U.S. patent application number 11/501276 was filed with the patent office on 2007-02-22 for linear compressor, particularly refrigerant compressor.
This patent application is currently assigned to Danfoss Compressors GmbH. Invention is credited to Poul Erik Hansen, Klaus Reinwand, Jan Thomsen.
Application Number | 20070041854 11/501276 |
Document ID | / |
Family ID | 37697256 |
Filed Date | 2007-02-22 |
United States Patent
Application |
20070041854 |
Kind Code |
A1 |
Hansen; Poul Erik ; et
al. |
February 22, 2007 |
Linear compressor, particularly refrigerant compressor
Abstract
The invention concerns a linear compressor (1), particularly a
refrigerant compressor, with a compression unit (3) having a
cylinder (8) and a piston (16) reciprocating in the cylinder (8),
and a linear motor (4) having an outer stator (18), an inner stator
(20) and an armature (22) located in a gap (21) formed between the
outer stator (18) and the inner stator (20), the armature (22)
being connected to the piston (16) via a piston rod (28). It is
endeavoured to design such a linear compressor in a simple manner
with the smallest possible dimensions. For this purpose, it is
ensured that the armature (22) is connected to the piston rod (28)
inside the axial length of the inner stator (20).
Inventors: |
Hansen; Poul Erik; (Sydals,
DK) ; Reinwand; Klaus; (Harrislee, DE) ;
Thomsen; Jan; (Aabenraa, DK) |
Correspondence
Address: |
MCCORMICK, PAULDING & HUBER LLP
CITY PLACE II
185 ASYLUM STREET
HARTFORD
CT
06103
US
|
Assignee: |
Danfoss Compressors GmbH
Flensburg
DE
D-24904
|
Family ID: |
37697256 |
Appl. No.: |
11/501276 |
Filed: |
August 9, 2006 |
Current U.S.
Class: |
417/417 |
Current CPC
Class: |
F04B 35/045
20130101 |
Class at
Publication: |
417/417 |
International
Class: |
F04B 35/04 20060101
F04B035/04 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 17, 2005 |
DE |
10 2005 038 785.3 |
Claims
1. A linear compressor, particularly a refrigerant compressor, with
a compression unit having a cylinder and a piston reciprocating in
the cylinder, and a linear motor having an outer stator, an inner
stator and an armature located in a gap formed between the outer
stator and the inner stator, the armature being connected to the
piston via a piston rod wherein the armature is connected to the
piston rod inside the axial length of the inner stator.
2. The linear compressor according to claim 1, wherein the
compression unit is located axially outside the linear motor.
3. The linear compressor according to claim 1, wherein the piston
rod is guided through the entire axial length of the linear motor,
a resonance spring arrangement being located on a side of the
linear motor facing away from the compression unit.
4. The linear compressor according to claim 3, wherein the piston
rod is guided by the piston and the resonance spring
arrangement.
5. The linear compressor according to claim 1, wherein the cylinder
is displaceable in relation to the outer stator during
mounting.
6. The linear compressor according to claim 1, wherein the armature
and the piston rod are connected to each other via at least one
connecting element, which is guided through at least two slots in
the inner stator.
7. The linear compressor according to claim 6, wherein the slots
are made to be through over the axial length of the inner
stator.
8. The linear compressor according to claim 6, wherein the
connecting element has an inner ring, which is connected to the
piston rod.
9. The linear compressor according to claim 8, wherein the inner
ring bears under a predetermined pressure on a circumferential
bearing surface of the piston rod.
10. The linear compressor according to claim 6, wherein the
connecting element has an outer ring, which is connected to the
armature.
11. The linear compressor according to claim 10, wherein the inner
ring and the outer ring are connected to each other by means of at
least two radially extending arms.
12. The linear compressor according to claim 1, wherein the
armature is formed by a cylinder pipe shaped permanent magnet
arrangement, whose longitudinal axis coincides with the axis of the
piston rod.
13. The linear compressor according to claim 1, wherein the piston
rod is connected to the armature in at least two positions, which
have a distance in the axial direction.
14. The linear compressor according to claim 1, wherein the axial
and radial positions of the armature in relation to the piston rod
are controlled by the connecting element.
