JP2805982B2 - Micro polishing method and micro polishing tool - Google Patents

Description

The present invention relates to a micro-polishing method and a micro-polishing tool. More specifically, in the field of manufacturing lenses, optical elements, and the like, in order to perform ultra-high precision processing, The present invention relates to a method for precisely polishing a minute area and a polishing tool used for performing the method.

[Conventional method]

Aspherical lenses and X-ray optical elements used in various electronic and optical devices are manufactured by polishing, but require extremely high precision processing with a product shape accuracy of 0.01 μm or less. Therefore, there is a demand for a processing method capable of performing such ultra-high-precision polishing. For that purpose, a polishing method that can precisely polish the polished surface to a small area is required.

Conventionally, as a high-precision polishing method, polishing, lapping, and the like have been adopted.
Since ultra-high-precision machining of μm or less has not been possible at all, a magnetic polishing method using a magnetic polishing fluid as an abrasive has attracted attention in recent years as a method capable of performing higher-precision machining.
Here, the magnetic polishing fluid refers to a magnetic fluid alone or a fluid obtained by suspending and dispersing a fine abrasive in the magnetic fluid.

In the magnetic polishing method, a magnetic polishing fluid is supplied and a magnetic field is applied between a polishing portion at the tip of a polishing tool and a workpiece. Then, the magnetic polishing fluid is held between the polishing portion and the material to be polished by the magnetic action while the polishing surface of the material to be polished is pressed. When the polishing tool is rotated at a high speed in this state, the magnetic polishing fluid is dragged by the rotation of the polishing tool and is rotated at a high speed, thereby performing a polishing process on the workpiece. At this time, by changing the direction and strength of the applied magnetic field, the pressure of the polishing surface by the magnetic polishing fluid is changed, or the motion of the magnetic polishing fluid is controlled.
Improvements in polishing performance have also been made. Specific examples of the magnetic polishing method are disclosed in, for example, JP-A-60-118466, JP-A-61-244457, and JP-B-1-16623.

According to this magnetic polishing method, since the abrasive can be intensively applied to a minute region of the polished surface by magnetic coercive force, it is possible to perform polishing with higher precision than the conventional polishing method. There are advantages. However, even with this magnetic polishing method, it has not been possible to sufficiently cope with ultra-high precision processing of 0.01 μm or less.

That is, in this method, the magnetic polishing fluid is rotated at a high speed by the high-speed rotation of the polishing tool, so that the finish of the polishing surface is directly affected by the state of rotation of the polishing tool. However, the rotation of the polishing tool is liable to cause fluctuations in the number of rotations and shaft runout. Therefore, in this method, fluctuations in the polishing amount, local bias in local polishing, and fluctuations in the polishing area occur in the finish of the polished surface. There was a problem of saying that. A mechanical operating mechanism such as a rotating mechanism needs a sufficient amount of space to allow each member to move smoothly, and therefore it is unavoidable that the movement of the polishing section will have some backlash. In addition, there is a problem that unevenness or fluctuation occurs in the finish of the polished surface. In short, as long as the polishing section is rotated at a high speed, it is impossible to completely prevent these problems.

In the conventional high-speed rotating magnetic polishing method, the pressing force for pressing the magnetic polishing fluid against the polishing surface is not generated by the rotation of the polishing tool itself, but is generated by the application of magnetism as described above. If the strength is not strong, sufficient polishing power will not be generated, and if the magnetic strength fluctuates, the polishing amount will change. Therefore, in this high-speed rotation magnetic polishing method, there is a problem that a magnetic generating means such as an electromagnet becomes large-scale, and it is necessary to strictly control a magnetic force.
Further, in the magnetic circuit for obtaining the pressing force, since the material to be polished needs to constitute a part thereof, there is a restriction that the material to be polished must be a magnetic conductor, that is, a magnetic material. However, even if the material to be polished is a non-magnetic material, a magnetic circuit can be formed through the non-magnetic material to be polished if the material is thin. However, even in this case, since the polishing surface pressure of the magnetic polishing fluid changes due to a slight change in the thickness of the material to be polished or a change in magnetic properties, there is a problem that it is difficult to control the polishing accuracy and the like of the polishing amount. The above-mentioned lens, optical element, and the like are non-magnetic and have a considerable thickness, so that the above-mentioned high-speed rotation magnetic polishing method cannot be applied.

