U.S. patent application number 11/800092 was filed with the patent office on 2007-12-13 for drive for vacuum pump.
This patent application is currently assigned to Pfeiffer Vacuum GmbH. Invention is credited to Juergen Wagner.
Application Number | 20070286749 11/800092 |
Document ID | / |
Family ID | 38325789 |
Filed Date | 2007-12-13 |
United States Patent
Application |
20070286749 |
Kind Code |
A1 |
Wagner; Juergen |
December 13, 2007 |
Drive for vacuum pump
Abstract
A drive arrangement for a vacuum pump includes a separation
member arranged between the motor stator and the motor rotor, and
at least two, coaxial with each other and axially spaced from each
other, guide surfaces, the separation member being formed as a
separation sleeve which is supported and centered between the at
least two guide surfaces, with the guide surfaces contacting an
outer surface of the separation sleeve.
Inventors: |
Wagner; Juergen;
(Mueschenbach, DE) |
Correspondence
Address: |
ABELMAN, FRAYNE & SCHWAB
666 THIRD AVENUE, 10TH FLOOR
NEW YORK
NY
10017
US
|
Assignee: |
Pfeiffer Vacuum GmbH
|
Family ID: |
38325789 |
Appl. No.: |
11/800092 |
Filed: |
May 2, 2007 |
Current U.S.
Class: |
417/410.1 |
Current CPC
Class: |
F04C 2220/10 20130101;
F04C 29/0064 20130101; F04C 18/344 20130101; F05C 2203/02 20130101;
F04C 18/126 20130101; H02K 5/128 20130101 |
Class at
Publication: |
417/410.1 |
International
Class: |
F04B 17/03 20060101
F04B017/03 |
Foreign Application Data
Date |
Code |
Application Number |
May 16, 2006 |
DE |
10 2006 022 772.7 |
Claims
1. A drive arrangement for a vacuum pump, comprising a motor
stator; a motor rotor; a separation member arranged between the
motor stator and the motor rotor; and at least two, coaxial with
each other and axially spaced from each other, guide surfaces, the
separation member having a separation sleeve which is supported and
centered between the at least two guide surfaces, with the guide
surfaces contacting an outer surface of the separation sleeve.
2. A drive arrangement as set forth in claim 1, comprising at least
two components which define, together with the separation member, a
chamber in which the motor stator is located, and wherein the at
least two guide surfaces are provided, respectively on the at least
two components, and the at least two components are aligned
relative to each other by respective surfaces provided on the at
least two components and arranged coaxially with the guide
surfaces.
3. A drive arrangement as set forth in claim 1, wherein the
separation sleeve is formed as a glass tube.
4. A drive arrangement as set forth in claim 3, further comprising
elastomeric ring means arranged on the outer side of the glass tube
for sealing a space inside the glass tube from outside.
5. A drive arrangement as set forth in claim 2, wherein the at
least two components form stationary, axially spaced from each
other, stops for the glass tube, with an axial distance between the
stops being greater than a length of the glass tube.
6. A drive arrangement as set forth in claim 1, wherein the motor
stator comprises electrical coils, and the motor rotor comprises
permanent magnets.
7. A vacuum pump, comprising pumping component;, a shaft for
supporting the pumping components; and a drive arrangement for
driving the shaft; the drive arrangement including motor stator and
rotor, a separation member arranged between the motor stator and
the motor rotor and at least two, coaxial with each other and
axially spaced from each other, guide surfaces, the separation
member having a separation sleeve which is supported and centered
between the at least two guide surfaces, with the guide surfaces
contacting an outer surface of the separation sleeve.
8. A vacuum pump as set forth in claim 7, further comprising
oil-lubricated bearing means for supporting the shaft.
9. A vacuum pump as set forth in claim 7, wherein the vacuum pump
is formed as a vane rotary pump.
10. A vacuum pump as set forth in claim 7, wherein the vacuum pump
is formed as a Roots pumps.
Description
A. BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a drive arrangement for a
vacuum pump and including a motor stator, a motor rotor, and a
separation member arranged between the motor stator and the motor
rotor.
[0003] 2. Description of the Prior Art
[0004] Vacuum pumps have rotating shafts the bearing of which are
often lubricated by operating means such as, e.g., oil. In many
vacuum pumps, this operating means is simultaneously used for
sealing the working chamber, e.g., in so-called vane rotary vacuum
pumps. Vacuum pumps have one or more shafts at least one of which
is driven and held.
[0005] Often, as a motor, an asynchronous motor is used. It is
generally forbidden to locate a motor in a space filled with
operating means. This requires a bulky, hermetical separation which
is realized, according to the state of the art, primarily by using
so-called split pot elements. The split pot element is arranged
either directly in the motor gap or in a magnetic coupling and is
formed of a material in which an alternating magnetic field
generates no or very small eddy currents. An example of use of a
split pot element in a vacuum pump is disclosed in German
Publication DE-OS 10 2004 024 554. The use of a split pot element
leads to increase of the motor gap which reduces the efficiency of
the motor and increases power consumption.
