JP2881385B2 - Molding method of metal molded product with toothed ridges - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding method for molding a metal molded article having toothed ridges such as splines and gear teeth. INDUSTRIAL APPLICATION This invention is applicable to the gear component used for the transmission of vehicles, for example.

[0002]

2. Description of the Related Art A gear part 1 (see FIG. 13) used for a vehicle transmission, for example, has been conventionally known as a metal molded product having toothed ridges. On the outer peripheral portion of the gear component 1, a number of splines 14 extending in the axial direction are arranged in rows at intervals in the circumferential direction.

When such a gear part 1 is formed by forging, as shown schematically in FIG. 14, a cylindrical carbon steel rough member 700 and a die 200 having a die hole 201 are formed.
And a mandrel 400 arranged substantially coaxially in the die hole 201 of the die 200, and a punch 550 that can be lowered toward the die hole 201. Then, by lowering the punch 550, the cylindrical coarse material 700 is inserted into the ring-shaped gap between the inner peripheral portion of the die hole 201 of the die 200 and the outer peripheral portion of the mandrel 400.
Press with force.

As a result, the die hole 20 of the die 200 is formed.
In the gap of the forming groove 270 formed in the inner peripheral portion
The material portion of the rough shaped material 700 flows in, and the plurality of splines 14 described above are formed. The die 200 is formed of a super hard material so as to withstand the load at the time of the spline molding. Further, the die 200 is pressed into the holding hole 600w of the die holding die 600 or shrink-fitted to be firmly attached to the die holding die 600. Is held.

[0005]

In recent years, there has been a demand for further improvement in dimensional accuracy of the spline 14. Even in the tooth trace direction of the spline 14, that is, in the axial length direction,
There is a demand for further improvement in dimensional accuracy. The present invention has been made in view of the above-described circumstances, and an object thereof is to form a tooth-shaped ridge such as a spline on a metal molded product.
It is an object of the present invention to provide a method of forming a metal molded product that is advantageous in ensuring dimensional accuracy of a toothed ridge such as a spline in a direction of a tooth ridge.

[0006]

The inventor of the present invention has found that when forming a tooth-shaped ridge such as a spline, the material of the coarse material 700 is filled in the die hole 201 of the die 200.
Flows in the direction of the arrow M1 in the forward direction of the back portion 201a of the die 200. Therefore, although there is little urging in the radially outward direction, that is, the direction of the arrow Q1 in the vicinity of the back portion 201a, the punch facing surface 203 which is the upper surface of the die 200 facing the punch 550. In the vicinity, the bias in the radial direction, that is, the direction of the arrow Q1 is large. Therefore, the radial bias in the vicinity of the punch facing surface 203 lowers the dimensional accuracy of the spline or the like in the tooth ridge direction. We paid attention to this factor. And if this is corrected, in view of the fact that the dimensional accuracy in the tooth lead direction of the tooth-shaped ridge such as a spline can be further secured,
The present invention has been completed.

That is, according to the method of forming a metal molded product having tooth-shaped protrusions according to the present invention, a plurality of tooth-shaped protrusions are arranged at an outer peripheral portion at intervals in a circumferential direction and extend in parallel with an axial direction. Is a method of obtaining a metal molded product having a metal rough part, and a die hole for restraining an outer peripheral part of the coarse part, and formed in an inner peripheral part of the die hole in a direction parallel to the axial direction. A die having a group of forming grooves formed of a number of forming grooves for forming tooth-shaped protrusions of an elongated metal molded product, a punch facing surface located on the side where the coarse material is pushed, and a die hole of the die. A constraining wall that is disposed substantially coaxially with the constraining portion and that constrains the inner peripheral portion of the coarse material; and a cavity that is formed on the opposing surface of the constraining wall and that is capable of elastically displacing at least a portion of the constraining wall in a radially inward direction. And a mandrel with a part, and are arranged at a position facing the punch-facing surface of the die, By using a punch movable toward the die hole of the chair, and moving the punch toward the die hole of the die, a ring-shaped gap between the inner peripheral portion of the die hole of the die and the constraint wall of the mandrel is formed. A large number of toothed ridges extending in a direction parallel to the axial direction are formed on the outer peripheral portion of the rough material by a group of forming grooves of a die, and the hollow portion of the mandrel is formed. Is characterized in that at least a part of the restraint wall defining the elastic member is elastically displaced in a radially inward direction of the mandrel.

