U.S. patent application number 09/801830 was filed with the patent office on 2001-12-20 for exhaust-gas turbocharger for an internal combustion engine.
Invention is credited to Fledersbacher, Peter, Hertweck, Gernot, Sumser, Siegfried, Willand, Juergen, Wirbeleit, Friedrich.
Application Number | 20010053329 09/801830 |
Document ID | / |
Family ID | 7634052 |
Filed Date | 2001-12-20 |
United States Patent
Application |
20010053329 |
Kind Code |
A1 |
Fledersbacher, Peter ; et
al. |
December 20, 2001 |
Exhaust-gas turbocharger for an internal combustion engine
Abstract
An exhaust-gas turbocharger for an internal combustion engine
has an exhaust-gas turbine in the exhaust tract and a compressor in
the intake tract, the exhaust-gas turbine and the compressor being
connected via a shaft which is supported in a casing of the
exhaust-gas turbocharger via at least one bearing. In order to
improve the efficiency of the turbocharger, the bearing has a
non-contact design, in that, when the exhaust-gas turbocharger is
in operation, the shaft is held at a distance from, and so as to be
virtually free of friction with, a bearing receptacle fixed to the
casing.
Inventors: |
Fledersbacher, Peter;
(Stuttgart, DE) ; Hertweck, Gernot; (Fellbach,
DE) ; Sumser, Siegfried; (Stuttgart, DE) ;
Willand, Juergen; (Stuttgart, DE) ; Wirbeleit,
Friedrich; (Esslingen, DE) |
Correspondence
Address: |
CROWELL & MORING LLP
Intellectual Property Group
P.O. Box 14300
Washington
DC
20044-4300
US
|
Family ID: |
7634052 |
Appl. No.: |
09/801830 |
Filed: |
March 9, 2001 |
Current U.S.
Class: |
417/407 ;
384/113; 384/119 |
Current CPC
Class: |
F05D 2240/515 20130101;
Y02T 10/12 20130101; Y02T 10/144 20130101; F05D 2240/53 20130101;
F01D 25/168 20130101; F02B 39/10 20130101; F02B 37/10 20130101;
F01D 25/166 20130101; F01D 25/22 20130101; F05D 2240/51 20130101;
F16C 2360/24 20130101; F05D 2220/40 20130101; F05D 2240/54
20130101 |
Class at
Publication: |
417/407 ;
384/113; 384/119 |
International
Class: |
F16C 032/06; F04B
017/00; F04B 035/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 9, 2000 |
DE |
100 11 419.9 |
Claims
What is claimed is:
1. An exhaust-gas turbocharger for an internal combustion engine,
comprising: an exhaust-gas turbine arranged in an exhaust tract; a
compressor arranged in an intake tract; a shaft coupling said
exhaust-gas turbine and said compressor; at least one bearing
supporting said shaft in a casing of the exhaust-gas turbocharger,
said bearing being a non-contacting bearing such that, when the
exhaust-gas turbocharger is in operation, said shaft is held at a
distance from a bearing receptacle fixed to the casing so as to be
virtually free of friction with the bearing receptacle.
2. The exhaust-gas turbocharger according to claim 1, wherein said
bearing is an air bearing having an air gap between the shaft and
the bearing receptacle fixed to the casing.
3. The exhaust-gas turbocharger according to claim 2, further
comprising an air supply device which supplies air to the air
gap.
4. The exhaust-gas turbocharger according to claim 3, wherein said
air bearing is an aerodynamic bearing, in which the air flows
through the air gap.
5. The exhaust-gas turbocharger according to claim 1, wherein said
at least one bearing is a radial bearing provided on a
compressor-side of the exhaust-gas turbocharger.
6. The exhaust-gas turbocharger according to claim 2, wherein said
at least one bearing is a radial bearing provided on a
compressor-side of the exhaust-gas turbocharger.
7. The exhaust-gas turbocharger according to claim 3, wherein said
at least one bearing is a radial bearing provided on a
compressor-side of the exhaust-gas turbocharger.
8. The exhaust-gas turbocharger according to claim 4, wherein said
at least one bearing is a radial bearing provided on a
compressor-side of the exhaust-gas turbocharger.
9. The exhaust-gas turbocharger according to claim 1, wherein said
at least one bearing is a combined axial/radial bearing provided
between the exhaust-gas turbine and the compressor.
