COMPACT HEATER WITH SHELLED TUBE RADIATOR

Description

[0001] The invention is based on a tubular heater with a connecting pin at each end of the tubular heater. A heating conductor is arranged inside the tubular heater in electrical connection between the connecting pins at both ends, and the remaining space in the tubular heater is filled with a powdered or granular metal oxide, in particular magnesium oxide. A tubular heater with the features specified in the preamble of claim 1 is known from GB 658 711 A and FR 2 723 284 A1. A similar tubular heater is known from US 6 104 011 A1. US 2 858 401 A discloses a tubular heater with two concentrically arranged heating coils of the same winding diameter.

[0002] For flexible tubular heaters with lower supply voltages up to 120V, especially up to 60V, as is common in the automotive sector, the available power relative to the tubular length is limited, as the low resistance required for high power can only be achieved with thick, stiff, and therefore non-flexible heating wires, whose surface load is then usually too high. Furthermore, compact, small-volume heaters, such as those required in the automotive industry, for example, for heating cooling water or exhaust gases, require tubular heaters with high power.

[0003] The object is therefore to produce a tubular heater with very high performance at voltages up to 120 V, in particular up to 60 V. Furthermore, the object of the invention is to produce a powerful compact heater for smaller supply voltages below 120 V, in particular up to 60 V, using a tubular heater, which, despite its high performance, requires only a small volume.

[0004] This object is achieved by a tubular heater having the features specified in claim 1 and a compact heater according to claim 14. Advantageous developments of the invention are the subject of subclaims.

[0005] According to the invention, instead of a single heating wire, at least four heating wire coils, for example five, are arranged inside the jacket tube. The heating wire coils are arranged concentrically. According to the invention, the coils all have the same winding diameter and are therefore axially aligned. The coils are wound into each other, thus forming a multiple helix.

[0006] The heating wires can touch each other at least partially. To avoid short circuits or voltage bridges and the associated changes in overall resistance, touching heating wire turns or those with a small turn spacing are insulated from each other in one design variant, preferably by an outer insulation layer such as an oxide layer. Surprisingly, however, it has been shown that tubular heaters with four or more coaxially wound heating wire coils can be manufactured without external heating wire insulation, even with a small turn spacing, without any significant change in resistance, since the spring force of the heating wires is very homogeneous. This design is preferred.

[0007] The heating wire coils can be attached individually or in groups to multiple terminal pins at each end. This allows different controllers to generate different resistance combinations and thus different power outputs. However, it is preferable for all heating wire coils to be attached to a common terminal pin at each end.

[0008] In one connection variant, the heating wire coils are attached to a preferably cylindrical side wall of connection pins. In this embodiment, the connection pin contacting the heating wire coils is preferably solid. The heating wires are advantageously attached by welding, in particular by spot welding. The heating wires are preferably attached to the connection pins axially offset, in particular along an axial line. According to the invention, the adjacent heating wires touch one another at least in the attachment area. This advantageously allows all wires to be attached in a single operation. Particularly in the case of heating wire coils with a small winding pitch, this attachment does not lead to unevenly wound heating wire coils with short circuits and voltage bridges.

[0009] An advantageous development of the invention provides that the terminal pins have an end section with a reduced thickness. This end section can extend into the heating wire coils and contact them, in particular by welding. To establish or improve electrical contact, the heating wire coils and terminal pins can be crimped, i.e., pressed together so tightly that plastic deformation occurs, for example, the round wire is slightly flattened. After crimping, welding can take place. It is also possible, in particular, for a sleeve to surround the contact area of ​​the heating wire coils and terminal pin, and for the sleeve to be crimped and / or welded after being pushed on.

[0010] In one connection variant, the ends of heating wire coils are joined, preferably twisted together, in a sleeve, and then routed to the outside. The attachment can be achieved, for example, by crimping or squeezing. If, as is preferred, the heating wire coils are made of round wire, the wire no longer has a circular cross-section at its crimped end section, but is slightly flattened. Alternatively or additionally, soldering or welding can be used. This sleeve can be designed as an end section of a terminal pin, but is preferably a separate component.

[0011] In the case of a separate sleeve, an end section of the connecting pin can be inserted into the sleeve from its opposite end face before fastening, so that the end of the connecting pin and the end of the heating wire coils in the sleeve are opposite each other with contact or a small distance.

[0012] In an advantageous embodiment, however, the heating wires extend to the opposite end of the sleeve. The end of the heating wires is preferably flush with the end of the sleeve. This can be achieved by post-processing, for example by inserting the heating wire coils into the sleeve and then cutting off or grinding off an end section of the sleeve together with the ends of the heating wires inserted therein. This creates a flat end face which can then be connected to the end face of the connecting pin, in particular by resistance welding. Before such post-processing, the sleeve can be pressed together with the heating wires located therein, i.e. plastically deformed, for example by compression molding. The sleeve and the connecting pin preferably have similar, very preferably identical, outer diameters.

