JP2014051960A - Stirling cycle engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Stirling cycle engine capable of reducing friction inside a cylinder.SOLUTION: Edge sections (101, 102 and 103) of sliding surfaces of a displacer 70 and a piston 20 are smoothly curved in a manner that recedes from an inner surface of cylinders (10 and 11) and thereby facilitating smooth flow of operating gas from the curved edge sections (101, 102 and 103) toward the sliding surfaces when the displacer 70 and the piston 20 reciprocate inside the cylinders (10 and 11). As a result, a gas lubrication function is achieved by layers of the operating gas formed between the sliding surfaces of the displacer 70 as well as the piston 20 and the inner surfaces of the cylinders (10 and 11). Thus, a Stirling cycle engine can significantly reduce friction inside the cylinders (10 and 11).

Description

  The present invention relates to a Stirling cycle engine that performs power generation, cooling, and the like using a Stirling cycle.

  A Stirling cycle engine having a structure in which a displacer and a piston are coaxially arranged in a cylinder has been widely known, and has been put into practical use as a generator or a refrigerator. Generally, in this type of Stirling cycle engine, a permanent magnet is attached to a piston, and a stator and a yoke are arranged with the permanent magnet interposed therebetween. In the case of a generator, the working gas is repeatedly compressed and expanded by a temperature difference given from the outside, so that the piston reciprocates, and the kinetic energy is converted into electric energy by the electromagnetic action between the permanent magnet and the stator. On the other hand, in the case of a refrigerator, the piston reciprocates by passing a driving current through the electromagnetic coil of the stator, and the working gas repeats compression and expansion along with the reciprocation, thereby causing a temperature difference between the low temperature part and the high temperature part. Occurs.

  In the Stirling cycle engine, when the displacer and the piston reciprocate in the cylinder, a loss due to friction between the two occurs. Conventionally, the loss due to friction has been reduced by applying a low-friction coating such as fluororesin to the outer surface of the displacer and the piston or the inner surface of the cylinder. However, since the loss due to the friction in the cylinder accounts for a large proportion of the total energy loss in the Stirling cycle engine, it is a problem to further suppress the friction.

  This invention is made | formed in view of this situation, The objective is to provide the Stirling cycle engine which can reduce the friction in a cylinder.

  A Stirling cycle engine according to the present invention includes a cylinder fixed in a casing, a displacer inserted in one end of the cylinder so as to be able to reciprocate, and a reciprocating motion inserted in the other end of the cylinder. And a piston. At least one of the displacer and the piston includes a sliding portion having a sliding surface that slides on the inner surface of the cylinder. The edge of the sliding surface is smoothly curved in a direction away from the inner surface of the cylinder.

  Preferably, the sliding surface of the sliding portion is formed so as to surround the entire circumference of the displacer or the piston having a circular cross section.

  Preferably, the Stirling cycle engine communicates the expansion chamber facing one end of the displacer, the compression chamber facing the other end of the displacer, and the expansion chamber and the compression chamber. A gas flow path, and a heat storage heat exchanger that stores heat of the working gas flowing in the gas flow path. The compression chamber is formed between the displacer and the piston.

  Preferably, at least one of the displacer and the piston includes a base portion made of metal and the sliding portion made of resin.

  ADVANTAGE OF THE INVENTION According to this invention, the Stirling cycle engine which can reduce the friction in a cylinder can be provided.

It is sectional drawing which shows an example of a structure of the Stirling cycle engine which concerns on embodiment of this invention. It is the figure which illustrated the principal part of the displacer and piston in the Stalin cycle engine shown in FIG. It is a figure which shows the rod for a displacer drive in the Stirling cycle engine shown in FIG.

  Hereinafter, a Stirling cycle engine applied to a generator will be described as an example of a Stirling cycle engine according to an embodiment of the present invention.

