Resistance adjusting type heater and catalytic converter

Abstract

A resistance adjusting type heater including a honeycomb structure having a large number of passages, at last two electrodes for energizing the honeycomb structure, and a resistance adjusting mechanism such as a slit provided between the electrodes to heat the gas flowing through the passages formed in the honeycomb structure. A catalytic converter includes a main monolith catalyst and the above-described heater placed adjacent to and upstream of the main monolith catalyst. A catalytic converter includes a honeycomb structure having a large number of passages, a catalyst carried on the honeycomb structure, at least two electrodes for energizing the honeycomb structure, and a resistance adjusting mechanism provided between the electrodes. A catalytic converter includes a main monolith catalyst, and a heater placed adjacent to and upstream of the main monolith catalyst. The heater includes a honeycomb structure having a large number of passages, a catalyst carried on the honeycomb structure, at least two electrodes for energizing the honeycomb structure, and a resistance adjusting mechanism provided between the electrodes.

What is claimed is: 
     
       1. .[.An.]. .Iadd.A .Iaddend.heating element for heating fluid flowing therethrough, comprising: an electrically conductive .[.integral.]. .Iadd.monolithic .Iaddend.honeycomb structure having a periphery and two ends, including a plurality of passages which are defined by partition walls and extend in an axial direction between the ends, and at least one slit which is formed through said partition walls.Iadd., said slit being open and unfilled in the area through which a fluid stream may pass through the honeycomb structure, and being substantially planar and extending substantially through the axial length of said honeycomb structure and substantially parallel to said axial direction and crossing the planes of a plurality of partition walls of the honeycomb structure; .Iaddend.and   at least two electrodes in electrical contact with said honeycomb structure;   wherein said slit is disposed between said electrodes such that said slit interrupts current flow through portions of said honeycomb structure between said electrodes for heating said honeycomb structure and fluid flowing through said passages.   
     
     
       2. The heating element of claim 1, wherein said slit pierces the periphery of said honeycomb structure. 
     
     
       3. The heating element of claim 1, wherein said electrodes are located on the periphery of said honeycomb structure. 
     
     
       4. The heating element of claim 1, wherein said electrodes are located in opposition to each other across a volume of said honeycomb structure, in a direction which is generally transverse to said axial direction. 
     
     
       5. The heating element of claim 4, wherein said slit is arranged at an angle .Iadd.with respect .Iaddend.to said axial direction. .[.6. The heating element of claim 4, wherein said slit is arranged perpendicular to 
     
     
        said axial direction..]. 7. The heating element of claim 1, wherein the member of passages per unit area in a plane crossing said axial direction 
     
     
        is non-uniform, for interrupting current flow between said electrodes. 8. The heating element of claim 1, further comprising a catalyst material 
     
     
        formed on said partition walls. 9. The heating element of claim 1, wherein 
     
     
        said slit is arranged parallel to said axial direction. 10. The heating element of claim .[.9.]. .Iadd.1.Iaddend., wherein the thickness of said partition walls is non-uniform for interrupting current flow between said 
     
     
        electrodes. 11. The heating element of claim .[.9.]. .Iadd.1, .Iaddend.wherein the lengths of said partition walls are non-uniform in said axial direction for interrupting current flow between said 
     
     
        electrodes. .[.12.  The heating element of claim 11, wherein one of said electrodes is located at one of the ends and another of said electrodes is 
     
     
        located at the periphery of said honeycomb structure..]. 13. The heating element of claim 1, wherein there are a plurality of slits which are 
     
     
        parallel to each other .[.through said partition walls.].. 14. A catalytic converter .[.disposed.]. .Iadd.for disposal .Iaddend.in a stream of fluid, comprising: (i) at least one main monolithic catalyst; and   (ii) .[.an.]. .Iadd.a .Iaddend.heating element disposed adjacent to said at least one main monolithic catalyst .[.in the flow direction of said stream of fluid.]., comprising:   an electrically conductive .[.integral.]. .Iadd.monolithic .Iaddend.honeycomb structure having a periphery and two ends, including a plurality of passages which are defined by partition walls and extend in an axial direction between the ends, and at least one slit which is formed through said partition walls.Iadd., said slit being open and unfilled in the area through which a fluid stream may pass through the honeycomb structure, and being substantially planar and extending substantially through the axial length of said honeycomb structure and substantially parallel to said axial direction and crossing the planes of a plurality of partition walls of the honeycomb structure; .Iaddend.and   at least two electrodes in electrical contact with said honeycomb structure;   wherein said slit is disposed between said electrodes such that said slit interrupts current flow through portions of said honeycomb structure between said electrodes for heating said honeycomb structures and fluid   
     
     
        flowing through said passages. 15. The catalytic converter of claim 14, further comprising a catalyst material formed on said partition walls. 
     
     
            The catalytic converter of claim 14, wherein said heating element is disposed upstream of said main monolithic catalyst .[.with respect to the flow direction of said fluid.]..