JP6422899B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine that controls the internal combustion engine, and more particularly, to a control device for an internal combustion engine that corrects a control amount of the internal combustion engine by measuring the humidity of fresh air sucked into the internal combustion engine.

  In recent years, regulations on fuel consumption and exhaust of vehicles such as automobiles are being strengthened, and these regulations tend to become stronger in the future. In particular, fuel consumption has become extremely interested due to the recent rise in gasoline prices, the impact on global warming, and the problem of exhaustion of energy resources. Under such circumstances, various technical developments for the purpose of improving the fuel efficiency of vehicles have been carried out. For example, improvement of the compression ratio, introduction of a large amount of external EGR, expansion of the stoichiometric combustion region, etc. have been carried out.

  In these techniques, it is important to optimize the combustion, and it is necessary to appropriately control the ignition timing together with the highly accurate management of the air-fuel mixture in the combustion chamber. In the combustion of an internal combustion engine, there is an ignition timing (hereinafter referred to as MBT ignition timing) at which the fuel efficiency is the best, and control is performed so as to approach the MBT ignition timing as much as possible. For example, when the exhaust gas is introduced into the combustion chamber by the external EGR, the combustion speed is reduced and the output is reduced. Therefore, it is necessary to correct and control the ignition timing to the advance side, and the ignition timing according to the exhaust gas amount of the external EGR. Is corrected.

  Furthermore, recently, in order to improve fuel efficiency, the demand for higher accuracy of ignition timing has been further increased, and a method for correcting the ignition timing in accordance with the humidity of the intake air has been studied. Humidity, like exhaust gas from external EGR, is a factor that inhibits combustion, so when the humidity is high, the ignition timing is corrected to the advance side, and conversely, when the humidity is low, the ignition timing is corrected to the retard side. I am doing so.

  As a method for correcting the ignition timing in accordance with the humidity as described above, for example, Japanese Patent Laid-Open No. 9-68146 (Patent Document 1) is known. In Patent Document 1, a basic ignition timing composed of a rotation speed and a load is stored as map data, a correction amount of the ignition timing is calculated from the detected humidity, and according to at least one of the rotation speed, load, and temperature. It is described that a reflection rate that reflects the correction amount is calculated and a final ignition timing is determined from the basic ignition timing, the correction amount, and the reflection rate. According to this method, the ignition timing can be corrected from the detected humidity.

  The ignition timing correction control based on the humidity information described in Patent Document 1 cannot correct the ignition timing correctly if an abnormal value is output due to a failure of the humidity sensor. When the combustion of the engine becomes unstable and misfires, misfires may occur, leading to an increase in exhaust harmful components discharged from the internal combustion engine and an increase in fuel consumption. In Patent Document 1, there is no suggestion about a technique corresponding to the abnormality of the humidity sensor.

  On the other hand, as a method for providing a humidity sensor in an exhaust system and detecting an abnormality of the humidity sensor, for example, Japanese Patent Laid-Open No. 2003-172192 (Patent Document 2) is known. In patent document 2, it aims at detecting the presence or absence of the failure of the humidity sensor provided in the vicinity of HC adsorbent of the exhaust system of an internal combustion engine. Then, in a state where the humidity detected value by the humidity sensor becomes substantially constant after the operation of the internal combustion engine is stopped, the presence or absence of a failure of the humidity sensor is detected based on the detected value. The detection of the presence or absence of failure is to determine whether the humidity detection value is within a range between a predetermined upper threshold value and a lower threshold value set according to the temperature state in the vicinity of the HC adsorbent. It is done by.

  However, Patent Document 2 determines a failure of the humidity sensor after the internal combustion engine is stopped, and does not describe a case where the internal combustion engine is operating. The purpose of Patent Document 2 is to correctly evaluate the deterioration of the HC adsorbent for adsorbing hydrocarbons (HC) in the exhaust gas, and control for controlling the control amount of the internal combustion engine such as ignition timing control. It is not a diagnosis to guarantee the operation of the device.

JP-A-9-68146 JP 2003-172192 A

  Incidentally, as control for correcting the control amount (control target value) of the internal combustion engine based on the magnitude of humidity, there is external EGR control in addition to the ignition timing control described above. In this external EGR control, a humidity sensor for measuring the humidity of the intake air is arranged on the inlet side of the intake pipe, and a mixed gas (hereinafter referred to as fresh air gas) in which the intake air and the exhaust gas (external gas) from the external EGR are mixed. The humidity sensor that measures the humidity is installed on the collector side. The external EGR rate is estimated from the humidity information of the plurality of humidity sensors to improve the accuracy of the external EGR control. The external EGR rate is also reflected in the correction amount for correcting the ignition timing as described above.

