JPH0441174A - Micropolishing method and micropolishing tool - Google Patents

Abstract

PURPOSE:To enlarge the amplitude of a micromotion in the XY direction, by using a lamination type electrostrictive element with the telescopic direction being made in the X direction and that with the telescopic direction in the Y direction with their combination as the actuator in the XY direction. 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 consisting of electrostrictive elements, in the state of a polishing material M being held between the polishing part 26 of the polishing tool 1 tip and a work W. Moreover, as for the actuators 24x, 24y in the XY direction the lamination type electrostrictive element whose telescopic direction is made in the X direction and that in the Y direction are used with their combination. As for the actuator 20 in the Z direction, the electrostrictive element of lamination type whose telescopic direction is made in the Z direction is used to polish the work W.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a micro-polishing method and a CF micro-polishing tool, and more specifically, it is used for ultra-high precision processing in the field of manufacturing lenses, optical elements, etc. The present invention relates to a method for precisely polishing a minute area, and a polishing tool used to carry out the method.

[Conventional technology]

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

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

Conventionally, polishing processing, roughing 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. The term "magnetic polishing fluid" as used herein refers to a rupturable fluid alone or one in which fine particles of abrasive material are suspended and dispersed in C.

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 part 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, it is possible to apply the abrasive material intensively to a minute area of the polishing surface using magnetic holding force, resulting in more precise polishing than the conventional polishing method. It has the advantage of being possible.

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 wobbling, this method results in fluctuations in the amount of polishing, local polishing bias, and fluctuations in the polishing area in the finished polished surface. There was a problem with this. 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 grinding section 9 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 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. To provide a micro-polishing method that can be used successfully in We have developed a micro-polishing method and a micro-polishing tool that make micro-movements in the Z direction and transmit the micro-movements of the polishing part 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 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 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 the 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 section is an extremely minute movement obtained by applying a voltage to the electrostrictive element, so the magnetic Vr fluid causes the polishing to occur only in an extremely small area around the polishing section. The material can be polished with high precision, and the surface of the material to be polished can be finely and uniformly gf polished. Much more uniform ′g compared to traditional high-speed rotation polishing methods
Since f-polishing is performed, ultra-high precision mirror finishing is also possible, and ultra-high precision polishing with a shape accuracy of 0.01 μm or less can be easily and reliably achieved.

Note that the micro-polishing method and micro-polishing tool using this novel driving method can also be used in a method that does not use a magnetic 5fF aqueous fluid as the 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.

That is, in the micropolishing method using this new drive method, one electrostrictive element constituting the XY direction actuator
Previously, bendable electrostrictive elements were used that could be driven individually in both the X and Y directions.Although bendable electrostrictive elements have the advantage of being able to achieve high frequencies, they require mechanical resonance in order to obtain large amplitudes in the X and Y directions. As a result of utilizing this phenomenon, as shown in Figure 4, it is inevitable that the above amplitude, that is, the displacement, will fluctuate depending on the magnitude of the external force (reaction force of the pressing force on the material to be polished), and it is difficult to control it. The problem is that it is impossible.

Further, there is a problem in that the amplitude in the xyx directions by the bending type electrostrictive element cannot be set very large because it utilizes a mechanical resonance phenomenon. As a result, for example, when the 'gfs part of the 'gF polishing odor' is composed of a polyurethane sheet, the above amplitude is smaller than the pore diameter of the polyurethane sheet, so machining marks are only partially formed on the polished surface. However, there have been cases where a machined shape of a desired size cannot be obtained.

Therefore, an object of the present invention is to provide a micro-polishing method and a micro-polishing tool using a novel drive method in which the amplitude in the XY directions does not change due to external force and can be easily controlled, and which can increase the amplitude. [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 workpiece to be polished, the polishing part is moved in XY directions parallel to the polishing surface using an actuator made of an electrostrictive element. and/or a laminated electrostrictive element whose expansion/contraction direction is in the X direction and a laminated type electrostrictive element whose expansion/contraction direction is in the Y direction as actuators in the The workpiece to be polished is polished by using a laminated type electrostrictive element whose expansion/contraction direction is the X direction as the two-direction actuator.

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. Y is composed of an X-direction actuator for movement and a laminated electrostrictive element, and its expansion/contraction action causes minute movement of the polishing part in the Y-direction parallel to the polishing surface and perpendicular to the X-direction.
The present invention includes a directional actuator and an X-direction actuator which is made of a laminated electrostrictive element and causes the polishing section to move minutely in the X 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 minutely move its polishing part in the direction horizontal to the polishing surface, that is, in the That is, it is made to make a minute movement in the X 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 portion can be composed of an Sn coating 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 a spherical surface is used, the actual width is larger than that of a flat surface even if the width is the same, and the width per machining mark can be increased. When the polishing part is made of polyurethane, if the amplitude of the micromovement in the XY direction of the polishing part is 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. This can be done by easily obtaining .