Therefore, the problem of the conventional high-speed rotating magnetic polishing method is solved, and more precise processing is possible. In addition, the polishing is not affected by the magnetic properties of the polishing target material, and the polishing target is made of a non-magnetic material. In order to provide a micro-polishing method that can also be applied favorably, the inventors first set the polishing part in an XY direction parallel to the polishing surface and perpendicular to the polishing surface with an actuator composed of an electrostrictive element, ie, a piezo element. We have developed a micro-polishing method and a micro-polishing tool that make micro-motion in the Z direction and transmit this micro-motion of the polishing unit to the magnetic polishing fluid to polish the polished surface of the workpiece.

The novel micro-polishing method and the micro-polishing tool using the actuator composed of the electrostrictive element do not need to rotate the polishing part at high speed, and also hold the material to be polished itself with the magnetic polishing fluid and pressurize the magnetic polishing fluid. Since it is not necessary to form a part of the magnetic circuit, the above-mentioned problems of the conventional high-speed rotation fine polishing method can be completely solved.

In other words, in the micro-polishing method using the novel driving method, the magnetic polishing fluid is pressed against the workpiece by the action of the electrostrictive element, and the polishing section is caused to slightly move along the polishing surface, thereby polishing the workpiece. I am trying to process it. In other words, the XY-direction actuator or the Z-direction actuator using the electrostrictive element gives a minute motion to the polishing section so that the magnetic polishing fluid makes a minute motion in the horizontal or vertical direction with respect to the polishing surface of the workpiece. Causing the magnetic polishing fluid to perform a minute polishing motion along the polishing surface by a minute motion in the horizontal direction with respect to the polishing surface,
The pressure applied to the polished surface is obtained by a minute movement in the direction perpendicular to the polished surface.

As described above, in the micro-polishing method using the novel driving method, the rotation of the polishing section is not required, so that there is no variation in polishing, surface roughness or unevenness due to rotation unevenness or shaft deviation. Since the actuator using the electrostrictive element has no mechanical sliding portion or operating mechanism at all, and is driven very accurately in accordance with the applied voltage, the movement of the magnetic polishing fluid is also stable. Even in such a point, there is no variation or unevenness in polishing. Since the motion of the magnetic polishing fluid in the XY direction by the actuator is much smaller than the conventional rotary motion, the material to be polished is finely polished to achieve ultra-high-precision mirror finishing with extremely small surface roughness. Make it possible.

In addition, in this novel micro-polishing method using a driving method, a pressing force for pressing a magnetic polishing fluid against a workpiece is applied by a Z-direction actuator using an electrostrictive element. This eliminates the need to provide them, and as a result, polishing can be performed without any problem even if the material to be polished is a non-magnetic material, and regardless of the difference in magnetic properties due to the material and thickness of the material to be polished, Since the pressure applied to the material to be polished can be set and controlled only by the applied voltage, the material and shape of the material to be polished do not affect the polishing efficiency and the polishing accuracy. The material to be polished is
In addition to magnetic materials such as steel that can be polished by the conventional high-speed magnetic polishing method, non-magnetic materials such as glass and ceramic that cannot be polished by the conventional high-speed magnetic polishing method can be used. The shape of the non-abrasive material can be widely applied, from a thin material to a thick material, and the polishing surface can be a flat surface, a spherical surface, or a free-form surface.

According to the micro-magnetic polishing method according to this novel driving method, as described above, the micro-movement of the polishing section is an extremely small motion obtained by applying a voltage to the electrostrictive element. In addition, the material to be polished can be polished with high precision only in an extremely small area around the polishing portion, and the surface of the material to be polished can be finely and uniformly polished. Compared to the conventional high-speed rotation polishing method, much more uniform polishing is performed, so ultra-high-precision mirror polishing is also possible, and ultra-high-precision polishing with a shape accuracy of 0.01 μm or less is realized easily and reliably. You can.

The micro-polishing method and the micro-polishing tool according to the novel driving method can be used for a method that does not use a magnetic polishing fluid as an abrasive.

[Problems to be solved by the invention]

However, subsequent research has revealed that the new micropolishing method and micropolishing tool have the following new problems.

In other words, in the micro-polishing method using this novel driving method, in order to improve the processing efficiency and the like, in order to enlarge the movement range of the polishing unit and increase the processing diameter,
There is a problem in that the shape of the processing mark is lost, a good spherical processing mark cannot be obtained, and unevenness is formed on the processing surface and a smooth finished surface cannot be obtained.

It is considered that such a problem occurs for the following reason.

