Shielding

Abstract

The invention relates to a shield (2) comprising at least two components (4, 5) which are designed to be connected to one another linearly adjacent to one another at at least one separating surface (6) in order to surround a three-dimensionally shaped contour or pipe (R) of an exhaust gas line (1) of an internal combustion engine over a length in the case of use. In order to modify the shield with further positive features while increasing its effect, it is proposed that the components (4, 5) of the shield (2) each include at least one electric heating system (3) which, in the installed position, is thermally directed toward the pipe (R) to be surrounded.

Description

Technical Field

[0001] The invention relates to a shielding element comprising at least two components which are designed to be connected to one another adjacent to one another at at least one separating surface in order to surround a three-dimensionally shaped contour or pipe element of an exhaust gas line of an internal combustion engine over a length in the case of use. Background Art

[0002] From the prior art, a variety of additional parts are known for arranging the shield as a closed housing or shell around a contour. In addition to the use of cut sleeves and segmented shields in the form of half or partial housings, a shield is provided in particular according to EP 1 702 803 B1 and with reference to its disclosure. By means of a shield designed in this way, relatively hot areas of the exhaust gas line, preferably in the vicinity of the internal combustion engine, are thermally shielded from adjacent sections and / or aggregates. In the assembly step, a cross-sectional contour that deviates from a circular shape can also be enclosed quickly and process-reliably.

[0003] The trend towards a more compact design of motor vehicle drives with internal combustion engines provides preferred areas of application for such shields along different sections of the exhaust gas line, from elbows heated to about 1100° C. to turbochargers and up to catalytic converters. Shields of this type are particularly advantageous in this regard due to their ease of assembly during production and good maneuverability during repairs due to their low dead weight with very few tools or other aids.

[0004] It is also known to construct shields alternatively or additionally for heat insulation, in particular by design of the outer surface and / or structure and filler material of the inner part, in order to reduce the radiation of sound. The shields are used alternatively or additionally to reduce the noise load, for example by means of corrugated outer surfaces and / or roughened outer surfaces. In the following, no distinction is made between shields with heat insulation and / or sound insulation. Summary of the invention

[0005] The object of the present invention is to improve a shield of the generic type with further positive features while increasing its effectiveness.

[0006] According to the invention, the object is achieved by the features of embodiment 1, namely that the components of the shielding element each include at least one electric heating system which is directed thermally toward the contour to be surrounded in the installed position. According to the invention, a known shielding element which is used as a finished component in an exhaust gas line is expanded so that it can be heated in a targeted manner in the area with the heating system. The known shielding element can only block the radiation of heat and / or sound, but according to the invention, it is additionally achieved by the known and usually existing components that the contour in the area defined by the heating system can be heated in a targeted manner while surrounding the pipe in a targeted manner independent of its cross-sectional shape. The heating can be easily electrically regulated in a manner familiar to the skilled person under the supply of the onboard power supply, so that the desired temperature can be reliably regulated. This combination results in an advantageous composite body which consists of a shielding element which has a blocking effect and an electric heater arranged therein.

[0007] Advantageous variants are the subject of the subordinate embodiments. The two components are thus connected via at least one bending line. This can significantly simplify assembly, since the number of components is reduced and their orientation relative to one another is clearly visible and indicated in advance during assembly.

[0008] In a preferred embodiment of the present invention, the bend is implemented as an omega-shaped crimp in the shield. In addition to the lower mechanical resistance when closing the shield during assembly, this type of crimp also provides additional space, for example, to safely and reliably accommodate and protect the electrical leads of the electric heating system.

[0009] According to a basic variant of the invention, the heating system is designed as a resistive conductor which is electrically insulated from the contour and has a meandering course extending over a length. Compared to other conductive structures, such as planar conductors or conductor networks, metal wires generally have the advantage of good deformability when designed as 3D structures. The meandering course of the heating wires allows for a uniform heat introduction and thereby a distribution that is as uniform as possible on a plane, without the plane influencing the deformability of the structure only insignificantly.

