Title of Invention	DRIVE TRAIN FOR A COMPRESSOR AND A HYDRAULIC PUMP AND METHOD FOR OPERATING A COMPRESSOR AND A HYDRAULIC PUMP
Abstract	The invention relates to a drive train (30) for a compressor (12) and a hydraulic pump (24) of a motor vehicle that, for assisting steering, has a hydraulic power steering (14) and an electric superimposed steering system (36). The compressor (12)and the hydraulic pump (24) are driven by a common output shaft (30) of a motor vehicle driving motor (16). According to the invention, means (10,20) are provided that reduce the power delivered via the output shaft (30) to the compressor (12) and the hydraulic pump (24) when the demands upon the compressor (12) and upon the power steering system (36) allow this to occur. The invention also relates to a method for driving a compressor and a hydraulic pump of a motor vehicle that, for assisting steering, has a hydraulic power steering as well as an electric superimposed steering system.

Title of Invention

DRIVE TRAIN FOR A COMPRESSOR AND A HYDRAULIC PUMP AND METHOD FOR OPERATING A COMPRESSOR AND A HYDRAULIC PUMP

Abstract

The invention relates to a drive train (30) for a compressor (12) and a hydraulic pump (24) of a motor vehicle that, for assisting steering, has a hydraulic power steering (14) and an electric superimposed steering system (36). The compressor (12)and the hydraulic pump (24) are driven by a common output shaft (30) of a motor vehicle driving motor (16). According to the invention, means (10,20) are provided that reduce the power delivered via the output shaft (30) to the compressor (12) and the hydraulic pump (24) when the demands upon the compressor (12) and upon the power steering system (36) allow this to occur. The invention also relates to a method for driving a compressor and a hydraulic pump of a motor vehicle that, for assisting steering, has a hydraulic power steering as well as an electric superimposed steering system.

