This content is not included in your SAE MOBILUS subscription, or you are not logged in.
Camless Variable Valve Actuation Designs with Two-Spring Pendulum and Electrohydraulic Latching
ISSN: 0148-7191, e-ISSN: 2688-3627
Published April 16, 2007 by SAE International in United States
Annotation ability available
Camless variable valve actuation (VVA) technologies have been known for improving fuel economy, reducing emissions, and enhancing engine performance. A family of VVA designs from LGD Technology, LLC (called LGD-VVA) has been configured to include a two-spring actuation, a bypass passage, and an electrohydraulic latch-release mechanism. The two-spring pendulum system provides efficient conversion between the moving mass kinetic energy and the spring potential energy and is less influenced, than a hydraulic actuation means, by operating conditions such as temperature. The electrohydraulic mechanism is used primarily for latch-release function, and it is also flexible enough in its design to offer different levels of energy input to overcome engine cylinder pressure, which can be substantial for exhaust valves.
The LGD-VVA designs offer better lift variability, higher power density, and lower electrical demand relative to electromagnetic VVA systems. They include three types of lift-control: fixed-lift, two-step-lift, and continuously-variable-lift. The engine valve release and actuation is triggered by one simple switch action of a four-way directional valve or its equivalent, and the engine valve completes the rest of the stroke, including soft-seating, without active control.
The combination of the two-spring pendulum and bypass design is able to reduce fluid flow during most of the engine valve travel, thus achieving actuator power consumption comparable to that of a conventional cam system. At 8-mm valve lift, up to 64% of the kinetic energy is converted to the spring potential energy before the snubber is engaged, and the energy conversion continues even after the snubber is engaged. The combination makes it possible to achieve a “short-tailed” soft-seating without the need for closed-loop control.
A numerical model of the designs is developed, and the simulation validates some benefits of the LGD-VVA philosophy.
CitationLou, Z., "Camless Variable Valve Actuation Designs with Two-Spring Pendulum and Electrohydraulic Latching," SAE Technical Paper 2007-01-1295, 2007, https://doi.org/10.4271/2007-01-1295.
- Brustle C Schwarzenthal D 2001 “VarioCam Plus - a highlight of the Porsche 911 turbo engine” SAE paper 2001-01-0245
- Duesmann M 2002 “Innovative valve train systems,” Spectrum: Technology Highlights and R&D Activities at FEV 19 3 February 2002
- Tai C Tsao TC Schorn NA Levin MB 2002 “Increasing torque output from a turbodiesel with camless valvetrain,” SAE Paper 2002-01-1108
- Tai C Tsao TC Levin MB Barta G Schechter MM 2003 “Using camless valvetrain for air hybrid optimization,” SAE Paper 2003-01-0038
- Lang O Salber W Hahn J Pischinger S Hortmann K Bucker C 2005 “Thermodynamical and mechanical approach towards a variable valve train for the controlled auto ignition combustion process,” SAE Paper 2005-01-0762
- FEV Spectrum 19 February 2002
- Turner CW Babbitt GR Balton CS Raimao MA Giordano DD 2004 “Design and control of a two-stage electro-hydraulic valve actuation system,” SAE Paper 2004-01-1265
- Milovanovic N Blundell D Gedge S Turner J 2005 “Cam profile switching (CPS) and phasing strategy vs fully variable valve train (FVVT) strategy for transitions between spark ignition and controlled auto ignition modes,” SAE Paper 2005-01-0766
- Denger D Mischker K 2005 “The electro-hydraulic valvetrain system EHVS - system and potential,” SAE Paper 2005-01-0774
- Schecter MM Levin MB 1996 “Camless engine,” SAE Paper 960581
- Warburton A Fleming L Scott J Butler N Wygnanski W 2005 “Intelligent Valve Actuation (IVA) System for gasoline and diesel engines,” SAE 2005-01-0772