JP3968705B2 - Control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for an internal combustion engine that corrects torque variations between cylinders and air-fuel ratio variations between cylinders of an internal combustion engine having a plurality of cylinders.
[0002]
[Prior art]
In general, in a multi-cylinder internal combustion engine, the intake air amount (in-cylinder charged air amount) of each cylinder varies due to differences in the intake manifold shape of each cylinder, variations in the valve clearance of the intake valves, and the like. Further, the amount of intake fuel in each cylinder varies due to individual differences in fuel injection valves of each cylinder, pressure distribution characteristics in the fuel pipe, evaporation gas distribution characteristics in the intake pipe when the evaporation gas purge is performed, and the like. Variations in the torque and air-fuel ratio of each cylinder occur due to variations in the intake air amount and intake fuel amount between the cylinders. When the torque variation between the cylinders becomes large, the in-cycle fluctuation of the engine torque becomes large, and there is a risk that vibrations unpleasant to the driver may occur. In addition, when the air-fuel ratio variation between cylinders increases, the in-cycle fluctuation of the air-fuel ratio of the exhaust gas flowing into the catalyst increases, so the fluctuation range of the exhaust gas air-fuel ratio protrudes from the catalyst purification window and the exhaust gas purification rate May decrease.
[0003]
As countermeasures against these problems, several methods for correcting torque variations between cylinders and air-fuel ratio variations have been proposed. For example, as disclosed in Japanese Patent Application Laid-Open No. Sho 62-17342, torque is detected for each cylinder by a torque sensor provided on a crankshaft, and the torque of each cylinder is determined to be the average torque of all cylinders. Some have corrected the fuel injection amount. Further, as disclosed in Japanese Patent Application Laid-Open No. 2000-220489, the air-fuel ratio of each cylinder is estimated based on the output of the air-fuel ratio sensor installed in the exhaust pipe, and each cylinder is reduced so that the variation in air-fuel ratio among the cylinders is reduced. In some cases, the fuel injection amount is corrected.
[0004]
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, an engine operating state, and the like. 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.
[0005]
[Problems to be solved by the invention]
However, in the intake air amount control based on the variable intake valve control described above, the lift amount of the intake valve becomes small at low load, so the variation in the actual lift amount with respect to the target lift amount in each cylinder (part tolerance or assembly tolerance of each cylinder). Variation), the variation in intake air amount between cylinders tends to increase. For this reason, the torque and air-fuel ratio of each cylinder tend to fluctuate due to the influence of the intake air amount variation between the cylinders, and the torque variation and air-fuel ratio variation between the cylinders tend to increase.
[0006]
Therefore, when the variation between the cylinders of one of the torque and the air-fuel ratio is corrected using the conventional method for correcting the variation between the cylinders, the correction amount becomes large, and the other cylinder (torque or air-fuel ratio) that has not been corrected is corrected. It is difficult to achieve both reduction in torque variation between cylinders and reduction in air-fuel ratio variation between cylinders, and it is difficult to achieve both drivability and exhaust emission. In addition, in the conventional variation correction method between cylinders, when correcting torque variation or air-fuel ratio variation between cylinders, it is difficult to correct with sufficient accuracy because intake air amount variation between cylinders is large. Furthermore, even when multiple factors such as variation in intake air amount and variation in intake fuel amount between cylinders are intertwined to cause torque variation or air-fuel ratio variation between cylinders, it is difficult to correct with sufficient accuracy. .
[0007]
The present invention has been made in view of these circumstances, and a first object is to be able to correct both torque variation and air-fuel ratio variation between cylinders, and a second object is In other words, the correction accuracy of torque variation between cylinders and / or air-fuel ratio variation is improved.
[0008]
[Means for Solving the Problems]
In order to achieve the first object, an internal combustion engine control apparatus according to claim 1 of the present invention is configured to take in each cylinder based on at least one of an intake air amount and an intake pipe pressure of an internal combustion engine having a plurality of cylinders. A first inter-cylinder variation value representing air amount variation is calculated by the first inter-cylinder variation estimation means, and at least of torque variation between cylinders and air-fuel ratio variation between cylinders based on the first variation value between cylinders. The first inter-cylinder variation correction for correcting one is executed by the first inter-cylinder variation correcting means. Then, the second cylinder representing the intake air amount variation and / or the intake fuel amount variation of each cylinder based on at least one of the combustion state of the internal combustion engine and the air-fuel ratio of the exhaust gas after execution of the first inter-cylinder variation correction. The inter-cylinder variation value is calculated by the second inter-cylinder variation estimation means, and at least one of the torque variation between the cylinders and the air-fuel ratio variation between the cylinders is corrected based on the second inter-cylinder variation value. The variation correction is executed by the second cylinder variation correcting means.
[0009]
In this configuration, first, the inter-cylinder variation correction is executed based on the first inter-cylinder variation value calculated based on the pre-combustion information (intake air amount and intake pipe pressure). The second cylinder is corrected based on the second cylinder-to-cylinder variation value calculated based on post-combustion information (combustion state and exhaust gas air-fuel ratio). By executing the variation correction between the cylinders, the torque variation between the cylinders and the air-fuel ratio variation between the cylinders are corrected.
[0010]
In this way, the correction of the torque variation between the cylinders and the correction of the air-fuel ratio variation between the cylinders can be performed separately in the first inter-cylinder variation correction and the second inter-cylinder variation correction. Even when the intake air amount control by the intake valve control is low, the variation in the intake air amount between the cylinders and the torque variation and the air-fuel ratio variation between the cylinders increase. Thus, it is possible to reduce both the torque variation and the air-fuel ratio variation between the cylinders.
[0011]
Further, since correction can be performed in two stages, that is, first cylinder-to-cylinder variation correction based on pre-combustion information and second cylinder-to-cylinder variation correction based on post-combustion information, the first inter-cylinder variation correction can be performed. Even if the effects of variations in intake air amount and intake fuel amount remain after the execution of the above, it can be corrected by the second cylinder variation correction, such as variations in intake air amount and intake fuel amount between cylinders, etc. Thus, it is possible to accurately correct the torque variation between cylinders and the air-fuel ratio variation between cylinders caused by a plurality of factors.
[0012]
The invention according to claim 1 is not limited to a system that performs intake air amount control by variable intake valve control, and may be applied to a system that performs intake air amount control by throttle valve control. It is possible to perform highly accurate air-fuel ratio control by accurately correcting variation in air-fuel ratio among cylinders.
[0013]
Generally, intake pulsation occurs in the intake pipe of an internal combustion engine having a plurality of cylinders corresponding to the intake stroke of each cylinder, so the waveform of the intake air amount detected by the air flow meter corresponds to the intake stroke of each cylinder. The pulsation waveform corresponding to the intake air amount of each cylinder is obtained.
[0014]
Therefore, as a specific example of the calculation method of the first inter-cylinder variation value, for example, as in claim 2, an average value of the intake air amount detected by the air flow meter for each period corresponding to the intake stroke of each cylinder, The first inter-cylinder variation value may be calculated based on at least one of the maximum value, the minimum value, the amplitude value, and the area. By calculating at least one of the average value, maximum value, minimum value, amplitude value, and area of the intake air amount detected by the air flow meter for each period corresponding to the intake stroke of each cylinder, the intake air amount of each cylinder Since the characteristic value of the pulsation waveform reflecting this can be calculated, the first inter-cylinder variation value reflecting the intake air amount variation of each cylinder can be calculated by using this characteristic value. Recently, since an air flow meter that has a high response and can detect the backflow of intake air has been put into practical use, the first inter-cylinder variation value can be calculated more accurately by using such an air flow meter. Can do.
