Heating unit for exhaust system of internal combustion engine

Abstract

The invention relates to a heating unit for an exhaust system of an internal combustion engine, comprising a heating unit housing which can be flowed through by a gas in a main flow direction of the exhaust gas, and a plurality of heating elements which are arranged in the heating unit housing in a meandering shape, each heating element having a plurality of heating sections which are successive in a longitudinal direction of the heating element and are substantially plate-shaped, the heating sections of each heating element which are successive in the longitudinal direction of the heating element are connected to one another by connection sections, each heating element has two connection regions which are arranged at a distance from one another in the longitudinal direction of the heating element, the heating element is conductively connectable in each connection region to a connection region of another heating element or / and to a voltage source, the heating conductor length between the connection regions of each heating element is greater than the extension of the heating element in the longitudinal direction of the heating element between the connection regions thereof, at least two heating elements have substantially the same heating conductor length.

Description

Technical Field

[0001] This invention relates to a heating unit for an exhaust system of an internal combustion engine. The heating unit includes a heating unit housing capable of being traversed by exhaust gas along the main exhaust flow direction and a plurality of zigzag-shaped heating elements arranged in the heating unit housing. Each heating element has a plurality of successively arranged, substantially plate-shaped heating sections along the longitudinal direction of the heating element. The successively arranged heating sections of each heating element along the longitudinal direction are connected to each other by connecting sections. Each heating element has two joint regions arranged at a distance from each other along the longitudinal direction of the heating element. The heating element is electrically connected or connectable to the joint region of another heating element and / or a voltage source in each joint region. The length of the heating conductor between the joint regions in each heating element is greater than the length of the heating element extending along the longitudinal direction between its joint regions. Background Technology

[0002] Such heating units are known from German patent application 10 2020 132 800, which was published later. Summary of the Invention

[0003] The purpose of this invention is to further develop such a heating unit to ensure more efficient and uniform heating of the gas flow guided through the heating unit.

[0004] According to the present invention, this objective is achieved by a heating unit for an exhaust system of an internal combustion engine, the heating unit comprising a heating unit housing through which gas (particularly exhaust gas emitted by an internal combustion engine) flows in the main exhaust flow direction, and a plurality of zigzag-shaped heating elements arranged within the heating unit housing, each heating element having a plurality of substantially plate-shaped heating sections arranged sequentially along the longitudinal direction of the heating element, the heating sections of each heating element arranged sequentially along the longitudinal direction of the heating element being connected to each other by connecting sections, each heating element having two joint regions arranged spaced apart from each other along the longitudinal direction of the heating element, the heating element being electrically connected or connectable to the joint region of another heating element and / or a voltage source in each joint region, and the length of the heating conductor between its joint regions in each heating element being greater than the length of the heating element extending along the longitudinal direction of the heating element between its joint regions.

[0005] The heating unit according to the invention is characterized in that at least two, preferably all, heating elements have substantially the same heating conductor length.

[0006] By providing heating elements with a tortuous or wavy structure, since the overall extension length of the heating element arranged in this tortuous structure along the longitudinal direction of the heating element is significantly smaller than the length of the heating conductor, i.e., the length of the heating element that is not arranged in a tortuous structure but extends in a straight line between its joint areas, it is ensured that a large surface area can be achieved with a relatively small volume to transfer heat to the gas circulating in the corresponding heating element. Thus, a large amount of heat can be transferred to the exhaust system, especially the system area of ​​the catalytic converter located downstream of the heating element, by the heat-absorbing gas, particularly the exhaust gas emitted by the internal combustion engine, and thus it can be quickly brought to the reaction temperature required to perform the catalytic reaction. Since the heating unit constructed according to the invention ensures that each heating element or at least some of the heating elements have substantially the same heating conductor length, and since the resistance of the different heating elements is also designed substantially uniformly, it is ensured that substantially the same amount of heat can be output to the exhaust gas circulating in it when each heating element is heated by the application of voltage, and thus the exhaust flow through the heating unit is heated substantially uniformly in its cross-section.

[0007] In the heating unit according to the invention, each heating element may be constructed of a curved flat strip and has a wide side arranged substantially parallel to the main exhaust flow direction and an end side arranged substantially orthogonal to the main exhaust flow direction. If at least two, preferably all, heating elements have substantially the same, preferably substantially constant, heating conductor width between their respective end sides and / or substantially the same, preferably substantially constant, thickness between their respective wide sides, it supports providing substantially the same resistance in the different heating elements and thus supports heating the gas flow as uniformly as possible.

[0008] In order to adapt the shape of the heating element to the cross-sectional geometry of the heating unit housing, it is proposed that: in at least one heating element, the transverse dimension, which is transverse to the main exhaust flow direction and transverse to the longitudinal direction of the heating element, is substantially constant along the longitudinal direction of the heating element, or / and in at least one heating element, the transverse dimension is variable along the longitudinal direction of the heating element.

