JP2007075888A - Press punching method, press punching die, and spring - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a press punching method in which burrs are hardly generated in a workpiece. <P>SOLUTION: The press punching method comprises a half-blanking step of forming a protruded part W1 by pressing a predetermined part of a workpiece W from one face side of the plate workpiece W and protruding the predetermined part to the other face side opposite to the one face side, a common pushing step of forming a restored part by pushing back the protruded part W1 from the other face side, and a drop-through step of forming a dropped-through part by dropping through the restored part from the other face side. The workpiece W is formed of spring steel. The clearance C1 between a half-blanking punch 36 used for the half-blanking step and a half-blanking die 26 is set to be ≥-10% and ≤-3%, where the thickness t of the workpiece W is defined as 100%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a press punching method and a press punching die for punching a plate-shaped workpiece. The present invention also relates to a spring produced by punching a plate-like workpiece.

  In a spring such as a leaf spring or a cylindrical spring, a curved portion, a slit, or the like is formed by a punching process in which a predetermined part of a workpiece is removed. Stress is likely to concentrate around these curved portions and slits during subsequent bending or when using a spring. For this reason, if a burr remains around the part to be removed, a crack may occur starting from the burr.

  Spring steel has high hardness and low elongation. For this reason, in the case of a type of spring that is subjected to bending after punching (for example, a cylindrical spring), when bending is performed with the burr generation side surface being the outer diameter side, there is a risk that cracks will occur starting from the burr. is there.

In this way, if the burr remains on the workpiece after the punching process, various problems may occur. For this reason, conventionally, burr has been removed by performing post-processing such as barrel polishing on the workpiece after punching.
Japanese Patent Laid-Open No. 2002-120025

  However, if post-processing is performed after punching, the number of press molding steps increases correspondingly, and productivity decreases. In addition, the manufacturing cost of the spring increases. In this regard, Patent Document 1 introduces a punching method in which a predetermined part of a workpiece is first half-cut and then the predetermined part is dropped.

  However, the workpiece used in the punching method is made of aluminum. Aluminum has low hardness and high elongation. For this reason, the punching method for aluminum cannot be used for spring steel. The reason is that, as described above, spring steel has high hardness and low elongation. For this reason, if the punching method is used for a workpiece made of spring steel, cracks occur early and fracture starts.

  The press punching method, the press punching die, and the spring of the present invention have been completed in view of the above problems. Accordingly, an object of the present invention is to provide a press punching method and a press punching die in which burr is hardly generated on a workpiece. Another object of the present invention is to provide a spring in which cracks caused by burr are unlikely to occur.

  (1) In order to solve the above-described problem, the press punching method of the present invention presses a predetermined portion of the workpiece from one surface side of the plate-like workpiece, and the predetermined portion on the other surface side facing the one surface side. Projecting part to form a projecting part, pushing back the projecting part from the other surface side, pressing back to form a restoring part, and removing the restoring part from the other surface side A punching step for forming a drop-off site, wherein the workpiece is made of spring steel, and the thickness of the workpiece is set to 100%. The clearance between the punch and the half die is set to -10% or more.

  Clearance refers to the size of the gap on one side of the punch and die. In this specification, the clearance is expressed as “+” when the punch hole area is larger than the punch hole area when the punch hole area is larger, and “−” when the punch hole is larger. Arbitrary number A “more than” means a plus direction including A. Arbitrary numeral A “below” means a negative direction including A. In addition, the “plate shape” in this specification is a concept including a belt shape.

  The clearance between the half punch and the half punch die is one of the important factors for suppressing the occurrence of burr. By setting the clearance to be negative, the hydrostatic pressure inside the workpiece can be increased and the occurrence of cracks can be suppressed. For this reason, the ratio of the shear area | region which occupies for the cut surface of the workpiece | work after a drop-off process can be enlarged. That is, the cut surface can be smoothed.

  When the clearance is -10% or more (plus direction including -10%) is less than -10% (minus side than -10%), the fracture occupies the cut surface of the workpiece after the removal process This is because the area ratio increases. That is, it is difficult to keep the cut surface smooth. Moreover, it is because a relatively large shear load is required in combination with the high hardness of the spring steel. That is, a press punching die that can output a relatively large press load is required, and the cost required for press punching increases.

  In the press punching method of the present invention, the thickness of the workpiece is set to 100%, and the clearance between the half punching punch and the half punching die used in the half punching step is set to -3% or less. And

  The clearance is set to -3% or less (minus direction including -3%) when it exceeds -3% (in the case of a plus side from -3%), the above-mentioned hydrostatic pressure inside the work is insufficient, and the cut surface This is because cracks may occur on the surface.

  According to the press punching method of the present invention, even when a workpiece made of spring steel having high hardness and small elongation is processed, burr is hardly generated on the workpiece. For this reason, it is not necessary to perform post-processing such as barrel polishing after the dropping step. Therefore, the number of press molding processes can be reduced. In addition, productivity is improved.

  Preferably, in order to absorb the deformation amount of the workpiece due to at least one of the half-punching step and the flat pushing step, it is better to set an absorption margin to the width of the workpiece. In the present specification, the width means at least one of a feed and an edge.

  In the half punching process and the flat pressing process, deformation such as distortion, warpage, and twist is likely to occur in the workpiece. For this reason, depending on the degree of deformation, it may be considered that the restoration site cannot be accurately removed in the subsequent removal step. If the dropout accuracy is poor, the dimensional accuracy of the product may deteriorate. Moreover, there is a possibility that a dent will be generated when the thread string, which is to be removed, is pushed into the workpiece.

  In this respect, according to this configuration, an absorption margin is set for the width of the workpiece. The amount of deformation of the workpiece can be absorbed by the absorption allowance. For this reason, in a drop-out process, a restoration part can be correctly dropped out. Therefore, there is little possibility that the dimensional accuracy of the product deteriorates or a dent is generated.

  Preferably, in order to absorb the deformation amount of the workpiece by at least one of the half-punching step and the flat pushing step, it is better to have a configuration in which a discard hole is arranged in the workpiece. According to this configuration, the hole is disposed in the workpiece. The amount of deformation of the workpiece described above can be absorbed by the discard hole. For this reason, in a drop-out process, a restoration part can be correctly dropped out. Therefore, there is little possibility that the dimensional accuracy of the product deteriorates or a dent is generated.

