Field of application

[0001] The present invention relates to a heat exchanger and a method for manufacturing said heat exchanger .

[0002] Preferably, the present invention belongs to the automotive field .

[0003] Speci fically, the present invention relates to a heat exchanger houseable in a vehicle so as to be fluidically connectable to a working fluid circulation system, preferably oil-based, and to a water circulation system of the vehicle . The flow of the two fluids , for example the working fluid and water, at di f ferent temperatures , inside the circulation passages present in the heat exchanger gives rise to a heat exchange .

[0004] It should be noted that in the present discussion, "working fluid" means an oil-based liquid, such as oil , but also other types of liquids .

[0005] It should be noted that in the present discussion, "water" means a water-based cooling liquid, i . e . , not necessarily comprising only water, but comprising other elements as well , for example glycol .

Background art

[0006] In the background art , heat exchangers are known comprising a plurality of plates , specially shaped and stacked to define a water flow area therein, in which water circulates , and a working fluid flow area, in which working fluid circulates . It is also known that the j oining of said plates is carried out by means of vacuum brazing .

[0007] A problem encountered in the known solutions of plate heat exchangers j oined by brazing is that of wear and tear of the plates due to the action of the water circulating in the water flow area .

[0008] Such wear and tear shorten the duration and li fe of the heat exchanger, thus requiring the replacement thereof .

Solution of the invention

[0009] The need is therefore strongly felt to provide a heat exchanger in which the aforesaid problem is faced and solved .

[0010] The obj ect of the present invention is to provide a heat exchanger suitable for resisting the wearing and corrosive action of water .

[0011] Such an obj ect is achieved by the heat exchanger claimed in claim 1 . Such an obj ect is achieved by the heat exchanger manufacturing method in accordance with claim 6 . The claims dependent thereon show preferred embodiments involving further advantageous aspects .

Description of the drawings [0012] Further features and advantages of the invention will become apparent from the description provided below of preferred exemplary embodiments thereof , given by way of non-limiting example , with reference to the accompanying drawings , in which :

[0013] - figure 1 is a perspective view of a heat exchanger, in accordance with the present invention, according to a preferred embodiment ,

[0014] - figure 2 is a sectional view of the heat exchanger of figure 1 ;

[0015] - figure 3 is an enlarged view of area A of figure 2 ;

[0016] - figure 4 is an enlarged diagrammatic view of area B of figure 3 , in a condition prior to the vacuum brazing operation;

[0017] - figure 4 ' is an enlarged view under the microscope of area B of figure 3 , in a condition prior to the vacuum brazing operation;

[0018] - figure 5 is an enlarged diagrammatic view of area B of figure 3 , in a condition following the vacuum brazing operation;

[0019] - figure 5 ' is an enlarged view under the microscope of area B of figure 3 , in a condition following the vacuum brazing operation;

[0020] - figure 6 is a summary table of the materials forming the layers of an intermediate plate of the heat exchanger obj ect of the present invention .

Detailed description

[0021] With reference to the accompanying drawings , reference numeral 1 indicates a heat exchanger in accordance with the present invention .

[0022] In accordance with the present invention, the heat exchanger 1 obj ect of the present invention is fluidically connectable to a working fluid circulation system, preferably oil-based, and to a water circulation system . Preferably, said working fluid circulation system and water circulation system are comprised in a vehicle .

[0023] In accordance with a preferred embodiment , the working fluid circulation system is fluidically connected with an operating group of the vehicle , for example the engine group and/or the transmission group and/or the gearbox group and/or the cooling group of a vehicle battery group and/or the air conditioning circuit of a vehicle .

[0024] In accordance with a preferred embodiment , the water circulation system is fluidically connected with a cooling group of the vehicle , for example a radiator group .

[0025] Furthermore , in accordance with the present invention, as shown in a non-limiting manner in the accompanying drawings , the heat exchanger 1 extends along a vertical axis V-V and two longitudinal axes X-X, Y-Y . In particular, the two longitudinal axes X-X, Y-Y lie on the same imaginary plane which is orthogonal to the vertical axis V-V .

