JP4432061B2 - Intake air amount detection device for internal combustion engine - Google Patents

Description

  The present invention relates to an intake air amount detection device for an internal combustion engine provided with an air flow meter for detecting the intake air amount of the internal combustion engine.

  An intake pulsation may occur in the intake pipe of the internal combustion engine corresponding to the intake stroke of each cylinder. When the air flow meter output pulsates due to the intake pulsation, the intake air amount detected by the air flow meter is actually The value deviates from the intake air amount. In view of this, there is a technique in which the error between the detected intake air amount and the actual intake air amount is reduced by correcting the intake air amount detected by the air flow meter in accordance with the fluctuation range of the air flow meter output (for example, patents). Reference 1).

On the other hand, in recent years, an internal combustion engine mounted on a vehicle is provided with a variable intake valve mechanism that varies a valve control amount such as a lift amount and opening / closing timing of an intake valve, and an intake valve according to an accelerator opening degree or an engine operating state. There is one that can control the intake air amount by varying the valve control amount. The intake air amount control by this variable intake valve control can reduce the intake air amount without reducing the intake passage with the throttle valve by reducing the lift amount and the valve opening period of the intake valve. There is an advantage that fuel consumption can be improved by reducing.
Japanese Examined Patent Publication No.59-17371 (2nd page, etc.)

  By the way, in the conventional intake air amount control by the general throttle valve control, the throttle valve is controlled to the closed position from the fully opened position in the normal operation (except for the full load) region. In the air amount control, the throttle valve is kept in a state of being largely opened near the fully opened position. Therefore, in the intake air amount control by the variable intake valve control, the intake pulsation is more easily transmitted to the upstream side of the throttle valve than in the conventional intake air amount control by the throttle valve control, and the air flow meter disposed on the upstream side of the throttle valve. As the output pulsation increases, the detection error of the air flow meter due to the intake pulsation (error between the detected intake air amount and the actual intake air amount) tends to increase. Therefore, even if the detected intake air amount of the air flow meter is corrected by the same correction method as before, the detected intake air amount cannot be corrected with sufficient accuracy, and the detection accuracy of the intake air amount is lowered.

  In addition, in the intake air amount control by the conventional throttle valve control, the opening degree of the throttle valve is reduced as the load becomes lower, so that the intake pulsation is less likely to be transmitted to the periphery of the air flow meter upstream of the throttle valve, The pulsation of the air flow meter output tends to be small. For this reason, the low load region, which is a practical region, has a feature that the detection error of the air flow meter is small and the adverse effect of the detection error of the air flow meter is small.

  In contrast, in the intake air amount control by the variable intake valve control, the lift amount and the valve opening period of the intake valve are reduced as the load decreases, so the intake interval between the cylinders increases and the intake pulsation increases as the load decreases. Therefore, the pulsation of the air flow meter output tends to increase. For this reason, in the low load region, which is a practical region, the detection error of the air flow meter becomes large and the detection accuracy of the intake air amount is lowered, and the air-fuel ratio control accuracy is lowered and the exhaust emission tends to deteriorate.

  The present invention has been made in view of such circumstances. Accordingly, the object of the present invention is to improve the accuracy of detecting the intake air amount even in the case of a system in which the detection error of the air flow meter becomes large. An object of the present invention is to provide an intake air amount detection device for an internal combustion engine that can improve the accuracy of fuel ratio control.

In order to achieve the above object, the invention according to claim 1 is directed to a variable intake valve mechanism capable of controlling an intake air amount by varying a valve control amount such as an intake valve lift amount and an opening / closing timing, and an internal combustion engine. In an intake air amount detection device for an internal combustion engine comprising an air flow meter for detecting an intake air amount, and an exhaust gas sensor for detecting an air-fuel ratio of the exhaust gas of the internal combustion engine or information correlated therewith,
(1) air-fuel ratio control means for executing air-fuel ratio control for matching the air-fuel ratio of the exhaust gas detected by the exhaust gas sensor with a target air-fuel ratio;
(2) Air flow meter detection error calculating means for calculating a detection error (hereinafter referred to as “air flow meter detection error”) of the intake air amount detected by the air flow meter based on an average value of the target air fuel ratio used in the air / fuel ratio control. When,
(3) Inter-cylinder variation calculating means for calculating an inter-cylinder variation value representing variation in intake air amount between cylinders of the internal combustion engine;
(4) Cylinder-specific detected intake air amount error for calculating an error in the detected intake air amount of each cylinder (hereinafter referred to as “cylinder-specific detected intake air amount error”) based on the airflow meter detection error and the inter-cylinder variation value. A calculation means;
(5) When the fluctuation state of the output of the air flow meter is a transient state and / or when the detection accuracy of the exhaust gas sensor is not guaranteed, the detected intake air amount error for each cylinder is used for each cylinder. The airflow meter includes a cylinder-specific detected intake air amount correcting unit that corrects the detected intake air amount of the air flow meter.

Since the air-fuel ratio of the exhaust gas changes according to the actual intake air amount actually sucked into the cylinder of the internal combustion engine, the output of the exhaust gas sensor that detects the air-fuel ratio of the exhaust gas accurately reflects the actual intake air amount Parameter. Further, in a system that executes air-fuel ratio feedback control that matches the air-fuel ratio of the exhaust gas detected by the exhaust gas sensor with the target air-fuel ratio, the air-fuel ratio of the exhaust gas is accurately controlled to the target air-fuel ratio. In consideration of these circumstances, the present invention calculates the air flow meter detection error using the average value of the target air-fuel ratio instead of the output of the exhaust gas sensor (the air-fuel ratio of the exhaust gas). If this air flow meter detection error is used, the detected intake air amount of the air flow meter can be corrected with high accuracy. Therefore, in the system that controls the intake air amount by the variable intake valve control as in the present invention, the air flow caused by the intake pulsation is used. Even when the meter detection error increases, the detection accuracy of the intake air amount can be improved, and the accuracy of the air-fuel ratio control (exhaust emissions) can be improved.

  In general, an exhaust gas sensor such as an air-fuel ratio sensor has a detection characteristic that the detection accuracy is high near the theoretical air-fuel ratio, and the detection accuracy decreases as the distance from the theoretical air-fuel ratio increases. In the high load range, the air-fuel ratio is controlled to be rich with an emphasis on the output. However, in the low load range, which is a practical range, exhaust emissions are emphasized to reduce the air-fuel ratio of the exhaust gas, such as a three-way catalyst. Control is performed in the vicinity of the theoretical air-fuel ratio, which is a window. Therefore, in the low load region, which is a practical region, the exhaust gas air-fuel ratio is controlled in the vicinity of the theoretical air-fuel ratio, and the detection accuracy of the exhaust gas sensor is controlled to be high.

  In the intake air amount control by the variable intake valve control, the detection error of the air flow meter tends to increase in the low load region which is a practical region. However, in the low load region as described above, the air-fuel ratio of the exhaust gas is the stoichiometric air-fuel ratio. Since the detection accuracy of the exhaust gas sensor is in the state of being controlled in the vicinity, the air flow meter detection error can be calculated more accurately based on the output of the exhaust gas sensor, and the effect of applying the present invention is great.

  By the way, in the intake air amount control by the variable intake valve control, the lift amount of the intake valve becomes small at low load. Therefore, the variation of the actual lift amount with respect to the target lift amount in each cylinder (variation due to component tolerance or assembly tolerance of each cylinder) ) Increases, and variation in intake air amount between cylinders tends to increase.

  Accordingly, the invention according to claim 1 calculates the inter-cylinder variation value representing the variation in the intake air amount between the cylinders of the internal combustion engine, and detects the detected intake air of each cylinder based on the air flow meter detection error and the inter-cylinder variation value. An error in the amount (hereinafter referred to as “cylinder-specific detected intake air amount error”), and when the fluctuation state of the output of the air flow meter is a transient state and / or when the detection accuracy of the exhaust gas sensor is not guaranteed, The detected intake air amount is corrected for each cylinder using the cylinder-specific detected intake air amount error. In this way, the detected intake air amount can be corrected for each cylinder in consideration of the intake air amount variation between the cylinders, so even if the intake air amount variation between the cylinders increases, In addition, the intake air amount can be detected with high accuracy.

Further, when calculating the air flow meter detection error based on the average value of the target air-fuel ratio , when the detection accuracy of the exhaust gas sensor is not guaranteed, the air-fuel ratio of the exhaust gas can be accurately controlled to the target air-fuel ratio. However, since the calculation accuracy of the air flow meter detection error based on the average value of the target air-fuel ratio is lowered, the fluctuation state of the output of the air flow meter is pulsating and the detection accuracy of the exhaust gas sensor is guaranteed. In this state, the air flow meter detection error may be calculated based on the average value of the target air-fuel ratio. Even in this case, the air flow meter detection error due to the intake pulsation can be accurately calculated.

  Further, as described in claim 3, when the fluctuation state of the output of the air flow meter is a transient state and / or when the detection accuracy of the exhaust gas sensor is not guaranteed, the detected intake air amount is detected using the air flow meter detection error. May be corrected by the detected intake air amount correcting means.

