Grinding method and grinding device

Abstract

A grinding device (100) rotates a grindstone (13) attached to a grindstone shaft (12) protruding from a grindstone seat (11) to perform internal grinding on a workpiece (1). An injection unit (21) for injecting grinding fluid is provided so as to cover the outer peripheral surface of the grindstone seat (11). In the injection unit (21), an injection hole (22) is provided in such a manner that the grinding fluid discharged from the injection unit (21) is supplied to the grinding site of the workpiece (1).

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a grinding method and a grinding device. BACKGROUND

[0002] Until now, in a grinding device that performs internal grinding of a workpiece, a shaft-mounted grinding stone (refer to Patent Literature 1) in which a grinding stone is mounted on a grinding stone shaft that rotates by a wheel head has been used.

[0003] In internal grinding, a grinding load acts on the grinding stone, so the grinding stone shaft is deflected. Since the magnitude of this deflection cannot be ignored in comparison with the machining accuracy required for grinding, in order to perform internal grinding with high accuracy, it is necessary to perform spark-out grinding in which the axial movement of the grinding stone shaft is stopped for several seconds until the deflection disappears. If a hole to be machined is long and thin, the grinding stone shaft used also needs to be long and thin in correspondence thereto. In this case, the rigidity of the grinding stone shaft becomes low, and the spark-out grinding for restoring the deflection of the grinding stone shaft takes time, so the machining time becomes long.

[0004] In addition, in internal grinding, it is necessary to supply a grinding fluid to the grinding site of the workpiece. In the case of machining a long and thin hole, it is necessary to arrange a jet port of the grinding fluid so that the grinding fluid smoothly enters the gap between the grinding stone shaft and the hole to be machined. If the hole to be machined is a blind hole, it is necessary to supply the grinding fluid to the grinding site of the workpiece from the same side as the grinding stone shaft. Patent Literature 1 discloses that a grinding fluid supply pipe is bent in the axial direction of the grinding stone shaft and a jet port of the grinding fluid is arranged toward the hole to be machined.

[0005] PRIOR ART DOCUMENTS

[0006] PATENT LITERATURE

[0007] Patent Literature 1: Japanese Laid-Open Patent Publication No. 2014-69303 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] However, if the grinding stone shaft is shortened to ensure the rigidity of the grinding stone shaft in order to shorten the machining time required for spark-out grinding, the distance between the workpiece and the wheel head becomes too short when the deepest part of the hole to be machined is ground, and it becomes difficult to appropriately arrange the jet port of the grinding fluid. If the grinding fluid cannot be sufficiently supplied to the grinding site, adverse phenomena such as grinding burn in which the temperature of the grinding site reaches 500°C or more, and shortening of the life of the grinding stone occur.

[0010] An object of the present disclosure is to provide a grinding method and a grinding device that can shorten the grinding stone shaft to ensure the rigidity of the grinding stone shaft and can sufficiently supply the grinding fluid to the grinding site of the workpiece.

[0011] Technical solution to solve the technical problem

[0012] The first aspect is a grinding method of rotating a grinding stone 13 mounted on a grinding stone shaft 12 protruding from a grinding stone seat 11 to perform internal circular grinding on a workpiece 1, the distance between the grinding stone seat 11 and the workpiece 1 during grinding being varied, the distance being 5 mm or less when the deepest part of the workpiece 1 is ground, and the grinding fluid discharged from a jet unit 21 provided so as to cover the outer peripheral surface of the grinding stone seat 11 being supplied to the grinding site of the workpiece 1.

[0013] In the first aspect, even if the grinding stone shaft 12 is shortened so that the distance between the grinding stone seat 11 and the workpiece 1 during grinding is 5 mm or less, the grinding fluid can be sufficiently supplied from the jet unit 21 covering the outer peripheral surface of the grinding stone seat 11 to the grinding site of the workpiece 1. Therefore, grinding burn can be suppressed, and the wear of the grinding stone 13 can be suppressed to lengthen the life of the grinding stone with shaft.

