Gear machining method

Abstract

To provide a gear processing method that enables a remaining processing site to assume a desired shape, when a part of a site processed by rough processing is left after finish processing.SOLUTION: A gear processing method includes: error estimation steps S11 and S21 of estimating an error Δθ between a synchronous command angle 84c and a synchronous actual angle 84r concerning a synchronous angle between a workpiece W and a gear skiving cutter T when finish processing is applied to tooth flanks 71 and 72 constituting a convex tooth subjected to rough processing; and processing steps S13-S16 and S23-S26 of performing processing by correcting a rough processing shape 70 of the convex tooth or processing conditions of the finish processing, on the basis of the estimated error Δθ.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present invention relates to a gear machining method. [Background technology]

[0002] Patent Document 1 describes a method for machining gears on a workpiece using a gear skiving cutter. In this type of gear machining method, rough machining of the gear's protruding teeth is performed, followed by heat treatment and then finish machining of the gear's protruding teeth. Before the finish machining, the position (phase) of the protruding teeth formed by the rough machining is detected to determine the initial positioning angle of the workpiece around its rotation axis. Then, while the workpiece and the gear skiving cutter rotate synchronously, the gear skiving cutter is moved relative to the workpiece in the axial direction, thereby performing the finish machining of the protruding teeth on the workpiece. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Special Publication No. 2014-516807 [Overview of the project] [Problems that the invention aims to solve]

[0004] In gear machining using a gear skiving cutter, the cutting edge position on one tooth surface constituting a convex tooth is different from the cutting edge position on the other tooth surface. As a result, the cutting resistance on one tooth surface is different from the cutting resistance on the other tooth surface. Therefore, the material removal amount (cutting depth) on each tooth surface differs in a single feed operation of the gear skiving cutter.

[0005] Incidentally, sometimes chamfers are formed on the tips of the protruding teeth of a gear. In such cases, the tooth tips are formed by rough machining, and then the tooth surfaces of the protruding teeth are finished in such a way that a portion of the chamfer remains. In such cases, as mentioned above, if the amount of material removed from each tooth surface differs during the finishing process, the size of the remaining chamfers on each tooth tip will differ after the finishing process. The same applies to other parts formed by rough machining that remain after the finishing process.

[0006] This invention has been made in view of the above problems, and aims to provide a gear machining method that allows the shape of the remaining machined portion to be a desired shape when a portion of the machined portion from rough machining is left after finishing machining. [Means for solving the problem]

[0007] One aspect of the present invention is a gear machining method for machining protruding teeth of a gear on a workpiece using a gear skiving cutter, This method is applicable to a machining process that involves rough machining of the tooth surface constituting the convex tooth and the adjacent portion of the tooth surface, and finishing machining of at least the tooth surface while leaving a portion of the adjacent portion after the rough machining. The aforementioned The protruding teeth that have been roughly machined The aforementioned against the tooth surface The aforementioned When performing finishing work, an error estimation step is performed to estimate the error between the synchronization command angle and the actual synchronization angle with respect to the synchronization angle between the workpiece and the gear skiving cutter. The process includes a machining step of correcting the rough machining shape of the convex tooth or the machining conditions for the finishing process based on the estimated error, and then performing the machining. 、 The aforementioned processing step is Based on the estimated error, the shape of the adjacent portion is corrected, and the rough machining is performed to form the tooth surface and the adjacent portion. After the rough machining, the tooth surface is machined based on the synchronized command angle, thereby performing the finishing machining on the tooth surface while leaving a portion of the adjacent area intact. It is located in the gear manufacturing method. Another aspect of the present invention is a gear machining method for machining protruding teeth of a gear on a workpiece using a gear skiving cutter, When performing finish machining on the tooth surface constituting the convex tooth that has been roughly machined, an error estimation step is performed to estimate the error between the synchronization command angle and the actual synchronization angle with respect to the synchronization angle between the workpiece and the gear skiving cutter, The process includes a machining step of correcting the rough machining shape of the convex tooth or the machining conditions for the finishing process based on the estimated error, The aforementioned machining step is a gear machining method that corrects the synchronization command angle so that the material removal amount for one tooth surface constituting the convex tooth and the material removal amount for the other tooth surface are the same based on the estimated error, and then performs the finishing machining on the tooth surface based on the corrected synchronization command angle. [Effects of the Invention]

[0008] In gear machining using a gear skiving cutter, as a machining command value, in one feed operation of the gear skiving cutter, it is set so that the machining allowance (cutting depth) of each tooth surface is the same. However, due to the difference in the cutting resistance on one tooth surface and the cutting resistance on the other tooth surface, in one feed operation of the gear skiving cutter, the machining allowance (cutting depth) of each tooth surface becomes different. As a result of intensive research on this phenomenon, it was found that an error occurs between the synchronous command angle and the actual synchronous angle with respect to the synchronous angle between the workpiece and the gear skiving cutter when performing finish machining.

[0009] Therefore, in the above aspect, in the error estimation step, it was decided to estimate the error between the synchronous command angle and the actual synchronous angle with respect to the synchronous angle between the workpiece and the gear skiving cutter. Then, in the machining step, based on the estimated error, the rough machining shape of the convex teeth or the machining conditions for finish machining are corrected to perform machining. As a result, when a part of the machined portion by rough machining is left after finish machining, the shape of the remaining machined portion can be made into a desired shape.

[0010] As described above, according to the above aspect, it is possible to provide a gear machining method capable of making the shape of the remaining machined portion into a desired shape when a part of the machined portion by rough machining is left after finish machining.

Brief Description of the Drawings

[0011] [Figure 1] It is a perspective view showing a gear machining apparatus. [Figure 2] (a) is a view showing a gear skiving cutter, and (b) is an enlarged view of the rake face of one cutting edge. [Figure 3] It is a flowchart showing the basics of a gear machining method. [Figure 4] (a) shows the rough machining shape of the convex teeth of the workpiece, (b) shows the area to be finish machined by the gear skiving cutter in the rough machining shape of the convex teeth, and (c) is a view showing the finish machining shape of the convex teeth. [Figure 5]This figure shows the state when the angle of the protruding teeth of a workpiece is detected by a sensor. [Figure 6] This diagram illustrates the process of finishing a workpiece using a gear skiving cutter. [Figure 7] (a) shows the rough-machined shape of the convex teeth of the workpiece, (b) shows the area of ​​the rough-machined shape of the convex teeth that is finished by a gear skiving cutter, and (c) shows the finished shape of the convex teeth. [Figure 8] This diagram illustrates the area processed by a single cutting edge within a single tooth groove. [Figure 9] This figure shows the definition point of a single cutting edge in the generation machining analysis. [Figure 10] (a) shows the analysis result showing the rake angle due to the leading edge, (b) shows the analysis result showing the rake angle due to the cutting edge, and (c) shows the analysis result showing the rake angle due to the trailing edge. [Figure 11] This is a flowchart showing the improved first gear machining method. [Figure 12] This is the measured data used to estimate the synchronization angle error in the first example. [Figure 13] This figure illustrates the first and second angle reference values ​​used to estimate the synchronization angle error in the third example. [Figure 14] This figure illustrates the first and second angle reference values ​​used to estimate the synchronization angle error in the fourth example. [Figure 15] This figure illustrates the first and second angle reference values ​​used to estimate the synchronization angle error in the fifth example. [Figure 16] (a) shows the rough-machined shape of the convex teeth of the workpiece, (b) shows the area of ​​the rough-machined shape of the convex teeth that is finished by a gear skiving cutter, and (c) shows the finished shape of the convex teeth. [Figure 17] This is a flowchart showing the improved second gear machining method. [Figure 18](a) shows the rough-machined shape of the convex teeth of the workpiece, (b) shows the area of ​​the rough-machined shape of the convex teeth that is finished by a gear skiving cutter, and (c) shows the finished shape of the convex teeth. [Modes for carrying out the invention]

[0012] (Embodiment) 1. Configuration of the gear processing machine 1 An example of the configuration of a gear machining apparatus 1 used for gear machining will be explained with reference to Figure 1. The gear machining apparatus 1 is a device that creates tooth profiles (gear teeth) on a workpiece W by moving the workpiece W and the gear skiving cutter T in a relative position while rotating them synchronously.

