Heat exchanger

Abstract

Oil passages 113 through which oil passes are formed with plates 111, 112 composed of aluminum or an aluminum alloy in an oil cooler, according to the present invention, that is a heat exchanger with an extended life. Moreover, fins 123 a composed of a material having a corrosion potential more negative than those of the plates 111, 112 are arranged in cooling water passages 123 through which cooling water, for exchanging heat with oil, passes. A sacrificial corrosive layer 301 having a corrosion potential more negative those of the plates 111, 112 and the fins 123 a is formed on each of the surfaces on the sides of the cooling water passages 123 of the plates 111, 112. As a result, the sacrificial corrosive layer 301 is preferentially corroded, and not only the plates 111, 112 but also the fins 123 a can be protected. Consequently, the pressure-proof strength of the oil cooler can be maintained, and the product life can be improved.

1 . A heat exchanger for carrying out a heat exchanger between oil and cooling water, which comprises: 
 a plurality of first plates and a plurality of second plates that are composed of aluminum or an aluminum alloy, and that are alternately laminated and joined by brazing;    oil passages which are each formed between one surface of one of the first plates and one surface of one of the second plates that is arranged to face the one surface of the first plate, and through which oil passes;    cooling water passages which are each formed between the other surface of the one of the first plates and one surface of one of the second plates that is arranged to face the other surface of the first plate, and through which cooling water passes;    cooling water side fins brazed to the inner wall surfaces of the cooling water passages, wherein the cooling water side fins are composed of aluminum or an aluminum alloy having a corrosion potential more negative than those of the core layers of the first plates and the core layers of second plates, and a sacrificial corrosive layer having a corrosion potential more negative than those of the core layers of the first plates, the core layer of the second plates and the cooling water side fins is formed on each of the other surface of the first plate and the other surface of the second plate that faces the other surface of the first plate; and    the corrosion potential of the cooling water side fins is 5 to 50 mV higher than those of the sacrificial corrosive layer of the first plates and the sacrificial corrosive layer of the second plates.    
   
   
       2 . A heat exchanger according to  claim 1 , wherein the heat exchanger is an oil cooler.  
   
   
       3 . A laminated type heat exchanger comprising: 
 a plurality of first plates and a plurality of second plates alternately laminated to form oil passages through which oil flows and cooling water passages through which cooling water flows alternately and joined by brazing;    each of the oil passages is formed between one surface of the first plate and one surface of the second plate;    each of the cooling water passages is formed between the other surface of the first plate and the other surface of the second plates; and    a cooling water side fin brazed to each of the other surfaces of the first plates and each of the other surfaces of the second plates; wherein    each of the first plates and the second plates comprises a laminated layer of a core layer made of aluminum or aluminum alloy completely covered by a sacrificial corrosive layer disposed on the other surface of the first plate and on the other surface of the second plate;    the sacrificial corrosive layer is made of a material of which an electrical potential is more negative than an electrical potential of the core layers and the cooling water side fins;    the cooling water side fins are made of a material of which an electrical potential is more negative than the core layers; and    the corrosion potential of the cooling water side fins is 5 to 50 mV higher than those of the sacrificial corrosive layer of the first plates and the sacrificial corrosive layer of the second plates.    
   
   
       4 . A heat exchanger according to  claim 3 , wherein the heat exchanger is an oil cooler.