JP6977595B2 - Punching method for metal plates - Google Patents

Description

The present invention relates to a method for punching a metal plate.

A thin steel sheet used for an automobile part or the like is used as an actual part through a process such as press forming after being sheared into a predetermined shape by punching. For example, the punched end face generated when a hole or a recess is provided in a thin steel sheet by punching is work-hardened due to the influence of the punching process, and the ductility of the end face is low. Therefore, in the subsequent molding step, breakage may occur from the end face when "punching and spreading molding" for extending the punched end face in the extension direction is added. In recent years, high-strength steel sheets have been used due to the need for weight reduction of automobiles. However, since high-strength steel sheets have relatively low ductility, problems of molding defects such as breakage due to deterioration of ductility of the punched end face become remarkable. It's getting better.

The techniques described in Patent Documents 1 to 5 are known as techniques for preventing breakage of the punched end face.
In Patent Document 1, when the outer shape of a steel plate is formed into a predetermined shape by using a punch with a protrusion and a die, the radius of curvature of the die cutting edge portion is set within a predetermined range, and a tangent line drawn from the punch cutting edge to the protruding shoulder. A method of punching a steel plate so that the angle formed in the direction perpendicular to the punch moving direction becomes a predetermined angle is described.
In Patent Document 2, when the outer shape of a steel plate is formed into a predetermined shape by using a punch with a protrusion and a die, the angle between the direction perpendicular to the punch moving direction and the tangent line drawn from the punch cutting edge to the protrusion is predetermined. It is an angle, and a method of punching a steel plate so that the distance between the tangent line drawn from the punch cutting edge to the protrusion and the contact point of the protrusion is within a predetermined range is described.
Patent Document 3 has a bottom surface whose outer peripheral edge serves as a cutting blade, and an outer peripheral surface extending in a direction parallel to a predetermined direction from the outer peripheral edge, and the outer peripheral edge includes a curved portion curved in a convex or concave shape in a plan view. A method of shearing a metal plate using a flat surface portion, a punch having a notch portion that is recessed in a predetermined direction from the flat surface portion and provided so as to include a curved portion in a plan view, and a die is described. ing.
In Patent Document 4, a portion where stretch flange cracking is likely to occur is specified in advance on the sheared surface of the work material, and during shearing, the side surface portion and the bottom surface are formed on the cutting edge of the punch facing the region including the specified portion. Described is a shearing method in which a recess is provided which is formed by a portion and the depth of the bottom portion from the bottom surface of the punch is 10 to 70% of the plate thickness of the work material, and shearing is performed using a punch having the recess. Has been done.
Patent Document 5 specifies a predetermined position of a sheared end portion having a risk of cracking during flange processing as an elongated flange cracking risk portion, and a concave curved shape for stretching and flange processing the sheared end portion after shearing. A shearing method is described in which a bead is applied to a metal plate and the metal plate is sheared as it is so that a predetermined tensile stress is applied to a portion that becomes a stretch flange cracking risk portion. ..

In the method described in Patent Document 1, the radius of curvature of the die cutting edge is set within a predetermined range, and the plastic strain generated by the die cutting edge is dispersed during shearing to reduce the plastic strain of the punched end face. Although the punching hole expandability is improved, there is a problem that the improvement effect is small because the reduction of plastic strain is dispersed over the entire punched end face.
In the method described in Patent Document 2, work hardening and burr generation of the punched end face are suppressed by attaching a protrusion having a specific shape to the punch and applying tension to the steel sheet and then performing shearing. In the method, as shown in FIG. 7 of the same document, shearing is performed in a state where the material is greatly bent by the protrusions attached to the punch, so that the tension applied to the steel sheet is not sufficient and the work hardening of the punched end face is performed. The suppression was inadequate.
In the method described in Patent Document 3, the extension flange crack is prevented by increasing the length of the fracture surface in the plate thickness direction in the portion cut by the notch portion as compared with the portion cut by the flat portion. However, due to design restrictions when providing a flat surface portion and a notched portion in the punch, it may not be possible to sufficiently increase the length of the fracture surface in the plate thickness direction. Further, when the punching shape is changed, it is necessary to redesign the shapes of the flat surface portion and the notch portion provided in the punch, and it may take an enormous amount of time to change the design.
In the method described in Patent Document 4, a recess is provided in the cutting edge of the punch and shearing is performed on a portion where stretch flange cracking is likely to occur, thereby reducing plastic deformation during shearing and preventing stretching flange cracking. However, due to design restrictions when providing recesses in the punch, it may not be possible to sufficiently reduce the plastic deformation during shearing. Further, when the punching shape is changed, it is necessary to redesign the shape of the concave portion provided in the punch, and it may take an enormous amount of time to change the design.
In the method described in Patent Document 5, a bead is applied to a metal plate and sheared to generate a tensile stress in a direction orthogonal to the shearing direction when the bead is formed, which becomes a stretch flange cracking risk portion. Although the strain of the bead is reduced and the deformability of the relevant part is increased, it is necessary to optimize the position, size, and shape of the bead in order to exert a sufficient effect, and the sufficient effect cannot always be obtained. was there.

Further, in the processing methods described in Patent Documents 1 to 5, the plate thickness, strength, etc. of the material to be processed such as a metal plate and a steel plate are changed, and the punching shape after shearing is changed. When this happened, it was necessary to readjust multiple parameters and reset them to the optimum range, which required enormous labor and time to change the design.

International Publication No. 2015/072465 Japanese Unexamined Patent Publication No. 2006-224121 International Publication No. 2016/092657 Japanese Patent No. 5821898 Japanese Patent No. 5386991

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for punching a metal plate, which can easily avoid molding defects such as breakage due to deterioration of ductility of the punched end face.

[1] A substrate portion having an opening and a bridge portion located in the opening and connected to the substrate portion are provided, and the bridge portion further has a slit extending in a direction toward the substrate portion. The blank made of metal plate and the provided blank
A punch having a bottom surface portion and a side surface portion, a corner portion where the bottom surface portion and the side surface portion are in contact with each other is a punch blade, and a protrusion is provided on the bottom surface portion.
Prepare a die and
A method for punching a metal plate, in which the bridge portion is separated from the substrate portion by shearing with the punch blade and the die while restraining the substrate portion and pressing the protrusion portion of the punch against the bridge portion.
[2] The bridge portion is provided with a plurality of branch portions and a joint portion for connecting the branch portions to each other, and the end portions of the branch portions are connected to the substrate portion and along the longitudinal direction of the branch portions. The slit is provided,
The method for punching a metal plate according to [1], wherein the bridge portion is separated from the substrate portion by shearing with the punch blade and the die while pressing the protruding portion of the punch against the joint portion of the bridge portion. ..
[3] The bridge portion is composed of two branch portions and the joint portion arranged between the two branch portions, and the two branch portions and the joint portion are linearly arranged. The method for punching a metal plate according to [2].
[4] The bridge portion is composed of three or more of the branch portions and the joint portion arranged between the branch portions, and the branch portion is directed toward the substrate portion with the joint portion as the center. The method for punching a metal plate according to [2], which is arranged so as to extend.
[5] The method for punching a metal plate according to any one of [2 ] to [4], wherein the slit is provided in at least one or more of the branches or all of the branches.
[6] The method for punching a metal plate according to any one of [1] to [5], wherein the opening of the blank is a divided opening divided by the bridge.
[7] In any one of [1] to [6], the plan view shape of the opening excluding the bridge portion is circular, elliptical or n-sided (where n is a natural number of 3 or more). The described method for punching a metal plate.
[8] An auxiliary pad is arranged at a position facing the punch with the blank sandwiched between the blank, and the auxiliary pad has an auxiliary protrusion portion that is in contact with the bridge portion on the substrate portion side of the pressing portion of the protrusion portion. The method for punching a metal plate according to any one of [1] to [7], wherein the shearing process is performed while the bridge portion provided and pressed by the protrusion is supported by the auxiliary protrusion. ..

In the method of punching a metal plate of the present invention, when the protrusion of the punch is pressed against the bridge portion, the bridge portion is elastically deformed and the pressing portion of the protrusion is sunk more than the substrate portion, and tensile stress is applied to the bridge portion. It occurs and stress is concentrated at the connection point between the bridge part and the board part. As the punch and die come closer to each other, the pushing amount of the bridge part increases and the stress further increases. Finally, the connection point between the bridge part and the substrate part is sheared by the punch blade and the die, and the bridge part is removed from the blank. Will be done. Since tensile stress was concentrated at the connection point between the bridge portion and the substrate portion during shearing, work hardening is significantly reduced at the shear portion on the substrate portion side, which is the end of the opening. In this way, work hardening due to shearing at the end of the opening can be partially reduced. Therefore, when the end surrounding the opening is extended in the extension direction, for example, the opening is expanded. In addition, cracking at the end can be suppressed.
Further, in the present invention, where the bridge portion and the substrate portion should be in a uniaxial tensile stress state, the width of the bridge portion has expanded to the extent that the uniaxial tensile stress state cannot be maintained due to the increase in the area of the opening shape. Even in this case, by providing the slit in the bridge portion, the effective width of the bridge portion can be reduced, and the state of the bridge portion and the substrate portion can be maintained in the uniaxial tensile stress state until immediately before shearing.
According to the present invention, for example, when the position of cracking in the hole expanding process can be predicted in advance, the metal plate obtained by the punching method of the metal plate of the present invention is applied as a blank material for the hole expanding process, and the metal plate is cracked. By locating the sheared portion of the substrate portion at the predicted position of, it is possible to prevent molding defects in the hole expanding process.

