Calculation of Oil Film Thickness on Bearing Raceway Grooves by Measuring Raceway Outer Ring Temperature 2021-01-0342
As electric powertrain for electric vehicles (EVs) and hybrid vehicles (HVs) are becoming more efficient and smaller, rolling bearings for these vehicles should be capable of operating at higher speeds than those for internal combustion engines (ICEs). One key factor in predict fatigue endurance of such bearings is the oil film thickness on the bearing raceway grooves. Direct measurement of the oil film in operating machines is virtually unfeasible, while calculation of the oil film requires the input of precise temperature variation around the film.
In this study, the oil film thickness on the bearing raceway grooves was calculated while in high-speed rotation by: (1) measuring the temperature profile of the bearing raceway outer ring; (2) calculating the temperature of the raceway groove using the basic formula for heat transfer; and (3) conducting an Elasto-Hydrodynamic Lubrication (EHL) analysis based on the temperature calculated in (2).
From the calculation results, the oil film thickness on the raceway grooves was found to be 0.3 μm under typical operating condition of the bearing. A comparison with other experimental data, determined that this oil film thickness value was appropriate.