JPH07100206B2 - Press molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention has a press molding method, and in particular, has a central flange and an outer peripheral flange, and is attached to a rotary shaft with the inner peripheral surface of the central flange as a reference surface. The present invention relates to a method capable of forming both flanges with high processing accuracy in a press-formed product.

(Prior Art) As a press-formed product of this type having a central flange and an outer peripheral flange, there is, for example, a wheel disc of a steel wheel for automobiles.
It is used by fixing the rim to the outer surface of the outer peripheral flange.

Here, as a conventional molding method of such a wheel disc, there is, for example, the method shown in the process chart of FIG.

In this forming method, first, an octagonal blank 1 as shown in FIG. 3 (a) is punched out from a coil material in a blanking step, and then this blank 1 is subjected to a first drawing step in a first drawing step. As shown in FIG. 3 (c), a dish-shaped overall preform 2 as shown in FIG. 3 (b) is formed, and in the second draw forming step, the overall preform 2 has a sectional shape as shown in FIG. 3 (c). In addition to the annular hat portion 3 having a chevron shape, the preforming portion 4 for the nut seat, the preforming portion 5 for the hub hole and the preforming portion 6 for the rib are respectively formed, and in the third drawing step, As shown in Fig. 3 (d), the joggle portion 7 is formed on the hat portion 3, the nut seats and ribs of the preforming portions 4 and 6 are formed into regular shapes, and the drum contact surface 8 is formed into a flat shape. And forming respectively.

After finishing various drawing processes in this way,
As shown in FIG. (E), the work w that is a draw-formed product is
An outer peripheral flange 9 as a fitting portion of the rim is formed with a required outer diameter dimension D, and at the same time, a burring pilot hole 10 in the central portion and a bolt hole 11 in the nut seat are pierced respectively, and in the subsequent step, As shown in FIG. 3 (f), the decorative hole 12 is pierced in the joggle portion 7. After that,
As shown in FIG. 3 (g), a burring process is performed around the burring pilot hole 10 so that a center flange having a predetermined inner diameter is formed.
13 and finally the nut seat and center flange 13
Then, the tapered surfaces 14 and 15 as shown in FIG. 3 (h) are coined.

The formation of the central flange 13 shown in FIG. 3 (g) will be described in more detail below.

4 (a) to 4 (f) are cross-sectional views showing the progress state of the burring process for forming the central flange 13 with respect to the half part of the work w, and here, first, FIG. 4 (a). As shown in, in the raised state of the upper holder 21,
The work w is interposed between the die 22 and the pad 23, and the lower surface of the outer peripheral flange 9 of the work w is supported by the lifter 24, while the upper surface of the work w is protruded downward from the die 22. Press down with pin 25. Therefore, in this state, not only the die 22 and the pad 23,
The work knockout 26 and the die ring 27 located inside and outside the die 22 in the radial direction also do not contact the work w.

And after that, by lowering the upper holder 21,
The die 22, the work knockout 26, and the die ring 27 are simultaneously lowered, and the lifter 24 is lowered by the pusher pin 28 that is integrally lowered with the upper holder 21, which causes the lower surface of the work w and the pad 23 to move. As shown in FIG. 4 (b), the work piece w is brought into contact with the work piece w, and the lowering of the upper holder 21 causes the spring force of the elastic body 29 supporting the pad 23 to cause the oil breaker pin 25 to retract. The upper surface of the die and the die 22 are brought into contact with each other as shown in FIG. 4 (c) to bring the lifter 24 apart from the lower surface of the outer peripheral flange of the work w. At this time, the work knockout 26 is also the oil breaker pin.
It approaches the work w by an amount corresponding to the retreat amount of 25, and as a result, the work knockout 26 comes into contact with the edge of the burring prepared hole 10 of the work w, but also approaches the work w in the same manner. The die ring 27 does not yet contact the outer peripheral flange 9 of the work w in this state.

