JP2008190727A - Linear motor compressor and stirling refrigerator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a linear motor compressor supporting a piston relative to a cylinder by using a fluid dynamic pressure bearing, which uses fewer parts and is reduced in size while using the fluid dynamic pressure bearing. <P>SOLUTION: This linear motor compressor includes: a casing 2; a linear motor 40 disposed in the casing 2; a compression piston 24 driven by the linear motor 40 to reciprocate in a compression cylinder 25, thereby compressing working gas in a compression space 22; and a fluid dynamic pressure bearing 50 supporting the compression piston 24 to the compression cylinder 25, wherein a dynamic pressure groove 70 to which the pressure of the working gas is applied, is formed in the compression piston 24, and the compression piston 24 is energized to rotate by the working gas introduced into the dynamic pressure groove 70 for rotation. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a linear motor compressor, and more particularly to a linear motor compressor configured to support a piston with respect to a cylinder using a fluid dynamic pressure bearing.

  In general, a Stirling refrigerator includes a compressor that generates pulsating pressure as main components, and an expander that includes a displacer that reciprocates out of phase with the pulsating pressure. And it is set as the structure which generate | occur | produces low temperature in expansion space by performing the reverse cycle (reverse Stirling cycle) of an external combustion engine within an expander. Since this Stirling refrigerator has high efficiency and a simple mechanism, there is an advantage that it is easy to reduce the size and weight. The compressor of the Stirling refrigerator is mainly a reciprocating reciprocating type, and a linear motor is often used as its driving method.

  Stirling refrigerators are used to cool infrared devices, high-temperature superconducting devices, various measuring instruments, and various gases. It is necessary to reduce wear between a cylinder and a piston that form a compression space for gas (refrigerant gas).

  Conventionally, as a method for reducing wear between a cylinder and a piston, as disclosed in Patent Document 1, an ejection hole for ejecting a working gas is provided in the piston, and the operation is performed between the piston and the cylinder through the ejection hole. There has been proposed a method for removing dust generated by wear by jetting gas. Further, as disclosed in Patent Document 2, there has also been proposed a method of supporting a piston in a state of being separated from a cylinder by using a fluid bearing.

  FIG. 5 shows a conventional example of a linear motor compressor for a Stirling refrigerator using a fluid dynamic pressure bearing. As shown in the figure, in the linear motor compressor 100, a compression piston 102 is disposed in a cylinder 105 formed in a casing 101. When the compression piston 102 is driven by a linear motor 103, an arrow X1 is provided. , X2 direction. Thereby, the volume of the compression space 106 is changed, and the linear motor compressor 100 is configured to generate pulsating pressure.

  In addition, as a means for preventing the compression piston 102 and the cylinder 105 from rubbing, the linear motor compressor 100 is provided with a fluid dynamic pressure bearing 104 and a rotary motor 107. The fluid dynamic pressure bearing 104 is constituted by a dynamic pressure groove formed in the compression piston 102, and the rotary motor 107 is configured to urge the compression piston 102 to rotate.

Therefore, when the compression piston 102 is rotated by the rotary motor 107, a high pressure layer of working gas is formed between the compression piston 102 and the cylinder 105 by the fluid dynamic pressure bearing 104, so that the compression piston 102 does not contact the cylinder 105. The bearing was supported, and thereby the friction between the compression piston 102 and the cylinder 105 was prevented.
JP 2003-166767 A JP 2002-188867 A

  The method using the fluid dynamic pressure bearing 104 as shown in FIG. 5 is an effective method because the friction between the compression piston 102 and the cylinder 105 is reliably prevented.

  However, in order for the fluid dynamic bearing 104 to function, it is necessary to rotate the compression piston 102. For this reason, conventionally, the rotary motor 107 for rotating the compression piston 102 has been provided. However, if the rotary motor 107 is provided, the linear motor compressor 100 is increased in size and the number of parts is increased, resulting in an increase in product cost. There was a problem.

