JP2016098798A - Abnormality detection device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect at least one of an air-fuel ratio imbalance abnormality and a common supply system abnormality even during operation at a lean air-fuel ratio. SOLUTION: A combustion mass ratio (MFB) is calculated by using in-cylinder pressure data acquired by using a crank angle sensor 42 and an in-cylinder pressure sensor 30. The crank angle (CA10) when the MFB becomes 10% is acquired. The fuel injection amount is corrected so that there is no difference between the actual SA-CA10 and the target SA-CA10 in the crank angle period from the ignition timing (SA) to the CA10. Of the plurality of cylinders of the internal combustion engine 10, the fuel injection correction factor of the predetermined cylinder has reached the upper limit or the lower limit of the predetermined range, and the fuel injection correction factor of the predetermined cylinder and the fuel injection correction factor of other cylinders other than the predetermined cylinder. When the difference from and above is equal to or greater than a predetermined value, it is determined that an air-fuel ratio imbalance abnormality or a common supply system abnormality has occurred. [Selection diagram] FIG. 9

Description

  The present invention relates to an abnormality detection device for an internal combustion engine.

  Conventionally, for example, as disclosed in Japanese Patent Application Laid-Open No. 2013-142302, a technique for detecting an air-fuel ratio imbalance or failure of an internal combustion engine is known. In this prior art, the air-fuel ratio CPS-A / F is detected from the absolute pressure value detected by the in-cylinder pressure sensor (CPS), and the air-fuel ratio AFS-A / F is detected from the output value of the air-fuel ratio (A / F) sensor. doing. Based on these values CPS-A / F and AFS-A / F, an air-fuel ratio imbalance or failure of the internal combustion engine is detected.

JP2013-142302A

  The above conventional technique has a problem that the abnormality detection accuracy of the air-fuel ratio imbalance is low. The reason is that the absolute value of the in-cylinder pressure sensor has low detection accuracy because it is difficult to calibrate the zero point. Even in the case of using the A / F sensor, since the stoichiometric point calibration is performed at the stoichiometric air-fuel ratio (stoichiometric), the air-fuel ratio detection accuracy becomes lower near the lean limit than the stoichiometric control. Thus, conventionally, no means has been found for accurately detecting a lean air-fuel ratio imbalance abnormality. Also, some configurations of the internal combustion engine are commonly used among a plurality of cylinders in order to supply air and fuel into the cylinders. This is also referred to as a “common supply system”. When an average air-fuel ratio deviation occurs in all the cylinders, there is a strong suspicion that there is an abnormality in the common supply system. It is also desired to perform more accurate detection with a lean air-fuel ratio for such common supply system abnormality detection.

  The present invention has been made to solve the above-described problems, and is an internal combustion engine capable of accurately detecting at least one of an air-fuel ratio imbalance abnormality and a common supply system abnormality even when operating at a lean air-fuel ratio. An object of the present invention is to provide an abnormality detection apparatus.

An abnormality detection apparatus for an internal combustion engine according to the present invention includes:
Crank angle determining means for detecting the crank angle of the internal combustion engine;
A fuel mass ratio calculating means for calculating a combustion mass ratio;
Crank angle acquisition means for acquiring a predetermined crank angle when the combustion mass ratio becomes a predetermined combustion mass ratio;
By calculating the fuel injection adjustment amount based on the difference between the crank angle period from the ignition timing to the predetermined crank angle or the correlation value of the crank angle period and the target value of the crank angle period or the correlation value, Adjusting means for adjusting the injection amount;
With
First determination means for determining abnormality of a common supply system that is commonly used among a plurality of cylinders of the internal combustion engine for supplying air and fuel into the cylinder, and second for determining abnormality of the air-fuel ratio imbalance It further comprises at least one means among the judging means,
The first determination means includes a fuel injection adjustment amount of a predetermined cylinder among a plurality of cylinders of the internal combustion engine that has reached an upper limit or a lower limit of a predetermined range, and the fuel injection adjustment amount of the predetermined cylinder and the predetermined cylinder When the difference between the fuel injection adjustment amount of other cylinders other than the cylinder is a predetermined value or less, it is determined that there is an abnormality in the common supply system,
The second determination means is configured such that the fuel injection adjustment amount of a predetermined cylinder among the plurality of cylinders of the internal combustion engine reaches an upper limit or a lower limit of a predetermined range, and the fuel injection adjustment amount of the predetermined cylinder and the predetermined cylinder It is determined that an air-fuel ratio imbalance abnormality has occurred when a difference from the fuel injection adjustment amount of a cylinder other than the cylinder is equal to or greater than a predetermined value.

  The crank angle period specified as the period from the ignition timing to the predetermined crank angle using the ignition timing as well as the predetermined crank angle when the predetermined combustion mass ratio is obtained, and the correlation value thereof include the air-fuel ratio including the lean region. And a parameter having a high correlation. By using the fuel injection adjustment amount calculated during the feedback control using the parameter, it is possible to accurately detect at least one of the air-fuel ratio imbalance abnormality and the common supply system abnormality even during the lean operation.

It is a figure for demonstrating the system configuration | structure of the internal combustion engine in embodiment of this invention. It is a figure showing the ignition timing and the waveform of a combustion mass ratio. It is a figure showing the relationship between each of NOx emission amount, fuel consumption, torque fluctuation, and SA-CA10 and the air-fuel ratio (A / F). It is a block diagram for demonstrating the outline | summary of the feedback control of the fuel injection quantity using SA-CA10 which concerns on embodiment of this invention. It is a flowchart of a routine executed in the embodiment of the present invention. It is a flowchart of the data acquisition routine for a detection concerning embodiment of this invention. It is a flowchart of the other data acquisition routine for detection concerning embodiment of this invention. It is a flowchart of the other data acquisition routine for detection concerning embodiment of this invention. It is a flowchart of the A / F imbalance abnormality detection routine concerning embodiment of this invention. It is a flowchart of the common supply system abnormality detection routine concerning embodiment of this invention.

[System configuration of the embodiment]
FIG. 1 is a diagram for explaining a system configuration of an internal combustion engine 10 according to an embodiment of the present invention. The system shown in FIG. 1 includes a spark ignition type internal combustion engine 10. Although only one cylinder is illustrated in FIG. 1 for convenience, the internal combustion engine 10 actually includes a plurality of cylinders, and may include four cylinders as an example. A piston 12 is provided in the cylinder of the internal combustion engine 10. A combustion chamber 14 is formed on the top side of the piston 12 in the cylinder. An intake passage 16 and an exhaust passage 18 communicate with the combustion chamber 14.