  In other words, when the fluctuation state of the output of the air flow meter is a transient state, or when the detection accuracy of the exhaust gas sensor is not guaranteed, the air flow meter detection error due to the intake pulsation cannot be calculated with high accuracy. Detected intake air using the air flow meter detection error calculated when the error can be calculated accurately and accurately (that is, when the fluctuation state of the output of the air flow meter is a pulsating state and the detection accuracy of the exhaust gas sensor is guaranteed) If the amount is corrected, even when the air flow meter detection error due to intake pulsation cannot be calculated accurately, the detected intake air amount of the air flow meter can be accurately corrected, improving the detection accuracy of the intake air amount. Can be made.

  Further, as a specific example of the calculation method of the air flow meter detection error, as in claim 4 (or claim 5), the actual intake air amount is calculated based on the output (or target air-fuel ratio) of the exhaust gas sensor and the fuel injection amount. The air flow meter detection error may be calculated by comparing the actual intake air amount with the detected intake air amount. The output (or target air-fuel ratio) of the exhaust gas sensor and the fuel injection amount may be used. In this way, since the actual intake air amount can be calculated with high accuracy, the air flow meter detection error can be calculated with high accuracy by comparing the actual intake air amount with the detected intake air amount.

  Further, in the invention according to claim 3, as in claim 6, when the air flow meter detection error is learned corresponding to the operating state of the internal combustion engine at that time and the detected intake air amount is corrected, the air flow meter detection error is corrected. An air flow meter detection error learning value corresponding to the operating state of the internal combustion engine at that time may be selected from the learning values and used. Alternatively, in the invention according to claim 1, as in claim 7, the detected intake air amount error for each cylinder is learned in accordance with the operating state of the internal combustion engine at that time, and the detected intake air amount is corrected for each cylinder. In doing so, the cylinder-specific detected intake air amount error learning value corresponding to the operating state of the internal combustion engine at that time may be selected and used from the cylinder-specific detected intake air amount error learned value.

  In this way, even when the air flow meter detection error due to the intake pulsation cannot be accurately calculated, it is compatible with the operating state of the internal combustion engine without being affected by variations in manufacturing of the control system or changes over time. The detected intake air amount can be corrected using an appropriate air flow meter detection error learning value (or cylinder-specific detected intake air amount error learning value), and the detection accuracy of the intake air amount can be further improved.

  Further, as a specific example of the method for calculating the inter-cylinder variation value, for example, the intake pipe pressure is detected by an intake pipe pressure sensor for each period corresponding to the intake stroke of each cylinder, and the intake pipe pressure is calculated. The inter-cylinder variation value may be calculated based on the above. Since the intake pipe pressure changes in accordance with the amount of air taken into the cylinder during the intake stroke of each cylinder, if the intake pipe pressure detected for each period corresponding to the intake stroke of each cylinder is used, A cylinder-to-cylinder variation value reflecting the intake air amount variation can be calculated.

  Alternatively, as described in claim 9, the rotational fluctuation may be detected for each period corresponding to the combustion stroke of each cylinder, and the inter-cylinder variation value may be calculated based on the rotational fluctuation. Since the combustion state of each cylinder changes according to the intake air amount of each cylinder and the value of the rotational fluctuation of each cylinder changes, if the rotational fluctuation detected for each period corresponding to the combustion stroke of each cylinder is used, It is possible to calculate the inter-cylinder variation value reflecting the variation in the intake air amount of the cylinder.

  Further, as in the tenth aspect, the air-fuel ratio of the exhaust gas may be detected by the exhaust gas sensor for each period corresponding to the exhaust stroke of each cylinder, and the inter-cylinder variation value may be calculated based on the air-fuel ratio. . Since the air-fuel ratio of the exhaust gas of each cylinder changes according to the intake air amount of each cylinder, if the air-fuel ratio of the exhaust gas detected for each period corresponding to the exhaust stroke of each cylinder is used, the intake air amount of each cylinder An inter-cylinder variation value reflecting the variation can be calculated.

  Further, as in claim 11, an in-cylinder pressure sensor for detecting the in-cylinder pressure is provided for each cylinder of the internal combustion engine, the in-cylinder pressure is detected by the in-cylinder pressure sensor for each cylinder, and the in-cylinder pressure is detected. The inter-cylinder variation value may be calculated based on this. The in-cylinder pressure in the compression stroke of each cylinder changes according to the intake air amount of each cylinder. Further, the combustion state of each cylinder changes according to the intake air amount of each cylinder, and the in-cylinder pressure in the combustion stroke of each cylinder changes. Therefore, if the in-cylinder pressure detected in the compression stroke or the combustion stroke of each cylinder is used, the inter-cylinder variation value reflecting the intake air amount variation of each cylinder can be calculated.

Further, the calculation time of the air flow meter detection error is not limited to when the fluctuation state of the output of the air flow meter is a pulsating state and the detection accuracy of the exhaust gas sensor is guaranteed, and the exhaust gas sensor as in claim 12 is used. The air flow meter detection error may be calculated based on the average value of the output of the exhaust gas sensor. In this case, as in claim 13, when the detection accuracy of the exhaust gas sensor is not guaranteed, the detected intake air amount may be corrected using the air flow meter detection error. Even in this case, the air flow meter detection error can be accurately calculated based on the average value of the output of the exhaust gas sensor, and the air flow meter detection error is detected even when the air flow meter detection error cannot be calculated accurately. The detected intake air amount can be accurately corrected, the detection accuracy of the intake air amount can be improved, and the air-fuel ratio control accuracy can be improved.

<< Embodiment (1) >>
Hereinafter, an embodiment (1) of the present invention will be described with reference to FIGS. First, a schematic configuration of the entire engine control system will be described with reference to FIG. For example, a four-cylinder engine 11 that is an internal combustion engine has four cylinders, a first cylinder # 1 to a fourth cylinder # 4, and an air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11. An air flow meter 14 for detecting the intake air amount is provided on the downstream side of the air cleaner 13. On the downstream side of the air flow meter 14, a throttle valve 15 whose opening is adjusted by a DC motor or the like and a throttle opening sensor 16 for detecting the throttle opening are provided.

  Further, a surge tank 17 is provided on the downstream side of the throttle valve 15, and an intake pipe pressure sensor 18 for detecting the intake pipe pressure is provided in the surge tank 17. The surge tank 17 is provided with an intake manifold 19 for introducing air into each cylinder of the engine 11, and a fuel injection valve 20 for injecting fuel is attached in the vicinity of the intake port of the intake manifold 19 of each cylinder. Yes. A spark plug 21 is attached to each cylinder of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by spark discharge of each spark plug 21.

  Further, the intake valve 28 and the exhaust valve 29 of the engine 11 are provided with a variable intake valve lift mechanism 30 and a variable exhaust valve lift mechanism 31, respectively, for varying the valve lift amount. Further, the intake valve 28 and the exhaust valve 29 may be provided with a variable intake valve timing mechanism and a variable exhaust valve timing mechanism that vary the valve timing (open / close timing), respectively. The exhaust valve 29 may be provided with only the variable exhaust valve timing mechanism without providing the variable exhaust valve lift mechanism 31.

  On the other hand, the exhaust pipe 22 of the engine 11 is provided with a catalyst 23 such as a three-way catalyst that purifies CO, HC, NOx, etc. in the exhaust gas, and detects the air-fuel ratio of the exhaust gas upstream of the catalyst 23. An air-fuel ratio sensor 24 (exhaust gas sensor) is provided. Further, a water temperature sensor 25 that detects the coolant temperature and a crank angle sensor 26 that outputs a pulse signal each time the crankshaft of the engine 11 rotates by a certain crank angle (for example, 30 ° C. A) are attached to the cylinder block of the engine 11. It has been. Based on the output signal of the crank angle sensor 26, the crank angle and the engine speed are detected.

  Outputs of these various sensors are input to an engine control circuit (hereinafter referred to as “ECU”) 27. The ECU 27 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium), so that the fuel injection amount of the fuel injection valve 20 can be changed according to the engine operating state. The ignition timing of the spark plug 21 is controlled.

  Next, the configuration of the variable intake valve lift mechanism 30 will be described with reference to FIGS. Note that the variable exhaust valve lift mechanism 31 has substantially the same configuration as the variable intake valve lift mechanism 30, and therefore description thereof is omitted.

  As shown in FIG. 2, a link arm 34 is provided between the camshaft 32 and the rocker arm 33 for driving the intake valve 28, and a motor 41 such as a stepping motor is rotated above the link arm 34. A control shaft 35 that is driven by movement is provided. The control shaft 35 is provided with an eccentric cam 36 so as to be integrally rotatable, and the link arm 34 swings via a support shaft (not shown) at a position eccentric with respect to the axis of the eccentric cam 36. It is supported movably. A swing cam 38 is provided at the center of the link arm 34, and a side surface of the swing cam 38 is in contact with an outer peripheral surface of a cam 37 provided on the cam shaft 32. Further, a pressing cam 39 is provided at the lower end portion of the link arm 34, and the lower end surface of the pressing cam 39 is in contact with the upper end surface of the roller 40 provided at the central portion of the rocker arm 33.