  Preferably, in order to suppress deformation of the workpiece due to the flat pushing process, it is better to have a configuration in which the pressing range and the protruding portion are substantially coincided when the protruding portion is pushed back. According to this configuration, the surface pressure during the flat pressing process is increased. For this reason, the deformation | transformation of the workpiece | work by a flat pushing process can be suppressed. Therefore, the restoration site can be accurately removed in the removal step. Moreover, there is little possibility that the dimensional accuracy of the product deteriorates or a dent is generated.

  Preferably, when a plurality of the projecting portions are formed, the flat pressing process is preferably performed immediately after the half-punching process. That is, this structure performs a flat pushing process immediately after a half-punching process, when forming a some dropping part in a workpiece | work. According to this configuration, pressing forces in opposite directions are continuously applied to the workpiece. For this reason, the deformation amount of the workpiece described above can be reduced. Therefore, the restoration site can be accurately removed in the removal step.

  (2) Preferably, the clearance between the drop punch used in the drop step and the drop die is preferably set to 3% or more. The reason why the clearance is set to 3% or more (plus direction including 3%) is that if it is less than 3% (in the case of minus side than 3%), cracks may occur on the cut surface.

  Preferably, the clearance between the drop punch used in the drop step and the drop die should be set to 10% or less. The clearance is set to 10% or less (minus direction including 10%) when it exceeds 10% (in the case of the plus side over 10%), the sagging area or the fracture area occupying the cut surface of the workpiece after the dropping process This is because the ratio of increases. That is, it is difficult to keep the cut surface smooth.

  Preferably, the absolute value of the clearance between the half punching punch and the half punching die used in the half punching process and the absolute value of the clearance between the punching punch and the punching die used in the dropping process are the same. Is better. If it carries out like this, it can suppress that a malfunction generate | occur | produces in the cut surface of a workpiece | work.

  (3) Preferably, the thickness of the workpiece is set to 100%, and the insertion amount of the half-punching punch into the workpiece is preferably set to 50% or more. The reason why the insertion amount is set to 50% or more is that when it is less than 50%, the ratio of the sagging area to the cut surface of the work after the dropping process is increased.

  Preferably, the thickness of the workpiece is 100%, and the insertion amount of the half-punch punch into the workpiece is preferably set to 80% or less. The reason why the insertion amount is set to 80% or less is that if it exceeds 80%, a relatively large shear load is required in combination with the high hardness of the spring steel. That is, a press punching die that can output a relatively large press load is required, and the cost required for press punching increases.

  (4) Preferably, it is better to have a configuration in which the protruding portion is set in a portion adjacent to the stress concentration portion of the workpiece after the dropping step. That is, this structure arrange | positions the protrusion site | part in the half extraction process (drop-out site | part in the extraction process) next to the stress concentration site | part of the workpiece | work after extraction.

  In this specification, the stress concentration part means a part where stress is concentrated when the product is used. Moreover, when processing (for example, bending process) to the workpiece | work after a drop-off process, the site | part where stress concentrates at the time of a process is included. A plurality of stress concentration sites may exist for a single product or workpiece.

  According to this configuration, burr hardly occurs on the plate thickness surface (cut surface) of the stress concentration portion of the workpiece. For this reason, when bending a workpiece, for example, cracks starting from burr are unlikely to occur. Moreover, when using a product, it is difficult for stress to concentrate on a specific part of the product.

  Also, when setting the protruding part to a part not adjacent to the stress concentration part, in other words, when the press punching method of the present invention is applied to the part not adjacent to the stress concentration part, it is also considered that the hardness of the spring steel is high. Therefore, a relatively large shear load is required. For this reason, a press punching die capable of outputting a relatively large press load is required, and the cost required for press punching increases. In addition, when a progressive die is used as the press punching die, the press load required for the half punching process, flat pressing process, and punching process is excessive compared to the press load required for other processes (for example, bending process). Become. For this reason, the press load balance is biased over the entire press punching die. Therefore, it may be considered that the molding is adversely affected.

  In this regard, according to the present configuration, the press punching method of the present invention is applied only to a portion adjacent to the stress concentration portion of the workpiece after the dropping step. For this reason, the surface pressure in the half punching process, the flat pressing process, and the dropping process can be increased. Therefore, it is not necessary to dare to use a press punching die that can output a relatively large press load, and the cost required for press punching can be reduced accordingly. In addition, when a progressive die is used as the press punching die, the press load required for the half punching process, flat pressing process, and drop-off process is less likely to be excessive compared to the press load required for other processes. . For this reason, it is possible to suppress unevenness of the press load balance over the entire press punching die. Therefore, it is difficult to adversely affect the molding.

  (5) Moreover, in order to solve the said subject, the press punching die of this invention presses the predetermined site | part of this workpiece | work from the one surface side of a plate-shaped workpiece | work, and the other surface side facing this one surface side, A press comprising: a half punching punch that forms a protruding portion by projecting a predetermined portion; and a half punching die that is disposed opposite to the half punching punch and has a half punching hole that accommodates the protruding portion. It is a punching die, the workpiece is made of spring steel, and the thickness of the workpiece is 100%, and the clearance between the half-punching punch and the half-punching die is set to -10% or more. Features.

  The clearance between the half punch and the half punch die is one of the important factors for suppressing the occurrence of burr. By setting the clearance to be negative, the hydrostatic pressure inside the workpiece can be increased and the occurrence of cracks can be suppressed. For this reason, the ratio of the shear area | region which occupies for the cut surface of the workpiece | work after extracting can be enlarged. That is, the cut surface can be smoothed.

  The reason why the clearance is set to -10% or more is that, when the clearance is less than -10%, the ratio of the fracture area to the cut surface of the workpiece after being removed increases. That is, it is difficult to keep the cut surface smooth. Moreover, it is because a relatively large shear load is required in combination with the high hardness of the spring steel. That is, a press punching die that can output a relatively large press load is required, and the cost required for press punching increases.

