Electric heater for a vehicle

Abstract

An electric heater (1) for a vehicle, adapted to heat a liquid crossing said heater, comprising : - a body (2) made of die-cast metal material; - at least one electrical resistor (3); - an inlet connection (12), projecting from the body (2), for the liquid to enter into said body (2); - an outlet connection (13), projecting from the body (2), for the liquid to exit from said body (2); - a first flow path (4) for the liquid, from said inlet connection (12) to said outlet connection (13), made on a first face of said body (2); - a first cover (6) that closes, with a first side thereof, the first flow path (4); wherein the first flow path (4) comprises at least one serpentine channel (21) which starts from the inlet connection (12) and ends in the outlet connection (13); wherein said at least one serpentine channel (21) comprises a first straight stretch (35) proximal to the inlet connection (12), a second straight stretch (36) proximal to the outlet connection (13), at least one third straight stretch (37) interposed between said first straight stretch (35) and said second straight stretch (36), and a plurality of hairpin bends (30), each hairpin bend (30) being arranged between one straight stretch and the next one; wherein a heating part of said first electrical resistor (3) is serpentine-shaped and comprises respective straight stretches (50, 50') and curved stretches (51), each curved stretch (51) being arranged between a straight stretch (50, 50') of said heating part and the next one; and wherein the straight stretches (50, 50') of said heating part are arranged transversely to the straight stretches (35, 36, 37) of said at least one serpentine channel (21).

Description

[0001] ELECTRIC HEATER FOR A VEHICLE

[0002] ★★★★★★★★★★★

[0003] Field of the invention

[0004] The present invention relates to an electric heater for vehicles, preferably but not necessarily electric or hybrid vehicles, in particular to heat a battery cooling liquid in case of low outdoor temperatures, keeping the ideal operating temperature constant, or to heat a liquid for use in an exchanger for heating the air in the passenger compartment.

[0005] Background art

[0006] The battery is essential for the operation of an electric or hybrid vehicle. It must provide the amount of energy necessary to operate the vehicle quickly and reliably. Most batteries are high-voltage hybrid lithium-ion and nickel-metal batteries.

[0007] It is essential for the batteries used to be operated within a determined temperature range. In fact, the service life starts reducing from an operating temperature of +40°C, while performance and power decrease below -10°C. Furthermore, the temperature difference between the single battery cells must not exceed a determined value. Exceeding the limit temperatures results in more rapid aging and therefore the corresponding early failure of the battery. Vehicle manufacturers aim for a battery life equal to that of the vehicle. Therefore, the aging process can only be counteracted by optimally managing the temperature.

[0008] The battery unit includes battery cells, a cooling plate and an auxiliary electric heater. The cooling plate, mounted in the battery cell block, is crossed by the cooling liquid composed, for example, of water and glycol.

[0009] To ensure higher performance and maximum service life of the battery, the temperature of the related coolant must be between about 15 and 30°C. When temperatures are too high, the liquid is cooled, for example, by a low-temperature radiator. If, on the contrary, the temperatures are too low, the coolant is heated by the auxiliary electric heater. The latter thus ensures sufficient control of the battery temperature at low outdoor temperatures. To carry out this heating, the battery is integrated into a secondary circuit. This circuit ensures constant maintenance of the ideal operating temperature, between 15° and 30°C.

[0010] Such an electric heater generally comprises at least one electric heating unit for generating heat and for discharging the generated heat to a heat carrier medium, represented by the aforementioned liquid, by means of a body made of metal material with which the electric heating unit is in contact.

[0011] Such a liquid can be, for example, water, glycol, water and glycol, or another suitable heat carrier liquid.

[0012] Such a liquid flows along a flow path comprising a plurality of serpentine channels connected in parallel, and is arranged on one face of said metal body and closed by a cover fastened onto said metal body. Said channels communicate directly at the ends thereof with the inlet section and the outlet section of the heater.

[0013] The electric heater must be compact and is generally shaped as a rectangular parallelepiped. The diameter of the inlet and outlet ports or pipe connections is defined by the section of the hydraulic circuit pipes.

