JP4452202B2 - Axial punch used for hydroforming - Google Patents

Description

The present invention is used for the manufacture of exhaust system parts, suspension system parts, body system parts, etc. for automobiles. After inserting a metal pipe into a mold and clamping the mold, the internal pressure and the pipe shaft the axial pushing punch used in hydroforming for molding into a predetermined shape by loading a pushing force in the direction.

  In recent years, hydroform technology has attracted attention in the automobile field as one of the means for reducing costs and reducing weight by reducing the number of parts. In 1999, it was applied to actual vehicles in Japan. Since then, the number of applicable parts for hydroforming has increased year by year, and the market size has greatly expanded.

  As mentioned above, the hydrofoam market has been growing year by year, and with this, the number of parts that are difficult to form is increasing. For example, in a part with a shape as shown in Fig. 1, the tube expansion ratio at the center (= (peripheral length after molding-peripheral length of the raw tube) / perimeter of the raw tube x 100%) is large, and we want to expand the pipe. Hydroforming is difficult because the location is far from the pipe end. This is because, in hydroforming, pipe expansion is performed not only by internal pressure but also by the action of axial compression force (hereinafter referred to as axial pressing) caused by axial pressing from the pipe end. This is because there are fewer.

  In hydroforming, the shaft is pushed while applying an internal pressure. Therefore, due to the action of the internal pressure, the outer surface of the pipe and the inner surface of the mold in the straight pipe section from the pipe end to the mold cavity (hereinafter simply referred to as the straight pipe section). Is larger than before the internal pressure load (FIG. 2 (a)). However, if the shaft is pushed while the internal pressure is low, buckling tends to occur in the straight pipe (Fig. 2 (b)).

  In general, the tip of the axial push punch for hydroforming is shaped to contact the inner surface of the tube for a short length to prevent buckling of the tube end (Fig. 3 (a)). Therefore, in order to solve the problem in the part having the long straight pipe portion as described above, it is conceivable to lengthen the portion in contact with the inner surface of the pipe as shown in FIG. However, the inner surfaces of industrially produced pipe materials (steel pipes, aluminum extruded pipes, etc.) are not necessarily completely circular, and have some flatness and uneven thickness.

  Therefore, if an axial push punch as shown in FIG. 3 (b) is to be inserted, there is a possibility that it will not be inserted well when the punch is inserted and the pipe material will buckle. Even if it does not reach buckling, it may be pushed in slightly due to the frictional force, but in that case, the axial push will start before the internal pressure is applied. As a result, the conditions are different from those of the original hydroforming process, and stable machining cannot be realized.

  On the other hand, it is not used in small-diameter pipes such as automobile steel pipes, but in the UO steel pipe manufacturing process, it is mechanically expanded from the inside of the pipe using the equipment shown in Fig. 4 (excerpt from Steel Handbook III (2) Maruzen). Things have been done. This device mechanically expands from the inner surface side of the pipe by sliding a segment (generally called jaw, shim, and die in the figure) divided on the cone having a taper surface in the pipe axis direction. It is equipment to do. However, the cone of this device is moved forward and backward from the rear by a hydraulic cylinder. However, such a large-scale structure is possible because it is a UO steel pipe with a diameter of at least 450 mm, and it is difficult to construct a similar structure with a small diameter pipe such as a steel pipe for automobiles.

The present invention improves the mechanical pipe expansion device used for the above-mentioned large-diameter UO steel pipes for small-diameter pipes, and inserts a punch into the pipe material when hydroforming a part with a long straight pipe length. The purpose of the present invention is to provide an axial punch used for hydroforming, which can be inserted smoothly but can be axially pressed while maintaining a position far from the pipe end during hydroforming. To do.

