JPH0441177A - Micro-polishing method and micro-polishing tool - Google Patents

Abstract

PURPOSE:To surely transmit to a polishing part the pressurizing force of an actuator in the Z direction without hindering the micromotion in the XY direction of a polishing part by supporting the polishing part via a connection part capable of the micromotion in the XY direction on a Z directional actuator, and acting the XY directional actuator between this connection part and polishing part. CONSTITUTION:A polishing part 26 is subjected to a micromotion in the XY direction parallel to a polishing face and/or the Z direction vertical to the polishing face by actuators 20, 24X, 24Y composed of electrostrictive elements, in the state of a polishing material M being held between the polishing part 26 of the polishing tool tip and a work W. Moreover the polishing part 26 is supported on the Z directional actuator 20 via a connection part 21 capable of the micromotion in the XY direction, the XY directional actuators 24X, 24Y are acted between this connection part 21 and polishing part 26, the motion in the XY direction of the Z directional actuator 20 is regulated as well and the work W is polished.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a micropolishing method and a micropolishing tool,
Specifically, the present invention relates to a method of precisely polishing a minute area in order to perform ultra-high precision processing in the field of manufacturing lenses, optical elements, etc., and a polishing tool used to implement the method.

[Conventional method]

Aspherical lenses, X-ray optical elements, etc. that are incorporated into various electronic and optical devices are manufactured by polishing, but extremely high-precision processing with a product shape accuracy of 0.01 μm or less is required. There is a need for a processing method that can perform such ultra-high precision polishing.

For this purpose, a polishing method that can precisely polish only a minute area of the polished surface is required.

Conventionally, polishing processing, lapping processing, etc. have been adopted as high-precision polishing methods, but the above-mentioned 0, 0
Ultra-high precision machining of 1 μm or less was completely impossible, so
In recent years, a magnetic polishing method that uses a magnetic polishing fluid as an abrasive has been attracting attention as a method that can perform processing with higher precision. Here, the term "magnetic polishing fluid" refers to a magnetic fluid alone or a magnetic fluid in which fine particles of abrasive material are suspended and dispersed.

In the magnetic polishing method, a magnetic polishing fluid is supplied and a magnetic field is applied between a polishing part at the tip of a polishing tool and a workpiece to be polished. Then, the magnetic polishing fluid is held between the polishing section and the material to be polished in a state where the polishing surface of the first material to be polished is pressurized by magnetic action.

In this state, when the polishing tool is rotated at high speed, the magnetic polishing fluid is dragged by the rotation of the polishing tool and is rotated at high speed, thereby polishing the material to be polished. At this time, by varying the direction and strength of the applied magnetic field, the force applied to the polishing surface by the magnetic polishing fluid can be varied, and the interlocking of the magnetic polishing fluid can be controlled to improve polishing performance. is also being carried out. Specific examples of this magnetic polishing method are disclosed in, for example, JP-A-60-118466, JP-A-61-244457, and JP-A-1-16623.

According to this magnetic polishing method, the magnetic holding force allows the abrasive to act intensively on a minute area of the polishing surface, making it possible to achieve higher precision polishing compared to conventional polishing methods. There are advantages.

However, even with this magnetic polishing method, it has not been possible to sufficiently cope with ultra-high precision machining of 0.01 μm or less.

That is, in this method, the magnetic polishing fluid is rotated at high speed by the high speed rotation of the polishing tool, so the finish of the polished surface is directly affected by the rotational state of the polishing tool. However, since the rotation of the polishing tool is prone to fluctuations in the rotational speed and shaft runout, this method does not allow fluctuations in the amount of polishing, local polishing bias, or fluctuations in the polishing area to affect the finish of the polished surface. There was a problem that it would become distorted. Mechanical operating mechanisms such as rotating mechanisms require sufficient space to allow each member to move smoothly, and it is unavoidable that there will be some wobble in the movement of the polishing unit. There was also the problem that unevenness and fluctuations occurred in the finish of the polished surface. In short, it has been impossible to completely prevent these problems as long as the polishing section is rotated at high speed.

In the conventional high-speed rotation magnetic polishing method, the pressure force for pressing the magnetic polishing fluid against the polishing surface is not generated by the rotation of the polishing tool itself, but by the application of magnetism as described above. If the magnetic strength is not strong enough, sufficient polishing force will not be generated, and if the magnetic strength changes, the amount of polishing will change. Therefore, this high-speed rotational magnetic polishing method requires a large-scale magnetism generating means such as an electromagnet, and also has the problem of requiring strict control of the magnetic force. Furthermore, since the material to be polished itself must constitute a part of the magnetic circuit for obtaining this pressing force, there is a restriction that the material to be polished must be a magnetic conductor, that is, a magnetic material. However, even if the fijf polishing material is a non-magnetic material, a magnetic circuit can be constructed through the non-magnetic polishing material as long as it is thin. However, even in this case, the pressing force of the magnetic polishing fluid on the polishing surface changes due to slight variations in the thickness of the material to be polished or variations in the magnetic properties, making it difficult to control the amount of polishing, polishing accuracy, etc.