Further, in the method for punching a metal plate of the present invention, the bridge portion is provided with a plurality of branch portions and a joint portion, the slit is provided along the longitudinal direction of the branch portion, and the protrusion of the punch is connected to the joint portion. Since the shearing process is performed while pressing against the branch, the tensile stress generated by the displacement of the joint can be applied to the branch, and the state of the bridge and the substrate can be changed by the presence of the slit provided in the branch. It can be maintained in a uniaxial tensile stress state.

Further, in the method of punching a metal plate of the present invention, since the two branch portions and the joint portion are arranged in a straight line, the connection points between the bridge portion and the substrate portion are concentrated in two places. As a result, a large amount of stress can be concentrated on the sheared portion, and work hardening due to shearing can be further reduced. Then, when the end portion surrounding the opening is extended in the extending direction, cracking of the end portion can be suppressed more reliably.
Further, in the method for punching a metal plate of the present invention, three or more branches and a joint are provided, and the branches are arranged so as to extend toward the substrate side with the joint as the center. Therefore, the connection points between the bridge part and the board part are provided at three or more places. As a result, the points where work hardening is reduced can be dispersed. Then, when the end portion surrounding the opening is extended in the extending direction, cracking of the end portion can be suppressed more reliably.

Further, in the method of punching a metal plate of the present invention, since the opening of the blank is divided by the bridge portion, the opening can be easily formed by shearing the bridge portion.
Further, in the method for punching a metal plate of the present invention, the shape of the opening can be made into a circular shape, an elliptical shape, or a polygonal shape having a triangle shape or more, and a design change or the like can be easily performed.

Furthermore, in the method of punching a metal plate of the present invention, an auxiliary pad is arranged at a position facing the punch with the blank sandwiched between them, and the auxiliary pad is provided on the bridge portion on the substrate portion side of the pressing portion of the protrusion portion. An auxiliary protrusion that comes into contact is provided, and shearing is performed while the bridge portion pushed by the protrusion is supported by the auxiliary protrusion. As a result, when the protrusion is pushed into the bridge, the connection between the branch and the substrate may be plastically deformed and the tensile tension may be reduced. By supporting the bridge portion on the substrate portion side, plastic deformation at the connection portion between the branch portion and the substrate portion is suppressed, and sufficient tensile stress can be applied to the connection portion.

As described above, according to the present invention, it is possible to easily avoid molding defects such as breakage due to deterioration of ductility of the punched end face.

The schematic diagram explaining the punching process of the metal plate which is 1st Embodiment of this invention. FIG. 3 is a perspective view of a punch used when manufacturing the blank shown in FIG. 1. The perspective view which shows the punch used in the punching process of the metal plate which is 1st Embodiment of this invention. The perspective view explaining the punching process of the metal plate which is 1st Embodiment of this invention. The schematic diagram explaining the punching process of the metal plate which is 1st Embodiment of this invention. It is a schematic diagram which shows the metal plate after punching manufactured by the punching process method of the metal plate which is 1st Embodiment of this invention, (a) is a planar schematic diagram, (b) is AA'of (a). The cross-sectional view corresponding to the line, (c) is an enlarged view of (b). The perspective view explaining the punching process of the metal plate which is the 2nd Embodiment of this invention. The schematic diagram explaining the punching process of the metal plate which is the 2nd Embodiment of this invention. The perspective view which shows another example of the auxiliary pad used in the 2nd Embodiment of this invention. The schematic diagram explaining the punching process of the metal plate which is the 3rd Embodiment of this invention. The plan view which explains the punching process of the metal plate which is the 4th Embodiment of this invention. The plan view which shows an example of the blank used in the punching process of the metal plate which is 5th Embodiment of this invention. The plan view which shows the modification of the blank used in the punching process of the metal plate which is 5th Embodiment of this invention. The schematic diagram explaining the punching process of the metal plate which is the 6th Embodiment of this invention. The perspective view which shows the punch used in the 6th Embodiment of this invention. The plan view which shows the blank applicable to this invention. The plan view which shows the blank applicable to this invention.

Punching has been known as a means for providing an opening in a metal plate. For punching, prepare a punch, die and restraint pad, and with the metal plate restrained by the die and restraint pad, bring the punch closer to the die along the thickness direction of the metal plate, and use the punch and die to press the metal plate. An opening is provided by shearing. When the metal plate undergoes shearing, a sheared surface is formed on the metal plate, and at this time, work hardening occurs on the sheared surface. That is, work hardening has occurred on the entire end face surrounding the opening. If a hole is widened in the opening in this state, cracks may occur on the work-hardened end face.

Therefore, as a method of providing an opening in the metal plate, the present inventors diligently studied to form an opening in advance in which the bridge portion remains, and then punch out the bridge portion to complete the opening 2 It has been found that work hardening of the sheared surface after removing the bridge portion can be suppressed by punching while generating tensile stress in the bridge portion when punching the bridge portion based on the step step.
Further, in the present invention, where the bridge portion and the substrate portion should be in a uniaxial tensile stress state, the width of the bridge portion has expanded to the extent that the uniaxial tensile stress state cannot be maintained due to the increase in the area of the opening shape. Even in this case, it was found that by providing a slit in the bridge portion, the effective width of the bridge portion can be made smaller than the actual width, and the state of the bridge portion and the substrate portion can be maintained in a uniaxial tensile stress state. rice field.

That is, the method for punching a metal plate according to the embodiment of the present invention includes a substrate portion having an opening and a bridge portion located in the opening and connected to the substrate portion, and further toward the substrate portion in the bridge portion. A blank made of a metal plate having a slit extending along the direction, a bottom surface portion and a side surface portion, and a corner portion where the bottom surface portion and the side surface portion are in contact with each other are used as a punch blade, and further on the bottom surface portion. Prepare a punch and a die provided with protrusions, restrain the substrate, press the protrusions of the punch against the bridge, and separate the bridge from the substrate by shearing with the punch blade and die. , It is a method of punching a metal plate.
In this case, the bridge portion may be separated from the substrate portion by shearing while pressing the protrusion portion of the punch against the central portion in the longitudinal direction of the bridge portion, or the protrusion portion of the punch may be separated from the central portion in the longitudinal direction of the bridge portion and the bridge portion. The bridge portion may be separated from the substrate portion by shearing while being pressed against the end portion on the substrate side of the above.

The bridge portion is provided with a plurality of branches and a joint portion for connecting each branch portion to each other, the end portion of the branch portion is connected to the substrate portion, and a slit is provided along the longitudinal direction of the branch portion. good. In this case, the slits may be formed independently for each branch, or the slits provided for each branch may be connected to each other. Further, the bridge portion may include two branch portions and a joint portion arranged between the two branch portions, and the two branch portions and the joint portion may be arranged linearly.
Further, the bridge portion includes three or more branches and a joint portion arranged between the branch portions so that each branch portion extends toward the substrate portion with the joint portion as the center. It may be arranged.
In these cases, it is preferable to separate the bridge portion from the substrate portion by shearing while pressing the protrusion portion of the punch against the joint portion of the bridge portion. Further, the bridge portion may be separated from the substrate portion by shearing while pressing the protrusion portion of the punch against a place other than the joint portion.

Further, the number of slits may be set according to the width of the branch portion, and one or two or more slits may be provided. Further, the slit portion may be provided on all the branch portions or may be provided on some branch portions. Furthermore, it is preferable to provide the slit along the extending direction of the branch portion, in other words, it is preferable to provide the slit so that the extending direction of the slit is parallel to the direction of the tensile stress applied to the branch portion. ..
Hereinafter, embodiments of the present invention will be described.

(First Embodiment)
In the method of punching a metal plate according to the first embodiment of the present invention, as shown in FIG. 1, a blank 1 composed of a metal plate 13 having a substrate portion 11 and a bridge portion 12 is prepared, and the bridge portion 12 and the substrate are prepared. This is a punching method for obtaining a metal plate 14 having an opening 2 by shearing a bridge portion 12 and a substrate portion 11 at a connection portion while applying tensile stress to the connection portion with the portion 11. The bridge portion 12 is provided with a slit 12d so that the bridge portion 12 and the substrate portion 11 can be maintained in a uniaxial tensile stress state until immediately before shearing. In FIG. 1, the planned shear line between the bridge portion 12 and the substrate portion 11 is shown by a dotted line. The same applies to the drawings after FIG. 1.

