Polishing Tool, Polishing Head, Polishing Apparatus, And Polishing Method

This application claims priority to Japanese Patent Application No. 2024-083446, filed on May 22, 2024, which is expressly incorporated herein by reference in its entirety.

The present invention relates to a polishing tool, a polishing method and the like that precisely polish the surface of workpieces such as lenses, optical elements and the like.

Optical elements or the like, such as aspherical lenses used in the state of being incorporated in electrical devices and optical devices, are manufactured by processes such as molding, grinding, and polishing. The optical elements require a high shape precision.

Examples of the polishing method adopted for the optical elements include a polishing work, a lapping work, and a magnetic polishing method. For example, in the magnetic polishing method, as shown in Patent Literature 1, a magnetic fluid alone is used or a particulate polishing material that is suspended and dispersed in the magnetic fluid is used as a magnetic polishing fluid, and the magnetic polishing fluid is supplied between the polishing surface at the forefront of a polishing tool and a workpiece for polishing. In this case, a Z-directional actuator formed of electrostrictive elements induces slight motions (micro-scale approach and separation) between the polishing surface and the workpiece in a Z-axis direction. At the same time, an X-directional actuator and a Y-directional actuator formed of electrostrictive (piezoelectric) elements are used to induce slight motions in the direction of an XY plane perpendicular to the Z axis.

In the case of the polishing apparatus in Patent Literature 1, a polishing tool block (polishing block) including the X-directional actuator and the Y-directional actuator is hung more on the front end side (polishing surface side) than the Z-directional actuator. As a result, the polishing block becomes larger, increasing the inertia and making the structure of the polishing block complicated. Therefore, various adjustments are required in order to control the polishing surface with high precision.

The present invention has been made in view of the above-mentioned problem and an object of the present invention is to provide a polishing tool and the like, capable of achieving high-precision polishing while simplifying the structure.

In order to accomplish the object as above, the present invention provides a polishing tool for polishing a workpiece by holding a polishing material between the workpiece and a polishing surface of the polishing tool, the polishing tool including: a main shaft part that has the polishing surface facing the workpiece at a front end and that extends along a polishing axis, the polishing axis being a virtual axis defined as a direction in which the center of the polishing surface approaches or moves away the workpiece; a plurality of elastic parts that are continuous from the main shaft part and that extend in a radially outward direction with respect to the polishing axis; and a plurality of seat parts that are continuous to a radially outside of the plurality of elastic parts, wherein a position at which the main shaft part connects to each of the elastic parts and a position at which the corresponding seat part connects to each of the elastic parts are different in a direction of the polishing axis, and when the respective seat parts are applied with equal amounts of displacement toward the same side that is either the radially inside or radially outside by a tool driving mechanism, the plurality of elastic parts elastically deform and the main shaft part is displaced so as to include an axial component with respect to the polishing axis, whereas when the respective seat parts are applied with different amounts of displacement toward the same side that is either the radially inside or radially outside, or the displacement toward different sides that are radially outside and the radially inside by the tool driving mechanism, the main shaft part is displaced so as to include a radial component with respect to the polishing axis.

In relation to the polishing tool, the plurality of elastic parts and the seat parts may be disposed at equal intervals in a circumferential direction with reference to the polishing axis.

In relation to the polishing tool, the number of the elastic parts and the number of the seat parts may each be three.

In order to accomplish the object described above, the present invention provides a polishing head having the polishing tool described above, the polishing head including: a tool base; and a tool driving mechanism that is disposed on the tool base to displace or elastically deform the polishing tool, wherein the tool driving mechanism includes a plurality of driving units that are disposed in the plurality of seat parts to radially displace the seat parts.

The polishing head may include a tool control device that controls the tool driving mechanism, wherein the tool control device may include a first frequency signal generator that generates a plurality of first frequency signals to periodically reciprocate and displace the plurality of driving units so that increase-decrease cycles of displacement amounts coincide with each other.

In relation to the polishing head, the tool control device may further include a second frequency signal generator that generates a plurality of second frequency signals to periodically reciprocate and displace the plurality of driving units so that the increase-decrease cycles of the displacement amounts coincide with each other, and a signal superimposing unit that generates driving signals for the respective driving units by superimposing the plurality of first frequency signals and the plurality of second frequency signals, wherein the plurality of first frequency signals generated by the first frequency signal generator may coincide with each other in increase-decrease phase, and the plurality of second frequency signals generated by the second frequency signal generator may be different from each other in increase-decrease phase.

