Stirling engine

Abstract

To provide a stirling engine that can improve safety even when an adhesive layer peels off after a long use.SOLUTION: A stirling freezer 1 as a stirling engine includes: a displacer 16 as a reciprocator provided such that it can reciprocate in a cylinder 15 with a center axis X; and a rod 29 as a movable body that operates by coupling to the displacer. A female screw part 47 is formed on the displacer 16, and a male screw part 46 is formed on the rod 29. They are engaged with each other and adhesive agent A is filled in a gap therebetween. Furthermore, discontinuous parts 46A, 47A are formed on the male screw part 46 and the female screw part 47, respectively. Thus, even if a layer of the adhesive agent A peels off from the make screw part 46 and the female screw part 47 due to aging after a long use, relative rotation of the displacer 16 and the rod 29 is suppressed, and hence loosening and falling of the female screw part 47 and the first male screw part 46 can be prevented.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a Stirling engine. [Background technology]

[0002] Conventionally, known Stirling engines of this type include a cylinder, a displacer (corresponding to the reciprocating body of the present invention) that can reciprocate axially within the cylinder, and a rod (corresponding to the movable body of the present invention) one end of which is fixed to the displacer. In these Stirling engines, a female thread is formed in the displacer, and a male thread formed on one end of the rod is screwed into this female thread, thereby fixing the displacer and the rod together (see Patent Document 1). The male and female threads are fixed together with an adhesive to prevent them from loosening. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7197615 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the adhesive layer that secures the female thread of the displacer to the male thread of the rod may peel off from the female thread and / or male thread over a long period of use. If the adhesive layer peels off in this way, the peeled surface of this layer has the same shape as the female thread or male thread, so there is a risk that the displacer may become rotatable around its axis relative to the rod. In the worst case scenario, the displacer may become detached from the rod, damaging the Stirling engine. The same problem exists between the piston, which can reciprocate axially within the cylinder with a predetermined phase difference from the displacer, and the elements connected to it.

[0005] SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and to provide a Stirling engine which can improve safety even if the adhesive layer peels off after long-term use. [Means for solving the problem]

[0006] The Stirling engine of claim 1 of the present invention has a reciprocating body that is arranged to be able to reciprocate within a cylinder having a central axis, and a movable body that is connected to the reciprocating body and moves together with the reciprocating body, wherein a male thread portion is formed on one of the reciprocating body and the movable body, and a female thread portion is formed on the other, these male thread portion and female thread portion are screwed together, adhesive is filled between the male thread portion and the female thread portion, and discontinuous portions are formed in the threads of the male thread portion and / or female thread portion.

[0007] A Stirling engine according to claim 2 of the present invention is the Stirling engine of claim 1, wherein the discontinuous portion has a surface that intersects with the axial direction of the male thread portion and / or female thread portion. [Effects of the Invention]

[0008] By configuring the Stirling engine according to claim 1 of the present invention as described above, even if the adhesive layer peels off from the male threaded portion and / or female threaded portion due to deterioration over time caused by long-term use, the relative rotation of the reciprocating body and the movable body is suppressed, thereby suppressing loosening of the female threaded portion and the male threaded portion and further suppressing detachment of the reciprocating body from the movable body.

[0009] Furthermore, since the discontinuous portion has a surface that intersects with the axial direction of the male thread portion and / or female thread portion, even if the adhesive layer peels off from the male thread portion and / or female thread portion, the surface and the surface of the adhesive layer formed corresponding to this surface will abut, thereby suppressing the relative rotation of the reciprocating body and the movable body, suppressing loosening of the female thread portion and the male thread portion, and further suppressing detachment of the reciprocating body from the movable body. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view of a Stirling refrigerator as a Stirling engine according to an embodiment of the present invention. [Figure 2] FIG. 10 is an enlarged cross-sectional view of the connection between the displacer and the rod of the first embodiment. [Figure 3] 1A and 1B are enlarged views of the female screw portion of the displacer of the first embodiment, where (a) is a cross-sectional view and (b) is an external view viewed in the axial direction. [Figure 4] 1A and 1B are enlarged views of the male thread portion of the rod of the same, where (a) is an external view as viewed in the axial direction, and (b) is an external view as viewed in the direction perpendicular to the axis. [Figure 5] 3 is a cross-sectional view taken along the thread in FIG. 2. [Figure 6] FIG. 2 is an enlarged cross-sectional view of a connecting portion between the piston and the connecting body according to the first embodiment. [Figure 7] FIG. 2 is an enlarged exploded cross-sectional view of the piston, the connector, and the mover of the first embodiment. [Figure 8] 7 is a cross-sectional view taken along the thread in FIG. 6. DETAILED DESCRIPTION OF THE INVENTION

