U.S. patent application number 13/994260 was filed with the patent office on 2013-10-17 for bearing arrangement for a turbocharger, and turbocharger.
This patent application is currently assigned to Schaeffler Technologies AG & Co. KG. The applicant listed for this patent is Andre Kuckuk, Christopher Mitchell, Thomas Motz, Heiko Schmidt, Peter Solfrank. Invention is credited to Andre Kuckuk, Christopher Mitchell, Thomas Motz, Heiko Schmidt, Peter Solfrank.
Application Number | 20130272854 13/994260 |
Document ID | / |
Family ID | 44925564 |
Filed Date | 2013-10-17 |
United States Patent
Application |
20130272854 |
Kind Code |
A1 |
Schmidt; Heiko ; et
al. |
October 17, 2013 |
BEARING ARRANGEMENT FOR A TURBOCHARGER, AND TURBOCHARGER
Abstract
A bearing arrangement for a turbocharger, including a bearing
housing-which extends in an axial direction, an anti-friction
bearing, situated within the bearing housing, having an outer
bearing ring and a number of rolling bodies and an axially
extending shaft which is rotatably mounted within the bearing
housing. It is provided that the shaft includes a rolling body
raceway for guiding the rolling bodies. Moreover, the invention
relates to a turbocharger having such a bearing arrangement. A
bearing arrangement of this type allows the secure mounting of a
shaft in a turbocharger with simple assembly and low costs.
Inventors: |
Schmidt; Heiko;
(Muehlhausen, DE) ; Solfrank; Peter; (Frensdorf,
DE) ; Mitchell; Christopher; (St Austell, GB)
; Kuckuk; Andre; (Herzogenaurach, DE) ; Motz;
Thomas; (Herzogenaurach, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Schmidt; Heiko
Solfrank; Peter
Mitchell; Christopher
Kuckuk; Andre
Motz; Thomas |
Muehlhausen
Frensdorf
St Austell
Herzogenaurach
Herzogenaurach |
|
DE
DE
GB
DE
DE |
|
|
Assignee: |
Schaeffler Technologies AG &
Co. KG
Herzogenaurach
DE
|
Family ID: |
44925564 |
Appl. No.: |
13/994260 |
Filed: |
November 14, 2011 |
PCT Filed: |
November 14, 2011 |
PCT NO: |
PCT/EP2011/070048 |
371 Date: |
June 14, 2013 |
Current U.S.
Class: |
415/170.1 |
Current CPC
Class: |
F05D 2240/54 20130101;
F16C 25/083 20130101; F01D 25/16 20130101; F16D 1/027 20130101;
F16C 19/185 20130101; F16D 1/068 20130101; F16C 33/581 20130101;
F16C 19/548 20130101; F02C 6/12 20130101; F16C 2360/24
20130101 |
Class at
Publication: |
415/170.1 |
International
Class: |
F01D 25/16 20060101
F01D025/16 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 17, 2010 |
DE |
10 2010 054 939.8 |
Claims
1-11. (canceled)
12. A bearing arrangement for a turbocharger, comprising: a bearing
housing extending in an axial direction; an anti-friction bearing
situated within the bearing housing and having an outer bearing
ring and a plurality of rolling bodies; and an axially extending
shaft rotatably mounted within the bearing housing, the shaft
having a shaft journal on an end-face side for fastening to a
turbine wheel.
13. A bearing arrangement for a turbocharger, comprising: a bearing
housing extending in an axial direction; an anti-friction bearing
situated within the bearing housing having an outer bearing ring
and a plurality of rolling bodies; and an axially extending shaft
rotatably mounted within the bearing housing, the shaft including a
rolling body raceway for guiding the rolling bodies, the outer
bearing ring being guided in the bearing housing by a support
ring.
14. The bearing arrangement as recited in claim 13 wherein the
shaft has a shaft journal on an end-face side for fastening to a
turbine wheel.
15. The bearing arrangement as recited in claim 13 wherein the
shaft, at least in the area of the rolling body raceway, is made of
steel.
16. The bearing arrangement as recited in claim 13 wherein the
shaft is composed of a plurality of axially adjacent shaft
sections.
17. The bearing arrangement as recited in claim 16 wherein the
shaft sections are welded together.
18. The bearing arrangement as recited in claim 13 wherein the
shaft includes an inner recess.
19. The bearing arrangement as recited in claim 13 wherein the
outer bearing ring includes a splash oil hole for acting on the
anti-friction bearing with lubricant.
20. The bearing arrangement as recited in claim 13 wherein the
shaft includes a plurality of grooves on its outer periphery for
positioning sealing elements.
21. The bearing arrangement as recited in claim 13 wherein the
shaft includes an oil separator.
