Strain Wave Gear Manufacturing Method

Abstract

A method for manufacturing a wave gear device comprises: a hot forming step of hot forming an alloy steel composed of nickel, copper, molybdenum, and silicon into a first molded product having a silk hat-type housing shape at a first temperature of 950 to 1300°C; a normalizing step of isolating the first molded product at the first temperature for a predetermined time and, after the isolating time has elapsed, slowly cooling the first molded product to a second temperature of 750 to 900°C; an austempering step of isolating the first molded product at the second temperature and then cooling it to a third temperature of 250 to 400°C to form residual austenite in the first molded product; a heat treatment step of isolating the first molded product that has undergone the austempering step at the third temperature and then cooling it at room temperature to stabilize the microstructure of the first molded product; and a gear forming step of turning and toothing the first molded product that has undergone the heat treatment step to form a second molded product having a soluble external gear shape. The method comprises a step and a trip step of applying impact to the surface of the second molded product to induce a processing-induced transformation in some of the austenite remaining in the second molded product, thereby transforming the surface of the second molded product into martensite.

Description

Technology Field

[0001] The following description relates to a method for manufacturing a wave gear device. Background Technology

[0003] Generally, a wave gear unit consists of a wave generator, a flex spline, and a circular spline. A wave gear unit is a type of high-precision wave gear unit that achieves reduction by utilizing the dimensional difference between the flex spline and the circular spline, which are shape-deformed by waves generated by the wave generator. Wave gear units are compact and lightweight, yet capable of achieving high reduction ratios, have a large capacity for transmitted torque, and have low backlash, so they are used in industrial fields that require precise reduction ratios.

[0004] Due to the usage characteristics of such wave gear devices, additional features such as flex splines and circular splines require wear resistance, fatigue strength, and impact resistance. Accordingly, there is a need to develop a method for manufacturing wave gear devices using an environmentally friendly heat treatment method that satisfies the wear resistance, fatigue strength, and impact resistance of the wave gear device material while minimizing surface deformation.

[0005] A patent for such a wave gear device is published patent application 10-2023-0121146.

[0006] The aforementioned background technology is one that the inventor possessed or acquired in the process of deriving the contents of the disclosure of the present application, and it cannot be considered as prior art disclosed to the general public prior to the filing of this application. The problem to be solved

[0008] The objective of the embodiment is to provide a method for manufacturing a wave gear device having higher surface hardness and tensile strength than the prior art.

[0009] The problems to be solved in the embodiments are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below. means of solving the problem

[0011] First, a method for manufacturing a wave gear device according to one embodiment will be described. A method for manufacturing a wave gear device according to one embodiment comprises: a hot forming step of hot forming an alloy steel composed of nickel, copper, molybdenum, and silicon into a first molded product having a silk hat-type housing shape at a first temperature of 950 to 1300°C; a normalizing step of isolating the first molded product at the first temperature for a predetermined time, and after the isolating time has elapsed, slowly cooling the first molded product to a second temperature of 750 to 900°C; an austempering step of isolating the first molded product at the second temperature and then cooling it to a third temperature of 250 to 400°C to form residual austenite in the first molded product; a heat treatment step of isolating the first molded product that has undergone the austempering step at the third temperature and then cooling it at room temperature to stabilize the microstructure of the first molded product; and turning and toothing the first molded product that has undergone the heat treatment step to form a second molded product having a soluble external gear shape. It includes a gear forming step and a trip step of applying impact to the surface of the second molded product to induce a processing-induced transformation in some of the austenite remaining in the second molded product, thereby transforming the surface of the second molded product into martensite.

[0012] According to one embodiment, the trip step can shot-peen the surface of the second molded product.

[0013] According to one embodiment, the hot forming step can hot forge the alloy steel at the first temperature.

