Gear machining apparatus and gear machining method

Abstract

To provide a gear machining apparatus and gear machining method that can extend the lifespan of machining tools. [Solution] In a gear machining apparatus, a roughing tool performs machining on a workpiece before hardening. A finishing tool performs machining on a workpiece after hardening. The roughing tool includes a second tool T12 and a first tool. The second tool T12 forms relief recesses in the tooth roots of the gears created in the workpiece. The first tool processes the workpiece before it is machined by the second tool T12. Each of the multiple second cutting edges 602 in the second tool T12 has a second protrusion 612 at its tip for forming relief recesses. Each of the multiple first cutting edges 601 in the first tool either has a first protrusion at its tip or does not have a first protrusion. If the first cutting edge 601 has a first protrusion, the amount of protrusion of the first protrusion is smaller than the amount of protrusion of the second protrusion 612.

Description

Technical Field

[0001] The present invention relates to a gear processing apparatus and a gear processing method.

Background Art

[0002] For example, as disclosed in Patent Document 1, there is known a gear processing method in which a gear is created on a workpiece by a processing tool. In the gear processing method described in Patent Document 1, a roughing tool for roughing the workpiece before finish machining has a so-called protrusion balance shape in which a convex portion is formed on the cutting edge. By providing the roughing tool with this protrusion balance shape, it is possible to form a relief recess at the tooth root of the gear on the workpiece. And the gear processing method described in Patent Document 1 reduces the load on the finishing tool used for finish machining by forming a relief recess at the tooth root of the gear, and aims to extend the life of the finishing tool.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the gear processing method described in Patent Document 1, since the roughing tool has a convex portion on the cutting edge, depending on the way of roughing, there is a risk of being easily damaged during processing. Therefore, from the viewpoint of extending the life of the roughing tool, it can be said that there is room for further improvement.

[0005] The present invention has been made in view of such problems, and aims to provide a gear processing apparatus and a gear processing method capable of extending the life of a processing tool.

Means for Solving the Problems

[0006] One aspect of the present invention is, A gear machining apparatus that creates a gear on a workpiece by synchronously rotating the machining tool and the workpiece, and moving the machining tool relative to the workpiece along the rotation axis of the workpiece, The aforementioned machining tool, A spindle is configured to rotatably hold the aforementioned machining tool and to allow the machining tool to be attached to and detached from it, The system includes a control device that controls the rotation of the machining tool and the workpiece, and the relative movement of the machining tool with respect to the workpiece. The aforementioned machining tool is A rough machining tool is used to perform rough machining on the workpiece before the hardening treatment, A finishing tool is included for performing finishing work on the workpiece after heat treatment, The aforementioned roughing tool is A second tool comprising a plurality of second cutting edges arranged in a circumferential direction, and which forms relief recesses in the tooth roots of the gears created in the workpiece, A first tool comprising a plurality of first cutting edges arranged in a circumferential direction, and for machining the workpiece before it is machined by the second tool, Each of the plurality of second cutting edges has a second protrusion at its tip that protrudes along the direction in which the plurality of second cutting edges are aligned, for forming the relief recess. Each of the plurality of first blades has a first protrusion at its tip that protrudes in the direction in which the plurality of first blades are aligned, or it does not have the first protrusion. In a gear machining apparatus, if the blade has the first protrusion, the amount of protrusion of the first protrusion is smaller than the amount of protrusion of the second protrusion.

[0007] Other aspects of the present invention include: A gear machining method for creating a gear in a workpiece by synchronously rotating the machining tool and the workpiece, and moving the machining tool relative to the workpiece along the rotation axis of the workpiece, The machining tool is rotatably held on a spindle that is configured to detachably hold the machining tool. A rough machining process is performed on the workpiece before the heat treatment, and relief recesses are formed in the tooth roots of the gears created in the workpiece. The process includes a finishing step in which machining is performed on the workpiece after the heat treatment, The aforementioned machining tool is At least two roughing tools used in the aforementioned roughing process, Includes a finishing tool used in the aforementioned finishing process, The aforementioned roughing tool is A second tool comprising a plurality of second cutting edges arranged in a circumferential direction, and which forms the relief recess, A first tool comprising a plurality of first cutting edges arranged in a circumferential direction, and for machining the workpiece before it is machined by the second tool, Each of the plurality of second cutting edges has a second protrusion at its tip that protrudes along the direction in which the plurality of second cutting edges are aligned, for forming the relief recess. Each of the plurality of first blades has a first protrusion at its tip that protrudes in the direction in which the plurality of first blades are aligned, or it does not have the first protrusion. In a gear machining method, if the blade has the first protrusion, the amount of protrusion of the first protrusion is smaller than the amount of protrusion of the second protrusion. [Effects of the Invention]

[0008] In the gear machining apparatus described above, the roughing tool includes a first tool and a second tool. Therefore, the load on the roughing tool can be reduced during roughing. As a result, damage to the roughing tool can be suppressed. Consequently, the lifespan of the roughing tool can be extended.

[0009] In the gear processing apparatus, the second tool forms a relief recess at the root of the gear to be formed on the workpiece. Therefore, during the finishing process, the load on the finishing tool can be reduced. As a result, damage to the finishing tool can be suppressed. Consequently, the service life of the finishing tool can be extended.

[0010] In the gear processing method, the roughing process is performed using the first tool and the second tool. Therefore, the load on the roughing tool in the roughing process can be reduced. As a result, the service life of the roughing tool can be extended.

[0011] Also, in the gear processing method, in the roughing process, a relief recess is formed at the root of the gear to be formed on the workpiece. Therefore, the load on the finishing tool in the finishing process can be reduced. As a result, the service life of the finishing tool can be extended.

[0012] As described above, according to the above aspect, a gear processing apparatus and a gear processing method capable of extending the service life of the processing tool can be provided.

