JPH0566219B2 - - Google Patents

Description

[Detailed Description of the Invention] "Industrial Application Field" The present invention has a relatively thin thickness and has no boss portion.
Alternatively, the present invention relates to a forming method suitable for manufacturing a gear in which the diameter of the boss portion is smaller than the root of the tooth, and a member having a similar shape to the gear, by cold forging.

``Conventional technology'' Conventionally, in cold forging, gears with relatively thin thickness and small or no boss portions are extruded by sealing slag in a die, because it is difficult for the material to flow to the tooth tips. It was extruded from a slug with a diameter larger than the tip diameter of the tooth, and finished by cutting the excess material on the top and bottom.

"Problems to be Solved by the Invention" The conventional method described above has a large cutting allowance, requires a long time for cutting, and wastes a lot of material. Furthermore, when the tooth profile is large and the area reduction rate is large, even with this method, there are problems such as difficulty in material flowing to the tooth tip, resulting in high molding load and mold breakage. The reason why it is not possible to create a sealed structure with no material cutting allowance is because in the case of gears, the cross-sectional area gradually decreases from the tooth base to the tooth tip, so the confinement rate of the extruded material increases as it goes toward the tooth tip. This is because if the load suddenly increases and the press is pressed even harder, the mold will be damaged.

The purpose of the present invention is to eliminate these drawbacks, and by providing a volume division process to obtain the necessary material for the tooth tip and a sizing process that produces a good molded shape with little excess material, processing can be performed using a press with a small capacity. Therefore, it is an object of the present invention to provide a method for molding gears and similar products, which has good molding accuracy, easy finishing cutting, no waste of material, and easy molding even when a boss is provided.

"Means and effects for solving the problem" The method of the present invention involves restraining the outer periphery of a cylindrical slug (material) at one end, pressing it in the axial direction, and then pressing the cylindrical slug (material) in the axial direction with the gear at the other end. The tooth profile is parallel to the radial direction and the tip direction is open, one or both sides are perpendicular to the axial direction at the center, and the outer periphery of the tooth profile is perpendicular to the axis as the outer circumference approaches. A semi-finished product is produced through a volume division process in which it is extruded into a cavity consisting of a surface that gradually opens from the top, and has an inner peripheral part with a tooth profile of the same shape as the product, and a small tooth profile with a required gap from the tooth profile of the product. Extrusion molding is performed in the axial direction in a closed chamber consisting of a flat surface that receives one side surface with an open gap and a flat surface that has the same tooth profile as the product and receives the other side surface, leaving some extra thickness in the gap between the tooth profiles. The product is completed in a sizing process to obtain the required tooth profile.

In the volume dividing process, the tooth profile has a parallel shape parallel to the radial direction and is sloped toward the outer periphery to make the material flow easier, and the thickened outer periphery is extruded to be thinner in the sizing process. It is easy to mold because it forms a tooth shape.
By adjusting the volume of the semi-finished product, excess metal can be reduced and the tooth profile can be completed accurately.

"Example" In FIGS. 1 to 3, processing steps of the present invention are shown. The cylindrical slug 1 shown in FIG. 1 is divided into volumes to produce the blank 2 shown in FIG. 2. The semi-finished product 2 has the same number of teeth as the product (gear), has a parallel part 3 whose tooth profile is parallel to the radial direction, has a free-form tooth tip formed by extrusion molding, and has one side, the lower side in figure b. is a flat surface, the other sides, the upper surface in FIG.

Next, this semi-finished product 2 is extruded into a molded product 5 shown in FIG. 3 in a sizing process. The outer shape of the molded product 5 in the circumferential direction is precisely molded to be equal to the outer shape of the product (gear), and there is a minimum amount of excess thickness 6 on the lower surface side between the solid line and the dotted line in figure a, as shown in figure b. is sticking out. The thickness between the upper and lower surfaces is the product (gear)
The thickness should be approximately equal to that of , or some allowance should be made for cutting. The product (gear) is completed by removing the excess thickness 6 of the molded product 5 by cutting.

FIG. 4 and FIG. 5 show an example of a mold for carrying out the volume dividing step and sizing step of the present invention.

