JP3532959B2 - Metal tube joint processing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connection in which a ring-shaped bead provided in the radial direction of a joint portion of a metal pipe of an O-ring shaft seal type has an external thread. By tightening a union nut engaging with the bead to the external thread of the connecting member until it abuts against the connecting end of the member, an O-ring groove is formed on the joint portion of the metal pipe connected to the connecting member by rolling using a round die. The present invention relates to a method of processing a joint portion of a metal pipe, for example, a method of processing a joint portion of a metal pipe constituting a car air-conditioning system. [0002] For example, when used for piping of a car air-conditioning system, metal pipes are often used in connection with each other due to restrictions on layout and the like. It is important to prevent liquid leakage at the connecting portion of the metal pipe because of the circulation of the like. for that reason,
The metal pipe is provided with a joint portion for connection, and various measures are taken in this joint portion to prevent liquid leakage. [0003] For example, a joint portion of a metal seal type as shown in FIG. 6 is flared at an end portion 26 so as to form a divergent shape, and a union nut 23 is connected to an external thread 24 of a connecting member 21.
To the inward flange 25 of the union nut 23 and the connecting end 22 of the connecting member 21 via the divergent end 26.
The liquid is prevented from leaking by abutting against.
However, metal pipes having metal-sealed joints are often made of aluminum or copper as the material, and tend to cause stress relaxation in the joints, so that liquid in the pipes easily leaks during use. There is a disadvantage that. The O-ring bead type shown in FIG. 7 is provided with a ring-shaped bead 16 protruding in the radial direction at a joint portion of a metal pipe, and this bead 16 is provided with an external screw 2.
The metal tube 2 is tightened by tightening the union nut 23 engaging with the bead 16 to the external thread 24 of the connecting member 21 until it abuts the connecting end 22 of the connecting member 21 having the connecting member 4.
Is connected to the connecting member 21 and the O-ring 17 is sandwiched between the connecting end 22 of the connecting member 21 and the bead 16 to prevent liquid leakage. However, this type of joint has the disadvantage that the O-link 17 is damaged when the central axis of the metal pipe and the connecting member is slightly displaced, and early leakage of fluid occurs. FIG. 8 shows an O-ring shaft seal type joint which improves on the disadvantages of the O-ring bead type joint. [0005] This O-ring shaft seal type joint 4
The O-ring bead type joint part and the connecting means are the same, but the means for preventing liquid leakage is different.
That is, the O-ring 17 is connected to the connection end 22 of the connection member 21.
Is located at a location different from the corner 16a of the bead 16 at which the metal pipe 2 meets the inner peripheral surface 21a of the connecting member 21.
By disposing it between the joint portion 4 and the outer peripheral surface 4a of the joint portion 4, the connecting portion 27 has a structure for preventing liquid leakage. [0006] The O-ring groove is mainly formed by a rolling method or a cutting method.
The thickness of the joint portion at the position where the ring groove is formed is shown in FIG.
When the groove depth is smaller than the groove depth of the O-ring groove as shown in (1), the cutting method cannot be used due to its structure.
The rolling method is less expensive in manufacturing cost than the cutting method, but is inferior in quality such as surface roughness and dimensional accuracy. Was the cause. Therefore, it was necessary to improve the quality. Accordingly, an object of the present invention is to form an O-ring groove of an O-ring shaft seal type joint portion by rolling with a round die so as to maintain a low production cost while maintaining surface roughness and dimensions. An object of the present invention is to provide a method for processing a joint portion of a metal pipe, which eliminates the drawbacks of the conventional rolling method in which quality such as accuracy is inferior to cutting. [0008] In order to achieve the above object, the present invention provides an O-ring shaft seal type metal pipe having a ring-shaped bead protruding in the radial direction of a joint portion for forming an external thread. The union nut engaging the bead is tightened to the external thread of the connecting member until it abuts against the connecting end of the connecting member, so that the joint portion of the metal tube connected to the connecting member is rolled by a round die. In the method for processing a joint portion of a metal pipe, which forms a ring groove, a step portion abutting against an edge of the joint portion, a guide portion extending into the joint portion from the step portion and closely fitting to the inner periphery of the joint portion; Rolling a jig having a mandrel extending outside the position corresponding to the O-ring groove with the same diameter at a smaller diameter than the portion and having an outer diameter less the groove bottom thickness of the desired O-ring groove Before fitting In the state where the end face of the joint portion is pressed by the step portion, the rolling process is performed with a round die until the rolling load at the mandrel portion is supported at the groove bottom of the O-ring groove. And a jig for removing a jig from the joint portion. In addition, the connection member here includes a connection part such as a radiator and an evaporator in addition to the metal pipe. In order to clarify the operation of the present invention, a detailed description will be given in comparison with a conventional method of forming an O-ring by a rolling process. FIG. 5 is a schematic view of the radial direction of the round dies when the O-rings are formed by the rolling method using three round dies 1 in order to explain the radial operation. In this rolling process, as shown in this figure, the metal tube 2 is rotated, and the round die 1 is rotated (without revolving) to reduce the axial distance 3 between the metal tube 2 and the round die 1. In the case where the metal pipe 2 is rolled by moving the metal die 2 in the direction, the metal die 2 is not rotated, and the circular die 1 is moved while revolving in the direction in which the distance 3 between the metal tube 2 and the circular die 1 is reduced. In some cases, the round die is rotated and rolled when it comes into contact with the tube 2. In either case, the round die 1 is moved in the direction of reducing the axial distance 3 between the metal tube 2 and the round die 1. After moving, the joint portion 4 of the metal pipe is rolled, and then the round die is moved to the original position 5 (the position indicated by the broken line in the figure).