Brief Description of the Drawings

[0013] [Figure 1] Conceptual diagram showing the configuration of the gear processing apparatus in Embodiment 1. [Figure 2] Diagram for explaining the operation of machining the workpiece with the processing tool in Embodiment 1. [Figure 3] View of the processing tool as seen from the radial direction of the cutting tool in Embodiment 1. [Figure 4] Partial cross-sectional view of the first tool for explaining the rake angle etc. of the first cutting edge in Embodiment 1. [Figure 5] Partial cross-sectional view of the second tool for explaining the rake angle etc. of the second cutting edge in Embodiment 1. [Figure 6] Partial cross-sectional view of the finishing tool in Embodiment 1. [Figure 7] Perspective view of the first cutting edge in Embodiment 1. [Figure 8] A perspective view of the second cutting edge in Embodiment 1. [Figure 9] A diagram showing the area near the tip of the first blade in Embodiment 1. [Figure 10] A diagram showing the area near the tip of the second cutting edge in Embodiment 1. [Figure 11] A cross-sectional view of the vicinity of the first interface in Embodiment 1, shown as a cross-sectional view taken along the line XI-XI in Figure 9. [Figure 12] A cross-sectional view of the vicinity of the second interface in Embodiment 1, shown as a cross-sectional view taken along the line XII-XII in Figure 10. [Figure 13] A diagram showing the area near the relief recess for the workpiece in Embodiment 1. [Figure 14] A view of the teeth of a workpiece in Embodiment 1, before cutting with the second tool, as seen from the direction of tooth extension. [Figure 15] An enlarged view of the area near the relief recess for the workpiece in Embodiment 1. [Figure 16] A flowchart showing the workflow of the workpiece machining process in Embodiment 1. [Figure 17] A diagram showing the area near the tip of the first blade in Embodiment 2. [Figure 18] A view of the teeth of the workpiece in Embodiment 2, before cutting with the second tool, as seen from the direction of tooth extension. [Figure 19] Enlarged view of the area near the relief recess for the workpiece in Embodiment 2. [Modes for carrying out the invention]

[0014] (Embodiment 1) 1. Configuration of the gear processing machine The gear machining apparatus 1 of Embodiment 1 will be described with reference to Figures 1 to 16. As shown in Figure 2, the gear machining apparatus 1 of this embodiment creates a gear on the workpiece W by moving the machining tool T relative to the workpiece W along the rotation axis of the workpiece W while synchronously rotating the machining tool T and the workpiece W.

[0015] As shown in Figure 1, the gear machining apparatus 1 comprises a machining tool T, a spindle 33b, and a control device 5. The spindle 33b rotatably holds the machining tool T. The spindle 33b is also configured to allow the machining tool T to be attached to and detached from it. The control device 5 controls the rotation of the machining tool T and the workpiece W, as well as the relative movement of the machining tool T with respect to the workpiece W.

[0016] The machining tool T includes at least two roughing tools T1 and a finishing tool T2, as shown in Figures 3 to 6. The roughing tools T1 perform rough machining on the workpiece W before hardening. The finishing tools T2 perform finishing machining on the workpiece W after hardening.

[0017] Furthermore, the roughing tool T1 includes a second tool T12 and a first tool T11, as shown in Figures 4 and 5. The second tool T12 has a plurality of second cutting edges 602 arranged in the circumferential direction, as shown in Figures 3 and 5, and forms relief recesses 80 (see Figure 13) at the tooth roots of the gears created in the workpiece W. The first tool T11 has a plurality of first cutting edges 601 arranged in the circumferential direction and processes the workpiece W before it is processed by the second tool T12.

[0018] Each of the multiple second cutting edges 602 has a second protrusion 612 at its tip that protrudes along the alignment direction D2 of the multiple second cutting edges 602, as shown in Figure 10, for forming a relief recess 80. Each of the multiple first cutting edges 601 has a first protrusion 611 at its tip that protrudes along the alignment direction D1 of the multiple first cutting edges 601 (see Figure 17 of Embodiment 2), or, as shown in Figure 9, does not have a first protrusion 611. When a first cutting edge 601 has a first protrusion 611, the amount of protrusion of the first protrusion 611 is smaller than the amount of protrusion of the second protrusion 612.

[0019] 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. In this embodiment, the machining tool T is a gear skiving cutter. In addition to the gear skiving cutter, other interchangeable machining tools T may include a hob cutter. By switching to a hob cutter, the gear machining device 1 becomes a device that machines tooth profiles (gear teeth) on the workpiece W by hobbing.

[0020] 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.

[0021] As shown in Figures 1 and 2, the gear machining apparatus 1 has, for example, three mutually orthogonal linear drive axes (X-axis, Y-axis, and Z-axis). The gear machining apparatus 1 is configured to allow the workpiece W and the machining tool T to move relative to each other in the X-axis, Y-axis, and Z-axis directions. Here, the direction parallel to the rotation axis Zt of the machining tool T (equal to the rotation axis of the main spindle 33b) 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.

[0022] Furthermore, the gear machining apparatus 1 has one rotary drive axis (B axis) for changing the relative orientation between the workpiece W and the machining tool T. In this embodiment, the B axis is a rotation axis with a rotation center parallel to the Y axis. The gear machining apparatus 1 also has a rotary drive axis (Ct axis) for rotating the machining tool T and a rotary drive axis (Cw axis) for rotating the workpiece W. In this embodiment, the Ct axis is a rotation axis with a rotation center 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 machining tool T may be configured to take an angle with respect to both the Z axis and the X axis.

[0023] In the gear machining apparatus 1, the configuration for relative movement between the workpiece W and the machining tool 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 machining apparatus 1 allows the machining tool T to move linearly in the Y axis and Z axis directions, allows the workpiece W to move linearly in the X axis direction, and allows the workpiece W to rotate on the B axis.

[0024] The gear machining apparatus 1 comprises a bed 10, a workpiece holder 20, and a tool holder 30. 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 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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 machining tool 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 machining tool T rotatable around the Ct axis by the drive of the rotary motor. In this way, the tool holder device 30 holds the machining tool T so that it can move in the Y-axis and Z-axis directions relative to the bed 10 and is rotatable around the Ct axis.

[0031] 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 a saddle 32, and the spindle 33b of the tool spindle unit 33 is rotatably supported by the housing 33a. A machining tool T is attached to the tip of this spindle 33b. In other words, the machining tool T is cantilevered to the spindle 33b of the tool spindle unit 33.