[0026] Preferably, in the description given below, when reference is made to planar position or elements , it is meant with respect to said longitudinal axes , i . e . , with respect to the imaginary plane on which they are housed . In other words , such components have an extension which is substantially parallel to the plane on which the longitudinal axes X-X, Y-Y lie . Similarly, in the description below, when referring to overlaps , heights and vertical extensions , reference is made to the direction parallel or coincident to the vertical axis V- V, therefore orthogonal to the longitudinal axes X-X, Y- Y .

[0027] It is emphasi zed that in the present description, the use of the terms "upper" and " lower" refers speci fically to the accompanying drawings , but does not in any way limit the use of the heat exchanger 1 or the positioning thereof inside a vehicle .

[0028] The heat exchanger 1 comprises , along said vertical axis V-V, an upper plate 2 , a plurality of intermediate plates 3 and a lower plate 4 . In other words , said plates are mutually stacked along the vertical axis V-V .

[0029] According to a preferred embodiment , the upper plate 2 and the lower plate 4 are suitable for sandwiching the plurality of intermediate plates 3 therebetween .

[0030] In accordance with the present invention, the stacking of said plates defines a water flow area 5 and a working fluid flow area 6 comprising a plurality of planar water flow regions 50 and a plurality of planar working fluid flow regions 60 , respectively, alternating along the vertical axis V-V therebetween .

[0031] Preferably, the heat exchanger 1 comprises respective vertical water ducts 51 , for inlet and outlet , fluidically connected to the respective planar flow regions 50 .

[0032] Preferably, the heat exchanger 1 comprises respective vertical working fluid ducts , 61 , for inlet and outlet , fluidically connected to the respective planar flow regions 60 .

[0033] According to a preferred embodiment , the heat exchanger 1 is of the closed type comprising both vertical working fluid ducts , for inlet and outlet , and vertical water ducts , for inlet and outlet . Said vertical ducts are in communication with respective planar flow regions .

[0034] In accordance with a preferred embodiment , the heat exchanger 1 is of the open type comprising vertical working fluid ducts , for inlet and outlet , in which the heat exchanger 1 is immersed inside a working chamber in which water circulates . Preferably, the water circulates inside planar flow portions in fluid communication with said chamber by means of passages included between pairs of mutually coupled intermediate plates to define the planar flow regions for the working f luid .

[0035] In accordance with a preferred embodiment , the water flow area 5 comprises two vertical water ducts 51 , for inlet and outlet .

[0036] In accordance with a preferred embodiment , the working fluid flow area 6 comprises two vertical working fluid ducts 61 , for inlet and outlet .

[0037] The present invention is not limited to the position of the vertical water ducts 51 with respect to the longitudinal directions .

[0038] Similarly, the present invention is not limited to the position of the vertical working fluid ducts 61 with respect to the longitudinal directions .

[0039] In accordance with a preferred embodiment , the plates are speci fically shaped so as to vertically align a plurality of speci fic through openings so as to identi fy the vertical ducts .

[0040] According to a preferred embodiment , the plates are speci fically shaped to identi fy speci fic planar, i . e . , longitudinal , passages therebetween .

[0041] In accordance with a preferred embodiment , the plates are speci fically shaped so as to have speci fic portions suitable for allowing mutual engagement .

[0042] In accordance with the present invention, said plates are mutually j oined by a vacuum brazing process .

[0043] Therefore , said plates are preferably made of a metal alloy, preferably aluminum alloy, which plates , following the vacuum brazing process , are mutually oined .

[0044] In accordance with the present invention, the intermediate plates 3 facing the water flow area 5 comprise a respective water face , and said intermediate plates 3 comprise Zinc in a region near the water face .

[0045] According to a preferred embodiment , each intermediate plate 3 comprises a water face which is facing and defining the water flow area and a working fluid face which is facing and defining the working fluid flow area .

[0046] Preferably, each intermediate plate 3 comprise a water face that , in the region thereof near the water flow area, comprises Zinc .

[0047] According to the present invention, the intermediate plates 3 facing the water flow area comprise a film 35 defining said water face, in which said film 35 is made of an aluminum alloy containing Zinc .

[0048] In accordance with the present invention, and hereinafter it will be described in an even more detailed manner, the amount of Zinc in the film 35 is between 0 . 2 and 1 % by weight , preferably between 0 . 4 % and 0 . 9% by weight . In particular, said percentages refer to the weight of the film 35 .

