Patent ID: 7077190

Claim:
An exhaust gas heat exchanger comprising: a plurality of exhaust gas passages each of which has a flat sectional shape and through which exhaust gas generated by combustion flows, wherein the plurality of exhaust gas passages are laminated so as to be disposed substantially parallel with each other; a tank containing the plurality of exhaust gas passages; a water passage formed in the tank through which cooling water flows to exchange heat with the exhaust gas passing through the plurality of exhaust gas passages; a cooling water inlet pipe disposed on the tank, through which the cooling water flows into the tank; a cooling water outlet pipe disposed on the tank, through which the cooling water is exhausted from the tank; and a guide provided in the water passage for leading the cooling water colliding with an inner wall of the tank toward an upstream side of at least one of the plurality of exhaust gas passages; wherein the guide is shaped such that a main flow of the cooling water from the cooling water inlet pipe is introduced into the water passage in a direction substantially perpendicular to a longitudinal direction of the plurality of exhaust gas passages at an upstream side of the plurality of exhaust gas passages; the cooling water inlet pipe is connected to the tank at an upstream side, in a flow direction of the exhaust gas passing through the plurality of exhaust gas passages, with respect to the cooling water outlet pipe; the cooling water inlet pipe is disposed in such a manner that the cooling water inlet pipe is capable of introducing the cooling water in a direction parallel to a flat surface of the exhaust gas passage, the plurality of exhaust gas passages are disposed in the tank to have a clearance between a first inner wall of the tank and the exhaust gas passages, the first inner wall of the tank facing the cooling water inlet pipe, and the guide is disposed on the flat surface of the exhaust gas passages, an overall length of the guide in the direction substantially perpendicular to the longitudinal direction of the plurality of exhaust gas passages being less than an overall length of the flat surface of the exhaust gas passage in the direction substantially perpendicular to the longitudinal direction of the plurality of exhaust gas passages to form a plurality of openings.