[0008]

According to the method of the present invention, by moving the punch toward the die hole of the die, the coarse material is filled in the ring-shaped gap between the inner peripheral portion of the die hole of the die and the restraining wall of the mandrel. Press hard. As a result, the material of the coarse material flows into the space defined by the forming groove of the die.
Therefore, a number of tooth-shaped ridges such as splines are formed on the outer peripheral portion of the rough material by the formed groove.

According to the method of the present invention, since the hollow portion is formed in the mandrel, at least a part of the constraint wall of the mandrel is allowed to elastically displace radially inward of the mandrel. Therefore, when molding the toothed ridge,
When the molding resistance of the material becomes excessive, at least a part of the constraint wall of the mandrel is elastically displaced radially inward. As a result, the molding resistance is prevented from becoming excessive. Therefore, according to the method of the present invention, the factor that reduces the dimensional accuracy of the tooth-shaped ridges, that is, the urging in the radial direction near the punch facing surface of the die is reduced or avoided.

According to the method of the present invention, the elastic displacement of the mandrel in the radial direction is allowed as described above.
There is a possibility that the inner diameter of the inner peripheral part of the metal molded product may fluctuate,
In the case of a metal molded product in which the inner diameter of the inner peripheral portion does not require strict dimensional accuracy, the inner peripheral portion may be left as it is, or in the case of a metal molded product requiring dimensional accuracy of the inner diameter of the inner peripheral portion In this case, the inner peripheral portion may be cut to a specified inner diameter.

[0011]

EXAMPLES Examples of the molding method of the present invention will be specifically described. (Embodiment 1) First, a gear part 1 as a metal molded product will be described with reference to FIG. The gear component 1 is the same as the gear component described in the related art, is used for an automatic transmission of an automobile, and is made of carbon steel.

As shown in FIG. 13, the gear part 1 has a cylindrical body 10, a flange 11 extending in the centrifugal direction integrally with the cylindrical body 10, and a large-diameter cylinder extending from the flange 11 in the axial direction. State body 12. The large-diameter cylindrical body 12 is coaxial with the cylindrical body 10 and is larger in diameter than the cylindrical body 10. In this embodiment, the intermediate molded body 8 to be the gear component 1 is molded. FIG. 1 shows a main part of the intermediate molded body 8. FIG.
Indicates the bottom surface of the intermediate molded body 8. The intermediate molded body 8 has a shape substantially similar to the gear component 1. Here, the intermediate molded body 8 is provided with a large number of splines 14 on its outer peripheral part, and the inner peripheral part 8i of the intermediate molded body 8 is cut and removed at a predetermined depth over the entire circumference to form the gear part 1 and the spline 14. I do.

That is, as shown in FIG. 1, a spline 14 as a toothed ridge is formed on the outer peripheral portion of the intermediate molded body 8. A large number of splines 14 are provided at intervals along the circumferential direction of the intermediate molded body 8, that is, in the direction of arrow R1 (total number of teeth 4).
7; 4 missing teeth). As can be understood from FIG. 1, the spline 14 has a substantially trapezoidal cross section.
The axial direction of the intermediate molded body 8 serving as the gear part 1, ie, the arrow P
It extends parallel to one direction. As can be understood from FIG. 1, the spline 14 is formed by a pair of opposing surfaces 14 facing each other.
a and an outer end surface 14b connecting the back surface 14a. The back surface 14a is defined by an involute curve, but is not limited to this.

As can be understood from FIGS. 1 and 2, in the intermediate molded body 8, there is a missing tooth region 16 in which the splines 14 are not formed. That is, the spline corresponding to the first position which is the reference position indicated by the arrow M1 in FIG. 2 does not exist and is defined as the toothless region 16, and the spline corresponding to the twelfth indicated by the arrow M2 does not exist and the toothless region 16 is defined. In addition, the spline corresponding to the 24th position indicated by the arrow M3 does not exist and is defined as the missing tooth region 16, and the spline corresponding to the 35th indicated by the arrow M4 does not exist and the missing tooth region 16 is defined.

