JP4455271B2 - Polishing method and apparatus - Google Patents

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.

As a method of performing general lens, a prism, a surface finish of an optical element such as a mirror, for polishing the elastic tool (hereinafter, referred to as the polishing dish) for polishing a polishing object and the slide motion to each other, interposed 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 is 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.)

  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 to high (Nakanaka) and dropouts, which are surface defects that occur at the center of rotation of the polished article. In other words, in order to reduce the surface nuisance generated in the region where the object to be polished protrudes from the polishing dish, 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 nuisance conspicuous. 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 ability to adjust (correct) the shape. 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 in which the polishing surface of an object to be polished is applied to the polishing surface of the 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 object to be polished and the polishing tool are driven to rotate independently, and one of the object to be polished and the polishing tool is swung with a constant width, and is formed between both rotating shafts at the center of the rocking. Either the reference relative angle or the reference relative position formed by the contact point of one rotary drive at the center of the swing and the center position of the other rotary drive , the relative angle / position is the smallest. It characterized in that it has a minimum relative angular / position and the relative angle / position is continuously changed between the maximum relative angular / position which is the maximum step, a polishing method.

A second aspect of the present invention is the polishing method according to the first aspect, wherein the swinging direction is along a direction in which the relative angle / position is continuously changed.

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 independently rotating the object to be polished and the polishing tool, a means for swinging one of the object to be polished and the polishing tool with a constant width, and both rotation shafts at the center of the swing reference relative angle in the formed, or, one of the reference relative position formed at the center position of the one rotary drive member contact points and the other rotary drive member at the center of the swing, the relative angle / position There configured and control means for continuously changing between the maximum relative angular / position minimum relative angular / position and the relative angle / position is the smallest is the largest.

According to the present invention, while keeping constant the swing width of the polishing tool against the object to be polished, and so as to continuously change the relative position of the polishing tool and the object to be polished, which is described later in detail 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.

The relationship between time and position at the time of polishing the optical element is shown in FIGS. 1A to 1C, 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 based on Preston's empirical rule representing the abrasion mechanism of the polishing process was performed, 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 to become 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 also in accordance with the technique of Patent Document 1 (Japanese Patent Laid-Open No. Hei 9-300191). As the swinging width increases, the distance between the rotation axis of the object to be polished and the polishing dish and the position change of the amount of protrusion from the polishing dish are changed. 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 pan 2, mainly the spherical balls heart 10 of a polished surface of the lens 1, the position of the reference relative angle 12 is the tilt angle determined from the shape of the lens 1 and the polishing disc 2, tilting the rotary shaft 19 Are arranged. 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 oscillating 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, if it has a structure in which its own weight also added Hairpin 4 and the upper shaft motor 8 not only the weight 6 as polishing load, the required polishing at low pressure, these self-weight 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. An operation signal is transmitted, and the rocking movement of the polishing dish 2 is performed at the rocking angle 15. 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. In this case the swing angle 15 is always kept constant, since only the relative angle is changed, FIG. 1 polisher 2 lens 1 while generating a position change as shown in (c) is gradually polished. The convenience of explanation embodiment, the reference relative angle 12 relative angle, minimum relative angle 13, and is shown in three different maximum relative angle 14, if the clear range of relative angular change during the swinging motion of the polishing 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 combined. Since this multiplexing is as shown in FIG. 3, a wear error due to polishing from the rotation center of the lens 1 to the outer peripheral portion 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 in 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. Device on the shaft 21 for not perform rocking motion in the spherical center of the lens 1 to be polished has a two-body structure, on the apparatus base 32 is a base of the polishing apparatus, the polishing dish lens 1 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. Similar to 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 of the lens 1 to be polished , 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 moving 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 or mounting position of the crank 27 is 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 of the lens 1 to the outer peripheral portion becomes small as in the first embodiment, and high shape accuracy can be obtained.

In the above embodiment, the case where a concave lens is used as an object to be polished has been described. However, the present invention also takes into account 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 position associated with the polishing time and adjustment work and operation when performing the polishing of the optical element, (a) shows the case with the loading and unloading operations before and after the hairpin, (b) in the case of Patent Document 1, (c) this In the case of invention, it is a characteristic view shown. 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 dish 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 Oscillating angle 16 Control device 18 Lens rotating shaft 19 Polishing dish rotating shaft 20 Recess 21 Upper shaft 22 Slider 23 Oscillating width 24 Reference relative position 25 Maximum relative position 26 Minimum relative position 27 Crank 28 Relative motor 29 Oscillating slider 30 Relative Slider 31 Relative shaft 32 Device base 33 Ball screw

Claims (3)

In a polishing method 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 object to be polished and the polishing tool are driven to rotate independently, and one of the object to be polished and the polishing tool is swung with a constant width, and is formed between both rotating shafts at the center of the rocking. The reference relative angle or the reference relative position formed by the contact point of one rotary drive member at the center of the swing and the center position of the other rotary drive member is the minimum relative angle / position. It characterized in that it has a certain minimum relative angular / position and said relative angular / position is continuously changed between the maximum relative angular / position which is the maximum step polishing method. The polishing method according to claim 1,
The polishing method according to claim 1, wherein the swinging direction is along a direction in which the relative angle / position is continuously changed. 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 independently rotating and driving the object to be polished and the polishing tool;
Means for swinging one of the object to be polished and the polishing tool with a constant width;
A reference relative angle formed between the two rotation shafts at the center of the swing, or a reference relative position formed by a contact point of one rotation drive body and the center position of the other rotation drive body at the center of the swing. one of the smallest relative angle / position and said relative angle / control means for the position, the user continuously changes between the maximum relative angular / position which is the maximum is said relative angular / position minimum,
A polishing apparatus comprising:

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