JPH04335962A - Free-piston compressor - Google Patents

Abstract

PURPOSE:To make it easy, in a linear-motor compressor for a Stirling refrigerating machine, to hold the piston at the neutral position and furthermore to enable stabilizing the operation of the compressor over a long period of time. CONSTITUTION:A piston (5) is supported in a casing (1) in a manner allowing reciprocating movement of the piston (5) in the casing (1) by using for the support a movable magnet (21) provided integrally on the piston (5) and a supporting means (15) which has a pair of stationary magnets (19), (20) fixed to the casing (1) and disposed to have the movable magnet (21) between the stationary magnets so that the repellent forces acting between the magnets (19), (20), (21) work to hold the piston (5) at the neutral position.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a free piston compressor having a free piston for compressing refrigerant supplied to the expander in a Stirling refrigerator having an expander that generates refrigeration through reciprocating motion of a displacer.

0002

2. Description of the Related Art Conventionally, a free displacer type Stirling refrigerator has been known as a type of small refrigerator that generates cryogenic cold. For example, as shown in FIG. 3, this refrigerator is a combination of a compressor (a) that compresses refrigerant gas and an expander (k) that expands the refrigerant gas discharged from the compressor (a). It is. The compressor (a) has a hermetic casing (b), for example.
and a cylinder (c) formed within the casing (b).
a piston (e) that is reciprocably fitted into the cylinder (c) and defines a compression chamber (d) in the space inside the cylinder (c); and a drive source that reciprocates the piston (e). It is equipped with a linear motor (f). This linear motor (f) has an annular permanent magnet (g) arranged around a cylinder (c), and this magnet (g) applies a magnetic field to a cylindrical gap concentric with the center of the cylinder (c). generate. A circumferential portion of a substantially cup-shaped movable body (h) integrally fixed to the piston (e) at the center is arranged in the gap so as to be able to reciprocate, and the outer periphery of the movable body (h) A drive coil (i) is wound thereon. In addition, the above movable body (
A piston spring (j) consisting of a coil spring for elastically supporting the piston (e) in a reciprocating manner is provided between the outer bottom surface of the piston (h) (the side opposite to the piston (e)) and the inner bottom surface of the casing (b). By applying an alternating current of a predetermined frequency to the drive coil (i), the coil (i) and the movable body (h) are
By driving the piston (e) to reciprocate 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 (l), and inside this cylinder (l) is a cylinder (
l) A free displacer (o) that divides the inner space into an expansion chamber (m) and a working chamber (n) is fitted so as to be able to reciprocate. This displacer (o) is filled with a metal regenerator material (o1) (regenerative heat exchanger), and the regenerator material (o1) is communicated with the expansion chamber (m) and the working chamber (n), respectively. Communication holes (o2) and (o3) are opened. Further, a displacer spring (p) made of a coil spring that elastically supports the displacer (o) in a reciprocating manner is disposed within the working chamber (n). Furthermore, the working chamber (n) is connected to the connecting pipe (
The displacer (o) is reciprocated by the refrigerant gas pressure from the compressor (a), and the refrigerant gas is transferred to the expansion chamber (m) via the compressor (a). )
By inflating the cold head at the tip of the cylinder (l), cold is generated (for example, "Refrigerator for Cryoge").
nic Sensors”, NASA Conference
nce Publication 2287, etc.).

0004

By the way, in the linear motor compressor (a) described above, the piston (e) is supported by the piston spring (j). It is difficult to reliably maintain the compressor (a) at the neutral position of its reciprocating stroke, and it is also necessary to consider the durability of the spring (j), making it difficult to operate the compressor (a) stably over a long period of time. There is.

[0005] The present invention has been made in view of the above points, and its purpose is to improve the means for keeping the piston in the neutral position, thereby making it easier to maintain the piston in the neutral position, and allowing the compressor to operate for a long period of time. The purpose is to operate stably over a period of time.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention maintains the piston neutrally by the repulsive force of the magnet.

Specifically, in the invention of claim 1, as shown in FIG. 1, the compressor includes a casing (1), a cylinder (4) provided in the casing (1), and a cylinder (4) a piston (5) that is reciprocatably fitted into the cylinder (4) and defines a compression chamber (6) in the inner space of the cylinder (4);
A linear motor (9) as a drive source for reciprocating the piston (5), and a cylinder (4) for driving the piston (5) back and forth.
The support means (15) elastically supports the casing (1) in a reciprocating manner within the casing (1).

[0008] The support means (15) is supported by first and second fixed magnets (1) which are fixed to the casing (1) facing each other at a predetermined distance in the axial direction of the cylinder (4).
19), (20), and both fixed magnets (19), (2
0) and a movable magnet (21) disposed facing each other and connected to the piston (5), and the movable magnet (21) and fixed magnets (19), (20) facing surfaces with the same magnetic poles, both fixed magnets (19) and (20
) and the movable magnet (21), the piston (5)
is characterized in that it is configured to be held at a neutral position of the reciprocating stroke.

