JP2017020406A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine capable of detecting failure of a humidity sensor used to correct a control target value of the internal combustion engine, with high accuracy in a state of driving the internal combustion engine.SOLUTION: A control device for an internal combustion engine includes intake air humidity measurement means (51) for measuring a relative humidity in an intake pipe, and intake air temperature measurement means (51) for measuring an intake air temperature, and humidity sensor failure determination means (52) is disposed to determine failure of a humidity sensor when the relative humidity is raised when the temperature is raised, or when the relative humidity is lowered when the temperature is lowered from the correlation of the intake air humidity and the intake air temperature. As the failure of the humidity sensor can be diagnosed in a state of driving the internal combustion engine, a correct control target value can be determined on the basis of a measurement value of the humidity sensor which normally functions.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an internal combustion engine control apparatus that controls an internal combustion engine, and more particularly to an internal combustion engine control apparatus that calculates a control target value such as an ignition timing in accordance with the humidity of 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 technologies, it is important to optimize combustion, and it is necessary to appropriately control the ignition timing. 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 external EGR is introduced into the combustion chamber, the combustion speed decreases and the output decreases. Therefore, it is necessary to correct and control the ignition timing to the advance side. The ignition timing is corrected according to the amount of exhaust gas from the external EGR. doing.

  Furthermore, recently, in order to improve fuel efficiency, the demand for higher accuracy in the 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 EGR gas, is a factor that inhibits combustion. If the humidity is high, the ignition timing is corrected to the advance side. Conversely, if the humidity is low, the ignition timing is corrected to the retard side. Yes. 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 as described in Patent Document 1 makes it impossible to correct the ignition timing when the humidity sensor fails and an abnormal value is output, and knocking or misfire occurs. As a result, the internal combustion engine may be damaged or stalled. Patent Document 1 does not disclose any technique for dealing with the abnormality of the humidity sensor.

  As a method of providing a humidity sensor in the 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.

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

  By the way, when the control target value such as the ignition timing of the internal combustion engine is corrected by the magnitude of the humidity, the humidity is measured while the internal combustion engine is driven, and the control target value is set corresponding to the measured humidity. It is necessary to correct. For this reason, it is necessary to detect a failure or abnormality of the humidity sensor while the internal combustion engine is being driven. In the following, failures and abnormalities are collectively referred to as failures.

  On the other hand, 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 guaranteeing the operation of the control based on the control target value of the internal combustion engine such as ignition timing control. Not a diagnosis for.

  An object of the present invention is to provide a novel control device for an internal combustion engine that can accurately detect a failure of a humidity sensor used to correct a control target value of the internal combustion engine while the internal combustion engine is being driven. Is to provide.

  The first feature of the present invention includes an intake humidity measuring means for measuring the relative humidity in the intake pipe and an intake air temperature measuring means for measuring the intake air temperature, and the intake air temperature rises based on the correlation between the intake air humidity and the intake air temperature. If the relative humidity increases when the intake air temperature decreases, or if the relative humidity decreases when the intake air temperature decreases, it is determined that the intake humidity measuring means has failed.

  The second feature of the present invention includes an intake humidity measuring means for measuring the relative humidity in the intake pipe and an intake air temperature measuring means for measuring the intake air temperature, and the output of the intake humidity measuring means has a predetermined upper limit value or lower limit value. Alternatively, when the upper and lower limit values are stuck, it is determined that the intake humidity measuring means is out of order.

  According to the present invention, since the failure diagnosis of the intake humidity measuring means can be performed while the internal combustion engine is being driven, an accurate control target value can be obtained based on the measured value of the normally functioning intake humidity measuring means. Can be sought.

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 explanatory drawing explaining the relationship between the flow velocity of intake air amount, and temperature. It is a moist air diagram which shows the relationship between temperature, relative humidity, and absolute humidity. It is a block diagram which shows the attachment state of the sensor which measures temperature and relative humidity. It is explanatory drawing which showed the correlation of the temperature change of intake air, and a relative humidity change. It is a control block diagram which shows the humidity sensor failure determination means which becomes this invention. It is explanatory drawing when performing failure determination of a humidity sensor from the temperature change of intake air and the relative humidity change according to the first embodiment of the present invention. It is explanatory drawing explaining the difference in the responsiveness of a temperature sensor and a humidity sensor. It is explanatory drawing which shows the temperature and relative humidity which digitally filtered the signal of the temperature sensor and the humidity sensor. It is the flowchart figure which showed the control flow of the failure diagnosis of a humidity sensor which becomes the 1st Embodiment of this invention. It is explanatory drawing when performing a failure determination of a humidity sensor from a temperature change and a relative humidity change, which is a modification of the first embodiment. It is the flowchart figure which showed the control flow of the failure diagnosis of a humidity sensor used as the modification of 1st Embodiment. It is explanatory drawing when performing the upper sticking failure determination of a humidity sensor from the temperature change and the relative humidity change according to the second embodiment of the present invention. It is the flowchart figure which showed the control flow of the upper-side sticking fault diagnosis of a humidity sensor which becomes the 2nd Embodiment of this invention. It is explanatory drawing at the time of performing failure determination of the lower side sticking of a humidity sensor from a temperature change and a relative humidity change, which is a modified example of the second embodiment. It is the flowchart figure which showed the control flow of the lower side sticking fault diagnosis of the humidity sensor used as the modification of 2nd Embodiment.

