JP5056548B2 - Intake system fault diagnosis device for in-vehicle internal combustion engine - Google Patents

Description

  The present invention relates to an intake system failure diagnosis device for an in-vehicle internal combustion engine that diagnoses the presence or absence of a failure in the intake system of the in-vehicle internal combustion engine.

  Generally, in an in-vehicle internal combustion engine, an air-fuel mixture is formed by mixing intake air sucked into a combustion chamber through an intake passage and fuel injected from a fuel injection valve so as to correspond to the amount of intake air. The driving force is obtained by burning the air-fuel mixture in the combustion chamber. Further, a throttle valve for adjusting the amount of intake air taken into the combustion chamber is provided in the intake passage of such an internal combustion engine, and the output of the internal combustion engine is adjusted through the adjustment of the intake air amount by the throttle valve. Is adjusted.

  In such an internal combustion engine, the amount of air sucked into the combustion chamber is the amount of air (intake air amount) measured by an intake air amount measuring device provided on the upstream side of the intake passage, that is, an air flow meter. . The amount of air taken into the combustion chamber is adjusted to a predetermined target amount by adjusting the opening of the throttle valve, and the output of the internal combustion engine is adjusted by the adjusted intake air amount. It is like that. For this reason, if there is a difference between the intake air amount measured by the air flow meter and the air amount sucked into the combustion chamber, it is difficult to adjust the output of the internal combustion engine.

Therefore, conventionally, as an apparatus for detecting whether there is a difference between the intake air amount measured through the air flow meter and the air amount sucked into the combustion chamber, for example, a device as described in Patent Document 1 has been proposed. Yes. In the device described in Patent Document 1, the fuel injection amount corresponds to the measured intake air amount based on the fact that the fuel injection amount changes according to the air amount sucked into the combustion chamber by air-fuel ratio control. It is detected whether or not it is larger than the basic injection amount of fuel, in other words, whether or not the amount of air actually taken into the engine combustion chamber is larger than the measured intake air amount. When it is detected that the amount of air actually sucked into the combustion chamber is larger than the measured intake air amount, it is determined that “the engine intake system has an air leak”. ing.
JP-A-5-280403

  By the way, the difference between the measured intake air amount and the air amount sucked into the combustion chamber as described above is not limited to “air leakage in the engine intake system”, and the air flow meter is an intake air amount measuring device. This also occurs in the case where the device is out of order. That is, even when the amount of air actually sucked into the engine combustion chamber is larger than the measured amount of intake air, the cause may be due to a failure of the air flow meter. As described above, in the device described in Patent Document 1, although it is possible to make a diagnosis of “air leakage in the engine intake system”, its reliability is low.

  The present invention has been made in view of such circumstances, and its object is to increase the malfunction of the intake system from the relationship between the amount of air sucked into the combustion chamber and the amount of intake air measured by the air flow meter. An object of the present invention is to provide an intake system failure diagnosis device for an onboard internal combustion engine that can be diagnosed with reliability.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
In order to solve the above-described problem, the invention according to claim 1 controls the opening degree of the intake air amount metering valve while learning the opening correction value of the intake air amount metering valve during engine idle operation. Idle speed control mechanism that controls the engine speed to the target speed, an air flow meter that measures the amount of air drawn into the engine, and the deviation of the air-fuel mixture supplied to the engine combustion chamber from the stoichiometric air-fuel ratio On-vehicle equipped with an air-fuel ratio control mechanism that is a mechanism that feedback-controls the ratio of the fuel injection amount to the intake air amount based on the oxygen concentration of the exhaust gas so as to maintain the air-fuel ratio of the mixture at the stoichiometric air-fuel ratio while learning the amount An in-vehicle internal combustion engine intake system failure diagnosis device for diagnosing the presence or absence of an intake system failure in an internal combustion engine, wherein the learning value by the idle rotation speed control mechanism is less than a predetermined value and the air flow meter When the amount of air is less than a predetermined value than the theoretical amount of air taken into the engine combustion chamber during engine idle speed control that is more measured, the amount of deviation of engine high load operation of the learning value by the air-fuel ratio control mechanism The gist is to diagnose that there is an intake leak failure in the intake system under a condition that tends to be larger in the engine idle operation region than in the region.

Normally, if the learning value by the idle rotation speed control mechanism is less than a predetermined value, that is, the range in which ISC learning is performed in an appropriate range, the intake air amount metering valve (throttle) among the malfunctions (abnormalities) of the intake system Excess deposits on the valve or ISC valve), ie, “increased metering valve deposits” and “increased engine friction” due to increased friction of the engine (engine) piston are excluded. In addition, if the air amount measured by the air flow meter is smaller than the theoretical air amount sucked into the engine combustion chamber during idle speed control by a predetermined value or more, the failure of the air flow meter itself may be a failure of the intake system. There is a high possibility of “air flow meter failure” or any air leak in the intake system, that is, “intake leak failure”. In this case, in the air-fuel ratio control mechanism, if the air flow meter is normal, the amount of deviation from the learning value, that is, the center value of the air-fuel ratio learning value, depends on whether or not there is an “intake leakage failure”. Each one shows a different tendency. In other words, when there is an “intake leakage failure”, the influence of the intake air amount due to this leak is greatly affected in the engine idle operation region where the intake air amount is originally small, while in the engine high load operation region where the intake air amount is large. Since the influence of the intake air amount due to leakage becomes negligible, the deviation amount of the air-fuel ratio learning value is also large in the engine idle operation region, and conversely is small in the engine high load operation region. Therefore, as described above, the learning value by the idle rotation speed control mechanism is less than the predetermined value, and the air amount measured by the air flow meter is larger than the theoretical air amount sucked into the engine combustion chamber during the idle rotation speed control. If the logical AND condition of monitoring that the difference between the learning value by the air-fuel ratio control mechanism is smaller than the predetermined value and the engine idle operation region tends to be larger than the engine high load operation region is monitored. Then, based on the fact that the AND condition is satisfied, it is possible to clearly determine “intake leakage failure”. As a result, the cause of the failure occurring in the intake system can be clearly diagnosed, and the labor required for maintenance and inspection of the in-vehicle internal combustion engine through such diagnosis can be greatly reduced.

According to the second aspect of the present invention, the engine rotational speed is set to the target rotational speed by learning the opening correction value of the intake air amount metering valve during engine idle operation and controlling the opening of the intake air amount metering valve. The idle rotation speed control mechanism, which is the mechanism that controls the engine, the air flow meter that measures the amount of air sucked into the engine, and the same mixture while learning the deviation from the stoichiometric air-fuel ratio of the air-fuel mixture supplied to the engine combustion chamber An in-vehicle internal combustion engine having an air-fuel ratio control mechanism, which is a mechanism that feedback-controls the ratio of the fuel injection amount to the intake air amount based on the oxygen concentration of the exhaust gas in order to maintain the air-fuel ratio of the air at the stoichiometric air-fuel ratio. An in-vehicle internal combustion engine intake system failure diagnosis device for diagnosing the presence or absence of a system failure, wherein a learning value by the idle rotation speed control mechanism is less than a predetermined value and an air amount measured by the air flow meter is When idle rotational speed control said predetermined value or more than the theoretical amount of air taken into the engine combustion chamber during small, and the air-fuel ratio deviation amount is the engine idle operation region of the learning value performed by the control mechanism and engine high load operation region The gist of this is to diagnose that the air flow meter is malfunctioning under the conditions that show the same tendency.

