JPH0516985B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a polishing method, and more particularly to a polishing method in which the pressing force of a polishing tool against an object to be polished is adjusted as appropriate. Such polishing is used, for example, to polish optical elements such as lenses, prisms, and mirrors.

[Prior art and its problems] Generally, optical elements such as lenses, prisms, and mirrors are manufactured by shaping a material such as glass into a predetermined shape and then polishing the functional surface, that is, the surface that transmits and/or reflects light. It is manufactured by gradually reducing the surface roughness and at the same time achieving a predetermined surface accuracy.

In the polishing process, a polishing method using free abrasive grains or a polishing method using fixed abrasive grains is employed. Free abrasive grains are often used in the form of an abrasive dispersed in an appropriate liquid, and while the abrasive is supplied between the polishing tool and the object to be polished, the polishing tool Polishing is performed by sliding. Further, the fixed abrasive grains are used while being fixed to at least the surface of the polishing tool, and polishing is performed by sliding the polishing tool against the object to be polished.

In such polishing, polishing conditions are appropriately set so as to obtain the desired surface precision. One of these polishing conditions is the pressing force of the polishing tool against the object to be polished. If the pressing force is increased, the polishing rate can be increased, but surface roughness tends to increase. Conversely, if the pressing force is reduced, the polishing rate will be reduced, but the surface roughness will be reduced and the surface shape precision can be maintained sufficiently well.

Therefore, depending on the desired polishing, for example, a relatively high pressing force is used in the initial stage of polishing to perform highly efficient polishing, and a relatively low pressure is used in the final stage of polishing to maintain the surface roughness small and to improve the surface shape. It is preferable to perform polishing that sufficiently increases precision.

Further, as polishing continues, the surface shape accuracy may gradually decrease, and in this case, corrective polishing is required. This tendency is particularly strong when the surface to be polished is a spherical surface.

In other words, optical elements with functional surfaces that are flat or spherical have traditionally 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 widely 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 surface shape is created, for example, by numerically controlled grinding, and the surface is polished to gradually reduce the surface roughness while maintaining the surface shape accuracy as much as possible. Therefore, when polishing an aspherical surface, the surface accuracy is particularly likely to deteriorate, so that corrective polishing becomes more necessary.

Even during such correction polishing, the amount of polishing removal is adjusted by appropriately changing the pressing force of the polishing tool locally so as to approximate the desired surface shape.

Conventionally, the adjustment of the pressing force of the polishing tool as described above is
For example, this is accomplished by applying a desired pressing force to the polishing tool using a pressing means such as an air cylinder. In order to maintain the pressing force more accurately, a pressure regulating valve (pressure servo valve) is interposed between the compressed air source that supplies compressed air to the air cylinder and the air cylinder, and the pressure servo valve An air pressure detection means is provided between the air cylinder and the pressure servo valve is appropriately adjusted based on the pressure detected by the detection means so that the detected pressure becomes a desired value.

However, in such conventional pressing force adjustment, there is friction when the contact part of the polishing tool against the surface to be polished moves and the piston of the air cylinder moves within the cylinder, so the pressure inside the cylinder remains the same as the polishing tool. Therefore, there is a problem in that the pressing force of the polishing tool against the workpiece cannot be accurately set to a desired value. Therefore, there has been a problem in that it is difficult to bring the surface shape accuracy of the surface to be polished close to a desired value with sufficiently good efficiency.

Therefore, an object of the present invention is to press a polishing tool against an object to be polished with a desired pressing force, thereby performing good polishing accurately under desired polishing conditions.

[Means for Solving the Problems] According to the present invention, in order to achieve the above objects, a polishing tool is pressed against an object to be polished by a pressing means, and a means for detecting the pressing force of the pressing means is provided. a detection signal from the detection means is input to a controller, and the controller controls the pressing means to polish the polishing tool, the polishing tool being subjected to the pressing force of the pressing means. A polishing sheet that directly contacts the object to be polished to perform a polishing action, and a pressure detection means disposed between the base and the polishing sheet, the pressing force that the polishing sheet receives from the object to be polished. A polishing method is provided, characterized in that the reaction of the pressure is detected by the pressure detection means, the detection signal is input to the controller, and the pressing means is controlled to perform polishing.

[Example] Hereinafter, specific examples of the present invention will be described with reference to the drawings.

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

In FIG. 1, reference numeral 2 denotes a polishing object holding means, and the holding means is adapted to be rotated in the vertical direction by a driving means (not shown).

An object to be polished 4 is fixedly held on the upper surface of the holding means 2. In this embodiment, 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.

Reference numeral 6 denotes a polishing tool, which includes a polishing sheet (for example, 0.5 mm made of foamed polyurethane) that directly contacts the base 6a and the object to be polished 4 to perform a polishing action.
~1.0mm thick sheet) and the polishing sheet above Basic 6
and a pressure detection means 6c disposed between the pressure detection means 6c and the pressure detection means 6c. As the pressure detection means, for example, a load cell using a piezoelectric body or the like can be used.

The polishing tool 6 is pressed against the object 4 to be polished. In this embodiment, an air cylinder 8 is used for this pressing. 10 is a piston within the cylinder, and 12 is a piston rod. The rod faces in the vertical direction, and the polishing tool base 6a is fixed to its lower end.

