JP2000065433A - Gas compressor and cold head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a stroke of a piston by opposing an outer periphery of the piston to an inner periphery of a cylinder via an infinitesimal gap, supporting thrust bearings axially movably in the direction of the cylinder axis, and reciprocating the piston axially in the cylinder. SOLUTION: A piston rod 8 is coupled to an end of a piston 4 at an opposite side to a compression chamber 5, and extended along an extension line of a central axis of the cylinder 3. The rod 8 is supported via thrust bearings 10, 11 axially movably so as to inhibit movement in the direction perpendicular to the axis. The piston 4 is held to form an infinitesimal gap between an inner periphery of the cylinder 3 and an outer periphery of the piston 4 to reciprocate the piston 4 in the axial direction in the cylinder 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas compressor and a cold head, and more particularly to a gas compressor suitable for use in a cooler and a cold head connected to the gas compressor.

[0002]

2. Description of the Related Art FIG. 3 shows a basic structure of a Stirling cooler. The Stirling cooler includes a gas compressor 101, a cold head 102, and a distribution duct 103 connecting them.
Having. The gas compressor 101 includes a cylinder 106 and a piston 107 reciprocating in the cylinder, and defines a compression chamber 108 between the cylinder 106 and the piston 107.

The cold head 102 includes a cylinder 109
And a displacer 111 disposed reciprocally therein. The displacer 111 is a cylinder
9 is elastically supported by a spring or the like so as to be movable in the axial direction. An expansion space 116 is defined between one end of the cylinder 109 and the displacer 111, and a compression space 117 communicating with the flow duct 103 is defined between the other end of the cylinder 109 and the displacer 111.

A gas flow path 112 for communicating a compression space 117 and an expansion space 116 is provided inside a displacer 111.
Is provided. The gas flow path 112 is filled with a cold storage material, and the refrigerant gas flowing in the gas flow path 112 exchanges heat with the cold storage material. The piston 107 and the displacer 111 reciprocate out of phase to execute a reverse Stirling cycle.

[0005] The reverse Stirling cycle is composed of four steps of isothermal compression, isovolume transfer, isothermal expansion and isovolume transfer of refrigerant gas. Hereinafter, the reverse Stirling cycle will be briefly described.

[0006] Initially, it is assumed that the displacer 111 is in a neutral position by a spring. When the piston 107 moves to the right in the drawing, the refrigerant gas flows into the compression space 117 of the cold head 102 through the circulation duct 103 while being isothermally compressed in the compression chamber 108. At this time, due to the fluid resistance of the gas flow path 112 filled with the cold storage material, the displacer 1
11 moves to the expansion space 116 side. That is, expansion space 1
As the space volume of 16 decreases, the operating pressure of the entire system reaches a maximum. The process leading to this state is isothermal compression.

When the piston 107 reaches the right end,
Since there is no gas flow, the compression chamber 108 and the expansion space 116
The pressure between and balance. Since the fluid resistance does not act, the displacer 111 returns to the neutral position by the restoring force of the spring. At this time, the compressed gas is supplied to the compression chamber 10.
Move to 8. This process is equal volume transfer.

When the moving direction of the piston 107 is reversed and moves to the left, the displacer 111 also moves to the left at substantially the same time due to the fluid resistance acting on the displacer 111. At this time, the space volume of the expansion space 116 increases, and the refrigerant gas expands. This step is isothermal expansion. In order to expand at an isothermal temperature, it is necessary to absorb heat from the outside, so that cold occurs.

At the time when the piston 107 reaches the maximum point on the left end, no fluid resistance acts, so the displacer 1
11 returns to the neutral position by the spring. The gas in the expansion space 116 is transferred in an equal volume. That is, the gas cooled in the expansion space 116 passes through the gas flow path 112 and passes through the compression space 117.
Return to Note that each step of the actual cooler does not operate in a completely isothermal state as described herein.

In such a Stirling cooler, since the expansion space 116 serves as a cold source, an object to be cooled is thermally coupled to the expansion space 116 and arranged. For example,
An infrared imaging device is arranged at the right end of the cold head 102.

FIG. 4 is a sectional view of a conventional gas compressor.
The pistons 107a and 107b are arranged to face each other, and the shaft 1
Driven by 31a, 131b. Axes 131a, 1
The movable coils 124a, 124b are coupled to the permanent magnets 31a, 31b, and the permanent magnets 121a, 121b and the yoke 122.
a, 122b are inserted into the gap of the magnetic circuit formed.

