Friction Calculations and Validation Measures on an External Component Test Bench of the Piston Pin Bearing under the Influence of Greater Elastic Deformation Caused by a Hydrostatic Bearing 2021-24-0001

Increasing combustion pressure, low viscosity oils, less oil supply and the increasing stress due to downsizing of internal combustion engines (ICE) lead to higher loads within the bearing. As the mechanical and tribological loads on the piston pin bearings have a direct impact on the service life and function of the overall engine system, it is necessary to develop a robust tribological design approach. Regarding the piston pin bearing of a diesel engine, this study aims to describe the effects of different parameters on a DLC-coated piston pin within the bearing. Therefore, an external engine part test rig, which applies various forces to the connecting rod and measures the torque on a driven pin, is used to carry out validation measurements. The special feature of the test bench is the way the piston is beared. For the first experiments, the piston crown is placed against a plate (plate-bearing); later, this plate-bearing is replaced by a hydrostatic bearing. The new bearing is designed to allow deformation under reoccurring pressure by pressing the piston into an oil bath. This should approximate the combustion chamber pressure. For the first validation of the measurement results so-called run-out tests are used, which represent the torque over a speed range. Therefore, the plate-bearing is used as well as static and dynamic load. Different lubrication variants are compared for both bearings, whereby the increased elastic deformation impacts on the lubrication. A good reproducibility is shown by repeating the same measurements several times. The running-in behaviour of the bearing is also discussed. Afterwards the parameters, which have the highest influence on the friction, will be pointed out. The test bench is used to validate a multi-body simulation with a lubricating film coupling. Due to the complexity of the calculation, a very precise validation is necessary in order to be able to make reliable statements about the physical events in the piston pin bearing. Different gap widths, fine geometries, oil temperatures, lubricant properties, surface properties and the deformation of the bodies in the model are taken into account. Finally, the first calculations are analysed, a validation method for the piston pin bearing calculation including DLC coated piston pins is developed and used for an MBS calculation with a lubricating film coupling.