Method for manufacturing helical gear forgings and forging apparatus

Abstract

We provide forging techniques that ensure sufficient meat flow. [Solution] The groove width of the helical groove 44 provided in the punch body 43 is set to G1, and the groove width of the helical groove 23 provided in the helical die 21 is set to G2. The groove width G1 of the helical groove 44 is set to be wider than the groove width G2 of the helical groove 23. The helical groove 23 and the helical groove 44 are connected via a tapered groove 24 provided on the helical die 21 side. During forging, a portion of the material flows from the helical groove 23 into the helical groove 44 as shown by arrow (1).

Description

Technical Field

[0001] The present invention relates to a manufacturing technology for forged products for helical gears.

[0002] [Explanation of Terms] · A helical gear is the English name for a skew gear. A skew gear is defined as a cylindrical gear whose tooth flanks are helical lines. · The helix angle is defined as the angle formed with the axis when the helical line is projected onto the axis of the gear. · A die and a mold are synonymous. In the background art, the former is used, and the latter is used after the summary of the invention.

Background Art

[0003] A helical gear can be obtained by cutting teeth on a cylindrical material with a machine tool, but this manufacturing method has the drawback of increasing processing costs. As one countermeasure, there is a known manufacturing method of obtaining a forged product for a helical gear in a form approximating the finished product by plastic processing (see, for example, Patent Document 1 (Figure 4)).

[0004] Patent Document 1 will be described based on the following figure. Figures 10(a) to (d) are diagrams for explaining a conventional manufacturing method of a forged product for a gear. As shown in Figure 10(a), a material 107 is set in a forging device 100 composed of a first die 101, a second die 102, a die pin 103, a die sleeve 104, a punch pin 105, and a punch sleeve 106, and the punch pin 105 and the punch sleeve 106 are lowered as indicated by the white arrows.

[0005] As shown in Figure 10(b), the material 107 is compressed, and teeth 108 are formed on the outer peripheral surface. If the molding is insufficient, as shown in Figure 10(c), the punch pin 105 and die pin 103 are removed from the material 107 during the molding process (while the punch pin 105 and punch sleeve 106 are descending). Recesses are created where the punch pin 105 and die pin 103 were removed. Material flows into these recesses. As the material flows to the left and right sides of the drawing, the molding of the teeth 108 can be improved.

[0006] The gear forging 109 obtained according to Figure 10(b) or Figure 10(c) is shown in Figure 10(d). However, the technology described in Patent Document 1 has the following shortcomings that need improvement.

[0007] First, in Figure 10(c), setting the timing for removing the punch pin 105 and die pin 103 from the material 107 is difficult. That is, if the removal timing is too late, there will be insufficient meat flow. If the removal timing is too early, the recess left by the removal will be too small. Therefore, a manufacturing technique (forging technique) is required that can form a recess of the desired size and allow sufficient material to flow in.

[0008] Next, in Figures 10(b) and 10(c), we focus on section Z (the upper end of the material 107). The gap 111 between the punch sleeve 106 and the first die 101 at section Z is small. It is not easy to allow the material to flow into the small gap 111. In Figures 10(a) and (b), the outer circumference of the punch sleeve 106 is round and appears to have a diameter smaller than the hole diameter of the first die 101. As a result, the tooth-shaped portion of the first die 101 becomes hollow, allowing a lot of excess material to flow through, making filling the tooth shape inefficient. As a countermeasure, a manufacturing technique (forging technique) is needed that promotes the flow of meat to the end of the tooth (the upper end 112 in this example).

[0009] Therefore, there is a need for a manufacturing technique (forging technique) that can form a recess of the desired size in the material and allow sufficient meat to flow in, and furthermore, a manufacturing technique (forging technique) that promotes the flow of meat all the way to the end of the tooth. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2024-135501 [Overview of the Initiative] [Problems that the invention aims to solve]

[0011] The present invention aims to provide a manufacturing technique (forging technique) that can form a recess of a desired size in a material and allow sufficient meat to flow in, and furthermore, to provide a manufacturing technique (forging technique) that promotes the flow of meat all the way to the end of the tooth. [Means for solving the problem]