  The intake port of the intake passage 16 is provided with an intake valve 20 that opens and closes the intake port, and the exhaust port of the exhaust passage 18 is provided with an exhaust valve 22 that opens and closes the exhaust port. The intake passage 16 is provided with an electronically controlled throttle valve 24.

  Each cylinder of the internal combustion engine 10 is provided with a fuel injection valve 26 for directly injecting fuel into the combustion chamber 14 (inside the cylinder) and an ignition plug 28 for igniting the air-fuel mixture. Further, an in-cylinder pressure sensor 30 for detecting the in-cylinder pressure is incorporated in each cylinder. Although not shown in the drawings, among the configurations of the internal combustion engine 10, a configuration that is commonly used by a plurality of cylinders for supplying fuel and air to each cylinder is also referred to as a “common supply system” for convenience. The “common supply system” specifically includes a fuel pump, a fuel pressure sensor, a delivery, a fuel pipe, a throttle valve 24, and an air flow meter 44. Therefore, the “common supply system” does not include components provided for each cylinder, specifically, fuel injection valves provided for each cylinder. Further, among the “common supply system”, a fuel-related one is also referred to as a “common fuel supply system”. The “common fuel supply system” includes a fuel pump, a fuel pressure sensor, a delivery, and a fuel pipe (not shown). The common fuel supply system is provided in common among the plurality of cylinders, and is connected to the fuel injection valve 26 of each cylinder at the end.

  Furthermore, the system of the present embodiment includes an ECU (Electronic Control Unit) 40. In addition to the in-cylinder pressure sensor 30 described above, an operating state of the internal combustion engine 10 such as a crank angle sensor 42 for acquiring the engine rotation speed and an air flow meter 44 for measuring the intake air amount is provided at the input portion of the ECU 40. Various sensors for acquiring are connected. Also, various actuators for controlling the operation of the internal combustion engine 10, such as the throttle valve 24, the fuel injection valve 26, and the spark plug 28, are connected to the output portion of the ECU 40. The ECU 40 performs predetermined engine control such as fuel injection control and ignition control by driving the various actuators based on the sensor output and a predetermined program. Further, the ECU 40 has a function of acquiring an output signal of the in-cylinder pressure sensor 30 by performing AD conversion in synchronization with the crank angle. Thereby, the in-cylinder pressure at an arbitrary crank angle timing can be detected within a range allowed by the AD conversion resolution. Further, the ECU 40 has a function of calculating the value of the cylinder volume determined by the position of the crank angle according to the crank angle.

ただし、上記（１）式において、Ｐは筒内圧力、Ｖは筒内容積、κは筒内ガスの比熱比である。また、Ｐ_０およびＶ_０は、計算開始点θ_０（想定される燃焼開始点に対して余裕をもって定められた圧縮行程中（ただし、吸気弁２０の閉弁後）の所定クランク角度θ）での筒内圧力および筒内容積である。また、上記（２）式において、θ_staは燃焼開始点（ＣＡ０）であり、θ_finは燃焼終了点（ＣＡ１００）である。 [Control of Embodiment]
(Ignition timing and combustion mass ratio)
FIG. 2 is a diagram showing the ignition timing and the combustion mass ratio waveform. According to the system of this embodiment including the in-cylinder pressure sensor 30 and the crank angle sensor 42, in-cycle pressure data (in-cylinder pressure waveform) can be acquired on a crank angle (CA) basis in each cycle of the internal combustion engine 10. . A combustion mass ratio (hereinafter referred to as “MFB”) having a waveform as shown in FIG. 2 can be calculated using the in-cylinder pressure waveform after the absolute pressure correction is performed by a known method. More specifically, the in-cylinder heat generation amount Q at an arbitrary crank angle θ can be calculated according to the following equation (1) using in-cylinder pressure data. Then, the MFB at an arbitrary crank angle θ can be calculated according to the following equation (2) using the calculated calorific value Q in the cylinder. Therefore, the crank angle (hereinafter referred to as “CAα”) when the MFB is a predetermined ratio α (%) can be obtained by using the equation (2).

In the above equation (1), P is the in-cylinder pressure, V is the in-cylinder volume, and κ is the specific heat ratio of the in-cylinder gas. Further, P ₀ and V ₀ are the calculation start point θ ₀ (the predetermined crank angle θ during the compression stroke (with the intake valve 20 closed) determined with a margin with respect to the assumed combustion start point). In-cylinder pressure and in-cylinder volume. In the above equation (2), θ _sta is the combustion start point (CA0), and θ _fin is the combustion end point (CA100).

  Here, a typical crank angle CAα will be described with reference to FIG. Combustion in the cylinder starts with a delay in ignition after the air-fuel mixture is ignited at the ignition timing. This combustion start point, that is, the point where the MFB rises is referred to as CA0. The crank angle period (CA0-CA10) from CA0 to MFB when the MFB is 10% corresponds to the initial combustion period, and the crank angle period from CA10 to the crank angle CA90 when the MFB is 90% ( CA10-CA90) corresponds to the main combustion period. Further, the crank angle CA50 when the MFB is 50% corresponds to the combustion gravity center position.

(Lean limit control using SA-CA10)
FIG. 3 is a diagram showing the relationship between the NOx emission amount, fuel consumption, torque fluctuation, and SA-CA10 and the air-fuel ratio (A / F). As a fuel efficiency technique for an internal combustion engine, a lean burn operation performed at an air / fuel ratio that is leaner than a stoichiometric air / fuel ratio is effective. As shown in FIGS. 3A and 3B, the leaner the air-fuel ratio, the better the fuel consumption and the lower the NOx emission amount. However, if the air-fuel ratio is made too lean, combustion deteriorates and fuel efficiency deteriorates. On the other hand, the torque fluctuation gradually increases as the air-fuel ratio becomes lean, as shown in FIG. 3C, and rapidly increases when the air-fuel ratio exceeds a certain value and becomes lean. The torque fluctuation here is a fluctuation value with respect to a time-series torque value. More specifically, filter processing in a specific frequency band is performed on the time-series torque value, and the time-series torque value amplitude, standard deviation, or absolute value average value after the filter process is obtained. Is. Hereinafter, the air-fuel ratio at the lean combustion limit of the air-fuel mixture, more specifically, the air-fuel ratio when the torque fluctuation value reaches the threshold value that becomes the limit from the viewpoint of drivability of the internal combustion engine 10 is referred to as “lean limit”.

  3A to 3C, in order to realize low fuel consumption and low NOx emission, the state of the internal combustion engine 10 is monitored, and the air-fuel ratio is as lean as possible within a range in which drivability does not deteriorate. It is preferable to control the air-fuel ratio in the vicinity of the lean limit. Hereinafter, such air-fuel ratio control is referred to as “lean limit control”.