15. The linear compressor according to claim 13, wherein the
armature is suspended axially between two connecting elements.
16. The linear compressor according to claim 13, wherein at least
one connecting element has a projection located radially inside the
armature, the armature bearing from the radial outside on said
projection.
17. The linear compressor according to claim 16, wherein the
projection is located in the area of the arms.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Applicant hereby claims foreign priority benefits under
U.S.C. .sctn. 119 from German Patent Application No. 10 2005 038
785.3 filed on Aug. 17, 2005, the contents of which are
incorporated by reference herein. This Application relates to
German Patent Applications No. 10 2005 038 783.7 (Attorney Docket
No. 6495-0168); No. 10 2005 038 784.5 (Attorney Docket No.
6495-0169); No. 10 2005 038 781.0 (Attorney Docket No. 6495-0172);
No. 10 2005 038 780.2 (Attorney Docket No. 6495-0173), filed on the
same date herewith.
FIELD OF THE INVENTION
[0002] The invention concerns a linear compressor, particularly a
refrigerant compressor, with a compression unit having a cylinder
and a piston reciprocating in the cylinder, and a linear motor
having an outer stator, an inner stator and an armature located in
a gap formed between the outer stator and the inner stator, the
armature being connected to the piston via a piston rod.
BACKGROUND OF THE INVENTION
[0003] Such a linear compressor is, for example, known from U.S.
Pat. No. 6,565,332 B2. Here, the cylinder is arranged radially
inside the inner stator. The armature being movable between inner
stator and outer stator has permanent magnets and is connected to
the piston rod by way of a radial flange arrangement transferring
the movement of the armature to the piston. The flange arrangement
is located axially between the motor and a resonance spring
arrangement.
[0004] A similar linear compressor is known from U.S. Pat. No.
6,793,470 B2. Here, the armature is not connected to the piston via
a piston rod but via some kind of cylinder pipe having
approximately the same outer diameter as the piston. Also here the
piston moves inside the inner stator, which causes that the stator
and thus the linear compressor must have a relatively large
diameter. Usually, such a linear motor will be operated in a lying
state. This means that, due to the large diameter of the linear
motor, the linear motor will have a relatively large height. When
the linear compressor is used as refrigerant compressor in a
domestic cooling appliance, for example a refrigerator or a
freezer, the height of the linear compressor reduces the space
available for the cooling chamber.
[0005] U.S. Pat. No. 5,772,410 shows another linear compressor, in
which the cylinder is located in an axial extension of the motor.
Here, the inner stator is located inside the piston and the
armature is connected directly to the side of the piston facing
away from the cylinder head. This enables a relatively compact
design, however, requires a relatively expensive manufacturing and
mutual alignment of the individual parts, as only one end of the
armature and of the inner stator can be fixed on the piston or on a
carrier, respectively.
BRIEF SUMMARY OF THE INVENTION
[0006] The invention is based on the task of providing a linear
compressor with a simple design and the smallest possible
dimensions.
[0007] With a linear compressor as mentioned in the introduction,
this task is solved in that the armature is connected to the piston
rod inside the axial length of the inner stator.
[0008] Thus, a connection between the armature and the piston rod
is guided through the inner stator. An arrangement located axially
outside the motor, via which the armature can be connected to the
piston rod, is no longer required. The result is a relatively short
design, which reduces the space required for the compressor. This
permits, for example, an increase of the space available for the
cooling chamber in a domestic cooling appliance with specified
dimensions.
[0009] Preferably, the compression unit is located axially outside
the linear motor. Thus, the diameter of the motor and also the
height of a horizontally located compressor can be kept small.
Usually, sufficient space is available for a domestic cooling
appliance in the width direction. The compressor can thus have a
relatively large axial length, when the consequence of this is that
its diameter and thus its height is reduced.
