Engine oil consumption must be reduced because it produces particulate matter in exhaust gases and poisons the catalyst in an aftertreatment system. Oil transport upward via piston ring gaps is one of the factors for oil consumption.
It is known that piston rings rotate circumferentially during engine operation, and that oil consumption increases when the ring gaps of multiple piston rings are close to each other. Force acting on a piston ring in the circumferential direction was investigated in a past study [3], and a wave form of the force was measured against the crank angle. Furthermore, the forces were varied according to the measurement position in the circumferential direction. It means that the ring gap tends to stay where the force showed a small value. The force shows a periodic wave form against the crank angle for each cycle, and some parts of the waveform show a correlation with piston slap motion [3].
Piston motion consists of lateral motion, tilting motion and up-and-down motion. In this study, the effect of such motions on the force which rotates the piston ring was investigated respectively using newly developed rig testers. The measured results of the rig tests were compared with the force measured during engine operation, and the mechanism of the ring rotation was analyzed.
