JP4435376B2 - Method of forming bolt holes in steel wheels - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming bolt holes in a steel wheel.
[0002]
[Prior art]
Conventionally, in steel wheels for trucks, the steel wheels mounted on the front side of the truck are bolted from the front side, but on the rear side of the truck, the two steel wheels are overlapped on the front side and the back side It is attached by bolting. Therefore, in the rear side steel wheel, tapered portions are formed on both sides (front and back sides) of the bolt hole.
[0003]
As a method of forming such bolt holes having tapered surfaces on both sides, if the method of forming from one side with a taper punch at a time is adopted, the track disk plate is usually quite thick (usually 8 mm). Sometimes flesh escapes to the periphery, adversely affecting the flatness and step of the back of the disc.
[0004]
Therefore, conventionally, first of all, the first hole is punched by pressing, and then one side is tapered by pressing, and then the other side is tapered by drilling. A method of forming the attached bolt hole is employed.
[0005]
[Problems to be solved by the invention]
As in the prior art, in the forming method by press working and drilling, there are two processes with different lines, and there is a problem that the machine equipment is bulky and the work efficiency is deteriorated and the product cost is increased.
[0006]
Therefore, the present invention aims to significantly reduce the cost as compared with the conventional processing method by making it possible to form all bolt holes having tapered surfaces on both sides as described above on one line of press processing. It is the purpose.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the first invention described in claim 1 is a first step of punching a pilot hole in the material by a punch provided on the front side of the material and a die arranged on the back side. ,
An upper coining punch having a tapered portion whose diameter is reduced at the front portion is arranged on the front side of the formed pilot hole, and a lower coining punch having a taper portion whose diameter is reduced at the front portion is arranged on the back side of the lower hole. The second step of forming a tapered surface on the front and back of the pilot hole with both coining punches,
The diameter of the pilot hole to be pulled out in the first step is set to be large as the hole diameter is small and fluctuated in the second step,
The punching punch is arranged on the upper coining punch side, and the diameter of the tapered portion of the upper die coining punch is set larger than the diameter of the tapered portion of the lower coining punch .
[0008]
In the present invention, the pilot hole is punched with a punch and a die, and the front and back (both sides) of the pilot hole is tapered with the upper and lower coining punches. . Therefore, all processing can be performed in a series of processing steps.
[0010]
Also, when the pilot hole is punched, if there is a difference in the inner diameter of the pilot hole, the inner diameter of the front side is smaller than the inner diameter of the back side, the diameter of the taper portion of the upper die coining punch is changed to the lower die coining punch. By setting the diameter larger than the diameter of the tapered portion, stable processing of the tapered surface can be performed.
[0011]
The second invention of claim 2, wherein, in the first aspect of the present invention, the tapered portion of the tapered portion and the lower die coining punch of the upper die coining punch is one that is formed by the taper of each second stage.
[0012]
In the present invention, at the time of taper machining, the rear taper portions of the two taper portions of both coining punches prevent the surplus thickness at the time of taper machining from moving to the front taper portion, and the taper diameter is reduced. Stability is achieved.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described based on the examples shown in the drawings.
[0014]
FIG. 1 shows a cross section of a disk portion of a steel wheel for trucks formed according to the present invention, and FIG. 2 shows an enlarged cross section of a bolt hole portion in the steel wheel.
[0015]
In this figure, reference numeral 1 denotes a disk portion of a steel wheel. A hub hole 2 is formed in the central portion, a flat portion 3 having front and back surfaces 3a and 3b is formed in the peripheral portion, and a bolt hole 4 is formed in the flat portion 3. Is formed. A stepped portion 5 is formed between the bolt hole 4 and the hub hole 2, and a decorative hole 6 is formed on the outer peripheral portion of the flat surface portion 3 for both heat release and decoration. A front side taper surface 4a is formed on the front side of the bolt hole 4, a back side taper surface 4b is formed on the back side, and a substantially vertical straight portion 4c is formed between the taper surfaces 4a and 4b.
[0016]
Next, a method for forming the bolt hole 4 having tapered surfaces on both sides will be described.
[0017]
First, as shown in FIG. 3, a pilot hole 9 is punched in the material 1a by press working at a position where a bolt hole is formed in the steel wheel material (molded plate) 1a, as shown in FIG. To do. In FIG. 3, 1b shows the piece extracted from the raw material 1a.
