JP2006308213A - Stirling engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a Stirling refrigerator capable of operating with high efficiency by preventing the occurrence of energy loss caused by friction at sliding contact parts. <P>SOLUTION: The Stirling refrigerator 100 comprises a cylinder 120 filled with operating gas; a piston 130 and a displacer 140 fittingly inserted in the cylinder 120; and a displacer rod 145 inserted through a through hole 134 provided in the piston 130. The surfaces of the cylinder 120, piston 130, displacer 140 and displacer rod 145 at the sliding contact parts formed between the cylinder 120 and piston 130, between the cylinder 120 and displacer 140 and between the displacer rod 145 and piston 130 are covered with coating layers containing tetrafluoroethylene resin, and a lubricant containing fluorine-based grease is applied to the surfaces of the coating layers. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a Stirling engine, and more particularly, to a Stirling engine in which the slidability of a piston and a displacer inserted in a cylinder is improved.

  In a heat cycle apparatus represented by a Stirling engine, a piston is inserted into a cylinder, and the piston reciprocates in the cylinder, whereby the working gas filled in the cylinder is compressed or expanded. Various thermal cycles are realized by compression or expansion of the working gas. In such a heat cycle device, it is preferable to reduce energy loss due to friction generated in the sliding contact portion between the piston reciprocating in the cylinder and the cylinder, and to reduce energy loss due to friction in the sliding contact portion. As a result, improvement in drive output, improvement in power generation efficiency, improvement in refrigeration efficiency, and the like are achieved.

  For example, in a Stirling refrigerator that is an application example of a Stirling engine, a piston and a displacer are generally arranged inside a cylinder, the piston is driven by a linear motor to reciprocate in the cylinder, and the displacer is reciprocated by a piston. The cylinder is configured to reciprocate in the cylinder in response to the gas pressure fluctuation of the generated working gas. Here, the displacer is not an operating body that is directly driven by a driving means such as a linear motor, but is an operating body that reciprocates in the cylinder like a piston, and is also referred to as a free piston. In the above operation, if the friction coefficient between the inner peripheral surface of the cylinder and the outer peripheral surface of the piston, and between the inner peripheral surface of the cylinder and the outer peripheral surface of the displacer is large, energy loss due to friction occurs in this portion, and Stirling The cooling efficiency of the refrigerator will be reduced. Therefore, if the slidability is improved at this portion, the generation of energy loss due to friction at these sliding contact portions can be suppressed, and as a result, the refrigeration efficiency can be improved.

Examples of documents disclosing the general configuration of the above Stirling refrigerator include, for example, Japanese Patent Application Laid-Open No. 2004-317108 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2005-042571 (Patent Document 2).
JP 2004-317108 A Japanese Patent Laying-Open No. 2005-042571

  The present invention has been made to reduce energy loss due to friction in the sliding contact portion, and provides a Stirling engine that can be operated with high efficiency by improving the slidability in the sliding contact portion. For the purpose.

  A Stirling engine according to the first aspect of the present invention includes first and second cylinders filled with a working gas, the first cylinder, the first cylinder disposed in the first cylinder, and driven by driving means. And a displacer that is disposed in the second cylinder and that slides in the second cylinder in response to a gas pressure fluctuation of the working gas generated by sliding of the piston. In the sliding contact portion between the first cylinder and the piston, at least one of the surface of the first cylinder and the surface of the piston is a coating layer containing a tetrafluoroethylene-based resin. And a lubricant containing a fluorinated grease is applied to the surface of the coating layer.

  A Stirling engine according to a second aspect of the present invention includes first and second cylinders filled with a working gas, and the first cylinder disposed in the first cylinder, which is driven by a driving means and is in the first cylinder. And a displacer that is disposed in the second cylinder and that slides in the second cylinder in response to a gas pressure fluctuation of the working gas generated by sliding of the piston. In the sliding contact portion between the second cylinder and the displacer, at least one of the surface of the second cylinder and the surface of the displacer is a coating layer containing a tetrafluoroethylene-based resin. And a lubricant containing a fluorinated grease is applied to the surface of the coating layer.

