JP2006105514A - Sound eliminating structure and stirling cooling box - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sound eliminating structure for reducing the noises of a Stirling engine, and to provide a Stirling cooling box equipped therewith. <P>SOLUTION: In a machine chamber 31 (a storage chamber) in which a Stirling refrigerator is provided, there is a partition wall part 32 which has an opening portion 32A on the wall opposed to a balancing mass 29. A sound absorbing part 33 is formed to be held between the wall of the machine chamber 31 and the partition wall part 32. The partition wall part 32 and the sound absorbing part 33 constitute a generally known Helmholtz resonator. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a silencing structure and a Stirling Refrigerator / Freezer, and more particularly to a silencing structure for reducing noise caused by a Stirling engine and a Stirling refrigerator equipped with the silencing structure.

  As what applied the heat exchange by a reverse Stirling cycle to a refrigerator, what was described in Unexamined-Japanese-Patent No. 2003-50073 (conventional example 1) etc. are mentioned, for example.

  In Conventional Example 1, the high temperature part for radiating the compression heat of the working gas due to the reverse Stirling cycle to the outside, the low temperature part for absorbing the expansion heat of the working gas due to the reverse Stirling cycle from the outside, and the heat at the low temperature part A low-temperature side circulation circuit comprising a closed circuit in which a low-temperature side condenser and a plurality of low-temperature side evaporators connected to form a thermosyphon are connected to each other, and a low-temperature heat transfer medium that conveys cold heat in a low-temperature part A Stirling refrigeration system is disclosed that is enclosed in a side circulation circuit.

  On the other hand, a Helmholtz resonator is conventionally known as a means for reducing noise.

  For example, Japanese Patent Laid-Open No. 10-306972 (conventional example 2) discloses a technique for reducing noise of a fan device provided in a machine room of a refrigerator by a Helmholtz resonator.

  In JP-A-59-52299 (conventional example 3), a sound absorbing material provided so as to cover the compressor and / or a sound absorbing material attached to the inner surface of the outer box of the outdoor unit. Disclosed is a sound absorbing device for an air conditioner characterized in that a large number of holes are formed at appropriate intervals on the compressor facing surface, and a small volume space slightly larger than each hole is formed at the back of each hole. Yes.

  In JP-A-11-259076 (conventional example 4), a volume chamber provided inside a sound absorbing material made of a porous material provided on the sound source side of the sound insulation panel, and a communication with the volume chamber are provided. There is disclosed a Helmholtz resonance structure including a straight pipe portion that opens toward a sound source side of a sound absorbing material.

  Further, in Japanese Patent Application Laid-Open No. 2001-41020 (conventional example 5), a plurality of protrusions extending in parallel to each other in a certain direction and having different heights are formed. It has a constant trapezoidal cross-sectional shape in the direction orthogonal to the extension direction, and orifice holes are opened at a fixed interval in the top plate portion, and each of the orifice holes and the respective holes are formed in a cavity formed between the ridge portion and the substrate. A sound-absorbing structure is disclosed in which a plurality of Helmholtz resonators are constituted by resonance cavities partitioned by virtual partitions at an intermediate position of the orifice hole.

Furthermore, in Japanese Patent Laid-Open No. 5-158484 (conventional example 6), the area is smaller than the area of the first sound absorbing material and the surface of the first sound absorbing material which is disposed on the first sound absorbing material. A shielding plate and a second sound absorbing material disposed on the shielding plate are stacked and configured, and a cabinet is provided to cover the side surfaces of the first and second sound absorbing materials and the bottom surface of the first sound absorbing material. A sound absorber is disclosed.
JP 2003-50073 A Japanese Patent Laid-Open No. 10-306972 JP 59-52299 A Japanese Patent Laid-Open No. 11-259076 Japanese Patent Laid-Open No. 2001-41020 JP-A-5-158484

  However, the above Stirling refrigeration system has the following problems.

