JP6528570B2 - U-shaped bent pipe manufacturing method and U-shaped bent pipe manufacturing apparatus - Google Patents

Description

  The present invention relates to a hollow tube used for a heat exchanger, an automobile part, etc., particularly a hollow tube (U-curved tube) having a U-shaped bent portion (U-curved portion) The present invention relates to a method for manufacturing a U-shaped bent tube having a curvature inside the U-shaped bent portion at or near zero by applying hydroforming, and a device used for the implementation thereof.

  In heat exchangers, automobile parts, building interior materials / exterior materials, or chemical plants, etc., use a hollow pipe with a U-shaped bent part as a part of a straight pipe (straight pipe) There is. Here, the U-shaped bent portion (U-shaped bent portion) is a protrusion between two or more straight pipe portions in a direction forming a predetermined angle with the axial direction of each straight pipe portion, and It can be rephrased that the projecting portion is a U-shaped portion. As a typical example, as shown in FIG. 18A, between two straight pipe sections 1A, 1B having a common axis O, with respect to the axial direction of those straight pipe sections 1A, 1B. There is a hollow tube (U-curved tube) 5 with a U-curved portion 3 projecting in a direction making a right angle. Here, in the case of the example of FIG. 18A, a first bend 9A that bends substantially straight from one straight pipe portion 1A toward the U-shaped bend 3 and a predetermined curvature in the U-shaped bend 3 At a total of three locations: a second bend (180 ° bend) 9B that bends approximately 180 ° and a third bend 9C that bends substantially perpendicularly from the U-shaped bend 3 to the other straight pipe portion 1B Have a bend in the

  For producing a hollow tube having such a U-shaped bent portion (hereinafter simply referred to as a U-shaped bent tube), in particular a U-shaped bent tube composed of a metal pipe such as a steel pipe, a copper pipe or an aluminum pipe As a conventional method, there is a method in which bending is repeated a plurality of times in a straight pipe by a shear bending press. Also, as a similar method, there is a method of bending a straight pipe using a so-called pipe bender. When forming a U-shaped bent pipe by bending a straight pipe, it is usual to previously fill the hollow pipe with a filler such as sand so that the hollow pipe is not crushed by bending.

  Also known is a method of manufacturing a U-shaped bent pipe directly from molten metal by casting or die casting. In this case, it is usual to form a hollow portion using a core and to form a hollow tube.

  In order to obtain a U-shaped bent pipe having a plurality of bends as shown in FIG. 18 (a) by a method of mechanically bending a straight pipe using a shear bending press and a pipe bender as described above In order to reduce the productivity, it is necessary to apply a plurality of bending processes. In addition, it is necessary to be filled with a filler such as sand in advance, and the operation for the filling and the removal of the filler after processing also becomes an impediment factor of the improvement in productivity.

  Furthermore, in these mechanical bending methods, the distance S between the parallel portions 3A and 3B on both sides of the U-shaped bending portion 3 is small, and the curvature radius of the inside of the 180 ° bending portion (the top of the U shape) 9B. It was difficult to obtain a small U-shaped bend tube with r. And depending on the application of the U-shaped bent tube, as shown in FIG. 18 (b), the distance S between the parallel portions 3A and 3B is substantially zero, and the radius of curvature r inside the 180 ° bent portion 9B. There is a need for a U-shaped bent pipe that is substantially zero, but in bending with a shear bending press or a pipe bender as described above, such a U-shaped bent pipe must be efficiently manufactured. Was difficult.

  On the other hand, it is difficult to manufacture a thin U-shaped bent pipe by the method of manufacturing a U-shaped bent pipe directly from molten metal by casting or die casting, and it is used as a cast or die cast product, Since cold working is not performed, problems may occur in terms of strength, etc., and productivity is low. In particular, it takes time and effort to form and remove the core, resulting in high cost. There is also.

  By the way, hydroforming uses a hollow tubular material (raw material pipe) such as steel pipe, stainless steel pipe, or aluminum pipe as a molding material, sets the raw material pipe in the cavity of the mold, and Etc., and apply high-pressure liquid pressure in the material tube, and compress (axially push) from both ends of the material tube along its axial direction to align the material tube with the inner surface shape of the mold This is a processing method of forming into an irregular shape, and since a hollow member having a complicated shape can be integrally formed, it has recently been applied to the manufacture of various parts such as automobiles.

  A method for producing a hollow tube having a bent portion while utilizing such hydroforming is proposed by, for example, Patent Document 1 and Patent Document 2 or the like.

  The method proposed in Patent Document 1 relates to a method of producing a hollow tube having a bent portion and having an enlarged diameter of the bent portion, that is, a bent tube having a bulged portion by hydroforming. The method of Patent Document 1 will be described with reference to (a) to (c) of FIG.

  In (a) of FIG. 19, the mold 10 is comprised by the upper mold | type 10A and lower mold | type 10B which can be isolate | separated up and down. A downward convex portion 12 is formed on the upper mold 10A, and an upward concave portion 13 is formed on the lower mold 10B corresponding to the convex portion 12 of the upper mold 10A. On the other hand, the tube ends 14A and 14B at both ends of the material tube 14 are sealed by the tube end sealing members 15A and 15B (see (c) in FIG. 19). These tube end sealing members 15A, 15B not only seal the space in the material tube 11 but also squeeze the pressing member for compressing (axially pressing) the material tube 14 along its axial direction. At least one of them is connected to a shaft pushing drive such as a hydraulic cylinder (not shown). Further, in these pipe end sealing members 15A, 15B, a flow path 17 for introducing a pressurizing liquid, for example, water, into the material pipe 11 or discharging residual air in the material pipe 11 is formed. Ru.

  Then, as shown in FIG. 19A, the material pipe 14 is disposed on the lower mold 10B in a state where the upper mold 10A and the lower mold 10B are separated (the mold open state), and the pipe end portion 14A is obtained. , 14B are supported by the material tube end supporting portions 16A and 16B of the lower mold 10B, and then the upper mold 10A is lowered as shown in (b) of FIG. It bends and deforms along the convex part 12 of this. Further, as shown in (c) of FIG. 19, the pressurizing liquid is introduced into the raw material pipe 14 (arrow in the figure), the inside of the raw material pipe 14 is filled with the pressurizing liquid, and the raw material pipe 14 is continued by the pressurizing liquid. Pressurize the inside to high pressure. At the same time, a load (axial pushing force) along the axial direction is applied to the material pipe 14 by the pipe end sealing members 15A and 15B which also serve as the axial pushing members. As a result, the bent portion of the material tube 14 is expanded in diameter, and a bent tube with a bulging portion is obtained.

  Although the method disclosed in Patent Document 1 applies hydroforming, it is mainly intended to increase the diameter (expansion) of the bent portion, and the shear bending press and pipe bender as described above are used. As in the case of using a U-shaped curved tube in which the distance S between the parallel portions in the U-shaped curved portion is small and the radius of curvature of the 180 ° bent portion 9B is small, particularly as shown in FIG. No consideration is given to producing a U-shaped bent tube in which the distance S between parallel parts is substantially zero and the radius of curvature r inside the 180 ° bend 9B is substantially zero.

  In addition, Patent Document 2 discloses a method of manufacturing a metal pipe having two or more bends and having an irregular cross section such as a square as a cross-sectional shape of the bend using hydroforming. However, the method of Patent Document 2 is also mainly intended to increase the diameter (expansion) of the bent portion, and the distance S between parallel portions in the U-shaped bent portion is the same as the method shown in Patent Document 1 A small U-shaped bent tube having a small radius of curvature of 180 ° bent portion 9B, in particular, a bent portion 9B having a substantially 180 ° spacing S between parallel portions as shown in FIG. 18B. No consideration is given to producing a U-curved tube whose inner radius of curvature r is substantially zero.

  And, using the apparatus shown in these patent documents 1 or patent documents 2, the interval S between the parallel parts in the U-shaped bending portion is substantially zero, and the 180 ° bending portion in the U-shaped bending portion 3 It was practically difficult to produce a U-shaped bent tube with an inner radius of curvature r at or near zero for 9B.

