Thin-film heating element and preparation method therefor, and electric heating device and electric vehicle

Abstract

A thin-film heating element and a preparation method therefor, and an electric heating device and an electric vehicle. The thin-film heating element comprises a resistive layer (10), the resistive layer (10) comprises a main body portion for forming resistance patterns, and the main body portion comprises deflection sections (11) and straight sections (12) that are electrically contiguous to the deflection sections (11) and are parallel to each other, wherein the sheet resistance of the deflection sections (11) is less than the sheet resistance of the straight sections (12). Reducing the sheet resistance of deflection sections can improve the localized heat accumulation at the deflection sections, and achieves the effect of mitigating current crowding.

Description

Thin film heating element and preparation method thereof, electric heating device and electric vehicle Technical Field

[0001] The present application relates to the field of electric heating equipment, and more particularly, to a thin film heating element and a preparation method thereof, an electric heating equipment and an electric vehicle. Background Art

[0002] At present, thin film heating elements mostly use materials such as nickel-chromium alloys, and the heating layer is prepared using a thermal spraying process. The stability is relatively good, and the material properties will not cause the resistance of the nickel-chromium alloy to change due to changes in operating temperature. Therefore, it can maintain a constant resistance within a larger temperature range.

[0003] In order to ensure that the thin film heating element has a large heating area and improve the heating efficiency, it is necessary to occupy the heating area as much as possible. During the design, the resistance layer (i.e., the heating layer) of the thin film heating element is mostly arranged in a spiral manner. This method inevitably has a deflection portion 11 (i.e., a bending area in the pattern of the resistance layer, wherein the deflection portion 11 is flanked by straight portions 12, and the dividing line between the two is the starting position of the deflected arc, i.e., the position shown by the bb surface in Figure 2). When the current flows in the resistance layer, the current will seek the path with the lowest resistance (or the shortest path) to flow. Specifically, the current density of the deflection portion 11 gradually decreases from the deflection center outward. For example, as shown in Figure 2, the deflection portion 11 can be divided into a first region 111, a second region 112, and a third region 113 from the deflection center outward, wherein the current density gradually decreases from the first region 111 to the third region 113, i.e., the current density of the first region 111 is 100%, the current density of the second region 112 is about 60%, and the current density of the third region 113 is about 20%. As for the corner regions 14 of the main body, the current density is less than 20%. This phenomenon causes uneven current distribution in the deflection portion, leading to current concentration and heat accumulation in the deflection portion. Specifically, the current concentration and heat accumulation are generally located in the area with a current density of more than 60%, which can be called a hot spot. The temperature in the hot spot area is higher than that in other areas, which ultimately manifests as a hot spot in the deflection portion, such as the bright area shown in Figure 3, which may eventually cause local damage to the thin-film heating element.

[0004] Therefore, how to solve the heat imbalance problem caused by the uneven current density in the deflection part of the thin film heating element becomes a technical problem that needs to be solved in this application.

[0005] Summary of the Invention

[0006] In view of this, the present application proposes a thin film heating element to improve the heat accumulation of the deflection part.

[0007] The present application provides a thin film heating element, wherein the thin film heating element includes a resistance layer, the resistance layer includes a main body portion for forming a resistance pattern, the main body portion includes a deflection portion and a straight portion electrically and continuously adjacent to the deflection portion and parallel to each other, and the cross-sectional resistance of the deflection portion is smaller than the cross-sectional resistance of the straight portion.

[0008] Optionally, the distance between the straight portions is 1.5 mm to 3 mm, and the width of the deflection portion is greater than the width of the straight portion.

[0009] Optionally, the thin film heating element comprises an insulating layer disposed under the resistive layer.

[0010] Optionally, the resistance layer includes a bridge arranged above the deflection portion, two ends of the bridge are respectively connected to adjacent straight portions of the deflection portion, and the conductivity of the material of the bridge is greater than the conductivity of the material of the main body.

[0011] Optionally, the jumper bridge is arranged close to the deflection center of the deflection part, so that the inner edge of the deflection part is located between the two side edges of the jumper bridge, and the outer edge of the jumper bridge is 1mm-2mm away from the outer edge of the deflection part.