Note that the above-mentioned lenses, optical elements, etc. are non-magnetic and have considerable thickness, so the high-speed rotational magnetic polishing method described above cannot be applied to them.

Therefore, by solving the problems of the conventional high-speed rotation magnetic polishing method mentioned above, it is possible to perform more precise processing, and it is possible to
In order to provide a micro-polishing method that is not affected by the magnetic properties of the abrasive material and can be successfully applied to materials to be polished made of non-magnetic materials, the inventors first electrically An actuator consisting of a strain element, that is, a piezo element, makes minute movements in the XY directions parallel to the polishing surface and in the Z direction perpendicular to the polishing surface, and this minute movement of the polishing part is transmitted to the magnetic polishing fluid to polish the polished surface of the workpiece. We have developed a micro-polishing method and a micro-polishing tool for polishing.

This new micro-polishing method and micro-polishing tool using an actuator consisting of an electrostrictive element does not require high-speed rotation of the polishing section, and also allows the material to be polished to hold and pressurize the magnetic polishing fluid. Since it is not necessary to make it a part of the magnetic circuit, the problems of the conventional high-speed rotation micro-polishing method described above can be completely solved.

In other words, in the micropolishing method using this new drive method,
The electrostrictive element forces the magnetic polishing fluid onto the workpiece and causes the polishing section to move minutely along the polishing surface, thereby polishing the workpiece. In other words, a fine movement is applied to the polishing part by an xy-direction actuator or a Z-direction actuator using an electrostrictive element, so that the magnetic polishing fluid is made to make a fine movement in the horizontal or vertical direction with respect to the polishing surface of the material to be polished. west,
The magnetic polishing fluid is made to perform a minute polishing movement along the polishing surface by making a minute movement in the horizontal direction with respect to the polishing surface, and to obtain a pressing force against the polishing surface by making a minute movement in the vertical direction to the polishing surface. .

In this way, the micro-polishing method using this novel drive method does not require rotation of the polishing section, and as a result, there are no variations in polishing or uneven surface roughness due to uneven rotation, shaft runout, or the like.

An actuator using an electrostrictive element has no mechanical sliding parts or operating mechanisms, and is driven extremely accurately according to an applied voltage, so that the movement of the magnetic polishing fluid is also stable.

In this respect as well, variations and unevenness in polishing are not caused. The movement of the magnetic polishing fluid in the X and Y directions by the actuator is much smaller than conventional rotational movement, so it is possible to finely polish the material to be polished and achieve ultra-high precision mirror finishing with extremely low surface roughness. possible.

In addition, in the micro-polishing method using this new drive method, the pressure force for pressing the magnetic polishing fluid onto the material to be polished is applied by a Z-direction actuator using an electrostrictive element, so the magnetic circuit connecting from the polishing part of the polishing tool to the material to be polished is As a result, even if the material to be polished is non-magnetic, it can be polished without any problem, and regardless of the difference in magnetic properties due to the material and thickness of the material to be polished, the actuator can be Since the pressure applied to the material to be polished can be set and controlled using only the applied voltage, polishing efficiency and polishing accuracy are not affected by the material or shape of the material to be polished. As the material to be polished, in addition to magnetic materials such as steel that can be polished by conventional high-speed rotational magnetic polishing methods, non-magnetic materials such as glass and ceramics that cannot be polished by conventional high-speed rotational magnetic polishing methods can also be used. The non-abrasive material can be used in a wide variety of shapes, from thin to thick, and the polished surface can be flat, spherical, or free-form.

According to the micro magnetic polishing method using this new driving method,
As mentioned above, the minute movement of the polishing part is an extremely small movement obtained by applying a voltage to the electrostrictive element, so the magnetic polishing fluid can only affect the material to be polished in an extremely small area around the polishing part. can be polished with high precision, and the surface of the material to be polished can be polished finely and uniformly. Compared to conventional high-speed rotation polishing methods, the polishing process is much more uniform, making it possible to perform ultra-high-precision mirror finishing, making ultra-high-precision polishing with a shape accuracy of 0.01 μm or less easier and more reliable. It can be achieved.