[0015]
The waveform of the intake pipe pressure detected by the intake pipe pressure sensor is also a pulsation waveform corresponding to the intake stroke of each cylinder, that is, a pulsation waveform reflecting the intake air amount of each cylinder. Between the first cylinders based on at least one of the average value, maximum value, minimum value, amplitude value, and area of the intake pipe pressure detected by the intake pipe pressure sensor for each period corresponding to the intake stroke of each cylinder The variation value may be calculated. Even in this case, the first inter-cylinder variation value reflecting the variation in the intake air amount of each cylinder can be calculated.
[0016]
In general, the air flow meter is disposed on the upstream side of the throttle valve, and the intake pipe pressure sensor 18 is disposed on the downstream side of the throttle valve 15. When the throttle valve is closed from the fully open position, the intake pulsation is reduced on the upstream side of the throttle valve, so the first inter-cylinder variation value is calculated based on the output of the air flow meter arranged on the upstream side of the throttle valve. Then, when the throttle valve is closed, the calculation accuracy of the first inter-cylinder variation value may be lowered.
[0017]
Therefore, as in claim 4, when the throttle opening of the internal combustion engine is smaller than the predetermined opening or when the intake pipe pressure is lower than the predetermined pressure, an intake pipe pressure sensor arranged downstream of the throttle valve is used. It is preferable to calculate a first inter-cylinder variation value based on the detected minimum value of the intake pipe pressure. Even when the throttle valve is closed from the fully opened position, a relatively large intake pulsation occurs on the downstream side of the throttle valve. Therefore, when the throttle opening is smaller than the predetermined opening (or the intake pipe pressure of the internal combustion engine is higher than the predetermined pressure). If the first cylinder variation value is calculated based on the output of the intake pipe pressure sensor arranged downstream of the throttle valve, the engine is always arranged upstream of the throttle valve. Compared with the case where the first inter-cylinder variation value is calculated based on the output of the air flow meter, the calculation accuracy of the first inter-cylinder variation value when the throttle valve is closed can be improved. In addition, when the throttle valve is closed, the intake pipe pressure fluctuates to the negative side due to the intake of air into each cylinder. Therefore, by using the minimum value of the intake pipe pressure, the calculation accuracy of the first inter-cylinder variation value can be improved. Can be increased.
[0018]
On the other hand, as a specific example of the calculation method of the second cylinder variation value, for example, as in claim 5, rotational fluctuation that becomes information on the combustion state of each cylinder is obtained for each period corresponding to the combustion stroke of each cylinder. Alternatively, the second inter-cylinder variation value may be calculated based on the rotation fluctuation. Since the combustion state of each cylinder changes according to the intake air amount and intake fuel amount of each cylinder and the value of the rotation fluctuation changes, if the rotation fluctuation of each cylinder is used, the variation in intake air quantity and intake fuel of each cylinder A second inter-cylinder variation value reflecting the amount variation can be calculated.
[0019]
Alternatively, as described in claim 6, the air-fuel ratio of the exhaust gas of each cylinder is detected by the air-fuel ratio sensor for each period corresponding to the exhaust stroke of each cylinder, and the second cylinder is detected based on the air-fuel ratio. The variation value may be calculated. Since the air-fuel ratio of the exhaust gas of each cylinder changes according to the intake air amount and intake fuel amount of each cylinder, if the air-fuel ratio of the exhaust gas of each cylinder is used, the intake air amount variation and intake fuel amount variation of each cylinder A second inter-cylinder variation value reflecting the above can be calculated.
[0020]
In addition, various combinations of the first cylinder variation correction and the second cylinder variation correction are conceivable, but the intake air amount variation between cylinders is low, such as when the intake air amount control by variable intake valve control is low. Is larger, the variation in torque between cylinders is corrected by correcting the ignition timing for each cylinder based on the variation value between the first cylinders as the first variation correction among cylinders. As the second cylinder-to-cylinder variation correction, the air-fuel ratio variation among the cylinders may be corrected by correcting the fuel injection amount for each cylinder based on the second cylinder-to-cylinder variation value.
[0021]
When the variation in intake air amount is large (when the variation in torque between cylinders or the variation in air-fuel ratio is large), if the variation in air-fuel ratio between cylinders is corrected by the first variation correction between cylinders, the variation in torque between cylinders is large. Since it is necessary to calculate the second cylinder variation value in a state where the rotation fluctuation of each cylinder interferes, the calculation accuracy of the second cylinder fluctuation value based on the rotation fluctuation of each cylinder decreases, The correction accuracy of the second cylinder variation correction decreases. Therefore, when the intake air amount variation between the cylinders is large, the torque variation between the cylinders is corrected by the first cylinder-to-cylinder variation correction, and then the air-fuel ratio variation between the cylinders is corrected by the second cylinder-to-cylinder variation correction. This combination is recommended.
[0022]
On the other hand, when the intake air amount variation is comparatively small, such as when the intake air amount control by the variable intake valve control is at a medium load / high load or when the intake air amount control is performed by the throttle control, As the first cylinder-to-cylinder variation correction, the fuel injection amount is corrected for each cylinder based on the first cylinder-to-cylinder variation value, thereby correcting the air-fuel ratio variation between the cylinders. The torque variation between the cylinders may be corrected by correcting the ignition timing for each cylinder based on the inter-cylinder variation value of 2.
[0023]
When the intake air amount variation is relatively small (when the torque variation between cylinders or the air-fuel ratio variation is small), even if the air-fuel ratio variation between cylinders is corrected by the first cylinder-to-cylinder variation correction, the torque variation between cylinders Therefore, the variation value between the second cylinders can be calculated in a state where the rotation fluctuations of the respective cylinders do not interfere with each other. Therefore, the second cylinder variation value can be accurately calculated based on the rotation fluctuations of the respective cylinders. Thus, the torque variation between the cylinders can be accurately corrected by the second variation correction between the cylinders. This combination is recommended especially when it is desired to suppress torque fluctuations while giving priority to air-fuel ratio control (exhaust emission reduction).
[0024]
Further, in the case of a system having a cylinder-specific intake air variable means for varying the intake air amount for each cylinder of the internal combustion engine as in claim 9, the first cylinder is corrected as the first cylinder variation correction. Based on the inter-cell variation value, the control amount of the cylinder-specific intake air variable means is corrected for each cylinder to correct the intake air amount for each cylinder, and the second inter-cylinder variation value is used as the second inter-cylinder variation correction. Based on the above, the fuel injection amount may be corrected for each cylinder. In this way, the first cylinder-to-cylinder variation correction and the second cylinder-to-cylinder variation correction directly correct the intake air amount variation between the cylinders and the intake fuel amount variation between the cylinders, respectively. Thus, the variation in the air-fuel ratio between the cylinders can be corrected, so that it is not necessary to correct the ignition timing, and the problem of a decrease in fuel consumption due to the ignition delay can be avoided.
[0025]
In addition, when the variation in intake air amount is relatively small and when emphasis is placed on the suppression of torque fluctuation (improvement of drivability), the first inter-cylinder variation is corrected as the first inter-cylinder variation correction. By correcting the ignition timing for each cylinder based on the value, the torque variation between the cylinders is corrected, and as the second cylinder variation correction, the ignition timing corrected by the first cylinder variation correction is used as the second cylinder. It is preferable to re-correct each cylinder based on the interval variation value. In this way, torque variation between cylinders can be corrected in two stages of correction between first cylinder variation and second cylinder variation correction, so that torque variation between cylinders can be corrected more accurately. Can improve the drivability improvement effect.