[0010] Preferably, the piston rod is guided through the entire
axial length of the linear motor, a resonance spring arrangement
being located on a side of the linear motor facing away from the
compression unit. The resonance spring arrangement has a resonance
frequency, which is adapted to the operation frequency of the
linear motor. The operation frequency is determined by the
frequency of the supplied current. When the linear compressor is
operated in the resonance range of the resonance spring
arrangement, it will require less energy. As the piston rod can now
be used to connect the resonance spring arrangement to the piston,
the resonance spring arrangement can be located on the side of the
linear motor lying opposite the compression unit. This decoupling
simplifies the design. The resonance spring arrangement will not
conflict with the movement of the piston.
[0011] Preferably, the piston rod is guided by the piston and the
resonance spring arrangement. Thus, the piston rod has no contact
points with the linear motor. Thus, the piston rod can also hold
the armature so that it is guided practically touch-free through
the gap between inner stator and outer stator.
[0012] Preferably, the cylinder is displaceable in relation to the
outer stator during mounting. In connection with a piston
compressor, it has certain significance that the compression
chamber formed by the piston and the cylinder has a minimal value
in the upper dead point of the piston. During mounting, the piston
can now be positioned in its upper dead point, and then the
cylinder can be displaced in relation to the outer stator, and thus
also in relation to the piston, so that the compression chamber
assumes the smallest permissible value. For example, the cylinder
can be displaced in a pipe-shaped intermediary piece. When the
desired position has been reached, the cylinder is fixed in the
intermediary piece, for example by welding, soldering or
gluing.
[0013] Preferably, the armature and the piston rod are connected to
each other via at least one connecting element, which is guided
through at least two slots in the inner stator. Thus, the armature
and the piston rod are connected to each other in two places in the
circumferential direction, which increases the stability of the
unit formed by the piston rod and the armature. The slots in the
inner stator are of minor importance for the magnetic behaviour of
the whole stator. In the inner stator, the magnetic field mainly
extends in the axial direction, but not in the circumferential
direction, so that the magnetic field is not much disturbed by the
axially extending slots.
[0014] It is preferred that the slots are made to be through over
the axial length of the inner stator. This means that the inner
stator can be made up of several segments. This simplifies the
manufacturing.
[0015] Preferably, the connecting element has an inner ring, which
is connected to the piston rod. Thus, the inner ring secures the
radial positioning of the connecting element in relation to the
piston rod.
[0016] It is preferred that the inner ring bears under a
predetermined pressure on a circumferential bearing surface of the
piston rod. Thus, the inner ring also secures the axial positioning
of the connecting element in relation to the piston rod and thus
the position of the piston rod and the armature in relation to each
other.
[0017] Preferably, the connecting element has an outer ring, which
is connected to the armature. With this embodiment, the armature is
held annularly, so that also its radial position in relation to the
piston rod is secured.
[0018] Preferably, the inner ring and the outer ring are connected
to each other by means of at least two radially extending arms.
These arms can be guided through the slots in the inner stator.
They preferably extend radially.
[0019] Preferably, the armature is formed by a cylinder pipe shaped
permanent magnet arrangement, whose longitudinal axis coincides
with the axis of the piston rod. The permanent magnets forming the
permanent magnet arrangement are radially magnetised, that is, all
their radial outsides have the same magnetical polarity. In a
simple manner, this permanent magnet arrangement can be kept
together by the outer ring.
[0020] Preferably, the piston rod is connected to the armature in
at least two positions, which have a distance in the axial
direction. This ensures that the armature cannot tilt in relation
to piston rod and vice versa. The allocation of armature and stator
can be maintained very accurately, which gives favourable operation
parameters. In particular, the gap, which is formed between the
inner stator and the outer stator, can be set at a minimum width,
as the risk that the armature will touch the stator is practically
non-existent.
[0021] Preferably, the axial and radial positions of the armature
in relation to the piston rod are controlled by the connecting
element. The armature and the piston rod thus form a unit, in which
all elements have a fixed allocation in relation to each other.
[0022] Preferably, the armature is suspended axially between two
connecting elements. This embodiment has two advantages. Firstly,
the armature is held in the axial direction. Secondly, it is
sufficient to let two stops of the piston rod act upon the
connecting elements from the radial outside. The armature is held
by means of the mounting of the connecting elements on the piston
rod and the tightening of the connecting elements on the piston
rod.