  The present invention has been made in view of the above points, and it is an object of the present invention to provide a linear motor compressor and a Stirling refrigerator that can reduce the number of parts and reduce the size while using a fluid dynamic pressure bearing.

  In order to solve the above-described problems, the present invention is characterized by the following measures.

The invention described in claim 1
A casing,
A linear motor disposed in the casing;
A piston that reciprocates in a cylinder portion formed in the casing by being driven by the linear motor, and compresses the working gas filled in the compression space;
In a linear motor compressor having a fluid dynamic pressure bearing that supports a piston with respect to the cylinder portion,
A dynamic pressure groove to which the pressure of the working gas is applied is formed in the piston, and the piston is rotationally biased by the working gas introduced into the dynamic pressure groove.

The invention according to claim 2
The linear motor compressor according to claim 1,
A bearing dynamic pressure groove constituting the fluid dynamic pressure bearing is used as the dynamic pressure groove.

The invention according to claim 3
The linear motor compressor according to claim 1 or 2,
The cogging force generated by the linear motor acts to urge the cylinder toward the compression space.

A Stirling refrigerator according to the invention of claim 4
A cold head with a heat exchanger fixed inside,
The linear motor compressor according to any one of claims 1 to 3, connected to one side of the heat exchanger;
It is arranged in an expansion space connected to the other side of the heat exchanger, reciprocates in response to a gas pressure fluctuation of the working gas generated by the reciprocating movement of the piston, and the working gas is moved in the expansion space. And a displacer that is inflated.

  According to the present invention, since the dynamic pressure groove to which the pressure of the working gas is applied is formed on the piston, the piston can be rotated by the pressure of the working gas applied to the dynamic pressure groove. Therefore, even if the fluid dynamic pressure bearing is used, it is not necessary to separately provide a motor for rotating the piston, and the number of parts and the size of the linear motor compressor can be reduced.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 shows a linear motor compressor 20 according to an embodiment of the present invention, and FIG. 2 shows a Stirling refrigerator 1 to which the linear motor compressor 20 is applied. First, the structure of the Stirling refrigerator 1 will be described with reference to FIG.

  The Stirling refrigerator 1 generally includes a linear motor compressor 20, an expander 30, a cold head 60, and the like. Further, in this embodiment, the linear motor compressor 20 and the expander 30 are integrated into one casing 2.

  The cold head 60 has a heat exchanger 10 made of, for example, a wire mesh fixed inside a head cylinder 62. As this heat exchanger 10, for example, a wire mesh of 180 mesh or more can be used, and about 300 mesh is desirable.

  One side (the upper side in the figure) of the heat exchanger 10 is connected to the expander 30 through a pipe 67 and a communication path 38 formed in the casing 2. Further, the other side (the lower side in the figure) of the heat exchanger 10 is connected to the linear motor compressor 20 via a communication path 28 formed in the casing 2.

  The expander 30 is configured such that a displacer piston 34 is movably disposed in a displacer cylinder 35. The displacer piston 34 is supported by an elastic support 39 so as to be reciprocally movable. The elastic support 39 is constituted by an elastic support made of a leaf spring, a coil spring or the like.

  The expander 30 communicates with the expansion space 32 for expanding the refrigerant gas using a pipe 67. The pipe 67 connecting the displacer piston 34 and the cold stage 66 is configured to be smaller than the inner diameter of the cylinder 62 of the cold head 60 incorporating the heat exchanger 10 so as to reduce the invalid space volume and improve the refrigeration effect. Has been.

  Next, the configuration of the linear motor compressor 20 will be described with reference to FIGS. 1 and 3 in addition to FIG. The linear motor compressor 20 is composed of a compression cylinder 25, a bobbin 27, a linear motor 40, a rotational dynamic pressure groove 70, and the like.

  The compression cylinder 25 is disposed in the compression cylinder 25 formed in the casing 2 so as to be movable in the directions of arrows X1 and X2 in the figure. A compression space 22 is formed between the compression cylinder 25 and the left end 24a of the compression piston 24 in the figure, and this compression space 22 is communicated to the lower side of the heat exchanger 10 via a communication passage 28. . In the present embodiment, the compression piston 24, the compression cylinder 25, the displacer piston 34, and the displacer cylinder 35 are configured to face each other on the same axis.

