Heating element for user-touchable surfaces in a vehicle and method for manufacturing such a heating element

Abstract

A heating element for user-touchable surfaces in a vehicle, comprising a foamed carrier material in which at least one heating conductor is embedded, and connecting conductors that are electrically connected to the ends of the heating conductor and form an electrical supply line, characterized in that the electrical connection of each connecting conductor of the supply line to each end of the at least one heating conductor is formed and enclosed by at least one connecting sleeve, and that the connecting sleeve is arranged within the foamed carrier material. A corresponding method for manufacturing such a heating element is also described.

Description

[0001] The present invention relates to a heating element for user-touchable surfaces in a vehicle according to the preamble of claim 1 and to a method for manufacturing such a heating element according to the preamble of claim 4.

[0002] These types of heating elements are used in vehicles for seat heating, steering wheel heating, and also for trim panels. Their basic structure consists of a foamed carrier material in which at least one heating conductor is embedded, preferably in a wave-like or meandering shape. The ends of the heating conductor protrude from the carrier material and form terminals for an electrical connection or are connected to leads as an electrical supply line.

[0003] Such heating elements are typically made from two layers of foam with the heating conductor embedded between them. To fix the heating conductor according to a required installation pattern, it is first attached to a carrier material or otherwise to at least one of the two foam layers.

[0004] DE 695 33 482 T2 describes a heating device, i.e., a heating element, according to the preamble of claim 1, for a foam molded cushion in a vehicle seat. The electric heating device is constructed in the form of strips that have an electrical conductor arranged in a pattern, for example, meandering, as shown in the figures. The ends of the electrical conductor are provided with a part called an embedding body. Such an embedding body has a cavity that is open towards a mounting surface. The mounting surface is usually flat, and the embedding body is attached to this mounting surface in a mold, i.e., a casting mold, by means of adhesive or the like, or by means of double-sided adhesive tape.This prevents the conductor ends from being embedded in the cushion during the casting process and instead allows them to remain accessible for electrical connection after casting.

[0005] US 2011 / 0 290 785 A1 refers to an item described as a steering device, steering wheel, dashboard, armrest, door panel, seat frame, headliner, upholstery, mounting, or seat. The figures show upholstery incorporating a climate control system with a heating element beneath a cover. The heating element is located directly under the cover and supported by a bracket. The item, including the upholstery, is designed to be temperature-controlled.

[0006] From DE 10 2006 004 145 A1 an electric heating element with a flat support and a heating conductor is known, wherein the heating conductor is sewn onto the support and is provided with an adhesive material.

[0007] DE 10 2014 005 190 A1 relates to a method for manufacturing an interior trim part with a visible side and a flat heating element. The heating element is placed in a mold cavity of a molding tool and surrounded by a foam material.

[0008] WO 2006 / 015 588 A1 describes a component with a rigid foam body and an electrical and / or electronic functional element embedded within it, for example, a light source, a heating element (which may be in the form of a foil heater), or a sensor. The corresponding functional element is electrically connected within the rigid foam body via a flat conductor set that is at least partially embedded in the foam and terminates in a connector. The connector may be embedded at the edge of the rigid foam body in such a way that the connector contacts are accessible for electrical connection.

[0009] German patent DE 37 25 408 A1 relates to a heated seat cushion for a vehicle seat in which an electric heating element is embedded in a foam cushion. The cushion can also consist of a two-part foam body between which the heating element is inserted and / or held in place by a form-fitting manner, with the two halves being bonded together. The heating element can also be embedded in a foam.

[0010] DE101 52 719 C1 describes a method for foaming cables, in particular for foaming a steering wheel frame fitted with cables. The mold has a cavity into which the ends of the electrical cables and an attached connector, which, for example, serve to connect a steering wheel heater, are inserted, so that when the steering wheel frame is foamed, the connecting cable with the connector does not come into contact with the foam.