When the upper holder 21 is further lowered, the die 22
Since the pressing force of the pressure pin 30 for depressing the force exceeds the spring force of the elastic body 29, the work w is sandwiched between the die 22 and the pad 23 and descends, and at the edge of the burring pilot hole 10,
As shown in FIG. 4 (d), the burring punch 31 is contacted.

Since the burring force required for the initial molding of the center flange 13 is sufficiently smaller than the die pressing force of the pressure pin 30, the lower holder 21 is lowered after the workpiece w and the burring punch 31 are brought into contact with each other. For the work w descending with 22, the burring punch 31
Initial molding of the central flange 13 will be performed. By the way, since the burring force required for the flange forming following the initial forming is larger than the die pressing force of the pressure pin 30, the upper holder 21 continues to descend after that, but the die is pressed. 22 and pad 2
3, and by extension, the work w does not descend further, and as a result, the die ring 27 that descends integrally with the upper holder 21.
Then, the contact with the outer peripheral surface of the outer peripheral flange 9 is started.

Here, when the upper holder 21 is further lowered, the die ring 27 is lowered by the nesting force that overcomes the spring back of the outer peripheral flange 9 as shown in FIG. This descent of the is continued until the nesting force balances the required burring force. On the other hand,
The work w does not descend until the equilibrium state is brought about, and is maintained at the end state of the initial forming of the central flange 13.

Then, when the nesting force of the die ring 27 exceeds the required burring force, the work w held between the die 22 and the pad 23 is lowered based on the nesting force,
The formation of the central flange 13 by the burring punch 31 will proceed. Note that, here, the required burring force gradually increases according to the degree of formation of the flange 13, and the required nesting force also increases in proportion to the descending amount of the die ring 27. The nests of the flanges 9 gradually move under the mutual balance of forces, and the work w held between the die 22 and the pad 23 descends at a lower speed than the descending speed of the die ring 27. To do.

FIG. 4F is a cross-sectional view showing a state where the formation of the central flange 13 is completed. In this state, the pad 23 contacts the pad retainer 32 and the die 22 contacts the upper holder 21, respectively.

(Problems to be Solved by the Invention) By the way, in the related art, the outer peripheral flange 9
Since the formation is performed in one molding step, there is a problem in the molding accuracy that the outer peripheral flange outer surface has a large unevenness and the springback amount in the circumferential direction varies greatly. Yes, and the central flange
In addition to advancing the formation of 13 on the basis of the outer peripheral flange 9 with low machining accuracy, the center flange 13 is burred while the outer peripheral flange 9 is not sufficiently nested. With the inner surface of the flange 13 as a reference, the runout accuracy of the roundness of the outer peripheral flange 9 is low,
Since the amount of eccentricity of the outer peripheral flange 13 with respect to the central flange 13 and its variation are large, the correction work has been difficult.

This invention advantageously solves the above-mentioned problems of the prior art, and makes the amount of irregularities on the outer peripheral surface of the outer peripheral flange sufficiently small, and evenly makes the amount of springback of the outer peripheral flange uniform, and The present invention provides a press molding method for improving the runout accuracy with respect to the central flange.

(Means for Solving Problems) In the press forming method of the present invention, in particular, after forming a preliminary flange having a diameter of, for example, a few mm larger than the required size of the outer peripheral flange, the center is formed on the work that has been drawn. The formation of the flange and the diameter reduction molding of the preliminary flange to the required outer peripheral flange are sequentially performed.

(Operation) In this press forming method, the outer peripheral flange is formed by two steps of forming the auxiliary flange and reducing the diameter of the auxiliary flange to sufficiently reduce the unevenness of the outer peripheral flange outer peripheral surface. As well as
Since the springback amount of the outer peripheral flange can be made almost uniform over the entire circumference, the molding accuracy of the outer peripheral flange itself is significantly improved, and here, after the molding of the central flange, Since the preliminary flange is reduced in diameter by using the central flange as a reference, the amount of eccentricity of the outer peripheral flange with respect to the central flange and the amount of variation thereof are significantly reduced.

(Examples) The present invention will be described below based on Examples.