[0012] Optionally, a cross section of the bridge has a step, so that the bottom of the bridge respectively engages with the main body and the insulating layer through the step.

[0013] Optionally, a covering layer is provided above the resistance layer.

[0014] Optionally, the covering layer is made of the same material as the insulating layer and can be formed into an integral structure with the insulating layer by thermal spraying the covering layer; and / or the covering layer is provided with an opening for arranging an electrical connection component.

[0015] Optionally, the thin film heating element includes a buffer layer disposed below the insulating layer and a substrate disposed below the buffer layer, wherein the buffer layer is formed of a metal material having a thermal expansion coefficient between that of the substrate and the insulating layer.

[0016] Optionally, the insulating layer is formed of aluminum oxide or zirconium oxide; and / or the main body is formed of a nickel-chromium alloy material or an iron-chromium-aluminum material.

[0017] Optionally, the resistance layer includes two resistance patterns arranged side by side, and each of the resistance patterns is provided with the deflection portion and the straight portion.

[0018] Optionally, the thin film heating element comprises a positive electrical connection component and a negative electrical connection component respectively used for the two resistance patterns; and / or, the two resistance patterns are symmetrically arranged.

[0019] The present application also provides an electric heating device, wherein the electric heating device includes the thin film heating element of the present application.

[0020] The present application also provides an electric vehicle, wherein the electric vehicle includes the electric heating device of the present application.

[0021] The present application also provides a method for preparing a thin film heating element, wherein the thin film heating element is the thin film heating element of the present application, the distance between the straight parts is 2mm-3mm, and the preparation method includes: S1. arranging a mapping tape so that the mapping tape forms a shielding pattern complementary to the pattern of the main body; S2. forming the main body by thermal spraying.

[0022] The present application also provides a method for preparing a thin film heating element, wherein the thin film heating element is the thin film heating element of the present application, the distance between the straight parts is 0.5 mm-3 mm, and the preparation method includes: S1'. forming a layered structure by thermally spraying a resistive material; S2'. removing part of the layered structure by laser to form the main body.

[0023] Optionally, the preparation method includes: S3. forming a jumper bridge by thermal spraying a material having an electrical conductivity greater than that of the main body, so that the two ends of the jumper bridge are respectively connected to the adjacent straight parts of the deflection part; and / or, S4. after forming the resistance layer, forming a covering layer by thermal spraying the same material as the insulating layer, so that the insulating layer and the covering layer form an integrated structure.

[0024] According to the technical solution of the present application, by reducing the cross-sectional resistance at the deflection portion, local heat accumulation at the deflection portion can be improved, and the current concentration can be improved.

[0025] Other features and advantages of the present application will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which constitute part of this application, are used to provide a further understanding of the application, and the exemplary embodiments of the application and their descriptions are used to explain the application. In the accompanying drawings:

[0027] FIG1 is a temperature simulation diagram showing an electric heater provided with a thin film heating element of the prior art;

[0028] FIG2 is a schematic diagram of current density distribution at a deflection portion of the thin film heating element in FIG1 ;

[0029] FIG3 is a temperature simulation diagram of FIG2 ;

[0030] FIG4 is a schematic diagram of a thermal spraying resistance pattern of a thin film heating element according to one embodiment of the present application;

[0031] 5 and 6 show the preparation process of the thin film heating element of Example 1;

[0032] FIG7 is a schematic diagram of a thin film heating element when thermally sprayed and bridged according to an embodiment of the present application;

[0033] FIG8 is a cross-sectional view taken along the BB plane in FIG7 ;

[0034] FIG9 is a cross-sectional view taken along the CC plane in FIG7 ;

[0035] FIG10 is an infrared temperature field diagram of an electric heater provided with the thin film heating element of Example 2. DETAILED DESCRIPTION

[0036] The technical solution of the present application will be described in detail below with reference to the accompanying drawings and in combination with the implementation methods.

[0037] According to one aspect of the present application, a thin film heating element is provided, wherein the thin film heating element includes a resistance layer 10, the resistance layer 10 includes a main body portion for forming a resistance pattern, the main body portion includes a deflection portion 11 and a straight portion 12 electrically and continuously adjacent to the deflection portion 11 and parallel to each other, and the cross-sectional resistance of the deflection portion 11 is smaller than the cross-sectional resistance of the straight portion 12.

