JP2009092007A - Stirling engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems that size of an engine is large in former technology because of a crank mechanism connecting a power source and a drive part, and that oil seal countermeasure is indispensable since a large quantity of lubricating oil is used on a crank chamber. <P>SOLUTION: This engine is provided with a rotary motor 20 rotating and driving a cylindrical rotor 23 including a cavity 23a penetrating through the same in an axial direction and provided in such a manner that the same can freely rotate in a circumference direction but can not linearly move in an axial direction, a cylindrical piston 12 inserted in the cavity 23a of the rotor 23 and provided in such a manner that the same can not rotate in the circumference direction but can freely linearly move in the axial direction, a circumferential direction guide groove 27 formed on an outer circumference surface of the cavity 23a of the rotor 23, and a projection 29 provided on an outer circumference surface of the piston 12 and engaged in the circumferential direction guide groove 27. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a cooling device that is driven in a Stirling cycle and a Stirling engine that is optimal for a power 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 linearly by a power source such as a rotary motor, and a displacer is synchronously reciprocated linearly with a predetermined phase difference with respect to the piston. The reciprocating linear motion of the piston and the displacer causes the working gas to move back and forth between the compression space and the expansion space. The working gas temperature rises in the compression space, and the working gas temperature falls in the expansion space. If the heat in the compression space (high temperature space) is dissipated through the high temperature heat transfer head to achieve isothermal compression change, and the external heat is absorbed into the expansion space (low temperature space) through the low temperature heat transfer head, the isothermal expansion change is realized. A reverse Stirling cycle is formed.

  As a structure of a conventional Stirling engine, for example, as described in Patent Document 1, there is one using a linear (type) motor for a drive unit. As shown in FIG. 7, this structure includes a cylinder 101 in the outer structure 100, a displacer 102 that partitions the outer structure 100 into an expansion space 105 and a compression space 106, a piston 103, and a piston 103 for reciprocating the piston 103. The linear motor 109, the regenerator 106 provided in the communication path communicating between the expansion space 104 and the compression space 105, and the heat absorption as a heat exchanger on the expansion space 105 side and the compression space 106 side of the regenerator 106, respectively. And a radiator 107. The leaf springs 110 and 111 support the displacer 102 and the piston 103, respectively, and reciprocate them by elastic force. The linear motor 109 is connected to an external power supply via a power supply terminal. Thus, although the linear motor type Stirling engine has a very compact structure, a linear motor which is a special motor is required, which is expensive and has a problem of low cost.

On the other hand, the structure of a Stirling engine using an inexpensive rotary (type) motor for cost reduction is described in Patent Document 2 and Patent Document 3, for example. While Patent Document 2 reciprocates a piston or the like through a crank mechanism with a rotary motion from a rotary motor, Patent Document 3 discloses a circumference in which one or more circumferential guide grooves are formed. The rod is configured to connect a cam, a piston and a displacer, and the circumferential cam, and the piston and the displacer are regulated by a circumferential guide groove of the circumferential cam, thereby allowing the Stirling cycle system to I was driving.
Japanese Patent Laying-Open No. 2005-69168 (FIG. 1) JP-A-64-53049 (FIG. 7) JP-A-6-235350 (FIG. 1)

  However, in the case of Patent Document 2, since it is a crank mechanism, the size becomes large, and an oil seal countermeasure is indispensable by using a large amount of lubricating oil in the crank chamber.

  In the case of Patent Document 3, the circumferential cam, the piston, and the displacer are connected to each other by a rod, so that there is a problem that the working space is required and the Stirling engine is enlarged.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a Stirling engine that uses an inexpensive rotary motor and can be downsized.

  In order to achieve the above object, a Stirling engine of the present invention has a cavity that penetrates in the axial direction, and rotates to drive a cylindrical rotor that is circumferentially rotatable and incapable of linear linear motion. A motor, a cylindrical piston that is inserted into the cavity of the rotor, cannot rotate in the circumferential direction, and is freely movable in the axial direction, and a circumferential direction formed on the outer peripheral surface of the cavity of the rotor A guide groove and a protrusion provided on the outer peripheral surface of the piston and engaged with the circumferential guide groove, and when the rotor is driven to rotate, along the circumferential guide groove of the rotor. The piston is reciprocated linearly by moving the projection of the piston.

