Method for manufacturing strain wave gear

Abstract

The present invention relates to a method for manufacturing a strain wave gear including: a ring-shaped internal-tooth gear having gear teeth provided on the inner diameter surface thereof and along the circumferential direction thereof and having multiple through-holes formed therethrough in the axial direction thereof; an external-tooth gear having gear teeth engaged with the gear teeth of the internal-tooth gear; a camshaft which is provided inside the external-tooth gear and has a wave generation part formed on the outer diameter surface thereof; and a bearing provided between the external-tooth gear and the camshaft, the external-tooth gear including: a cylindrical part having gear teeth provided on the outer diameter surface thereof and engaged with the gear teeth of the internal-tooth gear; a bottom part provided at the end of the cylindrical part; and a protruding part protruding from the bottom part in the axial direction thereof, wherein at least one of the internal-tooth gear, the external-tooth gear, and the camshaft is manufactured by sintering.

Description

Method for manufacturing strain wave gear

[0001] The present invention relates to a method for manufacturing a strain wave gear, and more particularly, to a method for manufacturing a strain wave gear that is suitable for mass production and reduces manufacturing costs.

[0002] As illustrated in FIG. 1, the strain wave gear (100) is a type of reducer, and includes a ring-shaped internal gear (110, circular spline) having gear teeth (115) formed on the inner diameter, an external gear (120, flex gear) which is a flexible cylindrical body provided within the internal gear (110) and having gear teeth (123) formed on the outer circumference, and a camshaft (140, wave generator) which is a wave generator having an oval-shaped wave generating portion provided within the external gear (120). A bearing (130) is provided between the camshaft (140) and the external gear (120).

[0003] The above internal gear (110) has a plurality of through holes formed along the circumferential direction. In Fig. 1, reference numeral 117 illustrates an extension provided in the internal gear (110) and extending in the axial direction.

[0004] The above-mentioned external gear (120) has a cup-shaped cylindrical portion (121) and a bottom portion (125), and includes a protrusion (127) that extends outward from the bottom portion (125), and a spline (129) is formed on the inner diameter of the protrusion (127). The gear teeth (123) are formed on the outer diameter surface of the cylindrical portion (121) of the above-mentioned external gear (120).

[0005] The camshaft (140) above has a jaw portion (145) formed on one axial side where the inner ring of the bearing (130) is engaged, and a concave portion (147) formed concavely along the circumferential direction is formed on the other side, and a wave generating portion (143) is formed between the jaw portion (145) and the concave portion (147).

[0006] In Fig. 1, reference numeral 131 denotes an inner ring, 133 denotes an outer ring, and 135 denotes a rolling element (135) aligned along the circumferential direction between the inner ring (131) and the outer ring (133). A plurality of rolling elements (135) are provided. The rolling elements (135) may be provided as spherical balls or as cylindrical rollers. In the above, the inner ring (131) may not be provided, and the rolling element (135) may be structured to directly contact the wave generating unit (143). In addition, the outer ring (131) may not be provided, and the rolling element (135) may be structured to directly contact the inner surface of the cylindrical portion (121) of the external gear (120), so that the cylindrical portion (121) acts as the outer ring.

[0007] Referring to FIG. 5, the manufacturing of the above components (110, 120, 140) forming the conventional strain wave gear (100) will be described.

[0008] The above-mentioned internal gear (110) is manufactured through the steps of creating a hollow body by forging or cutting a pipe material, turning the width, inner diameter and outer diameter of the hollow body, drilling a plurality of holes (113) along the circumferential direction and processing gear teeth (115) on the inner diameter.

[0009] The above-mentioned external gear (120) is manufactured by cutting a circular bar with a cross-section, forging the cut bar into a cup shape having a protrusion (127) on one side, turning the inner and outer diameters, processing a spline (129) penetrating the protrusion (127), processing a gear tooth (123) on the outer diameter surface of the end of the cylindrical portion, and then going through a shot peening step. In the process of turning the inner and outer diameters of the above-mentioned external gear (120), an internal diameter turning device and an external diameter turning device are required, respectively.

[0010] The above camshaft (140) is manufactured through a step of cutting a circular bar with a circular cross-section, turning the cut circular bar to form a concave portion (147) on one side and a jaw portion (145) on the other side, and turning an oval-shaped wave generating portion (143) between the concave portion (147) and the jaw portion (145).

