JP3989874B2 - Linear compressor and Stirling engine equipped with the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a structure of a cylinder in which a piston slides inside a component of a linear compressor and a structure of a linear actuator for reciprocating the piston. More specifically, the present invention relates to the structure of a linear actuator of a Stirling engine.
[0002]
[Prior art]
In recent years, Stirling institutions have attracted attention from the viewpoint of environmental issues. A Stirling engine is an external combustion engine that uses an external heat source to realize a Stirling cycle, which is a reversible cycle, and is less polluting than an internal combustion engine that requires fuel with excellent flammability and ignitability, such as gasoline. It is a heat engine with the advantage of being. A Stirling refrigerator is known as an apparatus to which this Stirling engine is applied.
[0003]
In general, a vapor compression refrigeration cycle is often used as a refrigeration cycle used in a refrigerator or the like. This vapor compression refrigeration cycle uses flon (chlorofluorocarbon) as a refrigerant as a working medium, and obtains a desired cooling performance by utilizing condensation and evaporation of freon.
[0004]
However, it has been pointed out that chlorofluorocarbons used as refrigerants have extremely high chemical stability, and when released into the atmosphere, they reach the stratosphere and destroy the ozone layer. Therefore, in recent years, the use and production of specific chlorofluorocarbons are regulated, and the reverse Stirling cycle has been intensively studied as a next-generation refrigeration cycle that replaces the vapor compression refrigeration cycle using chlorofluorocarbon.
[0005]
In the reverse Stirling cycle, helium gas, hydrogen gas, nitrogen gas, or the like can be employed as a working medium, so that there is no fear of adversely affecting the global environment. Moreover, the reverse Stirling cycle can generate cryogenic temperatures with a small device configuration, and can be applied to various refrigerators and the like. For these reasons, practical use of a Stirling refrigerator using a reverse Stirling cycle is expected.
[0006]
A Stirling refrigerator is a combination of a compressor that compresses and expands refrigerant gas, which is a working medium, using a piston, and an expander that compresses and expands refrigerant gas discharged from the compressor, using a displacer. is there. Conventionally, these compressors and expanders have been generally configured separately, but in recent years, the common use of a cylinder by arranging a piston and a displacer on the same axis is becoming common. . Furthermore, so-called free piston type Stirling refrigerators, which are configured so that the displacer resonates with the piston in response to the pressure change of the refrigerant gas generated by the reciprocating movement of the piston without directly driving the displacer, are becoming common. .
[0007]
In this free piston type Stirling refrigerator, a linear compressor using a linear actuator is used as a compressor. The linear compressor is a compressor configured to reciprocate a piston fitted in a cylinder using a linear actuator. Hereinafter, the structure of a conventional free piston type Stirling refrigerator will be described, and a linear compressor incorporated in the free piston type Stirling refrigerator will also be described.
[0008]
FIG. 5 is a schematic cross-sectional view showing the structure of a conventional free piston type Stirling refrigerator. As shown in FIG. 5, a conventional Stirling refrigerator 100C has a casing 10 filled with a working gas as a working medium. Inside the casing 10, a piston side cylinder 2a and a displacer side cylinder are provided. 2b. The piston side cylinder 2 a and the displacer side cylinder 2 b are arranged on the same axis and constitute one cylinder 2. The cylinder 2 is formed using a nonmagnetic material such as aluminum. The cylinder 2 is filled with the above-described working gas.
[0009]
In the cylinder 2, the piston 3 and the displacer 4 are coaxially fitted and positioned. The piston 3 and the displacer 4 divide the working space in the cylinder 2 into a compression chamber 6 and an expansion chamber 7. The compression chamber 6 is covered with a heat radiating portion (worm head) 8, and the expansion chamber 7 is covered with a heat absorbing portion (cold head) 9. A back pressure chamber 19 surrounded by the casing 10 is located in a space opposite to the displacer 4 when viewed from the piston 3.
