JPH05332626A - Linear motor compressor in stirling freezer - Google Patents

Abstract

PURPOSE:To increase an efficiency of a compressor by a method wherein a gas compression is carried out within a compression space in a linear motor compressor for a stirling freezer machine under an isothermal process. CONSTITUTION:There is provided a convection promoting means 15 for promoting a convection of gas in a space 17 around a cylinder 4 in a linear motor compressor C. Thermal radiation from the cylinder 4 acting as a wall part in the compression space 6 is promoted by the convection of gas around the compression space 6 and the gas compression at the compression space 6 is approached from its adiabatic stage to an isothermal stage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a linear motor compressor for compressing a refrigerant gas supplied to an expander in a Stirling refrigerator having an expander which produces cold by reciprocating motion of a displacer.

[0002]

2. Description of the Related Art Heretofore, this free displacer type Stirling refrigerator has been known as a kind of small refrigerator for generating cold at an extremely low temperature level. For example, as shown in Japanese Patent Publication No. 2-8155. It is a combination of a compressor that compresses a refrigerant gas in a predetermined cycle and an expander that expands the refrigerant gas discharged from the compressor.
The compressor is, for example, a cylinder arranged in a hermetically-sealed casing, and reciprocatingly fitted in the cylinder.
A piston for partitioning and forming a compression space is provided in the cylinder inner space, and the piston is reciprocally driven by a linear motor. This linear motor has a permanent magnet arranged around the cylinder, and this magnet generates a magnetic field in a cylindrical gap concentric with the center of the cylinder. A cylindrical bobbin, which serves as a coil mounting member and is integrally fixed to the piston, is reciprocally provided in the gap so as to be reciprocable, and a coil is wound around the outer circumference of the bobbin. Further, between the piston and the casing, a coil spring for elastically supporting the piston so as to reciprocate is installed.
By energizing the coil with an alternating current of a specified frequency, the coil and bobbin are driven by the action of the magnetic field passing through the gap to reciprocate the piston in the cylinder at the resonance frequency determined by the mass of the moving part and the spring constant of the coil spring. Then, the gas pressure of a predetermined cycle is generated in the compression space.

On the other hand, the expander has a cylindrical cylinder, and a free displacer for partitioning an internal space into an expansion space and an operating space is reciprocally fitted in the cylinder.
The displacer houses therein a regenerator that communicates with the expansion space and the working space, respectively. In addition, a coil spring that elastically supports the displacer so as to reciprocate is disposed in the working space. Further, the working space is connected to the compression space of the compressor via a connecting pipe, and by causing the displacer to reciprocate by the refrigerant gas pressure of the constant cycle from the compressor to expand the refrigerant gas in the expansion space. The cold head at the tip of the cylinder is designed to generate cold.

[0004]

However, in the above-described conventional linear motor compressor, heat is not rapidly removed from the compressed gas in the compression stroke in which the piston compresses the gas in the compression space, and the gas is adiabatic process. It is compressed in a state close to. Therefore, there is a limit to increase the efficiency of the compressor.

The present invention has been made in view of the above problems, and an object thereof is to increase the efficiency of a compressor by providing a means for performing gas compression in a compression stroke in a state close to an isothermal process. Is to let.

[0006]

In order to achieve the above-mentioned object, the solution means of the invention of claim 1 promotes the convection of gas in the space around the wall of the expansion space, and the convection of this gas causes the expansion space wall to expand. The heat release from the part is promoted.

That is, according to the present invention, as shown in FIG. 1, the cylinder (4) provided in the casing (1).
And a piston (5) for defining and forming a compression space (6) in the cylinder (4), and elasticity for elastically supporting the piston (5) reciprocally in the cylinder (4) with respect to the casing (1). A linear motor (10) having a supporting means (14), a magnet (11) and a coil (13), and reciprocatingly driving the piston (5) by supplying alternating current of a predetermined frequency to the coil (13). A linear motor compressor for a Stirling refrigerator is a prerequisite.

A convection promoting means (15) is provided for promoting the convection of gas at least in the space (17) around the cylinder (4) corresponding to the compression space (6).

According to a second aspect of the present invention, the convection promoting means (15) is connected to the piston (5) or the linear motor (1).
0) is a member integrally connected to the moving part (12).