  In Conventional Example 1, when a Stirling refrigerator (Stirling engine) is operated, noise is generated. This noise causes problems such as making the user feel uncomfortable when using the Stirling cooler (Stirling engine-equipped device).

  The Helmholtz resonators according to the conventional examples 2 to 6 are not applied to the Stirling engine. In the conventional examples 2 to 6, the configuration for effectively reducing the noise of the Stirling engine installed in the storage chamber is disclosed. It has not been.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a silencing structure that reduces sound generated from a Stirling engine and a Stirling refrigerator equipped with the silencing structure. .

  The silencing structure according to the present invention is a silencing structure that reduces noise generated from a free piston type Stirling engine having a balance mass, and is provided inside a storage chamber that receives the Stirling engine, and a wall portion facing the balance mass of the storage chamber. And a partition part provided with an opening, and a sound absorbing part formed so as to be sandwiched between the wall part and the partition part.

  According to this configuration, it is possible to reduce the noise of the Stirling engine with a simple structure. Further, there is a tendency that a louder sound is generated near the balance mass. By providing a silencing structure on the wall facing this, the silencing effect can be enhanced efficiently.

  The sound absorbing part in the sound deadening structure is provided with a sound absorbing material, a first part that acts on the sound of the first frequency, and a second part that is provided with the sound absorbing material and acts on the sound of the second frequency, It is preferable to have.

  The sound emitted from a free piston type Stirling engine tends to have a relatively high sound pressure level at a frequency that is an integral multiple of the engine frequency. According to the said structure, the muffling effect can be heightened by selectively reducing the sound of this specific frequency.

  A sound absorbing material may be provided on the partition wall. Thereby, reflection of the sound on the partition wall can be suppressed, and the muffled sound in the storage chamber can be reduced.

  A Stirling refrigerator according to the present invention includes the above-described sound deadening structure and a Stirling refrigerator as a Stirling engine.

  According to the silencing structure, the noise of the Stirling engine can be effectively reduced. Therefore, a Stirling cooler with reduced noise is provided.

  According to the present invention, the noise of the Stirling engine can be effectively reduced.

  In the following, an embodiment of a silencing structure and a Stirling refrigerator according to the present invention will be described with reference to FIGS. 1 to 6.

  In the present specification, the “cooling box” is a concept including all of “refrigerator”, “freezer”, and “freezer refrigerator”.

  Further, in the present embodiment, a Stirling cooler as a Stirling engine mounted device provided with a Stirling refrigerator will be described. However, the Stirling engine mounted device provided with the sound deadening structure according to the present invention is limited to the Stirling cooler. It is not something. The Stirling engine is also used as a generator, for example.

  FIG. 1 is a piping system diagram of a Stirling cooler according to one embodiment of the present invention.

  As shown in FIG. 1, the Stirling refrigerator 1 according to the present embodiment includes a Stirling refrigerator 4 (Stirling engine) having a heat radiating unit 2 and a heat absorbing unit 3, and a high-temperature side evaporator attached to the heat radiating unit 2. 5, a first high temperature side circulation circuit (first circulation circuit) including a high temperature side condenser 7 and pipes 2A, 2B, a high temperature side evaporator 5, a circulation pump 6, a dew prevention pipe 9 and pipes 2C, 2D, 2E, A second high temperature side circulation circuit (second circulation circuit) including 2F, and a low temperature side circulation circuit including a low temperature side condenser 10, a low temperature side evaporator 11, and pipes 3A and 3B attached to the heat absorption unit 3. The first high temperature side circulation circuit cools the heat radiating part 2 of the Stirling refrigerator 4, and the second high temperature side circulation circuit supplies heat to the dew condensation prevention pipe 9. In addition, the low-temperature side circulation circuit performs heat exchange between the air in the refrigerator and the heat absorption unit 3 of the Stirling refrigerator 4.

