JP2005007480A - Method and device for manufacturing bevel gear - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device for manufacturing a bevel gear which can dispense with machining after forging, in manufacturing the bevel gear by forging from a raw material in which a through hole is bored beforehand. <P>SOLUTION: A method for manufacturing a bevel gear 100 having a tooth profile 103 between a large end portion 101 and a small end portion 102 and also having a center hole 104, by forging using a forging die 20 provided with a tooth form 39 for molding the tooth profile. The raw material 110 in which a through hole 111 is bored beforehand has openings 112 and 113. In manufacturing the bevel gear 100, an upper mandrel 35 mounted in the forging die is inserted from the opening 112 which makes a top face inlet 105 on the small end side of the bevel gear. Then a taper portion 38 formed on the upper mandrel and inclined toward the tooth form causes the plastic flow of the material going to the tooth form and forms a chamfer 106 on the top face inlet by plastic working. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a bevel gear manufacturing method and a bevel gear manufacturing apparatus.

  For example, bevel gears are widely used to transmit rotation between two intersecting axes, such as a differential gear. A bevel gear is formed with a tooth profile on the conical surface between the large end and the small end, and is immediately classified into a bevel gear, a spiral bevel gear, a helical bevel gear, etc. . Bevel gears have considerable difficulty in manufacturing teeth because the tooth profile differs between the large end side and the small end side. However, in recent years, the productivity has been good due to the manufacturing process using conventional cutting. The manufacturing process has changed to forging. Especially, it is increasing by the closed forging and closed forging which belong to a precision forging technique (for example, refer patent document 1).

  A technique is also known in which a through hole is formed in advance in a pre-forging material before forging, and a gear is manufactured by inserting a mandrel into the through hole and performing forging (see, for example, Patent Document 2). .

  However, when a bevel gear is manufactured by forging using a forging die provided with a tooth mold that forms a tooth profile portion from a rough material in which through holes are formed in advance, the plastic flow of the material toward the tooth profile portion does not occur, and the tooth profile portion There is a possibility that a lack of material may occur without filling the material.

In addition, in the technology for manufacturing a bevel gear by forging, there is a demand for simplifying a series of manufacturing processes by making it possible to omit machining after the forging process.
JP-A-9-141380 JP 7-223033 A

  An object of the present invention is to provide a method of manufacturing a bevel gear and an apparatus for manufacturing a bevel gear, which can make it possible to omit machining after the forging process when manufacturing a bevel gear from a rough material having a through hole formed in advance by forging. It is to provide.

  The present invention for achieving the above object is achieved by the following means.

The present invention provides a bevel gear having a tooth profile portion between a large end portion and a small end portion and having a center hole by using a forging die having a tooth shape forming the tooth profile portion by forging. ,
Among the openings located at both ends along the axial direction of the through hole of the rough material in which the through hole is formed in advance, the forging is performed from the opening on the side that forms the top surface inlet on the small end side of the bevel gear. A mandrel provided in a mold is inserted, and a taper portion formed in the mandrel and inclined in a direction toward the tooth mold causes plastic flow of the material toward the tooth mold and is chamfered at the top surface inlet section. A method for manufacturing a bevel gear, characterized in that a part is plastically processed.

In addition, the present invention produces a bevel gear having a tooth profile portion between a large end portion and a small end portion and having a center hole by forging using a forging die having a tooth die forming the tooth profile portion. In the bevel gear manufacturing equipment,
Among the openings located at both ends along the axial direction of the through-hole of the rough material in which the through-hole is formed in advance, the through-hole is formed from the opening on the side forming the top surface inlet on the small end side of the bevel gear Having a mandrel inserted into the hole;
The mandrel is formed with a taper portion for causing plastic flow of the material toward the tooth mold and plastic processing of a chamfered portion at the top surface inlet portion in a direction toward the tooth mold. A bevel gear manufacturing apparatus.

  According to the present invention, when a bevel gear is manufactured from a rough material having a through-hole formed in advance by forging, the chamfered portion is plastically processed at the top surface inlet portion simultaneously with the forging process. Machining to form can be omitted. Furthermore, it is possible to prevent the lack of thickness at the tooth profile.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a cross-sectional view of a bevel gear manufacturing apparatus 10 according to an embodiment of the present invention, illustrating a state before forging die 20 is opened, and FIG. 2 is a diagram illustrating a closed forging die 20 of the manufacturing apparatus 10. FIG. 3 is a cross-sectional view showing a state in which the forging process is completed in the manufacturing apparatus 10. 4 is a cross-sectional view showing the main part of FIG. 2, and FIG. 5 is a cross-sectional view showing the main part of FIG. 6A is a cross-sectional view showing the coarse material 110 before forging used when manufacturing the bevel gear 100 and having the through hole 111 formed in advance, FIG. ) Is a cross-sectional view showing a bevel gear 100 manufactured by forging.

