Electric heater for vehicle

Abstract

An electric heater (1) for a vehicle, suitable for heating a liquid passing through said heater, comprising:-a body (2) made of a die-cast metal material; -at least one resistor (3) bonded at least partially along a first median plane (X) of the body (2); an inlet portion (10) and an outlet portion (11) for the liquid, both arranged on the same side of the heater; -a first flow path (4) for the liquid, from an inlet portion (10) to an outlet portion (11), formed on a first face of said body (2), arranged on a first side of said first median plane (X); -a second flow path (5) for the liquid, from the inlet portion (10) to the outlet portion (11), formed on a second face of the body (2), arranged on a second side of the first median plane (X) opposite to the first side; wherein the first flow path (4) and the second flow path (5) are arranged symmetrically with respect to the first median plane (X) and with respect to a second median plane (Y) of the body (2) perpendicular to the first median plane (X).

Description

Technical Field

[0001] The present invention relates to an electric heater for a vehicle, preferably but not necessarily an electric or hybrid vehicle, in particular for heating battery coolant in low outdoor temperatures to maintain a desired operating temperature constant, or for heating fluid used in an exchanger to heat the air in the passenger compartment. Background Art

[0002] Batteries are essential to the operation of electric or hybrid vehicles. They must provide the energy needed to propel the vehicle quickly and reliably. Most batteries are high-voltage hybrid lithium-ion and nickel metal ion batteries.

[0003] Batteries must operate within a defined temperature range. Service life decreases starting at an operating temperature of +40°C, while performance and power drop below -10°C. Furthermore, the temperature differences between individual cells must not exceed specific values. Exceeding these temperature limits leads to faster aging and, consequently, premature failure of the corresponding battery. Vehicle manufacturers aim to achieve a battery life equal to the life of the vehicle. Therefore, aging can only be counteracted through optimal temperature management.

[0004] A battery unit typically includes a cell, a cooling plate, and an auxiliary electric heater. A coolant, such as water and ethylene glycol, flows through the cooling plate installed in the cell module.

[0005] To ensure optimal battery performance and maximum service life, the coolant temperature must be between approximately 15 and 30°C. If the temperature is too high, the fluid is cooled, for example, by a low-temperature radiator. Conversely, if the temperature is too low, the coolant is heated by an auxiliary electric heater. This ensures adequate battery temperature control even at low outdoor temperatures.

[0006] To carry out this heating, batteries are integrated into the secondary circuit, which ensures that the ideal operating temperature is maintained constantly between 15 and 30°C.

[0007] Such an electric heater generally includes at least one electric heating unit for generating heat and releasing the generated heat to the heat transmission medium represented by the above-mentioned liquid through a body made of a metal material in contact with the electric heating unit.

[0008] Such a liquid may be, for example, water, ethylene glycol, water and ethylene glycol, or other suitable heat transfer liquid.

[0009] The liquid flows along a flow path including at least one channel arranged on one surface of the metal body and closed by a cover fastened to the metal body. The at least one channel is directly connected to the inlet and outlet portions of the heater at its ends.

[0010] Electric heaters must be compact and are usually shaped as cuboids. The diameter of the inlet and outlet ports or pipe connections is defined by the cross section of the hydraulic circuit piping.

[0011] The electric heating unit comprises a heating element, such as a tubular resistor embedded in the thickness of a metal body or a thin film resistor deposited on a surface of said metal body not in contact with the liquid.

[0012] The electric heating unit is connected to an electronic control unit which allows controlling the thermal power of the heating unit.

[0013] For example, the electronic control unit may include at least one electronic switch, such as a power transistor or other semiconductor power device, for example, for controlling the current in the heating unit or for controlling the voltage applied to the heating unit. For example, the power transistor may be an insulated gate bipolar transistor (IGBT). The power transistor may be electrically connected in series with the heating element. As a side effect, the electronic control unit typically generates heat, which must be dissipated to prevent the control unit from overheating.

[0014] Vehicle manufacturers prefer to use the same electric heater in all vehicle platforms, ie a heater with various orientation possibilities within the platform.

[0015] Disadvantageously, known solutions utilize only one face of the metal body as a heat exchange surface, and in some heater installation orientations, air pockets form in stagnant areas within the channel. Consequently, the possible installation orientations of the heater are limited. In particular, due to the very high power density applied to the metal body to minimize its size, an air and / or vapor layer can form at the solid / liquid interface, hindering heat transfer from the solid to the liquid to the point of triggering film boiling conditions, which can lead to catastrophic melting of the metal body.

