JPH08257897A - Method and device for polishing sphere provided with float having hole in center and circulating device of magnetic fluid containing abrasive grain - Google Patents

Abstract

PURPOSE: To continuously supply an abrasive grain to a sphere, so that the sphere can be polished in good sphericity, by opening a hole in the center of a float, increasing a work load by the float when made a motion of the sphere in a magnetic fluid, also to increase a speed of the sphere in rotation on its own axis and revolving around, and so as to circulate the magnetic fluid containing the abrasive grain through this hole. CONSTITUTION: A hole 8A is opened in the center part of a float 3. A negative pressure in a lower surface of the float 3, generated in the case of rotating this float 3, is made to escape from the hole 8A, thus to suppress a vertical vibration of the float 3, also to stabilize a motion of a ceramic ball 2 in rotation on its own axis and revolution around. Since a magnetic fluid 9 containing an abrasive grain is circulated through this hole 8A, the abrasive grain is continuously supplied to this ball 2. By action of the hole 8A of the float 3 thus performed, when performed a motion of the ceramic ball 2 in rotating on its own axis and revolving around along inside a vessel 4A together with rotary motion of a drive shaft 1, the float 3 presses the ball 2 by magnetic levitating force to the vessel 4A and a slope of the drive shaft further rotated, consequently to efficiently polish the ball 2 into a spherical shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for polishing a spherical body using a magnetic fluid and an apparatus therefor. More specifically, the magnetic fluid containing abrasive grains is used under the action of a magnetic field and is used for ball bearings and the like. The present invention relates to a polishing method and an apparatus therefor for mass-producing spheres with high sphericity.

More specifically, it is provided with a buoyancy (buoyancy plate) having a hole at the center, and further circulating a magnetic fluid containing abrasive grains.

[0003]

2. Description of the Related Art When polishing a hard and brittle sphere of a non-magnetic material such as (ceramic), the conventional V-groove lapping method uses expensive superabrasive grains such as diamond and requires a long processing time. Therefore, its processing cost is very high, which is an obstacle to its wide use in the industrial field.

In order to solve this problem, a magnetic fluid polishing method and its device, Japanese Patent Publication No. 5-41394, have been developed.
However, when this method is used on the premise of mass production of ceramic spheres, there is still an unclear part in the polishing mechanism, and high-precision and high-efficiency polishing of a large number of spheres has not been stably achieved to date.

[0005]

Therefore, the present invention has three points of shortening the polishing time, obtaining a ceramic sphere having a high sphericity, and obtaining a ceramic sphere having a good surface roughness, on the premise of mass production. A polishing method and a polishing apparatus for stably obtaining the above are developed.

[0006]

[Means for solving problems]