FIG. 1 is a molding process diagram showing an embodiment of the present invention.
1 (a)-(d) are respectively FIG. 3 (a)-(d).
A process corresponding to the process shown in FIG.

That is, in the step shown in FIG. 1A, blanking for punching an octagonal blank 41 from the coil material is performed, and in the step shown in FIG. And the first draw forming,
In the step shown in FIG. 1 (c), the entire preform 42 has a hat portion 43 having a chevron cross section, a nut seat preform portion 44, a hub hole preform portion 45, and a rib preform. Molding part 46
In the step shown in FIG. 1 (d), the juggle portion 47 is formed in the hat portion 3, and the preforming portions 44, 46 are formed in the nut seat and the rib. Molded into a regular shape and the drum contact surface
The third drawing is performed to form 48 into a flat shape.

Further, in this embodiment, a preliminary flange 49 having an outer diameter D + α that is larger by several mm than the required outer shape of the outer peripheral flange in the step shown in FIG. 1 (e) is provided on the work w that has undergone the respective draw forming steps as described above. The burring pilot hole 50 at the center and the bolt hole 51 at the nut seat are pierced while being formed, and in the step shown in FIG. Pierce the decorative hole 52. Next, in a step shown in FIG. 1 (g), a central flange 53 having a predetermined inner diameter is burred around the burring pilot hole 50, and subsequently, a preliminary flange 49 is used as a reference with respect to the central flange 53. The outer peripheral flange 54 having a required outer diameter D is reduced in diameter, and in the final step shown in FIG. 1 (h), the central flange 53 and the nut seat are coined with tapered surfaces 55 and 56, respectively.

Here, the formation mode of the central flange 13 and the outer peripheral flange 54 shown in FIG. 1 (g) will be described in detail with reference to FIG.

The upper and lower dies and the work w shown in the vertical cross section in FIG.
Although slightly different from that shown in the figure, the present invention continues to perform substantially the same actions as the respective actions of the upper and lower molds described with reference to FIGS. In order to avoid duplication, description of the action of the upper and lower molds corresponding to FIGS. 4 (a) to 4 (c) is omitted, and FIGS.
Those corresponding to will be described.

As shown in FIG. 2 (a), the die 22 and the pad 23
The work w clamped between and is the outer peripheral flange 54 of the required size.
Therefore, the holding flange 49 has an outer diameter larger by α, and this clamping force with respect to the work w causes the pressure pin 30 which is urged downward by the elastic means to the upper holder 21 on the upper surface of the die 22. The elastic body 29
Thus, the holding pin 58 biased upward with respect to the lower holder 57 is brought into contact with the lower surface of the pad 23.

Further, in this case, both the work knockout 26 pressed downwardly with respect to the upper holder 21 and the burring punch 31 provided upright on the lower holder are both attached to the edge portion of the burring prepared hole 10 of the work w from the vertical direction. Abutting,
The die ring 27 attached to the upper holder 21 via the adapter 59 and the retainer 60 is in contact with the edge portion of the preliminary flange 49.

Therefore, here, the pusher pin 28 fixed to the adapter 59 lowers the lifter 24 to some extent against the pressing force of the cushion 61, and the upper surface of the lifter 24 has a spare flange 49.
Is spaced below the lower end surface of the.

Note that reference numeral 62 in the figure denotes a stopper that functions to specify the upper limit position of the pad 23 that is biased upward by the elastic body 29.

In such a relative relationship of the upper and lower dies, the inner peripheral surface of the die 22 functions as a die hole in the burring process of the central flange 53, and the outer peripheral portion of the die 22 and the outer peripheral portion of the work knockout 26 are respectively. , Die ring 27 and die 22 work to remove the bite of work w.

Here, the action of the upper and lower dies when the upper holder 21 descends from the state shown in FIG. 4 (c) to the state shown in FIG. 2 (a) is as follows.