Water (H ₂ O) or the like is sealed as a refrigerant in the first and second high temperature side circulation circuits. The refrigerant evaporated in the high temperature side evaporator 5 reaches the high temperature side condenser 7 via the pipe 2A (high temperature side conduit) (broken line arrow in FIG. 1). The refrigerant is condensed by heat exchange with the outside air in the high temperature side condenser 7. In order to promote this heat exchange, a fan 8 that generates an air flow in the vicinity of the high-temperature side condenser 7 is provided. The condensed refrigerant returns to the high temperature side evaporator 5 through the pipe 2B (high temperature side return pipe). In the first high temperature side circulation circuit, the high temperature side condenser 7 is heated at a high temperature so that the heat generated in the heat radiating unit 2 can be transferred using the natural circulation caused by the evaporation and condensation of the refrigerant. It is arranged above the side evaporator 5. Further, the pressure in the circulation circuit system is adjusted in order to adjust the boiling point of the refrigerant.

  On the other hand, a pipe 2 </ b> C is connected to the lower part of the high temperature side evaporator 5. Liquid phase refrigerant flows from the high temperature side evaporator 5 into the pipe 2C. The refrigerant that has flowed into the pipe 2C reaches the circulation pump 6 provided below the Stirling refrigerator 4 through the pipe 2D. The refrigerant discharged from the circulation pump 6 is sent to the dew prevention pipe 9 through the pipe 2E. Here, the refrigerant flowing in the dew condensation prevention pipe 9 is kept at a relatively high temperature by the heat given from the heat radiating unit 2 of the Stirling refrigerator 4. Therefore, the dew condensation prevention pipe 9 can be disposed on the front surface of the refrigerator to suppress dew condensation on the door portion or the like. The refrigerant that has flowed through the dew condensation prevention pipe 9 returns to the high temperature side evaporator 5 through the pipe 2F. Thus, forced circulation by the circulation pump 6 is performed in the second circulation circuit.

  Carbon dioxide, hydrocarbons, and the like are sealed as refrigerant in the low-temperature side circulation circuit. The refrigerant condensed in the low temperature side condenser 10 reaches the low temperature side evaporator 11 through the pipe 3A (low temperature side conduit). Heat exchange is performed by evaporating the refrigerant in the low temperature side evaporator 11. In order to promote this heat exchange, a fan 12 that generates an air flow in the vicinity of the low-temperature evaporator 11 is provided. After the heat exchange, the gasified refrigerant returns to the low temperature side condenser 10 through the pipe 3B (low temperature side return pipe). In the low-temperature side circulation circuit, the low-temperature side evaporator 11 is thus condensed on the low-temperature side so that the cold generated in the heat-absorbing unit 3 can be transmitted using the natural circulation caused by the evaporation and condensation of the refrigerant. It is arranged below the vessel 10. Further, the pressure in the circulation circuit system is adjusted in order to adjust the boiling point of the refrigerant.

  When the Stirling refrigerator 4 is operated, the heat generated in the heat radiating unit 2 of the refrigerator 4 is exchanged with air through the high temperature side condenser 7. On the other hand, the cold generated in the heat absorption part 3 of the Stirling refrigerator 4 is heat-exchanged with the air in the refrigerator through the low temperature side evaporator 11. The warmed airflow from the inside of the refrigerator is sent again to the vicinity of the low-temperature side evaporator 11 and repeatedly cooled.

  When the Stirling refrigerator 4 is operated, noise due to vibration of the refrigerator 4 is generated. Therefore, it is preferable to provide a silencing structure for reducing this noise.

  FIG. 2 is a diagram illustrating an example of a silencing structure provided in the refrigerator main body 1A. Referring to FIG. 2, Stirling refrigerator 4 is provided in machine room 31 (storage room). Inside the machine room 31 (on the inner wall), a partition wall 32 having an opening 32A is provided. A sound absorbing portion 33 is formed so as to be sandwiched between the wall portion of the machine room 31 and the partition wall portion 32.

  The partition wall portion 32 and the sound absorbing portion 33 constitute a well-known Helmholtz resonator. According to the Helmholtz resonator, noise of a specific frequency can be effectively reduced by changing the size of the opening 32A, the volume of the sound absorbing portion 33 corresponding to the opening 32A, and the like.