  A Stirling engine according to a third aspect of the present invention includes first and second cylinders filled with a working gas, the first cylinder, the first cylinder disposed in the first cylinder, and driven by driving means. A piston that slides in the second cylinder, and a displacer that slides in the second cylinder in response to a gas pressure fluctuation of the working gas generated by sliding the piston. A displacer rod extending from the piston-side end surface of the displacer to support the displacer, and passing through an axial through hole provided in the piston, the displacer rod, the piston, In the sliding contact portion of the displacer rod, in the sliding contact portion between the displacer rod and the piston, At least one of the surface and the inner peripheral surface of the through hole of the piston is covered with a coating layer containing a tetrafluoroethylene-based resin, and a lubricant containing a fluorine-based grease is applied to the surface of the coating layer It is characterized by this.

  According to the present invention, it is possible to prevent the occurrence of energy loss due to friction in the sliding contact portion, and thus it is possible to provide a Stirling engine that can be operated with high efficiency.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following embodiment, a Stirling refrigerator that is an application example of a Stirling engine will be described as an example.

  FIG. 1 is a schematic cross-sectional view of a Stirling refrigerator in an embodiment of the present invention. 2 to 4 are enlarged sectional views of the sliding contact portion of the Stirling refrigerator in the present embodiment, and each figure is an enlarged sectional view corresponding to regions A, B, and C shown in FIG. It is.

  First, the structure of the Stirling refrigerator in the present embodiment will be described with reference to FIG. As shown in FIG. 1, the Stirling refrigerator 100 according to the present embodiment has a casing 110 filled with a working gas such as helium gas, hydrogen gas, or nitrogen gas as a working medium. A cylinder 120 filled with working gas is disposed inside the casing 110. The cylinder 120 is divided into a piston-side cylinder 120A, which is a first cylinder into which the piston 130 is inserted, and a displacer-side cylinder 120B, which is a second cylinder into which the displacer 140 is inserted, and these piston-side cylinders 120A. The piston-side cylinder 120A and the displacer-side cylinder 120B are arranged coaxially so that the center axis of the cylinder and the center axis of the displacer-side cylinder 120B overlap.

  A compression space 150 and an expansion space 160 are provided outside both ends of the displacer 140 in the reciprocating direction of the displacer 140 in the cylinder 120. The compression space 150 is partitioned by the piston 130 and the displacer 140 and is surrounded by the heat radiator 152. The radiator 152 is for removing the compression heat generated in the compression space 150. The expansion space 160 is partitioned by the displacer 140 and the closed end of the displacer side cylinder 120 </ b> B, and is surrounded by the heat absorber 162. The heat absorber 162 is for taking out the cold heat generated in the expansion space 160. The compression space 150 and the expansion space 160 communicate with each other via a working gas flow path provided on the radially outer side of the displacer side cylinder 120B, and a regenerator 180 is disposed on the flow path. The regenerator 180 is a kind of heat storage material that temporarily accumulates heat of the working gas passing through the inside.

  A linear motor 170 is installed in the back pressure space 112 located on the radially outer side of the piston-side cylinder 120A. The linear motor 170 includes a movable magnet 171 positioned at the tip of a magnet holder provided on the piston 130, an inner yoke 172 and an outer yoke 173 positioned so as to sandwich the movable magnet 171, and the inner yoke 172 and the outer yoke 173. And a piston driving coil 174 connected to a power source. When electric power is supplied to the piston driving coil 174 from an external power source, the linear motor 170 is operated, and when the movable magnet 171 is driven, the piston 130 reciprocates in the piston-side cylinder 120A in the axial direction. Since the piston 130 is fixed to the casing 110 via the flat spring 191, the piston 130 slides smoothly in the piston-side cylinder 120A with a predetermined period.

  The displacer 140 reciprocates in the displacer side cylinder 120B in the axial direction in response to the gas pressure fluctuation of the working gas generated by the reciprocating motion of the piston 130 described above. The displacer 140 is supported by a displacer rod 145 extending from an end face located on the piston 130 side of the end face in the reciprocating direction. The displacer rod 145 is inserted through the through-hole 134 provided in the piston 130, and the tip thereof is fixed to the casing body 110 via a flat spring 192 or the like. The displacer side cylinder 120B slides smoothly at a predetermined cycle with a predetermined phase difference.

