JPS63232936A - Polishing method and abrasive tool - Google Patents

Abstract

PURPOSE:To make a workpiece possible to be finished into good flat accuracy and surface roughness accuracy at high efficiency, by vibrating an abrasive tool, while making abrasive grains in an abradant collide with the work surface of an optical element from an oblique direction, and polishing it. CONSTITUTION:A tool active part 12d is reciprocatively moved in a V direction at amplitude (a) by vibration, and this amplitude (a) and a distance (b) are set so as not to come into contact with a polishing surface even in a position where the active part 12d is most approached to a workpiece 6. With this constitution, abrasive grains in an abradant 8 adjacent to the active part are accelerated to the workpiece 6 in the vibration direction, thus a work surface part D is polished. At this time, since a flow of the abradant is produced to go along the vibrating direction V, the abradant 8 inclusive of these abrasive grains once related to the polishing is moved to the outside of a polishing position, where by at the lower part of the tool active part 12d, a new abradant is fed to the polishing position from the right, so that polishing is performed in good efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a polishing method and a polishing tool, and more particularly to a polishing method that uses vibrational energy for polishing, and a polishing tool used in the polishing method. Such polishing is used, for example, to polish optical elements such as lenses, prisms, and mirrors.

[Prior art and its problems] 10 Q. After shaping a material such as glass into a predetermined shape, optical elements such as lenses, prisms, and mirrors have a functional surface, that is, a surface that transmits and/or reflects light. It is manufactured by polishing to gradually reduce the surface roughness and at the same time achieve a predetermined surface accuracy.

In the polishing process, a polishing method using free abrasive grains is often adopted. Free abrasive grains are often used in the form of an abrasive agent dispersed in an appropriate liquid, and are used in polishing tools. Polishing is performed by sliding a polishing tool against the workpiece while supplying the abrasive between the workpiece and the workpiece.

In this type of polishing, the polishing conditions are set appropriately to obtain the desired surface precision, but in some cases the surface precision may gradually deteriorate, and in this case, corrective polishing is required. .

This tendency is particularly strong when the surface to be polished is an aspherical surface.

In other words, as optical elements, those with a flat or spherical Rfe surface have generally been widely used, but in recent years, as optical performance has been gradually improved and special characteristics have been required, functional surfaces other than flat and spherical have been used. (so-called aspherical surfaces) are now being manufactured. Aspherical shapes include not only surfaces that are rotationally symmetrical around the optical axis but also surfaces that are rotationally asymmetrical around the optical axis. Such an aspherical shape is created, for example, by numerically controlled grinding.
Polishing is performed to gradually reduce the surface roughness of the chain portion while maintaining its surface shape accuracy as much as possible. Therefore, when polishing an aspherical surface, the surface precision is particularly likely to deteriorate, and the need for corrective polishing increases.

Corrective polishing has conventionally been performed by partially polishing the surface to be polished in the same manner as described above using a relatively small polishing tool. However, this method has the problem that the relative movement speed and movement stroke of the polishing tool with respect to the object to be polished cannot be made very large from the viewpoint of maintaining surface precision, and therefore the polishing efficiency is low.

On the other hand, ultrasonic processing is a method for efficient polishing. Ultrasonic machining mainly removes the damage caused by abrasive grains by interposing abrasive grains between the workpiece and the tool, applying ultrasonic vibration to the tool, and pressing the tool against the workpiece with appropriate pressure. Polishing is performed with great efficiency by micro-punching the polishing material.

However, such conventional ultrasonic machining has the disadvantage that good surface shape accuracy and surface roughness accuracy cannot be obtained.

Therefore, an object of the present invention is to perform polishing with good efficiency and to finish a polished object with good surface precision and good surface roughness precision.

[Means for Solving the Problems] According to the present invention, the above objects are as follows: An abrasive containing abrasive grains is interposed between an object to be polished and a polishing tool, and the tool is vibrated to perform polishing. This is achieved by a polishing method characterized in that polishing is performed by causing abrasive grains in a polishing agent to collide with the surface to be polished from an oblique direction.

Further, according to the present invention, a tool directly used for carrying out such a polishing method has an acting part that acts on the abrasive and a drive means that vibrates the acting part in one direction, and has the above-mentioned effect. An abrasive tool is provided, characterized in that the portion has at least a portion oblique to the vibration direction in its overall reference shape.