[0015] Next, a method for manufacturing a wave gear device according to another embodiment comprises: a hot forming step of hot forming an alloy steel composed of nickel, copper, molybdenum, and silicon into a first molded product having a silk hat-type housing shape at a first temperature of 950 to 1300°C; a normalizing step of isothering the first molded product at the first temperature for a predetermined time; a martensitizing step of rapidly cooling the first molded product to a temperature below the martensitizing temperature; an austempering step of heating the first molded product that has undergone the martensitizing step to a second temperature of 750 to 900°C, isothering the first molded product at the second temperature for a predetermined time, and then cooling the first molded product to a third temperature of 250 to 400°C to form residual austenite in the first molded product; and stabilizing the structure of the first molded product by isothering the first molded product that has undergone the austempering step at the third temperature and then cooling it at room temperature. The method includes a heat treatment step, a gear forming step in which the first molded product that has undergone the heat treatment step is turned and toothed to form a second molded product having a soluble external gear shape, and a tripping step in which impact is applied to the surface of the second molded product to induce a process-induced transformation in some of the austenite remaining in the second molded product, thereby transforming the surface of the second molded product into martensite.

[0016] According to one embodiment, the trip step can shot-peen the surface of the second molded product.

[0017] According to one embodiment, the hot forming step can hot forge the alloy steel at the first temperature. Effects of the invention

[0019] According to the embodiments, the method for manufacturing a wave gear device induces transformation-induced plasticity in the residual austenite through a tripping step to transform the surface of the second molded product into martensite. As a result, the second molded product increases both strength and elongation, thereby providing superior impact resistance and rigidity compared to the prior art.

[0020] In addition, the surface and interior of the second molded product are composed of a dual structure of martensite and retained austenite, allowing it to resist instantaneous impact forces through immediate changes in physical properties.

[0021] The effects of the method for manufacturing a wave gear device according to the embodiments are not limited to those mentioned above, and other unmentioned effects will be clearly understood by a person skilled in the art from the description below. Brief explanation of the drawing

[0023] FIG. 1 is a flowchart of a method for manufacturing a wave gear device according to one embodiment. FIG. 2 is a temperature graph from the hot forming step to the heat treatment step according to one embodiment. FIG. 3 is a flowchart of a method for manufacturing a wave gear device according to another embodiment. FIG. 4 is a temperature graph from the hot forming step to the heat treatment step according to another embodiment. FIG. 5 is a cross-sectional view of a wave gear device according to two embodiments. Specific details for implementing the invention

[0024] Hereinafter, embodiments are described in detail with reference to the attached drawings. However, various modifications may be made to the embodiments, and thus the scope of the patent application is not limited or restricted by these embodiments. It should be understood that all modifications, equivalents, and substitutions to the embodiments are included within the scope of the rights.

[0025] The terms used in the embodiments are for illustrative purposes only and should not be interpreted as intended to be limiting. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as "comprising" or "having" are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0026] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the embodiments pertain. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0028] In addition, when describing with reference to the attached drawings, identical components are assigned the same reference numeral regardless of drawing symbols, and redundant descriptions thereof are omitted. In describing the embodiments, if it is determined that a detailed description of related prior art could unnecessarily obscure the essence of the embodiments, such detailed description is omitted.

[0029] Additionally, terms such as first, second, A, B, (a), (b), etc., may be used when describing the components of the embodiments. These terms are intended merely to distinguish the components from other components, and the nature, order, or sequence of the components is not limited by these terms. Where it is stated that a component is "connected," "combined," or "joined" to another component, it should be understood that the component may be directly connected or joined to the other component, but that another component may also be "connected," "combined," or "joined" between each component.

[0030] Components included in any one embodiment and components having common functions shall be described using the same names in other embodiments. Unless otherwise stated, the descriptions given in any one embodiment may also apply to other embodiments, and specific descriptions shall be omitted to the extent of overlap.

[0031] An embodiment is described below with reference to FIGS. 1, 2, and 5. For reference, FIG. 1 is a flowchart of a method for manufacturing a wave gear device according to an embodiment, FIG. 2 is a temperature graph from a hot forming step (S1) to a heat treatment step (S4) according to an embodiment, and FIG. 5 is a cross-sectional view of a wave gear device (10) according to two embodiments.