In the micro-polishing method, with the periodically fluctuating acting force of the XY-direction actuator, the polishing unit performs a periodic motion such as to draw an arc-shaped Lissajous figure with the supporting point as a base point, and the motion of the polishing unit is performed. As a result, a spherical processing mark is formed. The polishing section is supported by a Z-direction actuator so as to perform not only movement in the XY direction but also movement in the Z direction. However, since this Z-direction actuator is made of an electrostrictive element and is not a rigid body like a structural material, when the movement of the polishing unit in the XY direction increases, the support force that becomes the base point of the movement of the polishing unit by the action force of the XY-direction actuator The location, that is, the Z-direction actuator also moves in the XY direction, and as a result, the movement trajectory of the polishing section is disturbed, and the accurate shape such as the arc-shaped Lissajous figure described above cannot be drawn.

Therefore, the present invention provides a micro-polishing method using a novel driving method capable of obtaining a smooth and good machined surface without disturbing the motion trajectory of the polishing unit even when the machined diameter is increased, and without causing the machining trace to collapse. It is an object to provide a micro polishing tool.

[Means for solving the problem]

The main configuration of the micro-polishing method and the micro-polishing tool according to the present invention for solving the above problems is as follows.

First, the micro-polishing method according to the present invention, while holding the polishing material between the polishing portion of the polishing tool tip and the material to be polished,
A connecting part capable of making the polishing part minutely move in an XY direction parallel to a polishing surface and / or a Z direction perpendicular to the polishing surface with an actuator composed of an electrostrictive element, and allowing the Z direction actuator to make a small movement in the XY direction. Supports the polishing section through
An XY-direction actuator is operated between the connecting portion and the polishing portion, and the movement of the Z-direction actuator in the XY direction is regulated so as to polish the workpiece.

Next, the micro-polishing tool according to the present invention comprises a polishing portion facing the polishing surface of the material to be polished, and a lamination type electrostrictive element. An X-direction actuator to move, a Y-direction actuator comprising a laminated type electrostrictive element, and a micro-movement of the polishing portion in a Y direction parallel to the polishing surface and perpendicular to the X direction by an expansion and contraction action; And a Z-direction actuator for micro-moving the polishing section in the Z-direction perpendicular to the polishing surface by the expansion and contraction action of the element. The polishing section is supported, an action point of the XY-direction actuator is provided between the connection section and the polishing section, and the Z-direction actuator is provided with XY-direction motion regulating means.

In the present invention, as in the case of the conventional high-speed rotating magnetic polishing method, the polishing tool can move the polishing portion at the tip along the workpiece while being supported by an appropriate support member. As the moving means, means used in various machine tools and the like are employed.

The polishing tool, by the micro-driving means described below, according to the shape and purpose of the material to be polished, the polishing portion, the micro-movement in the direction horizontal to the polishing surface, that is, in the XY direction, and in the direction perpendicular to the polishing surface, Make a small movement in the Z direction. Furthermore, if an operation such as tilting the shaft is performed, it is possible to polish a complicated curved surface or the like.

The material to be polished is processed into a property corresponding to the surface property of the polishing portion. This polishing part can be composed of a Sn plating layer, a polyurethane layer, or the like. The shape of the polishing portion may be flat, but if it is spherical, the corner of the polishing portion can easily be prevented from hitting the polishing surface. When the polishing section is made of polyurethane, if the minute movement in the XY direction of the polishing section is set to have an amplitude larger than the pore diameter of the polyurethane, partial polishing due to cutting out does not occur, and a processing mark of a desired shape is formed. Can be easily obtained.

The spherical polishing portion may be formed of a sphere that is rotatably held at the tip of the polishing tool. This is because the rolling prevents uneven wear of the polishing portion. The sphere may be held mechanically, like a sphere of a bearing mechanism, or may be held by magnetic force. Also, the viscosity may be maintained by the abrasive viscosity.

The abrasive used in the present invention is not limited to a so-called magnetic polishing fluid, but a non-magnetic polishing fluid can also be used.

The magnetic polishing fluid has properties as a so-called magnetic fluid,
It has a function as an abrasive, and the same material as that used in a normal magnetic polishing method can be used. A typical magnetic fluid is a magnetic fluid composed of Fe ₃ O ₄ or the like and fine magnetic particles having a particle size of about 10 nm or less dispersed in water or oil in a colloidal state. If the grains have abrasiveness to the material to be polished,
A magnetic fluid composed of such magnetic particles can be used as it is. As a specific example of the magnetic abrasive powder, α-
Fe ₃ O ₄ (Bengara) and the like. Further, a normal fluid having no magnetism may be suspended and dispersed in a magnetic fluid composed of magnetic powder having no abrasive properties. As the abrasive particles in this case, Al ₂ O ₃ or SiO ₂ is used,
Those having a particle size of about 100 nm or less are preferably used.

