Linear Compressor
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).
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 INVENTIONLinear 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 INVENTIONIt 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.
In a first aspect the invention may broadly be said to consist in 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.
In a further aspect the invention may broadly be said to consist in 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.
In a still further aspect the invention may broadly be said to consist in 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.
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.
In a still further aspect the invention may broadly be said to consist in 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.
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.
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.
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.
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.
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.
Referring to
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
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.
In the embodiment of
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.
Referring to the compressor embodiment of
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.
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
Another embodiment is disclosed with reference to
The embodiments of
However the embodiments of
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.
In the embodiment of
In an alternative embodiment illustrated in
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
In the embodiments of
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.
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)
Type: Application
Filed: Nov 1, 2005
Publication Date: Oct 22, 2009
Inventor: Ian Campbell McGill (Auckland)
Application Number: 11/577,230
International Classification: F04B 35/04 (20060101);