JP2003254334A - Rolling bearing and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling bearing provided with a rolling body made of ceramic material, sufficiently restricted in charge of the bearing, improved in service life of the bearing, and having excellent conductivity and abrasion resistance. <P>SOLUTION: An inner ring 2, an outer ring 3 and a ball (a rolling body) 4 are formed from conductive material. At least the ball 4 among the inner ring 2, the outer ring 3 and the ball 4 is made of ceramic material mainly composed of silicon nitride and containing silicon carbide, titanium nitride, and molybdenum silicon. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling bearing used for information equipment such as a hard disk drive (HDD) device and supporting a rotating body such as a disk medium.

[0002]

2. Description of the Related Art Rolling bearings using rolling elements made of a silicon nitride ceramics material are used for various purposes by effectively utilizing the excellent wear resistance of the ceramics material. ing. However,
This ceramic material is an insulating material, and therefore the inner and outer races of this conventional rolling bearing are electrically insulated.
Therefore, when this conventional rolling bearing is used in, for example, a spindle of an HDD device, the electric charge on the magnetic disk rotating with the outer ring (rotating ring) has no escape and is accumulated.
As a result, there is a possibility that a problem such as a head crash in which the head is electrically attracted and brought into contact with the charged magnetic disk may occur. Further, in order to prevent the above-mentioned head crash and the like, it has been proposed to add conductivity to silicon nitride by adding a conductivity-imparting substance such as silicon carbide to the silicon nitride. When such a conductivity-imparting substance is added, the original wear resistance of the silicon nitride ceramic material may be deteriorated, so that the extremely high rotation accuracy and durability are both required.
It was difficult to use as a bearing for a DD device or the like.

In view of the above conventional problems, the present invention is a rolling bearing provided with a rolling element made of a ceramic material, which can sufficiently suppress the charging of the bearing and prolong the life of the bearing. It is an object of the present invention to provide a rolling bearing excellent in conductivity and wear resistance capable of achieving the above, and a manufacturing method thereof.

[0004]

The rolling bearing of the present invention comprises:
A rolling bearing comprising an inner ring and an outer ring, and a plurality of rolling elements rotatably provided between the inner ring and the outer ring,
The inner and outer races and the rolling elements are made of a conductive material, and at least the rolling elements among the inner and outer races and the rolling elements are ceramic materials containing silicon nitride as a main component and containing silicon carbide, titanium nitride and molybdenum silicide. It is characterized by being constituted by (Claim 1).

In the rolling bearing constructed as described above,
By including silicon carbide, titanium nitride, and molybdenum silicide in the above silicon nitride as a ceramic material forming at least the rolling element, the inventors of the present invention can sufficiently suppress the charging of the bearing. Have found that it is possible to construct a bearing having excellent conductivity and wear resistance that can prolong the life of the bearing.

Further, in the rolling bearing (claim 1), it is preferable that the ceramic material contains 0.5 to 10% by weight of the molybdenum silicide. In this case, by setting the content ratio of molybdenum silicide to a value within the above range, conductivity can be effectively imparted, and abrasion resistance can be improved as compared with the above conventional example made of silicon nitride. it can.

In the above rolling bearing (claim 2), the ceramic material contains 10 to 2 of the silicon carbide.
It is preferable that the content of the titanium nitride is 0% by weight and the content of the titanium nitride is 1 to 10% by weight. In this case, 10-2
By containing 0% by weight of silicon carbide and further containing 1 to 10% by weight of titanium nitride, it is possible to more effectively impart conductivity without lowering wear resistance.

The method of manufacturing the rolling bearing of the present invention is
The method according to claim 1, wherein silicon carbide, titanium oxide, molybdenum silicide, and a sintering aid are added to silicon nitride and sintered.
To 3 are obtained (claim 4). In this case, the above-mentioned ceramic material containing silicon nitride, silicon carbide, titanium nitride, and molybdenum silicide can be obtained by chemically converting titanium oxide into titanium nitride.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments showing a rolling bearing and a manufacturing method thereof according to the present invention will be described below with reference to the drawings. In the following description, the rolling bearing of the present invention is applied to an HDD device as an example. FIG. 1 is a sectional view showing a ball bearing according to an embodiment of the present invention. In the figure, in the ball bearing 1 of the present embodiment,
An inner ring 2 as a fixed ring and an outer ring 3 as a rotating ring, a plurality of balls 4 as rolling elements arranged in a rollable manner between these inner and outer rings, and a cage 5 for holding each ball 4.
A sealing plate 6 made of synthetic resin for sealing the annular opening between the inner and outer rings is provided. The inner ring 2 and the outer ring 3 are attached to, for example, a spindle shaft of a spindle motor and a motor hub on which a magnetic disk is integrally rotatably mounted, and smoothly support disk rotation by the motor. The spindle shaft and the motor hub are made of a conductive material such as metal, and the spindle shaft is rotatably supported by a metal motor base and grounded via the base.