As described above, if the learning value by the idle rotation speed control mechanism is less than the predetermined value, there is a possibility of “accumulation of metering valve deposit” or “increase in engine friction” among malfunctions (abnormality) of the intake system. Is excluded. Further, if the air amount measured by the air flow meter is smaller than the theoretical air amount sucked into the engine combustion chamber at the time of idle speed control by a predetermined value or more, the possibility of the intake system failure is “the failure of the air flow meter” As described above, there is a high possibility that the problem is “intake leakage failure”. In this case, the amount of deviation of the air-fuel ratio learning value indicates the above-mentioned tendency depending on the presence / absence of the “intake leakage failure” and the engine operating region unless “air flow meter failure” occurs. If there is a “failure”, it is almost the same regardless of the engine operating range. Therefore, as described above, the learning value by the idle rotation speed control mechanism is less than the predetermined value, and the air amount measured by the air flow meter is larger than the theoretical air amount sucked into the engine combustion chamber during the idle rotation speed control. The logical AND condition is monitored to indicate that the difference between the learning value by the air-fuel ratio control mechanism is equal to or smaller than the predetermined value and the engine idle operation region and engine high load operation region tend to be equal. For example, it is possible to clearly determine “air flow meter failure” based on the fact that the AND condition is satisfied. As a result, the cause of the failure occurring in the intake system can be clearly diagnosed, and the labor required for maintenance and inspection of the in-vehicle internal combustion engine through such diagnosis can be greatly reduced.

According to a third aspect of the present invention, in the intake system failure diagnosis device for an on-vehicle internal combustion engine according to the first or second aspect, a learning value by the idle rotational speed control mechanism is less than a predetermined value and is measured by the air flow meter. The gist further comprises means for diagnosing that the air flow meter is malfunctioning on the condition that the amount of air is greater than a theoretical amount of air sucked into the engine combustion chamber during idle speed control. And

If the learning value by the idle rotation speed control mechanism is less than the predetermined value, the possibility of “increase in the amount of metering valve deposit” or “increase in engine friction” among the malfunctions (abnormalities) of the intake system is excluded. Is as described above. At this time, the possibility of “intake leakage failure”, “air flow meter failure”, etc., including the possibility of being “normal”, also appears. At least in this state, the amount of air measured by the air flow meter is It is impossible to reach a situation where the theoretical amount of air sucked into the engine combustion chamber is greater than a predetermined value during idle speed control unless it is an “air flow meter failure”. Therefore, as described above, when the learning value by the idle rotation speed control mechanism is less than the predetermined value, the air amount measured by the air flow meter is larger than the theoretical air amount sucked into the engine combustion chamber during the idle rotation speed control. If it is also monitored whether or not it is larger than a predetermined value, it becomes possible to immediately diagnose “air flow meter failure” when such a condition is affirmed.

According to a fourth aspect of the present invention, in the in-vehicle internal combustion engine intake system failure diagnosis device according to any one of the first to third aspects, a learning value by the idle rotational speed control mechanism is a predetermined value or more and the idle The amount of deposit deposited on the intake air amount metering valve is set on condition that the theoretical amount of air sucked into the engine combustion chamber at the time of rotational speed control is larger than a predetermined value by a predetermined amount than the air amount measured by the air flow meter. The gist of the invention is to further include means for diagnosing that the amount exceeds the allowable amount.

Normally, if the learning value by the idle rotation speed control mechanism is equal to or greater than a predetermined value, that is, if there is a tendency that excessive ISC learning is being performed, the above-described “increase in the accumulation of metering valve deposit” or “ There is a high possibility that an abnormality such as "increased engine friction" has occurred. In such a case, whether or not the theoretical amount of air sucked into the engine combustion chamber during idle speed control is greater than a predetermined value by a predetermined amount or more than the amount of air measured by the air flow meter, that is, intake air amount adjustment. By determining whether or not the amount of air corresponding to the opening is actually not flowing even though the valve is at the target opening, it is possible to determine whether the amount of accumulation in the metering valve deposit has increased. It can be determined whether the engine friction has increased. Therefore, as described above, the learning value by the idle speed control mechanism is greater than or equal to a predetermined value, and the theoretical amount of air drawn into the engine combustion chamber during idle speed control is greater than the amount of air measured by the air flow meter. By monitoring whether or not the value is larger than the value, it is possible to clearly determine that the amount of deposit in the metering valve deposit is large based on the affirmative determination of the same condition. Incidentally, in such a “large amount of accumulation of metering valve deposit”, the amount of air actually flowing (measured) tends not to increase even if the intake air amount metering valve is open.

According to a fifth aspect of the present invention, in the in-vehicle internal combustion engine intake system failure diagnosis device according to any one of the first to third aspects, a learning value by the idle rotational speed control mechanism is a predetermined value or more and the idle Means for diagnosing that the engine friction exceeds an allowable amount on condition that the theoretical amount of air sucked into the engine combustion chamber during rotation speed control is equal to the amount of air measured by the air flow meter. The gist is to provide further.

For the same reason as described above, under the condition that the learning value by the idle rotation speed control mechanism is equal to or larger than the predetermined value, the intake air amount metering valve is set at the target opening degree, but the opening degree depends on the opening degree. It is possible to determine whether the amount of deposit in the metering valve deposit is large or the increase in engine friction by determining whether or not the amount of air is not actually flowing. In other words, the “increase in engine friction” can be determined under the same condition based on the measurement of the amount of air corresponding to the opening of the intake air amount metering valve. Therefore, as described above, the learning value by the idle rotation speed control mechanism is equal to or greater than a predetermined value, and the theoretical air amount sucked into the engine combustion chamber during the idle rotation speed control and the air amount measured by the air flow meter. Is monitored, it is possible to clearly determine “increase in engine friction” based on an affirmative determination of the same condition. Incidentally, in such “increase in engine friction”, an intake air amount corresponding to the opening of the intake air amount metering valve can be obtained.

