JPH0427776A - Linear motor compressor for stirling refrigerator - Google Patents

Abstract

PURPOSE:To miniaturize a compressor while suppressing the fatigue failure of a coil spring by setting the resonance frequency of the spring mass system of a linear motor with an air spring, and holding a piston at the neutral point of the reciprocation with the coil spring. CONSTITUTION:A piston 7 is elastically supported by an air spring 17 arranged between its back face and a casing 2, and the spring constant is secured by the air spring 17. The piston 7 is held at the neutral position of the reciprocation by a coil spring 27. The piston 7 is supported by the air spring 17, and the coil spring 27 is used to hold the piston 7 at the neutral position. No fatigue failure occurs on the coil spring 27. The space of the coil spring 27 can be reduced, and a compressor 1 can be miniaturized.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a Stirling refrigerator that has an expander that generates cryogenic cold by the reciprocating motion of a displacer. The present invention relates to a motor compressor, and particularly to an elastic support structure for a piston driven by a linear motor.

(Prior Art) This free displacer type Stirling refrigerator has been known as a type of small refrigerator that generates cryogenic cold. For example, as shown in FIG. 2, this refrigerator combines a compressor (a) that compresses refrigerant gas and an expander (k) that expands the refrigerant gas discharged from the compressor (a). The above compressor (a
) includes, for example, a sealed casing (b), a cylinder (C) formed in the casing (b), and a space inside the cylinder (c) that is fitted in the cylinder (C) so as to be reciprocally movable. The piston (e) defines a compression chamber (d), and a linear motor (f) serves as a drive source for reciprocating the piston (e). This linear motor (f) has an annular permanent magnet (g) placed around the cylinder (C).
The magnet (g) generates a magnetic field in a cylindrical gap concentric with the center of the cylinder (C). A cup-shaped bobbin (h) integrally fixed to the piston (e) at the center is arranged in the gap so as to be able to reciprocate, and a drive coil (i) is disposed on the outer periphery of the bobbin (h). is wrapped around it. Further, between the outer bottom surface of the bobbin (h) (opposite side to the piston (e)) and the inner bottom surface of the casing (b), a piston is formed of a coil spring for elastically supporting the piston <e> so as to be able to reciprocate. A spring (j) is installed, and by applying an alternating current of a predetermined frequency to the drive coil (i), the coil (i) and bobbin (h) are driven by the action of the magnetic field passing through the gap, and the piston ( By reciprocating the cylinder (e) within the cylinder (C), gas pressure is generated at a predetermined period in the compression chamber (d).

On the other hand, the expander (k) has a cylindrical cylinder (1), and inside this cylinder <X>, the space inside the cylinder (J) is divided into an expansion chamber (m) and a working chamber (n). A free displacer (0) is fitted so as to be reciprocally movable. This displacer (0) has a metal cold storage material (o+) inside (
It is filled with regenerative heat exchanger), and the cold storage material (OL)
Communication holes (Ox) and (03) are opened to communicate the expansion chamber (m) and the working chamber (n), respectively.

Furthermore, in the working chamber (n), there is a displacer (o).
A displacer spring (p) made of a coil spring is provided to elastically support the displacer spring so that it can reciprocate. moreover,
The working chamber (n) is connected to the compression chamber (d) of the compressor (a) via the coupling pipe (q), and the working chamber (n) is connected to the compression chamber (d) of the compressor (a).
By reciprocating the displacer (0) by the refrigerant gas pressure from a) and expanding the refrigerant gas in the expansion chamber (m), cold is generated in the cold head at the tip of the cylinder (ff). For example, “Refrig
erator for Cryogenic 5ens
ors, NASA Conference Pu
(See B-order catfon 22B7, etc.).