[0010]
The piston 3 is driven by a linear actuator 14 that is a driving means. The linear actuator 14 includes an inner yoke 11 fitted to the outer peripheral surface of the piston-side cylinder 2a, an outer yoke assembly 12 disposed to face the outer side of the inner yoke 11, and the inner yoke 11 and the outer yoke assembly. It is comprised from the permanent magnet 13 arrange | positioned in the gap | interval located between the solid bodies 12. Here, the outer yoke assembly 12 is an assembly including a bobbin / coil 12a and an outer yoke 12b. The inner yoke 11 and the outer yoke 12b are made of a magnetic material such as iron.
[0011]
In the linear actuator 14 configured as described above, a magnetic circuit is configured by the inner yoke 11, the outer yoke 12 b and the permanent magnet 13. During the operation of the Stirling refrigerator 100C, a force is applied to the permanent magnet 13 due to a change in magnetic flux generated by inputting a current into the coil. Along with this, the piston 3 connected to the permanent magnet 13 via the connecting member 15 is driven.
[0012]
The piston 3 is connected to a support spring 17 fixed to the casing 10 via a support member 16a, an outer yoke assembly 12, and a support member 16b. For this reason, the piston 3 driven by the linear actuator 14 periodically reciprocates in the cylinder 2. The displacer 4 moves in the cylinder 2 in response to a change in gas pressure caused by the reciprocating movement of the piston 3, but via the support member 16a, the support member 16b, the outer yoke assembly 12, and the support member 16c. Since the support spring 18 fixed to the casing 10 is connected via the displacer rod 4a, the cylinder 2 reciprocates periodically. The reciprocating motion of the piston 3 and the reciprocating motion of the displacer 4 are performed in the same cycle with a constant phase difference during steady operation.
[0013]
A regenerator 5 is provided between the compression chamber 6 and the expansion chamber 7, and these two chambers communicate with each other via the regenerator 5, thereby forming a closed circuit in the Stirling refrigerator 100 </ b> C. . The working gas sealed in the closed circuit flows in accordance with the operation of the piston 3 and the displacer 4, thereby realizing a reverse Stirling cycle.
[0014]
As a document in which the Stirling refrigerator having the above structure is disclosed, there is JP-A-2002-139263 (Patent Document 1).
[0015]
[Patent Document 1]
JP 2002-139263 A
[Problems to be solved by the invention]
As described above, in the conventional Stirling refrigerator, the inner yoke is fitted and assembled to the outer peripheral surface of the cylinder. However, the part where the inner yoke and cylinder are assembled is a part that requires particularly strict dimensional accuracy in the internal structure of the Stirling refrigerator. If this dimensional accuracy is not realized, the desired piston operation can be obtained. Therefore, the product performance will be hindered. Therefore, in order to satisfy this requirement, it is necessary to finish the piston and the cylinder with a considerable processing accuracy, and also a considerable accuracy is required for the assembling accuracy, which causes an increase in cost.
[0017]
Moreover, in the said structure, since a cylinder and an inner side yoke are comprised by a separate member, as the number of parts increased, the assembly operation became complicated and led to the increase in manufacturing cost. Furthermore, it is necessary to take into consideration the thickness of the inner yoke in addition to the thickness of the cylinder, and there is a problem that the outer diameter of the Stirling refrigerator increases.
[0018]
Therefore, the present invention has been made to solve the above-described problems, and can be assembled with high accuracy, can be easily assembled in mass production, and can reduce the outer shape of the casing. An object is to provide a linear compressor and a Stirling engine equipped with the same.
[0019]
[Means for Solving the Problems]
The linear compressor based on this invention is provided with a casing, a cylinder, a piston, and a linear actuator. The cylinder is disposed inside the casing. The piston is driven by a linear actuator to reciprocate in the cylinder. The linear actuator includes an inner yoke, an outer yoke, and a permanent magnet. The inner yoke and the outer yoke are disposed to face each other, and a permanent magnet connected to the piston is disposed in a gap located between the inner yoke and the outer yoke. The cylinder includes a cylindrical portion in which the piston reciprocates, and a flange portion for fixing the cylindrical portion to the casing. At least a portion on the outer peripheral surface side of the cylindrical portion is formed of a magnetic material. As a result, the cylindrical portion and the inner yoke are integrally formed , thereby forming a cylinder / inner yoke body made of a single member. The flange portion is made of a nonmagnetic material.