  As shown in FIG. 6B, a bevel gear 100 manufactured by forging has a tooth profile 103 between a large end 101 and a small end 102 and a center hole 104. In the present embodiment, the chamfered portion 106 is plastically processed at the top surface entrance portion 105 on the small end portion 102 side simultaneously with the forging process.

  As shown in FIG. 6A, a through hole 111 is formed in advance in the rough material 110 before forging. Of the openings 112 and 113 located at both ends along the axial direction of the through-hole 111, the opening 112 on the upper side in the figure forms the top surface inlet 105 on the small end 102 side of the bevel gear 100 after forging. The lower opening 113 in the figure forms a rear inlet 107 on the large end 101 side of the bevel gear 100 after forging. Further, the through hole 111 becomes the center hole 104 of the bevel gear 100 after forging. The through-hole 111 may be either formed by cutting such as drilling or formed by plastic working on a solid material.

  The material of the bevel gear 100 is arbitrarily selected from steel materials such as JIS SC material, SNC material, SNCM material, SCr material, SCM material, SMn material, SMnC material, or steel materials to which appropriate alloy elements are added. There is no particular limitation.

  Such a bevel gear 100 is manufactured by the manufacturing apparatus 10 having the forging die 20, and the forging die 20 is provided with a tooth die 39 for forming the tooth profile portion 103.

  As shown in FIG. 1 to FIG. 5, the manufacturing apparatus 10 for the bevel gear 100, if outlined, has openings that are located at both ends along the axial direction of the through hole 111 of the rough material 110 in which the through hole 111 is formed in advance. 112 and 113, the upper mandrel 35 (corresponding to a mandrel) is inserted into the through-hole 111 from the opening 112 on the side forming the top surface inlet 105 on the small end 102 side of the bevel gear 100. ing. In the upper mandrel 35, a taper portion 38 that causes plastic flow of the material toward the tooth mold 39 and plastically processes the chamfered portion 106 at the top surface entrance portion 105 is inclined in a direction toward the tooth mold 39. It is formed. In the present specification, “mandrel” includes a member having a similar name such as piercing.

  Hereinafter, the manufacturing apparatus 10 will be described in detail.

  The forging die 20 is a die that is supplied with the rough material 110 shown in FIG. 6 (A) and performs closed forging to produce a forged product of the bevel gear 100 shown in FIG. 6 (B). As shown in FIG. 1, the forging die 20 has a lower die 40 and an upper die 30 provided so as to be movable toward and away from the lower die 40. The upper die 30 and the lower die 40 clamped to each other form the cavity 21 having the inner surface shape that matches the outer shape of the bevel gear 100 as well as the coarse material 110 (see FIGS. 2 and 4).

  The upper die 30 includes an upper holder 31 that is driven up and down, an upper die 33 that is held by the upper holder 31 and that has a recess 32 that opens downward at the center of the lower surface, and a center hole of the upper die 33. The ring-shaped upper punch 34 disposed at 33 a and the upper mandrel 35 disposed at the center hole 34 a of the upper punch 34 are provided. The upper punch 34 and the upper mandrel 35 are fixed to the upper holder 31.

  A tooth mold 39 that forms the tooth profile 103 of the bevel gear 100 is provided on the inner surface of the recess 32 of the upper die 33.

  In the upper mandrel 35, as described above, the taper portion 38 that causes plastic flow of the material toward the tooth mold 39 and plastically processes the chamfered portion 106 at the top surface inlet portion 105 is inclined in the direction toward the tooth mold 39. Is formed. The inclination angle θ of the taper portion 39 is not particularly limited, and is, for example, 25 degrees to 35 degrees (see FIG. 5).

  When the upper mandrel 35 reaches the forward limit position relative to the rough material 110, that is, when the upper mandrel 35 reaches the lower limit position, the tapered portion 38 and the plasticity of the chamfered portion 106 are formed. It is formed at a position where processing is performed.

  In the illustrated example, the upper mandrel 35 has a large diameter portion 36 and a small diameter portion 37, and the tapered portion 38 is an intermediate portion along the longitudinal direction of the upper mandrel 35, that is, the large diameter portion 36 and the small diameter portion 37. Is formed between. The small diameter portion 37 of the upper mandrel 35 has an outer dimension substantially equal to the inner diameter of the through hole 111 of the coarse material 110, that is, the center hole 104 of the bevel gear 100 (see FIG. 4). The tip of the small-diameter portion 37 of the upper mandrel 35 penetrates to the vicinity of the axis orthogonal line L including the bottom portion 108 on the large end 101 side along the axial direction in the tooth profile 103 when the upper mandrel 35 reaches the lower limit position. It has the length dimension inserted in the hole 111 (refer FIG. 5). The reason for setting such a length dimension is that it is necessary to insert the upper mandrel 35 to a position that substantially contributes to the formation of the tooth profile 103.

  It is preferable that the tip of the small diameter portion 37 of the upper mandrel 35 inserted into the through hole 111 does not exceed the axis orthogonal line L. The reason for this is that it is sufficient to insert the upper mandrel 35 to a position that substantially contributes to the formation of the tooth profile 103, and to facilitate the extraction of the upper mandrel 35 from the center hole 104 after forging. is there.

