MACHINING APPARATUS

Abstract

A machining apparatus includes: a rotating shaft rotatably supported by a housing; a rotary tool detachably attached to the rotating shaft; an attachment; and a bracket. The rotary tool includes a front end surface facing in a first direction lying along an axial direction of the rotating shaft, and a rear end surface facing in a second direction opposite to the first direction. The attachment is detachably connected to the front end surface of the rotary tool. The bracket rotatably supports the attachment in a state of being supported by the housing.

Claims

1. A machining apparatus comprising: a rotating shaft rotatably supported by a housing; and a rotary tool having a cylindrical shape and detachably attached to the rotating shaft, wherein the rotating shaft includes a protruding end portion protruding from the housing in a first direction lying along an axial direction of the rotating shaft, the rotary tool being attached to the protruding end portion, and the rotary tool includes a front end surface formed at an end portion of the rotary tool in the first direction and facing in the first direction, and a rear end surface formed at an end portion of the rotary tool in a second direction and facing in the second direction, the second direction being opposite to the first direction, the machining apparatus further comprising: an attachment detachably connected to the front end surface of the rotary tool; and a bracket supported by the housing and configured to rotatably support the attachment.

2. The machining apparatus according to claim 1, wherein the rotating shaft and the rotary tool are coupled by a first coupling member, the rotary tool and the attachment are coupled by a second coupling member, and the second coupling member is disposed outward of the first coupling member in a radial direction of the rotary tool.

3. The machining apparatus according to claim 1, wherein the attachment includes an auxiliary rotating shaft member extending in the first direction and aligned with the rotating shaft, and the bracket includes an insertion hole into which the auxiliary rotating shaft member is inserted, and a bearing interposed between a side surface of the auxiliary rotating shaft member and an inner surface of the insertion hole.

4. The machining apparatus according to claim 3, further comprising a first seal member and a second seal member, wherein the bearing is interposed between the first seal member and the second seal member in the axial direction.

5. The machining apparatus according to claim 3, further comprising a clamp configured to tighten the bearing from both the first direction and the second direction.

6. The machining apparatus according to claim 5, wherein the clamp includes a nut, a first spacer, and a second spacer, the bearing being interposed between the first spacer and the second spacer in the axial direction, the auxiliary rotating shaft member includes a threaded portion on the side surface of the auxiliary rotating shaft member, and the first spacer and the second spacer tighten the bearing as the nut is screwed onto the threaded portion.

7. The machining apparatus according to claim 3, wherein the bearing is a cylindrical roller bearing.

8. The machining apparatus according to claim 1, wherein the rotary tool is a grinding wheel, and the machining apparatus is a grinding apparatus.

9. The machining apparatus according to claim 8, wherein the grinding wheel includes a substrate made of a metallic material, and abrasive grains fixed to an outer surface of the substrate.

10. The machining apparatus according to claim 8, wherein the grinding wheel includes a grinding part having a helical shape and formed on an outer circumferential surface of the grinding wheel that is located between the front end surface and the rear end surface, and the grinding part grinds a toothed portion of a gear.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a side cross-sectional view of a main part of a machining apparatus (a grinding apparatus) according to an embodiment of the present disclosure;

[0011] FIG. 2 is a diagram schematically showing the configuration of an electroplated grinding wheel; and

[0012] FIG. 3 is an enlarged view of a main part showing a state in which a toothed portion of a gear is being ground by a grinding wheel.

DETAILED DESCRIPTION OF THE INVENTION

[0013] In the embodiment described below, an aspect will be illustrated in which a machining apparatus 10 shown in FIG. 1 is a grinding apparatus 10A for grinding a toothed portion T of a gear G shown in FIG. 3. In this case, a rotary tool 12 shown in FIG. 1 is a grinding wheel 30. However, the machining apparatus 10 is not limited to the grinding apparatus 10A. The machining apparatus 10 may be an apparatus that performs machining other than grinding. Therefore, the rotary tool 12 is not limited to the grinding wheel 30. Further, the grinding apparatus 10A is not limited to the grinding apparatus for gears. The grinding apparatus 10A may be an apparatus for grinding other workpieces.

[0014] In addition, in the following description, when simply referred to as an axial direction, the axial direction means an axial direction of a rotating shaft 20. The axial direction of the rotating shaft 20 refers to a direction parallel to a central axis L of the rotating shaft 20. Further, a direction along a radial direction of the rotating shaft 20 may be simply referred to as a radial direction. The radial direction of the rotating shaft 20 coincides with the radial direction of the grinding wheel 30. Therefore, the radial direction may mean a direction along the radial direction of the grinding wheel 30.

