U.S. patent application number 15/035492 was filed with the patent office on 2016-10-06 for rotor device for a vacuum pump, and vacuum pump.
The applicant listed for this patent is Oerlikon Leybold Vacuum GmbH. Invention is credited to Juergen Brezina, Markus Henry, Peter Koeppel, Robert Stolle.
Application Number | 20160290343 15/035492 |
Document ID | / |
Family ID | 51897252 |
Filed Date | 2016-10-06 |
United States Patent
Application |
20160290343 |
Kind Code |
A1 |
Henry; Markus ; et
al. |
October 6, 2016 |
ROTOR DEVICE FOR A VACUUM PUMP, AND VACUUM PUMP
Abstract
A rotor device for a vacuum pump comprises a rotor shaft and at
least one rotor element on the rotor shaft. The rotor element
contains aluminum, titanium and/or CFRP, while the rotor shaft
contains a chromium-nickel steel. This makes it in particular
possible to join the at least one rotor element to the rotor shaft
at room temperature using a pressing process.
Inventors: |
Henry; Markus; (Koeln,
DE) ; Brezina; Juergen; (Koeln, DE) ; Stolle;
Robert; (Kaarst, DE) ; Koeppel; Peter; (Koeln,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Oerlikon Leybold Vacuum GmbH |
Koln |
|
DE |
|
|
Family ID: |
51897252 |
Appl. No.: |
15/035492 |
Filed: |
November 5, 2014 |
PCT Filed: |
November 5, 2014 |
PCT NO: |
PCT/EP2014/073771 |
371 Date: |
May 10, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04D 29/321 20130101;
F05D 2300/173 20130101; F04D 19/04 20130101; F05D 2300/43 20130101;
F05D 2300/603 20130101; F04D 29/023 20130101; F04D 25/06 20130101;
F05D 2300/174 20130101; F04D 19/042 20130101 |
International
Class: |
F04D 19/04 20060101
F04D019/04; F04D 25/06 20060101 F04D025/06 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 12, 2013 |
DE |
20 2013 010 195.4 |
Claims
1. Rotor device for a vacuum pump, comprising a rotor shaft and at
least one rotor element arranged on the rotor shaft, wherein the at
least one rotor element contains aluminum, titanium and/or CFK and
the rotor shaft contains chromium-nickel steel.
2. Rotor device for a vacuum pump of claim 1, wherein the at least
one rotor element is made of aluminum, an aluminum alloy and/or
high-strength aluminum.
3. Rotor device for a vacuum pump of claim 1, wherein the at least
one rotor element is made of titanium and/or a titanium alloy.
4. Rotor device for a vacuum pump of claim 1, wherein the at least
one rotor element is made of CFK.
5. Rotor device for a vacuum pump of claim 1, wherein the rotor
shaft contains a chromium-nickel steel with added sulfur.
6. Rotor device for a vacuum pump of claim 1, wherein the rotor
shaft contains a stainless steel alloy.
7. Rotor device for a vacuum pump of claim 1, wherein the material
pair is selected such that the at least one rotor element can be
fitted on the rotor shaft at room temperature.
8. Rotor device for a vacuum pump of claim 1, wherein a plurality
of said rotor elements are arranged in the longitudinal direction
of the rotor shaft.
9. Rotor device for a vacuum pump of claim 6, wherein the rotor
elements are formed as rotor discs.
10. Rotor device for a vacuum pump of claim 8, further comprising
at least one spacer element is arranged between two of the rotor
elements.
11. Vacuum pump, in particular a turbomolecular pump, comprising a
rotor device for a vacuum pump of claim 1, the rotor shaft being
supported in a pump housing by bearing elements, a driver connected
to the rotor shaft, and at least one stator element arranged in the
pump housing.
12. Rotor device for a vacuum pump of claim 6, wherein the
stainless steel alloy is stainless steel X8CrNiS18-9.
Description
BACKGROUND
[0001] 1. Field of the Disclosure
[0002] The disclosure relates to a vacuum pump rotor device, as
well as to a vacuum pump.
[0003] 2. Discussion of the Back round Art
[0004] Vacuum pumps such as turbomolecular pumps, for example, have
a rotor shaft arranged in a pump housing. The rotor shaft typically
driven by an electric motor carries at least one rotor element. In
a turbomolecular pump a plurality of rotor elements in the form of
rotor discs is arranged on the rotor shaft. The rotor shaft is
rotatably supported in the pump housing via bearing elements.