  The lower mold 40 includes a lower holder 41 mounted on the base, a lower die 42 concentrically opposed to the upper die 33 and movable up and down with respect to the lower holder 41, and guides the movement of the lower die 42. In addition, a guide 43 for restricting the rising position of the lower die 42, a ring-shaped lower punch 44 disposed in the center hole 42a of the lower die 42, and a knockout provided in the center hole 44a of the lower punch 44 so as to be movable up and down. The ring 45 and the lower mandrel 46 disposed in the center hole 45a of the knockout ring 45 are included. The guide 43, the lower punch 44 and the lower mandrel 46 are fixed to the lower holder 41.

  The lower die 42 is slidably provided on the inner surface of the guide 43 and the outer peripheral surface of the lower punch 44. The center hole 42 a of the lower die 42 has an inner diameter that is slightly larger than the outer diameter of the coarse material 110. The lower die 42 is urged upward in the figure by the piston 52 of the cushion cylinder 51 via the cushion pin 50. Pressure oil whose pressure is adjusted is supplied to the cylinder chamber 53 from the hydraulic pressure generator 54.

  The lower punch 44 has a height dimension that is slightly lower than the upper surface of the lower die 42 when the lower die 42 is lowered to the lower limit position (see FIGS. 3 and 5). The center hole 44 a of the lower punch 44 has an inner diameter dimension substantially equal to the outer diameter of the ring-shaped boss portion 114 in the coarse material 110, that is, the ring-shaped boss portion 109 in the bevel gear 100.

  The lower mandrel 46 is concentric with the center hole 44 a of the lower punch 44 and has an outer diameter dimension substantially equal to the inner diameter of the through hole 111. The height of the lower mandrel 46 does not interfere with the tip of the upper mandrel 35 when the upper mandrel 35 reaches the lower limit position, and further, the height of the annular inner burr that can be formed in the center hole 104. It is defined from the viewpoint of limiting.

  The knockout ring 45 is slidably provided on the inner peripheral surface of the center hole 44 a of the lower punch 44 and the outer peripheral surface of the lower mandrel 46. The lower limit position of the knockout ring 45 is restricted to a position lower than the upper surface of the lower punch 44 by the height of the boss portions 109 and 114. The knockout ring 45 is pushed up by the knockout device 56 via the knockout pin 55. As a result, the forged product of the bevel gear 100 is protruded upward from the cavity 21.

  Next, the operation of this embodiment will be described.

  As shown in FIG. 1, the coarse material 110 is supplied into the center hole 42 a of the lower die 42 that has been raised to the ascent limit position with the upper die 30 opened. As shown in FIGS. 2 and 4, when the upper and lower molds 30 and 40 are closed, the upper die 33 contacts the lower die 42. The lower die 42 is biased by pressure oil through the cushion pin 50. When the lowering of the upper die 30 is started, the lower die 42 is lowered while being closed, and forging is started.

  As shown in FIGS. 3 and 5, when the upper die 30 is further lowered, the small diameter portion 37 of the upper mandrel 35 is inserted into the through hole 111 from the opening 112, and the cooperation between the upper punch 34 and the lower punch 44 is further performed. The coarse material 110 is pushed into the cavity 21 by the action.

  When the upper mold 30 is lowered to the lower limit position and the upper mandrel 35 reaches the lower limit position, the material is pushed in by the taper portion 38 of the upper mandrel 35 and moves toward the tooth mold 39 as indicated by an arrow in FIG. Plastic flow of the material occurs. As a result, the tooth profile 103 is sufficiently filled with material, and lack of thickness in the tooth profile 103 is prevented. In addition, since the rough material 110 in which the through holes 111 are formed in advance is used, a drilling process for forming the center hole 104 after the forging process is not necessary. Furthermore, since the center hole 104 is formed during forging, the concentricity between the tooth profile 103 and the center hole 104 can be easily increased.

  When the upper mandrel 35 reaches the lower limit position, the tip of the small diameter portion 37 of the upper mandrel 35 is inserted into the through hole 111 to the vicinity of the axis orthogonal line L. For this reason, the small-diameter portion 37 of the upper mandrel 35 substantially contributes to the formation of the tooth profile 103, and from this viewpoint, the tooth profile 103 is sufficiently filled with the material.

  The tip of the small diameter portion 37 of the upper mandrel 35 inserted into the through hole 111 does not exceed the axis orthogonal line L. For this reason, the upper mandrel 35 can be easily pulled out from the center hole 104 after forging while inserting the upper mandrel 35 to a position that substantially contributes to the formation of the tooth profile 103.

  Further, as a result of the material being pushed by the tapered portion 38 of the upper mandrel 35, the chamfered portion 106 is plastically processed at the top surface inlet portion 105 on the small end portion 102 side simultaneously with the forging process. For this reason, the machining for forming the chamfered portion 106 after the forging process can be omitted.