22. The bearing arrangement as recited in claim 12 wherein the
shaft, at least in the area of the rolling body raceway, is made of
steel.
23. The bearing arrangement as recited in claim 12 wherein the
shaft is composed of a plurality of axially adjacent shaft
sections.
24. The bearing arrangement as recited in claim 23 wherein the
shaft sections are welded together.
25. The bearing arrangement as recited in claim 12 wherein the
shaft includes an inner recess.
26. The bearing arrangement as recited in claim 12 wherein the
outer bearing ring includes a splash oil hole for acting on the
anti-friction bearing with lubricant.
27. The bearing arrangement as recited in claim 12 wherein the
shaft includes a plurality of grooves on its outer periphery for
positioning sealing elements.
28. The bearing arrangement as recited in claim 12 wherein the
shaft includes an oil separator.
29. A turbocharger comprising: a compressor wheel; a turbine wheel;
and a bearing arrangement as recited in claim 12, the compressor
wheel and the turbine wheel being connected via the shaft, and the
shaft being welded to the turbine wheel.
30. A turbocharger comprising: a compressor wheel; a turbine wheel;
and a bearing arrangement as recited in claim 13, the compressor
wheel and the turbine wheel being connected via the shaft, and the
shaft being welded to the turbine wheel.
Description
[0001] The present invention relates to a bearing arrangement for a
turbocharger, including a bearing housing, an anti-friction
bearing, situated within the bearing housing, having an outer
bearing ring and a number of rolling bodies, and an axially
extending shaft which is rotatably mounted within the bearing
housing.
[0002] Moreover, the present invention relates to a turbocharger
having an above-mentioned bearing arrangement.
BACKGROUND
[0003] A turbocharger is usually used for increasing the power of
internal combustion engines by utilizing exhaust gas energy. For
this purpose, the turbocharger is composed of a compressor and a
turbine which are connected to one another via a shaft mounted
within a bearing housing.
[0004] During operation, the turbine is set into rotation by an
exhaust gas flow, and via the shaft drives the compressor, which
draws in and compresses air. The compressed air is led into the
engine, a large quantity of air entering into the cylinders during
the induction stroke due to the increased pressure. As a result,
the oxygen content required for the combustion of fuel
correspondingly increases, so that more oxygen enters into the
combustion chamber of the engine with each intake stroke.
[0005] This results in an increase in the maximum torque, causing
the power output, i.e., the maximum power at a constant working
volume, to increase. This increase allows in particular the use of
a more powerful engine having approximately the same dimensions, or
alternatively, allows a reduction in the engine dimensions, i.e.,
achieving comparable power with smaller and lighter machines.
[0006] Since the shaft rotates at a high rotational speed during
operation of a turbocharger, the shaft must be securely mounted to
allow problem-free operation of the turbocharger.
[0007] A bearing unit, designed as a bearing mounting system, for a
turbocharger of the type mentioned at the outset is known from DE
689 08 244 T2. A shaft is situated within a bearing housing. The
bearing of the shaft within the bearing housing occurs via a pair
of anti-friction bearings designed as ball bearings. The ball
bearings in each case are composed of an outer bearing ring and an
inner bearing ring, the inner bearing rings being fixedly fastened
to the shaft.
SUMMARY OF THE INVENTION
[0008] Due to the above-mentioned configuration, a shaft of a
turbocharger may be securely mounted, even at increased rotational
speeds of the shaft. However, the use of a plurality of required
separate bearing components and the associated high assembly cost
do not represent a long-term solution for a bearing arrangement or
a turbocharger.
[0009] A first object of the present invention is to provide a
bearing arrangement which is improved over the related art, and
which allows the secure bearing of a shaft in a turbocharger with
simple assembly and low costs.
[0010] A second object of the present invention is to provide a
turbocharger having such a bearing arrangement.
[0011] The present invention provides a bearing arrangement for a
turbocharger, including a bearing housing which extends in an axial
direction, an anti-friction bearing, situated within the bearing
housing, having an outer bearing ring and a number of rolling
bodies, and an axially extending shaft which is rotatably mounted
within the bearing housing. It is provided that the shaft includes
a rolling body raceway for guiding the rolling bodies.
[0012] The present invention takes into account the fact that there
is concern for increased assembly effort as well as impairment of
the bearing components, and thus of the function of the
turbocharger, as the result of using a plurality of separate
bearing components. This is particularly true with regard to the
inner bearing rings that are usually used, which have corresponding
raceways at their outer periphery for guiding rolling bodies.
During assembly, the inner bearing rings are pushed onto the shaft,
and must be pressed onto the shaft so that no twisting relative to
the shaft is possible during operation. During the pressing, the
bearing rings are compressed in such a way that the axial distance
between the rolling body raceways is reduced, and thus the shaft
play is changed. In addition, the diameters of the rolling body
raceways, and thus also the bearing play, change.
