Method for manufacturing free piston stirling engine

Abstract

To enable precise manufacturing of a free piston Stirling engine.SOLUTION: A method for manufacturing a β-type free piston Stirling refrigerator 1 has: a displacer 16 that is reciprocable in the direction of a central axis X of a first cylinder 15A; a piston 23 that is reciprocable in the direction of the central axis X of a second cylinder 15B; and a rod 29 having one end of a first male threaded portion 37 fixed to a female threaded portion 38 of the displacer 16 by an adhesive A and passing through the piston 23 in the direction of the central axis X. The displacer 16 is inserted into the first cylinder 15A before the adhesive A between the first male threaded portion 37 and the female threaded portion 38 is cured. The piston 23 is inserted into the second cylinder 15B to cause the rod 29 to pass through the piston 23. The adhesive A is cured inside the first cylinder 15A. As a result, the displacer 16 and the rod 29 are connected.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a free piston Stirling engine.

Background Art

[0002] Conventionally, as this type of free piston Stirling engine, there is known one having a cylinder (corresponding to the first cylinder of the present invention), a displacer reciprocable in the axial direction of the cylinder, and a rod having one end fixed to the displacer. And in these free piston Stirling engines, a female screw portion is formed on the displacer, and the male screw portion formed at one end of the rod is screwed into the female screw portion to fix the displacer and the rod (see Patent Document 1). And in order that the male screw and the female screw are not loosened, both are fixed by an adhesive. Incidentally, the displacer and the rod were in a pre-assembled state by screwing and adhering the male screw and the female screw before being inserted into the cylinder.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, for example, in a β-type free piston Stirling engine, a piston is provided coaxially with the displacer. Therefore, in such a β-type free piston Stirling engine, the coaxiality of the rod and the piston becomes important. That is, if the rod is not accurately coaxially connected to the displacer, there is a risk that the rod may contact the through hole of the piston.

[0005] On the one hand, in a γ-type free piston Stirling engine, a reciprocating element called a displacer drive is provided on the other end side of the rod, and it has a second cylinder into which the displacer drive is inserted. Therefore, in such a γ-type free piston Stirling engine, the coaxiality between the first cylinder and the displacer, and the coaxiality between the second cylinder and the displacer drive become important. That is, if the displacer and the displacer drive are not accurately connected by the rod so that the first cylinder and the displacer are exactly coaxial and the second cylinder and the displacer drive are exactly coaxial, there is a risk that the displacer may contact the first cylinder or the displacer drive may contact the second cylinder.

[0006] However, in a β-type free piston Stirling engine, due to tolerances in dimensions, angles, etc. of the female threaded portion formed on the displacer, the male threaded portion of the rod, and the through hole of the piston, there is a risk that the coaxiality between the piston and the rod will be outside the allowable range when they are assembled. Similarly, in a γ-type free piston Stirling engine, due to tolerances in dimensions, angles, etc. of the female threaded portions formed on the displacer and the displacer drive and the male threaded portion of the rod, there is a risk that the coaxiality between the displacer and the first cylinder, and between the displacer drive and the second cylinder will be outside the allowable range when they are assembled.

[0007] The object of the present invention is to solve the above problems and enable the free piston Stirling engine to be manufactured with high precision.

Means for Solving the Problems

[0008] The manufacturing method of a free piston Stirling engine according to claim 1 of the present invention includes a first cylinder, a second cylinder, a displacer reciprocating in the axial direction of the first cylinder, a piston reciprocating in the axial direction of the second cylinder, and a rod having one end fixed to the displacer by an adhesive and passing through the piston in the axial direction. In the manufacturing method of the free piston Stirling engine, the adhesive is disposed between one end of the rod and the displacer, the displacer is inserted into the first cylinder before the adhesive cures, the piston is inserted into the second cylinder so that the rod passes through the piston, and the adhesive is cured in the first cylinder to connect the displacer and the rod.

[0009] Further, the manufacturing method of a free piston Stirling engine according to claim 2 of the present invention is, in claim 1, a male screw portion is formed on one of one end of the rod and the displacer, a female screw portion is formed on the other, the adhesive is disposed between the male screw portion and the female screw portion, after these male screw portion and female screw portion are lightly screwed together, the displacer is inserted into the first cylinder, and the piston is inserted into the second cylinder.

[0010] Further, the manufacturing method of a free piston Stirling engine according to claim 3 of the present invention is, in claim 1, a through hole is formed in the displacer, a female screw portion is formed on one end of the rod, a screw having a male screw portion that can be screwed into the female screw portion through the through hole is provided, the adhesive is disposed between the through hole of the displacer, the female screw portion of the rod, and the male screw portion of the screw, the male screw portion of the screw is lightly screwed into the female screw of the rod, the displacer is inserted into the first cylinder, and the piston is inserted into the second cylinder.

[0011] Further, in the manufacturing method of the free piston Stirling engine according to claim 4 of the present invention, in any one of claims 2 or 3, when the diameter of the thread crest of the male thread portion is D1, the diameter of the thread groove of the male thread portion is D2, the diameter of the thread crest of the female thread portion is D3, and the diameter of the thread groove of the female thread portion is D4, the male thread portion and the female thread portion are formed such that (D3 + D4) / 2 > (D1 + D2) / 2 ≧ D3.

[0012] Further, in the manufacturing method of the free piston Stirling engine according to claim 5 of the present invention, in any one of claims 2 or 3, when the diameter of the thread crest of the male thread portion is D1, the diameter of the thread crest of the female thread portion is D3, and the diameter of the thread groove of the female thread portion is D4, the male thread portion and the female thread portion are formed such that D4 > D1 ≧ (D3 + D4) / 2.

[0013] Further, in the manufacturing method of the free piston Stirling engine according to claim 6 of the present invention, in a manufacturing method of a free piston Stirling engine having a first cylinder, a second cylinder, a displacer reciprocable in the axial direction of the first cylinder, a displacer drive reciprocable in the axial direction of the second cylinder, and a rod having one end fixed to the displacer by an adhesive and the other end fixed to the displacer drive by an adhesive, the adhesive is disposed between one end of the rod and the displacer, the adhesive is disposed between the other end of the rod and the displacer drive, the displacer is inserted into the first cylinder and the displacer drive is inserted into the second cylinder before these adhesives are cured, and the adhesives are cured in the first cylinder and the second cylinder, thereby connecting the displacer, the rod, and the displacer drive.

[0014] Further, in the method for manufacturing a free piston Stirling engine according to claim 7 of the present invention, in claim 6, a male screw portion is formed on one of one end of the rod and the displacer, and a female screw portion is formed on the other; a male screw portion is formed on one of the other end of the rod and the displacer drive, and a female screw portion is formed on the other; the adhesive is disposed between these male screw portions and female screw portions respectively; after these male screw portions and female screw portions are lightly screwed together, the displacer is inserted into the first cylinder, and the displacer drive is inserted into the second cylinder.

[0015] Further, in the method for manufacturing a free piston Stirling engine according to claim 8 of the present invention, in claim 6, through holes are respectively formed in the displacer and the displacer drive; female screw portions are formed at both ends of the rod; screws having male screw portions that can be screwed into the female screw portions respectively through the through holes are provided corresponding to the female screw portions; the adhesive is disposed between the through hole of the displacer, the female screw portion of the rod, and the male screw portion of the screw, and between the through hole of the displacer drive, the female screw portion of the rod, and the male screw portion of the screw respectively; the male screw portion of the screw is lightly screwed into the female screw of the rod; the displacer is inserted into the first cylinder, and the displacer drive is inserted into the second cylinder.

[0016] Further, in the method for manufacturing a free piston Stirling engine according to claim 9 of the present invention, in any one of claims 7 or 8, when the diameter of the thread crest of the male screw portion is D1, the diameter of the thread root of the male screw portion is D2, the diameter of the thread crest of the female screw portion is D3, and the diameter of the thread root of the female screw portion is D4, the male screw portion and the female screw portion are formed such that (D3 + D4) / 2 > (D1 + D2) / 2 ≧ D3.

[0017] Furthermore, in the method for manufacturing a free piston Stirling engine according to claim 10 of the present invention, in any one of claims 7 or 8, when the diameter of the thread of the male thread portion is D1, the diameter of the thread of the female thread portion is D3, and the diameter of the thread groove of the female thread portion is D4, the male thread portion and the female thread portion are formed such that D4>D1≧(D3 + D4) / 2.

Advantages of the Invention

[0018] By doing as above, in the method for manufacturing a free piston Stirling engine according to claim 1 of the present invention, the displacer and the rod can be fixed by an adhesive in a positional relationship where the first cylinder and the displacer, and the second cylinder and the piston are coaxial.

[0019] Note that a male thread portion is formed on one of one end of the rod and the displacer, and a female thread portion is formed on the other. The adhesive is disposed between these male and female thread portions. After these male and female thread portions are lightly screwed together, the displacer is inserted into the first cylinder, and the piston is inserted into the second cylinder, so that in a state where the displacer and the rod are temporarily assembled, they can be easily inserted into the first cylinder.

[0020] Also, a through hole is formed in the displacer, a female thread portion is formed at one end of the rod, and a screw having a male thread portion that can be screwed into the female thread portion through the through hole is provided. The adhesive is disposed between the through hole of the displacer, the female thread portion of the rod, and the male thread portion of the screw. The male thread portion of the screw is lightly screwed into the female thread portion of the rod. The displacer is inserted into the first cylinder, and the piston is inserted into the second cylinder, so that in a state where the displacer and the rod are temporarily assembled, they can be easily inserted into the first cylinder.

[0021] Also, when the major diameter of the thread crest of the male screw portion is D1, the minor diameter of the thread valley of the male screw portion is D2, the major diameter of the thread crest of the female screw portion is D3, and the minor diameter of the thread valley of the female screw portion is D4, by forming the male screw portion and the female screw portion such that (D3 + D4) / 2 > (D1 + D2) / 2 ≧ D3, the thread crest of the male screw portion and the thread crest of the female screw portion are surely overlapped in the axial direction view. Even if the axial centers of the male screw portion and the female screw portion are displaced during the temporary assembly, the screwing state of both can be maintained.

[0022] Furthermore, when the major diameter of the thread crest of the male screw portion is D1, the major diameter of the thread crest of the female screw portion is D3, and the minor diameter of the thread valley of the female screw portion is D4, by forming the male screw portion and the female screw portion such that D4 > D1 ≧ (D3 + D4) / 2, the thread crest of the male screw portion and the thread crest of the female screw portion are surely overlapped in the axial direction view. Even if the axial centers of the male screw portion and the female screw portion are displaced during the temporary assembly, the screwing state of both can be maintained.

[0023] Also, the manufacturing method of the free piston Stirling engine according to claim 6 of the present invention can fix the displacer and the displacer drive to the rod in a state where the first cylinder and the displacer, and the second cylinder and the displacer drive are coaxial as described above.

[0024] Note that a male screw portion is formed on one of one end of the rod and the displacer, and a female screw portion is formed on the other; a male screw portion is formed on one of the other end of the rod and the displacer drive, and a female screw portion is formed on the other. The adhesive is disposed between these male screw portions and female screw portions respectively. After these male screw portions and female screw portions are lightly screwed together, the displacer is inserted into the first cylinder, and the displacer drive is inserted into the second cylinder. In this way, in a state where the displacer, the displacer drive, and the rod are temporarily assembled, the displacer can be easily inserted into the first cylinder, and the displacer drive can be easily inserted into the second cylinder.

[0025] Further, through holes are formed in the displacer and the displacer drive respectively, female screw portions are formed at both ends of the rod, and screws having male screw portions that can be screwed into the female screw portions through the through holes are provided corresponding to the female screw portions. The adhesive is disposed between the through hole of the displacer, the female screw portion of the rod, and the male screw portion of the screw, and between the through hole of the displacer drive, the female screw portion of the rod, and the male screw portion of the screw. The male screw portion of the screw is lightly screwed into the female screw of the rod, the displacer is inserted into the first cylinder, and the displacer drive is inserted into the second cylinder. In this way, in a state where the displacer, the displacer drive, and the rod are temporarily assembled, the displacer can be easily inserted into the first cylinder and the displacer drive can be inserted into the second cylinder.

[0026] Further, when the major diameter of the thread of the male screw portion is D1, the minor diameter of the thread of the male screw portion is D2, the major diameter of the thread of the female screw portion is D3, and the minor diameter of the thread of the female screw portion is D4, the male screw portion and the female screw portion are formed such that (D3 + D4) / 2 > (D1 + D2) / 2 ≧ D3. In this way, the threads of the male screw portion and the threads of the female screw portion surely overlap in the axial direction view. Even if the axial centers of the male screw portion and the female screw portion are displaced during temporary assembly, the screwed state of both can be maintained.

[0027] Furthermore, when the major diameter of the thread of the male screw portion is D1, the major diameter of the thread of the female screw portion is D3, and the minor diameter of the thread of the female screw portion is D4, the male screw portion and the female screw portion are formed such that D4 > D1 ≧ (D3 + D4) / 2. In this way, the threads of the male screw portion and the threads of the female screw portion surely overlap in the axial direction view. Even if the axial centers of the male screw portion and the female screw portion are displaced during temporary assembly, the screwed state of both can be maintained.