FIG. 1 is a cross-sectional view showing an example of the configuration of a Stirling cycle engine according to an embodiment of the present invention. FIG. 2 is a diagram illustrating the main parts of the displacer and the piston in the Stalin cycle engine shown in FIG.
A Stirling cycle engine shown in FIG. 1 includes a casing 1, an upper cylinder 10 and a lower cylinder 11 housed in the casing 1, a displacer 70 inserted into the upper cylinder 10 so as to reciprocate, and a lower cylinder 11. Piston 20 inserted so as to be able to reciprocate, stator 30 and yoke 18 arranged facing the inside and outside of piston 20, magnet 25 attached to the cylindrical wall of piston 20, displacer A spring member (elastic member) 51 that biases 70 and a spring member (elastic member) 52 that biases the piston 20 are included.

  Here, the casing 1 is an example of the casing in the present invention, the upper cylinder 10 and the lower cylinder 11 are examples of the cylinder in the present invention, and the displacer 70 is an example of the displacer in the present invention.

The casing 1 is a sealed container in which working gas (helium gas or the like) of a Stirling cycle engine is enclosed. In the example of FIG. 1, the casing 1 is formed by combining an upper casing 2, an intermediate casing 3, a cylinder holding portion 5, and a lower casing 7.
The upper casing 2 and the intermediate casing 3 form a columnar internal space that mainly accommodates the upper cylinder 10. The inner wall on the ceiling side of the upper cylinder 10 is rounded like a dome. The cylinder holding part 5 is in contact with the outer periphery of the lower cylinder 11 on its inner wall, and holds the lower cylinder 11 so that the position of the central axis is determined.

  The lower casing 7 forms a cylindrical internal space that mainly accommodates the lower cylinder 11, the stator 30, the yoke 18, and the spring members 51 and 52. Near the bottom of the lower casing 7 is provided a support base 43 that supports the entire mechanism (the upper cylinder 10, the lower cylinder 11, etc.) in the casing 1 from below. An opening is provided in the center of the bottom of the lower casing 7, and the opening is closed by a lid 8. The lid portion 8 includes a pipe (not shown) for introducing working gas into the casing 1 and for passing electrical wiring.

  The upper cylinder 10 and the lower cylinder 11 each have a cylindrical shape, and are arranged in the casing 1 with the central axes aligned. When the upper cylinder 10 and the lower cylinder 11 are regarded as one cylinder, the displacer 70 is removably inserted into the upper end of the cylinder, and the piston 20 is reciprocally movable at the lower end of the cylinder. Inserted. The upper cylinder 10 and the lower cylinder 11 may be formed by connecting separate parts, or may be formed integrally.

  The lower cylinder 11 is fixed to the support base 43 via a plurality of support columns 41. In the example of FIG. 1, the support column 41 is formed in a cylindrical shape, and a bolt 42 passes through a hole provided in the support base 43 and the cylindrical support column 41. The lower cylinder 11 is fixed to the support base 43 by screwing the male screw at the tip of the bolt 42 with the female screw on the lower surface of the lower cylinder 11. The spring member 51 has a hole through which the bolt 42 passes, and is fixed by being sandwiched between the support column 41 and the support base 43. In the example of FIG. 1, three spring members 51 are fixed to the support base 43.

  A space formed between the upper surface of the displacer 70 and the casing 1 is an expansion chamber 12 where the working gas is heated to increase its volume. On the other hand, the space formed between the displacer 70 and the piston 20 is the compression chamber 17, where the working gas is cooled to reduce its volume.

  A cylindrical space surrounded by the outer wall of the upper cylinder 10 and the inner wall of the casing 1 is a working gas flow path (gas flow path) that communicates the expansion chamber 12 and the compression chamber 17. A communication hole 16 connected to the compression chamber 17 is provided between the upper cylinder 10 and the lower cylinder 11. The expansion chamber 12 and the compression chamber 17 are connected through the communication hole 16 and the cylindrical space (gas flow path).

  In the cylindrical space (gas channel), a heat absorption fin 13, a heat storage heat exchanger (regenerator) 14, and a heat radiation fin 15 are arranged. The heat absorption fins 13 are disposed at positions close to the upper expansion chamber 12, the heat radiation fins 15 are disposed at positions close to the lower compression chamber 17, and the heat storage heat exchanger 14 is disposed between the heat absorption fins 13 and the heat radiation fins 15. Be placed. The heat storage heat exchanger 14 has a function of taking heat of the working gas flowing from the expansion chamber 12 to the compression chamber 17 and storing the heat, and giving the stored heat to the working gas flowing from the compression chamber 17 to the expansion chamber 12.

