JP2008275037A - Rolling bearing and swing arm - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling bearing having prolonged lifetime and improved low-torque properties while maintaining low dust generation properties with a simple structure. <P>SOLUTION: The rolling bearing (1) comprises an outer ring (2), an inner ring (3), a plurality of rolling elements (5), the annular cage (7) of a synthetic resin, and rigid seal plates (9) each extending from a section near the end part of the inner circumference surface of the outer ring (2) and to a section near the end part of the outer circumference surface of the inner ring (3). Grease composition (12) is filled within a space defined by the rigid seal plate (9), the outer ring (2) and the inner ring (3). The rolling bearing (1) includes an oil repellent film (11) adhered to at least one of the end (9c) of the rigid seal plate and the outer circumference portion (3a) of the inner ring which are close to and face each other in a non-contact state. The oil repellent film (11) contains a component that hardly gets wet with the grease composition. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a swing arm rolling bearing for swinging and supporting a magnetic disk such as a hard disk drive (hereinafter referred to as HDD), and more particularly to a rolling bearing for HDD having low dust generation and long life characteristics.

  Among the components that operate in the HDD device, there is a swinging motion part such as a swing arm. In such a rolling bearing, it is necessary to enclose as much lubricating oil as possible inside the rolling bearing in order to extend the life, but on the other hand, it prevents the lubricating oil from seeping out so as not to contaminate the magnetic head and the magnetic disk. There is a need. If the prevention of oozing is insufficient, there is a concern that the lubricating oil may be depleted and the service life may be reduced by using for a long time.

  For example, in Japanese Patent Application Laid-Open No. 8-283767 (Patent Document 1) and Japanese Patent Application Laid-Open No. 8-303467 (Patent Document 2), lubricating oil is used as a bearing for supporting a rotating portion in an information processing apparatus such as an HDD. A rolling bearing with low dust generation and long life is disclosed.

  4 is a sectional view of a conventional HDD rolling bearing, and FIG. 5 is a partially enlarged view of FIG.

  As shown in FIG. 4, the conventional rolling bearing 20 includes an outer ring 22, an inner ring 23, a rolling element 25, a cage 27, and a seal plate 29. The seal plate 29 is attached by caulking its one end 29 a to the inner peripheral surface recess 22 a of the outer ring 22. On the other hand, the other end portion 29c of the seal plate 29 is provided close to the outer peripheral surface recess 23a of the inner ring 23, and a labyrinth seal portion 28 is formed therebetween.

  However, in the conventional rolling bearing, as shown in FIG. 6, a plurality of slit holes 29b are formed radially in the circumferential direction for assisting deformation in order to facilitate caulking of one end portion 29a of the seal plate 29. . Therefore, there is a problem that the lubricating oil leaks from the inside of the bearing to the outside through the slit holes 29b. Further, since the labyrinth seal portion 28 is a non-contact seal, there is a possibility that the lubricating oil leaks out from here. If the lubricating oil leaks out and contaminates the magnetic disk, the magnetic head, etc., it will cause a head crash.

  In order to extend the life of the bearing, it is desirable to increase the amount of lubricating oil enclosed. However, if the amount of the lubricating oil inside the bearing is increased, the lubricating oil tends to leak to the outside of the bearing, so that there is a problem that the amount of dust generation also increases, which causes a failure as described above.

  And, in terms of long-term lubrication durability, it can be said that the swing arm rolling bearing is in a oscillating rotation, and therefore is under severe lubrication conditions. In the long term, there is a concern that durability may be reduced due to evaporation of lubricating oil.

Japanese Patent Application Laid-Open No. 2003-254342 (Patent Document 3) discloses a ball bearing that is improved in low torque by applying an oil repellency treatment to a seal or clearance and enclosing grease in the bearing. With this ball bearing, “It is not preferable to use grease with extremely low viscosity for the sealed ball bearing because grease easily leaks from the sealing member” (paragraph 0005). In order to improve the fluidity of the grease, at least one of the surfaces of the members surrounding the bearing space has oil repellency. The grease is enclosed in a space partitioned by a seal member 16 in which a core metal 16b, which is a core material, is covered with a rubber 16a. However, such a structure is complicated, and depending on the compatibility with the oil repellent, There is also a possibility of deteriorating the surface of the sealing member 16 such as rubber 16a (see Patent Document 2, paragraph 0013, etc.).
JP-A-8-283767 JP-A-8-303467 JP 2003-254342 A

  Accordingly, an object of the present invention is to provide a rolling bearing with a simpler configuration, capable of extending the life while maintaining low dust generation, and having improved low torque performance.

