EP3883338A1 - Compact heater with sheathed tubular heating element - Google Patents

Abstract

A jacket-tube heater with a jacket tube (1) and at least one electrical connection pin (2) at both ends (1.1) of the jacket tube (1) is described, with a heating conductor in electrical connection between the connection pins (2) inside the jacket tube (1). is arranged at the two ends (1.1) and the remaining space (7) in the jacket tube (1) is filled with a powdery or granular metal oxide, in particular magnesium oxide. According to the invention it is provided that the heating conductor consists of at least 4 heating wire coils (5.1-5.5) connected in parallel.

Description

The invention is based on a tubular heating element with a connecting pin at both ends of the tubular casing, with a heating conductor in electrical connection between the connecting pins at the two ends inside the tubular casing and the rest of the space in the tubular casing with a powdery or granular metal oxide, especially magnesium oxide, is replenished.

For bendable tubular heating elements with lower supply voltages of up to 120V, especially up to 60V, as is common in the automotive sector, the available power in relation to the tubular length is limited, as the small resistance required for high power is only increased with thick, stiff and therefore non-bendable heating wires can be realized, the surface load of which is then usually too high. They are also used for compact, small-volume radiators, such as those used in the automotive industry, for example for heating cooling water or exhaust gases. are required, tubular heating elements with high power are required.

The task is therefore to produce a tubular heating element with a very high output at voltages of up to 120V, in particular up to 60V. A further object of the invention is to use a tubular heating element to produce a powerful compact heater for smaller supply voltages below 120V, in particular of at most 60V, which, despite its high performance, only requires a small volume.

This object is achieved by a tubular heating element with the features specified in claim 1 and a compact heater according to claim 14. Advantageous further developments of the invention are the subject of subclaims.

According to the invention, instead of a single heating wire, at least 4 heating wire coils are arranged in the interior of the jacket tube, for example 5 heating wire coils. The heating wire coils can be arranged concentrically. The coils can have different winding diameters and can therefore be wound very compactly. However, the coils preferably all have the same winding diameter and are therefore on a line when viewed axially. The coils are twisted into one another, thus forming a multiple helix.

The heating wires can at least partially touch one another. In order to avoid short circuits or voltage bridges and the associated changes in overall resistance, contacting heating wire turns or those with a small turn spacing are insulated from one another in one embodiment, preferably by an outer insulation layer such as an oxide layer. Surprisingly, however, it has been shown that tubular heating elements with 4 or more coaxially wound heating wire coils without external heating wire insulation can also be produced with a small winding spacing without any significant change in resistance, since the spring force of the heating wires is very homogeneous. This configuration is preferred.

The heating wire coils can be attached individually or in groups to several connection pins per end. This allows different Controls produce different combinations of resistors and thus different powers. However, all heating wire coils are preferably fastened at the ends to a common connection pin.

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 fastened by welding, in particular by spot welding. The heating wires are preferably fastened to the connection pins in an axially offset manner, in particular along an axial line. In an extremely advantageous variant, the heating wires lying next to one another touch at least in the fastening area. As a result, all of the wires can advantageously be fastened in a single operation. In particular in the case of heating wire coils with a small winding spacing, this fastening does not lead to heating wire coils that are unevenly wound into one another with short circuits and voltage bridges.

An advantageous further development of the invention provides that the connecting pins have an end section which is of reduced thickness. This end section can protrude into the heating wire coils and contact them, in particular by welding. In order to establish or improve electrical contact, heating wire coils and connection pins can be squeezed, i.e. pressed so strongly that plastic deformation occurs, i.e. round wire, for example, is somewhat flattened. After the squeezing, welding can take place. It is also possible, in particular, for a sleeve to surround the contact area of the heating wire coils and connection pin and for the sleeve to be squeezed and / or welded after being pushed on.

In one connection variant, ends of heating wire coils are common, preferably twisted together, fastened in a sleeve and led to the outside. Fastening can take place, for example, by squeezing or crimping. If, which is preferred, the heating wire coils are made of round wire, the wire then no longer has a circular cross-section at its crimped end section, but is somewhat flattened. Alternatively or additionally, soldering or welding can take place. This sleeve can be designed as an end section of a connecting pin, but is preferably a separate component.

In the case of a separate sleeve, an end section of the connecting pin can be introduced into the sleeve from its opposite end face prior to fastening, so that the end of the connecting pin and the end of the heating wire coils in the sleeve are opposite one another with contact or a small distance.