The shafts 131a and 131b are provided with leaf springs 132a and 1a formed of a disk-shaped thin elastic metal diaphragm.
It is supported on the outer case by 33a and 132b, 133b. These leaf springs 132 and 133 elastically allow displacement of the shafts 131a and 131b in the movement axis direction. The current supplied to the movable coils 124a and 124b is
It is supplied via the lead wires 125a and 125b.

Such disc-shaped leaf springs 132, 133
It is possible to accurately support the piston 107 on the movement axis and to prohibit displacement in the direction orthogonal to the movement axis. For this reason, a clearance seal system that provides a narrow gap between the piston and the cylinder and minimizes the amount of gas leakage can be adopted. By employing the clearance seal method, it is possible to prevent wear of the piston and the displacer.

[0014]

In order to support the piston with a disc-shaped leaf spring and increase the stroke of the piston, it is necessary to increase the diameter of the leaf spring. For this reason,
The size of the gas compressor increases. It is difficult to increase the stroke of the piston without increasing the size of the gas compressor.

An object of the present invention is to provide a gas compressor capable of increasing the stroke of a piston without increasing the size.

Another object of the present invention is to provide a cold head capable of increasing the stroke of the displacer without increasing the size.

[0017]

According to one aspect of the present invention, a cylinder having a columnar inner peripheral surface and a piston disposed in the cylinder and having an outer peripheral surface aligned with the inner peripheral surface of the cylinder are provided. A thrust bearing that supports the piston such that the outer peripheral surface of the piston faces the inner peripheral surface of the cylinder with a small gap therebetween, and supports the piston so as to be movable in the axial direction of the cylinder; and And a reciprocating drive means for reciprocating in the axial direction of the gas compressor.

According to another aspect of the invention, there is provided a cylinder having a columnar inner peripheral surface, one end of which is closed, and an outer cylinder attached to the other end of the cylinder and defining a closed space together with the cylinder. A frame, a displacer disposed within the cylinder and having an outer peripheral surface aligned with an inner peripheral surface of the cylinder, the displacer defining an expansion space between one end of the cylinder and the displacer; A displacer that defines a compression space between the displacer and a gas flow path that communicates the expansion space and the compression space in the displacer; and A regenerator material that performs heat exchange with the gas flowing therethrough, and the displacer, wherein an outer peripheral surface of the displacer faces the inner peripheral surface of the cylinder with a small gap therebetween, and is disposed in an axial direction of the cylinder. And a thrust bearing for rotatably supporting communicates to the compression space, the cold head and a refrigerant gas supply passage to discharge the introduction of the refrigerant gas is provided.

Since the piston and the displacer are supported by the thrust bearing, a larger stroke can be secured as compared with the case where the piston and the displacer are supported by a leaf spring. Further, since the gap between the piston and the cylinder and the gap between the displacer and the cylinder are sealed with minute gaps, it is possible to prevent performance deterioration due to wear.

[0020]

FIG. 1 is a sectional view of a Stirling cooler according to an embodiment of the present invention. The Stirling cooler according to the embodiment includes a gas compressor 1, a cold head 50,
And a capillary tube 45 connecting them.

The gas compressor 1 has a plane-symmetric structure with the partition wall 2 interposed therebetween. Cylinders 3 are arranged on both sides of the partition 2. The cylinder 3 has a columnar inner peripheral surface, and is arranged such that the central axis thereof is perpendicular to the partition wall 2. A piston 4 is arranged in the internal cavity of the cylinder 3. The piston 4 has an outer peripheral surface that matches the inner peripheral surface of the cylinder 3. The compression chamber 5 is defined by the piston 4, the cylinder 3, and the partition 2. The compression chamber 5 communicates with a capillary tube 45 via a gas passage 6 formed in the partition 2.

A piston rod 8 is connected to an end of the piston 4 opposite to the compression chamber 5. The piston rod 8 extends along an extension of the center axis of the cylinder 3. The piston rod 8 has thrust bearings 10 and 11
, So as to be movable in the axial direction and prohibited from moving in a direction perpendicular to the axis. The thrust bearings 10 and 11 are fixed to the cylinder 3 via bearing support members 13 and 14, respectively.

The piston 4 has thrust bearings 10 and 1
1 holds the small gap between the inner peripheral surface of the cylinder 3 and the outer peripheral surface of the piston 4. If this gap is about 10 μm or less, it acts as a clearance seal.

