DE102018123906A1 - Heating element with a tissue electrode - Google Patents

Abstract

The invention relates to a heating element (1) with a first tissue electrode (12) and a second tissue electrode (14) and a heating resistance element (16) arranged between the first tissue electrode (12) and the second tissue electrode (14).

Description

Technical field

The present invention relates to a heating element with a tissue electrode and a heating system, for example for use in the heating of elements in motor vehicles, for example for use in a seat heater or a heated steering wheel.

State of the art

Heating elements are an important component in components today to temper them or to protect them from frost. Heating elements can also be used to heat the environment. For certain applications, heating elements are required that have efficient heat transfer and can also be installed as simply and flexibly as possible in the elements of the respective devices to be heated.

For example, heating elements with heating resistance elements are used, the heating resistance elements being contacted by means of sheet metal electrodes. However, such connections do not show satisfactory positive connections, do not have the desired flexibility and are not optimal in terms of weight.

The DE 10 2008 034 748 A1 describes a surface element with a layer sequence of a cold-conducting heating layer, a contacting layer and an adhesive layer, the contacting layer being a flat, broken contacting element. A surface element can be heated in a self-regulating manner by the contacting layer. The contacting element, ie the electrode, is introduced in a surface element.

Presentation of the invention

Starting from the known prior art, it is an object to provide an efficient heating element.

The object is achieved by a heating element with the features of claims 1 and 11. Advantageous further developments result from the subclaims.

Accordingly, a heating element is proposed, comprising a first tissue electrode and a second tissue electrode and a heating resistance element arranged between the first tissue electrode and the second tissue electrode.

By designing the heating element with a first and a second tissue electrode, between which a heating resistance element is arranged, a particularly efficient and flexible heating element can be provided that can be used in different areas of application.

For example, the heating element can be used to heat vehicle seats or steering wheels. The heating element can also be used to heat a drive battery of a motor vehicle.

According to a preferred embodiment, the first tissue electrode is arranged on an underside of the heating resistor element and / or the second tissue electrode is arranged on an upper side of the heating resistor element. The top can also be referred to as the first surface and the bottom as the second surface of the, in particular cuboid, heating element. The first surface and the second surface preferably represent the larger surface areas of the, preferably cuboid, heating element. The first and the second surface are parallel to each other. The heating element is thus arranged between the first and the second tissue electrode in a layer-like structure in order to heat the heating element from the first surface and the second surface.

The first tissue electrode and / or the second tissue electrode can be embedded in the heating resistance element. In one example, the first and second tissue electrodes are each embedded in the surface of the top and bottom of the heating resistor element.

According to a preferred embodiment, the first tissue electrode and / or the second tissue electrode each have at least one conductive thread and at least one non-conductive thread arranged orthogonally thereto, preferably a plurality of conductive threads arranged parallel to one another and a plurality of non-parallel ones arranged conductive threads are provided.

The distances between the plurality of threads arranged parallel to one another can be variable. In this way, the tissue electrodes can be adjusted for stiffness and heat generation, i.e. the smaller the distances between the threads, the stiffer the tissue electrode and the higher the current input per area into the heating resistor element.

Conversely, the larger the distance between the threads, the more flexible the electrode becomes are. The flexibility or rigidity created in this way can have an impact on the rigidity of the entire heating element.

The fabric electrode can also be designed as a knitted fabric, knitted fabric, fleece, scrim or similar variant of a fabric made of threads. In the following and so far, the term tissue electrode is used to represent all variants of electrodes made of flat structures made of threads.

Furthermore, a surface of the heating resistor element to be heated is flowed through more or more homogeneously by current due to a dense covering of conductive threads, so that stronger or more homogeneous heating can be achieved. In contrast, when the conductive threads are occupied further apart, less homogeneous heating is achieved.

