WO1994017289A1

WO1994017289A1 - Metallic honeycomb body with an electroconductive structure

Info

Publication number: WO1994017289A1
Application number: PCT/EP1994/000046
Authority: WO
Inventors: Rolf BRÜCK
Original assignee: Emitec Gesellschaft Für Emissionstechnologie Mbh
Priority date: 1993-01-26
Filing date: 1994-01-10
Publication date: 1994-08-04
Also published as: DE4302068A1; TW247279B

Abstract

A metallic honeycomb body through which a fluid can flow has a metallic housing and an electroconductive structure (1, 4) electrically insulated from the honeycomb body at least in partial areas and in good thermal contact with the honeycomb body or directly with the fluid. The structure (1, 4) may be connected by at least one connection (5, 6, 7) with an energy supply line (8, 9) arranged outside of the housing. The connection (5, 6, 7) runs through the housing in an electrically insulated manner. Both the connection (5, 6, 7) and the structure (4) in the area of the connection (5, 6, 7) have a lower resistance than the structure (1) inside the honeycomb body. The invention is particularly suitable for electrically heatable catalyst supporting bodies for cleaning motor vehicle exhaust fumes, when heating is ensured by voltages above 12 volts. The invention is also suitable for temperature sensors in catalyst supporting bodies. The thickened ends of the structure reduce the resistance and in heat conductors prevent overheating in this area, allowing it to be safely connected to copper cables. In temperature sensors, the lower resistance outside of the actual measurement area leads to more accurate measurements.

Description

DESCRIPTION

Metallic honeycomb body with an electrically conductive structure

The present invention relates to a metallic honeycomb body through which a fluid can flow, with a metallic housing and with an electrically conductive structure which is electrically insulated from the honeycomb body at least in some areas and which is in good thermal contact with the honeycomb body or directly with the fluid, the structure can be connected via at least one connection to a power supply line arranged outside the housing and the connection is guided through the housing in an electrically insulated manner. Honeycomb bodies with such structures are used in particular as electrically heatable catalyst carrier bodies in catalytic converters for cleaning motor vehicle exhaust gases. Such structures are also used as temperature sensors.

For example, heating structures are described in WO 92/02714, the honeycomb bodies in this document practically consisting only of heating structures. For other applications, however, it can also be advantageous to provide separate measuring or heating structures which are either in good contact with the fluid flowing in such a honeycomb body or with the honeycomb body itself. Such arrangements are described, for example, in the unpublished German patent application P 41 29 893.4 or the likewise unpublished German patent application P 42 23 134.5. Sheathed conductors are mentioned in these documents as particularly suitable measuring or heating structures, that is to say electrical conductors which are arranged in a metallic sheath and separated from it by a ceramic, usually powder-like insulation. Such sheathed conductors can in particular be rolled between two thin sheets. External soldering with thin sheet metal structures or other metallic structures is also possible. Due to the good thermal contact to adjacent metallic structures, even with heating conductors with a small cross-section, e.g. B. less than 1 mm ^2, a large heat output can be introduced into the honeycomb body. This is also necessary because electrically heated catalytic converters for motor vehicles are heated up, for example, with powers of 1000 to 4000 watts.

However, a problem arises in the arrangements described in the area of the bushings through the housing and the connections. In this area the heating conductors or heating structures are no longer cooled by flowing fluid and by close thermal contact with neighboring metallic structures, so that overheating would occur very quickly in this area if the same resistance per unit length as in the interior of the honeycomb body would be available. At least with a high utilization of the heating structures and heating with the maximum possible heating output, the bushings and connection areas would become particularly hot. This is undesirable on the one hand because of the operational safety and durability of the arrangement, but on the other hand it is particularly disadvantageous because copper cables which oxidize at high temperatures are usually to be connected to the connections of the heating structure. A similar problem arises with temperature sensors, namely that the area of the feedthrough, which actually no longer belongs to the measuring area, falsifies the measurement, because the resistance changes with the temperature there too.

