JP2001056084A - Thermoplastic resin joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoplastic resin joint allowing a friction melting joint in a stable state, and offering a highly strong connection body used for a heat resistant, pressure resistant and corrosion resistant piping. SOLUTION: While a subject joint part 20 of a piping material 2 is inserted into a joint part 30 provided inside a joint, a joint surface of the joint part 30 and the subject joint part 20 are friction-melted to join the joint part 30 with the subject joint part 20. When an external diameter D0 of the subject joint part 20 of the piping material 2 of a joint is 25 mm or less, guide parts 10 which have a taper angle gradually decreasing in the radial direction from the joint inlet side to the joint inner side, and guides an end edge of the subject joint part to the joint part maintaining the contact on an inner surface are provided on the joint inlet side of the joint part 30. The joint part 30 is formed as a parallel pipe extending inward from the boundaries with the guide parts 10. The inner diameter D of the joint satisfies the following equation with respect to D0 of the subject joint part of the piping material 2; 0.1 mm<=(D0-D)<=1.0 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-strength joined body which can be used for heat-resistant, pressure-resistant and corrosion-resistant piping by friction-welding a joint (spigot) of a pipe member such as a pipe to a joint. The present invention relates to a joint made of a thermoplastic resin which can obtain a resin.

[0002]

2. Description of the Related Art When a pipe or a pipe member such as an elbow, a cheese, a reducer, an increaser or the like (hereinafter, referred to as a pipe material) is joined to a joint by friction fusion welding, the area of the joint portion is determined by abutting end faces. Since it is equal to the area, it cannot be used for applications requiring high pressure resistance unless the joint strength is equal to that of the pipe. In addition, the diameter of the pipe material does not completely match even with the same nominal diameter, and since the diameter has a certain width, the cross section is not a perfect circle but an elliptical shape, so it is joined. A step is generated on the surface.

In order to solve this problem, a method has been proposed in which a joint and a pipe are provided with an inner taper and an outer taper, respectively, for joining (see Japanese Patent Publication No. 38-5432). However, this method has the problem of increasing the number of cutting steps to taper the end of the pipe on site, and it is necessary to reduce the taper to a small angle in order to increase the joint area. When a thinner portion becomes longer, and especially when cut into a small diameter pipe because it is a thin-walled pipe, there is a problem that, when the pipes are butted, the pipes are not rigid because the rigidity of the pipes is reduced, so that surface pressure does not rise.

As a means for solving this problem, there is known a method of joining an inner surface of a joint to an outer surface of a pipe. In this method, when joining by friction fusion welding, if the inner peripheral surface of the joint of the joint and the outer peripheral surface of the joining target of the pipe material inserted into this joint are not in contact, the inner peripheral surface of the joining and the joining target No frictional heat is generated with the outer peripheral surface. Therefore, the interface between the joining portion and the joining target portion does not melt, and the connection is incomplete.

If the inner surface of the joint is formed into a simple cylindrical shape, the inner diameter of the joint cannot be determined uniformly because the outer diameter of the pipe varies as described above. That is, if the outer diameter of the part to be welded is larger than the inner diameter of the joint, the part to be welded cannot be inserted into the welded part, and if the outer diameter of the part to be welded is too small, the outer wall surface of the part to be welded comes into contact with the inner peripheral surface of the welded part. Therefore, there is a problem that friction melting cannot be performed well.

In order to solve this problem, Japanese Patent Laid-Open Publication No. 50-151275 discloses that the joint is formed into a cylindrical shape whose diameter is gradually reduced from the entrance of the joint toward the inner part. A joint structure is disclosed that enables joining even if the outside diameter is different but the diameter difference is within the standard.

[0007]

However, according to the study of the present inventor, the joint structure disclosed in Japanese Patent Laid-Open No. 50-151275 has the following problems. Since the joining portion has a tapered shape, when the joining target portion is inserted into the joining portion of the joint by the joining amount, the joining target portion receives compressive stress from the joining inner peripheral surface. Then, when heated and softened in this state, a problem arises in that the joining target portion of the pipe member cannot maintain its shape and is easily buckled.