[0012] The invention according to claim 1 comprises a material preparation step of preparing a cylindrical material, A forging apparatus preparation step comprising: a forging apparatus comprising: a helical die having a hole for housing a cylindrical material and a helical groove on the circumferential surface of the hole; a die pin that moves along the central axis of the helical die toward the bottom surface of the material in the hole; a die sleeve that moves toward the bottom surface of the material while surrounding the die pin; a die body that supports the helical die while surrounding the die sleeve; a punch pin that moves along the central axis toward the top surface of the material in the hole; a punch sleeve that moves toward the top surface of the material while surrounding the punch pin; and a punch body that moves up and down while surrounding the punch sleeve; A material feeding step in which the punch pin, the punch sleeve, and the punch body are positioned upward, the material is fed into the hole of the helical die, and the material is placed on the die pin or the die sleeve, A punch lowering step in which the punch body is lowered and brought into contact with the upper surface of the helical die, and the punch pin and the punch sleeve are lowered and brought into contact with the upper surface of the material, raising the die pin in a state where it protrudes upward from the die sleeve and / or lowering the punch pin in a state where it protrudes downward from the punch sleeve to perform primary plastic working on the material, a pin retraction step of forming recesses on the bottom surface and the upper surface of the material by lowering the die pin to a position where it does not protrude from the die sleeve and raising the punch pin to a position where it does not protrude from the punch sleeve, a secondary plastic working step of obtaining a forged product by further raising the die sleeve and / or further lowering the punch sleeve and performing secondary plastic working on the material so that metal flows into the recesses, and a forged product protruding step of waiting the punch pin, the punch sleeve, and the punch body upward and protruding the forged product from the helical die with the die sleeve, providing a method for manufacturing a forged product for a helical gear.

[0013] The invention according to claim 2 is a forging apparatus for manufacturing a forged product for a helical gear, a helical die having a hole for storing a cylindrical material and having a helical groove on the circumferential surface of the hole, a die pin that moves along the central axis of the helical die toward the bottom surface of the material in the hole, A die pin movement mechanism that moves this die pin and , The aforementioned a die sleeve that moves toward the bottom surface of the material while surrounding the die pin, This die sleeve moving mechanism moves the die sleeve, The aforementioned a die body that supports the helical die while surrounding the die sleeve, a punch pin that moves along the central axis toward the upper surface of the material in the hole, This punch pin moving mechanism moves the punch pin, The aforementioned a punch sleeve that moves toward the upper surface of the material while surrounding the punch pin, This punch sleeve moving mechanism moves the punch sleeve, The aforementioned a punch body that moves up and down while surrounding the punch sleeve 、 This punch body movement mechanism moves the punch body, A control unit controls the die pin moving mechanism, the die sleeve moving mechanism, the punch pin moving mechanism, the punch sleeve moving mechanism, and the punch body moving mechanism, so as to raise the die pin so that it protrudes upward from the die sleeve, and / or lower the punch pin so that it protrudes downward from the punch sleeve to perform a first plastic deformation on the material; then lower the die pin to a position where it does not protrude from the die sleeve, and raise the punch pin to a position where it does not protrude from the punch sleeve to form recesses on the bottom and top surfaces of the material; and then raise the die sleeve further, and / or lower the punch sleeve further, so as to allow material to flow into the recesses and perform a second plastic deformation on the material. comprising The punch body has a spiral groove connected to the helical groove, the groove width of this spiral groove is set wider than the groove width of the helical groove, and the helical groove and the spiral groove are connected through a tapered groove provided on the helical die side.

Advantages of the Invention

[0014] In the invention according to claim 1, in the pin retraction step following the first plastic working step, the die sleeve is stationary and the die pin is lowered, and the punch sleeve is stationary and the punch pin is raised. As a result, a recess of a desired size can be formed in the material. In the subsequent second plastic working step, the die sleeve is raised and the punch sleeve is lowered to cause the material to flow into the recess. That is, according to the invention according to claim 1, a manufacturing technique (forging technique) is provided in which a recess of a desired size can be formed in the material and the flow of the material is sufficient.

[0015] In the invention according to claim 2, the groove width of the spiral groove of the punch body is made larger than the groove width of the helical groove of the helical die. Then, the narrow helical groove and the wide spiral groove are connected by a tapered groove. The material flows in while spreading from the helical groove to the spiral groove. Since the flow-in resistance is small, the flow-in amount increases. As a result, the diversion of the material is promoted up to the end of the tooth. That is, according to the invention according to claim 2, a manufacturing technique (forging technique) is provided in which a recess of a desired size can be formed in the material and the flow of the material is sufficient, and further a manufacturing technique (forging technique) is provided in which the diversion of the material is promoted up to the end of the tooth.

Brief Description of the Drawings

[0016] [Figure 1] It is a principle diagram of the forging apparatus according to the present invention. [Figure 2] It is a view taken in the direction of arrow 2-2 of FIG. 1. [Figure 3] (a) to (c) are diagrams for explaining the operation of the forging apparatus and the operation of the control unit. [Figure 4] (a) to (c) are diagrams illustrating the operation of the forging apparatus and the control unit. [Figure 5] (a) is a close-up view of the main part of Figure 1 (without the material), and (b) is a close-up view of the main part of Figure 4(b). [Figure 6] (a) is a view from arrow 6a in Figure 5(a), (b) is a diagram of the operation, and (c) to (f) are diagrams illustrating modified examples. [Figure 7] (a) to (c) are cross-sectional views of the bead-like projections. [Figure 8] (a) is a front view of a bead-like projection without chamfering, (b) is a front view of a bead-like projection with chamfering, and (c) is a partial enlargement of Figure 4(b). [Figure 9] This diagram illustrates the arrangement of the bead-like protrusions. [Figure 10] (a) to (d) are diagrams illustrating a conventional method for manufacturing forged gears. [Modes for carrying out the invention]

