Displacer for refrigerator and method for manufacturing the same

Abstract

To provide a displacer of a refrigerator which can prevent or suppress an exfoliation of a slide part from an intensity securement part, and can reduce manufacturing man-hours.SOLUTION: A main body member 5 of a displacer 3 has a hollow cylindrical intensity securement part 51 and a slide part 52 which is laminated on an external peripheral face side of the intensity securement part 51. The intensity securement part 51 has a first thermosetting resin 511 and a sheet-shaped first fiber base material 512 which is embedded into the first thermosetting resin 511. The slide part 52 has a second thermosetting resin 521 containing a filler which is low in a friction coefficient, and a sheet-shaped second fiber base material 522 embedded into the second thermosetting resin 521. The first thermosetting resin 511 and the second thermosetting resin 521 are formed of the same kind of resins, and the first thermosetting resin 511 and the second thermosetting resin 521 directly contact with each other, and are integrally connected to each other.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a displacer for a refrigerator and a method for manufacturing a displacer for a refrigerator. [Background technology]

[0002] For example, a GM (Gifford McMahon) refrigerator as shown in Patent Document 1 includes a cylinder member having a low-temperature end and a high-temperature end and filled with a working gas such as helium, a displacer filled with a regenerator and arranged reciprocally inside the cylinder member to move the working gas by moving inside the cylinder, a drive device for reciprocating the displacer inside the cylinder member, and a pressure oscillator for applying high and low pressures alternately to the cylinder member. The pressure oscillator applies high and low pressures alternately to the cylinder member in conjunction with the reciprocating movement of the displacer so that the volume and pressure of the working gas in the cylinder member change according to the GM cycle. This generates a low temperature in an expansion space surrounded by the low-temperature end of the cylinder member.

[0003] In a refrigerator having a cylinder and a displacer disposed in the cylinder, such as a GM refrigerator, the displacer is required to be lightweight, to have a desired mechanical strength at cryogenic temperatures, to have low thermal conductivity, and to have high sliding properties with respect to the inner circumferential surface of the cylinder. However, it is difficult to construct a displacer having all of the above characteristics using a single material.

[0004] For this reason, the displacer of this type of refrigerator can be configured to have a strength securing portion for securing mechanical strength and the like, and a sliding portion for enhancing sliding properties with the cylinder. In this case, in the past, from the viewpoints of the weight, mechanical strength, and thermal conductivity of the displacer, cloth-reinforced bakelite was used for the strength securing portion. Then, a sliding portion separate from the strength securing portion is bonded to the outer circumferential surface (surface facing the inner circumferential surface of the cylinder) of the strength securing portion (cloth-reinforced bakelite).

[0005] However, in such a configuration, since the strength ensuring part and the sliding part are made of different materials, the sliding part may peel off from the strength ensuring part due to the difference in thermal expansion coefficient between the strength ensuring part and the sliding part. Furthermore, in such a configuration, in order to manufacture a displacer, a process of manufacturing the strength ensuring part from cloth-reinforced Bakelite, a process of bonding the sliding part to the manufactured strength ensuring part, and a process of machining (finishing) the sliding part to ensure the dimensional accuracy of the bonded sliding part are required. As a result, the number of manufacturing steps increases, and the time required to manufacture the displacer becomes longer. Furthermore, the manufacturing cost of the displacer becomes higher. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2012-255590 A Summary of the Invention

[0007] (Problem to be solved by the invention) The present invention has been made in view of the above circumstances, and has an object to provide a displacer capable of preventing or suppressing the sliding portion from peeling off from the strength ensuring portion. Another object of the present invention is to provide a method for manufacturing a displacer capable of reducing the number of manufacturing steps.

[0008] (Means for solving the problem) In order to solve the above problems, a displacer (3) of a refrigerator (1) according to the present invention comprises: A displacer (3) of a refrigerator (1) that moves a working gas by moving inside a cylinder (21) of the refrigerator (1), a hollow cylindrical portion (5) having a space (310) formed therein capable of accommodating a cold storage material (33) and a sliding surface (501) on the outer periphery thereof which slides against the inner periphery of the cylinder (21); The hollow cylindrical portion (5) is A hollow cylindrical first layer (51) including a first thermosetting resin (511) and a sheet-like first fiber base material (512) embedded in the first thermosetting resin (511); a hollow cylindrical second layer (52) comprising a second thermosetting resin (521), a filler contained in the second thermosetting resin (521) and having a lower coefficient of friction than the second thermosetting resin (521), and a sheet-like second fiber base material (522) embedded in the second thermosetting resin (521) containing the filler, the hollow cylindrical second layer (52) being in direct contact with the first layer (51) and laminated on an outer circumferential surface of the first layer (51), at least a portion of the outer circumferential surface forming the sliding surface (501); The first thermosetting resin (511) and the second thermosetting resin (521) are the same type of resin, and the first thermosetting resin (511) and the second thermosetting resin (521) are in direct contact with each other and are bonded together.

[0009] According to the displacer (3) of the refrigerator (1) of the present invention, the first thermosetting resin (511) of the first layer (51) and the second thermosetting resin (521) of the second layer (52) are bonded together in a state of direct contact with each other, so that the second layer (52) is prevented or suppressed from peeling off from the first layer (51). Furthermore, according to the displacer (3) of the refrigerator (1) of the present invention, the first thermosetting resin (511) of the first layer (51) and the second thermosetting resin (521) of the second layer (52) are made of the same type of resin, so that the thermal expansion coefficients of the first layer (51) and the second layer (52) can be made the same or the difference in thermal expansion coefficient can be made small. For this reason, by using the first layer (51) as the strength securing portion of the displacer and the second layer (52) as the sliding portion, it is possible to prevent or suppress the generation of a force that would cause the first layer (51) and the second layer (52) to peel off from each other due to the difference in thermal expansion coefficient when the displacer (3) becomes extremely cold during use. Therefore, it is possible to enhance the effect of preventing or suppressing the peeling of the second layer (52) as the sliding portion from the first layer (51) as the strength securing portion.

