Abstract: An exemplary method for controlling an internal combustion engine system includes, when a desired torque is equal to or greater than a first torque, opening an exhaust valve and injecting pilot fuel into a combustion chamber at a first pressure before an exhaust top dead center in a cylinder cycle, opening an intake valve in the cylinder cycle after said injecting, and injecting main fuel in the cylinder cycle after said opening of said intake valve. The method further includes, when a desired torque is less than said first torque, opening said exhaust valve and injecting pilot fuel into the combustion chamber at a second pressure that is greater than the first pressure before an exhaust top dead center in the cylinder cycle, opening said intake valve in the cylinder cycle after said injecting, and injecting main fuel in the cylinder cycle after said opening of said intake valve.

Abstract: A method of controlling an internal combustion engine and system including the engine is provided. The method may include closing an exhaust valve of a combustion chamber of said engine during a cylinder cycle prior to opening an intake valve of said combustion chamber. The method may include, when a desired engine torque is a predetermined torque or greater, supplying a first pilot fuel into said combustion chamber after said exhaust valve closing and supplying a first main fuel into said combustion chamber after the combustion of said first preliminary fuel during the cylinder cycle. The method may include, when a desired engine torque is less than said predetermined torque, supplying a second pilot fuel into said combustion chamber after said exhaust valve closing during the cylinder cycle and supplying a second main fuel into said combustion chamber after the supplying of said second pilot fuel into said combustion chamber.

Abstract: A direct injection spark ignition engine comprises a cylinder, a piston, a fuel injector arranged at one side of a center axis of the cylinder for directly injecting fuel into the combustion chamber, and a smoothly continuous lowered recess formed on a top surface of the piston surface. The recess has a first cross section along a first plane including the cylinder center axis and a nozzle end of the injector. The first and second lower contours are smoothly connected with each other through a lowest point of the first cross section. The first lower contour is located at the one side of the cylinder center axis. The second lower contour is at the other side. The first contour has a larger radius than a radius of the second contour. Accordingly, the fuel spray having greater movement energy may impinge the recess at a regulated impinging angle.

Abstract: A direct injection spark ignition engine comprises a cylinder, a piston which is reciprocally movably arranged in the cylinder and defines with the cylinder a combustion chamber, a fuel injector arranged at one side of a center axis of the cylinder for directly injecting fuel into the combustion chamber, and a smoothly continuous lowered recess formed on a top surface of the piston surface for receiving at least part of fuel injected from the injector. The recess has a first cross section along a first plane including the cylinder center axis and a nozzle end of the injector. The first cross section has first and second lower contours substantially of arc shape with its center above the recess. The first and second lower contours are smoothly connected with each other through a lowest point of the first cross section. The first lower contour is located at the one side of the cylinder center axis. The second lower contour is located at the other side of the cylinder center axis.

Abstract: A fuel spray and a tumble collide with each other from approximately opposite directions in a cavity formed in a piston head so that a combustible mixture stays around a spark plug for an extended period of time. An upper opening of the cavity is elongated to both the left and right sides of a cylinder axis. The distance between a ceiling of the combustion chamber and a bottom surface of the cavity is smaller on the right side of the cylinder axis than on the left side thereof and largest at least at a point where the cylinder axis crosses the bottom surface of the cavity, and a portion of the cavity to the left of the cylinder axis has a larger volumetric capacity than a portion of the cavity to the right of the cylinder axis, whereby a strong tumble is maintained up to a fuel injection point.

Abstract: During stratified-charge combustion operation of a direct-injection spark ignition engine, at the cylinder compression stroke, a tumble is generated which flows between a spark plug electrode and a piston crown surface toward an injector. A fuel is injected from the injector in correspondence with the cylinder ignition timing by controlling the penetration of fuel spray from the injector to correspond to the tumble flow rate so that the fuel spray may go against the tumble, become a flammable mixture at the cylinder ignition timing and stay near the spark plug electrode. In the late stage of the compression stroke, diffusion of the flammable mixture is suppressed with squishes. Thus, fuel spray behavior in the combustion chamber is controlled to allow suitable mixture stratification over a wide engine operating condition range. This improves combustion quality and extends a stratified-charge combustion zone thereby providing enhanced fuel economy and power output.

Abstract: A fuel spray and a tumble collide with each other from approximately opposite directions in a cavity formed in a piston head so that a combustible mixture stays around a spark plug provided at an upper central part of a combustion chamber for an extended period of time. An upper opening of the cavity is elongated to both the left and right sides of a cylinder axis. The distance between a ceiling of the combustion chamber and a bottom surface of the cavity as measured parallel to the cylinder axis is smaller on the right side of the cylinder axis than on the left side thereof and largest at least at a point where the cylinder axis crosses the bottom surface of the cavity, and a portion of the cavity to the left of the cylinder axis has a larger volumetric capacity than a portion of the cavity to the right of the cylinder axis, whereby a strong tumble is maintained up to a fuel injection point, allowing satisfactory mixture strification.

Abstract: During stratified-charge combustion operation of a direct-injection spark ignition engine, at the cylinder compression stroke, a tumble is generated which flows between a spark plug electrode and a piston crown surface toward an injector. A fuel is injected from the injector in correspondence with the cylinder ignition timing by controlling the penetration of fuel spray from the injector to correspond to the tumble flow rate so that the fuel spray may go against the tumble, become a flammable mixture at the cylinder ignition timing and stay near the spark plug electrode. In the late stage of the compression stroke, diffusion of the flammable mixture is suppressed with squishes. Thus, fuel spray behavior in the combustion chamber is controlled to allow suitable mixture stratification over a wide engine operating condition range. This improves combustion quality and extends a stratified-charge combustion zone thereby providing enhanced fuel economy and power output.