JP3737318B2 - Hydraulic hole punching method for cylindrical members - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for punching a tubular member using internal fluid pressure inside the tubular member and a punching punch.
[0002]
[Prior art]
In recent years, there has been a demand for a vehicle body and chassis parts for the purpose of reducing the weight of the vehicle body for reducing CO ₂ and reinforcing the vehicle body for improving strength. As such vehicle body and chassis parts, there is an increasing movement to apply parts obtained by internal pressure molding of hollow cylindrical members. These components are subjected to internal fluid pressure molding into a predetermined shape, and then holes for attaching other components and holes for positioning are processed. However, recently, based on a demand for improvement in economic efficiency and processing accuracy, a processing method in which hole punching is performed in a series of processes of internal hydraulic forming has been studied.
[0003]
For example, as shown in FIG. 5A, the hole punch 61 is struck from the outside to the inside of the tubular member 64 while applying the internal fluid pressure P to the inside of the tubular member 64. A method of punching is disclosed (JP-A-6-292929). Further, as shown in FIG. 5B, while the internal hydraulic pressure P is applied to the inside of the cylindrical member 64, the punching punch 61 is retracted, the cylindrical member 64 is deformed, and the outer punching process is performed. A method is also disclosed (plasticity and processing, Vol. 39 (No. 453), p. 1049 (1998)).
[0004]
[Problems to be solved by the invention]
However, in the method shown in FIG. 5A, plastic deformation occurs in the peripheral portion 67 of the portion that becomes the punched residue 65 in the process of punching. For this reason, there has been a problem that, after punching, sagging occurs in the peripheral portion 67 of the hole, and the accuracy of the hole diameter is reduced. Further, in order to prevent this sagging, the internal fluid pressure P has to be considerably increased. For this reason, the pressure generating device and the processing equipment are increased in size, resulting in an increase in capital investment, and problems such as a reduction in space efficiency and an increase in cost. is there. Further, even in the method shown in FIG. 5 (b), the hole cannot be punched unless the internal hydraulic pressure P is considerably increased. Similarly, the pressure generating device and the processing equipment are enlarged, and the equipment investment is increased. There are problems such as reduced space efficiency and increased cost. Further, the portion that becomes the punched residue 66 is broken while expanding in a dome shape outside the cylindrical member 64 due to the load of the internal hydraulic pressure P, so that the surface roughness of the fracture surface 68 and the accuracy of the hole diameter are reduced. There was a problem.
[0005]
In order to solve these problems, the present invention provides a hydraulic member punching process for a cylindrical member that can form a hole with high hole diameter accuracy and surface accuracy of a holed portion and low sagging even at low internal fluid pressure. Provide a method.
[0006]
[Means for Solving the Problems]
The hydraulic hole punching method for a cylindrical member according to claim 1 is a processing method in which a hole is punched in the cylindrical member by a punching punch while applying an internal hydraulic pressure to the inside of the cylindrical member. Finally, by forming a protrusion having a convex shape and an outer shape substantially equal to the dimension to be punched in a direction opposite to the direction in which the hole is to be punched, the inner pressure and the tool are sandwiched on the outer periphery of the protrusion. Thus, the thickness reduction part is formed over the entire circumference along the hole punching shape, and the inside of the thickness reduction part is pressurized from the tip side of the protrusion, thereby performing the hole punching process.
[0009]
According to this invention, a protrusion having a convex shape and an outer shape substantially equal to the dimension to be punched is formed in a direction opposite to the direction in which the hole is finally punched, and the outer peripheral portion of the protrusion. Is pressed against the corners of the tool and becomes a thickness-decreasing portion over the entire circumference. And the deformation | transformation part which formed this protrusion becomes high to the rigidity with respect to the pressurization from the front end side of a protrusion. When pressure is applied to these protrusions from the tip side, the deformed part is concentrated on the boundary surface between the deformed part and the undeformed part, and the thickness of this part is reduced. Therefore, the deformed portion which is easily sheared and formed with the protrusion is integrally punched. As a result, even at a relatively low internal fluid pressure, the hole diameter accuracy and the surface accuracy of the holed portion can be excellent, and a hole with less sagging can be processed in the peripheral portion.
[0010]
According to a second aspect of the present invention, in the method of punching a cylindrical member according to the first aspect , the punching punch is retracted before or after the internal hydraulic pressure is loaded, The projection having a convex shape is formed on the outer side by the internal fluid pressure, and thereafter the punching punch is advanced to perform punching.
