PTC heating element
By optimizing the three-dimensional matrix design and material composition of PTC heating elements, the problems of low thermal conductivity and lead addition in high-pressure applications have been solved, realizing low-temperature high-efficiency heating and environmentally friendly heating elements suitable for motor vehicle air conditioning systems.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-11
- Publication Date
- 2026-04-14
AI Technical Summary
Existing PTC heating elements have increased thickness in high-pressure applications, resulting in low thermal conductivity, concentrated heat in the center, uneven surface cooling, and the need to add lead to increase the temperature, which poses an environmental burden.
A three-dimensional PTC heating element is designed. By adjusting the relationship between resistance and temperature, reducing the thickness and optimizing the material composition, lead-free ceramic materials are used and a conductive coating is added to ensure good heating performance and environmental friendliness.
It achieves efficient heating at lower temperatures, reduces material usage and structural space, avoids lead addition, improves thermal decoupling effect, and is suitable for automotive air conditioning systems.
Smart Images
Figure CN121865448A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a PTC heating element, particularly for use in electric heaters, especially in motor vehicles. This PTC heating element preferably operates at a maximum operating voltage level of 400 V, 800 V, or higher. Background Technology
[0002] PTC heating elements are well known in the prior art. PTC heating elements are typically composed of ceramic materials, such as those pressed into cuboids or cylindrical sheets, which usually have two substantially parallel surfaces for electrical contact. The thickness of the PTC element further determines resistance and thermal decoupling. To achieve high thermal decoupling at high thicknesses, a high reference temperature is set in the prior art, where the reference temperature is the temperature at which a reference resistance is reached, which is twice the minimum resistance in the resistance-temperature curve.
[0003] These PTC heating elements are commonly used in electric vehicles, particularly in motor vehicles. Electric heating or auxiliary heating is especially important in electric vehicles or hybrid vehicles in the passenger or commercial vehicle sector because there is little or no waste heat from the internal combustion engine. In electric vehicles, electric heaters are a simple and feasible solution for heating fluids such as air, water, or coolant. Here, electric heaters are crucial not only during startup (as in conventional internal combustion engines) but also during operation to ensure the maintenance of cabin interior temperature in cold ambient temperatures. In principle, there is a possibility of constructing air-side heaters or coolant-side electric heaters, especially as high-pressure heaters (HV heaters).
[0004] PTC heating elements currently used in series in the prior art for high-voltage applications in 400V operating voltage levels have a material thickness between 2.0 mm and 3.5 mm, with those in 800V operating voltage levels having a material thickness of at least 2.8 mm to about 3.5 mm or higher. A disadvantage of these PTC heating elements is that the thermal conductivity of the ceramic material is, in principle, not high. The thermal conductivity is only about 2 W / (mK). This results in the PTC heating element not heating constantly and uniformly during operation; instead, it is hottest in the center, in the core, and significantly cooler on the surface than in the core.
[0005] Commonly known PTC heating elements have a reference temperature (Tref) of at least 175ºC, with values reaching 215ºC and higher. In PTC heating elements operating at 800 V, the reference temperature (Tref) is even at least 185ºC or higher.
[0006] Thus, there is a development of PTC heating elements with an increasingly large material thickness within the current high voltage range (at least 2.0 mm or at least 2.8 mm up to 3.5 mm and more), where it is necessary to mix lead into the ceramic material in order to shift the operating range of the PTC heating element to higher temperatures. This also results in the above-mentioned disadvantages. However, the mixing of lead is particularly mentioned, which should be reduced or avoided due to the resulting environmental load. Summary of the Invention
[0007] Therefore, the task is to provide a PTC heating element that is improved compared to the prior art, improves or avoids the disadvantages in the prior art, operates at a lower operating temperature, and reduces or avoids the lead content.
[0008] This task is solved by the features of claim 1.
