Method for forming a threaded grinding wheel, apparatus for forming a threaded grinding wheel, and gear grinding apparatus

Abstract

The present invention provides a method for forming a screw-shaped grinding wheel with improved grinding wheel life, a device for forming a screw-shaped grinding wheel, and a gear grinding device. [Solution] A method for forming a barrel-shaped screw-shaped grinding wheel Ta using a rotary dresser 5, wherein the barrel-shaped screw-shaped grinding wheel Ta is dressed using the rotary dresser 5 based on a reference number of teeth, which is the number of teeth of the internal gear Wa processed by the barrel-shaped screw-shaped grinding wheel Ta, thereby forming a first region 41 having a first cutting edge 31 corresponding to the shape of the teeth 21 of the internal gear Wa over a predetermined length dimension in the direction of the grinding wheel axis Ct of the barrel-shaped screw-shaped grinding wheel Ta, and a second region 42 having a second cutting edge 32 having a different shape from the first cutting edge 31 is formed by dressing the barrel-shaped screw-shaped grinding wheel Ta at a position different from the first region 41 in the direction of the grinding wheel axis Ct of the barrel-shaped screw-shaped grinding wheel Ta using the rotary dresser 5.

Description

Technical Field

[0001] The present invention relates to a method for forming a threaded grinding wheel, a forming device for a threaded grinding wheel, and a gear grinding device.

Background Art

[0002] Conventionally, a technique for grinding a gear with a threaded grinding wheel has been known. The above-mentioned threaded grinding wheel is dressed by a dresser such as a rotary dresser. As such a technique, for example, Patent Document 1 (Japanese Patent No. 5524397) is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Patent Document 1 describes a dressing method for a threaded grinding wheel, in which dressing operation data is calculated based on the number of teeth less than the number of teeth of the specification data of the work internal gear, and the threaded grinding wheel is formed by dressing using a disk dresser.

[0005] According to the above technique, at the start of grinding, local loads are suppressed from being applied to both ends of the threaded grinding wheel, so irregular grinding loads and uneven wear are suppressed from occurring.

[0006] However, according to the above technique, there is a problem that the life of the threaded grinding wheel is short. This will be described below.

[0007] Figure 10 shows the relationship between the cutting edge radius, which is the distance between the cutting edge of a screw-shaped grinding wheel and the grinding wheel axis, and the position of the screw-shaped grinding wheel in the direction of the grinding wheel axis, for the prior art. The dashed line L1 shows the cutting edge radius when the screw-shaped grinding wheel is dressed based on the number of teeth in the gear specifications. The dashed line L2 shows an example of the cutting edge radius of the screw-shaped grinding wheel when it is dressed based on a number of teeth less than the number of teeth in the gear specifications.

[0008] Comparing the dashed lines L1 and L2 in Figure 10, the region N of the screw-shaped grinding wheel dressed based on a number of teeth fewer than the number of teeth in the gear specifications data, which has the same cutting edge radius as when dressed based on the number of teeth in the gear specifications data, is only a small part near the center of the screw-shaped grinding wheel in the direction of the grinding wheel axis. In other words, of the screw-shaped grinding wheel dressed based on a number of teeth fewer than the number of teeth in the gear specifications data, only a small part near the center of the screw-shaped grinding wheel in the direction of the grinding wheel axis has a machined surface that is identical to that of the gear teeth.

[0009] Although not shown in detail, in a screw-shaped grinding wheel, only a portion of one grinding blade, specifically the one formed near the center in the direction of the grinding wheel axis, has a machined surface identical to that of a gear tooth. Therefore, if even a small portion of the grinding blade with a machined surface identical to that of a gear tooth wears down, it becomes impossible to maintain the machining accuracy of the gear. Consequently, conventional screw-shaped grinding wheels have the problem of having a short grinding wheel life.

[0010] This invention has been made in view of the above problems, and aims to provide a method for forming a screw-shaped grinding wheel with improved grinding wheel life, a device for forming a screw-shaped grinding wheel, and a gear grinding device. [Means for solving the problem]

[0011] One aspect of the present invention is, A method for forming a screw-shaped grinding wheel using a dresser, The screw-shaped grinding wheel is dressed using the dresser based on a reference number of teeth, which is the number of teeth of the gear processed by the screw-shaped grinding wheel, thereby forming a first region having a first cutting edge corresponding to the shape of the gear teeth over a predetermined length dimension in the grinding wheel axis direction of the screw-shaped grinding wheel. The present invention relates to a method for forming a screw-shaped grinding wheel, wherein a second region having a second blade having a different shape from the first blade is formed by dressing the screw-shaped grinding wheel at a position different from the first region in the direction of the grinding wheel axis using the dresser.

[0012] Other aspects of the present invention include: A device for forming a screw-shaped grinding wheel, A grinding wheel support member that supports the aforementioned screw-shaped grinding wheel so that it can rotate around the grinding wheel axis, A dresser that is rotatably supported around the dresser axis and shapes the blade of the rotating screw-shaped grinding wheel, The system includes a control device that moves at least one of the screw-shaped grinding wheel and the dresser to a desired position and controls its rotation to shape the blade of the screw-shaped grinding wheel, The control device is By dressing the screw-shaped grinding wheel using the dresser based on the number of teeth of the gear, a first region is formed over a predetermined length dimension in the axial direction of the screw-shaped grinding wheel, having a first cutting edge corresponding to the shape of the gear teeth. The apparatus for forming a screw-shaped grinding wheel includes a method for forming a screw-shaped grinding wheel in which a second region having a second blade having a different shape from the first blade is formed by dressing the screw-shaped grinding wheel at a position different from the first region in the direction of the grinding wheel axis using the dresser.

[0013] Furthermore, yet another aspect of the present invention is: A gear grinding apparatus for grinding the tooth surface of a gear using the screw-shaped grinding wheel formed by the above-described method for forming a screw-shaped grinding wheel, A grinding wheel support member that supports the aforementioned screw-shaped grinding wheel so that it can rotate around the grinding wheel axis, A workpiece support member that supports the gear so as to be rotatable around the axis of the workpiece, A gear grinding apparatus comprising: a control device configured to move at least one of the helical grinding wheel and the gear to a desired position and control rotation to grind the teeth of the gear one tooth groove at a time.

Advantages of the Invention

[0014] According to one aspect, another aspect, and still another aspect of the present invention, since the teeth of the gear are ground by the first cutting edge formed in the first region, the teeth of the gear can be accurately ground.

[0015] In addition, since the first region having the first cutting edge is formed over a predetermined length dimension in the axial direction of the grinding wheel axis of the helical grinding wheel, even when the helical grinding wheel is worn, the machining accuracy of the gear can be maintained. As a result, the life of the helical grinding wheel can be improved.