  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 system 10 is, for example, a spark ignition type multi-cylinder engine having four cylinders, and a cylinder 11 including a cylinder head 11a and a cylinder block 11b and a slidably fitted in each cylinder of the cylinder 11. The piston 12 is inserted, and the piston 12 is connected to a crankshaft (not shown) via a connecting rod 13. In addition, a combustion chamber 14 having a ceiling with a predetermined shape is defined above the piston 12, and an ignition plug to which a high-voltage ignition signal is supplied from the ignition coil 15 is supplied to the combustion chamber 14 of each cylinder. 16 is provided.

  The combustion chamber 14 communicates with an intake passage 22 including 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 is the intake passage 22. Through the intake valve 24, which is driven to open and close by an intake camshaft 23 disposed at the end of the intake port 21, which is the downstream end of the intake passage 22, and is sucked into the combustion chamber 14 of each cylinder. ing. The intake manifold 20 of the intake passage 22 is provided with a fuel injection valve 25 for injecting fuel toward the intake port 21 for each cylinder.

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

  A mixture of the air sucked through the intake passage 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 an exhaust gas purification three-way catalyst 31 in which platinum, palladium, or the like is applied to a carrier such as alumina or ceria. A linear air-fuel ratio sensor 32 having a linear output characteristic with respect to the fuel ratio is disposed, and on the downstream side of the three-way catalyst 31, whether the post-catalyst air-fuel ratio is richer or leaner than stoichiometric (theoretical air-fuel ratio). An O2 sensor 33 that outputs a switching signal for identification is provided.

  A fuel injection valve 25 provided for each cylinder of the engine 10 is connected to a fuel tank 34. The fuel in the fuel tank 34 is supplied with a fuel pump 35, a fuel pressure regulator 36, and the like. The pressure is adjusted to a predetermined fuel pressure by the mechanism and supplied to the fuel injection valve 25. The fuel injection valve 25 to which fuel of a predetermined fuel pressure is supplied is driven to open 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 calculates various control target values, and includes, for example, a microcomputer for performing fuel injection control (air-fuel ratio control) using the fuel injection valve 25, ignition timing control using the spark plug 16, and the like. .

  The ECU 27 has a function of calculating at least one control target value of the internal combustion engine and a function of correcting at least one control target value of the control target value based on the relative humidity. It has. And this control function part is provided with the diagnostic function which detects the failure of a humidity sensor so that it may mention later.

  A humidity sensor 37 and a temperature sensor 38 are attached to the intake passage 20, and the humidity and temperature of the intake air flowing through the intake pipe are measured, and the measured humidity signal and temperature signal are transmitted to the ECU 27. Here, the position where the humidity sensor 37 and the temperature sensor 38 are mounted may be attached to the combustion chamber 14 side of the air flow sensor 26, and the air flow sensor 26 may have a function of measuring humidity and temperature. . In this embodiment, an example in which a humidity sensor 37 and a temperature sensor 38 are mounted between the air flow sensor 26 and the throttle valve 25 is described.

  FIG. 2 is an enlarged view of the vicinity of the intake passage 22 shown in FIG. When the throttle valve 18 is opened, the sucked air passes through the air cleaner 17, passes through the air flow sensor 26, humidity sensor 37, and temperature sensor 38, passes through the throttle valve 18, and is supplied to the combustion chamber.

  Here, since the intake air passes through the air cleaner 17, the temperature of the air that passes through the air cleaner 17 is affected by the temperature in the air cleaner 17 (hereinafter sometimes referred to as intake air). Further, the flow rate of the intake air varies depending on the opening degree of the throttle valve 18 and the time for passing through the air cleaner 17 is different, so that the temperature change of the intake air becomes different.

  For example, when the opening degree of the throttle valve 18 is large, the flow speed of the intake air is fast, so the time for passing through the air cleaner 17 is shortened, and the temperature rise of the intake air due to the temperature in the air cleaner 17 is small. On the other hand, when the opening degree of the throttle valve 18 is small, the flow rate of the intake air is slow, so the time for passing through the air cleaner 17 becomes long, and the temperature rise of the intake air due to the temperature in the air cleaner increases.

  2A shows the case where the flow velocity of the intake air is high, the time tA of the air passing through the air cleaner 17 and the air temperature TA near the humidity sensor 37, and FIG. 2B shows the case where the flow velocity of the intake air is slow. When the time tB passing through the air cleaner and the air temperature TB in the vicinity of the humidity sensor 37 are assumed, the air passing time in the air cleaner 17 has a relationship of tA <tB, and the air temperature in the vicinity of the humidity sensor 37 is , TA <TB.