[0009] The embodiment relates to a PTC heating element having a three-dimensional substrate with at least two opposing main surfaces, where the distance between the main surfaces of the substrate is the thickness D of the substrate, and where the resistance R of the PTC heating element as a function of temperature T has a minimum value as the temperature increases and has a continuously increasing resistance characteristic when the temperature further increases, where the reference temperature Tref is the temperature at which the resistance has twice the minimum value at Tmin, and where the value C of the PTC heating element is determined according to the following formula:
[0010] C = U / D,
[0011] where U = the rated voltage of the PTC heating element and D is the thickness of the PTC heating element,
[0012] where the following applies:
[0013] C > 350 V / mm.
[0014] Thus, it is possible to provide a PTC element that, despite having good heating power, can still be designed thinner and thus requires less material cost and less structural space.
[0015] Particularly advantageously, 350 V / mm < C < 600 V / mm. Thus, the reduction in thickness D is further improved.
[0016] It is also advantageously applicable that 500 V / mm < C < 1200 V / mm. Thus, the reduction in thickness D is also further improved.
[0017] It is also achieved in an advantageous embodiment that for the reference temperature Tref, the following applies:
[0018] Tref≤ 150ºC,
[0019] Especially
[0020] Tref≤ 130ºC,
[0021] Furthermore, especially
[0022] Tref≤ 120ºC,
[0023] Furthermore, especially
[0024] Tref≤ 110ºC,
[0025] Furthermore, especially
[0026] Tref≤ 100ºC.
[0027] Despite the reduced reference temperature Tref, high thermal power can be achieved in the small thickness D of the PTC element.
[0028] In an advantageous embodiment, it is also achieved that, for thickness D, the following applies:
[0029] D≤2 mm,
[0030] Especially
[0031] D≤1.5 mm,
[0032] Furthermore, especially
[0033] D≤1.0 mm,
[0034] Furthermore, especially
[0035] D≤0.8 mm.
[0036] The reduction in thickness results in significantly better decoupling of heat from the PTC element, because the thermal conductivity of the PTC element material is, in principle, very low, which has an advantage in thin structure types.
[0037] It is also suitable that a three-dimensional substrate having at least two back-to-back main faces is constructed as a cuboid or prism, particularly as a flattened cuboid or flattened prism, wherein the extension in the plane of the main face is at least five times or more greater than the thickness D. This provides a regular substrate that can be arranged in a space-saving manner within heating elements, such as those in electrically heated heat exchangers.
[0038] Also suitable is a matrix made of ceramic materials, particularly sintered barium titanate (BaTiO3) (optionally a mixture with additional additives and / or unavoidable contaminants). Ceramic materials allow for desirable resistance-temperature characteristics even at high voltages and acceptable current intensities.
[0039] Particularly preferred is that the PTC semiconductor ceramic comprises a BaTiO3-based compound as the main component, with the following chemical formula:
[0040] [Ba b Ca c Sr s Pb p R x [Ti] t A a Mn m O 3+z ,
[0041] Where R represents at least one element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb, and A represents at least one element selected from the group consisting of V, Nb, and Ta, and the variables b, c, s, p, x, t, a, m, and z are defined as follows:
[0042] b = 1 - cspx,
[0043] 0 <c+s+p<0.51,
[0044] 0.59 <b<0.999,
[0045] 0.0 <c<0.5,
[0046] 0.0 <s<0.5,
[0047] 0.0 <p<0.2,
[0048] 0.001 <x<0.01,
[0049] 1.0001 < (t + a + m) < 1.011575,
[0050] 0.9889 <t<1.000375,
[0051] 0.00010 <a<0.0012,
[0052] 0.0001 <m<0.01,
[0053] 0.0001 <z<0.01。
[0054] It is also suitable that the matrix is manufactured without the addition of lead and / or lead oxide. In this case, the variable p=0. Therefore, the environmental friendliness of the material for PTC heating elements is significantly improved.
[0055] It is also advantageous that at least one or both main surfaces of the substrate are provided with a conductive coating, especially a metallic coating, such as a silver or aluminum coating. This coating improves the current feed into the PTC heating element because it reduces the transition resistance, which is advantageous.
[0056] It is also advantageous that PTC heating elements are used in electrically operated heaters (such as heat exchangers) to circulate and heat air, such as those used in air conditioning systems for regulating the air inside motor vehicles. It may also be advantageous that other fluids, such as liquids, are heatable. Attached Figure Description
[0057] The present invention will then be described in detail based on embodiments and with reference to the accompanying drawings. Wherein:
[0058] Figure 1 A schematic diagram of an embodiment of the PTC heating element according to the present invention is shown.