[0015] FIG. 1 is a side cross-sectional view of a main part of the grinding apparatus 10A. The grinding apparatus 10A includes a housing 16 and the rotating shaft 20 rotatably supported by the housing 16. Note that FIG. 1 is a view viewed in a radial direction orthogonal to the central axis L (or the axial direction) of the rotating shaft 20.

[0016] The rotating shaft 20 includes a shaft body 200 and a holder member 210. The shaft body 200 is accommodated in a shaft hole 100 formed in the housing 16. A housing-side bearing 110 is interposed between a side circumferential surface of the shaft body 200 and an inner circumferential surface of the shaft hole 100. The housing-side bearing 110 is, for example, a ball bearing, but is not limited to the ball bearing.

[0017] A direction lying along the axial direction and directed from the inside to the outside of the housing 16 (a direction directed from the shaft body 200 to the holder member 210) is referred to as a first direction. A direction opposite to the first direction is referred to as a second direction. The shaft body 200 has a first end portion 202 facing in the first direction and provided with a fitting recess 204 recessed in the second direction. The shaft body 200 has a second end portion (not shown) facing in the second direction and connected to an output shaft of a rotary motor (not shown). When the rotary motor is driven and the output shaft rotates, the rotating shaft 20 rotates about the central axis L.

[0018] The holder member 210 includes a flange portion 212, a fitting projection 214, and a columnar protruding portion 216. An attachment hole 218 that forms a first coupling member 230 is formed in the flange portion 212. The fitting projection 214 extends in the second direction from an end surface of the flange portion 212 that faces in the second direction. The columnar protruding portion 216 extends in the first direction from an end surface of the flange portion 212 that faces in the first direction. A portion of the columnar protruding portion 216 that is located in a first insertion hole 316 is a tapered portion 220 that decreases in diameter in a tapered shape from the second direction side toward the first direction side.

[0019] The fitting projection 214 is fitted into the fitting recess 204 of the shaft body 200. Further, the holder member 210 and the first end portion 202 of the shaft body 200 are connected to each other by a bolt (not shown). In this state, the flange portion 212 and the columnar protruding portion 216 are located outside the housing 16 (outside the shaft hole 100). Therefore, an end portion of the rotating shaft 20 that faces in the first direction protrudes from the housing 16 (the shaft hole 100). Hereinafter, this end portion is referred to as a protruding end portion 22.

[0020] The grinding wheel 30 is detachably attached to the holder member 210. In a preferred embodiment, the grinding wheel 30 is an electroplated grinding wheel 30A. As shown in FIG. 2, the electroplated grinding wheel 30A includes a substrate 32 made of a metallic material, and abrasive grains 34. The abrasive grains 34 are, for example, diamond abrasive grains. The abrasive grains 34 are fixed to the outer surface of the substrate 32 by a plating layer 36 (electrodeposition layer). In this aspect, it is easy to provide a connecting hole 342 (described later) shown in FIG. 1 in the grinding wheel 30 by machining. This is because the substrate 32 (see FIG. 2) is made of a metallic material, and various types of machining can therefore be easily performed on the substrate 32.

[0021] However, the grinding wheel 30 is not limited to the electroplated grinding wheel 30A. The grinding wheel 30 may be a sintered grinding wheel obtained by sintering the abrasive grains 34 (for example, diamond abrasive grains).

[0022] As shown in FIG. 1, the grinding wheel 30 includes a hollow cylindrical body 313 whose both ends in the axial direction are opened, and a partition wall portion 314 provided so as to partition the hollow interior of the cylindrical body 313. The grinding wheel 30 has a cylindrical shape formed by the cylindrical body 313 and the partition wall portion 314. The cylindrical body 313 is an outer peripheral portion located on the outer peripheral side of the partition wall portion 314, and the partition wall portion 314 is an inner peripheral portion located on the inner peripheral side of the cylindrical body 313.

[0023] The cylindrical body 313 includes a front end surface 300, a rear end surface 302, and an outer circumferential surface 304. The front end surface 300 is a bottom surface of the grinding wheel 30 that faces in the first direction. The rear end surface 302 is a bottom surface of the grinding wheel 30 that faces in the second direction. The grinding wheel 30 includes a front recess 310 recessed from the front end surface 300 toward the rear end surface 302. When the grinding wheel 30 is viewed from the axial direction, the front end surface 300 has a circular ring shape (see FIG. 3). The grinding wheel 30 includes a rear recess 312 recessed from the rear end surface 302 toward the front end surface 300. When the grinding wheel is viewed from the axial direction, the rear end surface 302 has a circular ring shape in the same manner as the front end surface 300. In the illustrated example, the inner diameter of the rear recess 312 is larger than the inner diameter of the front recess 310.