  Conventional lean limit control generally detects torque fluctuation during operation by statistically processing the torque (or torque equivalent value), and controls the air-fuel ratio in the vicinity of the lean limit based on the detected torque fluctuation. That's it. However, with the conventional method, rapid lean limit control cannot be realized (there is a period during which such air-fuel ratio control cannot be performed). The reason is that torque fluctuation is a parameter based on statistical processing, and therefore cannot be calculated until a predetermined number of combustions (for example, 100 times) has elapsed. In addition, since it is a value based on fluctuations in engine torque during steady operation, it must be grasped separately from transient changes in torque due to various factors (such as vehicle accelerator pedal operation and air and EGR gas response delays). Is difficult. Further, in order to increase the control opportunity, it is necessary to allow a transitional change, which reduces the calculation accuracy of torque fluctuation. Furthermore, the conventional method cannot prevent deterioration of vibration noise of the internal combustion engine. The reason is that torque fluctuation is treated as a statistic and cannot cope with sudden deterioration of combustion. For example, when 99 out of 100 combustions are normal and the combustion deteriorates only once, such a sudden combustion deterioration does not appear in the calculated value of the torque fluctuation, but in the vicinity of the lean limit. Such combustion deterioration can occur. Furthermore, the conventional method is difficult to perform in a mode other than uniform control for all cylinders. This is because the engine generated torque is handled as a whole, not for each cylinder. If an attempt is made to calculate the torque fluctuation using the combustion torque for each cylinder, the problem described first becomes more prominent. In other words, if the predetermined number of combustions required for calculating torque fluctuations by statistical processing is required, for example, 100 times when performing all cylinders uniformly, the number of cylinders per 100 times when statistical processing is performed for each cylinder. The number of times of combustion is required. For this reason, when it is attempted to calculate the torque fluctuation for each cylinder, the time required for calculating the torque fluctuation is doubled according to the number of cylinders as compared with the case where the calculation is performed uniformly for all cylinders.

  As described above, it can be said that the technique using the torque fluctuation based on the statistical processing takes time and does not hold in the transient operation. Therefore, in the present embodiment, as a lean limit control method that solves such problems and does not depend on statistical processing, the crank angle period (SA−) from the ignition timing (SA) to CA10, which is the 10% combustion point. The fuel injection amount feedback control based on CA10) is performed for each cylinder.

  Here, an advantage of using SA-CA10 as a parameter of the lean limit control of the present embodiment will be described. SA-CA10 is a parameter representing ignition delay. As shown in FIG. 3D, SA-CA10 has a high correlation with the air-fuel ratio, and maintains a good linearity with respect to the air-fuel ratio even near the lean limit. For this reason, the use of SA-CA10 facilitates feedback control of the air-fuel ratio in the vicinity of the lean limit.

  Further, it can be said that SA-CA10 is more representative of the lean limit than the air-fuel ratio itself for the following reason. That is, it has been confirmed by experiments that the air-fuel ratio that becomes the lean limit changes depending on the operating conditions (for example, the engine water temperature), but the SA-CA10 is less likely to change depending on the operating conditions than the air-fuel ratio. In other words, since the air-fuel ratio that becomes the lean limit largely depends on the ignition factor of the air-fuel mixture, it can be said that the SA-CA10 that represents the ignition delay is less affected by the operating conditions than the air-fuel ratio itself. However, since the time per crank angle changes when the engine speed changes, the target SA-CA10 that is the target value of SA-CA10 is preferably set according to the engine speed. More preferably, since SA-CA10 also changes depending on the engine load factor, the target SA-CA10 may be set according to the engine load factor instead of or together with the engine rotation speed.

  Next, as a combustion point (predetermined crank angle when MFB becomes a predetermined combustion mass ratio) used to specify a crank angle period as an index of lean limit control of the present embodiment with respect to the ignition timing, CA10 is The reason why it is preferable compared to other combustion points will be described. The predetermined crank angle is not limited to CA10, and any other combustion point can be used. Even when other arbitrary combustion points are used, the obtained crank angle period basically has the advantages of high correlation with the above-described air-fuel ratio and high representativeness of the lean limit. It can be said that. However, when the combustion point in the main combustion period (CA10-CA90) after CA10 is used, the obtained crank angle period is a parameter (EGR rate, intake air temperature and intake gas temperature) that affects combustion when the flame spreads. Greatly affected by the tumble ratio). That is, the crank angle period obtained in this case is not purely focused on the air-fuel ratio, and is weak against disturbance. In order to eliminate the influence of such disturbance, the configuration in which the crank angle period is corrected in accordance with the above parameters increases the number of man-hours for adaptation. On the other hand, when the combustion point in the initial combustion period (CA0-CA10) is used, the obtained crank angle period is not easily influenced by the above parameters, and the influence of the factors affecting the ignition appears well. It becomes. As a result, controllability is improved. On the other hand, the combustion start point (CA0) and the combustion end point (CA100) are likely to have errors due to the influence of noise superimposed on the output signal from the in-cylinder pressure sensor 30 acquired by the ECU 40. The influence of this noise decreases as the distance from the combustion start point (CA0) or combustion end point (CA100) increases. Therefore, in consideration of noise resistance and reduction in the number of man-hours (conformity-less potential), it can be said that CA10 is the most excellent as the predetermined crank angle as used in the present embodiment.

(Outline of feedback control of embodiment)
FIG. 4 is a block diagram for explaining an outline of feedback control of the fuel injection amount using the SA-CA 10 according to the embodiment of the present invention. Feedback control using SA-CA10, which is control equivalent to the lean limit control of the present embodiment, is based on the difference between a predetermined target SA-CA10 near the lean limit and the actual SA-CA10 (more specifically, Is to adjust the fuel injection amount (so that the difference becomes zero).

  In this feedback control, as shown in FIG. 4, a target SA-CA10 is set in accordance with the engine operating state (specifically, the engine speed and the engine load factor). The actual SA-CA10 here is a crank angle period from the ignition timing to CA10 obtained from an analysis result of in-cylinder pressure data obtained using the in-cylinder pressure sensor (CPS) 30 and the crank angle sensor 42. This is a calculated value. The actual SA-CA10 is calculated for each cycle in each cylinder.

  In this feedback control, PI control is used as an example in order to adjust the fuel injection amount so that the difference between the target SA-CA10 and the actual SA-CA10 is eliminated. In this PI control, using the difference between the target SA-CA10 and the actual SA-CA10 and a predetermined PI gain (proportional term gain and integral term gain), fuel injection according to the difference and the magnitude of the integrated value is performed. An amount correction rate is calculated. The fuel injection amount correction factor calculated for each cylinder is reflected in the fuel injection amount of the target cylinder. Thus, the fuel injection amount supplied to each cylinder of the internal combustion engine (ENG) 10 is adjusted (corrected) by the feedback control.

