Lithium Grease Composition Sealed in a Small Motor Bearing to Reduce Noise

Abstract

A lithium grease composition which can be sealed in a small motor bearing to reduce noise, composed of 5-20% by weight of a thickener and 95-80% by weight of a base oil, wherein said grease composition adopts lithium soap as the thickener, which is synthesized from lithium hydroxide and a higher fatty acid with 10 to 20 carbon atoms and/or a higher hydroxyfatty acid with one or more hydroxyl groups and 10 or more carbon atoms, and the base oil includes, as a main component, a polymer ester oil (A) in which 8 or more ester groups are arranged in a comb tooth form on one side of chain molecules constituted by eight or more carbon atoms which is expressed by general formula 1: (In the formula, each of R₁, R₂, R₃ and R₄ is an alkyl group, where x is an integer and x≧2, and y is an integer and y≧2.) and the base oil (40 C) has a viscosity of 25 to 80 mm²/s.

Description

TECHNICAL FIELD[0001]The present invention relates to a grease composition for motor bearings for small motors, particularly home electric appliances such as an air conditioner, motor bearings for information equipment such as a hard disk driver and the like, and more specifically to a noise reduction grease sealed in a bearing for a small motor to reduce the rotation noise of the motor.BACKGROUND ART[0002]Generally the use of greases sealed in a bearing is known. The prior art shows a grease composition in which 8 or more ester groups are arranged in a comb tooth form on one side of the chain molecules of oil composed of 8 or more carbon atoms. The grease is formed by adding a urea thickener to a base oil in which a synthetic hydrocarbon oil and a synthetic ester oil are mixed in a weight ratio of 0.65-0.75:0.35-0.25. See Japanese Patent No. 3514574 and U.S. Pat. No. 5,910,470. This grease is sealed in a ball bearing that supports a belt driven pulley placed in the vicinity of an a...

AI Technical Summary

Benefits of technology

[0005]According to the invention, a noise reducing grease composition and a sealed bearing containing the composition are provided. The bearing is desirably used for small motors particularly for home electronic appliances for example air conditioners, a motor for information equipment such as a hard disk driver and the like, and sealed in a bearing for a small motor to reduce the rotation noise of the motor. The present invention provides a grease composition composed of 5 to 20% preferably greater than 5% and less than 20% by weight of a lithium soap thickener. The thickener is synthesized from lithium hydroxide and a higher fatty acid with 10 to 20 carbon atoms or a higher hydroxyfatty acid with one or more hydroxyl groups and 10 or more carbon atoms, or both. Desirably, the lithium soap thickener accounts for about 7.5% to about 17.5% by weight of the grease composition preferably about 10% to about 15% particularly about 12% to about 13% by weight.

Problems solved by technology

Such devices makes a quick change in its rotation speed.

This lithium-soap-ester grease, however, tends to spatter and has a problem of damaging a recording medium if it is used as is.

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