First, the blank 1 used in the present embodiment will be described. The blank 1 shown in FIG. 1 is composed of a metal plate 13 having a substrate portion 11 and a bridge portion 12. The substrate portion 11 is made of a metal material. The substrate portion 11 is provided with an opening. A linear bridge portion 12 is provided in the opening portion, and the opening portion is divided into two by the bridge portion 12. Hereinafter, in the present specification, the opening divided by the bridge portion 12 is referred to as a divided opening 22. The two divided openings 22 have a substantially semicircular shape in a plan view, and when the bridge portion 12 is removed, the two divided openings 22 become one circular opening 2. Further, as can be seen from the above description, the substrate portion 11 refers to a portion of the metal plate 13 excluding the bridge portion 12 and the split opening portion 22.

The bridge portion 12 is made of a metal material as well as the material constituting the substrate portion 11. The thickness of the bridge portion 12 is the same as that of the substrate portion 11. As shown in FIG. 1, the bridge portion 12 is a linear member having a predetermined width, and both end portions 12a in the longitudinal direction thereof are connected to the substrate portion 11. That is, the bridge portion 12 is connected to the substrate portion 11 at two points. Further, the bridge portion 12 is arranged so as to pass between the two divided openings 22.

Further, the bridge portion 12 is provided with a connecting portion 12c arranged between the two branch portions 12b and connecting the branch portions 12b to each other. The two branch portions 12b and the joint portion 12c are arranged in a straight line. The joint portion 12c is arranged at a position that is the center of the opening portion 2 after shearing.

Focusing only on the bridge portion 12 regarding the positional relationship between the branch portion 12b and the joint portion 12c, in the bridge portion 12 shown in FIG. 1, there is a joint portion 12c in the center thereof, and the length is the same from the joint portion 12c in two directions. A branch portion 12b having the same width is extended. The relative angle between the branch portions 12b in the longitudinal direction is approximately 180 °. The width of each branch portion 12b is substantially constant along the longitudinal direction of the branch portion 12b, but the present invention is not limited to this, and the width of the branch portion 12b may change along the longitudinal direction thereof.

Further, each branch portion 12b is provided with one slit 12d at the center in the width direction thereof. The slit 12d extends along the longitudinal direction of the branch portion 12b. When viewed from the coupling portion 12c side, the slit 12d extends toward the substrate portion 11. The end portion 12e of the slit 12d on the substrate portion 11 side is located closer to the joint portion 12c than the planned shear line shown in FIG. As described above, the slit 12d does not reach the substrate portion 11. The distance between the end portion 12e of the slit 12d and the planned shear line is preferably, for example, a distance of about the thickness of the metal plate 13. If the slit 12d reaches the substrate portion 11, the work hardening after shearing cannot be sufficiently reduced.

The number of slits 12d, the width dimension, and the total width dimension of the branch portion 12b are not particularly limited, but if they are not set appropriately, sufficient tension is applied to the entire connection portion between the branch portion 12b and the substrate portion 11 during shearing. It becomes impossible to apply stress, and work hardening may occur in a part of the sheared part. Therefore, the number of slits 12d, the width dimension, and the total width dimension of the branch portion 12b may be appropriately set according to the mechanical properties of the metal constituting the blank 1.

The blank 1 shown in FIG. 1 is manufactured by providing a split opening 22 and a slit 12d in a metal plate 13. As a method for forming the split opening 22 and the slit 12d, a processing method such as shearing, cutting, or laser processing may be used. When the split opening 22 is formed by the shearing method, work hardening occurs on the end face of the split opening 22, but as will be described later, the work hardening at the sheared portion of the bridge portion 12 becomes small, and cracks occur in the hole expanding process or the like. It will be possible to suppress the occurrence.

FIG. 2 shows a perspective view of the punch 33 used when manufacturing the blank 1. When the split opening 22 and the slit 12d as shown in FIG. 1 are formed by shearing, the punch 33 as shown in FIG. 2 may be used.

After preparing the blank 1, the bridge portion 12 is removed from the blank 1 by shearing to form the opening 2. At this time, shearing is performed while applying tensile stress to the bridge portion 12.

More specifically, the punch 3, the die 4 and the restraint pad 5 as shown in FIGS. 3 and 4 are prepared.
As shown in FIG. 3, the punch 3 has a cylindrical punch body 3a and a protrusion 3b provided on one end side of the punch body 3a. The punch main body 3a has a bottom surface portion 3c and a side surface portion 3d, and a protrusion portion 3b is provided on the bottom surface portion 3c. The plan view shape of the bottom surface portion 3c of the punch main body 3a is substantially the same as the shape of the split opening portion 22 and the bridge portion 12 of the blank 1 combined. Further, the corner portion 3e where the bottom surface portion 3c and the side surface portion 3d are in contact with each other is a punch blade 3f. The shape of the punch body 3a is not limited to a cylindrical shape, and the shape is particularly limited as long as it has a protrusion 3b and can shear the connection point between the bridge portion 12 and the substrate portion 11. It doesn't matter.

The protrusion 3b is arranged substantially in the center of the bottom surface 3c. The appearance of the protrusion 3b is a spherical shape that protrudes in the axial direction of the punch body 3a. The appearance of the protrusion 3b is not limited to a spherical shape, but may be a triangular shape in a cross-sectional view or a table-shaped cross-sectional view. However, if a shape that restrains the bridge portion 12 is adopted, the bridge portion 12 is plastically deformed when a tensile tension is applied to the bridge portion 12 by the punch 3, and as a result, the tensile stress becomes small. , The shape that does not easily restrain the bridge portion 12 is preferable, and as an example, the spherical shape shown in FIG. 3 is preferable.

The region between the outer peripheral edge of the protrusion 3b and the punch blade 3f is a flat surface, and this flat surface is the bottom surface portion 3c. The protrusion 3b is preferably arranged substantially in the center of the bottom surface 3c. In the present embodiment, by arranging the protrusion 3b in the center of the bottom surface 3c, the protrusion 3b is pressed against the center portion 12 in the longitudinal direction of the bridge portion 12. The portion where the protrusion 3b is pressed against the bridge portion 12 is not limited to the central portion 12b in the longitudinal direction of the bridge portion 12, and the protrusion may be pressed against any portion of the bridge portion.

The protrusion height h, which is the height difference between the bottom surface portion 3c and the tip of the protrusion portion 3b, is an important parameter in the present invention, and the tensile stress applied to the bridge portion 12 by adjusting the protrusion height h. You can adjust the size of. The higher the protrusion height h, the larger the tensile stress applied to the bridge portion 12, but if the protrusion height h is too high, the bridge portion 12 is plastically deformed before the bridge portion 12 is sheared, and the bridge is bridged. Sufficient tensile stress cannot be applied to the portion 12. Therefore, the height h of the protrusion may be set to an optimum value in consideration of the dimensions of the bridge portion 12, the size of the opening 2, the thickness of the metal plate 13, the strength of the metal plate 13, the Young's modulus, and the like.

As shown in FIG. 4, the die 4 and the restraint pad 5 are provided with through holes 4a and 5a into which the punch 3 can be inserted, respectively. In the die 4, the corner portion 4e in which the upper surface 4b of the die 4 and the inner peripheral surface 4c that divides the through hole 4a of the die 4 are in contact with each other is a blade 4f on the die side.

When punching out the bridge portion 12 of the blank 1, for example, the die 4, the restraint pad 5, and the punch 3 are arranged in this order from the lower side, as shown in FIG. The blank 1 is arranged between the die 4 and the restraint pad 5.

Next, with reference to FIG. 5, a method of punching the bridge portion 12 from the substrate portion 13 while applying tension to the bridge portion 12 will be described. 5 (a) to 5 (c) are views of the cross section of the bridge portion 12 along the longitudinal direction, and the substrate portion 11 and the bridge portion 12 of the blank 1 are shown, but the slit and 12d and The split opening 22 is not shown. 5 (d) is a plan view of the blank before processing in FIG. 5 (a), and FIG. 5 (e) is a plan view of the metal plate after processing in FIG. 5 (c).

As shown in FIG. 5A, the blank 1 is sandwiched between the die 4 and the restraint pad 5 to restrain the blank 1. More specifically, the die 4 and the restraint pad 5 are arranged on both sides of the substrate portion 11 of the blank 1 in the thickness direction to restrain the substrate portion 11. The split opening 22 and the bridge 12 of the blank 1 adjust the position of the blank 1 so as to overlap the through holes 4a and 5a of the die 4 and the restraint pad 5. As a result, the substrate portion 11 of the blank 1 is constrained in the thickness direction of the blank 1 and the direction orthogonal to the thickness direction, and the bridge portion 12 is not constrained in the thickness direction of the blank 1. Next, the punch 3 is lowered to the blank 1 so that the tip of the protrusion 3b is brought into contact with the coupling portion 12c of the bridge portion 12. Since the protrusion 3b is arranged in the center of the bottom surface 3c of the punch 3, the tip of the protrusion 3b abuts on the joint portion 12c in the center of the bridge portion 12 in the longitudinal direction as shown in FIG. 5 (d). Will be done. In FIG. 5D, the contact position of the protrusion 3b is indicated by reference numeral T.

