Processing device

Abstract

To provide a processing device which enables improvement of sphericity regardless of a state of a material for forming green balls.SOLUTION: A first surface plate 10 includes a first surface 10f and contacts with green balls 91. A second surface plate 20 includes a second surface 20f which faces the first surface 10f and contacts with the green balls. The second surface plate 20 includes an outer peripheral part 20B. Polishing layers 10C, 20C are included in at least one of the first surface plate 10 and the second surface plate 20. In a plan view, the first surface plate 10 is larger than the second surface plate 20. On the second surface plate 20f, a groove 25 in which the green balls 91 are fitted is formed.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a processing device. [Background technology]

[0002] When forming ceramic spheres made of silicon nitride, generally, a binder is included in the green ball, but there are cases where the binder is not included. According to the processing device disclosed in JP 2022-53267 A (Patent Document 1), even if a special method that does not include a binder is used, it is possible to suppress cracking during grinding of multiple green balls that have significantly different diameters from each other in the initial state. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-53267 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the technology disclosed in JP 2022-53267 A, when the green ball is polished, the green ball comes into contact with the first lower platen at one point and the second upper platen at one point, for a total of two points. In this case, the diameter difference, which is the difference between the maximum and minimum diameters of the green ball, becomes small, but there is an issue that the sphericity of the green ball becomes poor (the dimensional error relative to a perfect sphere becomes large).

[0005] An object of the present invention is to provide a processing device that can improve sphericity regardless of the state of the material used to form the green ball. [Means for solving the problem]

[0006] The processing device according to the present disclosure includes a first member, a second member, and a polishing layer. The first member includes a first surface that holds the green ball by contacting the green ball. The second member faces the first surface and includes a second surface that holds the green ball by contacting the green ball, and includes an outer periphery that extends so as to protrude in a first direction intersecting the second surface and surrounds the green ball sandwiched between the first surface and the second surface. The polishing layer is included in at least one of the first member and the second member, includes at least one of the first surface and the second surface, and polishes the green ball by contacting the green ball. The first member has a larger area in a plan view than the second member. The first member and the second member cause the green ball to revolve and rotate by relative motion of multiple systems. A groove into which the green ball fits is formed on the second surface. The direction perpendicular to the second surface and along the vertical direction is defined as the first direction. Here, the plan view means the same as the plan view in the JIS B 0001 standard. Effect of the Invention

[0007] According to the present disclosure, a processing device can be provided that can improve sphericity regardless of the state of the material used to form the green ball. [Brief description of the drawings]

[0008] [Figure 1] This is a schematic processing diagram showing an overall structure of the processing device used for polishing green balls in this embodiment. [Diagram 2] FIG. 2 is a schematic plan view showing the structure of a first polishing layer. [Diagram 3] FIG. 2 is a schematic plan view showing the structure of a second polishing layer. [Figure 4] 2 is a schematic cross-sectional view showing a first embodiment of a second polishing layer included in a second platen. FIG. [Diagram 5] 4 is a schematic cross-sectional view showing a second embodiment of a second polishing layer included in a second platen. FIG. [Figure 6] 10 is a schematic plan view showing a state in which a protrusion is seen through from above a second base plate in a plan view. FIG. [Figure 7]3 is a schematic cross-sectional view showing a first example of a cross-sectional shape of a groove in the present embodiment. FIG. [Figure 8] 6 is a schematic cross-sectional view showing a second example of the cross-sectional shape of a groove in the present embodiment. FIG. [Figure 9] FIG. 11 is a schematic cross-sectional view showing a third example of the cross-sectional shape of the groove in the present embodiment. [Figure 10] 13 is a schematic cross-sectional view showing a fourth example of the cross-sectional shape of the groove in the present embodiment. FIG. [Figure 11] 13 is a schematic plan view showing a second base plate having a fifth example of a cross-sectional shape of a groove in the present embodiment, as seen through from above in a plan view. FIG. [Figure 12] 10 is a schematic cross-sectional view showing a fifth example of the cross-sectional shape of a groove in the present embodiment. FIG. [Figure 13] 1 is a schematic cross-sectional view showing the positional relationship between a green ball and a second platen at the beginning of a polishing process. FIG. [Figure 14] 10 is a schematic cross-sectional view showing the positional relationship between the green ball and the second platen in a later stage of the polishing process. FIG. [Figure 15] 1A to 1C are schematic diagrams showing three examples of the state of the first surface and the second surface when the green ball makes one-point contact with each of the first surface and the second surface. [Figure 16] 16 is a schematic diagram showing how a green ball comes into contact with the first and second surfaces of each of the three examples in FIG. 15 and is polished. [Figure 17] This is a schematic diagram showing the planar shapes of a green ball with good sphericity and a green ball with poor sphericity stacked on top of each other. [Figure 18] 2 is a schematic plan view showing a first rotation state in which the first platen rotates counterclockwise and the second platen rotates clockwise. FIG. [Figure 19] 19 is a schematic cross-sectional view of a portion taken along line XIX-XIX in FIG. 18. [Figure 20] 19 is a schematic cross-sectional view of a portion taken along line XX-XX in FIG. 18. [Figure 21] 11 is a schematic plan view showing a second rotation state in which the first platen rotates counterclockwise and the second platen also rotates counterclockwise. FIG. [Figure 22]22 is a schematic cross-sectional view of a portion taken along line XXII-XXII in FIG. 21. [Diagram 23] 23 is a schematic cross-sectional view of a portion taken along line XXIII-XXIII in FIG. 21. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are given the same reference numerals, and the description thereof will not be repeated. For convenience of explanation, the X-direction and the Y-direction, which are horizontal and perpendicular to each other, and the Z-direction, which is perpendicular to these and parallel to the vertical direction, are introduced. The XY plane along the X-direction and the Y-direction may be referred to as a plane hereinafter.

[0010] Fig. 1 is a schematic processing diagram showing the structure of a processing device used for polishing green balls according to this embodiment. In other words, Fig. 1 shows the general characteristics of each example described below. Referring to Fig. 1, a processing device 1, which is a polishing device for green balls according to this embodiment, mainly includes a first base plate 10 as a first member and a second base plate 20 as a second member.

[0011] In Fig. 1, the first base plate 10 has a larger area in a plan view than the second base plate 20. In other words, the dimension D in Fig. 1 is larger than the dimension d. The first base plate 10 is disposed below the second base plate 20. As a result, the second base plate 20 is disposed directly above the first base plate 10 so as to face the first base plate 10 in the Z direction. However, this is not limiting, and for example, the second base plate 20 may be disposed directly below the first base plate 10 so as to face the first base plate 10 in the Z direction.

[0012] In FIG. 1, the leftmost end of the second platen 20 is located to the right of the central axis α of the first platen 10 in a plan view. In FIG. 1, the rightmost end of the second platen 20 is located to the left of the rightmost end of the first platen 10. Therefore, the dimension d in FIG. 1 is less than 1 / 2 of the dimension D. In this way, the axis α of the first platen 10 and the area adjacent thereto can be easily cleaned. However, the leftmost end of the second platen 20 may be located to the left of the central axis α of the first platen 10 in a plan view. Even in this case, at least the polishing performance does not change significantly from the example in FIG. 1.

[0013] The first base plate 10 includes a first surface 10f that holds the green ball 91 by contacting the green ball 91. The first surface 10f is a plane that extends along the XY plane including the X-axis and the Y-axis. The first base plate 10 includes a first flat plate portion 10A and a first outer peripheral portion 10B, and may further include a first polishing layer 10C. The first flat plate portion 10A is a main member that constitutes the first base plate 10, and its surface extends along the XY plane. The first flat plate portion 10A has a circular surface along the XY plane, for example, and has a disk shape with a substantially constant dimension in the Z direction throughout. The green ball 91 polished by the processing device 1 is preferably made of a powder of any one of ceramics and metal, and the powder may further include a resin material.