The distances between the conductive threads and the distances between the non-conductive threads can preferably be set independently of one another. For example, the conductive threads can be arranged at short distances from one another in such a way that the heating power is increased, but the non-conductive threads are arranged at wider distances from one another in order to nevertheless provide a certain flexibility of the tissue electrode.

By connecting the tissue electrodes to a voltage source, at least the conductive threads are energized, so that a current flow through the heating resistor element located in between is achieved and heat is thus generated.

A direct current is preferably applied to the tissue electrodes. However, it is also possible to use alternating current, e.g. from the alternator of a vehicle.

The arrangement of the heating resistance element between the tissue electrodes results in a current flow through the heating resistance element, so that a current flow through the volume of the heating resistance element is achieved and this can be used particularly effectively.

In one example, the conductive threads are made of a conductive material, in particular from the group of conductive metals such as aluminum, copper, stainless steel etc.

In one example, the non-conductive filaments are made of polyethylene or a basic polyethylene material.

The conductive threads can form the tissue structure of the respective tissue electrodes as warp threads and the non-conductive threads as weft threads. The assignment to the warp threads and the weft threads can also be reversed.

The tissue electrodes can be oriented in relation to one another such that the conductive threads of the first tissue electrode and the conductive threads of the second tissue electrode are arranged orthogonally to one another.

According to an alternative alignment of the tissue electrodes to one another, the conductive threads of the first tissue electrode and the conductive threads of the second tissue electrode are arranged essentially parallel to one another.

In one embodiment, in which each tissue electrode has only one polarity - for example the first tissue electrode is positive and the second tissue electrode is polarized negatively - in one example the non-conductive thread can be replaced by a conductive thread. As a result, current can be supplied to at least two conductive threads which are arranged orthogonally to one another, and thus the homogeneity of the area-wide current input into the heating resistor element can be improved.

In an alternative exemplary embodiment, the conductive threads of the first and / or second tissue electrode are alternately connected to the electrical positive pole and the electrical negative pole. In this embodiment, the conductive threads on the top and bottom are alternately connected to the electrical positive pole and to the electrical negative pole.

In a proposed heating resistor element, a polymer composition with a positive temperature coefficient is used. This composition corresponds to a PTC substance composition based on polymer and is also referred to as PPTC (polymeric positive temperature coefficient) composition. A heating resistor element based on a PPTC composition usually has a non-linear resistance curve. In other words, the electrical resistance of this material usually does not increase linearly with increasing temperature.

As current flows through the heating resistance element, heat is generated therein, which leads to an increase in the temperature and the resistance of the heating resistance element. As the electrical resistance increases, the current of the current flowing through the heating resistor element simultaneously drops with a constant voltage. Since the induced heat in the Heating resistor element is proportional to the square of the current, the induced heat correspondingly decreases with increasing temperature of the heating resistor element.

The use of a PPTC composition thus has the effect that, as the temperature of the material increases, a heat input induced by the current flow is throttled into the heating resistor element. Since the electrical resistance of this material increases nonlinearly with increasing temperature, a heating resistor element constructed from a PPTC composition enables rapid heating to a predetermined nominal temperature and, once the nominal temperature has been reached, rapid or abrupt throttling of the induced heat in order to prevent the heating resistor element from overheating .

The PPTC composition of the heating resistor element can be provided in such a way that the heating resistor element is transferred in a high-resistance state when the predetermined nominal temperature is reached. As a result, the heat input induced by the heating resistor element can be greatly reduced, so that when the nominal temperature is reached, the heating resistor element is no longer heated by the current applied.

The PPTC composition of the heating resistor element has at least one polymer. The polymer preferably forms a non-conductive polymer matrix in the PPTC composition, in which electrically conductive particles are embedded or dispersed. In this way, an electrical conductivity of the PPTC composition can be ensured, in particular below the nominal temperature. In addition, thermally conductive particles can be embedded or dispersed in the polymer matrix, which improve a thermal conductivity of the polymer composition.

