Manufacturing method of free piston stirling refrigeration machine

Abstract

To adjust a lift amount by adjusting a phase difference between a piston and a displacer easily and at low cost.SOLUTION: A manufacturing method is for a free piston stirling refrigeration machine 1 which includes: a piston 20 and a displacer 16 capable of reciprocating in a cylinder 10 stored in a casing 2; a displacer spring 34 and a rod 18 for controlling the reciprocation of the displacer 16; a linear motor 21 for driving the piston 20; an expansion chamber E; a compression chamber C; a regenerator 29 arranged between the expansion chamber E and the compression chamber C; an operation gas sealed in the casing 2; a drive circuit 41 for supplying power of a driving frequency f to the linear motor 21; and a vibration absorbing unit 36 for absorbing the vibration of resonance frequency fr. A displacer spring 34 is used which has a spring constant k in which a phase difference between the piston 20 and the displacer 16 is in a predetermined range when the power of the drive frequency f is supplied to the linear motor 21.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a free-piston Stirling refrigerator. [Background technology]

[0002] A known free-piston Stirling refrigerator of this type includes a casing having a cylindrical portion with a closed end and a body portion, a cylinder housed within the casing, a piston and a displacer reciprocating within the cylinder, a displacer spring and rod for controlling the reciprocating motion of the displacer, a linear motor for driving the piston, an expansion chamber formed between the closed end of the casing and the end of the displacer, a compression chamber at least partially defined by the displacer, the piston, and the cylinder, a regenerator disposed between the expansion chamber and the compression chamber, and a working gas sealed within the casing. The piston and displacer of this free-piston Stirling refrigerator reciprocate within the cylinder with a predetermined phase difference. In this free-piston Stirling refrigerator, the phase difference between the piston and the displacer is not fixed. The free-piston Stirling refrigerator also includes a vibration absorption unit for absorbing vibrations caused by the reciprocating motion of the piston and the displacer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3769751 Summary of the Invention [Problem to be solved by the invention]

[0004] The free-piston Stirling refrigerator exhibits good heat transfer performance when the piston and displacer reciprocate within a predetermined range of phase difference. For free-piston Stirling refrigerators with the same structure, the phase difference between the piston and displacer changes depending on the drive frequency f, as shown in Figure 8, and similarly, the heat transfer performance (hereinafter referred to as lift amount) also changes. Specifically, within the range of this graph, as the drive frequency f increases, the phase difference between the piston and displacer decreases, while the lift amount reaches a maximum at a certain frequency. In other words, it can be seen that the phase difference between the piston and displacer can be adjusted by adjusting the drive frequency f, and the lift amount can be adjusted by adjusting the phase difference between the piston and displacer.

[0005] However, adjusting the drive frequency f to adjust the phase difference and lift amount between the piston and displacer causes the following problems. For example, when the drive frequency f is adjusted, it is desirable to make the piston and displacer resonate at that drive frequency f, which ultimately results in the problem of having to change various structural parameters to match the drive frequency f. Another problem is that the program must be changed for each drive frequency f. Furthermore, in a free-piston Stirling refrigerator, vibrations caused by the reciprocating motion of the piston and displacer must be canceled out by a vibration absorbing unit. However, this vibration absorbing unit can only cancel vibrations of a specific frequency, so changing the drive frequency f, i.e., the frequency of the vibrations caused by the reciprocating motion of the piston and displacer, makes it impossible to absorb the vibrations.

[0006] An object of the present invention is to solve the above problems and to provide a method for manufacturing a free-piston Stirling refrigerator in which the lift amount can be adjusted by adjusting the phase difference between the piston and displacer easily and inexpensively. [Means for solving the problem]

[0007] The first aspect of the present invention provides a method for manufacturing a free-piston Stirling refrigerator having a casing having a cylindrical portion whose tip is closed and a body portion, a cylinder housed within the casing, a piston reciprocally mounted within the cylinder, a displacer reciprocally mounted within the cylinder, a displacer spring and rod for controlling the reciprocating motion of the displacer, a linear motor for driving the piston, an expansion chamber formed between the closed tip of the casing and the tip of the displacer, a compression chamber at least partially defined by the displacer, the piston, and the cylinder, a regenerator disposed between the expansion chamber and the compression chamber, a working gas sealed within the casing, a drive circuit for supplying power to the linear motor, and a vibration absorption unit for absorbing vibrations of a predetermined frequency, in which the drive frequency of the power supplied by the drive circuit is set to a fixed value, and the spring constant of the displacer spring is adjusted so that the phase difference between the piston and the displacer is within a predetermined range when power of the fixed drive frequency is supplied to the linear motor.

