Patent Grant
6886348
The present invention relates to a Stirling refrigerator used for generation of low temperatures and more specifically, to a structure of a linear motor for reciprocating a piston, a structure of piston elastic support means supporting the piston and a structure of displacer elastic support means supporting a displacer.
A free-piston Stirling refrigerator for generating cold heat is also called reverse Stirling refrigerator in terms of heat cycle. This Stirling refrigerator has a structure as described below with reference to FIG. 12.
A conventional Stirling refrigerator 100E has a cylinder 3 including a linearly reciprocating piston 1 and a displacer 2. Piston 1 and displacer 2 are coaxially structured and a rod 2a formed on displacer 2 passes through a slide hole 1a provided in a central part in the axial direction of piston 1. Piston 1 and displacer 2 are provided to be smoothly sidable along an inner-periphery slide surface 3a of cylinder 3.
At an upper part (on the right side in
Piston 1 is elastically fixed with respect to casing 15 by piston support spring 5 supported by a support member 31 fixed to casing 15. Displacer 2 is also elastically fixed with respect to casing 15 by displacer support spring 6 supported by support member 31.
The internal space formed by cylinder 3 is divided into two spaces by piston 1. A first space is a working space 7 formed at the side of displacer 2 with respect to piston 1. A second space is a back space 8 formed at the opposite side of displacer 2 with respect to piston 1. These two spaces are filled with such a working medium as helium gas at high pressure.
A linear motor 16 includes an inner yoke 13 fixed to cylinder 3, an outer yoke body 9 formed of an outer yoke 9b placed with a predetermined gap between itself and inner yoke 13 to enclose a bobbin/coil 9a, and a permanent magnet 12 attached to piston 1 and placed in the gap between inner yoke 13 and outer yoke 9b. Outer yoke 9b is fixed to casing 15 by a positioning block 30 supported by support member 31.
Piston 1 is axially reciprocated at predetermined cycles by the action of linear motor 16. The reciprocating motion of piston 1 causes the working medium to be repeatedly compressed and expanded in working space 7. Displacer 2 is linearly reciprocated by a change in pressure of the working medium which is compressed and expanded in working space 7. Piston 1 and displacer 2 are configured to reciprocate at the same cycles with a phase difference therebetween of approximately 90°.
Working space 7 is further divided into two spaces by displacer 2. A first working space is a compression space 7a located between piston 1 and displacer 2. A second working space is an expansion space 7b at the top of cylinder 3. Compression space 7a and expansion space 7b are coupled via a regenerator 4. Regenerator 4 is formed of a mesh-shaped copper member for example.
The working medium in expansion space 7b generates cold heat at a cold head 3c at the top of cylinder 3. Reverse Stirling heat cycle such as this principle of generation of cold heat is a well-known art and thus description thereof is not provided here.
Stirling refrigerator 100E of the above-discussed structure, however, has following problems.
First, components of coil/bobbin 9a and outer yoke 9b have low strength and thus these components must be handled carefully in assembly of mass production. Second, in the structure as shown in
One object of the present invention is to provide a Stirling refrigerator by which handling in assembly of mass production of a coil/bobbin and an outer yoke of an outer yoke body constituting a linear motor can be facilitated and a casing can be reduced in size of its outer shape.
A Stirling refrigerator according to the present invention includes a casing, a cylinder provided in the casing, a piston provided in the cylinder to be made movable in a reciprocating manner in the axial direction of the cylinder by a linear motor provided externally to the cylinder, and a displacer provided in the cylinder to form a compression space between itself and the piston in the cylinder and to be movable in a reciprocating manner in the axial direction. The linear motor includes an inner yoke provided on the outer periphery of the cylinder, an outer yoke assembly placed externally to the inner yoke to face the inner yoke, and a permanent magnet placed in a gap between the inner yoke and the outer yoke assembly and coupled to the piston. The outer yoke assembly includes a bobbin/coil placed to face the inner yoke, an outer yoke provided to cover the bobbin/coil from the casing and in the axial direction, and a pair of ring-shaped holding members provided to hold the outer yoke therebetween in the axial direction.