In relation to the polishing head, the tool control device may further include a second frequency signal generator that generates a plurality of second frequency signals to periodically reciprocate and displace the plurality of driving units so that the increase-decrease cycles of the displacement amounts coincide with each other, and a signal superimposing unit that generates driving signals for the respective driving units by superimposing the plurality of first frequency signals and the plurality of second frequency signals, wherein the first frequency signals may have a frequency higher than the frequency of the second frequency signals.

The polishing head may include a bias signal generator that generates a bias signal to be superimposed on at least one of the first frequency signals.

The polishing head may include a polishing head setting calculation unit that varies the bias signal generated by the bias signal generator by referring to scanning path information for the polishing surface regarding the workpiece and/or shape information on the workpiece.

In relation to the polishing head, the tool driving mechanism may vibrate the polishing surface along a spiral moving locus.

In relation to the polishing head, the tool driving mechanism may displace a spiral axis of the spiral moving locus on the polishing surface.

In order to accomplish the object described above, the present invention provides a polishing head, including: a polishing tool for polishing a workpiece by holding a polishing material between a polishing surface of the polishing tool and the workpiece; a tool base; a tool driving mechanism that is disposed on the tool base to displace the polishing tool; and a tool control device to control the tool driving mechanism, wherein the tool driving mechanism includes a plurality of driving units that are disposed along a circumferential direction with reference to a polishing axis to displace the polishing tool in a radial direction with reference to the polishing axis, the polishing axis being a virtual axis defined as a direction in which the center of the polishing surface approaches or moves away the workpiece, the tool control device includes a first frequency signal generator that generates a plurality of first frequency signals to periodically reciprocate and displace the plurality of driving units so that increase-decrease cycles of displacement amounts coincide with each other, a second frequency signal generator that generates a plurality of second frequency signals to periodically reciprocate and displace the plurality of driving units so that the increase-decrease cycles of the displacement amounts coincide with each other, and a signal superimposing unit that generates driving signals for the respective driving units by superimposing the plurality of first frequency signals and the plurality of second frequency signals, and the tool control device has a control mode that includes either a control mode where the plurality of first frequency signals generated by the first frequency signal generator coincide with each other in increase-decrease phase and the plurality of second frequency signals generated by the second frequency signal generator are different from each other in increase-decrease phase or a control mode where the first frequency signals have a frequency higher than the frequency of the second frequency signals.

In relation to the polishing head, the plurality of first frequency signals generated by the first frequency signal generator may coincide with each other in increase-decrease phase, and the plurality of second frequency signals generated by the second frequency signal generator may be different from each other in increase-decrease phase.

In relation to the polishing head, the first frequency signals may have a frequency higher than the frequency of the second frequency signals.

In order to accomplish the object described above, the present invention provides a polishing apparatus, including: a base; the polishing head described above; a polishing head holding mechanism that is provided on the base to hold the polishing head; a workpiece holding mechanism that is provided on the base to hold the workpiece; and a relative movement mechanism that relatively moves the workpiece and the polishing head in an axial direction of the polishing axis and in a radial direction with reference to the polishing axis.

In order to accomplish the object described above, the present invention provides a polishing method for polishing a workpiece by holding a polishing material between a polishing surface of a polishing tool and the workpiece, the polishing material containing abrasive grains dispersed in a fluid, the polishing method including: disposing a plurality of driving units along a circumferential direction with reference to a polishing axis to cause each of the driving units to displace a contact point with the polishing tool in a radial direction with reference to the polishing axis, the polishing axis being a virtual axis defined as a direction in which the center of the polishing surface approaches or moves away the workpiece; generating a synchronization frequency signal to periodically reciprocate and displace the plurality of driving units so that increase-decrease cycles and increase-decrease phases of displacement amounts coincide with each other; generating a plurality of first frequency signals to periodically reciprocate and displace the plurality of driving units so that the increase-decrease cycles of the displacement amounts coincide with each other; generating driving signals for the respective driving units by using at least the plurality of first frequency signals; and displacing the plurality of driving units by the plurality of driving signals so as to displace the polishing surface of the polishing tool in an axial direction and a radial direction with reference to the polishing axis.