[0010] In the above, the first thermosetting resin and the second thermosetting resin are said to be "the same type of resin" when they are resins belonging to any of the commonly known thermosetting resins (e.g., phenolic resin, epoxy resin, melamine resin, etc.). Therefore, if the first thermosetting resin and the second thermosetting resin are both phenolic resins, they are the same type of resin even if they each contain different components.

[0011] In this case, the first thermosetting resin (511) preferably does not contain the filler, or the volume fraction of the filler contained therein is lower than the volume fraction of the filler contained in the second thermosetting resin (521). This allows the mechanical strength of the first layer (51) to be higher than that of the second layer (52). Therefore, the first layer (51) can ensure the required mechanical strength of the displacer (3).

[0012] the first thermosetting resin (511) and the second thermosetting resin (521) are phenolic resins; The filler is a powder of polytetrafluoroethylene, The first fiber base material (512) and the second fiber base material (522) are sheet-like members made of synthetic resin. The following configuration can be applied.

[0013] According to this configuration, it is easy to provide the first layer (51) with the required mechanical strength, and the friction coefficient of the sliding surface (501) of the second layer (52) can be made lower than that of the first layer (51). Therefore, it is possible to improve the sliding property with the cylinder (21) of the refrigerator (1) while ensuring the required mechanical strength.

[0014] A method for manufacturing a displacer (3) of a refrigerator (1) according to the present invention includes the steps of: A method for manufacturing a displacer (3) for a refrigerator (1) having a hollow cylindrical first layer (51) for ensuring mechanical strength, and a second layer (52) laminated on an outer periphery of the first layer (51) and provided on the outer periphery with a sliding surface (501) having a lower friction coefficient than the first layer (51), comprising: A step of winding a sheet-like first prepreg (72) having a first fiber base material (512) impregnated with an uncured or semi-cured first thermosetting resin (511) into a cylindrical shape to form the first prepreg into a hollow cylindrical shape; a step of winding a sheet-like second prepreg (73) having a second fiber base material (522) impregnated with a second thermosetting resin (521) in an uncured or semi-cured state around an outer peripheral surface side of the first prepreg molded into a hollow cylinder, thereby laminating the second prepreg so as to be in direct contact with the first prepreg and integrating the first thermosetting resin (511) and the second thermosetting resin (521); A step of curing the first thermosetting resin (511) and the second thermosetting resin (521) by heating the laminated first prepreg (72) and the second prepreg (73); It has The first thermosetting resin (511) and the second thermosetting resin (521) are the same type of resin, The second thermosetting resin (521) contains a filler having a lower coefficient of friction than the first thermosetting resin (511) and the second thermosetting resin (521).

[0015] According to the manufacturing method of the displacer (3) of the refrigerator (1) of the present invention, it is possible to manufacture the displacer (3) of the refrigerator (1) having the first layer (51) which is a layer for ensuring mechanical strength and the second layer (52) which is a layer having a sliding surface (501) having a friction coefficient lower than that of the first layer (51). According to the manufacturing method of the displacer (3) of the refrigerator (1) of the present invention, the first thermosetting resin (511) of the first layer (51) and the second thermosetting resin (521) of the second layer (52) can be integrally bonded to each other while being in direct contact with each other (in other words, it is not necessary to provide a layer such as an adhesive between the first thermosetting resin (511) and the second thermosetting resin (521)). Therefore, it is possible to manufacture the displacer (3) in which the peeling of the second layer (52) from the first layer (51) is prevented or suppressed. Furthermore, according to the method for manufacturing the displacer (3) of the refrigerator (1) of the present invention, it is possible to reduce the number of manufacturing steps, as compared with a method in which the second layer (52), which is a separate member from the first layer (51), is bonded to the first layer (51).

[0016] the first thermosetting resin (511) and the second thermosetting resin (521) are phenolic resins; The filler is a powder of polytetrafluoroethylene, The first fiber base material (512) and the second fiber base material (522) are made of a synthetic resin. The following configuration can be applied.

[0017] According to this configuration, it is easy to provide the first layer (51) with the required mechanical strength, and the friction coefficient of the sliding surface (501) of the second layer (52) can be made lower than that of the first layer (51). Therefore, it is possible to manufacture a displacer (3) that can improve the sliding property with the cylinder (21) of the refrigerator (1) while ensuring the required mechanical strength.

[0018] In the above description, in order to facilitate understanding of the present invention, the names and / or symbols used in the embodiments described below are added in parentheses to the configurations of the invention corresponding to those embodiments. However, each component of the present invention is not limited to the embodiments defined by the names and / or symbols. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a cross-sectional schematic diagram showing the configuration of a GM refrigerator. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing the configuration of a displacer. [Diagram 3] FIG. 3 is a cross-sectional view of the main body of the displacer. [Figure 4] FIG. 4 is an enlarged view of part IV in FIG. [Diagram 5] FIG. 5 is a partial cross-sectional view showing the configuration of the composite material. [Figure 6A] FIG. 6A is a schematic diagram showing a method for producing a composite material. [Figure 6B] FIG. 6B is a schematic diagram showing a method for producing a composite material. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] (General configuration of a GM refrigerator) 1 is a partial cross-sectional schematic diagram of a GM refrigerator 1 (two-stage GM refrigerator) to which a displacer 3 according to this embodiment is applied. As shown in FIG 1, the GM refrigerator 1 includes a cylinder member 2, a displacer 3 according to this embodiment, a drive unit 13, a housing 11, and a pressure vibration device 4.

