JPH0531547A - Bended metal pipe and forming method therefor - Google Patents

Abstract

PURPOSE:To form bended metal pipes having small bending radius and larger diameters than the diameters of the bended parts at least at one end without buckling bended parts; moreover. CONSTITUTION:A segmental die 5 has an inserting hole 6 in which the metal pipe is inserted for bending, and the corved part 8 with a small diameter that is continued to the straight part 7 having an inlet with a large diameter and formed with the inserting hole 6. when a metal pipe that fits in the diameter of the straight part 7 is inserted from the inlet and extruded with a pressing mandrel, the metal pipe is pushed into the bended part 8, drawing is performed for a contracted diameter and simultaneously bending is performed. The top end of the metal pipe is then expanded with an enlarging mandrel 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bent metal pipe and a method for molding the bent metal pipe.

[0002]

2. Description of the Related Art An elbow-shaped exhaust pipe used in an exhaust system of an automobile cannot be formed by a conventional step of inserting and bending a pipe, and is divided into several steps.
That is, after forming the bent portion by the insertion bending method, the end portion is cut into a predetermined length, and the end portion is expanded or reduced in diameter. By doing this, buckling that occurs in the bent portion when bending and end widening (mouth widening) or diameter reduction (narrowing) processing at the same time in one step was avoided, but there are several steps. It was troublesome.

Therefore, as shown in FIG. 12 and FIG. 13, members 1 and 2 obtained by pressing an SUS plate material like a skin to be welded together are welded together without depending on the insertion and bending method to form an elbow-shaped exhaust. A manufacturing method for forming the tube 3 is widely used.

In FIGS. 12 and 13, the exhaust pipe 3 uses SUS401 having a plate thickness of 2 mm as a material for the members 1 and 2,
The outer diameter φ of the bent portion of the exhaust pipe 3 is 42.8 mm, the outer diameter Φ of both ends is 47.2 mm, and the bending radius R of the bent portion is 70 mm.

[0005]

Among the above-mentioned conventional techniques, the former is bent by the insertion bending method, and then the end portion is cut into a required length to perform expansion processing (flare processing) or diameter reduction (flare processing). There is a problem in that the number of processes is increased and the processing time is lengthened because the processing is performed.

Further, the latter not only has a loss in terms of material removal, but also has a problem that it takes a long time for welding. Furthermore, the collars 1a of the members 1 and 2 such as the inner skin,
Since 2a protrudes beyond the outer diameter of the bent portion, the overall outer shape becomes large, and there is a problem that the space utilization efficiency when mounting on a vehicle is poor.

Therefore, an object of the present invention is to provide a bent metal pipe which has a good space utilization factor in terms of shape and can be formed in one step in a short processing time, and a processing method thereof.

[0008]

In order to achieve the above object, the bent metal pipe of claim 1 has a large diameter portion (4a) at least at one end, and is connected to this large diameter portion (4a) and pushed through. It has a small-diameter bent portion (4c) that has been reduced in diameter by a bending method, and the bending radius (R) of the bent portion (4c) is not more than twice the pipe outer diameter (φ) of the bent portion (4c). It is characterized by

The bent metal pipe of claim 2 further has large-diameter portions (4a, 4b) at both ends, and one large-diameter portion (4b) is drawn and reduced by a push-through bending method. It is characterized by being expanded and formed later.

A bent metal pipe according to claim 3 is the bent metal pipe according to claim 1, which has a large diameter portion (4a) at one end and is connected to this large diameter portion (4a) and is squeezed by a push-bend method. It is characterized in that a small-diameter bent portion (4c) subjected to compression warping and the other end connected to this bent portion (4c) have a diameter smaller than that of the bent portion (4c).

According to a fourth aspect of the present invention, there is provided a method of forming a bent metal pipe, wherein the metal pipe is inserted into an insertion hole formed by a split die to bend the metal pipe. The hole (6) has a large-diameter straight line portion (7) at its entrance, and a bent portion (8) continuous with the straight line portion (7) has a smaller diameter than the straight line portion (7) and has a bending radius. Is less than twice the diameter of the bent portion (8), the metal pipe (4A) is inserted into the split-type pipe insertion hole (6) configured as described above, and the diameter of the bent portion is reduced at the same time as the bending processing. It is characterized by applying.

