JP2828146B2 - Extrusion molding method and apparatus for helical gear having shaft hole - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a molding method and an apparatus for extruding a helical gear having a shaft hole from a cylindrical material having a shaft hole.

"Prior art and its problems" Conventionally, in the production of helical gears, a generating cutting method using a hobbing machine is mainly used, and other rolling methods have been proposed. The hobbing process performed while escape lead determined by the helix angle β and the pitch circle diameter d _o of the tooth trace, there are inevitable, such as poor problem of the material yield due to generation of chips. on the other hand,
In cold rolling, it is difficult to form gears with a large gear,
Hot rolling requires strict temperature control, which is a factor that makes hot rolling not immediately applicable to actual production.

[Object of the Invention] An object of the present invention is to solve such a problem and to obtain a method and an apparatus capable of forming a helical gear having a shaft hole with high productivity and high precision by extrusion molding. And Another object of the present invention is to provide an extrusion molding method capable of simultaneously forming a shaft hole into both a simple hole and a shaft hole having internal teeth.

SUMMARY OF THE INVENTION In the present invention, when extruding a helical gear according to a tooth groove of a die on an outer surface of a cylindrical material having a shaft hole, a rotatable mandrel is fitted into the shaft hole of the cylindrical material. The mandrel has been completed based on the idea of performing the extrusion while rotating the mandrel according to the torsion angle of the skirt. As described above, it was confirmed that a high-precision helical gear can be formed by performing the extrusion while supporting the shaft hole portion with the mandrel and rotating the shaft hole portion according to the torsion angle.

According to one aspect of the present invention, a helical gear is formed by pressing a cylindrical material having a shaft hole against a die having a tooth groove of a helical gear on an inner peripheral surface and passing the die through the die. In the extrusion molding method for a helical gear having an axial hole, the rotation of the die is restrained, and the center of the die is freely rotated and does not change its axial position with the die during processing. Position the mandrel, and in this mandrel, a small diameter constant diameter shaft part that fits into the shaft hole of the cylindrical material, a tapered shaft part that expands the diameter of the shaft hole, and a large diameter corresponding to the shaft diameter after the diameter expansion. Providing a constant diameter shaft, the tapered shaft and the large diameter constant diameter shaft,
When extruding by passing the columnar material between the die and the mandrel according to the tooth groove of the die, the cylindrical material and the mandrel can be freely set according to the torsion angle of the tooth groove of the helical gear of the die. It is characterized in that a helical gear is machined on the outer peripheral surface of the columnar material while rotating.

In the tapered shaft portion and the large diameter constant diameter shaft portion of the mandrel, it is possible to form tooth grooves for forming internal teeth for forming internal teeth in the shaft holes of the cylindrical material, and the shaft of the cylindrical material is formed. The hole is
It passes through this tooth groove and is machined into a shaft hole having internal teeth.

According to another aspect of the present invention, a cylindrical material having a shaft hole is pressed against a die having a tooth groove of a helical gear on an inner peripheral surface thereof, and the helical gear is passed through the die. In the extrusion molding method for a helical gear having an axial hole, the rotation of the die is restrained, and the center of the die is freely rotated and does not change its axial position with the die during processing. Position the mandrel, and in this mandrel, a constant diameter shaft part that fits into the shaft hole of the cylindrical material and continues to the processing end position of the helical gear by the tooth groove of the die, and a smaller diameter that follows this constant diameter shaft part When the cylindrical material is extruded by passing the cylindrical material between the die and the mandrel according to the torsion angle of the helical It is characterized by processing while rotating the mandrel freely That.

The apparatus of the present invention for realizing the above-described method of the present invention includes a rotation-restricted die having a tooth groove for forming a helical gear on an inner peripheral surface of a cylindrical material having a shaft hole. A mandrel that is concentric with the die and fits in the shaft hole of the cylindrical material; a lower ram that is movable relative to the mandrel and rotatably supports the lower end of the mandrel; and between the die and the mandrel. The upper ram pressurizes the cylindrical material inserted into the die; the lower ram is held at a fixed value during the extrusion process, and the mandrel is rotatably supported without changing the axial position of the die with the die. A lower ram elevating mechanism for lowering the lower ram after processing is completed.