  The press punching die of the present invention is characterized in that the thickness of the workpiece is 100%, and the clearance between the half punch and the half punch die is set to -3% or less. The reason why the clearance is set to -3% or less is that when it exceeds -3%, the hydrostatic pressure inside the workpiece is insufficient, and cracks may occur on the cut surface.

  According to the press punching die of the present invention, even when a workpiece made of spring steel having high hardness and small elongation is processed, burr is hardly generated on the workpiece. For this reason, it is not necessary to perform post-processing such as barrel polishing after the removal. Therefore, the number of press molding processes can be reduced. In addition, productivity is improved.

  Preferably, in the configuration of (5) above, by further pushing back the protruding portion from the other surface side, a flat push punch that forms a restoring portion, and dropping the restoring portion from the other surface side, A punching punch for forming a punching site; and a punching die disposed opposite to the punching punch and having a punching hole capable of accommodating the punching site; In order to absorb the deformation amount of the work by at least one of the presses by the flat push punch, it is better to set an absorption allowance for the width of the work.

  In a half punching process using a half punch or a flat pressing process using a flat punch, deformation such as distortion, warpage, and twist is likely to occur in the workpiece. For this reason, depending on the degree of deformation, it may be considered that the restoration site cannot be accurately removed in the subsequent removal step. If the dropout accuracy is poor, the dimensional accuracy of the product may deteriorate. Moreover, there is a possibility that a dent will be generated when the thread string, which is to be removed, is pushed into the workpiece.

  In this respect, according to this configuration, an absorption margin is set for the width of the workpiece. The amount of deformation of the workpiece can be absorbed by the absorption allowance. For this reason, in the drop-out process using the drop-out punch, the restoration site can be accurately removed. Therefore, there is little possibility that the dimensional accuracy of the product deteriorates or a dent is generated.

  Preferably, in the configuration of (5) above, by further pushing back the protruding portion from the other surface side, a flat push punch that forms a restoring portion, and dropping the restoring portion from the other surface side, A punching punch for forming a punching site; and a punching die disposed opposite to the punching punch and having a punching hole capable of accommodating the punching site; In order to absorb the deformation amount of the work due to at least one of the presses by the flat push punch, it is better to have a configuration in which a discard hole is arranged in the work.

  According to this configuration, the hole is disposed in the workpiece. The amount of deformation of the workpiece described above can be absorbed by the discard hole. For this reason, in the drop-out process using the drop-out punch, the restoration site can be accurately removed. Therefore, there is little possibility that the dimensional accuracy of the product deteriorates or a dent is generated.

  Preferably, in the configuration of (5) above, by further pushing back the protruding portion from the other surface side, a flat push punch that forms a restoring portion, and dropping the restoring portion from the other surface side, A punching punch that forms a dropping part, and a dropping die that is arranged opposite to the dropping punch and has a dropping hole that can accommodate the dropping part, and is provided by pressing the flat punch In order to suppress the deformation of the workpiece, it is preferable that the pressing range and the protruding portion are substantially matched when the protruding portion is pushed back.

  According to this configuration, the surface pressure during the flat pressing process using the flat pressing punch is increased. For this reason, the deformation | transformation of the workpiece | work by a flat pushing process can be suppressed. Therefore, the restoration site can be accurately removed in the removal step. Moreover, there is little possibility that the dimensional accuracy of the product deteriorates or a dent is generated.

  Preferably, in the configuration of (5) above, by further pushing back the protruding portion from the other surface side, a flat push punch that forms a restoring portion, and dropping the restoring portion from the other surface side, A punching punch that forms a punching site; and a punching die that is disposed opposite to the punching punch and has a punching hole that can accommodate the punching site. A plurality of half-punch sets made of a punching die, a flat-pushing set having the flat-pushing punch, a drop-off punch and a drop-off set consisting of the drop-off die are each arranged. It is better to have a configuration in which they are arranged adjacent to each other with a predetermined interval.

  That is, this configuration is a press punching die that forms a plurality of drop-off portions on a workpiece, and a half punch set and a flat press set are arranged next to each other. According to this configuration, the pressing forces in opposite directions are simultaneously applied to the workpiece side by side. For this reason, the deformation amount of the workpiece described above can be reduced. Therefore, in the drop-out process using the drop-out set, the restoration site can be accurately removed.

  (6) Preferably, in the configuration of (5) above, a removal site is formed by removing a restoration site formed by pushing back the projecting site from the other surface side. A punching die comprising: a punching punch that is disposed opposite to the punching punch, and a punching die having a punching hole that can accommodate the punching site. It is preferable that the thickness is set to 100% and the clearance between the punching punch and the punching die is set to 3% or more. The reason why the clearance is 3% or more is that if it is less than 3%, cracks may occur on the cut surface.

  Preferably, the thickness of the workpiece is 100%, and the clearance between the drop punch and the drop die is preferably set to 10% or less. The reason why the clearance is set to 10% or less is that when it exceeds 10%, the ratio of the sagging area or the fracture area in the cut surface of the workpiece after being removed increases. That is, it is difficult to keep the cut surface smooth.

  (7) Preferably, in the configuration of (5) above, the thickness of the workpiece is 100%, and the insertion amount of the half-punching punch into the workpiece is set to 50% or more. Good. The reason why the insertion amount is set to 50% or more is that when it is less than 50%, the ratio of the sagging area to the cut surface of the workpiece after being removed increases.

  Preferably, the thickness of the workpiece is 100%, and the insertion amount of the half-punch punch into the workpiece is preferably set to 80% or less. The reason why the insertion amount is set to 80% or less is that if it exceeds 80%, a relatively large shear load is required in combination with the high hardness of the spring steel. That is, a press punching die that can output a relatively large press load is required, and the cost required for press punching increases.

  (8) Preferably, in the configuration of the above (5), the half-punching punch includes a convex portion for forming the protruding portion in a portion adjacent to the stress concentration portion of the workpiece after being removed. Better to do.

