JP2003049186A - Grease containing polymer-modified fine bead and ball bearing using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a grease reducing friction torque even in high speed and highly loaded revolutions, provide a ball bearing having little aperiodic revolution noises during revolution even with low surfaced machining accuracy at a low cost by using the same. SOLUTION: This grease contains at least a base oil such as a mineral oil, a synthetic oil or the like and a thickener such as a metal soap, a polyurea or the like as main ingredients and is mixed with fine small spherical beads modified on their surfaces with an organic polymer coupling agent in 10<-8> -10<-6> mol/m<2> surface density and having 0.05-1 μm in 1,000-20,000/m<3> density. Surface roughnesses of the surface of balls of the ball bearings using the grease and sliding surfaces of inner rings and outer rings are made to be <=1 μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grease and a ball bearing used for rotating equipment such as a motor and rotating parts such as an axle, and particularly to a grease and a ball used for a high speed and high precision rotating device such as a hard disk. It provides bearings.

[0002]

2. Description of the Related Art Conventionally used ball bearings are made of chrome steel or stainless steel with a high precision spherical shape in order to rotate the rotary shaft of a motor at high speed smoothly and with high precision. It has a structure in which a plurality of balls having a spherical diameter are rotatably held by donut-shaped guides called an inner ring and an outer ring. These balls are generally evenly arranged along the inner ring and the outer ring, and are usually separated by a cage or a cage called a separator so as not to come into contact with each other and generate frictional resistance. Further, a shield structure is provided for preventing evaporation of base oil contained in grease and at the same time preventing foreign matter such as dust from entering.

Grease is applied to the surfaces of the balls and the sliding surfaces of the inner ring and the outer ring in order to prevent the balls and the sliding surfaces of the inner ring and the outer ring from being worn or seized by friction during rotation. ing. As the grease used, it is general to use a mineral oil or a synthetic oil mixed with a thickener such as metal soap or polyurea to form a gel. This grease enters the interface between the sliding surface of the inner ring or the outer ring and the ball to improve the lubricity of the sliding surface, so that the rotating body mounted on the ball bearing can be smoothly rotated.

In particular, in a ball bearing used for a hard disk motor mainly used in computers and the like, in order to reduce periodical rotation noise during rotation, not only the roundness of the sliding surface of the inner ring and the outer ring but also the ball are rounded. The sphericity and external dimensions of are processed with extremely high precision. Further, in order to reduce aperiodic rotation noise during rotation, the surface roughness of the ball is set to about 0.2 μm or less, and the surface roughness of the sliding surface of the inner ring or the outer ring is set to about 1 μm or less. Is common. The surface roughness referred to below means Ra.

As another means of reducing the aperiodic rotation noise during rotation, the number of balls which are usually used is about 5 to 9 for the purpose of averaging and reducing the aperiodic rotation noise. , Some have increased to 10 to 16.

[0006]

However, in the conventional ball bearing, when the bearing is rotated at a high speed or the load is increased, grease is not sufficiently spread on the interface between the sliding surface of the inner ring or the outer ring and the ball. Alternatively, there has been a problem that the sliding surface of the outer ring and the balls come into direct contact with each other and the frictional force rapidly increases or seizure occurs.

Further, if the processing accuracy is improved in order to reduce the aperiodic rotation noise during rotation, the number of processing steps of the ball bearing constituent elements increases, and at the same time, the criteria such as ball diameter selection of the ball become strict, so that the cost is low. However, there is a problem that it is difficult to manufacture various products.

Further, even if the number of balls is increased to 12 to 16, it is difficult to reduce the aperiodic rotation noise to 0.2 μm or less.

[0009]

Means for Solving the Problems The present invention contains, as a grease used for a ball bearing, at least a base oil such as mineral oil or synthetic oil and a thickener such as metal soap or polyurea as main components. 1000 to 2000
An organic polymer coupling agent was added to the surface of fine spherical beads having an average particle diameter of 0.05 to 1 μm at a concentration of 0 particles / mm ³ and 10
^By modifying with a surface density of ⁻⁸ to 10 ⁻⁶ mol / m ² and mixing, a grease capable of easily reducing friction torque and aperiodic rotation noise can be produced, and the grease is used. Surface roughness of the ball surface of the ball bearing and the sliding surface of the inner and outer rings is 1 μm
By setting the following, the aperiodic rotation noise can be 0.2 μm or less even with relatively low surface processing accuracy,
At the same time, it has become possible to provide a high-precision ball bearing that is easy to manufacture and inexpensive, and has solved the above problems.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a grease which is a lubricant formed by adding a thickener such as metal soap or polyurea to a base oil such as mineral oil or synthetic oil to form a gel has an average particle diameter of 0.05 to 1 μm.
The surface of the inorganic or inorganic-organic composite spherical beads of m is mixed with polymer-modified spherical beads, which are modified with an organic polymer coupling agent at a predetermined surface density, and mixed at a predetermined concentration. The present invention provides a ball bearing capable of reducing friction torque and aperiodic rotation noise even if a ball bearing component having a normal processing accuracy is used by injecting into the sliding surface.