Full Text	WO 2006/099920 PCT/EP2006/001353 Drive train for a compressor and a hydraulic pump The invention reflates to a drive train for a compressor and a hydraulic pump of a motor vehicle which has a hydraulic power steering system and an electric superimposed steering system for providing steering assistance;, wherein the compressor and the hydraulic pump are driven By means of a common output shaft of a motor vehicle drive motor. The invention also relates to a method for operating a compressor and a hydraulic pump of a motor vehicle which has a hydraulic power steering system and an electric superimposed steering system for providing steering assistance, wherein the compressor and the hydraulic pump are driven by means of a common output shaft of a motor vehicle drive engine.. In modern 'motor vehicles, in particular in the field of utility vehicles, systems which are operated with compressed air are used in many cases. For example, the brakes, the pneumatic suspension, the transmission etc. use compressed air as a working medium. In the design and manufacture of such systems it is necessary to keep the power demand for providing compressed air as low as possible while ensuring continuous operational reliability of thie systems. Nowadays it is customary to allow the compressor used for providing compressed air to continue to be driven by the engine of the motor vehicle in phases in which it is not feeding any compressed air. The air which is fed at such a time is however not utilized to provide compressed air! but rather fed into the surrounding air. This typically causes a power loss of approximately 1 kW. A further system which is also usually driven by a motor vehicle engine is the hydraulic power steering system. This reduces the steering forces which have to WO 2006/099920 PCT/EP2006/001353 - 2 - be applied by the driver in the stationary state when maneuvering the vehicle or at low travel speeds of the vehicle. The power demand of such a steering system, also referred to as a power j steering system, is approximately 1 kW in the idling state and up to 8 k.W in the case of a high demand, for example during maneuver-ing. In most systems of this type, the hydraulic pump Of the steering assistance system is driven by means of a through-drive at the compressor. In order: to provide the driver with further functionalities in addition to the pure steering assistance, what is referred to as a superimposed steering system has been developed. In this system an additional torque is superimposed on the driver's manual torque, for example by means of an electric motor and a planetary gear mechanism at the steering column. With thi\|s superimposed steering system it is possible to carry out steering corrections in order to stabilize the vehicle as a function of the instantaneous driving state of the vehicle, for example using signals of an electronic stability program (ESP). It is also possible to implement functions such jas a variable transmission ratio as a function of the speed of the vehicle or the steering speed as well as a variable power assistance which imposes the superimposed torque as a function of the torque to be applied by the driver. The invention is based on the object of developing a drive train of the generic type in such a way that the compressor and the hydraulic pump can operate in a way which is efficient in terms of energy. This object is achieved by means of the features specified in the independent claims. Further developments and embodiments result from the dependent claims. WO 2006/099920 PCT/EP2006/001353 - 3 - The drive train according to the invention i s based on the generic prior art in that means are; provided which reduce the power which is output to the compressor and the hydraulic pump via the output shaft if the demands which are being made ' of the cpmpressor and of the steering assistance system permit it. This makes it possible for the power to be output to the compressor and hydraulic pump in a way which is largely suitable for the. demand, thus avoiding unnecessary consumption of energy, in this context it is possible, for example depending on the demand profile of the compressor and hydraulic pump, for the power which is to: be transmitted to be controllable in a plurality of stages, for example by means of a transmission or the like.. It is also possible, if appropriate, in this context for a power reduction on the part of the drive shaft to be compensated by an increased power output by the superimposed steering system. In one particularly preferred embodiment there is prov.i sion that the means reduce the power which is output to the compressor and to the hydraulic pump via the output shaft to zero if it is not necessary for the compressor to operate and the electric superimposed steering system can provide the necessary steering assistance alone. In particular at a sufficiently high traveling speed there is generally no need for steering assistance, or only a relatively low level of steering assistance is required. This can be applied solely by the superimposed steering system. If in addition the compressor does njot have to feed, the power flux to the compressor and hydraulic pump via the output shaft can be interrupted. In particular in the context explained above there is preferably also provision that the means comprise a clutch by means of which the power flux to the WO 2006/099920 PCT/EP2006/001353 - 4 - compressor and i to the hydraulic pump can be interrupted. Such a deactivation clutch constitutes a cost effective and robust embodiment for disconnecting the compressor and hydraulic pump from the drive engine during suitable operating states. The deactivation clutch can be activated, for example, in idling feed phases in which the compressor would feed into the surrounding air according to the prior art. It can also be advantageous that the means comprise an electric control device which determines, on the basis of parameter values fed to it, how far the power which is output to the compressor and to the hydraulic pump via the output shaft can be reduced. In this context, the power flux can be controlled by means of specific measurement variables and/or actuation variables which characterize the instantaneous and/or anticipated power demand of the compressor and hydraulic pump. It is also possible to take into account further operating conditions of the vehicle such as, for example, the instantaneous driving behavior of the vehicle and parameters for thje hydraulics, pneumatics or electrics. In this context the term control, also includes control, processes. In particular it may be advantageous for a hydraulic