  Then, the humidity is measured while the internal combustion engine is driven, and a target value such as an external EGR rate is obtained corresponding to the measured humidity. Or failure (hereinafter collectively referred to as failure) must be detected.

  For this reason, a humidity sensor that measures the humidity in the intake air provided at the inlet of the intake pipe and the humidity of fresh air gas mixed with external gas other than intake air, such as exhaust gas by external EGR, and intake air are measured. The development of a specific humidity sensor failure diagnosis technique for detecting an abnormality or failure of the humidity sensor is demanded. In addition to the exhaust gas from the external EGR, the purge gas from the canister is known as the external gas mixed with the intake air, and the fresh air gas is mixed with the external gas other than the intake air to enter the combustion chamber. It means the gas to be supplied.

  An object of the present invention is to provide a novel internal combustion engine that can accurately detect a failure of the humidity sensor that measures the humidity of the intake air and the humidity sensor that measures the humidity of the new gas while the internal combustion engine is driven. It is to provide a control device.

  The feature of the present invention is to compare the humidity information of the humidity sensor provided in the pipeline through which the intake air flows and the humidity information when the external gas in the humidity sensor provided in the pipeline through which fresh gas flows is shut off, When a difference greater than or equal to a predetermined value occurs in both humidity information, it is determined that a failure has occurred in one of the humidity sensors.

  According to the present invention, it is possible to accurately detect a failure of the humidity sensor that measures the humidity of the intake air and the humidity sensor that measures the humidity of the fresh gas while the internal combustion engine is being driven. .

1 is a configuration diagram showing an overall configuration of an internal combustion engine system equipped with a control device for an internal combustion engine to which the present invention is applied. It is a control block diagram which shows the humidity sensor failure determination means of this invention. It is explanatory drawing explaining the conditions which permit humidity sensor failure determination. It is explanatory drawing explaining the process which performs failure determination of a humidity sensor during humidity sensor failure determination permission. It is the flowchart figure which showed the control flow which performs failure determination of a humidity sensor.

  Embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments, and various modifications and application examples are included in the technical concept of the present invention. It is included in the range.

  FIG. 1 shows an internal combustion engine system equipped with a control device for an internal combustion engine to which the present invention is applied.

  The internal combustion engine 10 is, for example, a spark ignition type multi-cylinder internal combustion engine having four cylinders. The internal combustion engine 10 includes a cylinder 11 including a cylinder head 11a and a cylinder block 11b, and is slidably fitted in each cylinder. The piston 12 is connected to a crankshaft (not shown) via a connecting rod 13.

  In addition, a combustion chamber 14 having a ceiling portion with a predetermined shape is formed above the piston 12, and an ignition plug 16 to which an ignition signal having a high voltage is supplied from an ignition coil 15 to the combustion chamber 14 of each cylinder. Is erected.

  The combustion chamber 14 communicates with an intake pipe 22 having an air cleaner 17, a throttle valve 18, a collector 19, an intake manifold 20, an intake port 21, and the like, and air necessary for fuel combustion passes through the intake pipe 22. As described above, the air is drawn into the combustion chamber 14 of each cylinder through the intake valve 24 that is opened and closed by the intake camshaft 23 disposed at the end of the intake port 21 that is the downstream end of the intake pipe 22. ing. A fuel injection valve 25 for injecting fuel toward the intake port 21 is provided for each cylinder in the intake manifold 20 of the intake pipe 22.

  An air flow sensor 26 that detects the flow rate of intake air is disposed downstream of the air cleaner 17 in the intake pipe 22. In the air flow sensor 26, as the intake air amount (mass flow rate) increases, the current value flowing through the hot wire (heating resistor) arranged in the intake air flow to be measured increases, and the intake air amount decreases. The bridge circuit is configured so that the value of the current flowing through the hot wire decreases as the time goes. The heating resistance current value flowing through the hot wire of the air flow sensor 26 is detected as a voltage signal and transmitted to the ECU (engine control unit) 27.

