JPH1110274A - Helical gear, production method and producing device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a helical gear without generating an error of a tooth shape by preventing the generation of a twist residual stress of a blank. SOLUTION: This is a helical gear formed with a plurality of lines of teeth 13 in a continuous spiral shape from a taper part 12 in the axial line direction, on an end part of the taper part 12 side of each tooth 13, a bulging part 14 being made in a projection in the opposite direction of the extending direction of the tooth 13 in the circumferential direction and being continued to the face 13C of the down side of the tooth 13 in the case of taking the taper part 12 upside is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a helical gear and an apparatus and method for manufacturing the helical gear, and more particularly, to a helical gear cold forged by press-fitting a coarse material in an axial direction, and an apparatus and method for forging the helical gear. Things.

[0002]

2. Description of the Related Art An example of a helical pinion gear for steering, which is a kind of helical gear, and an apparatus and a method for manufacturing the helical pinion gear are disclosed in Japanese Patent Laid-Open No. 7-3.
No. 08729. The helical pinion gear to which the invention described in this publication is directed has a cylindrical shape as a whole, and has teeth that are spirally inclined on the outer peripheral surface, and a cylindrical part is formed on one end side of the tooth via a tapered part. The formed structure. If this kind of helical pinion gear is manufactured by cutting, the number of steps is increased, and the processing machine becomes expensive.Therefore, there is a disadvantage that the cost is increased, and according to the rolling,
In the case of an odd-numbered tooth, the processing load fluctuates, and as a result, there is a disadvantage that the accuracy of the tooth profile is reduced. Therefore, in the invention of Japanese Patent Application Laid-Open No. 7-308729, the helical pinion gear is cold forged by pressing a coarse material into a cylindrical die in the axial direction.

When a helical pinion gear is forged, the teeth to be formed are inclined with respect to the axial direction. Therefore, the angle between the surface at the end of the tooth and the surface on both sides (tooth surface) of the tooth is determined. Are different between one tooth surface and the other tooth surface.
As a result, the flow of the coarse material is different on both sides of the tooth, which results in poor tooth profile accuracy. Therefore, in the above-mentioned conventional invention, as shown in FIG. 7, the rough surface inflow direction P of the rough material at the time of forging (hereinafter, tentatively referred to as a tooth surface) 1 is attached to the rough material inflow side end. Is formed in a triangular build-up portion 2 having a surface inclined in the opposite direction to the inclination direction of the second. A forging die (die) that forms such a tooth profile
As shown in FIG. 8, a portion of the end surface 4 of the ridge 3 for forming the tooth space, which is on the side corresponding to the tooth upper surface 1 (hereinafter, referred to as a mold lower surface) 5 side, is cut into a triangular shape. Then, the cut-down portion 6 is formed here.

Therefore, in the above-mentioned conventional helical pinion gear, when the coarse material flows in the direction indicated by arrow P, a part thereof flows in the direction indicated by arrow P1 by the cut-down portion 6. Another part of the coarse material flows between the ridges 3, and the other surface of the ridge 3 (hereinafter, temporarily referred to as a mold upper surface) corresponding to another surface (hereinafter, temporarily referred to as a tooth lower surface) 7 which forms a tooth. It flows along 8. The direction is indicated by the arrow P2 in the figure. In this way, according to the above-described conventional forging method, the flow of the coarse material occurs almost evenly on both tooth surfaces, and as a result, the accuracy of the tooth profile is improved.

[0005]

In the conventional helical pinion gear described above, the overlaid portion 2 is provided at the end of the tooth, and the undercut portion 6 for forming the overlaid portion 2 is formed on the die. , The flow of the material to the tooth upper surface 1 side and the flow of the material in this portion are promoted. However, the flow direction of the material at the end of the tooth is indicated by the arrow P
As shown by 1 and P2, the direction is opposite to the circumferential direction. That is, the direction of the reaction force against the rough material generated by the cut-down portion 6 and the direction of the reaction force against the rough material generated below the substantially tooth forming portion are opposite in the circumferential direction. Therefore, the meat on the outer peripheral side is twisted in the spiral direction while the coarse material is restrained in the circumferential direction.

