JP2626364B2 - Linear motor compressor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear motor compressor for compressing a refrigerant to be supplied to an expander in a Stirling refrigerator, and more particularly to a measure for increasing the efficiency of a linear motor as a drive source.

[0002]

2. Description of the Related Art Conventionally, a free displacer type Stirling refrigerator is known as a kind of small refrigerator which generates cryogenic temperature. As an example of this refrigerator, for example, “Refrigerator for Cryogenic Sensor”
s "(NASA Conference Publication 2287). This refrigerator, as shown in FIG.
The compressor (a) compresses the refrigerant gas and the expander (k) expands the refrigerant gas discharged from the compressor (a). The compressor (a) includes, for example, a closed casing (b), a cylinder (c) formed in the casing (b), and a reciprocally fitted fit in the cylinder (c). (C) A piston (e) for forming a compression chamber (d) in the inner space and a linear motor (f) as a drive source for reciprocating the piston (e) are provided. The linear motor (f) has one annular permanent magnet (g) disposed around the cylinder (c),
The magnet (g) generates a magnetic field in a cylindrical gap concentric with the center of the cylinder (c). A substantially inverted cup-shaped bobbin (h) integrally fixed to the piston (e) at the center is reciprocally disposed in the gap, and a drive coil (i) is provided on the outer periphery of the bobbin (h). Is wrapped around. Further, a piston formed of a coil spring for elastically supporting the piston (e) reciprocally between a bottom outside of the bobbin (h) (an opposite side to the piston (e)) and an inside bottom of the casing (b). A spring (j) is provided, and an alternating current of a predetermined frequency is applied to the drive coil (i) through the conductors (i1) and (i1). Further, the piston (e) is linearly reciprocated in the cylinder (c) by driving the bobbin (h) to generate a gas pressure of a predetermined cycle in the compression chamber (d).

On the other hand, the expander (k) has a cylindrical cylinder (l) in which a space inside the cylinder (l) is divided into an expansion chamber (m) and a working chamber (n). A free displacer (o) is mounted so as to reciprocate. The displacer (o) is filled with a metal regenerator (o1) (regenerative heat exchanger) and communicates the regenerator (o1) with the expansion chamber (m) and the working chamber (n). The communication holes (o2) and (o3) are opened. In the working chamber (n), a displacer spring (p) composed of a coil spring elastically supporting the displacer (o) in a reciprocating manner is provided. Further, the working chamber (n) is connected to the compression chamber (d) of the compressor (a) via the coupling pipe (q), and the free displacer ( O) is reciprocated to expand the refrigerant gas in the expansion chamber (m), thereby generating cold in the cold head at the tip of the cylinder (l).

[0004]

Incidentally, a linear motor (f) which is a driving source of such a linear motor compressor is used.
As means for achieving higher efficiency, it is conceivable to increase the magnetic field intensity generated by the permanent magnet (g) or to make the magnetic flux density distribution uniform. That is, by increasing the size of the permanent magnet (g), the magnetic field strength around the permanent magnet (g) is increased, and the ratio between the output of the compressor (a) and the electric input to the linear motor (f) is increased. This improves the efficiency of the linear motor (f) by increasing the efficiency of the linear motor (f), or by increasing the size of the yoke to avoid the saturation of magnetic flux and increasing the size of the permanent magnet. It is conceivable to aim for.

However, in such a configuration, a large space for arranging the permanent magnet (g) and a space for the yoke section must be ensured, which leads to an increase in the size of the compressor. There is a problem that the reduction in size and weight intended for the above is hindered.

[0006] The present invention has been made in view of these points, and by making the magnetic flux density distribution uniform,
An object of the present invention is to obtain a linear motor compressor that can increase the efficiency of a linear motor without increasing the size of a permanent magnet.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention reduces the size of each magnet while maintaining the magnetic field strength by dividing and arranging permanent magnets along a magnetic circuit. The magnetic flux density distribution among the magnets is made uniform. Specifically, a fixed body (2) having a reciprocally movable piston (6) therein, a magnet (13) forming a magnetic circuit using the fixed body (2) as a yoke, and the piston ( 6) and a coil (15) disposed in the magnetic field of the magnetic circuit. Then, the coil (1) is attached to the fixed body (2).
First yokes portion facing the one side of the 5) and (4b), co
Of the second yoke portion (4
a) is provided. Also, the magnet (13) has a first
Of the first yoke portion (4b).
b) projecting from one side of the coil (15) towards one side
The magnet (13a) and the second yoke portion (4a) are provided.
From the second yoke portion (4a) to the coil (15).
A second magnet (13b) protruding toward the side surface.
Configuration.

