Exhaust Line for a Heat Engine

Abstract

The exhaust line for a heat engine comprises, between an exhaust inlet and an exhaust outlet, a nitrogen oxide trap which is fitted on a filtering portion. It comprises, between the nitrogen oxide trap and the exhaust inlet, a branching portion which is capable of branching the exhaust gases away from the nitrogen oxide trap and switching means for the exhaust gases in order to cause them to flow through the filtering portion or branching portion.

1 . An exhaust line for a heat engine, comprising:
 between an exhaust inlet and an exhaust outlet, a nitrogen oxide trap which is fitted on a filtering portion;   between the nitrogen oxide trap and the exhaust inlet, a branching portion which is capable of branching the exhaust gases away from the nitrogen oxide trap;   a switching feature for the exhaust gases in order to cause them to flow through the filtering portion or branching portion; and   a three-way catalyzer which is arranged between the exhaust inlet and the upstream portion of the filtering portion and the branching portion.   
     
     
         2 . The exhaust line according to  claim 1 , wherein the switching feature blocks the filtering portion immediately downstream of the nitrogen oxide trap. 
     
     
         3 . The exhaust line according to  claim 1 , wherein the switching feature comprises a three-way valve which connects in parallel the branching portion and the filtering portion to the remainder of the line. 
     
     
         4 . The exhaust line according to  claim 3 , including a fork which is arranged between the exhaust inlet and, on the one hand, the upstream portion of the filtering portion and, on the other hand, the upstream portion of the branching portion, and the three-way valve is arranged downstream of the filtering portion and the branching portion and is capable of selectively connecting them to a common downstream portion of the exhaust line. 
     
     
         5 . The exhaust line according to  claim 1 , including at least one sensor selected from the group comprising a sensor for sensing the position of at least one valve, a temperature sensor and a gas composition sensor and a diagnostic component for diagnosing the operating state of the switching feature based on the or each sensor. 
     
     
         6 . The exhaust line according to  claim 1 , including control for controlling the switching feature and for acquiring the outlet temperature of the exhaust gases from the engine, and wherein the switching feature is capable of generally branching the gases off towards the branching portion when the temperature of the gases is greater than 600° C. 
     
     
         7 . The exhaust line according to  claim 1 , including a control for controlling the switching feature and for acquiring stoichiometric operating conditions of the engine, and wherein the switching feature is capable of generally branching the gases off towards the branching portion when the engine operates in a state which is superstoichiometric in terms of fuel. 
     
     
         8 . The exhaust line according to  claim 6 , wherein the control is capable of periodically controlling the switching feature to temporarily cause the exhaust gases to flow through the filtering portion during the phases in which the exhaust gases generally flow through the branching portion. 
     
     
         9 . The exhaust line according to  claim 1 , including a control for controlling the switching feature and for acquiring the future occurrence of a phase for operating the engine with a lean mixture when the engine operates with a rich mixture, and wherein that the control is capable of controlling the switching feature to branch the gases off towards the filtering portion when such an operating phase of the engine with a lean mixture is detected. 
     
     
         10 . A propulsion assembly comprising:
 an engine which generally operates with a lean mixture; and   an exhaust line comprising between an exhaust inlet and an exhaust outlet, a nitrogen oxide trap which is fitted on a filtering portion;   between the nitrogen oxide trap and the exhaust inlet, a branching portion which is capable of branching the exhaust gases away from the nitrogen oxide trap;   a switching feature for the exhaust gases in order to cause them to flow through the filtering portion or branching portion; and   a three-way catalyzer which is arranged between the exhaust inlet and the upstream portion of the filtering portion and the branching portion.