Exhaust gas heat exchanger

Abstract

An exhaust gas heat exchanger for an internal combustion engine includes an exhaust passage and an offset fin. The offset fin includes a plurality of side walls and a plurality of top walls. The offset fin is defined into a plurality of segments that are offset from each other in an offset direction. One of the plurality of top walls of the offset fin has a projection that inwardly projects therefrom. The projection is provided to one of the plurality of segments. The projection of the one of the plurality of segments is opposed to an upstream end portion of the other one of the plurality of side walls of the other one of the plurality of segments that is positioned adjacently downstream of the one of the plurality of segments in the circulation direction.

1 . An exhaust gas heat exchanger for an internal combustion engine comprising:
 an exhaust passage, though which exhaust gas discharged from the internal combustion engine flows; and   an offset fin that is provided within the exhaust passage, wherein the offset fin has a cross sectional shape of a rectangular waveform taken along a plane perpendicular to a circulation direction of exhaust gas, wherein the offset fin includes a plurality of side walls, which forms leading and trailing parts of the waveform, and a plurality of top walls, which forms crest and valley parts of the waveform, wherein the offset fin is defined into a plurality of segments that are offset from each other in an offset direction, in which the plurality of side walls are arranged in series, wherein:   heat is exchanged between (a) exhaust gas flowing through the exhaust passage and (b) cooling fluid flowing at an exterior of the exhaust passage;   one of the plurality of top walls of the offset fin has a projection that inwardly projects therefrom;   the projection is provided to one of the plurality of segments; and   the projection of the one of the plurality of segments is opposed to an upstream end portion of the other one of the plurality of side walls of the other one of the plurality of segments that is positioned adjacently downstream of the one of the plurality of segments in the circulation direction.   
   
   
       2 . The exhaust gas heat exchanger according to  claim 1 , wherein:
 the projection is made by cutting a part of the one of the plurality of top walls and by folding the cut part such that the projection projects inwardly from the one of the plurality of top walls.   
   
   
       3 . The exhaust gas heat exchanger according to  claim 2 , wherein:
 the plurality of segments is arranged in the circulation direction of the exhaust gas and is alternately offset from each other;   the projection has a triangular shape and has a folding side, along which the projection is folded relative to the one of the plurality of top walls;   the projection is provided such that the folding side is angled relative to the circulation direction of the exhaust gas;   the projection is one of a plurality of projections, each of which projects from a corresponding one of the plurality of top walls;   the projection, which projects from the one of the plurality of top walls, is a first projection;   a second projection of the plurality of projections projects from the other one of the plurality of top walls that is positioned downstream of the one of the plurality of top walls in the circulation direction;   a projection amount, by which the first projection projects from the one of the plurality of top walls, is smaller than a projection amount, by which the second projection projects from the other one of the plurality of top walls; and   the folding sides of the plurality of projections are arranged in the circulation direction and are alternately angled relative to the circulation direction.   
   
   
       4 . The exhaust gas heat exchanger according to  claim 1 , wherein:
 exhaust gas is supplied to an inlet side of the internal combustion engine and is used for exhaust gas recirculation; and   cooling fluid is a coolant that cools the internal combustion engine.   
   
   
       5 . The exhaust gas heat exchanger according to  claim 1 , wherein:
 each of the plurality of segments has a first dimension measured in the circulation direction of exhaust gas;   the projection of the one of the plurality of segments has a second dimension measured in the circulation direction; and   the first dimension is equal to or greater than the second dimension; and   the first dimension is equal to or less than a dimension that is seven times larger than the second dimension.