  Accordingly, when the cam 37 rotates due to the rotation of the cam shaft 32, the swing cam 38 of the link arm 34 moves to the left and right following the outer peripheral surface shape of the cam 37, and the link arm 34 swings to the left and right. . When the link arm 34 swings left and right, the pressing cam 39 moves left and right. Therefore, the roller 40 of the rocker arm 33 moves up and down according to the lower end surface shape of the pressing cam 39, and the rocker arm 33 swings up and down. Move. The intake bubble 28 moves up and down by the up and down movement of the rocker arm 33.

  On the other hand, when the eccentric cam 36 is rotated by the rotation of the control shaft 35, the position of the support shaft of the link arm 34 is moved, and the initial contact point position between the pressing cam 39 of the link arm 34 and the roller 40 of the rocker arm 33 ( (See FIGS. 3 and 4). Further, as shown in FIG. 2, the lower end surface of the pressing cam 39 of the link arm 34 has a curvature at a left side so that the pressing amount of the rocker arm 33 is 0 (the valve lift amount of the intake valve 28 is 0). A curved surface 39a is formed, and the pressing curved surface 39b is formed with such a curvature that the amount of pressing of the rocker arm 33 increases (the valve lift amount of the intake valve 28 increases) from the base curved surface 39a to the right.

  As shown in FIG. 3, in the high lift mode in which the valve lift amount of the intake valve 28 is increased, the initial contact between the pressing cam 39 of the link arm 34 and the roller 40 of the rocker arm 33 by the rotation of the control shaft 35. Move the point position to the right. Thereby, when the pressing cam 39 moves to the left and right due to the rotation of the cam 37, the section of the lower end surface of the pressing cam 39 that contacts the roller 40 moves to the right, so that the maximum pressing amount of the rocker arm 33 increases. As a result, the maximum valve lift amount of the intake valve 28 increases, the period during which the rocker arm 33 is pressed becomes longer, and the valve opening period of the intake bubble 28 becomes longer.

  On the other hand, as shown in FIG. 4, in the low lift mode in which the valve lift amount of the intake valve 28 is reduced, the initial rotation between the pressing cam 39 of the link arm 34 and the roller 40 of the rocker arm 33 by the rotation of the control shaft 35. Move the contact point position to the left. As a result, when the pressing cam 39 moves to the left and right due to the rotation of the cam 37, the section of the lower end surface of the pressing cam 39 that contacts the roller 40 moves to the left, so that the maximum pressing amount of the rocker arm 33 is reduced. Accordingly, the maximum valve lift amount of the intake valve 28 is reduced, the period during which the rocker arm 33 is pressed is shortened, and the valve opening period of the intake bubble 28 is shortened.

  In the variable intake valve lift mechanism 30 described above, if the control shaft 35 is rotated by the motor 41, the initial contact point position between the pressing cam 39 of the link arm 34 and the roller 40 of the rocker arm 33 is continuously moved. As shown in FIG. 5, the maximum valve lift amount and the valve opening period (hereinafter simply referred to as “valve lift amount”) of the intake valves 28 of all the cylinders can be continuously varied.

  The ECU 27 executes a variable valve control program (not shown) stored in the ROM, thereby controlling the variable intake valve lift mechanism 30 based on the accelerator opening, the engine operating state, etc. The intake air amount is controlled by continuously changing the lift amount. In the case of a system using both the variable intake valve lift mechanism 30 and the variable intake valve timing mechanism, the intake air amount may be controlled by continuously varying both the valve lift amount and the valve timing.

Further, the ECU 27 executes each routine for correcting the detected intake air amount, which will be described later, so that the fluctuation state of the output Vs of the air flow meter 14 is in a pulsating state and the detection accuracy of the air-fuel ratio sensor 24 is guaranteed. Sometimes, an error ΔG (hereinafter referred to as “air flow meter detection error”) ΔG detected by the air flow meter 14 is calculated based on the air fuel ratio AF detected by the air fuel ratio sensor 24, and the output Vs of the air flow meter 14 is calculated. When the fluctuation state is a transient state or when the detection accuracy of the air-fuel ratio sensor 24 is not guaranteed, the detected intake air amount G0 detected by the airflow meter 14 is corrected using the airflow meter detection error ΔG.
Hereinafter, processing contents of each routine for correcting the detected intake air amount executed by the ECU 27 in the present embodiment (1) will be described.

[Detected intake air amount correction base routine]
The detected intake air amount correction base routine shown in FIG. 6 is executed at a predetermined cycle after an ignition switch (not shown) is turned on. When this routine is started, first, in step 101, the output Vs of the air flow meter 14 is read, and in the next step 102, a temporary detected intake air amount G0 corresponding to the output Vs of the air flow meter 14 is calculated by a map or the like. To do.

Thereafter, the routine proceeds to step 103, where it is determined whether or not the fluctuation state of the output Vs of the air flow meter 14 is a transient state, and air-fuel ratio feedback control (hereinafter referred to as “air-fuel ratio F / B” based on the output of the air-fuel ratio sensor 24 is determined. It is determined whether or not “control” is not permitted.
In this case, whether or not the variation state of the output Vs of the air flow meter 14 is a transient state is determined based on a determination result by a variation state determination routine shown in FIG.

  Further, whether or not the air-fuel ratio F / B control is not permitted is determined whether or not the air-fuel ratio sensor 24 is in an inactive state (for example, before the elapsed time after starting reaches the sensor activation determination time). Whether or not the air-fuel ratio sensor 24 is in a failed state (failure state). When the air-fuel ratio F / B control is permitted, the air-fuel ratio of the exhaust gas is controlled near the stoichiometric air-fuel ratio by the air-fuel ratio F / B control, and the detection accuracy of the air-fuel ratio sensor 24 is high. Therefore, if the air-fuel ratio F / B control is permitted, it can be determined that the detection accuracy of the air-fuel ratio sensor 24 is guaranteed.

  In step 103, it is determined that the fluctuation state of the output Vs of the air flow meter 14 is a pulsating state, and the air-fuel ratio F / B control is permitted (that is, the detection accuracy of the air-fuel ratio sensor 24 is guaranteed). If it is determined that the air flow meter detection error ΔG due to the intake pulsation can be accurately calculated, the process proceeds to step 104, and an air flow meter detection error calculation routine shown in FIG. And the actual intake air amount G1 is calculated on the basis of the air-fuel ratio AF detected by the air-fuel ratio sensor 24 and the fuel injection amount FUEL, and the actual intake air amount G1 is compared with the detected intake air amount G0. A meter detection error ΔG is calculated.

  Thereafter, the routine proceeds to step 105, where an air flow meter detection error learning routine shown in FIG. 10 described later is executed, and an air flow meter detection error learning value ΔG (AREA) corresponding to the engine operating state at that time is used using the air flow meter detection error ΔG. ) Is updated (learned).

  On the other hand, when it is determined in step 103 that the fluctuation state of the output Vs of the air flow meter 14 is a transient state, or the air-fuel ratio F / B control is not permitted (that is, the air-fuel ratio sensor 24). If it is determined that the detection accuracy is not guaranteed), the process proceeds to step 106, and a detected intake air amount correction routine shown in FIG. 12 to be described later is executed to detect an air flow meter detection error learning value ΔG (AREA ) Is selected from the air flow meter detection error learning value ΔG (AREA) corresponding to the engine operating state at that time, and the provisionally detected inhalation detected by the air flow meter 14 using the air flow meter detection error learning value ΔG (AREA). The final detected intake air amount G is obtained by correcting the air amount G0.

[Variation state determination routine]
The variation state determination routine shown in FIG. 7 is executed at a cycle sufficiently shorter than the rotation cycle of the engine 11 after the ignition switch is turned on (for example, 1 ms when the engine rotation speed is 1000 rpm). It plays a role as a state discriminating means. Note that the maximum value Vmax and minimum value Vmin of the output of the air flow meter 14 used in this routine, the value of the counter Cmax and the counter Cmin are Vmax = minus limit value and Vmin = plus in a predetermined cycle (for example, 180 ° C.), respectively. The side limit values are reset to Cmax = 0 and Cmin = 0.

  When this routine is started, first, at step 201, the output Vs of the air flow meter 14 is read, and then the routine proceeds to step 202, where it is determined whether or not the output Vs of the air flow meter 14 is larger than the maximum value Vmax. If it is determined that the output Vs of the air flow meter 14 is larger than the maximum value Vmax, the routine proceeds to step 203, where the maximum value Vmax is updated with the current output Vs value of the air flow meter 14.

  Then, in the next step 204, the counter Cmax for counting the time during which the output Vs of the air flow meter 14 continues to increase is incremented by "1", and then the routine proceeds to step 205, where the counter Cmax is greater than or equal to the transient judgment value Cs. It is determined whether or not. As a result, when it is determined that the counter Cmax is equal to or greater than the transient determination value Cs, the routine proceeds to step 206, where it is determined that the fluctuation state of the output Vs of the air flow meter 14 is a transient state (increase state). Exit.

  On the other hand, when it is determined that the counter Cmax is less than the transient determination value Cs, the routine proceeds to step 212, where it is determined that the fluctuation state of the output Vs of the air flow meter 14 is a pulsation state, and this routine is terminated. To do.

