Oil pressure, the most fundamental to engine's performance and longevity, is not only critical to ensure that the engine components are properly lubricated, cooled, and protected against wear and contamination, but also ultimately contributing to reliable engine performance. Due to several factors of engine such as, rotational fluctuation, aeration, functioning of hydraulic components there are fluctuations in oil pressure. In engines, with a crank-mounted fixed displacement oil pump (FDOP), these inherited pressure fluctuations cannot be eliminated completely.
However, it is very necessary to control the abnormal oil pressure fluctuation because abnormal pressure fluctuation may lead to malfunction of hydraulic component functioning like variable valve timing (VVT), hydraulic lash adjuster (HLA) and dynamic chain tensioner which can further cause serious issues like excessive or sudden load drops, unstable engine performance, valve train noise, improper valve lift operation etc.
In this paper, engine oil pressure fluctuation in HLA gallery is studied, and its impact was assessed on valve train system. Root cause analysis (RCA) was conducted using high frequency oil pressure measurement to understand the various reasons impacting high oil pressure fluctuations inside HLA galleries. Time domain analysis was performed to understand oil pressure fluctuations with respect to VVT cam phasing. Angle domain analysis was performed to assess the impact of oil pressure fluctuations on valve train behavior. Further findings from this study aim to enhance the understanding of impact of VVT cam phasing in oil pressure fluctuations.