Heat Treatment Method

Abstract

To suppress the generation of tempering upon hardening a workpiece using a laser beam.SOLUTION: A heat treatment method has a process where the hardening object part of a workpiece is hardened, in which the workpiece is made into the component part of an eccentric oscillation type gear device or a deflection mesh type gear device, and has a first heating step where the hardening object part is heated by a heat source; and a second heating step where the hardening object part heated by the heat source is heated to a hardening temperature or more by the irradiation of a laser beam.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present disclosure relates to a heat treatment method. [Background technology]

[0002] Patent Document 1 discloses a heat treatment method for partially hardening a workpiece by irradiating the workpiece with laser light. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-115681 A Summary of the Invention [Problem to be solved by the invention]

[0004] When hardening a workpiece using a laser beam, the laser beam is usually irradiated over the entire area of ​​the workpiece to be hardened, so the irradiation position of the laser beam needs to be moved. If the area hardened by the laser beam is re-irradiated with the laser beam during this process, there is a problem that the re-irradiated area will be softened by tempering. If this tempering occurs, it becomes impossible to obtain a uniform hardness distribution in the area of ​​the workpiece to be hardened, so an improvement in this case is desired.

[0005] One object of the present disclosure is to suppress the occurrence of tempering when hardening a workpiece using laser light. [Means for solving the problem]

[0006] The heat treatment method disclosed herein is a heat treatment method for hardening a portion of a workpiece to be hardened, the workpiece being a component part of an eccentric oscillating gear device or a flexible meshing gear device, and includes a first heating step of heating the portion to be hardened with a heat source, and a second heating step of heating the portion to be hardened heated by the heat source to a temperature equal to or higher than the hardening temperature by irradiating it with laser light.

[0007] Another heat treatment method disclosed herein is a heat treatment method for hardening a portion of a workpiece to be hardened, the workpiece having a hollow portion and the portion to be hardened on its outer periphery, the method including a first heating step of heating the portion to be hardened by a heat source disposed within the hollow portion, and a second heating step of heating the portion to be hardened heated by the heat source to a temperature equal to or higher than the hardening temperature by irradiating the portion with laser light.

[0008] Another heat treatment method disclosed herein is a heat treatment method for hardening a portion of a workpiece to be hardened, the workpiece having a hollow portion and the portion to be hardened in the hollow portion, the method including a first heating step of heating the portion to be hardened by a heat source arranged on the outer periphery of the workpiece, and a second heating step of heating the portion to be hardened heated by the heat source to a temperature equal to or higher than the hardening temperature by irradiating the portion with laser light. Effect of the Invention

[0009] According to the present disclosure, it is possible to suppress the occurrence of tempering when hardening a workpiece using laser light. [Brief description of the drawings]

[0010] [Figure 1] 1 is a side cross-sectional view of a transmission device according to a first embodiment. [Diagram 2] 2 is a side cross-sectional view showing a state in the middle of irradiating a workpiece with laser light in the heat treatment method of the first embodiment. FIG. [Diagram 3] 3 is a front view showing a state in which a laser beam is irradiated to an end point of an irradiation path of the laser beam in the heat treatment method according to the first embodiment. FIG. [Figure 4]FIG. 2 is an explanatory diagram showing an irradiation path of a laser beam in the first embodiment. [Diagram 5] FIG. 13 is an explanatory diagram showing a modified form of a laser light irradiation path. [Figure 6] 11 is a graph showing temperature transitions at overlapping portions of portions to be hardened by a heat treatment method according to a reference embodiment. [Figure 7] 4 is a graph showing temperature transitions at overlapping locations of portions to be quenched by the heat treatment method of the first embodiment. [Figure 8] FIG. 11 is a side cross-sectional view showing a state in the middle of irradiating a workpiece with laser light in a heat treatment method according to a second embodiment. [Figure 9] FIG. 11 is a side cross-sectional view showing a state in the middle of irradiating a workpiece with laser light in a heat treatment method according to a third embodiment. [Figure 10] FIG. 13 is a side cross-sectional view showing a state in the middle of irradiating a workpiece with laser light in a heat treatment method according to a fourth embodiment. [Figure 11] FIG. 13 is a side cross-sectional view showing a state in the middle of irradiating a workpiece with laser light in a heat treatment method according to a fifth embodiment. [Figure 12] FIG. 13 is a side cross-sectional view of a transmission device according to a sixth embodiment. [Figure 13] FIG. 13 is a side cross-sectional view showing a state in the middle of irradiating a workpiece with laser light in a heat treatment method according to a sixth embodiment. [Figure 14] FIG. 13 is a side cross-sectional view of a transmission device according to a seventh embodiment. [Figure 15] FIG. 13 is a side cross-sectional view showing a state in the middle of irradiating a workpiece with laser light in a heat treatment method according to a seventh embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment will be described. The same components are given the same reference numerals, and duplicated explanations will be omitted. In each drawing, for the sake of convenience, components are omitted, enlarged, or reduced as appropriate. The drawings should be viewed according to the orientation of the reference numerals.

[0012] (First embodiment) Please refer to Fig. 1. First, a transmission device 10 for which the heat treatment method of this embodiment is used will be described. The transmission device 10 includes an input shaft 12, a transmission mechanism 14 that changes the speed of rotation of the input shaft 12, an output member 16 that outputs output rotation from the transmission mechanism 14, and a casing 18 that houses the transmission mechanism 14.

[0013] The transmission device 10 of this embodiment is an eccentric oscillating gear device. The transmission mechanism 14 of this transmission device 10 includes an external gear 22 and an internal gear 24 that mesh with each other and one of which serves as an oscillating gear 20. This transmission mechanism 14 rotates one of the external gear 22 and the internal gear 24 on its axis by oscillating the oscillating gear 20, and the rotation component can be taken out from the output member 16 as output rotation.

[0014] The transmission 10 also includes an eccentric shaft 26 serving as the input shaft 12, an eccentric bearing 30 arranged between the eccentric 28 of the eccentric shaft 26 and the oscillating gear 20, carrier members 32A and 32B arranged on the axial sides of the oscillating gear 20, and a main bearing 34 arranged between the casing 18 and the carrier members 32A and 32B. The carrier members 32A and 32B include a first carrier member 32A arranged on one axial side (right side in the figure) of the oscillating gear 20 and a second carrier member 32B arranged on the other axial side (left side in the figure). The transmission 10 includes a first column member 36 protruding from the second carrier member 32B. In this embodiment, the oscillating gear 20 is an external gear 22, and the output member 16 is the second carrier member 32B.

[0015] The input shaft 12 can be rotated by rotational power transmitted from a drive source (not shown). The drive source is, for example, a motor, a gear motor, an engine, or the like.

[0016] The eccentric shaft 26 has a shaft 27 to which rotational power is transmitted from a drive source, and a plurality of eccentric bodies 28 that are provided on the outer peripheral side of the shaft 27 and can rotate integrally with the shaft 27. In this embodiment, the shaft 27 and the eccentric body 28 are provided integrally as part of the same member, but they may be provided separately from each other. The axis (not shown) of the eccentric body 28 is eccentric with respect to the axis CL1 (axis of the shaft 27) of the eccentric shaft 26, and the oscillating gear 20 can be oscillated by rotating around the axis. The eccentric phases of the plurality of eccentric bodies 28 are shifted by 360° / M when the number of the eccentric bodies 28 is M (three in this embodiment). The number of the eccentric bodies 28 is not particularly limited, and may be one, two, or four or more.