Hereinafter, an embodiment embodying the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a schematic configuration of an in-vehicle internal combustion engine equipped with an intake system failure diagnosis device and its peripheral devices.
In FIG. 1, a throttle valve 14 that adjusts the amount of air taken into the intake passage 12 is provided in the intake passage 12 of the internal combustion engine 10. A throttle motor 16 is connected to the throttle valve 14 to adjust its opening. That is, the opening degree of the throttle valve 14 is adjusted by the drive control of the throttle motor 16, and the amount of air taken into the engine combustion chamber 18 through the intake passage 12 is adjusted. The intake passage 12 is provided with a fuel injection valve 20, and fuel is injected into the intake passage 12 through the fuel injection valve 20. The fuel is injected into the intake passage 12 through the fuel injection valve 20 to form an air-fuel mixture composed of the air sucked into the intake passage 12 and the injected fuel. As the valve 30 is opened, it is sucked into the engine combustion chamber 18.

  Here, in the engine combustion chamber 18 of the internal combustion engine 10, the air-fuel mixture sucked from the intake passage 12 is ignited by the spark plug 22. By this ignition operation, the air-fuel mixture is combusted, the piston 24 is reciprocated, and the crankshaft 26 that is the engine output shaft is rotated. The combusted air-fuel mixture is sent out from the engine combustion chamber 18 to the exhaust passage 28 as exhaust gas when the exhaust valve 31 is opened. The opening / closing operation of the intake valve 30 and the exhaust valve 31 is performed based on the rotation of the intake camshaft 32 and the exhaust camshaft 33 to which the rotation of the crankshaft 26 is transmitted.

  An exhaust purification catalyst 34 is provided in the exhaust passage 28 of the internal combustion engine 10. That is, the exhaust sent from the engine combustion chamber 18 to the exhaust passage 28 is purified through the exhaust purification catalyst 34 and then released to the outside.

  On the other hand, the internal combustion engine 10 is provided with various sensors for detecting the operating state. As these various sensors, a crank sensor 52 for detecting the engine rotational speed NE, which is the rotational speed of the crankshaft 26, and an air flow meter 54 for detecting the amount of air taken into the intake passage 12 (intake air amount) GA. , And an accelerator sensor 56 for detecting the depression amount AC of the accelerator pedal 36 are provided. Further, a throttle sensor 58 for detecting the throttle opening degree TA which is the opening degree of the throttle valve 14 and a temperature sensor 62 for detecting the temperature of the engine cooling water are provided. Further, an air-fuel ratio sensor (oxygen sensor) 64 for detecting the oxygen concentration in the exhaust gas is provided in a portion of the exhaust passage 28 upstream of the exhaust purification catalyst 34. Based on the output of the air-fuel ratio sensor 64, it is detected whether the air-fuel ratio of the air-fuel mixture subjected to combustion in the engine combustion chamber 18 is lean or rich. Note that the air-fuel ratio sensor 64 is provided as a common to all cylinders at the joined portion of the exhaust manifold extending from the plurality of cylinders of the internal combustion engine 10.

  On the other hand, the diagnostic apparatus according to the present embodiment includes an electronic control unit 50 that is configured mainly by a microcomputer having, for example, an arithmetic device and a storage device. The electronic control unit 50 performs various calculations while acquiring detection signals from the various sensors, and executes various controls such as drive control of the throttle motor 16 and the fuel injection valve 20 based on the calculation results. In the present embodiment, the known idle speed control (ISC control), learning of the correction amount of the throttle opening TA in ISC control (ISC learning), air-fuel ratio control, and the theoretical air-fuel ratio of the controlled air-fuel ratio are determined. The engine intake system failure diagnosis is performed while learning the steady deviation amount (air-fuel ratio learning). Note that a non-volatile storage device is provided in the electronic control unit 50, and a predetermined area for storing the learned values and the like is secured in the storage device.

Hereinafter, main control and learning executed through the electronic control unit 50, and processing related to failure diagnosis executed while referring to the learning values will be described in order.
First, ISC control executed through the electronic control unit 50 will be described.

  In the ISC control, first, an engine state such as an engine warm-up condition grasped from the temperature of the cooling water detected by the temperature sensor 62 at that time is detected. In the ISC control, an ISC basic flow rate ISCqnt that is a theoretical air amount corresponding to a target rotational speed during engine idle operation according to the detected engine state, and a theoretical value for obtaining the ISC basic flow rate ISCqnt. A target opening that is the opening of the throttle valve 14 is calculated.

Further, an opening correction value of the throttle valve 14 is calculated based on a comparison result between the target rotational speed and the engine rotational speed NE. Then, an opening command value that is a driving amount of the throttle motor 16 is calculated from the target opening, the opening correction value of the throttle valve 14, and the ISC learning value ISCg described below. That is, the internal control is performed so that the engine rotational speed NE approaches the target rotational speed by the opening degree of the throttle valve 14 adjusted by the electronic control unit 50 controlling the drive amount of the throttle motor 16 based on the opening degree command value. The amount of air taken into the engine combustion chamber 18 of the engine 10 is adjusted.

  Next, ISC learning executed through the electronic control unit 50 will be described with reference to FIG. In this ISC learning, the ISC learning value ISCg is calculated from the opening correction value of the throttle valve 14 in the ISC control.

  FIG. 2 is a flowchart showing a routine for calculating the ISC learning value ISCg. This routine is repeatedly executed by the electronic control unit 50 at a predetermined cycle from the start of ISC control. The value calculated as the ISC learning value ISCg is stored and updated in a predetermined area of the storage device in the electronic control device 50 as described above.

  In this process, first, the electronic control unit 50 determines whether or not an ISC learning condition is satisfied (step S201 in FIG. 2). As the ISC learning condition, for example, there are various conditions shown below, and it is determined that the ISC learning condition is satisfied when all of these conditions are satisfied.

・ The temperature of the cooling water is higher than the specified temperature.
・ There is no electrical load.
・ The engine speed NE is stable.

When it is determined that the ISC learning condition is not satisfied (NO in step S201 in FIG. 2), the control device 50 once ends this ISC learning value calculation routine.
On the other hand, when it is determined that the ISC learning condition is satisfied (YES in step S201 in FIG. 2), the electronic control unit 50 determines whether or not the opening correction value of the throttle valve 14 is smaller than a predetermined opening correction upper limit value. Determination is made (step S202 in FIG. 2). When it is determined that the opening correction value of the throttle valve 14 is equal to or larger than the opening correction upper limit value (NO in step S202 in FIG. 2), the control device 50 increases the value of the ISC learning value ISCg by a predetermined amount. The calculation is performed and stored in a predetermined area of the storage device (step S203 in FIG. 2). Thereafter, the control device 50 executes a guard process in which the obtained ISC learning value ISCg is set to a value between the predetermined upper limit guard value IGH and the predetermined lower limit guard value IGL (step S206 in FIG. 2). The upper limit guard value IGH and the lower limit guard value IGL are values that are predetermined and stored in other areas of the storage device, and are ISC learning values ISCg that can suitably perform ISC control during engine idle operation. The maximum and minimum values that can be taken. Thereafter, the control device 50 once ends this ISC learning value calculation routine.

