JP5058677B2 - Method of forming hub hole flange portion of vehicle wheel - Google Patents

Description

  The present invention relates to a method for forming a hub hole flange portion of a vehicle wheel for forming a hub hole flange portion of a vehicle wheel.

  In the vehicle wheel, after assembling the tire, the hub hole is fitted into the axle of the vehicle, and the bolt hole provided in the hub mounting portion around the hub hole is disposed in the hub connected to the axle. It is fixed to the axle and the hub by fitting into a bolt and screwing a nut into the bolt from the front of the wheel and tightening. It is well known that a vehicle wheel has a cylindrical hub hole flange portion standing upright on the wheel surface along the opening edge of the hub hole.

  In the vehicle wheel described above, a steel one is usually formed by pressing a predetermined plate-like base material. In this press working process, a predetermined hub element hole is drilled in a plate-shaped substrate, and the peripheral edge of the hub element hole is formed behind the wheel by a predetermined shape mold (hole expanding punch). The hub hole and the hub hole flange are formed by expanding the holes so that the peripheral edge of the hole rises to the front of the wheel (for example, Patent Document 1).

  Here, in the hole expanding process of raising the hole peripheral part of the hub element circular hole, the hole peripheral part is bent to expand the diameter and extend in the circumferential direction. When the ratio of the diameter difference between the hole diameter of the hub element circular hole and the inner peripheral diameter of the hub hole flange portion formed by bending the hole expansion process with respect to the hole diameter of the hub element circular hole is defined as a hole expansion ratio. As the hole expansion ratio increases, the strain due to stretching in the circumferential direction increases, and it becomes easy to cause defects such as cracks at the tip of the hub hole flange part during the hole expansion process. Therefore, set a hole expansion rate that does not cause defects such as cracks based on experience and verification tests, etc., and form a hub element circular hole with a hole diameter corresponding to the hole expansion rate, or perform hole expansion processing multiple times. The method of carrying out divided into steps and gradually expanding the diameter was performed.

By the way, as a processing method for punching a metal material by press working, for example, as in Patent Document 2, the first step of half punching with a die having a small diameter difference and a punch, There has been proposed a method in which a second step of punching with a die having a diameter larger than that of the die and the punch is performed. In this method, in the first step, the inner peripheral surface of the recess formed in a half-cut state can be made into a mirror surface state by half-cutting with a die and a punch having a small difference in diameter. In the two steps, since the load required for punching is reduced, the end face of the hub element circular hole can be formed smoothly. In this method, the clearance between the die and the punch in the first step is set in a range of −10% to + 5%. By setting it as this range, the product is not distorted at the time of half-punching, and the effect that the end face of the hub element circular hole can be formed smoothly can be produced.
JP 2000-225432 A (paragraph number “0008”, FIGS. 1 (6) and (7)) JP-A-9-314250

  Since the inner diameter of the hub hole flange portion of the vehicle wheel corresponds to the hub hole diameter, the inner diameter (hub hole diameter) is set according to the outer diameter of the axle. Therefore, when the hub hole flange portion corresponding to the axles having different outer diameters is formed, it is necessary to form the hub round hole according to the hole expansion rate in consideration of the above-described hole expansion rate. . That is, the maximum value of the hole expansion rate is defined, and the hub element circular holes having different hole diameters must be formed according to the hole expansion rate. In this way, when forming the hub circular holes with different hole diameters, a dedicated die such as a punch for punching is required according to each, so that the replacement work of the die becomes complicated, or the manufacturing cost of the die Manufacturing costs will increase, such as higher purchase costs. Moreover, even when the hole expanding process is performed in a plurality of times as described above, a plurality of types of molds for the hole expanding process are required, and thus the manufacturing cost is similarly improved. Yes. Further, even if the hole expanding process is performed in a plurality of times, the total amount of processing strain generated by the hole expanding process is the same, so that there is a limit to the effect of reducing the occurrence of defects such as cracks.

  In addition, in the vehicle wheel described above, there is a type of configuration in which the height of the hub hole flange portion is set to be relatively high. Here, the height of the hub hole flange portion is determined by a radial difference between the hole diameter of the hub element circular hole and the inner peripheral diameter of the hub hole flange portion formed by the hole expanding process. Therefore, when molding a configuration in which the hub hole flange portion is relatively high, the hole expansion ratio must be increased, and it is necessary to perform the hole expansion processing in a plurality of times. For this reason, the above-described problems have occurred.

  On the other hand, when the above-described conventional method of half punching in the first process and punching in the second process is applied to the formation of the hub element circular hole, the hub element circular hole can be formed relatively well. However, if the hole peripheral portion of the hub round hole is subjected to hole expansion processing, defects such as cracking may occur when the hole expansion ratio is set to be relatively large. That is, there is a limit to the effect of suppressing the occurrence of defects such as cracks, and the above problems cannot be solved sufficiently.

  The present invention provides a hub hole flange portion molding method for a vehicle wheel that can suppress the occurrence of defects such as cracks even when the hub hole flange portion is formed with a relatively large hole expansion rate. Propose.

  The present invention provides an elemental hole processing step for forming a hub elemental hole in the center of a plate-like base material, and a hole expanding punch is pressed from the rear side of the wheel to the hole periphery part of the hub elemental hole. In the hub hole flange part forming method for a vehicle wheel for forming the hub hole flange part by sequentially performing the hole expanding process step of expanding the hole so as to stand up on the front side of the wheel, Drilling a pilot hole for installation in a plate-shaped substrate, a pre-processed punch having an outer diameter equal to the hole diameter of the hub element circular hole, and a plate-like shape facing the pre-processed punch A supporting die for supporting one side surface of the base material, and without restricting the hole end surface of the pilot hole, the peripheral edge of the pilot hole along the thickness direction has a predetermined indentation depth less than the plate thickness. The excess material pressed by the preliminary processing punch is And a pre-compression step that is provided in at least one of the pre-processed punch and the support die, and that is installed in an up-set air space that is smaller than the diameter of the hub circular hole and that opens to face the plate-like substrate; A hub hole flange portion forming method for a vehicle wheel, comprising: a step of drilling a hub element circular hole by a hole punch having an outer diameter equal to the hole diameter of the hub hole element circular hole. It is. Note that the down hole for upsetting is formed so as to penetrate the plate-like base material in the plate thickness direction, and in other words, it can also be expressed as an upsetting hole.

Here, as shown in FIGS. 13 (A) and 13 (B), the result of scrutinizing the case of using the conventional method in which the hub round hole 88 is drilled once by the predetermined punching punch 81 and the die 82 is shown. Detailed description.
When the hole peripheral edge 89 of the hub element circular hole 88 formed by this conventional method is observed, the punching direction of the punch punch 81 (from the top to the bottom) is performed at the hole peripheral edge 89 of the hub element circular hole 88 as shown in FIG. The striped structure 87 of the plate-like base material 21 is curved in the direction toward the head. The curved striped structure 87 is relatively large in the peripheral edge portion 89 of the hub element circular hole 88 because the striped structure 30 parallel to the plate surface direction is curved by the processing of the punch punch 81. It is clear that work distortion has occurred and work hardening has occurred. Further, a curved surface 86a that curves downward is formed at the uppermost portion of the hole end surface of the hub element circular hole 88, and is continuously below the curved surface 86a in the vertical direction (plate thickness direction). A shearing surface 86b that is cut substantially perpendicularly is formed, and a fracture surface 86c that is cut in the plate surface direction is formed continuously below the shearing surface 86b. And in this fracture surface 86c, it turns out that the form which the above-mentioned striped structure | tissue 87 curves is large compared with the shear surface 86b, and has produced work hardening largely. If the hole peripheral portion 89 of the hub element circular hole 88 is subjected to hole expansion processing so as to have a relatively large hole expansion rate, cracks and the like are likely to occur. The conclusion was reached that work hardening is the main cause of cracking due to hole expansion.

