A Small Direct Electromagnetic Valve Prototype Internal Combustion Engine

The problem addressed by this Phase I research project is high emissions from small reciprocating internal combustion engines, particularly in terms of frequent operation at non-ideal revolutions per minute (RPM) and torque loading as well as under cold-start conditions. There is an opportunity to substantially reduce emissions through the use of digitally controlled electric variable valve timing (EVVT). SBE has created digitally controlled camless valves driven by electromagnets. The core of the SBE design is described in a patent by project principal Bergstrom (U.S. Patent # 6,249,418, ¿System for control of an electromagnetic actuator¿). This valve has been built and is being tested at the automotive scale. Building on this physical and modeling experience, SBE currently has a simplified computer-modeled EVVT design for use in small, four-stroke overhead valve engines. Phase I objectives include completion of the mechanical design, prototype fabrication, and the embedded digital signal processor control software, as well as preliminary testing and control optimization of two EVVT systems retrofitted to a one-cylinder engine. Phase II objectives will include testing and optimization in a university laboratory (University of California¿Davis, or Alfred College). Areas of commercial application include use in lawn, utility, and off-road vehicles, as well as in hybrid automotive engines. Performance and anti-pollution advantages of VVT are being marketed currently by Nissan and BMW, and soon by Ford and others; however, VVT is being marketed with mechanical rather than electric implementation. Using EVVT in small engines achieves simplicity and economy by exploiting two features of small engines that control valve actuator design: (1) a lower maximum RPM requirement; and (2) more room for the valve actuator. SBE¿s throttleless design, with digital control of spark and fuel flow, including feedback from an exhaust oxygen sensor, leads to operation with improved efficiency and torque, as well as lowered emissions. Peri-stroke valve position control might allow for dynamic control of inlet manifold pressure instabilities¿the bane of combustion stability. Savings from elimination of the carburetor and camshaft assemblies partially offset actuator and controller costs, which may lead to a competitive economic package. Finally, because valve timing is now completely controlled, the engine can be started easily with compression relief and operated very efficiently when cold, or operating off-design. Fuel flow is actively controlled using feedback from an exhaust oxygen sensor, rather than passively by carburetion. In hybrid car engines, for example, the electric engine valves improve performance and engineering options by enabling accurate, stroke-by-stroke control of fuel, exhaust gas recirculation, and engine braking. They also dynamically permit quiet 4-, 8-, or 12-cycle operation for efficiency at reduced power.