[0024] The hollow interior of the cylindrical body 313 is divided into the front recess 310 and the rear recess 312 by the partition wall portion 314. The partition wall portion 314 includes the first insertion hole 316 and a second insertion hole 318. The first insertion hole 316 and the second insertion hole 318 extend along the axial direction of the rotating shaft and penetrate the partition wall portion 314.

[0025] The first insertion hole 316 is formed in a portion of the partition wall portion 314 through which the central axis L of the rotating shaft 20 passes. The central axis L of the rotating shaft 20 and the central axis of the first insertion hole 316 are aligned with each other. The columnar protruding portion 216 within the protruding end portion 22 is passed through the first insertion hole 316. The tapered portion 220 of the columnar protruding portion 216 is located in the first insertion hole 316. Therefore, the first insertion hole 316 is a tapered hole corresponding to the shape of the tapered portion 220. An end portion of the columnar protruding portion 216 in the first direction is located in the front recess 310.

[0026] The second insertion hole 318 is formed radially outward of the central axis L of the rotating shaft 20. The second insertion hole 318 forms the first coupling member 230 together with the attachment hole 218 and an attachment tool 330. Specifically, the flange portion 212 within the protruding end portion 22 is inserted into the rear recess 312. In a state where the second insertion hole 318 and the attachment hole 218 are aligned with each other, the attachment tool 330 is passed through the second insertion hole 318. The attachment tool 330 is, for example, an attachment bolt 332. In this case, a threaded portion (not shown) is formed on the inner surface of the attachment hole 218. As the attachment bolt 332 is screwed into the threaded portion, the grinding wheel 30 is coupled to the rotating shaft 20 by the first coupling member 230. As understood from this, the support of the grinding wheel 30 by the rotating shaft 20 is a cantilever support.

[0027] In order to firmly couple the rotating shaft 20 and the grinding wheel 30, it is preferable to provide a plurality of the first coupling members 230 on the rotating shaft 20 and the grinding wheel 30. However, in the case where the relative rotation between the rotating shaft 20 and the grinding wheel can be sufficiently suppressed by a single first coupling member 230, the number of the first coupling members 230 may be one.

[0028] An annular groove 320 having a circular ring shape is formed in the rear end surface 302 of the grinding wheel 30. On the other hand, an annular protrusion 104 having a circular ring shape is provided on a forward end surface 102 of the housing 16 that faces in the first direction. The annular protrusion 104 is inserted into the annular groove 320. This prevents foreign matter (grinding fluid or the like) from entering the rear recess 312 through a gap between the rear end surface 302 of the grinding wheel 30 and the forward end surface 102 of the housing 16. The annular protrusion 104 may be spaced apart from the inner surface of the annular groove 320. However, the annular protrusion 104 may come into sliding contact with the inner surface of the annular groove 320 when the grinding wheel 30 rotates.

[0029] The grinding wheel 30 includes the connecting hole 342 that forms a second coupling member 340. The connecting hole 342 is formed in the front end surface 300 of the grinding wheel 30. A connecting tool 430 for detachably connecting an attachment 40 (described later) is inserted into the connecting hole 342. The connecting tool 430 is, for example, a connecting bolt 432. In this case, a threaded portion is provided on the inner surface of the connecting hole 342. The second coupling member 340 is located further on the first direction side than the first coupling member 230.

[0030] The grinding wheel 30 includes a grinding part 306 on the outer circumferential surface 304. In the aspect in which the machining apparatus 10 is the grinding apparatus 10A, the grinding part 306 has a helical shape.

[0031] The grinding apparatus 10A further includes the attachment 40. The attachment 40 includes a substantially disk-shaped base portion 400. Hereinafter, an end surface of the base portion 400 that faces in the first direction is referred to as a main surface 402, and an end surface of the base portion 400 that faces in the second direction is referred to as a back surface 404. The back surface 404 faces the front end surface 300 of the grinding wheel 30.