[0032] The control device 5 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 5 controls the rotation of the machining tool 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 machining tool T.

[0033] In detail, as shown in Figure 2, the control device 5 positions the rotation axis Zt of the machining tool 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 5 rotates the B-axis rotary table 22 to position the workpiece W and the machining tool T so that they have an axial intersection angle α. Then, while synchronously rotating the workpiece W and the machining tool T, the control device 5 moves the machining tool 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. In this embodiment, convex teeth are created on the outer surface of the workpiece W.

[0034] Furthermore, the gear machining apparatus 1 is equipped with an automatic tool changer 4, as shown in Figure 1. The automatic tool changer 4 changes the machining tool T attached to the spindle 33b. In this embodiment, the automatic tool changer 4 is located on the side of the column 31. The automatic tool changer 4 comprises a magazine 41 that houses multiple machining tools T, and an arm 42 that attaches and detaches the machining tools T to and from the spindle 33b. The magazine 41 and the arm 42 are each configured to be rotatably driven by a drive device (not shown). The arm 42 exchanges the machining tool T designated by the control device 5 from among the multiple machining tools T housed in the magazine 41 with the machining tool T mounted on the spindle 33b. The arm 42 has a gripping portion (not shown) for gripping the machining tool T. In this embodiment, the magazine 41 is a chain-type magazine, but other types of magazines may be used, such as a matrix magazine that can store a larger number of tools.

[0035] The gear machining apparatus 1 is equipped with a sensor 50 for detecting the phase of the machining tool T. In this embodiment, the sensor 50 is located on the upper part of the workpiece spindle unit 23. The sensor 50 detects the phase of the machining tool T when it is mounted on the spindle 33b. The control device 5 controls the phase of the machining tool T based on the phase detection result of the sensor 50. Specifically, as shown in Figure 3, a groove 65 is formed on a part of the outer circumferential surface of the machining tool T. The control device 5 moves the X-axis moving table 21, column 31, and saddle 32 to move the machining tool T mounted on the spindle 33b to the vicinity of the sensor 50. Next, the sensor 50 detects the amount of phase deviation of the machining tool T by detecting the position of the groove 65 of the machining tool T. Then, the control device 5 adjusts the phase of the machining tool T based on the phase of the machining tool T detected by the sensor 50 and the positional relationship between the groove and the cutting edge of the machining tool T, which has been measured in advance. It is preferable to use a non-contact sensor for sensor 50. In this embodiment, sensor 50 is a non-contact eddy current sensor.

[0036] 2. Processing tool T The machining tool T is rotatably held on the spindle 33b. Specifically, the machining tool T is mounted on the spindle 33b and rotates integrally with the spindle 33b. As shown in Figure 3, the machining tool T comprises a cutting portion 6 that machines the workpiece W and has multiple cutting edges on its outer circumferential surface, a gripping portion 66, and a spindle mounting portion 67 that is mounted on the spindle 33b. On the cutting portion 6, the multiple cutting edges are arranged in the circumferential direction of the cutting portion 6. The gripping portion 66 is the part that is gripped by the arm 42 when the machining tool T is changed between the spindle 33b and the magazine 41 by the automatic tool changer 4. In this embodiment, the roughing tool T1 and the finishing tool T2, which are the machining tools T, have the same structure in parts other than the cutting edges on the cutting portion 6, such as the gripping portion 66 and the spindle mounting portion 67.

[0037] The first tool T11, which is a roughing tool T1, has a plurality of first cutting edges 601 on the outer circumferential surface of the cutting edge 6, as shown in Figure 4. The first cutting edges 601 are formed in a convex shape, and as shown in Figure 7, they are formed so that their width decreases as they move radially outward from the cutting edge 6.

[0038] The first cutting edge 601 of the first tool T1 has a first rake face 621, a first relief face 631, and a first boundary face 641. The first boundary face 641 connects the first rake face 621 and the first relief face 631 and is a surface with an R-chamfer. The first rake face 621 formed on each first cutting edge 601 is the end face on one side of the first cutting edge 601 in the direction of extension of the first cutting edge 601, opposite to the spindle 33b side, as shown in Figures 4, 7, and 9. In this embodiment, the first relief face 631 is a surface formed on the radially outer side of the cutting edge 6 and on both sides in the alignment direction D1 of the first cutting edge 601. Also, in this embodiment, the first cutting edge 601 does not have a first protrusion 611 at its tip, as shown in Figure 9. In other words, in this embodiment, the tips of each of the multiple first cutting edges 601 do not protrude along the alignment direction D1. In Figure 9, the first cutting edge 601 is shown by a solid line, the second cutting edge 602 of the second tool T12 is shown by a dashed line, and the finishing cutting edge 603 of the finishing tool T2 is shown by a dashed line. In this embodiment, the alignment direction D1 is also the circumferential direction of the cutting edge 6 of the first tool T11.

[0039] As shown in Figure 4, the first rake face 621 of the first cutting edge 601 has a rake angle γ1 that is inclined radially by an angle γ1 with respect to a plane perpendicular to the rotation axis Zt. The first rake face 621 also has a cutting angle ε1 that is inclined circumferentially by an angle ε1 with respect to a plane perpendicular to the rotation axis Zt. In this embodiment, the first cutting edge 601 has a helix angle β1 with respect to the rotation axis Zt. However, the first cutting edge 601 can also be formed such that the helix angle β1 is zero.

[0040] The second tool T12, which is a roughing tool T1, has a plurality of second cutting edges 602 on the outer circumferential surface of the cutting edge 6, as shown in Figures 3 and 5. The second cutting edges 602 are formed in a convex shape, and as shown in Figure 8, except for the tip, they are formed so that their width decreases as they move radially outward from the cutting edge 6.

