CN114147135A - Method for manufacturing bent pipe - Google Patents
Method for manufacturing bent pipe Download PDFInfo
- Publication number
- CN114147135A CN114147135A CN202111320356.XA CN202111320356A CN114147135A CN 114147135 A CN114147135 A CN 114147135A CN 202111320356 A CN202111320356 A CN 202111320356A CN 114147135 A CN114147135 A CN 114147135A
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- China
- Prior art keywords
- pipe
- straight
- pin
- bent
- punch
- Prior art date
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D51/00—Making hollow objects
- B21D51/16—Making hollow objects characterised by the use of the objects
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D19/00—Flanging or other edge treatment, e.g. of tubes
- B21D19/08—Flanging or other edge treatment, e.g. of tubes by single or successive action of pressing tools, e.g. vice jaws
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
- B21D22/02—Stamping using rigid devices or tools
- B21D22/025—Stamping using rigid devices or tools for tubular articles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D39/00—Application of procedures in order to connect objects or parts, e.g. coating with sheet metal otherwise than by plating; Tube expanders
- B21D39/08—Tube expanders
- B21D39/20—Tube expanders with mandrels, e.g. expandable
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D53/00—Making other particular articles
- B21D53/84—Making other particular articles other parts for engines, e.g. connecting-rods
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D7/00—Bending rods, profiles, or tubes
- B21D7/12—Bending rods, profiles, or tubes with programme control
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Bending Of Plates, Rods, And Pipes (AREA)
- Shaping Metal By Deep-Drawing, Or The Like (AREA)
Abstract
The invention provides a method for manufacturing a bent pipe, which comprises the following steps: a first pipe expanding step of shaping a second straight pipe portion of the bent pipe intermediate into an expanded second straight pipe portion; a second pipe expanding step of forming the intermediate body of the expanded second straight pipe portion and the bent pipe portion into an expanded second straight pipe portion and a bent pipe portion of a shape to be finally obtained, respectively; a drawing step of forming the widened second straight pipe part into an oblong second straight pipe part with an oblong cross section; and a projection forming step of forming the projection. In the drawing step, a drawing punch having a drawing pin built therein is used.
Description
Technical Field
The present invention relates to a method for manufacturing a bent pipe, for example, a method for manufacturing a bent pipe disposed in an engine compartment of an automobile.
Background
As a technique related to the method for manufacturing the bent pipe, for example, there is a technique described in patent document 1. Patent document 1 describes a method for producing a bent pipe, including: the front end surface of a punch for forming a projection including a stepped portion of a counterbore is brought into contact with a lower surface of a second hollow portion of a clamping die formed on an extension of a contact line on the side of a second straight tube where the first hollow portion and the outer peripheral surface of a first straight tube portion are in contact, so that the outer diameter of a bent tube portion in a diameter-expanded state at a predetermined position on the side close to the second straight tube portion is further expanded radially outward toward the inner peripheral surface of the stepped portion, and the projection is formed so as to contact the outer periphery of the first straight tube portion.
According to the method of manufacturing a bent pipe described in patent document 1, a bent pipe having a small gap or no gap between the end surface of the boss on the bent pipe portion side and the outer peripheral surface of the straight pipe portion can be manufactured.
Documents of the prior art
Patent document
[ patent document 1] Japanese patent No. 6546684 publication
Disclosure of Invention
Problems to be solved by the invention
The method of manufacturing the bent pipe described in patent document 1 is a method of manufacturing a bent pipe in which the projection is circular. In contrast, recently, there has been a demand for manufacturing a bent pipe having a convex shape not circular but elongated circular shape. In order to obtain a protrusion having an oblong shape, it is necessary to form the shape of the die portion for forming the protrusion into an oblong shape. However, if the change point from the manufacturing method of the bent pipe in the case where the projection is circular is simply the change of the shape of the die portion, it is difficult to make the oblong projection and the peripheral portion thereof have ideal shapes.
The present invention has been made in view of the above circumstances, and an object thereof is to provide a method of manufacturing a bent pipe, which can reduce or eliminate a gap between an end surface of a boss on a bent pipe portion side and an outer peripheral surface of a straight pipe portion, and can obtain a boss having an oblong shape of an ideal shape and a peripheral portion thereof having an ideal shape.
Means for solving the problems
The method for manufacturing a bent pipe according to the present invention includes:
a temporary bending step of applying bending work to a raw pipe leaving a first straight pipe portion on one end portion side of the raw pipe and a second straight pipe portion on the other end portion side of the raw pipe, and forming a bent portion between the first straight pipe portion and the second straight pipe portion;
an impact radius of curvature correcting step of arranging the bent pipe intermediate body obtained in the temporary bending step at a split die-shaped forming die provided with a hollow portion for forming the bent portion into the shape of the bent pipe intermediate body, and inserting an impact radius of curvature correcting pin from a pipe end of the first straight pipe portion or the second straight pipe portion, thereby expanding a curved surface of a bent outer side portion of the bent portion outward in a radial direction to form the bent portion into the shape of the bent pipe intermediate body;
a pipe fixing step of fixing the first straight pipe portion and the bent pipe portion intermediate body using a split die-shaped clamping die, the clamping die including: a first hollow portion for accommodating the first straight tube portion; a second hollow portion for receiving the bent pipe portion intermediate body and having a groove for widening a part of the bent pipe portion intermediate body; and a third hollow portion that is countersunk so as to have an inner diameter larger than an outer diameter of the second straight tube portion, and that has a lower surface that is formed on an extension of a contact line on the second straight tube portion side where the first hollow portion and an outer peripheral surface of the first straight tube portion are in contact, in a cross-sectional view of the first straight tube portion in a direction along an axial direction of the first straight tube portion arranged at the first hollow portion;
a first pipe expanding step of causing a first pipe expanding pin having an expanded diameter portion having an outer diameter larger than an inner diameter of the second straight pipe portion to face the pipe end of the second straight pipe portion projecting out of the clamp die in a state of being spaced apart therefrom, and thereafter inserting the first pipe expanding pin from the pipe end of the second straight pipe portion to expand the second straight pipe portion and shape the second straight pipe portion into an expanded diameter second straight pipe portion;
a second pipe expanding step of causing a second pipe expanding pin having an expanded portion having an oblong cross-section with a width larger than the inner diameter of the expanded second straight pipe portion to face in a state of being spaced apart from a pipe end of the expanded second straight pipe portion projecting out of the clamping die, and thereafter inserting the second pipe expanding pin from the pipe end of the expanded second straight pipe portion to expand a part of the intermediate body of the expanded second straight pipe portion and the elbow portion, and forming the intermediate body of the expanded second straight pipe portion and the elbow portion into an expanded second straight pipe portion and an elbow portion of a shape to be finally obtained, respectively;
a drawing step of causing a drawing punch to face the widened second straight tube portion protruding out of the clamping die in a state of being spaced apart from a tube end of the widened second straight tube portion, thereafter inserting the drawing pin from the tube end of the widened second straight tube portion, and causing a front end surface of the drawing punch to abut against the lower surface of the third hollow portion, thereby drawing the widened second straight tube portion, and forming the widened second straight tube portion into an oblong second straight tube portion having an oblong cross section, wherein the drawing punch has built-in therein a drawing pin having a shape holding portion having an oblong cross section, and has a drawing tapered portion having respective oblong cross sections whose opening gradually narrows from an inlet to a deep position, and a drawing cylindrical hole portion having an oblong cross section extending from the drawing tapered portion and formed in a deep position of the drawing tapered portion; and
and a boss forming step of forming the boss so as to be in contact with the outer periphery of the first straight tube portion by causing a boss punch to face the pipe end of the oblong second straight tube portion protruding out of the clamp die while being spaced apart therefrom, and then inserting the boss pin from the pipe end of the oblong second straight tube portion, and causing a tip end surface of the boss punch to abut against the lower surface of the third hollow portion, wherein the boss punch has a boss pin having an oblong cross-section shape retaining portion incorporated therein, and has a stepped portion formed at an inlet by counter-boring a predetermined depth in a size corresponding to a finally obtained oblong boss and a cylindrical hole portion having an oblong cross-section extending from the stepped portion and formed at a deep position of the stepped portion.
