Woven flexible heating fabric and method for producing such a heating fabric

Abstract

Woven flexible heating fabric (10) with warp threads (22) and weft threads (20), and an electrical circuit which is designed to perform a heating function when energized, wherein at least one electrically conductive thread is contained in an element of the warp threads and the weft threads, wherein at least one surface of the heating fabric (10) is printed with an electrically conductive conductor track structure (40) such that the at least one electrically conductive thread is in contact with the conductor track structure (40) such that the electrically conductive thread together with the conductor track structure (40) at least partially forms the electrical circuit, characterized in that the electrically conductive conductor track structure (40) has at least two semicircular conductor tracks (41, 42) of different potential, which are arranged relative to one another such that the two semicircular conductor tracks (41, 42) form a circle.

Description

[0001] The invention relates to a woven, flexible heating fabric with warp and weft threads. Furthermore, the invention relates to a method for producing such a woven, flexible heating fabric.

[0002] Textile fabrics are broadly understood to be two-dimensional textile products, regardless of their manufacturing technology. Examples of textile fabrics include (woven) fabrics, knitted or knitted fabrics, felts, nets, braids, multi-textiles, stitch-knitted fabrics, etc.

[0003] Textile fabrics in the form of woven, flexible heating fabrics or flat heating elements are known from the prior art, which are used as electric heating mats or electric flat heating elements, for example in connection with seat heating systems, preferably in motor vehicles.

[0004] Such conventional electrical flat heating elements are often provided as knitted fabrics, embroidered fabrics, leno fabrics, or foils. These conventional flat heating elements are usually only available as pre-cut pieces in various predefined sizes or are only offered as fully heatable parts. Accordingly, the heating form or design and the heating positions on the heating element cannot be freely selected or fully adapted to individual requirements, so that, in principle, only a specific, structurally predetermined heat distribution can be achieved across the surface of the flat heating element.

[0005] According to the state of the art, heating electrodes for generating heat energy (thermal energy) in flat heating elements are widely used in the form of wire strands. However, these are relatively stiff and, due to their dimensions, cause partial elevations or thick spots in a flat heating element such as a heating fabric, especially when folded. An example of such a known flat heating element is shown in Fig. 1, which shows a schematic representation of a conventional textile and flat heating element 10' with meandering heating cables 40' in the form of wire strands. These wire strands often have a diameter of more than 4 mm. As a result, winding the flat heating element is also difficult due to their high rigidity, which means that only small quantities of such flat heating elements can be wound. Furthermore, a thick spot or raised area caused by such thick wire strands is particularly inconvenient in a flat heating element when the heating element is used in connection with, for example, clothing, a vehicle seat, a wall surface, etc.

[0006] Further developments according to the state of the art have been made in that electric heating mats and flexible flat heating elements are produced using an embroidery technology in order to achieve a certain flexibility of textile, electric flat heating elements.

[0007] Furthermore, flexible heating foils with a PTC effect are also known from the state of the art. These use so-called PTC thermistors (PTC = "positive temperature coefficient"). Due to the characteristics of the PTC thermistors, a heating foil equipped with such PTC thermistors only heats up to a specific, specifically adjustable maximum temperature, for which no additional control technology is required. PTC thermistors are therefore often referred to as self-regulating heating elements or heating resistance elements in conjunction with flat heating foils, mats, fabrics, etc.

[0008] State-of-the-art heating fabrics, heating foils, or flat heating elements, unless they use PTC thermistors, require appropriate control devices to prevent overheating and the associated damage during heating. Furthermore, such state-of-the-art flat heating elements are extremely inflexible or rigid when using the wire strands described above, as they usually exceed a heating element thickness of 4 mm.

[0009] In many cases, freely adjustable heat distribution across the surface of the flat heating element is not possible due to the predetermined arrangement of the heating resistance elements within the flat heating element.

[0010] Furthermore, some of the heating fabrics or flat heating elements known from the prior art cannot be used in the low-voltage range and have disadvantages regarding their heating efficiency. Particularly if their resistance value is very high, they cannot be operated in the low-voltage range, as the desired temperature of the heating fabric could otherwise not be achieved. In this case, a voltage source delivering a voltage of 48 volts or more would be necessary.

[0011] Further prior art is formed by the documents DE 11 2012 004 179 T5, DE 10 2014 005 041 A1, DE 90 07 519 U1, DE 10 2018 123 906 A1, US 2003 / 0 207 107 A1 and US 2003 / 0 208 851 A1.