  On the other hand, if it is determined in step 202 that the output Vs of the air flow meter 14 is less than or equal to the maximum value Vmax, the process proceeds to step 207 to determine whether or not the output Vs of the air flow meter 14 is smaller than the minimum value Vmin. judge. If it is determined that the output Vs of the air flow meter 14 is smaller than the minimum value Vmin, the routine proceeds to step 208, where the minimum value Vmin is updated with the current output Vs value of the air flow meter 14.

  In the next step 209, the counter Cmin for counting the time during which the output Vs of the air flow meter 14 continues to decrease is incremented by "1", and then the process proceeds to step 210, where the counter Cmin is equal to or greater than the transient judgment value Cs. It is determined whether or not. As a result, when it is determined that the counter Cmin is equal to or greater than the transient determination value Cs, the routine proceeds to step 211, where it is determined that the fluctuation state of the output Vs of the air flow meter 14 is a transient state (decrease state), and this routine is executed. finish.

  On the other hand, when it is determined that the counter Cmin is less than the transient determination value Cs, the routine proceeds to step 212, where it is determined that the fluctuation state of the output Vs of the air flow meter 14 is the pulsation state, and this routine is terminated. To do.

  By the processing of this routine, as shown in FIG. 8A, when the fluctuation state of the output Vs of the air flow meter 14 is a pulsation state, the output Vs of the air flow meter 14 alternately repeats increasing and decreasing. Both Cmax and Cmin do not exceed the transient determination value Cs, and are determined to be in a pulsating state.

  On the other hand, as shown in FIG. 8B, when the fluctuation state of the output Vs of the air flow meter 14 is a transient state (for example, an increase state), the counter Cmax is incremented as the output Vs of the air flow meter 14 increases. Since the transient judgment value Cs is exceeded, it is judged as a transient state. FIG. 8B illustrates a transient state in which the output Vs of the air flow meter 14 increases. However, a transient state in which the output Vs of the air flow meter 14 decreases is similarly determined as a transient state. .

[Air flow meter detection error calculation routine]
The air flow meter detection error calculation routine shown in FIG. 9 is a subroutine started in step 104 of FIG. 6 and plays a role as air flow meter detection error calculation means in the claims.

  When this routine is started, first, at step 301, the temporarily detected intake air amount G0 detected by the air flow meter 14 is read, and then the routine proceeds to step 302 where the fuel injection time (injection pulse width) of the fuel injection valve 20 is reached. Read TAU. The fuel injection time TAU may be an average value or a smoothed value for a predetermined period.

Thereafter, the process proceeds to step 303, and the engine speed NE is read. The engine speed NE may be an average value or a smoothed value for a predetermined period.
Thereafter, the process proceeds to step 304, and after reading the invalid injection time TV of the fuel injection valve 20, the process proceeds to step 305, and the conversion coefficient KINJ for converting the fuel injection time TAU into the fuel injection amount is read.

In the next step 306, the fuel injection amount FUEL per unit time is calculated by the following equation using the fuel injection time TAU, the invalid injection time TV, the engine speed NE, and the conversion coefficient KINJ.
FUEL = (TAU-TV) × NE / 30 / KINJ

After calculating the fuel injection amount FUEL, the routine proceeds to step 307, where the air-fuel ratio AF detected by the air-fuel ratio sensor 24 is read. The air-fuel ratio AF may be an average value or a smoothed value for a predetermined period.
In the next step 308, the actual intake air amount G1 per unit time is obtained by multiplying the air-fuel ratio AF by the fuel injection amount FUEL per unit time.
G1 = AF x FUEL

Thereafter, the process proceeds to step 309, where the provisional detected intake air amount G0 detected by the air flow meter 14 is subtracted from the actual intake air amount G1 to obtain the air flow meter detection error ΔG.
ΔG = G1-G0

[Air flow meter detection error learning routine]
The air flow meter detection error learning routine shown in FIG. 10 is a subroutine started in step 105 of FIG. 6, and plays a role as air flow meter detection error learning means in the claims.

  When this routine is started, first, at step 401, the current engine operating state (engine rotational speed NE and actual intake air amount G1) in the map of the air flow meter detection error learning value ΔG (AREA) shown in FIG. Which operating region AREA is determined. The map of the air flow meter detection error learning value ΔG (AREA) shown in FIG. 11 is divided into a plurality of operation areas AREA using the engine speed NE and the actual intake air amount G1 as parameters, and for each operation area AREA, respectively. The air flow meter detection error learning value ΔG (AREA) is stored.

Thereafter, the routine proceeds to step 402, where the air flow meter detection error ΔG calculated by the air flow meter detection error calculation routine of FIG. 9 is smoothed and the air flow meter detection error learning value ΔG of the operation area AREA corresponding to the current engine operating state is processed. (AREA) is obtained, and the airflow meter detection error learning value ΔG (AREA) of the corresponding operation area AREA is updated with the value.
ΔG (AREA) = ΔG (AREA) old + K × {ΔG−ΔG (AREA) old}
Here, ΔG (AREA) is the current air flow meter detection error learning value, ΔG (AREA) old is the previous air flow meter detection error learning value, and K is the smoothing coefficient.

[Detected intake air amount correction routine]
The detected intake air amount correction routine shown in FIG. 12 is a subroutine started in step 106 of FIG. 6, and plays a role as detected intake air amount correction means in the claims.

  When this routine is started, first, at step 501, the current engine operating state (engine rotational speed NE and actual intake air amount G1) is shown in the map of the air flow meter detection error learning value ΔG (AREA) shown in FIG. Which operating region AREA is determined.

  Thereafter, the process proceeds to step 502, where a map of the air flow meter detection error learning value ΔG (AREA) shown in FIG. 11 is searched, and the air flow meter detection error learning value ΔG (AREA) of the operation area AREA corresponding to the current engine operating state. ).

Thereafter, the process proceeds to step 503, where the provisional detected intake air amount G0 detected by the air flow meter 14 is corrected by the following equation using the air flow meter detection error learning value ΔG (AREA) and the transient correction value GFWD, and finally obtained. The detected intake air amount G is obtained.
G = G0 + ΔG (AREA) + GFWD

Here, the transient correction value GFWD is a correction value for correcting the difference between the transient response of variable intake valve control or throttle control and the transient response of actual intake air.
An execution example of the detected intake air amount correction of the present embodiment (1) described above will be described with reference to the time chart shown in FIG.

  When the fluctuation state of the output Vs of the air flow meter 14 is a pulsating state and the air-fuel ratio F / B control is permitted (that is, the detection accuracy of the air-fuel ratio sensor 24 is guaranteed), the air-fuel ratio sensor 24 The actual intake air amount G1 is calculated on the basis of the air-fuel ratio AF and the fuel injection amount FUEL detected in step S1, and the actual intake air amount G1 is compared with the temporarily detected intake air amount G0 detected by the air flow meter 14 to compare the air flow. A meter detection error ΔG is calculated. The air flow meter detection error ΔG (AREA) corresponding to the engine operating state at that time is updated and learned using the air flow meter detection error ΔG.

  Thereafter, when the fluctuation state of the output Vs of the air flow meter 14 becomes a transient state or when the air-fuel ratio F / B control is not permitted (that is, the detection accuracy of the air-fuel ratio sensor 24 is not guaranteed). The final detected intake air amount G is obtained by correcting the provisional detected intake air amount G0 using the air flow meter detection error learning value ΔG (AREA) corresponding to the engine operating state at that time.

  In the present embodiment (1) described above, the actual intake air amount G1 calculated based on the air-fuel ratio AF detected by the air-fuel ratio sensor 24 and the fuel injection amount FUEL, and the detected intake air amount G0 detected by the air flow meter 14 are used. And the air flow meter detection error ΔG is calculated, so that the air flow meter detection error ΔG can be calculated with high accuracy. Since the detected intake air amount G0 of the air flow meter 14 is corrected using the air flow meter detection error ΔG, the detected intake air amount G0 can be corrected with high accuracy, and the intake air amount control by the variable intake valve control is performed. As described above, even in the case of a system in which an air flow meter detection error due to intake pulsation becomes large, the detection accuracy of the intake air amount can be improved and the accuracy of the air-fuel ratio control (exhaust emission) can be improved.

  In addition, in the intake air amount control by the variable intake valve control, the air flow meter detection error tends to increase in the low load region which is a practical region, but in the low load region, the air-fuel ratio of the exhaust gas by the air-fuel ratio F / B control. Is controlled in the vicinity of the theoretical air-fuel ratio, and the detection accuracy of the air-fuel ratio sensor 24 is high, so that the air flow meter detection error ΔG can be calculated with higher accuracy based on the output of the air-fuel ratio sensor 24. It is also possible to cope with the high accuracy of air-fuel ratio control required in the low load region that is the region.

  By the way, when the fluctuation state of the air flow meter output Vs is a transient state, it is difficult to accurately calculate the air flow meter detection error ΔG due to the intake pulsation. Further, when the detection accuracy of the air-fuel ratio sensor 24 is not guaranteed (for example, when the air-fuel ratio sensor 24 is in an inactive state or a failure state, or when the detection accuracy of the air-fuel ratio sensor 24 is bad) ), The calculation accuracy of the air flow meter detection error ΔG based on the output of the air-fuel ratio sensor 24 decreases.