  That is, since the temperature of the intake air changes depending on the opening degree of the throttle valve 18, the temperature of the air passing near the humidity sensor 37 and the temperature sensor 38 always changes. Note that the temperature of the air also varies depending on the temperature of the air from the outside. Therefore, it is only necessary that the temperature sensor 38 can detect the temperature of the air taken into the combustion chamber 14.

  FIG. 3 shows a wet air diagram showing the relationship between temperature, absolute humidity and relative humidity. This wet air diagram is well known. This wet air diagram shows the relationship between temperature, relative humidity, and absolute humidity. When the absolute humidity is constant, the relationship shows that the relative humidity changes as the temperature changes. That is, in the situation where the absolute humidity of the outside air is constant, the absolute humidity of the intake air is also constant. Therefore, the relative humidity may change due to the temperature change of the intake air that changes according to the throttle opening described in FIG. Recognize.

In FIG. 3, it can be seen that the relative humidity decreases as the temperature increases, and the relative humidity increases as the temperature decreases. The relative humidity can be expressed by the following equation.
RH = α / T (where RH: relative humidity (%), T: temperature (° C.), α: coefficient)
In other words, when the amount of moisture contained in the intake air is the same (= the absolute humidity is constant), the intake air temperature and the relative humidity have a correlation, so that the upstream side of the throttle valve 18 as shown in FIG. A failure of the humidity sensor 37 can be determined by comparing the relative relationship between the output values of the humidity sensor 37 and the temperature sensor 38 arranged.

  FIG. 5 shows measured value data of the intake air temperature and relative humidity. In FIG. 5, the correlation between the intake air temperature and the relative humidity is substantially unchanged, and the relationship of RH = α / T is established. However, in some cases, when the amount of moisture in the air changes abruptly, the relationship of RH = α / T may not be established during the period of abrupt fluctuation.

  However, the intake air temperature and relative humidity acquired in the present embodiment are assumed to be the intake passage 20 shown in FIG. 2, and are air containing almost the same amount of water as the outside air. For this reason, since the moisture content in the air of outside air does not fluctuate rapidly, the moisture content in the air near the humidity sensor 37 does not fluctuate rapidly. Therefore, it can be assumed that the relationship of RH = α / T is established.

  From such an idea, a control block for determining a failure of the humidity sensor as shown in FIG. 6 is proposed. FIG. 6 shows a control block for determining a failure of the humidity sensor. The humidity sensor failure determination means 52 detects the failure state of the intake humidity measurement means 51 from the information of the intake air temperature measurement means 50 and the intake humidity measurement means 51.

  The control block shown in FIG. 6 is a part of a control function unit that expresses a control function executed by the microcomputer as a block. Information from the intake air humidity measuring means and the intake air temperature measuring means provided in the intake pipe is input to the control function unit, and the control function unit receives the information from the intake humidity measurement means while the internal combustion engine is driven. Based on the correlation between the relative humidity information and the intake air temperature information from the intake air temperature measuring means, if the relative humidity rises when the intake air temperature rises, or if the relative humidity falls when the intake air temperature falls, the intake air A diagnostic function for determining that the humidity measuring means is out of order is provided.

  Here, as the intake air temperature measuring means 50, for example, means for directly measuring the temperature from the temperature sensor 38, means for estimating the temperature from other information without using the temperature sensor, and the like can be used. Further, the intake humidity measuring means 51 can use the humidity sensor 37 to be diagnosed.

  FIG. 7 shows an example of the determination method of the humidity sensor failure determination means 52 shown in FIG. FIG. 7 shows an example in which failure diagnosis of the humidity sensor 37 is executed from the relative relationship between the intake air temperature change and the relative humidity change. This figure shows an example when the intake air temperature and the relative humidity rise.

  The intake air temperature and the relative humidity are measured at a constant time interval (sampling time t), and a temperature change amount ΔT per t time is calculated as shown in (a) and (b). Here, as shown in (b), the diagnosis is executed when ΔT exceeds the diagnosis start threshold. This diagnosis start threshold is set when the temperature is in the increasing direction and when the temperature is in the decreasing direction, and FIG. 7 shows the time when the temperature is increasing.

  Similarly, as shown in (c) and (d), the amount of change ΔRH in relative humidity per t time is measured, and it is determined that a failure has occurred when ΔRH exceeds the failure determination threshold as shown in (d). Is. Therefore, when ΔT is equal to or greater than a predetermined value (diagnosis start threshold) and ΔRH is equal to or greater than a predetermined value (failure determination threshold), the humidity sensor NG counter is increased by “1” as shown in (e).

  When the humidity sensor NG counter reaches a predetermined number of times (for example, 3) or more as shown in (f), the failure determination flag of the humidity sensor is set to “1”, and it is confirmed that the humidity sensor 37 has failed. can do. The predetermined number of times of the humidity sensor NG counter is arbitrary, but when ΔRH changes below a predetermined value, the failure determination flag is reset to “0”.