[0020]
Thus, by forming the cylindrical portion of the cylinder which has been formed as a conventional separate member and the inner yoke in one body, the so high dimensional accuracy is achieved. As a result, the required accuracy can be reliably met, the assembly work can be simplified, and the manufacturing cost can be reduced. In addition, by integrating the cylindrical portion of the cylinder and the inner yoke, the outer diameter of the linear compressor can be reduced. By forming the flange portion of the cylinder from a nonmagnetic material, the magnetic flux formed in the magnetic circuit does not leak outside more than necessary, so that the piston can be efficiently slid.
[0021]
In the linear compressor according to the present invention, the cylinder / inner yoke body is preferably a compression molded product formed using soft magnetic powder.
[0022]
Thus, by forming the cylinder / inner yoke body by compression molding using a soft magnetic material, the cylindrical portion of the cylinder and the inner yoke can be easily integrated .
[0023]
In the linear compressor according to the present invention, the cylinder / inner yoke body is preferably composed of a molded product having a two-layer structure in the radial direction formed by extrusion or pultrusion molding. In addition, it is preferable that the inner peripheral surface layer of the two layers is formed of a nonmagnetic material, and the outer peripheral surface layer of the two layers is formed of a magnetic material.
By comprising in this way, a highly accurate shaping | molding is attained.
[0025]
A Stirling engine according to the present invention includes any one of the linear compressors described above.
[0026]
Thus, by using a Stirling engine including any one of the above-described linear compressors, assembly with high accuracy becomes possible and assembly work at the time of mass production is facilitated. Further, it is possible to provide a Stirling engine in which the outer shape of the casing is reduced.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiment, a Stirling refrigerator that is an application example of a linear compressor will be described as an example.
[0028]
(Embodiment 1)
FIG. 1 is a schematic cross-sectional view showing the structure of a Stirling refrigerator in Embodiment 1 of the present invention. FIG. 2 is an enlarged partial view showing a region II surrounded by a broken line in FIG.
[0029]
(Structure of Stirling refrigerator 100A)
As shown in FIG. 1, a Stirling refrigerator 100A in the present embodiment has a casing 10 filled with a working gas such as helium gas, hydrogen gas, nitrogen gas or the like as a working medium. Inside the casing 10, a cylinder / inner yoke body 1a and a displacer side cylinder 2b are arranged. The cylinder / inner yoke body 1 a and the displacer side cylinder 2 b are arranged on the same axis and constitute one cylinder 2. Here, the cylinder / inner yoke body 1 a has a cylindrical portion that functions as a cylinder and a flange portion for positioning and fixing the cylinder / inner yoke body 1 a with respect to the casing 10. The cylinder 2 is filled with the above-described working gas.
[0030]
Inside the cylinder 2, the piston 3 and the displacer 4 are coaxially fitted and positioned. The piston 3 and the displacer 4 divide the working space in the cylinder 2 into a compression chamber 6 and an expansion chamber 7. The compression chamber 6 is covered with a heat radiating part (worm head) 8. On the other hand, the expansion chamber 7 is covered with a heat absorption part (cold head) 9. A back pressure chamber 19 surrounded by the casing 10 is located in a space opposite to the displacer 4 when viewed from the piston 3.
[0031]
The piston 3 is driven by a linear actuator 14 that is a driving means. The linear actuator 14 includes a cylinder / inner yoke body 1a, an outer yoke assembly 12 disposed to face the outside of the cylinder / inner yoke body 1a, and the cylinder / inner yoke body 1a and the outer yoke assembly 12. And a permanent magnet 13 disposed in a gap located between the two. Here, the outer yoke assembly 12 is an assembly including a bobbin / coil 12a and an outer yoke 12b.