  By the way, as shown in FIG. 5, the sound emitted from the Stirling refrigerator 4 according to the present embodiment has peak frequencies (sounds) of about 70 Hz (= f0), about 140 Hz (= 2f0), and about 280 Hz (= 4f0). The frequency at which the pressure level is maximized). Note that the ratio of the sound pressure levels of f0, 2f0, and 4f0 is approximately 0.6: 1: 1. Here, f0 is a driving frequency of the piston in the Stirling refrigerator 4 (hereinafter sometimes referred to as an engine frequency). In general, it is said that the noise of a free piston type Stirling engine tends to have a peak frequency in the vicinity of an integer multiple of the engine frequency (for example, x1, x2, x4). Therefore, the noise of the Stirling refrigerator can be effectively reduced by adjusting the size of the opening 32A and the volume of the sound absorbing portion 33 so that the Helmholtz resonator acts on the sound near the peak frequency. it can. In particular, it is possible to efficiently reduce a booming sound having a relatively low frequency (for example, about 50 Hz to about 500 Hz) for which an effective silencing structure has not been provided. The value of the peak frequency varies depending on the characteristics of each Stirling engine, and is not limited to the above value. Further, the number of peak frequencies and the sound pressure level at each peak frequency are not limited as described above, and vary depending on the characteristics of the Stirling engine.

  By the way, the following has been clarified by the study of the present inventor.

  The balance mass 29 vibrates with the movement of the piston and the displacer inside the Stirling refrigerator 4. Therefore, there is a tendency that a louder sound is generated near the balance mass 29. Further, since the vibration direction of the balance mass 29 is mainly the vibration direction of the piston and the displacer (the left-right direction in FIG. 2), the air density (that is, the sound wave) due to this vibration is the same as that in FIG. Proceed with priority to the right.

  On the other hand, in the example shown in FIG. 2, the partition wall 32 is provided at a position close to the balance mass 29. Specifically, the partition wall portion 32 is provided along the inner wall of the machine chamber 31 so as to form the sound absorbing portion 33 along the wall portion of the machine chamber 31 facing the balance mass 29. In other words, the partition wall 32 is provided to face the main surface of the balance mass 29. That is, the Helmholtz resonator extends in a direction (here, a direction orthogonal) intersecting the vibration direction of the piston and the displacer of the Stirling refrigerator 4. The Helmholtz resonator is provided over the entire wall portion facing the balance mass 29. According to this configuration, the sound wave can be effectively guided to the Helmholtz resonator. Further, by bringing the Helmholtz resonator closer to the balance mass 29, the noise can be reduced before the noise is diffused, so that the silencing effect can be enhanced.

  FIG. 3 is a view showing a modification of the silencing structure shown in FIG. In the example shown in FIG. 3, the Helmholtz resonator has a wider range than the example shown in FIG. 2, specifically, the range from the upper surface of the machine chamber 31 through the side surface on the balance mass 29 side to the lower surface of the machine chamber 31. Is arranged. In other words, the partition wall 32 is provided so as to surround the balance mass 29. That is, the Helmholtz resonator has a portion extending along the vibration direction of the piston and the displacer of the Stirling refrigerator 4, and a portion extending in a direction intersecting the vibration direction (here, a direction orthogonal). The Helmholtz resonator is provided so as to face the main surface and the side surface of the balance mass 29. According to this configuration, although the cost is slightly increased, the silencing effect can be enhanced.

  The range in which the Helmholtz resonator is installed can be changed as appropriate, and is not limited to the range shown in FIGS. For example, a Helmholtz resonator may be installed over the entire inner wall of the machine room 31.

  As described above, the noise from the Stirling refrigerator 4 has a plurality of peak frequencies. On the other hand, the Helmholtz resonator according to the present embodiment has a portion (first portion) that acts on a sound having a first frequency (for example, f0 in FIG. 5) and a second frequency (for example, in FIG. 5). 2f0) (second portion) and a third frequency (for example, 4f0 in FIG. 5) portion (third portion). With this configuration, it is possible to selectively reduce the peak frequency sound and enhance the silencing effect.