[0014] The second aspect is a grinding device of rotating a grinding stone 13 mounted on a grinding stone shaft 12 protruding from a grinding stone seat 11 to perform internal circular grinding on a workpiece 1, the grinding device including a jet unit 21 provided so as to cover the outer peripheral surface of the grinding stone seat 11 and jetting a grinding fluid, and a plurality of jet holes 22 provided in the jet unit 21 in a manner to supply the grinding fluid discharged from the jet unit 21 to the grinding site of the workpiece 1.

[0015] In the second aspect, even if the grinding stone shaft 12 is shortened so that the distance between the grinding stone seat 11 and the workpiece 1 during grinding is 5 mm or less, the grinding fluid can be sufficiently supplied from the jet holes 22 of the jet unit 21 covering the outer peripheral surface of the grinding stone seat 11 to the grinding site of the workpiece 1. Therefore, grinding burn can be suppressed, and the wear of the grinding stone 13 can be suppressed to lengthen the life of the grinding stone with shaft.

[0016] The third aspect is based on the second aspect, and a plurality of holes 22 of 2 mm or less in diameter are arranged near the outer peripheral surface of the grinding stone seat 11 as the jet holes 22.

[0017] In the third aspect, since the plurality of holes 22 of small diameter are arranged near the outer peripheral surface of the grinding stone seat 11, the grinding fluid discharged from each hole 22 easily enters the gap between the inner wall surface of the processed hole of the workpiece 1 and the grinding stone shaft 12, so it becomes easy to supply the grinding fluid to the grinding site of the workpiece 1.

[0018] In the fourth aspect, the inclination angle a of the center line of the plurality of holes 22 with respect to the grinding stone shaft 12 is 20° or less, and the plurality of holes 22 are formed so that an extension line of the center line contacts the outer peripheral surface of the grinding stone 13.

[0019] In the fourth aspect, the grinding fluid can be efficiently supplied to the grinding site of the workpiece 1 from a gap between the inner wall surface of the processing hole of the workpiece 1 and the grinding stone shaft 12.

[0020] In the fifth aspect, the grinding stone seat 11 has a frustoconical portion 15 in which the grinding stone shaft 12 is provided at the top, and an inclination angle Θ of the outer peripheral surface of the frustoconical portion 15 with respect to the grinding stone shaft 12 is 0° or more and 20° or less at the top of the frustoconical portion 15.

[0021] In the fifth aspect, it becomes easy to provide the spray holes 22 in the direction toward the grinding site of the workpiece 1 in the spray unit 21 that covers the outer peripheral surface of the frustoconical portion 15. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a side view of the grinding device according to the embodiment (a view observed from a direction perpendicular to the grinding stone shaft).

[0023] Figure 2 is a perspective view of the grinding device according to the embodiment.

[0024] Figure 3 is a sectional view of the grinding device according to the embodiment.

[0025] Figure 4 is a sectional view of the spray unit of the grinding device according to the embodiment (a view showing a section perpendicular to the grinding stone shaft).

[0026] Figure 5 is a perspective view of the spray unit of the grinding device according to the embodiment (half of the spray unit is a sectional view (a view showing a section perpendicular to the grinding stone shaft)).

[0027] Figure 6 is a perspective view of the shaft-equipped grinding stone of the grinding device according to the embodiment.

[0028] Figure 7 is a side view of the shaft-equipped grinding stone of the grinding device according to the embodiment (a view observed from a direction perpendicular to the grinding stone shaft).

[0029] Figure 8 is a sectional view showing details of the spray unit and the shaft-equipped grinding stone of the grinding device according to the embodiment.

[0030] Figure 9 This is a perspective view of the grinding apparatus involved in the modified example.

[0031] Figure 10 This is a cross-sectional view of the grinding apparatus involved in Comparative Example 1.