In this gear part 1, the missing tooth region 1
6 is used in the following manner, for example. That is, an appropriate number of oil holes penetrating in the thickness direction are formed in the toothless region 16. When the gear component 1 is used, hydraulic fluid flows in through the oil hole due to the generated centrifugal force. It is preferable that there is no spline in the formation of the oil hole. However, the missing tooth region 16
Is not limited to this.

In FIG. 1, the target dimensions in the vicinity of the spline 14 are as follows: the thickness A of the spline 14 in the circumferential direction near the tooth bottom of the spline 14 is 4.81 mm;
6, the interval B between the tooth roots in the circumferential direction is 8.03 mm,
The outer diameter C is 96 mm, and the inner diameter E is 83.7 mm. Next, the main part of the forging device used in this embodiment will be described with reference to FIG. In FIG. 3, the die 2 is provided with a die hole 20 in the center area thereof, and defines and restricts the outer peripheral portion of the coarse material 7. The die hole 20 has a ring-shaped enlarged concave portion 22 on the upper surface opening side. The enlarged diameter concave portion 22 has a ring-shaped tapered surface 22e, a ring-shaped vertical wall surface 22f, and a ring-shaped bottom surface 22k. Dice 2
Is the punch facing surface 29 that faces the punch 55 before descending.

Further, ring-shaped pressure-resistant panels 30, 31 are arranged on the lower bolster side (not shown) of the forging apparatus. Further, a ring-shaped holder 33 is disposed on the lower bolster side of the forging device (not shown), and the die 2 is fitted and held in the holder 33. By attaching the ring-shaped holding plate 34 to the holder 33 with bolts 35, the dies 2
0 is fixed to the upper surface side.

The mandrel 4 has a substantially cylindrical shape, and the die 2
Are substantially coaxially arranged in the die hole 20 for defining and constraining the inner peripheral portion of the coarse material 7. A ring-shaped gap 44 including the enlarged diameter concave portion 22 is formed between the inner peripheral portion of the die hole 20 of the die 2 and the outer peripheral portion of the mandrel 4. The gap 44 serves as a molding cavity for molding the intermediate molded body 8 to be the gear component 1.

As shown in FIG. 3, the mandrel 4 and the die 2
And a knockout sleeve 50 for releasing, a knockout pin 5 for pushing up the knockout sleeve 50.
2 are arranged. Knockout pin 52 passes through pin passage 57 formed in mandrel 4. Further, a substantially cylindrical punch 55 functioning as a pressing die is held on the upper voltastatic side of the above-described forging device, which can be raised and lowered, and ring-shaped pressing plates 56 and 57 surrounding the punch 55 are held. Have been. At the tip of the punch 55, a ring-shaped pushing portion 55c that defines the concave portion 55a is formed. As shown in FIG. 3, the concave portion 55a is fitted to the distal end portion of the mandrel 4, thereby performing mutual positioning.

FIG. 4 shows a main part in a state where the mandrel 4 is inserted into the die hole 20 of the die 2. As can be understood from FIG. 4, a group of molding grooves 26 is formed in the inner peripheral portion of the die hole 20 of the die 2 described above. The forming groove group 26 is formed in the inner peripheral portion of the die hole 20 in a circumferential direction, that is, an arrow R1.
Formed grooves 2 formed at predetermined intervals along the direction
Consists of seven. The forming groove 27 is formed by the spline 14 described above.
And extends in the axial direction of the die 2, that is, in a direction parallel to the direction of the arrow P1. The molding groove 27 is
A pair of mold surfaces 27a facing each other, and a pair of mold surfaces 27a
And a mold surface 27b connecting the two.

5 to 7 show the mandrel 4. FIG. FIG.
Is a sectional view taken along line W3-W4-W5 of FIG. FIG.
FIG. 6 is a view as seen from the direction of arrow W1 in FIG. FIG. 7 is a view as seen from the direction of arrow W2 in FIG. As shown in FIG. 5, the outer peripheral portion of the mandrel 4 is
It is set to 4. A cylindrical cavity 46 is defined at the tip of the restraint wall 44. The tip of the cavity 46 is an opening 46a that is open outward.
The cavity 46 is defined by a bottom surface 46e and a ring-shaped inner wall surface 46f. Because of the hollow portion 46, the tip end side of the restraint wall 44 can be elastically displaced minutely in the radial direction, that is, in the direction of arrow J1.

