JP2006102821A - Method for forming tooth profile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for lengthening die life and improving quality of tooth profile in forming the tooth profile from tooth profile parts for a gear, a sprocket tooth, a spline tooth and the like by cold forging process. <P>SOLUTION: In the method, the tooth profile is formed by only the cold forging process without including a process for hot forging the tooth profile. An initial tooth profile having larger roundness at both sides of the tooth bottom than a finished tooth profile is formed into a swelled shape by the cold forging process and then, protrusion forming is performed so that a tooth tip is projected from the initial tooth profile by the cold forging process. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for forming a tooth profile of a tooth profile component such as a gear, a sprocket tooth, or a spline tooth by cold forging.

  A method of manufacturing a gear by cold forging using a metal material is known as disclosed in Patent Document 1.

  1A and 1B show a conventional spur gear manufacturing method by cold forging described in Patent Document 1. FIG. 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 bamboo H. Therefore, the tooth profile formed on the outer periphery of the material 10 has the regular full tooth bamboo H as well.

  1A and 1B, reference numeral 13 denotes a pitch circle. Reference numeral 14 indicates a tip circle of the tooth profile 12 of the mold 11, and reference numeral 15 indicates the root circle.

  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.

  In addition, the material 10 may be cold forged in a single process, but after being preformed hot or warm in advance, it is annealed, surface lubricated, etc., and then finished by cold forging. Sometimes.

  In the conventional method of manufacturing a gear by cold forging shown in FIG. 1, the quality of the final product gear is considered to account for 50 to 80% of the factors related to the forging die.

  In the method shown in FIG. 1, 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.

In the conventional method shown in FIG. 1, the finished dimension is obtained by cold forging the gear in one step. 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 ² to 280 kgf / mm ² . 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.

  On the other hand, as shown in Patent Document 2, it is swept into a primary working gear having a gear shape in which both the tooth tip and the tooth thickness are set smaller than the tooth profile of the gear shape of the spur gear from which the material is to be obtained. A first machining step, a second machining step in which the material is freely flowed in a portion other than the tooth profile in the primary machining gear, and compression molding into a secondary machining gear, and the secondary machining gear is ironed into a final product. A spur gear forging method is also known, which includes a third processing step, and performs each of these steps by cold forging.

  2A to 2E show the method described in Patent Document 2, FIG. 2A is a first processing step, and FIG. 2B is a gold for performing the second processing step. Represents a type.

  2A, reference numeral 200 denotes a die, and 201 denotes a tooth profile portion of the die 200. A punch 202 fitted into the die 200 and a knockout pin 204 inserted into the through hole 203 corresponding to the punch 202 are provided. Yes. Reference numeral 205 denotes a material, and 206 denotes a primary processing gear processed by the die 200.

  2B, 210 is a die, 211 is a tooth profile portion of the die 210, 212 is a through hole that communicates with the tooth profile portion 211 and penetrates the die 210, 213 is a punch that fits into the die 210, and 214 is a die 210. A knockout pin inserted into the through hole 212. Reference numeral 215 denotes a secondary machining gear machined by the die 200, and a material raised portion 216 is formed toward the through hole 212.

  In FIG. 2 (A), the primary working gear 206 upset from the raw material 205 is insufficiently filled in the die of the material, resulting in a lacking wall 207. Next, the primary working gear 206 is put into the die of FIG. 2B, the material is filled in the tooth profile portion 211 by compression molding with the punch 213, and the secondary processing gear 215 is molded.

  The secondary processing gear 215 formed in the compression molding by the punch 213 is formed by forming the raised portion 216 by freely flowing the material in a portion where the material is not restrained to a portion other than the tooth shape during the molding processing. Fills the tooth profile part 211 and eliminates the lack of thickness that occurs in the tooth tip part.

2 (C) to 2 (E) are diagrams comparing the tooth profile shapes of the primary processing gear 206 formed and processed in the first processing step and the primary processing gear 215 formed and processed in the second processing step. The tooth profile contour 206A formed in the first processing step is set so that the tooth tip and the tooth thickness are smaller than the tooth profile contour 215A formed in the second processing step.
Japanese Patent Laid-Open No. 9-300041 Japanese Patent No. 2913522

  In the method described in Patent Document 1, the maximum load during cold forging is often 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.

  In particular, when a helical gear is manufactured by cold forging, a load for applying the tooth profile 12 of the die 11 to only one side is applied, so the probability of breakage near the inclined surface 16 tends to increase. . As a result, the life of the mold 11 was shortened.

  According to the knowledge of the present inventor, in the case of processing a helical gear by cold forging, a load is intensively applied to one surface (front surface) of the mold tooth profile, and the back surface thereof is not much. No load is applied. 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.

  The method described in Patent Document 2 has the following problems.

  As shown in FIG. 2 (E), since the entire tooth profile including both the tooth tip and the tooth thickness is formed into a smaller (thinned) shape and size than the contour of the completed tooth profile, the plastic working rate is increased.

  When the processing rate increases, plastic work hardening of the processed product proceeds, deformation resistance increases, and molding becomes difficult.

  Furthermore, the shape factor increases, the overhang forming pressure (molding load) increases, and the distortion of the mold increases. Therefore, the accuracy of the processed product is lowered. Molds can be easily damaged by increasing the processing speed.

  As shown in FIG. 2 (E), the method of enlarging (thickening) the tooth profile formed small by primary processing is not preferable in terms of accuracy. For example, as the tooth width increases, the difference between the center width and the end face portion of the tooth width (formation degree) increases. The tooth profile becomes uneven and the cylindricity becomes worse.

  In particular, the method described in Patent Document 2 is not suitable as a method for mass-producing high-precision gears.

  When the molding load is increased in order to increase the accuracy, the distortion of the workpiece increases, and the processing distortion during the subsequent heat treatment increases. The greater the load, the easier the mold breaks.

