U.S. patent application number 11/577230 was filed with the patent office on 2009-10-22 for linear compressor.
Invention is credited to Ian Campbell McGill.
Application Number | 20090263262 11/577230 |
Document ID | / |
Family ID | 36319573 |
Filed Date | 2009-10-22 |
United States Patent
Application |
20090263262 |
Kind Code |
A1 |
McGill; Ian Campbell |
October 22, 2009 |
Linear Compressor
Abstract
A linear compressor (1) includes a cylinder (21) with a piston
(22) connected through a main spring (19) and a planar spring (20).
One or more flat blocks of permanent magnet material (17) with
large faces of the blocks facing a stator (15) and defining
armature poles are secured to a connecting rod (30). A lateral
support (52) acts between the cylind (21) and the connecting rod
(30) at a location midway between the permanent magnet material and
the piston (22) allowing axial movement of the connecting rod (30)
but transferring side loads to the cylinder (21).
Inventors: |
McGill; Ian Campbell;
(Auckland, NZ) |
Correspondence
Address: |
TREXLER, BUSHNELL, GIANGIORGI,;BLACKSTONE & MARR, LTD.
105 WEST ADAMS STREET, SUITE 3600
CHICAGO
IL
60603
US
|
Family ID: |
36319573 |
Appl. No.: |
11/577230 |
Filed: |
November 1, 2005 |
PCT Filed: |
November 1, 2005 |
PCT NO: |
PCT/NZ05/00287 |
371 Date: |
December 12, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60624252 |
Nov 2, 2004 |
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Current U.S.
Class: |
417/415 |
Current CPC
Class: |
F04B 35/045
20130101 |
Class at
Publication: |
417/415 |
International
Class: |
F04B 35/04 20060101
F04B035/04 |
Claims
1. A linear compressor comprising: a cylinder part including a
cylinder bore, a piston disposed in said bore and slidable therein,
a main spring connecting directly or indirectly said cylinder part
to said piston, a connecting member connecting between said main
spring and said piston, a stator having an air gap, said connecting
member passing through said air gap, and one or more substantially
flat blocks of permanent magnet material secured to said connecting
member with the large faces of said blocks facing the stator, said
permanent magnet material magnetised to define at least one
armature pole; and wherein said main spring comprises a combination
of a plurality of individual spring elements acting in
parallel.
2. A linear compressor as claimed in claim 1, wherein the
combination includes at least one planar spring element
contributing higher lateral stiffness.
3. A linear compressor as claimed in claim 1, wherein the
combination includes at least one planar spring and at least one
coil spring.
4. A linear compressor comprising: a cylinder part including a
cylinder bore, a piston disposed in said bore and slidable therein,
a main spring connecting directly or indirectly said cylinder part
to said piston, a connecting member connecting between said main
spring and said piston, a stator having an air gap, said connecting
member passing through said air gap, and at least one armature pole
located along said connecting member, wherein said connecting
member is supported only by said piston at one end and by said main
spring away from said one end, and said main spring comprises a
combination of individual spring elements acting in parallel.
5. A linear compressor as claimed in claim 4, wherein the
combination includes at least one planar spring element
contributing higher lateral stiffness.
6. A linear compressor as claimed in claim 4, wherein the
combination includes at least one planar spring and at least one
coil spring.
7. A linear compressor comprising: a cylinder part including a
cylinder bore, a piston disposed in said bore and slidable therein,
a main spring connecting directly or indirectly said cylinder part
to said piston, and a connecting member connecting between said
main spring and said piston, with a compliant element in said
connecting member transmitting side and axial loads but allowing
rotation about axes transverse to the axis of reciprocation of said
piston in said bore; wherein said main spring comprises a
combination of a plurality of individual spring elements acting in
parallel.
8. A linear compressor as claimed in claim 7, wherein the
combination includes at least one planar spring element
contributing higher lateral stiffness.
9. A linear compressor as claimed in claim 7, wherein the
combination includes at least one planar spring and at least one
coil spring.
10. A linear compressor comprising: a cylinder part including a
cylinder bore, a piston disposed in said bore and slidable therein,
a main spring connecting directly or indirectly said cylinder part
to said piston, a connecting member connecting between said main
spring and said piston and connecting said main spring to said
piston, a stator having an air gap, said connecting member passing
through said air gap, one or more substantially flat blocks of
permanent magnet material secured to said connecting member with
the large faces of said blocks facing the stator, said permanent
magnet material magnetised to define at least one armature pole,
and a lateral support acting between said cylinder part and said
connecting member, at a location intermediate said permanent magnet
material and said piston, said lateral support allowing axial
movement of said connecting rod, but transferring side loads to
said cylinder part.
