U.S. patent application number 12/584994 was filed with the patent office on 2010-03-04 for rotor assembly for an exhaust gas turbocharger.
Invention is credited to Peter Fledersbacher, Paul Loffler, Michael Scheydecker, Siegfried Sumser, Siegfried Weber.
Application Number | 20100054944 12/584994 |
Document ID | / |
Family ID | 39538000 |
Filed Date | 2010-03-04 |
United States Patent
Application |
20100054944 |
Kind Code |
A1 |
Fledersbacher; Peter ; et
al. |
March 4, 2010 |
Rotor assembly for an exhaust gas turbocharger
Abstract
In a rotor assembly for an exhaust gas turbocharger including a
turbine wheel and a compressor wheel mounted on a common shaft for
joint rotation wherein the turbine wheel consist of a metal
aluminide or of a high-temperature resistant titanium alloy, the
turbine wheel and the compressor wheel are disposed on the shaft in
spaced relationship by way of a bearing sleeve via which the
turbien wheel and the compressor wheel are axially firmly engaged
by axial clamping structures associated with the common shaft.
Inventors: |
Fledersbacher; Peter;
(Stuttgart, DE) ; Loffler; Paul; (Stuttgart,
DE) ; Scheydecker; Michael; (Nersingen, DE) ;
Sumser; Siegfried; (Stuttgart, DE) ; Weber;
Siegfried; (Stuttgart, DE) |
Correspondence
Address: |
KLAUS J. BACH
4407 TWIN OAKS DRIVE
MURRYSVILLE
PA
15668
US
|
Family ID: |
39538000 |
Appl. No.: |
12/584994 |
Filed: |
September 15, 2009 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP08/01996 |
Mar 13, 2008 |
|
|
|
12584994 |
|
|
|
|
Current U.S.
Class: |
416/204A |
Current CPC
Class: |
F05D 2220/40 20130101;
F01D 5/025 20130101; F05D 2300/133 20130101; F05D 2260/37
20130101 |
Class at
Publication: |
416/204.A |
International
Class: |
F01D 5/02 20060101
F01D005/02 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 16, 2007 |
DE |
10 2007 012 641.9 |
Claims
1. A rotor assembly for an exhaust gas turbocharger, comprising a
shaft (4) rotatable about an axis of rotation (5), a turbine wheel
(3) mounted on the shaft (11) for the expansion of a first gaseous
medium, and a compressor wheel (2) mounted on the shaft (4) for the
compression of a second gaseous medium, and the turbine wheel (3)
consisting of a metal aluminide, or of a high-temperature resistant
titanium alloy and being rotationally fixed with respect to the
compressor wheel (2) by means of the shaft (4), and the turbine
wheel (3) having an axial opening (6) at least partially extending
through the turbine wheel (3) and receiving the shaft (4) with a
rotationally fixed connection between the turbine wheel (3) and the
shaft (4) and a sleeve (10) disposed around the shaft (4) and
arranged between the turbine wheel (3) and the compressor wheel (2)
in firm axial engagement with the turbine wheel (3) and the
compressor wheel (2).
2. The rotor assembly according to claim 1, wherein the shaft (4)
has a first end (7) firmly engaged with the turbine wheel (3) and a
second end (8) provided with tensioning means (9) for axially
engaging the compressor wheel (2) with the turbine wheel (3) via
the intermediate sleeve (10).
3. Rotor assembly according to claim 2, wherein the shaft (4)
extends fully through the compressor wheel (3) and the tensioning
means is a nut (9) threaded onto the shaft (4) for axially engaging
the turbine wheel (3) and the compressor wheel (2) via the bearing
sleeve (10).
4. The rotor assembly according to claim 1, wherein the turbine
wheel (3) comprises a collar (13) at an end face (12) of the wheel
(12), provided with an annular first groove (11) for receiving
sealing elements.
5. The rotor assembly according to claim 4, wherein an annular
carrier (14) is disposed in the annular groove (11).
6. The rotor assembly according to claim 1, wherein a centering
collar (15) is provided at an end face (12) of the turbine wheel
(3) for engaging the sleeve (10).
7. The rotor assembly according to claim 6, wherein the centering
collar (15) and the sleeve (10) are firmly connected to each
another.
8. The rotor assembly according to claim 6, wherein an air gap is
provided between a first surface (17) of the centering collar (15)
facing away from the end face (12) of the turbine wheel (3) and a
second surface (18) of the sleeve (10) facing the end face (12) of
the turbine wheel (3).