[0011] Parts manufactured in the above manner are made so that the gear teeth (115) of the internal gear (110) and the gear teeth (123) of the external gear (120) mesh with each other as shown in Fig. 1, the bearing (130) is inserted into the inside of the external gear (120), and the wave generating part (143) is inserted into the bearing (130), and a snap ring (not shown) is installed in the concave part (147).

[0012] The conventional strain wave gear manufacturing method described above has the problem that all parts are made of turning and gear machining, so the processing amount is large, the cycle time is long, and the quality dispersion is large depending on the processing conditions, and therefore it is not suitable for applications such as automobiles that must be mass-produced.

[0013] The present invention aims at a method for manufacturing a strain wave gear suitable for mass production by reducing the product manufacturing cost, reducing the product manufacturing cycle time, and reducing quality variation.

[0014] For the above purpose, the present invention comprises an internal gear having a gear tooth on an inner diameter and a ring-shaped gear having a plurality of through holes formed along a circumferential direction and extending axially, an external gear having gear teeth meshing with the gear teeth of the internal gear, a camshaft provided on the inner side of the external gear and having a wave generating portion formed on an outer diameter surface, and a bearing provided between the external gear and the camshaft;

[0015] The above-mentioned external gear includes a cylindrical portion having gear teeth that mesh with the gear teeth of the internal gear on the outer diameter, a bottom portion provided at an end of the cylindrical portion, and a protrusion that protrudes axially from the bottom portion;

[0016] A method for manufacturing a strain wave gear is provided, characterized in that at least one of the internal gear, external gear, and camshaft is manufactured by sintering.

[0017] In the above, the internal gear, the external gear, and the camshaft are characterized in that they are manufactured by sintering.

[0018] In the above, the internal gear and the camshaft are manufactured by sintering, and the external gear is characterized in that after sintering, the outer diameter surface of the cylindrical portion of the sintered sintered molded product is turned and gear teeth are machined on the outer diameter surface; and the internal gear, the camshaft, and the external gear are assembled together with a bearing.

[0019] In the above, the internal gear is manufactured by sintering, and is characterized in that it is manufactured from a sintered material containing 0.35 to 0.45 wt% of C (carbon), 1.4 to 1.8 wt% of Ni (nickel), 2.4 to 2.6 wt% of Cr (chromium), the remainder being iron, and optionally containing trace elements.

[0020] In the above, the external gear is manufactured by including a step of sintering a sintered material to manufacture a sintered molded body having a cylindrical portion, a bottom portion provided at an end of the cylindrical portion, and a protrusion portion protruding from the bottom portion; a step of turning an outer diameter of the cylindrical portion of the external gear sintered molded body; and a step of machining a gear tooth on the outer diameter of the turned cylindrical portion.

[0021] It is characterized in that a bearing is inserted into the inner diameter of the cylindrical portion of the external gear manufactured as described above.

[0022] In the above, the external gear is manufactured by sintering, and is characterized in that it is manufactured from a sintered material containing 0.35 to 0.45 wt% of C (carbon), 0.1 to 0.35 wt% of Mo (molybdenum), 2.4 to 2.6 wt% of Cr (chromium), the remainder being iron, and optionally containing trace elements.

[0023] In the above, the external gear is manufactured by sintering, and is characterized in that it is manufactured from a sintered material containing 0.35 to 0.45 wt% of C (carbon), 0.1 to 0.35 wt% of Mo (molybdenum), 2.4 to 2.6 wt% of Cr (chromium), the remainder being iron, and optionally containing trace elements.

[0024] In the above, the external gear has a hardness in the range of 38 to 46 HRc, and the internal gear has a hardness in the range of 34 to 42 HRc; and the hardness of the external gear is characterized by being greater than the hardness of the internal gear.

[0025] According to the method for manufacturing a strain wave gear according to the present invention, it can be manufactured at a low manufacturing cost, the loss of material is greatly reduced, the product manufacturing cycle time is reduced, and quality dispersion is reduced, so it is suitable for mass production.

[0026] Figure 1 is a cross-sectional view showing an example of a strain wave gear.

[0027] Figure 2 is a perspective view showing an example of an internal gear provided in a strain wave gear.

[0028] Figure 3 is a perspective view showing an example of an external gear equipped in a strain wave gear.

