U.S. patent application number 14/084093 was filed with the patent office on 2014-05-22 for refrigeration compressor and a method for assembling such a refrigeration compressor.
The applicant listed for this patent is DANFOSS COMMERCIAL COMPRESSORS. Invention is credited to Patrice BONNEFOI, Gael MELDENER, Jean Michel PFISTER, Zhou XUEYOU.
Application Number | 20140140866 14/084093 |
Document ID | / |
Family ID | 48050852 |
Filed Date | 2014-05-22 |
United States Patent
Application |
20140140866 |
Kind Code |
A1 |
PFISTER; Jean Michel ; et
al. |
May 22, 2014 |
REFRIGERATION COMPRESSOR AND A METHOD FOR ASSEMBLING SUCH A
REFRIGERATION COMPRESSOR
Abstract
This refrigeration compressor includes an electric motor having
a stator and a rotor provided with an axial through passage, a
compression unit adapted for compressing refrigerant, and a drive
shaft adapted for driving the compression unit, the drive shaft
extending into the axial through passage of the rotor. The rotor is
slide-fitted on the drive shaft.
Inventors: |
PFISTER; Jean Michel; (Saint
Didier Au Mont D'Or, FR) ; XUEYOU; Zhou; (Tianjin,
CN) ; BONNEFOI; Patrice; (Saint Didier Au Mont D'Or,
FR) ; MELDENER; Gael; (Lyon, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DANFOSS COMMERCIAL COMPRESSORS |
Trevoux |
|
FR |
|
|
Family ID: |
48050852 |
Appl. No.: |
14/084093 |
Filed: |
November 19, 2013 |
Current U.S.
Class: |
417/365 |
Current CPC
Class: |
F04C 29/0071 20130101;
F04C 29/0085 20130101; F04C 23/02 20130101; F04C 2240/60 20130101;
F04C 15/008 20130101; F04C 18/0207 20130101; F04C 14/06 20130101;
F04C 28/06 20130101 |
Class at
Publication: |
417/365 |
International
Class: |
F04C 29/00 20060101
F04C029/00; F04C 18/02 20060101 F04C018/02 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 19, 2012 |
FR |
12/60987 |
Claims
1. A refrigeration compressor comprising: an electric motor having
a stator and a rotor, the rotor being provided with an axial
through passage, a compression unit adapted for compressing
refrigerant, a drive shaft shaft adapted for driving the
compression unit, the drive shaft extending into the axial through
passage of the rotor and being connected to the rotor, the drive
shaft extending, in use, substantially vertically, and a
positioning element secured on the drive shaft, the positioning
element having an axial stop surface on which rests a lower end
portion of the rotor, the axial stop surface being arranged to
slidably co-operate with a lower end portion of the rotor, wherein
the connection between the rotor and the drive shaft is arranged to
allow limited relative movements between the rotor and the drive
shaft during start and normal operations of the refrigeration
compressor.
2. The refrigeration compressor according to claim 1, wherein the
rotor is slide-fitted on the drive shaft.
3. The refrigeration compressor according to claim 1, further
comprising a locking element adapted to rotatably couple the drive
shaft to the rotor.
4. The refrigeration compressor according to claim 3, wherein an
outer surface of the drive shaft has a first longitudinal recess,
and an inner surface of the rotor has a second longitudinal recess,
the first and second longitudinal recesses being circumferentially
aligned and the locking element extending into the first and second
longitudinal recesses.
5. The refrigeration compressor according to claim 3, wherein the
locking element is adapted to allow limited relative angular
sliding movements between the rotor and the drive shaft.
6. The refrigeration compressor according to claim 1, wherein the
positioning element is a positioning ring secured to the drive
shaft.
7. The refrigeration compressor according to claim 1, wherein the
positioning element is heat shrink fitted to the drive shaft.
8. The refrigeration compressor according to claim 1, further
comprising a first axial abutment surface provided on the rotor and
a second axial abutment surface provided on the drive shaft, a
predetermined axial gap being provided between the first and second
axial abutment surfaces in order to allow limited relative axial
movements between the drive shaft and the rotor.
9. The refrigeration compressor according to claim 8, wherein the
first and second axial abutment surfaces are arranged to prevent
the rotor from axially moving beyond a predetermined position
towards the compression unit.
10. A method for assembling a refrigeration compressor according to
claim 1, comprising the steps of: connecting the rotor to the drive
shaft so as to allow limited relative movements between the rotor
and the drive shaft during start and normal operations of the
refrigeration compressor, and securing the positioning element to
the drive shaft so that the lower end portion of the rotor rests on
the axial stop surface of the positioning element.
