KR20230000774A - Method for manufacturing strain wave gear device - Google Patents

Abstract

A method for manufacturing a strain wave gear device is disclosed to improve wear resistance while suppressing thermal deformation and physical property deterioration. The method for manufacturing a strain wave gear device comprises: a step of hot forging a gear material at a temperature of 1200 to 1300 ℃ for one to five minutes; a quenching step of cooling the hot forged material to a martensite formation temperature or lower so as to increase the residual stress of the material and suppress the growth of crystal grains; a step of post heat-treating the quenched material; and a step of performing roughing, finishing, and gear cutting on the post heat-treated material to form gears.

Description

Wave gear device manufacturing method {METHOD FOR MANUFACTURING STRAIN WAVE GEAR DEVICE}

The embodiments below relate to a method for manufacturing a wave gear device.

In general, a wave gear device is composed of a wave generator, a flex spline, and a circular spline. The wave gear device is a type of high-precision reducer that realizes speed reduction by using a dimensional difference between a flex spline and a circular spline that are deformed by waves generated by a wave generator. The wave gear device is used in industrial fields that require a precise reduction ratio because it can obtain a high reduction ratio while being small and light, has a large transmission torque capacity, and has a small backlash.

Due to the nature of use of such a wave gear device, wear resistance, fatigue resistance and impact resistance are required at the same time. Accordingly, there is a need to develop a method for manufacturing a wave gear device using an environmentally friendly heat treatment method that satisfies the wear resistance, fatigue resistance, and impact resistance of the material for the wave gear device while reducing surface deformation.

The above background art is possessed or acquired by the inventor in the process of deriving the disclosure of the present application, and cannot necessarily be said to be known art disclosed to the general public prior to the present application.

An object of the embodiments is to provide a method for manufacturing a wave gear device that suppresses thermal deformation and decrease in physical properties and has improved wear resistance.

The tasks to be solved in the embodiments are not limited to the tasks mentioned above, and other tasks not mentioned will be clearly understood by those skilled in the art from the description below.

Disclosed is a method for manufacturing a wave gear device according to an embodiment. A method for manufacturing a wave gear device, Hot forging the gear material at a temperature of 1200 ° C to 1300 ° C for 1 minute to 5 minutes, cooling the hot forged material below the martensite formation temperature to increase the residual stress of the material and suppress grain growth? It is configured to include a quenching step, post-heat treatment of the quenched material, and forming a gear by roughing, finishing, and gear cutting the post-heat-treated material.

According to one side, the quenching step may be cooled using an oil bath.

According to one side, the post-heat treatment step is to heat the quenched material to 860 ° C. to 900 ° C. and maintain the constant temperature for 20 to 70 minutes to austenitize, and the temperature of the material in two steps. It may include a first cooling step of descending.

According to one side, the first cooling step is a first rapid cooling step of cooling the austenitized material to 490 ° C. to 710 ° C. and maintaining the constant temperature for 20 minutes to 70 minutes, and the first rapidly cooled material at 190 ° C. It may include a second rapid cooling step of cooling to 410 ° C. and maintaining a constant temperature for 20 minutes to 70 minutes.

According to one side, the second rapid cooling step may be cooled to a temperature equal to or higher than the martensite formation temperature of the material.

According to one side, the first rapid cooling step may be cooled using an oil bath or gas, and the second rapid cooling step may be cooled using an oil bath or salt bath.

According to one side, the post-heat treatment step is to heat the quenched material to 860 ℃ to 900 ℃ and maintain a constant temperature for 50 minutes to 250 minutes to austenitize, and furnace-cool the austenitized material Alternatively, a second cooling step of slowly cooling by air cooling may be included.

According to one side, in the second cooling step, the austenitized material may be furnace-cooled or air-cooled to room temperature.

According to one side, the second cooling step is a first slow cooling step of furnace-cooling or air-cooling the austenitized material to 760 ° C, and the first slowly cooled material at 640 ° C to 760 ° C for 50 minutes to 130 minutes. It may include a second slow cooling step of furnace cooling or air cooling to room temperature after maintaining constant temperature during the period.

According to one side, after the post-heat treatment step, a second post-heat treatment step of cooling after maintaining a constant temperature at 190° C. to 410° C. for 20 to 70 minutes may be further included.

According to one side, after the post-heat treatment step, a third post-heat treatment step of quenching and re-heating to a temperature below the martensite formation temperature may be further included.

As described above, according to the embodiments, the wave gear device manufacturing method can manufacture a wave gear device in which thermal deformation and physical property reduction of the wave gear device are suppressed and wear resistance is improved.

Effects of the wave gear device manufacturing method according to an embodiment are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description below.

