JPH0441175A - Micropolishing method and micropolishing tool - Google Patents

Abstract

PURPOSE:To enlarge the practical width of a polishing part without causing a deformed work trace even in case of the polishing face being inclined, etc., by forming the shape of the polishing part in a spherical face. CONSTITUTION:A polishing part 26 consisting of a spherical body 25 is provided at the polishing tool tip and a polishing material M is held between this polishing part 26 and a work W. In this state, the work W is polished with the polishing part 26 being subjected to a micromotion in the XY direction parallel to a polishing face and/or in the Z direction vertical to the polishing face by the actuator consisting of electrostrictive elements.

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 technology]

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 while applying pressure to the polishing surface of the material to be polished 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 movement 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, as the rotation of the polishing tool is prone to fluctuations in rotational speed and shaft deviation, this method results in fluctuations in the polishing amount, local polishing bias, and fluctuations in the polishing area in the finished polished surface. There was a problem that it would end up happening. 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 of unevenness and fluctuations in the finish of the polished surface. In short, it has been impossible to completely prevent these problems due to the high speed rotation of the polishing section.

In the conventional high-speed rotational magnetic polishing method, the pressure to press 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 material to be polished is a non-magnetic material, a magnetic circuit can be constructed through the non-magnetic material as long as it is thin. However, even in this case,
Since the pressing force of the magnetic polishing fluid on the polishing surface changes due to slight variations in the thickness or magnetic properties of the material to be polished, there has been a problem in that it is difficult to control the amount of polishing, polishing accuracy, etc. In addition,
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, we have solved the problems of the conventional high-speed rotation magnetic polishing method mentioned above, and it is possible to process with higher precision. In order to provide a micro-polishing method that can be successfully applied to the polishing surface, the inventors first moved the polishing section in the XY directions parallel to the polishing surface and in the We have developed a micro-polishing method and a micro-polishing tool that performs micro-movement in the Z direction and transmits this micro-movement to a magnetic polishing fluid to polish the polished surface of the workpiece.

This new micro-polishing method and micro-polishing tool using an actuator made 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 minute movement is applied to the polishing part by an XY-direction actuator or a Z-direction actuator that uses an electrostrictive element, so that the magnetic polishing fluid is caused to make a minute movement in the horizontal or vertical direction with respect to the polishing surface of the material to be polished. ,
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 mechanism, 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 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 and 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 micropolishing method using this new drive method,
As shown in Figure 4, the polishing part 2 located at the tip of the polishing tool
6 is moved in an arc as shown by the arc-shaped arrow in the figure.
Depending on the inclination of 3, the corner 261 of the polishing part 26 may be the target material W.
The resulting machining marks H
The problem is that the shape is deformed as shown by the solid line in the figure, and the desired beautiful shape such as an arc shape as shown by the dashed line in the figure cannot be obtained.

In addition, in order to increase the width of each machining mark H for the purpose of shortening the polishing time, it is necessary to increase the width l of the polishing part 26, but since the shape is flat,
There is also the problem that the width l of the polished portion cannot be made larger than the width of the machining marks, and there is a limit to the size of each machining mark H.

Therefore, it is an object of the present invention to provide a micro-polishing method and a micro-polishing tool using a novel drive method that can produce large and beautiful machining marks per piece.

[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, the micro-polishing method according to the present invention includes a spherical polishing section at the tip of the polishing tool, and with an abrasive being held between the polishing section and the workpiece, the polishing N section is made of an electrostrictive element. The material to be polished is polished by making small movements using the actuator in the XY directions parallel to the polishing surface and/or in the Z direction perpendicular to the polishing surface.

Next, the micro-polishing tool according to the present invention includes a spherical polishing section facing the polishing surface of the material to be polished, and an electrostrictive element, and the micro-polishing tool is configured to minutely move the polishing section in the XY directions parallel to the polishing surface. The present invention includes an actuator and a Z-direction actuator that is made of an electrostrictive element and causes the polishing section to move minutely in the Z direction perpendicular to the polishing surface by its expansion and contraction action.

