JP6842145B1 - Bending pipe manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce or eliminate a gap between an end surface of a bulge on a curved pipe portion side and an outer peripheral surface of a straight pipe portion, and in addition, an oval-shaped bulge having a well-formed shape. And to provide a method of manufacturing a bent pipe that can be a well-shaped peripheral part. SOLUTION: A method for manufacturing a bent pipe is a first pipe expanding step of forming a second straight pipe portion of a bent pipe intermediate into a diameter-expanded second straight pipe portion, a diameter-expanded second straight pipe portion and a curved pipe portion intermediate. The second straight pipe portion for widening and the curved pipe portion having the shape to be finally obtained, respectively, and the widening second straight pipe portion is formed into an elliptical second straight pipe portion having an oval cross section. It includes a drawing process and a bulge forming process for forming a bulge. In the above drawing step, a drawing punch having a built-in drawing pin is used. [Selection diagram] FIG. 20

Description

The present invention relates to a method for manufacturing a bent pipe, for example, a method for manufacturing a bent pipe arranged in an engine room of an automobile.

As a technique related to the method for manufacturing a bent pipe, for example, there is one described in Patent Document 1. In Patent Document 1, the tip surface of a punch for bulge forming having a counterbored step portion is in contact with the outer peripheral surface of the first cavity portion and the first straight pipe portion in the clamp type second cavity portion. By contacting the lower surface formed on the extension of the contact line on the side of the second straight pipe portion, the outer diameter of the curved pipe portion on the side close to the second straight pipe portion remains expanded at a predetermined position. A method for manufacturing a bent pipe is described in which the bulge is formed so as to be in contact with the outer periphery of the first straight pipe portion by further expanding the stepped portion in the radial direction and outward toward the inner peripheral surface of the step portion.

According to the method for manufacturing a bent pipe described in Patent Document 1, it is possible to manufacture a bent pipe having a small gap or no gap between the end surface of the bulge on the curved pipe portion side and the outer peripheral surface of the straight pipe portion.

Japanese Patent No. 6546684

The method for manufacturing a bent pipe described in Patent Document 1 is a manufacturing method when the bulge is circular. On the other hand, recently, there is a need for manufacturing a bent pipe having an oval shape instead of a circular bulge. In order to obtain an oval bulge, it is necessary to make the shape of the mold portion for forming the bulge an oval shape. However, if the only change from the method of manufacturing a bent pipe when the bulge is circular is to change the shape of the mold portion, the oval bulge and its peripheral portion should have a neat shape. Is difficult.

The present invention has been made in view of the above circumstances, and an object of the present invention is to reduce or eliminate the gap between the end surface of the curved pipe portion of the bulge and the outer peripheral surface of the straight pipe portion. In addition to being able to provide a method of manufacturing a well-shaped oval bulge and a bent pipe that can be a well-shaped peripheral portion thereof.

In the method for manufacturing a bent pipe of the present invention, the pipe base pipe is bent, the first straight pipe portion is on one end side of the pipe base pipe, and the second straight pipe portion is on the other end side of the pipe base pipe. A temporary bending step of forming a curved portion between the first straight pipe portion and the second straight pipe portion while leaving the pipe portion, and a cavity for forming the curved portion into the shape of a curved pipe portion intermediate body. The bending pipe intermediate obtained in the temporary bending step is placed in a split-shaped molding die provided with a portion, and a strike bending R straightening pin is placed from the pipe end of the first straight pipe portion or the second straight pipe portion. The strike bending R straightening step of expanding the curved surface of the bending outer portion of the curved portion outward in the radial direction and forming the curved portion into the shape of the curved pipe portion intermediate body by inserting the first straight portion. A first cavity for accommodating the pipe portion, a second cavity for accommodating the curved pipe intermediate, and a second cavity having a recess for widening a part of the curved pipe intermediate. The first straight pipe portion is counterbored so as to have an inner diameter larger than the outer diameter of the second straight pipe portion and is arranged in the first cavity portion in a direction along the axial direction of the first straight pipe portion. A third cavity having a lower surface formed on an extension of the contact line on the side of the second straight pipe where the first cavity and the outer peripheral surface of the first straight pipe are in contact with each other in the cross-sectional view of the above. It is a split-shaped clamp type provided with, and has a pipe fixing step for fixing the first straight pipe portion and the curved pipe portion intermediate body, and an enlarged diameter portion having an outer diameter larger than the inner diameter of the second straight pipe portion. The first pipe expansion pin is opposed to the pipe end of the second straight pipe portion protruding outside the clamp mold in a state of being separated from the pipe end, and then the first pipe expansion pin is inserted from the pipe end of the second straight pipe portion. By doing so, from the first pipe expansion step of expanding the diameter of the second straight pipe portion and forming the second straight pipe portion into the enlarged diameter second straight pipe portion, and from the inner diameter of the enlarged diameter second straight pipe portion. A second pipe expanding pin having a widened portion having an oval cross section having a large width is opposed to the pipe end of the diameter-expanded second straight pipe portion protruding outside the clamp mold, and then the second pipe is opposed to the pipe end. By inserting the pipe expansion pin from the pipe end of the diameter-expanded second straight pipe portion, the diameter-expanded second straight pipe portion and a part of the curved pipe portion intermediate are widened, and the diameter-expanded second straight pipe portion is widened. A second pipe expanding step of forming the portion and the curved pipe portion intermediate body into a widening second straight pipe portion and a curved pipe portion having a shape to be finally obtained, and a drawing pin having an oval shape holding portion. A built-in squeeze punch that extends from the squeeze taper portion of each oval cross section whose opening is gradually narrowed from the entrance to the back and the squeeze taper portion formed behind the squeeze taper portion. Squeeze of oval cross section A drawing punch provided with a tube hole portion is opposed to the tube end of the widening second straight tube portion protruding outside the clamp mold in a state of being separated from the pipe end, and then the drawing pin is placed on the widening second straight pipe portion. The widening second straight pipe portion is squeezed by inserting the tip surface of the drawing punch into contact with the lower surface of the third cavity portion, and the widening second straight pipe portion is cross-sectionald. It is a bulge punch with a built-in bulge pin that has a drawing process for forming into the second straight pipe part of an oval oval and a shape holding part with an oval cross section, and corresponds to the oval-shaped bulge to be finally obtained. A bulge punch including a step portion formed at the entrance by counterboreing to a predetermined depth with the specified dimensions and a tubular hole portion having an oval cross section extending from the step portion formed behind the step portion. The bulge pin is inserted from the pipe end of the elliptical second straight pipe portion and the bulge pin is inserted from the pipe end of the elliptical second straight pipe portion. The bulge forming step is provided in which the bulge is formed so as to be in contact with the outer periphery of the first straight pipe portion by bringing the tip surface of the bulge punch into contact with the lower surface of the third cavity portion.