  In consideration of these circumstances, in the present embodiment (1), when the variation state of the output Vs of the air flow meter 14 is a pulsating state and the detection accuracy of the air-fuel ratio sensor 24 is guaranteed, the air-fuel ratio sensor Since the air flow meter detection error ΔG is calculated based on the output of 24, the air flow meter detection error ΔG due to the intake pulsation can be reliably calculated with high accuracy.

  Further, in the present embodiment (1), when the variation state of the output Vs of the air flow meter 14 is a transient state or when the detection accuracy of the air-fuel ratio sensor 24 is not guaranteed, the air flow meter detection error ΔG due to the intake pulsation is calculated. Since it cannot be calculated with high accuracy, the air flow meter detection error ΔG due to intake pulsation can be calculated with high accuracy (that is, the fluctuation state of the output Vs of the air flow meter 14 is pulsating and the detection accuracy of the air-fuel ratio sensor 24 is guaranteed. The detected intake air amount G0 is corrected using the air flow meter detection error ΔG calculated in the state). Thereby, even when the air flow meter detection error ΔG due to the intake pulsation cannot be calculated with high accuracy, the detected intake air amount G 0 of the air flow meter 14 can be corrected with high accuracy, and the detection accuracy of the intake air amount can be improved.

  Moreover, in the present embodiment (1), when the air flow meter detection error ΔG is learned corresponding to the engine operating state and the detected intake air amount G 0 is corrected, the air flow meter detection error learning value ΔG (AREA) is selected. Since the air flow meter detection error learning value ΔG (AREA) corresponding to the engine operating state at that time is selected and used, the control system can be used even when the air flow meter detection error due to the intake pulsation cannot be accurately calculated. The detected intake air amount G0 can be corrected by using an appropriate air flow meter detection error learning value ΔG (AREA) corresponding to the engine operating state without being affected by manufacturing variations or changes over time. The detection accuracy can be further improved.

<< Embodiment (2) >>
By the way, in the intake air amount control by the variable intake valve control, the lift amount of the intake valve 28 becomes small at a low load. Therefore, the variation of the actual lift amount with respect to the target lift amount in each cylinder (depending on the component tolerance and assembly tolerance of each cylinder). The ratio of (variation) tends to increase, and the variation in intake air amount between cylinders tends to increase.

  Accordingly, in the embodiment (2) of the present invention shown in FIGS. 14 to 18, the inter-cylinder variation value ΔCYL # i representing the variation in the intake air amount between the cylinders of the engine 11 is calculated, and the air flow meter detection error ΔG and the cylinder are calculated. Based on the inter-cycle variation value ΔCYL # i, an error in detected intake air amount of each cylinder (hereinafter referred to as “individual detected intake air amount error”) ΔG # i is calculated, and the detected intake air amount error ΔG # i for each cylinder is calculated. Is used to correct the detected intake air amount G0 for each cylinder to obtain the final detected intake air amount G # i for each cylinder. Here, for example, in the case of a four-cylinder engine 11, # i = # 1 to # 4.

[Detected intake air amount correction base routine]
In the detected intake air amount correction base routine shown in FIG. 14 executed by the ECU 27 in this embodiment (2), first, in steps 601 and 602, the temporary detected intake air amount G0 corresponding to the output Vs of the air flow meter 14 is mapped. Then, the process proceeds to step 603, where an inter-cylinder variation calculation routine shown in FIG. 15 to be described later is executed, and the inter-cylinder variation value ΔCYL of each cylinder based on the intake pipe pressure MAP detected by the intake pipe pressure sensor 18. #i is calculated.

  In the next step 604, it is determined that the fluctuation state of the output Vs of the air flow meter 14 is a pulsation state, and the air-fuel ratio F / B control is permitted (that is, the detection accuracy of the air-fuel ratio sensor 24 is high). If it is determined that it is in a guaranteed state, the process proceeds to step 605 and executes the air flow meter detection error calculation routine shown in FIG. 9 and based on the air-fuel ratio AF detected by the air-fuel ratio sensor 24. The air flow meter detection error ΔG is calculated.

  Thereafter, the routine proceeds to step 606, where a cylinder-specific detected intake air amount error calculation routine shown in FIG. 16, which will be described later, is executed, and based on the air flow meter detection error ΔG and the inter-cylinder variation value ΔCYL # i of each cylinder. An error in detected intake air amount (detected intake air amount error for each cylinder) ΔG # i is calculated.

  Thereafter, the routine proceeds to step 607, where a cylinder-specific detected intake air amount error learning routine shown in FIG. 17 described later is executed, and the cylinder corresponding to the engine operating state at that time is detected using the cylinder-specific detected intake air amount error ΔG # i. The separately detected intake air amount error learning value ΔG # i (AREA) is updated and learned.

  On the other hand, if it is determined in step 604 that the variation state of the output Vs of the air flow meter 14 is a transient state, or the air-fuel ratio F / B control is not permitted (that is, the air-fuel ratio sensor 14). If it is determined that the detection accuracy is not guaranteed), the process proceeds to step 608 to execute a cylinder-specific detected intake air amount correction routine shown in FIG. A cylinder-specific detected intake air amount error learned value ΔG # i (AREA) corresponding to the engine operating state at that time is selected from the error learned values ΔG # i (AREA), and the detected intake air amount error learned value ΔG for each cylinder is selected. The temporary detected intake air amount G0 detected by the air flow meter 14 is corrected using #i (AREA) to obtain the final detected intake air amount G # i for each cylinder.

[Inter-cylinder variation calculation routine]
The inter-cylinder variation calculation routine shown in FIG. 15 is a subroutine started in step 603 of FIG. 14 and plays a role as the inter-cylinder variation calculation means in the claims.

  When this routine is started, first, at step 701, the output MAP of the intake pipe pressure sensor 18 is read, and then the routine proceeds to step 702, where the count value of the crank angle counter CCRNK is read. Since the crank angle counter CCRNK is incremented by “1” every 30 ° C. A, for example, based on the output signal of the crank angle sensor 26, 24 counts of the crank angle counter CCRNK correspond to one cycle (720 ° C. A). . The crank angle counter CCRNK is reset to “0” when it reaches “24”. The crank rotation position of the crank angle counter CCRNK = 0 corresponds to the compression top dead center (compression TDC) of the first cylinder # 1, and the crank rotation positions of the crank angle counters CCRNK = 6, 12, 18 are respectively It is set so as to correspond to the compression TDC of the third cylinder # 3, the fourth cylinder # 4, and the second cylinder # 2.

Thereafter, the process proceeds to step 703, where the minimum value MAPmin (#i) of the intake pipe pressure during the period corresponding to the intake stroke of each cylinder is calculated.
In calculating the intake pipe pressure minimum value MAPmin (# 1) of the first cylinder # 1, the intake pipe in the period of the crank angle counter CCRNK = 12 to 17, that is, the period corresponding to the intake stroke of the first cylinder # 1. The minimum value of the pressure MAP is calculated.

  When calculating the minimum intake pipe pressure value MAPmin (# 2) of the second cylinder # 2, the intake pipe in the period of the crank angle counter CCRNK = 6 to 11, that is, the period corresponding to the intake stroke of the second cylinder # 2. The minimum value of the pressure MAP is calculated.

  When calculating the minimum intake pipe pressure value MAPmin (# 3) of the third cylinder # 3, the intake pipe in the period corresponding to the crank angle counter CCRNK = 18 to 23, that is, the period corresponding to the intake stroke of the third cylinder # 3. The minimum value of the pressure MAP is calculated.

  When calculating the minimum intake pipe pressure value MAPmin (# 4) of the fourth cylinder # 4, the intake pipe during the period of the crank angle counter CCRNK = 0 to 5, that is, the period corresponding to the intake stroke of the fourth cylinder # 4. The minimum value of the pressure MAP is calculated.

Thereafter, the process proceeds to step 704, and after calculating an average value MAPmin (ave) of the intake pipe pressure minimum values MAPmin (# 1) to MAPmin (# 4) of all cylinders, the process proceeds to step 705, and the cylinder-to-cylinder variation of each cylinder is calculated. The value ΔCYL # i is calculated by the following equations.
ΔCYL # 1 = {100−MAPmin (# 1)} / {100−MAPmin (ave)}
ΔCYL # 2 = {100−MAPmin (# 2)} / {100−MAPmin (ave)}
ΔCYL # 3 = {100−MAPmin (# 3)} / {100−MAPmin (ave)}
ΔCYL # 4 = {100−MAPmin (# 4)} / {100−MAPmin (ave)}

  In this routine, the inter-cylinder variation value ΔCYL # i of each cylinder is calculated based on the minimum intake pipe pressure value MAPmin (#i) during the period corresponding to the intake stroke of each cylinder. The inter-cylinder variation value ΔCYL # i of each cylinder may be calculated based on the average value, area, etc. of the intake pipe pressure during the corresponding period.

[Detected air volume error calculation routine for each cylinder]
The cylinder-specific detected intake air amount error calculation routine shown in FIG. 16 is a subroutine started in step 606 of FIG. 14, and serves as a cylinder-specific detected intake air amount error calculation means in the claims.

  When this routine is started, first, in step 801, the inter-cylinder variation value ΔCYL # i of each cylinder is read, and then the process proceeds to step 802 to read the air flow meter detection error ΔG.