When a magnetic polishing fluid is used as the polishing material, in order to magnetically hold the magnetic polishing fluid between the polishing portion at the tip of the polishing tool and the workpiece, for example, the magnetic polishing fluid may be brought close to the polishing portion at the tip of the polishing tool. If the yoke is provided to form a magnetic circuit, the magnetic action can easily hold the magnetic polishing fluid near the polishing portion.

As an actuator for minutely moving the polishing section, an electrostrictive element called a piezo element, which expands and contracts by applying a voltage, is used. If the polishing section is connected to this actuator and a voltage that fluctuates periodically is applied to the actuator, the polishing section can be minutely moved. The frequency of the micro-motion of the actuator changes according to the frequency of the applied voltage, and the amplitude of the micro-motion of the actuator changes according to the magnitude of the applied voltage. This minute movement of the polishing part is transmitted to the abrasive, and the abrasive performs a minute movement similar to that of the polishing part, and the material to be polished is polished by the minute movement of the abrasive.

The X-direction actuator makes the polishing section minutely move in the X direction parallel to the polishing surface, and the Y-direction actuator makes the polishing section minutely move in the Y direction horizontal to the polishing surface and perpendicular to the X direction. Is finely moved in a direction parallel to the polishing surface of the material to be polished to polish the material to be polished. The movement of the polishing unit by the XY-direction actuator may be a single movement in the X-direction or the Y-direction, or may be a movement in which the movement in the X-direction and the movement in the Y-direction can be simultaneously performed.
For example, the Lissajous movement can be performed by controlling the phases of the movement in the X direction and the Y direction.

The Z-direction actuator moves the polishing portion in a direction perpendicular to the polishing surface, moves the polishing material so as to collide with the material to be polished from a vertical direction, and applies a pressing force to the material to be polished. Therefore, the pressure applied to the workpiece can be controlled by the magnitude of the voltage applied to the Z-direction actuator.
Further, the polishing material is sequentially supplied to the polishing surface by the pumping action by the minute movement of the Z-direction actuator.

The X-axis actuator and the Z-direction actuator can be configured such that voltage application wiring is separately provided in each direction. , Y, Z directions. The drive wiring for applying a voltage to each actuator is connected to a drive amplifier, a function generator, and the like. These drive circuits or drive mechanisms can employ the same structure as that of an actuator using an electrostrictive element in a normal mechanical device. In the case of an XY-direction actuator, by appropriately controlling the phases of the applied voltages in the X-direction and Y-direction, the movement trajectory of the tip of the XY-direction actuator, that is, the polishing portion, is changed from a simple linear movement to a complex movement such as a Lissajous movement. It can be changed freely.

It is preferable that the X-direction actuator, the Y-direction actuator, and the Z-direction actuator are configured using a laminated electrostrictive element. If a laminated type is used, X
A small motion in the direction, the Y direction or the Z direction is performed. The laminated electrostrictive element expands and contracts by applying a voltage to both ends thereof.
If such a laminated electrostrictive element is used, a large displacement can be obtained, and the displacement of the minute motion in the XY direction does not change depending on the magnitude of the external force.

The XY and Z-direction actuators do not normally drive the polishing unit directly, but rather drive the polishing unit by applying small horizontal and vertical movements to the polishing shaft whose tip is the polishing unit. I do.

According to the present invention, the polishing unit is supported on the Z-direction actuator via a connecting portion capable of minute movement in the XY direction, and the XY-direction actuator acts between the connecting portion and the polishing portion.
Various connecting mechanisms in a normal mechanical device can be used as the connecting portion capable of minute movement in the XY direction. For example, in the case of a ball-and-even connecting portion, a minute movement in the XY direction is free, and the polishing portion can be reliably supported. According to the ratio of the distance from the ball-to-even connection to the point of action of the XY-direction actuator to the distance from the ball-to-even connection to the polishing section, XY
The amount of expansion and contraction of the directional actuator is expanded to become the momentum of the polishing unit. Therefore, in this case, if the distance from the XY direction actuator to the polishing section is set long,
Even though the direction actuator has the same amount of expansion and contraction, the range of movement of the polishing section can be expanded.

Further, in the present invention, the Z-direction actuator is allowed to freely expand and contract in the Z-direction, but is restricted from moving in the XY-direction. As the motion restricting means, various motion restricting mechanisms in a normal mechanical device can be used as long as it has the above functions. For example, one end of a restricting bracket supported on the structural part side of the highly rigid tool body is applied to a position near the connecting portion of the Z-direction actuator so as to be immovable in the XY direction, and the restricting bracket is moved in the Z direction. The Z-direction actuator can be freely expanded and contracted if it can be bent freely.

