EP1063027A1

EP1063027A1 - Method of producing pipes of radial cross-section

Info

Publication number: EP1063027A1
Application number: EP99959950A
Authority: EP
Inventors: Toru Yawatayama Kojo Sango Co. Ltd. KURIMOTO
Original assignee: Sango Co Ltd
Current assignee: Sango Co Ltd
Priority date: 1998-12-22
Filing date: 1999-12-21
Publication date: 2000-12-27
Also published as: JP3066366B2; WO2000037192A1; JP2000190029A

Abstract

In a method of manufacturing a radial cross section pipe, in order to easily form a fold portion along a desired range in a direction of a pipe axis so that a level difference between a crest portion and a root portion is great, the same number of first pressing sheets (8) and second pressing sheets (9) are alternately arranged by positioning a pipe material (1) along a fold portion forming area in an axial direction at an outer periphery of the pipe material (1). A radial fold portion (12) is formed by deeply pressing the first pressing sheets (8) in a centripetal direction and shallowly pressing the second pressing sheets (9) in the centripetal direction.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a method of manufacturing a radial cross section pipe.

DESCRIPTION OF THE PRIOR ART

In general, in a radial cross section pipe in which a pipe wall is formed in a fold-shape in a peripheral direction, there is a case that it is desired to increase a protruding length of the fold portion. For example, in general, the radial fold portion is extended in a longitudinal direction of the pipe on a surface of a heat-transfer pipe of a heat exchanger, whereby a heat exchange is performed. In order to improve a heat exchanging efficiency, it is required to increase a crest height of the fold portion and a root depth of the fold portion.
As a method of manufacturing the radial cross section pipe having the fold portion as mentioned above, as shown in Fig. 17, there is disclosed, for example, in the Japanese Patent Unexamined Publication No. 7-24522, a conventional method of manufacturing a heat-transfer pipe 103 in which crest portions 101 and root portions 102 having curved cross sectional shapes in a direction of a pipe periphery are alternately formed and fine grooves 102a are formed on outer surfaces of the root portions 102, in accordance with a drawing process by means of a separation die.
Further, as shown in Fig. 18, there is disclosed, for example, in Japanese Utility Model Unexamined Publication No. 2-140176 a method of forming a heat radiation portion by winding a corrugated sheet 104 on which crest portions and root portions are previously formed, on an outer periphery of a pipe 105 and thereafter welding and fixing the corrugated sheet thereto.
In the conventional manufacturing method shown in Fig. 17, a plurality of dies arranged in the direction of the pipe periphery, a belt feeder for driving the pipe in an axial direction of a pipe and the like are required, and the facilities become large-scaled and complicated, and further, there is a problem that the method can not be applied to a short heat-transfer pipe and a structure having a changing axial cross sectional shape of a fold portion.
Further, in the manufacturing method shown in Fig. 18, since the corrugated sheet 104 is wound around the pipe 105, only a comparatively thin corrugated sheet can be applied, and an operation of welding the corrugated sheet 104 to the pipe 105 is required in addition to the process of forming the corrugated shape of the corrugated sheet 104, so that there is a problem that the method is not suitable for a mass-production.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method of manufacturing a radial cross section pipe which can manufacture a fold portion having an optional cross sectional shape by simple facilities at a low cost.
In order to achieve the object mentioned above, in accordance with the present invention, there is provided a method of manufacturing a radial cross section pipe comprising the steps of:
positioning a pipe material on an outer periphery of the pipe material along a fold portion forming area in an axial direction;
alternately arranging the same number of first and second pressing sheets; and
deeply pressing the first pressing sheets in a centripetal direction and shallowly pressing the second pressing sheets in the centripetal direction, thereby forming a radial fold portion.
Further, in accordance with the present invention, it is possible to arrange the first pressing sheets and the second pressing sheets at a uniform interval in a peripheral direction, form a pressing surface of the second pressing sheet longer in the peripheral direction than a pressing surface of the first pressing sheet, and simultaneously press both of the pressing sheets.
Further, in accordance with the present invention, it is possible to insert an inner insertion die having a horizontal cross sectional surface substantially coinciding with a final cross sectional shape of a horizontal cross sectional shape of the fold portion into the pipe material over the fold portion forming area of the pipe material, and press the first and second pressing sheets.

