Stamping Processing Method

Abstract

Provided is a stamping method capable of forming a perforated portion on a workpiece made of a tough material with higher precision. The stamping method of the present invention applies a first load to the workpiece made of a tough material by a stamping member to impart a preload within the elastic region of the workpiece, and then applies a second load exceeding the first load to the workpiece by the stamping member to provide a perforated portion in the workpiece, wherein the elastic region is larger than 0 MPa and is below the value of the shear stress at the limit of elastic deformation of the workpiece, the workpiece is a metal tube, and the first load and the second load are applied while the interior of the tube is hollow.

Description

Technical Field

[0001] The invention relates to a stamping method. Background Art

[0002] Conventionally, as such a stamping method, there is known a method of forming a perforated portion on a workpiece using a punch, such as shown in Patent Document 1. Patent Document 1 discloses a stamping method in which a portion of the workpiece is removed to form a thin-walled portion, and then a punching member is used to form a perforated portion in the thin-walled portion.

[0003] Prior Art Literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 11-147142 Summary of the invention

[0006] Summary of the Invention

[0007] Problems to be solved by the invention

[0008] However, the press working method of Patent Document 1 still has room for improvement from the viewpoint of forming a punched portion with higher accuracy in a workpiece made of a tough material.

[0009] Therefore, an object of the present invention is to solve the above-mentioned problems and to provide a press working method capable of forming a perforated portion with higher accuracy in a workpiece made of a tough material.

[0010] Solutions to Solve Problems

[0011] In order to achieve the above-mentioned object, the stamping method of the present invention applies a first load to a workpiece made of a tough material by a stamping member to impart a preload in the elastic region of the workpiece, and then applies a second load exceeding the first load to the workpiece by the stamping member to provide a perforated portion in the workpiece, wherein:

[0012] The elastic region is greater than 0 MPa and is less than or equal to the shear stress value at which the workpiece undergoes elastic deformation.

[0013] The workpiece is a metal pipe.

[0014] The first load and the second load are applied in a state where the interior of the tube is hollow.

[0015] Effects of the Invention

[0016] According to the press working method of the present invention, a punched portion can be formed with higher accuracy in a workpiece made of a tough material. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic perspective view showing a tube having a plurality of perforated portions formed by a press working method according to an embodiment of the present invention.

[0018] Figure 2 It is a flowchart showing the press working method according to the embodiment of the present invention.

[0019] Figure 3A This is a schematic cross-sectional view showing one step of a press working method according to an embodiment of the present invention.

[0020] Figure 3B yes Figure 3A A partial enlarged cross-sectional view of .

[0021] Figure 4 It means next Figure 3A A cross-sectional view of the process.

[0022] Figure 5 This is a graph showing an example of the relationship between the processing time and the processing load in the press processing method according to the embodiment of the present invention.

[0023] Figure 6 It is a cross-sectional view showing a pipe in which a perforated portion is formed by a press working method according to an embodiment of the present invention.

[0024] Figure 7 yes Figure 6 A partial enlarged cross-sectional view of .

[0025] Figure 8 It means through Figure 7 A cross-sectional view showing a state where oil is ejected from a perforated portion.

[0026] Fig. 9 This is a cross-sectional view showing a state where oil is ejected through a bored portion formed by a press working method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The stamping method of this embodiment applies a first load to a workpiece made of a tough material by a stamping member to apply a preload in the elastic region of the workpiece, and then applies a second load exceeding the first load to the workpiece by the stamping member to provide a perforated portion in the workpiece, wherein:

[0028] The elastic region is greater than 0 MPa and is equal to or less than the shear stress value at which the workpiece undergoes elastic deformation.

[0029] The workpiece is a metal pipe.

[0030] The first load and the second load are applied in a state where the interior of the tube is hollow.

[0031] According to this method, even if the workpiece made of tough material is pressed while the inside is still hollow, the perforated portion can be formed with higher accuracy. That is, when forming the perforated portion, it is not necessary to insert a mandrel or the like into the inside of the tube.

[0032] It should be noted that the preload may be applied to the vicinity of the upper limit of the elastic region of the workpiece by applying the first load. According to this method, a perforated portion can be formed with higher accuracy in a workpiece made of a tough material.