ADVANTAGEOUS EFFECTS OF INVENTION
According to the manufacturing method of the bent pipe of the present invention, the clearance between the end surface of the boss on the bent pipe portion side and the outer peripheral surface of the straight pipe portion can be reduced or eliminated, and further, the boss of the oblong shape of the ideal shape and the peripheral portion thereof of the ideal shape can be obtained.
Drawings
Fig. 1A is a diagram showing the shape of the tube blank.
Fig. 1B is a diagram showing the shape of the elbow intermediate after the temporary bending step.
Fig. 2 is a diagram showing a positional relationship among the intermediate bent pipe, the forming die, the impact radius correction pin, and the inner diameter restriction pin before the first impact radius correction step.
Fig. 3 is a diagram showing a state in which the first impact radius of curvature correction step is performed from the state shown in fig. 2.
Fig. 4 is a view showing a state in which the elbow intermediate body is inverted after the first impact radius curvature correction step to perform the second impact radius curvature correction step.
Fig. 5 is a perspective view showing a split mold type clamping mold.
Fig. 6 is a top view of the clamping die shown in fig. 5.
Fig. 7 is a perspective view showing the first pipe expanding pin.
Fig. 8 is a perspective view showing a second expanding punch.
Fig. 9 is a front view of the second expander punch shown in fig. 8.
Fig. 10 is a perspective view showing the second casing pin.
Fig. 11 is a perspective view showing a drawing punch.
Fig. 12 is a front view of the drawing punch shown in fig. 11.
Fig. 13 is a perspective view showing the drawing pin.
Fig. 14 is a perspective view showing a boss punch.
Fig. 15 is a front view of the raised punch shown in fig. 14.
Fig. 16 is a perspective view showing the projecting pin.
Fig. 17 is a view for explaining a sequence of the first pipe expanding step.
Fig. 18 is a view for explaining a sequence of the second pipe expanding step.
Fig. 19 is a diagram for explaining a procedure of the drawing step.
Fig. 20 is a view for explaining the sequence of the protrusion forming step.
Fig. 21 is a view showing a final form of the bent pipe.
Fig. 22 is a photograph of the bent pipe in a final form taken with the opening side of the oblong second straight pipe portion tilted upward.
Fig. 23 is a photograph of a bent pipe in a final shape taken with the opening side of the oblong second straight pipe portion being oriented in the lateral direction.
FIG. 24 is a photograph of a bent pipe in its final shape taken with the open side of the oblong second straight pipe portion facing downward.
Detailed Description
Hereinafter, embodiments of the present invention will be described.
Fig. 1A shows a tube blank 1 as a material of a bent tube. As the raw pipe 1, for example, an aluminum alloy pipe such as Al-Mn based aluminum alloy A3003 pipe, a carbon steel pipe STSW1-B for high pressure piping, a metal pipe such as a copper pipe, or the like is used. The outer diameter D1 of the tube blank 1 is not limited to this, and is, for example,. phi.17 mm. Further, the wall thickness of the tube blank 1 is not limited thereto, and is, for example, 1.2 mm.
(temporary bending step)
The temporary bending step will be explained. As shown in fig. 1B, the raw pipe 1 is bent by using a bending machine such as a numerically controlled bender to form a bent intermediate body 2 including a first straight pipe portion 2a, a bent portion 2c, and a second straight pipe portion 2B, while leaving the first straight pipe portion 2a on one end portion side of the raw pipe 1 and leaving the second straight pipe portion 2B on the other end portion side of the raw pipe 1, and forming the bent portion 2c between the first straight pipe portion 2a and the second straight pipe portion 2B.
(impact radius of curvature correction step)
The impact radius of curvature correction step will be explained. The curvature radius of the curved portion 2c is corrected to form the curved portion 2c into the shape of a curved pipe portion intermediate body 3c (see fig. 4). Fig. 2 is a diagram showing a positional relationship among the elbow intermediate body 2, the forming die 10, the impact radius correction pin 20, and the inner diameter regulation pin 30 before the first impact radius correction step.
The molding die 10 is a split die-shaped molding die and is composed of a pair of symmetrically shaped dies. In addition, the drawings showing the bent pipe intermediate bodies 2, 3 in the forming die 10 section shown in fig. 2 to 4 are drawings illustrating a case where a pipe is cut at a contact surface between a pair of dies. Fig. 2 and the like show only one of the forming dies 10 constituted by a pair of dies of a symmetrical shape. When the bent pipe intermediate body 2 is set at the forming die 10, the bent pipe intermediate body 2 is sandwiched by one die shown in fig. 2 or the like and the other die not shown.