[0013] In addition, pressing the inner bearing rings may result in
misalignment of same on the shaft. For example, it is possible that
the inner bearing rings are not coaxially aligned with the shaft
and with one another, which may result in undesirable seating at
the axial contact points between the bearing rings or the bearing
seats during balancing as well as during subsequent operation.
Furthermore, the balance quality may deteriorate over the running
time of the bearing, resulting in increased wear of the bearing
components. In any case, it is thus not possible to ensure
problem-free functioning of a turbocharger.
[0014] Lastly, the present invention recognizes that the
above-mentioned problems may surprisingly be overcome when the
shaft includes a rolling body raceway for guiding the rolling body.
The use of inner bearing rings to be separately installed may be
dispensed with entirely. In other words, the shaft itself takes
over the function of the inner bearing rings, so that a secure
bearing of the shaft in a turbocharger may be achieved by this type
of configuration at low cost and with ease of assembly.
[0015] In addition, the sum of the component tolerances may be
reduced by dispensing with separate inner bearing rings. The
usually additive shape and position defects of the inner bearing
rings on the shaft may thus be avoided, so that the overall
tolerance is smaller.
[0016] The shaft may be made of various materials, heat- and
corrosion-resistant materials being particularly suited. The shaft
may be manufactured in one piece, for example, with the aid of a
shaping process, a machining process, or a casting process. As an
alternative to the one-piece manufacture, multi-part manufacture is
possible. The rolling body raceway is integrated into the lateral
surface of the shaft, and may, for example, be introduced directly
into the lateral surface in one step during manufacture of the
shaft. Alternatively, the rolling body raceway may be subsequently
introduced into the lateral surface in a step following the
manufacture of the shaft base body. To ensure the necessary
stability of the shaft, the shaft preferably undergoes a finishing
operation after manufacture.
[0017] The shaft is rotatably mounted within a bearing housing in
the installed state. For this purpose, the bearing housing
preferably has a hollow cylindrical design. Due to the high
stresses during operation of a turbocharger, in particular heat-
and corrosion-resistant metallic materials are suited for
manufacturing the bearing housing. The bearing housing is in
particular provided with a location hole for the further components
of the bearing arrangement such as the anti-friction bearing.
[0018] The anti-friction bearing and the individual anti-friction
bearing components are also advantageously made of heat- and
corrosion-resistant materials, for example through-hardened steels
or also ceramics. The common types of bearings, for example
cylindrical roller bearings or also tapered roller bearings, are
basically usable as anti-friction bearings. Ball bearings, such as
double-row angular-contact ball bearings in particular, are
particularly suited. Two rolling body raceways situated at an axial
distance from one another are advantageously introduced into the
lateral surface of the shaft for guiding the rolling bodies of a
double-row angular-contact ball bearing.
[0019] The anti-friction bearing is also provided with at least one
outer bearing ring, on the inner periphery of which a rolling body
raceway is introduced, which likewise is used for guiding and
positioning the rolling bodies. In this regard, one-piece as well
as multi-piece manufacture of the outer bearing ring is possible.
For multi-piece manufacture, the outer bearing rings may, for
example, abut one another, thus preventing axial displacement of
the bearings on the shaft. Alternatively, the outer bearing rings
may be situated at an axial distance from one another with the aid
of a spring element, for example.
[0020] In particular a space, for example as a gap which surrounds
the outer bearing ring, for a so-called quenching oil film is
provided between the outer diameter of the outer bearing ring and
the inner periphery of the bearing housing. In this case, the
quenching oil film takes over the function of the vibration damper
and prevents undesirable contact between the outer bearing ring and
the bearing housing.
[0021] To supply the space with oil, a number of supply holes may
be introduced within the bearing housing, via which oil may be
metered from the engine oil circuit into the space. For this
purpose, the supply holes are in communicating connection with a
number of the grooves surrounding the outer periphery of the outer
bearing ring. Similarly, the grooves may be acted on by oil via the
supply holes. Starting from the grooves, the oil may be distributed
over the periphery of the outer bearing ring in the axial
direction, so that a uniform oil film forms between the outer
bearing ring and the inner wall of the bearing housing. The number
of supply holes and of the grooves is unlimited in principle, and
may be adapted, for example, to the dimensions of the bearing
housing and the thickness of the quenching oil film.