This situation is shown in FIG. 9. If the maximum torsion angle of the coarse material 9 is C °, the maximum torsion angle C ° is:
Occurs at the end of a tooth. FIG. 10 shows the relationship between the twist angle and the extrusion length L of the coarse material 9.

Therefore, in the helical pinion gear according to the above-mentioned conventional invention, since the inflow of the material to the tooth upper surface 1 is promoted and the residual stress due to the torsion of the coarse material is generated, the torsion after forging is performed. Deformation occurs. Such torsional deformation does not occur uniformly at all locations, and therefore, the tooth profile may be deviated, and eventually, the precision of the helical gear as a product may be low.

The present invention has been made in view of the above circumstances, and has as its object to improve the tooth profile accuracy of a helical gear.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, a first aspect of the present invention is a helical gear in which a plurality of teeth are formed in a spiral shape continuously from a tapered portion in an axial direction thereof. And at the tapered end side of each tooth,
A helical gear characterized by being convex in the direction opposite to the direction in which the teeth extend in the circumferential direction, and having a bulging portion that is continuous with the lower surface of the teeth when the tapered portion is on the upper side. is there.

According to a second aspect of the present invention, a rough material is press-fitted in the axial direction into a cylindrical die having a plurality of spiral ridges formed on an inner peripheral surface thereof. A method of manufacturing a helical gear in which a plurality of helical teeth are formed on an outer peripheral surface by plastically deforming a material, wherein the rough material is roughened in a torsion direction of the ridge when the rough material is pressed into a die. A method characterized by rotating a material.

Further, according to a third aspect of the present invention, the rough material is press-fitted in the axial direction into a cylindrical die having a plurality of spiral ridges formed on an inner peripheral surface thereof. A helical gear manufacturing apparatus for forming a plurality of helical teeth on an outer peripheral surface by plastically deforming a material, wherein two side surfaces forming the ridge at an end of the ridge on a coarse material introduction side. Wherein a rough material introduction surface is formed which is continuous with an end of the side surface facing the coarse material fed in the axial direction and has an inclination angle larger than the inclination angle of the side surface with respect to the axial direction. It is.

Therefore, in the helical gear according to the first aspect of the present invention, since the so-called bulging portion which is continuous with the lower surface of the tooth is formed at the end of the tooth, forging is performed with the bulging portion side as the introduction portion of the coarse material. In this case, the introduction of the material to the tooth lower surface side is promoted by the portion corresponding to the bulging portion. In addition, the reaction force generated by the flow of the material from the bulging portion toward the tooth lower surface side is caused by the formation of the teeth in which the direction of the component force in the circumferential direction is inclined with respect to the axial direction. Since the direction becomes the same as the component force of the reaction force generated, the rough material is rotated. At least a plurality of circumferentially opposite loads do not act simultaneously on the coarse material. As a result, the residual stress in the torsional direction is reduced, and the deformation due to the residual stress and the irregularity of the tooth profile resulting therefrom are prevented or suppressed.

According to the second aspect of the invention, the material flows while being guided by the ridges of the die, and the coarse material rotates accordingly. Therefore, there is no residual stress in the torsion direction in the coarse material, so that torsional deformation after forging and deformation of the tooth profile due to the torsional deformation are prevented or suppressed.

Further, according to the third aspect of the present invention, when the coarse material is pressed into the die, the material flows between the ridges formed on the inner surface of the die to form the teeth of the helical gear. In that case, the rough material introduction surface formed at the introduction side end,
Since the inclination direction is the same as the inclination direction of the ridge and the inclination angle is set to be larger than that of the ridge, the flow of the material becomes the same in the circumferential direction as a whole. Therefore, the introduction of the material into the portion forming the teeth is promoted, and the torsion of the coarse material is suppressed. Therefore, deformation of the tooth profile of the manufactured helical gear is prevented or suppressed, and a high-precision helical gear can be obtained.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to a specific example shown in the drawings. FIG. 1 schematically shows an example of a helical gear 10 according to the present invention, in which a tapered portion 12 is formed following a cylindrical or cylindrical shaft portion 11, and the tapered portion 12 extends from an intermediate portion in the axial direction. A plurality of teeth 13 are formed on the lower side of FIG. These teeth 13
A helical tooth is set at a predetermined twist angle α with respect to a plane passing through the central axis or a generatrix of a cylindrical portion continuous below the tapered portion 12 in FIG. The tooth surfaces 13B and 13C on both sides sandwiching the are formed in a curved surface simulating a cycloid curve. Note that, among these tooth surfaces 13B and 13C, the tooth surface 13B facing the shaft portion 11 side is temporarily referred to as an upper tooth surface 13B, and the opposite tooth surface 13C is temporarily referred to as a lower tooth surface 13C.

