JP2011218373A - Coining method and apparatus for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coining method by which the fatigue property of the whole sheared hole is improved by imparting sufficient and uniform compressive residual stress to both ends of the sheared hole and the whole inner peripheral surface of the sheared hole in the coining of one time.SOLUTION: An object of coining having the sheared hole is placed on a first die and the object of coining is pressed against the first die by a second die which is opposed to the first die. While inserting a center core which is projected from the distal end of a conning punch which is opposed to the second die and makes a set with the first punch into the sheared hole from one end of the sheared hole until arriving at the second die, the other end and the inner peripheral surface of the sheared hole are deformed plastically by the second die and the center core and also burrs which exist in the peripheral part of the one end of the sheared hole are crushed by the coining punch.

Description

  The present invention relates to a coining method and an apparatus for crushing burrs generated when a shearing hole such as a punched hole or a decorative hole is formed on a metal plate material such as a steel material or a light alloy material.

  In particular, the present invention relates to a coining method and an apparatus for applying the compressive residual stress to both ends and the inner peripheral surface of the shearing hole to improve the fatigue characteristics of the shearing hole.

  Since a metal plate material, particularly a steel plate material, is excellent in plastic workability, a shearing hole such as a punched hole or a decorative hole can be formed by a shearing process such as a punching process.

  The shearing hole has a sagging surface, a shearing surface, a fracture surface, and burrs from the side on which shearing is performed.

  Since the burr generated at one end of the shearing hole has a protrusion shape, stress tends to concentrate on the burr generation part and often becomes a starting point of fatigue failure. Therefore, it is desirable to remove the burr. Moreover, removal of burrs is generally performed from the point of view of beauty.

  As a method of removing burrs generated at one end of the shearing hole, there is a coining process. Non-Patent Document 1 discloses a method of removing burrs by performing coining with a conical punch on the burr generation side of a punched hole (shearing hole) of a hot-rolled high-strength steel sheet.

  In the method disclosed in Non-Patent Document 1, the head of the conical punch is inserted into the shearing hole from the side where the burrs of the shearing hole are generated, and the burrs having a protrusion shape that causes stress concentration are crushed. In addition, by compressing and deforming around the burr generation part of the shearing hole by coining, compressive residual stress is applied around the burr generation part of the shearing hole, and the fatigue characteristics of the shearing hole part are improved. It is.

  However, in the method of Non-Patent Document 1, the compressive residual stress is applied only in the vicinity of the burr generation part of the burr generation side end of the shearing hole and the inner peripheral surface of the shearing hole. Therefore, the improvement of fatigue characteristics at both ends of the shearing hole and the entire inner peripheral surface was not sufficient.

  In particular, the sag surface on the opposite side to the end where burrs are generated in the shearing hole is stretched during the shearing process, so that a residual tensile stress is applied, and the fatigue characteristics of the entire shearing hole Is a cause of significantly lowering.

  It is possible to insert the above-mentioned conical punch from the sag surface side of the shearing hole and compress it to the sag surface side end of the shearing hole and the vicinity of the sag surface of the inner peripheral surface of the shearing hole. However, it is necessary to perform coining twice on the burr generation side and the sag surface side, which increases the manufacturing cost of the member provided with the shearing hole.

  When coining is performed with a conical punch from both ends of the shearing hole, the vicinity of both ends of the shearing hole is sufficiently compressed and deformed, and the applied residual stress is sufficiently large. Of the peripheral surface, the vicinity of the thickness center of the member provided with the shearing hole is not sufficiently compressed and deformed, and the applied compressive residual stress is small.

  Further, when viewed as the entire inner peripheral surface of the shearing hole, it is difficult to improve the fatigue characteristics of the entire shearing hole because the applied compressive residual stress is not uniform.

Tetsuo Toyoda, Masaaki Miura, Michi Nakatani, Improvement of punched hole fatigue properties in Hot Rolled High Ten, Kobe Steel Technical Report, Japan, December 2004, Vol. 54, no. 3, pages 29-32

  In view of the above problems in the prior art, the present invention provides a single coining process for crushing a burr generated at one end of a shearing hole formed by shearing a metal plate material. An object of the present invention is to provide a coining method and apparatus capable of imparting sufficient and uniform compressive residual stress to the entire inner peripheral surface of the shearing hole and improving the fatigue characteristics of the entire shearing hole. .

  First, the present inventors use a coining processing apparatus having a first mold, a second mold, and a coining punch for a coining object having a shearing hole formed by shearing a metal plate material. When the coining process is performed from the burr generation side of the shearing hole, how the distribution of residual stress applied to the inner peripheral surface of the shearing hole changes depending on the tip shape of the coining punch and the amount of coining punch inserted. This was investigated by numerical analysis.

  FIG. 9 is a longitudinal cross-sectional view schematically showing the main parts of a coining machine and a numerical analysis model of a coining object.