[0022] Furthermore, an outlet hole which is in communicating
connection with a drainage groove which surrounds the outer bearing
ring on its outer periphery is preferably additionally introduced
into the bearing housing. It is thus ensured that the oil supplied
to the space via the supply hole may continuously drain off
[0023] Alternatively, the outer bearing rings may be guided in the
bearing housing via an additional support ring. In this case, the
support ring is embedded in the space. The support ring preferably
has a number of circumferential grooves on its outer periphery,
which in the installed state are in communicating connection with
the supply holes in the bearing housing. The quenching oil film is
then correspondingly provided in the space between the outer
periphery of the support ring and the inner wall of the bearing
housing. When a support ring is used, a drainage groove which is
introduced into the support ring on its outer periphery is
advantageously in communicating connection with an outlet hole, and
appropriately allows oil drainage.
[0024] Securing elements may be used to position the anti-friction
bearing within the bearing housing with anti-twist protection. In
principle, a plurality of securing elements is conceivable which
withstand the forces acting during operation of a turbocharger and
which allow an arrangement of the outer bearing ring within the
bearing housing with anti-twist protection. The securing elements,
the number of which is not limited in principle, may be designed,
for example, as securing pins or securing bolts which may be
inserted into holes provided for this purpose within the bearing
housing. Alternatively, the securing elements may be designed as
springs which may engage with depressions or grooves provided for
this purpose.
[0025] In one advantageous embodiment of the present invention, the
shaft, at least in the area of the rolling body raceway, is made of
a steel. In principle, various steels or metallic materials are
usable here. An alloyed anti-friction bearing steel is particularly
suited. For example, an anti-friction bearing steel of type
81MoCrV42-16 may be used, which in particular due to its heat
stability and corrosion resistance meets the necessary requirements
for use in turbochargers. The properties of the metallic material
or of the anti-friction bearing steel may be influenced by the
selection of the alloy components or by the composition. In
principle, it is possible to produce the entire shaft from an
anti-friction bearing steel. Alternatively, an anti-friction
bearing steel may be used only at the locations of the rolling body
raceways.
[0026] In another advantageous embodiment of the present invention,
the shaft is composed of a number of axially adjacent shaft
sections. The individual shaft sections may be welded together
prior to assembly of the bearing arrangement. The multi-piece
configuration allows, for example, the controlled introduction of
recesses into the shaft. These recesses provide an air volume
within the shaft, which in the installed state of the shaft in the
turbocharger reduces the thermal conduction from the turbine wheel
to the anti-friction bearing.
[0027] The costs for manufacturing the shaft and for manufacturing
the bearing arrangement may be reduced in particular by using
multiple shaft sections. This is made possible in particular in
that the shaft sections may be made of various materials. The shaft
sections into which the rolling body raceways are introduced are
preferably made of an anti-friction bearing steel which has the
required stability. Requirement-specific material, and accordingly
less expensive shaft material, may be used for the further shaft
sections.
[0028] The shaft sections are preferably joined to one another by
welding. Welding processes are particularly suited in this regard,
since their use provides the option of also joining materials
having different physical properties, for example joining steel to
aluminum.
[0029] The shaft preferably includes an inner recess. The inner
recess may be designed as a cavity which provides an additional air
volume. For example, the thermal conduction from the turbine wheel
to the bearing may be reduced in this way. In addition, the recess
may be used for accommodating a so-called welding discharge which
arises during the joining of the shaft to the turbine wheel or also
during the joining of multiple shaft sections to one another, and
which may then become caught within the recesses. In principle, a
recess may also be introduced into the turbine wheel. The same
applies to a multi-piece configuration of the shaft for the
individual shaft sections, which likewise may each be provided with
a recess. This further increases the interior air volume and
further reduces the thermal conductivity.
[0030] The shaft preferably has a shaft journal on the end-face
side for centering and fastening to a turbine wheel. The shaft
journal is preferably designed as a journal which extends in the
axial direction, and which in the installed state may engage with
the hole in a turbine wheel. Thus, a connection between the
components is possible even before the components are welded, which
simplifies the subsequent welding process. In principle, providing
a journal on the turbine wheel is also possible, in which case the
journal engages with a hole at the end face of the shaft.
[0031] It is also possible in principle to introduce a recess into
the journal which provides an air volume within the shaft. The
thermal conduction from the turbine wheel to the anti-friction
bearing may thus also be reduced with the aid of the journal.
[0032] The outer bearing ring advantageously includes a splash oil
hole for acting on the anti-friction bearing with lubricant. The
splash oil holes are connected to the grooves in the outer ring.
The oil may pass from the grooves into the bearing space via the
splash oil holes, thus being utilized for lubrication and
cooling.
[0033] The shaft also preferably includes a number of grooves on
its outer periphery for positioning sealing elements. The grooves
may be introduced into the outer periphery of the shaft on the
compressor side as well as on the turbine side, thus achieving a
sealing effect on both sides of the shaft. The required lubrication
of the anti-friction bearing positioned within the bearing housing,
which is achieved via splash oil holes, for example, may be ensured
in this way.
