Experimental and Analytical Evaluation of Contoured Thrust Bearings

Incessant demands to improve performance in automotive engines have popularized the use of contoured sector thrust bearings. This type of bearing has the mechanical ability generate a complete oil film that in turn can support high axial crankshaft loads and can reduce frictional drag torque. As a means of evaluating thrust bearing performance prior to production, we have designed and constructed an experimental apparatus. This experimental apparatus measures load, speed, torque, film temperature, and cross-film asperity contact resistance over a wide range of operating conditions representative in a real engine/ transmission combination. Concurrently, we have developed an analytical means of predicting oil film thickness, torque, and load using a finite element formulation of the Reynolds equation coupled with a mass-conserving cavitation algorithm. This allows for routine handling of arbitrary bearing profiles throughout the thrust pad area as well as ease in specification of arbitrary pressure and density boundary conditions along the thrust pad boundary. Results are presented for a sample ramp-flat thrust bearing at three fixed rotational speeds. Predicted frictional torque values are found to compare very well with experimentally-measured results, and computed film thickness correlates well with measured asperity resistance. In addition, a minimum film thickness value at which seizure occurs is also determined.