[0017] Embodiments of the present invention will be described below with reference to the attached drawings. [Examples]

[0018] [Forging equipment] As shown in Figure 1, the forging apparatus 20 comprises a helical die 21, a die pin 25, a die pin moving mechanism 47 that moves the die pin 25 along the central axis 21a of the helical die 21, a cylindrical die sleeve 28, a die sleeve moving mechanism 49 that moves the die sleeve 28 along the central axis 21a, a die body 35, a punch pin 38, a punch pin moving mechanism 51 that moves the punch pin 38 along the central axis 21a, a cylindrical punch sleeve 41, a punch sleeve moving mechanism 53 that moves the punch sleeve 41 along the central axis 21a, a punch body 43, a punch body moving mechanism 55 that moves the punch body 43 along the central axis 21a, and a control unit 57 that controls the die pin moving mechanism 47, die sleeve moving mechanism 49, punch pin moving mechanism 51, punch sleeve moving mechanism 53 and punch body moving mechanism 55.

[0019] [Helical die] The helical die 21 has a hole 22 for housing a cylindrical material 11, and a helical groove 23 on the circumferential surface of this hole 22. The helical die 21 is fixed to a frame or the like which is fixed to the foundation.

[0020] [Daipin] The die pin 25 has a frustoconical portion 26 at its tip (upper end) and moves along its central axis 21a toward the bottom surface 12 of the material 11.

[0021] [Dice Sleeves] The die sleeve 28 moves towards the bottom surface 12 of the material 11 while surrounding the die pin 25. Preferably, a second helical groove 29 is provided on the outer circumferential surface of the die sleeve 28. Preferably, a bead-shaped projection 31 is provided on the upper surface of the die sleeve 28. The bead-shaped projection 31 will be described in detail later.

[0022] [Die body] The die body 35 is a component that surrounds the die sleeve 28 and supports the helical die 21, and is fixed to a frame or the like that which is fixed to the foundation. Preferably, a guide pin 36 is provided on the die body 35, and the tip of this guide pin 36 is fitted into the second helical groove 29. As a result, the die sleeve 28 rotates around the central axis 21a when it moves up and down.

[0023] [Punch pin] The punch pin 38 is a member that moves along the central axis 21a toward the upper surface 13 of the material 11 inside the hole, and has a frustoconical portion 26 at its tip (lower end).

[0024] [Punch Sleeve] The punch sleeve 41 is a component that moves toward the upper surface 13 of the material 11 while surrounding the punch pin 38, and its outer surface is screw-connected to the punch body 43.

[0025] [Punch body] The punch body 43 is a component that surrounds the punch sleeve 41 and has a spiral groove 44 on its inner circumferential surface that connects to the helical groove 23.

[0026] [Various types of mobility mechanisms] Hydraulic cylinders are preferred for the die pin moving mechanism 47, die sleeve moving mechanism 49, punch pin moving mechanism 51, punch sleeve moving mechanism 53, and punch body moving mechanism 55. The die pin moving mechanism 47, the die sleeve moving mechanism 49, and the punch body moving mechanism 55 are supported by a foundation or a frame fixed to the foundation. In contrast, the punch pin moving mechanism 51 and the punch sleeve moving mechanism 53 are supported by the punch body moving mechanism 55 via the punch body 43.

[0027] The die sleeve moving mechanism 49 is positioned on the central axis 21a. This arrangement allows the die sleeve 28 to rotate. Similarly, the punch sleeve moving mechanism 53 is positioned on the central axis 21a. This arrangement allows the punch sleeve 41 to rotate.

[0028] [Control Unit] The control unit 57 performs the operations described later in Figures 3 and 4 in a single unit.

[0029] [Groove width] As shown in Figure 2, the groove width of the helical groove 44 provided in the punch body 43 is defined as G1, and the groove width of the helical groove 23 provided in the helical die 21 is defined as G2. The groove width G1 of the helical groove 44 is set to be wider than the groove width G2 of the helical groove 23. The helical groove 23 and the helical groove 44 are connected via a tapered groove 24 provided on the helical die 21 side.

[0030] During forging, a portion of the material flows from the helical groove 23 into the spiral groove 44, as indicated by arrow (1). If groove widths G1 and G2 are equal, a certain degree of inflow resistance will occur, hindering the flow. In contrast, as in the present invention, if the groove width G1 is wider than the groove width G2, and both are connected by a tapered groove 24 that widens along arrow (1), the inflow resistance is reduced, the flow (diversion) of the tooth material is promoted, and the tooth ends do not lose material.