  Accordingly, an object of the present invention is to provide a method capable of extending the life of a working die and forming a good tooth profile by cold forging.

  The solution of the present invention is exemplified by the following method for forming a tooth profile by cold forging.

  (1) It is a method of forming a tooth profile only by cold forging without including a step of forming a tooth profile by hot forging, and the roundness on both sides of the root is larger than the roundness on both sides of the root in the completed tooth profile. A method for forming a tooth profile, characterized in that an initial tooth profile is formed by cold forging, and thereafter, by cold forging, extrusion molding is performed so as to project the tooth tip from the initial tooth profile.

  (2) The above-described method for forming a tooth profile, wherein the overhang molding and the extrusion molding are continuously performed by using a single mold having a protruding tooth profile and a protruding tooth profile.

  (3) The above-described method for forming a tooth profile, wherein the overhang molding and the extrusion molding are performed in separate molds.

  According to one embodiment of the present invention, a preferred example of a part having a tooth profile is a gear, and a method of forming a gear tooth profile by cold forging includes a series of steps as follows.

(1) An initial step of forming an initial processed product having an initial tooth profile by cold forging from a metal material (for example, a solid material of a cylinder). At this time, an initial tooth profile in which the roundness on both sides of the root is larger than the roundness on both sides of the root in the completed tooth profile is used.

(2) Cold-forging the initial processed product of the initial tooth profile and maintaining it approximately the same as the initial tooth profile, or reducing the tooth thickness within a range of 10% or less and at the same time extruding the tip Process.

(3) After the intermediate process, a process of forming a complete tooth profile by sizing (finish drawing) the tooth profile.

  The tooth thickness is not increased during intermediate machining. The tooth thickness is approximately the same during intermediate machining or rather decreased (in the range of 10% or less). Thereby, forging can be performed with a lower load. As a result, not only the processing pressure can be reduced, but also the processing speed can be increased.

  Furthermore, for example, tooth profile parts such as gears and spline teeth can be manufactured with high accuracy by cold forging.

  If the intermediate process as described above is interposed, the tooth profile of the processed product easily matches the tooth profile of the mold in the final process. Even in the case of helical gears, even if the torsion angle of the teeth increases, there is not much difference in product accuracy.

  Compared with the conventional gear manufacturing method only by drawing, the die has no friction under high surface pressure, so the life of the die can be extended. For example, the number of lives is 3 to 10 times that of the conventional drawing method.

  Gears with narrow teeth, chain sprockets, etc. can be manufactured by cold forging. In this case, strength and production speed can be improved as compared with other forging methods.

  If the outer region in the circumferential direction of the metal material is thicker in the axial direction than the inner region, a fiber flow along the tooth profile is obtained, and a high strength can be obtained as compared with the cutting gear. The sagging and secondary breaks that occur with conventional precision shearing do not occur.

  If a plurality of different molds are used and the tooth profile is molded step by step according to each mold, the fiber flow will be good and no cracks will occur.

  Even if the same mold is used, if the tooth profile is formed in multiple stages step by step while changing the degree of “extrusion” or “overhang” in the intermediate process, the tip of the tooth has an arc or other chevron rounded shape (top) The curved surface is positioned in the middle of the mold, approaching the shape of the tip of the complete tooth profile in the mold, and the fiber flow becomes good and no cracks occur.

  For each of a plurality of cold forgings, forging can be performed with an even lower load immediately after that.

(1) Apply a lubricating coating.

(2) Apply softening annealing.

(3) Adjust the tooth profile. The tooth thickness is almost the same.

(4) In the case of a material having a high work hardening rate, the dimensions are distributed in consideration of the third work.

(5) All shapes and dimensions other than the tooth profile will be allocated so that the load will be low.

(6) Combine (1) to (5).

  Another embodiment of the present invention will be described.

  The outer diameter of the tooth profile after the intermediate process is formed slightly larger than the completed tooth profile. Thereby, an accurate tooth profile is obtained by subsequent sizing (finish drawing).

  The tooth thickness dimension of the processed product after the initial process is set to increase the tooth thickness within the range of the same or less than 10% of the completed tooth profile, and the roundness of the root of the initial tooth profile is set larger than that of the completed tooth profile. To do. In this case, if the processing rate between the initial process and the intermediate process is appropriately allocated, the desired completion is achieved by sizing (finishing process) between the intermediate process and the completion process even if the molding pressure (molding load) is reduced by 10 to 50%. A tooth profile can be obtained.

  In order not to increase the processing pressure, it is preferable not to approach the completely closed state (that is, non-closed forging). For example, in the initial process and the intermediate process, after cold forging, a space is left between the tip of the tooth tip of the mold tooth profile and the tip of the tooth tip of the processed tooth profile.

  Also, the part that will become the tip of the tooth profile of the initial machining type is set to a tooth thickness that is almost the same as or smaller than that of the completed tooth profile, and the roundness of the entire tooth tip of the processed product is an arc or other angled surface. Make the shape (the shape with the top located in the middle) and set it large. By increasing the roundness, the strength against cracking of the working die is improved.

  Starting with a coil material, the parts homer can form a complete tooth profile in 3 to 7 stages. In this case, the best mass production form can be taken in terms of cost. In the case of a helical tooth profile, the torsion angle can be formed accurately and accurately, so that it can be used as a reference surface for accuracy in the subsequent process.

  If the protruding height of the tooth tip is 60% or more of the completed tooth profile, a considerable effect is recognized.

  The present invention makes it possible to obtain a lower forming load by using non-closed forging as described above. The molding machine is preferably a forging press (particularly a part former).

  If it carries out as follows, it can process by a lower load in each cold forging.

(1) Apply molybdenum sulfide coating or lubricating film for bonding.

(2) In the case of steel, softening annealing is performed at 600 to 650 ° C. for 90 to 240 minutes.

(3) Adjust the tooth profile. The tooth thickness is almost the same between the initial machining and the intermediate machining. Combine the height of the tooth tip (tooth bamboo), the roundness of the tooth tip, and how to round the tooth tip.