First, the structure of the ball bearing according to the present invention will be described with reference to the drawings. FIG. 3 is a schematic perspective view showing the structure of the ball bearing of the present invention, and 11 is a first
Snap ring, 12 is the first shield, 13 is the first
Separator, 14 balls, 15 inner ring, 16 second
Separator, 17 is an outer ring, 18 is a second shield, 1
9 is a second snap ring. Ball 14 is inner ring 1
5 and the outer ring 17 are arranged in contact with a groove-shaped sliding surface circumscribing the balls 14, and the first separator 13 and the second separator 1 are arranged so that the balls 14 do not contact each other.
And 6 are spaced apart from each other.

Further, in order to prevent foreign matter such as dust from entering the sliding surfaces of the inner ring 15 and the outer ring 17 from the outside, and to prevent the volatile component of grease and abrasion powder due to abrasion from leaking to the outside. Both sides of the outer ring 17 are covered by the second shield 18 and the second shield 18. Then, these respective parts are integrally held by the first snap ring 11 and the second snap ring 19. The grease containing the polymer-modified microspherical beads of the present invention has an inner ring 15
And an appropriate amount is injected into the sliding surface of the outer ring 17. The grease of the present invention covers the surface of the ball 14 by this injection step.

In the ball bearing of the present invention having such a structure, the inner ring 15 and the outer ring 17 rotate relative to each other via the balls 14. Freely rotate an object by fixing the outer ring 17 of this ball bearing and mounting a rotating shaft inside the inner ring 15, or by mounting a fixed shaft inside the inner ring 15 and mounting a rotating body on the outer ring 17. You can

For the sake of simplicity, the grease of the present invention before the polymer-modified spherical beads are mixed will be referred to as a base grease hereinafter. That is, the grease of the present invention is produced by mixing the base grease with polymer-modified spherical beads having a predetermined particle size at a predetermined concentration.

Embodiments of the present invention will be described below with reference to the drawings. Generally, hard steel materials such as chrome steel and stainless steel are used as materials for balls, inner rings, and outer rings used for ball bearings.
Since the sliding surfaces of these parts are required to have a high processing accuracy, they are processed by precision cutting or grinding, and some are polished. In particular, for balls that are required to have a uniform sphere diameter, they are individually inspected after processing, and those having the same sphere diameter are selected and used.
Also, if the surface roughness of the balls or the sliding surface of the inner and outer rings is rough, or if there are processing flaws, the frictional force during rotation will increase, and non-periodic rotation noise will increase. In ball bearing parts used for motors for precision equipment such as, the surface roughness of the balls is suppressed to about 0.2 μm or less, and the surface roughness of the sliding surfaces of the inner ring and the outer ring is suppressed to about 1 μm or less.

However, it is difficult to completely smooth the surface of the ball and the sliding surface between the inner ring and the outer ring, and most of them have some irregularities on the surface. When processing flaws are present, these projections and depressions become deeper and larger.
Further, these convexes and concaves may be generated due to the inclusion of foreign matter from the outside. Hereinafter, how the grease of the present invention acts on such convex and concave portions will be described.

FIG. 1 is a conceptual diagram for explaining the action of spherical beads mixed with grease according to the present invention on the surface concave portion, 1 is organic polymer-modified spherical beads, 2 is base grease, 3 is balls, 4 is The sliding surface of the inner ring or the outer ring, 5 is a recess on the ball surface, and 6 is a recess on the sliding surface of the inner ring or the outer ring.

Since the grease of the present invention is mixed with minute spherical beads 1 modified with an organic polymer, the spherical beads 1 are embedded in these recesses 5 and 6 to form an apparently smooth surface. To do. Therefore, the aperiodic rotation noise caused by the recesses on the ball surface or the sliding surface between the inner ring and the outer ring is remarkably alleviated. Furthermore, since a plurality of organic polymer-modified spherical beads usually enter these recesses, the shear stress acting between the ball and the sliding surface is dispersed by the rotation and movement of these organic polymer-modified spherical beads. As a result, the friction torque is also reduced.

Furthermore, since the organic polymer-modified spherical beads 1 are modified with an organic polymer coupling agent having a long-chain polymer structure such as a silane-based organic polymer coupling agent on the surface, this organic polymer is used. The surface of the modified spherical beads 1 does not come into direct contact with the surfaces of the inner ring and the outer ring, but comes into contact with them through the organic polymer coupling agent that modifies the surface. As a result, the organic polymer-modified spherical beads 1
The frictional force acting on is reduced as compared with the case where the polymer is not modified on the surface.

FIG. 2 is a conceptual diagram for explaining the action of the spherical beads mixed with grease according to the present invention on the convex portion of the surface. 1 is organic polymer-modified spherical beads, 2 is base grease, and 3 is balls. 4 is a sliding surface of the inner ring or the outer ring, 7 is a convex portion on the ball surface, 8 is a convex portion on the sliding surface of the inner ring or the outer ring, and 9 is a rotation direction of the ball.

In this case, the method of accumulating the spherical beads is different from the case where the surface has a convex portion. Ball 3 rotates 9
When rotated in the direction indicated by, the relative flow direction of the organic polymer-modified spherical beads 1 contained in the base grease 2 is from right to left with respect to the balls and with respect to the sliding surface 4 of the inner ring or the outer ring. Goes from left to right. Therefore, the organic polymer-modified spherical beads 1 are accumulated on the right side surface on the convex portion 7 on the ball surface and on the left side surface on the convex portion 8 on the sliding surface of the inner ring or the outer ring. As a result, the convex portion formed on the surface of the ball becomes apparently smooth, and the aperiodic rotation noise is reduced.