Brief Description of the Drawings

[0028]

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Embodiments for Carrying Out the Invention

[0029] Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1 to 9. Since the operation and action of the free piston Stirling engine itself are already known, they will not be described again in this embodiment, and the structure, manufacturing method, and the effects of this manufacturing method will be described. 1 is a β-type free piston Stirling refrigerator as a free piston Stirling engine of the present invention. This Stirling refrigerator 1 has a metal casing 2. And this casing 2 has a first casing body 3 and a second casing body 4. The first casing body 3 is integrally formed with a cylindrical portion 5 formed in a small-diameter cylindrical shape and a large-diameter portion 6 with an open base end. And the cylindrical portion 5 has a closed tip portion 7, an intermediate portion 8, and a base portion 9. Further, the large-diameter portion 6 has an end face portion 10 formed in a substantially circular protruding curved surface shape and a short cylindrical side face portion 11. Similarly, the second casing body 4 has a cylindrical side face portion 12 and another end face portion 13 formed in a substantially circular protruding curved surface shape. And a cylindrical body portion 14 is formed by the large-diameter portion 6 and the second casing body 4.

[0030] Inside the cylindrical portion 5, a cylinder 15 extending to the inside of the body portion 14 is coaxially inserted into the cylindrical portion 5. That is, the central axis X of the cylinder 15 coincides with the central axis X of the cylindrical portion 5. And the cylinder 15 is formed using metal. This cylinder 15 has a first cylinder 15A on the tip side and a second cylinder 15B on the base end side and is integrally formed, but a part of the first cylinder 15A may be formed in combination with a material having low thermal conductivity. Note that the first cylinder 15A and the second cylinder 15B are formed coaxially and have the same inner diameter. Inside the first cylinder 15A, a displacer 16 is accommodated so as to be reciprocable in the direction of the central axis X. Also, an expansion chamber E1 is formed between the tip of this displacer 16 and the tip portion 7 of the cylindrical portion 5, and the inside and outside of the cylinder 15 communicate with each other through a gap 17. In the intermediate portion 8, a regenerator 18 is provided between the inner periphery of the cylindrical portion 5 and the outer periphery of the cylinder 15, and in the base portion 9, a communication hole 19 communicating the inside and outside of the cylinder 15 is formed in the cylinder 15 itself. Also, a heat absorption fin 20 is provided between the inner periphery of the tip portion 7 of the cylindrical portion 5 and the tip outer periphery of the cylinder 15, and an exhaust heat fin 21 is provided between the inner periphery of the cylindrical portion 5 and the outer periphery of the cylinder 15 between the regenerator 18 and the communication hole 19. And a path 22 is formed from the inner tip of the cylinder 15 through the gap 17, the heat absorption fin 20, the regenerator 18, the exhaust heat fin 21, and the communication hole 19 to the compression chamber C1 in the cylinder 15. Further, inside the body portion 4, a piston 23 is accommodated inside the second cylinder 15B so as to be reciprocable in the direction of the central axis X. And the base end portion of this piston 23 is coaxially connected to a linear motor 24. Note that this linear motor 24 includes a mover 26 connected to the base end of the piston 23 by a connecting body 25 and extending coaxially to the outer periphery of the base end side of the cylinder 15, and an annular stator 27 provided close to the outer periphery of this mover 26.

[0031] In addition, a first leaf spring 28 for controlling the operation of the piston 23 is connected to the connector 25 that connects the mover 26 to the piston 23. Further, one end of a rod 29 that operates together with the displacer 16 is connected to the base end face 16B side of the displacer 16, and a second leaf spring 30 is connected to the other end of the rod 29. Note that the rod 29 passes through the center of the piston 23 and extends in the direction of the central axis X. Also, the first and second leaf springs 28 and 30 are disposed outside the second cylinder 15B within the body 14, and the second leaf spring 30 is disposed at a position farther from the second cylinder 15B than the first leaf spring 28.

[0032] A detailed description will be given of the assembly of the piston 23, the connector 25, the mover 26, and the first leaf spring 28. The piston 23 is formed in a cylindrical shape. A through-hole 31 through which the rod 29 is inserted is formed at the center of the piston 23. Further, the proximal end side of the piston 23 is open, and an internal thread (not shown) is formed on the inner surface of this opening. The connector 25 has a through-hole (not shown) formed in the central axis X direction, and the rod 29 is inserted into this through-hole. An external thread (not shown) is formed on the piston 23 side of the connector 25 in the central axis X direction, and an external thread 32 is formed on the opposite side of this external thread. The mover 26 is configured to include a frame 33 and a cylindrical permanent magnet 34 fixed to one end side of the frame 33. The frame 33 is made of a non-magnetic material such as synthetic resin, and a through-hole 35 through which the external thread (not shown) of the connector 25 is inserted is formed. The permanent magnet 34 is fixed to the frame 33. Then, through the through-hole 35 of the frame 33, the external thread (not shown) of the connector 25 and the internal thread (not shown) of the piston 23 are screwed together. In this way, by screwing the external thread (not shown) of the connector 25 and the internal thread (not shown) of the piston 23 together, the frame 33 of the mover 26 is sandwiched between the proximal end of the piston 23 and the connector 25. As a result, the piston 23, the connector 25, and the mover 26 are integrated. A through-hole (not shown) is formed in the central portion of the first leaf spring 28, and the external thread 32 of the connector 25 is inserted into this through-hole. Then, after inserting the external thread 32 into the through-hole, a nut 36 is screwed onto the external thread 32, so that the first leaf spring 28 is sandwiched between the connector 25 and the nut 36.

[0033] A first male screw portion 37 is formed at one end of the rod 29. The first male screw portion 37 is screwed with a female screw portion 38 formed at the central portion on the base end face 16B side of the displayer 16. On the other hand, a second male screw portion 39 is formed at the other end of the rod 29. A through hole (not shown) is formed at the central portion of the second leaf spring 30, and the second male screw portion 39 is inserted into the through hole. After inserting the second male screw portion 39 into the through hole, a nut 40 is screwed onto the second male screw portion 39, whereby the second leaf spring 30 is sandwiched between the rod 29 and the nut 40.

[0034] As shown in FIG. 7, the major diameter of the thread of the first male screw portion 37 is D1, and the minor diameter of the thread is D2. Also, the major diameter of the thread of the female screw portion 38 is D3, and the minor diameter of the thread is D4. And the relationship among D1 to D4 is as follows.

[0035] (1): (D3 + D4) / 2 > (D1 + D2) / 2 ≥ D3

[0036] (2): D4 > D1 ≥ (D3 + D4) / 2

[0037] According to the condition of (1), even if the tip of the thread of the female screw portion 38 approaches or abuts against the bottom of the thread groove of the first male screw portion 37 as much as possible on one side, the thread on the opposite side of the first male screw portion 37 overlaps with the thread of the female screw portion 38 in the axial direction view. And according to the condition of (2), even if the tip of the thread of the first male screw portion 37 approaches or abuts against the bottom of the thread groove of the female screw portion 38 as much as possible on one side, the thread on the opposite side of the first male screw portion 37 overlaps with the thread of the female screw portion 38 in the axial direction view. That is, even if the central axes of the first male screw portion 37 and the female screw portion 38 are misaligned as much as possible, the threads of the first male screw portion 37 and the female screw portion 38 will surely overlap in the axial direction view over the entire circumference.

[0038] Note that 41 in Fig. 1 is a vibration absorption unit provided on the other end face portion 13 of the second casing body 4, and is arranged coaxially with the central axis X of the cylinder 15. Through a mounting portion 42 arranged to be coaxial therewith and a connecting portion 43 connected to the mounting portion 42, a leaf spring 44 and a balance weight 45 are arranged coaxially so as to overlap each other.

[0039] Next, the manufacturing process of the β-type free piston Stirling refrigerator 1 of the present embodiment will be described. First, it is pre-assembled to the state shown in Fig. 2. That is, the heat absorption fin 20, the regenerator 18, and the exhaust heat fin 21 are inserted into the cylindrical portion 5 of the first casing body 3, and the first cylinder 15A of the cylinder 15 in a state where the stator 27 is attached is inserted and fixed inside the heat absorption fin 20, the regenerator 18, and the exhaust heat fin 21. Similarly, the piston 23, the connector 25, and the mover 26 are integrated.

[0040] Next, as shown in Fig. 3, the displacer 16 and the rod 29 are assembled. In this process, after injecting the adhesive A into the female screw portion 38 of the displacer 16, or applying the adhesive A to the first male screw portion 37 of the rod 29, or doing both, the first male screw portion 37 is screwed into the female screw portion 38. Note that at this time, the female screw portion 38 and the first male screw portion 37 are not strongly screwed together, and the displacer 16 is made slightly movable in the axial direction perpendicular to the rod 29. This movable "play" is within (D4 - D1) / 2 or within (D3 - D2) / 2 in the axial direction perpendicular to the central axis of the female screw portion 38 and the central axis of the first male screw portion 37 in a state where they are aligned.

[0041] Next, as shown in Fig. 4, the thus assembled displacer 16 and rod 29 are inserted into the cylinder 15 from the side of the displacer 16 before the adhesive A hardens. At this time, the displacer 16 is inserted up to the first cylinder 15A.

[0042] Next, as shown in FIG. 5, the piston 23 is inserted into the second cylinder 15B. At this time, the rod 29 connected to the displacer 16 previously inserted into the first cylinder 15A is inserted into the through hole 31 formed in the piston 23. Further, as described above, since the piston 23 is integrated with the connector 25 and the mover 26, when the piston 23 is inserted into the second cylinder 15B, the mover 26 approaches the inside of the stator 27. By leaving it in this state for a while, the adhesive A hardens, and the first male screw portion 37 and the female screw portion 38, that is, the displacer 16 and the rod 29 are completely fixed. Note that when the female screw portion 38 is accurately formed at the center with respect to the displacer 16, the through hole 31 is accurately formed at the center with respect to the piston 23, and the first cylinder 15A and the second cylinder 15B are accurately coaxial, as shown in FIG. 8, the adhesive A hardens in a state where the first male screw portion 37 of the rod 29 is located at the center of the female screw portion 38 of the displacer 16. On the other hand, when the female screw portion 38 is slightly displaced from the center with respect to the displacer 16, by inserting the piston 23 into the second cylinder 15B, before the adhesive A hardens, the first male screw portion 37 slightly moves in the axial direction with respect to the female screw portion 38. As a result, as shown in FIG. 9, the adhesive A hardens in a state where the first male screw portion 37 is slightly displaced in the axial direction with respect to the female screw portion 38. Note that FIG. 9 shows the case where the female screw portion 38 is slightly displaced from the center with respect to the displacer 16, but the same applies when the through hole 31 is slightly displaced from the center with respect to the piston 23 or when the axial centers of the first cylinder 15A and the second cylinder 15B are slightly displaced.

[0043] Furthermore, as shown in FIG. 6, after the adhesive A has cured, the first leaf spring 28 is clamped between the connector 25 and the nut 36, and the second leaf spring 30 is clamped between the rod 29 and the nut 40. Further, the second casing body 4 to which the attachment portion 42 is fixed is connected to the first casing body 3 and hermetically welded. After the inside of the casing 2 is filled with the operating gas at a predetermined pressure, the connection portion 43, the leaf spring 44, and the balance weight 45 are connected to the attachment portion 42, thereby completing the β-type free piston Stirling refrigerator 1.

[0044] By assembling in this manner, even if there is a deviation in the first cylinder 15A, the second cylinder 15B, the female screw portion 38 of the displacer 16, or the through hole 31 of the piston 23, the alignment of the first cylinder 15A and the displacer 16, the second cylinder 15B and the piston 23, and the rod 29 and the piston 23 can be accurately performed without using any special jigs.

[0045] As described above, in the manufacturing method of the β-type free piston Stirling refrigerator 1 as a free piston Stirling engine having the first cylinder 15A, the second cylinder 15B, the displacer 16 reciprocable in the central axis X direction of the first cylinder 15A, the piston 23 reciprocable in the central axis X direction of the second cylinder 15B, and the rod 29 having one end fixed to the displacer 16 by the adhesive A and penetrating the piston 23 in the central axis X direction, the adhesive A is disposed between the first male screw portion 37, which is one end of the rod 29, and the displacer 16. Before the adhesive A cures, the displacer 16 is inserted into the first cylinder 15A, and the piston 23 is inserted into the second cylinder 15B so that the rod 29 penetrates the piston 23. By curing the adhesive A in the first cylinder 15A, the displacer 16 and the rod 29 are connected, so that the displacer 16 and the rod 29 can be fixed by the adhesive A in a positional relationship in which the first cylinder 15A and the displacer 16, and the second cylinder 15B and the piston 23 are coaxial.