  That is, this structure arrange | positions a convex part to a half punch punch. And the protrusion part forms a projecting part by the said convex part. According to this configuration, burr hardly occurs on the plate thickness surface (cut surface) of the stress concentration portion of the workpiece. For this reason, when bending a workpiece, for example, cracks starting from burr are unlikely to occur. Moreover, when using a product, it is difficult for stress to concentrate on a specific part of the product.

  In addition, when setting the projecting part to a part not adjacent to the stress concentration part, in other words, when applying the press punching die of the present invention to the part not adjacent to the stress concentration part, it is also considered that the hardness of the spring steel is high. Therefore, a relatively large shear load is required. For this reason, a press punching die capable of outputting a relatively large press load is required, and the cost required for press punching increases. In addition, when a progressive die is used as the press punching die, the press load required for the half punching process, flat pressing process, and punching process is excessive compared to the press load required for other processes (for example, bending process). Become. For this reason, the press load balance is biased over the entire press punching die. Therefore, it may be considered that the molding is adversely affected.

  In this regard, according to the present configuration, the half-cutting process is performed only on the part adjacent to the stress concentration part of the workpiece after the dropping process. For this reason, the surface pressure in the half punching process, the flat pressing process, and the dropping process can be increased. Therefore, it is not necessary to dare to use a press punching die that can output a relatively large press load, and the cost required for press punching can be reduced accordingly. In addition, when a progressive die is used as the press punching die, the press load required for the half punching process, flat pressing process, and drop-off process is less likely to be excessive compared to the press load required for other processes. . For this reason, it is possible to suppress unevenness of the press load balance over the entire press punching die. Therefore, it is difficult to adversely affect the molding.

  (9) Moreover, in order to solve the said subject, the spring of this invention is a spring provided with one surface, the other surface facing this one surface, and the board thickness surface which connects this one surface and this other surface. In the plate thickness surface included in the stress concentration site, from the one surface side toward the other surface side, a first sag region, a first shear region, a fracture region, a second shear region, And a second sagging region.

  The half punching process is performed in a direction from one surface to the other surface. The first sag region and the first shear region are formed on the cut surface (corresponding to the plate thickness surface of the spring) in the half punching process. The flat pressing process is performed in a direction from the other surface to the one surface. The second sag region and the second shear region are formed on the cut surface in the flat pushing process. The fracture region is formed on the cut surface in a pulling-out process in which scrap is pulled out from a work (corresponding to a spring).

  According to the spring of the present invention, burr hardly occurs at the boundary between the first sag region and the one surface and the boundary between the second sag region and the other surface. For this reason, it is not necessary to perform post-processing such as barrel polishing after the dropping step. Therefore, the manufacturing cost of the spring can be reduced. Further, according to the spring of the present invention, cracks caused by burr are unlikely to occur.

  Preferably, it is better to have a configuration in which no polishing mark is formed at the boundary between the first sag region and the one surface and the boundary between the second sag region and the other surface. According to this configuration, it is difficult for cracks due to polishing marks to occur.

  According to the present invention, it is possible to provide a press punching method and a press punching die in which burr is hardly generated on a workpiece. In addition, according to the present invention, it is possible to provide a spring in which cracks caused by burr are unlikely to occur.

  Hereinafter, embodiments of a press punching method, a press punching die, and a spring according to the present invention will be described.

  <First embodiment>

  First, the structure of the press punching die of this embodiment will be described. FIG. 1 shows a cross-sectional view of the press punching die of the present embodiment as viewed from the lateral direction. FIG. 2 is a cross-sectional view taken along the line II of FIG. 1 corresponds to a cross-sectional view taken along the line II-II in FIG. Further, these drawings show a press punching die when the die is opened.

  As shown in these drawings, the press punching die 1 is a progressive die. The press punching die 1 includes an upper die 2 and a lower die 3. The upper die 2 includes a die set 20, a backing plate 21, an upper die plate 22, a movable stripper plate 23, a stripper bolt 24, a guide bush 25, a half punch die insert 26, a flat push punch 27, and a drop punch 28. Yes. The half die insert 26 is included in the half die according to the present invention.

  The die set 20 is made of steel and has a rectangular plate shape. A bushing hole 200 and a first bolt hole 201 are formed in the die set 20. A total of two bush holes 200 are arranged at diagonal positions of the die set 20. The guide bush 25 is made of steel and has a cylindrical shape. The guide bush 25 is inserted and fixed in the bush hole 200. A total of four first bolt holes 201 are arranged at positions facing vertically in four corners of the backing plate 21 described later.

  The backing plate 21 is made of steel and has a rectangular plate shape. A total of four second bolt holes 210 are formed at the four corners of the backing plate 21. The inner diameter of the second bolt hole 210 is set smaller than the inner diameter of the first bolt hole 201.

  The upper mold plate 22 is made of steel and has a rectangular plate shape. A total of four third bolt holes 220 are formed at the four corners of the upper mold plate 22. The inner diameter of the third bolt hole 220 is set larger than the inner diameters of the first bolt hole 201 and the second bolt hole 210. In the center of the upper mold plate 22, half-cut die insert fixing holes 221, flat push punch fixing holes 222, and punching punch fixing holes 223 are formed in a line.

  The half die insert 26 is made of steel and has a bottomed rectangular tube shape that opens upward. A half punching hole 260 is formed in the lower bottom portion of the half punching die insert 26. The cross-section of the half punched hole 260 has an elongated oval shape (a shape in which a pair of parallel straight lines are connected by a semicircle, and so on). The upper end portion of the half die insert 26 is fixed to the half die insert fixing hole 221. The flat push punch 27 is made of steel and has a rectangular plate shape. The upper end portion of the flat press punch 27 is fixed to the flat press punch fixing hole 222. The punching punch 28 is made of steel and has a rectangular plate shape with a sharp lower end. The cross section of the lower end portion of the punching punch 28 has an elongated oval shape. The upper end portion of the punching punch 28 is fixed to the punching punch fixing hole 223.

