KR100811359B1 - Stirling engine - Google Patents

Abstract

The Stirling engine of the present invention has a piston and a displacer. When the piston reciprocates in the cylinder by the linear motor, the displacer reciprocates in the cylinder with a predetermined phase difference from the piston. The displacer and the cylinder containing the displacer are formed of metal on the side opposite to the compression space and low heat conductive material on the side opposite to the expansion space. And the fitting precision is established in a metal part.

Cylinder, Cylinder, Stirling Engine, Displacer, Metal Part

Description

Sterling Institution {STIRLING ENGINE}

The present invention relates to a Stirling engine.

Since the Stirling engine uses helium, hydrogen, nitrogen, and the like instead of chlorofluorocarbon as a working gas, it has attracted attention as a heat engine that does not cause destruction of the ozone layer. Patent Documents 1 and 2 show examples of sterling engines.

An important role in the Stirling engine is a piston reciprocating by a power source such as a linear motor, and a displacer synchronously reciprocating with a predetermined phase difference with respect to the piston. The piston and the displacer flow a working gas between the compression space and the expansion space to form a Stirling cycle. In the compression space, the temperature of the working gas rises based on the isothermal compression change, and in the expansion space, the temperature of the working gas decreases based on the isothermal expansion change. Thereby, the temperature of a compression space rises and the temperature of an expansion space falls. When the temperature of the compression space (high temperature space) is radiated through the high temperature heat transfer head, the expansion space (low temperature space) can absorb external heat through the low temperature heat transfer head. By this principle, the Stirling engine is used as a freezer.

Patent Document 1: Japanese Patent Laid-Open No. 2004-52866 (pages 5 to 6, Fig. 1)

Patent Document 2: Japanese Patent Laid-Open No. 2003-75005 (pages 3 to 6, Fig. 2)

In the Stirling engine, the displacer and the cylinder containing the displacer face both the compression space (high temperature space) and the expansion space (low temperature space). If heat is transferred from the compression space to the expansion space through the displacer and the cylinder, the efficiency of the Stirling engine is lowered. Therefore, it is preferable that the displacer and the cylinder have a structure that blocks the movement of heat.

It is generally conceivable as a structure to block the movement of heat to form the displacer and the cylinder with a low thermal conductive material such as synthetic resin or ceramic. On the other hand, although the displacer is made to float by using a gas bearing in the cylinder to make high speed movement, it is very difficult to realize the strict dimensional accuracy required for the gas bearing with a low thermal conductive material. It is not impossible to obtain the necessary gap by adopting a manufacturing technique in which the displacer and the cylinder are adjusted to each other one by one. However, this technique is hardly suitable for industrial mass production.

The present invention has been made in view of the above points, and the Stirling engine has a structure capable of industrially mass production while effectively preventing heat transfer from the compression space to the expansion space through the displacer and the cylinder, while ensuring the assembly attachment accuracy. The purpose is to provide.

In order to solve the said subject, in this invention, a Stirling engine is comprised as follows. In other words, a piston capable of reciprocating by a power source, and a displacer having a predetermined phase difference with respect to the piston, having a reciprocating motion, moving the working gas between the compression space (high temperature space) and the expansion space (low temperature space) In the Stirling engine, the displacer and the cylinder accommodating the displacer are each formed of the compression space side with a metal and the expansion space side with a low thermal conductivity material having a lower thermal conductivity than the metal. The displacer is characterized in that the metal portion has a larger outer diameter than the low thermally conductive material portion, and the cylinder portion has a smaller inner diameter than the low thermally conductive material portion.