[0031] Furthermore, after forging, the forged product is ejected from the helical die 21. During ejection, the die body 35 is moved upward, and the top surface of the helical die 21 is opened. The teeth of the forged product move along the helical groove 23 as shown by arrow (1). If the helical groove 23 is a groove of constant width, a certain amount of sliding resistance will be generated. In contrast, if a tapered groove 24 that expands upward is provided at the upper end, as in the present invention, the sliding resistance is reduced, and protrusion becomes easier.

[0032] [Operation of the control unit] Based on Figures 3(a) to 3(c) and 4(a) to 4(c), the operation of the control unit 57 shown in Figure 1, i.e., the operation of the forging apparatus 20, will be explained. In Figure 1, when plastically deforming the material 11 with a force along the central axis 21a, any of the following methods can be employed. 1. Keep the die pin 25 and die sleeve 28 stationary, and lower the punch pin 38 and punch sleeve 41. 2. Keep the punch pin 38 and punch sleeve 41 stationary, and raise the die pin 25 and die sleeve 28. 3. Lower the punch pin 38 and punch sleeve 41, and raise the die pin 25 and die sleeve 28.

[0033] Items 1 and 2 above are easier to control than item 3 above. The above 3. has the advantage that the die sleeve 28 or punch sleeve 41 is half the size of those in 1. and 2. above, thus shortening the cycle time required for forging. Therefore, it is at your discretion to adopt any of the above 1., 2., or 3. Figures 3 and 4, described below, were drawn using the method described in section 3 above for convenience. However, it goes without saying that methods 1 and 2 above would also be acceptable.

[0034] In the preceding step shown in Figure 3(a), a cylindrical material 11 as shown in Figure 3(a) is prepared (material preparation step).

[0035] [Wet blasting and application of one-component lubricant] Preferably, the material preparation process includes a material processing process. The material processing steps consist of wet blasting and a lubricant application process that follows the wet blasting. In wet blasting, a mixture of abrasive and liquid is projected onto the material to polish its surface and create fine irregularities on the surface. In the lubrication process, a one-component lubricant is applied to promote smooth forging.

[0036] Traditionally, this type of treatment was performed using Bonderizing. Bonde treatment requires a series of steps including degreasing, rinsing, etching, rinsing, phosphoric acid treatment, rinsing, neutralization, metal soap treatment, and drying, resulting in high wastewater disposal costs. In contrast, wet blasting only requires wet blasting, and the cost of disposing of the wastewater is minimal. Furthermore, similar to sandblasting and shot blasting, fine irregularities are formed on the surface of the material. These fine irregularities act as anchors for the one-component lubricant. This anchoring action makes it difficult for the lubricant to detach from the material, enabling smoother plastic deformation.

[0037] In parallel, a forging apparatus 20 as shown in Figure 1 is prepared (forging apparatus preparation process).

[0038] Then, as shown in Figure 3(a), the punch pin 38, punch sleeve 41, and punch body 43 are positioned upwards. Next, the material 11 is fed into the hole 22 of the helical die 21, and the material 11 is placed on the die pin 25 (material feeding step). The material 11 may also be placed on the die sleeve 28 instead of the die pin 25.

[0039] Next, the punch body 43 is lowered and brought into contact with the upper surface of the helical die 21. The punch pin 38 and punch sleeve 41 are lowered together with the punch body 43. Then, as shown in Figure 3(b), the punch pin 38 and punch sleeve 41 are lowered so that the punch pin 38 touches the upper surface of the material 11 (punch lowering process). Alternatively, the punch sleeve 41 may be used instead of the punch pin 38 to touch the upper surface of the material 11.

[0040] Next, as shown in Figure 3(c), the die pin 25 is raised so that it protrudes upward from the die sleeve 28, and / or the punch pin 38 is lowered so that it protrudes downward from the punch sleeve 41, thereby performing a first plastic deformation on the material 11 (first plastic deformation process). At this time, preferably, the bead-shaped projection 31 is embedded in the lower surface of the material 11.

[0041] Next, as shown in Figure 4(a), the die pin 25 is lowered to a position where it does not protrude from the die sleeve 28, and the punch pin 38 is raised to a position where it does not protrude from the punch sleeve 41 (pin retraction step). This step forms recesses 14 on the bottom and top surfaces of the material 11.

[0042] The above-mentioned non-protruding position refers to both the position where the upper end of the die pin 25 coincides with the upper surface of the die sleeve 28, and the position where the upper end of the die pin 25 is housed in the die sleeve 28. The same applies to the punch pin 38.