[0014] In FIG. 1, the first outer peripheral portion 10B is a separate member from the first flat plate portion 10A. However, the first outer peripheral portion 10B may be the same member, i.e., integral, as the first flat plate portion 10A. The first outer peripheral portion 10B has a shape that overlaps with the outermost edge of the first flat plate portion 10A in a plan view and the area adjacent to the outermost edge and the inner side of the first flat plate portion 10A in a plan view. If the first flat plate portion 10A is circular in a plan view, the first outer peripheral portion 10B is annular. The first outer peripheral portion 10B has a substantially constant dimension extending in the Z direction throughout. The first outer peripheral portion 10B extends so as to protrude from the first flat plate portion 10A upward in the Z direction (toward the second base plate 20). The first outer peripheral portion 10B is provided to prevent abrasive powder and the like from the green ball 91 from leaking out to the outside of the first base plate 10. Both the first flat plate portion 10A and the first outer peripheral portion 10B are formed from a commonly known steel material or the like.

[0015] In the Z direction, a first polishing layer 10C may be sandwiched between the first flat plate portion 10A and the first outer peripheral portion 10B. The first polishing layer 10C polishes the green ball 91 by contacting the green ball 91. The first polishing layer 10C has approximately the same planar shape and area as the first flat plate portion 10A. Therefore, the first polishing layer 10C is disposed so as to overlap approximately on the first flat plate portion 10A. The first outer peripheral portion 10B is disposed on the first polishing layer 10C. Therefore, the first surface 10f is exposed in the area of ​​the first polishing layer 10C except for the outermost edge and the area adjacent thereto in a plan view. For example, the surface of the first polishing layer 10C facing the second base plate 20 on the upper side corresponds to the first surface 10f.

[0016] When the first base plate 10 has the first polishing layer 10C, the first surface 10f is included in the first polishing layer 10C and serves as a polishing surface for polishing the green ball. In this case, the first surface 10f is the surface of the first polishing layer 10C that is closest to the second base plate 20 in the Z direction. When the first base plate 10 does not have the first polishing layer 10C, the first surface 10f is included in the first flat plate portion 10A but is not a polishing surface. In this case, the first surface 10f is the surface of the first flat plate portion 10A that is closest to the second base plate 20 in the Z direction.

[0017] The second base plate 20 includes a second surface 20f that faces the first surface 10f in the vertical direction, for example, and holds the green ball 91 by contacting the green ball 91. The second surface 20f is a plane that extends along the XY plane. The second base plate 20 includes a second flat plate portion 20A and a second outer peripheral portion 20B, and may further include a second polishing layer 20C. The second flat plate portion 20A is a main member that constitutes the second base plate 20, and has a surface that extends along the XY plane. The second flat plate portion 20A has a surface that is, for example, circular along the XY plane, and has a disk shape with a substantially constant dimension in the Z direction throughout.

[0018] In FIG. 1, the second outer peripheral portion 20B is a separate member from the second flat plate portion 20A. However, the second outer peripheral portion 20B may be the same member, i.e., integral, as the second flat plate portion 20A. The second outer peripheral portion 20B has a shape that overlaps with the outermost edge of the second flat plate portion 20A in a plan view and the area adjacent to the outermost edge and the inner side of the second flat plate portion 20A in a plan view. If the second flat plate portion 20A is circular in a plan view, the second outer peripheral portion 20B is annular. The second outer peripheral portion 20B has a substantially constant dimension extending in the Z direction throughout. As a result, the second outer peripheral portion 20B extends so as to protrude downward (toward the first base plate 10) from the second flat plate portion 20A in the Z direction (first direction). The second outer peripheral portion 20B is provided to surround the green ball 91 that is sandwiched between the first surface 10f and the second surface 20f. The second flat plate portion 20A and the second outer peripheral portion 20B are both formed of a commonly known steel material or the like.

[0019] In the Z direction, the second polishing layer 20C may be sandwiched between the second flat plate portion 20A and the second outer peripheral portion 20B, but it does not have to be sandwiched. The second polishing layer 20C polishes the green ball 91 by contacting the green ball 91. The second polishing layer 20C may have a planar shape and area (size) substantially the same as those of the second flat plate portion 20A. Alternatively, the second polishing layer 20C may have a slightly smaller area in plan view than the second flat plate portion 20A. It is preferable that the second polishing layer 20C has a planar area at least larger than the inner wall surface of the second outer peripheral portion 20B. In this way, the second polishing layer 20C can be fixed so as to be sandwiched between the second flat plate portion 20A and the second outer peripheral portion 20B. The second outer peripheral portion 20B is placed under the second polishing layer 20C. Therefore, the second surface 20f is exposed in the area of ​​the second polishing layer 20C except for the outermost edge in plan view and the area adjacent thereto. For example, the surface of the second polishing layer 20C facing the lower first platen 10 corresponds to the second surface 20f.

[0020] When the second base plate 20 has the second polishing layer 20C, the second surface 20f is included in the second polishing layer 20C and serves as a polishing surface for polishing the green ball 91. In this case, the second surface 20f is the surface of the second polishing layer 20C that is closest to the first base plate 10 in the Z direction. When the second base plate 20 does not have the second polishing layer 20C, the second surface 20f is included in the second flat plate portion 20A but is not a polishing surface. In this case, the second surface 20f is the surface of the second flat plate portion 20A that is closest to the first base plate 10 in the Z direction.

[0021] Both the first surface 10f and the second surface 20f contact the green ball 91 so as to sandwich the green ball 91. In FIG. 1, the first surface 10f is included in the first polishing layer 10C, and the second surface 20f is included in the second polishing layer 20C. Each of the multiple green balls 91 to be polished is arranged so as to be surrounded by the first polishing layer 10C, the second polishing layer 20C, and the second outer periphery 20B. The second base plate 20 is capable of rolling and holding the green ball 91 by surrounding the green ball 91 with the second flat plate portion 20A and the second outer periphery 20B.

[0022] 2 is a schematic plan view showing the structure of the first polishing layer. Referring to FIG. 2, the first polishing layer 10C as the polishing layer may be, for example, a grindstone. However, in this embodiment, the first polishing layer 10C is made of a lattice member such as a wire mesh having a lattice shape of lattice mesh 11a through which abrasive powder can pass. The wire mesh of the first polishing layer 10C is made of a generally known steel material. The dimensions of the lattice mesh 11a in the X and Y directions are, for example, d1, which is sufficiently smaller than the dimension d in FIG. 1.

[0023] Alternatively, although not shown, the first polishing layer 10C may be formed by a so-called texture instead of the wire mesh shown in FIG. 2. The texture is a structure having minute irregularities formed by melt processing by irradiating an electron beam on the surface of a generally known steel material similar to the wire mesh. The first polishing layer 10C may also be roughened by shot blasting. The first polishing layer 10C may be grooved (knurled) by a grindstone with a size of about 0.1 mm to 1.0 mm.

[0024] 3 is a schematic plan view showing the structure of the second polishing layer. Referring to FIG. 3, when the second polishing layer 20C is provided as the polishing layer, the second polishing layer 20C has the same structure as the first polishing layer 10C. That is, the second polishing layer 20C may be, for example, a grindstone. However, the second polishing layer 20C is made of a lattice member such as a wire mesh formed of a generally known steel material, and has a lattice shape with meshes 21a through which polishing powder can pass. Alternatively, although not shown, the second polishing layer 20C may be formed by a so-called texture instead of the wire mesh shown in FIG. 3.

[0025] The second surface 20f is formed with a groove 25 into which the green ball 91 fits. In this specification, the second surface 20f includes the inner wall surface of the groove 25 (a surface recessed by the groove 25 compared to the area other than the groove 25). The groove 25 is formed so as to extend in an annular shape in an area adjacent to the outer edge of the second polishing layer 20C or the second flat plate portion 20A in a plan view. For example, if the second flat plate portion 20A and the second polishing layer 20C have a disk shape, the groove 25 has a planar shape of an annular shape along their outer edges. The groove 25 in FIG. 3 is formed over the entire circumferential direction of the second polishing layer 20C. The circumferential direction is the direction along the circular circumference of the second polishing layer 20C (groove 25) in FIG. 3. However, the configuration is not limited to this, and the groove 25 may be formed so as to be partially intermittent in the circumferential direction.