[0013] Typically, a connecting pin in tubular heaters is made of steel. However, the connecting pin in the tubular heater according to the invention is preferably made of stainless steel, in particular of a stainless steel with a lower specific resistance than, for example, 0.6 ohm mm² / m, in particular less than 0.4 ohm mm² / m. This advantageously leads to a better welded joint, especially with a front-end welded joint.

[0014] Preferably, the connecting pins protrude from the jacket tube and contact the heating wire coils within the jacket tube. However, it is also possible for the heating wire coils to protrude from the jacket tube at one or both ends and also contact the connecting pin(s) outside the jacket tube. In this case, the connecting pin in question can also be brazed to the heating coils, since temperatures outside the jacket tube do not rise nearly as high as inside the jacket tube, even at high heating outputs.

[0015] The heating wire coils preferably have a relative pitch SR of at least 1, for example, 2 or more. The relative pitch SR is therefore preferably significantly greater than in conventional jacketed tubular heaters with only one or two heating wire coils. This advantageously allows for greater heating output. The relative pitch SR can be calculated for a given coil by dividing the pitch s associated with one revolution, defined as the axial distance between two adjacent turns of the same heating wire, by the outer diameter DA of the wire coil.

[0016] In a further advantageous embodiment, the outer diameter DA of the heating coil is 2.5 to 6 times, preferably only 2.5 to 4.5 times, the wire diameter d. This dimensioning has been shown to be particularly advantageous considering limited surface loading of the heating wire and a compact design.

[0017] Tubular heaters manufactured according to the invention preferably have a relative resistance of less than 1 ohm / m relative to the straight, heated tubular section. Nevertheless, the diameter of the tubular section is at most 12 mm, preferably at most 9 mm, and most preferably at most 7 mm.

[0018] According to the prior art, alloys of two or more metals are used as heating wires in jacketed tubular heaters. These alloys have a relatively high specific electrical resistance of over 1 Ohm mm 2< / m and a low tendency to oxidation. In a departure from this teaching, the invention preferably uses metal alloys as heating wires that have a specific resistance of less than 0.8 Ohm mm 2< / m, in particular less than 0.4 Ohm mm 2< / m, i.e., are not typical heating conductor alloys. In order to nevertheless withstand the high temperature caused by the high output, the preferred metal alloy simultaneously has a temperature resistance of at least 600°C, preferably at least 1000°C.

[0019] To create a powerful compact heater from such a tubular heater, the tubular heater is bent multiple times and / or continuously. In a preferred embodiment, the tubular heater is bent so that the two tubular ends have approximately the same spatial orientation. Advantageously, the tubular heater is bent in a helical and / or spiral and / or meandering manner. Most preferably, at least one bend has a diameter of at least 90° and a central bending radius of at most twice the tubular diameter. The tubular heater bent in this way results in an extremely powerful compact heater.

[0020] Further details and advantages of the invention are explained using exemplary embodiments with reference to the accompanying drawings. Identical and corresponding components are provided with identical reference numerals. They show: Fig. 1 schematically shows a jacket pipe radiator end in a tangential section, Fig. 2 a longitudinal section of another embodiment of a jacket pipe radiator end; Fig. 3 a detailed view of section X of Fig. 2 , Fig. 4 a cross section to Fig. 2 along the section line AA, Fig. 5 a longitudinal section of another embodiment of a jacket pipe radiator end, and Fig. 6a a detailed view of the section X of Fig. 5 , Fig. 6b cross-section to Fig. 5 along the section line AA, Fig. 7a a longitudinal section of another embodiment of a jacket pipe radiator end; Fig. 7b a detailed view of the section X of Fig. 7a , Fig. 7c a cross section to Fig. 7a along section line AA, Fig. 8 further embodiment of a jacketed tube radiator.

[0021] Fig. 1schematically shows an embodiment of a jacketed pipe heater according to the invention in a multi-section partial view. The first section is a tangential section in the axial direction of the jacketed pipe 1 to provide a view into the interior of the jacketed pipe 1. In a further section, the jacketed pipe 1 is cut off at a distance from the jacketed pipe end 1.1. Deviating from this, for better illustration, the heating wires 5.1 - 5.5 of the heating wire coils are individually cut off at a greater distance from the jacketed pipe end 1.1 than the jacketed pipe 1 itself. Without the cuts, the jacketed pipe 1 and the heating wires 5.1 - 5.5 would extend to an opposite second end of the jacketed pipe, which is not shown here.