[0032] Figure 11 This is a cross-sectional view of the grinding apparatus involved in Comparative Example 2. Detailed Implementation

[0033] (Implementation Method)

[0034] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings. It should be noted that this disclosure is not limited to the embodiments shown below, and various modifications can be made without departing from the technical concept of this disclosure. The accompanying drawings are for conceptual illustration of this disclosure; therefore, for ease of understanding, dimensions, scales, or quantities are sometimes exaggerated or simplified as needed. The specific values ​​of the various parameters described in the following embodiments are merely examples and are not limited thereto.

[0035] <Grinding device>

[0036] like Figures 1-7 As shown, the grinding device 100 mainly includes a shaft-mounted grinding stone 10, a wheel head 20, a spraying unit 21, and a grinding fluid supply unit 30. The shaft-mounted grinding stone 10 performs internal grinding on the workpiece 1; the wheel head 20 rotates the shaft-mounted grinding stone 10; the spraying unit 21 sprays grinding fluid; and the grinding fluid supply unit 30 supplies grinding fluid to the spraying unit 21.

[0037] The abrasive grinding stone 10 includes a grinding stone base 11, a grinding stone shaft 12, and a grinding stone 13. The grinding stone base 11 is made of metal; the grinding stone shaft 12 is elongated, with one end supported by the grinding stone base 11; the grinding stone 13 is replaceably mounted on the grinding stone shaft 12. The grinding stone base 11, for example, has a truncated cone portion 15 and a cylindrical portion 16, with the grinding stone shaft 12 positioned at the top of the truncated cone portion 15, and the cylindrical portion 16 connected to the bottom of the truncated cone portion 15 (see reference). Figure 7 The cylindrical portion 16 can also be machined into a wrench-like surface to facilitate its mounting to the wheel head 20. The grinding stone shaft 12 can also be integrally formed from the same material as the grinding stone base 11. If increased rigidity of the grinding stone shaft 12 is desired, it can be inserted into and engaged with the grinding stone base 11 using an ultra-hard material. The grinding stone 13 can be configured, for example, to be cylindrical and fixed to the grinding stone shaft 12 with the grinding stone shaft 12 inserted into its cylindrical hole. The grinding stone 13 rotates together with the grinding stone shaft 12 to perform internal grinding on the workpiece 1. The diameter of the grinding stone 13 is approximately a few millimeters smaller than the diameter of the hole formed in the workpiece 1.

[0038] The grinding stone base 11 of the axle-mounted grinding stone 10 has a fixing member 14 on the side opposite to the grinding stone shaft 12. This fixing member 14 is used to mount the axle-mounted grinding stone 10 onto the rotating mechanism (not shown) of the wheel head 20. The fixing member 14 may also be, for example, a mounting screw or a tapered pin (fastener). The wheel head 20 is configured to allow the axle-mounted grinding stone 10 to move forward and backward axially along the grinding stone shaft 12.

[0039] The spraying unit 21 is arranged to cover at least a portion of the outer peripheral surface of the grinding stone base 11. The spraying unit 21 is supported on the outer wall (non-rotating portion) of the wheel head 20 via a support member 21a, and does not rotate even when the grinding stone base 11 rotates. Viewed axially from the grinding stone shaft 12, the spraying unit 21 is annular, with an opening 21b at its center for insertion of at least the top of the grinding stone base 11. A spraying hole 22 is provided on the end face of the spraying unit 21 located on the grinding stone 13 side, through which grinding fluid is released to the grinding portion of the workpiece 1. Multiple spraying holes 22 are arranged around the opening 21b of the spraying unit 21. By providing multiple spraying holes 22, the flow rate of grinding fluid supplied to the grinding portion of the workpiece 1 can be sufficiently ensured.

[0040] An inlet hole 23, which connects to the grinding fluid supply unit 30, is formed on the outer periphery of the spraying unit 21. An annular connecting hole 24 is formed on the inner periphery of the spraying unit 21 (the portion adjacent to the opening 21b). The connecting hole 24 is connected to the spraying hole 22 and the inlet hole 23, respectively. Thus, the grinding fluid supplied from the grinding fluid supply unit 30 to the spraying unit 21 is supplied to the grinding part of the workpiece 1 through the inlet hole 23 and the connecting hole 24 via the spraying hole 22. The pipe in the grinding fluid supply unit 30 leading to the inlet hole 23 of the spraying unit 21 can also be arranged along the outer wall (non-rotating part) of the wheel head 20.

