JPH01271167A - Polishing device using magnetic fluid - Google Patents

Abstract

PURPOSE:To reduce the polishing time improving surface roughness of a ball unit further enhancing its polishing efficiency by charging spherical workpiece therebetween with a spacer. CONSTITUTION:While holding a group of spherical workpieces 3, arranged on a circumference, by a driving lap 1, float 5 receiving levitating force by a magnetic field formed in magnetic fluid 7 by a magnet 6 and the internal peripheral surface of a guide ring 4, the driving lap 1 is rotated, polishing these spherical workpiece 3. When these workpieces are polished, the adjacent spherical workpieces 3 are charged therebetween with a spacer 8. By this charging spacer 8, the spherical workpieces 3 can be prevented from colliding against each other during polishing, and the workpiece 3 enables its surface roughness and polishing efficiency to be improve, as the result the polishing time can be reduced.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a polishing device using a magnetic fluid, and more specifically, a polishing device that uses a magnetic fluid containing abrasive grains under the action of a magnetic field to polish a ball bearing or the like. The present invention relates to an apparatus for efficiently manufacturing spheres with high sphericity by polishing used spheres.

[Prior Art] Conventionally, a method and apparatus for polishing spheres used in ball bearings, etc. using a polishing liquid made of a magnetic fluid containing abrasive grains under the action of a magnetic field has been disclosed in Japanese Patent Laid-Open No. 17316/1983.
It is disclosed in Publication No. 6.

The polishing method and apparatus described in the publication apply ejection force to a sphere immersed in a magnetic fluid containing abrasive grains by the action of an external magnetic field acting from one side outside the magnetic fluid.
It is pressed against the surface of a driving jig (driving lap) located on the opposite side, thereby transmitting the motion of the driving jig to the sphere and causing it to move in the magnetic fluid containing abrasive grains. The feature is that the movement is controlled by a guide surface.

Also, at this time, if a buoyancy plate (float) is inserted so as to be located on the external magnetic field side of the sphere, ejection force is also applied to this buoyancy plate due to the action of the external magnetic field, and the sphere is more strongly pushed to the drive surface of the driving jig. It is disclosed that the polishing efficiency is significantly improved because the polishing is pressed against the (contact surface).

In the polishing device, a V-shaped groove and a partition plate are provided on the lower surface of the driving lap to control the movement of the sphere, and the plate functions as a guide surface for the movement of the sphere, thereby improving polishing efficiency and sphericity. ing. Another method is to polish the lower end of the driving lap by making it into an inverted triangular pyramid shape and moving the sphere while being pressed between the slope of the inverted triangular pyramid, the cylindrical container (guide ring), and the buoyancy plate. Efforts are being made to improve sphericity.

However, when using such conventional polishing equipment,
The sphericity of the obtained spheres is not necessarily sufficient, and the polishing efficiency is also not satisfactory.

[Problems to be Solved by the Invention] When polishing with such conventional polishing equipment, brittle ceramic spheres such as SiC may collide with each other during polishing, resulting in improvements in surface roughness and sphericity. There was a limit.

An object of the present invention is to provide a polishing apparatus that uses a magnetic fluid containing abrasive grains and further improves the sphericity and surface roughness of an object to be polished.

[Means for Solving the Problems] As a result of intensive studies to achieve the above object, the present inventors have developed a spherical polished object to prevent collisions between the polished objects during polishing. By loading a spacer made of a shock-absorbing material between them, the present invention has been completed in which there is no collision between the spheres at all during polishing, and the sphericity of the spheres and polishing efficiency are greatly improved.

That is, the present invention includes a guide ring, a float immersed in a magnetic fluid containing abrasive grains, a rotatable drive wrap, and a magnetic field that forms a magnetic field in the magnetic fluid and gives a levitation force to the float together with the magnetic fluid. A polishing device for polishing a spherical object to be polished by rotating the driving lap while holding the spherical object in the magnetic fluid by the driving lap, a float receiving a buoyant force, and an inner wall surface of a guide ring. , a polishing apparatus characterized in that a spacer is loaded between the spherical objects to be polished for polishing.

Hereinafter, a polishing apparatus using a magnetic fluid according to the present invention will be explained based on the drawings.

FIG. 1 is a sectional view showing an example of a polishing apparatus of the present invention, and FIG. 2 is a diagram showing an example of a spacer used in the polishing apparatus of the present invention. In the figure, 1 is the driving lap, 2 is the contact surface of the lower end of the driving lap with the spherical object to be polished, and 3 is the spherical object to be polished (
4 is a guide ring, 5 is a float, 6 is a magnet, 7 is a magnetic fluid containing abrasive grains, and E is the inclination angle of the contact surface at the lower end of the driving lap.

