ELECTRIC HEATING DEVICE

Abstract

The present invention relates to an electric heating device (3) in an exhaust gas system (1), having an outer circumferential, in particular circular, housing (4), wherein a rib structure is arranged in the housing (4), which rib structure can be heated by applying an electric current to it. The rib structure is arranged with rib rows (7) parallel to one another in the housing (4), wherein the parallel-arranged rib rows (7) are arranged such that are electrically connected to one another in series or in parallel.

Description

The present invention relates to an electric heating device in an exhaust gas system according to the features in the precharacterizing clause of claim 1.

To comply with legislation and market and customer expectations, internal combustion engines today are designed for maximum efficiency and therefore produce as little heat as possible.

At variance with this is the rapid heating of the exhaust gas components after a cold start and the maintenance of this temperature range during the usual test cycles in order to ensure optimum reaction conditions for converting harmful exhaust gas constituents into harmless elements.

In catalytic converters, this light-off starts from ca. 180° C., the reaction rate increases with the temperature. Since future licensing restrictions evaluate the exhaust gas composition immediately after a cold start, the light-off temperature should be reached as quickly as possible.

To this end, heating elements are used which enable active thermomanagement of the exhaust gas system within certain limits. These heating elements are currently usually spirally wound from thin sheet metal honeycomb structures (fin structures). The separation of the conductors (honeycomb strands) is ensured by an air gap. The overall design is strengthened by high-temperature soldering. The electrical insulation of the entire heating matrix usually takes place via ceramic pins (support pins), wherein these are pushed into the catalytic converter body.

Such a heating device is known, for example, from EP 2 802 752 B1.

Starting with the prior art, the object of the present invention is to demonstrate a heating device for an exhaust gas system, which can be produced in a cost-effective and simple manner but at the same time provides a highly effective heating power in order to be able to meet future demands for rapid external heating of the exhaust gas flow and to optionally realize creative degrees of freedom in terms of the mutual arrangement of the exhaust gas components.

The above-mentioned object is achieved by an electric heating device in an exhaust gas system having the features of claim 1.

Advantageous design variants are described in the dependent claims.

The electric heating device in an exhaust gas system can also be referred to as an exhaust gas system heating device or, alternatively, as a catalytic converter heating device. It has an outer circumferential, in particular circular, housing. The housing is, in particular, a radially circularly circumferential sheet metal housing, which has, in particular, an outer jacket. This can then be integrated in an exhaust gas system, in particular connected upstream of an exhaust gas post-treatment component, for example a catalytic converter, in the exhaust gas flow direction.

A rib structure is arranged in the housing itself. This rib structure can be electrically heated, i.e. designed for resistance heating. Consequently, the rib structure can be heated by applying an electric current to it. The rib structure or the plates or the plate from which the rib structure is formed can therefore also be referred to as a heating conductor.

Within the scope of the invention, three different design variants of the rib structure are essentially possible.

A first variant provides that the rib plate is formed in one piece and from a single material. The rib plate is preferably formed in one piece and from a single material, but again divided into a carrier plate and a fin plate. As mentioned, these are formed in one piece and from a single material and heat up together as a result of electric resistance heating when a current is applied.

A second variant provides that the fin plate and the carrier plate are produced separately and they are preferably coupled to one another, in particular with material fit, for example by soldering or spot welding. When a current is applied, the current flows through both the fin plate and the carrier plate and they both heat up as a result of the applied current.

A third variant provides that the rib structure is produced in two parts, by a fin plate and a carrier plate. These are preferably in turn coupled to one another. However, when a current is applied, the current flows only through the carrier plate and this heats up as a result of resistance heating. The fin plate coupled to the carrier plate heats up as a result of heat conduction, in particular via the arrangement or coupling points.

Common to all variants is that, owing to the exhaust gas flowing past, the heat of the rib structure is output to the exhaust gas as a result of convection.

Electrical connections are provided. In this case, the electrical connections reach, in particular, through the outer housing so that they can be coupled to corresponding electrical connections outside the housing.

