JPH09206874A - Manufacture of gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of underfill, and to reduce the forming load. SOLUTION: Upsetting is performed in two processes, and in the first process, a projected part 14b of a preform 14 formed with the constant width smaller than the width of a completed tooth profile and with approximately same tooth height (h) of the completed tooth profile, the friction resistance between a die and a rough material can be suppressed small in forming the preform, the preform 14 can be formed with relatively small load, the tooth height (h) of the projected part 14b of the preform 14 is formed approximately same as that of the completed tooth profile, and in the second process, generation of the underfill of a tooth tip part can be prevented because the fill-up can be easily performed to the tooth tip part.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for manufacturing a forged gear.

[0002]

2. Description of the Related Art After a disk-shaped forged rough material for gears is formed by hot or cold forging, the rough material for gears is cooled, annealed, shot-blasted and lubricated, and then cold-worked. The tooth profile is generally formed by forging, and upsetting is one of the methods for forming the tooth profile.

This upsetting is performed, for example, in FIGS.
As shown in FIG. 3, a tooth profile shaping portion 3a in which a work (blank) 1 having an outer diameter smaller than the small diameter a of the tooth profile of the gear is matched to the tooth profile.
Is placed inside the die 3 recessed in the inner peripheral portion (state of FIG. 7), and the work 1 is axially compressed by the punch 4 to plastically flow the meat of the work 1 in the radial direction. The method is to fill up the inside of each tooth profile forming part 3a and finish in a predetermined gear shape in one step.

In the upsetting of the gear, since a large number of teeth are formed on the outer peripheral portion of the work 1, the distance for plastically flowing the meat of the work 1 is long, and the shape of each tooth is from the root to the tooth. Since the width becomes gradually narrower toward the front, the free surface rapidly decreases as the fill-up to the tooth profile forming section 3a progresses,
As a result, the frictional resistance between the work 1 and the mold was increased, and the load required for molding was increased. Therefore, there is a problem in that a processing facility larger than the size of the work 1 is required.

Therefore, as a method for reducing the required forming load, a method of manufacturing a gear is performed in which the forming load required by forming by dividing into two steps of preforming and finish forming is reduced. ing.

FIG. 9 shows a conventional method for manufacturing a gear that is forged in two steps described in Japanese Patent Application Laid-Open No. 6-226391. By forging the rough land 5 having a shape in which the width gradually narrows toward the tip, and then forging using a die of the finished product shape in the finishing step, the tooth portion 5a of the rough land 5 is formed.
The contact between the die and the die 6 becomes a point or line contact so that the contact resistance between the waste land 5 and the die 6 becomes small.

[0007]

However, in the above-described conventional method for manufacturing a gear, since the rough shape is formed to be substantially similar to the finished shape having a large number of teeth 5a on the outer periphery, the shape is substantially similar. Although the forming load in the finishing process can be reduced by using this rough land 5, a large forming load is required when forming a similar shape smaller than the finished gear in the roughing process, and therefore the manufacturing equipment is also a product. A large one was needed for the size of the. Further, in the case of molding a gear having a large tooth length, there is a problem that it is difficult to fill the tooth tip portion with meat, and the tooth tip portion is likely to be lacked.

The present invention has been made in view of the above circumstances. It is possible to form a gear having a high tooth length by a relatively small load by preventing the tooth thinning of the tooth tip portion which is likely to occur in the forging process of the gear. The purpose is to do.

This object is achieved by forming the tooth height of the rough land to be substantially the same as the tooth height of the finished tooth profile and performing the finishing process using this rough land.

[0010]

Means for Solving the Problem and Its Action As a means for solving the above-mentioned problems, a method of manufacturing a gear according to the present invention has a large number of radially protruding outer peripheral portions of a roughly disk-shaped rough material. In the manufacturing method of the gear forging the tooth portion,
A first step of forming the rough material into a waste having a tooth length substantially the same as that of the finished tooth profile and having a substantially constant tooth width from the root to the tooth tip narrower than the tooth width of the finished tooth profile And a second step of upsetting the rough land obtained in the first step using a die formed to match the completed tooth profile.

