JP6489878B2 - Manufacturing method of joined tube - Google Patents

Description

  The present invention relates to a bonded tube body and a method for manufacturing the same. More specifically, the present invention relates to a joined tube body obtained by joining dissimilar metal tubes having different tensile strengths and a method for manufacturing the joined tube body.

  Generally, heat exchangers are used for water heaters, air conditioners, refrigerators, and the like. Since the heat exchanger is mainly incorporated in an outdoor unit, the pipe of the heat exchanger is required to be a material with high corrosion resistance. In addition, the heat exchanger is also required to be a material having high pressure resistance enough to withstand the gas pressure of the refrigerant gas supplied from the compressor, heat transfer for increasing heat exchange efficiency, and high jointability between pipes. . In consideration of corrosion resistance, pressure resistance, heat conductivity, bondability, and the like, a copper pipe is often used as a pipe of a heat exchanger.

  By the way, in recent years, the price of copper has soared, and it is required to use a material that replaces copper as a piping material for a heat exchanger. An example of a material that can replace copper is aluminum. However, the aluminum tube has a problem in terms of corrosion resistance in an outdoor environment. Thus, in recent years, attempts have been made to use stainless steel as a material to replace copper.

  However, generally, since there are few cases where all the copper tubes used in the heat exchanger are replaced with stainless steel tubes, many joints connecting the copper tubes and the stainless steel tubes are generated. In order to have high airtightness and bonding strength at the joint, as shown in FIG. 18, the inner metal tube 101 and the outer metal tube 102 are overlapped at the ends to form a connection body 100 ′, and then connected. The body 100 ′ is placed on the roller support shaft 200, the blade 201 having a rounded blade edge is pressed against the overlapping portion 110 ′ of the inner metal tube 101 and the outer metal tube 102, and the tube shaft 1 of the connection body 100 ′ is rotated. It is proposed to obtain a joined body by performing a process of caulking the inner metal tube 101 and the outer metal tube 102 while rotating the connecting body 100 ′ (Patent Document 1). In addition, when the gas pressure of the refrigerant gas supplied from the compressor is high, the outer metal tube 102 is made of a stainless steel tube and the copper tube having a low deformation resistance is made of an inner metal tube in order to suppress deformation of the joint structure due to the internal pressure. It is shown that it is preferable (patent document 2).

JP 2013-066911 A JP 2013-151013 A

  On the other hand, there is also a need to configure the outer metal tube 102 with a copper tube in order to match the piping with the appearance of the copper heat exchanger. However, when the outer metal tube 102 made of a copper tube and the inner metal tube 101 made of a stainless steel tube are combined, when the overlapping portion 110 ′ of the connection body 100 ′ is caulked and joined, Since the tensile strength is relatively low, a large reduction in plate thickness is likely to occur at locations that have been crimped. On the other hand, since the inner metal tube 101 has a relatively high tensile strength, only a slight deformation occurs even in a portion subjected to caulking. Therefore, there are cases where a caulking groove cannot be formed in the overlapping portion 110 ′ even if caulking is performed.

  For these reasons, when the stainless steel pipe is used as the inner metal pipe 101 and the copper pipe is used as the outer metal pipe 102, the joining strength between the metal pipes is that the copper pipe is the inner metal pipe 101 and the stainless steel pipe is the outer metal pipe 102. It is only about 30% of the joint strength when it is made.

  Thus, when the outer metal tube is made of a low-strength material such as copper and the inner metal tube is made of a high-strength material such as stainless steel, the outer metal tube of the low-strength material is locally used in the caulking portion. In particular, since the plate thickness is reduced, there is a problem that a desired bonding strength cannot be obtained.

  In order to solve the above-described problems, the present invention has good joint strength when an outer metal tube and an inner metal tube made of a metal material having a higher tensile strength than the outer metal tube are combined. The purpose is to provide a joined tube. It is another object of the present invention to provide a manufacturing method for stably mass-producing a bonded tube body without causing cracks in the bonded portion even when metal tubes having different tensile strengths are bonded.