[0012] DE 11 2012 004 179 T5 discloses a woven flexible heating fabric according to the preamble of claim 1.

[0013] The invention is therefore based on the object of further developing the flat heating elements, heating fabrics, and the like known from the prior art, as well as methods for producing such flat heating elements, in such a way that the aforementioned disadvantages of the prior art can be at least partially overcome. This object is achieved by the features of the independent claims. Advantageous embodiments and further developments of the invention are set forth in the dependent claims.

[0014] In particular, it is an object of the invention to further develop the flat heating elements, heating fabrics and the like known from the prior art as well as methods for producing such flat heating elements in such a way that a heat distribution on a surface of the heating fabric can be specified in an extremely adaptable manner.

[0015] Preferably, a further objective of the invention is to further develop the flat heating elements, heating fabrics and methods for producing such heating elements known from the prior art in such a way that the heating fabrics are extremely deformable and do not require any overheating control / regulation.

[0016] The woven flexible heating fabric according to the invention comprises warp threads and weft threads ora woven fabric body at least partially forming the heating fabric, comprising warp threads and weft threads, and an electrical circuit configured to perform a heating function when energized, wherein at least one electrically conductive thread is contained in an element made up of the warp threads and the weft threads, and wherein at least one surface of the heating fabric or of the fabric body is printed with an electrically conductive conductor track structure such that the at least one electrically conductive thread is in contact with the conductor track structure such that the electrically conductive thread, together with the conductor track structure, at least partially forms the electrical circuit, wherein the electrically conductive conductor track structure has at least two semicircular conductor tracks of different potential, which are arranged relative to one another such that the two semicircular conductor tracks form a circle.

[0017] Using the printed conductor pattern, a heating design or heating shape can be selected extremely freely to specify the heat distribution across the surface of the heating fabric. This also enables, among other things, the production of a heating fabric with heating elements up to a width of 270 cm, for example, while the thickness of the heating fabric can be kept extremely low, i.e., less than 0.5 mm, or 0.45 mm with a printed conductor pattern including the heating fabric or fabric body. This makes it possible to create a very flexible or pliable heating fabric, which, due to its good deformability and adaptability to other shapes, is particularly well suited for seat heating, etc.

[0018] As will be described in more detail below, the heating fabric is particularly preferably designed such that it is manufactured with PTC yarns running in the weft direction as conductive threads, while the threads running in the warp direction are non-conductive or electrically insulating, and the printing of the conductor track structure in a specific arrangement, such as that of two interlocking combs or two circular arcs forming a circle, is carried out using screen printing technology or digital printing. In special embodiments of the invention, all of the PTC yarns running in the weft direction can be formed as conductive threads, or only some of them. In a further embodiment of the invention, both the threads running in the weft direction and the threads running in the warp direction can be formed as electrically conductive threads, in which case the conductor track structure can be applied to different surfaces of the heating fabric orof the fabric body to provide a conductor track structure on a respective surface whose potential differs from the potential of the conductor track structure provided on the other surface.

[0019] The woven, flexible heating fabric according to the invention can advantageously be designed such that the at least one electrically conductive thread is contained in one element consisting of the warp threads or the weft threads, and at least one electrically non-conductive thread is contained in the other element consisting of the warp threads and the weft threads. For example, to simplify the manufacture of the heating fabric, only the threads running in the weft direction are at least partially formed as conductive threads, while the threads running in the warp direction are exclusively electrically non-conductive, or vice versa. For example, some of the weft threads can be electrically conductive, another part of the weft threads can be electrically non-conductive, and all of the warp threads can be electrically non-conductive.

[0020] Furthermore, the woven flexible heating fabric according to the invention can be particularly advantageously designed such that a section of the electrically conductive thread forms a heating element that is in contact with the respective conductor tracks of the conductor track structure. Different potentials are preferably applied to the respective conductor tracks.

[0021] In this context, the woven flexible heating fabric according to the invention can be realized in such a way that the portion of the electrically conductive thread forming the heating element is formed by a PTC thermistor.

[0022] For example, the section of the electrically conductive thread forming the heating element is in contact with a first conductor track and a second conductor track, to which different potentials can be applied. Thus, no control device for overheating protection is required for the heating fabric, as PTC material is used, whose resistance increases the higher its temperature.

[0023] Furthermore, the woven flexible heating fabric according to the invention can be designed such that the PTC thermistor has a non-linear resistance curve as a function of the temperature.

