Patent Publication Number: US-2012042632-A1

Title: Method and apparatus for processing exhaust gas in internal combustion engine

Description:
TECHNICAL FIELD 
     The present invention relates to a method and an apparatus for processing an exhaust gas introduced to an exhaust emission purifier in an internal combustion engine in which an exhaust turbocharger and the exhaust emission purifier are attached. 
     BACKGROUND ART 
     In recent years, for complying with strict exhaust gas regulations applied to an internal combustion engine, it is necessary to activate an exhaust emission purifier at the time of starting up the internal combustion engine for securely purifying the exhaust gas even at a warm-up time. Therefore, Patent Literature 1 has proposed an internal combustion engine in which an exhaust gas heating system is incorporated in an exhaust passage upstream of the exhaust emission purifier. The exhaust gas heating system supplies a high-temperature burning gas to the exhaust emission purifier prior to a warm-up of the internal combustion engine to perform activation of the exhaust emission purifier, and thereafter, the internal combustion engine is cranked, thus starting the warm-up thereof. Therefore, the exhaust gas heating system is generally provided with a fuel supplying valve for supplying fuel to the exhaust passage independently from a combustion chamber in the internal combustion engine and an igniting unit such as a glow plug for heating the fuel to be ignited in the exhaust passage, thereby generating a burning gas. 
     Citation List 
     Patent Literature 
     PTL 1: Japanese Patent Laid-Open No. 2003-522875 
     SUMMARY OF INVENTION 
     Technical Problem 
     The conventional exhaust gas heating system disclosed in Patent Literature 1 functions only in a case where the internal combustion engine is in a stop condition. Therefore, at a cold time of the internal combustion engine, long time is taken from start of a starting operation in the internal combustion engine to actual completion of the warm-up thereof, resulting in much wasteful consumption of the fuel. In addition, it is necessary to incorporate a supply source of secondary air such as a blower for supplying the burning gas to the exhaust emission purifier at a stop time of the internal combustion engine, into an engine room. For incorporating the supply source in the engine room, a relatively large space is required, thus interrupting downsizing of the engine room. In addition, when the exhaust gas heating system is activated during the operating of the internal combustion engine, the flame misses due to a flow speed of the exhaust gas flowing in the exhaust passage. Therefore, the exhaust gas heating system can not be used in a case where the exhaust emission purifier becomes inactive during the operating of the internal combustion engine or for maintaining an active state of the exhaust emission purifier. 
     An object of the present invention is to provide a method for processing an exhaust gas by which in an internal combustion engine in which an exhaust gas heating system is incorporated in an exhaust passage upstream of an exhaust emission purifier for heating an exhaust gas flowing in the exhaust passage, the exhaust gas heating system can be more effectively used. A further object of the present invention is to provide an apparatus for processing the exhaust gas, which can realize this method. 
     Solution to Problem 
     A first aspect of the present invention is provided with a method for processing an exhaust gas introduced to an exhaust emission purifier in a vehicle mounting an internal combustion engine thereon including a bypass valve for opening/closing a bypass passage of the exhaust gas branching from an exhaust passage upstream of an exhaust turbine in an exhaust turbocharger and merging with an exhaust passage positioned between the exhaust turbine and the exhaust emission purifier, a fuel supplying valve for supplying fuel to the exhaust passage upstream of a branch portion between the bypass passage and the exhaust passage, and igniting means for igniting the fuel supplied from the fuel supplying valve in the exhaust passage upstream of the branch portion between the bypass passage and the exhaust passage, comprising a first exhaust gas processing mode for opening the bypass valve, activating the igniting means, and supplying the fuel to the exhaust passage from the fuel supplying valve to ignite the supplied fuel, a second exhaust gas processing mode for closing the bypass valve and supplying the fuel to the exhaust passage from the fuel supplying valve without activating the igniting means, a step for, in a case of igniting the fuel by the igniting means, determining whether or not there is a flame failure (i.e. including flame-loss, flame-out, failure to ignite and ignition failure) of the fuel, and a step for selecting the first exhaust gas processing mode in a case where it is determined that there is not the flame failure of the fuel and selecting the second exhaust gas processing mode in a case where it is determined that there is the flame failure of the fuel. 
     In the present invention, in a case of an operating status of a vehicle in which a high-temperature burning gas obtained by igniting the fuel with the igniting means does not miss, the first exhaust gas processing mode is selected. In the first exhaust gas processing mode, the high-temperature burning gas is introduced from the bypass passage to the exhaust emission purifier to promote activation thereof. In reverse, in a case of the operating status of the vehicle in which the high-temperature burning gas obtained by igniting the fuel with the igniting means misses, the second exhaust gas processing mode is selected. In the second exhaust gas processing mode, the fuel supplied from the fuel supplying valve is introduced via the exhaust turbine to the exhaust emission purifier in a state of uniformly mixing with the exhaust gas from the internal combustion engine. 
     In the method for processing the exhaust gas according to the first aspect of the present invention, the step for determining whether or not there is the flame failure of the fuel may comprise a step for detecting an exhaust gas temperature, a step for detecting a flow rate of the exhaust gas flowing into the exhaust emission purifier, and a step for detecting an oxygen concentration in the exhaust gas. In addition, there may be further provided a third exhaust gas processing mode for closing the bypass valve, not activating the igniting means and not supplying the fuel to the exhaust passage from the fuel supplying valve, and a step for selecting the third exhaust gas processing mode in a case where the detected exhaust gas temperature exceeds a predetermined temperature. 