In this invention, the polishing tool is supported by a suitable support member and the polishing part at the tip is moved along the material to be polished, as in the case of the conventional high-speed rotation magnetic polishing method.
As this supporting means and moving means, means used in various machine tools and the like are employed.

The polishing tool uses micro-driving means, which will be described later, to move its polishing part minutely in a direction parallel to the polishing surface, that is, in the Makes minute movements 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 layer, a polyurethane layer, or the like. When the abrasive part is made of polyurethane, by making the amplitude of the micromovements of the abrasive part in the X and Y directions larger than the pore diameter of the polyurethane, partial polishing due to polishing breakage will not occur, and machining marks of the desired shape will be created. It can be easily obtained.

The spherical polishing tool is preferably composed of a sphere rotatably held at the tip of the polishing tool. This is because this rolling 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 with a particle size of 10 nm or less, such as Few ○4, in water, oil, etc. As long as the particles have 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-Faj04 (red iron) and the like. Alternatively, ordinary abrasive particles without magnetism may be suspended and dispersed in a magnetic fluid made of magnetic particles without abrasive properties. In this case, the abrasive powder particles are A1□0. YaS
10 z or the like, and those with a particle size of about 100 na+ 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 moves the polishing part minutely in the X-direction horizontal to the polishing surface, and the
The polishing section makes a small movement in the X direction that is horizontal to the polishing surface and perpendicular to the above-mentioned X direction, and the polishing material is made to make a small movement in a direction parallel to the polishing surface of the material to be polished, thereby polishing 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, by controlling the phase of the motion in the X direction and the X direction, it is possible to make a υ-J motion.

When the X-direction actuator and the X-direction actuator are constructed using laminated electrostrictive elements, a large displacement can be obtained, control is easy, and the amount of displacement does not vary due to the influence of external pressure. However, if a rod-shaped bent piezo element is used, it can serve as a single piezo element.

The Z-direction actuator moves the polishing section in a direction perpendicular to the polishing surface, moves the abrasive material so as to collide with the material to be polished from the perpendicular direction, and applies pressure to the material to be polished. Therefore, the pressing force applied to the material to be polished can be controlled by the magnitude of the voltage applied to the Z-direction actuator. Furthermore, the abrasive material is sequentially supplied to the polishing surface due to the pumping effect caused by the micro-movement of the Z-direction actuator.

For the XX direction actuator and the Z direction actuator, by wiring the voltage application in each direction separately, and in the case of the X direction and the Make small movements in the x, y, and z directions. Drive wiring that applies voltage to each actuator is connected to a drive amplifier, a function generator, and the like. For these drive circuits or drive structures, a structure similar to that of an actuator using an electrostrictive element in a normal mechanical device can be adopted. In the case of an XX-direction actuator, by appropriately controlling the phases of the applied voltages in the X-direction and the Even the movements can be changed freely.

If a bending type piezo element is used, the bending will result in
If a laminated type is used, it will make a minute movement in the X direction or the X direction by expanding and contracting. As the Z-direction actuator, it is preferable to use a stacked piezo element. A bendable piezo element is bent by providing two pairs of electrodes facing each other on the circumferential surface of its rod body and applying a control voltage to each pair. A stacked piezo element expands and contracts by applying a voltage to both ends of the element.

The XX-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 case, in order to reliably transmit the pressing force from the actuator in the Z direction to the polishing section and to allow the polishing section to move freely in the X and Y directions, it is necessary to place the polishing section between the actuator in the Z direction and the polishing section. It is preferable to provide a ball-to-corner connecting portion that allows minute movements in the XY directions, and to provide the point of action of the actuator in the XY directions between this connecting portion and the polishing portion.

The micro-movement of the polishing part is the above-mentioned micro-movement in the Z direction and the XY
Although it is most preferable to perform minute movements in both directions at the same time, it is also possible to perform the polishing process only in either the Z direction or the XY direction.

