JP3770960B2 - Manufacturing method of gear by cold forging and die used therefor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a die used for manufacturing a gear by cold forging.And manufacturing method using the moldIt is about.
[0002]
[Prior art]
  A method of manufacturing a gear by cold forging using a metal material is known.
[0003]
  FIG.1 and FIG.2 has shown the manufacturing method by the conventional cold forging which manufactures a spur gear. The cylindrical metal material 10 has a size close to the outer diameter of a desired gear. The lower end of the cylindrical metal material 10 is inserted into the hole 11A of the mold 11, pushed in from the direction of the arrow X, the metal material 10 is pressed by a punch (not shown), and the outer periphery of the material 10 is male. The tooth form is formed. The male tooth profile formed on the outer periphery of the material 10 corresponds to the tooth profile 12 of the mold 11. The relationship between the tooth root and the tooth tip of the tooth profile is reversed between the material 10 and the mold 11. The tooth profile 12 of this mold 11 has a regular full tooth depth H. Therefore, the tooth profile formed on the outer periphery of the material 10 has a regular full tooth depth H as well.
[0004]
  In FIG. 1, the code | symbol 13 has shown the pitch circle. 1 and 2, reference numeral 14 indicates a tip circle of the tooth profile 12 of the mold 11, and reference numeral 15 indicates the root circle.
[0005]
  In the conventional method of manufacturing a gear by cold forging, the end surface 16 of the tooth forming shape start portion of the tooth profile 12 of the die 11 is inclined, but the inclination angle B of the end surface 16 with respect to the surface perpendicular to the axis of the die 11 is 30. ° or less. The smaller the inclination angle B, the fewer incomplete tooth profile portions.
[0006]
  In addition, the material 10 may be cold forged in one step, but after preforming in advance or warm, it is annealed, surface lubricated, etc., and then finished with cold forging. Sometimes.
[0007]
  In the case of a gear that is relatively thin compared to the size of the teeth, a tooth shape is preliminarily formed by shear punching a plate-shaped metal material, and the tooth shape is formed by finish forging in a subsequent process.
[0008]
  Furthermore, a forging method for gears generally called closed forging is also known. That is, a material having a size smaller than the diameter of the root circle is inserted into the hole of the die, pressed from the end face, forged by the tooth shape of the die, and the metal material is formed by overhanging.
[0009]
[Problems to be solved by the invention]
  In the conventional cold forging gear manufacturing method shown in FIG. 1 and FIG. 2, the quality of the final gear is considered to be 50 to 80% of the factors related to the forging die. .
[0010]
  In the method shown in FIGS. 1 and 2, molding is performed inside a female mold, which is called in-die molding. The metal material used in this manufacturing method is a solid round bar, a ring-shaped material, a pre-processed product by hot or warm forging, or the like.
[0011]
  In any case, in the conventional method shown in FIGS. 1 and 2, a gear is cold forged in one process to obtain a finished dimension. Therefore, the load (pressure) applied to the inclined end surface 16 of the tooth forming shape start portion of the tooth profile 12 is 200 kgf / mm.²To 280kgf / mm²It also becomes. This load (pressure) is 70 to 90% of the breaking strength of the mold even if the material has the highest level as the mold material.
[0012]
  In many cases, the maximum load during cold forging is generated on the inclined end surface 16 of the tooth forming shape starting portion on the inner surface of the die. Conventionally, the life of the mold 11 was short because there was not enough device to reduce the maximum load. As a result, there is a drawback that product accuracy deteriorates.
[0013]
  In particular, when a helical gear is manufactured by cold forging, a load is applied to cause the tooth profile 12 of the mold 11 to fall only on one side, so that the probability of breakage near the inclined surface 16 tends to increase. there were. As a result, the life of the mold 11 was shortened.
[0014]
  According to the knowledge of the present inventor, in the case of processing of a helical gear by cold forging, a load is concentrated on one surface (front surface) of the mold tooth profile, Does not take much load. Therefore, the difference in load between the front side and the back side of the tooth profile is remarkable, and there are many tooth profile defects caused by the difference.
[0015]
  Therefore, an object of the present invention is to provide a method of manufacturing a gear by cold forging that can extend the life of the die and a die used for the method.
[0016]
  Another object of the present invention is to provide a method for producing a gear by cold forging, which can produce a high-quality gear, and a die used therefor.
[0017]
[Means for Solving the Problems]
  The present invention claims5 or 6The manufacturing method of the gear by the cold forging described in 1 is used as the gist.
