Device for electrically heating heat transfer liquid of motor vehicle

Abstract

The utility model relates to a device (1) for electrically heating a heat-transfer liquid of a motor vehicle, comprising a housing delimiting: at least one heating chamber (3) in which the heat-transfer liquid circulates and in which at least one electric heating element (31) extends; a housing (5) in which an electronic management printed circuit (51) is arranged, the housing (5) being arranged outside the heating chamber (3), the housing (5) comprising a bottom (52) at least partially formed by an outer wall of the heating chamber (3), characterized in that the printed circuit (51) comprises a thermal fuse (53) fastened to its surface facing the bottom (52) of the housing (5), and the bottom (52) of the housing (5) comprises a delimiting region (30) facing the thermal fuse (53), which delimiting region comprises a thermal paste (55) such that the thermal fuse (53) is at least partially immersed in the thermal paste (55), the delimiting region (30) being in thermal contact with the outer wall of the heating chamber (3). The utility model also relates to a method for producing such an electric heating device.

Description

Technical Field

[0001] The field of the invention is electrical devices for heating and circulating heat transfer liquids, in particular for heating, ventilating and / or air conditioning equipment for the passenger compartment of a motor vehicle. More specifically, the invention relates to electrical heating devices for such equipment in electric or hybrid motor vehicles equipped with a high-voltage power supply network. Background Art

[0002] The air for heat treatment of the passenger compartment of a motor vehicle with a heat engine is heated by heat exchange between the air flow and a heat transfer liquid through a radiator. In the case of hybrid or electric vehicles, an electric heating device is usually used to provide a source of heat energy, in which an electric current, usually with a high voltage, circulates in order to raise the temperature of an electric heating element built into the heating device. The heat transfer liquid to be heated thus passes through the electric heating device and comes into contact with the electric heating element; heat energy is then exchanged between the electric heating element and the heat transfer liquid. The heat transfer liquid then enters a radiator arranged in a heating, ventilation and / or air conditioning device to heat the air flow for the passenger compartment.

[0003] An electric heating element usually consists of an electric heating device, such as one or more heating resistors. In order to power such an electric heating element and to control it, the electric heating device usually comprises an electronic control printed circuit board. However, in certain cases, the temperature of the electric heating element can become too high, with the risk that the electric heating element overheats and burns the heating device. This can happen, for example, when a heat transfer fluid no longer circulates through the heating chamber of the heating device containing the electric heating element, or when there is not enough heat transfer fluid, such as in the case of a leak. In this case, the heat generated by the electric heating element cannot be discharged properly. This can lead to an excessive increase in temperature, which can cause a fire inside the heating device.

[0004] In order to prevent burn damage to the heating device due to overheating, the device may include one or more thermal fuses to interrupt the power supply to the electric heating device and reduce its temperature when the temperature is too high. The heating of the heat transfer liquid is also interrupted.

[0005] Thermal fuses are usually built into the heating device using retaining elements that enable them to be positioned close to the heating chamber to monitor temperature changes of the electric heating element arranged in the heating chamber. Adjusting these retaining elements can be very time consuming and can also complicate the component dimensioning phase. Summary of the invention

[0006] Therefore, the object of the present invention is to at least partially overcome the disadvantages of the prior art and to propose an improved electric heating device, which enables faster and easier installation of a thermal fuse on a printed circuit board arranged in the electric heating device.

[0007] The invention therefore relates to an electrical heating device for a heat transfer liquid for a motor vehicle, said electrical heating device comprising a housing defining:

[0008] at least one heating chamber, a heat transfer liquid being adapted to circulate in the heating chamber and at least one electric heating element extending in the heating chamber,

[0009] a base for placing the electronic management printed circuit board, said base being arranged outside the heating chamber, the base comprising a bottom formed at least partially by the outer wall of the heating chamber,

[0010] The electric heating device is characterized in that the printed circuit board includes a thermal fuse fastened to its surface facing the bottom of the base, and the bottom of the base has a defined area opposite to the thermal fuse containing the thermal compound, so that the thermal fuse is at least partially immersed in the thermal compound, and the defined area is in thermal contact with the outer wall of the heating chamber.

