Gear chamfering method, chamfering tool, and chamfering tool manufacturing method

Abstract

Provided is a gear chamfering method with which the axial-direction edge part of the tooth surface of each tooth of a gear can be chamfered in a short amount of time. This gear chamfering method comprises a chamfering step in which edge parts 15b, 15c of a plurality of teeth 12 of a gear 10 are chamfered by a chamfering tool 20 equipped with a machining blade 24. If a discretionary integer is represented as K, the number of teeth 12 is represented as Zw, and the number of machining blades 24 is represented as Zt, then in the chamfering step, the gear 10 is rotated by K・Zt / Zw around a rotation axis C1 every time the chamfering tool 20 is rotated once around a tool axis C2 in a machining posture in which the tool axis C2 is disposed non-parallel to the rotation axis C1. Due to this configuration, the machining blade 24 sequentially contacts the plurality of edge parts 15b, 15c, and the edge parts 15b, 15c are chamfered.

Description

[Technical Field]

[0001] The present invention relates to a method for chamfering a gear, a chamfering tool for chamfering a gear, and a method for manufacturing the chamfering tool. [Background technology]

[0002] A method is known in which the tips of each gear tooth are chamfered by rotating a gear while synchronously rotating a chamfering tool about a tool axis parallel to the rotation axis of the gear (Patent Document 1). This chamfering tool has multiple tool teeth around the tool axis, and chamfers the tooth tips of the gear by bringing the tool teeth into contact with the tooth tips of the gear. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 4-146022 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the chamfering tool disclosed in Patent Document 1 is designed to chamfer the tips of gear teeth, and it is difficult to chamfer the axial edges of the tooth flanks of each gear tooth. Also, a method is known in which the edges are chamfered one by one using the bottom cutting edge of an end mill, but this method has the problem of requiring a long processing time.

[0005] The present invention has been made to solve the above-mentioned problems, and aims to provide a gear chamfering method, a chamfering tool, and a method for manufacturing a chamfering tool that can chamfer the axial edge of the tooth flank of each gear tooth in a short period of time. [Means for solving the problem]

[0006] To achieve this object, the present invention provides a gear chamfering method that includes a chamfering step in which a gear having multiple teeth formed around a rotation axis is chamfered using a chamfering tool that rotates around a tool axis. Each of the multiple teeth has a tooth flank that faces the circumferential direction of the gear and an edge portion on the tooth flank in the axial direction of the rotation axis. The chamfering tool has at least one cutting blade formed around the tool axis in a shape corresponding to the shape of the edge portion. Let K be an arbitrary integer, Zw be the number of teeth, and Zt be the number of cutting blades. In the chamfering step, the gear is rotated K·Zt / Zw times around the rotation axis with the tool axis in a machining orientation in which the tool axis is positioned non-parallel to the rotation axis, and each time the chamfering tool rotates around the tool axis, the gear is rotated K·Zt / Zw times around the rotation axis, causing the cutting blade to sequentially contact the multiple edge portions and chamfer the gear. [Effects of the Invention]

[0007] The method for chamfering a gear according to claim 1 includes a chamfering step of chamfering the axial edge of the tooth flanks of multiple gear teeth with a chamfering tool having at least one cutting blade formed around a tool axis. In this chamfering step, the chamfering is performed in a processing position in which the tool axis is positioned non-parallel to the rotation axis. This makes it possible to chamfer the gear edge while rotating the chamfering tool and the gear synchronously.

[0008] If K is an arbitrary integer, Zw is the number of teeth, and Zt is the number of cutting edges, the above synchronous rotation means that for every rotation of the chamfering tool around the tool axis, the gear rotates K·Zt / Zw times around the rotation axis. This synchronous rotation allows the cutting edges, shaped according to the edge shape, to come into contact with multiple edges in sequence, chamfering the edges. This allows the gear edges to be chamfered in a short amount of time.

[0009] Claim 3The gear chamfering method described in claim 1 achieves the following effects in addition to the effects achieved by the gear chamfering method described in claim 1. The number of cutting blades Zt is two or more. In the chamfering process, different cutting blades are brought into contact with the tooth tip side and the tooth bottom side of one edge to perform chamfering. By independently designing the shape of the cutting blade that contacts the tooth tip side of the edge and the shape of the cutting blade that contacts the tooth bottom side of the edge, or by varying the cutting posture when the cutting blades contact, the size and angle of the chamfer on the edge can be adjusted (for example, made uniform) between the tooth tip side and the tooth bottom side.

[0010] Claim 4 The gear chamfering method described in claim 1 achieves the following effect in addition to the effect achieved by the gear chamfering method described in claim 1. The machining position is a state in which the tool axis, which is located on a first imaginary plane including the rotation axis, is translated in a direction perpendicular to the first imaginary plane. In this case, one or more of the edges of the multiple teeth approach parallel to the tool axis. In the chamfering process, by bringing the cutting blade into contact with the edge that has approached parallel to the tool axis and chamfering it, the entire edge can be chamfered with the cutting blade in a short time. As a result, the tooth tip side and tooth bottom side of the edge are chamfered equally by the cutting blade, so the size and angle of the chamfer on the edge can be made uniform across the entire edge.

[0011] Claim 5 The gear chamfering method described in claim 1 achieves the following effect in addition to the effect achieved by the gear chamfering method described in claim 1. The machining position is a state in which the tool axis is tilted with respect to a second imaginary plane perpendicular to the rotation axis. As a result, during the chamfering process, when viewed from the axial direction of the rotation axis, the cutting blade tilts toward the circumferential direction of the gear as the tool rotates around the tool axis. This tilt can cause the cutting blade and the tooth edge to approach parallelism. When the two are approaching parallelism, the cutting blade can be brought into contact with the edge to chamfer it, allowing the entire edge to be chamfered with the cutting blade in a short time. As a result, the cutting blade chamfers the tooth tip side and tooth bottom side of the edge in the same way, making the size and angle of the chamfer on the edge uniform across the entire edge.

[0012] Claim 6The gear chamfering method described in claim 1 achieves the following effect in addition to the effect achieved by the gear chamfering method described in claim 1. The chamfering tool has a rake face that extends from the cutting blade toward the tool axis and faces forward in the direction of rotation of the chamfering tool. Because the rake face and cutting blade are located on a third imaginary plane that includes the tool axis, the phase of the cutting blade rotating around the tool axis can be easily determined from the orientation of the rake face. Therefore, by determining the initial phase of the cutting blade when starting to rotate around the tool axis in the chamfering process using the rake face as a reference, it is easy to determine the initial phase.

[0013] Claim 7 The gear chamfering tool described in claim 6 The present invention relates to a method for chamfering a gear, which is described in the specification. The cutting edge has a radius smaller than the maximum radius of the chamfering tool and is formed on the axial tip side of the chamfering tool. The rake face extends from the position where the cutting edge is formed to the side opposite the tip side of the chamfering tool. This widens the rake face, which is the basis for determining the initial phase of the cutting edge, making it easier to obtain the orientation of the rake face using a sensor or the like, and to determine the initial phase.

