JP2006116678A - Polishing method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing method and a device capable of providing high shaping precision while stably moving a polishing object and a polishing plate without skilled technology. <P>SOLUTION: This polishing device to polish the polishing object 1 by relative sliding of the polishing object 1 and a polishing tool 2 by putting a polishing surface of the polishing tool 2 on a polishing surface of the polishing object 1 is furnished with a means to oscillate either of the polishing object 1 and the polishing tool 2 around an axis of rotation (18 or 19) by moving it to a position inclining or slipping the axis of rotation (18 or 19) against the other, a means to respectively and independently rotate and drive the polishing object 1 and the polishing tool 2 and a control means to continuously change positions of the moved axis of rotation (18 or 19) in the middle of working. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polishing method and apparatus for performing surface finishing of an object to be polished such as an optical element so that high shape accuracy can be obtained while stably moving the object to be polished and a polishing dish without requiring skilled skills. The present invention relates to a polishing method and apparatus.

In general, as a method of finishing the surface of optical elements such as lenses, prisms, mirrors, etc., polishing is performed by sliding an object to be polished and an abrasive tool for polishing (hereinafter referred to as a polishing dish) to each other and interposing them at the interface. A polishing method is used in which an object to be polished is removed with abrasive grains. In such a polishing method, there are many manufacturing forms that depend on human skills in order to ensure the accuracy of the polished surface. Among them, the swinging width of the polishing dish due to the sliding motion is changed during the polishing process, and the amount of protrusion of the polishing object from the polishing dish is changed, thereby reducing the shape accuracy generated on the outer periphery of the polishing object ( Hereinafter, this will be referred to as “face habit”. Further, ensuring the shape accuracy of the entire surface of the object to be polished is obtained by changing the rotation speed ratio between the object to be polished and the polishing dish during the swinging motion. (For example, refer to Patent Document 1.)
JP-A-9-300191

  By the way, reducing the wrinkle while changing the swinging width, which is the technique of the above-mentioned Patent Document 1, is effective only in the region where the object to be polished protrudes from the polishing dish. No effect can be expected with respect to medium-high and medium-level drops that occur in the center of rotation of the polished article. In other words, in order to reduce the surface habit that occurs in the area where the workpiece protrudes from the polishing pan, the boundary position that protrudes by dispersing the swing width during polishing is dispersed, and the amount of friction is dispersed and changed to make the surface habit noticeable. Therefore, there is no effect in reducing the middle height and middle drop generated at the center of rotation of the workpiece.

  Moreover, in the technique of the said patent document 1, in order to ensure the shape precision of the whole grinding | polishing surface of a to-be-polished object including medium height and drop-down, the ratio of the rotation speed of a to-be-polished object and a grinding | polishing dish is according to the position of both. It is obtained by changing. However, since the positions of the two always change with the change of the swing width, changing the rotation speed ratio according to the position always changes the conditions of the swing position, the rotational speed of the object to be polished, and the polishing dish. It becomes a complicated control and processing system that simultaneously controls the rotation speed and three factors. At the same time, the position and rotation speed of the object to be polished and the polishing dish constantly change, so that the polishing force due to the polishing action constantly fluctuates, and the polishing dish follows the processing surface of the object to be polished and exhibits a stable polishing action. This makes it difficult to perform stable polishing. In particular, since the magnitude and direction of the polishing force greatly vary with the movement, minute vibrations are likely to occur on the polishing surface of the object to be polished, and there is a concern of generating surface defects having fine irregularities on the object to be polished. .

  In addition, in the polishing method by sliding motion, skilled engineers can change the swinging distance and shaft rotation speed of the machine in order to obtain the shape and accuracy of the workpiece. The polishing conditions are adjusted by the above-mentioned method. In particular, the front and rear loading / unloading of the Kanzashi has a great change and the shape adjustment (correction) ability. The front and rear loading / unloading of the kanzashi here indicates the change and adjustment of the relative position between the object to be polished and the polishing dish, and automating this operation itself can ensure high shape accuracy.

