The Role of the Main Motion Drags in Middle-Class Passenger Car Drive System Development

The article analyses the significance of the four main resistances (drags) existing during the straight-line motion of a car, arising from rolling, longitudinal aerodynamics, road longitudinal inclination (grade), and inertia of the body and rotating parts. Their shares in the total resistance and the sensitivity of the resistance power to changes in the main parameters of the relationships that determine the said four resistance (drag) components were analysed. The method of analytical study of the problem was chosen. The applied method of relative sensitivity analysis was presented. It was considered in relation to the total resistance power, examining the impact of changes in individual drag components and in the selected parameters that determined their values. Formulas defining the relationships for the criteria quantities have been presented. Test conditions for constant speed and unsteady accelerated motion in the longitudinal direction are described. An example data set assumed to represent a middle-class passenger car with an internal combustion engine was presented. Results of calculations of the values of quantities and criteria functions for constant speed motion and straight-line accelerated motion were presented. The general conclusions were drawn. The consequences of the analyses for the vehicles with hybrid and electric drives were discussed.