[0041] In the grinding apparatus 100, the grinding stone 13 can be rotated at a high speed, while the workpiece 1 can be rotated at a low speed. In this case, the workpiece 1 can be held on a rotatable worktable. Alternatively, instead of the structure in which the axle-driven grinding stone 10 and the wheel head 20 move forward and backward together in the axial direction of the grinding stone shaft 12, the workpiece 1 and the worktable holding the workpiece 1 can move forward and backward together in the axial direction of the grinding stone shaft 12. Or, based on this structure, the workpiece 1 and the worktable holding the workpiece 1 can move forward and backward together in the axial direction of the grinding stone shaft 12.

[0042] <Jet Unit>

[0043] In the internal grinding of the workpiece 1, a grinding stone 13 is inserted into a recess (machining hole) provided on the workpiece 1 and rotated to grind the inner surface of the machining hole. The grinding stone 13 inserted into the machining hole of the workpiece 1 can move axially and radially along the grinding stone shaft 12. Thus, the inner surface of the machining hole can be machined into the desired shape.

[0044] In the grinding method of this embodiment, when internal grinding is performed on the workpiece 1, the grinding stone 13 is moved axially along the grinding stone shaft 12, thus changing the distance between the grinding stone seat 11 and the workpiece 1 (the end face of the workpiece 1 located on the side of the grinding stone seat 11). In this embodiment, a shaft-mounted grinding stone 10 with a relatively short grinding stone shaft 12 is used such that when grinding the deepest part of the machined hole of the workpiece 1 with the grinding stone 13 while avoiding contact between the grinding stone seat 11 and the workpiece 1, the distance between the grinding stone seat 11 and the workpiece 1 is 5 mm or less. Therefore, a jetting unit 21 for spraying grinding fluid is provided to cover the outer peripheral surface of the grinding stone seat 11 of the shaft-mounted grinding stone 10, and a jetting hole 22 is provided on the jetting unit 21 to supply the grinding fluid discharged from the jetting unit 21 to the grinding portion of the workpiece 1.

[0045] By mounting the spray unit 21 in such a way that it covers at least the outer peripheral surface near the top of the grinding stone base 11, a plurality of spray holes 22 can be arranged circumferentially around the grinding stone shaft 12 (see reference). Figure 2 Therefore, grinding fluid can be directly sprayed from the spray unit 21 into the grinding area inside the machining hole of the workpiece 1.

[0046] like Figure 8 As shown, the grinding fluid discharged from the injection hole 22 needs to be supplied to the grinding part from the narrow gap between the inner wall of the machining hole of the workpiece 1 and the grinding stone shaft 12. Therefore, the opening diameter of the injection hole 22 is set to about 2 mm or less, preferably a small diameter of about 1 mm or less. In addition, by arranging the injection hole 22 within about 3 mm of the outer peripheral surface of the grinding stone base 11, the distance between the injection hole 22 and the grinding stone shaft 12 is reduced. Furthermore, by providing multiple injection holes 22, even if the injection hole 22 is set to a small diameter, the flow rate of grinding fluid supplied to the grinding part of the workpiece 1 can be sufficiently ensured.

[0047] In addition, such as Figure 8As shown, the jet hole 22 is formed such that the extension line C of the centerline of the jet hole 22 contacts the outer peripheral surface of the grinding stone 13, in order to prevent the grinding fluid discharged from the jet hole 22 from contacting the workpiece 1 and the end faces of the grinding stone 13 located on the grinding stone base 11 side and rebounding. Specifically, the inclination angle α of the extension line C relative to the grinding stone axis 12 (the center axis J of the grinding stone axis 12) is set to 20° or less. In addition, the length of the jet hole 22 (the distance from the connection point with the connecting hole 24 to the opening on the grinding stone 13 side) is made greater than the opening diameter of the jet hole 22, so that the grinding fluid is discharged from the jet hole 22 along the extension line C.