[0043] Next, as shown in Figure 4(b), the die sleeve 28 is raised further and / or the punch sleeve 41 is lowered further, allowing material to flow into the recess 14, thereby performing a second plastic deformation on the material 11 to obtain a forged product 15 (second plastic deformation process). The forged product 15 is an abbreviation for a forged product for helical gears. Due to the second plastic deformation, the recess 14 is transformed into a smaller depression 16.

[0044] Next, as shown in Figure 4(c), the punch pin 38, punch sleeve 41, and punch body 43 are positioned upward. In this state, the die sleeve 28 is raised. The die sleeve 28 rises while rotating due to the guide pin (Figure 1, reference numeral 36) and the second helical groove (Figure 1, reference numeral 29). This rotation causes the forged product 15 to rotate and be ejected upward from the helical die 21 (forged product ejection process).

[0045] In the present invention described above, in the pin retraction step following the first plastic deformation step (Figure 4(a)), the die sleeve 28 is kept stationary and the die pin 25 is lowered, and the punch sleeve 41 is kept stationary and the punch pin 38 is raised. As a result, a recess 14 of the desired size can be formed in the material 11. In the subsequent second plastic deformation process (Figure 4(b)), the die sleeve 28 is raised and the punch sleeve 41 is lowered, allowing material to flow into the recess 14. In other words, the present invention provides a manufacturing technique (forging technique) that can form a recess 14 of a desired size and allows sufficient material to flow in.

[0046] The manufacturing method for forged products described above is preferably carried out using the forging apparatus 20 shown in Figure 1. This forging apparatus 20 incorporates various special structures in its details. The special structure and its function / effect will be explained below.

[0047] [Trusted cone section] As shown in Figure 1, a pointed frustoconical portion 26 is provided at the tip of the die pin 25, and a pointed frustoconical portion 26 is provided at the tip of the punch pin 38. Figure 5(a) is a magnified view of the main part of Figure 1 (without the material shown). Since the die sleeve 28 is cylindrical, a triangular cross-sectional space 61 is formed between the frustoconical portion 26 and the die sleeve 28.

[0048] [Function of the truncated cone] Figure 5(b) is an enlarged view of the main part of Figure 4(b). During the second plastic deformation, the material 11 is compressed, and a portion of the material 11 flows into the recess 14 and enters the space 61. In other words, the presence of the triangular cross-sectional space 61 promotes a flow separation effect. The improved flow diversion effect prevents material loss in the teeth, eliminating the need to excessively increase the pressing force to compensate for material loss, thus extending the lifespan of the mold.

[0049] In this embodiment, the material 11 is vertically symmetrical, but in the case of an asymmetrical shape, the frustoconical portion 26 can be provided on the important side (upper or lower) and omitted on the other side. Therefore, in Figure 1, the frustoconical portion 26 only needs to be provided at least one of the tips of the die pin 25 and the punch pin 38.

[0050] [Bead-shaped protrusion] In Figures 3(c) and 4(a)-(c), the bead-shaped projection 31 is embedded in the bottom surface of the material 11. Then, in Figure 4(c), the die sleeve 28 is raised and rotated. This raising and rotating motion allows the forged product 15 to be ejected from the helical die 21. During rotation, the bead-shaped projection 31's engagement ensures that the die sleeve 28 is reliably transmitted to the forged product 15. As a result, smooth ejection can be achieved.

[0051] Figure 6(a) is a view taken along arrow 6a in Figure 5(a), and Figure 6(b) is a diagram showing the operation. As shown in Figure 6(a), the bead-shaped protrusions 31 are arranged on radial lines 62 extending from the central axis 21a in a plan view. For example, three bead-shaped protrusions 31 are arranged around the central axis 21a at equal intervals (θ=120°). Furthermore, as shown in Figure 6(c), two bead-shaped protrusions 31 are arranged at equal pitches (θ=180°) around the central axis 21a. There may be four or more bead-shaped protrusions 31.

[0052] In Figure 4(b), the tissue near the bead-like projection 31 is divided into two streams, indicated by arrows (2) and (3). The tooth is formed via arrow (2). The tissue flows into the recess (Figure 5(b), reference numeral 14) via arrow (3). Figure 6(b) shows these stream divisions in a plan view.

[0053] As shown in Figure 6(b), arrow (2) moves away from the central axis 21a. Arrow (3) moves toward the central axis 21a. Because adjacent bead-shaped projections 31 are V-shaped, flow is promoted in the direction that opens the V-shape, and flow is hindered in the direction that closes the V-shape. As a result, the flow indicated by arrow (3) becomes smaller, and the flow indicated by arrow (2) becomes significantly larger than that of arrow (3). The flow indicated by arrow (2) contributes to the shaping of the tooth. As a result, the occurrence of tooth decay is prevented.