(Problems to be Solved by the Invention) By the way, in the above compressor (a), the piston (e
) is vibrated at the resonant frequency of the spring mass system of the linear motor (f), so in order to prevent fatigue failure of the piston spring (j), its diameter, length, number of turns, etc. must be sufficiently large. There is a need to. However, in that case, the space for the spring (j) becomes large, and the overall length and width of the compressor (a) become correspondingly large, making it difficult to downsize the compressor (a). There is also a method of elastically holding the piston (e) at a neutral point between two piston springs arranged in series, but in that case,
It is difficult to hold the piston (e) accurately at the neutral point.

The present invention has been made in view of the above-mentioned problems, and its purpose is to elastically support the piston with one spring and reduce fatigue of the spring by improving the elastic support structure of the piston of the linear motor described above. The objective is to downsize the compressor without causing damage.

(Means for Solving the Problem) In order to achieve the above object, in the invention according to claim (1), the piston is mainly elastically supported by an air spring on its back surface, and the mechanical spring supports the piston at a neutral point. used for

Specifically, the compressor of the present invention, as shown in FIG.
A casing (2), a cylinder (6) provided in the casing (2), and a compression chamber (11) fitted in the cylinder (6) so as to be reciprocally movable. A closed space (1) provided between a piston (7) forming a partition, the back surface of the piston (7), and the casing (2).
7a), the piston (7) is connected to the cylinder (6).
an air spring (17) that elastically supports the casing (2) so as to be able to reciprocate within the casing;
It has a coil spring (27) that holds the piston (7) in a neutral position of reciprocating motion, a magnet (15) and a coil (16), and the piston (7) is moved by supplying alternating current of a predetermined frequency to the coil (16). ) reciprocating linear motor (13)
It is characterized by having the following.

Further, in the invention according to claim (2), the spring constant of the air spring is variable.

That is, in addition to the structure of the invention according to claim (1), the present invention makes the spring constant of the air spring (17) variable by adjusting the volume of the closed space (17a) of the air spring (17). Spring constant variable means (28) is provided.

(Function) With the above configuration, in the invention according to claim (1), the piston (7) is elastically supported by the air spring (17) disposed between the back surface of the piston (7) and the casing (2). (17) ensures a spring constant. Further, the piston (7) is held at a neutral position of reciprocating motion by a coil spring (27).

In this way, since the piston (7) is supported by the air spring (17) and the coil spring (27) is used to maintain the neutral position of the piston (7), fatigue failure of the coil spring (27) will not occur. In addition, the space required is small, and the compressor can be made smaller.

Further, since the piston (7) is supported by an air spring (17) provided between the back surface of the piston (7) and the casing (2), the piston (7) is supported by the cylinder (6).
) It is supported not only by the inner peripheral surface but also by the member for forming the sealed space (17a), and the surface pressure on the sliding surface is dispersed. Therefore, wear of the seal portion of the piston (7) can be suppressed, and the life of the compressor can be extended.

In the invention according to claim (2), when changing the spring constant of the air spring (17), it is sufficient to increase or decrease the volume of the closed space (17a) of the air spring (17) using the spring constant variable means (28). , an increase in its volume results in a lower spring constant, while a decrease in volume results in a higher spring constant.

By doing so, the spring constant can be easily and simply changed.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows a compressor (1) for a Stirling refrigerator according to an embodiment of the present invention. This compressor (1) is combined with a conventionally known free displacer type expander (see FIG. 2), which is not shown, to constitute a refrigerator. The compressor (1) has a cylindrical casing (2).
) has a pair of left and right cylindrical casing assemblies (3), (3) of approximately the same configuration arranged concentrically, and a disc-shaped center base (4) between both casing assemblies (3), (3). ) are sandwiched in an airtight manner, and both casing assemblies (3), (3) and the center base (4) are made of pure iron. Above center base (4
) is formed with a cylinder insertion hole (5) in the center thereof,
A cylindrical cylinder (made of stainless steel as a non-magnetic material) with both ends open is inserted into the cylinder insertion hole (5).
6) is inserted and supported. A pair of left and right cylindrical pistons (7), (7) each having a bottomed center hole (7a) on the back surface are slidably fitted into this cylinder (6). The gap between the outer periphery and the inner periphery of the cylinder (6) is hermetically closed by a thin-walled cylindrical outer seal (8), and both pistons (7), (7)
) surrounded by the cylinder (6) is the compression chamber (1
1). A gas passage (12) is formed in the center base (4) that penetrates in the radial direction from the cylinder insertion hole (5) to the outer peripheral surface, and the inner end of the gas passage (12) is located at the center of the cylinder (6). It communicates with the compression chamber (11) through the hole (6a) formed through it, while the gas passage (
The outer end of 12) is connected to an expander (not shown) via a connecting pipe (not shown).