In an advantageous embodiment, however, the heating wires protrude 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 face which can then be connected to the face end of the connection pin, in particular by resistance welding. Before such post-processing, the sleeve can be pressed together with the heating wires located therein, that is to say plastically deformed, for example compression-molded. The sleeve and the connecting pin preferably have similar, extremely preferably the same, outer diameter.

A connecting pin in tubular heaters is usually made of steel. However, the connection pin in the tubular heater according to the invention is preferably made of stainless steel, in particular of a stainless steel with a specific resistance lower than, for example, 0.6 ohm mm ² / m, in particular less than 0.4 ohm mm ² / m. This advantageously leads to a better welded connection, in particular in the case of a welded connection on the end face.

The connecting pins preferably protrude from the jacket tube and contact the heating wire coils in the jacket tube. However, it is also possible that the heating wire coils also protrude from one or both ends of the jacket tube and the connection pin (s) also outside the jacket tube Contact the jacket pipe. In this case, the connection pin in question can also be hard-soldered to the heating coils, since the temperatures outside the casing pipe do not rise by far as high as in the casing pipe, even with high heating outputs.

The heating wire coils preferably have a relative pitch S _R of at least 1, for example 2 or more. The relative slope S _R is therefore preferably much greater than in conventional tubular heaters with only one or two heating wire coils. In this way, a greater heating output can advantageously be achieved. The relative pitch S _R 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 D _{A of} the wire coil.

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. As has been shown, this dimensioning is particularly advantageous taking into account the limited surface load on the heating wire and a compact design.

Jacketed tubular heating elements produced according to the invention preferably have a relative resistance of less than 1 ohm / m in relation to the straight, heated tubular jacket section. Nevertheless, the diameter of the jacket tube is at most 12 mm, preferably at most 9 mm, extremely preferably at most 7 mm.

According to the prior art, alloys of two or more metals are used as heating wires in tubular heating elements, which have a relatively high specific electrical resistance of over 1 ohm mm ² / m and have a low tendency to oxidation. In departure from this teaching, metal alloys are preferably used as heating wire according to the invention which have a specific resistance of less than 0.8 ohm mm ² / m, in particular less than 0.4 ohm mm ² / m, that is to say are not typical heating conductor alloys. In order to be able to withstand the high temperature caused by the high output the preferred metal alloy also has a temperature resistance of at least 600.degree. C., preferably at least 1000.degree.

In order to get to a powerful compact heater starting from such a tubular heating element, the tubular heating element is bent several times and / or continuously. In a preferred embodiment, the tubular heating element is bent in such a way that the two tubular tubular ends have approximately the same spatial orientation. The tubular heating element is advantageously bent in a helical and / or spiral and / or meandering manner. Most preferably, at least one bend has at least 90 ° and a central bending radius of at most twice the casing tube diameter. The tubular heating element bent in this way results in an extremely powerful compact heater.

Fig. 1

schematisch ein Mantelrohrheizkörperende in einem tangentialen Anschnitt,

Fig. 2

einen Längsschnitt eines weiteren Ausführungsbeispiels eines Mantelrohrheizkörperendes;

Fig. 3

eine Detailansicht des Ausschnitts X von Fig. 2,

Fig. 4

einen Querschnitt zu Fig. 2 entlang der Schnittlinie A-A,

Fig. 5

einen Längsschnitt eines weiteren Ausführungsbeispiels eines Mantelrohrheizkörperendes, und

Fig. 6a

eine Detailansicht des Ausschnitts X von Fig. 5,

Fig. 6b

einen Querschnitt zu Fig. 5 entlang der Schnittlinie A-A,

Fig. 7a

einen Längsschnitt eines weiteren Ausführungsbeispiels eines Mantelrohrheizkörperendes;

Fig. 7b

eine Detailansicht des Ausschnitts X von Fig. 7a,

Fig. 7c

einen Querschnitt zu Fig. 7a entlang der Schnittlinie A-A,

Fig. 8

weiteres Ausführungsbeispiel eines Mantelrohrheizkörpers.

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 symbols. Show it:

Fig. 1

schematically a tubular heating element end in a tangential cut,

Fig. 2

a longitudinal section of a further embodiment of a tubular heating element end;

Fig. 3

a detailed view of section X of Fig. 2 ,

Fig. 4

a cross section too Fig. 2 along the section line AA,

Fig. 5

a longitudinal section of a further embodiment of a tubular heating element end, and

Figure 6a

a detailed view of section X of Fig. 5 ,

Figure 6b

a cross section too Fig. 5 along the section line AA,

Figure 7a

a longitudinal section of a further embodiment of a tubular heating element end;

Figure 7b

a detailed view of section X of Figure 7a ,

Figure 7c

a cross section too Figure 7a along the section line AA,

Fig. 8

Another embodiment of a tubular heater.