  As a result of repeated studies to solve the above problems, the present inventors have arranged an elastic member on the inner surface of the rigid seal plate and the outer ring, and the inner ring side end of the rigid seal plate facing each other in close contact with each other. On the other hand, an oil repellent film is provided on at least one of the outer ring portion and the inner ring outer peripheral portion. On the other hand, by adding a predetermined amount of viscosity index improver to the grease composition, the grease composition can leak to the outside even when a grease composition having a high consistency is used. As a result, it has been found that a rolling bearing having excellent low torque and low dust generation and having a long life can be obtained, and the present invention has been completed.

  That is, the rolling bearing of the present invention includes an outer ring having an outer ring raceway on an inner peripheral surface, an inner ring having an inner ring raceway on an outer peripheral surface, and a plurality of rolling elements provided so as to be freely rollable between the inner ring raceway and the outer ring raceway. And an annular retainer for holding the rolling elements equally, and a rigid seal plate provided from the vicinity of the end of the inner peripheral surface of the outer ring to the vicinity of the end of the outer peripheral surface of the inner ring. A rolling bearing in which a grease composition is sealed in a gap defined by the rigid seal plate, the outer ring, and the inner ring, and is attached to the outer ring side end of the rigid seal plate, It is attached to at least one of the elastic member that is in contact with the recess formed on the inner peripheral surface, the end of the rigid seal plate that faces the non-contacting proximity, and the outer peripheral portion of the inner ring, and is wetted with the grease composition. An oil repellent film containing a component that is difficult to be removed, and the grease composition Consistency is at 310 or more, wherein the viscosity index improver is blended 0.1 to 10 mass% of the grease composition the total amount of.

  According to such a configuration, an oil repellent film containing a component that is difficult to wet with the grease composition is formed on at least one of the outer peripheral surface of the inner ring and the non-contact end portion of the seal plate. Even in the case of encapsulating the grease composition, the grease composition is repelled by the oil repellent film, so that the grease composition can be prevented from oozing out and the life can be extended.

  Moreover, since it is sealed with the elastic member, the confidentiality of the recess formed in the one end portion of the rigid seal and the inner peripheral surface of the outer ring is increased, and dust generation from the inside of the bearing is further suppressed.

  Furthermore, by adding a viscosity index improver such as a polymer, even if the grease composition has a high consistency and is very soft, it is difficult for oil separation to occur, and it can be enclosed in the air gap without oozing out. Are better.

  In the rolling bearing of the present invention, the cage is preferably made of a synthetic resin containing a lubricant.

  According to such a configuration, the lubricant oozes onto the surface of the cage as the rolling bearing rotates, and this lubricating oil is supplied to the lubricating surface over a long period of time, so that the durability can be further improved.

  Since the rolling bearing of the present invention as described above is excellent in low torque property and low dust generation property, it is particularly suitable for a swing arm for swinging and supporting a magnetic head such as an HDD.

  The rolling bearing of the present invention includes an oil repellent film containing a component that is difficult to get wet with a grease composition formed on at least one of the outer peripheral surface of the inner ring and the non-contact end portion of the seal plate, and between the seal plate and the outer peripheral surface of the outer ring. In addition, by adding a viscosity index improver to the grease composition, it is possible to prevent the grease composition from seeping out even if a grease composition having a low viscosity is enclosed. it can. As a result, the rolling bearing according to the present invention is excellent in low torque property, low dust generation property, and durability.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  1 to 3 show an example of a rolling bearing according to the present invention. FIG. 1 is a sectional view of a rolling bearing 1 according to the present invention.

  As shown in FIG. 1, a rolling bearing 1 includes a hollow cylindrical outer ring 2 having an outer ring raceway on an inner peripheral surface, a hollow cylindrical inner ring 3 having an inner ring raceway on an outer peripheral surface, and an inner ring raceway and an outer ring raceway. A plurality of rolling elements 5 provided so as to be freely rollable to each other, and the rolling elements 5 are equally distributed, and the annular retainer 7 and the outer peripheral surface of the inner ring 3 from the vicinity of the end of the inner peripheral surface of the outer ring 2 A metal rigid seal plate 9 provided to the vicinity of the end portion is provided, and a grease composition 12 is enclosed in a gap defined by the rigid seal plate 9 and the outer ring 2 and the inner ring 3.