     The step for determining whether or not there is the flame failure of the fuel may comprise a step for determining whether the vehicle is in the decelerating state or the internal combustion engine is in an idling state. Here, in the case where it is determined that the vehicle is in the decelerating state or the internal combustion engine is in the idling state, it may be determined that there is not the flame failure of the fuel, and in the case where it is determined that neither the vehicle is in the decelerating state nor the internal combustion engine is in the idling state, it may be determined that there is the flame failure of the fuel. In addition, there may be further provided a third exhaust gas processing mode for closing the bypass valve, not activating the igniting means and not supplying the fuel, a step for detecting an exhaust gas temperature, and a step for selecting the third exhaust gas processing mode in the case where the detected exhaust gas temperature exceeds a predetermined temperature. 
     There may be further provided a step for determining presence/absence of malfunction in an opening/closing action of the bypass valve based upon a variation in an exhaust gas temperature in a case where the first exhaust gas processing mode is changed to the second or third exhaust gas processing mode. In addition, the step for determining the presence/absence of the malfunction in the opening/closing action of the bypass valve may determine that the opening/closing action of the bypass valve is wrong in a case the exhaust gas temperature is not lowered at the time the first exhaust gas processing mode is changed to the second or third exhaust gas processing mode. 
     A second aspect of the present invention is provided with an apparatus, in which an exhaust turbocharger and an exhaust emission purifier are incorporated, for processing an exhaust gas introduced from an internal combustion engine to the exhaust emission purifier, comprising a bypass conduit for defining a bypass passage of the exhaust gas branching from an exhaust passage upstream of an exhaust turbine in the exhaust turbocharger and merging with an exhaust passage positioned between the exhaust turbine and the exhaust emission purifier, a bypass valve mounted on the bypass conduit for opening/closing the bypass passage, an actuator for performing an opening/closing action of the bypass valve, a fuel supplying valve for supplying fuel to the exhaust passage upstream of a branch portion between the exhaust passage and the bypass passage, igniting means for igniting the fuel supplied from the fuel supplying valve to the exhaust passage upstream of the branch portion between the exhaust passage and the bypass passage, and control means for controlling each of operations of the actuator, the fuel supplying valve and the igniting means, wherein the control means comprises a flame failure determining unit for determining, in a case where the fuel is ignited by the igniting means, whether or not there is a flame failure of the fuel, and a processing mode selecting unit for selecting a first exhaust gas processing mode for opening the bypass valve, activating the igniting means and supplying the fuel to the exhaust passage from the fuel supplying valve to ignite the fuel or a second exhaust gas processing mode for closing the bypass valve and supplying the fuel to the exhaust passage from the fuel supplying valve without activating the igniting means, based upon the determination result of the flame failure determining unit. 
     In the present invention, in a case of an operating status of a vehicle in which a high-temperature burning gas obtained by igniting the fuel with the igniting means does not miss, the first exhaust gas processing mode is selected, wherein the high-temperature burning gas is introduced from the bypass passage to the exhaust emission purifier to promote activation thereof. On the contrary, in a case of the operating status of the vehicle in which the high-temperature burning gas obtained by igniting the fuel with the igniting means misses, the second exhaust gas processing mode is selected. In the second exhaust gas processing mode, the fuel supplied from the fuel supplying valve is introduced via the exhaust turbine to the exhaust emission purifier in a state of uniformly mixing with the exhaust gas from the internal combustion engine. 
     The apparatus for processing the exhaust gas according to the second aspect of the present invention may be further provided with an exhaust gas temperature sensor for detecting a temperature of the exhaust passage, an exhaust gas flow sensor for detecting a flow rate of the exhaust gas flowing into the exhaust emission purifier, and an O 2  sensor for detecting an oxygen concentration in the exhaust gas. In this case, the flame failure determining unit in the control means may determine whether or not a flame failure of the fuel based upon the detected exhaust gas temperature, exhaust gas flow rate and oxygen concentration. In addition, the processing mode selecting unit in the control means may select the third exhaust gas processing mode for closing the bypass valve, not activating the igniting means and not supplying the fuel in a case where the exhaust gas temperature detected by the exhaust gas temperature sensor exceeds a predetermined temperature. 
     There may be further provided load detecting means for detecting a load of the internal combustion engine, wherein the flame failure determining unit in the control means determines that there is not the flame failure of the fuel in a case where the load detected by the load detecting means is below a light load and there is the flame failure of the fuel in the other case. In addition, there may be further provided an exhaust gas temperature sensor for detecting a temperature of the exhaust passage. Here, the processing mode selecting unit in the control means may select the third exhaust gas processing mode for closing the bypass valve, not activating the igniting means and further not supplying the fuel to the exhaust passage in a case where the exhaust gas temperature detected by the exhaust gas temperature sensor exceeds a predetermined temperature. 
     The control means may further comprise a failure determining unit for determining presence/absence of malfunction in an opening/closing action of the bypass valve based upon a variation in the exhaust temperature in a case where the first exhaust gas processing mode is changed to the second or third exhaust gas processing mode. In addition, the failure determining unit may determine that the opening/closing action of the bypass valve is wrong in a case where the exhaust gas temperature is not lowered at the time the first exhaust gas processing mode is changed to the second or third exhaust gas processing mode. 
     Advantageous Effects of Invention 
     According to the present invention, a time for warming-up of the exhaust emission purifier at a cold time can be made shorter than conventional, and the supply source of the secondary air becomes unnecessary. In addition, even while the internal combustion engine is operating, it is possible to maintain the active state of the exhaust emission purifier by using the fuel supplying valve and the igniting means. 