1. A spherical body and a float (a buoyancy plate) having a hole at the center are immersed in a magnetic fluid containing abrasive grains that are refluxed in a double cylindrical container having a low inner wall surface in which a magnet is arranged below, Due to the magnetic levitation phenomenon that occurs in the sphere and the float due to the action of the magnetic field formed by the magnet, the lower end of the drive shaft installed on the sphere and the upper part of the container has one end of the pipe cut into a conical surface with an apex angle of 90 ^0. When the sphere is made to move in a magnetic fluid containing abrasive grains by transmitting the motion of the drive shaft to the sphere by pushing it against the sphere, the float with a hole in the center not only increases the processing load, but also moves vertically due to its rotation. A polishing method in which vibration is suppressed, the rotation and revolution speed of the sphere is increased, and the magnetic fluid containing the abrasive circulates through the hole so that the abrasive is continuously supplied to the sphere. 2. An annular V-shaped groove was provided on the sphere and the upper surface in a magnetic fluid containing abrasive grains that was circulating in a double cylindrical container having a low inner wall surface in which a magnet was arranged below, and a hole was opened in the center. A float (buoyancy plate) is dipped, a sphere is placed in the groove, and the sphere is formed by the magnetic levitation phenomenon that occurs in the sphere and the float due to the action of the magnetic field formed by the magnet, and the plane of the drive shaft installed above the container. When the movement of the drive shaft is transmitted to the sphere by pressing it against the lower surface of the sphere and the sphere is moved in the magnetic fluid containing abrasive grains, the float with a hole in the center not only increases the processing load, but also A polishing method in which the vertical vibration associated with rotation is suppressed to increase the rotation and revolution speed of the sphere, and because magnetic fluid containing abrasive grains circulates through this hole, the abrasive grains are continuously supplied to the sphere. 3. The method according to claim 1 or 2, wherein the sphere is a ceramic sphere. 4. A groove between the outer walls of a double cylindrical container having a low inner wall surface is provided with a hole for discharging a magnetic fluid containing abrasive grains circulating between the container and an external storage tank, and a magnet is arranged at the bottom of the container. A hole for introducing a magnetic fluid containing abrasive grains that circulates between the magnet group and an external storage tank is provided in the center of the magnet group, and the lower end is at the upper part of the container and one end of the pipe is cut on a conical surface having an apex angle of 90 ^0. The sphere to be polished immersed in the magnetic fluid and the float immersed in the lower part of the sphere have a hole in the center, and the sphere is formed by the magnetic levitation phenomenon caused by the action of the magnetic field formed by the magnet. A sphere polishing apparatus configured to be pressed against the lower surface of a drive shaft installed at the upper part of a container so that the motion of the drive shaft is transmitted to the sphere so that the sphere moves in a magnetic fluid containing abrasive grains. 5. A groove between the outer walls of a double cylindrical container having a low inner wall surface is provided with a hole for discharging a magnetic fluid containing abrasive grains circulating between the container and an external storage tank, and a magnet is arranged at the bottom of the container. A hole for introducing a magnetic fluid containing abrasive grains that circulates between the magnet group and an external storage tank is provided at the center of the magnet group, and a drive shaft having a flat lower surface is installed above the container. The sphere to be dipped in and the float to be dipped below have a plurality of annular V-shaped grooves, and a hole is made in the center, and the sphere is formed by a magnetic levitation phenomenon caused by the action of a magnetic field formed by the magnet. A polishing apparatus for a spherical body, which is pressed against the lower surface of a drive shaft installed on the upper part of the drive shaft, and the motion of the drive shaft is transmitted to the spherical body so that the spherical body moves in a magnetic fluid containing abrasive grains.

The method for polishing spheres using a magnetic fluid, which is the basis of the present invention, is a method in which a ceramic sphere and a float are immersed in a magnetic fluid containing abrasive particles filled in a container in which a magnet is arranged. By the action of the magnetic field formed by the magnet, the ceramic sphere is pressed against the lower surface of the drive shaft (drive shaft jig) located at the upper part of the container by the magnetic levitation phenomenon that occurs in the ceramic sphere and the float to move the drive shaft. This is due to transmission to the ceramic spheres and movement of the ceramic spheres in a magnetic fluid containing abrasive grains. This polishing method is described in detail in JP-B-5-41394.

Among the components of the polishing method and apparatus according to the present invention, a hole is made in the center of the float, and a magnetic fluid containing abrasive grains is circulated between the polishing container and an external storage tank. The feature is to let.

[0009]

When polishing is carried out in the state of being installed as shown in FIG. 3, the distance between the float 3 and the magnet surface in this magnetic fluid polishing method is adjusted within the range of 0.5 mm-2 mm. A fine powder containing iron oxide as a main component, which is generated by deterioration of the magnetic fluid itself with the passage of polishing time, and rotation as a drive shaft, while it also functions as a lapping machine and is also a metal of stainless steel that is generated by grinding itself. Powder, abrasive fines,
Further, the ground ceramic powder gradually increases its content and stays in the magnetic fluid. The viscosity of the magnetic fluid increases with the increase in the volume concentration of the magnetic particles accompanying the evaporation of the dispersion medium due to the generation of frictional heat. As a result, those substances that cannot be suspended in the magnetic fluid stick to the upper wall of the container 4A, and some of them are diffused to the lower part of the float 3, and iron in particular sticks to the entire magnet surface. This is because the float moves up and down,
Until now, it has been impossible to obtain the ideal ceramic sphere by working with factors that are bad for the rotation and revolution of the sphere.

