Patent Publication Number: US-2011061380-A1

Title: Motor Vehicle Internal Combustion Engine EGR Loop

Description:
The invention relates to an EGR loop of an internal combustion engine of a motor vehicle, comprising the engine, a combustion-gas exhaust manifold, a turbine of a turbocharger, the exhaust gas recirculation (EGR) loop, with a cooler, a compressor of the turbocharger, receiving a portion of the exhaust gases and of the cool air and in which the pressure of the mixture is increased, an inlet manifold of the engine receiving the air from the compressor. 
     The EGR loop is intended to reduce the emission of nitrogen dioxide by reducing the combustion temperature, by a slowing of the combustion of the oxidant mixture and absorbing a portion of the calories. The cooler of the EGR loop makes it possible to reduce the combustion temperature at high engine speed (high load). 
     Usually, the EGR loop comprises a low-pressure, three-way valve downstream of the turbine of the turbocharger and a particle filter for retaining the soot that is in the exhaust gases before regeneration of the gases thus cleaned. 
     The originality of the invention lies in the fact that it is born of a problem that is particular but that has then been neglected in order to define the invention. 
     Hitherto, the particle filter was close to the engine, and even incorporated into the engine, and the EGR valve was downstream of the exhaust. As an EGR valve, three-way valves with one flap (single-flap) and three-way valves with two flaps (double-flap) are known but are more complex. 
     The problem that the applicant set itself is the distancing of the particle filter from the engine, that is to say in the passageway of the exhaust line under the bodyshell of the vehicle, and hence the problem of returning the cleaned gases to the engine. 
     It is in this situation that the applicant has had the idea of moving the single-flap, three-way EGR valve from the exhaust to the inlet, in other words from downstream of the turbine to upstream of the compressor of the turbocharger but without linking this movement to the position of the particle filter relative to the engine. 
     Therefore, the invention relates to an EGR loop of the type mentioned above, with a particle filter for cleaning the exhaust gases downstream of the turbine and a low-pressure, single-flap, three-way valve, said loop being characterized in that the valve is placed upstream of the compressor, connected thereto by its outlet and receiving, at its two inlets, cool air and the cleaned and cooled exhaust gases. 
     By virtue of the invention, the three-way EGR valve is a cold valve and no longer hot, which is a lower-cost valve, with electronics which no longer need to be cooled. 
     In the preferred embodiment of the EGR loop of the invention, the three-way valve and its single flap are arranged in order to operate according to one of the three modes i) inlet into the engine of cool air only, ii) inlet of a mixture of air and of EGR gases and iii) inlet of EGR gases only. 
    
    
     
       The invention will be better understood with the aid of the following description of the preferred embodiment of the EGR loop of the invention, with reference to the drawing, in which 
         FIG. 1  represents, in a simplified manner, the EGR loop of the invention; 
         FIG. 2  represents the single-flap, three-way valve of the loop of  FIG. 1  in a state of letting in cool air only; 
         FIG. 3  represents the single-flap, three-way valve of the loop of  FIG. 1  in the state of letting in a mixture of cool air and of EGR gases, and 
         FIG. 4  represents the single-flap, three-way valve of the loop of  FIG. 1  in a state of letting in EGR gases only. 
     
    
    
     The loop of  FIG. 1  comprises a vehicle engine  1 , with its exhaust manifold  2  and its inlet manifold  3 , a turbocharger  4  with a turbine  5 , downstream of the exhaust manifold, and a compressor  6  upstream of the inlet manifold, a particle filter  7 , downstream of the turbine  5  which is connected, on the other side, to the muffler of the vehicle and to an EGR branch line  8 , comprising in this instance an EGR cooler  9 , and a low-pressure, three-way valve  10 , connected via its outlet to the compressor  6  and, via its two inlets, to the outlet of the EGR cooler  9 , and to a cool air inlet  11 . The turbine  5  is rotated by the exhaust gases in order to drive in its turn the compressor  6 , connected at the outlet to the inlet manifold  3 , in this instance via a water-filled air cooler  12 , which may also be short-circuited by means of a valve  13 . 
     The low-pressure, three-way valve  10  comprises a body  14  connected to a first cool air inlet  15 , to a second inlet  16  for cleaned and regenerated EGR exhaust gases and an outlet  17  which is connected to the inlet manifold  3  of the engine. The body  14  in this instance has a substantially circular cross section and a single flap  18  is mounted inside it so as to rotate about a spindle  21  under the action of an actuator (not shown). The flap  18  is adapted to completely or partly close off one or the other of the two inlets  15 ,  16 . The actuator is controlled by a control system and position sensors are installed in the valve in order to determine the position of the flap  18 . 
     In  FIG. 2 , only cool air ( 15 ) is taken into the inlet manifold  3 . The inlet  16  is closed off by the flap  18 . 
     In  FIG. 3 , a mixture of cool air ( 15 ) and of exhaust gases ( 16 ) is taken into the inlet manifold. The pressure drop between the inlet and the exhaust is sufficient to ensure a good EGR ratio. 
     In  FIG. 4 , in order to increase the pressure drop between the inlet and the exhaust and to ensure a good EGR ratio, only the exhaust gases are taken into the inlet manifold  3 . The cool air inlet  15  is closed off by the flap  18 . 
     The three-way valve  10  can have a configuration that differs from the present example but nevertheless without departing from the context of the invention, notably the ducts  15 ,  16 ,  17  may vary in number and in position. Likewise, the single flap  18  may have a curved shape or have several inclined edges, depending on the arrangement of these ducts  15 ,  16 ,  17 .