In relation to the polishing method, a plurality of second frequency signals may be generated to periodically reciprocate and displace the plurality of driving units so that the increase-decrease cycles of the displacement amounts coincide with each other, the plurality of first frequency signals may coincide with each other in increase-decrease phase and the plurality of second frequency signals are different from each other in increase-decrease phase, the driving signals for the respective driving units may be generated by superimposing the plurality of first frequency signals and the plurality of second frequency signals, and the plurality of driving units may be displaced by the plurality of driving signals so as to displace the polishing surface of the polishing tool in the axial direction and the radial direction with reference to the polishing axis.

In relation to the polishing method, the driving signals for the respective driving units may be generated by superimposing a bias signal on at least one of the first frequency signals, and the plurality of driving units may be displaced by the plurality of driving signals so as to displace the polishing surface of the polishing tool in the axial direction and the radial direction with reference to the polishing axis.

In relation to the polishing method, the bias signal may be varied by referring to a scanning path information for the polishing surface regarding the workpiece and/or shape information on the workpiece.

In relation to the polishing method, the polishing surface may be vibrated along a spiral moving locus.

In relation to the polishing method, a spiral axis of the spiral moving locus on the polishing surface may be displaced.

In order to accomplish the object described above, the present invention provides a polishing method for polishing a workpiece by holding a polishing material between a polishing surface of a polishing tool and the workpiece, the polishing material containing abrasive grains dispersed in a fluid, the polishing method including: disposing a plurality of driving units along a circumferential direction with reference to a polishing axis to cause each of the driving units to displace a contact point with the polishing tool in a radial direction with reference to the polishing axis, the polishing axis being a virtual axis defined as a direction in which the center of the polishing surface approaches or moves away the workpiece; generating frequency signals that are at least twice as many as number of the driving units; inputting a driving signal to each of the driving units, the driving signal being obtained by superimposing at least two frequency signals among the frequency signals; and displacing the plurality of driving units by the plurality of driving signals so as to displace the polishing surface of the polishing tool in an axial direction and a radial direction with reference to the polishing axis.

The present invention can provide excellent advantageous effects that the workpiece surface can be polished with high accuracy with a simple structure.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

illustrates an overall configuration of a polishing apparatusaccording to the present embodiment. The polishing apparatusincludes: a base; a polishing head; a polishing head holding mechanismthat is provided on the baseto hold the polishing head; a workpiece holding mechanismthat is provided on the baseto hold a workpiece W; a relative rotation mechanismthat relatively rotates the workpiece W and the polishing head; a relative movement mechanismthat relatively moves the workpiece W and the polishing headin an axial direction and a radial direction R of a polishing axis J, and a polishing material supplying devicethat supplies a fluid-like polishing material between the workpiece W and the polishing head. The polishing apparatusfurther includes a tool control devicethat controls a tool driving mechanismin the polishing head, and a movement control devicethat controls the relative movement mechanism. Note that the tool control deviceand the movement control deviceoperate in conjunction with each other.

For convenience of explanation, the direction in which the center of the polishing surface of the polishing headapproaches or moves away the workpiece W (the left-to-right direction in) is defined as a Z-axis direction. In, a line passing through the center of the polishing surfaceof the polishing headand parallel to the Z-axis direction is defined as a virtual polishing axis J. Furthermore, a vertical direction perpendicular to the Z-axis direction (the top-to-bottom direction in) is defined as a Y-axis direction, and a direction perpendicular to both the Z-axis direction and the Y-axis direction (the direction perpendicular to the page on which the illustration inrests) is defined as an X-axis direction. Furthermore, a direction perpendicular to the polishing axis J (or Z-axis) is defined as a radial direction R with reference to the polishing axis, and a circumferential direction around the polishing axis J (or Z-axis) is defined as a circumferential direction S with reference to the polishing axis.

The workpiece holding mechanismholds a workpiece W to be polished. Although not particularly illustrated, the workpiece holding mechanismincludes a chuck that holds the workpiece W such that the surface to be polished on the workpiece W faces in the Z-axis direction.