It is preferable that the spherical convex section 5 is constituted by a spherical body which 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 the so-called magnetic fIg fluid, but also non-magnetic polishing fluids can 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-Fes 04 (red iron). 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 A I
= Os, Sin, etc. are used, and those with 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 VR polishing fluid between the polishing part at the tip of the polishing tool and the material to be polished, for example, the polishing fluid must be placed close to the polishing part at the tip of the polishing tool. If a magnetic circuit is constructed by providing a magnetic yoke, the magnetic polishing fluid can be easily held near the Vr due to 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 Y-direction actuator makes a small movement of the polishing part in the Y 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 XY direction actuator is in the X direction or in the Y direction.
It may be a single movement in the direction, or it may be a movement in which the movement in the X direction and the movement in the Y direction are related and can be moved simultaneously. For example, Lissajous motion can be achieved by controlling the phase of motion in the X and Y directions.

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.

For the XY 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 XY direction actuator, by appropriately controlling the phase of the applied voltages in the X and Y directions, the movement locus of the tip of the xyX direction actuator, that is, the polishing part, can be changed from a simple linear movement to a complex movement such as a surge movement. You can change it freely.

The X-direction actuator, the Y-direction actuator, and the X-direction actuator are constructed using laminated electrostrictive elements. If a laminated type is used, minute movements in the X direction or Y direction will be made by expansion and contraction. A stacked electrostrictive element expands and contracts by applying a voltage to both ends thereof.

The XY-direction actuator and the X-direction actuator usually do not directly drive the polishing section, but instead drive the polishing section by applying micro-drives in the horizontal or vertical direction to a polishing shaft whose tip is the polishing section. do.

In this case, in order to reliably transmit the pressurizing force from the seven actuators in the X direction to the polishing section and to allow the polishing section to move freely in the x and Y directions, the polishing section must be placed between the actuator in the X direction and the polishing section. It is preferable to provide a ball-to-corner connecting portion that allows small movements in the x, y, and x directions, and to provide the point of action of the actuator in the X and Y directions between this connecting portion and the polishing portion.

The micro-movement of the polishing part is the above-mentioned micro-movement in the X direction and the XY
Although it is most preferable to perform minute movements in both directions at the same time, polishing is also possible in either the X 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 X-direction actuator, and when magnetic holding force is used in combination, 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 X-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 pressure 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 X-direction actuator. In other words, the pressure applied by the X-direction actuator is subjected to feed-hack control. This feedbank control can, for example, always keep the pressure applied by the X-direction actuator at a predetermined level, or keep it large at the beginning of the machining process (rough grinding), moderate in the middle (medium grinding g), and small at the end ( Finish 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 X direction is held constant, if vibration is controlled to be added to the pressing force by the X direction actuator, the pumping action of this vibration will sequentially supply the abrasive to the polishing surface. Moreover, a phenomenon in which they are gradually eliminated begins to occur.

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 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]

In a laminated electrostrictive element, the stroke of expansion and contraction can be increased or decreased depending on the number of laminated elements, and as the number of laminated elements increases, the stroke becomes larger. Therefore, if a laminated electrostrictive element whose expansion/contraction direction is the X direction and a laminated electrostrictive element whose expansion/contraction direction is the Y direction are used in combination as an XY-direction actuator, a large amplitude can be obtained, and The magnitude of the amplitude of this minute movement, that is, the displacement, does not vary depending on the magnitude of the external force, as shown in FIG. When the polishing section is made of a polyurethane sheet, if the amplitude of the minute movement of the actuator in the XY directions is made larger than the pore diameter of the polyurethane sheet, partial polishing will not occur.

xyX of the polishing part between the actuator in the X direction and the polishing part
Providing a ball-to-corner connection that allows for small directional movements,
By providing the point of action of the actuator in the X and Y directions between this connecting portion and the polishing portion, the pressing force of the actuator in the X direction can be transmitted to the polishing portion without interfering with minute movements of the polishing portion in the X and Y directions. .

〔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 two directions 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 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 direction in the figure). The tip of the Y-direction actuator 24y is abutted and connected to the side surface). 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. , X direction,
It expands and contracts in the Y direction, presses the abrasive material against the material to be polished with minute movements in the X direction, and allows the abrasive material to move freely within the polishing surface of the material to be polished by a combination of minute movements in the X and Y directions. It looks like this.

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/finishing part 26 may be made of S'n plating, etc., but when it is made of a polyurethane layer, the magnetic polishing fluid M impregnated and held in this polyurethane layer is applied to the polishing surface of the material W to be polished. It is to polish.