According to the method for manufacturing a bent pipe of the present invention, in addition to being able to reduce or eliminate the gap between the end surface of the bulge on the curved pipe portion side and the outer peripheral surface of the straight pipe portion, in addition to being able to eliminate the gap. It can be a well-shaped oval bulge and its peripheral parts of a well-shaped shape.

It is a figure which shows the shape of a pipe raw pipe. It is a figure which shows the shape of the bending pipe intermediate after a temporary bending process. It is a figure which shows the positional relationship of the bending pipe intermediate, the molding die, the strike bending R straightening pin, and the inner diameter regulation pin before the 1st strike bending R straightening process. It is a figure which shows the state which performed the 1st strike bending R straightening process from the state shown in FIG. It is a figure which shows the state which the bending pipe intermediate was turned over after the 1st strike bending R straightening step, and the 2nd strike bending R straightening step was carried out. It is a perspective view which shows the clamp type of a split type. It is a top view of the clamp type shown in FIG. It is a perspective view which shows the 1st tube expansion pin. It is a perspective view which shows the 2nd tube expansion punch. It is a front view of the 2nd tube expansion punch shown in FIG. It is a perspective view which shows the 2nd tube expansion pin. It is a perspective view which shows the drawing punch. It is a front view of the diaphragm punch shown in FIG. It is a perspective view which shows the aperture pin. It is a perspective view which shows the bulge punch. It is a front view of the bulge punch shown in FIG. It is a perspective view which shows the bulge pin. It is a figure for demonstrating the procedure of the 1st pipe expansion process. It is a figure for demonstrating the procedure of the 2nd pipe expansion process. It is a figure for demonstrating the procedure of a drawing process. It is a figure for demonstrating the procedure of the bulge forming process. It is a figure which shows the final form of a bent pipe. It is a photograph of the bent pipe in the final form taken with the opening side of the second straight pipe portion of the oval facing diagonally upward. It is a photograph of the bent pipe in the final form taken with the opening side of the second straight pipe portion of the oval facing sideways. It is a photograph of the bent pipe in the final form taken with the opening side of the second straight pipe portion of the oval facing downward.

Hereinafter, modes for carrying out the present invention will be described.

FIG. 1A shows a pipe raw pipe 1 which is a material of a bent pipe. As the pipe element pipe 1, for example, an aluminum alloy pipe such as an Al-Mn-based aluminum alloy A3003 pipe, a carbon steel pipe STSW1-B for high-pressure pipe, or a metal pipe such as a copper pipe is used. The outer diameter D1 of the pipe raw pipe 1 is not limited to this, but is, for example, φ17 mm. Further, the wall thickness of the pipe raw pipe 1 is not limited to this, but is, for example, 1.2 mm.

(Temporary bending process)
The temporary bending process will be described. As shown in FIG. 1B, the pipe raw pipe 1 is bent using a bending machine such as an NC bender, and the first straight pipe portion 2a and the pipe raw pipe 1 are placed on one end side of the pipe raw pipe 1. A curved portion 2c is formed between the first straight pipe portion 2a and the second straight pipe portion 2b while leaving the second straight pipe portion 2b on the other end side of the first straight pipe portion 2a and the curved portion. A bent pipe intermediate 2 having 2c and a second straight pipe portion 2b is manufactured.

(Strike bending radius correction process)
The strike bending radius straightening process will be described. The bending R (radius of curvature) of the curved portion 2c is corrected to form the curved portion 2c into the shape of the curved tube portion intermediate 3c (see FIG. 4). FIG. 2 is a diagram showing the positional relationship between the bending pipe intermediate 2, the molding die 10, the strike bending R straightening pin 20, and the inner diameter regulating pin 30 before the first strike bending R straightening step.

The molding die 10 is a split-shaped molding die, and is composed of a pair of symmetrically shaped molds. The figures showing the bending pipe intermediates 2 and 3 in the molding mold 10 portion shown in FIGS. 2 to 4 show the case where the pipe is cut at the contact surface between the pair of molds. FIG. 2 and the like show only one of the molding dies 10 composed of a pair of symmetrically shaped dies. When the bending pipe intermediate 2 is set in the molding die 10, the bending pipe intermediate 2 is sandwiched between one mold shown in FIG. 2 and the other mold (not shown).

The molding die 10 has a hollow portion 10c for molding the curved portion 2c into the shape of the curved tube portion intermediate 3c (see FIG. 4). The hollow portion 10c corresponds to the first inner peripheral surface 10c1 having a shape (radius of curvature) corresponding to the curved surface of the curved outer portion of the curved tube portion intermediate 3c (see FIG. 4) and the curved surface of the curved inner portion of the curved portion 2c. It has a second inner peripheral surface 10c2 having a shape (radius of curvature). Further, the molding die 10 has cavities 10a and 10b for accommodating the first straight pipe portion 2a and the second straight pipe portion 2b.

The strike bending R straightening pin 20 has a cylindrical main body portion 20a and a claw portion 20b having a curved surface corresponding to the shape (radius of curvature) of the first inner peripheral surface 10c1. The inner diameter regulating pin 30 has a cylindrical main body portion 30a and a tip portion 30b whose outer diameter decreases toward the tip end.

The strike bending R straightening step of the present embodiment is a two-step strike bending R straightening step of a first strike bending R straightening step and a second strike bending R straightening step.

<1st strike bending radius correction process>
As shown in FIG. 2, the bending pipe intermediate 2 is arranged in the hollow portions 10a to 10c of the molding die 10, the strike bending R straightening pin 20 is inserted from the pipe end of the first straight pipe portion 2a, and the strike bending is performed. The inner diameter regulating pin 30 is inserted from the pipe end of the second straight pipe portion 2b on the side where the R straightening pin 20 is not inserted.