[0008] a linear motor for driving the piston; an expansion chamber formed between the closed end of the casing and the end of the displacer; a compression chamber at least partially defined by the displacer, the piston, and the cylinder; a regenerator disposed between the expansion chamber and the compression chamber; a working gas sealed within the casing; a drive circuit for supplying power to the linear motor; and a vibration absorption unit for absorbing vibrations of a predetermined frequency. In this method, the drive frequency of the power supplied by the drive circuit is set to a fixed value, and the porosity of the regenerator is adjusted so that the phase difference between the piston and the displacer is within a predetermined range when power of the fixed drive frequency is supplied to the linear motor.

[0009] a linear motor for driving the piston; an expansion chamber formed between the closed end of the casing and the end of the displacer; a compression chamber at least partially defined by the displacer, the piston, and the cylinder; a regenerator disposed between the expansion chamber and the compression chamber; a working gas sealed within the casing; a drive circuit for supplying power to the linear motor; and a vibration absorption unit for absorbing vibrations of a predetermined frequency. In this method, the drive frequency of the power supplied by the drive circuit is fixed, and the pressure of the working gas is adjusted so that the phase difference between the piston and the displacer falls within a predetermined range when power of the fixed drive frequency is supplied to the linear motor.

[0010] Furthermore, a fourth aspect of the present invention provides a method for manufacturing a free-piston Stirling refrigerator comprising: a casing having a cylindrical portion whose tip is closed and a body portion; a cylinder housed within the casing; a piston reciprocally mounted within the cylinder; a displacer reciprocally mounted within the cylinder; a displacer spring and rod for controlling the reciprocating motion of the displacer; a linear motor for driving the piston; an expansion chamber formed between the closed tip of the casing and the tip of the displacer; a compression chamber at least partially defined by the displacer, the piston, and the cylinder; a regenerator disposed between the expansion chamber and the compression chamber; a working gas sealed within the casing; a drive circuit for supplying power to the linear motor; and a vibration absorption unit for absorbing vibrations of a predetermined frequency, wherein the drive frequency of the power supplied by the drive circuit is set to a fixed value, and the mass of the displacer assembly including the displacer and rod is adjusted so that the phase difference between the piston and the displacer falls within a predetermined range when power of the fixed drive frequency is supplied to the linear motor. [Effects of the Invention]

[0011] The manufacturing method of the free-piston Stirling refrigerator according to claims 1 to 4 of the present invention, as described above, makes it possible to keep the phase difference between the piston and displacer within a predetermined range and increase the lift amount while keeping the drive frequency, i.e., the frequency of the reciprocating motion of the piston and displacer, constant. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is an explanatory diagram showing the structure of a free-piston Stirling refrigerator according to each embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged explanatory view of a part of the regenerator of the first embodiment. [Figure 3] 1 is a simple block diagram of the electrical circuit. [Figure 4]5 is a graph illustrating the relationship between the drive frequency, the phase difference, and the lift amount in the first embodiment of the present invention. [Figure 5] 10 is a graph illustrating the relationship between the drive frequency, the phase difference, and the lift amount in the second embodiment of the present invention. [Figure 6] 10 is a graph illustrating the relationship between the drive frequency, the phase difference, and the lift amount in the third embodiment of the present invention. [Figure 7] 10 is a graph illustrating the relationship between the drive frequency, the phase difference, and the lift amount in the fourth embodiment of the present invention. [Figure 8] 10 is a graph illustrating a general relationship between a drive frequency, a phase difference, and a lift amount. DETAILED DESCRIPTION OF THE INVENTION

[0013] A first embodiment of the present invention will be described below with reference to FIGS. 1 to 4. Because the operation and function of a free-piston Stirling refrigerator are well known, they will not be described again in this embodiment. Instead, the structure, manufacturing method, and the effects of this manufacturing method will be described. Reference numeral 1 denotes a gamma-type free-piston Stirling refrigerator, which is a free-piston Stirling refrigerator of the present invention. This Stirling refrigerator 1 has a metal casing 2. The casing 2 includes a cylindrical section 3 and a trunk section 4. The cylindrical section 3 includes a closed tip section 5, an intermediate section 6, and a base section 7. The trunk section 4 includes a main trunk section 8 that is coaxial with the cylindrical section 3, with respect to axis X1, and a pair of bottomed cylindrical drive unit covers 9, 9. The pair of drive unit covers 9, 9 are coaxial with axis X2, with axis X1 and axis X2 intersecting at right angles. The cylindrical section 3, main trunk section 8, and drive unit covers 9, 9 are formed in a cross shape.

