Device and method for operating a valve drive of an internal combustion engine

Claim 1

A device for operating a valve drive of an internal combustion engine, including a switching mechanism for switching to different valve lift curves of a gas exchange valve and incorporated in a cam follower which is disposed in driving relationship between a camshaft and the gas exchange valve, said device comprising: an outer casing; a hollow cylindrical housing received in the outer casing and defining an interior, said outer casing and said housing defining at their interface a first annular gap; an inner element axially displaceable in the interior of the housing and capable of being coupled thereto, said housing and said inner element defining at their interface a second annular gap; a first coupling element in the form of a piston displaceably received in a first radial bore arrangement comprised of one bore formed in the housing and another bore formed in the inner element, said bores of the first bore arrangement being aligned in a base circle phase of a cam arrangement of the camshaft for allowing the first coupling element to bridge the second annular gap for coupling the housing and the inner element to one another, said first coupling element being directly acted upon by a hydraulic medium for movement in one direction of displacement for coupling action and being spring-biased for loading in opposite direction of displacement; second coupling means including a second coupling element displaceably received in a second radial bore arrangement comprised of one bore formed in the housing and another bore formed in the outer casing, said bores of the second bore arrangement being aligned in a phase of maximum cam lift for allowing the second coupling element to bridge the first annular gap and thereby effect an uncoupling of the housing and the inner element from the cam arrangement while the first coupling element extends entirely within one or the other bore of the first bore arrangement.

Claim 2

A device for operating a valve drive of an internal combustion engine, including a switching mechanism for switching to different valve lift curves of a gas exchange valve and incorporated in a cam follower which is disposed in driving relationship between a camshaft and the gas exchange valve, said device comprising: an outer casing; a hollow cylindrical housing received in the outer casing and defining an interior, said outer casing and said housing defining at their interface a first annular gap; an inner element axially displaceable in the interior of the housing and capable of being coupled thereto, said housing and said inner element defining at their interface a second annular gap; a first coupling element in the form of a piston displaceably received in a first radial bore arrangement comprised of one bore formed in the housing and another bore formed in the inner element, said bores of the first bore arrangement being aligned in a base circle phase of a cam arrangement of the camshaft for allowing the first coupling element to bridge the second annular gap for coupling the housing and the inner element to one another, said first coupling element being directly acted upon by a hydraulic medium for movement in one direction of displacement for coupling action and being spring-biased for loading in opposite direction of displacement; second coupling means including a second coupling element displaceably received in a second radial bore arrangement comprised of one bore formed in the housing and another bore formed in the outer casing, said bores of the second bore arrangement being aligned in a phase of maximum cam lift for allowing the second coupling element to bridge the first annular gap and thereby effect an uncoupling of the housing and the inner element from the cam arrangement while the first coupling element extends entirely within one or the other bore of the first bore arrangement.

Claim 11

A method of operating a valve drive of an internal combustion engine of a type including a switching mechanism for switching to different valve lift curves of a gas exchange valve, with the switching mechanism cooperating with a cam follower arranged in driving relationship between a camshaft and a gas exchange valve and having a first element for effecting a large valve lift and a second element for effecting a small valve lift, said method comprising the steps of: so retaining in a first operational state the first element in a bottom dead center position at maximum cam lift as to disengage from the cam while being uncoupled from the second element; and returning in a second operational state the first element, disengaged from the cam and uncoupled from the second element, for abutment against the cam in an area along a cam flank section during which the gas exchange valve closes in a range from a maximum valve lift to a minimum valve lift.

Claim 12

A method of operating a valve drive of an internal combustion engine of a type including a switching mechanism for switching to different valve lift curves of a gas exchange valve, with the switching mechanism cooperating with a cam follower arranged in driving relationship between a camshaft and a gas exchange valve and having a first element for effecting a large valve lift and a second element for effecting a small valve lift, said method comprising the steps of: so retaining in a first operational state the first element in a bottom dead center position at maximum cam lift as to disengage from the cam while being uncoupled from the second element; and returning in a second operational state the first element, disengaged from the cam and uncoupled from the second element, for abutment against the cam in an area along a cam flank section during which the gas exchange valve closes in a range from a maximum valve lift to a minimum valve lift.