[0041] The second cutting edge 602 of the second tool T2 has a second rake face 622, a second relief face 632, and a second interface face 642. The second interface face 642 connects the second rake face 622 and the second relief face 632 and is a face with an R-chamfer. The second rake face 622 formed on each second cutting edge 602 is the end face on one side of the second cutting edge 602 in the direction of extension of the second cutting edge 602, opposite to the spindle 33b side, as shown in Figures 5, 8, and 10. In this embodiment, the second relief face 632 is a face formed on the radially outer side of the cutting edge 6 and on both sides in the alignment direction D2 of the second cutting edge 602. In this embodiment, the second tool T12 has the same basic structure as the first tool T11, except that it has a second protrusion 612, as shown in Figure 10. In other words, the second cutting edge 602 has the same basic structure as the first cutting edge 601 with a protrusion formed at its tip. In Figure 10, the second cutting edge 602 is shown with a solid line, the first cutting edge 601 with a dashed line, and the finishing cutting edge 603 of the finishing tool T2 with a dashed line. Also, in this embodiment, the alignment direction D2 is also the circumferential direction of the cutting edge 6 of the second tool T12.

[0042] As shown in Figure 5, the second rake face 622 of the second cutting edge 602 has a rake angle γ2 that is inclined radially by an angle γ2 with respect to a plane perpendicular to the rotation axis Zt. The second rake face 622 also has a cutting angle ε2 that is inclined circumferentially by an angle ε2 with respect to a plane perpendicular to the rotation axis Zt. In this embodiment, the second cutting edge 602 has a helix angle β2 with respect to the rotation axis Zt. However, the second cutting edge 602 can also be formed such that the helix angle β2 is zero.

[0043] As shown in Figure 10, each of the multiple second cutting edges 602 has a protuberance shape. In this embodiment, the second protrusion 612 is provided on the radially outer end of the second tool T12 of the second cutting edge 602 and is formed along the entire length of the second cutting edge 602 in the extending direction. Each of the multiple second cutting edges 602 has the second protrusion 612 on both sides in the alignment direction D2. That is, each second cutting edge 602 has two second protrusions 612. When viewed from the extending direction of the second cutting edge 602, the second protrusion 612 protrudes in a convex curved shape. The size of the second protrusion 612 can be determined based on, for example, the cutting allowance in the workpiece W or the effective tooth height of the mating gear.

[0044] As shown in Figure 6, the finishing tool T2 has a plurality of finishing cutting edges 603 on the outer circumferential surface of the blade portion 6. The plurality of finishing cutting edges 603 are arranged in the circumferential direction of the blade portion 6. The finishing cutting edges 603 are formed in a convex shape, and their width decreases towards the radially outward direction. The tips of each of the plurality of finishing cutting edges 603 do not protrude along the direction in which the plurality of finishing cutting edges 603 are aligned. As shown in Figures 9 and 10, in this embodiment, the width of the finishing cutting edges 603 is greater than the width of the first cutting edge 601 and the width of the second cutting edge 602. Also, the tips of the finishing cutting edges 603 are located radially inward of the blade portion 6 than the tip of the roughing tool T1.

[0045] The finishing tool T2 performs a finishing treatment on the tooth surface of a workpiece W that has been hardened by quenching. The finishing cutting edge 603 can be made of, for example, a cemented carbide alloy. The HRC hardness of the finishing cutting edge 603 can be, for example, 78 to 80.

[0046] The workpiece W, which has been machined with the finishing tool T2 to create a gear, has multiple teeth arranged in the circumferential direction of the workpiece W. The relief recess 80 is recessed along the direction of the gear teeth, as shown in Figure 13. The HRC hardness of the workpiece W can be, for example, 58 to 62.

[0047] Furthermore, the rake angle γ1 of the first cutting edge 601 (see Figure 4) is smaller than the rake angle γ2 of the second cutting edge 602 (see Figure 5). In this embodiment, the rake angle γ1 is less than or equal to half the rake angle γ2. Specifically, in this embodiment, the rake angle γ1 is 5° and the rake angle γ2 is 10°.

[0048] Furthermore, the cutting angle ε1 of the first cutting edge 601 (see Figure 4) is smaller than the cutting angle ε2 of the second cutting edge 602 (see Figure 5). In this embodiment, the cutting angle ε1 is less than or equal to 2 / 3 of the cutting angle ε2. Specifically, in this embodiment, the cutting angle ε1 is 10° and the cutting angle ε2 is 15°.

[0049] In this embodiment, the entire corner of the first tool T11 connecting the first rake face 621 and the first flank face 631 forms the first interface surface 641. Similarly, in this embodiment, the entire corner of the second tool T12 connecting the second rake face 622 and the second flank face 632 forms the second interface surface 642. The length CL1 (see Figure 11) from the edge of the first interface surface 641 on the first rake face 621 side to the edge of the first flank face 631 side is longer than the length CL2 (see Figure 12) from the edge of the second interface surface 642 on the second rake face 622 side to the edge of the second flank face 632 side.

[0050] As shown in Figure 11, in a cross-section perpendicular to the extension direction of the first boundary surface 641, the first boundary surface 641 is formed to follow a virtual circle VC1 with a radius of 50 μm or less. Also, as shown in Figure 12, in a cross-section perpendicular to the extension direction of the second boundary surface 642, the second boundary surface 642 is formed to follow a virtual circle VC2 with a radius of 20 μm or less. The radius of the virtual circle VC2 can be, for example, 10 to 20 μm. Also, as shown in Figure 11, in a cross-section perpendicular to the extension direction of the first boundary surface 641, the length in the direction perpendicular to the first rake face 621 of the first boundary surface 641 is defined as length L1. Also, as shown in Figure 12, in a cross-section perpendicular to the extension direction of the second boundary surface 642, the length in the direction perpendicular to the second rake face 622 of the second boundary surface 642 is defined as length L2. In this case, length L1 is longer than length L2. Length L1 can be, for example, 50 μm or less. The first interface 641 and the second interface 642 can be formed, for example, by applying a shot blast treatment to the first cutting edge 601 or the second cutting edge 602.

[0051] 3. Gear machining method (processing using a control device) In this gear machining method, a gear is created on the workpiece W by synchronously rotating the machining tool T and the workpiece W, while moving the machining tool T relative to the workpiece W along the rotation axis of the workpiece W.