According to this configuration, since the displacer and the cylinder housing the displacer are formed of a low thermal conductive material on the side facing the inflation space (expansion space side), heat is transferred from the compressed space to the inflation space through the displacer and the cylinder. It can block or suppress the movement. This improves the efficiency of the Stirling engine. On the other hand, since the side facing the compression space of the displacer and the cylinder (compression space side) is made of metal, it can withstand high temperature and can easily increase the fitting accuracy of the displacer and the cylinder. For this reason, when employing a gas bearing between the displacer and the cylinder, it is possible to industrially mass-produce what secures the gap accuracy necessary for forming and maintaining the gas bearing. In addition, since the displacer has a metal part having an outer diameter larger than that of the low thermal conductive material portion, and a cylinder part of the metal portion has an inner diameter smaller than that of the low thermal conductive material portion, the gap between the low thermal conductive material portions having poor dimensional accuracy is sufficiently sufficient. It can be secured and the accidental contact can be prevented.

In addition, the present invention includes a piston that can be reciprocated by a power source, and a displacer that reciprocates with a predetermined phase difference with respect to the piston, and operates between a compression space (high temperature space) and an expansion space (low temperature space). In the Stirling engine for moving gas, the displacer and the cylinder containing the displacer are each formed of a metal on the compression space side and a low thermal conductivity material having a lower thermal conductivity than the metal. The displacer between the metal portion and the low thermal conductive material portion in the displacer and the boundary between the metal portion and the low thermal conductive material portion in the cylinder do not overlap during the reciprocating motion of the displacer. The positional relationship (distance) of the boundary between the boundary and the boundary of the cylinder is set.

According to this configuration, the boundary between the metal portion and the low thermally conductive material portion in the displacer and the boundary between the metal portion and the low thermally conductive material portion in the cylinder do not overlap during the reciprocating motion of the displacer. Since the positional relationship (distance) between the boundary of the cylinder and the boundary of the cylinder is set, even if a reverse step is generated between the metal part and the low heat conductive material part at the boundary between the metal part and the low heat conductive part, Of movement is not impeded.

The present invention is also characterized in that, in the Stirling engine having the above-described configuration, a gas bearing is formed between the metal portion in the displacer and the metal portion in the cylinder.

According to this configuration, since the gas bearing is constituted between the metal part in the displacer and the metal part in the cylinder, the displacer is prevented from contacting the inner wall of the cylinder during operation of the Stirling engine, and the friction of the contact portion is prevented. There is no problem of energy loss or abrasion of contact.

The present invention is also characterized in that, in the Stirling engine having the above-described configuration, the displacer and / or the cylinder are formed by joining a metal part and a low heat conductive material part by a combination of a screw joint and an adhesive.

According to this configuration, the joining of the metal part and the low thermal conductive material part in the displacer and / or the cylinder is very strong, and the metal part and the low thermal conductive material part are not separated.

In addition, the present invention, in the Stirling engine of the above configuration, the displacer and / or the cylinder, in the portion where the metal portion and the low heat conductive material portion overlaps, the screw coupling portion is provided near the center of the overlap, the outside It is characterized in that the screw groove is not exposed.

According to this configuration, since the screw groove is not exposed to the outside in the displacer and / or the cylinder, the screw groove can be prevented from becoming the working gas passage.

In the Stirling engine of the above configuration, the displacer and / or the cylinder may be configured such that an adhesive is applied around the entire contact surface of the metal portion and the low thermal conductive material portion.

According to this configuration, the displacer and / or the cylinder can prevent the screw groove from becoming a working gas passage because the adhesive is applied around the entire contact surface of the metal portion and the low thermal conductive material portion.

Moreover, in the sterling engine of the said structure, you may comprise the said low heat conductive material part with the injection molded article of synthetic resin.

According to this configuration, the low heat conductive material portion can be mass produced at low cost.

1 is a cross-sectional view of a sterling engine.

2 is a cross-sectional view of the displacer and the cylinder containing it;

3 is an enlarged cross-sectional view of a portion of circle A in FIG. 2;

4 is an enlarged cross-sectional view showing another example of the configuration of a portion of circle A in FIG. 2;

[Description of the code]

1: sterling organ

10, 11: cylinder

11a, 13a: metal part

11b, 13b: part of low thermal conductivity material

12: piston

13: displacer

13c: screw connection

First, the structure of the Stirling engine to which the present invention is applied will be described based on FIG. 1 is a cross-sectional view of a Stirling engine.