In particular, when the difference between the outer diameters of the portions to be welded is large, in order to shorten the length of the joint, it is necessary to increase the taper angle of the welded portion. Even if the strength of the joint is not so required, there is a problem that the joint is buckled during insertion.
On the other hand, to increase the joining strength, the joining margin may be increased, but to increase the joining margin without buckling, the taper angle must be reduced. That is, a smaller taper angle contributes to uniform strength in the circumferential direction. This is because the gap due to the taper is not too large as compared with the gap due to the ellipse, so that the molten resin flows more in the circumferential direction. However, the compression stress can be reduced by reducing the taper angle, but the joint must be lengthened in order to absorb the magnitude of the diameter of the portion to be joined.

The present invention can solve the above-mentioned problems in the conventional friction joining of piping materials, can perform friction fusion joining in a more stable state, and can be used for heat-resistant, pressure-resistant and corrosion-resistant piping. It is an object of the present invention to provide a joint made of a thermoplastic resin that can obtain a joined body of the above.

[0010]

In order to achieve this object, a joint made of a thermoplastic resin according to the present invention has a joint portion provided inside a joint, in which a joint portion of a pipe material is inserted. In this state, the joint portion can be joined to the joint portion by friction-fusing the joint surface between the joint portion and the joint portion, and a resin joint having an outer diameter D0 of the joint portion of the pipe material of 25 mm or less. In, while gradually reducing the diameter at the taper angle from the joint entrance side toward the joint back side, and guide the guide to the joint while contacting the edge of the part to be welded to the inner surface, while providing a guide at the joint entrance side from the joint The joint portion is formed in a cylindrical shape extending in parallel from the boundary with the guide portion toward the back side, and the joint inner diameter D of the joint is as follows with respect to D0 of the joint target portion of the pipe material. It was configured to satisfy the formula. 0.1mm ≦ (D0−D) ≦ 1.0mm

[0011] The thermoplastic resin joint according to the present invention further comprises a joint between the joint and the joint to be joined in a state where the joint of the pipe material is inserted into the joint provided inside the joint. The joining target portion can be joined to the joining portion by friction-melting the surface. In a resin joint having an outer diameter D0 of 25 mm or less of the joining target portion of the pipe material, from the joint entrance side to the joint back side, While gradually reducing the diameter at the taper angle and providing a guide portion on the joint entrance side from the joint portion to guide the joint portion while abutting the edge of the portion to be joined to the inner surface, the joint portion is from the boundary portion with the guide portion. It is formed in a cylindrical shape extending toward the back side while gradually reducing the diameter at a taper angle smaller than the taper angle of the guide portion. A configuration that satisfies the following equation did. 0.1mm ≦ (D0−D) ≦ 1.0mm

In the present invention, the term "joint" refers to a socket-like joint made of a thermoplastic resin or a pipe member on the inserted side whose one end is enlarged in diameter. The portion to be joined is not particularly limited, but is, for example, a spigot portion of a pipe material on the insertion side such as an elbow, a cheese, a reducer, or an increaser, or a pipe end such as a straight pipe that is inserted into the joint and joined. Part, especially the outer peripheral surface thereof. The guide portion is a portion having a predetermined length from the joint entrance, which is an inner surface portion of the joint where an edge of the joint portion comes into contact when the joint portion is inserted into the joint before joining. The joint portion is a portion where the outer surface of the portion to be welded and the inner surface of the joint are in contact with each other after joining, and refers to a portion of the inner surface of the joint that is deeper than the guide portion.

The inner diameter of the guide portion at the joint entrance side is equal to or larger than the maximum value of the outer diameter standard of the portion to be joined, and the inner diameter at the boundary between the guide portion and the joint portion is usually the minimum value of the outer diameter standard of the portion to be joined. The following is assumed.

The friction welding method is not particularly limited. For example, a method of rotating the joint about the joint axis, vibration in the joint axis direction, or forward or reverse rotation in the joint axis direction can be used. Vibration and a method of vibrating in a combination direction thereof can be mentioned. As the resin forming the joint and the joint of the pipe material, a thermoplastic resin is preferable, and examples thereof include medium-density polyethylene, high-density polyethylene, polypropylene, polybutene, polyvinyl chloride, cross-linked polyethylene, and polyphenylene sulfide. . The method of manufacturing the joint is not particularly limited, but if there is no problem in shape, injection molding is considered to be good in terms of molding cost.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below.
This will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing an example of the tapered shape of the guide portion 10 and the joint portion 30 of the thermoplastic resin joint 3 of the present invention. In addition to the linear shape change, the angle continuously decreases in a curved line. Such a shape in which the diameter changes in a broad sense is also included. That is, (a) shows one example in which it changes linearly, (b) shows another example in which it changes linearly, and (c) shows one example in which it changes in a curved line.