  Here, in order to prevent erroneous determination of the failure diagnosis of the humidity sensor 37, the following two erroneous determination prevention methods are executed.

  As a first method for preventing erroneous determination, diagnosis is performed in consideration of a case where the amount of moisture in the air changes during diagnosis. As shown in FIG. 3, when the amount of moisture in the air (= absolute humidity) is constant, the relative humidity decreases when the temperature increases. However, for example, when the amount of moisture in the air increases, it is conceivable that the relative humidity increases when the temperature increases.

  As shown in FIG. 5, the correlation between the temperature change amount ΔT and the relative humidity change amount ΔRH does not change. However, when the temperature change amount ΔT is minute or the relative humidity change amount ΔRH is minute, it is conceivable that the correlation between the temperature and the relative humidity is lost even if the amount of moisture in the air is minute.

  In this case, there is a possibility of misdiagnosis. Therefore, in the fault diagnosis of the humidity sensor, the correlation between the change amount ΔT of temperature and the change amount ΔRH of relative humidity does not change even if the amount of moisture in the air changes. This is done when the amount of change becomes larger.

  As a second method for preventing erroneous determination, diagnosis is performed in consideration of the response characteristics of the humidity sensor 37 and the temperature sensor 38. The erroneous determination based on the response characteristics of the sensors 37 and 38 will be described with reference to FIG.

  FIG. 8 shows the difference in response between the humidity sensor 37 and the temperature sensor 38. As shown in FIG. 8A, the output signal of the temperature sensor 38 has characteristics of a detection start delay ta and a first-order delay time constant τa, and the output signal changes accordingly. Similarly, as shown in FIG. 8B, the output signal of the humidity sensor 37 has characteristics of a detection start delay tb and a first-order delay time constant τb, and the output signal changes accordingly.

  As described above, the humidity sensor 37 and the temperature sensor 38 have different detection start delays (= dead time) and time constants of primary delays. In other words, if the output characteristics of the sensor are not taken into consideration, there is a possibility that a “deviation” occurs in the timing at which the sensor value changes, and an erroneous determination may be made when correlation is diagnosed.

  In order to prevent erroneous determination based on this “deviation”, it is effective to perform digital filtering processing on the detected values of the intake air temperature and relative humidity, as shown in FIG. As an example, in FIG. 9, digital filtering processing is performed by moving average of 50 times within the sampling time t with respect to the detected intake air temperature and relative humidity. Furthermore, in order to prevent erroneous determination, the sampling time t shown in FIG. 7 may be sufficiently long. By the above-described method, the detected values of the intake air temperature and the relative humidity for diagnosing the correlation can be obtained.

FIG. 10 is a flowchart showing a control flow for executing a failure diagnosis of the humidity sensor 37 shown in FIG. 7, which will be described together with FIG. 7. First, in step S100, the intake air temperature value is detected from the temperature sensor 38 every predetermined sampling time. Similarly, the relative humidity value is acquired from the humidity sensor 37 every predetermined sampling time, and the digital filtering process shown in FIG. 9 is executed on the acquired temperature value and relative humidity value. When this is completed, the process proceeds to step S101. This digital filtering process may be obtained by another processing routine, or may be read in the following step S101.

  In step S101, as shown in FIGS. 7A and 7D, the intake air temperature value and the relative humidity value filtered in step S100 are acquired at a sampling time t at a constant time interval. For example, as shown in FIG. 9, this time interval is determined in correspondence with the time of 50 moving averages. When the intake air temperature and the relative humidity are acquired at regular time intervals, the process proceeds to step S102.

  In step S102, as shown in FIG. 7B, the intake air temperature value acquired in step S101 is compared with the intake air temperature value acquired last time, and the change amount (temperature value acquired this time−temperature value acquired last time). ) Is greater than or equal to a predetermined value that is a diagnosis start threshold on the increase side. If it is equal to or greater than the predetermined value, the process proceeds to the next step S103 because the diagnosis condition is satisfied. If it is not equal to or greater than the predetermined value, it is determined that the diagnosis condition is not satisfied. .

  In step S103, as shown in FIG. 7D, the relative humidity value acquired in step S101 is compared with the previously acquired relative humidity value, and the amount of change (the relative humidity value acquired this time minus the previous time). It is determined whether the acquired relative humidity value is equal to or greater than a predetermined value that is a failure determination threshold on the increase side. If it is equal to or greater than the predetermined value, it is assumed that a failure has occurred, and the process proceeds to step S104. If it is not equal to or greater than the predetermined value, the process ends after determining that no failure has occurred.