  The movable stripper plate 23 is made of steel and has a rectangular plate shape. Fourth bolt holes 230 are formed in the four corners of the movable stripper plate 23. The inner diameter of the fourth bolt hole 230 is set smaller than the inner diameter of the third bolt hole 220. The fourth bolt hole 230, the third bolt hole 220, the second bolt hole 210, and the first bolt hole 201 are arranged in series in the vertical direction. The stripper bolt 24 is made of steel and has a stepped hexagonal bolt shape. The stripper bolts 24 are inserted into the first bolt hole 201, the second bolt hole 210, the third bolt hole 220, and the fourth bolt hole 230 in order from the top. The lower end portion of the stripper bolt 24 is screwed into the fourth bolt hole 230. A total of four stripper bolts 24 are arranged as shown by a two-dot chain line in FIG. A coil spring 240 made of spring steel is mounted around the portion of the stripper bolt 24 where the third bolt hole 220 is inserted. The coil spring 240 is interposed between the lower surface of the upper backing plate 21 and the upper surface of the lower movable stripper plate 23. The coil spring 240 urges the backing plate 21 and the movable stripper plate 23 in a direction away from each other. The upper head of the stripper bolt 24 is locked to the upper surface of the backing plate 21 by the urging force of the coil spring 240.

  In the center of the movable stripper plate 23, a half punch die insert slide hole 231, a flat press punch slide hole 232, and a drop punch slide hole 233 are formed in a line. The half punching die insert slide holes 231 are arranged in series with the half punching die insert fixing hole 221 in the vertical direction. The half punching die insert slide hole 231 has a lower bottom portion of the half punching die insert 26 and the shape of the mold target. The lower bottom portion of the half die insert 26 is slidably accommodated in the half die insert slide hole 231. The flat push punch slide holes 232 are arranged in series with the flat push punch fixing holes 222 in the vertical direction. The flat push punch slide hole 232 has a lower end portion of the flat push punch 27 and the shape of the mold target. The flat push punch slide hole 232 accommodates the lower end portion of the flat push punch 27 so as to be slidable. The drop punch slide hole 233 is arranged in series with the drop punch fixing hole 223 in the vertical direction. The drop punch slide hole 233 has a lower end portion of the drop punch 28 and the shape of the mold target. The lower end portion of the drop punch 28 is slidably accommodated in the drop punch slide hole 233.

  The lower die 3 includes a base 30, a support base 31, a lower die plate 32, a post 33, a half punch punch 36, and a drop die insert 38. The drop die insert 38 is included in the drop die of the present invention.

  The base 30 is made of steel and has a rectangular plate shape. The post 33 is made of steel and has a cylindrical shape. A total of two posts 33 project from diagonal positions on the upper surface of the base 30. The post 33 is opposed to the guide bush 25 of the upper mold 2 in the vertical direction. The upper end of the post 33 is inserted into the guide bush 25 so as to be slidable.

  The support base 31 is made of steel and has a rectangular plate shape. The support base 31 is fixed to the upper surface of the base 30. The lower mold plate 32 is made of steel and has a rectangular plate shape. The lower mold plate 32 is fixed to the upper surface of the support base 31. In the center of the lower die plate 32, a half punch punch hole 320 and a drop die insert hole 321 are formed in a line. The cross section of the half punching punch 36 has an elongated oval shape. The half punch punch 36 is fixed to the half punch hole 320. The half punching punch 36 faces the half punching hole 260 in the vertical direction. The withdrawal die insert 38 is made of steel and has a rectangular plate shape. The drop-out die insert 38 is formed with a drop-off hole 380 having an oblong shape with a narrow cross section. The drop die insert 38 is fixed to the drop die insert hole 321. The dropout hole 380 faces the dropout punch 28 in the vertical direction.

  The workpiece W is made of SK5 and has a strip shape. The workpiece W is placed on the upper surface of the lower mold plate 32. In FIG. 2, the work W is arranged along the direction in which the half punching punch 36 and the punching die insert 38 are arranged. This direction is the feed direction of the workpiece W.

  Next, the press punching method of this embodiment will be described. The press punching method of the present embodiment includes a half punching process, a flat pressing process, and a dropping process. FIG. 3 shows a cross-sectional view seen from the lateral direction when the press punching die of the present embodiment is clamped. As shown in the drawing, at the time of mold clamping, the upper mold 2 approaches the lower mold 3 by relatively guiding the post 33 to the guide bush 25. At this time, the lower surface of the movable stripper plate 23 comes into elastic contact with the upper surface of the workpiece W by the biasing force of the coil spring 240. The upper surface of the workpiece W is included in the other surface of the present invention. By elastic contact with the lower surface of the movable stripper plate 23, deformation such as warping of the workpiece W during mold clamping is suppressed. In addition, the workpiece W can be quickly separated from the upper mold 2 when the mold is opened.

  In the half punching process, a projecting portion is formed on the workpiece W by pressing a predetermined portion of the workpiece W. FIG. 4 shows a schematic diagram of the half-punch process. As shown in the figure, in the present step, the lower surface of the half die insert 26 presses the upper surface of the workpiece W. The upper end portion of the half punching punch 36 protrudes from the upper surface of the lower mold plate 32 by an insertion amount S. The lower surface of the predetermined part of the workpiece W is relatively pressed from below by the projecting portion as indicated by a white arrow in the figure. Note that the lower surface of the workpiece W is included in one aspect of the present invention. The meat of the workpiece W raised upward by the pressing escapes into the half punching hole 260 while being regulated by the hole diameter of the half punching hole 260. In this way, the protruding portion W1 is formed in the half punching hole 260. In addition, when the workpiece W is deformed, a first sag region and a first shear region described later are formed on the cut surface of the workpiece W.

  In this process, the thickness C of the workpiece W is set to 100%, and the clearance C1 between the half punching punch 36 and the half punching die insert 26 is -6% (the half punching punch 36 is larger than the half punching hole 260). Negative clearance) is set. Further, assuming that the plate thickness t of the workpiece W is 100%, the insertion amount S of the half punching punch 36 into the workpiece W is set to 65%.

  In the flat pushing process, the restored portion is formed on the workpiece W by pushing back the protruding portion W1. FIG. 5 shows a schematic diagram of the flat pressing process. In the present process, the lower surface of the flat push punch 27 presses the upper surface of the workpiece W as indicated by the white arrow in the figure. Due to the pressing, the protruding portion W1 (see FIG. 4) once protruding upward in the previous process is pushed back downward again. In this way, the restoration site W2 is formed. In addition, when the workpiece W is deformed, a second sag region and a second shear region described later are formed on the cut surface on the upper surface side of the workpiece W.