The centers of the assembly of the Stirling engine 1 are the cylinders 10 and 11. The axes of the cylinders 10, 11 are arranged on the same straight line. The piston 12 is inserted into the cylinder 10, and the displacer 13 is inserted into the cylinder 11. The piston 12 and the displacer 13 reciprocate during operation of the Stirling engine 1 without contacting the inner walls of the cylinders 10 and 11 by a gas bearing described later. The piston 12 and the displacer 13 move with a predetermined phase difference. The structures of the cylinder 11 and the displacer 13 will be described later in detail.

The cup-shaped magnet holder 14 is fixed to one end of the piston 12. The displacer shaft 15 protrudes from one end of the displacer 13. The displacer shaft 15 penetrates the piston 12 and the magnet holder 14 freely in the axial direction.

The cylinder 10 holds the linear motor 20 outside of the operating region portion of the piston 12. The linear motor 20 includes an outer yoke 22 having a coil 21, an inner yoke 23 provided to contact an outer circumferential surface of the cylinder 10, and an outer yoke 22 and an inner yoke 23. The ring magnet 24 inserted into the annular space of the tube, the tubular body 25 surrounding the outer yoke 22, and the outer yoke 22, the inner yoke 23 and the tubular body 25 in a predetermined positional relationship. Synthetic resin end brackets 26 and 27 are provided. The magnet 24 is fixed to the magnet holder 14.

The center of the spring 30 is fixed to a portion of the hub of the magnet holder 14. The center of the spring 31 is fixed to the displacer shaft 15. The outer circumference of the springs 30 and 31 is fixed to the end bracket 27. The spacer 32 is arrange | positioned between the outer peripheral parts of the springs 30 and 31, and the springs 30 and 31 hold | maintain a fixed distance by this. The springs 30 and 31 are formed by inserting spiral grooves into a disc-shaped material, and causing the displacer 13 to have a predetermined phase difference (generally about 90 ° out of phase) with respect to the piston 12 to resonate. Play a role.

The heat transfer heads 40 and 41 are disposed outside the operating area portion of the displacer 13 in the cylinder 11. The heat transfer head 40 has a ring shape, and the heat transfer head 41 has a cap shape, and all of them are made of a metal having good thermal conductivity such as copper or a copper alloy. The heat transfer heads 40 and 41 are supported on the outside of the cylinder 11 in the form of interposing the ring-shaped internal heat exchangers 42 and 43, respectively. The internal heat exchangers 42 and 43 are each breathable and transmit heat of the working gas passing through the interior to the heat transfer heads 40 and 41. The cylinder 10 and the pressure vessel 50 are connected to the heat transfer head 40.

The annular space enclosed by the heat transfer head 40, the cylinders 10 and 11, the piston 12, the displacer 13, the displacer shaft 15 and the internal heat exchanger 42 is a compression space 45. do. The space enclosed by the heat transfer head 41, the cylinder 11, the displacer 13 and the internal heat exchanger 43 becomes the expansion space 46.

The regenerator 47 is disposed between the internal heat exchangers 42 and 43. The regenerator 47 is formed by filling a container with a filler (matrix) such as a wire mesh, or winding a thin metal sheet or a synthetic resin film in a coil shape, and has a space therein through which a working gas passes. The regenerator tube 48 surrounds the outer side of the regenerator 47. Regenerator tube 48 constitutes an airtight passage between heat transfer heads 40 and 41.

A cylindrical pressure vessel covering the linear motor 20, the cylinder 10, and the piston 12 forms the trunk portion 50. The inside of the body part 50 becomes the back pressure space 51.

The structure of the trunk | drum 50 is as follows. That is, the trunk | drum 50 is divided into two parts, the ring-shaped part 52 joined to the heat transfer head 40, and the cap-shaped part 53 joined to this ring-shaped part 52. As shown in FIG. The ring portion 52 and the cap portion 53 are also made of stainless steel. One end of the ring-shaped portion 52 is narrowed to a tapered shape to be a tapered portion 52a, and this portion is joined to the heat transfer head 40. The cap part 53 is a structure which welded the hard board 53a to the inner surface of the pipe.