Note that the micropolishing method and micropolishing tool using this novel driving method can also be used in a method that does not use a magnetic polishing fluid as an abrasive.

[Problem to be solved by the invention]

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

In other words, in the micro-polishing method using this new drive method, if you try to increase the working diameter of the polishing part by expanding the interlocking range of the polishing part for the purpose of improving machining efficiency, the shape of the machining mark will be distorted, and it will not be possible to obtain a good workpiece. Unable to obtain spherical machining marks,
There is a problem in that unevenness occurs on the machined surface, making it impossible to obtain a smooth finished surface.

The reason why such a problem occurs is considered to be as follows.

In the micro-polishing method, the polishing section moves periodically in an arcuate shape based on its support point by the periodically varying acting force of the XX direction actuator, and along with this movement of the polishing section, A spherical machining mark is formed. The polishing section is supported by an X-direction actuator so that it can move not only in the XX direction but also in the Z direction. However, since this X-direction actuator is made of an electrostrictive element and is not a rigid body like a structural material, the movement of the polishing part in the XX direction is large (in this case, the acting force of the XX-direction actuator causes the movement base of the polishing part to The supporting point, that is, the X-direction actuator also moves in the XX direction, and as a result, the locus of motion of the polishing section is disturbed, and an accurate shape such as the above-mentioned arc-shaped cross-section figure cannot be drawn.

Therefore, the present invention proposes a micro-polishing method using a novel drive system that prevents the movement locus of the polishing part from being disturbed even when the machining diameter is increased, and provides a smooth and well-machined surface without collapsing the machining marks. The objective is to provide a micro-polishing tool.

[Means for Solving the Problems] The main configurations of the micropolishing method and micropolishing tool according to the present invention for solving the above problems are as follows.

First, in the micro-polishing method according to the present invention, with an abrasive being held between a polishing part at the tip of a polishing tool and a material to be polished, the polishing part is moved in the XX direction parallel to the polishing surface using an actuator made of an electrostrictive element. and/or make a minute movement in the Z direction perpendicular to the polishing surface, and cause the X direction actuator to
The polishing part is supported via a connecting part that is capable of minute movement in the direction, and the XX direction actuator acts between the connecting part and the polishing part, and the movement of the X-direction actuator in the XX direction is regulated. , to polish the material to be polished.

Next, the micro-polishing tool according to the present invention includes a polishing section facing the polishing surface of the material to be polished, and a laminated electrostrictive element, and its expansion and contraction action causes the polishing section to be microscopically moved in the X direction parallel to the polishing surface. The X-axis is composed of an X-direction actuator for movement and a laminated electrostrictive element, and its expansion/contraction action causes the polishing part to minutely move in the X-direction parallel to the polishing surface and perpendicular to the X-direction.
A directional actuator, and an X-direction actuator which is made of a laminated electrostrictive element and whose expansion and contraction action causes the polishing part to move minutely in the Z direction perpendicular to the polishing surface, and the X-direction actuator is capable of making minute movements in the XX direction. A polishing section is supported via a ball-to-even coupling section, and a point of action of an XX direction actuator is provided between this coupling section and the polishing section.
In this invention, in which the directional actuator is provided with a movement regulating means in the XX direction, the polishing tool is supported by a suitable support member and the polishing portion at the tip is moved as in the case of the conventional high-speed rotating magnetic polishing method. It is moved along the material to be polished, and the supporting means and moving means used in various machine tools and the like are employed.

The polishing tool moves its polishing part in a direction parallel to the polishing surface, that is, in the XX direction, and also in a direction perpendicular to the polishing surface, that is, in the XX direction, depending on the shape and purpose of the material to be polished, by means of micro-driving means, which will be described later. Make a small movement in the Z direction. Furthermore, by performing operations such as tilting the axis, it is possible to polish complex curved surfaces.

The material to be polished is processed to have properties corresponding to the surface properties of the polished portion. This polishing part can be composed of a Sn plating layer, a polyurethane layer, or the like. The shape of the polishing part may be flat, but if it is made spherical, the corners of the polishing part can easily be prevented from coming into contact with the polishing surface.

When the polishing part is made of polyurethane, the
When the amplitude of the micromovement in the X direction is made larger than the pore diameter of the polyurethane, partial polishing due to polishing breakage does not occur, and machining marks of a desired shape can be easily obtained.

The spherical polishing section is preferably composed of a sphere that is movably held at the tip of the polishing tool. This is because this transfer prevents uneven wear of the polishing part. The sphere may be held mechanically, like the sphere of a bearing mechanism, or may be held magnetically. Alternatively, it may be held by the viscosity of the abrasive.