Furthermore, the result of scrutinizing the case where the hub hole element circular hole is formed by using the method of half-cutting in the first step and punching in the second step of Patent Document 2 described above will be described in detail.
In the first step, since the clearance between the punch and the die is small, the punch can be cut along the thickness direction. Here, in the portion of the plate-like substrate pressed by the outer peripheral edge of the punch, the clearance between the punch and the die is small, so compression deformation occurs in the plate thickness direction, and stretching in the plate surface direction accompanying the compression deformation Due to the deformation, work hardening occurs at a cutting portion of the plate-like base material cut by the punch (a portion that becomes the peripheral edge portion of the hub element circular hole). The surplus material generated in the plate thickness direction by punch pressing flows into the central opening of the die, but the surplus material due to the stretching deformation in the plate surface direction accompanying the compression deformation is generated in the plate surface direction. For this reason, it is difficult to flow into the central opening of the die. In particular, when the clearance is negative, there is a region sandwiched between the outer peripheral edge of the punch and the inner peripheral edge of the die, so that a relatively large amount of compressive deformation occurs, and processing associated with stretching deformation in the plate surface direction. Curing is likely to occur at the cutting site of the plate-like substrate cut by the punch. In the next second step, the amount of work to be cut by the punch (cutting distance in the plate thickness direction) is less than that of the above-described method of punching the hub element circular hole at a time, so that the work hardening can also be reduced. it can. However, since the work hardening generated in the first step remains, the work hardening generated at the peripheral edge portion of the hub element circular hole is reduced as compared with the method of punching out the hub element circular hole at once. It can be done, but the effect of reducing it is limited. Therefore, even if the hub round hole is formed by the first step and the second step, cracks and the like are caused by the hole expanding process due to work hardening occurring at the peripheral edge of the hub round hole. It is easy.

  In contrast to such a conventional method, as described above, the present invention forms a pilot hole for upsetting before performing the press working with the pre-processed punch, and the pre-processed punch in the next pre-compression process. And the supporting die, the hole end face of the pilot hole is pressed without being constrained, and the hub round hole is punched out in the round hole drilling step.

  Here, in the preliminary compression step, the annular region of the peripheral edge of the prepared pilot hole surrounded by the outer peripheral diameter of the preliminary processing punch and the opening diameter of the upset air region is compressed and deformed. The stretching deformation in the plate surface direction accompanying the deformation can be installed in the prepared hole. Thereby, it can suppress that work hardening arises by the said press work in the cutting | disconnection site | part of the plate-shaped base material cut | disconnected by the press work of a preliminary | backup process punch. Since the pilot hole for upsetting is formed in the plate thickness direction, it is easy to install surplus material due to stretching deformation in the plate surface direction in the pilot hole immediately after the start of pressing of the preliminary processing punch, and work hardening It has excellent suppression effect. Furthermore, since the hub round hole is partially formed in the preliminary compression process, in the next round hole drilling process, the remaining depth (thickness) of the indentation depth of the preliminary compression process by the punching punch Can be overcome. For this reason, the amount of processing by the punching punch is relatively small, so that the work hardening by the punching processing is reduced.

  In the pre-compression process, the peripheral edge portion of the prepared preparation hole is cut in the plate pressure direction by a shearing force when the pre-processing punch is pressed. Therefore, it can be cut relatively sharply by pressing the pre-processed punch. Thereby, when a plate-shaped base material has a striped structure, it can cut | disconnect, curving the striped structure of a cut surface in a plate | board thickness direction. Also from this, the effect which suppresses that a process effect arises in the cutting | disconnection site | part of the plate-shaped base material cut | disconnected by the press work of a pre-process punch is high.

  From the above, according to the round hole processing step of the present invention, it is possible to suppress work hardening from occurring at the peripheral edge portion of the hub round hole, so that the hub hole flange portion is formed by the next hole expanding step. It is difficult to cause cracks. Therefore, even when the hub hole diameter is set to be larger than the hole diameter of the hub circular hole, so-called hole expansion rate is relatively large, occurrence of defects such as cracks in the hub hole flange portion is suppressed. Can be.

  Further, according to the round hole drilling process of the present invention, as described above, in the preliminary compression process, it is possible to cut in the thickness direction while suppressing the work hardening by the preliminary punch, and in the round hole drilling process, the punching amount Therefore, a relatively large number of shear planes cut substantially perpendicularly along the plate thickness direction are formed on the hole end surface of the hub element circular hole. The hole end surface of the hub element circular hole has a significantly reduced fracture surface that causes burrs and roughness as compared with the case where it is formed by the conventional method described above, and is formed on a smooth surface as a whole. This also contributes to increasing the effect of suppressing the occurrence of cracks by the hole expanding process.

  In the pre-compression process, the surplus material generated by pressing the pre-processed punch flows into the prepared pilot hole and also flows into the installed air space as described above. In this way, the surplus material is installed in the upsetting airspace, which also helps to suppress the work hardening from occurring at the cutting portion of the plate-like base material cut by the preliminary processing punch. In addition, when the preliminary processing punch presses the peripheral edge portion of the down hole for installation in the plate thickness direction as a whole, surplus material generated in the plate thickness direction by the preliminary processing punch is mainly placed in the installation air space. To flow.

  In the present invention, the upsetting air space may be any one of the configurations provided in one or both of the preliminary processing punch and the supporting die. And the upsetting air space should just be comprised so that the surplus material produced by the press work of a preliminary | backup process punch may have sufficient volume. Moreover, the punching punch used in the round hole punching step can be the same as the preliminary processing punch.

  In a general manufacturing process of manufacturing a vehicle wheel by pressing a plate-like base material, a positioning hole is previously drilled in the center of the plate-like base material, and then the press is performed based on this. There is a way to perform machining. This positioning hole is usually formed in a polygonal shape in order to define the center position and the circumferential position. Then, when the positioning hole is provided, in the step of drilling the hub round hole, the guide hole is held in the positioning hole and the hub hole is drilled by a predetermined punch. I am doing so. That is, the positioning hole is used only to define the center position when the hub hole is formed. On the other hand, in the present invention, since the hub element circular hole is formed without restricting the hole end face of the installation prepared hole, the guide pin is like a positioning hole. Significantly different from what is inserted. Moreover, since the surplus material is installed from the surroundings, it is preferable that the installation prepared holes are circular holes so that they can be installed evenly in the circumferential direction.

  Further, in the pre-compression step, the hole in the pilot hole is formed with a pressing depth at which the pre-processed punch is 10% or more and 50% or less with respect to the plate thickness of the hole peripheral portion of the installation pilot hole. A method of pressing the peripheral edge can be suitably used. Since it is cut by the preliminary working punch up to this indentation depth, the height in the plate thickness direction of the part that can suppress the work hardening described above is determined. Further, the remaining depth (thickness) excluding the indentation depth is processed in the next round hole drilling step. Since the effect of suppressing the work hardening caused by the processing is improved as the depth processed in this round hole drilling process is shortened, the effect of suppressing the work hardening generated at the peripheral edge of the hub circular hole is generally improved. Further improvement. In addition, if the indentation depth is shallower than 10% of the plate thickness of the peripheral edge portion of the prepared preparation hole, the effect of suppressing work hardening in the round hole drilling process is reduced, and 50% If the depth is deeper, cracks or the like are likely to occur at the cutting site of the plate-like substrate cut by the pressing process during the pressing process by the preliminary processing punch.

  In the above-described vehicle wheel hub hole flange portion forming method, the supporting mold used in the preliminary compression step of the round hole processing step is an inner circular hole that opens to a smaller diameter than the outer peripheral diameter of the preliminary processing punch. Is formed by the inner circular hole, and the preliminary compression step supports the plate-like substrate from behind the wheel by the support mold, A method is proposed in which surplus material is installed in the prepared hole and the installation air space of the supporting mold by pressing the peripheral edge portion of the installed prepared hole from the front side of the wheel.

  In such a method, the support die becomes a so-called die, and surplus material generated by the press working of the preliminary working punch is placed in the upset air space opened in the support die. In other words, the clearance between the outer diameter of the pre-processed punch and the opening diameter of the support mold is set to be negative, and the annular region sandwiched between the two is compressed and deformed, and the surplus material generated thereby Can be installed in the upset air space of the support mold and the prepared preparation hole. According to such a method, the above-described effect of the present invention, which suppresses the occurrence of work hardening at the peripheral edge portion of the hub element circular hole, and suppresses the occurrence of cracks or the like due to the hole expanding process, is appropriately exhibited. It can be done.

