JPH0810879A - Formation of pipe end and forming die used for it - Google Patents

Abstract

PURPOSE:To prevent the lowering of strength and to improve the durability by forming a gradual diameter changing part and an expanded pipe cylindrical part for expanding the diameter of the pipe to be formed, pressurizing this tip end surface toward the pipe to be formed side and buckling to the angle state outward. CONSTITUTION:In a first process, the gradual diameter changing part 5 for expanding the diameter along a die surface 4b by pressing an expanding die 4 into the pipe while holding the pipe 1 to be formed with a first pipe holding die 2 and the expanded diameter cylindrical part having smaller diameter than the finish bulging diameter and paralleled with the pipe axis are formed. In a second process, the expanded diameter cylindrical part 6 is buckled along a flare forming surface 7b and the rest part forms a flange part 9 along a flange forming surface 8g, by pushing a forming die 8 to the pipe axial direction after inserting into the expanded diameter cylindrical part 6 while holding with the second pipe holding die 7 to push the pipe end surface with the abutting surface 8g. In such a way, the diameter expansion ratio of the expanded diameter cylindrical part 6 is made to be little in comparison with the conventional diameter expansion ratio, and the lowering and the breakage of the strength caused by reduction of the thickness are prevented and the durability can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a pipe end and a forming die used for the same. More specifically, the present invention relates to a pipe end, and more specifically, to an end portion of a metal pipe. TECHNICAL FIELD The present invention relates to a method for molding a bulging portion having a diameter-reduced portion that continuously reduces in diameter at the tip of the portion, and a molding die therefor.

[0002]

2. Description of the Related Art Conventionally, there is a joint portion of an exhaust pipe of an engine or a joint portion of other metal pipes, in which the structure of the joint portion is constructed as shown in FIG. That is, as shown in FIG.
A bulged portion 102 having a mountain-shaped cross section is formed at the end of the tube 01, a flare portion 104 having an enlarged diameter at the tube end of the second pipe 103, and a short flange portion 105 having a reduced diameter at the end are formed. The bulging portion 102 and the flare portion 104 are fitted with a gasket 106 interposed therebetween, and a clamp 107 having a mountain-shaped cross section and divided into two in the circumferential direction is fitted to the outer peripheral portion thereof, and this is bolted and There is one in which the pipes 101 and 103 are connected to each other by being tightened with a nut or the like in the pipe axis direction by the tapered portions of the bulging portion 102, the flare portion 104, and the clamp 107 (Japanese Patent Laid-Open No. 5-3).
No. 3890, FIG. 1).

[0003] As a method of forming the flared portion 104 and the flange portion 105 of the bulging portion of the second pipe 103, the following method has conventionally been adopted. First conventional molding method (FIG. 4) Molded pipe 108 made of a straight pipe of φA as shown in FIG.
First, as shown in (b), the pipe to be molded 108 is held in a pipe holding mold 110, and an expanding die 111 is press-fitted into the pipe from the open end of the pipe 108, as shown in FIG.
The flare portion 113 having an expanded diameter of φB and the flange forming portion 114 having a diameter of φB parallel to the tube axis are bulged from the tip end of the flare portion 113 with the outer pressing die 112. Next, (c)
As shown in FIG.
5 and presses the drawing die 116 toward the pipe holding die 115, thereby causing the flange forming portion 114 to
A flange 117 having a tip diameter reduced to φC is formed by squeezing the tip 13 so that the tip is inclined toward the center of the tube with the upper end of 13 being a bending point.

Conventional second forming method (FIG. 5) After forming a flange forming portion 114 as shown in FIG. 4B, a roll 118 is formed on the outer surface of the flange forming portion 114 as shown in FIG. The flange portion 117 is pressed and revolved to form a flange portion 117 whose tip diameter is reduced to φC as shown in FIG. Note that φA, φB, and φC indicate the same diameter portions as described above.