[0008]

With the above arrangement, in the present invention, the piston (6) reciprocates inside the fixed body (2) and changes the volume of the compression chamber as the compressor is driven. Thus, the fluid in the compression chamber is compressed, and the compressed fluid is discharged toward the expander. In the linear motor as a driving source of the compressor, the magnet (13) includes the first yoke (4).
b) a first magnet (13a) provided in
Since each of the magnets (13a) and (13b) is reduced in size, the magnetic flux is maintained without changing the total volume of the magnets (13) because the second magnet (13b) provided in the portion (4a) is provided. Since the density distribution can be made uniform and the magnetic field strength can be improved while suppressing the occurrence of magnetic flux saturation, the efficiency of the linear motor can be improved without increasing the size of the compressor. In addition, each magnet (13
a, 13b) are coils from the yoke portion (4a, 4b).
Since it protrudes toward (15), magnetic
As a result, the fixed body (2) and each magnet (13
a, 13b) from the magnetic circuit formed by
Field becomes small, and the integration rate of the magnetic flux density of the magnetic circuit increases.
I can do it.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a compressor (1) for a Stirling refrigerator according to the present embodiment. This compressor (1) constitutes a refrigerator in combination with a conventionally known free displacer type expander (not shown) (see FIG. 5). The compressor (1) has a cylindrical casing (2) as a fixed body. This casing (2) is provided with left and right end portions (3), (3) and a cylinder portion (4). The end face part (3),
(3) is a pair of left and right disc-shaped portions having substantially the same configuration,
They are arranged concentrically and face each other at a predetermined interval in the center line direction. The cylinder portion (4) is located between the end portions (3) and (3). The cylinder part (4) is made of pure iron, and is connected to the outer cylinder (4a) as a second yoke part and the first yoke.
The inner cylinder (4b) as an iron part is connected by a donut-shaped connecting portion (4c) to be integrally formed. The inner cylinder (4b) is a part that becomes an original cylinder, and the inside thereof is formed in a piston insertion hole (5). A pair of left and right cylindrical pistons (6) and (6) having a bottomed center hole (6a) are inserted into the piston insertion holes (5) of the cylinder inner cylinder (4b), respectively. A portion surrounded by the cylinder inner cylinder (4b) between the pistons (6) and (6) is a compression chamber (7). The outer diameter of the piston (6) is formed slightly smaller than the inner diameter of the cylinder inner cylinder (4b), and a small gap of, for example, about 10 μm is formed between the two. Is sealed by a fluid seal or the like so as to secure the airtightness of the compression chamber (7).

A gas passage (8) extending in a radial direction from the piston insertion hole (5) is formed in the cylinder (4), and one end of the gas passage (8) is opened to the compression chamber (7). On the other hand, the other end of the gas passage (8) is connected to the connecting pipe (1).
0) is connected to an expander (not shown).

The left and right pistons (6), (6) are drivingly connected to linear motors (11), (11) as driving sources for reciprocatingly driving the pistons (6), (6).

