JPH01271164A - Polishing device using magnetic fluid - Google Patents

Abstract

PURPOSE:To obtain a ball unit of high sphericity further enhancing polishing efficiency enabling long time continuous polishing to be performed by fixing an abrasive grain to a driving lap bottom end part in its contact surface with a spherical workpiece. CONSTITUTION:While holding a spherical workpiece 3 in magnetic fluid 7 by a driving lap 1, float 5 given floating force by the magnetic field formed in the magnetic fluid 7 by a magnetic field forming means (magnet) 6 and the internal peripheral surface of a guide ring 4, the driving lap 1 is rotated, polishing this workpiece 3. Here an abrasive grain 8 is fixed to the driving lap 1 in its bottom end contact surface 2 coming into contact with the workpiece 3. Thus enabling the workpiece 3 to improve its sphericity and polishing efficiency, continuous polishing can be performed over a long time.

Description

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

[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 device described in the publication apply ejection force to a sphere immersed in a magnetic fluid by the action of an external magnetic field acting from one side outside the magnetic fluid, and drive the sphere to be positioned on the opposite side. The sphere is pressed against the surface of a driving jig (driving lap), thereby transmitting the motion of the driving jig to the sphere to operate in the magnetic fluid, and the movement of the sphere is controlled by a guide surface. It is something to do.

At this time, if a buoyancy plate (float) is inserted so as to be located on the external magnetic field side of the sphere, a discharge force is also applied to this buoyancy plate due to the action of the external 6n field, and the sphere is more strongly polished by the driving jig. It is disclosed that the polishing efficiency is significantly improved because the polishing material is pressed against the 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 shape, the cylindrical container (guide ring), and the buoyancy plate. Efforts are being made to improve sphericity.

[Problem to be solved by the invention] However, when such a conventional polishing device is used,
The sphericity of the obtained spheres is not necessarily sufficient, and the polishing efficiency is also not satisfactory.

In other words, in conventional polishing devices that use magnetic fluid containing abrasive grains, not all the abrasive grains are involved in polishing.
In addition, since the abrasive grains are crushed by the collision between the objects to be polished,
It has not always been possible to obtain sufficient sphericity and polishing efficiency.

SUMMARY OF THE INVENTION An object of the present invention is to provide a polishing device that uses a magnetic fluid and further improves the sphericity of the sphere and the polishing efficiency.

[Means and Effects for Solving the Problems] As a result of intensive studies to achieve the above object, the present inventors fixed abrasive grains on the lower end of the drive lap on the contact surface with the spherical object to be polished. As a result, the present invention has been completed, which improves the sphericity of the object to be polished and the polishing efficiency.

That is, the present invention includes a guide ring, a float immersed in a magnetic fluid, 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 comprising: a driving lap 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; There is a polishing device characterized in that abrasive grains are fixed to a lower end portion of the surface that contacts the spherical object to be polished.

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 the polishing apparatus of the present invention.

In the figure, 1 is the drive lap, 2 is the contact surface with the spherical object to be polished,
3 is a spherical object to be polished (a spherical object to be polished), 4 is a guide ring, 5 is a float, 6 is a magnet, 7 is a magnetic fluid, and 8 is a fixed abrasive grain.

In the polishing apparatus shown in FIG. 1, a float 5 is placed in a magnetic fluid 7.
is immersed in the magnetic fluid 7, an external magnetic field is applied to the magnetic fluid 7 using a magnet 6, etc. to give buoyancy to the float 5, and the buoyancy causes the float 5 to float.
is raised, and the polished sphere 3 is held by the contact surface of the upper end of the float 5, 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. Polishing is performed efficiently by sliding the spherical body 3 to be polished and the fixed abrasive grains 8 fixed to the contact surface 2.

In FIG. 1, a drive wrap 1 is capable of horizontal rotation about a vertical axis and has a contact surface 2 at its lower end.

The angle of inclination of this contact surface 2 is preferably in the range of 20 to 80 degrees. Further, as another shape of the drive lap 1, it may be cylindrical as shown in FIG. 2, and in this case as well, the angle of the polished surface is preferably in the range of 20 to 80 degrees.

The material of the drive wrap 1 is not particularly limited, but includes, for example, stainless steel such as SO5304, metals such as brass, and aluminum.

In the present invention, fixed abrasive grains 8 are fixed to the tapered contact surface 2 of the drive lap 1 described above. The fixed abrasive grains mentioned here are exemplified by diamond, silicon carbide, boron nitride, or alumina such as corundum. As a method for fixing these fixed abrasive grains 8, a commonly used manufacturing method for grinding wheels can be applied as is. Specifically, when diamond is used, the contact surface 2 is plated with diamond abrasive grains dispersed and fixed by electrodeposition, and silicon carbide,
When using a grindstone made of alumina or boron nitride,
It is fixed to the tip of the drive wrap using resin or the like as an adhesive. In this way, by fixing the abrasive grains to the contact surface 2,
Compared to magnetic fluid containing free abrasive grains, polishing efficiency is higher and continuous polishing for a long time is possible. The reason for this is that when free abrasive grains are used, all the free abrasive grains participate in polishing (in the case of it <, and the abrasive grains are crushed by the collision between the polished spheres 3). This is because, although polishing efficiency decreases due to long-term use, such problems do not occur when fixed abrasive grains are used.