[0018]
  The present invention also includes claims.1Or4A die used in the method for producing a gear by cold forging described in any one of the above is also summarized.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
  The present invention extends the limits of manufacturing gears by cold forging. In particular, it has been recognized that helical gears are extremely difficult to manufacture by cold forging. However, the present invention enables efficient and high-precision production of helical gears or similar gears. To do.
[0020]
  Various gears can be produced by the method and mold of the present invention. A two-stage gear having two large and small gears, a gear with a flange, a chamfered chamfered gear, a gear with ratchet teeth, a gear with serrations, and the like can be formed by cold forging. Furthermore, cold forging of straight tooth bevel gears and similar gears is also possible.
[0021]
  According to the gear manufacturing method and mold of the present invention, the product accuracy of the processed gear can be JIS grade 5 to grade 7.
[0022]
  One of the features of the present invention is that regular teeth and low teeth are formed at the start portion of the tooth forming shape of the mold and are formed in a multistage shape. Thereby, the stress generated in the die at the beginning of cold forging is dispersed to reduce the local stress. For example, a temporary low tooth profile is first formed by cold forging with a low tooth having a lower tooth depth than a normal full tooth depth, and then the normal tooth profile is cold forged with a regular tooth having a normal full tooth depth. Form with.
[0023]
  In this case, it is most desirable in terms of production efficiency to form a temporary low tooth profile by cold forging with the low teeth of the mold and subsequently form a regular tooth profile of the mold by cold forging. This is because according to such a cold forging method, a desired gear can be formed in one forging process.
[0024]
  However, the present invention is not limited to such a method. For example, using two or more molds, only the last mold has regular teeth with full normal teeth, and the other molds have only low teeth with lower normal teeth. First, a temporary low tooth profile is formed by cold forging with the low tooth having the lowest tooth depth, and the tooth height is increased successively, and finally the normal tooth with the regular full tooth height is regular. The tooth profile can also be formed by cold forging.
[0025]
  Unlike the full tooth length of regular teeth, the low tooth depth is not always constant between the start and end of the low teeth, and may change in a stepped, linear or curved shape.
[0026]
  In any case, according to the cold forging method of the present invention, a single metal material can be integrally processed only by cold forging, even with a flanged gear, a two-stage gear, or a splined gear. it can.
[0027]
  However, the present invention includes a method of performing preforming by cold forging after preforming hot or warm, and a method of adding cutting or the like to the middle or the end of forging as necessary. In other words, the present invention is not limited to the method of manufacturing the final gear product from the beginning to the end only by cold forging.
[0028]
  The material used in the present invention is mainly a metal, such as a round bar, a ring-shaped material, a preform formed by hot or warm forging, or the like. In principle, any material that is normally used as a gear material can be used.
[0029]
  According to the production method of the present invention, it is easy to improve the JIS grade by 1 to 3 grades as compared with the conventional production method of FIGS.
[0030]
  When the gear accuracy is improved, the types of gears that can be cold forged are increased, and the scope of gear cold forging is expanded as a whole.
[0031]
  According to the present invention, it is possible to integrally mold the gear and the flange. Therefore, the range of application of products in cold forging is greatly expanded. According to the conventional manufacturing method, it has been said that processing by cold forging is impossible for a gear with a flange having a large size. However, according to the present invention, the outer diameter is twice to three times the outer diameter of the gear. Even a flange having a diameter can be integrally formed with a gear.
[0032]
  Furthermore, two types of large and small gears can be integrally formed in two stages.
[0033]
  Even if there is a change in the shape of the gear, such as with or without a shaft, it is possible to respond flexibly.
[0034]
  When producing gears with flanges or gears with multiple steps, conventionally, finish molding was performed once inside the mold or punch, so if the gear and flange are integrated, the outer diameter of the flange will be The molding limit was about 1.2 times the outer diameter of the gear. Since the diameter of the material is larger than the outer diameter of the gear and the molding load per unit area is large, the die life number is remarkably short. Compared to this, the effect of the present invention regarding the number of molds is outstanding.
[0035]
  Further, the present invention can improve accuracy and reduce quality variations. When higher accuracy is required, the desired accuracy can be obtained by performing sizing continuously by stacking necessary high-precision dies, or by performing press sizing by setting another process.
[0036]
  In addition, both straight-tooth gears and helical gears with a helix angle of 36 ° or less can be manufactured by using a conventional forging machine and simply changing the mold to that of the present invention to produce various gears by cold forging. Is possible.