The object of the present invention is to avoid the above-described disadvantages of the prior art and to create a honeycomb body with a measuring or heating structure which does not heat up excessively in the area of the connection and therefore z. B. can be connected with copper cables in a reliable manner or which in the area of the connection does not cause any resistance changes which strongly influence the measurement as a function of the temperature in the case of temperature sensors.

To achieve this object, a fluid-flowable metallic honeycomb body with a metallic housing, in particular an electrically heatable catalyst carrier body for cleaning motor vehicle exhaust gases, is used, with an electrically conductive structure that is electrically insulated from the honeycomb body at least in some areas and that is in good thermal contact with the Honeycomb body or directly with the fluid, the structure being connectable via at least one connection to a power supply line arranged outside the housing and the connection being guided through the housing in an electrically insulated manner, the connection and the structure also having a lower resistance in the region of the connection than the structure in the interior of the honeycomb body. By reducing the resistance in this area of the structure and at the connection, less ohmic heat per unit length arises at the same current strength as in the rest of the structure, so that a e Overheating is avoided when using the structure as a heat conductor. This is particularly the case in the edge area of a honeycomb body Typically, such a strong cooling by a flowing fluid is not particularly important. There is also no large-area contact with the housing when it is passed through a housing, so that heat dissipation is not possible there to the same extent as inside the honeycomb body. Overheating is reliably avoided by reducing the resistance, ie generally by increasing the conductor cross section. When using the structure as a temperature measuring conductor, the area of the connection influences the measurement only very slightly due to its low resistance, so that temperature changes in this area only slightly distort the measurement.

In the event that the structure is a conductor with a metallic sheath electrically insulated from the conductor, the inventive idea can be realized in that the conductor and the sheath have a larger cross section in the area of the connection than in the interior of the honeycomb body. The enlargement of the cross-section must go so far that overheating to critical temperatures cannot take place in the area of the connection or the resistance is reduced to an insignificant size for a measurement.

In the case of sheathed conductors, the inside of the measuring or heating conductor generally has a diameter of 10 to 35% of the outer diameter of the sheath, with inner conductors of 15 to 25% of the diameter of the sheath advantageously being used for the present applications. Such sheathed conductors can be reduced from an originally large diameter to a much smaller diameter by pulling, hammering or rolling, the length increasing accordingly. Sheathed conductors which have an original sheath diameter of 4 to 4 at the ends are particularly suitable for the present invention 8 mm, but in the area in between are reduced to a diameter of 0.5 to 2 mm. Particularly favorable values are a diameter of approximately 5 mm in the area of the connections and a diameter of approximately 1 mm in the interior of the honeycomb body.

In order to avoid the complex one-piece manufacture of such sheathed conductors in the lengths desired in each case, it can also be advantageous to weld thicker ends with sheath diameters of 4 to 8 mm to thinner intermediate pieces of 0.5 to 2 mm in diameter. It is important, however, that the electrical insulation between the inner conductor and the sheathed conductor is retained. A further advantage is achieved by the present invention, namely that the ends of the sheathed conductor at the connection have a size suitable for producing a plug connection. Thus, the thickened end of the heating conductor can protrude a little from the jacket at the connection and can be designed directly as a plug for a corresponding connection socket. It is even possible that the jacket is provided with an external thread for a union nut at the connection. In this case, a commercially available bushing with such a union nut can be screwed directly onto the jacket with a protruding inner conductor.

When the jacket of the measuring or heating conductor is passed through the housing, the metallic jacket can be welded to the housing in a sealing manner, which is important for many arrangements, in particular in the case of catalytic converters for motor vehicles.

Usually, a honeycomb body with an integrated measuring or heating conductor is first wound spirally, layered or otherwise entwined in a manner known per se and then inserted into a housing. To carry out an implementation for the measuring or heating conductor To create, it is advantageous if the housing has a slot from the front to the area of the connection through which the measuring or heating conductor with the jacket can be pushed into the desired position. The housing can then be tightly sealed by subsequently welding the slot and the casing to the housing. Apart from this last step, the production of a honeycomb body with an integrated measuring or heating conductor differs in many cases from the known production of metallic honeycomb bodies without a measuring or heating conductor.

