Method for manufacturing an electric heating device and electric heating device

Abstract

Method for manufacturing an electric heating device (10) with an electric heating element (12'') which is arranged embedded inside a multi-part tubular metal sheath (11) in an electrically insulating material (16,17), wherein the electric heating device (10) is located inside the multi-part tubular metal sheath (11) - has at least one end an unheated area (U) in which, when the electric heating device (10) is operated, the electric current also flows through at least one connecting wire (13), and / or at least one connecting sleeve (14) and / or at least one connecting bolt (15) which is in electrical contact with the electric heating element (12'') and furthermore - has a heated area (B) in which, when the electric heating device (10) is operated, the electric current flows only through a section of the electric heating element (12'') running in the heated area (B), where in the procedure - in a first process step in a first part (11.1) of the multi-part tubular metal jacket the heated area (B) is produced and compacted, -in a second process step carried out after the first process step, at least one section of the unheated area (U) is produced in a second part (11.2) of the multi-part tubular metal jacket, and - the first part (11.1) and the second part (11.2) of the multi-part tubular metal sheath (11) are connected together, characterized in that the electric heating element (12'') is coiled such that an end section of the electric heating element (12.1'') has a smaller coil diameter than a section of the electric heating element (12'') which is located in the heated area (B) of the finished electric heating device (10), wherein the electric heating element (12'') is coiled such that the end section (12.1'') of the electric heating element (12''), which has a smaller helix diameter than the section of the electric heating element (12'') that is located in the heated area of ​​the finished electric heating device (10), has a helix axis (W2) that is offset relative to the helix axis (W1) of the section of the electric heating element (12'') that is located in the heated area of ​​the finished electric heating device (10).

Description

[0001] Electric tubular heating elements are a type of electric heating device that has been known for many years. They are characterized by the fact that the electric heating element is arranged inside a tubular metal sheath, and is electrically insulated in the radial direction from the tubular metal sheath by embedding it in an electrically insulating but thermally conductive material, in many cases magnesium oxide, boron nitride or Al2O3, in the form of a powder or granules, or also as a molded body, especially made of one of these materials, in order to prevent an unwanted short circuit.

[0002] In many applications of electric tubular heaters, it is desirable for the heater to have an unheated area at at least one end. To provide this, it is known to connect the heater to the electric heating element using a connecting wire and / or connecting bolt that has a larger cross-section than the heating element. For example, in the case of a connecting wire, this bolt can be inserted into the coil interior of the heating element, or in the case of a connecting bolt, it can accommodate an end section of the heating element.

[0003] In addition to the larger cross-section of the connecting bolt, the heat generated in the area of ​​the connecting bolt is reduced in many cases by choosing a material with a lower specific resistance than that of the material from which the heating element is made; for example, by using copper or nickel as the material for the connecting bolt.

[0004] However, this well-known approach presents several problems, particularly in applications where available installation space is limited. First, the connecting wire and / or bolt obstructs the filling of the electrically insulating material. Second, the resulting unheated section of the electrical heating element is significantly more difficult to compact because only a small proportion of the electrically insulating material remains in the cross-section of this section. Consequently, a largely solid structure consisting of the connecting wire and / or bolt and a section of the electrical heating element must be compacted. This places enormous stress on the compaction machines and results in a short service life for the compaction equipment and its tools.

[0005] Further methods for manufacturing electric heating devices and electric heating devices manufactured by such methods are known in particular from US 5,864,941 A, DE 20 2017 100 786 U1, US 4,346,287 A and US 2019 / 0200417 A1. In particular, US 5,864,941 A discloses a method with the features of the preamble of claim 1 and an electric heating device that can be manufactured by this method.

[0006] The object of the invention is therefore to provide a method for manufacturing an electric heating device and an electric heating device that can be manufactured using such a method, in which filling with the electrically insulating material is easier and / or compacting the unheated area is possible with reduced load on the compaction machines.

[0007] This problem is solved by a method having the features of claim 1 and an electrical heating device having the features of claim 12. Advantageous further developments of the invention are the subject of the respective dependent claims.

[0008] The method according to the invention serves to manufacture an electric heating device with an electric heating element which is embedded in an electrically insulating material inside a multi-part tubular metal jacket, i.e., is arranged in an electrically insulated manner (e.g. by embedding in an electrically insulating powder or granules or by electrically insulating molded parts), wherein the electric heating device has an unheated area at at least one end within the multi-part tubular metal jacket, in which, when the electric heating device is operated, the electric current also flows through at least one connecting wire and / or at least one connecting sleeve and / or at least one connecting bolt which is in electrical contact with the electric heating element.

