Gear grinding machine and gear grinding method

Abstract

The invention relates to a gear grinding machine and a gear grinding method. A gear grinding machine includes a workpiece rotating mechanism, a grindstone rotating mechanism, and a moving mechanism. The workpiece rotation mechanism rotates a workpiece having a plurality of teeth on the outer peripheral surface about a workpiece axis, which is the central axis of the workpiece. The grindstone rotation mechanism rotates a grindstone having a helical groove on the outer peripheral surface about a grindstone axis, which is the central axis of the grindstone axis. The moving mechanism moves the grindstone relative to the workpiece. The grindstone axis is inclined with respect to the workpiece axis. In a gear grinding machine, a workpiece rotating mechanism and a grindstone rotating mechanism rotate a workpiece and a grindstone synchronously, and a moving mechanism moves the grindstone along a plane perpendicular to the axis of the workpiece, thereby grinding the workpiece.

Description

Gear grinding machines and gear grinding methods Technical Field

[0001] This invention relates to a gear grinding machine and a gear grinding method. Background Technology

[0002] Previously, gear grinding machines were known for grinding workpieces that form gears. In a gear grinding machine, a toothed workpiece and a grinding stone with helical grooves rotate synchronously, bringing them into contact so that the teeth of the workpiece mesh with the grooves of the grinding stone. Thus, the grinding stone grinds the teeth of the workpiece.

[0003] Conventional gear grinding machines are described, for example, in Patent Document 1.

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2022-188980 Summary of the Invention

[0005] In conventional gear grinding machines, in order to grind the teeth of the workpiece from one end to the other in the tooth width direction, the grinding stone is moved relative to the workpiece in the tooth width direction. That is, in conventional gear grinding machines, the grinding stone is moved relative to the workpiece in a direction parallel to the central axis of the workpiece.

[0006] However, in conventional grinding methods, the grinding stone moves over a large range in the tooth width direction. Therefore, for example, when grinding the small diameter portion of a workpiece for a multi-layered gear that includes both a small and a large diameter portion, there is a problem of interference between the grinding stone moving in the tooth width direction and the large diameter portion. Furthermore, besides multi-layered gears, the same problem occurs when the workpiece has a portion with a larger diameter than the tooth to be ground.

[0007] Therefore, the object of the present invention is to provide a technique that can grind a workpiece while limiting the range of movement of the grinding stone in a direction parallel to the central axis of the workpiece.

[0008] The first invention is a gear grinding machine for grinding workpieces that form gears, comprising: a workpiece rotation mechanism that rotates a workpiece having multiple teeth on its outer peripheral surface around its central axis, i.e., the workpiece axis; a grinding stone rotation mechanism that rotates a grinding stone having helical grooves on its outer peripheral surface around its central axis, i.e., the grinding stone axis; and a moving mechanism that moves the grinding stone relative to the workpiece, the grinding stone axis being inclined relative to the workpiece axis. The workpiece rotation mechanism and the grinding stone rotation mechanism cause the workpiece and the grinding stone to rotate synchronously, and the moving mechanism causes the grinding stone to move along a plane perpendicular to the workpiece axis, thereby grinding the workpiece.

[0009] The second invention is a gear grinding method for grinding a workpiece that forms a gear, comprising the following steps: rotating a workpiece having multiple teeth on its outer peripheral surface around its central axis (i.e., the workpiece axis) and rotating a grinding stone having helical grooves on its outer peripheral surface around its central axis (i.e., the grinding stone axis) while moving the grinding stone relative to the workpiece to grind the workpiece, wherein the grinding stone axis is inclined relative to the workpiece axis; in the above steps, the workpiece and the grinding stone rotate synchronously, and the grinding stone moves along a plane perpendicular to the workpiece axis to grind the workpiece.

[0010] According to the first and second inventions, it is possible to grind a workpiece while limiting the range of movement of the grinding stone in the axial direction of the workpiece. Attached Figure Description

[0011] Figure 1 is a diagram showing the structure of a gear grinding machine.

[0012] Figure 2 is a flowchart showing the operation process of a gear grinding machine.

[0013] Figure 3 is a diagram showing the state of the workpiece and grinding stone in step S4.

[0014] Figure 4 is a diagram showing the state of the workpiece and grinding stone in step S4.

[0015] Figure 5 is a diagram showing the state of the workpiece and grinding stone in step S4.

[0016] Figure 6 is a diagram showing the state of movement of the contact portion.