[0026] The polishing layers 10C, 20C are included in at least one of the first platen 10 and the second platen 20. That is, the polishing layer includes at least one of the first surface 10f and the second surface 20f. The polishing layers 10C, 20C polish the green ball 91 by contacting the green ball 91. By being polished, the green ball 91 becomes closer to a perfect sphere. At this time, the first platen 10 and the second platen 20 cause the green ball 91 to revolve and rotate by multiple relative motions. Note that the multiple relative motions of the first platen 10 and the second platen 20 include, for example, rotations of the first platen 10 and the second platen 20 around different axes, or a combination of rotation of one platen and straight movement of the other platen. As a result, the green ball 91 is subjected to an appropriate combination of revolution and rotation in various directions.

[0027] FIG. 4 is a schematic cross-sectional view showing a first embodiment of the second polishing layer included in the second platen. FIG. 4 shows a cross section perpendicular to the extension direction of the groove 25 (the same applies to the subsequent figures of the same embodiment). Referring to FIG. 4, the second polishing layer 20C may be formed thinly on the bottom surface of the second flat plate portion 20A, for example. In this case, the second polishing layer 20C is placed along the inner wall surface of the groove 25 of the second flat plate portion 20A so as to follow the shape of the groove 25 formed in the second flat plate portion 20A. Therefore, the second surface 20f of the second polishing layer 20C is formed in the shape of the groove 25.

[0028] Fig. 5 is a schematic cross-sectional view showing a second embodiment of the second polishing layer included in the second platen. Referring to Fig. 5, the second polishing layer 20C may be formed on the lowermost surface of the second flat plate portion 20A, for example, to be thicker than the example shown in Fig. 3, and may have a groove 25 formed in a part of it.

[0029] The other members will be described with reference to Fig. 1 again. In addition to the above, the processing device 1 further includes a protrusion 27, a first shaft 12, a second shaft 22, and a rotation reversal mechanism 21. The protrusion 27 is attached to the second surface 20f of the second base plate 20. The protrusion 27 protrudes toward the first surface 10f of the first base plate 10, for example, downward in the Z direction.

[0030] FIG. 6 is a schematic plan view showing the protrusions seen through from the upper side of the second base plate in a plan view. Referring to FIG. 6, the portion of the protrusions 27 that contacts and is fixed to the second surface 20f included in the second base plate 20 (the second flat plate portion 20A or the second polishing layer 20C) has a planar shape like an impeller. The protrusions 27 are plate-shaped members having an impeller shape of a centrifugal water pump. The protrusions 27 surround the center of the second base plate 20 in a plan view (the center portion passing through the axis β in FIG. 1 and FIG. 6), and are arranged at intervals in the circumferential direction. In FIG. 6, eight protrusions 27 are attached as an example. However, the number of protrusions 27 attached to one processing device 1 (second base plate 20) is not limited to this and is arbitrary. For example, the number of protrusions 27 provided on one processing device 1 may be any of 2, 3, 4, 6, 10, and 12. Alternatively, the number of protrusions 27 provided on one processing apparatus 1 may be any of 5, 7, 8, 9, and 11. These multiple protrusions 27 are fixed to the second abrasive layer 20C or the like at an interval W1 in the circumferential direction. The interval W1 need only have a width that allows the green ball 91 to pass through. Therefore, the interval W1 is larger than the maximum diameter of the green ball 91. To achieve this configuration, a pair of protrusions 27 adjacent to each other in the circumferential direction may partially overlap.

[0031] Each of the multiple protrusions 27 is attached to a region closer to the center of the second base plate 20 than the groove 25, i.e., closer to the axis β. In other words, each of the multiple protrusions 27 is disposed between the groove 25 and the center of the second base plate 20 in the radial direction (the direction along the diameter of the circle of the second base plate 20).

[0032] 6, each of the multiple (eight) protrusions 27 may be arranged such that one end in a plan view is closer to the center of the second base plate 20 than the other end opposite to the one end. One end of the protrusion 27 closer to the center of the second base plate 20 may be configured to have a shorter (thinner) width intersecting the extending direction in a plan view than the other end away from the center of the second base plate 20.

[0033] Each of the multiple protrusions 27 may be arranged such that the width between adjacent protrusions 27 in the circumferential direction increases as one moves from one end side to the other end side. In Fig. 6, the multiple protrusions 27 viewed from above (the rotation reversal mechanism 21 side) are curved so that the direction from one end to the other end is along the clockwise direction. When the green ball 91 is polished while the first base plate 10 and the second base plate 20 are rotated as described below, it is preferable that the multiple protrusions 27 are curved along the clockwise direction.

[0034] There is no particular limitation on the material of the protrusion 27. The protrusion 27 is formed of, for example, any one of a metal material, a resin material, and a ceramic material.

[0035] Referring again to FIG. 1, the first shaft 12 is connected to the first base plate 10 so as to protrude downward in FIG. 1, which is the side opposite to the side facing the second base plate 20. A bearing 13 is fitted to the outer peripheral surface of the first shaft 12. This bearing 13 is held by an outer peripheral member 14. With the above configuration, the first base plate 10 can rotate in the circumferential direction, for example as shown by the arrow R1 in FIG. 1, around an axis α that coincides with the central axis of the first shaft 12. In other words, the first shaft 12 rotates the first base plate 10 around the axis α that intersects with the center of the first surface 10f. Therefore, the first flat plate portion 10A can also rotate around the first shaft 12.

[0036] The second shaft 22 is connected to the second base plate 20 so as to protrude upward in FIG. 1, which is the side opposite to the side facing the first base plate 10. A bearing 23 is fitted to the outer peripheral surface of the second shaft 22. This bearing 23 is held by an outer peripheral member 24. With the above configuration, the second base plate 20 can rotate in the circumferential direction, for example as shown by the arrow R2 in FIG. 1, around an axis β that coincides with the central axis of the second shaft 22. In other words, the second shaft 22 rotates the second base plate 20 around an axis β that intersects with the center of the second surface 20f. Therefore, the second flat plate portion 20A can also rotate around the second shaft 22. Note that the axis β is different from the axis α, and the axis β is parallel to the axis α.

[0037] The rotation reversing mechanism 21 is capable of reversing the rotation direction of the second base plate 20, i.e., the rotation direction in which the second base plate 20 rotates around the axis β of the second shaft 22. The rotation reversing mechanism 21 in Fig. 1 is placed on the second shaft 22, penetrated by the axis β, and has a smaller area in plan view than the second shaft 22. However, the location where the rotation reversing mechanism 21 is installed and the area in plan view are not limited to those described above.

[0038] The rotation reversal mechanism 21 may be configured, for example, by a servo motor, a power supply for the servo motor, and a PLC (Programmable Logic Controller), but is not limited thereto. For example, the rotation reversal mechanism 21 having the above configuration controls the rotation direction, rotation speed, etc. of the second base plate 20 by the PLC. By constructing a ladder (a sequence program for ladder control) in the PLC, PLC control is possible. Specifically, a gap sensor (not shown) measures the distance in the Z direction between the first surface 10f of the first base plate 10 and the second surface 20f of the second base plate 20. When the polishing process of the green ball 91 progresses to a certain extent, the sensor detects that the distance in the Z direction has decreased to a certain value. At this time, an alarm signal is input from the sensor to the PLC. After that, the rotation direction of the servo motor is reversed by the sequence program. This reverses the rotation direction of the second base plate 20. At this time, as will be described later, the green ball 91 moves to the outside of the second base plate 20 or is polished while being fitted in the groove 25.