     By selecting the first exhaust gas processing mode in a case where the ignition of the fuel is possible, based upon the exhaust gas temperature, the exhaust gas flow rate and the oxygen concentration, the high-temperature exhaust gas can be efficiently introduced to the exhaust emission purifier without the missing thereof. In addition, by selecting the second exhaust gas processing mode in a case where the continuous combustion of the fuel is impossible, the fuel can be introduced to the exhaust emission purifier in a state of being uniformly dispersed by using the exhaust turbine. 
     In a case where the detected exhaust gas temperature exceeds the predetermined temperature, the third exhaust gas processing mode for closing the bypass valve, not activating the igniting means and not supplying the fuel to the exhaust passage from the fuel supplying valve is selected, thus making it possible to restrict wasteful consumption of the fuel. 
     Presence/absence of malfunction in the opening/closing action of the bypass valve maybe determined based upon a variation in the exhaust gas temperature in a case where the first exhaust gas processing mode is changed to the second or third exhaust gas processing mode. More specially it may be determined that the opening/closing action of the bypass valve is wrong in a case where the exhaust gas temperature is not lowered at the time the first exhaust gas processing mode is changed to the second or third exhaust gas processing mode. 
     In a case where it is determined that the fuel does not miss when the load of the internal combustion engine is below a light load and there is the flame failure of the fuel in the other case, for example, in a case where the vehicle is in the decelerating state or the internal combustion engine in an idling state, the first exhaust gas processing mode is selected. 
     Thereby the high-temperature burning gas can be efficiently introduced to the exhaust emission purifier without the missing thereof. In addition, by selecting the second exhaust gas processing mode in a case where neither the vehicle is in the decelerating state nor the internal combustion engine is in the idling state, the fuel can be introduced to the exhaust emission purifier in a state of being uniformly dispersed by using the exhaust turbine. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an outline diagram of an embodiment where the present invention is applied to a compression ignition type internal combustion engine; 
         FIG. 2  is a control block diagram of a primary portion in the embodiment shown in  FIG. 1 ; 
         FIG. 3  is a map schematically showing a relation between an intake air quantity, an exhaust gas temperature, an oxygen concentration, and an ignitable region; 
         FIG. 4  is flowchart showing the control procedure of the embodiment shown in  FIG. 1 ; and 
         FIG. 5  is a flow chart showing the control procedure of the other embodiment in the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS  
     An embodiment in which the present invention is applied to a compression ignition type internal combustion engine will be in detail explained with reference to  FIG. 1  to  FIG. 5 . The present invention is not, however, limited to the embodiment, and the construction thereof maybe freely modified corresponding to required characteristics. The present invention is effectively applied to a spark ignition type internal combustion engine in which gasoline, alcohol, LNG (Liquefied Natural Gas) or the like is used as fuel to be ignited by a spark plug, for example. 
     A primary portion of an engine system in the present embodiment is schematically shown in  FIG. 1 , and a control block thereof is shown in  FIG. 2 . It should be noted that in  FIG. 1 , a valve-operating mechanism for intake and exhaust in an engine  10 , a muffler and the like are omitted for convenience. 
     The engine  10  is a compression ignition type internal combustion engine in which light oil as fuel is directly injected into a combustion chamber  10   a  in a compressed state from a fuel injection valve  11  to generate spontaneous ignition of the fuel. 
     A quantity and injection timing of the fuel supplied into the combustion chamber  10   a  from the fuel injection valve  11  are controlled based upon operating status of the vehicle including a depressing travel of an accelerator pedal  12  by a driver by an ECU (Electric Control Unit)  13 . The depressing travel of the accelerator pedal  12  is detected by an accelerator opening sensor  14 , and the detection information is outputted to the ECU  13 . 
     The ECU  13  includes an operating status determining unit  13   a  for determining an operating status of the vehicle based upon information from the accelerator opening sensor  14 , various sensors to be described later and the like, a fuel injection quantity setting unit  13   b , and a fuel injection valve driving unit  13   c . The fuel injection quantity setting unit  13   b  sets an injection quantity and an injection timing of the fuel from the fuel injection valve  11  based upon the determination result from the operating status determining unit  13   a . The fuel injection valve driving unit  13   c  controls an operation of the fuel injection valve  11  in such a manner that the quantity of the fuel set by the fuel injection quantity setting unit  13   b  is injected at the set timing from the injection valve  11 . 
     An intake port  15   a  and an exhaust port  15   b  respectively exposed to the combustion chamber  10   a  are formed in a cylinder head  15 , which is provided with a valve-operating mechanism (not shown) incorporated therein and including an intake valve  16   a  for opening/closing the intake port  15   a  and an exhaust valve  16   b  for opening/closing the exhaust port  15   b . The aforementioned fuel injection valve  11  is also incorporated in the cylinder head  15 . 
     An intake conduit  17  is connected to the cylinder head  15  in such a manner as to be communicated with the intake port  15   a  for defining an intake passage  17   a  together with the intake port  15   a . The intake conduit  17  is provided with a throttle valve  19  incorporated therein for adjusting an opening of the intake passage  17   a  through a throttle actuator  18 . The ECU  13  further includes a throttle opening setting unit  13   d  and a throttle valve driving unit  13   e . The throttle opening setting unit  13   d  sets an opening of the throttle valve  19  based upon the determination result by the aforementioned operating status determining unit  13   a . The throttle valve driving unit  13   e  controls an operation of the throttle actuator  18  such that the throttle valve  19  opens in the degree of opening set by the throttle opening setting unit  13   d.    
