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Control of internal combustion engines depends on reduced idle speed and stabilized idling to improve fuel consumption.. Using a valve (ISC/V) to adjust air intake at idling, various idle speed control techniques have been proposed to improve response to variations in the target idle speed due to disturbance and to enhance speed control stability. Many conventional idle speed control systems utilize P and I control. They cannot compensate for the phase difference caused by the intake air volume between the throttle and intake valves. This leads to poor response to variations in the target idle speed and unsatisfactory control accuracy, that is, problems in preventing engine stalling and maintaining idle speed stability. To solve these problems, an idle speed control system based on fuzzy control(1)* theory is proposed. However, it is impossible to determine the control constant (membership function) theoretically.

This paper describes a new variable valve system that enables continuous control of valve events, i.e. time periods when the valve is open. In this system, valve events are controlled by varying the camshaft angular speed by means of an offset between the center of the camshaft and that of the medium member that transfers crankshaft torque to the camshaft. The medium member, a rotating disk, has a drive pin to enable the transfer of torque. The system has a mechanism that produces an offset between the center of the rotating disk and that of the camshaft as well as an actuator that drives the mechanism. This makes it possible to develop a compact system that can be installed in existing DOHC direct-acting valve train engines without making any major cylinder head modifications.