JP2001205384A - Method for forming gear with boss - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of forming gears with bosses for which a boss diameter is the groove bottom diameter of an outer tooth or less and the height is respectively different with a high material yield. SOLUTION: Pressurizing started in an initial state where the upper punch of a tightly closed die provided with a die where a tooth die corresponding to the outer tooth is formed and the upper punch and a lower punch for closing the die hole of the die is divided by a diameter equal to the boss outer diameter of a product to be obtained and the pressurizing surface of the inner punch is moved backward or forward from the pressurizing surface of an outer punch for a prescribed dimension. Pressurizing by the outer punch is continued as it is until work is ended. For pressurizing by the inner punch, a prescribed tool surface pressure is maintained after the tool surface pressure is raised to a prescribed value by integral pressurizing with the outer punch until the pressurizing surface is moved back for a fixed distance from the initial position and then it is cancelled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold gear using a hermetically closed mold of a gear, more specifically a spur gear or a helical gear having a boss on one end surface (hereinafter simply referred to as a bossed gear). Or, it relates to a warm forming method.

[0002]

2. Description of the Related Art Generally, the above-mentioned bossed gear is formed into a product by forming a blank by hot forging and subjecting the blank to a cutting process. However, this method requires a long manufacturing process of turning → hobbing → chamfering → shaving → carburizing and quenching → honing, resulting in high cost. For this reason, there is a strong demand for shortening the manufacturing process, and in order to meet this demand, various gear forming methods by cold forging using a mold have been conventionally developed.

FIG. 3 is a diagram illustrating one of the typical methods, which is referred to as a one-stage discarding axle method using an imperfectly closed mold that can be formed at a low tool surface pressure. FIG.

That is, in the one-stage discarding shaft method, as shown in the drawing, a tooth mold 1a corresponding to the external teeth of the product to be obtained is formed on the inner peripheral surface of the die hole, and meshes with the tooth mold 1a. The hollow work material 2 is arranged in the die 1 in which the lower punch 4 having the tooth mold 4a formed on the outer peripheral surface is meshed, and the large diameter portion is located at the axial center of the work material 2. The mandrel 5. Then, in this state, the inner material is pressurized by the upper punch 3 whose inner diameter is larger than the outer diameter of the large diameter portion of the mandrel 5, and the material 2 to be processed is filled in the gap defined by the inner diameter of the mandrel 5 and the upper punch 3 during processing. It is a method that is made to flow.

[0005] According to the one-stage discard shaft method, the portion of the material 6 flowing into the gap defined by the inner diameter of the mandrel 5 and the upper punch 3 can be regarded as a boss, and a bossed gear can be formed. is there. However, according to the single-step shaft method, the boss diameter is only about 40% or less in terms of the area ratio to the cross-sectional area of the entire gear, and the boss height can be formed only with a bossed gear having a constant height corresponding to the boss diameter. Has disadvantages. This is clear from the experimental results shown in FIG.

FIG. 4 shows a helical gear of the steel type S10C of the two steel types having the chemical compositions shown in Table 1 having the dimensional specifications shown in Table 2 and various inner diameters of the upper punch 3 shown in FIG. FIG. 7 is a diagram showing an example of a result when molding is performed at room temperature while changing the average tool surface pressure on the horizontal axis and the boss height on the vertical axis.

[0007] The average tool surface pressure on the horizontal axis is a value (MP) obtained by dividing the load acting on the lower punch by its pressure receiving area.
a), the boss height on the vertical axis is the boss height ratio (%) with respect to the total height including the boss, and the value in parentheses in the figure is the filling ratio (%) of the material for the die of the die 1.

FIG. 4 shows the results when the material 2 to be processed is 1.1 times the mass of the product after cutting.

[0009]

[Table 1]

[Table 2] As can be seen from FIG. 4, when the boss diameter is 33% or 40% in area ratio with respect to the cross-sectional area of the entire gear, the die 1
There is an average tool surface pressure at which the filling rate of the material with respect to the tooth mold 1a becomes 100%. Therefore, it is possible to form a gear with bosses (6 parts in FIG. 3) having complete external teeth.
However, the boss height is 40% of the total height including the boss when the boss area ratio is 33%, and 47% when the boss area ratio is 40%.
%, And bosses having a lower height or a higher boss cannot be formed.

On the other hand, the area ratio of the boss is 50% and 65%.
In the case of%, there is no average tool surface pressure at which the filling ratio of the material to the mold 1a of the die 1 becomes 100%. Therefore, the boss is formed, but the external teeth of the product are not formed, and it is impossible to form a bossed gear having complete external teeth. The boss area ratio of 65% means that the boss diameter is equal to the groove bottom diameter of the external teeth.