The casing 1 includes external fins 6 at portions that contact the heat radiating fins 15. The external fins 6 are heat radiating means for discharging the heat of the working gas to the outside of the casing 1. In the example of FIG. 1, the external fin 6 is fixed between the intermediate casing 3 and the cylinder holding portion 5. The external fins 6 are cooled by a cooling medium (water or the like) supplied from, for example, a pump (not shown) and held at a predetermined temperature.
On the other hand, the upper casing 2 is a heat absorbing means that transfers heat applied from an external heat source to the working gas in the expansion chamber 12, and the heat absorbing fins 13 are in contact with the inner wall of the upper casing 2.

The displacer 70 slides on the head 73 provided at one end facing the expansion chamber 12, the base 71 provided at the other end facing the compression chamber 17, and the inner surface of the upper cylinder 10. A sliding portion 72 and a cylindrical body 74.
The base portion 71 is an example of a base portion in the present invention, and the sliding portion 72 is an example of a sliding portion in the present invention.

  The head portion 73 constitutes a wall surface that partitions the expansion chamber 12. The head portion 73 is formed of, for example, a heat insulating resin (PPS or the like) and blocks heat conduction from the expansion chamber 12 to the compression chamber 17.

  The base 71 constitutes a wall surface that partitions the compression chamber 17. The base portion 71 is made of, for example, a metal such as aluminum or brass, and holds the head portion 73 and the sliding portion 72. By forming the base 71 from a metal, the amount of deformation of the component due to temperature is smaller than when the base 71 is formed from a resin or the like. Accordingly, a decrease in mechanical accuracy at a high temperature is suppressed.

  The sliding portion 72 is provided on the outer surface of the base portion 71 so as to slide on the inner surface of the upper cylinder 10, and has a ring-shaped sliding surface surrounding the entire circumference of the base portion 71 having a circular cross section. The sliding portion 72 is formed of a resin having low friction and excellent heat resistance and wear resistance, such as PPS.

The sliding portion 72 and the base portion 71 are integrally formed by insert molding. Specifically, for example, the base portion 71 and the sliding portion 72 are integrally formed by placing a base portion 71 prepared in advance in a predetermined mold and pouring and hardening the resin into the mold. As shown in the enlarged view on the left side of FIG. 2, the base 71 has a groove 75 for fixing the sliding portion 72. The groove 75 has a bottom that is wider than the opening. When the resin forming the sliding portion 72 is hardened in a state where the groove 75 is filled, the resin inside the groove 75 cannot be removed from the opening of the groove 75. Thereby, the base 71 and the sliding part 72 are firmly joined.
By integrally forming the base portion 71 and the sliding portion 72 by insert molding, a mechanical component for connecting them becomes unnecessary and assembly work is also eliminated. Thereby, since the sliding part 72 can be made as thin as possible without considering the ease of assembly work and the like, it is possible to minimize the amount of resin used which has a large amount of deformation due to heat.

  Further, as shown in the enlarged view on the left side of FIG. 2, the edge portion 101 of the sliding surface of the sliding portion 72 is smoothly curved in a direction away from the inner surface of the upper cylinder 10. When the displacer 70 reciprocates up and down in the upper cylinder 10, the working gas easily flows along the sliding surface from the curved edge portion 101, and the sliding surface of the sliding portion 72 and the upper cylinder 10 become easy to flow. A working gas layer is formed in a gap with the inner surface of the working gas. Since this working gas layer exhibits the function of gas lubrication, it is difficult for the sliding surface of the sliding portion 72 and the inner surface of the upper cylinder 10 to be in direct contact with each other, so the friction in the upper cylinder 10 is greatly reduced. To do.

  A cylindrical body 74 having a diameter smaller than that of the base 71 is fixed to the end wall of the base 71 on the compression chamber 17 side so as to be coaxial with the base 71. In the example of FIG. 1, a circular recess is formed at the center of the end wall of the base 71, and the upper end of the cylindrical body 74 is inserted into this recess.