  As described above, when it is determined in step S102 that the amount of change in intake air temperature has risen to a predetermined value or higher, it is determined in step S103 that the amount of change in relative humidity has increased to a predetermined value or higher. Since the correlation between the intake air temperature and humidity does not match, it can be considered that a failure has occurred in the humidity sensor. In other words, if the intake air temperature rises, the relative humidity naturally decreases, but if it is determined that the intake air temperature has risen but the relative humidity has risen, it is considered that the humidity sensor has failed. be able to. However, since there is a problem in the reliability of failure detection in one failure detection, when this step S103 is completed, the process proceeds to step S104.

  In step S104, as shown in FIG. 7E, the humidity sensor NG counter is incremented by “1” every time a failure is detected, and the number of times of failure detection is increased to increase the probability of occurrence of the failure. . When step S104 is completed, the process proceeds to step S105.

  In step S105, as shown in FIG. 7E, when the value of the humidity sensor NG counter exceeds the NG determination threshold value of the humidity sensor 37, it is confirmed that a failure has occurred in the humidity sensor 37. The process proceeds to step 106. On the other hand, when the value of the humidity sensor NG counter does not exceed the NG determination threshold value, the process returns to step S100 again in order to continue the count of the humidity sensor NG counter.

  In step S106, as shown in FIG. 7F, since the failure of the humidity sensor 37 has been determined in step S105, the failure determination flag of the humidity sensor 37 is finally set to “1” and the failure determination process of the humidity sensor 37 is performed. Exit and exit to the end.

  In this way, if the relative humidity increases when the temperature rises from the correlation between the relative humidity of the intake air and the temperature of the intake air, it can be determined that the humidity sensor has failed.

  Next, FIG. 11 shows a modification of the determination method of the humidity sensor failure determination means 52 shown in FIG. FIG. 11 shows an example in which failure diagnosis of the humidity sensor 37 is executed from the relative relationship between the intake air temperature change and the relative humidity change. This figure shows an example when the intake air temperature and the relative humidity are lowered.

  The intake air temperature and the relative humidity are measured at a constant time interval (sampling time t), and the change amount ΔT of the intake air temperature per t time is calculated as shown in (a) and (b). Here, as shown in (b), the diagnosis is executed when ΔT exceeds (below) the diagnosis start threshold. This diagnosis start threshold is set when the intake air temperature is in the downward direction.

  Similarly, as shown in (c) and (d), the amount of change ΔRH in the relative humidity per t time is measured, and when ΔRH exceeds the failure judgment threshold as shown in (d), a failure occurs. Is determined to have occurred. Therefore, when ΔT is equal to or greater than a predetermined value (diagnosis start threshold) and ΔRH is less than a predetermined value (failure determination threshold), the humidity sensor NG counter is increased by “1” as shown in (e). To do.

  When the humidity sensor NG counter reaches a predetermined number of times (for example, 3) or more as shown in (f), the failure determination flag of the humidity sensor is set to “1” to make a definite diagnosis that the humidity sensor has failed. be able to. The humidity sensor NG counter can be arbitrarily set a predetermined number of times, but when ΔRH changes below a predetermined value, the failure determination flag is reset to “0”.

  FIG. 12 is a flowchart showing a control flow for executing failure diagnosis of the humidity sensor 37 shown in FIG. 11, and will be described together with FIG.

  First, in step S120, the intake air temperature value is acquired from the temperature sensor 38 at every predetermined sampling time, and similarly, the relative humidity value is acquired from the humidity sensor 37 at every predetermined sampling time, and the acquired intake air temperature value and relative humidity value are obtained. The digital filtering process shown in FIG. 9 is executed. When this is completed, the process proceeds to step S121.

  In step S121, as shown in FIGS. 11A and 11D, the intake air temperature value and the relative humidity value filtered in step S120 are acquired at a sampling time t at a constant time interval. For example, as shown in FIG. 9, this time interval is determined in correspondence with the time of 50 moving averages. When the intake air temperature and the relative humidity are acquired at regular time intervals, the process proceeds to step S122.

  In step S122, as shown in FIG. 11B, the intake air temperature value acquired in step S121 is compared with the intake air temperature value acquired last time, and the change amount (temperature value acquired this time−temperature value acquired last time). ) Is greater than or equal to a predetermined value that is a diagnosis start threshold on the decreasing side. If it is equal to or greater than the predetermined value, the process proceeds to the next step S123 because the diagnosis condition is satisfied. If it is not equal to or greater than the predetermined value, it is determined that the diagnosis condition is not satisfied. .

  In step S123, as shown in FIG. 11D, the relative humidity value acquired in step S121 is compared with the previously acquired relative humidity value, and the amount of change (the relative humidity value acquired this time minus the previous time). It is determined whether the acquired relative humidity value is lower than a predetermined value that is a failure determination threshold on the decrease side. If it is less than the predetermined value, it is assumed that a failure has occurred, and the process proceeds to step S124. If it is not less than the predetermined value, it is determined that no failure has occurred and the process ends and the process ends. To do.