[0016] As described above, according to the above aspect, it is possible to provide a method for forming a helical grinding wheel with improved grinding wheel life, a forming apparatus for the helical grinding wheel, and a gear forming apparatus.

Brief Description of the Drawings

[0017] [Figure 1] Conceptual diagram showing a gear grinding apparatus according to Embodiment 1. [Figure 2] Cross-sectional view showing a barrel-shaped helical grinding wheel according to Embodiment 1. [Figure 3] Graph showing the relationship between the cutting edge radius and the position in the axial direction of the grinding wheel axis when the grinding edges of the barrel-shaped helical grinding wheel are formed based on different numbers of teeth in Embodiment 1. [Figure 4] Graph showing the relationship between the cutting edge radius and the position in the axial direction of the grinding wheel axis of the barrel-shaped helical grinding wheel according to Embodiment 1. [Figure 5] Partially cut-away cross-sectional view showing the meshing state of the barrel-shaped helical grinding wheel and the internal gear in Embodiment 1. [Figure 6] Schematic diagram for explaining the depth of abrasive grain cutting in Embodiment 1. [Figure 7] Flowchart showing the operation of the dressing apparatus according to Embodiment 1. [Figure 8] A partially cutaway cross-sectional view showing the meshing state between the barrel-shaped screw-type grinding wheel and the internal gear in Embodiment 2. [Figure 9] A partially cutaway cross-sectional view showing the meshing state between the drum-shaped screw-type grinding wheel and the external gear in Embodiment 3. [Figure 10] This graph shows the relationship between the cutting edge radius and the position along the grinding wheel axis for conventional threaded grinding wheels, specifically when the threaded grinding wheel is formed based on the number of teeth of a gear, and when the threaded grinding wheel is formed based on a number of teeth less than the number of teeth of a gear. [Modes for carrying out the invention]

[0018] (Embodiment 1) 1. Gear grinding device 1 Embodiment 1 will be described with reference to Figure 1. The gear grinding apparatus 1 according to Embodiment 1 grinds the tooth surface of a gear W using a screw-shaped grinding wheel T. The gear grinding apparatus 1 includes a dressing device 8. The dressing device 8 is an example of a device for forming the screw-shaped grinding wheel T. Since the gear W in Embodiment 1 is an internal gear Wa, an internal gear generating grinding machine is used as the gear grinding apparatus 1. Also, the screw-shaped grinding wheel T in Embodiment 1 is a barrel-shaped screw-shaped grinding wheel Ta. However, the gear grinding apparatus 1 according to Embodiment 1 is not limited to the above configuration, and may be, for example, a machining center or a gear skiving center (registered trademark). In this case, the dressing device 8 may be placed on a workpiece support member 3, and the dressing of the screw-shaped grinding wheel T may be performed while the gear W is held by the workpiece support member 3.

[0019] The gear grinding apparatus 1 comprises a grinding wheel support member 2, a barrel-shaped threaded grinding wheel Ta, a workpiece support member 3, a rotary dresser support member 4, a rotary dresser 5, a control device 6, and a storage device 7.

[0020] The workpiece support member 3 supports the gear W so that it can rotate around the workpiece axis Cg, which is parallel to the vertical direction (Y-axis direction), using the workpiece support motor Mg.

[0021] The dressing device 8 comprises a grinding wheel support member 2, a rotary dresser support member 4, a rotary dresser 5, and a control device 6.

[0022] The grinding wheel support member 2 supports the barrel-shaped threaded grinding wheel Ta so that it can rotate around the C axis by the grinding wheel support motor Mt. The C axis is the axis that coincides with the grinding wheel axis Ct of the barrel-shaped threaded grinding wheel Ta. The grinding wheel support member 2 is movable in the left-right direction in Figure 1 (hereinafter referred to as the X axis direction), the direction that penetrates the plane of the paper in Figure 1 (hereinafter referred to as the Z axis direction), and the Y axis direction. The barrel-shaped threaded grinding wheel Ta for grinding the gear W is mounted on the tip of the grinding wheel support member 2. Therefore, by moving the grinding wheel support member 2 in the X, Y, and Z axis directions and rotating it around the Ct axis, the barrel-shaped threaded grinding wheel Ta moves and rotates together with the grinding wheel support member 2.

[0023] The grinding wheel axis Ct is inclined with respect to the workpiece axis Cg, and the two intersect at a predetermined intersection angle. During grinding, the barrel-shaped threaded grinding wheel Ta rotates around the grinding wheel axis Ct, which intersects the workpiece axis Cg at the intersection angle.

[0024] The rotary dresser support member 4 supports the rotary dresser 5. The rotary dresser support member 4 supports the rotary dresser 5 so that it can rotate around the Cd axis by the rotary dresser support motor Md.

[0025] The rotary dresser 5 is formed in a disc shape. The rotary dresser 5 is equipped with multiple abrasive grains 35 such as diamonds on the side edges of the disc portion (see Figure 6). The rotary dresser 5 is an example of a dresser. However, the dresser is not particularly limited, and any dresser can be appropriately selected. For example, examples of dressers include a single-stone dresser (not shown) in which one diamond or the like grinding stone is placed at the tip of the jig, a multi-stone dresser (not shown) in which multiple diamond or the like grinding stones are placed at the tip of the jig, and a bonded dresser (not shown) in which multiple diamond or the like grinding stones are fixed to the tip of the jig with bond.

[0026] The gear grinding apparatus 1 according to this embodiment is configured such that the internal gear Wa can be rotated around the Cg axis and the barrel-shaped screw-type grinding wheel Ta can be rotated around the Ct axis.

[0027] The control device 6 is composed of, for example, a CPU (Central Processing Unit), a PLC (Programmable Logic Controller), or a CNC (Computerized Numerical Control) device. The control device 6 is configured to synchronously rotate the internal gear Wa and the barrel-shaped screw-shaped grinding wheel Ta by controlling the workpiece support motor Mg and the grinding wheel support motor Mt, and to grind the teeth 21 of the internal gear Wa with the barrel-shaped screw-shaped grinding wheel Ta by controlling the relative position between the internal gear Wa and the barrel-shaped screw-shaped grinding wheel Ta.

[0028] Furthermore, the control device 6 controls the rotary dresser support motor Md and the relative position between the barrel-shaped screw-shaped grinding wheel Ta and the rotary dresser 5, thereby shaping the first blade 31 and the second blade 32 of the barrel-shaped screw-shaped grinding wheel Ta with the rotary dresser 5.