[0046] Further, in the present invention, a male screw portion 37 is formed at one end of the rod 29, a female screw portion 38 is formed in the displacer 16, the adhesive A is disposed between the male screw portion 37 and the female screw portion 38, and after the male screw portion 37 and the female screw portion 38 are lightly screwed together, the displacer 16 is inserted into the first cylinder 15A, and the piston 23 is inserted into the second cylinder 15B. Thus, in a state where the displacer 16 and the rod 29 are temporarily assembled, they can be easily inserted into the first cylinder 15A.

[0047] Further, in the present invention, when the major diameter of the thread of the male screw portion 37 is D1, the minor diameter of the thread of the male screw portion 37 is D2, the major diameter of the thread of the female screw portion 38 is D3, and the minor diameter of the thread of the female screw portion 38 is D4, the male screw portion 37 and the female screw portion 38 are formed such that (D3 + D4) / 2 > (D1 + D2) / 2 ≥ D3. Thus, when viewed in the direction of the central axis X, the threads of the male screw portion 37 and the female screw portion 38 are surely overlapped, and even if the axial centers of the male screw portion 37 and the female screw portion 38 are displaced during temporary assembly, the screwed state of both can be maintained.

[0048] Furthermore, in the present invention, when the major diameter of the thread of the male screw portion 37 is D1, the major diameter of the thread of the female screw portion 38 is D3, and the minor diameter of the thread of the female screw portion 38 is D4, the male screw portion 37 and the female screw portion 38 are formed such that D4 > D1 ≥ (D3 + D4) / 2. Thus, when viewed in the direction of the central axis X, the threads of the male screw portion 37 and the female screw portion 38 are surely overlapped, and even if the axial centers of the male screw portion 37 and the female screw portion 38 are displaced during temporary assembly, the screwed state of both can be maintained.

[0049] Next, a second embodiment of the present invention will be described with reference to FIGS. 10 to 12. In this embodiment, except for the displacer 51 and the rod 52, it is the same as the first embodiment described above. Also, although illustration is omitted, the same reference numerals are given to the elements common to the first embodiment.

[0050] The β-type free piston Stirling refrigerator as a free piston Stirling engine according to this embodiment has a metal casing 2. And this casing 2 has a first casing body 3 and a second casing body 4. The first casing body 3 is integrally formed having a cylindrical portion 5 formed in a small-diameter cylindrical shape and a large-diameter portion 6 with an open base end. And the cylindrical portion 5 has a closed tip portion 7, an intermediate portion 8, and a base portion 9. Further, the large-diameter portion 6 has an end face portion 10 formed in a substantially circular protruding curved surface shape and a short cylindrical side face portion 11. Similarly, the second casing body 4 has a cylindrical side face portion 12 and another end face portion 13 formed in a substantially circular protruding curved surface shape. And a cylindrical body portion 14 is formed by the large-diameter portion 6 and the second casing body 4.

[0051] Inside the cylindrical portion 5, a cylinder 15 extending to the inside of the body portion 14 is coaxially inserted into the cylindrical portion 5. That is, the central axis X of the cylinder 15 coincides with the central axis X of the cylindrical portion 5. And the cylinder 15 is formed using metal. This cylinder 15 has a first cylinder 15A on the tip side and a second cylinder 15B on the base end side and is integrally formed, but a part of the first cylinder 15A may be formed in combination with a material having low thermal conductivity. Note that the first cylinder 15A and the second cylinder 15B are formed coaxially and have the same inner diameter. Inside the first cylinder 15A, a displacer 51 is accommodated so as to be reciprocable in the central axis X direction. Also, an expansion chamber E1 is formed between the tip of this displacer 51 and the tip portion 7 of the cylindrical portion 5, and the inside and outside of the cylinder 15 communicate with each other through a gap 17. Also, in the intermediate portion 8, a regenerator 18 is provided between the inner periphery of the cylindrical portion 5 and the outer periphery of the cylinder 15, and in the base portion 9, a communication hole 19 communicating the inside and outside of the cylinder 15 is formed in the cylinder 15 itself. Also, heat absorption fins 20 are provided between the inner periphery of the tip portion 7 of the cylindrical portion 5 and the tip outer periphery of the cylinder 15, and exhaust heat fins 21 are provided between the inner periphery of the cylindrical portion 5 and the outer periphery of the cylinder 15 between the regenerator 18 and the communication hole 19. And a path 22 is formed from the inner tip of the cylinder 15 through the gap 17, the heat absorption fins 20, the regenerator 18, the exhaust heat fins 21, and the communication hole 19 to the compression chamber C1 in the cylinder 15. Further, inside the body portion 4, a piston 23 is accommodated in the second cylinder 15B so as to be reciprocable in the central axis X direction. And the base end portion of this piston 23 is coaxially connected to a linear motor 24. Note that this linear motor 24 includes a mover 26 connected to the base end of the piston 23 by a connecting body 25 and extending coaxially to the outer periphery of the base end side of the cylinder 15, and an annular stator 27 provided close to the outer periphery of this mover 26.

[0052] In addition, a first leaf spring 28 for controlling the operation of the piston 23 is connected to the connector 25 that connects the mover 26 to the piston 23. Further, one end of a rod 52 that operates together with the displacer 51 is connected to the base end surface 51B side of the displacer 51, and a second leaf spring 30 is connected to the other end of the rod 52. Note that the rod 52 passes through the center of the piston 23 and extends in the direction of the central axis X. Also, the first and second leaf springs 28 and 30 are disposed outside the second cylinder 15B within the body portion 14, and the second leaf spring 30 is disposed at a position farther from the second cylinder 15B than the first leaf spring 28.

[0053] A detailed description will be given of the assembly of the piston 23, the connector 25, the mover 26, and the first leaf spring 28. The piston 23 is formed in a cylindrical shape. A through hole 31 through which the rod 52 is inserted is formed at the center of the piston 23. Further, the proximal end side of the piston 23 is open, and an internal thread (not shown) is formed on the inner surface of this opening. The connector 25 has a through hole (not shown) formed in the central axis X direction, and the rod 52 is inserted into this through hole. An external thread (not shown) is formed on the piston 23 side of the connector 25 in the central axis X direction, and an external thread 32 is formed on the opposite side of this external thread. The mover 26 is configured to include a frame 33 and a cylindrical permanent magnet 34 fixed to one end side of the frame 33. The frame 33 is made of a non-magnetic material such as synthetic resin, and a through hole 35 through which the external thread (not shown) of the connector 25 is inserted is formed. The permanent magnet 34 is fixed to the frame 33. Then, through the through hole 35 of the frame 33, the external thread (not shown) of the connector 25 and the internal thread (not shown) of the piston 23 are screwed together. In this way, by screwing the external thread (not shown) of the connector 25 and the internal thread (not shown) of the piston 23 together, the frame 33 of the mover 26 is sandwiched between the proximal end of the piston 23 and the connector 25. Thereby, the piston 23, the connector 25, and the mover 26 are integrated. A through hole (not shown) is formed at the center of the first leaf spring 28, and the external thread 32 of the connector 25 is inserted into this through hole. Then, after inserting the external thread 32 into the through hole, a nut 36 is screwed onto the external thread 32, so that the first leaf spring 28 is sandwiched between the connector 25 and the nut 36.

[0054] At one end of the rod 52, a cylindrical insertion portion 53 formed thinner than the diameter of the rod 52 is formed, and a stepped portion 54 is formed between the main portion of the rod 52 and the insertion portion 53. The insertion portion 53 is inserted into a cylindrical concave receiving portion 55 formed at the central portion on the base end surface 51B side of the displacer 51. On the other hand, a male screw portion 39 is formed at the other end of the rod 52. A through hole (not shown) is formed at the central portion of the second leaf spring 30, and the male screw portion 39 is inserted through this through hole. Then, after inserting the male screw portion 39 through the through hole, a nut 40 is screwed onto the male screw portion 39, so that the second leaf spring 30 is clamped between the rod 52 and the nut 40.

[0055] As shown in FIG. 10, the diameter of the rod 52 is D5, the diameter of the insertion portion 53 is D6, and the diameter of the receiving portion 55 is D7. And the relationship among these D5 to D7 is as follows.

[0056] (D5 + D6) / 2 ≧ D7 > D6 Due to this condition, even if the side surface of the insertion portion 53 abuts on the side surface of the receiving portion 55 at one side, on the side opposite to this abutting side, the outer edge of the stepped portion 54 abuts on the base end surface 51B side of the displacer 51. That is, even if the central axis of the insertion portion 53 and the central axis of the receiving portion 55 are maximally displaced, the outer edge of the stepped portion 54 abuts on the base end surface 51B side of the displacer 51 over the entire circumference. In the present embodiment, the stepped portion 54 is provided on the rod 52, but a flange portion may be provided on one end side of the rod 52 so that this flange portion abuts on the base end surface 51B side of the displacer 51.

[0057] Note that 41 is a vibration absorption unit provided on the other end surface portion 13 of the second casing body 4, and is coaxially arranged such that a plate spring 44 and a balance weight 45 overlap via a mounting portion 42 arranged to be coaxial with the central axis X of the cylinder 15 and a connecting portion 43 connected to this mounting portion 42.

[0058] Next, the manufacturing process of the β-type free piston Stirling refrigerator according to this embodiment will be described. First, similar to the first embodiment, it is pre-assembled to the state shown in FIG. 2. That is, the heat absorption fin 20, the regenerator 18, and the exhaust heat fin 21 are inserted into the cylindrical portion 5 of the first casing body 3, and the first cylinder 15A of the cylinder 15 in the state where the stator 27 is attached is inserted and fixed inside the heat absorption fin 20, the regenerator 18, and the exhaust heat fin 21. Similarly, the piston 23, the connector 25, and the mover 26 are integrated.

[0059] Next, the displacer 51 and the rod 52 are assembled. In this process, adhesive A is injected into the receiving portion 55 of the displacer 51, or adhesive A is applied to the insertion portion 53 of the rod 52, or both are performed, and then the insertion portion 53 is inserted into the receiving portion 55. Note that as the adhesive A, a highly viscous one is preferable. Further, the insertion portion 53 is made slightly movable in the axial direction perpendicular to the receiving portion 55. This movable "play" is within (D7 - D6) / 2 in the axial direction perpendicular to the central axis of the receiving portion 55 and the central axis of the insertion portion 53 in a state where they are aligned.

[0060] Next, similar to the first embodiment, the thus assembled displacer 51 and rod 52 are inserted into the cylinder 15 from the side of the displacer 51 before the adhesive A hardens. At this time, the displacer 16 is inserted up to the first cylinder 15A. It is desirable to insert the displacer 51 and the rod 52 into the cylinder 15 from below so that the side of the displacer 51 is on top. By doing so, the displacer 51 continues to abut against the stepped portion 54 of the rod 52 due to gravity, so that the displacer 51 can be prevented from falling off the rod 52 before the adhesive A hardens.

[0061] Next, similarly to the first embodiment, the piston 23 is inserted into the second cylinder 15B. At this time, the rod 52 connected to the displacer 51 previously inserted into the first cylinder 15A is inserted into the through-hole 31 formed in the piston 23. Further, as described above, since the piston 23 is integrated with the connector 25 and the mover 26, when the piston 23 is inserted into the second cylinder 15B, the mover 26 approaches the inside of the stator 27. By leaving this state as it is for a while, the adhesive A hardens, and the insertion portion 53 and the receiving portion 55, that is, the displacer 51 and the rod 52 are completely fixed. Note that when the receiving portion 55 is accurately formed at the center with respect to the displacer 51, the through-hole 31 is accurately formed at the center with respect to the piston 23, and the first cylinder 15A and the second cylinder 15B are accurately coaxial, as shown in FIG. 11, the adhesive A hardens in a state where the insertion portion 53 of the rod 52 is located at the center of the receiving portion 55 of the displacer 51. On the other hand, when the receiving portion 55 is slightly displaced from the center with respect to the displacer 51, by inserting the piston 23 into the second cylinder 15B, before the adhesive A hardens, the insertion portion 53 slightly moves in the axial direction perpendicular to the receiving portion 55. As a result, as shown in FIG. 12, the adhesive A hardens in a state where the insertion portion 53 is slightly displaced in the axial direction perpendicular to the receiving portion 55. Note that FIG. 12 shows the case where the receiving portion 55 is slightly displaced from the center with respect to the displacer 51, but the same applies when the through-hole 31 is slightly displaced from the center with respect to the piston 23, or when the axial centers of the first cylinder 15A and the second cylinder 15B are slightly displaced.

[0062] Further, similar to the first embodiment, after the adhesive A is cured, the first leaf spring 28 is clamped between the connector 25 and the nut 36, and the second leaf spring 30 is clamped between the rod 52 and the nut 40. Further, the second casing body 4 to which the mounting portion 42 is fixed is connected to the first casing body 3 and hermetically welded. After the inside of the casing 2 is filled with the operating gas at a predetermined pressure, the connecting portion 43, the leaf spring 44, and the balance weight 45 are connected to the mounting portion 42, thereby completing the β-type free piston Stirling refrigerator.