  In the drop-out process, the drop-out site W3 is formed by removing the restoration site W2. FIG. 6 shows a schematic diagram of the dropping process. As shown by the white arrow in the figure, in this step, the lower end portion of the punching punch 28 protruding from the lower surface of the movable stripper plate 23 causes the restoration site W2 (see FIG. 5 above) to enter the dropping hole 380. Remove it. In this way, a dropout portion W3 is formed. In addition, when the drop-off site W3 falls off, a fracture region described later is formed on the cut surface of the workpiece W.

  In this process, the thickness C of the workpiece W is set to 100%, and the clearance C2 between the punching punch 28 and the punching die insert 38 is 6% (the punching hole 380 is larger than the punching punch 28 plus Clearance) is set.

  In FIG. 7, the schematic diagram of the cut surface of the workpiece | work after a drop-off process is shown. For convenience of explanation, the cut surface is hatched. As shown in the figure, the first sag region F1, the first shear region F2, the fracture region F3, the second shear region F4, and the second sag region are formed on the cut surface F of the workpiece W from the lower surface side to the upper surface side. F5 is formed. Further, the cut surface F has no burr on the upper surface side or the lower surface side. FIG. 7 schematically shows each area, and the size of each area is not limited to that figure. The cut surface F is included in the plate thickness surface of the present invention.

  The first sag region F1 and the first shear region F2 are formed in the half-punch process (see FIG. 4 above). The first sag region F1 has a curved smooth surface shape. The first shear region F2 is a glossy surface and has vertical stripes in the vertical direction.

  The second sag region F5 and the second shear region F4 are formed in the flat pushing process (see FIG. 5 above). The second sag region F5 has a curved smooth surface shape. The second shear region F4 is a glossy surface and has vertical stripes in the vertical direction.

  The fracture region F3 is formed in the drop-out process (see FIG. 6 above). The fracture region F3 is formed by a crack (not shown) propagating from the upper end of the first shear region F2 and a crack (not shown) propagating from the lower end of the second shear region F4. In the fracture region F3, irregularities are formed as if the material was stripped. The workpiece W (see FIG. 6) after the dropping process is cut into a predetermined size. Subsequently, the workpiece W (see FIG. 2) is round-bent from both sides in the width direction. In this way, a C-shaped spring (not shown) is completed.

  Next, the operation of the press punching method, the press punching die, and the spring of this embodiment will be described. According to the present embodiment, the clearance C1 (see FIG. 4) between the half punch punch 36 and the half punch die insert 26 is set to be negative. The clearance C1 is one of important factors for suppressing the occurrence of burr. By setting the clearance C1 to be negative, the hydrostatic pressure inside the workpiece W can be increased and the occurrence of cracks can be suppressed. For this reason, the ratio of the 1st shear area | region F2 which occupies for the cut surface F (refer above-mentioned FIG. 7) of the workpiece | work W after a drop-off process can be enlarged. That is, the cut surface F can be smoothed.

  Further, according to the present embodiment, the clearance C1 (see FIG. 4) is set to −6% with the plate thickness t of the workpiece W being 100%. For this reason, the ratio of the fracture | rupture area | region F3 which occupies for the cut surface F (refer above-mentioned FIG. 7) of the workpiece | work W after a dropping process can be made small. In addition, the shear load can be smaller than when the clearance C1 is less than −6% (when the clearance C1 is on the minus side of −6%). In other words, the press load of the press punching die 1 can be small. Further, compared with a case where the clearance C1 exceeds -6% (a case where the clearance C1 is more positive than -6%), the hydrostatic pressure is sufficiently applied, and cracks due to dimensional variations of the half-punch die insert 26 and the half-punch punch 36 occur. Troubles such as occurrence can be prevented.

  Further, according to the present embodiment, even when a work W made of SK5 having high hardness and low elongation is processed, no burr is generated on the work W (see FIG. 7). For this reason, it is not necessary to perform post-processing such as barrel polishing after the dropping step. Therefore, the number of press molding processes can be reduced. In addition, productivity is improved. Further, when the workpiece W after the drop-off process is subjected to a round bending process, even if stress is concentrated near the cut surface F, cracks caused by burr do not occur.

  Further, according to the present embodiment, the absorption allowance is set for the width of the workpiece W and the width of the edge. The amount of deformation of the workpiece W due to the half-punching process and the flat pushing process can be absorbed by the absorption allowance. For this reason, the restoration site | part W2 can be accurately extracted in a drop-out process (refer above-mentioned FIG. 5, FIG. 6). Therefore, there is little possibility that the dimensional accuracy of the spring, which is a product, deteriorates or a dent is generated.

  Further, according to the present embodiment, the clearance C2 (see FIG. 6 above) is set to 6%, where the plate thickness t of the workpiece W is 100%. That is, the absolute value (= 6%) of the clearance C2 (= 6%) and the absolute value (= 6%) of the clearance C1 (= −6%) are the same. For this reason, it can suppress that a malfunction generate | occur | produces in the cut surface F. FIG.

  Further, according to the present embodiment, the insertion amount S (see FIG. 4) of the half punching punch 36 into the workpiece W is set to 65%, where the thickness of the workpiece W is 100%. For this reason, compared with the case where insertion amount S is less than 65%, the ratio of the 2nd droop area | region F5 which occupies for the cut surface F (refer above-mentioned FIG. 7) of the workpiece | work W after a drop-off process can be made small. . Further, the shear load can be reduced as compared with the case where the insertion amount S exceeds 65%. In other words, the press load of the press punching die 1 can be small.

  Further, according to the present embodiment, cracks caused by burr do not occur even when stress is concentrated near the cut surface F (see FIG. 7) when the spring is used. Further, no polishing mark is formed at the boundary between the first sag region F1 and the lower surface of the workpiece W and at the boundary between the second sag region F5 and the upper surface of the workpiece W. For this reason, cracks caused by polishing marks are unlikely to occur.