[0011] The present invention is based on the objective of providing a heating element suitable for user-touchable surfaces in a vehicle, as well as a method for manufacturing such a heating element which has a simple structure, particularly with regard to the connection of the heating element, and which is easy to manufacture, as well as a method for manufacturing such a heating element.

[0012] This problem is solved by a heating element according to claim 1 and a method according to claim 5. Advantageous embodiments of the heating element and the method are specified in the dependent claims.

[0013] The heating element, suitable for user-touched surfaces in a vehicle, has a foamed carrier material in which at least one heating conductor is embedded. User-touched surfaces include, among others, interior trim panels, seat surfaces, the steering wheel, gearshift knob, and selector lever. A key feature of the heating element according to the invention is that the electrical connection between the ends of the heating conductor and the electrical leads is formed and enclosed by at least one connecting sleeve. This connecting sleeve is located within the foamed carrier material and is completely encased in foam. This ensures that the connecting sleeve, which connects the heating conductor and the leads, is securely held and protected within the foam material.The foam material bonds not only to the connecting sleeve, but also to the heating conductor ends on one side and the supply lines on the other side of the connecting sleeve by adhering to them, thus contributing to strain relief.

[0014] According to the method, the at least one heating conductor is embedded in a foamed carrier material and the electrical connection of the respective connecting conductor of the supply line with the respective end of the at least one heating conductor is enclosed by at least one connecting sleeve; this connecting sleeve is arranged within the foamed carrier material.

[0015] To manufacture a heating element as described above, a mold is provided. The at least one heating conductor is inserted into the cavity of the mold according to a predetermined laying pattern, preferably wave- or meander-shaped. The heating conductor can be secured, held, and / or fixed in the cavity according to the laying pattern. The respective end of the heating conductor and the corresponding end of the connecting conductor are arranged in a heat-shrinkable connecting sleeve containing solder within the mold before the mold is closed. Subsequently, a local area of ​​the mold associated with the connecting sleeve is heated. This liquefies the solder in the connecting sleeve, thus establishing the electrical connection between the heating conductor and the connecting conductor.Here, the respective ends of the heating conductor and the corresponding ends of the supply cable are positioned either spaced apart or overlapping, such that the solder contained in the connecting sleeve is sufficient to solder the ends together. Simultaneously, the heat causes the connecting sleeve to shrink onto the connection point between the end of the stripped heating conductor and the end of the stripped supply cable, thus also sealing the connection point. It is also provided that, in addition to solder, an adhesive is applied to the inside of the connecting sleeve. This adhesive is activated and creates an additional bond between the ends of the heating conductor and the supply cable; this achieves excellent sealing against the ingress of liquids and also provides excellent strain relief, for example, against tensile stress on the supply cable.

[0016] Towards the end of the shrinking process, or after the shrinking process, the cavity is filled with a foaming material that foams up under heat or through the action of a reagent, thus filling the cavity of the mold. This encases the heating element, the connecting sleeve, and the leads connected within the sleeve. The heating element can then be removed from the mold. A two-component foam material is preferably used.

[0017] The pins in the mold create cavities or through-holes in the foamed substrate of the heating element when the element is removed from the mold. The size, type, and shape of these cavities or through-holes can be influenced by the appropriate shape and length of the pins, regardless of their function as guide elements to position and / or fix the heating element in the cavity before the injection, filling, foaming, or spraying process.

[0018] The inventive method thus produces a heating element in one operation in which the heating conductor is foamed into a foam material, in which the heating conductor is connected or soldered to the supply lines, thereby creating a firm and secure connection between the heating conductor and the supply lines, and the connection point, formed by the connecting sleeve, is embedded in the foam material.

[0019] The connecting sleeve, foamed into the carrier material, seals the connection area at least liquid-tight to ensure that no foam penetrates the connecting sleeve during the foaming process, which could adversely affect the connection point. Furthermore, this at least liquid-tight seal is intended to eliminate any tensile forces occurring between the heating wire and the supply cable through the adhesive bond within the connecting sleeve.