  Then, the upper and lower molds 30 and 40 are opened, the knockout ring 45 is pushed up to protrude the forged product upward, so that the center hole 104 is formed between the large end portion 101 and the small end portion 102 and the tooth shape portion 103. The bevel gear 100 is produced by a single process press. Thereafter, sizing is performed as necessary to ensure the tooth profile accuracy.

  As described above, the method for manufacturing the bevel gear 100 according to the present embodiment includes the bevel gear 100 having the tooth shape portion 103 and the center hole 104 between the large end portion 101 and the small end portion 102. When the forging die 20 including the tooth die 39 for forming is used for manufacturing by forging, the opening 112 is located at both ends along the axial direction of the through hole 111 of the rough material 110 in which the through hole 111 is formed in advance. , 113, the upper mandrel 35 provided in the forging die 20 is inserted into the upper mandrel 35 through the opening 112 on the side forming the top surface inlet 105 on the small end 102 side of the bevel gear 100. At the same time, the tapered portion 38 inclined in the direction toward the tooth mold 39 causes the plastic flow of the material toward the tooth mold 39, and the chamfered portion 106 is plastically added to the top surface inlet portion 105. Since, it is possible to prevent the underfill in the tooth portion 103 is sufficiently filled with material to tooth portion 103. Further, since the chamfered portion 106 is plastically processed at the top surface inlet portion 105 simultaneously with the forging process, machining for forming the chamfered portion 106 after the forging process can be omitted. Furthermore, since the center hole 104 is formed during forging, the concentricity between the tooth profile 103 and the center hole 104 can be increased.

  Further, the taper portion 38 is formed by the plastic flow of the material and the chamfered portion 106 when the upper mandrel 35 reaches the lower limit position, that is, when the upper mandrel 35 reaches the forward limit position relative to the coarse material 110. Since it is formed at a position where plastic processing is performed, filling of the tooth profile 103 with material and processing of the chamfered portion 106 can be performed reliably.

  The tapered portion 38 is formed at an intermediate portion along the longitudinal direction of the upper mandrel 35, and the tip of the upper mandrel 35 is large along the axial direction of the tooth profile portion 103 when the upper mandrel 35 reaches the lower limit position. Since it is inserted into the through-hole 111 to the vicinity of the axis orthogonal line L including the bottom portion 108 on the end portion 101 side, the upper mandrel 35 substantially contributes to the formation of the tooth profile portion 103. 103 is fully filled with material.

  Further, since the tip of the upper mandrel 35 inserted into the through-hole 111 does not exceed the axis orthogonal line L, the upper mandrel 35 is inserted into the position substantially contributing to the formation of the tooth profile portion 103 while forging. The upper mandrel 35 can be easily pulled out from the center hole 104 later.

  In addition, the manufacturing apparatus 10 for the bevel gear 100 according to the present embodiment forms the tooth profile 103 by using the bevel gear 100 having the tooth profile portion 103 and the center hole 104 between the large end portion 101 and the small end portion 102. In the manufacturing apparatus 10 of the bevel gear 100 manufactured by forging using the forging die 20 including the tooth die 39, the through holes 111 are positioned at both ends along the axial direction of the through holes 111 of the rough material 110 in which the through holes 111 are formed in advance. The upper mandrel 35 inserted into the through hole 111 from the opening 112 on the side of the top end entrance 105 on the small end 102 side of the bevel gear 100 of the openings 112 and 113 to be In the mandrel 35, a taper portion 38 that causes plastic flow of the material toward the tooth mold 39 and plastic processing of the chamfered portion 106 at the top surface inlet portion 105 is provided in the direction toward the tooth mold 39. Since it is formed to be inclined, as described above, it is possible to prevent the lack of thickness in the tooth profile portion 103, and to omit machining for forming the chamfered portion 106 after the forging process. The concentricity with the hole 104 can be increased.

  In addition, although embodiment which formed the taper part 38 in the intermediate part along the longitudinal direction of the upper mandrel 35 was demonstrated, this invention is not limited to this case. For example, the taper portion 38 having a function of performing plastic flow of the material and plastic processing of the chamfered portion 106 may be provided at the tip portion of the upper mandrel 35, and the lower mandrel 46 may be inserted to the upper position in the through hole 111.

(Second Embodiment)
The technical significance of the first embodiment is that the mandrel 35, 46 is inserted into the through-hole 111 previously formed in the rough material 110, and the bevel gear is manufactured by forging, and machining after the forging process is performed. Is to be omissible. The technical significance of the second embodiment is in common with the technical significance of the first embodiment, and machining after the forging process, specifically, serration is applied to the inner peripheral surface of the center hole. It is to be able to omit broaching for forming.

