Experimental Research on a Three-Dimensional Journal Orbit of a Crankshaft Bearing for an Internal Combustion Engine

The current experimental researches on the orbit of a journal center of a crankshaft bearing for an internal combustion engine were usually focused on the 2D movement locus of a crankshaft journal center in the cross section of the bearing. However, in the actual operation of an internal combustion engine, there exists the movement of a crankshaft journal along the bearing axis under the effect of various factors, such as the crankshaft deformation acted by load. Obviously the tribological performance of a crankshaft bearing is affected inevitably by the movement of the crankshaft journal along the bearing axis. In this paper, a four-stroke four-cylinder internal combustion engine was taken as the studying object, the 3D orbit (that includes the movement in the cross section of the bearing and the movement along the bearing axis) of the journal center of the crankshaft bearing for an internal combustion engine was measured under a number of operating conditions on the test bench of an internal combustion engine. The position of the journal in the crankshaft bearing was obtained by the measurement using eddy current gap sensors and the data post-process. The results show that there exists the movement of the crankshaft journal along the axial direction in the bearing for an internal combustion engine. The actual orbit of the journal center of the crankshaft bearing for an internal combustion engine is a 3D spatial curve. The orbit of the journal center of the crankshaft bearing in one operating cycle of an internal combustion engine is not a closed curve. There is relatively a large movement of the journal along the axial direction of the crankshaft bearing, and the numerical value of the movement is greater than the radial clearance of the bearing. The greater the rotational speed of the internal combustion engine, the larger the amount of axial movement of the journal. The periodic variation exists in the axial movement of the bearing journal in one operating cycle of the internal combustion engine at low engine speed, and the varying periodicity equals the number of engine cylinders. There is no obvious varying rule of the axial movement of the bearing journal in one operating cycle of the internal combustion engine at high engine speed.