[0017] Figure 7 is a diagram showing the state of grinding a workpiece having a first region and a second region.

[0018] Figure 8 is a side view of a modified grinding stone. Detailed Implementation

[0019] <1. Structure of a Gear Grinding Machine>

[0020] Figure 1 is a diagram showing the structure of a gear grinding machine 1 according to one embodiment. The gear grinding machine 1 is a machine tool for grinding a workpiece 9 that has become a gear.

[0021] The workpiece 9 is generally cylindrical, and its outer circumferential surface has multiple teeth 91. Hereinafter, the central axis of the workpiece 9 will be referred to as the "workpiece axis A1". The gear manufactured by grinding the workpiece 9 is, for example, a helical gear. The workpiece 9 forming the helical gear has helical teeth 91 centered on the workpiece axis A1. However, the gear manufactured by grinding the workpiece 9 can also be other gears such as spur gears.

[0022] As shown in Figure 1, the gear grinding machine 1 includes a workpiece rotation mechanism 10, a grinding stone 20, a grinding stone rotation mechanism 30, a moving mechanism 40, and a control unit 50. The workpiece rotation mechanism 10, the grinding stone rotation mechanism 30, and the moving mechanism 40 are mounted on a common base (not shown in the figure).

[0023] The workpiece rotation mechanism 10 is a mechanism that rotates the workpiece 9 about the workpiece axis A1. The workpiece rotation mechanism 10 includes a pair of grippers that hold the workpiece 9 and a motor that rotates the grippers. In this embodiment, the workpiece 9 is held and rotated with the workpiece axis A1 facing vertically. However, the direction of the workpiece axis A1 is not necessarily vertical.

[0024] The grinding stone 20 is a tool for grinding the teeth 91 of the workpiece 9. The grinding stone 20 is roughly cylindrical, and its outer circumferential surface has a spiral groove 21. Hereinafter, the central axis of the grinding stone 20 will be referred to as the "grind stone axis A2".

[0025] The grinding stone rotation mechanism 30 is a mechanism that rotates the grinding stone 20 around the grinding stone axis A2. The grinding stone rotation mechanism 30 includes: a tool head that holds the grinding stone 20; and a motor that rotates the tool head. The grinding stone 20 is held in an orientation where the grinding stone axis A2 is inclined relative to the workpiece axis A1. That is, in this embodiment, the grinding stone 20 is held in an orientation where the grinding stone axis A2 is inclined relative to both the horizontal and vertical directions.

[0026] The moving mechanism 40 is a mechanism that moves the grinding stone 20 relative to the workpiece 9. The moving mechanism 40 moves the grinding stone 20 and the grinding stone rotation mechanism 30 as a whole. The moving mechanism 40 includes a first mechanism, a second mechanism, and a third mechanism. The first mechanism moves the grinding stone 20 closer to and further away from the workpiece 9; the second mechanism moves the grinding stone 20 vertically; and the third mechanism moves the grinding stone 20 in the direction along the grinding stone axis A2 (hereinafter referred to as the "grind stone axis"). Each mechanism is implemented, for example, by a motor and a ball screw that converts the rotation of the motor into linear motion. Through these first, second, and third mechanisms, the moving mechanism 40 can move the grinding stone 20 relative to the workpiece 9 in any direction in three-dimensional space.

[0027] Alternatively, the moving mechanism 40 may also have a fourth mechanism for adjusting the tilt angle of the grinding stone axis A2 relative to the workpiece axis A1.

[0028] The control unit 50 is a unit that controls the operation of various parts of the gear grinding machine 1. The control unit 50 is, for example, a computer equipped with a processor such as a CPU, a memory such as RAM, and a storage unit such as a hard disk drive. The storage unit stores computer programs used to control the operation of the gear grinding machine 1.

[0029] Furthermore, the control unit 50 is communicatively connected to the workpiece rotation mechanism 10, the grinding stone rotation mechanism 30, and the moving mechanism 40. The control unit 50 controls the operation of these parts according to the aforementioned computer program. As a result, the grinding process of the workpiece 9 in the gear grinding machine 1 is performed.

[0030] <2. About Grinding Methods>

[0031] Next, the method for grinding the workpiece 9 that forms a gear using the gear grinding machine 1 described above will be explained. Figure 2 is a flowchart showing the operation flow of the gear grinding machine 1.