As shown in FIG. 3, when the strike bending R correction pin 20 is inserted, the claw portion 20b presses the curved portion 2c from the inside. As a result, the curved surface of the bent outer portion of the curved portion 2c of the bent pipe intermediate 2 expands outward in the radial direction. Further, the bent inner portion of the curved portion 2c is pulled inward and deformed inward by the bending outer portion expanding outward in the radial direction. As can be seen by comparing FIGS. 2 and 3, the radius of curvature of the curved surface of the curved outer portion of the curved portion 2c and the radius of curvature of the curved surface of the curved surface of the curved inner portion of the curved portion 2c are both smaller.

<Second strike bending radius correction process>
Next, as shown in FIG. 4, the bending pipe intermediate 2 is turned over and the bending pipe intermediate 2 is arranged in the cavities 10a to 10c of the molding die 10, and the inner diameter regulating pin 30 is inserted during the first strike bending R straightening step. The pipe of the first straight pipe portion 2a into which the strike bending R straightening pin 20 is inserted from the pipe end of the inserted second straight pipe portion 2b and the strike bending R straightening pin 20 is inserted during the first strike bending R straightening step. Insert the inner diameter regulating pin 30 from the end.

When the strike bending R correction pin 20 is inserted, the claw portion 20b presses the bending portion 2c from the inside. As a result, the curved surface of the bent outer portion of the curved portion 2c of the bent pipe intermediate 2 expands outward in the radial direction. Further, the bent inner portion of the curved portion 2c is pulled inward and deformed inward by the bending outer portion expanding outward in the radial direction.

By carrying out the first strike bending R straightening step and the second strike bending R straightening step, the curved portion 2c shown in FIG. 2 is formed into the shape of the curved tube portion intermediate 3c shown in FIG. The radius of curvature of the curved surface of the curved outer portion of the curved tube portion intermediate 3c and the radius of curvature of the curved surface of the curved surface of the curved inner portion of the curved tube portion intermediate 3c are smaller than the radius of curvature of the corresponding curved surface of the curved portion 2c. That is, the radius of curvature of the curved tube portion intermediate 3c is smaller than the radius of curvature of the curved portion 2c.

In the first strike bending R straightening step, the strike bending R straightening pin 20 is inserted from the pipe end of the second straight pipe portion 2b, and the inner diameter regulating pin 30 is inserted from the pipe end of the first straight pipe portion 2a. At the same time as inserting, during the second strike bending R straightening step, the strike bending R straightening pin 20 is inserted from the pipe end of the first straight pipe portion 2a, and the inner diameter regulating pin is inserted from the pipe end of the second straight pipe portion 2b. 30 may be inserted.

Further, the bend shown in FIG. 4 can be obtained only by inserting the strike bending R straightening pin 20 from the first straight pipe portion 2a or the pipe end of the second straight pipe portion, that is, by only one strike bending R straightening step. If the shape of the pipe intermediate 3c is obtained, it is not a two-step strike bending R straightening step of a first strike bending R straightening step and a second strike bending R straightening step, but a one-step strike bending R straightening step. You may. By carrying out the two-step strike bending R straightening step as described above, the curved portion 2c can be more reliably and stably formed into the shape of the curved tube portion intermediate 3c.

(Pipe fixing process)
The pipe fixing process will be described. 5 and 6 are views showing a split-shaped clamp mold 40 for setting (fixing) the bending pipe intermediate 3 after the strike bending R straightening step.

The clamp mold 40 is a split-shaped clamp mold, and is composed of a pair of symmetrical molds. 5 and 6 show only one of the clamp molds 40, which consists of a pair of symmetrical molds. When setting the bending pipe intermediate 3 in the clamp mold 40, in other words, when fixing the bending pipe intermediate 3 with the clamp mold 40, one mold shown in FIG. 5 and the other mold shown in FIG. Then, the bending pipe intermediate 3 is sandwiched.

The clamp type 40 includes a first cavity 40a for accommodating the first straight pipe portion 2a of the bent pipe intermediate 3, a second cavity 40b for accommodating the curved pipe intermediate 3c, and a second straight pipe portion 2b. It has a third cavity portion 40c that is counterbored so as to have an inner diameter larger than the outer diameter.

The second cavity portion 40b is a cavity portion for molding into the shape of the curved tube portion 4c (see FIG. 21) for which the curved tube portion intermediate 3c is finally obtained. The second cavity portion 40b has a recess 40b1 for widening a part of the curved pipe portion intermediate 3c (on the side of the second straight pipe portion 2b).

As shown in FIG. 17 and the like, the third cavity portion 40c is the first in a cross-sectional view of the first straight pipe portion 2a in the direction along the axial direction of the first straight pipe portion 2a arranged in the first cavity portion 40a. It has a lower surface 40c1 formed on an extension of a contact line L on the side of the second straight pipe portion 2b where the hollow portion 40a and the outer peripheral surface of the first straight pipe portion 2a come into contact with each other. The figure showing the bent pipe intermediate 3 in the clamp mold 40 portion shown in FIG. 17 shows the case where the pipe is cut at the contact surface between the pair of molds (the same applies to FIGS. 18 to 20). ..

In the clamp mold 40 composed of a pair of symmetrically shaped molds, at least a portion of the bent pipe intermediate 3 that is closer to the first straight pipe portion 2a and the curved pipe portion intermediate 3c. Is sandwiched and fixed.

As shown in FIG. 17 and the like, in the present embodiment, the pipe inner support pin 45 is inserted from the pipe end of the first straight pipe portion 2a to the vicinity of the curved pipe portion intermediate 3c in this pipe fixing step. By inserting the pipe inner support pin 45, it is possible to prevent the first straight pipe portion 2a from buckling in the subsequent steps (first pipe expansion step, second pipe expansion step, drawing step, and bulge forming step). it can. Depending on the length of the second straight pipe portion 2b, the second straight pipe portion 2b is set before the bending pipe intermediate 3 is set in the clamp mold 40 (the bending pipe intermediate 3 is fixed by the clamp mold 40). The second straight pipe portion 2b is shortened by cutting to a desired length.

