GREASE COMPOSITION AND ELECTRIC POWER STEERING APPARATUS

摘要

PROBLEM TO BE SOLVED: To provide a grease composition excellent in low friction properties and in wear resistance and to provide an electric power steering apparatus less prone to cause friction and wear in a speed reduction gear mechanism and excellent in gear efficiency. SOLUTION: The grease composition is used for the lubrication between gear teeth of a worm 12 and gear teeth of a worm wheel 11 in an electric power steering apparatus. The grease composition comprises a base oil, a lithium soap, a wax having a dropping point of not lower than 73°C and not higher than 105°C and a soap of a metal other than lithium wherein the product of an acid number (mgKOH/g) of the wax and the wax content (mass%) is not less than 31.6 and not more than 320; the standard electrode potential of the metal at 25°C is -2.37 V or less; and the content of the soap of the metal other than lithium is such an amount that the concentration of the metal which the soap comprises based on the total of the grease composition is a predetermined amount. COPYRIGHT: (C)2007,JPO&INPIT