[0032] When grinding workpiece 9, firstly, workpiece 9 is set on gear grinding machine 1 (step S1). Workpiece 9 is held by a pair of clamps of workpiece rotation mechanism 10. Then, the workpiece 9 is rotated about workpiece axis A1 by workpiece rotation mechanism 10 (step S2). In addition, the grinding stone 20 is rotated about grinding stone axis A2 by grinding stone rotation mechanism 30 (step S3).

[0033] The control unit 50 controls the workpiece rotation mechanism 10 and the grinding stone rotation mechanism 30 to rotate the workpiece 9 and the grinding stone 20 synchronously. Synchronous rotation means that the workpiece 9 and the grinding stone 20 rotate in a phase in which they can mesh with each other. When the workpiece 9 and the grinding stone 20 are rotating synchronously by the workpiece rotation mechanism 10 and the grinding stone rotation mechanism 30, the control unit 50 moves the grinding stone 20 relative to the workpiece 9 by the moving mechanism 40 (step S4).

[0034] Figures 3, 4, and 5 illustrate the states of the workpiece 9 and the grinding stone 20 in step S4. As shown in Figures 3 and 4, the moving mechanism 40 moves the grinding stone 20 along a plane perpendicular to the workpiece axis A1. Specifically, the moving mechanism 40 moves the grinding stone 20 along a straight path L between the first position P1 and the second position P2 shown in Figures 3 and 4. The grinding stone 20 contacts the workpiece 9 in the path L between the first position P1 and the second position P2. At this time, the workpiece 9 and the grinding stone 20 rotate synchronously, and therefore, they contact each other with the teeth 91 and the groove 21 meshing.

[0035] As shown in Figure 3, the grinding stone axis A2 is inclined relative to the workpiece axis A1. Therefore, the grinding stone 20 only contacts the workpiece 9 near the intersection of the workpiece axis A1 and the grinding stone axis A2 in Figure 3. Hereinafter, the part in contact between the grinding stone 20 and the workpiece 9 will be referred to as "contact portion C". At this contact portion C, the teeth 91 of the workpiece 9 and the grooves 21 of the grinding stone 20 slide in contact at a sliding speed corresponding to the intersection angle θ. As a result, the surface of the teeth 91 of the workpiece 9 is ground.

[0036] Preferably, the intersection angle θ between the grinding stone axis A2 and the workpiece axis A1 is, for example, 3° or more and 35° or less. This allows for the generation of an appropriate sliding speed at the contact portion C while suppressing the intersection angle θ. Furthermore, more preferably, the intersection angle θ between the grinding stone axis A2 and the workpiece axis A1 is 5° or more and 12° or less. This allows for the generation of an even more appropriate sliding speed at the contact portion C.

[0037] Figure 6 is a diagram showing the movement of the contact portion C. As shown in Figure 6, the length d2 of the grinding stone 20 in the direction parallel to the workpiece axis A1 (hereinafter referred to as the "workpiece axis") is longer than the length d1 of the tooth 91 of the workpiece 9 in the workpiece axis. More specifically, the length d2 of the portion of the grinding stone 20 that overlaps with the grinding stone axis A2 in Figure 6 in the workpiece axis is longer than the length d1 of the tooth 91 of the workpiece 9 in the workpiece axis. In step S4, by moving the grinding stone 20 along the path L, the position of the contact portion C is moved in the workpiece axis as shown in Figure 6. As a result, the tooth 91 of the workpiece 9 is ground from one end to the other in the workpiece axis.

[0038] After moving the grinding stone 20 from the first position P1 to the second position P2, the gear grinding machine 1 moves the grinding stone 20 from the second position P2 back to the first position P1 without changing the rotation direction of the workpiece 9 or the rotation direction of the grinding stone 20. This allows for multiple grinding operations on the surface of the teeth 91 of the workpiece 9. In this embodiment, the grinding stone 20 reciprocates between the first position P1 and the second position P2 without changing the rotation direction of the workpiece 9 or the rotation direction of the grinding stone 20. That is, the grinding stone 20 repeatedly moves from the first position P1 to the second position P2 and from the second position P2 back to the first position P1. This causes the grinding stone 20 to repeatedly contact the workpiece 9. As a result, the surface of the teeth 91 of the workpiece 9 can be sufficiently ground by the grinding stone 20.