Next, as shown in FIG. 5B, the punch 3 is lowered to push the protrusion 3b into the bridge portion 12, and the bridge portion 12 is elastically deformed. Since the bridge portion 12 is connected to the substrate portion 11 in the restrained state via the branch portion 12b extending from the joint portion 12c, the bridge portion 12 is elastically deformed so as to be pushed by the protrusion portion 3b of the punch 3 and project downward. .. The amount of elastic deformation of the bridge portion 12 continues to increase until the punch blade 3f of the punch 3 comes into contact with the blank 1. That is, the higher the protrusion height h, the larger the amount of elastic deformation. However, as described above, it is necessary to adjust the height h of the protrusion so that the bridge portion 12 is not plastically deformed.

When the punch 3 descends downward with respect to the branch portion 12b in which the end portion 12a is restrained by the substrate portion 11, the bridge portion 12 is elastically deformed and tensile stress is generated along the longitudinal direction of the branch portion 12b. .. The tensile stress is concentrated at the connection point between the end portion 12a of the branch portion 12b and the substrate portion 11, and also acts on the entire width direction of the bridge portion 12.
Here, since the branch portion 12b is provided with the slit 12d, the effective width of the branch portion 12b is smaller than that in the case without the slit 12d. As a result, the uniaxial tensile stress state is maintained between the branch portion 12b and the substrate portion 11 until immediately before shearing.

Then, as shown in FIG. 5C, when the punch 3 is further lowered, the punch blade 3f hits the connection portion between the bridge portion 12 and the substrate portion 11, and the connection portion is plastically deformed by shear stress, and finally. The bridge portion 12 is sheared and separated from the substrate portion 11. Until immediately before shearing, the bridge portion 12 is pushed by the protrusion portion 3b and elastically deformed, and is sheared in a state where tensile stress is applied to the connection portion between the bridge portion 12 and the substrate portion 11. As a result, work hardening is less likely to occur at the sheared portion on the substrate portion 11 side. It should be noted that shearing is not performed at a portion other than the connection portion between the bridge portion 12 and the substrate portion 11. As shown in FIG. 5 (e), the opening 2 is formed in the metal plate in which the bridge portion 12 is sheared.

FIG. 6A shows a schematic plan view of the metal plate 14 after punching, and FIG. 6B shows a cross-sectional view corresponding to the AA'line of FIG. 6A. FIG. 6 (c) is a diagram showing a main part of FIG. 6 (b), and shows an end portion 11a of a substrate portion 11 surrounding the opening 2. Further, FIG. 6A shows the position of the bridge portion 12 before punching by a alternate long and short dash line. By removing the bridge portion 12, the divided openings 22 are integrated, and the opening 2 is provided in the substrate portion 11. The opening 2 is a through hole provided at an arbitrary position of the substrate portion 11 and is surrounded by the end portion 11a of the substrate portion 11. The end portion 11a surrounding the opening 2 has a machined surface provided at the time of forming the split opening 22 (hereinafter referred to as a first machined surface 11b) and a machined surface formed by shearing the bridge portion 12 (hereinafter referred to as a first machined surface). 2 Processed surface 11c) is included.

Each machined surface includes a shear surface S and a region D other than the shear surface. Region D is the "who" or fracture surface created during shear.
When the split opening 22 is formed by, for example, shearing, the first work surface 11b of the end portion 11a is relatively work-hardened, while the second work surface 11c is formed by the shearing of the present embodiment. However, the area ratio occupied by the shear surface S in the second work surface 11c becomes relatively small, and work hardening becomes relatively small. As described above, since the work hardening of the second work surface 11c of the end portion 11a surrounding the opening 2 is small, for example, "punching and spreading molding" is added in which the end portion 11a of the opening 2 is stretched along its extending direction. In this case, cracks and breaks starting from the second machined surface 11c are less likely to occur. As a result, for example, when the position of cracking in the hole expanding process can be predicted in advance, the metal plate 14 obtained by the punching method of the present embodiment is applied as the blank material for the hole expanding process, and the predicted position of the crack is the first. 2 By locating the machined surface 11c, it becomes possible to prevent molding defects in the hole expanding process.

On the other hand, when the split opening 22 is formed by, for example, laser machining, work hardening hardly occurs on the first work surface 11b of the end portion 11a, and work hardening is small also on the second work surface 11c. .. In this way, the work hardening of the entire end portion 11a surrounding the opening 2 is reduced, and even when "punching and spreading molding" is applied, cracks and breakage starting from the second machined surface 11c are less likely to occur.

As described above, in the method of punching a metal plate of the present embodiment, when the protrusion 3b of the punch 3 is pressed against the bridge portion 12, the bridge portion 12 is elastically deformed and the pressed portion of the protrusion 3b is formed. It sinks more than the substrate portion 11, tensile stress is generated in the branch portion 12b of the bridge portion 12, and tensile stress is concentrated at the connection point between the branch portion 12b and the substrate portion 11. As the punch 3 and the die 4 come closer to each other, the pushing amount of the bridge portion 12 increases and the tensile stress further increases, and finally the connection point between the bridge portion 12 and the substrate portion 11 is sheared by the punch blade 3f and the die 4. The bridge portion 12 is removed from the blank 1. Since tensile stress was concentrated at the connection point between the branch portion 12b and the substrate portion 11 during shearing, work hardening is significantly reduced on the second work surface 11c of the end portion 11a surrounding the opening 2. In this way, work hardening due to shearing at the end 11a of the opening 2 can be partially reduced, so that the end 11a surrounding the opening 2 is extended in the extension direction, for example, the hole is widened with respect to the opening 2. When processed, cracking of the end portion 11a can be suppressed.

As a result, for example, when the position of cracking in the hole expanding process can be predicted in advance, the metal plate 14 obtained by the method of punching the metal plate of the present invention is applied as a blank material for the hole expanding process, and the predicted position of cracking is applied. By locating the sheared portion (second processed surface 11c) of the substrate portion 11 on the surface, it is possible to prevent molding defects in the hole expanding process.

Further, in the present embodiment, the bridge portion 12 and the substrate portion 11 should be in a uniaxial tensile stress state, but the bridge portion 12 is so large that the uniaxial tensile stress state cannot be maintained due to the increase in the area of the opening shape. Even when the width is widened, the effective width of the branch portion 12b can be reduced by providing the slit 12d in the branch portion 12b, and the state between the branch portion 12b and the substrate portion 11 is maintained in a uniaxial tensile stress state. can.

Further, in the method of punching the metal plate of the present embodiment, the shape of the opening 22 and the shape of the bridge 11 are not particularly limited, so that the design can be easily changed.

Further, in the method of punching a metal plate of the present embodiment, the bridge portion 12 is provided with two branch portions 12b and a joint portion 12c, a slit 12d is provided along the longitudinal direction of the branch portion 12b, and the punch 3 is provided. Since the shearing process is performed while pressing the protrusion 3b of the above against the joint portion 12c, the tensile stress generated by the displacement of the joint portion 12c can be applied to the branch portion 12b, and the slit provided in the branch portion 12b. The presence of 12d allows the state between the bridge portion 12 and the substrate portion 11 to be maintained in a uniaxial tensile stress state.

Further, since the two branch portions 12b and the connecting portion 12c are arranged in a straight line, the connection points between the bridge portion 12 and the substrate portion 11 are concentrated in two places. As a result, a large amount of stress can be concentrated on the sheared portion, and work hardening due to shearing can be further reduced. Then, when the end portion 11a surrounding the opening portion 2 is subjected to a process of extending in the extending direction thereof, cracking of the end portion 11a can be more reliably suppressed.

Further, since the opening 22 of the blank 1 is divided by the bridge portion 12, the opening 2 can be easily formed by shearing the bridge portion 12.

Further, in the punching method of the metal plate 13 of the present embodiment, punching can be performed by adjusting the height h of the protrusion, and other parameters do not need to be considered in particular. The design can be done relatively freely. Further, there are few restrictions on the shape of the blank 1. As described above, since there are few restrictions as compared with the conventional processing method, there is a possibility that the punch 3 and the die 4 can be used without changing the design even if the material and the plate thickness of the blank 1 are changed. It is possible to increase the degree of freedom in designing the punching process.

As described above, according to the present embodiment, it is possible to easily avoid molding defects such as breakage due to deterioration of ductility of the punched end face.