11. A linear compressor as claimed in claim 10, wherein the main
spring provides lateral support acting between said cylinder part
and said connecting member, at a location such that said armature
pole or poles are between said main spring location and said
lateral support located so that the armature of said motor is
supported at one end by said main spring and at the other end by
said lateral support.
12. A linear compressor as described in claim 10, wherein said
lateral support comprises one or more planar springs.
13. A linear compressor as described in claim 10, wherein said
lateral support comprises one or more sliding bearings acting on
the connecting member.
14. A linear compressor as claimed in claim 10, wherein, between
the lateral support and the piston, the connecting member is
laterally flexible or includes at least one flexible portion, so as
to effectively transmit axial forces but to have lateral and
angular compliance of the piston relative to the axis and line of
reciprocation of the connecting member.
15. (canceled)
Description
FIELD OF THE INVENTION
[0001] The present invention relates to linear compressors, and in
particular linear compressors of the type suitable for use in a
vapour compression refrigeration system.
BACKGROUND TO THE INVENTION
[0002] Linear compressors of a type for use in a vapour compression
refrigeration system are the subject of many documents in the prior
art. One such document is our co-pending PCT patent application
PCT/NZ2004/000108. That specification describes a variety of
developments relating to such compressors, many of which have
particular application to the linear compressors. The present
invention relates to further improvements to compressor embodiments
such as are described in that patent application which provides a
general exemplification of a compressor to which the present
invention may be applied. However the present may also be applied
beyond the scope of the particular embodiments of a linear
compressor disclosed in that application. Persons skilled in the
art will appreciate the general application of the ideas herein to
other embodiments of linear compressors such as are found in the
prior art.
SUMMARY OF THE INVENTION
[0003] It is an object of the present invention to provide
improvements relating to linear compressors or to at least provide
the industry with a useful choice.
[0004] In a first aspect the invention may broadly be said to
consist in a linear compressor comprising:
[0005] a cylinder part including a cylinder bore,
[0006] a piston disposed in said bore and slidable therein,
[0007] a main spring connecting directly or indirectly said
cylinder part to said piston,
[0008] a connecting member connecting between said main spring and
said piston,
[0009] a stator having an air gap, said connecting member passing
through said air gap, and
[0010] one or more substantially flat blocks of permanent magnet
material secured to said connecting member with the large faces of
said blocks facing the stator, said permanent magnet material
magnetised to define at least one armature pole; and wherein said
main spring comprises a combination of a plurality of individual
spring elements acting in parallel.
[0011] In a further aspect the invention may broadly be said to
consist in a linear compressor comprising:
[0012] a cylinder part including a cylinder bore,
[0013] a piston disposed in said bore and slidable therein,
[0014] a main spring connecting directly or indirectly said
cylinder part to said piston,
[0015] a connecting member connecting between said main spring and
said piston,
[0016] a stator having an air gap, said connecting member passing
through said air gap, and
[0017] at least one armature pole located along said connecting
member,
[0018] wherein said connecting member is supported only by said
piston at one end and by said main spring away from said one end,
and said main spring comprises a combination of individual spring
elements acting in parallel.
[0019] In a still further aspect the invention may broadly be said
to consist in a linear compressor comprising:
[0020] a cylinder part including a cylinder bore,
[0021] a piston disposed in said bore and slidable therein,
[0022] a main spring connecting directly or indirectly said
cylinder part to said piston, and
[0023] a connecting member connecting between said main spring and
said piston, with a compliant element in said connecting member
transmitting side and axial loads but allowing rotation about axes
transverse to the axis of reciprocation of said piston in said
bore;
[0024] wherein said main spring comprises a combination of a
plurality of individual spring elements acting in parallel.
[0025] In relation to the invention as set forth in any of the
above paragraphs said main spring may for example comprise a
combination of coil springs, a combination of coil springs and
planar springs or a combination of planar springs. Coil springs may
be formed from suitable high fatigue wire or springs machined from
thin walled cylinder stock. Preferably the combination includes at
least one planar spring element contributing higher lateral
stiffness. Most preferably the combination includes at least one
planar spring and at least one coil spring.