The abrasive used in this invention is not limited to so-called magnetic polishing fluids, but non-magnetic polishing fluids can also be used.

The magnetic polishing fluid has properties as a so-called magnetic fluid and functions as an abrasive, and can be the same as those used in normal magnetic polishing methods. - The magnetic fluid used for boat fishing is made by colloidally dispersing fine magnetic powder particles of approximately 10 nm or less in diameter, made of Fe50< etc., in water, oil, etc. However, as long as it has abrasive properties for the material to be polished, a magnetic fluid made of such magnetic powder particles can be used as is. Specific examples of the magnetic abrasive powder include α-Fe*Oa (red iron). Also,
It may also be one in which ordinary abrasive powder grains without magnetism are suspended and dispersed in a magnetic fluid made of magnetic powder grains without abrasiveness. In this case, the abrasive powder particles include AlzO- and Si.
O, etc. are used, and those having a particle size of about 1100 nm or less are preferably used.

When using a magnetic polishing fluid as an abrasive, in order to magnetically hold the magnetic polishing fluid between the polishing part at the tip of the polishing tool and the material to be polished, for example, the magnetic polishing fluid must be placed close to the polishing part at the tip of the polishing tool. If a magnetic circuit is configured by providing a yoke, the magnetic polishing fluid can be easily held near the polishing section by its magnetic action.

The actuator that makes minute movements of the polishing part uses an electrostrictive element, also called a piezo element, which expands and contracts by applying a voltage. By connecting the polishing section to this actuator and applying a periodically varying voltage to the actuator, the polishing section can be moved minutely. The frequency of the minute movement of the actuator changes depending on the frequency of the applied voltage, and the amplitude of the minute movement of the actuator changes depending on the magnitude of the applied voltage. This minute movement of the abrasive part is transmitted to the abrasive material, the abrasive material performs the same minute movement as the abrasive part, and the material to be polished is polished by this minute movement of the abrasive material.

The X-direction actuator makes a small movement of the polishing part in the X direction, which is horizontal to the polishing surface, and the X-direction actuator makes a small movement of the polishing part in the X direction, which is horizontal to the polishing surface and perpendicular to the above-mentioned X direction. The material to be polished is polished by making small movements in a direction parallel to the polishing surface of the material to be polished. The movement of the polishing section by the XX direction actuator may be an independent movement in the X direction or the X direction, or may be a movement in which the movement in the X direction and the movement in the X direction are related and can be moved simultaneously.

For example, Lissajous motion can be achieved by controlling the X direction and the phase of the motion in the X direction.

The X-direction actuator moves the polishing part in a direction perpendicular to the polishing surface, moves the abrasive so that it collides with the workpiece from the perpendicular direction, and applies pressure to the workpiece. Therefore, the pressing force applied to the material to be polished can be controlled by the magnitude of the voltage applied to the X-direction actuator. Moreover, the abrasive material is sequentially supplied to the polishing surface by the pumping effect caused by the minute movement of the X-direction actuator.

The XX direction actuator and the Make small movements in the X, Y, and X directions. Drive wiring that applies voltage to each actuator is connected to a drive amplifier, a function generator, and the like. These drive circuits or drive mechanisms can have a structure similar to that of actuators using electrostrictive elements in ordinary mechanical devices. In the case of an XX-direction actuator, by appropriately controlling the phases of the applied voltages in the X-direction and the
It is possible to freely change even complex movements such as the ju-movement.

The X-direction actuator, the Y-direction actuator, and the Z-direction actuator are preferably constructed using stacked electrostrictive elements. If a laminated type is used, minute movements in the X direction, Y direction, or Z direction can be made by expansion and contraction. A stacked 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 minute movements in the XY force directions does not vary depending on the magnitude of external force.

The XY-direction actuator and the Z-direction actuator usually do not directly drive the polishing section, but instead drive the polishing section by applying small horizontal or vertical movements to the polishing shaft whose tip is the polishing section. do.

In this invention, the polishing part is supported by the Z-direction actuator via a connecting part that can make small movements in the XY force directions, and the XY-direction actuator is caused to act between the connecting part and the polishing part. Various types of connection mechanisms in ordinary mechanical devices can be used as the connection part capable of minute movement in the XY force directions. for example,
The spherical-to-even connecting portion allows for free minute movement in the XY force directions, and can also reliably support the polishing portion. The amount of expansion and contraction of the XY direction actuator is expanded in accordance with the ratio of the distance from the ball-to-even joint to the point of action of the XY-direction actuator and the distance from the ball-to-even joint to the polishing part. The momentum of Therefore, in this case, XY
By setting a long distance from the directional actuator to the polishing section, the range of movement of the polishing section can be expanded even though the amount of expansion and contraction of the XY direction actuator remains the same.