[0017] The eccentric body bearing 30 includes a plurality of first rolling bodies 38. The eccentric body 28 also serves as the inner ring of the eccentric body bearing 30, and its outer peripheral surface forms a first inner rolling surface 40. A first through hole 44 (described later) of the external gear 22 also serves as the outer ring of the eccentric body bearing 30, and its inner peripheral surface forms a first outer rolling surface 42. In addition, the eccentric body bearing 30 may include dedicated outer and inner rings.

[0018] The external gear 22 is provided individually corresponding to the multiple eccentric bodies 28, and is supported by the corresponding eccentric bodies 28 via eccentric body bearings 30 so as to be rotatable relative to the corresponding eccentric bodies 28. The external gear 22 includes a first through hole 44 that axially passes through an axis (not shown) of the external gear 22, and multiple second through holes 46 that axially pass through positions offset from the axis. In this embodiment, the eccentric body shaft 26 passes through the first through hole 44, and the first pillar member 36 passes through the second through hole 46.

[0019] The internal gear 24 is integrated with the casing 18. The carrier members 32A, 32B include a third through hole 48 that penetrates the carrier members 32A, 32B. The carrier members 32A, 32B are generally disk-shaped.

[0020] The main bearing 34 is disposed on the outer periphery of the carrier members 32A, 32B, and allows relative rotation between the casing 18 and the carrier members 32A, 32B. The main bearing 34 is provided with a plurality of second rolling elements 52. The carrier members 32A, 32B also serve as the inner ring of the main bearing 34, and the outer periphery thereof constitutes the second inner rolling surface 54. The carrier members 32A, 32B are provided with the second inner rolling surface 54 provided on the outer periphery of the carrier members 32A, 32B. In addition to this, the main bearing 34 may be provided with a dedicated inner ring.

[0021] The first pillar members 36 are provided at intervals around the axis of the second carrier member 32B at positions offset from the axis of the second carrier member 32B. The first pillar members 36 can be synchronized with the rotation component of the external gear 22 when the external gear 22 as the oscillating gear 20 oscillates. This rotation component can be a positive value when the external gear 22 actually rotates, as well as a zero value when the external gear 22 does not rotate. A roller 50 is disposed between the first pillar member 36 and the external gear 22, capable of rolling contact with them.

[0022] The first pillar member 36 of this embodiment connects the first carrier member 32A and the second carrier member 32B. The first pillar member 36 of this embodiment is a part of the same member as the second carrier member 32B. The second carrier member 32B includes the first pillar member 36 in addition to the disk-shaped main body portion 56. Alternatively, the first pillar member 36 may be a separate member from the second carrier member 32B, or the first carrier member 32A and the second carrier member 32B may not be connected.

[0023] In the above-described transmission device 10, when the eccentric shaft 26 (input shaft 12) is rotated by the drive source, the oscillating gear 20 is oscillated by the eccentric 28. When the oscillating gear 20 oscillates, the meshing positions of the external gear 22 and the internal gear 24 change sequentially in the circumferential direction. As a result, either the external gear 22 or the internal gear 24 rotates on its axis, and the rotation component is taken out from the output member 16 as output rotation.

[0024] Please refer to FIG. 2. The transmission 10 includes a part 60 to be quenched. In this embodiment, the part 60 to be quenched is the eccentric shaft 26. The part 60 to be quenched is quenched when a workpiece W is heat-treated to obtain the part 60 to be quenched by the heat treatment method of this embodiment. The workpiece W is an intermediate product used in the manufacturing process of the part 60 to be quenched, and has a common shape with the part 60 to be quenched. The workpiece W is subjected to required post-processing including a heat treatment method to be described later, to become the part 60 to be quenched as a final product. The post-processing here includes, for example, a finishing process by grinding, a hole processing process to form a through hole, and the like. The part 60 to be quenched is made of a steel material such as chromium molybdenum steel material (SCM material as defined by JIS), that is, a metal material.

[0025] The transmission 10 further includes a contact part 62 that moves relative to the hardened part 60 and comes into contact with the hardened part 60 when the transmission 10 is in operation. The contact part 62 in this embodiment is the first rolling element 38 of the eccentric bearing 30.

[0026] The hardened part 60 has a hollow portion 64 penetrating the hardened part 60 in the axial direction X of the hardened part 60. The axial direction X here refers to a direction along the axial center CLa of the hardened part 60. In this embodiment, this axial center CLa is the axial center of the eccentric body shaft 26. The hollow portion 64 in this embodiment penetrates the axial center CLa of the hardened part 60 in the axial direction X. In addition, the hollow portion 64 may penetrate a position offset from the axial center CLa of the hardened part 60 in the axial direction X. This assumes, for example, a case in which the hardened part 60 is an external gear 22 and the hollow portion 64 becomes the second through hole 46 of the external gear 22.

[0027] The hardened part 60 has a contact surface 66 whose contact position with the contacting part 62 changes continuously when the hardened part 60 and the contacting part 62 move relative to each other. The contact position of the contacting part 62 with respect to the contact surface 66 of the hardened part 60 changes by at least one of rolling contact and sliding contact. In this embodiment, the contact surface 66 of the hardened part 60 is the first inner rolling surface 40 of the eccentric shaft 26, and the contact position of the contacting part 62 (first rolling element 38) with respect to the contact surface 66 changes by rolling contact.

[0028] The quenching target component 60 has at least one quenching target portion 68. In FIG. 2, only the quenching target portion 68 is hatched. The quenching target portion 68 is a portion of the workpiece W that is the quenching target component 60 that is to be quenched. The surface hardness of the quenching target portion 68 is higher than the surface hardness of the quenching target component 60 other than the quenching target portion 68. The microstructure of the quenching target portion 68 has, for example, a martensite structure as a main phase. The microstructure of the portion of the quenching target component 60 other than the quenching target portion 68 has, for example, a base material structure of the quenching target component 60 (for example, a mixed structure of ferrite and pearlite) as a main phase.

[0029] The quenching target portion 68 is, for example, a portion of the quenching target component 60 that requires wear resistance or fatigue strength. By increasing the hardness of a portion that requires one of these characteristics, the characteristic can be improved. In this embodiment, the quenching target portion 68 is the contact surface 66 of the quenching target component 60 that requires wear resistance against rolling contact or sliding contact. In detail, the quenching target portion 68 is the first inner rolling surface 40 of each of the multiple eccentric bodies 28. The quenching target portion 68 is provided on the outer periphery of the quenching target component 60 (the outer periphery of the eccentric body 28). In addition, the quenching target portion 68 may be the root portion 36a of the first column member 36 that requires fatigue strength against bending stress, as described later. The quenching target portion 68 here is plural, the same as the number of the eccentric bodies 28, but the number is not particularly limited and may be single.

