Patent Application
20050046187
1. Field of the Invention
The present invention relates to a pipe joint used to connect refrigerant pipes to each other in a refrigeration cycle or, in particular, to a structure for hermetically connecting an atmospheric side and a refrigerant side through two hermetic sealing-members.
2. Description of the Related Art
A conventional pipe joint of this type for the refrigeration cycle, which comprises a male joint 100 and a female joint 110 for connecting the refrigerant pipes, as shown in
The female joint 110 includes a fitting recess 111 cylindrically formed on the inner periphery thereof. The male joint 100 includes a fitting protrusion 101 formed cylindrically and a stepped portion 102 formed adjacently to the fitting protrusion 101 and having a smaller outer diameter than the fitting protrusion 101. An O-ring 120 constituting a second hermetic sealing-member arranged in the direction communicating with the refrigerant side and a backup ring 130 constituting a first hermetic sealing-member arranged in the direction communicating with the atmosphere side are adjacently fitted in the stepped portion 102. The outer periphery of the fitting protrusion 101, the O-ring 120 and the backup ring 130 is fitted in the fitting recess 111 thereby to hermetically seal the atmosphere side and the refrigerant side.
The backup ring 130 is a hermetic sealing-ring for preventing the displacement (sticking-out) of the O-ring 120 and formed by bias cutting of a PTFE (polytetrafluoroethylene) material. The backup ring 130 is arranged with a first end surface thereof pressed against the pressure-fitting wall portion 103 formed on the male joint 100.
As a result, with the refrigerant pressure imparted from the refrigerant side to a first end surface of the O-ring 120 adjacent to the backup ring 130, the first end surface of the backup ring 130 is pressed against the pressure-fitting wall portion 103 and plastically deformed, thereby filling the gap between the fitting recess 111 and the fitting protrusion 101. In this way, the O-ring is prevented from being displaced toward the low-pressure side while, at the same time, securing to hermetically seal the refrigerant side and the atmosphere side (See JIS (Japanese Industrial Standard) B2407: Backup ring for O-ring).
In the supercritical refrigeration cycle using carbon dioxide refrigerant, however, a rubber material or a resin material, when in contact with or immersed in the carbon dioxide refrigerant in the supercritical state, has been found to have a higher permeability than with the conventional flon or substitute flon refrigerant.
In the configuration described above, the backup ring 130 formed of PTFE (polytetrafluoroethylene) resin material has a comparatively high permeability coefficient to carbon dioxide refrigerant in supercritical state. As shown in
In view of the points described above, it is an object of the present invention to provide a pipe joint for a refrigeration cycle in which the first hermetic sealing-member leading to the atmosphere side is formed of a plastic material less permeable to a carbon dioxide refrigerant thereby to minimize refrigerant leakage.
The above-mentioned object is achieved by employing technical means according to first to fifth aspects of the invention.
Specifically, according to a first aspect of the invention, there is provided a pipe joint for connecting refrigerant pipes in a refrigeration cycle, comprising a male joint (10) and a female joint (20),
The first hermetic sealing-member (30) is formed as an endless ring having a cross section in the shape of a substantial rectangle, a substantial polygon or a substantial semicircle.
The male joint (10) includes a pressure-fitting wall portion (12) in pressure contact with the first end surface of the first hermetic sealing-member (30) fitted in the stepped portion (13). The first hermetic sealing-member (30) has a cross section of a substantial rectangle, a substantial polygon or a substantial semicircle and formed in such a shape that the contact area of the first end surface pressed against the pressure-fitting wall portion (12) is larger than the contact area of the other end surface contacted by the second hermetic sealing-member (31).
In the first aspect of the invention, the first hermetic sealing-member (30) arranged in the direction communicating with the atmosphere side is formed of a plastically deformable resin material having a smaller permeability coefficient than the second hermetic sealing-member (31) of an elastic material. Thus, the permeability coefficient to carbon dioxide refrigerant in the supercritical state can be reduced considerably as compared with the conventional material of PTFE (polytetrafluoroethylene). As a result, the amount of the refrigerant leaking through the first hermetic sealing-member (30) and the second hermetic sealing-member (31) can be minimized.
Further, as the first hermetic sealing-member (30) is formed of a plastically deformable resin material, the gap generated between the fitting recess (24) and the first hermetic sealing-member (30) can be positively filled due to the refrigerant pressure from the second hermetic sealing-member (31) for an improved hermeticity.