As described above, the pressure applied by the abrasive to the material to be polished is determined by the pressure applied by the Z-direction actuator, and when a magnetic holding force is used in combination, the holding force is also affected. However, this pressing force decreases with the progress of processing. Therefore, it is preferable to detect the value of the pressurizing load applied to the material to be polished and feed back the value to the control of the Z-direction actuator to perform the pressing force control. As the load detecting means for detecting the applied load value, a pressure sensor similar to that incorporated in ordinary various mechanical devices can be used as long as it can detect a vertical load applied to the workpiece. . For example, if the polishing process is performed with the material to be polished placed on the load cell, the magnitude of the pressing load applied to the material to be polished can be detected by the load cell and taken out as an electric signal.

The pressurized load value detected by the load detecting means is converted into an electric machine signal to control the driving of the actuator. Specifically, the detection signal is processed by an appropriate electric circuit, and is input to a drive circuit that applies a voltage to the actuator, where a predetermined pressure load value is compared with the detected pressure load value. Then, the voltage applied to the Z-direction actuator is increased or decreased. That is, the pressing force by the Z-direction actuator is feedback-controlled. This feedback control, for example, always keeps the pressing force by the Z-direction actuator at a predetermined level, is large at the beginning of the machining process (rough polishing), is medium at the middle stage (medium polishing), and is small at the end (finishing). (Polishing). Note that, even in the case of this multi-stage polishing, it is preferable to control the pressing force in each step to be constant.

As described above, when the pressing force in the Z direction is kept constant, if the vibration is applied to the pressing force by the Z direction actuator, the polishing material is sequentially supplied to the polishing surface by the pumping action due to the vibration, In addition, a phenomenon of being sequentially eliminated is caused.

The set value of the pressing force is appropriately determined according to conditions such as the material of the workpiece and the polishing accuracy.

When a magnetic polishing fluid is used as the polishing material, the polishing shaft becomes a central yoke as a part of a magnetic circuit for holding its magnetism, so that the polishing shaft is formed of a magnetic material. The opposing yoke is disposed so as to leave a gap serving as a magnetic gap between the opposing yoke and the polished portion at the tip of the central yoke. For example, an annular opposing yoke is arranged so as to surround the central yoke having a circular cross section at intervals.
By doing so, the magnetic polishing fluid can be favorably held around the polishing portion of the central yoke. In addition, a bar-shaped or plate-shaped opposed yoke may be arranged side by side with the central yoke. Since the opposing yoke also forms a part of the magnetic circuit, it goes without saying that it is formed of a magnetic material. It is preferable that the tip of the opposing yoke facing the center yoke be tapered, since the magnetic field can be concentrated on the tip of the opposing yoke.

A magnetic circuit is formed by connecting the center yoke and the opposing yoke by magnetic generating means. As the magnetism generating means, either a permanent magnet or an electromagnet can be adopted,
According to the present invention, it is not necessary to change the direction and magnitude of the magnetic field, so that the permanent magnet is preferable because of its simple structure. As the permanent magnet, a permanent magnet made of Sm-Co magnet or the like can be used.

[Action]

The polishing unit is supported on the Z-direction actuator via a connection part that can make small movements in the XY direction. If an XY-direction actuator is applied between this connection part and the polishing unit, the polishing unit in the XY-direction And the pressing force of the Z-direction actuator can be reliably transmitted to the polishing section.

However, in this method, when the movement range of the polishing unit is increased in order to increase the processing diameter, the connecting portion and the Z-direction actuator, which are the starting points when the polishing unit makes a minute movement in the XY direction, are moved by the movement of the polishing unit. Move in the XY direction. If the base point of the minute movement in the XY direction moves, the movement trajectory of the polishing unit drawn based on this base point will be disturbed.
That is, the polishing unit vibrates in a state where a higher-order vibration component due to the movement of the base point is added to the periodic expansion and contraction vibration of the XY-direction actuator.

Therefore, if the movement of the Z-direction actuator in the XY direction is regulated, the Z-direction actuator and the connecting portion
The polishing unit stops moving in the direction, and the polishing unit draws an accurate motion trajectory set in advance. That is, by increasing the rigidity of the Z-direction actuator and the connecting portion in the XY direction, the high-order vibration component described above is not generated, and the polishing portion performs only the original vibration due to the periodic expansion and contraction of the XY-direction actuator. . As a result, the shape of the processing mark determined by the movement trajectory of the polishing unit becomes accurate, and a smooth processing surface is obtained.