In order to solve the problem, the gist of the present invention is as follows.
A divided tip divided into a plurality of parts in the circumferential direction, a tapered part provided with a taper surface whose diameter increases toward the axial tip side in the axial direction of the metal tube, and a punch tip part on the front surface of the divided chip An axial press punch for hydroforming, wherein the punch tip part is axially movable by internal pressure, and the divided tip is pressed by the punch tip part moving in the axial direction by internal pressure and the tapered part The axial push punch for hydroforming is characterized in that it can move to the outer peripheral side in the radial direction by sliding on the taper surface of the metal tube and can press the inner surface of the metal tube freely.

  According to the present invention, it is possible to form a hydroform part having a long straight pipe part, which has been difficult to form. As a result, the parts to which hydroform technology is applied are further expanded. As a result, the weight reduction of automobiles is promoted, which can contribute to the prevention of global warming.

  Details of the present invention will be described with reference to FIGS. Note that the state above the center line in FIG. 5 shows the state before the internal pressure load, and the state below the center line shows the state after the internal pressure load.

  First, the structure of the fixing bolt used in the axial push punch of the present invention will be described. The head 16 of the fixing bolt preferably has a shape based on a so-called hexagon socket head bolt provided with a hexagon socket. And the location close to the head 16 is a large diameter portion 17, and a small diameter portion 18 from the middle. Further, a screw portion 19 is provided at the rear end. Moreover, since this example is a water injection side punch, the bolt 30 has a water injection hole 30 extending between the screw portion 19 and the head portion 16.

  The punch tip part 8, the taper part 10, the metal seal part 11, and the flange 12 are coupled in order by the fixing bolt. Almost half of the front end side of the punch tip part 8, the taper part 10, and the metal seal part 11 has an outer diameter that can be smoothly inserted into the metal tube 2. The almost half of the rear end side of the metal seal part 11 and the flange 12 have an outer diameter larger than the inner diameter of the metal tube 2. Among them, the punch tip part 8, the taper part 10 and the metal seal part 11 have through holes, and the flange 12 is tapped to screw the screw part 19 at the tip of the fixing bolt. The flange 12 is provided with a water injection hole communicating with the hole 30 of the fixing bolt screwed to the flange 12 as described above.

  However, the hole diameter of the through hole formed in the taper part 10 and the metal seal part 11 is designed to be larger than the outer diameter of the small diameter part 18 of the fixing bolt and smaller than the outer diameter of the large diameter part 17, and The diameter of the through hole formed in the portion 8 is designed to be larger than the outer diameter of the large diameter portion 17 of the fixing bolt and smaller than the outer diameter of the head portion 16. Furthermore, the length of the large diameter portion 17 of the fixing bolt is designed to be longer than the depth of the through hole of the punch tip part 8. Further, the length of the narrow diameter portion 18 of the fixing bolt is designed to be shorter than the total length of the through holes of the taper part 10 and the metal seal part 11. As a result, when the fixing bolt is tightened so that the screw portion 19 at the tip is screwed to the flange 12 through the through-hole formed in the punch tip component 8, the taper component 10 and the metal seal component 11, the taper component 10 and the metal seal part 11 are firmly fixed to the flange 12 by a step between the large diameter portion 17 and the small diameter portion 18 of the fixing bolt. On the other hand, the punch tip part 8 is movable in the axial direction by the difference between the length of the fixing bolt large diameter portion 17 and the hole depth of the punch tip part 8. That is, the sliding portion 21 of the punch tip part 8 can move in the axial direction inside the hole provided on the front surface side of the taper part 10.

  Next, the structure of the taper component 10 and the divided chip 9 will be described.

  As shown in FIG. 6A, the taper component 10 is provided with a tapered surface 22 on the tip side from the cylindrical portion 23. The tapered surface 22 is formed so as to become gradually thinner toward the distal end side in the tube axis direction. The taper surface 22 has a polygonal cross section when viewed from the tube axis direction (the left figure in the figure), and in this example is a hexagon. The divided tip 9 slides on the tapered surface 22 in the tube axis direction.