[0021] The cylinder member 2 has a first cylinder portion 21 and a second cylinder portion 22. The first cylinder portion 21 is formed in a cylindrical shape having a low-temperature end portion 211 which is one end portion thereof and a high-temperature end portion 212 which is the other end portion thereof opposite to the low-temperature end portion. The second cylinder portion 22 is formed in a cylindrical shape having a low-temperature end portion 221 which is one end portion thereof and a high-temperature end portion 222 which is the other end portion thereof opposite to the low-temperature end portion. In FIG. 1, the low-temperature ends (211, 221) of the cylinder portions (21, 22) are shown as upper ends, and the high-temperature ends (212, 222) are shown as lower ends, but "upper" and "lower" here are used for the convenience of explanation with reference to the drawings, and do not mean "upper" and "lower" in absolute space. In the following explanation, terms indicating directions such as "upper" and "lower" are used only for the convenience of explanation with reference to the drawings, and do not necessarily mean "upper" and "lower" in absolute space.

[0022] The inner diameter of the first cylinder portion 21 is larger than the inner diameter of the second cylinder portion 22, and the outer diameter of the first cylinder portion 21 is larger than the outer diameter of the second cylinder portion 22. The second cylinder portion 22 is connected to the upper part of the first cylinder portion 21. Therefore, the cylinder member 2 has a stepped cylindrical shape with a diameter that decreases toward the tip side (upper side in FIG. 1). In addition, the internal space of the first cylinder portion 21 is connected to the internal space of the second cylinder portion 22. Therefore, the shape of the internal space of the cylinder member 2 is a stepped cylindrical shape with a diameter that decreases toward the tip side (upper side in FIG. 1).

[0023] The displacer 3 according to this embodiment is reciprocably disposed in the internal space of the cylinder member 2, and moves the working gas by moving inside the cylinder member 2. The displacer 3 has a first piston portion 31 and a second piston portion 32, each of which has a cylindrical space formed therein. The inner diameter of the first piston portion 31 is larger than the inner diameter of the second piston portion 32, and the outer diameter of the first piston portion 31 is larger than the outer diameter of the second piston portion 32. The second piston portion 32 is connected to an upper portion of the first piston portion 31. Therefore, like the cylinder member 2, the displacer 3 also has a stepped cylindrical shape with a diameter that decreases toward the tip side (upward in FIG. 1).

[0024] The outer diameter of the first piston portion 31 is slightly smaller than the inner diameter of the first cylinder portion 21. The first piston portion 31 is coaxially disposed within the first cylinder portion 21. The outer diameter of the second piston portion 32 is slightly smaller than the inner diameter of the second cylinder portion 22. As shown in FIG. 1, the second piston portion 32 extends upward from the upper end surface of the first piston portion 31 in FIG. 1 and enters the internal space of the second cylinder portion 22.

[0025] The axial length (height) of the first piston portion 31 is shorter than the axial length (height) of the internal space of the first cylinder portion 21. Therefore, in the space within the first cylinder portion 21, a first expansion space 213 is formed above the upper end surface of the first piston portion 31, and a back space 214 is formed below the lower end surface of the first piston portion 31. As can be seen from FIG. 1, the first expansion space 213 is formed by the space within the low temperature end 211 of the first cylinder portion 21, and the back space 214 is formed by the space within the high temperature end 212 of the first cylinder portion 21. In addition, in the internal space of the second cylinder portion 22, a second expansion space 223 is formed above the upper end surface of the second piston portion 32. The second expansion space 223 is formed by the space within the low temperature end 221 of the second cylinder portion 22.

[0026] A lower end of the first piston portion 31 of the displacer 3 is connected to the drive device 13. The drive device 13 has an electric motor as a rotating electric machine, and a power conversion mechanism (both not shown) that converts the rotational driving force of the electric motor into a reciprocating driving force and transmits the converted reciprocating driving force to the displacer 3. Therefore, when the electric motor is driven, the displacer 3 is driven to reciprocate within the cylinder member 2.

[0027] The pressure vibration device 4 is configured to include, for example, a compressor 41, changeover valves 42 and 43, and a conduit 44 having one end connected to the back space 214. The changeover valves 42 and 43 switch between a high-pressure state in which a discharge port 41b of the compressor 41 is connected to the other end of the conduit 44, and a low-pressure state in which a suction port 41a of the compressor 41 is connected to the other end of the conduit 44. The pressure vibration device 4 applies high and low pressures alternately to the internal space of the cylinder member 2 at a predetermined timing.

[0028] The internal space of the first piston portion 31 is filled with a first cold storage material 33 made of a material having a large specific heat at a low temperature of about 60 to 100K. The first cold storage material 33 can be formed of a laminate such as a wire mesh made of a copper alloy. The internal space of the first piston portion 31 filled with the first cold storage material 33 is hereinafter referred to as a first cold storage chamber 310. The internal space of the second piston portion 32 is filled with a second cold storage material 34 made of a material having a large specific heat at a very low temperature of about 4 to 20K. For example, lead balls can be used as the second cold storage material 34. The internal space of the second piston portion 32 filled with the second cold storage material 34 is hereinafter referred to as a second cold storage chamber 320.

[0029] A plurality of passages 311, 312, and 313 are formed in the first piston portion 31. Through these passages 311, 312, and 313, the first cold storage chamber 310 communicates with the rear space 214, the first expansion space 213, and the lower side of the second cold storage chamber 320, respectively.

[0030] A passage 321 is formed in the second piston portion 32. Through the passage 321, the second cold storage chamber 320 communicates with the second expansion space 223.

[0031] A first seal ring 314 is attached circumferentially to a lower portion of the outer circumferential side surface of the first piston portion 31 in FIG. 1. The first seal ring 314 blocks communication between the back space 214 and the first expansion space 213. A second seal ring 322 is attached to a lower portion of the outer circumferential side surface of the second piston portion 32, which portion faces the inner circumferential side surface of the second cylinder portion 22. The second seal ring 322 blocks communication between the first expansion space 213 and the second expansion space 223.

[0032] (GM Refrigeration Unit Operation) The operation of the GM refrigerator 1 having the above configuration will be described below. When the driving device 13 is driven, the displacer 3 reciprocates within the cylinder member 2 along the axial direction of the cylinder member 2.