[0012]

1 and 2 show a bent metal pipe 4 shown in FIG.
5 is a view for explaining the molding method of No. 5, in which a split mold (mold) 5 has a pipe insertion hole 6 formed therein. The pipe insertion hole 6 has an inlet portion formed by a large-diameter straight portion 7, a bent portion 8 continuous to the straight portion 7 has a diameter smaller than the diameter of the straight portion 7, and a bending radius thereof equal to that of the bent portion 8. It is less than twice.

In FIGS. 1 and 2, only one of the split molds 5 is shown. The other split mold (not shown) is superposed on the one split mold 5 shown from above in the drawing and used by being integrally fastened with a bolt / nut or a hydraulic clamp device or the like. In this way, a complete pipe insertion hole is formed in a state where the two split molds are superposed, which is the same as the known technique.

Reference numeral 9 is a taper portion connecting the straight portion 7 and the bent portion 8. Reference numeral 10 is a push core metal, 11 is a core metal for expanding the mouth, and the core guide 12 for expanding the mouth is fixed to one side of the split mold 5 with a bolt, and the core centers of the core guide 12 and the split mold 5 are the same. It is secured to the split mold 5 so as to be removable.

Cylindrical pipe 4A which is a material before processing
2 is inserted into the straight inlet portion 7 of the split pipe insertion hole 6 as shown in FIG. (The diameter of the inlet straight portion 7 is determined to fit the pipe 4A properly.) Then, when the push core metal 10 pushes down, the tip (lower end) of the pipe 4A.
Is inserted into the bent portion 8 through the tapered portion 9 and is bent while the diameter of the drawing is reduced.

When the push core 10 is further pushed down, the tip of the pipe 4A is inserted between the mouth-spreading core 11 and the end of the pipe insertion hole 6 to widen (spread) the mouth. In this way, when the push core is pushed down to the state shown in FIG. 1, the tip of the pipe reaches the end of the pipe insertion hole 6 and hits the mouth-opening core bar guide 12, and the forming process is completed. Then, the mouth-opening core metal 11 is removed from the split mold 5, and the push core metal 1
While removing 0, the split mold is disassembled and the bent pipe 4 is taken out.

As shown in FIG. 3, the bent pipe 4 has large-diameter portions 4a and 4b at each end, and is connected to the large-diameter portion, and has a small-diameter bent portion 4c that has been subjected to drawing reduction processing by a push-through bending method. And the bending radius R of the bent portion is formed to be not more than twice the outer diameter φ of the pipe of the bent portion 4c.

The bent pipe 4 shown in this FIG.
Corresponding to the embodiment. The embodiment of FIG. 4 has a bent pipe 4
Is an elbow type having a large diameter portion 4a only at one end thereof, and the split mold 5 and the core metal 11A at the end when molding such a bent pipe 4 may be as shown in FIG. No need to process.

In the above embodiment, the large diameter portion 4 at the rear end of the pipe is used.
Although a is the size of the diameter of the pipe material, when a commercially available pipe material is used, the size (outer diameter) of the available material is limited, which may be inconvenient. In such a case, between the one end (rear end) 4a and the bent portion 4c, a portion 4d having an outer diameter intermediate between the outer diameters of the both can be formed. To do this, as shown in FIG. 7, a portion 6d having an intermediate diameter between the straight portion 7 and the bent portion 8 is provided in the pipe insertion hole 6 of the split mold 5, and this diameter is ,
This can be achieved by adjusting the diameter of the portion 4c of the bent pipe 4 as required.

In the embodiment shown in FIG. 6, the large diameter portion 4a may be cut and discarded if necessary. The pipe 4 shown in FIG. 8 corresponds to the embodiment of claim 3.

In this embodiment, the bent pipe 4 has a large-diameter portion 4a at one end and a small-diameter portion (4e) at the other end, which is reduced in diameter to a diameter smaller than the diameter ψ of the bent portion 4c. It is an elbow type. The bending radius R of the small-diameter bent portion 4c that has been reduced in diameter by the push-through bending method has a bending radius R that is not more than twice the outer diameter ψ of the pipe of the bent portion 4c, as in the embodiment of FIG. .

The pipe 4 shown in FIG. 8 is processed by the method shown in FIG. In this case, the outlet 13 of the insertion hole 6 of the split mold 5
Has a diameter smaller than the diameter of the bent portion 8, and a core metal 11B for aperture stop is detachably fixed to one side of the split mold 5 by a core bar guide 12B for aperture stop.

The unprocessed cylindrical material pipe is inserted into the inlet straight portion 7 of the pipe insertion hole 6 of the split mold 5, and the push core metal 10 is inserted.
When the pipe is pushed down by, the tip (lower end) of the pipe is inserted into the bent portion 8 through the taper portion 9 and bent while being reduced in diameter. Then, the tip of the pipe is further reduced in diameter by the outlet 13 and the core metal 11B for mouth-drawing, and is drawn into a shape shown in the drawing.