Also in this case, since a plurality of spherical beads are usually accumulated on these convex portions, the shear stress acting between the ball and the sliding surface is dispersed by the rotation and movement of these spherical beads. As a result, the friction torque is reduced.

Also in this case, as in the case shown in FIG. 1, the organic polymer-modified spherical beads 1 have the surface modified with an organic polymer coupling agent composed of a long-chain polymer such as a silane polymer coupling agent. Therefore, the surface of the organic polymer-modified spherical beads 1 does not come into direct contact with the surfaces of the inner ring and the outer ring, but comes into contact through the organic polymer coupling agent that modifies the surface. As a result, the frictional force acting on the organic polymer-modified spherical beads 1 is reduced as compared with the case where the surface is not modified with the organic polymer coupling agent.

The optimum average particle size of the spherical beads that maximizes the effect of the spherical beads described above varies depending on the size of the irregularities present on the ball surface and on the sliding surfaces of the inner ring and the outer ring. The optimum average particle size of the spherical beads is slightly different depending on the material composition of the base grease used, the size of the ball bearing, the number of revolutions, etc., but it is greatly different depending on the concentration of beads and the surface roughness of the balls.

However, the concentration of the spherical beads must be increased as the average particle size of the spherical beads becomes smaller, but if the average particle size of the spherical beads is made too small, the grease characteristics such as viscosity and fluidity will be impaired. In addition, since it is difficult to produce spherical beads, the average particle diameter of the spherical beads is 0.05 to 1 μm, and the concentration of the spherical beads is 100.
It is desirable that the number is 0 to 20000 pieces / mm ³ .

As the base grease, it is possible to use a base oil composed of a commonly used mineral oil or synthetic oil, mixed with a thickener such as metal soap. Examples of such grease include a grease obtained by blending an aromatic ester, a mixed oil of an aromatic ester and a polyol ester with a lithium soap thickener, and a commercially available Niguace (trade name;
Nihon Grease Co., Ltd., ASONIC GHY72 (trade name; manufactured by KLUBER Co.) and the like can be used. As a thickening agent other than metal soap, a base oil to which an isocyanate compound and amines are added and reacted can be used.

Further, in the hard disk, the volatile component of the grease volatilizes and contaminates the hard disk device. Therefore, it is required to use a base grease having a small volatile component. As such a base grease having a small amount of volatile components, it is possible to use a grease which uses paraffin hydrocarbon as a base oil and polyurea as a thickener.
Moreover, since the spherical beads are made of a metal oxide, the above-mentioned contaminants do not evaporate. Furthermore, as a polymer that modifies the surface of the spherical beads, by using a silane-based organic polymer coupling agent that has a strong binding force with inorganic spherical beads or inorganic-organic composite spherical beads, the surface-modified polymer volatilizes and the hard disk Will no longer pollute.

Next, the organic polymer used in the grease of the present invention
The modified spherical beads will be described. For grease of the present invention
The main component of the inorganic or inorganic-organic composite spherical beads used is S
iO _Two, TiO_Two, Or ZrO_TwoIs. like this
Spherical beads can be easily prepared by the sol-gel method.
it can. Inorganic or inorganic that can be produced by sol-gel method
The average particle size of the organic composite spherical beads is about 0.01 to 10 μm.
The degree of sphericity is extremely high.

In particular, the above-mentioned material is stable in the production conditions in the sol-gel method and has a high hardness, so that good spherical beads can be obtained. In particular, since SiO ₂ can be manufactured with extremely high purity, it has a feature that even if it is used for a motor or pivot for a hard disk, the hard disk device is not contaminated by an impurity element. As the main component of the spherical beads, any material other than those mentioned above can be used as long as it is a metal oxide, and these spherical beads can also be produced by the sol-gel method.

As a method of modifying the surface of the inorganic or inorganic-organic composite spherical beads with a polymer, there is known a method of reacting a reactive monomer or a coupling agent with a functional group on the surface of the spherical beads. A typical example of the functional group is a hydrosil group. In particular,
The spherical beads are dispersed in an organic solvent and then a modifier is added to modify the surface of the spherical beads, or the water in an aqueous dispersion of spherical beads is replaced with an organic solvent, and then the modifier is added to the surface of the spherical beads. There is a method to modify.

As a method for modifying the silane-based organic polymer coupling agent as the surface-modified polymer, the silane-based organic polymer coupling agent is dissolved in a low-polarity organic solvent and then the spherical beads are added. There is a method of reacting by heating. In this case, a functional group such as an OH group has a surface density of 3.0 × 10 ^{−6 to} 1.5 × 1 on the surface of the spherical beads.
It is important that the 0 ^-5 mol / ^{m 2} exist.

The surface density of the silane-based organic polymer coupling agent modified on the surface of the spherical beads is measured by sufficiently drying the spherical beads at 100 ° C., measuring the weight of the spherical beads, and then increasing the temperature to 1000 ° C. It is possible to obtain the weight from the change in weight and the molecular weight of the silane-based organic polymer coupling agent by measuring the weight of the spherical beads again after the temperature is raised to.