(4) In the case of a material having a high work hardening rate, the dimensions are distributed in consideration of an intermediate additional tertiary processing setting.

(5) Set and distribute the shape and dimensions other than the tooth profile.

(6) A guide portion is provided at the mouth of the mold for initial machining. The length of the guide portion is approximately the tooth width of the processed product. The loss of the dimensional difference between the intermediate machining die and the initial machining die is eliminated, and the increase (protrusion) of the tip height is effectively obtained. This is a practically effective method in mass production.

  Furthermore, another preferred embodiment of the present invention will be described as follows.

(1) The initial step of tooth molding is a molding in which a cylindrical material is placed in a mold and both ends of the material are pressed with a punch to project the side surface of the material outward. Further, extrusion molding is performed as an intermediate process, and the molding pressure at that time is lowered. In this way, the effect of improving accuracy and type number is great.

(2) Softening annealing and lubricating coating are performed immediately after the initial process. The main purpose of this is to obtain a good surface roughness.

(3) In the extrusion molding in the intermediate process, 0.02 to 0.10 sizing allowance (finish drawing allowance) is given to each surface of the tooth outer diameter, tooth surface, and tooth bottom. The extrusion molding may be performed three times on a case-by-case basis.

(4) Sizing (finish drawing) in the completion process to finish the tooth profile. The mold for sizing is provided with a guide part at the base of the hole of the mold, the tooth trace is fixed to the entire length of the blank, and the blank and the tooth surface of the mold are applied. As a result, it is possible to prevent the tooth traces from deviating due to sizing pressure. In this case, since the working pressure required for finishing the tooth profile is low, the internal stress is reduced and the accuracy is high.

(5) Cut the end faces and holes of the tooth profile parts. The processing reference surface is the tooth surface or the tooth outer diameter. Furthermore, chamfer cutting of the end face corner may be performed.

(6) Gears that are designated for heat treatment are hardened.

(7) Improve surface roughness and remove minute burrs. For example, barrel polishing or shot peening is performed. Electropolishing or chemical polishing may be performed.

(8) Grind the hole and end face of the tooth profile part. If not specified, grinding is not performed.

(9) Wash the tooth profile parts.

(10) Rust preventive treatment (generally with rust preventive oil) on tooth profile parts

  These series of steps (1) to (10) are typical examples. (1) to (4) are important steps.

  Still another embodiment of the present invention will be described.

  A material of a metal material (for example, a cylinder) having a cylindrical outer peripheral surface is inserted into a mold having a predetermined female tooth shape, and the metal material is stretched by punching in the mold, and the intermediate tooth shape is cold forged. Formed with.

  The diameter of the cylindrical material may be smaller than the diameter of the tip circle of the mold, or may be smaller than the trough diameter of the gear.

  The cylindrical material may be pressed along the axial direction and pressed in the circumferential direction toward the mold.

  A support member may be provided at one end in the axial direction of the columnar material, a pressing member may be provided at the other end, and the columnar material may be pressed toward the support member using the pressing member. Further, the support member and the pressing member may have a tooth profile corresponding to the tooth profile of the mold. You may provide a press member in the both ends of the axial direction of a cylindrical raw material.

  The cylindrical material has a hole penetrating in its axial direction, and a pin for maintaining the shape of the hole can be arranged in the hole.

  Using multiple different molds, the tooth profile may be molded in stages according to each mold, or using the same mold, the tooth profile may be molded in stages by changing the degree of protrusion of the tooth tip. good.

  After the cylindrical material is initially formed, the internal stress may be removed by softening annealing.

  The initial tooth profile may be formed by drawing. The initial tooth profile that has been drawn may be formed by extrusion of the tooth tip within the mold.

  Still another embodiment of the present invention will be described.

  The present invention is an improvement of a gear manufacturing method by cold forging. In particular, the present invention has a significant effect on the production of helical gears. Although it has been recognized that helical teeth are extremely difficult to manufacture by cold forging, according to the present invention, helical gears or similar gears can be manufactured efficiently and with high accuracy.

  Various gears can be produced by the method 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.

  According to the manufacturing method of the present invention, the product accuracy of the gear can be JIS standard class 2 to class 5.

  According to the manufacturing method of the present invention, even a flanged gear, a two-stage gear, or a splined gear can integrally process one metal material only by cold forging.

  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 before or during 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.

  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. A preferred metal material from the viewpoint of cost is a coil material. In principle, all materials that are normally used as gear materials can be used.

  It is advantageous in the following points if the outer periphery of the workpiece is thickened in advance.

(1) The fiber flow along the tooth profile is advantageous in terms of strength.

(2) Since the surface roughness of the tooth surface is almost the same as the mold, there is little deterioration of the surface roughness during mass production.

(3) The accuracy of the gear is transferred from the accuracy of the die.

(4) The post-process can be made the same as fine blanking.

  In the present invention, “overhanging” a metal material includes expanding the metal material. Inflating a metal material is also simply called “stretching”. “Extrusion” is a molding that concentrates and raises the portion of the tooth tip, and can be said to be a special overhang molding (however, the tooth thickness does not increase).

  The present invention can be applied to various gears in addition to a spur gear and a helical gear (also referred to as a spiral gear or a helical gear).

  The present invention can be applied to a thin tooth width and a thick tooth.

  In the present invention, a metal material overhanging process, a drawing process, and an extrusion process can be used in combination. If the tooth width of the gear becomes relatively large and it is difficult to obtain cylindricity only by overhanging and protrusion, it is possible to obtain a good effect by performing a drawing process by distributing an appropriate processing rate. Even in the case of a material with poor spreadability, it is effective to use drawing together. The processing rate is set in consideration of dimensions and materials.

  The material may have no holes, but may have holes before the tooth profile is formed. When there is a hole, a cored bar pin may be arranged at the center. In this case, the material length is longer for the material with holes than for the material without holes. During the initial overhanging process, the tooth profile can be formed by pressurizing both end faces while plastically processing the hole.