  The coining object 100 having a plate thickness of 3 mm placed on the first mold 10 is pressed against the first mold 10 by the second mold 30, and the first mold 10 and the second mold 30 are moved. The shearing hole 120 is coined by moving in the direction of the coining punch 20 (downward in FIG. 9). The coining object 100 is placed with the burr generation side 110 as the coining punch 20 side.

  In the actual coining process, the first die 10, the coining punch 20, the second die 30, and the coining object 100 are axisymmetric with respect to the one-dot chain line in FIG. In order to shorten, numerical calculation was performed with the right half model as shown in FIG.

  As shown in FIG. 9, the tip of the coining punch 20 was tapered, and numerical analysis was performed when the angle θ was 45 ° and 60 °.

Further, the amount of insertion of the coining punch 20 was changed in a range of 0 to 2 mm, and numerical analysis was performed. The insertion amount of the coining punch 20 was the length indicated by _Uy in FIG. 9 with the point where the tip surface 21 of the coining punch 20 reached the burr generation side 110 end surface of the shearing hole 120 as the origin.

The results are shown in FIG. Figure 10 is a graph showing insertion amount and U _y of tip shape and coining punch 20 of coining punch 20, the relationship between the residual stress imparted to shearing hole 120. 10A shows the residual stress on the burr generation side of the shearing hole 120, and FIG. 10B shows the residual stress on the sag surface side of the shearing hole 120.

  The residual stress on the burr generation side of the shearing hole 120 is a range from the end surface of the burr generation side 110 of the shearing hole 120 to the boundary 130 between the shearing surface 117 of the shearing hole 120 and the fracture surface 118. This is an average value of residual stress applied to the inner peripheral surface of the processed hole 120.

  The residual stress on the sag side of the shearing hole 120 is applied to the inner peripheral surface of the shearing hole 120 within a range of a depth of 0.5 mm from the end surface on the sag surface side 115 of the shearing hole 120. It is the average value of residual stress.

  10A and 10B, a positive residual stress value indicates a tensile compressive stress, and a negative residual stress value indicates a compressive residual stress.

FIG. 10 (a) and as is clear from FIG. 10 (b), the with increasing insertion amount U _y of coining punch 20, the residual stress of the burr side of the shearing hole 120 becomes small (large compressive residual stress is made) is the residual stress of the sagging side of the shearing hole 120, when the insertion amount U _y of coining punch 20 was about 0.7 mm, decrease saturation (residual compressive stress is imparted is saturated ).

  The coining object 100 is compressed and deformed on the burr generation side 110 as the coining punch 20 is inserted.

  On the other hand, on the sag surface side 115, the coining object 100 is stretched and deformed in the direction of the central axis of the shearing hole 120 (upward in FIG. 9) while compressively deforming in the insertion direction of the coining punch 20. It is difficult to apply compressive residual stress to the inner peripheral surface of the shearing hole 120 on the sag surface side.

  Therefore, the present inventors project a core that is thinner than the coining punch 20 from the tip 21 of the coining punch 20 until the tip of the core reaches the sag surface side 115 of the shearing hole 120. While the core is inserted into the shearing hole 120, the sag surface and the inner peripheral surface of the shearing hole are plastically deformed with the middle core, and the burrs are crushed by the coining punch 20, and both ends of the shearing hole 120 are sheared. Knowledge that compressive deformation of the entire inner peripheral surface of the processing hole 120 can impart compressive stress to both ends and the entire inner peripheral surface of the shearing hole 120, thereby improving the fatigue characteristics of the entire shearing hole 120. did.

  The present invention has been made based on the above findings, and the gist thereof is as follows.

(1) A coining method for crushing burrs generated at one peripheral edge of a shearing hole,
A coining object having the shearing hole is placed on a first mold, the coining object is pressed against the first mold by a second mold facing the first mold, and the first mold is pressed. A core that protrudes from the tip of a coining punch that faces the two molds and forms a pair with the first mold reaches the second mold from one end of the shearing hole to the shearing hole. The other die and the inner peripheral surface of the shearing hole are plastically deformed with the second mold and the center core while the burrs are crushed by the coining punch. Method.

(2) A gap exists between the outer peripheral surface of the core and the inner peripheral surface of the shearing hole until the tip of the core reaches a predetermined position in the depth direction of the shearing hole. The coining method according to (1), characterized in that it is characterized in that

(3) The above-mentioned (1), wherein the predetermined position in the depth direction of the shearing hole is closer to the insertion direction of the core than the boundary between the shearing surface and the fracture surface of the shearing hole. Or the coining processing method as described in (2).

(4) The above (1) to (3), wherein the core is a center core with a front end having a front end and a main body, and the outer periphery of the front end is smaller than the outer periphery of the main body. A coining method according to any one of the above.

(5) The coining method according to any one of (1) to (4), wherein the shearing hole is a punching hole.

