Patent ID: 8039423

Claim:
A lubricant composition having a mixing consistency (at 25° C.) adjusted to range from 265 to 475, for noise reduction of a speed reduction gear when filled into an engaged portion of a small gear and a large gear of the speed reduction gear, the lubricant composition consisting essentially of: a lubricating base oil; a thickener that is a calcium sulfonate-based thickener comprised of calcium sulfonate and that is mixed into the lubricating base oil to prevent oil separation; and buffer particles that are dispersed within the lubricating base oil so that the lubricant composition has the mixing consistency (at 25° C.) adjusted to range from 265 to 475, that have an average particle diameter, D 1 , ranging from 100 μm to 200 μm, and that are made of soft resin selected from the group consisting of polyolefin resin, polyamide resin, polyester resin, polyurethane resin, polyacetal resin, polyphenylene oxide resin, polyimide resin, fluororesin and thermosetting urethane resin, for use when one of the small gear and the large gear is made of a resin and another of the small gear and the large gear is made of a metal, in an amount of from 20 to 300 parts by weight, based on 100 parts by weight of a total amount of the lubricating base oil and the calcium sulfonate-based thickener.