11. The method according to claim 10, wherein the connecting step
consists in slide-fitting the rotor to the drive shaft.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a refrigeration compressor,
and in particular to a scroll-type refrigeration compressor.
BACKGROUND OF THE INVENTION
[0002] As known, a scroll-type refrigeration compressor comprises:
[0003] an electric motor having a stator and a rotor, the rotor
being provided with an axial through passage, [0004] a scroll
compression unit adapted for compressing refrigerant and including
an orbiting scroll member and a fixed scroll member, and [0005] a
drive shaft adapted for driving the orbiting scroll member of the
compression unit, the drive shaft extending into the axial through
passage of the rotor and being tightly fixed to the rotor for
example by press-fitting or heat shrink fitting the rotor to the
drive shaft.
[0006] During start-up of the compressor electric motor, the rotor
has a tendency to slightly axially move in the direction of the
compression unit, which leads to a corresponding axial movement of
the drive shaft and of the orbiting scroll member due to the fact
that the rotor is fixed to the drive shaft. Such a movement of the
orbiting scroll member could create excessive forces between the
fixed and orbiting scroll members, and thus damage the orbiting and
fixed scroll members or the sealing element disposed between the
spiral wrap of the orbiting scroll member and the end plate of the
fixe scroll member.
[0007] Further, in operation of such a refrigeration compressor,
deformations of the drive shaft, and more particularly flexions of
the drive shaft, may be transferred to the rotor and then damage
the latter.
[0008] Furthermore, in operation of such a refrigeration
compressor, torque variations occuring in the motor generate
vibrations which are transferred to the shaft and to the scroll
compression unit, which could damage some elements of the scroll
compression unit.
SUMMARY OF THE INVENTION
[0009] It is an object of the present invention to provide an
improved refrigeration compressor which can overcome the drawbacks
encountered in conventional refrigeration compressors.
[0010] Another object of the present invention is to provide a
refrigeration compressor which is reliable.
[0011] According to the invention such a refrigeration compressor
comprises: [0012] an electric motor having a stator and a rotor,
the rotor being provided with an axial through passage, [0013] a
compression unit adapted for compressing refrigerant, [0014] a
drive shaft adapted for driving the compression unit (8), the drive
shaft extending into the axial through passage of the rotor and
being connected to the rotor, the drive shaft extending, in use,
substantially vertically, and [0015] a positioning element secured
on the drive shaft, the positioning element having an axial stop
surface on which rests a lower end portion of the rotor, the axial
stop surface being arranged to slidably co-operate with a lower end
portion of the rotor, [0016] wherein the connection between the
rotor and the drive shaft is arranged to allow limited relative
movements between the rotor and the drive shaft during start and
normal operations of the refrigeration compressor.
[0017] Such a mounting of the rotor allows, during operations of
the refrigeration compressor, small angular movements of the rotor
in relation to the stator, which avoids transfer of mechanical
tensions from the drive shaft to the rotor and damps vibrations
generated by torque variations occuring in the motor. Such a
vibrations damping leads to a reduction of the noise level of the
compressor and to a reduction of the vibrations transmitted to the
piping connected to the compressor.
[0018] Further such a mounting of the rotor allows small axial
movements of the rotor in relation to the drive shaft during
start-up of the compressor electric motor, which reduces the impact
of the orbiting scroll member on the fixed scroll member.
[0019] As a result, any damage of the rotor and of the compression
unit can be prevented during operation of the refrigeration
compressor according to the invention.
[0020] According to an embodiment of the invention, the fit
interference between the rotor and the drive shaft is less than
0,0003, said fit interference being calculated with the following
formula: FI=(D.sub.DS-D.sub.R)/D.sub.R, where FI is the fit
interference between the rotor and the drive shaft, D.sub.DS is the
outer diameter of the portion of the drive shaft extending through
the axial through passage of the rotor, and D.sub.R is the inner
diameter of the rotor. The fit interference may be negative, in
such a case there is a clearance between the rotor and the drive
shaft. For example, the interference may be between -0,005 and
+0.0003.
[0021] According to an embodiment of the invention, the rotor is
slide-fitted on the drive shaft, which means that the maximal fit
interference is 0.
[0022] Such a mounting of the rotor, i.e. without applying
constraint to the rotor, allows small angular and axial movements
of the rotor in relation to the stator.