  FIG. 4 is an enlarged view of the Helmholtz resonator shown in FIGS. Referring to FIG. 4, the Helmholtz resonator (noise reduction structure) has a laminated structure in which a partition wall 32 is provided on a wall surface (cooler main body 1 </ b> A) of a machine room via a sound absorption part 33. The sound absorbing portion 33 between the plurality of openings 32A formed in the partition wall 32 is not provided with a partition, but the range of the sound absorbing portion 33 corresponding to each opening 32A is indicated by a broken line (a plurality of broken lines in FIG. It is naturally determined as in (substantially the center of the opening 32A). Therefore, a plurality of Helmholtz resonators having resonance portions of L1 × L2 (see FIG. 4) are arranged by simply overlapping the sound absorbing material (or air layer) and one partition wall on the inner wall of the machine room 31. A muffler structure equivalent to that can be easily obtained. In the example shown in FIG. 4, the sizes of the plurality of openings 32A are different from each other. Thereby, the part which acts on the sound of several peak frequency is formed.

  In the present embodiment, the first to third portions described above are provided according to the fact that there are three noise peak frequencies, but this number can be changed as appropriate. For example, when there are two peak frequencies, only the first and second portions may be provided, and when the peak frequency is four, in addition to the first to third portions, a fourth portion is further added. It may be provided. Moreover, even if there are three peak frequencies, only the first and second portions that act on the sound of two frequencies may be provided.

  The sound absorbing portion 33 may be an air layer, or a sound absorbing material such as glass wool may be provided therein. By arranging the sound absorbing material, it is possible to reduce noise in a region other than the resonance frequency of the Helmholtz resonator. Further, the resonance frequency may be varied by varying the sound absorbing material provided around each opening 32A.

  A sound absorbing material (not shown) is preferably provided on the partition wall 32. Thereby, reflection of the sound on the partition part 32 can be suppressed and the muffled sound in the machine room 31 can be reduced. The same effect can be obtained even if the partition wall 32 itself is made of a metal sound absorbing member.

  Moreover, it is preferable that a sound insulating material is provided on the outer wall of the machine room. Thereby, the radiation sound to the machine room exterior can be reduced.

  According to the silencing structure described above, the noise of the Stirling engine can be effectively reduced. Therefore, a Stirling cooler (Stirling engine-equipped device) with reduced noise is provided.

  Next, an example of the structure of the Stirling refrigerator 4 and its operation will be described with reference to FIG.

  As shown in FIG. 6, the Stirling refrigerator 4 of the present embodiment is a free piston type Stirling engine, and includes a casing 30, a cylinder 13 assembled to the casing 30, and a reciprocating motion in the cylinder 13. Piston 14 and displacer 15, regenerator 16, working space 17 including a compression space 17 </ b> A and an expansion space 17 </ b> B, a heat radiating portion 2, a heat absorbing portion 3, a linear motor 23 as a piston driving means, and a piston spring 24, a displacer spring 25, a displacer rod 26, and a back pressure space 27.

  In the example of FIG. 6, the outer shell (outer wall) of the Stirling refrigerator 4 is not formed of a single container, and is positioned on the back pressure space 27 side and the casing 30 (vessel portion) and on the working space 17 side. The heat dissipating part 2, the tube 18A and the heat absorbing part 3 are mainly configured. The casing 30 defines a back pressure space 27. Various parts including the cylinder 13, the linear motor 23, the piston spring 24, and the displacer spring 25 are assembled to the casing 30. The outer shell is filled with a working medium such as helium gas, hydrogen gas, or nitrogen gas.