[0033] The pressure vibration device 4 is operated in conjunction with the reciprocating movement of the displacer 3 in the cylinder member 2. As a result, the pressure in the cylinder member 2 changes according to the position of the displacer 3. Specifically, when the displacer 3 is located at the uppermost position in the cylinder member 2 in FIG. 1, high pressure is supplied into the cylinder member 2. Next, when the displacer 3 is displaced downward relative to the cylinder member 2, the high-pressure working gas in the back space 214 is introduced into the first cold storage chamber 310 through the second communication passage 311. The working gas introduced into the first cold storage chamber 310 is cooled by taking cold energy from the first cold storage material 33. Then, the working gas cooled by the first cold storage material 33 is introduced into the first expansion space 213 through the passage 312. As a result, the volume of the first expansion space 213 increases. Also, a part of the working gas introduced into the first cold storage chamber 310 is introduced into the second cold storage chamber 320 through the passage 313. The working gas introduced into the second cold storage chamber 320 is cooled by absorbing cold energy from the second cold storage material 34. Then, the working gas cooled by the second cold storage material 34 is introduced into the second expansion space 223 through the passage 321. This increases the volume of the second expansion space 223 (high pressure transfer process).

[0034] When the displacer 3 moves downward and reaches the lowest position in the cylinder member 2, low pressure is supplied into the cylinder member 2. As a result, the working gas in the first expansion space 213 located on the low temperature end 211 side of the first cylinder portion 21 and the working gas in the second expansion space 223 located on the low temperature end 221 side of the second cylinder portion 22 are expanded (reduced in pressure). The expansion work performed at this time generates cold heat in the respective expansion spaces 213, 223, i.e., in the low temperature end 211 of the first cylinder portion 21 and the low temperature end 221 of the second cylinder portion 22 (expansion process).

[0035] Next, when the displacer 3 is displaced upward relative to the cylinder member 2, the volumes of the second expansion space 223 and the first expansion space 213 are reduced. At the same time, the working gas in the second expansion space 223 is introduced into the back space 214 via the passage 321, the second cold storage chamber 320, the passage 313, the first cold storage chamber 310, and the passage 311. At this time, the working gas temperature rises as the second cold storage material 34 in the second cold storage chamber 320 and the first cold storage material 33 in the first cold storage chamber 310 take away cold energy. In addition, the working gas in the first expansion space 213 is introduced into the back space 214 via the passage 312, the first cold storage chamber 310, and the passage 311. At this time, the working gas temperature rises as the first cold storage material 33 in the first cold storage chamber 310 takes away cold energy (low pressure transfer process).

[0036] Next, high pressure is supplied into the cylinder member 2, which increases the pressure inside the cylinder member 2 and causes the working gas in the back space 214 to perform compression work (compression process). The heat generated by such compression work is radiated to the outside by a heat radiator (not shown).

[0037] In this manner, high and low pressures are applied to the cylinder member 2 in conjunction with the reciprocating motion of the displacer 3 in the cylinder member 2 so that the volume and pressure in each expansion space 213, 223 change according to the above-mentioned GM cycle (high pressure transfer stroke, expansion stroke, low pressure transfer stroke, compression stroke), thereby generating low temperatures in each expansion space 213, 223. Then, by repeating such a GM cycle, the first expansion space 213 is cooled to about 60 to 100K, and the second expansion space 223 is cooled to about 4 to 20K.

[0038] (Displacer configuration) Next, the displacer 3 according to this embodiment will be described. FIG. 2 is a cross-sectional view showing the configuration of the first piston portion 31 of the displacer 3. As shown in FIG. 2, the first piston portion 31 has a hollow cylindrical main body member 5, a low-temperature side cover member 61 provided at one end in the axial direction of the main body member 5, and a high-temperature side cover member 62 provided at the other end. A screw hole 503 is formed in the end face of the main body member 5, and the low-temperature side cover member 61 is fixed to the end of the main body member 5 by a screw 63. The high-temperature side cover member 62 has an inner cover member 621 and an outer cover member 622, and the inner cover member 621 is fixed to the end of the main body member 5 by a screw 63, and the outer cover member 622 is fixed to the inner cover member 621 by the screw 63. The first seal ring 314 is sandwiched between the inner cover member 621 and the outer cover member 622 of the low-temperature side cover member 61. Furthermore, a first cold storage material 33 is accommodated in the internal space of the first piston portion 31 (the space formed by the low-temperature side cover member 61 and the high-temperature side cover member 62).

[0039] The outer circumferential surface of the main body member 5 is provided with a sliding surface 501 that is slidable against the inner circumferential surface of the first cylinder portion 21 (in other words, capable of contacting the inner circumferential surface of the first cylinder portion 21), and a clearance surface 502 that does not slide against the inner circumferential surface of the first cylinder portion 21. In this embodiment, a total of two sliding surfaces 501 are provided, one at each end of the main body member 5 in the axial direction, and a portion having a smaller diameter than the sliding surface 501 is provided between the two sliding surfaces 501. This smaller diameter portion is the clearance surface 502.

[0040] FIG. 3 is a cross-sectional view showing the configuration of the main body member 5. FIG. 4 is an enlarged view of part IV in FIG. 3, and is a diagram showing a schematic internal structure of the main body member 5. As shown in FIG. 3, the main body member 5 has a hollow cylindrical shape with a through hole formed therethrough in the axial direction. The main body member 5 has a strength securing part 51 as a first layer and a sliding part 52 as a second layer. The strength securing part 51 and the sliding part 52 both have a hollow cylindrical shape. The sliding part 52 is stacked on the outer periphery side of the strength securing part 51. In other words, the main body member 5 has the strength securing part 51 and the sliding part 52 stacked on each other in the radial direction of the cylinder. The sliding part 52 is located on the outer periphery side of the strength securing part 51, and the outer periphery surface of the sliding part 52 (the surface opposite to the side stacked with the strength securing part 51) is exposed. A part of the outer periphery surface of the sliding part 52 forms a sliding surface 501, and the remaining part forms a relief surface 502.