[0014] The electric heating unit includes a heating element, for example a tubular resistor immersed in the thickness of the metal body or a film resistance deposited on a surface of said metal body which is not in contact with the liquid.

[0015] The electric heating unit is connected to an electronic control unit that allows the thermal power of the heating unit to be controlled.

[0016] Disadvantageously, in a known solution, a tubular resistor is embedded in the thickness of the metal body and has a serpentine shape comprising long straight stretches substantially parallel to the long straight stretches of the serpentine channels connected in parallel.

[0017] A hairpin bend of the tubular resistor connects two subsequent straight stretches of said tubular resistor.

[0018] A hairpin bend of the serpentine channels connected in parallel connects two subsequent straight stretches of said channels.

[0019] This solution does not allow avoiding the formation of undesired “hot spots” along the serpentine channels connected in parallel because the heat exchange is not optimal between metal heating body and liquid, with an uneven distribution of the temperature along the flow path.

[0020] Therefore, there is a need to manufacture an innovative electric heater to solve the aforementioned drawbacks.

[0021] Summary of the invention

[0022] It is an object of the present invention to provide an electric heater for vehicles which allows avoiding the formation of undesired “hot spots” along the flow path of the liquid inside the heater, due to the suboptimal heat exchange between metal heating body and liquid.

[0023] It is another object of the present invention to provide an electric heater which allows an optimal heat exchange between the metal heating body and liquid to be heated, preventing the excessive overheating of the metal body.

[0024] It is a further object of the present invention to provide an electric heater that allows increasing the center distance between the liquid inlet and outlet connections so as to have more space available for interposing the electric connectors.

[0025] The present invention achieves at least one of such objects, and other objects which that be apparent in light of the present description, by an electric heater for a vehicle, adapted to heat a liquid crossing said heater, comprising

[0026] - a body made of die-cast metal material;

[0027] - at least one first electrical resistor at least partially incorporated along a first plane X of said body;

[0028] - an inlet connection, projecting from the body, for the liquid to enter into said body;

[0029] - an outlet connection, projecting from the body, for the liquid to exit from said body;

[0030] - a first flow path for the liquid, from said inlet connection to said outlet connection, made on a first face of said body;

[0031] - a first cover which closes, with a first side thereof, the first flow path; wherein the first flow path comprises at least one serpentine channel which starts from the inlet connection and ends in the outlet connection; wherein said at least one serpentine channel comprises a first straight stretch proximal to the inlet connection, a second straight stretch proximal to the outlet connection, and at least one third straight stretch interposed between said first straight stretch and said second straight stretch; preferably wherein said first straight stretch, said second straight stretch and said at least one third straight stretch are parallel to one another; wherein said at least one serpentine channel is provided with a plurality of hairpin bends, each hairpin bend being arranged between a straight stretch of said at least one serpentine channel and the next one; wherein a heating part of said at least one first electrical resistor comprises respective straight stretches and at least one curved stretch arranged between a straight stretch of said heating part and the next one; and wherein the straight stretches of said heating part are arranged transversely to the straight stretches of said at least one serpentine channel.

[0032] Further features and advantages of the invention will become more apparent in light of the detailed description of exemplary but non-exclusive embodiments.

[0033] The dependent claims describe particular embodiments of the invention.

[0034] Brief description of the fioures

[0035] The description of the invention refers to the accompanying drawings, which are provided by way of non-limiting example, in which:

[0036] Fig. 1 shows a perspective view of an electric heater according to the invention;

[0037] Fig. 2 shows a partially sectioned perspective view of the electric heater in Fig. 1 ;

[0038] Fig. 3 shows a first perspective view of a first embodiment of a component of the electric heater according to the invention;

[0039] Fig. 3a shows a second perspective view, partially sectioned along a first plane, of said first embodiment of the component;

[0040] Fig. 3b shows a third perspective view, partially sectioned along a second plane, of said first embodiment of the component;

[0041] Fig. 4 shows a top plan view of a second embodiment of said component;

[0042] Fig. 5 shows a top plan view of a third embodiment of said component;

[0043] Fig. 6 shows a top plan view of a fourth embodiment of said component;

[0044] Fig. 7 shows a top plan view of a fifth embodiment of said component; Fig. 8 shows a top plan view of a sixth embodiment of said component;

[0045] Fig. 9 shows a fourth perspective view, partially sectioned along a third plane, of the first embodiment of the component in Fig. 3;

[0046] Fig. 10 shows a fifth perspective view, partially sectioned along a fourth plane, of the first embodiment of the component in Fig. 3.

