Electric heating device for a heat transfer fluid for a motor vehicle

Abstract

Electric heating device (1) for a heat transfer fluid for a motor vehicle, wherein the electric heating device (1) comprises a housing that limits the following: • at least one heating chamber (3) within which the heat transfer fluid is to circulate and in which at least one electric heating element (31) extends, • a receptacle (5) in which a printed electronic control circuit (51) is arranged, wherein the receptacle (5) is arranged outside the heating chamber (3), wherein the receptacle (5) has a base (52) which is at least partially formed by the outer wall of the heating chamber (3), characterized in that the printed circuit (51) has a thermal fuse (53) attached to its side facing the base (52) of the receptacle (5) and the base (52) of the receptacle (5) has a delimited area (30) opposite the thermal fuse (53) which contains a thermal paste (55), such that the thermal fuse (53) is at least partially immersed in the thermal paste (55), wherein the delimited area (30) is in thermal contact with the outer wall of the heating chamber (3).

Description

[0001] The field of the present invention is that of electrical devices for heating and circulating a heat transfer fluid, in particular for a ventilation, heating and / or air conditioning system for the passenger compartment of a motor vehicle. In particular, the invention relates to electrical heating devices used for such systems in motor vehicles, electric or hybrid vehicles, equipped with a high-voltage power supply network.

[0002] The heating of the air intended for the thermal treatment of the passenger compartment of a vehicle with an internal combustion engine is ensured by heat exchange between an airflow and a heat transfer fluid via a heating device. In hybrid or electric vehicles, these are typically electric heating devices that act as a heat source and in which an electric current, usually at high voltage, flows to heat an electric heating element integrated within the device. The heat transfer fluid to be heated thus passes through the electric heating device and comes into contact with the electric heating element, thereby facilitating an exchange of thermal energy between the electric heating element and the heat transfer fluid.This heat transfer fluid then flows into the radiator located in the ventilation, heating and / or air conditioning system to heat the airflow for the passenger compartment.

[0003] The electric heating element typically consists of electric heating elements, such as one or more heating resistors. To power and control such an electric heating element, the electric heating device usually contains an electronic printed control circuit. However, under certain circumstances, the temperature of the electric heating element can become excessively high, posing a risk of overheating and burning out the heating device. This situation arises, for example, if heat transfer fluid no longer circulates in the heating chamber of the device containing the electric heating element, or if there is insufficient heat transfer fluid present, for example, due to a leak. In this situation, the heat generated by the electric heating element is not dissipated properly.This can lead to an excessive temperature increase and thus potentially trigger a fire in the heating device.

[0004] To prevent damage to the heating element from burning due to overheating, the device may have one or more thermal fuses that interrupt the power supply to the electric heating element, thereby reducing its temperature if it becomes too high. The heating of the heat transfer fluid is also interrupted.

[0005] Normally, the thermal fuse is integrated into the heating device with retaining elements that allow it to be positioned near the heating chamber, thus monitoring the temperature profile of the electric heating element located within that chamber. Adjusting these retaining elements can prove time-consuming and laborious, and can also introduce a significant degree of complexity into the component design phase.

[0006] The object of the present invention is therefore to at least partially overcome the disadvantages of the prior art and to propose an improved electrical heating device that allows for faster and simpler installation of the thermal fuse on the printed circuit arranged inside it.

[0007] The present invention therefore relates to an electric heating device for a heat transfer fluid for a motor vehicle, wherein the electric heating device comprises a housing that limits the following: • at least one heating chamber within which the heat transfer fluid is to circulate and in which at least one electric heating element extends, • a receptacle in which a printed electronic control circuit is arranged, wherein the receptacle is arranged outside the heating chamber, wherein the receptacle has a bottom which is at least partially formed by the outer wall of the heating chamber, wherein the electrical heating device is characterized in that the printed circuit has a thermal fuse attached to its side facing the bottom of the receptacle and the bottom of the receptacle has a demarcated area opposite the thermal fuse which contains a thermal paste, so that the thermal fuse is at least partially immersed in the thermal paste, wherein the demarcated area is in thermal contact with the outer wall of the heating chamber.

[0008] Directly attaching the thermal fuse to the side of the printed circuit board facing the base of the housing allows it to be positioned as close as possible to the outer wall of the heating chamber without the need for a retaining element. This improves the compactness of the heating device and reduces the time required for dimensioning the components housed within. Regarding the thermal paste, in addition to ensuring good thermal contact between the thermal fuse and the base of the housing, which is at least partially formed by the outer wall of the heating chamber, the paste's viscosity can compensate for potential dimensional errors during the assembly of the heating device. Furthermore, the thermal paste's adhesion can help to secure the thermal fuse within the heating device.

[0009] According to one aspect of the invention, the delimited area is in the form of a tray, at the bottom of which the thermal paste is arranged, which comes into contact with the thermal fuse.

[0010] According to another aspect of the invention, the tub has edges that are designed to at least partially cover the thermal fuse.

[0011] According to another aspect of the invention, the edges of the tray are located at a distance from the printed circuit that is greater than the distance required to form arcs.

[0012] According to another aspect of the invention, the bottom of the tub has a shape that is complementary to the shape of the upper end of the thermal fuse.

[0013] According to another aspect of the invention, the thermal fuse is soldered onto the printed circuit board.

[0014] According to another aspect of the invention, the delimited area lies above a central section of the heating chamber.

[0015] According to another aspect of the invention, the thermal fuse is located in the high-voltage part of the printed circuit.

[0016] According to another aspect of the invention, the thermal fuse is located in the low-voltage part of the printed circuit.

[0017] The present invention also relates to an electric heating device for a heat transfer fluid for a motor vehicle, wherein the electric heating device comprises a housing that limits the following: • at least one heating chamber within which the heat transfer fluid is to circulate and in which at least one electric heating element is to extend, • a receptacle in which a printed electronic control circuit is to be arranged, wherein the receptacle is arranged outside the heating chamber, wherein the bottom of the receptacle is formed at least partially by the outer wall of the heating chamber, wherein the thermal fuse is positioned and attached to the printed circuit board, in particular by soldering, the thermal paste is located in the designated, enclosed area on the bottom of the holder, wherein the printed circuit is positioned in the receptacle so that the thermal fuse is immersed in the thermal paste which is applied in the demarcated area on the bottom of the receptacle.

[0018] Further features and advantages of the present invention will become more apparent upon reading the following description, which is given for illustrative purposes and in a non-limiting manner, and with reference to the accompanying drawings. These show: Fig. 1 A schematic representation of the electric heating device in a perspective sectional view. Fig. 2 A detailed view of the thermal fuse immersed in the thermal paste, which is located in the delimited area at the bottom of the heating device's mounting. Fig. 1 is arranged. Fig. 3. A flowchart of a process for manufacturing an electric heating device.

[0019] The different figures contain identical elements labelled with the same reference symbols.

[0020] The following descriptions are examples. Even if the description refers to one or more embodiments, this does not necessarily mean that every reference refers to the same embodiment or that the features apply only to a single embodiment. Individual features of different embodiments can also be combined and / or exchanged to offer further embodiments.

[0021] In this description, certain elements or parameters may be assigned an index, e.g., first element or second element, first parameter and second parameter, or first criterion and second criterion, etc. This is a simple indexing system used to distinguish and name elements, parameters, or criteria that are similar but not identical. This indexing does not imply any priority of one element, parameter, or criterion over another, and such names are easily interchangeable without exceeding the scope of this description. This indexing also does not imply any chronological order, e.g., for evaluating one criterion over another.

[0022] The electric heating device 1 comprises a housing that defines at least one heating chamber 3 with a cavity in which the heat transfer fluid is to circulate. According to the Fig. In the example shown in Figures 1 to 3, the housing as a whole has a parallelepiped shape, while the heating chamber 3 has a cylindrical profile. The cavity in which the heat transfer fluid circulates is also cylindrical. However, it is also possible to consider other shapes for the heating chamber 3, e.g., a parallelepiped shape, without departing from the scope of the present invention. The heating chamber 3 is, for example, made of aluminum or another robust material with a relatively high thermal conductivity.

[0023] Within the cavity of this heating chamber 3 extends at least one electrical heating element 31, which is provided for heating the heat transfer fluid. This electrical heating element 31 can, for example, have one or more electrical resistors with a spiral profile, as shown in Fig. 2 is shown.

[0024] The electric heating device 1 also has a receptacle 5 (e.g. in Fig. 2 visible), in which an electronic printed control circuit 51 is arranged. This receptacle 5 is arranged outside the heating chamber 3. The receptacle 5 has a base 52 which is at least partially formed by the outer wall of the heating chamber 3, as shown in particular in Fig. Figure 2 shows this special arrangement of the base 52 of the receptacle 5 within the electric heating device 1 makes it possible to design it in a particularly compact way.

[0025] The electronic printed circuit 51 is, in particular, a circuit for supplying and controlling the electric heating element 31. The electric heating device 1 thus has at least one electrical connection that enables the electrical supply of the printed circuit 51, generally with low-voltage current (e.g., 12 to 48 V), and also of the electric heating element 31, generally with high-voltage current (which, for example, can be over 500 V for an electric vehicle).