[0041] The strength ensuring portion 51 is a portion for ensuring the mechanical strength of the displacer 3, in particular, the mechanical strength at extremely low temperatures (specifically, the temperature inside the low-temperature end portion 211 of the first cylinder portion 21 during operation of the GM refrigerator 1). The mechanical strength in this embodiment is tensile strength, compressive strength, shear strength, fracture strength, etc. The mechanical strength of the strength ensuring portion 51 is higher than the mechanical strength of the sliding portion 52. As shown in FIG. 4, the strength ensuring portion 51 has a first thermosetting resin 511 and a sheet-like first fiber base material 512 embedded in the first thermosetting resin 511. The first fiber base material 512 is layered in the radial direction of the main body member 5 inside the strength ensuring portion 51.

[0042] The sliding portion 52 is a portion on which a sliding surface 501 is formed to ensure slidability with respect to the inner peripheral surface of the first cylinder portion 21 (reducing frictional resistance between the first piston portion 31 and the first cylinder portion 21 and preventing or suppressing wear on the inner peripheral surface of the first cylinder portion 21). The sliding portion 52 has a second thermosetting resin 521 and a sheet-like second fiber base material 522. The second thermosetting resin 521 contains a filler having a lower friction coefficient than the first thermosetting resin 511 and the second thermosetting resin 521. The second fiber base material 522 is embedded inside the second thermosetting resin 521 containing the filler, and is layered inside the second thermosetting resin 521 in the radial direction of the main body member 5.

[0043] The first thermosetting resin 511 of the strength securing portion 51 and the second thermosetting resin 521 of the sliding portion 52 are the same type of thermosetting resin. Specifically, phenol resin is applied to the first thermosetting resin 511 and the second thermosetting resin 521. Since the mechanical strength of phenol resin is high, phenol resin is preferably used as the first thermosetting resin 511 of the strength securing portion 51. The first thermosetting resin 511 of the strength securing portion 51 and the second thermosetting resin 521 of the sliding portion 52 are in direct contact with each other and are integrated. That is, no other member or material such as an adhesive layer is interposed between the strength securing portion 51 and the sliding portion 52. Therefore, the interface between the first thermosetting resin 511 of the strength securing portion 51 and the second thermosetting resin 521 of the sliding portion 52 does not clearly exist.

[0044] The filler contained in the second thermosetting resin 521 is a polytetrafluoroethylene powder. By dispersing polytetrafluoroethylene powder having good sliding properties in the phenol resin as the second thermosetting resin 521, the sliding properties of the sliding part 52 can be improved. The particle size of the polytetrafluoroethylene powder is preferably 20 μm or less. The lower limit of the particle size of the polytetrafluoroethylene powder is not particularly limited, but may be several μm (for example, 3 μm). In addition, if the content of the filler is too small, the sliding properties are low, and if it is too large, the strength and durability of the sliding part 52 are reduced. For this reason, the content of the filler is preferably 10% or more and 30% or less in volume fraction (proportion to the total volume of the second thermosetting resin 521 and the filler). However, the particle size and content of the filler are not limited to the above ranges, and are appropriately set according to the characteristics required for the sliding part 52. In short, it is sufficient that the sliding portion 52 contains a filler and thereby has higher sliding properties (eg, a smaller coefficient of friction) than when no filler is contained (or compared to the strength securing portion 51).

[0045] In this embodiment, the first thermosetting resin 511 of the strength securing portion 51 does not intentionally contain a filler, which is a powder of polytetrafluoroethylene. However, according to a manufacturing method of the displacer 3 described later, the filler contained in the second thermosetting resin 521 may diffuse (disperse) inside the first thermosetting resin 511. Therefore, the first thermosetting resin 511 of the strength securing portion 51 may contain the above-mentioned filler as an inevitable impurity. However, from the viewpoint of securing the mechanical strength of the strength securing portion 51, it is preferable that the first thermosetting resin 511 contains less filler. Specifically, for example, the volume fraction of the filler contained in the first thermosetting resin 511 (the ratio to the total volume of the first thermosetting resin 511 and the filler) is lower than the volume fraction of the filler contained in the second thermosetting resin 521. With such a configuration, the mechanical strength of the strength ensuring part 51 can be made higher than the mechanical strength of the sliding part 52, and it becomes easy to provide the strength ensuring part 51 with a desired mechanical strength. However, the allowable content of the filler in the first thermosetting resin 511 is appropriately set according to the mechanical strength required for the strength ensuring part 51, and is not specifically limited.

[0046] The first fiber base material 512 and the second fiber base material 522 are made of flexible sheet-like members made of chemical fibers (fibers made of synthetic resin). For example, fibers made of aramid (i.e., aramid fibers) are used as the chemical fibers. However, the chemical fibers are not limited to fibers made of aramid. The first fiber base material 512 and the second fiber base material 522 may be made of different materials. In addition, the first fiber base material 512 and the second fiber base material 522 may be made of fibers made of multiple types of resins, not just members made of fibers made of one type of resin. In this case, the resin fibers may be chemical fibers. The chemical fibers used for the first fiber base material 512 and the second fiber base material 522 preferably have a lower water absorption rate. This is because if the first fiber base material 512 and the second fiber base material 522 contain moisture, the moisture may freeze and expand during operation of the GM refrigerator 1, which may have an unexpected effect on the strength securing part 51 and the sliding part 52.