[0023] Furthermore such a mounting of the rotor avoids to secure
the rotor to the drive shaft by heat shrink fitting, and thus to
expose the rotor to high temperatures. Therefore, the present
invention allows the use of IPM (Interior Permanent Magnet) rotor
comprising permanent magnets which lose their magnet properties
when expose to high temperatures.
[0024] According to an embodiment of the invention, the rotor is
slide-fitted on the drive shaft in a slide-fit relationship
arranged to allow limited relative angular and/or axial sliding
movements between the rotor and the drive shaft. In other words,
the rotor is fitted on the drive shaft with an axial and/or angular
clearance.
[0025] The refrigeration compressor can further comprise a locking
element adapted to rotatably couple the drive shaft to the rotor.
For example, the locking element can be made of non-magnetic
material. According to an embodiment of the invention, the locking
element is adapted to allow limited relative angular sliding
movements between the rotor and the drive shaft.
[0026] According to an embodiment of the invention, an outer
surface of the drive shaft has a first longitudinal recess, and an
inner surface of the rotor has a second longitudinal recess, the
first and second longitudinal recesses being circumferentially
aligned and the locking element extending into the first and second
longitudinal recesses.
[0027] According to an aspect of the invention, the locking element
is slide-fitted into at least one of the first and second
longitudinal recesses.
[0028] According to an aspect of the invention, the section
dimensions of the locking element and of the first and second
longitudinal recesses are adapted to allow limited relative axial
sliding movements between the rotor and the drive shaft.
[0029] According to an aspect of the invention, the section
dimensions of the locking element and of the first and second
longitudinal recesses are adapted to allow limited relative angular
sliding movements between the rotor and the drive shaft.
[0030] The second longitudinal recess provided on the rotor can
extend substantially along the entire length of the rotor.
[0031] According to an embodiment of the invention, the positioning
element is a positioning ring secured to the drive shaft.
[0032] According to an embodiment of the invention, the positioning
element is heat shrink fitted to the drive shaft. For example, the
positioning element can be made of non-magnetic material.
[0033] According to an aspect of the invention, the refrigeration
compressor further comprises a first axial abutment surface
provided on the rotor and a second axial abutment surface provided
on the drive shaft, a predetermined axial gap being provided
between the first and second axial abutment surfaces in order to
allow limited relative axial movements between the drive shaft and
the rotor. For example, the predetermined axial gap is between
0,005 and 1 mm, and preferably between 0,5 and 1 mm.
[0034] According to an embodiment of the invention, the drive shaft
has a radial step delimiting the second axial abutment surface.
[0035] According to an embodiment of the invention, the first and
second axial abutment surfaces are arranged to prevent the rotor
from axially moving beyond a predetermined position towards the
compression unit.
[0036] The first axial abutment surface can be provided on an end
face of the rotor facing the compression unit.
[0037] According to an embodiment of the invention, the
refrigeration compressor is a scroll-type refrigeration
compressor.
[0038] According to an aspect of the invention, the drive shaft has
a first end adapted to drive a moving part of the compression
unit.
[0039] According to an embodiment of the invention, the rotor is an
IPM rotor.
[0040] The present invention also relates to a method for
assembling a refrigeration compressor according to the invention,
comprising the steps of: [0041] connecting the rotor to the drive
shaft so as to allow limited relative movements between the rotor
and the drive shaft during start and normal operations of the
refrigeration compressor, and [0042] securing the positioning
element to the drive shaft so that the lower end portion of the
rotor rests on the axial stop surface of the positioning
element.
[0043] According to an aspect of the invention, the connecting step
consists in slide-fitting the rotor to the drive shaft.
[0044] The method can further comprise the steps of: [0045] pushing
the rotor along the drive shaft towards the compression unit until
the first annular abutment surface provided on the rotor bears
against the second annular abutment surface provided on the drive
shaft, [0046] securing the positioning element to the drive shaft
at an axial distance from the rotor corresponding to the
predetermined axial gap.
[0047] According to an alternative aspect of the invention, the
method can further comprise the steps of: [0048] pushing the rotor
along the drive shaft towards the compression unit until the first
annular abutment surface provided on the rotor bears against the
second annular abutment surface provided on the drive shaft, [0049]
securing the positioning element to the drive shaft so that the
axial stop surface of the positioning element bears against the
lower end portion of the rotor.
[0050] According to an aspect of the invention, the securing step
includes the step of heat shrink fitting the positioning element to
the drive shaft.
[0051] The method can further comprise the steps of: [0052]
aligning the first and second longitudinal recesses, [0053]
inserting the locking element into the first and second
longitudinal recesses.