Further, the vacuum pump has a stator element arranged in the
housing. In a turbomolecular pump a plurality of stator elements
formed as stator discs are provided. Here, the stator discs and the
rotor discs are arranged alternating in the longitudinal direction
of the pump or in flow direction of the medium to be pumped.
[0005] With rotors constructed from individual rotor discs, the
individual rotor elements must be rigidly fastened to the rotor
shaft. Correspondingly strong, positionally accurate connections
between the rotor shaft and the rotor elements must be ensured
under all operational conditions, i.e. in particular under the
strong temperature and rotary speed variations that occur. With
known multi-part rotors, in particular rotors having a plurality of
rotor discs, this is achieved by a considerable oversize of the
rotor disc with respect to the rotor shaft for joining purposes.
For joining, it is then necessary to strongly cool the rotor shaft
and to strongly heat the rotor elements so that it is possible to
press the rotor elements onto the shaft. Here, it is in particular
necessary to cool the rotor shaft to temperatures in the range of
that of liquid nitrogen and, at the same time, to strongly heat the
rotor discs in an oven for example by induction. Joining must then
be followed by a storage at room temperature until both parts are
at room temperature. This takes a relatively long time. Only this
considerable oversize and a correspondingly complex joining process
can guarantee the required operating safety despite the strongly
varying temperatures and rotary speeds. The temperature of the
rotor elements, as well as of the rotor shaft reaches up to about
120.degree. C. in operation. The maximum rotary speeds are at ca.
1500 r/sec Therefore, it is necessary for joining the rotor
elements with the rotor shaft to cool the rotor shaft to about
-190.degree. C. in liquid nitrogen. Depending on the structural
size the cooling time is about 5 minutes. At the same time the
rotor elements must be heated in an oven, e.g. a convection oven,
to about 120.degree. C. The corresponding heating time is 1-2
hours. The time for heating the structural assembly thoroughly
after joining about is 1 2 hours to reach room temperature. This
known joining method is time-consuming and complex.
[0006] Tests have shown that joining a rotor or a disc-shaped rotor
element of aluminum onto a rotor shaft of aluminum is not possible
at room temperature due to the required oversize. Although the
oversize may be selected significantly smaller, since no different
thermal expansion coefficients of the rotor element and the shaft
exist, fitting by pressing is still not possible at room
temperature. Here, a galling or welding of the components to be
joined occurs. Therefore, a positionally accurate positioning of a
rotor element on the rotor shaft is not possible.
[0007] It is an object of the present disclosure to provide a
vacuum pump rotor device which is economic to manufacture, while
still providing high operating safety and preferably allowing the
components to be joined at room temperature or at only small
temperature differences between the components.
SUMMARY
[0008] The rotor device for a vacuum pump of the present disclosure
has a rotor shaft. At least one rotor element is arranged on the
rotor shaft. In particular in case of a rotor device of a
turbomolecular pump, a plurality of rotor elements in the form of
rotor discs are arranged in the longitudinal direction of the rotor
shaft.
[0009] Tests have shown that it is possible to fit rotors or rotor
elements at room temperature and with high operating safety at the
same time, if the rotor or the rotor element contains aluminum,
titanium and/or CFK and the rotor shaft comprises a chromium-nickel
steel (Cr--Ni steel). The use of aluminum, titanium and/or CFK as a
material for a rotor or a rotor element is advantageous in that it
is possible to achieve the required strength and stability relative
to the density of the material that is required in order to reach
the high rotary speeds and the great forces and tensions going
along therewith. The required properties of the shaft can be
achieved with a steel shaft, in particular a stainless steel shaft.
In particular, the shaft comprises Ni--Cr steel with added sulfur
and, as is particularly preferred, is made from chromium-nickel
steel with added sulfur.
[0010] In a preferred embodiment, the rotor or the on rotor element
is made of aluminum, an aluminum alloy and/or high-strength
aluminum.
[0011] It is particularly preferred to use high-strength aluminum
with a high tensile strength value of in particular at least 250
N/mm. High-strength aluminum further has the advantage that it has
a high fatigue strength also at operating temperatures of
100-120.degree. C. It is particularly preferred to use AW--Al Cu 2
Mg 1.5 Ni.
[0012] Further, it is preferred that the at least one rotor element
is made of titanium or a titanium alloy and/or of CFK.
[0013] The above described combination of the two components, as
provided by the present disclosure, allows to fit the at least one
rotor element on the rotor shaft at room temperature without any
galling or welding. Thereby, the manufacturing time can be
shortened significantly.