[0010] Preferably, the electrical insulation surrounds the resistance conductor. Thus, when the resistance conductor for improving heat transfer is arranged directly on the surface of the pipe, which is usually made of metal, an electrical short circuit through the pipe can also be excluded in this case.

[0011] In a variant of the invention, the insulation of the resistance conductor is designed in the form of a fabric, textile, braid or knit. When the thickness is 0.1 to 0.6 mm, the insulation is provided with fibers of a material with good electrical insulation or fibers of a mixture of high-performance thermal materials. The electrical insulation of the resistance conductor is alternatively or additionally designed as a ceramic coating, in particular as a coating formed by immersion in an emulsion or by spraying and subsequently thermally solidified.

[0012] The resistance conductor and the connected electrical energy supply are designed in such a way that, via the electrical insulation, they can heat the adjacent pipe as part of the exhaust gas line to approximately 200° to more than 550° C. As a result, the exhaust gas guided through the pipe can also be heated to a temperature above the limit temperature, from which the downstream catalytic converter can operate effectively during a cold start of the internal combustion engine. As a result, strict emission limit values ​​can also be adhered to.

[0013] The heating system of the component is preferably fastened in or on a heat barrier of the shield, wherein the barrier comprises, in the direction opposite to the pipe to be enclosed or outward, a mat of thermally poorly conducting fibers, in particular glass and / or ceramic fibers, thereby improving the heat flow from the heating system to the pipe to be heated.

[0014] In a preferred embodiment of the present invention, the heating system is fixed by sewing, needling and / or stapling the heating system in, on and / or with the fiber material of the heat barrier part.

[0015] At least one branch of the electric heater is advantageously fixed in one of the multiple sub-housings of the shielding device that are connected to one another in an articulated manner. In the installed position, the electric heating system surrounds the corresponding section of the exhaust gas line without the heating system having to be wound around this section. As an integral component of the shield, the electrically insulated resistance conductor is simply held and closed around the relevant pipe part by the shield.

[0016] According to a variant of the invention, multiple heating systems of the shielding component are provided and / or a cascade of individual heating powers is provided within each heating system. These cascades of heating powers are realized by disconnectable heating systems in the shielding component and / or by disconnectable resistor branches within the heating systems.

[0017] In one embodiment of the invention, in order to regulate the respective thermal work to be output, means for switching on and regulating the current through the electric heating system are provided, in particular electronic switches for generating pulse width modulation of the current through selected branches of the electric heating system.

[0018] According to the invention, the electric heater is integrally embedded in the shielding device, so that it can be safely and easily arranged on the section of the exhaust gas line and can also be retrofitted. In the use of a heat-blocking collar, such a shield is designed so that, when the electrical insulation of the relevant section of the exhaust gas line is sufficient, good thermal contact is produced for the electric heating system in the installation location. This allows a configuration to be achieved in a simple and reliable manner, as disclosed, for example, in DE 10 2018 117 049 A1. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The following text further describes other features and advantages of the embodiments according to the present invention in combination with examples and with the aid of drawings. In the schematic diagram:

[0020] Figure 1 A perspective view showing the shield in the installed position cut in plane AA;

[0021] Figure 2 Show Figure 1 An enlarged view of the AA portion;

[0022] Figure 3 Show Figure 1 An enlarged view of another part of BB, and

[0023] Figure 4 A perspective view of a section of an exhaust gas line of a diesel internal combustion engine known from the prior art is shown in a compact form with a Figure 1 Section AA of a shield implementation scheme in FIG.