[0013] The gear machining device 1 utilizes a general-purpose machine tool, such as a machining center. The machining center is configured to allow tool changes, enabling machining according to the installed tool. For example, interchangeable gear cutting tools include a gear skiving cutter T, as well as a hob cutter and a shaper cutter. By changing to a hob cutter or a shaper cutter, the gear machining device 1 becomes a device that machines tooth profiles (gear teeth) on the workpiece W through hobbing or shaping.

[0014] Other interchangeable tools besides gear cutting tools include, for example, end mills, milling tools, drills, turning tools, threading tools, and grinding tools. Note that the tool changing device and the tool magazine that houses multiple tools are not shown in Figure 1.

[0015] Furthermore, in this embodiment, the machining center used as the gear processing device 1 shown in Figure 1 is basically a horizontal machining center. However, the gear processing device 1 can also be configured with other configurations, such as a vertical machining center.

[0016] As shown in Figure 1, the gear machining apparatus 1 has, for example, three mutually orthogonal linear drive axes (X axis, Y axis, Z axis). The gear machining apparatus 1 is configured so that the workpiece W and the gear skiving cutter T can move relative to each other in the X axis direction, Y axis direction, and Z axis direction. Here, the direction parallel to the rotation axis Zt of the gear skiving cutter T (equal to the rotation axis of the tool spindle) is defined as the Z axis direction, and the two axes orthogonal to the Z axis direction are defined as the X axis and Y axis. In Figure 1, the horizontal direction is defined as the X axis direction, and the vertical direction is defined as the Y axis direction.

[0017] Furthermore, the gear machining apparatus 1 has one rotary drive axis (B axis) for changing the relative orientation between the workpiece W and the gear skiving cutter T. In this embodiment, the B axis is a rotary drive axis around an axis Yw parallel to the Y axis. The gear machining apparatus 1 also has a rotary drive axis (Ct axis) for rotating the gear skiving cutter T and a rotary drive axis (Cw axis) for rotating the workpiece W. In this embodiment, the Ct axis is a rotary drive axis around the rotation axis Zt of the gear skiving cutter T, which is parallel to the Z axis. The Cw axis is a horizontal axis that can take an angle with respect to the Z axis according to the B axis angle, and rotates around the rotation axis Zw of the workpiece W. However, the rotation axis Zt of the gear skiving cutter T may be configured to take an angle with respect to both the Z axis and the X axis.

[0018] In the gear machining apparatus 1, the configuration for relative movement between the workpiece W and the gear skiving cutter T can be selected as appropriate. For example, the gear machining apparatus 1 may have an A-axis around a rotation axis parallel to the X-axis instead of a B-axis. In the following, we will take as an example the case in which the gear skiving cutter T is capable of linear movement in the Y-axis and Z-axis directions, the workpiece W is capable of linear movement in the X-axis direction, and the workpiece W is capable of rotation on the B-axis.

[0019] The gear machining apparatus 1 comprises a bed 10, a workpiece holder 20, a tool holder 30, a sensor 40, and a control device 50. The bed 10 is installed on a mounting surface and is formed in a shape corresponding to the shape of the workpiece holder 20 and the shape of the tool holder 30. In this embodiment, the bed 10 is, for example, rectangular. A pair of X-axis guide rails 11 extending in the X-axis direction and a pair of Z-axis guide rails 12 extending in the Z-axis direction are formed on the upper surface of the bed 10.

[0020] The workpiece holding device 20 mainly comprises an X-axis moving table 21, a B-axis rotary table 22, and a workpiece spindle device 23. The X-axis moving table 21 is driven by a drive device such as a linear motor or a ball screw mechanism (not shown) and moves in the X-axis direction while being guided by the X-axis guide rail 11 of the bed 10.

[0021] The B-axis rotary table 22 is mounted on the upper surface of the X-axis moving table 21 and moves integrally with the X-axis moving table 21 in the direction of the X-axis. The B-axis rotary table 22 is also provided so as to be rotatable on the B-axis relative to the X-axis moving table 21. The B-axis rotary table 22 is equipped with a rotary motor and a rotation angle detector (not shown), and the B-axis rotary table 22 becomes rotatable on the B-axis when the rotary motor is driven.

[0022] The workpiece spindle device 23 is mounted on the B-axis rotary table 22 and rotates integrally with the B-axis rotary table 22 on the B-axis. The workpiece spindle device 23 rotatably holds the workpiece W. The workpiece spindle device 23 is equipped with a rotary motor and a rotation angle detector (not shown), and the workpiece spindle device 23 enables the workpiece W to rotate on the Cw axis by the drive of the rotary motor. In this way, the workpiece holding device 20 enables the workpiece W to move in the X-axis direction relative to the bed 10, to rotate on the B-axis, and to rotate on the Cw axis.

[0023] In detail, the workpiece spindle unit 23 comprises a housing 23a and a spindle 23b. The housing 23a of the workpiece spindle unit 23 is fixed to the B-axis rotary table 22, and the spindle 23b of the workpiece spindle unit 23 is rotatably supported by the housing 23a. The workpiece W is attached to the tip of this spindle 23b. In other words, the workpiece W is cantilevered to the spindle 23b of the workpiece spindle unit 23.

[0024] The tool holder 30 mainly comprises a column 31, a saddle 32, and a tool spindle device 33. The column 31 is driven by a drive device such as a linear motor or a ball screw mechanism (not shown) and moves in the Z-axis direction while being guided by the Z-axis guide rail 12 of the bed 10. A Y-axis guide rail 31a is formed on the vertically extending side surface of the column 31 (left surface in Figure 1). The saddle 32 is driven by a drive device such as a linear motor or a ball screw mechanism (not shown) and moves in the Y-axis direction while being guided by the Y-axis guide rail 31a of the column 31.

[0025] The tool spindle device 33 is mounted on the saddle 32 and moves integrally with the saddle 32 in the Y-axis direction. The tool spindle device 33 holds the gear skiving cutter T. The tool spindle device 33 is equipped with a rotary motor and a rotation angle detector (not shown), and the tool spindle device 33 makes the gear skiving cutter T rotatable on the Ct axis by the drive of the rotary motor. In this way, the tool holding device 30 holds the gear skiving cutter T so that it can move in the Y-axis and Z-axis directions relative to the bed 10 and is rotatable on the Ct axis.