〔Example〕

Next, an embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a polishing tool which is a main part of a polishing apparatus used for carrying out a fine polishing method according to the present invention. The main body 10 of the polishing tool 1 has a main body of a polishing apparatus (not shown).
Is supported and fixed by a support shaft 11. The support shaft 11 can freely move in the horizontal direction and the vertical direction, and can be inclined at an arbitrary angle. The operating mechanism of the support shaft 11 is the same as the operating mechanism of a normal machine tool such as a machining shaft.

In the center of the lower surface of the tool body 10, Z
A direction actuator 20 is provided, and a block 22 is suspended from a lower end thereof via a connecting portion 21 having a ball-to-corner connecting action. Here, the sphere-to-corner connection action means that the block 22 allows the Z-direction actuator 20 to freely move in the XY direction (vertical direction as viewed in the drawing) with respect to the Z-direction while allowing the micro-motion to freely move. This is a coupling operation that reliably transmits the Z-direction minute movement of the direction actuator 20 to the block 22.

The Z-direction actuator 20 is connected to a structural portion of the tool body 10 via a restricting member 80 as a movement restricting means in the XY direction at a portion immediately above the connecting portion 21. FIG. 2 shows the detailed structure of the regulating fitting 80. The regulating bracket 80 is Z
The central part 83 is sandwiched and attached between the directional actuator 20 and the connecting part 21, and includes bar-shaped regulating support parts 81 and 82 extending from the central part 83 in the XY direction. It is fixed to the tool body 10. Regulatory support 81,8
2, a constricted portion 84 is formed in the middle of the length direction, and the restricting support portions 81 and 82 can be bent and deformed by the constricted portion 84. Therefore, the Z-direction actuator 20
Cannot move in the axial direction, that is, the XY direction, of the restricting support portions 81 and 82, but the constricted portion 84 of the restricting support portions 81 and 82
In the bending direction, that is, the Z direction.

Next, the lower end of the block 22 has a central yoke serving as a polishing axis.
23 are integrally connected and hung. In FIG. 2, the block 22 and the central yoke 23 are screwed. At the upper part of the block 22, the tip of an X-direction actuator 24x is connected in contact with the horizontal X-direction side surface as viewed in the figure, and the Y-direction side surface horizontal and perpendicular to the X direction (FIG. 1). The tip of the Y-direction actuator 24y is in contact with the inner side surface of the actuator. In this embodiment, the Z-direction actuator 20
And X direction actuator 24x and Y direction actuator 24y
Are formed by laminating a large number of thin piezo elements, and expand and contract in the Z direction (axial direction of the central yoke 23), the X direction, and the Y direction by applying a voltage, and the abrasive material is moved by a minute movement in the Z direction. The polishing material can be freely moved within the polishing surface of the material to be polished by being pressed against the material to be polished and combined with the minute movement in the X and Y directions.

As the specifications of the XYZ direction actuators, those shown in Table 1 below can be used.

The tip of the center yoke 23 is gradually thinned, and the tip surface is spherical. This spherical portion is the polishing unit 26. The polishing section 26 may be made of a Sn plating layer or the like, but when it is made of a polyurethane layer, the magnetic polishing fluid M impregnated and held in the polyurethane layer polishes the polished surface of the workpiece W. is there.

In this embodiment, as shown in detail in FIG.
26 is a sphere that is rotatably held at the tip of the central yoke 23
It consists of 25, and the surface is finished with a Sn plating layer. In this embodiment, the sphere 25 is held at the tip of the central yoke 23 by viscousness of the magnetic polishing fluid M. However, such a sphere may be fitted inside the tip of the center yoke 23 and held mechanically, or may be held by magnetic force.

The drive wiring 50 of each of the actuators 20, 24x, 24y is electrically connected to a drive amplifier 51 including a 3CH piezo driver amplifier. Specific specifications of the 3CH piezo driver amplifier are, for example, 350 V, 100 mA, and 30 kHz. The drive amplifier 51 is connected to a signal generator 52 for the Z direction and a variable phase 2 output signal generator 53 for the XY direction. A voltage having a predetermined frequency is applied to each of the actuators 20, 24x, 24y from the signal generators 52, 53 via the drive amplifier 51, and the driving of each of the actuators 20, 24x, 24y is controlled.