  The inventors of the present invention have made extensive studies in order to solve the above problems. As a result, first, an inner caulking groove is formed in an inner metal tube made of a metal material having a higher tensile strength than that of the outer metal tube, and then the outer metal tube and the inner metal tube are connected to the inner caulking groove. After being arranged at a position overlapping the inner surface of the outer metal tube, a caulking groove is formed at a position overlapping the inner caulking groove on the outer surface of the outer metal tube, and the outer metal tube and the inner metal tube are caulked. Thus, the inventors have found that the above-described problems can be solved, and have completed the present invention. Specifically, the present invention provides the following.

  (1) The present invention is a bonded tube in which an outer metal tube and an inner metal tube made of a metal material having higher tensile strength than the outer metal tube and inserted inside the outer metal tube are caulked and bonded. The inner metal tube is a bonded tube body having an inner caulking groove having a depth of 0.5 mm or more on the outer surface.

  (2) The present invention is the bonded tube body according to (1), wherein the outer metal tube is a copper tube and the inner metal tube is a stainless steel tube.

  (3) In the present invention, at least one end of the outer metal tube is formed with a tube expansion portion having an inner diameter that is substantially the same as the outer diameter of the inner metal tube, and the base end of the tube expansion portion and the inner metal One end of the pipe is in contact, and the outer caulking groove is formed at a position overlapping the inner caulking groove on the outer surface of the outer metal pipe. The joined pipe body according to the above (1) or (2) is there.

  (4) This invention is a heat exchanger provided with the joining pipe body in any one of said (1) to (3).

  (5) The present invention provides an inner caulking groove forming step for forming an inner caulking groove in an inner metal tube made of a metal material having a higher tensile strength than the outer metal tube, and the inner caulking groove forming step. Thereafter, the step of arranging the outer metal tube and the inner metal tube at a position where the inner caulking groove overlaps the inner surface of the outer metal tube, and the inner caulking of the outer surface of the outer metal tube. And a caulking process step of forming a caulking groove at a position overlapping with the working groove and caulking the outer metal pipe and the inner metal pipe.

  (6) The present invention further includes a mark displaying step of displaying a mark on the outer surface of the outer metal tube and overlapping the inner caulking groove when the inner metal tube is overlapped in the arranging step. The caulking process step is a method for manufacturing a bonded tube body according to (5) above, wherein the caulking groove is formed according to the mark.

  (7) In the present invention, at least one end of the outer metal tube is formed with an expanded portion having an inner diameter that is substantially the same as the outer diameter of the inner metal tube. Is inserted into the expanded tube portion, and one end of the inner metal tube is abutted against the proximal end of the expanded tube portion, and the caulking process includes one end of the inner metal tube out of the outer surface of the expanded tube portion. The above (5), which is a step of forming a caulking groove at a position overlapping the inner caulking groove when abutting against the base end of the expanded pipe portion and caulking the outer metal tube and the inner metal tube. ).

  (8) In the present invention, prior to the arranging step, an outer caulking groove is formed on the outer metal tube at a position overlapping with the inner caulking groove when the inner metal tube is overlapped in the arranging step. An outer caulking groove forming step, wherein the placing step is a step of overlapping the inner caulking groove and the outer caulking groove, and the caulking step includes the inner caulking groove and the inner caulking groove. It is a manufacturing method of a joined tube object given in the above (5) which is a process of forming a caulking groove in the position which overlaps with the above-mentioned outside caulking processing groove.

  (9) The present invention is the method for manufacturing a bonded tube body according to any one of (5) to (8), wherein the outer metal tube is a copper tube and the inner metal tube is a stainless steel tube.

  (10) In the present invention, any one of the above (5) to (9), wherein the inner metal tube after the caulking process has an inner caulking groove whose depth in the tube radial direction is 0.5 mm or more. It is the manufacturing method of the joining pipe body as described in above.