[0032] A method for manufacturing a wave gear device according to one embodiment includes a hot forming step (S1), a normalizing step (S2), an austempering step (S3), a heat treatment step (S4), a gear forming step (S5), and a tripping step (S6).

[0033] The hot forming step (S1) is performed on an alloy steel composed of nickel, copper, molybdenum, and silicon, ranging from 950 to 1300 At the first temperature (100), a first molded product having a silk hat type housing shape is hot-molded.

[0034] At this time, the hot forming step (S1) hot forges the alloy steel at a first temperature (100). Through this, the hot forming step (S1) can increase the workability of the alloy steel and improve its mechanical properties. A high-pressure press or a hammer can be used as the forging device, and a mold process can be performed after hot forging to realize a silk hat shape.

[0035] The normalizing step (S2) involves keeping the first molded product at a first temperature (100) for a predetermined period of time, and when the constant temperature time has elapsed, keeping the first molded product at 750 to 900 The first molded product is cooled to a second temperature (110). Through this, the internal structure of the first molded product becomes uniform, and the hardness and strength are improved and residual stress is removed.

[0036] In addition, since the normalizing step (S1) utilizes the temperature at which the alloy steel was hot-formed as the normalizing start temperature, the process from forming the first product to the slow cooling during normalizing can be processed all at once, thereby reducing thermal energy consumption and shortening the production process.

[0037] The austempering step (S3) involves keeping the first molded product constant at the second temperature (110) for 250 to 400 The first molded product is cooled to a third temperature (120) to form residual austenite. At this time, the specific temperature settings of the second temperature (110) and the third temperature (120) may be determined according to the alloy steel composition of the first molded product. For example, the specific temperature values ​​of the second temperature (110) and the third temperature (120) may be set depending on whether the first molded product, whose material has been determined, forms residual austenite at the second temperature (110) and whether the first molded product can form a bainite structure at the third temperature (120). At this time, the isothermal time in the austempering step (S3) may vary depending on the thickness and size of the first molded product, but typically takes 30 to 60 minutes. In this process, the internal microstructure of the first molded product changes, and an austenite phase may be formed. For reference, austenite can improve the ductility and strength of alloy steel, thereby enabling the first formed product to have fracture resistance.

[0038] Meanwhile, the austempering step (S3) also utilizes the second temperature (110) from the previous normalizing step (S2) as the austempering start temperature, thereby enabling process minimization and energy efficiency maximization.

[0039] The heat treatment step (S4) stabilizes the structure of the first molded product by keeping the first molded product, which has undergone the austempering step (S3), at a third temperature (120) and then cooling it at room temperature. For example, the heat treatment step (S4) may be equipped with a heating element to maintain the third temperature (120) of the first molded product for a predetermined period of time, and after the constant temperature period, the structure of the first molded product may be stabilized by air cooling it at room temperature.

[0040] The gear forming step (S4) forms the first molded product, which has undergone the heat treatment step (S4), into a second molded product (140) having a usable external gear shape by turning and toothing. For example, the gear forming step (S4) involves turning the outer diameter of the first molded product to shape it into the required form and size. Turning can be performed using a fixed cutting tool, and the surface of the rotating first molded product can be cut.

[0041] Next, the gear forming step (S4) may perform tooth machining on the first molded product after turning. The tooth machining is intended to realize the tooth shape of an external gear, so that the first molded product can ultimately become a second molded product (140) having the shape of an external gear.

[0042] The turning and tooth processing equipment used in the gear forming step (S4) may include a high-precision CNC machine, which enables precise processing of the second formed product.

[0043] The tripping step (S8) applies impact to the surface of the second molded product (140) to induce a process-induced transformation in some of the austenite remaining in the second molded product, thereby converting the surface of the second molded product (140) into martensite. The residual austenite structure has high ductility and is unevenly distributed within the second molded product, which can reduce the strength and hardness of the second molded product. However, the tripping step (S8) increases the surface strength of the second molded product by inducing a process-induced transformation in the residual austenite located on the surface of the second molded product. The process-induced transformation generates stress in the residual austenite, and at this time, the residual austenite is converted into martensite as transformation-induced plasticity is induced. This method can improve both elongation and strength even after converting the austenite into martensite, thereby making the second molded product (140) a material with excellent impact resistance and rigidity.