[0024] Furthermore, the woven flexible heating fabric according to the invention can be realized such that a plurality of electrically conductive threads are contained in the one element of the warp threads and the weft threads, wherein the electrically conductive conductor pattern printed on the surface of the heating fabric is in contact with the plurality of electrically conductive threads such that a plurality of sections of the electrically conductive threads form heating elements which are connected to respective conductor patterns of the conductor pattern such that the heating elements are connected in parallel.

[0025] Furthermore, the woven flexible heating fabric according to the invention can be implemented in such a way that the electrically conductive conductor track structure is applied to the surface of the heating fabric by means of screen printing processes, transfer printing processes or digital printing processes, in particular laser printing processes.

[0026] Furthermore, in a non-claimed embodiment, the woven flexible heating fabric can be designed such that the electrically conductive conductor track structure is in the form of two interlocking combs to which different potentials can be applied.

[0027] Furthermore, the woven flexible heating fabric according to the invention can be designed such that the warp threads of the heating fabric have a thread thickness of 167 dtex and / or the heating fabric having the warp threads has a thread density of 19±10 warp threads / cm.

[0028] Furthermore, the woven flexible heating fabric according to the invention can be designed such that the heating fabric is formed with a weft density of 19±10 weft threads / cm, wherein the weft threads are formed as monofilament PTC thermistors, preferably with a diameter of 0.3 mm±0.2 mm or a weft thread thickness of 700±400 dtex.

[0029] A comparative example woven flexible heating fabric comprises warp threads and weft threads, wherein at least one electrically conductive thread is included in one element of the interwoven warp threads and the interwoven weft threads, while at least one electrically non-conductive thread is included in the other element of the interwoven warp threads and the interwoven weft threads.

[0030] The method according to the invention is intended for producing a woven flexible heating fabric comprising warp threads and weft threads and an electrical circuit configured to perform a heating function when energized, wherein at least one electrically conductive thread is contained in an element comprising the warp threads and the weft threads, the method comprising the following steps: Weaving the warp threads and weft threads so that the heating fabric or a fabric body of the heating fabric is at least partially formed, Printing at least one surface of the heating fabric or fabric body with an electrically conductive conductor track structure such that the at least one electrically conductive thread is in contact with the conductor track structure such that the electrically conductive thread together with the conductor track structure at least partially forms the electrical circuit, wherein the electrically conductive conductor track structure has at least two semicircular conductor tracks of different potential, which are arranged relative to one another such that the two semicircular conductor tracks form a circle.

[0031] As a result, the properties and advantages explained in connection with the woven flexible heating fabric according to the invention are achieved in the same or similar manner. Therefore, to avoid repetition, reference is made to the above explanations in connection with the woven flexible heating fabric according to the invention. The same applies mutatis mutandis to the preferred embodiment of the method according to the invention described below.

[0032] The method according to the invention can preferably be further developed so that it comprises the following steps Weaving the heating fabric, wherein the heating fabric has weft threads formed at least partially as PTC thermistors, Printing the conductor track structure onto the surface of the heating fabric in such a way that the weft threads are in contact with opposite conductor tracks of the conductor track structure, to which a different potential can be applied.

[0033] In particular, the manufacturing process is as follows: The heating fabric is manufactured in rolls, which can be wound up in several hundred meters.

[0034] After weaving the heated fabric, the fabric is passed over a stenter. This shrinks the heated fabric, reducing the resistance of the weft threads in the form of PTC yarns.

[0035] For example, the flat heating element is cut out of the roll of woven material using a laser based on CAD data, with precise contours and fray-proof properties, even in multiple layers if necessary.

[0036] The printed circuit structure is then printed using a printing process in a corresponding heating form (for example, the shape of two interlocking combs, hereinafter also referred to as a “comb structure”, or in the shape of a circle formed by two circular arc sections), whereby the printed circuit structure is applied in the form of the said comb structure using a conductive ink or a conductive paste (e.g. a silver conductive paste) using screen printing technology, transfer printing or digital printing.

[0037] The heating form and position in the fabric can be freely selected due to the printing process, so that the heat distribution over the surface of the heating fabric can be determined individually or to meet the corresponding requirements.

[0038] Afterwards, contacting or attaching a connection for a power supply to the conductor track structure can be carried out according to the respective requirements.

