JP2006220367A - Piston for stirling engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piston structure wherein required accuracy can be secured, and components are easily processed and assembled, in a piston used for a free piston type Stirling engine. <P>SOLUTION: This piston 12 is reciprocated in a cylinder 10 by a linear motor 20, and the bearing hole 71 of a displacer rod 15 to connect a displacer 13 with a spring 31 is formed in its axis. The piston 12 is composed of a main body 70 equipped with a hub part 72 having the bearing hole 71, a rim part 73 facing the inner surface of the cylinder 10, and an abdominal plate part 74 to connect the hub part 72 with the rim part 73 at one end of the piston 12, and a lid body 80 for closing the entrance part of an annular space 75 between the hub part 72 and the rim part 73. A check valve mechanism 82 for taking a working medium for a gas bearing mechanism into the annular space 75 is provided in the lid body 80 in such a manner that the lid body 80 itself is used as a valve base. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a piston used in a Stirling engine such as a Stirling refrigerator or a Stirling generator.

  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. In a Stirling engine used as a refrigerator, a piston is reciprocated by a power source such as a linear motor in a pressure vessel, and a displacer is synchronously reciprocated with a predetermined phase difference with respect to the piston. The piston and displacer move working gas back and forth 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 heat in the compression space (high temperature space) is radiated through the high temperature heat transfer head, external heat can be absorbed into the expansion space (low temperature space) through the low temperature heat transfer head.

  In a Stirling engine, a piston and a displacer reciprocate at high speed in a cylinder, and strict dimensional control is required for the piston and the displacer. Especially in the case of pistons with a free piston structure, the displacer rod that connects the displacer to the spring passes through the center of the piston, so in addition to controlling the finishing accuracy of the outer peripheral surface (all dimensions, roundness, surface roughness, etc.) The finishing accuracy of the inner peripheral surface of the hole in the center must also be precisely controlled. Patent Document 1 discloses a piston structure that can meet such a demand.

Further, in a Stirling engine, in order to reciprocate the piston and the displacer at a high speed, the piston and the displacer are often supported by floating from the inner surface of the cylinder with a gas bearing. A Stirling engine having such a mechanism is disclosed in Patent Document 2.
JP 2004-3436 A (Page 9 [0055]-Page 10 [0061], FIGS. 9 to 11) Japanese Patent Application Laid-Open No. 2002-349347 (pages 5 to 6, FIGS. 1 to 4)

  The piston disclosed in Patent Document 1 has a structure as shown in FIG. That is, the piston 100 is configured by combining the first member 110 and the second member 120. The first member 110 connects the hub portion 112 in which the bearing hole 111 of the displacer rod is formed at the shaft center, the rim portion 113 facing the inner surface of the cylinder, and the hub portion 112 and the rim portion 113 at one end of the piston 100. A belly plate 114 is provided. Similarly, the second member 120 includes a hub portion 121 in which a bearing hole 111 is formed at the shaft center, and a disc portion 122 that fits into the opening of the rim portion 113. When the first member 110 and the second member 120 are combined, the hub portions 112 and 121 abut each other near the center of the piston 100, and an annular space 115 is formed between the hub portions 112 and 121 and the rim portion 113.

  The piston 100 has two places that need to be sealed. One portion is a fitting portion between the rim portion 113 and the disk portion 122, and the remaining one portion is a matching portion between the hub portions 112 and 121. The fitting portion between the rim portion 113 and the disc portion 122 is relatively easy to seal, but the butted portion of the hub portions 112 and 121 is deep in the piston 100, so that sealing is difficult, and the bearing hole 111 and the space 115 are difficult to seal. In some cases, there was a leakage of working gas.

  Further, when the piston 100 is supported by being floated from the inner surface of the cylinder by a gas bearing, it is necessary to eject the working gas from the inside of the piston 100 into the gap between the piston 100 and the cylinder. For this reason, a communication hole 116 for communicating the external space and the space 115 is formed in the rim portion 113, and a check valve mechanism is provided in the abdominal plate portion 114. However, the abdominal plate portion 114 is located at a position recessed from the opening of the first member 110, and it is difficult to process the valve base to which the valve body of the check valve mechanism is attached. Therefore, similarly to the structure disclosed in Patent Document 2, it is necessary to combine the check valve mechanism with the first member 110 as a separate unit 130, increasing the number of parts and the number of assembling steps, resulting in an increase in cost.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a piston structure that can ensure necessary accuracy and can be easily processed and assembled in a piston used in a free piston type Stirling engine. .