[0026]
Further, when the intake air amount variation is relatively small and the air-fuel ratio control (exhaust emission reduction) is emphasized, the first inter-cylinder variation value is used as the first inter-cylinder variation correction as in claim 11. Based on this, the fuel injection amount is corrected for each cylinder to correct the air-fuel ratio variation between the cylinders, and as the second cylinder variation correction, the fuel injection amount corrected by the first cylinder variation correction is the second. It is preferable to recorrect each cylinder based on the inter-cylinder variation value. In this way, the air-fuel ratio variation between the cylinders can be corrected in two stages of the first cylinder-to-cylinder variation correction and the second cylinder-to-cylinder variation correction. Thus, exhaust emission can be effectively reduced.
[0027]
Further, when the variation in the intake fuel amount between the cylinders is very small (for example, when the individual difference of the fuel injection valve of each cylinder is small and the evaporative gas purge is not being executed), the variation among the first cylinders as in claim 12. As a correction, the control amount of the intake air variable means for each cylinder is corrected for each cylinder based on the first inter-cylinder variation value, and the intake air amount is corrected for each cylinder. The control amount of the cylinder-by-cylinder intake air variable means corrected by the first cylinder-to-cylinder variation correction may be recorrected for each cylinder based on the second cylinder-to-cylinder variation value. In this way, the variation in intake air amount between the cylinders can be corrected in two stages of the first cylinder correction and the second cylinder variation correction. It is possible to correct well, and it is possible to achieve both torque variation correction between cylinders and air-fuel ratio variation correction between cylinders. In addition, the ignition timing correction and the fuel injection amount correction are not necessary, and the problem of a reduction in fuel consumption can be avoided.
[0028]
By the way, since the combustion state of each cylinder changes for a while after changing the correction amount of the first inter-cylinder variation correction, immediately after the change of the correction amount of the first inter-cylinder variation correction, If the inter-cylinder variation value is calculated, the calculation accuracy of the second inter-cylinder variation value may decrease, and the correction accuracy of the second inter-cylinder variation correction may decrease.
[0029]
Therefore, as in claim 13, it is preferable to prohibit the calculation of the second inter-cylinder variation value until a predetermined period elapses after the correction amount change of the first inter-cylinder variation correction. In this manner, the first inter-cylinder variation value is avoided from being calculated in the period when the combustion state of each cylinder is changing immediately after the correction amount change of the first inter-cylinder variation correction is performed. Since it is possible to calculate the second inter-cylinder variation value after waiting for the combustion state of each cylinder to stabilize after a predetermined period has elapsed since the change in the correction amount of the inter-cylinder variation correction, the second inter-cylinder variation value is calculated. It is possible to improve the calculation accuracy of the value, and hence the correction accuracy of the second cylinder variation correction.
[0030]
Further, as in the fourteenth aspect, when the variation in the torque and / or the air-fuel ratio becomes equal to or less than a predetermined value due to the first inter-cylinder variation correction, the second inter-cylinder variation correction may be omitted. . In this way, when the torque correction or the air-fuel ratio is stabilized by the first cylinder-to-cylinder variation correction and the second cylinder-to-cylinder variation correction becomes unnecessary, the second cylinder-to-cylinder variation correction is not performed. That's it.
[0032]
The above claims 9 and 1 2 In this invention, the cylinder-specific intake air varying means for varying the intake air amount for each cylinder is claimed in claim 15 As described above, an independent variable intake valve mechanism may be provided for each cylinder, and the intake air amount may be varied for each cylinder by individually controlling the variable intake valve mechanism of each cylinder. Or claims 16 In this way, a variable intake valve mechanism is provided that can collectively change the valve control amount of the intake valves of all cylinders or multiple cylinders of the internal combustion engine, and the variable valve intake mechanism is driven at high speed for each intake stroke of each cylinder to control the valve. The amount of intake air may be varied for each cylinder by varying the amount. In either case, the intake air amount can be varied for each cylinder.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
<< 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. The air flow meter 14 is an air flow meter that can detect the backflow of intake air. 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.
[0034]
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.
[0035]
Further, the intake valve 28 and the exhaust valve 29 of the engine 11 are provided with variable valve lift mechanisms 30 and 31 for varying the valve lift amount, respectively. Further, the intake valve 28 and the exhaust valve 29 may each be provided with a variable valve timing mechanism that varies the valve timing (opening / closing timing). The exhaust valve 29 may be provided with only the variable valve timing mechanism without providing the variable valve lift mechanism 31.
[0036]
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 is provided. The cylinder block of the engine 11 includes a coolant 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). It is attached. Based on the output signal of the crank angle sensor 26, the crank angle and the engine speed are detected.
[0037]
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.
[0038]
Next, the configuration of the variable valve lift mechanism 30 of the intake valve 28 will be described based on FIG. Note that the variable valve lift mechanism 31 of the exhaust valve 29 has substantially the same configuration as the variable valve lift mechanism 30 of the intake valve 28, and thus description thereof is omitted.
[0039]
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.
[0040]
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.
[0041]
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 is changed. Change. Also, the lower end surface of the pressing cam 39 of the link arm 34 is formed with a base curved surface 39a with a curvature such that the pressing amount of the rocker arm 33 is 0 (the valve lift amount of the intake valve 28 is 0) on the left side. The pressing curved surface 39b is formed with such a curvature that the pressing amount of the rocker arm 33 increases (the valve lift amount of the intake valve 28 increases) as it goes rightward from the base curved surface 39a.
[0042]
In the high lift mode in which the valve lift amount of the intake valve 28 is increased, 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 moved rightward by the rotation of the control shaft 35. Let 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.
[0043]
On the other hand, in the low lift mode in which the valve lift amount of the intake valve 28 is reduced, 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 set to the left by the rotation of the control shaft 35. Move to. 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.
[0044]
In the variable valve lift mechanism 30 described above, if the control shaft 35 is rotated by the motor 41 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 is continuously moved, 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 (# 1 to # 4) can be continuously varied.
[0045]
The ECU 27 executes a variable valve control program (not shown) stored in the ROM to control the variable valve lift mechanism 30 of the intake valve 28 based on the accelerator opening, the engine operating state, etc. The amount of intake air is controlled by continuously varying the valve lift amount 28. In the case of a system using both the variable valve lift mechanism 30 and the variable valve timing mechanism, both the valve lift amount and the valve timing may be continuously varied to control the intake air amount.
[0046]
In addition, the ECU 27 executes each routine for correcting the variation between cylinders, which will be described later, thereby representing the variation in intake air amount of each cylinder based on information (intake air amount and intake pipe pressure) before combustion of the engine 11. One inter-cylinder variation value DEV1 is calculated, and a first inter-cylinder variation correction is executed based on the first inter-cylinder variation value DEV1, thereby correcting torque variation between cylinders and air-fuel ratio variation between cylinders. Then, after execution of the first inter-cylinder variation correction, a second value representing the variation in intake air amount and variation in intake fuel amount of each cylinder based on information after combustion of the engine 11 (combustion state and air-fuel ratio of exhaust gas). A cylinder-to-cylinder variation value DEV2 is calculated, and a second cylinder-to-cylinder variation correction is executed based on the second cylinder-to-cylinder variation value DEV2, thereby correcting torque variation between cylinders and air-fuel ratio variation between cylinders.
[0047]
Hereinafter, processing contents of each routine for correcting the variation between cylinders executed by the ECU 27 in the present embodiment (1) will be described.
[0048]
[Cylinder variation correction base routine]
The inter-cylinder variation correction base routine shown in FIG. 3 is executed at a predetermined cycle during engine operation. When this routine is started, first, in step 101, it is determined whether or not a condition for executing correction for variation among cylinders is satisfied. Here, the inter-cylinder variation correction execution condition is, for example, to satisfy all of the following conditions (1) to (3).
[0049]
(1) More than a predetermined time has passed after starting (that is, not in an unstable driving state immediately after starting)
(2) Not in a transient operation state (that is, in a steady operation state)
(3) The air-fuel ratio sensor 24 is in an active state.
[0050]
If all of the above conditions (1) to (3) are satisfied, the inter-cylinder variation correction execution condition is satisfied, but if any one of the conditions (1) to (3) is not satisfied, The inter-cylinder variation correction execution condition is not satisfied. If the output signal of the air-fuel ratio sensor 24 is not used when calculating the second cylinder variation value DEV2, the condition (3) may be omitted.
[0051]
If it is determined that the inter-cylinder variation correction execution condition is not satisfied, this routine is terminated without executing the subsequent inter-cylinder variation correction (steps 102 to 110).
[0052]
On the other hand, if it is determined in step 101 that the condition for executing cylinder-to-cylinder variation correction is satisfied, the cylinder-to-cylinder variation correction after step 102 is executed as follows. First, in step 102, a first inter-cylinder variation estimation routine shown in FIG. 4 described later is executed to calculate a first inter-cylinder variation value DEV1. In the present embodiment (1), the first inter-cylinder variation value DEV1 is calculated for each cylinder based on the intake air amount detected by the air flow meter 14.
[0053]
Thereafter, the process proceeds to step 103, and a first inter-cylinder variation correction routine shown in FIG. 10 to be described later is executed to execute the first inter-cylinder variation correction. In the present embodiment (1), as the first inter-cylinder variation correction, the torque variation between the cylinders is corrected by correcting the ignition timing for each cylinder based on the first inter-cylinder variation value DEV1 of each cylinder. To do.
[0054]
After this, the routine proceeds to step 104, where the corrected elapsed time counter CDEV that counts the elapsed time after the first cylinder variation correction correction amount change and the first cylinder variation correction correction amount change is “0”. It is determined whether or not a predetermined time KCDEV required for stabilizing the combustion state of each cylinder has elapsed since the correction amount of the first inter-cylinder variation correction was changed, depending on whether or not it has been reset to To do.
[0055]
Before the predetermined time KCDEV has elapsed since the correction amount of the first cylinder-to-cylinder variation correction was changed, the process proceeds to step 105, the post-correction elapsed time counter CDEV is incremented by "1", and then the process proceeds to step 106, where correction is performed. It is determined whether or not the count value of the post-elapsed time counter CDEV has exceeded a predetermined time KCDEV. If the count value of the post-correction elapsed time counter CDEV does not exceed the predetermined time KCDEV, this routine is terminated as it is.
[0056]
Thereafter, when it is determined in step 106 that the count value of the post-correction elapsed time counter CDEV has exceeded the predetermined time KCDEV, that is, the predetermined time KCDEV has elapsed since the correction amount of the first inter-cylinder variation correction was changed. At this point, the process proceeds to step 107, the post-correction elapsed time counter CDEV is reset to “0”, and then the process proceeds to step 108.
[0057]
By the processing in steps 104 to 107, the processing in step 109 (processing for calculating a second inter-cylinder variation value) described later until a predetermined time KCDEV has elapsed after the correction amount of the first inter-cylinder variation correction is changed. ) Is prohibited. The processing of these steps 104 to 107 plays a role as variation estimation prohibiting means in the claims.
[0058]
On the other hand, in step 104 described above, there is no change in the correction amount for the first inter-cylinder variation correction and the post-correction elapsed time counter CDEV is reset to “0”, that is, the correction amount for the first inter-cylinder variation correction. If it is determined that the predetermined time KCDEV has elapsed since the change of, the process proceeds from step 104 to step 108.
[0059]
In this step 108, it is determined whether or not both the torque of the engine 11 and the air-fuel ratio are stable. At this time, for example, it is determined whether or not the torque is stable (whether or not the variation in the cycle of the torque is equal to or less than a predetermined value) based on the behavior of the engine speed detected by the crank angle sensor 26, and the air-fuel ratio sensor. Based on the behavior of the air-fuel ratio detected at 24, it is determined whether or not the air-fuel ratio is stable (whether or not the variation in the cycle of the air-fuel ratio is not more than a predetermined value). It should be noted that depending on the combination of the first cylinder-to-cylinder variation correction and the second cylinder-to-cylinder variation correction, it is not always necessary to determine whether both the torque and the air-fuel ratio are stable. It may be determined whether one of the two is stable.
[0060]
If it is determined in step 108 that the torque or the air-fuel ratio is not stable, the routine proceeds to step 109, where a second inter-cylinder variation estimation routine shown in FIG. The value DEV2 is calculated. In the present embodiment (1), a second inter-cylinder variation value DEV2 is calculated for each cylinder based on the rotation fluctuation calculated based on the output signal of the crank angle sensor 26.
[0061]
Thereafter, the process proceeds to step 110, and a second inter-cylinder variation correction routine shown in FIG. 14 to be described later is executed to execute second inter-cylinder variation correction. In the present embodiment (1), as the second cylinder-to-cylinder variation correction, the fuel injection amount is corrected for each cylinder based on the second cylinder-to-cylinder variation value DEV2 of each cylinder, so that the air-fuel ratio variation among the cylinders is corrected. Correct.
[0062]
On the other hand, if it is determined in step 108 that the torque and the air-fuel ratio are stable, the first cylinder-to-cylinder variation correction reduces the air-fuel ratio variation between the cylinders and the torque variation between the cylinders. It is determined that it is not necessary to execute the second cylinder variation correction, the second cylinder variation estimation and the second cylinder variation correction are omitted, and this routine is terminated. The process of step 108 serves as a variation correction omission means in the claims.
[0063]
[First Cylinder Variation Estimation Routine]
The first cylinder variation estimation routine (step 102 in FIG. 3) shown in FIG. 4 calculates the first cylinder variation value DEV1 for each cylinder based on the intake air amount detected by the air flow meter 14. is there. This routine is repeatedly executed at a predetermined cycle (for example, 4 ms), and serves as a first cylinder-to-cylinder variation estimation unit in the claims.
[0064]
When this routine is started, first, in step 201, the output voltage VAFM after the filter process of the air flow meter 14 is read, and then the process proceeds to step 202, where a conversion map of the instantaneous intake air amount GAFM having the characteristics shown in FIG. To calculate the instantaneous intake air amount GAFM (instantaneous value of the intake air amount passing through the air flow meter 14) according to the current output voltage VAFM of the air flow meter 14.
[0065]
Thereafter, the process proceeds to step 203, and 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.
[0066]
Thereafter, the routine proceeds to step 204, where the intake air amount average value GGAave (#i) of each cylinder is calculated. Here, # i = # 1 to # 4.
When calculating the intake air amount average value GGAave (# 1) of the first cylinder # 1, a period of the crank angle counter CCRNK = 12 to 17, that is, a period corresponding to the intake stroke of the first cylinder # 1, for example, 6 The average value of the intake air amount instantaneous value GAFM of the batch is calculated.
[0067]
When calculating the intake air amount average value GGAave (# 2) of the second cylinder # 2, 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, for example, 6 The average value of the intake air amount instantaneous value GAFM of the batch is calculated.
[0068]
When calculating the intake air amount average value GGAave (# 3) of the third cylinder # 3, for example, 6 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 average value of the intake air amount instantaneous value GAFM of the batch is calculated.