[0052] The gear machining method comprises a rough machining step and a finish machining step. The rough machining step involves machining the workpiece W before hardening treatment and forming relief recesses 80 at the roots of the gear teeth created in the workpiece W. The finish machining step involves machining the workpiece W after hardening treatment. The machining tool T includes at least two rough machining tools T1 used in the rough machining step and a finish machining tool T2 used in the finish machining step. In other words, the control device 5 executes the rough machining step and the finish machining step. Furthermore, in this embodiment of the gear machining method, multiple gear teeth are created on the outer circumferential surface of the workpiece W.

[0053] Each step of the gear machining method will be explained based on the flowchart in Figure 16. In the rough machining step, as shown in Figure 13, the rough shape of the convex teeth of the gear is formed on the workpiece W before the hardening treatment. In this embodiment, in the rough machining step, first, as shown in step S1 of Figure 16, a first rough machining step is performed on the cylindrical workpiece W in which the gear has not yet been created, using the first tool T11 to cut, and as shown in Figure 14, the gear teeth W1 without the relief recess 80 are created. In other words, the control device 5 executes the first rough machining step using the first tool T11.

[0054] After the first rough machining process is completed, the process proceeds to step S2 in Figure 16, where the first tool T11 attached to the spindle 33b is replaced with the second tool T12. In this configuration, the machining tool T attached to the spindle 33b is replaced by the automatic tool changer 4, as described above. Specifically, the automatic tool changer 4 uses the arm 42 to remove the first tool T11 from the spindle 33b and to mount the second tool T12, which is stored in the magazine 41, onto the spindle 33b. After replacing the rough machining tool T1 attached to the spindle 33b from the first tool T11 to the second tool T12, the process proceeds to step S3 in Figure 16, where the sensor 50 adjusts the phase of the second tool T12. In other words, the control device 5 controls the automatic tool changer 4 to execute step S2, and then, based on the phase detection result of the sensor 50, adjusts the phase of the second tool T12 as necessary.

[0055] Next, the process proceeds to step S4 in Figure 16, where a second rough machining step is performed, in which the workpiece W is cut using the second tool T12. Specifically, in the second rough machining step, as shown by the dashed line in Figure 14, the second tool T12 is used to perform a relief recess forming process, in which relief recesses 80 are formed along the outline 602L of the region through which the corners connecting the second rake face 622 and the second relief face 632 of each second cutting edge 602 of the second tool T12 pass. In other words, the second protrusion 612 of the second tool T12 forms relief recesses 80 on both sides of the tooth root of the workpiece W in the alignment direction D3, as shown in Figures 13 to 15. The alignment direction D3 is the alignment direction of the multiple teeth in the gear created in the workpiece W. Furthermore, in this manufacturing method, the portion of the tooth W1 radially outside the area where the relief recess 80 is formed is also cut by the second tool T12. In other words, in this embodiment, when the control device 5 executes the second rough machining process, it controls the second tool T12 to cut not only the relief recess 80 but also the portion that will become the tooth surface of the gear tooth. As a result, as shown in Figures 13 and 15, teeth W2 with relief recesses 80 are created on the workpiece W. In addition, rough machining is performed while leaving a material to be removed. The dashed line in Figure 15 is the outline 601L of the region through which the corner connecting the first rake face 621 and the first relief face 631 of each first cutting edge 601 of the first tool T11 passes.

[0056] After forming a relief recess 80 in the workpiece W, the process proceeds to step S5 in Figure 16, where the automatic tool changer 4 replaces the machining tool T mounted on the spindle 33b from the second tool T12 to the finishing tool T2. Then, the process proceeds to step S6 in Figure 16, where the control device 5, similar to step S3, performs phase alignment of the finishing tool T2 as necessary, based on the phase detection result of the sensor 50 on the finishing tool T2 mounted on the spindle 33b.

[0057] Furthermore, after performing the second rough machining process, the workpiece W is subjected to a hardening treatment as shown in step S7 of Figure 16. In this embodiment, the hardening treatment is performed not in the gear machining apparatus 1 shown in Figure 1, but in another external device (not shown). 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 treatment is performed in another device. After the hardening treatment, the workpiece W is reattached to the gear machining apparatus 1, and the phase of the workpiece W is adjusted as necessary.

[0058] After hardening and aligning the phase of the finishing tool T2, the finishing process is performed using the finishing tool T2 as shown in step S8 of Figure 16. In other words, the control device 5 executes the finishing process using the finishing tool T2. In the finishing process, as shown by the dashed lines in Figures 13 and 15, the workpiece W is finished along the outline 603L of the region through which the corners connecting the finishing rake face 623 and the finishing relief face 633 of each finishing cutting edge 603 of the finishing tool T2 pass. The outline 603L also passes inside the relief recess 80 and radially outside the workpiece W beyond the bottom surface WS between the relief recesses 80 in the gear alignment direction D3. In other words, in the finishing process, the finishing tool T2 cuts the tooth surface portion of the workpiece W radially outside the relief recess 80 to the workpiece W, thereby creating the gear. Furthermore, in this embodiment, the bottom surface WS of the gear is not cut during the finishing process. In the finishing process, the remaining material on the workpiece W is removed to form the desired gear shape on the workpiece W.

[0059] Furthermore, in this embodiment, a single workpiece W is machined using multiple machining passes. One machining pass is the movement path of the workpiece W in the axial direction by the machining tool T, from the starting position to the ending position.

[0060] The number of passes used to cut the workpiece W by the first tool T11 can be, for example, 6 passes or less. Specifically, the number of passes used to cut the workpiece W by the first tool T11 can be, for example, 5 passes or 6 passes. Also, the number of passes used to cut the workpiece W by the second tool T12 can be, for example, 2 passes or less. Specifically, the number of passes used to cut the workpiece W by the second tool T12 can be, for example, 1 pass or 2 passes.

[0061] 4. Effects In the gear machining apparatus 1 described above, the roughing tool T1 includes a first tool T11 and a second tool T12. Therefore, the load on the roughing tool T1 can be reduced during roughing. As a result, damage to the roughing tool T1 can be suppressed. Consequently, the lifespan of the roughing tool T1 can be extended.