Here, if the area ratio of the boss exceeds 40%, it is impossible to form a bossed gear having complete external teeth because of the gap defined by the inner diameter of the mandrel 5 and the upper punch 3. Is too large, and the material inflow resistance into this gap is insufficient.

Although not shown, in the case of steel type SCr420H shown in Table 1, the average tool surface pressure on the horizontal axis is S10.
Although the deformation resistance is increased by a greater amount than in the case of C, the same result as in FIG. 4 was obtained. That is, the deformation resistance of S10C is 482 MPa when the strain is 1, and
At 0H, the average tool surface pressure was 623 MPa, which was 1.3 times that of the average pressure.

However, the bossed gears actually required include those having an area ratio of the boss exceeding 40% and those having various heights even when the boss area ratio is 40% or less. Specifically, for example, many bossed gears for a manual transmission of an automobile have a size range as shown in Table 3. In addition, some of the inner peripheral surfaces of the shaft holes have internal teeth called splines, and development of a method capable of forming such a bossed gear with a high material yield has been strongly desired. .

[0014]

[Table 3]

SUMMARY OF THE INVENTION A first object of the present invention is to provide a bossed gear in which the area ratio of the boss is 65% or less, that is, the boss diameter is not more than the groove bottom diameter of the external teeth and the height thereof is variously different. Is to provide a method that can be molded with a high material yield. A second object is to provide a method capable of forming a bossed gear with internal teeth having a sufficient depth over the entire height when a product to be obtained has a shaft hole with internal teeth. Is to do.

[0015]

The present inventor has conducted a number of experiments to achieve the above object. as a result,
The following has been found.

It is necessary to use an upper punch having an inner punch and an outer punch divided by a diameter equal to the diameter of a boss of a product to be obtained.

Pressing by the inner punch and the outer punch is not performed by a method in which the inner punch is initially set at a position retracted from the pressing surface of the outer punch by a dimension equal to the boss height of the product to obtain the pressing surface of the inner punch, and the pressing is not performed. Sufficient, it is necessary to initialize to one of the following and start pressurization with both inner and outer punches.

That is, one of them is a position where the pressing surface of the inner punch is retreated by a predetermined distance from the pressing surface of the outer punch, specifically, within a range of 90% or less of the boss height of the product to be obtained. Set to the retracted position. The other is to match the pressing surfaces of the inner and outer punches or to advance the pressing surface of the inner punch by a predetermined distance from the pressing surface of the outer punch, specifically, the height of the boss height of the product to be obtained. Set to a position advanced within 30% or less.

After the start of pressurization by both the inner and outer punches, pressurization by the outer punch may be continued as it is until processing is completed. During retraction, it is necessary to maintain a predetermined tool surface pressure, and then release the pressurization by the inner punch.

When the bossed gear to be obtained has a shaft hole with internal teeth, the outer diameter is equal to the shaft hole diameter.
A mandrel having a tooth pattern corresponding to the internal teeth of the product formed on its outer peripheral surface is arranged at the axial center of the material to be processed. However, this is not enough, and it is necessary to perform re-pressing by the inner punch at a predetermined tool surface pressure after the end of working by pressurizing only by the outer punch after releasing the press by the inner punch.

