Bending method of rod-shaped material and press die used for the method

Abstract

When a rod-shaped material is used as a raw material and bent a plurality of times by forming to obtain a final shape, the shape accuracy of the rod-shaped material currently distributed is not guaranteed in the first place. Therefore, every time the number of times of bending increases, the tolerance is accumulated, and the entire processing accuracy deteriorates.SOLUTION: An intermediate part of a bar-shaped material W is die-pressed by using a die-pressing press die 1, and a bending shape of the die-pressing press die 1 is transferred to the bar-shaped material W to form a pseudo blank gW, and further, while the bar-shaped material W is restrained by the die-pressing press die 1, a non-restrained part W2 is bent by using a bending press die 39 designed with one die of the die-pressing press die 1, for example, a movable die 19 as a working reference. The movable die 19 of the press die 1 for embossing includes a plane and two corner R parts, and the press die for bending is designed by using the plane as a reference plane, the circular arc center of one corner R part as a reference point, and a straight line connecting the circular arc centers of the respective corner R parts as a reference straight line.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for bending a rod-shaped material such as a bus bar. [Background technology]

[0002] Busbars are conductors used in areas where large amounts of current flow, and have traditionally been widely used in control panels, distribution boards, batteries, etc. Recently, with the spread of electric vehicles, bus bars have been attracting attention as a replacement for high-voltage harnesses, which are the mainstream of electrical wiring. Unlike high-voltage harnesses, bus bars have a fixed shape and must be pre-formed into a specific shape. However, with vehicle space being limited due to the installation of large-capacity batteries and other components, the requirements for precision in the three-dimensional shape of bus bars are becoming increasingly stringent so that they can fit neatly into that space. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-200848 Summary of the Invention [Problem to be solved by the invention]

[0004] However, if blanking is performed on a plate material and then press-forming it into the final shape, the yield will be low. Also, in recent years, materials have become thicker to accommodate larger currents, so blanking requires large-scale machinery. Therefore, this method is not economically viable. On the other hand, when bar stock is used as the raw material and bent multiple times using a forming machine to create the final shape, the yield is improved because the material is the same width as the product, but the forming machine starts processing from the end face of the bar stock and processes it in the length direction, so the dimensional accuracy from the start point to the end point is cumulative due to the processing from the end face, and the tolerance accumulates with each bending process. In addition, the shape accuracy of bar stock currently on the market is not guaranteed in the first place. This makes it difficult to control processing accuracy.

[0005] The present invention has been made in view of the above-mentioned problems of the conventional art, and has an object to provide a new and useful method for bending a rod-shaped material such as a bus bar, which can bend a rod-shaped material such as a bus bar with high processing accuracy in three dimensions without using a large-scale machine. [Means for solving the problem]

[0006] The present invention has been made to solve the above-mentioned problems, and is a bending method for rod-shaped material, which comprises using an embossing press die to emboss the middle part of the rod-shaped material, and transferring the bending shape of the embossing press die to the rod-shaped material, thereby creating a pseudo-blank, and then, while a portion of the rod-shaped material is constrained by the embossing press die, bending is performed on the unconstrained portion of the pseudo-blank using a bending press die designed with one of the dies of the embossing press die as a processing reference.

[0007] Preferably, one of the molds is a movable mold. Preferably, one of the embossing press dies includes a plane and two rounded corners, and the bending press die is designed with the plane as the reference plane, the center of the arc of one of the rounded corners as the reference point, and a straight line connecting the centers of the arcs of each of the rounded corners as the reference line. Preferably, one of the dies has a surface on which the bar-shaped material is placed, and the bending press die is designed with the above-mentioned surface as a reference plane. The stamping press die is designed for edgewise bending depending on the application of the rod material. [Effects of the Invention]