The opening diameter of the inner circular hole formed in the supporting mold described above is
D1-0.2t × 2 ≦ D2 <D1-0.1t × 2
(Where D1: outer diameter of the pre-processed punch, t: plate thickness of the plate-like substrate, D2: opening diameter)
A method provided to satisfy the above is proposed.

  In such a method, the opening diameter D2 of the inner circular hole of the supporting mold that constitutes the upset air space and the outer peripheral diameter D1 of the preliminary working punch are defined, and the preliminary processing punch has an outer peripheral diameter D1. The annular region of the peripheral edge portion of the installation pilot hole surrounded by the opening diameter D2 of the supporting mold is compressed. That is, as the opening diameter D2 becomes smaller, the annular region compressed by the preliminary machining punch becomes wider and wider. In this configuration, the annular region to be compressed is defined by the relationship between the outer peripheral diameter D1 and the opening diameter D2, and by setting within this range, the annular region is generated by being stretched and deformed in the plate surface direction by pressing the preliminary working punch. The action of installing the surplus material in the preparation hole is further improved, and the effect of suppressing work hardening at the cutting site of the plate-like base material cut by the preliminary machining punch as described above is further achieved. Rise.

  Here, in the case where the preliminary compression process is performed by a punch (preliminary processing punch) and a die (supporting die) in accordance with the relational expression of the above-described configuration, the punch is determined by the relationship between the outer peripheral diameter D1 and the opening diameter D2. The clearance with the die is in the range of less than -10% and -20% or more. That is, the clearance is increased in the minus direction as compared with the method of performing the first step and the second step of Patent Document 2 described above. If the clearance of this configuration is applied to the first step of Patent Document 2, since the annular region sandwiched between the punch and the die is wide, the amount of deformation of this compression also increases, and the accompanying plate surface direction The amount of deformation to be stretched is also increased. Therefore, the work hardening which arises in the cutting site | part of the plate-shaped base material cut | disconnected by a punch increases, and the problem that a crack etc. will arise more easily by the next hole expansion process arises. On the other hand, in the present invention, as described above, since the pilot hole for upsetting is formed in advance, the range of the present configuration in which the clearance is large in the negative direction (the range of less than −10% and −20% or more). ), The stretching deformation in the plate surface direction caused by the pressing process of the punch (preliminary processing punch) can be installed in the installation prepared hole. Therefore, it can fully suppress that work hardening arises in the cutting part of the plate-like substrate cut with a punch (preliminary processing punch).

  If the clearance is −10% or more (D2 ≧ D1−0.1t × 2), the region of the supporting mold that supports the force in the plate thickness direction by the preliminary processing punch becomes narrow. The tendency for the force in the thickness direction to act increases, and the processing strain in the thickness direction tends to occur at the cutting site of the plate-like base material cut by the preliminary processing punch. Therefore, the effect which suppresses the work hardening produced in the hole peripheral part of a hub element | circle hole will reduce. On the other hand, if the clearance is smaller than −20% (D2 <D1−0.2t × 2), the annular region sandwiched between the pre-processed punch and the support die becomes wide, and the plate surface direction accompanying the compression deformation is increased. In addition, the action of installing the surplus material of stretching deformation into the preparation hole for installation is reduced. Therefore, the effect of suppressing the work hardening described above is reduced, and the probability of occurrence of cracks or the like tends to increase due to the hole expanding process.

  Further, in the hub wheel flange portion molding method for a vehicle wheel described above, the preliminary processing punch used in the preliminary compression step of the round hole processing step has an annular shape, and the upset air region is defined by the air region opened inside thereof. In the preliminary compression step, the plate-like base material is supported from the rear side of the wheel by a support die, and the preliminary processing punch is installed from the front side of the wheel to the peripheral edge of the prepared hole. A method is proposed in which surplus material is placed in the prepared hole and the upsetting space of the pre-processed punch by pressing the portion.

  In such a method, the pre-processed punch has an annular shape with its outer diameter and opening diameter, and surplus material generated by pressing with the pre-processed punch is placed in the upset air space formed inside the pre-processed punch. This is the method that was set up. In this method, since the upsetting air space is formed in the pre-processed punch, when the pre-processed punch presses, the up-setting air space also includes the stretching deformation in the plate surface direction caused by the compression deformation due to the pressing. Easy installation. Therefore, the effect which suppresses the work hardening produced by the press work by a preliminary | backup process punch improves further. According to such a method, the above-described effect of the present invention, which suppresses the occurrence of work hardening at the peripheral edge portion of the hub element circular hole, and suppresses the occurrence of cracks or the like due to the hole expanding process, is appropriately exhibited. It can be done.

  In the hub hole flange portion forming method for a vehicle wheel of the present invention, a hole for installation is drilled in a plate-like base material, and then the peripheral edge portion of the hole is formed by a preliminary processing punch and a support die. By pressing, the surplus material pressed by the pre-processed punch is installed in the prepared hole and the up-set air space provided in at least one of the pre-processed punch and the supporting mold, and then the hub is formed by the punching punch. This is a method of forming a hub hole flange part by forming a round hole and then expanding the hole peripheral part of the hub round hole up to the wheel surface. By such a method, the stretching deformation in the plate surface direction generated by compressing and deforming the annular region of the peripheral edge of the prepared preparation hole surrounded by the outer diameter of the pre-processed punch and the opening diameter of the upsetting air region is reduced. Since it can be installed in the hole and in the upsetting air space, it is possible to suppress the occurrence of work hardening at the cutting site of the plate-like base material cut by the preliminary processing punch. Moreover, since the amount of processing by the subsequent punching punch is reduced, the work hardening by the punching processing can be reduced. Accordingly, it is possible to suppress work hardening at the peripheral edge of the hub element circular hole, so that it is difficult to cause cracks or the like when forming the hub hole flange part in the next hole expansion process, and the hole expansion rate is increased. Even if it sets so that it may set, it can suppress that malfunctions, such as a crack, arise.

  Further, the support die is formed with an inner circular hole having a smaller diameter than the outer diameter of the pre-processed punch, and the inner circular hole constitutes an upset air space, and is preliminarily compressed. In the process, if the surplus material pressed by the pre-processed punch is used as a method in which surplus material is installed in the prepared preparation hole and the installation air space of the supporting mold, the above-mentioned book It is possible to appropriately exert the effect of the invention that it is possible to suppress work hardening from occurring in the peripheral edge portion of the hub element circular hole and to suppress occurrence of cracking or the like due to the hole expanding process.

Here, the opening diameter of the inner circular hole formed in the support mold is
D1-0.2t × 2 ≦ D2 <D1-0.1t × 2
(Where D1: outer diameter of the pre-processed punch, t: plate thickness of the plate-like substrate, D2: opening diameter)
The method is provided so as to satisfy the above. In the case of this method, when the annular region defined by the opening diameter D2 of the support mold and the outer peripheral diameter D1 of the preliminary working punch is compressed and deformed, the stretching deformation in the plate surface direction accompanying the compression deformation is reduced for upsetting. Since it can be sufficiently installed in the hole and in the upsetting air space, the effect of suppressing the work hardening at the cutting site of the plate-like base material cut by the preliminary processing punch according to the present invention can be further enhanced. .

  Further, the pre-processed punch has an annular shape and is configured to form an upset air area by an air area opened inside thereof, and in the pre-compression process, surplus material pressed by the pre-process punch, In the case where the surplus material is installed in the preparation hole in the upsetting and the upsetting space of the preliminary processing punch, the stretching deformation in the plate surface direction caused by compressive deformation by the annular preliminary processing punch is performed. The pre-working punch is easily installed in the upsetting space, and the effect of suppressing work hardening occurring at the cutting site of the plate-like substrate cut by the pre-working punch is high. Therefore, it is possible to more appropriately exhibit the operational effect of the present invention described above in that work hardening can be suppressed in the peripheral edge portion of the hub element circular hole and cracks and the like can be suppressed from being generated by the hole expanding process.

  Embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a longitudinal sectional view of a steel vehicle wheel 1. The vehicle wheel 1 is formed by fitting a disc-shaped wheel disk 2 formed by pressing from a plate-like base material 21 (see FIG. 3) and a cylindrical wheel rim 3 formed by rolling. is there.