[0020] Preferably, solder is used to connect the heating element and the supply cable. For this purpose, the connecting sleeve should be coated with solder on its inside and should be a heat-shrinkable sleeve. Additionally, the connecting sleeve can also contain a hot-melt adhesive, preferably in the area of ​​the ends of the connecting sleeve, so that after shrinking the sleeve onto the connection point, an additional bond is achieved between the connecting sleeve and the heating element / supply cable.

[0021] A particularly preferred embodiment of the method provides that the heating conductor is inserted into the forming tool in a predetermined laying pattern, preferably wave-shaped, meandering, or in the form of a polygon. For this purpose, pins are arranged in the forming tool, which can be composed of at least two halves, around which the heating conductor is guided according to the intended laying pattern. The laying of the heating conductor, or even of several heating conductors, can be automated.

[0022] The pins therefore hold the heating conductor in a position so that, after the cavity is filled with foam, it lies in a plane that ensures it is embedded in and surrounded by the foam material on both sides. It is also provided that, if necessary, the leads leading to the connecting sleeve are also held in a predetermined position by such pins. The distance between the heating conductor and the top of the foamed support material, or the distance between the heating conductor and the bottom of the foamed support material, can vary.

[0023] To ensure that the heating conductor is held in a specific position relative to the length of the pins during installation, notches or supports / steps are provided on the pins into which the heating conductor is inserted or placed and is secured against slipping.

[0024] During the manufacture of the heating element, a temperature sensing element, preferably an NTC sensor (Negative Thermal Coefficient - thermistor), can be inserted into the cavity of the mold and encased in foam. Its connection ends can also be connected to leads via one or more corresponding connecting sleeves, as described above in relation to the heating element, with these connecting sleeves also being embedded in the foam material during the foaming of the cavity.

[0025] A closed-cell or open-cell foam can be formed in the cavity, with an open-cell foam being preferred. The foam or foam material is preferably injected into the mold without pressure in order to avoid affecting the position of the at least one heating element.

[0026] To connect the heating element to a surface to be heated, a preferred method is to insert fasteners into the mold that are associated with a surface of the heating element and bond with the foam material during the foaming process. After the heating element is removed from the mold, these fasteners are then located on one surface of the foam substrate. The fasteners can be adhesive tape or a portion of a hook-and-loop fastener, preferably a loop fastener.

[0027] Another essential feature of the heating element according to the invention is that no carrier material is required for positioning and fixing the heating conductor in the required laying pattern.

[0028] Further details and features of the invention will become apparent from the following description of exemplary embodiments with reference to the drawing. The drawing shows: Fig. 1. A top view of one half of a mold with a heating conductor and connecting sleeve laid inside it, Fig. 2 a cut along the cutting line AA in Fig. 1, however, with the base surface of an upper molded part that is not in Fig. 1 can be seen, Fig. 3 Another schematic representation of a top view of one half of a mold, comparable to Fig. 1, with an additional temperature sensing element and with an enlarged section of part of the heating element's path, Fig. 4A make a cut along the cutting line BB in Fig. 3, Fig. 4B another schematic representation according to the Fig. 4A, Fig. 5 A schematic top view of a connecting sleeve, such as that used for the heating element of the Fig. 1 and the Fig. 3 is used, Fig. 6 a flowchart illustrating the essential steps for manufacturing the heating element according to the invention, Fig. 7 schematically a vehicle steering wheel, and Fig. 8 a development in the direction of the double arrow in Fig. 7 of a part of a heating element for the steering wheel of the Fig. 8 with an enlarged section of part of the heating element's path

[0029] The heating element according to the invention is produced using a molding tool, which preferably consists of two molded parts 3, 3' that enclose a cavity or a hollow space 2.

[0030] The Fig. Figure 1 shows a top view of the inside and thus of the cavity 2 of one mold part 3 of a mold tool 1.