[0030] The hardened portion 68 in this embodiment is a circumferential portion provided on the part 60 to be hardened. Here, "circumferential" refers to a shape that is endlessly connected around the axis CLb of the part 68 to be hardened (the axis of the eccentric body 28 in this embodiment). The circumferential shape here may be, for example, a circular shape, a polygonal shape, or the like, or may be a shape in which unevenness is provided partially or entirely. The part 68 to be hardened in this embodiment is provided on the outer periphery of the part 60 to be hardened.

[0031] Next, a heat treatment apparatus 100 used in the heat treatment method of this embodiment will be described. The heat treatment apparatus 100 includes a heat source 102 for heating the workpiece W, which is the part 60 to be hardened, a head 106 for irradiating the workpiece W with a laser beam 104, and a chuck device (not shown) for moving the workpiece W in a chucked state. The heat source 102 is not particularly limited as long as it can heat the workpiece W. The heat source 102 is, for example, a sheath heater, a cast heater, a hot plate, a band heater, an induction heater, or the like. The heat source 102 may heat the workpiece W in a state of contact with the workpiece W, or may heat the workpiece W in a state of not contacting the workpiece W.

[0032] Next, a heat treatment method used for the workpiece W will be described with reference to Figs. 3 and 4. Fig. 4 is also a development view of the hardening target portion 68 cut at the cutting position Pc in Fig. 3, developed on a plane. In Fig. 4, a laser light irradiation path 110 (described later) is indicated by drawing a line at the point where the optical axis of the laser light 104 passes. In the example of Fig. 4, the start point S and end point G of the irradiation path 110 of the laser light 104 are in the same position.

[0033] In the heat treatment method of this embodiment, as described below, the quenching target portion 68 of the workpiece W is heated by moving the irradiation point of the laser beam 104 on the quenching target portion 68 along a predetermined irradiation path 110. To move the irradiation point of the laser beam 104, either the laser beam 104 or the workpiece W is moved. To achieve this, the head 106 that irradiates the laser beam 104 is moved, or the workpiece W is moved by a chuck device. FIG. 3 shows an example in which the irradiation point of the laser beam 104 is moved by rotating the workpiece W around the axis CLb of the quenching target portion 68.

[0034] The irradiation path 110 of the laser beam is set to satisfy the following path conditions. The first path condition is that the laser beam is irradiated to the entire region of the hardening target portion 68. The second path condition is that the irradiation point 114 of the subsequent laser beam partially overlaps with the irradiation point 112 of the preceding laser beam. In Figs. 3 and 4, the overlapping portion 116 of the laser beam is double hatched. To achieve this, the irradiation path 110 of the laser beam in this embodiment is continuous in an annular shape in order to irradiate the entire region of the circumferential hardening target portion 68 with the laser beam. In the irradiation path 110 that is continuous in an annular shape, a start point 118 that is the irradiation point 112 of the preceding laser beam overlaps with an end point 120 that is the irradiation point 114 of the subsequent laser beam.

[0035] A specific example for satisfying this path condition is not limited to this. In addition, in order to satisfy this path condition, the irradiation path 110 of the laser light may be composed of a plurality of linear paths 122A, 122B, and 122C, as shown in FIG. 5. The plurality of linear paths 122A, 122B, and 122C may be continuous in a meandering manner, as shown in FIG. 5. In addition, the plurality of linear paths 122A, 122B, and 122C may be continuous in a spiral manner, or may be arranged discontinuously. In this case, in order to satisfy the above-mentioned path condition, for example, it is sufficient that one adjacent linear path 122A that is the irradiation spot 112 of the preceding laser light and the other adjacent linear path 122C that is the irradiation spot 114 of the following laser light overlap each other.

[0036] Next, the heat treatment method of this embodiment will be described. First, for convenience of explanation, the heat treatment method of the reference embodiment will be described. Please refer to FIG. 6. R is room temperature, M f is the martensitic transformation finish point, Ms is the martensitic transformation start point, T A is the quenching temperature. The Ms point is the quenching temperature T A is the temperature at which martensitic transformation begins when cooling from M f The quenching temperature T is the temperature at which the martensitic transformation is completed. A is the temperature T A This is the temperature at which the material can be hardened by heating it to 100°C and then cooling it. A For example, the A3 point may be used for hypo-eutectoid steel, and the Ac1 point may be used for hyper-eutectoid steel. f Point, quenching temperature T A is set to a predetermined temperature depending on the material of the workpiece W.

[0037] The reference heat treatment method is to set the surrounding environment temperature to room temperature T R(e.g., 25° C.). In this heat treatment method, the quenching target portion 68 of the workpiece W is heated by moving the irradiated portion of the laser light along the above-mentioned irradiation path 110. In this process, the laser light is irradiated prior to the overlapping portion 116 of the quenching target portion 68 (see time point ta1). The laser light heats the quenching temperature T A By heating to the above temperature range, the ferrite structure at the irradiated area is transformed into an austenite structure.

[0038] After that, when the laser beam is no longer irradiated onto the overlapping portion 116 of the hardening target portion 68, the temperature falls to a temperature range below the Ms point (in this example, M f The overlap portion 116 is then cooled to a temperature range below the temperature point (see time ta2). As a result, the austenite structure of the overlap portion 116 is transformed into a martensite structure having high hardness.

[0039] Thereafter, the overlap portion 116 is irradiated again with the subsequent laser beam (see time ta3). Thereafter, when the laser beam is no longer irradiated to the overlap portion 116, the overlap portion 116 is self-cooled (air-cooled) (see time ta4). As a result, the martensite structure in the overlap portion 116 is cooled to the quenching temperature T A By cooling after heating to the above temperature, the material is transformed into a tempered structure such as a troostite structure or a sorbite structure. This tempered structure is the cause of softening due to tempering.

[0040] The outline of the heat treatment method of this embodiment, which is a countermeasure against this problem, will be described with reference to FIG. R , M f ,Ms,T. A The heat treatment method of the present embodiment is also the same as that of FIG. R This is carried out under the following conditions.

[0041] First, a first heating step is performed in which the portion 68 of the workpiece W to be quenched is heated by the heat source 102 (see time point tb1). In the first heating step, the portion 68 of the workpiece W to be quenched is heated so that the entire portion 68 of the workpiece W to be quenched can be maintained in a temperature range above the target temperature (e.g., the Ms point) in the subsequent second heating step. In this embodiment, the heating of the workpiece W by the heat source 102 continues in the subsequent second heating step as well, and the workpiece W is heated so that the temperature can be maintained in a temperature range above the target temperature in both the first heating step and the second heating step.

[0042] Next, the hardening target portion 68 heated by the heat source 102 is irradiated with laser light along the above-mentioned irradiation path 110 to heat the hardening target portion 68 to a hardening temperature T A In the second heating step, the overlapping portion 116 of the hardening target portion 68 is irradiated with the laser light in advance (see time point tb2). By irradiating the laser light in advance, the hardening temperature T A By heating to above this temperature, the ferrite structure at the irradiated area is transformed into an austenite structure.