[0044] Meanwhile, the tripping step (S8) performs shot peening on the surface of the second molded product (140). This is intended to induce a stress concentration phenomenon in the residual austenite by applying a physical impact to the surface of the second molded product, and the residual austenite with concentrated stress undergoes transformation-induced plasticity as described above, thereby having a higher elongation and strength.

[0045] In this configuration, the trip step (S6) causes the surface of the second molded product (140) to be composed of martensite and the interior of the second molded product (140) to be composed of retained austenite. This can enhance the impact resistance of the second molded product (140) because the impact force instantaneously transmitted through the surface of the second molded product (140) induces secondary transformation-induced plasticity in the retained austenite. That is, the second molded product (140) through the trip step (S6) can resist instantaneous impact force through immediate changes in physical properties.

[0046] Meanwhile, the method for manufacturing a wave gear device may further include a step of providing a wave bearing, a step of manufacturing an internal gear, and a joining step.

[0047] The wave bearing provision step may provide a wave bearing, in which an internal shaft is coupled, inside the second molded product, and subsequently, the internal gear manufacturing step may manufacture an internal gear in which the second molded product is provided, and the coupling step may combine the second molded product inside the internal gear.

[0048] Hereinafter, a method for manufacturing a wave gear device according to another embodiment will be described with reference to FIGS. 3 to 5. For reference, FIG. 3 is a flowchart of a method for manufacturing a wave gear device according to another embodiment, and FIG. 4 is a temperature graph from the hot forming step (S1) to the heat treatment step (S4) according to another embodiment.

[0049] A method for manufacturing a wave gear device according to another embodiment includes a hot forming step (S1), a normalizing step (S2), a martensitizing step (S20), an austempering step (S3), a heat treatment step (S4), a gear forming step (S5), and a tripping step (S6), and the exemplary description of steps other than the martensitizing step (S20) is the same.

[0050] The hot forming step (S1) is performed on an alloy steel composed of nickel, copper, molybdenum, and silicon, ranging from 950 to 1300 Hot forming is performed at the first temperature (100) to form a first molded product having a silk hat type housing shape.

[0051] The normalizing step (S2) keeps the first molded product at a first temperature (100) for a predetermined time.

[0052] The martensitization step (S20) rapidly cools the first molded product to a temperature below the martensitization temperature (130). For example, the martensitization step (S20) can be performed by immersing the first molded product in a cooling solution such as oil or water. At this time, the carbon atoms inside the first molded product do not escape the structure due to the instantaneous rapid cooling, and the structure changes into a martensitic structure.

[0053] In addition, the martensitization step (S20) replaces the cooling operation that would have been performed in the normalizing step (S2) with the martensitization of the first molded product, thereby minimizing and improving the efficiency of the continuous process steps.

[0054] The austempering step (S3) is performed on the first molded product that has undergone the martensitization step (S20) for 750 to 900 After heating to a second temperature (110), the first molded product is kept constant at the second temperature (110) for a predetermined time, and then the first molded product is heated to 250 to 400 Cool to the third temperature (120) to form residual austenite in the first molded product.

[0055] The heat treatment step (S4) stabilizes the structure of the first molded product by keeping it constant at the third temperature (120) and then cooling it at room temperature.

[0056] The gear forming step (S4) forms the first molded product, which has undergone the heat treatment step (S4), into a second molded product having a usable external gear shape by turning and toothing.

[0057] The trip step (S6) applies impact to the surface of the second molded product to induce a processing-induced transformation in some of the austenite remaining in the second molded product, thereby turning the surface of the second molded product into martensite and shooting peening the surface of the second molded product.