[0024] The same reference numerals are always used for the same elements across the various figures. In the following text, only one use case of the shield according to the invention as a component of the exhaust gas line of a diesel internal combustion engine of a motor vehicle is shown and explained, but this does not restrict the invention. However, it is obvious to the person skilled in the art that other application scenarios with advantageously regulated temperature control can be adapted in the same way by means of the enclosed shaped contour or component, in particular in the exhaust gas line of an Otto internal combustion engine, or in optional sub-areas of the drive unit and other application scenarios, in which the rated temperature must be reached and / or maintained in a very short time and at the same time a barrier to the various environments must be provided. DETAILED DESCRIPTION

[0025] The above description of the solution according to the invention thus includes in particular the various combinations of features defined by the embodiments which are subsequently numbered consecutively:

[0026] 1. A shield (2) comprising at least two components (4, 5) which are designed to be connected to one another adjacent to one another at at least one separating surface (6) in order to surround a three-dimensionally shaped contour or pipe (R) of an exhaust gas line (1) of an internal combustion engine over a length in the case of use,

[0027] in,

[0028] The components (4, 5) of the shield (2) each include at least one electric heating system (3) which, in the installed position, is directed thermally toward the pipe (R) to be surrounded.

[0029] 2. The shielding element according to the preceding embodiment, wherein the two components (4, 5) are connected via at least one bending line (7).

[0030] 3. The shielding element according to the preceding embodiment, wherein the bending line (7) is implemented as an omega-shaped bead.

[0031] 4. A shielding member according to any one of the preceding embodiments, wherein the heating system (3) is constructed as a resistive conductor (8) electrically insulated relative to the pipe (R), having a meandering curve extending in the exhaust gas flow direction over a length (L).

[0032] 5. The shield according to the preceding embodiment, wherein the resistive conductor (8) is provided with an electrical insulation (9).

[0033] 6. The shield according to the preceding embodiment, wherein the electrical insulation (9) of the resistor conductor (8) is constructed in the form of a fabric, textile, braid or knit.

[0034] 7. A shield according to any one of the two preceding embodiments, wherein the electrical insulation (9) of the resistance conductor (8) is provided with fibers consisting of a mixture of glass, silicate or high-performance thermal materials when the thickness of the insulation layer is approximately 0.1 to approximately 0.6 mm.

[0035] 8. A shield according to any of the preceding embodiments, wherein the resistance conductor (8) and the connected electrical energy supply are configured to heat an adjacent pipe as a component of an exhaust gas line to approximately 200° to above 550° C. via an electrical insulation (9).

[0036] 9. The shielding element according to any of the preceding embodiments, wherein the heating system (3) of the component (4, 5) is fixed in or on the heat barrier (10) of the shielding element (2).

[0037] 10. A shielding element according to the preceding embodiment, wherein the heating system (3) is fixed in or on the heat-blocking portion (10) of the components (4, 5) of the shielding element (2) by sewing, needling and / or stapling.

[0038] 11. The shielding element according to any of the preceding embodiments, wherein at least one branch (Z) of the electric heating system (3) is fixed in a partial housing of a plurality of partial housings of the shielding device that are articulated and connected to one another.

[0039] 12. A shielding element according to any of the preceding embodiments, wherein a plurality of heating systems (3) are provided for the components (4, 5) of the shielding element (2), and / or a cascade of respective thermal powers is provided within each heating system (3) through disconnectable heating systems (3) and / or disconnectable branches (Z) of the heating systems (3).

[0040] 13. The shielding element according to any of the preceding embodiments, wherein, in order to adjust the respective thermal work to be output, means for switching on and adjusting the current through the electric heating system (3) are provided.

[0041] 14. A shielding part according to any of the preceding embodiments, wherein a flange (F) is constructed in the area of ​​the separation surface (6) on the external surface (O), which is used to safely and reliably fix the shielding part (2) in a closed state around the tube (R).

[0042] Figure 4 A simplified diagram shows a perspective view of a section of an exhaust gas line 1 of a diesel internal combustion engine in compact form, which is currently used, for example, for a 2.0-liter diesel internal combustion engine for a passenger car according to the Euro VI standard. For thermal protection of adjacent assemblies and to reduce sound radiation, the section has been completely surrounded by a shield 2, the visible outer surface O of which is designed in a manner not shown for reducing sound radiation. In the flow direction of the exhaust gas flow G, in the section of the exhaust gas line 1 shown between the inlet E and the outlet A as system boundaries, a diesel oxidation catalyst DOC, a urea injector H with corresponding measuring sensors, a mixing section connected in a pipe R, and a combination of a diesel particulate filter SDPF coated with a selectively reducing catalyst and a selectively reducing catalyst SCR are passed through one after another in a small space.