    In the present invention, the Stirling engine piston is configured as follows.

  (1) In a piston for a Stirling engine in which a bearing hole of a displacer rod for connecting a displacer to a spring is formed in an axial center, a hub portion having the bearing hole, a rim portion facing the inner surface of the cylinder, and the hub portion And a main body having a belly plate portion for connecting the rim portion at one end of the piston, and a lid for closing the inlet portion of the annular space between the hub portion and the rim portion.

  According to this configuration, the dimensional accuracy for the cylinder and the dimensional accuracy for the displacer rod can be ensured by processing the main body. Then, the piston is assembled by closing the inlet portion of the annular space between the hub portion and the rim portion of the main body with a lid. In this case, since the seal location between the lid and the main body is located at the entrance of the annular space, sealing is easy and a piston assembly can be obtained at low cost.

  (2) The Stirling engine piston configured as described above has a gas bearing mechanism for injecting working gas into a gap between the cylinder and the check valve mechanism for taking the working gas into the annular space. It is characterized by being provided in.

  According to this configuration, since the check valve mechanism is provided on the lid that is a plate-like component, the lid can be used as it is as a valve base, and the number of parts and the number of assembly steps can be reduced.

  (3) In the piston for Stirling engine configured as described above, the main body and the lid can be easily coupled by bonding the main body and the lid with an adhesive, and a sealing effect is also achieved at the joint location. it can.

  (4) In the piston for Stirling engine configured as described above, after inserting a seal member between the hub portion of the main body and the lid body, the rim portion of the main body and the lid body are fitted to each other. By connecting the parts with an adhesive, a seal structure between the hub part of the main body and the lid can be established, and the main body and the lid can be easily combined, and at the same time, a sealing effect can be achieved at the joint location. it can.

  (5) In the Stirling engine piston configured as described above, the main body and the lid body are screw-coupled by a female screw portion formed on the inner surface of the rim portion of the main body and a male screw portion formed on the outer peripheral surface of the lid body. In addition, by inserting a seal member between the hub portion of the main body and the lid body, the seal structure between the hub portion of the main body and the lid body is established, and the main body and the lid body are securely connected. Can be combined.

  (6) In the piston for a Stirling engine configured as described above, the female screw part and the male screw part are coupled with an adhesive, thereby further strengthening the coupling, and at the same time providing a sealing effect at the coupling point. Can be achieved.

  (7) In the Stirling engine piston configured as described above, after a seal member is inserted between the hub portion of the main body and the lid body, the rim portion of the main body and the lid body are fitted to each other. By welding the portions, it is possible to firmly bond the main body and the lid body after establishing a seal structure between the hub portion of the main body and the lid body.

  (8) In the piston for Stirling engine configured as described above, the main body and the lid body are mutually connected by performing welding after bonding the fitting portion between the rim portion of the main body and the lid body with an adhesive. Welding can be performed in a state where it does not move easily, and welding can be performed easily. Moreover, the sealing effect is enhanced by the adhesive.

  According to the present invention, the dimensional accuracy with respect to the cylinder and the dimensional accuracy with respect to the displacer rod are ensured by processing the main body, and then the piston is closed by closing the inlet portion of the annular space between the hub portion and the rim portion of the main body with the lid. It can be assembled and is easy to process and assemble. Moreover, since the seal location between the lid and the main body is located at the entrance of the annular space, sealing is easy. Furthermore, the lid can be used as it is as a valve base, and overall parts processing and assembly costs can be greatly reduced.

  A first embodiment of the present invention will be described with reference to FIGS. 1 is a sectional view of a Stirling engine, FIG. 2 is a sectional view of a piston, and FIG. 3 is a side view of the piston.

  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. The piston 12 and the displacer 13 reciprocate without contacting the inner surfaces of the cylinders 10 and 11 by the gas bearing mechanism during operation of the Stirling engine 1. The piston 12 and the displacer 13 move with a predetermined phase difference.

