JPH0688089B2 - Forging die for step forming - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a step forming forging die used when forming a cylindrical step forged product by cold forging.

(Prior Art) When a large-diameter portion is bulged on the outer periphery of a tubular material by cold forging, holes 6 formed in the die 3 as shown in FIG.
The tubular material 10 is inserted into the tubular material 10 and the mandrel 8 is placed in the tubular material 10.
Conventionally, a method of inserting the punch 5 into the annular recess 7 formed on the opening side of the hole 6 in a state where the insert is inserted to form the large diameter portion 10a on the outer periphery of the tubular material 10 which is a molded product has been conventionally performed. Was there.

(Problems to be Solved by the Invention) When the above-mentioned conventional technique is adopted, a concave portion 11 called a "sinker" is formed on the inner peripheral surface side of the large diameter portion 10a of the tubular material 10 as a molded product. For example, as shown in FIG. 5, the large-diameter portion 10a of the tubular material 10 is in the middle of the upsetting by the punch 5.
Since the inner peripheral surface side of is controlled by the mandrel 8, the material flows outward as indicated by arrow A. As a result, the above-mentioned recessed portion 11 is formed in the portion where the material is most likely to flow outward in the annular recessed portion 7 (that is, substantially the middle portion in the height direction).

Since the formation of the concave portion 11 is a great obstacle to smoothing the inner peripheral surface of the tubular material 10, it is necessary to cut the entire inner peripheral surface of the tubular material 10 to eliminate the concave portion 11, It was a neck in forming and forging.

The present invention has been made in view of the above points, so that a portion of a tubular material in which a concave portion is formed is conversely a protruding protrusion, and a molded product can be obtained only by cutting the protruding portion. Therefore, the purpose is to facilitate the step forming forging process.

(Means for Solving Problems) According to the present invention, as a means for solving the above problems, a hole into which a cylindrical material can be inserted and a large size of the cylindrical material on the upper opening side of the hole are provided. In a step forming forging die including a die having an annular recess corresponding to the diameter portion, and a punch fitted into the annular recess from above, and bulging the large diameter portion around the outer periphery of the tubular material. , Upper and lower mandrels which are provided so as to oppose the die and the punch and which guide the tubular material from above and below and which are divided into upper and lower parts, and the inner peripheral surface side of the large diameter portion of the tubular material. A space is formed between the upper and lower mandrels at the lowering end of the punch or at the outer periphery of the end of the mandrel on at least one side.

(Operation) In the present invention, the following operations are obtained by the above means.

That is, on the outer periphery of the cylindrical material, the large diameter portion is bulged by the pressing force of the punch fitted in the annular recess of the die. In the process of bulging, the material is on the peripheral side of the annular recess (in other words, Then, at the same time as the flow toward the outer peripheral side), at the same time as the lowering operation end of the punch, it also flows between the upper and lower mandrels or the space part formed on the outer periphery of the end part of at least one of the mandrels. Means that a protruding portion is formed on the inner peripheral surface of the large diameter portion. A desired tubular stepped forged product can be obtained by cutting the protruding portion by cutting.

(Examples) Hereinafter, preferred examples of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a step forming forging die for cold forging according to an embodiment of the present invention.

This forging die has a hole 6 into which the tubular material 10 can be inserted and the hole 6
A die 3 having an annular recess 7 corresponding to the large-diameter portion 10a of the tubular material 10 on the upper opening side, and a punch 5 fitted into the annular recess 7 from above are provided. In this embodiment, as the tubular material 10, a material for forming an output gear is taken as an example.

The die 3 is a die clamp ring for the lower die holder 2 mounted and fixed on the hard plate 12 of the base 1.
It is connected through 13.

On the other hand, the punch 5 is the outer punch 5a in this embodiment.
The outer punch 5a is used for forming the large diameter portion 10a of the tubular material 10, and the inner punch 5b is used for forming the large diameter portion by the outer punch 5a ( During the so-called upsetting, the upper end of the tubular material 10 is abutted to serve to prevent the material from escaping upward. The punches 5a and 5b are supported by the upper holder 14 and the upper holder 14
Are coupled to the upper die holder 4 via punch clamp rings 15. The upper die holder 4 is constructed so as to be operated in the vertical direction by an appropriate driving means (not shown), and when the upper die holder 4 is lowered, the punch 5 is formed into an annular shape of the die 3. It can be fitted into the recess 7.

Further, upper and lower mandrels 8 and 9 which are opposed to the die 3 and the punch 5 and which guide the tubular material 10 from the vertical direction are divided into upper and lower mandrels 8 and 9 via mandrel holders 16 and 17, respectively. It is supported by the holder 2 and the upper holder 14, respectively.

The upper end of the lower mandrel 9 is located on the inner surface side of the large-diameter portion 10a of the tubular material 10 fitted in the hole 6 of the die 3 and substantially at the center in the height direction, while the upper mandrel 8 is The lower end is positioned so that a slight space 18 can be formed between the lower end of the punch 5 and the upper end of the lower mandrel 9. It should be noted that the space portion 18 is assumed to exist from the start of compression of the large-diameter portion 10a by the punch 5 to the completion of compression, and as in this embodiment,
In addition to those formed between the upper and lower mandrels 8 and 9,
As shown in the figure, the outer circumference of one mandrel (for example, the upper mandrel 8) may be cut off and formed between the inner surface of the cylindrical material 10 and the outer circumferences of the ends of both mandrels 8 and 9. May be cut off, or a large chamfer may be applied to the peripheral edge portions of both mandrels. That is, the space portion 18
Does not need to be formed into a large size.
A material in which a small amount of material can flow to the inner surface of 0 to form a small protrusion, and the protrusion does not hinder the removal of the tubular material 10 from the upper and lower mandrels 8 and 9. It is all right.

