WO2006085431A1

WO2006085431A1 - Piston for stirling engine

Info

Publication number: WO2006085431A1
Application number: PCT/JP2006/300479
Authority: WO
Inventors: Shinji Yamagami; Yoshiyuki Kitamura; Hiroshi Yasumura; Kazushi Yoshimura; Kenji Takai; Jin Sakamoto; Isao Ozaki
Original assignee: Sharp Kabushiki Kaisha
Priority date: 2005-02-10
Filing date: 2006-01-17
Publication date: 2006-08-17
Also published as: JP2006220367A

Abstract

A piston for a Stirling engine which is reciprocatingly moved in a cylinder by a linear motor and in which a bearing hole for a displacer rod connecting a displacer to a spring is formed at its axis. The piston comprises a body having a hub part with the bearing hole, a rim part facing the inner surface of the cylinder, and a web plate part connecting the hub part to the rim part at one end of the piston and a cover body closing the inlet part of an annular space between the hub part and the rim part. A check valve mechanism for taking a working gas for a gas bearing mechanism into the annular space by using the cover body itself as a valve base is installed in the cover body.

Description

Specification

Stirling engine piston technology

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

Background art

A Stirling engine uses helium, hydrogen, nitrogen, or the like as a working gas instead of Freon, and has attracted attention as a heat engine that does not cause destruction of the ozone layer. 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 moved back and forth with a predetermined phase difference with respect to the piston. The piston and displacer cause working gas to flow between the compression space and the expansion space, forming a Stirling cycle (in the case of a refrigerator, this is a reverse 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. As a result, the temperature of the compression space increases and the temperature of the expansion space decreases. 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, the piston and the displacer reciprocate at high speed in the cylinder, and strict dimensional control is required for the piston and the displacer. Especially for pistons with a free piston structure, the displacer rod that connects the displacer to the spring passes through the center of the piston. In addition, the finishing accuracy of the inner peripheral surface of the central hole must be precisely controlled. A piston structure capable of meeting such a request is disclosed in Patent Document 1. In Stirling engines, pistons and displacers are often supported by floating from the inner surface of the cylinder with gas bearings in order to reciprocate the piston and displacer at high speed. Patent Document 2 discloses a Stirling engine having such a mechanism.

Patent Document 1: Japanese Patent Laid-Open No. 2004-3436 (page 9 [0055]-page 10 [0061], FIG. 9) 11)

Patent Document 2: Japanese Patent Application Laid-Open No. 2002-349347 (Pages 5-6, Figure 1-Figure 4)

Disclosure of the invention

Problems to be solved by the invention

[0003] 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 includes a hub portion 112 having a bearing hole 111 of a displacer rod formed in the shaft center, a rim 対向 facing the inner surface of the cylinder, a nove 咅 112 and a rim 咅 113 as one end of the piston 100. It is provided with a belly plate portion 114 that is connected to the other side. 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 in the vicinity of 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.

[0004] 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 butting portion between the hub portions 112 and 121. The fitting part between the rim part 113 and the disk part 122 is relatively easy to seal.The hub part 1 12, 121 has a butting hole 111 and space where the seals are difficult to seal because the butted part is deep in the piston 100. There was a case where the working gas leaked between 115.

[0005] When the piston 100 is supported by being floated from the inner surface of the cylinder with 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. Therefore, 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 in a position that is 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. For this reason, like the structure disclosed in Patent Document 2, the check valve mechanism was forced to be combined with the first member 110 as a separate unit 130, resulting in an increase in the number of parts and the number of assembly steps, resulting in a cost increase. .

The present invention has been made in view of the above points, and is a free piston type Stirling machine. An object of the present invention is to provide a piston structure that can ensure the required accuracy and can be easily machined and assembled.

Means for solving the problem

[0007] In order to achieve the above object, the present invention provides a hub having a bearing hole 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 the shaft center. A body, a rim portion opposed to the inner surface of the cylinder, a body having a belly plate portion connecting the hub portion and the rim portion at one end of the piston, and an inlet portion of the annular space between the hub portion and the rim portion. It is characterized by the fact that a piston for Stirling engine is constituted by the lid to be closed.

[0008] 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. The piston can be assembled by closing the inlet of the annular space between the hub and rim of the main body with a lid. In this case, since the sealing portion 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.

In the Stirling engine piston having the above-described configuration, the present invention further includes a gas bearing mechanism that ejects a working gas into a gap between the cylinder and a check valve mechanism that takes the working gas into the annular space. It is provided on the body.