[0029] Fig. 4 is a perspective view showing an example of a camshaft equipped on a strain wave gear.

[0030] Figure 5 is a flowchart illustrating a method for manufacturing a strain wave gear using conventional technology.

[0031] Figure 6 is a flowchart illustrating a method for manufacturing a strain wave gear according to the present invention.

[0032] All technical and scientific terms used in the description of the present invention, unless otherwise defined, have the meanings commonly understood by those of ordinary skill in the art to which this disclosure pertains. All terms used in this disclosure have been selected for the purpose of more clearly explaining this disclosure and are not intended to limit the scope of rights under this disclosure.

[0033] Expressions such as “comprising,” “having,” and the like used in the description of the present invention should be understood as open-ended terms that imply the possibility of including other embodiments, unless otherwise stated in the phrase or sentence in which the expression is included.

[0034] The singular forms used in the description of the present invention may include plural meanings unless otherwise stated, and the same applies to the singular forms set forth in the claims.

[0035] When it is mentioned in the description of the present invention that a component is "connected" or "coupled" to another component, it should be understood that the component can be directly connected or coupled to the other component, or can be connected or coupled via a new other component.

[0036] Hereinafter, with reference to the attached drawings, a method for manufacturing a strain wave gear according to the present invention will be described in detail.

[0037] FIG. 1 is a cross-sectional view showing an example of a strain wave gear, FIG. 2 is a perspective view showing an example of an internal gear equipped in a strain wave gear, FIG. 3 is a perspective view showing an example of an external gear equipped in a strain wave gear, FIG. 4 is a perspective view showing an example of a camshaft equipped in a strain wave gear, and FIG. 6 is a flowchart showing a method for manufacturing a strain wave gear according to the present invention.

[0038] In the following description, the horizontal direction of Fig. 1 is described as the axial direction, and the vertical direction is described as the radial direction.

[0039]

[0040] As shown in Fig. 1, the strain wave gear (100) includes an internal gear (110), an external gear (120), a camshaft (140), and a bearing (130).

[0041] The above internal gear (110) is provided in a ring shape. The internal gear (110) is provided with gear teeth (115) on its inner diameter. The gear teeth (115) are formed along the inner diameter of the internal gear (110). The internal gear (110) is provided with a plurality of through holes (113) spaced apart along the circumferential direction and penetrating in the axial direction. The internal gear (110) is fixedly installed by inserting a fixing device such as a bolt into the through holes (113).

[0042] In Fig. 1, drawing reference numeral 117 illustrates an extension protruding from the radially inner side of the internal gear (110) to one axial side.

[0043] The above-mentioned external gear (120) is provided on the radially inner side of the above-mentioned internal gear (110). The above-mentioned external gear (120) is provided as a cylindrical hollow body that is opened on one axial side. The above-mentioned external gear (120) includes a cylindrical portion (121), a gear tooth (123), a bottom portion (125), and a protrusion portion (127).

[0044] The above cylindrical portion (121) is a hollow body having a circular cross-section and an opening in the axial direction. The thickness of the above cylindrical portion (121) is formed thinly, for example, in the range of 0.2 to 0.5 mm. The above cylindrical portion (121) is provided on the radially inner side of the internal gear (110). The above internal gear (110) is located on one axial side of the above cylindrical portion (121).

[0045] The above gear teeth (123) are formed on the outer diameter of the cylindrical portion (121). The gear teeth (123) are provided along the circumferential direction at one axial end of the cylindrical portion (121). The gear teeth (123) are provided to mesh with the gear teeth (115) of the internal gear (110) at the outer diameter of the cylindrical portion (121). The number of gear teeth (123) of the external gear (120) is smaller than that of the gear teeth (115) of the internal gear (110).

[0046] The above bottom part (125) is provided on the other end of the above cylindrical part (121). The above bottom part (125) is provided on the opposite side of the above cylindrical part (121) where the gear teeth (123) are formed.

[0047] The above protrusion (127) protrudes axially from the bottom portion (125). The protrusion (127) is provided to protrude from the bottom portion (125) in the opposite direction where the internal gear (110) is provided. The thickness of the protrusion (127) is formed to be thicker than the thickness of the cylindrical portion (121), and is formed to have a thickness of, for example, 1 to 5 mm. The protrusion (127) penetrates axially so that openings are formed on both axial sides. A spline (129) is formed on the inner diameter of the protrusion (127).