[0016] The orientation of the heat exchange surface can be either favorable or unfavorable for the removal of air and / or vapor from the exchange surface, and thus, for the formation of a boiling film. Gases tend to rise upwards, being less dense than the surrounding liquid, but the orientation of the heat exchange surface, depending on the location of the heater within a particular vehicle platform, can significantly affect the removal of air and / or vapor from the exchange surface.

[0017] Vehicle manufacturers prefer to use the same electric heater across all vehicle platforms while having the freedom to connect the heater inlet and outlet ports as desired.

[0018] Additionally, manufacturers need to achieve reliable operation under typical vehicle usage conditions, which involve variability in the orientation of gravity relative to the heater due to the longitudinal and transverse slope of the road, and inertial forces caused by accelerations from braking or direction changes.

[0019] Disadvantageously, in the known solution, the inlet and outlet ports of the heater are predetermined, since the power transistors are located in the inlet portion of the heater, which is unheated, and are arranged upstream of the active heating area in order to dissipate the heat generated by the electronic control unit through the liquid entering through the inlet port. Therefore, if the manufacturer installs the heater in such a way as to reverse the direction of liquid flow between the inlet and outlet, the electronic switches will no longer be adequately cooled, as they will be located in the outlet portion, where the liquid is overheated.

[0020] Besides these drawbacks, other requirements for manufacturers are:

[0021] - Since the vehicle centrifugal pump has a low head, to reduce the pressure loss in the liquid flow through the electric heater;

[0022] - prevent the formation of recirculation zones in the heating zone of one or more channels, which would lead to local overheating;

[0023] - curbing the temperature of the walls of one or more channels of the metal body to prevent degradation of the coolant;

[0024] - Reduce the weight and size of electric heaters.

[0025] However, the above requirements are conflicting because:

[0026] - To reduce pressure losses and recirculation zones, a large uniform channel cross-section is required, which is disadvantageous for size and requires the absence of discontinuities;

[0027] - In order to reduce the temperature of the walls of one or more channels, it is necessary to increase the heat exchange surface, which is disadvantageous in terms of size, or to introduce discontinuities in the flow, such as cross-sectional changes, turbulators, sharp turns, which exacerbate pressure losses.

[0028] For example, in some solutions the inlet and outlet parts of the heater are bulky collectors that are thermally isolated from the active heating area, resulting in considerable size and not contributing to the heating of the liquid, thereby reducing the heat exchange surface.

[0029] Furthermore, these inlet and outlet sections have a much larger cross-section than the inlet / outlet ports, resulting in strong liquid velocity variations, which increase pressure losses and involve the risk of overheating in the recirculation zone.

[0030] Therefore, it is necessary to provide an innovative electric heater to solve the above shortcomings. Summary of the Invention

[0031] An object of the present invention is to provide an electric heater for a vehicle that allows for any mounting orientation, prevents the formation of trapped air pockets within the flow path, and therefore does not trigger film boiling conditions that could lead to catastrophic melting of the metal body.

[0032] Another object of the present invention is to provide an electric heater which also allows the inlet and outlet ports of the heater to be arbitrarily connected to corresponding hydraulic circuits without any taboos.

[0033] Another object of the present invention is to provide an electric heater allowing better performance while ensuring good cooling of the electronic control unit, a larger heat exchange surface, low pressure losses, high heating power and reduced dimensions.

[0034] The present invention achieves at least one of these objects, as well as other objects that will become apparent from the present description, by an electric heater for a vehicle, the electric heater being adapted to heat a liquid passing through the heater, the electric heater comprising:

[0035] -Main body made of die-cast metal material;

[0036] - at least one resistor incorporated at least partially along the first median plane X of said body;

[0037] - an inlet section and an outlet section for the liquid, both arranged on the same side of the heater;

[0038] a first flow path for the liquid, from the inlet portion to the outlet portion, formed on a first face of said body, said first face being arranged on a first side of said first median plane X;

[0039] a second flow path for the liquid, from the inlet portion to the outlet portion, formed on a second face of the body, the second face being arranged on a second side of the first median plane X, opposite the first side;

[0040] The first flow path and the second flow path including the inlet portion and the outlet portion are symmetrically arranged relative to the first middle plane X and relative to a second middle plane Y of the body perpendicular to the first middle plane X.

[0041] Advantageously, the heater of the invention, in any installation position, always has at least one face of the metal exchanger body that presents an orientation of the exchange surface that favors the possibility of removing air and / or vapor, even in the event of a road inclination and in the presence of lateral acceleration, so that if another surface experiences film boiling conditions, this face can release heat and prevent catastrophic melting of the exchanger body.

[0042] Another advantage of the present invention is that the liquid circuit inside the heater is symmetrical and the flow direction can be freely reversed, allowing vehicle manufacturers to use the heater of the present invention in all vehicle platforms and freely connect the inlet and outlet ports of the heater.