[0031] A plurality of pins 5 are provided on a base surface 4 of the molded part 3, their axes extending perpendicular to the base surface 4 of the molded part 3. The pins 5 are positioned according to a predetermined path of a heating conductor 6, such that the heating conductor 6, when guided around the pins, runs in a wave-like or meandering pattern. In the example shown, the heating conductor 6 runs in two meandering sections, which are connected to each other by a connecting section 7 of the heating conductor 6, while the respective terminal end 8 of the heating conductor 6 is assigned to a connecting sleeve 9.

[0032] The connecting sleeve 9 is described in more detail in Fig. Figure 5 shows a schematic representation. The connecting sleeve 9 essentially consists of a sleeve section 10 with a circular or oval cross-section, the inner surface of which is coated with solder 11 in a central part. Between this area coated with solder 11 and the respective end of the sleeve section 10, the inner surface is also coated with an adhesive 12.

[0033] How Fig. Figure 1 shows that the respective end of the heating conductor 6 is inserted into the respective connecting sleeve 9 from one side, and the end of a connecting conductor of a supply line 13 is inserted into the opposite side of the connecting sleeve 9. The respective end of the supply line 13 and the connecting end 8 of the heating conductor 6 can be positioned in the connecting sleeve 9 such that they overlap each other in the area of ​​the solder 11, their ends touch each other, or the ends are aligned with a small gap between them. The respective ends of the heating conductor 6 and the respective ends of the connecting conductors of a supply line 13 are appropriately stripped before being inserted into the respective connecting sleeve 9.

[0034] As shown by the Fig. 1 and Fig. As can be seen in Figure 2, a small heating surface 14, located locally within the molding tool, is assigned to the base surface 4 of the molded part 3. Such a heating surface 14 can also be located in the upper molded part, which is only in Fig. 2 indicated and designated with the reference numeral 3', these heating surfaces 14 can be arranged. When the lower molded part 3 and the upper molded part 3' are assembled, the connecting sleeves 9 can be locally heated with these heating surfaces 14, causing the solder 11 to melt, the adhesive 12 (if present) of the connecting sleeve 9 to be activated, and the sleeve section 10 to shrink, tightly enclosing both the terminal end 8 of the heating conductor 6 and the end of the supply line 13, thus achieving at least a liquid-tight seal of the solder joint. Simultaneously, the solder 11 establishes the electrical connection between the terminal end 8 of the heating conductor 6 and the end of the supply line 13 by soldering them together.The heating temperature applied to the connecting sleeve 9 via the heating surfaces 14 should be in the range of the melting point of the solder used, preferably a eutectic tin alloy, preferably with a small proportion of copper and / or nickel and / or silver, from 200 °C to 240 °C. A soft solder made of a lead-free tin alloy is preferred. A sleeve made of an ethylene copolymer is particularly suitable. Eutectic alloy means that this type of alloy has a clearly definable melting point. This melting point is also the lowest of all mixtures of the same constituents. Mixtures with different proportions of the alloying elements, on the other hand, have a melting or solidification range in which a solid phase is present in addition to the melt.

[0035] The mold 1 is heated to a temperature between 40 °C and 80 °C, preferably 50 °C and 60 °C, and particularly preferably 55 °C. The heating surface 14, which can be heated locally within the mold 1, is heated within a temperature range of 200 °C to 250 °C.

[0036] As shown by the Fig. 1, but also based on the Fig. As can be seen in Figure 3, which will be described below, the connecting sleeves 9 are located inside the cavity 2 of the mold 1, so that only the two supply lines 13 are led out of the mold 1 at a suitable point. The cavity 2 is filled with foam to produce the heating element.

[0037] The Fig. Figure 3 shows a construction of a heating element comparable to that which can be produced with the mold 1, which is described in Fig. 1 is shown. Additionally, the heating element, which Fig. 3, which is designated by reference numeral 15 and whose foamed support material is designated by reference numeral 16, integrates a temperature sensing element 17. The two connecting wires 18 of this temperature sensing element 17 are connected by two further connecting sleeves 9, which are connected to further supply lines 19 by means of the connecting sleeves 9 already described above, which receive the connection ends 8 of the heating conductor 6, so that these connection points are also embedded in the foamed support material 16.