[0014] Claim 8 The gear chamfering tool according to the present invention comprises the following features: 5 The chamfering tool is used in the gear chamfering method described in any one of the above. The chamfering tool has a cutting edge formed around a tool axis. This cutting edge has a leading rake face facing forward in the rotation direction of the chamfering tool, a trailing rake face facing rearward in the rotation direction of the chamfering tool, and a connecting surface connecting the radially outer edges of the leading rake face and the trailing rake face. The intersection line between the connecting surface and the leading rake face and the intersection line between the connecting surface and the trailing rake face form a pair of cutting edges that chamfer the edge of the gear.

[0015] As a result, for example, during one rotation of the chamfering tool, one of two circumferentially adjacent edges can be chamfered with the cutting blade on the front rake face while the other of the adjacent edges can be chamfered with the cutting blade on the rear rake face. In this case, compared to when both adjacent edges are chamfered with the same cutting blade, the cutting blade can be formed to a shape suitable for each edge, making it easier to adjust the size and angle of the chamfer on each edge.

[0016] Claim 9 The method for manufacturing the chamfering tool according to the present invention comprises the steps of: 6 This chamfering tool has at least one cutting edge formed around a tool axis, and a rake face extending from the cutting edge toward the tool axis and facing forward in the direction of rotation of the chamfering tool.

[0017] In the gear setting process, the shape of the gear is set, including the shape of the chamfered portion to be formed when the gear edge is chamfered and the number of teeth Zw. In the rotation surface setting process, the shape of a virtual rotation surface that faces the rotation direction of the chamfering tool and rotates around the tool axis is set. In the condition setting process, the initial phase of the rotation surface set in the rotation surface setting process, the processing posture in the chamfering process, an arbitrary integer K, and the number of processing blades Zt are set.

[0018] In the subsequent acquisition step, based on the settings in the condition setting step and the gear setting step, the rotation surface is rotated once around the tool axis from the initial phase in the machining attitude, while the gear is rotated K·Zt / Zw around the rotation axis, and the intersection lines between the rotation surface and the chamfered portion are acquired for each phase. In the formation step, a chamfering tool is formed with a line tangent to the multiple intersection lines acquired in the acquisition step as the cutting edge, and the rotation surface closer to the tool axis than the cutting edge as the rake face. Therefore, the chamfered portion actually formed using this chamfering tool by the gear chamfering method recited in claim 1 can approximate the shape of the chamfered portion set in the gear setting step. [Brief explanation of the drawings]

[0019] [Figure 1]FIG. 2 is a perspective view of a gear and a chamfering tool illustrating a method for chamfering a gear according to the first embodiment. [Figure 2] 2(a) is a front view of the chamfering tool, and FIG. 2(b) is a bottom view of the chamfering tool as seen from the direction of arrow IIb in FIG. 2(a). [Figure 3] 3(a) is a partially enlarged front view of the gear as seen from the direction of arrow IIIa in FIG. 1, and FIG. 3(b) is a partially enlarged plan view of the gear as seen from the direction of arrow IIIb in FIG. 3(a). [Figure 4] 5A to 5C are schematic diagrams illustrating a part of a manufacturing method of a chamfering tool. [Figure 5] 5(a) is a front view of a chamfering tool used in the gear chamfering method according to the second embodiment, and FIG. 5(b) is a bottom view of the chamfering tool as seen from the direction of arrow Vb in FIG. 5(a). [Figure 6] FIG. 10 is a schematic diagram showing a method for chamfering a gear in a third embodiment. [Figure 7] FIG. 10 is a schematic diagram showing a method for chamfering a gear in a fourth embodiment. [Figure 8] 8(a) is a front view of a chamfering tool used in the gear chamfering method of the fifth embodiment, (b) is a side view of the chamfering tool as viewed from the direction of arrow VIIIb in FIG. 8(a), and (c) is a bottom view of the chamfering tool as viewed from the direction of arrow VIIIc in FIG. 8(a). DETAILED DESCRIPTION OF THE INVENTION

[0020] Preferred embodiments will now be described with reference to the accompanying drawings. FIG. 1 is a perspective view of a gear 10 and a chamfering tool 20 (hereinafter referred to as "tool 20") illustrating a method for chamfering the gear 10 in a first embodiment. FIG. 2(a) is a front view of the tool 20. FIG. 2(b) is a bottom view of the tool 20 as viewed from the direction of arrow IIb in FIG. 2(a). Note that the lower half of the gear 10 is not shown in FIG. 1. Also, the rear end side (upper side) of the tool 20 is not shown in FIGS. 1 and 2(a).

[0021] As shown in Figure 1, gear 10 is an external gear having multiple (18 in this embodiment) teeth 12 that protrude radially outward from the outer peripheral surface of a cylindrical body centered on rotation axis C1. The multiple teeth 12 are arranged at equal intervals around rotation axis C1 and have the same shape. Furthermore, the multiple teeth 12 extend parallel to rotation axis C1.

[0022] On the outer peripheral surface of the cylindrical body of gear 10, the surfaces between multiple teeth 12 are tooth root surfaces 13. The radial tip surface of each tooth 12 is tooth tip surface 12a, and a pair of surfaces connecting tooth tip surface 12a and tooth root surface 13 and facing in the circumferential direction are tooth flanks 12b and 12c. If the right side of FIG. 1 in the axial direction of rotation axis C1 (direction of arrow Y) is the front of gear 10, tooth flank 12b faces clockwise and tooth flank 12c faces counterclockwise in the front view.

[0023] The intersection of the end face 14 of the gear 10 in the axial direction of the rotation axis C1 with the tooth crest 12a is the edge 15a. The intersection of the end face 14 with the tooth flank 12b is the edge 15b. The intersection of the end face 14 with the tooth flank 12c is the edge 15c. The intersection of the end face 14 with the tooth root 13 is the edge 15d.

[0024] In such a gear 10, a plurality of teeth 12 are formed by a gear cutting device or a rolling device (not shown). Then, a plurality of edges 15b to 15d are chamfered by a tool 20. Finally, edge 15a is chamfered by another tool (not shown).

[0025] 2(a) and 2(b), the tool 20 includes a cylindrical shank 21 centered on the tool axis C2, a body 22 provided at the axial tip of the shank 21 (lower side in FIG. 2(a)), and a cutting edge 23 extending radially from the body 22. The body 22 tapers away from the shank 21 in the axial direction.

[0026] The rear end of the shank 21 (upper side in FIG. 2(a)), which is the axially opposite side of the body 22, is held by a machine tool such as a multi-tasking machine. A driving force is transmitted from the machine tool to rotate the tool 20 about the tool axis C2. As the tool 20 rotates, the edges 15b to 15d of the gear 10 are chamfered by the cutting portion 23. The rotation direction Rt of the tool 20 when chamfering with the cutting portion 23 is clockwise when viewed from the axially leading end side shown in FIG. 2(b).

[0027] The cutting edge 23 is a portion that protrudes radially outward from the outer peripheral surface of the body 22, and in this embodiment, only one cutting edge 23 is formed around the tool axis C2. The cutting edge 23 includes a processing blade 24 that chamfers the edges 15b to 15d, a rake face 25 that extends from the processing blade 24 toward the tool axis C2, and a clearance face 26 that extends from the processing blade 24 rearward in the rotational direction Rt.