The left and right pistons (7), (7) are drivingly connected to linear motors (13), (13) serving as drive sources for reciprocating the pistons (7), (7), respectively. That is, each linear motor (13) is a cylindrical member (made of pure iron) fixed to the center base (4).
14), and this cylindrical member (14) is a cylinder (6).
The outer periphery of the casing assembly (3) is fitted to the inner periphery of the casing assembly (3) with a predetermined gap therebetween. An annular permanent magnet (15) is fixed to the outer periphery of the cylindrical member (14) with a predetermined gap from the inner periphery of the casing assembly (3). 14
), the center base (4) and the casing assembly (3) are used as yoke to generate a magnetic field of a predetermined strength in the gap between the magnet (15) and the inner peripheral surface of the casing assembly (3).

Each of the pistons (7) has a flange (7b) extending radially outward from the end opposite to the center of the cylinder (6) of the piston (7), and on the outer periphery of the flange (7b), It extends toward the center of the cylinder (6) concentrically with the piston (7), and its tip is disposed in the gap between the magnet (15) and the inner peripheral surface of the casing assembly (3) so as to be able to reciprocate in the left-right direction. A bobbin (10) serving as a cylindrical coil winding portion is connected.

This bobbin (10) has a bottomed cylindrical bobbin body (10a) made of thin-walled stainless steel as a non-magnetic material, and a flange portion ( 10b) is formed. moreover,
On the outer periphery of the bobbin body (10a), an annular resin spacer (10c) is secured to the central end of the cylinder (6) by the flange (10b). In addition, a bottomed cylindrical resin cap (10d) is fitted to the end of the bobbin body (10a) opposite to the center of the cylinder (6) so that the bottom part is in close contact with the bottom of the bobbin body (10a). The outer diameter of this cap (10d) is the same as that of the spacer (10c).
It is said to be the same as Cap (10d) and spacer (
A coil (16) is wound around the bobbin body (10a) between the spacer (10c) and the cap (10d), and a predetermined interval is provided between the spacer (10c) and the cap (10d). It is being In addition, the above spacer (
10c) and cap (10d) are the bobbin body (10a
) of the cylinder (6) from the opposite end to the center, and then the coil (16) is wound between them.

Both pistons (7) are energized by alternating current at a predetermined frequency in synchronization with the coils (16), (16) of both linear motors (13), (13).

(7) are reciprocated in opposite directions at a period determined by the spring constant of an air spring (17), which will be described later, to generate gas pressure at a predetermined period in the compression chamber (11).

An air spring (17) is disposed on the back surface of each piston (7) to elastically support the piston (7) with respect to the casing so that the piston (7) can reciprocate within the cylinder (6). That is,
A spring assembly (21
) are fastened at the outer ends. This spring assembly (21) extends toward the center of the casing assembly (3), and at its inner end there is a thin-walled cylindrical inner cylinder (21) extending concentrically with the cylinder (6) toward the center of the cylinder (6).
18) is integrally formed, and this inner cylinder (18)
The front half of the piston (7) is slidably inserted into the center hole (7a) on the back surface of the piston (7), and the gap between the outer circumference of the inner cylinder (18) and the inner circumference of the piston (7) is a thin-walled cylindrical hole. It is airtightly closed by an inner seal (19). Further, the opening on the outside of the inner cylinder (18) (on the side opposite to the center of the cylinder (6)) is airtightly closed by a closing member (20), and the piston (7), the inner cylinder (18), Inner seal (19) and closing member (20)
An air spring (17a) having a closed space (17a) surrounded by
17) is configured.