[0009] The unheated area can preferably include an unheated transition zone in which, during operation of the electric heating device, the electric current flows simultaneously through the at least one connecting wire and / or the at least one connecting sleeve and / or the at least one connecting bolt, as well as through a section of the electric heating element located in the unheated transition zone, which section of the electric heating element is in electrical contact with the connecting wire or connecting bolt. In other words, the unheated transition zone contains a section of the electric heating element and at least one section of a connecting wire, a connecting sleeve, or a connecting bolt, these sections being connected in parallel rather than in series.

[0010] Furthermore, the electric heating device to be produced by the method has a heated area within the multi-part tubular metal jacket in which, when the electric heating device is operated, the electric current flows only through a section of the electric heating element running in the heated area.

[0011] It should be noted at this point that this does not preclude the use of the multi-part tubular metal sheath as a return conductor (because the aforementioned condition for the heated area only needs to be within the multi-part tubular metal sheath), nor does it preclude both connections being on the same side in the electric heating device.

[0012] The fact that the tubular metal casing is multi-part means in particular that it is composed of several parts - preferably several pipe sections - which may well be firmly connected to each other, for example by pressing or welding.

[0013] Furthermore, the term "unheated area" is to be interpreted in such a way that heat can still be generated in this area - which is unavoidable and therefore necessarily the case in most real-world embodiments - but to a significantly lesser extent than in the heated area, in which the electric heating device is intended to generate heat to fulfill its intended function.

[0014] According to the inventive method, in a first process step the heated area is produced and compacted in a first part of the multi-part tubular metal jacket, in a second process step carried out after the first process step at least a section of the unheated area is produced in a second part of the multi-part tubular metal jacket, and the first part and the second part of the multi-part tubular metal jacket are joined together.

[0015] The last-mentioned step can also be carried out before, during, or simultaneously with the compaction of the second part of the tubular metal casing, if such compaction is planned. It therefore does not necessarily have to take place only after the second process step.

[0016] By dividing the manufacturing process into two stages, with the first stage producing the "finished" heated section as an intermediate product and the second stage then joining the unheated section with a previously separate part of the tubular metal jacket, the compression processes for the individual parts of the electric heating device can be optimized. In particular, the compression of the heated section can be carried out using a piercing process.

[0017] At the same time, this measure significantly simplifies the filling process with the electrically insulating material, because the obstacle caused by the unheated area is eliminated.

[0018] The finished heated area present after the first process step can in particular correspond to an electric heating device with a tubular metal jacket, in which connections of the electric heating device protruding from the end face of the tubular metal jacket are formed by a section of the electric heating element with a connecting wire and / or a connecting sleeve arranged thereon, and thus form the unheated transition section in the fully completed electric heating device according to the invention.

[0019] In a preferred embodiment of the process, in the first process step, the section of the electrical heating element running in the heated area, i.e., the section that later forms the heated area, is positioned in a first part of the multi-part tubular metal jacket; the electrically insulating material, e.g., as a powder or granules or as a molded part, is introduced into this area of ​​the first part of the multi-part tubular metal jacket, so that the section of the electrical heating element arranged in the first part of the multi-part tubular metal jacket is insulated, i.e., embedded, by the electrically insulating material, and the first part of the multi-part tubular metal jacket, in particular the heated area, is compacted.

[0020] It should be noted at this point, firstly, that the aforementioned procedural steps are advantageously carried out in this order, and secondly, that further procedural steps can be carried out before, after, or between them within the framework of the first procedural phase.

[0021] In an advantageous embodiment of the invention, in the second process step carried out after the first process step, at least a section of the unheated area, including at least a part of the unheated transition area, is created by inserting a part of the electric heating element with a connecting wire and / or a connecting sleeve and / or a connecting bolt arranged thereon into a second part of the multi-part tubular metal sheath, wherein further electrically insulating material is introduced into the second part of the tubular metal sheath, so that the section of the electric heating element arranged in the second tubular metal sheath is electrically insulated, in particular embedded, by the electrically insulating material. Preferably, the second part of the multi-part tubular metal sheath is then also compacted.

[0022] In this second procedural phase, the aforementioned procedural steps can also advantageously be carried out in this order, and further procedural steps can be carried out before, after, or between them within the framework of the second procedural phase.