[0009] In order to support providing substantially the same resistance even in different shapes of such heating elements, in at least one heating element having a substantially constant lateral dimension, the lateral dimension may be smaller than the maximum lateral dimension of at least one heating element having a lateral dimension that varies along the longitudinal direction of the heating element.

[0010] For electrical contact heating elements, these heating elements may be electrically connected to contact elements in their joint areas, wherein at least two heating elements are electrically connected to one contact element in one of their joint areas and to another contact element in another of their joint areas.

[0011] To obtain a combination of heating elements that are electrically connected in parallel and in series with each other, it is proposed that: in a first group having at least two heating elements, the heating elements are electrically connected to a first contact element in one of their joint regions and to a second contact element in another of their joint regions; and in a second group having at least two heating elements, the heating elements are electrically connected to a third contact element in one of their joint regions and to a second contact element in another of their joint regions.

[0012] To ensure that the gas flow is heated as uniformly as possible, the number of heating elements in the first group can be equal to the number of heating elements in the second group.

[0013] The gas flow can be heated as uniformly as possible by inputting substantially constant heat across the cross-section of the heating unit in the following manner: in at least two, preferably all, heating sections that are directly successive to each other along the longitudinal direction of the heating element have substantially the same, preferably substantially constant, distance between each other along the longitudinal direction of the heating element, or / and in at least two, preferably all, heating sections that are directly successive to each other along the longitudinal direction of the heating element are arranged substantially parallel to each other.

[0014] In order to enable a catalytic reaction to be initiated in the heating unit itself for cleaning the exhaust gas circulating through the heating unit, it is advantageous that in at least one, preferably all, heating element, the exhaust contact surface is provided at least partially with a catalytically active material.

[0015] In order to position the heating element within the heating unit housing, a retaining unit may be provided for electrically insulatingly holding the heating element on the heating unit housing and / or for electrically insulatingly holding heating elements that are directly adjacent to each other in the transverse direction of the heating element's longitudinal direction relative to each other.

[0016] Here, the retaining unit may include a heating unit housing retaining region that substantially surrounds all heating elements in a ring shape, which is made of, for example, an electrically insulating fibrous material, such as ceramic fiber material or the like, and / or the retaining unit may include a heating element retaining region in conjunction with at least one, preferably each heating element.

[0017] In a simple and stable structure, at least a portion of the heating element holding area or all of the heating element holding areas can be constructed as one piece to each other, i.e., constructed as an integral structure or a single-unit structure.

[0018] In order to achieve a simple connection between the heating element and the holding unit, it is advantageous that at least one, preferably each heating element holding area includes two separate sections arranged successively along the main exhaust flow direction.

[0019] The heating element can be positioned in the holding unit in such a way that at least one, preferably each heating element holding region and at least one, preferably each heating element held therein have a form-locking holding portion to hold at least one, preferably each, connecting region of the at least one heating element held therein to prevent movement along the longitudinal direction of the heating element.

[0020] Therefore, at least one, preferably each, form-locking retaining portion may include a plurality of retaining protrusions that are respectively engaged between two directly adjacent connecting sections along the longitudinal direction of the heating element, or / and at least one, preferably each, form-locking retaining portion may include a plurality of retaining protrusions that are respectively engaged between two heating sections connected to each other by the connecting sections.

[0021] To avoid electrical short circuits caused by the retaining unit itself, it is proposed that the retaining unit be constructed of electrically insulating material or / and coated with electrically insulating material, at least in the area where it contacts the heating element.

[0022] In the heating unit constructed according to the invention, at least two, preferably all, heating elements may be arranged side by side transverse to the main exhaust flow direction, or / and at least two, preferably all, heating elements may be arranged in a heating element longitudinal direction that is substantially parallel to each other, or / and in at least one, preferably each, heating element, at least a portion, preferably all, of the heating sections are arranged substantially orthogonal to the heating element longitudinal direction.

[0023] The present invention also relates to an exhaust system for an internal combustion engine, the exhaust system including a heating unit constructed according to the invention, the heating unit being located upstream of an exhaust treatment unit, for example including a catalyst and / or a particulate filter. Attached Figure Description

[0024] The present invention will now be described in detail with reference to the accompanying drawings. In the drawings:

[0025] Figure 1 A cross-sectional view of a heating unit for an exhaust system of an internal combustion engine is shown.

[0026] Figure 2 A cross-sectional view is shown of an alternative embodiment of the heating unit for the exhaust system;

[0027] Figure 3 A partial cross-sectional view shows another alternative embodiment of the heating unit for an exhaust system of an internal combustion engine;

[0028] Figure 4 Different embodiments of the heating element holding region for holding the tortuous heating element in a defined position are shown in its figures a) and b).