The silane-based organic polymer coupling agent preferably has a chain structure having a hydrolyzable group at one end and has a low polarity. The molecular weight of the silane-based organic polymer coupling agent can be determined by molecular exclusion chromatography. The molecular weight of the silane-based organic polymer coupling agent in the case of producing the organic polymer-modified spherical beads is preferably in the range of 500 to 50,000, more preferably 10
The range is from 00 to 20000. If it is less than 500, the modifying effect is insufficient, and if it exceeds 20,000, the modifying effect does not increase. Further, at 1000 or more, the reduction of the friction torque becomes remarkably large.

In a hard disk motor using a ball bearing, the number of rotations is 4800 to 12000.
Rotate at high speed with rpm. Ball bearing balls used at speeds in the range of 4800-7200 rpm,
The inner ring and outer ring are made of chrome steel or stainless steel. However, in a ball bearing used at a rotation speed of 7200 rpm or more, seizure occurs due to heat generation due to high speed rotation. To prevent this, balls are made of ceramic balls. What you used has come to be used. Furthermore, for high-speed rotation, some inner and outer rings are made of ceramic.

However, in the ball bearing using the grease of the present invention, since the friction torque is small as described above, the heat generation is small even when rotated at a high speed.
It has been found that seizure is unlikely to occur even at high speed rotation of about 0 rpm.

Further, as a result of this small friction torque, the power consumption of the motor using the ball bearing using the grease of the present invention can be significantly reduced.

[0037]

Embodiments of the grease of the present invention and a ball bearing using the grease will be described below with reference to the drawings.

In the following examples, PAO401 (trade name; Nippon Steel Chemical Co., Ltd.), which is a paraffin hydrocarbon as a base oil, is used.
Then, 20% by weight of lithium soap (lithium stearate) was added as a thickener to prepare a grease, which was used as a base grease. Hereinafter, this grease will be referred to as a reference base grease for the sake of simplicity.

The ball bearing has an inner diameter of 6
mm, outer diameter 22 mm, width 7 mm, ball diameter 3.968 m
m and 6 balls were used. Hereinafter, this ball bearing will be referred to as a standard ball bearing for simplicity. In this standard ball bearing, the inner ring sliding surface has an outer diameter of 8.53 mm, and the outer ring sliding surface has an inner diameter of 16.47 mm. The inner and outer rings are free-cutting steel (JIS SUM24)
The surface roughness of these sliding surfaces is 0.6 to 9.8 μ.
It was m. The balls are commercially available carbon steel (JIS
The surface roughness was 0.14 ± 0.02 μm.

Next, a method for preparing the silane-based organic polymer coupling agent used in this example will be described. 602 g of maleic anhydride, 67 g of dry styrene and 140 ml of dry tetrahydrofuran were weighed in a container, and 40 ml of 3-mercaptopropyltrimethoxysilane and 2,2'- were added thereto.
0.8 g of azobisisobutyronitrile was added, and the mixture was refluxed at 70 ° C. for 3 hours under a nitrogen atmosphere. It was cooled to room temperature, dissolved in a sufficient amount of tetrahydrofuran, then precipitated in about 200 L of ether, separated by filtration, and dried under reduced pressure to obtain a silane-based organic polymer coupling agent.

A method of modifying the above-mentioned silane-based organic polymer coupling agent into spherical beads will be described. 500 g of the silane-based organic polymer coupling agent was placed in a container, 30 L of dimethoxyethane and 5 L of tetrahydrofuran were added thereto, and ultrasonic waves were applied to dissolve the silane-based organic polymer coupling agent. To this, 2.2 L of a sol in which spherical beads were dispersed in ethanol was added, 29 L of the solvent was extracted by heating at 90 ° C., 3 L of tetrahydrofuran was added, and the mixture was refluxed for 24 hours. Next, after performing centrifugal washing four times with acetone, centrifugal washing once with ether and drying under reduced pressure, spherical beads modified with a silane-based organic polymer coupling agent were prepared. The material of the spherical beads is SiO 2.
Inorganic spherical beads containing ₂ , ₂ , TiO ₂ , or ZrO ₂ materials as main components were used.

Example 1 As the spherical beads modified with the above silane-based organic polymer coupling agent composed of SiO ₂ , TiO ₂ and ZrO ₂ materials, the average particle diameter was 0.025 μm.
m, 0.05 μm, 0.1 μm, 0.2 μm, 0.5 μ
m, 1 μm, 2 μm, and 5 μm, respectively.

2000 g / mm of these spherical beads modified with a silane-based organic polymer coupling agent were added to a standard base grease.
^The mixture was stirred and mixed at a concentration of ³ and thoroughly defoamed to obtain a test grease. Inject 100 mg of this test grease into each standard ball bearing to make a ball bearing for evaluation.
The friction torque and rotation noise were measured.

The friction torque was measured by rotating the outer ring with a rubber roll pressed at a pressure of about 45 N and rotating at 2 r.
It was rotated at a speed of pm, the load applied to the fixed point of the cantilevered shaft mounted on the inner side of the inner ring was measured with a load cell, and then converted into a friction torque in a diameter from the shaft center to the ball center.