(6) a first mold for placing a coining object having a shearing hole formed by shearing a metal plate;
A second mold facing the first mold and pressing the coining object to the first mold;
A coining punch that crushes a burr formed at one end of the shearing hole, facing the second mold and forming a set with the first mold;
A core that protrudes from the coining punch and has an outer circumference that is larger than the inner circumference of the boundary between the shearing surface and the fracture surface of the shearing hole and smaller than the inner circumference of one end of the shearing hole;
The coining processing apparatus, wherein the core is inserted into the shearing hole from one end of the shearing hole, and the tip of the core reaches the second mold.

(7) The coining apparatus according to (6), wherein an outer periphery of the core is larger by a predetermined value than an inner periphery of a boundary between the shear surface and the fracture surface of the shearing hole.

(8) The maximum value of the predetermined value is a product of an upper limit value of a gap between a shearing punch and a shearing die forming the shearing hole and a plate thickness value of the metal plate material. The coining apparatus according to (7) above.

(9) The above (6) to (8), wherein the center core is a center core with a front end portion having a front end portion and a main body portion, and an outer periphery of the front end portion is smaller than an outer periphery of the main body portion. A coining apparatus according to any one of the above.

(10) The coining apparatus according to (9), wherein an outer periphery of the main body portion of the core with the front end is the same as an inner periphery of one end of the shearing hole.

(11) The coining apparatus according to any one of (6) to (10), wherein the shearing hole is a punching hole.

  According to the present invention, in addition to crushing the burr of the shearing hole with the coining punch and compressing and deforming the burr generation part of the shearing hole, the center core protruding from the coining punch is inserted into the shearing hole. Therefore, the sag surface of the shearing hole opposite to the burr generating part and the inner peripheral surface of the shearing hole can be compressed and deformed, and both ends and inner periphery of the shearing hole can be formed by one coining process. By applying compressive residual stress to the entire surface, the fatigue characteristics of the entire shearing hole can be improved.

It is a longitudinal cross-sectional view which shows an example of the coining processing apparatus for enforcing the coining processing method of this invention. FIG. 1A shows a state where a coining object is placed on the first mold, FIG. 1B shows a state where the coining object is pressed against the first mold by the second mold, FIG. ) Indicates the state during coining. It is the expanded longitudinal cross-sectional view which expanded the principal part of the coining punch and the front-end | tip part of a center core. It is a longitudinal cross-sectional schematic diagram which shows a state when the front-end | tip of a center core exceeds the depth direction predetermined position of a shearing hole. FIG. 3A shows a case where the tip of the center core exceeds the predetermined position in the depth direction of the shearing hole and is in front of the boundary between the shear surface and the fracture surface. FIG. Shows when the second mold is reached. It is a longitudinal cross-sectional view which shows the principal part of the shearing hole, the front-end | tip of a coining punch, and the front-end | tip of a center core, when coining the coining target object which carried out the shearing process of the steel plate with the cylindrical punch by the coining processing method of this invention. The positional relationship between the material before deformation and the space in which the material after deformation flows when the shearing hole is formed by a cylindrical punch and the coining punch and the core are cylindrical is shown. It is a longitudinal cross-sectional view. It is a perspective view which shows the core with a front end part which protruded from the coining punch. When a shearing hole is formed with a shearing punch of a shape other than a cylindrical punch and used as a coining object, the inner periphery with the burr on the shearing hole, the shear surface, It is explanatory drawing which showed the positional relationship of the surroundings of a central axis about the inner periphery of the boundary with a cross section, the outer peripheral surface of the main-body part of a core with a front end part, and the outer edge part of the front end part of a core with a front end part. When a coining object in which a shearing hole is formed by a cylindrical punch is coined by the method of the present invention, the relationship between the size of the outer periphery of the core and the residual stress applied to the shearing hole is numerically calculated. It is a graph which shows the calculated | required result. 8A shows the residual stress on the burr generation side of the shearing hole, and FIG. 8B shows the residual stress on the sag surface side of the shearing hole. It is the longitudinal cross-sectional view which modeled the principal part of the numerical analysis model of a coining processing apparatus and a coining process target object. It is a graph which shows the result of having calculated | required the relationship between the tip shape of a coining punch, the insertion amount of a coining punch, and the residual stress provided to the shearing hole by numerical analysis. 10A shows the residual stress on the burr generation side of the shearing hole, and FIG. 10B shows the residual stress on the sag surface side of the shearing hole.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view showing an example of a coining apparatus for carrying out the coining method of the present invention. FIG. 1A shows a state where a coining object is placed on the first mold, FIG. 1B shows a state where the coining object is pressed against the first mold by the second mold, FIG. ) Indicates the state during coining. In FIG. 1, reference numeral 1 denotes a coining apparatus of the present invention.