(Specific processing in the embodiment)
FIG. 5 is a flowchart illustrating a control routine executed by the ECU 40 in order to realize lean limit control using the SA-CA 10 according to the embodiment of the present invention. Note that this routine is repeatedly executed for each cycle at a predetermined timing after the end of combustion in each cylinder.

  In the routine shown in FIG. 5, the ECU 40 first determines whether or not the lean burn operation is being performed (step 100). In the internal combustion engine 10, a lean burn operation is performed at an air-fuel ratio leaner than the stoichiometric air-fuel ratio in a predetermined operating region. Here, it is determined whether or not it corresponds to an operation region in which such lean burn operation is performed.

  If it is determined in step 100 that the lean burn operation is being performed, the engine speed and the engine load factor are acquired using the crank angle sensor 42 and the air flow meter 44 (step 102). The engine load factor can be calculated based on the engine speed and the intake air amount.

  Next, the ECU 40 calculates a target SA-CA10 (step 104). The ECU 40 stores a map (not shown) in which the target SA-CA 10 is predetermined based on the relationship between the engine speed and the engine load factor based on the results of experiments and the like. In this step 104, with reference to such a map, target SA-CA10 is acquired based on the engine speed and engine load factor acquired in step 102.

  Next, the ECU 40 acquires in-cylinder pressure data measured during combustion using the in-cylinder pressure sensor 30 and the crank angle sensor 42 (step 106). Next, the ECU 40 acquires the ignition timing (step 108). The ECU 40 stores a map (not shown) that defines a target (requested) ignition timing (basically, an optimal ignition timing (hereinafter referred to as “MBT”)) based on the relationship between the engine load factor and the engine speed. In step 108, the ignition timing is acquired with reference to such a map.

  Next, the ECU 40 calculates the actual SA-CA10 (step 110). The actual SA-CA10 is calculated as a crank angle period from the ignition timing acquired in step 108 to CA10 obtained as an analysis result of the in-cylinder pressure data acquired in step 106. Since the actual SA-CA10 acquired by such a method includes a predetermined variation (the amount of combustion fluctuation that inevitably occurs), a raw value may be used. Becomes unstable. Therefore, here, the value after the combustion fluctuation is removed by performing a predetermined annealing process on the actual SA-CA10 is used for feedback control of the fuel injection amount. As such an annealing process, for example, a technique of taking a time-series moving average of the latest predetermined number of real SA-CA10 calculated values including the current calculated value can be used. Instead of such an annealing process, an equivalent range of variation of the calculated value of the actual SA-CA10 caused by the assumed amount of combustion fluctuation may be set as a control dead zone. That is, when the difference between a target SA-CA10 and an actual SA-CA10, which will be described later, is equal to or less than the above-described variation width, the fuel injection amount may not be corrected.

  Next, the ECU 40 calculates the difference between the target SA-CA10 calculated in steps 104 and 110 and the actual SA-CA10 (step 112). Next, the ECU 40 uses the calculated difference and a predetermined PI gain (proportional term gain and integral term gain) to calculate a fuel injection amount correction rate according to the difference and the magnitude of the integrated value (step). 114). After that, the ECU 40 corrects the fuel injection amount used in the next cycle based on the calculated fuel injection amount correction factor (step 116). Specifically, for example, when the actual SA-CA10 is larger than the target SA-CA10, this corresponds to the fact that the air-fuel ratio is deviated from the target value to the lean side from the relationship shown in FIG. Therefore, the fuel injection amount is increased with respect to the base value of the fuel injection amount in order to perform rich correction of the air-fuel ratio.

  According to the routine shown in FIG. 5 described above, the feedback control of the fuel injection amount is executed so that the difference between the target SA-CA10 and the actual SA-CA10 is eliminated. As described above, SA-CA10 has linearity with respect to the air-fuel ratio even near the lean limit. Unlike the method of the present embodiment, when the fuel injection amount is adjusted so that the predetermined crank angle becomes a certain target value using only the predetermined crank angle when the predetermined combustion mass ratio is obtained, There are the following problems. That is, when the ignition timing changes, the predetermined crank angle at which the predetermined combustion mass ratio is obtained changes accordingly. On the other hand, even if the ignition timing changes, the crank angle period from the ignition timing to the predetermined crank angle hardly changes. Therefore, by using the crank angle period (SA-CA10 in the present embodiment) as an index for adjusting the fuel injection amount, the influence of the ignition timing is eliminated as compared with the case where only the predetermined crank angle is used. Thus, the correlation with the air-fuel ratio can be suitably grasped. In addition, during an operation that requires precise combustion control, such as during lean burn operation or EGR operation that is performed by introducing a large amount of EGR gas, the current air-fuel ratio control by the air-fuel ratio sensor is effective in the vicinity of the lean limit. There is also a problem that it is difficult to accurately control the fuel ratio. Therefore, by adjusting the fuel injection amount based on the difference between the target SA-CA10 and the actual SA-CA10 by the method of this embodiment, the air-fuel ratio can be suitably controlled near the lean limit during the lean burn operation. .

  Further, since the method of the present embodiment does not use statistical processing unlike the conventional method described above, according to the present method, it is possible to perform rapid feedback control. For this reason, it can be satisfactorily applied even during transient operation. Therefore, according to this method, lean limit control can be realized in a wide range of operating conditions, and as a result, fuel efficiency and exhaust emission performance can be brought out. Further, it becomes possible to perform control for each cylinder.

  Further, according to the method of the present embodiment, the target SA-CA10 is set based on each of the engine rotation speed and the engine load factor. As a result, the target SA-CA10 can be appropriately set in consideration of the effects of changes in the engine rotation speed and the engine load factor.

  By the way, in embodiment mentioned above, the feedback control of the fuel injection amount using SA-CA10 was demonstrated. However, the present invention is not limited to the direct use of the crank angle period itself from the ignition timing to the predetermined crank angle when the predetermined combustion mass ratio is obtained as in SA-CA10, and instead of the crank angle period. The correlation value may be used.

  In the above-described embodiment, in order to calculate the combustion mass ratio (MFB), the analysis result of the in-cylinder pressure data acquired using the in-cylinder pressure sensor 30 and the crank angle sensor 42 is used. However, the calculation of the combustion mass ratio in the present invention is not necessarily limited to using the in-cylinder pressure data. That is, the fuel mass ratio may be calculated by, for example, detecting an ion current generated by combustion with an ion sensor and using the detected ion current, or measuring an in-cylinder temperature. If possible, it may be calculated using a history of in-cylinder temperature.