The gist of the present invention based on the above findings lies in the following method (1) to (3) for forming a bossed gear. (1) Using a die in which a tooth pattern corresponding to the external teeth of the product is formed on the inner peripheral surface of the die hole, and a closed die having an upper punch and a lower punch for closing the die hole of the die, When forming a bossed gear having a boss on one end face by pressing the work material arranged in the die hole mainly with an upper punch and completely filling the work material to every corner of the die hole, A split punch having a diameter equal to the outer diameter of the boss of the product to be obtained as the upper punch, divided into an outer punch and an inner punch, and having a pressing surface of the inner punch of 90% or less of the boss height of the product to be obtained. Pressurization by both the inner and outer punches is started in the initial setting state in which the inner punch is retracted from the pressurizing surface of the outer punch, and then pressurization by the outer punch is continued as it is, while pressurization by the inner punch is such that the pressurizing surface is From the default setting Until retreating by a certain distance, the pressurization by the inner punch is released after maintaining the predetermined tool surface pressure, and after the release of pressurization of the inner punch, the gear with boss that continues to pressurize by the outer punch further Molding method. (2) Using a die in which a tooth pattern corresponding to the external teeth of the product is formed on the inner peripheral surface of the die hole, and a closed die having a main punch and a lower punch for closing the die hole of the die, When forming a bossed gear having a boss on one end face by pressing the work material arranged in the die hole mainly with a main punch to completely fill the work material to every corner of the die hole, Use the split punch divided into an outer punch and an inner punch with a diameter equal to the outer diameter of the boss of the product to be obtained as the upper punch, and match the pressing surfaces of the inner and outer punches or obtain the pressing surface of the inner punch Pressing by both the inner and outer punches is started in an initial setting state in which the outer punch is advanced from the pressing surface of the outer punch within a range of 30% or less of the boss height of the product. Pressing with a punch Until the pressing surface retreats by a certain distance from the initial setting position, the pressing by the inner punch is released after maintaining the predetermined tool surface pressure, and after the releasing of the inner punch, the pressing by the outer punch is further performed. A method of forming a bossed gear that continues to be pressurized. (3) In the method of forming a bossed gear according to the above (1) or (2), when the product to be obtained has a shaft hole having internal teeth, an inner punch and a lower punch are provided at the shaft center of the material to be processed. The outer diameter penetrating the deep part of the shaft is equal to the diameter of the shaft hole, and a mandrel formed with a tooth pattern corresponding to the internal teeth of the product to be obtained is arranged on the outer peripheral surface thereof, while the pressure is released by the inner punch. After the pressing by the outer punch is completed, the outer punch is retracted, and then the deformation resistance of the material to be processed is 2.7 to 2.7.
3.3 A method of forming a bossed gear in which re-pressing is performed by an inner punch with a tool pressure three times as large.

In the above-mentioned method (1), it is preferable that the pressing is performed with the pressing surface of the inner punch being advanced from the pressing surface of the outer punch before the pressing by the inner and outer punches is started.

In the case of the former, the predetermined tool surface pressure in the methods of (1) and (2) is 2.5 times the deformation resistance of the work material or the load applied to the lower punch, 0.80 times or less of the average tool surface pressure obtained by dividing by the area, and in the latter case, 2.15 of the deformation resistance of the work material
It is preferable that the average tool surface pressure is 0.80 times or less of the average tool surface pressure obtained by dividing the load applied to the double punch or the lower punch by the pressure receiving area of the lower punch.

Further, the re-pressing by the inner punch in the method (3) causes the deformation resistance of the material to be processed to be 2.8 to 3.1.
It is more preferable to carry out with double tool surface pressure.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for forming a bossed gear of the present invention will be described in detail with reference to the accompanying drawings, taking a case where a product to be obtained is a helical gear as an example.

First, a completely closed mold used in the present invention will be described. The same members as those of the incompletely closed mold used in the conventional one-stage discard shaft method will be described with the same reference numerals.

FIG. 1 is a schematic longitudinal sectional view showing an example of a completely closed mold used in the method of the present invention. As shown in the figure, the mold is a die 1 having a die hole formed on the entire peripheral surface thereof with a tooth mold 1a for forming the external teeth of the helical gear over the entire length in the axial direction, and the teeth described above. A lower mold 4 is formed on the outer peripheral surface of the mold 4a meshing with the mold 1a, a part of which is meshed with the mold 1a, and a solid arranged in the hollow portion of the lower punch 4. A mandrel 50 having the same outer diameter in the axial direction, an inner punch 3a having an inner diameter substantially equal to the outer diameter of the mandrel 50, and an inner punch 3a having an inner diameter substantially equal to the outer diameter of the mandrel 50; The outer punch 3b is larger than the die hole diameter.

The lower surface of the die 1 is supported on a base 7 of a double-acting press by a telescopic member 8 such as a spring via an appropriate means such as a thrust bearing.

Among the above-mentioned tools constituting the mold, the lower punch 4, the mandrel 50, the inner punch 3a and the outer punch 3
b is individually connected to each ram of a double-acting press (a double-acting press having two cylinders at the bottom and three cylinders at the top, although not shown).

The press may be a mechanical press with a hydraulic die set. A load meter and a distance meter are attached to the ram to which the inner punch 3a is connected.
The tool surface pressure (pressing force) acting on the inner punch 3a and the relative movement distance of the inner punch 3a with respect to the outer punch 3b can be measured, and the tool surface pressure can be maintained at a predetermined value for a certain period of time. The load meter may be attached to each tool, and the distance meter is desirably attached to the outer punch 3b.

Next, the first method (the method described in claim 1 of the claims) will be described among the methods of forming the helical gear using the mold configured as described above.