[0029] Figure 5 Another partial cross-sectional view of a heating unit with an alternative shaped heating element holding area is shown;

[0030] Figure 6 As shown in its illustrations a) and b), for example in Figure 2 The heating element used in the heating unit retains the area;

[0031] Figure 7 Another cross-sectional view of a heating unit for an exhaust system of an internal combustion engine is shown;

[0032] Figure 8 This diagram shows a holding unit with a heating element holding area provided as an integral structure;

[0033] Figure 9 A schematic diagram of an exhaust system with a heating unit located upstream of the exhaust treatment unit is shown. Detailed Implementation

[0034] See below for reference Figures 1 to 8 Before explaining the implementation details of the heating unit, please refer to... Figure 9 Explain how such a heating unit can be integrated into the exhaust system of an internal combustion engine.

[0035] Figure 9 A portion of such an exhaust system 10 is shown, wherein a heating unit, generally indicated by 14, is arranged in a one-piece or tubular housing 12 assembled from multiple successive parts, and an exhaust treatment unit 16 is arranged downstream relative to the main exhaust flow direction A. The exhaust treatment unit 16 may include one or more catalysts and / or particulate filters and may function, for example, as an oxidation catalyst or the like. If the exhaust treatment unit 16 includes an SCR catalyst, an injector may be provided upstream of the heating unit 14 for introducing a reactant (e.g., urea / aqueous solution) into the exhaust flow guided within the tubular housing 12.

[0036] Through the heating unit 14, when voltage is applied to the heating unit during the start-up phase of the internal combustion engine's operation, heat can be transferred to the exhaust gas if it has a relatively low temperature, and then transported from the exhaust gas toward and to the exhaust treatment unit 16. Therefore, the exhaust treatment unit 16 can be quickly brought to the temperature required to perform the catalytic reaction. Alternatively, a gas flow (e.g., an air flow) can be guided through the tubular housing 12 before the internal combustion engine starts operating, so that heat is transferred in the heating unit 14 to the gas flow and thus also to the downstream successive exhaust treatment unit 16.

[0037] In a first embodiment of such a heating unit 14 Figure 1 As shown. The heating unit 14 includes, for example, a tubular heating unit housing 18, which may be provided, for example, by a tubular housing 12 of the exhaust system 10 itself, or may also be housed therein. Inside the heating unit housing 18, in Figure 1 In the embodiment shown, lateral to and Figure 1 Four heating elements 20, 22, 24, and 26 are arranged in the main exhaust flow direction A orthogonal to the plane of the figure. The heating elements 20, 22, 24, and 26 are constructed using flat strips bent in a zigzag or wavy structure (the flat strips are made of metal or other conductive materials that are heated thereon), and are constructed in a zigzag structure extending longitudinally along the longitudinal direction H of the heating element.

[0038] Such as using Figure 1 As shown in the heating element 20 on the left, each of these heating elements 20, 22, 24, and 26, constructed with a tortuous structure, has multiple plate-shaped heating sections 28 arranged substantially orthogonally to the longitudinal direction H of the heating element, and connecting sections 30 that connect two heating sections 28 that are directly adjacent to each other along the longitudinal direction H of the heating element. The connecting sections 30 provide corresponding vertex regions of the tortuous or wavy structure, and the lateral distance between two directly adjacent connecting sections 30 along the longitudinal direction H of the heating element, which is transverse to or orthogonal to the longitudinal direction H of the heating element, defines the lateral dimension Q of the respective heating element 20, 22, 24, and 26. Figure 1 It can be clearly seen that in the two heating elements 22 and 24 arranged in the central region of the heating unit 14, the lateral dimension Q is basically constant along the longitudinal direction H of the heating element. However, in order to adapt to the curved structure of the heating unit housing 18, the two external heating elements 20 and 26 have a lateral dimension Q that varies along the longitudinal direction H of the heating element. The maximum value of this varying lateral dimension is in the central region of the heating elements 20 and 26 located in the center along the longitudinal direction H of the heating element, and decreases in both directions from this central region.

[0039] As shown by means of heating element 26, each heating element 20, 22, 24, 26 has a connector region 32, 34 at its end region along the longitudinal direction H of the heating element. Each heating element 20, 22, 24, 26 is electrically connected to a plate-like or track-like contact element 36, 38, or 40 via each of its two connector regions 30, 32, 34. For example, the connection can be material-locked, i.e., achieved by brazing, welding, or bonding; or it can be form-locked, i.e., achieved by screws or rivets; or it can be force-locked, i.e., achieved by clamping, pressing, crimping, etc.

[0040] To ensure that no heat is generated in the area of ​​the contact elements 36, 38, 40 due to the current flowing through them, the contact elements 36, 38, 40 may, for example, be provided with a thickness greater than that of the heating elements 20, 22, 24, 26, or in principle, be constructed using a material with low resistance.

