In the present invention, an internal combustion engine is provided with an in-cylinder fuel injection valve and a secondary air supply device and is formed so as to make possible first catalyst warming control and second catalyst warming control that promote the raising of the temperature of an exhaust gas purification catalyst. The first catalyst warming control comprises control to inject fuel from the in-cylinder fuel injection valve during the compression stroke to form a stratified state, and control to greatly delay ignition timing. The second catalyst warming control comprises control to supply secondary air to an engine exhaust gas passage. The internal combustion engine executes the first catalyst warming control after startup and, after the first catalyst warming control is executed, carries out control (third catalyst warming control) to execute the first catalyst warming control and the second catalyst warming control simultaneously.

A variable valve device changes a valve lift amount in a cylinder head. The device includes: a camshaft having plural cams with different valve lift amounts; plural rocker arms in contact with the plural cams to move a valve; a switching mechanism that couples and separates the rocker arms by oil pressure; and an oil control valve that controls the oil pressure. The switching mechanism includes a hydraulic piston moveable forward and backward to couple and separate the rocker arms. First and second oil passages extend from the oil control valve to the hydraulic piston. The first oil passage includes an oil groove through which oil is allowed to pass at a predetermined rotation phase of the camshaft. The second oil passage is closed by the hydraulic piston after the rocker arms are separated from one another along the backward movement of the hydraulic piston.

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 variable valve device for an internal combustion engine is equipped with a variable valve mechanism capable of changing the working angle of an intake valve while holding the maximum lift amount of the intake valve constant. The variable valve device retards the timing for closing the intake valve as the load of the internal combustion engine rises, and enlarges the working angle, while holding the timing for opening the intake valve constant. Operating characteristics of the intake valve are provided in accordance with the load of the internal combustion engine.

An engine bank-to-bank airflow balancing technique includes calculating current and offset volumetric efficiencies of the engine and calculating a slope representing (i) a difference between the offset and current volumetric efficiencies and (ii) a difference between offset and current intake camshaft positions. Based on the respective exhaust gas oxygen concentrations, the technique involves calculating a volumetric efficiency correction corresponding to each cylinder bank and based on the slope and the volumetric efficiency corrections, calculating target intake camshaft position shifts. The technique further involves controlling offsets of the intake camshafts based on the target intake camshaft position shifts. After a predetermined number of target intake camshaft position shifts are determined and stored with respect to various combinations of engine speed and a ratio of intake manifold pressure to barometric pressure, final intake camshaft position shifts may be determined and utilized when determining the intake camshaft positions.

A variable valve device changes a valve lift amount in a cylinder head. The device includes: a camshaft having plural cams with different valve lift amounts; plural rocker arms in contact with the plural cams to move a valve; a switching mechanism that couples and separates the rocker arms by oil pressure; and an oil control valve that controls the oil pressure. The switching mechanism includes a hydraulic piston moveable forward and backward to couple and separate the rocker arms. First and second oil passages extend from the oil control valve to the hydraulic piston. The first oil passage includes an oil groove through which oil is allowed to pass at a predetermined rotation phase of the camshaft. The second oil passage is closed by the hydraulic piston after the rocker arms are separated from one another along the backward movement of the hydraulic piston.

A variable valve device changes a valve lift amount in a cylinder head. The device includes: a camshaft having plural cams with different valve lift amounts; plural rocker arms in contact with the plural cams to move a valve; a switching mechanism that couples and separates the plurality of rocker arms by oil pressure; and an oil control valve that control the oil pressure. The switching mechanism includes a coupling piston and a separation piston that are moved forward and backward by the oil pressure. The plural rocker arms are coupled to one another along forward movement of the coupling piston. The plural rocker arms are separated from one another along forward movement of the separation piston. The oil control valve moves the coupling piston forward at a predetermined rotation phase of the camshaft and moves the separation piston forward at a predetermined rotation phase of the camshaft.

Embodiments are directed toward an engine. In some embodiments, the engine includes a water pump and a balancer shaft. In some embodiments, the water pump has a plain bearing. In some embodiments, plain bearing is supplied with pressurized oil. In some embodiments, the balancer shaft drives the water pump as well as cam shafts.