[0023] Preferably, at least one connecting element has a projection
located radially inside the armature, the armature bearing from the
radial outside on said projection. This projection also fixes the
armature radially.
[0024] It is preferred that the projection is located in the area
of the arms. Here, the connecting element has its largest resisting
force, so that even larger forces will not make the armature
displace radially in relation to the connecting element.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] In the following, the invention is described on the basis of
a preferred embodiment in connection with the drawings,
showing:
[0026] FIG. 1 is a schematical, longitudinal section through a
linear compressor;
[0027] FIG. 2 is a top view on a component group comprising piston,
piston rod and armature; and
[0028] FIG. 3 is a section III-III according to FIG. 2.
DETAILED DESCRIPTION OF THE INVENTION
[0029] FIG. 1 shows a linear compressor, which is located in a
hermetically closed case 2.
[0030] The linear compressor 1 has a compression section 3, a drive
section 4 and a resonance spring arrangement 5. The unit formed by
the compression section 3, the drive section 4 and the resonance
spring arrangement 5 is suspended in the case 2 by means of two
plane annular springs 6, 7, each being formed as a spiral with one
winding. The annular springs 6, 7 are fixed on the drive section
4.
[0031] The compression section 3 has a cylinder 8, whose one front
side is covered by a cylinder head 9. Cylinder 8 and cylinder head
9 are joined in a capsule 10 in a cartridge-like manner. A suction
muffler 11 and a pressure muffler 12 are fixed on the cylinder head
9. The suction muffler 11 is connected to a suction opening 13 and
the pressure muffler 12 is connected to a pressure opening 14 in
the cylinder head.
[0032] The capsule 10 is inserted in an intermediary ring 15, which
is connected to the drive section 4. During mounting, the capsule
10 and thus the cylinder 8 can be displaced within certain limits
in the axial direction of the cylinder in relation to the
intermediary ring 15. When, during mounting, a predetermined
position of the cylinder in relation to the drive section 4 has
been reached, the capsule 10 is fixed in the intermediary ring, for
example by welding, soldering or gluing.
[0033] In the cylinder 8 is located a piston 16, which borders a
compression chamber 17 together with the cylinder 8 and the
cylinder head 9. Before the cylinder with the capsule 10 is fixed
in the intermediary piece 15, the piston 16 is moved to its upper
dead point, and the cylinder 8 is displaced, until the compression
chamber 17 has reached its smallest permissible extension.
[0034] The drive section 4 has a linear motor. The linear motor has
an outer stator 18 with a recess 19 for a winding, not shown in
detail, and an inner stator 20. Between the outer stator 18 and the
inner stator 20 is an annular gap 21, in which an armature 22 is
movable. The armature carries permanent magnets 23, which are
connected to each other by means of two outer rings 24, 25. The
outer rings 24, 25 can, for example, be made of a plastics
material. The outer rings 24, 25 are connected to inner rings 26,
27 via arms shown in FIGS. 2 and 3 and guided through slots in the
inner stator 20.
[0035] The inner rings 26, 27 are connected with a piston rod 28,
which again is connected to the piston 16.
[0036] The outer stator 18 and the inner stator 20 are connected to
each other via motor covers 29, 30, which are fastened against each
other by means of screw bolts 31. The screw bolts extend in
parallel to the movement direction of the piston rod 28.
[0037] The intermediary ring 15 is connected to the cylinder-side
motor cover 30, for example by soldering, gluing or welding.
[0038] The resonance spring arrangement 5, which is located at an
end of the drive section 4, which lies opposite the compression
section 3, has a spring pack 32 of several plate springs 33. The
spring pack 32 is connected in a central area 34 to the piston rod
28. An outer section 35 of the spring pack 32 is connected via
bolts 36 to a stop housing 37, which forms a stop for the spring
pack 32.
[0039] At the end projecting from the spring pack 32, the piston
rod 28 is connected to an oil pump arrangement 38, which immerses
in an oil sump, not shown in detail, which forms in the bottom part
of the case 2.