[0012] The features of this embodiment include:
The outer cylinder (4a) and the inner cylinder (4) of the cylindrical casing (2)
b) and a permanent magnet (13) arranged to generate a magnetic field having a predetermined strength. The permanent magnet (13) includes a first magnet (13a) and a second magnet (13).
b). The first magnet (13a) is made of a thin cylindrical permanent magnet externally fitted to the outer peripheral surface of the inner cylinder (4b). Further, the second magnet (13b) is provided with the first magnet (13b).
At a position facing the magnet (13a), the first magnet (1
3a) and a thin cylindrical permanent magnet fitted to the inner peripheral surface of the outer cylinder (4a) of the cylinder portion (4) with a predetermined gap. That is, the first magnet (13a) is connected to the inner cylinder (4
From the outer peripheral surface of b), the second magnet (13b) is an outer cylinder.
(4a) are disposed so as to protrude from the inner peripheral surface, respectively.
I have. As a result, a magnetic field of a predetermined strength is applied between the magnets (13a) and (13b) by using the magnets (13a) and (13b) as a yoke for the outer cylinder (4a), the inner cylinder (4b) and the connecting portion (4c). It is configured to generate. In this way, when the permanent magnet (13) is divided into two parts and arranged, as shown in FIG. 2, each of the magnets (13a) and (13b)
In this case, the magnetic flux density can be made uniform, so that the occurrence of magnetic flux saturation locally can be suppressed. That is, it is possible to increase the magnetic field strength without increasing the total volume of the permanent magnet.

On the other hand, each of the pistons (6) has a flange portion (6b) extending radially outward from an end of the piston (6) opposite to the center of the cylinder portion (4). ) Extends concentrically with the piston (6) toward the center of the cylinder portion (4), and has a coil (15) at a distal end thereof at a position facing the first magnet (13a) and the second magnet (13b). ) Are arranged.

An alternating current of a predetermined frequency (for example, 50 Hz) corresponding to a natural frequency determined by the mass of each piston (6) and a spring constant of a coil spring (19) described later is applied to both linear motors (11) and (11). ) Coil (15), (1
By energizing in synchronization with 5), both pistons (6) and (6) are reciprocated in opposite directions at the above-mentioned natural frequency so as to generate a gas pressure of a predetermined cycle in the compression chamber (7). Is configured.

On the back surface of each of the pistons (6), (6), the piston (6) is elastically supported on the end surface (3) of the casing (2) so as to be able to reciprocate in the cylinder portion (4). The coil spring (19) is disposed. And
Within the stroke range in which the piston (6) reciprocates, the coil spring (19) is set to always contract from its natural length.

Next, the operation of this embodiment will be described.
With the start of operation of the refrigerator, the coils (15), (1) of both linear motors (11), (11) in the compressor (1)
5) An AC power supply having a predetermined frequency (50 Hz) is synchronously energized. With this energization, the first and second permanent magnets (1
The coils (15) and (15) and the pistons (6) and (6) reciprocate in opposite directions while deforming the coil spring (19) by the action of the magnetic field generated between 3a) and (13b). The two pistons (6), (6) advance and retreat in synchronization with each other in the cylinder portion (4), so that the volume of the compression chamber (7) increases and decreases, and the pressure in the compression chamber (7) has a predetermined period. Waves occur. The compression chamber (7) is connected to the connecting pipe (1).
0), the displacer in the expander reciprocates in the same cycle as the pressure wave of the compression chamber (7), and the expansion of the gas in the expansion chamber causes refrigeration. The reciprocating reciprocation of the displacer cools the cold head at the tip of the cylinder to a cryogenic level.

When the compressor (1) is operated, if the permanent magnet (13) is divided into two parts as described above, as shown in FIG.
Since the magnetic flux densities in a) and (13b) can be made uniform, the occurrence of magnetic flux saturation locally is suppressed. Thereby, saturation of the magnetic flux can be avoided without changing the total volume of the permanent magnet as compared with the conventional one, and thereby the magnetic field is increased, so that the output of the compressor (1) is reduced. The ratio with the electric input to the linear motor (11) can be increased.
High efficiency of 1) can be achieved. That is, according to the configuration of the present example, the efficiency of the linear motor (11) can be increased without increasing the size of the compressor (1). Ma
Each magnet (13a, 13b) is located on the outer circumference of the inner cylinder (4b).
Surface and from the inner peripheral surface of the outer cylinder (4a) respectively.
The magnetic path is concentrated on this protruding part.
And the casing (2) and each magnet (13a, 13
b) the leakage magnetic field from the magnetic circuit formed by
And the integration rate of the magnetic flux density of the magnetic circuit can be increased.
You. Therefore, the height of the linear motor (11) is
Efficiency can be improved.