[0062] Furthermore, in the gear machining apparatus 1 described above, the second tool T12 forms a relief recess 80 at the tooth root of the gear created in the workpiece W. Therefore, during finishing, interference between the cutting edge of the finishing tool T2 and the tooth root of the workpiece W can be suppressed, and the load on the finishing tool T2 can be reduced. As a result, damage to the finishing tool T2 can be suppressed. Consequently, the lifespan of the finishing tool T2 can be extended.

[0063] In the gear machining method described above, the rough machining process is performed using a first tool T11 and a second tool T12. Therefore, the load on the rough machining tool T1 during the rough machining process can be reduced. As a result, the lifespan of the rough machining tool T1 can be extended.

[0064] Furthermore, in the gear machining method described above, a relief recess 80 is formed in the tooth root of the gear created in the workpiece W during the rough machining process. Therefore, the load on the finishing tool T2 during the finishing process can be reduced. As a result, the lifespan of the finishing tool T2 can be extended.

[0065] In the roughing process, the load on the roughing tool T1 is reduced by dividing the cutting operation on the workpiece W using at least two roughing tools T1. Furthermore, each of the multiple first cutting edges 601 has either a first protrusion 611 at its tip that protrudes less than the amount of the second protrusion 612, or it does not have a first protrusion 611. Therefore, the first cutting edge 601 can be less susceptible to damage compared to the second cutting edge 602. The second tool T12 then processes the workpiece W after machining with the first tool T11. Therefore, since machining is performed by the second tool T12 after machining with the less susceptible first tool T11, the amount of material removed from the workpiece W by the second tool T12 can be reduced. Therefore, even if the second protrusion 612 is formed on the second tool T12, damage to the second tool T12 can be suppressed. As a result, the lifespan of the second tool T12 can be extended.

[0066] Furthermore, by suppressing damage to the machining tool T, machining conditions can be improved. For example, the feed rate of the machining tool T relative to the workpiece W can be increased, or the depth of cut can be increased. As a result, productivity can be improved.

[0067] In the roughing process, the roughing tool T1 mounted on the spindle 33b is changed from the first tool T11 to the second tool T12, and then the phase of the second tool T12 is adjusted by the sensor 50. Therefore, the gear of the workpiece W can be created with sufficient precision. Furthermore, in this embodiment, the phase of the finishing tool T2 is also adjusted before the finishing process. Therefore, the gear of the workpiece W can be created with even greater precision.

[0068] The rake angle γ1 of the first cutting edge 601 is smaller than the rake angle γ2 of the second cutting edge 602. Therefore, damage to the first tool T11 is more easily suppressed. As a result, the lifespan of the machining tool T can be further extended. In addition, since the rake angle γ2 is larger than the rake angle γ1, the cutting performance of the second tool T12 against the workpiece W can be improved, and machining accuracy can be improved.

[0069] The cutting angle ε1 of the first cutting edge 601 is smaller than the cutting angle ε2 of the second cutting edge 602. Therefore, damage to the first tool T11 is more easily suppressed. As a result, the lifespan of the machining tool T can be further extended. In addition, since the cutting angle ε2 is larger than the cutting angle ε1, the cutting performance of the second tool T12 against the workpiece W can be improved, and machining accuracy can be improved.

[0070] In this embodiment, the length CL1 of the first interface 641 is longer than the length CL2 of the second interface 642. Therefore, damage to the first tool T11 is more easily suppressed. As a result, the lifespan of the machining tool T can be further extended. In addition, since the length CL2 is shorter than the length CL1, the cutting resistance during rough machining of the second tool T12 can be further reduced, and the machining accuracy of the workpiece W with respect to the second tool T12 can be further improved.

[0071] The gear machining apparatus 1 is equipped with an automatic tool changer 4. Therefore, the machining tool T mounted on the spindle 33b can be replaced efficiently. As a result, productivity can be improved.

[0072] As described above, this embodiment provides a gear machining apparatus 1 and a gear machining method that can extend the lifespan of the machining tool T.

[0073] (Embodiment 2) This embodiment is characterized in which a protrusion is formed on the first cutting edge 601 of the first tool T11. That is, as shown in Figure 17, each of the multiple first cutting edges 601 has a first protrusion 611 at its tip that protrudes along the alignment direction D1.

[0074] In the first tool T11, each of the multiple first cutting edges 601 has a protuberance shape, as shown in Figure 17. The first protrusion 611 is provided at the radially outer end of the first cutting edge 601 and is formed along the entire length of the first cutting edge 601 in the extending direction. Each of the multiple first cutting edges 601 has the first protrusion 611 on both sides in the alignment direction D1. In other words, each first cutting edge 601 has two first protrusions 611. When viewed from the extending direction of the first cutting edge 601, the first protrusion 611 protrudes in a convex curved shape. The size of the first protrusion 611 can be determined based on, for example, the cutting allowance in the workpiece W or the effective tooth height of the mating gear.

[0075] In this embodiment, the amount of protrusion of the first protrusion 611 is less than or equal to half the amount of protrusion of the second protrusion 612. That is, when the first cutting edge 601 is viewed from the first rake face 621 side and in the direction of extension of the first cutting edge 601, the height of the first protrusion 611 in the direction perpendicular to the contour line of the radially inner portion of the cutting edge 601 is defined as height H1. Similarly, when the second cutting edge 602 is viewed from the second rake face 622 side and in the direction of extension of the second cutting edge 602, the height of the second protrusion 612 in the direction perpendicular to the contour line of the radially inner portion of the cutting edge 602 is defined as height H2. In this case, height H1 is lower than height H2. Height H1 is less than or equal to half the height H2. Furthermore, when the first cutting edge 601 is projected in the direction of extension of the first cutting edge 601, the projected area of ​​the first protrusion 611 is less than half the projected area of ​​the second protrusion 612 when the second cutting edge 602 is projected in the direction of extension of the second cutting edge 602. In addition, the amount of protrusion of the first protrusion 611 and the amount of protrusion of the second protrusion 612 can be adjusted, for example, by considering the machining conditions, the material and shape of the workpiece W, the material and shape of the roughing tool T1, the cutting resistance, etc.