  The coining apparatus 1 includes a first die 10, a coining punch 20, and a second die 30. The 1st metal mold | die 10 and the 2nd metal mold | die 30 are arrange | positioned in the position which opposes. The coining punch 20 faces the second mold 30 and is arranged in a pair with the first mold 10. The coining punch 20 has a center core 40 protruding from the tip of the coining punch 20.

  The first mold 10 and the coining punch 20 may be arranged so as to slide, or may be arranged with a certain gap between them, but they form a set.

  The coining processing apparatus 1 is attached to a press processing apparatus (not shown) and performs coining by moving the second mold 30 up and down. An elastic body 60 is provided on the side of the first mold 10 and the core 40 opposite to the second mold 30.

  The coining object 100 is placed on the first mold 10. The coining object 100 is formed by shearing a steel plate to form a through hole, and has a shearing hole 120.

  The inner peripheral surface 125 of the shearing hole 120 has a sag surface 116, a shear surface 117, a fracture surface 118, and a burr 119. When placing the coining object 100 on the first mold 10, as shown in FIG. 1A, one end (burr 119 generation side) of the shearing hole 120 is connected to the coining punch 20 side (FIG. 1). (Lower side in (a)).

  The coining object 100 is not limited to a steel plate that is sheared, but may be a nonferrous metal plate such as an aluminum alloy that is sheared.

  The shearing method is generally punching, but is not limited to this, and may be fine blanking or the like.

  The coining object 100 placed on the first mold 10 is pressed against the first mold 10 by the second mold 30 facing the first mold 10. As shown in FIG. 1B, the core 40 protruding from the tip of the coining punch 20 is connected to the shearing hole 120 from one end of the shearing hole 120 (burr 119 generation side). The tip 41 is inserted until it reaches the second mold 30.

  The second mold 30 is further moved to the coining punch 20 side, and the burr generation side 110 of the coining object 100 is compressed and deformed by the coining punch 20 as shown in FIG. At this time, the burr 119 generated at the peripheral edge of the one end of the shearing hole 120 is crushed by the coining punch 20.

  FIG. 2 is an enlarged vertical cross-sectional view in which main parts of the tip portions of the coining punch 20 and the core 40 are enlarged.

  The inner peripheral surface 125 of the shearing hole 120 has the smallest inner periphery of the shearing hole 120 at the boundary 130 between the shearing surface 117 and the fracture surface 118. Moreover, the inner periphery of the part which the burr | flash 119 generate | occur | produced which is one end of the shearing hole 120 among the inner peripheral surfaces 125 of the shearing hole 120 is the largest.

  The size of the outer periphery of the core 40 is larger than the inner periphery of the boundary 130 between the shear surface 117 and the fracture surface 118 and smaller than the inner periphery of one end of the shearing hole 120 (end on the generation side of the burr 119). There is a need.

  When the size of the outer periphery of the core 40 is larger than the inner periphery of one end of the shearing hole 120 (end on the generation side of the burr 119), the second die 30 is moved to the coining punch 20 side. Without inserting the core 40 into the shearing hole 120, one end of the shearing hole 120 (the end on the generation side of the burr 119) is crushed (buckled).

  When the size of the outer periphery of the core 40 is smaller than the inner periphery of the boundary 130 between the shear surface 117 and the fracture surface 118, the tip 41 of the core 40 reaches the second mold 30 (FIG. 1 ( b) and FIG. 1C), the outer periphery of the center core 40 does not contact the inner peripheral surface 125 of the shearing hole 120, and the other end of the shearing hole 120 (the end on the sag surface 116 side). ) Also does not touch.

  The size of the outer periphery of the center core 40 is larger than the inner periphery of the boundary 130 between the shear surface 117 and the fracture surface 118 and smaller than the inner periphery of one end of the shearing hole 120 (end on the burr 119 generation side). Thus, when the core 40 is inserted into the shearing hole 120, the outer peripheral surface of the core 40 and the shearing hole until the tip 41 of the core 40 reaches a predetermined position 200 in the depth direction of the shearing hole 120. A gap G exists between the inner peripheral surface 125 of 120.

  When the front end 41 of the center core 40 exceeds the predetermined position 200 in the depth direction of the shearing hole 120 and the center core 40 is inserted into the shearing hole 120, the outer periphery of the center core 40 has the outer periphery of the shearing hole 120. The inner peripheral surface 125 is plastically deformed.

  The predetermined position 200 in the depth direction of the shearing hole 120 is a position where the size of the outer periphery of the core 40 is equal to the inner periphery of the shearing hole 120.

  The size of the inner periphery of the shearing hole 120 is the largest at one end of the shearing hole 120 (the end on the burr 119 generation side) and decreases toward the boundary 130 between the shearing surface 117 and the fracture surface 118. Therefore, the predetermined position 200 in the depth direction of the shearing hole 120 is closer to the insertion direction of the core 30 (lower side in FIG. 1) than the boundary 130 between the shearing surface 117 and the fracture surface 118.