[0014] A cylinder 10 is provided inside the casing 2. The cylinder 10 includes a first cylinder 11, a second cylinder 12, a pair of piston cylinders 13, 13, and a cylindrical connection space 14 connecting these cylinders. The first cylinder 11 and the second cylinder 12 are provided with the connection space 14 sandwiched between them. The first cylinder 11, the second cylinder 12, and the connection space 14 are provided coaxially with respect to the axis X1. The pair of piston cylinders 13, 13 are provided with the connection space 14 sandwiched between them and are also provided coaxially with respect to the axis X2. The pair of piston cylinders 13, 13 are provided perpendicular to the first cylinder 11, the second cylinder 12, and the connection space 14. That is, the cylinder 10, consisting of the first cylinder 11, the second cylinder 12, the pair of piston cylinders 13, 13, and the connection space 14, is formed in a cross shape. The pair of piston cylinders 13, 13 are provided at two-fold symmetry with respect to the axis X1. Furthermore, the first cylinder 11 is formed with a communication hole 15 that communicates the inside and outside of the first cylinder 11. The cylinder 10 is formed by casting, such as die casting, using a non-magnetic metal, and the inner and outer peripheries of the cylinder 10 are machined after casting.

[0015] A first cylinder 11 constituting the cylinder 10 is provided coaxially with respect to the cylindrical portion 3 inside the cylindrical portion 3 that constitutes the casing 2. A second cylinder 12 constituting the cylinder 10, a pair of piston cylinders 13, 13, and a connection space 14 are provided inside the trunk portion 4 that constitutes the casing 2. The second cylinder 12 and the connection space 14 are provided coaxially with respect to the main trunk portion 8. Meanwhile, the pair of piston cylinders 13, 13 are provided coaxially with respect to the pair of drive unit covers 9, 9.

[0016] A cylindrical displacer 16 is housed inside the first cylinder 11 so as to be reciprocable in the direction of axis X1. The displacer 16 has a distal end surface 16A and a proximal end surface 16B. Meanwhile, a cylindrical displacer drive 17 is housed inside the second cylinder 12 so as to be reciprocable in the direction of axis X1. The displacer drive 17 has an inner end surface 17A. The displacer 16 and the displacer drive 17 are connected by a rod 18. The displacer 16, the displacer drive 17, and the rod 18 form a displacer assembly 19. The displacer assembly 19 has a mass m. The rod 18 is made of a relatively hard metal, and its diameter is smaller than that of the displacer drive 17. Thus, even if the diameter of the rod 18 is smaller than that of the displacer drive 17, the coaxiality of the displacer 16 and the displacer drive 17, which are separated by a distance, can be ensured by forming the rod 18 from a relatively hard metal as described above. The diameter of the displacer drive 17 is smaller than the diameter of the displacer 16. Furthermore, within the pair of drive unit covers 9, pistons 20 are housed inside the pair of piston cylinders 13, respectively, so as to be able to reciprocate in the direction of the axis X2. These pistons 20 have the same mass and are formed in the same shape. The tip ends of these pistons 20 have opposing surfaces 20A, respectively, and are coaxially connected to linear motors 21. These linear motors 21 are composed of movers 22 connected to the base ends of the pistons 20 and stators 23 provided adjacent to the movers 22. The movers 22 are composed of short cylindrical frames 24 extending coaxially from the outer peripheries of the piston cylinders 13, and permanent magnets 25 fixed to the frames 24. The stators 23, 23 are configured to have annular electromagnetic coils 26, 26 and electromagnetic cores 27, 27 provided in the vicinity of the outer periphery of the permanent magnets 25, 25.

[0017] The pair of movers 22, 22 have the same physical configuration. That is, the movers 22, 22 have the same mass and the same shape, and the magnetic forces of the two permanent magnets 25, 25 are also the same. Therefore, the mass of the moving elements consisting of the pistons 20, 20 and the movers 22, 22 is the same. Similarly, the pair of stators 23, 23 also have the same physical configuration. That is, the material, thickness, and number of turns of the wire that makes up the two electromagnetic coils 26, 26 are the same, and the electrical and magnetic characteristics of the two electromagnetic cores 27, 27 are also the same.

[0018] An expansion chamber E is formed between the tip surface 16A of the displacer 16 and the tip end 5 of the cylindrical portion 3, and a gap 28 formed between the tip of the first cylinder 11 and the inner surface of the tip end 5 of the cylindrical portion provides communication between the inside and outside of the first cylinder 11. A regenerator 29 is provided in the intermediate portion 6 between the inner periphery of the cylindrical portion 3 and the outer periphery of the first cylinder 11, and the communication hole 15 is formed in the base portion 7. The regenerator 29 is formed into a cylindrical shape by rolling up a synthetic resin film 29F having a thickness T and on which numerous protrusions 29P are formed, resulting in a structure in which a gap G equal to the height H of the protrusions 29P is formed between the film 29F. Heat absorption fins 30 are provided between the inner periphery of the tip end 5 of the cylindrical portion 3 and the outer periphery of the tip of the first cylinder 11, and heat exhaust fins 31 are provided between the regenerator 29 and the communication hole 15 between the inner periphery of the cylindrical portion 3 and the outer periphery of the first cylinder 11. A path 33 is formed that runs from the inner tip of the first cylinder 11 through the gap 28, heat absorption fins 30, regenerator 29, heat exhaust fins 31, and communication hole 15 to the compression chamber C inside the cylinder 10. The compression chamber C is a space within the cylinder 10 that is surrounded by the base end surface 16B of the displacer 16, the inner end surface 17A of the displacer drive 17, and the opposing surfaces 20A, 20A of the pistons 20, 20.