[0022] Inside the jacket tube 1, four or more, for example five, heating wires 5.1 - 5.5 are arranged helically with the same winding diameter and the remaining space 7 is filled with metal oxide powder.

[0023] All heating wire coils have the same coil pitch; thus, there are approximately equal distances between adjacent heating wire coils. The arrangement of the heating wires 5.1 - 5.5 is maintained among each other along the entire length between the two ends of the jacket tube 1, i.e. the sequence between the heating wires 5.1 - 5.5 remains unchanged along the entire length. The heating wires 5.1 - 5.5 therefore form a multiple helix. At the jacket tube end 1.1, the ends of the heating wires 5.1 - 5.5 are wound or plugged onto an end section of a connection pin 2, also maintaining their sequence, the contact pin 4 of which protrudes from the jacket tube 1. Preferably, each heating wire 5.1 - 5.5 has contact with the connection pin 2 over at least one full coil, extremely preferably over at least three full coils. The fastening of the heating wires 5.1 - 5.5 to the cylindrical side wall of the connecting pin 2 is, in the exemplary embodiment, spot-welded with an elongated electrode, which simultaneously secures all heating wires 5.1 - 5.5 to the connecting pin 2. Advantageously, all fastening points 6.1 - 6.5 are located on one line, most preferably on an axial line of the connecting pin 2, with spacing between the heating wires 5.1 - 5.5 in this exemplary embodiment. However, the heating wires 5.1 - 5.5 are preferably arranged so as to touch one another at the fastening points 6.1 - 6.5. However, the fastenings can also be made one after the other, or the fastening points 6.1 - 6.5 can be distributed axially around the circumference at the same height of the connecting pin 2. Other types of fastening are also possible.

[0024] The finished jacket pipe radiator is sealed at its ends between the connecting pin 2 and the jacket pipe 1 by a bushing 3.

[0025] To create a compact heater, the straight tubular heater shown is bent several times or continuously after completion (not shown). This creates a powerful, compact heater.

[0026] In Fig. 1 the contact between heating wire coils and connection pin 2 of contact pin 4 is shown only schematically and not to scale. Fig. 2 shows a true-to-scale example of the contact between four heating wire coils 5.1 - 5.4 and a connecting pin 2. The connecting pin 2 has an end section 2.1 whose thickness is reduced, i.e. smaller than the remaining part of the connecting pin and in particular also smaller than the thickness of the contact pin 4 formed by the connecting pin 2 at the opposite end.

[0027] The end section 2.1 of the connection pin 2 protrudes into the heating wire coils 5.1 - 5.4. Fig. 3 shows a longitudinal section of a section of Fig. 2 and Fig. 4 shows a cross section of Fig. 2 The heating wire coils are made of round wire. After the heating wire coils have been plugged onto the end section 2.1 of the connecting pin 2, they can still be crimped there. This plastically deforms the heating wire 5.1 - 5.4 in this area, so that the cross-section of the heating wire 5.1 - 5.4 and the end section 2.1 of the connecting pin 2 is no longer circular, but somewhat flattened. The shared outer contour is reduced by compression and the reduction of the gaps, and the entire connection area is more compact. This increases the contact surface to the connecting pin 2. For a secure connection, the heating wire coils are preferably welded to the end section 2.1 of the connecting pin 2.

[0028] Additionally, the contact point may also have an outer sleeve 8 that surrounds the heating wires 5.1-5.4 with the end section 2.1. In this embodiment, compression by crimping the contact area is preferably performed before the connection by welding or soldering.

[0029] Fig. 5 as well as the Fig. 6a and 6b show another example of contact between four heating wire coils and a contact pin 2. This embodiment differs from the embodiment of the Figures 2 to 4Essentially, end section 2.1 is at least partially inserted into a sleeve 8 from the first side, and the ends of the heating wire coils 5.1 - 5.4 are inserted into the sleeve from the second side, with their end faces ideally touching. The sleeve 8 was pressed after being pushed on, which in turn plastically deformed the underlying end sections of the heating wires 5.1 - 5.4 and the end section 2.1, i.e., slightly flattened them. For secure contact, welding was also preferably performed in this design.

[0030] When using a sleeve 8, an end section of the connection pin can protrude into the heating coils. In the illustrated embodiment, however, the end section 2.1 of the connection pin 2 does not protrude into the heating wire coils 5.1 - 5.4; instead, the end of the connection pin 2 and the end of the heating wire coils 5.1 - 5.4 lie opposite each other in the sleeve 8 with contact or a small distance apart. In this embodiment, contact is preferably made by introducing solder into the sleeve 8. However, soldering is only effective in applications where the application temperature does not reach the solder melting temperature.

