Retention of wires in an induction heated gaseous emissions treatment unit
Techniques are disclosed to aid fixing of an elongate wire within an elongate, linear cell of a honeycomb ceramic substrate unit for a gaseous emissions treatment assembly. In one method, the wire is formed with a resiliently flexible element, and inserted into the cell, the insertion act causing the resiliently flexible element to flex and to cause a part of the element to bear against a wall of the cell and so provide frictional retention of the wire in the cell. In another, method, an adhesive is used either on the outside of the wire or the inside of the cell. In another method, the wire is scored at spaced intervals along its length to provide relief spaces for linear expansion of the wire to reduce stress at its interface with cell walls.
1. A gaseous emissions treatment assembly comprising a honeycomb ceramic substrate body having a plurality of linear cells for the passage of emissions gas, metal wires inserted into and retained within respective ones of a first set of the plurality of cells, the cells of the first set having a cross-sectional shape generally matching the cross-sectional shape of the wires located therein except that the cells of the first set are marginally greater in cross-sectional area than the cross-sectional area of the wires located therein, the wires within the cells each formed with a resiliently flexible portion, having a rest condition and a flexed condition, the flexible portion driven by engagement with an interior wall of a respective cell from the rest condition to the flexed condition by the wire being inserted into said respective cell, whereby a part of the wire bears against said interior wall, thereby to provide frictional retention of the wire in said respective cell.
2. The assembly of claim 1 , wherein the resiliently flexible portion is a bow form extending along at least a part of the respective wire.
3. The assembly of claim 1 , wherein the resiliently flexible portion is a crimp in a part of the respective wire.
4. The assembly of claim 1 , wherein the wire is made from wire stock pulled so that the wire has a twist in a first direction about its longitudinal axis, the wire has been caused to twist in the opposite direction by the act of threading the wire into a cell of the first set, and said resiliently flexible element is the inherent resilience of the wire seeking to restore the -twist in the first direction.
5. A gaseous emissions treatment assembly comprising a honeycomb ceramic substrate body having a plurality of linear cells for the passage of emissions gas, metal wire located in a first set of the cells, the cells of the first set each having a cross-sectional area shape generally matching the cross-sectional area shape of the wire located therein and being marginally greater in area than the cross-sectional area of the wire, the material of the wire having a higher coefficient of thermal expansion than the material of the ceramic substrate unit, the wire having reduced area regions that are spaced along the length of the wire to form relief regions whereby, when the assembly is subjected to a temperature increase, wire expansion forces developed at an interface between an inside cell surface and an outside wire surface are at least partially relieved by deformation of parts of the wire material into the relief regions.
6. A gaseous emissions treatment assembly comprising a honeycomb ceramic substrate body having a plurality of linear cells for the passage of emissions gas, metal wires located in a first set of the cells, the cells of the first set each having a cross-sectional area shape generally matching the cross-sectional area shape of the respective wire located therein and being marginally greater in area than the cross-sectional area of the respective wire, and a layer of adhesive bonding an outer surface of the metal wires to walls of respective cells of the first set thereof.
7. The assembly of claim 6 , wherein indentations are formed in the surface of the wire to provide accumulation sites for the adhesive.
8. The assembly of claim 6 , wherein the adhesive is a heat activated adhesive.
9. The assembly of claim 6 , the adhesive being a blend including a ceramic powder component.
10. The assembly of claim 6 , the adhesive being a blend including a metal powder component.
11. The assembly of claim 6 , the adhesive being a blend including a binder component.
12. The assembly of claim 6 , the adhesive being a blend including a wax component.