[0023] According to an advantageous embodiment of the method, in the first method step a connecting wire is brought into an electrically conductive connection with an end section of the electric heating element, in particular by inserting it into a coiled end section of the electric heating element and / or a connecting sleeve is brought into an electrically conductive connection with an end section of the electric heating element, in particular by sliding it onto a coiled end section of the electric heating element.

[0024] In both cases described, a (typically small) part of the transition area is also present within the first part of the multi-part tubular metal sheath, which has proven advantageous for process reliability, especially with regard to the electrical contacting of the electrical heating element.

[0025] In the method according to the invention, the electric heating element is coiled such that an end section of the electric heating element has a smaller coil diameter than a section of the electric heating element that lies in the heated area of ​​the finished electric heating device and, in particular, preferably is not an end section. This measure can, in particular, facilitate the filling of the first part of the multi-part tubular metal sheath with the electrically insulating material.

[0026] This coiling of the electric heating element is preferably carried out before its insertion into the first part of the multi-part tubular metal sheath.

[0027] The filling of the first part of the multi-part tubular metal jacket with the electrically insulating material can be made particularly effective if the electric heating element is coiled according to the invention in such a way that the end section of the electric heating element has a smaller coil diameter than the section of the electric heating element which is located in the heated area of ​​the finished electric heating device, and has a coil axis which is offset relative to the coil axis of the section of the electric heating element which is located in the heated area of ​​the finished electric heating device.

[0028] In some cases, it can also be advantageous if, in the first process step after compaction, a connection-side section of the first part of the multi-part tubular metal jacket and the layer of electrically insulating material radially adjoining it are cut off. As already mentioned, as a consequence of the manufacturing method according to the invention, the first part of the multi-part tubular metal jacket and the second part of the multi-part tubular metal jacket are subjected to different compaction processes.

[0029] By subsequently cutting off a connection-side section of the first part of the multi-part tubular metal sheath and the radially inwardly adjoining layer of electrically insulating material, a section of the transition zone, ultimately located in the second part of the multi-part tubular metal sheath, can be pre-compacted with the compaction parameters applied to the first part and then post-compacted with the compaction parameters applied to the second part. This can have a particularly positive effect on the quality of the electrical contact between the connecting wire, connecting sleeve, connecting bolt, and end section of the electrical heating element. Furthermore, the cutting can also contribute to a more homogeneous interface.to create a more homogeneous transition between the electrically insulating material in the first part of the multi-part tubular metal sheath and the electrically insulating material in the second part of the multi-part tubular metal sheath.

[0030] A further development of the process involves sliding the second part of the multi-part tubular metal jacket, with a clear cross-section large enough to accommodate the outer contour of the end section of the first part facing it (at least after compaction in the first process step), onto this end section and securing it there. This effectively prevents any gap between the first and second parts of the multi-part tubular metal jacket. Furthermore, a larger clear cross-section facilitates filling with electrically insulating material, particularly in the area with this cross-section.

[0031] In the further training described last, it is particularly advantageous if the second part of the multi-part tubular metal jacket is connected to the first part of the multi-part tubular metal jacket by pressing during compaction in the second process stage.

[0032] Advantageously, if the second compaction is provided, it is carried out in such a way that the resulting axial pressure creates an almost homogeneous transition zone between the electrically insulating material in areas that have been subjected to the first compaction and in areas that have been subjected to the second compaction.

[0033] For applications where it is important that the electric heating device has a constant outer contour along its entire length, the cross-section of the second part of the multi-part tubular metal jacket can be adapted to the cross-section of the first part of the multi-part tubular metal jacket during compaction in the second process step.

[0034] An unheated connection area can be designed particularly effectively if, in the second process step, before the electrically insulating material is introduced, a part of the electrical heating element with the connecting wire and / or connecting sleeve attached to it is inserted from one side into the second part of the multi-part tubular metal sheath, and a connecting bolt with an opening for receiving this part of the electrical heating element with the connecting wire attached to it is inserted from the opposite side into the second part of the multi-part tubular metal sheath and pushed onto this part of the electrical heating element with the opening.

[0035] Furthermore, in many cases where high-temperature treatment was previously necessary, which in particular prevented the use of copper connecting wires and / or connecting bolts, this material can be used with the process if at least one process step is carried out in which the intermediate product on which this process step is carried out is subjected to a thermal load and if at least the process step in which the highest thermal load occurs is carried out before the start of the second process section.