The forming die 10 has a hollow portion 10c for forming the bent portion 2c into the shape of the bent pipe portion intermediate 3c (see fig. 4). The hollow portion 10c has: a first inner peripheral surface 10c1 having a shape (radius of curvature) corresponding to the curved surface of the curved outer portion of the bent pipe portion intermediate 3c (see fig. 4), and a second inner peripheral surface 10c2 having a shape (radius of curvature) corresponding to the curved surface of the curved inner portion of the bent portion 2 c. The molding die 10 has hollow portions 10a and 10b for accommodating the first straight tube portion 2a and the second straight tube portion 2 b.
The impact radius of curvature correction pin 20 includes: a cylindrical main body portion 20a, and a claw portion 20b having a curved surface corresponding to the shape (curvature radius) of the first inner peripheral surface 10c 1. The inner diameter regulation pin 30 includes: a cylindrical body portion 30a, and a tip portion 30b having an outer diameter that decreases toward the tip.
The impact radius of curvature correction step of the present embodiment is a two-stage impact radius of curvature correction step of the first impact radius of curvature correction step and the second impact radius of curvature correction step.
< first impact radius of curvature correction step >
As shown in fig. 2, the elbow intermediate body 2 is disposed in the hollow portions 10a to 10c of the forming die 10, the impact radius of curvature correction pin 20 is inserted from the pipe end of the first straight pipe portion 2a, and the inner diameter regulation pin 30 is inserted from the pipe end of the second straight pipe portion 2b on the side where the impact radius of curvature correction pin 20 is not inserted.
As shown in fig. 3, when the impact radius of curvature 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 curved outer side portion of the curved portion 2c of the bent pipe intermediate body 2 is expanded radially outward. Further, the bent inner portion of the bent portion 2c is stretched inward and deformed toward the inside of the tube due to the above-mentioned bent outer portion expanding outward in the radial direction. As can be seen by comparing fig. 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 inner portion of the curved portion 2c are both small.
< second impact radius of curvature correction step >
Next, as shown in fig. 4, the elbow intermediate body 2 is inverted to arrange the elbow intermediate body 2 in the hollow portions 10a to 10c of the forming die 10, the impact radius of curvature correcting pin 20 is inserted from the pipe end of the second straight pipe portion 2b into which the inner radius limiting pin 30 is inserted at the time of the first impact radius of curvature correcting step, and the inner radius limiting pin 30 is inserted from the pipe end of the first straight pipe portion 2a into which the impact radius of curvature correcting pin 20 is inserted at the time of the first impact radius of curvature correcting step.
When the impact radius of curvature 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 curved outer side portion of the curved portion 2c of the bent pipe intermediate body 2 is expanded radially outward. Further, the bent inner portion of the bent portion 2c is stretched inward and deformed toward the inside of the tube due to the above-mentioned bent outer portion expanding outward in the radial direction.
By the implementation of the first and second impact radius-of-curvature correcting steps, the curved portion 2c shown in fig. 2 is formed into the shape of the curved pipe portion intermediate body 3c shown in fig. 4. The radius of curvature of the curved surface of the outer curved portion of the bent pipe portion intermediate body 3c and the radius of curvature of the curved surface of the inner curved portion of the bent pipe portion intermediate body 3c are smaller than the radius of curvature of the corresponding curved surfaces of the bent portions 2 c. That is, the radius of curvature of the bent pipe portion intermediate body 3c is smaller than the radius of curvature of the bent portion 2 c.
Further, at the time of the first impact radius of curvature correcting step, the impact radius of curvature correcting pin 20 may be inserted from the pipe end of the second straight pipe portion 2b, and the inner diameter restricting pin 30 may be inserted from the pipe end of the first straight pipe portion 2a, and at the time of the second impact radius of curvature correcting step, the impact radius of curvature correcting pin 20 may be inserted from the pipe end of the first straight pipe portion 2a, and the inner diameter restricting pin 30 may be inserted from the pipe end of the second straight pipe portion 2 b.
Further, if the impact radius of curvature correction pin 20 is inserted only from the pipe end of the first straight pipe portion 2a or the second straight pipe portion 2b, that is, if the shape of the elbow portion intermediate body 3c shown in fig. 4 is obtained by only one impact radius of curvature correction step, the impact radius of curvature correction step may be performed in one stage instead of the two-stage impact radius of curvature correction step of the first impact radius of curvature correction step and the second impact radius of curvature correction step. Further, by performing the two-stage impact radius of curvature correcting step, the curved portion 2c can be formed into the shape of the curved pipe portion intermediate body 3c more reliably and stably.
(tube fixing step)
The tube fixing step is explained. Fig. 5 and 6 are views showing a clamping die 40 for setting a split die shape of the intermediate body 3 of the elbow pipe after the (fixed) impact curvature radius correction step.
The clamping die 40 is a split die type clamping die, and is composed of a pair of symmetrically shaped dies. Fig. 5 and 6 show only one of the clamping dies 40 constituted by a pair of dies of symmetrical shape. When the bent tube intermediate body 3 is set at the clamping die 40, in other words, when the bent tube intermediate body 3 is fixed by the clamping die 40, the bent tube intermediate body 3 is sandwiched by using one die shown in fig. 5 or the like and another die not shown.
The clamping die 40 has: a first hollow section 40a for accommodating the first straight pipe section 2a of the bent pipe intermediate body 3; a second hollow portion 40b for accommodating the bent pipe portion intermediate body 3 c; and a third hollow portion counterbored to have an inner diameter larger than an outer diameter of the second straight tube portion.
The second hollow portion 40b is a hollow portion for forming the bent pipe portion intermediate body 3c into the shape of the bent pipe portion 4c (see fig. 21) to be finally obtained. The second hollow portion 40b has a recess 40b1 for widening a part (the second straight tube portion 2b side) of the bent tube portion intermediate body 3 c.
As shown in fig. 17 and the like, the third hollow portion 40c has a lower surface 40c1, and the lower surface 40c1 forms an extension of a contact line L on the second straight tube portion 2b side where the first hollow portion 40a and the outer peripheral surface of the first straight tube portion 2a are in contact, in a cross-sectional view of the first straight tube portion 2a in the direction along the axial direction of the first straight tube portion 2a arranged at the first hollow portion 40 a. In addition, the drawing showing the intermediate bent pipe body 3 in the portion of the clamping die 40 shown in fig. 17 is a drawing illustrating a case where the pipe is cut at the contact surface between the pair of dies (the same applies in fig. 18 to 20).
A portion of the bent pipe intermediate body 3 on the side close to at least the first straight pipe portion 2a of the first straight pipe portion 2a and the bent pipe portion intermediate body 3c is sandwiched and fixed by the clamping die 40 composed of a pair of dies having a symmetrical shape.
