JP3549750B2 - Forming method of high expansion pipe and high expansion pipe - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a method for forming a high-expansion pipe for forming an enlarged diameter portion about twice as large as an end of a pipe, and a high-expansion pipe.
[0002]
[Prior art]
Conventionally, for example, in a beam member or a frame member made of a metal pipe such as an interior part for a vehicle, the diameter of the pipe end is increased to improve the mounting strength, and the like. As a processing method for expanding the diameter of the pipe, there is known a processing technique in which the outer peripheral portion of a pipe material is clamped and held by a clamp type, and a tapered pipe-opening punch is pressed into the pipe hole from one end side of the pipe hole to expand the diameter.
[0003]
[Problems to be solved by the invention]
In such a processing technology, when the pipe diameter is expanded by press-fitting an expansion pipe punch, the material in the same part expands, the plate thickness decreases, and when the material reaches the elongation limit, the fracture starts from the end part, so In the case of the steel pipe described above, expansion is limited to about 1.4 times the diameter of the raw pipe, and further processing is difficult.
On the other hand, when press-fitting an expansion pipe, eccentric expansion may be formed by shifting the center of the raw tube and the center of the expansion punch, but in this case, the eccentric amount may cause a portion to be extended from the concentric expansion pipe. As a result, the sheet thickness difference of the material becomes large, and processing is generally more difficult than concentric expansion.
[0004]
Incidentally, FIG. 11 shows the results of the thickness measurement when the eccentric expansion was processed from a 1 mm-thick raw tube by the conventional method. From the results, the thickness reduction in the circumferential direction and the axial direction is shown. It can be seen that the portion where the maximum value is reduced to about 50% of the plate thickness of the raw tube.
For this reason, for example, a simple concentric expansion or an eccentric expansion is selectively used depending on the part of the vehicle, and the enlarged diameter portion is attached to the vehicle body side, or a part or the like is attached to the enlarged diameter portion. When the pipe is expanded about 1.4 times, the strength is insufficient and the plate thickness is generally reduced. Therefore, it is necessary to reinforce the pipe with a separate reinforcing member. Become.
[0005]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to form a concentric or eccentric enlarged portion by expanding the diameter of at least one end of a pipe, and to break the end of the pipe. It is an object of the present invention to provide a processing technique and a high-expansion tube capable of forming an enlarged-diameter portion approximately twice as large as the diameter of the raw tube without causing the expansion.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention relates to a method for forming a high expansion pipe according to claim 1, wherein the expansion pipe is press-fitted from a pipe hole to form a concentric or eccentric expanded portion. Pressing the outer surface of the pipe material of the press-fitted portion against the inner surface of the clamp mold is performed while applying an axial compressive force, and the expansion is performed so as to maintain 70% or more of the plate thickness of the raw tube as the thickness of the enlarged diameter portion. The diameter of the expanded portion is reduced to approximately twice the diameter of the base tube by press-fitting multiple expanded punches with different maximum diameters and the same taper angle into multiple stages in order from the smaller diameter. It was made to be molded.
[0007]
In forming the enlarged diameter part, the part where the expansion of the pipe material is maximum can be changed in the axial direction by press-fitting the expansion punch with different maximum diameters into multiple stages and the maximum expansion part is specified. It is possible to prevent a problem such as concentration at a location. Incidentally, the taper angles of such a plurality of tube expanding punches are all set to be the same.
[0008]
Further, in the second aspect, the adjustment of the compressive force in the axial direction on the pipe material at the press-fitted portion is performed by adjusting the taper angle of the expanding tube punch.
That is, if the taper angle is too large, only the radial expansion force acts on the pipe material of the press-fit portion, and it is impossible to effectively apply the axial compression force, and the taper angle is too small. However, similarly, it is impossible to effectively apply a compressive force to the pipe material of the press-fit portion, and the molding efficiency is deteriorated.
By appropriately setting the taper angle, it is possible to maintain 70% or more of the plate thickness of the blank tube as the plate thickness of the press-fit portion, and it is possible to prevent problems such as breakage even if the diameter is increased about twice.
[0009]
[0010]
According to a third aspect of the present invention , when the pipe is a seam welded pipe and the enlarged diameter portion is eccentric, the seam welded portion is phase-aligned in a direction in which the amount of eccentricity is maximized.