Flange-shaped portions 54 and 55 are provided at the other end of the ring-shaped portion 52 and the opening end of the cap-shaped portion 53 facing the other end of the ring-shaped portion 52. The flange portions 54 and 55 are all formed by welding a stainless steel ring to the ring portion 52 and the cap portion 53. Finally, the flange portions 54 and 55 are welded and closed. The body portion 50 is formed.

In the trunk | drum 50, the terminal part 28 for supplying electric power to the linear motor 20, and the pipe 50a for enclosing a working gas inside are arrange | positioned. All of them are provided to protrude in the radial direction from the outer circumferential surface of the cap portion 53.

The trunk portion 50 is provided with a vibration suppressing device 60. The vibration suppressing device 60 includes a base 61 fixed to the trunk portion 50, a plate-like spring 62 supported by the base 61, and a mass (mass) 63 supported by the spring 62. )

The interior of the piston 12 is a cavity 80. The cavity 80 communicates with the compression space 45 through a check valve 90 disposed on the end face of the piston 12. On the outer circumferential surface of the piston 12, a plurality of recesses 81 forming a gas bearing are arranged on the same circumference at predetermined angular intervals. A metal tubing 82 is driven into the bottom of the recess 81 in a form penetrating the piston 12, and a working gas flows from the cavity 80 into the recess 81 through the metal tubing 82. Supplied. The annular column of the recessed part 81 is formed in two or more spaces at intervals in the axial direction of the piston 12. That is, two or more gas bearings are formed.

The interior of the displacer 13 also has a cavity 85. The cavity 85 communicates with the compression space 45 via a check valve 90 disposed on the end face of the displacer 13. On the outer circumferential surface of the displacer 13, a plurality of recesses 86 forming a gas bearing are arranged on the same circumference at predetermined angular intervals. The working gas is supplied from the cavity 85 to the recess 86 through the metal tubing 87 embedded in the bottom of the recess 86.

The Stirling engine 1 operates as follows. When an alternating current is supplied to the coil 21 of the linear motor 20, a magnetic field penetrates the magnet 24 between the outer yoke 22 and the inner yoke 23, and the magnet 24 reciprocates in the axial direction. do. Supply power at a frequency that matches the total mass of the piston system (piston 12, magnet holder 14, magnet 24, and spring 30) and a resonant frequency determined by the spring constant of the spring 30 By doing so, the piston system initiates a smooth sinusoidal reciprocating motion.

In the displacer system (the displayer 13, the displacer shaft 15 and the spring 31), the total mass and the resonant frequency determined by the spring constant of the spring 31 drive the piston 12. Set to resonate with frequency.

By the reciprocating motion of the piston 12, compression and expansion are repeated in the compression space 45. With this change in pressure, the displacer 13 also reciprocates. At this time, a phase difference occurs between the displacer 13 and the piston 12 due to the flow resistance between the compression space 45 and the expansion space 46. In this way, the displacer 13 of the free piston structure vibrates synchronously with the piston 12 with a predetermined phase difference.

By the above operation, a sterling cycle is formed between the compression space 45 and the expansion space 46. In the compression space, the temperature of the working gas increases based on the isothermal compression change, and in the expansion space 46, the temperature of the working gas decreases based on the isothermal expansion change. For this reason, the temperature of the compression space 45 rises and the temperature of the expansion space 46 falls.

When the operating gas reciprocating between the compression space 45 and the expansion space 46 during operation passes through the internal heat exchangers 42 and 43, the heat having the heat is transferred to the heat transfer head through the internal heat exchangers 42 and 43. Pass it to (40, 41). Since the working gas flowing from the compression space 45 into the regenerator 47 is hot, the heat transfer head 40 is heated, and the heat transfer head 40 becomes a worm head. Since the working gas flowing into the regenerator 47 from the expansion space 46 is low temperature, the heat transfer head 41 is cooled, and the heat transfer head 41 becomes a cold head. By dissipating heat from the heat transfer head 40 to the atmosphere and lowering the temperature of the specific space in the heat transfer head 41, the Stirling engine 1 functions as a refrigeration engine.

