A method of providing a rocker arm set for a valvetrain includes providing a first rocker arm configured as a switching rocker arm for a first intake valve, and providing a second rocker arm configured as a fixed rocker arm for a second intake valve, the second rocker arm operating in a normal Otto cycle mode. The first rocker arm operates in a late intake valve closing (LIVC) mode where the first rocker arm is configured to close the first intake valve later than the second intake valve.

Systems and methods for operating an engine with deactivating and non-deactivating valves are presented. In one example, engine volumetric efficiency actuators are adjusted in response to a request to activate engine cylinders so that engine intake manifold pressure is drawn down quickly toward its normal state at the engine's present speed and torque.

A first swing arm of each cylinder is swung by a fixed cam of an intake camshaft, so as to operate a first intake valve according to a profile thereof. A second swing arm is swung by a second cam and its swing range is changed by a variable mechanism. Hereby, a lift amount of a second intake valve changes continuously. The second cam is selected from a plurality of cams on a cam piece provided around the intake camshaft.

A variable valve lift apparatus include a cam rotating together with a camshaft, a lever body being rolling-contacted to one end portion of the cam, and making a lever motion by receiving torque of the cam, two valves operating depending on a lever motion of the lever body, a valve gap control device being disposed at the other end portion of the lever body to simultaneously push the two valves by a main lift and controlling a gap of the valve, and an operation portion operated to selectively push a variable valve which is one among the two valves by a sub lift and disposed at the other end portion of the lever body.

The present disclosure provides a system and a method for controlling valve timing of a continuous variable valve duration. The method may include: classifying a plurality of control regions depending on an engine speed and an engine speed; applying a maximum duration to an intake valve in a first control region; maintaining the maximum duration of the intake valve and controlling the exhaust valve to reach a maximum duration in a second control region; advancing intake valve closing (IVC) timing and exhaust valve closing (EVC) timing in a third control region; controlling the IVC timing to be close to bottom dead center (BDC) in a fourth control region; controlling a throttle valve to be fully opened and controlling the IVC timing to an angle after BDC in a fifth control region; and controlling the throttle valve to be fully opened and advancing the IVC timing in a sixth control region.

A valvetrain for an engine includes a pair of valves that are disposed in a spaced apart relation to one another, and in which each of the valves has an elongated valve stem. The valvetrain further includes a valve bridge that is coupled to the pair of valves. The valve bridge is configured to define a pair of receptacles to at least partly receive the pair of valve stems therein. The valve bridge further defines a central recess that is located midway between the pair of receptacles and disposed in a co-planar relationship with the pair of receptacles.

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.

A valvetrain assembly has valves each having a valve stem; a main camshaft with main cams, a main cam corresponding to each valve; main rocker arms each corresponding to a valve and having a valve stem actuation portion, a pivot axis parallel to the main cam shaft, and a main cam follower for following the corresponding main cam, wherein the valve stem actuation portion, pivot axis, and main cam follower are arranged along the main rocker arm length distanced from each other; an auxiliary cam on the main camshaft; an auxiliary cam follower for each auxiliary cam, following the auxiliary cam, wherein each auxiliary cam follower is movable on one main rocker arm between a first and second position; a latch on respective main rocker arm(s) for locking the auxiliary cam follower in the first position; and an auxiliary camshaft with a selector cam for each latch, controlling the latch.

The present disclosure provides a system and a method for controlling valve timing of a continuous variable valve duration. The method may include: classifying a plurality of control regions depending on an engine speed and an engine speed; applying a maximum duration to an intake valve in a first control region; maintaining the maximum duration of the intake valve and controlling the exhaust valve to reach a maximum duration in a second control region; advancing intake valve closing (IVC) timing and exhaust valve closing (EVC) timing in a third control region; controlling the IVC timing to be close to bottom dead center (BDC) in a fourth control region; controlling a throttle valve to be fully opened and controlling the IVC timing to an angle after BDC in a fifth control region; and controlling the throttle valve to be fully opened and advancing the IVC timing in a sixth control region.

A first swing arm of each cylinder is swung by a fixed cam of an intake camshaft, so as to operate a first intake valve according to a profile thereof. A second swing arm is swung by a second cam and its swing range is changed by a variable mechanism. Hereby, a lift amount of a second intake valve changes continuously. The second cam is selected from a plurality of cams on a cam piece provided around the intake camshaft.