  According to the present invention, the inner caulking groove is provided in advance on the outer surface of the high-strength inner metal tube which is not easily deformed, and then the process of caulking the metal tubes is performed, so that the caulking groove is formed at the joint between the metal tubes. It is formed. Since the outer metal tube having a lower strength than the inner metal tube is deformed so as to enter the inner caulking groove, a reduction in plate thickness is suppressed, and the caulking groove is easily formed in a predetermined shape. Therefore, even when the inner metal tube is made of a metal material having a higher tensile strength than the outer metal tube, a bonded tube having good bonding strength can be obtained. In addition, even if metal tubes having different tensile strengths are joined together, cracks do not occur in the joints, and the joined tube bodies can be stably mass-produced. It can be applied to applications such as heat exchangers that require corrosion resistance, pressure resistance, heat transfer, and the like.

It is a figure explaining the joining pipe body of the present invention. It is a figure explaining the groove | channel formation process for inner side crimping in the manufacturing method of this invention. It is a figure explaining the groove | channel formation process for an inner side crimping process following the process of FIG. It is a figure explaining the arrangement | positioning process in the manufacturing method of this invention. It is a figure explaining the caulking process process in the manufacturing method of this invention. It is a figure explaining the groove | channel formation process for the outer side crimping process in the manufacturing method of this invention. It is a figure explaining the groove | channel formation process for an outer side crimping process following the process of FIG. It is a figure explaining the pipe expansion process of an outer side metal pipe regarding an Example. It is a figure explaining the groove | channel for the outer side crimping of an outer side metal pipe regarding an Example. It is a figure explaining the groove | channel for inner side crimping of an inner side metal pipe regarding an Example. It is a figure explaining the insertion fitting with an inner side metal tube and an outer side metal tube regarding an Example. It is a figure explaining the caulking process of an outer side metal tube and an inner side metal tube regarding an Example. It is a figure explaining the insertion fitting of an inner side metal tube and an outer side metal tube regarding a comparative example. It is a figure explaining the jig used in order to grasp an inner metal pipe (stainless steel pipe) with a chuck in a tension test. It is a figure explaining the jig used in order to grasp an outside metal pipe (copper pipe) with a chuck in a tension test. It is a figure which shows the cross-sectional shape of a joining pipe body regarding an Example. It is a figure which shows the cross-sectional shape of a joining pipe body regarding a comparative example. It is a figure explaining the conventional manufacturing method.

  Hereinafter, specific embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and may be implemented with appropriate modifications within the scope of the object of the present invention. can do.

<Joint tube>
FIG. 1 is a schematic diagram for explaining a bonded tube body 1 according to the present invention. The joined tube 1 includes an outer metal tube 2 and an inner metal tube 3 inserted inside the outer metal tube 2, and the outer metal tube 2 and the inner metal tube 3 are caulked and joined to each other. . The inner metal tube 3 is made of a metal material having a higher tensile strength than the outer metal tube, and has an inner caulking groove 31 having a depth of 0.5 mm or more in the tube radial direction on the outer surface. In this specification, “tensile strength” refers to “tensile strength” defined by JIS Z2241 for each of the outer metal tube and the inner metal tube.

<Outer metal tube>
The material of the outer metal tube 2 is not particularly limited as long as it has a lower tensile strength than the inner metal tube 3, and examples thereof include copper, aluminum, and alloys thereof. Because it has excellent corrosion resistance in the outdoor environment, pressure resistance that can withstand the gas pressure of the refrigerant gas that passes through the outside of the outer metal pipe 2, heat transfer to improve heat exchange efficiency, and excellent jointability between pipes, The material of the metal tube 2 is preferably copper or a copper alloy.

  Although the shape of the outer metal tube 2 is not particularly limited, the inner metal tube 3 is inserted until one end of the inner metal tube 3 abuts, and a predetermined length is measured from the base end 22. It is preferable that a tube expansion portion 2 </ b> C whose inner diameter is substantially the same as the outer diameter of the inner metal tube 3 is formed at at least one end of the outer metal tube 2. When the expanded tube portion 2C is formed, the base end 22 of the expanded tube portion 2C and the one end 32 of the inner metal tube 3 are in contact with each other, and the outer surface of the outer metal tube 2 is outside at a position overlapping the inner caulking groove 31. A caulking groove 21 is formed.