Further, a spring holder upper (23) is screwed and fastened to the center of the inner bottom surface of the closing member (20), and a spiral spring mounting groove (24) is formed on the outer periphery of the spring holder upper (23). There is. On the other hand, a spring holder lower (25) is screwed into the center of the bottom surface of the center hole (7a) of each piston (7), and a spiral spring mounting groove (2) is formed on the outer periphery of this spring holder lower (25).
6) is formed. One end of a coil spring (27) is screwed into the spring mounting groove (24) of the spring holder upper (23) so as not to be movable, and the other end of the coil spring (27) is attached to the spring holder lower (25). ) It is immovably attached to a spring mounting groove (26) on the outer periphery, and this coil spring (27) holds the piston (7) in a neutral position of reciprocating motion.

Further, a volume adjusting member (28) as a spring constant variable means for varying the spring constant of the air spring (17) is removably screwed into the center of the central side surface of the cylinder (6) of the spring holder upper (23). By replacing this adjustment member (28) with one of a different volume, the volume of the closed space (17a) of the air spring (17) can be increased or decreased, and the spring constant of the air spring (17) can be adjusted. I'm trying to change it.

In addition, an annular groove (29) centered on the cylinder axis is recessed in the surface of the spring assembly (21) on the center side of the cylinder (6).

Further, in the bottom wall of the bobbin (10), an annular groove (2) is formed on the surface facing the spring assembly (21).
An annular groove (30) is recessed corresponding to the groove 9). Two lead wires (31) (31) for supplying electric power to the coil (16) of the linear motor (13) are installed between both of these annular grooves (29) (30).

Next, the operation of the above embodiment will be explained.

With the start of operation of the refrigerator, the coils (16) of both linear motors (13), (13) in the compressor (1),
16), an AC power source of a predetermined frequency is energized synchronously.

With this energization, the coil (16) (16) and the piston (7) interact with the magnetic field generated by the magnet (15) (5).

Both pistons (7) and (7) reciprocate in opposite directions while increasing and decreasing the volumes of the air springs (17) and (17) and expanding and contracting the coil springs (27) and (27), respectively. ) move toward and away from each other within the cylinder (6), the volume of the compression chamber (11) increases or decreases, and the compression chamber (
11) A pressure wave of a predetermined period is generated within the range. This compression chamber (1
1) is connected to the expander via the connecting pipe, so in the expander the displacer reciprocates at the same frequency as the pressure wave in the compression chamber (11), and the expansion of the gas in the expansion chamber causes cold. The cold head at the tip of the cylinder is cooled to an extremely low temperature level by repeated reciprocating movements of the displacer.

In this embodiment, each piston (7) reciprocates at a resonant frequency due to the air spring (17) on its back surface, and the neutral position of the reciprocating motion of the piston (7) is set by the coil spring (27).
) is set by Since the coil spring (27) is thus used to maintain the neutral position of the piston (7), its fatigue failure does not occur. Moreover, the coil spring (2
Since the space required for 7) is small, it is possible to downsize the compressor (1).

Furthermore, since each piston (7) is supported by an air spring (17), the outer circumferential surface of the piston (7) is connected to the inner circumferential surface of the cylinder (6) via the outer seal (8), and to the center hole (7a). ) are respectively supported by the outer peripheral surface of the inner cylinder (18) via the inner seal (19). That is, since the piston (7) is supported on both the outer circumferential surface and the inner circumferential surface, the cylinder (6) and the inner cylinder (
As long as 18) and the piston (7) are arranged concentrically with each other, the surface pressure on the sliding surface of the piston (7) will be dispersed, thus suppressing wear on the sliding surface of the piston (7). This can extend the life of the compressor (1).