[0011] Fastening the thermal fuse directly to the surface of the electronic printed circuit board opposite the base bottom enables the thermal fuse to be placed as close as possible to the outer wall of the heating chamber without using retaining elements, which improves the compactness of the heating device and at the same time simplifies the dimensioning phase of the components housed therein. As for the thermal compound, in addition to ensuring good thermal contact between the thermal fuse and the base bottom formed at least in part by the outer wall of the heating chamber, the viscosity of the thermal compound can help to offset any dimensional defects during the assembly of the heating device. The adhesion of the thermal compound can also help to keep the thermal fuse inside the heating device.

[0012] According to one aspect of the invention, the defined area takes the form of a depression, at the bottom of which a thermal compound is placed in contact with the thermal fuse.

[0013] According to another aspect of the invention, the recess has an edge designed to at least partially cover the thermal fuse.

[0014] According to another aspect of the present invention, the distance between the edge of the recess and the printed circuit board is greater than the arc distance.

[0015] According to another aspect of the present invention, the shape of the bottom of the recess matches the shape of the top of the thermal fuse.

[0016] According to another aspect of the present invention, the thermal fuse is soldered to the printed circuit board.

[0017] According to another aspect of the invention, the defined area is located above a central portion of the heating chamber.

[0018] According to another aspect of the present invention, a thermal fuse is located in a high voltage portion of a printed circuit board.

[0019] According to another aspect of the invention, the thermal fuse is located in a low voltage portion of the printed circuit board.

[0020] The invention also relates to a method for manufacturing an electric heating device for a heat transfer liquid for a motor vehicle, said electric heating device comprising a housing defining:

[0021] at least one heating chamber, a heat transfer liquid being adapted to circulate in the heating chamber, and at least one electric heating element being adapted to extend in the heating chamber,

[0022] a base for placing the electronic management printed circuit board, the base being arranged outside the heating chamber, the bottom of the base being at least partially formed by the outer wall of the heating chamber,

[0023] The method comprises the following steps:

[0024] Specifically, the thermal fuse is positioned and fastened to the printed circuit board by soldering.

[0025] A thermal compound is deposited in a defined area on the bottom of the base for this purpose,

[0026] The printed circuit board is positioned in the mount such that the thermal fuse is immersed in the thermal compound deposited in a defined area on the bottom of the mount. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Further characteristics and advantages of the invention will become more apparent on reading the following description, provided by way of non-limiting example, and through the accompanying drawings, in which:

[0028] Figure 1 is a schematic cross-sectional perspective view of an electric heating device.

[0029] Figure 2 is a detailed view of a thermal fuse immersed in a Figure 1 Heat the thermal compound within a defined area on the bottom of the base of the heating device.

[0030] Figure 3 is a flow chart of a method for manufacturing an electric heating device.

[0031] In different figures, identical elements are provided with the same reference signs. DETAILED DESCRIPTION

[0032] The following embodiments are examples. Although the description relates to one or more embodiments, this does not necessarily mean that each reference numeral relates to the same embodiment, or that each feature applies to only one embodiment. Individual features of different embodiments may also be combined and / or exchanged to provide other embodiments.

[0033] In this specification, some elements or parameters may be indexed, such as the first element or the second element, and the first parameter and the second parameter or the first standard and the second standard, etc. In this case, the index is only to distinguish and represent similar but not identical elements or parameters or standards. Such indexing does not mean that one element, parameter or standard takes precedence over another element, parameter or standard, and such naming can be easily interchanged without departing from the scope of this specification. Such indexing does not mean any chronological order, such as when evaluating any given standard.

[0034] The electric heating device 1 has a housing which delimits at least one heating chamber 3, the heating chamber 3 having a cavity in which a heat transfer liquid circulates. Figures 1 to 3 In the example shown, the housing has an overall parallelepiped shape, while the heating chamber 3 has a cylindrical profile. The chamber for the circulation of the heat transfer liquid is also cylindrical. However, other shapes of the heating chamber 3, such as a parallelepiped, are fully conceivable without departing from the scope of the present invention. The heating chamber 3 is made, for example, of aluminum or any other strong material with relatively high thermal conductivity.

[0035] At least one electric heating element 31 for heating a heat transfer liquid extends within the cavity of the heating chamber 3. The electric heating element 31 may, for example, comprise one or more resistors having a spiral profile, such as Figure 2 shown.

[0036] The electric heating device 1 also has a base 5 (eg Figure 2 As shown in FIG. 1 , an electronic management printed circuit board 51 is arranged therein. The base 5 is arranged outside the heating chamber 3. The base 5 includes a bottom 52, which is at least partially formed by the outer wall of the heating chamber 3, as shown in FIG. Figure 2 This special arrangement of the bottom 52 of the base 5 inside the electric heating device 1 makes the device particularly compact.