[0029] The storage device 7 can be any known storage device such as RAM (Random Access Memory), ROM (Read Only Memory), a hard disk drive, or a USB (Universal Serial Bus) memory. The storage device 7 may be located in the gear grinding machine 1, or it may be a server connected via a network (not shown).

[0030] As shown in Figures 1 and 5, the gear W according to this embodiment 1 is an internal gear Wa. As shown in Figure 5, the internal gear Wa has teeth 21 that protrude inward on its inner circumferential surface. The barrel-shaped screw grinding wheel Ta according to this embodiment 1 grinds the tooth surfaces of the teeth 21.

[0031] 2. Barrel-shaped screw-type grinding wheel Ta The threaded grinding wheel T according to this embodiment 1 is a barrel-shaped threaded grinding wheel Ta. As shown in Figure 1, the barrel-shaped threaded grinding wheel Ta is equipped with a helical grinding blade 30. As shown in Figure 2, the grinding blade 30 protrudes radially outward from the barrel-shaped threaded grinding wheel Ta. The barrel-shaped threaded grinding wheel Ta may be a single-start thread or a multi-start thread. In the case of a multi-start thread, the barrel-shaped threaded grinding wheel Ta has a plurality of helical grinding blades. In the following description, the distance between the cutting edge of the barrel-shaped threaded grinding wheel Ta and the grinding wheel axis Ct of the barrel-shaped threaded grinding wheel Ta is defined as the cutting edge radius.

[0032] As shown in Figure 2, the barrel-shaped threaded grinding wheel Ta according to this embodiment 1 has the largest cutting edge radius at the center of the grinding wheel axis Ct and the smallest cutting edge radius at the ends in the direction of the grinding wheel axis Ct. The cutting edge radii at both ends in the direction of the grinding wheel axis Ct may be the same or different.

[0033] However, the threaded grinding wheel T may be a semi-barrel-shaped threaded grinding wheel, which is the shape of one or both of the cut barrel-shaped threaded grinding wheel Ta when the barrel-shaped threaded grinding wheel Ta is cut near the center in the direction of the grinding wheel axis Ct. Also, the threaded grinding wheel T may be formed in a cup shape that decreases in diameter as it approaches the other end from one end in the direction of the grinding wheel axis Ct. Furthermore, the threaded grinding wheel T may have a region in which the diameter of the rotational trajectory does not change in a part from one end to the other end in the direction of the grinding wheel axis Ct.

[0034] The grinding blade 30 comprises a first blade 31 and a second blade 32. The barrel-shaped screw-shaped grinding wheel Ta comprises a first region 41 having the first blade 31 and a second region 42 having the second blade 32, as shown in Figure 2.

[0035] The first region 41 in this embodiment 1 is formed in the barrel-shaped screw-shaped grinding wheel Ta, near the center in the direction of the grinding wheel axis Ct, over a predetermined length dimension in the direction of the grinding wheel axis Ct. The length dimension of the first region 41 in the direction of the grinding wheel axis Ct is not particularly limited, and any length dimension can be appropriately selected.

[0036] The first cutting edge 31 is formed by dressing a barrel-shaped screw-type grinding wheel Ta using a rotary dresser 5 based on a reference number of teeth, which is the number of teeth of the internal gear Wa. In this embodiment 1, the reference number of teeth of the internal gear Wa is set to 60. However, the reference number of teeth can be set arbitrarily. The distance between the cutting edge of the first cutting edge and the grinding wheel axis Ct is the first cutting edge radius R1.

[0037] In Figure 2, the dashed line L3 shows the hypothetical cutting edge shape of the barrel-shaped screw grinding wheel Ta when dressed using the rotary dresser 5 with the reference number of teeth set to 60, which is the number of teeth of the internal gear Wa. The first cutting edge 31 is formed based on the reference number of teeth (60 teeth), which is the number of teeth of the internal gear Wa. Therefore, the cutting edge of the first cutting edge 31 is formed along the dashed line L3. In other words, the shape of the cutting surface of the first cutting edge 31 corresponds to the shape of the tooth surface of the internal gear Wa.

[0038] As shown in Figure 2, the second region 42 of the barrel-shaped screw-shaped grinding wheel Ta according to this embodiment 1 is formed at a different position from the first region 41 of the barrel-shaped screw-shaped grinding wheel Ta, and is located closer to the end in the direction of the grinding wheel axis Ct. The length dimension of the second region 42 in the direction of the grinding wheel axis Ct is not particularly limited, and any length dimension can be appropriately selected.

[0039] The second blade 32 is formed in a different shape from the first blade 31 using the rotary dresser 5. The second blade edge radius R2, which is the distance between the cutting edge of the second blade 32 and the grinding wheel axis Ct of the barrel-shaped screw-shaped grinding wheel Ta, is formed to be smaller than the virtual blade edge radius Ri, which is the distance between the cutting edge of a virtual blade and the grinding wheel axis Ct of the barrel-shaped screw-shaped grinding wheel Ta, assuming that dressing is performed in the second region 42 using the rotary dresser 5 based on the reference number of teeth.

[0040] As explained earlier in Figure 2, the dashed line L3 represents the virtual cutting edge shape of the barrel-shaped screw grinding wheel Ta, assuming that it is dressed using the rotary dresser 5 based on the standard number of teeth. Therefore, the distance between the dashed line L3 and the grinding wheel axis Ct is the virtual cutting edge radius Ri.

[0041] As shown in Figure 2, the second cutting edge radius R2 of the second blade 32 formed in the second region 42 is smaller than the virtual cutting edge radius Ri.

[0042] The second cutting edge 32 is formed by dressing using a rotary dresser 5 based on a number of teeth that differs from the standard number of teeth of the gear W. In this embodiment 1, the number of teeth that are machined is less than the standard number of teeth. In this embodiment 1, the number of teeth that are machined is set to 59 or less.

[0043] In the second region 42 of this embodiment 1, the second cutting edge 32 is formed by changing the number of teeth to be machined in multiple stages. However, in the second region 42, the second cutting edge 32 may also be formed based on a single number of teeth to be machined.

[0044] Figure 3 shows the relationship between the cutting edge radius of the barrel-shaped screw grinding wheel Ta and the position of the barrel-shaped screw grinding wheel in the direction of the grinding wheel axis Ct, when the number of teeth of the internal gear Wa is changed. In Figure 3, the dashed line L3 is the cutting edge radius when the barrel-shaped screw grinding wheel Ta is formed based on the standard number of teeth, 60 teeth, as described above. The dashed line L4 is the cutting edge radius when the barrel-shaped screw grinding wheel Ta is formed based on one number of teeth, 57 teeth. The dashed line L5 is the cutting edge radius when the barrel-shaped screw grinding wheel Ta is formed based on another number of teeth, 55 teeth.

