Forging apparatus and gear manufacturing method

Abstract

The present invention provides a forging apparatus that can at least reduce the overall number of man-hours, and more preferably, allow for fine adjustment of the molded shape without replacing the apparatus. [Solution] The present invention comprises a punch 2 that presses a workpiece downward by moving downward, a counter punch 3 positioned below the punch 2 on which a workpiece W is placed, an annular molding die 5 with a molding groove 5a formed on its inner circumferential surface, and a collar member 74 positioned around the counter punch 3 or a moving member 721 which is an interlocking member that moves downward in conjunction with the downward movement of the counter punch 3, and which generates a frictional force against the downward movement of the moving member 721, wherein the frictional force of the moving member 721 and the collar member 74 is configured to change depending on the position of the moving member 721.

Description

Technical Field

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[0001] The present invention relates to a forging device and a method for manufacturing gears.

Background Art

[0002] The technology of forging devices is described in, for example, Japanese Patent Application Laid-Open No. 2017-209699. This publication discloses a forging device that cold-forges an intermediate cylindrical gear with a formed tooth profile to form a gear with crowning.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above forging device, after forming the intermediate cylindrical gear once, it is necessary to separately perform crowning forming, so the total man-hours increase. In addition, since the structure of the mold is complex, it is difficult to finely adjust the crowning forming. For example, when the frictional resistance of the forming die changes over time, the shape of the crowning may change.

[0005] An object of the present invention is to provide a forging device capable of shortening the total man-hours, and more preferably, a forging device capable of finely adjusting the forming shape without replacing the device. Another object of the present invention is to provide a method for manufacturing a gear capable of forming a tooth profile with good draft on a workpiece in the manufacture of a gear using the forging device.

Means for Solving the Problems

[0006] A forging apparatus according to a first embodiment of the present invention comprises: a punch that moves downward to press a workpiece downward; a counter punch positioned below the punch on which the workpiece is placed; a reaction force applying device that applies a reaction force to the downward movement of the counter punch due to the pressing of the punch; an annular forming die having a forming groove formed on its inner circumferential surface; an annular ring member positioned on the outer circumferential side of the forming die and configured to change the pressing force that presses the forming die according to its state; a drive unit that changes the state of the ring member; a detection unit that detects the vertical position information of the punch; and a control unit that controls the drive unit based on the detection result of the detection unit.

[0007] A forging apparatus according to a second embodiment of the present invention comprises a punch that moves downward to press a workpiece downward; a counter punch positioned below the punch on which the workpiece is placed; a reaction force applying device that applies a reaction force to the downward movement of the counter punch due to the pressing of the punch; an annular forming die with forming grooves formed on its inner circumferential surface; a detection unit that detects vertical position information of the punch; and a control unit that controls the reaction force applied by the reaction force applying device based on the detection result of the detection unit.

[0008] A forging apparatus according to a third embodiment of the present invention comprises a punch that presses a workpiece downward by moving downward, a counter punch positioned below the punch on which the workpiece is placed, an annular forming die with forming grooves formed on its inner circumferential surface, and a collar member positioned around the counter punch or a moving member which is an interlocking member that moves downward in conjunction with the downward movement of the counter punch, and which generates a frictional force against the downward movement of the moving member, wherein the moving member and the collar member are configured such that the frictional force changes depending on the position of the moving member.

[0009] A gear manufacturing method according to a fourth embodiment of the present invention is a gear manufacturing method using a forging apparatus comprising: a punch that moves downward to press a workpiece downward; a counter punch positioned below the punch on which the workpiece is placed; a reaction force applying device configured to apply a reaction force to the downward movement of the counter punch due to the pressing of the punch and to output fluid pressure as the reaction force; and an annular forming die having tooth-shaped forming grooves formed on its inner circumferential surface, wherein the method includes a drawing step in which the workpiece, whose outer diameter is larger than the minimum inner diameter of the forming die, is pressed into the forming die, and in the drawing step, with the reaction force applied to the counter punch by the reaction force applying device, the punch presses the workpiece into the forming die and compresses and deforms the workpiece.

[0010] A forging apparatus according to a fifth embodiment of the present invention comprises a punch that moves downward to press a workpiece downward; a counter punch positioned below the punch on which the workpiece is placed; a reaction force applying device that applies a reaction force to the downward movement of the counter punch due to the pressing of the punch; an annular forming die with forming grooves formed on its inner circumferential surface; and a pressing force adjusting means that adjusts the pressing force applied to the outer circumferential surface of the forming die to change the inner diameter of the forming die. [Effects of the Invention]

[0011] According to the first embodiment of the present invention, the ring member presses the molding die with a pressing force appropriate to the state, thereby elastically deforming the molding die and changing its inner diameter. The greater the pressing force of the ring member, the more the molding die is tightened radially inward, and the smaller its inner diameter becomes. In other words, it becomes possible to change the radial dimensions of the tooth profile during molding. As the diameter of the molding die decreases, the shape of the molding groove (groove width, etc.) also decreases proportionally. As a result, for example, when molding a crowned gear, the control unit changes the pressing force according to the position of the punch to change the inner diameter of the molding die, making it possible to mold a crowned gear with a single punch (without molding an intermediate cylindrical gear). Furthermore, with this configuration, the molding shape can be finely adjusted by adjusting the reaction force and / or pressing force, so there is no need to replace the device even if changes in frictional resistance occur.

[0012] According to a second embodiment of the present invention, the degree of deformation of the workpiece can be changed by changing the reaction force according to the position of the punch. In other words, the larger the reaction force, the greater the vertical clamping force on the workpiece and the greater the amount of radial outward bulging of the workpiece. As a result, for example, when forming a crowned gear, the control unit can change the reaction force according to the position of the punch, making it possible to form a crowned gear with a single punch (without forming an intermediate cylindrical gear). Furthermore, with this configuration, the formed shape can be finely adjusted by adjusting the reaction force, so there is no need to replace the device even if changes in frictional resistance occur. Thus, according to the first and second embodiments of the present invention, the overall man-hours can be reduced, and fine adjustments to the molded shape can be made without changing the equipment.

[0013] According to the third embodiment of the present invention, the reaction force during punching can be changed by changing the frictional force between the moving member (counterpunch or interlocking member) and the collar member according to the position of the moving member. This makes it possible to change the degree of deformation of the workpiece, as in the second embodiment. In other words, the larger the reaction force (frictional force), the greater the amount of radial outward bulging of the workpiece. This makes it possible, for example, to form a crowned gear with a single punch (without forming an intermediate cylindrical gear) without special control.