[0047] The same numbers and the same reference letters in the Figures identify the same elements or components.

[0048] Description of exemplary embodiments of the invention

[0049] With reference to the Figures, some examples of an electric heater for vehicles, in particular electric or hybrid vehicles, are illustrated.

[0050] Such an electric heater can be used, in particular, to heat a battery cooling liquid of an electric or hybrid vehicle, in case of low outdoor temperatures, keeping the ideal operating temperature constant, or to heat a liquid for use in an exchanger for heating the air in the passenger compartment.

[0051] In all the embodiments of the invention, the electric heater comprises:

[0052] - a body 2 made of die-cast metal material, preferably a single body 2;

[0053] - at least one first electrical resistor 3 at least partially incorporated along a first plane X of body 2;

[0054] - an inlet connection 12, projecting from body 2, for the liquid to enter into said body 2;

[0055] - an outlet connection 13, projecting from body 2, for the liquid to exit from said body 2;

[0056] - a first flow path 4 for the liquid, from the inlet connection 12 to the outlet connection 13, made on a first face of said body 2;

[0057] - a first cover 6 which closes, with a first side thereof, the first flow path 4 (Figure 2).

[0058] The body 2 can be a block of die-cast metal material, e.g., aluminum or another suitable material, having a substantially flat shape with two major dimensions (length and width), preferably at least double the third dimension (thickness).

[0059] Advantageously, the first flow path 4 comprises at least one serpentine channel 21 which starts from the inlet connection 12 and ends in the outlet connection 13, and comprising: -a first straight stretch 35 proximal to the inlet connection 12,

[0060] - a second straight stretch 36 proximal to the outlet connection 13,

[0061] - at least one third straight stretch 37 interposed between the first straight stretch 35 and the second straight stretch 36,

[0062] - a plurality of hairpin bends 30, each hairpin bend 30 being arranged between a straight stretch of said at least one serpentine channel and the next one.

[0063] Preferably, but not necessarily, said first straight stretch 35, said second straight stretch 36 and said at least a third straight stretch 37 are parallel to one another. Preferably, the hairpin bends 30 are 170-190°, preferably 180°, bends.

[0064] Advantageously, a heating part of the at least one first electrical resistor 3 comprises respective straight stretches 50, 50’ and at least one curved stretch 51 arranged between a straight stretch of said heating part and the next one; and the straight stretches 50, 50’ of said heating part are arranged transversely to the straight stretches 35, 36, 37 of the at least one serpentine channel 21 of the flow path 4.

[0065] This configuration allows the formation of undesired “hot spots” to be significantly reduced along the flow path of the liquid inside the heater, due to a suboptimal heat exchange between metal heating body and liquid.

[0066] In a preferred variant of the heater of the invention, the straight stretches 50, 50’ of the heating part are arranged at an angle from 80 to 100° with respect to the straight stretches 35, 36, 37 of said at least one serpentine channel 21 .

[0067] Preferably, the straight stretches 50, 50’ of the heating part of the at least one first electrical resistor 3 are parallel to each other and arranged perpendicular to the first straight stretch 35, the second straight stretch 36 and the at least one third straight stretch 37 of the at least one serpentine channel 21 of the flow path 4. Therefore, said first straight stretch 35, second straight stretch 36 and at least one third straight stretch 37 are also parallel to one another.

[0068] This solution optimizes the heat exchange between metal heating body 2 and liquid to be heated, preventing the excessive overheating of the metal body and the formation of undesired “hot spots” along the flow path of the liquid.