[0048] It should be noted that the end face of the spray unit 21 on the grinding stone 13 side is flush with the end face of the grinding stone base 11 on the grinding stone 13 side, or the end face of the spray unit 21 on the grinding stone 13 side is located further away from the grinding stone 13 than the end face of the grinding stone base 11 on the grinding stone 13 side. Conversely, if the spray unit 21 is located closer to the grinding stone 13 than the end face of the grinding stone base 11 on the grinding stone 13 side, the grinding stone shaft 12 (specifically, the portion between the grinding stone base 11 and the grinding stone 13) needs to be lengthened to prevent the spray unit 21 from contacting the workpiece 1. This would reduce the rigidity of the grinding stone shaft 12.

[0049] <Wheelstone with Axle>

[0050] As described above, in order to reduce the distance between the spray hole 22 of the spray unit 21 and the grinding stone shaft 12 and to make the tilt angle α of the center line (extension line C) of the spray hole 22 relative to the grinding stone shaft 12 (center axis J) less than 20°, the grinding stone 10 with shaft can also be configured as described below.

[0051] like Figure 7 As shown, the grinding stone base 11 with the shaft grinding stone 10 may have a frustum-shaped portion 15 with a grinding stone shaft 12 disposed at the top. At the top of the frustum-shaped portion 15, the inclination angle θ of the outer peripheral surface of the frustum-shaped portion 15 relative to the grinding stone shaft 12 (central axis J) is 0° or more and about 20° or less. In addition, at the top of the frustum-shaped portion 15, the step between the outer peripheral surface of the frustum-shaped portion 15 and the outer peripheral surface of the grinding stone shaft 12 is about 5 mm or less.

[0052] However, if the inclination angle θ of the entire outer circumferential surface of the frustum 15 is less than 20°, the rigidity of the frustum 15, i.e., the grinding stone base 11, will decrease. Therefore, in order to ensure sufficient space for the spray unit 21 so that the spray hole 22 (extension line C) faces the grinding area of ​​the workpiece 1, it is also possible to... Figure 7As shown, a concave surface 15a is provided on the outer peripheral surface of the frustum-shaped portion 15 of the grinding stone base 11. This suppresses any adverse effects on the rigidity of the grinding stone base 11, i.e., the shafted grinding stone 10, while facilitating the opening of the spray hole 22 in the desired direction. For example, the angle θ of the concave surface 15a of the frustum-shaped portion 15 relative to the grinding stone shaft 12 (central shaft J) may be 0° or more and 20° or less at the top of the frustum-shaped portion 15, increasing as it moves from the top to the bottom, and at the bottom of the frustum-shaped portion 15, the concave surface 15a has an angle of 40° or more and 90° or less. It connects to the outer peripheral surface of the cylindrical part 16. (Angle) It is equal to the angle of inclination of the concave surface 15a at the bottom of the truncated cone 15 relative to the central axis J of the grinding stone shaft 12.

[0053] The grinding stone base 11 is shaped by combining a frustum-shaped portion 15 and a cylindrical portion 16. The frustum-shaped portion 15 has an outer peripheral surface that is inclined at, for example, 45° relative to the bottom surface, and a fixing member 14 for mounting to the wheel head 20 is inserted into the cylindrical portion 16. However, Figure 7 In the example shown, the shape of the grinding stone base 11 is such that the outer peripheral surface of the truncated cone portion 15 is replaced by a curved concave surface 15a. For example... Figure 7 As shown, when the abrasive grinding stone 10 is viewed from a direction perpendicular to the grinding stone axis 12, the curve (e.g., parabola, circular arc) of the concave surface 15a begins at the top of the frustum-shaped portion 15, which has a diameter slightly larger than the diameter of the grinding stone 13 (e.g., about 1-2 mm), and extends from an angle θ of approximately 0-20° with respect to the grinding stone axis 12. The angle θ increases as it approaches the bottom of the frustum-shaped portion 15. This curve extends at an angle of 40° or more and 90° or less. It is connected to the outer circumferential surface of the cylindrical part 16, which has a diameter larger than that of the grinding stone 13.