[0041] exist Figure 1 In the arrangement shown, two heating elements 20 and 22, arranged side by side, are connected to a contact element 36 in their junction area 32 above the figure, and in their... Figure 1 The connector area 34 arranged below is electrically connected to the contact element 38. Therefore, the two heating elements 20 and 22 form the first group G1 heating elements electrically connected in parallel with each other. Similarly, Figure 1 The two heating elements 24 and 26 shown on the right side of the figure are electrically connected to contact element 40 via their upper connector region 32 and to contact element 38 via their lower connector region 34, thus forming a second group G2 heating element electrically connected in parallel. The heating elements of the two groups G1 and G2 are connected in series. For this purpose, contact elements 36 and 40 are connected or can be connected to the two poles of a voltage source (e.g., a battery or the like in a vehicle) via through-holes that are electrically insulated relative to the heating unit housing.

[0042] The heating elements of the two groups G1 and G2 are constructed substantially identically to each other with respect to the heating elements provided therein. Each group G1 and G2 includes heating elements 22 and 24 having a substantially constant lateral dimension Q, and each group G1 and G2 includes heating elements 20 and 26 having a variable lateral dimension Q. For this purpose, it is advantageous that the two heating elements 22 and 24 having a substantially constant lateral dimension Q are identical to each other, and the two heating elements 20 and 26 having a variable lateral dimension Q are also identical to each other.

[0043] The configuration of the heating elements 20, 22 or 24, 26 selected within groups G1 and G2 supports the same implementation with respect to the resistance present in each group G1 and G2.

[0044] To standardize the resistance, it is also helpful to [address the issue in heating unit 14]. Figure 1 In the structure shown, all heating elements 20, 22, 24, and 26 have substantially the same heating conductor length relative to each other. Due to the zigzag structure of heating elements 20, 22, 24, and 26, the heating conductor length is significantly greater than the longitudinal extension length L of the corresponding heating elements 20, 22, 24, and 26 between their junction regions 32 and 34 along the longitudinal direction H of the heating element. It should be noted that when the corresponding heating elements are in a longitudinally extended configuration, i.e., not provided in a zigzag or wavy structure and, for example, from... Figure 1 When the zigzag structure shown extends from its two joint regions 32 and 34 to its substantially straight structure, the length of the heating conductor is the length of the corresponding heating elements 20, 22, 24, 26 between their respective joint regions 32 and 34.

[0045] Furthermore, this embodiment, in which all heating elements 20, 22, 24, and 26 have the same heating conductor length, also contributes to having substantially the same resistance in each heating element 20, 22, 24, and 26. In particular, this also helps to ensure that, when comparing heating elements 22 and 24 with a constant lateral dimension Q, this lateral dimension Q is smaller than the maximum lateral dimension Q of the two heating elements 20 and 26 with varying lateral dimensions Q, but smaller than the minimum lateral dimension Q of these heating elements 20 and 26 with varying lateral dimensions Q.

[0046] To standardize the resistance of heating elements 20, 22, 24, and 26, it is also helpful to note that, viewed along the main exhaust flow direction A, these heating elements are arranged substantially orthogonally to the end sides 46 and 48 of the main exhaust flow direction (see...). Figure 9 The heating elements 20, 22, 24, 26 have the same and preferably constant width between each other, and all heating elements 20, 22, 24, 26 have the same and preferably substantially constant thickness, i.e., material thickness, between the two wide sides 50, 52 extending between their end sides 46, 48.

[0047] By utilizing this structure of heating elements 20, 22, 24, and 26 (which can be obtained, for example, by bending a blank of conductive flat material that is substantially the same to each other into different bent structures for heating elements 22 and 24 on one hand and for heating elements 20 and 26 on the other hand), it is ensured that substantially the same heating power is generated in the region of each of these heating elements due to the substantially the same resistance of the heating elements 20, 22, 24, and 26, and thus the same heat can be output to the gas flow (e.g., exhaust flow) of the circulating heating elements 20, 22, 24, and 26.

[0048] To further ensure a more uniform distribution of heat to the gas or exhaust flow, it is also helpful that the heating sections 28 of the heating elements 20, 22, 24, and 26 are spaced equidistant from each other. Figure 1 In the illustrated embodiment (where the heating sections 28 in each heating element 20, 22, 24, 26 are arranged substantially orthogonally to the longitudinal direction H of the heating element), the heating sections 28 are arranged parallel to each other and preferably have the same distance from each directly adjacent heating section 28 in all heating elements 20, 22, 24, 26. Furthermore, in the case of heating sections 28 that are not arranged parallel to each other, for example when directly adjacent heating sections 28 are arranged in a V-shape, the corresponding distances can be the same in each pair of directly adjacent heating sections 28, but vary laterally to the longitudinal direction H of the heating element. This also achieves the most uniform possible heat output to the gas flow across the entire cross-section of the heating unit 14, since substantially the same heating power is generated per unit cross-sectional area and therefore substantially the same amount of heat is provided to the gas flow or exhaust flow.