[0011]
According to the present invention, the punching punch retreats before or after applying the internal hydraulic pressure, so that the protrusion that protrudes toward the outside of the cylindrical member and the periphery of the protrusion on the retracted portion. A reduced thickness portion is formed. Since this protrusion has high rigidity against pressure from the tip end side of the protrusion, the deformed part forming the protrusion is integrated into the wall thickness by advancing the punching punch and applying pressure from the tip end side of the protrusion. Hole punching can be easily performed from the reduced portion.
[0012]
According to a third aspect of the present invention, in the hydraulic punching method for the cylindrical member according to the first aspect , the punching punch having a convex tip is advanced, and the inside of the cylindrical member is formed by the punching punch. Forming a protrusion having a convex shape on the side and a thickness reducing portion around the protrusion, and then retreating or retreating the punching punch while moving the tubular member outwardly by the internal hydraulic pressure. It is characterized by punching.
[0013]
According to this invention, the convex protrusion is formed on the inner side of the tubular member by advancing the punching punch having the convex tip. As described above, the protrusion has high rigidity against the pressure from the tip end side of the protrusion, and a thickness reduction portion is formed around the protrusion. Alternatively, it is possible to perform a hole punching process in the outer direction of the cylindrical member with a relatively low internal hydraulic pressure while being retracted. The deformed portion forming the protrusion is punched as a single piece, and is excellent in hole diameter accuracy and surface accuracy of the holed portion, and can process a hole without sagging.
[0014]
According to a fourth aspect of the present invention, in the hydraulic hole punching method for a cylindrical member according to the second or third aspect , the punching punch has a shear edge formed at an outer peripheral portion of a tip. Has characteristics.
[0015]
According to this invention, since the shear edge is formed on the outer peripheral portion of the tip of the punching punch, the biting mark of the shearing edge is formed on the outer surface of the tubular member by the advancement of the punching punch. This bite mark becomes a reduced thickness portion, and the shearing force applied when punching a projecting portion with increased rigidity can be further concentrated, so hole punching becomes easier and the fracture surface becomes smaller. become clean. As a result, the hole diameter accuracy and the surface accuracy of the holed portion are further improved, and a hole with less sagging can be processed even at a lower internal fluid pressure.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
[0017]
The cylindrical member hydraulic hole punching method according to the present invention is a processing method for punching a cylindrical member while applying an internal hydraulic pressure to the inside of the cylindrical member. This is a method in which after the formation of the reduced thickness portion over the circumference, the inside of the reduced thickness portion is pressurized and punched, and finally, in a direction opposite to the direction of punching, a convex shape is used. In addition, by forming a protrusion having an outer shape substantially equal to the dimension to be punched, a thickness reduction portion is formed on the outer periphery of the protrusion by sandwiching the internal hydraulic pressure and the tool, and then a punching punch or This is a method of punching the inside of the reduced thickness portion by applying pressure from the tip end side of the protrusion by internal liquid pressure. This hydraulic hole punching method includes (i) a method of forming a convex protrusion formed in the direction opposite to the direction of the hole punching process in the outer direction, and (ii) a cylindrical shape. The method is roughly divided into two methods of forming on the inner side of the member.
[0018]
First, a first method, that is, a method of punching by forming convex protrusions in the outer direction of the cylindrical member and then pressurizing the inside of the reduced thickness portion will be described. FIG. 1 is a front cross-sectional view showing an example of a method of hydraulic hole punching of a cylindrical member of the present invention. In FIG. 1, the processing is performed in the order from FIG. 1 (a) to FIG. 1 (c).
[0019]
First, as shown in FIG. 1A, the punching punch 11 is disposed at a position retracted from the contact surface 19 of the tool 16 disposed on the outer surface of the cylindrical member 14 by a predetermined length. The hole punch 11 may be disposed at such a position before or after the internal hydraulic pressure P of the cylindrical member 14 is loaded. As the method, it may be arranged in advance at a position separated from the contact surface 19 by a predetermined length, or may be disposed backward from the same position as the contact surface 19. Among these, as a method of retracting the punching punch 11 from the same position as the contact surface 19 of the tool 16, the punching punch 11 can be retracted by a relative difference between the internal hydraulic pressure P and the pressure Pc of the driving means of the punching punch 11. . For example, the cylindrical member 14 is deformed by increasing the internal fluid pressure P and the hole punch 11 is retracted, or the pressure Pc of the driving means of the hole punch 11 is reduced, and the cylindrical member is driven by the internal fluid pressure P. The punching punch 11 can be moved backward while deforming. Further, the punching punch 11 can be moved back mechanically.