[0008] The method for bending a rod-shaped material of the present invention applies press technology to bending processing, and can bend a rod-shaped material such as a bus bar in three dimensions with high processing accuracy using a press mold with a compact and simple configuration. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view of a bar-shaped material to be processed by a method for bending a bar-shaped material according to an embodiment of the present invention; [Figure 2] 3A to 3C are explanatory diagrams illustrating steps related to forming a pseudo-blank in the method for bending a bar according to the embodiment of the present invention. [Figure 3] FIG. 3 is an explanatory diagram of a process following FIG. 2. [Figure 4] FIG. 4 is a plan view of an embossing press die used in the steps of FIGS. 2 and 3. [Figure 5] FIG. 4 is a perspective view of a pseudo-blank formed in the steps of FIGS. 2 and 3. [Figure 6] 4 is an explanatory diagram of the steps relating to bending of the pseudo-blank, following FIG. 3. FIG. [Figure 7] FIG. 7 is an explanatory diagram of a process following FIG. [Figure 8] FIG. 8 is an explanatory diagram of a process following FIG. 7. [Figure 9] FIG. 9 is an explanatory diagram of a process following FIG. 8. DETAILED DESCRIPTION OF THE INVENTION

[0010] In the method for bending a bar according to the embodiment of the present invention, a bar W for a bus bar is processed as shown in Fig. 1. The bar W is made of aluminum and has a rectangular cross section with a thickness of 7 mm and a width of 20 mm. First, a pseudo blank gW is created in the middle of the bar W.

[0011] For this molding, a horizontal embossing press die 1 is used, as shown in Figure 2. The embossing press die 1 is made up of a fixed die 3 and a movable die 19. The fixed die 3 is detachably mounted on a fixed stand (not shown) fixed to the base and is fixed to the fixed stand. The fixed die 3 is configured in a flat block shape, and the surface perpendicular to the embossing direction is the transfer surface 5. The transfer surface 5 is perpendicular to the fixed stand, and when viewed from above, its outline is concave, with the center side recessed from the linear portions on the left and right outer sides. The concave bottom surface 7 is linear, and the concave side surfaces 13 and 15 are linearly connected on either side of the rounded corners 9 and 11 on the left and right. The concave side surface 13 tapers toward the concave opening, and the concave side surface 15 is approximately perpendicular to the concave bottom surface 7. The concave side surface 13 further widens in a tapered shape via a step surface 17, and then reaches the concave opening. The concave side surface 15 continues directly to the concave opening.

[0012] The movable mold 19 is detachably mounted on a slide base 35, which is mounted on a base and is capable of moving back and forth in the forward and backward directions, and is fixed to the slide base 35. This movable mold 19 is also configured in a flat block shape, and the embossing direction is the direction in which the slide base 35 moves forward and backward. The surface perpendicular to the embossing direction is the transfer surface 21. The transfer surface 21 is perpendicular to the slide base 35, and its outline is angularly convex when viewed from above. The convex top surface 23 is linear, and convex side surfaces 29, 31 are linearly connected on either side of the rounded corners 25, 27 on the left and right. The convex side surface 29 tapers toward the convex base end, and the convex side surface 31 is approximately perpendicular to the convex top surface 23. Convex side surface 29 is bent midway to become convex side surface 33 parallel to convex side surface 31, and reaches the convex base end. Convex side surface 31 continues to the convex base end.

[0013] As shown in FIG. 4, when viewed from above, the transfer surface 21 of the movable mold 19 is formed in a similar shape to but slightly smaller than the transfer surface 5 of the fixed mold 3. The flat upper surface of the slide base 35 is exposed to the convex top surface 23, the rounded corners 25, 27, and the nearby convex side surfaces 29, 31 that constitute the transfer surface 21 of the movable mold 19, and this flat upper surface serves as the mounting surface 35a for the bar-shaped material W. The bar-shaped material W is placed with the plate surface side of the middle part in contact with the mounting surface 35a. A hydraulic cylinder 37 is connected to the base end side of the movable die 19, and the extension and contraction of the hydraulic cylinder 37 causes the movable die 19 to move in the pressing direction and the return direction while being guided by the slide base 35.

[0014] In molding using the embossing press die 1, the transfer surface 5 of the fixed die 3 and the transfer surface 21 of the movable die 19 always face each other in the embossing direction. As the transfer surface 21 of the movable mold 19 moves toward the transfer surface 5 of the fixed mold 3 by the above-mentioned moving mechanism, the mounting surface 35a moves around to the underside of the lower surface of the fixed mold 3, and the middle part of the rod-shaped material W placed on the mounting surface 35a is pulled into the clearance, which is the gap between the transfer surface 5 and the transfer surface 21. Finally, as shown in FIG. 3, the rod W is sandwiched in the clearance between the transfer surface 5 and the transfer surface 21, and the shapes of the transfer surface 5 and the transfer surface 21 are transferred to the intermediate portion.