[0026] In detail, the tool spindle unit 33 comprises a housing 33a and a spindle 33b. The housing 33a of the tool spindle unit 33 is fixed to the saddle 32, and the spindle 33b of the tool spindle unit 33 is rotatably supported by the housing 33a. A gear skiving cutter T is attached to the tip of this spindle 33b. In other words, the gear skiving cutter T is cantilevered to the spindle 33b of the tool spindle unit 33.

[0027] The sensor 40 is provided, for example, on the saddle 32. The sensor 40 is capable of detecting the distance to the teeth on the workpiece W when the workpiece spindle device 23 is holding the workpiece W and the workpiece W is rotating. For example, it is preferable to use a non-contact distance sensor such as an eddy current or a laser for the sensor 40. However, it is also possible to use a contact-type sensor for the sensor 40. Since the sensor 40 is provided on the saddle 32, it moves together with the tool spindle device 33. Furthermore, the detection part of the sensor 40 may be provided so that it can move forward and backward.

[0028] The control device 50 is equipped with a processor (arithmetic processing unit) and a memory device, and controls each drive device by executing a machining program. In other words, the control device 50 controls the rotation of the gear skiving cutter T along the Ct axis, the rotation of the workpiece W along the Cw axis, and the relative movement between the workpiece W and the gear skiving cutter T.

[0029] In detail, the control device 50 positions the rotation axis Zt of the gear skiving cutter T so that it has an axial intersection angle α with respect to the rotation axis Zw of the workpiece W. In this embodiment, the control device 50 rotates the B-axis rotary table 22 to position the workpiece W and the gear skiving cutter T so that they have an axial intersection angle α. Then, while synchronously rotating the workpiece W and the gear skiving cutter T, the control device 50 moves the gear skiving cutter T relative to the workpiece W in a direction parallel to the rotation axis Zw of the workpiece W, thereby creating convex teeth on the outer or inner surface of the workpiece W.

[0030] 2. Gear skiving cutter T The gear skiving cutter T will be described with reference to Figure 2. As shown in Figure 2(a), the gear skiving cutter T has a plurality of cutting edges 60 on its outer circumference in the circumferential direction. Each cutting edge 60 is formed as a convex groove. Each cutting edge 60 has a rake face 61 which is the leading edge (left end face in Figure 2(a)) in the direction of extension of the cutting edge 60, a front relief face 62 which is the radially outer surface of the cutting edge 60, and side relief faces 63, 64 which are the sides of the cutting edge 60 in the direction of extension.

[0031] In this embodiment, the multiple cutting edges 60 have a helix angle β with respect to the rotation axis Zt of the gear skiving cutter T. However, the cutting edges 60 may be formed such that the helix angle β is zero.

[0032] The rake face 61 of the cutting edge 60 is inclined radially by an angle γ with respect to a plane perpendicular to the rotation axis Zt in a cross-section along the rotation axis Zt. Furthermore, the rake face 61 of the cutting edge 60 has a cutting angle ε. The cutting angle ε is the angle with respect to the plane perpendicular to the rotation axis Zt when viewed from the radially outside of the cutting edge 60. Here, the cutting angle ε of the cutting edge 60 is the angle obtained by subtracting the correction value ε2 of the cutting angle from the reference cutting angle ε1. The reference cutting angle ε1 is equal to the helix angle β of the cutting edge 60. The correction value ε2 of the cutting angle can be set arbitrarily.

[0033] Furthermore, the front relief surface 62 of the cutting edge 60 has a front relief angle η1. That is, the front relief surface 62 is inclined with respect to the rotation axis Zt. In other words, the circumscribing surface of the front relief surface 62 of the cutting edge 60 is formed in a conical shape. However, the front relief surface 62 of the cutting edge 60 may be formed so that the front relief angle η1 is zero. In this case, the circumscribing surface of the front relief surface 62 of the cutting edge 60 will be formed in a cylindrical shape. Also, the side relief surfaces 63 and 64 of the cutting edge 60 have a side relief angle η2. That is, the side relief surfaces 63 and 64 are inclined with respect to the extending direction of the cutting edge 60. One side relief surface 63 is located on the leading side in the rotation direction of the gear skiving cutter T, and the other side relief surface 64 is located on the trailing side.

[0034] As shown in Figure 2(b), the ridges of the rake face 61 of each cutting edge 60 are defined as follows: The leading edge portion of the rake face 61 in the rotational direction of the gear skiving cutter T is defined as the leading edge portion 61a. The leading edge portion 61a is the ridge formed by the rake face 61 and one side relief face 63. The trailing edge portion of the rake face T in the rotational direction of the gear skiving cutter T is defined as the trailing edge portion 61b. The trailing edge portion 61b is the ridge formed by the rake face 61 and the other side relief face 64. The cutting edge portion of the rake face 61 is defined as the cutting edge portion 61c. The cutting edge portion 61c is the ridge formed by the rake face 61 and the front relief face 62.

[0035] 3. Basic operation of gear machining method The basic operation of the gear machining method will be explained with reference to Figures 3 to 6. The basic operation of the gear machining method is to first perform rough machining on the workpiece W (S1), as shown in Figure 3. Rough machining is a process to form the rough machined shape 70 of the gear's convex teeth on the workpiece W, as shown in Figure 4(a). In this embodiment, the rough machining is an example in which the rough machined shape 71, 72 of the tooth surface (side surface of the convex tooth) of the gear's convex tooth is formed on the workpiece W, as well as the tooth tip chamfer portion 73, 74 which is adjacent to the rough machined shape 71, 72 of the tooth surface. In other words, the rough machined shape of the workpiece W is a shape having the rough machined shapes 70 of multiple convex teeth, and the rough machined shape 70 of each convex tooth has the rough machined shape 71, 72 of the tooth surface and the tooth tip chamfer portion 73, 74. The rough tooth surface symmetry line 75 is the center line of the opposing rough machined shapes 71, 72 of the tooth surfaces.

[0036] Furthermore, various gear machining processes such as gear skiving, hobbing, and shaping can be applied to the rough machining. In the gear machining apparatus 1 shown in Figure 1, rough machining is performed by attaching either a gear skiving cutter T, a hobbing cutter (not shown), or a shaper cutter (not shown). In rough machining, the machining of the rough shapes 71 and 72 of the tooth surface and the machining of the tooth tip chamfers 73 and 74 may be performed in simultaneous machining processes or in separate machining processes.

[0037] In the following, the tooth surface that is behind the workpiece W in the rotational direction will be referred to as the "first tooth surface," and the tooth surface that is ahead of it, i.e., the tooth surface located on the back surface of the first tooth surface, will be referred to as the "second tooth surface." Furthermore, the tooth tip chamfer adjacent to the first tooth surface will be referred to as the "first tooth tip chamfer," and the tooth tip chamfer adjacent to the second tooth surface will be referred to as the "second tooth tip chamfer."

[0038] After rough machining (S1), external processing such as heat treatment or coating is performed (S2). In this embodiment, the external processing is performed not in the gear machining apparatus 1 shown in Figure 1, but in a separate external device. Therefore, after rough machining is performed in the gear machining apparatus 1, the workpiece W is removed from the gear machining apparatus 1 and the external processing is performed in a separate device.