  When the outer metal tube 2 has the expanded portion 2C, the length in the longitudinal direction of the expanded portion 2C is not particularly limited, but the length in the longitudinal direction of the expanded portion 2C is preferably 10 mm or more and 100 mm or less. More preferably, it is 20 mm or more and 40 mm or less.

  In the inclined portion 2B formed between the outer tube main body 2A and the expanded tube portion 2C of the outer metal tube 2, the taper angle θ with respect to the outer tube main body 2A is not particularly limited, but the taper angle θ is 10 ° or more. It is preferably 80 ° or less, and more preferably 30 ° or more and 60 ° or less.

  The outer diameter of the outer tube main body 2A is not particularly limited, but the outer diameter of the outer tube main body 2A is preferably 4 mm or more and 90 mm or less, and more preferably 10 mm or more and 70 mm or less.

  The inner diameter of the outer tube main body 2A is not particularly limited, but the inner diameter of the outer tube main body 2A is preferably 3 mm or more and 88 mm or less, and more preferably 8 mm or more and 60 mm or less.

  The outer diameter of the expanded tube portion 2C is not particularly limited, but the outer diameter of the expanded tube portion 2C is preferably 6 mm or more and 150 mm or less, and more preferably 15 mm or more and 100 mm or less.

  The inner diameter of the expanded portion 2C is not particularly limited as long as it is substantially the same as the outer diameter of the inner metal tube 3, but the inner diameter of the expanded portion 2C is preferably 5 mm or more and 140 mm or less, and is 12 mm or more and 90 mm or less. It is more preferable.

  The wall thickness of the outer metal tube 2 is not particularly limited, but the wall thickness of the outer metal tube 2 is preferably 0.1 mm or more and 10 mm or less, and more preferably 0.3 mm or more and 3 mm or less.

  The depth of the outer caulking groove 21 is not particularly limited, but is preferably 0.1 mm or more and 1 mm or less, and more preferably 0.3 mm or more and 0.5 mm or less. If the outer caulking groove 21 is too shallow, the outer metal tube 2 and the inner metal tube 3 cannot be sufficiently caulked and fixed, and good bonding strength may not be obtained. If the outer caulking groove 21 is too deep, the inner metal tube 3 is excessively deformed, and due to work hardening of the metal material, a crack may occur at the bead position where the outer caulking groove 21 of the outer metal tube 2 is formed. There is sex.

<Inner metal tube>
The material of the inner metal tube 3 is not particularly limited as long as it has a higher tensile strength than the outer metal tube 2, and is easily available and has excellent corrosion resistance in an outdoor environment. The material 3 is preferably stainless steel.

  The shape of the inner metal tube 3 is not particularly limited and is not illustrated. However, in order to facilitate insertion into the outer metal tube 2, the outer diameter is at least one of the ends of the inner metal tube 2. In other words, a reduced diameter portion substantially the same as that may be formed.

  The outer diameter of the inner metal tube 3 is not particularly limited as long as it is substantially the same as the inner diameter of the outer metal tube 2 in the overlapping portion overlapping the outer metal tube 2, but the outer diameter of the inner metal tube 3 is 4 mm or more and 139 mm or less. It is preferable that it is 11 mm or more and 89 mm or less.

  The inner diameter of the inner metal tube 3 is not particularly limited, but the inner diameter of the inner metal tube 3 is preferably 3 mm or more and 137 mm or less, and more preferably 8 mm or more and 60 mm or less.

  The wall thickness of the inner metal tube 3 is not particularly limited, but the wall thickness of the inner metal tube 3 is preferably 0.1 mm or more and 10 mm or less, and more preferably 0.3 mm or more and 3 mm or less.