FIG. 8 shows a cross section of a main part of the cylindrical rough member 7. The rough material 7 is obtained by hot forging a steel material (for example, S45C) into a predetermined rough land shape by hot forging. The coarse material 7 includes a rough cylindrical body 70 and a rough cylindrical body 7.
0 and a coarse flange portion 71 extending in the centrifugal direction integrally.
And a large-diameter, large-diameter cylindrical body 72 extending in the axial direction from the rough flange portion 71. The rough cylindrical body 70 corresponds to the cylindrical body 10 of the gear component 1. The rough flange portion 71 corresponds to the flange portion 11 of the gear component 1, and has a shape similar to the flange portion 11 of the gear component 1.
Has dimensions. The large-diameter large-diameter cylindrical body 72 corresponds to the large-diameter cylindrical body 12 of the gear component 1 and has a shape and dimensions similar to those of the large-diameter cylindrical body 12 of the gear component 1.

In FIG. 8, according to the rough material 7, the inner diameter Da of the rough cylindrical body 70 is 83.8 mm, the outer diameter Db of the rough cylindrical body 70 is 100.2 mm, and the coarse cylindrical body 72 is large. Inner diameter D
c is 108 mm, and the outer diameter Dd of the large-diameter large cylindrical body 72 is 11
8 mm is a target value. The inside diameter and outside diameter mean the diameter. 8, in the present embodiment, the large diameter D4 (inner diameter) of the portion corresponding to the valley of the forming groove 27 of the die 2 is:
The value approximates the outer diameter Db of the coarse material 7, that is, 9
9.785 mm is set as the target value. The small diameter D5 (inner diameter) of the portion corresponding to the peak of the formed groove 27 is 95.786 m.
m is a target value. Vertical surface 22t of enlarged diameter concave portion 22
The target value of the inner diameter D3 is 118 mm. The outer diameter D6 of the mandrel 4 is a value approximating the inner diameter Da of the coarse material 7 and is 83.7 mm.

In the pressing step of this embodiment, as shown in FIG. 8, the inner peripheral portion of the die hole 20 of the die 2 and the mandrel 4
The rough cylindrical member 70 of the cylindrical rough member 7 faces the ring-shaped gap 44 between the outer peripheral portion of the cylindrical member and the cylindrical member 70. Then, in this state, the forging device (not shown) is driven to lower the punch 55 in the direction of arrow Y1 as shown in FIG. Then, punch 5
The rough shaped material 7 is strongly pressed by the ring-shaped pushing portion 55c of 5, and the rough shaped material 7 is forcibly pushed into the gap 44 between the die 2 and the mandrel 4. This pushing step is performed in a cold state in which the crude material 7 is at a normal temperature.

In the pressing step, the material of the rough cylindrical body 70 of the rough material 7 is mainly
The air flows into the gap defined by 7 in the direction of arrow N1 (see FIG. 9). As a result, a large number of splines 14 are formed on the outer peripheral portion of the crude material 7 by the mold surfaces 27a and 27b of the forming groove 27. The spline 14 has a shape substantially similar to the shape of the groove 27 and extends in the axial direction, that is, the direction parallel to the direction of the arrow P1 (see FIG. 1).

In such a pressing step, the punch facing surface 29 of the die 2 tends to be urged radially outward, that is, in the direction of the arrow J2 (see FIG. 9), and this is the dimensional accuracy of the spline 14 in the direction of the tooth trace. Is a factor in the decline of In this respect, in this embodiment, the mandrel 4
Is formed with a hollow portion 46, so that the distal end side of the restraint wall 44 is allowed to elastically displace in the radially inner direction, that is, the direction of the arrow J1. Therefore, when the molding resistance of the material becomes excessively large and the punch facing surface 29 side of the die 2 is urged in the radially outward direction (the direction of arrow J2), the tip end side of the restraining wall 44 is in the radially inward direction. It is elastically displaced in the direction of arrow J1. Therefore, the punch-facing surface 29 side of the die 2 is reduced or avoided from being biased in the radial direction, that is, in the direction of the arrow J2. Therefore, the dimensional accuracy of the spline 14 in the tooth trace direction is ensured.