[0038] Among them, the sheet resistance is a parameter that describes the resistance characteristics of a thin film resistor or a thin layer resistor material. Specifically, it refers to the resistance when the current flows perpendicular to the surface of the sheet in a thin sheet material. In the present application, the deflection portion 11 and the straight portion 12 are continuously arranged and both have a cross section perpendicular to the continuous extension direction. The cross section resistance of the deflection portion 11 is the resistance when the current flows perpendicular to the cross section of the deflection portion 11. For example, the aa section in Figure 2 is the point where the width of the deflection portion 11 is the smallest and the cross section resistance is the largest. The cross section resistance of the straight portion 12 is the resistance when the current flows perpendicular to the cross section of the straight portion 12 (i.e., the bb section in Figure 2).

[0039] According to another aspect of the present application, an electric heating device is provided, wherein the electric heating device includes the thin film heating element of the present application.

[0040] According to another aspect of the present application, an electric vehicle is provided, wherein the electric vehicle includes the electric heating device of the present application.

[0041] By reducing the cross-sectional resistance at the deflection portion, local heat accumulation at the deflection portion can be improved, and the current concentration can be improved.

[0042] In the present application, an appropriate method may be used to make the cross-sectional resistance of the deflection portion 11 smaller than the cross-sectional resistance of the straight portion 12 .

[0043] The distance between the straight portions 11 adjacent to both sides of the deflection portion 11 (ie, the dimension d of the spacer defined by the insulating material of the insulating layer 20 in FIG. 2 ) has a greater influence on heat accumulation at the deflection portion 11 .

[0044] According to an embodiment of the present application, when the distance between the straight portions 12 is 1.5 mm to 3 mm, the width of the deflection portion 11 can be greater than the width of the straight portion 12 .

[0045] By increasing the width of the deflection portion 11, the total area and heat capacity of the deflection portion 11 are increased. This, through the heat transfer properties of the metal resistor material, improves localized heat accumulation at the deflection portion 11 and improves current concentration. For example, when the width of the deflection portion 11 is 1.5 times the width of the straight portion 12, the heat capacity of the deflection portion 11 is increased by 1.5 times, making the thermal conductivity of the deflection portion 11 much higher than that of the adjacent insulating area, thereby increasing the temperature uniformity of the deflection portion 11. At the same time, the area of ​​the hotspot region (the region with a current density of 60% or more) is expanded by approximately 20%, reducing the temperature of the hotspot region while maintaining the heating power of the resistor strip.

[0046] To appropriately increase the total area and heat capacity of the deflection portion 11, the width of the deflection portion 11 can be appropriately set. Preferably, the width of the deflection portion 11 is 120%-150% of the width of the straight portion 12 to better balance the heat between the straight portion 12 and the deflection portion 11 and reduce the temperature difference between the straight portion 12 and the deflection portion 11.

[0047] According to another embodiment of the present application, when the turning radius of the deflection portion 11 is small, that is, the spacing between the straight portions 12 is further reduced, for example, the spacing is less than 1.5 mm (e.g., 0.4 mm-1.5 mm), and particularly less than 1 mm, current concentration becomes more pronounced, and a bridge 13 can be added to reduce the cross-sectional resistance of the deflection portion 11 and improve heat concentration. Of course, when the spacing d is larger, the bridge 13 can also be used to improve heat concentration.

[0048] Specifically, as shown in Figures 7 to 9, the resistive layer 10 may include a bridge 13 disposed above the deflection portion 11. The bridge 13 has two ends connected to the adjacent straight portion 12 of the deflection portion 11. The material of the bridge 13 has a greater electrical conductivity than the material of the main body. During use, at the deflection portion 11, the majority of the current flows through the bridge 13, effectively reducing the cross-sectional resistance at the deflection portion 11. This results in substantially no current flowing within the deflection portion 11, preventing excessive heat generation and thus preventing heat accumulation.