[0019] A displacer spring 34 for controlling the operation of the displacer drive 17 and the displacer 16 is connected to the displacer drive 17. Furthermore, piston springs 35 for controlling the operation of the pistons 20 are connected to supports 24 for connecting to the pistons 20.

[0020] 1 denotes a vibration absorbing unit provided at the end of the main body 8 in the direction of the axis X1, and a leaf spring 39 and a balance weight 40 are arranged so as to overlap coaxially via an attachment part 37 arranged coaxially with the axis X1 of the first cylinder 11 and the second cylinder 12 and a connection part 38 connected to this attachment part 37. The vibration absorbing unit 36 ​​acts to absorb vibrations at a resonance frequency fr determined by the spring constant of the leaf spring 39 and the mass of the balance weight 40.

[0021] 3 is a block diagram of an electrical circuit for operating the free-piston Stirling refrigerator 1. Reference numeral 41 denotes a drive circuit, which converts DC current supplied from power receiving terminals 42, 42 into AC current of a predetermined frequency (hereinafter referred to as drive frequency f), or converts it into a pseudo-AC current using PWM or the like, and supplies it to the electromagnetic coils 26, 26 of the stators 23, 23 of the linear motors 21, 21. By supplying AC current to the electromagnetic coils 26, 26 in this way, the pistons 20, 20 connected to the mover 21 reciprocate at a frequency fp, which is the same as the drive frequency f. Similarly, the displacer 16 and displacer drive 17 also reciprocate at a frequency fd, which is the same as the drive frequency f, in conjunction with the reciprocation of the pistons 20, 20. (∴f=fp=fd) As described above, the pair of pistons 20, 20, the pair of movers 22, 22, and the pair of stators 23, 23 all have the same physical configuration, and therefore, by reciprocating the pistons 20, 20 in opposite directions at the same frequency fp and in the same phase, vibrations caused by the reciprocating motion of these pistons 20, 20 are canceled out. Therefore, the vibrations absorbed by the vibration absorbing unit 36 ​​are vibrations of frequency fd caused by the reciprocating motion of the displacer 16 and displacer drive 17. If fd = fr, then the vibrations caused by the reciprocating motion of the displacer 16 and displacer drive 17 are canceled out by the vibration absorbing unit 36.

[0022] Furthermore, a working gas is sealed inside the casing 2. This working gas is sealed so that the pressure P becomes a predetermined value under predetermined temperature conditions. Furthermore, the working gas used is helium, which is the gas that is closest to an ideal gas among all real gases.

[0023] FIG. 4 is a graph for explaining the relationship among the driving frequency, the phase difference, and the lift amount. In this graph, the broken line is a curve showing the relationship between the "driving frequency f (Hz)" and the "phase difference (°) between the pistons 20, 20 / the displacer 16". On the other hand, the solid line is a curve showing the relationship between the "driving frequency f (Hz)" and the "lift amount (W)". In the graph, the points indicated by ● and ■ are the values when the spring constant k = k1 of the displacer spring 34, and the points indicated by ○ and □ are the values when the spring constant k = k2 of the displacer spring 34. Note that k1 < k2. Also, the data of ●■ and ○□ were measured under the condition that other than the value of the spring constant k of the displacer spring 34 are equal. As can be understood from this graph, at least in the measured range, if the value of the driving frequency f is the same, the larger the value of the spring constant k of the displacer spring 34, the larger the phase difference between the pistons 20, 20 and the displacer 16. Also, the larger the value of the spring constant k of the displacer spring 34, the higher the driving frequency f at which the phase difference between the pistons 20, 20 and the displacer 16 becomes the same value. As a result, the larger the value of the spring constant k of the displacer spring 34, the higher the value of the driving frequency f at which the lift amount becomes maximum. Conversely, in order to make the lift amount maximum at a predetermined driving frequency f, it suffices to adjust the value of the spring constant k of the displacer spring 34. In this example, the lift amount becomes a good value in the range where the phase difference between the pistons 20, 20 and the displacer 16 is approximately 55 to 80°.