The inner ring 2 and the outer ring 3 are made of a conductive material made of steel such as bearing steel (for example, SUJ2). The ball 4 is made of a silicon nitride ceramic material having conductivity, and rolls on raceway grooves formed in the inner and outer races 2 and 3, respectively. The above silicon nitride ceramic material contains silicon nitride (Si ₃ N ₄ ) as a main component, and silicon carbide (SiC) and titanium nitride (Ti
N) and molybdenum silicide (MoSi ₂ ), which is a ceramic material, and is electrically conductive without impairing the wear resistance inherent to the silicon nitride ceramic material. Therefore, the balls 4 roll on the raceway grooves to support the outer ring 3 and a rotating body such as a motor hub attached thereto, and electrically connect the inner and outer rings 2 and 3 via the balls 4. .

The above ceramic material contains 10 to 20% by weight of silicon carbide, 1 to 10% by weight of titanium oxide (titania; TiO ₂ ) and 0.5 to 20% by weight of molybdenum silicide as a sintering aid. Yttrium oxide (Y ₂ O ₃ )
And aluminum oxide (Al ₂ O ₃ ) are slightly added to silicon nitride, and the mixture is sintered at a predetermined temperature (for example, 1700 ° C.). The titania chemically changes to the titanium nitride during the sintering process.

The above-mentioned silicon carbide and titanium nitride are compounds capable of imparting conductivity to the silicon nitride ceramic material by individually adding a predetermined amount (for example, 20% by weight) to silicon nitride. Wear resistance inherent to the silicon nitride ceramic material,
The mechanical properties such as strength and rigidity are deteriorated. Therefore, by including molybdenum silicide in a content ratio within the above range, it is possible to sufficiently impart the conductivity and sufficiently suppress the deterioration of the mechanical properties. In addition, mechanical properties, particularly wear resistance, can be significantly improved as compared with a material in which silicon carbide or titanium nitride is added alone to impart conductivity to silicon nitride. Further, the more preferable content ratio of molybdenum silicide is 1 to 5
It is the weight%, and the above effect contributed by the molybdenum silicide can be more surely obtained by including it in such a ratio. Furthermore, by including silicon carbide and titanium nitride in the content ratios within the above ranges, conductivity can be more effectively imparted without causing a decrease in wear resistance. If the content ratio of molybdenum silicide is increased or decreased to a value outside the above range, the wear resistance of the ceramic material becomes inferior to that of the conventional example. Further, when the content ratio of each of silicon carbide and titanium nitride is out of the corresponding range, particularly when the content of at least one of them is increased, the wear resistance and strength of the ceramic material decrease. Also,
If the content ratio of any one of molybdenum silicide, silicon carbide, and titanium nitride is set to a value smaller than the corresponding range, the volume resistivity of the ceramic material increases and the conductivity decreases.

In addition to the above description, yttrium (Y), aluminum (Al), magnesium (M
g), cerium (Ce), hafnium (Hf), ytterbium (Yb), calcium (Ca), zirconium (Zr) and other complex oxides such as spinel (MgAl ₂ O ₄ ). A structure in which a compound is added as a sintering aid may be used. Furthermore, by adding an appropriate amount of an oxide of tungsten (W) or titanium (Ti), the sintering temperature can be lowered to facilitate the process of forming the ceramic material, or to obtain a predetermined color (for example, black). ) May be colored.

The cage 5 is a crown-shaped annular body in which pockets for retaining the balls 4 are arranged at a plurality of circumferential positions, and the cage 5 is entirely made of synthetic resin. Further, in this cage 5, the gap between the ball 4 and the pocket is set to an appropriate value to prevent the ball from clogging in the pocket and prevent the rotation failure of the bearing from occurring. The movement amount of the ball 4 is regulated to prevent the uneven distribution of the ball 4 in the circumferential direction from increasing,
It prevents the generation of non-synchronous runout and the increase of cage noise and vibration. The gap also functions as a reservoir for a lubricant such as grease supplied to the ball rolling surface, so that the occurrence of poor lubrication is suppressed.

Here, the durability test conducted by the inventors will be specifically described with reference to FIGS. 2 and 3. In this durability test, the test apparatus 10 shown in FIG. 2 was used to verify the wear resistance of the ceramic material of the present invention. This test apparatus 10 is equipped with a thrust type rolling life tester, for example, a spindle shaft 11 rotating in the R direction in FIG. 2 and a tip end portion of this spindle shaft 11 which are integrally rotatably mounted and are arranged in the circumferential direction. For example, 3 equally distributed along
An annular holding member 12 for holding two test balls 16
And have. Further, an annular sample flat plate 15 is arranged in the container 13 so that the contact portion with the test sphere 16 is immersed in the spindle oil 14 in the container 13, and the spindle shaft 11 is rotated to rotate the sample. Flat plate 15 and test ball 1
6 was brought into rolling contact.