As shown in fig. 17 and the like, in the present embodiment, in the pipe fixing step, the pipe inside support pin 45 is inserted from the pipe end of the first straight pipe portion 2a to the vicinity of the elbow portion intermediate body 3 c. By inserting the pipe inside support pin 45, buckling of the first straight pipe portion 2a in the subsequent steps (the first pipe expanding step, the second pipe expanding step, the drawing step, and the projection forming step) can be prevented. In addition, depending on the length of the second straight tube portion 2b, the second straight tube portion 2b is cut to a desired length before the elbow intermediate body 3 is set at the clamp die 40 (the elbow intermediate body 3 is fixed by the clamp die 40), and the second straight tube portion 2b is shortened.
(first pipe expanding step)
The first tube expanding step will be explained. Fig. 7 is a perspective view showing the first pipe expanding pin 50 used in the 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 diameter-expanded second straight pipe portion 3b (see fig. 18). Fig. 17 is a view for explaining a sequence of the first pipe expanding step.
As shown in fig. 7 and 17, the first casing pin 50 has: a diameter-enlarged portion 50a having a cylindrical shape with an outer diameter larger than the inner diameter of the second straight tube portion 2b, and a distal end claw portion 50b having a curved surface corresponding to the curved shape of the second hollow portion 40 b. The outer diameter of the distal end claw portion 50b is smaller than the outer diameter of the enlarged diameter portion 50 a. A tapered portion 50c having a narrow tip is provided between the tip claw portion 50b and the diameter-enlarged portion 50 a. Further, a flat surface portion 50a1 extending in the axial direction of the enlarged diameter portion 50a is provided on the surface of the enlarged diameter portion 50 a. The flat portions 50a1 are provided at two positions in total, shifted from each other by 180 degrees in the circumferential direction of the enlarged diameter portion 50 a. The distance between the two flat surface portions 50a1 is smaller than the outer diameter of the enlarged diameter portion 50 a. The two flat surface portions 50a1 may not be provided on the surface of the enlarged diameter portion 50 a. That is, the enlarged diameter portion 50a may have a completely cylindrical shape (circular cross section).
The first expanding pin 50 is built in the first expanding punch 60. The first expander punch 60 has a cylindrical portion 60 a. In a state where the first pipe expanding pin 50 is inserted into the bottomed cylindrical hole portion 60a1 of the cylindrical portion 60a, the first pipe expanding pin 50 is fixed to the first pipe expanding punch 60 by a bolt (not shown) or the like. The outer shape of the cylindrical portion 60a and the cylindrical hole portion 60a1 are both circular. A gap is present between the enlarged diameter portion 50a of the first pipe expanding pin 50 and the cylindrical hole portion 60a1 of the first pipe expanding punch 60, so that the second straight pipe portion 2b enters the gap.
As shown in fig. 17, the first expand punch 60 incorporating the first expand pin 50 is opposed in a state of being spaced apart from the pipe end of the second straight pipe portion 2b projecting out of the clamp die 40, and thereafter, the first expand pin 50 is inserted from the pipe end of the second straight pipe portion 2b, and the front end surface 60a2 of the first expand punch 60 is brought into abutment with the lower surface 40c1 of the third hollow portion 40c of the clamp die 40.
As shown on the right side in fig. 18, when the first tube enlarging pin 50 is inserted from the tube end of the second straight tube portion 2b, the tapered portion 50c and the enlarged diameter portion 50a of the first tube enlarging pin 50 enlarge the diameter of the second straight tube portion 2b, and the second straight tube portion 2b is formed as an enlarged diameter second straight tube portion 3b having a substantially circular cross section and a larger diameter than the second straight tube portion 2 b. Since the tapered portion 50c is provided at the first enlarged tube pin 50, the diameter of the second straight tube portion 2b can be smoothly enlarged. Further, since the two flat portions 50a1 are provided on the surface of the enlarged diameter portion 50a, the cross section of the formed enlarged diameter second straight tube portion 3b is not a perfect circle but a circle slightly long in the lateral direction, and the processing (tube expansion) of the enlarged diameter second straight tube portion 3b in the next step (second tube expansion step) is facilitated.
(second pipe expanding step)
The second tube expanding step will be explained. Fig. 8 is a perspective view illustrating the second expanding punch 80, and fig. 9 is a front view of the second expanding punch 80 illustrated in fig. 8. Fig. 10 is a perspective view showing the second pipe expanding pin 70. Fig. 18 is a view for explaining a sequence of the second pipe expanding step.
The second pipe expanding pin 70 has a widened portion 70a having an oblong cross-section with a width larger than the inner diameter of the second straight pipe portion 3 b. The widened portion 70a is constituted by a widened body portion 70a1 having a constant width and height and a widened distal end portion 70a2 having a narrow distal end.
The second expanding pin 70 is built in the second expanding punch 80. The second expander punch 80 has a cylindrical portion 80 a. In a state where the second pipe expanding pin 70 is inserted into the bottomed cylindrical hole portion 80a1 of the cylindrical portion 80a, the second pipe expanding pin 70 is fixed to the second pipe expanding punch 80 by a bolt (not shown) or the like. The cylindrical portion 80a has a circular outer shape, whereas the cylindrical hole portion 80a1 has an oval cross-section. Further, the second tube expanding punch 80 has tapered portions 80a2 each having an oblong cross section and opening gradually narrowing from the entrance to the depth. Bore portion 80a1 is formed deep within tapered portion 80a2 and extends from tapered portion 80a 2. A gap is present between the widened portion 70a of the second pipe expanding pin 70 and the cylindrical hole portion 80a1 of the second pipe expanding punch 80, so that the second straight pipe portion 3b is expanded in diameter to enter the gap.
As shown in fig. 18, the second expanding punch 80 incorporating the second expanding pin 70 is opposed to the tube end of the expanded second straight tube portion 3b protruding out of the clamping die 40 in a state of being spaced apart therefrom, and thereafter, the second expanding pin 70 is inserted from the tube end of the expanded second straight tube portion 3b, and the tip end surface 80a3 of the second expanding punch 80 is brought into abutment with the lower surface 40c1 of the third hollow portion 40c of the clamping die 40.