(Second embodiment)
Next, the second embodiment will be described with reference to FIGS. 7 and 8. As shown in FIGS. 7 and 8, in the present embodiment, an auxiliary pad 6 for preventing plastic deformation of the bridge portion 12 is arranged under the blank 1 during punching. Since the method is almost the same as the punching method of the first embodiment shown in FIGS. 1 to 6 except that the auxiliary pad 6 is used, the components shown in FIGS. 7 and 8 are shown in FIGS. 1 to 6. The same components as those shown are designated by the same reference numerals, and the description thereof will be omitted.

In the examples shown in FIGS. 1 to 6, when the bridge portion 12 is pushed down by the punch 3, the branch portion 12b is strongly pressed against the die blade 4f, and the branch portion 12b is plastically deformed at a position where it abuts on the die blade 4f. May be done. In addition, plastic deformation may occur at the connection point between the branch portion 12b and the joint portion 12c. In particular, in the present invention, since the slit 12d is provided in the branch portion 12b, the branch portion 12b is easily plastically deformed. Therefore, in the present embodiment, the auxiliary pad 6 is arranged at a position facing the punch 3 with the blank 1 interposed therebetween, and the bridge portion 12 pushed by the protrusion 3b is supported by the auxiliary protrusion 6a of the auxiliary pad 6. Shear.

As shown in FIGS. 7 and 8, the auxiliary pad 6 includes a cylindrical pad main body 6b and an auxiliary protrusion 6a provided on the upper surface portion 6c of the pad main body 6b. Further, as shown in FIG. 8, an elastic body such as a spring is attached to the lower portion of the auxiliary pad 6.

The pad body 6b has an upper surface portion 6c and a side surface portion 6d, and an auxiliary protrusion portion 6a is provided on the upper surface portion 6c. The plan view shape of the upper surface portion 6c of the pad body 6b is substantially the same as the plan view shape of the bottom surface portion 3c of the punch body 3a.

The auxiliary protrusion 6a has an annular shape in a plan view and a semicircular protrusion in a cross-sectional view. The position of the auxiliary protrusion 6a is preferably closer to the substrate portion 11 than the pressing portion of the bridge portion 12 by the protrusion 3b. In the present embodiment, since the pressing portion of the protrusion 3b is the joint portion 12c of the bridge portion 12, the position of the auxiliary protrusion 6a may be a position in contact with the branch portion 12b. More specifically, the auxiliary protrusion 6a may be formed on the peripheral edge of the pad body 6b, avoiding the center of the upper surface 6c.

Next, with reference to FIGS. 7 and 8, a method of punching out the bridge portion 12 while applying tension to the bridge portion 12 will be described. 8 (a) to 8 (c) are views of the cross sections of the branch portion 12b and the joint portion 12c of the bridge portion 12 as in FIGS. 5 (a) to 5 (c), and are views of the substrate portion 11 and the joint portion 12c. The bridge portion 12 is shown, but the slit 12d and the split opening 22 are not shown. 8 (d) is a plan view of the blank before processing in FIG. 8 (a), and FIG. 8 (e) is a plan view of the metal plate after processing in FIG. 8 (c).

As shown in FIG. 7, for example, the auxiliary pad 6, the die 4, the restraint pad 5, and the punch 3 are arranged in this order from the lower side. The blank 1 (not shown) is arranged between the die 4 and the restraint pad 5.

Similar to the first embodiment, as shown in FIGS. 8A and 8D, the die 4 and the restraint pad 5 are arranged on both sides of the substrate portion 11 of the blank 1 in the thickness direction to form the substrate portion 11. to restrict. Next, the punch 3 is lowered to bring the tip of the protrusion 3b into contact with the upper surface of the coupling portion 12c of the bridge portion 12. In FIG. 8D, the contact position of the protrusion 3b is indicated by reference numeral T. Further, the auxiliary pad 6 is raised so that the tip of the auxiliary protrusion 6a comes into contact with the lower surface of the bridge portion 12. Since the auxiliary protrusions 6a are arranged in an annular shape on the upper surface 6c of the auxiliary pad 6, they come into contact with the bridge portion 12 at a position closer to the substrate portion 11. More specifically, the auxiliary protrusion 6a comes into contact with the branch 12b. In FIG. 8D, the position of the auxiliary protrusion 6a is shown by a alternate long and short dash line.

Next, while the vertical position of the auxiliary pad 6 is fixed, the punch 3 is lowered to push the protrusion 3b into the bridge portion 12, and the bridge portion 12 is elastically deformed. Since the bridge portion 12 is supported from below by the auxiliary protrusion 6a of the auxiliary pad 6, the range in which the bridge portion 12 elastically deforms as the punch 3 descends is the range when the auxiliary protrusion 6a is viewed in a plan view. It becomes the inner area. On the other hand, since the branch portion 12b of the bridge portion 12 is supported by the auxiliary protrusion portion 6a, the end portion 12a of the branch portion 12b is not elastically deformed at the stage shown in FIG. 8B. Since the bridge portion 12 is substantially restrained by the auxiliary protrusion 6a, the joint portion 12c of the bridge portion 12 is pushed by the protrusion 3b of the punch 3 in the inner region of the auxiliary protrusion 6a and elastically deforms downward. do.

When the punch 3 further descends downward with respect to the bridge portion 12 restrained by the auxiliary projection portion 6a, the bridge portion 12 is elastically deformed, and tensile stress is applied to the branch portion 12b along the longitudinal direction thereof. Will be done. The tensile stress is concentrated at the connection point between the branch portion 12b and the substrate portion 11, and also acts on the entire width direction of the branch portion 12b. Since the end portion 12a of the branch portion 12b is neither elastically deformed nor plastically deformed, the tensile stress applied to the bridge portion 12 is not reduced.

Next, as shown in FIG. 8C, when the punch 3 is further lowered, the auxiliary pad 6 is also lowered, the punch blade 3f hits the connection point between the branch portion 12b and the substrate portion 11, and the shear stress causes the punch blade 3f. The connection portion is plastically deformed, and finally the bridge portion 12 is sheared from the substrate portion 11 and separated. Until immediately before shearing, the bridge portion 12 is pushed by the protrusion portion 3b and elastically deformed, and is sheared in a state where tensile stress is applied to the connection portion between the branch portion 12b and the substrate portion 11. As a result, work hardening is less likely to occur at the sheared portion on the substrate portion 11 side. As shown in FIG. 8 (e), the opening 2 is formed in the metal plate in which the bridge portion 12 is sheared.

As described above, in the present embodiment, the auxiliary pad 6 is arranged at a position facing the punch 3 with the blank 1 interposed therebetween, and the auxiliary pad 6 is on the substrate portion 11 side of the pressing portion of the protrusion portion 3b. An auxiliary protrusion 6a in contact with the bridge portion is provided, and shearing is performed while the bridge portion 12 pushed by the protrusion 3b is supported by the auxiliary protrusion 6a. As a result, when the protrusion 3b is pushed into the bridge portion 12, the connection portion between the branch portion 12b and the substrate portion 11 may be plastically deformed to reduce the tensile tension. By supporting the branch portion 12b of the bridge portion 12 on the substrate portion 11 side of the pressing portion, plastic deformation at the connection portion between the branch portion 12b and the substrate portion 11 is suppressed, and sufficient tensile stress is applied to the connection portion. Can be applied.

The auxiliary pad 6 is not limited to the one shown in FIGS. 7 and 8, and the auxiliary pad 16 as shown in FIG. 9 may be used. The auxiliary pad 16 shown in FIG. 9 includes a cylindrical pad main body 6b and a pair of auxiliary protrusions 16a provided on the upper surface portion 6c of the pad main body 6b. The auxiliary protrusion 16a has a linear shape in a plan view and a semicircular protrusion in a cross-sectional view. The pair of auxiliary protrusions 16a are arranged parallel to each other and separated from each other on the upper surface portion 6c of the pad body 6b. The protrusions 3b of the punch 3 are located between the auxiliary protrusions 16a. As a result, the auxiliary protrusion 16a shown in FIG. 9 comes into contact with the branch portion 12b on the substrate portion 11 side of the pressing portion of the bridge portion 12 by the protrusion portion 3b. Even when the auxiliary pad 16 shown in FIG. 9 is used, the same effect as that of the present embodiment can be obtained.