  The air-fuel mixture of the air sucked through the intake pipe 22 and the fuel injected from the fuel injection valve 25 is sucked into the combustion chamber 14 through the intake valve 24 and is generated by the spark plug 16 connected to the ignition coil 15. It is burned by spark ignition. Exhaust gas after combustion in the combustion chamber 14 is exhausted from the combustion chamber 14 through an exhaust valve 29 that is opened and closed by an exhaust camshaft 28, and passes through an exhaust port, an exhaust manifold, an exhaust pipe, and the like (not shown). The gas is discharged into the outside atmosphere through the exhaust passage 30 provided.

  The exhaust passage 30 is provided with a three-way catalyst 31 for purifying exhaust gas in which platinum, palladium or the like is applied to a carrier such as alumina or ceria. As an aspect of the vessel, an air-fuel ratio sensor 32 having a linear output characteristic with respect to the pre-catalyst air-fuel ratio is disposed, and the post-catalyst air-fuel ratio is less than stoichiometric (theoretical air-fuel ratio) downstream of the three-way catalyst 31. Is also provided with an O2 sensor 33 that outputs a switching signal for identifying the rich side or the lean side.

  Further, an EGR pipe 34 for recirculating exhaust gas from the upstream of the three-way catalyst 31 in the exhaust passage 30 to the upstream of the collector 19 of the intake pipe 22 is provided. Further, an EGR cooler 35 for cooling the exhaust gas passing through the EGR pipe 34 and an EGR valve 36 for controlling the EGR flow rate are mounted at appropriate positions on the EGR pipe 34.

  Moreover, although not shown in figure, the temperature sensor which measures the temperature of the cooling water which goes around an internal combustion engine is provided. In the present embodiment, the EGR pipe 34 is connected upstream of the three-way catalyst 31, but it is also possible to connect the EGR pipe 34 downstream of the three-way catalyst 31.

  A fuel injection valve 25 provided for each cylinder of the internal combustion engine 10 is connected to a fuel tank 37 via a fuel pipe (not shown), and the fuel inside the fuel tank 37 is a fuel pump. The fuel is supplied to the fuel injection valve 25 after being adjusted to a predetermined fuel pressure by a fuel supply mechanism including a fuel pressure regulator 38 and a fuel pressure regulator 39.

  Further, the fuel vapor in the fuel tank 37 is adsorbed by the activated carbon 42 in the charcoal canister 41 through the canister pipe 40 and connected to the purge introduction pipe 44 and the intake pipe 22 together with the air introduced from the fresh air introduction pipe 43. Flows into the section. The purge introduction pipe 44 is provided with a purge control valve 45 for adjusting the purge flow rate, and the purge flow rate is adjusted by the negative pressure in the intake pipe 22.

  The fuel injection valve 25 to which fuel of a predetermined fuel pressure is supplied is opened by a fuel injection pulse signal having a duty (pulse width: corresponding to the valve opening time) corresponding to the operating state such as the engine load supplied from the ECU 27. Then, an amount of fuel corresponding to the valve opening time is injected toward the intake port 21.

  The ECU 27 is a microcomputer for performing various controls of the internal combustion engine 10, for example, fuel injection control (air-fuel ratio control) by the fuel injection valve 25, ignition timing control by the spark plug 16, external EGR control, purge gas control, and the like. Built-in.

  An external gas different from the intake air (in this embodiment, exhaust gas from the external EGR and purge gas from the canister) is upstream of the external gas introduction port (preferably the pressure in the intake pipe 22 is substantially equal to the atmosphere). A first humidity sensor 46 is provided in the intake pipe 22 on the upstream side of the equal throttle valve 218. The first humidity sensor 46 is a humidity sensor that measures the humidity of only the intake air.

  On the other hand, a second humidity sensor 47 is attached downstream of the external gas inlet through which external gas different from the intake air flows into the intake pipe 22. In the present embodiment, a second humidity sensor 47 is disposed in the collector 19, and the second humidity sensor 47 measures the humidity of fresh air, which is a mixed gas of external gas different from intake air and intake air. Sensor.

  Each of the humidity sensors 46 and 47 measures the humidity of the intake air and new gas flowing in the intake pipe, and the measured humidity information signal is transmitted to the ECU 27. Here, the first humidity sensor 46 and the second humidity sensor 47 are sensors capable of detecting relative humidity or absolute humidity, and a temperature sensor and a pressure sensor (not shown) are incorporated in a chip for detecting humidity. In addition to the humidity, temperature information and pressure information are also transmitted to the ECU 27.

  The first humidity sensor 46 may be used with the airflow sensor 26 having a function of measuring humidity. The first humidity sensor 46 of the present embodiment shows an example that is mounted between the air flow sensor 26 and the throttle valve 18.