Therefore, according to the method of manufacturing a gear of the present invention, in the first step, the tooth portion of the rough land has a constant width narrower than the tooth width of the finished tooth profile and is substantially the same as the tooth height of the finished tooth profile. Since it is formed to a high height, the frictional resistance between the mold and the rough material can be kept small during the molding of rough terrain, and it is possible to mold the rough terrain with a relatively small load, and the tooth length of the rough terrain is molded to be almost the same as that of the completed tooth profile. Therefore, in the second step, it is possible to easily fill up the tip of the tooth and prevent the tooth tip from being thinned.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which the method for manufacturing a gear according to the present invention is applied to a case where a gear is manufactured by cold forging will be described below with reference to FIGS. 1 to 5.

FIGS. 1 to 3 show a first step of this manufacturing method, which is a roughing step. As shown in FIG. 1, first, a finished shape is formed inside a forging die 11 for roughing step. A blank 12 formed in a disk shape having an outer diameter slightly smaller than the small diameter of the gear is arranged.

The forging die 11 used for this has a plurality of tooth forming portions 13 recessed on the inner peripheral surface thereof, and each tooth forming portion 13 has a phase at a portion facing the inner peripheral surface of the forging die 11. The matching step portion forming groove 13a is formed in a shallow groove shape having the same width as the base end portion of the completed tooth profile (see FIG. 5), and at the center of the bottom portion of the phase matching step portion forming groove 13a, the completed tooth profile (see FIG. 5
Land portion 1 at a distance w1 equal to the width w1 of the tooth tip of
3b and 13b are provided, and a slit 13c having a width w1 is formed between both land portions 13b and 13b. Further, the inside of the slit 13c is gradually widened and then formed into a constant width to form a widened space 13d having a width w2 wider than the width w1 of the slit 13c.

When the blank 12 is upset-molded using the forging die 11, the material of the blank 12 axially compressed by a punch (not shown) causes plastic flow in the radial expansion direction, as shown in FIG. As shown, after filling the phase matching step portion forming groove 13a of the forging die 11, each tooth forming portion 1
3 flows into. At this time, the slit 13c serving as an inflow port
Since the opening width of is formed by the lands 13b and 13b on both sides to have a width w1, by passing through this slit 13c, a large number of tooth heights h are provided with a width w1 having a phase matching step 14a at the base end. Wasteland 14 having a protruding portion 14b of
Is formed (see FIG. 3).

As described above, when forming the rough land 14, the shape of the tooth forming portion 13 of the forging die 11 for performing upsetting is expanded to a width w by expanding the inside from the width w1 of the slit 13c serving as an inlet.
Since the widening space 13d has a width of 2, the protrusion 14b has a width w1.
Therefore, the protrusion 14b is in contact with the forging die 11 only at the root portions of both the land portions 13b, 1b.
3b only, the free surface in the forging die 11 does not decrease with the progress of the molding of the protrusion 14b, and the protrusion 1
There is no increase in the molding load due to the frictional resistance between the 4d and the forging die 11. Therefore, the forming load at the time of forming the rough land can be reduced.

Then, the rough land 14 formed as described above is placed in the forging die 15 for finish forming which is formed according to the completed tooth profile. At this time, each protruding portion 14b of the waste land 14 is formed to have a width w1 equal to the width of the tip of the completed tooth profile and a tooth length h equal to the tooth height of the completed tooth profile, and further to complete the width of the phase matching step 14a. Since it is formed to have the same width as the tooth root portion of the tooth profile, as shown in FIG. 4, each phasing step portion 14a of the rough land 14 is formed in the forging die 15 for finishing. The projections 14b are arranged in a state of being in contact with the innermost portion of the tooth profile forming portion 15a of the forging die 15 while being engaged with the portions to be phased.

Therefore, if the upsetting is performed in this state, the tip of the protruding portion 14b of the rough land 14 is arranged at the tip of the tooth profile forming portion 15a of the forging die 15 for finishing and the material is filled in advance. Therefore, the insufficient fill-up of the tooth tip does not occur. Further, since the phase matching step portion 14a formed on the rough land 14 is fitted to the widest tooth root portion of the tooth profile forming portion 15a of the forging die 15, the material causes plastic flow,
The resistance of the material flowing into each tooth profile forming part 15a is small, and therefore, the finished product can be smoothly finished by a relatively small forming load, and the tooth part 16a has no forging defects such as chipping. It can be molded into 16.