  The cylinder 13 has a substantially cylindrical shape, and receives therein a piston 14 and a displacer 15 as a free piston so as to be capable of reciprocating. In the cylinder 13, the piston 14 and the displacer 15 are coaxially spaced apart, and the piston 14 and the displacer 15 divide the working space 17 in the cylinder 13 into a compression space 17 </ b> A and an expansion space 17 </ b> B. More specifically, the working space 17 is a space located closer to the displacer 15 than the end face of the piston 14 on the displacer 15 side, and a compression space 17A is formed between the piston 14 and the displacer 15, and the displacer 15 and the heat absorbing portion. 3, an expansion space 17 </ b> B is formed. The compression space 17 </ b> A is mainly surrounded by the heat radiating part 2, and the expansion space 17 </ b> B is mainly surrounded by the heat absorption part 3.

  Between the compression space 17A and the expansion space 17B, a regenerator 16 in which a film is wound with a predetermined gap on the inner peripheral surface of the tube 18A is disposed. The compression space 17A and the expansion space 17B communicate with each other. Thereby, a closed circuit is formed in the Stirling refrigerator 4. The working medium sealed in the closed circuit flows in accordance with the operations of the piston 14 and the displacer 15, thereby realizing a reverse Stirling cycle described later.

  A linear motor 23 is disposed in the back pressure space 27 located outside the cylinder 13. The linear motor 23 includes an inner yoke 20, a movable magnet portion 21, and an outer yoke 22, and the piston 14 is driven in the axial direction of the cylinder 13 by the linear motor 23.

  One end of the piston 14 is connected to a piston spring 24 constituted by a leaf spring or the like. The piston spring 24 functions as an elastic force applying means for applying an elastic force to the piston 14. By applying an elastic force to the piston spring 24, the piston 14 can be reciprocated in the cylinder 13 more stably and periodically. One end of the displacer 15 is connected to a displacer spring 25 via a displacer rod 26. The displacer rod 26 is disposed through the piston 14, and the displacer spring 25 is constituted by a leaf spring or the like. The peripheral edge of the displacer spring 25 and the peripheral edge of the piston spring 24 are supported by a support member that extends from the linear motor 23 toward the back pressure space 27 of the piston 14 (hereinafter sometimes referred to as the rear).

  A back pressure space 27 surrounded by a casing 30 is disposed on the opposite side of the piston 14 from the displacer 15. The back pressure space 27 includes an outer peripheral region located around the piston 14 in the casing 30 and a rear region located closer to the piston spring 24 (rear side) than the piston 14 in the casing 30. There is also a working medium in the back pressure space 27.

  A heat exchanger 18 and a heat exchanger 19 are provided on the inner peripheral surfaces of the heat radiating unit 2 and the heat absorbing unit 3, respectively. The heat exchangers 18 and 19 perform heat exchange between the compression space 17A and the expansion space 17B and the heat radiating unit 2 and the heat absorbing unit 3, respectively.

  A balance mass 29 is attached to the rear side of the casing 30 via a leaf spring 28. The balance mass 29 is a mass member that absorbs vibration of the casing 30 that is generated when the piston 14 and the displacer 15 vibrate. Specifically, when the vibration is generated in the casing 30 due to the vibration of the piston 14 or the displacer 15, the balance mass 29 is vibrated so as to follow the vibration of the casing 30, whereby the Stirling refrigerator 4. Vibration is reduced.

  Next, the operation of the Stirling refrigerator 4 will be described.

  First, the linear motor 23 is actuated to drive the piston 14. The piston 14 driven by the linear motor 23 approaches the displacer 15 and compresses the working medium (working gas) in the compression space 17A.

  As the piston 14 approaches the displacer 15, the temperature of the working medium in the compression space 17 </ b> A rises, but heat generated in the compression space 17 </ b> A is released to the outside by the heat radiating unit 2. Therefore, the temperature of the working medium in the compression space 17A is maintained almost isothermal. That is, this process corresponds to an isothermal compression process in a reverse Stirling cycle.

  After the piston 14 approaches the displacer 15, the displacer 15 moves to the heat absorption unit 3 side. On the other hand, the working medium compressed in the compression space 17A by the piston 14 flows into the regenerator 16, and further flows into the expansion space 17B. At that time, the heat of the working medium is stored in the regenerator 16. That is, this process corresponds to an isovolumetric cooling process in a reverse Stirling cycle.