More specifically, the PPTC composition can have, for example, at least one polymer from the group comprising: polyethylene, polyethylene oxide, polybutadiene, polyethylene acrylates, ethylene-acrylic acid-ethyl ether copolymers, ethylene-acrylic acid copolymers, polyesters, polyamides, polyethers, polycaprolactam, fluorinated ethylene-propylene Copolymers, chlorinated polyethylene, sulfochlorinated polyethylene, ethyl vinyl acetate copolymers, polypropylene, polystyrene, styrene-acrylonitrile copolymers, polyvinyl chloride, polycarbonates, polyacetals, polyalkylene oxides, polyphenylene oxide, polysulfones and fluoroplastics. For example, two or more polymers from the above group can be included in the PPTC composition. The type of polymer and the composition ratios can be varied.

The electrically conductive particles included in the PPTC composition can have at least one type of particles from the group comprising: carbon black, silver powder, gold powder, carbon powder, graphite powder, copper powder, carbon fibers, nickel powder and silver-plated fine particles. For example, the electrically conductive particles included in the PPTC composition can comprise several types of particles from the group mentioned above. The type of electrically conductive particles and / or their particle size can be varied. For example, the electrically conductive particles can have a particle size between 1 μm and 200 μm.

The thermally conductive particles included in the PPTC composition can have at least one type of particles from the group comprising: silicon carbide, silicon nitride, beryllium oxide, selenium and aluminum oxide. For example, the thermally conductive particles included in the PPTC composition can comprise several types of particles from the group mentioned above. The type of thermally conductive particles and / or their particle size can be varied. For example, the thermally conductive particles can have a particle size between 1 μm and 200 μm.

The use of the PPTC composition for the heating resistor element provides a high degree of design freedom for the heating element. This can be attributed in particular to the fact that a component consisting of the PPTC composition can be produced comparatively easily and in any form.

In particular, the heating resistor element can also be formed from the PPTC composition as a film, so that a particularly thin and also flexible heating element can be provided.

According to a further aspect, a heating element is proposed, comprising at least two conductive threads and in each case at least one thread made of a polymer PTC material, the two conductive threads being connected to the thread made of the polymer PTC material such that the thread can be heated from the polymer PTC material by electrical contacting of the two conductive threads.

According to one embodiment, the two conductive threads are connected to a voltage source in such a way that the two conductive threads are alternately connected to an electrical positive pole and an electrical negative pole.

According to a further embodiment, the two conductive threads are arranged orthogonally to the at least one thread made of polymer PTC (PPTC) material.

In one example, the PPTC material is formed into a thin thread or wire or filament that can be processed by a textile processing process such as e.g. Weaving, knitting, crocheting, knitting or felting.

In another example, the cross section of the PPTC thread is round, oval or rectangular.

According to a further aspect, a heating system is proposed, comprising an element to be heated, a voltage source and a heating element. The heating element is arranged in the element to be heated and connected to the voltage source. The first tissue electrode is connected to a first pole of the voltage source and the second tissue electrode is connected to a second pole of the voltage source.

According to a further embodiment, the element to be heated is a seat surface or a steering wheel or a window in a vehicle.

According to a further aspect, a heating system is proposed, comprising an element to be heated, a voltage source, a heating element, the heating element being arranged in the element to be heated and the at least two conductive threads being connected to the voltage source by electrical contacting.

According to a further embodiment, the element to be heated is preferably a textile, in particular a piece of clothing.

In other words, an active heating element made of PPTC material is preferably proposed. The electrode is designed as a woven electrode, whereby electrically conductive and non-conductive threads can be interwoven and can be positively connected to the PPTC material.

The electrically conductive thread can either be energized with both poles (plus / minus) alternately from thread to thread. In the case of a multi-layer structure, a first tissue electrode can be provided on the top of a PPTC heating resistor element and a second tissue electrode on the underside thereof, i.e. The conductive threads on the top of the PPTC material form, for example, the positive pole and the conductive threads of the tissue electrode on the underside of the PPTC material form the negative pole.