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 subjected to feedbank control. 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 abrasive material is sequentially supplied to the polishing surface by the positive effect of this vibration, Moreover, a phenomenon in which they are gradually eliminated begins to occur.

The set value of the pressing force is appropriately determined depending on conditions such as the material of the material 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. In this way, the magnetic polishing fluid can be well retained 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 61 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 magnetism generating 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]

By making the shape of the polishing part spherical, it is easy to prevent the corners of the polishing part from coming into contact with the polishing surface, and the actual width is larger compared to a flat surface even if the width is the same, so the width of each machining mark can be increased. I can do it.

When the polishing part is composed of a freely rolling sphere, uneven wear of the polishing part does not occur.

〔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 11 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 main body 10 is a vertical wall X.
A direction actuator 20 is provided, and from its lower end, via a connection part 21 having a ball-to-corner connection action,
A block 22 is suspended. Here, the sphere-to-corner connection action means that the block 22 is allowed to make minute movements in the XY direction (vertical direction in the figure) that is perpendicular to the X direction with respect to the X direction actuator 20. Reliably blocks minute movements of the X-direction actuator 20 in the X-direction 2
It refers to the connecting action that is transmitted to 2. And this block 22
A central yoke 23, which is a polishing shaft, is integrally connected to the lower end of the polishing shaft and hangs down. At the top of the block 2, there is an X-direction actuator 24X on the horizontal X-direction side in the figure.
The tip of the Y-direction actuator 24y is abutted and connected to the Y-direction side surface (the opposite side in the figure) which is horizontal in the figure and perpendicular to the X direction. In this embodiment, the X-direction actuator 20, the X-direction actuator 24X, and the Y-direction actuator 24y are all
By stacking a large number of thin Ebizo elements and applying a voltage, they expand and contract in the X direction (axis direction of the central axis 23), X direction, and Y direction, and the abrasive material is moved to the workpiece by minute movements in the X direction. The abrasive material can be moved freely within the polishing surface of the material to be polished by pressing it against the surface of the material to be polished and by a combination of minute movements in the X and Y directions.

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

The tip of the central yoke 23 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, the polishing section 26, as shown in FIG.
A sphere 25 rotatably held at the tip of the central yoke 23
The surface is finished with a Sn plating layer. In this embodiment, the spherical body 25 is held within the tip recess 231 of the central yoke 23 by the viscosity of the magnetic polishing fluid M, as shown in FIG. 3(a). However, as shown in FIG.
As shown in FIG. 3(C), a permanent magnet 233 may be provided in the center yoke 23 and the center yoke 23 may be fitted into a recess 232 inside the tip of the A magnetic circuit that reaches the tip of the yoke 23 may be ordered so that it is magnetically held within the tip recess 234.

Drive wiring 50 for each actuator 20, 24x, 24y
is a drive amplifier 5 consisting of a 3CH piezo dryer 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 Z direction and a variable phase two-output signal generator 53 for the XY directions are connected to the drive amplifier 51. These signal generators 52
53 to each actuator 2 via the drive amplifier 51.
By applying a voltage having a predetermined frequency to 0, 24x, 24y, each actuator 20, 24x, 243'22x
, 22y.

A cylindrical body 30 made of a non-magnetic material is provided on the lower surface of the tool body 10.
is attached. In the middle 1 of the cylindrical body 30 (the right side surface in FIG. 1), an opening 31 is formed 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. A fluid supply path 33 is formed in the connecting body 32 and penetrates from the outer circumferential side surface toward the inner circumferential lower surface, and a fluid supply vibrator 34 is connected to the outer circumferential end of the fluid supply path 33.

When the magnetic polishing fluid is supplied to this fluid supply vibrator 34,
A magnetic polishing fluid is dripped and supplied from the fluid supply path 33 to the vicinity of the outer periphery of the tip of the central yoke 23 . A permanent magnet 40 made of a ring-shaped Sm-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. An opposing yoke 35 made of a magnetic material is attached to the lower end of the permanent magnet 40. 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, and a donut-shaped magnetic gap is formed between the central yoke 23 and the opposing yoke 35. will be constructed.

