JP2006110603A - Manufacturing method for metallic bent tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a metallic bent tube, by which, when manufacturing a metallic bent tube that is joined to an object to be joined via an O-ring, an O-ring groove is formed and the rising height from the object can be made lower by preventing roll over caused by press work at the end part of the tube, even in the case that a bent part with an extremely small bend radius is formed contiguously to the end part of a straight tube. <P>SOLUTION: A bent part 10 with an extremely small bend radius is formed by bending a portion contiguous to the end part of a straight tube. Then, the end part is slantwise cut so that a cut end part 19', where the side connecting to an outside bent part 10b of the bent part 10 is projected further than the side connecting to an inside bent part 10a, is formed. Next, a cylindrical expanded tube part 21 with an approximately constant wall thickness is formed by press-forming the cut end part 19' in the tube axial direction of the cut end part 19'. Finally, an O-ring groove is formed by applying roll forming to the outer peripheral face of the expanded tube part 21. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for manufacturing a metal bent pipe for fluid distribution, and more particularly to a technique for manufacturing a metal bent pipe optimal as a refrigerant distribution pipe connected to a car air conditioner or the like.

As a conventional technique, a refrigerant pipe joint provided with a metal bent pipe (refrigerant pipe) as shown in FIG. 6 has been proposed (see Patent Document 1). The refrigerant pipe connection joint 1 includes a fixed block 4 fixed to a connection object 2 with bolts 3 and a metal bent pipe 5 inserted and supported by the fixed block 4. The metal bent pipe 5 is L-shaped. Is bent. The fixed block 4 and the metal bent tube 5 are fixed in a state where the ring seal portion 11 and at least the inner bent portion 10a of the bent portion 10 are accommodated in the fixed block 4. Accordingly, the dimension between the connection surface of the fixed block 4 and the refrigerant pipe 5, that is, the height h ₁ of the refrigerant pipe connection joint ₁ is set low. In addition, an O-ring 13 is attached to an O-ring groove 12 provided at an end 19 of the metal bent pipe 5, and this end 19 is fitted into the internal passage 9 of the connection object 2, via the O-ring 13. It is in close contact. Thereby, the sealing property in the connection site | part of the metal bending pipe 5 and the connection target object 2 is ensured.

By the way, since the installation of various devices in the engine room is becoming increasingly dense in recent years, the height of the refrigerant pipe connection joint 1 (the rising height of the metal bent pipe 5 from the connection object 2) h ₁ is further reduced. Therefore, it was necessary to develop a more compact refrigerant pipe connection joint.

In order to further improve the refrigerant pipe connection joint 1 of the prior art 2 in order to cope with the above problems, the inventors reduced the bending radius of the inner curved portion 10a of the bent portion 10 of the metal bent tube 5 to substantially zero. At the same time, by omitting the ring seal part 11 of the metal bent pipe 5 and the ring accommodating part 17 of the fixed block 4, the height of the refrigerant pipe connection joint 1 (the rising height of the metal bent pipe 5 from the connection object 2). ) an attempt was made to lower the h ₁ as much as possible.

 However, after the fixing, an attempt was made to form the O-ring groove 12 in the end portion 19, but the following problem occurred. That is, in order to form the O-ring groove 12, it is necessary to preliminarily press the end 19 in the axial direction to adjust the shape. I couldn't.

For this reason, there was a situation in which a more compact refrigerant pipe connection joint in which the height h ₁ of the refrigerant pipe connection joint (the rising height of the metal bent pipe 5 from the connection object 2) ₁ was further lowered could not be obtained. .
Japanese Patent Laid-Open No. 7-12283

 Therefore, according to the present invention, even if a bent portion having a very small bending radius is formed in the vicinity of the end portion of the straight pipe, a predetermined O-ring groove can be formed by preventing the end portion from being set by pressing. Therefore, an object of the present invention is to provide a method for manufacturing a metal bent pipe that can further reduce the rising height from the connection object.

 As a result of investigating the cause of the settling and the like, the inventors of the present invention have made the inner bent portion 10a and the outer bent portion 10b of the bent portion 10 by a bending process in which the bending radius of the inner bent portion 10a is reduced to substantially zero. It has been found that the thickness of the pipes is greatly different, and this influence extends to the end part 19 which is a straight pipe part connected to the bent part 10. That is, when the tube is bent with a small curvature, as shown in FIG. 4, the inner curved portion 10a side of the bent portion 10 is compressed, so that excess wall gathers inside the tube, resulting in a thicker portion. The outer curved portion 10b side of 10 is thin because a tensile force is applied. The difference in thickness extends not only to the bent portion 10 but also to the end portion 19 which is a straight pipe portion connected to the bent portion 10. Therefore, when the end portion 19 is compressed in the tube axis direction by pressing in this state and formed into the expanded tube portion 21, as shown in FIG. 5, the expanded tube portion 21 on the thick inner curved portion 10a side. It has been found that settling occurs at the fixed block portion 4a in contact with the base of the tube, and build-up occurs near the base of the expanded portion 21.