When the second widening pin 70 is inserted from the tube end of the second straight tube portion 3b, the widened portion 70a of the second widening pin 70 widens the second straight tube portion 3 b. Further, as shown on the right side in fig. 19, in the process in which the front end surface 80a3 of the second expanding punch 80 abuts against the lower surface 40c1 of the third hollow portion 40c of the clamping die 40, the second straight tube portion 3b is recessed with its diameter expanded in the axial direction of the first straight tube portion 2a by the cylindrical hole portion 80a1 of the second expanding punch 80 having an oblong cross section. As a result, the enlarged diameter second straight tube portion 3b is shaped into an enlarged diameter second straight tube portion 4b having an oblong cross section. The widened second straight tube portion 4b is one turn larger than the oblong second straight tube portion 5b to be finally obtained as shown in fig. 20 and 21.
Further, since the cylindrical hole portion 80a of the second expanding punch 80 is oblong in cross section and the above-mentioned tapered portion 80a2 whose leading end is wide is provided at the leading end portion of the cylindrical hole portion 80a1, in the process of abutment of the leading end surface 80a3 of the second expanding punch 80 with the lower surface 40c1 of the third hollow portion 40c of the clamping die 40, as shown on the right side in fig. 19, a projection intermediate body 6 is formed at the boundary portion of the expanded second straight pipe portion 4b and the bent pipe portion 4c in the axial direction of the first straight pipe portion 2 a.
The projection intermediate 6 is a portion (projection) which becomes the projection 7 later. By forming the projection intermediate body 6 in this second expander arrangement, it is possible to shape the projection 7 of a more desirable shape in a subsequent projection forming step.
When the second pipe expanding pin 70 is inserted from the pipe end of the second straight pipe portion 3b, the expanded distal end portion 70a2 of the second pipe expanding pin 70 presses the bent pipe portion intermediate body 3c from the inside. Since the concave groove 40b1 (see fig. 5) is provided in the second hollow portion 40b of the clamp die 40, when the widened distal end portion 70a2 presses the intermediate bent pipe portion 3c from the inside, a part of the intermediate bent pipe portion 3c (the second straight pipe portion 2b side) is fitted into the concave groove 40b1 and is deformed so as to be widened, and as a result, the intermediate bent pipe portion 3c is formed into the bent pipe portion 4c (see fig. 21) having a shape to be finally obtained. As shown in fig. 21 and 24, the elbow portion 4c includes a pair of right and left expansion portions 5. The expanded portion 5 is a portion of the bent pipe portion intermediate body 3c (the second straight pipe portion 2b side) after being subjected to the widening deformation.
In this way, in the second pipe expanding step, the second straight pipe portion 3b and the intermediate bent pipe portion 3c are expanded in diameter to form the second straight pipe portion 4b and the bent pipe portion 4c, respectively.
(drawing step)
The drawing step is explained. Fig. 11 is a perspective view illustrating the drawing punch 100, and fig. 12 is a front view of the drawing punch 100 illustrated in fig. 11. Fig. 13 is a perspective view showing the drawing pin 90. Fig. 19 is a diagram for explaining a procedure of the drawing step.
The drawing pin 90 has a shape holding portion 90a having an oval cross section. The shape retaining portion 90a has a cross-sectional shape and a dimension substantially equal to the cross-sectional inner shape and the dimension of the oblong second straight tube portion 5b to be obtained in the present drawing step.
The drawing pin 50 is built into the drawing punch 100. The drawing punch 100 has a cylindrical portion 100 a. The drawing pin 90 is fixed to the drawing punch 100 by a bolt (not shown) or the like in a state where the drawing pin 90 is inserted into the bottomed drawing cylindrical hole portion 100a1 of the cylindrical portion 100 a. The cylindrical portion 100a has a circular outer shape, and the drawn cylindrical hole portion 100a1 has an oval cross-section. The drawing punch 100 has drawing tapered portions 100a2 each having an oblong cross section and having an opening gradually narrowing from the entrance to the depth. The drawn cylindrical hole portion 100a1 is formed deep in the drawn tapered portion 100a2 and extends from the drawn tapered portion 100a 2. As shown in fig. 19, a gap is provided between the shape retaining portion 90a of the drawing pin 90 and the drawing tube hole portion 100a1 of the drawing punch 100, and the widened second straight tube portion 4b enters the gap.
As shown in fig. 19, the drawing tapered portion 100a2 has an inclination angle α 1 with respect to the axial direction of the drawing punch 100 in the tapered portion 101 abutting against the inner curved portion 103 in the boundary portion between the widened second straight tube portion 4b and the bent tube portion 4c larger than an inclination angle α 2 with respect to the axial direction in the tapered portion 102 abutting against the outer curved portion 104 in the boundary portion.
The drawing punch 100 incorporating the drawing pin 90 is opposed to the tube end of the widened second straight tube portion 4b protruding out of the clamping die 40 in a state of being spaced apart therefrom, and thereafter the drawing pin 90 is inserted from the tube end of the widened second straight tube portion 4b, and the front end surface 100a3 of the drawing punch 100 is brought into contact with the lower surface 40c1 of the third hollow portion 40c of the clamping die 40.
As shown on the right side in fig. 20, in a process in which the front end surface 100a3 of the drawing punch 100 is in contact with the lower surface 40c1 of the third hollow portion 40c of the clamping die 40 from a state in which the drawing punch 100 is spaced apart from the tube end of the widened second straight tube portion 4b, the widened second straight tube portion 4b having an oblong cross section is drawn over the entire circumference by the drawing tapered portion 100a2 and the drawing tube hole portion 100a1 of the drawing punch 100, and as a result, the widened second straight tube portion 4b is formed into the oblong second straight tube portion 5b having an oblong cross section to be finally obtained. Further, by the drawing tapered portion 100a2 of the drawing punch 100, the projection intermediate body 6 is formed at the boundary portion of the oblong second straight tube portion 5b and the bent tube portion 4c at the entire periphery thereof.
Here, since the inclination angle α 1> the inclination angle α 2 is set, the intermediate boss 6 of the inner bending portion 103 is greatly extended toward the first straight tube portion 2a side than the intermediate boss 6 of the outer bending portion 104 by the draw tapered portion 100a2 (see fig. 20). The curved inner side portion 103 and the curved outer side portion 104 are portions of the protrusion 7 (see fig. 21) which are somewhat difficult to form into an ideal shape, and the curved inner side portion 103 is a portion of the protrusion 7 (see fig. 21) which is more difficult to form into an ideal shape than the curved outer side portion 104. Since the inclination angle α 1> the inclination angle α 2 is set, the boss intermediate body 6 of the curved inner portion 103 largely extends toward the first straight tube portion 2 a. As a result, the projections 7 are easily formed. Thereby, in the next protrusion forming step, the protrusion 7 of a more desirable shape can be formed at the curved inner side portion 103. In addition, it is not essential to make the inclination angle α 1> the inclination angle α 2.