On the lower surface of the tool body 10, a cylindrical body 30 made of a non-magnetic material is attached. An opening 31 into which the actuators 24x and 24y, the drive wiring 50 of each actuator, and the like are inserted is formed in an intermediate portion (the right side surface portion in FIG. 1) of the tubular body 30. A connection body 32 made of a ring-shaped magnetic body is screwed and connected to a lower portion of the cylindrical portion 30. A part of the inner peripheral portion of the connector 32 extends to a position close to the outer peripheral surface of the central yoke 23. The connecting body 32 is formed with a fluid supply path 33 penetrating from the outer peripheral side surface to the inner peripheral lower surface, and the fluid supply path 33
A fluid supply pipe 34 is connected to an outer peripheral end of the fluid supply pipe 34. When the magnetic polishing fluid is supplied to the fluid supply pipe 34, the magnetic polishing fluid is dropped and supplied from the fluid supply path 33 to the vicinity of the outer periphery of the tip of the central yoke 23. Ring-shaped Sm at the lower end of connector 32
A permanent magnet 40 made of a Co magnet is attached. The strength of the magnetic force of the permanent magnet 40 is, for example, about 5 kGauss.
An opposing yoke 35 made of a magnetic material is attached to a lower end of the permanent magnet 40. The opposing yoke 35 is conically narrowed toward the lower end, the inner peripheral portion at the tip is tapered, and the inner peripheral portion of the distal end is separated from the distal end of the central yoke 23 by a certain gap. They are arranged facing each other. As a result, the permanent magnet 40 passes through the connecting body 32 and the central yoke 23 to the opposite yoke.
A magnetic circuit that returns from the 35 to the permanent magnet 40 is formed, and a donut-shaped magnetic gap is formed between the central yoke 23 and the opposing yoke 35.

Below the central yoke 23 and the opposing yoke 35, a load cell 60 serving as a load detecting means is provided, and the workpiece W is polished while being placed on the load cell 60. The detection output of load cell 60 is
The pressure is input to the drive amplifier 51 via 61, and the pressure applied to the workpiece W from the Z-direction actuator 20 is feedback-controlled.

The drive amplifier 51 also receives a vibration application signal from the FG generator 70 to apply vibration to the pressing force of the Z-direction actuator 20.

The magnetic micropolishing method of the present invention, which is performed by using the polishing apparatus having such a structure, will be specifically described below.

The polishing tool 1 is placed on the workpiece W while the workpiece W is placed on the load cell 60. When the magnetic polishing fluid M is supplied from the fluid supply pipe 34 to the tip of the central yoke 23, the magnetic polishing fluid M is magnetically held near the magnetic gap between the central yoke 23 and the opposing yoke 35. In this state, as shown schematically in FIG. 3, the magnetic polishing fluid M is covered and held up to the lower surface of the front end of the central yoke 23, so that the magnetic polishing fluid M is polished by the magnetic action. Material W
It will be pressed against the surface of.

Next, when a periodic voltage is applied to the Z-direction actuator 20, the Z-direction actuator 20 causes a slight expansion and contraction movement in a direction perpendicular to the polished surface of the workpiece W (up and down direction in FIG. 1). Along with this, the polishing section 26, which is the tip of the central yoke 23, makes a small movement in the vertical direction (in the direction of the straight arrow) as seen in FIG. 3, and the magnetic polishing fluid M is applied to the surface (polishing surface) of the workpiece W. Press and press. XY direction actuator
A periodic voltage is also applied to 24x and 24y, and the block 22 with which the ends of the XY-direction actuators 24x and 24y are in contact swings in the horizontal direction (left and right directions in the figure). As a result, the polishing portion 26 largely swings about the spherical corner-shaped connecting portion 21 as shown by the arc-shaped arrow in FIG. This swing is a minute movement in the horizontal direction (XY direction) with respect to the surface (polishing surface) of the workpiece W. The minute movement in the XY direction and the minute movement in the Z direction are transmitted to the magnetic polishing fluid M, and the magnetic polishing fluid M
Grinds the surface (polished surface) of the workpiece W. Since the magnetic polishing fluid M presses the workpiece W only in the vicinity of the portion sandwiched between the tip of the center yoke 23 and the workpiece W to perform the polishing action, the workpiece W substantially has a central yoke. 23 polishing units
A processing mark H having a shape and a size corresponding to the movement range of 26 is formed.

When the entire polishing tool 1 is moved in a horizontal direction or a three-dimensional direction according to a predetermined polishing surface shape while performing such a polishing operation, and the processing trace H is spread over the entire polishing surface of the workpiece W, A desired polished surface such as a flat surface, a spherical surface, or a free-form surface can be freely obtained.