[0037]
  When cold forging a helical gear, the gear can be easily manufactured by setting the die or punch to be rotatable or by forcibly rotating the helical gear.
[0038]
  One of the greatest effects of the present invention is that the life of the mold can be increased by 2 to 3 times compared with the conventional one shown in FIGS. 1 and 2 (5000 or less gears per mold).
[0039]
  Furthermore, the present invention improves the yield of the material and the strength of the gear as compared with the gear for cutting gear.
[0040]
  As a result of investigation by the inventor of the present invention, it has been found that the shape of the tooth forming start portion of the mold greatly affects both the life of the mold and the accuracy of the gear product. In particular, the tip portion of the regular tooth of the gear product is extremely important as compared to the root portion. The present invention has been completed by paying attention to this point.
[0041]
  In the case of the present invention, the tooth tip portion of the regular tooth profile of the gear product is forged mainly by the low teeth of the mold, so that the spur is formed with good sharpness. In particular, when the tooth depth at the starting end of the low teeth has a small value and a sufficient level difference for escape is ensured, the frictional resistance becomes small and the sharpness becomes very good. As a result, the “sag” phenomenon of the tooth tip portion of the gear product is improved. The root portion of the regular tooth profile of the gear product is mainly formed by the tip portion of the regular tooth of the mold. At this time, since the root part of the regular tooth profile of the gear product has already been molded, the load applied to the regular tooth of the mold is accordingly small. Therefore, the root part of the regular tooth profile of the gear product is also shown in FIGS. Compared with the conventional method shown in FIG.
[0042]
【Example】
  Hereinafter, various aspects of the present invention will be described.referenceAn example will be described with reference to the drawings.
[0043]
  Reference example of Figs.
  3 and 4 show the present invention.referenceAn example is shown. thisreferenceIn the example, a spur gear is formed on the outer periphery of the solid cylindrical metal material 20.
[0044]
  The mold 21 has a hole 21A in the direction of the axial center 31, and a female tooth profile 27 is formed on the peripheral surface of the hole 21A. This tooth profile 27 is a regular tooth profile, and has a regular full tooth gap H. The tooth profile indicated by reference numeral 28 is a low tooth having a tooth depth h lower than the full tooth height H of the normal tooth profile 27 at its starting end.
[0045]
  When compared with the conventional mold 11 shown in FIGS. 1 and 2, the mold 21 of FIGS. 3 to 4 is different in that the tooth forming start portion is formed in two stages by the regular teeth 27 and the low teeth 28. As a result of the deletion of the portion indicated by the alternate long and short dash line 29 by reference numeral 29, the lower tooth 28 is formed.
[0046]
  The length L of the low teeth 28 in the direction of the axis 31 of the mold 21 is equal to or greater than the total tooth depth H of the normal tooth profile 27, and in order to reduce the frictional resistance, A step or clearance for escape is provided.
[0047]
  The low teeth 28 include a cylindrical surface 28B that is parallel to the axis 31 of the mold 21 and a substantially frustoconical inclined surface 28A that is inclined therefrom.
[0048]
  The length of the cylindrical surface 28B of the low tooth 28 in the direction of the axis 31 is preferably longer than the tooth depth h of the low tooth 28 at the starting end in order to ensure a step or clearance for escape. .
[0049]
  The boundary between the portion of the cylindrical surface 28B of the low tooth 28 and the portion of the truncated conical inclined surface 28A is preferably rounded. Furthermore, it is desirable that the boundary portion between the low tooth 28 and the regular tooth profile 27 is also rounded. Further, it is desirable that the first inclined surface of the tooth forming shape start portion of the die 21, that is, the substantially truncated cone-shaped inclined surface 26, and the boundary surface with the low teeth 28 are also rounded.
[0050]
  An inclination angle C1 of the first inclined surface 26 of the tooth forming shape starting portion with respect to a plane orthogonal to the axis 31 is 10 ° to 45 °, preferably 25 ° to 30 °. The inclination angle C2 of the truncated conical surface 28A with respect to the plane orthogonal to the cylindrical surface 28B of the low tooth 28 is set to 20 ° to 60 °, preferably 30 ° to 45 °. These inclination angles C1 and C2 can be appropriately set according to the shape of the low teeth 28 and the size of the tooth h.
[0051]
  Further, if the inclination angles C1 and C2 and the length L of the low teeth 28 are set small, the incompletely formed portion of the gear can be reduced accordingly.