  2 shows a view of the vicinity of one end 9c of the rigid seal plate 9 of the rolling bearing 1 shown in FIG. 1 and the outer peripheral portion of the inner ring 3. FIG. 3 shows the vicinity of the other end 9a of the rigid seal plate 9. The figure is shown. As shown in FIG. 2, an oil repellent film 11 containing a component that is difficult to get wet with the grease composition is formed on both one end portion 9c of the rigid seal plate 9 and the outer peripheral portion 3a of the inner ring 3 that face each other in a non-contact manner. A labyrinth seal portion 8A is formed. If comprised in this way, in the labyrinth seal part 8A, the grease composition 12 will be repelled by the oil repellent film 11, and the seepage of the grease composition 12 to the outside of the bearing will be effectively prevented. If a viscosity index improver is added, even a grease composition having a consistency of 310 or more can effectively prevent seepage, so that the torque can be greatly reduced by using such a grease composition. And the amount of dust generation is also suppressed.

  The oil repellent film 11 can be formed, for example, by applying an oil repellent or spraying an oil repellent to the entire bearing from the outside on a rolling bearing in which a grease composition is injected. The oil repellent may be diluted with a solvent as necessary. In FIG. 2, the oil repellent film 11 is formed on both the outer peripheral surface 3a of the inner ring and the non-contact end portion 9c of the seal plate, but it is sufficient if it is formed on at least one of the opposing surfaces. Further, the oil-repellent film 11 may be formed without any particular limitation as long as it is a portion other than the rolling contact surface (the rolling surface of rolling elements such as balls and rollers, the inner ring raceway and the outer ring raceway).

  Here, examples of the oil repellent component in the oil repellent include fluorine-based treatment agents such as a fluorine-based surfactant, a fluorine-based silane coupling agent, and a fluorine-based polymer. Preferably, an organic compound which is the above-described fluorosurfactant and has both a lipophilic group and a hydrophobic group on the molecular structure can be used.

  FIG. 3 shows an elastic member 10 </ b> A attached to the outer ring side end portion 9 a of the rigid seal plate 9 and abutting against the inner peripheral surface 9 a of the outer ring. The elastic member 10A is bonded by an adhesive over a part of the inner side surface 9b of the rigid seal plate 9 and the other end portion 9a. The end of the elastic member 10A is fitted into the recess 2a on the inner peripheral surface of the outer ring, and both are bonded. Further, in the contact seal portion, the elastic member 10A increases the confidentiality of the one end portion 9a of the rigid seal plate and the recess 2a on the inner peripheral surface of the outer ring, and dust generation from inside the bearing can be further suppressed.

  As the elastic member 10A, one of nitrile rubber, acrylic rubber, fluororubber, silicon rubber, synthetic resin (amide resin such as 46, 66 nylon), or urethane rubber, or a mixture of two or more types can be used. . The rigid seal plate can be made using a metal, an alloy, or a rigid resin that is excellent in corrosion resistance and hardly deforms. The elastic member preferably contains a fluorine-based oil repellent at a ratio of 0.01 to 3% by weight, and is attached so as to cover a part of the inner side surface of the rigid seal plate. Fluorine-based oil repellents have no oil repellent effect at a content of 0.01% by weight or less, and when the content is 3% by weight or more, the mixed state with the elastic member becomes poor, and the oil repellent is separated from the elastic member and leaks. Tend to occur. If the elastic member 10A covers the entire inner surface 9b of the rigid seal plate 9, the mutual adhesion between the elastic member 10A and the rigid seal plate 9 is enhanced, and the integration of both is further improved.

  The cage 7 used in the rolling bearing of the present invention is preferably a synthetic resin cage containing a lubricant in advance. The lubricant is preferably 0.1 to 80% by weight with respect to the weight of the cage 7. By containing the lubricant in advance, the lubricant oozes out on the surface of the cage 7 as the rolling bearing rotates, and this lubricating oil is supplied to the lubricating surface over a long period of time, thereby extending the durability life. .

  Here, as the oil content of the cage 7 increases, the lubrication life becomes longer, but on the other hand, the mechanical strength of the cage decreases. Since the cage is required to have some mechanical strength, it is preferable to maintain the mechanical strength by suppressing the content of the lubricating oil. However, in a rolling bearing used for a reciprocating rocking part such as a swing arm, the cage does not require a high mechanical strength, so that the oil content can be increased and the lubrication life can be extended. Oil content is possible. The oil content is particularly preferably 1 to 70% by weight. The lower limit of the oil content is 0.1% by weight, and if it is less than this, the supply amount from the cage is too small and the advantage in terms of lubrication does not appear.