"Examples of the Invention" The present invention will be described below with reference to illustrated examples. FIG. 1 is a longitudinal sectional view showing an example of an apparatus for performing the method of the present invention. The extrusion die 10 has a die land portion 10a protruding from the inner peripheral surface thereof, and a tip end of the die land portion 10a has a tooth groove 10b and an inclined approach portion 10c reaching the tooth groove 10b. The extrusion die 10 is press-fitted into a reinforcing ring 12 together with an annular container 11 located thereon to form a mold device. Both the inner diameter of the annular container 11 and the inner diameter of the extrusion die 10 are the outer diameter d _{k of the} helical gear to be formed.
It corresponds to.

The reinforcing ring 12 is supported on a support 13 having a center hole 13a, and the support 13 is supported on another support 14. These extrusion dies 10, annular containers 11,
The reinforcing ring 12, the support 13 and the support 14 are aligned and connected to each other.

A mandrel 15 concentric with the extrusion die 10, the annular container 11, and the support 13 is located at the center.
As shown in FIG. 2 (A), the mandrel 15 has a small diameter constant diameter shaft portion 15a, a tapered shaft portion 15b, a large diameter constant diameter shaft portion 15c, and a small diameter shaft portion 15d in order from the top. . Small diameter constant diameter shaft
15a is set in a radial d _a which fits into the shaft hole 20a of the cylindrical material 20, the large径定diameter shaft portion 15c is formed in a radial d _c to be expanded processing. The tapered shaft portion 15b smoothly connects the small diameter constant diameter shaft portion 15a and the large diameter constant diameter shaft portion 15c. The small diameter shaft portion 15d has a smaller diameter d _d than the large diameter constant diameter shaft portion 15c.

This mandrel 15 is rotatable on the upper end of the lower ram 17,
And is detachably supported. That is, a thrust bearing 18 that rotatably and detachably supports the mandrel 15 is provided at the upper end of the lower ram 17. The lower ram 17 is supported by the support base 14 via a lifting mechanism 16 so as to be able to move up and down.
Tapered shaft part 15b and large diameter constant diameter shaft part 15c of mandrel 15
Is maintained at the localization value located at the die land portion 10a of the extrusion die 10.

In the extrusion die 10 and the annular container 11, a preceding cylindrical material 20 to be processed and a succeeding cylindrical material 20 are inserted, and further, an annular spacer 19 having a shaft hole is inserted. The annular spacer 19 receives a compressive load from the upper ram 21 of the press.

For example, in the apparatus configured as described above, extrusion molding of a helical gear is performed as follows. The compressive load transmitted by the upper ram 21 of the press is transmitted to the succeeding cylindrical material 20 and the preceding cylindrical material 20 via the annular spacer 19. Then, an extrusion die 10 is provided on the outer peripheral surface of the preceding cylindrical material 20.
The tooth is formed by the tooth groove 10b. At this time, since the tooth groove 10b of the die 10 is twisted by the twist angle β, the columnar material 20 is extruded while rotating according to the twist angle as the teeth are formed. On the other hand, the shaft hole 20 of the cylindrical material 20
At the same time, the diameter a is subjected to a diameter increasing process through the tapered shaft portion 15b and the large diameter constant diameter shaft portion 15c of the mandrel 15. Therefore, the mandrel 15 and the columnar material 20 are in strong frictional contact. Since the mandrel 15 is supported by the thrust bearing 18 and can rotate in response to torsion while supporting the axial load, the rotation of the columnar material 20 in the above process is performed smoothly, and the helical gear Extrusion process is easily and reliably performed.

On the other hand, the shaft hole of the helical gear thus extruded is finished through the tapered shaft portion 15b and the large diameter constant diameter shaft portion 15c. Since the smaller diameter shaft portion 15d having a smaller diameter is located below the large diameter constant diameter shaft portion 15c, if the shaft is extruded downward as it is in accordance with the pushing of the subsequent sample, the formed helical gear becomes large diameter. Release contact with the constant diameter shaft 15c.