[0039] After the external processing (S2), preparation processing for finishing is performed (S3). As preparation for finishing, first, the control device 50 performs a detection process for the Cw axis angle of the rough machined shape 70 of the convex teeth that have been roughly machined on the workpiece W attached to the gear machining device 1 (S3a).

[0040] The detection process of the Cw axis angle of the convex tooth by the control device 50 (S3a) will be explained with reference to Figure 5. After the workpiece W is attached to the spindle 23b of the workpiece spindle device 23 of the gear machining apparatus 1, the rotation axis Zw of the workpiece W is positioned parallel to the Z axis direction. In this state, the workpiece W is rotated along the Cw axis. The sensor 40 is extended so that its tip is positioned near the tip of the tool spindle device 33. The detection area of ​​the sensor 40 is positioned opposite the convex tooth forming surface of the workpiece W, that is, the outer circumferential surface in the case of an external tooth, and the inner circumferential surface in the case of an internal tooth.

[0041] Then, while detecting the Cw axis angle of the workpiece W using the rotation angle detector of the workpiece spindle device 23, the distance to the surface of the convex tooth of the workpiece W facing the sensor 40 is detected by the sensor 40. In this way, the Cw axis angle at which the rough machined shape 70 of the convex tooth of the workpiece W is located is detected when the workpiece W is mounted on the workpiece spindle device 23.

[0042] Next, the workpiece W is positioned to begin the finishing process (S3b). Specifically, based on the Cw axis angle of the rough machining shape 70 of the convex teeth of the workpiece W detected, the workpiece W is rotated along the Cw axis to position the initial Cw axis angle of the workpiece W. The initial Cw axis angle of the workpiece W is determined based on the Ct axis angle of the gear skiving cutter T. Alternatively, the Ct axis angle of the gear skiving cutter T may be positioned instead of the Cw axis angle of the workpiece W. Furthermore, the workpiece W is rotated along the B axis to achieve the set axis intersection angle α.

[0043] Next, the workpiece W is finished using the gear skiving cutter T (S4). As shown in Figure 6, the finishing is performed by moving the gear skiving cutter T relative to the workpiece W in a direction parallel to the rotation axis Zw of the workpiece W while the workpiece W and the gear skiving cutter T are rotated synchronously. In this way, the rough machined shape 70 of the convex teeth of the workpiece W is finished by the gear skiving cutter T.

[0044] In the finishing process, as shown by the dashed lines in Figure 4(b), the finishing is performed along the outlines 81, 82, and 83 of the region through which the edges 61a, 61b, and 61c that constitute the rake face 61 of each cutting edge 60 (shown in Figures 2(a) and 2(b)) of the gear skiving cutter T pass. In other words, the portion of the rough-machined shape 70 of the convex teeth of the workpiece W that overlaps with the region enclosed by the outlines 81, 82, and 83 is the portion that undergoes finishing. The finished shape 70a of the convex teeth is the shape shown in Figure 4(c). For the sake of clarity, the outlines 81, 82, and 83 in Figure 4(b) represent the points through which the edges 61a, 61b, and 61c that constitute the rake face 61 pass, assuming that the rotation of the workpiece W is stopped.

[0045] In Figure 4(b), the rough shape 71 of the first tooth surface that is trailing in the rotational direction of the workpiece W, of the two adjacent convex teeth forming a single concave tooth groove 70, is finished along the outline 81 of the region through which the leading cutting edge 61a (shown in Figure 2(b)) of the gear skiving cutter T passes. Therefore, the finished shape 71a of the first tooth surface is machined by the leading cutting edge 61a to become the shape shown in Figure 4(c). At this time, the leading cutting edge 61a processes not only the rough shape 71 of the first tooth surface but also a portion of the first tooth tip chamfer 73. Therefore, the first tooth tip chamfer 73a remaining after finishing takes on the shape shown in Figure 4(c).

[0046] Furthermore, in Figure 4(b), the rough shape 72 of the second tooth surface that is leading in the rotational direction of the workpiece W, of the two adjacent convex teeth forming a single concave tooth groove 70, is finished along the outline 82 of the region through which the trailing cutting edge 61b (shown in Figure 2(b)) of the gear skiving cutter T passes. Therefore, the finished shape 72a of the second tooth surface is machined by the trailing cutting edge 61b to become the shape shown in Figure 4(c). At this time, the trailing cutting edge 61b machines not only the rough shape 72 of the second tooth surface but also a part of the second tooth tip chamfer 74. Therefore, the second tooth tip chamfer 74a remaining after finishing is the shape shown in Figure 4(c).

[0047] Furthermore, in Figure 4(b), the root portion of a single concave tooth groove formed by the rough-machined shapes 70 of two adjacent convex teeth, located between the rough-machined shape 71 of the first tooth surface and the rough-machined shape 72 of the second tooth surface, is finished along the outline 83 of the region through which the cutting edge portion 61c (shown in Figure 2(b)) of the gear skiving cutter T passes. However, depending on the rough-machined shape 70 of the convex teeth of the workpiece W, the cutting edge portion 61c may not finish the root surfaces of the rough-machined shapes 70 of adjacent convex teeth.

[0048] In Figure 4(b), the blade surface symmetry line 84 is the midpoint between the outline 81 of the region through which the leading blade portion 61a passes and the outline 82 of the region through which the trailing blade portion 61b passes. Also, in Figure 4(c), the finished tooth surface symmetry line 75a is the midpoint between the finished machining shape 71a of the opposing first tooth surface and the finished machining shape 72a of the second tooth surface. Ideally, the rough tooth surface symmetry line 75 shown in Figure 4(a) and the finished tooth surface symmetry line 75a shown in Figure 4(c) should coincide.

[0049] The gear machining method described above forms the finished shape 70a of the gear's convex teeth on the workpiece W. The finished shape 70a of the convex teeth has a finished shape 71a of the first tooth surface, a finished shape 72a of the second tooth surface, a first tooth tip chamfer 73a which constitutes part of the first tooth tip chamfer 73, and a second tooth tip chamfer 74a which constitutes part of the second tooth tip chamfer 74. In this embodiment, the tooth root surface located between the finished shapes 70a of adjacent convex teeth is the same as the tooth root surface located between the rough shapes 70 of adjacent convex teeth.

[0050] 4.Synchronization angle error Δθ In the finishing process, it was found that an error Δθ (hereinafter referred to as "synchronous angle error") occurs between the synchronous command angle issued by the control device 50 and the actual synchronous angle regarding the synchronous angle between the workpiece W and the gear skiving cutter T. The synchronous angle error Δθ will be explained below with reference to Figures 3 to 4 and Figure 7.

[0051] As described above, the ideal finished shape 70a of a convex tooth in the workpiece W is the shape shown in Figure 4(c). In other words, the finishing allowance (cutting depth) for the rough shape 71 of the first tooth surface and the finishing allowance (cutting depth) for the rough shape 72 of the second tooth surface are the same. As a result, both tooth tip chamfers 73a and 74a have a symmetrical shape with respect to the finished tooth surface symmetry line 75a. That is, the same amount of material is left on both tooth tip chamfers 73a and 74a.