  <Second embodiment>

  The difference between the present embodiment and the first embodiment is that a large number of projecting parts (restoration parts, dropping parts) are simultaneously formed on the workpiece. Moreover, it is the point by which the convex part is formed in the half punching punch. Therefore, only the differences will be described here.

  FIG. 8 is a partial perspective view of the vicinity of the half punching punch of the press punching die according to the present embodiment. In addition, about the site | part corresponding to FIG. 1, it shows with the same code | symbol. Moreover, the workpiece | work W in FIG. 8 is a thing after a dropping process. Further, for convenience of explanation, the lower mold plate 32 is shown in a transparent manner.

  As shown in FIG. 8, two convex portions 360 are formed on the upper surface of the half punching punch 36. The protrusion 360 protrudes upward from the upper surface of the lower mold plate 32 by an insertion amount S (see FIG. 4). A protruding portion is formed on the workpiece W by the convex portion 360. Note that the same number of half punch punches 36, half punch die inserts, flat push punches, punch punches and punch die inserts (not shown) are arranged.

  A number of slits W4 are formed in the workpiece W after the drop-out process. A large number of slits W4 are regularly arranged. The workpiece W after the drop-off process is subjected to a round bending process in an arc shape protruding upward in the drawing. Then, the cylindrical spring 9 for the piezoelectric actuator shown in FIG. 9 is completed.

  During the round bending process, stress concentrates in the vicinity of both ends of the slit W4 (indicated by hatching in the figure). That is, the stress concentrates on a portion adjacent to the portion where the convex portion 360 is arranged in the half punching process.

  The press punching method, press punching die, and spring of the present embodiment have the same effects as the press punching method, press punching die, and spring of the first embodiment. Moreover, according to this embodiment, many slits W4 can be drilled in a short time. Further, according to the present embodiment, a large number of half-punch punches 36 and a large number of flat-punch punches are arranged adjacent to each other in the feed direction of the workpiece W. For this reason, pressing forces in opposite directions are applied to the workpiece W at the same time adjacent to each other. Therefore, the deformation amount of the workpiece W accompanying the half-punch process or the flat pressing process can be reduced. If the deformation amount of the workpiece W is small, the restoration site of the workpiece W (see FIGS. 5 and 6) can be accurately removed in the dropping step.

  Further, according to the present embodiment, the convex portion 360 is disposed on the upper surface of the half punching punch 36. For this reason, no burr is generated on the slit W4 cut surface of the stress concentration portion of the workpiece W (hatched portion in FIG. 8). Accordingly, when the workpiece W is subjected to a round bending process, cracks starting from the burr hardly occur.

  Further, during use, a load is applied to the cylindrical spring 9 (see FIG. 9) in the axial direction as indicated by a white arrow in the figure. At this time, stress tends to concentrate on the hole edge of the slit W4. However, no burr is generated at the hole edge of the slit W4. For this reason, even when in use, cracks starting from burr hardly occur.

  Further, according to the present embodiment, the half-cutting process is performed only on a portion adjacent to the stress concentration portion (hatched portion in FIG. 8) of the workpiece W after the dropping step. For this reason, the surface pressure in the half punching process, the flat pressing process, and the dropping process can be increased. Therefore, it is not necessary to dare to use a press punching die that can output a relatively large press load, and the cost required for press punching can be reduced accordingly.

  In addition, when half punching is applied only to the part adjacent to the stress concentration part (hatched part in FIG. 8) of the workpiece W after the drop-off process, especially in the case of a progressive feed press punching die, the entire press punching die As a result, it is possible to suppress the unevenness of the press load balance.

  <Others>

  The embodiment of the press punching method, the press punching die, and the spring of the present invention has been described above. However, the embodiment is not particularly limited to the above embodiment. Various modifications and improvements that can be made by those skilled in the art are also possible.

  For example, as the spring of the present invention, any spring such as a cylindrical spring, a leaf spring, a disc spring, or a clamp (name may not be a spring) can be adopted. In the above embodiment, the elongated oval (that is, endless) slit W4 is formed, but an end-shaped slit such as a C-shape or U-shape may be formed. In addition to the slits, various curved shapes and linear shapes may be punched out.

  Moreover, the product manufactured by the press punching method and press punching die of the present invention is not limited to a spring. It may be made of spring steel. For example, it may be a clip, a metal fitting, a hairpin, a load bearing hook or the like. In the products manufactured by the press punching method and the press punching die of the present invention, the occurrence of burr is suppressed. For this reason, it is particularly suitable for punching a product that directly touches the hand.

  Further, in the above embodiment, the progressive die press punching die 1 is used, but a single shot type may be used. The press punching method of the present invention can also be embodied as a turret punch press.

  Further, in the above embodiment, SK5 is used as the spring steel, but other special steels (for example, S60C), stainless steel (for example, SUS300 series, 600 series), heat resistant alloy steel (for example, maraging, Ni base alloy). Etc. may be used. In particular, when the press punching method and the press punching die of the present invention are used for high hardness spring steel, a product (spring or the like) with high dimensional accuracy can be produced from high hardness spring steel which is difficult to be burred without shear.

  Hereinafter, the results of experiments performed on the press punching method, the press punching die, and the spring according to the first embodiment will be described with reference to FIGS. The purpose of the experiment is to control the height of the first sag region F1 (region width in the vertical direction of the workpiece W) and the second sag region F5 by changing the clearance C1, the insertion amount S, and the clearance C2. It is to be.

  The plate thickness t of the workpiece W was 1.6 mm. The material of the workpiece W is SK5 as in the first embodiment. The clearance C1 was set to four levels of −10%, −5%, −2.5%, and 0%, assuming that the plate thickness t was 100%. The insertion amount S was set to four levels of 60%, 70%, 80%, and 90%, with the plate thickness t being 100%. The clearance C2 was set to four levels of 0%, 2.5%, 5%, and 10% with the sheet thickness t being 100%.

  FIG. 10 is a graph showing the experimental results. In the figure, the horizontal axis indicates the insertion amount S (%). The vertical axis indicates the height (mm) of the first sag region F1 and the second sag region F5. When the clearance C1 is −10%, the first sagging region F1 height data is a white circle, and when the clearance C1 is −5%, the first sagging region F1 height data is a white triangle, and the clearance C1 is −2 The data of the first sag region F1 height when .5% is shown by a white square, and the data of the first sag region F1 height when the clearance C1 is 0% is shown by a white rhombus.