Further, by using the drawing punch 100 incorporating the drawing pin 90 having the shape retaining portion 90a having an oblong cross section in the drawing step, when the second straight tube portion 4b is drawn and widened by the drawing tapered portion 100a2 and the drawing tube hole portion 100a1 of the drawing punch 100, the inner surface of the widened second straight tube portion 4b is supported by the drawing pin 90, and therefore, the oblong second straight tube portion 5b having an ideal shape can be obtained. In the method for manufacturing a bent pipe described in patent document 1 (japanese patent No. 6546684), a member corresponding to the drawing pin 90 is not used in a step corresponding to the drawing step.
(bump forming step)
The protrusion forming step will be explained. Fig. 14 is a perspective view illustrating the boss punch 120, and fig. 15 is a front view of the boss punch 120 illustrated in fig. 14. Fig. 16 is a perspective view showing the projecting pin 110. Fig. 20 is a view for explaining the sequence of the protrusion forming step.
The projecting pin 110 has a shape retaining portion 110a having an oblong cross section. The shape retaining portion 110a has a cross-sectional shape and a size substantially equal to the cross-sectional inner shape and the size of the oblong second straight tube portion 5 b.
The above-described boss pin 110 is built in the boss punch 120. The boss punch 120 has a cylindrical portion 120 a. In a state where the boss pin 110 is inserted into the bottomed cylindrical hole portion 120a1 of the cylindrical portion 120a, the boss pin 110 is fixed to the boss punch 120 by a bolt (not shown) or the like. The cylindrical portion 120a has a circular outer shape, and the cylindrical hole portion 120a1 has an oblong cross-sectional shape. Further, the boss punch 120 has a stepped portion 120a2 formed at the inlet by counter boring a predetermined depth in a size corresponding to the boss 7 of the oblong shape to be finally obtained. The cylindrical hole portion 120a1 is formed deep in the step portion 120a2 and extends from the step portion 120a 2. As shown in fig. 20, there is a gap between the shape retaining portion 110a of the projecting pin 110 and the cylindrical hole portion 120a1 of the projecting punch 120, so that the oblong second straight tube portion 5b enters the gap.
As shown in fig. 15, the stepped portion 120a2 is an elongated circular ring because it is a stepped portion for forming the elongated circular protrusion 7. The width of the stepped portion 120a2 at the longitudinal center 105 of the stepped portion 120a2 is wider than the width at the longitudinal end 106 of the stepped portion 120a2 when the stepped portion 120a2 is viewed from the front. The width of the stepped portion 120a2 smoothly widens from the longitudinal end 106 toward the longitudinal center 105.
The longitudinal center portion 105 is a portion of the bent pipe intermediate body 3 corresponding to the inner bent portion 103 and the outer bent portion 104 (see fig. 20). These curved inner side portions 103 and curved outer side portions 104 are portions of the projections 7 (see fig. 21) which are somewhat difficult to form into an ideal shape. When the width at the lengthwise direction central portion 105 of the stepped portion 120a2 is wider than the width at the lengthwise direction end 106 of the stepped portion 120a2, the boss intermediate body 6 easily extends to the lengthwise direction central portion 105 of the stepped portion 120a2, and as a result, the boss 7 of a more desirable shape can be formed.
The width of the stepped portion 120a2 at the longitudinal center 105 may be equal to the width of the stepped portion 120a2 at the longitudinal end 106. That is, in the oval annular step portion 120a2, when the step portion 120a2 is viewed from the front, a step portion having a uniform width over the entire circumference can be obtained.
The boss punch 120 having the boss pin 110 built therein is opposed to the pipe end of the oblong second straight pipe portion 5b protruding out of the clamping die 40 in a state of being spaced apart therefrom, and thereafter, the boss pin 110 is inserted from the pipe end of the oblong second straight pipe portion 5b, and the front end surface 120a3 of the boss punch 120 is brought into abutment with the lower surface 40c1 of the third hollow portion 40c of the clamping die 40.
In the process of coming into abutment of the front end surface 120a3 thereof with the lower surface 40c1 of the third hollow portion 40c of the clamping die 40 from a state where the boss punch 120 is spaced apart from the tube end of the oblong second straight tube portion 5b, the boss intermediate body 6 is compressed in the axial direction of the oblong second straight tube portion 5b and extended in the radial direction by the step portion 120a2 of the boss punch 120. As a result, the boss intermediate body 6 is formed into an oblong boss 7 (see fig. 21) that contacts the outer periphery of the first straight tube portion 2 a. The oblong projection 7 is an oblong annular projection, in other words, an oblong flange, and is an oblong ring.
Further, the stepped portion 110b provided at the base end of the shape retaining portion 110a of the boss pin 110 becomes a stopper of the pipe end of the oblong second straight pipe portion 5 b. In the case where the distance in the axial direction of the boss punch 120 between the front end surface 120a3 of the boss punch 120 and the step portion 110b of the boss pin 110 is shorter than the distance in the axial direction of the oblong second straight pipe portion 5b between the pipe end of the oblong second straight pipe portion 5b protruding outside the clamping die 40 and the lower surface 40c1 of the third hollow portion 40c, the oblong second straight pipe portion 5b is pressed into the third hollow portion 40c by the step portion 110b of the boss pin 110 in the process of abutment of the front end surface 120a3 of the boss punch 120 with the lower surface 40c1 of the third hollow portion 40 c. Also by this action, the boss intermediate body 6 is compressed in the axial direction of the oblong second straight tube portion 5b and extends in the radial direction.
Further, the distance in the axial direction of the boss punch 120 between the front end surface 120a3 of the boss punch 120 and the stepped portion 110b of the boss pin 110 may be longer than the distance in the axial direction of the oblong second straight pipe portion 5b between the pipe end of the oblong second straight pipe portion 5b protruding out of the clamp die 40 and the lower surface 40c1 of the third hollow portion 40c, or may be the same distance.
Fig. 21 to 24 show the elbow 8 in its final form comprising the oblong shaped protrusion 7. As shown in fig. 21 to 24, the clearance between the end surface 7a of the bent pipe 8 on the bent pipe portion side of the boss 7 and the outer peripheral surface of the first straight pipe portion 2a, which is obtained through the above steps, is small (almost no clearance). That is, according to the method of manufacturing the bent pipe of the present embodiment, the gap between the end surface 7a of the boss 7 on the bent pipe portion side and the outer peripheral surface of the straight pipe portion can be reduced or eliminated.
