JPH0431774B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing bevel gears with high precision by forging.

Conventional technology As a manufacturing method for this type of bevel gear,
There are issues such as No. 59-153540.

Problems to be Solved by the Invention When attempting to form a bevel gear with a tooth profile accuracy of JIS grade 3 using only warm die forging as in the conventional technology described above, during the continuous mass production of bevel gears, the teeth of the mold slightly It is difficult to maintain such high precision even if the mold sag, and the mold life is extremely short. This tendency becomes more noticeable when closed die forging is performed on a heated blank. That is, the contact time between the heated blank and the mold is long, and the mold is likely to sag.

Therefore, cold sizing is required, which increases production costs, and even with cold sizing, it is difficult to maintain tooth profile accuracy of JIS grade 3 in mass production.

Measures to solve the problem A die forging process is carried out to obtain a bevel gear by die forging a heated blank to form the tooth profile, and then warm piercing is carried out while the bevel gear is still in the forging preheated state at 600° to 850°C.・Of the sizing mold, it is inserted into the hole of the die engraving part of the lower die, and then it is constantly urged downward by a compression spring interposed between the punch holder and the upper die, and the die holder By lowering the upper die whose outer periphery is supported, the bevel gear is pressed by the die groove of the upper die, and then the punch holder is lowered to compress the compression spring, lowering the punch and pressing the center of the bevel gear. Pierce the recess,
Subsequently, the punch holder is further lowered, its lower surface contacts the upper surface of the upper mold, and the upper mold is pressed downward, thereby sizing the bevel gear and performing the piercing and sizing process in which piercing and sizing are performed simultaneously in a warm environment. conduct.

Function: After the process of die forging bevel gears, a compression spring is interposed between the punch holder and the upper die to constantly urge the upper die downward at a temperature of 600° to 850°C.
By performing piercing and sizing in one warm step, high tooth profile accuracy is maintained even when the tooth profile accuracy during die forging is reduced, and the bevel gear located at the joint surface of the upper die and lower die is maintained. No burrs will be generated on the outer peripheral surface.

Example The present invention will be explained below based on examples.

Figure 1 is a process diagram in one embodiment of the present invention, Figure 2 is a process diagram of an embodiment of the present invention.
The figure is a cross-sectional plan view of a main part of a warm die forging process for a bevel gear, and FIGS. 3 and 4 are cross-sectional plan views of a main part of a warm piercing and warm sizing process.

In manufacturing bevel gears, first, a round bar material 1, 1 such as a hot rolled steel bar or a restretched coil is cut 2, 2a to the required length, scale is removed 3 by shotplast or pickling, and then the material is cut at 300° or more. 850
℃ heating, water-soluble carbon lubricant liquid is supplied to the mold or the heated blank 4a by spraying or dropping, and a chamfer is formed in the warm forging 5, and the chamfer is While the blank 5a remains in the forging residual heat state at a temperature range of about 100° to 300°C, it is immersed in a water-soluble carbon lubricant solution previously stored in a water tank 6 to form a lubricating film of, for example, about 10 to 20 μm on the surface of the blank 6a. .

Next, the blank 6a on which the lubricating film was formed,
Further, heating is performed by high frequency heating 7 at a heating rate of 200°C/min or more to a temperature range of 650 to 900°C,
A warm die forging process 8 is performed by charging the die into a die set in equipment such as a crank press (not shown).

This warm die forging 8 will be explained in detail.
As shown in the left half of Figure 2, knockout 1
The heated blank 7a is charged into the hole of the lower die 14 in which the tooth die 13 and the mandrel 16 are placed, as shown in the right half of FIG. The bevel gear 8a is formed by lowering the upper mold 11 and forging a blank between the upper and lower molds. The mandrel 12 of the upper mold 11 and the knockout 15 of the lower mold 14 are movable relative to the upper mold 11 and the lower mold 14, respectively, for tooth forming and product knockout.

Next, the gear 8a on which the toothed portion 8b has been formed is taken out, and the bevel gear 8a is knocked out as shown in FIG. 32
is charged into the hole of the lower die 30 facing the bottom of the die sink.