FIG. 4 is a graph showing the relationship between the average bead diameter and the friction torque obtained as a result of this embodiment. As the numerical value of the friction torque, the result when the value of the friction torque obtained by injecting only the reference base grease into the standard ball bearing is set to 1 is standardized and shown. Further, the horizontal axis of FIG. 4 is shown on an exponential scale.

As is apparent from FIG. 4, the relationship between the average bead diameter and the friction torque is expressed as a curve having the same tendency regardless of the material of the spherical beads, and the average bead diameter is 0.05 to 1 μm. In the range, it has been found that the grease containing the polymer-modified microspherical beads of the present invention exhibits a lower friction torque than when using the reference-base grease without beads.

As the material of the spherical beads, ZrO _{2 is used.}
Has the largest effect of reducing the friction torque, but it was found that ZrO ₂ maximizes the friction torque when the average bead diameter becomes 1 μm or more.

Next, FIG. 10 shows the structure of the in-hub type DC motor for hard disk used for measuring the rotation noise.
FIG. 10 is a schematic sectional view showing the structure of an in-hub type DC motor for a hard disk, 20 is a ball bearing,
21 is a shaft, 22 is a hub, 23 is a base plate,
24 is a coil, 25 is a yoke, 26 is a yoke support, 2
7 is a permanent magnet. The shaft 21 is fixed to the inner ring of the ball bearing 20, and the base plate 23 supports the shaft 21 and the yoke support 26. Further, the yoke support 26 is the yoke 2 around which the coil 24 is wound.
Holds 5. On the other hand, the hub 23 fixed to the outer ring holds a permanent magnet 27 that is divided and magnetized into a plurality of poles.

A rotating magnetic field is generated around the yoke due to the excitation current applied to the coil 24 from a motor driving circuit (not shown), and this rotating magnetic field interacts with the magnetic field of the permanent magnet 27 to cause the hub 22 to move. Rotational force is generated. Since the ball bearing 20 allows the hub 22 to move freely around the shaft 21, the DC motor is rotated by the rotational force.

As the ball bearing 20 in the hard disk DC motor shown in FIG. 10, the evaluation ball bearing manufactured in this example was used, and the ball bearing was 4800 rp.
With the DC motor for the hard disk rotated at m, the aperiodic rotation noise was measured from the top surface and the side surface of the hub 22 using a capacitance type displacement sensor. The average value of 100 rotations was used as the measurement value of the aperiodic rotation noise, and like the friction torque, the aperiodic rotation obtained by using the ball bearing in which only the reference base grease was injected into the standard ball bearing was used. The normalized value was compared when the noise measurement result was set to 1, and the results were compared. The aperiodic rotational noise in the axial direction was 0.2 μm when the standard base grease injected into the standard bearing was used.

FIG. 6 is a graph showing the relationship between the average bead diameter obtained as a result of this example and the aperiodic rotational noise in the axial direction. The vertical axis and the horizontal axis of FIG. 6 are shown on an exponential scale. As is apparent from FIG. 6, the relationship between the average bead diameter and the aperiodic rotation noise is represented by a curve having the same tendency regardless of the material of the spherical beads, and the average bead diameter is 0.0
It has been found that in the range of 5 to 1 μm, the grease containing the polymer-modified microspherical beads of the present invention exhibits less aperiodic rolling noise than when using the base grease without beads.

The material of the spherical beads is ZrO ₂
Has the largest aperiodic rotation noise reducing effect, but it was found that ZrO ₂ maximizes the rotation noise when the average bead diameter is 1 μm or more.

It was also found that the use of the ball bearing of this embodiment also reduces aperiodic rotational noise in the radial direction.

Example 2 Silane-based organic polymer coupling agent-modified spherical beads made of SiO ₂ , TiO ₂ , and ZrO ₂ materials having an average particle size of 0.2 μm were prepared.

These silane-based organic polymer-modified spherical beads were used as a reference base grease in 250 / mm ³ , 500 / m.
m ³ , 1000 pieces / mm ³ , 2000 pieces / mm ³ , 50
Each of them was stirred and mixed at a concentration of 00 pieces / mm ³ , 10,000 pieces / mm ³ , 20,000 pieces / mm ³ , and 50,000 pieces / mm ³ to sufficiently remove bubbles, and then used as a test grease. 100 mg of this test grease was injected into each standard ball bearing to obtain a ball bearing for evaluation, and the friction torque was measured. The method of measuring the friction torque was the same as in Example 1.

FIG. 5 is a graph showing the relationship between bead concentration and friction torque obtained as a result of this embodiment. As the numerical value of the friction torque, the standard value is used as in the first embodiment. Further, the horizontal axis of FIG. 5 is shown on an exponential scale.

As is clear from FIG. 5, the relationship between the bead concentration and the friction torque is represented by a curve having a similar tendency regardless of the material of the spherical beads, and the bead concentration is 1000-
It has been found that in the range of 20000 particles / mm ³ , the grease containing the microbeads of the present invention exhibits a smaller friction torque than the case where the reference base grease containing no beads is used.

The spherical beads are made of ZrO ₂
Has the largest friction torque reducing effect.