As will be described later in detail, for example, a joining device 1 as shown in FIG. 2 is used for joining the thermoplastic resin joint of the present invention to a piping material. FIG. 3 is a cross-sectional view for explaining the thermoplastic resin joint of the present invention in relation to the piping material 2. The joint 3 is provided with a guide part 10 and a joint part 30 in this order from both joint entrance sides, and has a cylindrical shape into which the joint target part 20 of the pipe member 2 is inserted and connected from both sides. That is, the guide part 10 is provided continuously to the joint part 30, and the minimum diameter part is smaller than the minimum diameter of the standard value of the pipe material 2, and the maximum diameter part is larger than the maximum diameter of the standard value of the pipe material. It has a diameter and is formed in a tubular shape extending in parallel from the inlet side of the joint toward the back side. On the other hand, the inner diameter D of the joining portion is a diameter that satisfies the following expression with respect to the outer diameter D0 of the joining target portion 20. 0.1 mm ≦ (D0−D) ≦ 1.0 mm Here, the joint inner diameter D means the minimum inner diameter of the joint.

As described above, the joint 3 is
The guide part 10 is provided on the joint entrance side of the joint, and the joint part 30 is formed in a cylindrical shape extending in parallel from the boundary with the guide part toward the back side, so that the joint length is increased. Without buckling, the buckling of the pipe end, which is the joining target portion 20, can be suppressed. In other words, the taper is given as a guide from the joint entrance side to a certain position, not the whole area, and the back part is made parallel to the pipe axis as a joint, thereby suppressing buckling and wastefully connecting the joint. It is possible to absorb inconveniences caused by the large and small outer diameters and elliptical shape of the pipe end portion of the pipe to be welded without increasing the length. In addition to the fact that the joint has a specific relationship, the joint and the piping material can be joined with high strength, reliably, and stably. Also, as for the joining strength, the joining area can be changed depending on the length of the joining portion, so that the design becomes easy.

The joint 3 shown in FIG.
In the same manner as the joint shown in (1), the guide 1
0, the joint 30 is provided in order, but the guide portion 10 is gradually reduced in diameter at a taper angle larger than the taper angle of the joint (see Example 3 to be described later). And different. Looking at the joint 30, the joint 30
Is gradually reduced in diameter from the inlet side of the joint to the inner side at a taper angle of 0 ° or more with respect to the pipe axis. It is the same as the joint shown in FIG. 3 in that the inner diameter D of the joint is a diameter satisfying the following expression with respect to the outer diameter D0 of the pipe member 20 to be joined. 0.1mm ≦ (D0−D) ≦ 1.0mm

As described above, the joint 3 is connected to the joint 30
The guide portion 10 is provided on the joint entrance side of the guide portion, and the joint portion 30 extends from the boundary with the guide portion 10 toward the back side while gradually reducing the diameter at a taper angle smaller than the taper angle of the guide portion. Since it is formed in a tubular shape, it is advantageous in that the workability when guiding the pipe end, which is the joining target portion 20 of the pipe member 2, into the joint is improved. Also,
By applying a taper as a guide from the joint entrance side to a certain position instead of the entire area, and giving a taper smaller than the guide part as a joint part at the back, it suppresses buckling and lengthens the joint unnecessarily. The above-mentioned effect of being able to absorb the inconvenience due to the size of the outer diameter of the pipe end portion of the portion to be welded and the elliptical shape without any problems is achieved more reliably, and the value of the inner diameter D of the welded portion is determined by joining the pipe material. D of target part
Together with the fact that the joint has a specific relationship to 0, it has become possible to join the joint and the piping material with high strength, reliably, and stably. However, the joint 30 is
Due to the fact that it is formed in a cylindrical shape extending gradually toward the back side while gradually reducing the diameter at a taper angle smaller than the taper angle of the guide part from the boundary part with the guide part, the industrial production is smaller than the joint shown in FIG. Requires advanced technology.