JP 2003-103314 A Unexamined-Japanese-Patent No. 2004-50279

  The present invention has been made against the background described above, and with high productivity, a hollow tube having a U-shaped bent portion, in particular, a bending inner side with a substantially zero spacing S between parallel parts in the U-shaped bent portion. It is an object of the present invention to provide a method capable of easily and efficiently obtaining a hollow tube (U-curved tube) having a radius of curvature of zero or almost zero, and to provide an apparatus most suitable for carrying out the method. There is.

  The inventor conducted various experiments and studies to solve the above-mentioned problems, and as a result, when bending a raw material pipe, the metallizing structure for hydroforming is elaborately devised and hydroforming is simultaneously performed. By making good use of the axial pushing force, the distance between parallel parts of 180 ° bends is small, and U-curved bends with small radius of curvature inside the bend, especially those with zero or near-zero U-curved bends It has been found that the hollow tube having can be easily manufactured, and the present invention has been made.

Accordingly, the subject matter of the present invention is as follows.
That is, a method of manufacturing a hollow tube (U-curved tube) having a U-curved portion according to the basic aspect (first aspect) of the present invention is
A method for manufacturing a hollow tube having a U-shaped bent portion which protrudes between two or more straight pipe sections in a direction forming a predetermined angle with the axial direction of the straight pipe section,
A groove is formed between the mold member forming the upper mold and the mold member forming the lower mold, into which the hollow material tube having a hollow tubular shape is inserted, and one of the upper and lower mold members is formed A recess is formed continuous with the space in the groove and recessed toward the inside of the mold member, and the other mold member of the upper and lower mold members is directed from the inner surface of the groove to the recess. Using a mold provided with a projecting portion
In a state where liquid pressure is applied to the inner space of the material pipe, the upper and lower mold members are clamped so that the material pipe is positioned in the groove portion, and the protruding portion A raw material pipe is formed by pressing the raw material pipe from both end sides in a direction along its axis while forming a local recessed portion in a part of the outer peripheral surface and subsequently continuing application of the hydraulic pressure. The both sides of the local recessed portion in the region are pushed into the recess while sliding relative to the protrusion, whereby the local bending portion is separated from the tip of the protrusion in the recess and the local portion thereof The raw material pipe is bent and deformed in the recess so that the both sides of the target hollow portion are close to each other, whereby a U-shaped bent portion of the raw material pipe is formed in the concave portion.

In the manufacturing method according to the first aspect, the local depressions formed on a part of the outer peripheral surface of the raw material pipe by clamping the upper and lower mold members in a state where hydraulic pressure is applied to the inner space of the raw material pipe Then, when the material tube is axially pressurized (axially pressed) from both ends, the material tube pressed into the recess becomes a starting point of bending deformation in a U-shape. That is, by pre-forming the local depression prior to axial pressing, the intermediate portion of the raw material tube (portions on both sides of the local concave portion) is pushed into the recess by axial pressing force. The U-shaped bending deformation in the recess of the is to be initiated (triggered).
Then, in the process of pushing the middle portion of the material tube into the recess, the local recessed portion is separated from the tip of the projection while the portions on both sides of the local recessed portion slide relative to the projection. Nothing intervenes between the parts on both sides of the target hollow part. As a result, the portions on both sides of the local recessed portion can be bent and deformed so as to be close to each other. Therefore, the distance between the parallel portions of the U-shaped bend and the radius of curvature of the top inside of the U-shaped bend can be shaped to be zero or close to zero.
Thus, the distance between the parallel portions of the U-shaped bend and the inside of the bend are made by a simple process of applying hydraulic pressure in the material tube and clamping it, and then axially pressing the material tube while applying hydraulic pressure. A hollow tube having a U-shaped bend having a small radius of curvature, particularly a distance between parallel portions and a U-shaped bend having a radius of curvature inside or near to zero can be easily and efficiently manufactured. .

  Further, in the method of manufacturing a hollow tube having a U-shaped bent portion according to the second aspect of the present invention, in the manufacturing method of the first aspect, portions on both sides of the local hollow portion in the raw material pipe In forming the bent portion, the material tube is bent and deformed until the portions on both sides of the local recessed portion contact each other.

  According to the manufacturing method of the second aspect, it is possible to manufacture a hollow tube having a U-shaped bent portion in which the distance between parallel portions is zero and the radius of curvature inside the bent portion is substantially zero.

  Further, in the method of manufacturing a hollow tube having a U-shaped bent portion according to the third aspect of the present invention, in the manufacturing method of the first or second aspect, portions on both sides of the local recessed portion in the material pipe are In forming the U-shaped bent portion by pressing into the recessed portion, after a part of the bent outer surface of the U-shaped bent portion contacts the bottom surface of the recessed portion, pressing of the material tube in the axial direction is continued It is characterized in that the outer surface of the U-shaped bent portion in the recess is formed in a shape along the inner surface of the recess by increasing the hydraulic pressure applied to the inner space of the material tube.

  According to the manufacturing method of the third aspect as described above, the outer surface shape of the U-shaped bent portion can be formed into a desired shape with high accuracy.

Furthermore, in the method of producing a hollow tube having a U-shaped bent portion according to the fourth aspect of the present invention, in the method of producing the first or second aspect,
The mold further includes a counter member capable of advancing and retracting to the other mold member in the recess, in the one mold member.
In order to form a U-shaped bend by pushing portions on both sides of the local recessed portion in the material pipe into a U-shaped bend, at least a part of the outer surface of the bend in the recess of the material pipe is a tip end surface of the counter member The counter member is retracted in the recess while being in contact with

  In the manufacturing method according to the fourth aspect, bending is performed while the top surface of the bent portion of the material pipe is in contact with the tip end surface of the counter member in the process of pressing the middle portion of the material pipe into the recess and bending deformation. Because of the deformation, the diameter of the material tube may locally expand in the recess, or the material tube may be deformed to an abnormal shape, and the original correct U-shaped bending shape may not be obtained. The occurrence can be effectively prevented.

  In the method of manufacturing a hollow tube having a U-shaped bent portion according to the fifth aspect of the present invention, in the manufacturing method of the fourth aspect, the inside of the recess is in contact with the tip end surface of the counter member. The U-curved portion in the concave portion is raised by increasing the hydraulic pressure applied to the inner space of the material tube while continuing the pressurization in the axial direction of the material tube after the counter member reaches the most retreated position in And forming a shape along the tip surface of the counter member and the inner surface of the recess.

  In the manufacturing method of the fifth aspect as described above, as in the manufacturing method of the fourth aspect, the outer surface shape of the U-shaped bent portion can be formed into a desired shape with high accuracy.

  In the method of producing a hollow tube having a U-shaped bent portion according to the sixth aspect of the present invention, the method according to any one of the first to fifth aspects is characterized in that After forming the above U-curved portion, one or more steps of forming the U-curved portion by the same method at another portion apart from the U-curved portion are performed one or more times, thereby having a large number of bent portions It is characterized in that a hollow tube is produced.

  On the other hand, the seventh to tenth aspects of the present invention are directed to an apparatus for manufacturing a hollow tube having a U-shaped bent portion.

That is, the apparatus for manufacturing a U-shaped bent pipe according to the seventh aspect of the present invention is
An apparatus for manufacturing a hollow tube having a U-shaped bent portion projecting in a direction forming a predetermined angle with the axial direction of a straight pipe portion between two or more straight pipe portions,
A mold comprising a mold member constituting an upper mold and a mold member constituting a lower mold ;
A tube end sealing member having a flow path for introducing a liquid for applying a hydraulic pressure to the inside of a hollow tubular material tube;
Mechanical pressure means for pressing and driving the tube end sealing member along the axial direction from the both end sides of the material tube toward the intermediate portion;
Equipped with
Between the upper and lower mold members, together with the groove in which the material pipe is inserted is formed, said one of the mold members of the upper and lower mold members, continuously in the space of the groove portion and the other mold member A recess that is recessed towards the interior of the
The other mold member of the upper and lower mold members is formed with a protrusion projecting from the inner surface of the groove toward the inside of the recess, and side surfaces on both sides of the protrusion in the lengthwise direction of the groove And the projection height of the projection from the inner surface of the groove toward the inside of the recess is from the inner surface of the groove to the bottom of the recess in the recess It is set smaller than the depth ,
The U-shaped bent portion is formed in the recess .