[0069] Preferably, the at least one serpentine channel 21 comprises at least two third straight stretches 37, for example only two (Figures 7-8), even more preferably at least three, for example four, third straight stretches 37 (Figures 3-6), interposed between the first straight stretch 35 and the second straight stretch 36. Thereby, the center distance between the inlet connection 12 and the outlet connection 13 of the liquid increases indeed so as to have more space available for interposing the electric connectors 80 of the heater.

[0070] In a first embodiment (Figures 4-7), only one first electrical resistor 3 is provided, with the heating part thereof having a serpentine shape and comprising respective straight stretches 50, 50’ and curved stretches 51 , each curved stretch 51 being arranged between one straight stretch of said heating part and the next one.

[0071] Instead, in a second embodiment of the invention (Figure 8), at least two, for example only two, first electrical resistors 3 are provided, arranged side-by-side on the first plane X, and with the heating part thereof being U-shaped, therefore each heating part having only two straight stretches 50 joined by a single curved stretch 51.

[0072] In all the embodiments of the invention, the number of hairpin bends 30 of the at least one serpentine channel 21 is preferably, but not necessarily, odd.

[0073] In a preferred variant, the straight stretch 50’ of the heating part of the electrical resistor 3 closest to the inlet connection 12 and the outlet connection 13 is provided with a V-shaped bend 54 in a lateral end portion of body 2, preferably interposed between said inlet connection 12 and said outlet connection 13 (Figures 5-6).

[0074] This configuration allows the flow of liquid to be heated in optimal manner also at at least one hairpin bend 30 of the at least one serpentine channel 21 , which is arranged in said lateral end portion of body 2.

[0075] In a third embodiment of the invention, a second resistor 3’ (Figures 7-8) is further provided, at least partially incorporated along the first plane X of body 2. This second resistor 3’ has a respective U-shaped heating part, arranged outside the heating part of said at least one first electrical resistor 3.

[0076] In the variant shown in Figure 7, only one first serpentine-shaped electrical resistor 3 is provided and, preferably, the heating part of said first electrical resistor 3 is substantially shaped as a capital M. Instead, in the variant in Figure 8, there are provided two first electrical resistors 3, arranged side-by-side and with the heating part thereof being U-shaped.

[0077] In a preferred variant, the U-shaped heating part of the second resistor 3’ comprises two respective substantially straight stretches 60, 60’, arranged transversely to the straight stretches 35, 36, 37 of said at least one serpentine channel 21 , and a further respective substantially straight stretch 61 arranged parallel to said straight stretches 35, 36, 37 of the at least one serpentine channel 21.

[0078] In a further preferred variant, the substantially straight stretch 60’ closest to the inlet connection 12 and the outlet connection 13 is provided with a V-shaped bend 64 in a lateral end portion of body 2, preferably interposed between said inlet connection 12 and said outlet connection 13.

[0079] In all the embodiments of the invention, the inlet connection 12 and the outlet connection 13 can be arranged on a same side of the heater and substantially aligned with the first straight stretch 35 and the second straight stretch 36, respectively, as shown in Figures 1 to 5 and 7-8, for example. “Substantially aligned” means arranged along the same longitudinal axis. In this case, the number of hairpin bends 30 is an odd number.

[0080] Alternatively, as shown in Figure 6 for example, the inlet connection 12 and the outlet connection 13 are arranged on opposite sides of the heater along a same longitudinal axis perpendicular to the first straight stretch 35 and the second straight stretch 36. Indeed, in some vehicles, the secondary heating circuit of the battery might not be prepared for the addition of the electric heater. In this case, a heater with inlet and outlet on opposite sides can be convenient because it can be integrated into the secondary circuit, interrupting the piping and placing the heater by connecting the two ends of the piping at the two opposite sides of the heater. The possibility of providing an even number of hairpin bends 30 is not excluded, whereby the inlet connection 12 and the outlet connection 13 are arranged on opposite sides of the heater.