[0045] As the number of teeth decreases from 60 to 57 to 55, the cutting edge radius at both ends of the grinding wheel axis Ct decreases. Furthermore, near the center of the grinding wheel axis Ct, the cutting edge radius hardly changes even when the reference number of teeth is changed from 60 to 57 to 55.

[0046] As described above, in the case of a barrel-shaped screw-type grinding wheel Ta, reducing the number of reference teeth results in a smaller cutting edge radius at the end in the direction of the grinding wheel axis Ct.

[0047] Figure 4 shows the relationship between the cutting edge radius and the position in the direction of the grinding wheel axis Ct in the barrel-shaped threaded grinding wheel Ta according to this embodiment 1. The shape of the barrel-shaped threaded grinding wheel Ta according to this embodiment 1 is shown by the solid line L6.

[0048] In the first region 41, the barrel-shaped screw-type grinding wheel Ta is formed based on a standard number of teeth, which is 60 teeth.

[0049] In the second region 42, the number of teeth to be machined may be changed one tooth at a time, or it may be changed multiple teeth at a time. In this embodiment 1, the number of teeth to be machined is set to two levels: 57 teeth and 55 teeth. In Figure 4, the portion indicated by the symbol P is the section in which a barrel-shaped screw-shaped grinding wheel Ta is formed with 57 teeth to be machined, and the portion indicated by the symbol Q is the section in which a barrel-shaped screw-shaped grinding wheel Ta is formed with 55 teeth to be machined.

[0050] However, the number of teeth to be machined may be configured to change one tooth at a time, for example, in the order of 59, 58, 57, 56, and 55 teeth, or it may be configured to change in any number of steps. Furthermore, the minimum number of teeth to be machined when the number of teeth to be machined is set to any value. In addition, there are no particular upper or lower limits to the number of teeth to be machined, and any values ​​can be set as needed.

[0051] The barrel-shaped threaded grinding wheel Ta according to this first embodiment is formed symmetrically with respect to the grinding wheel axis Ct direction. That is, the shape of the section formed based on the reference number of teeth and the shape of the section formed based on the number of teeth processed are formed symmetrically with respect to the grinding wheel axis Ct direction. However, the barrel-shaped threaded grinding wheel Ta may be formed asymmetrically with respect to the grinding wheel axis Ct direction.

[0052] The first cutting edge 31 formed in the first region 41 and the second cutting edge 32 formed in the second region 42 are continuously connected by the first connecting portion 33. In the graph shown in Figure 4, the portion labeled 33 corresponds to the first connecting portion 33. In this embodiment 1, as shown in Figure 4, the first cutting edge 31 formed in the first region 41 based on a standard number of 60 teeth and the second cutting edge 32 formed in the section P of the second region 42 based on a machining number of 57 teeth are continuously connected by the first connecting portion 33.

[0053] At the point where the second cutting edge radius R2 of the second cutting edge 32 changes, the second cutting edge 32 in the state before the change in the second cutting edge radius R2 and the second cutting edge 32 in the state after the change in the second cutting edge radius R2 are continuously connected by the second connecting portion 34. In the graph shown in Figure 4, the portion labeled 34 corresponds to the second connecting portion 34. In this embodiment 1, as shown in Figure 4, the second cutting edge 32 formed in section P based on a machining tooth count of 57 teeth and the second cutting edge 32 formed in section Q based on a machining tooth count of 55 teeth are continuously connected by the second connecting portion 34.

[0054] In the barrel-shaped threaded grinding wheel Ta according to this embodiment 1, the difference between the first cutting edge radius R1 and the second cutting edge radius R2 is formed to be equal to or less than the abrasive grain cutting depth g of the barrel-shaped threaded grinding wheel Ta. The abrasive grain cutting depth g will be described below. In addition, in the barrel-shaped threaded grinding wheel Ta according to this embodiment 1, the difference between the first cutting edge radius R1 and the second cutting edge radius R2 may be formed to be equal to or less than the amount of abrasive grain protrusion of the barrel-shaped threaded grinding wheel Ta.

[0055] Figure 6 shows a schematic diagram of the state in which the gear W is being ground by the screw-shaped grinding wheel T. Note that the shape of the screw-shaped grinding wheel T and the gear W shown in Figure 6 are different from the shape of the barrel-shaped screw-shaped grinding wheel Ta and the internal gear Wa in this embodiment 1.

[0056] The abrasive grain cutting depth g refers to the cutting depth of the abrasive grain 35 at the position where the chip thickness is maximum. The path taken by the abrasive grain 35a, located on the front side in the rotational direction of the screw-shaped grinding wheel T, to grind the gear W is the curve connecting point H and point I. Similarly, the path taken by the abrasive grain 35b, located on the rear side in the rotational direction of the screw-shaped grinding wheel T, to grind the gear W is the curve connecting point K and point J. Therefore, the chip of the abrasive grain 35b is the portion enclosed by points H, I, J, and K. The cutting depth at which the chip thickness is maximum is the length of the straight line with point I as one end and a point on the curve connecting points J and K as the other end.

[0057] As described above, the gear W according to this embodiment 1 is an internal gear Wa. The abrasive grain cutting depth g in internal grinding of an internal gear Wa is expressed by the following formula (1).

[0058]

number

[0059] The algebraic expressions in equation (1) are explained below. As mentioned above, g is the abrasive cutting depth (unit: mm). a is the abrasive cutting edge spacing (unit: mm). As shown in Figure 6, abrasive grains 35 are arranged on the surface of the screw-shaped grinding wheel T. The abrasive cutting edge spacing is the spacing between adjacent abrasive grains 35. Vw is the peripheral speed of the gear (unit: mm / min), and Vt is the peripheral speed of the screw-shaped grinding wheel T (mm / min). Dt is the diameter of the screw-shaped grinding wheel T (unit: mm), and Dw is the diameter of the gear W (unit: mm). t is the grinding depth of the screw-shaped grinding wheel T (unit: mm). As shown in Figure 6, the grinding depth t is the cutting depth in the radial direction of the gear W.

[0060] Furthermore, in this embodiment 1, the difference between the first cutting edge radius R1 of the first blade 31 and the second cutting edge radius R2 of the second blade 32 is formed to be equal to or less than the abrasive grain cutting depth g. In other words, the difference between the first cutting edge radius R1 of the first blade 31 in the first region 41 shown in Figure 4 and the second cutting edge radius R2 of the second blade 32 in section P is formed to be equal to or less than the abrasive grain cutting depth g. Note that in this embodiment 1, the difference between the first cutting edge radius R1 of the first blade 31 and the second cutting edge radius R2 of the second blade 32 may be formed to be equal to or less than the abrasive grain protrusion amount.