  The structure of the divided chip 9 is shown in FIG. In this example, corresponding to the hexagonal tapered surface 22, the divided chip 9 has a shape divided into six in the circumferential direction. The angle of the slide surface 25 of the divided chip 9 with respect to the tube axis direction is equal to the angle of the tapered surface 22 of the taper part 10 with respect to the tube axis direction. The peripheral surface 26 that comes into contact with the inner surface of the tube is designed to have a radius of curvature that is a perfect circle in the initial state (the state above the center line in FIG. 5).

  The thickness of each divided chip 9 is such that when each divided chip 9 moves to the front end side in the tube axis direction on the tapered surface 22 of the tapered part 10, the peripheral surface 26 of each divided chip 9 is the inner surface of the metal tube 2. However, when each divided tip 9 moves to the rear end side in the tube axis direction on the tapered surface 22 of the taper part 10, the circumferential surface 26 of each divided tip 9 comes into contact with the inner surface of the metal tube 2 in the middle. Is set. As will be described later, each of the divided chips 9 always comes into contact with a ring-shaped surface formed at the rear end of the outer peripheral surface of the punch tip part 8, and the divided chips 9 always move together in the tube axis direction. ing.

  As the divided chips 9 slide the taper surface 22 of the tapered part 10 to the outer peripheral side (large diameter side) in the radial direction (that is, to the rear end side in the tube axis direction), the gap between the divided chips 9 increases (see FIG. (See the figure below the center line in the left figure of 5). Therefore, since the position of each divided chip 9 may become unstable in the circumferential direction, it is desirable to fix the circumferential position. Therefore, in this example, a protrusion 24 that is continuous in the tube axis direction is provided on the tapered surface 22 of the taper component 10, and a slide recess 27 that engages with the protrusion 24 is provided on the slide surface 25 of one divided chip 9. . Thereby, even if the taper surface 22 slides, the divided chip 9 does not move in the circumferential direction, and can move to the larger diameter side while keeping the gaps between the divided chips 9 uniform.

  Further, it is necessary to devise so that the divided chip 9 does not come off from the tapered part 10. In this example, a circumferential concave portion 28 is provided on the peripheral surface 26 of the divided chip 9, and a rubber band 29 is circumferentially wound around the portion and fixed. Due to the tightening force of the rubber band 29, each of the divided chips 9 is urged so as to move the tapered surface 22 toward the distal end side (the direction of narrowing).

  Next, the structure of the punch tip part 8 will be described.

  A sliding part 21 having an outer diameter sufficiently smaller than the outer diameter of the punch tip part 8 is provided on the rear end side of the punch tip part 8, and as described above, the sliding part 21 is a tapered part 10. It slides in the inside of the hole provided on the front side. On the other hand, a circumferential groove for attaching the O-ring 13 is formed on the outer peripheral surface of the punch tip part 8, and the rear end side of the circumferential groove gradually increases in diameter toward the rear end side in the tube axis direction. It becomes such a taper shape. Further, a space between the rear end of the outer peripheral surface of the punch tip component 8 and the front end of the sliding portion 21 is formed in a ring-shaped surface centered on the tube center axis. Each divided chip 9 is in contact with this ring-shaped surface. As described above, each of the divided chips 9 is urged by the tightening force of the rubber band 29 so as to move the tapered surface 22 toward the tip side (in the direction of narrowing). Also moves to the front end side in the tube axis direction, and the punch tip part 8 is held at a position where it abuts against the head 16 of the fixing bolt. Further, as will be described later, when the punch tip part 8 moves to the rear end side in the tube axis direction, the divided tips 9 are pushed to the rear of the tube axis by the ring-shaped surface, and each divided tip 9 becomes a tapered surface 22 of the taper part 10. Are moved to the rear end side in the tube axis direction.

  Lastly, the metal seal part 11 is provided with a metal seal part 20 against which the end of the metal tube 2 hits. The metal seal component 11 has an outer diameter that allows the front end side of the metal seal portion 20 to be smoothly inserted into the metal tube 2, and the rear end side of the metal seal portion 20 is larger than the inner diameter of the metal tube 2. It has an outer diameter.