[0032] The base portion 400 includes a stepped hole 406. The stepped hole 406 forms the second coupling member 340 together with the connecting tool 430. Specifically, the stepped hole 406 is formed in the base portion 400 at a location other than a location where a main-surface-side protrusion 408 and a back-surface-side protrusion 410 are provided, and extends along the axial direction to penetrate the base portion 400. The shank of the connecting bolt 432 serving as the connecting tool 430 is passed through the stepped hole 406. The connecting bolt 432 is screwed into the threaded portion of the connecting hole 342 of the grinding wheel 30. In accordance therewith, the attachment is connected to the front end surface 300 of the grinding wheel 30 by the second coupling member 340. The head of the connecting bolt 432 is accommodated in the stepped hole 406. The attachment 40 is detached from the grinding wheel 30 by loosening the connecting bolt 432 from the connecting hole 342. In this manner, the attachment 40 is attachable to and detachable from the grinding wheel 30.

[0033] In order to firmly couple the grinding wheel 30 and the attachment 40, it is preferable to provide a plurality of the second coupling members 340 on the grinding wheel 30 and the attachment 40. In one aspect, the plurality of second coupling members 340 are disposed radially outward of the plurality of first coupling members 230. In this case, radial vibration of the grinding wheel 30 can be sufficiently suppressed. Alternatively, the plurality of second coupling members 340 may be disposed radially inward of the plurality of first coupling members 230. Alternatively, some of the plurality of second coupling members 340 may be disposed radially outward of some of the plurality of first coupling members 230, and the remaining second coupling members 340 may be disposed radially inward of the remaining first coupling members 230.

[0034] However, in the case where the relative rotation between the attachment 40 and the grinding wheel 30 can be suppressed by a single second coupling member 340, the number of the second coupling members 340 may be one. In this aspect as well, it is preferable that the second coupling member 340 be disposed radially outward of the first coupling member 230, but this is not essential.

[0035] The main-surface-side protrusion 408 having a substantially disk shape protrudes from the main surface 402 of the base portion 400, and the back-surface-side protrusion 410 having a substantially disk shape protrudes from the back surface 404 of the base portion 400. The protruding direction of the main-surface-side protrusion 408 is the first direction, and the protruding direction of the back-surface-side protrusion 410 is the second direction. The diameter of the back-surface-side protrusion 410 is larger than the diameter of the main-surface-side protrusion 408.

[0036] The back-surface-side protrusion 410 engages with the front recess 310 of the grinding wheel 30. The side surface of the back-surface-side protrusion 410 comes into contact with, for example, the inner circumferential surface of the front recess 310. However, it is not essential that the side surface of the back-surface-side protrusion 410 come into contact with the inner circumferential surface of the front recess 310. A relief recess 412 is formed at the center of the back-surface-side protrusion 410. The relief recess 412 prevents the back-surface-side protrusion 410 from interfering with the columnar protruding portion 216.

[0037] The attachment 40 further includes an auxiliary rotating shaft member 420. The auxiliary rotating shaft member 420 extends so as to protrude from the main-surface-side protrusion 408 along the first direction. The auxiliary rotating shaft member 420 and the rotating shaft 20 are aligned with each other. Therefore, when the grinding apparatus 10A is viewed from the axial direction of the rotating shaft 20, a central axis M of the auxiliary rotating shaft member 420 and the central axis L of the rotating shaft 20 substantially overlap each other. In other words, the amount of deviation between the central axis M of the auxiliary rotating shaft member 420 and the central axis L of the rotating shaft 20 falls within an allowable range.

[0038] The auxiliary rotating shaft member 420 includes a tapered portion 422 that gradually decreases in diameter in a tapered shape from the second direction side toward the first direction side, and a constant diameter portion 424 having a constant diameter. The tapered portion 422 is closer to the base portion 400 than the constant diameter portion 424 is. A threaded portion 426 is provided on the side surface of the auxiliary rotating shaft member 420.

[0039] In this manner, the rotating shaft 20 and the grinding wheel 30 are coupled by the first coupling member 230, and the grinding wheel 30 and the attachment 40 are coupled via the second coupling member 340. Therefore, when the rotating shaft rotates, the grinding wheel 30 and the attachment 40 rotate integrally with the rotating shaft 20.

[0040] The grinding apparatus 10A further includes a bracket 50. One end portion of the bracket 50 in the direction along the radial direction of the rotating shaft 20 is supported by the housing 16. In other words, the bracket 50 is firmly positioned and fixed to the housing 16. This prevents the bracket 50 from vibrating.

[0041] The bracket 50 includes an insertion hole 500 extending along the axial direction of the rotating shaft 20. A bracket-side bearing 502 (a bearing) is provided in the insertion hole 500. The auxiliary rotating shaft member 420 of the attachment is inserted into the insertion hole 500 and passed through the bracket-side bearing 502. Therefore, the bracket-side bearing 502 is interposed between the side surface of the auxiliary rotating shaft member 420 and the inner surface of the insertion hole 500. As a result, the attachment 40 is rotatably supported by the bracket 50. The bracket-side bearing 502 is located on the tapered portion 422 of the auxiliary rotating shaft member 420.