  FIG. 7 is a cross-sectional view showing the main part of the bevel gear manufacturing apparatus 10a according to the second embodiment of the present invention in a state where the forging die 20 is closed and forging is in progress, and FIG. 8 shows the manufacturing apparatus 10a. It is sectional drawing which shows the principal part of the state which the forging process was completed. FIG. 9 is a diagram showing the lower mandrel 76 used in the second embodiment. FIG. 10A is a cross-sectional view showing the coarse material 210 before forging used when manufacturing the bevel gear 200 and having the through holes 211 formed in advance, FIG. ) Is a cross-sectional view showing a bevel gear 200 manufactured by forging, and FIG. 10C is a view showing a cross-section of the bevel gear 200 after heat treatment together with a connecting shaft 230. FIG. 11 is a cross-sectional view showing a general bevel gear 300 in which serrations 321 are formed on the inner peripheral surface of the center hole 304. The bevel gear manufacturing apparatus 10a according to the second embodiment is substantially the same as the bevel gear manufacturing apparatus 10 according to the first embodiment except for the structure of the upper and lower mandrels 65 and 76. For this reason, about the member which is common in 1st Embodiment, it demonstrates using the same code | symbol, without showing in figure.

  In general, the gear having the center hole and the connecting shaft inserted and connected to the center hole have shaft side teeth formed on the outer peripheral surface of the connecting shaft in order to ensure transmission of torque, The center hole side teeth formed on the inner peripheral surface of the center hole are engaged with each other and connected. There are serrations and splines in the shaft side teeth and the center hole side teeth. When it is not necessary to slide the gear with respect to the connecting shaft, a serration with a fine tooth profile pitch and a large number of teeth is usually selected. In the following description, the case where the shaft side tooth portion and the center hole side tooth portion are serrations will be described as an example, but it goes without saying that the spline is not excluded.

  The bevel gear 300 shown in FIG. 11 has serrations 321 formed on the inner peripheral surface of the center hole 304. The serration 321 is formed by broaching. The broached bevel gear 300 is subjected to carburizing heat treatment to increase the surface hardness, and then is polished and finished.

  Here, due to distortion generated in the carburizing heat treatment, the diameter of the serration 321 of the center hole 304 may change depending on the position of the center hole 304 in the axial direction, and may not satisfy the dimensional standard. Specifically, if the serration diameter near the top entrance 305 is φa and the serration diameter near the back entrance 307 is φb, φa = φb after broaching. However, due to distortion during the carburizing heat treatment, φa> φb, which may not satisfy the dimensional standard.

  Further, when manufacturing a bevel gear of a new shape or a bevel gear made of a new material, a procedure of broach trial manufacture → carburization heat treatment → inspection of strain → manufacture of broach considering the strain must be performed. For this reason, there is a problem that it takes a long development period to make a good bevel gear.

  The second embodiment is intended to improve the above problems.

  As shown in FIG. 10B, the bevel gear 200 manufactured by forging has a tooth profile 203 between a large end 201 and a small end 202 and a center hole 204. In the second embodiment, the center hole side serration 221 that meshes with the shaft side serration 231 (corresponding to the shaft side tooth portion) formed on the connecting shaft 230 inserted and connected to the center hole 204 simultaneously with the forging process. (Corresponding to the center hole side tooth portion) is plastic processed. Further, similarly to the first embodiment, a chamfered portion 206 is plastically processed at the top surface entrance portion 205 on the small end portion 202 side.

  As shown in FIG. 10A, a through hole 211 is formed in advance in the coarse material 210 before forging, as in the coarse material 210 of the first embodiment. Of the openings 212 and 213 located at both ends along the axial direction of the through-hole 211, the upper opening 212 in the figure forms the top surface inlet 205 after forging, and the lower opening 213 in the figure After the forging, the back entrance 207 is formed. The through hole 211 becomes the center hole 204 of the bevel gear 200 after forging.

  Such a bevel gear 200 is manufactured by a manufacturing apparatus 10 a having a forging die 20, and the forging die 20 is provided with a tooth die 39 for forming a tooth profile portion 203.

  As shown in FIG. 7 and FIG. 8, the manufacturing apparatus 10 a in the second embodiment is positioned at both ends along the axial direction of the through hole 211 of the rough material 210 in which the through hole 211 is preliminarily formed. The lower mandrel inserted into the through-hole 211 from the opening 213 (corresponding to one opening) on the side forming the rear entrance 207 on the large end 201 side of the bevel gear 200 among the openings 212 and 213. 76 (corresponding to a mandrel). In the lower mandrel 76, a mandrel side tooth portion 77 that plastically processes the center hole side serration 221 that meshes with the shaft side serration 231 is formed to be tapered toward the distal end in the insertion direction. Then, the amount of taper of the mandrel side tooth portion 77, that is, the amount of change in diameter, is caused by distortion during the carburizing heat treatment (corresponding to the heat treatment) applied to the bevel gear 200 after forging. The diameter is set to be uniform regardless of the position of the center hole 204 in the axial direction.