[0024] The manufacturing method of adjusting the spring constant k of the displacer spring 34 while fixing the drive frequency f has several advantages. First, by keeping the drive frequency f constant, there is no need to change the program of the drive circuit 41. Second, by configuring components other than the displacer spring 34 to specified specifications and using the displacer spring 34 with a spring constant k that provides the desired performance at the drive frequency f, it is possible to mass-produce products with the desired performance. Furthermore, by using the displacer spring 34 with a spring constant k that provides the desired performance when f = fp = fd = fr, it is possible to reliably cancel vibrations of the free-piston Stirling refrigerator 1 without adjusting the vibration absorption unit 36.

[0025] As described above, the present invention provides a compressor comprising a casing 2 having a cylindrical portion 3 with a closed tip end and a body portion 4, a cylinder 10 housed in the casing 2, pistons 20, 20 reciprocally disposed within the cylinder 10, a displacer 16 reciprocally disposed within the cylinder 10, a displacer spring 34 and a rod 18 for controlling the reciprocating motion of the displacer 16, linear motors 21, 21 for driving the pistons 20, 20, an expansion chamber E formed between the closed tip end 5 of the casing 2 and the tip end surface 16A of the displacer 16, a compression chamber C at least partially defined by the displacer 16, the pistons 20, 20, and the cylinder 10, a regenerator 29 disposed between the expansion chamber E and the compression chamber C, a working gas sealed within the casing 2, This is a method for manufacturing a free-piston Stirling refrigerator 1 having a drive circuit 41 that supplies power to the linear motors 21, 21 and a vibration absorption unit 36 ​​that absorbs vibrations of a predetermined frequency fr, where the drive frequency f of the power supplied by the drive circuit 41 is set to a fixed value, and by using the displacer spring 34 with a spring constant k that brings the phase difference between the pistons 20, 20 and the displacer 16 into a predetermined range when power of the fixed drive frequency f is supplied to the linear motors 21, 21, it is possible to mass-produce products with desired performance, and by using the displacer spring 34 with a spring constant k that gives the desired performance when f = fr, it is possible to manufacture the free-piston Stirling refrigerator 1 that can reliably cancel vibrations without adjusting the vibration absorption unit 36.

[0026] Next, a second embodiment of the present invention will be described with reference to Figures 1 to 3 and 5. The free-piston Stirling refrigerator 1 manufactured according to this embodiment is similar to that of the first embodiment, and therefore a description of the structure will be omitted.

[0027] FIG. 5 is a graph for explaining the relationship among the driving frequency, the phase difference, and the lift amount. In this graph, the broken line is a curve showing the relationship between the "driving frequency f (Hz)" and the "phase difference (°) between the pistons 20, 20 / the displacer 16". On the other hand, the solid line is a curve showing the relationship between the "driving frequency f (Hz)" and the "lift amount (W)". In the graph, the points indicated by ● and ■ are the values when the porosity V of the regenerator 29 is V = V1, and the points indicated by ○ and □ are the values when the porosity V of the regenerator 29 is V = V2. Note that V1 < V2. And as described above, since the thickness of the film 29F of the regenerator 29 is T, and the height H (H1, H2) of the protrusion 29P is regarded as the interval between the films 29F that define the gap G, the porosity V of the regenerator 29 can be calculated. That is, when the height of the protrusion 29P is H1, the porosity V of the regenerator 29 is V = V1, when the height of the protrusion 29P is H2, the porosity V of the regenerator 29 is V = V2, and H1 < H2. Also, the data of ●■ and ○□ were measured under the condition that other than the value of the porosity V of the regenerator 29 is equal. As can be understood from this graph, at least in the measured range, if the value of the driving frequency f is the same, the larger the value of the porosity V of the regenerator 29, the larger the phase difference between the pistons 20, 20 and the displacer 16. Also, the larger the value of the porosity V of the regenerator 29, the higher the driving frequency f at which the phase difference between the pistons 20, 20 and the displacer 16 becomes the same value. Also, the larger the value of the porosity V, the larger the value of the lift amount. As a result, the larger the value of the porosity V of the regenerator 29, the higher the value of the driving frequency f at which the lift amount becomes maximum. Conversely, in order to make the lift amount maximum at a predetermined driving frequency f, the value of the porosity V of the regenerator 29 may be adjusted. In this example, the lift amount becomes a good value in the range where the phase difference between the pistons 20, 20 and the displacer 16 is approximately 55 to 80°.

