JP4300693B2 - Helical gear and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a helical gear, a method for manufacturing the helical gear, and a mold, and more particularly to a helical gear that is cold-forged by press-fitting a material in an axial direction, a manufacturing method using the forging, and a mold.
[0002]
[Prior art]
An example of a helical pinion gear for steering, which is a kind of helical gear, an apparatus for manufacturing the helical pinion gear, and an example of a manufacturing method thereof are disclosed in Japanese Patent Laid-Open Nos. 7-308729 and 11-10274. Are listed. The helical pinion gear targeted by these inventions has a cylindrical shape as a whole, and has a helically inclined tooth formed on the outer peripheral surface, and a cylindrical portion is formed on one end side of the tooth via a tapered portion. It is.
[0003]
If this type of helical pinion gear is manufactured by cutting, the number of processes increases, and the processing machine becomes expensive. In the case of an odd number of teeth, the machining load fluctuates, which causes a disadvantage that the accuracy of the tooth shape is lowered.
[0004]
Therefore, in JP-A-7-308729 and JP-A-11-10274, the helical pinion gear is cold forged by press-fitting a material into a cylindrical die in the axial direction.
[0005]
When forging a helical pinion gear, the teeth to be formed are inclined with respect to the axial direction, so the angle formed between the surface at the end of the tooth and the surfaces on both sides of the tooth (tooth surface) is one of the teeth. The tooth surface of this tooth is different from the other tooth surface. For this reason, the flow of the material is different on both sides of the tooth, which causes the accuracy of the tooth shape to deteriorate.
[0006]
Therefore, in the above-described conventional invention, as shown in FIG. 7 and FIG. 8 (the following FIG. 7 to FIG. 10 are cited from the above-mentioned Japanese Patent Application Laid-Open No. 11-10274), the material at the time of forging Is formed on the surface facing the inflow direction P, that is, the material inflow side end portion of the upper tooth surface 1B, and has a triangular-shaped built-up portion 2 having a surface inclined in the opposite direction to the inclination direction of the upper tooth surface 1B. (FIG. 7), or a triangular-shaped built-up portion 7 having a surface inclined in the same direction as the inclination direction of the upper tooth surface 8B is formed (FIG. 8).
[0007]
As shown in FIGS. 9 and 10, the forging die (die) for forming the tooth die having such a shape corresponds to the upper tooth surface 1B of the end surface 4 of the protrusion 3 for forming the tooth gap. The surface, that is, the portion on the mold lower tooth surface 3C side is cut into a triangular shape, and the cut-down portion 5 is formed here (FIG. 9), or the portion opposite to the mold lower tooth surface 6C is formed. A configuration in which a cut-out portion 9 is formed by cutting it into a triangular shape (FIG. 10) is employed.
[0008]
In the description of Japanese Patent Application Laid-Open No. 7-308729, therefore, as shown in FIG. 9, when the material is caused to flow in the direction indicated by the arrow P in the conventional helical pinion gear, a part of the material is drawn by the lowering portion 5 by the arrow P _1. It flows in the direction indicated by. Further, the other part of the material flows in between the ridges 3 to form other teeth, that is, along the other surfaces of the ridges 3 corresponding to the lower tooth surface 1C, that is, along the upper mold tooth surface 3B. Flowing. Its direction is indicated by arrow P ₂ in FIG. In this way, in the forging method of the above publication, the flow of the material occurs almost evenly on both tooth surfaces, and as a result, the accuracy of the tooth mold is improved.
[0009]
Further, the helical pinion gear disclosed in Japanese Patent Laid-Open No. 11-102742, as shown in FIG. 10, when flowing the material in the direction indicated by the arrow Q, the direction indicated by the arrow Q ₁ and in part by the devaluation 9 Flowing into. The other part of the material flows in between the ridges 6 and flows along the lower mold tooth surface 6C of the ridges 6 corresponding to the upper tooth surfaces 8B forming the teeth. Its direction is indicated by an arrow Q ₂ in FIG. In this way, in the forging method of the above publication, the flow of the material is promoted on both end sides, and similarly, the torsion of the material is suppressed. It is said that it is possible to obtain a highly accurate helical gear that does not cause mold errors.