At the end of each tooth 13 on the taper portion 12 side, there is formed a bulging portion 14 which protrudes in the direction opposite to the twisting direction of the tooth 13 starting from here. That is, the bulging portion 14
Is the lower tooth surface 1A of the tooth tip portion 13A in the tapered portion 12.
3C, the tapered portion 12 extends to a portion corresponding to the tooth bottom 13D, and the tooth surfaces 13B, 13B.
Since C is an inclined surface, the bulging portion 14 is formed in a triangular cross section. FIG. 2 shows the helical gear 1 described above.
FIG. 3 shows a partial cross section of FIG.
The shape of the end on the two sides is shown. In FIG. 3,
The broken line shows the tooth profile of the conventional helical gear without the bulging portion 14.

The helical gear 10 is made by forging. In that case, as known from the shape described above,
The coarse material is pressed from the shaft portion 11 side, and after being formed into a tapered shape, the material is further caused to flow to form the teeth 13. Therefore, the bulging portion 14 in each tooth 13
This is a place where the material is supplied to the portion 3 and formed as a surplus portion with the completion of forging.

Here, the die 20 for forging the helical gear 10 will be described. The schematic structure of the dice 20 is shown in FIG.
In short, since the rough material 21 is plastically deformed and formed into the above-described shape, the inner surface shape matches the outer shape of the helical gear 10 described above. That is, the die 20 has a substantially cylindrical shape as a whole, and one end in the axial direction (upper end in FIG. 4) is the introduction side of the coarse material 21 and a simple hollow cylindrical cylindrical portion 22 is provided here. Are formed. Subsequent to the cylindrical portion 22, a tapered portion 23 whose inner diameter gradually decreases is formed. This taper portion 23
Is for forming the tapered portion 12 in the helical gear 10 described above.

The lower side of the tapered portion 23 from the middle (FIG. 4)
A plurality of ridges 2 for forming the teeth 13
4 are formed. These ridges 24 are
And a portion where the inner diameter of the tapered portion 23 is the smallest, that is, the innermost diameter portion is a vertex portion. Therefore, the end surface of each of the ridges 24 is a part of the tapered portion 23 or a surface continuous with the tapered portion 23. Each ridge 24 is set at a predetermined twist angle α with respect to a plane passing through the central axis.

The top 24A of each ridge 24 is a portion corresponding to the tooth bottom 13D of the helical gear 10,
Therefore, the grooves 25 between the ridges 24 correspond to the teeth 13 of the helical gear 10. Therefore, each ridge 24
Are formed in a curved surface simulating a cycloid curve so as to form the respective tooth surfaces 13B, 13C of the helical gear 10. In addition, the side surface 2 facing the cylindrical portion 22 side among these side surfaces 24B and 24C.
Reference numeral 4B corresponds to the lower tooth surface 13C, and its side surface is temporarily referred to as a mold upper tooth surface 24B, and the opposite side surface 24C corresponds to the upper tooth surface 13B, and this side surface is temporarily referred to as a mold lower tooth surface 24C.

The upper end portion of the upper mold tooth surface 24B in FIG. 4, more precisely, the end portion of the upper mold tooth surface 24B, which enters the tapered portion 23, has a twist angle (inclination angle) when the upper mold tooth surface 24B is directly extended. ) Torsion angle larger than α (tilt angle)
The rough material introduction surface 26 is formed here. Therefore, the upper tooth surface 24B of the mold is an inclined surface corresponding to the lower tooth surface 13b, and the rough material introduction surface 26 is formed in the tapered portion 23. As shown, it is formed as a substantially triangular surface. That is, the inclination direction of the rough material introduction surface 26, in other words, the inclination direction with respect to a plane passing through the central axis or a plane parallel thereto is the same as the mold upper tooth surface 24B continuous with the rough material introduction surface 26.