Therefore, in the present invention, a great result is obtained by forming a hole in the center of the float 3 shown in FIG. That is, it is possible to let the negative pressure on the bottom surface of the float generated when the float rotates by opening a hole in the center of the float 3 from the hole, and the vertical vibration of the float that has conventionally been generated with the rotation speed of the float. It becomes possible to suppress the rotation of the ball, and to stabilize the rotation and revolution movement of the ball. Further, since the magnetic fluid containing abrasive grains circulates through this hole, the abrasive grains are continuously supplied to the sphere. Due to the action of the hole of the float, when the ceramic ball 2 rotates and revolves along the inside of the container 4A along with the rotational motion of the drive shaft 1, the float 3 causes the ceramic ball 2 to move to the container 4A by the magnetic levitation force. Not only pressing on the slope of the drive shaft, but also rotating by itself to assist the rotational movement of the ceramic ball 2,
The ceramic sphere 2 can be more efficiently spherically polished without polishing a specific portion.

That is, by making a hole in the float, the viscous resistance of the float is reduced, and even if the rotation speed of the same drive shaft is different, the rotation speed of the float is different, and the revolution speed of the ceramic ball is increased accordingly. Therefore, at the contact point between the ball and the drive shaft, the ratio of the rolling speed to the sliding speed becomes large. The entire sphere efficiently contacts the drive shaft and the like, and as a result, the sphericity is improved.

In addition, the circulation method in which the magnetic fluid containing abrasive grains filled in the container is continuously replaced has the effect of removing the factor acting as a bad factor in the polishing method described above. It discharges the magnetic powder containing the metal powder, the used abrasive powder, and the ground ceramic powder from the drive shaft to the back side of the container 4A in the form of an overflow, while it is discharged from the center of the magnet 5. By supplying the magnetic fluid containing new abrasive grains, the initial state of polishing can be maintained. Further, this means that even if abrasive grains having a relatively small grain size are used from the viewpoint of polishing ability, the polishing efficiency is not lowered, rather the finishing process is facilitated, and ceramic spheres having a good surface roughness can be obtained. Incidentally, it is desirable that the discharged magnetic fluid is introduced into the storage tank and then refluxed through the filter.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method and apparatus of the present invention will be described below with reference to the accompanying drawings and tables.

FIG. 1 Known polishing device, FIG. 2 Device according to the invention, FIG. 3 Preliminary device according to the invention, FIG. 4 Spheres arranged along the inside of the container of the device according to FIGS. FIG. 6 is a plan view showing the arrangement, FIG. 5 is a magnet, and FIG. 6 is a device of the present invention.
Both are explanatory views of the present invention.

1-6 drive shaft, 2 ceramic spheres, 3 floats, 4A container inner part, 4B container outer part, 5 magnets, 6 mounting base, 7 storage tanks, 8A, 8B, 8C Hole, 9 magnetic fluid, 10 water, 11 spindle, 12 flange.

Table 1 Polishing conditions

FIG. 1 is an explanatory view of a basic magnetic fluid polishing apparatus of Japanese Patent Publication No. 5-41394. FIG. 2 is an explanatory view of a polishing apparatus according to the present invention, and FIG. 3 is an explanatory view of each polishing apparatus before the completion of the present invention. The lower end of the drive shaft 1 shown in FIGS. 2 and 3 is one end of a pipe made of stainless steel and has an apex angle 90 ^0.
It was cut into a conical surface. The ceramic sphere 2 is in contact with this conical surface. The other end of the pipe is fixed to a flange, and linked to the spindle via the flange. It is important that the spindle has a high runout accuracy and is fixed to a robust housing.