Conventional Third Forming Method (FIG. 6) As shown in FIG. 6 (a), a tube 1 to be formed of a straight pipe of φA
08 is a pipe holding mold 11 having a tapered surface 119a.
9 and a mold 120 having a tapered mold surface 120a at the open end of the tube is engaged as shown in FIG.
0 is moved toward the pipe holding mold 119 along the pipe axis direction. As a result, the tube end is pressed by the molding die 120 and, as shown in FIGS.
The molded tube 108 buckles with the center of 20a as the buckling point,
The flare portion 121 and the flange forming portion 122 are formed in an equilateral mountain shape. Then, the flange forming portion 122 is cut by the cutter 123 to a necessary protruding length as shown in (d) to form a flange portion 124 having a tip diameter of φC. Note that φ
A and φB indicate the same diameter portion as above.

[0006]

In the above-mentioned first molding method (FIG. 4) and second molding method (FIG. 5),
It is necessary to temporarily expand the flare portion 113 and the flange forming portion 114 to φB which is larger than the tip diameter φC of the flange portion 117 in the final product state, and the diameter expansion ratio becomes excessive. Therefore, the amount of reduction in the plate thickness in the expanded portion becomes large, leading to a decrease in strength, the portion is likely to break during subsequent secondary processing, and the durability may also be reduced.

Further, the fact that the diameter expansion ratio is large and the plate thickness is greatly reduced tends to make the projection length X of the flange forming portion 114 non-uniform, or make the front and back surfaces in this X range non-smooth. If this occurs, the gasket 106 as shown in FIG. 8 cannot be held properly. For this reason, after this molding, a post-process such as finish cutting is required separately from the bulging process, and there is a problem that workability is poor and cost is high.

In addition, the above-mentioned third conventional molding method (FIG. 6)
In the above, it is necessary to cut the tip of the flange forming portion 122 to a required length after the bulging process, the cutting process and the process such as finish cutting of the cut surface are required separately from the bulging process, There is a problem that the workability is poor and the production cost increases due to the waste material 125. Further, as shown in FIG. 6 (b), since the buckling of the molded tube starts from a portion R not in contact with the mold, the buckling portion does not contact the mold, the buckling point varies, and a predetermined bulging shape is obtained. Sometimes you can't. Further, FIG.
As shown in (2), when the valley folds a and b before and after the bulge are extremely buckled, there is also a problem that the bulge C becomes irregular and a predetermined shape cannot be obtained.

Therefore, an object of the present invention is to provide a method of molding a pipe end and a molding die for solving the above problems.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the first aspect of the present invention is to provide a gradually changing diameter portion (5) at the end of the pipe (1) to be molded. And a tip portion of the expanded diameter cylindrical portion (6), which is continuous with the tip end portion of the expanded diameter cylindrical portion (6) and has a diameter smaller than the final expanded diameter and is parallel to the tube axis. A method of forming a pipe end, comprising a second step of pressurizing the expanded pipe (1) side to buckle the expanded diameter tubular portion (6) outward in a mountain shape.

In a second aspect of the invention, in the above second step,
The flared portion (1) is formed by extending the rear portion of the diameter-enlarging tubular portion (6) outward of the diameter gradually changing portion (5) at the same inclination as the diameter gradually changing portion (5).
0), and the front end of the enlarged diameter cylindrical portion (6) is bent and reduced in diameter from the tip of the flare portion (10) to form a flange portion (9) shorter than the flare portion (10). A method for forming a pipe end, characterized in that the enlarged-diameter tube (6) is buckled.

A third invention is a molding die used in the second step in the first and second inventions, wherein the molding tube (1) is used.
A pipe holding die (7) having a holding hole (7a) for holding the outer peripheral surface of the pipe, and a forming die (8) for expanding the tip of the pipe to be formed. The front end of the holding hole (7a) is formed with a flare forming surface (7b) that is expanded in a trumpet shape, and the forming die (8) is formed with the tube (1) held in the holding hole (7a). A first fitting surface (8b) that fits inside, and a tube that is located at the rear of the first fitting surface (8b), has a larger diameter than the first fitting surface (8b), and A second fitting die surface (8e) formed with a diameter smaller than the final bulging diameter of the second fitting die surface in parallel with the tube axis direction of the tube to be molded, and a tube located at a rear portion of the second fitting die surface (8e). It is characterized in that a contact surface (8f) with which the tip of (1) contacts is formed, and a flange forming surface (8g) rising from the corresponding contact surface (8f) inclining toward the pipe to be formed. Is a mold to be.

