JPH0688087B2 - Forging die for sheet metal gear-shaped parts - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION << Industrial Application Field >> The present invention relates to an improvement in a forging die for a sheet-metal gear-shaped component used in a pulley for a toothed belt or the like.

<< Prior art and its problems >> Gear-shaped parts made of sheet metal are widely adopted for pulleys used under relatively light loads, such as pulleys for toothed belts. This gear-shaped component (hereinafter, simply referred to as "component") 1 has a tooth portion 2 and a tooth bottom portion 3 on the outer circumference of the peripheral wall of a bottomed cylindrical body (so-called cup-shaped body) having a shallow bottom as shown in FIG.
7 which is integrally formed, and is a work 5 having a positioning attachment surface 4 formed in the center of a disk-shaped blank as shown in FIG. The part 1 is obtained by forging the work 6 shown in FIG. FIGS. 8A and 8B show a process of forging the work 5 to manufacture the component 1. When the work 5 is narrowed down by the cylindrical punch 8 in the cylindrical die 7, the work 5 is At the same time that the peripheral portion is cylindrically formed, the tooth portion 2 and the tooth bottom portion 3 are formed on the peripheral wall portion 5a. In FIGS. 8A and 8B, 9 is a counter punch, 10 is a cushion pin, 11 is a support plate, 12 is a substrate, and 13 is a cushion pad.

On the inner peripheral surface of the die 7, as shown in FIG. 9, there are formed ridge lines 14 and valley lines 15 for forming the tooth portion 2 and the tooth bottom portion 3 of the component 1, and the peripheral wall portion 5a of the work 5 is formed on the ridge portion. The bottom portion 3 is formed by being pushed by the streak 14, and the peripheral wall 5a of the work 5 is a trough
The tooth portion 2 is formed so as to bite into the tooth 15.

By the way, since the shape of the peak line 14 and the valley line 15 of the conventional die 7 is the shape shown in FIG. 9 according to, for example, Japanese Patent Laid-Open No. 59-4214, the taper surface 16 of the peak line 14 forms the tooth bottom portion. At the same time that the depth of 3 is formed, the taper surface 17 of the mountain line 14 forms the interval between the tooth portions 2 or the side surface of the tooth portion 2, and then the taper surface 18 of the valley line 15 forms the tooth portion 2 without the height of the tooth portion 2. A surface is formed. Thus, in the conventional die 7, the tooth bottom portion 3 and the tooth portion 2 are
Since the side surfaces are formed all at once, an excessive tensile force acts between the bottom wall portion 5b of the work 5 and the peripheral wall portion 5a, and based on this excessive tensile force, as shown in FIG. The effective tooth length is l
However, if the tooth length is relatively high as shown in Fig. 11, a defective product such as a crack between the bottom wall 5b and the peripheral wall 5a may appear. was there. It should be noted that FIG. 12 shows a so-called devil's horn 20 burr that occurs at the opening side end of the peripheral wall 5a.

On the other hand, in order to eliminate the inconveniences such as the above-mentioned sag 19
A forging method shown in FIGS. 13 (a) and 13 (b) has been proposed (JP-A-62-31770). In this forging method, as a first step, the work 6 formed by preforming the peripheral wall portion 6a is pushed into the first die 21 from the bottom wall portion 6b as shown in FIG. 13 (a),
Next, this work 6 is taken out from the first die 21, and then, as a second step, it is pushed into the second die 22 from the opposite direction as shown in FIG. 13 (b). According to this method, since the peripheral wall portion 6a is squeezed in the opposite direction, the length of the sag is reduced. However, this forging method is disadvantageous in terms of production efficiency because the process is divided into two stages and the work is reversed and the work surface needs to be coated with lubricant twice, and two types of dies and punches are prepared. The more it has to be, the more problematic it is in terms of equipment cost.

The present invention has been made to solve the above-mentioned problems all at once, and an object thereof is to provide a forging die capable of forging a component in one step without causing sagging or cracking.

<< Means for Solving the Problems >> The present invention for solving the above problems is a gear-shaped component formed by forming tooth portions and tooth bottom portions on a peripheral wall portion of a cup-shaped body integrally formed from a sheet metal. In a cylindrical die for forging by mutual fitting with a columnar punch, a mountain line for forming the tooth portion and the tooth bottom portion formed along the axial direction on the inner peripheral surface of the die and As the shape of the trough, as it goes from the opening on the insertion side of the die to the back, first the height of the mountain streak is gradually increased to reach the final height,
After the height of the mountain line reaches the final height, the width of the mountain line is gradually widened to reach the final width, and after the width of the mountain line reaches the final width, the depth of the valley line is gradually reduced. And reached the final depth.