The housing and the rib structure are themselves produced from a steel material. In particular, this steel material is thermally resistant to the occurring exhaust gas temperatures of up to 1000° and above. The rib structure is formed from an electrically conductive steel material, which has a corresponding ohmic resistance so that, when an electric current is applied, the rib structure heats up and the heat is transmitted to the exhaust gas flowing past as a result of the convection which occurs. The exhaust gas post-treatment component on which the thus heated exhaust gas impinges is connected downstream in the flow direction

According to the invention, rib rows are now arranged in the rib structure. These rib rows are arranged locally parallel to one another. The locally parallel-arranged rib rows are electrically connected in series or in parallel. The rib rows are designed to be linear.

According to the invention, owing to mutually parallel-arranged rib rows, it is possible to firstly produce these separately and then insert them into the housing.

The individual rib rows and the ribs in the rib rows can also be referred to as fins or heating fins. As result of the locally mutually parallel-arranged rib rows then being electrically connected to one another in parallel or preferably in series, an optimum current flow is realized such that the rib rows are uniformly heated and a correspondingly uniform heat transfer to the exhaust gas post-treatment component connected downstream takes place.

So that the rib rows themselves can be arranged locally parallel to one another, they can firstly be produced separately and independently from the housing. This is performed on the one hand for a rib row in one-piece and single-material form. However, a carrier plate or a current conductor plate can preferably be formed. A rib layer, also referred to as a fin layer or rib plate, is then arranged on the current conductor plate itself. The coupling can be realized, for example, with material fit by resistance spot welding or by soldering. The current conductor plate itself is formed, in particular, from a material which heats up resistively, i.e. as a result of resistance heating. The heat is then transferred to the fin layer via heat conduction. The fin layer increases the surface area available for the heat transmission and therefore transfers the heat to the exhaust gas flowing past.

All rib rows are likewise on the one hand preferably formed in one piece and from a single material. For example, the current-conducting plate can be bent from a single material in one piece, for example in a meandering manner. A current connection is then provided at the respective ends in the housing, so that a voltage can be applied so that current flows through one current conductor plate for heating purposes.

Alternatively, each rib row can be produced and arranged separately from one another. In this case, a respective rib row is then produced separately. Contact elements and/or spacers are arranged at the ends of each rib row.

The contact element itself can be formed, for example, by a respective contact plate. The contact plate itself ensures a physical contact and, at the same time, also a spacing. However, the contact plate is furthermore formed from an electrically conductive material and therefore serves both as a physical spacer and an electrical connector.

Alternatively, the current-conducting plates can also be elongated at the ends and a respective lug can then be formed, wherein the lugs of two mutually adjacent current conductor plates are coupled, for example via material-fitting coupling. Two neighboring rib rows are therefore electrically connected.

In turn, bracing plates can also be formed as connectors which are, for example, C-shaped in cross-section. These would then be arranged as a third structural part between two rib rows and would connect these electrically to one another.

In addition, spacers can also be formed between rib rows. These spacers are then preferably formed from an electrically insulating material, for example from ceramic. In a preferred embodiment variant, these spacers are coupled to the housing such that they reach fully to partially through it. The spacers are preferably formed as spacer plates or ceramic plates. They protrude inwards in the housing in the horizontal direction between two rib rows and maintain a physical spacing here. At the same time, the ceramic plates reach partially through the housing and have an opening here through which a holding means, for example a wire, is guided. The wire is then coupled to the outer side of the housing so that simplified assembly is possible.

A further essential component part of the invention provides that the longitudinal axis, in the exhaust gas flow direction of the heating element, can be arranged at an angle of greater than 1 degree with respect to the longitudinal axis of the catalytic converter. The angle is preferably greater than 2, in particular 3, degrees, particularly preferably greater than 5 degrees. The angled arrangement should, however, be smaller than 30 degrees overall. This is achieved in that the rib rows are positioned in the housing of the heating element by holding rods themselves. It is therefore possible to fully dispense with holding pins between the heating element and the catalytic converter connected downstream, which is why a problem-free physical decoupling and also any geometrical arrangement can be realized. It is also possible that the housing itself has a different cross-sectional geometry to the catalytic converter. Therefore, ceramic catalytic converters can also be used, upstream of which a heating element is connected.