Next, the result of evaluating the aperiodic rotation noise when the grease of this embodiment is used will be described. The evaluation method of the aperiodic rotation noise is the same as that shown in the first embodiment. The numerical value of the aperiodic rotation noise is shown using the standard value as in the first embodiment.

FIG. 7 is a graph showing the relationship between bead concentration and axial non-periodic rotation noise obtained as a result of this example. The vertical axis and the horizontal axis of FIG. 7 are shown on an exponential scale. As is apparent from FIG. 7, the relationship between the average bead diameter and the aperiodic rotation noise is represented by a curve having the same tendency regardless of the material of the spherical beads, and the average bead diameter is 0.05 to
It has been found that in the range of 1 μm, the grease containing the microbeads of the present invention exhibits less aperiodic rolling noise than when using the reference base grease without beads.

The spherical beads are made of ZrO ₂
Has the greatest aperiodic rotation noise reduction effect.

Further, it was found that, in the case of the present embodiment as in the case of the first embodiment, radial aperiodic rotation noise is reduced as well as axial aperiodic rotation noise.

(Embodiment 3) In the hard disk DC motor shown in FIG. 10, balls having various surface roughnesses were used as the balls of the ball bearing 20, and the relationship between the average bead diameter and the friction torque was investigated. . As the numerical value of the friction torque, the standard value is used as in the first embodiment. The surface roughness of the balls used was 0.012 μm, 0.
017μm, 0.11μm, 0.19μm, 1.23μ
m, 2.01 μm, and 9.81 μm. Further, the average particle diameter of SiO _{2 is} 0.025 μm, 0.0
5μm, 0.1μm, 0.2μm, 0.5μm, 1μ
m, 2 μm, and 5 μm silane-based organic polymer coupling agent-modified spherical beads were prepared.

These spherical beads were used as a base grease.
After thoroughly stirring and mixing at a concentration of 000 pieces / mm ³ to sufficiently remove bubbles, the obtained grease was injected into a ball bearing provided with balls processed to have the above-mentioned surface roughness, and the friction torque was measured. The method of measuring the friction torque is the same as the method shown in the first embodiment.

FIG. 11 is a diagram showing the influence of the surface roughness of the balls and the average particle diameter of the beads on the friction torque. In the figure, ○ indicates that the friction torque is smaller than that when the conventional ball bearing is used. Is the case where the friction torque does not change compared to the case where the conventional ball bearing is used,
× indicates that the friction torque increased as compared with the case of using the conventional ball bearing. As can be seen from FIG. 11, only when the surface roughness of the ball is 1 μm or less and the average bead diameter is 0.05 to 1 μm, the friction torque is improved as compared with the case of using the conventional ball bearing. I understood it.

(Example 4) Silane-based organic polymer coupling agent-modified spherical beads made of SiO ₂ having an average particle size of 0.2 μm were prepared.

On the surface of the spherical beads, high content of silane-based organic compound
Used when modifying the secondary silane coupling agent
The amount of orchid-based organic polymer silane coupling agent changed
Of these silane-based organic polymer-modified spherical beads
Coupling of silane-based organic polymer with modified surface
The surface density of the agent was measured to be 2.1 x 10^-9mo
l / m^Two, 8.0 × 10^-9mol / m^Two, 1.6 x 1
0^-8mol / m^Two, 7.2 × 10^-8mol / m^Two,
1.1 x 10^-7mol / m^Two, 6.2 × 10 ^-7mo
l / m^Two2.6 x 10^-6mol / m^Two, 9.5 × 1
0^-6mol / m^TwoThe surface density of was obtained.

2000 spheres / mm of spherical beads modified with a silane-based organic polymer coupling agent having these surface densities
^The mixture was stirred and mixed at a concentration of ³ and thoroughly defoamed to obtain a test grease. 100 mg of this test grease was injected into each standard ball bearing to obtain a ball bearing for evaluation, and the friction torque was measured. The method of measuring the friction torque was the same as in Example 1.

FIG. 8 is a graph showing the relationship between the surface density of the silane polymer coupling agent and the friction torque obtained as a result of this example. The numerical value of the friction torque is shown by using the standard value as in Example 1, but in this case, 2000 SiO ₂ spherical beads having an average particle diameter of 0.2 μm which are not modified with the silane-based organic polymer coupling agent are used. Pieces / mm ³
The value obtained by measuring the friction torque by mixing with the reference base grease at the concentration of is used as the reference. Further, the horizontal axis of FIG. 8 is shown on an exponential scale.

As is clear from FIG. 8, the relationship between the surface density of the silane-based organic polymer coupling agent and the friction torque is represented by a curve having a clear correlation. 10 ⁻⁸ to 10 ⁻⁶ mol /
It shows that the friction torque decreases in the range of m ² .

From this fact, there is an appropriate value for the surface density of the silane-based organic polymer coupling agent, and it is better to modify the silane-based organic polymer coupling agent than to mix the spherical beads directly into the reference base grease. It was found that mixing the spherical beads with the reference base grease has a great effect on reducing the friction torque.