10. The exhaust-gas turbocharger according to claim 2, wherein said
at least one bearing is a combined axial/radial bearing provided
between the exhaust-gas turbine and the compressor.
11. The exhaust-gas turbocharger according to claim 3, wherein said
at least one bearing is a combined axial/radial bearing provided
between the exhaust-gas turbine and the compressor.
12. The exhaust-gas turbocharger according to claim 4, wherein said
at least one bearing is a combined axial/radial bearing provided
between the exhaust-gas turbine and the compressor.
13. The exhaust-gas turbocharger according to claim 5, further
comprising a combined axial/radial bearing provided between the
exhaust-gas turbine and the compressor.
14. The exhaust-gas turbocharger according to claim 1, wherein said
at least one bearing is a magnetic bearing.
15. The exhaust-gas turbocharger according to claim 14, wherein
said magnetic bearing forms part of an electric motor, the shaft of
the exhaust-gas turbocharger being a rotor of the electric
motor.
16. The exhaust-gas turbocharger according to claim 2, wherein both
an air bearing and an electromagnetic bearing are provided.
17. The exhaust-gas turbocharger according to claim 1, further
comprising a contact bearing in addition to the non-contact
bearing.
18. The exhaust-gas turbocharger according to claim 17, wherein
said contact bearing is a roller bearing.
19. The exhaust-gas turbocharger according to claim 18, wherein
said roller bearing is arranged axially asymmetrically in the
exhaust-gas turbocharger and is provided in addition to the
non-contact bearing.
20. In an exhaust-gas turbocharger for an internal combustion
engine, a method for supporting a shaft of the exhaust-gas
turbocharger in a casing of the exhaust-gas turbocharger, the
method comprising the acts of: providing a gap between the shaft
and a bearing receptacle fixed to the casing; supplying air through
the gap when the turbocharger is in operation to form a supporting
air cushion, whereby the shaft is held at a distance from the
bearing receptacle in a virtually friction free manner.
21. The method according to claim 20, wherein the act of supplying
air further comprises the act of flowing the air axially through
the gap.
22. The method according to claim 21, further comprising the act of
introducing the air radially into the gap.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
[0001] This application claims the priority of German Application
No. 100 11 419.9, filed Mar. 9, 2000, the disclosure of which is
expressly incorporated by reference herein.
[0002] The invention relates to an exhaust-gas turbocharger for an
internal combustion engine.
[0003] A known exhaust-gas turbocharger is described in the German
Patent document DE 36 28 687 A1. The exhaust-gas turbocharger
comprises an exhaust-gas turbine which is arranged in the exhaust
tract and is driven by the exhaust-gas back pressure of the
internal combustion engine. Also, in the intake tract, a
compressor, which is operated by the exhaust-gas turbine via a
shaft, compresses fresh intake air to an increased boost pressure.
The shaft of the exhaust-gas turbocharger is supported in the
compressor casing via two rolling bearings. In order to achieve
vibration-damped mounting, in each case at least one rolling
bearing is supported in the compressor casing, with a gap-like
damping space being included as a hydraulic cushion and/or with a
radially acting spring body being included. This type of mounting
constitutes a spring damper system which makes it possible to avoid
the situation where the critical rotational speed of the shaft may
be set in the range near the maximum rotational speed of the
exhaust-gas turbocharger.
[0004] Rotor mountings of this type have, in principle,
incorporated a potential for improvement in terms of turbocharger
efficiency in connection with the friction occurring at the bearing
point between the shaft and the bearing receptacle. Particularly in
the range of low turbocharger rotational speeds, a considerable
percentage of the turbine power is lost in the form of bearing
power loss, so that, in the part-load range of the internal
combustion engine, a merely reduced boost pressure may be built up,
this manifesting itself in a delayed response behavior of the
internal combustion engine during acceleration.
[0005] Another problem is that the bearings have to be supplied
with lubricating oil, which presupposes an oil pump and an oil
supply line to the bearings. The supply of oil normally takes place
via the oil circuit of the internal combustion engine. For reasons
of construction, the situation cannot be ruled out where leakages
occur both on the turbine side and on the compressor side in the
exhaust-gas turbocharger, with lubricating oil escaping into the
exhaust-gas side or into the air side of the engine via these
leakages. In addition to the air and the exhaust gas being polluted
with lubricating oil, there is also the fear that various
components of the internal combustion engine, for example a
charge-air and exhaust-gas recirculation cooler or a soot filter,
may be contaminated with oil.