After the intermediate molded body 8 is formed as described above, the punch 55 is lifted in the direction of arrow Y2 to be separated from the die 2, and the knockout pin 52
Is pushed up to push up the knockout sleeve 50, whereby the intermediate molded body 8 is taken out from the die hole 20 of the die 2. Thereafter, the intermediate molded body 8 is set in a cutting machine in order to perform a removing step. Then, the inner peripheral portion 8i of the intermediate molded body 8 is cut and removed by a predetermined depth using a cutting tool of the cutting machine. Thus, the gear component 1 having the spline 14 is formed from the intermediate molded body 8.

(Test Example) In the above embodiment, as described above, the large diameter D4 (inner diameter) of the forming groove 27 of the die 2 is set to 9
To 9.785 mm, small diameter D5 (inner diameter) is 95.786 m
m. Further, two kinds of inner diameters of the hollow portion 46 of the mandrel 4 were set at 50 mm and 60 mm. The taper angle of the constraint wall 44 of the mandrel 4 is set to 1 degree. In the molding according to this embodiment, the variation in the tooth trace direction of the large diameter dimension of the spline 14 (corresponding to the large diameter D4 of the forming groove 27) was tested.

FIG. 10 shows the test results. The horizontal axis in FIG. 10 indicates the position of the spline 14 in the axial length direction, that is, in the tooth trace direction. The vertical axis of FIG. 10 indicates a large diameter dimension of the spline 14. In FIG. 10, ○ indicates that the inner diameter of the hollow portion 46 of the mandrel 4 is 50 mm, Δ indicates that the inner diameter of the hollow portion 46 of the mandrel 4 is 60 mm, and F indicates that the spline 14 is within the standard dimensions.

As shown by the characteristic line in FIG.
Even when the inner diameter of the hollow portion 46 is 50 mm,
Even in the case of mm, it was confirmed that the large diameter dimension of the spline 14 was within the standard dimension F1. Further, it was confirmed that even when the position of the spline 14 in the tooth streak direction changed, the large diameter dimension was within the standard dimension F1.

(Embodiment 2) Next, Embodiment 2 will be described. This example has a configuration basically similar to that of the first embodiment.
Therefore, a cavity 46 is formed at the tip of the mandrel 4. In this example, the same operation and effect as those of the first embodiment can be obtained. Hereinafter, points different from the first embodiment will be mainly described.

In this example, as in the first embodiment, there is a missing tooth region 16 where no spline 14 is formed. Since the spline 14 is not formed in the missing tooth region 16 in this way, the material portion of the coarse material 7 corresponding to the missing tooth region 16 becomes extra, and there is essentially no place to go.
Therefore, the extra material due to the missing tooth region 16 is likely to be burr. This example addresses such a problem.

In this example, as shown in FIG. 11, a relief groove 47 is formed in the outer peripheral portion 4x of the mandrel 4. Escape groove 4
Reference numeral 7 extends along the axial direction of the mandrel 4. A total of four such grooves 47 are provided so as to face the above-mentioned four missing tooth regions 16 respectively, and are arranged so as to have the same phase as the missing tooth region 16 in the circumferential direction, that is, the direction of the arrow R1. As can be understood from FIG. 11, the escape groove 47 includes a pair of groove side surfaces 47a and 47b facing each other, and a groove bottom surface 47c connecting the pair of groove side surfaces 47a and 47b.
The direction of depression of the escape groove 47 is opposite to the direction of depression of the forming groove 27 formed in the die 2.

Also in this example, the pressing step is performed in the same manner as in the first embodiment, and the gap 44 between the die 2 and the mandrel 4 is formed.
Inside, the cold crude material 7 is forcibly pushed. In this pushing step, mainly the material of the rough cylindrical body 70 of the rough material 7 flows into the space defined by the forming groove 27 of the die 2, and a large number of splines 14 are formed.

Since the spline 14 is not formed in the missing tooth region 16, the material portion of the coarse material 7 corresponding to the missing tooth region 16 becomes extra as described above, and there is essentially no place to go. . Therefore, excess material due to the missing tooth region 16 flows into the escape groove 47 of the mandrel 4. As a result, a surplus relief projection 80 as shown in FIG. 12 is formed.
Therefore, in this example, the ring-shaped intermediate molded body 8 having the extra thickness relief projections 80 (a total of four) in addition to the splines 14 is formed. In the circumferential direction, that is, in the direction of arrow R1,
The surplus relief projection 80 and the missing tooth region 16 are substantially in phase.