A cylindrical gap 16 is formed in the cylinder 3 from the end face opposite to the partition wall 2 toward the partition wall 2 so as to surround the inner peripheral surface. A permanent magnet 17 is mounted on the outer peripheral surface of the gap 16. The cylinder 3 also serves as a yoke, and a magnetic circuit is defined by the permanent magnet 17, the cylinder 3, and the gap 16.

An electromagnetic coil 20 is inserted into the gap 16 so as to link with the magnetic circuit. The electromagnetic coil 20 is connected to the piston rod 8 via the coil support member 21.
It is fixed to.

The current leads 23 and 2 are connected to the electromagnetic coil 20.
Current is supplied via 4. Current leads 23 and 24
Is configured to include a coil spring that connects between the bearing support member 14 fixed to the cylinder 3 and the coil support member 21 fixed to the piston rod 8. Coil spring 23
And 24 are elastically deformed in the axial direction of the piston rod 8. As the coil springs constituting the current leads 23 and 24, those in which the reciprocating motion of the movable part such as the piston 4 resonates with the operating frequency are employed.

The piston 4, the thrust bearings 10, 11,
The space in which the current leads 23, 24 and the like are arranged is sealed by the outer case 30.

The cold head 50 includes a cylinder 51, a displacer (piston) 52, a coil spring 53, and an outer frame 57. The cylinder 51 has a columnar surface, for example, a cylindrical inner peripheral surface. One end of the cylinder 51 is closed, and the other end is closed by an outer frame 57. A displacer 52 is inserted into the internal cavity of the cylinder 51. A seal member 54 is arranged between the outer peripheral surface of the displacer 52 and the inner peripheral surface of the cylinder 51.

The cylinder 51 and the displacer 52 define an expansion space 55 at the left end of the cylinder 51 in the figure, and the displacer 52 and the outer frame 57 define a compression space 56 at the right end of the figure. In the displacer 52,
Gas flow path 5 for communicating expansion space 55 and compression space 56
8 are provided. The gas flow path 58 is filled with a cold storage material 59 such as a copper wire net or lead ball.

The displacer 52 is elastically supported in the axial direction by a coil spring 53 disposed in a compression space 56. The compression space 56 communicates with the compression chamber 5 of the gas compressor 1 via the capillary tube 45 and the gas passage 6.

When an alternating current having a predetermined frequency is applied to the electromagnetic coil 20, the piston 4 reciprocates against the elastic force of the current leads 23 and 24. Two pistons 4 on both sides of partition 2
Control the phase of the alternating current so that they move in opposite directions. When the two pistons 4 move toward each other, the pressure inside the compression chamber 5 becomes high, and when they move away from each other, the pressure inside the compression chamber 5 becomes low. By repeating the reciprocating movement of the piston 4, the gas pressure can be changed periodically.

By repeatedly supplying and exhausting the refrigerant gas to and from the cold head 50, a reverse Stirling cycle can be executed, and cold can be generated in the expansion space 55.

The thrust bearings 10 and 11 support the piston 4 in the cylinder 3 with a predetermined clearance. For this reason, it is possible to prevent the abrasion of the piston 4 against the inner peripheral surface of the cylinder 3 due to one-sided contact, thereby improving reliability. Also, a larger stroke can be ensured as compared with the case where the piston 4 is supported by a leaf spring. Further, the thrust bearing does not cause fatigue failure unlike the leaf spring. By increasing the stroke of the piston 4, the performance of the Stirling cooler can be improved.

The thrust bearings 10 and 11 of the above embodiment
It is preferable to use grease for vacuum. The use of vacuum grease can prevent contamination of the refrigerant gas.

As the thrust bearing used in the above embodiment, for example, a linear bearing such as a linear ball bearing LB type manufactured by NSK Corporation can be used. Further, a slide bearing may be used instead of the linear bearing.

In the above embodiment, the case where the radial position of the displacer 52 is fixed by the seal member 54 has been described. The displacer 52 is also provided with the piston 4 of the gas compressor 1.
Similarly to the above, it may be supported by a thrust bearing.

FIG. 2 is a sectional view of a cold head in which a displacer is supported by a thrust bearing. In a cylindrical cylinder 61 whose low-temperature end is closed and whose high-temperature end is open,
Displacer 62 is inserted. A minute gap is defined between the inner peripheral surface of the cylinder 61 and the outer peripheral surface of the displacer 62. A part of the high temperature portion 62 a of the displacer 62 protrudes from the opening of the cylinder 61. A shaft 63 having a smaller diameter than the outer peripheral surface of the displacer 62 extends from the end surface of the high temperature portion 62a along the central axis.