  The displacer 70 is connected to the spring member 51 via a rod 61 extending in parallel with the axial direction of the cylinder (10, 11). One end of the rod 61 is connected to the base 71 through the cavity of the cylindrical body 74 of the displacer 70. The other end of the rod 61 is connected to a plate-like spring member 51 attached to the support base 43 of the lower casing 7. The displacer 70 is urged in the vertical direction (cylinder axial direction) by the elastic force of the spring member 51 connected via the rod 61.

FIG. 3 is a view showing a rod 61 in the Stirling cycle engine shown in FIG. As shown in this figure, the diameter of the rod 61 is relatively thick at the end portions 65 and 66 (D2, D3) and relatively thin at the center portion 64 (D1). The diameter of the central portion 64 is constant (D1), and the diameters of the end portions 65 and 66 gradually become thicker than the diameter D1 as approaching the end. The relatively thin diameter D1 of the central portion 64 is set to a value such that the central portion 64 can be elastically deformed by the biasing of the spring member 51 during the reciprocating motion of the displacer 70.
Since the rod 61 can be elastically deformed, the rod 61 is flexibly bent at the central portion 64 even if there is a slight deviation between the central axis of the displacer 70 and the central axis of the upper cylinder 10. Therefore, the displacer 70 can easily reciprocate smoothly. That is, an increase in friction due to the displacer 70 hitting a portion of the upper cylinder 10 is suppressed.

The piston 20 includes a base portion 21 having a cylindrical shape and sliding portions 23 and 24 provided on the outer surface of the base portion 21. One end of the base 21 is closed by the end wall.
The base portion 21 is an example of the base portion in the present invention, and the sliding portions 23 and 24 are examples of the sliding portion in the present invention.

  The base portion 21 faces the displacer 70 at one end wall portion that is closed, and this end wall portion constitutes a wall surface that partitions the compression chamber 17. The base portion 21 is formed of a metal such as aluminum or brass, and holds the sliding portions 23 and 24. By forming the base portion 21 from a metal, the amount of deformation of the component due to temperature is smaller than when the base portion 21 is formed from resin or the like, so that a decrease in mechanical accuracy at high temperatures is suppressed.

  The sliding portions 23 and 24 are provided on the outer surface of the base portion 21 so as to slide on the inner surface of the lower cylinder 11, and ring-shaped sliding surfaces surrounding the entire circumference of the cylindrical base portion 21 are provided. Have. The sliding parts 23 and 24 are made of a resin having low friction and excellent heat resistance and wear resistance, such as PPS.

The sliding portions 23 and 24 and the base portion 21 are integrally formed by insert molding in the same manner as the base portion 71 and the sliding portion 72 described above. Further, the base portion 21 has grooves 27 and 28 for fixing the sliding portions 23 and 24 as shown in the enlarged view on the left side of FIG. The grooves 27 and 28 have a width at the bottom that is wider than the width of the opening. Therefore, when the resin forming the sliding parts 23 and 24 is solidified in the state where the grooves 27 and 27 are filled, This resin cannot escape from the opening of the groove 75. Thereby, the base 21 and the sliding parts 23 and 24 are firmly joined.
By forming the base portion 21 and the sliding portions 23 and 24 integrally by insert molding, it is possible to minimize the amount of resin that is largely deformed by heat.

  Moreover, the edge parts 102 and 103 of the sliding surface of the sliding parts 23 and 24 are smoothly curved in the direction away from the inner surface of the lower cylinder 11, as shown in the enlarged view on the left side of FIG. As a result, as in the case of the sliding portion 72 described above, a working gas layer is formed in the gap between the sliding surfaces of the sliding portions 23 and 24 and the inner surface of the lower cylinder 11. Friction is greatly reduced.

  In the center of the end wall portion of the base portion 21 facing the displacer 70, a through portion 22 that receives the cylindrical body 74 of the displacer 70 is formed. In the example of FIG. 1, the penetrating portion 22 extends in a cylindrical shape parallel to the axial direction of the cylinder (10, 11). The cylindrical body 74 of the displacer 70 reciprocates up and down through the penetrating portion 22.