accumulator to tie provided which is kept filled in order to be able to make available sufficient steering assistance when demands are suddenly made of the hydraulic power steering system. For example, if the hydraulic pump receives a reduced level of power, or no power, from the drive shaft, it may be necessary to interrupt the power steering assistance by the hydraulics in order to keep the power steering system operationally available for an emergency. In this context: it may be advantageous to provide a particularly large hydraulic accumulator in order to WO 2006/099920 PCT/EP2006/001353 -5- ! i ■ cover the time period up to the resumption of operation by the hydraulic pump. The method according to the invention is based on the prior art of the generic type in that the power which is output to the compressor and the hydraulic pump via the output shaft is reduced if the demands which are being made of the compressor and the steering assistance system permit it. In this way, the advantages of the invention are also implemented within the scope of a method. This applies appropriately also to the developments of- the method according to subclaims 7 and 8. The invention is based on the idea that if a vehicle is traveling at a relatively high speed, for example on a freeway, only a small degree of power steering assistance is necessary. This can be provided, for example, solely by the superimposed steering system. It is thus possible to implement a deactivation clutch for the compressor, and thus also for the steering assistance pump. The deactivation clutch has to be controlled in an intelligent fashion. It is activated if the following conditions are met: The compressor does not have to feed. The demimd made of the power steering assistance system by the steering is low, which is determined for example by the pressure in the hydraulic system and by the speed of the vehicle. The power steering assistance is deactivated by the hydraulics by means of a suitable deactivation device in order to keep the hydraulic accumulator filled for an emergency. In addition it is proposed to enlarge the hydraulic accumulator in order to be, able to reliably cover the time period for switching on the clutch. WO 2006/099920 PCT/EP2006/001353 - 6 - The invention will now be explained by way of example with reference to the accompanying drawings and by means of preferred embodiments. In said drawings: figure 1 is a block diagram of an embodiment of the drive train according to the invention, and figure 2 is a flowchart explaining an embodiment of the method according to the invention. Figure 1 is a block diagram of an embodiment of the drive train according to the invention. The block diagram represents here in a schematic fashion components of a steering assistance system which comprises a hydraulic power steering system 14 and an electric superimposed steering system 36. Furthermore, a compressed air compressor 12 is shown as part of a compressed air system (not shown) and an internal combustion engine 16 of a motor vehicle. The illustration is Restricted here to the components which are necessary to describe the invention. The internal combustion engine 16 is connected to the compressed air compressor 12 and the hydraulic pump 24 via an output shaft 30. The output shaft 30 is provided with a deactivation clutch 20 between the internal combustion engine 16 and compressor 12. The hydraulic pump 24 is coupled to a through-drive of the compressor 12 and is part of a hydraulic power steering system 14. The power steering system 14 also comprises hydraulic components 32 which include/ inter alia, a hydraulic accumulator 28 and a deactivation device 22 as well as a hydraulic actuator 34. Furthermore, the steering assistance system comprises a superimposed steering system 36. The latter comprises, inter alia, an electric motor 18 which is connected to the steering column 38 via a planetary gear mechanism 26. The steering column 38 is WO 2006/099920 i PCT/EP2006/001353 — 7 — connected to a steering wheel 40 and a steering gear 4 2 which is in turn connected to the wheels 46 via a rod and lever arrangement. Furthermore, a control. 10 is provided. The latter is connected via control 1 incs 50, 52 to the deactivation clutch 20 and the deactivation device 22. in addition, there ate signal lines 54-58 between the control 10 and the compressor 12, the hydraulic pump 24 and the electric motor 18. First, the functionality of the power steering system 14 will be briefly explained. The hydraulic pump 24 generates the pressure which is required in the hydraulic systeml A power steering assistance for the steering system can be disabled by means of the deactivation device 22 and thus the pressure in the hydraulic system can be kept constant if the hydraulic pump 24 is stationary. The hydraulic components 32 make available the parts, such as valves, controllers etc., which are necessary for the functionality of the hydraulic system. The hydraulic accumulator 28 is dimensioned in such a way that it covers the time period required for the hydraulic pump 24 to start up in order to make available sufficient pressure to the hydraulic system when a sudden high demand for power occurs. : The overall operation of the arrangement is configured as follows: The internal comb\|ustion engine 16 drives the compressor 12 and the hydrlaulic pump 24 when the deactivation clutch 20 is closed. The control 10 determines the instantaneous state of the system via, inter alia, the signal lines 54-58 and, if appropriate, via other information lines (not illustrated here) and via: the control lines 50, 52. If the control 10 determines that the compressor 12 does not need to feed any compressed air at a particular time, it checks the instantaneous demand profile to the power steering system 14. if it WO 2006/099920 PCT/EP2006/001353 - 8 - becomes apparent from this that it can be anticipated that the torque which is requested by the system is so low that it can be provided solely by the superimposed steering system 36, the control 10 closes the deactivation device 22 via the signal line 52 and thus disables the provision of power steering assistance by the hydraulic system. The contriol 10 then opens the deactivation clutch 20 by means of the control line 50 and thus interrupts the power flux from the internal combustion engine 16 to the compressor 12 and to the hydraulic pump 24. In this operating state, the compressor 12 and the hydraulic pump 24 consume essentially no power of the internal combustion engine 16. Any steering assistance is then made available by the electric superimposed steering system 36. If either a raised