[0054] According to an aspect of the invention, the inserting step
includes the steps of slide-fitting the locking element into at
least one of the first and second longitudinal recesses.
[0055] These and other advantages will become apparent upon reading
the following description in view of the drawing attached hereto
representing, as non-limiting example, one embodiment of the
refrigeration compressor according to the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0056] The following detailed description of embodiment of the
invention is better understood when read in conjunction with the
appended drawings being understood, however, that the invention is
not limited to the specific embodiment disclosed.
[0057] FIG. 1 is a longitudinal section view of a scroll-type
refrigeration compressor according to the invention.
[0058] FIG. 2 is an enlarged view of a detail of FIG. 1.
[0059] FIG. 3 is an enlarged view of a detail of FIG. 2.
[0060] FIG. 4 is an exploded perspective view of a detail of the
refrigeration compressor of FIG. 1.
[0061] FIG. 5 is a perspective view of the different elements shown
in FIG. 4.
[0062] FIG. 5 is an exploded perspective view of a detail of the
refrigeration compressor of FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
[0063] FIG. 1 shows a scroll-type refrigeration compressor 2
occupying a vertical position. However, the refrigeration
compressor 2 according to the invention could occupy an inclined
position, or a horizontal position, without significant
modification to its structure.
[0064] The refrigeration compressor 2 shown in FIG. 1 comprises a
closed casing 3 defined by a shell 4 whose top and bottom ends are
respectively closed by cap 5 and a base 6.
[0065] The refrigeration compressor 2 also comprises a support
frame 7 fixed in the closed casing 3, the closed casing 3 and the
support frame 7 defining a low pressure volume underneath the
support frame 7 and a high pressure volume above the support frame
7.
[0066] The refrigeration compressor 2 further comprises a scroll
compression unit 8 disposed above the support frame 7, i.e. in the
high pressure volume. The scroll compression unit 8 has a fixed
scroll member 9 and an orbiting scroll member 11 interfitting with
each other. In particular the orbiting scroll member 11 is
supported by and in slidable contact with an upper face of the
support frame 7, and the fixed scroll member 11 is fixed in
relation to the closed casing 3. The fixed scroll member 11 could
for example be fixed to the support frame 7.
[0067] As known, the fixed scroll member 9 has an end plate 12 and
a spiral wrap 13 projecting from the end plate 12 towards the
orbiting scroll member 11, and the orbiting scroll member 11 has an
end plate 14 and a spiral wrap 15 projecting from the end plate 14
towards the fixed scroll member 9. The spiral wrap 15 of the
orbiting scroll member 11 meshes with the spiral wrap 13 of the
fixed scroll member 9 to form a plurality of compression chambers
16 between them. The compression chambers 16 have a variable volume
which decreases from the outside towards the inside, when the
orbiting scroll member 11 is driven to orbit relative to the fixed
scroll member 9. The refrigerant compressed in the compression
chambers 16 escapes from the centre of the fixed and orbiting
scroll members 9, 11 through an opening 17 in the fixed scroll
member 9 leading to a high-pressure chamber 18, from which the
compressed refrigerant is discharged by a discharge port 19.
[0068] The refrigeration compressor 2 further comprises an electric
motor disposed below the support frame 7. The electric motor has a
rotor 21 provided with an axial through passage 22, and a stator 23
disposed around the rotor 21. For example, the electric motor may
be a variable-speed electric motor, and the rotor 21 may be an IPM
rotor.
[0069] Furthermore the refrigeration compressor 2 comprises a drive
shaft 24 adapted for driving the orbiting scroll member 11 in an
orbital movement. The drive shaft 24 extends into the axial through
passage 22 of the rotor 21 and is rotatably coupled to the rotor 21
so that the drive shaft 24 is driven to rotate by the rotor 21
about a rotational axis.
[0070] The drive shaft 24 comprises, at its top end, an eccentric
pin 25 which is off-centered from the center of the drive shaft 24,
and which is inserted in a connecting sleeve part 26 of the
orbiting scroll member 11 so as to cause the orbiting scroll member
11 to be driven in an orbital movement relative to the fixed scroll
member 9 when the electric motor is operated.
[0071] The bottom end of the drive shaft 24 drives an oil pump 27
which supplies oil from a sump defined by the closed casing 3 to a
lubrication passage 30 formed inside the central part of the drive
shaft 24.
[0072] According to the invention, the rotor 21 is slide-fitted to
the drive shaft 24.