[0043] A further advantage of the invention is that, in a preferred embodiment, the flow direction can be reversed within the heater without jeopardizing the heat dissipation of the electronic control unit which is cooled by the liquid at an intermediate compromise temperature between the inlet and the outlet.

[0044] Further features and advantages of the present invention will become more apparent from the detailed description of exemplary but non-exclusive embodiments.

[0045] The dependent claims describe particular embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The invention is described with reference to the accompanying drawings, provided by way of non-limiting example, in which:

[0047] Figure 1 shows a perspective view of an electric heater according to the present invention;

[0048] Figure 2 Shown Figure 1 A cross section of an electric heater;

[0049] Figure 3 A surface view of a heat exchanger body made of a die-cast metal material in a first embodiment of the present invention is shown;

[0050] Figure 4 A surface view of a heat exchanger body made of a die-cast metal material in a second embodiment of the present invention is shown;

[0051] Figure 5 A surface view of a heat exchanger body made of a die-cast metal material in a third embodiment of the present invention is shown;

[0052] Figure 6 A surface view of a heat exchanger body made of a die-cast metal material in a fourth embodiment of the present invention is shown;

[0053] Figure 7 shows a cross-sectional view of a heater of the present invention along a first intermediate plane having a first resistor variation;

[0054] Figure 8 shows a cross-sectional view of a heater of the present invention along a first intermediate plane having a second resistor variation;

[0055] Figure 9 An enlarged cross-sectional view showing a portion of the flow path of the heater of the present invention;

[0056] Figure 10 Shown as Figures 3 to 6 Another enlarged cross-sectional view of two flow paths of the heater of the present invention is shown;

[0057] Figure 11 A perspective view showing components of a heater of the present invention;

[0058] Figure 12 A cross-sectional view showing some components of the heater of the present invention;

[0059] Figure 13 An exemplary view showing the positions of some components of the heater of the present invention;

[0060] Figure 14 a first cross-sectional view showing some details of the heater of the present invention;

[0061] Figure 15 a second cross-sectional view showing said detail of the heater of the invention;

[0062] Figure 16 A first variation of the components of the heater is shown;

[0063] Figure 17 Shown Figure 16 A second variant of the middle component;

[0064] Figure 18 Shown Figure 16 The third variant of the middle part;

[0065] Figure 19 Shown Figure 16 Fourth variant of the middle part.

[0066] The same reference numerals and letters in the drawings identify the same elements or components. DETAILED DESCRIPTION

[0067] Referring to the accompanying drawings, some examples of electric heaters for vehicles, particularly electric or hybrid vehicles, are shown.

[0068] In particular, such electric heaters can be used to heat the battery coolant in electric or hybrid vehicles when outdoor temperatures are low, thereby maintaining a constant ideal operating temperature, or to heat the fluid used in exchangers to warm the air in the passenger compartment.

[0069] In all embodiments of the present invention, the electric heater comprises:

[0070] - a body 2 made of die-cast metal material, preferably as Figures 2 to 10 A single subject as shown in the example;

[0071] - at least one resistor 3, 32, 33, which is at least partially incorporated along the first median plane X of the body 2 ( Figure 2 、 Figures 7 and 8 );

[0072] - an inlet section 10 and an outlet section 11 for the liquid, both arranged on the same side of the heater ( Figures 3 to 6 ).

[0073] Preferably, the body 2 is a block of die-cast metal material, such as aluminium or other suitable material, having a substantially flat shape, the two main dimensions of which (length and width) are preferably at least twice the third dimension (thickness).

[0074] Advantageously, there is provided ( Figures 2 to 6 and Figure 10 ) a first flow path 4 for liquid, from the inlet portion 10 to the outlet portion 11, the first flow path 4 being formed on a first face of the body 2, the first face being arranged on a first side of the first intermediate plane X; and a second flow path 5 for liquid, from the inlet portion 10 to the outlet portion 11, the second flow path 5 being formed on a second face of the body 2, the second face being arranged on a second side of the first intermediate plane X opposite to the first side. In other words, as Figure 2 and Figure 10 As shown, the first face of the body 2 is arranged on a first side of the first median plane X, while the second face of the body 2 is arranged on a second side of the first median plane X, opposite the first side. This allows vehicle manufacturers to use the heater of the present invention in any orientation within the vehicle platform, as the heater will always have at least one face of the exchanger body with a heat exchange surface that facilitates the removal of air and / or vapor that may form at the solid / liquid interface. Furthermore, this allows for more reliable operation under typical vehicle usage conditions, which involve variability in the orientation of gravity relative to the heater due to the longitudinal and transverse slopes of the road, as well as inertial forces caused by accelerations during braking or direction changes.

