Pistons for opposed-piston engines include an interior annular cooling gallery. The gallery is provided with inlet and drain passageways constructed to shield a jet of liquid coolant entering the gallery, thereby reducing interference between the incoming jet and liquid coolant circulating in the gallery.

Exemplary pistons and methods of making the same are disclosed. An exemplary piston may include a crown defining a combustion bowl and a ring land extending circumferentially around the combustion bowl. Exemplary pistons may further include a skirt supporting the crown. The skirt may include a pair of pin bosses defining a pin bore configured to receive a piston pin, and two opposing skirt supports defining surfaces configured to slide along a cylinder bore surface. The skirt supports each define a different radial stiffness.

A galleryless steel piston for an internal combustion engine is provided. The piston comprises an exposed undercrown surface, a ring belt with ring grooves, pin bosses, skirt panels, and struts. The piston further includes an inner undercrown region and outer pockets extending along the undercrown surface. The inner undercrown region is surrounded by the skirt panels, the struts, and the pin bosses, and each outer pocket is surrounded by a portion of the ring belt, one of the pin bosses, and two of the struts. The piston includes a plurality of oil slots extending through the back wall of one of the ring grooves, typically the third ring groove, to the inner undercrown region and/or the outer pockets to allow drainage of cooling oil. Each oil slot typically has a diameter ranging from 30% to 100% of an axial width of the ring groove.

A galleryless steel piston for an internal combustion engine is provided. The piston comprises an exposed undercrown surface, a ring belt with ring grooves, pin bosses, skirt panels, and struts. The piston further includes an inner undercrown region and outer pockets extending along the undercrown surface. The inner undercrown region is surrounded by the skirt panels, the struts, and the pin bosses, and each outer pocket is surrounded by a portion of the ring belt, one of the pin bosses, and two of the struts. The piston includes a plurality of oil slots extending through the back wall of one of the ring grooves, typically the third ring groove, to the inner undercrown region and/or the outer pockets to allow drainage of cooling oil. Each oil slot typically has a diameter ranging from 30% to 100% of an axial width of the ring groove.

A galleryless piston including a ring belt with three ring grooves is provided. Each ring groove is formed by an uppermost wall and a lower wall spaced from one another by a back wall. A pair of pin bosses depend from the upper wall, and pair of skirt panels depend from the ring belt and are coupled to the pin bosses by struts. An inner undercrown region is surrounded by the skirt panels and the struts and the pin bosses. A pair of outer pockets extend along the undercrown surface, and each outer pocket is surrounded by a portion of the ring belt and one of the pin bosses and the struts coupling the one pin boss to the skirt panels. The third ring groove includes an oil drain slot extending through the back wall to the outer pockets of the piston for conveying cooling oil.

A galleryless piston including a ring belt with three ring grooves is provided. Each ring groove is formed by an uppermost wall and a lower wall spaced from one another by a back wall. A pair of pin bosses depend from the upper wall, and pair of skirt panels depend from the ring belt and are coupled to the pin bosses by struts. An inner undercrown region is surrounded by the skirt panels and the struts and the pin bosses. A pair of outer pockets extend along the undercrown surface, and each outer pocket is surrounded by a portion of the ring belt and one of the pin bosses and the struts coupling the one pin boss to the skirt panels. The third ring groove includes an oil drain slot extending through the back wall to the outer pockets of the piston for conveying cooling oil.

A piston for an internal combustion engine is provided. The piston includes a piston body including an upper combustion surface, an annular side wall with a ring belt region, and a cooling gallery located within the piston body having a fluid inlet. A piston ring is located in a ring groove around the ring belt region and an alignment pin is secured in a hole in the piston side wall to restrict circumferential displacement of the piston ring. The piston body further includes a boss within the cooling gallery into which the hole and the alignment pin extend. The boss projects into the cooling gallery opposite the fluid inlet and is shaped to provide a flow splitter surface configured to divide cooling fluid flowing through the fluid inlet during use into first and second fluid flows and to direct the first and second fluid flows in opposite directions around the cooling gallery.

A piston for an internal combustion engine is provided. The piston includes a piston body including an upper combustion surface, an annular side wall with a ring belt region, and a cooling gallery located within the piston body having a fluid inlet. A piston ring is located in a ring groove around the ring belt region and an alignment pin is secured in a hole in the piston side wall to restrict circumferential displacement of the piston ring. The piston body further includes a boss within the cooling gallery into which the hole and the alignment pin extend. The boss projects into the cooling gallery opposite the fluid inlet and is shaped to provide a flow splitter surface configured to divide cooling fluid flowing through the fluid inlet during use into first and second fluid flows and to direct the first and second fluid flows in opposite directions around the cooling gallery.

A piston for an internal combustion engine has box walls (18), which are each formed between skirt walls (12) and gudgeon pin bosses (10). At least one of the box walls (18) on a thrust side at least on the lower edge and at least on the inner side, starting from the gudgeon pin boss (10), in a first portion (20), runs largely straight and is inclined outwards, and then runs curved inwards, and then, in a second portion (16), runs largely straight and inclined inwards to the skirt wall (12).

A piston for an internal combustion engine has box walls (18), which are each formed between skirt walls (12) and gudgeon pin bosses (10). At least one of the box walls (18) on a thrust side at least on the lower edge and at least on the inner side, starting from the gudgeon pin boss (10), in a first portion (20), runs largely straight and is inclined outwards, and then runs curved inwards, and then, in a second portion (16), runs largely straight and inclined inwards to the skirt wall (12).