Thereafter, the process proceeds to step 803, where the detected intake air amount error ΔG # i for each cylinder is calculated by the following equations.
ΔG # 1 = ΔG × ΔCYL # 1
ΔG # 2 = ΔG × ΔCYL # 2
ΔG # 3 = ΔG × ΔCYL # 3
ΔG # 4 = ΔG × ΔCYL # 4

[Detected routine air intake error error learning routine]
The cylinder-by-cylinder detected intake air amount error learning routine shown in FIG. 17 is a subroutine started in step 607 of FIG. 14, and serves as a cylinder-by-cylinder detected intake air amount error learning means.

  When this routine is started, first, in step 901, a current engine operating state (engine speed NE and actual engine speed NE are measured in a cylinder-specific detected intake air amount error learning value ΔG # i (AREA) map (not shown)). It is determined in which operating area AREA the intake air amount G1) is. Here, the map of the cylinder-by-cylinder detected intake air amount error learning value ΔG # i (AREA) is divided into a plurality of operation areas AREA having the engine speed NE and the actual intake air amount G1 as parameters, and each operation area AREA. For each, a cylinder-specific detected intake air amount error learning value ΔG # i (AREA) is stored.

Thereafter, the routine proceeds to step 902, where the cylinder-by-cylinder detected intake air amount error ΔG # i calculated by the cylinder-by-cylinder detected intake air amount error calculation routine is smoothed, and the operation region AREA corresponding to the current engine operating state is processed. The cylinder-by-cylinder detected intake air amount error learning value ΔG # i (AREA) is obtained, and the cylinder-by-cylinder detected intake air amount error learned value ΔG # i (AREA) of the corresponding operation area AREA is updated with the obtained value.
ΔG # 1 (AREA) = ΔG # 1 (AREA) old + K × {ΔG # 1−ΔG # 1 (AREA) old}
ΔG # 2 (AREA) = ΔG # 2 (AREA) old + K × {ΔG # 2−ΔG # 2 (AREA) old}
ΔG # 3 (AREA) = ΔG # 3 (AREA) old + K × {ΔG # 3−ΔG # 3 (AREA) old}
ΔG # 4 (AREA) = ΔG # 4 (AREA) old + K × {ΔG # 4−ΔG # 4 (AREA) old}
Here, ΔG # i (AREA) is the current detected intake air amount error learning value for each cylinder, ΔG # i (AREA) old is the previous detected intake air amount error error value for each cylinder, and K is an annealing coefficient.

[Detected air volume correction routine for each cylinder]
The cylinder-specific detected intake air amount correction routine shown in FIG. 18 is a subroutine started in step 608 of FIG. 14, and serves as cylinder-specific detected intake air amount correction means in the claims.

  When this routine is started, first, in step 1001, in the map (not shown) of the detected intake air amount error learning value ΔG # i (AREA) for each cylinder, the current engine operating state (engine speed NE and actual It is determined in which operating area AREA the intake air amount G1) is.

  Thereafter, the process proceeds to step 1002, where a map of the cylinder-specific detected intake air amount error learning value ΔG # i (AREA) is searched, and the cylinder-specific detected intake air amount error learning of the operation region AREA corresponding to the current engine operating state is searched. The values ΔG # 1 (AREA) to ΔG # 4 (AREA) are read.

Thereafter, the routine proceeds to step 1003, where the provisional detected intake air amount G0 detected by the air flow meter 14 is determined using the cylinder-specific detected intake air amount error learning value ΔG # i (AREA) and the cylinder-specific transient correction value GFWD # i. The final detected intake air amount G # i for each cylinder is obtained by correction according to the following equations.
G # 1 = G0 + ΔG # 1 (AREA) + GFWD # 1
G # 2 = G0 + ΔG # 2 (AREA) + GFWD # 2
G # 3 = G0 + ΔG # 3 (AREA) + GFWD # 3
G # 4 = G0 + ΔG # 4 (AREA) + GFWD # 4

Here, the cylinder specific transient correction value GFWD # i is obtained by multiplying the transient correction value GFWD by the inter-cylinder variation value ΔCYL # i.
GFWD # i = GFWD × ΔCYL # i

  In the present embodiment (2) described above, the cylinder-specific detected intake air amount error ΔG # i is calculated based on the air flow meter detection error ΔG and the inter-cylinder variation value ΔCYL # i, and this cylinder-specific detected intake air amount error. Since the final detected intake air amount G # i for each cylinder is obtained by correcting the detected intake air amount G0 for each cylinder using ΔG # i, The detected intake air amount G0 can be corrected for each cylinder, and the intake air amount can be accurately detected for each cylinder even when the variation in intake air amount between the cylinders becomes large.

<< Embodiment (3) >>
In the embodiment (2), the inter-cylinder variation value ΔCYL # i of each cylinder is calculated based on the intake pipe pressure MAP. In the embodiment (3) of the present invention shown in FIG. 19, the output of the crank angle sensor 26 is calculated. The inter-cylinder variation value ΔCYL # i of each cylinder is calculated based on the rotation fluctuation calculated based on the signal.

[Inter-cylinder variation calculation routine]
In the inter-cylinder variation calculation routine shown in FIG. 19 executed by the ECU 27 in this embodiment (3), first, in step 1101, the count value of the crank angle counter CCRNK is read. As described above, the crank angle counter CCRNK is incremented by “1” every 30 ° C. A based on the output signal of the crank angle sensor 26, for example.

  Thereafter, the process proceeds to step 1102, and time T30 (time from the previous increment timing of the crank angle counter CCRNK to the present increment timing) required for the crankshaft to rotate 30 ° C. A is read.

In the next step 1103, the minimum value T30MIN (#i) and the maximum value T30MAX (#i) of T30 in the period corresponding to the combustion stroke of each cylinder are calculated.
When calculating the minimum value T30MIN (# 1) and the maximum value T30MAX (# 1) of the first cylinder # 1, it corresponds to the period of the crank angle counter CCRNK = 0 to 5, that is, the combustion stroke of the first cylinder # 1. The minimum value and the maximum value of T30 in the period to be calculated are calculated.

  When calculating the minimum value T30MIN (# 2) and the maximum value T30MAX (# 2) of the second cylinder # 2, it corresponds to the period of the crank angle counter CCRNK = 18 to 23, that is, the combustion stroke of the second cylinder # 2. The minimum value and the maximum value of T30 in the period to be calculated are calculated.

  When calculating the minimum value T30MIN (# 3) and the maximum value T30MAX (# 3) of the third cylinder # 3, it corresponds to the period of the crank angle counter CCRNK = 6 to 11, that is, the combustion stroke of the third cylinder # 3. The minimum value and the maximum value of T30 in the period to be calculated are calculated.

  When calculating the minimum value T30MIN (# 4) and the maximum value T30MAX (# 4) of the fourth cylinder # 4, it corresponds to the period of the crank angle counter CCRNK = 12 to 17, that is, the combustion stroke of the fourth cylinder # 4. The minimum value and the maximum value of T30 in the period to be calculated are calculated.

Thereafter, the process proceeds to step 1104, and the rotational fluctuation ΔT30 (#i) of each cylinder is calculated by the following equations.
ΔT30 (# 1) = T30MAX (# 1) −T30MIN (# 1)
ΔT30 (# 2) = T30MAX (# 2) −T30MIN (# 2)
ΔT30 (# 3) = T30MAX (# 3) -T30MIN (# 3)
ΔT30 (# 4) = T30MAX (# 4) -T30MIN (# 4)

Thereafter, the process proceeds to step 1105, where an average value ΔT30 (ave) of the rotational fluctuations ΔT30 (# 1) to ΔT30 (# 4) of all cylinders is calculated, and then the process proceeds to step 1106, where the cylinder-to-cylinder variation value ΔCYL # i is calculated by the following equations.
ΔCYL # 1 = ΔT30 (# 1) / ΔT30 (ave)
ΔCYL # 2 = ΔT30 (# 2) / ΔT30 (ave)
ΔCYL # 3 = ΔT30 (# 3) / ΔT30 (ave)
ΔCYL # 4 = ΔT30 (# 4) / ΔT30 (ave)

<< Embodiment (4) >>
In the embodiment (4) of the present invention shown in FIGS. 20 and 21, the inter-cylinder variation value ΔCYL # i of each cylinder is calculated based on the air-fuel ratio AF detected by the air-fuel ratio sensor 24.

[Inter-cylinder variation calculation routine]
In the cylinder-to-cylinder variation calculation routine shown in FIG. 20 executed by the ECU 27 in this embodiment (4), first, in step 1201, the output AF of the air-fuel ratio sensor 24 is read, and then the routine proceeds to step 1202, where the crank angle counter CCRNK is set. Read the count value.

  Thereafter, the routine proceeds to step 1203, where the exhaust system delay time DELY required until the exhaust gas discharged from the engine 11 is detected by the air-fuel ratio sensor 24 is calculated. Since the exhaust system delay time DELY changes according to the engine operating state (for example, the engine speed NE and the actual intake air amount G1), a map of the exhaust system delay time DELY shown in FIG. The delay time DELY corresponding to the engine operating state (for example, the engine speed NE and the actual intake air amount G1) is calculated.