(1st pipe expansion process)
The first pipe expansion step will be described. FIG. 7 shows a first pipe expanding step of expanding the diameter of the second straight pipe portion 2b of the bent pipe intermediate body 3 and forming the second straight pipe portion 2b into the enlarged diameter second straight pipe portion 3b (see FIG. 18). It is a perspective view which shows the 1st tube expansion pin 50 to be used. FIG. 17 is a diagram for explaining the procedure of the first pipe expansion step.

As shown in FIGS. 7 and 17, the first pipe expansion pin 50 has a columnar diameter expansion portion 50a having an outer diameter larger than the inner diameter of the second straight pipe portion 2b and a curved surface shape of the second cavity portion 40b. It has a tip claw portion 50b having a corresponding curved surface. The outer diameter of the tip claw portion 50b is smaller than the outer diameter of the enlarged diameter portion 50a. A tapered portion 50c is provided between the tip claw portion 50b and the enlarged diameter portion 50a. Further, a flat surface portion 50a1 extending in the axial direction of the diameter-expanded portion 50a is provided on the surface of the diameter-expanded portion 50a. The flat surface portions 50a1 are provided at two locations in total, which are offset by 180 degrees from each other in the circumferential direction of the enlarged diameter portion 50a. The distance between the two flat surface portions 50a1 is smaller than the outer diameter of the enlarged diameter portion 50a. The two flat surface portions 50a1 may not be provided on the surface of the enlarged diameter portion 50a. That is, the enlarged diameter portion 50a may have a perfect cylindrical shape (circular cross section).

The first expansion pin 50 is built in the first expansion punch 60. The first expansion tube punch 60 has a tubular portion 60a. With the first tube expansion pin 50 inserted into the bottomed tubular hole portion 60a1 of the tubular portion 60a, the first tube expansion pin 50 is fixed to the first tube expansion punch 60 with a bolt (not shown) or the like. The outer shape of the tubular portion 60a and the tubular hole portion 60a1 are both circular. There is a gap between the enlarged diameter portion 50a of the first pipe expanding pin 50 and the tubular hole portion 60a1 of the first pipe expanding punch 60, and the second straight pipe portion 2b is inserted into this gap.

As shown in FIG. 17, the first pipe expansion punch 60 having the first pipe expansion pin 50 built therein is opposed to the pipe end of the second straight pipe portion 2b projecting to the outside of the clamp mold 40, and then opposed to the pipe end. The first pipe expansion pin 50 is inserted from the pipe end of the second straight pipe portion 2b, and the tip surface 60a2 of the first pipe expansion punch 60 is brought into contact with the lower surface 40c1 of the third cavity portion 40c of the clamp type 40.

As shown on the right in FIG. 18, when the first pipe expansion pin 50 is inserted from the pipe end of the second straight pipe portion 2b, the tapered portion 50c and the diameter expansion portion 50a of the first pipe expansion pin 50 become the second straight pipe. The diameter of the portion 2b is expanded, and the second straight pipe portion 2b is formed into an enlarged diameter second straight pipe portion 3b having a diameter larger than that of the second straight pipe portion 2b and having a substantially circular cross section. Since the first pipe expansion pin 50 is provided with the tapered portion 50c, the diameter of the second straight pipe portion 2b can be smoothly expanded. Further, since the two flat surface portions 50a1 are provided on the surface of the diameter-expanded portion 50a, the cross section of the formed diameter-expanded second straight pipe portion 3b becomes a slightly oblong circle instead of a perfect circle, and the next step ( It is easy to process (expand) the diameter-expanding second straight pipe portion 3b in the second pipe expanding step).

(Second pipe expansion process)
The second pipe expansion step will be described. FIG. 8 is a perspective view showing the second tube expansion punch 80, and FIG. 9 is a front view of the second tube expansion punch 80 shown in FIG. FIG. 10 is a perspective view showing the second expansion pin 70. FIG. 18 is a diagram for explaining the procedure of the second pipe expansion step.

The second pipe expanding pin 70 has a widening portion 70a having an oval cross section having a width larger than the inner diameter of the diameter-expanding second straight pipe portion 3b. The widening portion 70a is composed of a widening main body portion 70a1 having a constant width and height, and a tapered widening tip portion 70a2.

The second expansion pin 70 is built in the second expansion punch 80. The second expansion tube punch 80 has a tubular portion 80a. The second tube expansion pin 70 is fixed to the second tube expansion punch 80 with a bolt (not shown) or the like in a state where the second tube expansion pin 70 is inserted into the bottomed tube hole portion 80a1 of the tubular portion 80a. The outer shape of the tubular portion 80a is circular, whereas the tubular hole portion 80a1 has an elongated cross section. Further, the second expansion tube punch 80 has a tapered portion 80a2 having an oval cross section whose opening is gradually narrowed from the entrance to the back. The tubular hole portion 80a1 is formed behind the tapered portion 80a2 and extends from the tapered portion 80a2. There is a gap between the widening portion 70a of the second pipe expanding pin 70 and the tubular hole portion 80a1 of the second pipe expanding punch 80, and the diameter-expanding second straight pipe portion 3b is inserted into this gap.

As shown in FIG. 18, the second pipe expansion punch 80 in which the second pipe expansion pin 70 is built is opposed to the pipe end of the diameter-expanding second straight pipe portion 3b projecting to the outside of the clamp mold 40 in a state of being separated from the pipe end. After that, the second pipe expansion pin 70 is inserted from the pipe end of the diameter-expanding second straight pipe portion 3b, and the tip surface 80a3 of the second pipe expansion punch 80 abuts on the lower surface 40c1 of the third cavity portion 40c of the clamp type 40. Let me.

When the second pipe expansion pin 70 is inserted from the pipe end of the diameter-expanding second straight pipe portion 3b, the widening portion 70a of the second pipe expansion pin 70 widens the diameter-expanding second straight pipe portion 3b. In addition to this, as shown on the right in FIG. 19, in the process in which the tip surface 80a3 of the second tube expansion punch 80 comes into contact with the lower surface 40c1 of the third cavity portion 40c of the clamp type 40, the second tube expansion punch 80 The diameter-expanded second straight pipe portion 3b is recessed in the axial direction of the first straight pipe portion 2a by the tubular hole portion 80a1 having an oval cross section. As a result, the widened second straight pipe portion 3b is formed into the widened second straight pipe portion 4b having an elongated cross section. The widened second straight pipe portion 4b is slightly larger than the elliptical second straight pipe portion 5b shown in FIGS. 20 and 21.