[0010]
[Problems to be solved by the invention]
In Japanese Patent Laid-Open No. 7-308729, there is a built-up portion 2 at the end of a tooth, and a cut-down portion 5 for forming this is formed in a die so that the upper tooth surface 1B side. The inflow of the material and the flow of the material in this part are promoted. However, the flow direction of the material at the end of the tooth is opposite to the circumferential direction as indicated by the arrows P1 and P2. Therefore, the meat on the outer peripheral side is twisted in the spiral direction in a state where the material is constrained with respect to the circumferential direction.
[0011]
Therefore, in the helical pinion gear according to the above-described conventional invention, the inflow of the material to the upper tooth surface 1B side is promoted, and the residual stress resulting from the torsion of the material is generated. Occurs. Such torsional deformation does not occur uniformly at all locations, and therefore, the tooth shape is out of order, and eventually the accuracy of the helical gear as a product may be low.
[0012]
On the other hand, in Japanese Patent Laid-Open No. 11-10274, a bulging portion (filled portion 7) is provided on the opposite side to the built-up portion 2 of Japanese Patent Laid-Open No. 7-308729. That is, since the bulging portion (the build-up portion 7) that is continuously inclined in the tooth inclination direction is formed at the end portion of the tooth, when the forging is performed by pressing the material in the axial direction, the bulge The movement of the material from the portion corresponding to the portion to the portion corresponding to the tooth is promoted, and at the same time, twisting of the material is prevented or suppressed, and as a result, a tooth type error due to torsional deformation after manufacturing does not occur.
[0013]
However, with regard to the flow of the material, although the twist is prevented or suppressed, it is difficult to form the tooth shape as a die. In particular, the tooth tip portion becomes thin and the material is difficult to flow, so that it tends to be thin. In other words, the material tends to flow toward the wide space at the tooth root, and this portion is easy to fill the mold, but the tooth tip portion is narrow in the mold space, so the flow of the material is not promoted and filling is not possible. It tends to be enough. Since the material requires less energy to move in the axial direction (extending direction) than to move in the direction to fill the tooth tip, the material easily escapes in the axial direction. As a result, it is difficult to obtain an accurate tooth shape and accuracy.
[0014]
In addition, the above two preceding examples specify the triangular build-up portion 2 or 7 only for the connecting portion between the taper portion 12 and the tooth end portion, and an accurate tooth profile even if the shape of only this portion is manipulated. It is impossible to get. That is, the influence on the tooth forming part is limited by the operation of only this part and cannot be controlled.
[0015]
An object of the present invention is to solve the above-mentioned problems and to provide a method by which tooth profile accuracy can be easily obtained.
[0016]
[Means for Solving the Problems]
The above problem is solved by the following means. That is, the solving means of the first invention includes a substantially cylindrical shaft portion, a tapered portion extending from the shaft portion and gradually reducing its cross-sectional diameter, and a helical tooth extending from the tapered portion. A first tooth portion in which teeth having a muscle are formed and a second tooth portion further extending from the first tooth portion, along the spiral of the tooth muscle of the first tooth portion In the helical gear having the extended tooth trace and the second tooth portion on which the teeth for the gear transmission mechanism are formed, the first tooth portion is formed by a die. Sometimes, in order to adjust the flow of the material flowing into the second tooth portion, the cross-sectional shape of the material introduction mold portion having a cross-sectional shape larger than the cross-sectional shape of the second tooth portion by the amount of drawing in the entire region of the tooth profile. Is left behind .
[0018]
Solutions of the second invention, in the interior of the cylindrical die having a plurality of helical ridges on the inner peripheral surface is formed, by press-fitting the material toward the axial direction thereof, plastically deforming the material In the helical gear manufacturing method for forming a plurality of helical teeth on the outer peripheral surface, in order to adjust the flow of the material flowing into the mold part and the mold part forming the teeth for the gear transmission mechanism , A cylindrical die having a material introduction mold part having an inner peripheral surface that is larger by the amount of drawing in the entire region of the tooth profile than this is used.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described with reference to FIGS.