[Example] A specific example of the present invention will be described below with reference to one drawing.

FIG. 1 is an explanatory diagram of a first embodiment of the polishing method according to the present invention.

In FIG. 1, reference numeral 2 denotes a polishing tank, and a polishing object support 4 is disposed in the polishing tank. In this embodiment, an object to be polished 6 is fixedly supported on the support base, and the object to be polished is a parallel plane plate-like object, the surface of which has been pre-processed to have an appropriate surface roughness. The polishing tank z is filled with polishing agent 8. The abrasive is made of, for example, abrasive grains such as cerium oxide having a desired particle size dispersed in water.

Reference numeral 10 denotes an abrasive circulation means for circulating and supplying the abrasive in the polishing tank 2 to the polishing position, and includes a pump.

Reference numeral 12 denotes a polishing tool, which is held by a holding member 14, which is connected to a polishing tool attitude control device 16.
It is connected to the.

The polishing tool 12 includes a vibration generating section 12a including an ultrasonic vibrator made of a piezoelectric material such as PZT, an ultrasonic oscillator 12b for driving vibration of the vibrator, a horn 12c connected to the vibration generating section 12a, and an action portion 12d attached to the tip of the horn. The vibration direction of the ultrasonic vibrator is the direction of the arrow {circle around (2)}, which is a direction inclined by an angle O with respect to the surface to be polished of the object 6 to be polished.

FIG. 2(a) is an enlarged view of the abrasive tool acting portion 12d, and FIG. 2(b) is a B view thereof.

The acting part 12d has an overall standard shape along a plane S inclined by an angle θ with respect to the vibration direction, and furthermore, the acting part 12d has an overall standard shape along a plane S inclined by an angle θ with respect to the vibration direction.
It has a stepped shape with a sawtooth cross section in which a large number of small regions 20 are formed. The pitch of the sawtooth can be determined as appropriate, but it is preferably determined according to the particle size of the abrasive grains.
The angle α can be appropriately set in the range from 0 degrees to 180 degrees, but is preferably around 90 degrees.

During polishing, the abrasive circulating means 10 is operated to supply the abrasive 8 to the polishing position, and the ultrasonic oscillator 12b is operated to vibrate the vibrator. As a result, the vibration generating section 1
The vibration of the actuator 2a is amplified by the horn 12c to a desired amplitude, and the acting portion 12d vibrates in the direction of arrow V with a predetermined amplitude.

FIG. 3 is a diagram for explaining the Kenfu effect.

The working portion 12d of the polishing tool is arranged so that its overall standard shape surface S is parallel to the surface to be polished and is spaced apart from the surface by a distance.

Such an arrangement is set by the attitude control device 16. The tool action part 12d has an amplitude a (stroke 2) due to vibration.
In a), it reciprocates in the V direction between the dashed line position and the dashed-dotted line position. The numerical values a and b are set so that the action portion 12d does not come into contact with the polishing surface even at the position indicated by the broken line where it is closest to the object 6 to be polished.

As a result, the abrasive grains in the abrasive 8 adjacent to the action portion are accelerated toward the workpiece 6 in the vibration direction and collide with the surface to be polished. In this way, the portion of the surface to be polished corresponding to the working portion 12d is polished.

At this time, since the flow of the abrasive occurs along the vibration direction V, the abrasive containing the abrasive grains once involved in the polishing process immediately moves out of the polishing position (that is, to the left of the partial part).

Then, a new abrasive is supplied to the polishing position from the right side below the tool action portion 12d, and polishing is performed with good efficiency.

When polishing of a certain part is completed in the above manner, the tool posture control device 16 is then moved horizontally and polishing is performed in the same manner. good.

In the above polishing, when the object to be polished 6 is made of a relatively hard material, the amplitude a and the angle θ are made relatively large, and when the object to be polished 6 is made of a relatively soft material, the amplitude a is made relatively large. and the angle θ is made relatively small. Further, when the desired surface roughness is relatively small, in addition to appropriately setting the polishing abrasive grains, the above-mentioned amplitude a and angle 0 are made relatively small.

FIGS. 4 and 5 are explanatory diagrams of a second embodiment and a third embodiment of the polishing method according to the present invention, respectively. In these figures, the same members as in FIGS. 1 to 3 above are given the same reference numerals.

