JP6200255B2 - Metal double pipe manufacturing method - Google Patents

Description

  The present invention relates to a method of manufacturing a metal double pipe used for, for example, an oil supply pipe for injecting fuel such as gasoline into a fuel tank of an automobile.

  As a conventional method for manufacturing an oil supply pipe, for example, in Patent Document 1, a large-diameter portion is provided on one end side of a pipe, the small-diameter portion of the pipe is inserted into a cylindrical small-diameter side folding mold, and an arc-shaped groove is formed. The tip of the large-diameter portion is brought into contact with the groove of the large-diameter-side folded mold, an axial load is applied to the end of the large-diameter portion, and the folded-back portion is folded outside the cylindrical small-diameter-side folded mold. Next, it has been proposed to form a double pipe portion by expanding the small diameter portion and bringing the folded portion and the outer periphery of the small diameter portion into close contact with each other. The oil supply pipe is composed of an inlet pipe, a breather tube, and a retainer. The inlet pipe and the breather tube, and the inlet pipe and the retainer are joined by welding, brazing, or the like.

Usually, the tip of the expanded portion of the inlet pipe is flared, and the barrel is threaded to attach a cap for the oil filler port. In addition, the pipe expansion part is doubled in thickness to increase the strength in order to prevent deformation due to the tip of the fuel gun directly contacting the inside of the pipe expansion. The conventional double structure of the inlet pipe expanded portion is, as shown in the above-mentioned patent document 1, after expanding the tube to the intended outer diameter, the expanded expanded portion is folded outward from the end portion and doubled. To do.
In addition to this, after expanding the tube to the target outer diameter, the expanded tube portion is folded inward from the end portion to be doubled.

As another example of a conventional method of manufacturing an oil supply pipe, Patent Document 2 discloses that a reinforcement pipe is fitted to an end of an exhaust pipe, and then the end of the reinforcement pipe opposite to the tip of the exhaust pipe is provided. Keep the original pipe diameter, and then gradually expand both pipes gradually toward the tip of the exhaust pipe to form a double-contact tube, and fix the tip to the joint flange by welding and fixing it inside. It has been proposed. A double pipe structure is formed by covering the outer side of the oil pipe main body corresponding to the pipe expansion portion with a base pipe different from the main oil pipe main body to make a double pipe, and expanding both pipes simultaneously.
Since this method has a double structure using an element pipe different from the main body of the oil supply pipe, it does not require the folding process shown in Patent Document 1 and is less prone to problems in threading and flaring.

Japanese Patent No. 3927790 Japanese Patent No. 2828898

  However, in the method shown in Patent Document 1, in addition to tube expansion processing, folding processing, threading processing, and further, end flare processing and a plurality of processings are performed, so in particular, in threading processing or flare processing that is a subsequent process. In some cases, the material cracked. As the material for the oil supply pipe, domestic steel is ordinary steel, but stainless steel is required in areas with severe corrosive environments such as North America. In order to avoid this problem, there is a problem that the number of processing steps is increased or the annealing process is performed during the processing to soften the material, resulting in an increase in the number of processes.

Further, in the method shown in Patent Document 2, a step corresponding to the plate thickness is formed on the outside of the pipe expansion part, and therefore, when attaching another part (not shown) to the pipe expansion part, there is a restriction to avoid the position, and this When it was necessary to attach to the position, there was a need for a shim plate or the like to fill the gap. In addition, if there is a step on the outside, moisture or dust may enter from the gap of the step and cause corrosion.
The present invention has been devised to solve such problems, and as a bimetallic heavy pipe used for an oil supply pipe or the like, there is no need for folding processing, and any outside of the expanded portion is not required. It aims at providing the method of manufacturing a metal double pipe without a level | step difference simply.

In order to achieve the object, the manufacturing method of the metal double pipe of the present invention has an outer tube which is substantially matched to the inner diameter of the expanded portion, in the expanded portion where the end of the raw tube is expanded to less than the target expanded outer diameter. A method of manufacturing a metal double pipe, in which another pipe having a diameter is inserted as an auxiliary pipe to form a double pipe, and then the double pipe is expanded to the desired outer diameter. The tube is expanded to an inner diameter that substantially matches the outer diameter of the raw tube, and then a cut product of the raw tube is inserted into the expanded portion as an auxiliary tube.

According to the method of the present invention, since the folding process is not required, problems in the thread cutting process and the flare process are less likely to occur.
Moreover, since there is no level | step difference outside a pipe expansion part, when attaching another component to the said pipe expansion part, there is no restriction | limiting in the attachment position. Further, since there is no step on the outside, there is no gap, and the blocking effect against intrusion of moisture, dust and the like is enhanced. Therefore, the oil supply pipe using the double pipe manufactured by the present invention is less likely to be corroded, and its usefulness is enhanced.