  The bobbin 27 is a cylindrical member formed integrally with the compression piston 24 and is configured to surround the compression cylinder 25. A magnet 41 is disposed on the bobbin 27. In addition, a coil 42 is disposed at an outer peripheral position facing the magnet 41 of the compression cylinder 25 and an inner surface position facing the magnet 41 of the casing 2. Each 42 is disposed on a yoke 43 made of a magnetic material.

  The magnet 41 and the coil 42 constitute a linear motor 40. The linear motor 40 drives the bobbin 27 in the directions of arrows X1 and X2 in the figure. Therefore, the compression piston 24 formed integrally with the bobbin 27 is also driven in the directions of arrows X1 and X2 in the figure by the linear motor 40. Is done. By this linear motor 40, the compression piston 24 is driven at a drive frequency of 20 to 100 Hz, for example.

  Further, the linear motor 40 is set so that the cogging force generated acts on the compression space 22 side (in the direction of the arrow X1). This cogging force acts as a kind of spring force that urges the compression piston 24 in the direction of the arrow X1. The weight of each of the pistons 24, 34, the elastic constant of the elastic support 39, and the cogging force generated by the linear motor 40 are such that the operation phase difference between the compression piston 24 and the displacer piston 34 is a predetermined angle (for example, 30 (Degrees to 100 degrees).

  In the above configuration, when the compression piston 24 is driven by the linear motor 40 to reciprocate in the directions of the arrows X1 and X2 via the bobbin 27, pressure pulsating to the working gas (cooling gas such as helium gas) is generated in the compression space 22. To do. Since the displacer piston 34 reciprocates with a predetermined phase difference with respect to the compression piston 24 as described above, a reverse Stirling cycle is performed inside the expander 30. Therefore, cold is generated in the expansion space 32 communicating with the linear motor compressor 20 and the expander 30, and the cold stage 66 becomes extremely cold.

  Here, attention is paid to the compression piston 24. The linear motor compressor 20 according to this embodiment uses a fluid dynamic bearing 50 as a means for bearing the compression piston 24 in the compression cylinder 25. The fluid dynamic pressure bearing 50 includes a bearing dynamic pressure groove 51 formed on the surface of the compression piston 24.

  When the compression piston 24 rotates, a high pressure layer of working gas is formed between the compression piston 24 and the compression cylinder 25 by the bearing dynamic pressure groove 51 that forms the fluid dynamic pressure bearing 50. Thereby, the compression piston 24 is supported by the compression cylinder 25 in a non-contact manner, and friction between the compression piston 24 and the compression cylinder 25 is prevented.

  In the linear motor compressor 20 according to this embodiment, a plurality of rotational dynamic pressure grooves 70 are formed in the vicinity of the end 24 a of the compression piston 24 over the entire circumference. The rotational dynamic pressure groove 70 is formed on the surface of the compression piston 24 so as to have a predetermined angle with respect to the rotation axis X of the compression piston 24 (indicated by a one-dot chain line in the figure) (What is the rotation axis X?) Non-parallel). Furthermore, the end portion on the end portion 24 a side of each of the plurality of rotational dynamic pressure grooves 70 formed is configured to communicate with the compression space 22.

  As described above, the compression space 22 is filled with the high-pressure working gas as the compression piston 24 reciprocates in the X1 and X2 directions. Therefore, the pressure P of the working gas is applied to the end 24a of the compression piston 24 as shown in FIG. Further, since the end portion in the X1 direction of the rotational dynamic pressure groove 70 in the drawing is open to the compression space 22, the high-pressure working gas is introduced into the rotational dynamic pressure groove 70 as shown in FIG.

