Sensitivity Analysis of the Geometrical Dimensions of the Crankpin Bearing on the Tribological Property of an Engine

摘要

Under high-speed working conditions of an engine, the lubrication and tribological performance (LTP) of the crankpin bearing (CB) are strongly influenced by the oil film pressure (p) and asperity contact in the mixed lubrication regime (MLR) of CB, while these parameters mainly depend on the CB's geometrical dimensions including the bearing radius (r(b)), bearing width (B), surface roughness (sigma), gap between crankpin and bearing (c), and crankpin speed (omega). To analyze the sensitivity of the dynamic parameters of the r(b), B, sigma, c, and omega on the CB's LTP, a hybrid model of the piston-rod-crank dynamic and CB lubrication is proposed to establish the dynamic equations of the CB. An algorithm program written in MATLAB software is then applied to solve the dynamic equations. The effect of the dynamic parameters of the r(b), B, sigma, c, and omega on the CB's LTP is simulated and evaluated via the indexes of the p, asperity contact force, friction force, and friction coefficient. The research results show that all the parameters of r(b), B, sigma, c, and omega of the CB greatly affect the CB's LTP. To improve the CB's LTP, the r(b), B, and sigma should be slightly reduced whereas the c needs to be increased, especially, the values of 15 <= r(b) <= 20 mm,10 <= B <= 15mm, 2 <= sigma <= 4 mu m, and 15 <= c <= 20 mu m should be used to optimize the CB's LTP. Additionally, the engine speed should be maintained at 2000 rpm to improve the CB's LTP. The reduction of the geometric dimensions and the increase of the engine's power is being the development trend of the engine manufacturers; therefore, the research not only elucidates the influence of the CB parameters on the CB's LTP but also provides an optimal parameter range of the CB to further improve the LTP, fuel economy, and friction power loss, and durability of the engine.