The container (made of aluminum casting) shown in FIGS.
Is a double cylinder consisting of a portion 4A which acts as a guide surface for the movement of the sphere and a portion 4B which is integrated at the bottom. However, in one place on the bottom surface between 4A and 4B in FIG.
There is provided a discharge port 8B for guiding the magnetic fluid containing abrasive grains flowing over to the external storage tank. See also FIG.
The groove between 4A and 4B is filled with water to prevent the temperature rise of the magnetic fluid during polishing.

FIG. 4 shows ceramic balls of the same size as shown in FIG.
4 shows a state where the apparatus shown in FIG. 3 is installed along the inside of a container 4A. FIG. 5 is an assembly drawing of the magnet 5. A hole 8C is provided at the center of the magnet portion for guiding the magnetic fluid having abrasive grains into the polishing apparatus from the storage tank.

A hole 8A is formed in the center of the float 3 shown in FIG. 2 according to the present invention. The float 3 shown in FIG. 3 has no holes. Next, magnet 5, container 4
A and 4B are set on a mounting base 6 at the lower part thereof, can be moved in the vertical direction, and can be fixed at an arbitrary position for transmitting the motion of the drive shaft 1 to the ceramic sphere.

FIG. 6 shows a case in which the shape of the lower surface of the drive shaft is a disk, and shows an example in which a hole is formed in the center of the float 3 and an annular V-shaped groove is provided on the upper surface.

The ceramic spheres used (HIP silicon nitride spheres having a diameter of about 8 mm) were preliminarily measured with a micrometer (minimum scale 1 μm) at 10 locations, and each sphere installed as shown in FIG. After polishing for 40 minutes under the conditions of A and B shown in Table 1 below under a load of 0.5 N, the ceramic spheres were washed with water, and the diameters were measured again at 10 locations. The difference between the maximum value and the minimum value of the diameter of each sphere was calculated, and the average value of those values in all spheres was regarded as the diameter disparity in each polishing.

[0023]

[Table 1]

As a result, for a float with a 10 mm hole, A
In the case of 1, the diameter difference was reduced from 2.5μ to 1.0μ, while in the case of the float without a hole, in the case of B, the diameter difference was 1.5μ.
It increased from μ to 3.9μ. Also, after polishing the ceramic spheres obtained in A1 under the conditions of A2 for 40 minutes, washed with water,
As a result of re-measurement, the diameter difference was reduced from 1.0 μ to 0.5 μ.

Further, in the embodiment shown in FIG. 6 in which the lower surface of the drive shaft is disk-shaped and the float has an annular V-shaped groove, the diameters are different when the condition is shown in C with two rows of V grooves. Was reduced from 1.5μ to 1.0μ.

From this, it can be seen that the float having holes is effective in reducing the diameter difference. Also, when observing the polished spherical surface with and without holes with an optical microscope, many indentation scratches that were thought to have caused a lot of rolling between the drive shaft and the sphere were observed in the float with holes. On the other hand, many scratches were observed on the float without holes. As a result, the hole in the float facilitates the rotational movement of the float, which increases the orbital movement of the sphere, and as a result, the movement between the drive shaft and the sphere becomes more It is probable that the rolling motion was approaching.

[0027]

The object of the present invention is to mass-produce spheres having a higher sphericity than the conventional method for polishing spheres using magnetic fluid.

[Brief description of drawings]

FIG. 1 is an explanatory view of a known polishing device.

FIG. 2 is an explanatory view of a polishing apparatus of the present invention.

FIG. 3 is an explanatory view of a preliminary polishing apparatus according to the present invention.

FIG. 4 is an explanatory view showing an array of spheres arranged along the inside of the container of the apparatus of FIGS. 2 and 3;

FIG. 5 is an explanatory diagram of a magnet

FIG. 6 is an explanatory view of a polishing apparatus of the present invention.