[0020]
Next, as shown in FIG. 1B, the cylindrical member 14 is plastically deformed by the internal hydraulic pressure P to form a protrusion 15 having a convex shape in the outer direction of the cylindrical member 14. As described above, the punching punch 11 is disposed at a predetermined interval from the position of the outer surface of the cylindrical member 14, so that the convex protrusion 15 can be formed in the space. This protrusion 15 is formed by the internal hydraulic pressure P of the cylindrical member 14 added after that when the punching punch 11 is previously arranged at a predetermined position. Further, when the hole punch 11 is retracted to a predetermined position, the protrusion 15 is formed by the internal hydraulic pressure P of the cylindrical member 14 applied after the reverse, or the internal hydraulic pressure of the cylindrical member 14 is set. The protrusion 15 can be formed by retracting the punching punch 11 by P.
[0021]
Of these methods, in the method of forming the convex protrusion 15 while the hole punch 11 is moved backward by the internal pressure P, the relative difference between the internal pressure P and the pressure Pc of the driving means of the hole punch 11 is adjusted. Thus, there is a method of forming the convex protrusion 15 while forcibly retracting the hole punch 11. Specifically, by increasing the internal fluid pressure P, the relative difference from the pressure Pc is expanded to forcibly retract the hole punch 11, or by reducing the pressure Pc, The relative difference is enlarged to forcibly retract the hole punch 11. Alternatively, both the internal hydraulic pressure P and the pressure Pc may be changed simultaneously to increase the relative difference and forcibly retract the hole punch 11. The method of forcibly retracting the punching punch 11 by the relative difference between the pressures is usually preferably used because its control is simple in manufacturing.
[0022]
The protrusion 15 formed in this manner has a higher rigidity against pressure from the tip side of the protrusion 15 than that of the part that is not plastically deformed due to the accumulation of processing strain due to plastic deformation and the shape effect around the protrusion deformed into a dome shape. Become higher. The outer dimensions of the plastically deformed protrusion 15 are substantially the same as the outer dimensions of the retracted punching punch 11. Further, the periphery of the protrusion deformed into a dome shape is pressed against the corner of the tool 16 over the entire circumference, and the thickness reducing portion 20 is formed by the internal fluid pressure P and the tool 16 being pinched.
[0023]
Finally, as shown in FIG. 1C, the hole punching 11 is advanced to the inside of the cylindrical member 14 to perform hole punching. That is, the punching punch 11 is pressed forward from the tip side of the convex protrusion 15 toward the inner side of the tubular member 14 and advanced. At this time, as described above, the convex protrusion 15 has high rigidity against pressurization from the tip side of the protrusion 15, so that the rigidity is increased without plastic deformation and a portion where the rigidity is increased by plastic deformation. A boundary portion (hereinafter referred to as a “boundary portion”) with a non-exposed portion is pressurized by the punching punch 11, whereby the shearing force is concentrated, and this portion is a thickness reducing portion 20. Therefore, it becomes easy to concentrate the shearing force. As a result, when the punching punch 11 is advanced and the inside of the thickness reducing portion 20 is pressurized, the deformed portion forming the convex protrusion 15 is punched integrally. Since the fracture surface 17 thus perforated is fractured due to concentration of shearing force, the accuracy of the hole diameter and the surface accuracy of the perforated part are excellent even at a relatively low internal fluid pressure. There is little sagging around the periphery. The advancement and speed of the punching punch 11 at this time can be controlled by adjusting the relative difference between the internal fluid pressure P and the pressure Pc as described above, or can be controlled mechanically. .
[0024]
As described above, in the method in which the convex protrusion 15 is formed in the outer direction of the cylindrical member 14 and then the hole punching process is performed, the shape of the hole punch 11 is as shown in FIG. A flat tip 12 is usually used. Further, as shown in FIG. 2, a punching punch having a deeper tip 22 and a concave shape with a small radius of curvature facilitates the formation of the reduced thickness portion 20 and is preferably used. Furthermore, it is particularly preferable to use a punching punch 21 in which a shear edge 23 is formed on the outer peripheral portion of the concave tip 22. Since the punch 22 has a deep concave shape at the tip 22, it does not apply deformation stress to the convex protrusion 25 having increased rigidity. Further, since the shear edge 23 bites into the boundary portion when the punching punch 21 advances toward the inside of the cylindrical member 14, the shearing force due to the advancement of the punching punch 21 can be further concentrated. it can. As a result, the sheared fracture surface 27 becomes a clean surface, has excellent hole diameter accuracy, and does not cause sagging.