[0054] exist Figure 7 With the shape shown, the rigidity of the grinding stone base 11 is slightly reduced compared to the case where the outer peripheral surface of the truncated cone portion 15 is not concave 15a. However, the reduction in rigidity of the grinding stone base 11 is so small as to not be a problem compared to the increase in rigidity brought about by shortening the grinding stone shaft 11.

[0055] It should be noted that, Figure 8The structure of the shafted grinding stone 10 shown is an example. As long as the inclination angle θ of the outer peripheral surface of the truncated cone portion 15 relative to the grinding stone shaft 12 (central shaft J) at the top of the truncated cone portion 15 (the end on the grinding stone 13 side) is 0° or more and about 20° or less, the jet hole 22 can be opened in the desired direction even if the entire outer peripheral surface of the truncated cone portion 15 is not made concave 15a. Specifically, the outer peripheral surface near the top of the truncated cone portion 15 can be made concave. Alternatively, the outer peripheral surface of the truncated cone portion 15 can be formed by multiple inclined planes with different inclination angles, with the inclination angle of the inclined planes near the top of the truncated cone portion 15 being 0° or more and about 20° or less.

[0056] <Arrangement of injection holes>

[0057] In order to make the grinding fluid discharged from the injection hole 22 of the injection unit 21 contact the outer peripheral surface of the grinding stone 13, it can also be configured as follows. Figure 2 The spray unit 21 and the grinding stone 10 with shaft are shown.

[0058] The minimum distance L1 between the grinding stone base 11 and the workpiece 1 during grinding is 5 mm or less, for example, 4 mm. The distance L2 between the end face of the grinding stone base 11 located on the grinding stone 13 side and the end face of the grinding stone 13 located on the grinding stone base 11 side (the axial length of the portion of the grinding stone shaft 12 without the grinding stone 13) is, for example, 7.5 mm. The opening diameter of the jet hole 22 is about 2 mm or less, for example, 1 mm. The inclination angle α of the centerline (extension line C) of the jet hole 22 relative to the grinding stone shaft 12 (center axis J) is 20° or less, for example, 16°. The radius D2 of the top of the grinding stone base 11 is about 1 to 3 mm larger than the radius D1 of the grinding stone 13, for example, D1 is 5.75 mm and D2 is 7 mm.

[0059] In the above structure, the distance L3 between the center of the nozzle 22 and the grinding wheel shaft 12 (central shaft J) is greater than "D1+L2×tan(α)" (7.85mm in this example), for example, setting this distance L3 to 8.21mm. The reason is that if L3 is less than "D1+L2×tan(α)", the grinding fluid released from the nozzle 22 cannot reach the outer peripheral surface of the grinding wheel 13.

[0060] <Modified Example of Injection Unit>

[0061] exist Figure 9 In the embodiment shown, the spray unit 21 is arranged to surround the entire outer periphery of the grinding stone base 11 (frustum portion 15) with the shaft 10. This makes it easy to increase the number of spray holes 22.

[0062] On the other hand, Figure 10In the modified example shown, in order to facilitate the disassembly of the spray unit 21, the spray unit 21 is configured in a semi-circular or U-shaped manner, for example, to surround a portion of the outer periphery of the grinding stone base 11 (frustum-shaped portion 15) (about half a circumference in this example). When the grinding fluid supply section 30 is composed of a flexible pipe that is separate from the wheel head 20, the spray unit 21 can also be disassembled together with the pipe.