[Explanation of symbols]

 1 Drive shaft 2 Ceramic sphere 3 Float (buoyancy plate) 4A Container inner part 4B Container outer part 5 Magnet 6 Mounting stand 7 Storage tank 8A hole 8B hole 8C hole 9 Magnetic fluid 10 Water 11 Spindle 12 Flange

Claims (5)

[Claims] 1. A low inner wall surface on which a magnet is arranged below 2
A spherical body and a float (buoyancy plate) having a hole in the center are immersed in a magnetic fluid containing abrasive grains that are refluxed in a heavy cylindrical container, and the spherical body and the float are caused by the action of a magnetic field formed by the magnet. Due to the magnetic levitation phenomenon that occurs in, the lower end of the drive shaft installed at the upper part of the sphere and the container makes one end of the pipe apex angle 90 ^0.
When the drive shaft is pressed against the surface cut by the conical surface of the and the motion of the drive shaft is transmitted to the sphere to move the sphere in the magnetic fluid containing abrasive grains, the float with a hole in the center not only increases the processing load. Instead, it suppresses vertical vibrations due to its rotation, increases the rotation and revolution speed of the sphere, and the magnetic fluid containing the abrasive circulates through this hole, so that the abrasive is continuously supplied to the sphere. 2. A lower inner wall surface on which a magnet is arranged below 2
An annular V-shaped groove is provided on the sphere and the upper surface in a magnetic fluid containing abrasive grains that is refluxed in a heavy cylindrical container, and a float (buoyancy plate) with a hole at its center is immersed in the groove. By placing a sphere, the sphere is pressed by the magnetic levitation phenomenon that occurs in the sphere and the float due to the action of the magnetic field formed by the magnet, and the sphere is pressed against the flat lower surface of the drive shaft installed in the upper part of the container to make the sphere of the drive shaft moving. When the sphere is moved to move in a magnetic fluid containing abrasive grains, the float with a hole in the center not only increases the processing load, but also suppresses the vertical vibration due to its own rotation and the rotation and revolution speed of the sphere. And a magnetic fluid containing abrasive grains circulates through this hole so that the abrasive grains are continuously supplied to the sphere. 3. The spherical body is a ceramic sphere.
The method according to Item 2 or Item 2. 4. A double cylindrical container having a low inner wall surface has a hole for discharging a magnetic fluid containing abrasive grains which circulates between the outer storage tank and a groove in the groove between the outer walls, and a magnet is provided in a lower portion of the container. And a hole for introducing a magnetic fluid containing abrasive grains that circulates between the magnet group and the external storage tank in the center of the magnet group,
A drive shaft having a lower end and one end of a pipe cut into a conical surface with an apex angle of 90 ⁰ is installed in the upper part of the container, and a sphere to be dipped in the magnetic fluid and a float to be dipped in the lower part have a hole at the center. The sphere is pressed against the lower surface of the drive shaft installed in the upper part of the container by the magnetic levitation phenomenon caused by the action of the magnetic field formed by the magnet, and the motion of the drive shaft is transmitted to the sphere to cause the sphere to generate abrasive particles. An apparatus for polishing spheres configured to move in a magnetic fluid containing. 5. A hole between the outer walls of a double cylindrical container having a low inner wall surface for discharging a magnetic fluid containing abrasive grains that circulates between the outer storage tank and a magnet is provided at the bottom of the container. And a hole for introducing a magnetic fluid containing abrasive grains that circulates between the magnet group and the external storage tank in the center of the magnet group,
A drive shaft having a flat lower surface is installed on an upper portion of the container, and a sphere immersed in the magnetic fluid and a float immersed in the lower portion thereof have a plurality of annular V-shaped grooves, and a hole is formed at a center portion. The sphere is pressed against the lower surface of the drive shaft installed in the upper part of the container by the magnetic levitation phenomenon caused by the action of the magnetic field formed by the magnet, the motion of the drive shaft is transmitted to the sphere, and the sphere contains abrasive grains. A sphere polishing device configured to move in a magnetic fluid.