Next, the result of evaluating the aperiodic rotation noise when the grease of this embodiment is used will be described. The evaluation method of the aperiodic rotation noise is the same as that shown in the first embodiment. The numerical value of the aperiodic rotation noise is shown by using the standard value as in Example 1, but in this Example, SiO _{2 having an} average particle size of 0.2 μm and not modified with a silane organic polymer coupling agent is used. 2000 beads / mm
^The value obtained by measuring the aperiodic rotational noise by mixing with the base grease at the concentration of ³ was used as the reference value.

FIG. 9 is a graph showing the relationship between the surface density of the silane-based organic polymer coupling agent obtained as a result of this example and the aperiodic rotational noise in the axial direction. The vertical axis and the horizontal axis of FIG. 9 are shown on an exponential scale. As is clear from FIG. 9, the relationship between the surface density of the silane-based organic polymer coupling agent and the aperiodic rotation noise is represented by a curve having a clear correlation, and the surface density of the silane-based organic polymer coupling agent is It shows that the aperiodic rotation noise is slightly reduced in the range of 10 ⁻⁸ to 10 ⁻⁶ mol / m ² .

From this fact, there is an appropriate value for the surface density of the silane-based organic polymer coupling agent, and it is preferable to modify the silane-based organic polymer coupling agent rather than mixing the spherical beads directly into the reference base grease. It was found that mixing the spherical beads with the reference base grease had the effect of slightly reducing the aperiodic rotational noise.

Further, it was found that in the case of the present embodiment as in the case of the first embodiment, the radial non-periodic rotation noise is slightly reduced as well as the axial non-periodic rotation noise.

Example 5 The same evaluation as in Examples 1 and 2 was performed by using the following base grease instead of the above-mentioned reference base grease.

(Reference Base Grease 1) Alkyl-substituted diphenyl ether (trade name; Mores High Loop LS150) as a base oil, toluene diisocyanate and n-
Butylamine was added to produce diurea to obtain a base grease (diurea content 20% by weight).

(Reference Base Grease 2) To a medium fatty acid ester as a base oil, 20% by weight of lithium soap (lithium stearate) as a thickener was added to obtain a base grease.

(Reference Base Grease 3) Commercially available Niguace (trade name; manufactured by Nippon Grease Co., Ltd.) was used as the base grease.

(Reference base grease 4) Commercially available ASONIC
GHY72 (trade name; manufactured by KLUBER) was used as a base grease.

(Reference Base Grease 5) PAO401 (trade name; manufactured by Nippon Steel Chemical Co., Ltd.), which is a paraffin hydrocarbon as a base oil, and LIR-2, which is a liquid polyisoprene rubber, are used.
90 (trade name; manufactured by Kuraray Co., Ltd.) and isophorone diisocyanate were added to form polyurea to obtain a base grease (polyurea content 10% by weight).

(Reference Base Grease 6) PAO401 (trade name; manufactured by Nippon Steel Chemical Co., Ltd.), which is a paraffinic hydrocarbon as a base oil, and CANELOVE-8 which is a methacrylic polymer are used.
15 (trade name; manufactured by Kanebo NSC Co., Ltd.) and 1,6 hexane diisocyanate were added and stirred, and then n-dioctylamine was added dropwise to react to form polyurea to obtain a base grease (polyurea content 20% by weight).

With respect to the base greases 1 to 6 shown above, the relationship between the average bead diameter, the friction torque, and the aperiodic rotation noise described in Examples 1 and 2, the bead concentration, the friction torque, and the aperiodic rotation. 4 to 9 when the relationship with the noise and the relationship between the surface density of the silane-based organic polymer coupling agent and the friction torque and the aperiodic rotation noise were investigated.
Results similar to those shown in were obtained.

From the above, the characteristics of the grease containing the polymer-modified microbeads of the present invention and the ball bearing using the same depend on the type of the base grease of the grease characteristics containing the polymer-modified microbeads. Is small,
It was found that the average particle size of beads contained in the base grease, the bead concentration, and the surface density of the modified polymer were highly dependent.

That is, the base grease of the grease containing the polymer-modified spherical beads of the present invention may be a grease prepared by mixing a mineral oil or a synthetic oil with a thickener such as metal soap or polyurea. Anything can be used.

[0086]

As described above, according to the present invention, the grease used for the ball bearing contains at least a base oil such as mineral oil or synthetic oil and a thickener such as metal soap or polyurea as main components. 1000 in
Average particle size of 0.05 to 1 at a concentration of up to 20,000 particles / mm ^3.
Friction torque and aperiodic rotation noise can be easily reduced by modifying the surface of micro-sphere beads with a surface density of 10 ⁻⁸ to 10 ⁻⁶ mol / m ² and mixing them. It is possible to produce a grease that can be manufactured, and by setting the surface roughness of the ball surface of the ball bearing, the sliding surface of the inner ring and the outer ring using the grease to 1 μm or less, with relatively low processing accuracy. It has an effect that the aperiodic rotation noise can be set to 0.2 μm or less, and at the same time, a highly accurate ball bearing that is easy to manufacture and inexpensive can be provided.

Further, since the friction torque is reduced and the heat generation due to the rotation is suppressed by using the grease or the ball bearing of the present invention, by using this, the motor can be rotated at a higher speed without causing seizure. In addition to the above, there is an effect that the power consumption of the motor is reduced because the friction loss is eliminated. This is
It also leads to the result of suppressing the power consumption of the device itself, which is important to suppress the power consumption of portable information devices.