[0061] Furthermore, in this embodiment 1, at the point where the second cutting edge radius R2 of the second blade 32 changes, the difference between the second cutting edge radius R2 before the change and the second cutting edge radius R2 after the change is formed to be equal to or less than the abrasive grain cutting depth g. In other words, the difference between the second cutting edge radius R2 formed in section P in Figure 4 and the second cutting edge radius R2 formed in section Q is formed to be equal to or less than the abrasive grain cutting depth g. Note that in this embodiment 1, at the point where the second cutting edge radius R2 of the second blade 32 changes, the difference between the second cutting edge radius R2 before the change and the second cutting edge radius R2 after the change may be formed to be equal to or less than the abrasive grain protrusion amount.

[0062] As shown in Figure 5, when the barrel-shaped threaded grinding wheel Ta according to this embodiment 1 is meshed with the internal gear Wa, the first cutting edge 31 of the barrel-shaped threaded grinding wheel Ta and the teeth 21 of the internal gear Wa come into contact. As a result, the teeth 21 of the internal gear Wa are formed by the first cutting edge 31. The number of grinding blades 30 of the barrel-shaped threaded grinding wheel Ta in the cross-section shown in Figure 5 is not particularly limited, and any number of grinding blades 30 can be formed.

[0063] In Figure 5, three first cutting edges 31 are arranged in the direction of the grinding wheel axis Ct. In the cross-section shown in Figure 5, the teeth 21 of the internal gear Wa are formed by the three first cutting edges 31. As a result, even if one of the three first cutting edges 31 wears down, the teeth 21 of the internal gear Wa can still be ground by the remaining first cutting edges 31, thus extending the lifespan of the barrel-shaped screw-type grinding wheel Ta. However, although three first cutting edges 31 are shown in Figure 5, the number of first cutting edges 31 may be two or four or more.

[0064] Furthermore, the second cutting edge 32 grinds the material removed from the internal gear Wa (not shown) by contacting it. A gap is formed between the second cutting edge 32 of the barrel-shaped screw-shaped grinding wheel Ta and the teeth 21 of the internal gear Wa. This prevents the second cutting edge 32, which is located near both ends of the barrel-shaped screw-shaped grinding wheel Ta in the direction of the grinding wheel axis Ct, from making localized contact with the material removed from the internal gear Wa. As a result, uneven wear of the barrel-shaped screw-shaped grinding wheel Ta can be suppressed.

[0065] 3. Rotary Dresser 5 As shown in Figure 1, the rotary dresser 5 is formed in a disc shape. The rotary dresser 5 is rotatably supported by the rotary dresser support member 4 so as to rotate in the horizontal plane around the Cd axis. The rotation axis of the rotary dresser 5 and the Cd axis are arranged coaxially.

[0066] The rotary dresser 5 has a shape that outlines the cross-sectional shape (contact line with the grinding wheel) of one tooth 21 of the internal gear Wa. A cutting surface is formed on the edge along the circumferential surface of the rotary dresser 5. The rotary dresser 5 is configured to be able to dress the barrel-shaped screw-type grinding wheel Ta with the cutting surface.

[0067] In this embodiment 1, the barrel-shaped screw-shaped grinding wheel Ta moves in the left-right direction (X-axis direction), the front-back direction (Z-axis direction), and the up-down direction (Y-axis direction) as shown in Figure 1, while the rotary dresser 5 is configured to move in the left-right direction (X-axis direction) as shown in Figure 1. As a result, the rotary dresser 5 and the barrel-shaped screw-shaped grinding wheel Ta move relative to each other, and the rotary dresser 5 performs the desired dressing on the side surface of the blade of the barrel-shaped screw-shaped grinding wheel Ta.

[0068] 4. Forming process of barrel-shaped screw-type grinding wheel Ta Next, with reference to Figure 7, the method for forming the barrel-shaped threaded grinding wheel Ta according to this embodiment 1 will be described. Figure 7 shows a flowchart of the operation of the dressing device 8. However, the method for forming the barrel-shaped threaded grinding wheel Ta is not limited to the following description.

[0069] When the dressing device 8 is activated, the control device 6 acquires specification data (S1). The specification data includes the specification data of the internal gear Wa and the specification data of the barrel-shaped screw grinding wheel Ta. The specification data may be acquired via a network (not shown), entered by an operator, or pre-stored in the storage device 7.

[0070] Next, the control device 6 calculates and determines the machining conditions for the internal gear Wa based on the acquired parameter data (S2).

[0071] Next, the control device 6 determines the second cutting edge radius R2 at the end of the barrel-shaped screw-type grinding wheel Ta in the direction of the grinding wheel axis Ct (S3). In other words, the control device 6 determines to what extent the second cutting edge 32 should be retracted from the teeth 21 of the internal gear Wa at the end of the barrel-shaped screw-type grinding wheel Ta in the direction of the grinding wheel axis Ct.

[0072] Next, the control device 6 calculates the shape of the barrel-shaped screw grinding wheel Ta (S4). More specifically, the control device 6 calculates the shape of the barrel-shaped screw grinding wheel Ta based on the reference number of teeth. The control device 6 also calculates the shape of the barrel-shaped screw grinding wheel Ta based on the number of teeth machined. The number of teeth machined used in the calculation in S4 is the number of teeth from one less than the reference number of teeth up to the number of teeth that can form the second cutting edge radius R2 at the end of the barrel-shaped screw grinding wheel Ta. If the number of teeth machined is changed in multiple stages in the second region 42, the control device 6 calculates the shape of the barrel-shaped screw grinding wheel Ta based on each number of teeth machined. In other words, the control device 6 calculates the shape of the barrel-shaped screw grinding wheel Ta shown by the dashed line L3, the dashed line L4, and the dashed line L5 in Figure 3.

[0073] Next, the control device 6 determines, taking into account the abrasive cutting depth g, which section will be machined based on the reference number of teeth and which section will be machined based on the number of teeth to be machined (S5). Specifically, the control device 6 determines which section will be machined based on the reference number of teeth and which section will be machined based on the number of teeth to be machined, such that the step difference formed between the section to be machined based on the reference number of teeth and the section to be machined based on the number of teeth to be machined is equal to or less than the abrasive cutting depth g.

[0074] Furthermore, when the number of teeth to be machined is changed in multiple stages in the second region 42, the control device 6 determines the section to be machined based on the number of teeth to be machined in each stage. Specifically, the control device 6 determines the section to be machined based on one number of teeth and the section to be machined based on another number of teeth so that the step difference formed between the section to be machined based on one number of teeth and the section to be machined based on another number of teeth is equal to or less than the abrasive grain cutting depth g.