Further, in this invention, the Z-direction actuator is allowed to freely expand and contract in the Z-direction, but its movement in the XY force direction is restricted (the movement restriction means has the above-mentioned function). If so, various movement regulating mechanisms in ordinary mechanical devices can be used. For example, one end of a regulating fitting supported on the structural part side of a highly rigid tool body may be applied to a portion of the Z-direction actuator near the connection part. If the regulating metal fittings are made to be immovable in the X and Y force directions, and also to be bendable in the Z direction, the Z direction actuator can be freely expanded and contracted.

As mentioned above, the pressure applied by the abrasive to the material to be polished is
It is determined by the pressure applied by the Z-direction actuator, and if magnetic holding force is also used, it is also affected by this holding force. However, this pressing force decreases as processing progresses. Therefore, it is preferable to detect the value of the pressurizing load applied to the material to be polished and feed this back to the control of the Z-direction actuator to control the pressurizing force. As the load detection means for detecting the applied load value, pressure sensors similar to those built into various ordinary mechanical devices can be used as long as they can detect the vertical load applied to the material to be polished. . For example, if polishing is performed with the material to be polished placed on a load cell, the magnitude of the pressurized load applied to the material to be polished can be detected by the load cell and extracted as an electrical signal.

The pressurized load value detected by the load detection means is converted into an electric signal to control the drive of the actuator. Specifically, the detection signal is processed by an appropriate electric circuit and input to a drive circuit that applies voltage to the actuator, where the preset pressure load value and the detected pressure load value are compared. to increase or decrease the voltage applied to the Z-direction actuator. In other words, the pressure applied by the Z-direction actuator is feedback-controlled. This feedback control can, for example, always keep the pressure applied by the Z-direction actuator at a predetermined level, or increase it at the beginning of the machining process (rough polishing), medium at the middle (medium polishing), and small at the end (finishing). polishing).

Note that even in the case of this multi-step polishing, it is preferable to control the pressing force in each step to be constant.

In this way, when the pressing force in the Z direction is held constant, if the pressing force by the Z direction actuator is controlled so as to add vibration, the pumping effect of this vibration will increase the abrasive material by 5! A phenomenon occurs in which light is sequentially supplied to the r9 surface and sequentially removed.

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

When using magnetic polishing fluid as the polishing material, the polishing shaft is
The polishing shaft is made of a magnetic material because it serves as a central yoke as part of the magnetic circuit for maintaining the magnetism. The opposing yoke facing this is arranged with a gap forming a magnetic gap between it and the polishing portion at the tip of the central yoke. For example, a central yoke having a circular cross section is surrounded by annular opposing yokes at intervals. By doing so, the magnetic polishing fluid can be well maintained around the polishing portion of the central yoke. Note that a bar-shaped or plate-shaped opposing yoke may be arranged side by side with the central yoke. Since the opposing yoke also constitutes a part of the magnetic circuit, it goes without saying that it is made of a magnetic material. It is preferable that the distal end portion of the opposing yoke, which faces the central yoke, has a tapered shape so that the magnetic field can be concentrated at the distal end portion of the opposing yoke.

A magnetic circuit is constructed by connecting the central yoke and the opposing yoke with magnetism generating means. Although either a permanent magnet or an electromagnet can be used as the magnetic ordering means, in this invention, since there is no need to change the direction or magnitude of the magnetic field, a permanent magnet is preferable because it has a simpler structure. As the permanent magnet, a magnet made of Sm-Co magnet or the like can be used.

[For production]

If the polishing part is supported by the Z-direction actuator via a connection part that allows minute movements in the XY directions, and the XY-direction actuator is applied between this connection part and the polishing part, the polishing part can be moved in the XY directions by the XY-direction actuator. The micro-movement can be performed smoothly, and at the same time, the pressing force of the Z-direction actuator can be reliably transmitted to the polishing section.

However, with this method, when trying to increase the machining diameter,
When the range of motion of the polishing section is expanded, the connection section and the Z-direction actuator, which serve as a reference point when the polishing section makes minute movements in the xy force directions, move in the XY directions along with the movement of the polishing section. If the base point of the minute movement in the XY directions moves, the locus of movement of the polishing section drawn with this base point as a reference will also be disturbed. That is, the polishing section vibrates in a state in which a high-order vibration component due to the movement of the base point is added to the periodic stretching vibration of the XY direction actuator.