[0075] Advantageously, the first flow path 4 and the second flow path 5, which together comprise the inlet portion 10 and the outlet portion 11, are arranged symmetrically relative to a first median plane X and relative to a second median plane Y of the body 2, which is perpendicular to the first median plane X. Specifically, the first flow path 4 and the second flow path 5 are arranged symmetrically relative to each other relative to the first median plane X; and each flow path 4, 5 is also symmetrical relative to the second median plane Y. Thus, the first median plane X of the body 2 is the plane of symmetry for at least the portion of the body 2 that includes the first flow path 4 and the second flow path 5. In fact, median plane X divides the at least portion of the body 2 into two parts that correspond to the planar symmetry of plane X. This configuration of the fluid circuit within the heater of the present invention allows vehicle manufacturers to use the heater of the present invention in all vehicle platforms, freely connect the heater's inlet and outlet ports, and freely reverse the flow direction.

[0076] The heater of the present invention further comprises ( Figure 2 ):

[0077] a first cover 6 , the first side of which closes the first flow path 4 ;

[0078] a second cover 7 , the first side of which closes the second flow path 5 ;

[0079] An electronic control unit 8 , which is arranged on a second side of said first cover 6 or second cover 7 , opposite to the first side, and comprises at least one electronic switch 22 .

[0080] Preferably, the covers 6 , 7 are arranged parallel to each other and to the median plane X.

[0081] The covers 6, 7 are preferably placed in the pressure areas of corresponding sealing gaskets on the periphery of the first and second faces of the body 2. The covers 6, 7 are therefore separate components from the heating body 2, connected to it for example by screws and washers.

[0082] Preferably, in order to improve the compactness of the solution of the invention and at the same time increase the heat exchange between the body 2 and the liquid, the first flow path 4 and the second flow path 5 are each provided with an odd number of hairpin bends, preferably but not necessarily only three hairpin bends 30, 31 ( Figure 3-6 ), and comprises a plurality of substantially mutually parallel channels 21 which branch from an inlet portion 10 and flow into an outlet portion 11, both portions being arranged on the same side of the heater.

[0083] Advantageously, the channels 21 of the first flow path 4 and the second flow path 5 are delimited by partitions 9 protruding from the first and second faces of the body 2, respectively. Such partitions 9 and channels 21 can be made by machining the first and second faces of the body 2, or directly by die-casting, creating hollow areas on both faces where the partitions protrude.

[0084] The presence of baffles 9 on both faces of the body 2 improves the removal of heat by increasing the effective heat exchange surface while reducing the wall temperature of the channels without increasing the overall dimensions and without requiring discontinuities in the flow, thus avoiding excessive pressure losses.

[0085] Preferably, each channel 21 has a width of about 3-6 mm and a height of about 7-12 mm. Thus, the small height of the partition 9 increases its heat exchange efficiency.

[0086] As a non-limiting example, Figures 3 to 6 As shown, each flow path 4 , 5 comprises three channels 21 and two intermediate partitions 9 . Figures 3 to 6 Only the first flow path 4 provided on the first side of the body 2 is shown. The second flow path 5 is provided on the opposite and lower side, ie, on the second side of the body 2.

[0087] In a preferred configuration, for first flow path 4 and second flow path 5, the middle hairpin 30 of the three hairpins is arranged at the second midplane Y and is close to the side of the heater where the inlet portion 10 and the outlet portion 11 are arranged; while the two side hairpins 31 of the three hairpins are arranged symmetrically with respect to the second midplane Y and are away from the side of the heater where the inlet portion 10 and the outlet portion 11 are arranged. Therefore, the first flow path 4 and the second flow path 5 and the corresponding channel 21 have a substantially capital M shape, with the side legs of the M shape located at the inlet portion 10 and the outlet portion 11, respectively.

[0088] This M-shape of each flow path 4, 5 is defined by additional baffles 90, 91 formed on two opposite faces of the main body 2. Specifically, the two side baffles 91 are arranged symmetrically with respect to the second middle plane Y and branch off from the side of the main body 2 where the inlet portion 10 and the outlet portion 11 are arranged; while the central baffle 90 is arranged along the second plane Y and branches off from the side of the main body 2 opposite to the side where the inlet portion 10 and the outlet portion 11 are arranged.

[0089] Optionally, in the extensions connecting the inlet portion 10 to the proximal hairpin 31, the outlet portion 11 to the proximal hairpin 31 and the side hairpin 31 to the middle hairpin 30, respectively, the partitions 9, 90, 91 and the corresponding channels 21 have at least one wavy portion for generating minimal turbulence in the liquid.

