostics.

U
P

P
U

Fig. 5.44: Automatic reversing function of an alternating plow

U

Pressure measurement "pA"
Pressure measurement "pB"
or "pY0""pY" from "pA" & "pB"

Fig. 5.43: Block circuit diagram of the SB33-EHS2 valve electronics with two pressure sensors

the cylinder is reversed in dead center. To
complete this function the relevant SB33-

S

I

Strokemeasurement

function.

of a plow at the end of the ﬁeld, in whichU

AD

pressure-dependent reversing of a drive

A typical example of this is the turning

U

Current
measurement

AD

2.2

I
Output
stage

AD
RS232

2.1

Figure 5.43 shows the block circuit
diagram of the integrated electronics

Pilot valve withstroking piston andposition transducer

1.2
4.1

mounted in the electronic unit in theComputermonitoring

Error

Diagnosis
LED

1.1

A peculiarity of the SB33-EHS2 valve
are the pressure sensors, which can be

61

Directional and priority valves | Hydraulics in tractors

62

Hydraulics in tractors | Directional and priority valves

5.4

Joysticks – mechanical-

Bosch Rexroth AG

electronic control levers
For electronic directional valves, which
are manually controlled, a special control
lever, a so-called "joystick" is needed.
When actuating the lever, such joysticks
transmit a DC-voltage, a PWM or a CAN
signal via cable to the directional valve,causing the spool position to be adjusted
proportionally to the deﬂection angle ofthe joystick handle. This is similar to themechanical actuation.
Their design conﬁguration is based onmechanical-hydraulic devices, as havebeen standard for years in large construction machines for the control of valves in
the large power range. Figure 5.45 shows
both of the actual series THE and EJ. The

Fig. 5.45: Rexroth-joystick series THE and EJ

THE series was designed for construction machinery, especially excavators,
where they are used to control the main
working functions. Units of the EJ series

1

are smaller and were designed for use
in tractors and fork lift trucks. Mounting
dimensions and electrical connections
are identical however.
Figure 5.46 shows the design layout of

9

an EJ joystick, comprising the following
components:

5
6

1 Operator handle

8

2 Mounting ﬂange
3 Housing for sensors and electronic
controller

42
3

4 Hall sensor for angular measurement
5 Spring cup
6 Rubber bellow
7 Solenoid
8 Return spring
9 Connecting lever

7

Fig. 5.46: Design layout of a joystickBosch Rexroth AG

Directional and priority valves | Hydraulics in tractors

The operating handle (1) is via a lever(9) connected to the solenoid (7), which

Float position

solenoid in the ball joint to rotate and theangle of rotation is measured contactfree and free of wear with a Hall sensor.
It is possible to arrange two solenoids at

Lift

Lower

Float position

tion to the left or to the right – causes theLower

in a main axial direction – in the illustra-

Liftrotated in all directions. Shifting the leverContinuous consumer

is mounted in a ball joint which can be

the lever (9) in the area of the ball joint,of which the main directions of actuation

Continuous consumer

are 90° oﬀset against each other. In thismanner, two valve segments can be
operated with one lever – also simultaneously – see Figure 5.47.
The spring cup (5) is supported on a

Level 1 = valve 1
Level 2 = valve 2

Fig. 5.47: Functions of a 2-axis joystick

trumpet-bell-like sleeve so that the spring(8) provides a reset force to neutral position in any direction of deﬂection.

Battery

Mechanical pressure points can also
GND

detection of certain positions by the

5V Vcc supply

integrated in the housing generate an

ANA3lever deﬂection angle. With DC voltage
systems, this enables a direct control ofvalves. PWM or CAN BUS control signals
must be generated by the electronics

EJ
Base

Potentiometer

Reserved

operator e.g. "ﬂoat". The electronics
output voltage dependent on the joystick* Scaling
Output signal* Activation ﬂoat

EJ supply Vbat

be realized if desired, enabling a haptic

GND
DI1
DI2
DI3
Reserved
PWM1
PWM2

μC

installed, see Figure 5.47.
In tractors with smaller volumes, the EHS
valves are controlled with pulse widthmodulation (PWM). In tractors with larger
volumes, the control is usually realized by
CAN BUS.
Figure 5.48 shows the input and output
signals of the integrated electronic
controller of an EJ joystick with PWM
control.

Fig. 5.48: Input and output signals of the electronics of a Rexroth EJ joystick with PWM signal

63

64

Hydraulics in tractors | Directional and priority valves

5.5

Priority valves

Bosch Rexroth AG

The function of priority valves is based on
the principle of a 3-way ﬂow control valve,

Priority function
p2
p3

qv2

see Figure 5.49.

p2 qv31switching in parallel a variable metering

Metering
oriﬁceΔp1,2

A 3-way ﬂow controller is realized by
oriﬁce (1) with a pressure compensatorp1(2), controlling a valve spool. The controlled ﬂow through the metering oriﬁce
is independent of the load pressure p2.

qv1

2

1

2
Pressurecompensator

The pressure p1 upstream of the metering

p1

Control oriﬁce

Pressure compensator is arrangedin parallel to the metering oriﬁce

oriﬁce is connected to the piston sideand the pressure p2 downstream ofthe metering oriﬁce to the spring sideof the pressure compensator spool.