[0031] Another example of contacting is in Fig. 7shown. In this embodiment, only the heating wires 5.1 - 5.4 are inserted into a sleeve 8 and connected to the sleeve 8, preferably by welding. The internal heating wires 5.1 - 5.4 extend to the end face of the sleeve 8, which is made flat, in particular by machining. The end face of the end section 2.1 is then connected to this end face of the sleeve 8, in particular by resistance welding. The sleeve and the end section 2.1 preferably have similar, extremely preferably identical, outer diameters.

[0032] All of the above-shown examples of contact between heating wire coils 5.1 - 5.4 and end section 2.1 of the connecting pin 2 are preferably implemented such that this contact is located within the jacket tube 1. The contact pin 4 then protrudes from the jacket tube 1 and the end section 2.1 of the connecting pin 2 contacting the heating wire coils is in the jacket tube 1. However, it is also possible for the heating wire coils 5.1 - 5.4 to protrude from the jacket tube 1 and the contact between the heating wire coils 5.1 - 5.4 and end section 2.1 to be made outside the jacket tube 1, as in the Fig. 8 shown embodiment. Since the temperatures outside the jacket tube 1 are not nearly as high as inside the jacket tube 1, in this case, soldering or even just crimping or squeezing can be used to form the contact instead of welding. List of reference symbols

[0033] 1Jacket pipe 1.1Jacket pipe end 2Connection pin 2.1End section of the connection pin 3Socket 4Contact pin 5.1Heating wire 5.2Heating wire 5.3Heating wire 5.4Heating wire 5.5Heating wire 6.1Fastening 6.2Fastening 6.3Fastening 6.4Fastening 6.5Fastening 7Space 8Sleeve SSteep of a wire coil DA Outer diameter of a wire coil dDiameter of a heating wire

Claims

1. Sheathed tube heater comprising a sheath tube (1) and at least one electrical connection pin (2) at both ends (1.1) of the sheath tube (1), wherein a heating conductor is arranged inside the sheath tube (1) in electrical connection between the connection pins (2) at the two ends (1.1) and the remaining space (7) in the sheath tube (1) is filled with a powdered or granular metal oxide, in particular magnesium oxide, the heating conductor comprising of at least 4 heating wire coils (5.1 - 5.5) connected in parallel, which are arranged concentrically, characterised in that the heating wire coils (5.1 - 5.5) all have the same winding diameter and neighbouring heating wires touch each other at least in one fastening region.

2. Sheathed tube heater according to claim 1, characterised in that the connecting pins (2) each have an end section (2.1) at which they are contacted by the heating wire coils (5.1 - 5.5).

3. Sheathed tube heater according to claim 2, characterised in that the end section (2.1) has a reduced thickness.

4. Sheathed tube heater according to claims 2 or 3, characterised in that the end section (2.1) projects into the heating wire coils (5.1 - 5.5).

5. Sheathed tube heater according to any one of the preceding claims 1 to 3, characterised in that at least one of the connecting pins (2) contacts the heating wire coils (5.1 - 5.5) on an end face.

6. Sheathed tube heater according to any one of claims 1 to 5, characterised in that the heating wire coils (5.1 - 5.5) protrude from the sheath tube (1) at least at one end and contact the connecting pin (2) outside the sheath tube (1) at least at one end of the sheath tube (1).

7. Sheathed heater according to any one of claims 1 to 6, characterised in that the connecting pins (2) are compressed together with the heating wire coils (5.1 - 5.5).

8. Sheathed tube heater according to any one of claims 1 to 7, characterised in that the connecting pins (2) are welded to the heating wire coils (5.1 - 5.5).

9. Sheathed tube heater according to any one of claims 1 to 8, characterised in that the connecting pins (2) each project into a sleeve (8) in which they are contacted by the heating wire coils (5.1 - 5.5).

10. Sheathed tube heater according to any one of the preceding claims, characterised in that the metal tube (1) has an outer diameter of at most 12 mm.

11. Sheathed tube heater according to any one of the preceding claims, characterised in that after manufacture the resistance along the stretched heated length of the sheath tube (1) is less than 1 ohm / m.

12. Sheathed tube heater according to any one of the preceding claims, characterised in that the alloy of the heating wires (5.1 - 5.5) has a specific resistance of less than 0.8 Ohm mm2 / m, preferably less than 0.4 Ohm mm2 / m.

13. Sheathed tube heater according to any one of the preceding claims, characterised in that the heating wire coils (5.1-5.5) have a relative pitch SR of 1 or more.

14. Compact heater comprising at least one sheathed tube heater according to any one of claims 1 to 13, characterised in that the sheathed tube heater is bent in a helical and / or spiral and / or meandering manner, at least one bend having at least 90° and a central bending radius of at most twice the diameter of the sheath tube.