Methods and systems are provided for improving calibration of a variable compression ratio engine. Cylinder-to-cylinder compression ratio variations are detected and accounted for by comparing cylinder fuel flow and IMEP at each compression ratio setting. Dilution parameters including EGR and VCT schedule are also calibrated to account for the cylinder-to-cylinder compression ratio variations.

A piston and connecting rod assembly including concentric primary and secondary pistons, the secondary piston being axially movable within the primary piston, toward a limit position therein, by a spring. The spring compression is controlled in part by a spring support which is axially movable within the primary piston. A cam lobe at the upper end of the connecting rod projects at an upward angle to the axis of the connecting rod. During a compression stroke the cam lobe causes displacement of the spring support, upward and then downward, initially increasing compression in the spring and then decreasing it as the connecting rod approaches a top dead center position, thus enabling the secondary piston to be positioned according to the size of the fuel charge, substantially independent of inertial forces acting on the secondary piston, to optimize the compression ratio to the fuel charge.

A device for compensating for the operating clearances of an engine comprising a transmission device likely to move transversely in an engine block) during an engine cycle includes a pressing device exerting a holding force on the transmission device. The holding force is adjusted to the instantaneous speed of transverse movement of the transmission device in the engine block.

Methods and systems are provided for adjusting a fuel direct injection split ratio and injection timing in a variable compression ratio engine. In one example, as the compression ratio increases, the split ratio of fuel injected during an intake stroke relative to a compression stroke is increased, with a start of the intake stroke injection retarded and a start of the compression stroke injection advanced. Additionally, the fuel direct injection split ratio and injection timing may be further adjusted responsive to an indication of pre-ignition or knock.

Methods and systems are provided for adjusting a fuel direct injection split ratio and injection timing in a variable compression ratio engine. In one example, as the compression ratio increases, the split ratio of fuel injected during an intake stroke relative to a compression stroke is increased, with a start of the intake stroke injection retarded and a start of the compression stroke injection advanced. Additionally, the fuel direct injection split ratio and injection timing may be further adjusted responsive to an indication of pre-ignition or knock.

Disclosed is a reciprocating piston engine, comprising a combined structure with an optimized double-crankshaft and variable compression ratio pistons, characterized in that the variable compression ratio piston is a piston serving as a double-acting hydraulic cylinder, a control valve bush of a slide-valve type directional control valve is fixed in a central mounting hole of the inner piston, and a control valve core is mounted in a rotatory sliding or nut-ball screw manner in a central mounting hole in the inner surface of the piston top; and the double-crankshaft engine is formed by two reverse rotating crankshafts which are coupled by gears to be in synchronous reverse rotation motion together, each piston being connected to a connecting rod shaft of two crankshafts, and a piston control valve driving mechanism being mounted between the two crankshafts.

Provided is an engine that includes a first member, a second member, a first hydraulic pressure chamber formed between facing parts of the first and second members, and a hydraulic pressure adjustment mechanism. The hydraulic pressure adjustment mechanism has a plunger pump having a pump cylinder and a plunger and configured to supply hydraulic oil in the pump cylinder to the first hydraulic pressure chamber by pushing the plunger into the pump cylinder. The plunger pump moves in a stroke direction along with a piston and a power transmission section, and the plunger is pushed into the pump cylinder by receiving a reaction force opposite to reciprocating forces of the piston and the power transmission section.

A variable compression ratio device may include a piston pin having first and second plunger spaces, a plunger device including a first plunger that is disposed to reciprocate in the first plunger space, a second plunger and a connection pipe that connects between the first and second plungers, a first check valve disposed in a first check space to move oil from a pipe passage to the first check space in a first direction, a second check valve disposed in a second check space to move the oil from the pipe passage to a second check space in a second direction; and a return member elastically supporting the second plunger to one side.

Methods and systems are provided for adjusting an ignition timing of an internal combustion engine responsive to a biasing force of a pressure-reactive piston. In one example, an engine may include a pressure-reactive piston having a top wall biased away from a piston base by a pressure of gas contained within the base. An ignition timing of a combustion chamber including the piston is adjusted responsive to an estimated biasing force of the gas against the top wall.

An internal combustion engine includes: a variable compression ratio mechanism arranged to vary an engine compression ratio in accordance with a rotation position of a control shaft; an actuator arranged to vary the rotation positon of the control shaft; an arm portion extending from the control shaft in a radially outward direction; a lever arranged to link the actuator and the arm portion; a link pin which penetrates the lever and the arm portion, and which rotatably links the lever and the arm portion; and a wall portion which confronts an end surface of the link pin irrespective of the rotation position of the control shaft, and which retains the link pin to the lever or the arm portion.