WO2017149008A1

WO2017149008A1 - Heating cartridge with a protective tube

Info

Publication number: WO2017149008A1
Application number: PCT/EP2017/054760
Authority: WO
Inventors: Patrick Le Coent; Ulrich Schlachter
Original assignee: Eichenauer Heizelemente Gmbh & Co. Kg
Priority date: 2016-03-04
Filing date: 2017-03-01
Publication date: 2017-09-08
Also published as: EP3424266A1; DE102016111258A1; EP3424266B1

Abstract

The invention relates to a heating cartridge with a protective tube (2), in particular for heating solid cartridges in SCR systems. The heating cartridge (3) is inserted into the protective tube (2) at a distance therefrom, and the protective tube (2) contacts a medium to be heated on the outer face of the protective tube. According to the invention, at least one spring element (6, 66) which contacts the heating cartridge (3) and the protective tube (2) in a heat-conductive manner is inserted into an intermediate space between the heating cartridge (3) and the protective tube (2), and the spring element (6) has at least one surface pressing against the protective tube (2), said pressing surface being pressed elastically against the inner face of the protective tube (2) by the biasing force of the spring element (6, 66) in the assembled state.

Description

Patent application

Heating cartridge with a protective tube

description

The application relates to a heating cartridge, which is arranged in an outer protective tube. Such heating cartridges are required in particular for exhaust gas purification systems (SCR systems), for example for heating tanks containing urea solution, or cartridges containing an ammonia-containing solid or an enzyme, with the aid of ammonia or a urea solution is produced with a desired urea concentration ,

Electric heating cartridges are known, which include a heating element or a PTC element as a heating element. The electrical heating elements are introduced into a metallic cladding tube, wherein the cladding tube is sealed at one end, preferably by a metallic bottom, and at the other end, the connections are led out of the tube. The connection end can also be sealed, for example by a plastic compound. The cladding tube may be, for example, an extruded profile in which ceramic PTC elements are arranged, or a metal tube in which, for example, a heating coil embedded in insulating material is arranged. It is also possible that a thin-walled metal tube surrounds one or more extruded profiles as an additional cladding tube.

In order to be able to exchange such a cartridge interchangeably in a container with a content to be heated, it is also state of the art to introduce the heating cartridge into a surrounding protective tube which is sealed against the container contents, an air gap remaining between the jacket tube and the protective tube , In cartridge heaters in which an internally arranged heating wire is used for heat generation, the heat transfer from the cladding tube to the protective tube usually takes place via radiant heat, which is sufficient in most cases. If, on the other hand, a PTC-based heating element is used to generate heat, this type of heat transfer from the cladding tube to the thermowell is made more difficult because of the PTC element's property that is regulated at higher temperatures. The heat transfer could probably be improved if a good heat conducting material such as magnesium oxide would be filled in the air gap. But then the heating cartridge and the thermowell can not easily take apart again, which is often desired for replacement purposes. For example, in the case of exhaust gas purification systems, which contain cartridge-type, heated solids stores for the reducing agent, the cartridge can be exchanged, but these heated heating cartridges remain in the vehicle. Such solid storage may contain, for example, ammonia salts.

The object of the invention is therefore the improved heat transfer from the heating cartridge to the inside of the protective tube, which is in heat-conducting contact with its outside with the medium to be heated. The problem is solved by a heating cartridge with a protective tube with the features specified in claim 1. Thereafter, the heat transfer from the heating element, for example, directly from an extruded profile or from a min. An extruded profile surrounding cladding tube to the protective tube via the at least one spring element. The fact that pressure surfaces of the spring element are pressed with a biasing force to the inside of the protective tube, a particularly effective heat transfer is given.

In order to facilitate the installation and removal of the heating element, the mind. One spring element in an advantageous development material and / or positively secured to the heating element, for example, on the cladding tube, or protective tube.

In a heating element according to the invention one or more heating elements may be arranged in an extruded profile, which can then be regarded as a cladding tube. It is also possible that at least one extruded profile, which may be made of aluminum, for example, surrounded by a comparatively thin-walled cladding, such as stainless steel, and thus can be additionally protected. Furthermore, it is possible for one or more heating resistors, for example a heating coil, to be arranged in an insulator, for example ceramic powder, embedded in a thin-walled cladding tube.

In addition, the spring element preferably also has contact surfaces, which are pressed against the outside of the jacket tube with a biasing force. This ensures good heat transfer from the cladding tube to the spring element. For example, the spring element have at least one contact surface on the cladding tube, which is pressed in the installed state by the biasing force of the spring element resiliently against the outside of the cladding tube. It is even a narrow, strip-shaped contact surface by the contact pressure sufficient for a good heat transfer.

In an advantageous embodiment, the spring element is configured meander-shaped, with connecting sections in each case the pressure surfaces on both sides connect to the protective tube and to the cladding tube. Preferably, the spring element is configured in a meandering cross-section.