  An object of the present invention is to provide a polishing method and apparatus that obtains high shape accuracy while stably moving an object to be polished and a polishing dish without requiring skilled skills in view of the above-described conventional situation.

  A first aspect of the present invention is a polishing method using a polishing apparatus in which a polishing surface of a polishing tool is applied to a polishing surface of an object to be polished, and the object to be polished is polished by relative sliding between the object to be polished and the polishing tool. The polishing method is characterized in that the relative position between the object to be polished and the polishing tool is continuously changed while keeping the rocking width of the object to be polished and the polishing tool constant.

  In a second aspect of the present invention, in the first aspect, at least two or more relative positions are set, and polishing is performed while moving a rotating shaft of the object to be polished or the polishing tool between the relative positions. A polishing method characterized by

  According to a third aspect of the present invention, there is provided a polishing apparatus that applies a polishing surface of a polishing tool to a polishing surface of an object to be polished, and polishes the object to be polished by relative sliding between the object to be polished and the polishing tool. A means for moving either the object to be polished or the polishing tool to a position where the rotation axis thereof is inclined or shifted with respect to the other and swinging about the rotation axis, and the object to be polished and the polishing tool, respectively Means for independently rotating and driving, and control means for continuously changing the position of the moved rotating shaft during machining.

  According to the present invention, the relative position between the object to be polished and the polishing tool is continuously changed while keeping the rocking width of the polishing tool relative to the object to be polished, which will be described in detail later. However, the operation is almost equivalent to the continuous operation of the loading and unloading of Kanzashi performed by skilled technicians, and as a result, it is high while stably moving the object to be polished and the polishing dish without requiring skilled skills. Shape accuracy can be obtained.

  FIGS. 1A to 1C show the relationship between time and position when polishing an optical element, with the horizontal axis representing time and the vertical axis representing the position associated with the adjustment work / operation. FIG. 1 (a) shows the front / rear loading / unloading work of a Kanzashi performed by a technician to ensure the shape accuracy of the workpiece, and FIG. 1 (b) shows the adjustment method of Patent Document 1 (Japanese Patent Laid-Open No. 9-300191). 1 (c) shows the relative position adjustment of the present invention.

  When the work of the technician shown in FIG. 1A is analyzed, the machine operation is stopped as shown in the figure during the time when the machine is adjusted. It can be seen that the polishing operation is performed by changing the position of the dish rotation axis and swinging at that position. That is, the swinging width (amplitude) for swinging the polishing dish or the workpiece is not changed, and the center position, that is, the relative position of the swinging width is changed.

  In the adjusting method of Patent Document 1 (Japanese Patent Laid-Open No. 9-300191) shown in FIG. 1B, the amount by which the object to be polished protrudes from the polishing dish by changing the rocking width of the polishing dish by the sliding motion during the polishing process. By changing, surface defects generated on the outer peripheral portion of the object to be polished are reduced.

  In the relative position adjustment of the present invention shown in FIG. 1 (c), the upper and lower limit values for the rotation center axis position of the polishing dish calculated and set in advance from information such as the dimensions of the object to be polished and the polishing dish. (Position indicated by broken lines in the figure) is obtained, and polishing is performed while moving while maintaining the oscillation width (amplitude) set within the range, and the relative position between the object to be polished and the polishing dish is determined. It is continuously changed during polishing. This is a shape correction method based on experience work, which is similar to that of performing the Kanzashi taking in and out work continuously performed by the skilled technician shown in FIG. Very high polished surface accuracy can be obtained.

  Here, in order to provide a theoretical support for the importance of the work of changing the relative position, a trial calculation is performed based on Preston's empirical rule representing the abrasion mechanism of the polishing process, and the results are shown in FIGS. 3 shows.