[0042] In the illustrated example, the bracket-side bearing 502 is a cylindrical roller bearing 502A. The cylindrical roller bearing 502A has a high capacity of bearing a load acting along the radial direction. Therefore, it is possible to sufficiently suppress the radial vibration of the auxiliary rotating shaft member 420. However, the bracket-side bearing 502 is not limited to the cylindrical roller bearing 502A. The bracket-side bearing 502 may be another roller bearing such as a needle roller bearing. Alternatively, the bracket-side bearing 502 may be a ball bearing.

[0043] The grinding apparatus 10A includes a first seal member 510 and a second seal member 512. The first seal member 510 and the second seal member 512 have a so-called labyrinth sealing structure. In the insertion hole 500, the first seal member 510 is located further in the first direction than the bracket-side bearing 502, and the second seal member 512 is located further in the second direction than the bracket-side bearing 502. The bracket-side bearing 502 is interposed between a first spacer 524 and a second spacer 526. The first seal member 510 and the second seal member 512 prevent foreign matter from entering the insertion hole 500.

[0044] The grinding apparatus 10A includes a clamp 520. In the illustrated example, the clamp 520 includes a nut 522, the first spacer 524, and the second spacer 526. The nut 522 is screwed onto the threaded portion 426. An end portion of the first spacer 524 in the first direction is exposed from the insertion hole 500, and an end portion of the first spacer 524 in the second direction is inserted into the insertion hole 500 and comes into contact with the first seal member 510. The second spacer 526 is located, for example, outside the insertion hole 500. An end portion of the second spacer 526 in the first direction can come into contact with the second seal member 512. An end portion of the second spacer 526 in the second direction can come into contact with the main-surface-side protrusion 408.

[0045] A method of manufacturing the grinding apparatus 10A configured as described above will be briefly described. First, the connecting hole 342 is formed, by machining (for example, tapping), in the front end surface 300 of the grinding wheel 30, which is in the state of being detached from the rotating shaft 20. In the case where the grinding wheel 30 is the electroplated grinding wheel 30A shown in FIG. 2, the grinding wheel 30 can be easily machined because the substrate 32 is made of a metallic material. In the case where the grinding wheel 30 is a sintered grinding wheel, a compact including the connecting hole 342 is formed, and then the compact is sintered.

[0046] Next, as shown in FIG. 1, the grinding wheel 30 is coupled to the holder member 210 of the rotating shaft 20 by the first coupling member 230 in a state where the flange portion 212 of the holder member 210 is inserted into the rear recess 312 of the grinding wheel 30 and the columnar protruding portion 216 of the holder member 210 is passed through the first insertion hole 316 of the grinding wheel 30.

[0047] Next, the attachment 40 is connected to the front end surface 300 of the grinding wheel 30 by the second coupling member 340. Further, the auxiliary rotating shaft member 420 is passed through the insertion hole 500 of the bracket 50, and the bracket 50 is connected to the housing 16. As a result, the bracket 50 is firmly supported by the housing 16. Note that, at this stage, the nut 522 is temporarily fastened to the threaded portion 426.

[0048] Next, the nut 522 is screwed and moved in the second direction along the auxiliary rotating shaft member 420. In accordance with the screwing, the nut 522 moves in the second direction along the columnar protruding portion 216. The nut 522 that has moved in the second direction comes into contact with the first spacer 524. When the nut 522 further moves in the second direction, the first spacer 524 is pushed by the nut 522 and moves in the second direction. Therefore, the first seal member 510, the bracket-side bearing 502, the second seal member 512, and the second spacer 526 are pushed by the first spacer 524 and move in the second direction.

[0049] The second spacer 526 is stopped by coming into contact with the main-surface-side protrusion 408. In accordance therewith, the first spacer 524, the first seal member 510, the bracket-side bearing 502, and the second seal member 512 are also stopped. When the nut 522 is further screwed in this state, the bracket-side bearing 502 is tightened by the first spacer 524 and the second spacer 526 to which the load is applied from the nut 522 and the main-surface-side protrusion 408.

[0050] By this tightening, an inner ring 504 of the bracket-side bearing 502 is tightened and slightly expanded radially outward. This reduces a gap between the inner ring 504 and an outer ring 506. In some cases, the gap is substantially eliminated. In the case where the bracket-side bearing 502 is the cylindrical roller bearing 502A, the radial rigidity of the bracket-side bearing 502 is increased by the above-described tightening.