[0047] According to the displacer 3 of this embodiment, the strength ensuring portion 51 ensures the mechanical strength required for the main body member 5 of the displacer 3, and the sliding portion 52 ensures the slidability with respect to the inner circumferential surface of the cylinder portion. This improves the durability of the displacer 3. That is, the temperature of the displacer 3 of the GM refrigerator 1 is room temperature when the GM refrigerator is not operating, and is extremely low temperature when the GM refrigerator 1 is operating. For this reason, in a conventional configuration in which a sliding portion made of a separate member from the strength ensuring portion is bonded to the outer circumferential surface of the strength ensuring portion with an adhesive, a force (for example, a force in the shear direction or a force in the direction of peeling from each other) is generated between the strength ensuring portion and the sliding portion due to the difference in the thermal expansion coefficient (linear expansion coefficient) between the strength ensuring portion and the sliding portion, which may result in peeling of the sliding portion.

[0048] In contrast, according to this embodiment, the first thermosetting resin 511 of the strength securing portion 51 and the second thermosetting resin 521 of the sliding portion 52 are the same type of resin, and therefore have the same or almost the same thermal expansion coefficients, and as a result, no force (or no large force) is generated between the strength securing portion 51 and the sliding portion 52. Furthermore, the first thermosetting resin 511 of the strength securing portion 51 and the second thermosetting resin 521 of the sliding portion 52 are in direct contact with each other and integrally bonded together (in other words, there is no clear interface), so that peeling of the sliding portion 52 from the strength securing portion 51 is prevented or suppressed. Therefore, the durability of the displacer 3 can be improved.

[0049] Furthermore, since the first fiber base material 512 and the second fiber base material 522 are formed of chemical fibers, the water absorption of the strength securing portion 51 and the sliding portion 52 can be reduced. This can improve the handleability of the material of the displacer 3 and the manufactured displacer 3. That is, the cloth (fiber base material) embedded in the cloth-containing Bakelite has a higher water absorption than chemical fibers. Therefore, in a conventional configuration in which the displacer is formed of cloth-containing Bakelite, the moisture absorbed by the cloth may freeze and expand, causing an unexpected effect on the displacer. Therefore, when manufacturing the displacer and the GM refrigerator, it is necessary to avoid exposing the material of the displacer and the manufactured displacer to an environment that is prone to water absorption. In addition, if the material of the displacer and the manufactured displacer are exposed to an environment that is prone to water absorption, they must be dried afterwards. In contrast, according to the present embodiment, sheet-like members made of chemical fibers (specifically, aramid) are used for the first fiber base material 512 and the second fiber base material 522, so that it is possible to reduce the water absorption of the material of the displacer 3 and the manufactured displacer 3. Therefore, it is possible to improve the handleability of the material of the displacer 3 and the manufactured displacer 3.

[0050] In the above explanation, the main body member 5 of the first piston portion 31 has been described, but the second piston portion 32 may also have a main body member having a configuration similar to that of the main body member 5 of the first piston portion 31.

[0051] (Displacer Manufacturing Method) Next, a method for manufacturing the displacer 3 according to this embodiment will be described. The method for manufacturing the displacer 3 according to this embodiment includes a step of manufacturing a composite material 71, which is the material of the displacer 3 according to this embodiment, and a step of forming the manufactured composite material 71 into a predetermined size and shape. Fig. 5 is a partial cross-sectional view showing a schematic configuration of the manufactured composite material 71. Figs. 6A and 6B are schematic views showing the manufacturing process of the composite material 71.

[0052] As shown in FIG. 5, the composite material 71 has a hollow cylindrical shape. The composite material 71 has a hollow cylindrical inner layer 711 located on the inner periphery side of the cylinder, and a hollow cylindrical outer layer 712 located on the outer periphery side of the inner layer 711. In other words, the inner layer 711 and the outer layer 712 are laminated on each other in the radial direction of the cylinder. The outer layer 712 is exposed on the outer periphery side of the composite material 71. Furthermore, the inner layer 711 and the outer layer 712 are in direct contact with each other and are integrally bonded. The inner layer 711 is a portion corresponding to the strength securing portion 51 of the displacer 3, and the outer layer 712 is a portion corresponding to the sliding portion 52 of the displacer 3. Therefore, the outer layer 712 has the same configuration as the strength securing portion 51 described above. Similarly, the inner layer 711 has the same configuration as the sliding portion 52 described above.

[0053] The composite material 71 is manufactured using a first prepreg 72 and a second prepreg 73 as starting materials. The first prepreg 72 and the second prepreg 73 are both flexible sheet-like materials. The first prepreg 72 has a first fiber base material 512 and a first binder impregnated in the first fiber base material 512. The second prepreg 73 has a second fiber base material 522 and a second binder impregnated in the second fiber base material 522. The first fiber base material 512 and the second fiber base material 522 are both sheet-like members made of chemical fibers, and are aramid (aramid fiber) in this embodiment. The first binder and the second binder are both uncured or semi-cured thermosetting resins, and are uncured or semi-cured phenolic resins in this embodiment. The second binder contains the above-mentioned filler. The material, particle size, and content of this filler are as described above. On the other hand, the first binder does not contain this filler.

[0054] Then, as shown in FIG. 6A, the first prepreg 72 is wound around a mandrel (core material) 74 or the like to mold the first prepreg 72 into a cylindrical shape. In other words, a cylindrical material made of the first prepreg 72 is manufactured. At this time, the first fiber base material 512 included in the first prepreg 72 is overlapped with each other in the radial direction of the cylinder by winding (wrapping) the first prepreg 72 around the mandrel 74 multiple times. Next, as shown in FIG. 6B, the second prepreg 73 is wound around the outer periphery of the first prepreg 72 molded into a hollow cylindrical shape. In this way, the second prepreg 73 is molded into a cylindrical shape. At this time, the second prepreg 73 is wound around the first prepreg 72 multiple times to overlap with each other in the radial direction of the cylinder. Through such a process, a combined body of the first prepreg 72 and the second prepreg 73 having a cylindrical shape is manufactured.