[0052]
  An example of a method for producing a spur gear by cold forging using the mold 21 of FIGS.
[0053]
  Except for the shape of the die 21, the overall structure and usage of the forging machine is the present invention.Reference exampleSince no substantial difference is recognized between the conventional example of FIGS. 1 and 2, forging may be performed in the same manner as in the prior art.
[0054]
  However, the forging mechanism isReference exampleIt is peculiar to. First, a temporary low tooth profile is formed by cold forging by the low teeth 28 having the tooth depth h lower than the regular full tooth depth H. Thereafter, a normal tooth profile is formed by cold forging by the normal teeth 27 having the normal full tooth depth H. In this case, the temporary low tooth profile and the regular tooth profile are formed by a single process with one mold 21. A regular tooth profile is formed immediately after the provisional low tooth profile is formed.
[0055]
  The relationship between the full tooth depth H of the normal tooth profile and the tooth depth h at the starting end of the low tooth is 0.3H <h <0.8H.
[0056]
  The forging method of the example of FIGS. 3-4 is described in detail.
[0057]
  The cylindrical metal material 20 has a size close to the outer diameter of a desired spur gear. The lower end of the cylindrical metal material 20 is inserted into the hole 21A of the mold 21 and pushed in from the direction of the arrow X, and the metal material 20 is pressed by a punch (not shown) to The tooth form is formed. The male tooth profile formed on the outer periphery of the material 20 corresponds to the tooth profile of the mold 21, that is, the regular tooth profile 27 and the low tooth 28. The relationship between the tooth root and the tooth tip of the tooth profile is reversed between the material 20 and the mold 21. The regular tooth profile 27 of the mold 21 has a regular full tooth gap H. Therefore, the regular tooth profile formed on the outer periphery of the material 20 has the regular full tooth depth H as well. However, the portion corresponding to the first inclined surface 26 and the subsequent low teeth 28 of the tooth forming shape starting portion is lower than that and becomes an incomplete tooth shape portion.
[0058]
  3 to 4, reference numeral 23 denotes a pitch circle. Reference numeral 24 indicates a tip circle of the regular tooth profile 27 of the mold 21, and reference numeral 25 indicates the root circle.
[0059]
  When manufacturing with the die shown in FIGS. 3 and 4, relatively large stress is generated on the first inclined surface 26 of the tooth forming start portion at the start of forging, but the tooth depth h at the beginning of the low teeth 28 is small. Therefore, the pressure applied to the first inclined surface 26 of the tooth forming start portion is dispersed and reduced. A part of the dispersed pressure is applied to the low-tooth inclined surface 28 </ b> A located immediately before the regular tooth profile 27. Therefore, when viewed as a whole, the maximum stress and the offset load generated in the local portion of the mold 21 are greatly reduced. As a result, the first inclined surface 26 of the tooth forming start portion is not partially broken or locally deformed, and the mold life and the accuracy of the gear product are not deteriorated. This leads to good accuracy of the entire formed tooth profile.
[0060]
  In addition to this, if the dimensions of the material, metal structure, surface lubrication treatment, etc. are properly adjusted, the processing load can be further reduced.
[0061]
  Reference examples of Figs.
  5 and 6 show examples applied to the cold forging method of a helical gear.
[0062]
  5 and 6, a helical gear having an inclination D is formed on the outer periphery of a solid cylindrical metal material 60. The inclination D is typically 10 ° to 40 °.
[0063]
  The mold 61 has a hole 61A in the direction of the axis 71, and a female tooth profile 67 is formed on the peripheral surface of the hole 61A. This tooth profile 67 is a regular tooth profile and has a regular full tooth gap H. The tooth profile indicated by reference numeral 68 is a low tooth having a tooth depth h lower than the full tooth depth H of the normal tooth shape 67.
[0064]
  The mold 21 shown in FIGS. 3 to 4 and the mold 61 of FIGS. 5 to 6 are in a two-stage shape in which the tooth formation start portions are similar to each other. The portion of the one-dot chain line between the first inclined surface 66 and the regular tooth profile 67 of the tooth formation start portion is deleted, and the low tooth 68 is formed there.
[0065]
  The length L of the low teeth 68 in the direction of the axis 71 of the mold 61 is equal to or greater than the total tooth depth H of the normal tooth profile 67, and there are sufficient steps or gaps for escape there. Is provided. This reduces the frictional resistance during forging.
