The present invention relates to a method of increasing the thickness of a tube which increases the thickness of an end part of a tube and to an increased thickness tube increased in thickness by this.
As prior art for increasing the thickness of an end part of a tube, for example, there is the one disclosed in PLT 1. In the method of PLT 1, as shown in FIG. 1A, a tube 1 is placed in the middle of an upper die 2 and a lower die 3, then an upsetting punch 4 is pushed against this in the arrow direction to increase the thickness of an end part of the tube 1 as shown in FIG. 1B.
With the method of PLT 1, two split dies 2 and 3 are used, so after increasing the thicknesses of the two ends, the tube can be removed from the dies 2 and 3 and upsetting punch 4. However, as shown in
The present invention was made in consideration of the above situation and has as its object to enable an increase of thickness of an end part of a tube without a burr being formed.
To achieve the above object, the gist of the method of increasing the thickness of a tube of the present invention is as follows:
A method of increasing the thickness of a tube which increases a thickness of an end part of a tube having a first end part and a second end part, the method of increasing the thickness of a tube comprising using a mandrel having a small diameter part, a slanted surface part expanded in diameter continuing from the small diameter part, and a large diameter part continuing from the slanted surface part, a die having a small diameter hole part, a slanted hole surface part expanded in hole diameter following the small diameter hole part, and a large diameter hole part following the slanted hole surface part, a first upsetting punch arranged along the small diameter part of the mandrel and the small diameter hole part of the die, and a second upsetting punch arranged along the large diameter part of the mandrel and the large diameter hole part of the die so as to place the tube between the die and the mandrel, process the first end part of the tube by the first upsetting punch, and, further, process the second end part of the tube by the second upsetting punch to increase the thickness; pulling out the mandrel from the tube in the state using the second upsetting punch to constrain the second end part of the tube; and using the first upsetting punch to push up the first end part of the tube to take out the tube from the die.
Further, the increased thickness tube of the present invention is an increased thickness tube produced by the method of increasing the thickness of a tube of the present invention, the increased thickness tube characterized by having an end part increased in thickness to an inner surface side and an end part increased in thickness to an outer surface side.
According to the present invention, it is possible to increase the thickness of an end part of a tube without a burr being formed.
Below, referring to the attached drawings, a preferred embodiment of the present invention will be explained.
The press die is comprised of a mandrel 22, first upsetting punch 23, second upsetting punch 24, and die 25 with center axes 20 arranged coaxially. The mandrel 22, first upsetting punch 23, and second upsetting punch 24 are movable types able to be raised and lowered by a not shown lift mechanism, while the die 25 is a fixed type. For the lift mechanism, hydraulics, a servo motor, etc. may be used.
The tube 21 is a tube which has a first end part 21a and a second end part 21b and is constant in wall thickness from one end to the other end. For the tube 21, ordinary steel, stainless steel, aluminum, titanium, or other plastically formable material may be used.
The mandrel 22 has a small diameter part 22a, a slanted surface part 22b of a substantially frustoconical side shape with an expanding diameter continuing from the small diameter part 22a, and a large diameter part 22c continuing from the slanted surface part 22b. The outside diameter of the large diameter part 22c is substantially equal to the inside diameter of the tube 21. The outside diameter of the small diameter part 22a is smaller than the outside diameter of the large diameter part 22c for increasing the thickness of the first end part 21a of the tube 21.
The die 25 has a small diameter hole part 25a, a slanted hole surface part 25b of a substantially frustoconical side shape with an expanding hole diameter continuing from the small diameter hole part 25a, and a large diameter hole part 25c continuing from the slanted hole surface part 25b. The inside diameter of the small diameter hole part 25a is substantially equal to the outside diameter of the tube 21. The inside diameter of the large diameter hole part 25c is larger than the inside diameter of the small diameter hole part 25a for increasing the thickness of the second end part 21b of the tube 21.
The first upsetting punch 23 is arranged along the small diameter part 22a of the mandrel 22 and the small diameter hole part 25a of the die 25 and is substantially cylindrical in shape. The inside diameter of the first upsetting punch 23 is substantially equal to the outside diameter of the small diameter part 22a of the mandrel 22. The outside diameter of the first upsetting punch 23 is substantially equal to the inside diameter of the small diameter hole part 25a of the die 25.
The second upsetting punch 24 is arranged along the large diameter part 22c of the mandrel 22 and the large diameter hole part 25c of the die 25 and is substantially cylindrical in shape. The inside diameter of the second upsetting punch 24 is substantially equal to the outside diameter of the large diameter part 22c of the mandrel 22. The outside diameter of the second upsetting punch 24 is substantially equal to the inside diameter of the large diameter hole part 25c of the die 25.
Below, the operation of increasing the thickness of the tube 21 by the press die according to the present embodiment will be explained.
As shown in
Next, as shown in
In this case, the first upsetting punch 23 may be used to process the first end part 21a of the tube 21, then the second upsetting punch 24 may be used to process the second end part 21b of the tube 21. Alternatively, the second upsetting punch 24 may be used to process the second end part 21b of the tube 21, then the first upsetting punch 23 may be used to process the end part 21a of the tube 21. Alternatively, the two punches 23 and 24 may be used to simultaneously process the two end parts 21a and 21b of the tube 21.
Next, as shown in
Next, as shown in
As explained above, by increasing the thickness of one end part to the inner surface side and increasing the thickness of the other end part to the outer surface side, even if using a single-piece die, it becomes possible to take out the tube from the press die after increasing the thickness. When using a single-piece die to increase the thickness of the two ends of the tube to just one of the inner surface side or the outer surface side, it is not possible to take out the tube from the press die after increasing the thickness.
Further, since a single-piece die is used, it is possible to increase the thickness of an end part of the tube without a burr being formed.
The increased thickness tube obtained using the present invention is not particularly limited in application. In particular, the invention is effective when applied to a steel tube used at an exhaust part (for example, a center tube of an exhaust system) of an internal combustion engine (engine) mounted in an automobile, motorcycle, etc. A part used for an automobile or motorcycle is required to be lightened in weight from the viewpoint of the fuel economy efficiency, thermal efficiency, etc. The exhaust tube from the exhaust manifold to the muffler in the parts used for an automobile or motorcycle carries high temperature exhaust gas, so a stainless steel tube excellent in heat resistance and corrosion resistance has been used. Usually, these parts are formed by bending, expanding, or otherwise shaping a steel tube constant in wall thickness, then joining it with other parts. However, from the viewpoint of the heat resistance, corrosion resistance, and structure, each part does not necessarily have to be a steel tube with a constant wall thickness.
Above, the present invention was explained together with an embodiment. The above embodiment only shows a specific example of working the present invention. The technical scope of the present invention must not be interpreted in a limited manner due to these. That is, the present invention can be worked in various ways without departing from its technical idea or main features.
In the above embodiment, an example of increasing the thickness of the two ends of a tube was shown. The present invention also includes increasing the thickness of only one end part to the inner surface side or outer surface side. Further, after increasing the thickness, it is also possible to perform heat treatment or other post-treatment as needed.
Number | Date | Country | Kind |
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2015-047475 | Mar 2015 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2016/057192 | 3/8/2016 | WO | 00 |