Forging molding device and forging molding method

Abstract

To provide a forging molding device capable of extending the die life of a molding die.SOLUTION: A forging molding device K comprises a molding die S for performing forging molding on a material M and a punch P that pushes the material M toward the molding die S disposed on the front side in a molding direction. The molding die S molds an outer surface of the material M by a branch flow of material flow occurring in the material M during forging molding along a direction orthogonal to the molding direction, with respect to the material M having an outer dimension smaller than an outer dimension of a product W after forging molding, and includes a first molding die S1 that molds an intermediate molded body having an intermediate shape from the material M, and a second molding die S2 that molds a product W being a final molded body having a final shape whose outer dimension is smaller than the outer dimension of the intermediate shape from the intermediate molded body.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a forging apparatus and a forging method. [Background technology]

[0002] Conventionally, for example, a forging method and a forging device (hereinafter referred to as "forging method, etc.") disclosed in Patent Document 1 have been known. In the conventional forging method, in one forging step, the outer diameter of a material is constrained before the material is forced into a forming space of a forming die, and the material is forced into the forming space to perform forging. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-38032 Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional forging methods, a product is formed by forging a material whose outer diameter is constrained in one forging step. In this case, by constraining the outer diameter of the material before it is forced into the forming die, the material is forged while being prevented from being upset inside the forming cavity.

[0005] However, when a product shape is formed through only one forging process, the forging process generates a large amount of material flow, i.e., the forming volume is large, so there is a limit to how much the forming load can be reduced. As a result, the forging process places a load on the forming die, which may shorten the die life. Therefore, there is room for improvement in conventional forging methods, etc., in terms of extending the die life.

[0006] An object of the present invention is to provide a forging apparatus and a forging method that can extend the life of a forming die. [Means for solving the problem]

[0007] The forging forming device of the present invention comprises a forming die that performs forging on a raw material, and a punch that pushes the raw material toward the forming die that is positioned forward in the forming direction, and the forming die forms the outer surface of the raw material, which has an outer dimension smaller than the outer dimension after forging, by diverting the material flow that occurs in the raw material due to forging along a direction perpendicular to the forming direction, and includes a first forming die that forms an intermediate formed product having an intermediate shape from the raw material, and a second forming die that forms a final formed product from the intermediate formed product, which has a final shape with an outer dimension smaller than the outer dimension of the intermediate shape.

[0008] In addition, the forging method of the present invention includes a first forging process using the above-mentioned forging device to form an intermediate product from the raw material by forging the raw material using a first forming die, and a second forging process using a second forming die to form a final product from the intermediate product by forging the intermediate product. [Effects of the Invention]

[0009] According to the present invention, in the first forging step, a first forming die is used to form an intermediate product having an intermediate shape from a material having smaller outer dimensions than the intermediate product and the final product after forging, and in the second forging step, a second forming die is used to form the final product having the final shape from the intermediate product. This reduces the material flow per step, i.e., the forming amount, thereby reducing the forming load, and as a result, the load on the die associated with forging can be reduced and the die life can be extended. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a diagram illustrating a forging device. [Figure 2]FIG. 10 is a diagram illustrating an intermediate molded product. [Figure 3] FIG. 2 is a diagram for explaining the final molded product (product). [Figure 4] FIG. 10 is a diagram for explaining a cross-sectional area reduction rate. [Figure 5] 10A and 10B are diagrams for explaining whether molding is possible when the cross-sectional area reduction rate is outside the upper and lower limits. [Figure 6] FIG. 2 is a diagram illustrating a forging device that performs a first forging step of the first embodiment. [Figure 7] FIG. 2 is a diagram illustrating a forging device that performs a second forging step in the first embodiment. [Figure 8] FIG. 1 is a diagram for explaining a material of a first embodiment. [Figure 9] FIG. 2 is a cross-sectional view illustrating a first forming die of the first embodiment. [Figure 10] FIG. 3 is a cross-sectional view illustrating a second forming die of the first embodiment. [Figure 11] 3A and 3B are diagrams illustrating an intermediate molded product according to the first embodiment. [Figure 12] FIG. 2 is a diagram for explaining a final molded product (product) of the first embodiment. [Figure 13] FIG. 10 is a cross-sectional view illustrating a second forming die according to a modified example of the first embodiment. [Figure 14] FIG. 10 is a diagram for explaining a final molded product according to a modified example of the first embodiment. [Figure 15] FIG. 10 is a diagram illustrating a forging device that performs a first forging step and a second forging step according to a second embodiment. [Figure 16] FIG. 10 is a diagram for explaining a material according to a second embodiment. [Figure 17] FIG. 10 is a cross-sectional view illustrating a first forming die of a second embodiment. [Figure 18] FIG. 10 is a cross-sectional view illustrating a second forming die of a second embodiment. [Figure 19] FIG. 10 is a diagram illustrating an intermediate molded product according to a second embodiment. [Figure 20]FIG. 10 is a diagram for explaining a final molded product (product) of the second embodiment. [Figure 21] FIG. 10 is a diagram for explaining a material according to a modified example of the second embodiment. [Figure 22] 10A and 10B are diagrams for explaining the outer shapes of an intermediate molded product and a final molded product (product) according to a modified example of the second embodiment. [Figure 23] 10 is a diagram illustrating a forging device that performs a first forging step and a second forging step according to a modified example of the second embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] 1. Overview of forging using the forging device K of the present invention An overview of forging using the forging apparatus K of the present invention will be described with reference to the drawings. As shown in FIG. 1 , the forging apparatus K forges a raw material M having outer dimensions smaller than those of a product W without constraining the outer shape. Specifically, the forging apparatus K includes a punch P and a forming die S having a forming space. The punch P presses the raw material M into the forming space of the forming die S without constraining the outer shape, thereby causing material flow in the raw material M in a direction perpendicular to the axial direction (outward), thereby performing forging on the outer surface, particularly cold forging including drawing. Here, examples of the shapes of the raw material M and the product W include a disk, annular, polygonal, etc., in terms of the cross-sectional shape perpendicular to the axial direction of the raw material M and the product W. Examples of the product W include a gear, a spline shaft, a keyway, a key, etc. Furthermore, the "external dimensions" correspond to "external diameter dimensions" when the cross-sectional shapes of the material M and the product W are circular or annular, and correspond to "width dimensions" when the cross-sectional shapes of the material M and the product W are polygonal.

[0012] Incidentally, when the material M to be forged by the forging device K is forced into the forming space of the forming die S, material flows in the axial direction and outward, i.e., so-called divided flows occur, and the outer surface is formed while reducing the cross-sectional area of ​​the cross-sectional shape. In other words, before and after forging, the material M elongates in its entire length along the axial direction and also expands outward.