[0075] Furthermore, the control device 6 determines the shape of the first connecting portion 33 that continuously connects the first blade 31 formed in the first region 41 and the second blade 32 formed in the second region 42.

[0076] Furthermore, in the second region 42, when the number of teeth to be machined is changed in multiple stages, the control device 6 determines the shape of the second connecting portion 34 that continuously connects the second cutting edge 32 in the state before the second cutting edge radius R2 changes and the second cutting edge 32 in the state after the second cutting edge radius R2 changes.

[0077] The control device 6 ultimately determines the shape of the barrel-shaped screw-type grinding wheel Ta, as shown by the solid line L6 in Figure 4.

[0078] Next, the control device 6 calculates the control operation of the rotary dresser 5 based on the calculation results calculated in S4 and the shape determined in S5 (S6).

[0079] Next, the control device 6 uses the rotary dresser 5 to shape the barrel-shaped threaded grinding wheel Ta based on the control operation calculated in S6. Thus, the barrel-shaped threaded grinding wheel Ta is formed.

[0080] 5. Effects of this Embodiment 1 Next, the effects of this embodiment 1 will be described. This embodiment 1 is a method for forming a barrel-shaped screw-shaped grinding wheel Ta using a rotary dresser 5. In this embodiment 1, the barrel-shaped screw-shaped grinding wheel Ta is dressed using the rotary dresser 5 based on a reference number of teeth, which is the number of teeth of the internal gear Wa processed by the barrel-shaped screw-shaped grinding wheel Ta, thereby forming a first region 41 having a first cutting edge 31 corresponding to the shape of the teeth 21 of the internal gear Wa over a predetermined length dimension in the direction of the grinding wheel axis Ct of the barrel-shaped screw-shaped grinding wheel Ta. Furthermore, a second region 42 having a second cutting edge 32 having a different shape from the first cutting edge 31 is formed by dressing the barrel-shaped screw-shaped grinding wheel Ta at a position different from the first region 41 in the direction of the grinding wheel axis Ct using the rotary dresser 5.

[0081] According to this embodiment 1, the teeth 21 of the internal gear Wa are ground by the first cutting edge 31 formed in the first region 41, so that the teeth 21 of the internal gear Wa can be ground with high precision.

[0082] Furthermore, since a first region 41 equipped with a first cutting edge 31 is formed over a predetermined length dimension in the direction of the grinding wheel axis Ct of the barrel-shaped threaded grinding wheel Ta, the machining accuracy of the internal gear Wa can be maintained even when the barrel-shaped threaded grinding wheel Ta is worn. This improves the lifespan of the barrel-shaped threaded grinding wheel Ta.

[0083] Furthermore, in this embodiment 1, the second cutting edge radius R2, which is the distance between the cutting edge of the second blade 32 and the grinding wheel axis Ct of the barrel-shaped screw-shaped grinding wheel Ta, is formed to be smaller than the virtual cutting edge radius Ri, which is the distance between the cutting edge of a virtual blade and the grinding wheel axis when it is assumed that dressing is performed using a dresser based on the reference number of teeth in the second region 42.

[0084] Since the cutting edge radius of the second blade 32 is formed to be smaller than the virtual cutting edge radius Ri of the virtual blade, excessive biting of the second blade 32 formed in the second region 42 into the gear is suppressed. This makes it possible to suppress uneven wear of the barrel-shaped screw grinding wheel Ta.

[0085] Furthermore, in this embodiment 1, a first connecting portion 33 is formed that continuously connects the first blade 31 and the second blade 32.

[0086] According to this embodiment 1, the formation of a step between the first blade 31 and the second blade 32 of the barrel-shaped screw-shaped grinding wheel Ta is suppressed. This makes it possible to suppress uneven wear of the barrel-shaped screw-shaped grinding wheel Ta.

[0087] Furthermore, in this embodiment 1, the difference between the first cutting edge radius R1, which is the distance between the cutting edge of the first blade 31 and the grinding wheel axis Ct, and the second cutting edge radius R2 is formed to be equal to or less than the abrasive grain cutting depth g of the barrel-shaped screw-shaped grinding wheel Ta. The difference between the first cutting edge radius R1 and the second cutting edge radius R2 may also be formed to be equal to or less than the amount of abrasive grain protrusion of the barrel-shaped screw-shaped grinding wheel Ta.

[0088] According to this embodiment 1, the formation of a step in the teeth 21 of the internal gear Wa, which is formed by the boundary between the first blade 31 and the second blade 32, is suppressed. This makes it possible to suppress uneven wear of the barrel-shaped screw grinding wheel Ta.

[0089] The gear W in this embodiment 1 is an internal gear Wa. The second cutting edge 32 in this embodiment 1 is formed by dressing it using a rotary dresser 5 based on a number of teeth that differs from the reference number of teeth. The number of teeth that are machined in this embodiment 1 is less than the reference number of teeth.

[0090] According to this embodiment 1, the second cutting edge 32 can be formed by a simple method of reducing the number of teeth to be machined to less than the reference number of teeth.

[0091] The threaded grinding wheel T according to this embodiment 1 is a barrel-shaped threaded grinding wheel Ta in which the radius is largest at the center in the direction of the grinding wheel axis and the radius is smallest at the ends in the axial direction. Furthermore, the threaded grinding wheel T according to this embodiment 1 may be formed in the shape of one or both of the cut barrel-shaped threaded grinding wheel Ta when the barrel-shaped threaded grinding wheel Ta is cut near the center in the direction of the grinding wheel axis Ct. Furthermore, the threaded grinding wheel T according to this embodiment 1 may be formed in a cup shape that decreases in diameter as it approaches the other end from one end in the direction of the grinding wheel axis Ct.

[0092] Furthermore, in this embodiment 1, the second cutting edge 32 in the second region 42 is formed by changing the number of teeth to be machined in multiple stages.

[0093] According to this embodiment 1, the shape of the barrel-shaped screw-type grinding wheel Ta can be changed in the second region 42. This makes it possible to form the teeth 21 of the internal gear Wa with high precision.

[0094] Furthermore, in this embodiment 1, at the point where the second cutting edge radius R2 of the second blade 32 changes, a second connecting portion 34 is formed that continuously connects the second blade 32 in the state before the change in the second cutting edge radius R2 and the second blade 32 in the state after the change in the second cutting edge radius R2.

[0095] According to this embodiment 1, the formation of a step between the second blade 32 in the state before the second cutting edge radius R2 changes and the second blade 32 in the state after the second cutting edge radius R2 changes is suppressed. This makes it possible to suppress uneven wear of the barrel-shaped screw grinding wheel Ta.