According to a fourth invention, in the molding die (8) according to the third invention, the flare molding surface (8) is provided between the first fitting die surface (8b) and the second fitting die surface (8e). A molding die characterized by forming a pressing surface (8d) inclined in the same direction as 7b).

[0014]

According to the first and second aspects of the invention, when the pipe to be molded (1) is expanded in diameter into a tubular shape before being bulged by buckling, the diameter of the expanded diameter tubular portion (6). May be smaller than the final bulge diameter. Therefore, the enlarged-diameter tube portion (6)
Can be reduced as compared with the conventional molding method shown in FIGS. Such a small diameter expansion ratio can reduce the reduction in the plate thickness of the diameter expansion tubular portion (6) at the time of molding. This means that the projecting length X 'of the enlarged diameter cylindrical portion (6) shown in FIG. 1 (b) becomes uniform over the entire circumference and the front and back surfaces also become smooth.

In the case where the molding die according to the third aspect is used, a pipe (1) having a pre-formed enlarged diameter cylindrical portion (6) is held by a pipe holding die (7), and the enlarged diameter cylindrical portion (7) is held. The mold (8) is pressed and moved from the opening side of (6) into the pipe (1). As a result, the pipe end of the expanded diameter cylindrical portion (6) is pressed by the contact surface (8f), and due to the presence of the second fitting mold surface (8e), the expanded diameter cylindrical portion (6) is moved outward. Buckle. At the time of this buckling, the flare forming surface (7
b), and buckling occurs at the bending point R 'which is in contact with the flaring forming surface (7b) and the flange forming surface (8).
g) is formed, and a mountain-shaped bulging portion composed of a long flare portion 10 and a short flange portion (9) is accurately formed in a predetermined shape.

When the molding die according to the fourth aspect is used, the flared molding surface (7b) and the pressing die surface (8d) hold the gradually changing diameter portion (5) firmly, so that the shape of the bulging portion is improved. It can be formed more accurately and reliably.

[0017]

Next, an embodiment of the present invention shown in FIG. 1 will be described. FIG. 1 (a) shows a metal-made tube to be formed with a bulge at an end according to the present invention. This molded tube 1
Is a cylindrical tube, and its outer diameter is φA.

In the first forming step, first, a portion other than the bulging portion on the side of the tube 1 to be bulged as shown in FIG. It is held in the holding hole 2a of the pipe holding die (outer die) 2 of FIG. A first die surface 2b, which is a tapered surface and opens like a trumpet, is formed on the entire front edge of the holding hole 2a. The expansion diameter of the front end of the first mold surface 2b is formed to be smaller than the outer diameter of the flare portion to be finally expanded, and the diameter is φ.
D.

Next, an outer peripheral surface of a molded pipe (hereinafter, also simply referred to as a pipe) 1 which is held as described above and protrudes from a first pipe holding mold 2 (which is fixedly mounted in the pipe axis direction). The outer mold 3 is disposed in the pipe 1 and the expanding mold 4 is pressed into the pipe 1 from the open end of the pipe 1. The second die surface 3a of the outer die 3 has the same diameter as φD and is formed parallel to the tube axis. In addition, the third
The mold surface 4a is formed with an outer diameter φE obtained by subtracting the thickness of the tube 1 from the above φD. Further, the tip of the expanding die 4 is formed in a tapered shape by forming a fourth die surface 4b formed of a tapered surface in the same direction and at the same angle as the taper angle of the first die surface 2b. By press-fitting the expansion die 4 into the pipe 1, the pipe 1
As shown in FIG. 1 (b), the tip portion of the pipe 1 is expanded, and the diameter gradually changing portion 5 gradually expanding from the outer diameter φA of the pipe 1 along the mold surfaces 2b and 4b, and the outer diameter φA of the pipe 1. The enlarged diameter cylindrical portion 6 having a larger outer diameter φD and a flat surface parallel to the tube axis is formed.