In addition, in the elbow pipe 8 shown in fig. 22 to 24 which is actually manufactured, two reels 9 are formed in the first straight pipe portion 2 a. These reels 9 are not particularly relevant to the present invention.
In the present invention, after the two-stage pipe expanding step of the first pipe expanding step and the second pipe expanding step is performed, the drawing step is performed to form the second straight pipe portion 2b of the raw pipe 1 into the oblong second straight pipe portion 5b in the final form. By performing the two-stage pipe expanding step described above before the drawing step, the second straight pipe portion 2b of the raw pipe 1 can be gradually formed into the oblong second straight pipe portion 5b in the final form, and the oblong second straight pipe portion 5b of the desired shape connected from the projections 7 can be obtained. Further, the bent pipe portion 4c connected to the boss 7 may have an ideal shape having the pair of right and left expansion portions 5. Then, in the projection forming step, by forming the projection 7 of the oblong shape to be finally obtained, the projection 7 of the desired shape can be obtained. Since the projection 7 is oblong, the bent tube 8 can be disposed in a narrow place.
The above embodiment can be modified as follows.
The use of the inner diameter restricting pin 30 is not essential. That is, in the first impact radius of curvature correcting step, the inner diameter regulating pin 30 may not be used. In the second impact radius of curvature correction step, the inner diameter regulation pin 30 may not be used. The inner diameter regulation pin 30 may not be used in the impact radius of curvature correction step.
In the first pipe expanding step, the second pipe expanding step, the drawing step, and the projection forming step, it is not essential that the first straight pipe portion 2a is supported from the inside using the pipe inner support pin 45. That is, in the tube fixing step, the tube inner support pin 45 may not be used.
The first expander punch 60 is not necessary. For example, the first pipe expanding pin 50 held by any known method without using the first pipe expanding punch 60 may be opposed to the pipe end of the second straight pipe portion 2b protruding out of the clamping die 40 in a state of being spaced apart therefrom, and thereafter the first pipe expanding pin 50 may be inserted from the pipe end of the second straight pipe portion 2b to expand the diameter of the second straight pipe portion 2 b. In addition, as in the above-described embodiment, the diameter expansion of the second straight tube portion 2b by the first pipe expanding pin 50 is more stabilized by using the first pipe expanding punch 60.
The cylindrical hole portion 80a1 of the second pipe expanding punch 80 may be a hole portion having a circular cross section instead of an oval cross section. Even if the cylindrical hole portion 80a1 is a hole portion having a circular cross section, the diameter-enlarged second straight tube portion 3b can be enlarged by the second diameter-enlarging pin 70 having the enlarged width portion 70a having an oblong cross section having a larger width than the inner diameter of the diameter-enlarged second straight tube portion 3 b. When the diameter-expanded second straight tube portion 3b is expanded, the diameter-expanded second straight tube portion 3b is naturally recessed in the axial direction of the first straight tube portion 2 a. As a result, the enlarged diameter second straight tube portion 3b becomes an enlarged diameter second straight tube portion 4b having an oval cross section.
The second expander punch 80 is not necessary. For example, the second pipe expanding pin 70 held by any known method without using the second pipe expanding punch 80 may be opposed to the pipe end of the second pipe expanding portion 3b protruding out of the clamping die 40 in a state of being spaced apart from the pipe end, and thereafter the second pipe expanding pin 70 may be inserted from the pipe end of the second pipe expanding portion 3b to expand the diameter of the second straight portion 3b and a part of the intermediate bent portion 3 c. In addition, as in the above-described embodiment, the diameter expansion of the second straight tube portion 3b and a part of the intermediate bent tube portion 3c by the second pipe expanding pin 70 is more stabilized by using the second pipe expanding punch 80.
In the present application, "oblong" includes not only an oblong shape in which two long sides are parallel, but also a circular shape defined by an ellipse.
In addition, various changes can be made within the range that can be conceived by those skilled in the art.
Description of the reference numerals
1: pipe blank
2: elbow pipe intermediate
2 a: a first straight pipe part
2 b: a second straight pipe portion
2 c: bending part
3 b: diameter-expanded second straight pipe part
3 c: intermediate body of elbow part
4 b: widening the second straight pipe portion
4 c: elbow pipe part
5 b: oblong second straight tube portion
7: projection
8: bent pipe
10: forming die
10 c: hollow part
20: impact curvature radius correction pin
30: inner diameter limiting pin
40: clamping die
40 a: the first hollow part
40 b: second hollow part
40b 1: groove
40 c: the third hollow part
40c 1: lower surface
40: clamping die
50: first pipe expanding pin
50 a: expanding part
60: first pipe expanding punch
70: second pipe expanding pin
70 a: widening part
80: second pipe expanding punch
80a 1: bore part
80a 2: tapered portion
90: drawing pin
90 a: shape maintaining part
100: drawing punch
100a 1: drawing deep bore part
100a 2: drawing taper part
101. 102: tapered section
103: curved inner side
104: curved outer side portion
105: central part in the longitudinal direction
106: end part in the length direction
110: protruding pin
110 a: shape maintaining part
120: raised punch
120a 1: bore part
120a 2: step part
α 1, α 2: inclination angle
Claims (7)
1. A method of manufacturing an elbow, comprising:
a temporary bending step of applying bending work to a raw pipe leaving a first straight pipe portion on one end portion side of the raw pipe and a second straight pipe portion on the other end portion side of the raw pipe, and forming a bent portion between the first straight pipe portion and the second straight pipe portion;
an impact radius of curvature correcting step of arranging the bent pipe intermediate body obtained in the temporary bending step at a split die-shaped forming die provided with a hollow portion for forming the bent portion into the shape of the bent pipe intermediate body, and inserting an impact radius of curvature correcting pin from a pipe end of the first straight pipe portion or the second straight pipe portion, thereby expanding a curved surface of a bent outer side portion of the bent portion outward in a radial direction to form the bent portion into the shape of the bent pipe intermediate body;
a pipe fixing step of fixing the first straight pipe portion and the bent pipe portion intermediate body using a split die-shaped clamping die, the clamping die including: a first hollow portion for accommodating the first straight tube portion; a second hollow portion for receiving the bent pipe portion intermediate body and having a groove for widening a part of the bent pipe portion intermediate body; and a third hollow portion that is countersunk so as to have an inner diameter larger than an outer diameter of the second straight tube portion, and that has a lower surface that is formed on an extension of a contact line on the second straight tube portion side where the first hollow portion and an outer peripheral surface of the first straight tube portion are in contact, in a cross-sectional view of the first straight tube portion in a direction along an axial direction of the first straight tube portion arranged at the first hollow portion;