[0011] A first embodiment of the present invention will be described below with reference to FIGS. 1 to 8. Note that FIGS. 5 and 8 are cross-sectional views taken along the threads of male threaded portions 34, 46 and female threaded portions 32, 47 (described later), and therefore differ from the cross-sectional view taken along a plane perpendicular to the central axis X. Furthermore, since the operation and function of the Stirling engine itself are known, they will not be described again in this embodiment. Instead, the structure and the effects of this structure will be described. Reference numeral 1 denotes a free-piston Stirling refrigerator serving as a Stirling engine of the present invention. This Stirling refrigerator 1 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 the shape of a small cylinder and a large-diameter portion 6 with 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 one end surface 10 formed in the shape of a substantially circular convex curved surface and a short-cylindrical side surface 11. Similarly, the second casing body 4 has a cylindrical side portion 12 and an other end surface portion 13 formed in a substantially circular convex shape. The large diameter portion 6 and the second casing body 4 form a cylindrical trunk portion 14.

[0012] A cylinder 15 extending into the trunk portion 14 is inserted coaxially into the cylindrical portion 5 within 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. The cylinder 15 is formed using metal. The cylinder 15 is integrally formed with a first cylinder 15A at the tip end and a second cylinder 15B at the base end. However, a portion of the first cylinder 15A may be formed by combining it with a material having low thermal conductivity. The first cylinder 15A and the second cylinder 15B are coaxial and have the same inner diameter. A displacer 16 serving as a reciprocating body is accommodated inside the first cylinder 15A so as to be reciprocatable in the direction of the central axis X. An expansion chamber E is formed between the tip of the displacer 16 and the tip end 7 of the cylindrical portion 5, and a gap 17 connects the inside and outside of the cylinder 15. 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. A heat absorption fin 20 is provided between the inner periphery of the tip end portion 7 of the cylindrical portion 5 and the outer periphery of the tip end of the cylinder 15, and a heat exhaust 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. 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 heat exhaust fin 21, and the communication hole 19 to a compression chamber C in the cylinder 15. Furthermore, in the body portion 4, a piston 23 serving as a reciprocating body is accommodated inside the second cylinder 15B so as to be reciprocatable in the direction of the central axis X. The base end of the piston 23 is coaxially connected to a linear motor 24. The linear motor 24 is configured to have a mover 26 as a movable body, and an annular stator 27 provided in close proximity to the outer periphery of the mover 26. The mover 26 is connected to the base end of the piston 23 by a connector 25 as a movable body, and is provided coaxially extending from the outer periphery of the base end side of the cylinder 15.

[0013] A first leaf spring 28 for controlling the movement of the piston 23 is connected to the connecting member 25, which connects the mover 26 to the piston 23. Furthermore, one end of a rod 29 serving as a moveable body that moves together with the displacer 16 is connected to the base end surface 16B of the displacer 16, and a second leaf spring 30 is connected to the other end of the rod 29. The rod 29 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, 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.

[0014] The assembly of the piston 23, connecting body 25, and moving element 26 will now be described in detail. The piston 23 is formed in a hollow cylindrical shape. A through-hole 31, through which the rod 29 is inserted, is formed in the center of the tip end 23A of the piston 23. The base end 23B of the piston 23 is open, and a female thread portion 32 is formed on the inner surface of this opening. The connecting element 25 has a through-hole 33 formed in the direction of the central axis X, through which the rod 29 is inserted. A first male thread portion 34 and a second male thread portion 35 are formed on both sides in the direction of the central axis X. A first clamping surface 36 and a second clamping surface 37 are formed adjacent to the male thread portions 34 and 35, respectively. The moving element 26 includes a frame 38 and a cylindrical permanent magnet 39 fixed to one end of the frame 38. The frame 38 is made of a non-magnetic material such as synthetic resin. The frame 38 includes a clamped portion 40 formed in an annular shape, a guide tube portion 41 formed to extend from the outer periphery of the clamped portion 40 in the direction of the central axis X, a diameter-enlarged portion 42 formed to extend outward from the tip of the guide tube portion 41, and a cylindrical portion 43 formed to extend from the outer periphery of the diameter-enlarged portion 42 in the direction of the central axis X. The permanent magnet 39 is fixed to the cylindrical portion 43. The clamped portion 40 is formed with a through-hole 44 through which the first male thread portion 34 of the connecting body 25 is inserted. The first male thread portion 34 and the female thread portion 32 are threadedly engaged with each other through the through-hole 44. By threading the first male thread portion 34 and the female thread portion 32 together, the clamped portion 40 is clamped between the base end 23B of the piston 23 and the first clamping surface 36 of the connecting body 25. As a result, the piston 23, the connecting body 25, and the moving element 26 are integrated together. At this time, the base end 23B side of the piston 23 is inserted into the guide tube portion 41 of the frame body 38. A through hole (not shown) is formed in the center of the first leaf spring 28, and the second male threaded portion 35 is inserted into this through hole. After the second male threaded portion 35 is inserted into the through hole, a nut 45 is screwed onto the second male threaded portion 35, and the first leaf spring 28 is clamped between the second clamping surface 37 of the connecting body 25 and the nut 45.