[0032]
In the linear actuator 14 configured as described above, the cylinder / inner yoke body 1a, the outer yoke 12b, and the permanent magnet 13 constitute a magnetic circuit. During the operation of the Stirling refrigerator 100A, a force is applied to the permanent magnet 13 due to a change in magnetic flux generated when a current is input to the coil. Along with this, the piston 3 connected via the connecting member 15 is driven.
[0033]
The piston 3 is connected to a support spring 17 fixed to the casing 10 via a support member 16a, an outer yoke assembly 12, and a support member 16b. For this reason, the piston 3 driven by the linear actuator 14 periodically reciprocates in the cylinder 2. Further, the displacer 4 moves in the cylinder 2 in response to a change in gas pressure caused by the reciprocating movement of the piston 3, but via the support member 16a, the outer yoke assembly 12, the support member 16b, and the support member 16c. Since the support spring 18 fixed to the casing 10 is connected via the displacer rod 4a, the cylinder 2 reciprocates periodically. The reciprocating motion of the piston 3 and the reciprocating motion of the displacer 4 are performed in the same cycle with a constant phase difference during steady operation.
[0034]
A regenerator 5 is disposed between the compression chamber 6 and the expansion chamber 7, and the two chambers communicate with each other via the regenerator 5, thereby forming a closed circuit in the Stirling refrigerator 100 </ b> A. Yes. The working gas sealed in the closed circuit flows in accordance with the operation of the piston 3 and the displacer 4, thereby realizing a reverse Stirling cycle.
[0035]
(Operation of Stirling refrigerator 100A)
Next, the operation of the Stirling refrigerator 100A having the above configuration will be described. First, the linear actuator 14 is operated to drive the piston 3. The piston 3 driven by the linear actuator 14 approaches the displacer 4 and compresses the working gas in the compression chamber 6. As a result, the working gas temperature in the compression chamber 6 rises, but since the heat generated in the compression chamber 6 is released to the outside by the heat radiating portion 8, the working gas temperature in the compression chamber 6 becomes substantially isothermal. Maintained. That is, this process corresponds to an isothermal compression process in a reverse Stirling cycle.
[0036]
Next, the working gas compressed in the compression chamber 6 by the piston 3 flows into the regenerator 5 due to the pressure, and is further sent to the expansion chamber 7. At that time, the heat of the working gas is stored in the regenerator 5. That is, this process corresponds to an isovolumetric cooling process in a reverse Stirling cycle.
[0037]
Subsequently, the high-pressure working gas that has flowed into the expansion chamber 7 expands when the displacer 4 falls to the piston 3 side. As a result, the working gas temperature in the expansion chamber 7 is lowered, but external heat is transferred to the expansion chamber 7 by the heat absorbing portion 9, so that the inside of the expansion chamber 7 is kept substantially isothermal. That is, this process corresponds to an isothermal expansion process of a reverse Stirling cycle.
[0038]
Eventually, when the displacer 4 starts to rise away from the piston 3, the working gas in the expansion chamber 7 passes through the regenerator 5 and returns to the compression chamber 6 side again. At this time, since the heat stored in the regenerator 5 is given to the working gas, the working gas is heated. That is, this process corresponds to a constant volume heating process of a reverse Stirling cycle.
[0039]
By repeating this series of processes (isothermal compression process-isovolume cooling process-isothermal expansion process-isovolume heating process), an inverse Stirling cycle is configured. As a result, the endothermic portion 9 gradually becomes low temperature and has a very low temperature.
[0040]
(Cylinder and inner yoke body 1a)
In the Stirling refrigerator 100A in the present embodiment, the piston-side cylinder and the inner yoke, which are conventionally constituted by separate members, are integrally formed by the same member. That is, the cylinder / inner yoke body 1 a simultaneously functions as a cylinder for sliding the piston inside and as a function of the inner yoke constituting the magnetic circuit of the linear actuator 14.