[0014] According to the disclosure a significant reduction of
assembly costs can be achieved by the fact that the thermal
expansion coefficient of the rotor shaft differs as little as
possible from the thermal expansion coefficient of the at least one
rotor element. According to the disclosure a material pair is used
that does not tend to gall and which differ only slightly in
thermal expansion coefficient, so that less oversize is required
for joining than in prior art. As a consequence, the components can
be joined at room temperature due to the small required oversize
or, at most, the components only need to have a small temperature
difference. With such a material pair having slightly different
thermal expansion coefficients it is ensured that the operating
safety is guaranteed even at great temperature and rotary speed
variations. It is particularly preferred that the material pair
used is a material pair of in particular high-strength aluminum and
stainless steel. Here, it is preferred that the at least one rotor
element is made of aluminum and the rotor shaft is made of
stainless steel, in particular Cr--Ni steel with added sulfur.
[0015] It is particularly suitable to use stainless steel
X8CrNiS18-9 with the material number 1.4305 for the rotor
shaft.
[0016] In particular when using stainless steel X8CrNiS18-9 and
aluminum Al, it is possible to join the two components at room
temperature, in particular to join them by pressing. This is also
possible if in a particularly preferred embodiment the at least one
rotor element has an oversize with respect to the rotor shaft for
which expansions in the circumferential direction of 0.25% to 0.35%
may occur. Due to this oversize, operating safety can be ensured
despite the great temperature variations, while at the same time
the components can still be joined at room temperature.
[0017] In a preferred embodiment in which the rotor device is in
particular suited for uses in a turbomolecular pump, a plurality of
rotor elements are arranged in particular in the longitudinal
direction on the rotor shaft, in particular by pressing. However, a
corresponding rotor element may for example also be a disc-shaped
carrier of a Holweck stage. This carrier caries the tubular
elements of the Holweck stage or is integrally formed therewith.
According to the present disclosure, also such a rotor element or
such a rotor element carrier is made from the above mentioned
material, in particular aluminum, and is fitted on a stainless
steel shaft by pressing.
[0018] The rotor elements may be rotor discs, where, possibly,
spacer elements are provided in addition between rotor elements or
rotor discs. These elements may in particular serve to form an
intermediate inlet in a multi-inlet pump.
[0019] The disclosure further relates to a vacuum pump which in
particular is a turbomolecular pump. The vacuum pump of the present
disclosure has a rotor device of the present disclosure as
described above, in particular in one of the preferred
developments. Further, the vacuum pump has a pump housing in which
the rotor shaft is supported by bearing elements. Moreover, a
driving device is provided that drives the rotor shaft. Further, at
least one stator element is arranged in the pump housing, wherein
the stator element may be a stator disc. In this case, in a
turbomolecular pump, a plurality of stator discs is arranged
alternating with a plurality of rotor discs.
[0020] The disclosure will be explained in detail hereinafter with
reference to a preferred embodiment and to the accompanying
drawing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The FIGURE shows a greatly simplified schematic sectional
view of a turbomolecular pump.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0022] In the greatly simplified illustration of a turbomolecular
pump a plurality of rotor elements 12 in the form of rotor discs
are arranged on a rotor shaft 10 by being pressed thereon. Stator
elements 16 are arranged in a pump housing 14, which in the
embodiment illustrated may be stator discs 16.
[0023] The rotor shaft 10 is further supported in the pump housing
14 by bearing elements 18, 20 and is driven by a driving device
22.
[0024] In the embodiment illustrated a sleeve-like spacer element
24 is further provided between two rotor discs 12. Thereby, an
intermediate inlet 26 is formed.
[0025] Thus, the vacuum pump schematically illustrated in the
drawing draws the medium to be conveyed through a main inlet in the
direction of an arrow 28. Further, medium is drawn via the
intermediate inlet 26 in the direction of an arrow 30. The two
media taken in are conveyed towards an outlet as illustrated by an
arrow 32.
[0026] According to the disclosure the rotor shaft 10 is made, in a
preferred embodiment, of stainless steel. The individual rotor
elements 12 as well as the spacer element 24 are made of aluminum
in a preferred embodiment thereof. Fitting the rotor elements 12
and the spacer element 24 is performed by pressing at room
temperature. In particular, the individual rotor elements 12 as
well as the spacer element 24 show an oversize-related expansion in
the circumferential direction of 0.07% to 0.2%.
[0027] The pressing force with which the components can be joined
at room temperature is in a range from 5 to 50 kN.
* * * * *