[0028] The processing blade 24 is a cutting edge formed from the leading end to the trailing end in the axial direction of the tool 20 by the intersection line between the rake face 25 and the flank face 26. The shape of the processing blade 24 is determined according to the shape of the edges 15b to 15d to be chamfered. Specifically, the shape of the processing blade 24 extends perpendicularly to the tool axis C2 from the leading end in the axial direction of the tool 20, and then curves convex, concave, and convex in this order toward the trailing end.

[0029] The processing blade 24 is a portion that is smaller than the maximum radius of the tool 20 (shank 21). That is, the portion on the tip side of the imaginary line L in Fig. 2(a) is the processing blade 24. The edges 15b to 15d near the imaginary line L of the processing blade 24 and the linear portion that is connected to the processing blade 24 and extends rearward of the imaginary line L are not chamfered.

[0030] The rake face 25 is a surface for discharging chips generated during chamfering with the cutting blade 24, and faces forward in the rotation direction Rt of the cutting edge 23. The rake face 25 is located on an imaginary plane Pr that includes the tool axis C2, and extends rearward beyond the imaginary line L. The lower ends of the spiral supply holes 22a formed in the shank 21 open toward the rake face 25. When the tool 20 is used for chamfering (cutting), cutting fluid is supplied to the rake face 25 through the supply holes 22a to cool, lubricate, and clean the chamfered portion.

[0031] The flank 26 is a surface for preventing further contact between the portion chamfered by the cutting edge 24 and the tool 20. The flank 26 becomes more distal to the tool axis C2 as it moves away from the cutting edge 24 in the circumferential direction.

[0032] To manufacture the tool 20, the cylindrical alloy constituting the shank 21 is subjected to grinding to cut out the body 22, rake face 25, and flank 26. The surface roughness Rz (maximum height roughness) of the rake face 25 and flank 26 formed by this grinding process is preferably 1.6 or less. In this case, burrs are less likely to occur when the tool 20 is used for chamfering.

[0033] Next, a method for chamfering gear 10 using tool 20 will be described in detail with reference to Figures 1, 3(a), and 3(b). Note that the following describes the case where edge portions 15b to 15d on the right side of Figure 1 are chamfered using tool 20, but the same applies to the case where edge portions 15b to 15d on the left side of Figure 1 are chamfered.

[0034] Fig. 3(a) is a partially enlarged front view of gear 10 as seen in the direction of arrow IIIa (axial direction of rotation axis C1) in Fig. 1. Fig. 3(b) is a partially enlarged plan view of gear 10 as seen in the direction of arrow IIIb (radial direction) in Fig. 3(a).

[0035] To chamfer the edges 15b-15d of the gear 10 with the tool 20, first, the machining orientation of the tool 20 relative to the gear 10 is determined (preparation step). Next, in that machining orientation, the gear 10 is rotated in a rotation direction Rw about the rotation axis C1, while the tool 20 is rotated in a rotation direction Rt about the tool axis C2, so that the machining blade 24 sequentially contacts the edges 15b-15d (chamfering step). Note that the rotation direction Rw in this embodiment is a counterclockwise direction from the tooth surface 12c to the tooth surface 12b.

[0036] In the machining posture of this embodiment, the rotation axis C1 and the tool axis C2 are arranged so as to be perpendicular to each other, and the tip of the tool 20 is arranged so as to be in contact with the root surface 13 when viewed from the axial direction of the rotation axis C1. Since the rotation axis C1 and the tool axis C2 are perpendicular to each other, the tool axis C2 is located on a first imaginary plane P1 that includes the rotation axis C1 and on a second imaginary plane P2 that is perpendicular to the rotation axis C1. In addition, in FIG. 1, the axial direction of the rotation axis C1 is indicated by the arrow Y direction, the axial direction of the tool axis C2 is indicated by the arrow Z direction, and the direction perpendicular to the rotation axis C1 and the tool axis C2 is indicated by the arrow X direction.

[0037] In the chamfering process, the gear 10 is rotated K·Zt / Zw times for each rotation of the tool 20. "K" is an arbitrary integer and is set to 1 in this embodiment. "Zt" is the number of cutting edges 24 of the tool 20, which is 1 in this embodiment. "Zw" is the number of teeth 12 of the gear 10, which is 18 in this embodiment. That is, in the chamfering process of this embodiment, the gear 10 is rotated 1 / 18 times for each rotation of the tool 20. One rotation of the tool 20 constitutes one cycle in the chamfering process.

[0038] 3(a) and 3(b) show contact positions A to E between the edge portions 15b to 15d and the processing blade 24 during one cycle. Contact position A is the position where the processing blade 24 contacts the circumferential center of edge portion 15d. Contact position B is the position where the processing blade 24 contacts edge portion 15b. Contact position C is the position where the processing blade 24 contacts edge portion 15b at a higher position (toward the tooth tip surface 12a) than contact position B. Contact position D is the position where the processing blade 24 contacts edge portion 15c at the same height as contact position B. Contact position E is the position where the processing blade 24 contacts edge portion 15c at the same height as contact position C.

[0039] Furthermore, in Fig. 3(b), the position of the tool axis C2 at contact position A is shown as axis position C2A. Similarly, in Fig. 3(b), the positions of the tool axis C2 at each of contact positions B to E are shown as axis positions C2B to C2E, respectively. Also, in Fig. 3(b), the positions of the rake face 25 at each of contact positions A to E are shown by dashed lines.

[0040] 3(b) also shows by dashed lines the shape of chamfered portion 16d formed by chamfering edge 15d with processing blade 24. Also, in FIG. 3(b), the shape of chamfered portion 16b formed by chamfering edge 15b with processing blade 24 in the vicinity of contact positions B and C is shown by dashed lines. Similarly, the shape of chamfered portion 16c formed by chamfering edge 15c with processing blade 24 in the vicinity of contact positions D and E is shown by dashed lines.

[0041] 3(a) and 3(b), during one cycle of the chamfering process, the cutting blade 24 successively chamfers the edges 15b to 15d by passing through contact positions E, D, A, B, and C in that order. If the tool 20 is moved relative to the gear 10 during this one cycle, as shown in FIG. 3(b), the position of the tool axis C2 moves from axis position C2E to axis position C2C in the opposite direction to the rotation direction Rw, while the tool 20 rotates in the rotation direction Rt.

[0042] At contact position A, the tool axis C2 (axis position C2A) and the cutting edge 24 are aligned on a first imaginary plane P1 that passes through the circumferential center of the edge 15d. Therefore, the synchronous rotation of the tool 20 relative to the gear 10 is symmetrical on both sides of this first imaginary plane P1. This allows the chamfered portions 16b to 16d to be formed symmetrically on both sides of the gear 10 in the circumferential direction with respect to contact position A.

[0043] In the preparation step, the initial phase of the cutting blade 24 is determined so that the tool axis C2 and the cutting blade 24 are aligned on a first imaginary plane P1 that passes through the circumferential center of the edge 15d at the contact position A in the chamfering step. The initial phase of the cutting blade 24 is the position of the cutting blade 24 relative to the tool axis C2 and the gear 10 when the tool 20 (cutting blade 24) starts to rotate. By determining the initial phase in this way, the chamfered portions 16b to 16d can be formed symmetrically with respect to the contact position A, as described above.