[0063] By assembling in this way, even if there is a deviation in the first cylinder 15A, the second cylinder 15B, the receiving portion 55 of the displacer 51, or the through hole 31 of the piston 23, the first cylinder 15A and the displacer 51, the second cylinder 15B and the piston 23, and the rod 52 and the piston 23 can be accurately aligned without using a special jig.

[0064] As described above, the present invention relates to a method for manufacturing a β-type free piston Stirling refrigerator as a free piston Stirling engine having a first cylinder 15A, a second cylinder 15B, a displacer 51 reciprocable in the central axis X direction of the first cylinder 15A, a piston 23 reciprocable in the central axis X direction of the second cylinder 15B, and a rod 52 having one end fixed to the displacer 51 by an adhesive A and penetrating the piston 23 in the central axis X direction. In the method, the adhesive A is disposed between the insertion portion 53, which is one end of the rod 52, and the displacer 51. Before the adhesive A is cured, the displacer 51 is inserted into the first cylinder 15A, and the piston 23 is inserted into the second cylinder 15B so that the rod 52 penetrates the piston 23. By curing the adhesive A in the first cylinder 15A, the displacer 51 and the rod 52 are connected, so that the displacer 51 and the rod 52 can be fixed by the adhesive A in a positional relationship in which the first cylinder 15A and the displacer 51, and the second cylinder 15B and the piston 23 are coaxial.

[0065] Next, a third embodiment of the present invention will be described with reference to FIGS. 13 to 15. In this embodiment, elements other than the displacer 61, the rod 62, the washer 63, and the nut 64 are the same as those in the above-described first embodiment. Although illustration is omitted, the same reference numerals are given to the elements common to the first embodiment.

[0066] The β-type free piston Stirling refrigerator as a free piston Stirling engine of this embodiment has a metal casing 2. And this casing 2 has a first casing body 3 and a second casing body 4. The first casing body 3 is integrally formed with a cylindrical portion 5 formed in a small-diameter cylindrical shape and a large-diameter portion 6 having an open base end. And the said cylindrical part 5 has the front-end part 7 which was obstruct | occluded, the intermediate part 8, and the base part 9. Moreover, the said large-diameter part 6 has an end face part 10 formed in a substantially circular protruding curved surface shape, and a short cylindrical side face part 11. Similarly, the second casing body 4 has a cylindrical side face part 12 and the other end face part 13 formed in a substantially circular protruding curved surface shape. And the large-diameter part 6 and the second casing body 4 form a cylindrical body part 14.

[0067] Inside the cylindrical portion 5, a cylinder 15 extending to the inside of the body portion 14 is coaxially inserted into the cylindrical portion 5. That is, the central axis X of the cylinder 15 coincides with the central axis X of the cylindrical portion 5. And the cylinder 15 is formed using metal. This cylinder 15 has a first cylinder 15A on the tip side and a second cylinder 15B on the base end side and is integrally formed, but a part of the first cylinder 15A may be formed in combination with a material having low thermal conductivity. Note that the first cylinder 15A and the second cylinder 15B are formed coaxially and have the same inner diameter. Inside the first cylinder 15A, a displacer 61 is accommodated so as to be reciprocable in the central axis X direction. Also, an expansion chamber E1 is formed between the tip of this displacer 61 and the tip portion 7 of the cylindrical portion 5, and the inside and outside of the cylinder 15 communicate with each other through a gap 17. Also, in the intermediate portion 8, a regenerator 18 is provided between the inner circumference of the cylindrical portion 5 and the outer circumference of the cylinder 15, and in the base portion 9, a communication hole 19 communicating the inside and outside of the cylinder 15 is formed in the cylinder 15 itself. Also, heat absorption fins 20 are provided between the inner circumference of the tip portion 7 of the cylindrical portion 5 and the outer circumference of the tip of the cylinder 15, and exhaust heat fins 21 are provided between the inner circumference of the cylindrical portion 5 and the outer circumference of the cylinder 15 between the regenerator 18 and the communication hole 19. And a path 22 is formed from the inner tip of the cylinder 15 through the gap 17, the heat absorption fins 20, the regenerator 18, the exhaust heat fins 21, and the communication hole 19 to the compression chamber C1 inside the cylinder 15. Further, inside the body portion 4, a piston 23 is accommodated inside the second cylinder 15B so as to be reciprocable in the central axis X direction. And the base end portion of this piston 23 is coaxially connected to a linear motor 24. Note that this linear motor 24 includes a mover 26 connected to the base end of the piston 23 by a connecting body 25 and extending coaxially on the outer circumference of the base end side of the cylinder 15, and an annular stator 27 provided close to the outer circumference of this mover 26.

[0068] Further, a first leaf spring 28 for controlling the operation of the piston 23 is connected to the connector 25 that connects the mover 26 to the piston 23. Further, one end of a rod 62 that operates together with the displacer 61 is connected to the base end face 61B side of the displacer 61, and a second leaf spring 30 is connected to the other end of the rod 62. The rod 62 passes through the center of the piston 23 and extends in the direction of the central axis X. The first and second leaf springs 28 and 30 are disposed outside the second cylinder 15B within the body portion 14, and the second leaf spring 30 is disposed at a position farther from the second cylinder 15B than the first leaf spring 28.

[0069] A detailed description will be given of the assembly of the piston 23, the connector 25, the mover 26, and the first leaf spring 28. The piston 23 is formed in a cylindrical shape. A through-hole 31 through which the rod 62 is inserted is formed in the center of the piston 23. Further, the proximal end side of the piston 23 is open, and an internal thread (not shown) is formed on the inner surface of this opening. The connector 25 has a through-hole (not shown) formed in the direction of the central axis X, and the rod 62 is inserted into this through-hole. And an external thread (not shown) is formed on the piston 23 side of the connector 25 in the direction of the central axis X, and an external thread 32 is formed on the opposite side of this external thread. The mover 26 is configured to include a frame 33 and a cylindrical permanent magnet 34 fixed to one end side of the frame 33. The frame 33 is made of a non-magnetic material such as synthetic resin, and a through-hole 35 through which the external thread (not shown) of the connector 25 is inserted is formed. The permanent magnet 34 is fixed to the frame 33. And through the through-hole 35 of the frame 33, the external thread (not shown) of the connector 25 and the internal thread (not shown) of the piston 23 are screwed together. In this way, by screwing the external thread (not shown) of the connector 25 and the internal thread (not shown) of the piston 23 together, the frame 33 of the mover 26 is clamped between the proximal end of the piston 23 and the connector 25. Thereby, the piston 23, the connector 25, and the mover 26 are integrated. A through-hole (not shown) is formed in the central portion of the first leaf spring 28, and the external thread 32 of the connector 25 is inserted into this through-hole. And after inserting the external thread 32 into the through-hole, by screwing a nut 36 onto the external thread 32, the first leaf spring 28 is clamped between the connector 25 and the nut 36.

[0070] One end of the rod 62 is formed with a first male thread portion 65, and a flange portion 66 is formed at the base end portion of the first male thread portion 65. The first male thread portion 65 is inserted through a through hole 67 formed at the central portion on the base end face 61B side of the displayer 61. Then, a washer 63 and a nut 64 are attached to the tip side of the first male thread portion 65. That is, inside the displayer 61, the first male thread portion 65 is inserted through the washer 63 and screwed with the nut 64. Thereby, the base end face 61B side of the displayer 61 is clamped between the flange portion 66 of the rod 62 and the washer 63. On the other hand, a second male thread portion 39 is formed at the other end of the rod 62. A through hole (not shown) is formed at the central portion of the second leaf spring 30, and the second male thread portion 39 is inserted through this through hole. Then, after the second male thread portion 39 is inserted through the through hole, the nut 40 is screwed onto the second male thread portion 39, so that the second leaf spring 30 is clamped between the rod 29 and the nut 40.

[0071] As shown in FIG. 13, the diameter of the thread of the first male thread portion 65 is D8, the diameter of the flange portion 66 is D9. Also, the diameter of the through hole 67 is D10. And the relationship among D8 to D10 is as follows.

[0072] (D8 + D9) / 2 ≧ D10 > D8 Due to this condition, even if the tip of the thread of the first male thread portion 65 abuts on the side surface of the through hole 67 on one side, on the side opposite to the abutting side, the outer edge of the flange portion 66 abuts on the base end face 61B side of the displayer 61. That is, even if the central axis of the first male thread portion 65 and the central axis of the through hole 67 are maximally displaced, the outer edge of the flange portion 66 abuts on the base end face 61B side of the displayer 61 over the entire circumference.

[0073] Incidentally, 41 is a vibration absorption unit provided on the other end face portion 13 of the second casing body 4, and is arranged coaxially with the central axis X of the cylinder 15. Through a mounting portion 42 arranged to be coaxial therewith and a connecting portion 43 connected to the mounting portion 42, a leaf spring 44 and a balance weight 45 are arranged coaxially so as to overlap each other.

[0074] Next, the manufacturing process of the β-type free piston Stirling refrigerator of the present embodiment will be described. First, similar to the first embodiment, it is pre-assembled to the state shown in FIG. 2. That is, the heat absorption fin 20, the regenerator 18, and the exhaust heat fin 21 are inserted into the cylindrical portion 5 of the first casing body 3, and the first cylinder 15A of the cylinder 15 in a state where the stator 27 is attached is inserted and fixed inside the heat absorption fin 20, the regenerator 18, and the exhaust heat fin 21. Similarly, the piston 23, the connector 25, and the mover 26 are integrated.

[0075] Next, the displacer 61 and the rod 62 are assembled. In this process, after inserting the first male screw portion 65 of the rod 62 into the through hole 67 of the displacer 61, an adhesive is injected into the space between the first male screw portion 65 and the through hole 67, and then the tip of the first male screw portion 65 is passed through the washer 63, and further the nut 64 is screwed onto the tip of the first male screw portion 65. Incidentally, at this time, the first male screw portion 65 and the nut 64 are not strongly screwed, and the displacer 61 is made slightly movable in the axial direction perpendicular to the rod 62. This movable "play" is within (D10 - D8) / 2 in the axial direction perpendicular to the center axis of the first male screw portion 37 with the center axes of the first male screw portion 37 and the through hole 67 aligned.

[0076] Next, similar to the first embodiment, as shown in FIG. 4, the thus assembled displacer 61 and rod 62 are inserted into the cylinder 15 from the side of the displacer 61 before the adhesive A hardens. At this time, the displacer 61 is inserted up to the first cylinder 15A.

[0077] Next, in the same manner as in the first embodiment, the piston 23 is inserted into the second cylinder 15B. At this time, the rod 62 connected to the displacer 61 previously inserted into the first cylinder 15A is inserted into the through-hole 31 formed in the piston 23. Further, as described above, since the piston 23 is integrated with the connector 25 and the mover 26, when the piston 23 is inserted into the second cylinder 15B, the mover 26 approaches the inside of the stator 27. By leaving this state for a while, the adhesive A hardens, and the first male screw portion 65 and the through-hole 67, that is, the displacer 61 and the rod 62 are completely fixed. Note that when the through-hole 67 is accurately formed at the center of the displacer 61, the through-hole 31 is accurately formed at the center of the piston 23, and the first cylinder 15A and the second cylinder 15B are accurately coaxial, as shown in FIG. 14, the adhesive A hardens in a state where the first male screw portion 65 of the rod 62 is located at the center of the through-hole 67 of the displacer 61. On the other hand, when the through-hole 67 is slightly displaced from the center with respect to the displacer 61, by inserting the piston 23 into the second cylinder 15B, before the adhesive A hardens, the first male screw portion 65 slightly moves in the axial direction with respect to the through-hole 67. As a result, as shown in FIG. 15, the adhesive A hardens in a state where the first male screw portion 65 is slightly displaced in the axial direction with respect to the through-hole 67. Note that FIG. 15 shows the case where the through-hole 67 is slightly displaced from the center with respect to the displacer 61, but the same applies when the through-hole 31 is slightly displaced from the center with respect to the piston 23 or when the axial centers of the first cylinder 15A and the second cylinder 15B are slightly displaced.

[0078] Further, in the same manner as in the first embodiment, after the adhesive A is cured, the first leaf spring 28 is clamped between the connector 25 and the nut 36, and the second leaf spring 30 is clamped between the rod 62 and the nut 40. Further, the second casing body 4 to which the mounting portion 42 is fixed is connected to the first casing body 3 and hermetically welded. After the inside of the casing 2 is filled with the operating gas at a predetermined pressure, the connecting portion 43, the leaf spring 44, and the balance weight 45 are connected to the mounting portion 42, whereby the β-type free piston Stirling refrigerator is completed.

[0079] By assembling in this way, even if there is a deviation in the first cylinder 15A, the second cylinder 15B, the through hole 67 of the displacer 61, and the through hole 31 of the piston 23, the alignment of the first cylinder 15A and the displacer 61, the second cylinder 15B and the piston 23, and the rod 62 and the piston 23 can be accurately performed without using a special jig.