[0052] To obtain the ideal convex tooth finished shape 70a, it is necessary to make the rough tooth surface symmetry line 75 shown in Figure 4(a) coincide with the finished tooth surface symmetry line 75a shown in Figure 4(c). Here, the finished tooth surface symmetry line 75a shown in Figure 4(c) coincides with the cutting edge symmetry line 84 shown in Figure 4(b) during finishing. Therefore, to obtain the ideal convex tooth finished shape 70a, it is necessary to perform the finishing process so that the rough tooth surface symmetry line 75 shown in Figure 4(a) coincides with the cutting edge symmetry line 84 shown in Figure 4(b). In other words, when considered as the synchronization angle of the gear skiving cutter T with respect to the workpiece W, it is necessary to rotate synchronously so that the actual angle of the cutting edge symmetry line 84 shown in Figure 4(b) coincides with the rough tooth surface symmetry line 75 shown in Figure 4(a).

[0053] Therefore, in the finishing preparation (S3) shown in Figure 3, the Cw axis angle of the rough machined shape 70 of the convex tooth is detected. Then, the Cw axis angle of the workpiece W is positioned based on the Ct axis angle of the cutting edge 60 of the gear skiving cutter T, so that the rough tooth surface symmetry line 75 and the cutting edge surface symmetry line 84 of the rough machined shape 70 of the convex tooth coincide.

[0054] However, if finishing is performed while synchronously rotating with this state as the initial state, the actual angle 84r of the blade surface symmetry line 84 will deviate from the rough tooth surface symmetry line 75, as explained below. Specifically, when performing finishing on the rough machined shape 70 of the convex teeth shown in Figure 7(a), the control device 50 performs synchronous control to make the command angle 84c of the blade surface symmetry line coincide with the rough tooth surface symmetry line 75, as shown in Figure 7(b). However, as shown in Figure 7(b), the actual angle 84r of the blade surface symmetry line with respect to the rough tooth surface symmetry line 75 will be located in a position that has advanced forward in the rotational direction of the workpiece W (to the right in Figure 7(b)). This deviation angle is defined as the synchronous angle error Δθ. The command angle 84c of the blade surface symmetry line corresponds to the synchronous command angle between the workpiece W and the gear skiving cutter T, and the actual angle 84r of the blade surface symmetry line corresponds to the synchronous actual angle between the workpiece W and the gear skiving cutter T.

[0055] Thus, even if the control device 50 shown in Figure 7(b) commands the angle 84c of the blade surface symmetry line to match the rough tooth surface symmetry line 75 during finishing, the synchronization angle error Δθ causes the actual angle 84r of the blade surface symmetry line to shift forward in the rotational direction from the rough tooth surface symmetry line 75. In other words, due to the synchronization angle error Δθ, the leading blade portion 61a cuts more than the ideal material removal amount for the rough machined shape 71 of the first tooth surface. Conversely, the trailing blade portion 61b cuts less than the ideal material removal amount for the rough machined shape 72 of the second tooth surface.

[0056] As a result, the finished shape 70a of the convex tooth becomes the shape shown in Figure 7(c). Specifically, the finished tooth surface symmetry line 75a is shifted by a synchronization angle error Δθ relative to the rough tooth surface symmetry line 75, and the finished shape 71a of the first tooth surface and the finished shape 72a of the second tooth surface are formed. Because the finished shape 71a of the first tooth surface and the finished shape 72a of the second tooth surface are shifted by a synchronization angle error Δθ, the shapes of the first tooth tip chamfer 73a and the second tooth tip chamfer 74a become different from those in Figure 4(c).

[0057] Specifically, of the concave tooth groove formed by the rough machining shapes 70 of two adjacent convex teeth, the first tooth tip chamfer 73a adjacent to the finished machining shape 71a of the first tooth surface that is behind in the rotational direction has a larger material removal amount and is therefore smaller than the ideal shape shown in Figure 4(c). Conversely, the second tooth tip chamfer 74a adjacent to the finished machining shape 72a of the second tooth surface that is ahead in the rotational direction has a smaller material removal amount and is therefore larger than the ideal shape shown in Figure 4(c). In other words, the first tooth tip chamfer 73a and the second tooth tip chamfer 74a have asymmetrical shapes.

[0058] 5. Reasons for the occurrence of synchronization angle error Δθ The reason for the occurrence of the synchronization angle error Δθ will be analyzed in detail with reference to Figures 8 to 10. Figure 8 shows a view of one tooth groove in the workpiece W from the radially outer side, showing the portion between the finished shapes 70a of adjacent convex teeth. In the direction in which the tooth groove extends, the first tooth surface finished shape 71a and the first tooth tip chamfer 73a are present on one of the circumferentially opposing faces, and the second tooth surface finished shape 72a and the second tooth tip chamfer 74a are present on the other face.

[0059] In Figure 8, the white arrow indicates the direction of travel of one cutting edge 60 of the gear skiving cutter T. The hatched areas P1 and P2 in Figure 8 represent the areas machined when one cutting edge 60 of the gear skiving cutter T passes through one tooth groove of the workpiece W. The hatched area P1 on the right side of Figure 8 is the area finished by the leading cutting edge 61a, forming the finished shape 71a of the first tooth surface. On the other hand, the hatched area P2 on the left side of Figure 8 is the area finished by the trailing cutting edge 61b, forming the finished shape 72a of the second tooth surface.

[0060] In the operation of one cutting edge 60 machining one tooth groove, machining first begins with only the leading edge portion 61a (lower part of region P1 in Figure 8). Then, while machining is being performed by the leading edge portion 61a, machining by the trailing edge portion 61b begins. In other words, machining by the leading edge portion 61a and machining by the trailing edge portion 61b are performed simultaneously (upper part of region P1 and lower part of region P2 in Figure 8). After that, machining by the leading edge portion 61a is completed, and machining by only the trailing edge portion 61b continues (upper part of region P2 in Figure 8). Finally, machining by the trailing edge portion 61b is completed.

[0061] To perform a detailed analysis, as shown in Figure 9, the edges 61a, 61b, and 61c of the rake face 61 of the cutting edge 60 were defined using point clouds, and a generation machining analysis was performed. In Figure 9, the leading edge portion 61a is defined using a triangular point cloud, the trailing edge portion 61b is defined using a quadrilateral point cloud, and the cutting edge portion 61c is defined using a circular point cloud. Each defined point is distinguished by the numerical value in brackets [].

[0062] Generative machining analysis was performed to output the rake angle for each point [1] to

[33] that defines the edges 61a, 61b, and 61c of the rake face 61. The results are shown in Figure 10. Figure 10(a) shows the rake angle for each point [1] to

[14] that defines the leading edge portion 61a. Figure 10(b) shows the rake angle for each point

[15] to

[19] that defines the cutting edge portion 61c. Figure 10(c) shows the rake angle for each point

[20] to

[33] that defines the trailing edge portion 61b.