  The inner metal tube 3 has an inner caulking groove 31 on the outer surface. The depth of the inner caulking groove 31 in the tube diameter direction is 0.5 mm or more, preferably 0.6 mm or more, and more preferably 0.8 mm or more. If the depth of the inner caulking groove 31 in the tube radial direction is too shallow and less than 0.5 mm, the outer metal tube 2 and the inner metal tube 3 cannot be sufficiently caulked and fixed, and good joint strength can be obtained. It is not preferable because there is a possibility that it is not.

  The upper limit of the depth of the inner caulking groove 31 is not particularly limited, but if the groove is too deep, the amount of deformation of the inner metal tube 3 becomes excessive, and a crack at the bead position where the inner caulking groove 31 is formed may be caused. There is sex. Therefore, the depth of the inner caulking groove 31 is preferably 5 mm or less, and more preferably 4 mm or less.

<Heat exchanger>
Since the heat exchanger of the present invention includes the above-described bonded tube body 1, it is possible to provide a heat exchanger that is excellent in corrosion resistance, pressure resistance, heat conductivity, and bondability.

<Method for producing bonded tube>
Hereinafter, the manufacturing method of the joined pipe body 1 which concerns on this invention is demonstrated, referring FIGS. In the manufacturing method according to the present invention, an inner caulking groove forming step for forming an inner caulking groove 31 ′ in an inner metal pipe 3 made of a metal material having a higher tensile strength than the outer metal pipe 2 (FIGS. 2 and 3) and after this inner caulking groove forming step, the outer metal tube 2 and the inner metal tube 3 are arranged at positions where the inner caulking groove 31 'overlaps the inner surface of the outer metal tube 2 (FIG. 4) and a caulking groove (the outer caulking groove 21 and the inner caulking groove 31 in FIG. 1) is formed at a position P that overlaps with the inner caulking groove 31 ′ of the outer surface of the outer metal tube 2, and the outer metal tube 2 A caulking process step (FIG. 5) for caulking the inner metal tube 3.

<Inner caulking groove forming process>
2 and 3 are schematic cross-sectional views for explaining the inner caulking groove forming step. The inner caulking groove forming step is a step of forming the inner caulking groove 31 ′ in the inner metal tube 3.

  A method for forming the inner caulking groove 31 ′ is not particularly limited, and examples thereof include a rolling method. In the rolling method, the inner metal tube 3 is placed on the roll spindle 40, the blade 50 having a rounded blade edge is pressed against the outer surface of the inner metal tube 3, and the inner metal tube 3 is rotated while rotating in the tube axis direction. This is a technique for forming a caulking groove 31 ′.

  The depth in the tube diameter direction of the inner caulking groove 31 'is not particularly limited, but is preferably 0.5 mm or more and 5 mm or less, and more preferably 0.8 mm or more and 2 mm or less. If the inner caulking groove 31 ′ is too shallow, the outer metal tube 2 and the inner metal tube 3 cannot be sufficiently caulked and fixed, and good bonding strength may not be obtained. If the inner caulking groove 31 ′ is too deep, a crack may occur at the bead position of the outer metal tube 2.

  The position for forming the inner caulking groove 31 ′ is not particularly limited, but is preferably within a range of 5 mm to 95 mm from the end of the inner metal tube 3, and preferably within a range of 10 mm to 90 mm. More preferably.

<Arrangement process and caulking process>
FIG. 4 is a schematic diagram for explaining the arrangement step. The arranging step is a step of arranging the outer metal tube 2 and the inner metal tube 3 at a position where the inner caulking groove 31 ′ overlaps the inner surface of the outer metal tube 2 after the inner caulking groove forming step.

  FIG. 5 is a schematic diagram for explaining the caulking process. In the caulking process, a caulking groove (the outer caulking groove 21 and the inner caulking groove 31 in FIG. 1) is formed at the position P that overlaps the inner caulking groove 31 ′ on the outer surface of the outer metal tube 2, and the outer metal tube 2. And the inner metal pipe 3 are processed.