The regenerator 47 functions to pass only the working gas without transmitting heat of the compression space 45 and the expansion space 46 to the space on the opposite side. The high temperature working gas that enters the regenerator 47 from the compression space 45 via the internal heat exchanger 42 gives heat to the regenerator 47 when passing through the regenerator 47, and in a state where the temperature is lowered. It enters the expansion space 46. The low temperature working gas that enters the regenerator 47 from the expansion space 46 via the internal heat exchanger 43 recovers heat from the regenerator 47 when passing through the regenerator 47 and is compressed in a state where the temperature is raised. It flows into the space 45. In other words, the regenerator 47 serves as a storage of heat.

When the piston 12 and the displacer 13 reciprocate and the working gas moves, vibration occurs in the Stirling engine 1. The vibration suppressing device 60 suppresses this vibration.

A portion of the high pressure working gas in the compression space 45 enters the cavity 80 of the piston 12 and the cavity 85 of the displacer 13 via the check valve 90. Then, the jets are ejected from the recesses 81 and 86. By blowing working gas, a film of gas is formed between the outer circumferential surface of the piston 12 and the inner circumferential surface of the cylinder 10, and between the outer circumferential surface of the displacer 13 and the inner circumferential surface of the cylinder 11. Contact of the cylinder 10 and also of the displacer 13 and the cylinder 11 are prevented. As a result, there is no problem of energy loss due to friction of the contact portion or wear of the contact portion.

The piston 12 and the cylinder 10 are formed of metal, such as aluminum or stainless steel. The other displacer 13 and the cylinder 11 are formed of a part of metal and a part of a low heat conductive material such as a synthetic resin. Hereinafter, the structure of the displacer 13 and the cylinder 11 is demonstrated based on FIGS. 2 is a cross-sectional view of the displacer and the cylinder, and FIGS. 3 and 4 are enlarged cross-sectional views of the portion enclosed by the circle A in FIG.

As for the displacer 13 and the cylinder 11 which accommodates the said displacer 13, the side (compression space side) which opposes the compression space 45 is formed with metal, and is opposed to the expansion space 46 in both. The side (expansion space side) is formed of the low thermal conductivity material of the thermal conductivity lower than the said metal. The metal part 13a and the low thermally conductive material part 13b of the displacer 13 and the metal part 11a and the low thermally conductive material part 11b of the cylinder 11 are both covered by the former. Fit. That is, they are fitted with socket inserts. The fitting portion is bonded with an adhesive, but in the displacer 13 which itself reciprocates at high speed, the fitting portion is joined by using a combination of a screw and an adhesive to increase the bonding strength. 3 and 4 show structural examples of the screwing of the fitting portion.

In both the structural example of FIG. 3 and the structural example of FIG. 4, the screw coupling part 13c is comprised by the male thread part formed in the outer peripheral surface of the metal part 13a, and the female thread part formed in the inner peripheral surface of the low heat conductive material part 13b. have. In the structural example of Fig. 3, at the portion where the metal portion 13a and the low thermal conductive material 13b overlap, the screw engaging portion 13c is provided near the center of the overlap, and the screw groove is not exposed to the outside. As a result, the screw groove serves as a working gas passage, thereby preventing the unexpected flow of working gas (leakage) in and out of the display 13.

The metal portion 11a and the low thermal conductive material portion 11b of the cylinder 11 do not move in the cylinder itself, and thus the adhesive strength alone does not cause a lack of bonding strength. However, considering that the whole Stirling engine 1 vibrates due to the reciprocating motion of the piston 12 and the displacer 13, a screw coupling part is installed between the metal part 11a and the low heat conductive material part 11b and joined. The strength may be increased.

In the displacer 13, the adhesive may be applied to a suitable portion of the contact surface of the metal portion 13a and the low thermal conductive material portion 13b, but the application of the adhesive around the entire contact surface can prevent leakage of the working gas. If applied to the entire contact surface, the bonding can be made even stronger. The same can be said for the cylinder 11.