(Third embodiment)
Next, the third embodiment will be described with reference to FIG. In the present embodiment shown in FIG. 10, the contact position of the protrusion of the punch is not the center in the longitudinal direction of the bridge portion but the position closer to the substrate portion from the center in the longitudinal direction. Since the punching method is almost the same as that of the first embodiment shown in FIGS. 1 to 6 except that the contact position of the protrusion of the punch is changed, FIG. 1 to FIG. The same components as those shown in No. 6 are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 10A shows a plan view of the blank used in this embodiment. In FIG. 10A, the position of the protrusion of the punch is indicated by reference numeral T.
The blanks, dies and restraint pads in this embodiment are the same as the blanks 1, dies 4 and restraint pads 5 in the first embodiment. On the other hand, the punch in this embodiment is different from the punch 3 in the first embodiment. As the punch in the present embodiment, a punch having a protrusion located at a position deviated from the center of the bottom surface is used. Therefore, in the present embodiment, as shown in FIG. 10 (a), between one end portion 12a ₁ of the coupling portion 12c and the end portions 12a in the longitudinal direction of the bridge portion 12, the protrusions Be abutted. In FIG. 10A, the contact position of the protrusion is indicated by reference numeral T. As shown in FIG. 10A, the shape of the protrusions preferably has a width wider than the width of the bridge portion 12. As a result, the protrusion comes into contact with the entire bridge portion 12 divided by the slit 12d. This makes it possible to apply tensile stress evenly over the entire width direction of the bridge portion 12 when the bridge portion 12 is sheared from the substrate portion 11. If the protrusion does not contact the entire width direction of the bridge portion 12, the bridge portion 12 is twisted and sufficient tensile stress cannot be applied to the connection portion between the bridge portion 12 and the substrate portion 11.

In this state, as in the first embodiment, when the punch is lowered and the protrusion is pushed into the bridge 12 to elastically deform the bridge 12, the contact point of the protrusion becomes the other end of the bridge. _{Since it is closer to one} end 12a 1 than the portion 12a _{2 , the tensile stress at the connection point between the one} end 12a 1 of the bridge portion 12 and the substrate portion 11 is the other end of the bridge portion 12. It is larger than the tensile stress at the connection point between _{12a 2 and the substrate portion 11.} As a result, the work hardening of the sheared portion on the _one end 12a 1 side becomes smaller than the work hardening of the sheared portion on the _{other end 12a 2 side.} Then, when the bridge portion 12 is sheared, the opening 2 is formed in the metal plate.

10 (b) shows a cross-sectional view corresponding to the AA'line of FIG. 10 (a), and FIG. 10 (c) shows the substrate portion 11 surrounding the opening 2 which is the main part of FIG. 10 (b). The end portion 111a of is shown. 10 (b) and 10 (c) _{show one} end 12a 1 side end 111a of the bridge part 12.
Further, FIG. 10 (d) shows a cross-sectional view corresponding to the AA'line of FIG. 10 (a), and FIG. 10 (e) shows a substrate surrounding the opening 2 which is a main part of FIG. 10 (d). The end portion 111a of the portion 11 is shown. 10 (d) and 10 (e) show the other end 12a ₂ side end 111a of the bridge portion 12.

By removing the bridge portion 12, the divided openings 22 are integrated, and the opening 2 is provided in the substrate portion 11. The opening 2 is a through hole provided at an arbitrary position of the substrate portion 11 and is surrounded by the end portion 111a of the substrate portion 11. The end portion 111a surrounding the opening portion 2 is formed by shearing a machined surface (hereinafter referred to as a first machined surface 111b) provided at the time of forming the split opening portion 22 and one end portion 12a _{1 of the bridge portion 12.} A machined surface (hereinafter referred to as a second machined surface 111c) and _{a machined surface formed by shearing the other end portion 12a 2} of the bridge portion 12 (hereinafter referred to as a third machined surface 111d) are included.

When the split opening 22 is formed by, for example, shearing, the area ratio occupied by the shearing surface S in the first processed surface 111b of the end portion 111a is relatively large, and the work hardening is relatively high. .. On the other hand, the second machined surface 111c is _{formed by shearing one} end 12a 1 of the bridge portion 12, and the area ratio of the sheared surface S in the second machined surface 111c becomes relatively small. Work hardening is relatively small. Further, the third machined surface 111d is _{formed by shearing the other end 12a 2} of the bridge portion 12, and the area ratio occupied by the sheared surface S in the third machined surface 111d is the second machined surface 111c. It becomes larger and the work hardening becomes relatively large.

As described above, since the work hardening of the second work surface 111c of the end portion 11a surrounding the opening 2 is small, for example, "punching and spreading molding" is added in which the end portion 111a of the opening 2 is stretched along its extending direction. In this case, cracks and breaks starting from the second machined surface 111c are less likely to occur. As a result, for example, when the position of cracking in the hole expanding process can be predicted in advance, the metal plate 14 obtained by the punching method of the present embodiment is applied as the blank material for the hole expanding process, and the predicted position of the crack is the first. 2 By locating the machined surface 111c, it becomes possible to prevent molding defects in the hole expanding process.

According to the present embodiment, the bridge portion 12 is pressed from the substrate portion 11 while pressing the protrusion portion 13b of the punch 13 between the center in the longitudinal direction of the bridge portion 12 and one end portion 12a _{1 of both end portions 12a.} By separating by shearing, the work hardening of the second work surface 111c on _one end 12a 1 side of the bridge portion 12 is made smaller than the work hardening of the third work surface 111d on the _{other end 12a 2 side.} It is possible to consolidate the areas where work hardening is small in one place. As a result, work hardening due to shearing at the end 111a of the opening 2 can be partially reduced, so that the end 111a surrounding the opening 2 is extended in the extension direction, for example, a hole is widened for the opening 2. When this is applied, cracking of the end portion 111a can be suppressed.

The auxiliary pad used in the second embodiment may be applied to the present embodiment.

(Fourth Embodiment)
Hereinafter, a fourth embodiment of the present invention will be described with reference to FIG. 11 (a) is a schematic plan view of the blank used in the present embodiment, FIG. 11 (b) is a schematic plan view of the blank after processing, and FIG. 11 (c) is a schematic plan view of the blank on the blank. It is a figure which shows the shape and the pressing position of a protrusion with respect to a bridge. Comparing this embodiment with the first embodiment described above, the method of shearing the substrate portion and the bridge portion to remove the bridge portion from the blank is common, but the shape of the bridge portion is different. .. Therefore, in the following description, the blank used in this embodiment will be mainly described. When the blank of the present embodiment is sheared, an auxiliary pad may be used as in the second embodiment.

The blank 51 of the present embodiment shown in FIG. 11A is composed of a metal plate 13 having a substrate portion 11 and a bridge portion 52. The substrate portion 11 is made of a metal material. The substrate portion 11 is provided with an opening. A linear bridge portion 52 is provided in the opening portion, and the opening portion is divided into two by the bridge portion 52.

As shown in FIG. 11A, the bridge portion 52 is a linear member having a predetermined width, and both end portions 52a in the longitudinal direction thereof are connected to the substrate portion 11. That is, the bridge portion 52 is connected to the substrate portion 11 at two points. Further, the bridge portion 52 is arranged so as to pass between the two divided openings 22.

Further, the bridge portion 52 is provided with one slit 52d at the center in the width direction thereof. The slit 52d extends along the longitudinal direction of the bridge portion 52. The end portion 52e of the slit 52d on the substrate portion 11 side is located closer to the center of the bridge portion 52 in the longitudinal direction than the planned shear line shown in FIG. 11 (a). As described above, the slit 52d does not reach the substrate portion 11. The distance between the end portion 52e of the slit 52d and the planned shear line is preferably, for example, a distance of about the thickness of the metal plate 13. If the slit 52d reaches the substrate portion 11, the work hardening after shearing cannot be sufficiently reduced.

The blank 51 shown in FIG. 1 is manufactured by providing a split opening 22 and a slit 52d in a metal plate 13. As a method for forming the split opening 22 and the slit 52d, a processing method such as shearing, cutting, or laser processing may be used. When the split opening 22 is formed by the shearing method, work hardening occurs on the end face of the split opening 22, but as will be described later, the work hardening at the sheared portion of the bridge portion 52 becomes small, and cracks occur in the hole expanding process or the like. It will be possible to suppress the occurrence.

Then, with respect to the blank 51 shown in FIG. 11 (a), the slit portion is sheared from the substrate portion using a punch and a die in the same manner as in the first embodiment, so that the blank 51 is as shown in FIG. 11 (b). A metal plate 14 having an opening 2 is obtained.

Here, when the protrusion 53b of the punch is pressed against the bridge 52, the shape of the protrusion 53b may be a shape having a width wider than the width of the bridge 52, as shown in FIG. As a result, the protrusion 53b comes into contact with the entire bridge 52 divided by the slit 52d. This makes it possible to apply tensile stress evenly over the entire width direction of the bridge portion 52 when the bridge portion 52 is sheared from the substrate portion 11.

As described above, according to the present embodiment, by providing one slit 52d along the longitudinal direction of the bridge portion 52, work hardening of the sheared portion of the bridge portion 52 is performed in the same manner as in the first embodiment. Can be made smaller. Further, according to the present embodiment, it is not necessary to provide a joint portion in the center of the bridge portion 52 in the longitudinal direction, and it is not necessary to divide the bridge portion 52 into a plurality of branch portions, so that the shape of the bridge portion 52 is relatively different. The shape can be made simple, and the productivity of the metal plate 14 can be increased.