     A cylinder block  20  in which a piston  20   a  reciprocates is provided with a crank angle sensor  21  mounted thereon for detecting a rotational phase of a crank shaft  20   c  connected through a connecting rod  20   b  to the piston  20   a , that is, a crank angle thereof, which is outputted to the ECU  13 . The operating status determining unit  13   a  in the ECU  13  obtains in real time the rotational phase of the crank shaft  20   c , an engine rotational speed, further, a vehicle speed and the like, based upon information from the crank angle sensor  21 . 
     The engine  10  is provided with an EGR (Exhaust Gas Recirculation) system  23  recirculating a part of the exhaust gas flowing in the exhaust passage  22   a  to the intake passage  17   a , an exhaust turbocharger  24 , an exhaust emission purifier  25  and an exhaust gas processing apparatus  26 , which are incorporated therein. 
     The EGR system  23  designed to reduce nitrogen oxides in the exhaust gas and improve fuel consumption is provided with an EGR conduit  27  defining an EGR passage  27   a  and an EGR valve  28  provided in the EGR conduit  27  for controlling a flow rate of the exhaust gas flowing in the EGR passage  27   a . The EGR conduit  27  has one end communicated with an exhaust conduit  22  defining the exhaust passage  22   a  together with the exhaust port  15   b  and the other end communicated with the intake passage  17   a  between the aforementioned throttle valve  9  and a surge tank  17   b  arranged downstream of the throttle valve  19 . 
     In the present embodiment, in a case where the operating status determining unit  13   a  in the ECU  13  determines that a vehicle mounting the engine  10  thereon is in a preset EGR performance region, an opening of the EGR valve  28  is set in accordance with an operating status of the vehicle at this time by an EGR rate setting unit  13   f  in the ECU  13 . An EGR valve driving unit  13   g  in the ECU  13  controls the EGR valve  28  to an opening set by the EGR rate setting unit  13   f  and in the other case, basically drives the EGR valve  28  to a closing state in such a manner as to stop the EGR passage  27   a.    
     The exhaust turbocharger (hereinafter, described simply as turbocharger)  24  performs supercharging into the combustion chamber  10   a  by using kinetic energy of the exhaust gas flowing in the exhaust passage  22   a  to enhance a charging efficiency of intake air. The turbocharger  24  has a primary portion constructed of a compressor  24   a  and an exhaust turbine  24   b  rotating integrally with the compressor  24   a . The compressor  24   a  is incorporated in a portion of the intake conduit  17  positioned upstream of the throttle valve  19 . The exhaust turbine  24   b  is incorporated in a portion of the exhaust conduit  22  connected to the cylinder head  15  to be communicated with the exhaust port  15   b . It should be noted that, for reducing a temperature of intake air heated through the compressor  24   a  by transfer of heat from the exhaust turbine  24   b  exposed to the high-temperature exhaust gas, an intercooler  24   c  is incorporated in a portion the intake passage  17   a  between the compressor  24   a  and the throttle valve  19 . In addition, the aforementioned EGR conduit  27  has one end connected to the exhaust conduit  22  upstream of the exhaust turbine  24   b.    
     The exhaust emission purifier  25  for rendering harmful substances generated by combustion of a mixture in the combustion chamber  10   a  harmless is incorporated in the exhaust conduit  22  defining the exhaust passage  22   a  downstream of the exhaust turbine  24   b  in the turbocharger  24 . The exhaust emission purifier  25  in the present embodiment includes an oxidation catalytic converter  25   a  and a DPF (Diesel Particulate Filter)  25   b  in that order from the upstream side of the exhaust passage  22   a , but may further include the other catalytic converter such as a NO x  catalyst. The oxidation catalytic converter  25   a  oxidizes and dissolves unburned components in the exhaust gas, and the DPF  25   b  traps particulate matter contained in the exhaust gas and renders it harmless. 
     The exhaust gas processing apparatus  26  processes the exhaust gas to be introduced from the engine  10  to the exhaust emission purifier  25  to perform quick activation and holding of an active state of the exhaust emission purifier  25 , but is usable also for regeneration processing of the aforementioned DPF  25   b . The exhaust gas processing apparatus  26  in the present embodiment is provided with the fuel supplying valve  29 , a glow plug  30 , a bypass conduit  31 , a bypass valve  32 , and a bypass valve actuator  33 . Further, for smoothly controlling the exhaust gas processing apparatus  26 , the aforementioned ECU  13 , an airflow meter  34 , first and second exhaust gas temperature sensors  35  and  36 , and an O 2  sensor  37  are used. 
     The airflow meter  34  as an exhaust gas flow sensor of the present invention is mounted on a portion of the intake conduit  17  positioned upstream of the compressor  24   a  in the turbocharger  24  to detect a flow rate of intake air flowing in the intake passage  17   a , outputting the detected flow rate to the ECU  13 . Instead of the airflow meter  34 , an exhaust gas flow sensor having the same construction may be mounted on a portion of the exhaust conduit  22  positioned downstream of a merging portion with the bypass conduit  31  and upstream of the exhaust emission purifier  25 . The first exhaust gas temperature sensor  35  detects a temperature T 1n  within the exhaust passage  22   a  downstream of a connecting portion with one end of the EGR conduit  27  and upstream of a mounting position of the fuel supplying valve  29  and outputs the detected temperature to the ECU  13 . The second exhaust gas temperature sensor  36  is mounted on a portion of the exhaust conduit  22  positioned downstream of a merging portion with the bypass conduit  31  and upstream of the exhaust emission purifier  25 . Accordingly the second exhaust gas temperature sensor  36  detects a temperature T 2n  of the exhaust gas flowing in the exhaust passage  22   a  immediately before flowing into the exhaust emission purifier  25  and outputs the detection information to the ECU  13 . Instead of the first exhaust gas temperature sensor  35 , a catalyst temperature sensor may be incorporated between the oxidation catalytic converter  25   a  and the DPF  25   b  in the exhaust emission purifier  25 . The O 2  sensor  37  is mounted in a portion of the exhaust conduit  22  positioned downstream of the exhaust emission purifier  25  and detects an oxygen concentration D n  in the exhaust passage  22   a , which is outputted to the ECU  13 . It should be noted that instead of the O 2  sensor  37 , an air-fuel ratio detecting sensor may be used. 
