Particulate matter processing apparatus (as amended)

Abstract

An excessively large electric current is suppressed from flowing to an electrode. A particulate matter processing apparatus in which a processing part with an electrode installed therein is arranged in an exhaust passage of an internal combustion engine, wherein particulate matter is caused to aggregate by generating a potential difference between the electrode and the processing part, is provided with a power supply that is connected to the electrode and applies a voltage thereto, a current detection device that detects an electric current which passes through the electrode, an air fuel ratio detection device that detects or estimates an air fuel ratio of an exhaust gas which flows through the exhaust passage, and a voltage control device that makes the voltage applied to the electrode from the power supply smaller in cases where the air fuel ratio detected by the air fuel ratio detection device is a rich air fuel ratio, than in cases where it is a stoichiometric air fuel ratio or a lean air fuel ratio.

1 . A particulate matter processing apparatus in which a processing part with an electrode installed therein is arranged in an exhaust passage of an internal combustion engine, wherein particulate matter is caused to aggregate by generating a potential difference between the electrode and the processing part, said apparatus comprising:
 a power supply that is connected to said electrode and applies a voltage thereto;   a current detection device that detects an electric current which passes through said electrode;   an air fuel ratio detection device that detects or estimates an air fuel ratio of an exhaust gas which flows through said exhaust passage; and   a voltage control device that makes the voltage applied to said electrode from said power supply smaller in cases where the air fuel ratio detected or estimated by said air fuel ratio detection device is a rich air fuel ratio, than in cases where it is a stoichiometric air fuel ratio or a lean air fuel ratio.   
     
     
         2 . The particulate matter processing apparatus as set forth in  claim 1 , further comprising:
 an insulation part that insulates electricity between said processing part and said exhaust passage; and   a ground part that grounds said processing part;   wherein said current detection device detects the electric current in said ground part.   
     
     
         3 . The particulate matter processing apparatus as set forth in  claim 1 , wherein
 the lower the air fuel ratio detected or estimated by said air fuel ratio detection device, the smaller said voltage control device makes the voltage applied to said electrode from said power supply.   
     
     
         4 . The particulate matter processing apparatus as set forth in  claim 1 , further comprising:
 an exhaust gas amount detection device that detects or estimates an amount of exhaust gas of the internal combustion engine;   wherein the more the amount of exhaust gas detected or estimated by said exhaust gas amount detection device, the smaller said voltage control device makes the voltage applied to said electrode from said power supply.   
     
     
         5 . The particulate matter processing apparatus as set forth in  claim 2 , wherein
 the lower the air fuel ratio detected or estimated by said air fuel ratio detection device, the smaller said voltage control device makes the voltage applied to said electrode from said power supply.   
     
     
         6 . The particulate matter processing apparatus as set forth in  claim 2 , further comprising:
 an exhaust gas amount detection device that detects or estimates an amount of exhaust gas of the internal combustion engine;   wherein the more the amount of exhaust gas detected or estimated by said exhaust gas amount detection device, the smaller said voltage control device makes the voltage applied to said electrode from said power supply.   
     
     
         7 . The particulate matter processing apparatus as set forth in  claim 3 , further comprising:
 an exhaust gas amount detection device that detects or estimates an amount of exhaust gas of the internal combustion engine;   wherein the more the amount of exhaust gas detected or estimated by said exhaust gas amount detection device, the smaller said voltage control device makes the voltage applied to said electrode from said power supply.