That is, in the first method, as shown in FIG. 1A, the pressing surface of the inner punch 3a is initially set to a position retracted by a distance A from the pressing surface of the outer punch 3b. Before or after the initial setting, the work material 2 is loaded into the die hole of the die 1 and placed on the lower punch 4. At this time, as the material to be processed 2, the outer diameter is equal to or slightly smaller than the inner diameter of the die hole, the inner diameter is equal to or slightly larger than the outer diameter of the mandrel 50, and the mass is equal to the mass of the product to be obtained. A material having a mass obtained by adding a mass corresponding to a cutting allowance after molding is used.

Next, the inner punch 3a and the outer punch 3b are simultaneously lowered to apply pressure without changing the mutual positional relationship between the two punches, and continue until the tool surface pressure of the inner punch 3a reaches a predetermined value. Thereafter, the outer punch 3b continues pressurizing until the height of the external teeth reaches the height of the product to be obtained.

On the other hand, after the inner punch 3a reaches a predetermined tool surface pressure value by the integral pressurization with the outer punch 3b,
The material 2 to be processed is plastically deformed with the progress of pressurization.
After the state shown in FIG. 1C, the tool surface pressure is maintained at a predetermined value until the pressing surface of the inner punch 3a retreats by a predetermined distance B from the initial setting position, as shown in FIG. 1C. When the pressure is applied and the pressing surface of the inner punch 3a retreats by the distance B, the pressing by the inner punch is released.

When the work material 2 is pressed by the outer punch 3b and the inner punch 3a as described above, even when the area ratio of the boss exceeds 40%, the amount of material flowing upward along the mandrel 50 is increased. Is regulated by the pressing surface of the inner punch 3a, and as shown in FIG.
The filling rate of the material with respect to a becomes 100%.

Further, as shown in FIG. 1D, the height of the boss is such that the material receives the resistance of the inner die 3a due to the pressing by the outer punch 3b which continues even after the pressing by the inner die 3a is released. It is ensured because it flows upward along the mandrel 50 without any problem.

In the first method, the tool surface pressure of the inner punch 3a, which is maintained while the distances A and B and the inner punch 3a are retracted by the distance B, depends on the steel type of the bossed gear to be obtained. It is determined only by the ratio of the magnitude of the deformation resistance at the time of 1, but it depends on the size and gear specifications. Therefore, these values need to be determined as appropriate by conducting experiments in advance.
The gear body is also a helical gear shown in Table 2 above, and the area ratio of the boss is 40% and 50%, and the boss height is 40 to 50 of the total height including the boss.
In the case of a helical gear with a boss of%, the above distance A is 10 m
m, the distance B is 1 mm, and the tool surface pressure of the inner punch 3a, which is maintained while the pressing surface of the inner punch 3a is retracted by the distance B, is preferably in the range shown in Table 4 according to the area ratio of the boss.

[0038]

[Table 4] However, the distance A needs to be a value of 90% or less of the boss height of the product to be obtained. The reason is that if the distance A exceeds 90% of the boss height of the product to be obtained, the distance
Cannot be secured, and the average tool surface pressure acting on the lower punch 4 becomes excessive, which may damage the mold. For this reason, in the first method, the distance A is set within a range of 90% or less of the boss height of the product for which the distance A is to be obtained.

In the first method described above, when the area ratio of the boss is large, the upper external teeth are sufficiently formed during the forming, but the lower external teeth are not sufficiently formed during the forming. As a result, the die hole above the die 1 may become large. As a result, the overball die of the obtained product is large in the upper part and small in the lower part. Depending on the application, it does not satisfy the required dimensional specification, and in the case of extreme, it is called a flaw on the external teeth part Defects may occur.

For example, in the case of a gear with a boss having an area ratio of the boss of 50%, the difference between the upper and lower overball dias is 0.07 to 0.09 mm, which is unsuitable for an automobile transmission. In the case of a bossed gear having a boss area ratio of 65%, the above-described defect may occur.

The above-described problem that occurs in the first method can be solved by taking the following measures. That is, the means performs pre-pressurization in a state where the pressurized surface of the inner punch 3a is advanced from the pressurized surface of the outer punch 3b before the pressurization by both the inner and outer punches in the initial setting state starts. Is the way. When this preliminary pressurization is performed, the central portion of the workpiece 2 mainly undergoes compressive deformation, and the central portion in the longitudinal direction has a shape bulging outward. As a result, in the subsequent processing, the above-described deformation mode does not occur, and a product having a small difference between the upper and lower overball dies can be obtained.