[0038] The connecting sleeves 9, as used in the various embodiments, can also be combined to form a single, continuous unit. However, it must be ensured that the current paths for the respective connections are kept separate from one another. Multiple connecting sleeves 9 can also be connected to each other using additional heat shrink tubing or a suitable heat shrink sleeve.

[0039] The enlarged section of the heating element 15 in Fig. Figure 3 shows a portion of the heating conductor 6 and its associated pins 5 of a corresponding mold, illustrating that the heating conductor 6 can assume almost any shape by adjusting the number and positioning of the pins 5. After foaming and molding the heating element from the mold 1 by opening the mold parts 3 and 3' of the mold 1, cavities remain at the points where the pins 5 are inserted into the corresponding mold part 3 and / or 3'. These cavities can also serve as ventilation openings, particularly if they extend continuously through the foamed carrier material 16 from the top to the bottom.

[0040] In the Fig. 4A and Fig. 4B, which makes a cut along the cutting line BB in Fig. As shown in Figure 3, the pins 5, which extend between the bottom surfaces 4, 4' of the lower molded part 3 and the upper molded part 3', preferably approximately perpendicular thereto, form a notch 20 or bearing 23 in Fig. 4B, so that the heating conductor 6, which is guided along the pin 5, is inserted / placed therein and thus fixed in its position within the mold 1 on the pin 5. This indentation 20 should have only a shallow depth from the surface of the pin 5, so that the heating conductor 6 can be easily released from the indentations 20 of the foamed heating element 15 when the heating element 15 is removed from the mold 1.

[0041] Fig. Figure 6 again describes the process for manufacturing a heating element 15, as described above, using the described mold 1.

[0042] In a first step 101, the mold 1 is opened and, if provided, a suitable fastening element is inserted at least onto the bottom surface 4, 4' of one of the molded parts 3, 3'. This fastening element is then located on one of the top surfaces of the foamed heating element 15 and is intended to attach the heating element 15 to a surface to be heated. The fastening element can be one part of a hook-and-loop fastener, preferably a loop fastener, or an adhesive tape, which is initially covered by a protective film in the mold 1.

[0043] Then, in step 102, the respective connecting sleeve 9 is inserted into the forming tool 1 and the respective supply line 13 is inserted into the connecting sleeve 9. In step 103, the heating conductor 6 is routed by guiding it around the pins 5 of the molded part 3, 3' according to the intended routing pattern. Also in step 103, a temperature sensor (NTC) 17, if provided, is positioned and its stripped ends are placed in a corresponding connecting sleeve 9, and the additional supply line 19 for the temperature sensing element 17 is inserted into the corresponding connecting sleeve 9.

[0044] It should be noted that the individual work processes, as specified in steps 102 and 103, can be changed in order.

[0045] Advantageously, step 103, laying the heating conductor and / or the NTC, can be carried out semi- or fully automatically.

[0046] In step 104, after the mold parts 3, 3' of the molding tool 1 are closed, the heating surface 14 assigned to the connecting sleeves 9 is activated so that the connecting sleeve 9 shrinks onto the ends located in the sleeve and at the same time the wires are soldered together with the solder of the connecting sleeve 9 and the adhesive in the connecting sleeve is activated against liquid penetration, among other things.

[0047] In step 105, a foaming agent is injected into cavity 2 of the mold 1, thus surrounding the heating conductor 6 and the connecting sleeve 9 with foam. In step 106, the heating element 15 can then be removed.

[0048] It is evident that the manufacturing process of the heating element 15, as shown by the Fig. As described in section 6, the process can be fully automated, and during this process the supply lines 13 for the heating element 15 and the additional supply lines 19 for the temperature sensing element, if one is used, can be integrated into the foamed carrier material 16 of the heating element 15 simultaneously. A further advantage is that the heating conductor 6 can be integrated into the foamed carrier material 16 in any desired laying pattern without the need for a separate support to fix the heating conductor 6 to it according to a laying pattern before foaming.