(Function) It is considered that the design area as shown in FIG. 4 exists for the outer diameter D and the length of the joint of the joint to be subjected to friction fusion welding with respect to the outer diameter D0 of the joint. That is, in order to obtain high strength and stable joining strength, the joint inner diameter D needs to be between the upper limit by the melting amount limit and the lower limit by the deformation limit. The melting amount limit is the minimum required amount of molten resin and heat generated during frictional melting.If the inner diameter of the joint is larger than this limit, the gap between the joint and the joint is filled with molten resin. In addition, due to the lack of heat, the entanglement between the molecules of the joint and the molecules of the portion to be joined becomes insufficient, resulting in insufficient strength of the joint or leakage. The fusion limit is also related to the length of the joint, and if the inner diameter of the joint is the same, the shorter the length of the joint, the lower the amount of fusion.

The deformation limit is the limit at which the pipe is buckled when the part to be welded is inserted into the joint or during friction melting.
Since the inner diameter of the joint is smaller than the joint, the joint is subjected to compressive stress when the joint is inserted into the joint. If the inner diameter of the joint is too small, it will buckle at the stage of insertion. Even if there is no buckling at the stage of insertion, the portion to be welded is heated and softened during friction melting, thereby reducing rigidity. The heating also reduces the compressive stress, but if the degree of the decrease in the rigidity is large, the portion to be joined buckles.

The deformation limit is also related to the length of the joint, and if the inner diameter of the joint is the same, the longer the length of the joint, the easier the buckling. In particular, as in the present invention, when the outside diameter of the portion to be joined of the pipe material is 25 mm or less, the thickness of the portion to be joined is usually relatively thin and very easily buckled. As the outer diameter of the portion to be welded increases, that is, as the thickness of the portion to be welded increases, buckling becomes less likely to occur, and the deformation limit shifts to the smaller inner diameter side, thus expanding the design area. Therefore, in the case of friction welding of large diameter, it is not necessary to pay attention to the joint inner diameter as compared with the case of small diameter, but for the small diameter with small thickness, grasp the design area, and within the area where stable and high strength are exhibited. It is important to design the inner diameter of the joint.

The length of the joint varies depending on the required strength. It is sufficient that the length is equal to or greater than the length at which the required strength is exhibited. It is meaningless if the length is too long. . In addition, by providing the guide portion, when the portion to be joined of the pipe material is inserted into the joint portion of the joint, the pipe end can be guided by the guide portion so that the pipe axis matches the axis of the joint.

The taper is only provided at the joint of the joint,
Since it is not necessary to provide the pipe material at the portion to be joined, the on-site cutting step is not required. The inner surface of the joint is separated from the guide and joint from a simple taper shape, and the taper angle of the tube or joint parallel to the pipe axis is made smaller than the taper angle of the guide, reducing the insertion load at the pipe end. Further, the output of the power source for frictionally melting the joint can be reduced, and the size and cost of the device can be reduced.

[0025]

EXAMPLES Examples of the present invention will be specifically described below in comparison with comparative examples. First, the joining device 1 will be described. The device 1 grips the tube 2 and connects the two clamps 11 a, 11
b, a joint rotating jig 12 rotatable while holding the socket type joint 3, a motor 14 for rotating the joint rotating jig 12 via a timing belt 13, and one clamp 11 a. The clamp 11a is moved back and forth in the direction of the joint rotating jig 12, and the link 1
The air cylinder 15 is also adapted to move the clamp 11b back and forth in the direction of the joint rotating jig 12 via the joints 6 and 16.
And

The joining device 1 allows the joint 3
The joint 3 is gripped by the joint rotating jig 12 and the clamps 11a and 11b grip the pipe 2 to join the pipe 2 and the pipe 2. Next, the air cylinder 15 is operated to move the clamps 11a and 11b toward the joint rotating jig 12 so that the pipes 2 and 2 are inserted into the joint 3 from both sides until they come into contact with the joint central protrusion. I do. Thereafter, the motor 14 is driven to rotate the joint 3 together with the joint rotating jig 12, and during this time, a force is applied to the tube 2 in a direction of insertion into the joint 3 (parallel to the tube axis) to prevent the tube 2 from coming out. To keep.