[0036] The electrically insulating material, which is inserted into the second part of the multi-part tubular metal sheath, can also be inserted as a molded component. It can be particularly advantageous to impregnate the electrically insulating material in this section.

[0037] The electrical heating device according to the invention can be manufactured in particular according to a method according to one of claims 1 to 11, but does not necessarily have to be manufactured according to such a method.

[0038] It comprises, in particular, an electric heating element that is electrically insulated, and in particular embedded, within a multi-part tubular metal sheath comprising a first part and a second part, in an electrically insulating material. The electric heating device has a [missing information] within the multi-part tubular metal sheath. - at least one end has an unheated area in which, when the electric heating device is operated, the electric current also flows through at least one connecting wire and / or at least one connecting sleeve and / or at least one connecting bolt, wherein the at least one connecting wire and / or the at least one connecting sleeve and / or the at least one connecting bolt is in electrical contact with the electric heating element, and - a heated area in which, when the electric heating device is operated, the electric current flows only through a section of the electric heating element located in the heated area, wherein the heated area is arranged in the first part of the multi-part tubular metal jacket and the unheated area is arranged in the second part of the multi-part tubular metal jacket.

[0039] Dividing the tubular metal casing into several parts allows for optimized compression processes for each individual component of the electric heating device. This measure also significantly simplifies the filling process with the electrically insulating material.

[0040] Preferably, part of the unheated area is formed by an unheated transition area in which, when the electric heating device is operated, the electric current flows simultaneously through both the at least one connecting wire and / or connecting bolt and through a section of the electric heating element running in the unheated transition area, which is in electrical contact with the connecting wire and / or connecting bolt.

[0041] According to a preferred embodiment, a connecting wire is in an electrically conductive connection with an end section of the electrical heating element, which may in particular be inserted into a coiled end section of the electrical heating element.

[0042] Alternatively or additionally, a metal sleeve can be used as a connecting sleeve in an electrically conductive connection with an end section of the electric heating element and can be attached, in particular by sliding, soldering or welding the connecting sleeve onto a coiled end section of the electric heating element.

[0043] In both cases described, a (typically small) portion of the transition zone may also be present within the first part of the multi-part tubular metal sheath, which has proven advantageous for process reliability, particularly with regard to the electrical contact of the heating element. However, the transition zone must necessarily extend into the second part of the multi-part tubular metal sheath.

[0044] Filling with the electrically insulating material can be simplified by the fact that, according to the invention, the electrical heating element is coiled in such a way that an end section of the electrical heating element has a smaller coil diameter than a section of the electrical heating element which lies in the heated area of ​​the finished electrical heating device.

[0045] This effect is particularly strong if, according to the invention, the electric heating element is coiled in such a way that the end section of the electric heating element, which has a smaller coil diameter than the section of the electric heating element that lies in the heated area of ​​the finished electric heating device, has a coil axis that is offset relative to the coil axis of the section of the electric heating element that lies in the heated area of ​​the finished electric heating device.

[0046] The tightness of the multi-part tubular metal jacket is enhanced if the second part of the multi-part tubular metal jacket, with a clear cross-section that can accommodate the outer contour of the end section of the first part of the multi-part metal jacket facing it, at least after compaction in the first process step, is pushed onto this end section of the first part of the multi-part tubular metal jacket and fastened there.

[0047] The cross-section of the second part of the multi-part tubular metal jacket can be adapted to the cross-section of the first part of the multi-part tubular metal jacket by compaction in the second process step.

[0048] A particularly effective design of the unheated area provides that a part of the electric heating element with connecting wire and / or connecting sleeve attached to it is inserted from one side into the second part of the multi-part tubular metal sheath, and a connecting bolt with an opening for receiving this part of the electric heating element with connecting wire and / or connecting sleeve attached to it is inserted from the opposite side into the second part of the multi-part tubular metal sheath and pushed onto this part of the electric heating element with the opening.

[0049] The invention is explained in more detail below with reference to figures illustrating exemplary embodiments. These figures show: Fig. 1a: a view of one half of an electric heating device, Fig. 1b: a longitudinal section through the representation of the Fig. 1a, Fig. 1c: a first detailed enlargement from Fig. 1b, Fig. 1d: a second detailed magnification from Fig. 1b, Fig. 2: a section of a first intermediate stage in the execution of a process for manufacturing an electric heating device, Fig. 3: a section of a second intermediate stage in the execution of a process for manufacturing an electric heating device, Fig. 4: a section of a third intermediate stage in the execution of a process for manufacturing an electric heating device, Fig. 5: a section of a fourth intermediate stage in the execution of a process for the manufacture of an electric heating device, showing the intermediate product obtained after the first process stage, Fig. 6: a section of a fifth intermediate stage in the execution of a process for manufacturing an electric heating device, Fig. 7a: a first design of an end section of the electric heating element, Fig. 7b: a second design of an end section of the electric heating element, Fig. 7c: a design according to the invention of an end section of the electric heating element, Fig. 8a: a first design of an unheated transition area, Fig. 8b: a second design for an unheated transition area, Fig. 8c: a third design for an unheated transition area.