  As described above, when it is determined in step S122 that the change amount of the intake air temperature has decreased to a predetermined value or more, it is determined in step S123 that the change amount of the relative humidity has been decreased to a predetermined value or more. Since the correlation between the intake air temperature and humidity does not match, it can be considered that a failure has occurred in the humidity sensor. In other words, when the intake air temperature decreases, the relative humidity naturally increases, but if it is determined that the intake air temperature has decreased but the relative humidity has decreased, it is assumed that the humidity sensor has failed. be able to. Similarly to FIG. 10, there is a problem with the reliability of failure detection in one failure detection, and when step S123 is completed, the process proceeds to step S124.

  In step S124, as shown in FIG. 11E, the humidity sensor NG counter is incremented by “1” every time a failure is detected, and the number of times of failure detection is increased to increase the probability of occurrence of the failure. . When step S124 is completed, the process proceeds to step S125.

  In step S125, as shown in FIG. 11 (e), when the value of the humidity sensor NG counter exceeds the NG determination threshold value of the humidity sensor 37, it is confirmed that a failure has occurred in the humidity sensor 37. Control goes to step 126. On the other hand, when the value of the humidity sensor NG counter does not exceed the NG determination threshold, the process returns to step S120 again in order to continue the count of the humidity sensor NG counter.

  In step S126, as shown in FIG. 11 (f), since the failure of the humidity sensor 37 is confirmed in step S125, the failure determination flag of the humidity sensor 37 is finally set to “1”, and the failure determination process of the humidity sensor 37 is performed. Exit and exit to the end.

  In this way, if the relative humidity decreases when the temperature decreases due to the correlation between the relative humidity of the intake air and the intake air temperature, it can be determined that the humidity sensor has failed.

  Next, another embodiment of the control block that performs failure determination of the humidity sensor shown in FIG. 6 will be described. The control block shown in FIG. 6 is a part of a control function unit that expresses a control function executed by the microcomputer as a block. Information from the intake air humidity measuring means and the intake air temperature measuring means provided in the intake pipe is input to the control function unit, and the control function unit receives the information from the intake humidity measurement means while the internal combustion engine is driven. When the relative humidity information sticks to a predetermined upper limit value, a predetermined lower limit value, or a predetermined upper and lower limit value, a diagnosis function is provided that determines that the intake humidity measuring means has failed.

  FIG. 13 shows an example of the determination method of the humidity sensor failure determination means 52 shown in FIG. 6 which is another embodiment of the present invention. FIG. 13 shows an example in which a failure of the humidity sensor is detected by detecting that the output value of the humidity sensor 37 has stuck to the upper limit value. In particular, this example is suitable for determining a circuit open failure of the humidity sensor.

  In FIG. 13, the intake air temperature and the relative humidity are measured at a constant time interval (sampling time t), and the change amount ΔT of the intake air temperature per t time is calculated as shown in (a) and (b). Here, as shown in (b), the diagnosis is executed when ΔT exceeds the diagnosis start threshold value. This diagnosis start threshold is set when the intake air temperature is in the increasing direction.

  Similarly, as shown in (c), the relative humidity per t time is measured, and it is detected that the relative humidity does not change from the upper limit value RHmax. If ΔT is equal to or greater than a predetermined value (diagnosis start threshold) and the relative humidity does not change from the upper limit value RHmax, the humidity sensor NG counter is increased by “1” as shown in (d).

  Then, as shown in (d) and (e), when the humidity sensor NG counter reaches a predetermined number (for example, 3) or more, the failure determination flag of the humidity sensor is set to “1”, and the humidity sensor has failed. Can be confirmed. The humidity sensor NG counter can be arbitrarily set a predetermined number of times, but when the relative humidity changes from the upper limit value RHmax, the failure determination flag is reset to “0”.

FIG. 14 is a flowchart showing a control flow for executing failure diagnosis of the humidity sensor 37 shown in FIG. 13 and will be described together with FIG. 13. First, in step S140, the intake air temperature value from the temperature sensor 38 at every predetermined sampling time. Similarly, the relative humidity value is acquired from the humidity sensor 37 at every predetermined sampling time, and the digital filtering process shown in FIG. 9 is executed on the acquired intake air temperature value and relative humidity value. When this is completed, the process proceeds to step S141.

  In step S141, as shown in FIGS. 13A and 13D, the intake air temperature value and the relative humidity value filtered in step S140 are acquired at a sampling time t at a constant time interval. For example, as shown in FIG. 9, this time interval is determined in correspondence with the time of 50 moving averages. When the intake air temperature and the relative humidity are acquired at regular time intervals, the process proceeds to step S142.

  In step S142, as shown in FIG. 13B, the intake air temperature value acquired in step S141 is compared with the intake air temperature value acquired last time, and the change amount (temperature value acquired this time−temperature value acquired last time). ) Is greater than or equal to a predetermined value that is a diagnosis start threshold on the increase side. If it is equal to or greater than the predetermined value, the process proceeds to the next step S143 because the diagnosis condition is satisfied. If it is not equal to or greater than the predetermined value, it is determined that the diagnosis condition is not satisfied. .

