1990-02-01

Performance of Hydraulic Lash Adjusters with Regard to Valve Train Noise at Cold Starts and Short Term Start 900451

-The Hydraulic Valve Lash Compensation is a well known option to reduce the noise emission of a passenger car engine, especially at low engine speeds. Furthermore, the use of Hydraulic Valve Lash Adjusters reduces the costs of engine assembly and maintenance, and has thermodynamical advantages.Under some engine operating conditions the function of Hydraulic Valve Lash Adjusting Elements can be problematic, which, however, can be covered by an improved element design. For instance, a low oil temperature level at engine start-up can lead to the entrance of air into the high pressure chamber, which will cause tappet noise.A number of short term engine runs, each of which, followed by a short engine stand still time, can produce tappet noise as well.The “INA Labyrinth Design” improves the potential of the hydraulic element against tappet noise without a significant increase in cost. The main feature of this design is an improved internal flow direction.This paper explains the effects of the improved hydraulic element design on valve train noise at engine cold start and frequent engine start-stops, based on theoretical derivations, and supported by experimental data.

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