[0026] Regarding the printed circuit 51, it has a thermal fuse 53 attached to its side facing the base 52 of the receptacle 5, as shown in Fig. Figure 2 shows the thermal fuse 53. It can be located in the high-voltage section or the low-voltage section of the printed circuit 51, depending on the overall architecture of the heating device 1 and the printed circuit 51. This can also depend on the arrangement of the heating chamber 3 with respect to the high-voltage and low-voltage sections of the printed circuit 51. For example, the thermal fuse 53 is connected in series with a power supply to the heating element 31 and with the heating element 31 itself.

[0027] In general, the thermal fuse 53 is located near the heating chamber 3 at the point where the temperature is likely to be highest, which may correspond in particular to the central section of the heating chamber, in order to be loaded as early as possible when a temperature threshold is exceeded and to prevent damage to the heating device 1. The thermal fuse 53 is designed to interrupt the power supply as soon as the temperatures inside the heating chamber 3 exceed a predetermined threshold.

[0028] The thermal fuse 53 is soldered, for example, onto the printed circuit board 51. Soldering the thermal fuse 53 directly onto the printed circuit board 51 eliminates the need for an additional retaining element, which also improves the compactness of the design. Soldering is a reliable and cost-effective fastening method.

[0029] The base 52 of the receptacle 5 has a delimited area 30 opposite the thermal fuse 53, which contains the thermal paste 55, such that the thermal fuse 53 is at least partially immersed in the thermal paste 55. The term "delimited" here means that the area 30 containing the thermal paste 55 extends only over a specific section of the base 52 of the receptacle 5. The delimited area 30 is located, in particular, above the central section of the heating chamber 3. This depends on the overall architecture of the heating device 1, the position of the heating chamber 3, the arrangement of the printed circuit board 51, and the position of the thermal fuse 53 on this printed circuit board 51.

[0030] The enclosed area 30 is in thermal contact with the outer wall of the heating chamber 3; that is, the heat transfer from the heating chamber 3 through its outer wall to the enclosed area 30, which contains the thermal paste 55 and into which the thermal fuse 53 is partially immersed, is particularly effective. Effective heat transfer between the heating chamber 3, the enclosed area 30, and the thermal fuse 53 enables very early detection of a possible temperature threshold being exceeded in the heating chamber 3.

[0031] The effectiveness of this heat transfer depends heavily on the thermal paste 55 used. The selection of the thermal paste is based on various criteria, the primary criterion being thermal conductivity. In the application under consideration here, the thermal paste has, for example, a minimum thermal conductivity of 2 W / (mK) (watts per meter Kelvin). Other parameters, such as viscosity, adhesion to surfaces, long-term stability, or consistency within specific temperature ranges, can also be taken into account. For the application under consideration here, for instance, a silicone-based thermal paste, which is low-viscosity and electrically insulating, could be selected.

[0032] To maximize the cohesive force between the thermal paste 55 and the delimited area 30, the latter can be in the form of a tray, at the bottom of which the thermal paste 55 is located, which comes into contact with the thermal fuse 53, this particular embodiment being especially useful in the Fig. 2 and Fig. Figure 3 shows that the tub can have a rectangular shape, as in the following examples. Fig. 2 and Fig. 3, but also a round or oval shape. The shape of the tray can depend in particular on the shape of the upper end of the thermal fuse 53. More precisely, the bottom of the tray has a shape that is complementary to the shape of the upper end of the thermal fuse 53 in order to maximize the heat exchange surface between these two elements.

[0033] According to a first embodiment, the bottom of the reservoir is flat, as is the upper end of the thermal fuse 53. A flat bottom of the reservoir allows for a uniform distribution of the thermal paste 55 inside it. A flat bottom also allows for limiting the amount of thermal paste 55 required to ensure adequate interaction between the thermal fuse 53 and the reservoir, which forms the enclosed area 30.

[0034] According to a further embodiment of the tub and the thermal fuse 53, the latter has, for example, a curved, e.g. convex, upper end, while the tub then has a bottom with a cavity that is, for example, concave.

[0035] Furthermore, the tray can have edges 32 designed to at least partially cover the thermal fuse 53. The edges 32 also prevent the thermal paste 55 from overflowing outside the defined area 30 when the thermal fuse 53 is immersed in it.

[0036] Furthermore, an upper end of the edges 32 of the tray is located at a distance from the printed circuit 51 that is greater than the distance required to prevent the formation of arcs. This safety distance is closely related to the voltage flowing through the printed circuit 51 and is generally on the order of one millimeter.

[0037] In any case, and regardless of the shape chosen for the tub in this embodiment, at least a part of the tub, forming the delimited area 30, is in thermal contact with the outer wall of the heating chamber 3, which forms at least a part of the bottom 52 of the receptacle 5, which is particularly evident in Fig. 3 is shown.

