Gear material, manufacturing method thereof, and finishing method

Abstract

To provide a gear blank with a relatively large shape such as differential ring gear or the like having spur tooth profile or helical tooth profile on a circumference, that can improve yield of finished products, reduce running costs for gear cutting by a hob processing machine, dramatically increase a cutting speed to reduce a processing time, and reduce total manufacturing costs.SOLUTION: A gear blank comprises a ring shape having an outer diameter of 170 mm or more and a circumference thickness of 30 mm or more, and has spur tooth profile or helical tooth profile with a machining allowance of 0.2 to 2.0 mm on one side.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a gear material, a manufacturing method thereof, and a finishing method thereof, and more particularly to a gear material such as a differential ring gear (final gear) having a spur tooth profile or a helical tooth profile on its outer periphery, a manufacturing method thereof, and a finishing method using a hobbing machine. [Background technology]

[0002] Conventionally, differential ring gears have a relatively large shape, with an outer diameter of approximately 200 mm and a tooth width of approximately 40 mm, and therefore have been manufactured by the methods shown in (1) to (3), for example (see Patent Document 1). (1) Forging ring-shaped material using a 4000 ton press (2) The German Wagner method: forging → rolling → orbital rolling (3) Rolling method using two edge rolls and one backing roll In all of these methods, the outer periphery of the material is subjected to gear cutting using a hobbing machine to form a tooth profile on the outer periphery, and then shaving, carburizing heat treatment, and shot blasting are performed, and the tooth profile is finished by grinding or the like.

[0003] Of these, the method of forging the ring-shaped material (1) using a 4000 ton press involves, as shown in Figure 3, upsetting and forging the billet from above and below in the first step to form a barrel-shaped blank (a1), then rolling the blank (a1) from above and below to form a disk-shaped blank (a2) in the second step, die-forging this with a 4000 ton press to form the semi-finished product shape (a3) ​​in the third step, and finally punching out the central web in the fourth step to form the final product shape (a4). However, this method has the drawback of requiring a large number of steps, resulting in high mold costs.

[0004] In addition, in the German Wagner method of forging → rolling → swing rolling (2), as shown in Figure 4, in the first process, a billet (b1) is upset forged from above and below to form a disk-shaped blank (b2), and in the second process this is die-forged using a 1600 ton press to form the rough product shape (b3), and in the third process this is punched out to form the central web (b4), and then in the fourth process it is rolled to form the semi-finished product shape (b5), and finally in the fifth process it is swing rolled to form the final product shape (b6). However, this method requires a large number of different types of equipment, and the orbital rolling dies are very expensive.Furthermore, not only does it involve multiple processes, but because rolling and rolling are performed using two heats, the heating costs are doubled, so the overall material costs are still high.

[0005] In addition, the rolling method (3) using two edge rolls and one backing roll includes a forging press process in which a billet (c1) is set into a disk-shaped blank (c2-c3) and the center of the bottom of this blank (c3) is punched out, as shown in Figure 5, and then the forged blank (c4) is rolled using two edge rolls 11 and 12 that apply axial pressing force to the forged blank (c4) and one backing roll 13 that applies radially inward pressing force to give the outer peripheral surface shape of the final product, to form the final product shape (d). However, this method has the drawback that the final product shape (d) is ring-shaped, and when cutting the gears with a hobbing machine, the machining allowance is large, which reduces the processing yield and shortens the tool life. Also, the cutting speed is usually up to 200 m / min, which is time-consuming and increases the cost of the machining process. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 7-275989 Summary of the Invention [Problem to be solved by the invention]

[0007] In view of the problems associated with the conventional methods for manufacturing differential ring gears, the present invention improves the yield of finished products, reduces the running costs of gear cutting using a hob machine, dramatically increases the cutting speed, reduces processing time, and reduces total manufacturing costs. An object of the present invention is to provide a gear material having a relatively large shape, such as a differential ring gear having a spur tooth shape or a helical tooth shape on the outer periphery, and a manufacturing method thereof and a finishing method using a hob machine. [Means for solving the problem]

[0008] To achieve the above object, the gear material of the present invention is characterized in that it has a ring shape with an outer diameter of 170 mm or more (approximately 170 to 230 mm) and an outer peripheral thickness of 30 mm or more (approximately 30 to 50 mm), and has spur or helical teeth on the outer peripheral surface with a machining allowance of 0.2 to 2.0 mm on one side.