[0033] In addition, the second load may be applied continuously after the first load is applied. According to this method, a perforated portion can be formed with higher accuracy in a workpiece made of a tough material, and the processing time can be further shortened.

[0034] In addition, after applying the first load, the second load can be applied after a temporary stop. According to this method, the preload can be applied more reliably to the workpiece in the elastic region of the workpiece without paying special attention to the adjustment of the application speed of the first and second loads based on the punching member.

[0035] In addition, the inner diameter of the tube may be 5 mm or less. Even in this case, according to the method, a perforated portion can be formed with higher accuracy on a workpiece made of a tough material.

[0036] In addition, the diameter of the perforated portion may be 1.5 mm or less. Even in this case, according to the method, the perforated portion can be formed with higher accuracy for a workpiece made of a tough material.

[0037] In addition, the punching member may move at a first speed relative to the workpiece to apply the first load, and then move at a fixed second speed exceeding the first speed to apply the second load. That is, the first and second loads may be applied by changing the speed of the punching member. Even in this case, the perforated portion can be formed more accurately for the workpiece made of tough material.

[0038] In addition, the second speed may be 1000 mm / sec or more. According to this method, a perforated portion can be formed with higher accuracy in a workpiece made of a tough material.

[0039] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the present invention is not limited by the embodiments. In addition, in the accompanying drawings, substantially the same components are denoted by the same reference numerals.

[0040] Implementation Methods

[0041] Figure 1 It is a schematic perspective view showing a tube having a plurality of perforated portions formed by the press working method according to the present embodiment.

[0042] The tube 1 is an example of a workpiece made of a tough material. The tube 1 is, for example, a tube made of steel or an aluminum alloy. A plurality of perforations 2 are formed in the tube 1. In the present embodiment, the tube 1 is a structure that sprays oil through the plurality of perforations 2. The oil sprayed from the tube 1 is used, for example, for cooling a machine part or lubricating a sliding member.

[0043] In order to improve the cooling efficiency of mechanical parts and the lubrication of sliding components, for example, it is effective to spray the oil ejected from the perforated portion 2 more accurately toward the desired position without spreading as much as possible. In order to suppress the diffusion of oil, it is effective to form the perforated portion 2 with higher precision and smaller size (for example, diameter of less than 1.5 mm).

[0044] In addition, the perforated portion 2 is usually formed in a state where a mandrel is inserted into the inside of the tube 1. However, there is a case where the tube 1 is required to be used in a narrower space. In this case, the outer diameter of the tube 1 needs to be reduced (for example, a diameter of 8 mm or less), and with this, the inner diameter of the tube 1 is sometimes reduced to such an extent that the mandrel cannot be inserted (for example, a diameter of 5 mm or less). In contrast, according to the stamping method of this embodiment described later, the perforated portion 2 can be formed on the tube 1 with higher precision without using a mandrel.

[0045] Next, the press working method according to the present embodiment will be described.

[0046] Figure 2 It is a flowchart which shows the press working method of this embodiment. Figure 3A This is a schematic cross-sectional view showing one step of the press working method according to the present embodiment. Figure 3B yes Figure 3A A partial enlarged cross-sectional view of .

[0047] First, if Figure 3A and Figure 3B As shown in FIG. 1 , a punch pin 3 as an example of a punching member applies a first load, thereby imparting a preload to the tube 1. The first load ( Figure 2 In the present embodiment of the invention, the elastic region is larger than 0 MPa.

[0048] Figure 4 It means next Figure 3A A cross-sectional view of the process.

[0049] Following step S1, the punch 3 applies a second load to the tube 1. The second load is adjusted to exceed the first load. Figure 4 As shown, the punch pin 3 penetrates the tube 1 to form a perforated portion 2 ( Figure 2 In the present embodiment, the first and second loads are applied without using a mandrel and the interior of the tube 1 is hollow. In the present embodiment, the outer diameter of the tube 1 is 18 mm. The inner diameter of the tube 1 is 14 mm. The diameter of the perforated portion 2 is 1.2 mm.