[0039] In other words, the method according to the invention preferably comprises the following process steps: weaving the heating fabric with conductive PTC weft threads, followed by heat-setting, followed by cutting the heating fabric, followed by printing the cut heating fabric with the conductor track structure (e.g., in a comb structure), lamination if necessary, followed by contacting the conductor track structure and leading out connections for the power supply. Contacting to a power supply (e.g., a 6V, 12V, or 24V power source) can be achieved, for example, by soldering, crimping, gluing, etc.

[0040] Using the method according to the invention, the resistance value and the heating power can be influenced by varying the fabric density in the weft, selecting different PTC materials (PTC material with different base resistances and different temperature / resistance curves) and / or by varying the printed electrode spacings or conductor track spacings of the conductor track structure.

[0041] Using the method according to the invention, very large-area heating elements such as heating fabrics can be manufactured in a very short time with high precision and reproducibility, and this is possible in large quantities. For example, groups of heating fabrics with different resistance values ​​can be produced, which can also be created with a wide variety of heating elements according to specific requirements, so that the desired heating output can be achieved with the heating fabrics produced in this way. The heating fabric can be manufactured, for example, in a width of up to 270 cm.

[0042] Since the conductor structure of the heating fabric according to the invention does not use any relatively stiff contact strands, the heating fabric remains flexible and can therefore, for example, be easily deformed or follow corresponding contours. This is particularly advantageous for use in connection with seat heating, clothing, wall heating, mold heating, heated furniture, heating solutions for medical technology, etc.

[0043] Another comparative example method is for producing a woven flexible heating fabric with warp and weft threads and comprises the following step: Weaving the warp threads and weft threads such that at least one electrically conductive thread is included in one element of the interwoven warp threads and the interwoven weft threads, while at least one electrically non-conductive thread is included in the other element of the interwoven warp threads and the interwoven weft threads. Preferred embodiments of the invention are explained below by way of example with reference to the figures.

[0044] They show: Fig. 1 a schematic representation of a conventional textile heating fabric with meandering heating cables; Fig. 2 is a schematic representation of parts of a heating fabric serving as a comparative example; Fig. 3 a schematic representation of a part of the heating fabric of Fig. 2; Fig. 4 a schematic representation of a highly simplified circuit diagram of the heating fabric of Fig. 2; Fig. 5 a schematic representation of a more detailed circuit diagram of the heating fabric of Fig. 2, Fig. 6 a schematic representation of a part of a heating fabric according to the invention according to an embodiment, and Fig. 7 a schematic representation of a part of the heating fabric according to the invention according to a further embodiment.

[0045] Fig. Figure 2 shows a schematic representation of parts of a textile fabric in the form of a flat woven heating fabric 10, which serves as a comparison example and has essentially two surfaces. In the case of Fig. 2 is the flat woven heating fabric 10 or a woven flexible fabric body 60 with warp threads 22 and weft threads 20 (only schematically in Fig. 5). To clarify the weft direction (S) and warp direction (K), the Fig. 2-7 a corresponding coordinate system is shown. In this embodiment, at least some of the weft threads 20 of the heating fabric 10 running in the weft direction S are electrically conductive; furthermore, some of the weft threads running in the weft direction S are electrically non-conductive, but in the Fig. 2-7 are omitted for clarity. The distribution and arrangement of electrically conductive and non-conductive weft threads 20 is determined according to the requirements for heat distribution in the flexible heating fabric 10.

[0046] In this case, the weft threads 20 are formed by a PTC resistor, PTC resistor, or PTC thermistor (PTC thermistor = "Positive Temperature Coefficient Thermistor"), which is a temperature-dependent resistor with a positive temperature coefficient as its essential property and conducts electrical current better at low temperatures than at high temperatures. The electrically conductive weft threads 20 can be formed by a PTC thermistor, which exhibits a non-linear resistance curve depending on temperature.

[0047] On the other hand, the warp threads 22 running in warp direction K, as in Fig. 5 schematically indicated, formed by an ordinary and non-conductive yarn material.

[0048] Preferably, the heating fabric 10 or the fabric body 60 of the heating fabric 10 is formed by warp threads with a thread thickness of preferably 167 dtex, wherein the warp threads have a thread density of 19±10 warp threads / cm.

[0049] The heating fabric 10 is preferably formed with a weft density of 19±10 weft threads / cm, wherein the monofilament weft threads 20 are present as PTC thermistors, preferably with a diameter of 0.3 mm±0.2 mm or a weft thread thickness of 700±400 dtex.