  At this time, the high-pressure working gas has a predetermined angle with respect to the rotation axis X, in other words, abuts against the side wall of the rotational dynamic pressure groove 70 formed obliquely with respect to the working gas introduction direction (X2 direction). , Where F is the force acting on the side wall of the rotational dynamic pressure groove 70 by the high-pressure working gas per unit area, this force F is divided into the forces indicated by Fa and Fb in FIG. The component force Fc is orthogonal to the rotation axis X. This component force Fc acts as a force for rotating the compression piston 24, whereby the compression piston 24 starts to rotate in the direction of arrow A in the figure.

  Thus, the linear motor compressor 20 according to the present embodiment rotates the compression piston 24 using the pressure of the working gas in the compression space 22. Further, as the compression piston 24 rotates, the fluid dynamic pressure bearing 50 supports the compression piston 24 with respect to the compression cylinder 25 in a non-contact manner as described above. Therefore, even if the fluid dynamic pressure bearing 50 is used, it is not necessary to separately provide a motor (see the rotary motor 107 in FIG. 5) for rotating the compression piston 24 as in the prior art, and the number of parts of the linear motor compressor 20 is reduced. Can be reduced and downsized.

  In the embodiment described above, a configuration is shown in which a fluid dynamic pressure bearing 50 for bearing the compression piston 24 with respect to the compression cylinder 25 and a rotation dynamic pressure groove 70 for rotationally biasing the compression piston 24 are separately provided. However, as in the linear motor compressor 20 </ b> A according to the modification shown in FIG. 4, the rotational dynamic pressure groove 70 can also be used as the bearing dynamic pressure groove 51 that constitutes the fluid dynamic pressure bearing 50. It is.

  In the Stirling refrigerator 1 shown in FIG. 2, the configuration in which only the compression piston 24 is reciprocated in the X1 and X2 directions by the linear motor 40 is shown. However, the expander 30 is also a bobbin integrated with the displacer piston 34. Alternatively, the displacer piston 34 may be actively driven by providing a magnet, a coil, and the like constituting the linear motor.

  Further, the cold head 60 may be separated from the linear motor compressor 20 and the expander 30, and the cold head 60 and the linear motor compressor 20, and the cold head 60 and the expander 30 may be connected by piping or the like.

FIG. 1 is a cross-sectional view of a linear motor compressor according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of a Stirling refrigerator that is an embodiment of the present invention. FIG. 3 is a diagram for explaining the principle of a linear motor compressor according to an embodiment of the present invention. FIG. 4 is a sectional view showing a modification of the linear motor compressor shown in FIG. FIG. 5 is a cross-sectional view of a conventional linear motor compressor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stirling refrigerator 2 Casing 10 Heat exchanger 20, 20A Linear motor compressor 22 Compression space 24 Compression piston 25 Compression cylinder 30 Expansion machine 32 Expansion space 34 Displacer piston 35 Displacer cylinder 40 Linear motor 50, 50A Fluid dynamic pressure bearing 51 Dynamic pressure groove for bearing 60 Cold head 66 Cold stage 70 Dynamic pressure groove for rotation

Claims (4)

A casing,
A linear motor disposed in the casing;
A piston that reciprocates in a cylinder portion formed in the casing by being driven by the linear motor, and compresses the working gas filled in the compression space;
In a linear motor compressor having a fluid dynamic pressure bearing that supports a piston with respect to the cylinder portion,
A linear motor compressor characterized in that a dynamic pressure groove to which the pressure of the working gas is applied is formed in the piston, and the piston is rotationally biased by the working gas introduced into the dynamic pressure groove.   The linear motor compressor according to claim 1, wherein a dynamic pressure groove for a bearing constituting the fluid dynamic pressure bearing is used as the dynamic pressure groove.   The linear motor compressor according to claim 1, wherein a cogging force generated by the linear motor acts to urge the cylinder toward the compression space. A cold head with a heat exchanger fixed inside,
The linear motor compressor according to any one of claims 1 to 3, connected to one side of the heat exchanger;
It is arranged in an expansion space connected to the other side of the heat exchanger, reciprocates in response to a gas pressure fluctuation of the working gas generated by the reciprocating movement of the piston, and the working gas is moved in the expansion space. A Stirling refrigerator having a displacer for expansion.

Images