Stirling refrigerating machine

Details Stirling refrigerating machine Stirling refrigerating machine

1997-01-16

2002-10-08

Capossela, Ronald (Department: 3744)

Refrigeration

Gas compression, heat regeneration and expansion, e.g.,...

C060S520000

Reexamination Certificate

active

06460347

ABSTRACT:

TECHNICAL FIELD
This invention relates to a Stirling refrigerating machine in which a compressor is connected to an expander through a connection pipe, and particularly relates to improvements of a sealing structure provided at a joint between the compressor and the connection pipe.
BACKGROUND ART
A free displacer type Stirling refrigerating machine has been conventionally known as one of small size refrigerating machines which produce cold conditions at an extremely low temperature level. Such a refrigerating machine is disclosed in Japanese Patent Application Laid-Open Gazette No. 6-174321. The refrigerating machine is so composed that a compressor for compressing a gas refrigerant and an expander for expanding the gas refrigerant discharged from the compressor are connected to each other through a connection pipe.
Below, description will be made about the structure of the compressor.
As shown in
FIG. 6
, the compressor (a) includes a gastight casing (b), a cylinder (c) provided in the casing (b), a pair of pistons (e, e) reciprocatably fit in the cylinder (c) to form a compression room (d) in the cylinder (c), and linear motors (f, f) for reciprocating the pistons (e, e) respectively. The cylinder (c) has cylindrical recesses (c
1
, c
1
). The recesses (c
1
, c
1
) are formed around the compression room (d) in a manner coaxial with the cylinder (c).
The linear motor (f) has an annular permanent magnet (g) disposed in the recess (c
1
). The permanent magnet (g) generates a magnetic field with the cylinder (c) serving as a yoke. An inverted-cup-shaped bobbin (h) is reciprocatably placed in the recesses (c
1
). The bobbin (h) is provided with a drive coil (i). The drive coil (i) is opposed to the permanent magnet (g). The bobbin (h) is fixed at a center thereof to the piston (e). A lead (k) for supplying a current to the drive coil (i) is led out of the bobbin (h). The lead (k) is connected to a terminal (m) mounted on the casing (b). The outer bottom surface of the bobbin (h) (a side opposite to the piston) and the inner bottom surface of the casing (b) are bridged with a piston spring (j) formed of a coil spring. The piston spring (j) resiliently supports the piston (e) so as to allow reciprocating motions of the piston (e).
A gas passage (c
2
) is formed in the cylinder (c) and the casing (b). The gas passage (c
2
) is open at one end thereof to the compression room (d) and at the other end to the outer surface of the casing (b).
The compressor (a) is connected to one end of a connection pipe (n), so that the internal passage of the connection pipe (n) is communicated with the gas passage (c
2
). The other end of the connection pipe (n) is connected to an expander (not shown).
In operating the refrigerating machine, an alternating current of a specific frequency is supplied to the drive coils (i, i) through the leads (k, k). Thereby, a magnetic field generated around the drive coils (i, i) acts to reciprocate the bobbins (h, h). Attendantly, the pistons (e, e) lineally reciprocate in the cylinder (c) in opposite directions, so that a compressed gas generates in the compression room (d) in cycles. A pressure of a gas refrigerant thus compressed is introduced to the expander through the connection pipe (n). Thus, a high pressure and a low pressure repeatedly acts on the expander. In the expander, a gas refrigerant is expanded so that a cold condition is produced.
PROBLEM THAT THE INVENTION IS TO SOLVE
In such kind of refrigerating machine, it is required to maintain its operating performance at a high level. To satisfy the requirement, a compressed gas generated in the compressor (a) must be efficiently transferred to the expander. To cope with this, necessary positions surrounding the gas passage (c
2
) each have a sealing structure for preventing a leakage of a compressed gas.
Below, the conventional sealing structure will be described.
As shown in
FIG. 7
, O-rings (o, p, p) are disposed at a joint between the casing (b) and the connection pipe (n) and a contact part between the casing (b) and the cylinder (c), respectively. First, description is made about the sealing structure of the joint between the casing (b) and the connection pipe (n). A mount (b
1
) having a plain mounting surface is formed on the outer surface of the casing (b), while a plate-shaped flange (n
1
) is formed at one end of the connection pipe (n). A sealing groove (n
2
) is formed on the flange (n
1
). The sealing groove (n
2
) is annular and surrounds the internal passage of the connection pipe (n). A single O-ring (o) is inserted in the sealing groove (n
2
). The mount (b
1
) and the flange (n
1
) each have unshown screw holes. The gas passage (c
2
) is aligned with the internal passage of the connection pipe (n), and in this state the flange (n
1
) is brought into contact with the mounting surface of the mount (b
1
). Thereafter, screws (q, q) are screwed in both the screw holes, so that the connection pipe (n) is connected to the compressor (a). In this structure, since the single O-ring (o) is interposed between the flange (n
1
) and the mount (b
1
), this prevents a gas refrigerant flowing through the gas passage (c
2
) from leaking out of a clearance between the flange (n
1
) and the mount (b
1
) (See arrow A in FIG.
7
).
Next, description is made about the sealing structure of the contact part between the casing (b) and the cylinder (c). Sealing grooves (c
3
, c
3
) are formed at both sides (right and left in
FIG. 7
) of the gas passage (c
2
) of the cylinder (c). The sealing grooves (c
3
, c
3
) are formed over the circumference of the cylinder (c). The cylinder (c) is inserted into the casing (b) with O-rings (p, p) (two in total) fit into the sealing grooves (c
3
, c
3
) respectively. In this structure, the two O-rings (p, p) are interposed between the outer periphery of the cylinder (c) and the inner periphery of the casing (b). Accordingly, a gas refrigerant flowing through the gas passage (c
2
) is prevented from leaking out of a clearance between the cylinder (c) and the casing (b) to the inner space of the casing (b) (See arrow B in FIG.
7
).
However, the above sealing structure has the following problems: In the structure, a sealed part between the casing (b) and the cylinder (c) is formed over the circumference of the cylinder (c). In other words, the O-rings (p, p) each having a large diameter identical with the outer diameter of the cylinder (c) are used. Therefore, a sealed area becomes large. This makes it difficult to obtain a sufficient reliability of a sealing function, that is, the possibility that a gas refrigerant may leak out of the contact part between the casing (b) and the cylinder (c) to the inner space of the casing (b) is increased.
The present invention has been made in view of the above problem. An object of the invention is to increase a reliability of a sealing function of a contact part between a casing and a cylinder in a compressor of a Stirling refrigerating machine.
DISCLOSURE OF INVENTION
SUMMARY OF THE INVENTION
In the present invention, an end part of a connection pipe is inserted into insertion holes formed in a casing and a cylinder respectively. Then, a sealing function is provided to a joint between the end part of the connection pipe and the cylinder. In this arrangement, a sealed area is decreased, resulting in increase in reliability of the sealing function of the contact part between the casing and the cylinder.
FEATURES OF THE INVENTIONS
More specifically, a solution taken in claim 1 of the invention is described below. As shown in
FIGS. 1 and 3
, the solution is directed to a Stirling refrigerating machine having a compressor (
1
) and an expander (
2
). The Stirling refrigerating machine premises the following structure: The compressor (
1
) comprises, a cylinder (
4
) fit into a casing (
3
), a piston (
6
) which is inserted into the cylinder (
4
) so as to be capable of reciprocating motion relative to the cylinder (
4
) and forms a compression room (
7
) between the piston (
6
) and the cylinder (
4
), resilient means (
14
) for resil

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