[0044] Specifically, the initial phase may be a state in which the tool axis C2 and the cutting blade 24 are aligned on the first imaginary plane P1, or a state in which the gear 10 and the tool 20 are synchronously rotated from that state as in the chamfering process. For example, the initial phase may be the positional relationship between the tool axis C2, the cutting blade 24, and the gear 10 at contact positions B to E. Alternatively, the initial phase may be a state in which the gear 10 is synchronously rotated while the tool 20 is rotated 90 degrees or 180 degrees from the state of contact position A.

[0045] If the cutting blade 24 and the gear 10 interfere with each other in the initial phase, it is preferable to first move the tool 20 away from the gear 10 in the axial or radial direction of the rotation axis C1, and then move the tool 20 closer to the gear 10 during the chamfering process. This causes the cutting blade 24 to gradually cut deeper into the edges 15b to 15d, thereby preventing chipping of the cutting blade 24 and the edges 15b to 15d.

[0046] 2(b), the machining blade 24 and the rake face 25 are located on the virtual plane Pr that includes the tool axis C2, so the phase of the machining blade 24 that rotates around the tool axis C2 can be easily identified from the orientation of the rake face 25. Therefore, in the preparation step, the initial phase of the machining blade 24 can be easily determined by determining the initial phase based on the rake face 25.

[0047] 2(a), the rake face 25 extends further toward the rear end than the imaginary line L (the processing blade 24), so that the rake face 25, which is the reference for determining the initial phase of the processing blade 24, can be widened. This makes it easier to obtain the orientation of the rake face 25 using a sensor or the like, and makes it easier to determine the initial phase.

[0048] 3(a) and 3(b), the chamfered portion 16d is formed by chamfering substantially the entire edge portion 15d with the protruding portion closest to the tip of the processing blade 24. Therefore, the shape and angle of the chamfered portion 16d can be made substantially uniform over the entire circumferential direction.

[0049] Here, when the end face 14 of the gear 10 and the chamfered portions 16b-16d are parallel, the angle of the chamfered portions 16b-16d is defined as 0 degrees. At contact positions B-E, the inclination angle of the rake face 25 (cutting blade 24) relative to the end face 14 is approximately the same as the angle of the chamfered portions 16b, 16c. Therefore, the more the timing at which the chamfered portions 16b, 16c are formed by the cutting blade 24 differs between contact positions B, D and contact positions C, E in the chamfering process, the more the inclination angle of the rake face 25 changes, and the more the angles of the chamfered portions 16b, 16c are misaligned. In the third and fourth embodiments described later, methods for preventing the angles of the chamfered portions 16b, 16c from being misaligned will be described.

[0050] As described above, in the chamfering process of this embodiment, one cycle of successively chamfering the edges 15c, 15d, and 15b in order with the cutting blade 24 is repeated due to the synchronous rotation of the gear 10 and the tool 20, thereby successively chamfering the edges 15b to 15d of the multiple teeth 12. Therefore, the edges 15b to 15d of the gear 10 can be chamfered in a short time.

[0051] As described above, in this chamfering step, a processing blade 24 having a shape corresponding to the shape of the edge portions 15b to 15d is used. A method for manufacturing the tool 20, including a method for designing the processing blade 24, will be described with reference to Fig. 1 and Fig. 4. Fig. 4 is a schematic diagram showing a part of the method for manufacturing the tool 20.

[0052] First, the shape of the gear 10 to be chamfered is set using tool 20 (gear setting process). This shape of the gear 10 includes the dimensions of the gear 10, the number Zw of teeth 12, and the shapes of the chamfered portions 16b-16d to be formed when the edges 15b-15d are chamfered.

[0053] Next, the shape of a virtual surface of rotation that faces the rotation direction Rt of the tool 20 and rotates around the tool axis C2 is set (rotation surface setting process). This virtual surface of rotation is a surface that corresponds to the rake face 25. In this embodiment, the virtual surface of rotation set in the rotation surface setting process is set as a virtual plane Pr that includes the tool axis C2.

[0054] Next, the initial phase of the virtual plane Pr set in the rotation surface setting step, the machining posture in the chamfering step using the tool 20 under design, an arbitrary integer K, and the number Zt of machining blades 24 of the tool 20 are set (condition setting step). The machining posture, integer K, and number Zt in this embodiment are as described above in the description of the chamfering step. The initial phase of the virtual plane Pr is the same as the initial phase of the machining blade 24 (the rake face 25) in the chamfering step described above.

[0055] Next, similarly to the chamfering process, based on the settings in the condition setting process and the gear setting process, the gear 10 is rotated K·Zt / Zw around the rotation axis C1 while rotating the virtual plane Pr once around the tool axis C2 from the initial phase in the machining posture (acquisition process). In this acquisition process, the intersection line 28 between the virtual plane Pr and the chamfered portions 16b to 16d at each phase when the gear 10 and the virtual plane Pr are rotated synchronously is acquired.

[0056] In Fig. 4, some of the multiple intersection lines 28 acquired in the acquisition step are shown arranged on a virtual plane Pr. In addition, in Fig. 4, the number, size, direction, position, etc. of the intersection lines 28 are shown schematically to make it easier to understand how to design the shape of the cutting blade 24.

[0057] In the forming process after the obtaining process, the tool 20 is formed (designed) by defining a line (envelope) tangent to the multiple intersection lines 28 on the side opposite to the tool axis C2 as the cutting edge 24, and defining an imaginary plane Pr closer to the tool axis C2 than the cutting edge 24 as the rake face 25. As a result, the cutting edge 24 of the tool 20 formed in the forming process can actually chamfer the edges 15b-15d at positions close to the chamfered portions 16b-16d set in the gear setting process. Therefore, the chamfered portions 16b-16d actually formed by chamfering can be made to have shapes similar to the chamfered portions 16b-16d set in the gear setting process.

[0058] Furthermore, after the forming step, the shape of the chamfered portions 16b to 16d actually formed by the tool 20 may be compared with the shape of the chamfered portions 16b to 16d set in the gear setting step to determine whether the shape of the tool 20 needs to be reset (determination step). Note that the shape of the chamfered portions 16b to 16d actually formed by the tool 20 may be calculated on a PC based on the shape of the cutting blade 24 determined in the forming step.

[0059] In the determination step, for example, if the actual angles of the chamfered portions 16b to 16d are within -10 degrees to +10 degrees of the set angles of the chamfered portions 16b to 16d, it is determined that resetting is not necessary. On the other hand, if the angles are outside this range, it is determined that resetting is necessary. However, the method for determining whether resetting is necessary may be changed as appropriate depending on the shape of the gear 10, the processing conditions, etc.

[0060] If it is determined in the determination step that resetting is necessary, at least one of the settings in the rotation surface setting step and the condition setting step is changed (change step). After the change step, the acquisition step and formation step are performed again to form (design) the tool 20. If necessary, the determination step through the formation step may be repeated to complete the tool 20. As a result, the chamfered portions 16b to 16d actually formed by the tool 20 can be made closer to the shapes of the chamfered portions 16b to 16d set in the gear setting step.