In the event that the ends of the structure are led out of the honeycomb body at different points, two connections must of course be provided on the outside of the housing. However, it can be advantageous to lead both ends of the measuring or heating conductor out at a common point and to provide a common connecting socket. It is even more favorable if two measuring or heating conductors, which are connected to one another at one end, run in a common jacket and are guided through the housing in a common passage to the outside. In this case, the effort for bushings and connections is particularly low.

Embodiments of the invention, to which this is not limited, are explained in more detail below with reference to the drawing. 1 shows a schematic longitudinal section through a sheathed conductor with thickened ends, FIG. 2 shows a sheathed conductor rolled in between two sheets in cross section, FIG. 3 schematically shows the U-shaped course of a measuring or heating conductor within a bending position of a honeycomb body, 4 shows a cuboid honeycomb body made of alternately stacked smooth and corrugated sheets with an integrated measuring or heating conductor,

Fig. 5 shows a typical catalyst carrier body with an integrated measuring or heating conductor, such as by gobbling in opposite directions

Stack of sheets according to FIG. 4 can be produced.

1 shows a sheathed conductor with an inner conductor 1 and a metallic sheath 2, which are insulated from one another by an insulating layer 3. The inner conductor 1 has thickened ends 4, in which the electrical resistance is considerably lower than in the thin area. The jacket is also thickened in the end regions 5 and has an external thread 6 at the very end. The thickened inner conductor 4 has a piece 7 which protrudes beyond the thickened jacket 5 and its end 6 provided with an external thread. This protruding piece 7 can be inserted directly into a socket 8 as a plug, and the plug connection can be secured by means of the union nut 9 and the external thread 6. The outer diameter D in the area of the connections is, for example, 5 mm, while the outer diameter d of the jacket in the interior of the honeycomb body can be, for example, approximately 1 mm. The diameter of the inner conductor 1 or 4 is 15 to 25%, preferably about 20%, of the outer diameter of the jacket.

Fig. 2 shows schematically how a sheathed conductor can be arranged between two sheets 11, 12. The inner conductor 1 with the electrical insulation 3 surrounding it and the outer sheath 2 lies in a bulge 13 of the metal sheets 11, 12, this shape being able to be produced, for example, by rolling in with elastic rollers. The sheets 11, 12 can be soldered to one another on the side regions 14 to increase the stability of the structure. Such an arrangement can also be corrugated by corrugated rollers, so that a measuring or heating conductor can be integrated not only in smooth sheet metal layers but also in corrugated sheet metal layers.

Fig. 3 shows schematically that a sheathed conductor 2 can also run in a U-shape in or on a sheet metal layer 11, which is advantageous if the connections are to be close to each other.

In Fig. 4, a cuboid honeycomb body 20 is shown schematically, which consists of alternating layers of smooth 21 and corrugated 22 sheets. A sheathed conductor is integrated in its interior between two smooth sheet metal layers 11, 12, the thickened end 25 of which protrudes laterally. The sheathed conductor 25 in turn extends in bulges 13 of the sheet metal layers 11, 12. In the present exemplary embodiment, the sheathed conductor 25 has two inner conductors 27, 28, which are preferably connected to one another at their other ends, so that a U-shaped loop results overall.

FIG. 5 shows a typical honeycomb body for catalytic converters of motor vehicles, as can be produced in a manner known per se from a stack of sheets shown in FIG. 4 by intertwining the ends around two fixed points 33, 34. This honeycomb body 30 has a housing 35 which has a slot 31 starting from an end face. Between two sheet metal layers 11, 12 of the honeycomb body 13, a sheathed conductor is again integrated, the thickened end 5 of which is guided through the housing 35 to the outside with an external thread 6 and a projecting piece 7 of the inner conductor. Such a body is produced by first swallowing a body according to FIG. 4 in opposite directions and then pushing it into the housing 35 from one end face becomes. The connector 5, 6, 7 is pushed through the slot 31 into the desired position. Subsequently, the slot 31 can be welded, as indicated in the drawing, a tight connection 32 being produced between the casing 5 and the housing 35 at the same time.