[0050] Fig. Figure 1a shows one half of an embodiment of an electric heating device 10, the second half of which can be symmetrical to the first half and Fig. 1b a longitudinal section of this half, which, however, is slightly offset from the central plane. The electric heating device 10 has a multi-part tubular metal jacket 11 with a first part 11.1 of the multi-part tubular metal jacket 11 and a second part 11.2 of the multi-part tubular metal jacket 11, which has a larger clear cross-section than the first part 11.1 of the multi-part tubular metal jacket, overlaps it section by section and is connected to it, as can be seen in particular in the detailed representation of the Fig. 1d illustrates.

[0051] Inside the first part 11.1 of the multi-part tubular metal sheath 11 is the heated area B, which is formed by a section of an electric heating element 12 through which only this element carries an electric current during operation. An electrically insulating material 16, shown here transparently, ensures electrical insulation from the multi-part tubular metal sheath 11.

[0052] Inside the second part 11.2 of the multi-part tubular metal sheath 11, an unheated area U is present at the end, which includes an unheated transition area Ü1. The unheated transition area Ü1 is formed by a section 12.1 of the electric heating element 12, which is more tightly coiled than the electric heating element 12 in the heated area. A connecting wire 13 is inserted into this section, and a connecting sleeve 14 is pushed onto it. This sleeve is, in turn, received in an opening 15.1 of a connecting bolt 15, the solid end section of which lies in the unheated area U. This configuration is, for example, the result of the following: Fig. 1a and Fig. 1c is easy to see. How to... Fig. 8a to 8c, but not only the one described above, in Fig. The configuration shown in 8c can be used with connecting wire and connecting sleeve, but the connecting wire 13 can also be used optionally, as shown in Fig. 8b shown, or the connecting sleeve 14, as in Fig. 8a shown, should be omitted.

[0053] Accordingly, in the unheated area U, when the electric heating device 10 is operated, the electric current flows at least also through at least one connecting wire 13, a connecting sleeve 14, and / or a connecting bolt 15, which is in electrical contact with the electric heating element 12. The unheated area U also has an unheated transition area Ü1, in which, when the electric heating device 10 is operated, the electric current flows simultaneously through both the at least one connecting wire 13, the at least one connecting sleeve 14, and / or the at least one connecting bolt 15, and through a section 12.1 of the electric heating element 12 extending in the unheated transition area Ü1, which is in electrical contact with the connecting wire 13 and / or connecting bolt and has a smaller coil diameter. The unheated transition area extends into the first part 11.1 of the multi-part tubular metal casing 11 into it.

[0054] Inside the second part 11.2 of the multi-part tubular metal jacket 11, a transparently shown electrically insulating material 17 is arranged, which ensures insulation from the multi-part tubular metal jacket 11. A plug 18 closes the end face of the second part 11.2 of the multi-part tubular metal jacket 11. In this example, the first part 11.1 of the multi-part tubular metal jacket 11 with the components of the electric heating device 10 arranged therein, and the second part 11.2 of the multi-part tubular metal jacket 11 with the components of the electric heating device 11 arranged therein, are each compressed, but in different ways, in particular to different degrees, preferably with a weaker compression of the second part 11.2 of the multi-part tubular metal jacket 11. However, the invention also encompasses embodiments in which the second part 11.2 of the multi-part tubular metal jacket 11 with the components arranged therein is no longer compressed.

[0055] A method for manufacturing such an electric heating device is now described, with individual intermediate stages in the Fig. Numbers 2 to 6 are shown.

[0056] First, as in Fig. Figure 2 shows a coiled electric heating element 12, which in this embodiment has an end section 12.1 coiled with a smaller coil diameter, into which a connecting wire 13, e.g. made of Cu or Ni, is inserted at the end and which in the Fig. 7a is shown again in cross-section.