Further, the data of the second sag region F5 height when the clearance C2 is 0% is a black rhombus, the data of the second sag region F5 height when the clearance C2 is 2.5% is a black square, and the clearance C2 The data of the second sag region F5 height when the clearance is 5% is indicated by a black triangle, and the data of the second sag region F5 height when the clearance C2 is 10% is indicated by a black circle. Table 1 summarizes the conditions of each data described above.

  As shown by a straight line f1 (data white diamond, white square, white triangle, white circle approximated by the least square method) in FIG. 10, the first sag region F1 height depends on the insertion amount S and the clearance C1. It is almost constant (about 0.05 mm to 0.07 mm).

  On the other hand, as shown by a straight line f2 (a straight line obtained by approximating data black rhombus, black square, black triangle, and black circle by the least square method), the height of the second sag region F5 increases as the insertion amount S increases. Get smaller. Further, as can be seen by comparing data with the same insertion amount S, the height of the second sag region F5 increases as the clearance C2 increases.

  From the experiment, when producing a product in which the plate thickness surface constitutes a part of the stress concentration part or a product with a severe fitting condition with the counterpart member by the press punching method, the processing conditions of the press punching die (clearance C2) It was found that the height of the sagging area (second sagging area F5) can be optimized by the control based on the insertion amount S).

It is sectional drawing seen from the horizontal direction of the press punching die of 1st embodiment. It is II sectional drawing of FIG. It is sectional drawing seen from the horizontal direction at the time of the mold clamping of the press punching die of 1st embodiment. It is a schematic diagram of the half punching process of the press punching method of 1st embodiment. It is a schematic diagram of the flat pressing process of the press punching method. It is a schematic diagram of the dropping process of the press punching method. It is a schematic diagram of the cut surface of the workpiece | work after the punching-out process of the press punching method. It is a fragmentary perspective view of the half punching punch vicinity of the press punching die of 2nd embodiment. It is a perspective view of the cylindrical spring of the embodiment. It is a graph which shows an experimental result.

Explanation of symbols

1: Press punching die, 2: Upper die, 20: Die set, 200: Bush hole, 201: First bolt hole, 21: Backing plate, 210: Second bolt hole, 22: Upper die plate, 220: Third Bolt hole, 221: Half punch die insert fixing hole, 222: Flat punch punch fixing hole, 223: Drop punch punch fixing hole, 23: Movable stripper plate, 230: Fourth bolt hole, 231: Half punch die insert slide hole, 232: Flat push punch slide hole, 233: Drop punch slide hole, 24: Stripper bolt, 240: Coil spring, 25: Guide bush, 26: Half punch die insert (half punch die), 260: Half punch hole, 27 : Flat punch, 28: Dropping punch, 3: Lower mold, 30: Base, 31: Support base, 32: Lower mold plate, 320 Half die cutting punch holes, 321: vent drop die nest hole, 33: Post, 36: half die punches 360: protrusion, 38: vent drop die nest (excl drop die), 380: vent discharge hole.
C1: clearance, C2: clearance, F: cut surface, F1: first sag region, F2: first shear region, F3: fracture region, F4: second shear region, F5: second sag region, f1: straight line, f2: Straight line, S: Insertion amount, t: Plate thickness, W: Workpiece, W1: Projection site, W2: Restoration site, W3: Removal site, W4: Slit.

Claims (9)

A half punching step of forming a projecting portion by pressing a predetermined portion of the workpiece from one surface side of the plate-like workpiece and projecting the predetermined portion to the other surface side facing the one surface side;
A flat pushing step of forming a restoring part by pushing back the protruding part from the other side;
A drop-off step of forming a drop-off site by pulling out the restoration site from the other side;
A press punching method comprising:
The workpiece is made of spring steel, and the clearance between the half-punch punch and the half-punch die used in the half-punching process is set to be −10% or more and −3% or less, assuming that the thickness of the workpiece is 100%. A press punching method characterized by that.   2. The press punching method according to claim 1, wherein a clearance between a punching punch and a punching die used in the punching step is set to 3% or more and 10% or less.   2. The press punching method according to claim 1, wherein the thickness of the workpiece is set to 100%, and the insertion amount of the half-punch punch into the workpiece is set to 50% or more and 80% or less.   2. The press punching method according to claim 1, wherein the protruding portion is set in a portion adjacent to a stress concentration portion of the workpiece after the dropping step. A half-punch punch that forms a protruding portion by pressing a predetermined portion of the workpiece from one surface side of the plate-like workpiece and projecting the predetermined portion to the other surface side facing the one surface side;
A half die having a half punch hole disposed opposite the half punch punch and containing the protruding portion;
A press punching die comprising:
The workpiece is made of spring steel, and the thickness of the workpiece is set to 100%, and the clearance between the half-punching punch and the half-punching die is set to -10% or more and -3% or less. Press punching die. Furthermore, a withdrawal part that forms a withdrawal part by removing a restoration part formed by pushing back the protruding part from the other side,
A withdrawal die disposed opposite to the withdrawal punch and having a withdrawal hole capable of accommodating the withdrawal site;
A press punching die comprising:
6. The press punching die according to claim 5, wherein the thickness of the workpiece is set to 100%, and the clearance between the punching punch and the punching die is set to 3% or more and 10% or less.   The press punching die according to claim 5, wherein a thickness of the workpiece is set to 100%, and an insertion amount of the half punching punch into the workpiece is set to 50% or more and 80% or less.   The press punching die according to claim 5, wherein the half punching punch is provided with a convex portion for forming the protruding portion at a portion adjacent to the stress concentration portion of the workpiece after being dropped. A spring comprising: one surface; another surface facing the one surface; and a plate thickness surface connecting the one surface and the other surface;
The plate thickness surface included in the stress concentration portion includes a first sag region, a first shear region, a fracture region, a second shear region, and a second sag from the one surface side toward the other surface side. And a region formed therein.

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