  An example of a method for forming a helical gear using the present invention is shown below.

(1) The initial process of forming the helical tooth profile is overhanging. As a result, the twist angle can be accurately transferred, and the molding pressure can be lowered from intermediate processing.

(2) Immediately after the initial process, softening annealing and applying a lubricant film are performed. This process is mainly employed to obtain surface roughness.

(3) The workpiece is extracted from the mold in the initial process while rotating along the twist angle.

(4) The processed product is inserted into a mold for an intermediate process while being rotated along a twist angle to perform extrusion molding in the intermediate process. A sizing (finish drawing) allowance of 0.02 to 0.10 mm is given to each surface of the outer diameter, tooth surface, and root of the helical tooth. Extrusion molding may be performed three times on a case-by-case basis. Thereafter, the workpiece is extracted from the mold while rotating along the twist angle.

(5) Sizing is performed so as to reduce the thickness by 0.02 to 0.2 mm to finish the helical tooth profile. The sizing mold is provided with a guide portion at the base of the hole. A tooth streak is applied over the entire length of the blank (metal material). This prevents the tooth streak from being distorted by sizing pressure. Since the processing pressure required for tooth profile finishing is low, the internal stress is small and the accuracy is high.

(6) The end face and hole of the helical gear are processed by cutting. The processing reference surface is the tooth surface or the tooth outer diameter.

(7) Harden gears that have been designated for heat treatment.

(8) Barrel polishing and shot peening are performed for the purpose of improving the surface roughness and removing minute burrs. Electropolishing or chemical polishing may be performed.

(9) Grind the hole and end face of the gear. If not specified, no grinding is performed.

(10) Wash.

(11) Rust prevention treatment.

  In any of the above-described embodiments, the overhang molding and the extrusion molding are preferably compression molding using a punch or a pin to press the end face of a material or a processed product.

  Hereinafter, various embodiments of the present invention will be described with reference to the drawings.

Embodiment of FIG. 3 FIG. 3 shows one preferred embodiment of the present invention. In this embodiment, the metal material 20 is processed to form a spur gear. FIG. 3 shows a state before forming a tooth profile for the sake of explanation.

  The mold 21 has a hole 21 a penetrating in the direction of the axis 26. A female tooth profile 27 is formed on the peripheral surface of the hole 21a. The tooth profile 27 is a regular spur tooth profile. Reference numeral 23 denotes a pitch circle.

Reference numeral 24 indicates a tip circle of the tooth profile 27. Reference numeral 25 denotes a root circle of the tooth profile 27.

  When compared with the conventional example shown in FIG. 1, the metal material 20 of FIG. 3 is different in that its diameter is smaller than the diameter of the tooth tip circle 24. For example, when the diameter of the metal material 20 is about 35 mm, the diameter of the addendum circle 24 is 0.02 to 0.2 mm larger than that.

  A pressure pin 28 is provided as a pressing member above the metal material 20. The pressure pin 28 presses the metal material 20 in the arrow X direction. The pressure pin 28 has a tip 28 a that contacts the metal material 20. The diameter of the distal end portion 28 a is substantially the same as the diameter of the metal material 20.

  A support pin 29 is provided below the metal material 20 as a support member. The support pin 29 supports the metal material 20. The support pin 29 is not moved by support means (not shown). A male tooth profile 29 a is formed around the support pin 29. The male tooth profile 29 a of the support pin 29 corresponds to the female tooth profile 27 of the mold 21.

  An example of a method for manufacturing a helical gear by cold forging using a die 21 or the like will be described.

  First, the metal material 20 is inserted into the mold 21. A support pin 29 is installed immediately below the metal material 20.

  The metal material 20 inserted into the mold 21 is pressed by the pressure pin 28.

  First, as an initial step, the pressed metal material 20 is compressed by the first pressurization, the space between the upper and lower end surfaces is reduced, and the side surfaces are protruded outward to rise in the mold 21, and the mold 21. In the middle of the regular tooth profile 27, a tooth profile smaller than the tooth profile 27 is formed.

  In this way, the tooth profile is formed by the first pressing, and as an intermediate step, the forming pressure and the forming speed are changed, and the second tooth or the third pressing is performed to obtain a normal tooth profile corresponding to the normal tooth profile 27. Molded into a processed product.

  In this intermediate process, the tooth thickness is kept the same, and at the same time, the tooth tip protrudes in stages while forming a circular arc shape by a plurality of cold forgings and approaches the tooth tip of the completed tooth shape.

  Moreover, in the case of a product with a large tooth width or a product with high accuracy, high accuracy is obtained for the tooth profile and others by passing through a sizing die having a tooth profile as a completion process. In this case, an appropriate sizing amount is, for example, 0.01 to 0.2 mm.

  By changing the tooth profile of the mold during the initial process, the intermediate process, and the completion process, the spur gear can be formed in the same manner.

Embodiment of FIGS. 4-5 FIGS. 4-5 illustrate another embodiment of the present invention. In this embodiment, a spur gear is formed on the outer periphery of the metal material 30 with a relatively low load. FIG. 4 shows a state before forming a tooth profile for the sake of explanation. 5 is a cross-sectional view taken along the line AA in FIG.

  The mold 31 has a hole 31a penetrating in the direction of the axis 36. A female tooth profile 37 is formed on the peripheral surface of the hole 31a. The tooth profile 37 is a regular spur tooth profile. Reference numeral 34 represents a tip circle of the tooth profile 37. Reference numeral 35 denotes a root circle of the tooth profile 37. Reference numeral 30 a indicates the outer diameter of the metal material 30.

Reference numeral 31 b indicates a pitch circle of the mold 31.

  The metal material 30 is a thin plate having a cylindrical outer periphery, and both sides of the outer peripheral tooth forming portion are thickened over the same width. Although it is preferable to increase the thickness of both sides of the metal material 30 equally, only one of the sides may be increased.

