Grease composition and grease-packed rolling bearing

摘要

A grease composition for a rolling bearing for a motor to support a rotor of the motor, containing a pentaerythritol ester base oil with a kinematic viscosity at 40° C. of 20 to 55 mm2/s; 7 to 13 mass % of a diurea thickener represented by formula (A) where each R group is defined; and a rust inhibitor mixture selected from the group consisting of polyol ester type rust inhibitors and organic sulfonate type rust inhibitors. The grease composition can prevent a peculiar noise from being produced at low temperatures, satisfy the low torque performance over a wide temperature range, extend the bearing lubrication life even under the circumstances of high temperature, and exhibit excellent rust inhibiting effect on varnish.;

主权项

1. A grease composition for a rolling bearing for a motor to support a rotor of the motor, comprising a thickener, a base oil and a rust inhibitor, wherein:
the thickener is a diurea compound represented by formula (A), which is contained in an amount of 7 to 13 mass % in the composition; wherein R2 is a bivalent aromatic hydrocarbon group having 6 to 15 carbon atoms; and R1 and R3 each represents a cyclohexyl group or a straight-chain or branched alkyl group having 16 to 20 carbon atoms, with the ratio of the number of moles of the cyclohexyl group to the total number of moles of the cyclohexyl group and the straight-chain or branched alkyl group having 16 to 20 carbon atoms, as expressed by [((the number of cyclohexyl groups)/(the number of cyclohexyl groups + the number of straight-chain or branched C16-20 alkyl groups))×100] being 60 to 90 mol %; the base oil is a pentaerythritol ester oil having a kinematic viscosity at 40° C. of 20 to 55 mm2/s; and the rust inhibitor is a mixture of sorbitan trioleate and zinc sulfonate, and the total content of the rust inhibitor is 2 to 5 mass % based on the total mass of the grease composition with the minimum content of sorbitan trioleate being 1 mass % and the minimum content of zinc sulfonate being 1 mass %.