[0081] In all the embodiments of the invention, the inlet connection 12 and the first straight stretch 35 can be joined by a first inclined portion 52, and the second stretch 36 and the outlet connection 13 can be joined by a second inclined portion 53. The inclined portions reduce the pressure losses because the turbulence is reduced in the fluidic transition stretches from the inlet connection 12 to the heating area of the flow path, which is at the electrical resistor or the electrical resistors, and from said heating area of the flow path to the outlet connection 13, respectively.

[0082] Preferably, said first inclined portion 52 and said second inclined portion 53 have a longitudinal extension substantially equal to or less than the radius of at least one hairpin bend 30 provided in said lateral end portion of body 2.

[0083] For example, the V-shaped bend 54, 64 can be arranged in a stretch of body 2 enclosed between said first inclined portion 52 and said second inclined portion 53.

[0084] Figures 1 -10 show an embodiment of the heater of the invention in which the first face of body 2 is arranged at a first side of said first plane X, and only one flow path 4 is provided.

[0085] The cover 6 preferably rests in a compression area of a respective sealing gasket on the outer perimeter, respectively, of the first face of body 2. The cover 6 is thus a separate component from the heating body 2, being connected to the latter, for example, with screws and gaskets.

[0086] Alternatively, a further embodiment of the heater of the invention (not shown) also includes a second flow path for the liquid, from the inlet connection 12 to the outlet connection 13, obtained on a second face of body 2 arranged at a second side of said first plane X, opposite to the first side. There is provided a second cover that closes, with a side thereof, the second flow path.

[0087] With these two flow paths on opposite faces of body 2, vehicle manufacturers can use the heater of the invention with any orientation within vehicle platforms, as the heater will always have at least one face of the exchanger body that has a heat exchange surface favorable to the possibility of removing the air and / or steam that can form at the solid / liquid interface. Furthermore, this allows for more reliable operation under typical vehicle use conditions, which involve variability in the direction of the gravitational force with respect to the heater due to longitudinal and transverse slopes of the road path, as well as inertial forces caused by braking or direction change accelerations. In a preferred variant, the first flow path 4 and the second flow path at least partially include the inlet connection 12 and the outlet connection 13. In particular, the first flow path 4 and the second flow path 5 consist of a respective single channel 21 or of respective at least two serpentine channels connected in parallel. Preferably, the first flow path and the second flow path are symmetrically arranged with respect to the first plane X, and possibly also with respect to a second plane perpendicular to said first plane X.

[0088] In particular, the first flow path and the second flow path are arranged symmetrically to each other with respect to the first plane X; and each flow path is also symmetrical with respect to said second plane. Therefore, the first plane X of body 2 is a symmetry plane of at least one portion of body 2 comprising the first flow path and the second flow path. In fact, plane X divides said at least one portion of body 2 into two parts which reciprocally correspond in a planar symmetry of plane X. Such a configuration of the liquid circuit inside the heater of the invention allows vehicle manufacturers to use the heater of the invention in all vehicle platforms with the freedom to connect the inlet and outlet connections of the heater arbitrarily, freely reversing the flow direction.

[0089] First plane X and second plane can be median planes of body 2.

[0090] Inlet connection 12 and outlet connection 13 can be arranged symmetrically with respect to the second plane.

[0091] In all embodiments of the heater of the invention, the at least one serpentine channel is only one serpentine channel 21 (Figures 3-10) or comprises at least two serpentine channels connected in parallel, through which the liquid flows in parallel (solution not shown).

[0092] In Figures 3-10, each hairpin bend 30 in the single serpentine channel 21 connects two adjacent and substantially parallel straight stretches of channel 21. The shape of channel 21 is also defined by longitudinal bulkheads 90, 91 obtained on the first face of body 2 and which separate two consecutive straight stretches of channel 21 .

[0093] In particular, at least two longitudinal bulkheads 91 branch off from the side of body 2 where at least the inlet connection 12 is arranged; while at least one longitudinal bulkhead 90 branches off from the side of body 2 opposite to the side where at least the inlet connection 12 is arranged.

[0094] Optionally, the longitudinal bulkheads 90, 91 , and thus channel 21 , have at least one corrugated portion for generating a minimum turbulence of the liquid.