  Thus, the maximum inclination angle of the side surfaces in the longitudinal direction on both sides of the groove in the projection is within the range of more than 45 ° and 90 ° or less, and the projection height of the projection from the inner surface of the groove toward the inside of the recess By setting the length smaller than the depth from the inner surface of the groove to the bottom of the recess in forming the U-shaped bent tube, the axial pressing force is formed after clamping and forming a local recessed portion. In the process of pushing the middle part of the material tube into the recess by means, the parts on both sides of the local recessed part can be slid relative to the projection to separate the local recessed part from the tip of the projection, It is practically possible to shape the spacing between the parallel parts of the U-shaped bend and the inner radius of curvature of the U-shaped bend smaller.

  In the apparatus for manufacturing a hollow tube having a U-shaped bent portion according to the eighth aspect of the present invention, in the manufacturing apparatus according to the seventh aspect, the projection height of the protrusion from the inner surface of the groove toward the inside of the recess However, it is characterized in that it is 1/2 or less of the depth from the inner surface of the groove in the recess to the bottom of the recess.

  By thus setting the protrusion height of the protrusion from the inner surface of the groove toward the inside of the recess to 1/2 or less of the depth from the inner surface of the groove to the bottom of the recess, the axial pressing force In the process of pushing the middle portion of the material tube into the recess, it is more reliably possible to slide the portions on both sides of the local recessed portion against the projection to separate the local recessed portion from the tip of the projection. It becomes possible. The projection height of the projection from the inner surface of the groove toward the inside of the recess is preferably 1/10 or more and 1/4 or less of the depth from the inner surface of the groove to the bottom of the recess in the recess. desirable.

Furthermore, according to a ninth aspect of the present invention, there is provided an apparatus for producing a hollow tube having a U-shaped bent portion,
An apparatus for manufacturing a hollow tube having a U-shaped bent portion projecting in a direction forming a predetermined angle with the axial direction of a straight pipe portion between two or more straight pipe portions,
A mold comprising a mold member constituting an upper mold and a mold member constituting a lower mold ;
A tube end sealing member having a flow path for introducing a liquid for applying a hydraulic pressure to the inside of a hollow tubular material tube;
Mechanical pressure means for pressing and driving the tube end sealing member along the axial direction from the both end sides of the material tube toward the intermediate portion;
Equipped with
Between the upper and lower mold members, together with the groove in which the material pipe is inserted is formed, said one of the mold members of the upper and lower mold members, continuously in the space of the groove portion and the other mold member A recess recessed toward the inside of the mold, and the mold member is provided with a counter member capable of advancing and retracting to the other mold member of the upper and lower mold members in the recess;
The other mold member is formed with a protrusion projecting from the inner surface of the groove toward the inside of the recess, and the maximum inclination angle of the side surface in the longitudinal direction of the groove in the protrusion is 45 ° And the projection height of the projection from the inner surface of the groove toward the inside of the recess is smaller than the depth from the inner surface of the groove to the tip surface of the counter member in the recess. Yes,
The U-shaped bent portion is formed in the recess .

When such a device is used, the top surface of the bent portion of the material pipe is bent while being in contact with the tip end surface of the counter member, so that the diameter of the material pipe locally expands in the recess, or the material pipe Can be effectively prevented from occurring such that the original correct U-shaped bending shape can not be obtained.
In addition, here, the maximum inclination angle of side surfaces on both sides in the longitudinal direction of the groove in the projection is within a range of more than 45 ° and 90 ° or less, and the projection of the projection toward the inside of the recess from the inner surface of the groove By setting the height smaller than the depth from the inner surface of the groove in the recess to the front end surface of the counter member, the mold is tightened to form a local recessed portion in implementing the manufacturing method of the U-shaped bent tube And, in the process of pushing the middle portion of the material tube into the recess by the axial pressing force, the portions on both sides of the local recessed portion are slid relative to the projection to separate the local recessed portion from the tip of the projection Thus, it is practically possible to shape the spacing between the parallel parts of the U-shaped bend and the inner radius of curvature of the U-shaped bend smaller.

  In the apparatus for manufacturing a hollow tube having a U-shaped bent portion according to the tenth aspect of the present invention, in the manufacturing apparatus according to the ninth aspect, the projection height of the protrusion from the inner surface of the groove toward the inside of the recess However, it is characterized in that it is 1/2 or less of the depth from the inner surface of the groove in the recess to the front end surface of the counter member.

  By thus setting the protrusion height of the protrusion from the inner surface of the groove toward the inside of the recess to 1/2 or less of the depth from the inner surface of the groove to the bottom of the recess, the axial pressing force In the process of pushing the middle portion of the material tube into the recess, it is more reliably possible to slide the portions on both sides of the local recessed portion against the projection to separate the local recessed portion from the tip of the projection. It becomes possible. The projection height of the projection from the inner surface of the groove toward the inside of the recess is preferably 1/10 or more and 1/4 or less of the depth from the inner surface of the groove to the bottom of the recess in the recess. desirable.

  According to the present invention, the distance between the parallel portions on both sides of the U-shaped bending portion is small, and the radius of curvature of the bending inner side is small, particularly the distance between paralleling portions is zero or near. Hollow tubes with zero or near zero U-bends can be easily and efficiently manufactured.

It is a longitudinal cross-sectional front view which shows the apparatus for enforcing 1st Embodiment of the manufacturing method of U-shaped bending pipe of this invention in the state which open | released the metal mold | die. It is a longitudinal cross-sectional front view which shows the apparatus for implementing said 1st embodiment in the state (mold closed state) which clamped the mold. It is a vertical side view in the III-III line in FIG. It is a vertical side view in the IV-IV line in FIG. It is a cross-sectional top view in the VV line | wire in FIG. It is a perspective view which expands and shows the protrusion part vicinity in the metal mold | die member (lower mold member) of the apparatus shown in FIGS. It is a schematic longitudinal front view which shows in steps the situation which implements 1st Embodiment of this invention method using the apparatus shown in FIGS. 1-6. FIG. 1 is a perspective view showing an example of a hollow tube having a U-shaped bend manufactured according to a first embodiment of the method of the present invention. It is a general | schematic longitudinal longitudinal elevation view which shows three examples of the cross-sectional shape of the protrusion part of the lower mold member in the apparatus for enforcing the method of this invention. It is a longitudinal cross-sectional front view which shows the apparatus for implementing 2nd Embodiment of this invention in the state (mold closed state) which clamped the mold. It is a schematic longitudinal front view which shows in a step-wise the condition which implements 2nd Embodiment of this invention method using the apparatus shown in FIG. It is a vertical front view which shows another example of the counter member used for 2nd Embodiment of this invention method. It is a schematic solution drawing showing gradually an example of a method of manufacturing a hollow tube which has a plurality of U-shaped bending parts by applying the method of the present invention. As another example of the manufacturing method of the hollow tube which has a U-shaped bending part of this invention, it is a longitudinal cross-sectional view which expands and shows the part of the recessed part and protrusion part of a metal mold | die. It is a cross-sectional top view in the XV-XV line of FIG. As another example of the manufacturing method of the hollow tube which has a U-shaped bending part of this invention, it is a longitudinal side view which expands and shows the part of the recessed part and protrusion part of a metal mold | die. FIG. 17 is a cross-sectional plan view taken along line XVII-XVII in FIG. It is an approximate solution front view showing two examples of a hollow tube which has a U-shaped bent part which becomes a manufacturing object by the present invention. It is a schematic diagram showing gradually an example of the conventional method for manufacturing a hollow tube which has a bent part applying hydroforming.

  Next, the present invention will be described in detail.

  FIGS. 1 to 5 show the main part of the apparatus configuration for carrying out the method of manufacturing a hollow tube (U-curved tube) having a U-curved portion according to the first embodiment of the present invention, particularly a mold portion 6 is an enlarged view of a portion of the apparatus shown in FIGS. 1 to 5 (the portion of the protrusion of the lower mold member), and FIG. 7 is a view of the first embodiment. A method of manufacturing a hollow tube having a U-shaped bend is shown step by step, and further, FIG. 8 shows an example of a hollow tube having a U-shaped bend manufactured according to the first embodiment. Note that FIG. 1 shows the mold 31 in the open state, that is, in the unclamped state, and FIGS. 2 to 5 show the material pipe 37 disposed at the required portion of the mold 31 and in the clamped state. ing.