The opening at the high temperature end of the cylinder 61 is formed in a flange shape, and a cylindrical supporting member 6 is formed on the end surface of the flange.
7 is attached. The support member 67 is disposed so as to surround the high temperature part 62 a of the displacer 62 and the shaft 63. An opening 67 is provided on a side surface of the support member 67.
a is provided, and the inner and outer spaces communicate with each other through the opening 67a. A first thrust bearing 64 is attached to an end surface of a flange at a high temperature end of the cylinder 61, and a second thrust bearing 65 is attached to a tip of a support member 67 via a bearing support member 66. The first thrust bearing 64 and the second thrust bearing 65 connect the high-temperature portion 62a and the shaft 63 of the displacer 62, respectively.
It is supported to prohibit radial movement.

A coil spring 68 is mounted between the end of the high temperature portion 62 a of the displacer 62 and the tip of the bearing support member 66. The coil spring 68 elastically supports the displacer 62 in its axial direction.

An outer frame 70 is attached to the outermost periphery of the end face of the flange at the high temperature end of the cylinder 61. The joint between the two is kept airtight by an O-ring. The outer frame 70 defines an airtight compression space 69 that houses the hot section 62 a of the displacer 62, the shaft 63, the support member 67, the thrust bearings 64, 65, and the coil spring 68.

A compression space 69 communicates with, for example, the compression chamber 5 of the gas compressor 1 shown in FIG. 1 via a capillary tube 71 attached to the outer frame 70.

The displacer 62 is connected to a thrust bearing 64
And 65, and no seal member is arranged between the inner peripheral surface of the cylinder 61 and the outer peripheral surface of the displacer 62. Therefore, performance deterioration due to wear of the seal member can be prevented.

The present invention has been described in connection with the preferred embodiments.
The present invention is not limited to these. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0044]

As described above, according to the present invention,
By supporting the piston or displacer in the cylinder with the thrust bearing, a large stroke can be secured. Since the clearance between the inner peripheral surface of the cylinder and the outer peripheral surface of the piston can be sealed by a clearance seal method, performance deterioration due to wear of the seal member can be avoided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a Stirling cooler using a gas compressor according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a cold head of a Stirling cooler according to an embodiment of the present invention.

FIG. 3 is a schematic diagram showing a basic configuration of a Stirling cooler.

FIG. 4 is a sectional view of a conventional gas cycle engine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gas compressor 2 Partition wall 3 Cylinder 4 Piston 5 Compression chamber 6 Gas flow path 8 Piston rod 10, 11, 64, 65 Thrust bearing 13, 14 Bearing holding member 16 Gap 17 Permanent magnet 20 Electromagnetic coil 21 Coil holding member 23, 24 Current lead 30 Outer case 45, 71 Capillary tube 50 Cold head 51, 61 Cylinder 52, 62 Displacer 53, 68 Coil spring 54 Seal member 55 Expansion space 56, 69 Compression space 58 Gas flow path 59 Cold storage material 63 Shaft 66 Bearing support member 67 support member 70 outer frame

Claims (3)

[Claims] A cylinder having a columnar inner peripheral surface; a piston disposed in the cylinder and having an outer peripheral surface aligned with the inner peripheral surface of the cylinder; A thrust bearing that faces the inner peripheral surface of the cylinder with a small gap therebetween and supports the cylinder so as to be movable in the axial direction thereof, and a reciprocating drive unit that reciprocates the piston in the cylinder in the axial direction. A gas compressor having: 2. A cylinder having a columnar inner peripheral surface, one end of which is closed, an outer frame attached to the other end of the cylinder, and defining a closed space together with the cylinder; A displacer having an outer peripheral surface aligned with an inner peripheral surface of the cylinder, the displacer defining an expansion space between one end of the cylinder and the displacer, and a compression space between the outer frame and the displacer. The displacer is provided with a gas flow path that communicates the expansion space and the compression space in the displacer, and is disposed in the gas flow path and exchanges heat with a gas flowing in the gas flow path. A cool storage material to be used; and a slurry for supporting the displacer such that the outer peripheral surface of the displacer faces the inner peripheral surface of the cylinder with a small gap therebetween and is movable in the axial direction of the cylinder. DOO bearing and communicates to the compression space, the cold head and a refrigerant gas supply passage to discharge the introduction of refrigerant gas. 3. The cold head according to claim 2, further comprising an elastic member that elastically supports the displacer in an axial direction of the cylinder.