This makes it possible to achieve improved electrical connections between the tissue electrode and the PPTC material. Furthermore, the configuration of the electrode as a tissue electrode saves weight compared to the configuration as a sheet metal electrode. The arrangement of the tissue electrode on the top and bottom of the PTC materials also ensures simple and efficient production of the heating elements.

Furthermore, it is also provided to connect a thread made of PPTC material directly to an electrically conductive thread. This enables 3D mechanically flexible heating elements to be implemented. In addition, established manufacturing processes (e.g. weaving processes) can be used to connect the thread made of PPTC material to produce heating elements.

The design of the active heating element as a thread made of PPTC materials is also suitable for combination with other materials during weaving (e.g. for the production of functional clothing).

Figure list

• 1 eine perspektivische Ansicht eines Heizelements gemäß einem Ausführungsbeispiel;
• 2 eine schematische Seitenansicht des Heizelements gemäß einem Ausführungsbeispiel;
• 3 eine perspektivische Ansicht einer Gewebeelektrode des Heizelements gemäß einem weiteren Ausführungsbeispiel;
• 4 einen schematische Ansicht eines Heizelements gemäß einem weiteren Aspekt;
• 5 ein Schaltkreis mit dem Heizelement gemäß einem weiteren Ausführungsbeispiel;
• 6 eine schematische Darstellung des Heizelements in einem zu beheizenden Element;
• 7 ein Verfahren zur Herstellung eines Heizelements gemäß einem Ausführungsbeispiel; und
• 8 ein Verfahren zur Herstellung eines weiteren Heizelements gemäß einem Ausführungsbeispiel.

Preferred further embodiments of the invention are explained in more detail by the following description of the figures. Show:

• 1 a perspective view of a heating element according to an embodiment;
• 2nd is a schematic side view of the heating element according to an embodiment;
• 3rd a perspective view of a fabric electrode of the heating element according to another embodiment;
• 4th a schematic view of a heating element according to a further aspect;
• 5 a circuit with the heating element according to another embodiment;
• 6 a schematic representation of the heating element in an element to be heated;
• 7 a method for producing a heating element according to an embodiment; and
• 8th a method for producing a further heating element according to an embodiment.

Detailed description of preferred embodiments

Preferred exemplary embodiments are described below with reference to the figures. Identical, similar or equivalent elements in the different figures are provided with identical reference numerals, and a repeated description of these elements is partially omitted in order to avoid redundancies.

In 1 schematically shows an enlarged and perspective view of a section of a heating element according to an embodiment. The heating element 1 has a first tissue electrode 12th and a second tissue electrode 14 and a heating resistance element disposed between the first and second tissue electrodes 16 on.

In one embodiment, the first tissue electrode 12th on a bottom 16a of the heating resistor element 16 and the second tissue electrode 14 on a top 16b of the heating resistor element 16 arranged.

In a further exemplary embodiment, the first tissue electrode 12th and / or the second tissue electrode 14 in the heating resistor element 16 at least partially embedded.

In the in the 1 shown example has the first tissue electrode 12th and / or the second tissue electrode 14 at least one conductive thread each 13 and in each case at least one non-conductive thread arranged orthogonally thereto 15 on. A plurality of conductive threads arranged parallel to one another are preferred 13 and a plurality of non-conductive threads arranged in parallel to each other 15 intended.

This structure means that there is no direct electrical connection between the conductive threads 13 through the non-conductive threads 15 instead of. If the conductive threads 13 do not cut or touch each other, each conductive thread lies accordingly 13 essentially electrically insulated from the other conductive threads 13 in front.

2nd shows a schematic side view of the heating element 1 according to an embodiment. In the example shown here is the first tissue electrode 12th at the top 16a of the heating resistor element 16 arranged and is connected to an electrical positive pole 18th connected. The second tissue electrode 14 is at the bottom 16b of the heating resistor element 16 arranged and is at the electrical negative pole 20th connected. The polarity can also be reversed.