  The above is the structure of each part constituting the axial push punch of the present invention. Next, the operation and function of each part during hydroforming will be described.

  First, the axial push punch is inserted into the metal tube 2. In this case, as described above, the punch tip part 8, the punch tip O-ring 13, the taper part 10, and the metal seal part 11 are designed such that the tip side portion of the metal seal part 20 is smaller than the inner diameter of the metal tube 2. At this time, as shown in the figure shown above the center line of FIG. 5, each of the divided chips 9 has a front end side (in a narrowing direction) of the tapered surface 22 by the fastening force of the fixing rubber band 29. The peripheral surface 26 of each divided chip 9 is not in contact with the inner surface of the pipe.

  As a result, when the axial push punch is inserted into the metal tube 2, the axial push punch can be inserted smoothly, and finally the axial push is performed until the end of the metal tube 2 contacts the metal seal portion 20. The punch can be smoothly inserted into the metal tube 2.

  Next, water 6 is supplied to the inside of the metal pipe 2 through a water injection hole provided in the flange 12 and a fixing bolt hole 30. When the water 6 is filled inside the metal tube 2, the excess water 6 tends to leak from the gap between the axial push punch and the inner surface of the metal tube 2. Then, the O-ring 13 attached to the outer peripheral surface of the punch tip component 8 is pushed into the rear end side of the pipe by the water flow, and as a result, the taper portion of the circumferential groove formed on the outer peripheral surface of the punch tip component 8 is reduced. It slides and comes into close contact with the inner surface of the metal tube 2 as shown below from the center line of FIG. Thereby, the leakage of the water 6 inside the metal tube 2 is stopped and the sealed state is obtained.

  Even after sealing, when the water 6 is supplied into the metal tube 2, the pressure of the water 6 increases. The punch tip part 8 moves to the rear end side in the tube axis direction by the action of the internal pressure. As a result, the divided tip 9 in contact with the ring-shaped surface of the punch tip part 8 is also pushed and moved in the tube end direction, and slides the taper surface 22 of the taper part 10 toward the rear end side in the tube axis direction. . As a result, the peripheral surface 26 of the divided chip 9 comes into contact with the inner surface of the metal tube 2 and bites into the thickness of the metal tube 2.

  When the axial push punch is pushed in with the above state, the axial compressive force applied to the axial push punch is transmitted to the metal tube 2 through the divided tip 9, and the metal tube 2 is pushed in. Therefore, even in the case of a hydroform part shape with a long straight pipe part, the axial push is performed from the position where the divided tip 9 is in contact with the inner surface of the metal pipe 2 without pushing from the end of the metal pipe 2, that is, in the middle of the straight pipe part. It becomes possible to load. Although the metal seal portion 20 is pushed in, if the position of the divided chip 9 is fixed, the metal seal portion 20 is in principle only in contact with the pipe end and no pushing force is applied. Further, since the water 6 is sealed at the position of the punch tip O-ring 13, the internal pressure is not applied to the metal tube 2 on the tube end side from the position, and therefore, the water 6 is caused by the internal pressure as shown in FIG. The generated friction force is not generated. Therefore, the pushing force to the metal seal part 20 resulting from the frictional force is not loaded.

  The above is description of this invention using the example of FIG.5 and FIG.6. Next, the application example is described.

  In the example of FIG. 5, the taper part 10, the metal seal part 11, and the flange 12 are separate parts in the example of FIG. 5, but they may be integrated into one or two. In this case, the metal seal component O-ring 14 and the flange O-ring 15 are not required. In the example of Fig. 5, the reasons for the division are as follows: firstly, when integrated, the parts will be quite long, making it difficult to drill through holes. If only the metal seal part 11 is changed according to the length of the pipe part, it can be used for multiple types of hydroform parts. Third, the material can be changed depending on the shape of each part and the required function. (For example, the taper part 10 is a combination of tool steel, the metal seal part 11 is plain steel, and the flange 12 is a combination of cast iron, etc.).

