JP2542893B2 - Method for forming helical gears - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Purpose of the Invention (1) Field of Industrial Application The present invention relates to a helical tooth for forming helical gears having non-linear tooth traces such as helical teeth. The present invention relates to a method for forming gears.

(2) Conventional technology Conventionally, in manufacturing helical gears, a blank is formed by hot forging, the blank is cut with a hob cutter, a pinion cutter, or the like, and gear shaving or gear grinding is performed as necessary. It was common to add the following process to make it a product. However, such a method is currently used only for manufacturing an extremely expensive helical gear because of its long working process, slow production speed, and expensive production equipment.

Instead of such a cutting method, at present, a method of manufacturing a helical gear by cold or hot forging has been adopted, but this processing method requires plastic flow of the entire material, so the processing is performed. There is a problem in that the force becomes extremely high, a high-precision gear cannot be obtained, and the apparatus becomes large.

Therefore, as disclosed in JP-A-61-129248, the material is placed between the punch and the die, and the material is deformed until it breaks by moving the punch and the die non-linearly relative to each other. After that, a method has been proposed in which the tooth profile is finished by a shaving blade arranged behind one stroke of the punch and the die.

(3) Problems to be Solved by the Invention However, in the above-mentioned prior art, since the material breakage and the shaving molding are performed in one stroke of the press mold, the molding load becomes high, the wear and damage increase, and the apparatus becomes large. Not only that, since back pressure does not act on the material, defects such as sink marks on the tooth surface may occur.

The present invention has been made in view of such circumstances,
With a simple structure, it is possible to mold gears with a small load,
Moreover, it is an object of the present invention to provide a method for forming helical gears which is free from defects.

B. Configuration of the Invention (1) Means for Solving the Problems In order to achieve the above-mentioned object, the present invention relates to forming helical gears in which tooth traces of a helical tooth or the like are non-linear,
A rough tooth profile blank having a rough tooth profile on the outer circumference is provided with an outer lower die at a fixed position having a cutting edge for shaving forming the rough tooth profile and a tooth part meshing with the cutting edge in the axial direction. Mounted on a lower die consisting of an inner lower die and a lower die, which can be moved up and down, and a coarse tooth-shaped blank is sandwiched between the upper die and the inner lower die, which can be lifted above the inner lower die, and a predetermined counter The rough tooth profile blank is pushed into the outer lower die while applying pressure, and the coarse tooth profile blank is lowered while guiding the relative movement of the inner lower die and the outer lower die in order to avoid contact between the cutting edge and the tooth portion due to the action of counter pressure. Synchronously rotating the outer lower die and inner lower die relative to each other in the twisting direction, and shaving the rough tooth profile with the cutting edge. It is a feature of the.

In addition to the first feature, the present invention guides relative movement of the inner lower die and the outer lower die by the guide groove on one side of the inner lower die and the outer lower die and the roller on the other side rolling in the guide groove. The second feature is that the gap between the guide groove and the roller is smaller than the gap between the cutting edge and the tooth portion.

(2) Operation According to the first feature, the heated rough tooth blank is sandwiched between the inner lower die and the upper die and pushed into the outer lower die, so that the load can be relatively small and the siabic molding can be performed. Moreover, since the counter pressure acts, a stable shaved surface can be obtained.
Further, since the outer lower die and the inner lower die relatively rotate in the twisting direction in synchronization with the lowering of the rough tooth profile black, the shaving process of the non-linear rough tooth profile portion is performed accurately. Moreover, since the relative movement of the inner lower die and the outer lower die is guided so as to avoid the contact between the cutting edge and the tooth portion due to the action of the counter pressure, a predetermined counter pressure can be effectively applied to the rough tooth profile portion.

According to the second feature, since the gap between the guide groove and the roller is smaller than the gap between the cutting blade and the tooth portion, the tooth portion and the cutting blade of the inner lower die pressed upward by the counter pressure come into contact with each other. While avoiding this, the relative movement of the inner lower die and the outer lower die can be guided by simple adjustment.