[0069]
When calculating the intake air amount average value GGAave (# 4) of the fourth cylinder # 4, for example, 6 in the period corresponding to the crank angle counter CCRNK = 0 to 5, that is, the period corresponding to the intake stroke of the fourth cylinder # 4. The average value of the intake air amount instantaneous value GAFM of the batch is calculated.
[0070]
As shown in FIG. 9, in general, intake pulsation is generated in the intake pipe 12 of the engine 11 having a plurality of cylinders corresponding to the intake stroke of each cylinder. Therefore, the intake air amount detected by the air flow meter 14 is reduced. The waveform (the waveform of the output voltage VAFM) is a pulsation waveform corresponding to the intake stroke of each cylinder, that is, a pulsation waveform reflecting the intake air amount of each cylinder. Therefore, if the average value, maximum value, minimum value, amplitude value, area, etc. of the intake air amount detected by the air flow meter 14 are calculated for each period corresponding to the intake stroke of each cylinder, the intake air amount of each cylinder is reflected. Since the characteristic value of the pulsation waveform can be calculated, the first inter-cylinder variation value DEV1 reflecting the variation in the intake air amount of each cylinder can be calculated by using this characteristic value (for example, the average value). .
[0071]
Thereafter, the routine proceeds to step 205, where the average intake air amount value GGAave (#i) of each cylinder calculated in step 204 is smoothed to obtain the final intake air amount average value GAave (#i) of each cylinder. Ask for.
GAave (#i) = GAave (#i) old + k × {GGAave (#i) −GAave (#i) old}
Here, GAave (#i) is the current intake air amount average value, GAave (#i) old is the previous intake air amount average value, and k is the smoothing coefficient.
[0072]
Thereafter, in step 206, the first inter-cylinder variation value DEV1 (#i) of each cylinder is calculated by the following equation.
DEV1 (#i) = {GAave (#i) -AVEGAave} / AVEGAave
Here, AVEGAave is an average value of intake air average values GAave (# 1) to GAave (# 4) of all cylinders.
AVEGAave = {GAave (# 1) + …… + GAave (# 4)} / 4
[0073]
In the first inter-cylinder variation estimation routine shown in FIG. 4, the first inter-cylinder variation value DEV1 (#i) is calculated based on the intake air amount average value GAave (#i) of each cylinder. The first cylinder-to-cylinder variation value DEV1 (#i) may be calculated based on the maximum intake air amount GAmax (#i) and the minimum intake air amount GAmin (#i). Alternatively, the first cylinder variation value DEV1 (#i) may be calculated based on the intake air amount amplitude value GAwid (#i) of each cylinder. Further, the area of the intake air amount of each cylinder may be calculated.
[0074]
When the first inter-cylinder variation value DEV1 (#i) is calculated based on the maximum intake air amount GAmax (#i) of each cylinder, the processing after step 201 to step 203 in FIG. Proceeding to step 204a shown in FIG. 5, the maximum intake air amount GGAmax (#i) of each cylinder is calculated. In this case, the maximum value of the intake air amount instantaneous value GAFM in the period corresponding to the intake stroke of each cylinder is calculated as the maximum intake air amount value GGAmax (# 1) to GGAmax (# 4) of each cylinder.
[0075]
Thereafter, the routine proceeds to step 205a, where the intake air maximum value GGAmax (#i) of each cylinder is smoothed to obtain the final intake air maximum value GAmax (#i) of each cylinder.
GAmax (#i) = GAmax (#i) old + k × {GGAmax (#i) −GAmax (#i) old}
Here, GAmax (#i) old is the previous maximum amount of intake air.
[0076]
Then, in the next step 206a, the first inter-cylinder variation value DEV1 (#i) of each cylinder is calculated by the following equation.
DEV1 (#i) = {GAmax (#i) -AVEGAmax} / AVEGAmax
Here, AVEGAmax is an average value of the maximum intake air amount GAmax (# 1) to GAmax (# 4) of all cylinders.
AVEGAmax = {GAmax (# 1) + ...... + GAmax (# 4)} / 4
[0077]
On the other hand, when the first inter-cylinder variation value DEV1 (#i) is calculated based on the minimum intake air amount GAmin (#i) of each cylinder, the processing of step 201 to step 203 in FIG. 4 is executed. Then, the process proceeds to step 204b shown in FIG. 6 to calculate the minimum intake air amount GGAmin (#i) of each cylinder. In this case, the minimum value of the intake air amount instantaneous value GAFM in the period corresponding to the intake stroke of each cylinder is calculated as the minimum intake air amount value GGAmin (# 1) to GGAmin (# 4) of each cylinder. Note that the minimum intake air amount values GGAmin (# 1) to GGAmin (# 4) are set to negative values in order to match the variation direction with the intake air amount.
[0078]
In the next step 205b, the intake air minimum value GGAmin (#i) of each cylinder is smoothed to obtain the final intake air minimum value GAmin (#i) of each cylinder.
GAmin (#i) = GAmin (#i) old + k × {GGAmin (#i) −GAmin (#i) old}
Here, GAmin (#i) old is the previous minimum amount of intake air.
[0079]
Thereafter, the process proceeds to step 206b, and the first inter-cylinder variation value DEV1 (#i) of each cylinder is calculated by the following equation.
DEV1 (#i) = {GAmin (#i) −AVEGAmin} / AVEGAmin
Here, AVEGAmin is an average value of the minimum intake air amount values GAmin (# 1) to GAmin (# 4) of all cylinders.
AVEGAmin = {GAmin (# 1) + …… + GAmin (# 4)} / 4
[0080]
Further, when the first cylinder variation value DEV1 (#i) is calculated based on the intake air amount amplitude value GAwid (#i) of each cylinder, the processing of step 201 to step 203 in FIG. 4 is executed. Then, the process proceeds to step 204c shown in FIG. 7 to calculate the maximum intake air amount value GGAmax (#i) of each cylinder, and then proceeds to step 205c to calculate the minimum intake air amount value GGAmin (#i) of each cylinder.
[0081]
Thereafter, the routine proceeds to step 206c, where the intake air amount amplitude value GGAwid (#i) of each cylinder is calculated by the following equation.
GGAwid (#i) = GGAmax (#i)-GGAmin (#i)
[0082]
In the next step 207c, the intake air amount amplitude value GGAwid (#i) of each cylinder is smoothed to obtain the final intake air amount amplitude value GGAwid (#i) of each cylinder.
GAwid (#i) = GAwid (#i) old + k × {GGAwid (#i) −GAwid (#i) old}
Here, GAwid (#i) old is the previous intake air amount amplitude value.
[0083]
Thereafter, the process proceeds to step 208c, and the first inter-cylinder variation value DEV1 (#i) of each cylinder is calculated by the following equation.
DEV1 (#i) = {GAwid (#i) -AVEGAwid} / AVEGAwid
Here, AVEGAwid is an average value of intake air amount amplitude values GAwid (# 1) to GAwid (# 4) of all cylinders.
AVEGAwid = {GAwid (# 1) + …… + GAwid (# 4)} / 4
[0084]
It should be noted that two of the intake air amount average value GAave (#i), the intake air amount maximum value GAmax (#i), the intake air amount minimum value GAmin (#i), and the intake air amount amplitude value GAwid (#i). Based on the above, the first inter-cylinder variation value DEV1 (#i) may be calculated.
[0085]
[First Cylinder Variation Correction Routine]
The first cylinder-to-cylinder variation correction routine shown in FIG. 10 is a subroutine started in step 103 in FIG. 3, and corrects the ignition timing for each cylinder based on the first cylinder-to-cylinder variation value DEV1. Thus, the torque variation between the cylinders is corrected, and serves as the first cylinder variation correcting means in the claims.