In the drawings, reference numeral 19 is a lower holder for fixing the lower mandrel holder 17 to the lower die holder 2, 20 is a spacer, 21 is a knockout sleeve for pushing up a molded product after forging, and 22 is the knockout sleeve.
21 is a knockout pin for moving upward, 23 is a knockout sleeve for pushing up the knockout pin 22.
It is a linking pin for transmitting to 21.

Next, the operation of the step forming forging die according to the illustrated embodiment will be described with reference to FIG.

First, as shown in FIG. 2 (a), the tubular material 10 is inserted into the hole 6 of the die 3. The tubular material 10 is formed with a large-diameter portion 10a for performing a bulging process.
Is located in the annular recess 7 of the die 3, and at this time, a slight gap S is left on the outer peripheral side of the large diameter portion 10a. After that, when the upper holder 14 is moved downward by using a driving means (not shown) and the punch 5 is set up, the outer punch 5a of the punch 5 becomes larger in diameter than the large diameter portion of the tubular material 10.
A pressing force is applied to 10a, and the material of the large diameter portion 10a is the second
As shown in the figures (b) and (c), the space flows between the upper and lower mandrels 8 and 9 on the outer peripheral side as shown by arrow A so as to fill the gap S and on the inner peripheral side as shown by arrow B. Pour into part 18. Thus, finally, as shown in FIG. 2 (d), the cylindrical material 10 in which the large diameter portion 10a is bulged on the outer periphery is obtained by the pressing force of the outer punch 5a. At this time, on the inner peripheral surface of the large-diameter portion 10a, a protruding portion 24 facing the space portion 18 between the upper and lower mandrels 8 and 9 is formed to project, but since the protruding portion 24 is small, it is tubular. Material 10
It can be cut very easily by cutting the inner surface after taking out. It should be noted that the tubular material 10 which is a molded product obtained as shown in FIG. 2D is interlocked with the punch 5 by retracting the punch 5 upward and then activating the knock-out pin 22. It is taken out from above the annular recess 7 of the die 3 by the push-up force of the knockout sleeve 21.

The present invention is not limited to the illustrated embodiments, and it goes without saying that the design can be appropriately changed without departing from the scope of the invention.

(Effects of the Invention) As described above, according to the present invention, in the forging die for step forming, the cylindrical material provided so as to face the die and the punch and fitted in the hole of the die is vertically arranged. The upper and lower mandrels divided into upper and lower parts for guiding the insertion from the upper and lower mandrels are attached, and between the upper and lower mandrels at the lowering operation end of the punch on the peripheral surface side of the large diameter part of the tubular material or at least one side Since the space portion is formed on the outer circumference of the end portion, at the same time as the material flows to the outer peripheral side of the large diameter portion in the process of expanding the large diameter portion by the pressing force of the punch on the outer periphery of the cylindrical material, It flows between the upper and lower mandrels or at the side of the space formed on the outer circumference of the end of at least one mandrel, and does not cause sink marks as seen in the conventional example, but rather the inner circumference of the large diameter part. Since the protrusion is formed on the surface, there is an excellent effect that a desired tubular stepped forged product can be obtained very easily only by cutting the protrusion by cutting.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a step forming forging die according to an embodiment of the present invention, and FIGS. 2 (a), (b), (c) and (d).
FIG. 4 is a process drawing showing a forming sequence for forming a stepped forged product by using the forging die shown in FIG. 1, FIG. 3 is a sectional view showing the principal part of another embodiment of the present invention, and FIG. , A cross-sectional view showing a state before upsetting (left half) and a state after upsetting (right half) when using a conventional step forming forging die, FIG. 5 is a forging shown in FIG. It is sectional drawing which shows the flow of the material at the time of shape | molding a forged product using a metal mold | die. 3 ... Die 5 ... Punch 6 ... Hole 7 ... Annular recess 8 ... Upper mandrel 9 ... Lower mandrel 10 ... Cylindrical material 10a ... Large diameter part 18 ... Space part

Claims (1)

[Claims] 1. A large diameter portion (10a) is bulged around the outer circumference of a tubular material (10), the hole (6) into which the tubular material (10) can be inserted, and the hole (6). ), Which has an annular recess (7) corresponding to the large diameter portion (10a) on the upper opening side, and a punch (5) which is fitted into the annular recess (7) from above, The cylindrical material (10) provided so as to face the die (3) and the punch (5), respectively.
The upper and lower mandrels (8) and (9) which are vertically divided to guide the insertion of the punch and the punch (5).
At the lowering end of the movement, the large diameter part (10
a) On the inner peripheral surface side, the upper and lower mandrels (8),
(9) Mandrel between or at least one side (8)
Alternatively, a step forming forging die is provided with a space (18) formed on the outer periphery of the end of (9).