 In the above prior art, the problem that the above-mentioned settling or the like occurs during press working did not occur. The reason for this is considered as follows. That is, in the above prior art, the curvature of the bent portion 10 is larger than that of the present invention, and the difference in thickness between the bent portions 10a, 10b is originally small. In addition, the ring seal portion 11 is positioned in the vicinity of the bent portion 10. Since the press working is performed after forming, the part that is far from the bent portion 10 and less affected by the difference in thickness is pressed as compared with the present invention, and it is considered that the above-mentioned settling or the like has not occurred. It is done.

 Based on the results of this investigation, in order to prevent the above-mentioned settling or the like from occurring during press working, it is considered that the difference in thickness between the inner curved portion 10a and the outer curved portion 10b after compression molding should be as small as possible. As a result of intensive studies, the following invention has been completed.

 The invention according to claim 1 is a method for manufacturing a metal bent pipe connected to an internal passage of an object to be connected via an O-ring, wherein a portion adjacent to an end of a straight pipe is bent, and an inner bent portion is formed. A bending step of forming an L-shaped bent portion having a bending radius of approximately 0, and the end portion is cut obliquely, and the side connected to the outer bent portion of the bent portion protrudes longer than the side connected to the inner bent portion A cutting step of forming a cutting end, a pressing step of pressing the cutting end in the tube axis direction of the cutting end to form a cylindrical press end having a substantially constant thickness, and And a groove forming step of forming an O-ring groove for mounting the O-ring on the outer peripheral surface of the press end.

 According to a second aspect of the present invention, in the metal bent tube manufacturing method according to the first aspect, an end surface of the cut end portion is inclined by 3 to 15 degrees with respect to a plane perpendicular to the tube axis of the cut end portion. Is the method.

  Invention of Claim 3 is a manufacturing method of the metal bent pipe of Claim 1 or 2 whose said metal bent pipe is used for a refrigerant circuit.

 According to the present invention, even if a bent portion having a very small bending radius is formed in the vicinity of the end portion, the end portion is cut obliquely and then pressed to make the thickness of the processed portion substantially constant. As a result, it is now possible to prevent the processing site from becoming loose. As a result, a predetermined O-ring groove can be formed at the end, and a metal bent pipe that can further reduce the height of the refrigerant pipe connection joint can be provided.

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Structure of bent metal pipe]
FIG. 1 illustrates a bent metal pipe manufactured by the manufacturing method of the present invention. This example shows an example in which a metal bent pipe is applied to a refrigerant pipe constituting a refrigerant pipe connection joint. (A) is a side view of a refrigerant pipe connection joint, (b) is a top view of a refrigerant pipe connection joint. In addition, the same code | symbol was attached | subjected to the same components and site | part as the conventional refrigerant | coolant piping connection coupling shown in the said FIG. The refrigerant pipe connection joint 1 is used when connecting a refrigerant circuit of a car air conditioner. The fixed block 4 is fixed to an air conditioner device 2 as a connection target by a bolt 3 as a connection tool, and the fixed block 4. It consists of the refrigerant | coolant piping 5 as a metal bending pipe | tube supported in the state by which the edge part side was penetrated. Note that the air conditioner device 2 includes an internal passage 9 that communicates with the refrigerant pipe 5, and the refrigerant pipe 5 and the internal passage 9 are connected by fixing the fixed block 4 to the air conditioner device 2.

 The refrigerant pipe 5 is an aluminum pipe and includes a bent portion 10 bent in an L shape with an inner bending radius of approximately 0 (about 3 mm or less) on the side connected to the internal passage 9. That is, the refrigerant pipe 5 has an elbow shape on the side connected to the internal passage 9. The refrigerant pipe 5 includes an O-ring groove 12 that is recessed in an annular shape, and a sealing O-ring 13 is mounted in the O-ring groove 12.