In this embodiment, the polishing section 26 consists of a sphere 25 held at the tip of the central yoke 23 in a freely transferable manner, and the surface is made of Sn.
The surface is finished with a matte layer. In this embodiment, the sphere 25 is magnetically held at the tip of the central yoke 23 by the magnetic force of a permanent magnet 40. However, such a sphere may be held at the tip of the central yoke 23 by the viscosity of the magnetic polishing fluid M, or may be fitted inside the tip of the central yoke 23 and held mechanically.

Drive wiring 50 for each actuator 20, 24x, 24y
is electrically connected to a drive amplifier 51 consisting of a 3CH viezo driver amplifier. The specific specifications of the 3CH piezo driver amplifier are, for example, 350■, 10
0mA, 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. From these signal generators 5253, voltages having a predetermined frequency are applied to each actuator 20, 24x, 24y via the drive amplifier 51, and each actuator 20, 24x, 24)+2
2x, 22)'.

A cylindrical body 30 made of a non-magnetic material is provided on the lower surface of the tool body 10.
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. 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 pipe 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 pipe 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 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. 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,
The inner circumferential portion of the tip is tapered and pointed, and the inner circumferential portion of the tip is disposed to face the tip of the center yoke 23 with a certain gap therebetween. 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 inputted to the drive amplifier 51 via the controller 61, and the pressurizing force applied from the two-way actuator 20 to the material to be polished W is subjected to feedbank control.

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 1 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. 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 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-right direction 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 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,
The drive amplifier 51 lowers the voltage applied to the Z-direction actuator 20 to reduce the pressing force,
Conversely, if the pressure applied to the material to be polished W becomes less than 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 FC 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.

〔Effect of the invention〕

As described above, the present invention uses a laminated electrostrictive element whose expansion/contraction direction is the X direction and a laminated electrostrictive element whose expansion/contraction direction is the Y direction as an actuator in the XY directions in combination. The amplitude of minute movements in the X and Y directions increases, and it no longer fluctuates depending on the magnitude of external force.
Therefore, control becomes easy. Furthermore, according to the present invention, when the polishing section is composed of a polyurethane sheet, if the amplitude of the minute movement of the actuator in the XY directions is made larger than the pore diameter of the polyurethane sheet, partial polishing will not occur. In addition, a ball-to-corner connection part is provided between the actuator in the Z direction and the polishing part to allow minute movements of the polishing part in the x and y directions, and the point of action of the actuator in the By providing this between the polishing section and the polishing section, it becomes possible to transmit the pressing force of the actuator in the Z direction to the polishing section without interfering with the minute movements of the polishing section in the X and Y directions.

[Brief explanation of drawings]

Fig. 1 is a 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 explanatory diagram of the polishing action of the present invention, and Fig. 3 is a laminated type used in the present invention. FIG. 4 is a graph showing the characteristics of a bending type electrostrictive element. 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 M... Magnetic polishing fluid W... Retraction frequency of the material to be polished (Hz)

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 combination of a laminated electrostrictive element whose expansion/contraction direction is in the X direction and a laminated electrostrictive element whose expansion/contraction direction is in the Y direction for fine movement in the Z direction perpendicular to the plane, and as the XY direction actuator. A micropolishing method in which a laminated electrostrictive element whose expansion/contraction direction is in the Z direction is used as the Z-direction actuator to polish a material to be polished. 2. The micro-polishing method according to claim 1, wherein when the polishing section is composed of a polyurethane sheet, the amplitude of the micro-movement of the actuator in the X and Y directions is made larger than the pore diameter of the polyurethane sheet. 3 Place the X of the polishing part between the actuator in the Z direction and the polishing part.
3. The microscopic device according to claim 1, further comprising a ball-to-corner connecting portion that allows for free micro-movement in the Y direction, and a point of action of an actuator in the XY direction is provided between the connecting portion and the polishing portion. Polishing method. 4. The micropolishing method according to claim 1, wherein the abrasive is a magnetic polishing fluid and is held by magnetic force. 5. 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 which 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 electrostrictive element. a Y-direction actuator, which is made up of a strain element and causes the polishing section to move minutely in the Y direction parallel to the polishing surface and perpendicular to the X direction by its expansion and contraction; and a Y-direction actuator, which is made up of a laminated electrostrictive element and causes the polishing section to move minutely in the Y direction that is parallel to the polishing surface and perpendicular to the X direction; A micro-polishing tool comprising a Z-direction actuator for micro-movement in a Z-direction perpendicular to a polishing surface. 6 Place the X of the polishing part between the actuator in the Z direction and the polishing part.
6. The micro-polishing tool according to claim 5, further comprising a ball-to-corner connecting portion that allows fine movement in the Y direction, and a point of action of an actuator in the XY directions is provided between the connecting portion and the polishing portion. 7. Claim 5, 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 causing magnetism to flow through these yokes.
Or the micro-abrasive tool described in 6.