[0039] (Modifications of the shape of the groove 25) In the following figures, the second polishing layer 20C is omitted. However, the contents described below are applicable to both cases where the second polishing layer 20C is provided on the second base plate 20 and where it is not provided. FIG. 7 is a schematic cross-sectional view showing a first example of the cross-sectional shape of the groove in this embodiment. Referring to FIG. 7, the cross-section of the groove 25 perpendicular to the direction in which the groove 25 extends is a shape in which two wall surfaces extending in a direction inclined with respect to the Z direction intersect. Specifically, the groove 25A, which is a part of the second surface 20f in FIG. 7, has two inner wall surfaces 25a1 and 25a2. The inner wall surface 25a1 and the inner wall surface 25a2 are linear in the cross-sectional view of FIG. 7, but are actually curved surfaces extending in an annular shape when viewed from above in the Z direction. The two inner wall surfaces 25a1 and 25a2 having linear cross-sectional shapes intersect at the top in the Z direction, so that the groove 25A has a cross-sectional shape obtained by upside-down inversion of the letter V. The intersection of groove 25A and second surface 20f is a circular intersection line. The intersection line is shown as intersection points 21A and 21B in Fig. 7. Groove 25A formed by connecting the three points of the uppermost portion, intersection point 21A, and intersection point 21B forms a triangle (isosceles triangle) on the cross section of Fig. 7.

[0040] The green ball 91 that fits into the groove 25A contacts each of the inner wall surface 25a1, the inner wall surface 25a2, and the first flat plate portion 10A at one point. The contact point between the green ball 91 and the inner wall surface 25a1 is the second contact point 20P. The contact point between the green ball 91 and the inner wall surface 25a2 is the second contact point 20Q. The contact point between the green ball 91 and the first flat plate portion 10A is the first contact point 10R. In this way, the green ball 91 contacts the first base plate 10 at one point and the second base plate 20 at two points, for a total of three points. In other words, the green ball 91 contacts the processing device 1 at a total of three points.

[0041] For example, in FIG. 7, the angle between the inner wall surface 25a1 and the inner wall surface 25a2 is 90°. The green ball 91 is assumed to be spherical and its center is O. In this case, the angle θ1 between the line segment connecting the center O and the second contact point 20P and the line segment connecting the center O and the second contact point 20Q is 90°. From the viewpoint of obtaining the effect described below by the green ball 91 contacting the processing device 1 at a total of three points, the angle between the inner wall surface 25a1 and the inner wall surface 25a2 constituting the groove 25A may be any angle of 30° or more. The positions of the second contact point 20P and the second contact point 20Q change depending on the magnitude of the angle θ1.

[0042] When the second flat plate portion 20A and the second outer peripheral portion 20B are separate members, they (and the second abrasive layer 20C sandwiched between them) are preferably fixed by, for example, a screw member 30 having a male thread formed thereon. The male thread of the screw member 30 may be fitted into a female thread of a nut (not shown) to fix the second flat plate portion 20A and the second outer peripheral portion 20B. Alternatively, the second flat plate portion 20A and the second outer peripheral portion 20B may be formed with a female thread that fits with the male thread of the screw member 30. It is preferable that the portion from which the male thread of the screw member 30 extends extends so as to penetrate one of the lattice holes 11a.

[0043] FIG. 8 is a schematic cross-sectional view showing a second example of the cross-sectional shape of the groove in this embodiment. With reference to FIG. 8, the cross section of the groove 25 perpendicular to the direction in which the groove 25 extends may be an arc shape. Specifically, the groove 25B, which is a part of the second surface 20f in FIG. 8, has an arc shape that goes around the center of the second base plate 20. The cross-sectional shape of the groove 25B may be formed by an arc of a single circle. However, the cross-sectional shape of the groove 25B may be formed by smoothly connecting a plurality of circles with different curvatures. For example, the cross section of the groove 25B may be an arc shape with different curvatures between the top and bottom in FIG. 8.

[0044] The green ball 91 that fits into the groove 25B makes line contact at the upper part of the groove 25B (the area farthest from the first base plate 10). In other words, the surface of the green ball 91 and the curved surface of the groove 25B make contact at the line contact portion 20L. The line contact portion 20L forms a curve that has the same shape as the arc-shaped cross-sectional shape of the groove 25B.

[0045] In the cross section of FIG. 8, one end of the line contact portion 20L is the second contact 20P, and the end opposite to the second contact 20P is the second contact 20Q. At all points (for example, the second contact 20R) on the line contact portion 20L between the second contact 20P and the second contact 20Q, the surface of the green ball 91 and the curved surface of the groove 25B are in contact. However, at a position slightly away from the cross section of FIG. 8 in the depth direction (Y direction) of the paper, the surface of the green ball 91 and the curved surface of the groove 25B are not in contact. On the other hand, in FIG. 8, the green ball 91 and the first flat plate portion 10A are in contact at one point only at the first contact 10R, as in FIG. 7. Therefore, the green ball 91 is in contact with the processing device 1 at one point and one line.

[0046] In FIG. 8, the angle θ2 formed by the line segment connecting the center O and the second junction point 20P and the line segment connecting the center O and the second junction point 20Q is preferably 30° or more.

[0047] FIG. 9 is a schematic cross-sectional view showing a third example of the cross-sectional shape of the groove in this embodiment. Referring to FIG. 9, the cross section of the groove 25 perpendicular to the direction in which the groove 25 extends may be polygonal. Specifically, the groove 25C in FIG. 9 has three inner wall surfaces 25c1, 25c2, and 25c3. The inner wall surface 25c1 and the inner wall surface 25c2 correspond to the inner wall surfaces 25a1 and 25a2 in FIG. 7, but they do not intersect at the top in the Z direction. At the top of the groove 25C, an inner wall surface 25c3 that is a circular curved surface extending along the XY plane is disposed. The wall surface 25c1 and the inner wall surface 25c2 intersect with the inner wall surface 25c3. The groove 25C formed by the line segment connecting the intersection point 21A and the intersection point 21B and the inner wall surfaces 25c1, 25c2, and 25c3 is a quadrangle (trapezoid) on the cross section in FIG. 9.

[0048] 7, the green ball 91 that fits into the groove 25C contacts the inner wall surface 25c1 at the second contact point 20P, contacts the inner wall surface 25c2 at the second contact point 20Q, and contacts the first flat plate portion 10A at the first contact point 10R. As a result, the green ball 91 contacts the first base plate 10 at one point and the second base plate 20 at two points, for a total of three points.

[0049] Fig. 10 is a schematic cross-sectional view showing a fourth example of the cross-sectional shape of the groove in this embodiment. Referring to Fig. 10, the aspect shown here is roughly the same as Fig. 7. However, Fig. 10 is provided with an elastic member 50. In this respect, Fig. 10 differs from Fig. 7.

[0050] The elastic member 50 is in contact with the inner wall of the second outer periphery 20B. The elastic member 50 has the same shape as the second outer periphery 20B from the viewpoint of being able to inscribe the elastic member 50 in the second outer periphery 20B. Therefore, if the second outer periphery 20B is annular, the elastic member 50 is annular. The elastic member 50 is formed of any of rubber, resin, and sponge. The elastic member 50 is not limited to the configuration of FIG. 7, and may be used in the examples of FIG. 8 to FIG. 9 in the same manner as FIG. 10. The soft elastic member 50 can suppress the problem of the green ball 91 breaking when the green ball 91 moves from the inside to the outside in a plan view and hits the inner wall surface of the second outer periphery 20.

[0051] It is preferable that the inner wall surface of the second outer peripheral portion 20B in Figures 7 to 9 (or the elastic member 50 in Figure 10) closest to the central axis β of the second base plate 20 is sufficiently away from the axis β in the radial direction so as not to come into contact with the green ball fitted into the groove 25. In this way, the second outer peripheral portion 20B (or the elastic member 50) can suppress the problem that the green ball 91 that moves from the center side of the second base plate 20 toward the groove 25 passes over the groove 25 and does not fit into the groove 25. In other words, the second outer peripheral portion 20B (elastic member 50) has the role of guiding the green ball 91 that moves from the center side of the second base plate 20 to the outside so that it fits securely into the groove 25.