[0010]

With the above construction, in the invention of claim 1, the piston (5) reciprocates in the cylinder (4) due to the energization of the linear motor (10) with an alternating current of a predetermined frequency, and the piston (5) moves in the compression space (6). When the volume of the refrigerant gas is increased or decreased and the refrigerant gas therein is compressed in a predetermined cycle, the convection promoting means (15) is actuated along with the compression of the gas, so that at least the space (17) around the cylinder (4) is Convection of gas in the portion corresponding to the compression space (6) is promoted. This convection causes space (1
The separation of the gas boundary layer in 7) occurs and heat release from the cylinder (4), which is the wall of the compression space (6), is promoted, and the gas compression in the compression space (6) is changed from the adiabatic process to the isothermal process. They can be brought closer together, reducing the compressor input and increasing its efficiency.

In the invention of claim 2, the convection promoting means (15) is a piston (5) or a linear motor (10).
Since it is a member connected to the moving part (12), the movement of the piston (5) by the linear motor (10) can be used to promote the convection of the gas without the need for any other drive source, and the convection of the gas can be achieved. It can be promoted easily and inexpensively.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 shows the entire structure of a compressor (C) for a free displacer type Stirling refrigerator according to Embodiment 1 of the present invention. This compressor (C) is an expander (not shown). And constitute a refrigerator, and this refrigerator cools infrared sensing elements and various electromagnetic components to cryogenic levels. The compressor (C) has a closed cylindrical casing (1). This casing (1) is obtained by closing the upper open end of a bottomed cylindrical casing body (2) having a large and small two-stage structure with a lid member (3), and at the center of the bottom wall of the casing body (2), A cylinder (4) having a bottom wall formed by a part of the bottom wall of the casing body (2) is provided so as to project concentrically toward the lid member (3). A piston (5) is reciprocally fitted into the inside of the cylinder (4), and a portion defined by the piston (5) in the cylinder (4) is a compression space (6). .. The compression space (6) is connected to a communication hole (7) formed through the center of the bottom wall of the cylinder (4) (bottom wall of the casing body (2)), and the communication hole (7). It is connected to the expander via a connecting pipe (31).

The piston (5) is drivingly connected to a linear motor (10) as a drive source for reciprocally driving the piston (5). That is, the casing body (2)
An annular permanent magnet (11) is mounted in the upper large diameter portion (2a) such that the inner peripheral surface thereof is flush with the inner peripheral surface of the small diameter portion (2b) of the casing body (2). Magnet (1
1) Depending on the casing body (2) or cylinder (4)
Is used as a yoke to generate a magnetic field of a predetermined intensity between the inner peripheral surface of the magnet (11) and the cylinder (4).

A coil mounting member (12) having a diameter larger than that of the piston (5) is integrally connected to the upper end of the piston (5), and the coil (13) is attached to the outer periphery of the coil mounting member (12). ) Is wound so as to face the magnet (11), and by applying an alternating current of a predetermined frequency to this coil (13), resonance determined by the mass of the moving part and the spring constant of a coil spring (14) described later. The piston (5) is reciprocated within the cylinder (4) at a frequency to generate a gas pressure of a predetermined cycle in the compression space (6).

A coil spring (1) arranged concentrically with the piston (5) is provided at the center of the upper surface of the coil mounting member (12).
4) The lower end of 4) is locked and connected, and this spring (1
The upper end of 4) is connected to the lower surface of the lid member (3) so as not to come off. Therefore, the coil mounting member (1) integrated with the lid member (3) of the casing (1) and the piston (5) is used.
A coil spring (14) is hung between 2) and
The coil spring (14) constitutes an elastic support means for elastically supporting the piston (5) in the casing (1) so that the piston (5) can reciprocate.

Further, the upper end portion of the cylindrical convection promoting member (15) is provided with screws (16) on the outer peripheral portion of the lower surface of the coil mounting member (12) as the moving portion of the linear motor (10).
The convection promoting member (15) is attached integrally by (16), ..., and extends concentrically around the outer periphery of the cylinder (4) with a slight gap. The convection promoting member (15) allows the cylinder ( 4) In the surrounding space (17), the convection of gas in the portion corresponding to the compression space (6) is promoted.

Although not shown, the expander is a known one, and is a cylindrical cylinder having a bottom with a cold head at its tip, and is reciprocally fitted in the cylinder so that the space inside the cylinder is at the tip side. Of the expansion space and the working space on the base end side, a free displacer, a regenerator housed in the displacer, and a coil spring elastically supporting the displacer so as to reciprocate. The compression space (6) of the compressor (C) is connected to the working space via the connecting pipe (31), and the displacer is reciprocated in the cylinder by the refrigerant gas pressure from the compressor (C). By expanding the refrigerant gas in the expansion space by the cooling, cold is generated in the cold head at the tip of the cylinder.