Therefore, in the first method, before the pressurization by both the inner and outer punches in the initial setting state, the pressurized surface of the inner punch 3a is advanced from the pressurized surface of the outer punch 3b. It is preferable to perform preliminary pressurization. The pre-pressurizing amount at this time is as follows: when the height of the workpiece 2 before pressing is H ₀ and the height of the external teeth of the product is H ₁ , the upsetting ratio defined by the following equation: And about 15 to 25%.

Upsetting ratio = (1−H ₁ / H ₀ ) × 100 (%) However, the addition of the pre-pressing step causes an increase in processing time, but this problem is caused by a second method described below. (The method according to claim 4 in the claims).

FIG. 2 is a diagram for explaining the second method. As shown in FIG.
Pressing by both the inner punch 3a and the outer punch 3b is started in a state where the pressing surface of the inner punch 3a is initially set at a position advanced by a distance C from the pressing surface of the outer punch 3b, and thereafter the second punch is substantially turned on. This method employs the same steps as the method 1. Specifically, the pressurization by the outer punch 3b is continued as in the first method until the height of the external teeth reaches the height of the product to be obtained. On the other hand, the pressurization by the inner punch 3a starts with the work material 2 being plastically deformed from the time when the tool surface pressure rises to a predetermined value with the progress of pressurization integrated with the outer punch 3b. The state shown in FIG. 2C through (b),
That is, until the pressing surface of the inner punch 3a retreats from the initial setting position by a certain distance D, the tool surface pressure is maintained at a predetermined value and the pressing is performed.
At this point, the pressure by the inner punch is released.

When the work material 2 is pressed by the outer punch 3b and the inner punch 3a as described above, even when the area ratio of the boss exceeds 40%, as in the case of the first method, the mandrel is pressed. Since the amount of material flowing upward along 50 is regulated by the pressing surface of the inner punch 3a, FIG.
As shown in the figure, the filling ratio of the material to the tooth mold 1a of the die 1 becomes 100%.

Further, as shown in FIG. 2D, the material receives the resistance of the inner die 3a due to the pressing by the outer punch 3b which continues even after the inner die 3a releases the pressing, as shown in FIG. 2D. It is ensured because it flows upward along the mandrel 50 without any problem.

Further, the central portion of the material to be processed 2 is compressed and deformed by being pressed by the inner punch 3a at the initial stage of pressing, and the material shape becomes a shape in which the central portion in the longitudinal direction expands outward. A product with a small difference between the upper and lower overball dies can be obtained.

In the second method, similarly to the first method, the tool surface pressure of the inner punch 3a to be held while the distances C and D and the inner punch 3a are retracted by the distance D should be obtained. Depending on the steel type of the bossed gear, it is determined only by the ratio of the magnitude of the deformation resistance when the strain is 1.
It depends on its size and gear specifications. Therefore,
These values need to be determined as appropriate by conducting experiments in advance. For example, the steel type is made of S10C shown in Table 1 above, the gear body is a helical gear also shown in Table 2 above, and the area of the boss is In the case of a helical gear with a boss having a ratio of 40%, 50%, and 65% and a boss height of 30 to 50% of the total height including the boss, the distances C and D are all 1 mm,
The tool surface pressure of the inner punch 3a, which is maintained while the pressing surface of the inner punch 3a retreats by the distance D, is preferably in the range shown in Table 5 according to the area ratio of the boss.

[0049]

[Table 5] However, the distance C needs to be a value of 30% or less of the boss height of the product to be obtained. The reason is that if the distance C exceeds 30% of the boss height of the product to be obtained, the required boss height cannot be secured. Therefore, in this second method,
The distance C was set within a range of 30% or less of the boss height of the product to be obtained.

In the second method, it is not always necessary to set the initial positions of the pressing surfaces of the inner and outer punches as described above, and the pressing surface of the outer punch 3b and the pressing surface of the inner punch 3a are matched. Pressurization by both punches may be started. However, in this case, the difference between the upper and lower overball dies of the obtained product is slightly larger than that obtained by the first method. For this reason,
The initial position is preferably as described above.

Next, the third method (the method described in claim 6 of the claims) will be described. According to the third method, a bossed gear in which internal teeth called splines are formed on the inner peripheral surface of the shaft hole in the axial direction parallel to the axial direction by the first method or the second method. Is the way.

Therefore, in this third method,
Instead of the mandrel 50 shown in FIGS. 1 and 2, a mandrel having a tooth pattern corresponding to the internal teeth of the product to be obtained is used on the outer peripheral surface thereof, although not shown. However, in this case, only the first method or the second method described above forms the internal teeth of the portion facing the external teeth, but the internal teeth of the portion facing the boss, especially the boss. The internal teeth of the part facing the upper part are not formed. This is because the amount of deformation of the workpiece 2 in the axial direction during pressurization by the outer punch 3b, which is continued even after the pressurization by the inner punch 3a is released, is greater than the amount of deformation in the radial direction, and is formed on the mandrel. This is because the material is not sufficiently filled in the concave portion of the tooth mold.