  The upper mandrel 65 is formed with a tapered portion 68 that causes the plastic flow of the material toward the tooth mold 39 and plastically processes the chamfered portion 206 at the top surface entrance portion 205 so as to incline in the direction toward the tooth mold 39. Yes. The tapered portion 68 is formed at a position where plastic flow of the material and plastic working of the chamfered portion 206 are performed when the upper mandrel 65 reaches the lower limit position. In the illustrated example, the tapered portion 68 is formed at the tip portion of the upper mandrel 65.

  As shown in FIG. 9, the lower mandrel 76 has a base end portion 78 and a distal end portion 79, and a mandrel side tooth portion 77 that is tapered toward the distal end in the insertion direction is formed on the distal end portion 79. Yes. If the diameter of the mandrel side tooth portion 77 near the tip is φA and the diameter of the mandrel side tooth portion 77 near the base end portion 78 is φB, then a relationship of φA <φB is established. As described above, the amount of taper of the mandrel side tooth portion 77 is such that the diameter of the center hole side serration 221 is the axis of the center hole 204 due to distortion during carburizing heat treatment applied to the bevel gear 200 after forging. The amount is set to be uniform regardless of the direction position. The height dimension of the lower mandrel 76 is determined so as not to interfere with the tip of the upper mandrel 65 when the upper mandrel 65 reaches the lower limit position.

  Next, the operation of this embodiment will be described.

  As in the case of the first embodiment, the coarse material 210 is supplied into the center hole 42a of the lower die 42 that has been raised to the ascending limit position with the upper die 30 opened. As shown in FIG. 7, when the upper and lower molds 30 and 40 are closed, the upper die 33 contacts the lower die 42. The lower die 42 is biased by pressure oil through the cushion pin 50. The lower mandrel 76 is inserted into the through hole 211 from the opening 213. When the lowering of the upper die 30 is started, the lower die 42 is lowered while being closed, and forging is started.

  As shown in FIG. 8, when the upper die 30 is further lowered, the mandrel side tooth portion 77 of the lower mandrel 76 is further inserted into the through hole 211, and the coarse material 210 is moved by the cooperation of the upper punch 34 and the lower punch 44. It is pushed into the cavity 21.

  When the upper mold 30 is lowered to the lower limit position, the lower mandrel 76 relatively reaches the upper limit position, and the mandrel side tooth portion 77 of the lower mandrel 76 causes the center hole 204 to enter the center hole side serration 221 simultaneously with forging. Is plastically processed. Thereby, broaching which is machining for forming serrations on the inner peripheral surface of the center hole 204 after the forging process can be omitted. Moreover, since the rough material 210 in which the through-hole 211 is formed in advance is used, a drilling process for forming the center hole 204 after the forging process becomes unnecessary. Furthermore, since the center hole 204 is formed during forging, the concentricity between the tooth profile 203 and the center hole 204 can be easily increased.

  The mandrel side tooth portion 77 is tapered toward the distal end in the insertion direction. When the serration diameter near the top surface entrance portion 205 is φa and the serration diameter near the back surface entrance portion 207 is φb, the center hole side serration 221 after plastic working has a relationship of φa <φb (see FIG. 10B). ).

  The upper mandrel 65 also reaches the lower limit position, and the material is pushed in by the tapered portion 68 of the upper mandrel 65, and the plastic flow of the material toward the tooth mold 39 occurs as in the first embodiment. As a result, the tooth profile 203 is sufficiently filled with material, and lack of thickness in the tooth profile 203 is prevented. As in the first embodiment, the material is pushed by the tapered portion 68 of the upper mandrel 65. As a result, the chamfered portion 206 is plastically processed at the top surface inlet portion 205 on the small end portion 202 side simultaneously with the forging process. . For this reason, the machining for forming the chamfered portion 206 after the forging process can be omitted.

  Then, the upper and lower molds 30 and 40 are opened, the knockout ring 45 is pushed up to protrude the forged product upward, so that the center hole 204 is formed between the large end portion 201 and the small end portion 202 while having the tooth profile portion 203. The bevel gear 200 is produced by a single process press.

  Thereafter, carburizing heat treatment is performed on the bevel gear 200 after forging. Due to the heat during the carburizing heat treatment, the bevel gear 200 after forging is distorted. Here, the amount by which the mandrel side tooth portion 77 is tapered in advance is determined in consideration of the amount of strain generated during the carburizing heat treatment. Therefore, the center hole side serration 221 after the carburizing heat treatment has a relationship of φa = φb, and is uniform regardless of the position of the center hole 204 in the axial direction (see FIG. 10C). As a result, the quality related to the serration diameter of the center hole 204 can be stabilized.

  It is easier to correct the diameter of the mandrel side tooth portion 77 than in the case of manufacturing a broach in consideration of the amount of distortion during carburizing heat treatment. For this reason, the shape of the center hole side serration 221 after forging, that is, the forging shape can be arbitrarily and easily changed by slightly correcting the mandrel side tooth portion 77 in the lower mandrel 76. Therefore, even when manufacturing a bevel gear of a new shape or a bevel gear made of a new material, the shape of the center hole side serration 221 after forging can be quickly determined in consideration of the amount of strain generated during carburizing heat treatment. It can be shortened.