[0014] Furthermore, according to the fourth embodiment of the present invention, drawing (compression) is performed on the workpiece while a reaction force (intrusion resistance) due to fluid pressure is applied to it. This assists the flow of the workpiece (material) to the tooth tip during tooth profile formation. In other words, the pressing force that the workpiece (material) exerts on the bottom surface of the forming groove becomes larger during forming. This results in the formation of a tooth profile with good wall thickness.

[0015] According to the fifth embodiment of the present invention, similar to the first embodiment, the pressing force can be adjusted by the pressing force adjustment means, thereby changing the inner diameter of the molding die during molding. This provides the same effects as the first embodiment. [Brief explanation of the drawing]

[0016] [Figure 1] This is a diagram showing the configuration of a forging apparatus according to the first embodiment. [Figure 2] This is a conceptual diagram (viewed in the groove extension direction) showing the shape of the molded groove in the first embodiment. [Figure 3] This is a conceptual diagram (a cross-sectional explanatory diagram viewed from the side) showing the configuration of the molding groove in the first embodiment. [Figure 4] This is a conceptual diagram illustrating the position and pressing force of the ring member in the first embodiment. [Figure 5] This is a conceptual diagram of the crowning of the first embodiment. [Figure 6] This figure shows the workpiece after molding is complete according to the first embodiment. [Figure 7] This is a diagram showing the configuration of a forging apparatus according to the second embodiment. [Figure 8] It is a configuration diagram of the forging device according to the third embodiment. [Figure 9] It is a conceptual diagram (cross-sectional view) for explaining the first knockout pin and the collar member according to the third embodiment. [Figure 10] It is a conceptual diagram showing another example of the workpiece in the present embodiment. [Figure 11] It is a conceptual diagram for explaining another example of the workpiece and the forging device in the present embodiment.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described based on the drawings. In the following embodiments, parts that are identical or equivalent to each other are denoted by the same reference numerals in the drawings. Also, each drawing used in the description is a conceptual diagram. In this description, fixing is, for example, fixing by screwing. In the drawings, the display of the screws used for fixing by screwing and the fact that the inside of the member is hollow (for example, cylindrical) is omitted. Also, in FIG. 1, the left side of the two-dot chain line represents the state at the start of forming, and the right side represents the state after forming is completed. Also, in FIG. 7, the left side of the two-dot chain line represents the initial position of the device, and the right side represents the state after forming is completed. The forging device is symmetric about the left and right, and in the drawing display, the reference numerals in FIGS. 1 and 7 are attached only to either the left or the right for each member.

[0018] <First Embodiment> The first embodiment will be described by taking, as an example, a forging device for forging a gear with a crowning. The workpiece W to be formed is formed in an annular (cylindrical) shape. The forging device 1 according to the first embodiment is an electric servo press.

[0019] The forging apparatus 1 of the first embodiment, as shown in Figure 1, comprises a punch 2, a counter punch 3, a gas cylinder (corresponding to a "reaction force applying device") 4, a forming die 5, a ring member 6, a drive unit 7, a detection unit 8, and a control unit 9. The punch 2 is an upper punch member that presses the workpiece W downward by moving downward. The punch 2 comprises an inner punch portion 21, an outer punch portion 22, and a moving portion 23.

[0020] The inner punch portion 21 is a cylindrical punch member fixed to the movable portion 23 and extending downward from the movable portion 23. The outer punch portion 22 is a cylindrical punch member positioned on the outer circumference of the inner punch portion 21. The outer punch portion 22 is slidably engaged with the movable portion 23 in the vertical direction. The inner punch portion 21 is slidably positioned relative to the outer punch portion 22. At least from the start to the completion of forming, the lower end of the inner punch portion 21 is located below the lower end of the outer punch portion 22. The workpiece W is positioned below the lower end surface 22a of the outer punch portion 22.

[0021] The movable part 23 is a member that moves vertically under the control of the control unit 9. The movable part 23 has a recess 231 that opens downward. A projection 231a is formed at the opening of the recess 231. As a result, the upper end (flange portion) 221 of the outer punch portion 22 engages with the projection 231a, allowing it to slide between the bottom surface 231b of the recess 231 and the projection 231a. The inner punch portion 21 is fixed to the central part of the bottom surface 231b of the recess 231 (the upper end of the movable part 23). Therefore, the inner punch portion 21 moves together with the movement of the movable part 23.

[0022] When the movable part 23 moves downward, the outer punch part 22 moves downward by contacting the bottom surface 231b. Also, when the movable part 23 moves upward, the outer punch part 22 moves upward by contacting the projection 231a and the upper end portion 221. At the start of molding, the outer punch part 22 and the bottom surface 231b are in contact. Therefore, from the start to the completion of molding, the outer punch part 22 moves along with the downward movement of the movable part 23.

[0023] The counter punch 3 is positioned below the punch 2 and is the lower punch member on which the workpiece W is placed. The counter punch 3 is positioned opposite the punch 2. The workpiece W is placed between the punch 2 and the counter punch 3. The counter punch 3 moves downward due to the downward pressure from the punch 2. The counter punch 3 comprises, from the bottom, a pressure receiving portion 31, a cylindrical portion 32, and a cylindrical portion 33.

[0024] The pressure-receiving portion 31 is disc-shaped, and the pressure transmission portion 44 of the gas cylinder 4 is in contact with its lower surface. The pressure-receiving portion 31 is pressed upward by the gas cylinder 4 when the counter punch 3 moves downward. The cylindrical portion 32 is a cylindrical part that extends upward from the upper end surface of the pressure-receiving portion 31.

[0025] The cylindrical portion 33 has the same outer diameter as the columnar portion 32 and is a cylindrical part that extends coaxially upward from the upper end surface of the columnar portion 32. The upper end surface of the cylindrical portion 33 faces the lower end surface 22a of the outer punch portion 22 (the stepped surface of the punch 2). In other words, during forming, the workpiece W is sandwiched between the lower end surface 22a of the outer punch portion 22 and the cylindrical portion 33 of the counter punch 3. A recess 30 is formed at the upper end of the counter punch 3 by the cylindrical portion 33 and the upper end surface of the columnar portion 32. The inner punch portion 21 enters the recess 30 as the punch 2 moves downward. The inner punch portion 21, together with the guide die 50 described later, prevents axial misalignment of the workpiece W.

[0026] The gas cylinder 4 is a device that applies a reaction force to the downward movement of the counter punch 3 caused by the pressing of the punch 2. The gas cylinder 4 is a device that applies a reaction force to the counter punch 3 by fluid pressure (back pressure). The gas cylinder 4 comprises, from the bottom, a cylinder section 41, a piston section 42, a base section 43, and a pressure transmission section 44.