BRIEF DESCRIPTION OF THE DRAWINGS

Figs. 1A to 1C are views which show a first embodiment in accordance with the present invention, in which Fig. 1A is a vertical cross sectional view of a pipe material, Fig. 1B is a vertical cross sectional view which shows a manufacturing state and Fig. 1C is a cross sectional view taken along a line IC-IC in Fig. 1B;
Fig. 2 is a front elevational view of a radial cross section pipe manufactured in accordance with Figs. 1A to 1C;
Fig. 3 is a plan view of Fig. 2;
Fig. 4 is a bottom view of Fig. 2;
Fig. 5 is a left side view of Fig. 2;
Fig. 6 is a vertical cross sectional view of Fig. 2;
Fig. 7 is a cross sectional view taken along a line VII-VII in Fig. 6;
Figs. 8A and 8B are views which show a second embodiment in accordance with the present invention, in which Fig. 8A is a vertical cross sectional view, and Fig. 8B is a cross sectional view taken along a line VIIIB-VIIIB in Fig. 8A;
Fig. 9 is a front elevational view of a radial cross section pipe manufactured in accordance with Figs. 8A and 8B;
Fig. 10 is a plan view of Fig. 9;
Fig. 11 is a bottom view of Fig. 9;
Fig. 12 is a left side view of Fig. 9;
Fig. 13 is a right side view of Fig. 9;
Fig. 14 is a vertical cross sectional view of Fig. 9;
Fig. 15 is a cross sectional view taken along a line XV-XV in Fig. 14;
Fig. 16 is a cross sectional view taken along a line XVI-XVI in Fig. 14;
Fig. 17 is a horizontal cross sectional view which shows a heat-transfer pipe manufactured in accordance with a conventional drawing process; and
Fig. 18 is a perspective view of a heat-transfer pipe formed with a conventional corrugated sheet.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A description will be given of an embodiment in accordance with the present invention with reference to Figs. 1A to 16.
Figs. 1A to 7 show a first embodiment of a method of manufacturing a radial cross section pipe in accordance with the present invention.
Fig. 1A is a vertical cross sectional view of a pipe material, Fig. 1B is a view which shows a state of press-forming a fold portion from the pipe material and Fig. 1C is a cross sectional view taken along a line IC-IC in Fig. 1B.
A pipe material 1 shown in Fig. 1A is formed by contracting both end portions of a straight pipe 2 (a pipe shown by a chain line) having a diameter D1 and a peripheral length of a pipe material portion 3 thereof is set to a length substantially corresponding to a peripheral length of a heat radiating portion constituted by a fold portion 12 mentioned below. Then, the contracted portions provided in both end portions of the central pipe material portion 3 are structured such that first diameter-reduced portions 4 and 4a, first taper portions 5 and 5a expanded from the first contracted portions 4 and 4a, second contracted portions 6 and 6a following to the first taper portions 5 and 5a, and second taper portions 7 and 7a expanded from the second contracted portions 6 and 6a are continuously formed from an outer end side of the pipe toward a center side of the pipe in this order.
A diameter of the first contracted portions 4 and 4a is set to a diameter capable of being connected to a pipe connected to the first contracted portions, for example, an upstream side pipe and a downstream side pipe, and an outer diameter of the second contracted portions 6 and 6a is set to substantially the same diameter as an outer diameter of the fold portion 12 formed in accordance with a method mentioned below.
Then, the central pipe material portion 3 constitutes a forming area of the fold portion 12.
A working machine for forming the fold portion 12 in the pipe material 1 is arranged with a plurality of first pressing sheets 8 radially around a center of the pipe material 1 arranged as shown in Figs. 1B and 1C in a peripheral direction at a uniform interval, and further is arranged with a plurality of second pressing sheets 9 radially around the center of the pipe material 1 in the peripheral direction at a uniform interval so as to be positioned between the first pressing sheets 8 and 8, that is, the working machine is arranged alternately with the first pressing sheets 8 and the second pressing sheets 9 in the peripheral direction.
Further, the first pressing sheet 8 is a thin sheet and is formed so as to be long along an axis of the pipe material 1, and an axial length thereof is formed so as to have substantially the same length as a length of the fold portion forming area of the pipe material 1, that is, a length between the second contracted portions 6 and 6a in the pipe material 1. Further, a pressing surface 8a at a front end of the first pressing sheet 8 is structured such that a center portion 8b in an axial direction of the pipe material 1 is formed in a surface parallel to the axis of the pipe material 1, and both sides of the center portion 8b are formed in taper surfaces 8c and 8c open in a direction of a pipe end. Further, the pressing surface 8a at the front end is formed as thin as possible, that is, so thin that no buckling is generated when the pipe material is deformed, and the pressing surface 8a is formed in a curved surface having a center inside the pressing sheet 8.
The second pressing sheet 9 is formed so as to be thicker than the first pressing sheet 8 and be long along the axis of the pipe material 1, and an axial length thereof is formed so as to have substantially the same length as a length of the fold portion forming area of the pipe material 1, that is, a length between the second contracted portions 6 and 6a in the pipe material 1. Further, a pressing surface 9a at a front end of the second pressing sheet 9 is formed in a surface parallel to the axis of the pipe material 1, and is formed in a surface along an outer surface of a crest portion in a fold portion 12 to be formed, that is, a circular arc surface having a center outside the pressing sheet 9 in the illustrated embodiment, with respect to the peripheral direction of the pipe material 1, whereby the pressing surface 9a is formed so as to be longer in the peripheral direction than the pressing surface 8a of the first pressing plate 8.