In the invention as claimed in claim 2, as shown in FIG. It has first and second movable magnets (23) and (24) which are arranged facing each other at a predetermined interval in the axial direction of the piston (4) and are connected to the piston (5), and the movable magnet ( 23), (24) and the fixed magnet (22) have the same magnetic poles, so that both movable magnets (23), (24)
) and the fixed magnet (22), the piston (5)
is configured to maintain the reciprocating stroke in a neutral position.

0010

[Operation] With the above structure, in the invention of claim 1, when the linear motor (9) is energized with an alternating current of a predetermined frequency, the piston (5) reciprocates within the cylinder (4) due to its operation. The compression chamber (6) is created by the reciprocating movement of the piston (5).
The volume of the refrigerant increases or decreases, and the refrigerant inside is compressed at a predetermined period. A movable magnet (21) arranged between fixed magnets (19) and (20) on the casing (1) side is connected to the piston (5), and this movable magnet (21) and fixed magnets (19), ( 20) Due to the repulsion of the magnetic force between the piston (
5) is held at the neutral position, the piston (5) can be more reliably maintained at the neutral position compared to a support structure using a spring. Moreover, these fixed magnets (19), (2
0) and the movable magnet (21) due to the repulsive force between the piston (5
) support eliminates the need for conventional springs, increases durability and allows the compressor to operate stably over long periods of time.

In the invention of claim 2, movable magnets (23) and (24) are connected to the piston (5), and between these two movable magnets (23) and (24) there is a magnet fixed to the casing (1). A fixed magnet (22) is arranged, and this movable magnet (23)
, (24) and the fixed magnet (22), the piston (5) is held in a neutral position. Therefore, this invention also provides the same effects as the invention of claim 1.

0012

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings.

(Embodiment 1) FIG. 1 shows a compressor (A) for a free displacer type Stirling refrigerator according to Embodiment 1 of the present invention. A refrigerator is constructed in combination with the refrigerator (see Figure 2). The compressor (A) has a closed cylindrical casing (1). This casing (1) is a non-conductive bottomed cylinder whose lower end opening is sealed with a bottom wall (2), and in the center of the bottom wall (2) there is a center hole (3) extending vertically. is formed through it. This center hole (3) has a bottomed cylindrical cylinder made of stainless steel as a non-magnetic material (
4) are tightly fitted together, and a piston (5) in the shape of a substantially bottomed cylinder that is open upward is slidably fitted inside this cylinder (4). The portion surrounded by (4) is a compression chamber (6). A communication hole (7) is formed through the bottom of the cylinder (4), and one end of a communication pipe (31) communicating with the compression chamber (6) is fitted and fixed into this communication hole (7). Piping(
31) The other end is connected to an expander.

The piston (5) is drivingly connected to a linear motor (9) serving as a drive source for reciprocating the piston (5). That is, an annular recess (8) is formed on the upper surface (inner surface) of the bottom wall (2) of the casing (1), and the center hole (3)
), and an annular permanent magnet (10) is attached to the outer side surface of this recess (8) with a predetermined interval between it and the inner side surface.
0), a magnetic field of a predetermined strength is generated in the gap between the magnet (10) and the inner side surface of the recess (8) using the bottom wall (2) as a yoke.

[0015] The outer periphery of the open end of the piston (5) extends concentrically with the piston (5) and has a tip between the magnet (10) and the inner peripheral surface of the casing (1). A substantially bottomed cylindrical bobbin (11) disposed in the gap so as to be able to reciprocate in the left-right direction is connected to the bobbin at an inward flange (11a). This bobbin (11) is made of thin-walled stainless steel as a non-magnetic material, and a coil winding part (11b) formed by cutting out the outer circumferential surface over a predetermined width is attached to the magnet (10) on the outer periphery of its tip. correspondingly formed,
A coil (12) is wound around this coil winding portion (11b). Then, by applying an alternating current of a predetermined frequency (for example, 50 Hz) to the coil (12) of this linear motor (9), the piston (5) is reciprocated at a period determined by the spring constant of the support mechanism (15), etc., which will be described later. Let me,
The compression chamber (6) is configured to generate gas pressure at a predetermined period.

A support member (13) consisting of a horizontal disk is disposed inside the casing (1), and the support member (13)
The bottom wall (2) is connected to the bottom wall (2) by multiple mounting rods (14), (14), ... installed upright on the top surface of the bottom wall (2) of the casing (1).
It is fixed at a predetermined height position from the top.

