JP3813404B2 - Gear molding method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of press molding a gear, and more particularly, to a gear molding method in which the chamfered shape with respect to the left and right edges of teeth within the same rotational plane is asymmetrical (hereinafter simply referred to as a lateral symmetry). In addition, in this application, the edge part of a tooth | gear is a part which becomes a rotation direction side or the opposite side among the tooth outlines in a rotation surface. The left and right directions refer to the left and right directions with reference to a center line that coincides with the radial direction in the rotation plane of the gear. Further, the tooth width refers to the width in the rotation direction at any part of the tooth.
[0002]
[Prior art]
Japanese Patent Application Laid-Open No. 11-285771 shows a method of press molding a gear. Japanese Patent Publication No. 3-80574 discloses that the front and back of teeth are cold-forged to have a chamfered shape. However, these examples all relate to a method of manufacturing a gear having a symmetrical tooth shape, and a gear having a chamfered shape with an asymmetrical edge cannot be manufactured.
[0003]
FIGS. 5 to 7 show an example of a conventional method for manufacturing a gear having such a chamfered shape in which the edges are asymmetrical, and FIG. 5 is a view showing the gear teeth 2 from the direction of the rotation axis (hereinafter referred to as a plan view). 6 shows a cross-sectional shape of the line 6-6, and a chamfered portion 5 indicated by an oblique line intersecting with the edge of the tooth 2 is formed, and the chamfered portion is formed with respect to a center line C passing through the center of the tooth width. The left and right chamfered portions 5r and 5l have different sizes. That is, as shown in FIG. 6, the right chamfered portion 5r is formed by machining a cut portion 5b indicated by an imaginary line that is initially formed in the same shape as the left chamfered portion 5l along the cut line 5a. By cutting, it is formed larger than the left side.
[0004]
A process for manufacturing such a gear is shown in FIG. First, a portion corresponding to the main body portion having the outer diameter of the gear with respect to the base material is formed into a tapered shape by press molding (a), and then the main body portion is blanked in a circular shape from the base material and at the same time at the center. A square hole for positioning is opened (b), and then an initial tooth profile, which is a temporary tooth profile before the final shape, is formed around the main body (c). These a to c steps are press molding.
[0005]
The intermediate product thus obtained is transported to a processing machine installed at another location (d), where only the right chamfered portion 5r is cut line 5a so that the tooth tips have different chamfered shapes on the left and right sides. Then, the cut portion 5b is removed by machining, thereby forming the left and right chamfered portions 5r and 5l shown in FIG. 6 (e). Thereafter, a center hole is formed in the center (f) to obtain a product. A gear having such a left-right asymmetric chamfered shape is applied to an application that requires special smoothing of the gear.
[0006]
[Problems to be solved by the invention]
By the way, in the manufacturing method of the gear which has the said left-right asymmetric chamfering shape, the machining of e process is essential, As a result, many man-hours are required. In addition, a plurality of facilities such as a press molding machine and a machining facility are required, and the capital investment is increased, and conveyance (d process) between these facilities is also required.
[0007]
In addition, it is also conceivable to perform chamfering by the conventional press molding instead of machining in the e process. However, in this case, it is necessary to press-mold using a left-right asymmetric mold. However, since the molded part is relatively large, such a left-right asymmetric mold is not durable, and in practice a symmetrical mold is used. Without it, it cannot be molded. On the other hand, if the machining can be eliminated and the entire process can be press-molded, the production efficiency can be significantly improved. Therefore, it is desired that the entire process can be press-molded for molding such a special gear, and the present invention aims to realize such a requirement.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the gear molding method according to the present invention is a method of manufacturing a gear by pressing the left and right edges of the teeth in the same rotational surface into a left-right asymmetric chamfered shape with respect to either the front or back side of the gear. In this method, a tooth profile removing step of forming an initial tooth profile before chamfering by press molding on a circular body portion outer peripheral portion blanked from a base material, and a mold in which the tooth molding portion is symmetrical with respect to the initial tooth profile are used. A coining step of forming an intermediate tooth profile having a symmetrical chamfered portion by press molding, and subsequent to the same surface on which the intermediate tooth profile is formed, with a tooth width smaller than the mold of the coining step using a press mold having a molding portion of the symmetric and by press molding by shifting the press type phase, chamfering asymmetrical to teeth in the same plane of the gear And having a shaving forming a.
