Yihui Qiu

Design and experimental implementation of an electromagnetic engine valve drive

In conventional internal combustion engines, engine valve displacements are fixed relative to crankshaft position. If these valves were actuated as a variable function of crankshaft angle, significant improvements in fuel economy could be achieved. To this end, a new type of electromagnetic valve drive system (EMVD) for internal combustion engines was more recently proposed. This EMVD incorporates a disk cam with a very desirable nonlinear profile which that functions as a nonlinear mechanical transformer. Modeling and simulation results showed significant advantages of this EMVD over previously designed electromagnetic engine valve drives. In this articles, we describe an experimental implementation of the proposed EMVD, which was developed to confirm these benefits. The EMVD apparatus was designed, constructed, and integrated into a computer-controlled experimental test stand. The experimental results confirm the benefits of using a nonlinear mechanical transformer in a motordriven engine-valve spring system, as seen in the small average power consumption and low valve seating velocity. In addition, a valve transition time sufficient for 6000-rpm engine operation was achieved. The results also suggest ways to improve the EMVD apparatus in the future.

Design and experimental evaluation of an electromechanical engine valve drive

In conventional internal combustion (IC) engines, engine valve timing is fixed with respect to crankshaft angle. Flexibly controlled valve timing offers significant improvements in fuel efficiency, engine performance and emissions. One way to achieve variable valve timing (VVT) is by using an electromechanical valve drive (EMVD). In this paper, we describe the design and experimental evaluation of a new EMVD comprising an electric motor coupled by a nonlinear mechanical transformer to a resonant valve-spring system. Experimental results demonstrate that a 3.3 ms transition time adequate for 6 krpm engine speed, reasonable power consumption, and low valve seating velocity are obtained with the design.

Optimal cam design and system control for an electromechanical engine valve drive

An electromechanical valve drive system using a cam-based mechanical transformer has been proposed to achieve variable valve timing in internal combustion engines. This technique promises substantial improvements in fuel economy and emissions. However, there are several challenges to transform this concept into an attractive commercial product, especially achieving acceptable power consumption and actuator size. In this paper, significant reduction in power consumption, torque requirement, and transition time are achieved. These improvements are based on an effective nonlinear system model, optimized design of the cam — a key system component — and exploration of different control strategies to maximize performance.