  In FIG. 1 to FIG. 5, the mold 31 is constituted by a mold member 33A constituting an upper mold and a mold member 33B constituting a lower mold, and these mold members 33A and 33B are clamps not shown. It is configured to be clamped by means. The material of the mold members 33A and 33B constituting the mold 31 is not particularly limited, and may be made of FC 250, S50C, SKD11 or the like, as in the case of a normal hydroforming mold. In the following description, the mold member 33A constituting the upper mold is referred to as the upper mold member 33A, and the mold member 33B constituting the lower mold is referred to as the lower mold member 33B.

  The upper surface of the lower mold member 33B is formed to be flat as a whole in the present embodiment, and the upper surface of the lower mold member 33B has a horizontal half groove (lower mold groove) 35B having a semicircular cross section. It is formed upward along the direction. In the lower surface of the upper mold member 33A, a half groove (upper mold groove) 35A having a semicircular cross section is directed downward along the horizontal direction corresponding to the half groove (lower mold groove) 35B of the lower mold member 33B. Is formed. Then, in the clamped state, the lower mold groove 35B and the upper mold groove 35A form a groove 35 having a circular cross section as a whole. The groove 35 is for accommodating a hollow material tube 37 to which the manufacturing method of the present invention is applied. Therefore, the maximum diameter of the lower mold groove 35B and the upper mold groove 35A (that is, the inner diameter of the groove 35) is determined to be equal to or slightly larger than the outer diameter R of the material tube 37.

  Here, in the vicinity of both ends of the groove portion 35 (upper mold groove 35A, lower mold groove 35B) in the upper mold member 33A and lower mold member 33B, a tube end support portion for supporting the both ends 37A and 37B of the material tube 37 43A and 43B. The tube end support portions 43A and 43B are portions in the vicinity of both ends of the material tube 37 (more precisely, both ends 37A and 37B of the material tube 37 and the subsequent tube end sealing member 45A, The portion 45 B is configured to be supported so as to allow the portion to move along the length of the material tube 37. The tube end sealing members 45A, 45B not only seal the space in the material tube 37, but also mechanically pressurize the material tube 37 along its axial direction from its both end sides toward the intermediate portion ( It also serves as an axial pushing member for axial pushing. Then, a liquid such as water for applying a hydraulic pressure is introduced into the material pipe 37, and residual air is discharged (air is removed) from the material pipe 37 to the pipe end sealing members 45A, 45B. One or more flow paths 47A, 47B are formed along the axial direction.

  Further, the upper mold member 33A of the mold 31 is formed with a recess 39 which is continuous with the space in the upper mold groove 35A and is recessed upward (inside the upper mold member 33A). As shown in FIGS. 1 to 5, in the recess 39, the vertical cross section along the length direction of the upper mold groove 35A (therefore, the length direction of the material tube 37) has a substantially rectangular shape ( Therefore, the vertical cross section which is formed in an inverted U-shape or downward U-shape) and which is perpendicular to the longitudinal direction of the upper mold groove 35A (and hence the longitudinal direction of the material tube 37) is the maximum width of the upper mold groove 35A (hence It is made into the shape dented upward by width W1 (refer FIG. 3) substantially the same as the maximum width of the groove part 35). Here, the width W2 (see FIGS. 1 and 2) of the recess 39 in a direction parallel to the longitudinal direction of the upper mold groove 35A, that is, two inner side surfaces 39A and 39B orthogonal to the longitudinal direction of the upper mold groove 35A. The distance W2 between the two is set to substantially the same size as twice the outer diameter R of the material tube 37. Specifically, although the above-mentioned width W2 depends on the cross-sectional shape and the material, it is appropriate to set it within the range of about 2 to 2.2 times the outer diameter R of the material pipe 37. The depth D1 of the recess 39 (the distance from the inner surface of the upper mold groove 35A to the bottom surface 39C of the recess 39) may be determined according to the height of the U-shaped bent portion to be obtained. The depth is determined to be larger than the size of the outer diameter R, preferably twice or more the outer diameter R of the material tube 37.

  Further, in the lower mold groove 35B of the lower mold member 33B, a protrusion 41 is formed at a position corresponding to the center of the recess 39 of the upper mold member 33A. The protrusion 41 protrudes from the lower mold groove 35B toward the bottom surface 39C of the recess 39 of the upper mold member 33A, and the vertical cross section parallel to the length direction of the groove 35 has, for example, a substantially triangular shape. It is shaped like an eggplant. The cross-sectional shape and desirable dimensions of the projecting portion 41 will be described again later.

Next, a method of forming a U-shaped bent portion in the material pipe 37 using the apparatus shown in FIGS. 1 to 6 will be described with reference to FIGS. 7 (a) to 7 (e).
The material of the material tube 37 is not particularly limited as long as it is a material capable of plastic working in cold or warm, for example, carbon steel, stainless steel, copper or copper alloy, aluminum or aluminum alloy, titanium or titanium alloy Etc. can be applied. Also, the outer diameter and thickness of the material tube 37 are not particularly limited, but it is usually applicable to those having an outer diameter of about 21.7 to 114.3 mm and a thickness of about 1.2 to 5.0 mm.

  As shown to Fig.7 (a), the tube end sealing member 45A, 45B which served as the axial pushing member is previously attached to the both ends (tube end 37A, 37B) of the raw material pipe | tube 37. As shown in FIG. Then, as shown in FIG. 7A, in a state where the mold 31 is opened (in a state where the mold is not clamped), between the upper mold member 33A and the lower mold member 33B (upper mold groove 35A and lower mold groove 35B And the material tube 37 is placed). Then, the upper mold member 33A is lowered and clamped. Note that at a stage prior to this mold clamping, the material pipe 37 is filled with a liquid for applying hydraulic pressure such as water through the flow paths 47A and 47B of the pipe end sealing members 45A and 45B, Apply hydraulic pressure to the When the material tube 37 is filled with liquid, air is usually removed so that air does not remain in the material tube 37. The state immediately after the mold clamping is shown in FIG. 7 (b) and FIG.

  In the clamped state, the material tube 37 is supported between the upper mold member 33A and the lower mold member 33B in a mode in which both end portions 37A, 37B are allowed to move in the axial direction. The material tube 37 is in a state of being inserted into the groove portion 35 formed of the upper mold groove 35A and the lower mold groove 35B.

  Here, at the time of mold clamping, as shown in FIG. 7 (b) and FIG. 2, the lower surface of the intermediate portion corresponding to the recess 39 of the upper mold member 33 A in the material tube 37 is from the lower mold groove 35 B By coming into contact with the projecting portion 41 and further applying a mold clamping force, the projecting portion 41 is pushed upward into the recess 39. As a result, plastic deformation is locally applied to the lower surface of the middle portion of the material tube 37, and locally recessed in the reverse V shape or reverse U shape toward the inside of the recess 39. The local hollow portion of the material tube 37 is indicated by reference numeral 37D (see FIGS. 2 and 7B).

  Next, as shown in FIGS. 7 (c) to 7 (d), while applying the fluid pressure in the material tube 37, the tube end sealing members 45A, 45B are mechanically pressurized by a fluid pressure cylinder or the like (not shown). The pressure drive (i.e., axial pressing) is performed along the axial direction from both sides by means. Due to this axial pressing force, the portions 37E, 37F on both sides following the local recessed portion 37D in the middle portion of the material tube 37 are the side surfaces of the protrusion 41 (the side surfaces of one side and the other cross the length direction of the groove 35). While sliding relative to the side surface 41B, 41C, the local recessed portion 37D and the portions 37E, 37F on both sides following the local recessed portion 37D are pushed into the recessed portion 39. At this time, the material tube 37 includes the local recessed portion 37D while being generally bent and deformed into an inverted U shape having the local recessed portion 37D as a starting point of bending and the local recessed portion 37D as an apex, The portions 37E, 37F on both sides thereof will be pushed entirely into the recess 39 (raised in the recess 39). As a result, a U-shaped bent portion 3 is formed in the middle portion of the material pipe 3 in the recess 39.