This enables a current to flow between the first and the second tissue electrode 12th , 14 through the heating resistor element 16 can be achieved, whereby the heating resistor element is heated accordingly.

The first, upper tissue electrode 12th on the top is a tissue electrode attached to the electrical positive pole 18th is connected (schematic + symbol). The second, lower tissue electrode 14 , represents a tissue electrode 14 represents the electrical negative pole 18th is connected (schematic symbol).

In such a configuration, the non-conductive threads 15 can also be replaced by electrically conductive threads. As a result, current can be supplied to at least two conductive threads which are arranged orthogonally to one another, and thus the areas through which current flows in the heating resistor element 16 be increased, which can improve the efficiency and homogeneity of heat generation. Furthermore, this also improves the heat distribution within the heating element.

Another advantage of this embodiment is that the material of the heating resistor element can be better utilized, since the potential difference between the top (electrical positive pole) and underside (electrical negative pole) flows through the heating resistor element over the entire volume and not just along the surfaces.

3rd shows the first tissue electrode in a further example 12th . Here is the conductive thread 13 alternately to the electrical positive pole 18th and the negative electrical pole 20th connected. In this embodiment, the current flows through the electrically conductive threads on the top and on the bottom. This configuration can be used when the heating resistor element 16 specifically to flow through the surface of the top and bottom of the current.

The heating element 16 can be or consist of a polymer composition with a positive temperature coefficient.

In the proposed heating resistance element 16 the polymer composition with a positive temperature coefficient is used. This composition corresponds to a PTC substance composition based on polymer and is also referred to as PPTC (polymeric positive temperature coefficient) composition. A heating resistor element 16 based a PPTC composition exhibits a non-linear resistance curve. In other words, the electrical resistance of this material does not increase linearly with increasing temperature.

By current through the heating resistor element 16 flows, heat is generated therein, which leads to an increase in the temperature and the resistance of the heating resistor element 16 leads. As the electrical resistance increases, the current at the same time decreases with a constant voltage 16 flowing current. Because the induced heat in the heating resistor element 16 is proportional to the square of the current, the induced heat decreases correspondingly with increasing temperature of the heating resistor element 16 .

The PPTC composition of the heater element 16 has at least one polymer. The polymer preferably forms a non-conductive polymer matrix in the PPTC composition, in which electrically conductive particles are embedded or dispersed. In this way, an electrical conductivity of the PPTC composition can be ensured, in particular below the nominal temperature. In addition, thermally conductive particles can be embedded or dispersed in the polymer matrix, which improve a thermal conductivity of the polymer composition.

More specifically, the PPTC composition can have, for example, at least one polymer from the group comprising: polyethylene, polyethylene oxide, polybutadiene, polyethylene acrylates, ethylene-acrylic acid-ethyl ether copolymers, ethylene-acrylic acid copolymers, polyesters, polyamides, polyethers, polycaprolactam, fluorinated ethylene-propylene Copolymers, chlorinated polyethylene, sulfochlorinated polyethylene, ethyl vinyl acetate copolymers, polypropylene, polystyrene, styrene-acrylonitrile copolymers, polyvinyl chloride, polycarbonates, polyacetals, polyalkylene oxides, polyphenylene oxide, polysulfones and fluoroplastics. For example, two or more polymers from the above group can be included in the PPTC composition. The type of polymer and the composition ratios can be varied.

The electrically conductive particles included in the PPTC composition can have at least one type of particles from the group comprising: carbon black, silver powder, gold powder, carbon powder, graphite powder, copper powder, carbon fibers, nickel powder and silver-plated fine particles. For example, the electrically conductive particles included in the PPTC composition can comprise several types of particles from the group mentioned above. The type of electrically conductive particles and / or their particle size can be varied. For example, the electrically conductive particles can have a particle size between 1 μm and 200 μm.

The thermally conductive particles included in the PPTC composition can have at least one type of particles from the group comprising: silicon carbide, silicon nitride, beryllium oxide, selenium and aluminum oxide. For example, the thermally conductive particles included in the PPTC composition can comprise several types of particles from the group mentioned above. The type of thermally conductive particles and / or their particle size can be varied. For example, the thermally conductive particles can have a particle size between 1 μm and 200 μm.

By using the PPTC composition for the heating resistor element 16 a high degree of design freedom is provided for the heating element. This can be attributed in particular to the fact that a component consisting of the PPTC composition can be produced comparatively easily and in any form.

The first upper and / or second lower tissue electrode 12th , 14 can also be wholly or partly in the material of the heating resistor element 16 be embedded.

4th shows a schematic view of an alternative embodiment of a heating element. The heating element has at least two conductive threads 13 and at least one thread arranged for each 15a from a heating resistor element, for example a polymeric PTC material, the two conductive threads 12th so with the thread 15a are connected from polymer-PTC material that the thread from polymer-PTC material can be heated by electrical contacting of the two conductive threads.

The two leading threads 13 are connected to a voltage source in such a way that they alternately connect to an electrical positive pole 18th and an electrical negative pole 20th are connected. A multilayer structure with a first fabric electrode on the top and a second fabric electrode on the bottom is not necessary here due to the direct connection of the thread made of polymeric PTC material. This allows mechanically flexible heating elements to be implemented. Furthermore, established manufacturing processes (e.g. weaving processes) can be used to connect the thread made of PPTC materials. The design of the active heating element as a thread made of PPTC material is also very suitable for combination with other materials when weaving (eg for the production of functional clothing).

5 shows an example of the connection of the heating element 1 to a voltage source 34 . The top is an example 16a of the heating element 1 to the electrical negative pole 20th and the bottom 16b of the heating element 1 to the electrical positive pole 18th the voltage source 34 connected.

6 shows a schematic representation of the heating element 1 in a heating system 30th . The heating system has an element to be heated 32 , a voltage source 34 and a heating element 1 on. The heating element 1 is in the element to be heated 32 arranged and connected to the voltage source 34 connected. The voltage source can be in the element to be heated 32 be arranged or outside the element to be heated 32 be arranged.

• In einem ersten Schritt 102 werden eine erste Gewebeelektrode und eine zweiten Gewebeelektrode durch jeweils mindestens einen leitfähigen Faden und einem nichtleitfähigen Faden zusammengesetzt. In einem zweiten 104 Schritt wird die ersten Gewebeelektrode an eine Oberseite eines Heizwiderstandelements und die zweiten Gewebeelektrode an eine Unterseite des Heizwiderstandselements oder umgekehrt verbunden. In einem weiteren Schritt 106 wird die erste Gewebeelektrode an der Oberseite des Heizwiderstandelements an den elektrischen Pluspol und die zweite Gewebeelektrode an der Unterseite des Heizwiderstandelements an den elektrischen Minuspol angeschlossen

7 shows a process 100 for making a heating element 1 . The process has the following steps:

• In a first step 102 a first tissue electrode and a second tissue electrode are put together by at least one conductive thread and one non-conductive thread. In a second 104 Step, the first tissue electrode is connected to an upper side of a heating resistance element and the second tissue electrode to an underside of the heating resistance element or vice versa. In a further step 106 the first tissue electrode on the top of the heating resistance element is connected to the electrical positive pole and the second tissue electrode on the underside of the heating resistance element is connected to the electrical negative pole

In a preferred embodiment, the heating resistor element is made of a PPTC material.

8th shows a process 100 for making a heating element 2nd . The method has the step 202 in which at least two conductive threads are assembled with a thread made of PPTC material, the at least two conductive threads being assembled with the thread made of PPTC material by weaving, knitting, crocheting, knitting or felting.