[0063] As shown in Figures 10(a) to (c), the rake angle exhibits different values ​​depending on the definition points [1] to

[33] , and also exhibits different values ​​at each of the definition points [1] to

[33] depending on the Ct axis angle (tool rotation angle) of the gear skiving cutter T. For example, at definition point [1], the rake angle at the start of machining starts as positive, passes through zero, and then changes so that the absolute value of the negative value increases. A similar trend is observed for the other definition points. However, the initial value of the rake angle may be negative instead of positive depending on conditions such as the axis crossing angle α.

[0064] A detailed analysis reveals that the rake angle at the definition points

[20] to

[33] of the trailing cutting edge 61b has a larger negative maximum absolute value compared to the rake angle at the definition points [1] to

[14] of the leading cutting edge 61a.

[0065] Comparing the cases where the rake angle is positive and negative, a positive rake angle results in a smaller back force component of the cutting force applied to the tooth surface. The back force component of the cutting force is the component of the cutting force that is normal to the tooth surface. The cutting force is expressed by the main force component, the back force component, and the feed force component.

[0066] In other words, when the leading cutting edge 61a performs finishing on the rough-machined shape 71 of the first tooth surface, the magnitude of the back force of the cutting force is relatively smaller compared to when the trailing cutting edge 61b performs finishing on the rough-machined shape 72 of the second tooth surface.

[0067] 6. Description of the improved first gear machining method An improved first gear machining method for reducing the error in the finished shape 70a of the convex tooth caused by the synchronization angle error Δθ shown in Figure 7 will be explained with reference to Figures 11 to 16.

[0068] The improved first gear machining method estimates the synchronization angle error Δθ that occurs during finishing (S11: Error Estimation Process), as shown in Figure 11. Five types of methods for estimating the synchronization angle error Δθ are given below as examples.

[0069] The first example of estimating the synchronization angle error Δθ uses measured data of the synchronization angle error Δθ. In this case, as shown in Figure 12, the measured data of the synchronization angle error Δθ corresponds to the axis intersection angle α between the gear skiving cutter T and the workpiece W. At this time, it is preferable to use data that corresponds to the magnitude of the depth of cut, the magnitude of the torque of the rotary motor of the workpiece spindle device 23, and the magnitude of the torque of the rotary motor of the tool spindle device 33. In other words, the synchronization angle error Δθ in the first example is estimated by acquiring the axis intersection angle α, the depth of cut, and the torque of the rotary motor, and using the recorded data shown in Figure 12. Note that the depth of cut can be replaced with machining conditions that affect machining resistance, such as the tool feed rate, and the torque of the rotary motor can be replaced with characteristic values ​​that affect the tracking ability of the rotation axis, such as the gain value.

[0070] The second example of the method for estimating the synchronization angle error Δθ uses a relational expression that defines the synchronization angle error Δθ, with the axis intersection angle α between the gear skiving cutter T and the workpiece W as a parameter. In this case, for example, equation (1) can be used. C is a constant and is a value that corresponds to, for example, the magnitude of the depth of cut, the magnitude of the torque of the rotary motor of the workpiece spindle device 23, and the magnitude of the torque of the rotary motor of the tool spindle device 33. Δθ = C * 1 / sinα ... (1)

[0071] The third example of the method for estimating the synchronization angle error Δθ uses generational machining analysis. Specifically, the third example of the method for estimating the synchronization angle error Δθ uses the first angle reference value V, which corresponds to the rake angle in the rough machining shape 71 of the first tooth surface, obtained by the analysis. R And the second angle reference value V, which corresponds to the rake angle in the rough machining shape 72 of the second tooth surface. T The difference ΔV is used. First angle reference value V R As shown in Figure 13(a), this is the average value of the rake angle at each position of the leading blade portion 61a and at each Ct axis angle. In other words, the first angle reference value V R This corresponds to the average value of the rake angle of the leading cutting edge portion 61a at each position of the rough machining shape 71 of the first tooth surface.

[0072] Second angle reference value V T As shown in Figure 13(b), this is the average value of the rake angle at each position of the trailing blade portion 61b and at each Ct axis angle. In other words, the second angle reference value V T This corresponds to the average value of the rake angle of the trailing cutting edge portion 61b at each position of the rough machining shape 72 of the second tooth surface.

[0073] First angle reference value V R and the second angle reference value V T Using the difference ΔV, and further using the magnitude of the depth of cut, the magnitude of the torque of the rotary motor of the workpiece spindle device 23, and the magnitude of the torque of the rotary motor of the tool spindle device 33, the synchronization angle error Δθ is estimated using pre-set proportional equations and other relational equations or relational map data.

[0074] The estimation method of the synchronization angle error Δθ in the fourth example is different from the estimation method of the synchronization angle error Δθ in the third example in the estimation methods of the first angle reference value V R and the second angle reference value V T . The first angle reference value V R is the sum of the rake angles at each position of the leading cutting edge portion 61a and at each Ct-axis angle, as shown in FIG. 14(a). The sum value corresponds to the difference between the area of the positive region and the area of the negative region in the enclosed region shown in FIG. 14(a). That is, the first angle reference value V R corresponds to the sum of the rake angles of the leading cutting edge portion 61a at each position of the rough machining shape 71 of the first tooth surface.

[0075] The second angle reference value V T is the sum of the rake angles at each position of the trailing cutting edge portion 61b and at each Ct-axis angle, as shown in FIG. 14(b). The sum value corresponds to the difference between the area of the positive region and the area of the negative region in the enclosed region shown in FIG. 14(b). That is, the second angle reference value V T corresponds to the sum of the rake angles of the trailing cutting edge portion 61b at each position of the rough machining shape 72 of the second tooth surface.

[0076] The estimation method of the synchronization angle error Δθ in the fifth example is different from the estimation method of the synchronization angle error Δθ in the third example in the estimation methods of the first angle reference value V R and the second angle reference value V T . The first angle reference value V R is the maximum absolute value of the negative rake angles among the rake angles at each position of the leading cutting edge portion 61a and at each Ct-axis angle, as shown in FIG. 15(a). That is, the first angle reference value V R corresponds to the maximum absolute value of the negative rake angles of the leading cutting edge portion 61a at each position of the rough machining shape 71 of the first tooth surface.

[0077] The second angle reference value V T is the maximum absolute value of the negative rake angles among the rake angles at each position of the trailing cutting edge portion 61b and at each Ct-axis angle, as shown in FIG. 15(b). That is, the second angle reference value V TThis corresponds to the maximum absolute value of the negative rake angle of the trailing cutting edge portion 61b at each position of the rough machining shape 72 of the second tooth surface.

[0078] As shown in Figure 11, following the estimation step of the synchronization angle error Δθ (S11), a correction value for the rough machined shape 70 of the convex tooth is determined based on the estimated synchronization angle error Δθ (S12). The correction value for the rough machined shape 70 of the convex tooth will be explained with reference to Figure 16. As shown in Figure 16(a), the target of the correction for the rough machined shape 70 of the convex tooth is the shape of the tooth tip chamfers 73b and 74b of the rough machined shape 70 of the convex tooth.