Here, the projecting portion 41 for forming the local recessed portion 37D is integrally formed on the lower mold member 33B, and since the projecting height H from the lower mold groove 35B is constant, the locally recessed portion In a process in which 37D and the portions 37E and 37F on both sides thereof are entirely pushed into the recess 39 (ascends in the recess 39), the portions 37E and 37F near the local recessed portion 37D are the side surfaces 41B of the protrusion 41. . It is pushed upward while sliding with respect to 41 C, and the local recessed portion 37 D is separated from the tip of the protrusion 41. This means that the protrusion 41 is not interposed between the both side portions 37E and 37F in the vicinity of the local recessed portion 37D. Therefore, both side portions 37E and 37F in the vicinity of the local bending portion 37D are deformed in the direction in which the facing surfaces approach each other due to the axial pressing force, and finally the opposing portions of the both side portions 37E and 37F near the local bending portion 37D. The faces will be in contact.
In this deformation process, since the fluid pressure is applied to the inside of the material pipe 37, the material pipe 37 is bent and deformed without being crushed.

  Thus, by applying the axial pressing force while maintaining the application of the hydraulic pressure, the middle portion of the material tube 37 is pushed into the recess 39 while being deformed into an inverted U shape, and the deformed portion (U-curved portion 7) after the top surface 3C of the top portion 3C of the upper surface 3C contacts the inner bottom surface 39C of the recess 39, the outer surface of the U-curved portion 3 is the inner surface of the recess 39 as shown in FIG. It is molded into a shape substantially along the entire surface.

  After that, the application of the fluid pressure is stopped, the axial pressing force is released, and the mold 31 is opened. Before and after that, the pressurizing liquid in the material tube 37 is discharged, the material tube 37 is taken out from the mold 31, and the tube end sealing members 45A and 45B are removed from the material tube 37, a series of processing processes (U The manufacturing process of the hollow tube having the bent portion 3 is completed.

An example of the hollow tube 5 thus finished according to the present embodiment is shown in FIG.
As shown in FIG. 8, this hollow tube 5 is disposed between two straight tube portions 1A, 1B having a common axis O in a direction perpendicular to the axial direction of the straight tube portions 1A, 1B. It has a protruding U-shaped bend 3. In this hollow tube 5, the space S between the parallel portions 3A and 3B in the U-shaped bend 3 is zero or close to it, in other words, the radius of curvature r in the bending inner side of the U-shaped bend 3 is zero or near it. It has become a thing.

  The outer shape of the U-shaped bent portion 3 is determined by the inner surface shape of the recess 39. And in the case of this embodiment, since each inner surface shape of crevice 39 is made into the approximately flat respectively, U character bent part 3 is fabricated so that the outer surface may make the cross section rectangle shape, but it is not limited to this By changing the inner surface shape of the recess 39, as described later, it is possible to mold so as to have various different outer surface shapes.

  As described above, the portions 37E and 37F on both sides of the local recessed portion 37D are pushed into the recess 39 while being slid relative to the side surfaces 41B and 41C of the projecting portion 41 by the axial pressing force under application of the hydraulic pressure shaft. By generating a bending deformation in the recess 39 with the local recessed portion 37D as the starting point of bending, the hollow tube 5 having the U-shaped bent portion 3 having a radius of curvature inside of the U-shaped bending of zero or close to zero is obtained. be able to. Here, it can be said that the local depression 37D separates from the protrusion 41 in the above-mentioned deformation process, but the local depression 37D provides an initiation for causing a bending deformation.

  Here, various examples of the shape of the protrusion 41 protruding from the bottom of the lower mold groove 35B of the lower mold member 33B are shown in FIGS. 9A, 9B, and 9C, and the cross-sectional shape of the projection 41 The dimensions will be described with reference to FIGS. 9 (a), (b) and (c).

FIG. 9A shows the protrusion 41 in the first embodiment described above, and the protrusion 41 has a substantially triangular shape in a vertical cross section along the length direction of the lower mold groove 35B. ing. That is, the bottom 35B ₀ from both sides 41B of the lower die groove 35B, 41C rising as the inclined surface of the maximum inclination angle θ (<90 °), both side surfaces 41B, the upper end of the 41C, a small radius of curvature _{r P} It is continuous with the tip 41A having a curved sectional arc shape.

FIG. 9 (b) shows another example of the protrusion 41. The protrusion 41 has a vertical wall shape in a vertical cross section along the length direction of the lower mold groove 35B. Or side 41B from the bottom 35B ₀ on both sides of the lower die groove 35B, 41C rises at the vertical plane (and therefore the maximum inclination angle = 90 °), cross both side surfaces 41B, the upper end of the 41C, curved with a radius of curvature _{r P} It is continuous with the arcuate tip portion 41A.

FIG. 9 (c) shows still another example of the protrusion 41. The projection 41 is a side 41B from the bottom 35B ₀ on both sides of the lower die groove 35B, 41C rises as concave curved surface of the maximum inclination angle θ (≦ 90 °), both side surfaces 41B, the upper end of the 41C, small It is continuous with the tip 41A having a circular arc-like cross section curved with a radius of curvature r _P.

In FIGS. 9A, 9 B, and 9 C, the height H from the bottom 35 B ₀ of the lower mold groove 35 B to the end 41 A of the projection in the projection 41 is the outer diameter R of the material tube 37. The height H is set to be slightly larger than 1/2 (therefore slightly larger than the depth of the lower groove 35B) and smaller than the outer diameter R of the material tube 37, but not limited thereto. Alternatively, the diameter may be set smaller than 1⁄2 of the outer diameter R of the material tube 37 (thus, smaller than the depth of the lower mold groove 35B).

  The specific preferred range of the height H of the protrusion 41 varies depending on the size and material of the outer diameter R of the material tube 37, but is usually 0.1 times or more the outer diameter R of the material tube 37 The height is made sufficiently smaller than the depth D1 from the inner surface of the groove to the bottom of the recess in the recess.

  If the height H of the protrusion 41 is less than 0.1 times the outer diameter R of the material tube, the recess depth of the local recessed portion 37D formed by the protrusion 41 at the time of mold clamping is too small, and the material is thereafter removed. When an axial pressing force is applied from both sides of the tube 37 to press the middle portion of the material tube 37 into the recess 39, an action is made such that both side portions 37E and 37F are pushed and bent in the direction of mutual contact starting from the local recessed portion 37D. It can not be obtained reliably, and there is a possibility that abnormal deformation of the material tube 37 may occur in the recess 39.

  Here, if the height H of the protrusion 41 is equal to the depth D1 from the inner surface of the groove to the bottom of the recess, the portions 37E and 37F on both sides of the material tube local depression 37D are pushed into the recess 39 by axial pressing. , The portions 37E and 37F on both sides of the protrusion 41 do not slide against the side surfaces 41B and 41C of the protrusion 41, and the tip 41A of the protrusion 41 is in contact with the local recessed portion 37D from the beginning to the end of axial pressing. Become. That is, the local recessed portion 37D is not separated from the tip 41A of the protrusion 41. In other words, the protrusion 41 always intervenes between the portions 37E and 37F on both sides of the local recessed portion 37D, so that the space S between the portions 37E and 37F on both sides has a value near or near zero. As a result, it becomes difficult to set the inner radius of curvature of the U-shaped bend 3 to a value near or near zero.

  On the other hand, if the height H of the protrusion 41 is smaller than the depth D1 from the inner surface of the groove to the bottom of the recess, the portions 37E and 37F on both sides of the material tube local depression 37D are pushed into the recess 39 by axial pressing. In the process, it is possible to slide the portions 37E and 37F on both sides of the local recessed portion 37D against the side surfaces 41B and 41C of the projecting portion 41 to separate the local recessed portion 37D from the tip 41A of the projecting portion 41. Become.

  In particular, when the height H of the protrusion 41 is not more than half the depth D1 from the inner surface of the groove to the bottom of the recess, in the process of pushing the portions 37E and 37F on both sides of the local recessed portion 37D into the recess 39, It is certainly possible to make the local depression 37D sufficiently separate from the tip 41A of the projection 41 so that the space between the parts 37E, 37F on either side of the local depression 37D is at or near zero. Become. As a result, it is possible to reliably form a U-shaped bend 3 having a radius of curvature inside the bend of zero or close thereto. Therefore, the height H of the protrusion 41 is preferably 1/2 or less of the depth D1 from the inner surface of the groove to the bottom of the recess, but is preferably 1/10 or more and 1/4 or less.