Next, the operation of the above embodiment will be described. With the operation of the refrigerator, the coil (13) of the linear motor (10) in the compressor (C) is energized with an AC power source having a predetermined frequency. With this energization, the coil (13), the coil mounting member (12) and the piston (5) reciprocate in the cylinder (4) while expanding and contracting the coil spring (14) by the action of the magnetic field from the magnet (11). However, the volume of the compression space (6) increases or decreases due to the reciprocating movement of the piston (5), and when the piston (5) moves downward, the refrigerant inside the compression space (6) is compressed in a predetermined cycle to compress the compression space. A pressure wave having a predetermined period is generated in (6). Since the compression space (6) communicates with the working space inside the cylinder of the expander (not shown) through the connecting pipe (31), the inside of the cylinder of the expander is affected by the fluctuation of the gas pressure in the compression space (6). The displacer reciprocates while expanding and contracting the coil spring due to the differential pressure between the working space and the expansion space, adiabatic expansion of the gas in the expansion space causes cold, and by repeating the same cycle, the cold head at the tip of the cylinder It is gradually cooled to a cryogenic level.

In this embodiment, a convection promoting member (15) is arranged around the cylinder (4) in the compressor (C), and the convection promoting member (15) is a linear motor (10).
Since it is integrally attached to the coil attachment member (12), the convection promoting member (15) is compressed around the cylinder (4) as the piston (5) reciprocates in the cylinder (4). The space corresponding to the space (6) (1
The gas of 7) is agitated to promote its convection. Due to the convection of this gas, separation of the boundary layer occurs, and the compression space (6)
The heat release from the cylinder (4) that is the wall of the space to the space (17) is promoted, and the gas compression in the compression space (6) is approached from the adiabatic process to the isothermal process to lower the compressor input. The efficiency can be increased.

In that case, the convection promoting member (1
Since 5) is connected to the coil mounting member (12) as the moving part of the linear motor (10), it is not necessary to separately provide a driving source for driving the linear motor (10), and the piston ( The convection of gas can be promoted by utilizing the movement of 5), and the convection of gas can be facilitated at low cost.

In the above embodiment, the convection promoting member (1
5) is a coil mounting member (12) for the linear motor (10)
However, it may be connected to, for example, the piston (5).

(Embodiment 2) FIG. 2 shows Embodiment 2 of the present invention (note that the same parts as those in FIG. 1 are designated by the same reference numerals and detailed description thereof will be omitted), and a compressor (C) is used. It has an opposed piston, and the magnet (11) of the linear motor (10) is magnetically shielded from the outside.

That is, in this embodiment, the casing (1) is a hermetically-sealed one in which both open ends of the cylindrical casing body (2) are closed by the lid members (3) and (3), respectively. Inside this casing (1), a cylindrical cylinder (4) with both ends open is concentrically arranged.
A pair of pistons (5), (5) are reciprocally fitted into the cylinder (4) from both sides, and the piston (5), (5) is enclosed in a portion surrounded by the pistons (5), (5) in the cylinder (4). The compression space (6) is defined and formed, and the compression space (6) is formed.
Is connected to the expander through communication holes (7) and (8) and communication pipes (31) that penetrate through the central portions of the cylinder (4) and a yoke member (21) described later.

A linear motor (10) is connected to the rear surface of each piston (5). That is, a yoke member (21) concentric with the cylinder (4) is arranged around the cylinder (4), and the inner peripheral side of the yoke member (21) is cut out from both end surfaces thereof to near the center. The cylinder (4) is placed between the yoke member (21) and the cylinder (4).
Two annular spaces (17), (1
7) is formed, and an annular magnet (11) is fixed to the outer peripheral surface (yoke member (21)) of each space (17), and the outer peripheral surface of the cylinder (4) and the magnet are fixed by the magnet (11). (11) The magnetic field is generated in the space (17) between the inner peripheral surface. A bottomed cylindrical coil mounting member (12) is integrally mounted on the back surface of each piston (5), and the tip end of this coil mounting member (12) is an annular space (17) around the cylinder (4). A coil (13) is wound around the coil mounting member (12) in a range corresponding to the magnet (11). The tip of the coil mounting member (12) has an annular space (17).
A convection promoting member (15) that extends toward the inner back side and that promotes the convection of gas in the space (17) is formed by this tip portion.

A coil spring (14) is provided between the back surface of the coil mounting member (12) and the inner surface of the lid member (3) facing the coil mounting member (12).

Further, the outer circumference of the casing body (2) is covered with a thin-walled cylindrical magnetic shield member (22) made of permalloy or ferritic stainless steel.
The magnetic shield member (22) shields the magnetism from the magnet (11) of each linear motor (10) to the outside. The magnetic shield member (22) may be wound around the outer circumference of the casing body (2) in a single layer or multiple layers.

