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The Flex Engine
Since the first internal combustion engine was built the design has required a rotating camshaft to mechanically actuate the valve timing. The problem with actuating the valves on an engine with a camshaft is there are many added losses. Turning the camshaft consumes energy from the crankshaft which takes away from the overall power output; also the springs used to close the valves create a large amount of parasitic losses which take away from the engine performance. Some types of camshafts use a rocker arm assembly that requires many extra parts and adds a considerable amount of weight to the engine. Clearly, mechanical valve timing that uses a rotating camshaft has serious flaws; a new design that gets rid of the camshaft and its accessories could revolutionize the internal combustion engine. There are many companies competing to invent camless valve timing for engines, and all of which are at the basic R&D and prototyping stage. There are no camless four stroke engines being produced and sold on the market today. The objective of this project is to enter the camless actuation race and create a camless valve actuator that is driven by the forces from a piezoelectric crystal. Piezoelectric crystals expand when high voltage is applied to them. The expansion displacement is minimal, but the forces produced are impressive, making it undoubtedly possible to actuate the valves of an engine. Designing a new valve actuator that does not use a camshaft is greatly beneficial for many reasons. By eliminating the camshaft and the associated components, the engine design will be less complex, the overall timing components on the engine will weigh less, and the removed spring will reduce parasitic loss. Utilizing piezoelectric crystals and an electronic controller to actuate the valves and control the timing has the potential to increase the engine efficiency up to 20%, increase the potential horsepower up to 20%, and reduce exhaust emissions up to 50%. This technology has the potential to change the industry, and this project summarizes how the Cal Maritime senior capstone Flex Engine team is attempting to break into the camless internal combustion engine market.
A project submitted to the Department of Mechanical Engineering in partial fulfillment of the requirements for the B.S. degree. Department of Mechanical Engineering ME 494