Next, the tube 1 formed in the first step is subjected to bulging forming as a second forming step using a forming die shown in FIG. 1 (c). The mold used for this molding is composed of a second pipe holding mold 7 installed immovably in the pipe axis direction and a molding die 8 movable in the pipe axis direction.

The second pipe holding mold 7 is a circumferential split mold, and the diameter gradually changing portion 5 and the diameter expanding cylindrical portion 6 of the pipe 1 are used.
A holding hole 7a for holding other parts is formed. Further, a flare molding surface 7b formed of a tapered surface which is opened like a trumpet is formed over the entire circumference at the front end edge of the holding hole 7a. The taper angle of the flare forming surface 7b is set to the same angle as the taper angle of the first mold surface 2b in the first pipe holding mold 2. Further, the diameter φ of the front end of the flare molding surface 7b is increased.
F has a diameter larger than φD, and is formed slightly larger than the outer diameter φF ′ of the flare portion to be finally expanded.

A small-diameter portion 8a is formed at the distal end of the molding die 8 so as to protrude completely into the inner surface of the tube portion (portion held by the holding hole 7a) of the tube 1, and the small-diameter portion 8a is formed. The outer peripheral surface of the first fitting die surface 8b is a flat surface parallel to the pipe axis.
A chamfered portion 8c is formed on the outer periphery of the tip so as to be easily fitted into the tube.

At the rear portion of the first fitting die surface 8b of the small diameter portion 8a, there is formed a taper-shaped die surface 8d whose diameter gradually increases rearward. The inclination angle of the pressing surface 8d is formed in the same angle and the same direction as the flare forming surface 7b.

An enlarged diameter portion is formed at the rear of the pressing surface 8d, and the outer periphery is formed on the second fitting surface 8e. The second fitting surface 8e has a diameter φE having the same diameter as the third surface 4a.
Is formed in parallel with the tube axis. Further, as shown in FIG. 1 (e), the length of the second fitting die surface 8e in the tube axis direction is such that the pressing die surface 8d is in contact with the flare portion 10 (gradual diameter change portion 5). It is formed to be shorter than the length of the linear enlarged-diameter cylinder 6 so that the enlarged-diameter cylinder 6 sometimes buckles into a desired mountain shape.

At the rear end of the second fitting mold surface 8e, an abutting surface 8f rising outward is formed over the entire circumference. The rising angle α of the contact surface 8f is set to an angle of 90 ° with respect to a flange forming surface 8g described later, as shown in FIG. The length of the contact surface 8f in the tube axis direction is formed to be equal to the plate thickness of the tube 1.

On the outer peripheral portion of the contact surface 8f, a flange forming surface 8g that rises inclining in the direction of the second pipe holding die 7 is formed over the entire circumference. The inclination angle of the flange forming surface 8g with respect to the vertical line is formed at the same angle as the flare forming surface 7b of the second pipe holding die 7. Further, the expansion diameter of the front end of the flange molding surface 8g is formed to be φF which is the same diameter as the front end expansion diameter of the flare molding surface 7b.

Using the above-mentioned mold, first, the pipe 1 formed in FIG. 1B is held by a second pipe holding mold 7 as shown in FIG. 1C. Next, the molding die 8 is fitted into the expanded diameter tubular portion 6 of the pipe 1 from the opening end side thereof as shown in FIG. 1C, and the second pipe holding die 7 side is arranged along the pipe axial direction. The pressure is moved in the direction (arrow A direction).

By this pressurizing movement, as shown in FIG. 1D, the diameter gradually changing portion 5 of the pipe 1 is changed to the second pipe holding mold 7.
The pipe end face 6a is pressed in the direction of the gradually changing portion 5 by the contact face 8f while being held in contact with the flare forming face 7b in the inclined posture. As a result, the diametrically expanded tubular portion 6 is constrained from buckling inward in the diametrical direction of the tube due to the presence of the second fitting die surface 8e and buckles outward, and the buckling is in contact with the flare molding surface 7b. Buckling is performed by using the bending point R'that contacts the buckling point as a starting point of buckling.