  The five graphs shown in FIG. 2 indicate the amount of error in the amount of polishing friction when polishing is performed under each polishing condition. The graphs A2, B2, and C2 are when the relative position is changed, and the graphs B1, B2, and B3 are when the swinging width is changed. The horizontal axis indicated by the broken line in the graph indicates the radial position around the rotation center axis of the object to be polished, and similarly, the vertical axis of the broken line indicates the error amount of the amount by which the object is worn by the friction of polishing. That is, the curve in the graph shows the distribution of the wear error amount around the rotation axis of the object to be polished, and the larger the waviness of the curve, the greater the error in the amount of wear due to the position of the object to be polished, High shape accuracy cannot be obtained. On the other hand, in order to obtain high shape accuracy, the undulation of this curve is reduced, and the ideal is a horizontal line.

  Here, when the graphs B1, B2, and B3 change the swing width, the swing width increases in the order of B1, B2, and B3. It can be seen that the error amount is smaller as B3 increases the swinging width than B1. This is equivalent to the technique of Patent Document 1 (Japanese Patent Laid-Open No. 9-300191), and the positional change in the distance between the rotation axis of the object to be polished and the polishing dish and the amount of protrusion from the polishing dish is caused by the increase of the swinging width. Due to the large occurrence, the boundary position is dispersed and the error amount is small.

  On the other hand, graphs A2, B2 and C2 are the results of changing the relative position. However, when the relative position is changed, a large increase or decrease in the error amount as seen in the above-described increase or decrease in the swing width is not observed. Rather, it can be seen that the curve form of the error amount greatly changes. In the graph A2, the relative position is small, that is, the distance between the rotating shaft of the object to be polished and the polishing dish is short, so that the sliding movement at the outer peripheral part of the object to be polished increases and the wear of the outer peripheral part proceeds, as shown in FIG. Thus, the error distribution is such that the error in the outer peripheral portion increases. On the contrary, in graph C2, the distance between the rotating shaft of the object to be polished and the polishing dish is long, and at the same time, the amount of the object to be protruded from the polishing dish increases, so that the sliding motion of the object to be polished near the rotation center axis increases. The distribution of wear error is large in the vicinity of the rotation center axis.

  Here, the means for changing the relative position of the present invention continuously changes the relative position as shown in FIG. 1C, so each of the graphs A2, B2 and C2 shown in FIG. It becomes a composite pattern of the error amount curve. That is, in the graph A2, the error amount in the outer peripheral portion is large, but in the graph C2, the polishing can be performed with a conflicting error amount pattern in which the error amount in the central portion is large, and the error amount distribution can be offset. FIG. 3 shows an error amount distribution as a result of combining the graphs A2, B2, and C2 shown in FIG. As can be seen from the figure, the phase differences of the distribution patterns of the respective error amounts overlap to form a pattern with the smallest error amount.

Therefore, by continuously changing the relative position, the form (phase) of the error amount distribution by polishing can be changed, and high shape accuracy can be obtained.
Further, if the positions of the graphs A2 and C2 shown in FIG. 2 are known, it is possible to minimize the amount of wear error. The minimum relative position and maximum relative position described below are positions where the opposite phases for minimizing the wear error can be obtained, and the position where the error amount is minimized by combining the minimum relative position and the maximum relative position. That is.

  Further, the relative position change for obtaining high shape accuracy can be obtained by tilting or shifting the rotation axis. For example, a spherical center polishing machine used in lens polishing, that is, a device that swings (moves) around the spherical center that is the center point of the radius of curvature of the spherical surface that is the polishing surface of the lens that is the object to be polished. The relative position of the lens and the polishing dish can be changed by inclining the ball center. On the other hand, if the polishing machine performs a swinging (moving) movement independently of the lens center of the lens, such as the Oscar method, the lens rotation axis and the polishing dish rotation axis are shifted. The relative position can be changed with. In order to change the relative position, the structure of the apparatus is inclined if it is a spherical center system, and if the polishing apparatus is not a spherical center system, the rotational axis positions of the object to be polished and the polishing dish may be shifted. It will be.