[0059] Figure 2 It shows that according to Figure 1 Another view of the PTC heating element.
[0060] Figure 3 It shows that according to Figure 1 Another view of the PTC heating element, and
[0061] Figure 4 The resistance characteristics R vs. T of the PTC heating element are shown. Detailed Implementation
[0062] Figure 1 , 2 Figures 3 and 4 show a schematic diagram of a PTC heating element 1, which has a three-dimensional substrate 2 with at least two back-to-back main surfaces 3 and 4. The distance between the main surfaces 3 and 4 of the substrate 2 is the thickness D of the substrate 2.
[0063] In an advantageous example, the PTC heating element 1 is constructed into a cuboid or prism using its three-dimensional substrate 2 (having at least two back-to-back main faces 3, 4), particularly into a flattened cuboid or flattened prism, wherein the extension in the plane of the main faces 3, 4 is at least five times or more greater than the thickness D.
[0064] Preferably, the substrate 2 of the PTC heating element 1 is made of ceramic material, particularly sintered barium titanate (optionally a mixture with additional additives and / or unavoidable contaminants). The mixture can, for example, affect the positioning of the resistance characteristic curve in the graph.
[0065] Here, matrix 2 can also be manufactured, for example, without the addition of lead and / or lead oxide, which significantly improves environmental compatibility.
[0066] Furthermore, at least one main surface 3, 4, or both main surfaces 3, 4 of the substrate 2 may be provided with a conductive coating, particularly a metallic coating, such as a silver coating or an aluminum coating. This improves the electrical contact with the contact plate in the presence of the heater.
[0067] See Figure 4 The resistance R of the PTC heating element 1 (from the low temperature to the higher temperature) has the characteristic of having a minimum resistance and continuing to increase the resistance as the temperature is further increased. The reference temperature Tref is the temperature at which the resistance Rref has twice the minimum value at Tmin, that is, Rref = 2 * Rmin.
[0068] Due to the influence of the material selection and thickness of the PTC heating element 1, the resistance characteristics can be shifted horizontally and vertically in the graph, for example. Here, the operating range is the rising range of the resistance R within the bandwidth around the temperature Tref.
[0069] The value C is used as a characterization parameter for PTC heating element 1, and this value is determined according to the following formula:
[0070] C=U / D,
[0071] Where U is the rated voltage of PTC heating element 1, and D is the thickness of PTC heating element 1.
[0072] Among them, the applicable ones are:
[0073] C > 350 V / mm.
[0074] Alternative locations are also advantageous, and the following are applicable:
[0075] 350 V / mm < C < 600 V / mm.
[0076] Furthermore, the following are also applicable:
[0077] 500 V / mm < C < 1200 V / mm.
[0078] Therefore, the value of C is scaled using the reciprocal of the rated voltage U and the thickness D.
[0079] The applicable reference temperature Tref for PTC heating element 1 is:
[0080] Tref≤ 150 ºC,
[0081] Especially
[0082] Tref≤ 130 ºC,
[0083] In addition, especially
[0084] Tref≤ 120 ºC,
[0085] In addition, especially
[0086] Tref≤ 110 ºC,
[0087] In addition, especially
[0088] Tref≤100 ºC.
[0089] Therefore, even with a small thickness D, excellent thermal decoupling with the PTC heating element 1 is achieved because, given the poor thermal conductivity, heat only needs to travel a short distance from the typically hotter, thinner center of the PTC heating element 1 to its edges. Thus, even a low reference temperature Tref is sufficient to generate high thermal power.
[0090] According to an embodiment of the present invention, the following is provided for application to thickness D:
[0091] D ≤ 2 mm,
[0092] Especially
[0093] D ≤ 1.5 mm,
[0094] Furthermore, especially
[0095] D ≤1.0 mm,
[0096] Furthermore, especially
[0097] D ≤0.8 mm.