As described above, according to the gear manufacturing method of this embodiment, the gear is manufactured by the two steps of the rough molding step and the finish molding step, and the shape of the rough land 14 is changed to the tooth length of the completed tooth profile. Since it is formed to have a substantially constant tooth width, which is almost the same as that of the finished tooth profile and is narrower than the tooth width of the completed tooth profile, it is possible to reduce the forming load required for rough forming, and at the time of finish forming. Since the protruding portion 14b of the waste land 14 is arranged at the tooth tip portion where it is difficult to fill up, the tooth tip portion can be easily filled and the occurrence of wall thinning or the like can be prevented.
In particular, when molding a gear with a high tooth length, the tip of the protruding portion of the rough land is previously arranged at the tip of the tooth where flesh thickness is easily generated in the past, so accuracy without forging defects such as flesh thickness It is possible to manufacture high-quality gears.

In the above-mentioned embodiment, the case where the two steps of the rough forming step and the finish forming step are carried out continuously has been described. However, when forming a gear having a complicated tooth shape, for example, the rough forming is performed. A preforming step or the like may be performed before or after the step so that the molding can be performed more easily.

Further, although the above-mentioned embodiment has been described with reference to the case of cold forging, the same effect can be obtained in the case of hot or warm forging.

[0022]

As described above, in the method of manufacturing a gear in which a large number of radially projecting tooth portions are forged on the outer peripheral portion of a roughly disk-shaped rough material, the rough material is In the first step and the first step of forming into a waste land of a shape that is almost the same as the tooth length of the finished tooth profile and has a substantially constant tooth width from the root to the tip of the tooth that is narrower than the tooth width of the finished tooth profile Since the obtained rough land is subjected to two steps, that is, a second step of upsetting using a die formed to match the completed tooth profile,
In the step (1), the molding load required for forming the rough land can be reduced, and the equipment can be downsized. In addition, in the second step, it is easy to fill up the tip of the tooth, and it is possible to prevent the occurrence of wall thinning. Further, since the molding load is reduced, the amount of deformation of the mold at the time of molding is reduced, and the precision of the molded product is improved.

[Brief description of drawings]

FIG. 1 is a partially omitted cross-sectional plan view showing the relationship between a blank forging die used in an embodiment of a gear manufacturing method according to the present invention and a blank.

FIG. 2 is a cross-sectional plan view showing a relationship between a forging die for forming a waste land and a waste land in a waste land process.

FIG. 3 is a partially omitted plan view of a waste land.

FIG. 4 is a partially omitted cross-sectional plan view showing a relationship between a forging die for finish forming and a waste land.

FIG. 5 is a partially omitted cross-sectional plan view showing a finished product of a gear formed in a forging die for finish forming.

FIG. 6 is a partially omitted cross-sectional plan view showing the relationship between a general forging die used for upsetting and a blank.

FIG. 7 is a partially omitted sectional side view showing a forging die and a blank before upsetting.

FIG. 8 is a partially omitted sectional side view showing a forging die and a molded product after upsetting.

FIG. 9 is a cross-sectional plan view showing a conventional forging die for performing upsetting and a waste land.

[Explanation of symbols]

 11 Forging Die for Molding 12 Blank 13 Tooth Forming Part 13b Phase Matching Step 13c Widening Space 14 Waste 14a Phase Matching Step 14b Projection 15 Forging Die for Finishing 15a Tooth Profile 16 Finished Product 16a Tooth

Claims (1)

[Claims] 1. A method for manufacturing a gear in which a large number of radially projecting tooth portions are forged on an outer peripheral portion of a roughly disk-shaped rough material, wherein the rough material is a tooth height of a completed tooth profile. The first step of processing into a rough land having substantially the same tooth width from the root to the tip of the tooth having a substantially constant tooth width narrower than the tooth width of the completed tooth profile, and the rough land obtained in this first step, A method of manufacturing a gear, comprising two steps, a second step of upsetting using a mold formed to match a completed tooth profile.