The same operation is performed in which the rolling process is terminated by moving back and returning to the position shown in FIG. In the case of the conventional rolling process, the joint portion tip 9 is extended in the axial direction by the working force F1 of the round die 1 as shown in FIG. FIG.
0), the surface accuracy of the O-ring groove tip side surface 8 and the R
The shape cannot be processed (FIG. 13). As a method for preventing this, as shown in FIG. 10 (b), if the stopper 10 for pressing the joint end portion 9 is arranged to prevent the elongation in the axial direction, the R shape can be processed. Immediately after machining, when the round die 1 is pulled out of the O-ring groove and moved back to the original position 5 due to an increase in stress, the damage to the side wall 8 of the O-ring groove 6 tends to occur. In addition, since the stopper 10 is a fixed type, if the length of the joint portion varies, a processing failure or the like occurs. For example, if the length is short, the processing failure shown in FIG. 13 occurs. Roll forming was difficult. On the other hand, the method for processing the joint portion 4 of the metal pipe 2 according to the present invention has a stepped portion 12, a guide portion 13, and a mandrel portion 14, and has a sectional shape shown in FIG. Predetermined jig 1 having dimensions corresponding to O-ring groove dimensions
5 is disposed on the joint portion 4 (FIG. 2), and then rolled with a round die until the rolling load is supported on the mandrel at the bottom of the O-ring groove (FIG. 1). By increasing the force F1, transferring the precision machining shape including the surface roughness of the round die 1 shown in FIGS. 11A and 11B to the machining surface of the joint portion, and removing the jig 15 immediately after the machining is completed. Then, after removing the residual stress generated by the processing force F1, the round die 1 is pulled out from the O-ring groove 6 and is moved back to the original position, so that the O-ring groove 6 does not suffer from extraction damage, This makes it possible to easily obtain surface roughness and shape of quality. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment of a method for processing a joint portion 4 of a metal pipe 2 according to the present invention will be described with reference to FIG.
The metal pipe 2 shown in this figure is a joint part 4 of an O-ring shaft seal type. This joint part 4 has a ring-shaped bead 16 protruding in the radial direction, and an end edge 9 side of the bead 16. In order to prevent liquid leakage, an O-ring groove 6 for disposing an O-ring 17 is provided. This bead 16 is formed by inserting another metal tube into the metal tube 2, performing plastic working to expand the diameter, and then pressing the edge 9 of the metal tube 2 in the axial direction. Can be. Although FIG. 1 shows a case where the diameter of the metal tube 2 is different on the left and right across the bead 16, the diameter may be the same by selecting the processing conditions. The O-ring groove 6 is formed by a rolling process using a special jig 15. The jig 15 has a step 12, a guide 13, and a mandrel 14. These outer diameters D1, D2, D3 are such that the step 12 is larger than the inner diameter d1 of the edge 9 of the joint 4, the guide 13 is substantially equal to the inner diameter d1 of the edge 9, and the mandrel 14 Needs to be set to have an outer diameter obtained by subtracting a desired groove bottom thickness t1 of the O-ring groove 6. That is, the outer diameter D1 of the step portion 12 is set to be larger than the inner diameter d1 of the edge 9 of the joint portion 4 so as to abut against the edge 9 of the joint portion 4 so as to press the edge 9. Because
The reason why the outer diameter D2 of the guide portion 13 is made substantially equal to the inner diameter d1 of the edge 9 is that the center axis 18 of the mandrel portion 14 and the center axis line 19 of the metal tube 2 coincide with each other.