  A cup-shaped magnet holder 14 is provided at one end of the piston 12. A displacer rod 15 projects from one end of the displacer 13. The displacer rod 15 penetrates 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. Magnet 24 and synthetic resin end brackets 25 and 26 for holding the outer yoke 22 and the inner yoke 23 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 rod 15. The outer peripheral portions of the springs 30 and 31 are fixed to the end bracket 26. 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 the displacer 13 is caused to resonate with the piston 12 with a predetermined phase difference (ideally about 90 ° phase difference). Play a role.

  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.

  A space surrounded by the heat transfer head 40, the cylinders 10 and 11, the piston 12, the displacer 13, 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 47 is disposed between the internal heat exchangers 42 and 43. The regenerator 47 is formed by winding a resin film into a cylindrical shape, and a number of minute protrusions are scattered on one side of the film to form gaps corresponding to the height of the protrusions between the films. It is said. A regenerator tube 48 wraps the outside of the regenerator 47 and forms an airtight passage between the heat transfer heads 40 and 41.

  A cylindrical pressure vessel 50 wraps the linear motor 20, the cylinder 10, and the piston 12. The inside of the pressure vessel 50 becomes a back pressure space 51. On the peripheral surface of the pressure vessel 50, a terminal portion 52 for supplying electric power to the linear motor 20 and a pipe 53 for enclosing working gas therein are arranged.

  A dynamic vibration absorber 60 is attached to the outer surface of the pressure vessel 50. The dynamic vibration absorber 60 includes a shaft 61 protruding from the center of the end surface of the body portion 50, a plate-like spring 62 fixed at the center to the shaft 61, and a mass (mass) 63 disposed on the periphery of the spring 62. The spring 62 is a stack of a plurality of thin plate springs.

  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 (displacer 13, displacer rod 15, and spring 31), the resonance frequency determined by the total mass and the spring constant of the spring 31 and the drive frequency of the piston 12 are set to coincide with each other.

  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 reciprocates 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 45, 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.

  The working gas that moves back and forth between the compression space 45 and the expansion space 46 during operation passes through the internal heat exchangers 42 and 43 and transfers the heat it has to the heat transfer heads 40 and 41. Since the working gas flowing into the regenerator 47 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 47 from the expansion space 46 is at a low 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 47 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 47 from the compression space 45 through the internal heat exchanger 42 gives the heat to the regenerator 47 when passing through the regenerator 47, 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 47 from the expansion space 46 through the internal heat exchanger 43 recovers heat from the regenerator 47 when passing through the regenerator 47, and enters the compression space 45 in a state where the temperature has risen. Inflow. That is, the regenerator 47 serves as a heat storage means.

  When the piston 12 and the displacer 13 reciprocate, vibration occurs in the Stirling engine 1 and the dynamic vibration absorber 60 suppresses this vibration.

  The piston 12 has the structure shown in FIGS. The main parts of the piston 12 are a main body 70 and a lid body 80. The main body 70 includes a hub portion 72 formed with a bearing hole 71 of the displacer rod 15 as an axial center, a rim portion 73 facing the inner surface of the cylinder 10, and an abdomen that connects the hub portion 72 and the rim portion 73 at one end of the piston 12. The plate portion 74 is integrally formed of a metal material. An annular space 75 is formed between the hub portion 72 and the rim portion 73. A seal member mounting groove 76 is formed at the tip of the hub portion 72. The rim portion 73 is formed with a communication hole 77 for forming a gas bearing between the piston 12 and the cylinder 10.

  The lid 80 is disc-shaped and fits snugly into the entrance of the annular space 75. A center hole 81 corresponding to the bearing hole 71 is formed at the center of the lid body 80. The lid 80 is provided with a check valve mechanism 82 for taking in the working gas from the compression space 45 to the annular space 75. The check valve mechanism 82 is configured by using the lid body 80 itself as a valve base. The check valve mechanism 82 is formed in the lid body 80 and has a communication hole 83 that allows the compression space 45 and the annular space 75 to communicate with each other, and a lid that faces the annular space 75. The valve body 84 is attached to the side surface of the body and closes the communication hole 83 from the annular space 75 side. The valve body 84 is constituted by a metal spring piece.

  The piston 12 is completed by fitting the lid 80 to the main body 70 and joining them together. Before the lid 80 is fitted, a seal member 78 such as an O-ring is mounted in the seal member mounting groove 76 and is sandwiched between the hub portion 72 and the lid 80 so that a sealing effect is produced. deep.