[0051] Next, a method of using the grinding apparatus 10A will be described. As shown in FIG. 3, the grinding apparatus 10A is used to grind the toothed portion T of the gear G using the helical grinding part 306 of the grinding wheel 30.

[0052] In order to perform grinding, the gear G is held by a driven shaft (not shown) that is rotatable by being driven, and the toothed portion T of the gear G and the grinding part 306 of the grinding wheel 30 are engaged with each other. Next, a grinding fluid (not shown) is supplied to a portion to be ground, and the rotary motor is energized. As a result, the rotating shaft 20 starts to rotate. In accordance with this rotation, the grinding wheel 30 and the attachment 40 (see FIG. 1) rotate integrally with the rotating shaft 20.

[0053] Since the first seal member 510 and the second seal member 512 are inserted into the insertion hole 500 of the bracket 50, entering of the grinding fluid into the insertion hole 500 is suppressed. Further, since the annular protrusion 104 is inserted into the annular groove 320, the situation in which the grinding fluid enters the rear recess 312 from the gap between the rear end surface 302 of the grinding wheel 30 and the forward end surface 102 of the housing 16 is avoided. The same applies to foreign matter (dust or the like) other than the grinding fluid. Accordingly, the bracket-side bearing 502 and the housing-side bearing 110 are protected.

[0054] As described above, the rotating shaft 20 and the auxiliary rotating shaft member 420 are aligned with each other. In this state, the auxiliary rotating shaft member 420 is supported by the bracket-side bearing 502. Moreover, the bracket 50 is firmly positioned and fixed to the housing 16. Therefore, as shown in FIG. 3, in a state where the teeth of the gear G are in sliding contact with the grinding part 306 of the grinding wheel 30, radial vibration of the attachment 40 and the grinding wheel 30 is suppressed.

[0055] In the case where the bracket-side bearing 502 is the cylindrical roller bearing 502A, the cylindrical roller bearing 502A has a high capacity of bearing a radial load. Further, the gap between the inner ring 504 and the outer ring 506 is substantially eliminated by the tightening of the clamp 520. This further suppresses the radial vibration of the attachment and the grinding wheel 30.

[0056] For the above reasons, it is possible to avoid formation of minute undulations on the toothed portion T of the gear G (see FIG. 3) due to the vibration of the grinding wheel 30.

[0057] In the case where the grinding wheel 30 is worn, the grinding wheel 30 is replaced with a new one. In this case, first, the bracket 50 shown in FIG. 1 is detached from the housing 16 and the attachment 40, and then the attachment 40 is detached from the grinding wheel 30. Further, the grinding wheel 30 is detached from the holder member 210 of the rotating shaft 20. Thereafter, a new grinding wheel 30 is attached to the holder member 210.

[0058] A tubular body covering the outer periphery of the grinding wheel 30 and the outer periphery of the attachment 40 may be connected to the housing 16. The tubular body includes a pivot shaft member at a position offset from the center axis L of the rotating shaft 20. The bracket 50 is supported by the pivot shaft member. That is, in this case, the tubular body, the attachment 40, and the bracket 50 are unitized as an assembly. The bracket 50 is supported by the housing 16 via the tubular body.

[0059] In this configuration, the bracket 50 and the attachment can be integrally pivoted by removing the connecting tool 430 (the connecting bolt 432) from the connecting hole 342. The pivot center of the bracket 50 and the attachment 40 is the pivot shaft member. By this pivoting, the attachment 40 is separated from the grinding wheel 30. Therefore, in the case where the grinding wheel 30 is replaced, it is not necessary to detach the bracket 50 from the tubular body, and it is not necessary to detach the tubular body from the housing 16. Therefore, the work of replacing the grinding wheel 30 is easy.

[0060] The present embodiment has the following effects.

[0061] As shown in FIG. 1, the grinding apparatus 10A includes the grinding wheel 30 attached to the protruding end portion 22 of the rotating shaft 20. The attachment 40 is attached to the front end surface 300 of the grinding wheel 30, and the attachment 40 is rotatably supported by the bracket 50 supported by the housing 16.

[0062] According to such a configuration, the radial vibration of the attachment 40 and the grinding wheel 30 is suppressed. Therefore, the dimensional accuracy of the gear G (see FIG. 3) as a product is improved.

