Piston Crown and Corresponding Port Geometry

An engine assembly comprising:

• a cylinder wall extending annularly about and defining a cylinder bore;
• said cylinder bore defining a longitudinal axis that extends co-axially through said cylinder bore;
• said cylinder bore having a bore cross-section that is perpendicular to said longitudinal axis, said bore cross-section having a circular perimeter;
• a piston slidingly received within said cylinder bore for reciprocal movement therein along said longitudinal axis between a bottom dead-center position and a top dead-center position;
• said cylinder wall including an inner surface facing said piston;
• said piston including a piston crown spanning said bore cross-section and at least one ring groove that extends annularly about said piston in a ring plane that is perpendicular to said longitudinal axis and parallel to said bore cross-section;
• at least one piston ring received in said at least one ring groove, said piston ring having an annular shape and said at least one piston ring extending radially from said piston within said ring plane to seal against said inner surface of said cylinder wall;
• said cylinder wall having at least one port that includes a plurality of windows extending through said cylinder wall;
• each window of said plurality of windows being open to said cylinder bore and having a window perimeter extending about each window of said plurality of windows adjacent said inner surface of said cylinder wall;
• said at least one port having an oblique geometry relative to said ring plane where said plurality of windows are circumferentially spaced from one another about said cylinder bore in a path that is oblique to said ring plane to stagger entry and exit times of said at least one piston ring relative to said plurality of windows as said piston reciprocates within said cylinder bore between said bottom dead-center position and said top dead-center position;
• and
• said piston crown having a periphery adjacent said cylinder wall that is oblique to said ring plane and that has a shape corresponding to said oblique geometry of said at least one port such that said periphery of said piston crown opens and closes said plurality of windows at substantially the same time along said oblique geometry of said at least one port as said piston reciprocates within said cylinder bore between said bottom dead-center position and said top dead-center position.

An opposed-piston engine comprising:

• an engine block including a cylinder wall that extends about and defines a first cylinder, said first cylinder having a first longitudinal axis and a first inlet port and a first exhaust port that is longitudinally spaced from said first inlet port;
• a pair of first pistons including a first piston and a first opposing piston that are slidably disposed within said first cylinder and that are movable along said first longitudinal axis toward one another in a first mode of operation and away from one another in a second mode of operation;
• each piston of said pair of first pistons including a piston crown and at least one ring groove that extends about each piston of said pair of first pistons in a ring plane that is perpendicular to said first longitudinal axis;
• at least one piston ring received in said at least one ring groove of each piston of said pair of first pistons;
• and
• at least one of said first inlet port and said first exhaust port having an oblique geometry thereby defining at least one oblique port where said at least one oblique port includes a plurality of windows extending at least partially about said first cylinder in a path that is oblique to said ring plane to stagger entry and exit times of said at least one piston ring relative to said plurality of windows of said at least one oblique port as said pair of first pistons translate within said first cylinder.