(Fifth Embodiment)
Hereinafter, a fifth embodiment of the present invention will be described with reference to FIG. FIG. 12 is a schematic plan view of the blank used in this embodiment. Comparing this embodiment with the first embodiment described above, the method of shearing the substrate portion and the bridge portion to remove the bridge portion from the blank is common, but the shape of the bridge portion is different. .. Therefore, in the following description, the blank used in this embodiment will be mainly described. When the blank of the present embodiment is sheared, an auxiliary pad may be used as in the second embodiment.

The blank 101 of the present embodiment shown in FIG. 12 is composed of a metal plate 113 having a substrate portion 11 and a bridge portion 112. The substrate portion 11 is provided with an opening. A bridge portion 112 having four branch portions 112b is provided at the opening portion, and the opening portion is divided into four by each branch portion 112b. The four divided openings 122 have a substantially fan shape with a central angle of 90 ° in which a circle is divided into four equal parts in a plan view, and the bridge portion 112 is removed to form one circular opening.

Regarding the positional relationship between the branch portion 112b and the connecting portion 112c The bridge portion 112 includes four branch portions 112b and a connecting portion 112c that mutually connects the branch portions 112b. The branch portion 112b extends from the connecting portion 112c toward the substrate portion 11 in four directions. Each branch portion 112b is a linear member having a predetermined width, and its longitudinal end portion 112a is connected to the substrate portion 11. That is, the bridge portion 12 is connected to the substrate portion 11 by four branch portions 112b. Further, the joint portion 112c is arranged at a position that is the center of the opening after shearing.

Focusing only on the bridge portion 112, the bridge portion 112 shown in FIG. 12 has a joint portion 112c in the center thereof, and a branch portion 112b having the same length and the same width extends from the joint portion 112c in four directions. ing. The relative angle between the adjacent branch portions 112b in the longitudinal direction is approximately 90 °. Further, the branch portion 112b is arranged so as to pass between the four divided openings 122. The width of each branch portion 112b is substantially constant along the longitudinal direction of the branch portion 112b, but the present invention is not limited to this, and the width of the branch portion 112b may change along the longitudinal direction thereof. good.

Each branch portion 112b is provided with one slit 112d at the center in the width direction thereof. The slit 112d extends along the longitudinal direction of the branch portion 112b. When viewed from the coupling portion 112c side, the slit 112d extends toward the substrate portion 11. The end portion 112e of the slit 112d on the substrate portion 11 side is located closer to the joint portion 112c than the planned shear line shown in FIG. Therefore, the slit 112d does not reach the substrate portion 11. The distance between the end portion 112e of the slit 112d and the planned shear line is preferably, for example, a distance of about the thickness of the metal plate 113.

The blank 1 shown in FIG. 12 is manufactured by providing the metal plate 113 with the split opening 122 and the slit 112d. The method of forming the split opening 22 and the slit 112d is the same as that of the first embodiment.

After the blank 101 is prepared, the bridge portion 112 is removed from the blank 101 by shearing in the same manner as in the first embodiment to form a circular opening in a plan view. At this time, shearing is performed while applying tensile stress to the branch portion 112b of the bridge portion 112. In this way, a metal plate is obtained in which a circular opening in a plan view is provided in the substrate portion, and a region in which work hardening is reduced is formed in a part of an end portion surrounding the opening.

According to the present embodiment, the same effect as the effect in the first embodiment can be obtained, and the following effects can also be obtained.
That is, in the method of punching a metal plate of the present embodiment, four branch portions 112b and a joint portion 112c are provided so that the branch portion 112b extends toward the substrate portion 11 side with the joint portion 112c as the center. Since they are arranged, connection points between the bridge portion 112 and the board portion 11 are provided at four locations. As a result, the points where work hardening is reduced can be dispersed. Then, in the metal plate obtained by the present embodiment, when the end portion surrounding the opening is extended in the extending direction, cracking of the end portion can be more reliably suppressed.

In the present embodiment, an example in which the number of branches is four has been described, but the number of branches is not limited to four, and may be three or five or more. FIG. 13 shows a blank having a bridge portion having three branches.
The blank 201 shown in FIG. 13 is provided with a bridge portion 212 having three branch portions 212b at the opening. The opening is divided into three by each branch portion 212b.

The bridge portion 212 includes three branch portions 212b and a connecting portion 212c that mutually connects the branch portions 212b, and each branch portion 212b extends from the connecting portion 212c toward the substrate portion 11 in three directions. The end portion 212a of the branch portion 212b is connected to the substrate portion 11. The relative angle between the adjacent branch portions 212b in the longitudinal direction is approximately 120 °. Each branch portion 212b is provided with one slit 212d. The end portion 212e of the slit 212d on the substrate portion 11 side is located closer to the joint portion 112c than the planned shear line shown in FIG.

By shearing the blank 212 in the same manner as in the first embodiment, a circular opening in a plan view is provided in the substrate portion, and work hardening is reduced in a part of the end portion surrounding the opening. It is possible to obtain a metal plate in which a sheared region is formed.

(Sixth Embodiment)
Hereinafter, a sixth embodiment of the present invention will be described with reference to FIGS. 14 and 15. 14A and 14B are schematic views illustrating a method for punching a metal plate according to the present embodiment, FIG. 14A is a schematic plan view of a blank, and FIG. 14B is a schematic plan view showing a metal plate after punching. Is. Further, FIG. 15 is a perspective view of a punch used for punching the bridge portion. Comparing this embodiment with the first embodiment described above, the method of shearing the substrate portion and the bridge portion to remove the bridge portion from the blank is common, but the shapes of the bridge portion and the opening portion are different. It's different. When the blank of the present embodiment is sheared, an auxiliary pad may be used as in the second embodiment.

Among the blank components shown in FIG. 14 (a), the same components as those shown in FIGS. 1 and 5 are designated by the same reference numerals and the description thereof will be omitted. The blank 301 of the present embodiment shown in FIG. 14A is composed of a metal plate 313 having a substrate portion 11 and a bridge portion 312. The substrate portion 11 is provided with an opening. The opening is provided with a bridge portion 312 having four branch portions 312b, and the opening is divided into four by each branch portion 312b. The four divided openings 322 divided by the bridge portion 312 are fan-shaped having an elliptical arc formed by dividing the ellipse into four equal parts along the major axis and the minor axis, and one abbreviation is obtained by removing the bridge portion 312. It becomes an elliptical opening 302.

The bridge portion 312 comprises four branch portions 312b and a connecting portion 312c that interconnects the branch portions 312b. The branch portion 312b extends from the joint portion 312c toward the substrate portion 11 in four directions. Each branch portion 312b is a linear member having a predetermined width, and its longitudinal end portion 312a is connected to the substrate portion 11. Further, the joint portion 312c is arranged at a position centered on the opening 302 after shearing.

Focusing only on the bridge portion 312, the bridge portion 312 shown in FIG. 14A has a joint portion 312c in the center thereof, and a branch portion 312b extends from the joint portion 312c in four directions. The relative angle between the adjacent branch portions 312b in the longitudinal direction is approximately 90 °. Further, the branch portion 312b includes two long branches 312b _1, consisting of two short branches 312b ₂ Metropolitan overall length is shorter than Nagaeda portion 312b _1. The two long branch portions 3121b ₁ are arranged along the major axis direction of the ellipse, and the two short branch portions 312b ₂ are arranged along the minor axis direction of the ellipse. Further, the long _{branch portion 212b 1} and the short branch portion 212b ₂ are arranged so as to pass between the four divided openings 222.

The width of the short branch portion 312b ₂ is wider than that of the _{long branch portion 312b 1.} Therefore, in the present embodiment, the short branch portion 312b ₂ is provided with a pair of slits 312d. The slits 312d are provided on both sides of the short branch portion 312b _{2 in the width direction.} The slit 312d extends from one short branch portion 312b ₂ to the other short branch portion 312b _{2 along the direction in which the short branch portion 312b 2} extends from the coupling portion 312c side toward the substrate portion 11. It is provided. Further, the slit 312d is provided so as to pass through the connecting portion 312c sandwiched between the _{two short branch portions 312b 2.} By providing the slit 312d, the short branch portion 312b ₂ is divided into a plurality of parts in the width direction, and the effective width is reduced. As a result, the uniaxial tensile stress state can be maintained between the _{short branch portion 312b 2 and the substrate portion 11 during shearing.}

Further, the end portion 312e of the slit 312d on the substrate portion 11 side is located closer to the joint portion 312c than the planned shear line shown in FIG. 14 (a). As described above, the slit 312d does not reach the substrate portion 11. The distance between the end portion 312e of the slit 312d and the planned shear line is preferably, for example, a distance of about the thickness of the metal plate 313. When the slit 312d reaches the substrate portion 11, the uniaxial tensile stress state cannot be maintained between the _{short branch portion 312b 2 and the substrate portion 11 during shearing.}

In this embodiment, the long branch portion 3121b ₁ is not provided with a slit. This is because the long _{branch portion 312b 1} has a relatively small width dimension, so that a uniaxial tensile stress state can be maintained between the _{short branch portion 312b 2 and the substrate portion 11 even without a slit.}

The blank 301 is manufactured by providing the metal plate 313 with the split opening 322 and the slit 312d. The method of forming the split opening 322 and the slit 312d is the same as that of the first embodiment.