[0063] As shown in FIG. 1, the second coupling member 340 that couples the grinding wheel 30 and the attachment 40 is disposed radially outward of the first coupling member 230 that couples the rotating shaft 20 and the grinding wheel 30. In this case, the radial vibration of the attachment 40 and the grinding wheel 30 is further suppressed compared to a case where the first coupling member 230 is disposed radially outward of the second coupling member 340.

[0064] The attachment 40 includes the auxiliary rotating shaft member 420. The auxiliary rotating shaft member 420 and the rotating shaft 20 are aligned with each other. The bracket 50 includes the insertion hole 500 into which the auxiliary rotating shaft member 420 is inserted. The bracket-side bearing 502 (the bearing) is provided in the insertion hole 500. With this configuration, the attachment 40 can be rotatably supported by the bracket 50.

[0065] The bracket-side bearing 502 is interposed between the first seal member 510 and the second seal member 512 in the axial direction. Since the first seal member 510 and the second seal member 512 seal the insertion hole 500, foreign matter is prevented from entering the insertion hole 500. Therefore, for example, the bracket-side bearing 502 can be prevented from being wetted by a grinding fluid or the like supplied to a portion to be ground during the grinding. That is, the bracket-side bearing 502 is protected from the grinding fluid or the like.

[0066] The bracket-side bearing 502 is tightened by the clamp 520 from both the first direction and the second direction. As a result, the bracket-side bearing 502 becomes less likely to vibrate in the radial direction, and it is therefore possible to further suppress the vibration of the grinding wheel 30.

[0067] The clamp 520 includes the nut 522, the first spacer 524, and the second spacer 526. The bracket-side bearing 502 is interposed between the first spacer 524 and the second spacer 526 in the axial direction. As the nut 522 is screwed onto the threaded portion 426 of the auxiliary rotating shaft member 420, the first spacer 524 and the second spacer 526 tighten the bracket-side bearing 502.

[0068] In this manner, the bracket-side bearing 502 sandwiched between the first spacer 524 and the second spacer 526 can be easily tightened by a simple operation of screwing the nut 522 onto the threaded portion 426.

[0069] In a preferred embodiment, the bracket-side bearing 502 is the cylindrical roller bearing 502A. The cylindrical roller bearing 502A has a high capacity of bearing the radial load. Therefore, the auxiliary rotating shaft member 420 passed through the cylindrical roller bearing 502A becomes less likely to vibrate in the radial direction, and it is therefore possible to further suppress the radial vibration of the grinding wheel 30. In addition, in the case where the cylindrical roller bearing 502A is tightened by the clamp 520, the gap between the inner ring 504 and the outer ring 506 is reduced. Therefore, the attachment 40 becomes further less likely to vibrate in the radial direction.

[0070] In a preferred embodiment, the grinding wheel 30 is the electroplated grinding wheel 30A having the configuration shown in FIG. 2. The electroplated grinding wheel 30A includes the substrate 32 made of a metallic material. Since the substrate 32 is made of a metallic material, machining for connecting the grinding wheel 30 to the attachment 40 is easily performed on the grinding wheel 30. For example, machining for forming the connecting hole 342 in the front end surface 300 can be easily performed. Therefore, the attachment 40 can be easily connected to the existing grinding wheel 30.

[0071] The grinding wheel 30 includes, for example, the helical grinding part 306 formed on the outer circumferential surface 304. The grinding part 306 grinds the toothed portion T of the gear G. In this case, it is possible to avoid the formation of minute undulations on the toothed portion T of the gear G.

[0072] The following supplementary notes are further disclosed in relation to the above-described embodiment.

Supplementary Note 1

[0073] The machining apparatus (10) of the present disclosure includes: the rotating shaft (20) rotatably supported by the housing (16); and the rotary tool (12) having a cylindrical shape and detachably attached to the rotating shaft, wherein the rotating shaft includes the protruding end portion (22) protruding from the housing in the first direction lying along the axial direction of the rotating shaft, the rotary tool being attached to the protruding end portion, the rotary tool includes the front end surface (300) formed at an end portion of the rotary tool in the first direction and facing in the first direction, and the rear end surface (302) formed at an end portion of the rotary tool in the second direction and facing in the second direction, the second direction being opposite to the first direction, and the machining apparatus includes: the attachment (40) detachably connected to the front end surface of the rotary tool; and the bracket (50) supported by the housing and configured to rotatably support the attachment.

[0074] The attachment and the bracket suppress the radial vibration of the rotary tool. Therefore, the dimensional accuracy of the machined product can be improved.