  A punch 38 having teeth is provided above the metal material 30. The punch 38 presses the metal material 30 in the arrow X direction. The punch 38 has a male tooth profile 38a at the bottom. The male tooth profile 38 a corresponds to the female tooth profile 37 of the mold 31.

  A support pin 39 is provided below the metal material 30 as a support member. The support pin 39 supports the metal material 30. The support pin 39 is prevented from moving by support means (not shown). A male tooth profile 39 a is formed around the support pin 39. The male tooth profile 39 a of the support pin 39 corresponds to the female tooth profile 37 of the mold 31.

  An example of a method for producing a spur gear by cold forging using a die 31 or the like will be described.

  First, the metal material 30 is inserted into the mold 31. A support pin 39 is installed directly under the metal material 30.

  In the first forging, the metal material 30 inserted into the die 31 is pressed by the punch 38. Thereby, first, the thickened portion of the metal material 30 is pressed and protrudes outward, and the metal material 30 protrudes into the mold 31 by the second and subsequent presses, and is formed into a gear with the same accuracy as the mold 31. . Thus, a regular gear corresponding to the mold 31 can be obtained.

  Finally, as a completion process, the tooth profile of the processed product is sized and finished.

Embodiment of FIG. 6 FIG. 6 shows still another embodiment of the present invention, and in particular, shows a situation where the metal material is divided into one overhanging step and two overhanging steps. Reference numeral 40 in the figure denotes a crank sprocket as a gear of the present invention. Reference numeral 40a indicates a pitch circle.

  Hereinafter, each process will be described.

  In the first step, a metal material is inserted into a predetermined mold (not shown) and stretched by a punch. Thereby, the initial tooth profile 41 of the 1st process which has a tooth tip (tooth bamboo) lower than a regular tooth profile is obtained. The tooth tip of the tooth profile portion in the first step is indicated by reference numeral 41a. The tooth tip 41a is a large arc.

  In the second step, the initial tooth profile 41 obtained in the first step is further cold-forged by a die having a tooth thickness several percent smaller than the die used in the first step, and is extruded. Thereby, the tooth profile 42 of the second step is obtained. The tooth tip of the tooth profile portion in the second step is indicated by reference numeral 42a. This tooth tip 42a has a non-circular round curved surface shape.

  In the third step, the tooth profile 42 obtained in the second step is extrusion-molded with a tooth profile mold having a tooth thickness smaller by several percent than the mold used in the second process. Thereby, the tooth profile 43 of the third step is obtained. The tooth tip of the tooth profile in the third step is indicated by reference numeral 43a. The tooth tip 43a has a non-circular round curved surface shape.

  In this way, using three types of molds, changing the degree of overhang and protrusion, reducing the tooth thickness, forming the tooth profile step by step, and forming the tooth shape with stepped rounded teeth according to each type To do.

  The obtained tooth profile 43 has a sizing allowance in a regular tooth profile, the fiber flow is good, and no crack is generated.

  This tooth profile 43 performs finish sizing drawing.

Embodiment of FIGS. 7-10 FIGS. 7-10 illustrate yet another embodiment of the present invention. FIG. 10 also shows FIGS.

Reference numeral 50 in the figure denotes a gear. Reference numeral 54 denotes a pitch circle.

  Hereinafter, each process will be described.

  In the initial step, a metal material is inserted into a predetermined first mold (not shown) and stretched. Thereby, the initial tooth profile 51 of the initial step shown in FIG. 7 is obtained.

  In the intermediate process, the rounded root-shaped initial tooth profile 51 obtained in the initial process is inserted into a predetermined second mold (not shown) to perform extrusion molding. Thereby, the tooth profile 52 having a rounded root shape in the intermediate process shown in FIG. 8 is obtained.

  In this intermediate process, the tooth thickness is kept the same, and at the same time, the root protrudes in stages while changing the rounded shape by multiple cold forgings and approaches the tooth tip of the completed tooth profile. .

  In the completion process, the tooth profile 52 obtained in the intermediate process is finish-molded by sizing (ie, drawing). As a result, a complete tooth profile 53 shown in FIG. 9 is obtained.

  The obtained complete tooth profile 53 is a regular tooth profile, and the fiber flow is good and no crack is generated.

Embodiment of FIGS. 11-14 FIGS. 11-14 illustrate yet another embodiment of the present invention. In this embodiment, the overhang and protrusion of the metal material are divided into two steps and further combined with a sizing (finish drawing) step. Reference numeral 60 in the figure denotes a gear. Reference numeral 64 denotes a pitch circle.

  Hereinafter, each process will be described.

  In the initial step, a metal material is inserted into a predetermined mold (not shown) and stretched.

As a result, an initial tooth profile 61 having an arc-shaped tooth tip shown in FIG. 11 is obtained.

  In the intermediate process, the initial tooth profile 61 obtained in the initial process is inserted into a mold (not shown) different from the mold used in the initial process to perform extrusion molding. Thereby, the tooth profile 62 having the arcuate tooth tips shown in FIG. 12 is obtained.

  In the completion process, the tooth profile 62 obtained in the intermediate process is sized. Thereby, the tooth profile 63 shown in FIG. 13 is obtained.

  FIG. 14 shows FIGS. 11 to 13 together.

  Reference numeral 65 conceptually shows the fiber flow after the second step. The obtained tooth profile 63 has a good fiber flow 65 and does not crack.

Embodiment of FIG. 15 FIG. 15 shows yet another embodiment of the present invention.

  This example shows data obtained by measuring a tooth shape (A) and a tooth stripe (B) of a helical gear formed by projecting and projecting a metal material with a three-dimensional measuring machine.