When the molding die 8 is further moved under pressure,
The buckling point moves along the flare forming surface 7b, and
Buckles further outward, and the rear portion of the expanded diameter cylindrical portion 6 extends to the outside of the gradually changing diameter portion 5 while sticking to the flare molding surface 7b. When the front surface of the second pipe holding die 7 and the front surface of the molding die 8 come into contact with each other as shown in FIG. The flange 9 is formed by being bent along 8g.

In such buckling molding, the contact surface 8
Since f is inclined backward at an angle of 90 ° with respect to the flange forming surface 8g as described above, the pipe end surface 6a tilts in the direction of arrow E in FIG. On the other hand, the abutment surface 8f does not hinder the buckling of the enlarged-diameter cylindrical portion 6. At the end of buckling, the pipe end surface 6
Since the entire surface of the cylinder a is in contact with the contact surface 8f in parallel, the enlarged diameter cylindrical portion 6 can be pressed against the flare forming surface 7b and the flange forming surface 8g, and the enlarged diameter cylindrical portion 6 is seated in a predetermined shape. Can succumb.

As a result, as shown in FIGS. 1 (e) and 3, the flared portion 10 longer than the diameter gradually changing portion 5 and the flange portion 9 shorter than the flared portion 5 and having the pre-formed diameter expanding tube. A bulging portion having a mountain-shaped cross section having an outer diameter φF ′ that bulges out more than the diameter φD of the portion 6 is formed. This diameter φF ′ is the diameter φF at which the flare molding surface 7b and the flange molding surface 8g are expanded at the front ends.
It has a slightly shorter diameter.

The following operation is also achieved by pressing the end surface of the enlarged diameter cylindrical portion 6 by the contact surface 8f. In the case where the pipe 1 is formed by winding a flat plate and welding both ends thereof by electric resistance welding, when the ends are expanded and drawn as shown in FIG. A protrusion D protruding from C may be formed. In such a case, the pressing force is concentrated on the protrusion D by the end face pressurization of the expanded diameter tubular portion 6 by the contact surface 8f as described above, and the protrusion D
Is crushed and becomes the same flat surface as the other tube end surface C. Therefore, the process of cutting and removing the protruding portion D after the formation of the bulging portion becomes unnecessary.

Although the molded tube 1 shown in FIG. 1A is a straight tube for easy understanding, it is not such a straight tube, and as shown in FIG. The diameter of the flare portion 1 is slightly increased from
The present invention may be applied to the case of molding a bulging portion including 0 and the flange portion 9.

The material and diameter of the raw pipe of the molded pipe 1 are
The desired thickness is used. As an example, SUS40
A 9LT-E, φ38.1, 1.2 mm thick plate was used. Then, as a result of forming the raw tube into a shape as shown in FIG. 3 by the above-described forming method, it was possible to satisfactorily buckle and shape into a predetermined shape.

Expanding die 4 and forming die 8 in the above embodiment
Although not shown, a known driving device such as a hydraulic cylinder device is used. Further, the pipe holding dies 2, 7 and the outer die 3 are opened and closed as split molds in the circumferential direction to facilitate attachment and detachment of the pipe 1, and these opening and closing means are provided by a well-known driving device such as a hydraulic cylinder device. Used.

It is to be noted that the enlarged diameter cylindrical portion 6 in the first step described above is used.
The molding may be performed by a method other than the method of using the expanding die 4 or the like in the above embodiment.

[0037]

As described above, according to the first and second aspects of the present invention, at the time of forming the enlarged-diameter tube portion in the pre-process of bulging-forming by buckling, the diameter of the enlarged-diameter tube portion is increased. The ratio can be made smaller than the conventional diameter expansion ratio. This can suppress a decrease in strength due to a decrease in the wall thickness of the enlarged diameter cylindrical portion at the time of molding, and breakage at the portion during subsequent secondary processing such as bulging of the flared portion and the flange portion. Can be prevented, and the durability can be improved. Furthermore, the small diameter expansion ratio and small wall thickness reduction of the enlarged diameter cylindrical portion can make the protruding length uniform over the entire circumference of the enlarged diameter cylindrical portion and smoothen the front and back surfaces, and the subsequent end surface A post-process such as finish cutting of the front and back surfaces is not required, so that manufacturing is easy and manufacturing costs can be reduced.