  In the above-described embodiment, the lean burn operation in which the air-fuel ratio of the air-fuel mixture in the cylinder is controlled near the lean limit has been described as an example. However, the air-fuel ratio used in the operation targeted by the present invention is not necessarily limited to an air-fuel ratio that is leaner than the stoichiometric air-fuel ratio, and even if it is a stoichiometric air-fuel ratio or an air-fuel ratio richer than the stoichiometric air-fuel ratio. Good.

[Abnormality detection routine of embodiment]
Hereinafter, the abnormality detection routine according to the embodiment of the present invention will be described with reference to FIGS. 6 to 8 show routines for acquiring data used for abnormality detection, respectively. The routines shown in FIGS. 6 to 8 are repeatedly executed independently for each cylinder, and are executed in parallel for the number of cylinders. FIG. 9 is a flowchart of an A / F imbalance abnormality detection routine according to the embodiment of the present invention. FIG. 10 is a flowchart of a fuel system abnormality detection routine according to the embodiment of the present invention.

  The subscript i used in the routines of FIGS. 6 to 10 is an identification number indicating the current cycle number, and the subscript j is a cylinder number. For example, i = 10000 and j = 2 are used as subscripts as values for storing the calculation result for the second cylinder in the 10,000th cycle, and this plays the role of an identification number.

  FIG. 6 is a flowchart of the detection data acquisition routine according to the embodiment of the present invention. For each of the first to fourth cylinders, a plurality of routines shown in FIG. As a preferred mode, the routine of FIG. 6 may be started at ATDC 150 ° CA for each cylinder, whereby calculation can be started at a suitable timing when heat generation stops after the combustion stroke.

  In the routine of FIG. 6, first, at step 200, it is determined whether or not the ECU 40 is performing feedback control at a lean air-fuel ratio. If the feedback control at the lean air-fuel ratio is not performed, the current routine ends.

  If feedback control at the lean air-fuel ratio is being performed, the process proceeds to step 202. In step 202, the ECU 40 executes a process of storing the value of the fuel injection amount correction rate of the j-th cylinder in the i-th cycle in FFij. Specifically, for example, the calculation is performed for the second cylinder, and when it is the execution timing of step 202 after the 10,000th second cylinder combustion cycle, the fuel injection amount used in the second cylinder at the 10000th cycle The correction factor is stored in FF100002.

  Next, the ECU 40 executes processing for detecting the “number of correction rate pasting cycles” in steps 204, 206, and 208. “Correction cycle for number of correction ratios” refers to the case where a plurality of combustion cycles continue with the fuel injection amount correction rate fixed at the “upper limit” of the predetermined range, or the “lower limit” of the fuel injection amount correction rate within the predetermined range This is the number of consecutive times when a plurality of combustion cycles are continued while being fixed. The predetermined range is a range in which the fuel injection amount correction rate is increased or decreased in the feedback control. This predetermined range is also referred to as “feedback control width”. The feedback control width is predetermined in a range of 0.6 to 1.4, for example. The fuel injection amount correction factor cannot be set to a value larger than the upper limit value of the feedback control width or a value smaller than the lower limit value. When the fuel injection amount correction factor is calculated to the maximum value or the minimum value, the fuel injection amount correction factor is fixed to the upper limit value or the lower limit value of the feedback control range. It will stick to the value. The number of times this sticking is continued is the “correction rate sticking cycle number”.

  Specifically, first, in step 204, the ECU 40 executes a process of determining whether or not the value of | FFij−1 | is equal to or greater than a predetermined value A. In the present embodiment, the predetermined value A is set to 0.4. For example, when FFij, which is the fuel injection amount correction factor for the j-th cylinder in the i-th combustion cycle, is 0.9, | 0.9-1 | = 0.1 is calculated, and this value is Since the predetermined value A is smaller than 0.4, the determination result in step 204 is negative (No). On the other hand, when FFij is 0.6, | 0.6-1 | = 0.4 is calculated, and this value matches the predetermined value A = 0.4, and the determination result in step 204 is affirmative. (Yes).

  If the determination result in step 204 is affirmative (Yes), the counter value Cff is incremented. That is, 1 is added to the counter value Cffi-1j in the previous cycle i-1. As a result, for each cylinder, the number of consecutive cycles in which the fuel injection amount correction rate by feedback control keeps the upper limit or lower limit of the predetermined range is counted as the counter value Cff. On the other hand, if the determination result of step 204 is negative (No), the process proceeds to step 208, and zero is stored in the counter value Cff. Thereby, when the fuel injection correction factor takes an intermediate value smaller than the upper limit of the predetermined range (feedback control width) and larger than the lower limit, the counter value can be reset at that time.

  Next, in step 210, the ECU 40 executes a process of calculating correction rate average values Avff30i and Avff200i that are average values of fuel injection amount correction rates. In the present embodiment, two correction factor average values are calculated. The correction rate average value Avff30i is a value obtained by moving and averaging FFij for 30 cycles before the i-th cycle. The correction rate average value Avff200i is a value obtained by moving average of 200 cycles of FFij before the i-th cycle. Thereafter, the current routine ends.

  According to the above processing, correction rate average values Avff30i and Avff200i, which are moving average values for 30 cycles and 200 cycles before the current cycle (i-th cycle), can be calculated for each cylinder.

  FIG. 7 is a flowchart of another detection data acquisition routine according to the embodiment of the present invention. The routine in FIG. 7 is obtained by replacing the series of processing in steps 220 to 232 with the processing in step 210 in FIG.

  The routine of FIG. 7 is executed subsequent to step 206 or 208 of FIG. First, in step 220, the ECU 40 updates the values of the variables Aff30 and Aff200 (that is, adds the value of the current fuel injection amount correction factor to the previous value), and increments the counter values Cavff30 and Cavff200, respectively. Execute the process.

  Next, in step 222, the ECU 40 determines whether or not the counter value Cavff30 is 30. If the counter value Cavff30 is 30, the process proceeds to step 224, and the value obtained by dividing the variable Aff30 by 30 is stored in the correction factor average value Avff30. In the following step 226, zero is stored in the variable Aff and the counter value Cavff30. Thereafter, the current process ends.

  If the counter value Cavff30 is not 30 in step 222, the process proceeds to step 228. In step 228, the ECU 40 determines whether or not the counter value Cavff200 is 200. When the counter value Cavff200 is 200, the process proceeds to step 230, and a value obtained by dividing the variable Aff200 by 200 is stored in the correction factor average value Avff200. In the following step 232, zero is stored in the variable Aff and the counter value Cavff30. Thereafter, the current routine ends.