[0049] Before explaining in more detail below how heating elements 20, 22, 24, 26 and contact elements 36, 38, 40 are held in the heating unit housing 18 by means of a holding unit generally indicated by 54, refer to Figure 2 Describe an alternative arrangement for the electrical wiring of heating elements 20, 22, 24, and 26. Figure 2 In the heating unit 14 shown, all four heating elements 20, 22, 24, and 26 are electrically connected within their respective upper connector regions 32 to contact elements 36 covering all four heating elements 20, 22, 24, and 26, while the lower connector regions 34 of all heating elements 20, 22, 24, and 26 are connected to contact elements 38 located at the lower part. Contact elements 36 are connected to or can be connected to one pole of a voltage source via through-holes 42, and contact elements 38 are connected to or can be connected to the other pole of a voltage source via through-holes 44.

[0050] Even when heating elements 20, 22, 24, and 26 are connected in series, the structure of heating elements 20, 22, 24, and 26, as explained in detail above, ensures that heat is output substantially uniformly across the cross-section of the heating unit housing 18 to the gas flow passing through the heating unit housing 18.

[0051] Previous reference Figure 1 The retaining unit 54, as the outermost region, includes a ring that surrounds substantially all heating elements 20, 22, 24, 26 and contact elements 36, 38, and in... Figure 1In the case of 40, the heating unit housing retains region 56. It is constructed, for example, of an electrically insulating fibrous material (e.g., ceramic fiber material or the like) or is constructed as a molded part, and prevents electrical short circuits between different components and the heating unit housing 18, which is constructed entirely of metal material.

[0052] The holding unit 54 also includes five heating element holding regions 58, 60, 62, 64, and 66. For example, the two external heating element holding regions 58 and 66 located in the curved region of the heating unit housing 18 are constructed substantially identically to each other, and the corresponding heating element holding regions 60, 62, and 64 located between the two heating elements 20, 22, 24, and 26 can also be constructed substantially identically to each other.

[0053] Furthermore, the different heating element holding regions 58, 60, 62, 64, 66 can be constructed entirely of electrically insulating materials, such as plastic or ceramic materials, in order to particularly avoid electrical short circuits between heating elements 20, 22, 24, 26 that are directly adjacent to each other, or they can be constructed, for example, of metallic materials, which have an electrically insulating coating (e.g., with ceramic material or the like) at least at the location in contact with a corresponding heating element 20, 22, 24, 26.

[0054] In the circumferential direction, different contact elements 36, 38, 40 are arranged between the circumferential ends of two externally positioned heating element holding regions 58, 66, and the annular structure formed by the heating element holding regions 58, 66 and the contact elements 36, 38 and possibly 40 is surrounded by the previously described annular structure of the heating unit housing holding region 56.

[0055] The heating element holding regions 58, 60, 62, 64, and 66 ensure that not only are the heating elements 22, 24, and 26 held or supported relative to each other or relative to the heating unit housing 18 substantially transverse to the longitudinal direction H of the heating elements, but each heating element 20, 22, 24, and 26 is also held in its respective connecting section 30 to prevent movement, particularly along the longitudinal direction H of the heating unit. For this purpose, the heating element holding regions 58, 60, 62, 64, and 66, in conjunction with each heating element 20, 22, 24, and 26 held or supported therein, each have a form-locking holding portion generally indicated by 68. The form-locking retaining forming part 68, as explained below by different embodiments, ensures that a form-locking structure acting in the longitudinal direction H of the heating elements 20, 22, 24, 26 is generated in the respective connecting sections 30 and heating element retaining regions 58, 60, 62, 64, 66, so that the heating elements 22, 24, 26, 28 do not move substantially in the longitudinal direction H of the heating elements within the region of their connecting sections 30.

[0056] exist Figure 3 In the illustrated embodiment, the corresponding form-locking retaining portion 68 includes a plurality of retaining protrusions 70 that engage between two directly adjacent connecting sections 30. The mutual distance between directly adjacent retaining protrusions 70 along the longitudinal direction H of the heating element substantially corresponds to the extension of the connecting sections along the longitudinal direction H of the heating element or the mutual distance between the heating sections 28.

[0057] like Figure 4 As shown, these retaining protrusions 70 can be constructed continuously along the main exhaust flow direction A, i.e. along the extension direction of the connecting section 30 that is thus retained between the end sides 46 and 48, or they can be constructed as corresponding retaining protrusion sections 70a and 70b, which, for example, only function in the longitudinal regions adjacent to the end sides 46 and 48.

[0058] As will be explained in particular by the heating element holding region 60, the form-locking holding forming portion 68 Figure 5 In the extended or alternative embodiments shown, the retaining protrusion 70 can be provided with a wavy surface structure, particularly in the heating element retaining regions 60, 62, 64 acting between the respective two heating elements, which can be provided by their generally wavy structure. Specifically, the wavy structure of the form-locking retaining forming portion 68... Figure 5 In the embodiments shown, these form-locking retaining formations can be constructed on individual components or layers to be connected to each other or in a single integral component, each providing one of the heating element retaining areas.