[0041]
The cylinder / inner yoke body 1a is formed by compression molding using soft magnetic powder. Specifically, it is formed by enclosing a mixture of metal magnetic powder and resin powder in a mold having a desired shape and sintering under a high temperature and high pressure. As the metal magnetic powder, for example, a powder made of iron powder or an iron-based alloy is used. As the resin powder, for example, a powder made of a thermoplastic resin material such as polyethylene is used. The compression molding can be molded with a higher degree of freedom than molding only by grinding or the like, and is a molding method suitable for manufacturing the cylinder / inner yoke body 1a. Further, if the cylinder / inner yoke body 1a is formed using this compression molding, a complicated shape can be freely reproduced, so that the degree of freedom of design is greatly increased as compared with the conventional molding only. become.
[0042]
The compression-molded cylinder / inner yoke body 1a is further subjected to grinding so as to satisfy strict required accuracy. In the conventional Stirling refrigerator, since the dimensional accuracy of the sum of the cylinder dimensions and the inner yoke dimensions is required, the dimensional accuracy of the cylinder and the inner yoke before combination is more strictly required. there were. However, as in the Stirling refrigerator 100A of the present embodiment, the cylinder-inner yoke body 1a in which the piston-side cylinder and the inner yoke are integrally formed is used, so that the required accuracy can be easily achieved by machining such as grinding. Can be realized. In addition, since the assembly accuracy can be managed more easily than in the past, the structure is suitable for mass production. It should be noted that only the inner peripheral surface and the outer peripheral surface that require high dimensional accuracy are sufficient as a portion for actually grinding the cylinder / inner yoke body 1a.
[0043]
Further, as shown in FIG. 2, a coating 20 mainly composed of a resin material is formed on the inner peripheral surface of the cylinder / inner yoke body 1a. This coating 20 is applied in order to improve the slidability of the piston 3, thereby preventing the piston 3 from being worn. As this film 20, for example, fluorine coating, Teflon (R) coating, carbon coating and the like are suitable.
[0044]
(Action / Effect)
As described above, in the Stirling refrigerator in the present embodiment, since the cylinder and the inner yoke are formed as a single body, high dimensional accuracy is realized. For this reason, it becomes possible to easily achieve the strict required accuracy required for this part. For this reason, the performance of the Stirling refrigerator becomes stable and suitable for mass production. In addition, the assembly work can be simplified, and the manufacturing cost can be reduced. Further, by integrating the cylinder and the inner yoke, the outer diameter of the Stirling refrigerator can be reduced.
[0045]
(Embodiment 2)
FIG. 3 is a schematic cross-sectional view showing the structure of the Stirling refrigerator in the second embodiment of the present invention. FIG. 4 is a partially enlarged view showing a region IV surrounded by a broken line in FIG. In addition, about the part similar to the Stirling refrigerator shown in the above-mentioned Embodiment 1, the same code | symbol is attached | subjected in a figure, and the description is not repeated here.
[0046]
(Structure of Stirling refrigerator 100B)
As shown in FIGS. 3 and 4, also in the Stirling refrigerator 100B in the present embodiment, the piston-side cylinder and the inner yoke are integrally formed of the same member. However, unlike the cylinder / inner yoke body 1a in the first embodiment described above, the cylinder / inner yoke body 1b in the present embodiment is composed of only a cylindrical portion. The cylinder / inner yoke body 1b composed only of the cylindrical portion is fixed to the casing 10 via the flange 2c. A positioning projection 2c1 is used to fix the flange 2c and the cylinder / inner yoke body 1b.
[0047]
(Action / Effect)
In the Stirling refrigerator in the present embodiment, since the shape of the cylinder / inner yoke body to be compression-molded is more simplified than the Stirling refrigerator in the first embodiment described above, the manufacturing is further facilitated. You can do it. Further, by forming the flange from a non-magnetic material, the magnetic flux formed in the magnetic circuit does not leak outside more than necessary, and the piston can be efficiently slid.