FIG. 5 schematically shows a forging apparatus using the above-mentioned die 20. Ram 30 which can be moved up and down
A platen 31 is disposed below the ram 30 so as to face the ram 30, and a holder 32 is disposed at the center of the platen 31,
The die 20 is held by its holder 32 with its central axis oriented vertically. Further, inside the die 20, a knockout pin 33 having an outer diameter that is almost in close contact with the top 24A of the ridge 24 is arranged so as to move up and down by a spring or an actuator (each not shown).

On the lower surface of the ram 30, a punch 34 and a mandrel 35 are mounted downward. The punch 34 is a cylindrical member having an outer diameter substantially equal to the inner diameter of the cylindrical portion 22 of the die 20 and an inner diameter substantially equal to the inner diameter of a hole formed in the center of the helical gear 10. The mandrel 35 is a solid shaft-shaped member that is closely fitted inside the punch 34.
Has a predetermined dimension and protrudes from the front end of the punch 34. The die 20, the knockout pin 33, the punch 34, and the mandrel 35 are arranged on the same axis.

In order to form the helical gear 10 with this forging device, first, a cylindrical rough material 21 is fitted into a cylindrical portion 22 of a die 20. When the punch 34 and the mandrel 35 are lowered together with the ram 30 in that state, the tip of the punch 35 fits into the center of the coarse material 21, and then the tip of the punch 34 contacts the upper end of the coarse material 21, Punch 3
4 begins to push down the coarse material 21 gradually. In that case, first, the tip of the rough material 21 is deformed to a small diameter by the tapered portion 23 of the die 20, and then the ridge 24 cuts into the rough material 21 to form the teeth 13 and the tooth bottoms 13 </ b> D. That is, the material flows along the ridges 24.

More specifically, the ridges 24 of the coarse material 21
The material corresponding to the tooth 13 is pushed away, whereas the part between the ridges 24, ie the part corresponding to the tooth 13, is
There is no volume reduction factor. Therefore, the material displaced by the ridges 24 is supplied and filled between the ridges 24. This is schematically shown in FIG. 6, and when the coarse material 21 is pushed downward from the upper direction in FIG. 6, the material flows as indicated by the arrow. In particular, the rough material introduction surface 26 formed at the end of each ridge 24 is
Since the inclination angle of the first member 1 with respect to the descending direction is small, that is, the projected area in the descending direction is large, the material in contact with the rough material introduction surface 26 is caused to flow between the ridges 24 more positively. Accordingly, as shown by a plurality of arrows parallel to each other in FIG. 6, the material flow on the upper mold tooth surface 24B side is larger than the material flow on the lower mold tooth surface 24C side.

The velocity component in the circumferential direction due to the flow of the material as shown by the arrow in FIG. 6 is oriented in the same circumferential direction after being deformed by the ridge 24. That is, the reaction force caused by the plastic deformation of the rough material 21 acts as a torque for rotating the rough material 21 in a certain direction. Further, the coarse material 21 is restrained in the axial direction, but is not particularly restrained in the rotation direction, so that the rough material 21 rotates with the progress of forging. Therefore, although a torsional load acts on the coarse material 21, it hardly accumulates inside as a torsional deformation.

In this way, the entire amount of the coarse material 21 is
0, the forging ends, and the helical gear 10 having the shape shown in FIG. 1 is formed. Thereafter, by raising the ram 30 and raising the knockout pin 33, the helical gear 1
Extract 0. The helical gear 10 thus obtained is
A tapered portion 12 is formed following the shaft portion 11, and a plurality of teeth 13 are formed from the tapered portion 12 on the distal end side. A bulging portion 14 corresponding to the rough material introduction surface 26 of the die 20 is formed at the end of each tooth 13 on the taper portion 12 side.

Therefore, the helical gear 10 manufactured by the apparatus shown in FIG. 6 has almost no residual stress in the torsional direction. Therefore, when heat treatment after forging is performed, torsional deformation does not occur or is suppressed, so that the accuracy of the tooth profile does not change and the helical gear 10 can have high accuracy. Such an operation is performed by the shaft portion 11 of the tooth 13.
This is caused by forming the bulging portion 14 at the end on the side, and providing the coarse material introduction surface 26 on the die 20 for that purpose.

