Exhaust gas purification device for internal combustion engine

Abstract

An exhaust gas purification device for measuring air/fuel ratio accurately and for enhancing a purification performance without increasing a size of a catalyst. The exhaust gas purification device comprises: header pipes through which exhaust gas flows; a catalytic converter arranged downstream of the header pipes; a diffusion chamber arranged between the header pipe and the catalytic converter; and a receiving surface with which the exhaust gas flowing into the diffusion chamber collides. An orifice is formed in a downstream end plate of the diffusion chamber, and an air/fuel ratio sensor is arranged downstream of the orifice.

What is claimed is: 
     
         1 . An exhaust gas purification device for an internal combustion engine, comprising:
 at least one or more header pipe through which an exhaust gas emitted from cylinders of the engine flows;   a catalytic converter arranged downstream of the header pipe;   a diffusion chamber arranged between the header pipe and the catalytic converter;   a receiving surface formed in the diffusion chamber with which a mainstream of the exhaust gas flowing into the diffusion chamber via the header pipe collides;   an orifice formed in a downstream end plate of the diffusion chamber, a cross-sectional area thereof is smaller than a cross-sectional area of an internal space of the diffusion chamber; and   an air/fuel ratio sensor arranged downstream of the orifice to measure an air/fuel ratio of an air/fuel mixture supplied to the engine.   
     
     
         2 . The exhaust gas purification device as claimed in  claim 1 , wherein the orifice is formed in the downstream end plate of the diffusion chamber at a portion where an inner edge of the orifice is distant from the receiving surface of the diffusion chamber. 
     
     
         3 . The exhaust gas purification device as claimed in  claim 1 , wherein the orifice is formed on the downstream end plate of the diffusion chamber at a portion where a predetermined clearance is maintained between an inner edge of the orifice and the receiving surface of the diffusion chamber in a flowing direction of the mainstream of the exhaust gas flowing toward the receiving surface. 
     
     
         4 . The exhaust gas purification device as claimed in  claim 2 , wherein the orifice is formed on the downstream end plate of the diffusion chamber at a portion where a predetermined clearance is maintained between the inner edge of the orifice and the receiving surface of the diffusion chamber in a flowing direction of the mainstream of the exhaust gas flowing toward the receiving surface. 
     
     
         5 . The exhaust gas purification device as claimed in  claim 3 , further comprising:
 a retention surface formed on at least a portion of the downstream end plate between the receiving surface of the diffusion chamber and the inner edge of the orifice so as to prevent the exhaust gas colliding with the receiving surface from flowing into the catalytic converter.   
     
     
         6 . The exhaust gas purification device as claimed in  claim 4 , further comprising:
 a retention surface formed on at least a portion of the downstream end plate between the receiving surface of the diffusion chamber and the inner edge of the orifice so as to prevent the exhaust gas colliding with the receiving surface from flowing into the catalytic converter.