[0079] As shown in Figure 16(a), the first tooth tip chamfer 73b and the second tooth tip chamfer 74b are corrected to a different shape from the reference shape shown in Figure 4(a). Here, as shown in Figure 16(b), after finishing, and as shown in Figure 16(c), after finishing, the first tooth tip chamfer 73c and the second tooth tip chamfer 74c become symmetrical with respect to the finished tooth surface symmetry line 75a. In other words, the shape correction values ​​for the first tooth tip chamfer 73b and the second tooth tip chamfer 74b in rough machining are determined so that the first tooth tip chamfer 73c and the second tooth tip chamfer 74c become symmetrical after finishing. Specifically, the first tooth tip chamfer 73b is made larger, and the second tooth tip chamfer 74b is made smaller.

[0080] Next, as shown in Figure 11, rough machining is performed on the workpiece W as part of the machining process (S13). That is, as shown in Figure 16(a), rough machining is performed on the workpiece W so that the rough machined shape 70 of the convex tooth has a rough machined shape 71 on the first tooth surface, a rough machined shape 72 on the second tooth surface, a first tooth tip chamfer 73b, and a second tooth tip chamfer 74b. The first tooth tip chamfer 73b and the second tooth tip chamfer 74b have different shapes.

[0081] Next, as shown in Figure 11, as part of the machining process, after rough machining (S13), external treatments such as heat treatment and coating treatment are performed (S14). After the external treatments (S14), preparatory processing for finish machining is performed (S15). As preparation for finish machining, first, the control device 50 performs a detection process for the Cw axis angle of the rough machined shape 70 of the convex teeth that have been roughly machined on the workpiece W attached to the gear machining device 1 (S15a). At this time, for example, the angle of the rough tooth surface symmetry line 75, which corresponds to the center between the rough machined shape 71 of the first tooth surface and the rough machined shape 72 of the second tooth surface, is detected or calculated, rather than the center between the first tooth tip chamfer 73b and the second tooth tip chamfer 74b. Next, the workpiece W is positioned to start the finish machining (S15b).

[0082] In other words, as shown in Figure 16(b), the Cw axis angle of the workpiece W is positioned based on the Ct axis angle of the cutting edge 60 of the gear skiving cutter T, such that the command angle 84c of the rough tooth surface symmetry line 75 of the rough machined shape 70 of the convex tooth coincides with the command angle 84c of the cutting edge symmetry line.

[0083] Next, as part of the machining process, a gear skiving cutter T is used to perform finish machining on the roughly machined workpiece W (S16). Specifically, when performing finish machining on the convex tooth rough shape 70 shown in Figure 16(a), the control device 50 synchronizes the command angle 84c of the blade surface symmetry line to match the rough tooth surface symmetry line 75, as shown in Figure 16(b). As a result, as shown in Figure 16(b), the actual angle 84r of the blade surface symmetry line with respect to the rough tooth surface symmetry line 75 is located in a position that has advanced forward in the rotational direction of the workpiece W (to the right in Figure 16(b)). In other words, there is a synchronization angle error Δθ during the finish machining.

[0084] As a result, the leading cutting edge 61a makes a large cut into the rough machining shape 71 of the first tooth surface, while the trailing cutting edge 61b makes a small cut into the rough machining shape 72 of the second tooth surface.

[0085] As a result, the finished shape 70a of the convex tooth becomes the shape shown in Figure 16(c). Specifically, the finished tooth surface symmetry line 75a is shifted by a synchronization angle error Δθ relative to the rough tooth surface symmetry line 75, and the finished shape 71a of the first tooth surface and the finished shape 72a of the second tooth surface are formed. Because the finished shape 71a of the first tooth surface and the finished shape 72a of the second tooth surface are shifted by a synchronization angle error Δθ from the position of the target shape, the shapes of the remaining first tooth tip chamfer 73c and second tooth tip chamfer 74c are formed in a symmetric shape with respect to the finished tooth surface symmetry line 75a.

[0086] According to the improved first gear machining method, by correcting the rough machining shape 70 of the convex tooth, the finished machining shape 70a of the convex tooth can be made into a desired shape. In other words, the size of the first tooth tip chamfer 73c and the second tooth tip chamfer 74c can be made the same. Furthermore, when finishing the convex teeth of a gear that are intended to have different sizes for the first tooth tip chamfer 73c and the second tooth tip chamfer 74c, by applying a machining method similar to the improved first gear machining method, the convex teeth of a gear with different sizes for the first tooth tip chamfer 73c and the second tooth tip chamfer 74c can be finished with high precision.

[0087] 7. Description of the improved second gear machining method An improved second gear machining method for reducing the error in the finished shape 70a of the convex tooth caused by the synchronization angle error Δθ shown in Figure 7 will be described with reference to Figures 17 and 18.

[0088] The improved second gear machining method estimates the synchronization angle error Δθ that occurs during finishing (S21: Error Estimation Step), as shown in Figure 17. The method for estimating the synchronization angle error Δθ is the same as the method for estimating the synchronization angle error Δθ in S11 of the first gear machining method described above. In other words, any of the synchronization angle error Δθ estimation methods from the first to fifth examples can be applied.

[0089] Next, based on the estimated synchronization angle error Δθ, a correction value for the finishing machining conditions is determined (S22). In this embodiment, the correction value for the synchronization command angle in the finishing machining is determined as the correction value for the machining conditions (S22). The synchronization command angle will be explained with reference to Figure 18. The rough machining shape 70 of the convex tooth is the shape shown in Figure 18(a) (equal to the shape shown in Figure 4(a)). That is, the rough machining shape 70 of the convex tooth has rough machining shapes 71 and 72 on the tooth surface, and tooth tip chamfers 73 and 74. The rough tooth surface symmetry line 75 is the center line between the rough machining shape 71 of the first tooth surface and the rough machining shape 72 of the second tooth surface, and the rough machining shapes 71 and 72 on the tooth surface, and tooth tip chamfers 73 and 74 are formed in a symmetrical shape with respect to the rough tooth surface symmetry line 75.

[0090] As shown in Figure 18(b), in the finishing process, the command angle 84c of the blade surface symmetry line set by the control device 50 corresponds to the synchronization command angle between the workpiece W and the gear skiving cutter T. Also, as shown in Figure 18(b), by performing the finishing process, the actual angle 84r of the blade surface symmetry line is positioned forward in the rotational direction of the workpiece W from the command angle 84c of the blade surface symmetry line.

[0091] In the second gear machining method, the synchronous command angle for finishing is determined such that the material removal allowance for the rough machining shape 71 of the first tooth surface and the material removal allowance for the rough machining shape 72 of the second tooth surface are the same. Specifically, the command angle 84c of the blade surface symmetry line, which is the synchronous command angle, is determined so that the actual angle 84r of the blade surface symmetry line coincides with the rough tooth surface symmetry line 75. In other words, in Figure 7(b), the command angle 84c of the blade surface symmetry line was made to coincide with the rough tooth surface symmetry line 75, whereas in the second gear machining method, the actual angle 84r of the blade surface symmetry line is made to coincide with the rough tooth surface symmetry line 75.

[0092] The command angle 84c of the blade surface symmetry line is positioned behind the rough tooth surface symmetry line 75 by a synchronization angle error Δθ in the rotational direction of the workpiece W. Here, the synchronization angle error Δθ is the one estimated in S21.