  As shown in FIGS. 1 and 2, the wheel disc 2 described above has a hub mounting portion 7 having a hub hole 5 opened in the center. From the outer peripheral portion (hub surface round portion) 7 a of the hub mounting portion 7. A hat portion 8 is formed so as to protrude from the front side of the wheel. A plurality of decorative holes 10 are provided in the hat portion 8, and a disk flange portion 9 is formed on the outer side of the hat portion 8 along the wheel axial direction. Further, the hub mounting portion 7 is formed with a hub hole flange portion 6 standing up from the opening edge of the hub hole 5 toward the wheel surface, and a plurality of nut seats provided around the hub hole flange portion 6. Bolt holes 4 are formed at equal intervals on the same circumference.

  On the other hand, as shown in FIG. 1, the wheel rim 3 has a cylindrical shape with a deformed cross section, and flange portions 11 a and 11 b that support the sidewall portions of the tire (not shown) are formed on the outer end edges on both sides thereof. Continuously connected to the flange portions 11a and 11b, bead seat portions 12a and 12b for holding tire beads are formed substantially parallel to the axial direction. Further, a drop portion 13 that is recessed toward the inner diameter side of the wheel rim 3 is provided between the bead seat portions 12a and 12b. When the tire bead is dropped into the drop portion 13 when the tire is attached, the drop seat 13 is attached. It is easy. Further, the vehicle wheel 1 is formed by fitting and welding the above-described disk flange portion 9 of the wheel disk 2 to the inner peripheral surface of the drop portion 13. The vehicle wheel 1 according to the first embodiment is a so-called drop fitting wheel.

  The wheel disk 2 described above is formed by pressing a steel plate-like base material 21 which is a stretched material (see FIGS. 3 to 6). The plate-like base material 21 is cut out in a predetermined shape from a steel plate drawn in the plate surface direction, and has a striped structure along the plate surface direction.

  The above-described hub hole flange portion 6 is a predetermined hole expansion process in which an elemental hole processing step of forming a hub elemental hole 28 in the center of the plate-like base material 21 and a hole peripheral part 29 of the hub elemental hole 28 are expanded. The punch 54 is pushed up from the rear side of the wheel, and is formed by sequentially executing a hole expanding process step that stands up on the front side of the wheel. In addition, in the manufacturing process of the wheel disc 2, processes other than the round hole drilling process and the hole expanding process are performed in the same manner as in the prior art, and the description thereof is omitted.

  Below, the round hole processing step and the hole expansion processing step for forming the hub hole flange portion 6 according to the main part of the present invention will be described in detail.

  First, as shown in FIG. 3A, the back surface around the central portion of the plate-like substrate 21 is supported by a die 41. Then, as shown in FIG. 3 (B), a circular uphole 22 is drilled in the center of the plate-shaped substrate 21 by a cylindrical punching punch 42. Here, the pilot hole 22 is formed so as to penetrate the plate-like substrate 21 in the plate thickness direction. The step of drilling the pilot hole 22 is the step of drilling the pilot hole for installation according to the present invention. And this circular pilot hole 22 is for installing an excess material in the pre-compression process mentioned later.

  Following the above-described installation pilot hole drilling process, a pre-compression process of pressing the hole peripheral edge 23 of the installation pilot hole 22 is performed. As shown in FIG. 4, the pre-compression process includes a pre-processed punch 44 that presses the hole peripheral portion 23 of the pilot hole 22 from the front side of the wheel, and a central portion of the plate-like substrate 21 facing the pre-processed punch 44. Is pressed by a supporting die 43 that is supported from the back surface thereof. The pre-processed punch 44 has a substantially cylindrical shape, and the outer peripheral diameter D <b> 1 is equal to the hole diameter of the hub element circular hole 28. The support die 43 is formed with an inner circular hole 45 opened at the center thereof, and the opening diameter D2 is smaller than the outer diameter D1 of the preliminary machining punch 44 (outer diameter D1> opening diameter). D2). That is, the clearance between the preliminary machining punch 44 and the support die 43 is negative.

Here, the clearance between the preliminary machining punch 44 and the supporting die 43 is set to be smaller than −10% and larger than −20%. When the relationship between the outer peripheral diameter D1 of the preliminary machining punch 44 and the opening diameter D2 of the supporting die 43 is expressed using this clearance, the range of Expression (1) is obtained. In addition, Formula (1) is represented by the relationship with the plate | board thickness t of the plate-shaped base material 21. FIG.
D1-0.2t × 2 ≦ D2 <D1-0.1t × 2 (1)
In the first embodiment, the outer peripheral diameter D1 of the preliminary machining punch 44 and the opening diameter D2 of the support die 43 are set so that the clearance is set to −20%.

  Furthermore, in the first embodiment, the peripheral end portion of the pressing surface of the preliminary machining punch 44 is a rounded blade portion as shown in FIG. The rounded blade portion is referred to as a blade corner round portion 44a in the following description. The radius of the rounded corner 44a is set to be considerably smaller than the outer peripheral diameter D1 of the preliminary machining punch 44. Thus, by setting the peripheral end portion of the pressing surface of the pre-processed punch 44 as the blade corner rounded part 44a, it is possible to suppress the occurrence of a fracture surface that causes burrs and roughness, and to improve the durability life of the pre-processed punch 44. be able to.

  In the support die 43 described above, the air space constituted by the inner circular hole 45 is the upset air space 46 according to the present invention.

  In the pre-compression process, the back surface of the plate-like base material 21 is supported by a support die 43 as shown in FIG. 4 (A), and the peripheral edge portion of the installation lower hole 22 as shown in FIG. 4 (B). 23 is pressed along the plate thickness direction by the preliminary machining punch 44 from the front side of the wheel. Here, the preliminary processing punch 44 presses to a predetermined pressing depth h that is less than the plate thickness of the hole peripheral portion 23 of the prepared hole 22. This indentation depth h is in the first embodiment, and is about 50% of the plate thickness of the hole peripheral edge 23 of the prepared hole 22. The pushing depth h is preferably set in a range of 10% or more and 50% or less with respect to the plate thickness of the hole peripheral portion 23 of the prepared hole 22. Further, when pressing with the preliminary machining punch 44, it is carried out without inserting a guide pin or the like into the prepared hole 22. That is, the hole peripheral portion 23 of the pilot hole 22 is pressed by the preliminary machining punch 44 without restricting the hole end surface 22 a of the pilot hole 22.

  At the time of press working by the preliminary working punch 44, an annular region surrounded by a negative clearance between the preliminary working punch 44 and the support die 43 in the hole peripheral portion 23 of the setting-up pilot hole 22 is pinched. The This annular region is compressed and deformed in the plate thickness direction by the pressing process of the preliminary processing punch 44. Along with this compression deformation, stretching deformation occurs in the plate surface direction. The surplus material generated by this stretching deformation can be placed in the prepared hole 22 drilled in the plate thickness direction. Therefore, it can suppress that the said extending | transformation deformation | transformation arises in the cutting | disconnection site | part of the plate-shaped base material 21 cut | disconnected when the preliminary | backup process punch 44 presses, and can suppress that work hardening arises.

  On the other hand, the area directly above the inner circular hole 45 of the support die 43 in the hole peripheral portion 23 of the down hole 22 for installation is not supported by the support die 43, so that the preliminary processing punch 44 is pressed. By processing, it enters the upset air space 46 in the inner circular hole 45. In other words, the surplus material generated by the press working by the preliminary working punch 44 is placed in the upsetting air space 46.

  In addition, since the lower surface of the cutting portion of the plate-like base material 21 that is cut when the preliminary processing punch 44 is pressed in the preliminary compression step is supported by the supporting die 43, the shearing force of the preliminary processing punch 44 is obtained. Can cut relatively sharply in the thickness direction. Therefore, the first cut peripheral surface 26 (see FIG. 7A) formed by being cut by the preliminary machining punch 44 is a smooth surface.

  As described above, in the preliminary compression step, the hub peripheral hole 28 is pressed by pressing the hole peripheral edge portion 23 of the setting-up pilot hole 22 to a predetermined pressing depth h by the preliminary processing punch 44 and the supporting die 43. Is partially punched to partially form the hub round hole 28. And in this press work, as mentioned above, it is suppressed that work hardening arises in the cutting part (periphery part of the 1st cutting peripheral surface 26) of plate-like substrate 21 cut by preliminary processing punch 44. Yes.