[0095] A clearance can be provided between the end edge of the bulkheads 90, 91 and cover 6.

[0096] In Figures 3-6, four third straight stretches 37 and five hairpin bends 30 are provided. Therefore, two longitudinal bulkheads 90 and three longitudinal bulkheads 91 are provided.

[0097] In Figures 7-8, two third straight stretches 37 and three hairpin bends 30 are provided. Therefore, one longitudinal bulkhead 90 and two longitudinal bulkheads 91 are provided.

[0098] In a preferred variant, at least one curved deflector 31 , 3T is provided in each hairpin bend 30 of the low path, for a deflection the liquid at a sudden change in the direction of the motion thereof.

[0099] Preferably, at least two curved deflectors 31 , 3T, e.g., only two curved deflectors, are provided in each hairpin bend 30.

[0100] These curved deflectors 31 , 3T can be parallel to each other.

[0101] In a preferred variant, each curved deflector 31 , 3T has a curvilinear extension with an angle at the center of 80-190°, preferably 170-190°, e.g., 180°.

[0102] The presence of the curved deflectors allows the turbulence of the flow of liquid flowing in the single channel 21 to be reduced in the hairpin bends, and thus the pressure losses, despite the presence of the sudden changes in the direction in the flow path which however ensure a compactness of the heater.

[0103] In an example of the heater of the invention, each curved deflector 31 , 3T is a curved bulkhead projecting, preferably orthogonally, from the first face of body 2 so as to extend for at least 50%, preferably at least 70%, even more preferably at least 90%, of the distance between the first cover 6 and the bottom of channel 21 , in particular of the minimum distance between said first cover 6 and said bottom. In this variant, the curved deflectors also increase the heat exchange between heating body 2 and liquid. For example, such curved deflectors 31 , 31 ’ can be made by mechanically processing the first face of body 2 or be directly made by die-casting, producing a hollow area of body 2 from which the curved bulkheads project.

[0104] Preferably, a clearance is provided between the end edge of each curved bulkhead 31 , 31 ’ and the first cover 6.

[0105] In a preferred variant, at least one curved deflector 31 ’ in each hairpin bend 30, preferably only the innermost curved deflector with respect to body 2, is provided with a straight extension 34 exiting from the respective hairpin bend 30, considering a feeding direction A of the liquid in the flow path 4 (Figures 3a-3b).

[0106] Preferably, this straight extension 34 has a length in a range from 0.5 to 1 .5 times the radius of the curve defined by said curved deflector 31 ’. This small straight extension allows the flow of liquid exiting from the innermost stretch of the respective hairpin bend to be better guided, further reducing the turbulence, and therefore the localized pressure losses.

[0107] Preferably, the length of each straight stretch 35, 36, 37 is at least twice the width of channel 21 , which is kept substantially constant along the flow path.

[0108] In a preferred variant, as shown in Figures 3a and 9-10, a plurality of heat sinks 38 can be provided in the first straight stretch 35, in the second straight stretch 36 and in the at least one third intermediate straight stretch 37.

[0109] Preferably, said heat sinks 38 are in the form of fins, substantially longitudinal fins, projecting from the first face of body 2 so as to extend for less than 50%, preferably less than 30%, even more preferably less than 25%, of the distance between the first cover 6 and the bottom of the serpentine channel 21 , in particular of the minimum distance between said first cover 6 and said bottom.

[0110] The contained height of these heat sinks 38 allows the heat exchange surface to be increased between heating body 2 and liquid, but the pressure losses substantially do not increase because the flow of liquid remains substantially unaltered in the straight stretches of the single channel 21 .

[0111] It is also preferable for the number of heat sinks 38 in each straight stretch to be different from the number of curved deflectors 31 , 3T in each hairpin bend 30. This disparity in number increases the homogeneity of the temperature of the liquid because it prevents the formation of parallel and independent flow lines, for example it prevents the formation of channels connected in parallel, promoting the remixing of liquid between the next straight and curved stretches.