[0028] The manufacturing method of adjusting the porosity V of the regenerator 29 while fixing the drive frequency f has several advantages. First, by keeping the drive frequency f constant, there is no need to change the program of the drive circuit 41. Second, by configuring the components other than the regenerator 29 to specified specifications and using the regenerator 29 with a porosity V that provides the desired performance at the drive frequency f, it is possible to mass-produce products with the desired performance. Furthermore, by using the regenerator 29 with a porosity V that provides the desired performance when f = fp = fd = fr, it is possible to reliably cancel vibrations of the free-piston Stirling refrigerator 1 without adjusting the vibration absorption unit 36.

[0029] As described above, the present invention provides a compressor comprising a casing 2 having a cylindrical portion 3 with a closed tip end and a body portion 4, a cylinder 10 housed in the casing 2, pistons 20, 20 provided reciprocally within the cylinder 10, a displacer 16 provided reciprocally within the cylinder 10, a displacer spring 34 and a rod 18 for controlling the reciprocating motion of the displacer 16, linear motors 21, 21 for driving the pistons 20, 20, an expansion chamber E formed between the closed tip end 5 of the casing 2 and the tip end surface 16A of the displacer 16, a compression chamber C at least partially defined by the displacer 16, the pistons 20, 20, and the cylinder 10, a regenerator 29 disposed between the expansion chamber E and the compression chamber C, and a compressor sealed within the casing 2. a drive circuit 41 that supplies power to the linear motors 21, 21, and a vibration absorption unit 36 ​​that absorbs vibrations at a predetermined frequency fr; wherein the drive frequency f of the power supplied by the drive circuit 41 is set to a fixed value, and by using the regenerator 29 with a porosity V that causes the phase difference between the pistons 20, 20 and the displacer 16 to fall within a predetermined range when power of the fixed drive frequency f is supplied to the linear motors 21, 21, products with desired performance can be mass-produced; and by using the regenerator 29 with a porosity V that achieves the desired performance when f = fr, the free-piston Stirling refrigerator 1 can be manufactured in such a way that vibrations can be reliably canceled out without adjusting the vibration absorption unit 36.

[0030] Next, a third embodiment of the present invention will be described with reference to Figures 1 to 3 and 6. The free-piston Stirling refrigerator 1 manufactured according to this embodiment is similar to those of the first and second embodiments, and therefore a description of the structure will be omitted.

[0031] FIG. 6 is a graph for explaining the relationship among the drive frequency, the phase difference, and the lift amount. In this graph, the broken line is a curve showing the relationship between the "drive frequency f (Hz)" and the "phase difference (°) between the pistons 20, 20 / the displacer 16". On the other hand, the solid line is a curve showing the relationship between the "drive frequency f (Hz)" and the "lift amount (W)". In the graph, the points indicated by ● and ■ are the values when the pressure P = P1 of the working gas in the casing 2, and the points indicated by ○ and □ are the values when the pressure P = P2 of the working gas in the casing 2. Note that P1 < P2. Also, the data of ●■ and ○□ are measured under the condition that other than the value of the pressure P of the working gas are equal. As can be understood from this graph, at least in the measured range, if the value of the drive frequency f is the same, the larger the value of the pressure P of the working gas, the larger the phase difference between the pistons 20, 20 and the displacer 16. Also, the larger the value of the pressure P of the working gas, the higher the drive frequency f at which the phase difference between the pistons 20, 20 and the displacer 16 becomes the same value. Also, the smaller the pressure P of the working gas, the larger the value of the lift amount. As a result, the larger the value of the pressure P of the working gas, the higher the value of the drive frequency f at which the lift amount becomes maximum. Also, if the drive frequency f is the same, the smaller the pressure P of the working gas, the larger the value of the lift amount. Conversely, in order to make the lift amount maximum at a predetermined drive frequency f, it is only necessary to adjust the value of the pressure P of the working gas. In this example, the lift amount becomes a good value in the range where the phase difference between the pistons 20, 20 and the displacer 16 is approximately 55 to 80°.

[0032] There are several advantages to the manufacturing method in which the value of the driving frequency f is fixed and the value of the working gas pressure P is adjusted. First, by keeping the driving frequency f constant, there is no need to change the program of the drive circuit 41. Second, by configuring all components to specified specifications and sealing the working gas in the casing 2 at a pressure P that provides the desired performance at the driving frequency f, it is possible to mass-produce products with the desired performance. Furthermore, by sealing the working gas in the casing 2 at a pressure P that provides the desired performance, where f = fp = fd = fr, it is possible to reliably cancel vibrations of the free-piston Stirling refrigerator 1 without adjusting the vibration absorption unit 36.