A holding element is provided in the housing so that the rib rows themselves are arranged in a stationary fixed position in the housing. The holding element reaches through the rib rows for this purpose. In particular, the holding element is formed as a holding rod. Two holding rods are preferably in turn arranged at a parallel spacing from one another in the housing. To this end, the rib rows have, for example, a respective punched hole through which the holding rods reach. The holding rods themselves can be formed from an electrically insulating material, for example from a ceramic material. It is also possible that corresponding sleeves are provided in the rib rows. These are preferably ceramic sleeves. These sleeves are then at a respective spacing. A holding rod then preferably reaches through the sleeves themselves; for example, this holding rod can be formed from a steel material, in particular a stainless high-grade steel material.

Alternatively, it is also possible that respective spacer sleeves themselves reach inside one another and are therefore formed as a modular plug-in system. A plurality of sleeves then form a holding rod.

The sleeves are then pushed inside one another and therefore maintain the mutual parallel spacing of the rib rows whilst also holding the rib row stationary, in particular stationary in the exhaust gas flow direction, in the housing. A type of high-grade steel rivet or high-grade steel sleeve can be placed at the respective ends for the purpose of coupling, for example welding, the spacers to the housing.

So that homogenous heating takes place over the entire cross-section, it is furthermore provided that the rib rows have a varying width in their longitudinal direction. In particular, the width is greater in the region of the holding rod. The holding rod results in a smaller heatable surface area being present in the rib row itself. This would therefore be linked to a lower heat transfer to the exhaust gas in the region of the holding rod. As a result of the fact that the rib row is designed to be larger here in terms of its own width, an equally large area can be provided for the heat transmission. The current conductor cross-section in the rib row is thus likewise designed to be the same. As a result, homogenous heating of the flowing exhaust gas can therefore be realized over the entire cross-sectional area.

In a further preferred design variant, a smaller cross-sectional area is formed, in particular fewer ribs are arranged, in an end region of a respective rib row in relation to a center region. The center region extends over a large proportion of the length of the rib plate itself, preferably over more than 50%, in particular more than 60% and especially preferably over 70%, in particular more than 80% and particularly preferably more than 90% of the length of the rib plate itself. However, the remaining 10% or less in a respective end region then has a smaller area available for the heat transmission compared to the center region. A heat accumulation in the respective end region of the housing can therefore be avoided. It is thus also possible to achieve a more homogenous heating of the flowing exhaust gas over the entire cross-section.

Further advantages and features are described in the following figures. These serve for easy understanding of the invention. In the figures:

FIG. 1 shows a partial detail of an exhaust gas jet,

FIG. 2 shows a perspective view of the inventive heating device,

FIG. 3 shows an enlarged illustration of the rib rows in a partial sectional view,

FIGS. 4 and 5 show schematic illustrations of different couplings of the individual rib rows,

FIG. 6 shows a two-part illustration of the rib rows,

FIG. 7a shows a perspective view analogously to FIG. 2,

FIG. 7b shows a longitudinal sectional view with respect to FIG. 7a,

FIGS. 8a and b show preferred design variants of the inventive heating device,

FIG. 9 shows inventive embodiment variants,

FIGS. 10a to d show a design with the holding rods,

FIGS. 11a and b show different holding rods

FIG. 12 shows spacers, fastened to the housing,

FIG. 13 shows two holding rods made from ceramic; and

FIG. 14 shows an inventive angled arrangement of the heating element and catalytic converter with respect to one another.

FIG. 1 shows a partial detail of an exhaust gas system in an exploded illustration. An exhaust gas post-treatment component in the form of a catalytic converter 2 is illustrated herein. In the exhaust gas flow direction A, a heating coil in the form of a heating device 3 is connected upstream of the catalytic converter 2. This heating coil is wound in a meandering manner, as is known from the prior art. Within the scope of this invention, a meandering path is understood to mean a meandering path or zig-zag path.

An outer housing 4, in which the heating coil is inserted, is furthermore illustrated, and this housing 4 has an electrical connection 5 in order to apply an electric current to the heating coil.

