Lost-Motion VVA Systems for Enabling Next Generation Diesel Engine Efficiency and After-Treatment Optimization



SAE 2010 World Congress & Exhibition
Authors Abstract
The primary variable valve actuation strategies for diesel engines are variable late or early intake valve closing for control of effective compression ratio for Miller cycle and part-time HCCI, PCCI, or LTC; variable early exhaust valve opening for exhaust temperature control for after-treatment regeneration and improved engine transient response; on/off control of intake pre-bump and/or exhaust post-bump for IEGR and control of residual fraction; and on/off control of compression release and brake gas recirculation events for engine braking. Lost-motion hydraulic VVA is well suited to diesel engines due to the capability of on-off control of secondary events for IEGR and engine braking, high load capacity for early exhaust opening and engine braking, and inherent protection against valve-to-piston contact.
Production requirements for VVA systems include proven reliability/durability, cost effectiveness, compact packaging, cold start capability, acceptable valve seating velocity over the full operating range, and convenient lash setting. Several production-intent lost-motion VVA systems are described for variable late intake valve closing and IEGR intake pre-bump and for early exhaust valve opening and engine braking. Features include a lost-motion cam profile, a collapsing tappet located either between the rocker and the bridge or between the push-tube and the rocker, and a hydraulic circuit with a high-speed solenoid valve. Partial main event lift is provided with the tappet collapsed for failsafe operation and cold start. A valve catch to control valve seating during early intake valve closing is incorporated in the tappet assembly. A valve control unit, communicating with the fuel control, actuates the high-speed solenoid valves. The variable valve lift capabilities of several VVA systems and the valve-train parasitic loss over the range of operation are discussed, showing both simulation and test.
Meta TagsDetails
Schwoerer, J., Kumar, K., Ruggiero, B., and Swanbon, B., "Lost-Motion VVA Systems for Enabling Next Generation Diesel Engine Efficiency and After-Treatment Optimization," SAE Technical Paper 2010-01-1189, 2010, https://doi.org/10.4271/2010-01-1189.
Additional Details
Apr 12, 2010
Product Code
Content Type
Technical Paper