  A Stirling engine according to the present invention includes a rotary motor that rotates a cylindrical rotor that has a hollow that penetrates in the axial direction, is circumferentially rotatable, and is non-linearly movable in the axial direction. A cylindrical piston that is inserted into the cavity and cannot be rotated in the circumferential direction and is linearly movable in the axial direction, the circumferential guide groove formed on the outer peripheral surface of the piston, and a rotor A protrusion provided on an outer peripheral surface of the cavity and engaged with the circumferential guide groove, and when the rotor is driven to rotate, the protrusion of the rotor follows the circumferential guide groove of the piston. The piston is reciprocated linearly by being moved.

  If the circumferential guide groove has a sine wave shape, the reciprocating linear motion of the piston can be a single vibration, and the stroke can be easily controlled. In this case, if the circumferential guide groove has a sine wave shape having a wave number that is an integral multiple of one cycle, the number of reciprocations of the piston per unit time can be increased in proportion to the wave number. Furthermore, if the above-mentioned protrusions are provided in integer numbers at positions where the circumference is equally divided by the wave number, the rotational motion of the rotor can be stably converted into the reciprocating linear motion of the piston.

  According to the present invention, the crank mechanism and the connecting rod can be eliminated by directly fitting the circumferential guide groove of the rotor or piston and the protrusion of the piston or rotor. That is, the piston can be directly driven by the rotary motor without interposing a connecting part such as a crank mechanism or a rod, and the Stirling engine can be reduced in size and cost.

  The best mode for carrying out the present invention will be described with reference to the drawings. First, the structure of a Stirling engine that is a target of use of the piston of the present invention will be described with reference to FIG. FIG. 1 is a sectional view of a main part of a Stirling engine.

  The Stirling engine 1 is a free piston type used as a refrigerator, and a cylinder 10 is the center of its assembly. In particular, here is a description of a refrigerator. A cylindrical piston 12 and a displacer 13 are inserted into the cylinder 10. The piston 12 and the displacer 13 reciprocate linearly without contacting the inner wall of the cylinder 10 by the mechanism of the gas bearing during operation of the Stirling engine. The piston 12 and the displacer 13 move with a predetermined phase difference.

  A displacer shaft 15 projects from one end of the displacer 13. The displacer shaft 15 penetrates the piston 12 so that it can slide freely in the axial direction.

  Most of the operating area of the piston 12 is missing from the cylinder 10, and the rotary motor 20 is held on the missing part and the outside thereof. The rotary motor 20 has the same shape as a motor that is generally on the market at present, and a rotor 23 is arranged from the inside in the radial direction of the rotating shaft of the motor, and an assembly of the stator 22 and the coil 21 is arranged outside thereof. It is like. That is, the rotary motor 20 includes a stator 22 having a coil 21, a cylindrical rotor 23 provided so as to face the outer peripheral surface of the piston 12, and a cavity 23 a penetrating in the axial direction, and the stator 22. And a synthetic resin end bracket 24 held in a positional relationship. In the case of an embedded type (IPM motor), the magnet is enclosed in the rotor 23 and fixed. The rotor 23 is supported at both axial end portions by bearings 25 and 26 provided between the end bracket 24 and the end bracket 24 so that the rotor 23 can rotate in the circumferential direction and cannot move linearly in the axial direction.

  The central portion of the spring 30 is fixed to the end surface portion on the opposite side of the displacer 13 in the axial direction of the piston 12. 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 24 using a support 33. That is, the piston 12 and the displacer 13 are supported by the springs 30 and 31 so that they cannot rotate in the circumferential direction and can move linearly in the axial direction.

  A spacer (not shown) is disposed between the outer peripheral portions of the springs 30 and 31, and thereby the springs 30 and 31 maintain a certain distance. In the case of a free piston type Stirling engine, the springs 30 and 31 are, for example, disc-shaped materials with spiral cuts, and the displacer 13 is moved from the piston 12 by a predetermined phase difference (generally about a phase difference). It plays a role of resonating with a phase difference of 90 °. In the case of other than the free piston type, the same operation is performed by a crank mechanism or the like.

  As described above, the rotor 23 is supported so as to be freely rotatable in the circumferential direction and cannot be linearly moved in the axial direction, and the piston 12 arranged inside the rotor 23 is not rotatable in the circumferential direction and is capable of linearly moving in the axial direction. Supported. Since the rotor 12 is rotated in the circumferential direction of the axis of the piston 12 by the rotary motor 20, a movement direction conversion mechanism is required to cause the piston 12 to reciprocate linearly.