torque, which cannot be provided by the electric motor 18 is demanded or the compressor 12 has to feed, the control 10 closes the deactivation clutch 20 via the control line 50 ahd thus supplies the compressor 12 and the hydraulic pump 2 4 with power again.. In addition, the control 10 activates the hydraulic power steering system via the control line 52 and the deactivation device 22. Figure 2 shows a flowchart explaining an embodiment of the method according to the invention. The method starts with step S1. In step S2, the instantaneous demand profile which is required of the compressor is checked. If it is determined in this context that the compressor has to feed, it is checked with step S3 whether the clutqh which connects the compressor to the drive is opened. If said clutch is opened, it i.s closed with step S4 and the system returns to the starting point of the method. If a clutch is already closed in step S3, the method is also started again. If, on the other hand, it is determined in step S2 that the compressor can be deactivated, the demand profile which is being required of the hydraulic power steering WO 2006/099920 PCT/EP2006/001353 - 9 - system is checked in step S5. Tf said demand profile does not permit the system to be switched off, i t is checked with step S6 whether the hydraulic power steering assistance system is disab1ed at that particular time. If this is the case, the hydraulic assistance system is activated in step S7 and the method is continued with step S3. If the hydraulic assistance system is already active, the process is continued immediately with step S3. If there is a power steering profile which permits the system to be deactivated, the method is continued in step S8. In said step it is checked once more, as in step S6, whether the power steering assistance system is disabled. If this is not the case, this disabling process is carried out in step . S9. The method then continues with step S10. It is checked in said step whether the deactivation clutch 'is in the open state. In the event of a negative test result, the clutch is opened in step Sll. The method then continues with an opened clutch at the starting point S1. The features of the invention which are disclosed in the present description, In the\| drawings and in the claims can be essential for the ' implementation of the invention either individually or in any desired combination. WO 2006/099920 PCT/EP2006/001353 - 10 - List of reference numerals 10 Control 12 Compressor 14 Steering assistance system 16 Internal combustion engine; 18 Electric motor ! i 20 Deactivation clutch 22 Deactivation device 2 4 Hydraulic pump 2 6 Planetary gear mechanism 2 8 Hydraulic accumulator 30 Drive shaft 32 Hydraulic components 34 Hydraulic actuator 36 Superimposed steering system 38 Steering column 40 Steering wheel 42 Steering pear 46 Wheels 50, 52 Control lines 54-58 Signal lines International file number 3013-K PCT PCT/EP 2006/001353 CLAIMS 1. A drive traiin (20, 30) for a compressor (12) and a hydraulic pump (24) of a motor vehicle which has a hydraulic power steering system (14) and an electric superimposed steering system. (36) for providing, steering assistance, wherein the compressor .(12); and the hydraulic pump (24) are driven by means of a common output shaft (30) of a motor vehicle drive motor (16), wherein means (10, 20) are provided which reduce the power which is output to the compressor (12) and the hydraulic pump (24) via the output shaft (30) if the demands which are being made of t\|he compressor (12) and of the steering assistance system (36) permit it and which reduce the power which is output to the compressor (12) and to the hydraulic pump (24) via the output shaft (30) to zero if it is not necessary for the compressor (12) to operate and the electric superimposed steering system (36) can provide the necessary steering assistance alone. 2. The drive train as claimed in claim 1, characterized in that the means comprise a clutch (20) by means of which the power flux to the compressor (12) and to the hydraulic pump (24) can be interrupted. 3. The drive train as claimed in one of the preceding claims, characterized in that the means comprise an electric control device (10) which determines, on the basis of parameter values fed to lit, how far the power which is output to the compressor (12) and to the hydraulic pump (24) via the output shaft (30) can be reduced. 4. The drive train as claimed in claim 3, characterized in that a hydraulic accumulator (28) is -12- provided which is kept filled in order to be able to make available sufficient steering assistance when" demands are suddenly made of the hydraulic power steering system (14). 5. A method for operating a compressor (12) and a hydraulic pump (24) of a motor vehicle which has a hydraulic power steering system (14) and an electric superimposed steering system (36) for providing steering assistance, wherein the compressor (12) and the hydraulic pump (24) are driven by means of a common output shaft (30) of a motor vehicle drive motor, wherein the power which is output to the compressor (12) and the hydraulic pump (24) via the output shaft (30) is reduced if the demands which are being made of the compressor (12) and the steeping assistance system permit it and the power: which is output to the compressor (12) and to the hydraulic pump (24) via the output shaft (30) is reduced to zero if it is not necessary for the compressor (12) to operate and the electric superimposed steering system (36) can provide the necessary steering assistance alone. 6. The method as claimed in one of claims 5, characterized in that the degree to which the power which is output to the compressor (12) and to the hydraulic pump (24) via the output shaft (30) can be reduced is determined on the basis of suitable parameter values. The invention relates to a drive train (30) for a compressor (12) and a hydraulic pump (24) of a motor vehicle that, for assisting steering, has a hydraulic power steering (14) and an electric superimposed steering system (36). The compressor (12)and the hydraulic pump (24) are driven by a common output shaft (30) of a motor vehicle driving motor (16). According to the invention, means (10,20) are provided that reduce the power delivered via the output shaft (30) to the compressor (12) and the hydraulic pump (24) when the demands upon the compressor (12) and upon the power steering system (36) allow this to occur. The invention also relates to a method for driving a compressor and a hydraulic pump of a motor vehicle that, for assisting steering, has a hydraulic power steering as well as an electric superimposed steering system.