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.

In the Stirling engine piston having the above-described configuration, the main body and the lid body can be easily coupled by bonding the main body and the lid body with an adhesive, and a sealing effect can also be achieved at the coupling location. .

In the Stirling engine piston having the above-described configuration, a seal member is inserted between the hub portion of the main body and the lid body, and then the fitting portion between the rim portion of the main body and the lid body is bonded. By connecting with the agent, the seal structure between the hub and lid of the main body has been established, so that 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. . In the Stirling engine piston having the above-described configuration, the main body and the lid body are screwed together 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. At the same time, 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.

[0014] Further, in the Stirling engine piston having the above-described configuration, the female screw portion and the male screw portion are coupled with an adhesive, thereby further strengthening the coupling. Can be achieved.

In the Stirling engine piston having the above-described configuration, a sealing member is inserted between the hub portion of the main body and the lid body, and a fitting portion between the rim portion of the main body and the lid body is provided. By welding, 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.

In the Stirling engine piston having the above-described configuration, the main body and the lid body do not power each other 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 carried out in a state, and welding can be performed easily. Also, the sealing effect is enhanced by the adhesive.

The invention's effect

[0017] 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 the inlet portion of the annular space between the hub portion and the rim portion of the main body is closed with the lid. As a result, the piston can be assembled, and processing and assembly are easy. In addition, since the sealing part between the lid and the main body is located at the entrance of the annular space, sealing is easy. Furthermore, it is possible to use the lid as a valve base as it is, and the cost of parts processing and assembly can be greatly reduced overall. Brief Description of Drawings

FIG. 1 is a cross-sectional view of a Stirling engine according to a first embodiment.

[Fig.2] Cross section of piston

[Figure 3] Piston side view

FIG. 4 is a sectional view of the piston according to the second embodiment. 5] A sectional view of the piston according to the third embodiment

6] Cross section of conventional piston

Explanation of symbols

1 Stirling organization

10 cylinders

12 piston

13 Displacer

15 Displacer rod

20 linear motor

30, 31 Spring

70 body

71 Bearing hole

72 Hub

73 Rim part

74 Abdomen

75 Annular space

78 Seal member

79 Male thread

80 lid

82 Check valve mechanism

90 welds

BEST MODE FOR CARRYING OUT THE INVENTION

A first embodiment of the present invention will be described with reference to FIG. 1 and FIG. 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.

[0021] The centers of the assembly of the Stirling engine 1 are the cylinders 10 and 11, respectively. The axes of 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 do not come into contact with the inner surfaces of the cylinders 10 and 11 by the gas bearing mechanism during operation of the Stirling engine 1. Reciprocate. 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 that they can slide freely 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 provided with 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 inserted between the outer yoke 22 and the inner yoke 23. And a synthetic resin end bracket 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 die placer rod 15. The outer peripheries 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 so that 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 has a predetermined phase difference (ideally about 90 ° phase difference) with respect to the piston 12. Plays the role of resonating.

[0025] Heat transfer heads 40 and 41 are arranged 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 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. A cylinder 10 and a 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 arranged 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 between the films at the height of the protrusions. It is a way. A regenerator tube 48 wraps the outside of the regenerator 47 to form an airtight passage between the heat transfer heads 40 and 41.

[0028] 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 of 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.

[0030] 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 passing through 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.

[0031] In the displacer system (displacer 13, displacer rod 15, and spring 31), the resonance frequency determined by the total mass of the spring 31 and the panel constant of the spring 31 matches the driving frequency of the piston 12. Set to.

[0032] By the reciprocating motion of the piston 12, the compression space 45 is repeatedly compressed and expanded. Along with this change in pressure, the displacer 13 also reciprocates. At this time, due to the flow resistance between the compression space 45 and the expansion space 46, a phase difference is generated between the displacer 13 and the piston 12. In this way, the displacer 13 having a free piston structure reciprocates in synchronization with the piston 12 with a predetermined phase difference.

[0033] By the above operation, a Stirling cycle (reverse starring) is formed between the compression space 45 and the expansion space 46. One ring cycle) is formed. 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.

[0034] The working gas that moves between the compression space 45 and the expansion space 46 during operation transfers the heat it has to the heat transfer heads 40 and 41 as it passes through the internal heat exchangers 42 and 43. Compressed space 45 force Since the working gas flowing into the regenerator 47 is hot, 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 low in 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 with the heat transfer head 41, the Stirling engine 1 functions as a refrigeration engine.