  On the other hand, when it is determined that the opening correction value of the throttle valve 14 is smaller than the opening correction upper limit value (YES in step S202 in FIG. 2), the electronic control unit 50 sets the opening correction value of the throttle valve 14 to a predetermined value. It is determined whether or not it is larger than the opening correction lower limit value (step S204 in FIG. 2). When it is determined that the opening correction value of the throttle valve 14 is equal to or smaller than the opening correction lower limit value (NO in step S204 in FIG. 2), the control device 50 performs an operation to decrease the value of the ISC learning value ISCg by a predetermined amount. And store it in a predetermined area of the storage device. Thereafter, the control device 50 executes the guard process for the obtained ISC learning value ISCg (step S206 in FIG. 2), and once ends the ISC learning value calculation routine.

If it is determined that the opening correction value of the throttle valve 14 is larger than the opening correction lower limit (YES in step S204 in FIG. 2), the electronic control unit 50 does not update the value of the ISC learning value ISCg. The guard process is executed (step S206 in FIG. 2), and the ISC learning value calculation routine is temporarily terminated.

Thus, the opening correction value of the throttle valve 14 at the time of ISC control is learned, and the ISC learning value ISCg is stored in a predetermined area of the storage device.
Next, air-fuel ratio control executed through the electronic control unit 50 will be described.

  In the air-fuel ratio control, the fuel injected from the fuel injection valve 20 based on the comparison between the air-fuel ratio of the burned mixture and the stoichiometric air-fuel ratio so that the air-fuel ratio of the burned mixture becomes the stoichiometric air-fuel ratio. This is a well-known control in which the amount is feedback-controlled. That is, the electronic control unit 50 determines the basic injection amount corresponding to the expected control amount at which the air-fuel ratio of the burned air-fuel mixture becomes the stoichiometric air-fuel ratio, the air-fuel ratio feedback correction coefficient FAF, the air-fuel ratio learning region (engine operation region) i. Based on the air-fuel ratio learning value KGi described below in FIG. The air-fuel ratio feedback correction coefficient FAF is a correction coefficient calculated based on the deviation between the air-fuel ratio detected by the air-fuel ratio sensor 64 and the target air-fuel ratio (here, for example, 1.45 as the theoretical air-fuel ratio).

  Here, the air-fuel ratio learning executed through the electronic control unit 50 will be described with reference to FIG. In this air-fuel ratio learning, the air-fuel ratio learning value KGi is calculated from the air-fuel ratio feedback correction coefficient FAF in the air-fuel ratio control.

  FIG. 3 is a flowchart showing a routine for calculating the air-fuel ratio learning value KGi. This routine is also repeatedly executed by the electronic control unit 50 at a predetermined cycle from the start of the air-fuel ratio control. The electronic control unit 50 has its learning routine corresponding to a plurality of air-fuel ratio learning regions i (i = 1, 2, 3,...) Corresponding to the intake air amount GA (engine load) of the internal combustion engine 10. Is set. The storage device of the control device 50 is provided with areas where the air-fuel ratio learning value KGi and the air-fuel ratio learning completion flag X2i corresponding to each air-fuel ratio learning area i are stored. Then, in the air-fuel ratio learning, the respective air-fuel ratio learning values KGi calculated in the respective air-fuel ratio learning regions i and the set respective air-fuel ratio learning completion flags X2i are set to the predetermined values of the respective storage devices as described above. It is saved and updated in the area.

  In this process, first, the electronic control unit 50 determines whether or not the air-fuel ratio learning condition is satisfied (step S301 in FIG. 3). As the air-fuel ratio learning condition, for example, there are various conditions shown below, and it is determined that the air-fuel ratio learning condition is satisfied when all of these conditions are satisfied.

・ It is not warming up.
-Feedback control in air-fuel ratio control is being executed.
The learning of the air-fuel ratio learning value KGi in all the air-fuel ratio learning regions i has not been completed.

If it is determined that the air-fuel ratio learning condition is not satisfied (NO in step S301 in FIG. 3), the controller 50 once ends this air-fuel ratio learning calculation routine.
On the other hand, when it is determined that the air-fuel ratio learning condition is satisfied (YES in step S301 in FIG. 3), the electronic control unit 50 includes the current engine load in any of the air-fuel ratio learning regions i. Is determined (step S302 in FIG. 3). At the same time, it is determined whether or not “0” is set in the air / fuel ratio learning completion flag X2i corresponding to the determined air / fuel ratio learning region i (step S303 in FIG. 3). The air / fuel ratio learning completion flag X2i is a flag for determining whether or not learning of the air / fuel ratio learning value KGi in the air / fuel ratio learning region i has been completed, and when the air / fuel ratio learning has been completed. Is set to “1”, and “0” is set when the air-fuel ratio learning is not completed. The air / fuel ratio learning completion flag X2i corresponding to each air / fuel ratio learning region i is reset to “0” when the internal combustion engine 10 is stopped. When it is determined that the air / fuel ratio learning completion flag X2i is not “0” (NO in step S303 in FIG. 3), the controller 50 determines that the air / fuel ratio learning is completed in the air / fuel ratio learning region i. Then, this learning value calculation routine is temporarily terminated.

  On the other hand, when it is determined that the air-fuel ratio learning completion flag X2i is “0” (YES in step S303 in FIG. 3), the electronic control unit 50 has not completed air-fuel ratio learning in this air-fuel ratio learning region i. Judge. In this case, the control device 50 calculates an air-fuel ratio feedback correction coefficient average value FAFAV, which is an average value of air-fuel ratio feedback correction coefficients FAF for a plurality of past times, for example (step S304 in FIG. 3).

  The electronic control unit 50 that has thus calculated the air-fuel ratio feedback correction coefficient average value FAFAV next determines whether or not the air-fuel ratio feedback correction coefficient average value FAFAV is smaller than a predetermined correction coefficient upper limit value (step S305 in FIG. 3). . If it is determined that the air-fuel ratio feedback correction coefficient average value FAFAV is equal to or greater than the correction coefficient upper limit value (NO in step S305 in FIG. 3), the control device 50 increases the air-fuel ratio learning value KGi by a predetermined amount. The calculation is performed and stored in a predetermined area of the storage device (step S306 in FIG. 3). Next, the control device 50 executes a guard process that sets the air-fuel ratio learned value KGi to a value between the predetermined upper limit guard value KGH and the predetermined lower limit guard value KGL (step S310 in FIG. 3). Note that the upper limit guard value KGH and the lower limit guard value KGL are values that are determined in advance and stored at predetermined positions in the storage device, and are air-fuel ratio learning values that can suitably perform air-fuel ratio control in the air-fuel ratio learning region i. It is the maximum value and the minimum value that KGi can take. Thereafter, the control device 50 once ends this air-fuel ratio learning value calculation routine.