  As a method of performing the process of caulking the outer metal tube 2 and the inner metal tube 3, a method similar to the method of forming the inner caulking groove 31 'can be cited.

  By the way, in the present invention, when the outer metal tube 2 and the inner metal tube 3 are caulked in the caulking process, the caulking is performed at a position P that overlaps the inner caulking groove 31 ′ on the outer surface of the outer metal tube 2. Since the groove is formed, it is necessary to be able to specifically identify the position P. From this, there are a plurality of types of modes as specific modes of the arranging step and the caulking process.

(First aspect)
The first mode is a mode that further includes a mark display step of displaying a mark at a position on the outer surface of the outer metal tube 2 and overlapping the inner caulking groove 31 ′ when overlapped with the inner metal tube in the arranging step. It is. In this aspect, since the location of the position P can be specified from the mark, the caulking groove may be formed in accordance with the mark in the caulking process.

  The method for displaying the mark is not particularly limited as long as the position P can be specified by marking the position P by means such as coating, printing, or sticking a sticker.

(Second aspect)
A 2nd aspect is an aspect using the expanded metal part 2C in which an internal diameter is substantially the same as the outer diameter of the inner side metal tube 3 in the at least one edge part as the outer side metal tube 2. FIG. In this aspect, in the arrangement step, the inner metal tube 3 can be arranged at a unique position by inserting the inner metal tube 3 into the expanded tube portion 2C and abutting one end of the inner metal tube 3 against the proximal end of the expanded tube portion 2C. . Since the position of the inner caulking groove 31 ′ of the inner metal tube 3 can be measured and specified in advance, one end of the inner metal tube 3 of the outer surface of the expanded portion 2C in the outer metal tube 2 is the base end of the expanded portion 2C. The position P that overlaps the inner caulking groove 31 ′ when abutting against the inner caulking 22 can be easily identified. For this reason, in the caulking process, a caulking groove is formed at the position P and the outer metal tube 2 and the inner metal tube 3 are caulked.

(Third aspect)
6 and 7 are schematic diagrams for explaining the third mode. In the third mode, prior to the arranging step, the outer caulking groove 21 'is formed on the outer metal tube 2 at a position overlapping the inner caulking groove 31' when the inner metal tube 3 is overlapped in the arranging step. It is the aspect which further includes the groove | channel formation process for the outer side crimping to perform (FIG. 6). In this aspect, when the inner metal tube 3 is inserted into the outer metal tube 2 and reaches the position where the inner caulking groove 31 ′ and the outer caulking groove 21 ′ overlap each other in the arranging step, Engage securely. Therefore, in the caulking process, the caulking groove may be formed at a position P where the inner caulking groove 31 ′ and the outer caulking groove 21 ′ overlap (FIG. 7).

  As a method of forming the outer caulking groove 21 ′, a method similar to the method of forming the inner caulking groove 31 ′ can be given.

  The depth in the tube diameter direction of the outer caulking groove 21 ′ is not particularly limited, but is preferably 0.5 mm or more and 10 mm or less, and more preferably 1 mm or more and 5 mm or less. If the outer caulking groove 21 ′ is too shallow, there is a possibility that the outer metal tube 2 and the inner metal tube 3 do not play a role of alignment. If the outer caulking groove 21 ′ is too deep, the inner metal tube 3 may not be fitted into the outer metal tube 2.

  The first to third aspects are examples for specifically specifying the position P, and the present invention is not limited to these aspects. Further, any one of these first to third aspects may be selected, or a plurality of aspects may be selected.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

<Example>
As the outer metal tube 2, a copper tube having an outer diameter of 32.5 mm, a plate thickness of 2.3 mm, and a length of 100 mm was used. As the inner metal tube 3, a SUS304 stainless steel tube having an outer diameter of 32.0 mm, a plate thickness of 1.2 mm, and a length of 100 mm was used. The tensile strength of the outer metal tube was 210 N / mm ² , and the tensile strength of the inner metal tube was 672 N / mm ² .