The results of an experimental analysis performed to confirm the effects of the present embodiment will be described below. This analysis is a comparison of the isomagnetic flux density diagram and the magnetic flux density state between the arrangement of the permanent magnet (13) in the configuration of the present example and the arrangement of the conventional permanent magnet. FIGS. 2 (a) and 2 (b) show an isomagnetic flux density diagram and a magnetic flux density state in the configuration of the present example, respectively. FIG. 3 shows a permanent magnet arranged only inside the coil (15). FIG. 4 shows an equivalent magnetic flux density diagram and a magnetic flux density state in which permanent magnets are arranged only outside the coil (15). The total volume of each permanent magnet is the same. As can be seen from these figures, in the conventional configuration shown in FIGS. 3 and 4, the magnetic flux density is locally high (at the edge of the permanent magnet), and the magnetic flux is likely to be saturated in this portion. On the other hand, in this embodiment, the magnetic flux density distribution is made uniform. As described above, according to the configuration of the present example, the magnetic field strength can be increased by making the magnetic flux density distribution uniform, so that the motor efficiency can be improved without increasing the size of the compressor (1). Can be achieved.

In each of the embodiments described above, the compressor in which the piston (6) is reciprocated in the cylinder (4) has been described. However, the piston is fixed to the casing, and the piston is housed inside. And a compressor configured with a movable cylinder reciprocally movable with respect to the piston.

In the above-described embodiment, a non-contact type compressor in which a small gap is provided between the cylinder portion (4) and the piston (6) has been described. The present invention is not limited to this, and may be applied to a contact type compressor in which a small gap is not formed between a cylinder and a piston.

[0021]

As described above, according to the present invention,
Relative linear motor compressor, a magnet (13), first
A first magnet (13a) provided on the yoke portion (4b);
The second magnet (13) provided in the second yoke portion (4a)
b) , the magnets (13a) and (13b) can be reduced in size to reduce the size of the magnet (1).
The magnetic flux density distribution can be made uniform without changing the total volume of 3), whereby the saturation can be suppressed even if a magnet (13) having a volume in which the magnetic flux is saturated is conventionally used. Therefore, the magnetic field strength can be improved, and the efficiency of the linear motor can be improved without increasing the size of the compressor. In addition, each magnet (13a, 1
3b) is a coil (15) from the yoke portion (4a, 4b).
The magnetic path is concentrated on this protruding part
The fixed body (2) and each magnet (13a, 13
b) the leakage magnetic field from the magnetic circuit formed by
And the integration rate of the magnetic flux density of the magnetic circuit can be increased,
This can also improve the efficiency of the linear motor.
it can.

[Brief description of the drawings]

FIG. 1 is a sectional view of a linear motor compressor according to an embodiment of the present invention.

FIG. 2 shows an isomagnetic flux density diagram and a magnetic flux density state in the configuration of the present invention.

FIG. 3 is a diagram corresponding to FIG. 2 in a conventional configuration.

FIG. 4 is a diagram corresponding to FIG. 2 in another conventional configuration.

FIG. 5 is a vertical sectional side view showing a conventional Stirling refrigerator.

[Explanation of symbols]

 (1) Linear motor compressor (2) Casing (fixed body) (4a) Outer cylinder (second yoke part) (4b) Inner cylinder (first yoke part) (6) Piston (13) Permanent magnet (13a) First magnet (13b) Second magnet (15) Coil

Claims (1)

(57) [Claims] 1. A fixed body (2) having a reciprocally movable piston (6) therein, a magnet (13) using the fixed body (2) as a yoke portion to form a magnetic circuit, and the piston (2). 6)
And a coil (15) disposed in a magnetic field of the magnetic circuit, wherein the fixed body (2) faces one side of the coil (15).
The first yoke portion (4b) and the other side of the coil (15)
And a second yoke portion (4a) opposed to the first yoke portion. The magnet (13) is provided on the first yoke portion (4b).
From the first yoke portion (4b) to one of the coils (15).
A first magnet (13a) protruding toward the side surface;
The second yoke portion (4a) provided on the iron portion (4a);
Magnet protruding toward the other side of the coil (15) from the
(13b) A linear motor compressor comprising: