An internal combustion engine includes a cylinder block, a cylinder-block passage, a cylinder head, a cylinder-head passage, cylinders, an introducing portion, a restricting wall, and communicating portions. The introducing portion is configured to introduce coolant flowing in the cylinder-head passage into an EGR cooler. The restricting wall is configured to restrict flow of the coolant from a section corresponding to the spark plug toward the introducing portion. The communicating portions cause the cylinder-block passage and the cylinder-head passage to communicate with each other. A direction perpendicular to both the extending direction of the central axis of each cylinder and the cylinder arrangement direction is defined as a predetermined direction. Certain one or certain ones of the communicating portions are arranged at positions closer to an intake manifold than the restricting wall in the predetermined direction.

A water cooled engine is provided, including a cylinder head with minimized thermal strain. A head water jacket includes an inter-exhaust-port-wall water channel between a first exhaust entrance port wall and a second exhaust entrance port wall. The cylinder head includes a cooling water injection passage provided at a bottom wall thereof. The cooling water injection passage is positioned on the exhaust end side, and includes a passage entrance provided on the exhaust end side, and a passage exit directed toward the inter-exhaust-port-wall water channel. An exhaust port wall includes a heat dissipation fin extending from a first exhaust entrance port wall toward an exhaust end. The space between the heat dissipation fin and a second exhaust entrance port wall forms a water channel entrance of the inter-exhaust-port-wall water channel.

A water cooled engine is provided, including a cylinder head with minimized thermal strain. A head water jacket includes an inter-exhaust-port-wall water channel between a first exhaust entrance port wall and a second exhaust entrance port wall. The cylinder head includes a cooling water injection passage provided at a bottom wall thereof. The cooling water injection passage is positioned on the exhaust end side, and includes a passage entrance provided on the exhaust end side, and a passage exit directed toward the inter-exhaust-port-wall water channel. An exhaust port wall includes a heat dissipation fin extending from a first exhaust entrance port wall toward an exhaust end. The space between the heat dissipation fin and a second exhaust entrance port wall forms a water channel entrance of the inter-exhaust-port-wall water channel.

The present invention relates to a liquid-cooled internal combustion engine comprising an engine block, which includes a plurality of cylinders, and cylinder heads closing the cylinders, wherein each cylinder is surrounded by a respective cooling liner and each cylinder head has provided therein at least one separate cooling chamber connected to the cooling liner of the associated cylinder via at least one transition channel, wherein the transition channels of at least two cylinders are interconnected via a pressure compensation chamber.

A cylinder head comprises a cylinder head body. The cylinder head body has two intake ports placed on a first side of the cylinder head body with respect to the plug hole, and the two exhaust ports placed on a second side of the cylinder head body with respect to the plug hole. A water jacket of the cylinder head includes: an intake-port-to-intake-port passage portion communicating with the outside of the cylinder head and extending between the two intake ports; an exhaust-port-to-exhaust-port passage portion communicating with the outside of the cylinder head and extending between the two exhaust ports; and a central passage portion communicating with the intake-port-to-intake-port passage portion and the exhaust-port-to-exhaust-port passage portion, the central passage portion being formed so as to surround the plug hole.

A cylinder head comprises a cylinder head body. The cylinder head body has two intake ports placed on a first side of the cylinder head body with respect to the plug hole, and the two exhaust ports placed on a second side of the cylinder head body with respect to the plug hole. A water jacket of the cylinder head includes: an intake-port-to-intake-port passage portion communicating with the outside of the cylinder head and extending between the two intake ports; an exhaust-port-to-exhaust-port passage portion communicating with the outside of the cylinder head and extending between the two exhaust ports; and a central passage portion communicating with the intake-port-to-intake-port passage portion and the exhaust-port-to-exhaust-port passage portion, the central passage portion being formed so as to surround the plug hole.

A press-fit sleeve for sealing and cooling a component projecting through a fire deck opening in the cylinder head of an internal combustion engine is described. The press-fit sleeve includes a connecting point at a first end of the press-fit sleeve, said connecting point being designed for press fitting into an indentation at an end of the fire deck opening that faces away from a combustion chamber. Furthermore, the press-fit sleeve includes a radially inwardly protruding step at a second end of the press-fit sleeve lying opposite the first end. Between the first end and the second end, the press-fit sleeve includes a lateral surface which is closed in a fluid-tight manner and is or can be brought into contact with a water jacket surrounding the press-fit sleeve.

A press-fit sleeve for sealing and cooling a component projecting through a fire deck opening in the cylinder head of an internal combustion engine is described. The press-fit sleeve includes a connecting point at a first end of the press-fit sleeve, said connecting point being designed for press fitting into an indentation at an end of the fire deck opening that faces away from a combustion chamber. Furthermore, the press-fit sleeve includes a radially inwardly protruding step at a second end of the press-fit sleeve lying opposite the first end. Between the first end and the second end, the press-fit sleeve includes a lateral surface which is closed in a fluid-tight manner and is or can be brought into contact with a water jacket surrounding the press-fit sleeve.

An opposed-piston engine optionally contains an ignition system that is at least partially contained within the combustion chamber to enhance the combustion efficiency of a fuel-air mixture within the combustion system. More specifically, the ignition system contains at least one spark plug having an elongated center electrical delivery electrode, and, an elongated ground electrode. Accordingly, the elongated electrodes extend from an area adjacent to the inner periphery of the cylinder to a radially central area within the combustion chamber. Yet further, a cooling jacket is incorporated to provide cooling of the spark plug.

An opposed-piston engine optionally contains an ignition system that is at least partially contained within the combustion chamber to enhance the combustion efficiency of a fuel-air mixture within the combustion system. More specifically, the ignition system contains at least one spark plug having an elongated center electrical delivery electrode, and, an elongated ground electrode. Accordingly, the elongated electrodes extend from an area adjacent to the inner periphery of the cylinder to a radially central area within the combustion chamber. Yet further, a cooling jacket is incorporated to provide cooling of the spark plug.