[0039] After the grinding stone 20 reciprocates a predetermined number of times, the moving mechanism 40 stops the grinding stone 20 at either the first position P1 or the second position P2. Next, the grinding stone rotation mechanism 30 stops the rotation of the grinding stone 20 (step S5), and the workpiece rotation mechanism 10 stops the rotation of the workpiece 9 (step S6). Then, the workpiece 9 is removed from the gear grinding machine 1 (step S7). Alternatively, if the workpiece 9 is automatically changed by a loader and the grinding of the next workpiece 9 continues, step S5 can be omitted, and the rotation of the grinding stone 20 can continue.

[0040] As described above, in the gear grinding machine 1 of this embodiment, the moving mechanism 40 does not move the grinding stone 20 along the workpiece axis as in the conventional method, but instead moves the grinding stone 20 along a plane perpendicular to the workpiece axis A1 to grind the workpiece 9. Therefore, the workpiece 9 can be ground while limiting the range of movement of the grinding stone 20 along the workpiece axis.

[0041] In particular, in the gear grinding machine 1 of this embodiment, the moving mechanism 40 moves the grinding stone 20 along a straight line tangent to the workpiece 9 on a plane perpendicular to the workpiece axis A1. In this way, if the workpiece 9 is moved in a straight line, the direction of movement of the grinding stone 20 can be controlled more easily compared to the case of moving in a curved line.

[0042] The gear grinding machine 1 of this embodiment is particularly useful when grinding a workpiece 9 as shown in FIG. 7. The workpiece 9 in FIG. 7 has a first region 901 and a second region 902. The first region 901 protrudes radially relative to the workpiece axis A1. The second region 902 protrudes radially relative to the workpiece axis A1 and has a larger diameter than the first region 901. In the example of FIG. 7, the grinding stone 20 grinds the first region 901 of the workpiece 9. In this case, if the grinding stone 20 is moved axially along the workpiece as in the conventional case, the grinding stone 20 will come into contact with the second region 902 of the workpiece 9. However, in the operation method of this embodiment, the grinding stone 20 is moved along a plane perpendicular to the workpiece axis A1. Therefore, the first region 901 can be ground without the grinding stone 20 coming into contact with the second region 902.

[0043] The workpiece 9 in Figure 7 is, for example, a double-layer gear. In the above case, the first region 901 of the workpiece 9 becomes the small-diameter gear of the double-layer gear, and the second region 902 of the workpiece 9 becomes the large-diameter gear of the double-layer gear. In recent years, with the popularization of electric vehicles, there has been a demand for manufacturing double-layer gears as a single component. Furthermore, in order to miniaturize the gearbox of electric vehicles, it is required to reduce the axial length of the double-layer gear. In the above case, since the axial distance between the first region 901 and the second region 902 of the workpiece 9 is reduced, it is difficult to grind the first region 901 in conventional construction methods. However, as described above, according to the construction method of this embodiment, the first region 901 can be ground without the grinding stone 20 contacting the second region 902. Therefore, it can contribute to the miniaturization of the gearbox.

[0044] Compared to cutting processes such as gear shaving, grinding requires a higher circumferential speed of the grinding stone for optimal machining. In conventional gear grinding machines, this circumferential speed is ensured by increasing the diameter of the grinding stone. However, in conventional methods, increasing the diameter of the grinding stone results in the grinding stone 20 contacting the second region 902 of the workpiece 9, as described above. However, in the method of this embodiment, the intersection angle θ between the workpiece axis A1 and the grinding stone axis A2 is smaller than before, and the grinding stone 20 is moved along a plane perpendicular to the workpiece axis A1. Therefore, the diameter of the grinding stone 20 can be increased to a certain extent, while grinding the first region 901 without the grinding stone 20 contacting the second region 902.

[0045] <3. Variations>

[0046] The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments.

[0047] Figure 8 is a side view of a modified grinding stone 20. In the above embodiment, the profile of the groove 21 of the grinding stone 20, which ignores the outer peripheral surface, is a straight cylindrical shape. That is, in the above embodiment, the outer diameter of the grinding stone 20 at both ends along the grinding stone axis is the same as the outer diameter of the grinding stone 20 at its central portion along the grinding stone axis. In contrast, in the example of Figure 8, the profile of the groove 21 of the grinding stone 20, which ignores the outer peripheral surface, is convexly curved. That is, in the example of Figure 8, the outer diameter of the grinding stone 20 at both ends along the grinding stone axis is larger than the outer diameter of the grinding stone 20 at its central portion along the grinding stone axis. By using such a grinding stone 20, the grinding amount at both ends of the workpiece 9 along the workpiece axis can be further increased.