  The portion pressed by the preliminary processing punch 44 in the preliminary compression step is a half punching portion 48 to be removed in the next round hole drilling step, and the half punching portion 48 is generated in the preliminary compression step. Surplus material has been put in place.

  In the above-described preliminary compression step, the support die 43 is a support die according to the present invention. Further, the back surface of the plate-like substrate 21 supported by the supporting die 43 is one side according to the present invention. Further, the outer peripheral diameter D1 of the preliminary machining punch 44 (the hole diameter of the hub element circular hole 28) is set so that the hub hole 5 having a predetermined hole diameter is formed and the hub hole flange portion 6 having a predetermined height is formed. ing. That is, the pre-processed punch is formed so that the radial difference between the hole diameter of the hub element circular hole 28 and the inner peripheral diameter of the hub hole flange portion 6 formed in the hole expanding step described later becomes the height of the hub hole flange portion. An outer peripheral diameter D1 of 44 is set.

  After performing the above-described pre-compression process, a hub round hole 28 is formed by performing a round hole drilling process. As shown in FIG. 5, the round hole drilling step is performed by a substantially cylindrical hole punch 50 and a die 51 facing the hole punch 50. The hole punch 50 has an outer diameter D1 equal to the hole diameter of the hub element circular hole 28. Therefore, it is also possible to use the above-described preliminary processing punch 44 as the punching punch 50. In this case, the peripheral end portion of the pressing surface of the punching punch 50 is a blade corner rounded portion 50 a as in the preliminary processing punch 44. On the other hand, the die 51 has an opening diameter D <b> 3 opening at the center thereof larger than the outer diameter D <b> 1 of the punching punch 50. That is, the clearance between the punching punch 50 and the die 51 is set to be positive.

Here, the clearance between the punch 50 and the die 51 is set to be 12% or more and 28% or less. When the relationship between the outer peripheral diameter D1 of the punching punch 50 and the opening diameter D3 of the die 51 is expressed using this clearance, the following equation (2) is satisfied. In addition, Formula (2) is represented by the relationship between the plate | board thickness t of the plate-shaped base material 21, and the indentation depth h.
D1 + 0.12 (t−h) × 2 ≦ D3 ≦ D1 + 0.28 (t−h) × 2 (2)
In the first embodiment, the outer peripheral diameter D1 of the punching punch 50 and the opening diameter D3 of the die 51 are set so that the clearance is 24%.

  In the round hole drilling step, the back surface of the plate-like substrate 21 is supported by a die 51 as shown in FIG. Then, as shown in FIG. 5B, the half punching portion 48 pressed in the preliminary compression step is removed by the punching punch 50, and the hub element circular hole 28 is formed in the center of the plate-like substrate 21. . In this round hole drilling step, the first punching circumference formed by cutting the punch punch 50 with the preliminary machining punch 44 from the state where the hub round hole 28 has already been formed partway through the preliminary compression step. A hub round hole 28 is formed by driving along the surface 26. Here, the amount of processing punched by the punching punch 50 follows the remaining depth (thickness of hh) of the indentation depth h in the pre-compression process, so the amount of processing is also relatively small. For this reason, the second cutting peripheral surface 27 (see FIG. 7B) formed by punching with the punching punch 50 can suppress the occurrence of burrs, roughening, etc., and can be cut with the punching punch 50. Work hardening that occurs at the cutting site of the plate-like base material 21 (the peripheral site of the second cutting peripheral surface 27) can be reduced.

  As described above, the hub element circular hole 28 is formed in two steps by the preliminary compression process and the element hole forming process. And it can suppress that work hardening arises in the cutting part (surrounding part of the 1st cutting peripheral surface 26) of plate-like base material 21 cut with preliminary processing punch 44 at a preliminary compression process, and it is a round hole drilling process. Work hardening that occurs at the cutting site of the plate-like substrate 21 (the peripheral site of the second cutting peripheral surface 27) cut by the punching punch 50 can be reduced. Therefore, as a whole, work hardening that occurs in the formation process of the peripheral edge portion 29 of the hub element circular hole 28 is suppressed.

  The above-described preparation hole drilling step, pre-compression step, and round hole drilling step constitute the round hole processing step according to the present invention.

  Following the round hole drilling step, the hole expanding step is performed to form the hub hole flange portion 6. The hole expanding process is performed by a hole expanding punch 54 and an outer presser ring 55 as shown in FIG. The hole expanding punch 54 has an upper processed portion having a substantially conical shape and a lower processed portion having a cylindrical shape so that the peripheral edge portion 29 of the hub element circular hole 28 can be gradually raised. . In the first embodiment, the inner diameter of the outer retainer ring 55 is set equal to the outer diameter of the hub hole flange portion 6, and the outer diameter D 4 of the hole expanding punch 54 is set to The radius difference with the hole diameter is set to be a predetermined height of the hub hole flange portion 6. The hole expansion ratio is the ratio of the diameter difference between the hole diameter of the hub element circular hole 28 and the inner peripheral diameter of the hub hole flange portion 6 formed by bending the hole expansion process to the hole diameter of the hub element circular hole 28. It is. Therefore, in this embodiment, it can be said that the hole expansion rate is determined by the outer peripheral diameter D4 of the hole expanding punch 54 and the outer peripheral diameter (hole diameter of the hub element circular hole) D1 of the preliminary processing punch 44 (if approximated). , Hole expansion rate≈ (D4−D1) / D1 × 100%).

  As shown in FIG. 6A, the outer pressing ring 55 is brought into contact with the surface of the plate-like base material 21 so as to be concentric with the hub element circular hole 28. Then, as shown in FIG. 6B, the hole expanding punch 54 is pushed up from the back surface side of the peripheral edge portion 29 of the hub element circular hole 28 along the plate thickness direction. As a result, the peripheral edge portion 29 of the hub element circular hole 28 is bent and raised toward the wheel surface, and the hub hole flange portion 6 is formed.

  In this hole expanding process, even if the hole peripheral portion 29 of the hub element circular hole 28 is expanded to the front of the wheel, it is possible to suppress the occurrence of defects such as cracks in the hub hole flange portion 6. obtain. This is because work hardening occurring in the peripheral edge portion 29 of the hub element circular hole 28 is suppressed by the above-described pre-compression process and element hole forming process, and the hub element circular hole 28 is expanded in the hole expansion process. This is because even the breaking strain is not reached. And even if it sets so that the hole expansion rate which expands the hub raw circular hole 28 in a hole expansion process process may be comparatively large, it can prevent that a crack generate | occur | produces in the hub hole flange part 6. FIG. Therefore, even if the height of the hub hole flange portion 6 is set to a relatively high dimension and the hole expansion rate has to be set to be large, there is a problem such as cracking in the hole expansion process. It can be suppressed. Similarly, even when the inner peripheral diameter of the hub hole flange portion 6 is different, it is possible to form the hub element circular hole 28 having the same hole diameter. As described above, when manufacturing a configuration in which the height dimension and the inner peripheral diameter of the hub hole flange portion 6 are different, even if the hole expansion rate is increased, the occurrence rate of defective products can be significantly reduced. Therefore, the increase in manufacturing cost can be suppressed.

  In addition, since the prepared preparation hole 22 formed before the pre-compression process is formed in a circular shape, surplus material generated by the pre-process punch 44 when the pressing process is performed in the pre-compression process. It can be extended to 22 substantially uniformly over the circumferential direction. Thereby, the effect which suppresses work hardening substantially uniformly over the circumferential direction can be exhibited in the cutting | disconnection site | part (surrounding part of the 1st cutting | disconnection surrounding surface 26) of the plate-shaped base material 21 cut | disconnected with the preliminary | backup process punch 44. .