  According to the above processing, the correction factor average values Avff30i and Avff200i can be calculated for each cylinder.

  FIG. 8 is a flowchart of another detection data acquisition routine according to the embodiment of the present invention. The routine in FIG. 8 includes the same processing as the routine shown in FIG. 6 except for the processing in steps 242 and 244. The routine shown in FIG. 8 includes a process for evaluating a “correction rate guard excess amount” to be described later, in addition to the data acquisition routine described with reference to FIGS. 6 and 7.

  In the routine of FIG. 8, if the determination result of step 200 is affirmative, the ECU 40 acquires FFTij data and FFij data, respectively.

  First, FFTij data acquisition will be described. This is an operation of acquiring a target fuel injection amount correction factor value for each cycle and each cylinder. In order to adjust the fuel injection amount based on the difference between the target SA-CA10 and the actual SA-CA10, the target value of the fuel injection amount correction factor is calculated in step 114 in the routine of FIG. The calculated target fuel injection amount correction factor is stored in FFTij.

  On the other hand, the ECU 40 also acquires FFij data. The value of the fuel injection amount correction factor that is actually used is stored in FFij in a situation where “correction rate guard” is provided. The correction rate guard provides a certain limit to the numerical range of the fuel injection amount correction rate. This correction rate guard limits the upper and lower limits of the fuel injection amount correction rate that can actually be taken apart from the upper and lower limits (that is, the upper and lower limits of the feedback control range) in the calculation of the target fuel injection amount correction rate. . In the embodiment, as an example, the range of the fuel injection amount correction rate is limited to 0.7 to 1.3 from the viewpoint of control safety and the like. For example, when the target fuel injection amount correction factor is calculated to be 1.4 for the first cylinder in the cycle 10000, 1.4 is stored in the FFT 100001. On the other hand, since the fuel injection amount correction factor that is actually used is 1.3, which is the upper limit value of the correction factor guard, 1.3 is stored in FF1000001.

  Next, the ECU 40 executes a process for detecting the “sticking state” of the fuel injection amount correction rate in step 243, which is the same as the process in step 204 in FIGS. However, in step 243, it is compared whether or not | FFij−1 | is equal to or greater than a predetermined value A2. The predetermined value A2 to be compared is a value determined from the upper limit and the lower limit of the correction rate guard, and is 0.3 when the correction rate guard is 0.7 to 1.3.

  Next, the ECU 40 calculates the “correction rate guard excess amount” in step 244. In step 244, specifically, the ECU 40 executes a process of determining whether or not the value of | FFTij−FFij | is equal to or greater than a predetermined value AA. | FFTij−FFij | is a difference between the target fuel injection amount correction rate and the actual fuel injection amount correction rate, and is also referred to as “correction rate guard excess amount” for convenience. The correction rate guard excess amount indicates how large the excess is when the target fuel injection amount correction rate exceeds the correction rate guard. For example, when FFTij = 1.4 and FFij = 1.3, | FFTij−FFij | = 0.1. However, when the target fuel injection amount correction rate is within the upper and lower limits of the correction rate guard, the correction rate guard excess amount is zero. Specifically, when FFTij = 1.1, FFij = 1.1, and | FFTij−FFij | = 0.

  If the determination result is affirmative in both step 243 and step 244, the process proceeds to step 206, and the counter value Cffij is incremented. The process proceeds to step 206 because the current fuel injection amount correction rate FFij has reached the correction rate guard, and the target fuel injection amount correction rate FFTij and the current fuel injection amount correction rate FFij are a predetermined value AA (an example). As 0.1) or more.

  The width of the correction rate guard is preferably variably set according to the load, the engine speed, and other various conditions. When the width of the correction rate guard is set to be sufficiently narrow, a state in which the fuel injection amount correction rate sticks to the upper limit or the lower limit of the correction rate guard tends to occur. In this case, the A / F imbalance abnormality between the cylinders cannot be accurately detected only based on whether or not the actual fuel injection amount correction rate is stuck. Therefore, in the routine of FIG. 8, in addition to detecting the sticking state of the fuel injection amount correction rate, the correction rate guard excess amount is compared with the predetermined value AA. According to the comparison between the correction rate guard excess amount and the predetermined value AA, how much the target fuel injection amount correction rate for feedback control is actually calculated separately from the actual fuel injection amount correction rate value? That is, it is possible to evaluate how much the fuel injection amount should be changed when there is no correction rate guard. By using both the sticking state and the target fuel injection amount correction rate as a basis, it is possible to accurately detect an A / F imbalance abnormality between cylinders even in a situation where a correction rate guard is set.

  Thereafter, similarly to the routines of FIGS. 6 and 7, step 210 for calculating the correction factor average value is executed. As a result, the correction factor average values Avff30i and Avff200i can be calculated for each cylinder.

  The A / F imbalance abnormality detection routine according to the embodiment will be described with reference to FIG. The routine shown in FIG. 9 is executed every time the combustion cycle is completed in all the cylinders. For example, the routine is executed every time the first cylinder reaches the top dead center.

  In the routine of FIG. 9, first, in step 300, the ECU 40 executes a process of determining whether or not a condition for executing the A / F imbalance abnormality detection is satisfied. In the present embodiment, as an example, it is determined whether or not the engine rotation speed is in the range of 1600 rpm to 2400 rpm and the load KL is in the range of 50% to 90%. If this condition is not satisfied, the current routine ends.

  If the condition of step 300 is satisfied, the process proceeds to step 302. In step 302, the ECU 40 sets 1 to the cylinder index j. In the present embodiment, it is assumed that the internal combustion engine 10 has four cylinders and the processing proceeds in the order of cylinders 1, 2, 3, and 4.

  Next, the process proceeds to step 304, and the ECU 40 executes a process of determining whether or not the counter value Cffij counted in step 206 of FIG. The counter value Cffij is the number of consecutive cycles in which the fuel injection amount correction rate by feedback control keeps the upper limit or lower limit of the predetermined range. For example, when the counter value Cff100001 of the first cylinder in the 10000th cycle reaches a predetermined number of times (that is, the predetermined value B), an A / F imbalance abnormality occurs in the 1st cylinder at the time of the 10000th cycle. There is a high possibility. Therefore, if the determination result in step 304 is affirmative, 1 is set to the provisional detection flag Fimbj in step 306. On the other hand, if the determination result in step 304 is negative, zero is set to the temporary detection flag Fimbj in step 308. The provisional detection flag Fimbj is a flag indicating that there is a high possibility of an A / F imbalance abnormality.