  In FIG. 15, the numbers 1, 5, 10, and 14 on the upper side of (A) and (B) mean the sequential number of teeth. The numerical values on the lower side of (A) and (B) indicate the measured values measured with the reference value set to 0 and the accuracy grade of the JIS standard. The left side shows the shape of the left tooth surface, and the right side shows the shape of the right tooth surface.

Table 1 shows the number of teeth, module, pressure angle, torsion angle, dislocation coefficient, and basic circle diameter of the helical gear used in the embodiment of FIG.

  It can be seen that the highest grade gear can be formed even if the overhanging and protruding gears are formed.

Embodiment of FIG. 16 FIG. 16 shows yet another embodiment of the present invention.

  This example shows data obtained by measuring a tooth shape (A) and a tooth line (B) of a helical gear formed by projecting and projecting a metal material and then drawing and measuring with a three-dimensional measuring machine.

  In FIG. 16, the numbers 1, 5, 10, and 14 on the upper side of (A) and (B) mean the order numbers of the teeth. The numerical values on the lower side of (A) and (B) indicate the measured values measured with the reference value set to 0 and the accuracy grade of the JIS standard. The left side shows the shape of the left tooth surface, and the right side shows the shape of the right tooth surface.

  The number of teeth, the module, the pressure angle, the twist angle, the dislocation coefficient, and the basic circle diameter of the helical gear used in the example of FIG. 16 are the same as those in Table 1.

  The tooth profile is JIS standard 0 to 1 grade, but there is a difference of 2 to 5 grade between the left tooth surface and the right tooth surface of the tooth stripe. Although there is a measurement error, the ability value can be judged as 2nd to 4th grade.

Embodiment of FIG. 17 FIG. 17 shows yet another embodiment of the present invention. This embodiment is an example in which metal material overhang and protrusion are performed in combination with various cold forging processes. A crank sprocket is manufactured as a gear.

  Hereinafter, a series of manufacturing steps will be described.

  (A) has shown the cylindrical raw material 70 which cut | disconnected the solid cylindrical metal material from the coil raw material for every predetermined length.

  (B) shows a processed product obtained by processing the material 70 in the above-described state (A) by cold forging and forming a reduced diameter portion 71 and a recess 72 on the lower side.

  (C) shows a state in which the workpiece 70 in the state of (B) described above is processed by cold forging to form the upper recess 73 and the lower hole 74.

  (D) has shown the state which processed the workpiece 70 in the state of the above-mentioned (C) by cold forging, and shape | molded the enlarged diameter part 76 and the lower deep hole 75. FIG.

  (E) The workpiece 70 in the state of (D) described above is stretched and molded in a mold (not shown) to obtain an initial tooth profile 77 having a tooth thickness larger than a normal tooth profile and a low tooth tip. The molded state is shown. A hole 78 is newly formed on the lower side.

  After the above steps, the hole is penetrated to obtain the finished product shown in FIG.

  18-19 show a finished crank sprocket 79 having a regular tooth profile 87.

FIG. 19 is a schematic front view of FIG.

  A crank sprocket 79 shown in FIGS. 18 and 19 is a crank sprocket formed from the workpiece 70 of FIG.

  The tooth thickness of the initial tooth profile 77 is maintained substantially the same as that of the initial tooth profile 77, or the tooth thickness is reduced within a range of several percent smaller than the initial tooth profile 77, and at the same time, the tooth tip is protruded from the initial tooth profile 77. As a result, a finished product having a finished tooth profile 87 (FIGS. 18 to 20) is obtained.

Example of FIG. 20 FIG. 20 shows an example of manufacturing the sprocket shown in FIGS. FIG. 20 shows a state after the complete tooth profile 87 is formed.

  The mold set 81 includes a mold 81a and a mold 81b.

  A hole 81c passes in the direction of the axis 86 of the mold 81a. A female tooth profile 87 is formed on the peripheral surface of the hole 81c. This tooth profile 87 is a regular tooth profile. Reference numeral 87 a indicates a tip circle of the tooth profile 87. Reference numeral 87 b indicates a root circle of the tooth profile 87.

  The mold 81b is disposed below the mold 81a. A hole 81d having a smaller diameter than the hole 81c passes in the direction of the axis 86 of the die 81b. The peripheral surface of the hole 81d corresponds to the lower outer peripheral surface of the crank sprocket 79. The upper surface of the mold 81b supports the tooth profile 87.

  A punch 88 is provided as a pressing member above the crank sprocket 79.

The punch 88 presses the crank sprocket 79 in the arrow X direction.

  A male tooth profile 88 a is formed on the outer peripheral surface of the punch 88. The male tooth profile 88a corresponds to the female tooth profile 87 of the mold 81a. The punch 88 has a tip portion 88b on the lower side. The tip end portion 88 b has a shape corresponding to the shape of the upper surface of the crank sprocket 79.

  A knockout sleeve 89 for supporting the lower end of the crank sprocket 79 is provided below the crank sprocket 79. The knockout sleeve 89 is prevented from moving by support means (not shown).

  Inside the crank sprocket 79, a punch mandrel 82 passes.

  A method of forming a crank sprocket by cold forging using the mold of FIG. 20 will be described.

  First, a metal material (not shown) before tooth molding is inserted into the mold 81. A knockout sleeve 89 is installed directly under the metal material. A punch metal core 82 is inserted into the metal material.

  The metal material inserted into the mold 81 is pressed with a punch 88.

  The pressed metal material is stretched and has a tooth profile 87 corresponding to the tooth profile of the mold 81a.

  In this way, the crank sprocket 79 can be obtained by the set 81.

Embodiment of FIG. 21 FIG. 21 shows yet another embodiment of the present invention. In this embodiment, a helical tooth pinion is formed.

  An example of a method for forming the helical tooth pinion 90 will be described.

  A cylindrical metal material provided with holes in advance is placed in a predetermined mold (not shown). In a state where a pin (not shown) having a shape corresponding to the shape of the hole is inserted into the hole, the metal material is pressed along the axial direction. The pressed metal material is stretched in the circumferential direction, and then shaped by extrusion to have the same tooth profile as that of the corresponding mold.