In the displacer 13 assembled as described above, the outer diameter of the metal portion 13a is larger than that of the low thermal conductive material portion 13b. In the other cylinder 11, the inner diameter of the metal part 11a is smaller than the low heat conductive material part 11b. In general, the low thermal conductive material is inferior in dimensional accuracy, but by designing in this way, the space between the low thermal conductive material portions 13b and 11b is sufficiently secured, and it is possible to prevent accidental contact. Even when the coefficients of expansion of the low thermally conductive material portions 13b and 11b are large and the dimensions change considerably due to temperature change, safety (prevention of contact) can be confirmed thereby. This interval can be set to a value of 120 µm, for example.

Since the metal parts 13a and 11a can raise the dimensional accuracy, the fitting precision is established between them. And a functioning gap of the gas bearing is obtained. This gap can be set to a value of 20 µm, for example.

The boundary between the metal portion 13a and the low thermal conductive material portion 13b in the displacer 13, and the boundary between the metal portion 11a and the low thermal conductive material portion 11b in the cylinder 11. The distances D (see FIG. 2) of each other vary by the movement of the displacer 13. The positional relationship (distance) of the boundary of the displacer 13 and the boundary of the cylinder 11 is set so that these boundary portions do not overlap each other, that is, the distance D does not become zero. Therefore, even if a reverse step is generated between the metal part and the low heat conductive material part at the boundary between the metal part and the low heat conductive part, the movement of the displacer 13 is not hindered by the reverse step.

The low thermal conductive material portions 13b and 11b are formed by injection molding of the synthetic resin. This makes it possible to mass produce the low thermal conductive material portions 13b and 11b at low cost. As the synthetic resin, for example, polycarbonate can be adopted.

In addition, the metal part 11a of the cylinder 11 is integrated with the cylinder 10. Reference numeral 10a shown in FIG. 2 denotes a bridge portion extending from the cylinder 10. By setting it as such a structure, the positioning precision of the cylinders 10 and 11 can be improved.

As mentioned above, although the Example of this invention was described, further various changes can be added and implemented in the range which does not deviate from the main point of invention.

The present invention can be used throughout Stirling engines.

Claims (5)

A piston capable of reciprocating by a power source, and a displacer having a reciprocating motion with a predetermined phase difference with respect to the piston, and a sterling for moving the working gas between the compression space (high temperature space) and the expansion space (low temperature space). In the engine, The displacer and the cylinder accommodating the displacer are each formed of the compression space side as a metal and the expansion space side as a low thermal conductivity material having a lower thermal conductivity than the metal. Said displacer having a metal portion having a larger outer diameter than a low thermal conductive material portion and said cylinder having a metal portion having an inner diameter smaller than a low thermal conductive material portion. A piston capable of reciprocating by a power source, and a displacer having a reciprocating motion with a predetermined phase difference with respect to the piston, and a sterling for moving the working gas between the compression space (high temperature space) and the expansion space (low temperature space). In the engine, The displacer and the cylinder accommodating the displacer are each formed of the compression space side as a metal and the expansion space side as a low thermal conductivity material having a lower thermal conductivity than the metal. The boundary portion between the metal portion and the low thermally conductive material portion in the displacer and the boundary portion between the metal portion and the low thermally conductive material portion in the cylinder have a mutual distance such that they do not overlap during the reciprocating motion of the displacer. A sterling engine, which is set. The Stirling engine according to claim 1 or 2, comprising a gas bearing between the metal portion in the displacer and the metal portion in the cylinder. The Stirling engine according to claim 1 or 2, wherein the displacer, the cylinder, or a combination thereof is a metal part and a low thermal conductive material part joined by a combination of a screw joint and an adhesive. The Stirling engine according to claim 4, wherein in the region where the metal portion and the low thermal conductive material portion overlap, the screw coupling portion is provided near the center of the overlapping portion, and the screw groove is not exposed to the outside.

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