[0066]
  The low teeth 68 include a cylindrical surface 68B that is parallel to the axis 71 of the mold 61 and a substantially truncated cone-shaped inclined surface 68A that is inclined therefrom.
[0067]
  Although a square shape is shown in FIG. 5, the boundary between the cylindrical surface 68B of the low tooth 68 and the inclined surface 68A having a truncated cone shape is preferably rounded. Furthermore, it is desirable that the boundary portion between the low teeth 68 and the regular tooth profile 67 is also rounded. Further, it is desirable that the first inclined surface of the tooth forming start portion of the die 61, that is, the substantially truncated cone-shaped inclined surface 66 and the boundary surface between the low teeth 68 are rounded.
[0068]
  The inclination angle E of the first inclined surface 66 of the tooth forming start portion is 10 ° to 30 °, preferably 15 ° to 25 °. An inclination angle F of the truncated conical surface 68A with respect to a plane orthogonal to the cylindrical surface 68B of the low teeth 68 is set to 20 ° to 60 °, preferably 30 ° to 45 °. These inclination angles E and F can be appropriately set according to the shape of the low teeth 68 and the size of the tooth h.
[0069]
  Further, if the inclination angles E and F and the low tooth length L are set small, the incompletely formed portion of the gear can be reduced accordingly.
[0070]
  An example of a method for manufacturing a helical gear by cold forging using the die 61 of FIGS.
[0071]
  Except for the shape of the die 61, the overall structure and usage of the forging machine is the present invention.Reference exampleThere is no substantial difference between the conventional example and the conventional example.
[0072]
  The present inventionReference exampleIn this case, as in the prior art, forging is performed while rotating the die 61 and / or punch (not shown) according to the value of the slope D.
[0073]
  The forging mechanism is the present invention.Reference exampleFirst, a temporary low tooth profile is formed by cold forging by the low teeth 68 having the tooth depth h lower than the normal full tooth height H. Thereafter, a normal tooth profile is formed by cold forging by the normal teeth 27 having the normal full tooth depth H. In this case, a temporary low tooth profile and a regular tooth profile are formed by a single process using one die 61. Moreover, a regular tooth profile is formed immediately after the provisional low tooth profile is formed.
[0074]
  The relationship between the full tooth depth H of the normal tooth profile and the tooth depth h at the start of the low teeth is 0.3H <h <0.8H.
[0075]
  A more detailed description of such a manufacturing process.
[0076]
  The cylindrical metal material 60 has a size close to the outer diameter of a desired spur gear. The lower end of the cylindrical metal material 60 is inserted into the hole 61A of the mold 61, and the mold 61 and / or the punch is rotated from the direction of the arrow X while rotating, and the metal material 60 is punched (not shown). To form a male helical tooth profile on the outer periphery of the material 60. The male tooth profile formed on the outer periphery of the material 60 corresponds to the tooth profile of the mold 61, that is, the regular tooth profile 67 and the low tooth 68. The relationship between the tooth root and the tooth tip of the tooth profile is reversed between the material 60 and the mold 61. The regular tooth profile 67 of the mold 61 has a regular full tooth gap H. Therefore, the regular tooth profile formed on the outer periphery of the material 60 has the regular full tooth depth H as well. However, the first inclined end face 66 of the tooth formation start portion and the subsequent portion corresponding to the low tooth 68 are lower than that and become an incomplete tooth shape.
[0077]
  5 to 6, reference numeral 63 denotes a pitch circle. Reference numeral 64 indicates a tip circle of a regular tooth profile 67 of the mold 61, and reference numeral 65 indicates a root circle.
[0078]
  When a gear was experimentally manufactured using the mold 61 shown in FIGS. 5 and 6, a load of 35 to 40 tons was conventionally required in the X direction.Reference exampleAccording to the above, if the load is about 20 tons, cold forging can be sufficiently performed. In this case, the material 60 is made of S35C, the diameter of the cylindrical material 60 before forging is 14 mm, and the diameters of the pitch circle, the root circle, and the tip circle of the regular tooth 67 of the die 61 are 12.55 mm, respectively. 14.1 mm, 10.6 mm. The length L of the low teeth 68 was 2.5 mm. The inclination angles E and F were 20 ° and 45 °, respectively. The inclination D of the helical gear was two examples of 17 ° and 20 °.