The polishing head holding mechanismserves as a seating for holding the polishing head. The polishing head holding mechanismholds the polishing headso that the polishing axis J of the polishing headbecomes parallel to the Z-axis direction. Although not particularly illustrated, the polishing head holding mechanismpreferably includes a chuck that detachably holds the polishing headso that the polishing surface thereof faces in the Z-axis direction. When a normal cutting tool is equipped instead of the polishing head, which is held by the polishing head holding mechanismand by use of a chuck, the entire polishing apparatuschanged into a general-purpose cutting apparatus.

The relative rotation mechanismis a rotation mechanism that relatively rotates the workpiece W and the polishing surfaceabout the Z-axis. Herein, the relative rotation mechanismserves as a rotation main axis fixed to the base, and rotates the workpiece holding mechanismabout the Z-axis.

The relative movement mechanismis a mechanism that moves the workpiece W and the polishing headin the X-axis, Y-axis, and Z-axis directions, this movement being relative to the base. In the present embodiment, the relative movement mechanismincludes: a Y-axis linear motion devicethat moves the polishing head holding mechanismin the Y-axis direction; a Z-axis linear motion devicethat moves the Y-axis linear motion devicein the Z-axis direction; an X-axis linear motion devicethat moves the Z-axis linear motion devicein the X-axis direction; and a tilt mechanismthat tilts the polishing axis J of the polishing head holding mechanismwith reference to the Z-axis direction. Note that, in the present embodiment, the structure in which the polishing headis moved relative to the basein the X-axis, Y-axis, and Z-axis direction, and also in a tilt direction has been exemplified, but the present invention is not limited thereto. Some or all of the mechanisms for movement in the X-axis, Y-axis, and Z-axis directions, and the tilt direction may be provided on the side where the workpiece holding mechanismis provided. When the surface to be polished of the workpiece W is a flat surface, the tilt mechanismcan be eliminated. On the other hand, when the surface to be polished of the workpiece W has a three-dimensional shape, the polishing headis preferably tilted by the tilt mechanismso that the polishing axis J coincides with the direction vertical to the surface to be polished.

The polishing material supply devicecontinuously supplies a fluid-like polishing material between the workpiece W and the polishing surface of the polishing head. Specifically, the polishing material supply deviceincludes: a pump (not illustrated); a pipethat guides the polishing material discharged from the pump; a nozzlethat is attached to the forefront of the pipeand discharges the polishing material; and a nozzle holding mechanismthat holds the nozzleat a predetermined position.

As illustrated in an enlarged view of, the polishing headincludes: a tool base; a tool driving mechanismthat is disposed on the tool base; a polishing toolthat is held by the tool driving mechanism; and a tool control devicethat controls the tool driving mechanism.

The tool baseis a plate-shaped member that extends in the X-axis and Y-axis directions.

The polishing toolserves as a tool for polishing a workpiece W by holding the polishing material between its polishing surfaceand the workpiece W. For convenience of explanation, in the polishing tool, the side approaching the workpiece W along the polishing axis J (or the Z axis) is referred to as the front end side, and the side away from the workpiece W is referred to as the base end side. As illustrated into, the polishing toolincludes a main shaft part, a first elastic part, a second elastic part, a third elastic part, a first seat part, a second seat part, and a third seat part.

The main shaft partis a rod-shaped member that extends along the polishing axis J (or Z axis), has a polishing surfacethat is located on the front end side, and faces the workpiece W. More specifically, the main shaft parthas a central shaftA that extends along the polishing axis J, a first ribthat spreads from the central shaftA in a first radial direction Rand extends along the polishing axis J, a second ribthat spreads from the central shaftA in a second radial direction Rand extends along the polishing axis J, and a third ribthat spreads from the central shaftA in a third radial direction Rand extends along the polishing axis J. The first to third ribstoincrease the stiffness of the main shaft part. The polishing surfaceis provided at the front end in the central shaftA. Note that the polishing surfaceis not limited to a flat surface, and as illustrated in, the polishing surfacemay be a three-dimensional surface (for example, a convex surface such as a part of a spherical surface).

The first elastic partis a member that is continuous from the base end side of the main shaft partand extends from the polishing axis J toward the outside in the first radial direction (Rdirection). The first elastic partis elastically deformed in the polishing axis J direction and/or the first radial direction Rby an external force. The first seat partis a portion to be provided radially outward of the first elastic part, and provides a structural part (here, a seat surfaceA) such as a surface to be supported by the tool driving mechanismdescribed later.