  A bonded tube was manufactured according to the third aspect described above. First, as shown in FIG. 8, a portion from one end of the outer metal tube 2 to 30 mm was pressed with a mold having an outer diameter of 33.0 mm and a taper angle of 30 °, and the tube was expanded. Subsequently, as shown in FIG. 9, an outer caulking groove 21 ′ having a depth of 0.5 mm was provided over the entire circumference at a position 20 mm from the base end 22 of the expanded pipe portion 2 </ b> C by using a rolling method.

  Subsequently, as shown in FIG. 10, an inner caulking groove 31 ′ having a depth of 0.8 mm was provided over the entire circumference at a position 20 mm from one end of the inner metal tube 3 by using a rolling method.

  Subsequently, as shown in FIG. 11, when the inner metal tube 3 is inserted into the expanded portion 2C of the outer metal tube 2, and the outer caulking groove 21 ′ and the inner caulking groove 31 ′ reach a position where they overlap, Both grooves were securely engaged. Then, as shown in FIG. 12, the blade 50 having a rounded blade edge is pressed against the outer caulking groove 21 ′, and the outer metal tube 2 and the inner metal tube 3 are rotated in the tube axis direction while rotating the connecting body. By forming the caulking groove until the outer diameter of the caulking groove of the metal tube 3 reaches 32 mm, the outer metal tube 2 and the inner metal tube 3 are subjected to a process to obtain the bonded tube body 1 according to the example. It was.

<Comparative example>
As the outer metal tube and the inner metal tube, the same copper tube and stainless steel tube as in the example were used.

  First, as shown in FIG. 8, a portion from one end of the outer metal tube 2 to 30 mm was pressed with a mold having an outer diameter of 33.0 mm and a taper angle of 30 °, and the tube was expanded.

  Subsequently, as shown in FIG. 13, the inner metal tube 3 was inserted into the expanded portion of the outer metal tube 2, and one end of the inner metal tube 3 was abutted against the proximal end of the expanded portion. Then, the blade 50 having a rounded blade edge is pressed to a position 20 mm from the base end of the expanded pipe portion 2C, and the connection body of the outer metal tube 2 and the inner metal tube 3 is rotated in the tube axis direction while the outer metal tube 3 By forming a caulking groove until the outer diameter becomes 32 mm, the outer metal tube 2 and the inner metal tube 3 are subjected to a process to obtain a bonded tube body 60 according to a comparative example.

<Evaluation>
In order to evaluate the bonding strength of the bonded tube, a tensile test was performed on each bonded tube (length: about 170 mm) manufactured in the example and the comparative example. The caulking groove of the bonded tube was arranged so as to be approximately in the center of the two chucks of the tensile tester. Moreover, in order to prevent the joining tube body from being crushed into an elliptical shape during the tensile test, the jig shown in FIGS. 14 and 15 was used. FIG. 14 shows a jig used for gripping the inner metal tube 3 (stainless steel tube). A cylindrical curved surface having a diameter of 29.5 mm is inserted into the inner surface side of the inner metal tube 3, and a cylindrical curved surface having a diameter of 32.0 mm is formed. I grabbed it with a chuck. FIG. 15 is a jig used for grasping the outer metal tube 2 (copper tube). A cylindrical curved surface having a diameter of 27.8 mm is inserted into the inner surface side of the outer metal tube 2, and a cylindrical curved surface having a diameter of 32.0 mm is formed. I grabbed it with a chuck. The tensile speed was 10 mm / min and a load-stroke curve was measured. In both the examples and the comparative examples, the load reached the peak value when the caulking portion was broken. The bonding strength was obtained from this peak value.

  The joining pipe body 1 of the example had a joining strength of 11.42 kN, and the joining pipe body according to the comparative example had a joining strength of 6.03 kN. Compared to the bonded tube 60 of the comparative example, the bonded tube 1 of the example improved the bonding strength by about 89%. As described above, in the embodiment, since the inner caulking groove having a pipe radial depth of 0.8 mm is provided on the outer surface of the inner metal pipe, the connecting pipe having a good joint strength by caulking with the outer metal pipe. The body was obtained.