In the embodiment of FIG. 10, the large diameter portion 4a and the bent portion 4 are
Similar to the embodiment of FIG. 6, a portion 4d having an intermediate diameter outer diameter is formed between c and c, unlike the embodiment of FIG.
The method of processing the pipe 4 will be apparent from the above description without any particular description.

In the embodiment shown in FIG. 11, the large diameter portion 4a of the pipe shown in FIG. 10 is cut at the portion indicated by arrow B and discarded.

[0026]

Since the bent pipe of the present invention is constructed as described above, the flange does not overhang unlike the prior art in which the press shown in FIGS. 12 and 13 has a middle shape. Efficient space utilization when mounting.

Further, since the bending portion is bent while being reduced in diameter, the bending portion is seated at the bending portion due to the overhanging effect of the drawing processing even if a reaction force is exerted on the material by the expanding core metal or the drawing core metal. No buckling. Therefore, there is no risk of the pipe being crushed by bending. Therefore, as a bent metal pipe used for an exhaust pipe, there is also an advantage that it can be avoided from the disadvantage that the cross-sectional area of passage of exhaust gas is excessively deformed.

Further, according to the molding method of the present invention, not only is there no risk of the pipe being crushed at the bent portion, but also the mouth widening processing and the mouth narrowing processing can be performed at the same time. There are also advantages.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view illustrating a push-bend process of a molding method of the present invention.

FIG. 2 is a cross-sectional view illustrating a push-through bending step of the molding method of the present invention.

FIG. 3 is a vertical cross-sectional view of an example of a bent metal pipe of the present invention.

FIG. 4 is a vertical sectional view of another embodiment of the bent metal pipe of the present invention.

5 is a longitudinal sectional view of a main part for explaining a push-bend process of a method for forming the bent metal pipe of FIG.

FIG. 6 is a vertical sectional view of still another embodiment of the bent metal pipe of the present invention.

7 is a longitudinal sectional view of an essential part for explaining a push-bend process of a method for forming the bent metal pipe of FIG.

FIG. 8 is a vertical cross-sectional view of still another embodiment of the bent metal pipe of the present invention.

9 is a longitudinal sectional view of an essential part for explaining a push-through bending step of a method of forming the bent metal pipe of FIG.

FIG. 10 is a vertical cross-sectional view of still another embodiment of the bent metal pipe of the present invention.

FIG. 11 is a vertical sectional view of still another embodiment of the bent metal pipe of the present invention.

FIG. 12 is a side view of a conventional exhaust pipe.

13 is a sectional view taken along line AA of FIG.

[Explanation of symbols]

4 bent metal pipe 4A metal pipe 4a, 4b Large diameter part 4c Bend 4e Small diameter part 50% type 6 insertion holes 7 Straight section 8 Bend

Claims (4)

[Claims] 1. A large-diameter portion (4a) is provided at least at one end, and a small-diameter bent portion (4c) connected to the large-diameter portion (4a) and reduced in diameter by a press-bending method. The bending radius (R) of the bent portion (4c) is the bent portion (4c).
The bent metal pipe is characterized by having a diameter equal to or less than twice the pipe outer diameter (φ). 2. A large-diameter portion (4a, 4b) is provided at each of both ends, and one large-diameter portion (4b) is formed by being expanded and then reduced and reduced by a push-through bending method. The bent metal pipe according to claim 1, which is characterized in that. 3. A large diameter portion (4a) is provided at one end, and
The small diameter bent portion (4c) connected to the large diameter portion (4a) and drawn and compressed by the push-through bending method and the other end connected to the bent portion (4c) have a diameter smaller than that of the bent portion (4c). Is a small-diameter bent part (4
A bent metal pipe having e). 4. In a forming method of bending a metal pipe by pushing it through an insertion hole of a pipe formed by a split mold, the pipe insertion hole (6) formed in the split mold (5) has a large inlet portion. A straight portion (7) having a diameter, a bent portion (8) continuous to the straight portion (7) is smaller than the diameter of the straight portion (7), and the bending radius thereof is twice the diameter of the bent portion (8). The molding of a bent metal pipe characterized in that the metal pipe (4A) is inserted into the split-type pipe insertion hole (6) configured as described above, and the bending processing is performed at the same time when the bending diameter is reduced and reduced at the bending portion. Method.