  Output signals obtained from various sensors such as the air flow sensor 26, the first humidity sensor 46, the second humidity sensor 47, the air-fuel ratio sensor 32, and the O2 sensor 33 are sent to the ECU 27 (here, signal lines are shown). Not) A signal obtained from the accelerator opening sensor 48 is also sent to the ECU 27. The accelerator opening sensor 48 detects the depression amount of the accelerator pedal, that is, the accelerator opening. The ECU 27 calculates the required torque based on the output signal of the accelerator opening sensor 48. That is, the accelerator opening sensor 48 is used as a required torque detection sensor that detects a required torque for the internal combustion engine.

  Further, the ECU 27 calculates the rotation speed of the internal combustion engine based on the output signal of the crank angle sensor. The ECU 27 optimally calculates main control amounts of the internal combustion engine such as an air flow rate, a fuel injection amount, an ignition timing, an external EGR amount, and a purge amount based on the operation state of the internal combustion engine obtained from the outputs of the various sensors.

  FIG. 2 shows a control block for performing failure determination of the humidity sensor according to the present embodiment. The humidity information of the absolute humidity measuring means 50 for obtaining the absolute humidity from the output signal of the first humidity sensor 46, and the second The humidity sensor failure determination means 52 detects the failure state of the first humidity sensor 46 or the second humidity sensor 47 from the humidity information of the absolute humidity measurement means 51 for obtaining the absolute humidity from the output signal of the humidity sensor 47. is there.

  The control block shown in FIG. 2 is a failure determination function unit that represents a humidity sensor failure determination function executed by a microcomputer as a block.

  Humidity information from the absolute humidity measuring means 50 connected to the first humidity sensor 46 and humidity information from the absolute humidity measuring means 51 connected to the second humidity sensor are input to the humidity sensor failure determination means 52. Has been. Further, the humidity sensor failure determination means 52 includes EGR control state information from the EGR control operation determination unit 53, purge control state information from the purge control operation determination unit 54, and EGR valve failure state information from the EGR valve failure determination unit 55. The purge valve failure determination unit 56 receives purge valve failure state information.

  The EGR control state information from the EGR control operation determination unit 53, the purge control state information from the purge control operation determination unit 54, the EGR valve failure state information from the EGR valve failure determination unit 55, and the purge valve failure determination unit 56 from the purge valve failure determination unit 56 The reason for inputting the failure state information will be described later.

  The humidity sensor failure determination means 52 is the absolute humidity information obtained from the first humidity sensor 46 and the absolute humidity measurement means 50 arranged in the intake pipe 22 on the upstream side of the throttle valve 18 while the internal combustion engine is driven. A comparison function for comparing the second humidity sensor 47 arranged in the collector 19 and the absolute humidity information obtained from the absolute humidity measuring means 51 is provided. Further, when the absolute humidity information has a difference greater than or equal to a predetermined value, a failure determination that determines that one of the first humidity sensor 46 or the second humidity sensor 47 is defective. It has a function.

  Here, humidity information in the present embodiment will be described. Humidity includes relative humidity and absolute humidity, and relative humidity tends to depend on temperature. Since the environmental temperature in the vicinity of the airflow sensor 26 where the first humidity sensor 46 is installed is different from the environmental temperature inside the collector 19 where the second humidity sensor 47 is installed, the relative humidity is compared. It is not preferable to perform the failure determination.

  Therefore, it is desirable to compare the humidity information at an absolute humidity that does not depend on the temperature. In this embodiment, the comparison of the absolute humidity is also performed. Humidity sensors include a relative humidity sensor that detects relative humidity and an absolute humidity sensor that detects absolute humidity. For this reason, when a relative humidity sensor that detects relative humidity is used as the humidity sensor, it is necessary to compare the humidity after converting the relative humidity to absolute humidity.

  When comparing the absolute humidity converted from the relative humidity acquired from the relative humidity sensor with the absolute humidity acquired from the absolute humidity sensor, the output accuracy of the humidity sensor may be different or an error due to calculation may be considered. It is important to correct and compare. In the present embodiment, a relative humidity sensor is used for the first humidity sensor 46, and an absolute humidity sensor is used for the second humidity sensor 47. For this reason, since the humidity information of the first humidity sensor 46 is relative humidity, the humidity information is obtained after conversion to absolute humidity.