  The base 21 of the piston 20 is connected to a plate-like spring member 52 via a plurality of rods 62 extending in parallel with the axial direction of the cylinders (10, 11). In the example of FIG. 1, the spring member 52 is disposed between the lower cylinder 11 and the spring member 51, and is fixed to the lower cylinder 11 (or the support base 43) via a post (not shown). A through hole for passing the rod 61 is formed in the center of the spring member 52. One end of each of the plurality of rods 62 is connected to a symmetrical position around the through portion 22, and the other end is connected to a symmetrical position around the through hole of the spring member 52.

  As with the rod 61 (FIG. 3) described above, the driving rod 62 for the piston 20 has a large diameter at the end and a small diameter at the center. The central portion of the rod 62 has a constant diameter that is thin enough to cause elastic deformation by the spring member 52 during the reciprocating motion of the piston 20. Since the rod 62 can be elastically deformed, the rod 62 bends flexibly in the central portion even if there is a slight deviation between the central axis of the piston 20 and the central axis of the lower cylinder 11, and the piston 20 is within the lower cylinder 11. Becomes easy to reciprocate smoothly. That is, an increase in friction due to the piston 20 strongly hitting a part of the lower cylinder 11 is suppressed.

  A magnet 25 is fixed to the base 21 of the piston 20. The magnet 25 is provided in a ring shape so as to surround the entire circumference of the cylindrical base portion 21 between the separated sliding portions 23 and 24. A yoke 18 is fixed to the inner surface of the lower cylinder 11 facing the magnet 25. The yoke 18 is made of a magnetic material such as iron, and is formed, for example, in a ring shape so as to surround the magnet 25. A stator 30 is disposed inside the base portion 21 of the piston 20 at a position facing the yoke 18. The magnet 25 is sandwiched between the stator 30 and the yoke 18 and reciprocates up and down together with the piston 20. The magnet 25 generates a magnetic field that acts on the stator 30 and the yoke 18.

  The stator 30 includes a coil 33 formed by winding an electric wire in a ring shape, and a core 36 facing the yoke 18 with the coil 33 interposed therebetween.

  The coil 33 is disposed inside the cylindrical base portion 21 of the piston 20. Further, the coil 33 is arranged coaxially with the piston 20 so that the outer peripheral side thereof faces the magnet 25 of the piston 20.

  The core 36 is formed in a shape that surrounds the cross section of the coil 33 perpendicular to the winding direction of the electric wire, and a gap (a portion that does not surround the coil 33, a cut) is formed in a portion facing the magnet 25 and the coil 33. Have In the example of FIG. 1, the core 36 is divided into two blocks (36A, 36B) symmetrical in the vertical direction. The upper and lower blocks (36A, 36B) are respectively formed by overlapping and bonding thin magnetic material plates (silicon steel plates or the like).

  The core 36 is sandwiched between two parallel disk-shaped plate members, and the plate-shaped member is fixed to the support portion 40 by a coupling tool (not shown). The support portion 40 is fixed to the casing 1 together with the lower cylinder 11.

  Here, the operation of the Stirling cycle engine having the above-described configuration will be described.

  When the displacer 70 moves downward toward the piston 20, the compression chamber 17 becomes narrow, so that the working gas in the compression chamber 17 passes through the communication hole 16, the heat radiation fin 15, the heat storage heat exchanger 14, and the heat absorption fin 13. It flows into the hot expansion chamber 12. Since the working gas flowing into the expansion chamber 12 is heated and expands in volume, the pressure in the expansion chamber 12 and the compression chamber 17 increases. When the pressure in the expansion chamber 12 and the compression chamber 17 becomes higher than the pressure in the back pressure space 9 of the lower casing 7 defined by the piston 20, the piston 20 moves downward.

  When the pressure of the expansion chamber 12 and the compression chamber 17 decreases due to the downward movement of the piston 20 and becomes lower than the pressure of the back pressure space 9, the displacer 70 moves upward due to this pressure difference.

  When the displacer 70 moves upward, the expansion chamber 12 becomes narrow, so that the working gas in the expansion chamber 12 passes through the heat absorption fins 13, the heat storage heat exchanger 14, the heat radiation fins 15, and the communication holes 16, and the low temperature compression chamber 17. Flow into. Since the working gas that has flowed into the compression chamber 17 is cooled to reduce its volume, the pressure in the expansion chamber 12 and the compression chamber 17 is reduced. When the pressure in the expansion chamber 12 and the compression chamber 17 decreases, the moving direction of the piston 20 turns from the lower direction to the upper direction.