  On the other hand, as a result of observing the cross section of the cutting part (the peripheral part of the first cutting peripheral surface 26) of the plate-like base material 21 cut by the preliminary processing punch 44 after the pre-compression process described above, FIG. ), The striped structure 30 is substantially along the plate surface direction at the end portion of the first cut surface 26. As a result, it can be seen that at the cut portion of the plate-like base material 21 cut by the preliminary processing punch 44, the work hardening due to the press processing of the preliminary processing punch 44 hardly occurs. Moreover, as a result of observing the cross section of the hole peripheral portion 29 of the hub element circular hole 28 after performing the elemental hole drilling step, the plate-like substrate cut by the hole punch 50 as shown in FIG. A striped structure 31 slightly curved toward the back of the wheel was confirmed at 21 cutting sites (around the second cutting peripheral surface 27). Thereby, it can be said that some work hardening has arisen in the cutting | disconnection site | part of the plate-shaped base material 21 cut | disconnected by the perforation punch 50. FIG. Here, at the cutting part of the plate-like base material 21 cut by the punching punch 50 (the peripheral part of the second cutting peripheral surface 27), the curved form of the striped tissue 31 changes in the plate thickness direction. From this, it can be seen that the magnitude of work hardening also changes in the thickness direction.

For comparison with the first embodiment, in the case where the hub element circular hole 88 is formed by the hole punch 81 and the die 82 as shown in FIG. The cross section of the hole peripheral edge 89 of the hole 88 was observed. Note that the method of forming the hub round hole 88 at a time in this way is a method that has been generally performed conventionally, and the clearance between the punching punch 81 and the die 82 is set to + 12%. That is, the outer diameter D6 of the punch 81 and the opening diameter D7 of the die 82 have the following relationship. Here, t is the plate thickness of the plate-like substrate 21.
D6 + 0.12t × 2 = D7

  In this conventional method, a positioning reference hole 85 is previously drilled in the center of the plate-like base material 21. In the process of drilling the hub element circular hole 88, as shown in FIG. In addition, the back surface of the plate-like substrate 21 is supported by the die 82, and the guide pin 83 is inserted into the reference hole 85. Then, as shown in FIG. 13B, the guide pin 83 is fitted and held in the reference hole 85, and the hub element circular hole 88 is formed by the hole punch 81.

  In the case of such a conventional method, as shown in FIG. 14, a striped structure 87 curved in the plate thickness direction was confirmed at the hole end portion of the hub element circular hole 88. The striped structure 87 of the hub element circular hole 88 formed by this conventional method is greatly curved as compared with the stripe structure 31 of the hub element circular hole 28 formed in the first embodiment described above. The area is wide. In particular, in the lower part of the hub element circular hole 88 of the conventional method, the curved shape is extremely large, and the influence of breakage is strong. Thereby, in the case of the conventional method, it turns out that comparatively big work hardening has arisen in the hole edge part of the hub element circular hole 88. FIG.

  From these observation results, it is clear that the work hardening generated in the peripheral edge portion 29 of the hub raw circular hole 28 formed by the raw circular hole processing step of the first embodiment can be suppressed. Therefore, since this work hardening is suppressed, it is possible to prevent cracks and the like from occurring even if the hole peripheral portion 29 of the hub element circular hole 28 is erected in the hole expanding process. And even if it sets so that a hole expansion rate may become comparatively large in this hole expansion process, generation | occurrence | production of a crack etc. can be suppressed.

  On the other hand, when the hub hole flange portion 6 is formed by the hub hole flange portion forming method of the first embodiment, the hole expansion rate (%) that does not cause defects such as cracks at the tip of the hub hole flange portion 6 is obtained. A test was conducted to confirm the above. As described above, the hole expansion rate is the ratio of the diameter difference between the inner peripheral diameter of the hub hub hole flange portion 6 and the hole diameter of the hub element circular hole to the hole diameter of the hub element circular hole.

  In this test, as the plate-like substrate 21, a workable hot rolled high-tensile steel plate (SPFH590) having a plate thickness of 3.5 mm was used. In the pre-compression process, the pre-processed punch 44 has an outer diameter D1 of 36 mmφ, and the support die 43 has an opening diameter D2 of 35.2 mmφ and 34.6 mmφ. Two types are used. Here, when the opening diameter D2 is 35.2 mmφ, the clearance with the preliminary machining punch 44 is -11%, and when the opening diameter D2 is 34.6 mmφ, the clearance with the preliminary machining punch 44 is -20%. It is. Further, in the preliminary compression step, the indentation depth h of the preliminary processing punch 44 is set to 10%, 30%, and 50%, respectively, with respect to the plate thickness of the hole peripheral edge portion 23 of the installation lower hole 22. . Thus, the clearance and the indentation depth h are set as test conditions for the preliminary compression process. Further, in the round hole drilling step, the punch 50 having the same outer diameter D1 as that of the preliminary processing punch 44 is used, and the die 51 having an opening diameter D3 of 36.84 mmφ is used. Then, in the hole expanding process, the test is performed by changing the hole expanding rate by using the hole expanding punch 54 having a different outer peripheral diameter D4.

  The results of this test are shown in FIG. The value shown in FIG. 12 is the maximum value of the hole expansion rate that is effective for forming the hub hole flange portion 6 without causing defects such as cracks in the hub hole flange portion 6 by the hole expansion process. In the configuration of the first embodiment, it is possible to mold with a high hole expansion rate regardless of the set values of the clearance and the indentation depth h. In particular, when the indentation depth h at a clearance of 11% is 30%, the highest hole expansion rate is achieved. When the clearance is -20%, an extremely high hole expansion rate is achieved at both the indentation depths of 30% and 50%. From this test result, according to the hub hole flange portion forming method of the first embodiment, even when the hole expansion ratio is increased, the hub hole flange portion 6 does not suffer from defects such as cracks. It is apparent that the hub hole flange portion 6 can be formed.

  In addition, the test of the hole expansion rate was similarly performed also when the peripheral edge part of the pressing surface of the pre-processed punch was made into a right-angle shape. The results are also shown in FIG. All of the test conditions were the same as described above except that the peripheral end of the pre-processed punch was formed into a right-angled shape. From this result, the maximum value of the effective hole expansion rate tends to be reduced in the configuration in which the peripheral end portion of the preliminary processing punch has a right-angle shape as compared with the configuration in which the preliminary processing punch 44 has the rounded corner portion 44a. Although it exists (except when the clearance is -11% and the indentation depth h is 50%), a high hole expansion rate is achieved as a whole. Therefore, even if the peripheral end portion of the preliminary-working punch has a right-angle shape, similarly, when the hub hole flange portion 6 is formed with a high hole expansion rate, it can be formed without causing defects such as cracks.

  In the second embodiment, as shown in FIG. 8, in the preliminary compression step, an annular preliminary processing punch 64 is used, and the surplus material is installed in the upset air space 66 formed inside the preliminary processing punch 64. Yes. More specifically, the preliminary processing punch 64 is formed in an annular shape by opening a lower end portion of a cylindrical mold downward with a predetermined opening diameter. That is, a preliminary processing punch 64 for pressing is formed by the lower end portion of the mold. Thus, in the structure which has formed the preliminary processing punch 64 in the column-shaped metal mold | die lower end part, As the depth which the inner side of the preliminary processing punch 64 opens, the ceiling surface is plate-shaped in a preliminary compression process. The depth is set so as not to contact the base material 21. That is, it sets so that it may become deeper than the indentation depth h of a precompression process.

  In the second embodiment, the peripheral end portion 64a of the pressing surface of the preliminary machining punch 64 has a right-angle shape as shown in FIG.

  Similar to the first embodiment described above, the preliminary compression step is performed after the circular preparation hole 22 is formed in the center of the plate-like substrate 21 in the installation pilot hole drilling step. As shown in FIG. 8 (A), this pre-compression process supports the annular pre-processed punch 64 and the central portion of the plate-like base material 21 from the back surface so as not to cause deformation to the back side. This is performed by pressing with the mold 63.

The annular preliminary working punch 64 has an outer peripheral diameter D1 equal to the outer peripheral diameter of the hub element circular hole 28. Further, the inner peripheral diameter of the preliminary processing punch 64 is the opening diameter D2a according to the present invention since the preliminary processing punch 64 is open to the plate-like substrate 21 side. In the second embodiment, the relationship among the opening diameter D2a, the outer peripheral diameter D1, and the plate thickness t of the plate-like base material 21 is set to satisfy the following expression (3).
D1-0.4t × 2≈D2a (3)
In addition, the relationship between the opening diameter D2a, the outer peripheral diameter D1, and the plate thickness t of the plate-like base material 21 can be set so as to satisfy the following expression (4).
D1-0.5t × 2 ≦ D2a ≦ D1-0.1t × 2 (4)

  Further, the upside air space 66 according to the present invention is constituted by the inside air space of the preliminary machining punch 64.