Subsequently, by lowering the upper die 20 whose outer periphery is supported by the die holder 27 and which is constantly urged downward by the compression spring 26, the die engraving portion 21 of the upper die 20 is lowered.
The bevel gear 8a is pressed, and then the compression spring 26 is compressed, so that the punch 22 descends relative to the upper die 20 to pierce the bevel gear center recess 9c, and then the punch holder 2
The lower surface 25 of 4 contacts the upper surface 23 of the upper mold 20 and presses the upper mold 20 downward, so that the bevel gear 8
Sizing is performed on a to obtain a bevel gear 9a.

As described above, after the warm die forging step 8, even with a die in which a compression spring is interposed between the punch holder 24 and the upper die 20 to constantly urge the upper die 20 downward, the angle is 600° to 850°. When performing the warm piercing and sizing process 9 in which piercing and sizing are performed simultaneously in one process at warm temperature of ℃, the warm die forging process 8
The molds 11 and 14 of 2-4 can have a mold life of 2 to 4 times longer, and the molds 20 and 30 of warm sizing 9 can also have a mold life of about the same level as conventional cold sizing. The desired high tooth profile accuracy is maintained during the life of the mold. And deformation of the forged product caused by drilling can be completely prevented.

Further, burrs are not generated on the outer circumferential surface of the bevel gear located at the joint surface between the upper die 20 and the lower die 30.

Moreover, the bevel gear 9a formed in this way
Since piercing and sizing are performed simultaneously in one stroke while still in a high preheated state of approximately 600° to 850°C, the bevel gear does not become brittle. In addition, although the press forming capacity required for sizing, that is, the pressing force capacity of the press machine to form the bevel gear 8a, is low at about one-fourth to one-fifth of cold sizing, the surface roughness of the tooth surface is 8. ~10S, which is better than 11~15S of conventional cold sizing.

Note that the bevel gear 9a taken out after warm piercing and warm sizing is normalized in a non-oxidizing furnace, cooled, and subjected to required machining, carburizing, etc.

Effects As described above, according to the present invention, after the process of die forging a bevel gear, a compression spring is interposed between the punch holder and the upper die to constantly urge the upper die downward. By performing piercing and sizing in one step at a warm temperature of 600° to 850°C, high tooth profile accuracy is maintained even when the tooth profile accuracy during die forging deteriorates, and the joint surface between the upper and lower dies is maintained. Since burrs do not form on the outer circumferential surface of the bevel gear located at can be produced with high efficiency, and the bevel gear does not become brittle.

[Brief explanation of drawings]

FIG. 1 is a process diagram in one embodiment of the present invention. FIG. 2 is a cross-sectional plan view of the main part of the warm forging process of the bevel gear in FIG. 1. 3 and 4 are cross-sectional plan views of the main parts of the warm piercing sizing process. Explanation of symbols, 7a...Heating blank. 8...Die forging process. 8a...Bevel gear. 8b...Tooth profile part.
9...Earring sizing process. 9c...Central recess. 20... Upper mold. 21...Mold engraving department. 22...Punch. 23...Top surface. 24...Punch holder. 2
5...Bottom surface. 26... Compression spring. 27...
die holder. 30...Mold. 31...Mold engraving department.

Claims (1)

[Claims] 1. Die forging process 8 is performed to obtain the bevel gear 8a by die forging the heated blank 7a to form the toothed portion 8b, and then the bevel gear 8a is warm pierced while remaining in the forging preheated state at 600° to 850°C. Of the sizing molds 20 and 30, the lower mold 30 is inserted into the hole of the mold engraving part 31, and then continuously pressed downward by the compression spring 26 interposed between the punch holder 24 and the upper mold 20. By lowering the upper mold 20 whose outer periphery is supported by the die holder 27 while being urged by the die holder 27, the bevel gear 8a is
is pressed, and then the punch holder 24 is lowered to compress the compression spring 26, thereby lowering the punch 22 to pierce the central recess 9c of the bevel gear 8a. Piercing and sizing step 9 in which the bevel gear 8a is sized by bringing the lower surface 25 into contact with the upper surface 23 of the upper mold 20 and pressing the upper mold 20 downward, and piercing and sizing are performed simultaneously under warm conditions. A method for manufacturing a bevel gear, characterized by performing the following steps.