[0013] Generally, the larger the outer dimensions of the raw material M before forming relative to the outer dimensions of the formed product W, the larger the area reduction rate during forging. In other words, the area reduction rate represents the ratio of the cross-sectional area after forming to the cross-sectional area before forming, as shown in the following formula, and indicates the difficulty of deformation when performing forging involving drawing (the larger the area reduction rate, the more difficult the deformation). Cross-sectional area reduction rate = {1 - (cross-sectional area after molding / cross-sectional area before molding)} x 100 [%]

[0014] Furthermore, the principle of constant volume holds true before and after forging. As a result, the elongation amount of the overall length and the amount of outward expansion of the material M, i.e., the amount of forging, increases as the reduction in area increases. In other words, the greater the reduction in area, the greater the amount of outward expansion, and the formed shape on the outer surface (peripheral surface) of the material M, i.e., the transferred shape of the forming space of the forming die S, tends to be better, which is called thickness.

[0015] However, if the reduction of area is increased, the total amount of material movement during forging of the raw material M increases, and upsetting into the forming space may occur, resulting in a larger forming load during forging. Furthermore, if the forming load is large, a large reaction force against the forming load acts on the forming die S, shortening the die life.

[0016] Therefore, the forging device K performs forging (cold forging) on ​​a raw material M having outer dimensions smaller than those of the product W through a first forging process and a second forging process. That is, in the first forging process, the forging device K forms an intermediate product Fi having an intermediate shape similar to the final shape of the product W on the outer circumferential surface of the raw material M, as shown in FIG. 2. Then, in the second forging process, as shown in FIG. 3, the forging device K performs drawing as cold forging on the intermediate product Fi formed in the first forging process to form a final product Ff having the final shape. That is, by performing the first forging process and the second forging process, the forging device K distributes the forming amount until the final shape is formed in each process.

[0017] As a result, in the forging device K, the forming load generated in each process can be made smaller than the forming load generated when, for example, a product W is formed from a raw material M through one forging process, and as a result, the total forming load can also be made smaller. That is, in the forging device K, the area reduction rate in each process can be made relatively small, while a final formed product Ff, i.e., product W, with good thickness can be formed by drawing the intermediate formed product Fi formed in the first forging process in the second forging process.

[0018] When the intermediate shape of the intermediate product Fi and the final shape of the final product Ff are gear-shaped, the circumferential face width of the gear shape of the intermediate product Fi shown by the dashed line in Fig. 4 is larger than that of the final shape of the final product Ff shown by the solid line. Also, when the intermediate shape of the intermediate product Fi and the final shape of the final product Ff are gear-shaped, the radial tooth height of the gear shape of the intermediate product Fi shown by the dashed line in Fig. 4 is larger than that of the final shape of the final product Ff shown by the solid line. Therefore, by drawing the intermediate product Fi formed in the first forging step in the second forging step, it is possible to form a final product Ff, i.e., a product W, having a good thickness.

[0019] Here, the forging device K uses a different forming die S for each step so that the forming load in each of the first forging step and the second forging step can be reduced. Specifically, as shown in Fig. 1, the forging device K has, as the forming dies S, a first forming die S1 used in the first forging step and a second forming die S2 used in the second forging step.

[0020] In the forging device K, when forging is performed using the first forming die S1 and the second forming die S2, the first area reduction rate in the processing target portion MA of the material M and the second area reduction rate in the processing target portion MB of the intermediate formed product Fi are each set to be 10% to 40%, as shown by the filled-in dots in Fig. 4. In other words, in the forging device K, the internal dimensions of the forming spaces of the first forming die S1 and the second forming die S2 are set so that the first area reduction rate in the processing target portion MA of the material M and the second area reduction rate in the processing target portion MB of the intermediate formed product Fi are each 10% to 40%. Note that the "internal dimensions" correspond to "inner diameter dimensions" when the cross-sectional shapes of the material M and the intermediate formed product Fi are circular or annular, and to "width dimensions" when the cross-sectional shapes of the material M and the intermediate formed product Fi are polygonal.

[0021] As for the processing target portions MA and MB, when forming a plurality of external teeth, such as a gear, the portion where one external tooth is formed can be the processing target portion, or the portion where all the external teeth are formed can be the processing target portion, as shown in Fig. 4. Furthermore, when forming a single keyway or key, the processing target portions MA and MB can be the portion where the keyway or key is formed.

[0022] Here, if the reduction of area is less than 10%, for example, the material flow during the first forging process to form the intermediate product Fi is small (the amount of material formed is small), resulting in a small forming load. However, the material flow during the second forging process to form the final product Ff, i.e., the product W, is large (the amount of material formed is large), resulting in a large forming load. As a result, as shown in FIG. 5, the intermediate product Fi before being pressed into the forming space of the second forming die used in the second forging process is upset and expands outward, making forging impossible. Furthermore, if the reduction of area is set to less than 10%, even if the final product Ff, i.e., the product W, is formed through the second forging process, there will not be enough material flowing outward, i.e., toward the forming space of the second forming die, and the product W will not have sufficient thickness.

[0023] On the other hand, if the area reduction rate is set to be greater than 40%, for example, the material flow increases (the amount of material formed increases) when forming the intermediate product Fi in the first forging step, resulting in a larger forming load. As a result, as shown in Fig. 5, the material M before being pressed into the forming space of the first forming die used in the first forging step is upset and spreads outward, making forging impossible. Also, if the area reduction rate is set to be greater than 40%, even if the intermediate product Fi is formed through the first forging step, the intermediate product Fi before being pressed into the forming space of the second forming die used in the second forging step is upset and spreads outward, making forging impossible.

[0024] As described above, the reduction in area is preferably set to 10% to 40% from the viewpoint of forging formability, but is more preferably set to 10% to 30% from the viewpoint of reducing the forming load and increasing thickness, and is even more preferably set to 10% to 20%.

[0025] As described above, in the forging device K, the area reduction rate of the raw material M and the intermediate product Fi that have undergone the first forging process and the second forging process is set to a total of 10% to 40%. Therefore, one of the first and second area reduction rates, i.e., the forming amount for the raw material M and the intermediate product Fi, is set according to the other of the first and second area reduction rates (forming amount). In other words, when the first area reduction rate (forming amount) in the first forging process is set large, the second area reduction rate (forming amount) in the second forging process is set small, and when the first area reduction rate (forming amount) in the first forging process is set small, the second area reduction rate (forming amount) in the second forging process is set large.

[0026] 2. First Example 2-1. Configuration of the forging device 10 The configuration of a forging apparatus 10 of a first embodiment will be described with reference to Figures 6 and 7. The forging apparatus 10 includes a punch 11, a drive unit 12, a table 13, a pressure plate 14, and a forming die 20, and performs cold forging on an object to be formed. In the first embodiment, the object to be formed is a material M1 having a large-diameter disk portion M11 and a small-diameter shaft portion M12, as shown in Figure 8, and a case will be described in which cold forging is performed on the outer peripheral surface, which is the outer surface of the small-diameter shaft portion M12 of the material M1, to form a product W1.