     The fuel supplying valve  29  supplying fuel for performing activation of the exhaust emission purifier  25  or maintaining an active state thereof is mounted on the exhaust conduit  22  in such a manner as to be exposed to the exhaust passage  22   a  downstream of a connecting portion to one end of the EGR conduit  27  and upstream of a branch portion to the bypass conduit  31 . The fuel supplying valve  29 , in a case where the warming-up of the exhaust emission purifier  25  or the regeneration processing of the DPF  25   b  is required, supplies fuel toward the exhaust passage  22   a  positioned upstream of a branch portion to the bypass passage  31   a  defined by the exhaust passage  22   a  and the bypass conduit  31 . More specially in a case where a temperature detected by the second exhaust gas temperature sensor  36  to be described later is below a predetermined temperature (hereinafter, described as catalyst active temperature) T L , a predetermined quantity of fuel is supplied from the fuel supplying valve  29 . Therefore, the ECU  13  includes a fuel supplying valve driving unit  13   h  for controlling an operation of the fuel supplying valve  29 . 
     The glow plug  30  as the igniting means in the present invention is connected to an in-vehicle power source (not shown) through a switch (not shown) controlled to be ON/OFF by the ECU  13  to be capable of igniting at least a part of the fuel supplied from the fuel supplying valve  29 . A glow pug driving unit  13   i  in the ECU  13  changes an activation/deactivation of the glow plug  30  to be ON/OFF. 
     The ECU  13  includes, in a case where the fuel supplied from the fuel supplying valve  29  to the exhaust passage  22   a  is ignited by the glow pug  30 , a flame failure determining unit  13   j  for determining whether or not the fuel can continue to burn. A map shown in  FIG. 3  is stored in the flame failure determining unit  13   j  in the present embodiment. The flame failure determining unit  13   j  determines whether an operating status of the engine  10  is in an ignitable region of fuel or in an unignitable region thereof and outputs the determination result to a processing mode selecting unit  13   k  in the ECU  13 . The determination is made based upon detection signals from the airflow meter  34 , the second exhaust gas temperature sensor  36 , and the O 2  sensor  37 . In  FIG. 3 , a boundary between the ignitable region and the unignitable region in a case where the O 2  concentration is 15% is shown in a solid line to be associated with an intake air quantity and a first exhaust gas temperature. A broken line shows the boundary between the ignitable region and the unignitable region in a case where the O 2  concentration is 20%. That is, the flame failure determining unit  13   j  stores therein a plurality of maps for associating the intake air quantity with the first exhaust gas temperature corresponding to the O 2  concentration. 
     The bypass conduit  31  is arranged to define the bypass passage  31   a  connected to the exhaust passage  22   a  in a state of bypassing the exhaust turbine  24   b  in the turbocharger  24  and have a downstream end communicated with the exhaust passage  22   a  downstream of the exhaust turbine  24   b  in the turbocharger  24 . The bypass conduit  31  has an upstream end which branches from the exhaust conduit  22  to be positioned downstream of a connecting portion between the exhaust conduit  22  and one end of the EGR conduit  27  and upstream of the exhaust turbine  24   b . On the other hand, the downstream end of the bypass conduit  31  merges at a portion of the exhaust conduit  22  defining the exhaust passage  22   a  connected through the exhaust turbine  24   b  in the turbocharger  24  to the exhaust emission purifier  25 . 
     The bypass valve  32  driven by the bypass valve actuator  33  is mounted on the bypass conduit  31  to open/close the bypass passage  31   a . The bypass valve  32  is constructed of being capable of introducing the burning gas ignited by the glow plug  30  from the bypass passage  31   a  to the exhaust emission purifier  25  without via the exhaust turbine  24   b  in the opening state. The ECU  13  includes a bypass valve driving unit  131  for controlling an operation of the bypass valve actuator  33 . 
     The fuel supplying valve driving unit  13   h , the glow plug driving unit  13   i , and the bypass valve driving unit  13 I respectively drive the fuel supplying valve  29 , the glow plug  30 , and the bypass valve  32  according to the processing mode selected by the processing mode selecting unit  13   k  in the ECU  13 . 
     The processing mode selecting unit  13   k  selects the first to third exhaust gas processing modes based upon the determination result by the flame failure determining unit  13   j  in the ECU  13 . In the first exhaust gas processing mode, the fuel is supplied to the exhaust passage  22   a  from the fuel supplying valve  29 , the glow plug  30  is activated, and the bypass valve  32  is maintained to be in an opening state. The first exhaust gas processing mode is selected in a case where the vehicle is in an operating status in which when the fuel is ignited, the ignited fuel can be introduced toward the exhaust emission purifier  25  without the missing thereof. In the second exhaust gas processing mode, the fuel is supplied to the exhaust passage  22   a  from the fuel supplying valve  29 , the glow plug  30  is deactivated, and the bypass valve  32  is maintained to be in a closing state. The second exhaust gas processing mode is selected in a case where the vehicle is in an operating status in which the DPF  25   b  is under regenerating state and when the fuel is ignited, there is the flame failure of the fuel. In the third exhaust gas processing mode, the fuel is not supplied to the exhaust passage  22   a  from the fuel supplying valve  29 , the glow plug  30  is deactivated, and the bypass valve  32  is maintained to be in the closing state. The third exhaust gas processing mode is selected in a case where the vehicle is in an operating status in which the warming-up of the exhaust emission purifier  25  and the regeneration processing of the DPF  25   b  are not required. 