[0059] Compare Figure 3 and Figure 5 It can be seen that in the embodiment where the form-locking retaining forming part 68 is provided by a corrugated structure, the support sections 30 of directly adjacent heating elements 20, 22, 24, 26 are misaligned relative to each other along the longitudinal direction H of the heating element, while... Figure 3 In the embodiment shown, the retaining protrusions 70 and the grooves formed therebetween for receiving the corresponding connecting sections 30 are not misaligned relative to each other along the longitudinal direction H of the heating element.

[0060] exist Figure 6In the illustrated embodiment, the form-locking retaining portion 68 shown by the heating element retaining region 58 includes, for example, pin-shaped retaining protrusions 72a, 72b, positioned or shaped such that they engage between the heating sections 28 connected to each other by the connecting sections 30. To achieve this engagement, it is preferable to construct a heating element retaining region having a form-locking retaining portion 68 having two portions 74, 76 sequentially positioned relative to each other along the main exhaust flow direction A. Each portion 74, 76 has retaining protrusions 72a, 72b correspondingly paired with each other. During assembly, these two portions 74, 76 can be led from both sides to the end sides 46 or 48 until the retaining protrusions 72a, 72b occupy... Figure 6 b) is positioned and embedded in the tortuous structure of the heating element 20 shown here.

[0061] For optional or additional retention, a plurality of retaining protrusions 70 may be provided at one of the two portions 74, 76, wherein, as referenced above Figure 4 Each of these retaining protrusions 70 is embedded between two connection segments 30 that are then held by a pair of retaining protrusions 72a, 72b respectively.

[0062] Another alternative implementation of retaining unit 54 is in Figure 7 and 8 As shown in the diagram. Furthermore, the retaining forming portion 54 also includes a heating unit housing retaining region 56, for example constructed of ceramic fiber material or as a molded part made of ceramic material, which annularly surrounds the heating elements 20, 22, 24, 26 and the contact elements 36, 38, 40, and thus generates contact with… Figure 8 Electrical insulation of the heating unit housing not shown in the image.

[0063] In this embodiment, all heating element holding regions 58, 60, 62, 64, and 66 are provided as a single unit, i.e., a monolithic structure. This is to ensure ease of use in this embodiment as well. Figure 7 The retaining protrusions 72a and 72b shown, which are interlocked between corresponding two heating sections 28 connected by connecting sections 30, can also be provided in the overall or individual structure of the heating element retaining sections 58, 60, 62, 64, and 66, as shown in the figure. Figure 6 The structure shown has two successive sections along the main exhaust flow direction A. Each of these two sections is provided with a one-piece or monolithic structure that holds a corresponding portion of each heating element holding region 58, 60, 62, 64, 66.

[0064] A particularly advantageous feature of this overall structure is that grooves for receiving contact elements 36, 38, 40 can be provided, thereby keeping them in a defined position.

[0065] As previously mentioned, advantageously, the heating element holding regions 58, 60, 62, 64, and 66 can be constructed with an electrically insulating material, such as a ceramic material or a glass-ceramic material. Alternatively, the metal substrate can be provided with an electrically insulating sheath, which can also be constructed with a ceramic material, or alternatively, with a glaze layer or a glass-ceramic layer. The heating unit housing holding region 56, which is electrically insulating to the heating unit housing 18, can be constructed as a single piece or in multiple pieces, for example, a ceramic molded part, or can be provided with a fibrous material, such as ceramic fiber material, glass fiber material, mineral fiber material, or can also be provided as a rigid structure made of glass-ceramic.

[0066] In another particularly advantageous extension of the heating unit 14 according to the invention, one or more heating elements 20, 22, 24, 26 may be partially or completely coated with a catalytically active material 78. For example, for this purpose, the conductive structural material may be constructed from a steel alloy with an aluminum content of about 5%, such as 1.4767, and a TWC coating for use with a gasoline engine or a DOC coating for use with a diesel engine may be applied to the metal substrate depending on the application.

[0067] By providing such a catalytic coating, it is ensured that, since it can be directly electrically heated, the temperature at which the catalytic reaction begins can be reached very quickly after a cold start, thereby further significantly reducing the duration for which exhaust gases emitted from the internal combustion engine are released into the environment without a catalytic reaction.