In an extremely preferred embodiment, the distance of the connecting sections increases on both sides of a pressure surface from the middle of the connecting sections to the pressure surface connecting them. This results in Gesamtandruckflächen the cladding tube and / or protective tube, which are larger than the respective half outer or inner surface of Hüll- or protective tube, which causes a particularly good thermal coupling of the tubes to the spring element.

An advantageous development of the invention provides that the at least one spring element is attached to the cladding tube. Preferably, the spring element is attached only at one end to the cladding tube, so that it is movable with its other end relative to the heating cartridge in the longitudinal direction. Alternatively, it may be attached along at least one axial line. But it is also possible that the spring element is held only by clamping, so can move freely relative to the protective tube and the heating element or a cladding tube, for example, to compensate for thermally induced changes in length.

The spring element is preferably made of metal, for example made of sheet metal. Particularly suitable are aluminum-based alloys and copper-based alloys, for example CuSn6 or beryllium copper. The spring element is preferably in one piece. However, multi-part spring elements can increase the heat transfer.

In another advantageous embodiment of the at least one spring element protrude starting from the attached to the cladding pressure surfaces rippen- or tab-like connection areas, which pass into pressure surfaces on the protective tube, which are pressed under pretension on the protective tube. Thus, a spring plate may be slidably pushed onto the cladding tube, which has bent-out tabs whose end portions rest as pressure surfaces under pretension on the protective tube. An extremely advantageous development of the invention provides that several spring elements are in the space between the heating cartridge and the protective tube, For example, in the axial direction widening spring elements which are inserted into one another.

The attachment of the at least one spring element on the cladding tube can be done for example by spot welding or by clamping. In the case of several spring elements, these can also be held in their position by abutting or shape-adapted sections. These sections are preferably located in the region of the pressure surfaces on the cladding tube. Alternatively, it would also be conceivable to attach the at least one spring element to the inside of the protective tube, in which case the rib-like or tab-like connecting regions merge into pressure surfaces on the jacket tube.

In a preferred embodiment, the at least one spring element is reduced in height at at least one end, preferably bevelled. Beveling facilitates the assembly of the heating cartridge, spring element and protective tube. The resulting sharp edges can be crimped or folded. Alternatively, e.g. in the case of a meander-shaped spring element in the end region, the height of the spring element can only be reduced in such a way that it no longer bears under pretension on the cladding tube and / or protective tube. Sharp edges are not so advantageous.

An advantageous development of the invention provides that the immersion heater contains a heating element. For example, a heating insert with at least one PTC element can be arranged inside the cladding tube. The heater insert may include one or more ceramic PTC elements electrically contacted by a contact sheet. A ground contact may be made via a second contact sheet by placing the PTC element (s) are arranged between the two contact plates, or via a heat conducting body. The heater insert may additionally include a positioning frame that positions the heating element (s). In an advantageous embodiment, at least one ceramic PTC element with two contact plates is insulated in an opening of a heat conduction body, or is accommodated between heat conduction bodies made of a good heat conducting material such as aluminum. The heat-conducting bodies are preferably produced as extruded parts. As corrosion protection, the heating element can be incorporated into a cladding made of stainless steel or aluminum. To a good one

To obtain heat transfer between the heating element and the cladding tube, the heating element or the extruded profile may have at least one indentation on an outer side. By a molded-in corresponding indentation on the cladding tube, the cladding tube is contracted around the heating insert or the extruded profile around, whereby an intimate, good heat-transferring contact of heating insert and cladding tube is then given. Alternatively, the heating element can also be introduced under bias into the cladding tube.

It is also conceivable to dispense with a separate cladding tube, whereby the heat conduction then simultaneously represents the cladding tube.

A further advantageous development of the invention provides that the spring element is designed as a corrugated sleeve. The waves can follow each other in the circumferential direction or in the longitudinal direction of the sleeve. In other words, the waves can thus form longitudinal ribs or rings. In each case, the wave crests form contact surfaces on the protective tube, while the valleys between the shafts form contact surfaces on the extruded profile or the cladding tube. The shafts can each be provided with slots. In this way, the spring element can better fit its circumference to a given thermowell or thermally induced expansions and contractions. Preferably, the waves are provided with slots which terminate before the valleys adjacent to the shaft. In this way, the heat coupling to the extruded profile or the cladding tube is not impaired by the slits. At least in the case of the wave design in the longitudinal direction, the wave troughs are preferably designed as pressure surfaces in sections, and thus lie on a defined length in good heat-conducting contact with the heating element. The individual waves are preferably the same shape, but may also be shaped differently, for example, have different amplitudes or wavelengths.