Furthermore, since the non-periodic rotational noise in the axial direction and the radial direction is reduced by using the grease or the ball bearing of the present invention, it is difficult and expensive to make a fluid for a motor of a precision rotating device such as a hard disk. It is possible to use an inexpensive ball bearing without using a dynamic pressure bearing, and it is possible to achieve high-density recording at a lower cost than ever before.

[Brief description of drawings]

FIG. 1 is a conceptual diagram illustrating the action of an organic polymer-modified spherical bead mixed with grease according to the present invention on a surface recess.

FIG. 2 is a conceptual diagram for explaining the action of the organic polymer-modified spherical beads mixed with the grease according to the present invention on the convex surface portion.

FIG. 3 is a schematic perspective view showing the structure of the ball bearing of the present invention.

FIG. 4 is a graph showing the relationship between the average bead diameter and the friction torque obtained as a result of Example 1.

5 is a graph showing the relationship between bead concentration and friction torque obtained as a result of Example 2. FIG.

FIG. 6 is a graph showing the relationship between the average bead size obtained as a result of Example 1 and the aperiodic rotational noise in the axial direction.

FIG. 7 is a graph showing the relationship between bead concentration and axial aperiodic rotation noise obtained as a result of Example 2.

FIG. 8 is a graph showing the relationship between the surface density of the silane-based organic polymer coupling agent obtained as a result of Example 4 and the friction torque.

FIG. 9 is a graph showing the relationship between the surface density of the silane-based organic polymer coupling agent obtained as a result of Example 4 and the aperiodic rotational noise in the axial direction.

FIG. 10 is a schematic cross-sectional view showing the structure of an in-hub type DC motor for hard disk.

FIG. 11 is a diagram showing the influence of the surface roughness of the ball and the average bead size on the friction torque. ○ indicates that the friction torque was reduced as compared with the case of using the conventional ball bearing. Δ indicates that the friction torque does not change as compared with the case of using the conventional ball bearing. × is a case where the friction torque is increased as compared with the case where the conventional ball bearing is used.

[Explanation of symbols]

1. Organic polymer-modified spherical beads 2 ... Base grease 3 ... ball 4 ... Sliding surface of inner ring or outer ring 5 ... Recess on ball surface 6 ... Recess on inner or outer ring sliding surface 7 ... Projections on the ball surface 8 ... Convex portion on sliding surface of inner ring or outer ring 9 ... Ball rotation direction 11 ... First snap ring 12 ... the first shield 13 ... First separator 14 ... Ball 15 ... Inner ring 16 ... Second separator 17 ... Outer ring 18 ... Second shield 19 ... Second snap ring 20 ... Ball bearing 21 ... Shaft 22 ... Hub 23 ... Base plate 24 ... Coil 25 ... York 26 ... Yoke support 27 ... Permanent magnet

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) C10M 155/02 C10M 155/02 F16C 33/32 F16C 33/32 33/58 33/58 33/66 33 / 66 A // C10N 10:08 C10N 10:08 20:06 20:06 AZ 30:06 30:06 40:02 40:02 50:10 50:10 F term (reference) 3J101 AA02 AA32 AA42 AA52 AA62 BA01 BA25 BA45 BA53 BA54 BA55 EA31 EA64 EA78 FA01 FA32 FA41 FA44 GA02 GA24 GA53 4H104 AA13C AA22C AA28C BB17B CE14B CJ01C DA02A EA08C EA09C EB02 FA04 LA03 PA01

Claims (7)

[Claims] 1. A grease containing at least a base oil such as a mineral oil or a synthetic oil and a thickener such as a metal soap or polyurea as main components, wherein the grease is inorganic microsphere beads or organic-inorganic composite microsphere beads. A grease containing polymer-modified micro-beads, characterized in that polymer-modified micro-sphere beads obtained by modifying an organic polymer coupling agent on the surface of are mixed at a predetermined concentration. 2. The spherical beads have an average particle size of 0.0.
The grease containing the polymer-modified microbeads according to claim 1, wherein the grease has a thickness of 5-1 μm. 3. The concentration of the spherical beads is 1000-200.
The grease containing the polymer-modified microbeads according to claim 1 or 2, wherein the number is 00 / mm ³ . 4. The inorganic microsphere beads or inorganic-organic composite microsphere beads are made of SiO 2, TiO 2, or Zr.
A grease containing polymer-modified beads according to claim 1, which is made of a material containing O2 as a main component. 5. The organic polymer coupling agent is a silane organic polymer coupling agent, and the surface density of the silane organic coupling agent on the surface of the spherical beads is 10 ⁻⁸ to 10 ⁻⁶ mol /. The grease containing the polymer-modified beads according to claim 1, which is m ² . 6. A ball bearing having at least a plurality of balls formed of a hard material such as stainless steel or ceramics, and an inner ring and an outer ring for rotatably sandwiching the balls, as sliding elements. A ball bearing obtained by injecting grease containing the organic polymer-modified microbeads according to claim 1 into the moving part. 7. The ball bearing according to claim 6, wherein the surface roughness of the surfaces of the plurality of balls and the sliding surfaces of the inner ring and the outer ring is 1 μm or less.