  As a method for impregnating the cage with the lubricating oil, there are a method in which the cage is immersed in the lubricating oil and a method in which the lubricating oil is kneaded and molded into a resin. In the case of oil content of 3% by weight or less, a method of immersing the cage in the lubricating oil is simple, but the latter method is used when a larger amount of lubricating oil is impregnated in the cage. At that time, since the lubricating oil retaining ability of the resin differs depending on the type of resin forming the cage or the combination of the resin and the lubricating oil, it is necessary to consider these.

  The type of base oil of the grease composition to be enclosed in the rolling bearing according to the present invention is not particularly limited and can be used without any problem as long as it is generally used as a base oil for grease or lubricating oil. be able to.

  Specific examples of the base oil include mineral oil, synthetic oil, and animal and vegetable oils. The mineral oil is preferably a mineral oil refined to have a viscosity index of 100 or more by appropriately combining vacuum distillation, solvent removal, solvent extraction, hydrocracking, solvent dewaxing, sulfuric acid washing, clay refining, hydrorefining, etc. . More preferably, a so-called highly refined mineral oil refined to have a viscosity index of 120 or more is used.

  Synthetic oils include synthetic hydrocarbon oils, ester oils, ether oils, silicone oils, fluorine oils and the like.

  Examples of the synthetic hydrocarbon oil include poly α-olefins such as normal paraffin, isoparaffin, polybutene, polyisobutylene, 1-decene oligomer, 1-decene and ethylene co-oligomer, and hydrides thereof. Further, alkylbenzenes such as monoalkylbenzene, dialkylbenzene, and polyalkylbenzene, and alkylnaphthalenes such as monoalkylnaphthalene, dialkylnaphthalene, and polyalkylnaphthalene are also included.

  Examples of ester oils include dibutyl sebacate, di (2-ethylhexyl) sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, ditridecyl glutarate, and methyl acetyl ricinolate, trioctyl trimellitate, tri Aromatic ester oils such as decyl trimellitate and tetraoctyl pyromellitate, polyol ester oils such as trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol pelargonate, etc. A complex ester oil which is an oligoester of a mixed fatty acid of a basic acid and a dibasic acid and a polyhydric alcohol can be used.

  Further, as ether oil, polyglycols such as polyethylene glycol, polypropylene glycol, polyethylene glycol monoether, polypropylene glycol monoether, monoalkyl triphenyl ether, alkyl diphenyl ether, dialkyl diphenyl ether, tetraphenyl ether, pentaphenyl ether, monoalkyl tetra Examples thereof include phenyl ether oils such as phenyl ether and dialkyl tetraphenyl ether. In view of heat resistance, a thioether ether oil is also suitable. Examples thereof include (di) alkyl diphenyl thioether oil, (di) alkyl polyphenyl thioether oil, tetraphenyl thioether oil, and pentaphenyl thioether oil.

  Synthetic oils other than the above include tricresyl phosphate, perfluoroalkyl ether oil and the like. Examples of animal and vegetable oils include beef tallow, lard, soybean oil, rapeseed oil, rice bran oil, coconut oil, palm oil, palm kernel oil, and other oils or hydrides thereof. These base oils may be used alone or in combination of two or more.

  The type of thickener added to the grease composition used in the present invention is not particularly limited, and can be appropriately selected according to the application and use conditions. However, the grease composition is preferably prepared so as to have a consistency of 310 or more, and in that sense, it is preferably blended less than usual.

  Examples of the thickener include metal soap (metal is aluminum, barium, calcium, lithium, sodium, etc.) and metal composite soap (metal is lithium, calcium, aluminum, etc.). Urea compounds (diurea, triurea, tetraurea, polyurea, etc.), inorganic compounds (silica gel, bentonite, etc.), urethane compounds, urea / urethane compounds, sodium terephthalate compounds can also be used.

  When the rolling bearing of the present invention is used for an HDD, the inner quietness is one of the most important elements, and therefore it is preferable to add lithium soap having a particularly low sound.

  The type of viscosity index improver used in the present invention is not particularly limited. For example, polymethacrylate, olefin copolymer (polyisobutylene, ethylene-propylene copolymer), polyalkylstyrene, styrene-butadiene hydrogenated copolymer Viscosity index improvers such as a polymer system, a styrene-maleic anhydride copolymer system, and a star-shaped isoprene system can be used.

  The viscosity index improver is blended in an amount of 0.1 to 10% by mass, preferably 0.2 to 8% by mass, and more preferably 0.5 to 5% by mass, based on the total amount of the grease composition.

  Next, referring to Table 1, the above-described embodiment, other examples, and comparative examples will be compared and described. Here, the values obtained in the experiment under the following conditions are compared.