As compared with the conventional bias cut structure, the first hermetic sealing-member (30) is formed as an endless ring without seams, and therefore the refrigerant leakage which otherwise might be caused through the seams can be eliminated.
As the contact area with the pressure-fitting wall portion (12) is reduced, the stress on the first end surface is increased, thereby improving the hermeticity in the boundary surface with the pressure-fitting wall portion (12).
According to a second aspect of the invention, there is provided a pipe joint for the refrigeration cycle, wherein the first hermetic sealing-member (30) is formed of a resin material having a thermal deformation temperature of preferably about 60 degrees or lower in accordance with Rule A of JIS (Japanese Industrial Standard) K7191-2.
According to a third aspect of the invention, there is provided a pipe joint for the refrigeration cycle, wherein the first hermetic sealing-member (30) has an outer diameter preferably about 1.0 to 1.03 times as large as the inner diameter of the fitting recess (24).
According to a fourth aspect of the invention, there is provided a pipe joint for the refrigeration cycle, wherein the first hermetic sealing-member (30) is formed of selected one of PA11 (nylon 11), PA12 (nylon 12) and HDPE (high-density polyethylene). In the fourth aspect of the invention, the second hermetic sealing-member (31) is formed of an elastic material, such as IIR, H-NBR or EPDM, which is high in blister resistance against carbon dioxide refrigerant. Nevertheless, the former materials have a permeability coefficient to carbon dioxide refrigerant, and smaller than the latter materials, and, therefore, the refrigerant leakage due to the permeation can be considerably reduced as compared to a conventional PTFE (polytetrafluoroethylene) material.
According to a fifth aspect of the invention, there is provided a pipe joint for the refrigeration cycle, wherein the refrigeration cycle is the supercritical refrigeration cycle using the carbon dioxide refrigerant. In the fifth aspect of the invention, the resin material having a small permeability coefficient is preferably used for the supercritical refrigeration cycle.
The reference numerals inserted in the parentheses attached to each of the means described above designate the correspondence with the specific means in embodiments described later.
The present invention may be more fully understood from the description of the preferred embodiments of the invention set forth below, together with the accompanying drawings.
In the drawings:
(First Embodiment)
A pipe joint for the refrigeration cycle according to a first embodiment of the invention is explained below with reference to FIGS. 1 to 5.
This pipe joint, as shown in
The male joint 10 includes a fitting protrusion 14 formed cylindrically at an end thereof, and a stepped portion 13 cylindrically formed and extending toward the forward end from the fitting protrusion 14. The inner periphery of the male joint 10 is formed with a refrigerant path 11, and the other end of the male joint 10 is connected with the refrigerant pipe not shown. The stepped portion 13 has a smaller outer diameter than the fitting protrusion 14. The part of the stepped portion 13 nearer to the fitting protrusion 14 is formed with a pressure-fitting wall portion 12 against which a first end surface of the first hermetic sealing-member 30, described later, is pressed.
A backup ring 30 making up the first hermetic sealing-member arranged in the direction communicating with the atmosphere side and an O-ring 31 constituting the second hermetic sealing-member arranged on the refrigerant side are fitted adjacently to each other on the stepped portion 13. The outer periphery of the fitting protrusion 14, the backup ring 30 and the O-ring 31 is fitted in the fitting recess 24 of the female joint 20 thereby to attain hermeticity between the refrigerant side and the atmosphere side. The male joint 10 and the female joint 20 are coupled to each other by a fastening member such as a bolt not shown.
The O-ring 31 arranged in the direction communicating with the refrigerant side is formed of a hermetic sealing-member of an elastic material such as rubber or, especially, a selected one of IIR, H-NBR and EPDM having a high blister resistance hardly affected by bubbles generated by contact with, or immersion in, carbon dioxide in supercritical state (the state in which the liquid and the gas assume a single phase).
The backup ring 30 arranged in the direction communicating with the atmosphere side, on the other hand, is a hermetic sealing-member to prevent the O-ring 31, described above, from being deformed under the refrigerant pressure and displaced (stuck out) toward the atmosphere side. As shown in
The research conducted by the inventors shows that the rubber and resin materials described above including EPDM, H-NBR (acrylonitrile-butadiene rubber with a mid-high value of the coupling acrylonitrile amount), PTFE (polytetrafluoroethylene), IIR and PA12 (nylon 12) have a descending order of the permeability coefficient to carbon dioxide. PA11 (nylon 11), PA12 (nylon 12) and HDPE (high-density polyethylene) are formed of a crystalline resin material having a dense molecular structure and, therefore, have superior characteristics as gas barriers.
The backup ring 30 is required to be formed of a resin material plastically deformable to prevent the displacement of the O-ring 31. Specifically, this material is required to behave in such a manner that with the refrigerant pressure imparted to a first end surface of the O-ring 31 from the refrigerant side, the first end surface of the backup ring 30 is pressed against the pressure-fitting wall portion 12 while at the same time being plastically deformed and widened along the inner and outer diameters thereof, thereby filling the gap between the fitting recess 24 and the backup ring 30.
According to this embodiment, the material described above is formed to have a characteristic in which the thermal deformation temperature thereof is preferably about 60 degrees or lower. The thermal deformation temperature characteristic is determined based on Rule A of JIS K7191-2. As long as the refrigerant pressure imparted to the first end surface of the O-ring 31 is, for example, 1.80 MPa or higher, the backup ring 30 is plastically deformed and can fill the gap. On the other hand, the backup ring 30 has an outer diameter slightly larger than the outer diameter of the O-ring 31, and about 1.0 to 1.03 times as large as the inner diameter of the fitting recess 24.
Next, the operation of the pipe joint for the refrigeration cycle having the aforementioned configuration is explained with reference to
The relation between the materials of the O-ring 31 and the backup ring 30 and the refrigerant leakage amount has been experimentally confirmed and will be explained with reference to
In step A shown in
As the result of checking the refrigerant leakage amount in a similar way by selecting and combining materials of the backup ring 30 hard to develop plastic deformation with the O-ring 31 of IIR, it has also been found that the characteristics obtained from these combinations are inferior to those obtained by the combinations above.
With the pipe joint for the refrigeration cycle according to the first embodiment, a plastically deformable resin material smaller in permeability coefficient than the O-ring 31 of an elastic material like rubber is employed in forming the backup ring 30 arranged in the direction communicating with the atmosphere side, and therefore the permeability coefficient to carbon dioxide refrigerant in supercritical state can be remarkably reduced as compared with the conventional pipe joint of PTFE (polytetrafluoroethylene), thereby making it possible to minimize the refrigerant leakage through the backup ring 30 and the O-ring 31.
Further, since the backup ring 30 is formed of a plastically deformable resin material, the gap formed between the fitting recess 24 and the backup ring 30 can be positively filled due to the refrigerant pressure from the O-ring 31 for an improved hermeticity.
Also, in view of the fact that the conventional bias cutting is replaced by an endless ring having seams less than those of the bias-cutting, the refrigerant leakage which otherwise might occur from the seams can be eliminated.
The backup ring 30 is formed of a resin material having a thermal deformation temperature of preferably about 60° C. or lower according to Rule A of JIS K7191-2, and therefore is easily plastically deformed under the pressure of the refrigerant side. As a result, the gap formed between the fitting recess 24 and the backup ring 30 can be positively filled under the refrigerant pressure from the O-ring 31 for an improved hermeticity. Incidentally, a resin material hardly deformed plastically has been found to be inferior in hermeticity.
The backup ring 30 has a larger outer diameter than the O-ring 31. Therefore, the hermeticity is achieved positively on the one hand and the displacement of the O-ring 31 to the low pressure side can be accurately prevented on the other hand. Further, in view of the fact that the outer diameter of the backup ring 30 is preferably 1.0 to 1.03 times as large as the inner diameter of the fitting recess 24, a high mountability in the fitting recess 24 is secured.
Specifically, the backup ring 30 is formed of a selected one of PA11 (nylon 11), PA12 (nylon 12) and HDPE (high-density polyethylene). The backup ring 30 formed of any of these materials is combined with the O-ring 31 of, for example, IIR as an elastic material having a high blister resistance against the carbon dioxide refrigerant. Thus, the refrigerant leakage due to the permeability can be remarkably reduced as compared with the conventional material of PTFE (polytetrafluoroethylene). Also, these materials are preferably used for the supercritical refrigeration cycle with the carbon dioxide refrigerant.
(Second Embodiment)
According to the first embodiment described above, the backup ring 30 has a substantially rectangular cross section. Alternatively, instead of the substantially rectangular cross section, the cross section of the backup ring 30 may be substantially polygonal or substantially semicircular as shown in
In
(Other Embodiments)
Specific numerical values included in the embodiments are only examples to which this invention is not limited.
While the invention has been described by reference to specific embodiments chosen for the purposes of illustration, it should be apparent that numerous modifications could be made thereto by those skilled in the art without departing from the basic concept and scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-282075 | Jul 2003 | JP | national |