[0027] The cylinder portion 41 is filled with gas. The piston portion 42 is housed in the cylinder portion 41 so as to be movable in the vertical direction. Pressure is applied to the lower end surface of the piston portion 42. A predetermined reaction force (upward pressing force) is applied to the piston portion 42 by the pressure against the downward stroke.

[0028] The base portion 43 is a disc-shaped member fixed to the upper end surface of the piston portion 42. Multiple cylinder portions 41 and piston portions 42 are arranged below the base portion 43. The upper end surface of the base portion 43 abuts against the lower unit (housing) 1a of the forging apparatus 1, restricting its upward movement. A through hole is formed in the center of the base portion 43 through which a knockout pin 72 is inserted.

[0029] The pressure transmission section 44 is a member that transmits back pressure (reaction force) and is provided on the upper end surface of the base section 43. The pressure transmission section 44 extends in the vertical direction. The upper end of the pressure transmission section 44 is in contact with the pressure receiving section 31 of the counter punch 3. The upward pressing force received by the piston section 42 is transmitted to the counter punch 3 via the base section 43 and the pressure transmission section 44.

[0030] The gas cylinder 4 constantly applies a reaction force to the counter punch 3 during the forming of the workpiece W. In other words, the forming of the workpiece W is carried out with a reaction force (back pressure) applied to the counter punch 3. This results in the formation of a well-defined tooth profile in the workpiece W.

[0031] The molding die 5 is an annular die with a molding groove 5a formed on its inner circumferential surface. When the workpiece W is pressed into the inner circumferential side of the molding die 5, a shape corresponding to the molding groove 5a is formed on the outer circumferential surface of the workpiece W. The molding die 5 of the first embodiment is composed of a plurality of dies with equal vertical widths, namely inner dies 51 and outer dies 52. The inner die 51 is an inner annular member having a molding groove 5a.

[0032] The outer die 52 is an annular member positioned on the outer circumference of the inner die 51. The inner surface of the outer die 52 is shaped to match the outer surface of the inner die 51. The inner surface of the outer die 52 and the outer surface of the inner die 51 are in full contact. The outer surface of the outer die 52 is tapered, becoming larger in diameter towards the bottom. In other words, the outer diameter of the molding die 5 increases towards the bottom.

[0033] A guide die 50 is positioned above the molding die 5, coaxially with the molding die 5. Like the molding die 5, the guide die 50 is composed of two dies. The guide die 50 is positioned (fixed) relative to the molding die 5. The guide die 50 guides the movement of the workpiece W. At the start of molding, the workpiece W is positioned inside the guide die 50. The punch 2 and the workpiece W enter the inside of the molding die 5 through the guide die 50.

[0034] The ring member 6 is an annular member positioned on the outer circumference of the molding die 5, and is configured such that the pressing force applied to the molding die 5 changes according to its vertical position. The molding die 5 is press-fitted into the ring member 6. The ring member 6 can be described as a press-fit ring. The inner circumferential surface of the ring member 6 is tapered to match the outer circumferential surface of the molding die 5. In other words, the inner diameter of the ring member 6 increases as it moves downwards. The inner circumferential surface of the ring member 6 and the outer circumferential surface of the molding die 5 are in contact. The ring member 6 and the molding die 5 are configured such that the pressing force applied to the ring member 6 changes according to the vertical position of the ring member 6. The ring member 6 and the molding die 5 are configured such that the pressing force applied to the ring member 6 decreases as the ring member 6 moves upwards.

[0035] The drive unit 7 is a device that moves the ring member 6 in the vertical direction. The drive unit 7 comprises a drive source 71, a knockout pin 72, and a power transmission member 73. The drive source 71 is a device that drives the knockout pin. The drive source 71 comprises, for example, a motor and a linear motion conversion member, and converts the rotational force of the motor into vertical movement force and applies it to the knockout pin 72.

[0036] The knockout pin 72 is a component for removing the workpiece W from the forming die 5 after the forming process is complete. The knockout pin 72 is a rod-shaped member (for example, a cylindrical member) that extends vertically and moves vertically by the driving force of the drive source 71. The knockout pin 72 is positioned below the counter punch 3. When the knockout pin 72 moves upward, it contacts the lower end surface of the counter punch 3 and then moves the counter punch 3 upward. The workpiece W after the forming process is moved upward by the upward movement of the knockout pin 72 and the counter punch 3 and is pushed above the guide die 50. At this time, the movable part 23 of the punch 2 also moves upward along with the movement of the knockout pin 72. The forging apparatus 1 of the first embodiment is configured to push the workpiece W into the forming die 5 from above and remove it from above.

[0037] The power transmission member 73 is a member that transmits the vertical movement (power) of the knockout pin 72 to the ring member 6. The power transmission member 73 moves vertically in conjunction with the vertical movement of the knockout pin 72. The power transmission member 73 comprises a base portion 731 and a plurality of connecting portions 732. The base portion 731 is a plate-shaped portion fixed to the knockout pin 72. The upper end of the knockout pin 72 is fixed to the central part of the base portion 731.

[0038] The connecting portion 732 is a rod-shaped member extending upward from the outer circumference of the base portion 731. The lower end of the connecting portion 732 is fixed to the base portion 731, and the upper end is fixed to the ring member 6. In other words, the connecting portion 732 connects the base portion 731 and the ring member 6. The knockout pin 72 and the ring member 6 are linked by the power transmission member 73. In other words, the knockout pin 72, the ring member 6, and the power transmission member 73 move up and down as a single unit.

[0039] The detection unit 8 is a device that detects the vertical position information of the punch 2. The detection unit 8 is, for example, a linear gauge (linear sensor) that measures the linear displacement of the punch 2. The detection unit 8 transmits the detection result to the control unit 9. The position of the workpiece W can be estimated from the position of the punch 2. As in the first embodiment, in the electric servo press, the control unit 9 knows the position of the punch 2 using the linear gauge (detection unit 8).

[0040] The detection unit 8 may be a digital caliper. The position of the punch 2 is not limited to direct positional information such as the detection result of a linear gauge, but may also be calculated based on, for example, the rotational position of the motor, the load on the punch 2, or the elapsed time since the punch 2 started operating. In other words, the detection unit 8 may be, for example, a rotation angle sensor, a load sensor, or a timer function (time measurement function) of the control unit 9 as a means of detecting the position of the punch 2. It can also be said that the detection unit 8 detects the movement (amount of movement) of the punch 2.