[0006] The undesirable infiltration of the lubricating oil into air
and exhaust gas or the contamination of various components with oil
necessarily represent a loss of lubricating oil which has to be
regularly compensated. Moreover, the high temperatures on the
exhaust-gas side in the region of the turbine damage the oil, and
the useful life of the oil is reduced.
[0007] The problem on which the invention is based is to improve
the efficiency of an exhaust-gas turbocharger for an internal
combustion engine. The ease with which the internal combustion
engine is maintained and the useful life of the exhaust-gas
turbocharger are also expediently to be improved.
[0008] This problem is solved, according to the invention, by an
exhaust-gas turbocharger for an internal combustion engine,
comprising an exhaust-gas turbine in the exhaust tract, and a
compressor in the intake tract. The exhaust-gas turbine and the
compressor are connected via a shaft which is supported in a casing
of the exhaust-gas turbocharger via at least one bearing. The
bearing has a non-contact design, such that, when the exhaust-gas
turbocharger is in operation, the shaft is held at a distance from,
and so as to be virtually free of friction with, a bearing
receptacle fixed to the casing.
[0009] According to the innovation, the bearing of the rotor shaft
of the exhaust-gas turbocharger in the casing has a non-contact
design, in that, at least when the exhaust-gas turbocharger is in
operation, the shaft is held at a distance, with a bearing gap,
from the bearing receptacle fixed to the casing. A virtually
friction-free mounting of the shaft in this case is thereby
possible, with the result that the efficiency of the turbocharger,
particularly at low rotational speeds, is appreciably improved,
since virtually no bearing losses occur any longer. The response
behavior of the internal combustion engine is improved, because,
even in the low rotational-speed range of the internal combustion
engine and with a correspondingly low exhaust-gas back pressure, a
notable turbine power can be generated, which is transmitted via
the shaft to the compressor. Thus, even in the lower
rotational-speed range, this brings about an increase in the boost
pressure and therefore, concomitantly, an increase in the power of
the internal combustion engine.
[0010] Moreover, the result of the friction-free mounting is that
the use of lubricating oil may be dispensed with. As a consequence
of which, on the one hand, the design of the exhaust-gas
turbocharger is appreciably simplified, because devices for
supplying oil to the turbocharger are no longer required and, on
the other hand, the problem of undesirable contamination of the
intake air, the exhaust gas or various assemblies of the internal
combustion engine with oil, is avoided. Furthermore, there is no
fear that the quality of the engine oil will be impaired because
the oil is heated to an undesirable extent, nor do any additional
oil losses occur.
[0011] According to a first advantageous development, the bearing
is designed as an air bearing, in which an air gap is formed
between the shaft and the bearing receptacle fixed to the casing.
Air, which can expediently be supplied via an air supply device,
flows into the air gap, the air bearing advantageously being
designed as an aerodynamic bearing, in which the supplied air flows
through the air gap, with the result that a supporting air cushion
is generated. As a result of the compressibility of the air, when
the shaft rotates, an over pressure zone and an under pressure zone
are formed, the pressure difference ensuring adjustment or
centering of the shaft in the bearing receptacle.
[0012] Alternatively to an aerodynamic bearing, an aerostatic
bearing may also be used, in which air is pressed into the bearing
gap from outside. When the bearing is under load, a higher pressure
is formed in the narrowed bearing gap than in the widened bearing
gap; this pressure difference gives rise to the load-bearing
capacity. Aerostatic bearings may expediently be used in the case
of shafts in which a relatively high load is to be expected.
[0013] According to a second advantageous version, which may be
used both alternatively to and in addition to the air bearing, the
bearing is designed as a magnetic bearing and forms, in particular,
part of an electric motor, in which the shaft of the exhaust-gas
turbocharger or a component connected to and rotating with the
shaft is identical to the rotor or armature of the electric motor.
The design as an electric motor affords the advantage that, in
addition to the non-contact and friction-free mounting of the
shaft, an additional drive of the shaft is provided, which,
particularly in ranges of low exhaust-gas back pressure, can be
cut-in in order to achieve an increase in boost pressure. By
contrast, in ranges of higher exhaust-gas back pressure, the
electric motor can be operated as a generator.