In the polishing apparatus shown in FIG. 1, a magnetic fluid 7 containing abrasive grains is used.
The float 5 is immersed in the liquid, and an external magnetic field is applied to the magnetic fluid 7 using a magnet 6 or the like to give buoyancy to the float 5. The float 5 is raised by the buoyancy, and the sphere 3 to be polished is brought into contact with the upper end of the float 5. It is held by the contact surface 2 of the lower end of the drive wrap 1 and the inner wall surface of the guide ring 4. Then, by driving the driving lap 1 and rotating it in the horizontal direction, the movement of the rotation is transmitted to the spherical object 3 to be polished, so that it moves in the magnetic fluid 7 containing abrasive grains. This polished sphere 3
By generating a relative movement between the magnetic fluid 7 containing the abrasive grains, polishing is efficiently performed on the surface where the spherical object 3 to be polished is held, particularly on the tapered contact surface 2 at the lower end of the drive lap 1. It will be done.

The drive lap 1 shown in the polishing apparatus of FIG. 1 is capable of horizontal rotation about a vertical axis and has a contact surface 2 at its lower end. Further, since the driving lap 1 is worn out by polishing the spherical body 3 to be polished, it is necessary to lower the driving lap 1 each time, so that vertical movement is also possible. This contact surface 2 plays an important role in holding the spherical object 3 to be polished on the orbit between the float 5 and the inner wall surface of the guide ring 4, and performs stable and smooth rotational polishing. This contributes to improving the level of performance. Here, when the inclination angle E of the contact surface 2 in the outer circumferential direction with respect to the vertical direction is 20 to 80 degrees, the sphericity of the sphere can be improved. If the inclination angle E of the contact surface 2 exceeds 80 degrees, the force pressing the sphere 3 to be polished against the inner wall surface of the guide ring 4 will be weak, and if it is less than 20 degrees, the contact surface will not effectively press the sphere 3 to be polished. Since no processing pressure is applied from 2,
In each case, the motion of the polished sphere 3 becomes unstable and the sphericity does not improve, which is not preferable.

Further, another shape of the drive wrap 1 may be a cylindrical one, and in this case as well, the inclination angle E of the contact surface is preferably in the range of 20 to 80 degrees.

The material of the driving lap 1 is not particularly limited in the case of rough machining, and examples include stainless steel such as 5US304, metals such as brass and aluminum, and in the case of finishing, brittle materials such as cast iron and ceramics, etc. Preferably, it is made of resin or the like. The guide link 4 provided in the polishing apparatus shown in FIG. 1 keeps the polished sphere 3 rotating together with the contact surface 2 of the driving lap 1 and the float 5 constant during polishing, thereby contributing to improving the sphericity of the sphere. do. Here, the inner wall surface of the guide ring 4 is preferably made of a material that suppresses the vibration of the guide ring during polishing of the sphere. For example, the inner wall surface of the guide ring 4 is lined with rubber or plastic with a high elastic modulus. Ru.

Next, the float 5 immersed in the magnetic fluid of the polishing device is
Buoyancy is applied by the action of an external magnetic field such as the magnet 6, and the float 5 floats to strongly press the spherical object 3 to be polished against the contact surface 2 of the lower end of the drive lap 1. This float 5 is
Together with the contact surface 2 of the driving lap I and the inner wall surface of the guide ring 4, the rotating spherical object 3 to be polished is held constant during polishing, thereby contributing to improving the sphericity. The shape of the float 5 in contact with the spherical object 3 to be polished may be a flat shape or a chiller shape that makes contact at one point, or a V-shaped cross section or an R-shaped dish so that it makes contact at two points or a circumferential portion. A recessed portion may be provided.

As the material of the float 5, various materials such as metal, plastic, ceramics, rubber, etc. can be appropriately selected and used.

The buoyant force acting on the float 5 is determined by the strength of the external magnetic field acting from below, the size of the float 5, the distance from the magnet 6 etc. to the float 5, etc., and by changing these, the required processing pressure can be controlled arbitrarily. can do.

It is not an absolute condition that the specific gravity of the float 5 is lighter than the specific gravity of the magnetic fluid 7 containing abrasive grains, but it is sufficient that the float 5 can generate buoyancy by the action of an external magnetic field acting from below.

The spacer shown in FIG. 2 used in the present invention is S
This is particularly effective when polishing brittle ceramic spheres such as ICs.

By loading these spacers between the spheres 3 to be polished, the spheres to be polished are held constant during polishing to prevent collisions between the spheres and improve the surface roughness. The shape of the spacer is not limited to those shown in FIGS. 2(a) to 2(d), and any shape may be used as long as it can effectively prevent the spheres from colliding with each other. This spacer is attached to the polished sphere 3.
It may also be used by loading it at the same time as loading it into the polishing device.

