Exhaust emission control device

Abstract

An exhaust emission control device includes an adsorbent trapper having an adsorbent for adsorbing and desorbing hydrocarbon in exhaust gas, a catalytic converter, a main exhaust gas passage with a first valve, a bypass exhaust gas passage with a second valve and a control unit. The bypass exhaust gas passage bypassing the first valve is connected with the adsorbent. The control unit controls the first and second valves to desorb the hydrocarbon from the adsorbent when a condition is satisfied. The condition is that the catalyst converter is in active, an oxygen adsorption amount of the catalyst converter is not less than a first predetermined amount and an exhaust gas amount is not more than a second predetermined amount. The first valve is opened and the second valve is closed when the condition is not satisfied during desorption of the hydrocarbon from the adsorbent.

1 . An exhaust emission control device comprising:
 an adsorbent trapper having an adsorbent that can adsorb hydrocarbon in exhaust gas discharged from an internal combustion engine on the adsorbent a low temperature thereof and desorb the hydrocarbon from the adsorbent at a high temperature thereof;   a catalytic converter that is arranged at a downstream side of the adsorbent trapper and has catalyst for purifying the exhaust gas;   a main exhaust gas passage arranged between the internal combustion engine and the catalytic converter so that the main exhaust passage can flow the exhaust gas discharged from the internal combustion engine to the catalytic converter;   a first valve that is arranged in the main exhaust gas passage and is capable of opening and closing to flow the exhaust gas through the main exhaust gas passage and shut the main exhaust gas passage;   a bypass exhaust gas passage that has an upstream portion connected with an upstream portion of the main exhaust gas passage to bypass the first valve and have the adsorbent trapper in the bypass exhaust gas trapper;   a second valve that is arranged in the bypass exhaust gas passage and is capable of opening and closing to flow the exhaust gas through the bypass exhaust gas passage and shut the bypass exhaust gas passage; and   a control unit that controls the first valve and the second valve, wherein   the control unit controls the first valve and the second valve to open so that the exhaust gas flow through the main exhaust gas passage and the bypass exhaust gas passage so as to desorb the hydrocarbon from the adsorbent when a condition is satisfied, where the condition is that the catalyst converter is in active, an oxygen adsorption amount of the catalyst converter is not less than a first predetermined amount and an exhaust gas amount is not more than a second predetermined amount, wherein   the control unit controls the first valve to open and the second valve to close when the condition is not satisfied during desorption of the hydrocarbon from the adsorbent.   
   
   
       2 . The exhaust emission control device according to  claim 1 , wherein
 the control unit controls the second valve to open to flow the exhaust gas through the bypass exhaust gas passage so as to desorb the hydrocarbon from the adsorbent while a fuel injection is halted, a motor vehicle is slowing down and the exhaust gas amount is not more than a second predetermined amount after the catalytic converter becomes in an activation state.   
   
   
       3 . The exhaust emission control device according to  claim 1 , wherein
 the internal combustion engine is supplied with rich mixture of fuel/air ratio when the second valve is closed to shut the bypass exhaust gas passage during a valve open/close control where the exhaust gas flows through the bypass exhaust gas passage.   
   
   
       4 . The exhaust emission control device according to  claim 1 , wherein
 the first predetermined amount may be set appropriately, and it is set to be a value corresponding to approximately 50% of the maximum oxygen adsorption amount of the catalytic converter.   
   
   
       5 . The exhaust emission control device according to  claim 1 , wherein
 The second predetermined amount is set to be an amount of the exhaust gas discharged from the internal combustion engine at a low engine speed.   
   
   
       6 . The exhaust emission control device according to  claim 1 , wherein
 the adsorbent trapper and the catalytic converter are contained in a main case, and wherein   the main case is provided with a sound attenuation means for suppressing noise of the exhaust gas.   
   
   
       7 . The exhaust emission control device according to  claim 6 , wherein
 the sound attenuation means is a resonant chamber.   
   
   
       8 . The exhaust emission control device according to  claim 6 , wherein
 a resonance frequency of the sound attenuation means is set to suppresses the noise caused by the exhaust gas entering the bypass exhaust gas passage.   
   
