Patent Publication Number: US-2013228228-A1

Title: Method and device for judging propriety of egr valve operation

Description:
TECHNICAL FIELD 
     The present invention relates to a method and a device for judging propriety of an EGR valve operation. 
     BACKGROUND ART  
     For example, in an engine for an automobile, so-called exhaust gas recirculation (EGR) has been employed in which part of exhaust gas is extracted from an exhaust side and is returned to an intake-air side. The exhaust gas returned to the intake-air side suppresses combustion of fuel in the engine to lower a combustion temperature, thereby reducing NO x  generation. 
     Generally, for execution of this kind of exhaust gas recirculation, an exhaust system from an exhaust manifold to an exhaust pipe is connected with an intake-air system from an intake pipe to an intake manifold through an EGR pipe constituting an EGR system, the exhaust gas being recirculated via the EGR pipe. 
     A water-cooled type EGR cooler may be incorporated in the EGR pipe which recirculates the exhaust gas to the engine since cooling of the exhaust gas to be recirculated to the engine during its passing through the EGR pipe will lower and reduce a temperature and a volume of the exhaust gas, which results in lowering of a combustion temperature without substantially lowering engine output and can effectively reduce nitrogen oxides generated. 
     There exists, for example, the following Patent Literature 1 as prior art document relating to this kind of EGR device. 
     CITATION LIST 
     Patent Literature 
     [Patent Literature 1] JP 2001-123889A 
     SUMMARY OF INVENTION 
     Technical Problems 
     However, in such an EGR device, an EGR valve may be frozen due to flocculated water generated in an EGR pipe for example in a particular condition where an engine is stopped after a long-term idling thereof in a cold climate or the like; then, in a next cold start, the frozen EGR valve may not be actuated in spite of operating command from the controller to the EGR valve for recirculation of the exhaust gas. When such malfunction of the EGR valve due to freezing is detected as abnormality, then unnecessary exchange of the EGR valve may be conducted owing to the detected abnormality irrespective of a fact that the EGR valve may be normally operated after thawing. 
     The invention was made in view of the above and has its object to prevent malfunction of an EGR valve due to freezing from being detected as abnormality and unnecessarily exchanged. 
     Solution to Problems 
     The invention is directed to a method for judging propriety of an EGR valve operation characterized by detecting a temperature surrounding the EGR valve, judging on the basis of the detected temperature whether an inside of a gas passage in said EGR valve is frozen or not, and forbidding and allowing outputting of an operating command to an actuator for said EGR valve when the inside of the gas passage in said EGR valve is judged to be frozen and unfrozen, respectively. 
     In specifically executing the method for judging propriety of an EGR valve operation according to the invention, provided are a temperature sensor for detecting a temperature surrounding the EGR valve, judging means for judging on the basis of the detected temperature by said temperature sensor whether an inside of a gas passage in said EGR valve is frozen or not and a controller for controlling an operation of said EGR valve, said controller being adapted to forbid and allow an output of an operating command to an actuator for said EGR valve when the inside of the gas passage in said EGR valve is judged by said judging means to be frozen or unfrozen, respectively. 
     Thus, the temperature surrounding the EGR valve is detected by the temperature sensor, and whether the inside of the gas passage in the EGR valve is frozen or not is judged by the judging means on the basis of the detected temperature by the temperature sensor. When the inside of the gas passage is judged by the judging means to be frozen, an output of the operating command to the actuator for the EGR valve is forbidden to prevent the malfunction of the EGR valve due to the freezing from being detected as abnormality. 
     When the inside of the gas passage in the EGR valve is judged by the judging means to be unfrozen, then the output of the operating command to the actuator for the EGR valve is allowed to judge and detect as usual a malfunction of the EGR valve not due to freezing to be actual abnormality such as mechanical failure. 
     Advantageous Effects of Invention 
     According to a method and a device for judging propriety of an EGR valve operation as mentioned in the above, a temperature surrounding an EGR valve is detected and, on the basis of the detected temperature, whether an inside of a gas passage in the EGR valve is frozen or not is judged; when the inside of the gas passage in the EGR valve is judged to be frozen, an output of an operating command to an actuator for the EGR valve can be forbidden, which brings about an excellent effect that malfunction of the EGR valve due to freezing can be prevented from being detected as abnormality to prevent unnecessary exchange of the EGR valve. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic view showing an embodiment of the invention; and 
         FIG. 2  is a flowchart for illustration of judgment logic on propriety of EGR valve operation. 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     An embodiment of the invention will be disclosed in conjunction with the drawings. 
       FIG. 1  shows the embodiment of the invention. In the illustrated embodiment, intake air  3  from an air cleaner  1  is sent through an intake pipe  4  to a compressor  2   a  of a turbocharger  2 . The intake air  3  pressurized by the compressor  2   a  is sent to an intercooler  5  where the air is cooled and is further guided to an intake manifold  6  where the air is distributed to respective cylinders  7  of the engine (an in-line six-cylinder engine is illustrated in  FIG. 1 ). 