[0043] In the course of tests, it was surprisingly clear that the pipe R enclosed here by a dashed line or the mixing section as a support for the urea injector H is of particular importance for reducing pollutant emissions, especially during cold starts of motor vehicles. The section of this pipe R downstream of the diesel oxidation catalyst DOC and upstream of the diesel particulate filter SDPF coated with a selectively reducing catalyst is now only provided with at least one electric heating system 3 on the outside over a certain length L in order to bring the exhaust gas flow G to a minimum temperature of approximately 200° C., which is necessary for denitrification in the subsequent urea conversion state. This avoids any changes within the exhaust gas line shown or changes within only one component. The new functional feature of targeted heatability has been incorporated into the existing shielding 2.

[0044] Figure 1 Shown in the installation position as Figure 4 A perspective view with a cross section of an embodiment of a correspondingly extended shielding element 2 with an enlarged part. In order to surround the pipe R with a cross-sectional profile that deviates significantly from a circle in a manner suitable for mass production and by means of the shielding element 2 that acts as a barrier, the shielding element 2 here consists of two parts 4, 5, which are connected to one another as half-shells and each carry an electric heating system 3. The parts 4, 5 are shaped so that in the illustrated application case they are connected to one another adjacent to one another at a separation surface 6 and completely surround the three-dimensionally shaped pipe R. As a result, a number of heating systems 3 corresponding to the parts 4, 5 also surround the pipe R, without having to wrap the pipe R around, for example, with resistance wires or the like. On the outside, wrapping the pipe R around is not process-reliable and cannot be realized within an acceptable production time. Internal installation is excluded as an intrusion into an existing system that includes mutually coordinated accessories from different manufacturers. Without intruding into the described system, the mounting of the components 4 , 5 carrying the heating system 3 of the present exemplary embodiment of the shielding element 2 does not differ from the previously known installation of the shielding element 2 having a barrier effect on the shielding line 1 .

[0045] exist Figure 1 On the shielding element 2 of FIG. 1 , the outer surface O of the shielding element 2 in the region of one of the two separating surfaces 6 transforms into a bending line 7, via which the half-shell parts 4, 5 are connected to each other in an articulated manner by means of an omega-shaped bead 7 as a hinge. When the shielding element 2 is closed around the pipe R during assembly, the bead 7 is characterized by a lower mechanical bending resistance and provides additional space, for example, to safely and securely accommodate and protect the electrical leads of the heating system 3, which is not further illustrated in the figure. Opposite the bead 7, a flange F is formed in the region of the separating surface 6 on the outer surface O, which flange is used to securely fix the shielding element 2 in the closed state around the pipe R.

[0046] In the present exemplary embodiment, the separating surfaces 6 all lie in a plane which also extends centrally through the inlet and outlet regions B of the tube R. This plane thus forms a mirror surface of the shield 2, the components 4, 5 being designed as half-shells in mirror-image fashion to one another in the particular case shown.

[0047] Each of the semi-shell components 4, 5 comprises a plurality of branches Z, which are individually controllable components of the electric heating system 3, which in the arranged installation position is directed to the contour to be surrounded or the pipe R for intensive heat introduction. Each branch Z of the heating system 3 comprises at least one resistance conductor 8 electrically insulated from the pipe R, which has a section extending over a length L in the flow direction of the exhaust gas flow G or has a meandering section. For this purpose, the resistance conductor 8 is surrounded by an electrical insulation 9 in the form of a fabric, which consists of temperature-resistant glass fibers and / or ceramic fibers. In order to improve the heat conduction from the resistance conductor 8 into the pipe R, the electrical insulation 9 is selected to be as thin as possible.