  FIG. 3 is a schematic vertical cross-sectional view showing a state where the tip 41 of the core 40 has exceeded a predetermined position 200 in the depth direction of the shearing hole 120. FIG. 3A shows a state where the tip 41 of the core 40 exceeds the predetermined position 200 in the depth direction of the shearing hole 120 and is in front of the boundary 130 between the shear surface 117 and the fracture surface 118. ) Indicates when the tip 41 of the core 40 has reached the second mold 30.

  When the tip 41 of the core 40 exceeds the predetermined position 200 in the depth direction and is in front of the boundary 130, the material constituting the coining object 100 is the second as shown by the arrow in FIG. Plastic flow in the direction of the mold 30.

  When the core 40 is further inserted and the tip 41 of the core 40 reaches the second mold 30, as shown in FIG. 3B, the pre-deformation material 70 before the core 40 is inserted. Is compressed and deformed while plastically flowing into a space 71 surrounded by the sag surface 116, the second mold 30, and the core 40.

  As apparent from FIGS. 3A and 3B, the second mold 30 side (the upper side in FIGS. 3A and 3B) from the predetermined position 200 in the depth direction of the shearing hole 120. The material constituting the coining object 100 is compressed and deformed, and compressive residual stress is applied to the inner peripheral surface 125 of the shearing hole 120.

  As shown in FIG. 1C, one end of the shearing hole 120 is compressed and deformed by the coining punch 20, and the other end (sagging surface 116 side) of the shearing hole 120 is the second gold. The inner peripheral surface 125 between one end and the other end of the shearing hole 120 is compressed and deformed by the mold 30, and compression residual stress is applied to the entire shearing hole 120 by being compressed and deformed by the core 30. In addition, the fatigue characteristics of the entire shearing hole 120 can be improved.

  Then, both ends and the inner peripheral surface of the shearing hole 120 that have been compressed and deformed have improved surface roughness and improved aesthetics, as well as deterioration of fatigue characteristics due to notch in the surface of the shearing hole 120. Reduced.

  When the shearing hole 120 is sheared (punched) from a steel plate with a cylindrical punch, the cross section of the shearing hole 120 and the cross section of the coining punch 20 and the core 40 for coining the shearing hole 120 are shown in FIG. As shown in FIG.

  FIG. 4 shows a main part of the shearing hole 120, the tip of the coining punch 20, and the tip of the core 40 when the coining object 100 obtained by shearing a steel plate with a cylindrical punch is coined by the coining method of the present invention. FIG.

One end (burr 119 generation side) of the shearing hole 120 has a diameter φ ₀ , and a boundary 130 between the shear surface 117 and the fracture surface 118 has a diameter φ ₁ . The relationship between the diameter φ ₁ and the diameter φ ₀ is φ ₁ <φ ₀ , and the diameter φ ₁ is the smallest diameter among the inner peripheral surfaces 125 of the shearing hole 120.

Since the outer periphery of the core 40 is larger than the inner periphery of the boundary 130 and needs to be smaller than the inner periphery of one end of the shearing hole 130 (burr 119 generation side), φ ₁ <φ ₃ <φ ₀ It is necessary to satisfy the relationship.

The lower limit value of φ ₃ is preferably a value such that the volume of the material 70 before deformation and the volume of the space 71 are balanced in FIG.

  Since the periphery of the sag surface 116 of the shearing hole 120 is stretched when the steel plate is sheared, the periphery of the sag surface 116 is generally in a state in which residual tensile stress exists. is there.

  In this state, when the pre-deformation material 70 is plastically deformed by the core 30 and plastically flows into the space 71 (see FIG. 3B), the volume of the pre-deformation material 70 and the volume of the space 71 are balanced. In this case, the residual stress on the sag surface 116 side of the shearing hole 120 is close to zero.

  FIG. 5 shows a pre-deformation material 70 and a space 71 (see FIG. 3B) when the shearing hole 120 is formed by a cylindrical punch and the coining punch 20 and the core 40 have a cylindrical shape (see FIG. 4). It is the longitudinal cross-sectional view which abbreviate | omitted the core 30 and showed the positional relationship with these.

As shown in FIG. 5, the xy coordinates are defined with the change point 140 between the sagging surface 116 and the shearing surface 117 as the origin, and the sagging surface 116 is approximated by a parabola y = (d ₀ / d ₁ ² ) x ² . To do.

At this time, the balance of the volume of the volume and the space 71 of the undeformed material 70 is represented by the following formula (a), a preferable lower limit value of phi ₃ is, phi ₃ in formula (a).
2/3 × (d ₁ ² / d ₀ ) × (φ ₃ −φ ₁ ) ^3/2 +1/2 {t− (d ₁ −d ₂ )} × (φ ₃ −φ ₁ ) + 2/3 × d ₀ × d ₁ = 0 (a)

Here, as shown in FIG. 5, t is the plate thickness of the coining object 100, d ₀ is the circumferential width of the shearing hole 120 on the sag surface 116, and d ₁ is the plate of the coining object 100 on the sag surface 116. The height in the thickness direction, d ₂ is the height in the plate thickness direction of the coining object 100 on the shear surface 117, φ ₀ is the diameter of one end of the shearing hole 120 (burr 119 generation side), and φ ₁ is the boundary of the shearing hole 120. 130 in diameter, phi ₃ is the diameter of the central core 40.

