JP2007285661A - Stirling engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a Stirling engine with stable and continuous bonding by an adhesive of a metal body and a synthetic resin cap composing a displacer. <P>SOLUTION: The Stirling engine 1 is provided with a piston 12 and the displacer 13. When the piston 12 is reciprocated in a cylinder 10 by a linear motor 20, the displacer 13 is reciprocated in a cylinder 11 with a predetermined phase difference with respect to the piston 12, and working gas is moved between a compression space 45 and an expansion space 46. The displacer 13 is comprised of the metal body 13a facing the compression space 45, and the synthetic resin made cap 13b facing the expansion space 46, and connection parts 13c, 13d integrally formed so as to protrude toward each other are engaged and bonded by the adhesive. The connection parts 13c, 13d are smaller than the body 13a and the cap 13d in diameter. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

    The present invention relates to a Stirling engine.

  The Stirling engine is attracting attention as a heat engine that does not cause destruction of the ozone layer because helium, hydrogen, nitrogen or the like is used as a working gas instead of Freon. An example of a Stirling engine can be seen in Patent Document 1.

  In Stirling engines, the components that determine the performance and reliability are a piston that reciprocates by a power source such as a linear motor, and a displacer that reciprocates synchronously with a predetermined phase difference with respect to this piston. is there. The piston and displacer flow the 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 increases 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 compression space rises and the temperature of expansion space falls. If 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. Based on this principle, the Stirling engine is used as a refrigerator.

  In a Stirling engine, the displacer faces both the compression space (high temperature space) and the expansion space (low temperature space). In order to improve the performance of the Stirling engine, it is necessary that the heat in the compression space and the cold heat in the expansion space do not interfere with each other, that is, both the spaces are insulated. If heat is transferred from the compression space to the expansion space through the displacer, the efficiency of the Stirling engine is reduced. Therefore, it is desirable that the displacer itself has a structure that blocks heat transfer.

  There is another requirement for improving the performance of Stirling engines. That is, the working gas in the compression space and the working gas in the expansion space do not interfere with each other, that is, there is no leakage of the working gas. For this reason, the gap (clearance) between the displacer and the cylinder should be as small as possible, and an appropriate seal structure is required.

  The heat insulation of the displacer itself is achieved by forming the displacer with a synthetic resin which is a low heat conductive material. However, since resin molding has low processing accuracy and large dimensional variation, it is difficult to mass-produce a displacer with high dimensional accuracy in which the clearance with the cylinder is constant. For the purpose of preventing working gas leakage, metal parts with high processing accuracy and small dimensional variations are suitable.

Therefore, in the Stirling engine described in Patent Document 1, the side of the displacer facing the expansion space is made of synthetic resin to insulate, and the side facing the compression space is made of metal to withstand high temperatures, and the cylinder To keep the clearance between and small.
JP-A-2005-345209 ([0045]-[0053], FIG. 1-3)

When the displacer described in Patent Document 1 is realized with a metal and a synthetic resin, considering durability, as shown in FIG. 4, the metal body 101 and the synthetic resin cap 102 are placed on the convex side of the body 101. It is natural to have a structure in which the cap 102 is fitted into the concave side, and the fitting portion is coated with an adhesive and firmly joined. However, both the metal and the synthetic resin
The expansion required by the coefficient of linear expansion x temperature change occurs. If both have the same linear expansion coefficient, there is no problem. However, since the linear expansion coefficient of the synthetic resin is larger, the cap 102 has a larger expansion value for the same temperature change, that is, the diameter is larger. Thus, thermal stress is generated at the joint portion with the body 101. When the thermal stress reaches a certain level, the adhesive is peeled off and a gap is formed, causing a gas leak. This leads to performance degradation and quality degradation of the Stirling engine.

  Further, if the amount of the adhesive is too large or the place to be applied is shifted, the adhesive may ooze out from the joint between the body 101 and the cap 102, which may come into contact with the inner surface of the cylinder. Such a situation must be avoided. However, if the amount of the adhesive is too small, the strength of the joint portion may be insufficient. As described above, the displacer that combines the metal body 101 and the synthetic resin cap 102 is difficult to control quality from the viewpoint of mass productivity.

    The present invention has been made in view of the above points, and has an object of stably joining a metal body constituting a displacer and a synthetic resin cap with an adhesive, and facilitating mass production. To do.