[0014] In a preferred embodiment, an additional contact bearing, in
particular a rolling bearing, is provided, which takes effect in
operating states where the supporting force of the non-contact
bearing is not sufficient. Particularly when an air bearing is
used, the contact bearing affords the advantage that the dry or
mixed friction that occurs when an aerodynamic air bearing is
started up, and that leads to an increased starting torque and wear
can be compensated or reduced by means of the contact bearing.
[0015] Other objects, advantages and novel features of the present
invention will become apparent from the following detailed
description of the invention when considered in conjunction with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a diagrammatic illustration of a charged internal
combustion engine which has an air cell supplying the air bearings
of the exhaust-gas turbocharger;
[0017] FIG. 2 is a cross-section through an exhaust-gas
turbocharger, the shaft of which is held in the turbocharger casing
in a non-contact manner; and
[0018] FIG. 3 is a cross-section through a further version of an
exhaust-gas turbocharger which has a contact bearing in addition to
the bearing operating in a non-contact manner.
DETAILED DESCRIPTION OF THE DRAWINGS
[0019] Identical components are given the same reference symbols in
the figures described below.
[0020] The internal combustion engine 1 generally illustrated in
FIG. 1 is assigned an exhaust-gas turbocharger 2, which comprises a
compressor 4 in the intake tract 3 and a turbine 5 in the exhaust
tract 6. The exhaust-gas turbine 5 is driven by the pressurized
exhaust gases from the internal combustion engine 1. The rotational
movement of the exhaust-gas turbine 5 is transmitted via a shaft 7
to the compressor 4 which sucks in combustion air at the ambient
pressure p.sub.um and compresses it to an increased boost pressure
p.sub.2.
[0021] The turbine 5 is expediently equipped with a variable
turbine geometry 8, which makes it possible to set the effective
turbine inlet cross section variably as a function of the state of
the internal combustion engine. As a result, an increase in the
drive power or brake power can be achieved both in the powered
driving mode and in the engine-braking mode. The variable turbine
geometry may take the form of an axially displaceable guide-vane
cascade, a guide-vane cascade with rotary vanes or else a
varioturbine which is designed, for example, as a flap turbine with
flow directed towards the turbine wheel and which can be shut off
via a flap.
[0022] Provided in the intake tract 3 of the internal combustion
engine is an air filter 9, in which the combustion air sucked in at
ambient pressure p.sub.um is filtered. After filtration, the
purified combustion air is delivered at the pressure p.sub.1 to the
compressor 4. Directly downstream of the compressor 4, the
compressed combustion air has the boost pressure p.sub.2. The
compressed combustion air is first cooled in a charge-air cooler 10
and is subsequently supplied to the cylinder inlet of the engine at
the boost pressure p.sub.2s.
[0023] Also provided is an exhaust-gas recirculation system 11
which consists of an adjustable recirculation valve 12 in a
recirculation line 13 between the exhaust tract 6 and the intake
tract 3 and also of an exhaust-gas recirculation cooler 14
downstream of the valve 12 in the recirculation line 13.
[0024] A silencer and a catalyst 15 are arranged in the exhaust
tract 6 downstream of the turbine 5. The exhaust gas in the exhaust
tract 6 enters the turbine 5 at the exhaust-gas back pressure
p.sub.3, and, downstream of the turbine 5, the exhaust gas has the
expanded outlet pressure p.sub.4 at which the exhaust gas is
supplied to the silencer or catalyst 15. After flowing through the
silencer or catalyst, the purified exhaust gas is discharged into
the atmosphere at the ambient pressure p.sub.um.
[0025] The exhaust-gas turbocharger 2 advantageously has an air
mounting, via which the shaft 7 of the exhaust-gas turbocharger 2
is held in a bearing receptacle of the turbocharger casing in a
non-contact and friction-free manner. In order to assist and
maintain the air mounting, an air supply device 16 is provided, via
which air (if appropriate pressurized air) can be supplied, as
required or permanently, to the air bearing in the exhaust-gas
turbocharger 2. The air supply device 16 comprises an air cell 17
which communicates via air supply lines 18a, 18b and 18c with
various air bearings in the exhaust-gas turbocharger 2, an
adjustable air supply valve 19 in the supply line 18a and an air
filter 20 located downstream of the air supply valve 19. A pump 21
is also provided, which is operated by the engine and supplies the
air cell 17 with air.
[0026] If appropriate, the air supply device 16 may also be
supplied directly by the air pump 21. In this case, the air cell
may be eliminated.