[0034] The shaft also preferably includes an oil separator. The oil
separator may, for example, be mounted on the shaft as a separate
component, or also integrated into the shaft. In particular, the
oil separator is designed as an oil separator which operates by
making use of the centrifugal force principle.
[0035] The second object of the present invention is achieved
according to the present invention by a turbocharger, including a
compressor wheel, a turbine wheel, and a bearing arrangement
corresponding to the above-mentioned embodiments, the compressor
wheel and the turbine wheel being situated at the opposite ends of
the shaft. It is provided that the shaft is welded to the turbine
wheel.
[0036] As explained at the outset, the turbine wheel of the turbine
of a turbocharger is set into rotation by an exhaust gas flow, and
drives the compressor via the shaft. The compressor draws in and
compresses air. The compressor operates continuously, and is
characterized by a small pressure rise and a high volumetric flow
rate. The compressed air is conducted into the engine, a large
quantity of air entering into the cylinders during the induction
stroke due to the increased pressure. As a result, the oxygen
content required for the combustion of fuel correspondingly
increases, so that more oxygen enters into the combustion chamber
of the engine with each intake stroke.
[0037] The shaft is welded to the turbine wheel to achieve a secure
attachment of the turbine wheel to the shaft, and thus to be able
to ensure a connection between the compressor wheel and the turbine
wheel. Various welding processes are suited for this purpose.
[0038] For example, a friction welding process may be used.
Friction welding allows secure joining of components for the same
or also different material combinations. This involves a pressure
welding process, the heating of the parts to be joined being
produced by mechanical friction. The heating is generally produced
by a movement between a rotating component and a stationary
component, which are joined together under force without filler
metal.
[0039] As an alternative to the friction welding process, the shaft
may also be joined to the turbine wheel with the aid of an electron
beam welding process. Due, for example, to the high energy density
that is introduced into the welding zone, this process allows the
joining of a variety of different materials such as high-melting
metals. Electron beam welding allows high welding speeds with
extremely deep, narrow weld seams. Warping may be kept very low due
to the small weld seam widths and the high degree of
parallelism.
[0040] Laser beam welding, for example, is also conceivable, thus
allowing joining of components at a high welding speed, having a
thin, narrow weld seam shape, and with low thermal warping. Laser
beam welding is generally carried out without supplying a filler
metal.
[0041] The turbine wheel is preferably pressed onto the shaft. This
procedure is advantageously carried out prior to the welding
process. For this purpose, the shaft is provided on the turbine
side, for example with a shaft journal which extends in the axial
direction and which is pressed into a hole in the turbine wheel.
Due to this press fit, a connection between the shaft and the
turbine wheel is possible even before the welding, so that the two
components subsequently need to be welded together only at the
preferably flat contact points. As an alternative, of course, the
turbine wheel may be provided with a journal, and the shaft may be
provided with a hole at its end face, so that the shaft is pressed
into the turbine wheel.
[0042] The compressor wheel is advantageously fastened to the shaft
with the aid of a nut. For this purpose, the compressor wheel is
pushed onto the shaft during assembly, and lastly is clamped at
that location with the aid of the nut. A secure connection also
between the compressor wheel and the shaft is ensured in this
way.
[0043] In principle, the bearing components of the bearing
cartridge may be preassembled and pushed into the bearing housing
starting from the turbine side. This allows delivery of the bearing
cartridge with less effort and with low assembly effort for
customers.
[0044] Further advantageous embodiments are provided in the
subclaims directed to the bearing arrangement, which may be
analogously transferred to the turbocharger.
BRIEF DESCRIPTION OF THE DRAWING
[0045] Exemplary embodiments of the present invention are explained
below with reference to a drawing. FIGS. 1 through 4 each show a
turbocharger having a bearing arrangement in a longitudinal
section.
DETAILED DESCRIPTION
[0046] FIG. 1 shows a turbocharger 1 having a bearing arrangement
3. The turbocharger has a compressor wheel 5 and a turbine wheel 7
situated at the opposite ends of a shaft 9 which extends in the
axial direction.
[0047] Shaft 9 is part of bearing arrangement 3, and is rotatably
mounted within a bearing housing 11 which likewise extends axially.
Bearing arrangement 3 also includes an anti-friction bearing 13,
having two axially adjacent outer bearing rings 15, 17, situated
within bearing housing 11. Outer bearing rings 15, 17 are situated
at a distance from one another with the aid of a pretensioned
spring element 19 situated in between.
[0048] Anti-friction bearing 13 also has rolling bodies 21 designed
as spheres, which in each case are held in rows in cages 23.