  Next, another application example of the fixing method of the divided chip 9 and the taper component 10 will be described.

  In the example of FIG. 6, the structure is as shown in FIG. 7A in which the divided chip 9 is provided with a concave portion and the tapered part 10 is provided with a convex part, but conversely, the divided chip 9 has a convex part and the tapered part 10 has a concave part. A structure as shown in FIG. Further, when the projections and recesses are provided with an angle as shown in FIGS. 3C and 3D, the taper component 10 does not come off even if the fixing rubber band 29 is not wound around the divided chip 9. The same effect can be obtained even if a tee groove is provided as shown in FIGS.

  However, when the fixing rubber band 29 is omitted in the structure shown in FIGS. 5C to 5F, the divided chip 9 is not in the initial state shown in the figure above the center line in FIG. Is not necessarily located on the small diameter side of the tapered surface 22. Therefore, in that case, it is necessary to devise such as adding a component such as a spring 31 to the rear surface of the divided chip 9 as shown in FIG. In the example of FIG. 5, the number of the divided chips 9 is six, but any number may be used as long as it is plural. In general, it is desirable to decrease the number as the inner diameter of the metal tube 2 is smaller and increase the number as the inner diameter increases.

  Next, an application example regarding the groove for attaching the O-ring 13 of the punch tip part 8 will be described. In the example of FIG. 5, the tapered surface is provided because there is not always a standard in which the outer diameter dimension of the O-ring exactly matches the inner diameter dimension of the metal tube 2. Therefore, when there is an O-ring with the right combination, a normal O-ring groove without a taper as shown in FIG. 9 may be used.

  Next, an application example of the metal seal part 20 will be described.

  In the axial push punch of the present invention, in principle, the metal seal portion 20 has only an auxiliary role to seal with the punch tip O-ring 13. Therefore, the metal seal portion may not be provided as shown in FIG. 10 (a), and even if it exists, it may not be in contact with the pipe end as shown in FIG. 10 (b).

  However, in general, O-ring seals are inferior in sealing performance at high pressures compared to metal seals. Therefore, in the case of hydroform parts that need to be loaded to a high pressure, it is preferable to use a metal seal as an auxiliary. In that case, it is more effective to provide a stepped metal seal portion 32 as shown in FIG. 3C and a tapered metal seal portion 33 as shown in FIG.

  11 to 13 show an embodiment of the present invention.

  The metal pipe 2 was a steel pipe with an outer diameter of 63.5 mm, a wall thickness of 2.3 mm, and a total length of 360 mm, and the steel grade was STKM11A, a carbon steel pipe for machine structures. Using the hydroform upper and lower molds 3 and 4 as shown in FIG. 11, a test for forming the metal tube 2 into a T-shape was performed. At that time, a normal axial push punch (punch having a structure as shown in FIG. 3A) was used from the left side toward the paper surface, and the axial push punch of the present invention was used on the long right side of the straight line portion. Detailed dimensions of the axial push punch of the present invention are shown in FIG. In the example of the present invention, about 130 mm from the tip of the axial push punch is inserted into the metal tube 2, and the metal tube 2 is pushed in with a divided tip located about 30 mm from the tip of the axial push punch. In other words, the shaft can be pushed from a position about 100mm from the pipe end.

In the hydroform molding according to this example, the left and right axial push punches are advanced while the internal pressure is kept constant at 30 MPa, and the left side where the normal axial push punch is pushed is stopped at a 25 mm axial push amount δ _L. The influence of the axial push amount δ _R on the right side to be pushed by the axial push punch of the example of the present invention was varied between 20 and 100 mm, and the influence was investigated. As the investigated item, the branch pipe height h of the T-shaped part as shown in FIG. 11 was selected. In addition, in order to compare with a normal axial push punch, a test using a normal axial push punch similar to the left axial push punch was performed for the right axial push.