[0080] As described above, the present invention is a method for manufacturing a β-type free piston Stirling refrigerator as a free piston Stirling engine having a first cylinder 15A, a second cylinder 15B, a displacer 61 reciprocable in the central axis X direction of the first cylinder 15A, a piston 23 reciprocable in the central axis X direction of the second cylinder 15B, and a rod 62 having one end fixed to the displacer 61 by an adhesive A and penetrating the piston 23 in the central axis X direction. In this method, the adhesive A is disposed between a first male screw portion 65 which is one end of the rod 62 and a through hole 67 of the displacer 61. Before the adhesive A cures, the displacer 61 is inserted into the first cylinder 15A, and the piston 23 is inserted into the second cylinder 15B so that the rod 62 penetrates the piston 23. Then, the adhesive A is cured within the first cylinder 15A to connect the displacer 61 and the rod 62, whereby the displacer 61 and the rod 62 can be fixed by the adhesive A in a positional relationship in which the first cylinder 15A and the displacer 61, and the second cylinder 15B and the piston 23 are coaxial.

[0081] Next, a fourth embodiment of the present invention will be described with reference to FIGS. 16 to 18. In this embodiment, elements other than the displacer 61, the rod 72, the washer 63, and the screw 74 are the same as those in the first embodiment described above. Although illustration is omitted, the same reference numerals are given to elements common to the first embodiment.

[0082] The β-type free-piston Stirling refrigerator as a free-piston Stirling engine of the present embodiment has a metal casing 2. And this casing 2 has a first casing body 3 and a second casing body 4. The first casing body 3 is integrally formed with a cylindrical portion 5 formed in a small-diameter cylindrical shape and a large-diameter portion 6 with an open base end. And the cylindrical portion 5 has a closed tip portion 7, an intermediate portion 8, and a base portion 9. Further, the large-diameter portion 6 has an end face portion 10 formed in a substantially circular protruding curved surface shape and a short cylindrical side face portion 11. Similarly, the second casing body 4 has a cylindrical side face portion 12 and the other end face portion 13 formed in a substantially circular protruding curved surface shape. And a cylindrical body portion 14 is formed by the large-diameter portion 6 and the second casing body 4.

[0083] Inside the cylindrical portion 5, a cylinder 15 extending to the inside of the body portion 14 is coaxially inserted into the cylindrical portion 5. That is, the central axis X of the cylinder 15 coincides with the central axis X of the cylindrical portion 5. And the cylinder 15 is formed using metal. This cylinder 15 has a first cylinder 15A on the tip side and a second cylinder 15B on the base end side and is integrally formed, but a part of the first cylinder 15A may be formed in combination with a material having low thermal conductivity. Note that the first cylinder 15A and the second cylinder 15B are formed coaxially and have the same inner diameter. Inside the first cylinder 15A, a displacer 61 is accommodated so as to be reciprocable in the direction of the central axis X. Also, an expansion chamber E1 is formed between the tip of this displacer 61 and the tip portion 7 of the cylindrical portion 5, and the inside and outside of the cylinder 15 communicate with each other through a gap 17. Further, in the intermediate portion 8, a regenerator 18 is provided between the inner circumference of the cylindrical portion 5 and the outer circumference of the cylinder 15, and in the base portion 9, a communication hole 19 communicating the inside and outside of the cylinder 15 is formed in the cylinder 15 itself. Also, a heat absorption fin 20 is provided between the inner circumference of the tip portion 7 of the cylindrical portion 5 and the outer circumference of the tip of the cylinder 15, and an exhaust heat fin 21 is provided between the inner circumference of the cylindrical portion 5 and the outer circumference of the cylinder 15 between the regenerator 18 and the communication hole 19. And a path 22 is formed from the inner tip of the cylinder 15 through the gap 17, the heat absorption fin 20, the regenerator 18, the exhaust heat fin 21, and the communication hole 19 to the compression chamber C1 in the cylinder 15. Further, inside the body portion 4, a piston 23 is accommodated so as to be reciprocable in the direction of the central axis X inside the second cylinder 15B. And the base end portion of this piston 23 is coaxially connected to a linear motor 24. Note that this linear motor 24 is configured to have a mover 26 connected to the base end of the piston 23 by a connector 25 and extending coaxially to the outer circumference on the base end side of the cylinder 15, and an annular stator 27 provided close to the outer circumference of this mover 26.

[0084] Further, a first leaf spring 28 for controlling the operation of the piston 23 is connected to the connecting body 25 that connects the mover 26 to the piston 23. Further, one end of a rod 72 that operates together with the displacer 61 is connected to the base end face 61B side of the displacer 61, and a second leaf spring 30 is connected to the other end of the rod 72. The rod 72 penetrates the center of the piston 23 and extends in the direction of the central axis X. The first and second leaf springs 28 and 30 are disposed outside the second cylinder 15B within the body portion 14, and the second leaf spring 30 is disposed at a position farther from the second cylinder 15B than the first leaf spring 28.

[0085] A detailed description will be given of the assembly of the piston 23, the connector 25, the mover 26, and the first leaf spring 28. The piston 23 is formed in a cylindrical shape. A through-hole 31 through which the rod 72 is inserted is formed at the center of the piston 23. The proximal end side of the piston 23 is open, and an internal thread (not shown) is formed on the inner surface of this opening. The connector 25 has a through-hole (not shown) formed in the central axis X direction, and the rod 72 is inserted into this through-hole. An external thread (not shown) is formed on the piston 23 side of the connector 25 in the central axis X direction, and an external thread 32 is formed on the opposite side of this external thread. The mover 26 is configured to include a frame 33 and a cylindrical permanent magnet 34 fixed to one end side of the frame 33. The frame 33 is made of a non-magnetic material such as synthetic resin, and a through-hole 35 through which the external thread (not shown) of the connector 25 is inserted is formed. The permanent magnet 34 is fixed to the frame 33. Then, via the through-hole 35 of the frame 33, the external thread (not shown) of the connector 25 and the internal thread (not shown) of the piston 23 are screwed together. In this way, by screwing together the external thread (not shown) of the connector 25 and the internal thread (not shown) of the piston 23, the frame 33 of the mover 26 is clamped between the proximal end of the piston 23 and the connector 25. Thereby, the piston 23, the connector 25, and the mover 26 are integrated. A through-hole (not shown) is formed at the center of the first leaf spring 28, and the external thread 32 of the connector 25 is inserted into this through-hole. Then, after inserting the external thread 32 into the through-hole, a nut 36 is screwed onto the external thread 32, so that the first leaf spring 28 is clamped between the connector 25 and the nut 36.

[0086] One end of the rod 72 is formed with a large-diameter portion 75, and an internal thread portion 76 is formed on the large-diameter portion 75. The internal thread portion 76 is screwed with the external thread portion 74A of the screw 74 through a through-hole 67 and a washer 63 formed at the central portion on the base end face 61B side of the displacer 61. On the other hand, an external thread portion 39 is formed at the other end of the rod 72. A through-hole (not shown) is formed at the central portion of the second leaf spring 30, and the external thread portion 39 is inserted through the through-hole. Then, after inserting the external thread portion 39 through the through-hole, a nut 40 is screwed onto the external thread portion 39, whereby the second leaf spring 30 is clamped between the rod 72 and the nut 40.

[0087] As shown in FIG. 16, the diameter D10 of the through-hole 67 of the displacer 61 is larger than the diameter D11 of the thread crest of the external thread portion 74A of the screw 74. The diameter of the washer 63 and the diameter of the large-diameter portion 75 are sufficiently larger than the diameter D10 of the through-hole 67. Thereby, regardless of the positional relationship in the axial direction perpendicular to the axis of the screw 74 and the through-hole 67, the openings on both sides of the through-hole 67 are blocked by the washer 63 and the large-diameter portion 75. That is, even if the central axis of the screw 74 and the central axis of the through-hole 67 are maximally displaced, the openings on both sides of the through-hole 67 are blocked by the washer 63 and the large-diameter portion 75.

[0088] Reference numeral 41 denotes a vibration absorption unit provided on the other end surface portion 13 of the second casing body 4. A plate spring 44 and a balance weight 45 are coaxially arranged so as to overlap each other via a mounting portion 42 arranged to be coaxial with the central axis X of the cylinder 15 and a connecting portion 43 connected to the mounting portion 42.

[0089] Next, the manufacturing process of the β-type free piston Stirling refrigerator according to the present embodiment will be described. First, as in the first embodiment, it is pre-assembled to the state shown in FIG. 2. That is, the heat absorption fin 20, the regenerator 18, and the exhaust heat fin 21 are inserted into the cylindrical portion 5 of the first casing body 3, and the first cylinder 15A of the cylinder 15 in the state where the stator 27 is attached is inserted and fixed inside the heat absorption fin 20, the regenerator 18, and the exhaust heat fin 21. Similarly, the piston 23, the connector 25, and the mover 26 are integrated.

[0090] Next, the displacer 61 and the rod 72 are assembled. In this process, adhesive A is injected into the female screw portion 76 of the rod 72, and adhesive A is injected into the through hole 67 of the displacer 61. Then, the male screw portion 74A of the screw 74 and the female screw portion 76 of the rod 72 are screwed together through the washer 63 and the through hole 67. At this time, the female screw portion 76 of the rod 72 and the male screw portion 74A of the screw 74 are not strongly screwed together, and the displacer 61 is slightly movable in the axial direction perpendicular to the rod 72. This movable "play" is within (D10 - D11) / 2 in the axial direction perpendicular to the center axis of the through hole 67 and the center axis of the screw 74 from the state where the center axes are aligned.

[0091] Next, as in the first embodiment, as shown in FIG. 4, the thus-assembled displacer 61 and rod 72 are inserted into the cylinder 15 from the displacer 61 side before the adhesive A hardens. At this time, the displacer 61 is inserted up to the first cylinder 15A.

[0092] Next, in the same manner as in the first embodiment, the piston 23 is inserted into the second cylinder 15B. At this time, the rod 72 connected to the displacer 61 previously inserted into the first cylinder 15A is inserted into the through-hole 31 formed in the piston 23. Further, as described above, since the piston 23 is integrated with the connector 25 and the mover 26, when the piston 23 is inserted into the second cylinder 15B, the mover 26 approaches the inside of the stator 27. By leaving this state for a while, the adhesive A hardens, and the screw 74, the through-hole 67, and the female screw portion 76, that is, the displacer 61 and the rod 72 are completely fixed. Note that when the through-hole 67 is accurately formed at the center of the displacer 61, the through-hole 31 is accurately formed at the center of the piston 23, and the first cylinder 15A and the second cylinder 15B are accurately coaxial, as shown in FIG. 17, the adhesive A hardens in a state where the female screw portion 76 of the rod 72 and the screw 74 are located at the center of the through-hole 67 of the displacer 61. On the other hand, when the through-hole 67 is slightly deviated from the center with respect to the displacer 61, by inserting the piston 23 into the second cylinder 15B, before the adhesive A hardens, the female screw portion 76 of the rod 72 and the screw 74 slightly move in the axial direction with respect to the through-hole 67. As a result, as shown in FIG. 18, the adhesive A hardens in a state where the female screw portion 76 of the rod 72 and the screw 74 are slightly deviated in the axial direction with respect to the through-hole 67 of the displacer 61. Note that FIG. 18 shows the case where the through-hole 67 is slightly deviated from the center with respect to the displacer 61, but the same applies when the through-hole 31 is slightly deviated from the center with respect to the piston 23 or when the axial centers of the first cylinder 15A and the second cylinder 15B are slightly deviated.

[0093] Furthermore, similar to the first embodiment, after the adhesive A is cured, the first leaf spring 28 is clamped between the connector 25 and the nut 36, and the second leaf spring 30 is clamped between the rod 72 and the nut 40. Further, the second casing body 4 to which the mounting portion 42 is fixed is connected to the first casing body 3 and hermetically welded. After the inside of the casing 2 is filled with the operating gas at a predetermined pressure, the connecting portion 43, the leaf spring 44, and the balance weight 45 are connected to the mounting portion 42, thereby completing the β-type free piston Stirling refrigerator 1.

[0094] By assembling in this way, even if there is a deviation in the first cylinder 15A, the second cylinder 15B, the through hole 67 of the displacer 61, and the through hole 31 of the piston 23, the first cylinder 15A and the displacer 61, the second cylinder 15B and the piston 23, and the alignment of the rod 72 and the piston 23 can be accurately performed without using a special jig.

[0095] As described above, the present invention relates to a method for manufacturing a β-type free piston Stirling refrigerator as a free piston Stirling engine having a first cylinder 15A, a second cylinder 15B, a displacer 61 reciprocable in the central axis X direction of the first cylinder 15A, a piston 23 reciprocable in the central axis X direction of the second cylinder 15B, and a rod 72 having one end fixed to the displacer 61 by an adhesive A and penetrating the piston 23 in the central axis X direction. In this method, the adhesive A is disposed between one end of the rod 72 and the displacer 61. Before the adhesive A is cured, the displacer 61 is inserted into the first cylinder 15A, the piston 23 is inserted into the second cylinder 15B so that the rod 72 penetrates the piston 23, and the adhesive A is cured in the first cylinder 15A. By connecting the displacer 61 and the rod 72, the displacer 61 and the rod 72 can be fixed by the adhesive A in a positional relationship in which the first cylinder 15A and the displacer 61, and the second cylinder 15B and the piston 23 are coaxial.