[0061] Next, a second embodiment will be described with reference to Figures 5(a) and 5(b). In the first embodiment, a tool 20 equipped with one cutting blade 24 was described. In contrast, in the second embodiment, a chamfering tool 30 (hereinafter referred to as "tool 30") equipped with two cutting blades 32, 36 will be described. Note that the same parts as in the first embodiment are designated by the same reference numerals, and the following description will be omitted.

[0062] Fig. 5(a) is a front view of a chamfering tool 30 used in the method for chamfering a gear 10 according to the second embodiment. Fig. 5(b) is a bottom view of the chamfering tool 30 as viewed from the direction of arrow Vb in Fig. 5(a). Note that the rear end (upper side) of the tool 30 is not shown in Fig. 5(a).

[0063] The tool 30 is for chamfering the same gear 10 as in the first embodiment. The tool 30 includes a shank 21, a body 22, and two cutting edges 31 and 35 that extend radially from the outer circumferential surface of the body 22 and are formed around a tool axis C2.

[0064] The two cutting edges 31, 35 are arranged 180 degrees apart from each other around the tool axis C2. The cutting edge 31 includes a cutting edge 32 that chamfers the edges 15b to 15d of the gear 10, a rake face 33 extending from the cutting edge 32 toward the tool axis C2, and a flank face 34 extending from the cutting edge 32 rearward in the rotation direction Rt. Similarly, the cutting edge 35 includes a cutting edge 36, a rake face 37, and a flank face 38. The rake faces 33, 37 and the flank faces 34, 38 have the same functions as the rake face 25 and the flank face 26 in the first embodiment, respectively, and therefore will not be described here.

[0065] The machining blade 32 is a cutting edge formed by the intersection line between the rake face 33 and the flank face 34, extending from the front end to the rear end in the axial direction of the tool 30. The machining blade 36 is a cutting edge formed by the intersection line between the rake face 37 and the flank face 38, extending from the front end to the rear end in the axial direction of the tool 30. Both machining blades 32 and 36 are located on an imaginary plane Pr that includes the tool axis C2.

[0066] 5(a), which shows the rake face 33 from the front, shows the cutting blade 36 rotated 180 degrees around the tool axis C2 and overlapped with the cutting blade 32, as indicated by a two-dot chain line. According to this Fig. 5(a), at the front end of the tool 30, the cutting blade 32 is positioned radially outward of the cutting blade 36. On the other hand, at the rear end of the tool 30, the cutting blade 36 is positioned radially outward of the cutting blade 32.

[0067] Of these processing blades 32, 36, the portions located relatively radially outward are primarily chamfered at the edges 15b-15d to form chamfered portions 16b-16d. The shape of these outer portions is designed in the same manner as the processing blade 24 of the first embodiment. On the other hand, the shape of the portions located relatively radially inward of the processing blades 32, 36 is designed taking into consideration strength, ease of manufacture, and the like.

[0068] The chamfering method in the second embodiment will be described mainly in terms of differences from the chamfering method in the first embodiment. In the chamfering step using the tool 30 in the second embodiment, assuming that an arbitrary integer K is 1, first, while the tool 30 makes half a revolution, the continuous edges 15b-15d are chamfered by the processing blade 32. Next, while the tool 30 makes another half a revolution, the continuous edges 15b-15d that are adjacent to the chamfered edges 15b-15d in the circumferential direction are chamfered by the processing blade 36.

[0069] Here, when the number Zw of teeth 12 of gear 10 is an odd number, edges 15b to 15d that were chamfered by processing blade 32 during the first rotation of gear 10 are chamfered by processing blade 36 during the second rotation. At this time, a portion of processing blade 36 that is positioned radially outward of processing blade 32 comes into contact with edges 15b to 15d and is chamfered, and other portions are not chamfered.

[0070] Similarly, the edges 15b to 15d that were chamfered by the processing blade 36 during the first rotation of the gear 10 are chamfered by the processing blade 32 during the second rotation. At this time, the portion of the processing blade 32 that is positioned radially outward of the processing blade 36 comes into contact with the edges 15b to 15d and is chamfered, while the remaining portions are not chamfered.

[0071] If the number Zw of teeth 12 of the gear 10 is even, the cutting blades 32, 36 continue to chamfer the same edges 15b to 15d. Therefore, when the gear 10 rotates one or more times during the chamfering process, the synchronous rotation of the gear 10 and the tool 30 is stopped. After that, the gear 10 is rotated 1 / Zw or the tool 30 is rotated 1 / 2 to change the phase, and then the synchronous rotation of the gear 10 and the tool 30 is resumed. After this resumption, the edges 15b to 15d are chamfered with cutting blades 32, 36 different from those used before the resumption, as in the second rotation when the number Zw of teeth 12 is odd.

[0072] If the number Zw of teeth 12 is an even number, the processing posture can be changed before and after the synchronous rotation is resumed during the chamfering process. This allows the size and angle of the chamfer on edges 15b to 15d to be changed between the first and second rotations.

[0073] In either case, the tooth tip 12a side of the edges 15b to 15d of one tooth 12 can be chamfered by the cutting blade 36, and the tooth bottom 13 side of the edges 15b to 15d can be chamfered by the cutting blade 32. This allows the shapes of the cutting blades 32 and 36 for chamfering the edges 15b to 15d to be set independently. This allows the size and angle of the chamfer on the tooth tip 12a side and the tooth bottom 13 side to be adjusted (for example, made uniform).

[0074] Next, a third embodiment will be described with reference to Figure 6. In the first embodiment, a case where a gear 10 is chamfered with a tool 20 in a machining posture in which the rotation axis C1 and the tool axis C2 are perpendicular to each other is described. In the third embodiment, a case where a gear 10 is chamfered with a chamfering tool 40 (hereinafter referred to as "tool 40") in a machining posture in which the tool axis C2 is tilted in the direction of arrow Y from the machining posture of the first embodiment is described. Note that the same parts as in the first embodiment are given the same reference numerals, and the following description will be omitted.

[0075] Fig. 6 is a schematic diagram showing a method for chamfering a gear 10 according to a third embodiment. Fig. 6 shows a pair of tooth flanks 12b, 12c that are circumferentially opposed to each other and are part of the circumference of the gear 10. The gear 10 shown in Fig. 6 has its edges 15b-15d chamfered to form chamfered portions 16b-16d. Fig. 6 also shows only the tool axis C2 and cutting blade 41 of a tool 40 that chamfers the gear 10.

[0076] The machining blade 41 of the tool 40 is a cutting edge formed around the tool axis C2 from the leading end to the trailing end in the axial direction of the tool 40. The tool 40 including the machining blade 41 is configured substantially identically to the tool 20 of the first embodiment, except for a partial difference in shape. Note that the shape of the machining blade 41 is designed by changing the machining posture in the acquisition process as in the third embodiment described below, in the same way as in the design method described in the first embodiment.