Therefore, if the movement of the Z-direction actuator in the XY directions is restricted, the Z-direction actuator and the connecting portion will move in the
It no longer moves in the Y direction, and the polishing section draws an accurate preset movement trajectory. In other words, by increasing the rigidity of the Z-direction actuator and the connecting part in the XY directions, the above-mentioned high-order vibration components are no longer generated, and the polishing part only performs the original vibration due to the periodic expansion and contraction of the XY-direction actuator. . As a result, the shape of the machining marks determined by the locus of movement of the polishing part becomes accurate, and a suitable machined surface can be obtained.

〔Example〕

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

FIG. 1 shows a polishing tool which is the main part of a polishing apparatus used to carry out the micropolishing method according to the present invention. This polishing tool 1 has a main body 10 that is a polishing device main body (not shown).
is supported and fixed by a support shaft 11. This support shaft 11 can move freely in the horizontal and vertical directions, and can also be tilted at any angle.

The operating mechanism of the support shaft (1) is similar to that of a machining shaft or the like in a normal machine tool.

At the center of the bottom surface of the tool body 10 is a vertical wall Z.
A seven-direction cutuator 20 is provided, and from its lower end, via a connecting portion 21 having a ball-to-corner connecting action,
A block 22 is suspended. Here, the sphere-to-corner connection action means that the block 22 can be freely moved in the XY directions perpendicular to the Z direction (vertical direction in the figure) with respect to the Z direction actuator 20. Reliably blocks small movements of the Z-direction actuator 20 in the Z direction 2
It refers to the connecting action that is transmitted to 2.

The Z-direction actuator 20 is connected to the structural part of the tool body 10 via a restriction fitting 80, which is a movement restriction means in the XY directions, at a portion immediately above the connection portion 21. Second
The figure shows the detailed structure of the regulating fitting 80. The regulating fitting 80 includes a central portion 83 that is sandwiched and attached between the X-direction actuator 20 and the connecting portion 21;
3 and a rod-shaped regulation support part 81.82 extending in the XY direction from the tool body part 1.
Fixed to 0. A constricted portion 84 is formed in the middle of the restricting support portion 81°82 in the length direction, and the restricting support portion 81°82 can be bent and deformed at the constricted portion 84. Therefore, although the X-direction actuator 20 cannot move in the axial direction of the regulation support part 81.82, that is, the xyX direction, it can expand and contract in the bending direction of the constriction part 84 of the regulation support part 81.82, that is, in the X direction. be.

Next, a central yoke 23 serving as a polishing shaft is integrally connected to the lower end of the block 22 and hangs down, as shown in FIG.
The block 22 and the central yoke 23 are screwed together.

At the top of the block 22, the tip of an X-direction actuator 24x is connected in contact with the side surface in the X direction that is horizontal in the figure, and the side surface in the Y direction that is horizontal in the figure and perpendicular to the X direction (
The tip of the Y-direction actuator 24y is abutted and connected to the opposite side surface in FIG. In this embodiment, the X-direction actuator 20, the X-direction actuator 24x, and the Y-direction actuator 24y are all formed by stacking a large number of thin episodic elements, and are activated in the X direction (the axial direction of the central yoke 23) by applying a voltage. , expands and contracts in the X and Y directions, presses the abrasive material against the material to be polished with minute movements in the X direction, and
The abrasive material can be freely moved within the polishing surface of the material to be polished by a combination of minute movements in the direction and the Y direction.

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

The tip of the center yoke 23 in Table 1 is gradually tapered and has a spherical tip surface. This spherical portion is the polishing portion 26. This polishing part 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 retained in this polyurethane layer polishes the polishing surface of the material W to be polished. be.

In this embodiment, as shown in detail in FIG.
6 consists of a sphere 25 held movably at the tip of a central yoke 23, the surface of which is finished with a Sn plating layer. In this embodiment, the sphere 25 is held at the tip of the central yoke 23 by the viscosity of the magnetic polishing fluid M. However, such a sphere is
It may be held mechanically by being fitted inside the tip of the holder, or it may be held by magnetic force.

Drive wiring 50 for each actuator 20, 24x, 24y
is a drive amplifier 5 consisting of a 3CH piezo driver amplifier.
1 is electrically connected to. The specific specifications of the 3CH piezo driver amplifier are, for example, 350V, 100V,
mA, 30kHz. A signal generator 52 for the X direction and a variable phase two-output signal generator 53 for the XYX directions are connected to the drive amplifier 51. These signal generators 52
53 to each actuator 2 via the drive amplifier 51.
A voltage having a predetermined frequency is applied to actuators 20, 24x, and 24y to control the driving of each actuator 20, 24x, and 24y.