(3) Example Hereinafter, one example of the present invention will be described with reference to the drawings. First, in FIG. 1, for example, in forming a helical gear, a rough tooth profile blank 1 is prepared by forging in a heated state. The rough tooth profile blank 1 has a non-linear tooth trace, for example, a helical tooth-shaped rough tooth profile 2a on its outer periphery, and one end of the rough tooth profile 2 has a burr 2a generated during forging.
Has been left all around. The rough tooth-shaped blank 1 is supplied to the molding device 3 while being heated to a shaving temperature of, for example, 700 to 950 ° C.
By this, the shaving process of the rough tooth profile portion 2 is performed.

The forming apparatus 3 includes a lower die 6 including an inner lower die 4 and an outer lower die 5, an upper die 7 for holding the coarse tooth blank 1 between the inner die 4 and pressing the coarse tooth blank 1 into the outer lower die 5, and an upper die 7.
And a rotation drive mechanism 8 for rotating the outer lower die 5 in synchronism with the downward movement.

A die plate 10 is fixed on the fixed die set plate 9, and a cylindrical die holder 11 is fixed on the die plate 10. The die holder 11 includes an upper holder portion 12, a middle holder portion 13, and a lower holder portion 14, each formed in a cylindrical shape, being coaxially stacked and fixed to each other. The die holder 11 supports an outer lower die 5 which is basically cylindrical and is rotatably supported around an axis extending vertically at a position where a gap is formed between the outer die 5 and the upper surface of the die plate 10. Further, on the inner surface near the upper portion of the outer lower die 5, a cutting blade 15 formed in a helical shape for shaving the coarse tooth profile 2 is provided.

The inner lower die 4 is basically formed in a cylindrical shape, and is arranged coaxially in the outer lower die 5 so as to be able to move up and down. In addition, a tooth portion 16 meshing with the cutting edge 15 of the outer lower die 5 is provided on an outer surface of an upper portion of the inner lower die 4.
Is provided. A lower end of the inner lower die 4 is provided with a flange portion that slides on the inner surface of the lower holder portion 14 of the die holder 11.
4a is provided. Further, the upper end surface of the inner lower die 4 has a rough tooth profile blank 1 on which the rough tooth profile blank 1 is placed.
Is formed in a shape corresponding to the lower surface of the.

2, 3, 4, and 5, an annular recess 17 is formed at the inner edge of the upper end of the outer lower die 5.
A phase matching guide member 18 is fitted and fixed in the annular concave portion 17 so as to be flush with the upper end surface of the outer lower die 5. This guide member 18 is basically formed in a short cylindrical shape, and a guide tooth portion 19 corresponding to the rough tooth profile portion 2 of the short tooth profile blank 1 is connected to the cutting edge 15 of the outer lower die 5 at the lower inner surface thereof. Is provided.

A lower portion of a knockout pin 20 that penetrates the die set plate 9 and the die plate 10 so as to be vertically movable is connected to driving means such as a cylinder (not shown). The knockout pin 20 extends vertically at a central portion of the inner lower die 4. It is possible to ascend inside the drilled through hole 4b and abut on the lower surface of the coarse tooth profile blank 1. Further, in the lower part of the outer lower die 5, cylinders 21 each having an axis line extending in the vertical direction are embedded and arranged in a plurality of places at equal intervals in the circumferential direction. The piston rods 22 of these cylinders 21 are arranged from the lower surface of the outer lower die 5. It extends downward and contacts the upper surface of the lower flange portion 4a of the inner lower die 4.

