Kajiki, Y., Takata, H., Ashihara, K., Honda, A. et al., "Friction Reduction Effect of the New Concept Bearing with Partial Twin Grooves in Cold Condition," SAE Technical Paper 2015-01-2038, 2015, doi:10.4271/2015-01-2038.
Engine friction reduction is an effective means to improve fuel consumption. Fluid friction reduction of main bearing is examined for engine friction reduction in cold condition. As one of the examinations, it was focused on low temperature of lubricating oil in the early stage during engine cold start. In hydrodynamic lubrication, the oil film temperature is maintained by balance between heat generation and heat transfer. The heat generation is generated by shear of lubricating oil. The factors of the heat transfer, the following elements are considered as follows, A) The heat transfer to a crank shaft, B) The heat transfer to a bearing, C) The heat transfer by convection. If the heat generation is constant, oil film temperature is increased by reduction of heat transfer. It is considered that the reduction of oil leakage and reduction of the heat transfer by convection is equivalent. Therefore, reduction of oil leakage is an effective means for the acceleration of temperature rise of lubricating oil. The new bearing with Partial Twin Grooves were developed to reduce of oil leakage. The new bearing decreases approximately 8% in the amount of oil leakage compared with the conventional bearing. A rise of lubricating oil temperature and FMEP (Friction Mean Effective Pressure) reduction effect of this bearing was investigated by engine bench test in cold condition. The temperature rise rate of lubricating oil by the new bearing was improved 10% compared with the conventional bearing in JC08 cold mode. The FMEP reduction of this bearing exhibits 2.0%. If improvement effect of fuel consumption in JC08 cold mode was recalculated from the FMEP reduction effect, this value corresponds to 0.14% approximately.