(Example 1) A cross-linked polyethylene pipe (Eslopex 13A, manufactured by Sekisui Chemical Co., Ltd., having an outer diameter of 17 mm, a wall thickness of 2 mm, and a length of 30 cm), which is a thermoplastic cross-linked resin pipe;
A joint whose dimensions are shown in Fig. 5 (made of cross-linked polyethylene)
3 is set in the above-mentioned joining apparatus 1, and after inserting a pipe into the joint from both sides at a pressure of 1.5 MPa, the joint is rotated at a rotational speed of 0.45 m / sec.
The bonding was performed by rotating at a speed of 0.89 m / s for 7 seconds. A rotating tube was given an insertion force of 0.4 MPa in the axial direction of the tube. After sufficient cooling, the joint was removed from the device.
Similarly, a total of nine joints were manufactured. At the time of joining, pipe 2
When the pipe was inserted into the joint 3, the pipe end, which was the part to be welded 20 of the pipe 2, was lightly brought into contact with the guide section 10 of the joint 3, and was smoothly guided into the joint. The pipe did not buckle on the inner surface of the pipe. The bonded product is subjected to a hot internal pressure test (JIS K 6
787) When the internal pressure was 13.5 kg / cm2, the pipe was broken after 200 hours.

Embodiment 2 FIG. 6 shows a joint used for joining. The same tubes as in Example 1 were used, and a total of nine bonded articles were manufactured under the same bonding conditions as in Example 1. At the time of joining,
When the pipe was inserted into the joint, the guide smoothly guided the pipe into the joint. The pipe did not buckle on the inner surface of the pipe. When the bonded product was subjected to a hot internal pressure test (JISK 6787), it was broken from the tube after 200 hours at an internal pressure of 13.5 kg / cm2.

(Embodiment 3) As shown in FIG. 7, the joint used for joining is provided with a guide portion 10 and a joining portion 30 in order from the entrance side of both joints. A taper whose diameter was gradually reduced at a large taper angle was used. The same tubes as in Example 1 were used, and a total of nine bonded articles were manufactured under the same bonding conditions as in Example 1. At the time of joining, when the pipe was inserted into the joint, the pipe was smoothly guided into the joint by the guide portion. The pipe did not buckle on the inner surface of the pipe. When the bonded product was subjected to a hot internal pressure test (JISK 6787), it was broken from the tube after 200 hours at an internal pressure of 13.5 kg / cm2.

Comparative Example 1 FIG. 8 shows a joint used for joining. The same tubes as in Example 1 were used, and a total of nine bonded articles were manufactured under the same bonding conditions as in Example 1. At the time of joining,
When the pipe was inserted into the joint, the guide smoothly guided the pipe into the joint. The pipe did not buckle on the inner surface of the pipe. When the joined product was subjected to a hot internal pressure test (JIS K 6787), all leaked from the joined portion while the pressure was increased to 13.5 kg / cm2.

Comparative Example 2 FIG. 9 shows a joint used for joining. The same tubes as in Example 1 were used, and a total of nine bonded articles were manufactured under the same bonding conditions as in Example 1. At the time of joining,
When the pipe was inserted into the joint, the guide smoothly guided the pipe into the joint. However, the pipe buckled on the inside of the pipe. The joint was subjected to a hot internal pressure test (JIS K6787).
All leaked from the joint during pressurization to 3.5 kg / cm2.

Comparative Example 3 FIG. 10 shows a joint used for joining. The same tube as in Example 1 was used. At the time of joining, when the pipe was inserted into the joint, the pipe did not enter the joint.

Comparative Example 4 FIG. 11 shows a joint used for joining. When the length of the joint was designed so that the amount of fusion was the same as that of the joint of Example 1, the length of the joint was at least three times the length of the joint of Example 1. The same tubes as in Example 1 were used, and a total of nine bonded articles were manufactured under the same bonding conditions as in Example 1. At the time of joining, when the pipe was inserted into the joint, the pipe was smoothly guided into the joint by the taper. The pipe did not buckle on the inner surface of the pipe. When the bonded product was subjected to a hot internal pressure test (JISK 6787), it was broken from the tube after 200 hours at an internal pressure of 13.5 kg / cm2. * Table 1 below shows the occurrence of buckling and other characteristics of the above Examples and Comparative Examples.