FIG. 2 shows a perspective view of an inventive heating device 3. This has an outer housing 4. The housing 4 is a radially circumferential sheet metal jacket. This can have a small width B in the exhaust gas flow direction A. However, the housing 4 can also be designed to be considerably longer in the exhaust gas flow direction, as illustrated here. Two electrical connections 5 are furthermore provided for applying an electric current to the rib structure 6 arranged in the heating device 3. According to the invention, individual rib rows 7 are arranged in the heating device 3. As seen locally, the rib rows 7 are arranged parallel above one another relative to a horizontal direction H illustrated here.

The individual rib rows 7 are now electrically connected to one another in series so that the electric current flow E, likewise illustrated by a dashed line, is produced in a meandering manner. To this end, contact plates 9 are arranged in the respective end regions 8 of the rib rows 7, which is also illustrated in FIG. 3, which shows an enlarged illustration of the rib rows 7 in a partial sectional view. The contact plates 9 are only arranged between every second rib row 7 in each case, so that the meandering electric current flow E is produced.

So that the rib rows 7 are themselves held in the housing 4, a holding element in the form of a holding rod 10, in this exemplary embodiment in the form of two holding rods 10, is furthermore provided. The holding rod 10 extends through all rib rows 7 relative to the vertical direction V and is coupled to the housing 4 at the top and bottom in each case, as illustrated in FIG. 2. The rib rows 7 are therefore arranged in a fixed position in the exhaust gas flow direction A and at a parallel spacing from one another.

As illustrated in FIG. 3, the holding rod 10 can be formed from a metallic inner rod 11 and, for example, ceramic spacer sleeves 12, wherein a spacer sleeve 12 is itself associated with each rib row 7.

According to FIG. 4 and FIG. 5, different mutual couplings of the individual rib rows 7 are illustrated schematically. As illustrated in FIG. 6, the rib rows 7 themselves are preferably formed in two parts. These have a current-conducting plate 13 and a rib plate 14, also known as a fin plate, arranged thereon. The current-conducting plate 13 and rib plate 14 are then preferably coupled, for example with material fit via a soldering procedure or the like. According to embodiment variants of FIG. 6, two rib rows 7 can be bent in their end region 8 as a result of a bending procedure. Each rib row 7 can also be produced separately. As already mentioned in the description, it is also possible that all rib rows 7 are produced from one piece and are then produced in a bending technique and extend in a meandering manner.

According to FIG. 4, the individual rib rows 7 are coupled to one another in their respective end region 8 via a contact lug 15. This means that the current-conducting plate 13 is designed to be longer, is bent and is coupled one to another, for example, via a spot weld P or the like.

According to the design variant of FIG. 5, the rib rows 7 are coupled to one another in their end regions 8 via a bracing plate 16. This bracing plate 16 is itself formed in a C shape, for example. The bracing plate 16 then connects two rib rows 7 and current-conducting plates 13 to one another in the end regions 8 in each case, but always leaves out a coupling inbetween so that a meandering electric current flow E again results in an electrical series connection of the rib rows 7 here.

FIGS. 7a and 7b show a perspective view—according to FIG. 7a, analogously to FIG. 2 only without showing the current flow. FIG. 7b shows a longitudinal sectional view through FIG. 7a. In the longitudinal sectional view, it can be seen, in particular, that the holding rods 10 are arranged in a fixed position with respect to one another, reaching through the individual rib rows, relative to the vertical direction V. It can likewise be seen that electrical insulation with respect to the housing 4 is present at the electrical connections 5; the electrical connection is consequently connected to the rib structure in a current-conducting manner but is arranged such that it is electrically insulated from the housing 4. The contact plates are, on the one hand, arranged in the respective end regions. Additional spacer plates 17 are arranged between them; an additional spacer plate 17 is arranged for every second rib row 7 in each case. The spacer plate 17 is preferably produced from a ceramic material.

FIGS. 8a and b show a preferred design variant of the inventive heating device 3. In this case, respective rib rows 7 are in turn connected to one another in a meandering manner via a continuous current-conducting plate 13. Alternatively, the connections, already arranged in FIGS. 3, 4 and 5, can also be produced in the end region 8 between two adjacent rib rows 7. However, in this case, the width B of the rib rows 7, as measured in the exhaust gas flow direction A, is designed such that it varies. This means that the width B changes in the longitudinal direction L of the rib rows 7. The width B itself is measured in the exhaust gas flow direction A. The width is therefore designed to be greater in the region of the holding rods 10. The same area is therefore effectively also available in the region of the holding rods 10 so that substantially the same heat transmission can be observed over the entire cross-section of the heating device 3 and an exhaust gas flow which is heated uniformly in cross-section can be generated.