Most preferably, the trough portion has a longitudinal slot. This makes it possible to mount the spring under prestress and thus to achieve an even better heat transfer from the heating cartridge to the spring.

Further advantages, features and details of the invention will become apparent from the claims, the following description of the drawings and the drawings. Identical and corresponding components are identified therein with corresponding reference numerals. Showing:

1 shows a longitudinal section of a container with a protective tube,

2 shows a cross section through an exemplary embodiment of a heating cartridge according to the invention with a protective tube and a container;

3 shows a further embodiment of a heating cartridge according to the invention with spring element, but without protective tube.

4 shows a further embodiment of spring elements of a heating cartridge according to the invention; and

Fig. 5 is a single spring element of the embodiment shown in Fig. 4.

Fig. 1 shows schematically the longitudinal section through a container 1 with a medium to be heated, for example, the solid cartridge of a reducing agent system. In the container 1, a protective tube 2 is attached fluid-tight. In this protective tube 2, a heating element 3 is introduced. Between the protective tube 2 and the heating element 3 is an air gap 4. In the air gap 4, a spring element 6 (shown schematically) is arranged. The spring element 6 is a corrugated sleeve, wherein the waves are formed as elevations 6.1, which in Um- follow each other. The valleys 6.2 between the waves thus extend in the longitudinal direction of the heating element.

At its inner end 6.5, the spring element 6 is chamfered such that the outer diameter of the spring element is smaller than the diameter of the protective tube inside at this point. While in this illustration, the heating cartridge 3 is fixedly connected to a bottom part 5, the container 1 is removable. In the case of a solid cartridge this is removable from the vehicle and thereby rechargeable or exchangeable.

Fig. 2 shows a cross section through the container 1 with protective tube 2 and immersion heater 3, which has a cladding tube 7 on its outer side. In the air gap 4 between the protective tube 2 and cladding tube 7, a spring element 6 is arranged. This spring element is made of metal, for example an aluminum-based alloy or a copper-based alloy, and is designed to be integrally closed here. But also conceivable are several individual segments or versions with a longitudinal slot. The spring element 6 has in this embodiment a meandering shape with pressure surfaces 6.1 on the inside of the protective tube 2 and pressure surfaces 6.2 on the outside of the cladding tube 7. The pressure surfaces 6.1, 6.2 are connected to each other by connecting sections 6.3. The middle of the connecting sections 6.4 is indicated on the left half of the drawing. Starting from this middle 6.4, the distance between adjacent connecting sections 6.3 increases to the connecting this pressure surface 6.1, 6.2 out. As a result, the spring element 6 can advantageously adapt well to the air gap width, and overall pressure surfaces on the cladding tube 7 and protective tube 2 which are larger than the respective outer and inner surfaces of Hüllbzw. Protective tube, which causes a particularly good thermal coupling of the tubes on the spring element 6. Inside the cladding tube 7, a Wärmeleitprofil 8 is arranged, for example, an extruded profile of aluminum or another metal. A ceramic PTC element 9 with two contact plates 10 is insulated by an insulating 1 1 in an opening 12 of the Wärmeleitprofiles 8 added. The PTC Element 9 or the PTC elements can be held by a positioning frame, which can additionally hold one or both contact plates 10. On its outer side, the heat conduction 8 has two indentations 8.1. Formed by corresponding indentations 7.1 on the cladding tube, the cladding tube 7 is contracted around the heat conduction 8 around, whereby an intimate, good heat transfer contact of Wärmeleitprofil 8 and cladding tube 7 is given.

In the exemplary embodiment of Figure 2, the protective tube 2 and the heating element 3 are made approximately round. Other cross sections, e.g. oval or flat but are also conceivable. Likewise, the air gap 4 at different locations may also be different widths.

Fig. 3 shows a further embodiment of a heating cartridge with a spring element 6. Similarly as in the embodiment described above, the heating element 3 has a heating insert with a Wärmeleitprofil 8, for example, an extruded profile of aluminum or another metal, in the one or two contact plates 10 and one or more ceramic PTC elements 9 are used on one or two sides isolated. The one or more PTC elements 9 may be held by a positioning frame 22. The heat conduction 8 is not surrounded by a separate cladding in this embodiment. The Wärmeleitprofil 8 thus forms a cladding tube of the heating element. However, also in this embodiment, a separate cladding tube can be added as in the above embodiment. The end of the Wärmeleitprofils 8 may be sealed, for example by means of a plastic cap, not shown.

The spring element 6 is formed in the embodiment shown in FIG. 3 as a corrugated sleeve, for example as a corrugated tube. In contrast to the embodiment of FIG. 2, the waves are not formed as elevations, which follow one another in the circumferential direction. Instead, the waves are formed as elevations, which follow one another in the longitudinal direction. Each of the waves forms a pressure surface 6.1 for the protective tube and surrounds in the embodiment shown in Fig. 3, the heat conduction 8 annular.