  In the next step 1204, the average value of the air-fuel ratio AF of the exhaust gas during the period corresponding to the exhaust stroke of each cylinder is calculated based on the count value of the crank angle counter CCRNK and the exhaust system delay time DELY. Then, the air-fuel ratio average value AF (#i) of each cylinder is calculated.

Thereafter, the process proceeds to step 1205, and after calculating the average value AF (ave) of the air-fuel ratio average values AF (# 1) to AF (# 4) of all cylinders, the process proceeds to step 1206, and the inter-cylinder variation value of each cylinder. ΔCYL # i is calculated by the following equations.
ΔCYL # 1 = AF (# 1) / AF (ave)
ΔCYL # 2 = AF (# 2) / AF (ave)
ΔCYL # 3 = AF (# 3) / AF (ave)
ΔCYL # 4 = AF (# 4) / AF (ave)

<< Embodiment (5) >>
In the embodiment (5) of the present invention shown in FIG. 22, each cylinder of the engine 11 is provided with an in-cylinder pressure sensor or a spark plug with an in-cylinder pressure sensor (both not shown), The cylinder-to-cylinder variation value ΔCYL # i of each cylinder is calculated based on the in-cylinder pressure CP detected by the pressure sensor.

[Inter-cylinder variation calculation routine]
In the inter-cylinder variation calculation routine shown in FIG. 22 executed by the ECU 27 in this embodiment (5), first, in step 1301, the in-cylinder pressure CP detected by the in-cylinder pressure sensor of each cylinder is read, and then in step 1302. Then, the count value of the crank angle counter CCRNK is read.

Thereafter, the routine proceeds to step 1303, where the maximum value CPmax (#i) of the in-cylinder pressure during the period corresponding to the compression stroke of each cylinder is calculated.
When calculating the in-cylinder pressure maximum value CPmax (# 1) of the first cylinder # 1, the in-cylinder period of the crank angle counter CCRNK = 18 to 23, that is, the period corresponding to the compression stroke of the first cylinder # 1 The maximum value of the pressure CP is calculated.

  When calculating the in-cylinder pressure maximum value CPmax (# 2) of the second cylinder # 2, the in-cylinder period of the crank angle counter CCRNK = 12 to 17, that is, the period corresponding to the compression stroke of the second cylinder # 2 The maximum value of the pressure CP is calculated.

  When calculating the in-cylinder pressure maximum value CPmax (# 3) of the third cylinder # 3, the in-cylinder period of the crank angle counter CCRNK = 0 to 5, that is, the period corresponding to the compression stroke of the third cylinder # 3. The maximum value of the pressure CP is calculated.

  When calculating the in-cylinder pressure maximum value CPmax (# 4) of the fourth cylinder # 4, the in-cylinder period of the crank angle counter CCRNK = 6 to 11, that is, the period corresponding to the compression stroke of the fourth cylinder # 4 The maximum value of the pressure CP is calculated.

Thereafter, the process proceeds to step 1304, the average value CPmax (ave) of the in-cylinder pressure maximum values CPmax (# 1) to CPmax (# 4) of all cylinders is calculated, and then the process proceeds to step 1305, where the cylinder-to-cylinder variation of each cylinder is determined. The value ΔCYL # i is calculated by the following equations.
ΔCYL # 1 = CPmax (# 1) / CPmax (ave)
ΔCYL # 2 = CPmax (# 2) / CPmax (ave)
ΔCYL # 3 = CPmax (# 3) / CPmax (ave)
ΔCYL # 4 = CPmax (# 4) / CPmax (ave)

  In this routine, the inter-cylinder variation value ΔCYL # i of each cylinder is calculated based on the in-cylinder pressure maximum value CPmax (#i) in the period corresponding to the compression stroke of each cylinder. The inter-cylinder variation value ΔCYL # i of each cylinder may be calculated on the basis of the average value, area, in-cylinder pressure detection value at a predetermined crank angle, and the like during the corresponding period. Alternatively, the inter-cylinder variation value ΔCYL # i of each cylinder is calculated based on the maximum value, average value, area, in-cylinder pressure detection value at a predetermined crank angle, etc. during the period corresponding to the combustion stroke of each cylinder. You may make it do.

<< Embodiment (6) >>
In each of the above embodiments (1) to (5), the variation state of the output Vs of the air flow meter 14 is determined by the variation state determination routine shown in FIG. 7, but the determination method may be changed as appropriate, for example, FIG. The variation state of the output Vs of the air flow meter 14 may be determined by the variation state determination routine shown in FIG.

[Variation state determination routine]
In the fluctuation state determination routine shown in FIG. 23, first, in step 1401, the output Vs of the air flow meter 14 is read, and then the process proceeds to step 1402, where the current output Vs (i) of the air flow meter 14 is changed to the previous output Vs (i). -1) is subtracted to obtain the amount of change ΔVs (i) in the air flow meter output Vs.
ΔVs (i) = Vs (i) −Vs (i−1)

  Thereafter, the routine proceeds to step 1403, where it is determined whether or not the engine 11 has rotated a predetermined crank angle (for example, 180 ° C. A) after starting the processing of this routine. The process of calculating the change amount ΔVs (i) of Vs (steps 1401 and 1402) is repeated.

  Thereafter, when the engine 11 rotates at a predetermined crank angle after the processing of this routine is started, the routine proceeds to step 1404, where the sum ΣΔVs (i) of the variation ΔVs (i) of the air flow meter output Vs is calculated.

  Thereafter, the process proceeds to step 1405, where it is determined whether or not the sum ΣΔVs (i) of the change amount ΔVs (i) of the air flow meter output Vs is larger than the transient determination value A. As a result, if it is determined that the sum ΣΔVs (i) is larger than the transient determination value A, the process proceeds to step 1407, where it is determined that the fluctuation state of the output Vs of the air flow meter 14 is a transient state (increase state). To end this routine.

  On the other hand, if it is determined in step 1405 that the total sum ΣΔVs (i) of the change amount ΔVs (i) of the air flow meter output Vs is equal to or less than the transient determination value A, the process proceeds to step 1406 and the total sum ΣΔVs (i). Is smaller than the transient determination value (−A). As a result, when it is determined that the sum ΣΔVs (i) is smaller than the transient determination value (−A), the process proceeds to step 1407, and the fluctuation state of the output Vs of the air flow meter 14 is a transient state (decrease state). This routine is terminated.

  If it is determined that the total sum ΣΔVs (i) of the change amount ΔVs (i) of the air flow meter output Vs is within the range from the transient determination value A to −A, the process proceeds to step 1408 and the output of the air flow meter 14 is output. It is determined that the fluctuation state of Vs is a pulsation state, and this routine is finished.

  In each of the embodiments (1) to (6) described above, when the air flow meter output Vs is in a pulsating state and the detection accuracy of the air / fuel ratio sensor 24 is guaranteed, the output of the air / fuel ratio sensor 24 is output. The air flow meter detection error ΔG is calculated based on this, but the present invention is not limited to this, and the air flow meter detection is detected based on the output of the air fuel ratio sensor 24 when the detection accuracy of the air fuel ratio sensor 24 is guaranteed. The error ΔG may be calculated. In this case, further, when the detection accuracy of the air-fuel ratio sensor 24 is not guaranteed, the detected intake air is detected using the air flow meter detection error ΔG calculated when the detection accuracy of the air-fuel ratio sensor 24 is guaranteed. The amount G0 may be corrected. Even in this case, the air flow meter detection error ΔG can be calculated with high accuracy based on the output of the air-fuel ratio sensor 24, and even when the air flow meter detection error ΔG cannot be calculated with high accuracy, it can be detected with the air flow meter. The detected intake air amount G0 can be accurately corrected, the detection accuracy of the intake air amount can be improved, and the accuracy of air-fuel ratio control can be improved.

  In the above embodiments (1) to (6), the air flow meter detection error ΔG is calculated based on the air-fuel ratio AF detected by the air-fuel ratio sensor 24. However, the air-fuel ratio AF detected by the air-fuel ratio sensor 24 is the target. When executing air-fuel ratio feedback control that matches the air-fuel ratio, the air flow meter detection error ΔG may be calculated based on the target air-fuel ratio. Specifically, the target air-fuel ratio of air-fuel ratio feedback control may be used in place of the air-fuel ratio AF in steps 307 and 308 of the air flow meter detection error calculation routine of FIG.

  While the air-fuel ratio feedback control is being executed, the air-fuel ratio AF of the exhaust gas is accurately controlled to the target air-fuel ratio. Therefore, even if the air flow meter detection error ΔG is calculated based on the target air-fuel ratio, it is detected by the air-fuel ratio sensor 24. It is possible to obtain the same effect as when the air flow meter detection error ΔG is calculated based on the air-fuel ratio AF.

Further, in each of the above embodiments (1) to (6), the present invention is applied to a system equipped with the air-fuel ratio sensor 24 for detecting the air-fuel ratio of the exhaust gas, but the oxygen sensor for detecting rich / lean of the exhaust gas. Alternatively, the present invention may be applied to a system equipped with other exhaust gas sensors.
The scope of application of the present invention is not limited to a four-cylinder engine, and the present invention may be applied to an engine having five or more cylinders or three or less cylinders.