[0023]
FIG. 1 schematically shows an example of a helical gear 10 according to the present invention, and FIG. 2 is an enlarged view of a main part thereof. 3 is a cross-sectional view taken along the line AA in FIG. 2, and is a view of the teeth 16 and the tooth portions 13 as viewed from the left side.
[0024]
In the helical gear 10, a tapered portion 12 is formed following the columnar or cylindrical shaft portion 11, and a plurality of teeth 16 are formed on the lower side of FIG. 1 from an intermediate portion in the axial direction of the tapered portion 12. ing. This region is referred to as a material introduction unit 14.
[0025]
The plurality of teeth 16 in the material introducing portion 14 are set to have a larger shape than a plurality of teeth 13 (that is, the teeth 13 for the gear transmission mechanism) described later for meshing with the rack as a pinion. 5 and 6 (FIG. 6 is an enlarged view), this portion is set in a shape indicating the teeth 16 by a one-dot chain line, and is larger in the whole area than the tooth portion 13 indicated by the solid line. It has become.
[0026]
In FIG. 6, the tooth 16 sets the aperture amount such as T 1, T 2, T 3, and T 4 with respect to the tooth portion 13 as illustrated. Although T1 to T4 are displayed as the same amount of aperture in FIG. 6, they are not necessarily equal. Rather, T1 may be small, and T3 and T4 should not be the same. Usually, the amount of T1 to T4 is set to about 0 to 0.5 mm.
[0027]
Although the axial length of the material introduction part 14 differs between the tooth bottom part 16D and the tooth tip part 16A, it is preferable to set the tooth bottom part 16D as well. Practically, the length of the material introducing portion 14 is about 1 to 2 mm at the root portion 16D. The length of the material introducing portion 14 and the throttle amounts T1 to T4 should be set by adjusting the details according to the shape and size of the workpiece, and by doing so, a more accurate helical gear can be obtained.
[0028]
These teeth 16 are helical teeth set at a predetermined twist angle α (FIG. 2) with respect to a plane passing through the central axis or a generatrix of the cylindrical portion continuous below the tapered portion 12 in FIG. Yes, the tooth surfaces 16B and 16C on both sides of the tooth 16 sandwiching the tooth tip portion 16A are formed into curved surfaces having a substantially involute curve. Of these tooth surfaces 16B and 16C, the tooth surface 16B facing the direction of the shaft portion 11 is assumed to be an upper tooth surface 16B, and the tooth surface 16C on the opposite side is assumed to be a lower tooth surface 16C.
[0029]
At the end of each tooth 16 on the tapered portion 12 side, the tooth 16 starting from here is formed, and the triangular bulge as shown in the conventional example is not formed.
[0030]
A constricted portion 15 is provided on the extension of the material introducing portion 14 following the material introducing portion 14, and the constricted portion 15 causes a plurality of teeth 16 of the material introducing portion 14 to a plurality of teeth 13 of the forming portion 17. A connecting portion that reaches the shape of is formed.
[0031]
The narrowed portion 15 plays a role of connecting the material introducing portion 14 and the forming portion 17, but the shape is connected by a smooth and loose taper so that the material can easily flow plastically, and the connecting portion between the taper and the straight portion is a circle. It is an arc-shaped round (not shown). That is, between the material introduction part 14 and the molding part 17, there is provided a narrowing part that continuously connects the shapes of the two with a curved surface. An appropriate angle of the aperture is usually about 2 to 10 degrees.
[0032]
Following the narrowed portion 15, a molding portion 17 is formed on the lower side of FIG. 1 or FIG. 2 so as to be an extension of the plurality of teeth 16 of the material introducing portion 14. A plurality of tooth portions 13 are formed in the molding portion 17. Similar to the teeth 16 of the material introduction portion 14, these teeth 13 have a predetermined twist angle α with respect to the plane passing through the central axis or the generatrix of the cylindrical portion continuous below the tapered portion 12 in FIG. 1. The set tooth is a tooth, and the tooth surfaces 13B and 13C on both sides of the tooth portion 13 with the tooth tip 13A interposed therebetween are formed into curved surfaces with an involute curve. Of these tooth surfaces 13B and 13C, the tooth facing the shaft 11 side is defined as an upper tooth surface 13B, and the tooth surface 13C on the opposite side is defined as a lower tooth surface.