[0041] The control unit 9 controls the drive unit 7 (drive source 71) based on the detection result of the detection unit 8. The control unit 9 is an electronic control unit (ECU) or computer having a CPU, memory, etc. The control unit 9 is capable of communicating with the controlled object by wire or wireless. The control unit 9 controls the positions of the punch 2 and the knockout pin 72. The punch 2 and the knockout pin 72 can be controlled to move in conjunction with each other. For example, the control unit 9 moves the knockout pin 72 in synchronization with the movement of the punch 2. In other words, the control unit 9 moves the ring member 6 in accordance with the movement of the punch 2.

[0042] (Shaping of crowned gears) In the following description, the pressing force exerted by the ring member 6 against the molding die 5 will be referred to as the "ring pressing force." When forming a crowned gear (here, a helical gear), the control unit 9 controls the drive unit 7 so that the ring pressing force when the upper or lower end of the workpiece W is located at a predetermined position P (see Figure 3) in the vertical direction of the molding die 5 is greater than the ring pressing force when the middle part of the workpiece W is located at the predetermined position P of the molding die 5. The molding groove 5a is formed in the shape of teeth.

[0043] As shown in Figure 2, in this example, the molding groove 5a has a groove width (length in the direction perpendicular to the groove's extension direction) that decreases towards the radially outward (bottom) side. Also, as shown in Figure 3, the molding groove 5a of the molding die 5 is provided with an approach section 5a1 and a land section 5a2. The approach section 5a1 constitutes the upper end of the molding groove 5a and is a part that is inclined so that it is located radially inward as it goes downward. The approach section 5a1 allows the workpiece W to be gradually deformed and inserted into the molding die 5.

[0044] The land portion 5a2 is the part of the molded groove 5a formed below the approach portion 5a1. The land portion 5a2 extends downward at the same position as the radially innermost position of the approach portion 5a1. In other words, the land portion 5a2 is the part that extends downward in order to maintain the maximum radially inward projection height (maximum groove depth) of the approach portion 5a1. The predetermined position P in the first embodiment corresponds to the upper end of the land portion 5a2 (or the lower end of the approach portion 5a1).

[0045] The molding groove 5a is formed such that when the workpiece W is pressed downwards, it enters the approach portion 5a1 and undergoes elastic deformation, and then undergoes plastic deformation when it reaches the land portion 5a2. In other words, when the workpiece W is located at a predetermined position P, the shape of the portion of the workpiece W facing the predetermined position P is determined. When the workpiece W reaches the land portion 5a2, deformation occurs in the plastic region of the workpiece W. The outer diameter of the workpiece W is greater than the minimum inner diameter of the molding die 5 (molding groove 5a) but less than the maximum inner diameter (minimum inner diameter of molding die 5 < outer diameter of workpiece W < maximum inner diameter of molding die 5). Also, during molding (at least after the workpiece W enters the land portion 5a2), the workpiece W and the bottom surface of the molding groove 5a are in contact. In other words, no gap occurs between the bottom surface of the molding groove 5a and the workpiece W during molding. The outer diameter of the workpiece W is maintained below the maximum inner diameter of the molding die 5 by the guide die 50. However, molding in this embodiment is possible even if the outer diameter of the workpiece W is greater than or equal to the maximum inner diameter of the molding die 5.

[0046] The control unit 9 controls the position of the ring member 6 so that the ring pressing force becomes relatively larger when the lower end of the workpiece W is located at a predetermined position P in the molding groove 5a. At the start of molding, the control unit 9 moves the ring member 6 slightly downward. As shown in Figure 4, when the ring member 6 moves downward, the tapered surface acts, and the inner diameter of the ring member 6 corresponding to the upper end of the molding die 5 becomes smaller. As a result, the outer surface of the molding die 5 is pressed against the ring member 6, and the diameter of the molding die 5 becomes smaller. In this state, molding begins, the punch 2 descends, the workpiece W enters the approach section 5a1, reaches the reduced-diameter land section 5a2, and the lower end of the workpiece W is molded.

[0047] Then, when the detection unit 8 detects that the lower end of the workpiece W is about to pass through a predetermined position P, the control unit 9 moves the ring member 6 upward, increasing the inner diameter of the ring member 6 that corresponds to the upper end of the molding die 5 (see Figure 4). As a result, the ring pressing force decreases and the diameter of the molding die 5 increases. In this state, the middle portion of the workpiece W (the portion excluding the lower and upper ends) enters the predetermined position P. The middle portion of the workpiece W is formed by a land portion 5a2 with a larger diameter than when the lower end was formed.

[0048] When the middle portion of the workpiece W passes the predetermined position P and the upper end of the workpiece W is about to enter the predetermined position P, the control unit 9 moves the ring member 6 downward and increases the ring pressing force again. As a result, the upper end of the workpiece W is formed by the small-diameter molding die 5, just like the lower end.

[0049] The amount of downward movement of the ring member 6 is the same when forming the upper end and the lower end of the workpiece W. When the upper end of the workpiece W is located at the predetermined position P, the diameter of the molding die 5 becomes smaller overall, and therefore the diameter of the molding die 5 corresponding to the middle and lower ends of the workpiece W that have passed the predetermined position P also becomes smaller. However, the change in the diameter of the molding die 5 due to the movement of the ring member 6 is a change in the elastic region (a change on the order of tens of micrometers). Therefore, even if the middle and lower ends of the workpiece W are deformed when forming the upper end of the workpiece W, this is elastic deformation and does not affect the shape of the workpiece W after molding is complete.

[0050] In this way, the control unit 9 increases the ring pressing force at the upper and lower ends of the workpiece W to reduce the diameter of the forming die 5, and decreases the ring pressing force at the middle of the workpiece W to increase the diameter of the forming die 5. As the diameter of the forming die 5 decreases, the shape of the forming groove 5a also decreases proportionally. In other words, the smaller the diameter of the forming die 5, the smaller the groove width of the forming groove 5a becomes. Therefore, according to the above control, the tooth width of the formed workpiece W is relatively smaller at the upper and lower ends and relatively larger at the middle. For example, as shown in Figures 5 and 6, the tooth profile and crowning are formed on the workpiece W after forming is completed by a single punch.

[0051] In the first embodiment, the movement of the punch 2 and the movement of the ring member 6 (knockout pin 72) are set to be linked, allowing molding to be performed without stopping the punch 2. For example, the control unit 9 positions the punch 2 and the ring member 6 at predetermined positions when molding begins, gradually moves the ring member 6 upward as the middle part of the workpiece W approaches the predetermined position P, and gradually moves the ring member 6 downward as the lower end of the workpiece W approaches the predetermined position P. It is also possible to change the position of the ring member 6 after stopping the punch 2.