[0018]
The clearance C between the punching punch 7 and the punching die 8 is set to 15 to 20% with respect to the plate thickness (original thickness) of the material 1a. The clearance C is about 10% in normal punching, but increasing as 15 to 20% as described above reduces the shearing surface portion 9a and enlarges the fracture surface portion 9b, and bites the punching punch 7. This is to reduce the amount and increase the force for tearing the material to generate a large sag (deformation) 9c on the front side. The reason why the sagging 9c is increased in this way is to eliminate as much as possible the difference in machining resistance that occurs when tapering from both sides during taper machining, which will be described later.
[0019]
Further, the diameter of the prepared hole 9 is set to a nominal value of the bolt hole diameter +0.5 mm. That is, the relationship of the extracted dimension L ₁ shown in FIG. 4A to the dimension L ₂ of the finished bolt hole shown in FIG. 4B is set to L ₂ +0.5 mm = L ₁ . The reason why the drawing dimension L ₁ of the pilot hole 9 is set larger than the dimension L _{2 of the} finished product in this way is that the diameter of the bolt hole fluctuates during taper processing, which will be described later. It is to keep it. Since the amount of variation varies depending on conditions such as the taper angle, the material plate thickness, and the material expansion force, in practice, it is set to a predetermined value that meets these conditions. The above value of 0.5 mm shows an example in the case of a material of SAPH440 having a plate thickness of 8 mm.
[0020]
Next, taper surfaces are formed by press working on the front side and the back side of the lower hole 9 using an upper coining punch 10 and a lower coining punch 11 as shown in FIG.
[0021]
The upper coining punch 10 is formed with a straight portion 10a having a vertical surface with a predetermined diameter on the lower side, a first taper portion 10b whose upper side is expanded on the upper portion, and an upper portion (rear side) on the upper portion. It has a two-step taper shape in which a second taper portion 10c that expands upward is formed. The outer diameter of the straight portion 10a is set to be equal to the inner diameter of the straight portion 4c in the bolt hole diameter of the finished product. Further, the length of the straight portion 10a in the vertical direction is set as desired, but is preferably set to 0.5 mm at the minimum. This is because if the set value is small, the surplus that has entered during taper molding may enter the gap between the upper and lower coining punches 10 and 11, so the length of the straight portion 10a is increased to prevent this. In this way, the surplus meat hits the straight portion 10a so as not to enter the gap.
[0022]
Further, the taper angle in the first taper portion 10b, that is, the taper angle α with respect to the front and back surfaces of the material 1a is set as desired. Usually, in the steel wheel for trucks, the taper angle of the bolt hole is approximately 80 degrees. Therefore, in this embodiment, it is set to approximately 80 degrees.
[0023]
Further, the taper angle β in the second taper portion 10c is set to about 3 degrees.
[0024]
Further, the lower die coining punch 11 is formed in a two-step taper shape in which a first taper portion 11b whose upper side expands on the upper side is formed and a second taper portion 11c whose lower side expands on the lower side (rear side) is formed. It has become. The lower die coining punch 11 is not formed with the straight portion as described above.
[0025]
Further, the taper angle α of the first taper portion 11b is set to about 80 ° as described above, and the taper angle β of the second taper portion 11c is set to about 3 degrees as described above.
[0026]
Then, when the upper hole coining punch 10 and the lower die coining punch 11 are used for coining by press working as shown in FIG. As shown in FIG. 4, the shear surface portion 9a at the time of punching of the pilot hole hits the straight portion 10a of the upper die coining punch 10 to form the straight portion 4c of the bolt hole 4, and at the time of punching of the pilot hole, The sag 9c hits the second taper portion 10b, and one side (front side) taper surface 4a is formed. Further, the die receiving surface at the time of drilling the prepared hole hits the first tapered portion 11b of the lower die coining punch 11, and the other one surface (back side) of the tapered surface 4b is formed. Further, the fracture surface 9b at the time of punching of the pilot hole is deformed by pressurization by the upper and lower coining punches 10 and 11, and a deformed portion 4d is formed between the straight portion 4c and the tapered surface 4b.