A support mechanism (15) is provided for elastically supporting the piston (5) with respect to the casing (1) so that it can reciprocate within the cylinder (4). That is, an insertion hole (16) is formed in the center of the support member (13) so as to be concentric with the cylinder (4), and a cylindrical bush (17) is fitted and fixed in the insertion hole (16). ing. A rod (18) is slidably inserted into this bush (17), and the lower end of this rod (18) is connected to the piston (5).
) is screwed to the center of the inner bottom surface of the piston (5), and this structure suppresses the swinging of the piston (5) from the cylinder axis.

[0018] A supporting member (
13) A cylindrical part (13a) that opens downward is provided on the lower surface of the cylinder (13) and protrudes concentrically with the cylinder (4) and integrally with the support member (13). ) is fixed with a disk-shaped first fixed magnet (19), and a second fixed magnet (20) is fixed on the opening side (lower part in the figure) with the outer peripheral edge. ) and (20) are arranged facing each other at a predetermined interval in the axial direction of the cylinder (4). Both stationary magnets (19) and (20) have the same disc shape, and central holes (19a) and (20a) are formed in the center thereof, through which the rod (18) is inserted.

On the other hand, a disc-shaped movable magnet (21) is located between the first and second fixed magnets (19) and (20) in the rod (18).
9) and (20) are movably attached so as to face each other vertically with a predetermined interval. That is, this movable magnet (21) is connected to the piston (5) via the rod (18). The top surface of the movable magnet (21) and the bottom surface of the first fixed magnet (19) facing it are both of the same N magnetic pole, for example, and the bottom surface of the movable magnet (21) and the bottom surface of the second fixed magnet (19) facing it ( The upper surfaces of both fixed magnets (19) and (20) have the same S magnetic pole.
The piston (5) is held at the neutral position of the reciprocating stroke by the repulsive force of the same magnetic poles of the movable magnet (21) and the movable magnet (21).

Next, the operation of the above embodiment will be explained. With the start of operation of the refrigerator, an AC power source of a predetermined frequency is applied to the coil (12) of the linear motor (9) in the compressor (A). With this energization, the coil (12) and the piston (5) reciprocate due to the action of the magnetic field generated by the magnet (10), and the cylinder (
4) The volume of the compression chamber (6) increases or decreases due to the reciprocating movement within the compression chamber (6), and when the piston (5) moves downward, the refrigerant inside the compression chamber (6) is compressed at a predetermined period, and the refrigerant is compressed into the compression chamber (6). A pressure wave with a predetermined period is generated within the chamber. This compression chamber (6) is connected to the connecting pipe (
31), the displacer in the expander reciprocates in the same cycle as the pressure waves in the compression chamber (6), and the expansion of the gas in the expansion chamber causes cooling. This repeated reciprocation of the displacer cools the cold head at the tip of the cylinder to an extremely low temperature level.

In this case, the piston (
5) and the movable magnet (21) on the rod (18) that is integrated with the movable rod.
is fixed, and this movable magnet (21) is attached to the casing (1).
The first and second fixed magnets (19), (20
) between the movable magnet (21) and both fixed magnets (19).
) and (20), the piston (5) is held in the neutral position by the repulsion of the magnetic force between the movable magnet (21) and the fixed magnets (19) and (20). Ru. When alternating current is applied to the linear motor (9), the piston (5) reciprocates up and down from the neutral position against the repulsive force of the magnetic force. In this way, the piston (5) is held in the neutral position by the repulsion of the magnetic force, so the piston (5) can be reliably maintained in the neutral position, and the repulsion of the magnets (19), (20), and (21) Supporting the piston (5) by force eliminates the need for a conventional spring to maintain the neutral position, and even if the piston (5) repeatedly reciprocates, it does not deteriorate due to fatigue. A) can be operated stably for a long period of time.

[0022] Moreover, the piston (5) is a rod (18).
Since it is supported by the casing (1), its movement in the horizontal direction orthogonal to the reciprocating direction is restricted. As a result, the outer circumferential surface of the piston (5) no longer comes into sliding contact with the wall surface of the cylinder (4), and no wear occurs due to sliding between the two, which prevents the seal gap in the compression chamber (6) from increasing. The gas compression efficiency of the compressor (A) can be increased.

(Example 2) FIG. 2 shows Example 2 (in addition,
The same parts as in FIG. 1 are given the same reference numerals and detailed explanation thereof is omitted), and the objects to which the movable magnet and fixed magnet are attached are changed.

That is, in this embodiment, the support member (1
A disk-shaped fixed magnet (22) is fixed at the outer peripheral edge to the opening side (lower part in the figure) of the cylindrical part (13a) of 3), and a rod (18) is fixed at the center of this fixed magnet (22). ) is formed into a central hole (22a) through which the hole (22a) is inserted.