Further, the tube hole portion 80a1 of the second tube expansion punch 80 has an elongated cross section, and the tapered portion 80a2 having a widened tip is provided at the tip portion of the tube hole portion 80a1. As shown on the right in FIG. 19, in the process in which the tip surface 80a3 abuts on the lower surface 40c1 of the third cavity 40c of the clamp type 40, the widening second straight pipe portion is widened in the axial direction of the first straight pipe portion 2a. The bulge intermediate 6 is formed at the boundary between the 4b and the curved tube portion 4c.

The bulge intermediate 6 is a portion (convex portion) that will later become the bulge 7. By forming the bulge intermediate 6 in this second tube expansion step, it is possible to form a bulge 7 having a more neat shape in a later bulge forming step.

Further, when the second pipe expansion pin 70 is inserted from the pipe end of the diameter-expanding second straight pipe portion 3b, the widening tip portion 70a2 of the second pipe expansion pin 70 presses the curved pipe portion intermediate 3c from the inside. Since the second cavity 40b of the clamp type 40 is provided with a recess 40b1 (see FIG. 5), when the widening tip 70a2 presses the curved tube intermediate 3c from the inside, it is one of the curved tube intermediates 3c. The portion (second straight pipe portion 2b side) is widened and deformed so as to fit into the recess 40b1, and as a result, the curved pipe portion intermediate 3c becomes a curved pipe portion 4c (see FIG. 21) having a shape to be finally obtained. It is molded. As shown in FIGS. 21 and 24, the curved tube portion 4c has a pair of left and right bulging portions 5. The bulging portion 5 is a portion in which a part (second straight pipe portion 2b side) of the curved pipe portion intermediate 3c is widened and deformed.

In this way, by the second pipe expanding step, the diameter-expanded second straight pipe portion 3b and the curved pipe portion intermediate 3c are formed into the widened second straight pipe portion 4b and the curved pipe portion 4c, respectively.

(Aperture process)
The drawing process will be described. FIG. 11 is a perspective view showing the diaphragm punch 100, and FIG. 12 is a front view of the diaphragm punch 100 shown in FIG. FIG. 13 is a perspective view showing the aperture pin 90. FIG. 19 is a diagram for explaining the procedure of the drawing process.

The drawing pin 90 has a shape-holding portion 90a having an oval cross section. The cross-sectional shape of the shape-retaining portion 90a and its dimensions are substantially equal to the cross-sectional inner shape of the elliptical second straight pipe portion 5b to be obtained in the main drawing step and its dimensions.

The aperture pin 90 is built in the aperture punch 100. The drawing punch 100 has a tubular portion 100a. With the diaphragm pin 90 inserted into the bottomed diaphragm hole 100a1 of the tubular portion 100a, the diaphragm pin 90 is fixed to the diaphragm punch 100 with bolts (not shown) or the like. The outer shape of the tubular portion 100a is circular, and the throttle tubular hole portion 100a1 has an oval cross section. Further, the drawing punch 100 has a drawing tapered portion 100a2 having an oval cross section whose opening is gradually narrowed from the entrance to the back. The diaphragm hole portion 100a1 is formed behind the diaphragm taper portion 100a2 and extends from the diaphragm taper portion 100a2. As shown in FIG. 19, there is a gap between the shape holding portion 90a of the throttle pin 90 and the throttle cylinder hole portion 100a1 of the throttle punch 100, and the widening second straight pipe portion 4b enters the gap. There is.

As shown in FIG. 19, the throttle taper portion 100a2 is the shaft of the throttle punch 100 in the taper portion 101 of the boundary portion between the widening second straight pipe portion 4b and the curved pipe portion 4c and which abuts on the curved inner portion 103. The inclination angle α1 with respect to the direction is made larger than the inclination angle α2 with respect to the axial direction in the tapered portion 102 that abuts on the curved outer side portion 104 of the boundary portion.

A diaphragm punch 100 having a built-in throttle pin 90 is opposed to the end of the widening second straight pipe portion 4b protruding outside the clamp mold 40 in a state of being separated from the pipe end, and then the throttle pin 90 is placed at the widening second straight pipe portion 4b. While inserting from the pipe end of 4b, the tip surface 100a3 of the drawing punch 100 is brought into contact with the lower surface 40c1 of the third cavity portion 40c of the clamp type 40.

As shown on the right in FIG. 20, from the state where the drawing punch 100 is separated from the pipe end of the widening second straight pipe portion 4b, the tip surface 100a3 hits the lower surface 40c1 of the third cavity portion 40c of the clamp type 40. In the process of contacting, the widening second straight pipe portion 4b having an elongated cross section is narrowed over the entire circumference by the narrowing taper portion 100a2 and the narrowing cylinder hole portion 100a1 of the drawing punch 100, and as a result, the widening second straight pipe portion 4b is squeezed. It is formed into an elliptical second straight pipe portion 5b having an oval cross section to be finally obtained. Further, the drawing taper portion 100a2 of the drawing punch 100 forms a bulge intermediate 6 over the entire circumference at the boundary between the elliptical second straight pipe portion 5b and the curved pipe portion 4c.

Here, since the inclination angle α1> the inclination angle α2, the bulge intermediate 6 of the bent inner portion 103 is a first straight pipe than the bulge intermediate 6 of the bent outer portion 104 due to the throttle taper portion 100a2. It greatly extends toward the portion 2a (see FIG. 20). The bent inner portion 103 and the bent outer portion 104 are portions that are somewhat difficult to form into a well-shaped bulge 7 (see FIG. 21), and the bent inner portion 103 has a more neat shape than the bent outer portion 104. This is a portion that is difficult to mold into the bulge 7 (see FIG. 21). Since the inclination angle α1> the inclination angle α2, the bulge intermediate 6 of the bending inner portion 103 greatly extends toward the first straight pipe portion 2a side. As a result, the bulge 7 can be easily formed. As a result, in the next bulge forming step, the bulge 7 having a more neat shape can be formed at the bent inner portion 103. It is not essential that the tilt angle α1> the tilt angle α2.