FIG. 9 shows a further inventive embodiment variant. In this case, a continuous current-conducting plate 13 is also folded or bent in one piece. Two rib rows 7 are directed such that they are parallel-facing one another, wherein two layers of the current-conducting plate 13 are subsequently in turn arranged at a spacing from one another, albeit without a rib row 7, in turn followed by two rib rows 7 arranged parallel to one another. This enables simple production during a bending procedure of the rib structure arranged in the housing 4. This is in turn held by the holding rods 10 and connected to the electrical connections 5.

As is shown at least on the right-hand side of FIG. 9, the density of the ribs is designed to be lower in the respective end region 8 of the rib rows 7. A possibly turbulent flow and/or compaction of the flow can result in excessive heating in the end region of the housing 4 here, which can be compensated or avoided by a lower density of the ribs in the end region 8.

FIGS. 10a to d show the design with the holding rods 10, wherein the holding rods 10 are not formed continuously in one piece here, but by respective plug-in sleeves 18. A respective preferred ceramic plug-in sleeve 18 can therefore fix the respective rib row 7 in position with form fit as well as electrically insulate it from another. The plug-in sleeve 18 can therefore function simultaneously as a spacer and as an electrical insulator. A metallic sleeve 19, for example, can be arranged at the ends of the holding rods 10 in order to be coupled to the housing 4. This embodiment variant also has a continuous current-conducting plate 13 between the rib structures. However, this is arranged in a meandering manner in each case, so that a rib row is arranged parallel to the next rib row 7 on the current-conducting plate 13 in each case. The spacer sleeves 12 can therefore be inserted during the folding procedure and are held by the mutually bent rib rows 7 themselves. The overall structure can then be subsequently inserted into the housing 4 and fixed in position with form fit by the sleeves 19.

FIGS. 10b, c and d show a respective longitudinal sectional view, perspective top and bottom view of such a rib row 7. The rib row 7 has a current-conducting plate 13 and a rib plate 14. Indicated therein are the spacer sleeves 12 as ceramic sleeves, which simultaneously realize electrical insulation as well form-fitting positional fixing.

The current-conducting plate 13 and the rib plate 14 according to the overall invention can be formed from a high-grade steel material, which preferably has a thickness or wall thickness of 0.1 to 0.2, in particular 0.15 mm.

In contrast, FIGS. 11a and b show an embodiment variant in which a respective rod 11 is formed such that it reaches through the rib rows 7 in one piece. Respective spacer sleeves 12 are arranged as electrical insulators here, which spacer sleeves space the individual rib rows 7 with respect to one another with form fit and electrically insulate them from one another.

FIG. 12 shows a further design variant of the present invention. In this case, contact plates for the respective rib rows 7 are arranged in the end region, specifically between every second rib row 7. Spacer plates 17, as ceramic plates, are then furthermore also arranged between every second rib row 7 in each case. They are arranged here such that they reach partially through the housing 4 and have a hole so that they are reached-through outside the housing 4 and are held in a fixed position by means of a weld spot 21. The spacer plates 17 can therefore be subsequently inserted into the housing 4 and fixed in position here with form fit.

FIG. 13 shows a further design variant of the invention. The respective rod 11 is formed as a ceramic rod here, so that is arranged holding the rib rows 7 at a spacing with form fit but, at the same time, from in electrically insulating fashion. The entire product can be produced separately, consequently the rib structure and then are inserted into the housing. Pre-assembly can also take place and then overall soldering of the entire structure can take place in a soldering device.