<Operation> In the forging by the die configured as described above, since it is formed step by step from the tooth bottom of the part to the tooth side surface and further to the tooth tip end surface from the inside to the outside, the part or punch or die It is difficult to apply excessive force to
Therefore, it is possible to prevent the parts from sagging or cracking and to extend the life of the punch or die.

Example An example of the present invention will be described below with reference to the drawings. FIG. 1 shows a vertical cross section of the inner peripheral wall of the die 25 according to the present invention. As shown in the figure, a mountain line 26 and a valley line 27 are formed alternately and continuously along the axial direction on the inner peripheral surface of the die 25. The mountain line 26 and the valley line 27 form the teeth of the component 1. The part 2 and the tooth bottom part 3 are formed.

The mountain line 26 rises from a position slightly behind the insertion side opening 28 of the die 25, rises gradually, and extends to the inside of the die 25. Specifically, this mountain line 26 forms an α portion from its rise to almost the central portion, and then a relatively short β portion,
Continuing with the γ portion and the Δ portion, the tip is made to have a substantially constant cross-sectional shape. The above α part is, so to speak, a part for preforming, and the taper surfaces 29, 30 in the height direction are formed on the rising part and the intermediate part.
Is formed, and straight portions 31 and 32 having a substantially constant height are formed in front of and behind the intermediate tapered surface 30. In addition, it is preferable that the tapered surface 29 of the rising portion is not a conical shape so that a good narrowing effect can be obtained. The cross-sectional shape of the α portion is the shape shown by the solid line in FIG. 2 (a) if the A section of the straight portion 31 is shown, and has a relatively gentle waveform. On the other hand, the straight part
The section B of 32 has a shape shown by a chain line in FIG. 2A, and the height of the mountain line 26 is slightly higher.

Next, the β portion is for forming the tooth bottom portion 3 of the component 1, and comprises a tapered surface 33 for pushing the peripheral wall portion 6a of the work 6 to the final depth of the tooth bottom portion 3. Next, the γ portion is for forming the side surface of the tooth portion 2 of the component 1, and is composed of a tapered surface 34 whose height is substantially constant but whose width gradually increases. The final cross-sectional shape of this γ portion is shown in FIG. 2 (b) when the cross-sectional shape is shown by the cross-section C, and the width P of the mountain line 26 forms the final mutual spacing between the tooth portions 2. Then, the height and the width of the mountain line 26 continue to the depth of the die 25 in a constant state.

Next, the valley line 27 is formed between the mountain lines 26, and
The linear portion 35 is formed up to the portion, β portion, and γ portion, the Δ portion is formed where the γ portion ends, and the linear portion 36 is formed again thereafter. The Δ portion is for forming the tip end surface of the tooth portion 2 of the component 1, and includes a tapered surface 37 that presses the peripheral wall portion 6a of the work 6 to the final height of the tooth portion 2. The final cross-sectional shape of the Δ portion is shown in FIG. 2C when the final cross-sectional shape is shown by the D section, and the depth H of the valley line 27 forms the final height of the tooth portion 2.

Next, the shape of the punch 40 will be described with reference to FIG. The punch 40 has a columnar shape, and a mountain line 41 and a valley line 42 which match the tooth portion 2 and the tooth bottom portion 3 of the component 1 are formed on the peripheral surface thereof. And the mountain line 41 of the punch 40 is the valley line 27 of the die 25
Further, the mountain line 26 of the die 25 and the valley line 42 of the punch 40 are fitted to each other with the peripheral wall portion 6a of the work 6 sandwiched therebetween, thereby forming the peripheral surface shape of the component 1. A step 43 is formed at the end of the mountain streak 41 with which the peripheral wall 6a of the work 6 is fitted, and a slight gap S is formed between the step 43 and the work 6 when the work 6 is set. Are formed.
The height T of the stepped portion 43 is slightly smaller than the plate thickness of the work 6 in order to avoid closed forging, and is preferably in the range of 0.05t ≦ T ≦ 0.5t. By forming such a stepped portion 43, it is possible to suppress the occurrence of so-called demon horn 20. If closed forging is performed, the load of the punch 40 becomes large, and seizure with the die 25 may occur.