a first pipe expanding step of causing a first pipe expanding pin having an expanded diameter portion having an outer diameter larger than an inner diameter of the second straight pipe portion to face the pipe end of the second straight pipe portion projecting out of the clamp die in a state of being spaced apart therefrom, and thereafter inserting the first pipe expanding pin from the pipe end of the second straight pipe portion to expand the second straight pipe portion and shape the second straight pipe portion into an expanded diameter second straight pipe portion;
a second pipe expanding step of causing a second pipe expanding pin having an expanded portion having an oblong cross-section with a width larger than the inner diameter of the expanded second straight pipe portion to face in a state of being spaced apart from a pipe end of the expanded second straight pipe portion projecting out of the clamping die, and thereafter inserting the second pipe expanding pin from the pipe end of the expanded second straight pipe portion to expand a part of the intermediate body of the expanded second straight pipe portion and the elbow portion, and forming the intermediate body of the expanded second straight pipe portion and the elbow portion into an expanded second straight pipe portion and an elbow portion of a shape to be finally obtained, respectively;
a drawing step of causing a drawing punch to face the widened second straight tube portion protruding out of the clamping die in a state of being spaced apart from a tube end of the widened second straight tube portion, thereafter inserting the drawing pin from the tube end of the widened second straight tube portion, and causing a front end surface of the drawing punch to abut against the lower surface of the third hollow portion, thereby drawing the widened second straight tube portion, and forming the widened second straight tube portion into an oblong second straight tube portion having an oblong cross section, wherein the drawing punch has built-in therein a drawing pin having a shape holding portion having an oblong cross section, and has a drawing tapered portion having respective oblong cross sections whose opening gradually narrows from an inlet to a deep position, and a drawing cylindrical hole portion having an oblong cross section extending from the drawing tapered portion and formed in a deep position of the drawing tapered portion; and
and a boss forming step of forming the boss so as to be in contact with the outer periphery of the first straight tube portion by causing a boss punch to face the pipe end of the oblong second straight tube portion protruding out of the clamp die while being spaced apart therefrom, and then inserting the boss pin from the pipe end of the oblong second straight tube portion, and causing a tip end surface of the boss punch to abut against the lower surface of the third hollow portion, wherein the boss punch has a boss pin having an oblong cross-section shape retaining portion incorporated therein, and has a stepped portion formed at an inlet by counter-boring a predetermined depth in a size corresponding to a finally obtained oblong boss and a cylindrical hole portion having an oblong cross-section extending from the stepped portion and formed at a deep position of the stepped portion.
2. The method of manufacturing an elbow pipe according to claim 1, wherein the step of correcting the impact radius of curvature includes:
a first impact radius of curvature correcting step of disposing the bent pipe intermediate body at the forming die, inserting the impact radius of curvature correcting pin from a pipe end of the first straight pipe portion or the second straight pipe portion, and inserting an inner diameter regulating pin from a pipe end of the first straight pipe portion or the second straight pipe portion on a side where the impact radius of curvature correcting pin is not inserted; and
a second impact radius of curvature correcting step of inverting the bent pipe intermediate body to arrange the bent pipe intermediate body at the forming die, inserting the impact radius of curvature correcting pin from a pipe end of the first straight pipe portion or the second straight pipe portion into which the inner diameter correcting pin is inserted at the first impact radius of curvature correcting step, and inserting the inner diameter correcting pin from a pipe end of the first straight pipe portion or the second straight pipe portion into which the impact radius of curvature correcting pin is inserted at the first impact radius of curvature correcting step.
3. The method of manufacturing a bent pipe according to claim 1 or 2, wherein in the first pipe expanding step, a first pipe expanding punch incorporating the first pipe expanding pin is opposed to a pipe end of the second straight pipe portion protruding outside the clamp die in a state of being spaced apart therefrom, and thereafter, the first pipe expanding pin is inserted from the pipe end of the second straight pipe portion, and a tip end surface of the first pipe expanding punch is brought into abutment with the lower surface of the third hollow portion.
4. The method of manufacturing a bent pipe according to any one of claims 1 to 3, wherein in the second pipe expanding step, a second pipe expanding punch incorporating the second pipe expanding pin is opposed to the pipe end of the diameter-expanded second straight pipe portion protruding out of the clamp die in a state of being spaced apart therefrom, and thereafter, the second pipe expanding pin is inserted from the pipe end of the diameter-expanded second straight pipe portion, and a tip end surface of the second pipe expanding punch is brought into abutment with the lower surface of the third hollow portion.
5. The method for manufacturing an elbow pipe according to claim 4, wherein the second pipe expanding punch includes tapered portions each having an oblong cross section whose opening gradually narrows from an inlet to a deep portion, and a cylindrical hole portion having an oblong cross section extending from the tapered portion and formed at a deep portion of the tapered portion.
6. The manufacturing method of the bent pipe according to any one of claims 1 to 5, wherein an inclination angle of the draw tapered portion of the draw punch with respect to an axial direction of the draw punch in a tapered portion abutting against a bend inner side portion in a boundary portion of the widened second straight pipe portion and the bent pipe portion is larger than an inclination angle of the tapered portion abutting against a bend outer side portion in the boundary portion with respect to the axial direction.
7. The method of manufacturing a bent pipe according to any one of claims 1 to 6, wherein, with respect to the step portion of the bulging punch, when the step portion is viewed from the front, the width of the step portion at a lengthwise central portion is wider than the width of the step portion at lengthwise end portions.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2020-201479 | 2020-12-04 | ||
| JP2020201479A JP6842145B1 (en) | 2020-12-04 | 2020-12-04 | Bending pipe manufacturing method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN114147135A true CN114147135A (en) | 2022-03-08 |
| CN114147135B CN114147135B (en) | 2022-11-25 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202111320356.XA Active CN114147135B (en) | 2020-12-04 | 2021-11-09 | Method for manufacturing bent pipe |
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| Country | Link |
|---|---|
| JP (1) | JP6842145B1 (en) |
| CN (1) | CN114147135B (en) |
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Also Published As
| Publication number | Publication date |
|---|---|
| CN114147135B (en) | 2022-11-25 |
| JP6842145B1 (en) | 2021-03-17 |
| JP2022089247A (en) | 2022-06-16 |
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