  On the other hand, when it is determined that the air-fuel ratio feedback correction coefficient average value FAFAV is smaller than the correction coefficient upper limit value (YES in step S305 in FIG. 3), the electronic control unit 50 determines that the air-fuel ratio feedback correction coefficient average value FAFAV is a predetermined correction. It is determined whether or not the coefficient is lower than the lower limit value (step S307 in FIG. 3). When it is determined that the air-fuel ratio feedback correction coefficient average value FAFAV is equal to or smaller than the correction coefficient lower limit value (NO in step S307 in FIG. 3), the control device 50 performs an operation to decrease the air-fuel ratio learning value KGi by a predetermined amount. This is performed and stored in a predetermined area of the storage device (step S308 in FIG. 3). Thereafter, the control device 50 executes the guard process for the air-fuel ratio learned value KGi (step S310 in FIG. 3), and once ends the air-fuel ratio learned value calculation routine.

  On the other hand, when it is determined that the air-fuel ratio feedback correction coefficient average value FAFAV is larger than the correction coefficient lower limit value (YES in step S307 in FIG. 3), the controller 50 determines the air-fuel ratio learning completion flag X2i of the air-fuel ratio learning value KGi. Is set to “1”. The control device 50 executes the guard process for the air-fuel ratio learning value KGi (step S310 in FIG. 3), and then ends the air-fuel ratio learning value calculation routine.

Thus, air-fuel ratio learning is executed for each air-fuel ratio learning region i, and the learning value, that is, the air-fuel ratio learning value KGi is stored in a predetermined region of the storage device for each air-fuel ratio learning region i.
Next, an intake system failure diagnosis process according to the present embodiment, which is executed by the electronic control device 50 with reference to each of the learning values described above, will be described. This intake system failure diagnosis is a process for diagnosing the presence or absence of an intake system failure and the cause or location of the failure.

First, in the intake system failure diagnosis of the present embodiment, among the intake system failures, “engine friction,” which is caused by excessive deposit accumulation on the throttle valve 14, such as “increased deposit of throttle deposit”, increased friction of the piston 24, etc. Diagnosis for “increased”. Further, in this intake system failure diagnosis, a diagnosis of “air flow meter failure” that is a failure of the air flow meter 54 itself and “intake leakage failure” that is some air leak in the intake system is performed. The intake system failure diagnosis is performed during the engine idle operation in which the intake air amount GA has little fluctuation. This is because there is little fluctuation in the intake air amount GA during the engine idle operation, so there is little possibility that the fluctuation of the intake air amount GA will affect the determination such as “increased accumulation of throttle deposit” and “increase in engine friction”. This is because these determinations can be made more accurately. Next, an outline of the determination conditions for each failure will be described.

(A) Diagnosis of “Intake Leakage Failure” If the ISC learning value ISCg is less than a predetermined value, that is, the ISC learning is performed in an appropriate range, among the intake system failures (abnormalities), the “throttle valve deposit” The possibility of “increased accumulation” and “increased engine friction” is excluded. If the intake air amount GA measured by the air flow meter 54 is smaller than the ISC basic flow rate ISCqnt sucked into the engine combustion chamber 18 during idle rotation speed control by a predetermined value or more, the possibility of an intake system failure is “air flow. There is a high possibility that it is a “meter failure” or “intake leakage failure”. In this case, in the air-fuel ratio control, if the air flow meter 54 is normal, the deviation amount from the center value of the air-fuel ratio learning value KGi is determined depending on whether or not there is an “intake leakage failure”. Each one shows a different tendency. In other words, when there is an “intake leakage failure”, the influence of this leakage is large in the engine idle operation region where the intake air amount GA is originally small, but can be ignored in the engine high load operation region where the intake air amount GA is large. Therefore, the deviation amount of the air-fuel ratio learning value KGi is also large in the engine idle operation region, and conversely is small in the engine high load operation region. Therefore, the ISC learning value ISCg is less than the predetermined value, the measured intake air amount GA is smaller than the ISC basic flow rate ISCqnt by a predetermined value or more, and the deviation amount of the air-fuel ratio learning value KGi is smaller than that in the engine high load operation region. Monitor the logical AND condition of showing a tendency to increase in the idle operating range. Accordingly, it is possible to clearly determine “intake leakage failure” based on the fact that the monitored AND condition is satisfied.

(B) Diagnosis of “air flow meter failure” (Part 1)
As described above, if the ISC learning value ISCg is less than the predetermined value, the possibility of “increase in the deposit of throttle deposit” or “increase in engine friction” among the malfunctions (abnormality) of the intake system is excluded. In addition, if the measured intake air amount GA is smaller than the ISC basic flow rate ISCqnt by a predetermined value or more, the possibility of an intake system failure is "air flow meter failure" or "intake leakage failure". Is as described above. In this case, the deviation amount of the air-fuel ratio learning value shows the above-described tendency according to the presence or absence of the “intake leakage failure” and the air-fuel ratio learning region i unless “air flow meter failure” occurs. In the case of “air flow meter failure”, it is almost the same regardless of the engine operating range. Therefore, the ISC learning value ISCg is less than the predetermined value, the measured intake air amount GA is smaller than the ISC basic flow rate ISCqnt by a predetermined value, and the deviation amount of the air-fuel ratio learning value KGi is between the engine idle operation region and the engine high load. Monitor the logical AND condition of showing the same tendency in the operation area. Accordingly, it is possible to clearly determine “air flow meter failure” based on the fact that the monitored AND condition is satisfied.

(C) Diagnosis of “air flow meter failure” (Part 2)
As described above, if the ISC learning value ISCg is less than the predetermined value, the possibility of “accumulation of throttle deposit” or “increase in engine friction” among the malfunctions (abnormality) of the intake system is excluded. . At this time, the possibility of “intake leakage failure”, “air flow meter failure”, etc., including the possibility of being “normal”, also appears. At least in this state, the measured intake air amount GA is the ISC. It is impossible to reach a situation where the flow rate is larger than the basic flow rate ISCqnt by a predetermined value or more unless it is an “air flow meter failure”. Therefore, if the ISC learning value ISCg is less than a predetermined value, it is also monitored whether the measured intake air amount GA is larger than the ISC basic flow rate ISCqnt by a predetermined value or more.
When such a condition is affirmed, it is possible to immediately diagnose “airflow meter failure”.

(D) Diagnosis of “increased accumulation of throttle deposit” Normally, if the ISC learning value ISCg is equal to or greater than a predetermined value, that is, if there is a tendency for excessive ISC learning, the above-described “throttle deposit” There is a high possibility that an abnormality such as “accumulation of accumulation” or “increase in engine friction” has occurred. In such a case, it is determined whether or not the ISC basic flow rate ISCqnt is larger than the measured intake air amount GA by a predetermined value or more. That is, whether or not the throttle valve 14 has reached the target opening degree, whether or not the amount of air corresponding to the opening degree actually flows does not increase the "throttle deposit accumulation". It can be determined whether the engine friction has increased. Therefore, if the ISC learning value ISCg is greater than or equal to a predetermined value and whether or not the ISC basic flow rate ISCqnt is greater than the measured intake air amount GA by a predetermined value or more, the same condition is positively determined. Based on this, it can be clearly determined that “the amount of accumulated throttle deposit” is large. Incidentally, in the case of “large amount of accumulated throttle deposit”, the intake air amount GA measured (actually flowing) tends not to increase even when the throttle valve 14 is open.