9. The rotor assembly according to claim 6, wherein an insulation
sleeve (20) is arranged in the axial opening (6) between the
turbine wheel (3) and the shaft (4).
10. The rotor assembly according to claim 6, wherein an insulating
disk (21) is provided between a collar (13) of the turbine wheel
(3) and the sleeve (10).
11. The rotor assembly according to claim 6, wherein the compressor
wheel (2) is provided with a bearing collar (25) which is
positively connected to an end of the sleeve (10) facing the
bearing collar (25) for engagement with the compressor wheel (2).
Description
[0001] This is a Continuation-In-Part Application of pending
International patent application PCT/EP2008/001996 filed Mar. 13,
2008 and claiming the priority of German patent application 10 2007
012 641.9 filed Mar. 10, 2007.
BACKGROUND OF THE INVENTION
[0002] The invention relates to a rotor assembly for an exhaust gas
turbocharger including a compressor wheel and a turbine wheel
mounted on a common shaft, wherein the turbine wheel consists of a
metal aluminide or a high temperature-resistant titanium alloy.
[0003] DE 10 2005 015 947 B3 discloses a method for the connection
of a first component of a metal aluminide or a high-melting Ti
alloy with a second component of steel, wherein the connection is
produced by a friction welding process. The two components can be
joined in a positive manner by means of a nickel-containing
intermediate piece. The presence of two joints is characteristic
for the connection. This method serves especially for the
production of a rotor assembly of an exhaust gas turbocharger,
which comprises a turbine wheel consisting of aluminide or of a
high-melting Ti alloy and a shaft of steel.
[0004] The advantage of a turbine wheel of a metal aluminide or a
high-melting Ti alloy resides in a lower weight and, consequently,
a reduction of the moment of inertia of the turbine wheel, whereby
the response-behavior of an exhaust gas turbocharger is
considerably to be improved.
[0005] It is the object of the present invention to provide a rotor
assembly which comprises a reliable connection between a turbine
wheel of a metal aluminide or a high-melting Ti alloy and a shaft
of steel even at high temperature and high rotational speeds of the
rotor assembly.
SUMMARY OF THE INVENTION
[0006] In a rotor assembly for an exhaust gas turbocharger
including a turbine wheel and a compressor wheel mounted on a
common shaft for joint rotation wherein the turbine wheel consist
of a metal aluminide or of a high-temperature resistant titanium
alloy, the turbine wheel and the compressor wheel are disposed on
the shaft in spaced relationship by way of a bearing sleeve via
which the turbien wheel and the compressor wheel are axially firmly
engaged by axial clamping structures associated with the common
shaft.
[0007] Due to the rotationally fixed connection between the turbine
wheel and the compressor wheel via the shaft of the rotor assembly
and a shaft sleeve disposed between the turbine wheel and the
compressor wheel, an exhaust gas turbocharger having a reduced
moment of inertia and thus an improved response behavior with high
operational safety can be realized.
[0008] In one arrangement, the rotationally fixed connection can be
made by means of at least one tensioning element arranged at one
end of the shaft. A positive connection is thereby either provided
between the other end of the shaft and the turbine wheel, or the
other end comprises a further tensioning element for providing the
axial engagement. Alternatively, the other end itself may be used
to form a tensioning element. A secure positive connection between
the compressor wheel and the turbine wheel can thus advantageously
established by axial engagement which is not affected by the
centrifugal forces and the high temperatures to which the turbine
wheel is objected during high speed operation of the
turbocharger.
[0009] The invention will become more readily apparent from the
following description thereof on the basis of the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 shows, in a longitudinal sectional view, a first
embodiment of a rotor assembly according to the invention,
[0011] FIG. 2 shows a second embodiment of the rotor assembly
wherein the turbine wheel of the rotor assembly comprises an
integral elongated collar,
[0012] FIG. 3 shows a third embodiment of the rotor assembly in a
third version, wherein the turbine wheel comprises a positive
connection with a bearing sleeve,
[0013] FIG. 4 shows a fourth embodiment of the rotor assembly,
wherein the turbine wheel comprises an insulating sleeve and an
insulating disk, and
[0014] FIG. 5 shows a fifth embodiment of the rotor assembly in,
wherein the shaft is positively installed in the turbine wheel in a
positive manner.
DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS
[0015] In the figures, the same or functionally equal components
are provided with the same reference numerals.
[0016] FIG. 1 shows a first embodiment of the rotor assembly 1 in a
longitudinal sectional view. The rotor assembly 1 comprises a
compressor wheel 2 for taking in and compressing combustion air, a
turbine wheel 3 for the expansion of exhaust gas and a shaft 4 with
a rotational axis 5 connecting the compressor wheel 2 with the
turbine wheel 3 in a rotationally fixed manner.
[0017] The rotor assembly 1 is provided especially for an exhaust
gas turbocharger, which comprises a housing receiving the rotor
assembly 1 in a rotatable manner. The housing comprises an air
guide section, an exhaust gas guide section and a bearing section.
The compressor wheel 2 is disposed in the air guide section, the
turbine wheel 3 is disposed in the exhaust guide section, and the
shaft 4 is rotatably supported in the bearing section.
[0018] The exhaust gas turbocharger serves for increasing the
performance of an internal combustion engine. The internal
combustion engine usually has an combustion air intake duct, and an
exhaust gas line, wherein the air guide section is arranged in the
intake duct and the exhaust guide section in the exhaust gas line.
During the operation of the internal combustion engine, the turbine
wheel 3 is rotated by the exhaust gas of the internal combustion
engine, and the compressor wheel 2 is rotated by means of the shaft
4, so that it takes in combustion air and compresses it.
[0019] The turbine wheel 3 is made of a metal aluminide or a
high-temperature resistant titanium aluminum alloy. The advantage
of these materials is, in addition to a low heat expansion, is
their favorable strength-density ratio, that is, they have a high
strength with a low density. The mass of the turbine wheel 3 is
reduced by about half compared to a turbine wheel 3 consisting of
for example the usual material Inconel 713 C. The moment of inertia
of the mass of the rotor assembly 1, which characterizes the
response behavior of the exhaust gas turbocharger, can thus be
reduced considerably. The turbine wheel 3 as shown in FIG. 1 has an
axial opening 6 which extends fully through the turbine wheel 3 and
in which the shaft 4 is received. Due to the opening 6, there are
essentially no radial and centrifugal forces, which occur during
operation of the exhaust gas turbocharger and which may lead,
depending on their size, to deformation and finally to breakage of
the turbine wheel 3, effective between the shaft and the turbine
wheel 3 via the surface delimiting the opening 6 at its
circumference.
[0020] If the turbine wheel 3 were made of a usual material (e.g.
Inconel 713 C), it would have a relatively low durability during
operation with the arrangement according to the invention, as, due
to the large mass the tensions occurring as a result of the
centrifugal forces at the opening 6 would be so large, that the
strength of the usual material would be too low for a continuous
operation. The centrifugal forces need to be accommodated in the
radial direction and, at the same time, torsional forces need to be
transmitted in the tangential direction, which are so high that,
with a turbine wheel 3 made of a usual material, the operation of
the exhaust gas turbocharger would result in early material failure
of the rotor assembly 1.
[0021] The shaft 4 is accommodated in the opening 6, and the
turbine wheel 3 is arranged adjacent an end head 7 of the shaft 4
and is connected to the shaft 4 for example by a press-fit. The
press-fit already constitutes a form of the positive connection, as
the connection between the shaft 4 and the turbine wheel 3 is
effected by means of frictional forces.
[0022] The compressor wheel 2 is positioned at an end 8 of the
shaft 4 opposite the first end head 7. A sleeve 10 is arranged on
the shaft 4 between the turbine wheel 3 and the compressor wheel 2,
which sleeve forms a low-friction bearing of the shaft 4 in the
bearing section.
[0023] The shaft 4 comprises a tensioning element 9 arranged at the
second end 8 for the rotationally fixed connection of the turbine
wheel 3 with the compressor wheel 2, wherein an axial force
transmission is provided by means of a tensioning element 9.
[0024] The shaft 4 includes the end head 7 in the shape of a nut,
so that the first end 7 represents a tensioning engagement element
which may also be in the form of a nut threaded onto the shaft 4.
By the action of a force provided by the tensioning element 9, the
rotationally fixed connection between the turbine wheel 3, the
shaft 4, the sleeve 10 and the compressor wheel 2 can be
established, whereby the connecting forces extend mostly in axial
direction of the shaft 4.