FIG. 12 is an enlarged view of the vicinity of the extra thickness relief projection 80. In FIG. 12, imaginary lines T1 and T2 extend in the radial direction of the intermediate molded body 8 and virtually connect the roots of the end surfaces 80h and 80i in the circumferential direction of the surplus relief projection 80 to the center axis of the intermediate molded body 8. Line. As shown in FIG. 12, one end face 80 h of the extra thickness relief projection 80 in the circumferential direction
(From another viewpoint, the groove side surface 47a of the escape groove 47) is located inside the imaginary line T1 by an angle α. Similarly, the other end surface 80i (from another viewpoint, the groove side surface 47b of the escape groove 47) is also at an angle β (α = β) greater than the imaginary line T2.
It is located inside.

In this example, let SA be the cross-sectional area of one surplus relief projection 80 (ie, the cross-sectional area of the escape groove 47).
Assuming that the cross-sectional area of each of the splines 14 (that is, the cross-sectional area of the formed groove 27) is SB, according to a test performed by the present inventor, in order to avoid burrs, the relationship between the two is SB ≦ SA.
It is preferred that Also in this example, after forming the intermediate molded body 8 provided with the excess thickness relief projection 80, the punch 55 is lifted in the direction of arrow Y2 to be separated from the die 2, and the knockout pin 52 is pushed up to push the knockout sleeve. The intermediate body 8 is taken out from the die hole 20 of the die 2 by pushing up 50.

Thereafter, the intermediate molded body 8 is set in a cutting machine in order to carry out a removing step. Then, the surplus relief projection 80 of the intermediate molded body 8 is cut by the cutting tool of the cutting machine.
To remove. In this case, a mode in which the entire inner peripheral portion 8i of the intermediate molded body 8 including the excess thickness relief projection 80 is cut and removed by a predetermined depth may be adopted. Alternatively, the extra relief projection 8
A configuration in which only 0 is removed by cutting may be adopted. Thus, the gear component 1 having the spline 14 is formed from the intermediate molded body 8.

In this example, as shown in FIG.
In a case where the groove depth of the groove 7 is K1 and the groove width of the escape groove 47 is L1, the inventors of the present invention have conducted tests and found that even if the groove depth K1 is large, the burr becomes smaller as the groove width L1 becomes smaller. It was confirmed that burrs are more likely to occur, and that even when the groove depth K1 is small, burrs are less likely to occur as the groove width L1 increases.

However, when the groove width L1 is excessively large, the material portion which should flow into the forming groove 27 and originally form the spline 14 may not easily flow into the forming groove 27. In this sense, making the groove width L1 excessively large is
Not preferred. Therefore, as shown in FIG. 12, between the end face 80 h of the excess thickness relief projection 80 and the root of the spline 14,
It is preferable to set an interval of ΔL.

From the test results performed by the inventor, it was found that in the spline 14 according to the present embodiment, the groove width L1 of the escape groove 47 is preferably about 6 mm and the groove depth K1 is preferably about 2 mm. (Other Examples) In the above-described embodiment, the number of missing tooth regions 16 is four, but the number is not limited to this, and may be smaller or larger.

In the above-described embodiment, the tooth-shaped ridges are applied to the molding of the spline 14, but may be applied to a shape other than the spline. For example, a form in which the teeth are applied to gear teeth extending in the axial direction may be used. It is needless to say that the present invention is not limited to the dimensional relationship described above, and can be changed as needed.

The above-mentioned example is an example applied to forging, but is not limited to this, and is applied to an extrusion molding apparatus for forming a spline by extruding a rough material using an extrusion die and a mandrel. You can also. Others
The present invention is not limited to only the embodiments described above and shown in the drawings, but can be appropriately selected as needed without departing from the gist.