As far as applicable, all individual features that are shown in the exemplary embodiments can be combined and / or exchanged with one another without leaving the scope of the invention.

Reference list

1, 2

Heating element

12th

first tissue electrode

13

conductive thread

14

second tissue electrode

15

non-conductive thread

15a

Thread made of PPTC material

16

Heating resistor element

16a

Top of the heating element

16b

Bottom of the heating resistor element

18th

electrical positive pole

20th

electrical negative pole

30, 40

Heating system

32

element to be heated

34

Voltage source

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102008034748 A1 [0004]

Claims (16)

Heating element (1) with a first tissue electrode (12), a second tissue electrode (14) and a heating resistance element (16) arranged between the first tissue electrode (12) and the second tissue electrode (14). Heating element (1) after Claim 1 , characterized in that the first tissue electrode (12) on an underside (16a) of the heating resistor element (16) and / or the second tissue electrode (14) on an upper side (16b) of the heating resistor element (16) are arranged. Heating element (1) after Claim 1 or 2nd , characterized in that the first tissue electrode (12) and / or the second tissue electrode (14) are embedded in the heating resistor element (16). Heating element (1) according to one of the preceding claims, characterized in that the first tissue electrode (12) and / or the second tissue electrode (14) each have at least one conductive thread (13) and in each case at least one non-conductive thread (15) arranged orthogonally thereto ), wherein a plurality of conductive threads arranged parallel to one another and a plurality of non-conductive threads arranged parallel to one another are preferably provided. Heating element (1) after Claim 4 , characterized in that the conductive threads as warp threads and the non-conductive threads as weft threads form the fabric structure of the respective fabric electrodes (12, 14). Heating element (1) after Claim 4 or 5 , characterized in that the conductive thread of the first tissue electrode (12) and the conductive thread of the second tissue electrode (14) are arranged orthogonally to one another. Heating element (1) after Claim 4 or 5 , characterized in that the conductive thread of the first tissue electrode (12) and the conductive thread of the second tissue electrode (14) are arranged parallel to one another. Heating element (1) according to one of the preceding claims, characterized in that the first tissue electrode (12) and the second tissue electrode (14) are connected to a voltage source such that they have opposite polarities. Heating element (1) according to one of the preceding claims, characterized in that the first tissue electrode (12) is arranged on the upper side (16b) of the heating resistance element (16) and is connected to an electrical positive pole (18) and the second tissue electrode (14) is connected to an electrical negative pole (20) on the underside (16a) of the heating resistor element (16). Heating element (1) according to one of the preceding claims, characterized in that the heating resistance element (16) comprises a PPTC material. Heating element (2), comprising at least two conductive threads (13) and in each case at least one thread (15a) made of a PPTC material, the two conductive threads (13) being electrically contacted with the thread (15a) made of the PPTC material. Heating element (2) after Claim 11 , characterized in that the two conductive threads (13) are connected to a voltage source such that the two conductive threads (13) are alternately connected to an electrical positive pole (18) and an electrical negative pole (20). Heating element (2) after Claim 11 or 12th , characterized in that the two conductive threads are arranged orthogonally to the at least one thread made of PPTC material. Heating system (30) comprising an element (32) to be heated, a voltage source (34) and a heating element (1) according to one of the Claims 1 - 10th , wherein the heating element (1) is arranged in the element (32) to be heated and the first tissue electrode (12) is connected to a first pole of the voltage source (34) and the second tissue electrode (14) is connected to a second pole of the voltage source (34 ) connected. Heating system (30) after Claim 14 , characterized in that the element to be heated (32) is a seat or a steering wheel or a disc. Heating system (40) comprising an element (32) to be heated, a voltage source (34) and a heating element (2) according to one of the Claims 11 - 13 The heating element (2) is arranged in the element (32) to be heated and the at least two conductive threads (13) are connected to the voltage source (34).

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