[0015] Specifically, between the corner R portion 9 of the transfer surface 5 and the corner R portion 25 of the transfer surface 21, the bending shape of the corner R portion 9 is transferred to the bar W on the outer R side, and the bending shape of the corner R portion 25 is transferred to the bar W on the inner R side. Furthermore, between the corner R portion 11 of the transfer surface 5 and the corner R portion 27 of the transfer surface 21, the bending shape of the corner R portion 11 is transferred to the outer R side, and the bending shape of the corner R portion 27 is transferred to the bar W on the inner R side. The transfer accuracy is high in all areas, but the transfer accuracy on the inner R side is even higher because the bar W is deformed while hitting the movable die 19, which corresponds to the punch. In both cases, the bar W is expanded in the width direction, resulting in a so-called edgewise bend. The areas sandwiched between the other transfer surfaces 5 and 19, i.e., the area sandwiched between the concave bottom surface 7 and the convex top surface 23, the area sandwiched between the concave side surface 13 and the convex side surface 29, and the area sandwiched between the concave side surface 15 and the convex side surface 31, are not bent because clearance is secured to maintain the width dimension of the rod-shaped material W.

[0016] This embossing process causes the middle part of the bar W to take on a U-shape, as shown in Figure 5. At bent sections A and B, the bar W is expanded in the width direction, changing its width, but it is not expanded in the thickness direction, resulting in a shape expanded on a single plane similar to a blank made by punching a flat plate. In other words, it is a "pseudo-blank gW."

[0017] This pseudo-blank gW is subjected to bending processing using a vertical bending press die 39 while being set in the stamping press die 1. The pseudo-blank gW is constrained to the embossing press die 1 at the constrained portion W1 but is not constrained at the non-constrained portion W2, and specifically, the non-constrained portion W2 is subjected to bending. The bending press die 39 is disposed outside the convex side surface 29 of the movable die 19 of the stamping press die 1 in the left-right direction. The processing points that form the transfer surface of the bending press die 39 are designed with the movable die 19 as the processing reference.

[0018] The mounting surface 35a, which is a plane integral with the movable mold 19, is used as the reference plane. Furthermore, as shown in the enlarged view of FIG. 4, of the arc centers R1 and R2 of the rounded corners 25 and 27 of the movable mold 19, the arc center R1 on the reference plane is used as the reference point (origin). Furthermore, the line connecting the arc centers R1 and R2 on the reference plane is used as the reference line. Thus, an xyz coordinate system is established, with the direction vertically perpendicular to the reference plane (zero plane) being the z-axis, the reference line on the reference plane being the x-axis, and the direction perpendicular to the reference line being the y-axis. Note that in the enlarged view of FIG. 4, the arcs of the rounded corners 25 and 27 are exaggerated for ease of visualization. Based on this xyz coordinate system, processing points that form the bending portion of the dies 41, 43, 45, and 47 that form the bending press die 39 are set in accordance with the bending shape that is desired to be imparted to the unconstrained portion W2 of the bar W.

[0019] The pseudo-blank gW has a restrained area W1 in its middle, where it is sandwiched between the fixed mold 3 and the movable mold 19 of the embossing press mold 1, but the outside of that is not restrained and forms a non-restrained area W2. The bending press die 39 bends and deforms this free unconstrained region W2 in the z-axis direction by sandwiching the free unconstrained region W2 from above and below with dies 41, 43, 45, and 47.