Rolling bodies 21 are each guided in rolling body raceways 25, 27
which are integrated into the lateral surface of shaft 9. Rolling
body raceways 25, 27 are introduced into the lateral surface in one
step directly during manufacture of the shaft. The use of inner
bearing rings to be separately installed may thus be dispensed
with, since shaft 9 takes over the function of the inner bearing
rings.
[0049] This reduces the effort during assembly, in which the inner
bearing rings must be pushed onto the shaft and pressed onto same.
In addition, the axial distance between rolling body raceways 25,
27 always remains the same, so that the shaft play does not change
either.
[0050] In addition, the sum of the component tolerances may be
reduced by dispensing with separate inner bearing rings. The
usually additive shape and position defects of the inner bearing
rings on shaft 9 may thus be avoided, so that the overall tolerance
is smaller.
[0051] Entire shaft 9 is manufactured in one piece from a
heat-resistant anti-friction bearing steel. The shaft is welded to
turbine wheel 7 with the aid of a friction welding process, thus
achieving a secure connection between shaft 9 and turbine wheel
7.
[0052] In addition, recesses 29, 31 are introduced into shaft 9 as
well as into turbine wheel 7. Recesses 29, 31 provide an air
volume, so that the thermal conduction from turbine wheel 7 to
anti-friction bearing 13 during operation of turbocharger 1 is
reduced. Furthermore, the recesses provide space for welding
discharge during machining of the shaft.
[0053] Shaft 9 is connected to compressor wheel 5 on the side
opposite from turbine wheel 7. For this purpose, compressor wheel 5
is pushed onto the shaft and is clamped at that location with the
aid of a nut 33.
[0054] Grooves 35 for positioning sealing elements 37 are
introduced on the outer periphery of shaft 9. Sealing elements 37
seal against leaks and contaminants, on the sides of compressor
wheel 5 as well as on the sides of turbine wheel 7.
[0055] For assembling the turbocharger, the bearing components may
be preassembled and pushed into bearing housing 11 starting from
the turbine side. Since the outer diameter of outer bearing rings
15, 17 is slightly smaller than the inner diameter of bearing
housing 11, a gap-shaped space 39 results between bearing housing
11 and outer bearing rings 15, 17. Space 39 is acted on by oil via
supply hole 41 in bearing housing 11, so that a quenching oil film
forms at that location. Supply holes 41, 42 are in communicating
connection with grooves 43, 44 on the outer periphery of outer
bearing rings 15, 17. In addition, the oil, starting from grooves
43, 44, is distributed into the bearings through splash oil holes
45, 46 connected to grooves 43, and may thus be used for
lubrication. An outlet hole 47 is included for drainage.
[0056] In addition, an oil separator 49 which operates according to
the centrifugal force principle is mounted on shaft 9.
[0057] FIG. 2 shows another turbocharger 61 having a bearing
arrangement 63. Turbocharger 61 has a compressor wheel 65 and a
turbine wheel 67 which are situated at the opposite ends of a shaft
69 which extends in the axial direction. In FIG. 2 as well, the
entire shaft 69 is manufactured in one piece from a heat-resistant
steel.
[0058] Since the function and the individual components of
turbocharger 61 in FIG. 2 essentially correspond to those of
turbocharger 1 in FIG. 1, at this point reference is made to the
detailed description and illustration in FIG. 1, which may be
analogously transferred to the discussion below.
[0059] In contrast to FIG. 1, turbine wheel 67 is connected to
shaft 69 with the aid of electron beam welding. For this purpose,
turbine wheel 67 is pressed onto shaft 69. Turbine wheel 67 has a
corresponding hole 111 into which shaft journal 113 of the shaft is
pressed at the end face of the shaft. Shaft journal 113 is designed
as a journal which extends in the axial direction.
[0060] Turbine wheel 67 and shaft 69 are subsequently welded only
at flat contact surfaces 115 of turbine wheel 67 and of shaft 69 by
an electric beam.
[0061] Furthermore, shaft 69 is clamped to compressor wheel 65 on
the side opposite from turbine wheel 67 with the aid of a nut 93.
In addition, an oil separator 109 which operates according to the
centrifugal force principle is mounted on shaft 69 on the same
side.
[0062] FIG. 3 shows another turbocharger 121 having a bearing
arrangement 123. Turbocharger 121 likewise has a compressor wheel
125 and a turbine wheel 127 which are situated at the opposite ends
of a shaft 129 which extends in the axial direction. Shaft 129 is
rotatably mounted within a bearing housing 131 which likewise
extends axially.
[0063] For this purpose, bearing arrangement 123 has an
anti-friction bearing 133, having two axially adjacent outer
bearing rings 135, 137, within bearing housing 131. Outer bearing
rings 135, 137 are situated at a distance from one another with the
aid of a pretensioned spring element 139 situated in between.
