Design and analysis of new, quick-response, latching electromagnetic linear actuators.

摘要

The traditional valvetrain in the combustion engine is the mechanically driven camshaft system. It can provide one fixed valve timing determined by the shape of cams and engine crank angle, and the shape of cams is designed in view of the tradeoff among fuel efficiency, emissions, and engine torque and etc. This optimization of the shape of cams, however, is efficient at very short range of engine operation. Therefore, variable valve timing (VVT) is highly required to achieve the significant improvement in the fuel economy, lower emissions and better torque output.; To provide the variable valve timing to the combustion engine, several new devices using mechanical, electro-hydraulic, and electromagnetic principle have been studied and proposed in the past years. One device, which simple and provides great freedom in valve timing, is the double solenoid actuator. However, solenoid actuator of this type can provide the most flexible valve timing but have significant drawbacks such as a high current draw during start-up, and a continuous current necessary to latch the valve. These drawbacks result in poor power efficiency in valve operation.; In this dissertation, new electromagnetic engine valve actuators are introduced. To overcome the problems that double solenoid type of actuators has, permanent magnets are employed in proposed actuators. The new actuators introduced in following chapters are classified into two types. One is permanent magnet-nonmoving type and the other is permanent magnet-moving type. The performance and characteristics of proposed actuators are compared, and the advantages of proposed actuators over conventional double-solenoid actuator are studied.; Finite element (FE) analysis is performed to confirm their performance and characteristics. Several shortcomings in previous researches using the lumped parameter models to simulate electromagnetic engine valve system were found: the eddy current effects were not included, the nonlinear property of material was oversimplified, and the flux leakage to the air was neglected. The FE models in this dissertation dealt successfully with these shortcomings and presented more accurate simulation results. The results of simulations of the proposed actuator showed improvement in performance and a great possibility of practical employment.