[0079]
  In the manufacturing method shown in FIGS. 5 and 6 as well, although a relatively large stress is generated on the inclined surface 66 of the tooth forming start portion, the tooth h at the starting end of the low tooth 68 is small, and therefore the tooth profile thereof. The pressure applied to the first inclined surface 66 at the molding start portion is dispersed and becomes smaller. Part of the dispersed pressure is applied to the inclined surface 68A immediately before the regular tooth profile 67. Therefore, when viewed as a whole, the maximum stress and the offset load generated in the local portion of the mold 61 are greatly reduced. As a result, the first inclined surface 66 of the tooth forming start portion is partially broken or locally deformed, and the life of the mold and the accuracy of the gear product are less deteriorated. This leads to good accuracy of the entire formed tooth profile.
[0080]
  In addition to this, if the dimensions of the material, metal structure, surface lubrication treatment, etc. are properly adjusted, the processing load can be further reduced.
[0081]
  According to the inventor's knowledge, in the production of helical gears and similar gears, the relationship between H and h is 0.3H <h <0.8H, preferably 0.5H <h <0. By setting 6H, the bending stress generated at the tooth forming shape starting portion can be reduced in inverse proportion to the square of the height. In particular, if the length L of the low teeth 68 (particularly the portion of the cylindrical surface 68B) is increased, the regular tooth profile 67 is formed in a state where the torsion is guided, so that the bending stress generated in the mold 61 is significantly reduced. Become.
[0082]
  Although the load or pressure is different between the front side and the back side of each tooth in the tooth profile of the mold 61, the difference can be reduced by providing the low teeth 68. That is, by providing the low teeth 68, the load difference between the front and back of each tooth can be reduced.
[0083]
  The inclination angle E of the first inclined surface 66 of the tooth forming start portion is 10 to 30 ° (preferably 15 to 25 °) as described above. The best inclination angle E is 20 ° from the viewpoint of accuracy. However, this does not mean that the inclined surface 66 should always be a flat surface. The inclined surface 66 may be a curved surface.
[0084]
  Further, if the tooth h of the low tooth 68 is made smaller, the bending stress becomes smaller in inverse proportion to the square of the height, so the probability of breakage is reduced accordingly. In particular, when the length L of the low teeth 68 is made longer and a step or clearance for escaping is secured, the regular tooth profile 67 is formed in a state where the twist is guided accordingly. The generated bending stress is significantly reduced. In particular, the point to be emphasized regarding the manufacture of the helical gear is that the load difference is reduced between the front side and the back side of the regular tooth profile 67. Unless such measures are taken, particularly in the case of cold forging of a helical gear, the phenomenon that the pressure is large on the front side of the tooth profile and the pressure is small on the back side is inevitable.
[0085]
  For better accuracy, the low teeth 68 can be further divided into a number of stages. Then, the forging process is finally performed with the regular tooth profile 67. By continuously forging such a number of stepped low teeth and one final regular tooth profile, it becomes possible to obtain a higher accuracy than the conventional method.
[0086]
  Reference example of Figure 7
  FIG. 7 shows another embodiment of the present invention.referenceAn example is shown.
[0087]
  In the example of FIG. 7, the mold of the regular teeth 12 and the mold of the low teeth 68 are separate. As the mold of the regular teeth 12, those of FIGS. The low tooth 68 mold has a depth of h throughout the mold that is smaller than the normal full depth. Various shapes can be employed for the low teeth 68.
[0088]
  Reference example of FIG.
  FIG. 8 shows still another embodiment of the present invention.referenceAn example is shown.
[0089]
  (A) has shown the state which forged the cylindrical-shaped metal raw material 60 using the type | mold 61 of FIGS. 5-6, and formed the low tooth | gear 68 and the regular tooth profile 67 by one forging process. .
[0090]
  (B) shows a state in which a flange 81 is formed on the upper side of the regular tooth profile 67 by forging the material 60 in the state of (A) described above in another process. Due to the formation of the flange 81, the portion of the low teeth 68 described above has substantially disappeared due to plastic deformation.
[0091]
  (C) is the state in the middle of the process which is using the type | mold 61 of FIGS. 5-6 on the outer periphery of the flange 81 of the semi-finished product 60 shown in the above-mentioned (B), and is forming the regular tooth profile 67 and the low tooth 68. Is shown.
[0092]
  (D) shows a state in which the regular tooth 67 is formed on the entire outer periphery of the flange 81 by further pushing forward the step (C) described above. As a result, the two large and small regular teeth 67, 67 are formed in the form of two-stage teeth. Both of these regular teeth are helical gears.
[0093]
  The process (B) described above is generally called an upset forging process.