  As described above, the method for manufacturing the bevel gear 200 according to the present embodiment includes the bevel gear 200 having the tooth hole portion 203 and the center hole 204 between the large end portion 201 and the small end portion 202. When manufacturing by forging using the forging die 20 having the tooth die 39 for forming the through hole 211, the opening 212 is located at both ends along the axial direction of the through hole 211 of the rough material 210 in which the through hole 211 is formed in advance. The lower mandrel 76 provided in the forging die 20 is inserted from one opening 213 of 213, and the mandrel side tooth portion 77 formed on the lower mandrel 76 and tapering toward the distal end in the insertion direction, The center hole side serration 221 that meshes with the shaft side serration 231 formed on the connecting shaft 230 inserted and connected to the center hole 204 is plastically processed. Thus, the amount of taper of the mandrel side tooth portion 77 depends on the axial position of the center hole 204 due to the distortion during carburizing heat treatment applied to the bevel gear 200 after forging. Since the center hole side serration 221 is plastically processed simultaneously with the forging process, the broaching process, which is a machining process for forming the center hole side serration 221 after the forging process, may be omitted. it can. In addition, since the plastic-processed center hole side serration 221 takes into account the amount of strain generated during the carburizing heat treatment, the center hole side serration 221 after the carburizing heat treatment becomes uniform regardless of the position of the center hole 204 in the axial direction. As a result, the quality related to the diameter of the center hole side serration 221 can be stabilized. Furthermore, even when manufacturing a bevel gear of a new shape or a bevel gear made of a new material, the shape of the center hole side serration 221 after forging can be quickly determined in consideration of the amount of strain generated during carburizing heat treatment, and the development period can be increased. It can be shortened.

  Further, since the shaft side tooth portion 231 and the center hole side tooth portion 221 are serrations, torque transmission between the bevel gear 200 and the connecting shaft 230 is ensured.

  Further, the manufacturing apparatus 10a of the bevel gear 200 according to the present embodiment forms the tooth profile portion 203 by forming the bevel gear 200 having the tooth shape portion 203 and the center hole 204 between the large end portion 201 and the small end portion 202. In the manufacturing apparatus 10a of the bevel gear 200 manufactured by forging using the forging die 20 including the tooth die 39, the through hole 211 is positioned at both ends along the axial direction of the through hole 211 of the coarse material 210 in which the through hole 211 is formed in advance. The lower mandrel 76 is inserted into the through hole 211 from one of the openings 212 and 213 to be formed, and the lower mandrel 76 is formed on the connecting shaft 230 inserted and connected to the center hole 204. The mandrel side tooth portion 77 that plastically processes the center hole side serration 221 that meshes with the shaft side serration 231 is tapered toward the distal end in the insertion direction. The amount of taper of the mandrel side tooth portion 77 is determined by the distortion at the time of heat treatment applied to the bevel gear 200 after forging, so that the diameter of the center hole side serration 221 becomes the axial position of the center hole 204. However, as described above, broaching, which is machining for forming the center hole side serration 221 after the forging process, can be omitted and the center hole side serration 221 can be omitted. It is possible to stabilize the quality related to the diameter of the steel, and it is possible to shorten the development period when manufacturing a bevel gear having a new shape.

  Although the second embodiment in which the chamfered portion 206 is plastically processed in addition to the plastic processing of the center hole side tooth portion 221 at the same time as the forging processing has been described, depending on the shape of the bevel gear, the center hole side tooth It is also possible to change only the part 221 to the form which carries out plastic working.

  Needless to say, it is possible to insert a mandrel from the opening 212 side when the tendency of occurrence of distortion during heat treatment is different.

It is sectional drawing which shows the state before the forging in which the forge type | mold was opened of the manufacturing apparatus of the bevel gear which concerns on embodiment of this invention. It is sectional drawing which shows the state in the middle of a forge process with the forging die closed of the manufacturing apparatus. It is sectional drawing which shows the state which the forging process of the manufacturing apparatus was completed. It is sectional drawing which shows the principal part of FIG. It is sectional drawing which shows the principal part of FIG. FIG. 6 (A) is a rough material before forging used when manufacturing a bevel gear, and is a cross-sectional view showing a rough material in which a through hole is formed in advance, and FIG. 6 (B) is obtained by forging. It is sectional drawing which shows the bevel gear manufactured. It is sectional drawing which shows the principal part of the state in the middle of a forge process with the forging die closed of the manufacturing apparatus of the bevel gear concerning the 2nd Embodiment of this invention. It is sectional drawing which shows the principal part of the state which the forging process of the manufacturing apparatus was completed. It is a figure which shows the lower mandrel used in 2nd Embodiment. FIG. 10 (A) is a rough material before forging used when manufacturing a bevel gear, and is a cross-sectional view showing the rough material in which a through hole is formed in advance, and FIG. 10 (B) is obtained by forging. Sectional drawing which shows the manufactured bevel gear, FIG.10 (C) is a figure which shows the cross section of the bevel gear after heat processing with a connection shaft. It is sectional drawing which shows the general bevel gearwheel in which the serration was formed in the internal peripheral surface of a center hole.