[0057] Other variants of 12' or 12'' electric heating elements can be found in the Fig. 7b and Fig. 7c, which illustrate in particular that the electric heating element 12' does not necessarily have to taper at its end or that the electric heating element 12'' has an end section 12.1'' which has a smaller helix diameter and is wound about a different helix axis W2 than the helix axis W1, about which the helixes with a larger helix diameter are wound which are located in the heated area b of the finished electric heating device; more precisely, about a helix axis W2 that is offset parallel to the helix axis W1.

[0058] Based on the one in Fig. In the intermediate stage shown in Figure 2, a thin-walled, electrically conductive connecting sleeve 14 is now pushed onto the end section 12.1 of the electric heating element 12, which leads to the Fig. The intermediate stage shown in point 3 leads to this.

[0059] The electrical heating element 12, prepared in this way and including connecting wire 13 and connecting sleeve 14, is now inserted into the first part 11.1 of the multi-part tubular metal sheath 11. Electrically insulating material 16 is sprinkled in as a powder or granules and the assembly is compacted, resulting in the intermediate stage according to Fig. 4, which already represents a “finished” electric tubular heater of conventional design, in which – unlike known tubular heaters – the connections of the electric heating device protruding from the end face of the tubular metal jacket are formed by a section of the electric heating element with a connecting wire and / or a connecting sleeve arranged thereon, and thus form the unheated transition section in the fully completed electric heating device according to the invention.

[0060] Next, an end portion of the first part 11.1 of the multi-part tubular metal sheath 11 is cut off together with the electrically insulating material 16. The reason for this is that higher pressures can be used during the compression process of the first part 11.1 of the multi-part tubular metal sheath 11, resulting in a desirable, close press-fit connection between the crimped section 12.1 of the electrical heating element 12 and the connecting wire 13 and the terminal sleeve 14. Accordingly, it can be advantageous to perform this crimping initially on a longer section, provided that sufficient filling with the electrically insulating material 16 is still possible. This is also the reason why the entire section 12.1 is not simply crimped.1 of the electrical heating element 12 is initially embedded and pressed in; in this case, the improvement in fillability with the electrically insulating material 16 would be largely negated.

[0061] To move from the intermediate stage of Fig. 5 to the intermediate stage of Fig. To reach 6, the connecting bolt 15 with its opening 15.1 is pushed onto the arrangement from section 12.1 of the electrical heating element 12 with the connecting wire 13 inserted and the connecting sleeve 14 pushed on.

[0062] The in Fig. The finished electric heating device 1 shown in 1a to 1d is obtained from the intermediate stage according to Fig.6 by sliding the second part 11.2 of the multi-part tubular metal jacket 11 onto it until it overlaps with and is attached to the first part 11.1 of the multi-part metal jacket 11, and then filling this part with electrically insulating material 17, closing it with the plug 18 and preferably compacting it appropriately. Reference symbol list 10 electric heating device 11 multi-part tubular metal casing 11.1 Part One 11.2 Part Two 12,12',12'' electric heating element 12.1,12.1'' Section 13 Connecting wire 14 Connection sleeve 15 connecting bolts 15.1 Opening 16 electrically insulating material 17 electrically insulating material 18 plugs B heated area U unheated area Ü1 unheated transition area W1,W2 helical axes