In the case of such an eccentric high-expansion pipe, the direction in which the amount of eccentricity is the largest is the part where the tensile force is the largest and the material elongation is the largest, and in the case of a seam welded pipe, the seam welded part is the other part. It is a part that is harder than Therefore, by aligning the phase of the seam welded portion in the direction in which the amount of eccentricity is maximized , breakage of the portion is prevented.
[0011]
Further, in the high-expansion pipe according to the fourth aspect , a pipe-expanding punch is press-fitted from a pipe hole to have a diameter-expanded portion approximately twice as large as the diameter of the raw pipe. to a certain way, pipes be a seam welded pipe, and so the seam weld is phasing in the direction of maximum eccentricity.
Such a high-expansion pipe can be formed by the above-mentioned forming method.
[0012]
In the high-expansion tube according to the fifth aspect , the end of the enlarged diameter portion is subjected to flange processing.
If the end is flanged in this way, it is convenient, for example, to increase the rigidity by using it as a mounting part.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to the accompanying drawings.
Here, FIG. 1 is an explanatory view of general pipe expansion forming, FIG. 2 is an explanatory view of an expanding pipe punch, FIG. 3 is an explanatory view of a high expanding pipe, and FIG. 4 is an explanation of processing a concentric high expanding pipe in three steps. FIG.
[0014]
The high expansion pipe according to the present invention is formed by using a pair of clamp dies 1a and 1b and an expansion punch 2 as shown in FIG. After being clamped by being clamped by the split grooves C, C, the expanding pipe punch 2 having a tapered tip is pressed in from the hole on the tip side of the pipe P while being pressurized. Pa (FIG. 3) is formed.
[0015]
For this reason, the concave grooves C, C on the front side of the clamp dies 1a, 1b are formed as outer peripheral restraining portions Ck, Ck that expand in a tapered shape toward the outside.
[0016]
As shown in FIG. 2, the tube expanding punch 2 has a press-fit portion 2 t having a tapered tip end, and the press-fit portion 2 t and the taper angle of the outer peripheral restraint portion Ck are substantially the same.
The taper angle θ of the expansion pipe punch 2 and the taper angle of the outer peripheral restraining portion Ck of the clamp dies 1a and 1b are set to about 7 degrees, which are shallower than those of conventional general expansion punches and clamp dies. The diameter of the distal end of the expanding pipe 2 is substantially the same as the inner diameter of the pipe P, the maximum diameter D of the expanding pipe 2 is the inner diameter of the expanding pipe, and the diameter E on the base end side is larger than the maximum diameter D. The diameter is reduced to prevent an increase in resistance at the time of press fitting, and the length F of the maximum diameter D portion is set to 2 to 5 mm.
[0017]
Here, the tapered angle θ of the expanding pipe 2 and the taper angle of the outer peripheral restraining portion Ck of the clamp dies 1a and 1b are about 7 degrees, and the expanding punch 2 is press-fitted from the tip hole of the pipe P to form the expanded diameter Pa. In the meantime, the present inventor has repeatedly conducted experiments to apply a compressive force in the axial direction (press-fitting direction) to the enlarged-diameter portion Pa so as not to cause end breaks or the like due to a change in plate thickness. If the angle is made larger than this angle, the radial force on the expanded portion Pa becomes excessively large at the time of press-fitting of the tube expanding punch 2, and the fracture starts before the diameter is expanded to about twice, and even if the angle is smaller than this angle, the expanded diameter is increased. The compressive force cannot be effectively applied to the portion Pa, and the molding efficiency is deteriorated.
[0018]
In the embodiment, since the diameter of the expanded portion Pa is increased to about twice the diameter of the raw pipe, the concentric high expansion is divided into three stages as shown in FIG. Although shown in the figure, the processing is performed in four steps.
[0019]
That is, as shown in FIGS. 4 (A) to 4 (C), the maximum diameter DA of the first-stage tube expanding punch 2A (FIG. 4 (A)) is 1.4 times the tube diameter d, The maximum diameter DB of the eye-expanding punch 2B (FIG. 4 (B)) is 1.2 times that of DA, and the maximum diameter DC of the third-stage expanding pipe 2C (FIG. 4 (C)) is 1 of DB. .2 times.
