JPH059488A - Grease for sealing bearing - Google Patents

Abstract

PURPOSE:To provide the title grease which allows a bearing having a noncontact sealing device to run very quietly without polluting a clean atmosphere. CONSTITUTION:The title grease comprises a base oil consisting of a polyol ester oil or diester oil having a kinematic viscosity at 40 deg.C of 50-200cSt and 15-40wt.% thickener consisting of a sodium salt of 12-hydroxystearic or another fatty acid. A bearing sealed with the grease runs very quietly with very little dust being generated, i.e., without polluting a clean atmosphere.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing enclosing grease which is used by enclosing it in a bearing.

[0002]

2. Description of the Related Art Generally, there are a non-contact type sealing device and a contact type sealing device as sealing devices for preventing dust and lubricating oil from scattering outside the bearing. The former is a narrow gap between a shaft and a bearing. With a gap filled with grease,
It is superior to the latter in quietness during rotation and simple structure.

However, further quietness and cleanliness are required for rotating parts related to electronic devices these days, and for example, hard disk drive devices (hereinafter abbreviated as HDD) and laser beam printers (hereinafter LBP) are required. In such a device, when fine oil particles or contaminant particles such as dust (hereinafter referred to as dust) are mixed in the atmosphere used, head crash occurs in the HDD, or reflection of an optical reflection surface occurs in the LBP. It is said that the rate will decrease.

In order to mechanically avoid such a situation, a method is known in which a magnetic fluid sealing device is attached instead of or together with the non-contact type sealing device of the bearing. In this magnetic fluid seal, a magnet member is fixed to opposite end surfaces of a holding member of a bearing rolling element, and magnetic fluid is collected between the end surfaces to enhance the hermeticity.

On the other hand, there is no grease that is sealed in such a sealing device or a bearing, which has not been particularly improved to prevent dust. Mineral oil or synthetic oil having a relatively low viscosity is used as a base oil, and lithium, calcium, Those having a general composition having a thickening agent of metallic soap containing sodium as a salt have been used.

[0006]

However, the demand for the above-mentioned electronic equipment-related devices is becoming higher and higher, and as a lubricant for a specific purpose, a magnetic fluid seal is used as a lubricant for further miniaturization and reduction in production cost. It has been required to develop a grease that satisfies the above quietness and cleanliness even for bearings that do not have it.

As described above, the present invention solves the problem that the conventional grease cannot lubricate the bearing in a quiet and clean atmosphere unless a magnetic fluid seal having a complicated structure is attached. An object of the present invention is to provide a bearing-encapsulating grease that is excellent in quietness and can be used in a clean atmosphere simply by enclosing it in a bearing equipped with a sealing device.

[0008]

In order to solve the above problems, in the present invention, the kinematic viscosity at 40 ° C. is 50 to 50 ° C.
A composition was used in which a 200 cSt ester oil was used as a base oil and 15 to 40% by weight of a higher fatty acid sodium salt was blended as a thickener.

The details will be described below.

First, as the ester oil in the present invention, a diester type lubricating oil obtained as a reaction product of an organic acid and an alcohol and a polyol ester as a hindered ester can be exemplified. Examples of the diester oil include diesters obtained from linear dibasic acids such as sebacic acid, azelaic acid, and adipic acid, and a higher alcohol having a side chain, that is, di-2-ethylhexyl sebacate, di-2- Examples thereof include ethylhexyl adipate. Further, as the polyol ester oil, pentaerythritol, dipentaerythritol,
Examples include fatty acid esters of trimethylolpropane and mixtures thereof, such as pentaerythritol tetrahexaate.

The kinematic viscosity of the above ester oil at 40 ° C. is 50 to 200 cSt. Because 50 cSt
If the viscosity is less than less than 200, the dust generation reducing effect is small,
This is because if the viscosity is higher than cSt, the thickener is likely to be unevenly dispersed in the manufacturing stage, which is not preferable for quietness and torque of the bearing.

Next, as the higher fatty acid sodium salt in the present invention, a fatty acid sodium salt having 12 to 24 carbon atoms is preferable, and sodium 12 hydroxystearate having 18 carbon atoms is particularly preferable. The compounding ratio of such sodium salt of higher fatty acid is 15 to 40% by weight.
This is because if the amount is less than 15% by weight, the dust generation reducing effect is small, and if the amount is more than 40% by weight, the grease becomes too hard to be easily filled in the bearing, and the quietness is poor.

[0013]

【Example】

Examples 1 to 3: Polyol ester having a kinematic viscosity of 80 cSt or 150 cSt at 40 ° C. and sodium 12-hydroxystearate were mixed at a ratio shown in Table 1 so that the total weight was 100%, and 0.5% was added to this mixture. Was added as an antioxidant and heated with stirring until the total amount became liquid. After cooling, it was homogenized with a three-stage roller to obtain a grease composition.

The following dust generation test was conducted on the above grease composition, and the results are shown in Table 1.

Dust generation test: 17 mg of a grease composition was sealed in a sealed rolling bearing 695 equipped with a non-contact type sealing device (nitrile rubber LB seal) on both sides, and this bearing 2
Installed on the drive shaft as a set, thrust load 1kgf,
It was operated under the conditions of 3600 rpm. At this time, dust of 0.3 μm or more generated from the set of bearings was measured.

[0016]

[Table 1]

Comparative Examples 1 and 2: Commercially available greases with known raw material names of base oil and thickener were used in Examples 1 to 1.
The same test as in Example 3 was performed, and the results are also shown in Table 1.

Comparative Examples 3 to 5: Kinematic viscosity at 40 ° C. is 1
Examples of 50 cSt polyol ester and lithium 12-hydroxystearate (11.5% by weight, 7% by weight) or 80 cSt polyol ester and sodium 12-hydroxystearate (7.5% by weight) were used as mixing ratios shown in Table 1. A grease composition was obtained in exactly the same manner as 1-3. The above dust generation test was conducted on this grease composition, and the results are also shown in Table 1.

As is clear from the test results in Table 1, Comparative Examples 1 to 4 in which the thickener is a fatty acid lithium salt or lithium soap and the thickener is a fatty acid sodium salt
In Comparative Example 5 having a blending ratio of 5% by weight or less, the amount of dust generated was 1256 to 6274, which was an extremely high value. On the other hand, the grease produced by using polyol ester oil of 80 to 150 cSt as the base oil and blending 15% by weight or more of a thickener of fatty acid sodium salt has a dust generation amount of 240 to
It showed an extremely low value of 591.

[0020]

As described above, the present invention uses, as a base oil, an ester oil having a predetermined kinematic viscosity, and limits use of a sodium salt among thickeners which are metal salts of higher fatty acids. The amount of dust generated from the bearing in which is sealed is extremely small, and even if there is no magnetic fluid seal, the clean atmosphere is not contaminated and the bearing can be used while maintaining quietness. Therefore, it is possible to reduce the number of parts of the device including the rotating portion by using such a bearing, and it is possible to reduce the size of the device and to reduce the manufacturing cost.

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Claims (1)

1. A kinematic viscosity at 40 ° C. of 50 to 200 c.
A grease for bearing encapsulation, which comprises an ester oil of St as a base oil and 15 to 40% by weight of a higher fatty acid sodium salt as a thickener.