(E) Diagnosis of “Increase in Engine Friction” For the same reason as described above, under the condition that the ISC learning value ISCg is equal to or greater than a predetermined value, the throttle valve 14 is at the target opening degree. By determining whether or not the amount of air corresponding to the opening does not actually flow, it can be determined whether “the amount of accumulated throttle deposit” or “the increase in engine friction”. In other words, the “increase in engine friction” can be determined under the same conditions based on the fact that the air flow meter 54 measures the amount of air commensurate with the opening of the throttle valve 14. Accordingly, whether or not the ISC learning value ISCg is equal to or greater than a predetermined value and the ISC basic flow rate ISCqnt sucked into the engine combustion chamber 18 during idle speed control is equal to the intake air amount GA measured by the air flow meter 54 is determined. By monitoring, it becomes possible to clearly determine “increase in engine friction” based on the positive determination of the same condition. Incidentally, in the “increase in engine friction”, an intake air amount GA corresponding to the opening of the throttle valve 14 can be obtained.

  FIG. 4 is a flowchart showing a specific routine for performing the processing related to the above-described intake system failure diagnosis. Hereinafter, an example of the failure diagnosis procedure according to the above (A) to (E) will be described with reference to FIG. This routine is also repeatedly executed by the electronic control device 50 at a predetermined cycle.

  In this process, first, the electronic control unit 50 determines whether or not the internal combustion engine 10 is in an engine idle operation (step S1 in FIG. 4). Here, whether or not the engine is idling is determined based on the depression amount AC of the accelerator pedal 36 detected by the accelerator sensor 56, the vehicle speed, and the like. It is determined that the engine is idling because the speed is “0”. If it is determined that the engine is not idling (NO in step S1 in FIG. 4), the controller 50 once ends the intake system failure diagnosis routine.

  On the other hand, when it is determined that the engine is idling (YES in step S1 in FIG. 4), the electronic control unit 50 determines whether the ISC learning value ISCg is equal to or greater than a predetermined value q1. The predetermined value q1 is a value determined in advance through a test or the like in order to determine whether “increase in throttle deposit accumulation” or “increase in engine friction” occurs in the intake system. The value is 95% of the value IGH.

  If it is determined that the ISC learning value ISCg is equal to or greater than the predetermined value q1 (YES in step S2 in FIG. 4), then the electronic control unit 50 determines that the ISC basic flow rate ISCqnt is the intake air amount GA and the predetermined value q2. It is determined whether or not the value is equal to or greater than the added value (step S3 in FIG. 4). The predetermined value q2 is a value determined in advance through a test or the like in order to determine whether the failure in the intake system is “accumulation of throttle deposit accumulation” or “increase in engine friction”, for example, the ISC basic flow rate ISCqnt. Of “50%”. When it is determined that the ISC basic flow rate ISCqnt is greater than or equal to the sum of the intake air amount GA and the predetermined value q2 (YES in step S3 in FIG. 4), the control device 50 determines that “the throttle deposit is large”. Then, after the determination result is stored in the diagnosis result storage area of the storage device (step S4 in FIG. 4), the intake system failure diagnosis routine is temporarily ended.

  On the other hand, when it is determined that the ISC basic flow rate ISCqnt is less than the sum of the intake air amount GA and the predetermined value q2 (NO in step S3 in FIG. 4), the electronic control unit 50 determines that “engine friction has increased”. Then, after the determination result is stored in the diagnosis result storage area of the storage device (step S5 in FIG. 4), the intake system failure diagnosis routine is temporarily ended.

  On the other hand, when it is determined that the ISC learning value ISCg is less than the predetermined value q1 (NO in step S2 in FIG. 4), the electronic control unit 50 then determines that the intake air amount GA is the ISC basic flow rate ISCqnt and the predetermined value q3. It is determined whether or not the value is equal to or greater than the value obtained by adding (step S6 in FIG. 4). The predetermined value q3 is a value determined in advance through a test or the like in order to determine whether or not it is “air flow meter failure”, and is, for example, a value of “20%” of the ISC basic flow rate ISCqnt. . When it is determined that the intake air amount GA is equal to or greater than the value obtained by adding the ISC basic flow rate ISCqnt and the predetermined value q3 (YES in step S6 in FIG. 4), the control device 50 determines that the air flow meter has failed. After the determination result is stored in the diagnosis result storage area of the storage device (step S7 in FIG. 4), the intake system failure diagnosis routine is temporarily terminated.

On the other hand, when it is determined that the intake air amount GA is less than the value obtained by adding the ISC basic flow rate ISCqnt and the predetermined value q3 (NO in step S6 in FIG. 4), the electronic control unit 50 then determines that the intake air amount GA is It is determined whether or not the value is equal to or less than the value obtained by subtracting the predetermined value q4 from the ISC basic flow rate ISCqnt (step S8 in FIG. 4). The predetermined value q4 is a value determined in advance through a test or the like in order to determine whether it is a failure of “intake leakage failure” or “air flow meter failure”, and is, for example, “20%” of the ISC basic flow rate ISCqnt. Value. When it is determined that the intake air amount GA is equal to or smaller than the value obtained by subtracting the predetermined value q4 from the ISC basic flow rate ISCqnt (YES in step S8 in FIG. 4), the control device 50 continues the air-fuel ratio learning value KGi. It is determined whether or not the deviation amount tends to be larger in the engine idle operation region than in the engine high load operation region (step S9 in FIG. 4). The deviation amount of the air-fuel ratio learning value KGi is a value indicating an error amount that is constantly generated with respect to the basic injection amount at that time in each air-fuel ratio learning region i, and the air-fuel ratio learning value KGi. Based on. More specifically, the deviation amount ΔKG1 of the air-fuel ratio learning value KGi in the engine idle operation region (“1” indicates the engine idle operation region in the air-fuel ratio learning region i) is the engine relative to the basic injection amount during engine idle operation. This value is obtained from the ratio of the air-fuel ratio learning value KGi in the idle operation region. Further, the deviation amount ΔKGn (“n” indicates the engine high load operation region in the air fuel ratio learning region i) of the air fuel ratio learning value KGi in the engine high load operation region is the engine relative to the basic injection amount during the high load operation. This value is obtained from the ratio of the air-fuel ratio learning value KGi in the high load operation region. In this embodiment, when the ratio of the deviation amount ΔKG1 in the engine idle operation region to the deviation amount ΔKGn in the engine high load operation region is four times or more, “the deviation amount of the air-fuel ratio learning value KGi is higher than the engine high It tends to be larger in the engine idle operation region than in the load operation region. For example, when the deviation amount ΔKGn in the engine high load operation region is “5%” and the deviation amount ΔKG1 in the engine idle operation region is “20%” or more, “the deviation amount of the air-fuel ratio learning value KGi is the engine It is judged that the engine idling operation region tends to be larger than the high load operation region. When it is determined that the deviation amount of the air-fuel ratio learned value KGi tends to be larger in the engine idle operation region than in the engine high load operation region (YES in step S9 in FIG. 4), the control device 50 determines that “the intake system” After the determination is made and the determination result is stored in the diagnosis result storage area of the storage device (step S10 in FIG. 4), the intake system failure diagnosis routine is temporarily terminated.