[0112] By mere way of non-limiting example, the number of heat sinks in each straight stretch can be equal to two or three, while the number of curved deflectors in each hairpin bend can be equal to one or two.

[0113] Moreover, it is preferable for the heat sinks 38 and curved deflectors 31 , 31 ’ to alternate along the only one channel 21 of the flow path 4 in a discontinuous manner, interrupted in space. Also this alternation of heat sinks and curved deflectors, with an interrupting space therebetween, increases the homogeneity of the temperature of the liquid because it prevents the formation of parallel and independent flow lines, promoting the remixing of fluid between the successive straight and curved stretches.

[0114] A further variant of the heater of the invention includes that, when at least one curved deflector 31 , 31 ’, e.g., only one curved deflector, is provided with the aforesaid straight extension 34 exiting from the hairpin bend 30, at least one heat sink 38 in the form of longitudinal fin is provided, in the straight stretch downstream of said hairpin bend 30, with an end 39 bent towards said straight extension 34 (see the example in Figures 9-10). This contrivance allows any localized pressure losses to be further reduced. This bent end 39 can be provided, for example, in the second straight stretch 36 and in the at least one third straight stretch 37.

[0115] However, there is always a discontinuity between heat sinks 38 and curved deflectors 31 , 3T.

[0116] With reference, for example, to Figure 9, the height of the fins 38 with respect to the bottom of channel 21 is reciprocally equal. The possibility of providing fins 38 having different heights from one another is not excluded. If, for example, there are three fins 38, one of these fins could have a higher height than the other two fins. Therefore, the amount of aluminum employed can be reduced because only the fins extending the closest to the electrical resistor would be higher than the others.

[0117] Also the width of the fins 38 can be reciprocally equal or different. With reference to, for example, Figure 9, there are three fins 38, one of which having a greater width with respect to the other two fins. Also in this last case, the amount of aluminum employed can be reduced.

[0118] Finally, also the longitudinal extension of the fins 38, which are not necessarily parallel to one another, can be reciprocally equal or different. Some fins 38 can also have some interruptions along the longitudinal extension thereof (Figures 9-10).

[0119] Preferably, the fins 38 can be smooth along the longitudinal flanks, or corrugated along said longitudinal flanks, to locally cause a slight turbulence and to further increase the heat exchange between heating body 2 and liquid.

Claims

CLAIMS1 . An electric heater (1 ) for a vehicle, adapted to heat a liquid crossing said heater, comprising- a body (2) made of die-cast metal material;- at least one first electrical resistor (3) at least partially incorporated along a first plane (X) of said body (2);- an inlet connection (12), projecting from the body (2), for the liquid to enter into said body (2);- an outlet connection (13), projecting from the body (2), for the liquid to exit from said body (2);- a first flow path (4) for the liquid, from said inlet connection (12) to said outlet connection (13), made on a first face of said body (2);- a first cover (6) that closes, with a first side thereof, the first flow path (4); wherein a heating part of said at least one first electrical resistor (3) comprises respective straight stretches (50, 50’) and at least one curved stretch (51) arranged between a straight stretch (50, 50’) of said heating part and the next one; characterized in that the first flow path (4) comprises at least one serpentine channel (21) which starts from the inlet connection (12) and ends in the outlet connection (13); said at least one serpentine channel (21 ) comprises a first straight stretch (35) proximal to the inlet connection (12), a second straight stretch (36) proximal to the outlet connection (13), and at least one third straight stretch (37) interposed between said first straight stretch (35) and said second straight stretch (36); said at least one serpentine channel (21 ) is provided with a plurality of hairpin bends (30), each hairpin bend (30) being arranged between a straight stretch of said at least one serpentine channel and the next one; and the straight stretches (50, 50’) of the heating part of said at least one first electrical resistor (3) are arranged transversely to the straight stretches (35, 36, 37) of said at least one serpentine channel (21 ).

2. A heater according to claim 1 , wherein the straight stretches (50, 50’) of said heating part are arranged at an angle from 80° to 100° with respect to the straight stretches (35, 36, 37) of said at least one serpentine channel (21).