  FIG. 2 is a development view of the outer peripheral surface of the cavity (the inner peripheral surface of the rotor) as seen by cutting in the axial direction at one location in the circumferential direction of the rotor. As shown in FIG. 2, circumferential guide grooves 27 having a constant width and thickness are formed on the outer peripheral surface of the cavity 23 a of the rotor 23 (inner peripheral surface of the rotor 23). The circumferential guide groove 27 is sinusoidal for one cycle when viewed in a plane. As shown in FIG. 1, one cylindrical protrusion 29 that is engaged with the circumferential guide groove 27 is provided on the outer peripheral surface of the piston 12. Accordingly, the protrusion 29 of the piston 12 moves along the circumferential guide groove 27 of the rotor 23, and as a result, the piston 12 reciprocates linearly in the direction of the cylinder axis of the cylinder 10.

  The circumferential guide groove 27 may have a sine wave shape having a wave number that is an integral multiple of one period. In this case, the reciprocating number of the reciprocating linear motion of the piston 12 is equal to the wave number of the sine wave when the rotor 23 makes one revolution. That is, the reciprocation number of the piston 12 per unit time is a value obtained by multiplying the rotation number of the rotor 12 per unit time by the wave number of the sine wave. The amplitude of the piston 12 corresponds to the amplitude of the circumferential guide groove 27 formed in a sine wave. In this case, by providing an integral number of protrusions 29 at positions where the outer circumference of the piston 12 is equally divided by the wave number, the rotational motion of the rotor 23 can be stably converted into the reciprocating linear motion of the piston 12. become.

  An example of a method for inserting the piston 12 into the cavity 23a of the rotor 23 will be described. FIG. 3 is a perspective view of the rotor 23 shown by cutting a part of the cylinder. As shown in FIG. 3, a protrusion insertion groove 23 b extending from the axial end face to the circumferential guide groove 27 is formed on the outer peripheral surface of the cavity 23 a of the rotor 23. Therefore, if the piston 12 is inserted into the cavity 23a of the rotor 23, the circumferential position of the piston 12 is adjusted to engage the projection 29 with the projection insertion groove 23b, and further the piston 12 is inserted, the projection 29 is circumferentially moved. The guide groove 27 can be engaged. Finally, a groove filling bar 23c having the same shape as the protrusion insertion groove 23b and the same material as that of the rotor 23 is press-fitted and welded to the protrusion insertion groove 23b to fill the protrusion insertion groove 23b.

Here, the position where the protrusion insertion groove 23b is formed on the outer peripheral surface of the cavity 23a of the rotor 23 will be considered. FIG. 4 is a diagram schematically showing the trajectory of the protrusion 29 that moves in the circumferential guide groove 27 during operation of the Stirling engine. There is a pressure difference between the compression space 45 and the back pressure space 51. Specifically, when the pressure of the back pressure space 51 is P1, and the pressure of the compression space 45 is P2,
(1) When the piston 12 is at the center position of the reciprocating motion (position with zero amplitude), P1 = P2
(2) When the piston 12 is on the back pressure space side with respect to the center position of the reciprocating motion, P1> P2
(3) When the piston 12 is on the back pressure space side with respect to the center position of the reciprocating motion, P1 <P2
It becomes. Therefore, as shown in FIG. 4, the protrusion 29 always receives a force in the direction of the center line C in the drawing, and the wall surface of the opposing wall surfaces of the circumferential guide groove 27 that is closer to the center line C It will slide while in contact. Therefore, in order to smoothly move the protrusion 29 without affecting the difference between the sliding surfaces, the distance from the center line C among the opposing wall surfaces of the circumferential guide groove 27 is communicated. In addition, it is desirable to form the protrusion insertion groove 23b. In the example of FIG. 3, the peak of the portion biased toward the back pressure space 51 with respect to the center line C of the circumferential guide groove 27 is farther from the center line C after the opposing wall surfaces, that is, the back pressure. The protrusion insertion groove 23b is formed so as to communicate with the wall surface on the space 51 side.