In order to position the mandrel 4 at the center in the joint portion 4 and to make the outer diameter of the mandrel portion 14 to be the outer diameter D3 obtained by subtracting the groove bottom thickness t1 of the desired O-ring groove 6, This is because the rolling load is supported by the mandrel portion 14 during the forming process. Therefore, the appropriate dimension of the jig 15 is naturally determined by various conditions such as the diameter and thickness of the joint portion 4 of the metal pipe 2 and the groove depth of the O-ring groove 6. Next, an O-ring groove 6 is formed in the joint 4 of the metal pipe 2.
Will be described with reference to FIG. First,
In the joint portion 4, the step 12 of the jig 15 is attached to the edge 9 of the joint portion 4.
The mandrel part 14 and the guide part 13 are sequentially inserted until the jig 15 abuts, and the jig 15 is arranged at a predetermined position of the joint part 4.
Thereafter, the clamp 20 located outside the metal tube 2 is closed to fix the metal tube 2 (FIG. 4A). Then, the three round dies 1 are revolved (not rotated) using a hydraulic cylinder (not shown), and moved in a direction in which the distance 3 between the axis of the metal tube 2 and the round dies 1 is reduced. (FIG. 5), the rolling process is started by bringing the metal tube 2 into contact with the outer surface of the joint portion 4 (FIG. 4B). This rolling process is performed by gradually moving the round die 1 in a direction to decrease the distance 3 between the axes until the round die 1 reaches a predetermined O-ring groove position (FIG. 1 (c)). )) Causes the mandrel portion 14 to support the rolling load during the rolling process in which the round die reaches a predetermined O-ring groove position. As means for detecting that the round die 1 has reached a predetermined O-ring groove position, for example,
It is desirable to detect by the electric signal, that is, to input the movement position of the die to the hydraulic cylinder device in advance and detect by the positioning sensor built in the device, but there is no particular limitation. Immediately after the processing is completed, the jig 15 is removed from the joint portion 4, and the round die 1 is moved backward to return to the original position 5 (FIG. 4 (d)). With this procedure,
A desired O-ring groove is formed in the joint. The joint portion 4 in which the O-ring groove 6 is formed as described above,
After the ring 17 has been placed, the bead 1 is held until the bead 16 abuts the connection end 22 of the connecting member 21 having an external thread.
By connecting the union nut 23 engaging with the connecting member 21 to the connecting member 21 by tightening the outer screw 24 of the connecting member 21, liquid leakage can be prevented. (Quality Evaluation) Next, O
The quality of the joint part 4 of the metal pipe 2 in which the ring groove 6 was formed was evaluated. The metal tube 2 was made of an aluminum alloy and had an outer diameter of φ16 and a thickness of 2 mm. Examples 1 to 4 correspond to FIG.
According to the above-described procedure shown in (a) to (d), the metal tube 2
O-ring groove 6 is formed in joint portion 4 of mandrel portion 14.
Are set to 11.2, 11.6, 12.
0 and 12.3. For comparison, as shown in FIG. 9, a comparative example 1 in which an O-ring groove is formed by cutting the joint portion by an NC lathe, and an edge of the joint portion as shown in FIG. The quality was evaluated together with Comparative Example 2 in which an O-ring groove was formed by a conventional rolling method in a state where a conventional stopper was disposed at the position. The quality evaluation includes the presence or absence of damage on the surface of the O-ring groove 6 and other surface roughness, the accuracy of the groove depth of the O-ring groove 6 (the difference between the major and minor diameters of φA and φB), and other dimensions and shapes. And went for. Note that φA is the groove bottom diameter of the O-ring groove, and φB is the outer diameter of the O-ring groove. Table 1 shows the evaluation results of and. The smaller the value in the table, the better. [Table 1] From the results shown in Table 1, it can be seen that Examples 1 to 4 show a remarkable improvement in the shortest diameter difference accuracy as compared with Comparative Example 2 in which an O-ring groove is formed by a conventional rolling process. As compared with Comparative Example 1 in which the O-ring groove was formed, almost the same accuracy could be obtained. Examples 1 to 3
Although the surface of the O-ring groove was not damaged and the surface appearance was good, in Example 4, some cracks occurred at the bottom of the O-ring groove. This is because the outer diameter of the mandrel portion of the jig exceeds an appropriate range. Therefore, in this quality evaluation, the appropriate outer diameter of the mandrel part is 1