[0096] Furthermore, in this embodiment 1, at the point of change in which the second cutting edge radius R2 of the second blade 32 changes, the difference between the second cutting edge radius R2 in the state before the change and the second cutting edge radius R2 in the state after the change is made equal to or less than the abrasive grain cutting depth g. However, at the point of change in which the second cutting edge radius R2 of the second blade 32 changes, the difference between the second cutting edge radius R2 in the state before the change and the second cutting edge radius R2 in the state after the change may be made equal to or less than the abrasive grain protrusion amount.

[0097] According to this embodiment 1, the formation of steps on the teeth 21 of the internal gear Wa, which are formed by the region near the change point where the second cutting edge radius R2 changes, is suppressed. This makes it possible to suppress uneven wear of the barrel-shaped screw grinding wheel Ta.

[0098] The dresser according to this first embodiment is a rotary dresser 5.

[0099] According to this embodiment 1, the second cutting edge 32 can be formed more efficiently compared to when a point dresser is used.

[0100] The dressing device 8, which is a forming device for a barrel-shaped threaded grinding wheel Ta according to this first embodiment, comprises a grinding wheel support member 2, a rotary dresser 5, and a control device 6. The grinding wheel support member 2 supports the barrel-shaped threaded grinding wheel Ta so that it can rotate around the grinding wheel axis Ct. The rotary dresser 5 is supported so that it can rotate around the dresser axis Cd and forms the grinding blades 30 of the rotating barrel-shaped threaded grinding wheel Ta.

[0101] The control device 6 moves at least one of the barrel-shaped screw-shaped grinding wheel Ta and the rotary dresser 5 to a desired position and controls its rotation to shape the grinding blades 30 of the barrel-shaped screw-shaped grinding wheel Ta. The control device 6 dresses the barrel-shaped screw-shaped grinding wheel Ta using the rotary dresser 5 based on the number of teeth of the internal gear Wa, thereby forming a first region 41 with first blades 31 corresponding to the shape of the teeth 21 of the internal gear Wa over a predetermined length dimension in the direction of the grinding wheel axis Ct of the barrel-shaped screw-shaped grinding wheel Ta. The control device 6 then dresses the barrel-shaped screw-shaped grinding wheel Ta at a position different from the first region 41 in the direction of the grinding wheel axis Ct using the rotary dresser 5, thereby forming a second region 42 with second blades 32 having a different shape from the first blades 31.

[0102] Furthermore, the gear grinding apparatus 1 according to this embodiment 1 grinds the teeth 21 of the internal gear Wa using a barrel-shaped screw-shaped grinding wheel Ta formed by the above-described method for forming the barrel-shaped screw-shaped grinding wheel Ta. The gear grinding apparatus 1 includes a grinding wheel support member 2 that supports the barrel-shaped screw-shaped grinding wheel Ta so that it can rotate around the grinding wheel axis Ct, a workpiece support member 3 that supports the internal gear Wa so that it can rotate around the workpiece axis Cg, and a control device 6 that moves at least one of the barrel-shaped screw-shaped grinding wheel Ta and the internal gear Wa to a desired position and controls its rotation to process the teeth 21 of the gear one tooth groove at a time.

[0103] According to the gear grinding apparatus 1 of this embodiment 1, the internal gear Wa can be ground with high precision.

[0104] (Embodiment 2) Next, Embodiment 2 will be described with reference to Figure 8. Note that, unless otherwise specified, reference numerals used in Embodiment 2 and later that are the same as those used in the previously described embodiments represent the same components as those in the previously described embodiments.

[0105] In this second embodiment, the dressing device 8 calculates the shape of the barrel-shaped screw grinding wheel Tb based on the reference number of teeth, and then calculates the second cutting edge radius R2 at both ends of the grinding wheel axis Ct. The second cutting edge 32 in the second region 42 is not calculated based on the number of teeth to be machined, but is formed by simply reducing the cutting edge radius of the cutting edge calculated based on the reference number of teeth. In this respect, embodiment 2 differs from embodiment 1.

[0106] The first cutting edge 31 of the barrel-shaped screw-type grinding wheel Tb according to this second embodiment is formed in a shape corresponding to the teeth 21 of the internal gear. Furthermore, the second cutting edge 32 of the barrel-shaped screw-type grinding wheel Tb according to this second embodiment is formed so as not to interfere excessively with the teeth 21 of the internal gear Wa. In other words, a gap is formed between the second cutting edge 32 of the barrel-shaped screw-type grinding wheel Tb and the teeth 21 of the internal gear Wa.

[0107] According to this second embodiment, the step of calculating the second cutting edge 32 based on the number of teeth to be machined can be omitted, thus simplifying the molding process of the barrel-shaped screw-type grinding wheel Tb.

[0108] (Embodiment 3) Next, with reference to Figure 9, Embodiment 3 will be described. The gear W in this Embodiment 3 is an external gear Wb. The external gear Wb has teeth 21 that protrude outward. The dressing device 8 in this Embodiment 3 forms the second cutting edge 32 of the drum-shaped screw-shaped grinding wheel Tc based on a number of processed teeth that is greater than the reference number of teeth. This makes it possible to form the second cutting edge 32 by a simple method of making the number of processed teeth greater than the reference number of teeth. For example, the first cutting edge 31 can be formed with a reference number of 60 teeth, and the second cutting edge 32 can be processed with a number of processed teeth of 65 teeth. However, the reference number of teeth and the number of processed teeth can be selected as any values.

[0109] Furthermore, in the dressing device 8 according to this embodiment 3, the second cutting edge 32 in the second region 42 may be formed not based on the number of teeth to be machined, but simply by reducing the cutting edge radius of the cutting edge calculated based on the number of teeth to be machined.

[0110] The screw-shaped grinding wheel T according to this third embodiment is a drum-shaped screw-shaped grinding wheel Tc in which the radius is smallest at the center in the direction of the grinding wheel axis Ct and the radius is large at the end in the direction of the grinding wheel axis Ct, or a semi-drum-shaped screw-shaped grinding wheel having the shape of one or both of the drum-shaped screw-shaped grinding wheel Tc that is cut when the drum-shaped screw-shaped grinding wheel Tc is cut near the center in the direction of the grinding wheel axis Ct.

[0111] As shown in Figure 9, the second cutting edge 32 of the drum-shaped screw-type grinding wheel Tc according to this embodiment 3 is formed so as not to interfere excessively with the teeth 21 of the external gear Wb. In other words, a gap is formed between the second cutting edge 32 of the drum-shaped screw-type grinding wheel Tc and the teeth 21 of the external gear Wb.

[0112] Furthermore, the abrasive grain cutting depth g in external grinding, such as that of the external gear Wb according to this embodiment 3, is expressed by the following formula (2). Note that the algebraic expression in formula (2) is the same as in formula (1), so the redundant explanation is omitted.