  In step S143, as shown in FIG. 13C, it is determined whether or not the relative humidity value acquired in step S141 changes from the upper limit value RHmax. If the value does not change from the upper limit value RHmax, it is assumed that a failure has occurred, and the process proceeds to step S144. If the value has changed, it is determined that no failure has occurred and the process ends and the process ends. .

  As described above, if it is determined in step S142 that the amount of change in the intake air temperature has risen to a predetermined value or more and it is determined in step S143 that there is no change from the upper limit value RHmax, a failure occurs in the humidity sensor. Can be regarded as being. However, since there is a problem with the reliability of failure detection in one failure detection, when step S143 is completed, the process proceeds to step S144.

  In step S144, as shown in FIG. 13D, the humidity sensor NG counter is incremented by “1” every time the upper limit value RHmax is detected, and the number of failure detections is increased to increase the accuracy of failure occurrence. ing. When step S144 is completed, the process proceeds to step S145.

  In step S145, as shown in FIG. 13D, when the value of the humidity sensor NG counter exceeds the NG determination threshold value of the humidity sensor 37, a definite diagnosis is made that a failure has occurred in the humidity sensor 37. Control goes to step 146. On the other hand, when the value of the humidity sensor NG counter does not exceed the NG determination threshold value, the process returns to step S140 again in order to continue the count of the humidity sensor NG counter.

  In step S146, as shown in FIG. 13E, since the failure of the humidity sensor 37 has been determined in step S105, the failure determination flag of the humidity sensor 37 is finally set to “1” and the failure determination process of the humidity sensor 37 is performed. Exit and exit to the end.

  In this way, when the relative band humidity sticks to the upper limit value RHma, it can be determined that the humidity sensor has failed.

  Next, FIG. 15 shows a modification of the determination method of the humidity sensor failure determination means 52 shown in FIG. FIG. 15 shows an example of detecting a failure of the humidity sensor by detecting that the output value of the humidity sensor has stuck to the lower limit value. In particular, this example is suitable for determining a short circuit failure of the humidity sensor.

  In FIG. 15, the intake air temperature and the relative humidity are measured at a constant time interval (sampling time t), and the change amount ΔT of the intake air temperature per t time is calculated as shown in (a) and (b). Here, as shown in (b), the diagnosis is executed when ΔT exceeds the diagnosis start threshold value. This diagnosis start threshold is set when the intake air temperature is in the downward direction.

  Similarly, as shown in (c), the relative humidity per t time is measured, and it is detected that the relative humidity does not change from the upper limit value RHmin. If ΔT is equal to or greater than a predetermined value (diagnosis start threshold) and the relative humidity does not change from the upper limit value RHmin, the humidity sensor NG counter is increased by “1” as shown in (d).

  Then, as shown in (d) and (e), when the humidity sensor NG counter reaches a predetermined number (for example, 3) or more, the failure determination flag of the humidity sensor is set to “1”, and the humidity sensor has failed. Can be confirmed. The humidity sensor NG counter can be arbitrarily set a predetermined number of times, but when the relative humidity changes from the upper limit value RHmin, the failure determination flag is reset to “0”.

FIG. 16 is a flowchart showing a control flow for executing failure diagnosis of the humidity sensor 37 shown in FIG. 15 and will be described together with FIG. Similarly, the relative humidity value is acquired from the humidity sensor 37 at every predetermined sampling time, and the digital filtering process shown in FIG. 9 is executed on the acquired intake air temperature value and relative humidity value. When this is completed, the process proceeds to step S161.

  In step S161, as shown in FIGS. 13A and 13D, the intake air temperature value and the relative humidity value filtered in step S160 are acquired at a sampling time t at a constant time interval. For example, as shown in FIG. 9, this time interval is determined in correspondence with the time of 50 moving averages. When the intake air temperature and the relative humidity are acquired at regular time intervals, the process proceeds to step S162.

  In step S162, as shown in FIG. 15B, the intake air temperature value acquired in step S161 is compared with the intake air temperature value acquired last time, and the change amount (temperature value acquired this time−temperature value acquired last time). ) Is less than a predetermined value which is a diagnosis start threshold value on the decreasing side. When the value is below the predetermined value, the process proceeds to the next step S163 because the diagnosis condition is satisfied. When the value is not greater than the predetermined value, the process proceeds to the end without performing the failure diagnosis, assuming that the diagnosis condition is not satisfied. finish.

  In step S163, as shown in FIG. 15C, it is determined whether or not the relative humidity value acquired in step S161 changes from the lower limit value RHmin. If the value does not change from the lower limit value RHmin, it is assumed that a failure has occurred, and the process proceeds to step S164. If the value has changed, it is determined that no failure has occurred and the process ends and the process ends. .

  As described above, if it is determined in step S162 that the amount of change in the intake air temperature has fallen below the predetermined value, and it is determined in step S163 that there is no change from the lower limit value RHmin, a failure occurs in the humidity sensor. Can be regarded as being. However, since there is a problem in the reliability of failure detection in one failure detection, when step S163 is completed, the process proceeds to step S164.