Anti-friction bearing 133 also has rolling bodies 141 designed as
spheres, which in each case are held in rows in cages 143. Rolling
bodies 141 are each guided in rolling body raceways 145, 147 which
are integrated into the lateral surface of shaft 119 129.
[0064] In the installed state, a gap-shaped space 159 which is
acted on by oil via two supply holes 161 in bearing housing 131 is
provided between the outer diameter of outer bearing rings 135, 137
and bearing housing 131. A quenching oil film forms in the space.
Supply holes 161, 162 are in communicating connection with grooves
163, 164 on the outer periphery of outer bearing rings 135, 137.
Starting from grooves 163, 164, the oil is additionally distributed
into the bearings via splash oil holes 165, 166, and may thus be
used for lubrication. An outlet hole 167 is also included for
drainage.
[0065] The difference in turbocharger 121 from turbochargers 1, 61
previously shown lies in the nature of shaft 129. Shaft 129 is
composed of various shaft sections 171, 173, 175. Accordingly,
rolling body raceways 145, 147 are introduced into only one shaft
section 173. Shaft section 173 correspondingly takes over the
function of the inner bearing rings which would otherwise be
necessary.
[0066] Shaft section 173 is composed of heat-resistant steel,
whereas the two axially adjacent shaft sections 171, 175 are made
of a less expensive, requirement-specific metallic material.
[0067] Shaft sections 171, 173, 175 have axially inwardly extending
recesses 176, 177, 178, 179. Inner recesses 176, 177, 178, 179 are
designed as cavities which provide an additional air volume. For
this reason, they cause a reduction in the thermal conduction from
turbine wheel 127 to the bearings. Turbine wheel 127 also has a
recess 180 which additionally increases the air volume and thus
reduces the thermal conduction.
[0068] In the present case, shaft sections 171, 173, 175 are welded
together. After shaft sections 171, 173, 175 are welded, shaft
section 175 is lastly welded to turbine wheel 127. For this
purpose, friction welding is used, as previously described for
turbocharger 1 according to FIG. 1.
[0069] Lastly, welded shaft sections 171, 173, 175, i.e., shaft
129, is/are welded to turbine wheel 127 at the side of shaft
section 175 with the aid of a friction welding process. Turbine
wheel 127 also has an inner recess 180, which further decreases the
air volume for reducing the thermal conduction from turbine wheel
127 to anti-friction bearing 133 during operation of turbocharger
121.
[0070] Compressor wheel 125 is fastened to shaft 129 by pushing the
compressor wheel onto shaft 129 on the side of the shaft opposite
from turbine wheel 127, and is fastened at that location with the
aid of a nut 153. In addition, an oil separator 169 which operates
according to the centrifugal force principle is mounted on shaft
129.
[0071] FIG. 4 shows another turbocharger 181 having a bearing
arrangement 183. Turbocharger 181 has a compressor wheel 185 and a
turbine wheel 187 situated at the opposite ends of a shaft 189
which extends in the axial direction. Shaft 189 is rotatably
mounted within a bearing housing 191 which likewise extends
axially.
[0072] Bearing arrangement 183 also includes an anti-friction
bearing 193, having two axially adjacent outer bearing rings 195,
197, situated within bearing housing 191; the outer bearing rings,
the same as in the preceding figures, are situated at a distance
from one another with the aid of a pretensioned spring element 199
situated in between. Anti-friction bearing 193 also has rolling
bodies 201 designed as spheres, which in each case are held in rows
in cages 203. Rolling bodies 201 are guided in rolling body
raceways 205, 207.
[0073] Since the function and the individual components of
turbocharger 181 in FIG. 4 essentially correspond to those in the
exemplary embodiments previously described, at this point reference
is made to the detailed description there, which may be analogously
transferred to the discussion below.
[0074] The same as in FIG. 3, shaft 189 is manufactured from three
separate shaft sections 237, 239, 241. Shaft sections 237, 239, 241
are made of various materials, shaft section 239 being made of
heat-resistant steel. The two other shaft sections 237, 241 are
made of a less expensive metallic material.
[0075] Rolling body raceways 205, 207 are accordingly introduced
only into shaft section 239, which is made of the steel. Shaft
section 239 takes over the function of the inner bearing rings, so
that the costs as well as the assembly effort are reduced, and the
accuracy is increased.
[0076] Shaft section 239 is provided on each end face with two
axially extending shaft journals 243, 245. In the installed state,
these shaft journals 243, 245 engage with holes 247, 249 which in
each case are provided at the axial contact points of shaft
sections 237, 241. Shaft journals 243, 245 are appropriately
pressed into holes 247, 249 during assembly. Thus, a connection
between the components is possible even before the components are
welded, which simplifies the subsequent welding process. The
individual shaft sections are welded together only at contact
surfaces 251, 253 due to the press fit between same.