[0048] In order to permanently prevent the movement of a part of the resistance conductor 8 or to prevent the movement of a part of the branch Z, the heating system 3 or its branch is fixed in the parts 4, 5 of the shield 2 and / or on the heat barrier 10 of the shield 2. The fixing of the heating system 3 is achieved by sewing, needling and / or stapling in or on the heat barrier 10 of the parts 4, 5 of the shield 2. In one embodiment, the resistance conductor 8 is located on the heat barrier 10 and is covered by a seam along its center axis or is roughly sewn. In another embodiment, point-shaped sewing is also sufficient, so that the seam is essentially perpendicular to the meandering course of the resistance conductor 8. It is also sufficient to indirectly fix the resistance conductor 8 by fixing the insulation 9 consisting of fibers to the heat barrier 10 through the electrical insulation 9 consisting of fibers of the resistance conductor 8, for example by some kind of winding. When forming the barrier in the form of a mechanically loadable shaped part, in an embodiment not further shown, the following procedure is adopted, namely, when the thickness of the insulation layer is approximately 0.1 to approximately 0.6 mm, the thermal barrier 10 together with the at least one resistance conductor 8 with fiber insulation 9 is wetted with an emulsion, and the thermal barrier 10 and the at least one resistance conductor 8 with fiber insulation 9 are connected to each other via a ceramic structure, which is constructed by a temperature control process immediately after the forming process.

[0049] Figure 2 Show Figure 1 This is an enlarged view of the AA section. Figure 1and Figure 2 , a schematic construction of a one-piece shield 2 with adjacent branches Z of a heating system 3 is shown, which are connected to one another in an articulated manner by means of an omega bead 7. Due to its structure, the omega bead 7 forces the two parts of the heat barrier 10 to form a butt joint and thereby closes any heat dissipation that would otherwise be possible. The omega bead 7 simultaneously provides space in which the leads (not shown further here) to the branches Z of at least the associated heating system are enclosed and guided securely.

[0050] In the installed state, a further separating surface 6 is located opposite the omega-shaped bead 7. After installation during production, the separating surface 6 is closed around the tube R and mechanically permanently connected, for example by welding, riveting, clamping, gluing or the like.

[0051] Figure 3 Show Figure 1 The arrangement can also be applied to a two-part housing system or a multi-part housing system, wherein, after assembly, the adjacent separating surfaces 6 on the outer surface O extend flatly outward to form a flange F and are mechanically and permanently connected in the manner and method given above.

[0052] The shielding element 2 described above can be designed for application temperatures up to 900° C. and can also be used for temperatures up to about 1500° C. at least temporarily if necessary. In the illustrated embodiment, the integrated heating system 3 has a thermal power of about 1.5 kW to 5 kW when the supply voltage is 12 V or 48 V. With a diameter of 20 mm to 500 mm, the shielding element 2 can have a shape with maximum freedom in relation to its cross section. The total length L to be heated should be less than 1000 mm. The heat barrier 10 has a layer thickness of about 5 mm and is surrounded by a metal outer surface of stainless steel or aluminum with a thickness of about 0.4 mm. The metal outer surface is provided with an embossed structure in order to adjust the special acoustic properties.

[0053] The system according to the invention is usually assembled in multiple parts in a symmetrical arrangement. As described above, this is possible, for example, with partial housings. In some applications, in addition to the solution with two separate half housings, a one-piece solution is also possible, which connects more than two partial housings on the other side of the separation surface 6 to each other essentially straight or also linearly and only with minor shape deviations, for example, by a plurality of omega-shaped beads in the form of joints or hinges of the type taught in EP1702803B1.