A cylindrical body 30 made of non-magnetic material is provided on the lower surface of the tool body IO.
is attached. An opening 31 is formed in the middle portion of the cylindrical body 30 (the right side surface portion in FIG. 1), into which the actuators 24x, 24y, drive wiring 50 of each actuator, etc. are inserted. A connecting body 32 made of a ring-shaped magnetic material is screwed and connected to the lower part of the cylindrical portion 30 . A portion of the inner peripheral portion of the connecting body 32 extends to a position close to the outer peripheral surface of the central yoke 23. The connecting body 32 has a fluid supply path 33 penetrating from the outer circumferential side to the inner circumferential lower surface.
A fluid supply pipe 34 is connected to the outer peripheral end of the fluid supply path 33. When the magnetic polishing fluid is supplied to the fluid supply pipe 34, the magnetic polishing fluid is supplied to the fluid supply path 3.
3 to the vicinity of the outer periphery of the tip of the central yoke 23. A permanent magnet 40 made of a ring-shaped S m -Co magnet is attached to the lower end of the connecting body 32 . The strength of the magnetic force of the permanent magnet 40 is, for example, about 5 Gauss.

At the lower end of the permanent magnet 40 is an opposing yoke 35 made of a magnetic material.
is installed. The opposing yoke 35 narrows in a conical shape toward the lower end, and has a tapered inner circumferential portion at the tip, and a certain gap is left between this inner circumferential tip and the tip of the central yoke 23. They are placed opposite each other. As a result, a magnetic circuit is formed from the permanent magnet 40, through the connecting body 32, the central yoke 23, and from the opposing yoke 35 back to the permanent magnet 40.
5, a donut-shaped magnetic gap is formed.

A load cell 60 serving as a load detection means is installed below the central yoke 23 and the opposing yoke 35, and the workpiece W to be polished is polished while being placed on the load cell 60. The detection output of the load cell 60 is input to the drive amplifier 51 via the controller 61, so that the pressing force applied from the Z-direction actuator 20 to the material to be polished W is feedback-controlled.

A vibration application signal is also input to the drive amplifier 51 from the FG generator 70 in order to apply vibration to the pressing force of the Z-direction actuator 20 .

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

The polishing tool I is placed on the workpiece W with the workpiece W placed on the load cell 60. Fluid supply pipe 34
When the magnetic polishing fluid M is supplied to the tip of the central yoke 23 from 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 schematically shown in FIG. 3, the magnetic polishing fluid M is held covering the lower surface of the tip of the central yoke 23, so that the magnetic polishing fluid M is held by the magnetic action. It is pressed against the surface of the material W.

Next, when a periodic voltage is applied to the Z-direction actuator 20, the Z-direction actuator 20 causes minute expansion and contraction movements in a direction perpendicular to the polishing surface of the material W to be polished (vertical direction as seen in FIG. 1). Accordingly, the polishing portion 26, which is the tip of the central yoke 23, moves in the vertical direction (in the direction of the straight arrow) as seen in FIG.
A minute movement is made to press the magnetic polishing fluid M against the surface (polishing surface) of the workpiece W to be polished. Further, a periodic voltage is also applied to the XY direction actuators 24x and 24y,
The block 22, to which the tips of the XY direction actuators 24x and 24y are abutted, swings in the horizontal direction (left and right directions as seen in the figure). As a result, the polishing portion 26 forms a ball-to-corner connecting portion 2.
1 as the center, as shown by the arc-shaped arrow in FIG. This oscillation results in a minute movement in the horizontal direction (XY direction) with respect to the surface (polishing surface) of the material to be polished W. This X
The small movement in the Y direction and the small movement in the Z direction are transmitted to the magnetic polishing fluid M, and the magnetic polishing fluid M polishes the surface (polishing surface) of the material to be polished W. The magnetic polishing fluid M performs a polishing action by pressurizing the workpiece W only in the vicinity of the portion sandwiched between the tip of the central yoke 23 and the workpiece W. A machining mark H having a shape and size corresponding to the range of motion of the polishing portion 26 of the yoke 23 is formed.

While performing such a polishing action, the entire polishing tool 1 is moved in a horizontal direction or three-dimensional direction according to a predetermined polishing surface shape, and when the machining mark H has been spread over the entire polishing surface of the material to be polished W, Desired polished surfaces such as flat, spherical, or free-form surfaces can be obtained freely.