[0049] Preferably, said film 35 is obtained following the vacuum brazing operation between a layer of 4000 series aluminum alloy, preferably of the 4147 type , and a layer of 7000 series aluminum alloy .

[0050] Preferably said film 35 has a single-layer structure .

[0051] Preferably said film 35 has a multilayer structure .

[0052] In accordance with a preferred embodiment , the concentration of Zinc inside the film 35 has a trend of increasing composition with a substantially monotonous trend passing from a minimum of 0 . 4 % by weight near the outer surface corresponding to the water face to a maximum between 0 . 8 % and 1 % by weight at the region of the film 35 near the inner core of the intermediate plate 3 .

[0053] According to a preferred embodiment , similarly, the same trend in the amount of Zinc is also noticeable at a welding j oint between adj acent intermediate plates 3 .

[0054] In accordance with the present invention, said film 35 has a thickness between 19% and 22 % of the thickness of the intermediate plate 3 . Preferably, said film 35 has a thickness superior to 16% of the thickness of the intermediate plate 3 .

[0055] In accordance with a preferred embodiment , the intermediate plate 3 has a thickness of about 600 pm and the film 35 has a thickness between 120 pm and 130 pm .

[0056] Preferably, said film 35 has an amount of Magnesium less than 0 . 4 % by weight , preferably less than 0 . 3% by weight . In particular, said percentages refer to the weight of the film 35 .

[0057] In accordance with a preferred embodiment , each intermediate plate 3 is a multilayer consisting of aluminum layers , preferably aluminum alloy, comprising a 3000 series aluminum alloy layer in a central position, a 7000 series aluminum alloy layer in an intermediate central position and two outer brazing layers in 4000 series aluminum alloy positioned at the two outer positions .

[0058] In other words , each intermediate plate 3 comprises an intermediate central layer in 7000 series aluminum alloy .

[0059] As mentioned, the present invention also relates to a manuf cturing method of a heat exchanger 1 with the features described above .

[0060] The manufacturing method firstly comprises the step of forming the intermediate plates 3 by laminating a plurality of specially shaped planar layers , comprising : a first outer brazing layer 31 in a 4000 series aluminum alloy, preferably suitable for identi fying a working fluid face , preferably oil-based, delimiting the working fluid flow area, preferably oil-based;

- a central core layer 32 in a 3000 series aluminum metal alloy, preferably 3359 series , engaged to the first outer brazing layer 31 ;

- an intermediate central layer 33 , in an aluminum metal alloy comprising Zinc in an amount between 2 % and 2 . 5% by weight , engaged to the central core layer 32 , on the opposite side with respect to the first outer brazing layer 31 ; a second outer brazing layer 34 in a 4000 series aluminum alloy, engaged to the intermediate central layer 33 , preferably suitable for identi fying a water face delimiting the water flow area .

[0061] According to a preferred embodiment , said one intermediate central layer 33 is in a 7000 series aluminum alloy .

[0062] Following said step, the manufacturing method comprises the steps of: stacking the upper plate 2, the plurality of intermediate plates 3 and the lower plate 4; carrying out the vacuum brazing so as to join the plates together.

[0063] In accordance with the invention, in the vacuum brazing step, the intermediate central layer 33 and the second outer layer 34 form a protective film 35 comprising Zinc.

[0064] In other words, following the vacuum brazing process, the intermediate central layer 33 brings the Zinc necessary to form a sacrificial anodic protection layer on the water face of the intermediate plates 3.

[0065] In accordance with a preferred embodiment, the intermediate central layer 33 is made of an aluminum metal alloy also comprising Magnesium in an amount between 0.25 and 0.45% of the weight. In particular, said percentages refer to the weight of the intermediate central layer 33.

[0066] In addition, according to a preferred embodiment, the intermediate central layer 33 is made of an aluminum metal alloy comprising Silicon in an amount between 0.25% and 0.45% by weight. In particular, said percentages refer to the weight of the intermediate central layer 33.

[0067] According to a preferred embodiment, the intermediate central layer 33 has a thickness between 16% and 20% , preferably has a thickness of 18 % , with respect to the total thickness of the plurality of laminated layers , i . e . , the thickness of the intermediate plate before the vacuum brazing process .