[0077] The chamfering method of the third embodiment will be described mainly in terms of differences from the chamfering method of the first embodiment. In the machining posture of the third embodiment, the tool axis C2 is positioned on a first imaginary plane P1 (see FIG. 3(b)), which is a YZ plane including the rotation axis C1 (see FIG. 1). Furthermore, in this machining posture, the tool axis C2 is tilted in the direction of arrow Y by an inclination angle θ with respect to a second imaginary plane P2 (see FIG. 3(b)), which is an XZ plane. Note that in FIG. 6, an imaginary line 42 extending from the tip of the tool axis C2 parallel to the second imaginary plane P2 is shown by a two-dot chain line. The angle between this imaginary line 42 and the tool axis C2 is the inclination angle θ.

[0078] When the chamfering process is performed in this processing position, the cutting blade 41 tilts in the circumferential direction of the gear 10 as the tool 40 rotates, as viewed from the direction of arrow Y (the axial direction of the rotation axis C1). This can cause the cutting blade 41 and the edges 15b, 15c of the tooth 12 (the portions before the chamfered portions 16b, 16c are formed) to approach parallelism. When the two are approaching parallelism, for example by adjusting the inclination angle θ, the cutting blade 41 is brought into contact with the edges 15b, 15c to chamfer them. This allows the cutting blade 41 to chamfer the entire edges 15b, 15c in a short time. As a result, the cutting blade 41 chamfers the tooth tip and tooth bottom sides of the edges 15b, 15c in the same way.

[0079] Specifically, as explained with reference to Fig. 3(b), the inclination angle of the processing blade 41 when it comes into contact with the edge portions 15b, 15c, and the inclination angle of the processing blade 41 with respect to the end face 14 can be made uniform on the tooth tip side and the tooth bottom side. Therefore, the size and angle of the chamfering of the processing blade 41 on the edge portions 15b, 15c can be made uniform over the entire edge portions 15b, 15c.

[0080] Next, a fourth embodiment will be described with reference to Figure 7. In the first embodiment, a case where a gear 10 is chamfered by a tool 20 in a machining posture in which the rotation axis C1 and the tool axis C2 are perpendicular to each other is described. In the fourth embodiment, a case where a gear 10 is chamfered by a chamfering tool 50 (hereinafter referred to as "tool 50") in a machining posture in which the tool axis C2 is translated in the direction of arrow X from the machining posture of the first embodiment is described. Note that the same parts as in the first embodiment are designated by the same reference numerals, and the following description will be omitted.

[0081] Fig. 7 is a schematic diagram showing a method for chamfering a gear 10 according to a fourth embodiment. Similar to Fig. 6, Fig. 7 shows a portion of the gear 10 in the circumferential direction. The gear 10 shown in Fig. 7 has its edges 15b-15d chamfered to form chamfered portions 16b-16d. Fig. 7 also shows only the tool axis C2 and cutting blade 51 of a tool 50 used to chamfer the gear 10.

[0082] The machining blade 51 of the tool 50 is a cutting edge formed around the tool axis C2 from the leading end to the trailing end in the axial direction of the tool 50. The tool 50 including the machining blade 51 is configured substantially identically to the tool 20 of the first embodiment, except for a partial difference in shape. Note that the shape of the machining blade 51 is designed by changing the machining posture in the acquisition process as in the fourth embodiment described below, in the same manner as in the design method described in the first embodiment.

[0083] The chamfering method in the fourth embodiment will be described mainly in terms of differences from the chamfering method in the first embodiment. The machining posture in the fourth embodiment is such that the tool axis C2 is parallel to the direction of the arrow Z, and the tool axis C2 is translated from on the first imaginary plane P1 (see FIG. 3(b)) in the direction of the arrow X, which is perpendicular to the first imaginary plane P1.

[0084] In this machining posture, one or more of the edge portions 15b, 15c (portions before the formation of the chamfered portions 16b, 16c) of the multiple teeth 12 approach parallel to the tool axis C2. In Fig. 7, when the tool 50 is pointed downward, the edge portion 15b (edge of the tooth surface 12b) of the tooth 12 at the upper right of the gear 10 approaches parallel to the tool axis C2.

[0085] In the chamfering process, the cutting blade 51 is brought into contact with the edge 15b that has approached parallel to the tool axis C2 to chamfer it. This allows the entire edge 15b to be chamfered in a short time by the cutting blade 51. As a result, the cutting blade 51 chamfers both the tooth tip side and the tooth bottom side of the edge 15b in the same manner.

[0086] Specifically, as explained with reference to Fig. 3(b), the inclination angle of the processing blade 51 when it comes into contact with the edge portion 15b, that is, the inclination angle of the processing blade 51 with respect to the end face 14, can be made uniform on the tooth tip side and the tooth bottom side. Therefore, the size and angle of the chamfering of the edge portion 15b by the processing blade 51 can be made uniform over the entire edge portion 15b.

[0087] After chamfering edge 15b, the chamfering step is performed by partially changing the processing posture to also chamfer edge 15c. As described above with reference to Figure 7, when tool 50 is pointed downward, edge 15b of tooth 12 at the top right of gear 10 approaches parallelism with tool axis C2. At this time, edge 15c (edge of tooth flank 12c) of tooth 12 at the top left of gear 10 also approaches parallelism with tool axis C2.

[0088] Therefore, in the chamfering process for edge 15c, the processing posture (position in the direction of arrow X) is adjusted so that cutting blade 51 contacts edge 15c approaching parallel to tool axis C2, and edge 15c is chamfered. As a result, similar to when chamfering edge 15b, the size and angle of chamfering edge 15c by cutting blade 51 can be made uniform over the entire edge 15c.

[0089] Next, a fifth embodiment will be described with reference to Figures 8(a) to 8(c). In the first embodiment, a tool 20 in which one cutting blade 24 is formed on a cutting portion 23 was described. In the fifth embodiment, a chamfering tool 60 (hereinafter referred to as "tool 60") in which two cutting blades 62, 64 are formed on a cutting portion 61 will be described. Note that the same parts as in the first embodiment are given the same reference numerals, and the following description will be omitted.

[0090] Fig. 8(a) is a front view of a tool 60 used in the method for chamfering a gear 10 according to the fifth embodiment. Fig. 8(b) is a side view of the tool 60 as viewed from the direction of arrow VIIIb in Fig. 8(a). Fig. 8(c) is a bottom view of the tool 60 as viewed from the direction of arrow VIIIc in Fig. 8(a). Note that the rear end (upper side) of the tool 60 is not shown in Figs. 8(a) and 8(b).

[0091] The tool 60 is for chamfering the same gear 10 as in the first embodiment. The tool 60 includes a cylindrical shank 21 centered on a tool axis C2, a cylindrical body 22 provided at the axial tip of the shank 21, and a cutting edge 61 extending radially from the outer peripheral surface of the body 22.

[0092] The cutting edge 61 includes a leading rake face 63 facing forward in the rotation direction Rt, a trailing rake face 65 facing backward in the rotation direction Rt, and a connecting surface 66 connecting the radially outer edges of the leading rake face 63 and the trailing rake face 65. A processing blade 62 is formed by the intersection line between the leading rake face 63 and the connecting surface 66. A processing blade 64 is formed by the intersection line between the trailing rake face 65 and the connecting surface 66. The processing blades 62, 64 are cutting edges formed from the leading end to the trailing end in the axial direction of the tool 60.