  On the other hand, when it is determined that the deviation amount of the air-fuel ratio learning value KGi does not tend to become larger in the engine idle operation region than the engine high load operation region, that is, shows a tendency to be substantially equal (NO in step S9 in FIG. 4). The electronic control unit 50 determines that “the air flow meter has failed” and stores the determination result in the diagnosis result storage area of the storage device (step S7 in FIG. 4). Thereafter, the control device 50 once terminates the intake system failure diagnosis routine.

  On the other hand, when it is determined that the intake air amount GA is larger than the value obtained by subtracting the predetermined value q4 from the ISC basic flow rate ISCqnt (NO in step S8 in FIG. 4), the electronic control unit 50 determines that the intake system is “normal”. After the determination and the determination result is stored in the diagnosis result storage area of the storage device (step S11 in FIG. 4), the intake system failure diagnosis routine is temporarily ended.

Such a diagnosis process is repeatedly executed at a predetermined cycle as described above.
As described above, according to the intake system failure diagnosis apparatus of the present embodiment, the effects listed below can be obtained.

  (1) The ISC learning value ISCg is less than the predetermined value q1, the measured intake air amount GA is smaller than the ISC basic flow rate ISCqnt by the predetermined value q4, and the deviation amount of the air-fuel ratio learning value KGi in the engine high load operation region The AND condition indicating that the deviation amount ΔKG1 of the air-fuel ratio learning value KGi in the engine idle operation region becomes larger than ΔKGn is monitored. Accordingly, it is possible to clearly determine “intake leakage failure” based on the fact that the AND condition is satisfied. As a result, the cause of the failure occurring in the intake system can be clearly diagnosed, and the labor required for maintenance and inspection of the in-vehicle internal combustion engine through such diagnosis can be greatly reduced.

  (2) The ISC learning value ISCg is less than the predetermined value q1, the measured intake air amount GA is smaller than the ISC basic flow rate ISCqnt by the predetermined value q4, and the deviation amount ΔKG1 of the air-fuel ratio learning value KGi in the engine idle operation region And an AND condition indicating that the deviation amount ΔKGn of the air-fuel ratio learning value KGi in the engine high load operation region tends to be equal. As a result, it is possible to clearly determine “air flow meter failure” based on the fact that the AND condition is satisfied. As a result, the cause of the failure occurring in the intake system can be clearly diagnosed, and the labor required for maintenance and inspection of the in-vehicle internal combustion engine through such diagnosis can be greatly reduced.

  (3) When the ISC learning value ISCg is less than the predetermined value q1, whether or not the measured intake air amount GA is larger than the ISC basic flow rate ISCqnt by the predetermined value q3 is also monitored. As a result, when such a condition is affirmed, it is possible to immediately diagnose “air flow meter failure”.

  (4) Whether or not the ISC learning value ISCg is equal to or greater than the predetermined value q1 and the ISC basic flow rate ISCqnt is greater than the intake air amount GA to be measured by a predetermined value q2 is monitored. Accordingly, it is possible to clearly determine that “the throttle deposit is large” based on the positive determination of the same condition.

(5) The ISC learning value ISCg is equal to or greater than the predetermined value q1, and it is monitored whether or not the ISC basic flow rate ISCqnt is equal to the measured intake air amount GA. Accordingly, it is possible to clearly determine “increase in engine friction” based on the positive determination of the condition.

In addition, the said embodiment can also be implemented in the following aspects, for example.
In the above embodiment, the ISC basic flow rate ISCqnt is calculated as a theoretical air amount corresponding to the target rotational speed during engine idle operation, that is, a value corresponding to the amount of air sucked into the engine combustion chamber 18. At this time, parameters other than the ISC basic flow rate ISCqnt may be added to the calculation of the air amount equivalent value.

  In the above embodiment, the predetermined value q1 is “95%” of the upper guard value IGH, but the value of the predetermined value q1 is not limited to this. In other words, the value of the predetermined value q1 may be any value as long as it can be determined whether or not “the throttle deposit is increased” or “the engine friction is increased”.

  In the above embodiment, the predetermined value q2 is set to “50%” of the ISC basic flow rate ISCqnt, but the value of the predetermined value q2 is not limited to this. In other words, the value of the predetermined value q2 may be any value as long as it can be determined as one of “increase in throttle deposit accumulation” and “increase in engine friction”.

  In the above embodiment, the predetermined value q3 and the predetermined value q4 are “20%” of the ISC basic flow rate ISCqnt, but the predetermined value q3 and the predetermined value q4 are not limited to these values. That is, the value of the predetermined value q3 may be any value as long as it can be determined whether or not it is “air flow meter failure”. Also, the value of the predetermined value q4 may be any value as long as it can be determined as “intake leakage failure” or “air flow meter failure”.

  In the above-described embodiment, the deviation amount ΔKG1 at the time of engine idle operation is large and the deviation amount ΔKGn at the time of engine high load operation tends to be small, “intake leakage failure”, and the respective deviation amounts ΔKG1, ΔKGn are equal. Judgment was made as “air flow meter failure” under the conditions showing However, the present invention is not limited to this, and the method for determining whether the intake air leak failure or the air flow meter failure is based on the value based on the learning value of each air-fuel ratio, other methods can be used as long as each failure can be determined. Even if it is a method, it can employ | adopt suitably. For example, if the air-fuel ratio learning value during engine idle operation is large and the air-fuel ratio learning value during engine high-load operation tends to be small, `` intake leakage failure '', each air-fuel ratio learning value tends to be equal. It is also possible to judge “air flow meter failure” under the conditions shown.

  In the above embodiment, when the ratio of the deviation amount ΔKG1 of the engine idle operation region to the deviation amount ΔKGn of the engine high load operation region is “four times” or more, “the deviation amount of the air-fuel ratio learning value KGi is the engine It shows a tendency to become larger in the engine idle operation region than in the high load operation region. However, the present invention is not limited to this, and the ratio of the deviation amount in the engine idle operation region to the deviation amount in the engine high load operation region may be a value larger than “1 time”.