[0054] [Variations of bead-shaped protrusions] Furthermore, multiple bead-shaped protrusions 31 may be arranged in parallel, as shown in Figure 6(d). Furthermore, as shown in Figure 6(e), an annular bead 63 may be added to the radial bead-like projection 31. The annular bead 63 can be used to distinguish between arrow (2) and arrow (3). Furthermore, as shown in Figure 6(f), an annular bead 64 may be added to the radial bead-like projection 31.

[0055] [Twist angle of the second helical groove] The die sleeve 28 in Figure 1 has a second helical groove 29 on its outer surface. In order to synchronize the vertical stroke and rotation of the die sleeve 28 and the helical die 21, the twist angle of the second helical groove 29 is appropriately set according to the diameter of the point of application (distance from the central axis 21a (radius)). In this embodiment, since the diameters of the points of application of the die sleeve 28 and the helical die 21 are different, the helix angle of the second helical groove 29 is set to a different angle from the helix angle of the helical groove 23. However, if the diameters of the points of application are the same, the helix angle of the second helical groove 29 is set to be the same as the helix angle of the helical groove 23.

[0056] By synchronizing the rotation of the die sleeve 28 with the rotation of the forged product 15, smooth ejection can be achieved. In addition, since the rotational moment increases in proportion to the distance from the center of rotation, the rotational moment can be easily increased by arranging multiple bead-shaped protrusions 31 at equal pitches along the radial lines 62, as shown in Figure 6(a). A larger rotational moment allows for smoother projection.

[0057] [Cross-sectional shape of the bead-like protrusion] As shown in Figure 7(a), the cross-section of the bead-shaped projection 31 may be rectangular. The rectangular cross-section bead-like projection 31 has the advantage of reducing processing costs due to its simple structure, but it has the disadvantage of making it difficult to extrude the forged product (Figure 4(c), reference numeral 15). In addition, when a horizontal force P is applied to the upper end of the bead-like projection 31, the bending stress at the base increases. As a countermeasure, it is necessary to increase the width of the bead-like projection 31.

[0058] Alternatively, as shown in Figure 7(b), the cross-section of the bead-shaped projection 31 may be an isosceles trapezoid. The isosceles trapezoidal bead-shaped projection 31 has the advantage of facilitating the protrusion of the forged product (Figure 4(c), reference numeral 15) and reducing stress at the base. However, the forged product tends to move upward along the leg 65. An upward axial force is applied to the forged product. This affects the helical groove 23 of the helical die 21 shown in Figure 4(c). Specifically, this has the disadvantage of increasing the wear rate of the helical groove 23.

[0059] Figure 7(c) provides a structure that can overcome the shortcomings of Figures 7(a) and (b). The bead-shaped projection 31 shown in Figure 7(c) has an unequal-legged trapezoidal cross-section. The unequal-legged trapezoid consists of an upper base 66, a lower base 67 that is longer than the upper base 66, and a pair of legs 65. Of the pair of legs 65, the one that leads during upward rotation is called the front leg 68, and the other is called the rear leg 69. The inclination angle θ2 of the rear leg 69 is set to be larger than the inclination angle θ1 of the front leg 68 with respect to the central axis 21a.

[0060] The unequal-legged trapezoidal bead-shaped projection 31 has the advantage of extending the lifespan of the helical die 21 because, since the front legs 68 are upright, no upward axial force is applied to the forged product. In addition, because it protrudes upward, it has the advantage of easily separating the forged product from the bead-shaped projection 31 during ejection. Furthermore, because the rear legs 69 are angled, it has the advantage of reducing stress at the base.

[0061] As shown in Figure 8(a), the bead-like projection 31 may be a simple horizontally elongated rectangular shape. However, as shown in Figure 8(b), it is preferable that the bead-shaped projection 31 has a beveled surface 71 at the end closer to the central axis 21a.

[0062] Figure 8(c) is a magnified view of a portion of Figure 4(b). Since the bead-shaped projection 31 protrudes upward, the forged product 15 can be easily separated upward from the bead-shaped projection 31. Additionally, a small portion of the meat flows into slope 71. This has the advantage of promoting the separation of the meat. Therefore, Figure 8(b) can be said to be a more preferable structure than Figure 8(a).

[0063] [Arrangement of bead-like protrusions] As shown in Figure 9, preferably, the bead-shaped projection 31 is positioned to bite into the bottom surface of the material 11 (forged product 15) between a pair of adjacent helical teeth 17, among the multiple helical teeth 17 formed on the material 11 (forged product 15).

[0064] The flow of tissue toward the helical teeth 17 is slightly obstructed by the bead-like projections 31. However, by placing the bead-like projections 31 between adjacent pairs of helical teeth 17, the reduction in tissue flow can be minimized. As a result, the flow is not obstructed, and healthy helical teeth 17 can be formed.