[0090] Preferably, in the heater of the present invention, there is provided:

[0091] - a first port or pipe connection 12 which extends from the body 2 and communicates with the inlet portion 10;

[0092] and a second port or pipe connection 13 , which extends from the body 2 and communicates with the outlet portion 11 .

[0093] The first port 12 and the second port 13 may be arranged symmetrically with respect to the second middle plane Y.

[0094] Advantageously, the ratio between the width W of the first flow path 4 and the second flow path 5 and the inner diameter of the first port 12 and the second port 13 is in the range of 1 to 2, preferably in the range of 1.2 to 1.6. This ratio is such that the liquid does not experience strong velocity variations at the inlet and outlet of the heater, which would increase pressure losses and imply a risk of overheating in possible backflow zones.

[0095] For example Figure 3 The width W shown is the width of the flow path, comprising the width of the channels 21 of the path and the thickness of the intermediate partitions 9 between the channels 21. In the example of the figures, the width of the flow path is composed of the width of three channels 21 and the thickness of two intermediate partitions 9.

[0096] A preferred variant of the heater according to the invention provides for at least one electronic switch 22 to be arranged in the vicinity of the second median plane Y, in a position distal to the inlet section 10 and the outlet section 11. Even more preferably, this position is distal and intermediate between the inlet section 10 and the outlet section 11, i.e., equally distal. This configuration allows the direction of flow of the liquid in the heater to be reversed without jeopardizing the heat dissipation of the electronic control unit 8, which is in fact cooled by the liquid at an intermediate compromise temperature between the inlet and outlet sections.

[0097] Preferably, in order to dissipate the heat generated by the electronic control unit, effectively prevent it from overheating, and limit the pressure loss as much as possible, at least one longitudinal fin 40 ( Figures 10 to 12 ), the fin protrudes from the first side of the first cover 6 at the at least one electronic switch 22 and is inserted into the corresponding longitudinal recess 41 ( Figures 3 to 6 ) or longitudinal interruption, so that the longitudinal flanks of the at least one longitudinal fin 40 define a portion of the side walls of two adjacent channels 21 ( Figure 10 ).

[0098] In other words, the longitudinal fin 40 of the cover 6 arranged at the electronic switch 22 is configured to partially replace a portion of the partition 9 that defines two adjacent channels 21 of the liquid flow path 4, and the portion of the partition 9 corresponds to the space where the longitudinal recess 41 or the longitudinal interruption is set.

[0099] In more detail, for example Figures 3 to 6 and Figures 10 to 12 As shown, the shape of each longitudinal fin 40 is substantially complementary to the shape of the corresponding longitudinal recess 41 or longitudinal interruption of the corresponding partition 9, thereby keeping the side walls of two adjacent channels 21 substantially unchanged. This means that the longitudinal fin 40 occupies all the free space of the longitudinal recess 41 or longitudinal interruption of the corresponding partition 9. In particular, the longitudinal extension of each longitudinal fin 40 is substantially equal to the longitudinal extension of the corresponding recess or longitudinal interruption 41 provided in the corresponding partition 9.

[0100] Thus, the electronic switch 22 is adequately cooled, as the heat exchange surface beneath the switch is increased, without increasing the pressure loss, since the flow of the liquid remains essentially unchanged, particularly compared to the flow of the liquid flowing in a channel without longitudinal recesses or longitudinal interruptions in the partitions. In other words, the insertion of each longitudinal fin 40 into the corresponding longitudinal recess 41 of the corresponding partition 9 allows the side walls of two adjacent channels 21 to be completely reconstructed.

[0101] In one variant, at least two electronic switches 22 are provided, preferably only two electronic switches are provided, and at least one longitudinal fin 40 is provided at each electronic switch 22 and is inserted into a corresponding longitudinal recess 41 or longitudinal interruption of the corresponding partition 9 .

[0102] In another variant, at least two longitudinal fins 40, preferably only two longitudinal fins, are provided at each electronic switch 22, which are inserted into corresponding longitudinal recesses 41 or longitudinal interruptions of at least one corresponding partition 9 (e.g. a single partition 9) or at least two corresponding partitions 9 (e.g. two corresponding partitions 9). Figure 10 、 Figure 11 、 Figure 13 ).

[0103] In other variations, the following may be provided:

[0104] an even number of electronic switches 22 , arranged symmetrically with respect to the second middle plane Y,

[0105] - or an odd number of electronic switches, which are arranged symmetrically with respect to the second middle plane Y, or there may be only one electronic switch.