[0049] Preferably, as shown in Figure 7, the jumper bridge 13 is arranged close to the deflection center of the deflection part 11, so that the inner edge of the deflection part 11 is located between the two side edges of the jumper bridge 13, and the outer edge of the jumper bridge 13 (the right side edge of the jumper bridge 13 in Figure 7) is at a distance L1 of 1mm-2mm from the outer edge of the deflection part 11.

[0050] Furthermore, the thin-film heating element of the present application includes an insulating layer 20 disposed beneath the resistive layer 10. To facilitate the placement of the bridge 13, the bridge 13 has a stepped cross-section, such that the bottom of the bridge 13 engages the main body and the insulating layer 20, respectively, via the stepped cross-section. This ensures a stable placement of the bridge 13 and facilitates fabrication of the thin-film heating element.

[0051] In the present application, the insulating layer 20 can be made of a suitable material to provide insulation and be suitable for the operating environment of the thin film heating element. Preferably, the insulating layer 20 is formed of aluminum oxide or zirconium oxide. The resistive layer 10 can be made of a suitable conductive material, wherein the main body can be formed of a nickel-chromium alloy material or an iron-chromium-aluminum material, and the bridge 13 can be formed of a highly conductive material such as silver, copper, or aluminum.

[0052] Furthermore, a covering layer 30 is disposed above the resistor layer 10. The covering layer 30 protects the thin-film heating element and insulates it from the outside. Preferably, the covering layer 30 is made of the same material as the insulating layer 20 and can be thermally sprayed to form an integral structure with the insulating layer 20. This facilitates the placement of the covering layer 30 and allows the covering layer 30 and the insulating layer 20 to be integrated, providing better restraint for the resistor layer 10 between the covering layer 30 and the insulating layer 20.

[0053] In addition, as shown in Figures 5, 6, 8 and 9, the thin film heating element may include a buffer layer 60 arranged below the insulating layer 20 and a substrate arranged below the buffer layer 60, wherein the buffer layer 60 is formed of a metal material having a thermal expansion coefficient between that of the substrate and the insulating layer 20 (for example, the same material as the main body) to buffer the temperature change between the substrate and the insulating layer 20.

[0054] In the present application, the resistance pattern of the resistance layer 10 can be configured as needed, that is, the shape, position, and number of the resistance patterns can be configured as needed. Preferably, to fully utilize the space occupied by the resistance layer 10, the resistance layer 10 can include two resistance patterns arranged side by side, each of which is provided with the deflection portion 11 and the straight portion 12. For example, in the embodiment shown in Figure 4, the two resistance patterns can both be continuous patterns in a serpentine shape, with a deflection portion 11 at each winding turn.

[0055] Furthermore, the thin-film heating element may include a positive electrical connection component 40 and a negative electrical connection component 50, respectively, for the two resistor patterns. To facilitate the placement of the electrical connection components, the cover layer 30 may be provided with openings for accommodating the electrical connection components. The location and number of the openings may be designed based on the resistor pattern of the resistor layer 10. To further improve the space utilization of the resistor layer 10 and to optimize the placement of the openings and electrical connection components, the two resistor patterns may be symmetrically arranged.

[0056] In addition, two positive electrical connection components 40 and two corresponding negative electrical connection components 50 can be provided, one for each of the two resistor patterns. Preferably, to simplify the process and reduce the number of openings, the two resistor patterns can share a positive electrical connection component 40 or a negative electrical connection component 50. For example, in the embodiment shown in FIG4 , the resistor layer 10 is provided with two symmetrical resistor patterns, which are merged at the center of symmetry to form a parallel connection. The two resistor patterns are respectively provided with a negative electrical connection component 50 and share a positive electrical connection component 40 at the merged point, and the negative electrical connection component 50 is provided on both sides of the positive electrical connection component 40. To this end, the cover layer 30 can be provided with only three adjacent openings.

[0057] Each resistor pattern is in a winding shape, and the two resistor patterns are arranged symmetrically, which can significantly increase the heating power. Specifically, as shown in FIG4 , the resistance of each resistor pattern is R, and the total heating power is the sum of the powers of the two parallel resistor patterns, that is, 2×U 2 / R (U is the voltage between the positive and negative electrical connection components). Assuming that only one single resistance pattern is set in the same area occupied by the two resistance patterns, the resistance of the single resistance pattern is 2R, and its heat generation power is U 2 / 2R. It can be seen from this that using the resistor pattern shown in FIG4 increases the heat generation power by 4 times compared to the case where a single resistor pattern is provided.