[0068] Preferably, with an intermediate plate having a thickness of 600 pm, the intermediate central layer 33 has a thickness between 96 pm and 120 pm, preferably between 105 and 110 pm .

[0069] In accordance with a preferred embodiment , the first outer brazing layer 31 and the second outer brazing layer 34 have a thickness between 6% and 10% , respectively, preferably, they have a thickness of 8 % with respect to the total thickness of the plurality of laminated layers , i . e . , the thickness of the intermediate plate before the vacuum brazing process .

[0070] Preferably, with an intermediate plate having a thickness of 600 pm, the first outer brazing layer 31 and the second outer brazing layer 34 have a thickness between 36 pm and 60 pm, preferably between 45 pm and 50 pm, preferably corresponding to 48 pm .

[0071] Preferably, the thickness of the first outer brazing layer 31 is substantially equal to the thickness of the second brazing layer 34 .

[0072] Preferably, the thickness ratio between the first outer brazing layer 31 and/or between the second outer brazing layer 34 and the intermediate central layer 33 is between 0.375 and 0.5, preferably said ratio is between 0.4 and 0.45, preferably equal to 0.44.

[0073] According to a preferred embodiment, the central core layer 32 has an indicative thickness between 60% and 65% with respect to the total thickness of the plurality of laminated layers, i.e., the thickness of the intermediate plate before the vacuum brazing process.

[0074] According to a preferred embodiment, the sum of the thickness of the intermediate central layer 33 and of the second outer brazing layer 34 is between 22% and 30%, preferably equal to 26%, of the total thickness of the plurality of laminated layers, i.e., the thickness of the intermediate plate before the vacuum brazing process.

[0075] According to a preferred embodiment, the sum of the thickness of the intermediate central layer 33 of the first outer layer 31 and of the second outer layer 34 is between 28% and 40%, preferably equal to 34%, of the total thickness of the plurality of laminated layers, the thickness of the intermediate plate before the vacuum brazing process.

[0076] Preferably, the thickness of the central core layer 32 is greater than 50% of the total thickness of the plurality of laminated layers, of the thickness of the intermediate plate before the vacuum brazing process .

[0077] Preferably, the thickness of the central core layer 32 is equal to 66% of the total thickness of the plurality of laminated layers . Preferably the thickness of the remaining layers is equal to 34 % , with the thickness of the intermediate central layer 33 between 16% and 20% and the respective thickness of the outer brazing layers 31 and 34 between 6% and 10% (with the sum of the thicknesses giving 100% ) .

[0078] According to a preferred embodiment , the first outer brazing layer 31 and the second outer brazing layer 34 are made of a 4000 series aluminum metal alloy of the 4104 series and 4147 series , respectively .

[0079] According to a preferred embodiment , the first outer brazing layer 31 is made of an aluminum alloy comprising Magnesium in an amount between 1 % and 2 % by weight . Preferably, the aluminum alloy of the first outer brazing layer 31 comprises Silicon in an amount between 10 . 5% and 9% by weight .

[0080] According to a preferred embodiment , the second outer layer 34 is made of an aluminum alloy comprising Magnesium in an amount between 0 . 5% and 0 . 1 % by weight . Preferably, the aluminum alloy of the second outer brazing layer 34 comprises Silicon in an amount between 13% and 11 % by weight . [0081] The presence of Magnesium in the outer layers and in the intermediate central layer makes the intermediate plate workable by vacuum brazing .

[0082] Preferably, the presence of Silicon in the outer layers improves the brazing of the layers in which it is comprised .

[0083] The amount of Magnesium in the outer layers combined with the thickness of said layers makes the intermediate plates vacuum brazable .

[0084] In particular, the amount of Magnesium in the intermediate central layer 33 is less than 0 . 5% by weight .

[0085] Preferably, the amount of Magnesium in the second outer brazing layer 34 is between 0 . 5% and 0 . 1 % by weight .

[0086] In accordance with such a preferred embodiment , the film 35 is obtained following the vacuum brazing between a layer of 4000 series aluminum alloy and a layer of 7000 series aluminum alloy .

[0087] According to a preferred embodiment , the vacuum brazing step is carried out in a braz ing oven .

[0088] In accordance with a preferred embodiment , the oven brazing step occurs at a temperature between 580 ° C and 640 ° C, preferably at 590 ° C .