On the other hand, the upper limit value of the diameter φ ₃ of the core 40 is the product of the upper limit value of the gap between the shearing punch and the shearing die when forming the shearing hole 120 and the plate thickness value of the coining object 100. In addition, it is preferable to add the value of the diameter φ ₁ of the boundary 130 between the shearing surface 117 of the shearing hole 120 and the fracture surface 118.

In FIG. 5, the upper limit value of the diameter φ ₃ of the center core 40 is φ ₁ + Ct. Here, C is the upper limit value of the clearance (clearance) between the shearing punch and the shearing die when the shearing hole 120 is formed. In addition, the plate thickness value t of the coining target object 100 shall be the same as the plate thickness value t of the steel plate before shearing hole formation.

  The appropriate range of the gap between the shearing punch and the shearing die is determined by the diameter and depth of the shearing hole and the material of the steel plate forming the shearing hole. The upper limit of the appropriate range is defined as the gap C. .

Here, the upper limit value of the diameter φ ₃ of the core 40 is set to φ ₁ + Ct, that is, the value obtained by adding Ct to the diameter φ ₁ of the boundary 130 between the shear surface 117 and the fracture surface 118 is as follows.

When the diameter φ _{3 of the} core 40 exceeds φ ₁ + Ct, when the core 40 is inserted into the shearing hole 120, the tip 41 of the core 40 bites into the inner peripheral surface 125 of the shearing hole 120. .

  When the insertion of the core 40 proceeds with the tip 41 biting into the inner peripheral surface 125 of the shearing hole 120, the inner peripheral surface 125 of the shearing hole 120 is scraped off at the outer periphery of the central core 40. When the tip 41 of 40 reaches the second mold 30, the scraped inner peripheral surface 125 remains as burrs on the sag surface side 115 (see FIG. 1A). The design of the end portion 115 of the sag surface is impaired.

Thus, the outer periphery 49 of the central core 40, shearing hole 120 inner peripheral surface 125 without scraped off of, for ironing, it is preferable that the diameter phi ₃ of the central core 40 than phi _{1 +} Ct.

Further, when the center core 40 is a center core with a front end portion having a front end portion and a main body portion, and the outer periphery of the front end portion is made smaller than the outer periphery of the main body portion, φ ₀ = φ ₃ can be obtained.

  FIG. 6 is a perspective view showing the core 45 with a front end protruding from the coining punch 20. The center core 45 with the front end portion has a main body portion 46 and a front end portion 47.

When the diameter of the main body 46 is φ ₃ and the diameter of the front end portion 47 is φ ₂ (φ ₂ <φ ₃ ), φ ₀ = φ ₃ can be established. More preferably, R is applied to the outer edge portion 48 of the front end portion 47.

  By setting the middle core 40 as such a middle core 45 with a front end, when the front end 41 of the middle core 45 with the front end is inserted into the shearing hole 120, the center axis of the shearing hole 120 and the front end are attached. Even when the center axis of the center core 45 is slightly shifted, the outer edge 48 of the center core 45 with the front end does not contact the inner periphery of the shearing hole 120 on the burr 119 generation side, and the center core with the front end smoothly. 45 can be inserted into the shearing hole.

Therefore, the diameter φ ₃ of the main body 46 is the same as the diameter φ ₀ (see FIG. 4) of one end (the burr 119 generation side) of the shearing hole 120 that serves as an inlet into which the center core 45 with the front end is inserted. can do. That is, added to plastic deformation on the inner peripheral surface 125 of the shearing hole 120, since the diameter phi ₃ of the main body portion 46 is the upper limit value, the entire inner peripheral surface 125 of the shearing hole 120, the residual stress of sufficient compression Can be granted.

  So far, in order to simplify the description of the size of the outer periphery of the core 40 and the size of the shearing hole 120, the embodiment shown in the example in which the shearing hole 120 is sheared with a cylindrical punch will be described. The effects of the present invention are not limited to the above.