  Further, in a general polishing apparatus, a polishing dish is rotated via a driving source such as a motor, and a lens that is an object to be polished is dependently rotated by a sliding force caused by the polishing process. In addition, a drive source is provided on both shafts of the polishing dish, and the rotary motion is forcibly performed. When changing the relative position of both rotary shafts to obtain high shape accuracy, if the distance between the two rotary shafts is increased, the transmission of the rotational motion due to the sliding force transmitted from the polishing dish will deteriorate, and the object to be polished will rotate stably. You can't get it. In this means for polishing by the rotational movement of both, since the accuracy of the shape cannot be ensured if the rotational speed is not stable, this apparatus is configured to give stable rotation to both shafts via the drive source. ing.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 4 is a cross-sectional view illustrating the internal configuration of the polishing apparatus according to Embodiment 1 of the present invention. The present embodiment is a technique using a ball center polishing machine, and shows a polishing method and apparatus newly obtained by paying attention to the loading and unloading work of a Kanzashi performed by a skilled technician.

  During the polishing process, the holder 3 inserts and holds the concave lens 1 serving as an object to be polished while one side is open. Between the lens 1 and the holder 3, the lens 1 is held via a sheet-like cushioning material 3a such as polyurethane or silicone rubber. A polishing dish 2 having an approximate shape to the polishing surface is in contact with the polishing surface of the lens 1 via a polishing sheet 2a such as polyurethane. Here, the polishing sheet 2a is formed by being attached to the surface of the polishing dish 2 with an adhesive or the like. The polishing dish 2 has a rotating shaft 19 at a reference relative angle 12 that is an inclination angle determined from the shape of the lens 1 and the polishing dish 2 around the spherical spherical center 10 that is the polishing surface of the lens 1. It is arranged to be inclined. Here, the reference relative angle 12 is an angle formed by the lens rotating shaft 18 and the polishing dish rotating shaft 19 and is calculated empirically or according to the radius of curvature of the spherical surface of the lens 1, the diameter dimension, and the diameter dimension of the polishing dish 2. Is an angle at which the spherical shape of the lens 1 and its accuracy can be obtained most stably. In order to move the polishing dish 2 to the reference relative angle 12, a swing motor 11 is connected to the polishing dish 2, and is configured to be capable of turning and swinging about the ball core 10. The swing motor 11 performs control for determining the position of the reference relative angle 12 and control for causing the polishing dish 2 to swing at a swing angle 15 around the reference relative angle or another relative angle. A device 16 is connected. A lower shaft motor 9 is attached to the polishing dish 2 in order to exert a polishing action by a sliding motion with the lens 1 and is configured to rotate.

  Further, the holder 3 has a recess 20 on the opposite side of the opening for holding the lens 1 and is pressed against the polishing dish 2 via the lens 1 by a kanzashi 4 having a spherical body fitted to the recess 20 at the tip. A transmission pin 5 is attached to the tip of the kanzashi 4 so that the rotational power of the kanzashi 4 is transmitted to the holder 3 while the kanzashi 4 presses the holder 3. Yes. The Kanzashi 4 is attached to the upper shaft 21 of the polishing machine via a bush 7 such as an air bearing that is held in a non-contact manner by air pressure so as to be vertically rotatable. An upper shaft motor 8 that rotationally drives the Kanzashi 4 is attached to the upper shaft 21 via a slider 22 that can move in the vertical direction. A weight 6 for applying a polishing load for polishing the lens 1 is attached to the upper end portion of the Kanzashi 4.

  The operation when performing polishing using the above-described polishing apparatus will be described below. The swinging motor 11 is operated at a reference relative angle 12 by a signal (command) from the control device 16, and the polishing dish 2 is tilted. The lens 1 is mounted in the holder 3 and brought into contact with the polishing dish 2 that has been inclined. The abutting lens 1 is pressed by a Kanzashi 4 that moves up and down via a holder 3. The pressing force at this time is the Kanzashi 4, the upper shaft motor 8 that is the rotational drive source, and the weight 6. Here, the apparatus of the present embodiment has a structure in which not only the weight 6 but also the weights of the kanzashi 4 and the upper shaft motor 8 are added as the polishing load. In order to eliminate this, the structure 4 may be pulled upward, but is omitted because it is not an essential requirement for the contents of the present embodiment.