[0058] The thin film heating element of the present application can be prepared by an appropriate method. Specifically, the present application also provides a method for preparing a thin film heating element, wherein the thin film heating element is the thin film heating element of the present application, wherein:

[0059] When the distance between the straight portions 12 is 2 mm to 3 mm, the preparation method may include: S1. arranging a mapping tape 70 so that the mapping tape 70 forms a shielding pattern complementary to the pattern of the main body; S2. forming the main body by thermal spraying;

[0060] When the distance between the straight portions 12 is 0.5 mm to 3 mm, the preparation method may include: S1'. forming a layered structure by thermally spraying a resistive material; S2'. removing a portion of the layered structure by laser to form the main body.

[0061] That is, when the distance between the straight portions 12 is large, the main body can be formed by providing a mapping tape 70. It is understood that when the distance between the straight portions 12 is 2mm-3mm, S1' and S2' can also be used to form the main body.

[0062] When constructing the main body of the resistor layer 10, a blocking pattern is formed by setting a mapping tape 70, that is, the blocking pattern blocks the part that does not need to form the main body, so that the material of the main body can be prevented from being formed at the blocking pattern during subsequent thermal spraying, so that the material can only be formed on a pattern that is complementary to the blocking pattern and forms the main body of the desired pattern. Among them, pattern complementarity means that the blocking pattern and the resistor pattern can be pieced together to form a spraying plane for thermal spraying. Specifically, taking the embodiment shown in Figure 4 as an example, a blocking pattern with a winding shape is formed by the mapping tape 70, and then two winding (winding directions are opposite and symmetrical about the midline) resistor patterns complementary to the blocking pattern are formed by thermal spraying (the two resistor patterns are symmetrical and merged at the center of symmetry to form a continuous pattern, which can be formed by thermal spraying at one time). The two resistor patterns form a total of four deflection parts 11, and the deflection parts 11 are marked with dotted lines in the figure.

[0063] Depending on the structure of the thin-film heating element, a mapping tape 70 can be placed in an appropriate position and thermally sprayed. For example, in the case of a buffer layer 60, the preparation method includes: S0. forming the buffer layer 60 on the substrate by thermal spraying, and forming the insulating layer 20 on the buffer layer 60 by thermal spraying; wherein, in step S1, the mapping tape 70 is placed on the insulating layer 20.

[0064] The patterning tape 70 is used to block the formation of the molding material during thermal spraying, and is preferably a high-temperature resistant patterning tape, such as high-temperature spray masking tape YC-628. After the main body is formed by thermal spraying, the patterning tape 70 can be removed to facilitate subsequent processing. Specifically, when a jumper bridge 13 is provided, the preparation method includes: S3. After removing the patterning tape 70, the jumper bridge 13 is formed by thermal spraying a material with a greater electrical conductivity than the main body, so that the two ends of the jumper bridge 13 are respectively connected to the adjacent straight portion 12 of the deflection portion 11; and S4. After forming the resistor layer 10, the covering layer 30 is formed by thermal spraying the same material as the insulating layer 20, so that the insulating layer 20 and the covering layer 30 form an integrated structure. If the jumper bridge 13 is not provided, only step S4 can be implemented.

[0065] When forming the jumper bridge 13 , the portion outside the area where the jumper bridge 13 is required to be provided may be covered again with the mapping tape 70 so as to form the jumper bridge 13 only.

[0066] The following describes embodiments of the preparation method and thin film heating element of the present application with reference to the accompanying drawings.

[0067] Example 1

[0068] In which, the main body includes two symmetrically arranged resistance patterns, each resistance pattern is a winding shape as shown in Figure 4, the distance between adjacent straight parts 12 is 2.5 mm, and the cross-sectional resistance is reduced by widening the width of the deflection part 11. The width at the aa section is 150% of the width of the straight part 12.