[0050] Next, the relationship between the processing time and the processing load in the press processing method of this embodiment will be described. Figure 5 This is a graph showing an example of the relationship between the processing time and the processing load in the press processing method according to the present embodiment.

[0051] Here, the “processing time” is the time during which the punch 3 acts on the tube 1 to form the perforated portion 2 in the tube 1. Figure 5 In the embodiment, the moment when the tube 1 and the punch pin 3 start to contact is set to 0 seconds. In the present embodiment, the period from 0 seconds to about 0.001 seconds in the processing time corresponds to step S1. In step S1, the punch pin 3 moves at a first speed relative to the tube 1. The value of the second speed in step S2 described later is set to exceed the first speed. The "processing load" is the load applied by the punch pin 3 to the tube 1. In the present embodiment, the first load is adjusted so that the preload applied to the tube 1 is less than 0.5 kN.

[0052] In addition, in the present embodiment, the processing time from about 0.001 seconds to about 0.003 seconds corresponds to step S2. In step S2, the value of the processing load increases, and reaches the maximum load of 2.7 kN in this stamping process at about 0.0015 seconds. Then, the processing load decreases as the punch ejector 3 penetrates the tube 1. In step S2, the speed at which the punch ejector 3 moves relative to the tube 1, that is, the processing speed as an example of the second speed is a fixed speed of, for example, 1000 mm / second or more. In the present embodiment, the processing speed in step S2 is 1250 mm / second.

[0053] Figure 6 It is a cross-sectional view showing a tube 1 in which a perforated portion 2 is formed by the press working method according to the present embodiment. Figure 7 yes Figure 6 A partial enlarged cross-sectional view of .

[0054] Generally, in the punching method, when the perforated portion 2 is formed in the tube 1, a depression or a collapsed edge is formed in the outer peripheral portion 21 of the outer side of the perforated portion 2. In addition, a flash is formed in the outer peripheral portion 22 of the inner side of the perforated portion 2. The above-mentioned depression, collapsed edge or flash is formed because the tube 1 is plastically deformed by the load applied to the tube 1 by the punch ejector 3 without elastically deforming the tube 1 in advance. The depression, collapsed edge or flash affects the accuracy of the ejection direction of the oil ejected from the perforated portion 2, so it is desired to be as small as possible.

[0055] When a perforated portion 2 with a diameter of 1.2 mm is formed on a tube 1 with an outer diameter of 18 mm and an inner diameter of 14 mm by the punching method of the present embodiment, almost no depression or collapsed edge is generated on the outer peripheral portion 21 of the outer side of the perforated portion 2. Moreover, the height H of the burr is 0.3 mm. In contrast, when a perforated portion 2 with a diameter of 1.2 mm is formed on a tube 1 with an outer diameter of 18 mm and an inner diameter of 14 mm by the conventional punching method, the depth of the depression is 0.2 mm, the size of the collapsed edge is R0.1, and the height of the burr is 0.5 mm. Thus, it is confirmed that the punching method according to the present embodiment can form the perforated portion 2 with higher precision.

[0056] Figure 8 and Fig. 9 It means through Figure 7 The cross-sectional view of the perforated portion 2 is shown in FIG.

[0057] The oil flowing into the tube 1 is ejected toward the outside of the tube 1 through the perforated portion 2. When there is a depression or a collapsed edge in the outer peripheral portion 21 of the perforated portion 2, the oil ejected from the perforated portion 2 is pulled toward the depression or the collapsed edge due to the viscosity of the oil, thereby being easily diffused. In contrast, according to the stamping method of this embodiment, the depression or the collapsed edge of the outer peripheral portion 21 of the perforated portion 2 can be made smaller, thereby further suppressing the diffusion of the oil. For example Fig. 9 As shown, at a position 50 mm in front of the perforated portion 2, the spread of oil can be suppressed within a range of about 5 mm in diameter.

[0058] As described above, according to the punching method of this embodiment, a process of applying a first load to the tube 1 by the punch pin 3 to give a preload in the elastic region of the tube 1 is included. After the above process, a process of providing the perforated portion 2 in the tube 1 by applying a second load exceeding the first load to the tube 1 by the punch pin 3 is included. According to this method, the perforated portion 2 can be formed on the tube 1 with higher precision.