[0106] exist Figures 3 to 6 and Figure 13In the example, two electronic switches 22 are provided, the two electronic switches 22 are symmetrically arranged with respect to the second plane Y, and the distance between one switch and the inlet portion 10 is equal to the distance between the other switch and the outlet portion 11.

[0107] In all these variants, the longitudinal fin or fins 40 may be smooth along the longitudinal flanks or corrugated along said longitudinal flanks for inducing a slight turbulence locally and for increasing the heat exchange between the electronic switch 22 and the liquid.

[0108] In order to further increase the dissipation of heat generated by the electronic control unit, in addition to the longitudinal fins 40, linear protrusions 46 or raised pins 47 ( Figure 17 ), the linear protrusions 46 are preferably, but not necessarily, parallel to each other, and are formed by the recesses ( Figure 16 ) separated by .

[0109] An alternative variant does not provide longitudinal fins 40, but only provides linear protrusions 46 ( Figure 18 ) or raised pin 47 ( Figure 19 ), the linear protrusions 46 are preferably, but not necessarily, parallel to each other and are separated by recesses.

[0110] like Figure 9 and Figure 10 As shown, in another preferred variation of the heater of the present invention, gaps 14 are respectively provided between the end edges 15 of the partition 9 in the middle of the channels 21 and the first cover 6 and the second cover 7, whereby the channels 21 of each flow path 4, 5 are laterally connected to each other at the gaps.

[0111] Gaps may also be provided between the end edges of the further partitions 90 , 91 and the respective covers 6 , 7 .

[0112] Preferably, the gap 14 is also in the range of 0.01 to 0.4 mm.

[0113] Optionally, the end edges 15 of the partitions 9, 90, 91 are rounded edges.

[0114] The liquid flow entering the heater is diverted into the inlet portion 10 of the two flow paths 4, 5 and proceeds primarily along the shape of the partitions into the channels 21. However, due to the gaps between the apex of the partitions and the respective covers 6, 7, the channels 21 are not sealed, and a secondary flow transverse to the channels 21, i.e., a secondary bypass flow between the inlet and outlet portions, is generated. Therefore, the channels 21, which are substantially parallel to each other, are not connected in parallel between the inlet and outlet portions, as there is always a transverse flow from one channel to the other.

[0115] The advantages of setting this gap are multiple:

[0116] - avoidance of hyperstatic resting of the covers 6 , 7 on the corresponding faces of the body 2 , taking into account the flatness tolerances of the components, thus avoiding assembly tensions between the components;

[0117] - avoiding prolonged thermal contact between the body 2 and the cover on which the electronic control unit 8 is fixed, so as to minimize any heat transfer from the partition to the electronic control unit; for this purpose, the end edges or tips of the partition may also be rounded to minimize heat transfer from any accidental contact points;

[0118] - Due to the relative gravity, the bubbles are encouraged to move upwards, preventing any bubbles in the liquid from being trapped in the channel, especially in the case of slow flow in the M-shaped flow path.

[0119] If one or more longitudinal fins 40 are provided at the first side of the first cover 6 at one or more electronic switches 22, in addition to the gaps 14 between the end edges 15 of the partitions 9 and the first cover 6 and the second cover 7, respectively, a second gap 14′ can also be provided between the longitudinal fins 40 and the corresponding longitudinal recess 41 or longitudinal interruption of the corresponding partition 9 of the flow path 4 ( Figure 10 ). Therefore, the channels 21 adjacent to each other in the flow path 4 are also connected at the gap 14'.

[0120] The second gap 14' is also preferably in the range of 0.01 to 0.4 mm.

[0121] In a variant, the end edges of the partitions 9 , 90 , 91 and / or of the longitudinal fins 40 and / or of the longitudinal recesses 41 are rounded edges.

[0122] exist Figures 14 and 15 In another variant shown, in order to further reduce the heat transfer from the heating body 2 to the cover 6, which also accommodates the electronic control unit, a further gap 48 between the body 2 and the cover 6 is also conveniently provided in the peripheral area close to the sealing gasket 43, which is arranged in said peripheral area to prevent liquid from leaking from the corresponding flow path to the outside of the heater.

[0123] The sealing gasket 43 is arranged in a peripheral housing 45 formed on the corresponding cover and / or on the corresponding surface of the body 2 .

[0124] Another gap 48 is preferably provided on the outside of the housing 44 of the fastening screw ( Figure 15 ), the two covers 6, 7 and the main body 2 arranged between them are fastened to each other by fastening screws, and the other gap 48 is also provided on the inner and outer sides of the peripheral shell 45 ( Figure 14 ),.

[0125] In all variants of the heater according to the invention, each flow path 4 , 5 can be produced according to different embodiments.