[0065] [Guide pin position] As shown in Figure 1, a horizontally extending guide pin 36 is inserted into the die body 35, and the tip of the guide pin 36 is fitted into the second helical groove 29 on the die sleeve 28 side. As the second helical groove 29 is guided by the guide pin 36, the die sleeve 28 rotates while rising. During this process, the die sleeve 28 rises over a long distance from Figure 3(a) to Figure 4(c).

[0066] To achieve this, a long second helical groove 29 is provided on the outer surface of the die sleeve 28. Since the die sleeve 28 is a long material that extends vertically, the long second helical groove 29 can be easily provided on the die sleeve 28.

[0067] Furthermore, the die sleeve 28 is made of expensive and hard mold steel, while the guide pin 36 is made of inexpensive and softer ordinary steel than the die sleeve 28. In this case, the guide pin 36 will wear out. However, since the guide pin 36 is simply attached to the die body 35, it is easy to replace. Therefore, by inserting the guide pin 36 into the die body 35, maintenance and management of the forging apparatus 20 becomes easier.

[0068] [Comparison between the depth of the depression and the height of the bead-like protrusion] The forged product (forged product for helical gear) 15 shown in Figure 4(c) has a recess 16 remaining in which material has flowed into the recess (Figure 4(a), reference numeral 14) formed by the die pin 25. The recess 16 has a smaller cross-section than the recess (Figure 4(a), reference numeral 14).

[0069] On the other hand, the greater the height Hb of the bead-shaped projection 31, the better its bonding performance with the material 11. However, the presence of the bead-shaped projection 31 obstructs the flow separation shown by arrows (2) and (3) in Figure 4(b). The inhibition of the bead-shaped projection 31 is reduced as its height Hb decreases. Thus, setting the height Hb of the bead-shaped projection 31 is important. Therefore, we will consider the height Hb.

[0070] In Figure 4(c), it is desirable to set the height Hb of the bead-shaped projection 31 to be smaller than the depth L of the depression 16. Note that the depth L of the recess 16 varies with each forged product 15. However, the amount of variation is small. Therefore, the depth of the recesses of multiple prototypes is measured, and the average value is taken as the depth L of the recess 16. Alternatively, because the amount of variation is small, the depth L of the recess 16 can be estimated by simulation on the drawing.

[0071] If the height Hb of the bead-shaped projection 31 is less than the depth L of the depression 16, the flow diversion shown in Figure 4(b) (arrows (2) and (3)) is well maintained, and as a result, the gingiva is preferably filled all the way to the lower end of the tooth.

[0072] Furthermore, while the manufacturing method for helical gear forgings of the present invention can be performed using the forging apparatus 20 shown in Figure 1, it is also permissible to manufacture them using a forging apparatus with a similar structure. [Industrial applicability]

[0073] This invention is suitable for manufacturing forged products for helical gears. [Explanation of symbols]

[0074] 11...Material, 12...Bottom surface, 13...Top surface, 14...Recess, 15...Forged product, 16...Indentation, 17...Helical tooth, 20...Forging device, 21...Helical die, 21a...Central axis, 22...Hole, 23...Helical groove, 24...Tapered groove, 25...Die pin, 26...Truss-cone section, 28...Die sleeve, 29...Second helical groove, 31...Bead-shaped projection, 35...Die body, 36...Guide pin, 38...Punch pin, 41...Punch sleeve, 43...Punch body, 44...Helical groove, 47... Die pin moving mechanism, 49... Die sleeve moving mechanism, 51... Punch pin moving mechanism, 53... Punch sleeve moving mechanism, 55 Punch body moving mechanism, 57... Control unit, 62...Radial, 65...Legs, 66...Upper base, 67...Lower base, 68...Fore legs, 69...Third legs, 71...Slope, G1...Groove width of spiral groove, G2...Groove width of helical groove, Hb...Height of bead-like projection, L...Depth of depression.

Claims

1. The material preparation process involves preparing cylindrical material, A forging apparatus preparation step comprising: a forging apparatus comprising: a helical die having a hole for housing a cylindrical material and a helical groove on the circumferential surface of the hole; a die pin that moves along the central axis of the helical die toward the bottom surface of the material in the hole; a die sleeve that moves toward the bottom surface of the material while surrounding the die pin; a die body that supports the helical die while surrounding the die sleeve; a punch pin that moves along the central axis toward the top surface of the material in the hole; a punch sleeve that moves toward the top surface of the material while surrounding the punch pin; and a punch body that moves up and down while surrounding the punch sleeve; A material feeding step in which the punch pin, the punch sleeve, and the punch body are positioned upward, the material is fed into the hole of the helical die, and the material is placed on the die pin or the die sleeve, A punch lowering step in which the punch body is lowered and brought into contact with the upper surface of the helical die, and the punch pin and the punch sleeve are lowered and brought into contact with the upper surface of the material, A first plastic deformation step in which the die pin is raised so that it protrudes upward from the die sleeve, and / or the punch pin is lowered so that it protrudes downward from the punch sleeve, thereby performing a first plastic deformation on the material, A pin retraction step is performed by lowering the die pin to a position where it does not protrude from the die sleeve, and raising the punch pin to a position where it does not protrude from the punch sleeve, thereby forming recesses on the bottom and top surfaces of the material. A second plastic deformation step is performed on the material to obtain a forged product by further raising the die sleeve and / or further lowering the punch sleeve, thereby allowing material to flow into the recess, A method for manufacturing a forged product for a helical gear, comprising: a forging product ejection step in which the punch pin, the punch sleeve, and the punch body are positioned upward, and the forged product is ejected from the helical die by the die sleeve.