1 is a front view of a wave gear device according to an embodiment.
2 is a flowchart illustrating a method of manufacturing a wave gear device according to an embodiment.
FIG. 3 is a temperature-time graph of the hot forging step and the quenching step of FIG. 2 .
4 is a temperature-time graph of a post-heat treatment step of FIG. 2 according to an embodiment.
5 is a temperature-time graph of a post-heat treatment step of FIG. 2 according to another embodiment.
FIG. 6 is a temperature-time graph showing another embodiment of the second cooling step of FIG. 5 .
FIG. 7 is a temperature-time graph showing another embodiment of the second cooling step of FIG. 5 .
8 is a temperature-time graph of a post-heat treatment step of FIG. 2 according to another embodiment.
The following drawings attached to this specification illustrate preferred embodiments of the present invention, and together with the detailed description of the invention serve to further understand the technical idea of the present invention, the present invention is limited only to those described in the drawings. and should not be interpreted.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. However, since various changes can be made to the embodiments, the scope of the patent application is not limited or limited by these embodiments. It should be understood that all changes, equivalents or substitutes to the embodiments are included within the scope of rights.

Terms used in the examples are used only for descriptive purposes and should not be construed as limiting. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as "include" or "have" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art to which the embodiment belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in the present application, they should not be interpreted in an ideal or excessively formal meaning. don't

In addition, in the description with reference to the accompanying drawings, the same reference numerals are given to the same components regardless of reference numerals, and overlapping descriptions thereof will be omitted. In describing the embodiment, if it is determined that a detailed description of a related known technology may unnecessarily obscure the gist of the embodiment, the detailed description will be omitted.

In addition, in describing the components of the embodiment, terms such as first, second, A, B, (a), and (b) may be used. These terms are only used to distinguish the component from other components, and the nature, order, or order of the corresponding component is not limited by the term. When an element is described as being “connected,” “coupled to,” or “connected” to another element, that element may be directly connected or connected to the other element, but there may be another element between the elements. It should be understood that may be "connected", "coupled" or "connected".

Components included in one embodiment and components including common functions will be described using the same names in other embodiments. Unless stated to the contrary, descriptions described in one embodiment may be applied to other embodiments, and detailed descriptions will be omitted to the extent of overlap.

For reference, FIG. 1 is a front view of a wave gear device according to an embodiment, FIG. 2 is a flowchart illustrating a method of manufacturing a wave gear device according to an embodiment, and FIG. 3 is a hot forging step and quenching process of FIG. Figure 4 is a temperature-time graph of the post-heat treatment step of FIG. 2 according to one embodiment, Figure 5 is a temperature-time graph of the post-heat treatment step of FIG. 2 according to another embodiment, 6 is a temperature-time graph showing another embodiment of the second cooling step of FIG. 5, FIG. 7 is a temperature-time graph showing another embodiment of the second cooling step of FIG. 5, and FIG. It is a temperature-time graph of the post-heat treatment step of FIG. 2 according to the embodiment.

Referring to FIG. 1, the wave gear device 1 includes an internal gear 20 having internal teeth formed on an inner circumferential surface, an external tooth gear 10 provided inside the internal gear 20 and having external teeth formed on an outer circumferential surface, and an external gear 10 It is provided inside and is configured to include a wave generator 30 formed in an elliptical shape.

The internal gear 20 is formed in a ring shape and made of a rigid material.

The external tooth gear 10 is configured to include a body 11 formed in a cylindrical shape and having flexibility, and an external tooth 12 formed on the outer circumferential surface of the front end opened in the body 11.

The wave generator 30 has an elliptical shape and is made of a rigid material.

In the present embodiment, heat treatment may be performed to suppress thermal deformation and decrease in physical properties of the externally toothed gear 10 having flexibility among the wave gear devices 1 and to improve wear resistance. However, heat treatment may be performed not only on the external gear 10 but also on the internal gear 20 .

Referring to FIG. 2, the external gear 10 includes a step of hot forging a gear material (S100), a quenching step (S200), a post-heat treatment step (S300), and a step of forming a gear (S400). It can be manufactured by

Referring to Figure 3, in the step of hot forging the gear material (S100), the gear material is heated to a predetermined temperature and permanently deformed to produce a gear shape. At this time, the predetermined temperature may be a temperature higher than the temperature at which recrystallization of the gear material proceeds. For example, the gear material may be hot forged at a temperature of 1200° C. to 1300° C. for 1 minute to 5 minutes. In the step of hot forging the gear material (S100), the gear material is shaped by forging deformation and has an internal stress generating effect.

Here, in the hot forging step (S100), by heating the material through an induction coil, it is possible to easily shape the material by giving a large deformation even with a small force. Here, carbon steel may be used as the material. However, the material used here is not limited thereto, and high-elastic iron-based materials such as bearing steel and spring steel may be used.