[0043] After this, when the laser beam is no longer irradiated onto the overlapping portion 116, the hardening temperature T A (see time point tb3). At this time, since the overlap portion 116 has been heated by the heat source 102 in the first heating step, the temperature of the overlap portion 116 can be maintained in a temperature range equal to or higher than a target temperature (here, the Ms point) which is higher than the surrounding environmental temperature. This makes it possible to suppress the occurrence of martensitic transformation of the austenitic structure in the overlap portion 116, compared to the case where heating is not performed by the heat source 102. At this time, the austenitic structure in the overlap portion 116 is maintained in a state of a supercooled austenitic structure.

[0044] After this, the overlap portion 116 is irradiated with the subsequent laser beam again (see time tb4). At this time, in the overlap portion 116, the supercooled austenite structure, not the martensite structure, is quenched to the hardening temperature TA Therefore, even if the overlap portion 116 is irradiated with the subsequent laser beam again, the transformation from the martensite structure to the tempered structure can be suppressed.

[0045] After this, when the laser beam is no longer irradiated onto the overlapping portion 116, the hardening temperature T A At this time, since the overlap portion 116 is heated by the heat source 102 in the first heating step, the overlap portion 116 can be maintained in a temperature range above the target temperature (here, the Ms point) which is higher than the surrounding environmental temperature.

[0046] Thereafter, after the irradiation of the laser light, a cooling step is performed to cool the entire portion to be hardened 68 (see time point tb6). As a result, martensitic transformation proceeds all at once throughout the portion to be hardened 68, and the supercooled austenitic structure of the portion to be hardened 68 is transformed into a martensitic structure.

[0047] As described above, the heat treatment method of this embodiment is performed in the order of the first heating step, the second heating step, and the cooling step. Each step will be described in detail below with reference to FIGS. 2 and 7.

[0048] In the first heating step, as described above, the heat source 102 heats the portion 68 to be hardened 68 (see time tb1). As described above, the heat source 102 heats the workpiece W so that the entire portion 68 to be hardened 68 of the workpiece W can be maintained in a temperature range equal to or higher than the target temperature when the second heating step is performed. This target temperature is, for example, the Ms point super-hardening temperature T A It is set in the temperature range below.

[0049] In this embodiment, the heat source 102 is disposed in the hollow portion 64 of the workpiece W. The heat source 102 heats the quenching target portion 68 on the outer periphery of the workpiece W. In the first heating step, the heat source 102 inputs heat to a portion of the workpiece W other than the quenching target portion 68. The heat source 102 of this embodiment inputs heat to the inner circumferential surface of the hollow portion 64, which serves as the "other portion" here. The portion to which heat is input by the heat source 102 in this embodiment overlaps radially with the quenching target portion 68. In this embodiment, the heat input portion is the range covering the entire circumference of the hollow portion 64 of the workpiece W. The "radial direction" here refers to the radial direction with the axis CLb of the quenching target portion 68 as the center of the circle.

[0050] In the second heating step, as described above, the hardening target portion 68 of the workpiece W heated by the heat source 102 is irradiated with the laser beam 104 to heat the hardening temperature T A The heating is performed within the above temperature range (see time points tb2 and tb4). The upper limit of the heating temperature in the second heating step is not particularly limited, but in reality, the melting point of the material of the part 60 to be hardened is the upper limit.

[0051] In the second heating step, the irradiated portion of the laser beam is moved along the irradiation path 110 described above, so that the entire area of ​​the hardening target portion 68 is heated to the hardening temperature T A The hardened portion 68 is heated to the above temperature range. In this embodiment, the irradiation position of the laser beam is changed around the axis CLb of the hardened portion 68, so that the laser beam is irradiated along the irradiation path 110 (see FIG. 3). Also, in this embodiment, as described above, the start point 118 and the end point 120 of the irradiation path 110 overlap. Therefore, after the laser beam is irradiated over the entire circumferential range of the circumferential hardened portion 68, the laser beam is irradiated again at the overlapping point 116.

[0052] In the second heating step, the hardening target portion 68, which has been maintained in a temperature range above the target temperature (for example, the Ms point) by heating with the heat source 102, is heated to a hardening temperature T Aor more. In the second heating step of this embodiment, in order to maintain the portion 68 to be quenched in a temperature range above the target temperature, as described above, the laser light is irradiated while the heating by the heat source 102 is continued. Alternatively, the portion 68 to be quenched may be heated by the heat source 102 to a temperature range sufficiently higher than the target temperature in the first heating step, and the remaining heat may be used to maintain the portion 68 to a temperature range above the target temperature in the second heating step. In this case, the laser light is irradiated in the second heating step with the heating by the heat source 102 stopped. In this case, it is preferable to make the time interval from the start to the end of the second heating step as short as possible. Thereby, the portion irradiated with the laser light cools down to the quenching temperature T A When the temperature is cooled to a temperature range below the target temperature (here, the Ms point), it is possible to avoid a situation in which the temperature is cooled to a temperature range below the target temperature (here, the Ms point) (see time points tb3 and tb5).

[0053] In the cooling step, as described above, the entire quenching target portion 68 is cooled, thereby quenching the entire quenching target portion 68 (see time tb6). This cooling step is performed at a timing when the heating of the entire quenching target portion 68 by the laser light is completed. In other words, the cooling step is performed at a timing when the irradiation of the laser light along the irradiation path 110 of the laser light is completed. In this embodiment, M f The surrounding environmental temperature (in this embodiment, room temperature T R ) the entire portion 68 to be hardened is hardened by cooling the entire portion 68 to a temperature range of 0.1 to 100° C.

[0054] In the cooling step, the quench-hardening target portion 68 is cooled at a cooling rate capable of causing martensitic transformation (for example, a cooling rate equal to or higher than the lower critical cooling rate). To achieve this, in this embodiment, the heating of the quench-hardening target portion 68 by the heat source 102 is stopped. This allows the quench-hardening target portion 68 to be cooled by air cooling until the surrounding environmental temperature becomes equal to or lower than the Ms point. This cooling mode is not particularly limited, and may be water cooling, oil cooling, or the like.

[0055] When the hardening target component 60 has a plurality of hardening target portions 68, a series of steps consisting of the first heating step, the second heating step, and the cooling step may be performed for each of the hardening target portions 68. Alternatively, each step may be performed collectively on a plurality of the hardening target portions 68. For example, the first heating step may be performed collectively on a plurality of the hardening target portions 68, the second heating step may be performed individually on each of the plurality of the hardening target portions 68, and the cooling step may be performed collectively on the plurality of the hardening target portions 68.

[0056] Also, in the second heating step, a time interval tx (see FIG. 7) is assumed from the start of irradiation of the hardened portion 68 with the laser light to the end of the cooling step. If this time interval tx is too long, a pearlite structure, a bainite structure, or the like will be generated in the hardened portion 68 instead of a martensite structure due to isothermal transformation. To avoid this, it is preferable to set this time interval tx as a predetermined time interval at which isothermal transformation does not occur. This time interval tx may be obtained by experiment, analysis, or the like.

[0057] The effects of the above heat treatment method will now be described.