It is a schematic block diagram of the whole engine control system in Embodiment (1) of this invention. It is a front view of a variable intake valve lift mechanism. It is a figure for demonstrating operation | movement at the time of the high lift mode of a variable intake valve lift mechanism. It is a figure for demonstrating the operation | movement at the time of the high lift mode of a variable intake valve lift mechanism. . It is a valve lift characteristic view for explaining the continuously variable operation of the valve lift amount by the variable intake valve lift mechanism. It is a flowchart which shows the flow of a process of the detection intake air quantity correction | amendment base routine of embodiment (1). It is a flowchart which shows the flow of a process of the fluctuation state determination routine of Embodiment (1). (A) is a time chart which shows the pulsation state of an air flow meter output, (b) is a time chart which shows the transient state of an air flow meter output. It is a flowchart which shows the flow of a process of the airflow meter detection error calculation routine of embodiment (1). It is a flowchart which shows the flow of a process of the airflow meter detection error learning routine of Embodiment (1). It is a figure which shows notionally the map of airflow meter detection error learning value (DELTA) G (AREA). It is a flowchart which shows the flow of a process of the detection intake air amount correction | amendment routine of embodiment (1). It is a time chart which shows the example of execution of embodiment (1). It is a flowchart which shows the flow of a process of the detection intake air amount correction | amendment base routine of embodiment (2). It is a flowchart which shows the flow of a process of the variation calculation routine between cylinders of embodiment (2). It is a flowchart which shows the flow of a process of the detection air amount error calculation routine classified by cylinder of Embodiment (2). It is a flowchart which shows the flow of a process of the detection air amount error learning routine classified by cylinder of Embodiment (2). It is a flowchart which shows the flow of a process of the detection air amount correction | amendment routine classified by cylinder of embodiment (2). It is a flowchart which shows the flow of a process of the variation calculation routine between cylinders of embodiment (3). It is a flowchart which shows the flow of a process of the variation calculation routine between cylinders of embodiment (4). It is a figure which shows notionally the map of the delay time DELY of an exhaust system. It is a flowchart which shows the flow of a process of the variation calculation routine between cylinders of Embodiment (5). It is a flowchart which shows the flow of a process of the fluctuation state determination routine of Embodiment (6).

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 14 ... Air flow meter, 15 ... Throttle valve, 18 ... Intake pipe pressure sensor, 20 ... Fuel injection valve, 21 ... Spark plug, 22 ... Exhaust pipe, 24 ... Air-fuel ratio Sensor (exhaust gas sensor), 26 ... crank angle sensor, 27 ... ECU (fluctuation state discriminating means, air flow meter detection error calculating means, air flow meter detection error learning means, detected intake air amount correcting means, inter-cylinder variation calculating means, for each cylinder Detected intake air amount error calculating means, cylinder-specific detected intake air amount error learning means, cylinder-specific detected intake air amount correcting means), 28 ... intake valve, 29 ... exhaust valve, 30 ... variable intake valve lift mechanism, 31 ... variable exhaust Valve lift mechanism

Claims (13)

Variable intake valve mechanism capable of controlling intake air amount by varying valve control amount such as intake valve lift amount and opening / closing timing, air flow meter for detecting intake air amount of internal combustion engine, and exhaust gas of internal combustion engine An intake air amount detection device for an internal combustion engine comprising an exhaust gas sensor for detecting an air-fuel ratio of the engine or information correlated therewith,
Air-fuel ratio control means for performing air-fuel ratio control for matching the air-fuel ratio of the exhaust gas detected by the exhaust gas sensor with a target air-fuel ratio;
An air flow meter detection error calculating means for calculating a detection error (hereinafter referred to as “air flow meter detection error”) of the intake air amount detected by the air flow meter based on an average value of a target air fuel ratio used in the air fuel ratio control;
An inter-cylinder variation calculating means for calculating an inter-cylinder variation value representing an intake air amount variation between cylinders of the internal combustion engine;
Cylinder-specific detected intake air amount error calculating means for calculating an error in the detected intake air amount of each cylinder (hereinafter referred to as “cylinder-specific detected intake air amount error”) based on the air flow meter detection error and the inter-cylinder variation value; ,
When the fluctuation state of the output of the air flow meter is a transient state and / or when the detection accuracy of the exhaust gas sensor is not guaranteed, the air flow meter is detected for each cylinder using the detected intake air amount error for each cylinder. An intake air amount detection device for an internal combustion engine, comprising: a cylinder-specific detection intake air amount correction means for correcting the detected intake air amount. Fluctuation state determination means for determining whether the fluctuation state of the output of the air flow meter is a transient state or a pulsation state,
The air flow meter detection error calculating means calculates the average of the target air fuel ratio used in the air fuel ratio control when the fluctuation state of the output of the air flow meter is a pulsating state and the detection accuracy of the exhaust gas sensor is guaranteed. 2. The intake air amount detection device for an internal combustion engine according to claim 1, wherein the air flow meter detection error is calculated based on a value .   When the fluctuation state of the output of the air flow meter is a transient state and / or when the detection accuracy of the exhaust gas sensor is not guaranteed, the detected intake air amount of the air flow meter is corrected using the air flow meter detection error. 3. The intake air amount detection device for an internal combustion engine according to claim 2, further comprising a detection intake air amount correction means for detecting the intake air amount.   The air flow meter detection error calculating means calculates an actual intake air amount based on an output of the exhaust gas sensor and a fuel injection amount, and compares the actual intake air amount with the detected intake air amount to detect the air flow meter. The intake air amount detection device for an internal combustion engine according to claim 1 or 3, wherein an error is calculated.   The air flow meter detection error calculating means calculates an actual intake air amount based on a target air-fuel ratio and a fuel injection amount used in the air-fuel ratio control, and compares the actual intake air amount with the detected intake air amount. 4. The intake air amount detection device for an internal combustion engine according to claim 1, wherein the air flow meter detection error is calculated. An air flow meter detection error learning means for learning an air flow meter detection error calculated by the air flow meter detection error calculation means corresponding to the operating state of the internal combustion engine at that time,
The detected intake air amount correcting means corrects the detected intake air amount from the air flow meter detection error learning value learned by the air flow meter detection error learning means, and the air flow corresponding to the operating state of the internal combustion engine at that time. 4. The intake air amount detection device for an internal combustion engine according to claim 3, wherein a meter detection error learning value is selected and used. A cylinder-specific detected intake air amount error learning unit that learns a cylinder-specific detected intake air amount error calculated by the cylinder-specific detected intake air amount error calculating unit according to the operating state of the internal combustion engine at that time,
The cylinder-specific detected intake air amount correction means corrects the detected intake air amount for each cylinder among the cylinder-specific detected intake air amount error learning values learned by the cylinder-specific detected intake air amount error learning means. 2. The intake air amount detecting device for an internal combustion engine according to claim 1, wherein a learning value for each cylinder detected intake air amount corresponding to the operating state of the internal combustion engine at that time is selected and used. An intake pipe pressure sensor for detecting an intake pipe pressure of the internal combustion engine;
The inter-cylinder variation calculating means detects the intake pipe pressure by the intake pipe pressure sensor for each period corresponding to the intake stroke of each cylinder, and calculates the inter-cylinder variation value based on the intake pipe pressure. The intake air amount detection device for an internal combustion engine according to claim 1 or 7.   The cylinder-to-cylinder variation calculation means detects a rotation variation for each period corresponding to the combustion stroke of each cylinder, and calculates the variation value between the cylinders based on the rotation variation. The intake air amount detection device for an internal combustion engine according to any one of claims 8 to 10.   The inter-cylinder variation calculation means detects an air-fuel ratio of exhaust gas by the exhaust gas sensor for each period corresponding to an exhaust stroke of each cylinder, and calculates the inter-cylinder variation value based on the air-fuel ratio. An intake air amount detection device for an internal combustion engine according to any one of claims 1, 7 to 9. An in-cylinder pressure sensor for detecting an in-cylinder pressure for each cylinder of the internal combustion engine;
The cylinder-to-cylinder variation calculating means detects an in-cylinder pressure by the in-cylinder pressure sensor for each cylinder, and calculates the inter-cylinder variation value based on the in-cylinder pressure. The intake air amount detection device for an internal combustion engine according to any one of claims 1 to 10. Variable intake valve mechanism capable of controlling intake air amount by varying valve control amount such as intake valve lift amount and opening / closing timing, air flow meter for detecting intake air amount of internal combustion engine, and exhaust gas of internal combustion engine An intake air amount detection device for an internal combustion engine comprising an exhaust gas sensor for detecting an air-fuel ratio of the engine or information correlated therewith,
When the detection accuracy of the exhaust gas sensor is guaranteed, the detection error (hereinafter referred to as “air flow meter detection error”) of the intake air amount detected by the air flow meter based on the average value of the output of the exhaust gas sensor An intake air amount detection device for an internal combustion engine, comprising an air flow meter detection error calculation means for calculating.   In the state where the detection accuracy of the exhaust gas sensor is not guaranteed, a detection intake air amount correction means for correcting the detected intake air amount of the air flow meter using the air flow meter detection error is provided. The intake air amount detection device for an internal combustion engine according to claim 12.

Images