  As described above, when the polishing load of the weight 6 is applied to the lens 1 via the Kanzashi 4 and the holder 3, the control device 16 applies the oscillating motor 11 according to the empirical value or the calculated value similarly to the reference relative angle 12. The operation signal is transmitted, and the wobbling motion of the polishing dish 2 at the wobbling angle 15 is performed. The rocking angle (width) at this time is a constant value, and the rocking motion is performed symmetrically around the reference relative angle 12. In this state, an instruction to gradually change the reference relative angle 12 is issued from the control device 16, so that the relative angle position changes, and the angle is continuously changed between the minimum relative angle 13 and the maximum relative angle 14 in FIG. The lens 1 is polished while changing. At this time, the rocking angle 15 is always maintained at a constant value, and only the relative angle changes. Therefore, the polishing plate 2 polishes the lens 1 while causing the position change as shown in FIG. Further, for convenience of explanation, the relative angles are shown as three types: the reference relative angle 12, the minimum relative angle 13, and the maximum relative angle 14. However, if the range of relative angles that change during the rocking motion of the polishing is clarified, the relative angle is implemented. Therefore, the reference relative angle 12 does not necessarily become necessary position information, and can be implemented if two positions of the minimum relative angle 13 and the maximum relative angle 14 are known.

  Here, since only the relative angle is changed while the rocking angle 15 is kept constant, the distribution pattern of the wear error of the lens 1 as the object to be polished is the pattern of graphs A2, B2, and C2 shown in FIG. It changes between the distribution pattern graph A2 of the wear error occurring at the position of the relative angle 13 and the distribution pattern graph C2 occurring at the position of the maximum relative angle 14. For this reason, when the relative angle changes during polishing, the polishing process is completed in a state where the graphs A2, B2, and C2 are synthesized. Since this multiplexing is as shown in FIG. 3, a wear error due to polishing from the rotation center to the outer periphery of the lens 1 is reduced, and high shape accuracy can be obtained.

  FIG. 5 is a cross-sectional view illustrating the internal configuration of the polishing apparatus according to Embodiment 2 of the present invention. This figure shows an embodiment using a polishing apparatus such as a conventional Oscar type polishing machine, which is not the ball center swinging system shown in the first embodiment. The basic idea is the same as that of the first embodiment. Since the first embodiment is a ball center swinging method, the positional relationship between the lens and the polishing dish is adjusted by a relative angle. However, the only difference is that the adjustment is based on the relative position, not the relative angle, and the same parts are denoted by the same reference numerals and the description thereof is omitted.

  Although a mechanism for rotating the polishing dish 2 is possessed, the axis of the polishing dish 2, which is the lower shaft, is fixed at the vertical position or the inclined position, and is shown in the vertical position in this embodiment. The upper shaft 21 of the apparatus has a two-body structure because the swinging movement of the lens 1 that is the object to be polished is not performed at the ball center, and the lens 1 is placed on the apparatus base 32 that is the foundation of the polishing apparatus. In order to move relative to 2, a relative shaft 31 is installed via a relative slider 30 that can move in the left-right direction in the figure. The relative shaft 31 is installed between the device base 32 serving as a base and the upper shaft 21 so as to be sandwiched so as to be movable in the left-right direction in FIG. One end of the relative shaft 31 is connected to a ball screw 33 for transmitting power from a relative motor 28 for moving the relative shaft 31 relative to the polishing dish 2. A relative motor 28 fixed to the apparatus base 32 is connected to the ball screw 33, and the relative motor 28 is connected to a control device 16 that performs position calculation processing and motor operation control. Further, the upper shaft 21 and the attached device structure shown in the first embodiment are attached to the relative shaft 21 via a swinging slider 29 that can move in the left-right direction in FIG. Here, a crank 27 which is a crankshaft is connected to the upper shaft 21, and one end thereof is connected to the swinging motor 11 fixed to the relative shaft 31.