A movement driving apparatus (not shown) such as a well-known cylinder or the like is provided in the first pressing sheet 8 and the second pressing sheet 9, respectively, whereby the structure is made such as to respectively move forward and backward both of the pressing plates 8 and 9 in a centripetal direction and an opposite direction thereto.
Next, a description will be given of a method of manufacturing a radial cross section pipe.
At first, in a state that each of the pressing sheets 8 and 9 is retracted outward from the outer diameter of the pipe material 1, the pipe material 1 in which both end portions are previously contracted as maintained above is set in an opposing center portion of each of the pressing sheets 8 and 9 and is held by suitable means.
Next, each of the first pressing sheets 8 is deeply pressed in a centripetal direction to a substantially center point of the pipe material 1, and the same time, each of the second pressing sheets 9 is shallowly pressed in the centripetal direction. Due to the pressing operation of the first pressing sheets 8, a portion of the pipe material portion 3 in the pipe material 1 at which the first pressing sheet 8 is positioned is deeply pressed and bent in the centripetal direction as shown in Fig. 1C, and a root portion 10 is formed in the pressing front end portion. Further, due to the pressing operation of the second pressing sheets 9, the pipe material portion 3 between the first pressing sheets 8 and 8 is pressed as shown in Fig. 1C so as to be formed in a circular arc crest portion 11, and a horizontal cross sectional shape of the pipe material portion 3 is formed in a petal shape similar to a triangle. In the case of alternately arranging three first pressing sheets 8 and three second pressing sheets 9 as shown in Fig. 1C, a flow passage 14 constituted by three petal-shaped fold portions 12 is formed.
As mentioned above, the reason for providing the second pressing sheets 9 is as follows: a cross section of the flow passage becomes narrow due to a deformation resistance of the pipe material portion 3 and an enough cross sectional area of the flow passage can not be secured when pressing only the first pressing sheets 8 in the centripetal direction. However, when the second pressing sheets 9 are pressed at the same time of pressing the first pressing sheets 8 the material flow of the pipe material which is supposed to flow much in the centripetal direction with the first pressing plate 8 is assisted by shallowly pressing the outer surface with the second pressing sheets 9, so that a total material flow can be smoothly and naturally performed and it is possible to accurately obtain the fold portion 12 having a desired shape without accompanying a buckling and a deformation.
Then, due to the pressing operation mentioned above, as shown in Fig. 1C, it is possible to press the pipe material of the root portion 10 at the maximum near the axial core, so that it is possible to form the root at the lowermost. Accordingly, the petal-shaped fold portion 12 having a great level difference in the diametrical direction is formed, whereby a surface area of the pipe can be increased.
In this case, the first contracted portions 4 and 4a, the first taper portions 5 and 5a, the second contracted portions 6 and 6a, and the second taper portions 7 and 7a are contracted by a spinning process, a die inserting process or the like. The contracting process of the pipe end portion may be performed before processing the fold portion 12 as shown in the drawing or may be performed after processing the fold portion 12.
A radial cross section pipe 13 manufactured in accordance with the method mentioned above is shown in Figs. 2 to 7. When using the radial cross section pipe 13 as a heat-transfer pipe, connecting, for example, an upstream side exhaust pipe of an internal combustion engine to one first contracted portion 4 and connecting a downstream side exhaust pipe to another first contracted portion 4a so as to flow the exhaust gas from one first contracted portion 4, the exhaust gas flows through each of the petal-shaped flow passages 14 and flows out from another first contracted portion 4a. At this time, the exhaust gas is smoothly separated into each of the flow passages 14 due to a taper portion 15 formed by the taper surface 8c of the first pressing sheet 8. Further, at this flowing time, a heat exchange is performed by the fold portion 12 having a great area at a high efficiency.
In this case, it is possible to form fine grooves on a die surface of the first pressing sheet 8 and the second pressing sheet 9 so as to form fine grooves shown in Fig. 17 on a surface of the formed fold portion. In accordance with the structure mentioned above, a heat radiating efficiency is further improved in the case of using as a heat radiating pipe.
Figs. 8A and 8B show a second embodiment of a method of manufacturing a radial cross section pipe in accordance with the present invention.
In the second embodiment, the radial cross section pipe is manufactured by inserting an interior insertion die 20 having a horizontal cross section coinciding a final cross sectional shape of a horizontal cross section of the fold portion along the fold forming area of the pipe material 1.
The interior insertion die 20 is constituted by a convex portion 21 forming the crest portion 11 of the fold portion 12 and a concave portion 22 forming the root portion 10, and the convex portion 21 and the concave portion 22 are formed along a total length in an axial direction so that the internal insertion die 20 can be drawn after manufacturing the fold portion. In this case, driving means (not shown) such as a cylinder or the like for inserting, drawing and moving the internal insertion die 20 is provided in the internal insertion die 20. Further, in the present second embodiment, the pipe material 1 is not constituted by the first contracted portions 4 arid 4a, the first taper portions 5 and 5a, the second contracted portions 6 and 6a, and the second taper portions 7 and 7a which are provided in the first embodiment. Since the other structures are the same as those of the first embodiment mentioned above, the same reference numerals are attached to the same elements and a description thereof will be omitted.