[0058] (A) In the heat treatment method of the embodiment, the portion 68 to be quenched of the workpiece W heated by the heat source 102 is irradiated with laser light to a quenching temperature T A or more. Therefore, when the portion 68 to be hardened is self-cooled after being heated by irradiation with the laser beam, a large temperature drop that would promote martensitic transformation can be avoided, compared to a case where heating is not performed by the heat source 102. In this embodiment, a large temperature drop refers to a temperature drop below the target temperature (Ms point). This makes it possible to suppress the occurrence of tempering when the laser beam is re-irradiated to the portion irradiated with the laser beam. Furthermore, softening is less likely to occur due to partial tempering in the irradiated range of the laser beam, making it easier to obtain a uniform hardness distribution in the portion 68 to be hardened.

[0059] (B) In the first heating step, the heat source 102 disposed in the hollow portion 64 of the workpiece W is used to heat the portion 68 to be hardened that is on the outer periphery of the portion 68 to be hardened. Therefore, when the workpiece W is heated by the heat source 102, the heat emitted from the heat source 102 is easily trapped in the hollow portion 64 of the workpiece W. As a result, compared to the case where the heat source 102 is disposed outside the hollow portion 64 of the workpiece W, it is possible to easily heat the workpiece W to a desired temperature (a temperature higher than the target temperature in this embodiment) more quickly.

[0060] (C) In the second heating step, the start point 118 and end point 120 of the laser beam irradiation path 110 overlap. Even when following such a laser beam irradiation path 110, tempering at the overlapping portion 116 can be prevented.

[0061] (D) In ​​the first heating step, heat is input from the heat source 102 to a portion of the workpiece W other than the portion 68 to be hardened. This makes it easier to avoid interference between the head 106 irradiating the laser light and the heat source 102 in the second heating step.

[0062] (E) The location where heat is input by the heat source 102 is located radially overlapping with the hardening target portion 68 of the workpiece W. Therefore, compared to when the heat input location by the heat source 102 is the side surface of the workpiece W in the axial direction X, it is easier to homogenize the temperature distribution in the axial direction X of the hardening target portion 68.

[0063] (Second embodiment) Please refer to FIG. 8. In the second embodiment, the components of the transmission device 10 in the first embodiment are the quenching target components 60. More specifically, the quenching target components 60 in the second embodiment are the second carrier member 32B, and the contact components 62 that contact the quenching target components 60 are the second rolling elements 52 of the main bearings 34. When the quenching target components 60 are the carrier member 32B, the axis CLa of the quenching target components 60 is the axis of the main body 56 of the carrier member 32B. In addition, the contact surface 66 of the quenching target components 60 is the second inner rolling surface 54, and the quenching target portion 68 is the second inner rolling surface 54. In this embodiment, the axis CLb of the quenching target portion 68 is the same as the axis CLa of the quenching target components 60. In addition, the hollow portion 64 of the quenching target components 60 is the third through hole 48 of the carrier member 32.

[0064] In the first heating step, the heat source 102 is disposed inside the hollow portion 64 (third through hole 48) of the workpiece W which is the hardening target part 60, similarly to the first embodiment. In other respects, the heat treatment method is similar to that of the first embodiment. For example, in the second heating step, similarly to the first embodiment, the laser light is irradiated along a circularly continuous irradiation path 110 by changing the irradiation position of the laser light around the axis CLb of the hardening target part 68.

[0065] The heat treatment method of this embodiment also includes the components explained above in (A) to (E), and provides the effects corresponding to those explanations.

[0066] (Third embodiment) See FIG. 9. In the third embodiment, the components of the transmission device 10 in the first embodiment are the hardened parts 60. More specifically, the hardened parts 60 in the third embodiment are the second carrier member 32B. Unlike the above-mentioned embodiment, the hardened part 68 in this embodiment is not the contact surface 66 of the hardened part 60, but a circumferential part provided on the outer periphery of the root part 36a of the first pillar member 36 in the second carrier member 32B. The root part 36a of the first pillar member 36 is required to have fatigue strength against bending stress. By increasing the hardness of the outer periphery of this root part 36a, it is possible to improve the fatigue strength. The axis CLb (axis of the pillar member 36) of this hardened part 68 is offset from the axis CLa of the hardened part 60.

[0067] In the first heating step, the heat source 102 is disposed on the side in the axial direction X of the workpiece W, which is the hardening target part 60 (second carrier member 32B). In the first heating step, similarly to the first embodiment, the heat source 102 inputs heat to a portion of the workpiece W other than the portion 68 to be hardened. To achieve this, the portion 68 to be hardened in this embodiment is located on one side of the workpiece W in the axial direction X, and the heat source 102 is disposed on the other side of the workpiece W in the axial direction X. The portion where heat is input by the heat source 102 in this embodiment overlaps in the axial direction X with the portion 68 to be hardened.

[0068] In other respects, the heat treatment method is the same as in the first embodiment. For example, in the second heating step, as in the first embodiment, the laser light is irradiated along a circularly continuous irradiation path 110 by changing the irradiation position of the laser light around the axis CLb of the hardening target portion 68.

[0069] The heat treatment method of this embodiment also includes the components explained in (A), (C), and (D) above, and provides the effects corresponding to those explanations.

[0070] (Fourth embodiment) Please refer to FIG. 10. In the fourth embodiment, the components of the transmission 10 in the first embodiment are the hardened parts 60. More specifically, the hardened parts 60 in the fourth embodiment are the external gear 22, and the contact parts 62 that contact the hardened parts 60 are the internal gear 24. The axis CLa of the hardened parts 60 is the axis of the external gear 22. The contact surface 66 of the hardened parts 60 is the tooth surface 130 provided on the outer periphery of the external gear 22, and the hardened part 68 is the tooth surface 130. In this embodiment, the axis CLb of the hardened part 68 is the same as the axis CLa of the hardened parts 60. The hollow part 64 of the hardened parts 60 is the first through hole 44 of the external gear 22.

[0071] In the first heating step, the heat source 102 is disposed inside the hollow portion 64 of the hardening target part 60 which becomes the first through hole 44 of the external gear 22. In other respects, the heat treatment method is the same as in the first embodiment. For example, in the second heating step, as in the first embodiment, the laser light is irradiated along a circularly continuous irradiation path 110 by changing the irradiation position of the laser light around the axis CLb of the hardening target part 68.

[0072] The heat treatment method of this embodiment also includes the components explained above in (A) to (E), and provides the effects corresponding to those explanations.

[0073] (Fifth embodiment) See FIG. 11. In the fifth embodiment, the components of the transmission 10 in the first embodiment are the hardened components 60. More specifically, the hardened components 60 in the fifth embodiment are the external gear 22, and the contact components 62 that come into contact with the hardened components 60 are the first rolling elements 38 of the eccentric bearing 30. The contact surface 66 of the hardened components 60 is the first outer rolling surface 42 of the first through hole 44 in the external gear 22, and the hardened portion 68 is the first outer rolling surface 42. In this embodiment, the axis CLb of the hardened portion 68 is the same as the axis CLa of the hardened components 60. The hollow portion 64 of the hardened components 60 is the first through hole 44 of the external gear 22.

[0074] In the first heating step, the heat source 102 is disposed on the side in the axial direction X of the workpiece W which is the hardening target part 60. In other respects, the heat treatment method is the same as in the first embodiment. For example, in the second heating step, as in the first embodiment, the laser light is irradiated along a circularly continuous irradiation path by changing the irradiation position of the laser light around the axis CLb of the hardening target part 68.