On the other hand, in the rod (18), a disk-shaped first
and the second movable magnets (23), (24) are connected to the cylinder (4).
The movable magnets (23), (
24) is connected to the piston (5) via a rod (18). The lower surface of the first movable magnet (23) and the upper surface of the fixed magnet (22) facing it are both of the same N magnetic pole, for example, and the upper surface of the second movable magnet (24) and the fixed magnet (22) facing it ( 22) Both the lower surfaces have the same S magnetic pole, and the piston (
5) is held in the neutral position of the reciprocating stroke. The rest of the structure is the same as that of the first embodiment.

Therefore, in this embodiment as well, the piston (
Movable magnets (23) and (24) are connected to the casing (1) side, and a fixed magnet (22) located between the two movable magnets (23) and (24) is fixed to the casing (1) side. The repulsion of the magnetic force between the magnets (23), (24) and the fixed magnet (22) causes the piston (5) to be held at the neutral position, so that the same effect as the invention of the first embodiment can be obtained.

[0027] In each of the above embodiments, the fixed magnet (19)
, (20), (22) and movable magnets (21), (23)
, (24) are disk-shaped, but any arrangement or shape may be used as long as magnetic repulsion can be obtained between the movable magnet and both fixed magnets.

[0028]

As explained above, in the invention of claim 1, the piston in a free piston compressor for a Stirling refrigerator is provided with a movable magnet integrally provided with the piston, and a movable magnet that is sandwiched between the piston and the casing. The piston is supported reciprocally by a supporting means having a pair of fixed magnets arranged in the casing and fixed to the casing, so that the piston is held at a neutral position by the repulsive force between the movable and fixed magnets. Further, in the invention of claim 2, supporting means for supporting the piston with respect to the casing includes a pair of movable magnets integrally provided with the piston, and a fixed magnet disposed between the two movable magnets and fixed to the casing. The piston is supported so as to be reciprocally movable, and the piston is held at a neutral position by the repulsive force between the movable and fixed magnets. Therefore, according to these inventions, it is possible to reliably maintain the piston in the neutral position, eliminate the need for a conventional spring, increase the durability of the compressor, and enable stable operation over a long period of time.

[Brief explanation of drawings]

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

FIG. 2 is an enlarged sectional view of a compressor according to a second embodiment of the present invention.

FIG. 3 is a sectional view showing a conventional example of a Stirling refrigerator.

[Explanation of symbols]

(A)...Compressor (1)...Casing (4)...Cylinder (5)...Piston (6)...Compression chamber (9)...Linear motor (10)...Magnet (12)...Coil (15), (15' )…Support mechanism (support means) (19)
…First fixed magnet (20)…Second fixed magnet (21)…Movable magnet (22)…Fixed magnet (23)…First movable magnet (24)…Second movable magnet

Claims (2)

[Claims] [Claim 1] A casing (1) and a casing (
1) a cylinder (4) provided in the cylinder (4);
), the piston (5) is reciprocably fitted in the cylinder (4) and defines a compression chamber (6) in the inner space of the cylinder (4); a linear motor (9) that reciprocates the piston (5); The support means (15) elastically supports the piston (5) with respect to the casing (1) so as to be reciprocally movable within the cylinder (4), and the support means (15) includes (4) first and second fixed magnets (19) fixed oppositely at a predetermined interval in the axial direction;
(20), and the first and second fixed magnets (19), (
a movable magnet (21) which is arranged to face each other between the movable magnet (20) and connected to the piston (5);
1) and the fixed magnets (19), (20) have the same magnetic poles on their opposing surfaces, and both the fixed magnets (19), (20)
A free piston compressor characterized in that the piston (5) is held in a neutral position of the reciprocating stroke by the repulsive force between the movable magnet (21) and the movable magnet (21). [Claim 2] A casing (1) and a casing (
1) a cylinder (4) provided in the cylinder (4);
), the piston (5) is reciprocably fitted in the cylinder (4) and defines a compression chamber (6) in the inner space of the cylinder (4); a linear motor (9) that reciprocates the piston (5); The support means (15) elastically supports the piston (5) against the casing (1) so as to be able to reciprocate within the cylinder (4), and the support means (15') A fixed fixed magnet (22), and first and second magnets arranged opposite to each other at a predetermined interval in the axial direction of the cylinder (4) on both sides of the fixed magnet (22) and connected to the piston (5). 2 movable magnets (23), (24), and the movable magnets (23), (24) and the fixed magnet (22
) have the same magnetic poles, and the piston (5) is held at the neutral position of the reciprocating stroke by the repulsive force between both movable magnets (23), (24) and the fixed magnet (22). A free piston compressor characterized by comprising: