JP5764471B2 - Pipe joint structure - Google Patents

Description

  The present invention relates to a pipe joint structure using an inner ring, and more specifically, piping of high-purity liquid or ultrapure water handled in manufacturing processes in various technical fields such as semiconductor manufacturing, medical / pharmaceutical manufacturing, food processing, chemical industry, etc. The present invention relates to a pipe joint structure suitable for the above.

In the pipe joint structure using the inner ring, a fluid transfer tube is formed on the tip side with a tapered diameter-expanding part that press-fits into the end of the tube from the tip and expands the inner periphery of the end of the tube. An inner ring having an outer peripheral portion and an inner peripheral portion that is a fluid transfer channel, a pipe joint body or fluid device having a cylindrical threaded portion with a male screw formed on the outer peripheral side, and a cylindrical screw It comprises a union nut formed with a female screw that is screwed into the male screw of the joint. As such a thing, what was disclosed in patent document 1 is known, for example.
In this Patent Document 1, a cylindrical threaded portion provided in a pipe joint body with a male screw formed on the outer periphery, an inner peripheral portion as a fluid flow passage, and an annular large diameter portion on a radially outer side. A raised inner ring for fixing a tube, and a union nut formed with a female screw that is screwed into the male screw are provided.

In the pipe joint structure, in order to connect the tube to the pipe joint main body, first, the inner ring is press-fitted into the end of the tube from the opening of the tube, and the end of the tube is expanded and deformed by the annular large diameter portion. Let
Next, the tube with the inner ring whose diameter has been deformed is inserted into the cylindrical threaded portion.
Next, the female screw of the union nut is screwed into the male screw of the cylindrical screwing portion.
Then, the union nut is screwed, and the tube is connected by pressing the tube with the inner ring in the axial direction with the union nut.

By the way, in order to press-fit the inner ring into the end portion of the tube from the opening of the tube, a dedicated press-fitting jig (press-fitting device) is used.
The forced press-fitting performed using this press-fitting jig (press-fitting device) is disclosed in, for example, Patent Document 2 and Patent Document 3.
In those disclosed in Patent Document 2 and Patent Document 3 and the like, the inner ring is fitted into the extrusion mechanism, while the tube is fixed to the clamp jig so that the end of the tube protrudes, and the operation of the extrusion mechanism is performed. The inner ring is pressed in the axial direction so as to be press-fitted into the end portion of the tube from the opening of the tube.

  In this press-fitting jig (press-fitting device), the relative positions and directions of the axial centers of the clamp jig and the push-out mechanism are precisely matched so that the tube and the inner ring can be press-fitted straight and tightly.

When the axial centers X and P of the tube and the inner ring are press-fitted without being inclined, they are as follows.
That is, as shown in FIG. 10, because the inner peripheral surface of the end portion 4C of the tube 4 and the outer peripheral surface 3G of the inner ring 3 are pressed together in a ring shape as shown in the cross-hatching, In any of the important points, a ring-shaped seal state without any interruption (no missing circular portion) is formed.

Further, in the case where the inner ring 3 in the conventional pipe joint structure shown in FIG. 9 is press-fitted into the end portion 4C of the tube 4 in such a manner that the respective axial centers X and P are not inclined and shown in FIG. This will be described below with reference to FIG.
First, the conventional inner ring 3 shown in FIG. 9 is formed with an enlarged diameter portion 3f having a conical tapered outer peripherally enlarged diameter surface 3a and a maximum diameter portion 3b. A conical surface-shaped outer peripheral portion 3c is formed from the diameter portion 3b, and a linear trunk outer peripheral portion 3d having the same outer diameter is formed from the outer peripheral portion 3c.

When this inner ring 3 is press-fitted into the end 4C of the tube 4,
A ring-shaped first press contact portion a1 shown in FIG.
A ring-shaped second pressure contact portion a2 shown in FIG. 10 is configured from between the outer peripheral enlarged surface 3a and the maximum diameter portion 3b to the maximum diameter portion 3b.
A ring-shaped third press contact portion a3 shown in FIG. 10 is configured from the maximum diameter portion 3b to the widest outer peripheral portion 3c from the maximum diameter portion 3b.
A fourth pressure contact portion a4 is formed between the forward outer peripheral portion 3c and the trunk outer peripheral portion 3d,
A ring-shaped fifth press-contact portion a5 shown in FIG.
Thus, when the ring-shaped first to fifth press contact portions a1 to a5 are configured, the end portion 4C of the tube 4 and the inner ring 3 are well sealed, and not only there is no fluid leakage. , There is no room for fluid to enter between 4C and 3.

  However, in an actual press-fitting operation, there may be a case where an ideal state in which the axial centers X and P of the tube and the inner ring are press-fitted together without inclining as described above. As a result of diligent research and analysis on the case where this ideal state is not achieved, it is mainly due to the following reasons (1) to (3).

(1) A resin tube is fixed to a clamp jig to project the end of the tube. Since the inner ring is forcibly pressed and pressed into the protruding end portion of the tube by the pushing mechanism, the protruding end portion of the tube may be slightly bent and deformed. When this bending deformation occurs, there is a case where the axial center P of the inner ring is press-fitted with a slight inclination with respect to the axial center X of the end portion of the tube.

(2) The end face of the tube cut by an artificial operation at the site is not necessarily cut at right angles to the axis of the tube, and may be cut in a slightly inclined state. When the inner ring is pressed against the tube whose end face is slightly inclined and press-fitted, there is a time difference so that the press-fitting starts sequentially from the portion of the tube that protrudes most in the axial direction. Accordingly, the frictional force accompanying the press-fitting does not act uniformly over the entire circumference of the tube, but acts in a biased manner in the circumferential direction, so that the axial center P of the inner ring is the end of the tube as in (1). There is a case where it is press-fitted slightly with respect to the axis X of the part.

(3) The resin tube is delivered in a state of being continuously extruded and wound around a cable core. The wound tube has a curved wrinkle and is straightened, but it is difficult to completely remove the bent wrinkle, and it is almost curved slightly in the axial direction. Depending on the degree of this bend, if this bend is large, the inner ring axis P may not be pressed straight into the tube center X but may be slightly tilted. is there.

For this reason, the axial centers X and P of the tube and the inner ring are inclined. The inclination of the tube is a small deviation within 1 degree at most with respect to the inclinations of the axial centers X and P. However, if the axial centers X and P are inclined, the following problems occur.
That is, as shown in FIG. 11, the second to fifth press contact portions a <b> 2 to a <b> 5 show the same press contact situation as that shown in FIG. 10, but the first press contact portion a <b> 1 has a conical outer peripheral enlarged surface 3 a. In this case, a narrow belt-like region is formed at the tip of the inner ring which is easily deformed by diameter reduction due to the rigidity of the tube. Since the maximum diameter portion 3b of the inner ring is in pressure contact with the inner periphery of the tube 4 and the end portion 4C of the tube 4 is inclined with respect to the axis X starting from the pressure contact portion, the narrow first pressure contact portion a1 is the pressure contact. The portion does not have a ring shape and is interrupted in the circumferential direction, and a surface pressure drop portion n or a non-contact portion n is generated.
When this surface pressure drop part n or non-contact part n occurs, the larger the fluid is the more permeable liquid, the larger the outer peripheral diameter-enlarged surface from the point where the surface pressure drop part n or non-contact part n becomes due to capillary action There is a possibility that the gap portion k between the tapered contact portion 4a, which is expanded and deformed of the tube 4 and the tube 4 is soaked and reaches just before the maximum diameter portion 3b.
Presence of such a surface pressure drop portion n or non-contact portion n is determined by the presence or absence of a flaw detection penetrating liquid that has penetrated between the inner ring and the tube after the tube has been pressed into the inner ring and immersed in the flaw detection penetrating solution for a certain period of time. be able to.

Thus, if it penetrates to the gap part k, the following malfunction will come out.
That is, even if the next fluid is flowed after cleaning the inside of the tube or the fitting body, the previous old fluid is accumulated in the gap portion k, and the previous old fluid is reduced to the surface pressure drop portion n or the non-contact portion. n is devastating and mixed into the new fluid that has been replaced, so the purity of the new fluid is reduced, the new fluid is altered, and a lot of time is spent on cleaning and replacement to prevent contamination as much as possible. There is a problem that a lot of cleaning liquid and a lot of replacement fluid are consumed.

Japanese Patent Laid-Open No. 10-054489 JP 2001-041364 A JP 2008-194799 A

  The object of the present invention is to provide a fluid between the end of the tube and the outer peripheral enlarged surface of the inner ring from the front end side of the outer peripheral enlarged surface of the inner ring even when the inner ring is tilted and pressed into the end of the tube. It is an object of the present invention to provide a pipe joint structure that is prevented from being soaked in between, and thus can solve the above-mentioned problems.

As illustrated in FIGS. 5 and 8A, the invention according to claim 1
A fluid transfer tube 4;
An outer peripheral portion 3G having a tapered diameter-enlarged portion 3F formed on the distal end side thereof, which is press-fitted into the end portion 4C of the tube 4 from the distal end to expand the inner peripheral portion of the end portion 4C of the tube 4; An inner ring 3 having an inner circumferential part 3w which is a transfer channel;
A pipe joint body 1 or a fluid device 1 having a cylindrical threaded portion 1A in which a male screw 7 is formed on the outer peripheral side;
A union nut 2 formed with a female screw 13 to be screwed into the male screw 7 of the cylindrical screw part 1A,
The inner ring 3 is inserted into the cylindrical threaded portion 1A in a state where the inner peripheral portion of the end portion 4C of the tube 4 is expanded, and the tip side of the inner ring 3 is the cylindrical shape. In a pipe joint structure that is pressed in a state where the tube 4 is sandwiched between the union nut 2 screwed to the male screw 7 of the screwing portion 1A,
The diameter-enlarging portion 3f of the inner ring 3 is an end portion of the tube 4 that appears at that time as a state in which only the portion of the inner peripheral portion of the end portion 4C of the tube 4 whose diameter is expanded to the maximum is expanded to the maximum. 4C is configured to have a larger diameter than the naturally tapered inner circumferential enlarged surface 4u of the inner circumferential portion of the 4C, and to have a tapered outer circumferential enlarged surface 3a having a convex curved surface ,
The thickness of the tube 4 that has not been expanded and deformed is t4, the thickness of the maximum diameter portion 3b of the expanded portion 3f is t3, and t3 / t4 is in the range of 1.2 to 2.5. , The thickness of the maximum diameter portion 3b is set,
A rear end side of the inner ring 3 is in contact with seal components m and 1a provided in the pipe joint main body 1 or the fluid device 1 when the front end side of the inner ring 3 is pressed by the union nut 2. Seal element portions 14 and 15 constituting the seal portions S3 and S4 are formed .

  According to a second aspect of the present invention, in the pipe joint structure according to the first aspect, as illustrated in FIG. 5, the tapered outer peripheral enlarged surface 3 a and the inner peripheral portion of the end 4 </ b> C of the tube 4 The length in the axial direction of the contact portion is pa, and the length in the axial direction from the boundary 3g between the tapered outer diameter expansion surface 3a and the maximum diameter portion 3b to the tip of the inner ring 3 is pb. The shape of the tapered outer peripheral enlarged surface 3a is set so that pb is in the range of 0.5 to 1.0 (0.5 ≦ pa / pb ≦ 1.0) in the circumferential direction. Features.

  According to a third aspect of the present invention, in the pipe joint structure according to the first or second aspect, the axial direction of the contact portion between the tapered outer peripheral enlarged surface 3a and the inner peripheral portion of the end 4C of the tube 4 The length is pa, and the axial length from the boundary 3g between the tapered outer diameter-enlarged surface 3a and the maximum diameter portion 3b to the tip of the inner ring 3 is pb, and this pa / pb is 0 in the circumferential direction. The tapered outer peripheral diameter-enlarged surface 3a is shaped so as to be in the range of 0.7 to 1.0 (0.7 ≦ pa / pb ≦ 1.0).

According to the first aspect of the present invention, the diameter of the end 4C of the tube 4 is expanded in a state where only the largest diameter portion 3b of the diameter-enlarged portion 3f is formed on the entire outer diameter-enlarged surface 3a of the tapered inner ring 3. When deformed, the inner ring is formed in a convex curved surface having a larger diameter than the inner circumferential enlarged surface 4u of the natural tapered portion of the inner circumferential portion of the end 4C of the tube 4 that appears in the inner ring. The outer peripheral expanded surface 3a of the inner ring is in contact with the inner peripheral portion of the tube 4C over a wide range, and the outer peripheral expanded surface 3a of the inner ring is interposed between the outer peripheral expanded surface 3a of the inner ring and the inner peripheral portion of the tube 4. It is possible to form a wide pressure contact portion that covers the entire surface of the film.
Accordingly, even if the inner ring 3 is press-fitted with a slight inclination with respect to the tube 4, the press-contact portion formed between the end 4 </ b> C of the tube 4 and the outer circumferential enlarged surface 3 a of the inner ring 3 is interrupted. Therefore, it is possible to effectively prevent a situation in which almost the entire circumferential direction is reliably pressed and the fluid permeates from the front end side of the outer peripheral enlarged diameter surface 3a during this time.
As a result, the above-mentioned problem, that is, the old fluid that has flowed first, accumulates in the gap portion k, and the old fluid that has flowed away from the surface pressure drop portion n or the non-contact portion n is mixed into the replaced new fluid. As a result, the purity of the new fluid decreases, the new fluid changes in quality, or a lot of time, a large amount of cleaning liquid, or a large amount of replacement fluid is spent on cleaning and replacement to prevent contamination. Can be resolved.

As in the first aspect of the invention, if the thickness of the maximum diameter portion 3b is set so that the t3 / t4 is in the range of 1.2 to 2.5, the thickness of the inner ring 3 is reduced. Thus, the problem that the inner ring 3 creeps in a short period of time and obstructs long-term reliable pressure contact is prevented. On the contrary, the inner ring 3 becomes too thick, and the end portion 4C of the tube 4 is excessively expanded and deformed. Due to this excessive expansion, the end portion 4C of the tube 4 creeps in a short time. It is possible to prevent problems such as obstructing long-term reliable pressure welding. Therefore, the press contact between the inner ring 3 and the end portion 4C of the tube 4 can be ensured for a long period of time.

Further, as in the first aspect of the present invention, a seal configuration is provided on the rear end side of the inner ring 3 and provided on the pipe joint body 1 or the fluid device 1 when the front end side of the inner ring 3 is pressed by the union nut 2. If the seal element portion (14 or / and 15) constituting the back seal portion (S3 or / and S4) is formed in pressure contact with the portion (m or / and 1a), the inner ring 3 and the pipe joint body 1 are formed. Alternatively, the back side can be sealed in relation to the fluid device 1, and the back side seal completely prevents the situation where fluid enters the inner ring 3 and the end 4C of the tube 4 from the back side. can do.

  As in the second aspect of the invention, the inner ring 3 can be obtained by setting the shape of the tapered outer peripheral enlarged surface 3a so that the pa / pb is in the range of 0.5 to 1.0 in the circumferential direction. Therefore, it is possible to reliably press-fit without causing any trouble in the press-fitting work, and it is possible to provide a preferable pipe joint structure.

  In the invention of claim 2, as illustrated in FIG. 5, the contact portion between the tapered outer peripheral enlarged surface 3 a of the enlarged diameter portion 3 f and the inner peripheral portion of the end 4 </ b> C of the tube 4 has a corresponding axis. It is assumed that contact portions that are not separated are formed in the direction length pa. However, not only in this state, but between the outer diameter-enlarged surface 3a of the enlarged-diameter portion 3f and the boundary 3g on the inner-ring tip side of the largest-diameter portion 3b and the tip of the inner ring, contact portions of three or more parts The sum of the axial lengths of the contact portions of the plurality of portions is defined as pa, and with respect to the pb, pa / pb is 0.5 to 1.0 (0.5 ≦ pa / pb ≦ The same effect as described above can be expected also in the pipe joint structure in which the tapered outer diameter-enlarged surface 3a is set so as to be in the range of 1.0).

  According to a third aspect of the present invention, the tapered outer periphery is expanded so that the pa / pb is in the range of 0.7 to 1.0 (0.7 ≦ pa / pb ≦ 1.0) in the circumferential direction. If the shape of the radial surface 3a is set, an excellent pipe joint structure can be provided in which a more reliable pressure contact state can be secured without hindering the press-fitting operation of the inner ring 3 and high pressure fluid can be sealed.

  In the invention of claim 3, as illustrated in FIG. 5, the contact portion between the tapered outer peripheral enlarged surface 3 a of the enlarged diameter portion 3 f and the inner peripheral portion of the end 4 </ b> C of the tube 4 has a corresponding axis. It is assumed that contact portions that are not separated are formed in the direction length pa. However, not only in this state, but between the outer diameter-enlarged surface 3a of the enlarged-diameter portion 3f and the boundary 3g on the inner-ring tip side of the largest-diameter portion 3b and the tip of the inner ring, contact portions of three or more parts The sum of the axial lengths of the contact portions of the plurality of parts is defined as pa, and pa / pb is 0.7 to 1.0 (0.7 ≦ pa / pb ≦ The same effect as described above can be expected even when the tapered outer diameter-enlarged surface 3a is set so as to be in the range of 1.0).

Side view of inner ring Cross section of the inner ring of FIG. Sectional drawing which shows the pipe joint structure using the inner ring of FIG. 1 (Embodiment 1) FIG. 3 is an enlarged sectional view showing the main part of FIG. Sectional view showing the general pressure welding situation by press fitting between the tube and inner ring 1 is a cross-sectional view of an inner ring having a structure different from that of FIG. Sectional drawing which shows the pipe joint structure using the inner ring of FIG. 6 (Embodiment 2) (A) expands and deforms the end portion of the tube using a cylinder 30 formed to have the same diameter as the maximum diameter portion of the inner ring, and at this time, the natural constriction of the inner peripheral portion of the end portion of the tube that appears there FIG. 6B is a cross-sectional view showing the state of the inner peripheral expanded surface 4u of FIG. 1B, when the outer peripheral expanded surface of the tapered inner ring of FIG. 1 or FIG. 6 is press-fitted into the end portion of the tube and expanded in diameter. Enlarged sectional view of Sectional drawing which shows the inner ring used for the conventional pipe joint structure Sectional drawing which shows the favorable press-contact state of the tube and inner ring in the conventional pipe joint structure Sectional drawing which shows the troubled pressure welding situation of the tube and inner ring in the conventional pipe joint structure Sectional view showing the inner ring for experiments The penetration | invasion experiment result by the inner ring for experiment and a tube is shown, (a) is a case where t3 / t4 = 1.2, (b) is a case where t3 / t4 = 1.8.

  Hereinafter, embodiments of the pipe joint structure of the present invention will be described with reference to the drawings.

Embodiment 1
1 and 2 show an inner ring 3, and FIGS. 3 and 4 show a pipe joint structure of Embodiment 1 in which a tube 4 is connected using the inner ring 3, that is, a tube 4 for fluid transfer, This shows a pipe connection device A to which this is connected.
This pipe connecting device A is composed of a pipe joint for connecting tubes, and has a pipe joint main body 1, a union nut 2, and an inner ring 3. The inner ring main body 3A is press-fitted into the end 4C of the tube 4. In this state, the tube 4 is connected in communication. The pipe joint body 1, the union nut 2, the inner ring 3, and the tube 4 are all made of a resin such as a fluororesin (eg, PTFE, PFA, ETFE, CTFE, ECTFE, etc.) having excellent heat resistance and chemical resistance.
In addition, when the pipe joint main body 1, the union nut 2, and the tube 4 are comprised with the said fluororesin, in the inner ring 3, you may form with resin, such as polyamide, a polypropylene, and polyethylene. Moreover, all of the pipe joint main body 1, the union nut 2, and the inner ring 3 can be formed of a resin such as polyamide, polypropylene, or polyethylene.

The pipe joint body 1 includes a cylindrical body 1C, a cylindrical threaded portion 1A provided on the distal end side in the axial center Y direction, and a cylindrical receptacle provided on the proximal end side in the axial center Y direction. 1B, one small-diameter cylindrical portion 1a formed on the inner diameter side of the root portion of the cylindrical threaded portion 1A, the other small-diameter cylindrical portion 1b formed on the inner diameter side of the receiving port 1B, and an internal flow path 6. It is a cylindrical structure.
A male screw 7 is formed on the cylindrical threaded portion 1A from the outer periphery of the tip portion toward the back side, and an inner peripheral surface 8 is formed on the inner periphery of the tip portion. A linear inner peripheral surface 9 having the same inner diameter is formed.
A linear outer peripheral surface 10 having the same outer diameter is formed in the small-diameter cylindrical portion 1 a, and an inclined inner peripheral surface 5 that is widened toward the internal flow path 6 is formed on the distal end side of the outer peripheral surface 10. Yes.
A cylindrical annular groove m is formed between the outer peripheral surface 10 of the small diameter cylindrical portion 1a and the inner peripheral surface 9 of the cylindrical threaded portion 1A.
In addition, as shown in FIG. 3, the pipe joint main body 1 has the receiving port 1B having the same structure as the cylindrical threaded portion 1A, and the other small diameter cylindrical portion 1b having the same structure as the one small diameter cylindrical portion 1a. However, the receiving port 1B and the other small-diameter cylindrical portion 1b may have other structures.

The union nut 2 is made of a resin nut, and has an internal thread 13 that is screwed into the male screw 7 of the cylindrical threaded portion 1A and an annular flange that protrudes radially inward to the terminal end side of the female screw 13. Part 12.
The inner diameter of the flange 12 is set to be slightly larger than the outer diameter of the tube 4 so that the tube 4 can be inserted. The inner end portion (in the illustrated example, the inner corner portion) of the inner peripheral surface 12a of the flange portion 12 is the tip outer peripheral surface of the end portion 4C of the tube 4 into which the inner ring main body 3A is press-fitted, and the shaft of the pipe joint main body 1 It is configured as a pressing portion 12b that pushes in the center Y direction, and the pressing portion 12b pushes the distal end side outer peripheral surface of the end portion 4C of the tube 4 to the pipe joint body by screwing the female screw 13 into the male screw 7 of the cylindrical screwing portion 1A. 1 is pushed in the Y axis direction.
The inner peripheral surface 12a of the flange portion 12 has a constant inner diameter, but may be formed on a tapered inner peripheral surface where the inner diameter gradually increases as the distance from the female screw 13 increases.

As shown in FIGS. 1 to 4, the inner ring 3 includes an inner ring main body 3 </ b> A that is press-fitted into the end 4 </ b> C of the tube 4 from the opening of the tube 4, and the tube 4 is connected to the rear end side of the inner ring main body 3 </ b> A. It is a cylindrical structure which has the fitting cylinder part 3B which protrudes from an open port.
The inner ring main body 3A and each inner peripheral portion 3w of the fitting cylinder portion 3B are formed to have the same diameter and serve as a fluid flow passage.
The inner ring main body 3A has a diameter-enlarged portion 3f formed on the outer peripheral portion 3G, and a tapered outer diameter-enlarged surface 3a is formed on the distal end side of the enlarged-diameter portion 3f. On the rear end side of the enlarged diameter portion 3f, there is a maximum diameter portion 3b, and an outer peripheral portion that expands toward the rear end portion side of the maximum diameter portion 3b and whose outer diameter decreases toward the fitting tube portion 3B. 3c is formed. Further, a barrel outer peripheral portion (cylinder outer peripheral surface) 3d having a constant outer diameter is formed on the rear end portion side of the widened outer peripheral portion 3c.

  In the drawings of the present application, the maximum diameter portion 3b of the inner ring is described as a structure having a certain axial length, but the boundary where the outer peripheral expanded surface 3a immediately changes to the outer peripheral portion 3c that expands forward. Even if the structure corresponds to the above, there is no technical problem. In that case, the boundary 3g described in paragraph 0018 or the like coincides with the maximum diameter portion 3b.

The tapered outer peripheral enlarged surface 3a of the enlarged diameter portion 3f is formed in a convex curved surface that is convex outward in the radial direction, and the maximum diameter portion 3b is formed on the rear end side of the outer peripheral enlarged surface 3a. The outer diameter-enlarged surface 3a and the maximum diameter portion 3b are formed and pressed into the end 4C of the tube 4 so that the end 4C of the tube 4 is expanded and deformed.
In addition, a cut-shaped deformation preventing portion 16 that narrows toward the rear side of the axis P of the inner ring main body 3A is formed at the distal end portion of the outer peripheral enlarged diameter surface 3a. After the outer peripheral enlarged surface 3a is press-fitted into the end 4C of the tube 4 by the deformation preventing portion 16, the distal end side of the outer peripheral enlarged surface 3a is deformed and protrudes in the radially inward direction (fluid flow passage side). Further, the deformation preventing portion 16 prevents the distal end side of the outer peripheral enlarged diameter surface 3a from further deforming and projecting in the radially inward direction (fluid flow path side) at the momentum and speed of the fluid flow. The pressure contact force at the tip of the outer peripheral enlarged surface 3a is prevented from decreasing.

The fitting cylinder portion 3B is formed by a protruding cylindrical portion 14 that is press-fitted into the annular groove m of the pipe joint main body 1 and an annular small protruding portion 15 that is located inside the protruding cylindrical portion 14 and has an inclined outer peripheral surface 11. Has been. A cut-shaped deformation preventing portion 17 is formed at the distal end portion of the annular small protrusion portion 15 so as to narrow toward the distal end portion of the axis P of the inner ring main body 3A. The deformation preventing portion 17 prevents the distal end side of the annular small protrusion portion 15 from deforming and projecting in the radially inward direction (fluid flow passage side).
An annular recess is formed between the inclined outer peripheral surface 11 of the annular small protrusion 15 and the inner peripheral surface 14a of the projecting cylindrical portion 14, and the small-diameter cylindrical portion 1a of the pipe joint body 1 is inserted into this recess. By this insertion, the inclined outer peripheral surface 11 of the annular small protrusion 15 and the inclined inner peripheral surface 5 of the small diameter cylindrical portion 1a can come into contact with each other.
Further, the diameter difference (step) between the outer peripheral surface 3e of the fitting cylindrical portion 3B and the outer peripheral portion 3d is as small as possible between the outer peripheral surface 4B of the tube 4 and the inner peripheral surface 9 of the cylindrical threaded portion 1A. In order not to occur, it is set to be approximately equal to the thickness of the tube 4.

The tube 4 is formed by press-fitting the inner ring main body 3A into the end portion 4C thereof and expanding and deforming, thereby causing the tapered pressure contact portion 4a to be in pressure contact with the outer peripheral enlarged diameter surface 3a of the inner ring main body 3A, and the inner ring main body. A maximum diameter expanded pressure contact portion 4b that is in pressure contact with the maximum diameter portion 3b of 3A, a pre-expanded pressure contact portion 4c that is in pressure contact with the outer peripheral portion 3c of the inner ring body 3A, and a body pressure contact that is in pressure contact with the body outer periphery 3d of the inner ring body 3A A portion 4d is formed.
In this formed state, the diameter of the internal flow path 4w of the tube 4 and the diameter of the inner peripheral portion 3w of the inner ring 3 and the diameter of the internal flow path 6 of the pipe joint body 1 are only the diameter of the internal flow path 4w of the tube 4. Although it is set to be substantially flush (ie, substantially the same diameter), it is not limited to the case where it is set to be flush.

The tube 4 is equipped by inserting the inner ring main body 3 </ b> A into the end 4 </ b> C and then inserting it into the pipe joint main body 1. Then, as shown in FIGS. 3 and 4, the female thread 13 of the union nut 2 is screwed into the male thread 7 of the cylindrical threaded portion 1 </ b> A of the pipe joint body 1, so that the tube 4 is pressed by the pressing portion 12 b of the union nut 2. The outer peripheral surface of the distal end side of the end portion 4C (the outer peripheral surface of the tapered contact portion 4a) is pressed in the direction of the axis Y.
By this pressing, the protruding cylindrical portion 14 of the inner ring 3 is press-fitted into the annular groove m of the pipe joint main body 1, and the inclined outer peripheral surface 11 of the inner ring 3 abuts on the inclined inner peripheral surface 5 of the pipe joint main body 1. Press contact.

As described above, when the tube 4 with the inner ring 3 is inserted and connected to the pipe connection device (pipe joint) A, the following first seal part S1 to fourth seal part S4 are configured.
That is,
The first seal portion S1 is formed by pressure contact between the tapered pressure contact portion 4a of the tube 4 and the outer diameter-enlarged surface 3a of the inner ring body 3A, the maximum diameter pressure contact portion 4b of the tube 4 and the maximum diameter portion of the inner ring body 3A. 3b, the pressure contact portion 4c of the tube 4 that is widened and the outer peripheral portion 3c of the inner ring main body 3A, and the pressure contact portion 4d of the tube 4 and the outer peripheral portion 3d of the inner ring main body 3A. It is a seal part.

The second seal portion S <b> 2 is a seal portion configured by pressure contact between the pre-expanded pressure contact portion 4 c of the tube 4 and the pre-expanded inner peripheral surface 8 in the cylindrical threaded portion 1 </ b> A of the pipe joint body 1.
The third seal portion S3 is a press-contact between the outer peripheral surface of the fitting cylindrical portion 3B of the inner ring 3 and the inner peripheral surface 9 on the inner side of the cylindrical threaded portion 1A of the pipe joint body 1, and further, the third sealing portion S3 of the fitting cylindrical portion 3B. It is a seal portion configured by pressure contact between the inner peripheral surface and the outer peripheral surface 10 of the small-diameter cylindrical portion 1 a of the pipe joint body 1.
The fourth seal portion S4 is a seal configured by pressure contact by abutting contact between the inclined outer peripheral surface 11 of the annular small protrusion 15 of the inner ring 3 and the inclined inner peripheral surface 5 of the small diameter cylindrical portion 1a of the pipe joint body 1. Part.

Since the first seal portion S1 to the fourth seal portion S4 are configured, the fluid flowing in the tube 4, the inner ring 3, and the pipe joint main body 1 is in a cylindrical threaded portion 1 A of the pipe joint main body 1. And the end 4C of the tube 4 does not enter or leak, and is completely sealed.
In addition, if the 1st seal part S1 and the 2nd seal part S2 are reliably sealed among these 1st seal | sticker parts S1-4th seal | sticker part S4, the said fluid will be the cylindrical screwing of the pipe joint main body 1. FIG. A good seal is ensured without entering or leaking from between the portion 1A and the end 4C of the tube 4. However, in order to ensure a more complete seal, it is preferable to provide at least one of the third seal portion S3 and the fourth seal portion S4.

By the way, in the first seal portion S1, the pressure contact between the tapered pressure contact portion 4a of the tube 4 and the outer circumferential enlarged surface 3a of the inner ring main body 3A is particularly configured as follows.
That is, as shown in FIG. 4, the tapered outer peripheral diameter-enlarging surface 3a of the inner ring main body 3A has the entire diameter in the radial dimension of the maximum diameter part 3b of the enlarged diameter part 3f of the inner ring main body 3A (maximum When the end portion 4C of the tube 4 is expanded and deformed (in the state of only the diameter portion 3b), the inner peripheral expanded surface of the natural constriction of the inner peripheral portion of the end portion 4C of the tube 4 that appears (appears) there. 4u [This symbol 4u is shown in FIG. The outer diameter-enlarged surface 3 a is configured to be in pressure contact with the inner peripheral portion of the end portion 4 C of the tube 4.

8 (a) and 8 (b) with respect to the naturally tapered inner peripheral enlarged surface 4u and the outer peripheral enlarged surface 3a having a larger diameter than the inner peripheral enlarged surface 4u and formed in a convex curved surface. ) Will be described.
The cylinder 30 shown in FIG. 8A has an outer diameter D that is the same diameter as the maximum diameter portion 3b of the inner ring body 3A. The cylinder 30 is press-fitted into the end portion 4C of the tube 4 having the inner diameter d that has not been expanded and deformed, and the end portion 4C of the tube 4 is expanded and deformed. As a result, a naturally tapered inner circumferential enlarged surface 4u is formed between the enlarged diameter portion 4K of the tube 4 and the diameter portion 4M of the tube 4 that has not been enlarged and deformed.
In general, the shape and size of the inner circumferential enlarged surface 4u of this natural tapered shape are different in the material of the tube 4, the thickness (thickness) t, the diameter expansion amount ((D−d) / 2), and the like. Depending on the material, thickness t, and diameter expansion amount of these tubes 4, their characteristics (shape and dimensions) change each time.

  On the other hand, the outer peripheral enlarged surface 3a of the inner ring main body 3A is a cross section of the enlarged portion 3f as shown in FIG. The outer contour line in this case is formed into a curved surface that is convex outward, that is, a convex curved surface. The surface of this convex curved surface is a spherical surface that is the surface of a circular sphere, an elliptic spherical surface that is the surface of an elliptic sphere, or the like. Further, the outer diameter of the convex curved surface, that is, the diameter of the outer peripherally enlarged surface 3a of the tapered shape is larger in all directions along the axis P than the inner peripherally enlarged surface 4u of the natural tapered shape. It is formed in the diameter.

In this way, when the tapered outer diameter-enlarged surface 3a has a large diameter and a convex curved surface, the following effects can be obtained.
Now, the inner ring main body 3A is press-fitted into the end 4C of the tube 4. However, since the inner ring main body 3A is inclined and press-fitted, as shown in FIG. 5, the axis P of the inner ring main body 3A and the axis X of the tube X It is assumed that there is a relative angle θ between
Even in such an unforeseen situation where the inner ring body 3A is press-fitted in an inclined manner, the entire outer diameter-expanded surface 3a of the inner ring body 3A is only the maximum diameter portion 3b of the inner ring body 3A. When the diameter of the end portion 4C is increased, the inner diameter of the end portion 4C of the tube 4 that appears in the end portion 4C is larger than the inner diameter expansion surface 4u of the natural constriction, and is formed in a convex curved surface. Therefore, a first pressure contact portion a1 is formed between the outer peripheral enlarged diameter surface 3a of the inner ring main body 3A and the tapered pressure contact portion 4a of the tube 4, and the first pressure contact portion a1 is interrupted in the circumferential direction. In this way, a continuous ring shape and a wide contact area in the direction of the axis P can be obtained. That is, this wide area pressure contact is just from the conventional first pressure contact part a1 to the second pressure contact part a2 shown in FIG. 10 regardless of the material of the tube, the thickness (thickness), and the diameter expansion amount. It becomes a pressure welding that is integrated continuously.

If a relative angle θ exists between the axis P of the inner ring main body 3A and the axis X of the tube, the free diameter portion of the tube 4 is formed at the outer portion s in the bending direction of the tube 4 as shown in FIG. The bend (expansion bend) of the portion where the diameter is expanded from the portion (indicated by reference numerals 4A and 4B in FIG. 5) to the tapered pressure contact portion 4a becomes gentle. Accordingly, the angle formed between the outer peripheral enlarged surface 3a of the inner ring main body 3A and the tapered pressure contact portion 4a is reduced, and the pressure contact acts in a stronger direction. Then, at the inner portion v in the bending direction of the tube 4, the bending (expansion bending) of the portion where the diameter of the tube 4 changes from the free diameter portion to the tapered pressure contact portion 4 a becomes severe (abrupt), and the inner portion The angle formed by the outer circumferential enlarged surface 3a of the ring main body 3A and the constricted pressure contact portion 4a is increased and acts in a direction in which the pressure contact is weakened.
However, even in the bending direction inner portion v where the pressure contact is weakened, the ring-shaped first pressure contact portion a1 having the wide area is realized (maintained) and can be sufficiently pressure-contacted as in the conventional case. Problems such as the occurrence of the pressure drop portion n or the non-contact portion n can be solved.

As described above, the ring shape has a wide area from the distal end in the direction of the axial center P between the outer diameter-enlarged surface 3a of the inner ring main body 3A and the constricted pressure contact portion 4a of the tube 4 and is not interrupted. When the first press contact portion a1 having a good thickness is formed, even if the fluid is a highly permeable liquid, the inner ring main body 3A is inclined and press-fitted as shown in FIG. It is possible to prevent a problem that the gap n between the outer peripheral enlarged surface 3a of the inner ring main body 3A and the constricted pressure contact portion 4a of the tube 4 penetrates from the portion n.
As a result of this prevention, the old fluid that has accumulated in the gap k as in the prior art is misplaced from the non-contact portion n and mixed with the new fluid that is replaced. It is possible to eliminate problems such as deterioration in the later new fluid. In addition, it is possible to eliminate the problem of spending a lot of time, a lot of cleaning liquid, and a lot of substitution fluid for cleaning and replacement.

Further, as an alternative to the invention in which the outer peripheral enlarged surface 3a of the inner ring main body 3A has a large diameter as described above and has a convex curved surface, the outer peripheral enlarged surface of the conventional inner ring main body 3A shown in FIG. The means for making the angle with respect to the axis P looser than 3a, that is, the means for making the angle τ of the outer peripheral diameter-enlarged surface 3a of the tapered conical surface more gentle was also considered.
However, in order to obtain a first press-contact portion that is not interrupted in the circumferential direction by this means, the length in the direction of the axis P must be made considerably long. 9) Longer than that. In addition, when there is a relative angle between the axis P of the inner ring main body 3A and the axis X of the tube, as described above, the bending direction inner portion (the “bending direction inner portion v shown in FIG. )), The pressure contact between the tube 4 and the inner ring 3 becomes weak, and there is a risk of penetration.

In the first embodiment, the outer diameter-enlarged surface 3a of the inner ring body 3A is relatively convex as a spherical convex curved surface, and the shape of the natural diameter-enlarged deformed portion 4H of the tube 4 is provided by the resin. Due to the elasticity, the shape generally becomes as shown in FIG. 8A (a shape that expands into a convex curved shape when viewed from the inside of the tube), and therefore, the outer diameter expansion surface 3a and the tapered pressure contact portion 4a The pressure contact force advances from the tube 4C corresponding to the inner ring maximum diameter portion 3b along the inner circumference of the tube in the direction of the axis P of the convex curved surface, and reaches an intermediate value of the diameter expansion amount [(D−d) / 2]. The setting becomes larger as it gets closer. The convex curved surface constituting the outer peripheral enlarged surface 3a of the inner ring main body 3A is not limited to a spherical surface, but may be a smooth convex curved surface such as a suspended curved surface.
Accordingly, even when the natural diameter-enlarged deformed portion 4H is expanded into a concave curved surface shape or linearly expanded, the outer peripheral expanded surface is increased without increasing the dimension in the axis P direction of the outer peripheral expanded surface 3a. The radial surface 3a and the constricted pressure contact portion 4a can be brought into a pressure contact state, and the above-mentioned conventional problem (the risk of penetration) can be prevented.

