Valve control arrangement

Claim 1

A valve control arrangement for controlling closing and opening time of a valve actuatable by a valve control cam of a cam shaft via an axially displaceable valve plunger, in a displacement piston-internal combustion engine, the valve control arrangement comprising means forming a stroke transmitting chamber between the valve control cam and the valve plunger and arranged to be filled with a working medium; means forming a controllable opening for supplying the pressure medium into said stroke transmitting chamber and withdrawing the pressure medium from the latter so as to change an axial dimension of said stroke transmitting chamber between the valve control cam and the valve plunger; means for controlling said opening so that a stroke of the valve control cam which acts with beginning of a valve opening adjusts said opening to an unloading cross-section so that to a closing point of time of the valve, a partial quantity of the pressure medium can flow out of said stroke transmitting chamber, and so that over a time of valve actuation said opening is completely closed within a first operational region and is only partially closed to a partial unloading cross-section of said opening during a second operational region said controlling means including an electromagnetic control valve which has a throughflow opening as said opening and being formed so that the adjustment of the unloading cross-section of said opening is performed only in idle running region and in a lower partial load region of the internal combustion engine, said control valve having a valve seat which surrounds said throughflow opening, a valve needle which cooperates with said valve seat for adjusting the unloading cross-section, and an electromagnet with an armature connected with said valve needle, said control valve also having a first return spring which engages said valve needle and holds said valve needle in a valve opening position in which said valve needle releases a full cross-section of said throughflow opening when said electromagnet is not excited, and a second return spring which is connected with said valve needle and acts after a predetermined displacement path of said valve needle from the valve opening position, said second return spring and said first return spring having identical acting directions, and the displacement path of said valve needle until said second return spring is actuated being selected so that before its reaction said throughflow opening is adjusted to the unloading cross-section and a partial excitement is provided in said electromagnet so as to overcome a return force of said first return spring.