[0093] Next, as shown in Figure 17, rough machining is performed on the workpiece W as part of the machining process (S23). That is, as shown in Figure 18(a), rough machining is performed on the workpiece W so that the rough machined shape 70 of the convex tooth has a rough machined shape 71 of the first tooth surface, a rough machined shape 72 of the second tooth surface, a first tooth tip chamfer 73, and a second tooth tip chamfer 74. The first tooth tip chamfer 73 and the second tooth tip chamfer 74 have symmetrical shapes with respect to the finished tooth surface symmetry line 75a.

[0094] Next, as shown in Figure 17, as part of the machining process, after rough machining (S23), external treatments such as heat treatment and coating treatment are performed (S24). After the external treatments (S24), preparatory processing for finish machining is performed (S25). As preparation for finish machining, first, the control device 50 performs a detection process for the Cw axis angle of the rough machined shape 70 of the convex teeth that have been roughly machined on the workpiece W attached to the gear machining device 1 (S25a). Next, the workpiece W is positioned to start the finish machining (S25b).

[0095] In other words, as shown in Figure 18(b), the synchronization command angle is corrected so that the actual angle 84r of the rough tooth surface symmetry line 75 and the cutting edge surface symmetry line of the rough-machined shape 70 of the convex tooth coincide. Specifically, the workpiece W is positioned by correcting the Cw axis angle based on the Ct axis angle of the cutting edge 60 of the gear skiving cutter T. Alternatively, the workpiece W may be positioned by correcting the Ct axis angle of the cutting edge 60 of the gear skiving cutter T based on the Cw axis angle of the workpiece W. The correction value of the synchronization command angle used in the finishing process should take into account the rotational speed ratio between the gear skiving cutter T and the workpiece W.

[0096] Next, as part of the machining process, a gear skiving cutter T is used to perform finish machining on the roughly machined workpiece W (S26). Specifically, when performing finish machining on the convex tooth rough shape 70 shown in Figure 18(a), as shown in Figure 18(b), the control device 50 corrects the synchronization command angle so that the actual angle 84r of the blade surface symmetry line is aligned with the rough tooth surface symmetry line 75, and then performs synchronous control. As a result, as shown in Figure 18(b), the actual angle 84r of the blade surface symmetry line is located in the forward direction of rotation of the workpiece W (to the right in Figure 18(b)) from the command angle 84c of the blade surface symmetry line. Therefore, the actual angle 84r of the blade surface symmetry line is aligned with the rough tooth surface symmetry line 75. In other words, the synchronization angle error Δθ becomes zero during finish machining.

[0097] As a result, the material removal amount of the rough shape 71 of the first tooth surface processed by the leading cutting edge 61a and the material removal amount of the rough shape 72 of the second tooth surface processed by the trailing cutting edge 61b become the same. Consequently, the finished shape 70a of the convex tooth becomes the shape shown in Figure 18(c). Specifically, the finished shape 71a of the first tooth surface and the finished shape 72a of the second tooth surface are formed so that the finished tooth surface symmetry line 75a coincides with the rough tooth surface symmetry line 75. Because the finished shape 71a of the first tooth surface and the finished shape 72a of the second tooth surface coincide with the target shape, the shapes of the remaining first tooth tip chamfer 73c and second tooth tip chamfer 74c are formed in a symmetrical shape with respect to the finished tooth surface symmetry line 75a.

[0098] According to the improved second gear machining method, by correcting the command angle 84c of the blade surface symmetry line, which is the synchronous command angle, the finished shape 70a of the convex tooth can be made into the desired shape. Furthermore, the difference between the material removal amount on the first tooth surface and the material removal amount on the second tooth surface can be reduced. As a result, the lifespan of the gear skiving cutter T can be extended and the machining time can be shortened. In addition, the first tooth tip chamfer 73c and the second tooth tip chamfer 74c can be made into a symmetrical shape after finishing. Moreover, when finishing the convex teeth of a gear targeting a shape in which the first tooth tip chamfer 73c and the second tooth tip chamfer 74c are of different sizes, by applying a machining method similar to the improved second gear machining method, the convex teeth of a gear with a shape in which the first tooth tip chamfer 73c and the second tooth tip chamfer 74c are of different sizes can be finished with high precision. [Explanation of symbols]

[0099] 70 Rough machining shape of convex teeth 70a Finished shape of convex teeth 71 Rough machining shape of the first tooth surface 71a Finished shape of the first tooth surface 72 Rough machining shape of the second tooth surface 72a Finished shape of the second tooth surface T Gear Skiving Cutter W Workpiece Δθ is the error between the synchronous command angle and the synchronous actual angle. S11,S21 Error estimation process S13~S16,S23~S26 Processing process

Claims

1. A gear machining method for machining protruding teeth of a gear onto a workpiece using a gear skiving cutter, This method is applicable to a machining process that involves rough machining of the tooth surface constituting the convex tooth and the adjacent portion of the tooth surface, and finishing machining of at least the tooth surface while leaving a portion of the adjacent portion after the rough machining. When performing the finishing process on the tooth surface constituting the convex tooth that has been roughly machined, an error estimation step is performed to estimate the error between the synchronization command angle and the actual synchronization angle with respect to the synchronization angle between the workpiece and the gear skiving cutter. The process includes a machining step of correcting the rough machining shape of the convex tooth or the machining conditions for the finishing process based on the estimated error, The aforementioned processing step is Based on the estimated error, the shape of the adjacent portion is corrected, and the rough machining is performed to form the tooth surface and the adjacent portion. A gear machining method comprising, after the rough machining, machining the tooth surface based on the synchronous command angle, thereby performing the finishing machining on the tooth surface while leaving a portion of the adjacent portion intact.

2. The gear machining method according to claim 1, wherein the adjacent portion of the tooth surface is the tooth tip chamfer of the convex tooth.

3. The gear machining method according to claim 2, wherein in the rough machining, one of the tooth tip chamfers and the other tooth tip chamfer constituting the convex tooth are corrected to different shapes so that the one tooth tip chamfer constituting the convex tooth and the other tooth tip chamfer constituting the convex tooth become symmetrical after the finishing process.

4. A gear machining method for machining protruding teeth of a gear on a workpiece using a gear skiving cutter, When performing finish machining on the tooth surface constituting the convex tooth that has been roughly machined, an error estimation step is performed to estimate the error between the synchronization command angle and the actual synchronization angle with respect to the synchronization angle between the workpiece and the gear skiving cutter, The process includes a machining step of correcting the rough machining shape of the convex tooth or the machining conditions for the finishing process based on the estimated error, The gear machining method comprising the machining step of correcting the synchronization command angle so that the material removal amount for one tooth surface constituting the convex tooth and the material removal amount for the other tooth surface are the same based on the estimated error, and performing the finishing machining on the tooth surface based on the corrected synchronization command angle.

5. The gear machining method according to claim 4, applicable to a machining method which includes rough machining of the tooth surface and adjacent portions of the tooth surface constituting the convex tooth, and finishing machining of at least the tooth surface while leaving a portion of the adjacent portions after the rough machining.

6. The gear machining method according to any one of claims 1 to 5, wherein the error estimation step estimates the error by actual measurement or analysis.

7. A gear machining method according to any one of claims 1 to 5, wherein the error is estimated using a relational expression that defines the error with respect to the axial intersection angle between the gear skiving cutter and the workpiece as a parameter.

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