Above the die plate 10, cylinders 23 having an axis extending in the vertical direction are embedded and arranged at a plurality of circumferential positions surrounding the knockout pin 20, and these cylinders 23
Piston rod 24 is in contact with the lower surface of the inner lower die 4. Moreover, each cylinder 23 is arranged such that, in the original position where the rough tooth blank 1 is placed on the inner lower die 4, the upper end edge of the inner lower die 4 is positioned slightly lower than the upper inner end edge of the outer lower die 5. When the inner lower die 4 descends from the original position shown in FIG. 1, the inner lower die 4 or the rough tooth profile blank 1 is exerted in opposition to the downward pressing force of the inner tooth die 4. It exerts upward resilience to exert counter pressure on.

The upper die 7 has a lower surface corresponding to the upper surface of the rough tooth-shaped blank 1 and is basically formed in a columnar shape. The upper die 7 is fixed to a movable die plate 25 capable of ascending and descending by being connected to an elevating and lowering driving means (not shown). The holder 26 is held while allowing relative movement within a limited range. On the outer surface of the upper die 7, a tooth portion 27 having a tooth trace extending in the axial direction is provided.

An annular stripper 28 surrounding the upper die 7 is suspended from the holder 26. Ie stripper
The base ends of a plurality of vertically extending rods 29 are fixed to the rod 28, and a regulating collar 30 provided on the upper ends of these rods 29.
Is vertically slidably closed at both ends and is slidably fitted in a holding hole 31 provided in the holder 26. In addition, a spring 32 or a hydraulic cylinder is provided between the upper closed end of the holding hole 31 and the control collar 30, and the stripper 28 is elastically biased downward by the repulsive force of the spring 32 or the hydraulic cylinder. To be done. Therefore, the stripper 28 can move relative to the upper die 7 in a vertically limited range while being elastically urged downward.

A projecting portion 28a protruding downward is provided at a lower portion of an inner edge of the stripper 28, and a lower end of the projecting portion 28a has an upper end surface of the rough tooth profile portion 2 of the rough tooth profile blank 1 placed on the inner lower die 4. Can abut. Moreover, the inner surface of the stripper 28 is provided with teeth 33 that mesh with the teeth 27 of the upper die 7.

The rotary drive mechanism 8 is for driving the outer lower die 5 to rotate about its axis in response to the vertical movement of the upper die 7, and has a screw shaft 35 having an axis extending vertically and connected to the upper die 7. A drive gear 36 screwed to the screw shaft 35 and a driven gear 37 meshing with the drive gear 36 are provided.

A sleeve 38 extending in the up-down direction is fixed to the upper holder portion 12 of the die holder 11, and a sleeve 39 is fixed to the lower holder portion 14 coaxially with the sleeve 38. The drive gear 36 is rotatably supported between the sleeves 38 and 39 about the axis. In addition, screw shaft 35, both sleeves 3
8,39 through the screw shaft
The threaded portion 35a engraved on the outer surface of the intermediate portion of the drive gear 35 is
It is screwed into the inner surface of 6. The driven gear 37 is engraved on the outer surface of the outer lower die 5.
37 is engaged with the drive gear 36. Therefore, the drive gear 36 is rotationally driven according to the axial movement of the screw shaft 35, and the driven gear 37, that is, the outer lower die 5 is angularly displaced.

At the lower part of the screw shaft 35, an engaging portion 35b having a non-circular cross section is provided.
Movably penetrates a locking member 40 provided on the lower holder portion 14 so as to prevent the rotation operation. As a result, the rotation operation of the screw shaft 35 is prevented. The lower end of the screw shaft 35 extends up and down and abuts on the upper end of a piston rod 42 of a cylinder 41 fixed to the die plate 10.
The screw shaft 35
Operates upward.

A connecting rod 43 is coaxially connected to the upper end of the screw shaft 35. At the upper end of this connecting rod 43, a collar 43a is formed.
Is provided on the movable die plate 25a.
The movable die plate 25 is held between the holding member 44 fixedly provided on the lower surface thereof and the movable die plate 25 while allowing vertical relative movement within a limited range. As a result, the screw shaft 35 moves up and down in response to the up and down operation of the upper die 7, that is, the movable die plate 25.