During this time, in the load cell 60 on which the workpiece W is placed, the pressure applied by the polishing section 26 of the polishing tool 1 to the workpiece W through the magnetic polishing fluid M is detected as a pressure load value. The pressure load signal is fed back to the drive amplifier 51 via the controller 61. Therefore, for example, if the pressure applied to the material W to be polished exceeds a specified value,
The drive amplifier 51 lowers the voltage applied to the Z-direction actuator 20 to reduce the pressing force,
On the other hand, if the pressure applied to the material W to be polished falls below a specified value, the drive amplifier 51 increases the voltage applied to the Z-direction actuator 20, thereby increasing the pressure. On the other hand, in the process of machining one machining mark,
Since the pressurizing force tends to decrease over time,
The load cell 60 also detects this tendency and feeds back the detection result to the drive amplifier 51, thereby ensuring that the pressing force is always constant. In addition, the signal generator 52 for the Z direction is configured such that in the process of machining one machining mark, the pressing force is large at the beginning, the pressing force is medium in the middle period, and the pressing force is small at the final stage. A control signal is issued to the drive amplifier 51. Meanwhile, the FG generator 70
A vibration imparting signal for imparting vibration to the pressing force of the Z-direction actuator 20 is continuously emitted to the drive amplifier 51.

FIG. 4 shows the machining state when the range of motion of the polishing section 26 is expanded and the machining diameter is increased using the method of the above-mentioned embodiment and the method of a comparative example in which the restriction fitting 80 is not attached to the Z-direction actuator 20. The machining marks H' obtained by the comparative method shown in FIG. 4(b) do not have a spherical shape and are uneven and lose their shape, whereas the machining marks H′ obtained by the comparative method shown in FIG. 4(a) The machining mark H in this example has a smooth and good spherical shape.

〔Effect of the invention〕

As described above, this invention provides a Z-direction actuator with x
By supporting the polishing part through a connecting part that allows minute movements in the y direction, and by operating an XY-direction actuator between this connecting part and the polishing part, the polishing part can be moved in the Z direction without interfering with the fine movements in the XY directions. It becomes possible to reliably transmit the pressing force of the actuator in the direction to the polishing section, and it becomes possible to favorably exhibit the polishing action by micro-movement of the polishing section in the Z direction and the XY direction. Moreover, by restricting the movement of the Z-direction actuator in the XY directions, the base point of the minute movement of the polishing part in the XY directions does not move and an accurate movement trajectory is drawn. The shape of the machining marks formed is accurate and a smooth finish can be obtained. In particular, even if a large machining mark is formed by expanding the range of motion of the polishing part, the shape of the machining mark will not collapse and the finish will be smooth, which will greatly contribute to improving the efficiency of the polishing process.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a polishing tool which is the main part of the polishing device used to carry out the micro-polishing method according to the present invention, Fig. 2 is an exploded perspective view of the actuator portion, and Fig. 3 is an explanatory diagram of the polishing action of the present invention. , FIG. 4(a) (bl represents a cross-sectional view of the machining marks, FIG. 4(a) is the case of the embodiment of this invention, and FIG. 4('b) is the case of the comparative example. 1. - Polishing tool 20...Z direction actuator 2
1... Ball-to-corner connection part 23... Central yoke 2
4x...X direction actuator 24y...Y direction actuator 26... Polishing section 35... Opposing yoke 80... Regulating fitting M... Magnetic polishing fluid W.
... Name of agent for polished material Patent attorney Shigetaka Awano Figure 1 Figure 1 Polishing tool Figure 2

Claims (1)

[Claims] 1. With an abrasive material held between a polishing part at the tip of a polishing tool and a workpiece to be polished, the polishing part is polished in XY directions parallel to the polishing surface and/or in an actuator made of an electrostrictive element. A polishing part is supported through a connecting part that allows minute movements in the Z direction perpendicular to the surface and allows the Z-direction actuator to make minute movements in the XY directions, and an XY-direction actuator is placed between the connecting part and the polishing part. A micro-polishing method in which a material to be polished is polished by controlling the movement of a Z-direction actuator in the X and Y directions. 2. A polishing part facing the polishing surface of the material to be polished, an X-direction actuator that is made of a laminated electrostrictive element and moves the polishing part minutely in the X direction parallel to the polishing surface by the expansion and contraction action of the electrostrictive element, and a laminated electric a Y-direction actuator, which is made up of a strain element and causes the polishing part to move minutely in the Y direction parallel to the polishing surface and perpendicular to the X direction by its expansion and contraction action; The polishing part is provided with a Z-direction actuator that makes minute movements in the Z direction perpendicular to the polishing surface, and the polishing part is supported by the Z-direction actuator via a ball-to-even connecting part that can make minute movements in the XY directions. A micro-abrasive tool in which an action point of an XY-direction actuator is provided between the parts, and a movement regulating means in the XY-directions is provided on the Z-direction actuator.