[0006] The negative influence of the split pot element on the width
of the motor gap is based on a sum of separate effects. On one
hand, the walls, because of manufacturing conditions, are parallel
to each other only at a small degree, therefore, the wall thickness
increases from the pot bottom to the attachment flange. On the
other hand, a one-sided attachment by the attachment flange causes
tilting of the pot element. The pot element height acts as an
elongate lever, and tilting at the pot element bottom is the
greatest. Therefore, the motor gap must be correspondingly large.
Generally, attachment with the flange can lead in many non-magnetic
materials to a danger of distortion due to stresses caused by a
non-uniform application of force over the flange connection.
[0007] An object of the invention is to provide a drive arrangement
with a hermetically sealed separation between the rotor and stator
components of an electric motor and with as small as possible motor
gap.
B. SUMMARY OF THE NEW INVENTION
[0008] This and other objects of the present invention, which will
become apparent hereinafter, are achieved by a drive arrangement
which includes at least two, coaxial with each other and axially
spaced from each other, guide surfaces, and in which the separation
member is formed as a separation sleeve which is supported and
centered between the at least two guide surfaces, with the guide
surfaces contacting the outer surface of the separation sleeve.
[0009] By forming the separation member as a separation sleeve
which is supported and centered between at least two guide
surfaces, with the guide surfaces contacting an outer surface of
the separation sleeve, it is possible to form the separation member
very precisely. Sleeves can be produced with high precision by
grinding, turning, or drawing process which provides for a uniform
wall thickness over the sleeve length. Arrangement of the sleeve
within coaxial surfaces insures a precise alignment of the
separation sleeve, resulting in a small motor gap. In order to
prevent problems which might be caused by a thermal effect, the
guide surfaces are so arranged that they contact the sleeve outer
surface. This is advantageous with separation sleeves formed of a
weak magnetic material, because generally the sleeve may be heated
by eddy currents and, as a result, would expand greater than the
components with guide surfaces. Thereby, leakage can be
produced.
[0010] Vice versa, even with non-magnetic materials, this
arrangement is advantageous as such separation sleeve does not
become heated and, therefore, does not expand. When the components
with the guide surfaces slightly expands, the tension which is
produced in the separation sleeve, can cause distortion.
[0011] According to an advantageous embodiment of the invention,
there are provided at least two components which define, together
with the separation member, a chamber in which the motor stator is
located. The at least two guide surfaces are provided,
respectively, on the at least two components. The at least two
components are aligned relative to each other by respective
connection surfaces provided on the at least two components and
arranged coaxially with the guide surfaces. With two components
carrying the guide surfaces, a guide surface is provided at each
axial end of the coils. Therefore, the separation sleeve can be
held at its ends and be precisely positioned.
[0012] Advantageously, the separation sleeve is formed as a glass
tube. Glass has a very small heat expansion coefficient, is
non-magnetic, so that no eddy current is generated, and the glass
tube can be produced with precise dimensions. In addition, a type
of glass having a high chemical resistance can be used.
[0013] According to a further advantageous embodiment of the
invention, elastomeric ring means is arranged on the outer side of
the glass tube for sealing a space inside the glass tube from
outside. The elastomeric ring means bears against the outer surface
of the separation sleeve. Thus, even when the separation sleeve
expands, sealing of the arrangement is insured.
[0014] According to a still further advantageous embodiment of the
invention, the at least two components form stationary, axially
spaced from each other, stops for the glass tube, with an axial
distance between the stops being greater than a length of the glass
tube. This insures that the separation sleeve is not stressed, but
rather is floatingly supported in the axial direction.
[0015] With the motor rotor including permanent magnets and the
motor stator including electrical coils, there is formed a motor
with a high efficiency and a narrow motor gap.
[0016] A vacuum pump according to the present invention includes
pumping components, a shaft for supporting the pumping components,
and a drive arrangement for driving the shaft. The drive
arrangement includes, as discussed above, motor stator and rotor, a
separation member arranged between the motor stator and the motor
rotor, and at least two, coaxial with each other and axially spaced
from each other, guide surfaces. The separation member is formed as
a separation sleeve which is supported and centered between the at
least two guide surfaces, with the guide surfaces contacting an
outer surface of the separation sleeve. With such a vacuum pump,
the motor rotor can be formed integrally with the shaft, so that
the bearings in the motor region can be dispensed with. This
reduces costs of production and sources of failure.
[0017] The use of the inventive drive arrangement in vacuum pumps
formed as vane rotary pumps or Roots pumps enhances the advantages
the inventive drive arrangement provides.
[0018] The novel features of the present invention, which are
considered characteristics for the invention, are set forth in the
appended claims. The invention itself, however, both as to its
construction and its mode of operation, together with additional
advantages and objects thereof, will be best understood from the
following detailed description of preferred embodiments when read
with reference to the accompanying drawings.
C. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The drawings show:
[0020] FIG. 1 shows a cross-sectional view of a vane rotary vacuum
pump; and
[0021] FIG. 2 shows a cross-sectional view of a further embodiment
of a vacuum pump drive arrangement according to the present
invention.
D. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] FIG. 1 shoes a vane rotary vacuum pump 1, further just a
vacuum pump, sealed and lubricated with oil 16. The main component
of the vacuum pump is a support 2 to which components of the pump
system, on one hand, and the drive arrangement, on the other hand,
are secured. A shaft 3 is rotatably supported in a slide bearing 4
and eccentrically extends through a cylindrical hollow chamber of
the vacuum pump 1. The hollow chamber is formed by a body having a
cylindrical opening and cover plates at its opposite axial ends.
The shaft 3 supports one or more vanes 5 which contact the walls of
the hollow chamber, thereby forming a compression chamber 6. The
rotation of the shaft 3 and the resulting movement of the vanes
produce the per se known pumping effect.
[0023] For simplicity sake, vanes which are well known in the state
of the art are not shown. The shaft 3 carries permanent magnets 7
which cooperate with electrical coils 8 for rotating the shaft 3.
Between the permanent magnets 7 and the electrical coils 8, there
is provided a motor gap, shown at an increased, overproportional
scale. In the motor gap, a separation member 9, which is formed as
a glass tube, is arranged. The glass tube 9 is supported against a
cylindrical guide surface 10 provided on the support 2 and against
a likewise cylindrical guide surface 11 provided on a cover 12. The
guide surfaces 10 and 11 are coaxial and are axially spaced apart
from each other. With the glass tube having a constant outer
diameter, the guide surfaces 10,11 would have the same radices. In
order to prevent stresses, which can be produced by a non-uniform
heat expansion of the glass tube and support and/or cover, the
guide surfaces 10,11 contact the outer surface of the glass tube 9.
A spacer 14 connects the cover 12 and the support 23. Together with
a separation sleeve, these components form a chamber in which the
electric coils 8 are arranged. Connection surfaces 17 insure
coaxiality of the guide surfaces 10,11. The connection surfaces 17
are provided on the inner side of the spacer 14, on the support 2
and on the cover 12. In the right low portion of FIG. 1, this
arrangement is shown in exploded view, the connection surfaces,
which are provided on the support 2 and the cover 12, are
designated with a reference numeral 17a, and the connection
surfaces on the spacer 14 are designated with a reference numeral
17b. The connection surfaces 17b of the spacer 14 can be produced
in a common operational step, e.g., by turning. Likewise, the guide
surface 10 and the connection surface 17a on the support 2 and the
guide surface 11 and the connection surface 17a on the cover 12 can
be produced in one operational step. The alignment of the cover 12
and the support 2 and, thereby, of the guide surfaces 10 and 17a
is, as a result, very precise and produces a small motor gap.
[0024] The support 2 and the cover 12 provide stops in both axial
directions. The distance between the stops is greater than the
axial length of the glass tube so that the glass tube has a certain
axial play. It is advantageous when the guide surfaces do not have
narrow tolerances as no preload is produced. In this case, the
glass tube is displaceable within certain limits. Elastomeric rings
13 support the glass tube 9 floatingly for axial and radial
displacement, with the guide surfaces 10,11 guiding the glass tube
9.
[0025] FIG. 2 shows an improved embodiment of the inventive drive.
In this embodiment, the support 2 is formed that it simultaneously
functions as a spacer. The support 2, the separation tube 9, and
the cover 12, form a chamber in which the electrical coils 8 are
arranged. The embodiment of FIG. 2 is more compact than that of
FIG. 1.
[0026] Another advantage of the embodiment of FIG. 2 consists in
that the number of coaxial with each other surfaces is reduced.
Only one connection interface between the cover 2 and support 2 is
needed, so that the guide surfaces 17 are provided only in this
region. The guide surfaces on the support can be formed in one
operational step.
[0027] In a second operational step, the guide surface 11 and the
connection surface on the cover can be formed. As a result, the
coaxiality of the guide surfaces with respective connection
surfaces and of the guide surfaces with each other is very precise.
All of this insures a very high precision of the entire
arrangement, and a clearance between the permanent magnets 7, which
are supported on the shaft 3, and the electrical coils 8 can be
retained optimally small. The power parameters of the motor are
correspondingly improved or a necessary motor power consumption is
reduced as losses, which are associated with the motor gap, are
significantly reduced.
[0028] Though the present invention was shown and described with
references to the preferred embodiments, such are merely
illustrative of the present invention and are not to be construed
as a limitation thereof and various modifications of the present
invention will be apparent to those skilled in the art. It is,
therefore, not intended that the present invention be limited to
the disclosed embodiments or details thereof, and the present
invention includes all variations and/or alternative embodiments
within the spirit and scope of the present invention as defined by
the appended claims.
* * * * *