Fig. 1 shows schematically an embodiment of a tubular heating element according to the invention in a multiple cut partial view. The first section is a tangential section in the axial direction of the jacket tube 1 in order to reveal the inside of the jacket tube 1. In a further section, the jacket tube 1 is cut off at a distance from the jacket tube end 1.1. Deviating from this, the heating wires 5.1-5.5 of the heating wire coils are cut off individually at a greater distance from the casing pipe end 1.1 than the casing pipe 1 itself for better illustration. Without the cuts, the jacket tube 1 and the heating wires 5.1-5.5 would extend to an opposite second end of the jacket tube, which is not shown here.

In the interior of 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.

All heating wire coils have the same pitch; so it has approximately the same distances between adjacent heating wire turns. The arrangement of the heating wires 5.1-5.5 among one another is retained over the entire distance between the two ends of the jacket tube 1, ie the sequence between the heating wires 5.1-5.5 remains unchanged over the entire distance. The heating wires 5.1-5.5 thus form a multiple helix. At the casing pipe end 1.1, the ends of the heating wires 5.1-5.5 are also wound or plugged onto an end section of a connecting pin 2, also in compliance with their sequence, the contact pin 4 of which protrudes from the casing pipe 1. Each heating wire 5.1-5.5 preferably has at least one full turn, extremely preferably at least three full turns, contact with the connecting pin 2. The fastening of the heating wires 5.1-5.5 on the cylindrical side wall of the connecting pin 2 is in the exemplary embodiment by spot welding with a elongated electrode takes place, which fixes all heating wires 5.1-5.5 on the connection pin 2 at the same time. Advantageously, all of the fastening points 6.1-6.5 lie on one line, extremely preferably on an axial line of the connection pin 2, in this exemplary embodiment with spacings between the heating wires 5.1-5.5. However, the heating wires 5.1-5.5 are preferably in mutual contact the fastening points 6.1 - 6.5 arranged. The fastenings can, however, also take place one after the other, or the fastening points 6.1-6.5 are distributed circumferentially and axially at the same height as the connecting pin 2. Other types of fastening are also possible.

The finished tubular heating element is sealed at its ends between the connecting pin 2 and the tubular casing 1 by a socket 3.

In order to obtain a compact heater, the straight tubular heating element shown is bent several times or continuously after its completion (not shown). This creates a powerful, compact radiator.

In Fig. 1 the contact between the heating wire coils and the connection pin 2 of the 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 connection pin 2. The connection pin 2 has an end section 2.1, the thickness of which is reduced, i.e. smaller than the remaining part of the connection pin and, in particular, also smaller than the thickness of the connection pin 2 formed contact pins 4 at the opposite end.

The end section 2.1 of the connecting pin 2 protrudes into the heating wire coils 5.1-5.4. Fig. 3 shows a longitudinal section of a portion of FIGS. 2 and 4 shows a cross section to 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 connection pin 2, the heating wire coils can still be squeezed there. As a result, the heating wire 5.1-5.4 is plastically deformed 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 are no longer circular there, but rather flattened somewhat. The common outer contour is reduced by the compression with the reduction of the gaps and the entire connection area is more compact. In this way, the contact area to the connection pin 2 is increased. For a secure connection, the heating wire coils are preferably welded to the end section 2.1 of the connecting pin 2.

In addition, the contacting point can also have an outer sleeve 8 which surrounds the heating wires 5.1-5.4 with the end section 2.1. Before the connection by welding or soldering, compression by squeezing the contact area is also preferably carried out in this embodiment.

Fig. 5 as well as the Figures 6a and 6b show a further example of the contact between four heating wire coils and a contact pin 2. This exemplary embodiment differs from the exemplary embodiment in FIG Figures 2 to 4 essentially in that the end section 2.1 is at least partially pushed into a sleeve 8 from the first side and the ends of the heating wire coils 5.1-5.4 are pushed into the sleeve from the second side, their end faces ideally touching. The sleeve 8 was pressed after it had been pushed on, as a result of which in turn the underlying end sections of the heating wires 5.1-5.4 and the end section 2.1 were plastically deformed, that is to say pressed somewhat flat. In this embodiment too, welding is then preferably carried out for secure contacting.