[0048]
In the present embodiment, the case where the cylinder / inner yoke body composed of only the cylindrical portion is formed by sintering a soft magnetic material has been described as an example. The forming method is not limited to this. For example, you may form by methods other than sintering (for example, cutting, extrusion molding, casting, or these combination) using magnetic materials, such as iron. When extrusion (drawing) molding is adopted, the cylindrical cylinder / inner yoke body has a two-layer structure in the radial direction, the inner peripheral surface side is a layer of nonmagnetic material, and the outer peripheral surface side is made of magnetic material. It is also possible to form a layer. In this case, high-precision molding becomes possible.
[0049]
In the above-described first and second embodiments, the description has been given by exemplifying the free piston type Stirling refrigerator, but the application target of the present invention is not particularly limited to this free piston type Stirling refrigerator. In the first and second embodiments described above, the Stirling refrigerator in which the linear compressor and the displacer are integrated has been described as an example. However, the present invention is not limited to this. The present invention can be applied to any configuration as long as it is a Stirling refrigerator that realizes a reverse Stirling cycle by reciprocating a piston or a displacer. Furthermore, the present invention is naturally applicable not only to Stirling refrigerators but also to general Stirling engines. More broadly, the present invention can be applied not only to Stirling engines but also to other devices having a linear compressor.
[0050]
Thus, the above-described embodiments disclosed herein are illustrative in all respects and are not restrictive. The technical scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
[0051]
【The invention's effect】
According to the present invention, it is possible to provide a linear compressor that can be assembled with high accuracy, can be easily assembled in mass production, and can reduce the outer shape of the casing, and a Stirling engine including the same. Is possible.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing the structure of a Stirling refrigerator in a first embodiment of the present invention.
FIG. 2 is a partially enlarged view showing a region II surrounded by a broken line in FIG. 1 in an enlarged manner.
FIG. 3 is a schematic cross-sectional view showing the structure of a Stirling refrigerator in a second embodiment of the present invention.
4 is a partially enlarged view showing a region IV surrounded by a broken line in FIG. 3 in an enlarged manner.
FIG. 5 is a schematic cross-sectional view showing the structure of a conventional Stirling refrigerator.
[Explanation of symbols]
1a, 1b Cylinder / inner yoke body, 2 cylinder, 2b displacer side cylinder, 2c flange, 2c1 protrusion, 3 piston, 4 displacer, 4a displacer rod, 5 regenerator, 6 compression chamber, 7 expansion chamber, 8 heat dissipation section, 9 Heat absorbing part, 10 casing, 12 outer yoke assembly, 12a bobbin / coil, 12b outer yoke, 13 permanent magnet, 14 linear actuator, 15 connecting member, 16a, 16b, 16c supporting member, 17, 18 supporting spring, 19 back pressure Chamber, 20 coatings, 100A, 100B Stirling refrigerator.

Claims (4)

A casing,
A cylinder disposed inside the casing ;
A piston that reciprocates in the cylinder;
A linear compressor comprising a linear actuator that drives the piston,
The linear actuator is
An inner yoke,
An outer yoke disposed opposite the inner yoke;
A permanent magnet disposed in a gap located between the inner yoke and the outer yoke and connected to the piston,
The cylinder includes a cylindrical portion in which the piston reciprocates, and a flange portion for fixing the cylindrical portion to the casing.
By forming at least part of the outer peripheral surface of the cylindrical portion of a magnetic material, said cylindrical portion and said inner yoke is constituted by a cylinder and inner yoke body formed by integrally molded ,
A linear compressor in which the flange portion is formed of a nonmagnetic material .   The linear compressor according to claim 1, wherein the cylinder / inner yoke body is a compression molded product formed using soft magnetic powder. The cylinder and inner yoke body is a molded product having a two-layer structure in the radial direction formed by extrusion or pultrusion molding,
The linear compression according to claim 1, wherein a layer on the inner peripheral surface side of the two layers is formed of a nonmagnetic material, and a layer on the outer peripheral surface side of the two layers is formed of a magnetic material. Machine.   A Stirling engine comprising the linear compressor according to any one of claims 1 to 3.

Images