[0059] It should be noted that it is preferable to apply the first load to give a preload up to the vicinity of the upper limit of the elastic region of the tube 1. As described above, when the tube 1 is not elastically deformed in advance (that is, when the preload is not applied), the punch pin 3 applies a load (that is, the second load) to the tube 1 to cause plastic deformation of the tube 1, thereby forming a dent, a collapsed edge, or a flash.

[0060] On the other hand, the closer the value of the stress generated on the tube 1 by the preload is to the upper limit of the elastic region, the smaller the dents, collapsed edges or flashes generated on the outer peripheral portions 21 and 22 on the outside and inside of the perforated portion 2 can be when the tube 1 is plastically deformed by the second load. In other words, the closer the value of the stress generated on the tube 1 by the preload is to the plastic region in the elastic region, the smaller the dents, collapsed edges or flashes generated on the outer peripheral portions 21 and 22 on the outside and inside of the perforated portion 2 can be when the tube 1 is plastically deformed by the second load. Therefore, the perforated portion 2 can be formed on the tube 1 with higher accuracy.

[0061] In the present embodiment, the elastic region is larger than 0 MPa, and the "upper limit of the elastic region" is the value of the shear stress at the limit of elastic deformation of the workpiece. The value of the shear stress at the limit of elastic deformation of the workpiece is obtained by converting from the value of the yield point related to the workpiece. Moreover, in the present embodiment, "near the upper limit of the elastic region" refers to, for example, a range of 50% or more relative to the value of the upper limit of the elastic region and below the value of the upper limit of the elastic region. Preferably, "near the upper limit of the elastic region" is a range of 70% or more relative to the value of the upper limit of the elastic region and below the value of the upper limit of the elastic region. More preferably, "near the upper limit of the elastic region" is a range of 80% or more relative to the value of the upper limit of the elastic region and below the value of the upper limit of the elastic region.

[0062] The value of the yield point is different for each workpiece, for example, based on the standards planned and formulated by so-called standardization groups such as the International Organization for Standardization (ISO). According to Mises' yield condition, the value of the shear stress at which the workpiece undergoes elastic deformation can be obtained by dividing the value of the yield point by √3. For example, under the Japanese Industrial Standard (JIS), according to JIS G 3445 prescribed for carbon steel pipes for mechanical structures, the yield point of STKM12A is above 175MPa. Therefore, the shear yield stress of STKM12A is above 101MPa (=175 / √3MPa). That is, when STKM12A is used as a workpiece, the upper limit of the elastic region is 101MPa.

[0063] For example, according to JIS G 3445, the yield point of STKM17C is 480 MPa or more. Therefore, the shear yield stress of STKM17C is 277 MPa (=480 / √3 MPa) or more. That is, when STKM17C is used as a workpiece, the upper limit of the elastic region is 277 MPa.

[0064] For example, according to JIS H 4080, which is specified for aluminum and aluminum alloy seamless pipes under JIS, the yield strength of A7075-T6 drawn pipe is 460 MPa or more. Therefore, the shear yield stress of A7075-T6 drawn pipe is 265 MPa (=460 / √3 MPa) or more. That is, when A7075-T6 drawn pipe is used as a workpiece, the upper limit of the elastic region is 265 MPa.

[0065] According to the punching method of this embodiment, a first load is applied to the tube 1 by the punch pin 3 to give a preload in the elastic region of the tube 1. Then, a second load exceeding the first load is applied to the tube 1 by the punch pin 3 to provide the perforated portion 2 in the tube 1. The elastic region is greater than 0 MPa and is less than the value of the shear stress at which the tube 1 is elastically deformed, the tube 1 is a metal tube, and the first load and the second load are applied in a state where the inside of the tube 1 is hollow.

[0066] In this case, even if the workpiece made of tough material is pressed while being hollow inside, the perforated portion can be formed with higher accuracy. That is, when forming the perforated portion, it is not necessary to insert a mandrel or the like into the inside of the tube.

[0067] Furthermore, the preload may be applied to the vicinity of the upper limit of the elastic region of the tube 1 by applying the first load. According to this method, the perforated portion 2 can be formed in the tube 1 with higher accuracy.