[0098] Thickness D is the distance between the two principal faces 3 and 4. It is particularly advantageous that the three-dimensional base 2, having at least two back-to-back principal faces 3 and 4, is constructed as a cuboid or prism, especially as a flattened cuboid or flattened prism, wherein the extension of the base 2 in the plane of the principal faces 3 and 4 is at least five times or more greater than the thickness D. Preferably, at least one direction in the plane of the principal faces 3 and 4 is considered.
[0099] The PTC heating element 1 is configured such that the substrate 2 is made of a ceramic material, particularly of sintered barium titanate (optionally a mixture with additional additives and / or unavoidable contaminants). Preferably and optionally, the substrate 2 is manufactured without the addition of lead and / or lead oxide.
[0100] Figure 2 and Figure 3 As shown, in an advantageous embodiment, at least one main surface 3, 4 or both main surfaces 3, 4 of the substrate 2 are provided with a conductive coating, particularly a metallic coating, such as a silver coating or an aluminum coating. Alternatively, the coating may be composed of other materials or omitted.
[0101] In preferred applications, a single PTC heating element 1 or multiple PTC heating elements 1 can be used in an electrically operated heater (such as a heat exchanger) to circulate and heat air or other fluids. For example, such a heater can be arranged in an air conditioning system used to regulate the airflow in the interior space of a motor vehicle.
[0102] List of reference numerals
[0103] 1PTC heating element
[0104] 2 matrix
[0105] 3 main sides
[0106] 4 main sides
Claims
1. A PTC heating element (1), wherein the PTC heating element has a three-dimensional substrate (2) with at least two back-to-back main surfaces (3, 4), wherein, The distance between the substrate (2) and the main surfaces (3, 4) is the thickness D of the substrate (2), and wherein the resistance R of the PTC heating element (1) has a minimum value as a function of temperature T as the temperature increases, and has a resistance characteristic that continues to increase as the temperature further increases, wherein the reference temperature Tref is the temperature at which the resistance has twice the minimum value at Tmin, and wherein the value C of the PTC heating element (1) is determined according to the following formula: C=U / D, Where U = the rated voltage of the PTC heating element (1), and D is the thickness of the PTC heating element (1). The applicable ones are: C>350 V / mm.
2. The PTC heating element (1) according to claim 1, characterized in that, Applicable voltage is 350 V / mm. <C<600 V / mm。 3. The PTC heating element (1) according to claim 1 or 2, characterized in that, Applicable voltage is 500 V / mm. <C<1200 V / mm。 4. The PTC heating element (1) according to any one of the preceding claims, characterized in that, The reference temperature Tref is applicable to, Tref≤150 ºC, Especially Tref≤130 ºC, Furthermore, especially Tref≤120 ºC, Furthermore, especially Tref≤110 ºC, Furthermore, especially Tref≤100ºC.
5. The PTC heating element (1) according to any one of the preceding claims, characterized in that, For thickness D, the applicable thickness is... D≤2 mm, Especially D≤1.5 mm, Furthermore, especially D≤1.0 mm, Furthermore, especially D≤0.8 mm.
6. The PTC heating element (1) according to any one of the preceding claims, characterized in that, A three-dimensional substrate (2) having at least two back-to-back main faces (3, 4) is constructed as a cuboid or prism, particularly as a flat cuboid or flat prism, wherein the extension in the plane of the main faces (3, 4) is at least five times or more greater than the thickness D.
7. The PTC heating element (1) according to any one of the preceding claims, characterized in that, The matrix (2) is made of ceramic material, particularly sintered barium titanate, which may optionally have a mixture of additional additives and / or unavoidable contaminants.
8. The PTC heating element (1) according to claim 7, characterized in that, The matrix (2) is manufactured without the addition of lead and / or lead oxide.
9. The PTC heating element (1) according to any one of the preceding claims, characterized in that, At least one main surface (3, 4) or both main surfaces (3, 4) of the substrate (2) are provided with a conductive coating, especially a metal coating, such as a silver coating or an aluminum coating.
10. The PTC heating element (1) according to any one of the preceding claims, characterized in that, The PTC heating element is used in an electrically operated heater to circulate and heat air, and the heater is arranged in an air conditioning system for conditioning the interior space of a motor vehicle.