Claims

[1] Method for manufacturing an electric heating device (10) with an electric heating element (12'') which is arranged inside a multi-part tubular metal sheath (11) embedded in an electrically insulating material (16,17), wherein the electric heating device (10) is located inside the multi-part tubular metal sheath (11) - has at least one end an unheated area (U) in which, when the electric heating device (10) is operated, the electric current also flows through at least one connecting wire (13), and / or at least one connecting sleeve (14) and / or at least one connecting bolt (15) which is in electrical contact with the electric heating element (12'') and furthermore - has a heated area (B) in which, when the electric heating device (10) is operated, the electric current flows only through a section of the electric heating element (12'') running in the heated area (B), where in the procedure - in a first process step in a first part (11.1) of the multi-part tubular metal jacket the heated area (B) is produced and compacted, -in a second process step carried out after the first process step, at least one section of the unheated area (U) is produced in a second part (11.2) of the multi-part tubular metal jacket, and - the first part (11.1) and the second part (11.2) of the multi-part tubular metal casing (11) are connected together, characterized by, that the electric heating element (12'') is coiled such that an end section of the electric heating element (12.1'') has a smaller coil diameter than a section of the electric heating element (12'') which is located in the heated area (B) of the finished electric heating device (10), wherein the electric heating element (12'') is coiled such that the end section (12.1'') of the electric heating element (12'') which has a smaller coil diameter than the section of the electric heating element (12'') which is located in the heated area of ​​the finished electric heating device (10) has a coil axis (W2) which is offset relative to the coil axis (W1) of the section of the electric heating element (12'') which is located in the heated area of ​​the finished electric heating device (10). [2] Method for manufacturing an electric heating device (10) according to claim 1, characterized bythat in the first stage of the proceedings - the section of the electric heating element (12'') running in the heated area (B) is positioned in a first part (11.1) of the multi-part tubular metal sheath (11), - the electrically insulating material (16) is introduced into this area of ​​the first part (11.1) of the multi-part tubular metal sheath (11), so that the section of the electrical heating element (12'') arranged in the first part (11.1) of the multi-part tubular metal sheath (11) is insulated by the electrically insulating material (16), and - the first part (11.1) of the multi-part tubular metal jacket (11), in particular the heated area (B), is compressed. [3] Method for manufacturing an electric heating device (10) according to claim 1 or 2, characterized by, that an electric heating device (10) is manufactured in which the unheated area (U) comprises an unheated transition area (Ü1) in which, when the electric heating device (10) is operated, the electric current flows simultaneously through both the at least one connecting wire (13) and / or connecting bolt (14) and through a section (12.1'') of the electric heating element (12'') extending in the unheated transition area (Ü1) which is in electrical contact with the connecting wire (13) and / or the connecting sleeve (14) and / or the connecting bolt (15), and that in the second process step carried out after the first process step, at least one section of the unheated area (U) including at least one part of the unheated transition area (Ü1) is created by a section (12.1'') of the electric heating element (12'') with connecting wire (13) and / or connecting sleeve (14) and / or connecting bolt (15) arranged thereon is inserted into a second part (11.2) of the multi-part tubular metal sheath (11) by inserting the electrically insulating material (17) into the second part (11.2) of the multi-part tubular metal sheath (11), so that the section (12.1'') of the electric heating element (12'') arranged in the second part (11.2) of the multi-part tubular metal sheath (11) is embedded in the electrically insulating material (17). [4] Method according to any one of claims 1 to 3, characterized by, that in the first process step a connecting wire (13) is brought into an electrically conductive connection with an end section of the electric heating element (12''), in particular by inserting it into a coiled end section of the electric heating element (12''), and / or that in the first process step a connecting sleeve (14) made of metal is brought into an electrically conductive connection with an end section of the electric heating element (12''), in particular by sliding, soldering or welding the connecting sleeve (14) onto a coiled end section of the electric heating element (12''). [5] Method according to any one of claims 1 to 4, characterized by, that in the second process step the second part (11.2) of the multi-part tubular metal jacket (11) with the components arranged therein is compacted, wherein preferably the second compaction is carried out in such a way that the resulting axial pressing pressure creates an almost homogeneous transition area between the electrically insulating material (16) in areas that were subjected to compaction in the first process step and the electrically insulating material (17) in areas that were subjected to the second compaction in the second process step. [6] Method according to any one of claims 1 to 5, characterized by , that in the first process step after compaction a connection-side section of the first part (11.1) of the multi-part tubular metal jacket (11) and the layer of electrically insulating material (16) adjoining it radially inwards is cut off. [7] Method according to any one of claims 1 to 6, characterized by , that the second part (11.2) of the multi-part tubular metal jacket (11) with a clear cross-section that can accommodate the outer contour of the end section of the first part (11.1) of the multi-part metal jacket (11) facing it, at least after compaction in the first process step, is pushed onto this end section of the first part (11.1) of the multi-part tubular metal jacket (11) and fastened there. [8] Method according to claim 7, characterized by , that the second part (11.2) of the multi-part tubular metal jacket (11) is joined to the first part (11.1) of the multi-part tubular metal jacket (11) by pressing during compaction in the second process step. [9] Method according to claim 7 or 8, characterized by, that the cross-section of the second part (11.2) of the multi-part tubular metal jacket (11) is adapted to the cross-section of the first part (11.1) of the multi-part tubular metal jacket (11) during compaction in the second process stage. [10] Method according to any one of claims 1 to 9, characterized by, that in the second process step, before the electrically insulating material (17) is introduced, a section of the electric heating element (12.1'') with connecting wire (13) and / or connecting sleeve (14) arranged thereon is inserted from one side into the second part (11.2) of the multi-part tubular metal jacket (11), and a connecting bolt (15) with an opening (15.1) for receiving this part of the electric heating element (12'') with connecting wire (13) and / or connecting sleeve (14) arranged thereon is inserted from the opposite side into the second part (11.2) of the multi-part tubular metal jacket (11) and is pushed onto this part of the electric heating element (12'') with the opening (15.1). [11] Method according to any one of claims 1 to 10, characterized by, that at least one process step in which the intermediate product on which this process step is carried out is subjected to a thermal load is performed, and that at least the process step in which the highest thermal load is applied is carried out before the start of the second process section. [12] An electric heating device (10) that can be manufactured according to a method according to any one of claims 1 to 11, comprising an electric heating element (12'') that is embedded inside a multi-part tubular metal jacket (11) having a first part (11.1) and a second part (11.2) in an electrically insulating material (16, 17), wherein the electric heating device (10) is located inside the multi-part tubular metal jacket (11) - has at least one end an unheated area (U) in which, when the electric heating device (10) is operated, the electric current also flows through at least one connecting wire (13) and / or at least one connecting sleeve (14) and / or at least one connecting bolt (15) which is in electrical contact with the electric heating element (12''), and furthermore - has a heated area (B) in which, when the electric heating device (10) is operated, the electric current flows only through a section of the electric heating element (12'') running in the heated area (B), wherein the heated area (B) is arranged in the first part (11.1) of the multi-part tubular metal jacket (11) and the unheated area (U) is arranged in a second part (11.2) of the multi-part tubular metal jacket (11), characterized by, that the electric heating element (12'') is coiled such that an end section (12.1'') of the electric heating element (12'') has a smaller coil diameter than a section of the electric heating element (12'') which is located in the heated area (B) of the finished electric heating device (10), wherein the electric heating element (10) is coiled such that the end section (12.1'') of the electric heating element (12'') which has a smaller coil diameter than the section of the electric heating element (12'') which is located in the heated area of ​​the finished electric heating device (10) has a coil axis (W1) which is offset relative to the coil axis (W2) of the section of the electric heating element (12'') which is located in the heated area (B) of the finished electric heating device (10). [13] Electric heating device (10) according to claim 12, characterized by, that the unheated area (U) comprises an unheated transition area (Ü1) in which, when the electric heating device (10) is operated, the electric current flows simultaneously through both the at least one connecting wire (13) and / or the at least one connecting sleeve (14) and / or the at least one connecting bolt (15) and through a section (12.1'') of the electric heating element (12'') running in the unheated transition area (Ü1), which is in electrical contact with the connecting wire (13) and / or the connecting sleeve (14) and / or the connecting bolt (15). [14] Electric heating device (10) according to one of claims 12 or 13, characterized by , that a connecting wire (13) is in an electrically conductive connection with an end section of the electric heating element (12''), in particular is inserted into a coiled end section of the electric heating element (12''). [15] Electric heating device (10) according to any one of claims 12 to 14, characterized by , that a metal connecting sleeve (14) is in an electrically conductive connection with an end section of the electric heating element (12''), in particular by sliding, soldering or welding the connecting sleeve (14) onto a coiled end section of the electric heating element (12''). [16] Electric heating device (10) according to any one of claims 12 to 15, characterized by , that the second part (11.2) of the multi-part tubular metal jacket (11) with a clear cross-section that can accommodate the outer contour of the end section of the first part (11.1) of the multi-part metal jacket (11) facing it, at least after compaction in the first process step, is pushed onto this end section of the first part (11.1) of the multi-part tubular metal jacket (11) and fastened there. [17] Electric heating device (10) according to claim 16, characterized by , that the cross-section of the second part (11.2) of the multi-part tubular metal jacket (11) was adapted to the cross-section of the first part (11.1) of the multi-part tubular metal jacket (11) during compaction in the second process stage. [18] Electric heating device (10) according to any one of claims 12 to 17, characterized by, that a part of the electric heating element (12'') with connecting wire (13) and / or connecting sleeve (14) arranged thereon is inserted from one side into the second part (11.2) of the multi-part tubular metal sheath (11) and a connecting bolt (15) with an opening (15.1) for receiving this part of the electric heating element (12'') with connecting wire (13) and / or connecting sleeve (14) arranged thereon is inserted from the opposite side into the second part (11.2) of the multi-part tubular metal sheath (11) and is pushed onto this part of the electric heating element with connecting wire (13) and / or connecting sleeve (14) arranged thereon with the opening (15.1).

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