     The ECU  13  includes a failure determining unit  13   m  for detecting presence/absence of malfunction in an opening/closing action of the bypass valve  32  and an indicator driving unit  13   n . The failure determining unit  13   m  determines, in a case where the first exhaust gas processing mode in the middle of the executing is changed to the second exhaust gas processing mode or the third exhaust gas processing mode, when a variation of an exhaust gas temperature T 2n  to be detected does not show a reducing inclination based upon information of the exhaust gas temperature from the second exhaust gas temperature sensor  36 , that the opening/closing action of the bypass valve  32  is wrong. In the first exhaust gas processing mode, the high-temperature burning gas is in a state of entering into the exhaust emission purifier  25 . In a case where this state changes to the second exhaust gas processing mode or the third exhaust gas processing mode, ignition of the fuel by the glow plug  30  is not executed, which is therefore the ground that the temperature T 2n  of the exhaust gas flowing into the exhaust emission purifier  25  is substantially reduced. The indicator driving unit  13   n  serves to inform a driver that the opening operation of the bypass valve  32  is wrong, based upon the determination result of the failure determining unit  13   m . A warning indicator  38  for it is provided in the vehicle compartment (not shown). The warning indicator  38  may be only provided for causing a driver to draw attention aurally or visually. 
     The ECU  13  is a well-known one chip microprocessor and includes a CPU, a ROM, a RAM, an involatile memory, and an input/output interface which are connected with each other by a data bus, and the like. The ECU  13  executes a predetermined computing processing based upon detection signals of the aforementioned sensors  14 ,  21 , and  35  to  37 , the airflow meter  34 , and the like in such a manner as to provide a smooth action of the engine  10 . In addition, operations of the fuel injection valve  11 , the throttle valve  19 , the EGR valve  28 , the glow plug  30 , the fuel supplying valve  29 , the bypass valve  32  and the like are controlled according to preset programs. 
     An intake air supplied into the combustion chamber  10   a  from the intake passage  17   a  forms a mixture with fuel injected into the combustion chamber  10   a  from the fuel injection valve  11 . The mixture is usually burned by spontaneous ignition immediately before a compression top dead center of a piston  20   a , and an exhaust gas generated by it is discharged from the exhaust conduit  22  through the exhaust emission purifier  25  to an atmosphere. In this case, unburned components in the exhaust gas are oxidized and dissolved by the oxidation catalytic converter  25   a , and the particulate material is trapped by the DPF  25   b  to be purified, which is discharged to an atmosphere. 
     It should be noted that, when the particulate matter continues to be trapped by the DPF  25   b , since the DPF  25   b  is gradually clogged with the particulate matter, it is necessary to eliminate the clogging of the DPF  25   b  by burning the particulate matter. The regeneration processing of the DPF  25   b  is therefore executed at a DPF regeneration processing unit  13   o  in the ECU  13  based upon information of a cumulative fuel injection quantity injected by the fuel injection valve  11 , a cumulative operating time of the engine  10 , a difference between an exhaust gas pressure upstream of the DPF  25   b  and an exhaust gas pressure downstream thereof, and the like. The DPF regeneration processing unit  13   o  provides an injection quantity of fuel from the fuel injection valve  11  for regenerating the DPF  25   b , and in addition thereto, in the present embodiment, fuel is supplied into the exhaust passage  22   a  also from the fuel supplying valve  29 . That is, a supplying operation of the fuel into the exhaust passage  22   a  from the fuel supplying valve  29  is basically performed in a case where the exhaust emission purifier  25  is in an inactive state. However, for quickly executing the regeneration processing of the DPF  25   b  in the exhaust emission purifier  25 , the fuel can be also supplied into the exhaust passage  22   a  from the fuel supplying valve  29 . 
     As a result, in addition to the activation of the exhaust emission purifier  25  and the maintenance of the active state thereof, the regeneration processing of the DPF  25   b  can be also quickly executed. Particularly the exhaust gas processing apparatus  26  is remarkably advantageous in improving a so-called cold emission state immediate after a cold start of the engine  10 . Further, since an ignition position of fuel is at a distance from the fuel supplying valve  29 , uniform mixing between the fuel and the exhaust gas is possible, thus making it possible to more largely reduce incomplete combustion of the fuel than the conventional exhaust gas heating system. 