[0076] In this embodiment, in the first rough machining step, the first tool T11 creates gear teeth W1 in a cylindrical workpiece W in which no gears have been created, as shown in Figure 18. In addition, in the first rough machining step, the first protrusion 611 of the first tool T11 forms a recess 800 at the tooth root that is shallower in depth than the relief recess 80 formed by the second tool T12. In other words, the control device 5 executes the first rough machining step in which the recess 800 is formed in the workpiece W using the first tool T11.

[0077] After the first roughing process, the automatic tool changer 4 replaces the roughing tool T1 mounted on the spindle 33b from the first tool T11 to the second tool T12. After the roughing tool T1 is replaced, the control device 5 adjusts the phase of the second tool T12 mounted on the spindle 33b as needed, based on the detection results of the sensor 50.

[0078] Next, as shown by the dashed line in Figure 18, a relief recess 80 is formed in the workpiece W along the outline 602L of the region through which the corners connecting the second rake face 622 and the second relief face 632 of each second cutting edge 602 of the second tool T12 pass. In this embodiment, the second tool T12 forms a relief recess 80 in relation to the recess 800 formed by the first tool T11. As a result, as shown in Figure 19, a tooth W2 with a relief recess 80 is created in relation to the workpiece W. Otherwise, it is the same as in Embodiment 1. Note that, among the reference numerals used in Embodiment 2 and later, those that are the same as those used in the previously described embodiments represent the same components, etc., as in the previously described embodiments, unless otherwise specified.

[0079] In this embodiment, each of the multiple first cutting edges 601 has a first protrusion 611 at its tip. The second tool T12 forms a relief recess 80 in the recess 800 formed in the workpiece W by the first tool T11. In other words, by forming a part of the relief recess 80 with the first tool T11, the cutting resistance when the second tool T12 forms the relief recess 80 can be reduced. Therefore, the load on the second tool T12 during the roughing process can be further reduced. As a result, the lifespan of the second tool T12 can be further extended. Furthermore, it has the same effects and advantages as Embodiment 1.

[0080] In embodiments 1 and 2 described above, the control device 5 controls the second tool T12 to not only form relief recesses 80 in the workpiece W, but also to cut the portion that will become the tooth surface of the gear teeth. However, the control device can also control the second tool to form only the relief recesses without cutting the portion that will become the tooth surface of the gear teeth in the workpiece. In other words, the control device can also control the rough machining process to cut the portion that will become the tooth surface of the gear teeth in the workpiece using only the first tool.

[0081] In embodiments 1 and 2 described above, the rough machining process is performed using the first tool T11 and the second tool T12. However, the rough machining process can also be performed using, for example, three or more rough machining tools.

[0082] The present invention is not limited to the embodiments described above, and can be applied to various embodiments without departing from its spirit.

[0083] <Other> The features of this invention are as follows. [Section 1] A gear machining apparatus that creates a gear on a workpiece by synchronously rotating the machining tool and the workpiece, and moving the machining tool relative to the workpiece along the rotation axis of the workpiece, The aforementioned machining tool, A spindle is configured to rotatably hold the aforementioned machining tool and to allow the machining tool to be attached to and detached from it, The system includes a control device that controls the rotation of the machining tool and the workpiece, and the relative movement of the machining tool with respect to the workpiece. The aforementioned machining tool is A rough machining tool is used to perform rough machining on the workpiece before the hardening treatment, A finishing tool is included for performing finishing work on the workpiece after heat treatment, The aforementioned roughing tool is A second tool comprising a plurality of second cutting edges arranged in a circumferential direction, and which forms relief recesses in the tooth roots of the gears created in the workpiece, A first tool comprising a plurality of first cutting edges arranged in a circumferential direction, and for machining the workpiece before it is machined by the second tool, Each of the plurality of second cutting edges has a second protrusion at its tip that protrudes along the direction in which the plurality of second cutting edges are aligned, for forming the relief recess. Each of the plurality of first blades has a first protrusion at its tip that protrudes in the direction in which the plurality of first blades are aligned, or it does not have the first protrusion. A gear machining apparatus in which, when each blade has the first protrusion, the amount of protrusion of the first protrusion is smaller than the amount of protrusion of the second protrusion. [Section 2] The gear machining apparatus according to item 1, wherein the rake angle of the first cutting edge is smaller than the rake angle of the second cutting edge. [Section 3] The gear machining apparatus according to item 1 or 2, wherein the cutting angle of the first cutting edge is smaller than the cutting angle of the second cutting edge. [Section 4] The blades of the first tool are The first scooping surface, First escape route, The first rake face and the first relief face are connected, and the first interface surface has an R-chamfer, The second cutting edge of the second tool is The second scooping surface, The second escape route, The second rake face and the second relief face are connected, and a second interface surface with an R-chamfer is provided, The gear machining apparatus according to any one of claims 1 to 3, wherein the length from the edge on the first rake face side to the edge on the first flank face side of the first interface is longer than the length from the edge on the second rake face side to the edge on the second flank face side of the second interface. [Section 5] A gear machining apparatus according to any one of claims 1 to 4, comprising an automatic tool changer for changing the machining tool attached to the spindle. [Section 6] A gear machining method for creating a gear in a workpiece by synchronously rotating the machining tool and the workpiece, and moving the machining tool relative to the workpiece along the rotation axis of the workpiece, The machining tool is rotatably held on a spindle that is configured to detachably hold the machining tool. A rough machining process is performed on the workpiece before the heat treatment, and relief recesses are formed in the tooth roots of the gears created in the workpiece. The process includes a finishing step in which machining is performed on the workpiece after the heat treatment, The aforementioned machining tool is At least two roughing tools used in the aforementioned roughing process, Includes a finishing tool used in the aforementioned finishing process, The aforementioned roughing tool is A second tool comprising a plurality of second cutting edges arranged in a circumferential direction, and which forms the relief recess, A first tool comprising a plurality of first cutting edges arranged in a circumferential direction, and for machining the workpiece before it is machined by the second tool, Each of the plurality of second cutting edges has a second protrusion at its tip that protrudes along the direction in which the plurality of second cutting edges are aligned, for forming the relief recess. Each of the plurality of first blades has a first protrusion at its tip that protrudes in the direction in which the plurality of first blades are aligned, or it does not have the first protrusion. A gear machining method wherein, when the blade has the first protrusion, the amount of protrusion of the first protrusion is smaller than the amount of protrusion of the second protrusion. [Section 7] The gear machining method according to item 6, wherein the rake angle of the first cutting edge is smaller than the rake angle of the second cutting edge. [Section 8] The gear machining method according to item 6 or 7, wherein the cutting angle of the first cutting edge is smaller than the cutting angle of the second cutting edge. [Section 9] The blades of the first tool are The first scooping surface, First escape route, The first rake face and the first relief face are connected, and the first interface surface has an R-chamfer, The second cutting edge of the second tool is The second scooping surface, The second escape route, The second rake face and the second relief face are connected, and a second interface surface with an R-chamfer is provided, The gear machining method according to any one of claims 6 to 8, wherein the length from the edge on the first rake face side to the edge on the first flank face side of the first interface is longer than the length from the edge on the second rake face side to the edge on the second flank face side of the second interface. [Section 10] The gear machining method according to any one of items 6 to 9, wherein the machining tool attached to the spindle is replaced by an automatic tool changer. [Explanation of symbols]