[0020]
The taper angle θ of each of the expanding pipes 2A, 2B, and 2C is the same, that is, about 7 degrees, and the expansion is maximized by sequentially press-fitting the expanding pipes 2A, 2B, and 2C having different maximum diameters. It is possible to change the portion in the axial direction, and it is possible to prevent a problem that the maximum portion of elongation is concentrated at a specific portion and the thickness of the portion is greatly reduced.
[0021]
Here, FIG. 5 shows that a concentric high-expansion tube having a diameter-expanded portion Pa about twice as large is formed from a pipe P having a diameter of 25.4 mm and a plate thickness of 1 mm by the above-described forming method. It is a figure showing the result of having measured plate thickness. As a result, the thickness change of the enlarged diameter portion Pa in the circumferential direction and the axial direction is such that the maximum change portion is a thickness of 0.766 mm around the end portion, and the thickness of all portions is 76 mm of the shell thickness. % Was confirmed.
[0022]
By the way, in the case of the eccentric high-expansion pipe, if it is attempted to form the diameter-expanded portion Pa approximately twice, as shown in FIG. It can be seen that the elongation in the direction in which the amount of eccentricity ε is maximum becomes maximum.
Therefore, in the present invention, when forming the seam welded pipe, the seam welded portion s is formed in such a manner as to be aligned with the direction in which the amount of eccentricity ε is maximum (the direction in which elongation is maximum).
[0023]
By the way, in the present embodiment, in forming the eccentric high expansion pipe, expansion pipe punches 2A, 2B, 2C, and 2D (not shown) having different maximum diameters are divided into four stages and sequentially press-fitted.
[0024]
That is, the maximum diameter DA of the first-stage expansion pipe 2A is 1.4 times the raw tube diameter d, and the maximum diameter DB of the second-stage expansion punch 2B is 1.11 times DA. The second stage is concentrically expanded at a taper angle of 7 degrees, the third stage is the maximum diameter DC of the expansion punch 2C, 1.16 times DB, and the fourth stage is the maximum diameter DD of the expansion punch 2D. , And DC, and the eccentric amount of each of the third and fourth stages is 5.5 mm.
[0025]
Here, FIG. 7 shows an eccentric high-expansion pipe having an eccentric amount of 5.5 mm and an expanded portion Pa of about twice as large from a pipe P having a diameter of 25.4 mm and a plate thickness of 1.2 mm by the above-described forming method. FIG. 4 is a view showing the result of measuring the plate thickness. As a result, the minimum value of the plate thickness in the circumferential direction and the axial direction was 0.894 mm, which was a maximum change of 74% with respect to the original plate thickness.
[0026]
FIG. 8 shows that the above-mentioned forming method is used to form an eccentric high-expansion pipe having an eccentric amount of 6 mm and an expanded portion Pa of about twice from a pipe P having a diameter of 28.6 mm and a thickness of 1.2 mm. It is a figure as a result of measurement. As a result, the minimum value of the plate thickness in the circumferential direction and the axial direction was 0.948 mm, which was a maximum change of 79% with respect to the original plate thickness.
[0027]
An eccentric high expansion pipe having an eccentric amount of 2 to 7 mm and an enlarged diameter part Pa of about twice was tested by the above-described method of forming an eccentric high expansion pipe. In any case, the plate thickness was 72% or more. Was secured.
[0028]
Note that a flange f as shown in FIG. 9 may be machined at the end of the enlarged diameter portion Pa of the above concentric and eccentric high-expansion pipe. In this case, the mounting strength and the like can be further increased.
[0029]
By the way, such a concentric and eccentric high-expansion pipe, for example, as shown in FIG. Is produced, which is advantageous in strength. Further, as shown in FIG. 10B, when utilized as a structural member of a beam, the cross-sectional area becomes approximately four times as large as that of the raw pipe, which is advantageous in strength.
[0030]
Further, if the high expansion pipe according to the present invention is applied to, for example, a door beam of a vehicle, a steering hanger beam, or the like, a bracket or the like of each tightening portion can be eliminated. It is also possible to increase the tightening pitch at the time of the tightening. Further, if the present invention is applied to a fuel supply pipe or the like, the entire structure can be integrated, so that the weight can be reduced.