 The fixed block 4 is a block body made of aluminum and includes a bolt insertion hole 15 through which the bolt 3 is inserted and a pipe insertion hole 16 through which the connection end 19 side of the refrigerant pipe 5 is inserted. The pipe insertion hole 16 is provided with a bent housing portion 18 that covers the inner curved portion 10 a of the bent portion 10 of the refrigerant pipe 5.

 As described above, in the prior art, the ring seal portion 11 is provided in the refrigerant pipe 5, and the ring seal portion 11 is accommodated in the ring accommodating portion 17 provided in the fixed block 4, whereby the fixed block 4 and the refrigerant pipe 5 are connected. Although fixed, the ring seal portion 11 and the ring housing portion 17 are omitted in the present invention.

[Production method of bent metal pipe]
Next, the manufacturing method of the said metal bending pipe (refrigerant piping) 5 is demonstrated in description of the manufacturing method of the refrigerant | coolant piping connection joint 1 whole. First, using a bending apparatus (see Japanese Patent Laid-Open No. 8-323425) for bending a pipe with a minimum curvature at a portion close to the end of the extruded aluminum refrigerant pipe 5, an inner bending radius is used. Is formed into an L-shaped elbow shape with substantially zero.

 On the other hand, the fixed block 4 made of aluminum having the bolt insertion hole 15 and the tube insertion hole 16 is formed by cutting from an extruded material.

 Next, the end of the refrigerant pipe 5 is inserted into the tube insertion hole 16 of the fixed block 4, and the inner curved portion 10 a is fitted into the bent housing portion 18.

 Next, the end 19 of the refrigerant pipe 5 protruding from the fixed block 4 is cut obliquely, and as shown in FIG. 2, the side of the bent portion connected to the outer curved portion 10b is more than the side connected to the inner curved portion 10a. Make it stick out longer. The end 19 after cutting is referred to as a cut end 19 '.

 Then, by pressing, the cut end portion 19 ′ having an oblique end face is compressed in the tube axis direction of the cut end portion 19 ′, and is formed into a cylindrical tube expanded portion 21 as shown in FIG. 3. Since the thin side of the cut end 19 ′ is long and the thick side is shortened in advance by the oblique cutting, the thickness after compression molding is reduced between the inner curved portion 10a and the outer curved portion 10b. Since the expanded portion 21 having a substantially constant wall thickness is obtained at the periphery, the material supply does not become excessively excessive or insufficient, and the above-described sag does not occur.

 The appropriate degree of inclination α of the cut surface (the end surface of the cut end portion 19 ′) that obliquely cuts the end portion 19 depends on the difference in thickness between the bent inner portion 10a and the outer bent portion 10b, and the bent portion. Although it may vary depending on the distance to the cut surface, for example, it is preferable to incline by 3 to 15 ° with respect to the plane perpendicular to the tube axis of the cut end 19 ′. That is, if the inclination angle is less than 3 °, the difference in the protruding length from the bent portion 10 between the outer bent portion 10b and the inner bent portion 10a is too small, and the meat of the bent portions 10a, 10b after the bending process is too small. The thickness difference cannot be completely eliminated, and the material is left on the thick inner curved portion 10a side, and the possibility of the occurrence of the above-mentioned settling on the inner curved portion 10a side during compression molding remains. On the other hand, if the inclination angle exceeds 15 °, the difference in the protruding length becomes too large and exceeds the amount necessary to eliminate the wall thickness difference. On the contrary, the material is formed on the inner curved portion 10a side. This is because the possibility of occurrence of the remaining shape of the cut surface on the inner curved portion 10a side is increased.

 Next, the O-ring groove 12 is formed on the outer peripheral surface of the expanded pipe portion 21 by rolling. Thereafter, the O-ring 13 is mounted in the O-ring groove 12 to complete the refrigerant pipe connection joint 1.

[Modification]
In the said embodiment, although aluminum was illustrated as a material of the metal bending pipe (refrigerant piping) 5 and the fixed block 4, other materials, such as aluminum alloy, copper, brass, stainless steel, may be used. Moreover, the material of the refrigerant | coolant piping 5 and the fixed block 4 is not necessarily restricted to the same material, It is good also as a different material. The O-ring groove 12 is formed by rolling, but may be formed by cutting or pressing. Moreover, although the bolt was illustrated as the connection tool 3, you may use other means, such as the engagement structure engaged by a screw and fitting. Moreover, although the example which forms the fixed block 4 by cutting from an extrusion material was shown, you may form by the press cold forging technique and the die-casting technique. Although the example which uses the refrigerant | coolant piping connection joint 1 for the connection of the refrigerant circuit of a car air conditioner was shown, it can be used also for the connection of the refrigerant circuit of a room air conditioner and a refrigerator. Therefore, although the air-conditioner apparatus was illustrated as the connection target object 2, it can be used also for a refrigerator.