3. A heater according to claim 1 or 2, wherein said first straight stretch (35), said second straight stretch (36) and said at least one third straight stretch (37) are parallel to one another; and preferably wherein the straight stretches (50, 50’) of the heating part of the at least one first electrical resistor (3) are parallel to each other and arranged perpendicularly to said first straight stretch (35), to said second straight stretch (36) and to said at least a third straight stretch (37) of the at least one serpentine channel (21).

4. A heater according to any one of the preceding claims, wherein only one first electrical resistor (3) is provided, the heating part thereof being serpentine-shaped and comprising respective straight stretches (50, 50’) and curved stretches (51), each curved stretch (51 ) being arranged between a straight stretch of said heating part and the next one; or wherein at least two first electrical resistors (3) are provided, arranged side-by- side on the first plane (X) and with the heating part thereof being U-shaped, each heating part having only two straight stretches (50) joined by a single curved stretch (51 ).

5. A heater according to any one of the preceding claims, wherein the straight stretch (50’) of the heating part closest to the inlet connection (12) and to the outlet connection (13) is provided with a V-shaped bend (54) in a lateral end portion of the body (2), preferably interposed between said inlet connection (12) and said outlet connection (13).

6. A heater according to any one of claims 1 to 3, wherein a second resistor (3’) is provided, at least partially incorporated along said first plane (X) of the body (2); and wherein said second resistor (3’) has a respective U-shaped heating part, arranged outside the heating part of said at least one first electrical resistor (3).

7. A heater according to claim 6, wherein only one first electrical resistor (3) is provided, the heating part thereof being serpentine-shaped, preferably substantially in the shape of a capital M; or wherein at least two first electrical resistors (3) are provided, arranged side-by- side and with the heating part thereof being U-shaped.

8. A heater according to claim 6 or 7, wherein the U-shaped heating part of said second resistor (3’) comprises two respective substantially straight stretches (60,60’), arranged transversely to the straight stretches (35, 36, 37) of said at least one serpentine channel (21 ), and a further respective substantially straight stretch (61 ) arranged parallel to said straight stretches (35, 36, 37) of the at least one serpentine channel (21 ); preferably wherein the substantially straight stretch (60’) of said second resistor (3’) closest to the inlet connection (12) and the outlet connection (13) is provided with a V-shaped bend (64) in a lateral end portion of the body (2), preferably interposed between said inlet connection (12) and said outlet connection (13).

9. A heater according to claim 5 or 8, wherein the inlet connection (12) and the outlet connection (13) are arranged on a same side of the heater and aligned with the first straight stretch (35) and the second straight stretch (36), respectively; or wherein the inlet connection (12) and the outlet connection (13) are arranged on opposite sides of the heater along a same longitudinal axis perpendicular to the first straight stretch (35) and the second straight stretch (36).

10. A heater according to claim 5 or 8 or 9, wherein the inlet connection (12) and the first straight stretch (35) are joined by a first inclined portion (52); wherein the second straight stretch (36) and the outlet connection (13) are joined by a second inclined portion (53); preferably wherein said first inclined portion (52) and said second inclined portion (53) have a longitudinal extension substantially equal to or less than the radius of at least one hairpin bend (30) provided in said lateral end portion of the body (2).11 . A heater according to any one of the preceding claims, wherein the first face of said body (2) is arranged at a first side of said first plane (X); and wherein a second flow path for the liquid is provided, from said inlet connection (12) to said outlet connection (13), obtained on a second face of said body (2) arranged at a second side of said first plane (X), opposite to the first side; and wherein a second cover that closes, with a first side thereof, the second flow path is provided; preferably wherein the first flow path (4) and the second flow path, which at least partially include said inlet connection (12) and said outlet connection (13), are symmetrically arranged with respect to said first plane (X) and possibly also with respect to a second plane perpendicular to said first plane (X).

12. A heater according to any one of the preceding claims, wherein said at least one serpentine channel is only one serpentine channel (21 ) or comprises at least two serpentine channels connected in parallel, through which the liquid flows in parallel.

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