[0075] The heat treatment method of this embodiment also includes the components explained in (A), (C), and (D) above, and provides the effects corresponding to those explanations.

[0076] (Sixth embodiment) See Fig. 12. The transmission 10 using the heat treatment method of this embodiment is a flexible mesh type gear device, unlike the above-mentioned embodiments. The transmission mechanism 14 of this transmission 10 includes an external gear 152 and internal gears 154A, 154B that mesh with each other and one of which is a flexible gear 150. This transmission mechanism 14 rotates one of the external gear 152 and the internal gears 154A, 154B on its axis by flexibly deforming the flexible gear 150 using a vibration exciter 158, and the rotation component can be taken out as output rotation from the output member 16. The transmission 10 of this embodiment is a cylindrical flexible mesh gear device using a plurality of internal gears 154A, 154B.

[0077] The transmission device 10 also includes an exciter shaft 156 which serves as the input shaft 12, an exciter bearing 160 arranged between an exciter 158 of the exciter shaft 156 and the flexible gear 150, a first cover 162A arranged on one axial side of the flexible gear 150, and a second cover 162B arranged on the other axial side of the flexible gear 150. The flexible gear 150 in this embodiment is an external gear 152, and the output member 16 is the second cover 162B.

[0078] The vibrator shaft 156 includes an exciter 158 and shaft portions 159 provided on both axial sides of the exciter 158. The exciter 158 has a degree of rigidity that allows it to flexibly deform the flexible gear 150 by rotating itself. The outer peripheral shape of the exciter 158 is elliptical in a cross section perpendicular to the axial direction of the exciter shaft 156. The outer peripheral shape of the shaft portions 159 is circular in a cross section perpendicular to the axial direction of the exciter shaft 156. In this specification, the term "ellipse" is not limited to a geometrically strict ellipse, but also includes an approximate ellipse.

[0079] The vibrator bearings 160 correspond to the multiple internal gears 154A, 154B, respectively, and are individually disposed inside the corresponding internal gears 154A, 154B. The vibrator bearings 160 include multiple third rolling elements 164. The outer peripheral surface of the vibrator 158 also serves as the inner ring of the vibrator bearing 160, and this outer peripheral surface constitutes a third inner rolling surface 166. Alternatively, the vibrator bearing 160 may include a dedicated inner ring.

[0080] The external gear 152 constituting the flexure gear 150 is a flexible cylindrical member.

[0081] The internal gears 154A, 154B have a degree of rigidity that does not deform following the rotation of the vibration exciter 158. The internal gears 154A, 154B include a first internal gear 154A having a number of internal teeth (e.g., 102) different from the number of external teeth of the external gear 152 (e.g., 100), and a second internal gear 154B having the same number of internal teeth as the number of external teeth of the external gear 152.

[0082] The casing 18 includes a first casing member 168 that also serves as the first internal gear 154A, and a second casing member 170 that is disposed on the outer periphery of the second internal gear 154B. The first casing member 168 and the second casing member 170 are integrated together by being connected to each other. A main bearing 34 that allows relative rotation between the second casing member 170 and the second internal gear 154B is disposed between them. The first cover 162A is integrated with the casing 18 by being connected to the casing 18. The second cover 162B is integrated with the second internal gear 154B by being connected to the second internal gear 154B.

[0083] In the above-described transmission device 10, when the vibrator shaft 156 (input shaft 12) is rotated by the driving source, the flexible gear 150 is flexibly deformed to form an elliptical shape that matches the shape of the vibrator 158. When the flexible gear 150 is flexibly deformed in this manner, the meshing positions of the external gear 152 and the internal gears 154A and 154B change in the rotation direction of the vibrator 158. At this time, the meshing positions of the external gear 152 and the first internal gear 154A, which have different numbers of teeth, shift in the circumferential direction every time they make one revolution. As a result, one of them (the external gear 152 in this embodiment) rotates on its axis, and the rotation component is taken out from the output member 16 as the output rotation. At this time, since the external gear 152 and the second internal gear 154B have the same number of teeth, they are synchronized without rotating relative to each other even if their meshing positions make one revolution. Therefore, the rotation component of the external gear 152 is taken out from the second cover 162B serving as the output member 16 through the second internal gear 154B that is synchronized with the external gear 152.

[0084] 13. Here, in this embodiment, the hardening target part 60 is the vibrator shaft 156, and the contact part 62 that contacts this hardening target part 60 is the third rolling element 164 of the vibrator bearing 160. The axis CLa of this hardening target part 60 is the axis of the vibrator shaft 156. In addition, the contact surface 66 of the hardening target part 60 is the third inner rolling surface 166 provided on the outer periphery of the vibrator 158, and the hardening target portion 68 is the outer periphery (third inner rolling surface 166) of the vibrator 158. In this embodiment, the axis CLb of this hardening target portion 68 is the same as the axis CLa of the hardening target part 60.

[0085] In the first heating step, the heat source 102 is disposed inside the hollow portion 64 of the workpiece W which is the part 60 to be hardened, similarly to the first embodiment. In other respects, the heat treatment method is similar to that of the first embodiment. For example, in the second heating step, similarly to the first embodiment, the laser light is irradiated along a circularly continuous irradiation path 110 by changing the irradiation position of the laser light around the axis CLb of the part 68 to be hardened.

[0086] The heat treatment method of this embodiment also includes the components explained above in (A) to (E), and provides the effects corresponding to those explanations.

[0087] (Seventh embodiment) See Fig. 14. The transmission 10 to which the heat treatment method of this embodiment is applied is a planetary transmission 10, specifically a traction drive, unlike the above-mentioned embodiments. The transmission mechanism 14 of this transmission 10 includes a sun member 180 to which the rotation of the input shaft 12 is transmitted, a plurality of planetary members 182 that revolve while rotating due to the rotation of the sun member 180, a second pole member 184 that penetrates the planetary members 182, a third carrier member 186 that is integrated with the second pole member 184 and synchronizes with the orbital component of the planetary members 182, and a needle bearing 188 that is disposed between the second pole member 184 and the planetary members 182.

[0088] The output member 16 in this embodiment is integrated with the third carrier member 186. In this embodiment, the sun member 180 and the planetary member 182 constitute a sun roller and a planetary roller, and power is transmitted between them by friction transmission. Alternatively, the sun member 180 and the planetary member 182 may constitute a sun gear and a planetary gear. The planetary member 182 has a fourth through hole 190 through which the second pillar member 184 passes.

[0089] The needle bearing 188 includes a plurality of fourth rolling elements 192. The fourth through hole 190 of the planetary member 182 doubles as the outer ring of the needle bearing 188, and its inner circumferential surface defines a second outer rolling surface 194 on which the fourth rolling elements 192 roll. Alternatively, the needle bearing 188 may include a dedicated outer ring.

[0090] In the above-described transmission device 10, when the sun member 180 is rotated by the rotation of the input shaft 12, the planetary members 182 revolve while rotating on their axes. When the planetary members 182 revolve, the orbital component is taken out as output rotation from the output member 16 via the third carrier member 186.