[0094]
  Moreover, the intermediate process of the above-mentioned (C) and the above-mentioned (B) and (D) is shown, and the large regular tooth profile 67 is called a through-molding tooth profile. There, eventually, the portion of the low teeth 68 disappears.
[0095]
  Strictly speaking, at the upper end of the small regular tooth profile 67, the low teeth 68 partially remain in the state of (B) to (D) in FIG. 8, but this point is detailed in the drawing. Not shown.
[0096]
  The component having two large and small helical gears shown in FIG. 8D has a great merit that the fiber flow is good and the life is long. Another advantage is that the two large and small regular helical gears 67 are exactly concentric. Furthermore, in the case of such two large and small helical gears, since the relative positions of the two gears 67 and 67 are fixed, it is possible to achieve very accurate concentricity.
[0097]
  Reference example of Fig. 9
  FIG. 9 shows an example of forging a helical gear with a flange.
[0098]
  First, (A) shows a state in which regular helical teeth 67 and low teeth 68 are continuously formed on a cylindrical material 70 using the molds shown in FIGS.
[0099]
  Next, (B) shows a state in which a flange 90 is formed by applying a load from the upper part by upset forging from the state of (A) described above.
[0100]
  With the formation of the flange 90, the portion of the low teeth 68 is substantially lost, and only the regular tooth profile 67 remains. Strictly speaking, although some of the low teeth 68 may remain, they are not shown in FIG. This can be clearly recognized from the fiber flow by looking at the cut surface.
[0101]
  Reference example of FIG.
  FIG. 10 shows a forging example of a helical gear with a shaft.
[0102]
  First, as shown in FIG. 6A, a regular helical tooth 67 and a subsequent low tooth 68 are forged at one end of a long cylindrical material 91 using a die shown in FIG. At this time, the portion where the normal helical teeth 67 and the low teeth 68 (upper part of the figure) are slightly larger in diameter, and the other part 92 (lower part of the figure) is the shape of the shaft. It has become.
[0103]
  (B) shows a state in which the above-described low teeth 68 are substantially eliminated by cold forging the above-mentioned (A) to form a flange 93 at the upper end of the shaft-shaped portion 92. Show.
[0104]
  Reference example of FIG.
  FIG. 11 shows one development example of the manufacturing method of FIG.
[0105]
  The cold forging process from (A) to (F) is an example of a cold forging machine marketed under the trade name “Parts Homer BPF650”.
[0106]
  The processing step (G) is an example of a cold forging machine marketed under the trade name “My Press L1C200”.
[0107]
  First, (A) shows an elongated round bar-shaped material 111. The material of the round bar-shaped material 111 is S35C.
[0108]
  (B) shows a semi-processed product 115 formed by plastic working both ends 116 of the above-described round bar-shaped material 111.
[0109]
  (C) has shown the state which narrowed down the right end part of the half-finished product 115, and formed the thin part 117. FIG.
[0110]
  In the step (D), the thin portion 117 is forged into two steps to form two thin portions 118 and 119.
[0111]
  In (E), the left end portion of the semi-processed product 115 is forged to form a portion 100 having a slightly larger diameter.
[0112]
  Further, in (F), the forging process described with reference to FIG. 10 is performed on the slightly thick cylindrical portion 200. That is, the regular helical tooth profile 67 and the subsequent low teeth 68 are formed in the thick cylindrical portion 200 by one forging process.
[0113]
  In (G), the flange-like portion 201 is formed, so that the aforementioned low teeth 68 are substantially eliminated, and the flange-like portion 201 is positioned after the regular helical tooth profile 67. This regular tooth profile 67 is a helical gear having an inclination of 20 °.
[0114]
  Further, in (G), a serration 202 (square cross-sectional axis) is formed in a portion 118 having a relatively small diameter on the right side. This serration 202 is also processed by cold forging.
[0115]
  Example of FIG.
  FIG.2Of the present invention in FIGS.Improved reference examplesAn example is shown.
[0116]
  A region of low teeth 303 is formed between the regular tooth 300 of the mold and the first inclined surface 301 of the tooth forming start portion. In particular, the portion between the inclined surface 303A of the low tooth 303 and the first inclined surface 301 is the same as that shown in FIGS.referenceRetracted from the cylindrical surfaces 28B and 68B of the example,As is clear from FIG.There is a step to escape the fiber flow.From the start of tooth formationIt is configured.