[0086]
When this routine is started, first, in step 301, the first inter-cylinder variation values DEV1 (# 1) to DEV1 (# 4) of each cylinder are read, and then the process proceeds to step 302, in which the first The minimum value DEV1min is selected from among the cylinder-to-cylinder variation values DEV1 (# 1) to DEV1 (# 4).
[0087]
Thereafter, the routine proceeds to step 303, where a map of the basic correction amount FAOP1 of the ignition timing having the characteristics shown in FIG. 11 is searched, and the first inter-cylinder variation value DEV1 (#i) and the minimum value DEV1min are determined for each cylinder. A basic correction amount FAOP1 (#i) of the ignition timing according to the difference is calculated.
[0088]
The map of the ignition timing basic correction amount FAOP1 in FIG. 11 is such that the basic correction amount FAOP1 decreases (the ignition timing retardation amount increases) as the value of DEV1 (#i) -DEV1min increases. Only (torque down side) is set. Further, in a region where DEV1 (#i) −DEV1min is equal to or smaller than a predetermined value, the basic correction amount FAOP1 = 0 is set and the ignition timing is not corrected.
[0089]
Thereafter, the process proceeds to step 304, in which the engine rotational speed NE detected by the crank angle sensor 26 is read and the intake air amount GA detected by the air flow meter 14 is read. Then, the process proceeds to step 305, and the correction coefficient FAOP2 shown in FIG. And a correction coefficient FAOP2 (#i) corresponding to the current engine operating state (for example, engine speed NE and intake air amount GA) is calculated for each cylinder.
[0090]
Thereafter, the routine proceeds to step 306, where the basic correction amount FAOP1 (#i) of each cylinder is multiplied by the correction coefficient FAOP2 (#i) to obtain the ignition timing correction amount FAOP (#i) of each cylinder.
FAOP (#i) = FAOP1 (#i) × FAOP2 (#i)
[0091]
Thereafter, the process proceeds to step 307, and the ignition timing correction amount FAOP (#i) of each cylinder is added to the average ignition timing AOP of all cylinders before correction to obtain the final ignition timing AOP (#i) of each cylinder.
AOP (#i) = AOP + FAOP (#i)
[0092]
By the above processing, the ignition variation of each cylinder is retarded in accordance with the first inter-cylinder variation value DEV1 of each cylinder, and the torque of each cylinder is appropriately reduced to reduce the torque variation between the cylinders.
[0093]
In this routine, the torque variation between the cylinders is corrected by using only the torque reduction by correcting the retard of the ignition timing. Therefore, it is possible to prevent the ignition timing from being corrected to advance and exceeding the knock limit. If there is a margin on the advance side of the ignition timing, the torque variation between cylinders should be reduced by using both the torque up by the ignition timing advance correction and the torque down by the retard correction. Anyway.
[0094]
[Second Cylinder Variation Estimation Routine]
The second cylinder-to-cylinder variation estimation routine shown in FIG. 13 is a subroutine started at step 109 in FIG. 3, and the second cylinder-to-cylinder variation is based on the rotation fluctuation calculated based on the output signal of the crank angle sensor 26. The value DEV2 is calculated for each cylinder, and serves as second inter-cylinder variation estimation means in the claims.
[0095]
When this routine is started, first, at step 401, 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.
[0096]
Thereafter, the routine proceeds to step 402, where 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 403, a minimum value T30MIN (#i) and a maximum value T30MAX (#i) of T30 in a period corresponding to the combustion stroke of each cylinder are calculated.
[0097]
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.
[0098]
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.
[0099]
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.
[0100]
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.
[0101]
Thereafter, the process proceeds to step 404, where the rotational fluctuation ΔTT30 (#i) of each cylinder is calculated by the following equation.
ΔTT30 (#i) = T30MAX (#i) −T30MIN (#i)
The rotation fluctuation ΔTT30 (#i) of each cylinder calculated in this way is a value corresponding to the combustion torque of each cylinder.
[0102]
In the next step 405, the rotational fluctuation ΔTT30 (#i) of each cylinder calculated in step 404 is smoothed to obtain the final rotational fluctuation ΔT30 (#i) of each cylinder.
ΔT30 (#i) = ΔT30 (#i) old + k × {ΔTT30 (#i) −ΔT30 (#i) old}
Here, ΔT30 (#i) old is the previous rotation fluctuation.
[0103]
Thereafter, the process proceeds to step 406, and after calculating an average value ΔT30ave of the rotational fluctuations ΔT30 (# 1) to ΔT30 (# 4) of all the cylinders, the process proceeds to step 207 and the second inter-cylinder variation value DEV2 ( #i) is calculated by the following formula.
DEV2 (#i) = {ΔT30 (#i) −ΔT30ave} / ΔT30ave
[0104]
[Second Cylinder Variation Correction Routine]
The second cylinder-to-cylinder variation correction routine shown in FIG. 14 is a subroutine started in step 110 in FIG. In this routine, the second cylinder variation value DEV2 of each cylinder is used as the second cylinder variation correction when the second cylinder variation value DEV2 is calculated based on the rotational fluctuation ΔT30 (#i) of each cylinder. By correcting the fuel injection time (fuel injection amount) for each cylinder based on the above, the air-fuel ratio variation between the cylinders is corrected. As a second inter-cylinder variation correcting means in the claims, Play a role.
[0105]
When this routine is started, first, at step 501, the second inter-cylinder variation value DEV2 (#i) of each cylinder is read, and then the routine proceeds to step 502 where the basic fuel injection time with the characteristics shown in FIG. The map of the correction amount KTAU1 is searched, and the basic correction amount KTAU1 (#i) corresponding to the second inter-cylinder variation value DEV2 (#i) is calculated for each cylinder.
[0106]
The map of the basic correction amount KTAU1 in FIG. 15 is set so that the basic correction amount KTAU1 becomes smaller as the second inter-cylinder variation value DEV2 (#i) increases, but DEV2 (#i) becomes 0. In a predetermined area near, the basic correction amount KTAU1 = 1.0 is set, and the fuel injection time is not corrected.
[0107]
Thereafter, the process proceeds to step 503, and after reading the engine speed NE and the intake air amount GA, the process proceeds to step 504, where a map of the correction coefficient KTAU2 shown in FIG. A correction coefficient KTAU2 (#i) corresponding to (for example, the engine speed NE and the intake air amount GA) is calculated.
[0108]
In consideration of the fact that the inertial force increases and the rotational fluctuation ΔT30 decreases as the engine speed NE increases, the map of the correction coefficient KTAU2 in FIG. 16 shows that the correction coefficient KTAU2 increases as the engine speed NE increases. Is set to
[0109]
Thereafter, the process proceeds to step 505, where the basic correction amount KTAU1 (#i) of each cylinder is multiplied by the correction coefficient KTAU2 (#i) to obtain the fuel injection time correction coefficient KTAU (#i) of each cylinder.
KTAU (#i) = KTAU1 (#i) × KTAU2 (#i)
[0110]
In the next step 506, the average fuel injection time TAU of all cylinders before correction is multiplied by the fuel injection time correction coefficient KTAU (#i) of each cylinder to obtain the final fuel injection time TAU (#i) of each cylinder. Ask for.
TAU (#i) = TAU × KTAU (#i)
By the above process, the fuel injection amount of each cylinder is corrected in accordance with the second inter-cylinder variation value DEV2 of each cylinder, thereby reducing the air-fuel ratio variation between the cylinders.
[0111]
An execution example of the cylinder-to-cylinder variation correction of this embodiment (1) described above will be described with reference to the time chart shown in FIG.