[0063] <Features of the implementation methods (including variations)>

[0064] The grinding method of this embodiment is a grinding method that uses a grinding stone 13 mounted on a grinding stone shaft 12 protruding from the grinding stone base 11 to perform internal grinding on the workpiece 1. The distance between the grinding stone base (11) and the workpiece (1) changes during grinding, and the distance is less than 5 mm when grinding the deepest part of the workpiece (1). Grinding fluid discharged from the spray unit 21, which is provided in a manner that covers the outer peripheral surface of the grinding stone base 11, is supplied to the grinding part of the workpiece 1.

[0065] In the grinding method of this embodiment, even if the grinding stone shaft 12 is shortened so that the distance between the grinding stone seat 11 and the workpiece 1 during grinding is 5 mm or less, grinding fluid can still be adequately supplied to the grinding portion of the workpiece 1 from the spray unit 21 covering the outer peripheral surface of the grinding stone seat 11. Therefore, grinding burns can be suppressed, and wear of the grinding stone 13 can be suppressed, thus extending the life of the shafted grinding stone. In addition, since the grinding stone shaft 12 can be shortened, the reduction in machining accuracy caused by the deflection of the grinding stone shaft 12 can be suppressed, and the time required for sparkless grinding can be shortened, thereby reducing the machining time and increasing the machining speed.

[0066] The grinding apparatus 100 of this embodiment rotates a grinding stone 13 mounted on a grinding stone shaft 12 protruding from a grinding stone base 11 to perform internal grinding on a workpiece 1. The grinding apparatus 100 includes a spray unit 21 arranged to cover the outer peripheral surface of the grinding stone base 11. The spray unit 21 has spray holes 22 for spraying grinding fluid. The spray holes 21 are provided in the spray unit 22 to supply grinding fluid discharged from the spray holes 22 to the grinding portion of the workpiece 1.

[0067] In the grinding apparatus 100 of the embodiment, even if the grinding stone shaft 12 is shortened so that the distance between the grinding stone seat 11 and the workpiece 1 during grinding is 5 mm or less, grinding fluid can still be adequately supplied to the grinding portion of the workpiece 1 from the spray holes 22 of the spray unit 21 covering the outer peripheral surface of the grinding stone seat 11. Therefore, grinding burns can be suppressed, and wear of the grinding stone 13 can be suppressed, thus extending the life of the shafted grinding stone. In addition, since the grinding stone shaft 12 can be shortened, the reduction in machining accuracy caused by the deflection of the grinding stone shaft 12 can be suppressed, and the time required for sparkless grinding can be shortened, thereby reducing the machining time and increasing the machining speed.

[0068] On the other hand, if the grinding fluid supply pipe is bent along the axial direction of the grinding stone shaft and the nozzle of the grinding fluid supply pipe is arranged towards the machining hole as in the past, if like Figure 11 As shown in Comparative Example 1, where the grinding stone shaft 12 is longer, the grinding fluid injection nozzle 31 can be arranged toward the machining hole. However, if, like in Comparative Example 1, the grinding stone shaft 12 is longer, the grinding fluid injection nozzle 31 can be arranged toward the machining hole. Figure 10 As shown in Comparative Example 2, where the grinding stone shaft 12 is shorter, it is impossible to arrange the grinding fluid injection nozzle 31 towards the machining hole. It should be noted that... Figure 11 Comparative Example 1 and Figure 3 In Comparative Example 2 shown, for the comparison with Figure 11 The same elements in the illustrated implementation are labeled with the same symbols. As mentioned above, to ensure rigidity, it is desirable to keep the grinding stone shaft as short as possible. However, if the distance between the grinding stone base, the wheel head, and the workpiece becomes approximately 5mm or less, then... ​ As shown in Comparative Example 2, the machining hole of the workpiece is blocked by the grinding stone seat and wheel head, making it impossible to properly arrange the grinding fluid injection nozzle. As a result, the grinding fluid cannot be adequately supplied to the grinding part of the workpiece, leading to adverse phenomena such as grinding burns where the temperature of the grinding part reaches 500°C or higher, and a shortened grinding stone life.