Full Text

WO 2006/099920 PCT/EP2006/001353
Drive train for a compressor and a hydraulic pump
The invention reflates to a drive train for a compressor
and a hydraulic pump of a motor vehicle which has a
hydraulic power steering system and an electric
superimposed steering system for providing steering
assistance;, wherein the compressor and the hydraulic
pump are driven By means of a common output shaft of a
motor vehicle drive motor.
The invention also relates to a method for operating a
compressor and a hydraulic pump of a motor vehicle
which has a hydraulic power steering system and an
electric superimposed steering system for providing
steering assistance, wherein the compressor and the
hydraulic pump are driven by means of a common output
shaft of a motor vehicle drive engine..
In modern 'motor vehicles, in particular in the field of
utility vehicles, systems which are operated with
compressed air are used in many cases. For example, the
brakes, the pneumatic suspension, the transmission etc.
use compressed air as a working medium. In the design
and manufacture of such systems it is necessary to keep
the power demand for providing compressed air as low as
possible while ensuring continuous operational
reliability of thie systems. Nowadays it is customary to
allow the compressor used for providing compressed air
to continue to be driven by the engine of the motor
vehicle in phases in which it is not feeding any
compressed air. The air which is fed at such a time is
however not utilized to provide compressed air! but
rather fed into the surrounding air. This typically
causes a power loss of approximately 1 kW.
A further system which is also usually driven by a
motor vehicle engine is the hydraulic power steering
system. This reduces the steering forces which have to

WO 2006/099920 PCT/EP2006/001353
- 2 -
be applied by the driver in the stationary state when
maneuvering the vehicle or at low travel speeds of the
vehicle. The power demand of such a steering system,
also referred to as a power j steering system, is
approximately 1 kW in the idling state and up to 8 k.W
in the case of a high demand, for example during
maneuver-ing. In most systems of this type, the
hydraulic pump Of the steering assistance system is
driven by means of a through-drive at the compressor.
In order: to provide the driver with further
functionalities in addition to the pure steering
assistance, what is referred to as a superimposed
steering system has been developed. In this system an
additional torque is superimposed on the driver's
manual torque, for example by means of an electric
motor and a planetary gear mechanism at the steering
column. With thi|s superimposed steering system it is
possible to carry out steering corrections in order to
stabilize the vehicle as a function of the
instantaneous driving state of the vehicle, for example
using signals of an electronic stability program (ESP).
It is also possible to implement functions such jas a
variable transmission ratio as a function of the speed
of the vehicle or the steering speed as well as a
variable power assistance which imposes the
superimposed torque as a function of the torque to be
applied by the driver.
The invention is based on the object of developing a
drive train of the generic type in such a way that the
compressor and the hydraulic pump can operate in a way
which is efficient in terms of energy.
This object is achieved by means of the features
specified in the independent claims.
Further developments and embodiments result from the
dependent claims.

WO 2006/099920 PCT/EP2006/001353
- 3 -
The drive train according to the invention i s based on
the generic prior art in that means are; provided which
reduce the power which is output to the compressor and
the hydraulic pump via the output shaft if the demands
which are being made ' of the cpmpressor and of the
steering assistance system permit it. This makes it
possible for the power to be output to the compressor
and hydraulic pump in a way which is largely suitable
for the. demand, thus avoiding unnecessary consumption
of energy, in this context it is possible, for example
depending on the demand profile of the compressor and
hydraulic pump, for the power which is to: be
transmitted to be controllable in a plurality of
stages, for example by means of a transmission or the
like.. It is also possible, if appropriate, in this
context for a power reduction on the part of the drive
shaft to be compensated by an increased power output by
the superimposed steering system.
In one particularly preferred embodiment there is
prov.i sion that the means reduce the power which is
output to the compressor and to the hydraulic pump via
the output shaft to zero if it is not necessary for the
compressor to operate and the electric superimposed
steering system can provide the necessary steering
assistance alone. In particular at a sufficiently high
traveling speed there is generally no need for steering
assistance, or only a relatively low level of steering
assistance is required. This can be applied solely by
the superimposed steering system. If in addition the
compressor does njot have to feed, the power flux to the
compressor and hydraulic pump via the output shaft can
be interrupted.
In particular in the context explained above there is
preferably also provision that the means comprise a
clutch by means of which the power flux to the