[0055] In addition, by winding the second prepreg 73 directly around the outer peripheral surface of the first prepreg 72 molded into a cylindrical shape, the first binder of the first prepreg 72 and the second binder of the second prepreg 73 are brought into direct contact with each other. In other words, no other member or material (e.g., adhesive) is interposed between the first prepreg 72 and the second prepreg 73. Through this process, the first binder (i.e., the first thermosetting resin 511 in an uncured or semi-cured state) and the second binder (i.e., the second thermosetting resin 521 in an uncured or semi-cured state) come into direct contact with each other and are integrated.

[0056] Next, the combined body of the first prepreg 72 and the second prepreg 73 molded into a cylindrical shape is heated. The heating conditions (heating temperature, heating time, etc.) are appropriately set according to the types (properties) of the first thermosetting resin 511 and the second thermosetting resin 521, and are not particularly limited. When the first binder and the second binder are cured by heating, the inner layer 711 is molded by the first prepreg 72, and the outer layer 712 is molded by the second prepreg 73. That is, a composite material 71 is manufactured, which has the inner layer 711 composed of the first thermosetting resin 511 in which the first fiber base material 512 is embedded and which does not contain a filler (or the filler content is less than that of the second thermosetting resin 521), and the outer layer 712 composed of the second thermosetting resin 521 in which the second fiber base material 522 is embedded and which contains a filler. Since the first binder and the second binder are in direct contact with each other and are integrated together, the first thermosetting resin 511 and the second thermosetting resin 521 are in direct contact with each other and are integrated together.

[0057] In addition, during the period from laminating the second prepreg 73 on the first prepreg 72 to curing the first binder and the second binder by heating, the filler contained in the second binder of the second prepreg 73 may diffuse into the first binder of the first prepreg 72. If the filler is dispersed into the first binder, the mechanical strength of the inner layer 711 to be molded may be reduced. For this reason, from the viewpoint of the strength of the composite material 71 and the displacer 3 to be manufactured, it is preferable to prevent or suppress the filler from diffusing into the first binder as much as possible. Therefore, in this case, it is preferable that the time from manufacturing the bonded body of the first prepreg 72 and the second prepreg 73 to completing the firing is short.

[0058] Then, the manufactured composite material 71 is machined to manufacture the body member 5 of the displacer 3 from the composite material 71. Specifically, the inner peripheral surface, outer peripheral surface, and end surfaces of the composite material 71 are machined to form the composite material 71 into a predetermined size and shape. The outer peripheral surface (i.e., the outer layer 712) of the composite material 71 is machined to form the sliding surface 501 and the relief surface 502. Furthermore, a screw hole 503 is formed in the end surface, and a hole that communicates from the outer peripheral surface to the inner peripheral surface is formed to form the third communication passage 312. Through the above steps, the body member 5 of the displacer 3 is manufactured.

[0059] According to this embodiment, the number of manufacturing steps can be reduced compared to the conventional method. That is, the conventional method of manufacturing a displacer requires a step of manufacturing a strength ensuring portion by machining a material, a step of bonding a sliding portion to the outer circumferential surface of the manufactured strength ensuring portion, and a step of performing machining (finishing) to give the bonded sliding portion a predetermined dimensional shape. In contrast, according to this embodiment, the step of bonding the sliding portion 52 is not necessary, and the main body member 5 of the displacer 3 can be manufactured by machining alone. Furthermore, according to this embodiment, machining of the outer circumferential surface of the strength ensuring portion 51 is not necessary.

[0060] Furthermore, since the water absorption rate of the inner layer 711 and the outer layer 712 of the composite material 71 is lower than that of conventional cloth-containing Bakelite, the handleability of the material before and during the manufacturing process of the displacer 3, as well as the handleability of the main body member 5 of the manufactured displacer 3, are improved.

[0061] (Modification) Here, a modified example of the main body member 5 of the displacer 3 will be described. The strength securing portion 51 of the displacer 3 according to the modified example has a sheet-shaped metal mesh instead of the first fiber base material 512. The material of the metal mesh is not particularly limited, but for example, stainless steel can be used. With this configuration, the strength of the strength securing portion 51 can be increased and the water absorption can be reduced compared to a configuration in which the strength securing portion 51 has the first fiber base material 512 made of synthetic resin. Furthermore, when the strength securing portion 51 has a stainless steel mesh, the thermal expansion coefficient of the displacer 3 becomes close to that of stainless steel (i.e., the thermal expansion coefficient becomes small). Therefore, the dimensional change of the displacer 3 during the operation of the GM refrigerator 1 becomes small, and the dimensional control of the displacer 3 becomes easy.

[0062] In addition, in a configuration in which the strength securing part 51 has a metal mesh instead of the first fiber base material 512 made of synthetic resin, the metal mesh may be exposed on the surface (inner peripheral surface) of the displacer 3. Therefore, the displacer 3 has a layer made of only a resin material on the inner peripheral side (i.e., the innermost side) of the strength securing part 51 having the metal mesh. That is, the displacer 3 according to the modified example has a three-layer structure consisting of a layer located on the innermost peripheral side, a strength securing part 51 having a metal mesh located on the outer peripheral side thereof, and a sliding part 52 located on the outermost peripheral side. In this case, the same structure as the above-mentioned "strength securing part 51 having the first fiber base material 512 made of synthetic resin" can be applied to the layer located on the innermost peripheral side. In addition, the above-mentioned configuration can be applied to the sliding part 52.

[0063] The manufacturing method of the main body member 5 of the displacer 3 according to the modified example is as follows. First, a hollow cylindrical composite material is manufactured using the first prepreg 72, the third prepreg, and the second prepreg 73 as starting materials. The first prepreg 72 and the second prepreg 73 are as described above. The third prepreg has a sheet-like metal mesh and a third binder impregnated in the sheet-like metal mesh. The third binder is an uncured or semi-cured thermosetting resin, like the first binder and the second binder described above, and specifically, is an uncured or semi-cured phenolic resin. Note that this third binder does not contain a filler.