  Further, it is preferable that the maximum inclination angle θ of the side surfaces 41B and 41C of the protrusion 41 be in the range of 45 ° <θ ≦ 90 °.

  When the maximum inclination angle θ of the side surfaces 41B and 41C of the protrusion 41 is 45 ° or less, the axial depression force is applied from both sides of the raw material pipe 37 to push the middle portion of the raw material pipe 37 into the recess 39. It becomes difficult to slide the portions 37E and 37F on both sides with respect to the side surfaces 41B and 41C of the projecting portion 41. In that case, abnormal deformation of the material tube 37 occurs in the recess 39. On the other hand, when the maximum inclination angle θ of the projection 41 exceeds 90 ° and the side surfaces 41B and 41C of the projection 41 become a so-called undercut (reverse taper), The portions 37E and 37F on both sides of the local recessed portion 37D do not slide against the side surface of the projecting portion 41, making it difficult for the local recessed portion 37D to separate from the projecting portion 41, and the abnormality of the material tube 37 in the recessed portion 39. Deformation may occur.

  In addition, when an axial pressing force is applied to press the middle portion of the material tube 37 into the recess 39, the portions 37E and 37F on both sides of the local recessed portion 37D are smoothly slid on the side surfaces 41B and 41C of the projecting portion 41. In order to reduce the surface roughness of the side surfaces 41B and 41C of the projecting portion 41, the outer surface of the raw material tube 37 and the side surfaces 41B and 41C of the projecting portion 41 are appropriately lubricated. It is desirable to reduce the frictional resistance between the and the side surfaces 41B and 41C of the protrusion 41. Therefore, for example, it is desirable that the surface roughness of the side surfaces 41B and 41C of the protruding portion 41 be about 6.3 μm or less in center line average roughness, and it is desirable to use an aqueous film-based lubricant as a lubricant.

Moreover, the radius of curvature _{r P} of the distal end portion 41A of the projecting portion 41 is preferably in the range of about 0.5 mm to 1.0 mm.

When the tip 41A of the protrusion 41 is too sharp, when the tip 41A of the protrusion 41 abuts on the outer surface of the material tube 37 at the time of mold clamping and the local recessed portion 37D is formed, stress concentration causes that If there is a possibility that a crack may occur in the contact portion or it may break, while the radius of curvature r _P of the tip end portion 41A of the protrusion 41 is too large, the U-shaped bend 3 is finally formed in the material tube 37 In this state, the radius of curvature r inside the bent portion may be increased. When the radius of curvature r _P of the end portion 41A is about 0.5 mm or more, the risk of cracking or breakage when the local recessed portion 37D is formed can be reduced, and the radius of curvature r _{P of the} end portion 41A is Below about 1.0 mm, it becomes easy to make the inner radius of curvature of the U-shaped bent portion 3 of the product zero or close to zero.

  Furthermore, the axial moving speed (axial pushing speed) of both side portions of the raw material pipe 37 when pushing the middle portion of the raw material pipe 37 into the recess 39 by applying axial pushing force from both sides of the raw material pipe 37 is particularly limited. The optimum speed also differs depending on the material, hardness, and dimensions (outer diameter and thickness) of the material tube 37, but the outer diameter is about 21.7 to 114.3 mm and the thickness is 1.2 to 5. In the case where a general structural carbon steel pipe of about 0 mm is targeted, it is preferable to determine the axial pushing speed to be about 1.0 to 10.0 mm / sec. The axial pressing force may be determined by the material, hardness, dimensions (outside diameter and thickness), etc. of the material tube 37 so as to obtain the above-described axial pressing speed, and for the general structure described above In the case of a carbon steel pipe, it may be about 10 kN to 3000 kN.

  The hydraulic pressure to be applied to the material pipe 37 is not particularly limited either, and the optimum speed varies depending on the material, hardness, and dimensions (outer diameter and thickness) of the material pipe 37, but the outer diameter is 21. When a general structural carbon steel pipe having a thickness of about 7 to 114.3 mm and a thickness of about 1.2 to 5.0 mm is targeted, it is preferable that the hydraulic pressure be set to be about 10 MPa to 200 MPa.

  However, in the case of the method of the present invention, the main purpose of adding the hydraulic pressure is different from the case shown in the prior art, not for expanding (expanding) the material tube but for the material at the time of mold clamping and axial pressing. The purpose is to prevent the tube from collapsing or locally causing concave deformation. If the fluid pressure at the time of axial pressing becomes excessively large, the material tube expands and deforms in the recess 39 and can not be separated from the local recessed portion 37D and the tip 41A of the projecting portion 41, as a result There is a possibility that it becomes impossible to form the U-time bending portion 3C where the inner radius of curvature of the bending portion is zero or close to zero. Therefore, it is desirable to keep the hydraulic pressure at the time of axial pressing small within the range in which the material tube is not crushed or deformed. From the same point of view, after clamping, starting from axial pressing, the fluid pressure is maintained constant until the top of the portion bent and deformed into a U shape contacts the bottom surface 39C of the recess 39 in the recess. Is desirable.

FIG. 10 shows the mold part of the apparatus used in the second embodiment of the present invention, and FIGS. 11 (a) to (e) use it to carry out the method of the second embodiment. Show the situation in progress. In FIG. 10, the material pipe 37 is disposed at a required position of the mold 31 and clamped.
In addition, in FIG. 10 and FIG. 11, the same code | symbol is attached | subjected about the element same as the apparatus used for 1st Embodiment shown to FIGS. 1-5, and the detail is abbreviate | omitted.

  In FIG. 10, for example, a thick plate-like or block-like counter member 49 is disposed in the recess 39 of the upper mold member 33A. The counter member 49 has a shape similar to the shape of the horizontal cross section of the recess 39 as the shape of the horizontal cross section, and is larger than the size of the horizontal cross section of the recess 39 so as to be vertically movable (liftable) in the recess 39. It is made in slightly smaller dimensions. The lower surface (tip surface) 49A of the counter member 49 is a substantially horizontal plane. The counter member 49 is configured to be able to move up and down in the recess 39 by means of forward and backward drive means 51 such as a fluid pressure cylinder.

  In the method of the second embodiment, in the mold open state before clamping (see FIG. 11A), the lower surface (tip surface) 49A of the counter member 49 is on the upper mold groove 35A. It is determined to be located slightly above the bottom surface position. Then, in the same manner as described in the first embodiment, the upper mold member 33A is disposed in a state where the material pipe 37 is disposed between the upper mold groove 35A and the lower mold groove 35B and the fluid pressure is applied in the material pipe 37. When it is lowered and clamped, as shown in FIG. 11 (b), the local recessed portion 37D is formed at a predetermined position on the lower surface side of the material pipe 37 in the same manner as described above. At this time, the tube wall (tube wall on the upper surface side) 37G opposite to the local recessed portion 37D in the material tube 37 by 180 degrees is also curved so as to protrude upward by the height h, but the upper surface at that time It is desirable to determine the position of the counter member 49 at the time of mold clamping so that the side curved projecting portion 37G is in contact with the front end surface (lower surface) of the counter member 49.

  After clamping, if axial pressing force is applied to the material pipe 37 from both sides in the length direction in a state where the application of hydraulic pressure is continued, a part of the material pipe 37 as described in the first embodiment, That is, while both side portions 37E and 37F of the local recessed portion 37D are pushed into the recess 39 while sliding with respect to the side surface of the protrusion 41, the both side portions 37E and 37F of the local recessed portion 37D are the local recessed portion The U-shaped bend 3 is formed by bending and deforming in the recess 39 starting from 37D. The process is shown to FIG.11 (c)-(e).