[0009] In this case, the gear module may be 1.5 to 3.5.

[0010] The method for producing a gear material of the present invention is characterized in that the gear material is formed from a billet only by hot forging.

[0011] The method for finishing a gear material of the present invention is characterized in that the gear material is finish-processed by a hobbing machine at a cutting speed of 250 to 500 m / min. Here, the cutting speed is a value when a cutter made of high-speed tool steel (HSS) is used. [Effects of the Invention]

[0012] The gear material, manufacturing method thereof, and finishing method using a hobbing machine of the present invention can improve the yield of finished gear materials having a relatively large shape, such as differential ring gears having spur teeth or helical teeth on the outer periphery, reduce the running costs of gear cutting using a hobbing machine, dramatically increase the cutting speed to reduce processing time, and reduce total manufacturing costs. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is an explanatory diagram showing an embodiment of a method for manufacturing a gear material according to the present invention. [Figure 2] 1A is an explanatory diagram of the hob machining allowance of the present invention and the conventional example, and FIG. 1B is an explanatory diagram of the yield of the finished product of the present invention and the conventional example. [Figure 3] This is an explanatory diagram of the method for forging a ring-shaped material using a 4000 ton press. [Figure 4] This is an explanatory diagram of the German Wagner method of forging → rolling → orbital rolling. [Figure 5] FIG. 1 is an explanatory diagram of a rolling method using two edge rolls and one backing roll. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of a gear material, a manufacturing method thereof, and a finishing method using a hobbing machine according to the present invention will be described with reference to the drawings.

[0015] FIG. 1 shows an embodiment of the method for manufacturing a gear material according to the present invention. This manufacturing method for gear material uses a line that was previously used to forge ring gears without gears, and forms the tooth profile in a series of processes. First, a billet (cylindrical blank) 1 is heated to a predetermined temperature in an induction heating furnace. In a multi-step upsetting process, it is upset into a disk-shaped blank 2. In a roughing process, the volume is distributed and formed into blank 3 with a thick outer wall. In a finishing process, a forging die (a forging die formed to a shape corresponding to the spur tooth or helical tooth profile that forms the inner peripheral surface) is used to form gear blank 4 into a ring-shaped gear blank 4 with an outer diameter of 170 mm or more (approximately 170 to 230 mm), an outer peripheral thickness of 30 mm or more (approximately 30 to 50 mm), and a module 1.5 to 3.5 spur tooth or helical tooth profile (helix angle: maximum 35°) with a machining allowance of 0.2 to 2.0 mm (preferably 0.2 to 1.5 mm, more preferably 0.2 to 1.0 mm) on each side. In a final piercing process, a hole is formed in the gear blank 5 to obtain the gear blank 5. Here, the tooth profile portion has a small volume and is prone to temperature loss, so it is necessary to maintain the temperature. However, in this process, the gear blank 5 is formed from the billet 1 by hot forging alone in a press, and the process is completed in a short period of time. Since the temperature is sufficiently high, no reheating is required. More specifically, the cycle time for each process of forming the gear blank 5 from the billet 1 is set to 10 seconds or less, for example, about 4 to 6 seconds. This facilitates temperature control and reduces the amount of oxide scale that forms.

[0016] After hot forging, the gear material 5 is subjected to material heat treatment (forged high-temperature annealing or normalizing, or as-forged), shot blasting, and then race and hole machining, hobbing (machining the tooth profile on the outer peripheral surface using a hobbing machine), heat treatment (carburizing or induction hardening and tempering, etc.), and tooth surface grinding, etc., as necessary, to be finished into a finished product.