Further, the tapered outer peripheral enlarged surface 3a of the inner ring main body 3A in the inner ring 3 of the pipe connecting device A according to the pipe joint structure of the first embodiment includes the outer peripheral enlarged diameter surface 3a and the end 4C of the tube 4. The length in the axial direction (length in the axial center direction) of the contact portion is pa, and pa / pb is 0.5 to 1.0 with respect to the axial length pb from the boundary 3g of the maximum diameter portion 3b to the tip of the inner ring. The shape is set to satisfy the following range [that is, 0.5 ≦ (pa / pb) ≦ 1.0].
If the outer diameter-enlarged surface 3a that is tapered in such a range is set in shape, when the inner ring main body 3A is press-fitted into the end portion 4C of the tube 4, the end portion 4C of the tube 4 is excessively expanded and deformed. The above-described effects (that is, a good ring-shaped press-contact state having a wide area in the direction of the axis P) can be obtained without hindering the press-fitting work of the inner ring main body 3A.

In response to the above examination, as shown in FIG. 12, the fitting tube portion 3B, which is one end portion of the inner ring, is formed as a lump without holes, and the inner peripheral portion 3w is made of a dead end shape. The experimental inner ring 3 was manufactured, and the press-fit state of the fluororesin (PFA) tube 4 and the experimental inner ring 3 was evaluated under the following conditions. Here, the conditions of the experiment are as follows (1) to (4).
(1) Tube diameter of the pipe joint used in the experiment: 1/2 "(inch)
(2) Material: Both inner ring and tube for experiment are PFA (tetrafluoroethylene perfluoroalkyl vinyl ether copolymer)
(3) Sealing fluid (Flaw detection penetrant): Penetrant [Eishin Chemical Co., Ltd., Red Mark R-1A (NT)]
(4) Experimental method: The tube 4 was inserted into the tip of the experimental inner ring 3 in which the fitting tube portion (end portion) 3B was a blind plug, and the tube was filled with a flaw detection penetrant and pressurized. Refer to FIG. 12 for the shape of the experimental inner ring (blur sleeve) 3 and the like.
The results are as shown below (see FIGS. 13A and 13B).
When t3 / t4 = 1.2, the penetration of the flaw detection penetrating liquid was not observed at 0.70 ≦ pa / pb until the hydraulic pressure reached 1500 Kpa.
When t3 / t4 = 1.8 was set, no penetration of the flaw detection penetrating liquid was observed at 0.40 ≦ pa / pb when the hydraulic pressure was greater than 1000 Kpa.

Further, the wall thickness of the maximum diameter portion 3b of the inner ring body 3A in the pipe joint structure of the first embodiment, as shown in FIG. When the thickness of the maximum diameter portion 3b is t3, t3 / t4 is set to be in the range of 1.2 to 2.5 [that is, 1.2 ≦ (t3 / t4) ≦ 2.5]. ing.
For example, if the thickness t4 of the tube 4 is 1.5 mm, the thickness t3 of the maximum diameter portion 3b of the inner ring body 3A is set to 1.8 to 3.75 mm. A more preferable range of t3 / t4 is a range of 1.4 to 1.8 (that is, 1.4 ≦ (t3 / t4) ≦ 1.8). In this case, the thickness t4 of the tube 4 is If the thickness is 1.5 mm, the wall thickness t3 of the maximum diameter portion 3b of the inner ring main body 3A is set to 2.1 to 2.7 mm.

If the thickness of the maximum diameter portion 3b of the inner ring main body 3A is set so as to achieve such a thickness ratio, the thickness of the inner ring main body 3A balances with the thickness of the tube 4 in strength and size. Therefore, it is possible to prevent problems caused by insufficient thickness or excessive thickness of the inner ring body 3A.
That is, when the thickness of the maximum diameter portion 3b of the inner ring main body 3A is insufficient, the inner ring main body 3A creeps in a short period of time, and the sealing performance due to the pressure contact with the end 4C of the tube 4 ends in a short time. You can look around. However, when the ratio is 1.2 or more, the thickness of the inner ring main body 3A is appropriately secured, and the sealing performance by the pressure contact between the inner ring main body 3A and the end portion 4C of the tube 4 is maintained over a long period of time. Can be secured.

Conversely, if the thickness of the maximum diameter portion 3b of the inner ring main body 3A is excessive, the outer diameter of the maximum diameter portion 3b becomes too large, and the end portion 4C of the tube 4 is excessively expanded and deformed. This excessive diameter expansion deformation not only hinders the press-fitting work of the inner ring body 3A, but also the end portion 4C of the tube 4 creeps in a short period of time, and the sealing performance due to the pressure contact with the inner ring body 3A. Can look around for a short-term failure.
However, by making this ratio within 2.5, it is possible to suppress the amount of expansion of the diameter of the end portion 4C of the tube 4 from becoming excessive, thereby ensuring the smoothness of the press-fitting work of the inner ring body 3A. In addition, it is possible to ensure a sealing property by pressure contact between the inner ring main body 3A and the end portion 4C of the tube 4 over a long period of time.

[Embodiment 2]
As shown in FIGS. 6 and 7, the inner ring 3 in the pipe joint structure of the second embodiment is different from the inner ring 3 in the pipe joint structure of the first embodiment only in the configuration of the fitting cylinder portion 3B. is there. Due to this difference, also in the pipe connection device A, the configuration of the fitting cylinder portion 3B of the pipe joint main body 1 is different. In FIG. 7, the receiving port 1 </ b> B and the other small-diameter cylindrical portion 1 b are described in the same thing as that of the pipe joint main body 1 shown in FIG. 3.

That is, in the fitting tube portion 3B of the inner ring 3, an outer peripheral surface 3e, an inner peripheral portion 3w, and a tapered inner peripheral surface 20 that narrows toward the front end portion side of the inner ring 3 are formed on the rear end surface. ing. On the other hand, in the pipe joint main body 1, a tapered small-diameter cylindrical portion 1 a having an outer peripheral surface 18 that becomes smaller in diameter toward the distal end side of the pipe joint main body 1 on the inner diameter side of the root portion of the cylindrical threaded portion 1 </ b> A. An annular groove 19 is formed between the outer peripheral surface 18 of the small-diameter cylindrical portion 1a and the inner peripheral surface 9 of the cylindrical threaded portion 1A so that the rear end portion of the fitting cylindrical portion 3B is fitted. Has been.
A cut for preventing the fluid from entering and staying at the distal end of the small diameter cylindrical portion 1a is deformed and protrudes in the radially inward direction (fluid flow passage side) at the distal end of the small diameter cylindrical portion 1a. A shape-shaped deformation preventing portion 21 is formed.