[0037] The electronic printed circuit board 51 is in particular a power supply and control circuit for the electric heating element 31. The electric heating device 1 therefore comprises at least one electrical connection element capable of supplying power to the printed circuit board 51, typically with a low-voltage current (e.g. 12 to 48 V), and also to the electric heating element 31, typically with a high-voltage current (e.g. more than 500 V for electric vehicles).

[0038] like Figure 2As shown, the printed circuit board 51 comprises a thermal fuse 53, which is fastened to the surface of the printed circuit board opposite to the bottom 52 of the base 5. Depending on the overall structure of the heating device 1 and the printed circuit board 51, the thermal fuse 53 can be located in the high-voltage part of the printed circuit board 51 or in the low-voltage part of the printed circuit board 51. This may also depend on the position of the heating chamber 3 relative to the high-voltage part and the low-voltage part of the printed circuit board 51. The thermal fuse 53 is, for example, arranged in series with the power supply of the heating element 31 on one side and in series with the heating element 31 itself on the other side.

[0039] Typically, the thermal fuse 53 is placed at a location near the heating chamber 3 where the temperature may be highest, particularly at the central portion of the heating chamber, so that if a threshold temperature value is exceeded, the thermal fuse can be compressed as quickly as possible, thereby preventing damage to the heating device 1. The thermal fuse 53 is designed to cut off power once the temperature in the heating chamber 3 exceeds a predetermined threshold.

[0040] The thermal fuse 53 is, for example, soldered to the printed circuit board 51. Soldering the thermal fuse 53 directly to the printed circuit board 51 eliminates the need for additional retaining elements, which also contributes to improved compactness. Soldering is a reliable and inexpensive fastening method.

[0041] The bottom 52 of the base 5 comprises a defined area 30 facing the thermal fuse 53 and containing the thermal compound 55, so that the thermal fuse 53 is at least partially immersed in the thermal compound 55. In this case, "defined" means that the area 30 containing the thermal compound 55 covers only a defined part of the bottom 52 of the base 5. The defined area 30 is located in particular above the central part of the heating chamber 3. Again, this depends on the overall structure of the heating chamber 1 and the location of the heating chamber 3, as well as the arrangement of the printed circuit board 51 and the location of the thermal fuse 53 on this printed circuit board 51.

[0042] The delimited area 30 is in thermal contact with the outer wall of the heating chamber 3, i.e. the heat transfer from the heating chamber 3 through its outer wall to the delimited area 30 containing the thermal compound 55, in which the thermal fuse 53 is immersed, is particularly effective. The effective heat transfer between the heating chamber 3, the delimited area 30 and the thermal fuse 53 enables any exceeding of a temperature threshold in the heating chamber 3 to be identified very quickly.

[0043] The efficiency of this heat transfer depends largely on the thermal compound 55 used. The choice of the thermal compound depends on several criteria, the main one being thermal conductivity. In the applications envisaged herein, the thermal compound has, for example, a minimum thermal conductivity of 2 W / (m·K) (watts per meter·Kelvin). Other parameters may also be considered, such as viscosity, adhesion to the surface, durability or even consistency within a given temperature range. For the applications envisaged here, for example, a low-viscosity, electrically insulating, silicon-based thermal compound may be selected.

[0044] In order to maximize the cohesive force between the thermal compound 55 and the defined area 30, the defined area 30 can be in the form of a recess, and the thermal compound 55 in contact with the thermal fuse 53 is placed at the bottom of the recess. Figure 2 and Figure 3 The depression may be quadrilateral, for example Figure 2 and Figure 3 The shape of the depression depends in particular on the shape of the top of the thermal fuse 53. More specifically, the shape of the bottom of the depression matches the shape of the top of the thermal fuse 53, thereby maximizing the heat exchange surface between the two elements.

[0045] Thus, according to a first embodiment, the bottom of the recess is, for example, flat, and the top of the thermal fuse 53 is also flat. The flat bottom of the recess enables a uniform distribution of the thermal compound 55 within the recess. The flat bottom may also help limit the amount of thermal compound 55 required to ensure sufficient cooperation between the thermal fuse 53 and the recess forming the delimited area 30.

[0046] According to another embodiment of the recess and the thermal fuse 53, the thermal fuse 53 has, for example, a rounded top, for example convex, and the recess has, for example, a concave bottom with a cavity.