[0027] The exhaust-gas turbocharger 2 has a first air bearing
designed as a radial bearing 22 and a second air bearing designed
as a radial/axial bearing 23, the first radial bearing 22 being
arranged in the region of the compressor 4 and the second
radial/axial bearing 23 being arranged symmetrically in the
turbocharger between the compressor 4 and the turbine 5. The air
supply line 18b extends axially into the radial bearing 22 and the
air supply line 18c extends radially into the radial/axial bearing
23.
[0028] The internal combustion engine 1 is also assigned a
regulating and control unit 24, via which the various assemblies of
the internal combustion engine and the internal combustion engine
itself can be controlled and regulated. The regulating and control
unit 24 communicates with (1) actuators of brake valves 25 in the
internal combustion engine, (2) injection devices of the internal
combustion engine, (3) air supply devices for the internal
combustion engine, (4) the exhaust-gas recirculation system 11, (5)
the actuating member of the variable turbine geometry 8 of the
exhaust-gas turbine 5, (6) the air supply valve 19 of the air
supply device 16, and (7) the pump 21 which is assigned to the air
supply device 16.
[0029] FIG. 2 illustrates in cross section an exhaust-gas
turbocharger 2 mounted in a non-contact and friction-free manner.
The exhaust-gas turbocharger 2, together with the compressor 4 and
the turbine 5, in a turbocharger casing 26, has the two bearings 22
and 23 which, in the exemplary embodiment, are designed as air
bearings and via which the shaft 7 of the exhaust-gas turbocharger
2 is supported relative to the turbocharger casing 26. The bearing
22 is designed as a radial bearing and is located on the compressor
side 4 in the compressor casing 28, which forms part of the
turbocharger casing 26. The radial bearing 22 extends axially into
the air inlet duct 29 of the compressor 4. The radial bearing 22
consists, on the shaft side, of an inner bearing sleeve 30 which is
connected to the shaft 7 of the exhaust-gas turbocharger 2 and, on
the casing side, of an outer approximately hollow-cylindrical
mounting element 31 which radially surrounds the inner bearing
sleeve 30 and is connected firmly to the compressor casing 28, in
particular by means of supporting ribs 32 which extend radially
between the inner duct wall of the air inlet duct 29 and the outer
mounting element 31. The inner bearing sleeve 30 is connected
releasably to the shaft 7.
[0030] In order to increase the damping capacity of the mounting,
the wall thickness of the inner bearing sleeve 30 is kept very
small, thus making it possible to have geometric deformation which
brings about material damping. Additional damping is achieved by
the outer mounting element 31 being held on the radially running
supporting ribs 32.
[0031] The radial bearing 22 is advantageously designed as an air
bearing, in particular as an aerodynamic air bearing. Between the
outside of the inner bearing sleeve, rotating when the turbocharger
is in operation, and the inside of the outer mounting element 31,
held fixedly on the casing, an annular air gap 33, through which
air flows when the turbocharger is in operation, is formed with the
result that a supporting air cushion is formed between the rotating
bearing sleeve 30 and the fixed mounting element 31.
[0032] The flow advantageously passes through the annular air gap
33 axially. The outer mounting element 31 has, on the side facing
the entrance to the air inlet duct 29, a dome-shaped element 34
provided with an air inlet orifice which is connected to the air
supply line 18b. Air, if appropriate pressurized air, is injected
via the air supply line 18b into the interior of the outer mounting
element 31. The injected air flows into the annular air gap 33
between the bearing sleeve 30 and the mounting element 31 and flows
through this air gap 33 in the axial direction, with the result
that the supporting air cushion is formed. Located on the end face
opposite the air inlet, between the inner bearing sleeve 30 and the
outer mounting element 31, is an overflow orifice 35, via which the
air flowing axially through the air gap 33 re-enters the air inlet
duct 29 of the compressor 4.
[0033] Alternatively or additionally to the axial entry of the
inflowing air into the air gap 33, it may also be expedient for the
air to be introduced radially into the annular air gap 33. The
inner bearing sleeve 30 consists of an inner wall 36 and of an
outer wall 37, an inner annular space 38 being formed between the
inner and the outer wall 36 and 37, respectively. The inner annular
space 38 is open on one axial end face; air can flow through this
orifice into the inner annular space 38 and can flow out again into
the annular air gap 33 via radial orifices expediently introduced
in the outer wall 37.