[0069] In the grinding apparatus 100 of this embodiment, a plurality of small-diameter injection holes 22 (2 mm or less) may be arranged near the outer peripheral surface of the grinding stone base 11. This allows the grinding fluid released from the injection holes 22 to easily enter the gap between the inner wall of the workpiece 1's machining hole and the grinding stone shaft 12, thus facilitating the supply of grinding fluid to the grinding portion of the workpiece 1. In this case, each injection hole 22 may be provided with an inclination angle α of 20° or less relative to the grinding stone shaft 12 (central axis J) of the centerline (extension line C) of the injection hole 22, and with the extension line C contacting the outer peripheral surface of the grinding stone 13. This allows for efficient supply of grinding fluid to the grinding portion of the workpiece 1 from the gap between the inner wall of the workpiece 1's machining hole and the grinding stone shaft 12.

[0070] In the grinding apparatus 100 of the embodiment, the grinding stone base 11 may have a frustum-shaped portion 15 with a grinding stone shaft 12 disposed at its top, and the angle θ of the outer peripheral surface of the frustum-shaped portion 15 relative to the grinding stone shaft 12 is 0° or more and 20° or less. In this way, it becomes easier to provide spray holes 22 in the spray unit 21 covering the outer peripheral surface of the frustum-shaped portion 15 toward the grinding portion of the workpiece 1.

[0071] (Other implementation methods)

[0072] The embodiments and variations have been described above. However, it should be understood that various changes can be made to the methods and specific circumstances without departing from the spirit and scope of the claims. Furthermore, the above embodiments, variations, and other embodiments can be appropriately combined or substituted.

[0073] -Industry Applicability-

[0074] In summary, this disclosure is useful for grinding methods and grinding apparatus.

[0075] - Symbol Explanation -

[0076] 1. Workpiece

[0077] 11. Millstone base

[0078] 12 millstone shafts

[0079] 13. Grinding stone

[0080] 15. Frustum conical section

[0081] 21 Injection Units

[0082] 22 Injection holes

[0083] 100 Grinding Device

Claims

1. A grinding method of rotating a grinding stone (13) mounted on a grinding stone shaft (12) protruding from a grinding stone seat (11) to perform internal grinding of a workpiece (1), characterized in that: a distance between the grinding stone seat (11) and the workpiece (1) during grinding is varied, the distance when grinding a deepest portion of the workpiece (1) is 5 mm or less, and grinding fluid discharged from a discharge unit (21) provided so as to cover an outer circumferential surface of the grinding stone seat (11) is supplied to a grinding site of the workpiece (1).

2. A grinding device of rotating a grinding stone (13) mounted on a grinding stone shaft (12) protruding from a grinding stone seat (11) to perform internal grinding of a workpiece (1), characterized in that: the grinding device includes a discharge unit (21) provided so as to cover an outer circumferential surface of the grinding stone seat (11) and discharge grinding fluid, and a plurality of discharge holes (22) are provided in the discharge unit (21) so as to supply the grinding fluid discharged from the discharge unit (21) to a grinding site of the workpiece (1).

3. The grinding device according to claim 2, characterized in that: a plurality of holes (22) of a small diameter of 2 mm or less are arranged near the outer circumferential surface of the grinding stone seat (11) as the discharge holes (22).

4. The grinding device according to claim 3, characterized in that: a tilt angle α of a center line of the plurality of holes (22) with respect to the grinding stone shaft (12) is 20° or less, and the plurality of holes (22) are opened so that an extension line of the center line contacts an outer circumferential surface of the grinding stone (13).

5. The grinding device according to any one of claims 2 to 4, characterized in that: the grinding stone seat (11) has a circular truncated cone portion (15) in which the grinding stone shaft (12) is provided at a top portion, and a tilt angle Θ of an outer circumferential surface of the circular truncated cone portion (15) with respect to the grinding stone shaft (12) is 0° or more and 20° or less at the top portion of the circular truncated cone portion (15). ​ ​ ​ ​ ​ ​ ​ ​ ​

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