In the first embodiment, the shape of the surface to be polished of the object to be polished 6 is flat, but in the second embodiment, the surface to be polished is convex. In this example, the surface to be polished is a concave surface. In these embodiments, the overall reference shape surface S of the tool acting portion 12d is made into a spherical shape corresponding to the shape of the surface to be polished. That is, tj
In the case of diagram IJ4, the radius of curvature of the surface to be polished is R, and the surface S
The radius of curvature of the surface S is (R+b), and in the case of FIG.
It is.

These cases differ from the first embodiment in that the object to be polished 6 and/or the polishing tool 12 are moved along a spherical surface in order to move the grinding center position, but there are other differences. The polishing operation is the same as in the first embodiment.

FIG. 6(a) is an explanatory diagram of a fourth embodiment of the polishing method according to the present invention, and FIG. 6(b) is its B parent diagram.

In this embodiment, the polishing tool acting portion 12d has a spherical shape that is rotationally symmetrical with respect to the vibration direction V. A large number of small holes 22 with appropriate depths are formed in the vibration direction. In the case of this embodiment, the same polishing operation as in the first to third embodiments described above is performed.

According to this embodiment, it is possible to perform desired polishing while freely adapting to the shape of the surface to be polished of the object 6 to be polished. In this case, the relative movement between the tool and the object 6 to be polished may be performed in an appropriate manner depending on the shape of the surface to be polished.

Furthermore, in this embodiment, polishing can be performed while rotating the polishing tool 12 around the vibration direction at an appropriate speed. This further enhances the flow of the abrasive 8 and further improves the supply of new abrasive grains to the polishing position.

FIG. 7 shows the polishing removal efficiency distribution (a) of the polished surface when the tool 12 is used in a non-rotating state in this embodiment, and the polishing removal efficiency distribution (a) of the polished surface when the tool 12 is used in a rotating state in this embodiment. Comparison with removal efficiency distribution (b) 0 As shown in the figure, in the non-rotating state, a relatively narrow area is polished with high efficiency, and the polishing efficiency rapidly decreases in the surrounding area. . On the other hand, in a rotating state, good polishing efficiency can be obtained over a relatively wider range than in a non-rotating state. Therefore, the presence or absence of rotation may be determined as appropriate depending on the purpose.

In the present invention, the particle size of the abrasive grains contained in the abrasive can be determined as appropriate depending on the desired degree of surface roughness, ranging from a minute particle size for obtaining an optical surface to a degree of a faded surface. Furthermore, any grain size may be used to obtain a surface roughness called a ground surface.

[Effects of the Invention] According to the present invention as described above, polishing can be performed with good efficiency without substantially moving the polishing tool relative to the workpiece, and the workpiece can be polished with good surface precision and It can be finished with good surface roughness accuracy and is particularly suitable for partial polishing of objects to be polished.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the polishing method according to the present invention. FIG. 2(a) is an enlarged view of the polishing tool action section, and FIG. 2(b) is its B parent view. FIG. 3 is a diagram for explaining the polishing action. 4 and 5 are both explanatory diagrams of the polishing method according to the present invention. FIG. 6(a) is an explanatory diagram of the polishing method according to the present invention,
FIG. 6(b) is its B parent diagram. FIG. 7 is a diagram showing the polishing removal efficiency distribution of the surface to be polished. 2: polishing tank, 6: object to be polished, 8: polishing agent,
12: Polishing tool, 12a: Vibration generating part,
12b: Oscillator, 12c: Horn, 12d:
Working part. Agent Patent Attorney Seki Yamashita Figure 1 Figure 3 Figure 4 μl Figure 5

Claims (6)

[Claims] (1) An abrasive containing abrasive grains is interposed between the object to be polished and a polishing tool, and the tool is vibrated to cause the abrasive grains in the abrasive to collide with the surface to be polished from an oblique direction. A polishing method characterized by: (2) The polishing method according to claim 1, wherein the polishing tool is vibrated obliquely with respect to the surface to be polished. (3) It has a working part that acts on the abrasive and a driving means that vibrates the working part in one direction, and the working part has at least a part oblique to the vibration direction in the overall standard shape. and polishing tools. (4) The polishing tool according to claim 3, wherein the action portion has a plurality of small areas oblique with respect to the overall standard shape. (5) The polishing tool according to claim 3, wherein the operating portion has an overall reference shape that is rotationally symmetrical around the vibration direction. (6) The polishing tool according to claim 5, further comprising a drive means for rotating the action portion around the vibration direction.