[0096] Further, in the present invention, a through hole 67 is formed in the displacer 61, a female screw portion 76 is formed at one end of the rod 72, and a screw 74 having a male screw portion that can be screwed into the female screw portion 76 through the through hole 67 is provided. The adhesive A is disposed between the through hole 67 of the displacer 61, the female screw portion 76 of the rod 72, and the male screw portion 74A of the screw 74. The male screw portion 74A of the screw 74 is lightly screwed into the female screw portion 76 of the rod 72. By inserting the displacer 61 into the first cylinder 15A and inserting the piston 23 into the second cylinder 15B, the displacer 61 and the rod 72 can be easily inserted into the first cylinder 15A in a temporarily assembled state.

[0097] Next, a fifth embodiment of the present invention will be described with reference to FIGS. 19 to 21. In this embodiment, elements other than the displacer 81 and the rod 72 are common to the first embodiment described above. Although illustration is omitted, the same reference numerals are given to the elements common to the first embodiment.

[0098] The β-type free piston Stirling refrigerator as a free piston Stirling engine of the present embodiment has a metal casing 2. The casing 2 has a first casing body 3 and a second casing body 4. The first casing body 3 is integrally formed with a cylindrical portion 5 formed in a small-diameter cylindrical shape and a large-diameter portion 6 having an open base end. The cylindrical portion 5 has a closed tip portion 7, an intermediate portion 8, and a base portion 9. The large-diameter portion 6 has an end face portion 10 formed in a substantially circular protruding curved surface shape and a short cylindrical side face portion 11. Similarly, the second casing body 4 has a cylindrical side face portion 12 and another end face portion 13 formed in a substantially circular protruding curved surface shape. A cylindrical body portion 14 is formed by the large-diameter portion 6 and the second casing body 4.

[0099] Inside the cylindrical portion 5, a cylinder 15 extending to the inside of the body portion 14 is coaxially inserted into the cylindrical portion 5. That is, the central axis X of the cylinder 15 coincides with the central axis X of the cylindrical portion 5. And the cylinder 15 is formed using metal. This cylinder 15 has a first cylinder 15A on the tip side and a second cylinder 15B on the base end side and is integrally formed, but a part of the first cylinder 15A may be formed in combination with a material having low thermal conductivity. Note that the first cylinder 15A and the second cylinder 15B are formed coaxially and with the same inner diameter. And inside the first cylinder 15A, a displacer 81 is accommodated so as to be reciprocable in the central axis X direction. Also, an expansion chamber E1 is formed between the tip of this displacer 81 and the tip portion 7 of the cylindrical portion 5, and the inside and outside of the cylinder 15 communicate with each other through a gap 17. Further, in the intermediate portion 8, a regenerator 18 is provided between the inner periphery of the cylindrical portion 5 and the outer periphery of the cylinder 15, and in the base portion 9, a communication hole 19 communicating the inside and outside of the cylinder 15 is formed in the cylinder 15 itself. Also, heat absorption fins 20 are provided between the inner periphery of the tip portion 7 of the cylindrical portion 5 and the outer periphery of the tip of the cylinder 15, and exhaust heat fins 21 are provided between the inner periphery of the cylindrical portion 5 and the outer periphery of the cylinder 15 between the regenerator 18 and the communication hole 19. And a path 22 is formed from the inner tip of the cylinder 15 through the gap 17, the heat absorption fins 20, the regenerator 18, the exhaust heat fins 21, and the communication hole 19 to the compression chamber C1 inside the cylinder 15. Further, inside the body portion 4, a piston 23 is accommodated inside the second cylinder 15B so as to be reciprocable in the central axis X direction. And the base end portion of this piston 23 is coaxially connected to a linear motor 24. Note that this linear motor 24 includes a mover 26 connected to the base end of the piston 23 by a connecting body 25 and extending coaxially to the outer periphery of the base end side of the cylinder 15, and an annular stator 27 provided close to the outer periphery of this mover 26.

[0100] Further, a first leaf spring 28 for controlling the operation of the piston 23 is connected to the connector 25 that connects the mover 26 to the piston 23. Further, one end of a rod 72 that operates together with the displacer 81 is connected to the base end surface 81B side of the displacer 81, and a second leaf spring 30 is connected to the other end of the rod 72. Note that the rod 72 passes through the center of the piston 23 and extends in the central axis X direction. Also, the first and second leaf springs 28 and 30 are disposed outside the second cylinder 15B within the body portion 14, and the second leaf spring 30 is disposed at a position farther from the second cylinder 15B than the first leaf spring 28.

[0101] The assembly of the piston 23, the connector 25, the mover 26, and the first leaf spring 28 will be described in detail. The piston 23 is formed in a cylindrical shape. A through hole 31 through which the rod 72 is inserted is formed in the center of the piston 23. Further, the proximal end side of the piston 23 is open, and an internal thread (not shown) is formed on the inner surface of this opening. The connector 25 has a through hole (not shown) formed in the central axis X direction, and the rod 72 is inserted into this through hole. An external thread (not shown) is formed on the piston 23 side of the connector 25 in the central axis X direction, and an external thread 32 is formed on the opposite side of this external thread. The mover 26 is configured to include a frame 33 and a cylindrical permanent magnet 34 fixed to one end side of the frame 33. The frame 33 is made of a non-magnetic material such as synthetic resin, and a through hole 35 through which the external thread (not shown) of the connector 25 is inserted is formed. The permanent magnet 34 is fixed to the frame 33. Then, via the through hole 35 of the frame 33, the external thread (not shown) of the connector 25 and the internal thread (not shown) of the piston 23 are screwed together. In this way, by screwing the external thread (not shown) of the connector 25 and the internal thread (not shown) of the piston 23 together, the frame 33 of the mover 26 is sandwiched between the proximal end of the piston 23 and the connector 25. As a result, the piston 23, the connector 25, and the mover 26 are integrated. A through hole (not shown) is formed in the central portion of the first leaf spring 28, and the external thread 32 of the connector 25 is inserted into this through hole. Then, after inserting the external thread 32 into the through hole, a nut 36 is screwed onto the external thread 32, so that the first leaf spring 28 is sandwiched between the connector 25 and the nut 36.

[0102] One end of the rod 72 is formed with a large-diameter portion 75, and an internal thread portion 76 is formed on the large-diameter portion 75. The internal thread portion 76 is screwed with an external thread portion 82 formed at the center of the base end surface 81B side of the display retainer 81. The external thread portion 82 is formed integrally with the display retainer 81, but may be integrated with the display retainer 81 by insert molding a metal screw or the like, for example. On the other hand, an external thread portion 39 is formed at the other end of the rod 72. A through hole (not shown) is formed at the center of the second leaf spring 30, and the external thread portion 39 is inserted through the through hole. Then, after inserting the second external thread portion 39 through the through hole, a nut 40 is screwed onto the external thread portion 39, so that the second leaf spring 30 is clamped between the rod 29 and the nut 40.

[0103] As shown in FIG. 19, the diameter of the thread crest of the external thread portion 82 of the display retainer 81 is D1, and the diameter of the thread root is D2. The diameter of the thread crest of the internal thread portion 76 of the rod 72 is D3, and the diameter of the thread root is D4. The relationship among D1 to D4 is as follows.

[0104] (1): (D3 + D4) / 2 > (D1 + D2) / 2 ≥ D3

[0105] (2): D4 > D1 ≥ (D3 + D4) / 2

[0106] According to the condition of (1), even if the tip of the thread crest of the internal thread portion 76 approaches or abuts against the bottom of the thread root of the external thread portion 82 at one side to the maximum extent, the thread crest on the opposite side of the external thread portion 82 overlaps with the thread crest of the internal thread portion 76 in the axial direction view. And according to the condition of (2), even if the tip of the thread crest of the external thread portion 82 approaches or abuts against the bottom of the thread root of the internal thread portion 76 at one side to the maximum extent, the thread crest on the opposite side of the external thread portion 82 overlaps with the thread crest of the internal thread portion 76 in the axial direction view. That is, even if the central axis of the external thread portion 82 and the central axis of the internal thread portion 76 are displaced to the maximum extent, the thread crest of the external thread portion 82 and the thread crest of the internal thread portion 76 will surely overlap in the axial direction view over the entire circumference.

[0107] Note that reference numeral 41 is a vibration absorption unit provided on the other end face portion 13 of the second casing body 4, and a plate spring 44 and a balance weight 45 are coaxially arranged so as to overlap via a mounting portion 42 arranged coaxially with the central axis X of the cylinder 15 and a connecting portion 43 connected to the mounting portion 42.

[0108] Next, the manufacturing process of the β-type free piston Stirling refrigerator of the present embodiment will be described. First, similar to the first embodiment, it is pre-assembled to the state shown in FIG. 2. That is, the heat absorption fin 20, the regenerator 18, and the exhaust heat fin 21 are inserted into the cylindrical portion 5 of the first casing body 3, and the first cylinder 15A of the cylinder 15 in a state where the stator 27 is attached is inserted and fixed inside the heat absorption fin 20, the regenerator 18, and the exhaust heat fin 21. Similarly, the piston 23, the connector 25, and the mover 26 are integrated.

[0109] Next, the displacer 81 and the rod 72 are assembled. In this process, adhesive A is applied to the male screw portion 82 of the displacer 81, or adhesive A is injected into the female screw portion 76 of the rod 72, or both are performed, and then the male screw portion 82 is screwed into the female screw portion 76. At this time, the female screw portion 76 and the male screw portion 82 are not strongly screwed, and the displacer 81 is slightly movable in the axial direction perpendicular to the rod 72. This movable "play" is within (D4 - D1) / 2 or within (D3 - D2) / 2 in the axial direction perpendicular to the state where the central axes of the female screw portion 76 and the male screw portion 82 are aligned.

[0110] Next, similar to the first embodiment, the thus-assembled displacer 81 and rod 72 are inserted into the cylinder 15 from the displacer 81 side before the adhesive A hardens. At this time, the displacer 81 is inserted up to the first cylinder 15A.

[0111] Next, similarly to the first embodiment, the piston 23 is inserted into the second cylinder 15B. At this time, the rod 72 connected to the displacer 81 previously inserted into the first cylinder 15A is inserted into the through-hole 31 formed in the piston 23. Further, since the piston 23 is integrated with the connector 25 and the mover 26 as described above, when the piston 23 is inserted into the second cylinder 15B, the mover 26 approaches the inside of the stator 27. By leaving it in this state for a while, the adhesive A hardens, and the male screw portion 82 and the female screw portion 76, that is, the displacer 81 and the rod 72 are completely fixed. Note that when the male screw portion 82 is accurately formed at the center of the displacer 81, the through-hole 31 is accurately formed at the center of the piston 23, and the first cylinder 15A and the second cylinder 15B are exactly coaxial, as shown in FIG. 20, the adhesive A hardens in a state where the male screw portion 82 of the displacer 81 is located at the center of the female screw portion 76 of the rod 72. On the other hand, when the male screw portion 82 is slightly deviated from the center with respect to the displacer 81, by inserting the piston 23 into the second cylinder 15B, before the adhesive A hardens, the male screw portion 82 slightly moves in the axial direction with respect to the female screw portion 76. As a result, as shown in FIG. 21, the adhesive A hardens in a state where the male screw portion 82 is slightly displaced in the axial direction with respect to the female screw portion 76. Note that FIG. 21 shows the case where the male screw portion 82 is slightly deviated from the center with respect to the displacer 81, but the same applies when the through-hole 31 is slightly deviated from the center with respect to the piston 23 or the axial centers of the first cylinder 15A and the second cylinder 15B are slightly deviated.

[0112] Furthermore, similar to the first embodiment, after the adhesive A has cured, the first leaf spring 28 is clamped between the connector 25 and the nut 36, and the second leaf spring 30 is clamped between the rod 72 and the nut 40. Further, the second casing body 4 to which the mounting portion 42 is fixed is connected to the first casing body 3 and hermetically welded. After the inside of the casing 2 is filled with the operating gas at a predetermined pressure, the connection portion 43, the leaf spring 44, and the balance weight 45 are connected to the mounting portion 42, thereby completing the β-type free piston Stirling refrigerator.

[0113] By assembling in this way, even if there is a deviation in the first cylinder 15A, the second cylinder 15B, the male screw portion 82 of the displacer 81, and the through hole 31 of the piston 23, the first cylinder 15A and the displacer 16, the second cylinder 15B and the piston 23, and the rod 72 and the piston 23 can be accurately aligned without using a special jig.