Here, as illustrated in, a position at which the main shaft part(polishing axis J) connects to the first elastic partis defined as a main shaft-side continuous pointA, and a portion of the first seat part(seat surfaceA) in the first elastic partis defined as a seat part-side continuous pointB. With respect to the main shaft-side continuous pointA, the seat part-side continuous pointB is located at a position shifted along the polishing axis J, specifically, on the base end side. When a central axis in an extending direction of the member of the first elastic partis defined as a first arm axisJ, the first arm axisJ is an inclined member that is displaced from a front end side to a base end side of the polishing axis J as it extends from the inside toward the outside in the first radial direction Rof the polishing axis J. The first arm axisJ may be defined as a straight-line component connecting the main shaft-side continuous pointA and the seat-side continuous pointB. As illustrated in, in the first elastic part, a constriction partK is formed on the proximal side of the main shaft-side continuous pointA. The dimensionKw in the constriction partK in a direction perpendicular to the first arm axisJ is smaller than the dimensionEw of any optional point on the farther side thereto. As a result, the constriction partK in the first elastic parthas a lower stiffness, so that the constriction partK tends to elastically deform. On the inside of the first seat partin the first radial direction R, a first escape spaceK is formed.

In the present embodiment, a case has been illustrated where the main shaft-side continuous pointA is located on the front end side and the seat part-side continuous pointB is located on the base end side. However, the present invention is not limited thereto, and a structure in which the main shaft-side continuous pointA is located on the base end side and the seat part-side continuous pointB is located on the front end side may be adopted.

The first seat partprovides a surface that faces outward in the first radial direction R. The first seat partreceives a first external force Fthat is applied from the outside toward the inside in the first radial direction R. The first seat surfaceA provided on the first seat partis a concave part that is recessed in a partially spherical shape here. When the tool driving mechanismdescribed later is engaged with the first seat surfaceA, the first seat partis supported and pressed from the outside toward the inside in the first radial direction R. The pressure provided to the first seat partin an initial state serves as a holding pressure (pressurization) to maintain a holding posture of the polishing tool.

The second elastic partis a member that is continuous from the base end side of the main shaft partand extends from the polishing axis J toward the outside in the second radial direction (Rdirection). The second elastic partis elastically deformed in the polishing axis J direction and/or the second radial direction Rby an external force. The second seat partis a portion to be provided radially outward of the second elastic part, and provides a structural part (here, a seat surfaceA) such as a surface to be supported by the tool driving mechanismdescribed later.

Here, as illustrated in, a position at which the main shaft part(polishing axis J) connects to the second elastic partis defined as a main shaft-side continuous pointA, and a portion of the second seat part(seat surfaceA) in the second elastic partis defined as a seat part-side continuous pointB. With respect to the main shaft-side continuous pointA, the seat part-side continuous pointB is located on the base end side of the polishing axis J. In other words, the main shaft-side continuous pointA and the seat part-side continuous pointB are at different positions along the polishing axis J. When a central axis in an extending direction of the member of the second elastic partis defined as a second arm axisJ, the second arm axisJ is an inclined member that is displaced from a front end side to a base end side of the polishing axis J as it extends from the inside toward the outside in the second radial direction Rof the polishing axis J. In the second elastic part, a constriction partK is formed on the near side of the main shaft-side continuous pointA. As a result, the constriction partK has a lower stiffness, so that the constriction partK tends to elastically deform. On the inside of the second seat partin the second radial direction R, a second escape spaceK is formed.

In the present embodiment, a case has illustrated where the main shaft-side continuous pointA is located on the front end side and the seat part-side continuous pointB is located on the base end side. However, the present invention is not limited to this configuration, and a structure in which the main shaft-side continuous pointA is located on the base end side and the seat part-side continuous pointB is located on the front end side may be adopted.

The second seat partprovides a surface that faces outward in the second radial direction R. The second seat partreceives a second external force Fthat is applied from the outside toward the inside in the second radial direction R. The second seat surfaceA provided on the second seat partis a concave part that is recessed in a partially spherical shape here. When the tool driving mechanismdescribed later is engaged with the second seat surfaceA, the second seat partis supported and pressed from the outside toward the inside in the second radial direction R. The pressure provided to the second seat partin an initial state serves as a holding pressure (pressurization) to maintain a holding posture of the polishing tool.