Further, since the expanded diameter cylindrical portion is formed in advance and buckled and bulged outward from its diameter, the amount of buckling is reduced as compared with the conventional one shown in FIG. 5, and a predetermined shape can be easily formed. The molding can be performed reliably, and the post-processes such as the cutting process after bulging and the finishing process which are required in the related art are not required, and the manufacturing is easy and the manufacturing cost can be reduced.

According to the third aspect of the present invention, it is possible to provide a molding die capable of easily and accurately performing the bulging molding due to the buckling as described above. Further, according to the invention of the fourth aspect, since the pressing surface is provided, the bulged portion can be molded into a predetermined shape more accurately and surely.

[Brief description of drawings]

FIGS. 1A to 1E are cross-sectional views showing a molding step of the present invention.

FIG. 2 is an enlarged cross-sectional view showing the shape of a contact surface 8f.

FIG. 3 is a side view in which an upper half surface of a tube formed according to the present invention is cut.

4A to 4C are cross-sectional views showing a first example of a conventional molding process.

FIG. 5 is a sectional view showing a second example of a conventional molding method.

FIGS. 6A to 6E are cross-sectional views showing a third example of a conventional molding process.

FIG. 7 is a side view showing a protruding portion of a weld bead portion in a molded pipe.

FIG. 8 is a sectional side view showing an example of use of a tube formed by bulging according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Tube to be molded 2 ... First pipe holding mold 3 ... Outer mold 4
... Expanding die 5 ... Diameter gradually changing part 6 ... Diameter expanding cylinder part 7 ... Second pipe holding die 7a ... Holding hole 7b ... Flare forming surface 8 ...
Mold 8b ... First fitting mold surface 8d ... Pushing surface 8e ... Second fitting mold surface 8f ... Abutting surface 8g ... Flange molding surface 9
... Flange part 10 ... Flare part

Claims (4)

[Claims] 1. An end portion of a tube to be molded (1) is provided with a gradually changing diameter portion (5) which gradually increases in diameter, and an expanding portion which is continuously smaller in diameter than the final bulge diameter and parallel to the tube axis at the end thereof. First for forming the cylindrical part (6)
And a second step of pressing the distal end surface of the enlarged diameter cylindrical portion (6) toward the molded pipe (1) to buckle the enlarged diameter cylindrical portion (6) outward in a mountain shape. A method for forming a pipe end, characterized in that: 2. The second step according to claim 1, wherein a rear portion of the enlarged-diameter cylindrical portion (6) is slanted outward from the gradually-diameter-varying portion (5) with the gradually-diameter-varying portion (5). To extend the flare (1
0), and the tip of the expanded diameter tubular portion (6) is bent and reduced in diameter from the tip of the flare portion (10) to form a flange portion (9) shorter than the flare portion (10). A method for forming a pipe end, characterized in that the expanded cylindrical portion (6) is buckled. 3. A molding die used in the second step according to claim 1 or 2, comprising a holding hole (7a) for holding an outer peripheral surface of a pipe to be molded (1). And a molding die (8) for expanding the tip of the pipe to be molded. The front end of the holding hole (7a) in the pipe holding die (7) has a flared molding surface (7b) which is expanded in a trumpet shape. ) Is formed, and a first fitting die surface (8) fitted in the forming pipe (1) held in the holding hole (7a) is formed in the forming die (8).
b), which is located at the rear of the first fitting die surface (8b), has a larger diameter than the first fitting die surface (8b), and a smaller diameter than the final bulging diameter of the tube. The second formed parallel to the pipe axis direction
A fitting surface (8e) and an abutment surface (8) located at the rear of the second fitting surface (8e), with which the tip of the molded pipe (1) abuts.
f) and a flange forming surface (8g) rising from the corresponding contact surface (8f) in the direction of the pipe to be formed. 4. The first mating surface (8b) according to claim 3,
And the second mating die surface (8e).
A molding die characterized by forming a pressing surface (8d) inclined in the same direction as b).