[0114] As described above, the present invention provides a method for manufacturing a β-type free piston Stirling refrigerator as a free piston Stirling engine having a first cylinder 15A, a second cylinder 15B, a displacer 81 reciprocable in the central axis X direction of the first cylinder 15A, a piston 23 reciprocable in the central axis X direction of the second cylinder 15B, a rod 72 having one end fixed to the displacer 81 by an adhesive A and penetrating the piston 23 in the central axis X direction. In this method, the adhesive A is disposed between the female screw portion 76 at one end of the rod 72 and the displacer 81. Before the adhesive A cures, the displacer 81 is inserted into the first cylinder 15A, the piston 23 is inserted into the second cylinder 15B so that the rod 72 penetrates the piston 23, and the adhesive A is cured in the first cylinder 15A. By connecting the displacer 81 and the rod 72, the displacer 81 and the rod 72 can be fixed by the adhesive A in a positional relationship in which the first cylinder 15A and the displacer 81, and the second cylinder 15B and the piston 23 are coaxial.

[0115] Further, in the present invention, a female screw portion 76 is formed at one end of the rod 72, a male screw portion 82 is formed on the displacer 81, the adhesive A is disposed between the male screw portion 82 and the female screw portion 76, and after the male screw portion 82 and the female screw portion 76 are lightly screwed together, the displacer 81 is inserted into the first cylinder 15A, and the piston 23 is inserted into the second cylinder 15B. Thus, in a state where the displacer 81 and the rod 72 are temporarily assembled, they can be easily inserted into the first cylinder 15A.

[0116] Further, in the present invention, when the diameter of the thread crest of the male screw portion 82 is D1, the diameter of the thread groove of the male screw portion 82 is D2, the diameter of the thread crest of the female screw portion 76 is D3, and the diameter of the thread groove of the female screw portion 76 is D4, the male screw portion 82 and the female screw portion 76 are formed such that (D3 + D4) / 2 > (D1 + D2) / 2 ≥ D3. Thus, when viewed in the direction of the central axis X, the thread crests of the male screw portion 82 and the female screw portion 76 surely overlap. Even if the axis of the male screw portion 82 and the axis of the female screw portion 76 are displaced during temporary assembly, the screwed state of both can be maintained.

[0117] Furthermore, in the present invention, when the diameter of the thread crest of the male screw portion 82 is D1, the diameter of the thread crest of the female screw portion 82 is D3, and the diameter of the thread groove of the female screw portion 76 is D4, the male screw portion 82 and the female screw portion 76 are formed such that D4 > D1 ≥ (D3 + D4) / 2. Thus, when viewed in the direction of the central axis X, the thread crests of the male screw portion 82 and the female screw portion 76 surely overlap. Even if the axis of the male screw portion 82 and the axis of the female screw portion 76 are displaced during temporary assembly, the screwed state of both can be maintained.

[0118] Next, a sixth embodiment of the present invention will be described with reference to FIGS. 22 to 30. Since the operation and action of the free piston Stirling engine itself are already known, they will not be described again in this embodiment, and the structure, manufacturing method, and the effects of this manufacturing method will be described. 101 is a γ-type free piston Stirling refrigerator as a free piston Stirling engine of the present invention. This Stirling refrigerator 101 has a metal casing 102. And this casing 102 is configured to have a cylindrical portion 103 and a body portion 104. The cylindrical portion 103 has a closed tip portion 105, an intermediate portion 106, and a base portion 107. Further, the body portion 104 is configured to have a main body portion 108 provided coaxially with the cylindrical portion 103 with reference to the axis X1, and a pair of bottomed cylindrical drive portion covers 109, 109. Note that the pair of drive portion covers 109, 109 are provided coaxially with reference to the axis X2. Also, the axis X1 and the axis X2 are orthogonal. That is, the cylindrical portion 103, the main body portion 108, and the drive portion covers 109, 109 are formed in a cross shape.

[0119] Inside the casing 102, a cylinder 110 is provided. This cylinder 110 is composed of a first cylinder 111, a second cylinder 112, a pair of piston cylinders 113, 113, and a cylindrical connection space portion 114 that connects these cylinders. The first cylinder 111 and the second cylinder 112 are provided with the connection space portion 114 interposed therebetween. And the first cylinder 111, the second cylinder 112, and the connection space portion 114 are provided coaxially with respect to the axis X1. Also, the pair of piston cylinders 113, 113 are provided with the connection space portion 114 interposed therebetween and are provided coaxially with respect to the axis X2. Further, with respect to the first cylinder 111, the second cylinder 112, and the connection space portion 114, the pair of piston cylinders 113, 113 are provided orthogonally. That is, the cylinder 110 composed of the first cylinder 111, the second cylinder 112, the pair of piston cylinders 113, 113, and the connection space portion 114 is formed in a cross shape. Also, the pair of piston cylinders 113, 113 are provided symmetrically with respect to the axis X1 twice. Further, in the first cylinder 111, a communication hole 115 that communicates the inside and outside of the first cylinder 111 is formed. And the cylinder 110 is formed by performing casting such as die casting using a non-magnetic metal, and the inner and outer circumferences of the cylinder 110 are machined after casting.

[0120] Inside the cylindrical portion 103 that constitutes the casing 102, the first cylinder 111 that constitutes the cylinder 110 is provided coaxially with the cylindrical portion 103. Also, inside the body portion 104 that constitutes the casing 102, the second cylinder 112, the pair of piston cylinders 113, 113, and the connection space portion 114 that constitute the cylinder 110 are provided. Note that the second cylinder 112 and the connection space portion 114 are provided coaxially with respect to the main body portion 108. On the other hand, the pair of piston cylinders 113, 113 are provided coaxially with respect to the pair of drive unit covers 109, 109.

[0121] Inside the first cylinder 111, a cylindrical displacer 116 is accommodated so as to be reciprocable in the direction of the axis X1. This displacer 116 has a front end face 116A and a base end face 116B. On the other hand, inside the second cylinder 112, a cylindrical displacer drive 117 is accommodated so as to be reciprocable in the direction of the axis X1. This displacer drive 117 has an inner end face 117A. And the displacer 116 and the displacer drive 117 are connected by a rod 118. This rod 118 is formed of a relatively hard metal, and its diameter is smaller than the diameter of the displacer drive 117. Thus, even if the diameter of the rod 118 is smaller than the diameter of the displacer drive 117, as described above, since the rod 118 is formed of a relatively hard metal, the coaxiality of the displacer 116 and the displacer drive 117 which are separated from each other can be ensured. Also, the diameter of the displacer drive 117 is smaller than the diameter of the displacer 116. Further, inside the pair of drive unit covers 109, 109, inside the pair of piston cylinders 113, 113, pistons 119, 119 are respectively accommodated so as to be reciprocable in the direction of the axis X2. These pistons 119, 119 are formed to have the same mass and the same shape. And the base end portions of these pistons 119, 119 have opposing faces 119A, 119A respectively and are coaxially connected to linear motors 120, 120. Incidentally, these linear motors 120, 120 are configured to have movers 121, 121 connected to the base ends of the respective pistons 119, 119 and stators 122, 122 provided in proximity to these movers 121, 121. The movers 121, 121 are configured to have short cylindrical frames 123, 123 coaxially extending on the outer peripheries of the piston cylinders 113, 113 and permanent magnets 124, 124 fixed to these frames 123, 123. Also, the stators 122, 122 are configured to have annular electromagnetic coils 125, 125 and electromagnetic cores 126, 126 provided in proximity to the outer peripheries of the permanent magnets 124, 124.

[0122] Note that the pair of the movers 121, 121 have physically the same configuration. That is, these movers 121, 121 have the same mass, the same shape, and the magnetic forces of both permanent magnets 124, 124 are also the same. Therefore, the masses of the movable elements composed of the pistons 119, 119 and the movers 121, 121 are the same. Similarly, the pair of the stators 122, 122 also have physically the same configuration. That is, the materials, thicknesses, and number of turns of the electric wires constituting both electromagnetic coils 125, 125 are the same, and the electrical and magnetic characteristics of both electromagnetic cores are also the same.

[0123] In addition, an expansion chamber E2 is formed between the front end surface 116A of the displacer 116 and the front end portion 105 of the cylindrical portion 103, and the inside and outside of the first cylinder 111 communicate with each other through a gap 128 formed between the front end of the first cylinder 111 and the inner surface of the front end portion 105 of the cylindrical portion. Also, in the intermediate portion 106, a regenerator 129 is provided between the inner periphery of the cylindrical portion 103 and the outer periphery of the first cylinder 111, and a communication hole 115 is formed in the base portion 107. Further, a heat absorption fin 130 is provided between the inner periphery of the front end portion 105 of the cylindrical portion 103 and the outer periphery of the front end of the first cylinder 111, and a heat exhaust fin 131 is provided between the inner periphery of the cylindrical portion 103 and the outer periphery of the first cylinder 111 between the regenerator 129 and the communication hole 115. Then, a path 133 is formed from the inner front end of the first cylinder 111 through the gap 128, the heat absorption fin 130, the regenerator 129, the heat exhaust fin 131, and the communication hole 115 to the compression chamber C2 in the cylinder 110. Note that the compression chamber C2 is a space in the cylinder 110 surrounded by the base end surface 116B of the displacer 116, the inner end surface 117A of the displacer drive 117, and the opposing surfaces 119A, 119A of the pistons 119, 119.

[0124] A first leaf spring 134 for controlling the operations of the display actuator drive 117 and the display actuator 116 is connected to the display actuator drive 117. Further, second leaf springs 135, 135 for controlling the operations of the pistons 119, 119 are connected to supports 123, 123 to which the pistons 119, 119 are connected.

[0125] A first male screw portion 136 is formed at one end of the rod 118. The first male screw portion 136 is screwed into a female screw portion 137 formed at the central portion on the base end face 116B side of the display actuator 116. On the other hand, a second male screw portion 138 is formed at the other end of the rod 118. The second male screw portion 138 is screwed into a female screw portion 139 formed at the central portion on the inner end face 117A side of the display actuator drive 117. Note that the first male screw portion 136 and the second male screw portion 138 have the same shape. Also, the female screw portion 137 of the display actuator 116 and the female screw portion 139 of the display actuator drive 117 have the same shape.

[0126] As shown in FIG. 27, the major diameter of the thread of the first male screw portion 136 is D1, and the minor diameter thereof is D2. The major diameter of the thread of the female screw portion 137 of the display actuator 116 is D3, and the minor diameter thereof is D4. As described above, since the first male screw portion 136 and the second male screw portion 138 have the same shape, as shown in FIG. 28, the second male screw portion 136 also has a major diameter of D1 and a minor diameter of D2. Similarly, since the female screw portion 137 of the display actuator 116 and the female screw portion 139 of the display actuator drive 117 have the same shape, the female screw portion 139 of the display actuator drive 117 also has a major diameter of D3 and a minor diameter of D4. And the relationship among D1 to D4 is as follows.

[0127] (1): (D3 + D4) / 2 > (D1 + D2) / 2 ≧ D3

[0128] (2): D4 > D1 ≧ (D3 + D4) / 2

[0129] Under the condition of (1), even if the tip of the thread of the female thread portion 137 or 139 approaches or contacts the bottom of the thread groove of the first male thread portion 136 or the second male thread portion 138 as much as possible on one side, the thread of the first male thread portion 136 or the second male thread portion 138 on the opposite side overlaps with the thread of the female thread portion 137 or 139 in the axial direction view. And under the condition of (2), even if the tip of the thread of the first male thread portion 136 or the second male thread portion 138 approaches or contacts the bottom of the thread groove of the female thread portion 137 or 139 as much as possible on one side, the thread of the first male thread portion 136 or the second male thread portion 138 on the opposite side overlaps with the thread of the female thread portion 137 or 139 in the axial direction view. That is, even if the central axis of the first male thread portion 136 and the central axis of the female thread portion 137 are maximally displaced, the thread of the first male thread portion 136 and the thread of the female thread portion 137 will necessarily overlap in the axial direction view over the entire circumference. Similarly, even if the central axis of the second male thread portion 138 and the central axis of the female thread portion 139 are maximally displaced, the thread of the second male thread portion 138 and the thread of the female thread portion 139 will necessarily overlap in the axial direction view over the entire circumference.

[0130] Next, the manufacturing process of the γ-type free piston Stirling refrigerator 101 of the present embodiment will be described. First, as shown in FIG. 23, the cylinder 110 is prepared. Next, as shown in FIG. 24, the displacer 116, the displacer drive 17, and the rod 118 are assembled. In this process, adhesive A is injected into the female screw portion 137 of the displacer 116 and the female screw portion 139 of the displacer drive 117, or adhesive A is applied to the first male screw portion 136 and the second male screw portion 138 of the rod 118, or both are performed. Then, the first male screw portion 136 is screwed into the female screw portion 137, and the second male screw portion 138 is screwed into the female screw portion 139. At this time, the female screw portion 137 and the first male screw portion 136 are not strongly screwed together, and the displacer 116 is made slightly movable in the axial direction perpendicular to the rod 118. Similarly, the female screw portion 139 and the second male screw portion 138 are not strongly screwed together, and the displacer drive 117 is made slightly movable in the axial direction perpendicular to the rod 118. This movable "play" is within (D4 - D1) / 2 or within (D3 - D2) / 2 in the axial direction from the state where the central axes of the female screw portion 137 and the first male screw portion 136 are aligned. Similarly, it is within (D4 - D1) / 2 or within (D3 - D2) / 2 in the axial direction from the state where the central axes of the female screw portion 139 and the second male screw portion 138 are aligned.