Claims

1. A heating unit for an exhaust system of an internal combustion engine, the heating unit comprising a heating unit housing (18) through which gas flows in the main exhaust flow direction (A) and a plurality of tortuous heating elements (20, 22, 24, 26) arranged in the heating unit housing (18), each heating element (20, 22, 24, 26) having a plurality of plate-shaped heating sections (28) arranged sequentially along the longitudinal direction (H) of the heating element, the heating sections (28) of each heating element (20, 22, 24, 26) arranged sequentially along the longitudinal direction (H) of the heating element being connected to each other by connecting sections (30), each heating element (20, 22, 24, 26) being connected to each other by connecting sections (30), each heating element (20, 22, 24, 26) being connected to each other by connecting sections (30), each heating element (20, 22, 24, 26) being connected to each other by connecting sections (30), the heating elements ... Heating elements (20, 22, 24, 26) have two junction regions (32, 34) arranged spaced apart from each other along the longitudinal direction of the heating element. Each junction region (32, 34) of the heating element (20, 22, 24, 26) is electrically connected or connectable to the junction region (32, 34) of the other heating element (20, 22, 24, 26) and / or a voltage source. The length of the heating conductor between the junction regions (32, 34) of each heating element (20, 22, 24, 26) is greater than the length of the heating element (20, 22, 24, 26) extending along the longitudinal direction (H) of the heating element between its junction regions (32, 34). The characteristic feature is that... - At least two heating elements (20, 22, 24, 26) have the same heating conductor length. - In at least one of the at least two heating elements (20, 22, 24, 26) having the same heating conductor length, the lateral dimension (Q) which is transverse to the main exhaust flow direction (A) and transverse to the longitudinal direction (H) of the heating element is constant along the longitudinal direction (H) of the heating element, and in at least one of the at least two heating elements (20, 22, 24, 26) having the same heating conductor length, the lateral dimension (Q) varies along the longitudinal direction (H) of the heating element.

2. The heating unit according to claim 1, characterized in that, All heating elements (20, 22, 24, 26) have the same heating conductor length.

3. The heating unit according to claim 1 or 2, characterized in that, Each heating element (20, 22, 24, 26) is constructed by means of a curved flat strip and has a wide side (50, 52) arranged parallel to the main exhaust flow direction (A) and an end side (46, 48) arranged orthogonally to the main exhaust flow direction (A). At least two heating elements (20, 22, 24, 26) have the same heating conductor width between their respective end sides (46, 48) and / or the same thickness between their respective wide sides (50, 52).

4. The heating unit according to claim 3, characterized in that, All heating elements (20, 22, 24, 26) have the same heating conductor width between their respective end sides (46, 48) and / or the same thickness between their respective wide sides (50, 52).

5. The heating unit according to claim 3, characterized in that, At least two heating elements (20, 22, 24, 26) have the same, constant heating conductor width between their respective end sides (46, 48) and / or the same, constant thickness between their respective wide sides (50, 52).

6. The heating unit according to claim 1 or 2, characterized in that, In the at least one heating element (22, 24) having a constant lateral dimension (Q), the lateral dimension (Q) is smaller than the maximum lateral dimension of the at least one heating element (20, 26) having a lateral dimension (Q) that varies along the longitudinal direction (H) of the heating element.

7. The heating unit according to claim 1 or 2, characterized in that, Heating elements (20, 22, 24, 26) are electrically connected to contact elements in their junction regions (32, 34), and at least two heating elements (20, 22, 24, 26) are electrically connected to one of the contact elements (36, 38, 40) in one of their junction regions (32, 34) and to another of the contact elements (36, 38, 40) in another of their junction regions (32, 34).

8. The heating unit according to claim 7, characterized in that, In a first group (G1) having at least two of the heating elements (20, 22, 24, 26), the heating element (20, 22) is electrically connected to a first contact element of the contact elements (36, 38, 40) in one of its joint regions (32) and electrically connected to a second contact element of the contact elements (36, 38, 40) in its other joint region (34). In a second group (G2) having at least two of the heating elements (20, 22, 24, 26), the heating element (24, 26) is electrically connected to a third contact element of the contact elements (36, 38, 40) in one of its joint regions (32) and electrically connected to the second contact element of the contact elements (36, 38, 40) in its other joint region (34).

9. The heating unit according to claim 8, characterized in that, The number of heating elements (20, 22) in the first group (G1) is equal to the number of heating elements (24, 26) in the second group (G2).

10. The heating unit according to claim 1 or 2, characterized in that, In at least two heating elements, heating sections (28) that are directly adjacent to each other along the longitudinal direction (H) of the heating elements have the same distance between them along the longitudinal direction (H) of the heating elements, or / and in at least two heating elements (20, 22, 24, 26), heating sections (28) that are directly adjacent to each other along the longitudinal direction (H) of the heating elements are arranged in parallel to each other.

11. The heating unit according to claim 10, characterized in that, In all heating elements, heating sections (28) that are directly adjacent to each other along the longitudinal direction (H) of the heating element have the same distance between them along the longitudinal direction (H) of the heating element, or / and in all heating elements (20, 22, 24, 26), heating sections (28) that are directly adjacent to each other along the longitudinal direction (H) of the heating element are arranged in parallel to each other.

12. The heating unit according to claim 10, characterized in that, In at least two heating elements, heating sections (28) that are directly adjacent to each other along the longitudinal direction (H) of the heating elements have the same constant distance from each other along the longitudinal direction (H) of the heating elements.

13. The heating unit according to claim 1 or 2, characterized in that, In at least one heating element (20, 22, 24, 26), the exhaust contact surface is provided at least partially with a catalytically active material (78).

