Ferreira, D., Howell, T., and Jo, P., "Hydraulic Lash Adjuster Compatible Engine Brake," SAE Int. J. Engines 9(4):2286-2291, 2016, doi:10.4271/2016-01-8063.
Current heavy duty diesel valvetrains are not able to utilize hydraulic lash adjusters (HLA) in conjunction with an engine brake. During a braking event the engine brake introduces substantial lash into the vehicle valvetrain. The HLA reacts by pumping out to take up the lash encountered during braking, thereby preventing the valves from properly seating at the end of the cycle. Jacobs Vehicle Systems has developed a new mechanism to allow the inclusion of an engine brake into a valvetrain equipped with hydraulic lash adjusters. The fulcrum system maintains a load on the hydraulic lash adjuster during engine brake operation preventing the HLA from extending. HLA are appealing to engine manufacturers because they allow for simpler manufacturing, less maintenance, reduced NVH and valve motion enhancements. This paper describes the design, simulation and testing of the lashless valvetrain with engine brake including the next steps in the development of the valvetrain.