In the present embodiment, the pipe material 1 is set to the opposing center portion of each of the pressing sheets 8 and 9 in the same manner as that of the structure mentioned above, the internal insertion die 20 is inserted at a predetermined position within the pipe material 1, and next the respective pressing sheets 8 and 9 are simultaneously pressed in the same manner as that of the first embodiment mentioned above. Accordingly, the petal-shaped fold portion 12 is formed in the same manner as that of the first embodiment, however, it is possible to accurately form the fold portion 12 by providing the internal insertion die 20 as in the present second embodiment.
Then, after formation, both of the pressing sheets 8 and 9 are retracted outward, the internal insertion die 20 is drawn out and the formed radial cross section pipe is taken out.
Further, a contraction process is suitably applied to the end portion of the pipe material 1 if necessary. The contraction process is performed by a well-known technique, for example, by inserting the pipe end portion into the die or by a spinning process after forming the fold portion 12 mentioned above and taking out the respective pressing sheets 8 and 9 and the internal insertion die 20.
Figs. 9 to 16 show a third embodiment of a radial cross section pipe in accordance with the present invention.
In the present embodiment, the heat-transfer pipe is provided in an upstream side of a pipe receiving a catalyst carrier in a downstream side. The fold portion 12 is formed in an upstream pipe 30 in the same manner as that of the embodiment mentioned above, and a catalyst carrier 32 is received within a downstream pipe 31 formed downstream the upstream pipe 30 in series.
A method of manufacturing the pipe is constituted by the steps of, for example, contracting the upstream pipe 30 from one pipe material or expanding the downstream pipe 31 therefrom so as to form the upstream pipe 30 and the downstream pipe 31 having different diameters, thereafter forming the fold portion 12 in the upstream pipe 30 in accordance with the process mentioned above, and inserting the catalyst carrier 32 or the like into the downstream pipe 31. Further, the pipe contraction or the pipe expansion mentioned above is performed by a spinning process, a die inserting process or the like. Further, both of the pipe end portions are contracted in accordance with a well-known technology such as the spinning process, the die inserting process or the like and further the processing of the pipe end portions is performed at an appropriate time before or after processing the upstream pipe 30 and the downstream pipe 31.
In this case, the upstream pipe 30 and the downstream pipe 31 may be obtained by separately forming them and welding and connecting them.
In the case of cooling the exhaust gas so as to communicate with the catalyst, the present embodiment is effective to the case of integrally forming the heat-transfer pipe excellent in a heat exchange in an upstream side of the pipe receiving the catalyst carrier.
In this case, it is possible to increase the number of the fold portions 12 by increasing the number of the first pressing sheets 8 and the second pressing sheets 9 in each of the embodiments mentioned above.
Further, the present invention is not limited to the exhaust system of the internal combustion engine, and can be applied to a method of manufacturing all the pipes such as a fluid pipe, a structure pipe or the like as well as the other heat-transfer pipe. In particular, the present invention is preferable in a use for an internal pipe, an external pipe or a heat-transfer pipe of various kinds of heat exchanger.
Since the structure is made as mentioned above, in accordance with the present invention, it is possible to form the fold portion having a radial shape and a great level difference between the crest portion and the root portion only by pressing the first pressing sheets and the second pressing sheets by the well-known pressing means so as to deform and process the pipe material, so that it is possible to make the provision more compact, simpler and lower cost in comparison with the conventional drawing process, and it is possible to desirably form in a required range in accordance with the length of the pressing sheets in both of the long fold portion and the short fold portion in the direction of the pipe axis. Further, it is possible to easily form the fold portion in which the height gradually changes in the direction of the pipe axis. Further, it is also possible to easily form the fold portion having a relatively great thickness. Further, since the welding process in the conventional art is not required, the present invention is suitable for a mass production.
Further, in accordance with the present invention, the first pressing sheets and the second pressing sheets are arranged at a uniform interval in a peripheral direction, a pressing surface of the second pressing sheet is formed so as to be longer in the peripheral direction than a pressing surface of the first pressing sheet, and both of the pressing sheets are simultaneously pressed, whereby the first pressing sheets are deeply pressed, so that a material flow of a whole of the pipe material can be smoothly and naturally performed by shallowly pressing the outer surface with the second pressing sheets so as to prevent the pipe material from much flowing in the centripetal direction. Accordingly, it is possible to accurately obtain the fold portion having a desired shape without accompanying a buckling and a deformation.
Further, in accordance with the present invention, since the fold portion can be formed in such a manner as to be held between the pressing sheets corresponding to the external die and the internal inserting die corresponding to the interior die by inserting an inner insertion die having a horizontal cross sectional surface substantially coinciding with a final cross sectional shape of a horizontal cross sectional shape of the fold portion into the pipe material along the fold portion forming area of the pipe material and pressing the first and second pressing sheets, it is possible to further accurately form the fold portion.