(Bearing type and lubricating grease composition)
The test bearing is a non-contact metal seal type (Z type) single row deep groove ball bearing (nominal number 695). The dimensions are 5 mm inside diameter x 13 mm outside diameter x 4 mm width. The test grease composition contains about 70 mm ² / s (40 ° C.) ester oil as a base oil, lithium soap as a thickener, and polymethacrylate as a viscosity index improver at 3% by mass of the total amount of grease. About 30% by volume of the space volume was sealed inside the bearing by a syringe.

For the oil repellent treatment, Knox Guard ST-420 (manufactured by Nippon Mektron Co., Ltd.) was used. In the examples and comparative examples of this test, 20 mass% of the above-mentioned ester oil of about 70 mm ² / s (40 ° C.) was mixed in a resin cage.

(Measurement of dust generation)
The dust generation was measured using an out party counter. In the out-particle counter, while rotating the bearing at 7200 rpm in the sealed container (rotating the outer ring), clean air filtered by a filter is supplied to this sealed container, and the air that has passed through the bearing is introduced into the measurement unit. The number of fine particles blocking the light was measured by irradiating with laser light. In this case, fine particles having a particle size of 0.1 μm or more existing in 0.1 cf (legislature feet) were measured as measurement objects. The measurement time was 1 hour, and the total was taken as the amount of dust repellent.

(Swing endurance test)
As described above, 695 bearings were used, and torque was measured under the following conditions.

Vibration frequency: 30Hz
Outer ring swing angle: 8 °
Axial load: 9.8N
Number of cycles: 10 million times Ambient temperature: Normal temperature (about 25 ° C)
Judgment criteria: The test is done by disassembling the bearing after the test, and ◎ (pass) if there is no wear on the inner raceway surface, ○ (standard) if there is a running track, and × if there is wear. (Failed).

(Bearing torque test)
As described above, 695 bearings were used, and torque was measured under the following conditions.

Bearing rotation speed: 1800 min ^-1
Axial load: 9.8N
Atmospheric temperature: Normal temperature (about 25 ° C)
Measurement method: The torque value measured 5 minutes after the start of the test. Judgment criteria: Based on the measured value, the following evaluation was made. The second decimal place was rounded off. The unit is “× 10 ⁻⁴ N · m”.

○: 0.9 or less (pass)
Δ: 1 to 1.5 (standard)
X: 1.6 or more (failed)

  As shown in Table 1, it was found that Examples 1 to 3 which are rolling bearings according to the present invention are of high quality with low dust generation and low torque.

  Comparative Examples 1 and 2 having a low consistency are inferior in torque performance. Further, it was observed that when the viscosity index improver polymethacrylate was too much or too little, the durability against rocking was poor. In Comparative Example 5 where no oil repellent treatment was performed, the amount of dust generation was very large and the performance was clearly inferior.

It is sectional drawing of the rolling bearing which concerns on one Embodiment of this invention. It is an expanded sectional view of the inner ring side end of the rigid seal plate of the rolling bearing shown in FIG. 1 and the outer periphery of the inner ring. FIG. 2 is an enlarged cross-sectional view of the periphery of an outer ring side end portion of a rigid seal plate of the rolling bearing shown in FIG. 1. It is sectional drawing of the conventional rolling bearing for HDD. It is a partially expanded sectional view of FIG.

Claims (3)

An outer ring having an outer ring raceway on the inner peripheral surface, an inner ring having an inner ring raceway on the outer peripheral surface, a plurality of rolling elements provided between the inner ring raceway and the outer ring raceway, and the rolling elements arranged equally. An annular retainer for holding, and a rigid seal plate provided from the vicinity of the end of the inner peripheral surface of the outer ring to the vicinity of the end of the outer peripheral surface of the inner ring, and the rigid seal plate and the outer ring A rolling bearing in which a grease composition is enclosed in a gap defined by the inner ring,
An elastic member attached to the outer ring side end of the rigid seal plate and abutting against a recess formed in an inner peripheral surface of the outer ring;
An oil repellent film that is attached to at least one of the end portion of the rigid seal plate and the outer peripheral portion of the inner ring that face each other in close contact with each other and includes a component that is difficult to wet with the grease composition,
A rolling bearing in which the consistency of the grease composition is 310 or more and the viscosity index improver is blended in an amount of 0.1 to 10% by mass of the total amount of the grease composition.   The rolling bearing according to claim 1, wherein the cage is made of a synthetic resin containing a lubricant.   A swing arm comprising the rolling bearing according to claim 1.

Images