  Here, in the case of the second embodiment, the counter member 49 is raised in the process of pushing the both side portions 37E and 37F of the local recessed portion 37D into the recess 39 by axial pressing. The rising speed of the counter member 49 at this time is approximately equal to the pushing speed per side of the material tube 37. By doing this, as shown in FIGS. 11C to 11D, the bent portion of the material tube 37 rises in the recess 39 while the upper surface thereof contacts the lower surface (tip surface) 49A of the counter member 49. And bending deformation will proceed. That is, since there is no extra space above the bending portion during the progress of bending deformation, the raw material pipe 37 expands locally in the recess 39 and the diameter of the raw material pipe 37 is enlarged or abnormal. It is possible to effectively prevent the occurrence of a situation where the original correct U-shaped bending shape can not be obtained due to the deformation into the shape.

  Also in the case of the second embodiment, various shapes as shown in FIGS. 9A to 9C can be applied as the shape of the protruding portion 41.

Further, the height H of the protrusion 41 in the case of the second embodiment, that is, the height H from the bottom 35B ₀ of the lower mold groove 35B to the end 41A of the protrusion is 0.1 times the outer diameter R of the material tube 37 This is more than the depth D2 from the inner surface of the groove 35 to the tip surface 49A of the counter member 49 in the state where the counter member 49 is retracted most (represented by the chain line in FIG. 10) in the recess 39 Small height. The reason is the same as the reason why the height H of the protrusion 41 is sufficiently smaller than the depth D1 from the inner surface of the groove 35 to the bottom surface of the recess 39 in the first embodiment.

  Furthermore, in the second embodiment, the height H of the protrusion 41 is the same as the above, from the inner surface of the groove 35 in the state where the counter member 49 is retracted most (raised) (the state shown by the chain line in FIG. 10). It is preferable to set it as 1/2 or less of the depth D2 to the front end surface 49A, and more preferably 1/10 or more and 1/4 or less. The reason is also the same as the reason why the depth D1 from the inner surface of the groove to the bottom of the recess is preferably 1/2 or less, and more preferably 1/10 or more and 1/4 or less in the first embodiment.

  In addition, the maximum inclination angle of the protrusion 41 and the radius of curvature of the tip 41 A of the protrusion 41 may be the same as those described in the first embodiment.

  In the second embodiment described above, the lower surface 49A of the counter member 49 is substantially flat, but as shown in FIG. 12, the lower surface 49A of the counter member 49 is a concave curved surface. Also good. In that case, when pushing the middle portion of the material tube 37 into the recess 39, the bent portion 3 of the material tube 37 can be brought into contact with the lower surface (curved surface) 49A of the counter member 49 with a wide area. It is possible to more reliably prevent deformation into an abnormal shape.

  As a method for forming a U-shaped bent portion at two or more places separated in the length direction in the material pipe 37, for example, as shown in FIGS. 13 (a) and 13 (b), A first U-shaped bent portion 3J is formed in part by the method of the present invention (for example, the method according to the first embodiment), and then again at another place in the material tube 37 as shown in FIG. If the second U-shaped bent portion 3K is formed by the method of the present invention (for example, the method according to the first embodiment), and further such process is repeated successively, a large number of U as shown in FIG. It is possible to produce hollow tubes with bent portions 3J, 3K, 3L.

  In each of the above-described embodiments, by forming the inner bottom surface and the side surface of the recess 39 as a substantially flat surface, the hollow tube in which the outer shape of the U-shaped bent portion 3 has a rectangular shape is manufactured. In the method of the present invention, by changing the shapes of the inner bottom surface and the side surface of the recess 39, it is possible to form U-curved portions having various outer surface shapes.

For example, when it is desired to obtain a U-shaped bent portion whose outer surface shape is circular, as shown in FIGS. 14 and 15, the cross sectional shapes of the inner bottom surface 39C and the side surfaces 39D and 39E of the recess 39 are It should be round. Further, for example, when it is desired to obtain a U-shaped bent portion whose outer surface shape is a polygon, as shown in FIGS. 16 and 17, the cross-sectional shape of the inner bottom surface 39C and the side surfaces 39D and 39E of the recess 39 is a concave step. It may be a shape or a polygon. In addition, U-shaped bent portions having various cross-sectional shapes can be formed as needed.
When the counter member is disposed in the recess, instead of the cross sectional shape of the inner bottom surface of the recess, the cross sectional shape of the tip end surface of the counter member is a concave curved half circle or concave step or Of course, it may be set to a polygon or the like.

  In each of the above embodiments, the recess 39 is formed in the upper mold member 33A of the mold 31 and the projection 41 is formed in the lower mold member 33B. It is a matter of course that the projecting portion 41 may be formed on the upper mold member 33A while forming the recessed portion 39 in 33B.

  Examples of the present invention are shown below. The following examples are for confirming the action and effects of the present invention, and it is needless to say that the conditions described in the examples do not limit the technical scope of the present invention.

Example 1
This example 1 corresponds to the first embodiment, and as a mold, one shown in FIGS. 1 to 6 is used, and a material is produced according to the method shown in FIGS. 7 (a) to 7 (e). The tube was processed to produce a hollow tube with a U-shaped bend. Here, the groove 35 in the mold 31 has a circular cross section as a whole and has an inner diameter of 38.1 mm. Further, the recess 39 of the upper mold member 33A has an inner surface in a direction orthogonal to the lengthwise direction of the groove 35, with a width W2 (distance between the inner side surfaces 39A and 39B) W2 in the direction along the lengthwise direction of the groove 35 The distance W1 is 40.0 mm, and the depth D1 is 120.0 mm. On the other hand, as the protrusion 41, as shown in FIG. 9A, the cross section has a substantially triangular shape, and the height H thereof is 5.0 mm (therefore 0.13 times the outer diameter R of the material tube), The inclination angle θ of both side surfaces was 60.0 °, and the tip end surface was convexly curved with a curvature radius of 0.5 mm. As a raw material pipe | tube, the hollow pipe which consists of carbon steel pipe for machine structure: STKM13B which is 38.1 mm in outer diameter and 2.3 mm in thickness was used.

  Specifically, tube end sealing members 45A and 45B are attached to both ends of the material tube 37, disposed between the upper die groove 35A and the lower die groove 35B, and the material tube is filled with water as a pressure liquid. A pressure of 20 MPa was applied to the water in the material tube 37, and the mold was clamped in that state. Subsequently, a pressure of 50 kN (axial pushing force) is applied in the axial direction to the pipe end sealing members 45A and 45B, and while the application of the hydraulic pressure is continued, the speed of the material pipe 37 is 5.0 mm / sec from both sides thereof. The axis was pushed by The hydraulic pressure was raised to 70 MPa when a portion of the material pipe was in contact with the inner bottom surface of the recess 39.

  As a result, as shown in FIG. 8, it was possible to obtain a hollow tube having a U-shaped bent portion and having a substantially zero inner radius of curvature of the U-shaped bent portion. Here, when the hollow tube product after molding was examined, it was confirmed that the outer surface of the U-shaped bent portion was accurately processed into the shape along the inner surface of the recess. Furthermore, it was also confirmed that the appearance of the U-shaped bent portion has a good appearance quality without any occurrence of cracks, irregularities, and wrinkles, in particular.

Example 2
The second embodiment corresponds to the second embodiment, and as a manufacturing apparatus, one having a counter member 49 as shown in FIG. 10 is used, and as a material tube, the same machine as the first embodiment is used. Structural carbon steel pipe: Using a material with an outer diameter of 38.1 mm and a thickness of 2.3 mm consisting of STKM 13B, the material pipe is processed according to the method shown in FIGS. A hollow tube with a part was produced. Here, the groove 35 of the mold 31 has a circular cross section as a whole and has an inner diameter of 38.1 mm. Further, the recess 39 of the upper mold member 33A has an inner surface in a direction orthogonal to the lengthwise direction of the groove 35, with a width W2 (distance between the inner side surfaces 39A and 39B) W2 in the direction along the lengthwise direction of the groove 35 The distance W1 is 40.0 mm, and the depth is 120.0 mm. On the other hand, as the protrusion 41, as shown in FIG. 9A, the cross section has a substantially triangular shape, and the height H thereof is 5.0 mm (therefore 0.13 times the outer diameter R of the material tube), The maximum inclination angle θ of both side surfaces was 60.0 °, and the tip surface was curved in a convex shape with a curvature radius of 0.5 mm.