Next, the hot forged material is quenched (S200). In the quenching step (S200), the hot forged material is cooled to a martensite formation temperature (M _s) or less. Here, the quenching step (S200) may be cooled using an oil bath. In the quenching step (S200), additional internal stress may be generated in the gear material by quenching the material in an oil bath. By simultaneously performing the hot forging step (S100) and the quenching step (S200), residual stress generation can be maximized. In addition, it has the effect of maximizing the nucleation of the microstructure of the gear material due to the generation of residual stress, and shortening the crystal grain refinement and heat treatment time.

Next, the quenched material is post-heat treated (S300). The post heat treatment step (S300) includes austenitizing the quenched material (S301) and a first cooling step (S302) of lowering the temperature of the material.

Referring to FIG. 4, in the step of austenitizing the quenched material (S301), the material is heated above the transformation temperature region of the material and isothermally maintained to convert the material into an austenite structure. For example, in the step of austenitizing the quenched material (S301), the quenched material may be heated to 860° C. to 900° C. and maintained at a constant temperature for 20 minutes to 70 minutes.

Next, the temperature of the material is lowered (S302). The first cooling step (S302) of lowering the temperature of the material may include a first rapid cooling step (S3021) and a second rapid cooling step (S3022) to lower the temperature of the material in two steps.

For example, in the first rapid cooling step (S3021), the austenitized material may be cooled to 490° C. to 710° C. and maintained at a constant temperature for 20 minutes to 70 minutes. Here, the first rapid cooling step (S3021) may be cooled using an oil bath or gas.

In addition, in the second rapid cooling step (S3022), the first rapidly cooled material may be cooled to 190 ° C. to 410 ° C., which is higher than the martensite formation temperature of the material, and maintained at a constant temperature for 20 minutes to 70 minutes. Here, in the second rapid cooling step (S3022), cooling may be performed using an oil bath or a salt bath.

The first rapid cooling step (S3021) and the second rapid cooling step (S3022) serve to maximize the thermal residual stress of the material and suppress the growth of crystal grains generated by dynamic recrystallization. Here, the first rapid cooling step (S3021) and the second rapid cooling step (S3022) are preferably rapidly cooled in a short time to avoid precipitation of pearlite and ferrite. For example, the cooling time may be performed for 1 second to 10 seconds, but is not limited thereto and may be changed.

Further, the post heat treatment step (S310) according to another embodiment includes austenitizing the quenched material (S311) and a second cooling step (S312) of lowering the temperature of the material. Here, the second cooling step (S312) is slowly cooled by furnace cooling or air cooling, unlike the first cooling step (S302). The second cooling step (S312) serves to generate metal nuclei and control crystal grain growth.

Referring to FIG. 5 , in step S311 of austenitizing the quenched material, the material is heated above the transformation temperature region of the material and isothermally maintained to convert the material into an austenite structure. For example, in the austenitizing step (S311), the quenched material may be heated to 860° C. to 900° C. and maintained at a constant temperature for 50 minutes to 250 minutes.

Next, the temperature of the material is lowered (S312). In the second cooling step (S312) of lowering the temperature of the material, it may be slowly cooled to room temperature by furnace cooling or air cooling.

In addition, the post heat treatment step (S320) according to another embodiment may further include a second post heat treatment step (S350) after the post heat treatment step (S320).

Referring to FIG. 6 , the heat treatment up to the second post heat treatment step (S350) is the same as that of FIG. 5, and then the second post heat treatment (S350) may be performed. For example, in the second post-heat treatment step (S350), the quenched material is heated to 860 ° C. to 900 ° C., maintained at a constant temperature for 50 minutes to 250 minutes to austenitize, and oil bath or salt bath at 190 ° C. to 410 ° C. After quenching using, it may be cooled after maintaining a constant temperature at 190 ° C to 410 ° C for 20 minutes to 70 minutes.

In addition, the post heat treatment step (S320) according to another embodiment may further include a third post heat treatment step (S360) after the post heat treatment step (S320).

Referring to FIG. 7 , the heat treatment up to the third post heat treatment step (S360) is the same as that of FIG. 5, and then the third post heat treatment (S360) can be performed. For example, in the third post-heat treatment step (S360), after the post-heat treatment step (S320), rapid cooling to a temperature below the martensite formation temperature and reheating may be performed.