[0020] 6 to 9, the non-constrained portion W2 is bent. The movable die 19 is omitted from the drawings for ease of visualization. Mold 41 having an upper flat surface 41a abuts against the plate surface of non-constraint region W2 from below, and mold 43 having a lower flat surface 43a and a lower inclined surface 43b abuts against the plate surface of non-constraint region W2 from above, with the non-constraint region W2 sandwiched between the upper flat surface 41a of mold 41 and the lower flat surface 43a of mold 43. Furthermore, mold 45 having an upper flat surface 45a and an upper inclined surface 45b abuts against mold 41 and also abuts against the plate surface of non-constraint region W2 from below, with the non-constraint region W2 sandwiched between the upper inclined surface 45b of mold 45 and the lower inclined surface 43b of mold 43. Next, a mold 47 having a lower flat surface 47a and a lower inclined surface 47b abuts against the mold 43 and abuts against the plate surface of the non-constrained portion W2 from above, sandwiching the non-constrained portion W2 between the upper flat surface 45a and upper inclined surface 45b of the mold 45 and the lower flat surface 47a and lower inclined surface 47b of the mold 47. At the boundary between the inclined surface and the flat surface of the mold, the non-constrained portion W2 is bent in the thickness direction of the plate, forming bent portions C and D at two locations.

[0021] The pseudo-blank gW is formed according to the die standard of the embossing press die 1, and for the subsequent bending process, it is treated as an integrated part with the embossing press die 1, including the non-constrained portion W2. The bending press die 39 used in the next bending process is designed with the movable die 19 of the stamping press die 1 as the processing reference. Therefore, the bending shape of the unconstrained portion W2 is guaranteed to have the machining accuracy based on the die.

[0022] In reality, bus bars are bent in multiple locations in the x, y, and z directions, but by manufacturing and arranging multiple bending press dies 39 based on the above processing standards, a single long rod-shaped material W is bent in multiple locations as if in a progressive press process, thereby achieving high overall processing precision.

[0023] Although the embodiments of the present invention have been described in detail above, the specific configuration is not limited to these embodiments, and the invention also includes design changes within the scope of the present invention without departing from the gist of the present invention. For example, the portion of the rod-shaped material W that is clamped by the stamping press die 1 will be set in a location that can efficiently meet conditions such as the installation location of the bending press die 39, in accordance with the final three-dimensional processed shape, and is not necessarily limited to the central portion. For example, if the mold has three or more rounded corners, these may be used as the processing standard. The bending press die 39 may include those for edgewise bending and those for torsional bending. [Explanation of symbols]

[0024] 1... Embossing press mold 3... Fixed mold 5... Transfer surface 7...Concave bottom surface 9, 11...Corner R section 13, 15...Concave side surface 17...Step surface 19...Movable mold 21...Transfer surface 23...Convex top surface 25, 27...Corner R section 29, 31...Convex side surface 33...Convex side surface 35...Slide base 35a...Placement surface 37...Hydraulic cylinder 39...Bending press die 41...Die 41a...Upper surface 43...Mold 43a...Lower surface 43b...lower inclined surface 45...mold 45a...upper flat surface 45b...upper inclined surface 47...mold 47a...lower flat surface 47b…Downward slope W...Bar material gW...Pseudo blank W1: Restrained area of ​​the pseudo-blank W2: Unrestrained area of ​​the pseudo-blank R1, R2...Arc center

Claims

1. A method for bending a rod-shaped material, comprising: A quasi-blank is created by embossing an intermediate portion of the rod-shaped material using an embossing press die and transferring the bending shape of the embossing press die to the rod-shaped material; A bending method characterized by bending the unconstrained portion of the pseudo-blank using a bending press die designed with one of the dies of the embossing press die as the processing reference, while leaving a portion of the pseudo-blank in a constrained state to the embossing press die.

2. 2. The method for bending a rod-shaped material according to claim 1, A bending method characterized in that one of the dies is a movable die.

3. 3. The method for bending a rod-shaped material according to claim 2, A bending method characterized in that one of the embossing press dies includes a plane and two rounded corners, and the bending press die is designed using the plane as a reference plane, the center of the arc of one of the rounded corners as a reference point, and a straight line connecting the centers of the arcs of each of the rounded corners as a reference line.

4. 4. The method for bending a rod-shaped material according to claim 3, A bending method characterized in that one of the dies has a surface for placing the rod-shaped material, and the bending press die is designed using the above-mentioned surface as a reference plane.

5. 5. The method for bending a rod according to claim 4, A bending method characterized in that the stamping press die is for edgewise bending.

6. A press die used in the method for bending a rod-shaped material according to any one of claims 1 to 5.

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