WO 2006/099920 PCT/EP2006/001353
- 4 -
compressor and i to the hydraulic pump can be
interrupted. Such a deactivation clutch constitutes a
cost effective and robust embodiment for disconnecting
the compressor and hydraulic pump from the drive engine
during suitable operating states. The deactivation
clutch can be activated, for example, in idling feed
phases in which the compressor would feed into the
surrounding air according to the prior art.
It can also be advantageous that the means comprise an
electric control device which determines, on the basis
of parameter values fed to it, how far the power which
is output to the compressor and to the hydraulic pump
via the output shaft can be reduced. In this context,
the power flux can be controlled by means of specific
measurement variables and/or actuation variables which
characterize the instantaneous and/or anticipated power
demand of the compressor and hydraulic pump. It is also
possible to take into account further operating
conditions of the vehicle such as, for example, the
instantaneous driving behavior of the vehicle and
parameters for thje hydraulics, pneumatics or electrics.
In this context the term control, also includes control,
processes.
In particular it may be advantageous for a hydraulic
accumulator to tie provided which is kept filled in
order to be able to make available sufficient steering
assistance when demands are suddenly made of the
hydraulic power steering system. For example, if the
hydraulic pump receives a reduced level of power, or no
power, from the drive shaft, it may be necessary to
interrupt the power steering assistance by the
hydraulics in order to keep the power steering system
operationally available for an emergency. In this
context: it may be advantageous to provide a
particularly large hydraulic accumulator in order to

WO 2006/099920 PCT/EP2006/001353
-5-
! i ■
cover the time period up to the resumption of operation
by the hydraulic pump.
The method according to the invention is based on the
prior art of the generic type in that the power which
is output to the compressor and the hydraulic pump via
the output shaft is reduced if the demands which are
being made of the compressor and the steering
assistance system permit it.
In this way, the advantages of the invention are also
implemented within the scope of a method. This applies
appropriately also to the developments of- the method
according to subclaims 7 and 8.
The invention is based on the idea that if a vehicle is
traveling at a relatively high speed, for example on a
freeway, only a small degree of power steering
assistance is necessary. This can be provided, for
example, solely by the superimposed steering system. It
is thus possible to implement a deactivation clutch for
the compressor, and thus also for the steering
assistance pump. The deactivation clutch has to be
controlled in an intelligent fashion. It is activated
if the following conditions are met:
The compressor does not have to feed.
The demimd made of the power steering
assistance system by the steering is low, which
is determined for example by the pressure in
the hydraulic system and by the speed of the
vehicle.
The power steering assistance is deactivated by
the hydraulics by means of a suitable
deactivation device in order to keep the
hydraulic accumulator filled for an emergency.
In addition it is proposed to enlarge the hydraulic
accumulator in order to be, able to reliably cover the
time period for switching on the clutch.

WO 2006/099920 PCT/EP2006/001353
- 6 -
The invention will now be explained by way of example
with reference to the accompanying drawings and by
means of preferred embodiments.
In said drawings:
figure 1 is a block diagram of an embodiment of the
drive train according to the invention, and
figure 2 is a flowchart explaining an embodiment of
the method according to the invention.
Figure 1 is a block diagram of an embodiment of the
drive train according to the invention. The block
diagram represents here in a schematic fashion
components of a steering assistance system which
comprises a hydraulic power steering system 14 and an
electric superimposed steering system 36. Furthermore,
a compressed air compressor 12 is shown as part of a
compressed air system (not shown) and an internal
combustion engine 16 of a motor vehicle. The
illustration is Restricted here to the components which
are necessary to describe the invention. The internal
combustion engine 16 is connected to the compressed air
compressor 12 and the hydraulic pump 24 via an output
shaft 30. The output shaft 30 is provided with a
deactivation clutch 20 between the internal combustion
engine 16 and compressor 12. The hydraulic pump 24 is
coupled to a through-drive of the compressor 12 and is
part of a hydraulic power steering system 14. The power
steering system 14 also comprises hydraulic components
32 which include/ inter alia, a hydraulic accumulator
28 and a deactivation device 22 as well as a hydraulic
actuator 34. Furthermore, the steering assistance
system comprises a superimposed steering system 36. The
latter comprises, inter alia, an electric motor 18
which is connected to the steering column 38 via a
planetary gear mechanism 26. The steering column 38 is

