Abstract
A common¨Crail injection system has needs of speed up of response and controllability of variable injection-rate for improving diesel fuel tail-pipe emissions. Currently a piezo-electric actuator is applied to control a needle valve, however, has some issues of small displacement and seal for fluid. Coping with this issue, two types of injection-rate controllable injectors for 160MPa diesel and 15MPa substitution fuels have been developed. Both of them have the hydro-mechanical position-feedback slots on the main needle valve and are operated by a two-port pilot valve. The lift of main needle valve is positioned linearly to the pilot valve opening by a hydro-mechanical position-feedback slot. The lift of pilot valve is controlled linearly to electric current by a tandem-arrayed Giant-Magnetostrictive-Actuator, GMA. The GMA consists of three pieces of small GMM rods, Giant-Magnetostrictive Material rods, and they are assembled in a Z-shaped cylindrical rod-holder at fun angles of 120¡ãfor eliminating bending moment. The Z-shaped holder obtains double the stretch of each GMM by connecting rods serially in one magnetic field. It stretches 50¦Ìm at 100kA/m in magnetization intensity by using rods of 30mm in length and 3.5mm in diameter. This paper expresses bond graphs analysis for optimum design of the injector and variable injection-rate results. The diesel injector with a nozzle of 6-holes¡Á0.16mm-diameter controls injection-rate of 30mm3/ms at 160MPa and the substitution fuel nozzle of 6-holes x 0.46mm does 100mm3/ms at Ps=15.8MPa within on/off lag times of 0.3ms by energizing the solenoid of 300 turns coil with inductance of 1.16mH and resistance of 1.5¦¸.