Moreover, in order to apply the same pressure to the back surface of the connecting rod 43 and the back surface of the upper die 7, the movable die plate 25 is provided with a passage 45 connecting the spaces facing these back surfaces.

In FIG. 6, guide grooves 46 having an inclination angle α corresponding to the cutting teeth 15 are formed in the inner surface of the outer lower die 5 at a plurality of positions in the circumferential direction. A roller 47 rolling around is pivotally supported. Moreover, the gap between the guide groove 46 and the roller 47 (for example, 0.03 to 0.06 m
m) is the gap between the incisor tooth 15 and the tooth portion 16 (e.g. 0.1 to 0.
5 mm).

Next, the processing procedure of the coarse tooth blank 1 by the molding device 3 will be described. First, the coarse tooth blank 1 heated to 700 to 950 ° C. is removed from the guide tooth portion 19 of the guide member 18.
Thus, the coarse tooth profile 2 is placed on the lower die 6 so that the phase of the coarse tooth profile 2 matches the cutting edge 15 of the outer lower die 5.

Next, when the movable die blade 25 is moved down, the rough tooth blank 1 is sandwiched between the inner lower die 4 and the upper die 7 in the lower die 6 as shown in FIG. Movable die plate in this state
When 25 is lowered, the coarse tooth blank 1 is pushed into the outer lower die 5 while being held between the inner lower die 4 and the upper die 7.

In addition, the screw shaft 35 is also lowered by the lowering of the movable die plate 25 and the upper die 7, and the outer lower die 5 is driven to rotate in synchronization with the lowering of the coarse tooth blank 1 by the operation of the rotary drive mechanism 8.
Therefore, the outer lower die 5 and the inner lower die 4 rotate relative to each other in the twisting direction in synchronization with the lowering of the coarse tooth blank 1, and the cutting edge is rotated by the relative rotation.
At 15, the coarse tooth profile 2 can be shaved.

At the time of this shaving process, a shaving load (tensile stress) is applied to the rough tooth profile portion 2 by the cutting edge 15. If a load in such a fixed direction remains applied, the cutting edge
Due to the resistance of 15, chatter and sink of the tooth tip and cracks due to secondary shear occur in the coarse tooth profile portion 2, and even when knocking out by the knockout pin 20, the product does not come off from the cutting blade 15 smoothly and the same as described above. Defects will occur.

However, a counter pressure by the plurality of cylinders 23 acts on the inner lower die 4 when it descends. Moreover,
The guide groove 46 and the roller 47 are more than the gap between the cutting edge 15 and the tooth portion 16.
Since the gap between the cutting edge 15 and the teeth is small as shown in FIG. 7 (a), the roller 47 contacts the side surface of the guide groove 46 before the cutting edge 15 and the tooth portion 16 mesh with each other. The gap between the portions 16 is maintained, the counter pressure can be prevented from acting on the cutting edge 15, the counter pressure can be surely applied to the rough tooth profile portion 2, and the rolling of the roller 47 along the guide groove 46 can be performed. As a result, a smooth rotation operation of the outer lower die 5 can be obtained in synchronization with the lowering of the rough tooth-shaped blank 1. As a result, the shaving load and the compressive load due to the counter pressure that opposes the shaving load act on the rough tooth profile portion 2, so that the shaving process of the rough tooth profile portion 2 can be performed with a constant balance of tension and compression stress. Will be done. On the other hand, when the roller 47 and the guide groove 46 are not provided, if the constant molding conditions are not satisfied, the tooth portion 16 of the inner lower die 4 comes into contact with the cutting edge 15 as shown in FIG. 7 (b). However, since the counter pressure is prevented from effectively acting on the rough tooth profile portion 2, a good shaving surface cannot be obtained.