  After the extrusion molding, the helical tooth pinion 90 is extracted from the mold while rotating along the twist angle.

  An example of the helical tooth pinion 90 is that the twist angle (twist direction) is 25 ° (left) and the tooth accuracy is JIS grade 4 or grade 5.

If the relative movement distance between the embodiment mold of FIG. 22 and FIG. 23 and the workpiece is reduced, a workpiece closer to the accuracy of the mold can be obtained. An example of the method will be described below with reference to FIGS.

  FIG. 22 shows the starting state of the workpiece. FIG. 23 shows a completed state of the workpiece.

  A main mold for forming teeth is a mold 101. For ease of understanding, the mold 101 is depicted in a fixed state in FIG. In practice, the mold 101 may move.

  The mold 101 has a hole 101 a penetrating in the direction of the axis 106. A female tooth profile 107 is formed on the peripheral surface of the hole 101a. The tooth profile 107 is a regular tooth profile. Reference numeral 103 denotes a pitch circle. Reference numeral 104 indicates a tip circle of the tooth profile 107. Reference numeral 105 denotes a root circle of the tooth profile 107.

  Above the metal material 100, an upper extrusion pin 108 is provided as a pressing member. The upper extruding pin 108 presses the metal material 100 from above.

  An upper sleeve 102 is provided around the upper push pin 108. The upper sleeve 102 supports the metal material 100 and the upper push pin 108 from the side.

  Below the metal material 100, a lower extrusion pin 109 is provided as a pressing member. The lower extrusion pin 109 presses the metal material 100 from below.

  A lower sleeve 104 is provided around the lower push pin 109. The lower sleeve 104 is fixed and supports the metal material 100 and the lower extrusion pin 109 from the side.

  An example of a method for manufacturing a gear by cold forging using the mold 101 of FIG.

  The metal material 100 is put into the center of the mold 101. Thereafter, the upper push pin 108 and the upper sleeve 102 move downward to confine the metal material 100.

  The upper sleeve 102 and the lower sleeve 104 are stopped.

  A pressure in the direction of arrow C is applied to the upper push pin 108. A pressure in the direction of arrow D is applied to the lower push pin 104. The upper sleeve 102 is stopped in a state where the mold 101 is sandwiched by hydraulic pressure or spring pressure. In this way, the metal material 100 is projected toward the tooth profile 107 of the mold 101 and molded. Using the same mold, forging conditions (such as molding pressure and speed) are changed for each molding, or various molds are used for each molding.

  An arrow E in FIG. 23 schematically shows the flowing direction of the metal material.

  In order to take out the molded product 110 from the mold 101, the upper extrusion pin 108 and the upper sleeve 102 are moved upward, and then the lower extrusion pin 109 is moved upward to take the molded product 110 out of the mold 101.

  If molded in this way, the relative movement distance between the molded gear and the mold is extremely small, so that the gear can be molded with high accuracy.

Embodiment of FIG. 24 FIG. 24 shows yet another embodiment of the present invention. In this embodiment, after a metal material is protruded in a mold in an intermediate process, a tooth profile is formed by further drawing as a sizing for finishing.

  The drawing die 111 has a hole 111 a penetrating in the direction of the axis 116. A female tooth profile 114 is formed on the peripheral surface of the hole 111a. Reference numeral 117 indicates a pitch circle.

  The drawing die 111 includes a guide part 112 and a drawing part 113.

  The guide portion 112 is provided for copying the mouth of the drawing die 111. The diameter of the pitch circle 117 of the guide portion 112 is preferably slightly larger than the diameter of the pitch circle of the previous process product that has been extruded. For example, it may be 0.05 to 0.2 mm larger. The axial length of the guide part 112 is preferably 5 times or more of the tooth module.

  The aperture portion 113 is provided at the lower end of the guide portion 112. The tooth profile 114 of the restrictor 113 is a regular tooth profile.

  When forming the complete tooth profile, the initial process is a metal material overhanging process, and then an extrusion process. This forms a precise tooth stripe. Further, a metal material is inserted into the hole 111a. Then, the drawn tooth surface is used as a copying surface, and the metal material is drawn by 0.05 to 0.2 mm by the drawn portion 113. As a result, the tooth profile error can be extremely reduced.

  In any of the above-described embodiments, for each of a plurality of cold forgings (at least during the overhanging protrusion), the processed product is removed from the die, and a lubricating film is applied or softening annealing is performed to perform low load forging. Preferably it is possible.

  In any of the above-described embodiments, the tooth tip of the processed product reaches the tooth tip of the die in each of the multi-stages (a plurality of cold forgings), except that the final stage is not used. It is preferable to stop molding before in order to avoid an increase in molding load.

Embodiment of FIGS. 25-28 FIGS. 25-28 illustrate yet another embodiment of the present invention. In this embodiment, the overhang and protrusion of the metal material are divided into two steps and further combined with a sizing (finish drawing) step. Reference numeral 120 in the figure denotes a gear. Reference numeral 124 denotes a pitch circle.

  Hereinafter, each process will be described.

  In the initial step, a metal material is inserted into a predetermined shape of the tooth profile 120a to perform overhang molding. Thereby, it has the big circular-arc-shaped tooth tip shown in FIG. An initial tooth profile 121 is obtained. At this time, a crescent-shaped space indicated by reference numeral 120b remains between the tooth tip of the initial tooth profile 121 of the processed product and the tooth tip of the mold tooth profile 120a.

  In the intermediate process, the initial tooth profile 121 obtained in the initial process is inserted into a mold 120c different from the mold used in the initial process to perform extrusion molding. Thereby, the tooth profile 122 shown in FIG. 26 is obtained. Reference numeral 120d indicates a sizing allowance. Note that the tooth profile 122 may not come into contact with the entire contour of the mold 120c depending on the pressure.