[0048] The camshaft (140) is provided on the inside of the external gear (120). The camshaft (140) is provided radially inwardly from the external gear (120). The camshaft (140) includes a shaft body (141), a wave generating portion (143), a jaw portion (145), and a concave portion (147).

[0049]

[0050] The above shaft body (141) is provided on the radially inner side of the external gear (120). One axial side of the shaft body (141) is provided to protrude axially outward from an opening of the external gear (120). The shaft body (141) has a circular cross-section. A shaft hole is formed through the center of the shaft body (141) into which a shaft (not shown) can be inserted in the axial direction.

[0051] The above wave generating part (143) is formed on the outer diameter surface of the shaft body (141). The wave generating part (143) has an elliptical cross-section. The cross-section of the wave generating part (143) may be formed in a form in which a plurality (e.g., three) protrusions are spaced at equal intervals along the circumferential direction of the wave generating part (143). The protrusions are formed to have a smaller arc angle than the arc angle forming the circumferential direction of the wave generating part (143).

[0052] The above concave portion (147) is formed concavely along the circumferential direction of the shaft body (141) on the outer surface of the shaft body (141). The above concave portion (147) is formed on one side in the axial direction with the wave generating portion (143) as the center. The above concave portion (147) is formed at a position protruding axially outward from the opening of the external gear (120) in the shaft body (141). A snap ring is coupled to the above concave portion (147) to prevent the bearing (130) into which the camshaft (140) is inserted from being detached.

[0053] The above jaw portion (145) is provided on the outer surface of the shaft body (141). The jaw portion (145) protrudes radially outward from the shaft body (141). The jaw portion (145) is provided on the other axial side with respect to the wave generating portion (143). The jaw portion (145) is formed to protrude radially outward from the shaft body (141) so that the bearing (130) into which the camshaft (140) is inserted is caught on the jaw portion (145).

[0054] The above bearing (130) is provided in a ring shape. The bearing (130) is provided radially between the external gear (120) and the cap shaft (140).

[0055] The above bearing (130) is formed by including an inner ring (131) having a ring shape and an inner ring raceway formed on the outer diameter, an outer ring (133) having a ring shape and an outer ring raceway formed on the inner diameter, and a plurality of rolling elements (135) aligned along the circumferential direction between the inner ring (131) and the outer ring (133). The rolling elements (135) may be provided as spherical balls or as cylindrical rollers.

[0056] In the bearing (130), a camshaft (140) is inserted into the inner diameter of the inner ring (131), and one axial side of the bearing (130) is engaged with the shoulder (145) of the camshaft (140). The bearing (130) is engaged with the inner ring (131) of the camshaft (140).

[0057] In the above, the bearing (130) may be structured so that the inner ring (131) is not provided and the rolling element (135) is in direct contact with the wave generating portion (143). In addition, the bearing (130) may be structured so that the outer ring (131) is not provided and the rolling element (135) is in direct contact with the inner surface of the cylindrical portion (121) of the external gear (120), so that the cylindrical portion (121) acts as the outer ring.

[0058]

[0059] Hereinafter, a method for manufacturing a strain wave gear according to the present invention will be described with reference to FIG. 6.

[0060] The above strain wave gear (100) is manufactured and assembled by manufacturing the internal gear (110), external gear (120), camshaft (140), and bearing (130).

[0061] The above internal gear (110) is manufactured by sintering, and manufacturing is completed by the above sintering.

[0062] The sintered material manufactured into the above internal gear (110) contains 0.35 to 0.45 wt% of C (carbon), 1.4 to 1.8 wt% of Ni (nickel), 2.4 to 2.6 wt% of Cr (chromium), and the remainder is iron. The sintered material forming the above internal gear (110) may optionally contain trace elements in addition to the above components. The trace elements may include, for example, trace elements (0.01 wt% or less) such as vanadium (V).

[0063] If the above C (carbon) is less than 0.35 wt%, there is concern that the core density may decrease during heat treatment, and if it exceeds 0.45 wt%, there is concern that the impact resistance may decrease due to brittleness after heat treatment.

[0064] If the above Ni (nickel) is less than 1.4 wt%, the desired hardness and strength are low and the corrosion resistance is weak. If it exceeds 1.8 wt%, the material is brittle and weak to impact and the wear resistance is poor.