[0015] A first male threaded portion 46 is formed on one end of the rod 29. This first male threaded portion 46 is threadedly engaged with a female threaded portion 47 formed in the center of the base end surface 16B of the displacer 16. Meanwhile, a second male threaded portion 48 is formed on the other end of the rod 29. A through hole (not shown) is formed in the center of the second leaf spring 30, and the second male threaded portion 48 is inserted into this through hole. After the second male threaded portion 48 is inserted into the through hole, a nut 49 is threaded onto the second male threaded portion 48, whereby the second leaf spring 30 is sandwiched between the rod 29 and the nut 49.

[0016] In addition, 50 in Figure 1 is a vibration absorption unit provided on the other end surface portion 13 of the second casing body 4, and a leaf spring 53 and a balance weight 54 are arranged so as to overlap coaxially via an attachment portion 51 arranged so as to be coaxial with the central axis X of the cylinder 15 and a connection portion 52 connected to this attachment portion 51.

[0017] The first male thread portion 46 of the rod 29 and the female thread portion 47 of the displacer 16 will now be described in detail. A discontinuous portion 46A is formed in the first male thread portion 46 by cutting out its thread parallel to the central axis X. This discontinuous portion 46A has a surface 46F that intersects with the direction around the central axis X of the rod 29. On the other hand, a discontinuous portion 47A is formed in the female thread portion 47 by cutting out its thread parallel to the central axis X. This discontinuous portion 47A has a surface 47F that intersects with the direction around the central axis X of the displacer 16. Furthermore, a layer of adhesive A is formed between the first male thread portion 46 and the female thread portion 47. That is, the first male thread portion 46 and the female thread portion 47 are threadedly engaged and bonded together by the adhesive A. This firmly secures the rod 29 and the displacer 16 together. Then, the layer of adhesive A hardens so as to fill the space formed between the first male thread portion 46 and the female thread portion 47. Therefore, the layer of adhesive A has portions that correspond to the discontinuous portions 46A and 47A.

[0018] The first male thread portion 34 of the connecting body 25 and the female thread portion 32 of the piston 23 will now be described in detail. A discontinuous portion 34A is formed in the first male thread portion 34 by cutting out the thread parallel to the central axis X. The discontinuous portion 34A has a surface 34F that intersects with the direction around the central axis X of the connecting body 25. Meanwhile, a discontinuous portion 32A is formed in the female thread portion 32 by cutting out the thread parallel to the central axis X. The discontinuous portion 32A has a surface 32F that intersects with the direction around the central axis X of the piston 23. Furthermore, a layer of adhesive A is formed between the first male thread portion 34 and the female thread portion 32. That is, the first male thread portion 34 and the female thread portion 32 are threadedly engaged and bonded by the adhesive A. This firmly fixes the connecting body 25 and the piston 23. Then, the layer of adhesive A hardens so as to fill the space formed between the first male thread portion 34 and the female thread portion 32. Therefore, the layer of adhesive A has portions that resemble the discontinuous portions 34A, 32A.

[0019] Next, the operation of this embodiment will be described. When power is supplied to the linear motor 24, the piston 23 connected to the mover 26 reciprocates within the cylinder 15 in the direction of the central axis X. The reciprocating movement of the piston 23 causes the displacer 16 to reciprocate within the cylinder 15 in the direction of the central axis X with a predetermined phase difference from the piston 23. By reciprocating the piston 23 and the displacer 16 with a predetermined phase difference in this way, heat is absorbed from the tip portion 7 and released from the base portion 9.