  The test results are shown in FIG. From this result, the branch pipe height h is higher when the shaft is pushed by the shaft push punch according to the present invention than by a normal shaft push punch. This is because the axial push punch of the present invention grips the position 100 mm from the tube end and pushes the shaft, so that it is easier for the material to flow into the branch pipe portion than the normal axial push punch. In particular, the effect increases as the shaft push amount increases.

  Also, with a normal axial push punch, when a shaft push amount of 80 mm or more was applied, buckling occurred in the straight pipe part, and after that, almost no material flowed into the branch pipe part. On the other hand, in the axial push punch of the present invention example, the straight pipe portion did not buckle even with a 100 mm axial push. This is because there are two reasons that there is a physical restriction from the inside of the metal pipe 2 and that the frictional resistance is reduced because the inner pressure is not loaded on the pipe end side by the O-ring.

  INDUSTRIAL APPLICABILITY The present invention can be used for hydroforming suitable for manufacturing automobile exhaust parts, suspension parts, body parts, and the like.

It is explanatory drawing of the hydrofoam molded product with a long straight pipe part. It is explanatory drawing of the subject in a hydrofoam molded product with a long straight pipe part. It is explanatory drawing of the axial push punch at the time of lengthening the insertion part in order to prevent buckling of a straight pipe part. It is explanatory drawing of the mechanical pipe expansion apparatus used for manufacture of a UO steel pipe. It is explanatory drawing of the axial push punch for hydroforming of this invention. It is explanatory drawing of the taper component and division | segmentation chip | tip of the axial push punch for hydroforming of this invention. It is explanatory drawing of the split chip fixing method of this invention. It is explanatory drawing of a structure when not fixing the division | segmentation chip | tip of this invention with the rubber band for fixation. It is explanatory drawing when the groove | channel for O-rings of the punch tip component of this invention is not a taper shape. It is explanatory drawing of the various metal seal shape used by this invention. It is explanatory drawing of T-shaped shaping | molding which is an Example of this invention. It is explanatory drawing of the axial pushing punch used in the Example of this invention. It is explanatory drawing of the T-shaped shaping | molding test result tested as an Example of this invention.

Explanation of symbols

1 …… Hydrofoam molding 2 …… Metal pipe 3 …… Hydroform upper mold 4 …… Hydrofoam lower mold 5 …… Normal axial push punch 6 …… Pressure medium (eg water)
7 ... Axial push punch with long insertion part inside the tube 8 ... Punch tip part 9 ... Split tip 10 ... Taper part 11 ... Metal seal part 12 ... Flange 13 ... O-ring for punch tip 14 ... ... O-ring for metal seal parts 15 …… O-ring for flange 16 …… Fixing bolt head 17 …… Fixing bolt large diameter part 18 …… Fixing bolt small diameter part 19 …… Fixing bolt tip screw part 20 …… Metal seal Part 21 ...... Punch tip sliding part 22 ...... Taper part taper surface 23 ...... Taper part cylindrical part 24 ...... Taper part projection 25 …… Divided chip slide surface 26 …… Divided chip contact surface 27 …… Divided chip slide Recessed part 28 ...... Recessed part for fixing the split chip 29 ... Rubber band for fixing the split part 30 ... Hole for pouring water 31 ... Spring for fixing the split part 32 ... It stepped metal seal portion 33 ...... tapered metal seal part

Claims (1)

  A divided tip divided into a plurality of parts in the circumferential direction, a tapered part provided with a taper surface whose diameter increases toward the axial tip side in the axial direction of the metal tube, and a punch tip part on the front surface of the divided chip An axial press punch for hydroforming, wherein the punch tip part is axially movable by internal pressure, and the divided tip is pressed by the punch tip part moving in the axial direction by internal pressure and the tapered part Axial punch for hydroforming, characterized in that it can move to the outer peripheral side in the radial direction by sliding on the taper surface of the metal tube and push the inner surface of the metal tube freely.

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