ppm to diesel engine oil setting the arithmetic mean roughness of the sliding member to 2 10 nm and upon converting the sommerfeld number viscosity to pa u00b7 s the speed to s u2212 1 and the load to mean hertzian stress then the lubrication conditions for use are within the range of 2 12365 u00d7 10 u2212 19 to 5 94509 u00d7 10 u2212 19 application_number US 201113993136 A description in the following the embodiments of the present invention are explained by referring to the attached drawings as the embodiments of the present invention in a bearing structure for example one of the sliding members is a shaft and the peripheral surface the sliding surface of said shaft was coated by titanium carbon nitride tialn which is a titanium nitride based material according to the physical vapor deposition pvd technique the arithmetic mean roughness of the shaft surface was made 5 0 nm on the other hand as the other sliding member a bearing at least inner race was made from high carbon chromium bearing steel suj2 as a lubricant diesel engine oil of japanese automotive standards organization u201c dh 2 u201d to which molybdenum dithiocarbamate modtc with molybdenum in the amount of 700 ppm had been added was used such bearing was used under the sliding conditions mixed lubricating region of the sommerfeld number of 2 12365 u00d7 10 u2212 19 here the sommerfeld number.