[0009]
【The invention's effect】
For a symmetrical intermediate tooth profile formed in the coining process, a press mold having a symmetrical part with a smaller tooth width than the mold in the coining process on the same surface of the gear is used, and the phase of this press mold Since the shaving process for press molding is provided by shifting, a left-right asymmetric chamfered portion can be formed using a press mold having a left-right symmetrical formed portion. Therefore, even gears that have an asymmetric chamfered shape on the same tooth surface of the gear can be press-molded in all processes, reducing the number of molding and conveying processes, improving manufacturing efficiency, and conventional machining. Equipment can be made unnecessary, so capital investment can be reduced.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment will be described below with reference to the drawings. In addition, about a common part with the said prior art example (FIG. 5, 6), a common code | symbol is used and the overlapping description is abbreviate | omitted. FIG. 1 is a diagram for explaining the molding process by changing the cross-section of the tooth tip portion, FIG. 2 is an enlarged plan view of a part of the teeth in this gear, FIG. It is the whole process figure in manufacture of this gear.
[0011]
First, the finished product gear shown in FIG. 4F, which is the final step of the present embodiment method, has a circular main body 1, the teeth 2 formed on the outer periphery thereof, and a center hole 3 formed in the center. . The main body 1 has a cone-like taper portion so that the center protrudes to one side.
[0012]
As shown in FIG. 2 showing an enlarged view of an arbitrary tooth 2 in the gear of this embodiment and FIG. 3 showing a cross-sectional shape in the tooth width direction, the thick wall portion which is a general thick portion of the tooth 2 4 is formed with a chamfered portion 5 indicated by cross diagonal lines, and left and right portions of the chamfered portion 5 are a left chamfered portion 5l and a right chamfered portion 5r, and are asymmetrical with respect to the center line C1 in the tooth width direction. ing.
[0013]
In the present embodiment, the right chamfered portion 5r on the rotation direction side is formed larger than the left chamfered portion 5l on the opposite side, the plan view width of the left chamfered portion 5l is d1, and the plan view width of the right chamfered portion 5r is d2. Then, d1 <d2. However, the overall section modulus is the same as the conventional one in the cross section of the same part, and the same tooth tip strength can be obtained.
[0014]
In addition, the code | symbol 6 is the outline of the tooth | gear 2, ie, the outer end part of the chamfering part 5, and the chamfering part 5 inclines so that the thickness of the tooth | gear 2 may become thin toward an outer end part. Reference numeral 7 denotes a ridge line formed at the boundary between the thick portion 4 and the chamfered portion 5 of the tooth 2. C1 is a center line passing through the middle of the tooth width W1 in the intermediate tooth profile (described later), and coincides with a radius passing through the center O of the main body 1. C2 is a center line passing through the middle of the tooth width W2 of the same part in the finished product, and has a phase difference of an angle θ described later with respect to the center line C1.
[0015]
Next, the manufacturing method of this gear is demonstrated. As shown in FIG. 4, this gear is formed in six steps A to F. In FIG. 4, the planar shape and the cross-sectional shape are shown up and down for each process. First, a taper forming step (A) is performed on the base material 10 made of an appropriate metal such as iron so as to form a primary shape portion 11 by performing draw forming so that the cross section in the diameter direction has the same predetermined inclination as that of the product. A piercing step (B) for punching and forming a square hole 12 for positioning in the center of the primary shape portion 11 is performed. Furthermore, the blank process (C) which blanks the main-body part 12 from the base material 10 in substantially product shape, and forms the initial tooth profile 13 in the outer peripheral part simultaneously is performed. This initial tooth profile 13 is before chamfering of the tooth tip.
[0016]
Subsequently, a coining step (D) for the initial tooth profile 13 is performed. In this process, the periphery of the tooth tip portion is chamfered symmetrically by coining molding (press molding) in which the initial tooth profile 13 is embossed symmetrically. A shaving step (E) for obtaining a final tooth profile in which the left-right asymmetric chamfered portion 5 is formed by a press die whose phase is slightly changed is performed on the left-right symmetrical intermediate tooth profile obtained in this way. Thereafter, when a center hole forming step (F) is performed in which the center square hole 12 portion is press-molded to punch out the center hole 3 of the round hole necessary for the product, a finished gear as a final product is obtained.
[0017]
FIG. 1 is a diagram for explaining the above process by a change in a tooth width direction cross section at an arbitrary position of a tooth, and each of the cross-sectional views shown in A to D is at a common cross-sectional position. Among these, A shows the initial tooth profile obtained in the blanking process (C in FIG. 4), has a substantially constant thickness T as a whole, and small drooping portions 13a associated with the blank are formed at the left and right corners. . And the edge forms the initial outline 8 (FIG. 1).