[0026] In a still further aspect the invention may broadly be said
to consist in a linear compressor comprising:
[0027] a cylinder part including a cylinder bore,
[0028] a piston disposed in said bore and slidable therein,
[0029] a main spring connecting directly or indirectly said
cylinder part to said piston,
[0030] a connecting member connecting between said main spring and
said piston and connecting said main spring to said piston,
[0031] a stator having an air gap, said connecting member passing
through said air gap,
[0032] one or more substantially flat blocks of permanent magnet
material secured to said connecting member with the large faces of
said blocks facing the stator, said permanent magnet material
magnetised to define at least one armature pole, and
[0033] a lateral support acting between said cylinder part and said
connecting member, at a location intermediate said permanent magnet
material and said piston, said lateral support allowing axial
movement of said connecting rod, but transferring side loads to
said cylinder part.
[0034] In relation to the invention as set forth in the above
paragraph said main spring may comprise a single spring element or
a combination of a plurality of spring elements acting in parallel.
Preferably the main spring also provides lateral support acting
between said cylinder part and said connecting member, at a
location such that said armature pole or poles are between said
main spring location and said lateral support located so that the
armature of said motor is supported at one end by said main spring
and at the other end by said lateral support.
[0035] According to a further aspect of the invention, said lateral
support comprises one or more planar springs, for example cut from
sheet material or formed from spring wire bent into a spring line
within a plane. Alternatively said radial support may comprise one
or more sliding bearings acting on the connecting member.
[0036] According to a further aspect of the invention, in the
region of the connecting member between the lateral support and the
piston the connecting member is laterally flexible or includes one
(or preferably two) flexible portion, so as to effectively transmit
axial forces but to have lateral and angular compliance of the
piston relative to the axis and line of reciprocation of the
connecting member.
[0037] The cylinder part may include provision for aerostatic gas
bearings receiving compressed gases and supplying these through a
plurality of spaced bearing ports spaced along and around the
cylinder bore to support the piston in operation. However the
armature radially (or laterally) supported at both ends and
compliancy in the connecting member between the lateral support and
the piston the inventors expect that the benefits of the gas
bearings and reduced friction may be exceeded by the consumption of
compressed gas in the gas bearings.
[0038] To those skilled in the art to which the invention relates,
many changes in construction and widely differing embodiments and
applications of the invention will suggest themselves without
departing from the scope of the invention as defined in the
appended claims. The disclosures and the descriptions herein are
purely illustrative and are not intended to be in any sense
limiting.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] FIG. 1 is a plan elevation in cross-section of a linear
compressor according to a first embodiment. The first embodiment
has a main spring comprising a combination of a flat spring and a
coil spring. The flat motor armature is radially supported at one
end by the main spring and at the other end by the piston. FIG. 1
is a cross-section taken through line DD of FIG. 2.
[0040] FIG. 2 is a side elevation in cross-section of the
embodiment of FIG. 1, taken through line CC of FIG. 1.
[0041] FIG. 3 is a plan elevation in cross-section of a linear
compressor according to a second embodiment. The second embodiment
has a main spring comprising a stack of flat springs. The flat
motor armature is radially supported at one end by the main spring
and at the other end by another flat spring. There is a compliant
connection to the piston. FIG. 3 is a cross-section taken through
line EE of FIG. 4.
[0042] FIG. 4 is a side elevation in cross-section of the
embodiment of FIG. 2, taken through line BB of FIG. 3.
[0043] FIG. 5 is a plan elevation in cross-section of a linear
compressor according to a third embodiment. The third embodiment
has a main spring comprising a combination of a flat spring and a
coil spring. The flat motor armature is radially supported at one
end by the main spring and at the other end in a sliding bearing.
There is a compliant connection to the piston.
[0044] FIG. 5 is a cross-section taken through line FF of FIG.
6.
[0045] FIG. 6 is a side elevation in cross-section of the
embodiment of FIG. 5, taken through line AA of FIG. 5.
DETAILED DESCRIPTION
[0046] Referring to FIGS. 1 to 6 the compressor for a vapour
compression refrigeration system includes a linear compressor 1
supported inside a housing 2. Typically the housing 2 is
hermetically sealed and includes a gases inlet port 3 and a
compressed gases outlet port 4. Uncompressed gases flow within the
interior of the housing surrounding the compressor 1. These
uncompressed gases are drawn into the compressor during intake
stroke, compressed between the piston crown 14 and valve plate 5 on
the compression stroke and expelled through discharge valve 6 into
a compressed gases manifold 7. Compressed gases exit the manifold 7
to the outlet port 4 in the shell through a flexible tube 8. To
reduce the stiffness effect of discharge tube 8, the tube is
preferably arranged as a loop or spiral transverse to the
reciprocating axis of the compressor. Intake to the compression
space may be through the piston (with an aperture and valve in the
crown) or through the head, divided to include suction and
discharge manifolds and valves. The illustrated compressors have
suction through the head, with suction manifold 13 and suction
valve 29.