[0084] 1...Gear machining device, 5...Control device, 33b...Spindle, 80...Relief recess, 601...First cutting edge, 602...Second cutting edge, 611...First protrusion, 612...Second protrusion, D1...Alignment direction, D2...Alignment direction, T...Machining tool, T1...Roughing tool, T2...Finishing tool, T11...First tool, T12...Second tool, W...Workpiece

Claims

1. A gear machining apparatus that creates a gear on a workpiece by synchronously rotating the machining tool and the workpiece, and moving the machining tool relative to the workpiece along the rotation axis of the workpiece, The aforementioned machining tool, A spindle is configured to rotatably hold the aforementioned machining tool and to allow the machining tool to be attached to and detached from it, The system includes a control device that controls the rotation of the machining tool and the workpiece, and the relative movement of the machining tool with respect to the workpiece. The aforementioned machining tool is A rough machining tool is used to perform rough machining on the workpiece before the hardening treatment, A finishing tool is included for performing finishing work on the workpiece after heat treatment, The aforementioned roughing tool is A second tool comprising a plurality of second cutting edges arranged in a circumferential direction, and which forms relief recesses in the tooth roots of the gears created in the workpiece, A first tool comprising a plurality of first cutting edges arranged in a circumferential direction, and for machining the workpiece before it is machined by the second tool, Each of the plurality of second cutting edges has a second protrusion at its tip that protrudes along the direction in which the plurality of second cutting edges are aligned, for forming the relief recess. Each of the plurality of first blades has a first protrusion at its tip that protrudes in the direction in which the plurality of first blades are aligned, or it does not have the first protrusion. A gear machining apparatus in which, when each blade has the first protrusion, the amount of protrusion of the first protrusion is smaller than the amount of protrusion of the second protrusion.

2. The gear machining apparatus according to claim 1, wherein the rake angle of the first cutting edge is smaller than the rake angle of the second cutting edge.

3. The gear machining apparatus according to claim 1 or 2, wherein the cutting angle of the first cutting edge is smaller than the cutting angle of the second cutting edge.

4. The blades of the first tool are The first scooping surface, First escape route, The first rake face and the first relief face are connected, and the first interface surface has an R-chamfer, The second cutting edge of the second tool is The second scooping surface, The second escape route, The second rake face and the second relief face are connected, and a second interface surface with an R-chamfer is provided, The gear machining apparatus according to claim 1 or 2, wherein the length from the edge on the first rake face side to the edge on the first relief face side of the first interface is longer than the length from the edge on the second rake face side to the edge on the second relief face side of the second interface.

5. The gear machining apparatus according to claim 1 or 2, further comprising an automatic tool changer for changing the machining tool attached to the spindle.

6. A gear machining method for creating a gear in a workpiece by synchronously rotating the machining tool and the workpiece, and moving the machining tool relative to the workpiece along the rotation axis of the workpiece, The machining tool is rotatably held on a spindle that is configured to detachably hold the machining tool. A rough machining process is performed on the workpiece before the heat treatment, and relief recesses are formed in the tooth roots of the gears created in the workpiece. The process includes a finishing step in which machining is performed on the workpiece after the heat treatment, The aforementioned machining tool is At least two roughing tools used in the aforementioned roughing process, Includes a finishing tool used in the aforementioned finishing process, The aforementioned roughing tool is A second tool comprising a plurality of second cutting edges arranged in a circumferential direction, and which forms the relief recess, A first tool comprising a plurality of first cutting edges arranged in a circumferential direction, and for machining the workpiece before it is machined by the second tool, Each of the plurality of second cutting edges has a second protrusion at its tip that protrudes along the direction in which the plurality of second cutting edges are aligned, for forming the relief recess. Each of the plurality of first blades has a first protrusion at its tip that protrudes in the direction in which the plurality of first blades are aligned, or it does not have the first protrusion. A gear machining method wherein, when the blade has the first protrusion, the amount of protrusion of the first protrusion is smaller than the amount of protrusion of the second protrusion.

7. The gear machining method according to claim 6, wherein the rake angle of the first cutting edge is smaller than the rake angle of the second cutting edge.

8. The gear machining method according to claim 6 or 7, wherein the cutting angle of the first cutting edge is smaller than the cutting angle of the second cutting edge.

9. The blades of the first tool are The first scooping surface, First escape route, The first rake face and the first relief face are connected, and the first interface surface has an R-chamfer, The second cutting edge of the second tool is The second scooping surface, The second escape route, The second rake face and the second relief face are connected, and a second interface surface with an R-chamfer is provided, The gear machining method according to claim 6 or 7, wherein the length from the edge on the first rake face side to the edge on the first relief face side of the first interface is longer than the length from the edge on the second rake face side to the edge on the second relief face side of the second interface.

10. The gear machining method according to claim 6 or 7, wherein the machining tool attached to the spindle is replaced by an automatic tool changer.

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