[0020] If the Stirling refrigerator 1 is operated for a long period of time, the connections between the components may be damaged. For example, the portion where the female thread 47 of the displacer 16 is threadedly joined to the first male thread 46 of the rod 29 may be damaged. If the layer of adhesive A peels off from the first male thread 46 or the female thread 47, the positional relationship between the piston 23 and the displacer 16 may shift if the displacer 16 rotates relative to the rod 29 in a direction that loosens the threaded connection, potentially preventing the expected performance. In the worst case scenario, the displacer 16 may come off the rod 29, destroying the Stirling refrigerator 1. Similarly, the portion where the female thread 32 of the piston 23 is threadedly joined to the first male thread 34 of the connector 25 may be damaged. If the layer of adhesive A peels off from the first male thread portion 34 or the female thread portion 32, when the piston 23 rotates in a direction that loosens the screw connection with the connecting body 25, play will occur between the piston 23 and the moving element 26, which may cause repeated collisions between the piston 23, the connecting body 25 and the moving element 26, resulting in the risk of noise generation, and in the worst case scenario, the piston 23 may come off the connecting body 25, causing the Stirling refrigerator 1 to be destroyed.

[0021] However, even if the layer of adhesive A peels off from the first male thread portion 46 of the rod 29 or the female thread portion 47 of the displacer 16, as described above, the layer of adhesive A has portions that resemble the discontinuous portion 46A of the first male thread portion 46 and the discontinuous portion 47A of the female thread portion 47, and therefore the portions that resemble these discontinuous portions 46A, 47A come into contact with the surfaces 46F, 47F of the discontinuous portions 46A, 47A, thereby preventing the displacer 16 from rotating relative to the rod 29. This prevents the displacer 16 from falling off the rod 29, even if the layer of adhesive A peels off from the first male thread portion 46 of the rod 29 or the female thread portion 47 of the displacer 16. Similarly, even if the layer of adhesive A peels off from the first male thread portion 34 of the connecting body 25 or the female thread portion 32 of the piston 23, as described above, the layer of adhesive A has portions that resemble the discontinuous portion 34A of the first male thread portion 34 and the discontinuous portion 32A of the female thread portion 32, and therefore the portions that resemble these discontinuous portions 34A, 32A come into contact with the surfaces 34F, 32F of the discontinuous portions 34A, 32A, thereby preventing the piston 23 from rotating relative to the connecting body 25. This prevents the piston 23 from falling off the connecting body 25, even if the layer of adhesive A peels off from the first male thread portion 34 of the connecting body 25 or the female thread portion 32 of the piston 23.

[0022] Although the above-mentioned effect can be achieved to some extent by simply providing a discontinuous portion 47A or 46A in either the female thread portion 47 of the displacer 16 or the first male thread portion 46 of the rod 29, it is preferable to provide discontinuous portions 47A, 46A in both the female thread portion 47 and the first male thread portion 46, respectively. By providing discontinuous portions 47A, 46A in both the female thread portion 47 and the first male thread portion 46, respectively, it is possible to prevent the displacer 16 from rotating relative to the rod 29 even if the layer of adhesive A peels off from either the female thread portion 47 or the first male thread portion 46, or even if it peels off from both. Similarly, the above-mentioned effect can be achieved to some extent by simply providing a discontinuous portion 32A or 34A in either the female thread portion 32 of the piston 23 or the first male thread portion 34 of the connecting body 25, it is preferable to provide discontinuous portions 32A, 34A in both the female thread portion 32 and the first male thread portion 34, respectively. In this way, by providing discontinuous portions 32A, 34A in both the female thread portion 32 and the first male thread portion 34, it is possible to prevent the piston 23 from rotating relative to the connecting body 25 even if the layer of adhesive A peels off from either the female thread portion 32 or the first male thread portion 34, or even if it peels off from both.

[0023] If Stirling refrigerator 1 continues to operate with the layer of adhesive A peeled off from first male thread portion 46 of rod 29 or female thread portion 47 of displacer 16, or with the layer of adhesive A peeled off from first male thread portion 34 of connector 25 or female thread portion 32 of piston 23, the peeled layer of adhesive A may be destroyed. However, in this case, abnormal vibrations are expected to occur, and a fail-safe can be achieved by monitoring the vibrations generated by Stirling refrigerator 1 with a vibration sensor or the like (not shown).