As the sample flat plate 15, sample No. 1 shown in Table 1 below. 1-3 were prepared, and as the test ball 16, a ball made of SUJ2 having a diameter of 3/8 inch was prepared. This sample No. 1 contains 78% by weight of silicon nitride (including yttrium oxide and aluminum oxide as a sintering aid), 15% by weight of silicon carbide, 5% by weight of titanium oxide, and 2% by weight of molybdenum silicide. It is the product of the present invention added and sintered. In addition, the sample No. 2 is 78 to 79
Conductivity obtained by adding 1 to 2% by weight of titanium oxide and about 20% by weight of silicon carbide to silicon nitride (including yttrium oxide and aluminum oxide as a sintering aid) of weight% and sintering. Conventional equivalent product (hereinafter referred to as conventional product 1
It is also referred to as a sample No. 3 is 98 to 99% by weight
Silicon nitride (containing yttrium oxide and aluminum oxide as a sintering aid) to which 1 to 2% by weight of titanium oxide is added and sintered, which is a conventional equivalent product having no conductivity (hereinafter, conventional) (Also referred to as item 2). Then, the wear amount in the ball rolling portion of the sample flat plate 15 when the spindle shaft 11 was continuously rotated at 1200 r / min for 100 hours and 400 hours under a load of 2450 N in the direction of the arrow P in the figure was measured. It was measured. The amount of wear was evaluated by measuring the shape of the ball rolling portion with a surface profiler and measuring the depth of wear from the non-rolling portion. Fig.3 (a)-
(C) is an example of surface shape measurement after 400 hours respectively, and 1 cm in the vertical direction of the figure corresponding to the wear direction (depth direction) is 0.05 μm. Further, 1 cm in the left-right direction in the figure is 0.2 mm.

[0017]

[Table 1]

As shown in the results of Table 1, the wear amount of the product of the present invention after the elapse of 400 hours is about 50% of that of the conventional product 1, which is equal to or more than that of the conventional product 2. Further, when the electric resistances of the product of the present invention and the conventional products 1 and 2 were measured, the volume resistivity of the product of the present invention and the conventional product 1 was 10
^{It was 5} to 10 ⁷ Ω · cm, and was sufficiently conductive for antistatic. On the other hand, the volume resistivity of the conventional product 2 is 10 ¹⁰ Ω · c
It was confirmed that it was m or more and that it had substantially no conductivity.

As described above, in the ball bearing 1 and the method of manufacturing the same of the present embodiment, silicon nitride is the main component and silicon carbide,
Since the balls 4 are made of a ceramic material containing titanium nitride and molybdenum silicide, the balls 4 having excellent conductivity and wear resistance can be formed. Further, in combination with the fact that the inner and outer races 2 and 3 are made of bearing steel (conductive material), almost the same antistatic effect as that when the balls 4 are made of steel can be obtained, and the ball bearing 1 is charged. (Static electricity) can be sufficiently suppressed. Further, since the above ceramic material has excellent wear resistance, it is possible to prolong the life of the ball 4, and hence the ball bearing 1. In addition, since the static electricity can be sufficiently suppressed, it is possible to suppress the adsorption of foreign matter such as dust from the atmosphere, and it is also possible to prevent the generation of abnormal noise or vibration due to the adsorbed foreign matter.

Further, H using the ball bearing 1 of this embodiment
In the DD device, the electric charge of the magnetic disk rotating with the outer ring 3 can be released through the bearing,
Unlike the above-mentioned conventional example, it is possible to prevent charges from being accumulated on the magnetic disk. As a result, it is possible to prevent a problem such as a head crash where the charged magnetic disk collides with the head due to the accumulated charges. Moreover, it is not necessary to separately provide a grounding means such as a magnetic fluid seal on the bearing or the HDD device, and the configurations of the bearing and the HDD device can be simplified. Further, compared with the case where a contact-type conductive member is separately provided, the rotation torque can be reduced.

In the above description, the case where the inner and outer rings 2, 3 are made of steel such as bearing steel has been described, but the present invention is not limited to this, and the inner and outer rings 2, 3 One of the races, preferably both races, may be made of the ceramic material of the present invention like the ball 4. Depending on the diameter of the inner and outer races 2, 3, the races of the inner and outer races 2, 3 may be different. It is also possible to form only the groove with the ceramic material. When the inner and outer races 2, 3 and the balls 4 are made of the above ceramic material in this way, the wear at their rolling contact portions can be further suppressed, and the life of the bearing can be further extended.