When using a sleeve 8, an end section of the connecting pin can protrude into the heating coils. In the embodiment shown, the end section 2.1 of the connecting pin 2 does not protrude into the heating wire coils 5.1-5.4, but the end of the connecting pin 2 and the end of the heating wire coils 5.1-5.4 are opposite each other in the sleeve 8 with contact or a small distance. In this embodiment, the contact is preferably made by introducing solder into the sleeve 8. However, soldering is only effective in applications in which the application temperature does not reach the solder melting temperature.

Another example of contacting is in Fig. 7 shown. In this embodiment, only the heating wires 5.1-5.4 are introduced into a sleeve 8 and connected to the sleeve 8, preferably welded. The internal heating wires 5.1-5.4 protrude up 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 connected by resistance welding. The sleeve and the end section 2.1 preferably have similar, extremely preferably the same, outer diameter.

All of the examples shown above of the contact between heating wire coils 5.1-5.4 and the end section 2.1 of the connection pin 2 are preferably implemented in such a way that this contact lies 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 pipe 1. However, it is also possible that the heating wire coils 5.1-5.4 protrude from the jacket pipe 1 and the contact between heating wire coils 5.1 - 5.4 and end section 2.1 takes place outside of the jacket pipe 1, as in the case of Fig. 8 embodiment shown. Since the temperatures outside the jacket tube 1 are by far not as high as in the jacket tube 1, instead of welding, soldering or even just crimping or squeezing can be used to form contacts in this case

List of reference symbols

• 1 jacket pipe
• 1.1 End of the jacket pipe
• 2 connector pin
• 2.1 End section of the connector pin
• 3 socket
• 4 contact pin
• 5.1 Heating wire
• 5.2 Heating wire
• 5.3 Heating wire
• 5.4 Heating wire
• 5.5 Heating wire
• 6.1 Attachment
• 6.2. Attachment
• 6.3 Attachment
• 6.4 Attachment
• 6.5 Attachment
• 7 room
• 8 sleeve
• S pitch of a wire helix
• D _A outer diameter of a wire helix
• d diameter of a heating wire

Claims (14)

Jacketed heating element with a jacket tube (1) and at least one electrical connection pin (2) at both ends (1.1) of the jacket tube (1), with a heating conductor in electrical connection between the connection pins (2) on the inside of the jacket tube (1) Ends (1.1) is arranged and the remaining space (7) in the jacket tube (1) is filled with a powdery or granular metal oxide, in particular magnesium oxide, characterized in that the heating conductor consists of at least 4 heating wire coils (5.1-5.5) connected in parallel . Jacketed tubular heating element according to Claim 1, characterized 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). Jacketed tubular heating element according to Claim 2, characterized in that the end section (2.1) has a reduced thickness. Jacketed tubular heating element according to claim 2 or 3, characterized in that the end section (2.1) protrudes into the heating wire coils (5.1-5.5). Jacketed tubular heating element according to one of the preceding claims 1 to 3, characterized in that at least one of the connecting pins (2) touches the heating wire coils (5.1-5.5) on the front side. Jacketed tube heater according to one of claims 1 to 5, characterized in that the heating wire coils (5.1-5.5) protrude from the jacket tube (1) at at least one end and the connecting pin (2) at at least one end of the jacket tube (1) outside the jacket tube ( 1) contact. Jacketed tubular heating element according to one of Claims 1 to 6, characterized in that the connecting pins (2) are pressed together with the heating wire coils (5.1-5.5). Jacketed tubular heating element according to one of Claims 1 to 7, characterized in that the connecting pins (2) are welded to the heating wire coils (5.1-5.5). Jacketed tubular heating element according to one of Claims 1 to 8, characterized in that the connecting pins (2) each protrude into a sleeve (8) in which they are contacted by the heating wire coils (5.1-5.5). Jacketed tubular heating element according to one of the preceding claims, characterized in that the metal tube (1) has an outer diameter of a maximum of 12 mm. Jacketed tube heating element according to one of the preceding claims, characterized in that the resistance after production along the extended heated length of the jacket tube (1) is less than 1 ohm / m. Jacketed tubular heating element according to one of the preceding claims, characterized in that the alloy of the heating wires (5.1-5.5) has a specific resistance of less than 0.8 ohm mm ² / m, preferably less than 0.4 ohm mm ² / m. Jacketed tubular heating element according to one of the preceding claims, characterized in that the heating wire coils (5.1-5.5) have a relative pitch S _R of 1 or more. Compact heater with at least one tubular heating element according to one of claims 1 to 13, characterized in that the tubular heating element is bent in a helical and / or spiral and / or meandering shape, with at least one bend having at least 90 ° and a central bending radius of at most twice the tubular casing diameter.

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