When the upper holder 21 is lowered, the pressing force of the die by the pusher pin 30 is larger than the burring force required for the initial forming of the central flange 53. Therefore, the work w is based on the pressing force of the pusher pin 30 and the die 22 and the pad. It is clamped by 23 and descends with respect to the burring punch 31, and as a result, the center flange 53 is initially formed around the burring prepared hole 50 of the work w as shown in FIG. 2 (a). Will be seen.

And the upper holder after the completion of such initial molding
In the further lowering of 21, the burring force required for further molding of the central flange 53 becomes larger than the pressing force of the pressure pin 30, so the lowering of the die 22 and the pad 23, and by extension, the work w, is stopped. A relative lowering of the die ring 27 with respect to them is brought about. As a result, the die ring 27 comes into contact with the upper edge portion of the preliminary flange 49 as shown in FIG. 2A while the lifter 24 is separated from the preliminary flange 49.

Here, the timing at which the die ring 27 comes into contact with the auxiliary flange 49 is earlier than that in the prior art by the amount that the outer diameter is larger than the required outer diameter of the outer peripheral flange 54.

Next, when the upper holder 21 is further lowered while the die ring 27 and the auxiliary flange 49 are in contact with each other, the die ring
The force required to reduce the diameter of the spare flange 49 with 27 is
Since the burring force of the central flange 53 is much larger than the required burring force, the work w, together with the die 22 and the pad 23, with respect to the burring punch 31 is subjected to the diameter reduction forming or after the slight reduction forming is started. As a result, a central flange 53 having a required size and shape is formed in the central portion of the work w as shown in FIG. 2 (b).

After finishing the formation of the central flange 53 in this way,
The pad 23 contacts the pad retainer 32, and the pad 23 and the work w cannot be further lowered. Therefore, when the upper holder is further lowered with respect to the work w, the die ring 27 is used. The preliminary flange 49 is reduced in diameter by the reference to the already formed central flange 53, and when the lower limit position of the die ring 27 is reached, the preliminary flange 49 is changed to the one shown in FIG. 2 (c). As shown, the outer peripheral flange 54 is concentric with the central flange 53.

Although the molding method of the present invention has been described above based on the illustrated example, according to the present invention, after forming the preliminary flange having a diameter somewhat larger than the required size of the outer peripheral flange, the formation of the central flange and the preliminary flange, The number of steps can be increased or decreased as required, as long as it is a method of sequentially performing the diameter-reducing molding to the required outer peripheral flange, and the forming mode of both flanges, in other words, the operating mode of the upper and lower dies can be appropriately changed. It can be changed to.

(Effect of the invention) Therefore, according to the present invention, the required outer peripheral flange is formed by press molding in two steps, whereby the accuracy of forming the outer peripheral flange is increased and the amount of irregularities on the outer peripheral surface is sufficiently reduced. be able to. In addition, here, after the center flange has been formed, the preliminary flange is reduced in diameter with reference to the center flange, so that the amount of eccentricity of the outer peripheral flange with respect to the center flange and the amount of variation thereof are significantly reduced. For this reason, when this molding method is applied to the manufacture of wheel discs for automobiles, it is possible to easily obtain high-precision products, and it is possible to significantly improve the ride comfort of the vehicle by eliminating the need for subsequent balance correction. Can be made.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a forming process of the present invention, FIG. 2 is an enlarged cross-sectional view illustrating a forming mode of a central flange and an outer peripheral flange, FIG. 3 is a forming process diagram showing a conventional example, and FIG. It is an expanded sectional view which illustrates formation correspondence of a center flange and a peripheral flange in an example. w …… Workpiece, 49 …… Spare flange 50 …… Burring pilot hole, 53 …… Center flange 54 …… Outer peripheral flange

Claims (1)

[Claims] 1. A central flange and an outer peripheral flange,
When manufacturing a press-formed product that is attached to the rotary shaft with the inner peripheral surface of the central flange as a reference surface, after forming a preliminary flange (49) having a diameter slightly larger than the required size of the outer peripheral flange (54), Flange (53)
And a reduction molding of the preliminary flange to a required outer peripheral flange are sequentially performed.