[0033]
The above helical pinion gear is made by forging (plastic working). In this case, as is known from the above-described shape, the material is pressurized from the shaft portion 11 side, and after forming into a tapered shape, the material flows to form the material introduction portion 14. Teeth 16 are formed by the material introducing portion 14. Further, the throttling portion 15 causes the material to flow to form the tooth portion 13 of the molding portion 17.
[0034]
Therefore, the material introduction part 14 which reaches each tooth part 13 becomes a part which supplies material to the part of the tooth part 13 from here, and is formed as a surplus part with the end of forging (plastic working). That is, the material introduction part 14 is a part in which the inner surface shape of a later-described die is left as it is.
[0035]
Here, the die 20 for forging the helical gear 10 will be described. FIG. 4 is a partial cross-sectional view showing a schematic structure of the die 20. FIG. 11 is a perspective view of the die 20 cut out. Since the die 20 is mainly formed by plastically deforming the material 21 and formed into the shape described above, the inner surface shape thereof matches the outer shape of the helical gear 10 described above.
[0036]
That is, the die 20 as a whole has a substantially cylindrical shape, and one end portion in the axial direction (the upper end portion in FIG. 4) is the introduction side of the material 21, and here a simple hollow cylindrical cylindrical shape A portion 22 is formed. Following this cylindrical part 22, a tapered part 23 whose inner diameter gradually decreases is formed. This taper type part 23 is for forming the taper part 12 in the helical gear 10 mentioned above.
[0037]
A plurality of ridges 28 for forming the teeth 16 of the material introduction portion 14 are formed on the material introduction mold portion 26 from the middle portion of the taper mold portion 23 to the lower side (lower side in FIG. 4). . Note that the material introduction mold portion 26 has a shape similar to a plurality of ridges 24 described later, and is formed in a slightly larger dimension than the ridges 24.
[0038]
These ridges 28 are portions that protrude toward the center of the die 20, and the portion where the inner diameter of the tapered portion 23 is the smallest is the apex portion. Therefore, the end face of each ridge 28 is a part of the taper-type part 23 or a surface continuous to the taper-type part 23. Each ridge 28 is set to a predetermined twist angle α with respect to a plane passing through the central axis.
[0039]
The top portion 28 </ b> A of each ridge 28 is a portion corresponding to the tooth bottom portion 16 </ b> D of the material introduction portion 14 in the helical gear 10, and the groove portion 29 between the ridges 28 is in the material introduction portion 14 of the helical gear 10. Corresponds to tooth 16. Accordingly, both side surfaces 28B and 28C of each ridge 28 are formed into curved surfaces having a substantially involute curve so that the tooth surfaces 16B and 16C of the helical gear 10 are formed.
[0040]
Of these side surfaces 28B and 28C, the side surface 28B facing the cylindrical mold portion 22 side corresponds to the lower tooth surface 16C, and this side surface is assumed to be the mold upper tooth surface 28B, and the opposite side surface 28C is the upper surface. Corresponding to the tooth surface 16B, this side surface is assumed to be a mold lower tooth surface 28C.
[0041]
The upper end portion of the upper mold tooth surface 28B in FIG. 4, more precisely, the end portion entering the tapered mold portion 23 is a twist angle (tilt angle) α when the upper mold tooth surface 28B is extended as it is. It is almost the same. Therefore, the triangular introduction surface as in the conventional example is not provided.
[0042]
On the extension of the material introduction mold part 26, a diaphragm mold part 27 is provided continuously, and this corresponds to the diaphragm part 15 of the helical gear 10. In other words, a drawing die portion 27 is provided between the material introduction die portion 26 and a molding die portion described later to continuously connect the inner surface shapes of both of them with a curved surface.