[0131] Next, as shown in FIG. 25, before the adhesive A cures, the assembled displayer 116, displayer drive 117, and rod 118 are inserted into the cylinder 110 from the side of the displayer drive 117. At this time, the displayer 116 is inserted up to the first cylinder 111, and the displayer drive 117 is inserted up to the second cylinder 112. By leaving it in this state for a while, the adhesive A cures, and the first male screw portion 136 and the female screw portion 137, that is, the displayer 116 and the rod 118 are completely fixed. Similarly, when the adhesive A cures, the second male screw portion 138 and the female screw portion 139, that is, the displayer drive 117 and the rod 118 are completely fixed. In addition, when the female screw portion 137 is accurately formed at the center with respect to the displayer 116, the female screw portion 139 is accurately formed at the center with respect to the displayer drive 117, and the first cylinder 111 and the second cylinder 112 are exactly coaxial, as shown in FIG. 29, the adhesive A cures in a state where the first male screw portion 136 of the rod 118 is located at the center of the female screw portion 137 of the displayer 116, and the second male screw portion 138 of the rod 118 is located at the center of the female screw portion 139 of the displayer drive 117. On the other hand, when the female screw portion 137 is slightly deviated from the center with respect to the displayer 116, by inserting the displayer 116 into the first cylinder 111 and the displayer drive 117 into the second cylinder 112, before the adhesive A cures, the first male screw portion 136 slightly moves in the axial direction with respect to the female screw portion 137. As a result, as shown in FIG. 30, the adhesive A cures in a state where the first male screw portion 136 is slightly deviated in the axial direction with respect to the female screw portion 137. Note that FIG. 30 shows the case where the female screw portion 137 is slightly deviated from the center with respect to the displayer 116, but the same applies when the female screw portion 139 is slightly deviated from the center with respect to the displayer drive 117, or when the axial centers of the first cylinder 111 and the second cylinder 112 are slightly deviated.

[0132] Furthermore, as shown in FIG. 26, after the adhesive A has cured, the first leaf spring 134 is connected to the displacer drive 117. Thereafter, the remaining other elements are assembled, and the inside of the casing 2 is filled with an operating gas at a predetermined pressure. In this way, the γ-type free piston Stirling refrigerator 101 is completed.

[0133] By assembling in this way, even if there is a deviation in the first cylinder 111, the second cylinder 112, the female screw portion 137 of the displacer 116, and the female screw portion 139 of the displacer drive 117, the alignment of the first cylinder 111 and the displacer 116, and the second cylinder 112 and the displacer drive 117 can be accurately performed without using a special jig.

[0134] As described above, in the method for manufacturing a γ-type free piston Stirling refrigerator 101 as a free piston Stirling engine having a first cylinder 111, a second cylinder 112, a displacer 116 reciprocable in the axial direction X1 of the first cylinder 111, a displacer drive 117 reciprocable in the axial direction X1 of the second cylinder 112, and a rod 118 having one end fixed to the displacer 116 by an adhesive A and the other end fixed to the displacer drive 117 by the adhesive A, an adhesive A is disposed between one end of the rod 118 and the displacer 116, and the adhesive A is disposed between the other end of the rod 118 and the displacer drive 117. Before these adhesives A are cured, the displacer 116 is inserted into the first cylinder 111 and the displacer drive 117 is inserted into the second cylinder 112, and the adhesive A is cured in the first cylinder 111 and the second cylinder 112 to connect the displacer 116, the rod 118, and the displacer drive 117, so that the first cylinder 111 and the displacer 116, and the second cylinder 112 and the displacer drive 117 are coaxially arranged, and the displacer 116 and the displacer drive 117 can be fixed by the rod 118.

[0135] Further, in the present invention, a first male thread portion 136 is formed at one end of the rod 118, a female thread portion 117 is formed on the displacer 116, a second male thread portion 138 is formed at the other end of the rod 118, and a female thread portion 139 is formed on the displacer drive 117. The adhesive A is disposed between the male thread portions 136, 138 and the female thread portions 137, 139 respectively. After the male thread portions 136, 138 and the female thread portions 137, 139 are lightly screwed together, the displacer 116 is inserted into the first cylinder 111, and the displacer drive 117 is inserted into the second cylinder 112. In this way, in the state where the displacer 116, the displacer drive 117, and the rod 118 are temporarily assembled, the displacer 116 can be easily inserted into the first cylinder 111, and the displacer drive 117 can be easily inserted into the second cylinder 112.

[0136] Also, when the major diameter of the thread crest of the male thread portions 136, 138 is D1, the minor diameter of the thread crest of the male thread portions 136, 138 is D2, the major diameter of the thread crest of the female thread portions 137, 139 is D3, and the minor diameter of the thread crest of the female thread portions 137, 139 is D4, by forming the male thread portions 136, 138 and the female thread portions 137, 139 such that (D3 + D4) / 2 > (D1 + D2) / 2 ≧ D3, the thread crests of the male thread portions 136, 138 and the thread crests of the female thread portions 137, 139 overlap surely in the axial direction view. Even if the axes of the male thread portions 136, 138 and the axes of the female thread portions 137, 139 are displaced during temporary assembly, the screwed state of both can be maintained.

[0137] Furthermore, when the major diameter of the thread crest of the male thread portions 136, 138 is D1, the major diameter of the thread crest of the female thread portions 137, 139 is D3, and the minor diameter of the thread crest of the female thread portions 137, 139 is D4, by forming the male thread portions 136, 138 and the female thread portions 137, 139 such that D4 > D1 ≧ (D3 + D4) / 2, the thread crests of the male thread portions 136, 138 and the thread crests of the female thread portions 137, 139 overlap surely in the axial direction view. Even if the axes of the male thread portions 136, 138 and the axes of the female thread portions 137, 139 are displaced during temporary assembly, the screwed state of both can be maintained.

[0138] Incidentally, although the description is omitted, in the γ-type free piston Stirling refrigerator similar to the sixth embodiment, the displacer and the rod similar to those in the second to fifth embodiments, and the fixing structure and method of the displacer drive and the rod may be adopted. In this case, the same operations and effects as those in the second to fifth embodiments are exhibited.

[0139] Note that the present invention is not limited to the above embodiments, and various modifications can be made within the scope of the gist of the invention. For example, in each of the above embodiments, the first cylinder and the second cylinder are integrally formed, but if accuracy can be achieved, the first cylinder and the second cylinder may be formed separately. Further, in the first and sixth embodiments, the female screw portion formed in the displacer is a bottomed hole, but a female screw may be formed in a through hole. In this case, an effect of reducing the adhesive leaking to the outside of the displacer, that is, the compression chamber side, can be considered. Furthermore, in the fourth embodiment, by making the diameter D10 of the through hole 67 larger than the diameter D11 of the male screw portion 74A of the screw 74, the displacer 61 can be moved in the axial direction with respect to the screw 74, that is, the rod 72 into which this screw 74 is screwed. However, similar to the first, fifth, and sixth embodiments, the "play" between the male screw portion 74A and the female screw portion 76 may be used to make the displacer 61 movable in the axial direction with respect to the rod.

Explanation of Reference Numerals

[0140] 1 β-type free piston Stirling refrigerator (free piston Stirling engine) 15, 110 cylinder 15A, 111 first cylinder 15B, 112 second cylinder 16, 51, 61, 81, 116 displacer 23 piston 29, 52, 62, 72, 118 rod 31 through hole 37 first male screw portion (male screw portion) 38 female screw portion 74 screws 74A male screw part 76 female screw part 82 male screw part 101 γ-type free piston Stirling refrigerator (free piston Stirling engine) 117 displacer drive 136 first male screw part 137 female screw part 138 second male screw part 139 female screw part A adhesive D1 diameter of the thread crest of the first male screw part D2 diameter of the thread root of the first male screw part D3 diameter of the thread crest of the female screw part D4 diameter of the thread root of the female screw part

Claims

1. In a method for manufacturing a free piston type Stirling engine having a first cylinder, a second cylinder, a displacer reciprocating in the axial direction of the first cylinder, a piston reciprocating in the axial direction of the second cylinder, and a rod having one end fixed to the displacer by an adhesive and penetrating the piston in the axial direction, a method for manufacturing a free piston type Stirling engine, characterized in that the adhesive is disposed between one end of the rod and the displacer, the displacer is inserted into the first cylinder before the adhesive cures, the piston is inserted into the second cylinder so that the rod penetrates the piston, and the adhesive is cured in the first cylinder to connect the displacer and the rod.

2. A method for manufacturing a free piston type Stirling engine according to claim 1, characterized in that a male screw portion is formed on one of one end of the rod and the displacer, a female screw portion is formed on the other, the adhesive is disposed between the male screw portion and the female screw portion, the male screw portion and the female screw portion are lightly screwed together, and then the displacer is inserted into the first cylinder and the piston is inserted into the second cylinder.

3. A method for manufacturing a free piston type Stirling engine according to claim 1, characterized in that a through hole is formed in the displacer, a female screw portion is formed on one end of the rod, a screw having a male screw portion that can be screwed into the female screw portion through the through hole is provided, the adhesive is disposed between the through hole of the displacer, the female screw portion of the rod, and the male screw portion of the screw, the male screw portion of the screw is lightly screwed into the female screw portion of the rod, the displacer is inserted into the first cylinder, and the piston is inserted into the second cylinder.

4. When the diameter of the thread crest of the male screw portion is D1, the diameter of the thread groove of the male screw portion is D2, the diameter of the thread crest of the female screw portion is D3, and the diameter of the thread groove of the female screw portion is D4, ((D3 + D4) / 2) > ((D1 + D2) / 2) ≥ D3 A method for manufacturing a free piston type Stirling engine according to any one of claims 2 or 3, characterized in that the male screw portion and the female screw portion are formed so as to satisfy the above condition.

5. When the diameter of the thread crest of the male screw portion is D1, the diameter of the thread crest of the female screw portion is D3, and the diameter of the thread groove of the female screw portion is D4, D4 > D1 ≥ (D3 + D4) / 2 The method for manufacturing a free piston type Stirling engine according to any one of claims 2 or 3, wherein the male screw portion and the female screw portion are formed so as to satisfy the above condition. **Claim 6** In a method for manufacturing a free piston type Stirling engine having a first cylinder, a second cylinder, a displacer reciprocable in the axial direction of the first cylinder, a displacer drive reciprocable in the axial direction of the second cylinder, and a rod one end of which is fixed to the displacer by an adhesive and the other end of which is fixed to the displacer drive by an adhesive, the adhesive is disposed between one end of the rod and the displacer, the adhesive is disposed between the displacer drive and the other end of the rod, the displacer is inserted into the first cylinder and the displacer drive is inserted into the second cylinder before the adhesives are cured, and the adhesives are cured within the first cylinder and the second cylinder, thereby connecting the displacer, the rod, and the displacer drive. The method for manufacturing a free piston type Stirling engine is characterized by this. **Claim 7** A male screw portion is formed on one of one end of the rod and the displacer, and a female screw portion is formed on the other; a male screw portion is formed on one of the other end of the rod and the displacer drive, and a female screw portion is formed on the other; the adhesives are respectively disposed between these male screw portions and female screw portions; after these male screw portions and female screw portions are lightly screwed together, the displacer is inserted into the first cylinder, and the displacer drive is inserted into the second cylinder. The method for manufacturing a free piston type Stirling engine according to claim 6 is characterized by this. **Claim 8** Form through holes in the displacer and the displacer drive respectively, form female screw portions at both ends of the rod, provide screws having male screw portions that can be screwed into the female screw portions through the through holes corresponding to the female screw portions, and arrange the adhesive between the through hole of the displacer, the female screw portion of the rod, and the male screw portion of the screw, and between the through hole of the displacer drive, the female screw portion of the rod, and the male screw portion of the screw respectively. Slightly screw the male screw portion of the screw into the female screw portion of the rod, insert the displacer into the first cylinder, and insert the displacer drive into the second cylinder. The manufacturing method of the free piston type Stirling engine according to claim 6, characterized by the above.

9. When the diameter of the thread crest of the male screw portion is D1, the diameter of the thread groove of the male screw portion is D2, the diameter of the thread crest of the female screw portion is D3, and the diameter of the thread groove of the female screw portion is D4, (D3 + D4) / 2 > (D1 + D2) / 2 ≥ D3 The manufacturing method of the free piston type Stirling engine according to any one of claims 7 or 8, characterized in that the male screw portion and the female screw portion are formed so as to satisfy the above.

10. When the diameter of the thread crest of the male screw portion is D1, the diameter of the thread crest of the female screw portion is D3, and the diameter of the thread groove of the female screw portion is D4, D4 > D1 ≥ (D3 + D4) / 2 The manufacturing method of the free piston type Stirling engine according to any one of claims 7 or 8, characterized in that the male screw portion and the female screw portion are formed so as to satisfy the above.

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