[0093] The leading rake face 63 is a surface for discharging chips generated when the cutting blade 62 is used for chamfering. The lower end of a spiral supply hole 68 formed in the shank 21 opens toward the leading rake face 63. When chamfering with the tool 60, cutting fluid is supplied to the leading rake face 63 through the supply hole 68 to cool, lubricate, and clean the chamfered portion.

[0094] The trailing rake face 65 is a surface for discharging chips generated when the cutting blade 64 is used for chamfering. The lower end of a spiral supply hole 69 formed in the shank 21 opens toward the trailing rake face 65. When chamfering with the tool 60, cutting fluid is supplied to the trailing rake face 65 through the supply hole 69 to cool, lubricate, and clean the chamfered portion.

[0095] Since the front rake face 63 and the rear rake face 65 face in opposite directions, the spiral directions of the supply holes 68 and 69 that supply cutting fluid to them are also opposite. However, the supply holes 68 and 69 are formed so as to be offset from each other in the radial direction. This allows the supply holes 68 and 69 to be formed in the shank 21 in different directions without interfering with each other.

[0096] As described above, a pair of processing blades 62, 64 are formed on the cutting portion 61 of the tool 60. Therefore, by adjusting the processing posture during the chamfering process, during one rotation of the tool 60, the edge 15b can be chamfered with the processing blade 62, while the edge 15c adjacent to the edge 15b in the circumferential direction can be chamfered with the processing blade 64. In this case, compared to the first embodiment in which both adjacent edges 15b, 15c are chamfered with the same processing blade 24, the processing blades 62, 64 can be formed in shapes suitable for each of the edges 15b, 15c, making it easier to adjust the size and angle of the chamfer on each of the edges 15b, 15c.

[0097] Specifically, the cutting edge 62 and the front rake face 63 are inclined forward in the direction of rotation as they approach the rear end. This inclination is set so that when the cutting edge 62 and the edge 15b come into contact, the contact area between them is wide from the tooth tip side to the tooth bottom side. This allows the cutting edge 62 to chamfer the entire edge 15b in a short time, and the cutting edge 62 chamfers both the tooth tip side and the tooth bottom side of the edge 15b in the same way. Therefore, the size and angle of the chamfer can be made uniform over the entire edge 15b.

[0098] Similarly, the cutting edge 64 and the trailing rake face 65 are inclined rearward in the direction of rotation as they approach the rear end. This inclination is set so that when the cutting edge 64 and the edge 15c come into contact, the contact area between them is wide from the tooth tip side to the tooth bottom side. This allows the cutting edge 64 to chamfer the entire edge 15c in a short time, and the cutting edge 64 chamfers both the tooth tip side and the tooth bottom side of the edge 15c in the same way. Therefore, the size and angle of the chamfer can be made uniform over the entire edge 15c.

[0099] The present invention has been described above based on an embodiment, but the present invention is not limited to the above embodiment, and it can be easily inferred that various improvements and modifications are possible within the scope of the present invention.

[0100] The numerical values given in the above embodiment are merely examples, and other numerical values can of course be adopted. For example, the number Zt of cutting edges 24, 32, 36, 41, 51, 62, 64 (hereinafter referred to as "cutting edges 24, etc.") provided on tools 20 to 60 may be one or two or more. The surface roughness Rz of the rake faces 25, 33, 37 and flank faces 26, 34, 38, etc. may be greater than 1.6.

[0101] In the above embodiment, the gear 10 is an external gear, but this is not limiting. The gear 10 may be an internal gear in which a plurality of teeth 12 protrude radially inward from the inner peripheral surface of an annular member. Furthermore, the tooth trace direction of the extending teeth 12 does not necessarily have to be parallel to the rotation axis C1, and the tooth trace direction may be inclined relative to the rotation axis C1.

[0102] In the above embodiment, the supply holes 22a, 68, 69 of the tools 20, 60 are formed in a spiral shape, but this is not limited thereto. For example, the supply holes 22a, 68, 69 may be formed in a straight line. Furthermore, the supply holes 22a, 68, 69 may be formed in a spiral or straight line in the tools 30, 40, 50.

[0103] In the above embodiment, the machining blades 24, 32, 36, 41, and 51 are located on an imaginary plane Pr including the tool axis C2. However, the machining blades 24, 32, 36, 41, and 51 do not have to be located on the imaginary plane Pr, as in the case of the machining blades 62 and 64. In this case, a reference plane for determining the initial phase of the machining blade 24 and the like is preferably provided on the outer peripheral surface of the shank 21 or the body 22. This reference plane is preferably parallel to the imaginary plane Pr to make it easier to identify the phase of the machining blade 24 and the like rotating around the tool axis C2.

[0104] In the above embodiment, the case where edge 15b and edge 15c are chamfered by the machining blades 24, 32, 36, 41, and 51 of the same tools 20 to 50 in the chamfering step has been described, but this is not limited to this. The machining posture, machining conditions, and shapes of tools 20 to 50 may be appropriately changed so that only edge 15b is chamfered by tools 20 to 50. In this case, only edge 15c may be chamfered using a tool different from the tools 20 to 50 that chamfer edge 15b.

[0105] In the second embodiment, the cutting blade 32 that chamfers the bottom side of the edges 15b to 15d and the cutting blade 36 that chamfers the tip side of the edges 15b to 15d are provided on a single tool 30. However, this is not limiting. A tool that chamfers the bottom side of the edges 15b to 15d and a tool that chamfers the tip side of the edges 15b to 15d may be prepared separately. For example, after the edges 15b to 15d are entirely chamfered with the tool 20, only the tip side of the edges 15b to 15d may be further chamfered with a separate tool.

[0106] In the above embodiment, the chamfering process is described as being performed in such a manner that the rotational direction Rw of the gear 10 and the rotational direction Rt of the tools 20-60 are almost identical near the portion to be chamfered. However, this is not limited to this. Only the rotational direction Rw may be reversed relative to the identical tracing direction. In the reverse direction, the cutting blade 24 quickly chamfers the edges 15b-15d of the gear 10 to form the chamfered portions 16b-16d, which tends to reduce the angles of the chamfered portions 16b-16d. In this case, the outer diameter of the tools 20-60 can be reduced to increase the angles of the chamfered portions 16b-16d and adjust the angles. In other words, the outer diameter of the tools 20-60 is easier to reduce in the reverse direction compared to the tracing direction.

[0107] In the above embodiment, the machining posture in the chamfering process is exemplified, but the machining posture is not limited to the exemplified one. The machining posture may be any posture in which at least the rotation axis C1 and the tool axis C2 are non-parallel. For example, the machining posture may be such that the tool axis C2 is tilted in the direction of arrow Y with respect to the second imaginary plane P2, as in the third embodiment, and the tool axis C2 is translated from the first imaginary plane P1 in a direction perpendicular to the first imaginary plane P1, as in the fourth embodiment.