In the above description, the ball bearing 1 having the balls 4 as rolling elements is applied to the HDD device. However, the rolling bearing according to the present invention includes inner and outer races and rolling elements made of a conductive material. Of the inner and outer rings and the rolling elements, at least the rolling elements are made of a ceramic material containing silicon nitride, silicon carbide, titanium nitride, and molybdenum silicide, which are main components, and the inner and outer rings are provided through the rolling elements. The shape and the like of the rolling elements are not particularly limited as long as they electrically connect between them. Furthermore, the present invention is suitable for use as a bearing that is attached to a predetermined portion between the fixed body and the rotating body and rotatably supports the rotating body, as long as it rotates the rotating body with respect to the fixed body. can do. Further, the conductive ceramic material used in the present invention can be used in applications where both conductivity and mechanical properties are highly required, other than the bearing.

[0023]

The present invention constructed as described above has the following effects. According to the rolling bearing of claim 1, the inner and outer races and the rolling elements are made of a conductive material, and at least the rolling elements among the inner and outer races and the rolling elements are made of silicon nitride, which is a main component, of silicon carbide, titanium nitride, And a ceramic material containing molybdenum silicide, it is possible to sufficiently suppress the charging of the bearing and to extend the life of the bearing, which has excellent conductivity and wear resistance. Can be configured. Moreover, since the above ceramic material has excellent wear resistance and conductivity, it is possible to support the rotating body with high accuracy for a long period of time, and the bearing performance does not deteriorate due to electrification. Can be configured. Furthermore, in a device in which a bearing is incorporated, the charge of the rotating body on the device side that rotates together with the rotating wheel can be released through the bearing, so that it is possible to prevent problems such as the above head crash, Since it is not necessary to provide a grounding means such as a magnetic fluid seal on the bearing and the device, the structure of the bearing and the device can be simplified.

According to the rolling bearing of claim 2,
Since 0.5 to 10% by weight of molybdenum silicide is contained in the ceramic material, conductivity can be effectively imparted, and the material added to impart conductivity is only silicon carbide. The wear resistance can be improved as compared with the conventional example.

According to the rolling bearing of claim 3, 1
Since 0 to 20% by weight of silicon carbide and 1 to 10% by weight of titanium nitride are further contained in the ceramic material containing the above% by weight of molybdenum silicide, the conductivity is improved without lowering the wear resistance. It can be effectively added.

According to the rolling bearing manufacturing method of the present invention, titanium oxide is chemically converted into titanium nitride, whereby the ceramic material containing silicon nitride, silicon carbide, titanium nitride and molybdenum silicide is used. By forming at least the rolling element among the inner and outer races and the rolling elements using this ceramic material, it is possible to sufficiently suppress the charging of the bearing and to extend the life of the bearing. It is possible to form a bearing having excellent conductivity and wear resistance.

[Brief description of drawings]

FIG. 1 is a sectional view showing a ball bearing according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing a test device used in a durability test carried out by the inventors of the present invention.

3 is a diagram showing a test result by the test apparatus shown in FIG. 2, (a) is a diagram showing a measurement result of a surface shape of a sample flat plate made of the ceramic material of the present invention, and (b) is a conductive sample. It is a figure which shows the measurement result of the surface shape of the conventional equivalent sample flat plate which consists of the ceramic material to which the conductivity was not provided, (c) is another conventional equivalent sample flat plate which consists of the ceramic material to which electroconductivity was added. It is a figure which shows the measurement result of the surface shape of.

[Explanation of symbols]

1 Ball bearing (rolling bearing) 2 inner ring 3 outer ring 4 balls (rolling elements)

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hisashi Harada             3-5-8 Minamisenba, Chuo-ku, Osaka Koyo             Within Seiko Co., Ltd. F term (reference) 3J101 AA02 AA62 BA10 DA20 EA03                       EA41 EA43 EA44 EA72 FA11                       GA53

Claims (4)

[Claims] 1. A rolling bearing comprising an inner ring and an outer ring, and a plurality of rolling elements rotatably provided between the inner ring and the outer ring, wherein the inner and outer rings and the rolling elements are made of a conductive material. A rolling bearing, characterized in that, of these inner and outer rings and rolling elements, at least the rolling elements are made of a ceramic material containing silicon nitride as a main component and containing silicon carbide, titanium nitride, and molybdenum silicide. 2. The rolling bearing according to claim 1, wherein the ceramic material contains 0.5 to 10% by weight of the molybdenum silicide. 3. The ceramic material contains 10 to 20% by weight of the silicon carbide and 1 to 10 of the titanium nitride.
The rolling bearing according to claim 2, wherein the rolling bearing is contained in a weight percentage. 4. Silicon carbide, titanium oxide, molybdenum silicide,
A method of manufacturing a rolling bearing, wherein the ceramic material according to any one of claims 1 to 3 is obtained by adding a sintering aid to silicon nitride and sintering.