[0052] (Effects of the first embodiment) According to the first embodiment, the ring member 6 presses the molding die 5 with a ring pressing force corresponding to its position, thereby elastically deforming the molding die 5 and changing its inner diameter. The greater the ring pressing force, the more the molding die 5 is tightened radially inward, and the smaller its inner diameter becomes. In other words, it becomes possible to change the radial dimensions of the tooth profile during molding. As the diameter of the molding die 5 decreases, the shape of the molding groove 5a (groove width, etc.) also decreases proportionally. As a result, for example, when molding a crowned gear, the control unit 9 changes the ring pressing force according to the position of the punch 2 to change the inner diameter of the molding die 5, making it possible to mold a crowned gear with a single punch (without molding an intermediate cylindrical gear).

[0053] Furthermore, with this configuration, the molded shape can be finely adjusted by adjusting the reaction force and / or ring pressing force, so there is no need to replace the device even if changes in frictional resistance occur. For example, the control unit 9 can adjust the position of the ring member 6, i.e., the ring pressing force, to adjust the tooth width, dimensions, etc., formed on the workpiece W.

[0054] Furthermore, the width of the teeth formed on the workpiece W can be adjusted by adjusting the pressure (back pressure) of the gas cylinder 4. For example, the higher the pressure of the gas cylinder 4, the less likely the punch 2 is to move downward, and the workpiece W is gripped between the punches with greater force. As a result, radial deformation of the workpiece W is promoted, and the workpiece W (teeth) is pushed towards the bottom side of the forming groove 5a. This makes it possible to adjust the formed shape.

[0055] Thus, according to the first embodiment, the overall man-hours can be reduced, and fine adjustment of the molded shape can be made without changing the equipment. Furthermore, by synchronizing the position control of the ring member 6 with the movement of the punch 2, continuous molding control becomes possible. The configuration of the first embodiment is particularly effective in the manufacture of crowned gears. Note that the pressure of the gas cylinder 4 may be adjusted, for example, by replacing the gas cylinder 4 or by pressure control by the control unit 9 (see the second embodiment described later).

[0056] Furthermore, since the position of the ring member 6 can be changed by utilizing the configuration of the knockout pin 72, the parts can be used effectively. After molding is complete, when the knockout pin 72 rises and the workpiece W is removed, the ring member 6 also rises, reducing the ring pressing force (for example, the press-fitting of the ring member 6 into the molding die 5 is released), making it easier to remove the workpiece W.

[0057] Thus, when removing the workpiece W from the molding die 5, that is, before or during the removal of the workpiece W from the molding die 5, the control unit 9 controls the drive unit 7 to reduce the ring pressing force to less than the ring pressing force during molding of the workpiece W (the minimum value during molding). In the configuration of the first embodiment, in which the knockout pin 72 is used as part of the drive unit 7, when removing the workpiece W, the ring pressing force decreases as the knockout pin 72 rises. On the other hand, even if the drive unit 7 is configured independently of the knockout pin 72, the control unit 9 only needs to control the drive unit 7 so that the ring pressing force is reduced when removing the workpiece W. As a result, the inner diameter of the molding die 5 becomes larger than during molding, the knockout load is reduced, and the workpiece W becomes easier to remove as described above. With this configuration, unnecessary force applied to the tooth surface of the workpiece W after molding is completed is suppressed, and the dimensional accuracy of the product can be better maintained. The control unit 9 may, for example, set the ring pressing force to the minimum value in the configuration when removing the workpiece W.

[0058] <Second Embodiment> The forging apparatus 100 of the second embodiment differs from the first embodiment in that it lacks the ring member 6 and the power transmission member 73, and the control unit 9 is configured to adjust the pressure (back pressure) of the gas cylinder 4. Therefore, only the differing parts will be described, and the description of the other parts will be omitted. In describing the second embodiment, you can refer to the description and drawings of the first embodiment.

[0059] As shown in Figure 7, the forging apparatus 100 includes a punch 2, a counter punch 3, a gas cylinder (corresponding to a "reaction force applying device") 4, a forming die 5, a detection unit 8, and a control unit 9. The control unit 9 controls the reaction force (back pressure) applied by the gas cylinder 4 based on the detection result of the detection unit 8. In the second embodiment, the control unit 9 changes the reaction force in accordance with (synchronously with) the movement of the punch 2.

[0060] Taking the manufacture of crowned gears as an example, the control unit 9 controls the gas cylinder 4 such that the reaction force when the upper or lower end of the workpiece W is located at a predetermined position P in the vertical direction of the molding die 5 is smaller than the reaction force when the middle part of the workpiece W is located at the predetermined position P of the molding die 5.

[0061] The gas cylinder 4 is equipped with a pressure regulator (e.g., a solenoid valve) 45 as a means for adjusting the reaction force, which adjusts the pressure inside the cylinder section 41. The control unit 9 controls the reaction force by controlling the pressure regulator 45. During molding, as in the first embodiment, a reaction force (back pressure) from the gas cylinder 4 is constantly applied to the counter punch 3. This forms a tooth profile with good wall thickness on the workpiece W. In the second embodiment, there is no pressure transmission section 44, and the base section 43 directly presses against the counter punch 3.

[0062] The gas cylinder 4 may also be configured to include, for example, multiple cylinders with different pressures and a cylinder switch. The cylinder switch is a solenoid valve that switches the connected cylinder. In this case, the control unit 9 controls the cylinder switch to adjust the output pressure of the gas cylinder 4.

[0063] (Effects of the second embodiment) According to the second embodiment, by changing the reaction force according to the position of the punch 2, the degree of deformation of the workpiece W can be changed, similar to the adjustment of the gas cylinder 4 in the first embodiment. In other words, the larger the reaction force, the greater the vertical clamping force on the workpiece W, and the greater the amount of radial outward bulging of the workpiece W. As a result, for example, when forming a crowned gear, the control unit 9 changes the reaction force according to the position of the punch 2, making it possible to form a crowned gear with a single punch (without forming an intermediate cylindrical gear). Furthermore, with this configuration, the forming shape can be finely adjusted by adjusting the reaction force, so even if changes in frictional resistance occur, there is no need to replace the device.

[0064] Thus, according to the second embodiment, the overall man-hours can be reduced, and fine adjustments to the molded shape can be made without changing the equipment. Furthermore, by synchronizing the pressure control of the gas cylinder 4 with the movement of the punch 2, continuous molding control becomes possible. The configuration of the second embodiment is also particularly effective in the manufacture of crowned gears.