[0126] like Figure 3 As shown, the first embodiment of the flow path provides three hairpin bends 30 , 31 . The three hairpin bends 30 , 31 are bends with a central angle greater than 180°, preferably greater than 180° and less than 220°.

[0127] exist Figure 3 In a non-limiting example, the middle hairpin 30 has a center angle of approximately 190-200°; and the two side hairpins 31 have a center angle of approximately 200-220°.

[0128] In this embodiment, the channel 21 has a cross section that is as uniform as possible, and the three hairpin bends 30, 31 are rounded to further reduce pressure loss. The heat exchange surface obtained by the partition is increased rather than the shape of the bends 30, 31 to promote heat exchange.

[0129] like Figure 4 As shown, the second embodiment of the flow path provides three hairpin bends 30, 31, which are bends with a central angle of approximately 180°; and at least one channel 21, preferably the innermost channel, has a width A measured parallel to the second middle plane Y at the two side hairpin bends 31, which is greater than the width B of the channel itself measured perpendicular to the second middle plane Y.

[0130] This second embodiment allows to optimize the weight and manufacturability of the body 2. Compared to the first embodiment, the hairpin is less rounded; however, in order to reduce turbulence and pressure losses, the width of at least one channel 21 at the side hairpin 31 is increased (A>B), so that the fluid slows down in the bend and generates less turbulence.

[0131] like Figure 5 As shown, the third embodiment of the flow path is provided with a partition 9, in particular an intermediate partition between one channel 21 and an adjacent channel, which is provided with at least one corresponding recess 16 at its end edge 15. Preferably, but not necessarily, the recess 16 is arranged symmetrically with respect to the median plane Y. Figure 5 In FIG. 1 , the number of recesses 16 is equal to six, but their number may be greater or less than six.

[0132] The depth of the recess 16 is preferably between 0.2 and 3 mm, preferably between 1 and 3 mm.

[0133] These recesses 16 further promote the aforementioned transverse flow between the channels 21. By varying their number and position, it is possible to define predetermined design values ​​for the flow transverse to the channels.

[0134] like Figure 6 As shown, a fourth embodiment of the flow path is provided with at least some baffles 9, particularly intermediate baffles between one channel 21 and an adjacent channel, which are completely interrupted at an intermediate or central hairpin 30 and in which a plurality of protrusions 23 are provided.

[0135] The protrusions 23 can be in the form of studs of various possible shapes (circular, oval, rectangular cross-section, etc.), suitable for locally increasing the heat exchange surface. Indeed, it is possible that at least one resistor 3 has a greater power density at the central hairpin 30. This local increase in heat exchange is achieved by replacing the flow path with a substantially M-shaped channel with a flow path with two U-shaped channel extensions, also defined by a partition 91 and connected in sequence from a central bend region, from which the studs 23 protrude and where the flows of the channels completely converge.

[0136] Figure 5 and Figure 6 It is shown that the features described in the third and fourth embodiments are combined with the above-mentioned features of the first embodiment. Alternatively, the features described in the third and fourth embodiments can be combined with the above-mentioned features of the second embodiment.

[0137] In all embodiments of the heater of the invention, preferably, at least one resistor 3 is a tubular resistor partially incorporated along the first median plane X of the body 2 .

[0138] In particular, the heating portion of said at least one resistor 3 is fully integrated into the body 2 along said first intermediate plane X.

[0139] Figure 7 A first variant is shown, in which only one tubular serpentine resistor 3 is provided, preferably arranged symmetrically with respect to the second mid-plane Y.

[0140] Figure 8 A second variant is shown, in which at least three tubular resistors 33 , 32 are provided, which can be electrically connected in series or in parallel; preferably, in which the assembly of at least three tubular resistors is arranged symmetrically with respect to the second median plane Y.

[0141] In all the variants, a single resistor 3 or all resistors 33 , 32 are arranged only along the first median plane X, being partially incorporated into a single body 2 .

Claims

1. An electric heater (1) for a vehicle, adapted to heat a liquid passing through the heater, comprising: - a body (2) made of die-cast metal material; - at least one resistor (3) at least partially integrated into the body (2) along a first median plane (X) of the body (2); - an inlet section (10) and an outlet section (11) for the liquid, both arranged on the same side of the heater; a first flow path (4) for the liquid, from the inlet portion (10) to the outlet portion (11), formed on a first face of the body (2), the first face being arranged on a first side of the first median plane (X); a second flow path (5) for the liquid, from the inlet portion (10) to the outlet portion (11), formed on a second face of the body (2), the second face being arranged on a second side of the first median plane (X) opposite to the first side; The first flow path (4) and the second flow path (5) including the inlet portion (10) and the outlet portion (11) are symmetrically arranged relative to the first middle plane (X) and relative to a second middle plane (Y) of the main body (2) perpendicular to the first center plane (X).