  Next, a failure determination condition for the humidity sensor will be described. In order to compare the humidity information of the first humidity sensor 46 and the second humidity sensor 47 and execute the failure determination, the detection environments of the first humidity sensor 46 and the second humidity sensor 47 are the same or equivalent. There must be. That is, if the absolute humidity of the intake air detected by the first humidity sensor 46 and the absolute humidity of the fresh air detected by the second humidity sensor 47 are not equal, the first humidity sensor 46 and the second humidity sensor This is because the failure information cannot be determined by comparing the 47 humidity information.

  Therefore, in order to make the detection environments of the first humidity sensor 46 and the second humidity sensor 47 the same or equivalent, the humidity sensor failure determination means 52 includes the EGR control state information from the EGR control operation determination unit 53, purge The purge control state information from the control operation determination unit 54, the EGR valve failure state information from the EGR valve failure determination unit 55, and the purge valve failure state information from the purge valve failure determination unit 56 are input.

  As shown in FIG. 1, the intake air flowing from the intake pipe 22 passes through the first humidity sensor 46 and flows into the collector 19, passes through the second humidity sensor 47, and is supplied to the combustion chamber 14. The In this case, the first humidity sensor 46 detects the absolute humidity based on the moisture contained in the intake air IA.

  On the other hand, when the exhaust gas EG is re-inhaled into the intake pipe 22 upstream of the collector 19 by executing the external EGR control, the fresh air gas CG flowing through the collector 19 becomes “CG = IA + EG”. The fresh air gas CG is added with moisture contained in the exhaust gas EG in addition to moisture contained in the intake air IA.

  Thus, since the moisture content of the intake air that has passed through the first humidity sensor 46 and the moisture content of the fresh air gas that has passed through the second humidity sensor 47 are different, the absolute humidity detected by the first humidity sensor 46. The absolute humidity detected by the second humidity sensor 47 is different.

  Therefore, when the external EGR control is being executed, the humidity information (output value) of the first humidity sensor 46 and the second humidity sensor 47 cannot be compared. It is important not to execute the humidity sensor failure determination. Thus, in order to determine the state in which the EGR control is being executed, the EGR control state information from the EGR control operation determination unit 53 is used.

  Similarly, when the purge gas PG is re-inhaled into the intake pipe 22 upstream of the collector 19 by executing the purge control, the fresh air gas CG flowing through the collector 19 becomes “CG = IA + PG”. The fresh air gas CG is added with moisture contained in the purge gas PG in addition to moisture contained in the intake air IA.

  Thus, since the moisture content of the intake air that has passed through the first humidity sensor 46 and the moisture content of the fresh air gas that has passed through the second humidity sensor 47 are different, the absolute humidity detected by the first humidity sensor 46. The absolute humidity detected by the second humidity sensor 47 is different.

  Therefore, since the humidity information (output value) of the first humidity sensor 46 and the second humidity sensor 47 cannot be compared in the state in which the purge control is being executed, the humidity sensor is in operation when the purge control is operating. It is important not to execute the failure determination. In order to determine the state in which the purge control is executed in this way, the purge control state information from the purge control operation determination unit 54 is used. Of course, the same applies to an internal combustion engine system in which both EGR control and purge control are incorporated.

  Further, as shown in FIG. 1, even if the operation of the EGR control is stopped and the EGR valve 36 is changed from the “open state” to the “closed state”, the exhaust gas is supplied to the EGR pipe 34 between the EGR valve 36 and the suction pipe 22. However, the exhaust gas inflow is not immediately stopped. Therefore, since the remaining exhaust gas flows into the collector 19 and is mixed with the intake air, the absolute humidity detected by the first humidity sensor 46 and the absolute humidity detected by the second humidity sensor 47 Will be different.

  Therefore, the humidity information (output value) of the first humidity sensor 46 and the second humidity sensor 47 cannot be compared until the predetermined time elapses after the EGR control is stopped. It is important not to execute the humidity sensor failure determination. The EGR control state information from the EGR control operation determination unit 53 is used to determine a state in which a predetermined time has elapsed since the EGR control was stopped in this way. In this case, it is only necessary to measure a predetermined time with a timer starting from the stop time of EGR control, and to execute a failure determination of the humidity sensor when the predetermined time has elapsed.

  Similarly, it is important not to execute the humidity sensor failure determination until the purge control is stopped and a predetermined time elapses. In order to determine a state in which a predetermined time has elapsed since the purge control was stopped in this manner, the purge control state information from the purge control operation determination unit 54 is used. In this case, a predetermined time is measured with a timer starting from the stop time of the purge control, and when the predetermined time has elapsed, failure determination of the humidity sensor may be executed.