[0065] If the above Cr (chromium) is less than 2.4 wt%, there is concern about a deterioration in the mechanical properties of the material, and if it exceeds 2.6 wt%, there is a problem of an increase in the material cost, a deterioration in formability, and oxidation of chromium during sintering.

[0066] An internal gear molding is manufactured using a sintered material forming the internal gear (110), and the sintered material is heated and sintered in a temperature range of 1180 to 1300°C. If the sintering temperature is lower than 1180°C, material diffusion between powders is not smooth, and if it exceeds 1300°C, mass productivity may be significantly reduced.

[0067] The internal gear (110) manufactured by sintering as described above has a hardness in the range of 34 to 42 HRc. Since the internal gear (110) must function as a rigid body that maintains its circular shape during operation, a sintered material having the above-described composition is used to ensure high hardness and wear resistance.

[0068] The above-mentioned external gear (120) is manufactured through a sintering step of sintering a sintered material to manufacture a sintered molded body, an external turning step of turning the sintered molded body, an external tooth processing step of processing a gear tooth (123), and a shot peening step.

[0069] In the above sintering step, a sintered material is sintered to produce a sintered molded body. The sintered molded body is formed to a thickness of 1 to 5 mm. The sintered molded body includes a cylindrical cylindrical portion (121), a bottom portion (125) provided at an end of the cylindrical portion (121), and a protrusion (127) protruding from the bottom portion (125). A spline (129) provided on the inner diameter of the protrusion (127) is formed together in the sintering step.

[0070] The sintered material manufactured into the above external gear (120) contains 0.35 to 0.45 wt% of C (carbon), 0.1 to 0.35 wt% of Mo (molybdenum), 2.4 to 2.6 wt% of Cr (chromium), and the remainder is iron. The sintered material manufactured into the above external gear (120) may optionally contain trace elements in addition to the above components. The trace elements may include, for example, trace elements (0.01 wt% or less) such as vanadium (V).

[0071] If the above C (carbon) is less than 0.35 wt%, there is concern that the core density may decrease during heat treatment, and if it exceeds 0.45 wt%, there is concern that the impact resistance may decrease due to brittleness after heat treatment.

[0072] The above Mo (molybdenum) is added in small amounts to increase hardenability, corrosion resistance, toughness, etc., but when it exceeds 0.35 wt%, it has the problem of becoming brittle and weak to impact.

[0073] If the above Cr (chromium) is less than 2.4 wt%, there is concern about a deterioration in the mechanical properties of the material, and if it exceeds 2.6 wt%, there is a problem of an increase in the material cost, a deterioration in formability, and oxidation of chromium during sintering.

[0074] A sintered molded body is manufactured from the sintered material forming the above-mentioned external gear (110), and the sintered material is heated and sintered in a temperature range of 1180 to 1300°C. If the sintering temperature is lower than 1180°C, material diffusion between powders is not smooth, and if it exceeds 1300°C, mass productivity may be significantly reduced.

[0075] The above-mentioned external gear (120) is a component that elastically deforms according to the rotation of the camshaft (140), and can be manufactured from a sintered material having the above-mentioned composition to have sufficient hardness and durability. The external gear (120) manufactured from a sintered material having the above-mentioned composition has a hardness in the range of 38 to 46 HRc and a fatigue limit (fatugue bending stress R=-1) of 350 MPa or more.

[0076] The hardness of the above-mentioned external gear (120) is greater than the hardness of the above-mentioned internal gear (110). It is preferable that the above-mentioned external gear (120) has a hardness in the range of 38 to 46 HRc, and the above-mentioned internal gear (110) has a hardness in the range of 34 to 42 HRc.

[0077] The above-mentioned external gear (120) is a component that is elastically deformed by an external force transmitted through a bearing (130) according to the rotation of the camshaft (140). Therefore, the internal gear (110) must have a rigidity much greater than that of the external gear (120), and it is preferable that the circular shape be maintained even when the camshaft (140) rotates.

[0078] As described above, by making the hardness of the external gear (120) greater than that of the internal gear (110), the deformation of the external gear (120) can be cushioned to a certain extent by the internal gear (110), thereby improving the lifespan of the external gear (120) or the internal gear (110). In particular, by making the hardness of the external gear (120) greater than that of the internal gear (110), the lifespan can be significantly improved.

