EGR system of engine

An exhaust gas recirculation (EGR) system of an engine, comprising:

• an engine body including:
• a cylinder head provided in an upper part of the engine body and forming a plurality of combustion chambers in which combustion is performed, a first end surface, and a second end surface, the plurality of combustion chambers being lined up between the first end surface and the second end surface;
• an intake passage configured to introduce intake air into each of the plurality of combustion chambers via an intake manifold attached to the cylinder head;
• an exhaust passage connected to the cylinder head and through which exhaust gas is discharged from the combustion chambers;
• and
• an EGR passage connecting the exhaust passage to the intake passage and configured to recirculate the exhaust gas as EGR gas to the intake passage, the EGR passage including:
• an EGR cooler configured to cool the EGR gas while the EGR gas flows from a gas inflow port to a gas outflow port;
• an EGR internal passage passing through the cylinder head, on an upstream side of the EGR cooler;
• and
• a relay passage extending outside the cylinder head and connecting the EGR internal passage to the EGR cooler,
• wherein the cylinder head is formed in the first end surface with a head EGR gas exit from which the EGR gas is discharged after passing through the cylinder head,
• wherein the EGR cooler is formed in a columnar shape having the gas inflow port at one end side in a longitudinal direction and the gas outflow port at the other end side in the longitudinal direction, and is arranged above the intake manifold so as to locate the gas inflow port on the first end surface side and the gas outflow port on the second end surface side, the relay passage communicating with the EGR internal passage, on an external side of the engine compared to the head EGR gas exit, and
• wherein the EGR cooler inclines downward from the gas outflow port toward the gas inflow port, and the relay passage is connected to the gas inflow port while being bent downward toward the upstream side.