In the mold 7 used in the volume dividing process shown in FIG. 4, a die 10 having a notch with a side surface 3 parallel to the lower mold 8 and a counter punch 9 that fits the die are installed upright, and a cut is made in the die. A slug 1 that is equal to or slightly smaller than the inscribed circle diameter 15 of the notch is introduced, and a punch 11 that fits concentrically with the die 10 is lowered and extruded into the cavity 14 to produce a semi-finished product 2. As shown in figure b, the hole of the die 10 has a closed shape with a semicircular part and a parallel part which is a slight extension of the parallel part 3 in the tooth tip direction of the blank product 2, and when the blank product 2 is molded. An extra space 16 is left in the direction of the tooth tip. The punch 11 fits into the hole of the die 10, and also has a lower surface of a central part recessed from the upper end surface of the counter punch 9 by the thickness of the blank 2, and a riser from this center that fits the upper surface of the tooth profile of the blank 2. An inclined surface 13 is provided.

Mold 1 used in the sizing process shown in Figure 5
8 is provided with a die 20 having a hole of the same shape as the outer shape of the product (gear) in the lower mold 19, and a gap 21 that fits concentrically with the die 20 and is shown in Figure b between the inner periphery of the tooth profile of the hole of the die 20. A counter punch 22 having a tooth profile is installed vertically, and a punch 24 having an outer shape that fits the hole of the die 20 is installed vertically on the upper die 23, and the blank 2 is inserted into the hole of the die 20 as shown in Fig. c. The molded product 5 is manufactured by supplying it as shown in FIG.

Note that instead of providing the gap 21 on the side surface of the molded product 5, it may be provided in the direction of the tooth tip, and the excess material 6 may be made to protrude in the direction of the tooth tip.

"Effects of the Invention" As is clear from the above description, according to the present invention, both sides of the tooth profile in the radial direction are made parallel in the volume dividing process, the tooth tip direction is open, and the slope becomes thicker toward the tooth tip. The load is small,
Since the material flows easily, the press capacity is small and there is no heavy burden on the mold. In the sizing process, the semi-finished product of this process is extruded in the thickness direction and the thickened tooth tips are pressed to form the tooth profile, resulting in good molding accuracy of the tooth profile and improved product accuracy. In addition, it is easy to adjust the excess thickness to make it smaller, which facilitates cutting and finishing in the post-process, and reduces waste of material. This process can be carried out as a partial process, so the load is small and the press capacity is small. Therefore, no excessive load is applied to the mold, resulting in a long life. It has great practical effects and advantages.

[Brief explanation of the drawing]

Figure 1 shows the slag (raw material), Figure 2 shows the semi-finished product produced in the volume dividing process, and Figure 3 shows the molded product produced in the sizing process, with figure a being a plan view and figure b being a front view. Figure 4a is a vertical sectional front view of the mold in the volume dividing process, Figure b is a cross-sectional view of Figure a, Figure 5 a is a vertical front view of the mold in the sizing process, and Figure b is a cross-sectional view of Figure A. Figures 1 and 2 are plan views of main parts showing a state in which a semi-finished product is supplied to the die. 1 is a slag, 2 is a semi-finished product, 3 is a parallel part, 4 is an angle of inclination, 5 is a molded product, 6 is extra thickness, 7 is a mold, 8 is a lower mold, 9 is a counter punch, 10 is a die, 11
is a punch, 12 is an upper mold, 13 is an inclined surface, 14 is an empty space, 15 is a diameter of the inscribed circle of the notch, 16 is an extra space, 18 is a mold, 19 is a lower mold, 20 is a die, 2
1 is the gap, 22 is the counter punch, 23 is the upper die,
24 is punch.

Claims (1)

[Claims] 1 A cylindrical slug is pressed in the axial direction by constraining the outer circumference of one end, and the other end has a tooth profile with the same number of teeth as the product, parallel to the radial direction, and open in the tooth tip direction. A semi-finished product is made by extrusion molding into a cavity in which the side or two sides have a central part that is perpendicular to the axis and a toothed part that is spaced from a surface that is perpendicular to the axis by about the outer circumference. One side is flat and the other side is smaller than the outer shape of the product by the gap where the outer circumference of the tooth profile is, and the gap is open. Characteristic gear molding method.