  In the completion process, the tooth profile 122 obtained in the intermediate process is sized. As a result, a complete tooth profile 123 shown in FIG. 27 is obtained.

  FIG. 28 shows FIGS.

  Reference numeral 125 conceptually indicates the fiber flow after the second step. The obtained tooth profile 123 has a good fiber flow 125 and does not crack. The diameter r indicated by reference numeral 120e in the figure may have a wide tolerance as long as it is on the plus side.

Embodiment of FIG. 29 FIG. 29 shows yet another embodiment of the present invention. In this embodiment, the overhang and protrusion of the metal material are divided into two steps and further combined with a sizing (finish drawing) step. The code | symbol 130 in a figure shows a gearwheel. Reference numeral 134 denotes a pitch circle.

  Hereinafter, each process will be described.

  In the initial step, a metal material is inserted into a predetermined mold (not shown) and stretched. As a result, an initial tooth profile 131 having a large arc-shaped tooth tip is obtained.

  In the intermediate process, the initial tooth profile 131 obtained in the initial process is inserted into a mold (not shown) different from the mold used in the initial process to perform extrusion molding. As a result, a tooth profile 132 having another large arc-shaped tooth tip is obtained.

  In the completion process, the tooth profile 132 obtained in the intermediate process is sized. Thereby, the tooth profile 133 is obtained. Reference numeral 130d indicates a sizing allowance.

  Reference numerals 131a and 133a indicate tooth shapes of the processed product. At that time, spaces indicated by reference numerals 135a and 135b remain inside the mold. The top of the tooth tip of the tooth profile formed by the protrusion is not in contact with the tooth tip of the tooth profile of the mold. Since the tooth profile 133a does not have a small angle R, the fracture resistance (cracking resistance) strength of the mold is improved. The shape of the top of the tooth tip of the tooth profile formed by the protrusion is not limited to the circular arc, but can be a rounded shape or other free shape as long as the protrusion is advantageous.

  In addition, this invention is not limited to the above-mentioned Example. For example, the present invention is not limited to the form of closed forging, but includes the form of non-closed forging.

FIG. 1A is a cross-sectional view taken along line 1-1 of FIG. 1B and shows a conventional spur gear manufacturing method by cold forging. FIG. 1 (B) shows the tooth-forming start portion of the mold as seen from the direction of arrow A in FIG. 1 (A). (A) is sectional drawing of the metal mold | die used at the 1st processing process in another other conventional method. (B) is sectional drawing of the metal mold | die used at a 2nd manufacturing process. (C)-(E) are the comparison figures of the tooth profile shape-molded by the above-mentioned 1st process process and a 2nd process process. 1 shows one embodiment of the present invention. 4 shows another embodiment of the present invention. It is AA sectional drawing of FIG. Yet another embodiment of the present invention will be described. The tooth profile 51 obtained in yet another embodiment of the present invention is shown. The tooth profile 52 obtained in the next step of FIG. 7 is shown. The tooth profile 53 obtained in the next step of FIG. 8 is shown. 7 to 9 are shown together. The tooth profile 61 obtained in yet another embodiment of the present invention is shown. The tooth profile 62 obtained in the next step of FIG. 11 is shown. The tooth profile 63 obtained in the next step of FIG. 12 is shown. FIGS. 11 to 14 are shown together. Yet another embodiment of the present invention will be described. Yet another embodiment of the present invention will be described. Yet another embodiment of the present invention will be described. 1 shows an example of a finished crank sprocket manufactured according to the present invention. It is a schematic front view of FIG. Yet another embodiment of the present invention will be described. Yet another embodiment of the present invention will be described. It is another Example of this invention, and the shaping | molding start state of a to-be-processed object is shown. FIG. 23 shows a completed state of the workpiece of FIG. Yet another embodiment of the present invention will be described. The tooth profile 121 obtained in yet another embodiment of the present invention is shown. The tooth profile 122 obtained in the next step of FIG. 25 is shown. The tooth profile 123 obtained in the next step of FIG. 26 is shown. 25 to 27 are shown together. Yet another embodiment of the present invention will be described.

Explanation of symbols

20, 30, 70, 100 Metal material 21, 31, 81a, 81b, 101 Mold 23, 31a, 40a, 54, 64, 103, 117, 124 Pitch circles 24, 34, 87a, 104 Tooth tip circles 25, 35, 87b, 105 Root circle 26, 36, 86, 106, 116 Axle 27, 37, 87, 107, 114 Female tooth profile 28 Pressing pin 28a, 88b Tip 29, 39 Supporting pin 29a, 38a, 39a, 88a Male tooth profile 30a Outer diameter 38, 88 Punch 40, 79 Crank sprocket 41, 42, 43, 51, 52, 53, 61, 62, 63, 77, 87, 121, 122, 123 Tooth profile 41a, 42a, 43a, 65 , 125 Fiber flow 50, 60, 120 Gear 71 Reduced diameter portion 72, 73 Recess 74, 75, 78 Hole 76 Expanded portion 82 Punch core metal pin 89 Knockout sleeve 90 Helical tooth pinion 102 Upper sleeve 104 Lower sleeve 108 Upper extrusion pin 109 Lower extrusion pin 111 Drawing tool 112 Guide portion 113 Drawing portion 126 Portion

Claims (3)

  It is a method of forming a tooth profile only by cold forging without including a step of forming a tooth profile by hot forging, and an initial tooth profile in which the roundness on both sides of the root is larger than the roundness on both sides of the root in the completed tooth profile. A method for forming a tooth profile, comprising: forming by overhanging by cold forging and then performing extrusion forming so as to protrude the tooth tip from the initial tooth shape by cold forging.   2. The method for forming a tooth profile according to claim 1, wherein the overmolding and the extrusion molding are continuously performed by a single mold having a projecting tooth profile and a projecting tooth profile. 2. The method for forming a tooth profile according to claim 1, wherein the overhang molding and the extrusion molding are performed in separate molds.

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