A valve actuation system comprises a cylinder deactivation controller operatively connected to and in fluid communication with intake and exhaust deactivators for at least one cylinder. The valve actuation system further comprises an engine braking controller operatively connected to and in fluid communication with the engine braking actuators for the at least one cylinder. A braking-dependent deactivator controller is disposed between and in fluid communication with the cylinder deactivation controller and the intake deactivators, and in fluid communication with the engine braking controller via a control input. The braking-dependent deactivator controller is configured, in a first state based on its control input, to permit hydraulic fluid flow in hydraulic fluid control passages for the intake deactivators when in a non-1.5-stroke engine braking mode and, in a second state, to vent the hydraulic fluid control passages for the intake deactivators when in a 1.5-stroke engine braking mode.

A valve actuation system comprises a cylinder deactivation controller operatively connected to and in fluid communication with intake and exhaust deactivators for at least one cylinder. The valve actuation system further comprises an engine braking controller operatively connected to and in fluid communication with the engine braking actuators for the at least one cylinder. A braking-dependent deactivator controller is disposed between and in fluid communication with the cylinder deactivation controller and the intake deactivators, and in fluid communication with the engine braking controller via a control input. The braking-dependent deactivator controller is configured, in a first state based on its control input, to permit hydraulic fluid flow in hydraulic fluid control passages for the intake deactivators when in a non-1.5-stroke engine braking mode and, in a second state, to vent the hydraulic fluid control passages for the intake deactivators when in a 1.5-stroke engine braking mode.

An internal-combustion engine has a plurality of cylinders each with two intake valves driven by respective pumping pistons operatively associated to cams of a camshaft, by respective hydraulic circuits. The hydraulic has its pressure chamber communicating with hydraulic actuators of the two intake valves, so that the two intake valves of each cylinder are controlled, via two different hydraulic circuits, by cams associated to two different cylinders. Each cam is configured to give rise to a cycle of opening and closing of each of the intake valves in an angular range of rotation of the crankshaft less than 180 such that, in each operating cycle of a cylinder, only the first intake valve initially opens and closes while the second intake valve remains closed, and then the second intake valve opens and closes while the first intake valve remains closed.

An internal-combustion engine has a plurality of cylinders each with two intake valves driven by respective pumping pistons operatively associated to cams of a camshaft, by respective hydraulic circuits. The hydraulic has its pressure chamber communicating with hydraulic actuators of the two intake valves, so that the two intake valves of each cylinder are controlled, via two different hydraulic circuits, by cams associated to two different cylinders. Each cam is configured to give rise to a cycle of opening and closing of each of the intake valves in an angular range of rotation of the crankshaft less than 180 such that, in each operating cycle of a cylinder, only the first intake valve initially opens and closes while the second intake valve remains closed, and then the second intake valve opens and closes while the first intake valve remains closed.

An engine brake for an engine, having a rocker shaft carrying rocker arms along a rocker shaft, has an eccentric mounted to the rocker shaft and couples one of the rocker arms to the rocker shaft to pivot eccentrically about the rocker shaft as the eccentric pivots. The eccentric may take a braked condition or an unbraked condition. An actuator is capable of pivoting the eccentric about the rocker shaft to move the eccentric from the unbraked condition to the braked condition. An anti-clatter assembly is movable from an active state associated with the unbraked position of the eccentric to an inactive state associated with the braked condition of the eccentric. The anti-clatter assembly provides to the eccentric a restraining force in the active state and a yielding force in the inactive state. The restraining force is greater than the yielding force. The restraining force is sufficient to impede the eccentric from pivoting about the rocker shaft in the unbraked condition. The yielding force is insufficient to impede pivoting of the eccentric in the braked condition.

An engine brake for an engine, having a rocker shaft carrying rocker arms along a rocker shaft, has an eccentric mounted to the rocker shaft and couples one of the rocker arms to the rocker shaft to pivot eccentrically about the rocker shaft as the eccentric pivots. The eccentric may take a braked condition or an unbraked condition. An actuator is capable of pivoting the eccentric about the rocker shaft to move the eccentric from the unbraked condition to the braked condition. An anti-clatter assembly is movable from an active state associated with the unbraked position of the eccentric to an inactive state associated with the braked condition of the eccentric. The anti-clatter assembly provides to the eccentric a restraining force in the active state and a yielding force in the inactive state. The restraining force is greater than the yielding force. The restraining force is sufficient to impede the eccentric from pivoting about the rocker shaft in the unbraked condition. The yielding force is insufficient to impede pivoting of the eccentric in the braked condition.

In order to provide a more reliable configuration for a hydraulic drive for accelerating and braking in particular a gas exchange valve (20) of internal combustion engines or other reciprocating engines, in particular if the occurring maximum travel of the moving mass can deviate considerably from an expected setpoint position, it is proposed that the drive piston (23) has at least one control edge (31) corresponding to an inflow opening (33), which, when a defined travel h.sub.ab has been attained, prevents the inflow of drive pressure p.sub.1 into the drive chamber (27) and/or prevents the low-loss outflow of pressure medium from the brake chamber (29) to the basic pressure level (40), wherein the remaining hydraulic drive force vanishes, becomes small or changes its sign when said travel h.sub.ab is attained.

In order to provide a more reliable configuration for a hydraulic drive for accelerating and braking in particular a gas exchange valve (20) of internal combustion engines or other reciprocating engines, in particular if the occurring maximum travel of the moving mass can deviate considerably from an expected setpoint position, it is proposed that the drive piston (23) has at least one control edge (31) corresponding to an inflow opening (33), which, when a defined travel h.sub.ab has been attained, prevents the inflow of drive pressure p.sub.1 into the drive chamber (27) and/or prevents the low-loss outflow of pressure medium from the brake chamber (29) to the basic pressure level (40), wherein the remaining hydraulic drive force vanishes, becomes small or changes its sign when said travel h.sub.ab is attained.

A hydraulic valve actuation system with controlled valve seating velocity and method therefor are proposed. The system includes an actuator with a housing and a drive assembly formed from a drive piston within the housing and an adjustment pin. In an internal combustion engine application, the adjustment pin contacts and moves an engine valve that controls air and fuel entering an engine cylinder. The actuator provides velocity dampening of the drive piston, via an annulus-shaped fluid communication path defined by at least one surface of the drive piston and at least one opposing surface of a damping chamber formed within the housing. The dampening hydraulically cushions the impact of a bottom of the drive piston against a bottom stop of the actuator during opening of the engine valve, which reduces noise and engine wear. In another example, the system is configured to control an engine valve seating velocity.

A hydraulic valve actuation system with controlled valve seating velocity and method therefor are proposed. The system includes an actuator with a housing and a drive assembly formed from a drive piston within the housing and an adjustment pin. In an internal combustion engine application, the adjustment pin contacts and moves an engine valve that controls air and fuel entering an engine cylinder. The actuator provides velocity dampening of the drive piston, via an annulus-shaped fluid communication path defined by at least one surface of the drive piston and at least one opposing surface of a damping chamber formed within the housing. The dampening hydraulically cushions the impact of a bottom of the drive piston against a bottom stop of the actuator during opening of the engine valve, which reduces noise and engine wear. In another example, the system is configured to control an engine valve seating velocity.