  In step S164, as shown in FIG. 15D, the humidity sensor NG counter is incremented by “1” every time the lower limit value RHmin is detected, and the number of failure detections is increased to increase the probability of occurrence of the failure. ing. When step S164 is completed, the process proceeds to step S165.

  In step S165, as shown in FIG. 15D, when the value of the humidity sensor NG counter exceeds the NG determination threshold value of the humidity sensor 37, a definite diagnosis is made that the humidity sensor 37 has failed. Control goes to step 166. On the other hand, when the value of the humidity sensor NG counter does not exceed the NG determination threshold, the process returns to step S160 again in order to continue the count of the humidity sensor NG counter.

  In step S166, as shown in FIG. 15E, since the failure of the humidity sensor 37 is confirmed in step S165, the failure determination flag of the humidity sensor 37 is finally set to “1”, so that the failure determination process of the humidity sensor 37 is performed. Exit and exit to the end.

  In this way, when the relative humidity is stuck to the lower limit value RHmin, it can be determined that the humidity sensor has failed.

  In the second embodiment, the failure of the humidity sensor 37 is detected using either the upper limit value RHmax or the lower limit value RHmin. However, the failure of the humidity sensor 37 is detected using both the upper limit value RHmax and the lower limit value RHmin. It may be good.

  As described above, according to the present invention, the intake humidity measuring means for measuring the relative humidity in the intake pipe and the intake air temperature measuring means for measuring the intake air temperature are provided, and the intake air temperature is determined based on the correlation between the intake air humidity and the intake air temperature. When the relative humidity rises when it rises, or when the relative humidity falls when the intake air temperature falls, it is determined that the humidity sensor has failed.

  According to this, since the failure diagnosis of the humidity sensor is possible while the internal combustion engine is driven, an accurate control target value can be obtained based on the measured value of the humidity sensor functioning normally.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, 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 system, 11 ... Cylinder, 11a ... Cylinder head, 11b ... Cylinder block, 12 ... Piston, 13 ... Connecting rod, 14 ... Combustion chamber, 15 ... Ignition coil, 16 ... Point or plug, 17 ... Air cleaner, 18 ... Throttle valve, 19 ... collector, 20 ... intake manifold, 21 ... intake port, 22 ... intake passage, 23 ... intake camshaft, 24 ... intake valve, 25 ... fuel injection valve, 26 ... air flow sensor, 27 ... ECU, 28 ... exhaust camshaft, 29 ... exhaust valve 30 ... exhaust passage, 31 ... three-way catalyst, 32 ... linear air-fuel ratio sensor, 33 ... _{O 2} sensor, 37 ... humidity sensor, 38 ... temperature sensor.

Claims (5)

An internal combustion engine having a function of calculating at least one control target value of the internal combustion engine and a function of correcting at least one control target value of the control target value according to the magnitude of relative humidity Control device for
Information from the intake air humidity measuring means and the intake air temperature measuring means provided in the intake pipe is input to the control function unit,
The control function unit increases the intake air temperature based on a correlation between relative humidity information from the intake air humidity measuring unit and intake air temperature information from the intake air temperature measuring unit while the internal combustion engine is driven. When the relative humidity is sometimes raised, or when the relative humidity is lowered when the intake air temperature is lowered, a diagnosis function is provided for determining that the intake humidity measuring means has failed. A control device for an internal combustion engine. The control device for an internal combustion engine according to claim 1,
The diagnostic function is:
The amount of change in the intake air temperature when the amount of change in the intake air temperature when the intake air temperature rises is greater than or equal to a predetermined value and the amount of change in the relative humidity is greater than or equal to a predetermined value, or when the intake air temperature decreases. A control apparatus for an internal combustion engine, wherein when the amount of change in the relative humidity is equal to or greater than a predetermined value, the intake humidity measuring means is determined to be malfunctioning. An internal combustion engine having a function of calculating at least one control target value of the internal combustion engine and a function of correcting at least one control target value of the control target value according to the magnitude of relative humidity Control device for
Information from the intake air humidity measuring means and the intake air temperature measuring means provided in the intake pipe is input to the control function unit,
The control function unit, when the relative humidity information from the intake humidity measuring means sticks to a predetermined upper limit value, a predetermined lower limit value, or a predetermined upper and lower limit value while the internal combustion engine is driven A control device for an internal combustion engine, further comprising a diagnostic function for determining that the intake humidity measuring means is malfunctioning. In the control device for an internal combustion engine according to claim 1 or 3,
The control device for an internal combustion engine, wherein the control function unit obtains the relative humidity information from the intake humidity measuring means and the intake air temperature information from the intake air temperature measuring means by performing a digital filtering process. In the control device for an internal combustion engine according to claim 1 or 3,
The internal combustion engine control apparatus according to claim 1, wherein the diagnosis function counts the number of times that the failure is determined and determines the failure when the predetermined number of times is reached.

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