[0035] The regenerator 47 does not transmit the heat of the compression space 45 and the expansion space 46 to the space on the other side, and functions to pass only the working gas. 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 the expansion space 46 in a state where the temperature is lowered. Flow into. The low-temperature working gas that has entered the regenerator 47 from the expansion space 46 via the internal heat exchanger 43 recovers heat from the regenerator 47 as it passes through the regenerator 47, and the compressed space 45 rises in a state where the temperature has risen. Flow into. That is, the regenerator 47 serves as a heat storage means.

[0036] When the piston 12 and the displacer 13 reciprocate, vibration is generated in the Stirling engine 1, and the dynamic vibration absorber 60 suppresses this vibration.

[0037] 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 connecting 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 73 is formed with a communication hole 77 for forming a gas bearing between the piston 12 and the cylinder 10.

[0038] The lid 80 is disk-shaped and fits snugly into the entrance of the annular space 75. A central hole 81 corresponding to the bearing hole 71 is formed in the center of the lid 80. The lid 80 has a compression A check valve mechanism 82 is provided for taking working gas from the space 45 into the annular space 75. The check valve mechanism 82 is configured with the lid body 80 itself as a valve base. The valve body 84 is attached to the side surface of the lid and closes the communication hole 83 to the side of the annular space 75. The valve body 84 is constituted by a metal spring piece.

[0039] When the lid body 80 is fitted to the main body 70 and joined together, the piston 12 is completed. Before fitting the lid 80, a sealing member 78 such as an O-ring is fitted in the sealing member fitting groove 76 so that it is sandwiched between the hub portion 72 and the lid 80 so as to produce a sealing effect. deep.

By configuring as 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 outer peripheral sealing part and the central sealing part of the lid 80 are located at the entrance of the annular space 75. A piston assembly can be obtained.

[0041] Further, the check valve mechanism 82 for taking the working gas into the annular space 75 is provided with a lid base 80, which is a plate-like part, as a valve base, and is a separate check valve mechanism unit. Since it is not assembled to the lid 80, the number of parts and assembly man-hours can be reduced.

[0042] The main body 70 and the lid body 80 are combined, and in the first embodiment, this is performed by an adhesive. That is, an adhesive is applied in advance to the fitting portion of the main body 70 and the lid body 80, and then the lid body 80 is fitted to the main body 70. As a result, the main body 70 and the lid 80 can be easily coupled, and a sealing effect can also 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 based on 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 provided with an internal thread portion 79 formed on the inner peripheral surface of the rim portion 73 of the main body 70, and an external thread portion 85 formed on the outer peripheral surface of the lid body 80. Connect with screws. The seal member 78 is mounted in the seal member mounting groove 76 before the lid 80 is screwed into the main body 70. [0045] According to the configuration of the second embodiment, the main body 70 and the lid body 80 can be reliably coupled after establishing a seal structure between the hub portion 72 of the main body 70 and the lid body 80.

[0046] 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 by the force of both the screw and the adhesive. As a result, the bond 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.

[0048] In the third embodiment, the seal member 78 is inserted into the seal member housing groove 76, the lid 80 is fitted to the main body 70, and then the rim 73 of the main body 70 and the lid 80 are fitted. Weld the joint. 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.

[0049] If welding is performed after the fitting portion between the rim portion 73 and the lid body 80 is bonded with an adhesive, the welding is advanced in a state where the main body 70 and the lid body 80 do not move relative to each other. Therefore, welding can be performed easily.

[0050] Although each embodiment of the present invention has been described above, various modifications can be made without departing from the spirit of the invention.

Industrial applicability

[0051] The present invention is applicable to a piston for a free piston type Stirling engine.

Claims

The scope of the claims

[1] A piston for a Stirling engine that is reciprocated in a cylinder by a power source, and a bearing hole of a displacer rod that connects the displacer to a spring is formed at the shaft center,

A main body including a hub portion having the bearing hole, a rim portion facing the inner surface of the cylinder, and a belly plate portion that connects the hub portion and the rim portion to one end of a piston; and the hub portion; A Stirling engine piston, characterized by comprising a lid that closes an inlet of an annular space between rims.

[2] The gas sensor according to claim 1, further comprising a gas bearing mechanism that ejects working gas into a gap between the cylinder and a check valve mechanism that takes the working gas into the annular space. The piston for Stirling engine as described.