[0027] Although not described here, the material M1 is formed into the product W1 by forming spur or helical external teeth on the large-diameter disk portion M11. In this case, the external teeth may be formed on the large-diameter disk portion M11 by cutting using a hob cutter, a frazing cutter, or the like, or by cold forging using a forging method described later.

[0028] As shown in Figures 6 and 7, the punch 11 is a member that is driven along its axial direction by a drive unit 12 to push the material M1 toward the forming die 20. In the following description, the direction in which the punch 11 pushes the material M1 toward the forming die 20 is referred to as the "forming direction." In the first embodiment, as shown in Figure 1, a case is exemplified in which the punch 11 pushes the material M1 into the forming die 20 in a forming direction that is along the vertical direction. However, the forming direction is not limited to the vertical direction and may be, for example, a horizontal direction.

[0029] 6 and 7 (FIGS. 15 and 23 described later), for ease of understanding, the punch 11 (punch 16) is shown as being virtually divided into two halves along the axis. In this case, the left side of the figure shows the punch 11 (punch 16) in a raised state, and the right side of the figure shows the punch 11 (punch 16) in a lowered state. It goes without saying that the actual punch 11 (punch 16) is not divided into left and right halves, and is raised or lowered as a unit by the drive unit 12.

[0030] The drive unit 12 drives the punch 11 in the axial direction, i.e., the forming direction. The drive unit 12 includes, as its main elements, for example, a hydraulic mechanism, an electric mechanism, or a mechanism combining a hydraulic mechanism and an electric mechanism (not shown), and transmits the driving force generated by these mechanisms to the punch 11. In the first embodiment, the drive unit 12 transmits the driving force to the punch 11 so as to raise or lower the punch 11 in the vertical direction, which is the forming direction.

[0031] The table 13 is a plate-like member that is disposed in front of the punch 11 in the forming direction, i.e., in the first embodiment, below the punch 11 in the vertical direction, and supports the drive unit 12. The table 13 also has a through hole in its center, and supports the annular (cylindrical) forming die 20, pressure plate 14, and holding plate 15 coaxially with the through hole. The table 13 also supports the forming load that occurs during cold forging, which will be described later.

[0032] The pressure plate 14 is an annular member having a through-hole on the inner side. The pressure plate 14 supports the forming die 20 arranged rearward in the forming direction. Also, as will be described later, the pressure plate 14 is arranged coaxially with the through-hole of the table 13 while being supported by the table 13, and the small-diameter shaft portion M12 of the intermediate formed product Fi and the final formed product Ff (product W1) that have been cold-forged by the forming die 20 is inserted therethrough.

[0033] 2-2. Configuration of the forming die 20 Next, the configuration of the forming die 20 will be described. The forming die 20 of the first embodiment includes a first forming die 21 and a second forming die 22.

[0034] As shown in FIG. 9, the first forming die 21 has a guide portion 211 arranged rearward (upward in the vertical direction in the first embodiment) in the forming direction, and a forming space 212 arranged forward (downward in the vertical direction in the first embodiment) in the forming direction with respect to the guide portion 211. The guide portion 211 guides the small-diameter shaft portion M12 of the material M1 that advances forward (downward in the vertical direction) in the forming direction through the forming space 212. For this reason, the guide portion 211 has a guide portion 211A along the inner peripheral surface so as to guide the small-diameter shaft portion M12 of the material M1 toward the forming space 212 without tilting. The forming space 212 has a forming portion 212A along the inner peripheral surface so as to form a temporary external tooth M13 (see FIG. 11) in a helical shape with respect to the rotation axis on the small-diameter shaft portion M12.

[0035] Here, as shown in FIG. 9, the inner diameter dimension D0 of the guide portion 211A in the guide portion 211 is set to be larger (or the same) than the outer diameter dimension Dm1 (see FIG. 8) of the small-diameter shaft portion M12 of the material M1. Also, the inner diameter dimension D1 of the forming portion 212A of the forming space 212 is set to be smaller than the outer diameter dimension Dm1 of the small-diameter shaft portion M12 of the material M1. Further, the inner diameter dimension D2 of the forming portion 212A of the forming space 212 is set to be larger than the outer dimension of the intermediate formed product Fi (the outer diameter dimension of the temporary external tooth M13 which is an intermediate shape in the first embodiment). That is, regarding the inner diameter dimensions of the first forming die 21, the relationship D1 < Dm1 ≦ D0 < D2 holds.

[0036] As a result, when the small diameter shaft portion M12 of the material M1 is pressed into the first forming die 21 by the punch 11, the guide portion 211A of the guide portion 211 first guides the small diameter shaft portion M12 toward the forming space 212. In this case, the guide portion 211A guides the small diameter shaft portion M12 toward the forming space 212 without tilting the small diameter shaft portion M12 (so-called, a good fit). Then, the forming portion 212A of the forming space 212 forges and forms the temporary external teeth M13 by drawing the small diameter shaft portion M12 that has been guided by the guide portion 211A and entered the forming space 212. Here, the outer peripheral surface of the temporary external teeth M13 does not abut against the portion of the forming space 212 with the inner diameter dimension D2.

[0037] 10, the second forming die 22 has a guide portion 221 arranged rearward in the forming direction (vertically upward in the first embodiment), and a forming space 222 arranged forward in the forming direction relative to the guide portion 221 (vertically downward in the first embodiment). The guide portion 221 has a guide portion 221A provided on its inner circumferential surface to engage with temporary external teeth M13 formed on the small-diameter shaft portion M12 of the intermediate formed product Fi moving forward in the forming direction (vertically downward), and to guide the intermediate formed product Fi into the forming space 222. The forming space 222 has a forming portion 222A along its inner circumferential surface to form external teeth M14 (see FIG. 12) that are helical teeth that are spirally shaped relative to the rotation axis of the final formed product Ff, i.e., the product W1, from the temporary external teeth M13 of the intermediate formed product Fi.

[0038] Here, in the first embodiment, as shown in FIG. 10, the inner diameter dimension D3 of the guide portion 221A in the guide portion 221 of the second forming die 22 is smaller than the inner diameter dimension D0 of the guide portion 211A in the guide portion 211 of the first forming die 21, that is, smaller than the outer diameter dimension Dm1 of the small-diameter shaft portion M12, and is set larger than the inner diameter dimension D1 of the forming portion 212A of the forming space 212. Also, in the first embodiment, as shown in FIG. 10, the inner diameter dimension D4 of the forming portion 222A of the forming space 222 of the second forming die 22 is set smaller than the inner diameter dimension D1 of the forming portion 212A of the forming space 212 of the first forming die 21. Further, the inner diameter dimension D5 of the forming space 222 is set smaller than the outer dimension of the intermediate formed product Fi (in the first embodiment, the outer diameter dimension of the provisional external teeth M13 which is an intermediate shape). That is, regarding the inner diameter dimensions of the second forming die 22, the relationship D4 < D1 < D3 < Dm1 ≦ D0 < D5 holds.