[0079] In the above outer diameter turning step, the outer diameter surface of the cylindrical portion (121) of the sintered molded product sintered in the above sintering step is turned.

[0080] In the past, in the process of turning the inner and outer diameters after forging, inner and outer diameter turning equipment were required, respectively, but in the present invention, only outer diameter turning is performed after the sintering step, so turning is minimized.

[0081] The cylindrical portion (121) of the above-mentioned external gear (120) must be manufactured with a thin thickness (e.g., in the range of 0.2 to 0.5 mm), and as in the present invention, the external gear (120) can be manufactured by sintering, and only the outer diameter of the cylindrical portion (121) can be manufactured by turning. That is, during sintering, the inner diameter of the cylindrical portion (121) is sintered to the finished dimension, and the outer diameter of the cylindrical portion (121), which is relatively easy to process, is made larger than the finished dimension, so that only the outer diameter of the cylindrical portion (121) can be manufactured by turning.

[0082] In addition, the inner diameter of the cylindrical portion (121) of the sintered molded product of the above-mentioned external gear (120) can be manufactured without additional processing, so material loss is small, and rapid manufacturing is possible by turning only the outer diameter portion, which is relatively easy to process.

[0083] In the above-mentioned external tooth processing step, a gear tooth (123) is processed on the outer diameter of the cylindrical portion (121) that was turned in the above-mentioned external diameter turning step. After the above-mentioned external tooth processing step, the outer diameter surface of the above-mentioned external gear (120) is further shot peened.

[0084] A bearing (130) is assembled into the inner diameter of the outer gear (120) manufactured through the steps described above, and the outer diameter surface of the outer ring (133) of the bearing (130) comes into contact with the inner diameter surface, which is the sintered surface of the outer gear (120).

[0085] The above camshaft (140) is manufactured by sintering, and manufacturing is completed by the above sintering.

[0086] The sintered material manufactured from the above camshaft (140) may contain, for example, 0.35 to 0.45 wt% of C (carbon), 1.4 to 1.8 wt% of Ni (nickel), 2.4 to 2.6 wt% of Cr (chromium), and the remainder may be iron. The sintered material forming the internal gear (110) may optionally contain trace elements in addition to the above components. The trace elements may include, for example, trace elements (0.01 wt% or less) such as vanadium (V).

[0087] If the above C (carbon) is less than 0.35 wt%, there is concern that the core density may decrease during heat treatment, and if it exceeds 0.45 wt%, there is concern that the impact resistance may decrease due to brittleness after heat treatment.

[0088] If the above Ni (nickel) is less than 1.4 wt%, the desired hardness and strength are low and the corrosion resistance is weak. If it exceeds 1.8 wt%, the material is brittle and weak to impact and the wear resistance is poor.

[0089] If the above Cr (chromium) is less than 2.4 wt%, there is concern about a deterioration in the mechanical properties of the material, and if it exceeds 2.6 wt%, there is a problem of an increase in the material cost, a deterioration in formability, and oxidation of chromium during sintering.

[0090] The sintered material used to manufacture the camshaft (140) described above is an example and is not limited to the above.

[0091] A camshaft molded body is manufactured from a sintered material forming the camshaft (140), and the sintered material is heated and sintered in a temperature range of 1180 to 1300°C. If the sintering temperature is lower than 1180°C, material diffusion between powders is not smooth, and if it exceeds 1300°C, mass productivity may be significantly reduced.

[0092] The bearing (130) above is manufactured with the rolling element (135), inner ring (131), and outer ring (133) forming the bearing (130) made of bearing steel, carburized steel, etc. The manufacturing method of the bearing (130) is a conventionally known technology, so a description thereof is omitted.

[0093] To briefly explain the hardness of the above bearing (130) with an example, the outer ring (133) and inner ring (131) have a hardness range of 58 to 62 HRc, and the rolling element (135) has a hardness range of 60 to 64 HRc.

[0094]

[0095] In the strain wave gear (100) manufactured by the strain wave gear manufacturing method according to the present invention, the internal gear (110) and the camshaft (140) are completely manufactured by sintering, and only the external gear (120) is manufactured by sintering and then machining the outer surface of the cylindrical portion (121) and the gear teeth (123), and these parts are assembled together with the bearing (130) to manufacture the strain wave gear (100). Therefore, the quality dispersion of each part is small, the parts can be manufactured quickly, and the amount of material wasted in the manufacturing process can be minimized.