[0065] <Common manufacturing method> The common manufacturing method for the crowned gear described above will now be explained. The manufacturing method of this embodiment includes a deep drawing step in which a workpiece W, whose outer diameter is larger than the minimum inner diameter of the forming die 5, is pressed into the forming die 5. In the deep drawing step, a reaction force is applied to the counter punch by a reaction force application device (e.g., a gas cylinder 4), and the punch 2 pushes the workpiece W into the forming die 5, compressing and deforming the workpiece W. In other words, deep drawing (compression) is performed on the workpiece W while a reaction force (intrusion resistance) due to fluid pressure is applied. This assists the flow of the tooth tips in the formation of the tooth profile, and increases the pressing force that the workpiece W (tooth tips) presses against the bottom surface of the forming groove 5a during forming. In other words, a tooth profile with good wall thickness is formed on the workpiece W.

[0066] <Third Embodiment> The forging apparatus 100A of the third embodiment differs from the second embodiment in that, instead of the control unit 9 adjusting the reaction force, the frictional force when the moving member (counter punch or first knockout pin 721) moves changes according to the position of the moving member. Therefore, only the differing parts will be described, and the description of the other parts will be omitted. In the description of the third embodiment, you can refer to the descriptions and drawings of the first and second embodiments.

[0067] As shown in Figure 8, the forging apparatus 100A includes a punch 2, a counter punch 3, a forming die 5, a first knockout pin (corresponding to the "interlocking member" and "moving member") 721, a second knockout pin 722, a collar member 74, a detection unit 8, and a control unit 9.

[0068] The first knockout pin 721 is a rod-shaped interlocking member that moves downward in conjunction with the downward movement of the counterpunch 3. The first knockout pin 721 is positioned below the counterpunch 3. In its initial position, the upper end surface of the first knockout pin 721 is in contact with the lower end surface of the counterpunch 3. The detailed configuration will be described later.

[0069] The second knockout pin 722 is a rod-shaped member positioned below the first knockout pin 721. The second knockout pin 722 is spaced apart from the first knockout pin 721 and is positioned so as not to come into contact with the first knockout pin 721 when the counter punch 3 is at its lowest point (i.e., when molding is complete) (or so as to come into contact with it when the counter punch 3 is at its lowest point).

[0070] The second knockout pin 722 moves upward together with the first knockout pin 721 while in contact with it, due to the operation of the drive source 71. In other words, the first knockout pin 721 and the second knockout pin function as a single knockout pin 72, pushing the counterpunch 3 upward. A knockout pin is also called a knockout rod.

[0071] The collar member 74 is positioned around the first knockout pin 721 and generates a frictional force against the movement of the first knockout pin 721. The collar member 74 is formed in an annular shape and is configured so that the first knockout pin 721 is inserted through the central through hole 741. The collar member 74 holds the first knockout pin 721 so that it can move up and down by frictional force, preventing the first knockout pin 721 from moving downward due to gravity.

[0072] (Details of the first knockout pin and collar component) The first knockout pin 721 and the collar member 74 are configured such that the frictional force between the first knockout pin 721 and the collar member 74 changes depending on the position of the first knockout pin 721.

[0073] The first knockout pin 721 is provided with a first protrusion 721a that protrudes outward. The first protrusion 721a is formed in an annular shape that protrudes around the entire circumference in a portion of the axial direction of the first knockout pin 721. As shown in Figure 9, the first protrusion 721a is formed such that the outer diameter of the first knockout pin 721 gradually increases from the upper end to the apex and gradually decreases from the apex to the lower end.

[0074] The collar member 74 has a second protrusion 74a that protrudes toward the inner circumference. The first knockout pin 721 and the collar member 74 are configured such that the frictional force between the first knockout pin 721 and the collar member 74 increases when the first protrusion 721a and the second protrusion 74a come into contact with each other.

[0075] The second protrusion 74a is formed as an annular shape that protrudes around the entire circumference in a portion of the axial direction of the collar member 74. The second protrusion 74a is formed such that the inner diameter of the collar member 74 gradually decreases from the upper end to the apex and gradually increases from the apex to the lower end. In this example, the second protrusion 74a is configured to abut only the first protrusion 721a. In other words, the minimum diameter of the second protrusion 74a is larger than the outer diameter of the first knockout pin 721 excluding the first protrusion 721a.

[0076] The first protrusion 721a is configured to abut against the inner circumferential surface of the collar member 74. In other words, in this example, the maximum diameter of the first protrusion 721a is greater than the maximum inner diameter of the collar member 74. Therefore, the first knockout pin 721 is press-fitted into the collar member 74. In its initial position, the first protrusion 721a abuts against the inner circumferential surface of the collar member 74 above the second protrusion 74a. The first knockout pin 721 in its initial position is positioned by the frictional force between the first protrusion 721a and the collar member 74.

[0077] As forging begins and the counterpunch 3 moves downward, the first knockout pin 721 is pressed down by the counterpunch 3 and moves downward. As the first protrusion 721a moves downward, it comes into contact with the second protrusion 74a. As the first protrusion 721a moves downward, the diameter of the through hole 741 decreases due to the second protrusion 74a. In other words, the press-fit allowance increases in the area where the second protrusion 74a is formed. As a result, the resistance (frictional force) of the first protrusion 721a trying to pass through the second protrusion 74a increases, and the reaction force against the downward movement of the counterpunch 3 increases.

[0078] The frictional force (reaction force) is maximum when the apex of the first protrusion 721a and the apex of the second protrusion 74a come into contact. Then, as the first protrusion 721a moves below the apex of the second protrusion 74a, the frictional force decreases. Because the second protrusion 74a is formed with a gentle slope, the frictional force changes gradually. In other words, as the first protrusion 721a and the second protrusion 74a come into contact, the frictional force gradually increases as the first protrusion 721a moves downward, and then gradually decreases after passing the apex of the second protrusion 74a.

[0079] Thus, with respect to the mountain-shaped second protrusion 74a, the press-fit allowance (frictional force during passage) is maximized at the apex of the second protrusion 74a and gradually decreases toward the upper and lower ends. In other words, the first knockout pin 721 and collar member 74 of the third embodiment are configured such that the frictional force when the upper or lower end of the workpiece W is located at a predetermined position P in the vertical direction of the molding die 5 is smaller than the frictional force when the middle part of the workpiece W is located at a predetermined position P of the molding die 5. Furthermore, the molding groove 5a is formed in a toothed shape.