It was in the range of 1.2 to 12.0. The other surface roughness of the O-ring groove 6 and the other dimensions and shape of the O-ring groove 6 were good in Examples 1 to 4 and Comparative Examples 1 and 2. According to the present invention, after a predetermined jig is provided at the joint portion, the rolling by the round die is performed until the rolling load is supported at the mandrel portion at the groove bottom of the O-ring groove. By performing the processing, the quality such as the surface roughness and the dimensional accuracy is improved by increasing the processing force F1 during the rolling.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a state in which a predetermined jig 15 having a step portion 12, a guide portion 13, and a mandrel portion 14 is disposed on a joint portion 4;
FIG. 4 is a diagram for illustrating a method of processing a joint portion of a metal pipe according to the present invention, showing a state at the time of rolling processing by a round die 1. FIG. 2 is a view showing a state in which a predetermined jig 15 having a step portion 12, a guide portion 13, and a mandrel portion 14 is arranged on a joint portion 4 and before rolling by a round die 1 is performed. It is a figure for explaining a joint part processing method of a metal tube. FIG. 3 is a sectional view showing a predetermined jig 15 having a step portion 12, a guide portion 13, and a mandrel portion 14. FIG. 4 is a view for explaining a procedure for forming an O-ring groove 6 in the joint portion 4 of the metal pipe 2 according to the present invention. FIG. 5 is a schematic view of the round dies viewed in the axial direction for explaining the radial operation of the round dies when forming an O-ring groove by a rolling process using three round dies. FIG. 6 is a view showing a state in which a conventional metal seal type joint and a connecting member are connected. FIG. 7 is a view showing a state where a conventional O-ring bead type joint portion and a connecting member are connected. FIG. 8 is a view showing a state in which a conventional O-ring shaft seal type joint portion and a connecting member are connected. FIG. 9 is a view showing a comparative example 1 in a state where an O-ring shaft seal type joint portion in which an O-ring groove is formed by cutting with an NC lathe and a connecting member are connected. FIG. 10A is a diagram showing a state when an O-ring is formed by a conventional rolling process, and FIG. 10B is a diagram in which a stopper is provided at a position where the O-ring abuts on an edge of a joint portion. FIG. 11 is a diagram of Comparative Example 2 showing a state when an O-ring is formed by a conventional rolling method. FIG. 11A is a side view of a round die, and FIG.
FIG. 3A is an enlarged view of a processed portion of the round die shown in FIG. 3A to show the surface state of the round die 1 which has been subjected to precision processing including surface roughness. FIG. 12 is a partial cross-sectional view of a joint portion of a metal pipe rolled using the round die shown in FIG. 11 (a). 13A is a view showing a state of an O-ring groove 6 having reduced surface accuracy when formed by a conventional rolling process, and FIG. 13B is an enlarged view of an upper portion 11 of a side wall thereof. FIG. 4 is a diagram showing a processing defect. [Description of Signs] 1 Round die 2 Metal tube 3 Distance between the axis of round die and metal tube 4 Joint 4a Outer peripheral surface of joint 5 Original position of round die 6 O-ring groove 7 Working part of joint 8 O-ring Side wall of groove 9 Edge of joint 10 Stopper 11 Upper part of side wall of O-ring groove 12 Step 13 Guide 14 Mandrel 15 Jig 16 Bead 17 O-ring 18 Center axis of mandrel 19 Center axis of metal pipe 20 Clamp 21 Connecting member 21a Inner peripheral surface 22 of connecting member Connection end 23 Union nut 24 Outer thread 25 of connecting member Inward flange 26 Diverging end 27 Connecting portion 28 Bolt 29 Flange 30 Joint

Claims (1)

(57) [Claim 1] A ring-shaped bead provided in a joint portion of a metal pipe of an O-ring shaft seal type protruding in a radial direction abuts a connection end of a connection member having an external thread. Until the union nut engaging with the bead is tightened to the external thread of the connecting member to form an O-ring groove in the joint portion of the metal tube connected to the connecting member by rolling with a round die. In the joint part processing method, a step part which abuts against an edge of the joint part, a guide part which extends into the joint part from the step part and fits tightly on the inner periphery of the joint part, has a smaller diameter than the guide part. A jig having an outer diameter extending outside the position corresponding to the ring groove and having the same diameter as that extending from the position corresponding to the ring groove and having a desired groove bottom thickness of the O-ring groove is disposed at the joint before rolling. Press the end face of the joint with the step In this state, the rolling process is performed with a round die until the rolling load is supported on the mandrel at the groove bottom of the O-ring groove, and the jig is removed from the joint immediately after the process is completed. Joint processing method.