[0052] Fig. 11 is a schematic plan view showing a second base plate having a fifth example of the cross-sectional shape of the groove in this embodiment, seen through from above in a plan view. The cross-sectional shape of the groove 25 perpendicular to the direction in which the groove 25 extends may be different between a part of the region of the circumferential groove 25 and another part of the region. Specifically, referring to Fig. 11, in the second base plate 20, the groove 25 has two types of symmetric grooves 25P and asymmetric grooves 25Q. In this respect, Fig. 11 is structurally different from Fig. 6, in which the entire circumferential groove 25 is symmetric groove 25P.

[0053] 12 is a schematic cross-sectional view showing a fifth example of the cross-sectional shape of the groove in this embodiment. Referring to FIG. 12, the cross-sectional shape of the groove 25 in this embodiment, particularly the asymmetric groove 25Q, is asymmetric with respect to an axis of symmetry extending in the Z direction (a straight line extending in the Z direction from the midpoint in the X direction of the line segment connecting the intersections 21A and 21B, not shown). Specifically, the groove 25D, which is a part of the second surface 20f in FIG. 12, has two inner wall surfaces 25d1 and 25d2. The inner wall surface 25d1 and the inner wall surface 25d2 correspond to the inner wall surfaces 25a1 and 25a2 in FIG. 7, but the inner wall surface 25d1 and the inner wall surface 25d2 are not symmetric with respect to the above-mentioned axis of symmetry (not shown). The angle between the inner wall surface 25d1 and the XY plane is different from the angle between the inner wall surface 25d2 and the XY plane. The position where the inner wall surface 25d1 and the inner wall surface 25d2 intersect is not on the above-mentioned axis of symmetry (not shown).

[0054] In the above respects, groove 25D in Fig. 12 is structurally different from groove 25A in Fig. 7. In other words, inner wall surface 25a1 and inner wall surface 25a2 constituting groove 25A in Fig. 7 are symmetrical with respect to the above-mentioned symmetry axis (not shown). The angle between inner wall surface 25a1 and the XY plane is equal to the angle between inner wall surface 25a2 and the XY plane. The position where inner wall surface 25a1 and inner wall surface 25a2 intersect is on the above-mentioned symmetry axis (not shown).

[0055] In this case, symmetric groove 25P in Fig. 11 may be groove 25A in Fig. 7, and asymmetric groove 25Q in Fig. 11 may be groove 25D in Fig. 12. Alternatively, symmetric groove 25P in Fig. 11 may be either groove 25B or 25C in Fig. 8 to Fig. 9, and asymmetric groove 25Q in Fig. 11 may be either groove 25B or 25C in Fig. 8 to Fig. 9, which has an asymmetric shape with respect to the axis of symmetry. Grooves 25B and 25C in Fig. 8 to Fig. 9 are both symmetric with respect to the axis of symmetry.

[0056] When the region of the asymmetric groove 25Q shown in FIG. 11 is an arc, the central angle θ4 of the arc is arbitrary. For example, the central angle θ4 is preferably 1 / 6 to 1 / 3 of the whole, that is, 60° to 120°. In this case, when the region of the symmetric groove 25P is an arc, the central angle of the arc is obtained by subtracting the central angle θ4 from 360°. That is, the central angle of the region of the symmetric groove 25P is preferably 2 / 3 to 5 / 6 of the whole, that is, 240° to 300°. The contact point between the green ball 91 and the inner wall surface 25d1 in FIG. 12 is the second contact point 20P, and the contact point between the green ball 91 and the inner wall surface 25d2 is the second contact point 20Q. In this case, the angle θ5 between the line segment connecting the center O of the green ball 91 and the second contact point 20P and the line segment connecting the center O and the second contact point 20Q is an arbitrary angle of 30° or more.

[0057] (Processing method using processing device 1) Referring again to FIG. 1, the green ball 91 is polished using a processing device 1 having the second base plate 20 of FIG. 6 and having the groove 25A of FIG. 7 formed therein. The processing method in this case will be described below. First, the green ball 91 is placed so as to be sandwiched between the first surface 10f and the second surface 20f at the center (inner side) of the second base plate 20 closer to the axis β than the protrusion 27 in a plan view. As a result, the green ball 91 comes into contact with the first surface 10f of the first base plate 10 at one point and the second surface 20f of the second base plate 20 at one point, for a total of two points. In this state, the first base plate 10 rotates in a counterclockwise direction R1 when viewed from above (the same applies below), and the second base plate 20 rotates in a clockwise direction R2. In other words, the first base plate 10 and the second base plate 20 are rotated in opposite directions. Such a rotation state will be referred to as a first rotation state hereinafter. The rotation direction here is the rotation direction when the processing apparatus 1 is viewed in plan from the upper side in the Z direction (the second base plate 20 side).

[0058] The green ball 91 is then polished at the portion in contact with the polishing layers 10C, 20C. At this time, the diameter D (see FIG. 1) of the first base plate 10 in plan view is, for example, 700 mm, and the rotation speed is, for example, 4 rpm. The diameter d (see FIG. 1) of the second base plate 20 in plan view is, for example, 300 mm, and the rotation speed is, for example, 150 rpm. As a result, in the initial stage of the polishing process, the green ball 91 rotates while remaining in an inner region closer to the axis β than the protrusion 27, and the surface is polished.

[0059] The green ball 91 always tries to move outward in a plan view, that is, away from the axis β, due to the rotation of the first base plate 10 and the second base plate 20. However, the protrusion 27 comes into contact with the green ball 91 and prevents the green ball 91 from moving outward. Therefore, the green ball 91, which is usually on the inside of the protrusion 27, will not reach the groove 25 unless the rotation direction of the second base plate 20 is reversed as described below.

[0060] Next, while maintaining the rotation direction and rotation speed of the first base plate 10, the rotation direction of only the second base plate 20 is reversed. In other words, the second base plate 20 is switched to rotate in the same counterclockwise direction R1 as the first base plate 10. This rotation state is hereinafter referred to as the second rotation state. The switching is performed by the above-mentioned rotation reversal mechanism 21 (see Figure 1). Note that while the rotation direction of the second base plate 20 is reversed, its rotation speed is maintained. However, the rotation speed of the second base plate 20 does not need to be maintained in the initial period immediately after reversal. As a result, the green ball 91 begins to move toward the outside of the second base plate 20. In other words, the green ball 91 moves toward the groove 25 while passing through the area between a pair of adjacent protrusions 27.

[0061] After that, it is preferable to reverse the rotation direction of the second base plate 20 again using the rotation reversal mechanism 21. Specifically, for example, at the time when the green ball 91 is fitted into the groove 25 or thereafter, it is preferable to set the rotation direction of the second base plate 20 to the clockwise direction R2 again. That is, the processing device 1 is returned to the first rotation state again. The green ball 91 fitted into the groove 25 contacts the first surface 10f of the first base plate 10 at one point and the second surface 20f of the second base plate 20 at two points, a total of three points. In this state, the surface of the green ball 91 is polished at the part that contacts the polishing layers 10C, 20C. This is the later stage of the polishing process. After the green ball 91 is fitted into the groove 25, the green ball 91 does not return to the center of the second base plate 20. This is due to the centrifugal force of the second base plate 20 being applied to the green ball 91, the fact that it is fitted into the groove 25, and the presence of the protrusion 27.

[0062] FIG. 13 is a schematic cross-sectional view showing the positional relationship between the green ball and the second surface plate at the beginning of the polishing process. Referring to FIG. 13, at the beginning of the polishing process, the green ball 91 is sandwiched between the first surface 10f and the flat second surface 20f that is not the groove 25 in an area inside the protrusion 27. If the distance in the Z direction between the first surface 10f and the flat second surface 20f at this time is H1, after the green ball 91 is sandwiched and before the start of polishing, the distance H1 as the diameter of the green ball 91 becomes a maximum value. At this time, the distance G1 in the Z direction between the first surface 10f and the bottom surface of the protrusion 27 also becomes a maximum value. The depth α in the Z direction of the groove 25 (groove 25A) can be designed arbitrarily, but it is desirable to pay attention to the following points.