[0039] Thereby, when the provisional external teeth M13 of the intermediate formed product Fi are pushed into the second forming die 22, first, the guide portion 221A of the guide portion 221 fits with the provisional external teeth M13 and guides the provisional external teeth M13 toward the forming space 222. Then, for the provisional external teeth M13 guided and entering the forming space 222, the forming portion 222A of the forming space 222 forges and forms the external teeth M14 which are the final shape by drawing. Here, the outer peripheral surface of the provisional external teeth M13 is constrained by contacting the portion with the inner diameter dimension D5 in the forming space 222.

[0040] In addition, the difference in the axial length is set based on the difference in the cross-sectional reduction rate, that is, the difference in the bulging toward the outside. For example, the larger the cross-sectional reduction rate, the longer the axial length is set so as to hold the material M1 and the intermediate formed product Fi during cold forging. In the present embodiment, in order to exemplify the case where the cross-sectional reduction rate in the second step becomes large, the second forming die 22 is longer.

[0041] Therefore, the forming die 20 has a spacer 23 that is combined with the first forming die 21 shown in Fig. 6 and a spacer 24 that is combined with the second forming die 22 shown in Fig. 7 so that the forging device 10 can be shared in the first forging process and the second forging process. In these cases, the holding plate 15 holds the pressure plate 14, the first forming die 21, and the spacer 23 together with the table 13, or holds the pressure plate 14, the second forming die 22, and the spacer 24 together with the table 13.

[0042] 2-3.Forging method Next, a description will be given of a forging method of a first embodiment using the above-mentioned forging apparatus 10 and forming die 20. In the forging method of the first embodiment, as shown in Fig. 6, a first forging step is performed in which, with a first forming die 21 attached to the forging apparatus 10, cold forging is performed on the small diameter shaft portion M12 of the material M1 to form an intermediate formed product Fi, and as shown in Fig. 7, a second forging step is performed in which, with a second forming die 22 attached to the forging apparatus 10, cold forging is performed on the intermediate formed product Fi to form a final formed product Ff, i.e., a product W1.

[0043] First, the first forging step will be described. To perform the first forging step, a first forming die 21 and a spacer 23 are assembled in the forging device 10, as shown in Fig. 6. Then, in the first forging step, a material M1 that has not been subjected to cold forging for the small diameter shaft portion W12 is set so as to be sandwiched between the punch 11 and the first forming die 21.

[0044] In the first forging step, with the material M1 set so as to abut against the first forming die 21, the drive unit 12 transmits a driving force to the punch 11 toward the front in the forming direction (downward in the vertical direction). As a result, the punch 11 moves forward in the forming direction (downward in the vertical direction) and pushes the material M1 into the guide portion 211 of the first forming die 21. As a result, the guide portion 211A of the guide portion 211 guides the small diameter shaft portion M12 toward the forming space 212 so as not to tilt the small diameter shaft portion M12.

[0045] Then, the punch 11 of the forging device 10 presses the small diameter shaft portion M12 of the material M1 into the forming space 212 of the first forming die 21. As a result, in the process in which the small diameter shaft portion M12 moves relative to the forming portion 212A of the forming space 212, temporary external teeth M13 are formed on the outer circumferential surface of the small diameter shaft portion M12, as shown in Fig. 11. In other words, by going through the first forging process, an intermediate formed product Fi having temporary external teeth M13 on the small diameter shaft portion W12 is formed.

[0046] Once the intermediate product Fi has been formed, it is removed from the first forming die 21. In this case, because the temporary external teeth M13 are formed on the small diameter shaft portion M12, for example, the intermediate product Fi is rotated about its axis to move the intermediate product Fi backward in the forming direction (upward in the vertical direction) and then removed from the first forming die 21. Although not shown, when rotating the intermediate product Fi, for example, the punch 11 can be rotated to rotate the intermediate product Fi together with the punch 11, or the first forming die 21 can be rotated to rotate the first forming die 21 relative to the intermediate product Fi.

[0047] Here, the inner diameter dimension D1 of the forming portion 212A of the forming space 212 in the first forming die 21 is set so that the first area reduction rate of the processing target portion MA of the small diameter shaft portion M12 is within the range of 10% to 40%, as described above. Specifically, in the first embodiment, as described above, the inner diameter dimension D1 of the forming portion 212A in the first forming die 21 is set larger than the inner diameter dimension D2 of the forming portion 222A in the second forming die 22. In other words, in the first embodiment, the first area reduction rate in the first forging process is set smaller than the second area reduction rate in the second forging process.

[0048] Therefore, in the first embodiment, when cold forging is performed on the small diameter shaft portion M12 of the unprocessed material M1 in the first forging process, the first area reduction rate is set relatively small compared to the second forging process, thereby making it possible to relatively reduce the driving force transmitted by the drive unit 12 to the punch 11, in other words, the forming load relative to the stroke of the punch 11. This makes it possible to reduce the reaction force, i.e., the load, that the first forming die 21 receives due to the forming load associated with cold forging, and makes it possible to extend the die life of the first forming die 21.

[0049] Next, the second forging step will be described. To perform the second forging step, a second forming die 22 and a spacer 24 are assembled in the forging device 10, instead of the first forming die 21 and the spacer 23, as shown in Fig. 7. Then, in the second forging step, the intermediate formed product Fi, in which the temporary external teeth M13 have been formed on the small diameter shaft portion W12 in the first forging step, is set so as to be sandwiched between the punch 11 and the second forming die 22.

[0050] In the second forging step, with the intermediate product Fi set so as to abut against the second forming die 22, the drive unit 12 transmits a driving force to the punch 11 forward in the forming direction (downward in the vertical direction). As a result, the punch 11 moves forward in the forming direction (downward in the vertical direction) and pushes the intermediate product Fi into the guide portion 221 of the second forming die 22. As a result, the guide portion 221A of the guide portion 221 engages with the temporary outer teeth M13 of the intermediate product Fi and guides the temporary outer teeth M13 toward the forming space 212.

[0051] Then, the punch 11 of the forging device 10 presses the temporary outer teeth M13 of the intermediate formed product Fi into the forming space 222 of the second forming die 22. As a result, during the process in which the temporary outer teeth M13 move relative to the forming portion 222A of the forming space 222, the temporary outer teeth M13 are drawn to form the external teeth M14 as shown in FIG. 12. In other words, through the second forging process, a final formed product Ff having the external teeth M14, which is the final shape, i.e., the product W1, is formed. Then, once the final formed product Ff has been formed, it is removed from the second forming die 22, similar to the first forging process described above.

[0052] Here, the inner diameter dimension D4 of the forming portion 222A of the forming space 222 in the second forming die 22 is set so that the second area reduction rate of the processing target portion MB of the provisional external tooth M13 is within the range of 10% to 40%, as described above. Specifically, in the first embodiment, as described above, the inner diameter dimension D4 of the forming portion 222A in the second forming die 22 is set smaller than the inner diameter D1 of the forming portion 212A in the first forming die 21. That is, in the first embodiment, the second area reduction rate in the second forging process is set larger than the first area reduction rate in the first forging process, and the provisional external tooth M13 of the intermediate formed product Fi is drawn to form the external tooth M14, which is the final shape.