  When the piston 130 is driven by the linear motor 170, the piston 130 moves toward the compression space 150 and compresses the working gas in the compression space 150. The compressed working gas moves through the regenerator 180 to the expansion space 160. The working gas that has flowed into the expansion space 160 expands as the displacer 140 moves toward the compression space 150, and the working gas temperature in the expansion space 160 also decreases as the pressure decreases. Therefore, by repeating the above-described operation, the working gas temperature in the expansion space 160 is cooled to a very low temperature, and accordingly, a very low temperature is also generated in the heat absorber 162.

  In the Stirling refrigerator 100 in the present embodiment described above, the sliding contact portion is constituted by the outer peripheral surface of the piston 130 and the inner peripheral surface of the piston-side cylinder 120A, and the cooling efficiency of the Stirling refrigerator 100 is improved. In order to achieve this, it is essential to improve the slidability at the sliding contact portion between the piston 130 and the piston-side cylinder 120A. Therefore, in the Stirling refrigerator 100 in the present embodiment, as shown in FIG. 2, the inner surface 121a of the base 121 of the piston side cylinder 120A is coated with a tetrafluoroethylene resin (PTFE resin). The lubricant is covered with the layer 122, the outer surface 131 a of the base 131 of the piston 130 is covered with a coating layer 132 containing a tetrafluoroethylene-based resin, and a fluorine-based grease is included between the coating layers 122, 132. The grease application layer 200 is formed by applying

  Further, in the Stirling refrigerator 100 according to the present embodiment, sliding contact portions are also formed on the outer peripheral surface of the displacer 140 and the inner peripheral surface of the displacer side cylinder 120B, and the cooling efficiency of the Stirling refrigerator 100 is improved. In order to achieve this, it is necessary to improve the slidability at the sliding contact portion between the displacer 140 and the displacer side cylinder 120B. Therefore, in the Stirling refrigerator 100 according to the present embodiment, as shown in FIG. 3, the inner surface 121a of the base 121 of the displacer side cylinder 120B is covered with a coating layer 122 containing a tetrafluoroethylene-based resin. At the same time, the outer peripheral surface 141a of the base 141 of the displacer 140 is covered with a coating layer 142 containing a tetrafluoroethylene-based resin, and a lubricant containing a fluorine-based grease is applied between the coating layers 122, 142. The grease application layer 200 is formed.

  Furthermore, in the Stirling refrigerator 100 according to the present embodiment, a sliding contact portion is also formed on the outer peripheral surface of the displacer rod 145 and the inner peripheral surface of the piston 130, that is, the surface of the through hole 134 of the piston 130. In order to improve the cooling efficiency of the machine 100, it is necessary to improve the slidability at the sliding contact portion between the displacer rod 145 and the piston 130. Therefore, in the Stirling refrigerator 100 according to the present embodiment, as shown in FIG. 4, the surface 146a of the base 146 of the displacer rod 145 is covered with a coating layer 147 containing a tetrafluoroethylene-based resin, and the piston 130 The surface 131b on the inner peripheral side of the base 131 is covered with a coating layer 132 containing a tetrafluoroethylene-based resin, and a lubricant containing a fluorine-based grease is applied between the coating layers 147 and 132, thereby applying a grease application layer. 200 is formed.

  Here, the bases 121, 131, and 141 of the cylinder 120, the piston 130, and the displacer 140 are parts constituting the outer shell of the cylinder 120, the piston 130, and the displacer 140, and are formed of a hard material. The bases 121, 131, and 141 are usually formed of a metal material such as a stainless alloy, but may be formed of a hard resin material, and the material is particularly limited. It is not something.

  Further, the coating layers 122, 132, 142 formed on the surfaces of the base parts 121, 131, 141 may contain any resin material such as epoxy resin, polyamideimide resin, acrylic resin, etc. as a main component, at least as described above. What is necessary is just to contain the tetrafluoroethylene-type resin as a part of the component.