The reason is that φ ₀ and φ ₁ are defined as the distance from the position of the center of gravity of the shearing hole 120, and φ ₂ and φ ₃ of the center core 40 with respect to the shape of the shearing hole 120 are the positions of the center of gravity of the shearing hole. This is because it is defined as the distance from

That is, the dimensions φ ₀ and φ ₁ representing an arbitrary position on the inner peripheral surface 125 of the shearing hole 120 and the dimensions φ ₂ and φ ₃ representing an arbitrary position on the outer periphery of the core 40 are the shearing hole 120 and the middle Although it varies depending on the position in the depth direction of the core 40 (the vertical position in FIGS. 4 and 6), since the start lines (reference lines) of φ ₀ , φ ₁ , φ ₂ and φ ₃ are the same, φ ₀ , Φ ₁ , φ _2, and φ _3, the arbitrary positions in the shearing hole 120 and the center core 40 are uniquely determined as a relative positional relationship.

  Examples of shearing the shearing hole 120 by means other than a cylindrical punch include an ellipse, a polygon having an R at the apex, and the like, for example, as shown in FIG.

  FIG. 7 shows a burr generation side of the shearing hole 120 with respect to the shearing hole 120 and the center core 45 with the front end when the shearing hole is formed with a shearing punch having a shape other than the cylindrical punch to form the coining object 100. The inner periphery 120, the inner periphery of the boundary 130 between the shear surface 117 and the fracture surface 118, the outer periphery 49 of the main body portion 46 of the front end-attached core 45, and the outer edge 48 of the front end portion 47 of the front end-attached core 45. It is explanatory drawing which showed the positional relationship of the periphery of a center axis | shaft.

  As shown in FIG. 7, the outer periphery 49 of the main body portion 46 (see FIG. 6) is larger than the boundary 130 between the shear surface 117 and the fracture surface 118 (see FIG. 4), and one end (burr 119) of the shearing hole 120. It is necessary to be smaller than the inner circumference 120 (see FIG. 4) on the generation side.

  Since the outer edge portion 48 (see FIG. 6) of the front end portion 47 is smaller than the outer periphery 49 (see FIG. 6) of the main body portion 46, the inner core 45 with the front end portion is smaller than the outer periphery 49 of the main body portion 46 and the shearing hole 120. One end (burr 119 generation side) inner circumference 120 may be the same.

  Moreover, the lower limit value of the size of the outer periphery of the main body 46 is the volume of the pre-deformation material 70 and the volume of the space 71 when the cross section taken along the line AA in FIG. It is preferable to set the size of the outer periphery of the main body 46 so as to be balanced.

  On the other hand, the upper limit of the size of the outer periphery of the main body 46 may be made larger by the amount corresponding to Ct × 2 than the size of the inner periphery of the boundary 130 between the shear surface 117 and the fracture surface 118 of the shearing hole 120. preferable. That is, in FIG. 7, the upper limit value of the distance L between the outer periphery 49 of the main body 46 and the boundary 130 is preferably Ct.

  Here, C is the upper limit value of the gap between the shearing punch and the shearing die when the shearing hole 120 is formed. In addition, the plate thickness value t of the coining target object 100 shall be the same as the plate thickness value t of the steel plate before shearing hole formation.

  Next, the present invention will be further described with reference to examples. Conditions in the examples are one example of conditions adopted to confirm the feasibility and effects of the present invention, and the present invention is examples of these one condition. It is not limited to. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

  About the coining object 100 in which the shearing hole 120 is formed using the cylindrical punch, using the first mold 10, the coining punch 20, the second mold 30, and the center core 40 shown in FIG. 4, The shearing hole 120 was coined, and the relationship between the size of the outer periphery of the core 40 and the residual stress applied to the shearing hole 120 was determined.

First, a preliminary study was conducted by numerical analysis. Diameter phi ₁ of the boundary 130 between the shearing hole 120 Jae sectional 117 and broken surface 118 was set to 10.00 mm. Moreover, the plate | board thickness of the shearing target object 100 was 3.00 mm same as the steel plate before a shearing process. Then, the diameter φ _{3 of the} core 30 was changed in the range of 10.00 to 10.25 mm, and (φ ₁ −φ ₃ ) was changed in the range of 0 to −0.25 mm, and numerical analysis was performed.

  The results are shown in FIG. 8A shows the residual stress on the burr 119 generation side of the shearing hole 120, and FIG. 8B shows the residual stress on the sag surface 116 side of the shearing hole 120.

  The residual stress on the burr 119 generation side of the shearing hole 120 is the range from the end surface of the burr 119 generation side of the shearing hole 120 to the boundary 130 between the shearing surface 117 and the fracture surface 118. This is an average value of residual stress values applied to the peripheral surface 125.

  Further, the residual stress on the sag surface 116 side of the shearing hole 120 is given to the inner peripheral surface 125 of the shearing hole 120 within a range from the end surface on the sag surface 116 side of the shearing hole 120 to a depth of 0.5 mm. It is the average value of the applied residual stress.

  8A and 8B, a positive residual stress indicates a tensile residual stress, and a negative residual stress indicates a compressive residual stress.

Figure 8 (a) and as is clear from FIG. 8 (b), with a diameter phi ₃ of the central core 40 increases, burr 119 occurs side, the sagging face 116 side both the value of the residual stress is reduced, i.e., It was confirmed that a large amount of compressive residual stress was applied.