[0108] In the above embodiment, the edge portions 15b to 15d of the gear 10 are chamfered by the tools 20 to 60 in the chamfering process, but this is not limiting. The machining posture or the shapes of the tools 20 to 60 may be changed so that the tools 20 to 60 chamfer the edge portions 15b and 15c of the gear 10 but not the edge portion 15d. Conversely, the machining posture or the shapes of the tools 20 to 60 may be changed so that the tools 20 to 60 chamfer the edge portion 15d but not the edges 15b and 15c. Furthermore, the machining posture or the shapes of the tools 20 to 60 may be changed so that the tools 20 to 60 also chamfer the edge portion 15a of the gear 10.

[0109] In the chamfering process using the tools 20, 30, 40, and 60, the processing posture may be changed so that only one of the edges 15b and 15c is chamfered and the other is not chamfered. In this case, as in the fourth embodiment, after a part of the processing posture is changed, only the other of the edges 15b and 15c that was not chamfered before the change may be chamfered.

[0110] In the above embodiment, the case where the arbitrary integer K in the chamfering process is 1 has been exemplified, but the integer K may be 2 or more. However, in the chamfering process when the integer K is 1, the multiple teeth 12 lined up in the circumferential direction can be chamfered by the processing blade 24 or the like without skipping any teeth. In the chamfering process when the integer K is 2 or more, the multiple teeth 12 lined up in the circumferential direction are chamfered by the processing blade 24 or the like while skipping one or more teeth.

[0111] For example, when the integer K is 2, the teeth 12 are chamfered every other tooth 12. In this case, when the number Zw of teeth 12 is odd, the teeth 12 that were skipped in the first rotation of the gear 10 are chamfered in the second rotation. In other words, when the integer K is 2 and the number Zw of teeth 12 is odd, the same chamfering can be applied to each of the teeth 12 without temporarily stopping the synchronous rotation of the gear 10 and the tools 20 to 60, just as when the integer K is 1. The same applies when the integer K and the number Zw of teeth 12 are relatively prime.

[0112] When the integer K and the number Zw of teeth 12 are not coprime, such as when the integer K is 2 and the number Zw of teeth 12 is an even number, it is necessary to temporarily suspend the synchronous rotation and then resume it by rotating only one of the gear 10 or the tools 20 to 60, as in the chamfering process of the second embodiment. In this case, the machining posture can be changed before and after the synchronous rotation is resumed. This allows the size and angle of the chamfer on the teeth 12 to be changed before and after the synchronous rotation is resumed. [Explanation of symbols]

[0113] 10 Gears 12 teeth 12b, 12c tooth surface 15b,15c Edge 16b, 16c Chamfered part 20, 30, 40, 50, 60 chamfering tools 24,32,36,41,51,62,64 Machining blade 25, 33, 37 Rake face 61 Blade part 63 Front scooping face 65 Rear rake face 66 Connecting surface C1 rotation axis C2 tool axis P1 First virtual plane P2 Second virtual plane Pr Virtual plane (third virtual plane, surface of revolution)

Claims

1. A method for chamfering a gear, the method comprising: a chamfering step of chamfering a gear having a plurality of teeth formed around a rotation axis, using a chamfering tool that rotates around a tool axis, the method comprising: The plurality of teeth have tooth surfaces that face in the circumferential direction of the gear; and an edge portion of the tooth surface in the axial direction of the rotation shaft, the chamfering tool includes at least one cutting blade formed around the tool axis in a shape corresponding to the shape of the edge portion, Let K be an arbitrary integer, let Zw be the number of teeth, and let Zt be the number of cutting blades, In the chamfering step, the gear is rotated by K·Zt / Zw about the rotation axis with each rotation of the chamfering tool about the tool axis in a processing attitude in which the tool axis is arranged non-parallel to the rotation axis, and the processing blade is brought into contact with multiple edge portions sequentially to chamfer the gear.

2. A method for chamfering a gear as described in claim 1, characterized in that the machining posture is such that the tool axis is positioned on a first virtual plane including the rotation axis.

3. The number Zt of the processing blades is 2 or more, 2. The method for chamfering a gear according to claim 1, wherein the chamfering step involves bringing different cutting blades into contact with the tooth tip side and the tooth bottom side of one edge portion, respectively.

4. the machining posture is a state in which the tool axis, which is located on a first imaginary plane including the rotation axis, is translated in a direction perpendicular to the first imaginary plane, 2. The method for chamfering a gear according to claim 1, wherein the cutting blade is formed from the leading end to the trailing end in the axial direction of the chamfering tool, and the leading end of the cutting blade chamfers an edge portion in the axial direction of the rotation shaft at a tooth root surface, which is a surface between multiple teeth.

5. 2. The method for chamfering a gear according to claim 1, wherein the machining posture is such that the tool axis is inclined with respect to a second imaginary plane perpendicular to the rotation axis.

6. the chamfering tool has a rake face extending from the cutting blade toward the tool axis and facing forward in a rotation direction of the chamfering tool, the rake face and the cutting edge are located on a third imaginary plane including the tool axis, 2. The method for chamfering a gear according to claim 1, wherein an initial phase of the cutting blade when the cutting blade starts to rotate around the tool axis in the chamfering step is determined based on the rake face.

7. 7. The chamfering tool used in the gear chamfering method according to claim 6, the processing blade is a portion having a radius smaller than the maximum radius of the chamfering tool, and is formed on a tip side in an axial direction of the chamfering tool, The chamfering tool is characterized in that the rake face extends to a side opposite to the tip side beyond a position where the cutting edge is formed.

8. 6. The chamfering tool used in the gear chamfering method according to claim 1, a cutting edge formed around the tool shaft; The blade portion is a front rake face facing forward in the rotation direction of the chamfering tool; a rear rake face facing rearward in the rotation direction of the chamfering tool; a connecting surface connecting radially outer edges of the leading rake face and the trailing rake face, A chamfering tool characterized in that the pair of processing blades that chamfer the edge portion are formed by the intersection line between the connecting surface and the front scooping surface, and the intersection line between the connecting surface and the rear scooping surface.

9. 7. A method for manufacturing the chamfering tool used in the gear chamfering method according to any one of claims 1 to 6, comprising: the cutting blade; and a rake face extending from the cutting blade toward the tool axis and facing forward in the rotation direction of the chamfering tool, a gear setting step of setting a shape of the gear including a shape of a chamfered portion to be formed when the edge portion is chamfered and the number of teeth Zw; a rotation surface setting step of setting a shape of a virtual rotation surface that faces the rotation direction of the chamfering tool and rotates around the tool axis; a condition setting step of setting the initial phase of the rotation surface, the processing posture, an arbitrary integer K, and the number Zt of processing blades set in the rotation surface setting step; an acquiring step of acquiring an intersection line between the rotation surface and the chamfered portion at each phase when the gear is rotated by K·Zt / Zw around the rotation axis while rotating the rotation surface once around the tool axis from the initial phase in the machining attitude based on the settings in the condition setting step and the gear setting step; a forming process for forming the chamfering tool by using a line tangent to the plurality of intersection lines acquired in the acquisition process as the processing blade and using the rotation surface closer to the tool axis than the processing blade as the rake surface.