[0063] FIG. 14 is a schematic cross-sectional view showing the positional relationship between the green ball and the second base plate in the later stage of the polishing process. Referring to FIG. 14, in the later stage of the polishing process, the green ball 91 is sandwiched between the first surface 10f and the groove 25. Since the green ball 91 is fitted into the groove 25 having a depth α, the green ball 91 is disposed on the second base plate 20 side in the Z direction by a dimension less than the depth α compared to the state of FIG. 13. Also, after the polishing has progressed particularly in FIG. 14, the diameter of the green ball 91 is slightly reduced compared to FIG. 13. As a result, in the state of FIG. 14, the distance H2 in the Z direction between the first surface 10f and the flat second surface 20f is reduced more than the distance H1 in FIG. 13. That is, compared to the early stage of the polishing process in FIG. 13, the second base plate 20 is lowered by (H1-H2) in the later stage of the polishing process in FIG. 14. Therefore, it is required that the protrusion 27 does not come into contact with the first surface 10f even in the later stage (just before the end) of the polishing process in FIG. 14 when the green ball 91 with the smallest diameter expected to be processed by the processing device 1 is processed. In other words, it is preferable that the protrusion 27 has a Z-direction dimension that can ensure a Z-direction distance G2>0 from the first surface 10f in the later stage (just before the end) of the polishing process of the green ball 91 with the smallest diameter expected to be processed. More specifically, it is preferable that the Z-direction dimension of the protrusion 27 is less than the value obtained by subtracting the Z-direction depth α of the groove 25 from the diameter after polishing of the green ball 91 with the smallest diameter expected to be processed. The Z-direction dimension of the second outer periphery 20B is also similar to the Z-direction dimension of the protrusion 27.

[0064] In the above, green ball 91 is basically polished on the inside of protrusion 27 in the early stage, and on the outside of protrusion 27 in the later stage. However, for example, when second base plate 20 having groove 25 on the inside of protrusion 27 is used, the above may be reversed. In other words, green ball 91 may be polished on the outside of protrusion 27 in the early stage, and on the inside of protrusion 27 in the later stage. As another example of the processing method, for example, a polishing process on the inside of protrusion 27 and a polishing process on the outside of protrusion 27 may be performed alternately multiple times.

[0065] <Action and effect> The processing device 1 according to the present disclosure includes a first base plate 10 as a first member, a second base plate 20 as a second member, and polishing layers 10C, 20C. The first base plate 10 includes a first surface 10f that holds the green ball 91 by contacting the green ball 91. The second base plate 20 faces the first surface 10f and includes a second surface 20f that holds the green ball 91 by contacting the green ball 91, and includes an outer periphery 20B that extends to protrude in a first direction (Z direction) intersecting the second surface 20f and surrounds the green ball 91 sandwiched between the first surface 10f and the second surface 20f. The polishing layers 10C, 20C are included in at least one of the first base plate 10 and the second base plate 20, include at least one of the first surface 10f and the second surface 20f, and polish the green ball by contacting the green ball 91. The first base plate 10 has a larger area in a plan view than the second base plate 20. The first base plate 10 and the second base plate 20 revolve and rotate the green ball 91 by means of a plurality of relative motions. A groove 25 into which the green ball 91 fits is formed on the second surface 20f.

[0066] With this configuration, the green ball 91 is fitted into the groove 25 formed in the second surface 20f, which is a part of the polishing layer (second polishing layer 20C) of the second base plate 20, which has a smaller area in plan view. As a result, the green ball 91 makes two-point contact with the groove 25, or makes curved line contact with the inner wall surface of the groove 25. The green ball 91 also makes one-point contact with the first surface 10f, which is a part of the polishing layer (first polishing layer 10C) of the first base plate 10, which has a larger area in plan view. Therefore, the green ball 91 makes three-point contact with the entire processing device 1, or one-point and curved line contact, if the first surface 10f and the second surface 20f are combined. In any case, the sphericity of the green ball 91 after polishing is improved (the dimensional error relative to a perfect sphere is reduced) compared to when the green ball 91 makes one-point contact with both the first surface 10f and the second surface 20f, and it is possible to prevent the green ball 91 from becoming closer to a triangle than a perfect circle in plan view.

[0067] FIG. 15 is a schematic diagram showing three examples of the state of the first surface and the second surface when the green ball makes one-point contact with each of the first surface and the second surface. FIG. 16 is a schematic diagram showing the state in which the green ball makes contact with the first surface and the second surface of each of the three examples of FIG. 15 and is polished. FIG. 17 is a schematic diagram showing the planar shapes of a green ball with good sphericity and a green ball with poor sphericity superimposed on each other. With reference to FIG. 15, for example, if the green ball 91 makes contact at a position where the first surface 10f1 and the second surface 20f1 extend in the left-right direction of the figure as shown in (A), the comparative green ball 92 is processed so that the upper and lower ends of the figure, which are the contact positions with the first surface 10f1 and the second surface 20f1, are sharper than other parts as shown in FIG. 16. This is because the points at which pressure is applied to the green ball 91 and it is cut are located at positions that are shifted in phase by 180° relative to the center of the green ball 91, and therefore the stress difference between the cutting points and positions at which no pressure is applied and that are shifted in phase by, for example, 90° relative to the center of the green ball 91 is large.

[0068] When the second surface 20f1 and the green ball 91 come into contact over a wide area, the green ball 91 receives stress from the plane of the second surface 20f1. As a result, the green ball 91 is polished so that the planar portion where the green ball 91 and the second surface 20f1 (first surface 10f1) come into contact has a shape close to a parallel plane. Stress is applied to the surface of the green ball 91 from the first surface 10f1 and the second surface 20f1. Therefore, the green ball 91 is more likely to follow the planar shape of the first surface 10f1 and the second surface 20f1. As a result, the comparative example green ball 92 tends to have a pointed portion.

[0069] Furthermore, similarly to the above, if the green ball 91 comes into contact at a position where the first surface 10f1 and the second surface 20f1 extend in the inclined direction of the figure, as in Figures 15(B) and (C), the green ball 91 will be sharper than other parts due to the inclination of the first surface 10f2 (first surface 10f3) and the second surface 20f2 (second surface 20f3) that sandwich it, as shown in Figure 16. Therefore, as shown in Figures 16 and 17, the comparative green ball 92, which is machined while making two-point contact, has more sharp parts than the spherical green ball 91, and has a shape closer to a triangle. In other words, the comparative green ball 92 has inferior sphericity.

[0070] Comparative example green ball 92, which has poor sphericity, does not have good sphericity even after the sintering process that follows the processing by processing device 1. After sintering, the raw sphere is very hard and difficult to polish. For this reason, if the raw sphere is subjected to a polishing process (rough polishing) again to improve the sphericity after the sintering process, the raw sphere with poor roundness will suffer chipping and scratches due to inappropriate contact with the diamond surface plate. In addition, raw spheres with poor roundness require a large machining allowance, which increases costs. Raw spheres with poor roundness take a long time to process because the processing pressure cannot be increased immediately after polishing.

[0071] However, if the green ball 91 contacts the processing device 1 at three points in total as in this embodiment, for example, as shown in FIG. 7, the green ball 91 does not contact the second surface 20f (groove 25A) in the area between the contact point 20P and the contact point 20Q between the second surface 20f (groove 25A) and the green ball 91. This is because a gap G is formed between the green ball 91 and the inner wall surfaces 25a1 and 25a2, and the surface portion of the green ball 91 that contacts the gap G does not contact the surface. Therefore, in the area other than the total three contact points, the green ball 91 does not contact the second surface 20f and the first surface 10f. Therefore, if the total three contact points are not deflected in one direction with respect to the center of the green ball 91 and are, for example, symmetrical with each other with respect to the center, the possibility of deformation due to the application of force to positions other than the three contact points is reduced. Therefore, if the total three contact points are contacted, the green ball 91 can be polished to have a shape closer to a perfect sphere than in the case of a total of two contact points.

[0072] In addition, even in the case of curved line contact, it is possible to avoid machining that would result in a sharp shape as in Fig. 16 and Fig. 17, which is assumed in the case of two-point contact. This is because the curved line contact area is unlikely to attempt to come into planar contact as in the first surfaces 10f1-10f3 and second surfaces 20f1-20f3 in Fig. 15 due to elastic deformation. For this reason, even when the second base plate 20 having the groove 25B is used, it is expected to have the same effect as when the second base plate 20 assuming three-point contact such as the groove 25A is used.