The pair of ring-shaped holding members can thus be provided to achieve an integral structure holding, between the paired holding members, the coil/bobbin and the outer yoke of the outer yoke body which constitutes the linear motor. Accordingly, an integral strength can be obtained from the outer yoke assembly in assembly of the Stirling refrigerator to facilitate handling of the outer yoke assembly.
Preferably, according to the present invention, the Stirling refrigerator further includes displacer support means for elastically supporting the displacer to make the displacer movable in a reciprocating manner in the cylinder, and the displacer support means includes an elastic member coupled to the displacer and elastic-member support means for supporting the elastic member and provided on an end in the axial direction of the outer yoke assembly.
Preferably, according to the present invention, the Stirling refrigerator further includes piston support means for elastically supporting the piston with respect to the casing to make the piston movable in a reciprocating manner in the cylinder, and displacer support means for elastically supporting the displacer with respect to the casing to make the displacer movable in a reciprocating manner in the cylinder. The piston support means includes a first elastic member coupled to the piston and first-elastic-member support means for supporting the first elastic member and fixed to an end in the axial direction of the outer yoke assembly. The displacer support means includes a second elastic member coupled to the displacer and second-elastic-member support means for supporting the second elastic member and fixed to the end in the axial direction of the outer yoke assembly.
This structure can be employed to place the elastic-member support means, the first-elastic-member support means and the second-elastic-member support means on the upper side of the linear motor and thereby reduce the size of the outer shape of the casing. Accordingly, in terms of the strength of the casing, the thickness of the casing can be reduced and thus the weight and cost of the stirling refrigerator can be reduced.
As for the conventional structure, the support means is constituted of a long member passing along the side of the linear motor, resulting in accidental deformation of the long member in assembly of the Stirling refrigerator to make it difficult to define the center of axis of each component. According to the present invention, such a situation can be avoided.
Still preferably, according to the present invention, the first elastic member and the second elastic member are substantially disk-shaped, and the first elastic member has an outer diameter smaller than that of the second elastic member and the first-elastic-member support means is placed at a height lower than that of second-elastic-member support means.
This structure can be employed to prevent one of respective fastening parts at which the first-elastic-member support means and the second-elastic-member support means are respectively fastened from influencing the other fastening part. In other words, as these components are independently fixed to the elastic member support means, the elastic members never come apart and thus the Stirling refrigerator can be improved in its reliability.
Still preferably, according to the present invention, at least one of the elastic-member support means the first-elastic-member support means and the second-elastic-member support means is provided at a ring-shaped base plate. Still more preferably, according to the present invention, at least one of the elastic-member support means, the first-elastic-member support means and the second-elastic-member support means is post-shaped. This structure can be employed to improve the working efficiency in attachment of the first elastic member and the second elastic member each.
Still preferably, according to the present invention, one holding member of the paired holding members is provided integrally with the ring-shaped base plate. This structure can be employed to reduce the number of components.
A structure of a Stirling refrigerator according to each embodiment of the present invention is hereinafter described with reference to the drawings. It is noted that any component which is the same as or corresponding to the component of the conventional art described in connection with
Referring to
Referring to
A structure of outer yoke assembly 11 is described with reference to
Referring to
Referring again to
Referring to
As shown in
Piston-support-spring support member 14A is fixed with respect to upper holding plate 10a of outer yoke assembly 11 with bolts (not shown). For positioning of piston-support-spring support member 14A with respect to upper holding plate 10a, a jig (not shown) is used. Displacer-support-spring support member 14B is also fixed with respect to piston-support-spring support member 14A with bolts.
The Stirling refrigerator according to this embodiment employs an integral structure of outer yoke assembly 11 constituting linear motor 16 and having coil/bobbin 9a and outer yoke 9b that are held between upper holding plate 10a and lower holding plate 10b to obtain an integral strength from outer yoke assembly 11 and facilitate handling of outer yoke assembly 11.
In attachment of outer yoke assembly 11 to cylinder 3, outer yoke assembly 11 is surely positioned with respect to cylinder 3 to make it possible to simultaneously position coil/bobbin 9a, outer yoke 9b, piston-support-spring support member 14A and displacer-support-spring support member 14B with respect to cylinder 3 and accordingly shorten the cycle time for manufacturing the Stirling refrigerator.