Explanation of symbols

10, 10a Bevel gear manufacturing device,
20 forging die,
30 Upper mold,
35 Upper mandrel (mandrel),
36 Large diameter part,
37 Small diameter part,
38 taper,
39 tooth type,
40 Lower mold,
46 Lower mandrel,
65 upper mandrel,
68 taper,
76 Lower mandrel (mandrel),
77 Mandrel side teeth,
100, 200 bevel gear,
101, 201 large end,
102, 202 small end,
103, 203 tooth profile,
104, 204 Center hole,
105, 205 Top entrance,
106, 206 Chamfered part,
107, 207 Rear entrance,
108 bottom,
110, 210 Crude material,
111, 211 through holes,
112 opening (opening on the side forming the top surface entrance),
113 opening,
212 opening,
213 opening (one opening),
221 center hole side serration (center hole side tooth),
230 connecting shaft,
231 Shaft side serration (shaft side teeth),
L axis orthogonal line.

Claims (8)

When producing a bevel gear having a tooth profile portion between the large end portion and the small end portion and having a center hole by forging using a forging die having a tooth shape forming the tooth profile portion,
Among the openings located at both ends along the axial direction of the through hole of the rough material in which the through hole is formed in advance, the forging is performed from the opening on the side that forms the top surface inlet on the small end side of the bevel gear. A mandrel provided in a mold is inserted, and a taper portion formed in the mandrel and inclined in a direction toward the tooth mold causes plastic flow of the material toward the tooth mold and is chamfered at the top surface inlet section. A method of manufacturing a bevel gear, characterized in that a part is plastically processed.   The tapered portion is formed at a position where plastic flow of the material and plastic processing of the chamfered portion are performed when the mandrel reaches a forward limit position relative to the rough material. A method for manufacturing a bevel gear according to claim 1.   The tapered portion is formed at an intermediate portion along the longitudinal direction of the mandrel, and the tip of the mandrel is positioned at the large end portion along the axial direction of the tooth profile when the mandrel reaches the forward limit position. The method for manufacturing a bevel gear according to claim 2, wherein the bevel gear is inserted into the through hole up to the vicinity of an axis orthogonal line including a bottom portion on the side.   The method of manufacturing a bevel gear according to claim 3, wherein a tip of the mandrel inserted into the through hole does not exceed the axis orthogonal line. A bevel gear manufacturing apparatus for manufacturing a bevel gear having a tooth profile portion between a large end portion and a small end portion and having a center hole by forging using a forging die having a tooth shape forming the tooth profile portion. In
Among the openings located at both ends along the axial direction of the through-hole of the rough material in which the through-hole is formed in advance, the through-hole is formed from the opening on the side forming the top surface inlet on the small end side of the bevel gear Having a mandrel inserted into the hole;
The mandrel is formed with a taper portion for causing plastic flow of the material toward the tooth mold and plastic processing of a chamfered portion at the top surface inlet portion in a direction toward the tooth mold. Equipment for manufacturing bevel gears. When producing a bevel gear having a tooth profile portion between the large end portion and the small end portion and having a center hole by forging using a forging die having a tooth shape forming the tooth profile portion,
A mandrel provided in the forging die is inserted into one of the openings located at both ends along the axial direction of the through hole of the rough material in which the through hole is formed in advance, and formed in the mandrel The center hole side tooth portion meshed with the shaft side tooth portion formed on the connecting shaft inserted and connected to the center hole by the mandrel side tooth portion tapering toward the distal end in the insertion direction is plastically processed,
The amount of taper of the mandrel side teeth is made uniform regardless of the axial position of the center hole due to distortion during heat treatment applied to the bevel gear after forging. A method for manufacturing a bevel gear, characterized in that the amount is set.   The method for manufacturing a bevel gear according to claim 6, wherein the shaft side tooth portion and the center hole side tooth portion are serrations. A bevel gear manufacturing apparatus for manufacturing a bevel gear having a tooth profile portion between a large end portion and a small end portion and having a center hole by forging using a forging die having a tooth shape forming the tooth profile portion. In
A mandrel inserted into the through-hole from one of the openings located at both ends along the axial direction of the through-hole of the rough material in which the through-hole is formed in advance,
A mandrel side tooth portion that plastically processes a center hole side tooth portion that meshes with a shaft side tooth portion formed on a connecting shaft that is inserted and connected to the center hole is tapered on the mandrel toward the distal end in the insertion direction. Become
The amount of taper of the mandrel side teeth is made uniform regardless of the axial position of the center hole due to distortion during heat treatment applied to the bevel gear after forging. An apparatus for manufacturing a bevel gear, characterized in that the amount is set.

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