[0047] The illustrated linear compressor 1 has, broadly speaking, a
cylinder part and a piston part connected by a main spring. The
cylinder part includes cylinder housing 10, cylinder head 11, valve
plate 5 and a cylinder 12. The cylinder part also includes stator
parts 15 for a linear electric motor. An end portion 18 of the
cylinder part, distal from the head 11, mounts the main spring
relative to the cylinder part. In the embodiment illustrated in
FIGS. 1 and 2 and the embodiment illustrated in FIGS. 5 and 6, the
main spring is formed as a combination of coil spring 19 and flat
spring 20. In the embodiment illustrated in FIGS. 3 and 4 the main
spring comprises a stack of a plurality of planar springs 16.
[0048] The piston part includes a hollow piston 22 with sidewall 24
and crown 14. A rod 26 connects between the crown 14 and a
supporting body 30 for linear motor armature 17. The linear motor
armature 17 comprises a body of permanent magnet material (such as
ferrite or neodymium) magnetised to provide one or more poles
directed transverse to the axis of reciprocation of the piston
within the cylinder liner. An end portion 32 of armature support
30, distal from the piston 22, is connected with the main
spring.
[0049] In the embodiment of FIGS. 1 and 2 the rod 26 has a flexible
portion 28, located at approximately the centre of the hollow
piston 22. In the embodiment of FIGS. 3 and 4 and the embodiment of
FIGS. 5 and 6 the rod 21 is narrow over its whole length.
[0050] The linear compressor 1 is mounted within the shell 2 on a
plurality of suspension springs to isolate it from the shell. In
use the large outer body of the linear compressor, the cylinder
part, will oscillate along the axis of reciprocation of the piston
part within the cylinder part. In the preferred compressor the
piston part is purposely kept very light compared to the cylinder
part so that the oscillation of the cylinder part is small compared
with the relative reciprocation between the piston part and
cylinder part. In the illustrated form the linear compressor is
mounted on a set of four suspension springs 31 generally positioned
around the periphery. Alternate suspension spring arrangements are
illustrated in PCT/NZ2004/000108. The ends of each suspension
spring fit over elastomeric snubbers connected with the linear
compressor 1 at one end of each spring and connected with the
compressor shell 2 at the other end of each spring.
[0051] Referring to the compressor embodiment of FIGS. 1 and 2,
this illustrates a variation of a compressor of a type disclosed in
our earlier patent application, PCT/NZ2000/000201. In that
application we disclosed a compressor including a linear motor with
a substantially flat permanent magnet armature operating in an air
gap of a stator carried by the cylinder part. The flat armature was
positioned part way along a connecting member extending from the
piston, to one side of the stator, to the main spring, on the other
side of the stator. The connecting member, and therefore the side
forces exerted by the linear electric motor, were laterally
supported at one end by the piston within the cylinder and at the
other end by the lateral stiffness of the main spring.
[0052] In that earlier PCT application we disclosed a main spring
of substantially singular construction involving a double helical
loop of heavy gauge high fatigue strength steel wire. This main
spring provides sufficient lateral stiffness and appropriate axial
stiffness in a single essentially unitary element, but is not a
stock item and is complex to manufacture.
[0053] In one aspect the present invention is a variation of main
spring involving a plurality of separate spring elements working in
combination. For example in the embodiment of FIGS. 1 and 2 and the
embodiment of FIGS. 5 and 6 the main spring comprises a combination
of a coil spring 19 and a planar spring 20. The planar spring 20
provides the lateral stiffness, while the coil spring 19 may add
any desired additional axial stiffness. The planar spring 20 may be
of any conventional form, for example cut from a spring steel
sheet, or may be of a form such as illustrated in our earlier
patent application, PCT/NZ2000/000202.
[0054] Another embodiment is disclosed with reference to FIGS. 3
and 4 in which the main spring comprises the combined stack of four
planar springs 16 all operating together. In this case each of the
planar springs offers both lateral stiffness and axial stiffness.