Piston-support-spring support member 14A and displacer-support-spring support member 14B are placed at the upper part corresponding to an end in the axial direction of linear motor 16 and thus the size of the outer shape of casing 15 can be reduced. Accordingly, casing 15 can be reduced in thickness in terms of the strength of casing 15 and thus the Stirling refrigerator can be reduced in weight as well as cost.
In addition, while the support member of the conventional structure is constituted of a long member passing along the side of linear motor 16, resulting in accidental deformation of the long member in assembly of the Stirling refrigerator to make it difficult to define the center of the axis of each component, such a situation can be avoided here.
Referring to
As compared with the structure of Stirling refrigerator 100A in the first embodiment discussed above, Stirling refrigerator 100B of the second embodiment includes a support-spring support member 14C instead of piston-support-spring support member 14A and displacer-support-spring support member 14B. An outer yoke assembly 11 in this embodiment has the same structure as that of the Stirling refrigerator 100A in the first embodiment.
According to this embodiment, a piston support spring 5 and a displacer support spring 6 have different outer shapes respectively, and support-spring support member 14C supports both of piston support-spring 5 and displacer support spring 6. Referring to
The Stirling refrigerator of the second embodiment also achieves the function and effect similar to those of the first embodiment as discussed above. Moreover, piston support spring 5 and displacer support spring 6 are formed differently in outer shape and are fixed at different positions and accordingly, it never occurs that one of the fastening parts at which piston support spring 5 and displacer support spring 6 are respectively fastened influences the other fastening part.
Referring to
As compared with the structure of Stirling refrigerator 100B of the second embodiment discussed above, support-spring support member 14D of Stirling refrigerator 100C of the third embodiment has post-shaped support portions for supporting a piston support spring 5 and a displacer support spring 6. An outer yoke assembly 11 here has the same structure as that of Stirling refrigerator 100A of the first embodiment.
Referring to
The Stirling refrigerator according to the third embodiment also achieves the function and effect similar to those of the first and second embodiments discussed above. Moreover, as support portions 141 and 142 are provided at post-shaped portions 143, working efficiency in attachment of piston support spring 5 and displacer support spring 6 can be improved. Further, the Stirling refrigerator can be reduced in weight.
Referring to
As compared with the structure of Stirling refrigerator 100C of the third embodiment discussed above, Stirling refrigerator 100D of the fourth embodiment similarly has post-shaped support portions for supporting a piston support spring 5 and a displacer support spring 6, while an upper holding plate 10a constituting an outer yoke assembly 11 is formed at a base 140 formed of a ring-shaped base plate.
Referring to
The Stirling refrigerator of the fourth embodiment also achieves the function and effect similar to those of the first to third embodiments discussed above. Moreover, by employing the integral structure in which upper holding plate 10a is integrally formed with support-spring support member 14E, the number of components can be reduced.
The embodiments disclosed above should be taken by way of illustration and example and not by way of limitation in terms of every respect. The scope of the present invention is defined not in the description above but in the appended claims and it is intended that the same includes all of modifications and variations equivalent in the meaning and within the scope of the invention.
The Stirling refrigerator according to the present invention has a pair of ring-shaped holding members to achieve an integral structure having the coil/bobbin and the outer yoke of the outer yoke body constituting a linear motor that are held between the holding members. Accordingly, in assembly of the Stirling refrigerator, the integral strength can be obtained from the outer yoke assembly to facilitate handling of the outer yoke assembly.
Moreover, the first-elastic-member support means and the second-elastic-member support means can be placed at an upper part of the linear motor to reduce the size of the outer shape of the casing. In terms of the strength of the casing, the thickness of the casing can thus be reduced and the Stirling refrigerator can be reduced in weight and cost.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2000-334199 | Nov 2000 | JP | national |
This application is the national phase under 35 U.S.C. § 371 of PCT International Application No. PCT/JP01/09527 which has an International filing date of Oct. 30, 2001, which designated the United States of America.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCTJP01/09527 | 10/30/2001 | WO | 00 | 5/1/2003 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO0237036 | 5/10/2002 | WO | A |
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| Number | Date | Country | |
|---|---|---|---|
| 20040093873 A1 | May 2004 | US |