  The tube end sealing members 45A and 45B are attached to both ends of the raw material pipe 37 in the same manner as in Example 1 and disposed between the upper mold groove 35A and the lower mold groove 35B, and the raw material pipe is filled with water as a pressurizing liquid. Then, a pressure of 50 MPa was applied to the water in the material tube 37, and the mold was clamped in that state. Subsequently, while applying 35 kN of pressing force (axial pushing force) in the axial direction to the pipe end sealing member to continue applying the hydraulic pressure, the raw material pipe 37 is axially pushed from both sides at a speed of 5.0 mm / sec. I was driven. Then, at a stage where a part of the material pipe was in contact with the inner bottom surface of the recess 39, the hydraulic pressure was raised to 65 MPa.

  As a result, as shown in FIG. 8, it was possible to obtain a hollow tube having a U-shaped bent portion and having a substantially zero inner radius of curvature of the U-shaped bent portion. Here, when the hollow tube product after molding was examined, it was confirmed that the outer surface of the U-shaped bent portion was accurately processed into the shape along the inner surface of the recess. Furthermore, it was also confirmed that the appearance of the U-shaped bent portion has a good appearance quality without any occurrence of cracks, irregularities, and wrinkles, in particular.

  Although the preferred embodiments and examples of the present invention have been described above, the present invention is of course not limited to these embodiments and examples, and additions and omissions of configurations are possible without departing from the scope of the present invention. , Substitution, and other changes are possible.

  The method and apparatus for manufacturing a U-shaped bent pipe according to the present invention is a heat exchanger, or an automobile part, an interior part of an building, an exterior part of an building, an outdoor device such as a gate, other parts of a chemical plant, or parts of various liquid processing devices Suitable for the production of hollow tubes used in

1A, 1B straight pipe portion 3, 3A to 3L U-shaped bent portion 5 hollow pipe (U-shaped bent pipe)
31 mold 33A upper mold member 33B lower mold member 35 groove portion 37 material tube 37A, 37B both end portions 37D local recessed portion 37E, 37F both side portions 39 recessed portion 39A, 39B side surface 39C bottom surface 41 protruding portion 41A tip 41B, 41C side surface 42 Drive means 45A, 45B Tube end sealing member 49 Counter member 49A Tip surface

Claims (10)

A method for manufacturing a hollow tube having a U-shaped bent portion which protrudes between two or more straight pipe sections in a direction forming a predetermined angle with the axial direction of the straight pipe section,
A groove is formed between the mold member forming the upper mold and the mold member forming the lower mold, into which the hollow material tube having a hollow tubular shape is inserted, and one of the upper and lower mold members is formed A recess is formed continuous with the space in the groove and recessed toward the inside of the mold member, and the other mold member of the upper and lower mold members is directed from the inner surface of the groove to the recess. Using a mold provided with a projecting portion
In a state where liquid pressure is applied to the inner space of the material pipe, the upper and lower mold members are clamped so that the material pipe is positioned in the groove portion, and the protruding portion A raw material pipe is formed by pressing the raw material pipe from both end sides in a direction along its axis while forming a local recessed portion in a part of the outer peripheral surface and subsequently continuing application of the hydraulic pressure. The both sides of the local recessed portion in the region are pushed into the recess while sliding relative to the protrusion, whereby the local bending portion is separated from the tip of the protrusion in the recess and the local portion thereof The material tube is bent and deformed in the recess so that the both sides of the target hollow portion are close to each other, thereby forming the U-shape bending portion of the material tube in the recess. Production method.   In pressing the portions on both sides of the local recessed portion in the material tube into the recess to form a bend, the portions on both sides of the local recessed portion in the material tube are bent and deformed until they contact each other. The method of manufacturing a U-shaped bent pipe according to claim 1.   In order to form a U-shaped bent portion by pressing portions on both sides of the local recessed portion in the material pipe into a U-shaped bent portion, a portion of the bending outer surface of the U-shaped bent portion contacts the bottom surface of the recessed portion The outer surface of the U-shaped bent portion in the recess is formed into a shape along the inner surface of the recess by increasing the hydraulic pressure applied to the inner space of the source tube while continuing pressurizing the material tube in the axial direction. The method for manufacturing a U-shaped bent pipe according to any one of claims 1 and 2, characterized in that: The mold further includes a counter member capable of advancing and retracting to the other mold member in the recess, in the one mold member.
In order to form a U-shaped bend by pushing portions on both sides of the local recessed portion in the material pipe into a U-shaped bend, at least a part of the outer surface of the bend in the recess of the material pipe is a tip end surface of the counter member The method for manufacturing a U-shaped bent pipe according to any one of claims 1 and 2, characterized in that the counter member is retracted in the recess while being in contact with the second member.   After the counter member reaches the last retreat position in the recess while a portion of the material pipe is in contact with the tip end surface of the counter member, while the pressurization in the axial direction of the material pipe is continued, the inner space of the material pipe is The U-shaped bend tube according to claim 4, characterized in that the U-shaped bend portion in the recess is formed in a shape along the tip end face of the counter member and the inner surface of the recess by increasing the hydraulic pressure applied. Manufacturing method.   After forming one or more U-shaped bent portions at predetermined locations in the middle portion of the material pipe by the method according to any one of claims 1 to 5, further, the U-shaped bent portions A process for producing a U-shaped bend, characterized in that the step of forming the U-shaped bend at another location by the same method is performed one or more times, thereby producing a hollow tube having a large number of bends. An apparatus for manufacturing a hollow tube having a U-shaped bent portion projecting in a direction forming a predetermined angle with the axial direction of a straight pipe portion between two or more straight pipe portions,
A mold comprising a mold member constituting an upper mold and a mold member constituting a lower mold ;
A tube end sealing member having a flow path for introducing a liquid for applying a hydraulic pressure to the inside of a hollow tubular material tube;
Mechanical pressure means for pressing and driving the tube end sealing member along the axial direction from the both end sides of the material tube toward the intermediate portion;
Equipped with
Between the upper and lower mold members, together with the groove in which the material pipe is inserted is formed, said one of the mold members of the upper and lower mold members, continuously in the space of the groove portion and the other mold member A recess that is recessed towards the interior of the
The other mold member of the upper and lower mold members is formed with a protrusion projecting from the inner surface of the groove toward the inside of the recess, and side surfaces on both sides of the protrusion in the lengthwise direction of the groove And the projection height of the projection from the inner surface of the groove toward the inside of the recess is from the inner surface of the groove to the bottom of the recess in the recess It is set smaller than the depth ,
An apparatus for manufacturing a U-shaped bent tube , wherein the U-shaped bent portion is formed in the recess .   The projection height of the projection from the inner surface of the groove toward the inside of the recess is not more than half the depth from the inner surface of the groove to the bottom of the recess in the recess. U-shaped bend tube manufacturing equipment. An apparatus for manufacturing a hollow tube having a U-shaped bent portion projecting in a direction forming a predetermined angle with the axial direction of a straight pipe portion between two or more straight pipe portions,
A mold comprising a mold member constituting an upper mold and a mold member constituting a lower mold ;
A tube end sealing member having a flow path for introducing a liquid for applying a hydraulic pressure to the inside of a hollow tubular material tube;
Mechanical pressure means for pressing and driving the tube end sealing member along the axial direction from the both end sides of the material tube toward the intermediate portion;
Equipped with
Between the upper and lower mold members, together with the groove in which the material pipe is inserted is formed, said one of the mold members of the upper and lower mold members, continuously in the space of the groove portion and the other mold member A recess recessed toward the inside of the mold, and the mold member is provided with a counter member capable of advancing and retracting to the other mold member of the upper and lower mold members in the recess;
The other mold member is formed with a protrusion projecting from the inner surface of the groove toward the inside of the recess, and the maximum inclination angle of the side surface in the longitudinal direction of the groove in the protrusion is 45 ° And the projection height of the projection from the inner surface of the groove toward the inside of the recess is smaller than the depth from the inner surface of the groove to the tip surface of the counter member in the recess. Yes,
An apparatus for manufacturing a U-shaped bent tube , wherein the U-shaped bent portion is formed in the recess .   The projection height of the projection from the inner surface of the groove toward the inside of the recess is not more than half the depth from the inner surface of the groove in the recess to the tip surface of the counter member. The manufacturing apparatus of the U-shaped bending pipe as described in 9.

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