  The operation when performing polishing using the polishing apparatus of Example 2 described above will be described below. In the same manner as in the first embodiment, the control structure 16 is moved from the control structure 16 to the reference relative position 24 empirically or calculated from the radius of curvature of the spherical surface to be polished of the lens 1, the diameter dimension, and the diameter dimension of the polishing dish 2. The relative motor 28 is operated by a signal (command), and the unit above the relative shaft 21 moves. The lens 1 is mounted in the holder 3 at the tip of the moved Kanzashi 4, and is pressed by the Kanzashi 4 that moves up and down to come into contact with the polishing dish 2.

  Similarly to the reference relative position 24, an operation signal is transmitted from the control device 16 to the relative motor 28 by an empirical value or a calculated value, and a moving motion is performed between the maximum relative position 25 and the minimum relative position 26. As for the swinging width 23 at this time, the rotational motion of the swinging motor 11 is transmitted to the upper shaft 21 via the crank 27 and the swinging motion is always performed at a constant value with respect to the relative shaft 21. If the length and the mounting position of the crank 27 are changed, the swinging width 23 changes. However, during the polishing process, the swinging motion 23 is transmitted with the set length of the crank 27 without being changed. do not do. As a result, even in the case of an Oscar type polishing machine, the swinging width 23 is always maintained at a constant value and only the relative position changes, so that the position change as shown in Example 1 or FIG. The polishing dish 2 advances the polishing of the lens 1, and the wear error due to the polishing from the rotation center to the outer peripheral portion of the lens 1 is reduced as in the first embodiment, and high shape accuracy can be obtained.

  In the above embodiment, a case where a concave lens is used as an object to be polished has been described. However, the present invention takes into consideration the shape of the surface to be polished in polishing other optical elements such as a convex lens, a prism, and a mirror. However, it can be similarly applied.

The relationship between the polishing time at the time of polishing the optical element and the position associated with the adjustment work / operation, (a) is the case where the front and rear loading / unloading work is involved, (b) is the case of Patent Document 1, and (c) is the present case. In the case of invention, it is a characteristic view shown about. It is the figure which showed the error amount of the grinding | polishing wear amount at the time of polishing process on each grinding | polishing condition. FIG. 3 is a characteristic diagram obtained by synthesizing the graphs A2, B2, and C2 illustrated in FIG. It is sectional drawing explaining the internal structure of the grinding | polishing apparatus in Example 1 of this invention. It is sectional drawing explaining the internal structure of the grinding | polishing apparatus in Example 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lens 2 Polishing plate 2a Polishing sheet 3 Holder 3a Buffer material 4 Kanzashi 5 Transmission pin 6 Weight 7 Bush 8 Upper shaft motor 9 Lower shaft motor 10 Ball center 11 Oscillating motor 12 Reference relative angle 13 Minimum relative angle 14 Maximum relative angle 15 Swing angle 16 Control device 18 Lens rotation shaft 19 Polishing plate rotation shaft 20 Recess 21 Upper shaft 22 Slider 23 Swing width 24 Reference relative position 25 Maximum relative position 26 Minimum relative position 27 Crank 28 Relative motor 29 Swing slider 30 Relative Slider 31 Relative shaft 32 Device base 33 Ball screw

Claims (3)

In a polishing method by a polishing apparatus that applies a polishing surface of a polishing tool to a polishing surface of an object to be polished, and polishes the object to be polished by relative sliding between the object to be polished and the polishing tool,
A polishing method, wherein a relative position between the object to be polished and the polishing tool is continuously changed while maintaining a constant swing width of the object to be polished and the polishing tool.   2. The polishing method according to claim 1, wherein at least two relative positions are set, and polishing is performed while moving a rotating shaft of the object to be polished or the polishing tool between the relative positions. In a polishing apparatus that applies a polishing surface of a polishing tool to a polishing surface of an object to be polished, and polishes the object to be polished by relative sliding between the object to be polished and the polishing tool,
Means for moving either the object to be polished or the polishing tool to a position where the rotation axis is inclined or shifted with respect to the other, and swinging about the rotation axis;
Means for independently rotating and driving the object to be polished and the polishing tool;
Control means for continuously changing the position of the moved rotary shaft during processing;
A polishing apparatus comprising:

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