  If 1 is set in the temporary detection flag in step 306, then in step 310, the ECU 40 executes a process of calculating the correction factor cylinder difference Davjj. The correction rate inter-cylinder difference Davjj is obtained by calculating the difference between the fuel injection amount correction rates of two cylinders selected from a plurality of cylinders of the internal combustion engine 10. The subscript jj is used as an index indicating the two cylinders for which the difference is calculated. For example, when the difference in fuel injection amount correction rate between the first cylinder and the second cylinder is calculated, the difference between the correction rate cylinders is stored in Dav12, and fuel injection is performed between the second cylinder and the third cylinder. When the difference in the amount correction rate is calculated, the correction rate difference between cylinders is stored in Dav23. In the present embodiment, it is assumed that the difference in fuel injection amount correction rate average value among a plurality of cylinders is calculated using one of Avff 30i and Avff 200i calculated in step 210. Since the cylinder index j is 1 at present, the ECU 40 calculates the correction rate cylinder differences Dav12, Dav13, Dav14 between the first cylinder and the second to fourth cylinders, and then sets the maximum value among them as the maximum value Davmax. Set to. Similarly, if the cylinder index j = 2, correction rate cylinder differences Dav23 and Dav24 are calculated between the second cylinder and the third and fourth cylinders, and the current maximum value is set to the maximum value Davmax. . The correction rate inter-cylinder difference Dav21 between the second cylinder and the first cylinder is the same value as the correction rate inter-cylinder difference Dav12 calculated for the first cylinder when the cylinder index J = 1. Accordingly, the calculation of Dav21 is omitted in order to avoid duplicate calculation. Similarly, the correction rate inter-cylinder difference Davjj and the maximum value Davmax are calculated based on the third cylinder when the cylinder index j = 3 and based on the fourth cylinder when the cylinder index j = 4.

  Next, in step 312, the ECU 40 executes processing for determining whether or not the maximum value Davmax is equal to or greater than a predetermined value C. When the maximum value Davmax is greater than or equal to the predetermined value C, the process proceeds to step 314. In step 314, the ECU 40 sets Fimbj (currently, the first cylinder is subject to j = 1 and Fimb 1) in the abnormality flag Fimb, and the process further proceeds to step 316. On the other hand, if the determination result of step 312 is negative, the process proceeds directly from step 312 to step 316.

  Next, in step 316, the ECU 40 executes a process of determining whether or not the value of the cylinder index j is an abnormality in the number of cylinders D. In this embodiment, since there are four cylinders, D = 4. Since j = 1 at the present time, the determination result in step 316 is negative, and the process proceeds to step 318, where the value of the cylinder index is incremented, and then the processes after step 304 are executed again. By executing the processing of steps 304 to 316 in the respective states of j = 2 to 4, the A / F imbalance abnormality detection routine for the second to fourth cylinders is similarly executed. When the process of step 316 is finally reached with j = 4, the current routine ends.

  Here, for simplicity of explanation, the value of D is the same as the number of cylinders, but the present invention is not limited to this. All combinations of two cylinders arbitrarily selected from the four cylinders (1-2 cylinder, 1-3 cylinder, 1-4 cylinder, 2-3 cylinder, 2-4 cylinder, 3-4 cylinder) In order to calculate the correction rate difference between cylinders), it is sufficient to perform three loops, so D = 3 may be set.

  According to the routine of FIG. 9 described above, when the ECU 40 determines that an air-fuel ratio imbalance abnormality has occurred, the following first condition and second condition can be set as necessary conditions. The first condition is that a state in which the fuel injection adjustment amount of a predetermined cylinder among a plurality of cylinders of the internal combustion engine 10 reaches an upper limit or a lower limit of a predetermined range continues for a predetermined number of times (predetermined value B). This condition can be determined in step 304 of the routine of FIG. 9 using the data Cffij acquired by the routines of FIGS. The second condition is that the difference between the fuel injection adjustment amount of the predetermined cylinder and the fuel injection adjustment amount of other cylinders other than the predetermined cylinder is equal to or greater than the predetermined value C, which is determined in step 312 of the routine of FIG. can do.

  The common supply system abnormality detection routine according to the embodiment will be described with reference to FIG. The routine of FIG. 10 is executed every time the combustion cycle is completed in all the cylinders, and for example, is executed every time the first cylinder reaches the top dead center.

  In the routine of FIG. 10, first, in step 301, the ECU 40 executes a process of determining whether or not a condition for executing the common supply system abnormality detection is satisfied. In the present embodiment, as an example, it is determined whether feedback control is being performed at a lean air-fuel ratio. If this condition is not satisfied, the current routine ends.

  If the condition of step 301 is satisfied, the process proceeds to step 302. In step 302, the ECU 40 sets 1 to the cylinder index j. As an example, in the present embodiment, it is assumed that the internal combustion engine 10 has four cylinders, and the processing proceeds in the order of cylinders 1, 2, 3, and 4.

  Next, the process proceeds to step 320, and the ECU 40 executes a process of determining whether or not the counter value Cffij counted in step 206 of FIG. The counter value Cffij is the number of consecutive cycles in which the fuel injection amount correction rate by feedback control keeps the upper limit or lower limit of the predetermined range. For example, when the counter value Cff100001 of the first cylinder in the 10000th cycle reaches a predetermined number of times (that is, the predetermined value B), a common supply system abnormality may have occurred in the 1st cylinder at the time of the 10000th cycle. High nature. Therefore, if the determination result in step 320 is affirmative, 1 is set to the temporary detection flag Fsupj in step 322. On the other hand, if the determination result in step 320 is negative, zero is set to the temporary detection flag Fsupj in step 324. The temporary detection flag Fsupj is a flag indicating that there is a high possibility of a common supply system abnormality.

  If 1 is set to the temporary detection flag in step 322, then in step 310 similar to the flowchart of FIG. 9, the ECU 40 executes a process of calculating the correction rate cylinder difference Davjj and its maximum value Davmax. .

  Next, in step 326, the ECU 40 executes a process for determining whether or not the maximum value Davmax is equal to or less than a predetermined value F. When the maximum value Davmax is less than or equal to the predetermined value F, the process proceeds to step 328. On the other hand, if the determination result of step 326 is negative, the process proceeds directly from step 326 to step 316.

  The maximum value Davmax being equal to or less than the predetermined value F means that the variation in the fuel injection amount correction rate of the plurality of cylinders is within a certain range determined by the predetermined value F. If the determination result in step 320 is affirmative and the determination result in step 326 is also affirmative, the fuel injection amount correction rate in one cylinder indicates an abnormal value of the upper limit or the lower limit, and the other cylinders are averaged. In particular, the fuel injection amount correction rate is biased toward the upper limit side or the lower limit side. In this state, it can be concluded that an abnormality relating to fuel injection occurs on average for all cylinders.