Planar springs are generally very stiff laterally compared with
their axial stiffness and an embodiment as illustrated in FIGS. 3
and 4 will probably exhibit unnecessarily high lateral stiffness to
obtain a suitable axial stiffness, although it would be appreciated
that the desired axial stiffness will depend on the desired running
speed for the compressor.
[0055] The embodiments of FIGS. 3 and 4 and FIGS. 5 and 6
illustrate a further aspect of the present invention. In the
compressor embodiment of FIGS. 1 and 2 and in the aforementioned
patent application PCT/NZ2000/000201, the piston rod, carrying the
armature 17, is supported against lateral loading by the main
spring at one end and through the piston at the other end. This is
desirable for its compactness and simplicity however it does result
in increased side loading of the piston within the cylinder bore.
This extra side loading can be managed and examples of how to
manage it are given in our patent applications, including in
relation to the embodiment of FIGS. 1 and 2 herein.
[0056] However the embodiments of FIGS. 3 and 4 and 5 and 6 herein
provide an alternative approach to dealing with the lateral forces
resulting from the flat permanent magnet linear motor, where the
motor is located on the member connecting between the main spring
and the piston.
[0057] According to this aspect of the invention a radial or
lateral support is provided to act between the cylinder part 1 and
the connecting member at a location between the armature magnets
and the piston. The support transmits the side loads from the
connecting member directly to the cylinder part 10.
[0058] In the embodiment of FIGS. 3 and 4 the radial support
comprises a planar spring 40 connected at its outer edge 41 to said
cylinder part 10 and at its hub 43 to an end 45 of the armature
supporting body 30. The planar spring 40 offers substantial lateral
stiffness and the armature supporting body 30 is substantially
rigid. Accordingly the lateral loads from the flat permanent
magnetic linear electric motor, which can be substantial, are
supported at one end by flat spring 40 and at the other by the main
spring, which includes further planar springs 16. The planar spring
40 may be mounted within an annular ring portion 42 of cylinder
part 10.
[0059] In an alternative embodiment illustrated in FIGS. 5 and 6
the lateral support is provided by an axial sliding bearing. The
end portion 50 of armature support member 30 is formed to provide a
substantially cylinder shaft of constant diameter. This shaft
portion passes through a sliding bearing 52 forming part of the
cylinder part 10. The sliding bearing 52 may for example comprise a
bush of a suitable low friction hardwearing material. The bush may
for example be a spherical bush of PTFE plastic material (or
similar) retained within a suitable internally spherical housing.
This arrangement will also allow for certain misalignment of the
armature support member 30 relative to the cylinder part 10.
[0060] It is preferred in either case to retain reasonable gas flow
in the vicinity of the armature. Accordingly an open frame
construction, such as illustrated in FIGS. 4 and 5, is used to
support the lateral support (e.g. planar spring or sliding bearing)
relative to the cylinder part 10. Alternatively a plurality of
windows or apertures, such as openings 56 in FIGS. 5 and 6 may be
provided which communicate both with the region of the cylinder
part housing the linear electric motor and with the region of the
cylinder part housing the cylinder and piston. This gases flow
capability into the inside of the cylinder part 10 is also useful
to reduce any gas pressure effects on the back face of the piston
22 and to provide gas flow paths to the back face of piston 22 in
embodiments where suction gases flow is provided through the crown
of the piston rather than through the compressor head.
[0061] In the embodiments of FIGS. 3 to 6 where the armature
supporting member 30 is fully supported against lateral loading, a
preferred connection between the armature supporting member 30 and
the piston 22 has considerable lateral compliancy while retaining
axial stiffness. A suitable linkage would include a narrow metal
rod embedded at one end in the end of the armature supporting
member 30 and at the other end in the piston crown 14. The thin rod
21 should have sufficient compliancy to allow the orientation of
piston 22 to adapt to any misalignment between the armature support
member 30 and the cylinder 12, and sufficient axial stiffness that
it will not buckle as the linear motor and springs drive the piston
toward the cylinder head during the compression stroke of the
compressor in operation.
[0062] While a compressor according to these embodiments, where the
flat permanent magnetic armature is fully supported, may still
provide for aerostatic gas bearings to operate between the cylinder
12 and piston 22 it is expected that the side loads from the piston
22 to the cylinder 12 will be very low. With modern hardware and
coatings the arrangement may operate effectively and with
sufficient longevity without either oil lubrication or aerostatic
bearings.
* * * * *