Abstract: An oil cooler is contained in a radiator tank. It includes a connecting pipe having an enlarged diameter portion, a heat exchange part including elements and a communicating passage fluidically communicating the elements, and a pipe connector. The pipe connector has a first retaining portion seated on one side of a wall portion of the radiator tank to contain and fix at least a part of the enlarged diameter portion of the connecting pipe by caulking, and a second retaining portion inserted through a through-hole of the wall portion and an one end portion of the communicating passage to fix the heat exchanger part and the wall portion at the other side of the wall portion by caulking.

Abstract: An air cooled oil cooler has an upper plate, a lower plate and a plurality of tubes and outer fins disposed therebetween. Each tube contains an inner offset fin, and the outer fins formed in a corrugated shape and each having one return louver on an intermediate portion between a top portion and a bottom portion of the outer fin. The outer fins is disposed between the tubes so that the tubes and the outer fins are arranged alternatively and stacked in a pile between the upper and lower plates. The tubes are formed to be flat tubes having a height-width ratio of the tube to be 4.8-7.4%.

Abstract: An oil cooler is contained in a radiator tank. It includes a connecting pipe having an enlarged diameter portion, a heat exchange part including elements and a communicating passage fluidically communicating the elements, and a pipe connector. The pipe connector has a first retaining portion seated on one side of a wall portion of the radiator tank to contain and fix at least a part of the enlarged diameter portion of the connecting pipe by caulking, and a second retaining portion inserted through a through-hole of the wall portion and an one end portion of the communicating passage to fix the heat exchanger part and the wall portion at the other side of the wall portion by caulking.

Abstract: An air cooled oil cooler has an upper plate, a lower plate and a plurality of tubes and outer fins disposed therebetween. Each tube contains an inner offset fin, and the outer fins formed in a corrugated shape and each having one return louver on an intermediate portion between a top portion and a bottom portion of the outer fin. The outer fins is disposed between the tubes so that the tubes and the outer fins are arranged alternatively and stacked in a pile between the upper and lower plates. The tubes are formed to be flat tubes having a height-width ratio of the tube to be 4.8-7.4%.