Moreover, when the rough tooth profile blank 1 is pushed down by the upper die 7, the projection 28a at the lower end of the stripper 28 abuts the upper end surface of the rough tooth profile 2 as shown in FIG. It works effectively. Further stripper
The spring 28 compresses the spring 32 according to the downward relative movement of the holder 26 with respect to the stripper 28, thereby applying a back pressure to the rough tooth profile 2. Therefore, the counter pressure and the counter pressure acting against the counter pressure act on the coarse tooth profile portion 2, and the internal pressure of the coarse tooth profile portion 2 can be increased, and defects such as chatter, sink marks and drooling occur during shaving processing. Can be reliably prevented.

When the inner lower die 4 is lowered to the lowermost limit, the shaving process of the rough tooth profile portion 2 is completed. At this time, the shaving slag portion 2b generated by shaping is pressure-bonded to the burr portion 2a, and the burr portion 2a and the shaving slag portion 2b. Remains in a half-blanked state immediately before being completely separated from the end face of the rough tooth profile 2 after molding, and the burr 2a and the shaving slag 2b are not dispersed in the molding device 3. After that, the upper die 7 is raised, and at this time, the cylinder 41 is extended and the screw shaft 35 is raised, and accordingly, the outer lower die 5 rotates in a direction opposite to that at the time of processing, whereby the inner lower die 4 rises. . Therefore, the rough tooth-shaped blank 1 after the shaving process is removed from the lower die 6 by the knockout pin 20, and the flash portion produced by the shaving process is cut off to obtain a product.

The relationship between the amount of sink mark on the tooth surface and the counter pressure is shown in FIG. 8. If the allowable amount of sink is 2 mm, the counter pressure must be 3 kg / mm ² or more. FIG. 9 shows the relationship between the shaving temperature and the moldability. FIG. 9 shows the relationship between the droop amount and the shaving temperature. When the allowable droop amount is 1 mm, the shaving temperature is required to be 950 ° C. or less. Further, if the shaving temperature is lower than 700 ° C, the processed portion is cracked during processing, so that the shaving temperature is required to be 700 to 950 ° C.

Next, a specific example when a helical gear is formed according to the present invention will be described.

A coarse tooth profile blank made of SCM420 and SCr420 and having a diameter of 77 mmΦ is forged by a 1000-ton press in a heated state. Next, in the heating state of 700 ~ 950 ℃, shaving cost 0 ~ 0.6 mm, shaving speed 90 ~ 25 mm / sec, shaving load 60 ~ 140 Ton, counter pressure 3 ~ 8 k.
Under the condition of g / mm ² , the tip circle diameter is 76 mmΦ and the number of teeth is 27.
~ 29, module 2.5 involute helical gear with a helix angle of 36 degrees was formed.

At this time, the circumferential surface roughness of the tooth portion is R1, and the axial roughness is R
2, the product accuracy of NO.1 and NO.2 is 9 in DIN grade.
The following table shows the target values corresponding to the classes.

As can be seen from these results, even if the helical gear is formed according to the present invention, a gear with sufficiently high precision can be obtained.

C. Effect of the Invention As described above, according to the first feature of the present invention, when molding a helical gear having non-linear tooth traces such as a helical tooth, it has a rough tooth profile on its outer periphery. An outer lower die having a cutting edge for shaving molding of a rough tooth profile on an inner circumference and an outer lower die in a fixed position and an inner lower die capable of axially moving with a tooth part meshing with the cutting edge. Placed in a heated state on a lower die consisting of and a coarse tooth profile blank is sandwiched between an upper die and an inner lower die that can be raised and lowered above the inner lower die, and a predetermined counter pressure is applied to the coarse tooth profile. The blank is pushed into the outer lower die, the outer lower die and the inner lower die are rotated relative to each other in the torsional direction in synchronization with the lowering of the rough tooth profile blank, and the rough tooth profile is shaving molded by the cutting edge. The shape of the rough tooth profile is non-linear due to the relative rotation of the outer lower die and the inner lower die in the twisting direction because it is possible to perform the Shabin Woo molding with a relatively small load and contributes to downsizing of the molding device. The shaving process can be performed accurately. Further, during shaving, a compression load due to a predetermined counter pressure is applied to the rough tooth profile portion against the shaving load, so that the shaving molding can be performed while balancing the load, and the accuracy of the product can be improved. Furthermore, since the relative movement of the inner lower die and the outer lower die is guided to avoid the contact between the cutting edge and the tooth portion due to the action of the counter pressure, it is possible to make sure that the counter pressure acts on the rough tooth profile portion to cause defects as much as possible. Can be prevented.