     An operational procedure of the exhaust gas processing apparatus  26  in the present embodiment will be explained with reference to a flow chart in  FIG. 4 . First, at a step of S 11 , it is determined whether or not an exhaust gas temperature T 2n  detected by the second exhaust gas temperature sensor  36  is below a catalyst active temperature T L . Here, when it is determined that the exhaust gas temperature T 2n  is below the catalyst active temperature T L , that is, it is necessary to heat the exhaust emission purifier  25  for activation or maintain an active state thereof, the process goes to a step of S 12 . At this step of S 12 , a first exhaust gas temperature T 1n , an intake air flow rate Q n , and an oxygen concentration D n  in the exhaust gas respectively are detected by the first exhaust gas temperature sensor  35 , the airflow meter  34 , and the O 2  sensor  37 . In addition, at a step of S 13 , the flame failure determining unit  13   j  determines whether or not a current operating status of the engine  10  is in an ignitable region of fuel based upon the detection information. Here, in a case where it is determined that the current operating status of the engine  10  is in the ignitable region, that is, the current operating status is an atmosphere where a high-temperature burning gas can continue to be generated by igniting the fuel supplied to the exhaust passage  22   a  by the glow plug  30 , the process goes to a step of S 14 . At this step of S 14 , the first exhaust gas processing mode, in which the bypass valve  32  is in an opening state, the glow plug  30  is changed to an ON-state as a power supplying state and the fuel from the fuel supplying valve  29  is supplied to the exhaust passage  22   a , is executed. In consequence, the burning gas which has become high in temperature due to ignition of the fuel is introduced from the bypass passage  31   a  to the exhaust emission purifier  25 . That is, since the high-temperature burning gas bypasses the exhaust turbine  24   b  as a flow resistance, the heat of the high-temperature burning gas is not absorbed by the exhaust turbine  24   b , and the exhaust emission purifier  25  is efficiently heated. 
     Subsequent to the step of S 14 , at a step of S 15 , a flag showing that the bypass valve  32  is opened is set, and steps after the first step of S 11  are repeated. 
     In a case where at the aforementioned step of S 13 , it is determined that the current operating status of the vehicle is not in the ignitable region, that is the current operating status is an atmosphere where even when the fuel supplied to the exhaust passage  22   a  is ignited by the glow plug  30 , there is the flame failure of the fuel, the process goes to a step of S 16 . At this step of S 16 , it is determined whether or not the DPF  25   b  is in the regeneration processing. Here, in a case where it is determined that the DPF  25   b  is in the regeneration processing, that is, it is determined that, although the fuel can not be ignited, it is effective to supply the fuel to the exhaust emission purifier  25  for the regeneration processing of the DPF  25   b , the process goes to a step of S 17 . At this step of S 17 , the second exhaust gas processing mode, in which the bypass valve  32  is in a closing state, the glow plug  30  is changed to an OFF-state as a non-power supplying state, and the fuel from the fuel supplying valve  29  is supplied to the exhaust passage  22   a , is executed. In consequence, the fuel supplied to the exhaust passage  22   a  is introduced through the exhaust turbine  24   b  to the exhaust emission purifier  25 . In this case, since dispersion of the fuel into the exhaust gas is promoted by a stirring effect of the exhaust turbine  24   b , the reforming and the thermal decomposition of the fuel by the oxidation catalytic converter  25   a  in the exhaust emission purifier  25  is promoted. Thereby the high-temperature exhaust gas burned in the oxidation catalytic converter  25   a  is introduced to the DPF  25   b , thus making it possible to efficiently perform the regeneration thereof. 
     Subsequent to the step of S 17 , at a step of S 18  it is determined whether or not a flag is set. Here, in a case where it is determined that the flag is set, that is, the bypass valve  32  is changed from the opening state to the closing state, the process goes to a step S 19 . At this step of S 19 , the failure determining unit  13   m  determines a variation of the exhaust gas temperature T 2n  detected by the second exhaust gas temperature sensor  36 , that is, whether or not the detected exhaust gas temperature T 2n  is below the previously detected exhaust gas temperature T 2 (n−1) . Here, in a case where it is determined that the exhaust gas temperature T 2n  is below the previously detected exhaust gas temperature T 2 (n−1) , that is, a reduction of the exhaust gas temperature T 2n  is generated since the ignition of the fuel by the glow plug  30  is not performed, it is determined that there is no malfunction in the opening/closing action of the bypass valve  32 , and the process goes to a step of S 20 . At this step of S 20 , the flag is reset, and steps after S 11  are again repeated. In addition, in a case where it is determined that the flag is not set, that is, the bypass valve  32  is not changed from the opening state to the closing state, steps after S 11  are again repeated. 
     On the other hand, in a case where it is determined at the step of S 16  that the DPF  25   b  is not during the regeneration processing, that is, there is a possibility of imposing an adverse effect on the exhaust emission purifier  25  by supplying fuel, the process goes to a step of S 21 . Also in a case where at the step of S 11 , it is determined that the exhaust gas temperature T 2n  is higher than the catalyst active temperature T L , that is, it is not necessary to heat the exhaust emission purifier  25  since the exhaust emission purifier  25  is in an active state, the process goes to the step of S 21 . At this step of S 21 , the third exhaust gas processing mode for stopping an operation of the exhaust gas processing apparatus  26  is executed. That is, the bypass valve  32  is closed, the power supply to the glow plug  30  changes into an OFF-state, and supply of the fuel from the injection supplying valve  29  is stopped. Thereafter, the process goes to the step of S 18 , wherein it is determined whether or not a flag showing that the bypass valve  32  is opened is set. 
     In a case where at the step of S 19 , it is determined that the exhaust gas temperature T 2n  is equal to or higher than the previously detected exhaust gas temperature T 2 (n−1) , that is, it is determined that there is malfunction in the glow plug  30 , the bypass valve  32  or the bypass valve actuator  33 , the process goes to a step of S 22 . At the step of S 22 , the indicator driving unit  13   n  drives the warning indicator  38  to inform a passenger of the malfunction of the exhaust gas processing apparatus  26 , and outputs a failure warning for promoting the repair and resets the flag, thus completing the control in regard to the exhaust gas processing. 