Therefore, in the third method, after the pressurization by the outer punch 3b which is continued even after the pressurization by the inner punch 3a is released (FIG. 1 and FIG. 2D), the outer punch 3b is retracted. After that, re-pressing by the inner punch 3a is performed.

However, if the pressing force at the time of re-pressing by the inner punch 3a, that is, the tool surface pressure of the inner punch 3a is not appropriate, the required inner teeth are not formed. Therefore,
The tool surface pressure at the time of re-pressing by the inner punch 3a needs to be set to a predetermined value, and this value differs depending on the required material filling ratio of the internal teeth.

For this reason, it is necessary to determine the tool surface pressure appropriately by conducting experiments in advance. For example, the steel type is made of S10C shown in Table 1 above, and the gear body is the same as that shown in Table 2 shown in Table 2 above. With gear, large diameter of internal teeth (groove bottom diameter of internal teeth) is 35m
m, small diameter (shaft hole diameter) is 33 mm, number of teeth is 24, boss area ratio is 40%, 50%, and 65%, and boss height is 30 to 50% of the total height including the boss. In the case of a helical gear with a boss having a boss, the tool surface pressure is preferably equal to or greater than the value shown in Table 6 according to the required material filling ratio of the internal teeth.

However, in consideration of the life of the mold, the upper limit is preferably 3.3 times or less, more preferably 3.1 times or less. This is one of the two steel types shown in Table 1 above.
In the case of steel type SCr420H, the tool surface pressure is SCr42
If the deformation resistance is more than 3.3 times the deformation resistance of 0H, the mold may be damaged.

[0057]

[Table 6] The above description is for the case where the external teeth are helical gears. However, when the external teeth are spur gears, the tooth mold formed on the die 1 and the lower punch 4 is formed by using a spur gear. It is possible.

[0058]

EXAMPLES Example 1 The steel type was S10 shown in Table 1 above.
C, the gear body has the dimensions shown in Table 2 above, the area ratio of the boss is 40% and 50%, and the boss height is 40% of the total height including the boss.
〜50% bossed helical gears were formed by the first method.

At this time, the pressing surface of the inner punch 3a was initially set to a position retracted by 10 mm from the pressing surface of the outer punch 3b. Pressing by the inner punch 3a changed the tool surface pressure variously, and the pressure was held constant while the pressing surface was retracted by 1 mm from the initial setting position.

In any case, the material to be processed 2 has an outer diameter of 55.1 mm, an inner diameter of 35.2 mm, and a height of 30.5 mm.
The thing of 5 mm was used.

The material filling ratio and the boss height of the external teeth of the helical gear with boss obtained by molding under each condition are examined, while the upsetting ratio and the lower punch 4 under each condition are examined. The average tool surface pressure was also examined.

The results of the above investigation are shown in Table 7 together with the molding conditions.

[0063]

[Table 7] As can be seen from Table 7, when the area ratio of the boss is 40%, the material filling rate of the external teeth is 100% under any condition.
% And a boss height of 40% or more were obtained, but in Test No. 3, the average tool surface pressure of the lower punch 4 was 3.3 times the deformation resistance of the work material, so the steel type was S10C. Although there is no problem in the case of SCr420H, there was a risk of mold damage.

When the boss area ratio was 50%, a boss height of 40% or more was obtained under any conditions. However, in Test Nos. 4 to 6, the material filling rate of the external teeth was 60%.
%, The material filling rate of the external teeth is 100% in Test Nos. 14 and 15, but the average tool surface pressure of the lower punch 4 is 3.3 times as large as the deformation resistance of the work material. Because
There was a risk of mold damage.

As described above, the tool surface pressure of the inner punch 3a in the case of forming a helical gear with a boss of the above steel type and dimensions by the first method is set to the range shown in Table 4 described above. Means better.

Although not shown in Table 7, the difference between the upper and lower overball dies of the products having good pass / fail judgment results in each test number was 0.07 to 0.09 mm.

Example 2 The steel type was S1 shown in Table 1 above.
0C, the gear body has the dimensions shown in Table 2 above, the boss area ratio is 40%, 50%, and 65%, and the boss height is 30 to 50% of the total height including the boss. Molded by the second method.