[0053] Therefore, in the first embodiment, the temporary outer teeth M13 formed in the first forging process are subjected to drawing as cold forging, so the driving force transmitted by the drive unit 12 to the punch 11, in other words, the forming load relative to the stroke of the punch 11, can be made relatively smaller than when the outer teeth M14 are formed from the material M1 in one forging process. This makes it possible to reduce the reaction force, i.e., the load, that the second forming die 22 receives due to the forming load associated with cold forging, and it becomes possible to extend the life of the second forming die 22.

[0054] 2-4. Modification of the first embodiment As described above, the second forming die 22 constituting the forming die 20 has the guide portion 221A of the guide part 221 set to an inner diameter dimension D3 smaller than the outer diameter dimension Dm1 of the small diameter shank portion M12, on the rear side in the forming direction with respect to the forming space 222. Therefore, when the external teeth M14 are formed in the second forging forming process described above, as shown in Fig. 12, the guide portion 221A forms a guide groove M15 shallower than the provisional external teeth M13 in the small diameter shank portion M12 at the end of the small diameter shank portion M12 on the large diameter disk portion M11 side of the material M1.

[0055] Therefore, when the first forging process using the first forming die 21 of the first embodiment and the second forging process using the second forming die 22 are performed, the guide groove M15 remains at the end of the forming range R of the external teeth M14 on the large-diameter disk portion M11 side of the final formed product Ff (product W1), as shown in Fig. 12. In other words, if the guide groove M15 is included in the forming range R as it is, the axial length of the forming range R will be longer by the portion M16 of the guide groove M15 that is not functionally used (hereinafter, this portion will be referred to as the "unused portion M16"), and ultimately the axial length of the product W1 will be longer.

[0056] Therefore, in a modification of the first embodiment, in order to reduce the unused portion M16 included in the forming range R, a forming portion 223 having an inner diameter D1 is provided in at least a part of the guide portion 221A of the guide unit 221 in the second forming die 22, as shown in Fig. 13. This allows the forming portion 223 to substantially shorten the length along the forming direction of the portion of the guide portion 221A that is set to the inner diameter dimension D3. Then, the forming portion 223 can form the provisional external tooth M13 along the guide groove M15 that forms the unused portion W16, similar to the forming portion 212A of the forming space 212 in the first forming die 21.

[0057] As a result, in the second forging process, for example, by relatively moving the second forming die 22 closer to the large-diameter disk portion M11 of the intermediate formed product Fi than in the first embodiment described above, the forming portion 223 can form the temporary external teeth M13 along the guide groove M15 of the unused portion M16, as shown in FIG. 14. Then, the forming portion 222A of the forming space 222 draws the temporary external teeth M13 newly formed in the unused portion M16 to form the external teeth M14. As shown in FIG. 14, compared to the first embodiment shown in FIG. 12, the effective forming portion M17 of the forming range R, which effectively functions as the external teeth M14, can be expanded toward the large-diameter disk portion M11. This allows the axial dimension of the product W1 to be shortened, thereby achieving a more compact product W1.

[0058] 3. Second Example In the first embodiment described above, a material M1 having a large-diameter disk portion M11 and a small-diameter shaft portion M12 was exemplified. In contrast, in the second embodiment, an annular material M2 having a through-hole M21 as shown in Fig. 16 is exemplified as an object to be cold forged by the forging device 10 shown in Fig. 15, and a pinion gear is formed as a product W2 by cold forging the outer circumferential surface of a side portion M22 of the material M2. Note that, as shown in Fig. 16, the material M2 has chamfered portions M23 formed in advance at both axial ends.

[0059] 3-1. Configuration of the forging device 10 15, in the forging apparatus 10 of the second embodiment, a punch 16 having a mandrel 15 that is inserted into the through hole M21 of the material M2 during cold forging is provided instead of the punch 11 of the forging apparatus 10 described in the first embodiment. As a result, in the second embodiment, since the material W2 is hollow, more specifically, annular, the first forging process and the second forging process are performed with the mandrel 15 inserted into the through hole M21 during cold forging.

[0060] Here, the mandrel 15 may be attached to the punch 16 when cold forging the annular material M2, or may be provided integrally with the punch 16 exclusively for cold forging the annular material M2. When versatility is taken into consideration, it is preferable to adopt a system in which a separate mandrel 15 is attached to the punch 16.

[0061] The forging apparatus 10 of the second embodiment differs from the forging apparatus 10 of the first embodiment described above only in the mandrel 15 and punch 16. That is, like the forging apparatus 10 of the first embodiment, the forging apparatus 10 of the second embodiment also includes a drive unit 12, a table 13, a pressure plate 14, and a holding plate 15. Therefore, a description of the drive unit 12, the table 13, the pressure plate 14, and the holding plate 15 will be omitted.

[0062] 3-2. Configuration of the forming die 20 Next, the configuration of the forming die 20 of the second embodiment will be described. The forming die 20 of the second embodiment is configured to include a first forming die 25 and a second forming die .

[0063] 17, the first forming die 25 has a guide portion 251 disposed rearward in the forming direction (vertically upward in the second embodiment), and a forming space 252 disposed forward in the forming direction relative to the guide portion 251 (vertically downward in the second embodiment). The guide portion 251 has a holding portion 251A on its inner peripheral surface along the axial direction so as to stably insert and guide the material M2 advancing forward in the forming direction (vertically downward) into the forming space 252. The forming space 252 has a forming portion 252A on its inner peripheral surface along the axial direction so as to form temporary external teeth M23 (see FIG. 19) parallel to the rotation axis on the side portion M22 of the material M2.

[0064] Here, as shown in FIG. 17, the inner diameter dimension D6 of the holding portion 251A in the guide portion 251 is set to be slightly larger than the outer diameter dimension Dm2 of the material M2 (see FIG. 16). Also, as shown in FIG. 17, the inner diameter dimension D6 of the holding portion 251A of the guide portion 251 is set to be larger than the inner diameter dimension D7 of the forming portion 252A of the forming space 252. That is, regarding the inner diameter dimension of the first forming die 25, the relationship D7 < Dm2 ≤ D6 holds.

[0065] Thereby, when the material M2 is pushed into the first forming die 25, first, the holding portion 251A of the guide portion 251 holds the material M2 without rattling. Then, with respect to the material M2 held by the holding portion 251A and entering the forming space 252, the forming portion 252A of the forming space 252 forms the provisional external teeth M23. Incidentally, similar to the guide portion 221A of the first embodiment described above, the holding portion 251A can also form guide grooves on the side portion M22 of the material M2. Also, the outer peripheral surface of the provisional external teeth M23 does not contact the inner peripheral surface of the forming space 252.