Fig. 5.49: Design and schematic of a 3-way ﬂow controller

If port 1 carries an oil ﬂow larger thanthat desired, the pressure compensatorspool will be shifted to the right until theforces through the pressure diﬀerential
Δp = p1–p2 at the piston are equal to thespring force.

P

ZMS23 ﬂange
YW
W
YL
PL

Y
YB

This condition is necessarily reached andthe metering oriﬁce with a cross section A
then carries a controlled ﬂow qv ~ A × √ Δp

ZMS23 ﬂange

to port 2. The surplus rest ﬂow goes toport 3. Port 2 thus always has priority
over port 3. Priority valves work on thesame principle.
However, the schematic illustrated in
Figure 5.49 with one control spool oriﬁce
only works if the pressure at port 3 islower than at port 2, which is not thecase with priority valves. Depending on
the hydraulic system and on customer
requirements, diﬀerent design variants ofpriority valves have come into being.
Figure 5.50 shows a priority valve insandwich plate design, which can be
integrated in valve blocks together with
SB23 directional valves.

Fig. 5.50: Rexroth priority valve in sandwich plate design with SB23 bolt hole pattern

Bosch Rexroth AG

Directional and priority valves | Hydraulics in tractors

In the sectional view and in the schematic

LT46

illustrated in Figure 5.50, the spool functions as a pressure compensator. PL is

LT43

the connection to the prioritized con-

LT41
Priority valve

sumer and YL the load feedback, picked

Pressure
reduction

up downstream of its metering oriﬁce.
W is the continuing path to the consum-

LT42
1
3

Priority
valve
Steering +trailer brake

Lubrication
Cooling
Filtrationpressure compensator spool. This spool
has two sides with control edges, which
can be activated as control oriﬁces
depending on the pressure conditions.
is higher than in the prioritized function
the control edge from red to green isPriority valvesyellow. However, the priority valve spool

Priority 23

is controlled like the one in the 3-way ﬂow

Priority 12

controller and is arranged parallel to the
CHP (LT...)

downstream of the metering oriﬁce of theprioritized consumer is connected to thespring side and the upstream pressure to

Priority to AKP

the piston side of the spool.
Priority in BV

Multiple priority stages can be combined
into one unit, which is the case withvalves of the LT series for a central
hydraulic system with a variable pump,see Figure 5.51.
Bosch Rexroth has diﬀerent design
versions of priority valves for integrating
directional valve series into valve blocks,
see Table 5.2.
Special solutions for steering systems
and integrated priority valves for trailer
brake valves BV are dealt with in therelevant chapters.

Gearbox

Hitch

Prio 4

SB23-LS
Directional valve

Coupling I

Directional valve

Coupling II

Directional valve

Coupling III

Fig. 5.51: Priority functions in the Rexroth valve block LT 46 for LS systems with a variable pumpactive, otherwise the one from red tometering oriﬁce. The load pressure YL

Prio 3

EHR23
Hitch valvethat the pump ﬂow is also led to the

Brake

Prio 1

A10CO

If the pressure in the continuing path W

2

Pilot pressure

ers without priority.
The schematic in Figure 5.50 shows,

Prio 2

1

4

DFR

Steering

Table 5.2:

Preferred applications▶

for valve series SB23▶

priority for steering or for constant pressure▶

priority for steering or for constant pressure▶

for large oil ﬂows▶

with multiple priority functions (BV, steering, low pressure)▶
▶

with BV possible
can be ﬂanged onto AKP (A10...)▶

1 or 2 priority functions▶

possible with BV▶

only priority for BV possible

Variants of Rexroth priority valves65

2Hydraulics in tractors | Imprint

Imprint
Knowledge in Detail

Hydraulics in Tractors

Publisher:
Bosch Rexroth AG
Mobile Applications
Glockeraustrasse 489275 Elchingen, Germany

Reproduction, duplication and translation, in whole or in part, is only permissible with
our prior written consent and with indication of source.
We shall not accept liability for the compliance of the contents with valid statutory
speciﬁcations.
Subject to change.
1st edition (June 2014)
Material number: R961009447
ISBN 978-3-9814879-9-2© This document, as well as the data, speciﬁcations and other information set forth init, are the exclusive property of Bosch Rexroth AG. It may not be reproduced or given tothird parties without its consent.

Bosch Rexroth AG

tractors and presents components and system solutions. These solutions – when engineeredto the speciﬁc application – are also deployable to other mobile machines. The reader of thisbook should have a good knowledge of hydraulics and be familiar with the symbols used inhydraulic schematics to fully grasp and enjoy the information conveyed.

Knowledge in Detail

Hydraulics in Tractors

Hydraulics in Tractors

This book provides an overview of the most important hydraulic functions of agricultural

Knowledge in DetailBosch Rexroth AG
Drive & Control Academy
Bahnhofplatz 297070 Würzburg, Germany
Phone: +49 9352 18-1920
Fax: +49 9352 18-1040
media@boschrexroth.dewww.boschrexroth.com/academy© Bosch Rexroth AG 2014
Material number: R961009447

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