Further, in FIG. 8A, even when (φ ₁ −φ ₃ ) is −0.15 mm or less, the residual stress value is substantially constant at −1000 MPa. This means that even if (φ ₁ −φ ₃ ) is set to −0.15 mm or less, the effect of applying compressive residual stress is saturated.

Therefore, the lower limit value of (φ ₁ −φ ₃ ) is preferably −0.15 mm. That is, the upper limit value of φ ₃ is preferably φ ₁ +0.15 mm.

In FIG. 8B, when (φ ₁ −φ ₃ ) is −0.05 mm or more, the residual stress value is positive, that is, the compressive residual stress is not obtained.

Therefore, the upper limit value of (φ ₁ −φ ₃ ) is preferably −0.05 mm. That is, the lower limit value of φ ₃ is preferably φ ₁ +0.05 mm.

  From the above examples, it was confirmed that the residual stress of compression could be sufficiently applied to the shearing hole by the coining method of the present invention.

  In addition, the place mentioned above is only what illustrated embodiment of this invention, and this invention can add a various change within the description range of a claim.

  As described above, according to the present invention, in addition to crushing the burr of the shearing hole with the coining punch and compressing and deforming the burr generation part of the shearing hole, the core protruding from the coining punch is sheared. By inserting into the processing hole, the sag surface of the shearing hole on the side opposite to the burr generating part and the inner peripheral surface of the shearing hole can be compressed and deformed. By applying compressive residual stress to the whole, it is possible to improve the fatigue characteristics of the entire sheared hole. The present invention has high utility value industrially.

DESCRIPTION OF SYMBOLS 1 Coining processing apparatus 10 1st metal mold | die 20 Coining punch 30 2nd metal mold | die 40 Center core 41 Front-end | tip 45 Center core with a front end 47 Front end part 48 Outer edge part 49 Outer periphery 60 Elastic body 70 Material before deformation 71 Space 100 Coining object 110 Burr generation side 115 Sag surface side 116 Sag surface 117 Shear surface 118 Fracture surface 119 Burr 120 Shearing hole 125 Inner peripheral surface 130 Boundary 140 Change point 200 Depth direction predetermined position G Gap

Claims (11)

A coining method for crushing burrs generated at one peripheral edge of a shearing hole,
A coining object having the shearing hole is placed on a first mold, the coining object is pressed against the first mold by a second mold facing the first mold, and the first mold is pressed. A core that protrudes from the tip of a coining punch that faces the two molds and forms a pair with the first mold reaches the second mold from one end of the shearing hole to the shearing hole. The other die and the inner peripheral surface of the shearing hole are plastically deformed with the second mold and the center core while the burrs are crushed by the coining punch. Method.   A gap exists between the outer peripheral surface of the core and the inner peripheral surface of the shearing hole until the tip of the core reaches a predetermined position in the depth direction of the shearing hole. The coining method according to claim 1.   The predetermined position in the depth direction of the shearing hole is before the insertion direction of the core from the boundary between the shearing surface and the fracture surface of the shearing hole. Coining method.   The said center core is a center core with a front end part which has a front-end part and a main-body part, The outer periphery of the said front-end part is smaller than the outer periphery of the said main-body part, The any one of Claims 1-3 characterized by the above-mentioned. The coining method described.   The coining method according to any one of claims 1 to 4, wherein the shearing hole is a punching hole. A first mold for placing a coining object having a shearing hole formed by shearing a metal plate;
A second mold facing the first mold and pressing the coining object to the first mold;
A coining punch that crushes a burr formed at one end of the shearing hole, facing the second mold and forming a set with the first mold;
A core that protrudes from the coining punch and has an outer circumference that is larger than the inner circumference of the boundary between the shearing surface and the fracture surface of the shearing hole and smaller than the inner circumference of one end of the shearing hole;
The coining processing apparatus, wherein the core is inserted into the shearing hole from one end of the shearing hole, and the tip of the core reaches the second mold.   The coining apparatus according to claim 6, wherein an outer periphery of the center core is larger by a predetermined value than an inner periphery of a boundary between the shear surface and the fracture surface of the shearing hole.   The maximum value of the predetermined value is a product of an upper limit value of a gap between a shearing punch and a shearing die that form the shearing hole and a plate thickness value of the metal plate material. The coining processing apparatus according to 7.   The said center core is a center core with a front end part which has a front-end part and a main-body part, The outer periphery of the said front-end part is smaller than the outer periphery of the said main-body part, The any one of Claims 6-8 characterized by the above-mentioned. The coining processing apparatus described.   The coining apparatus according to claim 9, wherein an outer periphery of the main body portion of the core with the front end is the same as an inner periphery of one end of the shearing hole.   The coining apparatus according to any one of claims 6 to 10, wherein the shearing hole is a punching hole.

Images