During this time, in the load cell 60 on which the workpiece W is placed, the pressing force applied to the workpiece W by the polishing unit 26 of the polishing tool 1 via the magnetic polishing fluid M is detected as a pressing load value.
This pressure load signal is sent to the drive amplifier 51 via the controller 61.
Feedback. Therefore, for example, if the pressure applied to the workpiece W is equal to or more than a specified value, the drive amplifier 51 controls the pressure to be reduced by lowering the voltage applied to the Z-direction actuator 20 or the like. When the pressure applied to the workpiece W falls below a predetermined value, the drive amplifier 51 controls the pressure to be increased by increasing the voltage applied to the Z-direction actuator 20 or the like. On the other hand, in the process of processing one processing mark, the pressing force tends to decrease with the passage of time.
Detects this tendency and feeds back the detection result to the drive amplifier 51 so that the applied pressure is always constant. Further, the signal generator 52 for the Z direction is provided with the processing mark 1.
In the process of processing individual pieces, the pressing force is initially large,
A control signal is issued to the drive amplifier 51 so that the pressure is medium in the middle period and is small at the end.
During that time, the FG generator 70 continues to issue a vibration applying signal to the drive amplifier 51 to apply vibration to the pressing force of the Z-direction actuator 20.

FIG. 4 shows a method according to the above-described embodiment and a method according to a comparative example in which the regulating bracket 80 is not attached to the Z-direction actuator 20.
FIG. 4B shows a processing state in which the movement range of the polishing section 26 is enlarged to increase the processing diameter. According to the comparison method shown in FIG. While the shape is collapsed, the processing mark H of the embodiment shown in FIG. 4 (a) has a smooth and good spherical shape.

〔The invention's effect〕

As described above, the present invention relates to a Z-direction actuator.
The polishing section is supported via a connecting section capable of minute movement in the XY direction, and an XY direction actuator is actuated between the connecting section and the polishing section. The pressing force of the actuator in the direction can be reliably transmitted to the polishing section, and the polishing action by the minute motion of the polishing section in the Z direction and the XY direction can be exhibited well. Moreover, the XY of the Z-direction actuator
By restricting the movement in the direction, the starting point of minute movement in the XY direction of the polishing part does not move and it draws an accurate movement trajectory, so the shape of the processing mark formed according to the movement trajectory of the polishing part However, an accurate and smooth finish can be obtained. In particular, even if a large processing mark is formed by enlarging the range of movement of the polishing section, the shape of the processing mark can be finished smoothly without being deformed, which can greatly contribute to the improvement of the efficiency of the polishing processing.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a polishing tool, which is a main part of a polishing apparatus used for carrying out a fine polishing method according to the present invention, FIG. 2 is an exploded perspective view of an actuator portion, and FIG. 4 (a) and 4 (b) are cross-sectional views of processing marks, FIG. 4 (a) is a case of an embodiment of the present invention, and FIG. 4 (b) is a case of a comparative example. 1 ... polishing tool, 20 ... Z-direction actuator, 21 ...
Ball-to-corner connection, 23 ... Center yoke, 24x ... X-direction actuator, 24y ... Y-direction actuator, 26 ...
… Polishing part, 35… Opposing yoke, 80… Regulator, M…
Magnetic polishing fluid, W: Material to be polished

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-2-65968 (JP, A) (58) Fields studied (Int. Cl. ⁶ , DB name) B24B 37/00

Claims (2)

(57) [Claims] In a state where a polishing material is held between a polishing portion at a tip of a polishing tool and a material to be polished, said polishing portion is moved in an XY direction parallel to a polishing surface and / or a polishing surface by an actuator comprising an electrostrictive element. Micro-movement in the vertical Z-direction, and the Z-direction actuator supports the polishing section via a connecting section capable of micro-movement in the XY direction, and causes the XY-direction actuator to act between this connecting section and the polishing section. A micro-polishing method for polishing a workpiece by restricting the movement of the Z-direction actuator in the XY direction. 2. An X-direction actuator, comprising: a polishing portion facing a polishing surface of a material to be polished; a stack-type electrostrictive element; The polishing portion is made of a laminated type electrostrictive element, and the expansion and contraction action causes the polishing portion to be parallel to the polishing surface and perpendicular to the X direction.
A Y-direction actuator for micro-moving in the direction, and a Z-direction actuator composed of a laminated electrostrictive element and making the polishing portion move in the Z-direction perpendicular to the polishing surface by the expansion and contraction action. The polishing unit is supported via a ball-and-even connecting portion capable of minute movement of the XY-direction actuator, and an action point of the XY-direction actuator is provided between the connecting portion and the polishing portion. A micro polishing tool provided with.