In the present embodiment, when the blank 301 is sheared, the punch shown in FIG. 13 may be used. FIG. 15A exemplifies a punch 303 in which three hemispherical protrusions 303b are arranged along the major axis direction of an ellipse on a bottom surface portion 303c of an elliptical pillar-shaped punch main body 303a. Further, in FIG. 15B, a punch 403 is provided on the bottom surface portion 403c of the elliptical pillar-shaped punch main body 403a so that one bead-shaped protrusion 403b extends along the major axis direction of the ellipse. Illustrate. The protrusions 303b and 403b of the punches 303 and 403 are positioned so as to be pressed against the joint portion 312c of the bridge portion 312 of the blank 301. Further, punch blades 303f and 403f are provided at the corners between the bottom surface portions and the side surface portions of the punch main bodies 303a and 403a of the punches 303 and 403.

After preparing the blank 301 and the punch 303 or 403, the bridge portion 312 is removed from the blank 301 by shearing in the same manner as in the first embodiment to form an elliptical opening in a plan view. At this time, the protruding portion 303b or 403b of the punch 303 or 403 is pressed against the connecting portion 312c of the bridge portion 312, and shearing is performed while applying tensile stress to the branch portion 312b of the bridge portion 312. In this way, as shown in FIG. 14 (b), the substrate portion 11 is provided with an elliptical opening 302 in a plan view, and a portion of the end portion 11a surrounding the opening 302 is a region where work hardening is reduced. Is formed, a metal plate 314 is obtained.

According to the present embodiment, the same effect as the effect in the first embodiment can be obtained, and the following effects can also be obtained.
That is, in the method of punching a metal plate of the present embodiment, the effective width of the short branch portion 312b _{2 can be reduced by providing the two slits 312d in the relatively wide short branch portion 312b 2} , which is short. Shearing can be performed while maintaining the state between the branch portion 312b ₂ and the substrate portion 11 in a uniaxial tensile stress state, and work hardening at the sheared portion can be reduced. Then, in the metal plate 314 obtained by the present embodiment, when the end portion 11a surrounding the opening 302 is subjected to a process of extending in the extending direction thereof, the cracking of the end portion 11a can be more reliably suppressed.

Although the first to sixth embodiments of the present invention have been described, the present invention is not limited to these embodiments.
For example, in the above embodiment, an example in which the plan view shape of the blank opening is circular is shown, but the present invention is not limited to this, and as shown in FIGS. 16A and 16B, the opening is not limited to this. The plan view shape of 122 may be elliptical.
Further, as shown in FIGS. 16A and 16B, when the plan view shape of the opening 122 is made elliptical, as shown in FIG. 16A, the bridge portion 501 has an elliptical major axis. It may be arranged along the direction, or as shown in FIG. 16B, the bridge portion 501 may be arranged along the minor axis direction of the ellipse. Further, it may be arranged along a direction other than the major axis direction or the minor axis direction. Further, the bridge portion 501 may be located off the center of the ellipse. As shown in FIG. 16A, the slits 501d provided in the bridge portion 501 may be provided at two locations in the longitudinal direction of the bridge portion 501. In this case, a coupling portion 501c will be formed in the bridge portion 501. Further, as shown in FIG. 16B, it may be provided at one location in the longitudinal direction of the bridge portion 501.

Further, as shown in FIGS. 16 (c) and 16 (d), the plan view shape of the opening 122 may be a quadrangle.
As shown in FIGS. 16 (c) and 16 (d), when the plan view shape of the opening 122 is quadrangular, as shown in FIG. 16 (c), the end portion surrounding the quadrangular opening 122 is formed. Of these, the bridge portion 501 may be arranged so as to connect the end portions facing each other, or as shown in FIG. 16D, the bridge portion 501 may be arranged along the diagonal line of the rectangular opening 122. May be good. Further, the shape of the opening 122 is not limited to a quadrangle, and may be an n-sided polygon (where n is a natural number of 3 or more). Further, the bridge portion 501 may be located at a position deviating from the center of gravity of the quadrangle.

Further, as shown in FIGS. 16 (e) and 16 (f), the shape of the opening 122 may be a shape surrounded by a pair of parallel straight portions and a curved portion connecting the ends of these straight portions. ..
As for the bridge portion 501, as shown in FIG. 16E, one bridge portion 501 is arranged so as to connect a pair of parallel straight line portions surrounding the opening 122, and the center of the bridge portion 501 in the width direction. One slit 501d may be provided in the bridge portion 501, or two slits 501d may be arranged in the width direction of the bridge portion 501 as shown in FIG. 16 (f).

Further, as shown in FIG. 17A, the plan view shape of the opening 122 may be elliptical, and a bridge portion 501 having four branches 501b may be provided. Each branch 501b is provided with a slit 501d, and each branch 501b is joined by a joint 501c.

Furthermore, as shown in FIGS. 17 (b) and 17 (c), the plan view shape of the opening 122 may be a quadrangle, and a bridge portion 501 having four branches 501 b may be provided. Each branch 501b is provided with a slit 501d, and each branch 501b is joined by a joint 501c. As shown in FIG. 17 (b), among the ends surrounding the rectangular opening 122, the bridge portions 501 may be arranged so as to connect the ends facing each other, or shown in FIG. 17 (c). As such, the bridge portion 501 may be arranged along the diagonal line of the rectangular opening 122.

1, 101, 201, 301 ... Blank 2, 302 ... Opening, 3 ... Punch, 3b ... Projection, 3c ... Bottom, 3d ... Side, 3e ... Square, 3f ... Punch blade, 4 ... Die, 5 ... Restraint pad, 6, 16 ... Auxiliary pad, 6a, 16a ... Auxiliary protrusion, 11 ... Board part, 12, 112, 212, 312 ... Bridge part, 12a, 112a, 212a, 312a ... End part (branch part) End), 12b, 112b, 212b, 312b ... Branch, 12c, 112c, 212c, 312c ... Joint, 13, 113, 213, 313 ... Metal plate (metal plate before punching), 14, 314 ... Metal Plate (metal plate after punching), 22, 122, 222, 222 ... Divided opening.

Claims (8)

A substrate portion having an opening and a bridge portion located in the opening and connected to the substrate portion are provided, and the bridge portion is further provided with a slit extending in a direction toward the substrate portion. A blank made of a metal plate and
A punch having a bottom surface portion and a side surface portion, a corner portion where the bottom surface portion and the side surface portion are in contact with each other is a punch blade, and a protrusion is provided on the bottom surface portion.
Prepare a die and
A method for punching a metal plate, in which the bridge portion is separated from the substrate portion by shearing with the punch blade and the die while restraining the substrate portion and pressing the protrusion portion of the punch against the bridge portion. The bridge portion is provided with a plurality of branch portions and a joint portion that connects the branch portions to each other, an end portion of the branch portion is connected to the substrate portion, and the slit is formed along the longitudinal direction of the branch portion. It is provided,
The method for punching a metal plate according to claim 1, wherein the bridge portion is separated from the substrate portion by shearing with the punch blade and the die while pressing the protruding portion of the punch against the joint portion of the bridge portion. .. A claim that the bridge portion is composed of two branch portions and a joint portion arranged between the two branch portions, and the two branch portions and the joint portion are linearly arranged. Item 2. The method for punching a metal plate according to Item 2. The bridge portion is composed of three or more of the branch portions and the joint portion arranged between the branch portions, and the branch portion extends toward the substrate portion side with the joint portion as the center. The method for punching a metal plate according to claim 2, wherein the metal plate is arranged in such a manner. The method for punching a metal plate according to any one of claims 2 to 4, wherein the slit is provided in at least one or more of the branches or all of the branches. The method for punching a metal plate according to any one of claims 1 to 5, wherein the opening of the blank is a divided opening divided by the bridge. The metal according to any one of claims 1 to 6, wherein the planar view shape of the opening excluding the bridge portion is circular, elliptical or n-square (where n is a natural number of 3 or more). Punching method for boards. An auxiliary pad is arranged at a position facing the punch with the blank interposed therebetween, and the auxiliary pad is provided with an auxiliary protrusion portion that is in contact with the bridge portion on the substrate portion side of the pressing portion of the protrusion portion. The method for punching a metal plate according to any one of claims 1 to 7, wherein the shearing process is performed while the bridge portion pressed by the protrusion is supported by the auxiliary protrusion.

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