[0073] In the processing device 1, a protrusion 27 that protrudes toward the first surface 10f is attached to the second surface 20f. The protrusions 27 may be arranged at intervals in the circumferential direction, surrounding the center of the second base plate 20 in a plan view. The protrusions 27 are attached closer to the center of the second base plate 20 than the grooves.

[0074] According to the embodiment described later, the sphericity of the green ball 91 is improved by first performing two-step processing in which the green ball 91 is first contacted at two points as shown in Figs. 15 to 17 and then processed at three points, rather than performing polishing processing with three points (or one point contact and curved line contact) from the beginning. Such two-step processing can be realized by the processing device 1 having the protrusion 27. The protrusion 27 is capable of preventing the green ball 91 from moving from the center of the second base plate 20 to the outer edge where the groove 25 is formed. In other words, the protrusion 27 allows the green ball 91 to maintain a state of one-point contact with each of the first base plate 10 and the second base plate 20 at the center of the second base plate 20 (the center side of the protrusion 27) at the beginning of the polishing process. In addition, in the later stage of the polishing process, the green ball 91 moves to the outer edge side of the protrusion 27 and fits into the groove 25, resulting in the state shown in Figs. 7 to 10 and 12. For this reason, the green ball 91 can be polished to a shape closer to a perfect sphere by making a total of three contact points with the processing device 1. This is because, as described above, at points other than the three contact points, the processing device 1 and the green ball 91 do not come into contact due to, for example, the gap G in Fig. 7, and therefore the green ball 91 is less likely to be subjected to a force that could deform it from a spherical shape.

[0075] In the above processing apparatus 1, the first platen 10 rotates around a first shaft 12 that intersects with the center of the first surface 10f. The second platen 20 rotates around a second shaft 22 that intersects with the center of the second surface 20f. The processing apparatus 1 may further include a rotation reversing mechanism 21. The rotation reversing mechanism 21 is capable of reversing the direction of rotation of the second platen 20 around the second shaft 22.

[0076] At the beginning of the polishing process, the green ball 91 is polished at the center of the second platen 20 by contact with the processing device 1 at a total of two points, and then the rotation direction of the second platen 20 is reversed by the rotation reversal mechanism 21. This allows the green ball 91 to move from the center to the outer edge of the second platen 20 and fit into the groove 25. As a result, the green ball 91 comes into contact with the processing device 1 at a total of three points, and the green ball 91 can be polished to a shape closer to a perfect sphere.

[0077] Since the protrusions 27 and the rotation reversal mechanism 21 are provided, the contact state can be easily changed from two-point contact in the early stage of the polishing process to three-point contact in the later stage of the polishing process by using only one processing device 1. Therefore, the green ball 91 can be polished to a shape closer to a perfect sphere by using only one processing device 1. This eliminates the need to replace the surface plate, for example. Also, the need to change the setup using multiple processing devices is eliminated. This reduces the time required for setup and the cost required for the device.

[0078] In the above processing device 1, the groove 25 is formed to extend in a ring shape in a region adjacent to the outer edge of the second base plate 20 in a plan view. The cross section of the groove 25 perpendicular to the direction in which the groove 25 extends may be a shape in which two wall surfaces extending in a direction inclined with respect to the first direction (Z direction) intersect. The cross section of the groove 25 perpendicular to the direction in which the groove 25 extends may be a polygonal shape. The cross section of the groove 25 perpendicular to the direction in which the groove 25 extends may be an arc shape. In any of these shapes, the inner wall surface of the groove 25 and the surface of the green ball 91 can be prevented from coming into linear contact. Therefore, when the green ball 91 is polished, a total of three points of contact with the processing device 1, or one point of contact with the first surface 10f and line contact with the second surface 20f are made. Therefore, it is possible to polish the green ball 91 to a shape closer to a perfect sphere.

[0079] In the above processing device 1, the polishing layers 10C, 20C may be formed of a wire mesh. In either case, the polishing layers 10C, 20C can polish the green ball 91 smoothly. EXAMPLES

[0080] Referring again to Figure 1, for example, when using a processing device 1 having the second base plate 20 of Figure 6 and groove 25A of Figure 7, the relationship between the conditions for polishing green ball 91 and the roundness of green ball 91 after polishing is as shown in Table 1 below. Note that the roundness is investigated here because the sphericity can be adequately evaluated by measuring the roundness of green ball 91. Note that the roundness was measured with a micrometer.

[0081] [Table 1]

[0082] In Table 1, the number of green balls 91 for which the roundness was investigated was five for each condition. Table 1 lists the maximum and minimum values ​​of the roundness of the five green balls 91. When polished only in a process of contacting the processing device 1 at a total of two points, the roundness was 0.05 mm to 0.20 mm. In contrast, when polished only in a process of contacting the processing device 1 at a total of three points, the roundness was 0.05 mm to 0.08 mm. When polished with two-point contact at the beginning of the polishing process and with three-point contact at the later stage as in this embodiment (denoted as "2 points → 3 points" in the table), the roundness was 0.02 mm to 0.03 mm. From this, it can be said that it is most preferable from the viewpoint of improving the roundness (sphericity) to perform polishing while using both two-point contact and three-point contact using the processing device 1 of this embodiment.

[0083] Better roundness can be achieved by first machining with two-point contact and then machining with three-point contact than by machining with three-point contact from the beginning. This is because two-point contact machining forms a triangular component of a sphere, but three-point contact machining forms a quadrangular component of a sphere. It is thought that by first machining with two-point contact to form a triangular component of a sphere, and then machining with three-point contact to round the triangular component first, roundness can be improved.

[0084] (reference) As described above, after the rotation of the second base plate 20 is reversed to move the green ball 91 from the center to the outer edge of the second base plate 20, the rotation of the second base plate 20 is reversed again during the polishing process in the groove 25. Reversing the rotation of the second base plate 20 again during polishing is not essential, but is preferably performed. By reversing again, the first rotation state is achieved during polishing processing in the groove 25. This allows the movement of the green ball 91 held on the second base plate 20 to be closer to ideal. This is explained below.

[0085] Fig. 18 is a schematic plan view showing a first rotation state in which the first base plate rotates counterclockwise and the second base plate rotates clockwise. Referring to Fig. 18, two green balls are shown. Of these, the ball closer to the center (axis α) of the first base plate 10 is green ball 91A, and the ball farther from the center (axis α) is green ball 91B. Consider the case where the first base plate 10 rotates counterclockwise R1 at 4 rpm and the second base plate 20 rotates clockwise R2 at 150 rpm.

[0086] FIG. 19 is a schematic cross-sectional view of a portion along line XIX-XIX in FIG. 18. In the region shown in FIG. 19, the second base plate 20 applies a large leftward rotational force, indicated by an arrow in the figure, to the green ball 91A from above. The magnitude of this leftward force is, for example, 10. At this time, the first base plate 10 also applies a leftward rotational force, indicated by an arrow in the figure, to the green ball 91A. However, the rotational force of the first base plate 10 is weaker than that of the second base plate 20, and is in the same direction (leftward) as the rotational force of the second base plate 20 at the position of FIG. 19. Therefore, the first base plate 10 applies a rotational force to the green ball 91A from below, which cancels out the rotational force that the second base plate 20 applies to the green ball 91A. The rotational force that the first base plate 10 applies to the green ball 91 is a canceling force, and is, for example, -2. The absolute value of the leftward force of the first base plate 10, 2, is calculated as a guideline based on the rotational speed of the first base plate 10 and the distance of the first base plate 10 from the axis α. Adding these together, the rotational force applied to the green ball 91A is 10-2=8.