[0064] Then, the first prepreg 72 is wound around a mandrel 74 or the like to mold the first prepreg 72 into a cylindrical shape. Next, a third prepreg is wound around the outer periphery of the first prepreg 72 molded into a hollow cylindrical shape. This molds the third prepreg into a cylindrical shape. At this time, the third prepreg is wound around the first prepreg 72 multiple times, so that the metal meshes contained in the third prepreg overlap each other in the radial direction of the cylinder. After that, the second prepreg 73 is wound around the outer periphery of the third prepreg molded into a cylindrical shape. Through these steps, a combined body of the first prepreg 72, the third prepreg, and the second prepreg 73 having a cylindrical shape is manufactured.

[0065] Next, the cylindrically molded assembly of the first prepreg 72, the third prepreg, and the second prepreg 73 is heated to harden the first binder, the third binder, and the second binder. This produces a composite material having a hollow cylindrical shape and a three-layer structure. The produced composite material is then machined to produce the body member 5 of the displacer 3 according to the modified example from the composite material.

[0066] Although the embodiment of the present invention has been described above, the present invention should not be limited to the above embodiment. The present invention can be modified without departing from the spirit of the present invention. For example, in the above embodiment, the strength securing portion 51 and the sliding portion 52 are molded from phenolic resin, but the strength securing portion 51 and the sliding portion 52 are not limited to phenolic resin. For example, epoxy resin may be applied to the strength securing portion 51 and the sliding portion 52. Furthermore, the strength securing portion 51 and the sliding portion 52 may be molded from a thermosetting resin that is bonded together when they come into contact with each other, and may not be formed from the same type of thermosetting material. In other words, the strength securing portion 51 and the sliding portion 52 may be molded from different types of thermosetting resins that are compatible with each other.

[0067] In the above embodiment, the sliding portion 52 is laminated over the entire outer circumferential surface of the strength ensuring portion 51, but the present invention is not limited to such a configuration. For example, the strength ensuring portion 51 may have a ring-shaped sliding portion 52 laminated over a portion of the outer circumferential surface. In this case, the number of sliding portions 52 is not limited, and the main body member 5 may have one ring-shaped sliding portion 52, or may have multiple ring-shaped sliding portions 52 spaced apart from each other in the axial direction.

[0068] In the above embodiment, the second thermosetting resin 521 (sliding portion 52) contains a filler having a lower friction coefficient than the first thermosetting resin 511 and the second thermosetting resin 521, and the first thermosetting resin 511 (strength securing portion 51) does not contain the filler, but the present invention is not limited to such a configuration. For example, in order to make the second thermosetting resin 521 exhibit a predetermined effect other than ensuring or improving the slidability, in addition to the filler, a filler made of a material different from the filler may be contained. Similarly, in order to make the first thermosetting resin 511 exhibit a predetermined effect, a filler made of a material different from the filler may be contained. [Explanation of symbols]

[0069] Reference Signs List 1...GM refrigerator, 2...cylinder member, 3...displacer, 5...main body member of first piston portion, 51...strength securing portion, 52...sliding portion, 501...sliding surface, 502...flank surface, 511...first thermosetting resin, 512...first fiber base material, 521...second thermosetting resin, 522...second fiber base material

Claims

1. A displacer of a refrigerator that moves a working gas by moving inside a cylinder of the refrigerator, The cooling device has a hollow cylindrical portion having a space formed therein capable of accommodating a cooling material and a sliding surface on an outer circumferential side thereof that slides against the inner circumferential surface of the cylinder, The hollow cylindrical portion is A hollow cylindrical first layer including a first thermosetting resin and a sheet-like first fiber base material embedded in the first thermosetting resin; a second thermosetting resin, a filler contained in the second thermosetting resin and having a lower coefficient of friction than the second thermosetting resin, and a sheet-like second fiber base material embedded in the second thermosetting resin containing the filler; and a hollow cylindrical second layer in direct contact with the first layer and laminated on an outer circumferential surface of the first layer, at least a part of the outer circumferential surface forming the sliding surface; The first thermosetting resin and the second thermosetting resin are the same type of resin, and the first thermosetting resin and the second thermosetting resin are in direct contact with each other and are integrally bonded to each other. Refrigeration machine displacer.

2. 2. A displacer for a refrigerator according to claim 1, the first thermosetting resin and the second thermosetting resin are phenolic resins; The filler is a powder of polytetrafluoroethylene, The first fiber base material and the second fiber base material are sheet-like members made of synthetic resin. Refrigeration machine displacer.

3. A method for manufacturing a displacer for a refrigerator having a hollow cylindrical first layer for ensuring mechanical strength, and a second layer laminated on an outer periphery of the first layer and having a sliding surface on the outer periphery thereof, the sliding surface having a lower friction coefficient than the first layer, comprising: A step of winding a sheet-like first prepreg having a first fiber base material impregnated with an uncured or semi-cured first thermosetting resin into a cylindrical shape to form the first prepreg into a hollow cylindrical shape; A step of winding a sheet-like second prepreg having a second fiber base material impregnated with a second thermosetting resin in an uncured or semi-cured state around an outer peripheral surface side of the first prepreg molded into a hollow cylinder, thereby laminating the second prepreg so as to be in direct contact with the first prepreg and integrating the first thermosetting resin and the second thermosetting resin; curing the first thermosetting resin and the second thermosetting resin by heating the laminated first prepreg and the second prepreg; It has the first thermosetting resin and the second thermosetting resin are the same type of resin, The second thermosetting resin contains a filler having a lower coefficient of friction than the first thermosetting resin and the second thermosetting resin. A method for manufacturing a displacer for a refrigerator.

4. A method for manufacturing a displacer for a refrigerator according to claim 3, comprising the steps of: the first thermosetting resin and the second thermosetting resin are phenolic resins; The filler is a powder of polytetrafluoroethylene, The first fiber base material and the second fiber base material are made of a synthetic resin. A method for manufacturing a displacer for a refrigerator.

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