[0069] During fabrication, a nickel-chromium alloy (Ni80Cr20) is first thermally sprayed onto the aluminum substrate to form the buffer layer 60. Subsequently, alumina is thermally sprayed onto the buffer layer 60 to form the insulating layer 20. Mapping tape 70 is then placed on the insulating layer 20 to form a masking pattern, and the nickel-chromium alloy (Ni80Cr20) is thermally sprayed to form the main portion of the desired resistor pattern, as shown in Figure 5. After removing the mapping tape 70, alumina is thermally sprayed onto the cover layer 30 with openings, forming a single unit with the insulating layer 20. Finally, electrical connectors are thermally sprayed onto the openings, as shown in Figure 6.

[0070] Example 2

[0071] Among them, the main body includes two symmetrically arranged resistance patterns, each resistance pattern is a winding shape, the distance between adjacent straight parts 12 is 0.8 mm, and the cross-sectional resistance is reduced by setting a bridge 13. The width of the bridge 13 is 1-3 mm, and the distance L1 between the outer edge and the outer edge of the deflection part 11 is 1-3 mm.

[0072] During preparation, iron-chromium-aluminum (0Cr25AL5) is first thermally sprayed onto the substrate (aluminum alloy) to form the buffer layer 60. Subsequently, alumina is thermally sprayed onto the buffer layer 60 to form the insulating layer 20. Iron-chromium-aluminum (0Cr25AL5) is then thermally sprayed onto the insulating layer 20 to form a layered structure. A portion of the resistive material is then removed by laser to form the main body of the desired resistive pattern. A patterning tape 70 is placed near the deflection portion 11 and copper is thermally sprayed to form the bridge 13, as shown in FIG8 . Subsequently, the patterning tape 70 is removed, and a cover layer 30 having an opening is formed by thermally spraying alumina, so that the cover layer 30 and the insulating layer 20 form an integral structure, as shown in FIG9 . Finally, electrical connection components are thermally sprayed at the opening.

[0073] Comparative Example

[0074] The thin film heating element was manufactured by the method of Example 1, wherein the width of the deflection portion 11 and the straight portion 12 were the same.

[0075] The thin-film heating elements of Example 1 and the comparative example were used in an electric heating device of the same specifications (the electric heating device includes a heating chamber assembly defined by a chamber cover and a chamber bottom plate, and an upper cover and a lower cover disposed on the upper and lower sides of the heating chamber assembly, respectively; the thin-film heating element is disposed between the heating chamber assembly and the lower cover; the heating chamber assembly has a water inlet, a water outlet, and a flow channel connected between the water inlet and the water outlet). A comparison of operating parameters is shown in Table 1 below. The highest point of the deflection portion is located in the portion corresponding to the first region 111 and the second region 112 in Figure 1 .

[0076] Table 1

[0077] It can be seen that under the same working conditions, the maximum temperature of the deflection part of Example 1 is only 120°C-140°C, which is 20°C lower than that of Comparative Document 1, and the local heat accumulation is significantly reduced.

[0078] Figure 10 is an infrared temperature field diagram of the thin-film heating element used in an electric heating device in Example 2. Figure 1 is a temperature field simulation diagram of a thin-film heating element of the same specification in the comparative example, obtained through multi-physics field coupling simulation. As can be seen from the figure, the deflected portion of the comparative example exhibits a distinct bright area (circled in the figure), with a significant temperature difference from the straight portion and significant localized heat accumulation. The deflected portion of Example 2 is a dark area (boxed at positions B×1 to B×4 in the figure), with a lower temperature than the surrounding area, and significantly reduced localized heat accumulation.

[0079] The preferred embodiments of the present application are described in detail above. However, the present application is not limited to the specific details of the above embodiments. Within the technical concept of the present application, various simple modifications can be made to the technical solution of the present application, and these simple modifications all fall within the scope of protection of the present application.

[0080] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner unless there is any contradiction. In order to avoid unnecessary repetition, this application will not further describe various possible combinations.

[0081] In addition, the various implementation methods of the present application may be arbitrarily combined, and as long as they do not violate the concept of the present application, they should also be regarded as the contents disclosed in the present application.