In the example described above, an example is shown in which the teeth 13 are formed from the intermediate portion of the tapered portion 12, but the present invention is not limited to the above example, and the helical gear of the present invention is A structure in which teeth are continuously formed may be used. Therefore, in that case, the portion from the end of the shaft portion to the tooth bottom is formed in a tapered shape. In addition, since the present invention can be applied to a forged product having spiral teeth, the present invention is not limited to a helical gear for steering but can also be applied to a spline or the like.

[0030]

As described above, according to the helical gear of the present invention, since the bulging portion continuously inclined in the direction of inclination of the teeth is formed at the end of the teeth, the swelling material is axially coarse. When forging is performed by pressing the material, the flow of the material from the portion corresponding to the bulging portion to the portion corresponding to the tooth is promoted, and at the same time, the twisting of the coarse material is prevented or suppressed, and as a result, And a high-precision helical gear free from tooth profile errors due to torsional deformation of the helical gear.

Further, in the manufacturing method of the present invention, since the coarse material is rotated in the torsional direction of the teeth during forging, no residual stress is generated in the torsional direction, and as a result, a tooth profile error due to torsional deformation after manufacturing is generated. Can be prevented.

Further, according to the apparatus of the present invention, the introduction of the material into the portion corresponding to the teeth, in particular, the so-called lower tooth flank side, can be promoted by the coarse material introduction surface, and at the same time, the load of the load for preventing the rotation of the coarse material is prevented. Since the rotation of the coarse material is promoted by preventing the occurrence, it is possible to prevent inconveniences such as residual torsional stress and occurrence of tooth profile errors due to this, and ultimately, high precision A helical gear can be obtained.

[Brief description of the drawings]

FIG. 1 is a front view showing an example of a helical gear according to the present invention.

FIG. 2 is a partial sectional view thereof.

FIG. 3 is a partial view showing the shape of the bulging portion.

FIG. 4 is a view showing an example of a die of the present invention, showing a part of a cross-sectional shape and a developed shape of an inner surface continuous with the part.

FIG. 5 is a schematic view showing an example of a forging device using the die shown in FIG.

FIG. 6 is a view for explaining a flow of a material generated at an end of a ridge of the die shown in FIG. 4;

FIG. 7 is a front view showing an example of a conventional helical pinion gear.

FIG. 8 is a view for explaining the flow of material generated at a material introduction portion of a die used when forging a conventional helical pinion gear.

FIG. 9 is a diagram showing a maximum torsion angle of a coarse material due to forging.

FIG. 10 is a diagram showing the relationship between the extrusion length and the amount of twist.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Helical gear 11 Shaft part 12 Taper part 13 Teeth 13B, 13C Tooth surface 14 Swelling part 20 Dice 21 Rough material 23 Taper part 24 Convex 24B, 24C (Convex) side surface 26

 ────────────────────────────────────────────────── ─── Continued on front page (72) Inventor Tatsuo Arima 4-24-24 Kano, Higashiosaka-shi, Osaka Inside Yamanaka Gokin Co., Ltd.

Claims (3)

[Claims] In a helical gear in which a plurality of teeth are spirally formed continuously from the tapered portion in the axial direction thereof, the direction in which the teeth extend in the circumferential direction is defined at the tapered end side of each tooth. A helical gear which is convex in the opposite direction and has a continuous bulging portion formed on the lower surface of the tooth when the tapered portion is on the upper side. 2. A coarse material is press-fitted in an axial direction into a cylindrical die having a plurality of spiral ridges formed on an inner peripheral surface thereof to plastically deform the coarse material. A method of manufacturing a helical gear having a plurality of spiral teeth formed on an outer peripheral surface thereof, wherein the coarse material is rotated in a torsion direction of the ridges as the coarse material is pressed into a die. Helical gear manufacturing method. 3. A coarse material is press-fitted in an axial direction into a cylindrical die having a plurality of spiral ridges formed on an inner peripheral surface thereof to plastically deform the coarse material. An apparatus for manufacturing a helical gear in which a plurality of spiral teeth are formed on an outer peripheral surface, wherein an end of the ridge on the rough material introduction side has a rough surface which is fed in an axial direction among two side surfaces forming the ridge. A helical gear manufacturing apparatus, characterized in that a rough material introduction surface is formed at an end of a side surface facing the material and at an inclination angle larger than an inclination angle of the side surface with respect to an axial direction.