[0117]
  Of FIG.In (A), the stepped portion 303B has a cylindrical shape and is parallel to the axis 311 of the mold by 0.02 to 0.5 mm.From the start of tooth formationIt slips inward and retracts.
[0118]
  Of FIG.In (B), the step 303B is inclined by 0.5 ° to 10 ° with respect to the axis 311 of the mold.From the start of the tooth formationIt has a frustoconical surface that is recessed inward and inclined in the opposite direction.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view taken along line 1-1 of FIG. 2 and shows a conventional method for manufacturing a spur gear by cold forging.
FIG. 2 shows the tooth formation start part of the mold as seen from the direction of arrow A in FIG.
FIG. 3 is a sectional view taken along line 3-3 in FIG.Reference exampleThe manufacturing method of the spur gear by the cold forging by is shown.
FIG. 4 shows the tooth formation starting part of the mold as seen from the direction of arrow A in FIG.
FIG. 5 shows another embodiment of the present invention.referenceThe manufacturing method of the cold forging of the helical gear by an example is shown.
6 shows a tooth profile formation start portion of the mold used in the manufacturing method of FIG. 5 as seen in the direction of arrow A in FIG. 5;
FIG. 7 shows still another embodiment of the present invention.referenceAn example is shown.
FIGS. 8A to 8D show a series of steps for manufacturing a two-stage gear part having two large and small gears from a cylindrical material.
9A and 9B show two processes for manufacturing a flanged gear from a cylindrical material.
FIGS. 10A and 10B show a situation in which a part having a flange and a shaft is made from a cylindrical material.
FIGS. 11A to 11G show a series of steps of forging an elongated round bar to make a part having gears, flanges, shafts, and serrations.
FIGS. 12A and 12B are views of a step for escaping in a low tooth at a tooth forming shape start portion.Of the present inventionTwo typicalImplementationAn example is shown.
[Explanation of symbols]
  10 Metal materials
  11 type
  12 Tooth profile
  13 pitch circle
  14 type tip circle
  Type 15 tooth root circle
  16 First inclined surface
  20 Metal materials
  21 type
  21A hole
  23 pitch circle
  24 type tip circle
  25 type tooth root circle
  26 First slope
  27 Tooth profile
  28 Low teeth
  28A inclined surface
  28B Cylindrical surface
  31 axis
  60 Metal materials
  61 type
  61A hole
  63 pitch circle
  Type 64 tip circle
  65 type tooth root circle
  66 First slope
  67 Tooth profile
  68 low teeth
  68A inclined surface
  68B Cylindrical surface
  71 axis
  81 Flange
  90 flange
  91 materials
  92 Shaft-shaped part
  95 Semi-finished product
  100 regular tooth profile
  101 First slope
  102 low teeth
  103 virtual straight line
  111 materials
  115 Semi-finished product
  116 both ends
  117, 118, 119 Narrow part
  200 Thick cylindrical part
  201 Flange-shaped part
  202 Serration

Claims (6)

In a mold for manufacturing gears by cold forging, regular teeth having regular full teeth and low teeth having lower depth than regular full teeth are formed in a multi-stage shape. A die characterized in that a fiber escape step is formed in the middle of the tooth so as to be retracted inward from the end of the first inclined surface of the tooth forming start portion.   The mold according to claim 1, wherein 0.3H <h <0.8H, where H is the total tooth length of the regular teeth and h is the tooth depth at the beginning of the low teeth.   3. The step portion for escaping the fiber has a cylindrical shape, and is retracted inward by 0.02 to 0.5 mm in parallel to the axis of the mold. The mold according to item 1.   The step portion of the fiber escape is inclined by 0.5 ° to 10 ° with respect to the axis of the mold and retracted inward, and has a truncated conical surface inclined in the opposite direction. The mold according to any one of claims 1 to 2. In the method of manufacturing a gear by cold forging, first, a temporary low tooth profile is formed by cold forging with low teeth having a lower tooth depth than a regular full tooth depth, and then has a normal full tooth depth. A regular tooth profile is formed by cold forging with regular teeth, and a temporary tooth profile and a regular tooth profile are formed with one mold according to any one of claims 1 to 4, and a temporary tooth profile is formed with low teeth. When forming the tooth profile, the fiber flow escapes due to the inwardly retracted fiber flow relief step formed from the end of the first inclined surface of the tooth formation start part in the middle of the low tooth A method for manufacturing a gear by cold forging.   6. The method of manufacturing a gear by cold forging according to claim 5, wherein two gears of large and small are formed from a single material by a series of cold forging.

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