Sectional view during the first tube expansion process in the conventional manufacturing method Sectional drawing after the 1st pipe expansion process in embodiment of this invention Sectional drawing after insertion of the insertion tube in embodiment of this invention (the 1) Sectional drawing after insertion of the insertion tube in embodiment of this invention (the 2) Sectional drawing after the 2nd pipe expansion process in embodiment of this invention

1: Main pipe 2: Auxiliary pipe 3: Mold for first expansion 4: Restraining mold for first expansion 5: Mold for second expansion 6: Restraining mold for second expansion

As described above, the expanded portion is provided at the end portion of the oil supply pipe, and the expanded portion has a doubled base plate to increase the strength in order to prevent deformation. That is, the vicinity of the expanded portion at the tube end is a double tube.
Various methods have been proposed for making the vicinity of the tube end expanded portion a double tube structure, but as described above, each has its own problems.
The present inventors diligently studied a method for producing a metal double tube by a simple method, and reached the present invention.

Hereinafter, the present invention will be described with reference to the drawings.
As a simple method of forming a double pipe structure tube expansion portion at the tube end, as shown in FIG. 1, the first tube expansion die 3 is formed at the tube end with the auxiliary tube 2 inserted inside the main body tube 1. It is assumed that the pipe is expanded by pushing.
However, when processing is performed by this method, the main body pipe 1 is deformed by the expansion, but the auxiliary pipe 2 cannot withstand the axial force of the expansion mold and moves in the same direction as the pushing direction of the expansion mold. For this reason, there is a problem that the auxiliary pipe 2 is not accompanied by pipe expansion deformation, or a predetermined pipe expansion length cannot be obtained even if the pipe is expanded, and the target metal double pipe cannot be manufactured.

Therefore, in the present invention, the first pipe expansion process is performed to form an inner diameter that roughly matches the outer diameter of the auxiliary pipe so that the auxiliary pipe is expanded at the same time as the main pipe without moving. We decided to play the role of a stopper that hinders the movement of the tube.
That is, as shown in FIG. 2, first, the first tube expansion die 3 having a truncated conical surface at the tip is pushed into the tube end of the body tube 1 so that one end of the body tube is less than the target expanded tube outer diameter. Pipe expansion is performed to form a pre-expansion section. In FIG. 2, reference numeral 4 denotes a first expanding tube constraining die.

Thereafter, as shown in FIG. 3, another elementary pipe having an outer diameter substantially coinciding with the inner diameter of the preliminary expanded portion is inserted as the auxiliary pipe 2 to form a double pipe.
At this time, the other pipe inserted as the auxiliary pipe 2 may be a cut product of the pipe constituting the main pipe 1, or a material different from or different from the pipe before forming the preliminary expanded portion. It may be a plate having a thickness.
When the pipe inserted as the auxiliary pipe 2 is a cut product of the raw pipe constituting the main body pipe 1, as shown in FIG. 4, the inner diameter of the pre-expanded section formed by the first pipe expansion process is the same as that before the pipe expansion. It is approximately the same as the outer diameter of the raw tube.
Of course, in the first tube expansion process when the tube inserted as the auxiliary tube 2 is a material tube different from the material tube before forming the preliminary expanded portion or a plate thickness of a different plate thickness, the inner diameter of the preliminary expanded portion is naturally This is performed so as to substantially match the outer diameter of the auxiliary pipe.

Next, as shown in FIG. 5, the second tube expansion die 5 having a truncated conical surface at the tip is formed on the preliminary tube expanded portion in a double tube state so as to have a desired tube expansion diameter. Push in and perform the second tube expansion process. In addition, in FIG. 5, 6 is a restraint metal mold | die of a 2nd pipe expansion.
In the second pipe expanding step, the inclined surface formed by the conical surface formed in the first pipe expanding step serves as a stopper that prevents the movement of the auxiliary pipe.
Therefore, in order to ensure that the stopper function is manifested, it is better that the inclination angle θ of the inclined surface is larger. However, if the inclination angle θ is extremely large, it is difficult to expand the tube. The inclination angle that can be taken is determined.
In the above description, the second tube expansion process is described as being performed in one stage, but may be performed in a plurality of stages depending on the degree of processing.

Embodiments of the present invention will be described below with reference to FIGS.
Ferritic stainless steel having an outer diameter of φ25.4 mm and a plate thickness of 0.5 mm was used for both the main pipe 1 and the auxiliary pipe inserted into the main pipe. The length of the main pipe was 200 mm, and the length of the auxiliary pipe was 100 mm. As shown in FIG. 2, the first tube expansion process was first performed by pressing from the tube end of the main body tube to a length of 100 mm with a mold having an outer diameter of φ26 mm and an inclination angle θ of 30 degrees.
Next, as shown in FIG. 4, an auxiliary tube was inserted into the expanded portion of the main body tube.
Further, as shown in FIG. 5, a second pipe expansion process is performed by pressing with a die having a length of about 80 mm from the tube end of the main body tube, an outer diameter of φ50 mm, and an inclination angle θ of 30 degrees, and the target metal A double tube was manufactured.

Claims (1)

Inserting another element pipe having an outer diameter that roughly matches the inner diameter of the expanded pipe section as an auxiliary pipe into the expanded pipe processing section expanded to less than the outer diameter of the expanded pipe intended for one end of the raw pipe to form a double pipe, Subsequently, a method of manufacturing a metal double pipe that expands the double pipe to an intended outer diameter ,
After expanding one end of the raw tube to an inner diameter that roughly matches the outer diameter of the raw tube, insert a cut product of the raw tube as an auxiliary tube into the expanded portion
A method of manufacturing a metal double pipe.

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