[0077] For fastening to turbine wheel 187, shaft section 241
additionally has a shaft journal 255 on the side opposite from hole
249 which is pressed into hole 257 in turbine wheel 187. After the
pressing, the two components, i.e., shaft 189 and turbine wheel
187, are welded to contact points 259. Laser beam welding is used
for this purpose, thus allowing joining of components at a high
welding speed, having a thin, narrow weld seam shape, and with low
thermal warping. Laser beam welding is carried out without
supplying a filler metal.
[0078] For fastening compressor wheel 185 to shaft 189, the
compressor wheel is pushed onto shaft 189 on the side opposite from
turbine wheel 187, and is clamped at that location with the aid of
a nut 213. A secure connection also between compressor wheel 185
and shaft 189 is ensured in this way. In addition, an oil separator
229 which operates according to the centrifugal force principle is
mounted on shaft 189.
LIST OF REFERENCE NUMERALS
[0079] 1 turbocharger [0080] 3 bearing arrangement [0081] 5
compressor wheel [0082] 7 turbine wheel [0083] 9 shaft [0084] 11
bearing housing [0085] 13 anti-friction bearing [0086] 15 outer
bearing ring [0087] 17 outer bearing ring [0088] 19 spring element
[0089] 21 rolling body [0090] 23 cage [0091] 25 rolling body
raceway [0092] 27 rolling body raceway [0093] 29 recess [0094] 31
recess [0095] 33 nut [0096] 35 groove [0097] 37 sealing element
[0098] 39 space [0099] 41 supply hole [0100] 42 supply hole [0101]
43 groove [0102] 44 groove [0103] 45 splash oil hole [0104] 46
splash oil hole [0105] 47 outlet hole [0106] 49 oil separator
[0107] 61 turbocharger [0108] 63 bearing arrangement [0109] 65
compressor wheel [0110] 67 turbine wheel [0111] 69 shaft [0112] 71
bearing housing [0113] 73 anti-friction bearing [0114] 75 outer
bearing ring [0115] 77 outer bearing ring [0116] 79 spring element
[0117] 81 rolling body [0118] 83 cage [0119] 85 rolling body
raceway [0120] 87 rolling body raceway [0121] 89 recess [0122] 91
recess [0123] 93 nut [0124] 95 groove [0125] 97 sealing element
[0126] 99 space [0127] 101 supply hole [0128] 102 supply hole
[0129] 103 groove [0130] 104 groove [0131] 105 splash oil hole
[0132] 106 splash oil hole [0133] 107 outlet hole [0134] 109 oil
separator [0135] 111 hole [0136] 113 shaft journal [0137] 115
contact surface [0138] 121 turbocharger [0139] 123 bearing
arrangement [0140] 125 compressor wheel [0141] 127 turbine wheel
[0142] 129 shaft [0143] 131 bearing housing [0144] 133
anti-friction bearing [0145] 135 outer bearing ring [0146] 137
outer bearing ring [0147] 139 spring element [0148] 141 rolling
body [0149] 143 cage [0150] 145 rolling body raceway [0151] 147
rolling body raceway [0152] 153 nut [0153] 155 groove [0154] 157
sealing element [0155] 159 space [0156] 161 supply hole [0157] 162
supply hole [0158] 163 groove [0159] 164 groove [0160] 165 splash
oil hole [0161] 166 splash oil hole [0162] 167 outlet hole [0163]
169 oil separator [0164] 171 shaft section [0165] 173 shaft section
[0166] 175 shaft section [0167] 176 recess [0168] 177 recess [0169]
178 recess [0170] 179 recess [0171] 180 recess [0172] 181
turbocharger [0173] 183 bearing arrangement [0174] 185 compressor
wheel [0175] 187 turbine wheel [0176] 189 shaft [0177] 191 bearing
housing [0178] 193 anti-friction bearing [0179] 195 outer bearing
ring [0180] 197 outer bearing ring [0181] 199 spring element [0182]
201 rolling body [0183] 203 cage [0184] 205 rolling body raceway
[0185] 207 rolling body raceway [0186] 213 nut [0187] 215 groove
[0188] 217 sealing element [0189] 219 space [0190] 221 supply hole
[0191] 223 groove [0192] 225 splash oil hole [0193] 227 outlet hole
[0194] 229 oil separator [0195] 237 shaft section [0196] 239 shaft
section [0197] 241 shaft section [0198] 243 shaft journal [0199]
245 shaft journal [0200] 247 hole [0201] 249 hole [0202] 251
contact surface [0203] 253 contact surface [0204] 255 shaft journal
[0205] 257 hole [0206] 259 contact surface
* * * * *