[0058] In this embodiment, the method for manufacturing a wave gear device of the two embodiments induces transformation-induced plasticity in the residual austenite through a tripping step to transform the surface of the second molded product into martensite. As a result, the second molded product increases both strength and elongation, thereby providing superior impact resistance and rigidity compared to the prior art.

[0059] In addition, the surface and interior of the second molded product (140) are formed of a dual structure of martensite and retained austenite, so that it can resist instantaneous impact force with an immediate change in physical properties.

[0060] In addition, an efficient process is established by configuring the heat treatment temperature from the previous process step to be continuously utilized during the continuous process.

[0061] Although the embodiments have been described above with reference to the limited drawings, those skilled in the art can apply various technical modifications and variations based on the above. For example, suitable results may be achieved even if the described techniques are performed in a different order than described, and / or if the components of the described system, structure, device, circuit, etc. are combined or assembled in a form different from described, or replaced or substituted by other components or equivalents.

[0062] Therefore, other implementations, other embodiments, and equivalents to the claims also fall within the scope of the claims set forth below. Explanation of the symbols

[0064] S1: Hot forming step S2: Normalizing Step S3: Austempering stage S4: Heat treatment step S5: Gear forming stage S6: Trip stage; S20: Martensitic stage 10: Wave gear device 100: First temperature 110: Second temperature 120: Third temperature 130: Martensitic temperature 130: Second molded part

Claims

Claim 1 A hot forming step of hot forming an alloy steel composed of nickel, copper, molybdenum, and silicon into a first molded product having a silk hat-type housing shape at a first temperature of 950 to 1300°C; a normalizing step of isolating the first molded product at the first temperature for a predetermined time, and then, after the isolating time has elapsed, slowly cooling the first molded product to a second temperature of 750 to 900°C; an austempering step of isolating the first molded product at the second temperature and then cooling it to a third temperature of 250 to 400°C to form residual austenite in the first molded product; a heat treatment step of isolating the first molded product that has undergone the austempering step at the third temperature and then cooling it at room temperature to stabilize the structure of the first molded product; and a gear forming step of turning and toothing the first molded product that has undergone the heat treatment step to form a second molded product having a soluble external gear shape. A method for manufacturing a wave gear device comprising: a tripping step of applying impact to the surface of the second molded product to induce a processing-induced transformation in some of the austenite remaining in the second molded product, thereby transforming the surface of the second molded product into martensite. Claim 2 In claim 1, the trip step is a method for manufacturing a wave gear device that involves shot peening the surface of the second molded product. Claim 3 In claim 1, the hot forming step is a method for manufacturing a wave gear device by hot forging the alloy steel at the first temperature. Claim 4 A hot forming step of hot forming an alloy steel composed of nickel, copper, molybdenum, and silicon into a first molded product having a silk hat-type housing shape at a first temperature of 950 to 1300°C; a normalizing step of isothering the first molded product at the first temperature for a predetermined time; a martensitizing step of rapidly cooling the first molded product to a temperature below the martensitizing temperature; an austempering step of forming residual austenite in the first molded product by heating the first molded product that has undergone the martensitizing step to a second temperature of 750 to 900°C, isothering the first molded product at the second temperature for a predetermined time, and then cooling the first molded product to a third temperature of 250 to 400°C; a heat treatment step of stabilizing the structure of the first molded product by isothering the first molded product that has undergone the austempering step at the third temperature and then cooling it at room temperature; and the first molded product that has undergone the heat treatment step. A method for manufacturing a wave gear device comprising: a gear forming step of forming a second molded product having a soluble external gear shape by turning and toothing a first molded product; and a tripping step of applying impact to the surface of the second molded product to induce a process-induced transformation in some of the austenite remaining in the second molded product, thereby transforming the surface of the second molded product into martensite. Claim 5 In paragraph 4, the trip step is a method for manufacturing a wave gear device that involves shot peening the surface of the second molded product. Claim 6 In paragraph 4, the hot forming step is a method for manufacturing a wave gear device by hot forging the alloy steel at the first temperature.

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