[0066] As shown in FIG. 18, the second forming die 26 has a guide portion 261 disposed rearward (upward in the vertical direction in the second embodiment) in the forming direction and a forming space 262 disposed forward (downward in the vertical direction in the second embodiment) with respect to the guide portion 261 in the forming direction. The guide portion 261 is provided along the axial direction on the inner peripheral surface so as to fit into the provisional external teeth M23 formed on the side portion M22 of the intermediate formed product Fi advancing forward (downward in the vertical direction) in the forming direction, and has a guide portion 261A for guiding to the forming space 262. The forming space 262 has a forming portion 262A provided along the axial direction on the inner peripheral surface so as to form flat teeth M24 (see FIG. 20) parallel to the rotation axis of the final formed product Ff, that is, the product W2, by performing a drawing process on the provisional external teeth M23 of the intermediate formed product Fi.

[0067] Here, in the second embodiment, as shown in FIG. 18, the inner diameter dimension D8 of the guide portion 261A of the guide portion 261 of the second forming die 26 is set smaller than the inner diameter dimension D6 (see FIG. 17) of the holding portion 251A of the guide portion 251 of the first forming die 25. Also, in the second embodiment, as shown in FIG. 18, the inner diameter dimension D9 of the forming portion 262A of the forming space 262 of the second forming die 26 is set smaller than the inner diameter dimension D7 of the forming portion 252A of the forming space 252 of the first forming die 25. That is, regarding the inner diameter dimensions of the second forming die 26, the relationship D9 < D7 < D8 < Dm2 ≤ D6 holds.

[0068] Thereby, when the provisional external teeth M23 of the intermediate formed article Fi are pushed into the second forming die 26, first, the guide portion 261A of the guide portion 261 engages with the provisional external teeth M23 and guides the provisional external teeth M23 toward the forming space 262. Then, the forming portion 262A of the forming space 262 performs a squeezing process on the provisional external teeth M23 that are guided and enter the forming space 262, forming the flat teeth M24 that are the final shape. Here, the outer peripheral surface of the provisional external teeth M23 is constrained by contacting the inner peripheral surface of the forming space 262.

[0069] In addition, in the forging and forming apparatus 10 of the second embodiment, as shown in FIG. 15, the first forming die 25 and the second forming die 26 are arranged in series along the forming direction (vertical direction). That is, in the forging and forming apparatus 10 of the second embodiment, the material M2 is pushed into the first forming die 25 by the punch 16, and subsequently, is pushed into the second forming die 26 by the punch 16. Thereby, the provisional external teeth M23 and the flat teeth M24 are continuously formed on the material M2.

[0070] Here, assuming a situation in which the front end of the intermediate formed product Fi during cold forging enters the second forming die 26 and the rear end thereof passes through the first forming die 25, both the forming load of the provisional outer teeth M23 formed by the first forming die 25 and the forming load of the spur teeth M24 formed by the second forming die 26 act on the punch 16. Also, in the second embodiment, since the inner diameter D9 of the second forming die 26 is smaller than the inner diameter D7 of the first forming die 25, material flow occurs rearward in the forming direction, which may cause the intermediate formed product Fi to be upset into the first forming die 25. In this case, the forming load increases, which may affect the life of the first forming die 25 and other dies.

[0071] For this reason, in the forging apparatus 10 of the second embodiment, a spacer 27 constituting the forming die 20 is provided so that the first forming die 25 and the second forming die 26 are spaced apart from each other in the forming direction. Specifically, the spacer 27 separates the first forming die 25 and the second forming die 26 by a distance greater than the axial dimension of the intermediate formed product Fi (material M2), i.e., the thickness dimension of the intermediate formed product Fi (material M2). As a result, the spacer 27 can prevent a situation from occurring in which the front of the intermediate formed product Fi during forging enters the second forming die 26 and the rear of the intermediate formed product Fi in the forming direction passes through the first forming die 25, thereby suppressing an increase in the forming load.

[0072] 3-3.Forging method Next, a forging method of a second embodiment using the forging apparatus 10 and the forming die 20 described above will be described. In the forging method of the second embodiment, as shown in Fig. 15, a first forming die 25 is disposed rearward in the forming direction (vertically upward) of the forging apparatus 10, and a second forming die 26 is disposed forward of the first forming die 25 in the forming direction via a spacer 27. In other words, the first forming die 25 and the second forming die 26 are attached so as to be in series along the forming direction. The forging method of the second embodiment uses the forging apparatus 10 to successively perform a first forging step in which the side portion M22 of the material M2 is cold forged to form an intermediate formed product Fi, and a second forging step in which the intermediate formed product Fi is cold forged to form a final formed product Ff, i.e., a product W2.

[0073] 15, in the forging device 10 of the second embodiment, the first forming die 25, the spacer 27, and the second forming die 26 are assembled in this order from rear to front in the forming direction (from top to bottom in the vertical direction). Then, the material M2 whose side portion M22 has not been cold forged is set so as to be sandwiched between the punch 16 and the first forming die 25 with the mandrel 15 inserted into the through hole M21.

[0074] In the first forging step of the second embodiment, the drive unit 12 transmits a driving force to the punch 16 toward the front in the forming direction (downward in the vertical direction) with the material M2 set so as to abut against the holding portion 251A of the guide portion 251 of the first forming die 25. As a result, the punch 16 moves forward in the forming direction (downward in the vertical direction) together with the mandrel 15, and pushes the material M2 guided by the holding portion 251A toward the forming space 252.

[0075] 19 is formed on the side portion M22 of the material M2 pressed into the forming space 252 while the material M2 moves relative to the forming portion 252A of the forming space 252. That is, in the second embodiment as well, an intermediate formed product Fi having the temporary external teeth M23 on the side portion M22 is formed by undergoing the first forging step.

[0076] The intermediate formed product Fi is further advanced in the forming direction (downward in the vertical direction) by the punch 16 and is ejected from the forming space 252 of the first forming die 25. This completes the first forging step in the second embodiment. Then, after the first forging step has been completed, the intermediate formed product Fi is further advanced in the forming direction (downward in the vertical direction) by the punch 16, passes through the spacer 27, and reaches the second forming die 26.

[0077] As described above, in the second embodiment, the inner diameter dimension D7 of the forming portion 252A of the forming space 252 in the first forming die 25 is set so that the area reduction rate of the processing target portion MA of the side portion M22 of the material M2 is within the range of 10% to 40%, and is set larger than the inner diameter dimension D9 of the forming portion 262A in the second forming die 26. In other words, also in the second embodiment, the first area reduction rate in the first forging process is set smaller than the second area reduction rate in the second forging process.