Furthermore, since a volume adjustment member (28) is removably disposed in the closed space (17a) of each air spring (17), when changing the spring constant of the air spring (17), the volume adjustment member (28) Adjust the volume of the closed space (17g) by replacing it.

For example, to increase the spring constant of the air spring (17),
When the long and large volume adjustment member (28) is attached,
The volume of the closed space (17a) decreases and the spring constant increases. On the other hand, in order to reduce the spring constant, it is sufficient to attach a short and small volume adjustment member (28), and the closed space (
The volume of 17a) increases and the spring constant decreases. Therefore, the spring constant can be changed easily and simply.

In the above embodiment, when changing the volume of the closed space (17a) to change the spring constant of the air spring (17), the volume adjusting member (28) is replaced, but other configurations may be adopted. You can also. For example, the amount of protrusion of the adjustment member relative to the closed space may be continuously changed.

Further, in the above embodiment, there are two pistons (7), two linear motors (13), etc., but the present invention can also be applied to a compressor equipped with one of these.

(Effects of the Invention) As explained above, according to the invention according to claim (1), in a linear motor compressor for a Stirling refrigerator, the piston is elastically supported on the casing by an air spring and a mechanical coil spring, While the air spring sets the resonant frequency of the spring mass system of the linear motor, the coil spring holds the piston at the neutral point of reciprocating motion, thereby suppressing fatigue failure of the coil spring and reducing the size of the compressor. It is possible to aim for Further, since the piston is supported by both the cylinder and the air spring, the partial pressure on the sliding surface of the piston can be dispersed, thereby extending the life of the compressor.

According to the invention according to claim (a), the spring constant of the air spring can be easily and easily changed by variably adjusting the spring constant by changing the volume of the sealed space of the air spring.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of a compressor according to an embodiment of the present invention. FIG. 2 is a sectional view showing a conventional example of a Stirling refrigerator. (1)...Compressor (2)...Casing (6)...Cylinder (7)...Piston (11)...Compression chamber (13)...Linear motor (15)...・Magnet (16)...Coil (17)...Air spring (17a)...Closed space (27)...Coil spring (28)...Volume adjustment member (spring constant variable means) Agent

Claims (2)

[Claims] (1) A casing (2), a cylinder (6) provided in the casing (2), and a compression chamber (6) fitted in the cylinder (6) so as to be reciprocally movable in the cylinder (6). 1
1), a piston (7) defining a section;
) and the casing (2).
an air spring (17) that elastically supports the casing (2) so as to be able to reciprocate within the casing;
It has a coil spring (27) that holds the piston (7) in a neutral position of reciprocating motion, a magnet (15) and a coil (16), and the piston (7) is moved by supplying alternating current of a predetermined frequency to the coil (16). ) reciprocating linear motor (13)
A linear motor compressor for a Stirling refrigerator, comprising: (2) A casing (2), a cylinder (6) provided in the casing (2), and a compression chamber (6) fitted in the cylinder (6) so as to be reciprocally movable in the cylinder (6). 1
1), a piston (7) defining a section;
) and the casing (2).
an air spring (17) that elastically supports the casing (2) so as to be able to reciprocate within the casing;
It has a coil spring (27) that holds the piston (7) in a neutral position of reciprocating motion, a magnet (15) and a coil (16), and the piston (7) is moved by supplying alternating current of a predetermined frequency to the coil (16). ) reciprocating linear motor (13)
and a spring constant variable means (28) for varying the spring constant of the air spring (17) by increasing or decreasing the volume of the closed space (17a) of the air spring (17). A linear motor compressor for Stirling refrigerators featuring: