The plane bearing is made up of a row of steel balls (with a retainer), a shaft ring (fitted with the shaft) and a seat ring (fitted with the shaft hole). The balls rotate between the shaft and the seat. It can only bear axial load in one direction, but not radial load. Because the axial load is evenly distributed on each ball, the load capacity is larger. But when working, the temperature rise is larger and the allowable limit speed is lower. 2. The advantage of plane bearing is that the choice of high-precision cylindrical roller (needle roller) increases the contact length, so that the bearing can obtain high load capacity and high stiffness in a small space; Another advantage is that if adjacent parts surface suitable for raceway surface can be eliminated gasket, can make the design compact, DF plane needle roller bearings and flat cylindrical roller bearings using needle roller and cylindrical roller cylinder surface for the modification surface, can reduce the edge stress, improve the service life. 3. The plane bearing plays the role of shock absorption and movable link of the car body on the car to avoid direct friction between the shafts.