[0043]
Following this drawing mold part 27, a mold part 30 is formed continuously on the extension of the drawing mold part 27. A plurality of ridges 24 for forming the tooth portion 13 are formed on the mold portion 30. These ridges 24 are portions that are convex toward the center of the die 20, as with the ridges 28, are extensions of the ridges 28, and have the die innermost diameter portion as the apex portion. Each ridge 24 is set to a predetermined twist angle α with respect to a plane passing through the central axis.
[0044]
The top 24 </ b> A of each ridge 24 corresponds to the tooth bottom 13 </ b> D in the helical gear 10, and the groove 25 between the ridges 24 corresponds to the tooth 13 in the helical gear 10. Therefore, both side surfaces 24B and 24C of each ridge 24 are formed into curved surfaces having an involute curve so that the tooth surfaces 13B and 13C of the helical gear 10 are formed.
[0045]
Of these side surfaces 24B and 24C, the side surface 24B facing the cylindrical mold portion 22 side corresponds to the lower tooth surface 13C, this side surface is the mold upper tooth surface 24B, and the opposite side surface 24C is the upper tooth surface. Corresponding to the surface 13B, this side surface is referred to as a mold lower tooth surface 24C. The length of the molding die 30 in the axial direction is generally about 1 to 5 mm, and has a role as a molding land.
[0046]
On the lower side of the mold part 30 (lower side in FIG. 4), a relief part that is slightly larger than the mold part 30 is continuously formed. The escape amount of the escape portion is set to about several microns to several tens of microns.
[0047]
In order to form the helical gear 10 using the die in FIG. 4, first, the cylindrical material 21 is fitted into the cylindrical portion of the die 20. In this state, the material 21 is pushed into the die 20 by a punch (not shown). In that case, first, the tip end portion of the material 21 is deformed to a small diameter by the taper mold portion 23 of the die 20, and then the protrusions 28 bite into the material 21 to form the teeth 16 and the tooth bottom portion 16D. That is, the material flows along the ridges 28.
[0048]
More specifically, the portion of the material 21 corresponding to the ridges 28 is pushed away, whereas the portion between the ridges 28, that is, the portion corresponding to the teeth 16, has no volume reduction factor. Therefore, the material pushed away by the ridges 28 is supplied and filled between the ridges 28. At this time, since the material flows suddenly, the shape of the ridge 28 is not realized accurately in the molding of this portion, and it is likely to be in a state of lacking.
[0049]
In this way, the material flow is adjusted while passing through the material introduction mold part 26 while the material is in a thin state, and further the material is pushed out, so that the teeth 16 bite into the drawing mold part 27 and the whole The molding part 17 is molded by the molding die part 30. In the mold 30, the material passes through the ridges 24 to form the tooth portion 13, the tooth surfaces 13 </ b> B and 13 </ b> C, and the tooth bottom portion 13 </ b> D. That is, the flow of the material along each protrusion 24 is generated by the forming die portion 30 through the drawing die portion 27.
[0050]
At this time, since the incomplete teeth 16 are again formed by material flow, the shape of the ridges 24 is accurately transferred, and the tooth portion 13 having both accuracy and shape is obtained.
[0051]
Thus, by forcing the whole amount of the raw material 21 into the inside of the die 20, forging is completed, and the helical gear 10 having the shape shown in FIG. 1 is formed. Thereafter, the helical gear 10 is extracted from the die 20 by retracting the punch and pushing it up from below with a knockout pin (not shown). The helical gear 10 thus obtained has a tapered portion 12 formed after the shaft portion 11 and a plurality of tooth portions 13 formed on the distal end side from the tapered portion 12. Between each tooth portion 13 and the taper portion 12, a material introducing portion 14 corresponding to the material introducing die portion 26 in the die 20 and a drawing portion 15 corresponding to the drawing die portion 27 are formed.
[0052]
Therefore, in the helical gear 10 manufactured by the die 20 shown in FIG. 4, since the shape and accuracy of the tooth mold are transferred as the die 20, the accuracy of the tooth mold does not occur and the high-precision helical gear 10 is obtained. Can do. Such an effect is that the flow of the material is adjusted in the process of forming the teeth 16 at the material introducing portion 14 before the tooth is formed, and then the throttle portion 15 is formed continuously. This is caused by providing the die 20 with the material introduction die portion 26, the drawing die portion 27, and the molding die portion 30 described above.