[0078] Furthermore, when the intermediate product Fi discharged from the forming space 252 passes through the spacer 27, a state occurs in which the intermediate product Fi is not subjected to any forging. In other words, by providing the spacer 27, the first forging process and the second forging process, which are executed consecutively, can be separated. This makes it possible to prevent the forming load associated with cold forging in the first forging process from increasing. Therefore, also in the second embodiment, when cold forging is performed on the side portion M22 of the unprocessed material M2 in the first forging process, the first area reduction rate is set relatively small compared to the second forging process. This reduces the reaction force, i.e., load, that the first forming die 25 receives from the forming load associated with cold forging, and thereby makes it possible to extend the die life of the first forming die 25.

[0079] The intermediate product Fi that has passed through the spacer 27 reaches the second forming die 26. As a result, in the second embodiment, a second forging process is performed. In the second forging process, the punch 16 of the forging device 10 advances in the forming direction (descends vertically) and pushes the intermediate product Fi into the guide portion 261 of the second forming die 26. As a result, the guide portion 261A of the guide portion 261 engages with the temporary outer teeth M23 of the intermediate product Fi and guides the temporary outer teeth M23 toward the forming space 262.

[0080] The punch 16 then presses the temporary outer teeth M23 of the intermediate formed product Fi into the forming space 262 of the second forming die 26. As a result, while the temporary outer teeth M23 move relative to the forming portion 262A of the forming space 262, the temporary outer teeth M23 are drawn, thereby forming spur teeth M24 as shown in FIG. 20 . That is, in the second embodiment as well, the second forging step is performed to form a final formed product Ff, i.e., a product W2, having the spur teeth M24, which is the final shape. The punch 16 then further advances in the forming direction (descends vertically), and the final formed product Ff is ejected from the forming space 262 of the second forming die 26. This completes the second forging step in the second embodiment.

[0081] Here, the inner diameter dimension D9 of the forming portion 262A of the forming space 262 in the second forming die 26 is set so that the area reduction rate of the processing target portion MB of the provisional outer tooth M23 is within the range of 10% to 40%, as described above. Also in the second embodiment, as described above, the second area reduction rate in the second forging process is set to be larger than the first area reduction rate in the first forging process, and the provisional outer tooth M23 of the intermediate formed product Fi is drawn to form the spur tooth M24, which is the final shape.

[0082] Therefore, in the second embodiment as well, the temporary outer teeth M23 formed in the first forging step are subjected to drawing as cold forging, so the forming load can be reduced compared to when the spur teeth M24 are formed from the material M2 in one forging step. As a result, in the second embodiment as well, the reaction force, i.e., the load, that the second forming die 26 receives from the forming load associated with cold forging can be reduced, and the life of the second forming die 26 can be extended.

[0083] Furthermore, by forming the provisional outer teeth M23 in the first forging process and then performing the final drawing process in the subsequent second forging process, the material flow can be made gentler than when the spur teeth M24 are formed from the raw material M2 in a single forging process. This makes it possible to suppress the occurrence of burrs and sagging on both axial end faces of the product W2, such as a pinion gear. Therefore, it is possible to omit at least some of the additional processing (such as cutting and grinding) on ​​the product W2 after cold forging, thereby reducing the manufacturing cost of the product W2.

[0084] 3-4. Modification of the second embodiment As described above, the second embodiment illustrates a case in which the provisional external teeth M23 are formed on the side portion M22 of the annular material M2 having the through hole M21, and then the spur teeth M24, which represent the final shape, are formed. Alternatively, as shown in FIG. 21 , a shaft-shaped material M3 having a shaft portion M31 and a large-diameter portion M32 can be used as the workpiece. In this case, as shown in FIG. 22 , using the forging device 10, an intermediate formed product Fi having provisional external teeth M33, indicated by a dashed line parallel to the rotation axis, can be formed on the outer circumferential surface of the large-diameter portion M32, as in the second embodiment. Then, the provisional external teeth M33 of the intermediate formed product Fi can be drawn to form a final formed product Ff, i.e., a product W3, having the spur teeth M34, which represent the final shape.

[0085] Specifically, in the forging device 10, as shown in Fig. 23, the punch 16, from which the mandrel 15 described in the second embodiment has been removed, pushes one end of the shaft-shaped material M3 forward in the forming direction, i.e., toward the first forming die 25. Note that, in the forging device 10 of the modified example, similarly to the second embodiment described above, the forming die 20, i.e., the first forming die 25, the spacer 27, and the second forming die 26 are attached. Note that the spacer 27 is arranged so that the first forming die 25 and the second forming die 26 are spaced apart by at least the length along the axial direction of the large diameter portion M32 of the material M3.

[0086] As a result, similar to the second embodiment described above, the forming portion 252A of the forming space 252 in the first forming die 25 forms the temporary external teeth M33 on the outer peripheral surface of the large-diameter portion M32 of the material M3 in the first forging process. Then, similar to the second embodiment described above, after the intermediate formed product Fi having the temporary external teeth M33 on the large-diameter portion M31 passes through the spacer 27, the forming portion 262A of the forming space 262 in the second forming die 26 forms the final formed product Ff, i.e., the product W3, having the spur teeth M34. That is, similar to the second embodiment described above, in the modified example, the temporary external teeth M33 can be formed on the outer peripheral surface of the large-diameter portion M31 of the material M3 in the first forging process, and the spur teeth M34 can be formed by drawing the temporary external teeth M33 in the second forging process. Therefore, similar effects to those of the second embodiment can be achieved in the modified example.

[0087] 4. Other Modifications In the second embodiment described above, the case where spur teeth M24 parallel to the rotation axis are formed on the side portion M22 of the material M2 is illustrated. However, as in the first embodiment described above, it is also possible to form spirally shaped helical teeth relative to the rotation axis on the side portion M22 of the material M2. In this case, the forging device 10 may include, for example, the first forming die 21 and the second forming die 22 arranged in series via a spacer 27. In this case, the second forming die 22 is provided to be freely rotatable in the forming direction so that the circumferential phase of the temporary external teeth formed by the first forming die 21 coincides with the circumferential phase of the guide portion 221A of the guide portion 221 of the second forming die 22. As a result, the second forming die 22 rotates in accordance with the phase of the intermediate formed product Fi having the temporary external teeth that has reached the guide portion 221, thereby allowing the temporary external teeth to fit into the guide portion 221A and guiding the temporary external teeth into the forming space 222. Therefore, in this case, helical teeth can be formed by cold forging on the side portion M22 of the material M2.

[0088] Here, the forging forming device of the first form of the present invention comprises a forming die that performs forging on a material, and a punch that pushes the material toward the forming die that is arranged forward in the forming direction, and the forming die forms the outer surface of the material, for a material having an outer dimension smaller than the outer dimension after forging, by diverting the material flow that occurs in the material due to forging along a direction perpendicular to the forming direction, and includes a first forming die that forms an intermediate formed product having an intermediate shape from the material, and a second forming die that forms a final formed product having a final shape with an outer dimension smaller than the outer dimension of the intermediate shape from the intermediate formed product.