(Supplementary Note) The following technical idea can be understood from the above embodiment. 2. The method according to claim 1, wherein the mandrel is provided with a relief groove arranged substantially in the same phase as the toothless region in the circumferential direction, and the excess material of the coarse material is poured into the relief groove, and the excess material is formed in addition to the spline. A method of forming a metal molded product having tooth-shaped ridges, wherein a relief projection is formed. According to this method,
This is advantageous in reducing or avoiding that the material portion that becomes excess becomes burrs. Therefore, it is advantageous for reducing and avoiding flaws caused by burrs.

[0045]

According to the method of the present invention, since the hollow portion is formed in the mandrel, at least a part of the restraining wall is allowed to elastically displace radially inward of the mandrel. Therefore, when molding the toothed ridge, a factor that reduces the dimensional accuracy of the toothed ridge in the tooth lead direction, that is, the urging in the radial direction near the punch facing surface of the die is reduced or avoided. You. Therefore, the elastic deformation near the punch-facing surface of the die having the forming groove for forming the spline is reduced and avoided.

Therefore, according to the method of the present invention, it is advantageous to secure the dimension of the tooth-shaped ridge in the tooth lead direction with high accuracy.

[Brief description of the drawings]

FIG. 1 is a perspective view of the vicinity of a spline of an intermediate molded body serving as a gear component.

FIG. 2 is a bottom view of the intermediate molded body.

FIG. 3 is a longitudinal sectional view of a main part of the forging device.

FIG. 4 is an enlarged perspective view of a main part showing a state where a mandrel is inserted into a die hole of the die.

FIG. 5 is a cross-sectional view of the mandrel along W3-W4-W5 in FIG. 7;

FIG. 6 is a view of FIG. 5 as viewed from the direction of arrow W1.

FIG. 7 is a diagram of FIG. 5 viewed from the direction of arrow W2.

FIG. 8 is a cross-sectional view showing a state in which a coarse material is positioned above a die.

FIG. 9 is a cross-sectional view showing a state in which a coarse material is pressed into a die hole of a die by a punch.

FIG. 10 is a graph showing a change in a large-diameter dimension of a spline in a spline direction of a spline.

FIG. 11 is an enlarged perspective view of a main part showing a state where a mandrel is inserted into a die hole of a die according to the second embodiment.

FIG. 12 is a configuration diagram of a main part in the vicinity of a spline and a surplus relief projection according to the second embodiment.

FIG. 13 is a perspective view of a gear component provided with splines showing a partially cut state.

FIG. 14 is a cross-sectional view schematically showing a state in which a coarse material is pressed into a die hole of a die by a punch according to a conventional technique.

[Explanation of symbols]

In the drawing, 1 is a gear part (metal molded product), 14 is a spline (toothed ridge), 16 is a missing tooth region, 2 is a die, 26 is a group of forming grooves, 27 is a forming groove, and 29 is a punch facing. The surface, 4 is a mandrel, 44 is a restraining wall, 46 is a cavity, 55 is a punch, 7 is a coarse material, and 8 is an intermediate molded body.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B21K 1/30 B21J 5/12

Claims (1)

(57) [Claims] 1. A method for obtaining a metal molded product having a plurality of toothed ridges arranged in the outer peripheral portion at intervals in a circumferential direction and extending in parallel with an axial direction, comprising the steps of: A plurality of die-shaped holes formed in the inner peripheral portion of the die hole and extending in a direction parallel to the axial length direction to form the tooth-shaped ridge of the metal molded product; A die having a group of forming grooves composed of the above-mentioned forming grooves and a punch-facing surface located on the side into which the coarse material is pressed; and a die substantially coaxially arranged in a die hole of the die. A mandrel having a restraining wall for restraining an inner peripheral portion of the restraining wall, and a cavity formed on the side of the restraining wall facing the punch and capable of elastically displacing at least a part of the restraining wall in a radially inward direction; It is arranged at a position facing the punch facing surface of the die,
By using a punch movable toward the die hole of the die, and moving the punch toward the die hole of the die, an inner peripheral portion of the die hole of the die and a restraining wall of the mandrel are formed. A large number of tooth-shaped ridges extending in a direction parallel to the axial length direction to the outer peripheral portion of the coarse material by a group of forming grooves of the die, by strongly pressing the coarse material into a ring-shaped gap between the dies. And forming at least a part of the constraint wall defining the cavity of the mandrel elastically in a radially inward direction of the mandrel. .