When the extrusion of the preceding cylindrical material 20 is completed, the lower ram 17 is lowered by the lifting mechanism 16. Then, the subsequent cylindrical material 20 has already undergone a certain degree of compressive deformation, and the shaft hole 20a and the small diameter constant diameter shaft portion 15a of the mandrel 15 are already in a frictional contact state, so the mandrel 15 is held at the same position Is done. Therefore, the extruded helical gear having the shaft hole can be taken out from the gap between the mandrel 15 and the lower ram 17. When the cylindrical material 20 reaches the small diameter shaft portion 15d of the mandrel as described above, the mandrel 15
Since the frictional contact state with the tire is released, it can be easily removed.

After removal, lower ram 17 is raised again and mandrel 15
The lower end of is held at the localization value. After the upper ram 21 is raised and the annular spacer 19 is removed, the subsequent cylindrical material 20 is inserted into the annular container 11. The annular spacer 19 is inserted into the annular container 11 again, the upper ram 21 is lowered, a load is applied by the annular spacer 19, and the preceding cylindrical material 20 is subjected to the same extrusion.

By repeating this operation, a molded product of a helical gear having a continuous shaft hole can be obtained. Mandrel 15
It is desirable that the size of the tapered shaft portion 15b and the large diameter constant diameter shaft portion 15c be determined by the value of the cross-sectional reduction rate r% of the sample necessary for forming the gear teeth of the formed gear to a predetermined value. .

According to the present invention, the module perpendicular to the tooth section _mn = 1.5, the pressure angle α
_{n =} 20 °, a cross section perpendicular to the shaft module m _s = 1.596, the pressure angle α
_{s =} 21.2 °, the torsional angle β = 20 °, the number of teeth Z = 18, addendum modification coefficient x = + 0.09, the outer shape of the outer diameter d _k = 32 mm, the cylindrical material 20 d _o = 32
mm, it was applied to the inner diameter d _i = 14 mm, the large径定diameter shaft portion 15c part of the diameter d _c = 15~18mm mandrel 15 conditions. The die and the mandrel 15 shown in FIGS. 1 and 2 are used for cold forging die steel SKD11.
The material of the columnar material 20 is S15C, S45C, SC
After machining to the required shape using M415, phosphate coating treatment was applied.

As a result, a helical gear having teeth formed at a predetermined tooth height and a shaft hole was obtained. In particular, if the value of the cross-sectional reduction rate r% obtained from the area of the cross section perpendicular to the axis of the sample before processing and the area of the cross section perpendicular to the axis of the completed formed helical gear is 30% or more,
Good results were obtained. These tooth surfaces form a vanishing surface,
Microscopic observation did not show the occurrence of fine cracks, and a good molded product was obtained.

FIG. 2 (C) shows an embodiment in which tooth grooves 15e for forming internal teeth are formed in the tapered shaft portion 15b and the large diameter constant diameter shaft portion 15c of the mandrel 15. When this mandrel 15 is used, internal teeth can be formed in the shaft hole 20a of the columnar material 20. FIG. 2B is an example of a mandrel 15 having a constant diameter shaft portion 15f fitted into the shaft hole 20a of the columnar material 20 and a subsequent small diameter shaft portion 15d having a smaller diameter. The constant diameter shaft portion 15f is provided up to a position corresponding to the tooth space 10b of the extrusion die 10. Also in this example, since the cylindrical material 20 is subjected to the compression processing, the fixed diameter shaft portion 15f and the shaft hole 20a can be brought into frictional contact with a sufficient force, so that the mandrel 15 is rotated together with the cylindrical material 20. While the helical gear can be extruded.