Furthermore, when diamond is used as the fixed abrasive grains 8 used in the present invention, the shape of the contact surface 2 at the lower end of the drive lap 1 hardly changes due to the hardness of diamond, and the shape of the contact surface 2 of the drive lap 1 does not change much. It also contributes to longer life and stability.

In addition, the guide ring 4 provided in the polishing device shown in FIG.
The inner wall surface of the guide ring is preferably lined with rubber or resin to suppress vibration of the guide ring.

Next, the float 5 immersed in the magnetic fluid of the polishing device is
Buoyancy is given by the action of an external magnetic field such as 6th stone 6,
The float 5 floats and strongly pushes the spherical object 3 to be polished against the contact surface 2 of the lower end of the drive lap 1. This float 5
are the contact surface 2 of the drive wrap 1 and the guide ring 4
Together with the inner wall surface of the rotating polishing target sphere 3, it is held constant during polishing to contribute to perfect spherical alignment. The shape of the float 5 in contact with the spherical object 3 to be polished may be a flat or tapered shape that makes contact at a negative point, or a V-shaped cross section or an R-shaped dish that 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 is determined by the strength of the external magnetic field acting from below, the size of the float, the distance to the float, etc., and by changing these factors, the required processing pressure can be arbitrarily controlled.

It is not an absolute requirement that the specific gravity of the float be lighter than the specific gravity of the magnetic fluid, but it is sufficient as long as it generates buoyancy by the action of an external magnetic field acting from below.

As the 611 fluid 7, one in which ferrite, magnetite, etc. is dispersed using water or oil as a medium is used.

The magnet 6 used as the external 6n field may be a single magnet, a group of magnets arranged with the same polarity, or a group of magnets combined so that adjacent magnets have different poles (indicated by arrows in the figure). . 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 St=N4 is used, and the polished sphere is used for ball bearings and the like.

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 based on Examples and Comparative Examples.

Example A predetermined amount of magnetic fluid (W-40; manufactured by Taiho Kogyo Co., Ltd.) and a thickness of 2 mm were added to a brass guide ring (inner diameter 37 mm) lined with urethane rubber of the device shown in Fig. 1.
An acrylic disk-shaped float of 1.0 mm in diameter was placed in a container, and 11 Si and N4 spheres (initial true spheres of 400 μm) with a diameter of 7.7 mm were placed in a container, and the surface in contact with the polished spheres was placed in a container. After polishing for 10 or 40 minutes using a driving lap to which diamond abrasive grains (#400; manufactured by GE) were fixed by electrodeposition at 9000 revolutions per minute, the sphere to be polished was rinsed with water to improve polishing efficiency and accuracy. The ball banquet was calculated and the results are shown in Table 1.

Comparative Example The procedure was the same as in Example 1, except that diamond abrasive grains (#400: manufactured by GE) were contained in the magnetic fluid and a driving lap was used in which the diamond abrasive grains were not fixed on the contact surface with the sphere to be polished. Polishing was performed, and the grinding efficiency and true sphere performance were calculated, and the results are shown in Table 1.

1. Determined after polishing for 10 minutes *2. Measured after polishing for 40 minutes As shown in Table 1, examples in which abrasive grains were fixed to the contact surface of the tip of the driving lap showed that the free Compared to the comparative example using abrasive grains, the polishing efficiency measured after polishing for 10 minutes is three times better, and the polishing efficiency measured after polishing for 40 minutes is nine times better. Also,
In terms of sphericity, the examples are also 40 times or more superior to the comparative examples.

[Effects of the Invention] As explained above, according to the polishing apparatus of the present invention, a sphere with high sphericity can be obtained, the polishing efficiency is high, and continuous polishing for a long time is possible.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing an example of a polishing apparatus according to the present invention, and FIG. 2 is a side sectional view showing an example of a driving lap used in the present invention. 1: Driving lap, 2: Contact surface, 3: Polished sphere, 4 Guide ring, 5: Float,
6: Magnet, 7: Magnetic fluid, 8: Fixed abrasive grain.

Claims (1)

[Claims] 1. A guide ring, a float immersed in a magnetic fluid, a rotatable driving wrap, and a magnetic field forming device that forms a magnetic field in the magnetic fluid to provide a levitation force to the float together with the magnetic fluid. In a polishing apparatus 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 device characterized in that abrasive grains are fixed to the lower end of the drive lap on the contact surface with the spherical object to be polished. 2. The polishing apparatus according to claim 1, wherein the fixed abrasive grains are made of one selected from diamond, silicon carbide, alumina, and boron nitride.