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 FC 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 vibe 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. 2, 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 abrasive 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 minute motion in the Y direction and the minute motion 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 size corresponding to the shape of the tip of the yoke 23 is formed.

While performing such a polishing action, the entire polishing tool 1 is moved horizontally or three-dimensionally according to a predetermined polishing surface shape, and the above-mentioned processing [H] is spread over the entire polishing surface of the material W to be polished. 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,
Drive amplifier 5I to Z direction actuator 20 (7)
The applied pressure is controlled to become smaller by lowering the applied pressure, etc. Conversely, if the applied force applied to the material W to be polished becomes less than a specified value, the driving amplifier 51 controls the Z-direction actuator 20.
The pressurizing force is controlled to increase by increasing the voltage applied to, for example. On the other hand, in the process of machining g
Make sure that the pressure is always constant. In addition, the signal abolisher 52 for the Z direction is used for machining [in the process of machining one piece, the pressurizing force is large in the initial stage (in the process, the pressurizing force is medium in the middle stage,
Then, in the final stage, the drive amplifier 5
A control signal is issued to 1. During this time, the FC generator 70 continues to issue a vibration imparting signal to the drive amplifier 51 for imparting vibration to the pressing force of the Z-direction actuator 20 .

〔Effect of the invention〕

In the present invention, since the shape of the polishing part is spherical as described above, even if the polishing axis is tilted, machining marks of deformed shape are not generated, and the substantial width of the polishing part is increased. Further, according to the present invention, by forming the polishing part with a freely rolling sphere, uneven wear of the polishing part can be prevented.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a polishing tool which is the main part of a polishing device used to carry out the micro-polishing method according to the present invention, Fig. 2 is an explanatory diagram of the polishing action of the present invention, and Fig. 3 is a sphere constituting the polishing section. FIG. 4 is a sectional view showing a holding method of the polishing part, and FIG. 4 is a side view showing a conventional polishing part. ■... Polishing tool 20... Z direction actuator 2
3... Central yoke 24x... X direction actuator 24y... Y direction actuator 25... Sphere 26... Polishing section 35... Opposing yoke M...
Magnetic polishing fluid W...Name of agent for polished material Patent attorney Shigetaka Awano (1 person) Figure 2 CG) Figure (C) Figure (b)

Claims (1)

[Claims] 1. A spherical polishing part is provided at the tip of a polishing tool, and with an abrasive material being held between the polishing part and the workpiece, the polishing part is brought into contact with the polishing surface by an actuator consisting of an electrostrictive element. A micro-polishing method in which a material to be polished is polished by micro-movement in parallel XY directions and/or Z-direction perpendicular to the polishing surface. 2. The micro-polishing method according to claim 1, wherein the polishing section is composed of a freely rolling sphere. 3. The micropolishing method according to claim 2, wherein the sphere is held at the tip of the polishing tool by the viscosity of the polishing material. 4. The micropolishing method according to claim 2, wherein the sphere is mechanically held at the tip of the polishing tool. 5. The micropolishing method according to claim 2, wherein the sphere is held at the tip of the polishing tool by magnetic force. 6. The micropolishing method according to claim 1, wherein the abrasive is a magnetic polishing fluid and is held by magnetic force. 7. A spherical polishing section facing the polishing surface of the material to be polished, an XY direction actuator that minutely moves the polishing section in the XY directions parallel to the polishing surface, which is made up of an electrostrictive element, and an expansion and contraction action of the electrostrictive element. and a Z-direction actuator that causes the polishing part to move minutely in the Z direction perpendicular to the polishing surface. 8. The micro-polishing tool according to claim 7, wherein the polishing surface is comprised of a rotatably held sphere. 9. Claim 8, further comprising: a central yoke having a polishing section at the tip; opposing yokes for creating a magnetic gap around the polishing section; and magnetism generating means for flowing magnetism through these yokes.
The micro-abrasive tool described.