Further, by using the drawing punch 100 having the drawing pin 90 having the shape holding portion 90a having an oval cross section built-in in the drawing step, the second straight pipe widened by the drawing taper part 100a2 and the drawing tube hole part 100a1 of the drawing punch 100. When the portion 4b is squeezed, the inner surface of the widening second straight pipe portion 4b is supported by the diaphragm pin 90, so that the oval second straight pipe portion 5b having a well-formed shape can be obtained. In the bending pipe manufacturing method described in Patent Document 1 (Patent No. 6546684), the member corresponding to the drawing pin 90 is not used in the step corresponding to the drawing step.

(Bulge forming process)
The bulge forming process will be described. FIG. 14 is a perspective view showing the bulge punch 120, and FIG. 15 is a front view of the bulge punch 120 shown in FIG. FIG. 16 is a perspective view showing the bulge pin 110. FIG. 20 is a diagram for explaining the procedure of the bulge forming step.

The bulge pin 110 has a shape-holding portion 110a having an oval cross section. The cross-sectional shape of the shape-holding portion 110a and its dimensions are substantially equal to the cross-sectional inner shape of the elliptical second straight pipe portion 5b and its dimensions.

The bulge pin 110 is built in the bulge punch 120. The bulge punch 120 has a tubular portion 120a. With the bulge pin 110 inserted into the bottomed tubular hole portion 120a1 of the tubular portion 120a, the bulge pin 110 is fixed to the bulge punch 120 with a bolt (not shown) or the like. The outer shape of the tubular portion 120a is circular, and the tubular hole portion 120a1 has an oval cross section. Further, the bulge punch 120 has a step portion 120a2 formed at the entrance by counterboreing to a predetermined depth with dimensions corresponding to the oval-shaped bulge 7 to be finally obtained. The tubular hole portion 120a1 is formed behind the stepped portion 120a2 and extends from the stepped portion 120a2. As shown in FIG. 20, there is a gap between the shape holding portion 110a of the bulge pin 110 and the tubular hole portion 120a1 of the bulge punch 120, and the oval second straight pipe portion 5b is inserted into this gap.

As shown in FIG. 15, since the step portion 120a2 is a step portion for forming the oval bulge 7, it has an oval ring shape. When the step portion 120a2 is viewed from the front, the width of the step portion 120a2 at the longitudinal central portion 105 of the step portion 120a2 is wider than the width of the step portion 120a2 at the longitudinal end portion 106. .. Further, the width of the step portion 120a2 is smoothly widened from the longitudinal end portion 106 toward the longitudinal central portion 105.

The longitudinal central portion 105 is a portion of the bent pipe intermediate 3 corresponding to the bent inner portion 103 and the bent outer portion 104 (see FIG. 20). The bent inner portion 103 and the bent outer portion 104 are portions that are somewhat difficult to form into a well-shaped bulge 7 (see FIG. 21). When the width of the step portion 120a2 at the longitudinal central portion 105 is wider than the width of the step portion 120a2 at the longitudinal end portion 106, the bulge intermediate 6 tends to extend to the longitudinal central portion 105 of the step portion 120a2. As a result, a bulge 7 having a more neat shape can be formed.

The width of the step portion 120a2 at the central portion 105 in the longitudinal direction may be equal to the width of the step portion 120a2 at the end portion 106 in the longitudinal direction. That is, in the oval-shaped ring-shaped step portion 120a2, when the step portion 120a2 is viewed from the front, the step portion may have a width of uniform dimensions over the entire circumference.

The bulge punch 120 in which the bulge pin 110 is built is opposed to the pipe end of the elliptical second straight pipe portion 5b protruding outside the clamp mold 40, and then the bulge pin 110 is placed on the oval second straight pipe portion 5b. The tip surface 120a3 of the bulge punch 120 is brought into contact with the lower surface 40c1 of the third cavity portion 40c of the clamp type 40.

In the process in which the bulge punch 120 is separated from the pipe end of the elliptical second straight pipe portion 5b and its tip surface 120a3 comes into contact with the lower surface 40c1 of the third cavity portion 40c of the clamp type 40, the step portion 120a2 of the bulge punch 120 As a result, the bulge intermediate 6 is compressed in the axial direction of the elliptical second straight pipe portion 5b and extends in the radial direction. As a result, the bulge intermediate 6 is formed into an oval-shaped bulge 7 (see FIG. 21) that is in contact with the outer circumference of the first straight pipe portion 2a. The oval-shaped bulge 7 is an oval-shaped annular convex portion, in other words, an oval-shaped brim and an oval-shaped ring.

The stepped portion 110b provided at the base end of the shape holding portion 110a of the bulge pin 110 serves as a stopper for the pipe end of the elliptical second straight pipe portion 5b. The axial distance of the bulge punch 120 between the tip surface 120a3 of the bulge punch 120 and the stepped portion 110b of the bulge pin 110 is the pipe end and the third cavity portion of the elliptical second straight pipe portion 5b protruding outside the clamp mold 40. When the distance between the oval second straight pipe portion 5b and the lower surface 40c1 of 40c is shorter than the axial distance, the tip surface 120a3 of the bulge punch 120 comes into contact with the lower surface 40c1 of the third cavity 40c, and the bulge pin The stepped portion 110b of 110 pushes the elliptical second straight pipe portion 5b into the third cavity portion 40c. Also by this action, the bulge intermediate 6 is compressed in the axial direction of the elliptical second straight pipe portion 5b and extends in the radial direction.

The axial distance of the bulge punch 120 between the tip surface 120a3 of the bulge punch 120 and the stepped portion 110b of the bulge pin 110 is the pipe end and the third of the elliptical second straight pipe portion 5b protruding outside the clamp mold 40. It may be longer than the axial distance of the elliptical second straight pipe portion 5b between the hollow portion 40c and the lower surface 40c1, or may be the same distance.

