Electric heating catalyst

Abstract

The electricity is suppressed from flowing through a case ( 5 ) of an electric heating catalyst ( 1 ). The electric heating catalyst ( 1 ) comprises a heat generating element ( 3 ) which generates heat by applying electricity; a case which accommodates the heat generating element ( 3 ); an inner tube ( 4 ) which is provided between the heat generating element ( 3 ) and the case ( 5 ); a mat ( 6 ) which is provided between the heat generating element ( 3 ) and the inner tube ( 4 ) and between the inner tube ( 4 ) and the case ( 5 ) and which insulates the electricity; and an electrode ( 7 ) which is connected to the heat generating element ( 3 ) and which supplies an electric power to the heat generating element ( 3 ); wherein the inner tube ( 4 ) protrudes from the mat ( 6 ) toward an upstream side and a downstream side in a flow direction of an exhaust gas; and a distance between the heat generating element ( 3 ) and the inner tube ( 41 ), which is provided on an upstream side from the electrode ( 7 ), is shorter than a distance between the heat generating element ( 3 ) and the inner tube ( 42 ) which is provided on a downstream side from the electrode ( 7 ).

1 . An electric heating catalyst comprising:
 a heat generating element which generates heat by applying electricity;   a case which accommodates the heat generating element;   an inner tube which is provided between the heat generating element and the case;   a mat which is provided between the heat generating element and the inner tube and between the inner tube and the case and which insulates the electricity; and   an electrode which is connected to the heat generating element and which supplies an electric power to the heat generating element, wherein:   the inner tube protrudes from the mat toward an upstream side and a downstream side in a flow direction of an exhaust gas; and   a distance between the heat generating element and the inner tube, which is provided on an upstream side from the electrode, is shorter than a distance between the heat generating element and the inner tube which is provided on a downstream side from the electrode.   
     
     
         2 . An electric heating catalyst comprising:
 a heat generating element which generates heat by applying electricity;   a case which accommodates the heat generating element;   an inner tube which is provided between the heat generating element and the case;   a mat which is provided between the heat generating element and the inner tube and between the inner tube and the case and which insulates the electricity; and   an electrode which is connected to the heat generating element and which supplies an electric power to the heat generating element, wherein:   the inner tube protrudes from the mat toward an upstream side and a downstream side in a flow direction of an exhaust gas; and   a plate thickness of the inner tube, which is provided on an upstream side from the electrode, is thicker than a plate thickness of the inner tube which is provided on a downstream side from the electrode.   
     
     
         3 . The electric heating catalyst according to  claim 1 , wherein an outer diameter of the inner tube, which is provided at a portion at which the inner tube protrudes from the mat toward the upstream side in the flow direction of the exhaust gas, is smaller than an outer diameter of the inner tube which is provided at a portion at which the mat is provided. 
     
     
         4 . The electric heating catalyst according to  claim 1 , wherein a plate thickness of a certain part of the inner tube, which is provided at a portion at which the inner tube protrudes from the mat toward the upstream side in the flow direction of the exhaust gas, is thinner than plate thicknesses of other parts of the inner tube which are provided on an upstream side and a downstream side from the certain part. 
     
     
         5 . The electric heating catalyst according to  claim 1 , wherein a member, which has a thermal conductivity lower than that of the mat, is provided in the mat disposed between the inner tube and the case on the upstream side from the electrode. 
     
     
         6 . The electric heating catalyst according to  claim 2 , wherein an outer diameter of the inner tube, which is provided at a portion at which the inner tube protrudes from the mat toward the upstream side in the flow direction of the exhaust gas, is smaller than an outer diameter of the inner tube which is provided at a portion at which the mat is provided. 
     
     
         7 . The electric heating catalyst according to  claim 2 , wherein a plate thickness of a certain part of the inner tube, which is provided at a portion at which the inner tube protrudes from the mat toward the upstream side in the flow direction of the exhaust gas, is thinner than plate thicknesses of other parts of the inner tube which are provided on an upstream side and a downstream side from the certain part. 
     
     
         8 . The electric heating catalyst according to  claim 3 , wherein a plate thickness of a certain part of the inner tube, which is provided at a portion at which the inner tube protrudes from the mat toward the upstream side in the flow direction of the exhaust gas, is thinner than plate thicknesses of other parts of the inner tube which are provided on an upstream side and a downstream side from the certain part. 
     
     
         9 . The electric heating catalyst according to  claim 2 , wherein a member, which has a thermal conductivity lower than that of the mat, is provided in the mat disposed between the inner tube and the case on the upstream side from the electrode.