Method of variable valve timing in an internal combustion engine
View Patent ↗A method of variable valve timing in an internal combustion engine in which the valve opening and closing timing of the actuated gas exchange valves of the internal combustion engine can be varied as a function of engine speed by adjusting means for adjusting at least one camshaft relative to a crankshaft, said internal combustion engine comprising hydraulic valve lash adjusters for adjusting a valve lash of the gas exchange valves, said lash adjusters being configured at least on one of an inlet side and an outlet side as idle stroke elements which, when actuated, at first produce an engine speed-dependent idle stroke and to provide a method of variable valve timing for internal combustion engines comprising a camshaft adjustment and a hydraulic valve adjustment with an idle stroke function that guarantees favorable valve timing in all operational situations of the internal combustion engine and, at the same time, improves the thermodynamic exploitation of such internal combustion engines, at each adjustment of the at least one camshaft, the respective idle stroke of the valve lash adjusters is taken into account.
1. A method of variable valve timing in an internal combustion engine in which a valve opening and closing timing of actuated gas exchange valves of the internal combustion engine can be varied as a function of engine speed by adjusting means for adjusting at least one camshaft relative to a crankshaft, said internal combustion engine comprising hydraulic valve lash adjusters for adjusting a valve lash of the gas exchange valves, said lash adjusters being configured at least on one of an inlet side and an outlet side as idle stroke elements which, when actuated, at first produce an engine speed-dependent idle stroke wherein, at each adjustment of the at least one camshaft, a respective idle stroke of the valve lash adjusters is taken into account.
2. A method of claim 1 , wherein in an internal combustion engine comprising two camshafts through which an inlet valve timing and an outlet valve timing of the gas exchange valves can be set independently of one another and in which the idle stroke of the idle stroke elements is designed for a maximum engine speed, through a resetting of the camshaft adjustment during idle running, the valve overlap does not fall below a defined minimum valve overlap value during idle running.
3. A method of claim 2 , wherein the camshaft actuating the inlet valves is reset in direction of an advanced inlet opening.
4. A method of claim 1 wherein, at cold start of an internal combustion engine comprising two camshafts through which the inlet valve timing and the outlet valve timing of the gas exchange valves can be set independently of one another, through a resetting of the camshaft adjustment during idle running, a defined maximum valve overlap is not exceeded during idle running.
5. A method of claim 4 , wherein the camshaft actuating the inlet valves is reset in direction of a retarded inlet opening.
6. A method of claim 1 , wherein in an internal combustion engine comprising only one camshaft through which the inlet valve timing and the outlet valve timing of the gas exchange valves can be adjusted in mutual dependence on each other, said engine comprising valve lash adjusters with idle stroke function on the inlet side and on the outlet side, a camshaft adjustment in direction of a retarded inlet and outlet closing is effected in a medium engine speed range in operative connection with an earlier inlet and outlet closing caused by the idle stroke of the gas exchange valves.
7. A method of claim 1 , wherein in an internal combustion engine comprising only one camshaft through which the inlet valve timing and the outlet valve timing of the gas exchange valves can be adjusted in mutual dependence on each other, said engine comprising valve lash adjusters with idle stroke function only on the inlet side, a camshaft adjustment in direction of a retarded inlet and outlet closing is effected in a medium engine speed range in operative connection with an earlier inlet and outlet closing caused by the idle stroke of the gas exchange valves.