[0054] Across the entire exhaust gas line 1, different areas upstream of the catalytic converter and / or different areas around the catalytic converter can be electrically heated separately and independently of one another in a controllable manner during simple assembly. The assembly can be carried out in successive sections, which are then usually connected to one another in a known manner via clips, which are also used for fixing to the floor of the motor vehicle. The conversion can also be carried out on an already existing exhaust gas line and, in the advantageously almost unchanged assembly on the exhaust gas line, no structural changes in the exhaust gas line itself need to occur. Externally, in these embodiments, only switching elements and regulating elements for regulating and controlling the electrical energy to be supplied and its distribution on the branch Z, which has an ohmic thermal resistor or a heating wire, need to be provided.

[0055] Reference numerals list

[0056] 1 Exhaust pipe

[0057] 2 Shielding

[0058] 3 Heating system

[0059] 4 Components

[0060] 5 Components

[0061] 6 Separation surface

[0062] 7 bend lines (omega-shaped curling)

[0063] 8 Resistor Conductor

[0064] 9 Electrical insulation

[0065] 10 Heat barrier

[0066] A Exit

[0067] B The inlet area and outlet area of ​​the pipe R

[0068] E entrance

[0069] F Flange

[0070] G Exhaust flow

[0071] H Urea Injector

[0072] L The length of the heating system in the direction of exhaust gas flow

[0073] O The outer surface of the shield 2

[0074] R Pipe Fittings

Claims

1. A shield (2) comprising at least two components (4, 5) which are designed to be connected to one another adjacent to one another at at least one separating surface (6) in order to surround a three-dimensionally shaped contour or pipe (R) of an exhaust gas line (1) of an internal combustion engine over a length in the case of use, It is characterized in that The components (4, 5) of the shielding element (2) each include at least one electric heating system (3) which, in the installed position, is thermally directed toward the pipe (R) to be surrounded, wherein the electric heating system (3) is constructed as a resistance conductor (8) electrically insulated relative to the pipe (R), having a meandering course extending in the exhaust gas flow direction over a length (L), wherein the resistance conductor (8) is provided with an electrical insulation portion (9).

2. The shielding element according to claim 1, characterized in that The two components (4, 5) are connected via at least one bending line (7).

3. The shielding element according to claim 2, characterized in that: The bending line (7) is designed as an omega-shaped bead.

4. The shielding element according to claim 1, characterized in that The electrical insulation (9) of the resistance conductor (8) is designed in the form of a fabric, textile, braid or knit.

5. The shielding member according to claim 1, characterized in that: When the thickness of the insulating layer is 0.1 to 0.6 mm, the electrical insulation (9) of the resistance conductor (8) is provided with fibers consisting of glass, silicate or a mixture of high-performance thermal materials.

6. The shielding element according to any one of claims 1 to 5, characterized in that: The resistance conductor (8) together with the connected electrical energy supply is designed to heat an adjacent pipe as part of an exhaust gas line to 200° to 550° C. via an electrical insulation (9).

7. The shielding element according to any one of claims 1 to 5, characterized in that: The electric heating system (3) of the component (4, 5) is fixed in or on the heat barrier (10) of the shield (2).

8. The shielding element according to claim 7, characterized in that The fixing of the electric heating system (3) in or on the heat-blocking part (10) of the components (4, 5) of the shielding element (2) is achieved by sewing, needling and / or stapling.

9. The shielding element according to any one of claims 1 to 5, characterized in that: At least one branch (Z) of the electric heating system (3) is fixed in one of a plurality of partial housings of the shielding device that are connected to one another in an articulated manner.

10. The shielding element according to any one of claims 1 to 5, characterized in that: A plurality of electric heating systems (3) of components (4, 5) of the shielding element (2) are provided, and / or a cascade of the respective heating powers is provided within each electric heating system (3) through disconnectable electric heating systems (3) and / or disconnectable branches (Z) of the electric heating systems (3).

11. The shielding element according to any one of claims 1 to 5, characterized in that: In order to regulate the respective thermal work to be output, means are provided for switching on and regulating the current through the electric heating system (3).

12. The shielding element according to any one of claims 1 to 5, characterized in that: A flange (F) is formed in the region of a separating surface (6) on the outer surface (O) and serves to securely fix the shield (2) in a closed state around the pipe (R).

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