  In the pre-compression process, as shown in FIG. 8A, the hole peripheral portion 23 of the setting-up pilot hole 22 is supported by a supporting mold 63. Then, as shown in FIG. 8B, the wheel is pressed from the front side of the wheel by the annular preliminary working punch 64. Even in this pre-compression process, similarly to the first embodiment described above, a guide pin or the like is not inserted into the prepared hole 22 and the hole end surface 22a of the prepared hole 22 is not restricted. At the time of pressing by the preliminary processing punch 64, the annular region pressed by the preliminary processing punch 64 is compressed and deformed in the plate thickness direction. Then, along with the compression deformation in the plate thickness direction, stretching deformation occurs in the plate surface direction, and surplus material generated by the stretching deformation flows into the pilot hole 22 and the upset air space 66. Therefore, it can suppress that work hardening arises in the cutting part (surrounding part of the 1st cutting peripheral surface 67) of plate-like base material 21 cut by preliminary processing punch 64. FIG. Here, in the second embodiment, since the upsetting air space 66 is provided inside the annular preliminary working punch 64, the stretching deformation described above is started immediately after the start of the pressing process by the preliminary working punch 64. The surplus material due to is easy to flow into the upset airspace 66, and in particular, the work hardening that occurs at the cutting site of the plate-like substrate 21 (the peripheral site of the first cutting peripheral surface 67) cut by the preliminary processing punch 64. Excellent suppression effect.

  Also in the second embodiment, the indentation depth h of the preliminary machining punch 64 is set to about 50% with respect to the plate thickness of the hole peripheral edge portion 23 of the installation lower hole 22. The indentation depth h of the press working by the annular pre-working punch 64 is preferably 10% or more and 50% or less with respect to the plate thickness of the hole peripheral portion 23 of the prepared hole 22.

  The part surrounded by the annular region pressed by the pre-processed punch 64 in this pre-compression process is a half-punched part 68 to be removed in the next round hole punching process. The surplus material generated in the pre-compression process is installed.

  After performing the preliminary compression step in this way, a round hole drilling step is performed as shown in FIG. As shown in FIG. 9 (A), the back surface of the plate-like substrate 21 is supported by a die 51, and the half punching portion 68 is punched out by a punching punch 60 as shown in FIG. 9 (B). To drill. Here, the punch 60 has the same size and shape as the pre-processed punch 64 used in the pre-compression process. The die 51 is the same as that used in the first embodiment. The clearance between the punching punch 60 and the die 51 is set in the same manner as in the first embodiment described above (see formula (2)). Here, as the punching punch 60, a cylindrical punching punch can be used as in the first embodiment. After the hub round hole 28 is drilled in the round hole drilling process, the hole expanding process is performed in the same manner as in the first embodiment to form the hub hole flange portion 6 (see FIG. 6).

  In the second embodiment, the steps other than the above-described round hole processing step are performed in the same manner as in the first embodiment, and the description thereof is omitted.

  Even in the hub hole flange portion 6 formed in this way, it is possible to suppress the occurrence of defects such as cracks as in the first embodiment. That is, even in the second embodiment, work hardening occurring at the peripheral edge portion 29 of the hub element circular hole 28 is suppressed, so that even if the hub element circular hole 28 is expanded in the hole expansion process, the fracture strain is reduced. Does not reach the point and does not crack. Thus, even in the molding method of the second embodiment, the same operational effects as those of the first embodiment described above can be exhibited.

  FIG. 10 shows a result of observing a cross section of the cutting portion (the peripheral portion of the first cutting peripheral surface 67) of the plate-like base material 21 cut by the preliminary processing punch 64 after the preliminary compression step. At the cutting portion of the plate-like base material 21 cut by the preliminary processing punch 64, a striped structure 30 substantially along the plate surface direction is seen at the upper part, and a striped structure 61 that curves slightly downward at the lower end part. It was confirmed. Thereby, it turns out that work hardening can be suppressed by performing the preliminary compression process of the present Example 2. Therefore, the hub round hole 28 formed by the round hole drilling step can suppress the work hardening at the hole peripheral edge portion 29. Therefore, even if the hole peripheral portion 29 of the hub element circular hole 28 is erected in the hole expanding process, it is possible to prevent cracks and the like from occurring.

  Even in Example 2 as described above, as in Example 1 described above, a test was performed to confirm the hole expansion rate without causing defects such as cracks at the tip of the hub hole flange portion 6. Here, the opening diameter D2a of the preliminary machining punch 64 is set so as to satisfy the above-described formula (3). Specifically, the outer peripheral diameter D1 of the preliminary machining punch 64 is set to 36 mmφ, and the opening diameter D2a is set to 33.2 mmφ. Others were carried out in the same manner as the test in Example 1 described above. The test results are shown in FIG. Even if the indentation depth h is 10%, 30%, or 50%, it is possible to mold with a high hole expansion rate. In particular, as the indentation depth h increases, the hole expansion rate tends to increase, and the highest hole expansion rate is achieved at 50%. From this test result, according to the hub hole flange portion forming method of the second embodiment, the hub hole flange portion 6 can be formed in the hub hole flange portion 6 even when the hole expansion rate is increased as in the first embodiment. It is apparent that the hub hole flange portion 6 can be formed without causing problems such as cracks.

  In the third embodiment, as shown in FIG. 11, the pre-compression process is performed using an annular pre-processed punch 74 and a support die 73. Here, upset air spaces 76 and 77 are provided in both the preliminary processing punch 74 and the supporting die 73.

  As in the second embodiment, the annular pre-processed punch 74 has an outer peripheral diameter D1 equal to the outer peripheral diameter of the hub element circular hole 28, and the inner peripheral diameter is the opening diameter D2a according to the present invention. is there. And the upside air space 76 concerning this invention is comprised by the inner side air space of the preliminary | backup process punch 74. FIG.

  The supporting die 73 is formed with an inner circular hole 78 opened at the center thereof, and the opening diameter D2 is smaller than the outer peripheral diameter D1 of the preliminary machining punch 74. That is, the clearance between the preliminary machining punch 74 and the support die 73 is negative. In the support die 73, the air space constituted by the inner circular hole 78 is the upsetting air space 77 according to the present invention.

  Furthermore, the opening diameter D2a of the preliminary machining punch 74 is set so as to satisfy Expression (4) of Example 2 described above. Similarly, the opening diameter D2 of the support die 73 is set so as to satisfy the above-described formula (1) of the first embodiment. The opening diameter D2a of the preliminary machining punch 74 and the opening diameter D2 of the supporting die 73 may be the same or different. That is, both of the opening diameter D2a of the preliminary machining punch 74 and the opening diameter D2 of the supporting die 73 are the opening diameter according to the present invention. Here, in the third embodiment, the outer diameter D1 and the opening diameter D2 are set so that the clearance between the outer diameter D1 of the preliminary machining punch 74 and the opening diameter D2 of the supporting die 73 is -20%. And are set. Further, the opening diameter D2a of the preliminary machining punch 74 is set by the above-described formula (3) of the second embodiment. Therefore, the opening diameter D2a of the preliminary machining punch 74 is smaller than the opening diameter D2 of the supporting die 73.

  In the pre-compression process, as shown in FIG. 11A, the center of the plate-like substrate 21 is supported from the back surface thereof by a support die 73. Then, as shown in FIG. 11B, the peripheral edge portion 23 of the downhole 22 for upsetting is pressed from the wheel surface by the preliminary processing punch 74. During the pressing process, the annular region sandwiched between the preliminary processing punch 74 and the supporting die 73 is compressed and deformed, and is deformed by stretching in the plate surface direction along with the deformation. The surplus material due to the stretching deformation flows mainly into the pilot hole 22 and the upset air space 76 of the preliminary processing punch 74. Furthermore, surplus material also flows into the upset air space 77 of the support die 73. Thus, since the surplus material generated by the press working of the pre-processed punch 74 flows into the pilot hole 22 and the upsetting air spaces 76 and 77, the cutting portion (first portion) of the plate-like base material 21 to be cut into the pre-processed punch 74. It is possible to suppress work hardening occurring in the peripheral portion of the cutting peripheral surface 79.