The final form of the bent pipe 8 provided with the oval bulge 7 is shown in FIGS. 21 to 24. As shown in FIGS. 21 to 24, the bent pipe 8 obtained through each of the above steps has a small gap between the end surface 7a of the bulge 7 on the curved pipe portion side and the outer peripheral surface of the first straight pipe portion 2a. (There are almost no gaps). That is, according to the method for manufacturing a bent pipe of the present embodiment, the gap between the end surface 7a of the bulge 7 on the curved pipe portion side and the outer peripheral surface of the straight pipe portion can be reduced or eliminated. ..

Regarding the actually manufactured bent pipes 8 shown in FIGS. 22 to 24, two spools 9 are formed in the first straight pipe portion 2a. These spools 9 have nothing to do with the present invention.

In the present invention, after performing a two-step pipe expanding step of a first pipe expanding step and a second pipe expanding step, a drawing step is performed to form the second straight pipe portion 2b of the pipe raw pipe 1 in an oval shape, which is the final form. 2 Form into a straight pipe portion 5b. By performing the above-mentioned two-step pipe expanding step before performing the drawing step, the second straight pipe portion 2b of the pipe raw pipe 1 can be gradually made into the final form of the elliptical second straight pipe portion 5b. It can be a well-shaped elliptical second straight pipe portion 5b connected to the bulge 7. Further, the curved pipe portion 4c connected to the bulge 7 can also be a curved pipe portion 4c having a pair of left and right bulging portions 5 and having a well-shaped shape. Then, in the bulge forming step, the oval bulge 7 to be finally obtained is formed to obtain a bulge 7 having a neat shape. Since the bulge 7 has an oval shape, the bent pipe 8 can be arranged in a narrow place.

The above embodiment can be modified as follows.

It is not essential to use the inner diameter regulating pin 30. That is, it is not necessary to use the inner diameter regulating pin 30 in the first strike bending R straightening step. Further, in the second strike bending R straightening step, it is not necessary to use the inner diameter regulating pin 30. In the strike bending R straightening step, it is not necessary to use the inner diameter regulating pin 30.

In the first pipe expanding step, the second pipe expanding step, the drawing step, and the bulge forming step, it is not essential to support the first straight pipe portion 2a from the inside with the pipe inner support pin 45. That is, it is not necessary to use the pipe inner support pin 45 in the pipe fixing step.

The first expansion punch 60 is not essential. For example, the first pipe expansion pin 50 held by some known method without using the first pipe expansion punch 60 is opposed to the pipe end of the second straight pipe portion 2b protruding outside the clamp mold 40 in a state of being separated from the pipe end. After that, the diameter of the second straight pipe portion 2b may be expanded by inserting the first pipe expansion pin 50 from the pipe end of the second straight pipe portion 2b. By using the first pipe expansion punch 60 as in the above embodiment, the diameter expansion of the second straight pipe portion 2b by the first pipe expansion pin 50 becomes more stable.

The tubular hole portion 80a1 of the second expansion tube punch 80 may be a hole portion having a circular cross section instead of an oval cross section. Even if the tubular hole portion 80a1 is a hole portion having a circular cross section, the diameter is expanded by the second tube expansion pin 70 having the widening portion 70a having an oval cross section having a width larger than the inner diameter of the diameter-expanding second straight pipe portion 3b. 2 The straight pipe portion 3b can be widened. When the diameter-expanded second straight pipe portion 3b is widened, the diameter-expanded second straight pipe portion 3b is naturally recessed in the axial direction of the first straight pipe portion 2a. As a result, the widened second straight pipe portion 3b becomes the widened second straight pipe portion 4b having an elongated cross section.

The second expansion punch 80 is not essential. For example, the second pipe expansion pin 70 held by some known method without using the second pipe expansion punch 80 faces the pipe end of the diameter-expanding second straight pipe portion 3b protruding outside the clamp mold 40 in a state of being separated from the pipe end. Then, by inserting the second pipe expansion pin 70 from the pipe end of the diameter-expanded second straight pipe portion 3b, even if a part of the diameter-expanded second straight pipe portion 3b and the curved pipe portion intermediate 3c is widened. Good. By using the second pipe expanding punch 80 as in the above embodiment, the widening of a part of the diameter-expanded second straight pipe portion 3b and the curved pipe portion intermediate 3c by the second pipe expanding pin 70 becomes more stable.

In the present application, the "ellipse" includes not only an ellipse whose two long sides are parallel but also a circle defined by an ellipse.

In addition, it is of course possible to make various changes within the range that can be assumed by those skilled in the art.

1: Pipe raw pipe 2: Bent pipe intermediate 2a: 1st straight pipe 2b: 2nd straight pipe 2c: Curved 3b: Expanded diameter 2nd straight pipe 3c: Curved pipe intermediate 4b: Widening 2nd Straight pipe part 4c: Curved pipe part 5b: Oval second straight pipe part 7: Bulge 8: Bending pipe 10: Molding mold 10c: Cavity part 20: Strike bending R straightening pin 30: Inner diameter regulating pin 40: Clamp type 40a: First cavity 40b: Second cavity 40b1: Recess 40c: Third cavity 40c1: Lower surface 40: Clamp type 50: First tube expansion pin 50a: Diameter expansion 60: First tube expansion punch 70: Second Tube expansion pin 70a: Widening portion 80: Second tube expansion punch 80a1: Tube hole portion 80a2: Tapered portion 90: Squeezing pin 90a: Shape holding portion 100: Squeezing punch 100a1: Squeezing tube hole portion 100a2: Squeezing taper portion 101, 102: Tapered Part 103: Bending inner part 104: Bending outer part 110: Bulge pin 120: Bulge punch 120a1: Cylinder hole part 120a2: Step part α1, α2: Tilt angle

Claims (7)