[0089] In addition, a second form of the forging device of the present invention is the forging device of the first form described above, in which the first forming die forms an intermediate shape for the material so that a first area reduction rate, which represents the ratio of the cross-sectional area of ​​the intermediate formed product to the cross-sectional area of ​​the material along a direction perpendicular to the forming direction in the forming target portion where the intermediate shape is formed for the material, is 10% to 40%, and the second forming die forms a final shape for the intermediate formed product so that a second area reduction rate, which represents the ratio of the cross-sectional area of ​​the final formed product to the cross-sectional area of ​​the intermediate formed product along a direction perpendicular to the forming direction in the forming target portion where the final shape is formed for the intermediate formed product, is 10% to 40%.

[0090] A forging apparatus according to a third aspect of the present invention is the forging apparatus according to the second aspect, wherein the first area reduction rate is set smaller than the second area reduction rate.

[0091] Furthermore, a fourth form of the forging device of the present invention is a forging device according to any one of the first to third forms, in which a first forming die forms an intermediate shape in a material so that the intermediate shape has an outer dimension larger than that of a final formed product, and a second forming die performs drawing on the intermediate shape of the intermediate formed product to form the final shape.

[0092] A forging apparatus according to a fifth aspect of the present invention is the forging apparatus according to any one of the first to fourth aspects, in which the first and second forming dies are arranged in series along the forming direction.

[0093] A forging apparatus according to a sixth aspect of the present invention is the forging apparatus according to the fifth aspect, wherein a first forming die is disposed rearward in the forming direction and a second forming die is disposed forward in the forming direction.

[0094] Furthermore, a seventh aspect of the forging apparatus of the present invention is the forging apparatus of the fifth or sixth aspect, in which the first and second forming dies are arranged so as to be separated by a distance greater than the size of the intermediate formed product in the forming direction.

[0095] Furthermore, the eighth form of the forging device of the present invention is a forging device of any one of the first to seventh forms, wherein the first forming die has a guide portion that guides the material to be pressed in by the punch and a forming space in which forging is performed on the material guided by the guide portion, and the second forming die has a guide portion that guides the intermediate formed piece to be pressed in by the punch and a forming space in which forging is performed on the intermediate formed piece guided by the guide portion.

[0096] Furthermore, a ninth form of the forging forming apparatus of the present invention is the forging forming apparatus of the eighth form, wherein at least a portion of the internal dimensions of the guide portion of the second forming die have internal dimensions set to the forming space of the first forming die.

[0097] Furthermore, a tenth form of the forging device of the present invention is a forging device of any one of the first to ninth forms, in which the intermediate shape of the intermediate formed product and the final shape of the final formed product are gear shapes, and the intermediate shape is larger than the final shape in terms of circumferential tooth width of the gear shape, and the intermediate shape is larger than the final shape in terms of radial tooth height of the gear shape.

[0098] Furthermore, the forging method of the present invention is a forging method for forging a raw material using a forging device of any one of the first to tenth forms, and includes a first forging process for forging the raw material using a first forming die to form an intermediate product from the raw material, and a second forging process for forging the intermediate product using a second forming die to form a final product from the intermediate product. [Explanation of symbols]

[0099] 10...Forging device, 11...Punch, 12...Driver, 13...Table, 14...Pressure plate, 15...Mandrel, 16...Punch, 20...Forming die, 21...First forming die, 211...Guide portion, 211A...Guide portion, 212...Forming space, 212A...Forming portion, 22...Second forming die, 221...Guide portion, 221A...Guide portion, 222...Forming space, 222A...Forming portion, 23...Spacer, 24...Spacer, 25...First forming die A, 251...guide portion, 251A...holding portion, 252...molding space, 252A...molding portion, 26...second molding die, 261...guide portion, 261A...guiding portion, 262...molding space, 262A...molding portion, 27...spacer, M, M1, M2, M3...material, Fi...intermediate molded product, Ff...final molded product, W1, W2, W3...product, P...punch, S...molding die, S1...first molding die, S2...second molding die, MA, MB...molded part

Claims

1. a forming die for forging the material; a punch that pushes the material toward the forming die that is disposed forward in the forming direction, The forming die For the material having an outer dimension smaller than the outer dimension after the forging, the outer surface of the material is shaped by a diversion of material flow occurring in the material during the forging along a direction perpendicular to the forming direction, a first forming die for forming an intermediate product having an intermediate shape from the material; a second forming die for forming a final shape from the intermediate shape, the final shape having an outer dimension smaller than the outer dimension of the intermediate shape.

2. The first forming die forming the intermediate shape on the raw material so that a first cross-sectional area reduction rate, which represents a ratio of a cross-sectional area of ​​the intermediate molded product to a cross-sectional area of ​​the raw material along a direction perpendicular to the molding direction, is 10% to 40% in a molding target portion where the intermediate shape is formed on the raw material; The second forming die 2. The forging device according to claim 1, wherein the final shape is formed on the intermediate formed product so that a second area reduction ratio, which represents a ratio of a cross-sectional area of ​​the final formed product to a cross-sectional area of ​​the intermediate formed product along a direction perpendicular to the forming direction, is 10% to 40% in a forming target portion where the final shape is formed on the intermediate formed product.

3. The first cross-sectional reduction rate is The forging device according to claim 2 , wherein the reduction in area is set to be smaller than the second reduction in area.

4. The first forming die forming the intermediate shape in the blank so that the intermediate shape has an outer dimension larger than an outer dimension of the final molded product; The second forming die The forging device according to claim 1 , wherein the final shape is formed by drawing the intermediate shape of the intermediate formed product.

5. The first forming die and the second forming die, The forging device according to claim 1 , wherein the forging devices are arranged in series along the forming direction.

6. The first forming die is disposed rearward in the forming direction, The forging device according to claim 5 , wherein the second forming die is disposed forward in the forming direction.

7. The first forming die and the second forming die, The forging device according to claim 5 , wherein the intermediate forged products are disposed so as to be spaced apart from each other at a distance greater than the size of the intermediate forged product in the forming direction.

8. The first forming die a guide portion that guides the material pushed in by the punch; a forming space in which the forging is performed on the material guided by the guide portion, The second forming die a guide portion that guides the intermediate formed product that is pressed by the punch; The forging device according to claim 1 , further comprising: a forming space in which the forging is performed on the intermediate product guided by the guide portion.

9. At least a part of the inner dimensions of the guide portion of the second forming die is The forging device according to claim 8 , wherein the forming space of the first forming die has a set internal dimension.

10. The intermediate shape of the intermediate molded product and the final shape of the final molded product are It is gear-shaped, the intermediate shape has a larger circumferential face width than the final shape; The forging apparatus according to claim 1 , wherein the intermediate shape has a larger radial tooth height than the final shape.

11. A forging method for forging the material using the forging device according to any one of claims 1 to 10, a first forging step of forging the material using the first forming die to form the intermediate product from the material; a second forging step of forging the intermediate product using the second forming die to form the final product from the intermediate product.

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