     An exhaust gas  8  discharged from the respective cylinders  7  is sent through an exhaust manifold  9  to a turbine  2   b  of the turbocharger  2 . The exhaust gas  8  having driven the turbine  2   b  is sent through an exhaust pipe  10  to outside of a vehicle. 
     An end of the exhaust manifold  9  in a direction of arrangement of the respective cylinders  7  is connected to a portion of the intake pipe  4  adjacent to an inlet of the intake manifold  6  through an EGR pipe  11  so as to extract part of the exhaust gas  8  from the exhaust manifold  9  into the intake pipe  4 . 
     The EGR pipe  11  is provided with an openable and closable EGR valve  12  and an EGR cooler  13  for cooling of the exhaust gas  8  to be recirculated. In the EGR cooler  13 , cooling water (not shown) is heat-exchanged with the exhaust gas  8  so as to lower a temperature in the exhaust gas  8 . 
     Arranged in an actuator  14  for opening/closing operation of the EGR valve  12  are a temperature sensor  15  for detection of a temperature in the actuator  14  as temperature surrounding the EGR valve  12  as well as an IC chip  16  (judging means) for receiving a detection signal  15   a  from the temperature sensor  15  to judge on the basis of the detected temperature whether an inside of a gas passage in the EGR valve  12  is frozen or not. A judgment result from the IC chip  16  is inputted as a judgment signal  16   a  to a controller  17  controlling the EGR valve  12 . (In  FIG. 1 , for convenience of illustration, the temperature sensor  15  and the IC chip  16  are drawn outside of the actuator  14 .) 
     In the controller  17 , an output of the operating command  17   a  is forbidden and allowed when the inside of the gas passage in the EGR valve  12  is judged by the IC chip  16  to be frozen and unfrozen, respectively. 
     Specifically, judgment logic on propriety of the EGR valve  12  operation will be explain with respect to a flowchart of  FIG. 2 . Firstly in step S 1  on the actuator  14  side, judged is whether the detected temperature by the temperature sensor  15  is on or above a predetermined temperature which is a threshold value for judgment on whether an inside of the gas passage in the EGR valve  12  is frozen or not. When the detected temperature is lower than the predetermined temperature, then the procedure proceeds to Step S 2  where the inside of the gas passage in the EGR valve  12  is judged to be frozen. Then, in Step S 3  on the controller  17  side, forbidden is an output of an operating command  17   a  to the actuator  14 . 
     When the judgment in Step S 1  on the actuator  14  side is to be on or above the predetermined temperature, the procedure proceeds to Step S 4  where the inside of the gas passage in the EGR valve  12  is judged not to be frozen. Then, in Step S 5  on the controller  17  side, allowed is the output of the operating command  17   a  to the actuator  14 . 
     In the illustrated embodiment, the IC chip  16  incorporated in the actuator  14  for the EGR valve  12  is used as judging means for judging on being frozen or not. Of course, alternatively, a judgment program corresponding to the judging means may be incorporated on the controller  17  side to receive on the controller  17  side the detection signal  15   a  from the temperature sensor  15 , so that the judgment program in the controller  17  is used as the judging means for judging, on the controller  17  side, on being frozen or not. 
     Thus, with the device for judging propriety of an EGR valve  12  operation constructed as mentioned in the above, the inner temperature of the actuator  14  is detected by the temperature sensor  15  as the temperature surrounding the EGR valve  12 . On the basis of the detected temperature by the temperature sensor  15 , whether the inside of the gas passage in the EGR valve  12  is frozen or not is judged by the IC chip  16 . When the inside of the gas passage in the EGR valve  12  is judged by the IC chip  16  to be frozen, then the output of the operating command  17   a  to the actuator  14  for the EGR valve  12  is forbidden by the judgment signal  16   a,  so that the malfunction of the EGR valve  12  due to the freezing is prevented from being detected as abnormality. 
     When the inside of the gas passage in the EGR valve  12  is judged by the IC chip  16  not to be frozen, the output of the operating command  17   a  to the actuator  14  for the EGR valve  12  is allowed by the judgment signal  16   a,  so that the malfunction of the EGR valve  12  not due to the freezing is detected as usual as actual abnormality such as mechanical failure. 
     Thus, according to the above-mentioned embodiment, the temperature surrounding the EGR valve  12  is detected. On the basis of the detected temperature, judgment is made on whether the inside of the gas passage in the EGR valve  12  is frozen or not. When the inside of the gas passage in the EGR valve  12  is judged to be frozen, the output of the operating command  17   a  to the actuator  14  for the EGR valve  12  can be forbidden, so that the malfunction of the EGR valve  12  due to freezing can be prevented from being detected as abnormality to prevent unnecessary exchange of the EGR valve  12 . 
     It is to be understood that a method and a device for judging propriety of an EGR valve operation are not limited to the above-mentioned embodiment. For example, illustrated in the above-mentioned embodiment is detection of the inner temperature of the actuator for the EGR valve by means of the temperature sensor arranged in the actuator; however, the temperature sensor may be arranged in any other position where the temperature surrounding the EGR valve can be detected. 
     REFERENCE SIGNS LIST 
     
         
           12  EGR valve 
           14  actuator 
           15  temperature sensor 
           15   a  detection signal 
           16  IC chip (judging means) 
           16   a  judgment signal 
           17  controller 
           17   a  operating command