When the inter-cylinder variation correction execution condition is satisfied and the correction execution flag is turned on, first, the first inter-cylinder variation value DEV1 (# 1) to DEV1 of each cylinder is based on the intake air amount detected by the air flow meter 14. Calculate (# 4). In the first cylinder-to-cylinder variation correction, the ignition timing correction amounts FAOP (# 1) to FAOP (for each cylinder are based on the first cylinder-to-cylinder variation values DEV1 (# 1) to DEV1 (# 4) for each cylinder. # 4) is calculated, and torque variations among the cylinders are corrected by correcting the ignition timing of each cylinder using these ignition timing correction amounts FAOP (# 1) to FAOP (# 4).
[0112]
Thereafter, after the ignition timing is corrected by the first inter-cylinder variation correction (after the ignition timing correction amount FAOP is changed), a predetermined time KCDEV required for the combustion state of each cylinder to stabilize has elapsed. Based on the rotation fluctuation ΔT30 (#i) calculated based on the output signal of the crank angle sensor 26, second cylinder variation values DEV2 (# 1) to DEV2 (# 4) of each cylinder are calculated. In the second cylinder variation correction, the fuel injection time correction coefficient KTAU (# 1) to KTAU for each cylinder based on the second cylinder variation values DEV2 (# 1) to DEV2 (# 4) for each cylinder. (# 4) is calculated, and the fuel injection time of each cylinder is corrected using these fuel injection time correction coefficients KTAU (# 1) to KTAU (# 4) to correct the air-fuel ratio variation among the cylinders.
[0113]
With the above processing, the indicated mean effective pressure of each cylinder can be made substantially equal to suppress the occurrence of rotational fluctuations, drivability can be improved, and the air-fuel ratio of each cylinder can be made almost uniform to reduce the exhaust gas. The air-fuel ratio can be controlled in the purification window of the catalyst 23, and exhaust emission can be reduced.
[0114]
In the present embodiment (1) described above, correction of torque variation between cylinders and correction of air-fuel ratio variation between cylinders are performed separately for the first cylinder-to-cylinder variation correction and the second cylinder-to-cylinder variation correction. Therefore, even when the intake air amount variation between cylinders is large and the torque variation or air-fuel ratio variation between cylinders is large, such as when the intake air amount control by variable intake valve control is low, Both torque variation correction and air-fuel ratio variation correction between cylinders can be achieved, and both torque variation and air-fuel ratio variation between cylinders can be reduced.
[0115]
By the way, when the variation in intake air amount is large (when the variation in torque between the cylinders or the variation in air-fuel ratio is large) as in the case of a low load of intake air amount control by variable intake valve control, the first inter-cylinder variation correction is performed. When the air-fuel ratio variation between cylinders is corrected, the torque variation between the cylinders is large. Therefore, it is necessary to calculate the second cylinder variation value in a state where the rotation fluctuations of each cylinder interfere with each other. The calculation accuracy of the second inter-cylinder variation value DEV2 based on the variation ΔT30 (#i) decreases, and the correction accuracy of the second inter-cylinder variation correction decreases.
[0116]
In this regard, in the present embodiment (1), the torque variation between cylinders is corrected by the first inter-cylinder variation correction, and the air-fuel ratio variation between cylinders is corrected by the second inter-cylinder variation correction. Even if the second cylinder variation value DEV2 is calculated based on the rotational fluctuation ΔT30 (#i) of each cylinder, the calculation accuracy can be prevented from being lowered, and the second cylinder variation correction can be corrected. A decrease in accuracy can be prevented, and correction of torque variation between cylinders and correction of variation in air-fuel ratio between cylinders can be achieved more effectively.
[0117]
Furthermore, in the present embodiment (1), the calculation of the second inter-cylinder variation value DEV2 is prohibited until the predetermined time KCDEV has elapsed since the correction amount was changed in the first inter-cylinder variation correction. The first inter-cylinder variation is avoided by calculating the second inter-cylinder variation value DEV2 during the period when the combustion state of each cylinder is changing immediately after the correction amount is changed by the first inter-cylinder variation correction. The second inter-cylinder variation value DEV2 can be calculated after waiting for the predetermined time KCDEV to elapse after the correction amount is changed by the correction and the combustion state of each cylinder to become stable, and the second inter-cylinder variation value to be calculated. It is possible to improve the calculation accuracy of the value DEV2, and thus the correction accuracy of the second cylinder variation correction.
[0118]
Further, in the present embodiment (1), when the torque or air-fuel ratio of the engine 11 is stabilized by the first inter-cylinder variation correction, the torque variation between the cylinders or the inter-cylinder air variation is corrected by the first inter-cylinder variation correction. Since the variation in the fuel ratio has been reduced, it is determined that there is no need to execute the second cylinder variation correction, and the second cylinder variation estimation and the second cylinder variation correction are omitted. It is not necessary to execute the second cylinder variation estimation or the second cylinder variation correction.
[0119]
<< Embodiment (2) >>
In the above embodiment (1), the first inter-cylinder variation value DEV1 is calculated for each cylinder based on the intake air amount detected by the air flow meter 14, but the embodiment of the present invention shown in FIGS. In 2), the first cylinder variation value DEV1 is calculated for each cylinder based on the intake pipe pressure detected by the intake pipe pressure sensor 18.
[0120]
[First Cylinder Variation Estimation Routine]
The first inter-cylinder variation estimation routine shown in FIG. 18 executed by the ECU 27 in this embodiment (2) is repeatedly executed at a predetermined cycle (for example, 4 ms). When this routine is started, first, in step 601, the output voltage VMAP after the filter processing of the intake pipe pressure sensor 18 is read. Then, the routine proceeds to step 602, where the intake pipe pressure instantaneous value PMAP having the characteristics shown in FIG. The map is searched, and the intake pipe pressure instantaneous value PMAP corresponding to the current output voltage VMAP of the intake pipe pressure sensor 18 is calculated.
[0121]
Thereafter, the process proceeds to step 603, and after the count value of the crank angle counter CCRNK is read, the process proceeds to step 604, and the intake pipe pressure average value PPMave (#i) of each cylinder is calculated.
[0122]
When calculating the intake pipe pressure average value PPMave (# 1) of the first cylinder # 1, for example, six intake pipes in the period corresponding to the intake stroke of the first cylinder # 1 (period of CCRNK = 12 to 17) The average value of the instantaneous pressure value PMAP is calculated.
[0123]
In calculating the intake pipe pressure average value PPMave (# 2) of the second cylinder # 2, for example, six intake pipes in a period corresponding to the intake stroke of the second cylinder # 2 (period of CCRNK = 6 to 11). The average value of the instantaneous pressure value PMAP is calculated.
[0124]
In calculating the intake pipe pressure average value PPMave (# 3) of the third cylinder # 3, for example, six intake pipes in a period corresponding to the intake stroke of the third cylinder # 3 (period of CCRNK = 18 to 23). The average value of the instantaneous pressure value PMAP is calculated.
[0125]
When calculating the intake pipe pressure average value PPMave (# 4) of the fourth cylinder # 4, for example, six intake pipes in the period corresponding to the intake stroke of the fourth cylinder # 4 (period of CCRNK = 0 to 5). The average value of the instantaneous pressure value PMAP is calculated.
The intake pipe pressure average values PPMave (# 1) to PPMave (# 4) are set to negative values in order to match the intake air amount and the variation direction.
