JP4766056B2 - Rolling bearing - Google Patents

Description

  The present invention relates to a rolling bearing, and particularly used for a rotation support portion of a hard disk drive (HDD), a video tape recorder (VTR), a digital audio tape recorder (DAT), a laser beam printer (LBP), a small cooling fan motor for information equipment and the like. The present invention relates to a rolling bearing.

  The computer-related industry has a faster technological innovation speed despite the fact that it has a shorter history than other industries. Especially for HDDs, new models (high precision and compactness) are born one after another in addition to the short existence period of one model. Along with this, rolling bearings used in HDDs are also used at high temperatures and at high speeds, and usage conditions are becoming increasingly severe. On the other hand, high performance such as low torque, low noise, and long life is desired.

  For rolling bearings used in conventional VTRs, HDDs, DATs, LBPs, etc., lubrication is applied to the lubrication system in which grease is filled or the bearing raceway surface, etc., for low torque, low noise and long life. In addition, a lubrication system in which grease is sealed is employed. For example, in rolling bearings used for HDDs, a lubrication system in which grease is sealed is the mainstream.

On the other hand, low torque, low noise, and long life have been achieved by simply applying lubricating oil to the bearing raceway surface without using any grease. For example, Japanese Patent Laid-Open No. 5-149343 discloses. Apply a thick oil (1 mg / cm ² or more) of lubricating oil such as poly α-olefin oil, polyol ester oil, polyphenyl ether oil, fluorine oil, etc. to the inner and outer ring raceways, rolling elements and cage surfaces. Thus, a rolling bearing is described in which abnormal noise is prevented particularly during cold weather. Similarly, Japanese Patent Application Laid-Open No. 64-46011 also describes a rotation support device in which a lubricating oil film is formed.

  However, there is a trade-off relationship between low torque and low noise and long life, and it is difficult to satisfy both at the same time in any lubrication method. In order to reduce the torque, it is necessary that the stirring resistance of the grease or the lubricating oil film is small, and for this purpose, a low-viscosity base oil or lubricating oil must be used. On the other hand, in order to achieve low noise and long life, it is advantageous to use a base oil or lubricating oil with a certain degree of viscosity in order to secure and maintain an oil film on the contact surface. Therefore, if low torque is prioritized, surface contact wear due to slippage will occur on the contact surface at an extremely early time, and the generated wear powder will adhere to the rolling surface and generate abnormal noise or reduce the durability life. .

  Such a problem becomes a more weight problem in the situation where high temperature and high speed rotation are required as described above. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a rolling bearing that can greatly reduce the torque, noise, and service life, and can sufficiently cope with high temperature and high speed rotation.

The above object is achieved by holding a plurality of rolling elements via a cage between the inner ring and the outer ring according to the present invention, and the kinematic viscosity of the base oil at 40 ° C. is 60 mm ² / s or less. There, a metallic detergent-dispersant comprising a calcium sulfonate or barium sulfonates Natick DOO, 0.5 to 10 wt.% of the grease total volume sum of the ashless detergent-dispersant comprising a succinic acid ester, Tae trachomatis sill hydrogen phosphate This is achieved by a rolling bearing characterized in that a grease containing 0.5 to 10% by weight of the total amount of grease containing an anti-fighting agent is enclosed.

  According to the present invention, it is possible to provide a rolling bearing that can greatly reduce the torque, noise, and service life, and can sufficiently cope with high temperature and high speed rotation.

  Hereinafter, the rolling bearing of the present invention will be described in detail with reference to the drawings.

  In the present invention, the configuration and structure of the rolling bearing itself are not limited. For example, as shown in FIG. 1, a plurality of balls 13 as rolling elements are held between the inner ring 10 and the outer ring 11 via a cage 12. The ball bearing 1 comprised by doing can be illustrated. The balls 13 may be steel balls or ceramic balls. Further, a grease (not shown) described later is sealed by the seal 14.

In the grease, the type of base oil is not limited, but it is preferable to use ester oil or a mixed oil of ester oil and another lubricating oil in consideration of lubricity, heat resistance and the like. Further, the base oil has a kinematic viscosity at 40 ° C. of 60 mm ² / s or less in order to reduce the torque.