The air cylinder 8 is fixedly held by a holder 14. The holder is mounted so as to be movable in the horizontal direction while being guided by a guide 16. A motor 18 is attached to the guide, and a feed screw 20 extending in the direction of the guide 16 (horizontal direction) is connected to the drive rotation shaft of the motor. The feed screw is attached to the air cylinder holder 14.
Therefore, by rotating the feed screw 20 by the motor 18, the holder 14 is moved along the guide 16.

The air cylinder 8 is connected to a compressed air source through a pipe 22, and a pressure servo valve 24 is disposed in the middle of the pipe. Further, an air pressure detection means 26 is disposed in the middle of the piping on the side of the air cylinder from the servo valve 24.

Note that 28 is a pipe for supplying abrasive between the object to be polished 4 and the polishing tool 6.

The output of the pressure detection means 6c of the polishing tool and the output of the air pressure detection means 26 are controlled by the controller 3.
It is input to 0. Further, the controller issues a valve opening command signal to the pressure servo valve 24.

During polishing, while supplying abrasive from the abrasive supply pipe 28 to the polishing position, the object holding means 2
Rotate. Then, the motor 18 is driven to rotate the feed screw 20 to move the air cylinder 8 horizontally along the guide 16, thereby moving the polishing tool 6 to a desired position in the radial direction on the workpiece 4. move it.

The compressed air source has a constant pressure of, for example, 5 kg/cm ² , and the air pressure supplied to the air cylinder 8 is set by appropriately adjusting the opening degree of the pressure servo valve 24. The controller 30 issues a valve opening command signal to the servo valve 24 in order to achieve a desired air pressure.

The pressing force applied by the air cylinder 8 is transmitted to the polishing tool 6 by the piston rod 12,
As a result, the polishing sheet 6b is pressed against the object to be polished 4 with an appropriate pressure. The reaction force of the pressing force is detected by the pressure detection means 6c, and the reaction force is detected by the pressure detection means 6c.
It is input to 0. If the detected pressure is different from the predetermined pressure for desired polishing at the polishing position,
The controller 30 issues a command to the pressure servo valve 24 to change the valve opening so that the air pressure eliminates the pressure difference. Detected air pressure is constantly inputted from the air pressure detection means 26 to the controller 30, and the pressure servo valve 24 is thereby controlled.

Then, by sampling the pressing force detected by the pressure detection means 6c at appropriate time intervals and performing control to eliminate deviation from the desired value as described above, extremely accurate pressing force can be obtained. The desired polishing rate, surface roughness, and surface shape accuracy are achieved.

In the polishing described above, the desired pressing force may be appropriately set in advance depending on the polishing stage and polishing position. Then, the motor 18 is driven to move the polishing tool 6 in the rotational radius direction of the object to be polished 4, and in response to this change in the polishing position, the polishing tool 6 is pressed against the object to be polished 4 at the set pressing force value as desired. can be polished.

FIG. 2 is an explanatory diagram of a second embodiment of a polishing apparatus for carrying out the polishing method according to the present invention. In this figure, the same members as in FIG. 1 are given the same reference numerals.

In this embodiment, the surface to be polished of the object to be polished 4 has a convex spherical shape, and the polishing tool 6 has a surface shape corresponding to this. Further, the air cylinder 8 is attached to the holder 14 so as to be rotatable in a direction (horizontal direction) perpendicular to both the vertical direction and the direction of the guide 16, and its inclination angle is set by a driving means (not shown). be done.

In this embodiment, when the polishing tool 6 is driven by the motor 18 and moves along the radial direction of the object 4 to be polished, the attitude of the piston rod 12 is controlled so that it always faces the center of curvature of the surface to be polished. 6b
is always adapted to the surface to be polished.

This embodiment also has the same effects as the first embodiment.

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 matte surface level and a matte surface level. may be of any grain size up to the level required to obtain a surface roughness called a ground surface.

Further, although the above embodiments show polishing using free abrasive grains, the present invention can be similarly applied to polishing using fixed abrasive grains.

[Effects of the Invention] According to the present invention as described above, the polishing tool directly detects the reaction of the pressure acting on the surface to be polished and adjusts the pressing force of the polishing tool based on the detected value. The object to be polished is pressed with a desired pressing force, thereby making it possible to accurately perform good polishing under desired polishing conditions.

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams of a polishing apparatus for carrying out the polishing method according to the present invention. 4: Polished object, 6: Polishing tool, 6a: Substrate, 6
b: polishing sheet, 6c: pressure detection means, 8: air cylinder, 16...: guide, 18: motor,
20: Feed screw, 24: Pressure servo valve, 26: Air pressure detection means.

Claims (1)

[Scope of Claims] 1. Pressing a polishing tool against an object to be polished by a pressing means, detecting the pressing force of the pressing means by a detecting means, and inputting a detection signal from the detecting means to a controller; A method of polishing by controlling the pressing means by the controller, the polishing tool comprising: a base body that receives the pressing force of the pressing means; a polishing sheet that directly contacts the object to be polished and performs a polishing action; a pressure detection means disposed between the base body and the polishing sheet, the pressure detection means detects a reaction of the pressing force that the polishing sheet receives from the object to be polished, and inputs the detection signal to the controller. A polishing method characterized in that polishing is performed by controlling the pressing means.