[0053]
Since the present invention can be applied to a forged product in which spiral teeth are formed, the present invention is not limited to a helical pinion gear for steering, and can also be applied to a spline or the like.
[0054]
【The invention's effect】
Since the present invention is as described above, according to the helical gear of the present invention, the introduction portion set continuously larger than the completed dimension in the tooth inclination direction is formed at the end portion of the tooth. When forging by pressing the material in the axial direction, the flow of the material from the portion corresponding to the introduction portion to the portion corresponding to the tooth is smoothly arranged, and also appropriate according to the molding state of the tooth As a result, it is possible to obtain a highly accurate helical gear with little tooth pattern error after manufacture.
[0055]
Furthermore, according to the die of the present invention, the plastic flow of the material can be performed smoothly and smoothly due to the effects of the material introduction mold part and the drawing mold part, so that a highly accurate helical gear with little tooth profile error can be obtained. .
[Brief description of the drawings]
FIG. 1 is an overall view schematically showing an example of a helical gear 10 according to the present invention.
FIG. 2 is an enlarged view of a main part of the helical gear 10 of FIG.
3 is a cross-sectional view of a tooth 16 and a tooth portion 13 as viewed from the left side in the AA cross section in FIG. 2;
4 is a partial cross-sectional view showing a schematic structure of a die 20. FIG.
FIG. 5 is a partial cross-sectional view of a pinion gear including a tooth portion 13 for meshing with a rack.
6 is an enlarged cross-sectional view of FIG. 5 showing the teeth 16 by a dashed line.
FIG. 7 is an explanatory diagram for explaining a pinion gear in the prior art.
FIG. 8 is an explanatory diagram for explaining a pinion gear in another conventional technique.
FIG. 9 is an explanatory diagram for explaining a material flow in a forging die (die) according to a conventional technique.
FIG. 10 is an explanatory diagram for explaining a flow of a material in another conventional forging die (die).
FIG. 11 is a perspective view showing a die 20 cut out according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Helical gear 11 Shaft part 12 Tapered part 13 Tooth part 13A Tooth tip 13B, 13C, 16B, 16C Tooth surface 13D, 16D Tooth bottom part 14 Material introduction part 15 Restriction part 16 Tooth 16A Tooth tip part 16B, 13B Upper tooth surface 16C, 13C Lower tooth surface 17 Molding part 20 Die 21 Material 22 Cylindrical part 23 Tapered mold part 24, 28 Convex strips 24A, 28A, Top parts 24B, 28B, Mold upper tooth surface 24C, 28C Mold lower tooth surface 25, 29 Groove part 26 Material Introduction mold part 27 Drawing mold part 30 Mold part

Claims (2)

A substantially cylindrical shaft,
A tapered portion extending from the shaft portion and gradually reducing its cross-sectional diameter;
A first tooth portion extending from the tapered portion and having a tooth having a spiral tooth trace;
A second tooth portion further extending from the first tooth portion, having a tooth trace extending along a spiral of the tooth trace of the first tooth portion, and a tooth for a gear transmission mechanism; In the helical gear having the formed second tooth portion,
When the helical gear is molded with a die, the first tooth portion has a tooth profile cross section rather than the cross sectional shape of the second tooth portion in order to adjust the flow of the material flowing into the second tooth portion . helical gears, characterized in der Rukoto that the cross-sectional shape of the material introduction type unit having a throttle amount as large cross-section in the whole was left. The material is plastically deformed by pressing the material in the axial direction into a cylindrical die having a plurality of spiral ridges formed on the inner peripheral surface, and a plurality of spiral ridges are formed on the outer peripheral surface. In the manufacturing method of the helical gear that forms teeth,
In order to adjust the flow of the material that flows into the mold part and the mold part that forms the teeth for the gear transmission mechanism, the material is formed with an inner peripheral surface that is larger by the amount of squeezing than the entire area of the tooth profile cross section . A helical gear manufacturing method using a cylindrical die having an introduction mold part.

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