  Further, the lubricant containing the fluorine-based grease applied on the coating layers 122, 132, 142 only needs to contain tetrafluoroethylene as a thickener, and the base oil is polyfluoroether, Any of mineral oil, organic benzonite, silica gel, urea and the like may be used.

  As described above, a coating layer containing a tetrafluoroethylene-based resin is formed on the surface of a base portion facing each sliding contact portion, and a lubricant containing a fluorine-based grease is applied between these coating layers, As a result, the surface roughness of the sliding contact surface at each sliding contact portion is reduced and the coefficient of friction is greatly reduced, so that the slidability at each sliding contact portion is remarkably improved, and energy loss due to friction at the sliding contact portion is achieved. Will be prevented. Therefore, it is possible to improve the refrigeration efficiency of the Stirling refrigerator.

  In the above-described embodiment, a coating layer containing an ethylene tetrafluoride-based resin on both surfaces of the base portion facing each other in any of the sliding contact portions constituted by the cylinder, the piston, and the displacer. However, it is not always necessary to form a coating layer on both surfaces of the base, and even if the coating layer is formed only on one surface, the slidability can be improved. Figured.

  In the above-described embodiment, the case where the present invention is applied to all the sliding contact portions between the cylinder and the piston, between the cylinder and the displacer, and between the piston and the displacer rod has been described as an example. Thus, there is no necessity to apply the present invention to all the sliding contact portions, and the refrigeration efficiency of the Stirling refrigerator can be improved even when any one or two locations are used.

  The present inventor conducted a verification experiment for confirming how much the improvement of the slidability contributes to the refrigeration efficiency of the Stirling refrigerator. In the following, the results will be described.

Example 1
As Example 1, the present inventor prepared a free piston type Stirling refrigerator having a Teflon (registered trademark) coating on the inner peripheral surface of the cylinder and the outer peripheral surface of the displacer rod. Fluorine-based grease was applied at a thickness of 2 μm to 5 μm at all three sliding contact portions between the displacer and between the piston and the displacer rod, and a verification experiment was performed using this. As a result, even when the piston amplitude is switched to various amplitudes, the output of the Stirling refrigerator is improved by about 10% over the entire range of the piston amplitude, compared to the case where the coating layer and the grease are not applied, and the refrigeration efficiency Was confirmed to improve by about 4%.

(Example 2)
As Example 2, the present inventor prepared a free piston type Stirling refrigerator in which a Teflon (registered trademark) coating was applied to each of an outer peripheral surface of a piston, an outer peripheral surface of a displacer, and an outer peripheral surface of a displacer rod. Fluorine-based grease was applied at a thickness of 2 μm to 5 μm at all three sliding contact portions between the piston, between the cylinder and the displacer, and between the piston and the displacer rod, and a verification experiment was performed using this. As a result, even when the piston amplitude is switched to various amplitudes, the output of the Stirling refrigerator is improved by about 10% over the entire range of the piston amplitude, compared to the case where the coating layer and the grease are not applied, and the refrigeration efficiency Was confirmed to improve by about 4%.

(Example 3)
As Example 3, the present inventor applied Teflon (registered trademark) coating to each of the inner peripheral surface of the cylinder, the outer peripheral surface of the piston, the inner peripheral surface of the piston, the outer peripheral surface of the displacer, and the outer peripheral surface of the displacer rod. Prepare a free piston type Stirling refrigerator, and apply fluorine-based grease to a thickness of 2 μm to 5 μm at all three sliding contact portions between the cylinder and the piston, between the cylinder and the displacer, and between the piston and the displacer rod, A verification experiment was conducted using this. As a result, even when the piston amplitude is switched to various amplitudes, the output of the Stirling refrigerator is improved by about 15% over the entire range of the piston amplitude, compared with the case where the coating layer and the grease are not applied, and the refrigeration efficiency is improved. Has been confirmed to improve by about 6%.

