At the time of increasing an actual intake air amount by increasing a valve overlap period of intake and exhaust valves (2; 3), an actual compression ratio is temporarily decreased to be lower than a steady-state target compression ratio. This makes it possible to increase the valve overlap period without causing interference of the intake and exhaust valves (2; 3) with a piston (8).

At the time of increasing an actual intake air amount by increasing a valve overlap period of intake and exhaust valves (2; 3), an actual compression ratio is temporarily decreased to be lower than a steady-state target compression ratio. This makes it possible to increase the valve overlap period without causing interference of the intake and exhaust valves (2; 3) with a piston (8).

A control device for an internal combustion engine controls a control object device based on an output value of a relative angle sensor that detects a relative angle of an output shaft of an actuator, and an output value of an absolute angle sensor that detects an absolute angle of a drive shaft coupled to the output shaft of the actuator via a speed reducer. In this event, the control device for the internal combustion engine corrects an output value of the absolute angle sensor based on an absolute angle of the drive shaft that is obtained from an output value of the relative angle sensor using, as a reference point, an output value of the absolute angle sensor at the start-up of the internal combustion engine, and an output value of the absolute angle sensor.

A control device for an internal combustion engine controls a control object device based on an output value of a relative angle sensor that detects a relative angle of an output shaft of an actuator, and an output value of an absolute angle sensor that detects an absolute angle of a drive shaft coupled to the output shaft of the actuator via a speed reducer. In this event, the control device for the internal combustion engine corrects an output value of the absolute angle sensor based on an absolute angle of the drive shaft that is obtained from an output value of the relative angle sensor using, as a reference point, an output value of the absolute angle sensor at the start-up of the internal combustion engine, and an output value of the absolute angle sensor.

A variable compression ratio mechanism of an internal combustion engine includes an operation element, an input actuator, and a reverse input torque cutoff clutch. The reverse input torque cutoff clutch includes a fixed member, a movable member, clearance, a wedge member, and a moving device. A peripheral surface of the fixed member is formed such that the clearance is formed with: a rotation prevention area that prevents the movable member from rotating in a reverse input torque acting direction. When the movable member moves in the direction to change a mechanical compression ratio, the moving device moves the wedge member from the rotation prevention area to the rotation allowable area in an opposite direction and holds the wedge member in the rotation allowable area.

A variable compression ratio mechanism of an internal combustion engine includes an operation element, an input actuator, and a reverse input torque cutoff clutch. The reverse input torque cutoff clutch includes a fixed member, a movable member, clearance, a wedge member, and a moving device. A peripheral surface of the fixed member is formed such that the clearance is formed with: a rotation prevention area that prevents the movable member from rotating in a reverse input torque acting direction. When the movable member moves in the direction to change a mechanical compression ratio, the moving device moves the wedge member from the rotation prevention area to the rotation allowable area in an opposite direction and holds the wedge member in the rotation allowable area.

Systems and methods are provided for varying a compression ratio in an engine having a pressure reactive piston. The pressure reactive piston may include a piston crown, and a spring positioned within the piston crown, wherein the spring includes a first ring, a second ring comprising a plurality of apertures, a rolling element positioned within each of the plurality of apertures, and a third ring. The first ring, the second ring, and the third ring of the spring may be arranged concentrically and the second ring may be positioned between the first ring and the third ring.

Systems and methods are provided for varying a compression ratio in an engine having a pressure reactive piston. The pressure reactive piston may include a piston crown, and a spring positioned within the piston crown, wherein the spring includes a first ring, a second ring comprising a plurality of apertures, a rolling element positioned within each of the plurality of apertures, and a third ring. The first ring, the second ring, and the third ring of the spring may be arranged concentrically and the second ring may be positioned between the first ring and the third ring.

The present invention relates to a method for increased exhaust gas temperature and emission reduction at partial loads in a diesel engine, wherein said engine comprises a cylinder with a reciprocating piston, a variable compression volume (VCR), and at least one exhaust valve and at least one inlet valve, the latter being equipped with variable valve timing (WT). According to the prevailing engine power requirement, an engine control system determines when to open and close said inlet valve, and the size of said compression volume in order to achieve a sufficiently elevated exhaust gas temperature so that correct exhaust gas purification can be achieved. The method is characterized in that the cylinder pressure during the expansion stroke is managed by the engine control system by means of the VCR and VVT functions, such that said pressure reaches atmospheric or sub atmospheric levels at or before bottom dead centre, at engine loads at or below 25% of the maximum engine load, whereby the inlet valve is opened to allow air to mix with the combustion gases. The invention also relates to a corresponding device and a diesel engine comprising said device.

The present invention relates to a method for increased exhaust gas temperature and emission reduction at partial loads in a diesel engine, wherein said engine comprises a cylinder with a reciprocating piston, a variable compression volume (VCR), and at least one exhaust valve and at least one inlet valve, the latter being equipped with variable valve timing (WT). According to the prevailing engine power requirement, an engine control system determines when to open and close said inlet valve, and the size of said compression volume in order to achieve a sufficiently elevated exhaust gas temperature so that correct exhaust gas purification can be achieved. The method is characterized in that the cylinder pressure during the expansion stroke is managed by the engine control system by means of the VCR and VVT functions, such that said pressure reaches atmospheric or sub atmospheric levels at or before bottom dead centre, at engine loads at or below 25% of the maximum engine load, whereby the inlet valve is opened to allow air to mix with the combustion gases. The invention also relates to a corresponding device and a diesel engine comprising said device.