[0089] In accordance with a preferred embodiment , the oven brazing step occurs at a pressure between 10 ^A -2 and 10 ^A -4 Pa, preferably at 10 ^A -3 Pa .

[0090] In accordance with the present invention, the brazing step occurs in the absence of flux .

[0091] In accordance with the present invention, the features of the layers 31 , 32 , 33 and 34 and of the film 35 described for the intermediate plates are usable for the upper plate 2 and for the lower plate 4 , preferably in the case in which said plates comprise faces suitable for delimiting the water flow region .

[0092] Figure 6 shows , by way of example , a table with the composition of the various layers forming an intermediate plate 3 , thus other elements forming the aforesaid aluminum alloys in addition to those mentioned above are also listed in such a table . In particular, in said table , the minimum and maximum values of said elements , ore the maximum values of some elements , are indicated .

[0093] With particular reference to some speci fic amounts described above , the present invention is not limited thereto , taking into account and protecting also speci fic embodiments with values comprised in a range of tolerances . With particular reference to the 600 pm of the thickness of the intermediate plate 3 these have a variability between -50 pm and +50 pm

[0094] Innovatively, the heat exchanger and heat exchanger manufacturing method largely ful fill the obj ect of the present invention, overcoming the typical problems of the background art .

[0095] Advantageously, the heat exchanger has a high resistance to wear and tear due to the action o f water .

[0096] Advantageously, the plates of the heat exchanger facing the water flow regions are protected by the presence of a film having a predefined thickness si zed so as to ensure suf ficient resistance to corrosion and at the same time an adequate mechanical-structural resistance of the heat exchanger .

[0097] Advantageously, the plates of the exchanger facing the water flow regions comprise a protective film obtained by means of an outer brazing layer and a central intermediate layer having a magnesium content not higher than 0 . 5% . Such an amount allows ensuring adequate vacuum brazing between the plates of the exchanger, ensuring adequate sliding of the plating useful for obtaining a mechanically resistant j oint , suitable for the stable coupling between plates and reducing the number of process rej ects .

[0098] Advantageously, the plates of the exchanger facing the water flow regions comprise a protective film obtained by an outer brazing layer and a central intermediate layer having a magnesium content not higher than 0 . 5% and a limited total thickness with respect to the total thickness of the plate itsel f . Said combination allows ensuring the vacuum brazability of the plates , ensuring the formation of a protective film thick enough to ensure the corrosion resistance of the heat exchanger . Advantageously, the outer brazing layers and the intermediate central layer comprise an amount of Magnesium useful to allow the vacuum brazing process without the aid of fluxes .

[0099] Advantageously, the plates of the exchanger comprise brazing layers of controlled thickness with respect to the intermediate central layer, reducing the brazing alloy content , the cost of the plates and of the exchanger .

[00100] Advantageously, the plates of the exchanger comprise a central layer occupying at least hal f of the total thickness defined by the lamination of the layers forming the intermediate plate , preferably 2 / 3 of the total thickness ensuring the maintenance of the mechanical resistance properties required by automotive applications in which the heat exchanger i s used .

[00101] Advantageously, plates having an outer brazing layer positioned adj acent to the central intermediate layer, having a controlled Magnesium content and a thickness ratio comprised in a predefined range allows favoring the formation of a protective film of adequate thickness and at the same time an adequate j oining between plates by vacuum brazing .

[00102] Advantageously, the central core layer is protected from corrosion . Advantageous ly, the central core layer is protected from pitting corrosion .

[00103] Advantageously, the multilayer structure forming each intermediate plate has high structural properties .

[00104] Clearly, in order to satis fy contingent needs , a person skilled in the art could make changes to the heat exchanger and the manufacturing method thereof described above , all contained in the scope of protection as defined by the following claims .

List of reference symbols :

[00105]

1 heat exchanger

2 upper plate

3 intermediate plates

31 first outer layer

32 central core layer

33 central intermediate layer

34 second outer layer

35 film

4 lower plate 5 water flow area

50 planar water flow region

51 vertical water duct

6 working fluid flow area 60 planar working fluid flow region

61 vertical working fluid duct

X-X, Y-Y longitudinal axes

V-V vertical axis