[0049] The Fig. Figure 7 schematically shows a vehicle steering wheel 21 and Fig. Figure 8 shows the development in the direction of the double arrow 22 in Fig. 7 of a part of a heating element 15 for the steering wheel 21. Fig. Figure 8 additionally shows an enlarged section of part of the path of the heating element 15, which again is comparable to the representation of the Fig. Figure 3 shows a number of pins 5 around which the heating conductor 6 is routed. Very thin pins 5 are used for the heating element of a steering wheel to achieve a tighter routing pattern on a small area. These pins 5 also have notches 20 or shoulders 23 (not shown) into which the heating conductor 6 fits and is thus secured against slippage. Alternatively, the heating element 15 is connected via one or more connecting sleeve(s) 9, which are integrated into the foamed carrier material 16.

Claims

[1] Heating element for user-touchable surfaces in a vehicle comprising a foamed carrier material in which at least one heating conductor is embedded and with connecting conductors which are electrically connected to the ends of the heating conductor and form an electrical supply line, characterized by , that the electrical connection of the respective connecting conductor of the supply line (13) with the respective end of the at least one heating conductor (6) is formed and enclosed by at least one connecting sleeve (9), that the connecting sleeve (9) is arranged within the foamed carrier material and is completely foamed over, and that the connecting sleeve (9) seals the area of ​​the connection at least in a liquid-tight manner. [2] Heating element according to claim 1, characterized by , that the connecting sleeve (9) is a sleeve containing solder (11) and shrinking under heat. [3] Heating element according to claim 1 or 2, characterized by, that the connecting sleeve (9) is a sleeve containing hot melt adhesive (12). [4] Method for manufacturing a heating element for user-touchable surfaces in a vehicle, wherein at least one heating conductor is embedded in a foamed carrier material and wherein connecting conductors are electrically connected to the ends of the heating conductor, the connecting conductors forming an electrical supply line, characterized by , that the electrical connection of the respective connecting conductor of the supply line (13) with the respective end of the at least one heating conductor (6) is enclosed by at least one connecting sleeve (9), that the connecting sleeve (9) is arranged within the foamed carrier material and is completely foamed over, and that the connecting sleeve (9) seals the area of ​​the connection at least in a liquid-tight manner. [5] Method according to claim 4, characterized by, that a forming tool (1) is provided, into the cavity (2) of the forming tool (1) the at least one heating conductor (6) is inserted according to a predetermined laying pattern, and the respective end of the heating conductor (6) and the end of the connecting conductor associated with this end are arranged in a heat-shrinkable connecting sleeve (9) containing a soldering medium (11) within the forming tool (1), the forming tool (1) is closed, subsequently a local area of ​​the forming tool (1) associated with the connecting sleeve (9) is heated so that the soldering medium (11) liquefies and the electrical connection between the heating conductor (6) and the supply line (13) is established, and simultaneously the connecting sleeve (9) shrinks onto the connection point between the end of the heating conductor (6) and the end of the supply line (13),Towards the end of the shrinking process or after the shrinking process, the cavity (2) of the mold (1) is filled with a foaming material which reacts and forms a foam, so that the cavity (2) is foamed and both the heating conductor (6) and the connecting sleeve (9) are foamed over, and the heating element (15) is removed from the mold (1). [6] Method according to claim 4 or 5, characterized by , that the connecting sleeve (9) is foamed into the carrier material. [7] Method according to claim 5 or 6, characterized by , that the heating conductor (6) is guided into the forming tool (1) according to the laying pattern around pins (5). [8] Method according to claim 7, characterized by , that the pins (5) have a notch (20) or a shoulder / support (23) into which the heating conductor (6) is inserted / rests. [9] Method according to any one of claims 4 to 8, characterized by, that fasteners are placed in the mold tool (1) which are assigned to a surface of the heating element (15) and which bond with the foam material when the cavity (2) is foamed.

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