The material used for the spacer may be any material as long as it has impact absorption properties and has a small coefficient of friction against the polished sphere, such as fluorocarbon resin, polyamide resin, etc.
Polyimide resins, acrylic resins, hard vinyl chloride resins, and the like are preferably used.

As the magnetic fluid 7, one in which ferrite or magnetite is dispersed using water or oil as a medium is used.

As the abrasive grains contained in the magnetic fluid 7, known polishing abrasive grains can be appropriately selected and used. For example, 8Ω203
(corundum), 5iC (silicon carbide; carborundum), diamond, etc., or abrasive grains with added magnetism may be used.

The magnet 6 used as the external magnetic field may be a single magnet or a group of 6i1 stones arranged with the same polarity, but rather it may be a combination of magnets such that adjacent magnets have different poles (indicated by arrows in the figure). Preferably, it is a group. Combining a group of magnets so that the poles of adjacent magnets are different from each other increases the buoyancy of the abrasive grains and the float 5, and also causes a magnetic discharge force to act in the horizontal direction, so as to resist the direction of movement of the polished sphere 3. This is to keep the abrasive grains in place. This magnet or group of magnets may be a permanent magnet or an electromagnet.

Further, as the polished sphere 3 applied to the present invention, Si
A material made of ceramic or metal such as C%Si, N4, etc. is used, and the polished sphere is used for applications such as ball bearings.

In addition, although the spherical object to be polished has been described in the present invention,
It is possible to polish not only spherical objects but also flat plates, cylinders, etc.

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Big! ff1ll-5- In the polishing apparatus shown in FIG. 1, a polishing test was conducted using the spacer shown in FIG. 2(a). Spacer materials include Teflon, polyamide resin,
Those made of polyimide resin, hard vinyl chloride resin, and acrylic resin were used.

In this case, the drive wrap was made of 5US304 and had a contact surface of 60 degrees. In addition, the float is made of acrylic and has 2
A flat one with a thickness of mm was used. The polishing test conditions are as follows.

Test conditions Magnetic fluid W-40 (manufactured by Taiho Industries) Material of the sphere to be polished [SiC Surface roughness 5.0 μm (R□,) Number of spheres and diameter 11 spheres, 7.1 mr6 abrasive grain SiC
GC#400 Polishing time: 10 minutes Drive lap rotation speed: 900 Or, p, m.

Among these Examples, FIG. 3 shows the cross-sectional curve of the surface roughness test of the spherical surface when polished using the Teflon spacer of Example 1.

Further, the results of these polishing tests are summarized in Table 1.

Comparative Example 1 A polishing test was conducted under exactly the same conditions as Examples 1 to 5 without using a spacer.

The cross-sectional curve of the surface roughness test of the obtained spherical surface is shown in FIG.

Further, the results of the polishing test of this comparative example are shown in Table 1 together with the results of Examples 1 to 5.

In Table 1, Figures 3 and 4, the vertical axis is 1 per 1cI11.
(Shows surface roughness (R□,) of 1 micron, horizontal axis is 1 cm
The distance between the surfaces of the spheres is 0.2 aua.

As is clear from the above Examples and Comparative Examples, when polishing was performed with a spacer made of wear-resistant rubber or elastic plastic loaded in the polishing machine, the comparison was made when polishing was performed without loading a spacer. It can be seen that the surface roughness is significantly improved.

[Effects of the Invention] As explained above, according to the polishing apparatus using the magnetic fluid of the present invention, a sphere with extremely improved surface roughness can be obtained.

Furthermore, by improving polishing efficiency, polishing time is shortened and economical efficiency is improved.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing an example of a polishing apparatus according to the present invention, FIGS. 2(a) to (d) are top views showing an example of a spacer used in the present invention, and FIG. 4 is a diagram showing a cross-sectional curve of the surface roughness test of the spherical surface obtained in Comparative Example 1. FIG. driving lap, 2: contact surface at lower end of driving lap, 3: sphere to be polished, 4 guide ring, 5: float, 6: stone, 7: magnetic fluid containing abrasive grains, E: lower end of driving lap Inclination angle of the contact surface of the part, 8 Ni spacer - 0

Claims (1)

[Claims] 1. A guide ring, a float immersed in a magnetic fluid containing abrasive grains, a rotatable drive wrap, and a magnetic field forming means that forms a magnetic field in the magnetic fluid to give a levitation force to the float together with the magnetic fluid. A polishing apparatus that polishes a spherical object to be polished by rotating the driving lap while holding the spherical workpiece in the magnetic fluid by the driving lap, a float receiving a buoyant force, and the inner wall surface of the guide ring. A polishing apparatus characterized in that a spacer is loaded between the spherical objects to be polished arranged on top of the polishing apparatus.