US Patent 7296933 Tapered roller bearing

A tapered roller bearing 1 comprises an inner ring 2, an outer ring 3, a plurality of tapered rollers 4 rollably disposed between the inner and outer rings, and a cage 5 for holding the tapered rollers at predetermined circumferential intervals. In this tapered roller bearing, the roller coefficient {y=(the number of rollers ×mean roller diameter)/(π×PCD)} is greater than 0.94. At least one of the members, i.e., the outer ring, inner ring, and rolling elements, has a nitrogen rich layer. The grain size number of austenite crystal grains in the nitrogen rich layer exceeds number 10.