The pipe raw pipe is bent, and the first straight pipe portion is left on one end side of the pipe raw pipe and the second straight pipe portion is left on the other end side of the pipe raw pipe. A temporary bending step of forming a curved portion between the pipe portion and the second straight pipe portion,
The bent pipe intermediate obtained in the temporary bending step is arranged in a split mold having a cavity for forming the curved portion into the shape of the curved pipe intermediate, and the first straight pipe portion is formed. Alternatively, by inserting a strike bending R straightening pin from the pipe end of the second straight pipe portion, the curved surface of the bending outer portion of the curved portion is enlarged outward in the radial direction, and the curved portion is inserted in the middle of the curved pipe portion. Strike bending R correction process to shape the body shape,
A second cavity portion accommodating the first straight pipe portion and a second cavity portion accommodating the curved pipe portion intermediate body having a recess for widening a part of the curved tube portion intermediate body. The first straight pipe portion is counterbored so as to have an inner diameter larger than the outer diameter of the cavity portion and the second straight pipe portion, and is arranged in the first cavity portion in a direction along the axial direction of the first straight pipe portion. A third having a lower surface formed on an extension of a contact line on the side of the second straight pipe portion where the first cavity portion and the outer peripheral surface of the first straight pipe portion come into contact with each other in a cross-sectional view of the straight pipe portion. A pipe fixing step of fixing the first straight pipe portion and the curved pipe portion intermediate with a split-shaped clamp type including a hollow portion.
A first pipe expansion pin having a diameter-expanded portion having an outer diameter larger than the inner diameter of the second straight pipe portion is opposed to the pipe end of the second straight pipe portion protruding outside the clamp mold in a state of being separated from the pipe end. After that, by inserting the first pipe expansion pin from the pipe end of the second straight pipe portion, the diameter of the second straight pipe portion is expanded, and the second straight pipe portion is expanded into the second straight pipe portion. The first tube expansion step to mold and
The second pipe expansion pin having a widening portion having an oblong cross section having a width larger than the inner diameter of the diameter-expanding second straight pipe portion is separated from the pipe end of the diameter-expanding second straight pipe portion protruding outside the clamp mold. Then, by inserting the second pipe expansion pin from the pipe end of the diameter-expanded second straight pipe portion, the diameter-expanded second straight pipe portion and a part of the curved pipe portion intermediate body are inserted. A second pipe expanding step of widening the diameter and forming the widened second straight pipe portion and the curved pipe portion intermediate body into the widened second straight pipe portion and the curved pipe portion having the shape to be finally obtained, respectively.
A diaphragm punch with a built-in diaphragm pin having a shape-retaining portion with an oval cross section, and a diaphragm taper portion of each elliptical cross section whose opening is gradually narrowed from the entrance to the back, and a diaphragm taper portion deeper than the diaphragm taper portion. In a state where the diaphragm punch including the diaphragm hole portion having an oblong cross section extending from the throttle taper portion formed in the clamp mold is separated from the pipe end of the widening second straight pipe portion protruding to the outside of the clamp mold. After that, the throttle pin is inserted from the tube end of the widening second straight pipe portion, and the tip surface of the throttle punch is brought into contact with the lower surface of the third cavity portion to bring the widening second. A drawing process in which the straight pipe portion is squeezed and the widened second straight pipe portion is formed into an elliptical second straight pipe portion having an oval cross section.
It is a bulge punch with a built-in bulge pin having a shape holding part with an oval cross section, and is formed at the entrance by counterbore to a predetermined depth with dimensions corresponding to the oval bulge to be finally obtained. The elliptical second straight pipe portion in which a bulge punch having a stepped portion and a tubular hole portion having an oblong cross section extending from the stepped portion formed behind the stepped portion is projected to the outside of the clamp mold. The bulge pin is inserted from the pipe end of the elliptical second straight pipe portion, and the tip surface of the bulge punch is brought into contact with the lower surface of the third cavity portion. A bulge forming step of forming the bulge so as to be in contact with the outer periphery of the first straight pipe portion.
A method of manufacturing a bent pipe. In the method for manufacturing a bent pipe according to claim 1,
The strike bending radius correction step is
The bending pipe intermediate is arranged in the molding die, the strike bending R straightening pin is inserted from the pipe end of the first straight pipe portion or the second straight pipe portion, and the strike bending R straightening pin is inserted. The first strike bending R straightening step of inserting the inner diameter regulating pin from the pipe end of the first straight pipe portion or the second straight pipe portion on the side not to be inserted,
The first straight pipe portion or the second straight pipe portion in which the bending pipe intermediate is turned over and the bending pipe intermediate is placed in the molding die and the inner diameter regulating pin is inserted during the first strike bending R straightening step. The pipe end of the first straight pipe portion or the second straight pipe portion into which the strike bending R straightening pin is inserted and the strike bending R straightening pin is inserted during the first strike bending R straightening step. The second strike bending R straightening step of inserting the inner diameter regulating pin from
A method of manufacturing a bent pipe. In the method for manufacturing a bent pipe according to claim 1 or 2.
In the first pipe expansion step, the first pipe expansion punch incorporating the first pipe expansion pin is opposed to the pipe end of the second straight pipe portion protruding outside the clamp mold, and then, the above. The first pipe expansion pin is inserted from the pipe end of the second straight pipe portion, and the tip surface of the first pipe expansion punch is brought into contact with the lower surface of the third cavity portion.
How to manufacture bent pipes. In the method for manufacturing a bent pipe according to any one of claims 1 to 3.
In the second pipe expansion step, the second pipe expansion punch incorporating the second pipe expansion pin is opposed to the pipe end of the diameter-expanding second straight pipe portion protruding outside the clamp mold, and then opposed to the pipe end. The second pipe expansion pin is inserted from the pipe end of the diameter-expanding second straight pipe portion, and the tip surface of the second pipe expansion punch is brought into contact with the lower surface of the third cavity portion.
How to manufacture bent pipes. In the method for manufacturing a bent pipe according to claim 4.
The second expansion tube punch has a tapered portion of each oval cross section whose opening is gradually narrowed from the entrance to the back, and a cylinder having an oval cross section extending from the tapered portion formed behind the tapered portion. With a hole,
How to manufacture bent pipes. In the method for manufacturing a bent pipe according to any one of claims 1 to 5.
The squeeze taper portion of the squeeze punch has an inclination angle with respect to the axial direction of the squeeze punch at the tapered portion of the boundary portion between the widening second straight pipe portion and the curved pipe portion that abuts on the curved inner portion. It is made larger than the inclination angle with respect to the axial direction in the tapered portion of the boundary portion that abuts on the bent outer portion.
How to manufacture bent pipes. In the method for manufacturing a bent pipe according to any one of claims 1 to 6.
When the step portion of the bulge punch is viewed from the front, the width of the step portion at the central portion in the longitudinal direction is wider than the width at the end portion of the step portion in the longitudinal direction.
How to manufacture bent pipes.