Supplementary Note 2

[0075] In the machining apparatus according to Supplementary Note 1, the rotating shaft and the rotary tool may be coupled by the first coupling member (230), the rotary tool and the attachment may be coupled by the second coupling member (340), and the second coupling member may be disposed outward of the first coupling member in the radial direction of the rotary tool.

[0076] According to this configuration, the radial vibration of the rotary tool can be further suppressed.

Supplementary Note 3

[0077] In the machining apparatus according to Supplementary Note 1, the attachment may include the auxiliary rotating shaft member (420) extending in the first direction and aligned with the rotating shaft, and the bracket may include the insertion hole (500) into which the auxiliary rotating shaft member is inserted, and the bearing (502) interposed between the side surface of the auxiliary rotating shaft member and the inner surface of the insertion hole.

[0078] According to this configuration, the attachment can be rotatably supported by the bracket.

Supplementary Note 4

[0079] The machining apparatus according to Supplementary Note 3 may further include the first seal member (510) and the second seal member (512), and the bearing may be interposed between the first seal member and the second seal member in the axial direction.

[0080] The insertion hole is sealed by the first seal member and the second seal member. Accordingly, the situation in which foreign matter enters the insertion hole is avoided. Therefore, for example, it is possible to prevent the bearing from being wetted by a coolant (for example, a grinding fluid) or the like supplied to a portion to be machined during the machining.

Supplementary Note 5

[0081] The machining apparatus according to Supplementary Note 3 or 4 may further include the clamp (520) configured to tighten the bearing from both the first direction and the second direction.

[0082] As the clamp tightens the bearing, the bearing becomes less likely to vibrate in the radial direction. Therefore, the vibration of the rotary tool can be further suppressed.

Supplementary Note 6

[0083] In the machining apparatus according to Supplementary Note 5, the clamp may include the nut (522), the first spacer (524), and the second spacer (526), the bearing being interposed between the first spacer and the second spacer in the axial direction, the auxiliary rotating shaft member may include the threaded portion (426) on the side surface thereof, and the first spacer and the second spacer may tighten the bearing as the nut is screwed onto the threaded portion.

[0084] In this case, the bearing sandwiched between the first spacer and the second spacer can be easily tightened by a simple operation of screwing the nut onto the threaded portion.

Supplementary Note 7

[0085] In the machining apparatus according to any one of Supplementary Notes 3 to 6, the bearing may be the cylindrical roller bearing (502A).

[0086] The cylindrical roller bearing has a high capacity of bearing a radial load. Therefore, the attachment becomes less likely to vibrate in the radial direction, and it is therefore possible to further suppress the radial vibration of the rotary tool. Further, in the case where the cylindrical roller bearing is tightened by the clamp, a gap between the inner ring and the outer ring of the cylindrical roller bearing is reduced. Therefore, the attachment becomes less likely to vibrate in the radial direction.

Supplementary Note 8

[0087] In the machining apparatus according to any one of Supplementary Notes 1 to 7, the rotary tool may be the grinding wheel (30), and the machining apparatus may be the grinding apparatus (10A).

[0088] In this case, the radial vibration of the grinding wheel during grinding is suppressed. Therefore, the dimensional accuracy of the product obtained by the grinding is improved.

Supplementary Note 9

[0089] In the machining apparatus according to Supplementary Note 8, the grinding wheel may include the substrate (32) made of a metallic material, and the abrasive grains (34) fixed to the outer surface of the substrate.

[0090] Since the substrate is made of a metallic material, machining for connecting the grinding wheel to the attachment is easily performed on the grinding wheel. For example, tapping can be easily performed on the front end surface of the grinding wheel.

Supplementary Note 10

[0091] In the machining apparatus according to Supplementary Note 8 or 9, the grinding wheel may include the grinding part (306) having a helical shape and formed on the outer circumferential surface (304) located between the front end surface and the rear end surface, and the grinding part may grind the toothed portion (T) of the gear (G).

[0092] According to this feature, it is possible to avoid the formation of minute undulations on the toothed portion of the gear.

[0093] Although the present disclosure has been described in detail, the present disclosure is not limited to the above-described individual embodiments. Various additions, replacements, modifications, partial deletions, and the like can be made to these embodiments without departing from the essence and gist of the present disclosure, or without departing from the essence and gist of the present disclosure derived from the claims and equivalents thereof. Further, these embodiments can also be implemented in combination. For example, in the above-described embodiments, the order of operations and the order of processes are shown as examples, and are not limited to these. Furthermore, the same applies to a case where numerical values or mathematical expressions are used in the description of the above-described embodiments.