In the case of the pipe joint structure according to the second embodiment, the union nut 2 is screwed into the cylindrical threaded portion 1A of the pipe joint body 1. As a result, the distal end side outer peripheral surface of the end portion 4C of the tube 4 (the outer peripheral surface of the tapered pressure contact portion 4a) is pressed in the direction of the axis Y by the pressing portion 12b of the union nut 2.
As a result, the rear end portion of the fitting cylinder portion 3B of the inner ring 3 is pushed into the annular groove 19 of the pipe joint body 1, and the tapered outer peripheral surface 18 of the pipe joint body 1 (an example of a seal component) A tapered inner peripheral surface 20 (an example of a seal element portion) of the inner ring 3 collides with and comes into pressure contact with each other, thereby forming a third seal portion (an example of a back seal portion) S3.
In order to make the third seal portion S3 function completely, that is, the rear end portion of the fitting tube portion 3B comes into contact with the bottom surface of the annular groove 19, and the tapered inner peripheral surface 20 is formed into a cylindrical screw. The end surface of the rear end portion of the fitting tube portion 3B is formed in a cut-off contact avoiding portion 22 so as not to be in a non-pressure contact state with the outer peripheral surface 18 of the joint portion 1A.

  The connection between the tube 4 and the pipe joint body 1 using the inner ring 3 in the pipe joint structure of the second embodiment is the embodiment shown in FIGS. 3 and 4 except for the third seal part S3 (back seal part). Since this is the same as that of the pipe joint structure of FIG. 1, the reference numerals shown in FIGS.

[Another Example]
The fluid transfer tube 4 to be sealed as a pipe joint structure includes a tube-like portion (cylindrical threaded portion 1A) protruding from another pipe joint main body, a fluid device such as a pump or a valve. FIG. 8 is a schematic diagram (principle diagram) for simply expressing the technical idea of the present invention. Therefore, as the tube 4, the natural diameter-enlarged deformed portion 4 </ b> H has a substantially curved shape (tapered shape) in addition to a concave curved shape in a direction perpendicular to the axis P as shown in FIG. 8. Is also possible. In the pipe joint structure of the present invention, the fluid device 1 may be a constituent element instead of the pipe joint body 1. That is, the cylindrical screw part 1A is a pump or a valve formed integrally with the case, and these pumps and valves are collectively defined as the fluid device 1.

1 Fitting body (fluid equipment)
DESCRIPTION OF SYMBOLS 1A Cylindrical threading part 1a Seal structure part 2 Union nut 3 Inner ring 3G Outer peripheral part of inner ring 3a Outer peripheral enlarged diameter surface 3b Maximum diameter part 3f Expanded part 3w Inner peripheral part 4 Tube 4C End part of tube 4u Naturally tapered inner peripheral enlarged surface 7 Male screw 13 Female screw 14, 15 Seal element part S3, S4 Back seal part m Seal component part pa The inner peripheral enlarged surface of the tapered part and the end of the tube Axial length of the contact portion with the peripheral portion pb Axial length from the boundary between the tapered outer peripheral enlarged surface and the maximum diameter portion to the tip of the inner ring t3 Thickness at the maximum diameter portion of the inner ring t4 Thickness of the tube that has not been deformed

Claims (3)

A fluid transfer tube 4;
An outer peripheral portion 3G having a tapered diameter-enlarged portion 3F formed on the distal end side thereof, which is press-fitted into the end portion 4C of the tube 4 from the distal end to expand the inner peripheral portion of the end portion 4C of the tube 4; An inner ring 3 having an inner circumferential part 3w which is a transfer channel;
A pipe joint body 1 or a fluid device 1 having a cylindrical threaded portion 1A in which a male screw 7 is formed on the outer peripheral side;
A union nut 2 formed with a female screw 13 to be screwed into the male screw 7 of the cylindrical screw part 1A,
The inner ring 3 is inserted into the cylindrical threaded portion 1A in a state where the inner peripheral portion of the end portion 4C of the tube 4 is expanded, and the tip side of the inner ring 3 is the cylindrical shape. A pipe joint structure that is pressed in a state in which the tube 4 is sandwiched between the union nut 2 screwed to the male screw 7 of the screwing portion 1A;
The diameter-enlarging portion 3f of the inner ring 3 is an end portion of the tube 4 that appears at that time as a state in which only the portion of the inner peripheral portion of the end portion 4C of the tube 4 whose diameter is expanded to the maximum is expanded to the maximum. 4C is configured to have a larger diameter than the naturally tapered inner circumferential enlarged surface 4u of the inner circumferential portion of the 4C, and to have a tapered outer circumferential enlarged surface 3a having a convex curved surface ,
The thickness of the tube 4 that has not been expanded and deformed is t4, the thickness of the maximum diameter portion 3b of the expanded portion 3f is t3, and t3 / t4 is in the range of 1.2 to 2.5. , The thickness of the maximum diameter portion 3b is set,
A rear end side of the inner ring 3 is in contact with seal components m and 1a provided in the pipe joint main body 1 or the fluid device 1 when the front end side of the inner ring 3 is pressed by the union nut 2. A pipe joint structure in which seal element portions 14 and 15 constituting the seal portions S3 and S4 are formed .   The axial length of the contact portion between the tapered outer peripheral enlarged surface 3a and the inner peripheral portion of the end 4C of the tube 4 is pa, and the tapered outer peripheral expanded surface 3a and the maximum diameter portion 3b are the same. The axial length from the boundary 3g of the inner ring 3 to the tip of the inner ring 3 is pb, and this pa / pb is in the range of 0.5 to 1.0 (0.5 ≦ pa / pb ≦ 1.0) over the circumferential direction. The pipe joint structure according to claim 1, wherein the tapered outer diameter-enlarged surface 3 a is set so that   The axial length of the contact portion between the tapered outer peripheral enlarged surface 3a and the inner peripheral portion of the end portion 4C of the tube 4 is pa, and the tapered outer peripheral enlarged surface 3a and the maximum diameter portion 3b. The length in the axial direction from the boundary 3g of the inner ring 3 to the tip of the inner ring 3 is pb, and this pa / pb is in the range of 0.7 to 1.0 (0.7 ≦ pa / pb ≦ 1.0) in the circumferential direction. The pipe joint structure according to claim 1 or 2, wherein the shape of the tapered outer peripheral enlarged surface 3a is set so that

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