[0025]
Next, in the second method, that is, by forming a convex protrusion on the inner side of the cylindrical member, a reduced thickness portion is formed around the protrusion, and then the inside of the reduced thickness portion is pressurized to punch holes. How to do will be described. FIG. 3 is a front cross-sectional view showing another example of the method of punching a cylindrical member according to the present invention. In FIG. 3, the processing is performed in the order from FIG. 1 (a) to FIG. 1 (b). In this method, a punching punch 31 having a convex tip 32 is used.
[0026]
First, as shown in FIG. 3A, the punching punch 31 having a convex tip 32 is advanced from the outside to the inside of the cylindrical member 14, so that the convex protrusion 35 is formed inside the cylindrical member 14. Form on the side. As a method of advancing the punching punch 31, it can be advanced by a relative difference between the internal hydraulic pressure P and the pressure Pc of the driving means of the punching punch 31. Specifically, by increasing the pressure Pc of the driving means of the punching punch 31, the relative difference from the internal fluid pressure P is expanded to advance the punching punch 31, or the internal fluid pressure P is reduced. As a result, the relative difference from the pressure P is enlarged and the punching punch 31 is advanced. Alternatively, both the internal hydraulic pressure P and the pressure Pc may be changed simultaneously to increase the relative difference and advance the punching punch 31. The method of forcibly retreating the punching punch 31 by adjusting the relative difference between the pressures is usually more preferable than mechanically controlled advancement because the control is simple in manufacturing.
[0027]
The convex protrusion 35 formed by advancing the punching punch 31 has the same properties as the protrusion 15 described above, that is, accumulation of processing distortion based on plastic deformation and the shape effect deformed into a dome shape. The rigidity with respect to the pressurization is higher than that of the portion around the protrusion that is not plastically deformed. The outer dimensions of the plastically deformed protrusions 35 are substantially the same as the outer dimensions of the advanced punching punch 31. At this time, as shown in FIG. 3 (a), the punching punch 31 is pushed to the outer peripheral edge 36, thereby forming a thin reduced portion 30 at the boundary. The thickness reducing portion 30 is formed by the outer peripheral portion of the protrusion 35 being pressed against the corner portion of the tool 16, and the internal hydraulic pressure P and the tool 16 being held.
[0028]
Next, as shown in FIG. 3B, the punching punch 31 is moved backward from the tip end side of the convex protrusion 35 toward the outer side of the tubular member 14. At this time, as described above, the convex protrusion 35 has high rigidity against pressurization from the tip end side of the protrusion 35, so that the boundary portion is pressurized by the internal hydraulic pressure P, so that shear force is generated. Further, since the boundary portion is the thickness reduction portion 30, the shearing force is more likely to be concentrated. As a result, by retreating the punching punch 31 and pressurizing the inside of the thickness reducing portion 30, the convex protrusion 35 formed on the cylindrical member 14 can be prevented from being generated at the boundary portion even at a relatively low internal fluid pressure P. Shears and is punched together. At this time, the hole punching punch 31 may be retracted and then pressed by the internal liquid pressure P, or may be punched by pressurizing the internal punching pressure 31 while the hole punching punch 31 is retracted. The method of retracting the punching punch 31 is controlled by the method already described, that is, by adjusting the relative difference between the internal fluid pressure P and the pressure Pc of the driving means of the punching punch 31 as appropriate. Can be done. Since the fracture surface 37 thus perforated is broken due to the concentration of shearing force, the accuracy of the hole diameter is excellent, and the sagging of the peripheral portion of the hole is small.
[0029]
Further, it is possible to use a punching punch having a convex tip provided with a shear edge. FIG. 4 shows an example. The punching punch 41 has a convex tip 42 and a shear edge 43 on the outer periphery. A recess 44 is formed between the tip 42 and the shear edge 43. When such a punching punch 41 is advanced to the inside of the cylindrical member, a convex protrusion pushed by the tip 42 of the punching punch 41 is formed on the inner side of the cylindrical member. At that time, the shear edge 43 provided in the punching punch 41 forms a bite mark on the outer surface of the tubular member. This bite mark generally coincides with the boundary portion, and an apparent thickness reduction portion is formed in that portion. As a result, when the hole punching is subsequently retracted, the shearing force is further concentrated on the bite mark due to the pressure applied from the front end side of the convex protrusion, and shearing is facilitated. Thus, the fractured surface after being punched becomes cleaner, and the hole diameter accuracy becomes better.