An example of dimensions of the piston 12, the protrusion 29, the rotor 23, and the circumferential guide groove 27 is as follows.
Piston φ40mm
Protrusion φ8mm, L10mm
Rotor (inner diameter) φ42mm
Circumferential guide groove Amplitude ± 7mm

  In FIG. 1, a protrusion 29 is provided on the piston 12 side and a circumferential guide groove 27 is provided on the rotor 23 side. However, as shown in FIG. 5, the circumferential guide groove 27 is provided on the piston 12 side and the rotor 12 side is provided on the rotor 12 side. A protrusion 29 may be provided. Also in this case, for the same reason as described above, as shown in FIG. 6, the center line of the opposite wall surface with respect to the portion deviated toward the back pressure space 51 with respect to the center line C of the circumferential guide groove 27 If the protrusion insertion groove 12a is formed on the outer peripheral surface of the piston 12 so as to communicate with the wall farther from C, that is, the wall on the back pressure space 51 side, the groove filling rod 12b is welded after being pressed into the protrusion insertion groove 12a. However, the projection 29 may be moved smoothly without the influence of the gap of the sliding surface.

  As shown in FIG. 1, a high temperature side heat transfer head 40 and a low temperature side heat transfer head 41 are arranged outside the portion corresponding to the operating region of the displacer 13 in the cylinder 10. The high temperature side heat transfer head 40 has a ring shape, and the low temperature side 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. A ring-shaped high-temperature side internal heat exchanger 42 is mounted on the inner peripheral surface of the high-temperature side heat transfer head 40, and a ring-shaped low-temperature side internal heat exchanger 43 is also mounted on the inner peripheral surface of the low-temperature side heat transfer head 41. Installed. Each of the high temperature side internal heat exchanger 42 and the low temperature side internal heat exchanger 43 has air permeability, and transfers the heat of the working gas passing through the inside to the high temperature side heat transfer head 40 and the low temperature side heat transfer head 41. The high temperature side internal heat exchanger 42 and the low temperature side internal heat exchanger 43 can be formed, for example, by corrugating and compressing a thin plate of copper or copper alloy.

  The high temperature side heat transfer head 40 and the low temperature side heat transfer head 41 are thus supported outside the cylinder 10 with the high temperature side internal heat exchanger 42 and the low temperature side internal heat exchanger 43 interposed therebetween. The cylinder 10 and the body portion 50 are connected to the high temperature side heat transfer head 40.

  An annular space surrounded by the high temperature side heat transfer head 40, the cylinder 10, the displacer 13, the piston 12, the displacer shaft 15, and the high temperature side internal heat exchanger 42 becomes a compression space 45. A space surrounded by the low temperature side heat transfer head 41, the cylinder 10, the displacer 13, and the low temperature side internal heat exchanger 43 becomes an expansion space 46.

  A regenerator 70 is disposed between the high temperature side internal heat exchanger 42 and the low temperature side internal heat exchanger 43. A regenerator tube 48 wraps the outside of the regenerator 70 to form an airtight passage between the high temperature side heat transfer head 40 and the low temperature side heat transfer head 41. The regenerator tube 48 can be formed of stainless steel, for example.

  A cylindrical pressure vessel covering the rotary motor 20, the cylinder 10, and the piston 12 forms the body portion 50. The interior of the body part 50 is a back pressure 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 high temperature side 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 to a taper shape and brazed to the high temperature side 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 of the state is formed.

  The body portion 50 is provided with a terminal portion 28 for supplying electric power to the rotary motor 20 and a pipe 50a for enclosing the 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 vibration suppressing device 60 is attached to the body portion 50. The vibration suppression device 60 includes a base 61 fixed to the body portion 50, a plate-like spring 62 supported by the base 61, and a balance weight 63 supported by the spring 62. That is, the vibration suppressing device 60 is a passive dynamic vibration absorber.

  The Stirling engine 1 operates as follows. When an alternating current is supplied to the coil 21 of the rotary motor 20, an electromagnetic force is generated between the stator 22 and the rotor 23 of the rotary motor 20, the rotor 23 rotates in the axial direction, and the rotary motion of the rotor 23 is a reciprocating straight line of the piston 12. It is converted into motion and the piston 12 operates.

  By the reciprocating linear motion of the piston 12, the working gas is repeatedly compressed and expanded in the expansion space 46 and the compression space 45. As the pressure changes, the displacer 13 also performs a reciprocating linear motion. 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, an inverse 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, and in the expansion space 46, the temperature of the working gas decreases. For this reason, the temperature of the compression space 45 rises and the temperature of the expansion space 46 falls.