[Effect of the Invention] As described above, according to the present invention, a helical gear having a shaft hole can be extruded at room temperature. In particular, it can be molded with high precision and efficiency, and is superior in terms of manufacturing time and material yield as compared with conventional methods, thus reducing the mass production cost of helical gears. Can be.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an example of an apparatus for carrying out the method of the present invention, and FIGS. 2 (A), (B) and (C) are front views showing examples of the shape of a mandrel. 10 …… Extrusion die, 10a …… Die land part, 10b ……
Tooth groove, 11 ... annular container, 12 ... reinforcing ring, 13, 14
… Support, 15… Mandrel, 15a… Small diameter constant diameter shaft part, 15b …… Taper shaft part, 15c …… Large diameter constant diameter shaft part, 15d…
... Small diameter shaft part, 15e ... Tooth groove, 15f ... Constant diameter shaft part, 16 ... Lifting mechanism, 17 ... Lower ram, 18 ... Thrust bearing, 19 ...
Annular spacer, 20 …… Cylindrical material, 20a …… Shaft hole, 21…
... the upper ram.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Takeshi Okano 3-65 Midorigaoka, Toyota City, Aichi Prefecture Inside Taitoyo Kogyo Co., Ltd. (56) References JP-A-1-170544 (JP, A) Japanese Patent Publication No. Sho 62-2890 (JP, B2) (58) Field surveyed (Int. Cl. ⁶ , DB name) B21K 1/30

Claims (4)

(57) [Claims] A cylindrical material having a shaft hole is pressed against a die having a tooth groove of a helical gear on an inner peripheral surface thereof, and is passed through the die to form a shaft hole serving as a helical gear. In the extrusion molding method for a helical gear, the rotation of the die is restrained, and a mandrel that freely rotates and does not change its axial position with the die during processing is positioned at the center of the die. A small-diameter constant-diameter shaft portion fitted into the shaft hole of the cylindrical material, a tapered shaft portion for expanding the diameter of the shaft hole, and a large-diameter constant-diameter shaft corresponding to the shaft diameter after the diameter expansion. The tapered shaft portion and the large diameter constant diameter shaft portion correspond to the tooth groove portion of the die, and when the cylindrical material is passed between the die and the mandrel and extruded, the die dies Do not freely rotate the cylindrical material and mandrel according to the torsion angle of the gear tooth space. A method for extruding a helical gear having a shaft hole, wherein a helical gear is machined on an outer peripheral surface of the columnar material. 2. A method for extruding a helical gear according to claim 1, wherein the tapered shaft portion and the large-diameter constant-diameter shaft portion of the mandrel have internal teeth for forming internal teeth in a shaft hole of a cylindrical material. A method for extruding a helical gear, wherein a tooth groove for tooth shaping is provided, and the shaft hole passes through the tooth groove and is formed into a shaft hole having internal teeth. 3. A cylindrical material having a shaft hole is pressed against a die having a tooth groove of a helical gear on an inner peripheral surface, and is passed through the die to form a shaft hole serving as a helical gear. In the extrusion molding method for a helical gear, the rotation of the die is restrained, and a mandrel that freely rotates and does not change its axial position with the die during processing is positioned at the center of the die. A fixed-diameter shaft portion that fits into the mandrel in the shaft hole of the columnar material and continues to the processing end position of the helical gear by the tooth groove of the die; In order to make the constant diameter shaft part correspond to the tooth groove part of the die, and to extrude by passing the cylindrical material between the die and the mandrel, according to the torsion angle of the Shaft characterized by processing while rotating mandrel freely A method for extruding a helical gear having holes. 4. A rotation-restricted die having a tooth groove for forming a helical gear on an outer peripheral surface of a cylindrical material having a shaft hole on an inner peripheral surface; and a cylindrical material concentric with the die. A lower ram that is movable relative to the mandrel and rotatably supports the lower end of the mandrel; and presses a cylindrical material inserted between the die and the mandrel. The upper ram and the lower ram are held in a fixed position during the extrusion process, and the mandrel is rotatably supported in the axial position with the die without changing the position. After the extrusion process, the lower ram is lowered. An extruding device for a helical gear having a shaft hole.