  The type of ester oil is not limited, but diester oil, aromatic ester oil, hindered ester oil, carbonate ester oil and the like are suitable.

  Diester oils include dioctyl adipate (DOA), diisobutyl adipate (DIBA), dibutyl adipate (DBA), dioctyl azelate (DOZ), dibutyl sebacate (DBS), dioctyl sebacate (DOS), methyl acetylricinolate ( MAR-N).

  Examples of the aromatic ester oil include trioctyl trimellitate (TOTM), tridecyl trimellitate, tetraoctyl pyromellitate and the like.

  Examples of hindered ester oils include those obtained by appropriately reacting the following polyhydric alcohols and monobasic acids. The monobasic acid may be used alone or in combination. Moreover, you may use as a complex ester which is an oligoester of a polyhydric alcohol and the mixed fatty acid of a dibasic acid and a monobasic acid.

  Examples of the polyhydric alcohol include trimethylolpropane (TMP), pentaerythritol (PE), dipentaerythritol (DPE), tripentaerythritol (TRPE), neopentyl glycol (NPG), 2-methyl-2-propyl-1, 3-propane (MPPD) etc. are mentioned.

As the monobasic acid, C _{4 to} C ₁₈ monovalent aliphatic groups are mainly used. Specifically, acetic acid, valeric acid, caproic acid, caprylic acid, enanthic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, myristylic acid, palmitic acid, beef tallow fatty acid, stearic acid, caproleic acid, undecylenic acid, Lindel Examples thereof include acid, tuzuic acid, fizeteric acid, myristoleic acid, palmitoleic acid, petrothelic acid, oleic acid, elaidic acid, sorbic acid, linoleic acid, linolenic acid, sabinic acid, and ricinoleic acid.

  Examples of the lubricating oil that can be mixed with the ester oil include refined mineral oil, synthetic hydrocarbon oil, and ether oil. The mixing ratio with the ester oil is appropriately adjusted according to the type of the lubricating oil so as to satisfy the above base oil viscosity.

Specifically, the refined mineral oil can be used in either naphthenic or paraffinic form. As the synthetic hydrocarbon oil, poly α-olefin oil and co-oligomer oil of α-olefin and ethylene are preferable because of low volatility. Examples of ether oils include phenyl ether oils derived from C ₁₂ -C ₂₀ (di) alkyl chains such as diphenyl, triphenyl, tetraphenyl, etc. (di) Alkyl polyphenyl ether oil and the like are preferable. Examples of the lubricating oil having an ether structure include (di) alkyl diphenyl ether oil, (di) alkyl polyphenyl ether oil, tetraphenyl ether oil, pentaphenyl ether oil, and polyalkylene glycol oil. Furthermore, in consideration of heat resistance, thioether oil can also be preferably used, and examples thereof include (di) alkyl diphenyl thioether oil, (di) alkyl polyphenyl thioether oil, tetraphenyl thioether oil, and pentaphenyl thioether. .

  The thickener is not limited as long as it can form grease with the above base oil. For example, metal soaps such as barium soap, lithium soap and aluminum soap, non-soaps such as urea compounds and lipophilic bentonite. System thickeners can be used.

  The consistency of the grease is preferably 300 or less as defined by JIS K2220. If the consistency exceeds 300, the grease may be too soft and flow during the rotation of the bearing, and part of it may adhere to the raceway surface, limiting the rotation of the rolling elements and causing slippage, which may cause surface damage. There is. The lower limit of the consistency is not particularly limited, but the grease should not be extremely hard.

The grease is added in combination with the metal-based detergent-dispersant comprising a calcium sulfonate or barium sulfonate, and ashless detergent-dispersant comprising a succinic acid ester. FIG. 4 shows an electron microscope in which each of the test bearings of Example 1 (enclosed with a grease added with a cleaning dispersant) and Comparative Example 1 (enclosed with an additive-free grease) rotated after 5000 hours was photographed. Although it is a photograph, the unevenness | corrugation resulting from adhesion of an abrasion powder exists in multiple places in the track surface of the comparative example 1, whereas such an unevenness | corrugation is not seen in the track surface of Example 1. FIG. . From this, it can be seen that the addition of the cleaning dispersant can prevent the abrasion powder from adhering to the rolling surface.

  The total amount of the metal-based detergent dispersant and the ashless detergent-dispersant is preferably 0.5 to 10% by weight, particularly 1 to 9% by weight, based on the total amount of grease. If the addition amount of the cleaning dispersant is less than 0.5% by weight, the effect of preventing the adhesion of the wear powder is not sufficiently obtained, and if it exceeds 10% by weight, not only the improvement of the effect corresponding to the increment cannot be obtained, but also The amount of other grease components including oil is relatively reduced, which leads to poor lubrication.

  Further, the mixing ratio of the ashless detergent / dispersant to the metal detergent / dispersant is such that the content of the ashless detergent / dispersant is greater than the content of the metal detergent / dispersant. In particular, the content of the ashless detergent / dispersant is preferably about twice the content of the metal detergent / dispersant.

In addition to the above-mentioned detergent and dispersant, it is preferable to add an antiwear agent to the grease, and to add at least one of an extreme pressure agent, an oily agent, and an antioxidant. The addition amount is preferably individually or in total, 0.5 to 10% by weight of the total amount of grease. If the addition amount is less than 0.5% by weight, the effect of addition is not sufficient, and if it exceeds 10% by weight, the properties of the grease may change, for example, there is a risk of hardening or softening.

Since the antiwear agent has an action of suppressing wear, the synergistic effect with the detergent-dispersant can more effectively suppress the familiar wear and further improve the acoustic durability life. In the present invention, ditetracosyl hydrogen phosphite is used as an antiwear agent.

  Since the extreme pressure agent has an action of suppressing wear, the synergistic effect with the detergent-dispersant can more effectively suppress the familiar wear and further improve the acoustic durability life. In particular, it becomes more effective when used in combination with the above-mentioned antiwear agent.

  Examples of extreme pressure agents include metal alkyldithiophosphate compounds such as zinc dithiophosphate (Zn-DTP) and molybdenum dithiophosphate (Mo-DTP), zinc dithiocarbamate (Zn-DTC), and nickel dithiocarbamate (Ni Metal alkyl dithiocarbamate compounds such as -DTC) and molybdenum dithiocarbamate (Mo-DTC) are preferred.

  The oily agent is not particularly limited, but higher fatty acids and derivatives thereof are preferable, and examples thereof include oleic acid, stearic acid, naphthenic acid, lanolinic acid, lauryl alcohol, oleyl alcohol, stearylamine, and cetylamine. .

  The antioxidant is not particularly limited, but a mixture of a nitrogen-containing compound-based antioxidant and a phenol-based antioxidant is preferable. Antioxidants are particularly effective in improving acoustic properties, but sufficient effects cannot be obtained by adding only one of nitrogen-containing compound-based antioxidants and phenol-based antioxidants. In addition, it is preferable that the mixing ratio of the nitrogen-containing compound-based antioxidant and the phenol-based antioxidant in the mixture is 2: 8 to 8: 2.

The nitrogenous compound based antioxidant may be, for example, phenyl α-naphthylamine, diphenylamine, phenylenediamine, oleyl amide amines, phenothiazine. Examples of phenolic antioxidants include hindered phenols such as p-tert-butyl-phenyl salicylate and 2,6-di-tert-butyl-p-phenylphenol.

  In addition to the above-mentioned additives, additives generally added to grease, such as a viscosity index improver, can be added to the grease as long as the effects of the present invention are not impaired.

  The grease whose composition is adjusted as described above is sealed in the bearing so as to occupy 15 to 35% by volume of the bearing space. Here, the bearing space is a volume obtained by subtracting the volumes of the rolling elements and the retainer (or a seal in some cases) from a ring-shaped space defined by the inner ring and the outer ring. If the amount of grease filled is less than 15% by volume of the bearing space, the absolute amount is too small to provide a lubricating oil replenishment effect, resulting in early life. On the other hand, when the grease filling amount exceeds 35% by volume of the bearing space, the rolling motion of the rolling element is hindered, and the possibility of causing rolling element slip is increased.