The forging die 25 and the punch 40 of the component 1 are configured as described above. When the work 6 coated with the lubricant is set on the punch 40 and press-fitted into the die 25 as shown in FIG.
First, as shown by the solid line in FIG. 4 (a), the work 6 peripheral wall portion 6a is pressed by the α portion of the mountain reed 26 of the die 25 to be preformed, and then the peripheral wall portion 6a is pressed by the β portion of the mountain reed 26. The final depth of the tooth bottom portion 3 is formed, then the side surface of the tooth portion 2 is pressed by the γ portion of the mountain line 26 to form the final side surface shape of the tooth portion 2, and finally the tip end surface of the tooth portion 2 is Δ portion. The final tip end surface shape of the tooth portion 2 is formed by being pressed by.

As described above, in the present invention, since the peripheral surface shape of the component 1 is formed stepwise from the inner side to the outer side, an unreasonable force is unlikely to be generated on the work 6, the die 25, etc.
As shown in FIG. 5, the length of the sagging 19 caused in FIG. 5 can be made extremely short, which makes it possible to secure an effective tooth length and to make the component 1 thin and compact, and to extend the service life of the die 25 and the like.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made. For example, a pinion is meshed with the inner peripheral surface of the work 6 peripheral wall portion 6a. The present invention can be applied to the case of forming the tooth portion and the tooth bottom portion. Further, in the above embodiment, the α portion of the mountain line 26,
The β part, the γ part and the Δ part of the valley line are formed stepwise and continuously, but it is conceivable that these parts may be separated from each other depending on the shape of the product, and the parts should be separated from each other as long as the product is not affected. It is also possible to reconstruct the duplication.

<Effects of the Invention> As described above, the present invention is formed stepwise from the bottom of the gear-shaped part to the side surface of the tooth and further toward the tip of the tooth from the inside to the outside, so that an unreasonable force is exerted on the workpiece. It is hard to take, and as a result, it is possible to suppress sagging at the tooth end of the gear-shaped part, secure an effective tooth length and make the part compact, and at the same time prevent cracks from occurring in advance and improve the yield. However, since it does not require excessive force, its life can be extended.

[Brief description of drawings]

1 to 5 show an embodiment of the present invention. FIG. 1 is a longitudinal sectional view of a die, and FIGS. 2 (a) to (c).
Is a cross-sectional view of the mountain bar of the die, FIG. 3 is a cross-sectional view of the lower end of the punch, FIGS. 4 (a) to 4 (c) are cross-sectional views of the tooth portion of the gear-shaped component, and FIG. FIG.
6 to 13 show a conventional example, FIG. 6 is a perspective view of a gear-shaped component, and FIGS. 7 (a) and 7 (b) are vertical cross-sectional views of a work for the component, respectively. Figure, Figure 8 (a),
(B) is a vertical sectional view of the die and punch, FIG. 9 is a perspective view of the inner peripheral surface of the die, FIG. 10 is a sectional view of the tooth end of the gear-shaped component, and FIG. 11 is a gear-shaped component with a crack. FIG. 12 is a partial perspective view of the open end of the gear-shaped component in which the devil's horn is formed, and FIGS. 13 (a) and 13 (b) are split dies and punches according to another conventional example. FIG. 1 ... Gear-shaped part, 2 ... Tooth part 3 ... Tooth bottom part, 25 ... Die 26 ... Mountain streak, 27 ... Valley streak 28 ... Insertion side opening, 40 ... Punch

Claims (1)

[Claims] 1. A cylindrical die for forging a gear-shaped component having a tooth portion and a tooth bottom portion formed on a peripheral wall portion of a cup-shaped body integrally molded from sheet metal by mutual fitting with a cylindrical punch. In, in the inner peripheral surface of the die, formed along the axial direction, the shape of the mountain line and the valley line for forming the tooth portion and the tooth bottom portion, as going from the insertion side opening of the die to the back, First, the height of the mountain line is gradually increased to reach the final height, and after the height of the mountain line reaches the final height, the width of the mountain line is gradually increased to reach the final width. A forging die for a sheet-metal gear-shaped component, characterized in that after the width of the streak reaches the final width, the depth of the valley streak is gradually reduced to reach the final depth.