  The high-pressure working medium that has flowed into the expansion space 17B expands when the displacer 15 moves to the piston 14 side (rear side). As the displacer 15 moves rearward in this way, the center portion of the displacer spring 25 is also deformed so as to protrude rearward.

  As described above, when the working medium expands in the expansion space 17B, the temperature of the working medium in the expansion space 17B decreases, but external heat is transferred into the expansion space 17B by the heat absorbing unit 3, The inside of the expansion space 17B is kept almost isothermal. That is, this process corresponds to an isothermal expansion process of a reverse Stirling cycle.

  Thereafter, the displacer 15 starts to move away from the piston 14. Thereby, the working medium in the expansion space 17B passes through the regenerator 16 and returns to the compression space 17A side again. At this time, since the heat stored in the regenerator 16 is applied to the working medium, the working medium is heated. That is, this process corresponds to a constant volume heating process of a reverse Stirling cycle.

  By repeating this series of processes (isothermal compression process-isovolume cooling process-isothermal expansion process-isovolume heating process), an inverse Stirling cycle is configured. As a result, the endothermic part 3 gradually becomes low temperature and has a very low temperature. On the other hand, the heat radiating part 2 gradually becomes high temperature. As described above, the cold heat in the heat absorption unit 3 is supplied into the refrigerator through the low temperature side circulation circuit, and the heat in the heat dissipation unit 2 is released to the outside of the refrigerator through the first and second high temperature side circulation circuits. Is done.

  Although the embodiments of the present invention have been described above, the embodiments disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a piping system diagram of a Stirling cooler according to one embodiment of the present invention. It is the figure which showed the silencing structure in the machine room in the Stirling refrigerator which concerns on one embodiment of this invention. It is the figure which showed the silencing structure in the machine room in the modification of the Stirling refrigerator which concerns on one embodiment of this invention. It is the figure which showed the silence structure which concerns on one embodiment of this invention. It is the figure which showed the relationship between the frequency of the sound emitted from a Stirling engine, and a sound pressure level. It is the sectional side view which showed the Stirling refrigerator in the Stirling refrigerator which concerns on one embodiment of this invention.

Explanation of symbols

  1 Stirling refrigerator, 2 heat dissipating section, 2A to 2F pipe (high temperature side circulation circuit), 3 heat absorption section, 3A, 3B pipe (low temperature side circulation circuit), 4 Stirling refrigerator, 5 high temperature side evaporator, 6 circulation pump, 7 High-temperature side condenser, 8 fan, 9 Dew prevention pipe, 10 Low-temperature side condenser, 11 Low-temperature side evaporator, 12 Fan, 13 Cylinder, 14 Piston, 15 Displacer, 16 Regenerator, 17 Working space, 17A Compression space, 17B Expansion space, 18, 19 Heat exchanger, 20 Inner yoke, 21 Movable magnet, 22 Outer yoke, 23 Linear motor, 24 Piston spring, 25 Displacer spring, 26 Displacer rod, 27 Back pressure space, 28 Leaf spring, 29 Balance Mass, 30 casing, 31 machine room, 32 spaces Wall part, 32A opening part, 33 sound absorption part.

Claims (3)

A muffler structure that reduces noise generated from a free piston type Stirling engine having a balance mass,
A containment chamber for receiving the Stirling engine;
A partition wall provided inside the wall facing the balance mass of the storage chamber and having an opening;
A sound deadening structure comprising a sound absorbing portion formed so as to be sandwiched between the wall portion and the partition wall portion.   The sound absorbing portion in the silencing structure is provided with a sound absorbing material, a first portion that acts on the sound of the first frequency, and a second portion that is provided with the sound absorbing material and acts on the sound of the second frequency. The muffler structure according to claim 1, comprising a portion. The muffler structure according to claim 1 or 2,
A Stirling refrigerator equipped with a Stirling refrigerator as the Stirling engine.

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