An EGR gas distributor includes a gas chamber, a gas inflow passage to introduce EGR gas on its upstream side, gas outflow passages to discharge the EGR gas to branch pipes on their downstream side. An inner wall on a downstream side of the gas chamber is divided into downstream-side divided walls corresponding to the respective gas outflow passages, and the downstream-side divided walls are curved or slanted to be of protrusion-like shape protruding toward the corresponding gas outflow passages. Downstream-side dividing ridges are provided each between the adjacent downstream-side divided walls. An inner wall on the upstream side of the gas chamber is placed to face the downstream-side inner wall and provided with at least one upstream-side ridge protruding toward the downstream-side divided walls in each area corresponding to the downstream-side divided walls.

An EGR cooler 5 is attached to an engine 1 via a bracket 6. The bracket 6 has an exhaust introduction path 65 for introducing some exhaust discharged from a cylinder head 11 to the EGR cooler 5, an exhaust recirculation path 66 for recirculating exhaust that has passed through the EGR cooler 5 toward the engine 1, a cooling water introduction path 67 for introducing cooling water from cooling water supply parts (3, 13-15) to the EGR cooler 5, and a cooling water recirculation path 68 for recirculating cooling water that has passed through the EGR cooler 5 to the cooling water supply parts.

An EGR cooler 5 is attached to an engine 1 via a bracket 6. The bracket 6 has an exhaust introduction path 65 for introducing some exhaust discharged from a cylinder head 11 to the EGR cooler 5, an exhaust recirculation path 66 for recirculating exhaust that has passed through the EGR cooler 5 toward the engine 1, a cooling water introduction path 67 for introducing cooling water from cooling water supply parts (3, 13-15) to the EGR cooler 5, and a cooling water recirculation path 68 for recirculating cooling water that has passed through the EGR cooler 5 to the cooling water supply parts.

A cylinder head includes: an exhaust port configured to lead out exhaust gas from combustion chamber; an intake port configured to introduce fresh air into the combustion chamber; an intake air aggregate part configured to aggregate the intake port; and a second EGR pipe in which EGR gas flows, wherein exhaust outlets of the exhaust port and an EGR gas inlet of the second EGR pipe are arranged side-by-side on a flat left side surface, and a fresh air inlet of the intake air aggregate part and an EGR gas outlet of the second EGR pipe are arranged side-by-side on a flat right side surface.

An exhaust gas recirculation system for a multi-cylinder engine is provided, which includes an exhaust manifold connected to a cylinder head, a catalyst connected to a downstream end of the exhaust manifold in terms of an exhaust gas flow, an EGR gas outlet provided downstream of the catalyst, an in-head EGR passage penetrating the cylinder head, and an EGR pipe extending from the EGR gas outlet and directly connected to an inlet of the in-head EGR passage to lead EGR gas thereto. The catalyst is disposed so that the exhaust gas flows therein from a first side to a second side in an engine cylinder lined-up direction. The EGR gas outlet is located on the second side with respect to the center of the engine in the cylinder lined-up direction, and the inlet of the in-head EGR passage is located in the first side with respect to the engine center.

An exhaust gas recirculation structure includes an EGR cooler and an EGR duct, and the EGR duct includes an inflow portion into which the exhaust gas flowing out from the EGR cooler flows, a flow path, and an outflow portion from which the exhaust gas flows out. The flow path is provided such that the height on the side of the inflow portion is lower than the height on the side of the outflow portion, and has a region in which the distance between the center line of a flow path cross section of the flow path and a line along the lowest end in the height direction gradually increases from the outflow portion side toward the inflow portion side.

An exhaust gas recirculation structure includes an EGR cooler and an EGR duct, and the EGR duct includes an inflow portion into which the exhaust gas flowing out from the EGR cooler flows, a flow path, and an outflow portion from which the exhaust gas flows out. The flow path is provided such that the height on the side of the inflow portion is lower than the height on the side of the outflow portion, and has a region in which the distance between the center line of a flow path cross section of the flow path and a line along the lowest end in the height direction gradually increases from the outflow portion side toward the inflow portion side.

An engine 1 includes an exhaust manifold, an intake manifold, and an EGR device configured to supply EGR gas from the exhaust manifold to the intake manifold. An upper end of the EGR cooler extended downward is attached to a downwardly extending attachment part provided to the exhaust manifold.

An engine 1 includes an exhaust manifold, an intake manifold, and an EGR device configured to supply EGR gas from the exhaust manifold to the intake manifold. An upper end of the EGR cooler extended downward is attached to a downwardly extending attachment part provided to the exhaust manifold.

A cylinder head cooling system may include a main water jacket formed on a cylinder head, an exhaust port formed on the cylinder head, and an exhaust port water jacket formed to cool the exhaust port, wherein, the exhaust port water jacket includes an inlet that communicates with the main water jacket and a plurality of outlets separated from the main water jacket.