  (1) To achieve the above object, the present invention comprises a piston reciprocated by a power source, and a displacer reciprocating with a predetermined phase difference with respect to the piston, and a compression space (high temperature space) and expansion In a Stirling engine that moves a working gas between spaces (cold spaces), the displacer includes a metal body that faces the compression space and a synthetic resin cap that faces the expansion space. The small-diameter connecting portions integrally molded so as to protrude toward the side are fitted into an uneven shape and joined with an adhesive.

  According to this configuration, since the connecting portion between the body and the cap has a small diameter, even if an expansion dimensional difference due to a difference in thermal expansion coefficient occurs, the value is small. Therefore, it is difficult for the adhesive to peel off, and the situation where the body and the cap are separated does not occur. Even if the adhesive protrudes from the connecting portion, it does not contact the inner surface of the cylinder. Therefore, it is possible to quickly assemble without worrying about the protruding adhesive, which improves productivity.

  (2) Further, the present invention is characterized in that, in the Stirling engine configured as described above, a male screw is formed on one side of the connecting portion and a female screw is formed on the other side, and the body and the cap are screwed together.

  According to this configuration, since the screw connection is added to the bonding by the adhesive, the body and the cap can be more firmly connected.

  According to the present invention, the displacer is configured by combining a metal body facing the compression space and a synthetic resin cap facing the expansion space so that the body and the cap protrude toward the other side. Since the integrally formed small-diameter connecting portions are unevenly fitted and joined with an adhesive, the expansion dimensional difference due to the difference in thermal expansion coefficient between the metal and the synthetic resin can be expressed only with a small value in the small-diameter connecting portion. Therefore, it is difficult for the adhesive to peel off and the body and the cap do not need to be separated, and the adhesive protruding from the connecting portion does not come into contact with the inner surface of the cylinder, so that the adhesive does not worry about protruding. Can be assembled quickly. Thereby, the high quality displacer 13 can be provided with high productivity.

  First, the structure of a Stirling engine to which the present invention is to be applied will be described with reference to FIG. FIG. 1 is a 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 and 11 are aligned on the same straight line. A piston 12 is inserted into the cylinder 10, and a displacer 13 is inserted into the cylinder 11. During the operation of the Stirling engine 1, the piston 12 and the displacer 13 reciprocate 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 in detail later.

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

  The cylinder 10 holds the linear motor 20 outside the portion corresponding to the operation region of the piston 12. The linear motor 20 includes an outer yoke 22 having a coil 21, an inner yoke 23 provided so as to be in contact with the outer peripheral surface of the cylinder 10, and a ring shape inserted into an annular space between the outer yoke 22 and the inner yoke 23. , A tube 25 surrounding the outer yoke 22, an outer yoke 22, an inner yoke 23, and synthetic resin end brackets 26 and 27 that hold the tube 25 in a predetermined positional relationship. The magnet 24 is fixed to the magnet holder 14.

  The central portion of the spring 30 is fixed to the hub portion of the magnet holder 14. The center portion of the spring 31 is fixed to the displacer shaft 15. The outer peripheral portions of the springs 30 and 31 are fixed to the end bracket 27. A spacer 32 is disposed between the outer peripheries of the springs 30 and 31, whereby the springs 30 and 31 maintain a certain distance. The springs 30 and 31 are disc-shaped materials with spiral cuts and serve to resonate the displacer 13 with a predetermined phase difference with respect to the piston 12.

  Heat transfer heads 40 and 41 are disposed outside the portion of the cylinder 11 corresponding to the operating region of the displacer 13. The heat transfer head 40 has a ring shape, and the heat transfer head 41 has a cap shape, both of which are made of a metal having good heat conductivity such as copper or copper alloy. The heat transfer heads 40 and 41 are respectively supported outside the cylinder 11 with ring-shaped internal heat exchangers 42 and 43 interposed therebetween. Each of the internal heat exchangers 42 and 43 has air permeability, and transfers the heat of the working gas passing through the inside to the heat transfer heads 40 and 41. The cylinder 10 and the pressure vessel 50 are connected to the heat transfer head 40.

  An annular space surrounded 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 becomes a compression space 45. A space surrounded by the heat transfer head 41, the cylinder 11, the displacer 13, and the internal heat exchanger 43 becomes an expansion space 46.

  A regenerator 70 is disposed between the internal heat exchangers 42 and 43. The regenerator 70 is formed by filling a container with a filler (matrix) such as a wire mesh, or winding a thin metal plate or a synthetic resin film in a coil shape, and has a gap through which a working gas passes. A regenerator tube 48 wraps outside the regenerator 70. The regenerator tube 48 forms an airtight passage between the heat transfer heads 40 and 41.