   
       9 . The exhaust emission control device according to  claim 6 , wherein
 a resonance frequency of the sound attenuation means is set to suppresses the noise caused by confluence of the exhaust gasses that have passed through the main exhaust gas passage and the bypass exhaust gas passage.   
   
   
       10 . An exhaust emission control device including:
 an adsorbent trapper having an adsorbent that can adsorb hydrocarbon in exhaust gas discharged from an internal combustion engine on the adsorbent a low temperature thereof and desorb the hydrocarbon from the adsorbent at a high temperature thereof;   a catalytic converter that is arranged at a downstream side of the adsorbent trapper to purify exhaust gas;   a main exhaust gas passage arranged between the internal combustion engine and the catalytic converter so that the main exhaust passage can flow the exhaust gas discharged from the internal combustion engine to the catalytic converter;   a first valve that is arranged in the main exhaust gas passage and is capable of opening and closing to flow the exhaust gas through the main exhaust gas passage and shut the main exhaust gas passage;   a bypass exhaust gas passage that has an upstream portion connected with an upstream portion of the main exhaust gas passage to bypass the first valve and have the adsorbent trapper in the bypass exhaust gas trapper;   a second valve that is arranged in the bypass exhaust gas passage and is capable of opening and closing to flow the exhaust gas through the bypass exhaust gas passage and shut the bypass exhaust gas passage; and   a control unit that controls the first valve and the second valve, wherein   the control unit controls the first valve to close and the second valve to open during from engine start to time where temperature of the adsorbent becomes a desorption temperature of the hydrocarbon, the control unit controlling the first valve to open and the second valve to close during from the time where the temperature of the adsorbent becomes the desorption temperature of the hydrocarbon to time where temperature of the catalyst becomes activation temperature thereof, the control unit controlling the first valve and the second valve to open during from the time where the temperature of the catalyst becomes the activation temperature to time where the hydrocarbon is desorbed from the adsorbent, and the control unit controlling the first valve to open and the second valve to close after the hydrocarbon is desorbed from the adsorbent.   
   
   
       11 . The exhaust emission control device according to  claim 10 , wherein
 the control unit controls the second valve to open to flow the exhaust gas through the bypass exhaust gas passage so as to desorb the hydrocarbon from the adsorbent while a fuel injection is halted, a motor vehicle is slowing down and the exhaust gas amount is not more than a second predetermined amount after the catalytic converter becomes in an activation state.   
   
   
       12 . The exhaust emission control device according to  claim 10 , wherein
 the internal combustion engine is supplied with rich mixture of fuel/air ratio when the second valve is closed to shut the bypass exhaust gas passage during a valve open/close control where the exhaust gas flows through the bypass exhaust gas passage.   
   
   
       13 . The exhaust emission control device according to  claim 10 , wherein
 the end of the desorption of the hydrocarbon from the adsorbent is set to be a predetermined time after the engine starts.   
   
   
       14 . The exhaust emission control device according to  claim 10 , wherein
 the end of the desorption of the hydrocarbon from the adsorbent is judged based on a signal outputted from a sensor for detecting a hydrocarbon concentration.   
   
   
       15 . The exhaust emission control device according to  claim 10 , wherein
 the adsorbent trapper and the catalytic converter are contained in a main case, and wherein   the main case is provided with a sound attenuation means for suppressing noise of the exhaust gas.   
   
   
       16 . The exhaust emission control device according to  claim 15 , wherein
 the sound attenuation means is a resonant chamber.   
   
   
       17 . The exhaust emission control device according to  claim 15 , wherein
 a resonance frequency of the sound attenuation means is set to suppresses the noise caused by the exhaust gas entering the bypass exhaust gas passage.   
   
   
       18 . The exhaust emission control device according to  claim 15 , wherein
 a resonance frequency of the sound attenuation means is set to suppresses the noise caused by confluence of the exhaust gasses that have passed through the main exhaust gas passage and the bypass exhaust gas passage.