[0050] One of the two surfaces of the heating fabric 10 is provided by means of a printing process with an electrically conductive conductor track structure 40, for example made of a silver conductive paste or a corresponding conductive varnish, as also in Fig. 2. This conductor track structure 40 is shown in Fig. 3 is shown again separately in a schematic representation as a part of the heating fabric 10.

[0051] As in particular Fig. As can be seen from Figure 3, the electrical conductor structure 40 basically has two conductor tracks 401 and 402, to which different potentials can be applied. The shape of the electrically conductive conductor structure 40, or rather the two conductor tracks 401 and 402, is that of two interlocking combs, which is also referred to above as a "comb structure."

[0052] In particular, each conductor track 401 and 402 has a respective main conductor track 43 and 44, to which different potentials can be applied via a schematically illustrated terminal 50 and from which several secondary conductor tracks 41, 42 extend substantially at right angles. The respective secondary conductor tracks 41, 42 of the respective conductor tracks 401 and 402 are arranged alternately opposite one another, parallel in the warp direction K, and at a predetermined distance in the weft direction S, as shown in Fig. 3 can be seen, resulting in the shape of two interlocking combs.

[0053] In Fig. 2, the conductor track structure 40 is thus printed onto the surface of the heating fabric 10 in such a way that the electrically conductive weft threads 20 are in contact with the conductor track structure 40, so that a plurality of heating elements or heating resistance elements 25 are formed on the surface of the heating fabric 10. This means that the heating elements 25 are formed in respective sections of the electrically conductive weft threads 20 that lie between respective secondary conductor tracks 41, 42 of different potential. Accordingly, the conductor track structure 40, together with the heating elements 25, forms an electrical circuit that can perform a heating function when energized.

[0054] Fig. 4 shows a schematic representation of a highly simplified circuit diagram of the heating fabric 10 according to Fig. 2, which shows the basic electrical conductor structure 40, which is achieved by printing the surface of the heating fabric with the conductor structure 40 and the resulting contacting of the electrically conductive weft threads 20 (PTC thermistors). Fig. 5 a schematic representation of a more detailed circuit diagram of the heating fabric of Fig. 2.

[0055] As from Fig. 4, the printing of the surface of the heating fabric 10 or the fabric body 60 of the heating fabric 10, which has the electrically conductive weft threads 20 designed as PTC thermistors, with the conductor track structure 40 results in principle in the illustrated conductor track structure arrangement, in which the heating elements 25 are connected as PTC thermistors between the respective secondary conductor tracks 41, 42, which - as also from Fig. 4, can be connected to different potentials via a DC voltage source 26. The heating elements 25, as PTC thermistors, are thus connected in parallel in the circuit.

[0056] In Fig. 5 is the conductor structure of Fig. 4 is extended in an equivalent manner by further heating element groups 30 with respective heating elements 25 as well as further secondary conductor tracks 41, 42 of the conductor track structure 40, so that in this case too a parallel connection of the respective heating element groups 30 results. In Fig. In the case shown in Figure 5, instead of the direct current voltage source, only corresponding connections 50 are shown, which are led out of the heating fabric and to which different potentials can be applied.

[0057] The process for producing the woven flexible heating fabric 10 is as follows: First, the heating fabric 10 or the heating fabric body 60 of the heating fabric 10 is woven, wherein - as mentioned above - PTC thermistors are formed by at least some weft threads 20, while the warp threads 22 are formed by conventional non-conductive textile.

[0058] Subsequently, a surface (top or bottom side) of the heating fabric 10 or the heating fabric body 60 of the heating fabric 10 is printed with the above-described electrically conductive conductor track structure 40 by means of a printing process such that the electrically conductive weft threads 20 are contacted with the conductor track structure 40, whereby corresponding heating elements 25, formed by PTC thermistors, are formed on the surface of the heating fabric 10.

[0059] The conductor track structure 40 is then connected to the corresponding terminals 50, which are led out of the heating fabric 10 and to which a different potential can be applied using a voltage source.

[0060] Fig. Figure 6 shows a schematic representation of a portion of a woven flexible heating fabric 10 according to an embodiment of the invention, similar to that shown in Fig. 3, wherein identical or similar elements are designated by identical or similar reference numerals.

[0061] In Fig. 6, the electrically conductive conductor structure 40 differs from that of Fig. 3 in that it has two semicircular secondary conductor tracks 41, 42 of different potential, which are arranged in such a way that these two semicircular secondary conductor tracks 41, 42 form a respective circle, in the illustrated case thus a total of two circles. This results in a Fig. 3 different heat distribution in the heating fabric 10 is achieved. In Fig. In the case shown in Figure 6, different potentials can be applied within the respective circuits and between the respective circuits. This leads to a different resistance distribution of the PTC thermistors, in that their resistance value is higher between the circuits than within the respective circuits. Thus, a different heat distribution is realized in surface areas within the circuits compared to a surface area between the circuits.