[0033] As described above, the present invention provides a compressor comprising a casing 2 having a cylindrical portion 3 with a closed tip end and a body portion 4, a cylinder 10 housed in the casing 2, pistons 20, 20 reciprocally provided in the cylinder 10, a displacer 16 reciprocally provided in the cylinder 10, a displacer spring 34 and a rod 18 for controlling the reciprocating motion of the displacer 16, linear motors 21, 21 for driving the pistons 20, 20, an expansion chamber E formed between the closed tip end 5 of the casing 2 and the tip end surface 16A of the displacer 16, a compression chamber C at least partially defined by the displacer 16, the pistons 20, 20, and the cylinder 10, a regenerator 29 disposed between the expansion chamber E and the compression chamber C, a working gas sealed in the casing 2, This method for manufacturing a free-piston Stirling refrigerator 1 has a drive circuit 41 that supplies power to the linear motors 21, 21 and a vibration absorption unit 36 ​​that absorbs vibrations of a predetermined frequency fr, wherein the drive frequency f of the power supplied by the drive circuit 41 is set to a fixed value, and when power of the fixed drive frequency f is supplied to the linear motors 21, 21, the working gas is sealed in the casing 2 at a pressure P that brings the phase difference between the pistons 20, 20 and the displacer 16 into a predetermined range, making it possible to mass-produce products with desired performance, and by sealing the working gas in the casing 2 at a pressure P that gives the desired performance when f = fr, it is possible to manufacture the free-piston Stirling refrigerator 1 that can reliably cancel vibrations without adjusting the vibration absorption unit 36.

[0034] Next, a fourth embodiment of the present invention will be described with reference to Figures 1 to 3 and 7. The free-piston Stirling refrigerator 1 manufactured according to this embodiment is similar to those of the first to third embodiments, and therefore a description of the structure will be omitted.

[0035] FIG. 7 is a graph for explaining the relationship among the drive frequency, the phase difference, and the lift amount. In this graph, the broken line is a curve showing the relationship between the "drive frequency f (Hz)" and the "phase difference (°) between the pistons 20, 20 / the displacer 16". On the other hand, the solid line is a curve showing the relationship between the "drive frequency f (Hz)" and the "lift amount (W)". In the graph, the points indicated by ● and ■ are the values when the mass m = m1 of the displacer assembly 19, and the points indicated by ○ and □ are the values when the mass m = m2 of the displacer assembly 19. Note that m1 < m2. Also, the data of ●■ and ○□ were measured under the condition that other values than the value of the mass m of the displacer assembly 19 are equal. As can be understood from this graph, at least in the measured range, if the value of the drive frequency f is the same, the larger the value of the mass m of the displacer assembly 19, the larger the phase difference between the pistons 20, 20 and the displacer 16. Also, the larger the value of the mass m of the displacer assembly 19, the higher the drive frequency f at which the phase difference between the pistons 20, 20 and the displacer 16 becomes the same value. As a result, the larger the value of the mass m of the displacer assembly 19, the higher the value of the drive frequency f at which the lift amount becomes maximum. Conversely, in order to make the lift amount maximum at a predetermined drive frequency f, it is only necessary to adjust the value of the mass m of the displacer assembly 19. As a method for adjusting the mass of the displacer assembly 19, the mass of the displacer 16 is adjusted, the mass of the displacer drive 17 is adjusted, or an additional mass is added to the displacer assembly 19. In this example, the lift amount becomes a good value in the range where the phase difference between the pistons 20, 20 and the displacer 16 is approximately 55 to 80°.

[0036] There are several advantages to the manufacturing method in which the drive frequency f is fixed and the mass m of the displacer assembly 19 is adjusted. First, by keeping the drive frequency f constant, there is no need to change the program of the drive circuit 41. Second, by configuring the components other than the displacer assembly 19 to specified specifications and using the displacer assembly 19 with a mass m that provides the desired performance at the drive frequency f, it is possible to mass-produce products with the desired performance. Furthermore, by using the displacer assembly 19 with a mass m that provides the desired performance when f = fp = fd = fr, it is possible to reliably cancel vibrations of the free-piston Stirling refrigerator 1 without adjusting the vibration absorption unit 36.

[0037] As described above, the present invention comprises a casing 2 having a cylindrical portion 3 with a closed tip end and a body portion 4, a cylinder 10 housed in the casing 2, pistons 20, 20 provided so as to be able to reciprocate within the cylinder 10, a displacer 16 provided so as to be able to reciprocate within the cylinder 10, a displacer spring 34 and a rod 18 for controlling the reciprocating motion of the displacer 16, linear motors 21, 21 for driving the pistons 20, 20, an expansion chamber E formed between the closed tip end 5 of the casing 2 and the tip end surface 16A of the displacer 16, a compression chamber C at least partially defined by the displacer 16, the pistons 20, 20 and the cylinder 10, a regenerator 29 disposed between the expansion chamber E and the compression chamber C, and an operating device enclosed within the casing 2. This is a method for manufacturing a free-piston Stirling refrigerator 1 having a gas, a drive circuit 41 that supplies power to the linear motors 21, 21, and a vibration absorption unit 36 ​​that absorbs vibrations at a predetermined frequency fr, wherein the drive frequency f of the power supplied by the drive circuit 41 is set to a fixed value, and by using the displacer assembly 19 with a mass m that causes the phase difference between the pistons 20, 20 and the displacer 16 to fall within a predetermined range when power of the fixed drive frequency f is supplied to the linear motors 21, 21, it is possible to mass-produce products with desired performance, and by using the displacer assembly 19 with a mass that achieves the desired performance when f = fr, it is possible to manufacture the free-piston Stirling refrigerator 1 that can reliably cancel vibrations without adjusting the vibration absorption unit 36.