  With the configuration described above, the dimensional accuracy with respect to the cylinder 10 and the dimensional accuracy with respect to the displacer rod 15 can be ensured by processing the main body 70. The piston 100 can be assembled by closing the inlet portion of the annular space 75 between the hub portion 72 and the rim portion 73 of the main body 70 with the lid body 80. The sealing part between the lid 80 and the main body 70 is easy to seal and inexpensive because both the sealing part on the outer peripheral side and the sealing part on the center side of the lid 80 are located at the entrance of the annular space 75. A piston assembly can be obtained.

  Further, the check valve mechanism 82 for taking the working gas into the annular space 75 is provided with a lid body 80 as a valve base as a valve base, and a separate check valve mechanism unit is attached to the lid body 80. Since it is not assembled, the number of parts and the number of assembly steps can be reduced.

  This is the connection between the main body 70 and the lid body 80. In the first embodiment, this is performed with an adhesive. That is, an adhesive is applied in advance to a fitting portion between the main body 70 and the lid body 80, and the lid body 80 is fitted to the main body 70 thereon. Thereby, the main body 70 and the lid body 80 can be easily coupled, and a sealing effect can be achieved at the coupling location. Needless to say, the seal member 78 is mounted in the seal member mounting groove 76 before the lid 80 is fitted to the main body 70.

  A second embodiment will be described with reference to FIG. FIG. 4 is a sectional view of the piston 12.

  In the second embodiment, the main body 70 and the lid body 80 are screwed together by a female screw portion 79 formed on the inner peripheral surface of the rim portion 73 of the main body 70 and a male screw portion 85 formed on the outer peripheral surface of the lid body 80. To do. The seal member 78 is mounted in the seal member mounting groove 76 before the lid 80 is screwed into the main body 70.

  According to the structure of 2nd Embodiment, after establishing the sealing structure between the hub part 72 of the main body 70 and the cover body 80, the main body 70 and the cover body 80 can be couple | bonded reliably.

  If the lid 80 is screwed after the adhesive is applied to the female screw portion 79 and the male screw portion 85, the main body 70 and the lid body 80 are coupled with both the screw and the adhesive. Becomes stronger and a sealing effect can be achieved at the joint.

  A third embodiment will be described with reference to FIG. FIG. 5 is a sectional view of the piston 12.

  In the third embodiment, the seal member 78 is inserted into the seal member housing groove 76, the lid body 80 is fitted to the main body 70, and the fitting portion between the rim portion 73 of the main body 70 and the lid body 80 is welded. . Welding is performed by laser welding. As a result, the main body 70 and the lid body 80 are firmly coupled, and the welded portion 90 also serves as a sealing means.

  If welding is performed after the fitting portion between the rim portion 73 and the lid 80 is joined with an adhesive, the welding can proceed without the main body 70 and the lid 80 moving relative to each other. Can be easily performed.

  Each embodiment of the present invention has been described above, but various modifications can be made without departing from the spirit of the present invention.

  The present invention is applicable to a piston for a free piston type Stirling engine.

Sectional drawing of the Stirling engine which concerns on 1st Embodiment Cross section of piston Piston side view Sectional drawing of the piston which concerns on 2nd Embodiment Sectional drawing of the piston which concerns on 3rd Embodiment Cross section of conventional piston

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stirling engine 10 Cylinder 12 Piston 13 Displacer 15 Displacer rod 20 Linear motor 30, 31 Spring 70 Main body 71 Bearing hole 72 Hub part 73 Rim part 74 Abdomen plate part 75 Annular space 78 Seal member 79 Male thread part 80 Cover body 82 Check valve Mechanism 90 Welded part

Claims (2)

A piston for a Stirling engine that is reciprocated in a cylinder by a power source, wherein a bearing hole of a displacer rod that connects the displacer to a spring is formed in the shaft center.
A body having a hub portion having the bearing hole, a rim portion facing the inner surface of the cylinder, and a belly plate portion connecting the hub portion and the rim portion at one end of a piston; and between the hub portion and the rim portion A Stirling engine piston characterized by comprising a lid for closing an inlet of an annular space.   2. The Stirling according to claim 1, wherein the lid body is provided with a check valve mechanism that has a gas bearing mechanism that ejects working gas into a gap between the cylinder and takes the working gas into the annular space. Piston for engine.

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