Aktiv ventilstyrning

Sammanfattning

To achieve an optimal combustion, an even air/fuel ratio in the combustion

chamber is required. An optimal combustion leads to reduced amount of

emissions due to a more complete combustion, which is an important matter

because of the sharpened environmental laws. This can be attained, among

other things, by applying entirely variable cam times. To optimize the

engines efficiency and its emissions at all workloads and speeds, an active

valve control can be applied. This means that the intake and exhaust-valves

can be opened and closed at any time, independent of the crankshaft

position.

The aim for this project was to design a prototype where a valve thought for

a camless engine can be controlled. The traditional valve was used and the

importance was to study and develop control system and damping of this

part.

The work resulted in an electromagnetic system where two electromagnets

together operates and drives a permanent magnet, which is in direct

connection to the valve. The Permanent magnet and thus the valve is

attracted and repelled at the same time by the electromagnets, which leads

to the valve being either opened or closed. To accomplish this, a control

unit was prepared to generate different operating conditions. The movement

and damping of the valve is enabled trough an H-bridge, which is an

electronic circuit that allows the change in current direction, to make it

possible to achieve the quick polarity switch that is desired for the

electromagnets.

The results of the measurements were close to the target set. Apart from the

desired frequency, we could find that damping trough polarity change was

possible and also that a stabile system could be achieved with reasonable

power consumption.