  Further, as shown in FIG. 1, when the EGR valve 36 fails, for example, the EGR valve 36 is controlled to be “closed” in the external EGR control. There is a state that is not "state". For this reason, although the exhaust gas recirculation is stopped as the external EGR control, the exhaust gas containing moisture actually flows into the intake pipe 22.

  For this reason, since the moisture content of the intake air passing through the first humidity sensor 46 and the moisture content of fresh air passing through the second humidity sensor 47 are different, the humidity is reduced when the EGR valve 36 is malfunctioning. It is important not to perform sensor failure determination. Thus, in order to determine the state in which the EGR valve has failed, the failure state information of the EGR valve from the EGR valve failure determination unit 55 is used.

  Similarly, it is important not to execute the humidity sensor failure determination when the purge valve has failed. In order to determine the state in which the purge valve has failed in this way, the purge valve failure state information from the purge valve failure determination unit 56 is used.

  Next, conditions for permitting execution of a humidity sensor failure determination will be described. FIG. 3 shows a state in which the execution of the failure determination of the humidity sensor is permitted when the EGR control is stopped from the operating state.

  (A) shows the failure determination state of the EGR valve, and is EGR failure state information from the EGR failure determination unit 55. In this state, the EGR valve 36 is operating normally. The failure determination unit 55 can generate a failure flag or a normal flag to indicate the failure state of the EGR valve.

  (B) shows the EGR control state, which is EGR control state information from the EGR control operation determination unit 53. In this state, EGR control is executed from time t0 to time t1, and EGR control is stopped after time t1. Similarly, the EGR control operation determination unit 53 can generate a control execution flag or a control stop flag to indicate the control state of the EGR valve.

  (C) shows the absolute humidity information (output value) of the first humidity sensor 46 and the second humidity sensor 47. Since the EGR control is executed from time t0 to time t1, the first humidity sensor 46 measures the absolute humidity of the intake air, and the second humidity sensor 47 is a mixed gas of the intake air and the exhaust gas by the EGR control. The absolute humidity of a fresh gas is measured. Since fresh air has a larger amount of moisture than the amount of inflow of exhaust gas, the absolute humidity information of the second humidity sensor 47 is larger.

  Although the EGR control is stopped at time t1, the exhaust gas remaining in the EGR pipe 34 flows into the collector 19, so that the absolute humidity information of the second humidity sensor 47 is immediately after the external EGR control is stopped. It does not respond, gradually decreases with a predetermined inclination, and finally outputs the same absolute humidity information as the first humidity sensor 46.

  (D) has shown the determination result of whether to permit execution of failure determination of the humidity sensors 46 and 47. FIG. Since the EGR control is executed from time t0 to time t1, execution of failure determination of the humidity sensors 46 and 47 is not permitted. Further, the EGR control is stopped at time t1, but the exhaust gas remaining in the EGR pipe 34 flows into the collector 19. For this reason, the absolute humidity information of the second humidity sensor 47 gradually decreases with a predetermined inclination until the same absolute humidity information as that of the first humidity sensor 46 is finally output. During this period, the execution of the failure determination of the humidity sensors 46 and 47 is not permitted.

  Therefore, in the present embodiment, a predetermined time Ta that is longer than the time until the absolute humidity information of the second humidity sensor 47 finally outputs the same absolute humidity information as the first humidity sensor 46 has elapsed. Later, the execution of the failure determination of the humidity sensors 46 and 47 is permitted.

  In this way, the conditions for permitting the execution of the humidity sensor failure determination are determined. When the condition for permitting the execution of the failure determination is satisfied, the actual failure determination is executed.

  Next, a specific processing operation of the humidity sensor failure determination will be described. FIG. 4 shows a process of executing a humidity sensor failure determination when the humidity sensor failure determination is permitted based on the conditions shown in FIG.

  (A) has shown the determination result whether to permit execution of failure determination of the humidity sensors 46 and 47, as shown in FIG. At time t2, the failure determination transitions from the non-permitted state to the permitted state. Therefore, after time t2, the failure determination process for the humidity sensors 46 and 47 can be executed.

  (B) shows changes in humidity information of the humidity sensors 46 and 47. This indicates that a failure occurs in the second humidity sensor 47 at a certain time after time t2, and the output values of the humidity information of the first humidity sensor 46 and the humidity information of the second humidity sensor 47 are different. Yes. In this case, the second humidity information tends to gradually increase as the failure progresses.