  Further, the above-described deviation amounts may be compared by “difference”. That is, from the difference between the deviation amount ΔKGn in the engine high load operation region and the deviation amount ΔKG1 in the engine idle operation region, “the deviation amount of the air-fuel ratio learning value KGi tends to be larger in the engine idle operation region than in the engine high load operation region. It may be determined whether or not it is shown. For example, if the threshold value of the determination is “10%”, the deviation amount ΔKG1 is “20%”, the deviation amount ΔKGn is “5%”, and the difference is “15%”. It is also possible to appropriately adopt a method for determining that the deviation amount of the engine is larger in the engine idle operation region than in the engine high load operation region.

  In the above embodiment, the intake air amount GA of the intake passage 12 is adjusted by adjusting the opening of the throttle valve 14 in the ISC control. However, the present invention is not limited to this, and adjustment of the intake air amount in the intake passage in ISC control may be performed by an idle speed control valve (ISCV) provided in a bypass passage that bypasses the throttle valve. Other devices may be used.

  -In the above embodiment, the diagnosis of the possibility that the intake system failure diagnosis may be "increased accumulation of throttle deposit" or "increase in engine engine friction", diagnosis when it can only be "failure of air flow meter", "intake leakage failure" "Or" Air flow meter failure "in order of diagnosis. However, the order of performing the intake system failure diagnosis and the combination of the diagnosis are not limited to the order described above, specifically the one shown in the flowchart of FIG. That is, since each diagnosis (A) to (E) shown in the above embodiment can obtain the result of the diagnosis independently, the order of each diagnosis is changed in the intake system failure diagnosis. Of course, only a single diagnosis may be performed.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram and engine schematic which show the structure about one Embodiment of the intake system failure diagnostic apparatus of the vehicle-mounted internal combustion engine concerning this invention. The flowchart which shows the example of a procedure which learns the correction value in ISC control. The flowchart which shows the example of a procedure which learns the correction value in air-fuel ratio control. The flowchart which shows the diagnostic procedure about the intake system failure diagnosis by the apparatus of the embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 12 ... Intake passage, 14 ... Throttle valve which comprises idle rotational speed control mechanism, 16 ... Throttle motor which comprises idle rotational speed control mechanism, 18 ... Engine combustion chamber, 20 ... Air fuel ratio control mechanism Fuel injection valve, 22 ... spark plug, 24 ... piston, 26 ... crankshaft, 28 ... exhaust passage, 30 ... intake valve, 31 ... exhaust valve, 32 ... intake camshaft, 33 ... exhaust camshaft, 34 ... exhaust purification Catalyst, 36 ... accelerator pedal, 50 ... electronic control device constituting idle speed control mechanism and air-fuel ratio control mechanism, 52 ... crank sensor constituting idle speed control mechanism, 54 ... air flow meter, 56 ... accelerator sensor, 58 ... Throttle sensor constituting idle rotation speed control mechanism, 62 ... Temperature sensor, 64 ... Empty Air-fuel ratio sensor which constitutes the ratio control mechanism.

Claims (5)

Idle rotation speed is a mechanism that controls the engine rotation speed to the target rotation speed by learning the opening correction value of the intake air volume adjustment valve during engine idle operation and controlling the opening of the intake air volume adjustment valve A control mechanism, an air flow meter that measures the amount of air taken into the engine, and the amount of deviation from the stoichiometric air-fuel ratio of the air-fuel mixture supplied to the engine combustion chamber while learning the air-fuel ratio of the air-fuel mixture to the stoichiometric air-fuel ratio A vehicle-mounted internal combustion engine having an air-fuel ratio control mechanism that is a mechanism for feedback-controlling the ratio of the fuel injection amount to the intake air amount based on the oxygen concentration of the exhaust to maintain the vehicle. An intake system failure diagnosis device for an internal combustion engine,
When the learning value by the idle rotation speed control mechanism is less than a predetermined value and the air amount measured by the air flow meter is smaller than the theoretical air amount sucked into the engine combustion chamber during the idle rotation speed control by a predetermined value or more. In addition, it is diagnosed that there is an intake leak failure in the intake system under the condition that the deviation amount of the learning value by the air-fuel ratio control mechanism tends to be larger in the engine idle operation region than in the engine high load operation region. Intake system failure diagnosis device for in-vehicle internal combustion engine. Idle rotation speed is a mechanism that controls the engine rotation speed to the target rotation speed by learning the opening correction value of the intake air volume adjustment valve during engine idle operation and controlling the opening of the intake air volume adjustment valve A control mechanism, an air flow meter that measures the amount of air taken into the engine, and the amount of deviation from the stoichiometric air-fuel ratio of the air-fuel mixture supplied to the engine combustion chamber while learning the air-fuel ratio of the air-fuel mixture to the stoichiometric air-fuel ratio A vehicle-mounted internal combustion engine having an air-fuel ratio control mechanism that is a mechanism for feedback-controlling the ratio of the fuel injection amount to the intake air amount based on the oxygen concentration of the exhaust to maintain the vehicle. An intake system failure diagnosis device for an internal combustion engine,
When the learning value by the idle rotation speed control mechanism is less than a predetermined value and the air amount measured by the air flow meter is smaller than the theoretical air amount sucked into the engine combustion chamber during the idle rotation speed control by a predetermined value or more. In addition, it is diagnosed that the air flow meter is malfunctioning under a condition that the amount of deviation of the learned value by the air-fuel ratio control mechanism tends to be equal between the engine idle operation region and the engine high load operation region. Intake system failure diagnosis device for in-vehicle internal combustion engine. In the in-vehicle internal combustion engine intake system failure diagnosis device according to claim 1 or 2,
The learned value by the idle rotational speed control mechanism is less than a predetermined value, and the air amount measured by the air flow meter is larger than the theoretical air amount sucked into the engine combustion chamber during idle rotational speed control by a predetermined value or more. An intake system failure diagnosis device for an on-vehicle internal combustion engine, further comprising means for diagnosing that the air flow meter is malfunctioning on the condition of In the in-vehicle internal combustion engine intake system failure diagnosis device according to any one of claims 1 to 3,
The learning value by the idle rotation speed control mechanism is greater than or equal to a predetermined value, and the theoretical air amount sucked into the engine combustion chamber during the idle rotation speed control is greater than or equal to a predetermined value than the air amount measured by the air flow meter. An intake system failure diagnosis device for an on-vehicle internal combustion engine, further comprising means for diagnosing that the amount of deposit deposited on the intake air amount metering valve exceeds an allowable amount on the condition. In the in-vehicle internal combustion engine intake system failure diagnosis device according to any one of claims 1 to 3,
The learning value by the idle rotation speed control mechanism is equal to or greater than a predetermined value, and the theoretical air amount sucked into the engine combustion chamber during the idle rotation speed control is equal to the air amount measured by the air flow meter. An intake system failure diagnosis device for an on-vehicle internal combustion engine, further comprising means for diagnosing that the engine friction is greater than or equal to an allowable amount on the condition of

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