     In the aforementioned embodiment, it is determined whether or not the fuel is ignitable based upon the first exhaust gas temperature T 2n , the intake air flow rate Q n , and the O 2  concentration D n , but it is possible also to determine whether or not the fuel is ignitable based upon a load of the engine  10 . More specially in a case where the load of the engine  10  is below a light load, for example, a vehicle is in the decelerating state or the engine  10  is in an idling state, it can be determined that there is no possibility that there is the flame failure of the ignited fuel since a flow speed of the exhaust gas flowing in the exhaust passage  22   a  is slow. In reverse, in a case where the load of the engine  10  is in a state other than the above, it can be determined that there is a possibility that there is the flame failure of the ignited fuel since the flow speed of the exhaust gas flowing in the exhaust passage  22   a  is rapid. In this case, the load detection of the engine  10  can be calculated by the operating status determining unit  13   a  in the ECU  13 . More specially the load of the engine  10  can be calculated based upon a depressing travel of the accelerator pedal  12  detected by the accelerator opening sensor  14  and an engine rotation speed calculated based upon the detection information from the crank angle sensor  21 . That is, the ECU  13  includes load detecting means in the present invention. 
     A control flow in the other embodiment of the present invention is shown in  FIG. 5 , but steps having the same functions as the above embodiment are referred to as identical codes, and the identical explanation is omitted. In the present embodiment, at the step of S 11 , when it is determined that the exhaust gas temperature T 2n  is below the catalyst active temperature T L , that is, it is necessary to heat the exhaust emission purifier  25  for activation or maintain an active state thereof, the process goes to a step of S 23 . Further, it is determined whether or not the vehicle is in the decelerating state. In a case where it is determined that the vehicle is in the decelerating state, that is, the accelerator pedal  12  is not depressed and an engine rotational speed is reduced or a negative acceleration is generated, the process goes to the step of S 14 . As a result, the first exhaust gas processing mode is executed. In addition, in a case where at the step of S 23  it is determined that the vehicle is not in the decelerating state, the process goes to a step of S 24 , wherein it is determined whether or not the engine  10  is in an idling state. Here, in a case where it is determined that the engine  10  is in the idling state, that is, the accelerator pedal  12  is not depressed and the engine rotational speed is in an idling rotational region, the process goes to the step of S 14 , wherein the first exhaust gas processing mode is executed. 
     In a case where at the step of S 24  it is determined that the engine  10  is not in the idling state, that is, the load of the engine is not below a light load, the process goes to the step of S 16 , wherein it is determined whether or not the DPF  25   b  is during regeneration processing, and thereafter the same procedure as that of the above embodiment is executed. 
     It should be noted that, the present invention should be interpreted based only upon the matters described in claims, and in the aforementioned embodiments, all changes and modifications included within the spirit of the present invention can be made other than the described matters. That is, all the matters in the described embodiments are made not to limit the present invention, but can be arbitrarily changed according to the application, the object and the like, including every construction having no direct relation to the present invention. 
     Reference Signs List
       10  ENGINE     10   a  COMBUSTION CHAMBER     11  FUEL INJECTION VALVE     12  ACCELERATOR PEDAL     13  ECU     13   a  OPERATING STATUS DETERMINING UNIT     13   b  FUEL INJCETION SETTING UNIT     13   c  FUEL INJECTION VALVE DRIVING UNIT     13   d  THROTTLE OPENING SETTING UNIT     13   e  THROTTLE VALVE DRIVING UNIT     13   f  EGR RATE SETTING UNIT     13   g  EGR VALVE DRIVING UNIT     13   h  FUEL SUPPLYING VALVE DRIVING UNIT     13   i  GLOW PLUG DRIVING UNIT     13   j  FLAME FILURE DETERMINING UNIT     13   k  PROCESSING MODE SELECTING UNIT     13   l  BYPASS VALVE DRIVING UNIT     13   m  FAILURE DETERMINING UNIT     13   n  INDICATOR DRIVING UNIT     13   o  DPF REGENERATION PROCESSING UNIT     14  ACCELERATOR OPENING SENSOR     15  CYLINDER HEAD     15   a  INTAKE PORT     15   b  EXHAUST PORT     16   a  INTAKE VALVE     16   b  EXHAUST VALVE     17  INTAKE CONDUIT     17   a  INTAKE PASSAGE     17   b  SURGE TANK     18  THROTTLE ACTUATOR     19  THROTTLE VALVE     20  CYLINDER BLOCK     20   a  PISTON     20   b  CONNECTING ROD     20   c  CRANK SHAFT     21  CRANK ANGLE SENSOR     22  EXHAUST CONDUIT     22   a  EXHAUST PASSAGE     23  EGR SYSTEM     24  EXHAUST TURBOCHARGER     24   a  COMPRESSOR     24   b  EXHAUST TURBINE     24   c  INTERCOOLER     25  EXHAUST EMISSION PURIFIER     25   a  OXIDATION CATALYTIC CONVERTER     25   b  DPF     26  EXHAUST GAS PROCESSING APPARATUS     27  EGR CONDUIT     27   a  EGR PASSAGE     28  EGR VALVE     29  FUEL SUPPLYING VALVE     30  GLOW PLUG     31  BYPASS CONDUIT     31   a  BYPASS PASSAGE     32  BYPASS VALVE     33  BYPASS VALVE ACTUATOR     34  AIRFLOW METER     35  FIRST EXHAUST GAS TEMPERATURE SENSOR     36  SECOND EXHAUST GAS TEMPERATURE SENSOR     37  O 2  SENSOR     38  WARNING INDICATOR