  In the above-described preliminary compression step, the support die 73 is a support die according to the present invention. Moreover, the back surface of the plate-like base material 21 supported by the supporting die 73 is one side according to the present invention.

  In the third embodiment, the pressing depth h of the preliminary machining punch 74 is about 50% with respect to the plate thickness of the hole peripheral edge portion 23 of the installation lower hole 22 as in the second embodiment. It is said. The indentation depth h is preferably 10% or more and 50% or less with respect to the plate thickness of the hole peripheral portion 23 of the pilot hole 22.

  After performing the pre-compression process in this way, a round hole drilling process is performed in the same manner as in Example 2 described above (see FIG. 9). In this round hole drilling step, it is possible to use the annular pre-processed punch 74 used in the pre-compression step, and also use the cylindrical hole punch 50 as in the first embodiment. May be implemented. After the hub round hole 28 is drilled in the round hole drilling process, the hole expanding process is performed in the same manner as in the first embodiment to form the hub hole flange portion 6 (see FIG. 6).

  In the third embodiment, the processes other than the above-described round hole processing step are performed in the same manner as in the first embodiment, and the description thereof is omitted.

  Even in the hub hole flange portion 6 formed in this way, it is possible to suppress the occurrence of defects such as cracks as in the first embodiment. That is, even in the third embodiment, work hardening occurring at the hole peripheral portion 29 of the hub element circular hole 28 is suppressed. Therefore, even if the diameter of the hub element circular hole 28 is expanded in the hole expansion process, the fracture strain is reduced. Does not reach the point and does not crack. Thus, even in the molding method of the third embodiment, the same effects as those of the first embodiment described above can be exhibited.

  In the first embodiment described above, the peripheral end portion of the pre-working punch 44 is configured to have a blade corner rounded portion 44a. As another configuration, the peripheral end portion of the pre-working punch is formed into a right-angle shape or chamfered. It is also possible to have a shape. Any shape produces substantially the same effect as the first embodiment. Similarly, even in the pre-processed punches 64 and 74 of the second and third embodiments, the peripheral end portion thereof can be any of a rounded shape and a chamfered shape in addition to a right-angled shape. It is.

  In Embodiments 1 to 3 described above, a circular uphole 22 is provided in the center of the plate-like substrate 21. As another method, a polygonal pilot hole such as a quadrangle or a pentagon may be provided in the center of the plate-like substrate 21.

  The present invention is not limited to the above-described embodiments, and can of course be appropriately changed within the scope of the present invention. For example, the vehicle wheel 1 according to the first to third embodiments described above is a so-called bead fitting wheel formed by fitting the disc flange portion 9 of the wheel disc 2 to the inner peripheral surface of the drop portion 13. The present invention can also be applied to so-called bead fitting wheels and full face wheels. And even if it is a case where this invention is applied to such a bead fitting wheel or a full face wheel, the effect similar to the case of a bead fitting wheel can be exhibited.

1 is a cross-sectional view of a vehicle wheel 1. 1 is a perspective view of a wheel disc 2 constituting a vehicle wheel 1. FIG. 6 is a processing explanatory diagram of a setting-up pilot hole drilling step according to the first embodiment. FIG. 4 is a process explanatory diagram of a pre-compression process of Example 1. FIG. 5 is a process explanatory diagram of a circular hole drilling step of Example 1. FIG. 3 is a process explanatory diagram of a hole expanding process of Example 1. In Example 1, (A) the cross-sectional structure state of the hole peripheral portion 23 of the installation pilot hole 22 after the pre-compression step, and (B) the peripheral edge of the hub circular hole 28 after the raw circular hole drilling step. It is the schematic which shows the cross-sectional structure | tissue state of the part 29. FIG. FIG. 10 is a process explanatory diagram of a pre-compression process of Example 2. FIG. 10 is a processing explanatory diagram of a bare hole drilling step of Example 2. It is the schematic which shows the cross-sectional structure | tissue state of the hole peripheral part 23 of the preparation lower hole 22 after the precompression process of Example 2. FIG. FIG. 6 is a process explanatory diagram of a pre-compression process of Example 3. It is a graph which shows the test result which confirmed the hole expansion rate which does not produce a crack etc. in the hub hole flange part 6 when the shaping | molding method of Example 1, 2 is applied. It is explanatory drawing which shows the conventional process process which drills the hub raw circular hole 88. FIG. It is the schematic which shows the cross-sectional structure | tissue state of the hole peripheral part 89 of the hub raw circular hole 88 formed in the conventional process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle wheel 6 Hub hole flange part 21 Plate-shaped base material 22 Pilot hole 22a Hole end surface 23 (Pole hole 22) Hole peripheral part 28 Hub element | circle hole 29 (Hub element | circle hole 28) Hole peripheral portions 30, 31, 61 Striped structures 43, 73 Support dies (support dies)
44, 64, 74 Pre-processed punches 45, 78 Inner circular holes 46, 66, 76, 77 Upsetting air space 50, 60 Perforation punch 54 Hole expansion punch 63 Support mold D1 (for pre-processed punches 44, 67, 74 ) Peripheral diameter D2, D2a Opening diameter t Thickness of plate-like substrate 21

Claims (4)

A round hole machining step for drilling a hub round hole in the center of the plate-like base material, and a hole expanding punch is pressed from the back of the wheel to the peripheral edge of the hub round hole so that the peripheral edge of the hole is faced to the wheel. In the hub hole flange portion molding method for a vehicle wheel for forming the hub hole flange portion by sequentially performing the hole expansion processing step of expanding the hole so as to stand upright,
The round hole drilling process is
An installation pilot hole drilling process for drilling an installation pilot hole in a plate-like substrate;
The hole end surface of the pilot hole is not constrained by a pre-processed punch having an outer peripheral diameter equal to the hole diameter of the hub element circular hole and a support mold for supporting one side surface of the plate-like substrate facing the pre-processed punch. In addition, by pressing the peripheral edge of the pilot hole along the plate thickness direction to a predetermined indentation depth less than the plate thickness, the surplus material pressed by the preliminary processing punch is removed from the pilot hole and the preliminary processing. Provided in at least one of a punch and a support die, a pre-compression step of installing in a set-up air space having a diameter smaller than the diameter of the hub circular hole and opening facing the plate-like substrate;
A hub hole flange portion forming method for a vehicle wheel, comprising: a step of drilling a hub element circular hole by a hole punch having an outer diameter equal to the hole diameter of the hub hole element circular hole. . The support die used in the preliminary compression step of the raw circular hole processing step is formed with an inner circular hole having a smaller diameter than the outer peripheral diameter of the preliminary processing punch, and the inner circular hole constitutes an upset air space. Which is
In the preliminary compression step, the plate-like base material is supported from the rear side of the wheel by the supporting mold, and the pilot hole is pressed against the peripheral edge portion of the pilot hole for installation from the front side of the wheel by the preliminary processing punch. 2. The method for forming a hub hole flange portion of a vehicle wheel according to claim 1, wherein surplus material is installed in the installation air space of the support mold. The opening diameter of the inner circular hole formed in the support mold is
D1-0.2t × 2 ≦ D2 <D1-0.1t × 2
(Where D1: outer diameter of the pre-processed punch, t: plate thickness of the plate-like substrate, D2: opening diameter)
The hub hole flange portion forming method for a vehicle wheel according to claim 2, wherein the hub hole flange portion forming method is provided. The pre-working punch used in the pre-compression process of the raw hole processing step is configured to form an upset air space by an air space opened inside thereof,
The pre-compression process is performed by supporting the plate-like base material from the rear side of the wheel with a support mold, and pressing the pre-processed punch from the front side of the wheel to the peripheral edge portion of the prepared preparation hole. The method for forming a hub hole flange portion of a vehicle wheel according to claim 1, wherein surplus material is installed in the installation air space of the preliminary processing punch.

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