FIG. 14 shows a further essential advantage of the invention, according to which an angled arrangement is geometrically decoupled and possible in any desired manner within the scope of this invention. To this end, the heating device 3 can be arranged with its longitudinal axis 22 at an angle α of greater than 1 degree with respect to a longitudinal axis 23 of the catalytic converter 2 or the exhaust gas post-treatment component. This gives a greater creative degree of freedom in terms of the path of the exhaust gas system 1, for example in the underfloor region of the motor vehicle. This yields advantages in terms of making optimum use of the installation space for axle-component transmissions, components or an internal combustion engine. As a result of the physical decoupling of the heating device 3 and exhaust gas post-treatment component, the angled arrangement can be freely selected, as is illustrated in FIG. 14.

LIST OF REFERENCE SIGNS

1—Exhaust gas system

2—Catalytic converter

3—Heating device

4—Housing

5—Electrical connection

6—Rib structure

7—Rib rows

8—End region of 7

9—Contact plate

10—Holding rod

11—Rod

12—Spacer sleeve

13—Current-conducting plate

14—Rib plate

15—Contact lug

16—Bracing plate

17—Spacer plate

18—Plug-in sleeve

19—Sleeve

20—Wire

21—Weld spot

22—Longitudinal axis of 3

23—Longitudinal axis of 2

A—Exhaust gas flow direction

H—Horizontal direction

V—Vertical direction

E—Electric current flow

L—Longitudinal direction of 7

B—Width

P—Spot weld

Claims

1-13. (canceled)

14. An electric heating device in an exhaust gas system, the electric heating device comprising: an outer circumferential housing; anda rib structure arranged in the housing, whereinthe rib structure is heatable in response to an electric current applied thereto,the rib structure comprises a plurality of rib rows parallel to one another in the housing,each rib row of the plurality of rib rows comprises a plurality of ribs, andthe plurality of rib rows are electrically connected to one another in series or in parallel.

15. The electric heating device according to claim 14, wherein the housing comprises a radially circumferential lateral surface.

16. The electric heating device according to claim 14, further comprising at least one holding element holding the plurality of rib rows in the housing.

17. The electric heating device according to claim 14, wherein the plurality of rib rows are parts of a continuous sheet metal strip.

18. The electric heating device according to claim 14, further comprising an electrically conductive connecting element arranged in a respective end region of each rib row of the plurality of rib rows.

19. The electric heating device according to claim 18, wherein the connecting element comprises a contact plate.

20. The electric heating device according to claim 14, further comprising an electrically insulating spacer arranged in a respective end region of each rib row of the plurality of rib rows.

21. The electric heating device according to claim 20, wherein the spacer is coupled to the housing.

22. The electric heating device according to claim 14, wherein a width of each rib row of the plurality of rib rows varies along an exhaust gas flow direction.

23. The electric heating device according to claim 16, wherein each rib row of the plurality of rib rows has a widened region through which the at least one holding element extends.

24. The electric heating device according to claim 23, wherein the at least one holding element comprises a plurality of plug-in sleeves coupled together.

25. The electric heating device according to claim 14, wherein each rib row of the plurality of rib rows comprises an electric conductor plate and a rib plate coupled to the electric conductor plate.

26. The electric heating device according to claim 25, wherein, in each rib row of the plurality of rib rows, fewer of the ribs are arranged in an end region of the rib plate than in a center region of the rib plate, wherein the center region extends over a majority proportion of a length of the rib plate.

27. The electric heating device according to claim 14, wherein the housing is circular.

28. The electric heating device according to claim 16, wherein the at least one holding element comprises two holding rods which extend through the plurality of rib rows.

29. The electric heating device according to claim 18, wherein the connecting element comprises a contact lug.

30. The electric heating device according to claim 18, wherein the connecting element comprises a bracing plate.

31. The electric heating device according to claim 20, wherein the spacer comprises a ceramic plate.

32. The electric heating device according to claim 20, wherein the spacer is coupled to the housing, and the spacer extends partially through the housing.

33. An electric heating device in an exhaust gas system, the electric heating device comprising: an outer circumferential housing; anda rib structure arranged in the housing, whereinthe rib structure is heatable in response to an electric current applied thereto,the rib structure comprises a plurality of rib rows parallel to one another in the housing,each rib row of the plurality of rib rows comprises a plurality of ribs, anda longitudinal axis of the heating device is arranged at an angle of greater than 1 degree with respect to a longitudinal axis of an exhaust gas post-treatment component in an exhaust gas flow direction.