[0027]
The angle of the second taper surfaces 10c and 11c is as small as about 3 degrees as described above. Therefore, the shape is the shape shown in FIG. At the time of forming the tapered portion by the lower die coining punch 11, the second tapered surfaces 10c and 11c are used to form the second outer periphery of the front tapered surface 4a and the rear outer periphery of the rear tapered surface 4b as shown in FIG. Tapered surfaces 4e and 4f are formed. As described above, the reason for forming the second tapered surfaces 10c and 11c is to prevent the surplus thickness generated during the taper molding from moving to the tapered surfaces 4a and 4b, thereby preventing the taper surfaces from being adversely affected by the movement of the surplus thickness. This stabilizes the taper diameter and prevents variations in plate thickness.
[0028]
Further, as shown in FIG. 5, the maximum diameter L ₃ of the first taper portion 10 c in the upper die coining punch 10 is set larger than the maximum diameter L ₄ of the first taper portion 11 b in the lower die coining punch 11. There is a difference, specifically, the upper coining punch 10 side is set larger by about 0.3 mm. Note that the value of this difference is arbitrary. The reason for making the difference in this way is to form a thick plate, so that the diameter L ₃ and the diameter L ₄ may be the same as long as the press machine has sufficient capability. However, first of all, there is a difference in the diameter of the hole on the front side and the back side in the pilot hole drilling process. For example, when the plate thickness is 8 mm, the diameter on the front side is about 3 mm smaller than the diameter on the back side. For this reason, a difference occurs in the required molding processing force. This results in a difference in the hole diameter expansion rate during taper processing. Secondly, although it affects the ability of the machine, 100% molding may not be possible by press molding. As a result, when the gap is generated, the machining is pushed in to the direction where the machining force is weak, and in this case, the machining is performed with priority on the back surface, that is, on the tapered surface side of the lower die coining punch 11. For this reason, stable machining can be performed with the above-described dimensional difference.
[0029]
As described above, since the formation of the pilot hole 9 and the formation of both tapered surfaces 4a and 4b (including strictly 4e and 4f) are press work, a series of work can be performed on one press work line. .
[0030]
【The invention's effect】
As described above, according to the invention described in claim 1, since both the pilot hole molding and the taper molding of the front and back of the pilot hole can be performed by pressing, a series of pressing processes can be performed. Compared to the conventional method in which the taper molding is performed in two different steps of press working and machining, the machine equipment is inexpensive and the work efficiency is improved, and the cost of the product can be reduced.
[0031]
In addition, stable processing of the tapered surface can be performed.
[0032]
According to the invention described in claim 2 , the taper diameter can be further stabilized.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a disk portion of a steel wheel formed with bolt holes according to the present invention.
FIG. 2 is an enlarged cross-sectional view of a bolt hole portion in FIG.
FIG. 3 is a cross-sectional view illustrating a prepared state of a prepared hole in the present invention.
FIG. 4 is a cross-sectional view showing the relationship between the pilot hole diameter and the formed bolt hole diameter in the present invention.
FIG. 5 is a view showing upper and lower coining punches according to the present invention.
FIG. 6 is a cross-sectional view showing an apparent shape of a bolt hole formed by the method of the present invention.
7 is a cross-sectional view showing a state in which a tapered portion is formed with a coining punch and showing an actual forming shape of the bolt hole in FIG.
[Explanation of symbols]
1a Material 7 Die punch 8 Die 9 Pilot hole 10 Upper die coining punch 10b, 10c Taper part 11 Lower die coining punch 11b, 11c Taper part L ₃ Taper diameter L of upper coining punch L ₄ Taper diameter of lower coining punch

Claims (2)

A first step of punching a hole in the material with a punch placed on the front side of the material and a die placed on the back side ;
An upper coining punch having a tapered portion whose diameter is reduced at the front portion is arranged on the front side of the formed pilot hole, and a lower coining punch having a taper portion whose diameter is reduced at the front portion is arranged on the back side of the lower hole. The second step of forming a tapered surface on the front and back of the pilot hole with both coining punches,
The diameter of the pilot hole to be pulled out in the first step is set to be large as the hole diameter is small and fluctuated in the second step,
The bolt in the steel wheel , wherein the punching punch is disposed on the upper coining punch side, and the diameter of the taper portion of the upper die coining punch is set larger than the diameter of the taper portion of the lower coining punch. Hole forming method. The tapered portion of the upper die coining taper portion and the lower die coining punch punches, forming method of the bolt holes in the steel wheel of claim 1, wherein are formed of taper of each second stage.

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