[0031]
Note that the present invention is not limited to the above embodiments. Those having substantially the same configuration as those described in the claims of the present invention and exhibiting the same functions and effects belong to the technical scope of the present invention.
[0032]
【The invention's effect】
As described above, according to the present invention, when forming a concentric or eccentric enlarged diameter portion by press-fitting a pipe expansion punch from a pipe hole, the outer surface of the pipe material of the press-fit portion is pressed against the inner surface of the clamp mold. While applying the compressive force in the axial direction by applying, the enlarged diameter portion is formed with different maximum diameters and the same taper angle so that the thickness of the enlarged diameter portion is maintained at 70% or more of the tube thickness. Since a plurality of tube expansion punches are divided into a plurality of stages and press-fitted in order from a smaller diameter, and the expanded portion is formed into a diameter approximately twice as large as the raw tube diameter, thereby obtaining a high expanded tube. In this way, it is possible to prevent a problem such as breakage from occurring, and it is possible to obtain a highly expanded tube which is advantageous in strength.
Further, if the adjustment of the compressive force in the axial direction to the pipe material at the press-fitting portion is performed by adjusting the taper angle of the expanding pipe punch, the molding can be easily performed simply by press-fitting the expanding punch.
[0033]
Also as in claim 3, the pipe is seam welded pipe, and when the enlarged diameter portion is eccentric, by the eccentric amount is molded by phase matching the seam welded portion in a direction having the maximum claim 4 If such an eccentric high expansion tube is obtained, molding can be performed while preventing breakage and the like efficiently.
Further, if flange processing is performed on the end of the enlarged diameter portion as in claim 5 , it is convenient that the rigidity is increased, for example, by using it as a mounting portion.
[Brief description of the drawings]
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view of a general pipe expansion molding. FIG. 2 is an explanatory view of an expansion pipe punch. FIG. 3 is an explanatory view of processing a concentric high expansion pipe in three stages. FIG. 4 is an explanatory view of a high expansion pipe. , (A) is a concentric high expansion pipe, (B) is an eccentric high expansion pipe. [FIG. 5] A diagram of the result of thickness measurement of the concentric high expansion pipe. [FIG. 6] A seam welded part when forming a seam weld pipe into an eccentric high expansion pipe. Explanatory drawing [Fig. 7] Result of thickness measurement of eccentric high expansion tube [Fig. 8] Result of thickness measurement of eccentric high expansion tube according to another example [Fig. 9] State in which a flange portion is formed at the enlarged end [Fig. 10] Explanatory diagram showing an example of the form of use of high-expansion pipes.
2, 2A, 2B, 2C: Expanding punch, P: Pipe, Pa: Expanding portion, θ: Taper angle, ε: Eccentricity, s: Seam welded portion.

Claims (5)

A high-expansion molding method for press-fitting a pipe-expanding punch from a pipe hole to form a concentric or eccentric enlarged-diameter portion. This is performed while applying a compressive force in the axial direction, and in order to maintain the thickness of the expanded portion at 70% or more of the plate thickness of the base tube, the expanded portion is formed with different maximum diameters and the same taper angle. A method for forming a high-expansion pipe, wherein a plurality of expansion pipe punches are divided into a plurality of stages and press-fitted in ascending order. 2. The method for forming a high-expansion pipe according to claim 1, wherein the adjustment of the axial compressive force of the press-fit portion to the pipe material is performed by adjusting the taper angle of the expansion pipe punch. . The method for forming a high-expansion pipe according to any one of claims 1 and 2, wherein the pipe is a seam welded pipe, and the enlarged diameter portion is eccentric, so that the eccentric amount is maximized. A method for forming a high-expansion pipe, comprising forming a seam-welded portion in phase. Tube expanding punch from the pipe hole is pressed by a high pipe expansion polarized heart with twice the diameter of the base pipe diameter, thickness of the enlarged diameter portion is located at least 70% of the thickness of the mother tube The pipe is a seam welded pipe, and the seam weld is phase-aligned in a direction in which the amount of eccentricity is maximized. The high-expansion pipe according to claim 4, wherein an end of the enlarged-diameter portion is flanged.

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