The present invention is particularly suitable for the electrical heating of and / or the temperature measurement in catalytic converters for motor vehicles. The invention is particularly advantageous to use in cases in which a voltage higher than 12 volts is to be used for heating. When heating with 12 volts, high currents are required, which in turn require thick supply lines and relatively complex switching devices. This effort can be partially avoided by heating with a higher voltage if a corresponding voltage converter is available.

Claims

1. Metallic honeycomb body (20, 30) through which a fluid can flow and with a metallic housing (35), in particular catalyst

Carrier body for cleaning motor vehicle exhaust gases, with an electrically conductive structure (1, 4) which is electrically insulated from the honeycomb body (20, 30) at least in some areas and which is in good thermal contact with the honeycomb body (20, 30) or directly with the fluid stands, the structure (1, 4) via at least one connection (5,

6, 7) can be connected to a power supply line (8, 9) arranged outside the housing (35) and the connection (5, 6, 7) is guided through the housing (35) in an electrically insulated manner, characterized in that the connection (5, 6, 7) and the structure (4) in the area of

Connection (5, 6, 7) have a lower resistance than the structure (1) inside the honeycomb body (20, 30).

2. honeycomb body according to claim 1, characterized in that the structure (1, 4) is a conductor (1, 4) with a metallic jacket (2, 5) electrically insulated from the conductor (1, 4), the conductor (4) and the sheath (5) in the area of the connection has a larger cross section (D) than the diameter (d) of the conductor (1) and sheath (2) in the interior of the honeycomb body (20, 30).

Honeycomb body according to claim 2, characterized in that the sheath (2, 5) of the conductor (1, 4) from an original passage Knife (D) of the jacket (2, 5) of 4 to 8 mm in the inside (20, 30) of the honeycomb body (20, 30) is reduced to a diameter (d) of 0.5 to 2 mm, for example by pulling, hammering or rolling .

4. honeycomb body according to claim 2, characterized in that the conductor (1) inside the honeycomb body (20, 30) has a Mantel¬ diameter (d) of 0.5 to 2 mm, at the ends of the conductor (4) with Jacket diameters (D) of 4 to 8 mm are welded on.

5. honeycomb body according to claim 2, 3 or 4, characterized in that the end (7) of the conductor (1, 4) at the connection (5, 6, 7) protrudes a bit from the jacket (5, 6) and as a plug is designed for a corresponding connection socket (8, 9).

6. honeycomb body according to claim 5, characterized in that the jacket (5, 6) at the connection (5, 6,

7) is provided with an external thread (6) for a union nut (9).

Honeycomb body according to one of the preceding claims, characterized in that the conductor (4) with jacket (5) is guided outwards through the housing (35) and the jacket (5) is welded to the housing (35) in a sealing manner.

8. honeycomb body according to claim 7, characterized in that the

Conductor (4) with sheath (5) in the area of the connection (5, 6, 7) protrudes from the honeycomb body (20, 30) and is guided to the outside through a slot (31) in the housing, the slot (31) from one end of the housing to the connection (5, 6, 7) and after assembling the housing (35) and honeycomb body (30) is welded.

9. honeycomb body according to one of the preceding claims, characterized in that two connections (5, 6, 7) for the structure (1, 4) are provided.

10. honeycomb body according to one of claims 2 to 8, characterized gekenn¬ characterized in that two conductors (27, 28) which are connected at one end to each other in a common jacket (25) and in a common implementation to the outside through the Housing are guided.

11. honeycomb body according to one of the preceding claims, characterized in that the structure (1, 4) is a heating conductor for heating the honeycomb body.

12. honeycomb body according to one of claims 1 to 10, characterized gekenn¬ characterized in that the structure (1, 4) is a measuring conductor, in particular a conductor with temperature-dependent resistance for temperature measurement.