[0096]

[0097] While the method for manufacturing a strain wave gear according to the present invention has been described with reference to the embodiments illustrated in the drawings, these are merely exemplary, and anyone skilled in the art will understand that various modifications and equivalent implementations are possible. Therefore, the true scope of technical protection should be determined by the technical spirit of the appended claims.

[0098] The method for manufacturing a strain wave gear according to the present invention is efficient in that it can manufacture a strain wave gear at a low manufacturing cost by significantly reducing material loss, and the product manufacturing cycle time is reduced and quality variation is reduced, making it easy for mass production.

Claims

1. It includes an internal gear (110) in the shape of a ring having a gear tooth (115) formed on the inner diameter and formed along the circumference and having a plurality of through holes (113) formed in the axial direction, an external gear (120) having a gear tooth (123) that meshes with the gear tooth (115) of the internal gear (110), a camshaft (140) provided on the inner side of the external gear (120) and having a wave generating portion (143) formed on the outer diameter surface, and a bearing (130) provided between the external gear (120) and the camshaft (140); The above-mentioned external gear (120) includes a cylindrical portion (121) having a gear tooth (123) that meshes with a gear tooth (115) of an internal gear (110) on the outer diameter, a bottom portion (125) provided at an end of the cylindrical portion (121), and a protrusion (127) that protrudes axially from the bottom portion (125); A method for manufacturing a strain wave gear, characterized in that at least one of the internal gear (110), external gear (120), and camshaft (140) is manufactured by sintering.

2. A method for manufacturing a strain wave gear, characterized in that in the first paragraph, the internal gear (110), the external gear (120), and the camshaft (140) are manufactured by sintering.

3. In the second paragraph, the internal gear (110) and the camshaft (140) are manufactured by sintering, and the external gear (120) is manufactured by turning the outer surface of the cylindrical portion (121) of the sintered sintered molded product after sintering, and a gear tooth (123) is machined on the outer surface; and a strain wave gear manufacturing method characterized in that the internal gear (110), the camshaft (140), and the external gear (120) are assembled together with a bearing (130).

4. A method for manufacturing a strain wave gear, characterized in that in the first or second paragraph, the internal gear (110) is manufactured by sintering and is manufactured from a sintered material containing 0.35 to 0.45 wt% of C (carbon), 1.4 to 1.8 wt% of Ni (nickel), 2.4 to 2.6 wt% of Cr (chromium), the remainder being iron, and optionally containing trace elements.

5. In the first or second paragraph, the external gear (120) is manufactured by including the steps of: sintering a sintered material to manufacture a sintered molded body having a cylindrical portion (121), a bottom portion (125) provided at an end of the cylindrical portion (121), and a protrusion portion (127) protruding from the bottom portion (125); the step of turning the outer diameter of the cylindrical portion of the sintered molded body of the external gear; and the step of processing a gear tooth (123) on the outer diameter of the turned cylindrical portion. A method for manufacturing a strain wave gear, characterized in that a bearing (130) is inserted into the inner diameter of a cylindrical portion (121) of an external gear (120) manufactured as described above.

6. A method for manufacturing a strain wave gear according to claim 1 or 2, wherein the external gear (120) is manufactured by sintering and is manufactured from a sintered material containing 0.35 to 0.45 wt% of C (carbon), 0.1 to 0.35 wt% of Mo (molybdenum), 2.4 to 2.6 wt% of Cr (chromium), the remainder being iron, and optionally containing trace elements.

7. In the fifth paragraph, the external gear (120) is manufactured by sintering, and is characterized in that it is manufactured by a sintered material containing 0.35 to 0.45 wt% of C (carbon), 0.1 to 0.35 wt% of Mo (molybdenum), 2.4 to 2.6 wt% of Cr (chromium), the remainder being iron, and optionally containing trace elements.

8. A method for manufacturing a strain wave gear, characterized in that in the second paragraph, the external gear (120) has a hardness in the range of 38 to 46 HRc, and the internal gear (110) has a hardness in the range of 34 to 42 HRc; and the hardness of the external gear (120) is greater than the hardness of the internal gear (110).

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