  A cylindrical pressure vessel covering the linear motor 20, the cylinder 10, and the piston 12 forms the body portion 50. The interior of the body part 50 is a bounce space 51.

  The structure of the body part 50 is as follows. That is, the body part 50 is divided into two parts: a ring-like part 52 joined to the heat transfer head 40 and a cap-like part 53 joined to the ring-like part 52. Both the ring-shaped part 52 and the cap-shaped part 53 are made of stainless steel. One end of the ring-shaped portion 52 is narrowed down in a tapered shape and brazed to the heat transfer head 40. The cap-shaped part 53 has a structure in which an end plate 53a is welded 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 open end of the cap-shaped portion 53 facing the ring-shaped portion 52. The flange-shaped portions 54 and 55 are both formed by welding a stainless steel ring to the ring-shaped portion 52 and the cap-shaped portion 53. Finally, the flange-shaped portions 54 and 55 are welded and sealed. The body part 50 in a state is formed.

  The body portion 50 is provided with a terminal portion 28 for supplying power to the linear motor 20 and a pipe 50a for enclosing a working gas therein. These are all provided so as to protrude in the radial direction from the outer peripheral surface of the cap-shaped portion 53.

  A dynamic vibration absorber 60 is attached to the body portion 50. The dynamic vibration absorber 60 includes a base 61 fixed to the body 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 via a check valve 90 disposed on the end face of the piston 12. On the outer peripheral surface of the piston 12, a plurality of concave portions 81 forming a gas bearing are arranged on the same circumference at a predetermined angular interval. A metal thin tube 82 is driven into the bottom of the recess 81 so as to penetrate the piston 12, and the working gas is supplied from the cavity 80 to the recess 81 through the metal thin tube 82. Two or more annular rows of the recesses 81 are formed at intervals in the axial direction of the piston 12. That is, gas bearings are formed at two or more locations.

  The inside of the displacer 13 is also 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 peripheral surface of the displacer 13, a plurality of recesses 86 forming gas bearings 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 thin tube 87 driven into 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 penetrating the magnet 24 is generated between the outer yoke 22 and the inner yoke 23, and the magnet 24 reciprocates in the axial direction. By supplying power with a frequency that matches the resonance frequency determined by the total mass of the piston system (piston 12, magnet holder 14, magnet 24, and spring 30) and the spring constant of the spring 30, the piston system has a smooth sine. Start wavy reciprocating motion.

  In the displacer system (the displacer 13, the displacer shaft 15, and the spring 31), the resonance frequency determined by the total mass and the spring constant of the spring 31 is set to resonate with the driving frequency of the piston 12.

  By the reciprocating motion of the piston 12, the compression space 45 is repeatedly compressed and expanded. As the pressure changes, the displacer 13 also reciprocates. At this time, a phase difference is generated between the displacer 13 and the piston 12 due to flow resistance between the compression space 45 and the expansion space 46. In this way, the displacer 13 having a free piston structure vibrates in synchronization with the piston 12 with a predetermined phase difference.

  By the above operation, a Stirling 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 working gas reciprocates between the compression space 45 and the expansion space 46 during operation passes through the internal heat exchangers 42 and 43, the working gas passes through the internal heat exchangers 42 and 43 and the heat transfer heads 40 and 41. To tell. Since the working gas flowing into the regenerator 70 from the compression space 45 is high temperature, the heat transfer head 40 is heated, and the heat transfer head 40 becomes a warm head. Since the working gas flowing into the regenerator 70 from the expansion space 46 is low in temperature, the heat transfer head 41 is cooled, and the heat transfer head 41 becomes a cold head. The Stirling engine 1 functions as a refrigeration engine by dissipating heat from the heat transfer head 40 to the atmosphere and lowering the temperature of the specific space by the heat transfer head 41.

  The regenerator 70 functions to pass only the working gas without transferring the heat of the compression space 45 and the expansion space 46 to the counterpart space. The hot working gas that has entered the regenerator 70 from the compression space 45 through the internal heat exchanger 42 gives the heat to the regenerator 70 when passing through the regenerator 70, and enters the expansion space 46 in a state where the temperature is lowered. Inflow. The low-temperature working gas that has entered the regenerator 70 from the expansion space 46 via the internal heat exchanger 43 recovers heat from the regenerator 70 when passing through the regenerator 70, and enters the compression space 45 in a state where the temperature has risen. Inflow. That is, the regenerator 70 serves as a heat storage.

  When the piston 12 and the displacer 13 reciprocate and the working gas moves, the Stirling engine 1 is vibrated. The dynamic vibration absorber 60 suppresses this vibration.