[0040] When the winding located in the recess 19 is energised, the
armature 22 moves in one direction and takes along the piston rod
28 in this direction. If the direction of the current is reversed,
the armature 22 with the piston rod 28 moves in the opposite
direction, thus also moving the piston 16 in the opposite
direction. This periodically increases and reduces the volume of
the compression chamber 17. The resonance spring arrangement 5 is
adapted to the frequency of the current, so that the movable part
of the linear compressor 1, which is formed by the armature 22, the
piston rod 28, the piston 16, the oil pump arrangement 38 and the
moving part of the resonance spring arrangement 5 oscillates in
resonance.
[0041] FIGS. 2 and 3 now show the allocation of the piston rod 28
and the armature 22 with further details.
[0042] In the area of the piston-side end, the piston rod 28 has a
circumferential projection 41, on which the inner ring 27 bears
from the side lying opposite the piston 16. On the opposite side of
the projection 41 a connecting element 42 bears, with which the
piston rod 28 is connected to the piston 16.
[0043] The axial fixing of the inner ring 27 in relation to the
piston rod 28 also ensures axial fixing of the outer ring 25. It
forms an axial stop for the permanent magnets 23.
[0044] The second inner ring 26 is also pushed onto the piston rod
28. Thus, the second outer ring 24 comes to rest on the opposite
axial front side of the permanent magnets 23, which are then fixed
between the two outer rings 24, 25. The second inner ring 26 is
fixed by an end piece 43 screwed onto the piston rod 28. The end
piece 43 can also be connected to the piston rod 28 in other ways.
The fact that in the axial direction the two inner rings 26, 27 are
pressed against each other causes that the permanent magnets 23 are
fixed between the outer rings 24, 25 in the axial direction.
[0045] An outer ring 24, 25, an inner ring 26, 27 and in the
present embodiment three arms 40 form a connecting element 39. Of
course, the number of arms 40 can also be chosen to be different.
However, at least two arms are available. The connecting elements
39 can be made of a plastics material.
[0046] Each arm 40 has an axial projection 44, on which the
permanent magnets 23 bear from the outside. As the permanent
magnets 23 form a hollow cylinder, the projections 44 are
sufficient to fix the permanent magnets 23 reliably between the two
connecting elements 39 in the radial direction. Thus, the permanent
magnets 23 are fixed in relation to the piston rod 28 in two
positions, which have an axial distance to each other, so that the
permanent magnets 23 cannot tilt in relation to the piston rod 28.
On the contrary, they can be guided in parallel with the piston rod
28 with a relatively high accuracy. The piston rod is merely
supported via the piston in the compression section 3 and in the
spring pack 32 in the resonance spring arrangement 5. Thus, it can
be guided through the inner stator in a touch-free manner.
Accordingly, the armature 22 can also be supported in the annular
gap 21 in a touch-free manner, which reduces frictional losses. The
piston rod 28 can also be guided through the motor covers 29, 30 in
a touch-free manner.
[0047] The compression unit with the cylinder 8 and the piston 16
is located axially outside the linear motor, that is, the driving
section 4. Accordingly, the compression unit 3 must not be
considered with regard to the diameter. The linear motor can
therefore be built with a relatively small diameter. The piston rod
is guided through the total axial length of the linear motor. At
one end it is provided with the oil pump arrangement 38, so that
the oil used for lubricating the compression section 3 can also be
used to dissipate a certain heat amount from the drive section
4.
[0048] The slots required for the arms 40 in the inner stator 20
are of minor importance with regard to the magnetical properties of
the stator. In the inner stator 20, the magnetic field is directed
mainly axially. Merely in the axial end, the magnetic field is
deflected to the radial direction. However, the magnetic field has
practically no component in the circumferential direction, so that
the air gaps formed by the slots are not significantly
disturbing.
[0049] Guiding the armature 22, together with the piston rod 28 and
the connected oil pump arrangement 38, by means of the arms 40 in
the inner stator 20 prevents that the armature can rotate in the
circumferential direction. This secures that the oil pump
arrangement is always immersed in the oil sump.
[0050] While the present invention has been illustrated and
described with respect to a particular embodiment thereof, it
should be appreciated by those of ordinary skill in the art that
various modifications to this invention may be made without
departing from the spirit and scope of the present invention.
* * * * *