[0025] The sleeve 10 is in the form of a hollow cylinder and has a
reinforcement at its end facing the turbine wheel 3, in which an
annular first recess 11 is arranged at the circumference of the
sleeve 10. The recess 11 serves especially for the reception of
sealing elements.
[0026] In a second version of the exhaust gas turbocharger
according to FIG. 2, the turbine wheel 3 includes an axial collar
13 extending from its end face 12, wherein the annular first recess
11 is arranged. The sleeve 10 comprises a simple cylindrical
structure without reinforcement.
[0027] It is an advantage of the second embodiment that the sleeve
10 has a small wall thickness W, so that only a small expansion of
the sleeve 10 during the operation of the rotor assembly 1 as a
result of heat generation can be expected during operation even at
high rotational speed of the rotor assembly 1. Additionally,
temperature stresses at the collar 13 are smaller, so that an
improved centering of the turbine wheel 3 on the shaft 4 is
achieved.
[0028] In a further embodiment, an annular carrier 14 in the form
of a ring carrier with a U-profile is positioned in the first
annular recess 11, the manufacture of which can be integrated into
a manufacture process for the turbine wheel 3, for example by a
casting method. This ring carrier 14 is provided for the reduction
of wear and consists of a corresponding material, for example
ceramics.
[0029] For ensuring the operation of the exhaust gas turbocharger,
the rotor assembly 1 needs to be balanced as well as possible,
which can be achieved by maintaining the radial position of the
turbine wheel 3, the shaft 4, the compressor wheel 2 and the sleeve
10. The corresponding centering may be obtained by a feature of a
third embodiment as shown in FIG. 3. The turbine wheel 3 comprises
a centering collar 15 at its collar 13, by means of which the
sleeve can be accurately fixed radially with respect to the turbine
wheel 3. The sleeve 10 includes at its end facing the centering
collar 15 a recess 16, in which the centering collar 15 is
accommodated.
[0030] As the bearing locations in the bearing section have to be
kept as cool as possible, the heat transport from the turbine wheel
3 to the shaft 4 or to the sleeve 10 has to be limited. For
reducing the heat transport from the turbine wheel 3 to the sleeve
10, an air gap 19 is provided between a first surface 17 of the
centering collar 15 facing away from the of the turbine wheel 3 and
a second surface 18 of the second recess facing the turbine wheel
3.
[0031] In a further embodiment, the end of the sleeve 10 facing the
compressor wheel 2 is firmly connected to a bearing collar 25 of
the compressor wheel 2.
[0032] In a fourth version according to FIG. 4, an insulating
sleeve 20 in the shape of a hollow cylinder is arranged in, the
opening 6 extending along the rotational axis 5 for the heat
insulation and/or centering. The insulating sleeve 20 is connected
to the turbine wheel 3 in rotationally fixed manner by a press-fit.
The shaft 4 is accommodated in the insulating sleeve 20.
[0033] The arrangement of an annular insulating disk 21 between the
collar 13 and the sleeve 10 provides for further thermal decoupling
of the hot turbine wheel 3 and the sleeve 10 particularly with a
suitable choice of materials. The heat transfer between the turbine
wheel 3 and the bearing locations in the bearing section to be kept
cool can thereby be kept low. As the rotor assembly 1 according to
the invention is suitable for a ball or air suspension in the
exhaust gas turbocharger, the cooling of the bearing locations is
especially important with a ball or air suspension bearings of the
rotor assembly 1 due to very small bearing gaps.
[0034] In a fifth version according to FIG. 5, a positive
connection is provided between the turbine wheel 3 and the shaft 4.
The shaft 4 comprises a thread 22 at its first end 7, wherein the
shaft 4 is preferably a tension bolt. The opening 6 is formed only
partially extending through the turbine wheel 3 starting from the
collar 13 in the direction of the rotational axis 5. A mating
thread 24 for the positive connection of the turbine wheel 3 to the
shaft 4 is provided at the third end 23 of the opening 6 arranged
opposite the collar 13.
[0035] With the firm axial engagement between the turbine wheel 3
and the compressor wheel 2 via the sleeve 10 which also forms a
bearing structure for the rotor assembly 1 the high temperatures
and the high centrifugal forces to which the turbine wheel is
subjected at high speeds do not affect the engagement between the
turbine wheel and the compressor wheel via the sleeve 10.
* * * * *