In addition, the post heat treatment step (S340) according to another embodiment includes the second cooling step (S342), the first slow cooling step (S3421) and the second slow cooling step (S3422) to lower the temperature of the material in two stages. can make it

Referring to FIG. 8, in the same manner as in FIG. 5, the quenched material may be austenitized (S341), and the second cooling step (S342) may be divided into two steps. For example, the first slow cooling step (S3421) furnace-cools or air-cools the austenitized material to 760 ° C, and then the second slow cooling step (S3422) heats the first slowly cooled material to 640 ° C to 760 ° C for 50 minutes. After maintaining the constant temperature for 130 minutes, it may be furnace-cooled or air-cooled to room temperature.

Returning to FIG. 2 again, a gear is formed after the post-heat treatment step (S300) (S400). In the step of forming a gear (S400), a gear is formed by roughing, finishing, and gear cutting the post-heat treated material. Here, the roughing process is a process of cutting by relatively increasing the cutting width and feed of the tool when the machining margin of the material is large. By performing roughing, dimensions can be machined with more precision in subsequent machining, such as finishing and gear cutting.

Finishing processing is processing to obtain dimensions and processing surfaces determined according to the standard of the wave gear device, and tooth cutting processing is a process of making a tooth shape by cutting the surface of the wave gear device. The final shape of the wave gear device can be manufactured through finishing machining and gear cutting.

According to the present embodiments, in the method for manufacturing a wave gear device, the heat treatment time can be shortened by simultaneously performing the hot forging step and the quenching step.

In addition, the wave gear device manufacturing method maximizes thermal residual stress and refines crystal grains by simultaneously obtaining stress due to hot forging deformation and stress generated from rapid cooling in the quenching step to manufacture a wave gear device with improved hardness. there is.

As described above, although the embodiments have been described with limited drawings, those skilled in the art can apply various technical modifications and variations based on the above. For example, the described techniques may be performed in an order different from the method described, and/or components of the described system, structure, device, circuit, etc. may be combined or combined in a different form than the method described, or other components may be used. Or even if it is replaced or substituted by equivalents, appropriate results can be achieved.

Therefore, other implementations, other embodiments, and equivalents of the claims are within the scope of the following claims.

Claims (11)

Hot forging the gear material at a temperature of 1200 ° C to 1300 ° C for 1 minute to 5 minutes;
A quenching step of cooling the hot-forged material to a martensite formation temperature or less to increase residual stress of the material and suppress crystal grain growth;
Post heat treatment of the quenched material; and
Forming gears by roughing, finishing, and gear cutting the post-heat-treated material;
Wave gear device manufacturing method comprising a. According to claim 1,
The quenching step is a method of manufacturing a wave gear device for cooling using an oil bath. According to claim 1,
In the post-heat treatment step,
austenitizing the quenched material by heating it to 860° C. to 900° C. and maintaining the constant temperature for 20 to 70 minutes; and
A first cooling step of lowering the temperature of the material in two steps;
Wave gear device manufacturing method comprising a. According to claim 3,
The first cooling step,
A first rapid cooling step of cooling the austenitized material to 490° C. to 710° C. and maintaining a constant temperature for 20 to 70 minutes; and
A second rapid cooling step of cooling the first rapidly cooled material to 190° C. to 410° C. and maintaining the constant temperature for 20 minutes to 70 minutes;
Wave gear device manufacturing method comprising a. According to claim 4,
The second rapid cooling step is a method of manufacturing a wave gear device for cooling to a temperature equal to or higher than the martensite formation temperature of the material. According to claim 4,
The first rapid cooling step is cooled using an oil bath or gas,
The second rapid cooling step is a wave gear device manufacturing method for cooling using an oil bath or a salt bath. According to claim 1,
In the post-heat treatment step,
austenitizing the quenched material by heating it to 860° C. to 900° C. and maintaining the constant temperature for 50 minutes to 250 minutes; and
A second cooling step of slowly cooling the austenitized material by furnace cooling or air cooling;
Wave gear device manufacturing method comprising a. According to claim 7,
In the second cooling step,
A method for manufacturing a wave gear device in which the austenitized material is furnace-cooled or air-cooled to room temperature. According to claim 7,
In the second cooling step,
A first slow cooling step of furnace-cooling or air-cooling the austenitized material to 760° C.; and
A second slow cooling step of furnace-cooling or air-cooling the first slowly cooled material to room temperature after maintaining a constant temperature at 640° C. to 760° C. for 50 minutes to 130 minutes;
Wave gear device manufacturing method comprising a. According to claim 7,
A method for manufacturing a wave gear device further comprising a second post-heat treatment step of cooling after maintaining a constant temperature at 190 ° C to 410 ° C for 20 to 70 minutes after the post-heat treatment step. According to claim 7,
A method for manufacturing a wave gear device further comprising a third post-heat treatment step of rapidly cooling and re-heating to a temperature below the martensite formation temperature after the post-heat treatment step.

Images