14. The heating unit according to claim 13, characterized in that, In all heating elements (20, 22, 24, 26), the exhaust contact surface is provided at least partially with a catalytically active material (78).

15. The heating unit according to claim 1 or 2, characterized in that, A holding unit (54) is provided for electrically insulatingly holding the heating elements (20, 22, 24, 26) on the heating unit housing (18), and / or for electrically insulatingly holding heating elements (20, 22, 24, 26) that are directly adjacent to each other in the longitudinal direction (H) of the heating elements.

16. The heating unit according to claim 15, characterized in that, The holding unit (54) includes a heating unit housing holding region (56) that surrounds all heating elements (20, 22, 24, 26) in an annular shape, or / and the holding unit (54) includes a heating element holding region (58, 60, 62, 64, 66) in association with at least one heating element (20, 22, 24, 26).

17. The heating unit according to claim 16, characterized in that, The holding unit (54) is configured to include a heating element holding area (58, 60, 62, 64, 66) in conjunction with each heating element (20, 22, 24, 26).

18. The heating unit according to claim 16, characterized in that, At least a portion of the heating element holding areas (58, 60, 62, 64, 66) are constructed as one piece to each other.

19. The heating unit according to claim 18, characterized in that, All heating element holding areas (58, 60, 62, 64, 66) are constructed as one piece to each other.

20. The heating unit according to claim 16, characterized in that, At least one heating element holding area (58, 60, 62, 64, 66) includes two separately constructed portions (74, 76) arranged successively along the main exhaust flow direction (A).

21. The heating unit according to claim 20, characterized in that, Each heating element holding area (58, 60, 62, 64, 66) includes two separately constructed portions (74, 76) arranged successively along the main exhaust flow direction (A).

22. The heating unit according to claim 16, characterized in that, At least one heating element holding region (58, 60, 62, 64, 66) is provided with a form-locking holding portion (68) in cooperation with at least one heating element (20, 22, 24, 26) therethereby, for holding at least one connecting section (30) of the at least one heating element (20, 22, 24, 26) therethereby to prevent movement along the longitudinal direction (H) of the heating element.

23. The heating unit according to claim 22, characterized in that, Each heating element holding region (58, 60, 62, 64, 66) is provided with a form-locking holding portion (68) in conjunction with each heating element (20, 22, 24, 26) thereby holding each connecting segment (30) of the at least one heating element (20, 22, 24, 26) in order to prevent movement along the longitudinal direction (H) of the heating element.

24. The heating unit according to claim 22, characterized in that, At least one form-locking retaining forming portion (68) includes a plurality of retaining protrusions (70; 70a, 70b) that are respectively engaged between two directly adjacent connecting sections (30) along the longitudinal direction (H) of the heating element, or / and at least one form-locking retaining forming portion (68) includes a plurality of retaining protrusions (72a, 72b) that are respectively engaged between two heating sections (28) connected to each other by the connecting sections (30).

25. The heating unit according to claim 24, characterized in that, Each form-locking retaining part (68) includes a plurality of retaining protrusions (70; 70a, 70b) that are respectively engaged between two directly adjacent connecting sections (30) along the longitudinal direction (H) of the heating element, and / or each form-locking retaining part (68) includes a plurality of retaining protrusions (72a, 72b) that are respectively engaged between two heating sections (28) connected to each other by the connecting sections (30).

26. The heating unit according to claim 16, characterized in that, The retaining unit (54) is constructed of or / and coated with an electrically insulating material at least in the area where it contacts the heating elements (20, 22, 24, 26).

27. The heating unit according to claim 26, characterized in that, The retaining unit (54) is constructed entirely of electrical insulating material or / and uses an electrical insulating material coating.

28. The heating unit according to claim 1 or 2, characterized in that, At least two heating elements (20, 22, 24, 26) are arranged side by side with each other transverse to the main exhaust flow direction (A), or / and at least two heating elements (20, 22, 24, 26) are arranged in parallel heating element longitudinal directions (H), or / and in at least one heating element (20, 22, 24, 26), at least a portion of the heating section (28) is arranged orthogonally to the heating element longitudinal direction (H).

29. The heating unit according to claim 28, characterized in that, All heating elements (20, 22, 24, 26) are arranged side by side with each other transverse to the main exhaust flow direction (A), or / and all heating elements (20, 22, 24, 26) are arranged in parallel longitudinal directions (H) with each other, or / and in each heating element (20, 22, 24, 26), all heating sections (28) are arranged orthogonally to the longitudinal direction (H).

30. An exhaust system for an internal combustion engine, the exhaust system comprising a heating unit (14) according to any one of claims 1 to 29, the heating unit being located upstream of the exhaust treatment unit (16).

31. The exhaust system according to claim 30, characterized in that, The exhaust treatment unit (16) includes a catalyst and / or a particulate filter.

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