At this time, the pressing surface of the inner punch 3a was initially set to a position advanced by 1 mm from the pressing surface of the outer punch 3b. Pressing by the inner punch 3a changed the tool surface pressure variously, and the pressure was held constant while the pressing surface was retracted by 1 mm from the initial setting position.

However, the trial number 26 is 0.5 mm and the trial number 27 is
Is 0.3 mm, sample number 28 is 0.2 mm, sample numbers 29 and 30
Is 0.1 mm, the test numbers 31 to 35 are 4 mm, and while the pressurizing surface of the inner punch is retracted from the initial setting position, the tool surface pressure is kept constant and pressurized. This is intended to increase the boss height ratio while increasing the material filling ratio of the external teeth before forming the boss.

The material to be processed 2 has an outer diameter of 55.1 mm, an inner diameter of 35.2 mm and a height of 30.
The thing of 5 mm was used.

While the material filling ratio and the boss height of the external teeth of the helical gear with boss obtained by molding under each condition were examined, the upsetting ratio and the lower punch 4 under each condition were examined. The average tool surface pressure was also examined.

The results of the above investigation are shown in Table 8 together with the molding conditions.

[0073]

[Table 8] As can be seen from Table 8, when the area ratio of the boss is 40%, the material filling rate of the external teeth is 100% under any conditions.
No. 19 and 20 are 30% of the target
The above boss height could not be obtained.

When the boss area ratio was 50%, boss heights of 30% or more were obtained in Test Nos. 21 to 29. Of these, Test Nos. 21 and 22 showed that the material filling ratio of the external teeth was lower. 85
% Or less. In Test No. 30, the material filling ratio of the external teeth was 100%, but the target boss height of 30% or more could not be obtained.

Further, when the boss area ratio is 65%,
In Test Nos. 31 to 38, boss heights of 30% or more were obtained, and among Test Nos. 31 and 32, the material filling rate of the external teeth was 6%.
Only less than 0% was obtained. In Test No. 39, the material filling ratio of the external teeth was 100%, but the target boss height of 30% or more was not obtained.

The above description indicates that the tool surface pressure of the inner punch 3a in the case of forming a helical gear with a boss of the above-mentioned steel type and dimensions by the second method is set in the range shown in Table 5 described above. Means better.

Although the description in Table 8 is omitted, the difference between the upper and lower overball dia of the products having good pass / fail judgment results in each test number is 0.02 to 0.04 mm.
This method is much smaller than the method according to the method described above, and has sufficient dimensional accuracy for a transmission of an automobile.

Example 3 The steel type was S1 shown in Table 1 above.
0C, the gear body has the dimensions shown in Table 2 above, the area ratio of the boss is 40%, 50%, and 65%, the boss height is 30 to 50% of the total height including the boss, and the inner diameter (small diameter) is 33 mm.
The groove bottom diameter (large diameter) is 35 mm and the number of teeth is 2 on the inner peripheral surface of the shaft hole.
A bossed helical gear having 4 internal teeth was formed by the third method.

At this time, the steps up to re-pressurization by the inner punch 3a are the same as the trial number 24 in the second embodiment,
After retreating the outer punch 3b, it was repressurized with various tool surface pressures.

Then, the material filling ratio of the entire internal teeth of the helical gear with boss obtained by molding under each condition and the internal teeth of the portion facing the boss was examined. As a result, the material filling ratio of the entire internal teeth and the portion of the internal teeth facing the boss was the same regardless of the area ratio of the boss, as shown in Table 9.

[0081]

[Table 9] As is clear from Table 9, the material filling rate of the internal teeth varies depending on the tool surface pressure of the inner punch at the time of re-pressing. For example, in general, the material filling rate of the entire internal teeth as a product is 8%.
In order to obtain 0% or more, it is necessary to apply a tool surface pressure of 2.7 times or more of the deformation resistance of the material to be processed.
It can be seen that in order to obtain 0%, it is necessary to pressurize at a tool surface pressure of 2.8 times or more.

This means that the tool surface pressure of the inner punch 3a at the time of re-pressing when forming a helical gear with a boss having internal teeth of the above-mentioned steel type and dimensions by the third method is as described above. It means that it is better to set it in the range shown in Table 6.

The upper limit value 3.3 described in Table 6 is:
As described in Example 1 above, if the steel type exceeds this, there is a risk of mold breakage when the steel type is SCr420H, and from the viewpoint of reliably avoiding mold breakage, it is desirable that the ratio be 3.1 times or less. It is a determined value.