[0048] Furthermore, in the above embodiment, the moving mechanism 40 moves the grinding stone 20 along a straight path L. However, the moving mechanism 40 can also move the grinding stone 20 along a curved path. For example, the moving mechanism 40 can also move the grinding stone 20 along an arc tangent to the workpiece 9 on a plane perpendicular to the workpiece axis A1.

[0049] Furthermore, the elements appearing in the above-described implementation methods and variations can be appropriately combined within a range that does not create contradictions.

[0050] <4. Summary>

[0051] This technology can adopt the following structure.

[0052] (1) A gear grinding machine for grinding a workpiece forming a gear, comprising: a workpiece rotation mechanism that rotates a workpiece having multiple teeth on its outer peripheral surface around its central axis, i.e., the workpiece axis; a grinding stone rotation mechanism that rotates a grinding stone having helical grooves on its outer peripheral surface around its central axis, i.e., the grinding stone axis; and a moving mechanism that moves the grinding stone relative to the workpiece, the grinding stone axis being inclined relative to the workpiece axis, the workpiece rotation mechanism and the grinding stone rotation mechanism causing the workpiece and the grinding stone to rotate synchronously, and the moving mechanism causing the grinding stone to move along a plane perpendicular to the workpiece axis, thereby grinding the workpiece.

[0053] (2) The gear grinding machine as described in (1), wherein the moving mechanism causes the grinding stone to move along a straight line tangent to the workpiece on the plane.

[0054] (3) The gear grinding machine as described in (1) or (2), wherein the length of the grinding stone in the axial direction of the workpiece is longer than the length of the teeth of the workpiece in the axial direction of the workpiece.

[0055] (4) The gear grinding machine as described in any one of (1) to (3), wherein the angle between the grinding stone axis and the workpiece axis is more than 3° and less than 35°.

[0056] (5) The gear grinding machine as described in any one of (1) to (4), without changing the rotation direction of the workpiece and the rotation direction of the grinding stone, wherein the moving mechanism causes the grinding stone to reciprocate relative to the workpiece, thereby causing the grinding stone to repeatedly contact the workpiece.

[0057] (6) The gear grinding machine as described in any one of (1) to (5), wherein the outer diameter of the grinding stone at both ends in the axial direction of the grinding stone is larger than the outer diameter of the grinding stone at the center in the axial direction of the grinding stone.

[0058] (7) A gear grinding machine as described in any one of (1) to (6), wherein the workpiece has: a first region that protrudes radially relative to the axis of the workpiece; and a second region that protrudes radially relative to the axis of the workpiece and has a diameter larger than that of the first region, wherein the grinding stone grinds the first region.

[0059] (8) A gear grinding method for grinding a workpiece forming a gear, comprising the following steps: rotating a workpiece having multiple teeth on its outer peripheral surface around its central axis (i.e., the workpiece axis) and rotating a grinding stone having a spiral groove on its outer peripheral surface around its central axis (i.e., the grinding stone axis) while moving the grinding stone relative to the workpiece to grind the workpiece, wherein the grinding stone axis is inclined relative to the workpiece axis, wherein the workpiece and the grinding stone rotate synchronously in the step, and the grinding stone moves along a plane perpendicular to the workpiece axis to grind the workpiece.

[0060] (9) The gear grinding method as described in (8) wherein, in the process, the grinding stone is moved along a straight line tangent to the workpiece on the plane.

[0061] (10) The gear grinding method as described in (8) or (9) wherein the length of the grinding stone in the axial direction of the workpiece is longer than the length of the teeth of the workpiece in the axial direction of the workpiece.

[0062] (11) In any one of (8) to (10) the gear grinding method, the angle between the grinding stone axis and the workpiece axis is more than 3° and less than 35°.

[0063] (12) The gear grinding method of any one of (8) to (11), wherein in the process, the grinding stone is moved back and forth relative to the workpiece without changing the rotation direction of the workpiece and the rotation direction of the grinding stone, thereby causing the grinding stone to repeatedly contact the workpiece.

[0064] (13) The gear grinding method of any one of (8) to (12), wherein the outer diameter of the grinding stone at both ends in the axial direction of the grinding stone is larger than the outer diameter of the grinding stone at the center in the axial direction of the grinding stone.

[0065] (14) The gear grinding method of any one of (8) to (13), wherein the workpiece has: a first region that protrudes radially relative to the axis of the workpiece; and a second region that protrudes radially relative to the axis of the workpiece and has a diameter larger than that of the first region, wherein the grinding stone grinds the first region.