[0038] According to a particular embodiment, the tank can be formed in one piece with the heating chamber 3 and, optionally, with the receptacle 5. In this case, these elements of the heating device 1 are manufactured, in particular, using one and the same manufacturing process, for example, by casting. The tank and the heating chamber 3 can be made of aluminum or an aluminum-containing alloy.

[0039] According to another embodiment, the tub can be an add-on component. In this case, the material used for the tub may differ from the material used for the heating chamber 3, but in any case, the materials used enable good heat transfer.

[0040] Fig. Figure 3 shows a flowchart of a process for manufacturing an electric heating device 1, as previously described. The process comprises the following steps: • a first step 101 to position and secure the thermal fuse 53 on the printed circuit 51, in particular by soldering, • a second step 102 for introducing the thermal paste 55 into the designated demarcated area 30 on the base 52 of the receptacle 5, and • a third step 103 to position the printed circuit 51 in the receptacle 5, so that the thermal fuse 53 is immersed in the thermal paste 55 which was applied in the delimited area 30 on the edge 52 of the receptacle 5.

[0041] Such a method therefore comprises a relatively small number of steps 101, 102, and 103, which can lead to time savings in the manufacture of the heating device 1. This device is characterized by an advantageous compactness, which can facilitate its installation in the motor vehicle. The insertion and retention of the thermal fuse 53 in its position is facilitated by soldering this component to the printed circuit 51 before the printed circuit 51 is installed in the receptacle 5 within the heating device 1, and by utilizing the various properties of the thermal paste 55.

Claims

[1] Electric heating device (1) for a heat transfer fluid for a motor vehicle, the electric heating device (1) comprising a housing which delimits: • at least one heating chamber (3) within which the heat transfer fluid is to circulate and in which at least one electric heating element (31) extends, • a receptacle (5) in which a printed electronic control circuit (51) is arranged, wherein the receptacle (5) is arranged outside the heating chamber (3), wherein the receptacle (5) has a bottom (52) which is at least partially formed by the outer wall of the heating chamber (3), characterized bythat the printed circuit (51) has a thermal fuse (53) attached to its side facing the bottom (52) of the receptacle (5), and the bottom (52) of the receptacle (5) has a delimited area (30) opposite the thermal fuse (53) which contains a thermally conductive paste (55), so that the thermal fuse (53) is at least partially immersed in the thermally conductive paste (55), the delimited area (30) being in thermal contact with the outer wall of the heating chamber (3). [2] Electric heating device (1) according to the preceding claim, characterized by that the delimited area (30) is in the form of a trough, at the bottom of which the thermal paste (55) is arranged, which comes into contact with the thermal fuse (53). [3] Electric heating device (1) according to the preceding claim, characterized by that the tray has edges (32) which are designed to at least partially cover the thermal fuse (53). [4] Electric heating device (1) according to the preceding claim, characterized by that an upper end of the edges (32) of the trough is at a distance from the printed circuit (51) which is greater than the distance for the formation of arcs. [5] Electric heating device (1) according to one of claims 2 to 4, characterized by that the bottom of the tub has a shape complementary to the shape of the upper end of the thermal fuse (53). [6] Electric heating device (1) according to one of the preceding claims, characterized by that the thermal fuse (53) is soldered to the printed circuit (51). [7] Electric heating device (1) according to one of the preceding claims, characterized by that the demarcated area (30) lies above a central section of the heating chamber (3). [8] Electric heating device (1) according to one of the preceding claims, characterized bythat the thermal fuse (53) is located in the high-voltage part of the printed circuit (51). [9] Electric heating device (1) according to one of the preceding claims, characterized by that the thermal fuse (53) is connected in series with a power supply of the heating element (31) and with the heating element (31). [10] Electric heating device (1) for a heat transfer fluid for a motor vehicle, the electric heating device (1) comprising a housing which delimits: • at least one heating chamber (3) within which the heat transfer fluid is to circulate and in which at least one electric heating element (31) is to extend, • a receptacle (5) in which a printed electronic control circuit (51) is to be arranged, wherein the receptacle (5) is to be arranged outside the heating chamber (3), wherein the bottom of the receptacle (5) is at least partially formed by the outer wall of the heating chamber (3), • wherein the thermal fuse (53) is fixed and positioned on the printed circuit (51), in particular by soldering, • wherein the thermal paste (55) is located in the designated delimited area (30) on the bottom (52) of the receptacle (5), • wherein the printed circuit (51) is positioned in the receptacle (5) so that the thermal fuse (53) is immersed in the thermal paste (55) which is introduced in the delimited area (30) on the bottom (52) of the receptacle (5).

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