  (C) shows a change in the difference between the humidity information of the first humidity sensor 46 and the second humidity sensor 47. When the first humidity sensor 46 and the second humidity sensor 47 are normal, the difference hardly occurs. However, for example, when the failure occurs in the second humidity sensor 47, the difference becomes large. When the difference exceeds a predetermined value a at time t3, it is temporarily determined that a failure has occurred, and the time after time t3 is a failure determination area for the humidity sensors 46 and 47.

  (D) shows a failure determination state. When a failure occurs in the second humidity sensor 47, the difference increases, and when the difference exceeds a predetermined value a at time t3, it is temporarily determined that a failure has occurred, but in this embodiment, over a predetermined time Tb or more. If the difference continues beyond the predetermined value a, it is determined that a failure has occurred in the first humidity sensor 46 or the second humidity sensor 47.

  In other words, a difference equal to or greater than the predetermined value a occurs at time t3, but there is a possibility that it cannot be determined whether the occurrence of this difference is really due to the failure of the second humidity sensor 47. This is because, for example, an event occurs in which the difference becomes large only for a short time due to an output error of the first humidity sensor 46 or the second humidity sensor 47 or an intrusion of noise. Therefore, the risk of erroneous determination is increased when failure determination is performed using a difference in a short time.

  Therefore, in the present embodiment, even if the predetermined time Tb elapses, if the difference continues to exceed the predetermined value a, the failure of the first humidity sensor 46 or the second humidity sensor 47 is determined. I have to. As a result, the risk of erroneous determination can be reduced, and accurate failure determination of the humidity sensor can be performed.

  Although the above description is about the failure of the second humidity sensor 47, the same failure determination can be made when a failure occurs in the first humidity sensor 46.

  Next, a specific control flow of the failure determination processing shown in FIGS. 3 and 5 will be described in detail using the flowchart shown in FIG.

<< Step S10 >>
In step S10, the EGR control operation determination unit 53 and the EGR failure determination unit 56 detect the control state of the external EGR control and also detect the failure state of the EGR 36 valve. The determination of the control state can be obtained with reference to a control execution flag, a control stop flag, etc., and the failure determination can be obtained with reference to a failure flag, a normal flag, etc.

<< Step S11 >>
In step S11, it is determined whether or not the EGR valve 36 is operating normally from the control execution flag, control stop flag, failure flag, normal flag, and the like obtained in step S10. When it is determined that the external EGR control is stopped and the EGR valve 36 has not failed, the process proceeds to step S12. This state is processing corresponding to the operation at time t1 in FIG. On the other hand, if it is determined that the external EGR control is operating or the EGR valve 36 is malfunctioning, the process goes to the end and the process is terminated.

<< Step S12 >>
In step S12, it is determined whether a predetermined time Ta has elapsed since the EGR control was stopped. If it is determined that the predetermined time Ta has elapsed, the process proceeds to step S13. If it is determined that the predetermined time Ta has not elapsed, the process ends and the process ends. This state is processing corresponding to the operation between time t1 and time t2 in FIG. Here, as described above, the predetermined time Ta is a time longer than the time during which the exhaust gas remaining in the EGR pipe 34 passes through the collector 19 and the second humidity sensor 47.

<< Step S13 >>
In step S <b> 13, absolute humidity information is acquired from the first humidity sensor 46 and the second humidity sensor 47. At this time, when the first humidity sensor 46 or the second humidity sensor 47 is a relative humidity sensor that acquires the relative humidity, it is necessary to convert the relative humidity to the absolute humidity.

<< Step S14 >>
In step S14, the absolute humidity information of the first humidity sensor 46 is compared with the absolute humidity information of the second humidity sensor, and the difference is calculated. When both the humidity sensors have not failed, the humidity of the same intake air is measured, so that the difference in humidity information hardly occurs. On the other hand, if one of the humidity sensors has a failure, the difference in humidity information becomes large. When the difference in humidity information is obtained, the process proceeds to step S15.

<< Step S15 >>
In step S15, it is determined whether or not the difference between the absolute humidity information obtained in step S14 is equal to or greater than a predetermined value a and the duration of the state has exceeded a predetermined value time Tb. If it is determined in step S15 that the difference in absolute humidity information is greater than or equal to the predetermined value a and the duration of the state exceeds the predetermined value time Tb, the process proceeds to step S16. This state is processing corresponding to the operation between time t3 and time t4 in FIG. On the other hand, if it is determined that the difference between the absolute humidity information is not equal to or greater than the predetermined value a or the duration does not exceed the predetermined value time Tb, the process ends and the process ends.

