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2 Journal of KONES

2 2009

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The necessity for using of valves made of light materials in camless valve timing of internal combustion engines

Zbierski K., Siczek K.

Journal of KONES

2009

Vol. 16, No. 4

521-530

The essence of the camless valve timing for combustion engine has been discussed in the article. It has been put the attention on the different criteria of distinction for such valve timings. The characteristic features of the camless electric and hydraulic valve timing has been discussed. Basing on the valve lift course the possibility of changes for values of geometrical parameters for valve timing has been explained. The performance of electric and hydraulic valve timing has been described with the help of schematic diagrams. It has been put the attention on significant differences between them. The specific, possible to generation, values of the loading valve forces have been presented. Next, the problems connecting with the increasing of the force loading valve and with the decreasing of masses for moving elements of valve timing have been discussed. The masses of valves made of steel, of TiAl alloy and of ceramic composites have been compared. It has been proven, basing on the camless magnetoelectrical valve timing case, that the valve mass influences the combustion engine speed. It was found that the use of lightweight valves instead of steel valves in the camless valve timing of combustion engines can give the decreasing of the valve mass about 50% in respect to the steel valve mass. The use of lightweight valves instead of steel valves in the camless valve timing, with the same geometry, allows to obtain the maximal engine speed which is greater about 11% in respect to the case of combustion engine with classic steel valves. Thanks to lightweight valves it is possible to decrease the pressure values ofoperating fluid in the hydraulic systems of the drives.

The control of valve timing with magnetoelectric actuators

Siczek K., Kuchar M.

Journal of KONES

2009

Vol. 16, No. 3

357-365

The new control algorithm for the valve timing in camless combustion engine is presented in the article. The magnetoelectric actuators have been used in the valve timing for analyzed popular combustion engine. Each titanium valve has been connected with the coil of actuator. Such coil can move in the magnetic field, generated in magnet circuit containing sintered Nd-Fe-B magnets, the core, pole shoes and air gaps. The movement of coil can occur when current flows in the coil winds and then electrodynamic force is generated. The nonlinear curves of generated electrodynamic force versus displacement of coil - valve assembly and vs. current in the coil have been computed using FEM method and presented in the article. The new mathematical model has been elaborated to calculate valve lift vs. coil lift for different coil currents and dynamic parameters of the coil. The values of current in coil should be controlled by the elaborated algorithm with the feedback. This algorithm has been based on tracing of position points of valve, during valve movement. The modelled course of valve lift vs. time has been first elaborated, for the needed rpm of engine. Next the first approximated current pulse train has been generated, the movement of the coil - valve assembly could be obtained. The calculated position of valve has been compared with the valve position from modelled course of valve lift vs. time. Basing on obtained difference of valve lift, the next current pulse train has been corrected in such a way, to obtain in any moment the closest position of valve to the one from modelled course. The obtained courses of valve lift vs. time for different modelled courses of valve lift vs. time and vs. rpm of engine have been presented in the article.