[0062] Fig. Figure 7 shows a further schematic representation of a part of the heating fabric according to the invention according to a further embodiment, similar to that in Fig. 6, with the difference that the same potential can be applied between the respective circuits, for example, by swapping the secondary conductors 41, 42 of the lower circuit. Accordingly, almost no heat is generated in the surface area between the respective secondary conductors 41, while heat is generated within the respective circuits. This results in a Fig. 6 different heat distributions achieved.

[0063] The features of the invention disclosed in the above description, in the drawings and in the claims may be essential for the realization of the invention both individually and in any combination.

Claims

[1] Woven flexible heating fabric (10) with warp threads (22) and weft threads (20), as well as an electrical circuit which is designed to perform a heating function when energised, wherein at least one electrically conductive thread is contained in an element of the warp threads and the weft threads, wherein at least one surface of the heating fabric (10) is printed with an electrically conductive conductor track structure (40) such that the at least one electrically conductive thread is in contact with the conductor track structure (40) such that the electrically conductive thread together with the conductor track structure (40) at least partially forms the electrical circuit, characterized by that the electrically conductive conductor track structure (40) has at least two semicircular conductor tracks (41, 42) of different potential, which are arranged relative to one another in such a way that the two semicircular conductor tracks (41, 42) form a circle. [2] Woven flexible heating fabric (10) according to claim 1, wherein the at least one electrically conductive thread is contained in one of the warp threads or the weft threads, and at least one electrically non-conductive thread is contained in the other of the warp threads and the weft threads [3] Woven flexible heating fabric (10) according to claim 1 or 2, wherein a portion of the electrically conductive thread forms a heating element (25) which is in contact with respective conductive tracks (41, 42) of the conductive track structure (40). [4] Woven flexible heating fabric (10) according to claim 3, wherein the portion of the electrically conductive thread forming the heating element (25) is formed by a PTC thermistor. [5] Woven flexible heating fabric (10) according to claim 4, wherein the PTC thermistor has a non-linear resistance curve as a function of temperature. [6] Woven flexible heating fabric (10) according to one of claims 1 to 5, wherein a plurality of electrically conductive threads are included in the one element of the warp threads and the weft threads, wherein the electrically conductive conductor pattern (40) printed on the surface of the heating fabric is in contact with the plurality of electrically conductive threads such that a plurality of sections of the electrically conductive threads form heating elements which are connected to respective conductor patterns (41, 42) of the conductor pattern (40) such that the heating elements (25) are connected in parallel. [7] Woven flexible heating fabric (10) according to one of claims 1 to 6, wherein the electrically conductive conductor track structure (40) is applied to the surface of the heating fabric (10) by means of screen printing methods, transfer printing methods or digital printing methods, in particular laser printing methods. [8] Woven flexible heating fabric (10) according to one of the preceding claims, wherein the warp threads (22) of the heating fabric have a thread count of 167 dtex and / or the heating fabric comprising the warp threads (22) has a thread count of 19±10 warp threads / cm. [9] Woven flexible heating fabric (10) according to one of the preceding claims, wherein the heating fabric is formed with a weft density of 19±10 weft threads / cm, wherein the weft threads (20) are formed as monofilament PTC thermistors, preferably with a diameter of 0.3mm±0.2mm or a weft thread thickness of 700±400 dtex. [10] Method for producing a woven flexible heating fabric (10) with warp threads (22) and weft threads (20), and an electrical circuit which is designed to perform a heating function when energised, wherein at least one electrically conductive thread is contained in an element of the warp threads and the weft threads, the method comprising the following steps: Weaving the warp threads (22) and weft threads (20) so that the heating fabric (10) is at least partially formed, Printing at least one surface of the heating fabric (10) with an electrically conductive conductor track structure (40) in such a way that the at least one electrically conductive thread is in contact with the conductor track structure (40) in such a way that the electrically conductive thread together with the conductor track structure at least partially forms the electrical circuit, wherein the electrically conductive conductor track structure (40) has at least two semicircular conductor tracks (41, 42) of different potential, which are arranged relative to one another in such a way that the two semicircular conductor tracks (41, 42) form a circle.

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