  Hereinafter, the present invention will be further described with reference to examples and comparative examples, but the present invention is not limited thereto.

(Test-1: Examples 1 to 3 and Comparative Examples 1 to 14 )
As a test bearing, a single row deep groove ball bearing as shown in FIG. 1 (non-contact rubber seal (V type), nominal number: 694, dimensions: inner diameter 4 mm × outer diameter 10 mm × width 2 mm, rolling element diameter: 1.0 mm) The grease prepared with the formulation shown in Table 1 was sealed so as to occupy 20% by volume of the bearing space.

  And the bearing acoustic test was done using the test apparatus shown in FIG.2 and FIG.3. The illustrated test apparatus has a structure in which a test bearing placed in a housing 20 is rotated by the power of a motor 23 via a rubber belt 21 and a pulley 22. Further, the entire apparatus is housed in a thermostatic chamber (not shown) during the test and maintained at a predetermined temperature.

  In the test, first, the Anderon value (initial Anderon value) of the test bearing immediately after sealing the grease was measured using an Anderon meter. Next, a test bearing was mounted on the test apparatus, and the test apparatus was rotated for 5000 hours at an rotational load of 7200 rpm (outer ring rotation) and an axial load of 10N. After rotation, the test bearing was taken out and the Anderon value was measured with an Anderon meter, and the difference from the initial Anderon value was calculated.

  1000 test bearings were prepared for each grease, and the above acoustic measurements were performed for each. And the raise value from an initial Anderon value was set to 1.0 or less as pass, and 1.1 or more was set as failure, and the failure rate (%) per 1000 pieces was calculated. The results are also shown in Table 1 as relative values with the rejection rate of Comparative Example 2 as 1.

  It can be seen from Table 1 that better acoustic durability can be obtained by using a metal-based detergent dispersant and an ashless detergent-dispersant in combination. In addition, the acoustic durability is improved by using a cleaning dispersant and an antiwear agent in combination.

(Test-2: Verification of additive amount of detergent dispersant)
According to the formulation shown in Example 1, grease was prepared by changing the amount of the detergent dispersant (Ba-sulfonate and alkenyl succinic acid were mixed in the same amount), and the same bearing acoustic measurement as in Test-1 was performed. The results are shown in FIG. 5 as relative values to the rejection rate of Comparative Example 2, and satisfactory acoustic durability can be obtained if the amount of the detergent dispersant added is in the range of 0.5 to 10% by weight of the total amount of grease. It turns out that it is obtained.

It is sectional drawing which shows the single row deep groove ball bearing which is one Embodiment of the rolling bearing of this invention. It is a schematic block diagram (perspective view) which shows the test apparatus used for the bearing acoustic test in the Example. FIG. 3 is a side view of the test apparatus shown in FIG. 2. It is the electron micrograph which image | photographed the track surface after rotating 5000 hours about the bearing of Example 1 and Comparative Example 1. It is a graph which shows the relationship between the addition amount of the cleaning dispersant obtained in Test-2, the rejection rate ratio, and the grease consistency.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ball bearing 10 Inner ring 11 Outer ring 12 Cage 13 Ball 14 Seal

Claims (2)

A metal composed of calcium sulfonate or barium sulfonate, which is configured by holding a plurality of rolling elements through a cage between an inner ring and an outer ring, and the base oil has a kinematic viscosity at 40 ° C. of 60 mm ² / s or less. A total of 0.5 to 10% by weight of the total amount of grease and an ashless detergent and dispersant composed of succinic acid ester, and an antiwear agent composed of ditetracosyl hydrogen phosphite and a total amount of 0. A rolling bearing characterized in that grease containing 5 to 10% by weight is enclosed.   2. The rolling bearing according to claim 1, wherein the grease contains barium sulfonate and succinate in a ratio of 1.5 to 8% by weight of the total amount of grease.