[0080] (Effects of the third embodiment) According to the third embodiment, the reaction force can be changed by changing the frictional force between the first knockout pin 721 and the collar member 74 depending on the position of the counter punch 3. This makes it possible to change the degree of deformation of the workpiece W, as in the second embodiment. In other words, the larger the reaction force (frictional force), the greater the amount of radial outward bulging of the workpiece. This makes it possible, for example, to form a crowned gear with a single punch (without forming an intermediate cylindrical gear) without special control when forming a crowned gear.

[0081] Furthermore, the frictional force can be finely adjusted by changing the shape and surface roughness of the first protrusion 721a and / or the second protrusion 74a (for example, by filing). In other words, the back pressure (reaction force) can be adjusted by the press-fit allowance between the first knockout pin 721 and the collar member 74, and / or the surface roughness of the contact surfaces between them. Also, as the counter punch 3 moves downward, frictional force is always generated by the press-fit action, so a tooth profile with good wall thickness is formed on the workpiece W.

[0082] (Modified version of the third embodiment) The first protrusion 721a may be formed to contact only the second protrusion 74a. In this case, the contact between the first protrusion 721a and the second protrusion 74a causes the first knockout pin 721 to engage with the collar member 74. In other words, in this case, the first protrusion 721a and the second protrusion 74a are in contact from the initial position. When the apex position of the first protrusion 721a is below the lower end of the second protrusion 74a, the frictional force is eliminated, and the first knockout pin 721 and the second knockout pin 722 come into contact. Even with this configuration, a crowned gear can be manufactured.

[0083] Furthermore, the minimum inner diameter of the second protrusion 74a may be smaller than the minimum diameter of the first knockout pin 721. In other words, in the initial position, the second protrusion 74a may be in contact with the outer circumferential surface of the first knockout pin 721. For example, in this case, the maximum diameter of the first protrusion 721a may be smaller than the maximum inner diameter of the collar member 74. In other words, even when the first protrusion 721a and the second protrusion 74a are not in contact, the design may be such that frictional force is generated by at least one of the first protrusion 721a and the second protrusion 74a.

[0084] Furthermore, as shown by the dotted line in Figure 8, a reaction force application device (e.g., a gas cylinder 4) may be positioned below the first knockout pin 721. In this case, the counter punch 3 will be subjected to a reaction force consisting of back pressure from the reaction force application device and frictional force between the first knockout pin 721 and the collar member 74. The reaction force application device may be configured to allow control of the reaction force.

[0085] Furthermore, the first protrusion 721a may be provided on the counter punch 3 (corresponding to the "movable member"). In this case, the collar member 74 having the second protrusion 74a is arranged around the counter punch 3. This also produces the same effect as described above. Thus, the collar member 74 is arranged around the counter punch 3, or the interlocking member (first knockout pin 721) that moves downward in conjunction with the downward movement of the counter punch 3. In other words, the movable member, which is either the first knockout pin 721 (interlocking member) or the counter punch 3, is arranged inside the collar member 74. Note that the interlocking member is not limited to the first knockout pin 721, but may be another member.

[0086] <Other> The present invention is not limited to the above embodiments. For example, the molded product may be something other than a crowned gear. In other words, the forging apparatus 1, 100 can also mold products other than crowned gears. Furthermore, the control of the ring pressing force is not limited to switching between the upper, middle, and lower ends of the workpiece W, but can be set according to the molding objective. Also, the widths of the upper and lower ends of the workpiece W can be set according to the design of the crowning. In addition, the reaction force applying device that applies a reaction force to the counter punch 3 may be a back pressure applying device that outputs fluid pressure as a reaction force (for example, a gas cylinder 4 or a stroke simulator), or it may be something else.

[0087] Furthermore, the land portion 5a2 of the molding groove 5a may be located radially outward (the groove is shallower) in the portion below the upper end than the upper end. In other words, it may be configured so that only the upper end of the land portion 5a2 is located radially inward (the groove is deeper). To put it another way, the portion of the molding groove 5a that includes a predetermined position P is convex toward the center of the molding die 5. This makes it possible to suppress the molding groove 5a from pressing against the already molded middle and lower ends of the workpiece W when the diameter of the molding die 5 decreases during molding of the upper end of the workpiece W. Also, the groove width of the molding groove 5a does not have to decrease towards the radially outward side as shown in Figure 2, and may be a constant width, for example.

[0088] Furthermore, the ring member 6 may be a member configured so that the ring pressing force can be controlled by the control unit 9, such as a vise with a molding die 5 positioned inside. In this case, the drive unit 7 becomes a device that rotates the handle of the vise. In other words, in the present invention, the ring member 6 is a member configured so that the pressing force (ring pressing force) that presses the molding die 5 changes depending on the state, and the drive unit 7 is a device that changes the state of the ring member 6. The state is, for example, the vertical position of the ring member 6 or the rotation position of the handle, and can also be said to be the state of the part of the ring member 6 that applies pressing force to the molding die 5 (value of the minimum inner diameter).

[0089] Furthermore, the workpiece W is not limited to annular shape; for example, as shown in Figure 8, it may be a shafted member (a shafted gear after molding) in which a shaft-like portion is provided on the gear portion. In this case, for example, as shown in Figure 9, the lower end of the punch 2 and the upper end of the counter punch 3 are formed in a concave shape with a recessed central portion. The shaft-like portion of the workpiece W is positioned within the recess of each punch. Even with this configuration, the same effects as in the above embodiment can be achieved.

[0090] In the concept of the present invention, the forging apparatus 1 is equipped with a pressing force adjustment means (ring member 6, drive unit 7, and control unit 9) that changes the inner diameter of the forming die 5 by adjusting the pressing force (corresponding to the ring pressing force) applied to the outer circumferential surface of the forming die 5. As in the first embodiment, the pressing force adjustment means changes the variable pressing force in accordance with the movement of the punch 2. Furthermore, the pressing force adjustment means makes the variable pressing force when the upper or lower end of the workpiece W is located at a predetermined position P in the vertical direction of the forming die 5 greater than the variable pressing force when the middle part of the workpiece W is located at the predetermined position P of the forming die 5.

[0091] Furthermore, the pressing force adjustment means reduces the variable pressing force to a lower value than that applied during the molding of the workpiece W when removing the workpiece W from the molding die 5. The gear manufacturing method includes a removal step in which the workpiece W is removed from the molding die 5 after the molding of the workpiece W is complete. In this removal step, the pressing force adjustment means reduces the pressing force applied to the outer surface of the molding die 5 (hereinafter referred to as the variable pressing force) to a lower value than that applied during the molding of the workpiece W. This increases the inner diameter (internal dimension, passage cross-sectional area) of the molding die 5, allowing the workpiece W to be removed with high precision after the molding is complete. [Explanation of Symbols]

[0092] 1, 100, 100A... Forging device, 2... Punch, 3... Counter punch (moving member), 4... Gas cylinder (reaction force applying device), 5... Forming die, 5a... Forming groove, 6... Ring member, 7... Drive unit, 721... First knockout pin (interlocking member, moving member), 74... Collar member, 8... Detection unit, 9... Control unit, W... Workpiece.