[0068] In addition, the second load may be applied continuously after the first load is applied. In this case, the perforated portion 2 can be formed in the tube 1 with higher accuracy, and the processing time can be further shortened.

[0069] In addition, after applying the first load, the second load may be applied after a temporary stop. In this case, there is no need to pay special attention to the adjustment of the application speed of the first load and the second load applied by the punch ejector 3, and the preload can be more reliably applied to the tube 1 in the elastic region of the tube 1.

[0070] Furthermore, according to the press working method of the present embodiment, even if the inner diameter of the tube 1 is 5 mm or less, the perforated portion 2 can be formed in the tube 1 with higher accuracy.

[0071] Furthermore, according to the press working method of the present embodiment, even if the diameter of the hole portion 2 is 1.5 mm or less, the hole portion 2 can be formed in the tube 1 with higher accuracy.

[0072] In addition, according to the punching method of this embodiment, the punch ejector pin 3 can move at a first speed relative to the tube 1 to apply the first load, and then move at a fixed second speed exceeding the first speed to apply the second load. That is, the first and second loads can be applied by changing the moving speed of the punch ejector pin 3. In this case, the perforated portion 2 can be formed on the tube 1 with higher accuracy.

[0073] Furthermore, according to the press working method of the present embodiment, even if the second speed is 1000 mm / sec or more, the perforated portion 2 can be formed in the tube 1 with higher accuracy.

[0074] It should be noted that the present invention is not limited to the above-mentioned embodiment, and can be implemented in various other forms. For example, in the above, the punch pin 3 is moved relative to the tube 1, thereby applying a first load to the tube 1, and then the punch pin 3 is moved to apply a second load. However, the present invention is not limited to this. For example, the tube 1 can be moved relative to the punch pin 3, thereby applying a first load to the tube 1, and then the punch pin 3 can be moved to apply a second load to the tube 1. In this case, the perforated portion 2 can be formed on the tube 1 with higher accuracy.

[0075] In addition, in the foregoing, as an example of a tough material, i.e., a workpiece, a pipe 1 having a circular cross section is shown. However, the present invention is not limited thereto. For example, the workpiece as a tough material may be a plate. In this case, the perforated portion 2 can also be formed on the plate with higher precision.

[0076] The present invention has been fully described with reference to the accompanying drawings and in connection with the preferred embodiments, but various modifications and variations are apparent to those skilled in the art, and such modifications and variations are to be understood as being included therein as long as they do not depart from the scope of the present invention based on the appended claims.

[0077] Industrial Applicability

[0078] As described above, the press working method of the present invention can form a perforated portion with higher accuracy in a workpiece made of a tough material, and is therefore useful as a method for processing a tube used for cooling a machine part or lubricating a sliding portion, for example.

[0079] Explanation of symbols

[0080] 1 tube

[0081] 2. Perforation

[0082] 21 The outer peripheral portion of the outer side of the perforated portion

[0083] 22 The inner peripheral part of the perforated part

[0084] 3 Punch ejector pin

[0085] H Height of the burr

Claims

1. A stamping method, wherein a first load is applied to a workpiece made of a tough material by a stamping member to impart a preload in an elastic region of the workpiece, and then a second load exceeding the first load is applied to the workpiece by the stamping member to provide a perforated portion in the workpiece, wherein: The elastic region is greater than 0 MPa and is less than or equal to the shear stress value at which the workpiece undergoes elastic deformation. The workpiece is a metal pipe. The first load and the second load are applied in a state where the interior of the tube is hollow, The punching member moves relative to the workpiece at a first speed to apply the first load, and then moves relative to the workpiece at a fixed second speed exceeding the first speed to apply the second load.

2. The stamping method according to claim 1, wherein: After the first load is applied, the second load is continuously applied.

3. The stamping method according to claim 1, wherein: After the first load is applied, a temporary stop is performed and then the second load is applied.

4. The punching method according to any one of claims 1 to 3, wherein: The inner diameter of the tube is 5 mm or less.

5. The punching method according to any one of claims 1 to 3, wherein: The diameter of the perforated portion is 1.5 mm or less.

6. The stamping method according to claim 1, wherein: The second speed is greater than 1000 mm / sec.

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