Exhaust gas purifying apparatus

Abstract

In a hybrid vehicle equipped with an exhaust gas purifying apparatus, when a gasoline engine stops, an exhaust gas passage is closed by a pair of upstream-side and downstream-side throttle units to form an accommodation space. A pressure reduction unit reduces a pressure of the closed accommodation space where a three way catalyst is placed. The exhaust gas around the three way catalyst in the closed accommodation space does not leak into either an outside atmosphere side or into the gasoline engine side. Reducing the pressure in the closed accommodation space decreases heat conduction through the exhaust gas toward the outside. It is thereby possible to prevent the temperature drop of the three way catalyst and to keep the three way catalyst at a temperature of not less than its activation temperature for a long period of time even if the gasoline engine stops.

1 . An exhaust gas purifying apparatus, to be mounted to a hybrid vehicle equipped with an internal combustion engine and an electric motor as power sources, capable of purifying an exhaust gas emitted from the internal combustion engine, the exhaust gas purifying apparatus comprising:
 an exhaust gas pipe that forms an exhaust gas passage through which an exhaust gas emitted from the internal combustion engine flows;   a catalyst unit with catalyst placed in the exhaust gas passage; and   a pair of an upstream-side throttle unit and a downstream-side throttle unit, placed at an upstream side and a downstream side observed from the catalyst unit along the exhaust gas passage, respectively, capable of opening and closing the exhaust gas passage.   
   
   
       2 . The exhaust gas purifying apparatus according to  claim 1 , wherein the throttle units completely close the exhaust gas passage in which the catalyst unit with the catalyst is placed. 
   
   
       3 . The exhaust gas purifying apparatus according to  claim 2 , further comprising a pressure reducing means capable of decreasing a pressure in the exhaust gas passage closed by the upstream-side throttle unit and the downstream-side throttle. 
   
   
       4 . The exhaust gas purifying apparatus according to  claim 2 , further comprising a heating means capable of heating the exhaust gas remained in the exhaust gas passage closed by the upstream-side throttle unit and the downstream-side throttle. 
   
   
       5 . The exhaust gas purifying apparatus according to  claim 2 , further comprising a fuel injecting means, placed between the catalyst unit with the catalyst and the upstream-side throttle unit, capable of injecting fuel into the inside of the exhaust gas passage positioned before the catalyst unit placed in the exhaust gas passage closed by the upstream-side throttle unit and the downstream-side throttle unit. 
   
   
       6 . The exhaust gas purifying apparatus according to  claim 1 , further comprising a control means capable of instructing the upstream-side throttle unit and the downstream-side throttle to close the exhaust gas passage when detecting the stop of the internal combustion engine. 
   
   
       7 . The exhaust gas purifying apparatus according to  claim 2 , further comprising a control means capable of instructing the upstream-side throttle unit and the downstream-side throttle to close the exhaust gas passage when detecting the stop of the internal combustion engine. 
   
   
       8 . The exhaust gas purifying apparatus according to  claim 6 , wherein the control means is an electronic control unit composed of a microcomputer that comprises a central control unit, a read only memory, and a random access memory. 
   
   
       9 . The exhaust gas purifying apparatus according to  claim 1 , wherein the catalyst is a three way catalyst placed in the catalyst unit.