Further, according to the second feature, the inner lower die and the outer lower die are guided relative to each other by the guide groove on one side and the roller on the other side rolling in the guide groove to guide the relative movement of the inner lower die and the outer lower die. Since the gap between the rollers is smaller than the gap between the cutting edge and the teeth, it is possible to guide the relative movement of the inner lower die and outer lower die with simple adjustment while avoiding contact between the cutting edge and the teeth. Become.

[Brief description of drawings]

The drawings show one embodiment of the present invention. FIG. 1 is a vertical cross-sectional view of a molding apparatus, which is a cross-sectional view taken along the line II of FIG. 2, and FIG. 2 is a line II-II of the FIG. Sectional view, Fig. 3 is III of Fig. 1.
FIG. 4 is an enlarged view of a portion, FIG. 4 is a sectional view corresponding to FIG. 3 at the end of molding, FIG. 5 is a sectional view taken along line VV of FIG. 3, and FIG. 6 is a sectional view taken along line VI-VI of FIG. FIG. 7 is a vertical cross-sectional view of a cutting edge portion for showing the action state of the counter pressure on the rough tooth profile portion, FIG. 8 is a graph showing the relationship between the counter pressure and the sink amount of the tooth surface, and FIG. It is a graph which shows the relationship between temperature and the amount of dripping. 1 ... Coarse tooth blank, 2 ... Coarse tooth portion, 4 ... Inner lower die, 5 ... Outer lower die, 6 ... Lower die, 7 ... Upper die, 15 ... Cutting edge, 16 ... Tooth portion, 46
...... Guide groove, 47 …… Roller

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiaki Kano 1-10-1 Shin-Sayama, Sayama-shi, Saitama Honda Engineering Co., Ltd. (56) References JP-A-57-134230 (JP, A) JP-A-SHO 56-68540 (JP, A) JP-A-62-28040 (JP, A)

Claims (2)

(57) [Claims] 1. When molding a helical gear having a non-linear tooth trace such as a helical tooth, a rough tooth profile blank having a rough tooth profile portion on the outer periphery is cut for shaving the rough tooth profile portion. On the lower die, which is composed of an outer lower die having a blade on the inner circumference and at a fixed position and an inner lower die having a tooth portion meshing with the cutting blade and axially movable, is placed in a heated state, and the inner die The rough tooth profile blank is sandwiched between the upper die and the inner lower die that can be raised and lowered above the lower die, and the rough tooth profile blank is pushed into the outer lower die while applying a predetermined counter pressure, and the cutting blade is acted by the counter pressure. The outer lower die and the inner lower die are guided in synchronization with the lowering of the coarse tooth profile blank while guiding the relative movement of the inner lower die and the outer lower die in order to avoid the contact of the teeth. B is relatively rotated in the direction twist, forming method of the helical gear such that characterized in that the shaving mold the rough gear portion at the cutting edge. 2. A guide groove on one side of the inner lower die and the outer lower die and a roller on the other side rolling in the guide groove to guide relative movement of the inner lower die and the outer lower die, and a gap between the guide groove and the roller. Is smaller than the gap between the cutting edge and the tooth portion, the method for forming helical gears according to item (1).