[0047] Additionally, the recess may have an edge 32 that is designed to at least partially cover the thermal fuse 53. The edge 32 may also help prevent the thermal compound 55 from escaping the defined area 30 when the thermal fuse 53 is immersed therein.

[0048] In addition, the top of the recessed edge 32 is located at a distance greater than the arc distance from the printed circuit board 51. The safety distance is closely related to the voltage flowing through the printed circuit board 51 and is generally in the order of millimeters.

[0049] In any case, regardless of the shape of the recess in this embodiment, at least a portion of the recess forming the delimited area 30 is in thermal contact with the outer wall of the heating chamber 3, which forms at least a portion of the bottom 52 of the base 5, such as Figure 3 shown.

[0050] According to a particular embodiment, the recess may be integral with the heating chamber 3 and, where applicable, with the base 5. In this case, these elements of the heating device 1 are in particular made in a single manufacturing process, for example by molding. The recess and the heating chamber 3 may be made of aluminum or an aluminum-containing alloy.

[0051] According to another embodiment, the recess may be an attachment part. In this case, the material used for the recess may be different from the material used for the heating chamber 3, but in any case the material used enables a good heat transfer.

[0052] Figure 3 A flow chart of a method for producing an electric heating device 1 as described above is shown.

[0053] The method comprises the following steps:

[0054] In a first step 101, the thermal fuse 53 is positioned and fastened to the printed circuit board 51, in particular by welding.

[0055] A second step 102 of depositing a thermal compound 55 in a defined area 30 on the bottom 52 of the base 5 for this purpose, and

[0056] A third step 103 is positioning the printed circuit board 51 in the base 5 so that the thermal fuse 53 is immersed in the thermal compound 55 deposited in the defined area 30 on the bottom 52 of the base 5 .

[0057] Thus, the method comprises relatively few steps 101, 102 and 103, which can save time during the manufacture of the heating device 1. The device is notable for its advantageous compactness, which can facilitate its installation in a motor vehicle. By soldering the thermal fuse 53 to the printed circuit board 51 before mounting the printed circuit board 51 in the base 5 in the heating device 1 and utilizing various properties of the thermal compound 55, the integration and retention of the thermal fuse 53 in place can be facilitated.

Claims

1. An electrical heating device (1) for a heat transfer liquid in a motor vehicle, the electrical heating device (1) comprising a housing defining: at least one heating chamber (3), the heat transfer liquid being adapted to circulate in the heating chamber and at least one electric heating element (31) extending in the heating chamber, a base (5) for placing an electronic management printed circuit board (51), said base (5) being arranged outside said heating chamber (3), said base (5) comprising a bottom (52) at least partially formed by the outer wall of said heating chamber (3), It is characterized in that The printed circuit board (51) comprises a thermal fuse (53), which is fastened to the surface of the printed circuit board facing the bottom (52) of the base (5), and the bottom (52) of the base (5) has a defined area (30) opposite to the thermal fuse (53) containing a thermal compound (55), so that the thermal fuse (53) is at least partially immersed in the thermal compound (55), and the defined area (30) is in thermal contact with the outer wall of the heating chamber (3).

2. The electric heating device (1) according to claim 1, characterized in that: The defined area (30) takes the form of a depression, at the bottom of which a thermal compound (55) is placed in contact with the thermal fuse (53).

3. The electric heating device (1) according to claim 2, characterized in that: The recess has an edge (32) designed to at least partially cover the thermal fuse (53).

4. The electric heating device (1) according to claim 3, characterized in that: The distance between the top of the recessed edge (32) and the printed circuit board (51) is greater than the arc distance.

5. The electric heating device (1) according to any one of claims 2 to 4, characterized in that: The shape of the bottom of the recess matches the shape of the top of the thermal fuse (53).

6. The electric heating device (1) according to any one of the preceding claims, characterized in that The thermal fuse (53) is soldered to the printed circuit board (51).

7. The electric heating device (1) according to any one of the preceding claims, characterized in that The defined area (30) is located above the central portion of the heating chamber (3).

8. The electric heating device (1) according to any one of the preceding claims, characterized in that The thermal fuse (53) is located in the high voltage portion of the printed circuit board (51).

9. The electric heating device (1) according to any one of the preceding claims, characterized in that The thermal fuse (53) is arranged in series with the power supply of the heating element (31) and the heating element (31).

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