Claims

1. A thin film heating element, characterized in that: The thin film heating element comprises a resistance layer (10), the resistance layer (10) comprises a main body portion for forming a resistance pattern, the main body portion comprises a deflection portion (11) and a straight portion (12) electrically and continuously adjacent to the deflection portion (11) and parallel to each other, the cross-sectional resistance of the deflection portion (11) being smaller than the cross-sectional resistance of the straight portion (12).

2. The thin film heating element according to claim 1, characterized in that The distance between the straight parts (12) is 1.5 mm to 3 mm, and the width of the deflection part (11) is greater than the width of the straight parts (12).

3. The thin film heating element according to claim 1, characterized in that The thin film heating element comprises an insulating layer (20) arranged on the lower side of the resistance layer (10).

4. The thin film heating element according to claim 3, characterized in that The resistance layer (10) includes a bridge (13) arranged above the deflection portion (11), two ends of the bridge (13) are respectively connected to the adjacent straight portion (12) of the deflection portion (11), and the electrical conductivity of the material of the bridge (13) is greater than the electrical conductivity of the material of the main body.

5. The thin film heating element according to claim 4, characterized in that The bridge (13) is arranged close to the deflection center of the deflection portion (11), so that the inner edge of the deflection portion (11) is located between the two side edges of the bridge (13), and the outer edge of the bridge (13) is 1 mm to 2 mm away from the outer edge of the deflection portion (11).

6. The thin film heating element according to claim 4, characterized in that The cross section of the bridge (13) has a step, so that the bottom of the bridge (13) respectively engages with the main body and the insulating layer (20) through the step.

7. The thin film heating element according to claim 3, characterized in that A covering layer (30) is provided above the resistance layer (10).

8. The thin film heating element according to claim 7, characterized in that The covering layer (30) is made of the same material as the insulating layer (20) and can be formed into an integral structure with the insulating layer (20) by thermal spraying the covering layer (30); and / or the covering layer (30) is provided with an opening for arranging an electrical connection component.

9. The thin film heating element according to claim 3, characterized in that The thin film heating element comprises a buffer layer (60) arranged below the insulating layer (20) and a substrate arranged below the buffer layer (60); the buffer layer (60) is formed of a metal material having a thermal expansion coefficient between that of the substrate and the insulating layer (20).

10. The thin film heating element according to claim 3, characterized in that The insulating layer (20) is formed of aluminum oxide or zirconium oxide; and / or the main body is formed of a nickel-chromium alloy material or an iron-chromium-aluminum material.

11. The thin film heating element according to any one of claims 1 to 10, characterized in that The resistance layer (10) comprises two resistance patterns arranged side by side, and each of the resistance patterns is provided with the deflection portion (11) and the straight portion (12).

12. The thin film heating element according to claim 11, characterized in that The thin film heating element comprises a positive electrical connection component (40) and a negative electrical connection component (50) respectively used for the two resistance patterns; and / or the two resistance patterns are symmetrically arranged.

13. An electric heating device, characterized in that: The electric heating device comprises the thin film heating element according to any one of claims 1 to 12.

14. An electric vehicle, characterized in that: The electric vehicle includes the electric heating device according to claim 13.

15. A method for preparing a thin film heating element, characterized in that: The thin film heating element is the thin film heating element according to claim 1, the distance between the straight parts (12) is 2 mm to 3 mm, and the preparation method comprises: S1. Setting a mapping tape (70) so that the mapping tape (70) forms a shielding pattern complementary to the pattern of the main body; S2. Forming the main body by thermal spraying.

16. A method for preparing a thin film heating element, characterized in that: The thin film heating element is the thin film heating element according to claim 1, the distance between the straight parts (12) is 0.5 mm to 3 mm, and the preparation method comprises: S1 'by thermal spraying the resistive material to form a layered structure; S2'. Removing part of the layered structure by laser to form the main body.

17. The method for preparing a thin film heating element according to claim 15 or 16, characterized in that: The preparation method comprises: S3. forming a bridge (13) by thermal spraying a material having a greater electrical conductivity than the main body, so that both ends of the bridge (13) are respectively connected to the adjacent straight portion (12) of the deflection portion (11); and / or, S4. After forming the resistance layer (10), forming a covering layer (30) by thermal spraying the same material as the insulating layer (20), so that the insulating layer (20) and the covering layer (30) form an integrated structure.

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