WO 2006/099920 i PCT/EP2006/001353
— 7 —
connected to a steering wheel 40 and a steering gear 4 2
which is in turn connected to the wheels 46 via a rod
and lever arrangement. Furthermore, a control. 10 is
provided. The latter is connected via control 1 incs 50,
52 to the deactivation clutch 20 and the deactivation
device 22. in addition, there ate signal lines 54-58
between the control 10 and the compressor 12, the
hydraulic pump 24 and the electric motor 18.
First, the functionality of the power steering system
14 will be briefly explained. The hydraulic pump 24
generates the pressure which is required in the
hydraulic systeml A power steering assistance for the
steering system can be disabled by means of the
deactivation device 22 and thus the pressure in the
hydraulic system can be kept constant if the hydraulic
pump 24 is stationary. The hydraulic components 32 make
available the parts, such as valves, controllers etc.,
which are necessary for the functionality of the
hydraulic system. The hydraulic accumulator 28 is
dimensioned in such a way that it covers the time
period required for the hydraulic pump 24 to start up
in order to make available sufficient pressure to the
hydraulic system when a sudden high demand for power
occurs. :
The overall operation of the arrangement is configured
as follows:
The internal comb|ustion engine 16 drives the compressor
12 and the hydrlaulic pump 24 when the deactivation
clutch 20 is closed. The control 10 determines the
instantaneous state of the system via, inter alia, the
signal lines 54-58 and, if appropriate, via other
information lines (not illustrated here) and via: the
control lines 50, 52. If the control 10 determines that
the compressor 12 does not need to feed any compressed
air at a particular time, it checks the instantaneous
demand profile to the power steering system 14. if it

WO 2006/099920 PCT/EP2006/001353
- 8 -
becomes apparent from this that it can be anticipated
that the torque which is requested by the system is so
low that it can be provided solely by the superimposed
steering system 36, the control 10 closes the
deactivation device 22 via the signal line 52 and thus
disables the provision of power steering assistance by
the hydraulic system. The contriol 10 then opens the
deactivation clutch 20 by means of the control line 50
and thus interrupts the power flux from the internal
combustion engine 16 to the compressor 12 and to the
hydraulic pump 24. In this operating state, the
compressor 12 and the hydraulic pump 24 consume
essentially no power of the internal combustion engine
16. Any steering assistance is then made available by
the electric superimposed steering system 36. If either
a raised torque, which cannot be provided by the
electric motor 18 is demanded or the compressor 12 has
to feed, the control 10 closes the deactivation clutch
20 via the control line 50 ahd thus supplies the
compressor 12 and the hydraulic pump 2 4 with power
again.. In addition, the control 10 activates the
hydraulic power steering system via the control line 52
and the deactivation device 22.
Figure 2 shows a flowchart explaining an embodiment of
the method according to the invention. The method
starts with step S1. In step S2, the instantaneous
demand profile which is required of the compressor is
checked. If it is determined in this context that the
compressor has to feed, it is checked with step S3
whether the clutqh which connects the compressor to the
drive is opened. If said clutch is opened, it i.s closed
with step S4 and the system returns to the starting
point of the method. If a clutch is already closed in
step S3, the method is also started again. If, on the
other hand, it is determined in step S2 that the
compressor can be deactivated, the demand profile which
is being required of the hydraulic power steering

WO 2006/099920 PCT/EP2006/001353
- 9 -
system is checked in step S5. Tf said demand profile
does not permit the system to be switched off, i t is
checked with step S6 whether the hydraulic power
steering assistance system is disab1ed at that
particular time. If this is the case, the hydraulic
assistance system is activated in step S7 and the
method is continued with step S3. If the hydraulic
assistance system is already active, the process is
continued immediately with step S3. If there is a power
steering profile which permits the system to be
deactivated, the method is continued in step S8. In
said step it is checked once more, as in step S6,
whether the power steering assistance system is
disabled. If this is not the case, this disabling
process is carried out in step . S9. The method then
continues with step S10. It is checked in said step
whether the deactivation clutch 'is in the open state.
In the event of a negative test result, the clutch is
opened in step Sll. The method then continues with an
opened clutch at the starting point S1.
The features of the invention which are disclosed in
the present description, In the| drawings and in the
claims can be essential for the ' implementation of the
invention either individually or in any desired
combination.