[0030]
As described above, in the method of punching a cylindrical member according to the present invention, the convex protrusion formed in the direction opposite to the direction of the final punching is formed in the outer direction of the cylindrical member. Regardless of whether it is a method of forming or a method of forming on the inner side of the tubular member, a relatively low internal fluid pressure can be obtained by forming a thickness-reduced portion in advance in the portion to be punched. In this case, the hole diameter accuracy and the surface accuracy of the holed portion are excellent, and the punching process without sagging can be performed. The hole shape to be punched by this method may be any of a round hole, a square hole, and a deformed hole, and a hole punch suitable for the desired shape can be used.
[0031]
Moreover, although the aluminum alloy is normally used for the cylindrical member used by this invention, the kind of material and alloy is not specifically limited. Furthermore, the hole punching method of the present invention can be applied to a generally used internal hydraulic pressure processing method. Therefore, the conditions, that is, the type of fluid and the internal hydraulic pressure are performed within the range of general conditions of the internal hydraulic forming apparatus. For example, the internal liquid pressure is about 500 to 1500 atm.
[0032]
【The invention's effect】
As described above, according to the hydraulic hole punching method of the tubular member of the present invention, after forming the thickness reducing portion over the entire circumference once along the punching shape, the inside of the thickness reducing portion is This is a method of pressurizing and punching, and the protrusion formed in the direction opposite to the direction of the final punching process has higher rigidity against the pressure from the tip end side of the protrusion. Therefore, when pressure is applied from the front end side of the projection, the shearing force is concentrated on the thickness reduction portion, which is a boundary portion between the projection portion having increased rigidity and the peripheral portion of the projection not having increased rigidity. And the part of the protrusion whose rigidity is enhanced is integrally sheared and punched. As a result, the hole diameter accuracy and the surface accuracy of the holed portion are excellent, and a hole with less sagging around the periphery can be processed even at a relatively low internal fluid pressure.
[0033]
By adopting the hole punching method of the present invention, when forming a pipe-shaped hollow cylindrical member by the internal hydraulic forming method, the forming process and the hole punching process are performed in a series of steps of the internal hydraulic forming process. Can be done at the same time. As a result, it is possible to obtain a vehicle body or a chassis component that is excellent in economy.
[Brief description of the drawings]
FIG. 1 is a front cross-sectional view showing an example of a method of punching a cylindrical member according to the present invention.
FIG. 2 is a front cross-sectional view showing a form of punching using another form of punching punch used in the present invention.
FIG. 3 is a front cross-sectional view showing another example of the method of punching a cylindrical member according to the present invention.
FIG. 4 is a front sectional view showing an example of a tip shape of a punching punch used in the present invention.
FIG. 5 is a front sectional view showing an example of a conventional hydraulic hole punching method for a cylindrical member.
[Explanation of symbols]
11, 21, 31, 41 Hole punch 12, 22, 32, 42 Tip 14 Cylindrical member 15, 25, 35 Protrusion 16 Tool 17, 27, 37 Fracture surface 19 Contact surface 20, 30 Thickness reducing portion 23, 43 Shear edge 36 Outer peripheral edge 44 Recess P Internal fluid pressure Pc Pressure of driving means for punching punch

Claims (4)

In the processing method of punching the cylindrical member by a punching punch while applying an internal hydraulic pressure to the inside of the cylindrical member , the convex shape is once opposite to the direction of the final punching process. In addition, by forming a projection having an outer shape substantially equal to the dimension to be punched, a thickness reduction portion is formed over the entire circumference along the punched shape by sandwiching the inner pressure and the tool on the outer periphery of the projection. Then, a hydraulic hole punching method for a cylindrical member , wherein the hole is punched by pressurizing the inside of the thickness reducing portion from the tip side of the protrusion . Before or after applying the internal hydraulic pressure, the hole punch is retracted to form the convex protrusion on the outside of the cylindrical member by the internal hydraulic pressure, and then the hole punch is advanced. The hydraulic hole punching method for a cylindrical member according to claim 1 , wherein hole punching is performed. The tip of the punching punch is advanced, the punching punch forms the projection on the inner side of the tubular member, and then the punching punch is retracted or retracted, 2. The method of punching a cylindrical member according to claim 1 , wherein the cylindrical member is punched in the outer direction by the internal hydraulic pressure. The hydraulic punching method for a cylindrical member according to claim 2 or 3 , wherein the punching punch has a shear edge formed on an outer peripheral portion of a tip thereof.

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