Claims

A method of manufacturing a radial cross section pipe comprising the steps of:

positioning a pipe material on an outer periphery of the pipe material along a fold portion forming area in an axial direction;

alternately arranging the same number of first and second pressing sheets; and

deeply pressing the first pressing sheets in a centripetal direction and shallowly pressing the second pressing sheets in the centripetal direction, thereby forming a radial fold portion.
A method of manufacturing a radial cross section pipe as claimed in claim 1, wherein said first pressing sheets and the second pressing sheets are arranged at a uniform interval in a peripheral direction, a pressing surface of the second pressing sheet is formed longer in the peripheral direction than a pressing surface of the first pressing sheet, and both of said pressing sheets are simultaneously pressed.
A method of manufacturing a radial cross section pipe as claimed in claim 1, wherein an inner insertion die having a horizontal cross sectional surface substantially coinciding with a final cross sectional shape of a horizontal cross sectional shape of the fold portion is inserted into the pipe material along the fold portion forming area of said pipe material, and said first and second pressing sheets are pressed.
A method of manufacturing a radial cross section pipe as claimed in claim 2, wherein an inner insertion die having a horizontal cross sectional surface substantially coinciding with a final cross sectional shape of a horizontal cross sectional shape of the fold portion is inserted into the pipe material along the fold portion forming area of said pipe material, and said first and second pressing sheets are pressed.