Claims

1. A punch that moves downwards to press the workpiece downwards, A counterpunch is positioned below the punch on which the workpiece is placed, A reaction force applying device that applies a reaction force to the downward movement of the counterpunch caused by the pressing of the punch, An annular molding die with molding grooves formed on its inner circumferential surface, An annular ring member is positioned on the outer circumference of the molding die and configured to change the pressing force that presses the molding die depending on the state, A drive unit that changes the state of the ring member, A detection unit for detecting the vertical position information of the punch, A control unit that controls the drive unit based on the detection result of the detection unit, A forging apparatus equipped with [a specific feature].

2. The forging apparatus according to claim 1, wherein the control unit moves the ring member in synchronization with the movement of the punch.

3. The aforementioned molding groove is formed in the shape of a tooth, The control unit, The forging apparatus according to claim 1 or 2, wherein the drive unit is controlled such that the pressing force when the upper or lower end of the workpiece is located at a predetermined position in the vertical direction of the forming die is greater than the pressing force when the middle portion of the workpiece is located at the predetermined position of the forming die.

4. The ring member and the molding die are configured such that the pressing force changes according to the vertical position of the ring member. The forging apparatus according to any one of claims 1 to 3, wherein the drive unit moves the ring member in the vertical direction.

5. The aforementioned drive unit is A knockout pin for removing the workpiece from the molding die after molding is complete, A drive source for driving the aforementioned knockout pin up and down, A power transmission member that transmits the vertical movement of the knockout pin to the ring member, The forging apparatus according to claim 4, comprising:

6. The forging apparatus according to claim 5, wherein the ring member and the forming die are configured such that the pressing force decreases as the ring member moves upward.

7. The forging apparatus according to any one of claims 1 to 6, wherein the control unit controls the drive unit to reduce the pressing force to less than the pressing force during the forming of the workpiece when removing the workpiece from the forming die.

8. A punch that moves downwards to press the workpiece downwards, A counterpunch is positioned below the punch on which the workpiece is placed, A reaction force applying device that applies a reaction force to the downward movement of the counterpunch caused by the pressing of the punch, An annular molding die with molding grooves formed on its inner circumferential surface, A detection unit for detecting the vertical position information of the punch, A control unit that controls the reaction force applied by the reaction force applying device based on the detection result of the detection unit, A forging apparatus equipped with [a specific feature].

9. The forging apparatus according to claim 8, wherein the control unit changes the reaction force in synchronization with the movement of the punch.

10. The aforementioned molding groove is formed in the shape of a tooth, The control unit, The forging apparatus according to claim 8 or 9, wherein the reaction force applying device is controlled such that the reaction force when the upper or lower end of the workpiece is located at a predetermined position in the vertical direction of the forming die is smaller than the reaction force when the middle portion of the workpiece is located at the predetermined position of the forming die.

11. The forging apparatus according to any one of claims 1 to 10, wherein the reaction force applying device continuously applies the reaction force to the counter punch during the forming of the workpiece.

12. A punch that moves downwards to press the workpiece downwards, A counterpunch is positioned below the punch on which the workpiece is placed, An annular molding die with molding grooves formed on its inner circumferential surface, A collar member is arranged around the counterpunch or a moving member which is an interlocking member that moves downward in conjunction with the downward movement of the counterpunch, and generates a frictional force against the downward movement of the moving member. Equipped with, A forging apparatus in which the moving member and the collar member are configured such that the frictional force changes depending on the position of the moving member.

13. The moving member has a first protrusion that protrudes outward on the outer circumference, The aforementioned color member has a second protrusion that protrudes toward the inner circumference, The forging apparatus according to claim 12, wherein the moving member and the collar member are configured such that the frictional force is increased when the first protrusion and the second protrusion come into contact with each other.

14. The aforementioned molding groove is formed in the shape of a tooth, The forging apparatus according to claim 12 or 13, wherein the moving member and the collar member are configured such that the frictional force when the upper or lower end of the workpiece is located at a predetermined position in the vertical direction of the forming die is smaller than the frictional force when the middle portion of the workpiece is located at the predetermined position of the forming die.

15. A punch that moves downwards to press the workpiece downwards, A counterpunch is positioned below the punch on which the workpiece is placed, A reaction force applying device configured to apply a reaction force to the downward movement of the counterpunch caused by the pressing of the punch, and to output the pressure of a fluid as the reaction force, An annular molding die having tooth-shaped molding grooves formed on its inner circumferential surface, A method for manufacturing gears using a forging apparatus equipped with, The process includes a drawing step in which the workpiece, whose outer diameter is larger than the minimum inner diameter of the forming die, is pressed into the forming die, A method for manufacturing gears, wherein in the deep drawing process, the punch presses the workpiece into the forming die while the reaction force is applied to the counter punch by the reaction force applying device, thereby compressing and deforming the workpiece.

16. The process includes removing the workpiece from the molding die after the molding of the workpiece is completed. The forging apparatus includes a pressing force adjustment means for adjusting the pressing force applied to the outer surface of the forming die, The method for manufacturing a gear according to claim 15, wherein in the extraction step, the pressing force adjustment means reduces the pressing force to a level lower than the pressing force used when forming the workpiece.

17. A punch that moves downwards to press the workpiece downwards, A counterpunch is positioned below the punch on which the workpiece is placed, A reaction force applying device that applies a reaction force to the downward movement of the counterpunch caused by the pressing of the punch, An annular molding die with molding grooves formed on its inner circumferential surface, A pressing force adjustment means for adjusting the pressing force applied to the outer surface of the molding die to change the inner diameter of the molding die, A forging apparatus equipped with [a specific feature].

18. The forging apparatus according to claim 17, wherein the pressing force adjusting means changes the pressing force in accordance with the movement of the punch.

19. The aforementioned molding groove is formed in the shape of a tooth, The forging apparatus according to claim 17 or 18, wherein the pressing force adjusting means makes the pressing force when the upper or lower end of the workpiece is located at a predetermined position in the vertical direction of the forming die greater than the pressing force when the middle portion of the workpiece is located at the predetermined position of the forming die.

20. The forging apparatus according to any one of claims 17 to 19, wherein the pressing force adjusting means reduces the pressing force when removing the workpiece from the forming die to less than the pressing force used when forming the workpiece.

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