2. The heater according to claim 1, wherein The heater is provided with: - a first cover (6), a first side of which closes the first flow path (4); - a second cover (7), a first side of which closes the second flow path (5); - an electronic control unit (8) arranged on a second side of the first cover (6) or the second cover (7) opposite to the first side; The electronic control unit (8) comprises at least one electronic switch (22), which is arranged near the second middle plane (Y) and at a remote position away from the inlet portion (10) and the outlet portion (11).

3. The heater according to claim 1 or 2, wherein The first flow path (4) and the second flow path (5) are both provided with an odd number of hairpin bends and include a plurality of channels (21) that branch from the inlet portion (10) and flow into the outlet portion (11); preferably, the channels (21) of the first flow path (4) and the second flow path (5) are defined by partitions (9) protruding from the first side and the second side of the main body (2), respectively.

4. The heater according to claim 3, wherein Three hairpin bends are provided, and for the first flow path (4) and the second flow path (5), a middle hairpin bend (30) among the three hairpin bends is arranged at a second middle plane (Y) and close to a side of the heater where an inlet portion (10) and an outlet portion (11) are arranged; and two side hairpin bends (31) among the three hairpin bends are arranged symmetrically with respect to the second middle plane (Y) and away from the side of the heater.

5. A heater according to any one of the preceding claims, wherein The heater is provided with: - a first pipe connection piece (12) extending from the main body (2) and communicating with the inlet portion (10); - a second pipe connection piece (13) extending from the main body (2) and communicating with the outlet portion (11); Preferably, the first pipe connector (12) and the second pipe connector (13) are arranged symmetrically relative to the second center plane (Y). The heater according to claim 5 , wherein: The ratio between the width (W) of the first flow path (4) and the second flow path (5) and the inner diameter of the first pipe connection (12) and the second pipe connection (13) is in the range of 1 to 2, preferably in the range of 1.2 to 1.

6.

7. The heater according to any one of claims 3 to 6, wherein A gap (14) is provided between the end edge (15) of the partition (9) and the first cover (6) and the second cover (7), respectively; the first cover (6) closes the first flow path (4) with its first side, and the second cover (7) closes the second flow path (5) with its second side, so that the channels (21) are laterally connected to each other at the gap (14); preferably, the end edge (15) of the partition (9) is a circular edge.

8. The heater according to claim 7, wherein The partition (9) is provided with at least one corresponding recess (16) at the end edge (15).

9. The heater according to any one of claims 5 to 8, wherein At least some of the partitions (9) are interrupted at an intermediate hairpin bend (30) between the first flow path (4) and the second flow path (5), the intermediate hairpin bend being arranged at the second intermediate plane (Y) and close to the side of the heater where the inlet portion (10) and the outlet portion (11) are arranged; and a plurality of protrusions (23) are provided in the intermediate hairpin bend (30).

10. The heater according to any one of claims 4 to 9, wherein The hairpin bends (30, 31) are bends with a central angle greater than 180°, preferably greater than 180° and less than 220°.

11. The heater according to any one of claims 4 to 9, wherein The three hairpin bends (30, 31) are bends with a central angle of approximately 180°; and wherein at least one channel has a width A measured parallel to the second midplane at two side hairpin bends (31), and the width A is greater than the width B of the channel itself measured perpendicular to the second midplane.

12. A heater according to any one of the preceding claims, wherein The at least one resistor (3) is at least a tubular resistor.

13. The heater according to any one of claims 2 to 12, wherein A sealing gasket (43) is provided, which is arranged in a peripheral housing (45), which is formed on the corresponding cover (6, 7) and / or on the corresponding face of the body (2), and wherein a gap (48) is provided between the body (2) and the cover (6, 7) at the peripheral housing (45), and the electronic control unit (8) is arranged on the second side of the cover (6, 7).

14. The heater according to any one of claims 3 to 13, wherein At least one longitudinal fin (40) is provided, which protrudes from a first side of the first cover (6) or the second cover (7) at the at least one electronic switch (22) and is inserted into a corresponding longitudinal recess (41) or longitudinal interruption of at least one partition (9), so that the longitudinal flanks of the at least one longitudinal fin (40) define a part of the side wall of two adjacent channels (21).

15. The heater according to claim 2 or 14, wherein Linear protrusions (46) or raised pins (47) are also provided on all or part of the first side of the first cover (6) or second cover (7), the linear protrusions preferably being parallel to each other and separated by recesses.

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