The spring element 6 may have a continuous longitudinal slot 20. Such a longitudinal slot 20 makes it easier to arrange the spring element 6 around the Wärmeleitprofil 8 around. In addition, the longitudinal slot 20 facilitates adaptation to thermally induced changes in length or the insertion into a protective tube, so that the sections between the shafts, so the pressure surfaces 6.2 always keep good thermal contact with the heat conduction 8 and 8, a cladding. For this purpose, the spring element is extremely preferably applied under pretension on the cladding tube. For this purpose, the radius of the pressure surfaces in the relaxed state may be smaller than the cladding tube radius.

The elevations, which form the pressure surfaces 6.1 for the thermowell, not shown in Fig. 3, each have a plurality of slots 21. These slots 21 terminate before the survey each adjacent trough, ie before the pressure surfaces 6.2. The slots 21 divide the elevations and thus also the pressure surfaces 6.1 in several strips, which are oriented in the longitudinal direction of the heating element. The slots 21 thus facilitate the compressibility of the spring element 6 without impairing the thermal contact with the heat-conducting profile 8 or the cladding tube.

The spring element 6 is preferably attached to the heat-conducting profile 8 or the cladding tube at a single end. In this way, the pressure surfaces 6.2 can shift in the longitudinal direction, so that the spring element can adapt to thermally induced changes in length or change its length when introduced into a protective tube.

FIG. 4 shows a possibility of how the spring element 6 of the exemplary embodiment shown in FIG. 3 can be replaced by a plurality of spring elements 66. These spring elements 66 are inserted into each other in the axial direction. FIG. 5 shows one of the spring elements 66 shown in FIG. 4 in a single view. The spring element 66 has an annular base portion, from which resilient spring see go out, which are each attached at one end to the base portion and are free at the other end. When installed, these free ends then lie under pretension on the protective tube. For better assembly, the outermost regions of the free ends can be reduced in their axial height, for example curved away from the protective tube or rolled up. The base portion may be formed as a slotted ring and form a pressure surface 6.2 as described above.

Claims

claims

Heating cartridge with a protective tube (2), in particular for heating solid cartridges in SCR systems, wherein the heating cartridge (3) with distance in the protective tube (2) is inserted and the protective tube (2) on its outside with a medium to be heated in contact stands, characterized in that in a space between the heating cartridge (3) and the protective tube (2) at least one spring element (6, 66) is inserted, which is in heat-conducting contact with the heating cartridge (3) and the protective tube (2), wherein the spring element (6) has at least one pressure surface on the protective tube (2), which is pressed in the installed state by the biasing force of the at least one spring element (6, 66) resiliently against the inside of the protective tube (2).

Heating cartridge with a protective tube (2) according to claim 1, characterized in that the heating cartridge (3) by a cladding tube (7) is surrounded and in a space between the cladding tube (7) and the protective tube (2) the at least one spring element (6 , 66) which is in heat-conducting contact with the cladding tube (7) and the protective tube (2).

Heating cartridge with a protective tube (2) according to one of the preceding claims, characterized in that the at least one spring element (6, 66) is made of metal, preferably of an aluminum-based alloy or a copper-based alloy.

Heating cartridge with a protective tube (2) according to any one of the preceding claims, characterized in that the at least one spring element (6, 66) has a longitudinal slot (20) extending from a first end of the spring element (6, 66) to a second End of the spring element (6, 66) extends.

5. heating cartridge with a protective tube (2) according to any one of the preceding claims, characterized in that the at least one spring element (6, 66) has a plurality of longitudinal slots (21),

6. immersion heater with a protective tube (2) according to any one of the preceding claims, characterized in that the at least one spring element (6) is designed as a corrugated sleeve.

7. heating cartridge with a protective tube (2) according to claim 6, characterized in that the waves are formed as elevations, which follow one another in the circumferential direction.

8. immersion heater with a protective tube (2) according to claim 6, characterized in that the waves are formed as elevations, which follow one another in the longitudinal direction.

9. immersion heater with a protective tube (2) according to claim 7 or 8, characterized in that the elevations each have a plurality of slots (21).

10. immersion heater with a protective tube according to claim 9, characterized in that the plurality of slots (21) which are arranged in one of the elevations, each ending in front of adjacent elevations.

1 heating element with a protective tube (2) according to any one of the preceding claims, characterized in that the spring element (6) is attached at one of its ends to the heating element (3) and the other end in the longitudinal direction relative to the heating element (3) is mobile.

12. immersion heater with a protective tube (2) according to any one of the preceding claims, characterized in that in the intermediate space between the heating cartridge (3) and the protective tube (2) a plurality of spring elements (66) are used.

13. immersion heater with a protective tube (2) according to claim 12, characterized in that the spring elements (66) are inserted into one another.