[0034]

[Table 1]

[0035]

The thermoplastic resin joint according to the present invention is constructed as described above, and is provided with a tapered guide portion on the inner surface. Absorbing, the pipe end is guided by the guide portion, and the pipe axis can be aligned with the axis of the joint, and the seat of the pipe end, which is the part to be joined, can be used without unnecessarily increasing the length of the joint. It is possible to obtain a high-strength bonded body in combination with the fact that the value of the inner diameter D of the bonded portion has a specific relationship with D0 of the portion to be welded of the piping material. it can. Therefore, it can be suitably used, for example, for joining pipes that require heat resistance and pressure resistance, such as gas, water supply, and hot water supply, and pipes that require corrosion resistance, such as hot springs. On the other hand, the taper is provided only at the joint of the joint and is not required at the joint of the pipe material, so that a cutting step on site is unnecessary. In addition, when a joint having a taper smaller than the taper angle of the guide portion is provided, workability when joining the piping material becomes better, and in addition, without unnecessarily increasing the length of the joint. The above effect of being able to suppress buckling of the pipe end which is the part to be joined is further enhanced.
Can be played reliably. In addition, the inner surface of the joint is formed from a cylindrical or simple tapered shape parallel to the pipe axis,
Separated from the joint, the taper angle of the joint is made smaller than the taper angle of the guide, so the insertion load at the pipe end can be reduced, and the output of the power source that frictionally melts the joint can be reduced, miniaturizing the equipment. , And the price can be reduced.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing an example of a tapered shape of a thermoplastic resin joint of the present invention, where (a) is an example that changes linearly, and (b) is an example that changes linearly. Another example, (c)
FIG. 3 is a cross-sectional view showing an example of a change in a curved shape.

FIG. 2 is a front view showing an example of a joining apparatus suitable for joining a thermoplastic resin joint and a pipe member of the present invention.

FIG. 3 is a cross-sectional view for explaining a method for joining a thermoplastic resin joint and a pipe member according to the present invention.

FIG. 4 is a view for explaining a design area of a joint inner diameter D of the thermoplastic resin joint of the present invention.

FIG. 5 is a dimensional view of a joint used in Example 1.

FIG. 6 is a dimensional view of a joint used in Example 2.

FIG. 7 is a dimensional view of a joint used in Example 3.

FIG. 8 is a dimensional view of a joint used in Comparative Example 1.

FIG. 9 is a dimensional view of a joint used in Comparative Example 2.

FIG. 10 is a dimensional view of a joint used in Comparative Example 3.

FIG. 11 is a dimensional view of a joint used in Comparative Example 4.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Joining apparatus 2 Piping material (pipe) 3 Joint 10 Guide part 20 Joint part 30 Joint part

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3H019 FA07 FA08 FA14 GA06 4F211 AD05 AD12 AD23 AG08 AG26 AG27 AH11 AM33 TA01 TC11 TD07 TD11 TH02 TH18 TN20 TN21

Claims (2)

[Claims] 1. A joining target portion of a pipe material is inserted into a joining portion provided inside a joint, and a joining surface between the joining portion and the joining target portion is friction-fused by joining the joining target portion to the joining portion. In a resin joint having an outer diameter D0 of 25 mm or less at the joint of the pipe material, the diameter of the joint gradually decreases from the joint entrance side toward the joint inner side at a taper angle. A guide portion that guides the joint portion while the edge is in contact with the inner surface is provided on the joint entrance side from the joint portion, and the joint portion is formed in a cylindrical shape extending parallel from the boundary with the guide portion toward the back side. Wherein the inner diameter D of the joint of the joint satisfies the following equation with respect to D0 of the part to be joined of the pipe material. 0.1mm ≦ (D0−D) ≦ 1.0mm 2. A joining target portion of a pipe material is inserted into a joining portion provided inside a joint, and a joining surface between the joining portion and the joining target portion is friction-melted by friction welding. In a resin joint having an outer diameter D0 of 25 mm or less at the joint of the pipe material, the diameter of the joint gradually decreases from the joint entrance side toward the joint inner side at a taper angle. A guide portion that guides the joint portion while the edge is in contact with the inner surface is provided on the joint entrance side from the joint portion, and the joint portion is gradually reduced from the boundary with the guide portion at a taper angle smaller than the taper angle of the guide portion. A thermoplastic resin characterized in that the joint inner diameter D of the joint satisfies the following formula with respect to D0 of the joint to be joined of the pipe material. Resin fitting. 0.1mm ≦ (D0−D) ≦ 1.0mm