Therefore, in this embodiment, when the compressor (C) is in operation, alternating currents of the same frequency are supplied to both linear motors (10), (10), and both linear motors (1)
The pistons (5) integrated with the coils (13) and the coil mounting member (12) are driven by the driving means (0) and (10) so as to come into contact with and separate from the opposing pistons (5) in the cylinder (4). The gas reciprocates, whereby the gas in the compression space (6) is compressed in a predetermined cycle.

The convection promoting member (1) is attached to the tip of the coil mounting member (12) of each of the linear motors (10).
5), the convection promoting member (15) is provided.
Reciprocating in the annular space (17) promotes gas convection in the space (17), and promotes heat radiation from the cylinder (4) around the compression space (6), thereby isothermalizing the gas compression process. Can approach. Therefore, the same effect as that of the first embodiment can be obtained.

Further, in this embodiment, the casing (1)
Since the outer circumference of the casing body (2) is covered with a cylindrical magnetic shield member (22), the magnetic shield member (22) allows the magnetism from the magnets (11) of each linear motor (10) to the outside. Leakage can be suppressed. Therefore, even if the object to be cooled by the refrigerator is an infrared sensing element, an electromagnetic component, or the like that dislikes the magnetic field, the influence of the magnetic noise from the compressor (C) on them or the deterioration of the performance is reduced. It can be prevented well.

(Embodiment 3) FIG. 3 shows Embodiment 3 (see FIG. 2).
The same reference numerals are given to the same portions as those of (1) and detailed description thereof will be omitted), and in the second embodiment, the magnetic shield member (2
2) is arranged over the entire outer circumference of the casing body (2), whereas it is arranged on the outer circumference of the yoke member (21) inside the casing (1).

Therefore, in this embodiment, in addition to the same operational effects as those of the above-described second embodiment,
Since the magnetic shield member (22) is arranged on the outer circumference of the yoke member (21) and the magnetic shield member (22) is limited to the portion where the magnetic field from the magnet (11) is strong, the shield member having a small area. With (22), magnetic shielding can be effectively performed.

(Embodiment 4) FIG. 4 shows Embodiment 4 in which a magnetic shield member (22) is replaced with a magnet (11) and a coil (1).
It is arranged on the outer periphery of the yoke member (21) so as to cover only 3). Therefore, in this embodiment, the magnetic shield can be effectively performed with the shield member (22) having a smaller area than that of the second embodiment.

[0034]

As described above, according to the first aspect of the invention, by providing the convection promoting means for promoting the convection of the gas in the space around the cylinder in the linear motor compressor for the Stirling refrigerator, the compression is achieved. The convection of the gas in the part corresponding to the space promotes heat release from the cylinder, which is the wall of the compression space, and makes it possible to bring the gas compression in the compression space closer to the isothermal process from the adiabatic process. It is possible to improve.

According to the second aspect of the present invention, the convection promoting means is a member connected to the moving portion of the piston or the linear motor, so that the convection of the gas can be promoted by utilizing the movement of the piston by the linear motor. Convection can be facilitated at low cost.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a Stirling refrigerator compressor according to a first embodiment of the present invention.

FIG. 2 is a view corresponding to FIG. 1 showing a second embodiment.

FIG. 3 is a view corresponding to FIG. 1 showing a third embodiment.

FIG. 4 is a view corresponding to FIG. 1 showing a fourth embodiment.

[Explanation of symbols]

 (C) Compressor (1) Casing (4) Cylinder (5) Piston (6) Compression space (10) Linear motor (11) Magnet (12) Coil mounting member (moving part) (13) Coil (14) Coil spring (Elastic Support Means) (15) Convection Promoting Member (17) Space (29) Magnetic Shielding Member

Claims (2)

[Claims] 1. A cylinder (4) provided in a casing (1), a piston (5) partitioning and forming a compression space (6) in the cylinder (4), and the piston (5) being a cylinder ( 4) Having an elastic supporting means (14) for elastically supporting the casing (1) so that it can reciprocate in the casing (1), a magnet (11) and a coil (13), and supplying an alternating current of a predetermined frequency to the coil (13). In a linear motor compressor of a Stirling refrigerator provided with a linear motor (10) that reciprocally drives the piston (5) according to the above, a space (17) around the cylinder (4) corresponds to at least the compression space (6). A linear motor compressor for a Stirling refrigerator, which is provided with a convection promoting means (15) for promoting convection of gas in a portion to be heated. 2. The linear motor compressor for a Stirling refrigerator according to claim 1, wherein the convection promoting means (15) is integrally connected to the piston (5) or the moving part (12) of the linear motor (10). A linear motor compressor for a Stirling refrigerator, which is a member.