As is apparent from the results of Examples 1 to 3 described above, according to the present invention, even if the boss area ratio is not less than 40% or less than 40%, the boss area of the product is not limited. By properly setting the tool surface pressure of the inner punch according to the area ratio of the boss, it is possible to form a bossed gear with bosses with different heights and with internal teeth with an appropriate material filling rate I understand that.

[0085]

According to the present invention, a boss having a boss having an outer diameter of not more than the groove bottom diameter of the external teeth and having various heights, and a boss with high dimensional accuracy having internal teeth on the inner peripheral surface of the shaft hole. Can be manufactured with high material yield and high efficiency.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a first method of the present invention.

FIG. 2 is a diagram for explaining a second method of the present invention.

FIG. 3 is a view for explaining a conventional one-stage discard axis method.

FIG. 4 is a view showing an example of a result in a case where bossed gears having different area ratios are formed by a conventional one-stage discarding shaft method.

[Explanation of symbols]

 1: die, 2: work material, 3: upper punch, 3a: inner punch, 3b: outer punch, 4: lower punch, 5, 50: mandrel, 6: material (corresponding to boss), 7: base, 8: Elastic member.

Claims (7)

[Claims] 1. A closed die comprising a die having a tooth pattern corresponding to the external teeth of a product formed on an inner peripheral surface of the die hole, and an upper punch and a lower punch for closing the die hole of the die. When forming a bossed gear having a boss on one end face by pressing the work material arranged in the die hole of the die mainly with the upper punch and completely filling the work material to every corner of the die hole Using a split punch having a diameter equal to the outer diameter of the boss of the product to be obtained as the upper punch and being divided into an outer punch and an inner punch, and having a pressing surface of the inner punch of 90% or less of the boss height of the product to obtain the pressing surface In the initial setting state in which the outer punch is retracted from the pressing surface of the outer punch within the range, the pressing by both the inner and outer punches is started, and then the pressing by the outer punch is continued as it is, while the pressing by the inner punch is performed on the pressing surface. Is the initial setting A bossed gear that releases the pressurization by the inner punch after maintaining a predetermined tool surface pressure until it is retracted by a certain distance from, and continues pressurization by the outer punch even after the pressurization of the inner punch is released Molding method. 2. The method for forming a bossed gear according to claim 1, wherein the pressing is performed with the pressing surface of the inner punch advanced beyond the pressing surface of the outer punch before the pressing by the inner and outer punches is started. 3. The average tool surface pressure obtained by dividing the predetermined tool surface pressure by 2.5 times the deformation resistance of the workpiece or the load applied to the lower punch by the pressure receiving area of the lower punch is 0.80.
The method for forming a bossed gear according to claim 1 or 2, wherein the number is not more than twice. 4. A closed die having a die in which a die corresponding to the external teeth of the product is formed on the inner peripheral surface of the die hole, a main punch for closing the die hole of the die, and a lower punch, When forming a bossed gear having a boss on one end face by pressing the work material arranged in the die hole of the die mainly with the main punch and completely filling the work material to every corner of the die hole Using a split punch divided into an outer punch and an inner punch with a diameter equal to the outer diameter of the boss of the product to be obtained as the upper punch, and matching the pressing surfaces of the inner and outer punches or the pressing surface of the inner punch. Pressing by both the inner and outer punches is started in an initial setting state in which the outer punch is advanced beyond the pressing surface of the outer punch within a range of 30% or less of the boss height of the product to be obtained. ,
Pressing by the inner punch is continued until the pressing surface retreats by a certain distance from the above-mentioned initial setting position. A method of forming a bossed gear that continues to pressurize with an external punch even after release. 5. The average tool surface pressure obtained by dividing the predetermined tool surface pressure by 2.15 times the deformation resistance of the workpiece or the load applied to the lower punch by the pressure receiving area of the lower punch.
The method for forming a bossed gear according to claim 4, wherein the gear is set to 0 times or less. 6. A method for forming a bossed gear according to any one of claims 1 to 5, wherein when a product to be obtained has a shaft hole provided with internal teeth, an inner punch is provided at a shaft center portion of the material to be processed. The outer diameter of the lower punch penetrating the shaft deep portion is equal to the above-mentioned shaft hole diameter, and a mandrel having a tooth pattern corresponding to the internal teeth of the product is disposed on the outer peripheral surface thereof. A method of forming a bossed gear, in which after the pressurization by the punch is completed, the outer punch is retracted, and then the inner punch is repressurized with a tool surface pressure of 2.7 to 3.3 times the deformation resistance of the workpiece. 7. The method for forming a bossed gear according to claim 6, wherein the re-pressing by the inner punch is performed at 2.8 to 3.1 times the deformation resistance of the material to be processed.