  Therefore, in step 328, the ECU 40 sets Fsupj indicating that there is an abnormality in the abnormality flag Fsup meaning “common supply system abnormality” (j = 1 and Fsup1 because the first cylinder is currently targeted) Further, the process proceeds to Step 316. The “common supply system” is a configuration that is commonly used by a plurality of cylinders in order to supply fuel and air to each cylinder among the configurations of the internal combustion engine 10. The “common supply system” specifically includes a fuel pump, a fuel pressure sensor, a delivery, a fuel pipe, a throttle valve 24, and an air flow meter 44. The “common supply system” does not include parts provided for each cylinder, specifically, fuel injection valves provided for each cylinder. Of the “common supply system”, a common part of a mechanism for supplying fuel to the plurality of cylinders of the internal combustion engine 10 may be an abnormality detection target, particularly as a “common fuel supply system”. The “common fuel supply system” includes a fuel pump, a fuel pressure sensor, a delivery, and fuel piping, and is a common part of a mechanism that supplies fuel to a plurality of cylinders of the internal combustion engine 10. Instead of the abnormality flag Fsup, Ffuel which is an abnormality flag for the common fuel supply system may be used in step 328.

  Next, in step 316, the ECU 40 executes a process for determining whether or not the value of the cylinder index j is equal to or greater than a predetermined value D. In the routine of FIG. 10, in order to calculate the correction rate inter-cylinder difference Davjj for all four cylinders, D = 3 may be set. Since j = 1 at the present time, the determination result in step 316 is negative, and the process proceeds to step 318. After the cylinder index value is incremented, the processes after step 320 are executed again.

  The correction rate inter-cylinder differences Dav12, Dav13, Dav14, Dav23, Dav24, and Dav34 are calculated for all combinations of the four cylinders until the process of step 316 is finally reached in a state where j = 3. Those maximum values are stored in Davmax, compared with a predetermined value F in step 326, and the value of the abnormality flag Fsup in step S328 is set according to the comparison result. Eventually, the process proceeds to step 328 at least once while the processes of steps 320 to 318 are looped. When Fsupj indicating an abnormality is input to the abnormality flag Fsup, after the routine of FIG. It is determined that a “system abnormality” has occurred. On the other hand, if the process does not proceed to step 328 while the processes of steps 320 to 318 are looped, that is, if the result of step 326 is never affirmative (Yes), the abnormality flag Fsup remains zero, The common supply system is determined to be normal. Thereafter, the current routine ends.

  According to the routine of FIG. 10 described above, when the ECU 40 determines that an abnormality has occurred in the “common supply system”, the following third condition and fourth condition can be set as necessary conditions. The third condition is that the state in which the fuel injection adjustment amount of a predetermined cylinder among the plurality of cylinders of the internal combustion engine 10 reaches the upper limit or the lower limit of the predetermined range continues for a predetermined number of times (predetermined value B). This condition can be determined in step 320 in the routine of FIG. 10 using the data Cffij acquired in the routines of FIGS. The fourth condition is that the difference between the fuel injection adjustment amount of the predetermined cylinder and the fuel injection adjustment amount of other cylinders other than the predetermined cylinder is smaller than the predetermined value F, which is determined in step 312 in the routine of FIG. can do.

  In the above-described embodiment, CA10 is the “predetermined crank angle” in the present invention, and the target SA-CA10 is the “target value” in the present invention, and the difference between the target SA-CA10 and the actual SA-CA10. Corresponds to the “difference” in the present invention. Further, the ECU 40 detects the crank angle using the crank angle sensor 42, thereby realizing the “crank angle determination means” in the present invention. The ECU 40 acquires the in-cylinder pressure sensor 30 and the crank angle sensor 42. The "fuel mass ratio calculating means" in the present invention is realized by calculating the combustion mass ratio using the in-cylinder pressure data during the combustion period, and the ECU 40 uses the calculation result of the combustion mass ratio to calculate the CA10. The “crank angle acquisition means” in the present invention is realized by acquiring the above, and the “adjustment means” in the present invention is realized by the ECU 40 executing the processing of steps 112 to 116 described above. The ECU 40 calculates the “fuel injection” by executing the process of step 114 of the routine of FIG. Correction factor "is equivalent to" fuel injection adjustment amount "in the present invention. 9 is executed using the data Cffij acquired in the routines of FIGS. 6 to 8, and the processing of steps 312 and 314 of the routine of FIG. The “second determination means” in the invention is realized. Further, the processing of step 304 of the routine of FIG. 9 is executed using the data Cffij acquired by the routines of FIGS. 6 to 8, and the processing of steps 326 and 328 of the routine of FIG. The “first determination means” in the invention is realized.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Piston 14 Combustion chamber 16 Intake passage 18 Exhaust passage 20 Intake valve 22 Exhaust valve 24 Throttle valve 26 Fuel injection valve 28 Spark plug 30 In-cylinder pressure sensor 40 ECU (Electronic Control Unit)
42 Crank angle sensor 44 Air flow meter

Claims (1)

Crank angle determining means for detecting the crank angle of the internal combustion engine;
A fuel mass ratio calculating means for calculating a combustion mass ratio;
Crank angle acquisition means for acquiring a predetermined crank angle when the combustion mass ratio becomes a predetermined combustion mass ratio;
By calculating the fuel injection adjustment amount based on the difference between the crank angle period from the ignition timing to the predetermined crank angle or the correlation value of the crank angle period and the target value of the crank angle period or the correlation value, Adjusting means for adjusting the injection amount;
With
First determination means for determining abnormality of a common supply system that is commonly used among a plurality of cylinders of the internal combustion engine for supplying air and fuel into the cylinder, and second for determining abnormality of the air-fuel ratio imbalance It further comprises at least one means among the judging means,
The first determination means includes a fuel injection adjustment amount of a predetermined cylinder among a plurality of cylinders of the internal combustion engine that has reached an upper limit or a lower limit of a predetermined range, and the fuel injection adjustment amount of the predetermined cylinder and the predetermined cylinder When the difference between the fuel injection adjustment amount of other cylinders other than the cylinder is a predetermined value or less, it is determined that there is an abnormality in the common supply system,
The second determination means is configured such that the fuel injection adjustment amount of a predetermined cylinder among the plurality of cylinders of the internal combustion engine reaches an upper limit or a lower limit of a predetermined range, and the fuel injection adjustment amount of the predetermined cylinder and the predetermined cylinder An abnormality detection apparatus for an internal combustion engine, wherein it is determined that an air-fuel ratio imbalance abnormality has occurred when a difference from the fuel injection adjustment amount of a cylinder other than the cylinder is equal to or greater than a predetermined value.

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