2. A forging apparatus for manufacturing forged products for helical gears, A helical die having a hole for housing a cylindrical material and a helical groove on the circumferential surface of this hole, A die pin moves along the central axis of this helical die toward the bottom surface of the material in the hole, This dipin moving mechanism moves the dipin, A die sleeve that surrounds the die pin and moves toward the bottom surface of the material, This die sleeve moving mechanism moves the die sleeve, A die body that surrounds the die sleeve and supports the helical die, A punch pin that moves along the central axis toward the upper surface of the material in the hole, This punch pin moving mechanism moves the punch pin, A punch sleeve that moves toward the upper surface of the material while surrounding the punch pin, This punch sleeve moving mechanism moves the punch sleeve, A punch body that moves up and down while enclosing the punch sleeve, A punch body movement mechanism that moves the punch body, The device comprises a control unit that controls the die pin moving mechanism, the die sleeve moving mechanism, the punch pin moving mechanism, the punch sleeve moving mechanism, and the punch body moving mechanism, thereby performing a first plastic deformation on the material by raising the die pin so that it protrudes upward from the die sleeve, and / or lowering the punch pin so that it protrudes downward from the punch sleeve; then lowering the die pin to a position where it does not protrude from the die sleeve, and raising the punch pin to a position where it does not protrude from the punch sleeve, thereby forming recesses on the bottom and top surfaces of the material; and then raising the die sleeve further, and / or lowering the punch sleeve further, thereby performing a second plastic deformation on the material by allowing material to flow into the recesses. A forging apparatus characterized in that the punch body has a spiral groove connected to the helical groove, the width of the spiral groove is set to be wider than the width of the helical groove, and the helical groove and the spiral groove are connected via a tapered groove provided on the helical die side.

3. A forging apparatus according to claim 2, A forging apparatus characterized in that at least one of the tips of the die pin and the punch pin is a pointed frustoconical portion.

4. A forging apparatus according to claim 2, The die sleeve is characterized in that it has a plurality of bead-shaped protrusions at its tip that bite into the bottom surface of the material, and the bead-shaped protrusions are arranged radially from the central axis in a plan view.

5. A forging apparatus according to claim 4, The bead-shaped protrusions are evenly arranged at equal pitches around the central axis in a plan view. The forging apparatus is characterized in that the die sleeve has a second helical groove that rotates itself around the central axis when raised, and the twist angle of this second helical groove is set to be synchronized with the stroke amount of the helical die.

6. A forging apparatus according to claim 5, The forging apparatus is characterized in that the bead-like projection has a cross-section of an unequal-legged trapezoid, the unequal-legged trapezoid consists of an upper base, a lower base longer than the upper base, and a pair of legs, and when the leg that leads during upward rotation is called the front leg and the other leg is called the rear leg, the inclination angle of the rear leg is set to be greater than the inclination angle of the front leg with respect to the central axis.

7. A forging apparatus according to claim 4, The forging apparatus is characterized in that the bead-like projection has a beveled surface at the end closest to the central axis.

8. A forging apparatus according to claim 4, The forging apparatus is characterized in that the bead-like projection is positioned between a pair of adjacent helical teeth among a plurality of helical teeth formed on the material, so as to bite into the bottom surface of the material.

9. A forging apparatus according to claim 5, A forging apparatus characterized in that the die body is provided with a guide pin that fits into the second helical groove.

10. A forging apparatus according to claim 4, The forged helical gear has a recess remaining on its bottom surface in which material has flowed into a recess formed by the die pin. A forging apparatus characterized in that the height of the bead-like projection is set to be less than the depth of the depression.

11. A method for manufacturing a forged product for helical gears according to claim 1, The aforementioned material preparation process includes a material processing process, The aforementioned material processing process consists of a wet blasting treatment and a lubricant application treatment following this wet blasting treatment. In the aforementioned wet blasting process, a mixture of abrasive and liquid is projected onto the material to polish the surface of the material and create fine irregularities on the surface. A method for manufacturing a forged product for helical gears, characterized in that the lubricant application process involves applying a one-component lubricant that promotes smooth forging.

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