  In the above-described embodiment, the Stirling refrigerator in which the first and second cylinders are separately formed has been described as an example. However, these are not necessarily divided, The first and second cylinders may be integrated. In the above-described embodiment, the Stirling refrigerator in which the piston and the displacer are arranged on the same axis is described as an example. However, it is not always necessary to arrange them on the same axis. The first and second cylinders may be arranged on different axes.

  Although not particularly mentioned in the above-described embodiment, the present invention provides a fine hole for injecting high-pressure gas on the sliding contact surface with the piston or / and the cylinder of the displacer. Of course, the present invention can also be applied to a Stirling refrigerator having a bearing.

  In the above-described embodiment, the case where the present invention is applied to a Stirling refrigerator that is an application example of a Stirling engine has been described as an example. However, the present invention is applied to a Stirling engine itself as a heat engine. Of course it is also possible to do.

  Thus, the one embodiment disclosed this time is illustrative in all respects and is not restrictive. The technical scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a schematic cross section of the Stirling refrigerator in the embodiment of the present invention. It is an expanded sectional view of the area | region A in FIG. 1 of the Stirling refrigerator in embodiment of this invention, and is an expanded sectional view of the sliding contact part comprised with a piston and a cylinder. It is an expanded sectional view of the area | region B in FIG. 1 of the Stirling refrigerator in embodiment of this invention, and is an expanded sectional view of the sliding contact part comprised by a displacer and a cylinder. It is an expanded sectional view of the area | region C in FIG. 1 of the Stirling refrigerator in embodiment of this invention, and is an expanded sectional view of the sliding contact part comprised with a piston and a displacer rod.

Explanation of symbols

  100 Stirling refrigerator, 110 casing, 112 back pressure space, 120 cylinder, 120A piston side cylinder, 120B displacer side cylinder, 121, 131, 141, 146 base, 121a, 131a, 131b, 141a, 146a surface, 122, 132, 142,147 coating layer, 130 piston, 134 through hole, 140 displacer, 145 displacer rod, 150 compression space, 152 radiator, 160 expansion space, 162 heat absorber, 170 linear motor, 171 movable magnet, 172 outer yoke, 172 inner Yoke, 173 outer yoke, 174 piston drive coil, 180 regenerator, 191, 192 flat spring, 200 grease application layer.

Claims (3)

First and second cylinders filled with working gas, a piston disposed in the first cylinder, driven by a driving means and sliding in the first cylinder, and in the second cylinder A Stirling engine provided with a displacer that slides in the second cylinder in response to a gas pressure fluctuation of the working gas generated by sliding of the piston,
In the sliding contact portion between the first cylinder and the piston, at least one of the surface of the first cylinder and the surface of the piston is covered with a coating layer containing a tetrafluoroethylene-based resin. A Stirling engine in which a lubricant containing a fluorine-based grease is applied to the surface of a coating layer. First and second cylinders filled with working gas, a piston disposed in the first cylinder, driven by a driving means and sliding in the first cylinder, and in the second cylinder A Stirling engine provided with a displacer that slides in the second cylinder in response to a gas pressure fluctuation of the working gas generated by sliding of the piston,
In the sliding contact portion between the second cylinder and the displacer, at least one of the surface of the second cylinder and the surface of the displacer is covered with a coating layer containing a tetrafluoroethylene-based resin. A Stirling engine in which a lubricant containing a fluorine-based grease is applied to the surface of a coating layer. First and second cylinders filled with working gas, a piston disposed in the first cylinder, driven by a driving means and sliding in the first cylinder, and in the second cylinder A displacer that slides in the second cylinder in response to a gas pressure fluctuation of the working gas caused by sliding of the piston, and an end surface on the piston side of the displacer for supporting the displacer A Stirling engine provided with a displacer rod extending from the axial through hole provided in the piston,
At the sliding contact portion between the displacer rod and the piston, at least one of the surface of the displacer rod and the inner peripheral surface of the through hole of the piston is covered with a coating layer containing a tetrafluoroethylene-based resin, A Stirling engine in which a lubricant containing a fluorinated grease is applied to the surface of the coating layer.

Images