[0024] As described above, the free-piston Stirling refrigerator 1 as a Stirling engine of the present invention comprises a displacer 16 and a piston 23 as reciprocating bodies provided so as to be able to reciprocate within a cylinder 15 having a central axis X, and a rod 29 and a connecting body 25 as movable bodies coupled to the displacer 16 and the piston 23, respectively, and operating together with the displacer 16 and the piston 23. In the Stirling refrigerator 1, a female screw portion 47 is formed on the displacer 16, a first male screw portion 46 is formed on the rod 29, a female screw portion 32 is formed on the piston 23, and a first male screw portion 34 is formed on the connecting body 25. The first male screw portion 46 and the female screw portion 47 and the first male screw portion 34 and the female screw portion 32 are threadedly engaged with each other, and connections are made between the first male screw portion 46 and the female screw portion 47 and between the first male screw portion 34 and the female screw portion 32. As adhesive A is filled, discontinuous portions 46A, 47A are formed in the threads of the first male threaded portion 46 and the female threaded portion 47, respectively, and discontinuous portions 34A, 32A are formed in the threads of the first male threaded portion 34 and the female threaded portion 32, respectively. As a result, even if the layer of adhesive A peels off from the male threaded portion 46 and / or the female threaded portion 47 due to deterioration over time during long-term use, or even if the layer of adhesive A peels off from the male threaded portion 34 and / or the female threaded portion 32, relative rotation between the displacer 16 and the rod, or between the piston 23 and the connecting body 25, is suppressed. This prevents loosening of the female threaded portion 47 and the first male threaded portion 46, or the female threaded portion 32 and the first male threaded portion 34, and further prevents detachment of the displacer 16 from the rod 29 or the piston 23 from the connecting body 25.

[0025] Furthermore, in the present invention, the discontinuous portion 46A has a surface 46F that intersects with the direction about the central axis X of the first male thread portion 46, the discontinuous portion 47A has a surface 47F that intersects with the direction about the central axis X of the female thread portion 47, the discontinuous portion 34A has a surface 34F that intersects with the direction about the central axis X of the first male thread portion 34, and the discontinuous portion 32A has a surface 32F that intersects with the direction about the central axis X of the female thread portion 32. Therefore, even if the layer of adhesive A peels off from the first male thread portion 46 and / or the layer of adhesive A peels off from the first male thread portion 34 and / or the first male thread portion 34 and / or the Even if the displacer 16 peels off from the female thread portion 32, the surfaces 46F, 47F, 34F, 32F and the surfaces of the layer of adhesive A formed corresponding to these surfaces will abut against each other, and therefore the relative rotation of the displacer 16 and the rod 29 is suppressed, thereby suppressing loosening of the female thread portion 47 and the first male thread portion 46, or the relative rotation of the piston 23 and the connecting body 25 is suppressed, thereby suppressing loosening of the female thread portion 32 and the first male thread portion 34, and furthermore, it is possible to suppress detachment of the displacer 16 from the rod 29, or to suppress detachment of the piston 23 from the connecting body 25.

[0026] It should be noted that the present invention is not limited to the above-described embodiments, and various modifications are possible within the spirit and scope of the invention. For example, in the above-described embodiments, the displacer 16 is formed with a female thread 47 and the rod 29 is formed with a male thread 46. However, the same effects can be achieved by forming a male thread on the displacer and a female thread on the rod. Similarly, in the above-described embodiments, the piston 23 is formed with a female thread 32 and the connector 25 is formed with a male thread 34. However, the same effects can be achieved by forming a male thread on the piston and a female thread on the connector. Furthermore, in the above-described embodiments, a free-piston Stirling refrigerator that applies the reverse Stirling cycle is exemplified as a Stirling engine, but a free-piston Stirling engine that applies the Stirling cycle may also be used. [Explanation of symbols]

[0027] 1. Free-piston Stirling refrigerator (Stirling engine) 15 cylinders 15A First Cylinder 15B Second cylinder 16 Displacer (reciprocating body) 23 Piston (reciprocating body) 24 Linear motor 25 Connecting body (movable body) 26 Mover (movable body) 29 Rod (movable body) 32 Female thread 32A Discontinuity 32F side 34 First male thread 34A Discontinuity 34F side 46 First male thread 46A Discontinuity 46F side 47 Female thread 47A Discontinuity 47F A adhesive X center axis

Claims

1. A Stirling engine having a reciprocating body provided so as to be able to reciprocate within a cylinder having a central axis, and a movable body coupled to the reciprocating body and moving together with the reciprocating body, A Stirling engine characterized in that a male screw portion is formed on one of the reciprocating body and the movable body, and a female screw portion is formed on the other, these male screw portion and female screw portion are screwed together, adhesive is filled between the male screw portion and the female screw portion, and discontinuous portions are formed in the threads of the male screw portion and / or the female screw portion.

2. 2. A Stirling engine according to claim 1, wherein the discontinuous portion has a surface that intersects with the direction around the axis of the male thread portion and / or the female thread portion.

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