[0066] [Industrial Applicability]

[0067] This invention can be used in gear grinding machines and gear grinding methods.

[0068] (Symbol Explanation)

[0069] 1 Gear grinding machine; 9 Workpiece; 10 Workpiece rotation mechanism; 20 Grinding stone; 21 Groove; 30 Grinding stone rotation mechanism; 40 Moving mechanism; 50 Control unit; 91 Gear; 901 First area; 902 Second area; A1 Workpiece axis; A2 Grinding stone axis; C Contact part; L Path; P1 First position; P2 Second position; θ Cross angle.

Claims

1. A gear grinding machine for grinding workpieces that form gears, characterized in that, The device comprises: a workpiece rotation mechanism that rotates a workpiece having multiple teeth on its outer circumferential surface around its central axis; a grinding stone rotation mechanism that rotates a grinding stone having helical grooves on its outer circumferential surface around its central axis; and a moving mechanism that moves the grinding stone relative to the workpiece, the grinding stone axis being inclined relative to the workpiece axis. The workpiece rotation mechanism and the grinding stone rotation mechanism cause the workpiece and the grinding stone to rotate synchronously, and the moving mechanism causes the grinding stone to move along a plane perpendicular to the workpiece axis, thereby grinding the workpiece.

2. The gear grinding machine as described in claim 1, characterized in that, The moving mechanism causes the grinding stone to move along a straight line tangent to the workpiece on the plane.

3. The gear grinding machine as described in claim 1 or 2, characterized in that, The length of the grinding stone in the workpiece axial direction is longer than the length of the teeth of the workpiece in the workpiece axial direction.

4. The gear grinding machine as described in claim 1 or 2, characterized in that, The angle between the grinding stone axis and the workpiece axis is greater than 3° and less than 35°.

5. The gear grinding machine as described in claim 1 or 2, characterized in that, Without changing the rotation direction of the workpiece and the rotation direction of the grinding stone, the moving mechanism causes the grinding stone to reciprocate relative to the workpiece, thereby causing the grinding stone to repeatedly contact the workpiece.

6. The gear grinding machine as described in claim 1 or 2, characterized in that, The outer diameter of the grinding stone at both ends along the axial direction is larger than the outer diameter of the grinding stone at the center along the axial direction.

7. The gear grinding machine as described in claim 1 or 2, characterized in that, The workpiece has: a first region that protrudes radially relative to the axis of the workpiece; And a second region, which protrudes radially relative to the workpiece axis and has a larger diameter than the first region, the grinding stone grinding the first region.

8. A gear grinding method for grinding a workpiece that forms a gear, characterized in that, The process involves rotating a workpiece with multiple teeth on its outer circumferential surface around its central axis (the workpiece axis) and rotating a grinding stone with spiral grooves on its outer circumferential surface around its central axis (the grinding stone axis). Simultaneously, the grinding stone moves relative to the workpiece to grind it. The grinding stone axis is inclined relative to the workpiece axis. In this process, the workpiece and the grinding stone rotate synchronously, and the grinding stone moves along a plane perpendicular to the workpiece axis to grind the workpiece.

9. The gear grinding method as described in claim 8, characterized in that, In the process, the grinding stone is moved along a straight line tangent to the workpiece on the plane.

10. The gear grinding method as described in claim 8 or 9, characterized in that, The length of the grinding stone in the workpiece axial direction is longer than the length of the teeth of the workpiece in the workpiece axial direction.

11. The gear grinding method as described in claim 8 or 9, characterized in that, The angle between the grinding stone axis and the workpiece axis is greater than 3° and less than 35°.

12. The gear grinding method as described in claim 8 or 9, characterized in that, In the process, without changing the rotation direction of the workpiece and the rotation direction of the grinding stone, the grinding stone is moved back and forth relative to the workpiece, thereby causing the grinding stone to repeatedly contact the workpiece.

13. The gear grinding method as described in claim 8 or 9, characterized in that, The outer diameter of the grinding stone at both ends along the axial direction is larger than the outer diameter of the grinding stone at the center along the axial direction.

14. The gear grinding method as described in claim 8 or 9, characterized in that, The workpiece has: a first region that protrudes radially relative to the axis of the workpiece; And a second region, which protrudes radially relative to the workpiece axis and has a larger diameter than the first region, the grinding stone grinding the first region.

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