  In order to consider the reason why the bonding strength was improved in the present invention, the cross-sectional shape including the caulking groove was photographed in the bonded tube bodies 1 and 60 according to the example and the comparative example (magnification: 10 times). FIG. 16 is a schematic diagram illustrating a cross-sectional shape of the bonded tube body 1 according to the embodiment based on the photograph, and FIG. 17 is a schematic diagram illustrating a cross-sectional shape of the bonded tube body 60 according to the comparative example. It is.

  16 and FIG. 17, the inner caulking groove 31 is formed on the outer surface of the inner metal tube 3 in the bonded tube body 1 (FIG. 16) according to the embodiment. On the other hand, in the joined tube body 60 (FIG. 17) according to the comparative example, the deformation of the inner metal tube 3 is very small, and the inner caulking groove 3 is hardly formed on the outer surface of the inner metal tube 3. This is presumably because, in the bonded tubular body 60 according to the comparative example, the bonded state is maintained only by the frictional force at the interface.

DESCRIPTION OF SYMBOLS 1 Joining pipe body 2 Outer metal pipe 21 Outer caulking groove 22 Expanded part base end 3 Inner metal pipe 31 Inner caulking groove 32 One end 40 Roll support shaft 50 Blade P Overlapping position

Claims (4)

An inner caulking groove forming step for forming an inner caulking groove in an inner metal pipe made of a metal material having a higher tensile strength than the outer metal pipe; and
After the inner caulking groove forming step, the outer metal tube and the inner metal tube are arranged in a position where the inner caulking groove overlaps the inner surface of the outer metal tube;
A joined tube body including a caulking process step of forming a caulking groove at a position overlapping with the inner caulking groove on the outer surface of the outer metal pipe, and performing a caulking process on the outer metal pipe and the inner metal pipe. A manufacturing method of
At least one end of the outer metal tube is formed with an expanded portion whose inner diameter is substantially the same as the outer diameter of the inner metal tube,
The arranging step is a step of inserting the inner metal tube into the expanded portion, and abutting one end of the inner metal tube against a proximal end of the expanded portion,
In the caulking process step, a caulking groove is formed at a position overlapping with the inner caulking groove when one end of the inner metal tube is abutted against a base end of the expanded pipe part of the outer surface of the expanded pipe part, A method for manufacturing a joined tube, which is a step of caulking an outer metal tube and the inner metal tube. An inner caulking groove forming step for forming an inner caulking groove in an inner metal pipe made of a metal material having a higher tensile strength than the outer metal pipe; and
After the inner caulking groove forming step, the outer metal tube and the inner metal tube are arranged in a position where the inner caulking groove overlaps the inner surface of the outer metal tube;
A joined tube body including a caulking process step of forming a caulking groove at a position overlapping with the inner caulking groove on the outer surface of the outer metal pipe, and performing a caulking process on the outer metal pipe and the inner metal pipe. A manufacturing method of
Prior to the arranging step, an outer caulking groove is formed on the outer metal tube so as to form an outer caulking groove at a position overlapping the inner caulking groove when overlapped with the inner metal tube in the arranging step. Further comprising a step,
The arranging step is a step of overlapping the inner caulking groove and the outer caulking groove,
The caulking process step is a method for manufacturing a bonded tube body, wherein the caulking groove is formed at a position where the inner caulking groove and the outer caulking groove overlap. The method for manufacturing a bonded tube body according to claim 1 or 2 , wherein the outer metal tube is a copper tube, and the inner metal tube is a stainless steel tube. The said inner metal pipe after the said caulking process process is a manufacturing method of the joining pipe body in any one of Claim 1 to 3 which has an inner side caulking groove whose depth of a pipe diameter direction is 0.5 mm or more.

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