[0073] As shown in FIG. 2, the refrigeration compressor 2 includes
a first annular axial abutment surface 28 provided on the rotor 21
and a second annular axial abutment surface 29 provided on the
drive shaft 24. As particularly shown in FIG. 3, a predetermined
axial gap is provided between the first and second axial abutment
surfaces 28, 29 in order to allow relative axial sliding movements
between the rotor 21 and the drive shaft 24. For example, the
predetermined axial gap is between 0,5 and 1 mm.
[0074] Particularly, the first annular axial abutment surface 28 is
provided on the upper end face of the rotor 21, and the drive shaft
24 has a radial step delimiting the second annular axial abutment
surface 29. The first and second annular axial abutment surfaces
28, 29 are arranged to prevent the rotor 21 from axially moving
relative to the drive shaft 24 beyond a predetermined position
towards the compression unit 8.
[0075] The refrigeration compressor 2 further includes a
positioning ring 31 secured to the drive shaft 24. For example, the
positioning ring 31 is heat shrink fitted to the drive shaft 24.
Advantageously the positioning ring 31 is made of non-magnetic
material.
[0076] The positioning ring 31 has an axial stop surface 32 on
which rests a lower end portion of the rotor 21, and more precisely
a radial abutment surface 33 provided on the lower end portion of
the rotor 21. Thus the positioning ring 31 is arranged to axially
position the rotor 21.
[0077] The refrigeration compressor 2 further comprises a locking
pin 34 adapted to rotatably couple the drive shaft 24 to the rotor
21. For example the locking pin 34 is made of non-magnetic
material.
[0078] The locking pin 34 extends respectively into a first
longitudinal recess 35 provided on the outer surface of the drive
shaft 24 and into a second longitudinal recess 36 provided on the
inner surface of the rotor 21, the first and second longitudinal
recesses 35, 36 being circumferentially aligned. The section
dimensions of the locking pin 34 and of the first and second
longitudinal recesses 35, 36 are adapted to allow relative axial
and angular sliding movements between the rotor 21 and the drive
shaft 24. According to the embodiment shown on the figures, the
locking pin 34 is slightly larger than the first longitudinal
recesses 35 so that the locking pin 34 is press fitted into the
first longitudinal recess 35, and the locking pin 34 is
slide-fitted into the second longitudinal recess 36. However, the
locking pin 34 may be slide-fitted into the first and second
longitudinal recesses 35, 36.
[0079] The second longitudinal recess 36 provided on the rotor 21
can extend along the entire length of the rotor 21. Advantageously,
the first longitudinal recess 35 extends only along a partial
length of the drive shaft 24 and delimits an axial stop surface 37
for the upper end of the locking pin 34. Furthermore the axial stop
surface 32 provided on the positioning ring 31 forms also an axial
stop for the lower end of the locking pin 34.
[0080] The method for assembling the refrigeration compressor 2
according to the invention comprises at least the following steps:
[0081] tight fitting the locking pin 34 into the first longitudinal
recess 35 so that the upper end face of the locking pin 34 bears
against the axial stop surface 37 provided on the drive shaft 24,
[0082] engaging the rotor 21 around the drive shaft 24 from the
lower end portion of the drive shaft 24, [0083] aligning the second
longitudinal recess 36 with the locking pin 34, [0084] pushing the
rotor 21 along the drive shaft 24 towards the compression unit 8
until the first annular abutment surface 28 provided on the rotor
21 bears against the second annular abutment surface 29 provided on
the drive shaft 24, [0085] heating the positioning ring 31, [0086]
engaging the positioning ring 31 around the drive shaft 24 from the
lower end portion of the drive shaft 24, [0087] positionning the
support surface 32 of the positioning ring 31 at an axial distance
from the radial abutment surface 33 provided on the rotor 21
corresponding to the predetermined axial gap, and [0088] cooling
down the positioning ring 31.
[0089] When assembled, the refrigeration compressor 2 is vertically
positioned. As a consequence the rotor 21 slides axially by gravity
along the drive shaft 24 until the radial abutment surface 33
provided on the rotor 21 bears against the support surface 32 of
the positioning ring 31, and the predetermined axial gap between
the first and second axial abutment surfaces 28, 29 is
introduced.
[0090] It should be noted that the positionning step may consist in
positionning the support surface 32 of the positioning ring 31
against the radial abutment surface 33 provided on the rotor 21. In
such a case, a very small axial gap (few micrometers) is finally
provided between the first and second axial abutment surfaces 28,
29 due to the cooling down of the positioning ring 31.
[0091] Of course, the invention is not restricted to the embodiment
described above by way of non-limiting example, but on the contrary
it encompasses all embodiments thereof.
* * * * *