  The refrigerant pipe connection joint 1 was manufactured by the manufacturing method described in the above embodiment. The bent metal pipe (refrigerant pipe) 5 has an inner bending radius of about 21 mm from the end of an aluminum pipe having an outer diameter of 12 mm and a wall thickness of 1.75 mm, using the bending apparatus (Opton Corporation). Was formed into an L-shaped elbow shape with substantially zero. The fixed block 4 was formed into an aluminum block shape having one bolt insertion hole 15 and one tube insertion hole 16 as shown in FIG. 1 by cutting.

  Then, the refrigerant pipe 5 was fitted into the fixed block 4.

 Next, as shown in FIG. 2, the end 19 of the refrigerant pipe 5 protruding downward from the bottom surface of the fixed block 4 has a protruding length L from the bottom surface of the fixed block 4 after cutting of 12.5 mm. The angle α was variously changed in the range of 2 to 20 °, and was cut obliquely to form a cut end 19 ′. Next, each of the cut end portions 19 ′ was pressed to form the expanded portion 21.

 Each refrigerant pipe 5 after the press work was cut into half cracks, and the cross section near the expanded portion 21 was macro-observed to investigate the occurrence of sag, build-up, and remaining shape of the cut surface.

An example of cross-sectional observation is shown in FIGS. The survey results are shown in Table 1. When the inclination angle α of the cut surface is 2 ° (less than 3 °), as shown in FIG. 7, on the inner curved portion 10a side, the occurrence of sag is observed in the fixed block portion 4a in contact with the root of the expanded portion 21. In addition, the occurrence of buildup was observed near the base of the expanded tube portion 21. On the other hand, when the inclination angle α of the cut surface is 20 ° (over 15 °), as shown in FIG. 8, the shape of the cut surface remains on the inner curved portion 10a side, and a predetermined shape / dimension is obtained. I couldn't. However, when the inclination angle α of the cut surface was in the range of 3 to 15 °, no stickiness, build-up, or generation of the remaining shape of the cut surface was observed in any part.

It is a figure which shows an example of the metal bending pipe manufactured with the manufacturing method of this invention, (a) is a side view, (b) is a top view. It is sectional drawing of the cutting end part vicinity after cut | disconnecting the edge part of a metal bending pipe | tube in embodiment. It is sectional drawing of the pipe expansion part vicinity after pressing the cut end part of a metal bending pipe in embodiment. It is sectional drawing of the bending part vicinity of the metal bending pipe after a bending process. It is sectional drawing of the bending part vicinity of the metal bending pipe after the press work in a comparative example. It is a side view of the refrigerant | coolant piping connection joint of a prior art. In an Example, it is a side view of the refrigerant | coolant piping connection coupling in the case of (alpha) = 2 degrees. It is a side view of the refrigerant | coolant piping connection coupling in the case of (alpha) = 20 degrees in an Example.

Explanation of symbols

2 ... Connection object (air conditioner equipment)
5. Metal bent pipe (refrigerant pipe)
DESCRIPTION OF SYMBOLS 9 ... Internal passage 10 ... Bending part 10a ... Inner curved part 10b ... Outer curved part 13 ... O-ring 19 ... End part 19 '... Cutting end part 21 ... Expanding part alpha ... Inclination angle of a cut surface

Claims (3)

A method for producing a bent metal pipe connected to an internal passage of a connection object via an O-ring,
Bending a portion adjacent to the end of the straight pipe to form an L-shaped bent portion having a bending radius of the inner curved portion of approximately 0;
A cutting step of cutting the end portion obliquely to form a cut end portion that protrudes longer than the side continuous with the inner curved portion on the side continuous with the outer curved portion of the bent portion;
Pressing the cut end in the tube axis direction of the cut end to form a cylindrical press end having a substantially constant thickness; and
A groove forming step of forming an O-ring groove for mounting the O-ring on the outer peripheral surface of the press end;
A method of manufacturing a metal bent pipe, comprising:   The manufacturing method of the metal bending pipe | tube of Claim 1 in which the end surface of the said cutting end part inclines 3-15 degrees with respect to the surface perpendicular | vertical to the pipe axis of the said cutting end part. The method of manufacturing a metal bent pipe according to claim 1 or 2, wherein the metal bent pipe is used in a refrigerant circuit.

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