When the pressure of the expansion chamber 12 and the compression chamber 17 rises due to the upward movement of the piston 20 and becomes higher than the pressure of the back pressure space 9, the displacer 70 moves downward due to this pressure difference. When the displacer 70 moves downward toward the piston 20, the working gas again flows from the compression chamber 17 to the expansion chamber 12, the pressure in the expansion chamber 12 and the compression chamber 17 increases, and the movement direction of the piston 20 changes from the upward direction. Turn down.
By repeating the above, the displacer 70 and the piston 20 reciprocate up and down.

  When the piston 20 reciprocates, the magnet 25 moves up and down between the yoke 18 and the stator 30, and the magnetic field of the coil 33 changes periodically, so that an electromotive force is generated in the coil 33 and a current flows.

  As described above, in the Stirling engine according to this embodiment, the edges (101, 102, 103) of the sliding surfaces of the displacer 70 and the piston 20 are smoothly moved away from the inner surface of the cylinder (10, 11). It is formed to be curved. Thus, when the displacer 70 and the piston 20 reciprocate inside the cylinder (10, 11), the working gas smoothly flows from the curved edges (101, 102, 103) toward the sliding surface. It becomes easy. As a result, a working gas layer is formed between the sliding surface of the displacer 70 and the piston 20 and the inner surface of the cylinder (10, 11), and the gas lubrication function is realized by this gas layer. 11), the internal friction can be greatly reduced.

  In addition, this invention is not limited only to embodiment mentioned above, The other various variation is included.

  In the embodiment described above, both edges of the sliding surfaces of the displacer 70 and the piston 20 are curved for gas lubrication, but in other embodiments of the present invention, only one of the edges is curved. You may make it do.

  In the above-described embodiment, an example of a generator of a Stirling cycle engine is given, but the present invention is not limited to this, and can be applied to a refrigerator of a Stirling cycle engine, for example.

  The present invention can be applied to a Stirling engine with an output of 1.2 kW, and can be widely applied to various other Stirling engines.

DESCRIPTION OF SYMBOLS 1 ... Casing, 2 ... Upper casing, 3 ... Middle part casing, 5 ... Cylinder holding part, 6 ... External fin, 7 ... Lower casing, 8 ... Cover part, 10 ... Upper cylinder, 11 ... Lower cylinder, 12 ... Expansion chamber , 13 ... endothermic fins, 14 ... heat storage heat exchanger (regenerator), 15 ... radiating fins, 16 ... communication hole, 17 ... compression chamber, 18 ... yoke, 19 ... yoke holding part, 20 ... piston, 21 ... base part , 22 ... penetrating part, 23, 24 ... sliding part, 25 ... magnet, 30 ... stator, 33 ... coil, 36 ... core, 40 ... support part, 41 ... column, 43 ... support base, 51, 52 ... Spring member, 61, 62 ... rod, 70 ... displacer, 71 ... base, 72 ... sliding part, 73 ... head part.

Claims (4)

A cylinder fixed in the casing;
A displacer inserted into one end of the cylinder so as to reciprocate;
A piston inserted in the other end of the cylinder so as to be capable of reciprocating,
At least one of the displacer and the piston includes a sliding portion having a sliding surface that slides on the inner surface of the cylinder.
The edge of the sliding surface is smoothly curved in a direction away from the inner surface of the cylinder,
Stirling cycle agency. The sliding surface of the sliding part is formed so as to surround the entire circumference of the displacer or the piston having a circular cross section.
The Stirling cycle engine according to claim 1. An expansion chamber facing one end of the displacer;
A compression chamber facing the other end of the displacer;
A gas flow path communicating the expansion chamber and the compression chamber;
A heat storage heat exchanger for storing heat of the working gas flowing in the gas flow path,
The compression chamber is formed between the displacer and the piston.
The Stirling cycle engine according to claim 2. At least one of the displacer and the piston is
A base formed of metal;
Including the sliding part formed of resin,
The Stirling cycle engine according to claim 2 or 3.