[0113]

number

[0114] The present invention is not limited to the embodiments described above, and can be applied to various embodiments without departing from its spirit. [Explanation of Symbols]

[0115] 1: Gear grinding device, 2: Grinding wheel support member, 3: Workpiece support member, 4: Rotary dresser support member, 5: Rotary dresser, 6: Control device, 7: Memory device, 8: Dressing device, 21: Tooth, 30: Grinding blade, 31: First blade, 32: Second blade, 33: First connecting part, 34: Second connecting part, 41: First area, 42: Second area, Cd: Dresser axis, Cg: Workpiece axis, Ct: Grinding wheel axis, g: Abrasive grain cutting depth, R1: First cutting edge radius, R2: Second cutting edge radius, Ri: Virtual cutting edge radius, T: Screw-shaped grinding wheel, Ta, Tb: Barrel-shaped screw-shaped grinding wheel, Tc: Drum-shaped screw-shaped grinding wheel, W: Gear, Wa: Internal gear, Wb: External gear

Claims

1. A method for forming a screw-shaped grinding wheel using a dresser, The screw-shaped grinding wheel is dressed using the dresser based on a reference number of teeth, which is the number of teeth of the gear processed by the screw-shaped grinding wheel, thereby forming a first region having a first cutting edge corresponding to the shape of the gear teeth over a predetermined length dimension in the grinding wheel axis direction of the screw-shaped grinding wheel. A method for forming a screw-shaped grinding wheel, comprising dressing the screw-shaped grinding wheel at a position different from the first region in the direction of the grinding wheel axis using the dresser to form a second region having a second blade having a different shape from the first blade.

2. A method for forming a screw-shaped grinding wheel according to claim 1, wherein the second cutting edge radius, which is the distance between the cutting edge of the second blade and the grinding wheel axis of the screw-shaped grinding wheel, is formed to be smaller than the virtual cutting edge radius, which is the distance between the cutting edge of a virtual blade and the grinding wheel axis when it is assumed that the dressing is performed using the dresser based on the reference number of teeth in the second region.

3. A method for forming a screw-shaped grinding wheel according to claim 2, comprising forming a first connecting portion that continuously connects the first blade and the second blade.

4. A method for forming a screw-shaped grinding wheel according to claim 2, wherein the difference between the first cutting edge radius, which is the distance between the cutting edge of the first blade and the axis of the grinding wheel, and the second cutting edge radius is formed to be equal to or less than the abrasive grain cutting depth of the screw-shaped grinding wheel.

5. The aforementioned gear is an internal gear, The second cutting edge is formed by dressing it using the dresser based on a number of teeth that differs from the reference number of teeth. The method for forming a screw-shaped grinding wheel according to claim 2, wherein the number of processed teeth is less than the number of reference teeth.

6. The aforementioned screw-shaped grinding wheel is A method for forming a screw-shaped grinding wheel according to claim 5, wherein the grinding wheel is a barrel-shaped screw-shaped grinding wheel in which the radius is largest at the center in the axial direction of the grinding wheel and the radius is smallest at the axial end, a grinding wheel having the shape of one or both of the cut pieces of the barrel-shaped screw-shaped grinding wheel when the barrel-shaped screw-shaped grinding wheel is cut near the center in the axial direction of the grinding wheel, or a grinding wheel formed in a cup shape that decreases in diameter as it approaches the other end from one end in the axial direction of the grinding wheel.

7. The aforementioned gear is an external gear, The second cutting edge is formed by dressing it using the dresser based on a number of teeth that differs from the reference number of teeth. The method for forming a screw-shaped grinding wheel according to claim 2, wherein the number of processed teeth is greater than the number of standard teeth.

8. The aforementioned screw-shaped grinding wheel is A method for forming a screw-shaped grinding wheel according to claim 7, wherein the grinding wheel is a drum-shaped screw-shaped grinding wheel in which the radius is smallest at the center in the direction of the grinding wheel axis and the radius is large at the end in the direction of the grinding wheel axis, or a semi-drum-shaped screw-shaped grinding wheel having the shape of one or both of the cut pieces of the drum-shaped screw-shaped grinding wheel when the drum-shaped screw-shaped grinding wheel is cut near the center in the direction of the grinding wheel axis.

9. A method for forming a screw-shaped grinding wheel according to any one of claims 5 to 8, wherein in the second region, the second cutting edge is formed by changing the number of processing teeth in multiple stages.

10. A method for forming a screw-shaped grinding wheel according to claim 9, wherein at a change point in which the radius of the second cutting edge of the second blade changes, a second connecting portion is formed that continuously connects the second blade in the state before the change in the radius of the second cutting edge and the second blade in the state after the change in the radius of the second cutting edge.

11. A method for forming a screw-shaped grinding wheel according to claim 10, wherein at a change point in which the second cutting edge radius of the second blade changes, the difference between the second cutting edge radius in the state before the change in the second cutting edge radius and the second cutting edge radius in the state after the change in the second cutting edge radius is equal to or less than the abrasive grain cutting depth.

12. The method for forming a screw-shaped grinding wheel according to claim 1, wherein the dresser is a rotary dresser.

13. A device for forming a screw-shaped grinding wheel, A grinding wheel support member that supports the aforementioned screw-shaped grinding wheel so that it can rotate around the grinding wheel axis, A dresser that is rotatably supported around the dresser axis and shapes the blade of the rotating screw-shaped grinding wheel, The system includes a control device that moves at least one of the screw-shaped grinding wheel and the dresser to a desired position and controls its rotation to shape the blade of the screw-shaped grinding wheel, The control device is By dressing the screw-shaped grinding wheel using the dresser based on the number of teeth of the gear, a first region is formed over a predetermined length dimension in the axial direction of the screw-shaped grinding wheel, having a first cutting edge corresponding to the shape of the gear teeth. A device for forming a screw-shaped grinding wheel, wherein a second region having a second blade having a different shape from the first blade is formed by dressing the screw-shaped grinding wheel at a position different from the first region in the direction of the grinding wheel axis using the dresser.

14. A gear grinding apparatus for grinding the tooth surface of a gear using a screw-shaped grinding wheel formed by the method for forming a screw-shaped grinding wheel described in any one of claims 1 to 8, A grinding wheel support member that supports the aforementioned screw-shaped grinding wheel so that it can rotate around the grinding wheel axis, A workpiece support member that supports the gear so as to be rotatable around the axis of the workpiece, A gear grinding apparatus comprising: a control device that moves at least one of the screw-shaped grinding wheel and the gear to a desired position and controls its rotation to machine the teeth of the gear one tooth groove at a time.

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