[0017] Here, the spur tooth profile or helical tooth profile formed using the forging mold for the gear material 5 can be hobbed (finishing the tooth profile on the outer surface using a hobbing machine) by matching the phase of the tooth profile with a hobbing machine that is used to process conventional ring-shaped materials. As shown in Figure 2(a), the gear blank 5 has a tooth profile on its outer circumferential surface with a machining allowance of 0.2 to 2.0 mm on each side. This allows for a small machining allowance and allows for finish machining at a high speed of up to 500 m / min (250 to 500 m / min), thereby shortening the machining time. The cutting speeds shown here are values ​​obtained when using a cutter made of high-speed tool steel (high-speed steel) (cutter diameter: φ85 mm, number of threads: 4, number of grooves: 14). Generally, the cutting speed of a cutter made of high-speed tool steel (high-speed steel) is around 200 m / min.

[0018] The specifications (example) of the finished product (gear blank 5) manufactured in this manner are shown below. [Specifications of the finished product (gear material 5)] ·Outer diameter: 206mm Reference circle diameter: 163mm -Outer circumference thickness (tooth width): 40mm Number of teeth: 51 Module: 3.2 ·Tooth length: 8.7mm Twist angle: 31° Removal allowance: 0.2~1.0mm per side

[0019] This improves the yield of finished gear materials with relatively large shapes, such as differential ring gears with spur or helical teeth on the outer periphery, reduces the running costs of gear cutting using a hob machine (including tool costs due to improved tool life), dramatically increases cutting speeds, reduces processing time, and reduces total manufacturing costs. Specifically, as shown in FIG. 2(b), by setting the machining allowance to 0.2 to 2.0 mm (preferably 0.2 to 1.5 mm, more preferably 0.2 to 1.0 mm) on one side, the yield of the finished product is improved by approximately 10%, from 56% in the conventional example (ring gear without gear) to 65% in the example, and the amount of cutting required for hobbing (finishing the tooth profile on the outer surface using a hobbing machine) can be reduced (the amount of cutting can be reduced to approximately 1 / 2 to 1 / 3). Furthermore, since it is possible to increase the cutting speed to 250-500 m / min, combined with the reduction in the amount of cutting, the actual processing time can be reduced from approximately 42 seconds in the conventional example (ring gear without gears) to approximately 14 seconds in the example, thereby shortening the cycle time (by more than 40%). Furthermore, since the cutting load due to the hobbing is small, the temperature rise of the workpiece (gear material 5) is suppressed, and temperature control during the hobbing is not required. Furthermore, the spur tooth profile or helical tooth profile formed on the outer peripheral surface of the gear material 5 using a forging die has a high strength because the metal flow is not cut.

[0020] The gear material, manufacturing method thereof, and finishing method thereof according to the present invention have been described above based on the embodiments. However, the present invention is not limited to the configurations described in the above embodiments, and the configurations can be changed as appropriate within the scope of the invention. [Industrial Applicability]

[0021] The gear material, manufacturing method and finishing method thereof of the present invention can improve the yield of finished products, reduce the running costs of gear cutting using a hob machine, dramatically increase the cutting speed to reduce processing time, and reduce total manufacturing costs. Therefore, the gear material can be widely used for gear materials with relatively large shapes, such as differential ring gears having spur teeth or helical teeth on the outer periphery, as well as for manufacturing and finishing methods thereof. [Explanation of symbols]

[0022] 1 Billet (cylindrical material) 2 blank 3 Blank 4 Gear material 5 Gear material

Claims

1. A manufacturing method for a gear material, comprising forming a gear material from a billet by only hot forging, into a ring-shaped gear material having an outer diameter of 170 mm or more and an outer peripheral thickness of 30 mm or more, the gear material having a spur tooth profile or a helical tooth profile with a machining allowance of 0.2 to 2.0 mm on one side on an outer peripheral surface parallel to the gear axis.

2. A method for manufacturing a gear material as described in claim 1, characterized in that the gear module of the gear material is 1.5 to 3.

5.

3. A method for manufacturing a gear material as described in claim 1 or 2, characterized in that the gear material is formed using a forging mold whose inner surface is formed in a shape corresponding to the spur tooth shape or helical tooth shape to be formed in the finishing process.

4. A method for finishing a gear material, comprising finishing a gear material manufactured by the manufacturing method of a gear material according to claim 1, 2 or 3 with a hobbing machine at a cutting speed of 250 to 500 m / min.

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