  The working gas that travels between the compression space 45 and the expansion space 46 during operation passes through the high-temperature side internal heat exchanger 42 and the low-temperature side internal heat exchanger 43 to transfer the heat of the working gas to the high-temperature side internal heat exchanger The temperature is transferred to the high temperature side heat transfer head 40 and the low temperature side heat transfer head 41 through 42 and the low temperature side internal heat exchanger 43. Since the working gas flowing into the regenerator 70 from the compression space 45 is high temperature, the high temperature side heat transfer head 40 is heated, and the high temperature side heat transfer head 40 becomes a worm head. Since the working gas flowing into the regenerator 70 from the expansion space 46 is at a low temperature, the low temperature side heat transfer head 41 is cooled, and the low temperature side heat transfer head 41 becomes a cold head. By dissipating heat from the high temperature side heat transfer head 40 to the atmosphere and lowering the temperature of the specific space with the low temperature side heat transfer head 41, the Stirling engine 1 functions as a refrigeration device.

  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 via the high temperature side internal heat exchanger 42 gives its heat to the regenerator 70 when passing through the regenerator 70, and the expansion space with the temperature lowered. 46 flows in. The low-temperature working gas that has entered the regenerator 70 from the expansion space 46 through the low-temperature side internal heat exchanger 43 collects heat from the regenerator 70 when passing through the regenerator 70, and the compressed space in a state where the temperature has risen. 45 flows in. That is, the regenerator 70 serves as a heat storage means.

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

  According to the present embodiment, the crank mechanism and the connecting rod can be eliminated by directly fitting the circumferential guide groove 27 of the rotor 23 and the protrusion 29 of the piston 12. That is, the piston can be directly driven by the rotary motor without interposing a connecting part such as a crank mechanism or a rod, and the Stirling engine can be reduced in size and cost.

  In addition, this invention is not limited to the said embodiment. For example, the circumferential guide groove has a sine wave shape, but may have a triangular wave shape or a pulse wave shape.

Cross section of an example Stirling engine Development view of the outer peripheral surface of the rotor cavity where circumferential guide grooves are formed A perspective view of a rotor with a part cut out of a cylinder The figure which shows typically the locus | trajectory of the protrusion which moves in the circumferential guide groove at the time of driving | operation of a Stirling engine. Sectional view of Stirling engine with circumferential guide grooves and protrusions opposite to FIG. 5 is a perspective view of the piston of the Stirling engine of FIG. Is a cross-sectional view of a conventional Stirling engine described in Patent Document 1

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stirling engine 10 Cylinder 12 Piston 13 Displacer 15 Displacer shaft 20 Rotating motor 21 Coil 22 Stator 23 Rotor 23a Cavity 23b Protrusion insertion groove 23c Groove filling rod material 24 End bracket 25, 26 Bearing 27 Circumferential guide groove 29 Protrusion

Claims (5)

A rotary motor having a cavity penetrating in the axial direction, rotating in the circumferential direction, and rotationally driving a cylindrical rotor disposed so as not to be linearly movable in the axial direction;
A cylindrical piston that is inserted into the cavity of the rotor and is non-rotatable in the circumferential direction and arranged so as to be linearly movable in the axial direction;
A circumferential guide groove formed on the outer peripheral surface of the cavity of the rotor;
A protrusion provided on the outer peripheral surface of the piston and engaged with the circumferential guide groove;
With
A Stirling engine, wherein when the rotor is rotationally driven, the piston reciprocates linearly by moving the projection of the piston along the circumferential guide groove of the rotor. A rotary motor having a cavity penetrating in the axial direction, rotating in the circumferential direction, and rotationally driving a cylindrical rotor disposed so as not to be linearly movable in the axial direction;
A cylindrical piston that is inserted into the cavity of the rotor and is non-rotatable in the circumferential direction and arranged so as to be linearly movable in the axial direction;
The circumferential guide groove formed on the outer peripheral surface of the piston;
A protrusion provided on the outer peripheral surface of the cavity of the rotor and engaged with the circumferential guide groove;
With
A Stirling engine, wherein when the rotor is rotationally driven, the protrusion of the rotor is moved along the circumferential guide groove of the piston, whereby the piston reciprocates linearly.   The Stirling engine according to claim 1, wherein the circumferential guide groove has a sinusoidal shape.   The Stirling engine according to claim 1, wherein the circumferential guide groove has a sine wave shape having a wave number that is an integral multiple of one cycle.   5. The Stirling engine according to claim 4, wherein the protrusion is provided at a position obtained by equally dividing the circumference by the wave number.

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