[0018]
FIG. 1B shows an intermediate tooth profile obtained by a coining process (D in FIG. 4), and this molding is performed by press molding using a mold (not shown) having a symmetrical chamfered molding portion. A symmetrical intermediate chamfer 14 is formed. Among these, left and right symmetrical chamfered left intermediate chamfered portions 14l and right intermediate chamfered portions 14r are respectively formed. The left intermediate chamfered portion 14l and the right intermediate chamfered portion 14r are wider in plan view than the left chamfered portion 5l and the right chamfered portion 5r, respectively, and each outer edge portion has an initial contour 8.
[0019]
C in FIG. 1 shows a forming method in the shaving process (E in FIG. 4), and D in FIG. 1 shows a cross section of the final tooth profile obtained as a result of FIG. First, in FIG. 1C, a press die 15 that forms a slightly smaller tooth width W2 than the conventional tooth width W1 is used.
[0020]
The press die 15 has a blade 16, and the blade 16 is formed symmetrically. The press die 15 is overlaid on the main body 1 obtained in B above, and is slightly rotated in parallel with the rotation surface of the gear (main body 1) to shift the phase by a small angle θ from the center C1 to C2. Change.
[0021]
Then, the blade 16 on the left intermediate chamfered portion 14l moves to the right in the drawing and becomes on the left contour 6 that enters from the initial contour 8 by a relatively large dimension d3. At the same time, the blade 16 on the right intermediate chamfered portion 14r moves on the right contour 6 which is inward by the initial contour 8 and the minute dimension d4.
[0022]
When the main body 1 is press-molded by the press die 15 in this state, the periphery of the intermediate chamfered portion 14 is cut to obtain the chamfered portion 5 forming the final tooth profile. At this time, as indicated by D, the left intermediate chamfered portion 14l is cut from the initial contour 8 by the dimension d3 to become the left chamfered portion 51, and the cut edge becomes the left contour 6 of the final tooth profile.
[0023]
Similarly, the right intermediate chamfered portion 14r is cut from the initial contour 8 by a minute dimension d4 to become the right chamfered portion 5r, and the cut edge is also the right contour 6 of the final tooth profile. When the cut amount is different between the left and right, the left chamfered portion 5l and the right chamfered portion 5r become asymmetric.
[0024]
FIG. 2 also shows this molding process in a plan view, and the blade of the press die 15 in the same phase as the main body side indicated by the phantom line with respect to the intermediate chamfered part 14 indicated by the phantom line in the drawing. 16 has a substantially similar shape symmetrical to the center C1.
[0025]
Therefore, if the press die 15 is rotated to the center C2 to form a phase difference having an angle θ, the blade 16 matches the contour 6 of the final tooth profile indicated by the solid line. A portion indicated by a two-dot chain line hatching between the contour 6 and the initial contour 8 (intermediate chamfered portion 14) at this time is a cut portion to be removed by the press die 15.
[0026]
As described above, according to the method of the present embodiment, the left and right asymmetric chamfered portion 5 can be easily obtained by using a press mold whose forming portion is bilaterally symmetrical and performing press forming after changing the phase of the angle θ. Can do. Therefore, since all the six processes can be press-molded without requiring the machining that has been necessary in the past, the same press-molding machine can be used, and the gear production can be made extremely efficient. In addition, since the conveyance between facilities becomes unnecessary, the production efficiency can be further improved. In addition, capital investment can be reduced because conventional machining is not required.
[Brief description of the drawings]
FIG. 1 is a view showing a molded part in a main part process of an embodiment. FIG. 2 is a plan view showing an enlarged part of teeth in this gear. FIG. 3 is a sectional view taken along line 2-2 in FIG. Gear manufacturing process diagram [FIG. 5] A plan view in which a part of the teeth in the conventional example is enlarged. [FIG. 6] A sectional view taken along line 6-6 of FIG.
1: body part, 2: teeth, 3: center hole, 4: thick wall part, 5: chamfered part, 6: contour, 7: ridgeline

Claims (1)

In the method of manufacturing a gear in which the left and right edges of the teeth in the same rotational surface are asymmetrical chamfered shapes by press molding with respect to either one of the front and back sides of the gear,
Tooth profile punching process for forming the initial tooth profile before chamfering by press molding on the outer periphery of the circular main body blanked from the base material;
A coining step of forming an intermediate tooth profile having a symmetrical chamfered portion on the tooth by press-molding a mold portion of the tooth symmetrical with respect to the initial tooth profile,
Subsequently, a press die having a symmetrical molding part with a smaller tooth width than the die of the coining step is used on the same surface on which the intermediate tooth profile is formed , and the press die is shifted in phase. And a shaving step of forming a left-right asymmetric chamfered portion in the tooth profile on the same surface of the gear by molding.

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