WO 2006/099920 PCT/EP2006/001353
- 10 -
List of reference numerals
10 Control
12 Compressor
14 Steering assistance system
16 Internal combustion engine;
18 Electric motor
! i
20 Deactivation clutch
22 Deactivation device
2 4 Hydraulic pump
2 6 Planetary gear mechanism
2 8 Hydraulic accumulator
30 Drive shaft
32 Hydraulic components
34 Hydraulic actuator
36 Superimposed steering system
38 Steering column
40 Steering wheel
42 Steering pear
46 Wheels
50, 52 Control lines
54-58 Signal lines

International file number 3013-K PCT
PCT/EP 2006/001353
CLAIMS
1. A drive traiin (20, 30) for a compressor (12) and a
hydraulic pump (24) of a motor vehicle which has a
hydraulic power steering system (14) and an electric
superimposed steering system. (36) for providing,
steering assistance, wherein the compressor .(12); and
the hydraulic pump (24) are driven by means of a common
output shaft (30) of a motor vehicle drive motor (16),
wherein means (10, 20) are provided which reduce the
power which is output to the compressor (12) and the
hydraulic pump (24) via the output shaft (30) if the
demands which are being made of t|he compressor (12) and
of the steering assistance system (36) permit it and
which reduce the power which is output to the
compressor (12) and to the hydraulic pump (24) via the
output shaft (30) to zero if it is not necessary for
the compressor (12) to operate and the electric
superimposed steering system (36) can provide the
necessary steering assistance alone.
2. The drive train as claimed in claim 1,
characterized in that the means comprise a clutch (20)
by means of which the power flux to the compressor (12)
and to the hydraulic pump (24) can be interrupted.
3. The drive train as claimed in one of the preceding
claims, characterized in that the means comprise an
electric control device (10) which determines, on the
basis of parameter values fed to lit, how far the power
which is output to the compressor (12) and to the
hydraulic pump (24) via the output shaft (30) can be
reduced.
4. The drive train as claimed in claim 3,
characterized in that a hydraulic accumulator (28) is

-12-
provided which is kept filled in order to be able to
make available sufficient steering assistance when"
demands are suddenly made of the hydraulic power
steering system (14).
5. A method for operating a compressor (12) and a
hydraulic pump (24) of a motor vehicle which has a
hydraulic power steering system (14) and an electric
superimposed steering system (36) for providing
steering assistance, wherein the compressor (12) and
the hydraulic pump (24) are driven by means of a common
output shaft (30) of a motor vehicle drive motor,
wherein the power which is output to the compressor
(12) and the hydraulic pump (24) via the output shaft
(30) is reduced if the demands which are being made of
the compressor (12) and the steeping assistance system
permit it and the power: which is output to the
compressor (12) and to the hydraulic pump (24) via the
output shaft (30) is reduced to zero if it is not
necessary for the compressor (12) to operate and the
electric superimposed steering system (36) can provide
the necessary steering assistance alone.
6. The method as claimed in one of claims 5,
characterized in that the degree to which the power
which is output to the compressor (12) and to the
hydraulic pump (24) via the output shaft (30) can be
reduced is determined on the basis of suitable
parameter values.

The invention relates to a drive train (30) for a compressor (12) and a hydraulic
pump (24) of a motor vehicle that, for assisting steering, has a hydraulic power
steering (14) and an electric superimposed steering system (36). The
compressor (12)and the hydraulic pump (24) are driven by a common output
shaft (30) of a motor vehicle driving motor (16). According to the invention,
means (10,20) are provided that reduce the power delivered via the output shaft
(30) to the compressor (12) and the hydraulic pump (24) when the demands
upon the compressor (12) and upon the power steering system (36) allow this to
occur. The invention also relates to a method for driving a compressor and a
hydraulic pump of a motor vehicle that, for assisting steering, has a hydraulic
power steering as well as an electric superimposed steering system.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=PC652E1NVWAPJLfwE/gDXQ==&loc=wDBSZCsAt7zoiVrqcFJsRw==

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Patent Number

268506

Indian Patent Application Number

3607/KOLNP/2007

PG Journal Number

36/2015

Publication Date

04-Sep-2015

Grant Date

31-Aug-2015

Date of Filing

24-Sep-2007

Name of Patentee

KNORR-BREMSE SYSTEME FUR NUTZFAHRZEUGE GMBH

Applicant Address

MOOSACHER STR. 80, 80809 MUNCHEN

Inventors:

#	Inventor's Name	Inventor's Address
1	GERUM, EDUARD	HIRSCHGARTENSTRASSE 01 83026 ROSENHEIM

PCT International Classification Number

B60K 25/02

PCT International Application Number

PCT/EP2006/001353

PCT International Filing date

2006-02-15

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	10 2005 013 027.5	2005-03-22	Germany