<< Step S16 >>
In step S16, it is determined that either one of the first humidity sensor 46 and the second humidity sensor 47 is out of order, and it is determined that the process is ended. In this way, it is possible to easily execute the failure determination of the two humidity sensors.

  As described above, according to the present invention, the humidity information of the humidity sensor provided in the pipeline through which the intake air flows and the humidity information when the external gas in the humidity sensor provided in the pipeline through which fresh air gas flows are shut off. When a predetermined difference occurs in both humidity information, it is determined that a failure has occurred in one of the humidity sensors.

  According to this, it becomes possible to accurately detect the failure of the humidity sensor that measures the humidity of the intake air and the humidity sensor that measures the humidity of the fresh gas while the internal combustion engine is being driven.

  In addition, this invention is not limited to above-described embodiment, Various modifications are included. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations described. Further, a part of the configuration of an embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of an embodiment. Moreover, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 11 ... Cylinder, 11a ... Cylinder head, 11b ... Cylinder block, 12 ... Piston, 13 ... Connecting rod, 14 ... Combustion chamber, 15 ... Ignition coil, 16 ... Spark plug, 17 ... Air cleaner, 18 ... Throttle valve , 19 ... collector, 20 ... intake manifold, 21 ... intake port, 22 ... intake pipe, 23 ... intake camshaft, 24 ... intake valve, 25 ... fuel injection valve, 26 ... air flow sensor, 27 ... ECU, 28 ... exhaust cam Shaft, 29 ... exhaust valve, 30 ... exhaust passage, 31 ... three-way catalyst, 32 ... air-fuel ratio sensor, 33 ... O2 sensor, 34 ... EGR piping, 35 ... EGR cooler, 36 ... EGR valve, 37 ... fuel tank, 38 ... Fuel pump, 39 ... Fuel pressure regulator, 40 ... Canister piping, 41 ... Charcoal canister, 42 ... Activated carbon, 43 Fresh air introduction pipe, 44 ... purge introduction pipe, 45 ... purge control valve, 46 ... first humidity sensor, 47 ... second humidity sensor, 48 ... accelerator opening sensor, 50 ... absolute humidity of the first humidity sensor Measuring means 51... Absolute humidity measuring means of the second humidity sensor 52. Humidity sensor failure determining means 53 53 EGR control operation determining section 54. Purge control operation determining section 55 55 EGR valve failure determining section 56. Purge valve failure determination unit.

Claims (5)

An intake pipe for supplying intake air to a combustion chamber of an internal combustion engine; an external gas inlet for supplying an external gas different from the intake air to the intake pipe; and the intake pipe disposed upstream of the external gas inlet. A first humidity sensor that detects the humidity of the intake air; and a second humidity sensor that is disposed in the intake pipe downstream of the external gas inlet and detects the humidity of fresh air mixed with the intake air and the external gas. In a control apparatus for an internal combustion engine comprising a humidity sensor, and a control unit that corrects a control amount for controlling an operation state of the internal combustion engine based on humidity information of the first humidity sensor and the second humidity sensor,
The control means compares the humidity information of the first humidity sensor with the humidity information of the second humidity sensor when the external gas from the external gas inlet is shut off, If a predetermined difference or more occurs between the humidity information of the first humidity sensor and the humidity information of the second humidity sensor, a failure occurs in either the first humidity sensor or the second humidity sensor. A control device for an internal combustion engine, comprising: failure determination means for determining failure. The control apparatus for an internal combustion engine according to claim 1,
The humidity control information obtained from the first humidity sensor and the humidity information obtained from the second humidity sensor are absolute humidity information. The control apparatus for an internal combustion engine according to claim 2,
The control device for an internal combustion engine, wherein the failure determination means has a function of executing failure determination after a predetermined time after the control of the valve for controlling the supply of the external gas is stopped. The control apparatus for an internal combustion engine according to claim 3,
The failure determination means causes the first humidity when a difference of a predetermined value or more occurs between the humidity information of the first humidity sensor and the humidity information of the second humidity sensor and this state continues for a predetermined time. A control apparatus for an internal combustion engine, comprising a function for determining whether a failure has occurred in either the sensor or the second humidity sensor. The control apparatus for an internal combustion engine according to claim 4,
The control apparatus for an internal combustion engine, wherein the external gas supplied from the external gas inlet to the intake pipe is at least one of exhaust gas by external EGR control and purge gas by canister purge control.

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