  A part 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 through the check valve 90. And it ejects from the recessed parts 81 and 86. FIG. A gas film is formed between the outer peripheral surface of the piston 12 and the inner peripheral surface of the cylinder 10 by the jetting working gas, and between the outer peripheral surface of the displacer 13 and the inner peripheral surface of the cylinder 11. And the contact between the displacer 13 and the cylinder 11 are prevented. For this reason, the problem of the energy loss by the friction of a contact part, or abrasion of a contact part does not generate | occur | produce.

  The cylinders 10 and 11 and the piston 12 are made of a metal such as aluminum or stainless steel. On the other hand, as shown in FIG. 2, the displacer 13 has a metal body 13a on the side facing the compression space 45, and a cap 13b made of synthetic resin on the side facing the expansion space 46. For example, polycarbonate can be used as the synthetic resin.

  A cylindrical connecting portion 13c protrudes from the center of the end face of the body 13a facing the cap 13b, and a cylindrical connecting portion 13d having an open end protrudes from the center of the end face of the cap 13b facing the body 13a. The connecting portion 13c has a smaller diameter than the body 13a, and the connecting portion 13d has a smaller diameter than the cap 13b. The connecting portion 13c and the connecting portion 13d are concavo-convexly fitted. That is, the connecting portion 13c enters the connecting portion 13d, and both are engaged with each other. Before the fitting, an adhesive is applied to the outer peripheral surface of the connecting portion 13c, the inner peripheral surface of the connecting portion 13d, or both. Thereby, the connection parts 13c and 13d are firmly joined with the adhesive.

The displacer 13 formed as described above expands during operation of the Stirling engine 1. The thermal expansion dimension in the radial direction is expressed by the thermal expansion dimension in the radial direction = linear expansion coefficient of the material × temperature change × diameter. From this equation, it can be seen that the smaller the diameter, the smaller the thermal expansion dimension. Therefore, if the connecting portion has a small diameter, the difference in expansion dimension is reduced and the thermal stress is reduced. For example, if the diameter of the connecting portion is about half of the diameter of the body 13a and the cap 13b, the difference in expansion dimension is also about half. Therefore, it is difficult for the adhesive to peel off, and it is not necessary to cause a situation where the body 13a and the cap 13b are separated. Even if the adhesive protrudes from the end of the connecting portion 13d, it does not contact the inner peripheral surface of the cylinder 11. Therefore, the displacer 13 can be quickly assembled without worrying about the adhesive protruding. Thereby, the high-quality displacer 13 can be provided with high productivity.

  Even if it is said that it is better that the diameters of the connecting portions 13c and 13d are smaller, the bonding area becomes too small and the durability of the displacer 13 deteriorates if the diameter is smaller than a certain size. Accordingly, the diameters of the connecting portions 13c and 13d need to be appropriately determined in consideration of the size of the displacer 13, the pressure applied thereto, the operating temperature, and the like.

  FIG. 3 shows the structure of the displacer 13 according to the second embodiment of the present invention. In this embodiment, a male screw 13e is formed on the outer peripheral surface of the connecting portion 13c, a female screw 13f is formed on the inner peripheral surface of the connecting portion 13d, and both are screwed together to connect the body 13a and the cap 13b. . Prior to screwing, an adhesive is applied to one or both of the thread grooves of the male screw 13e and the female screw 13f. According to this configuration, screw connection is added to the bonding by the adhesive, and the body 13a and the cap 13b are more firmly connected.

    Although the embodiments of the present invention have been described above, various modifications can be made without departing from the spirit of the invention.

    The present invention is applicable to all Stirling engines.

Cross section of Stirling engine Disassembled sectional view of the displacer Exploded sectional view of a displacer according to the second embodiment Cross section of conventional displacer

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stirling engine 10, 11 Cylinder 12 Piston 13 Displacer 13a Metal body 13b Synthetic resin cap 13c, 13d Connection part 13e Male screw 13f Female screw

Claims (2)

A Stirling that includes a piston reciprocated by a power source and a displacer that reciprocates with a predetermined phase difference with respect to the piston, and moves the working gas between the compression space (high temperature space) and the expansion space (low temperature space). In the institution
The displacer includes a metal body facing the compression space and a synthetic resin cap facing the expansion space, and each of the small-diameter coupling portions integrally molded so as to protrude toward the other side. A Stirling engine characterized by being fitted with irregularities and joined with an adhesive.   2. The Stirling engine according to claim 1, wherein a male screw is formed on one side of the connecting portion and a female screw is formed on the other side, and the body and the cap are screwed together.

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