[0091] 15. In this embodiment, the hardening target component 60 is a planetary member 182, and the contact component 62 that contacts the hardening target component 60 is the fourth rolling element 192 of the needle bearing 188. The axis CLa of the hardening target component 60 is the axis of the planetary member 182. The contact surface 66 of the hardening target component 60 is the second outer rolling surface 194 of the fourth through hole 190 of the planetary member 182, and the hardening target portion 68 is the second outer rolling surface 194, that is, the inner circumferential surface of the hollow portion 64. In this embodiment, the axis CLb of the hardening target portion 68 (the axis of the hollow portion 64) is the same as the axis CLa of the hardening target component 60. The hollow portion 64 of the hardening target component 60 is the fourth through hole 190 of the planetary member 182.

[0092] In the first heating step, unlike the previous embodiment, the heat source 102 is disposed on the outer periphery of the workpiece W which is the hardening target part 60 (planet member 182). In other respects, the heat treatment method is the same as in the first embodiment. For example, in the second heating step, as in the first embodiment, the laser light is irradiated along a circularly continuous irradiation path by changing the irradiation position of the laser light around the axis CLb of the hardening target portion 68.

[0093] The heat treatment method of this embodiment also includes the components explained in (A), (C), (D), and (E) above, and provides the effects corresponding to those explanations.

[0094] Other variations of each component are described.

[0095] In the first embodiment and the like, the center crank type in which the eccentric body shaft 26 is disposed on the axis of the internal gear 24 has been described as an example of the type of eccentric oscillating gear device. This type is not particularly limited, and a distributed type in which a plurality of eccentric body shafts 26 are disposed at positions offset from the axis of the internal gear 24 may also be used. In the distributed type, the eccentric body shaft 26 is often of a solid structure. When hardening the eccentric of the eccentric body shaft 26 having a solid structure, the first heating step may be performed by placing the heat source 102 opposite, for example, the axial end face of the eccentric body shaft 26 or the outer periphery of the shaft portion adjacent to the eccentric. In addition, in the eccentric oscillating gear device, the internal gear 24 may be the oscillating gear 20 instead of the external gear 22. In the eccentric oscillating gear device, a specific example of the output member 16 is not particularly limited, and may be a casing 18 or the like.

[0096] The flexible mesh gear device has been described taking a cylindrical type as an example. This type is not particularly limited, and may be, for example, a cup type or a top hat type. In addition, in the flexible mesh gear device, the internal gear 24 may be a flexible gear 150 instead of the external gear 22. In the flexible mesh gear device, the output member 16 is not particularly limited, and may be a casing 18, etc.

[0097] In relation to the effect of (A), when heat-treating the workpiece W that is the hardening target part 60 used in the eccentric oscillating gear device or the flexible meshing gear device, the presence or absence of the hollow part 64 in the workpiece W is not an issue. For example, the workpiece W that is the eccentric body shaft 26, the vibration exciter shaft 156, or the second carrier member 32B may not have the hollow part 64. Also, when heat-treating the workpiece W that is the hardening target part 60 used in the eccentric oscillating gear device, the specific example of the hardening target part 60 is not particularly limited. The workpiece W has been described as being the eccentric body shaft 26 (first embodiment), the second carrier member 32B (second and third embodiments), or the external gear 22 (fourth and fifth embodiments). In addition, the workpiece W may be the casing 18 of the eccentric oscillating gear device, or may be a component part (e.g., outer ring, inner ring) of a bearing such as the main bearing 34 or the eccentric bearing 30. Furthermore, when heat treatment is performed on the workpiece W that is the hardening target component 60 used in the flexural mesh gear device, the specific example is not particularly limited. An example in which the workpiece W is the vibration exciter shaft 156 (sixth embodiment) has been described. In addition to this, the workpiece W may be the casing 18 and covers 162A and 162B of the flexural mesh gear device, or may be a component part of a bearing such as the main bearing 34 or the vibration exciter bearing 160.

[0098] In relation to the effect of (A), when the workpiece W has a hollow portion 64 and the portion to be hardened 68 is the outer periphery or the hollow portion 64 of the workpiece W, the specific example of the transmission device 10 in which the hardened part 60 obtained from the workpiece W is used is not particularly limited. This transmission device 10 may be, for example, a motor, a belt conveyor, or the like, in addition to a gear device. Furthermore, when this transmission device 10 is a gear device, the type of this gear device is not particularly limited. As specific examples, in addition to an eccentric oscillating gear device and a flexible meshing gear device, a parallel shaft gear device, an orthogonal shaft gear device, a simple planetary gear device, or the like may be used.

[0099] Furthermore, when the outer periphery of the workpiece W having the hollow portion 64 is the hardening target portion 68, there is no particular limitation on the specific example of the hardening target part 60 obtained from the workpiece W. For example, the hardening target part 60 may be various components of the gear device described above (e.g., the casing 18, the internal gear 24, the outer ring or inner ring of the bearing, etc.).

[0100] Furthermore, when the hollow portion 64 of the workpiece W having the hollow portion 64 is the hardening target portion 68, there is no particular limitation on a specific example of the hardening target part 60 obtained from the workpiece W. For example, the hardening target part 60 may be any of the various components of the gear device described above (e.g., the eccentric body shaft 26, the external gear 22, the internal gear 24, the vibrator shaft 156, etc.). Furthermore, when a planetary member 182 is used as the hardening target part 60 that satisfies this condition, the planetary member 182 may be a planetary gear or the like in addition to a planetary roller.

[0101] In the above example, the target temperature is the Ms point when the heat source 102 is heated in the first heating step so that the quenching target portion 68 of the workpiece W can be maintained in a temperature range above the target temperature when the second heating step is performed. This target temperature may be any temperature that can avoid the promotion of martensitic transformation in the self-cooling in the second heating step compared to the case where heating is not performed by the heat source 102 (that is, it may be any temperature that can suppress softening due to tempering). As long as this condition can be satisfied, the specific temperature may be a temperature below the Ms point.

[0102] Although an example has been described in which the hardening target portion 68 is a circumferential portion, the present invention is not limited to this. The hardening target portion 68 may be, for example, a partial range that is continuous in the circumferential direction of the hardening target part 60. This assumes, for example, a case in which the hardening target part 60 obtained from the workpiece W is a gear, and the hardening target portion 68 is only the tooth contact surface of the gear.

[0103] There is no particular limitation on the relative positional relationship between the portion 68 to be hardened in the workpiece W and the portion where heat is input by the heat source 102. For example, these may be different from or the same as those in the embodiment.

[0104] Furthermore, the position of the portion 68 to be hardened in the workpiece W and the location of the heat source 102 are not particularly limited. For example, when heat treating the workpiece W which will be the eccentric body shaft 26 or the vibrator shaft 156, either the hollow portion 64 or the side surface in the axial direction X may be the portion to be hardened 68. Furthermore, when heat treating this workpiece W, the heat source 102 may be disposed outside the workpiece W instead of inside the hollow portion 64 of the workpiece W.

