A piston for a reciprocating piston machine includes a piston crown, a piston recess, and an annular groove formed in the piston crown. The annular groove extends in a radial direction of the piston outwards and a cross-section of the annular groove has a half-teardrop shape. The half-teardrop shape has a first radius and a second radius where the second radius is directly contiguous with the first radius outwards in the radial direction of the piston and where the second radius is greater than the first radius.

In a compression-ignition engine having a two-stage cavity, the distribution ratio between fuel for an upper cavity and fuel for a lower cavity is maintained even when the operational state of the engine changes. A piston of the compression-ignition engine includes a lower cavity, an upper cavity, and a lip portion between the lower cavity and the upper cavity. A controller causes a main injection and at least one pilot injection to be executed when the engine operates in a first state and a second state in which the load is higher than the load in the first state. The fuel spray is distributed to the lower cavity and the upper cavity. The controller causes a ratio of injection amount per pilot injection to the total injection amount to be higher when the engine operates in the second state than when the engine operates in the first state.

A fuel injection control device causes an injector to execute main injection or pilot injection toward a joint portion, and low penetration injection to inject fuel at timing earlier than the pilot injection in a PILOT region or at timing later than the main injection in an AFTER region. The fuel injection control device causes the low penetration injection to be executed to inject the fuel only in a radial central region of a combustion chamber.

A fuel injection control causes a fuel injection valve to execute at least: a main injection to inject fuel at timing when a piston is positioned near a compression top dead center; a pilot injection to inject the fuel at timing earlier than the main injection; and a low penetration injection to inject the fuel at timing earlier than the pilot injection or timing later than the main injection. The fuel injection control device includes: a first injection control module that executes at least one of the main injection or the pilot injection at timing to inject the fuel toward a joint portion of a cavity; and a second injection control module that executes the low penetration injection to inject the fuel only into a radial central region of a combustion chamber.

The invention relates to an air-compressing internal combustion engine, comprising at least one piston (1) having a combustion chamber trough (3) substantially rotationally symmetrical to a piston axis (2), which has a trough bottom (4) with a substantially cone-like elevation (5) and a circumferential trough wall (6), wherein the trough wall (6) forms a substantially torus-like first section (6a) having a maximum inner first trough diameter (d1), a second section (6b) having a minimum inner second trough diameter (d2) smaller than the inner first trough diameter (d1), and a third section (6c), whereinas seen in a meridian section of the piston (1)the first section (6a) has a concave first radius of curvature (R1) and the second section (6b) has a convex second radius of curvature (R2), and wherein the third section (6c) forms a first annular surface (8) adjoining the second section (6b) and a second annular surface (9) terminating in the piston end surface (7), which second annular surface (9) defines an angle () with the first annular surface (8), wherein the first annular surface (8) and the second annular surface (9) are formed to be inclined to a normal plane () on the piston axis (2), and wherein in the transition between the first annular surface (8) and second annular surface (9) an edge (11) is formed with a defined third radius of curvature (R3),

In order to prevent soot formation phenomena, it is provided that, as viewed in a meridian section of the piston (1), the first annular surface (8) together with a normal plane () on the piston axis (2) forms a first angle () between 10 and 20, preferably 15.2.

In a compression-ignition engine having a two-stage cavity, the distribution ratio between fuel for an upper cavity and fuel for a lower cavity is maintained even when the operational state of the engine changes. A piston of the compression-ignition engine includes a lower cavity, an upper cavity, and a lip portion between the lower cavity and the upper cavity. A controller causes a main injection and at least one pilot injection to be executed when the engine operates in a first state and a second state in which the load is higher than the load in the first state. The fuel spray is distributed to the lower cavity and the upper cavity. The controller causes a ratio of injection amount per pilot injection to the total injection amount to be higher when the engine operates in the second state than when the engine operates in the first state.

A fuel injection control device causes an injector to execute main injection or pilot injection toward a joint portion, and low penetration injection to inject fuel at timing earlier than the pilot injection in a PILOT region or at timing later than the main injection in an AFTER region. The fuel injection control device causes the low penetration injection to be executed to inject the fuel only in a radial central region of a combustion chamber.

A fuel injection control causes a fuel injection valve to execute at least: a main injection to inject fuel at timing when a piston is positioned near a compression top dead center; a pilot injection to inject the fuel at timing earlier than the main injection; and a low penetration injection to inject the fuel at timing earlier than the pilot injection or timing later than the main injection. The fuel injection control device includes: a first injection control module that executes at least one of the main injection or the pilot injection at timing to inject the fuel toward a joint portion of a cavity; and a second injection control module that executes the low penetration injection to inject the fuel only into a radial central region of a combustion chamber.

A piston with an improved bowl geometry includes a piston body having a generally planar crown and a skirt extending from the crown. An oval or multi-lobed bowl rim of a combustion bowl that is recessed in the crown so that the sides of the bowl rim are provided with increased material to resist fatigue along the pin plane, optionally along the thrust/antithrust plane and generally optionally along other planes between the pin plane and the thrust/antithrust plane.

A piston with an improved bowl geometry includes a piston body having a generally planar crown and a skirt extending from the crown. An oval or multi-lobed bowl rim of a combustion bowl that is recessed in the crown so that the sides of the bowl rim are provided with increased material to resist fatigue along the pin plane, optionally along the thrust/antithrust plane and generally optionally along other planes between the pin plane and the thrust/antithrust plane.