[0087] FIG. 20 is a schematic cross-sectional view of a portion along the line XX-XX in FIG. 18. In the region shown in FIG. 20, if we consider the region shown in FIG. 19 in the same way, the second base plate 20 applies a large rightward rotational force, indicated by the arrow in the figure, to the green ball 91B from above. The magnitude of this rightward force is, for example, 10. At this time, the first base plate 10 tries to apply a leftward rotational force, indicated by the arrow in the figure, to the green ball 91B. The magnitude of this leftward force is, for example, 4. These directions are opposite to each other. Therefore, the leftward rotational force from the lower side by the first base plate 10 acts to strengthen the rightward rotational force from the upper side by the second base plate 20. Therefore, the force applied by the first base plate 10 and the force applied by the second base plate 20 are added together, and the rotational force applied to the green ball 91B is 10+4=14.

[0088] The rotational force imparted to the green ball 91A and the rotational force imparted to the green ball 91B are added together, so that the rotational force imparted to the green ball in the first rotation state is 14+8=22.

[0089] Fig. 21 is a schematic plan view showing a second rotation state in which the first base plate rotates counterclockwise and the second base plate also rotates counterclockwise. With reference to Fig. 21, a case is considered in which the first base plate 10 rotates counterclockwise R1 at 4 rpm and the second base plate 20 rotates counterclockwise R1 at 150 rpm.

[0090] Fig. 22 is a schematic cross-sectional view of a portion taken along line XXII-XXII in Fig. 21. In the region shown in Fig. 22, the second base plate 20 applies a large rightward rotational force, as indicated by the arrow in the figure, to the green ball 91A from above. The magnitude of this rightward force is, for example, 10. Meanwhile, the first base plate 10 applies a leftward rotational force (magnitude 2), as indicated by the arrow in the figure, to the green ball 91A from below. As in the first rotation state, the two forces are in opposite directions, so they reinforce each other. Therefore, the rotational force applied to the green ball 91A is 10+2=12.

[0091] Fig. 23 is a schematic cross-sectional view of a portion taken along line XXIII-XXIII in Fig. 21. In the region shown in Fig. 23, the second base plate 20 applies a large leftward rotational force, indicated by the arrow in the figure, to the green ball 91B from above. The magnitude of this leftward force is, for example, 10. Meanwhile, the first base plate 10 applies a leftward rotational force (magnitude 4), indicated by the arrow in the figure, to the green ball 91B from below. As in the first rotation state, the two forces are in the same direction, so they weaken each other. Therefore, the rotational force applied to the green ball 91B is 10-4=6.

[0092] The rotational force applied to green ball 91A and the rotational force applied to green ball 91B are added together. As a result, the rotational force applied to the green ball in the second rotation state is 12+6=18. Since 22>18, the rotational force applied to the green ball in the first rotation state is greater than that in the second rotation state. In other words, the processing capacity of the green ball is higher in the first rotation state than in the second rotation state. For this reason, it is more preferable that polishing processing in groove 25 be performed in the first rotation state.

[0093] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. Unless inconsistent, at least two of the embodiments disclosed herein may be combined. The basic scope of the present disclosure is indicated by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0094] Various aspects of the present disclosure are summarized below as appendices.

[0095] (Appendix 1) a first member including a first surface that contacts the green ball to hold the green ball; a second member including a second surface facing the first surface and contacting the green ball to hold the green ball, and including an outer periphery extending in a first direction intersecting the second surface and surrounding the green ball sandwiched between the first surface and the second surface; a polishing layer that is included in at least one of the first member and the second member, includes at least one of the first surface and the second surface, and polishes the green ball by contacting the green ball; the first member has a larger area in a plan view than the second member, The first member and the second member cause the green ball to revolve and rotate by multiple relative motions, A processing device, wherein the second surface has a groove formed therein into which the green ball fits.

[0096] (Appendix 2) A protrusion protruding toward the first surface is attached to the second surface, The protrusions surround the center of the second member in a plan view, and are arranged at intervals in the circumferential direction. The processing device described in Appendix 1, wherein the protrusion portion is attached closer to the center of the second member than the groove.

[0097] (Appendix 3) the first member rotates about a first axis that intersects with a center of the first surface; the second member rotates about a second axis that intersects with a center of the second surface; The processing apparatus according to claim 1 or 2, further comprising a rotation reversing mechanism capable of reversing the direction of rotation of the second member around the axis of the second shaft.

[0098] (Appendix 4) The groove is formed to extend annularly in a region adjacent to an outer edge of the second member in a plan view, 4. The processing device according to any one of claims 1 to 3, wherein a cross section of the groove perpendicular to the direction in which the groove extends has a shape in which two wall surfaces extending in a direction inclined with respect to the first direction intersect.

[0099] (Appendix 5) The groove is formed to extend annularly in a region adjacent to an outer edge of the second member in a plan view, 4. The processing device according to any one of claims 1 to 3, wherein a cross section of the groove perpendicular to a direction in which the groove extends is polygonal.

[0100] (Appendix 6) The groove is formed to extend annularly in a region adjacent to an outer edge of the second member in a plan view, 4. The processing device according to any one of claims 1 to 3, wherein a cross section of the groove perpendicular to a direction in which the groove extends is in the shape of a circular arc.

[0101] (Appendix 7) 7. The processing apparatus according to any one of claims 1 to 6, wherein the polishing layer is formed of a wire mesh. [Explanation of symbols]

[0102] 10 first surface plate, 10A first flat plate portion, 10B first outer peripheral portion, 10C first polishing layer, 10f, 10f1, 10f2, 10f3 first surface, 10R first contact point, 11a, 21a grid, 12 first shaft, 13, 23 bearing, 14, 24 outer peripheral member, 20 second surface plate, 20A second flat plate portion, 20B second outer peripheral portion, 20C second polishing layer, 20f, 20f1, 20f2, 20f3 second surface, 20L line contact portion, 20P, 20Q, 20R second contact point, 21 rotation reversal mechanism, 21A, 21B intersection point, 25, 25A, 25B, 25C, 25D groove, 25a1, 25a2, 25c1, 25c2, 25c3, 25d1, 25d2 Inner wall surface, 30 screw member, 50 elastic member, 91, 91A, 91B green balls, 92 comparative example green ball, G gap, R1 counterclockwise, R2 clockwise.

Claims

1. a first member including a first surface adapted to contact the green ball and thereby hold the green ball; a second member including a second surface facing the first surface and contacting the green ball to hold the green ball, and including an outer periphery extending in a first direction intersecting the second surface and surrounding the green ball sandwiched between the first surface and the second surface; a polishing layer that is included in at least one of the first member and the second member, includes at least one of the first surface and the second surface, and polishes the green ball by contacting the green ball; The first member has a larger area in a plan view than the second member, The first member and the second member cause the green ball to revolve and rotate by a plurality of relative motions, A processing device, wherein the second surface has a groove formed therein into which the green ball fits.

2. A protrusion protruding toward the first surface is attached to the second surface, The protrusions surround the center of the second member in a plan view, and are arranged at intervals in the circumferential direction. The processing device according to claim 1 , wherein the protrusion is attached closer to a center of the second member than the groove.

3. The first member rotates about a first axis that intersects with a center of the first surface, the second member rotates about a second axis that intersects with the center of the second surface; The processing apparatus according to claim 1 or 2, further comprising a rotation reversing mechanism capable of reversing a rotation direction in which the second member rotates about the second shaft.

4. The groove is formed to extend annularly in a region adjacent to an outer edge of the second member in a plan view, The processing device according to claim 1 , wherein a cross section of the groove perpendicular to a direction in which the groove extends has a shape in which two wall surfaces extending in a direction inclined with respect to the first direction intersect with each other.

5. The groove is formed to extend annularly in a region adjacent to an outer edge of the second member in a plan view, The processing device according to claim 1 or 2, wherein a cross section of the groove perpendicular to the direction in which the groove extends is polygonal.

6. The groove is formed to extend annularly in a region adjacent to an outer edge of the second member in a plan view, The processing device according to claim 1 or 2, wherein a cross section of the groove perpendicular to a direction in which the groove extends is in the shape of a circular arc.

7. 3. The processing apparatus according to claim 1, wherein the polishing layer is formed of a wire mesh.

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