[0105] Besides, when the workpiece W to be the carrier members 32A and 32B is subjected to heat treatment, the quenching target portion 68 may be, for example, the outer periphery of the first pillar member 36, the through hole 48 of the carrier member 32B, etc. When the second inner rolling surface 54 of the carrier members 32A and 32B is the quenching target portion 68 (see FIG. 8), the heat source 102 may be disposed on the side of the workpiece W in the axial direction X instead of inside the hollow portion 64 of the workpiece W. When the root portion 36a of the first pillar member 36 of the carrier member 32 is the quenching target portion 68 (see FIG. 9), the heat source 102 may be disposed on the inside of the hollow portion 64 of the workpiece W instead of on the side of the workpiece W in the axial direction X.

[0106] Besides, when the tooth surface 130 of the external gear 22 of the eccentric oscillating gear device is the hardening target portion 68 (see FIG. 10), the heat source 102 may be arranged on the side of the workpiece W in the axial direction X instead of inside the hollow portion 64 of the workpiece W. Furthermore, when the first through hole 44 or the second through hole 46 of the external gear 22 is the hardening target portion 68 (see FIG. 11), the heat source 102 may be arranged on the inside of the hollow portion 64 of the workpiece W instead of on the side of the workpiece W in the axial direction X. The hollow portion 64 of the workpiece W here may be either the first through hole 44 or the second through hole 46 of the external gear 22.

[0107] The above-mentioned embodiment and modified forms are merely examples. The technical ideas abstracted from these should not be interpreted as being limited to the contents of the embodiment and modified forms. Many design changes are possible in the contents of the embodiment and modified forms, such as changing, adding, or deleting components. In the above-mentioned embodiment, the contents in which such design changes are possible are emphasized by adding the notation "embodiment". However, design changes are also permitted even in contents without such notation. The hatching on the cross section of the drawing does not limit the material of the object to which the hatching is added.

[0108] Any combination of the above components is also effective. For example, any description of another embodiment may be combined with the embodiment, or any description of an embodiment and another variation may be combined with the variation. [Explanation of symbols]

[0109] W...workpiece, 22...external gear, 26...eccentric body shaft, 28...eccentric body, 32A, 32B...carrier member, 34...main bearing, 36...column member, 36a...root portion, 44, 46...through hole, 64...hollow portion, 68...area to be hardened, 102...heat source, 104...laser light, 110...irradiation path, 118...starting point, 120...end point, 130...tooth surface, 156...vibrator shaft, 158...vibrator.

Claims

1. A heat treatment method for hardening a target portion of a workpiece, comprising the steps of: The workpiece is a component part of an eccentric oscillating gear device or a flexible meshing gear device, A first heating step of heating the portion to be quenched by a heat source; a second heating step of heating the portion to be quenched, which has been heated by the heat source, to a temperature equal to or higher than the quenching temperature by irradiating the portion with a laser beam; a cooling step of quenching the hardening target portion by cooling the hardening target portion after the irradiation of the laser light, the hardening target portion has an overlapping portion where an irradiated portion of a subsequent laser beam overlaps an irradiated portion of a preceding laser beam, A heat treatment method in which, in the first heating step, the portion to be quenched, which has the overlapping portion in the second heating step, is heated by the heat source so that the portion to be quenched can be maintained in a temperature range higher than the martensitic transformation start point and lower than the quenching temperature in the second heating step.

2. The portion to be hardened is a circumferential portion, In the second heating step, the quenching target portion is heated by moving an irradiation point of the laser light on the quenching target portion along an irradiation path; The heat treatment method according to claim 1 , wherein the start point and the end point of the irradiation path overlap each other.

3. The heat treatment method according to claim 1 or 2, wherein in the first heating step, the heat source applies heat to a portion of the workpiece other than the portion to be hardened.

4. A heat treatment method for hardening a target portion of a workpiece, comprising the steps of: The workpiece is a component part of an eccentric oscillating gear device or a flexible meshing gear device, A first heating step of heating the portion to be quenched by a heat source; a second heating step of heating the portion to be quenched, which has been heated by the heat source, to a temperature equal to or higher than the quenching temperature by irradiating the portion with a laser beam; a cooling step of quenching the hardening target portion by cooling the hardening target portion after the irradiation of the laser light, the hardening target portion has an overlapping portion where an irradiated portion of a subsequent laser beam overlaps an irradiated portion of a preceding laser beam, In the first heating step, the portion to be quenched having the overlapping portion in the second heating step is heated by the heat source so that the portion to be quenched having the overlapping portion in the second heating step can be maintained in a temperature range above a martensitic transformation start point; the workpiece serves as an eccentric shaft having an eccentric in the eccentric oscillating gear device and has a hollow portion; The hardening target portion is an outer periphery of the eccentric body, The heat source is disposed within the hollow portion.

5. A heat treatment method for hardening a target portion of a workpiece, comprising the steps of: The workpiece is a component part of an eccentric oscillating gear device or a flexible meshing gear device, A first heating step of heating the portion to be quenched by a heat source; a second heating step of heating the portion to be quenched, which has been heated by the heat source, to a temperature equal to or higher than the quenching temperature by irradiating the portion with a laser beam; a cooling step of quenching the hardening target portion by cooling the hardening target portion after the irradiation of the laser light, the hardening target portion has an overlapping portion where an irradiated portion of a subsequent laser beam overlaps an irradiated portion of a preceding laser beam, In the first heating step, the portion to be quenched having the overlapping portion in the second heating step is heated by the heat source so that the portion to be quenched having the overlapping portion in the second heating step can be maintained in a temperature range above a martensitic transformation start point; the workpiece serves as a vibration exciter shaft having a vibration exciter in the flexure mesh type gear device and has a hollow portion; The hardening target portion is the outer periphery of the vibrator, The heat source is disposed within the hollow portion.

6. A heat treatment method for hardening a target portion of a workpiece, comprising the steps of: The workpiece is a component part of an eccentric oscillating gear device or a flexible meshing gear device, A first heating step of heating the portion to be quenched by a heat source; a second heating step of heating the portion to be quenched, which has been heated by the heat source, to a temperature equal to or higher than the quenching temperature by irradiating the portion with a laser beam; a cooling step of quenching the hardening target portion by cooling the hardening target portion after the irradiation of the laser light, the hardening target portion has an overlapping portion where an irradiated portion of a subsequent laser beam overlaps an irradiated portion of a preceding laser beam, In the first heating step, the portion to be quenched having the overlapping portion in the second heating step is heated by the heat source so that the portion to be quenched having the overlapping portion in the second heating step can be maintained in a temperature range above a martensitic transformation start point; The workpiece is a carrier member disposed axially to the side of the external gear, The hardening target portion is an inner rolling surface of a main bearing disposed on an outer periphery of the carrier member, or a base portion of a pillar member protruding from the carrier member and penetrating the external gear, A heat treatment method in which the heat source is placed inside a hollow portion provided in the workpiece or on an axial side of the workpiece.

7. The workpiece becomes the external gear of the eccentric oscillating gear device, the hardening target portion is an inner circumferential surface or a tooth surface of a through hole provided in the external gear, 4. The heat treatment method according to claim 1, wherein the heat source is disposed inside a hollow portion of the workpiece that serves as the through hole, or on a lateral side in the axial direction of the workpiece.

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