[0038] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention. For example, in the first embodiment, a displacer spring 34 with a spring constant k that achieves the desired performance is used. However, multiple displacer springs may be stacked and the number of stacked displacer springs may be adjusted to achieve the spring constant k that achieves the desired performance. Furthermore, in the second embodiment, the height H of the protrusions 29P is adjusted to achieve the regenerator 29 with a porosity V that achieves the desired performance. However, the regenerator 29 with a porosity V that achieves the desired performance may be achieved by selecting one of several films with different thicknesses. Furthermore, although the above embodiments have been described with respect to the manufacture of a gamma-type free-piston Stirling refrigerator, the present invention is also applicable to the manufacture of a beta-type free-piston Stirling refrigerator. [Explanation of symbols]

[0039] 1. γ-type free-piston Stirling refrigerator 2 Casing 3 Cylindrical part 4. Torso 10 cylinders 16 Displacer 16A Tip surface 16B Proximal surface 18 Rod 19 Displacer assembly 20 pistons 21 Linear motor 29 Regenerator 34 Display Spring 36 Vibration absorption unit 41 Drive circuit C Compression chamber E Expansion chamber P, P1, P2 Working gas pressure V, V1, V2 Porosity of regenerator 29 f driving frequency fp Piston 19 vibration frequency fd Displacer 16 frequency fr Resonance frequency of vibration absorption unit 36 k, k1, k2: Spring constants of the displacer spring 34 m, m1, m2 Mass of displacer assembly 19

Claims

1. a linear motor for driving the piston; an expansion chamber formed between the closed end of the casing and the end of the displacer; a compression chamber at least partially defined by the displacer, the piston, and the cylinder; a regenerator disposed between the expansion chamber and the compression chamber; a working gas sealed within the casing; a drive circuit for supplying power to the linear motor; and a vibration absorption unit for absorbing vibrations of a predetermined frequency, the method comprising the steps of: a drive frequency of the power supplied by the drive circuit is fixed, and the spring constant of the displacer spring is adjusted so that the phase difference between the piston and the displacer falls within a predetermined range when power of the fixed drive frequency is supplied to the linear motor.

2. a linear motor for driving the piston; an expansion chamber formed between the closed end of the casing and the end of the displacer; a compression chamber at least partially defined by the displacer, the piston, and the cylinder; a regenerator disposed between the expansion chamber and the compression chamber; a working gas sealed within the casing; a drive circuit for supplying power to the linear motor; and a vibration absorption unit for absorbing vibrations of a predetermined frequency, the method comprising the steps of: a driving frequency of the power supplied by the drive circuit is fixed, and the void fraction of the regenerator is adjusted so that a phase difference between the piston and the displacer falls within a predetermined range when power of the fixed driving frequency is supplied to the linear motor.

3. a linear motor for driving the piston; an expansion chamber formed between the closed end of the casing and the end of the displacer; a compression chamber at least partially defined by the displacer, the piston, and the cylinder; a regenerator disposed between the expansion chamber and the compression chamber; a working gas sealed within the casing; a drive circuit for supplying power to the linear motor; and a vibration absorption unit for absorbing vibrations of a predetermined frequency, the method comprising the steps of: a driving frequency of the power supplied by the drive circuit is fixed, and the pressure of the working gas is adjusted so that the phase difference between the piston and the displacer falls within a predetermined range when power of the fixed driving frequency is supplied to the linear motor.

4. a linear motor for driving the piston; an expansion chamber formed between the closed end of the casing and the end of the displacer; a compression chamber at least partially defined by the displacer, the piston, and the cylinder; a regenerator disposed between the expansion chamber and the compression chamber; a working gas sealed within the casing; a drive circuit for supplying power to the linear motor; and a vibration absorption unit for absorbing vibrations of a predetermined frequency, the method comprising the steps of: a drive frequency of the power supplied by the drive circuit is fixed, and a mass of a displacer assembly including the displacer and a rod is adjusted so that a phase difference between the piston and the displacer falls within a predetermined range when power of the fixed drive frequency is supplied to the linear motor.

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