[0034] Located approximately centrically in the exhaust-gas
turbocharger 2 is a further bearing 23, which is designed as a
radial/axial bearing and is expediently likewise an air bearing.
The bearing 23 has both a radial and an axial supporting function.
The bearing 23 consists, on the shaft side, of an inner bearing
sleeve 40, which is connected firmly to the shaft 7, and of a
bearing disc 39 which is seated radially on the inner bearing
sleeve 40 and is connected firmly to the bearing sleeve 40. The
bearing disc 39 is guided in an annular space which is delimited on
the two axial sides and on the radially outer side by an annular
element 41 fixed to the casing. The annular space in the annular
element 41 is dimensioned such that, between the bearing disc 39
and the inner walls of the annular space, an air gap is formed
axially and radially, in which a supporting air cushion can be
formed. Provided on the circumferential side of the annular element
41 are air inflow orifices connected to supply lines 18c, via which
air can be supplied to the annular space. The air injected radially
into the annular space can flow out again via sealing gaps 42 and
43, the sealing gaps 42 and 43 being located on the radially inner
side of the annular element 41 fixed to the casing and extending on
axially opposite sides with respect to the bearing disc 39. The
sealing gap 42 is located on the side facing the compressor 4, and
air can be introduced via the sealing gap 42 from the annular space
into the air flow duct through the compressor 4. The axially
opposite sealing gap 43 faces the turbine 5, and air can
correspondingly be guided out of the annular space via the sealing
gap 43 into the exhaust-gas outlet 44 of the turbine 5.
[0035] In a further expedient version, there may be provision for
at least one of the bearings operating in a non-contact and
friction-free manner, in particular the radial/axial bearing 23, to
be designed as a magnetic bearing and expediently form part of an
electric motor. In this version, the bearing disc 39 fixed to the
shaft is designed as an armature disc or as a rotor of the electric
motor, and the annular element 41 fixed to the casing
correspondingly forms the stator of the electric motor. This
version, in addition to having the non-contact mounting, affords
the additional advantage that the shaft 7 can be driven
electromotively, which can be utilized for increasing the power of
the internal combustion engine, particularly in engine operating
ranges in which only a slight exhaust-gas back pressure is
available for driving the turbine.
[0036] The sectional illustration according to FIG. 3 shows a
similar exemplary embodiment to FIG. 2, but with an additional
rolling mounting which takes effect in operating states in which
the supporting force of the air bearing is not sufficient. In the
exemplary embodiment according to FIG. 3, the radial bearing 22 in
the compressor 4 is provided with a roller mounting 45. The rolling
mounting 45 is located between the shaft 7 of the exhaust-gas
turbocharger 2 and the inner bearing sleeve 30 which is seated
radially on the shaft 7 and, in the exemplary embodiment shown, can
execute a relative rotation with respect to the shaft 7 with the
aid of the roller mounting 45. If the supporting force of the air
bearing is not yet sufficient to stabilize the shaft centrically,
for example when the exhaust-gas turbocharger is being started up,
then, by means of an eccentric displacement of the shaft 7, the
bearing sleeve 30 connected to the shaft can come into contact with
the inner wall of the mounting element 31 fixed to the casing. By
virtue of the friction between the mounting element 31 and the
bearing sleeve 30, the bearing sleeve 30 experiences a deceleration
in the direction of rotation, which, however, on account of the
roller mounting 45, is not transmitted or is transmitted only
partially to the shaft 7, so that, in spite of a possibly eccentric
position, the shaft 7 can rotate essentially unimpeded and free of
friction.
[0037] As soon as a load-bearing air cushion has been formed in the
annular air gap 33 between the bearing sleeve 30 and the mounting
element 31, the shaft 7 is stabilized in its central position and
can rotate in a completely non-contact manner.
[0038] A corresponding roller mounting or comparable contact
bearing may also be provided in the case of the radial/axial
bearing 23.
[0039] The roller mounting or comparable contact bearing may be
combined both with air bearings and with magnetic bearings.
[0040] When air bearings are used, both aerodynamically and
aerostatically designed bearings may be employed.
[0041] The foregoing disclosure has been set forth merely to
illustrate the invention and is not intended to be limiting. Since
modifications of the disclosed embodiments incorporating the spirit
and substance of the invention may occur to persons skilled in the
art, the invention should be construed to include everything within
the scope of the appended claims and equivalents thereof.
* * * * *