[0126]
Similar to the waveform of the intake air amount detected by the air flow meter 14 (the waveform of the output voltage VAFM), the waveform of the intake pipe pressure detected by the intake pipe pressure sensor 18 (the waveform of the output voltage VMAP) is also the intake stroke of each cylinder. , That is, a pulsation waveform reflecting the intake air amount of each cylinder. Therefore, if the average value, maximum value, minimum value, amplitude value, area, etc. of the intake pipe pressure detected by the intake pipe pressure sensor 18 are calculated for each period corresponding to the intake stroke of each cylinder, the intake air amount of each cylinder is calculated. Since the characteristic value of the pulsation waveform reflecting the above can be calculated, if this characteristic value (for example, the average value) is used, the first inter-cylinder variation value DEV1 reflecting the intake air amount variation of each cylinder can be calculated. Can do.
[0127]
Thereafter, the process proceeds to step 605, where the average intake pipe pressure value PPMave (#i) of each cylinder calculated in step 604 is smoothed to obtain the final intake pipe pressure average value PMave (#i) of each cylinder. Ask for.
PMave (#i) = PMave (#i) old + k × {PPMave (#i) −PMave (#i) old}
Here, PMave (#i) old is the previous intake pipe pressure average value.
[0128]
In the next step 606, the first inter-cylinder variation value DEV1 (#i) of each cylinder is calculated by the following equation.
DEV1 (#i) = {PMave (#i) -AVEPMave} / AVEPMave
Here, AVEPMave is an average value of the intake pipe pressure average values PMave (# 1) to PMave (# 4) of all cylinders.
[0129]
In the first inter-cylinder variation estimation routine shown in FIG. 18, the first inter-cylinder variation value DEV1 (#i) is calculated based on the intake pipe pressure average value PMave (#i) of each cylinder. The first inter-cylinder variation value DEV1 (#i) may be calculated based on the intake pipe pressure maximum value PMmax (#i) and the intake pipe pressure minimum value PMmin (#i). Alternatively, the first inter-cylinder variation value DEV1 (#i) may be calculated based on the intake pipe pressure amplitude value PMwid (#i) of each cylinder. Further, the area of the intake pipe pressure of each cylinder may be calculated.
[0130]
In the case of calculating the first inter-cylinder variation value DEV1 (#i) based on the intake pipe pressure maximum value PMmax (#i) of each cylinder, after performing the processing of step 601 to step 603 in FIG. Proceeding to step 604a shown in FIG. 19, the intake pipe pressure maximum value PPMmax (#i) of each cylinder is calculated. In this case, the maximum value of the intake pipe pressure instantaneous value PMAP in the period corresponding to the intake stroke of each cylinder is calculated as the intake pipe pressure maximum value PPMmax (# 1) to PPMmax (# 4) of each cylinder.
[0131]
Thereafter, the routine proceeds to step 605a, where the intake pipe pressure maximum value PPMmax (#i) of each cylinder is smoothed to obtain the final intake pipe pressure maximum value PMmax (#i) of each cylinder.
PMmax (#i) = PMmax (#i) old + k * {PPMmax (#i) -PMmax (#i) old}
Here, PMmax (#i) old is the previous intake pipe pressure maximum value.
[0132]
In the next step 606a, the first inter-cylinder variation value DEV1 (#i) of each cylinder is calculated by the following equation.
DEV1 (#i) = {PMmax (#i) -AVEPMmax} / AVEPMmax
Here, AVEPMmax is an average value of the intake pipe pressure maximum values PMmax (# 1) to PMmax (# 4) of all cylinders.
[0133]
On the other hand, when the first inter-cylinder variation value DEV1 (#i) is calculated based on the intake pipe pressure minimum value PMmin (#i) of each cylinder, the processing of step 601 to step 603 in FIG. 18 is executed. Then, the process proceeds to step 604b shown in FIG. 20, and the intake pipe pressure minimum value PPMmin (#i) of each cylinder is calculated. In this case, the minimum value of the intake pipe pressure instantaneous value PMAP in the period corresponding to the intake stroke of each cylinder is calculated as the minimum intake pipe pressure value PPMmin (# 1) to PPMmin (# 4) of each cylinder. The intake pipe pressure minimum values PPMmin (# 1) to PPMmin (# 4) are set to negative values in order to match the intake pipe pressure and the variation direction.
[0134]
Thereafter, the process proceeds to step 605b, and the intake pipe pressure minimum value PPMmin (#i) of each cylinder is smoothed to obtain the final intake pipe pressure minimum value PMmin (#i) of each cylinder.
PMmin (#i) = PMmin (#i) old + k × {PPMmin (#i) −PMmin (#i) old}
Here, PMmin (#i) old is the previous minimum value of the intake pipe pressure.
[0135]
Thereafter, the process proceeds to step 606b, and the first inter-cylinder variation value DEV1 (#i) of each cylinder is calculated by the following equation.
DEV1 (#i) = {PMmin (#i) −AVEPMmin} / AVEPMmin
Here, AVEPMmin is an average value of the intake pipe pressure minimum values PMmin (# 1) to PMmin (# 4) of all cylinders.
[0136]
Further, when the first cylinder variation value DEV1 (#i) is calculated based on the intake pipe pressure amplitude value PMwid (#i) of each cylinder, the processing of step 601 to step 603 in FIG. 18 is executed. Then, the process proceeds to step 604c shown in FIG. 21, and the intake pipe pressure maximum value PPMmax (#i) of each cylinder is calculated. Then, the process proceeds to step 605c, and the intake pipe pressure minimum value PPMmin (#i) of each cylinder is calculated.
[0137]
Thereafter, the process proceeds to step 606c, and the intake pipe pressure amplitude value PPMwid (#i) of each cylinder is calculated by the following equation.
PPMwid (#i) = PPMmax (#i) −PPMmin (#i)
[0138]
Thereafter, the process proceeds to step 607c, where the intake pipe pressure amplitude value PPMwid (#i) of each cylinder is smoothed to obtain the final intake pipe pressure amplitude value PMwid (#i) of each cylinder.
PMwid (#i) = PMwid (#i) old + k × {PPMwid (#i) −PMwid (#i) old}
Here, PMwid (#i) old is the previous intake pipe pressure amplitude value.
[0139]
Then, in the next step 608c, the first inter-cylinder variation value DEV1 (#i) of each cylinder is calculated by the following equation.
DEV1 (#i) = {PMwid (#i) -AVEPMwid} / AVEPMwid
Here, AVEPMwid is an average value of the intake pipe pressure amplitude values PMwid (# 1) to PMwid (# 4) of all cylinders.
[0140]
Two of the intake pipe pressure average value PMave (#i), the intake pipe pressure maximum value PMmax (#i), the intake pipe pressure minimum value PMmin (#i), and the intake pipe pressure amplitude value PMwid (#i) Based on the above, the first inter-cylinder variation value DEV1 (#i) may be calculated.
[0141]
<< Embodiment (3) >>
In general, the air flow meter 14 is disposed upstream of the throttle valve 15, and the intake pipe pressure sensor 18 is disposed downstream of the throttle valve 15. When the throttle valve 15 is closed from the fully opened position, the intake pulsation is reduced on the upstream side of the throttle valve 15, so that the first cylinder-to-cylinder interval is determined based on the output of the air flow meter 14 arranged on the upstream side of the throttle valve 15. If the variation value DEV1 is calculated, the calculation accuracy of the first inter-cylinder variation value DEV1 may decrease when the throttle valve 15 is closed.
[0142]
Accordingly, in the embodiment (3) of the present invention shown in FIG. 23, the minimum value PMmin (#i) of the intake pipe pressure detected by the intake pipe pressure sensor 18 when the throttle opening degree TA is smaller than the predetermined opening degree KTA. By calculating the first inter-cylinder variation value DEV1 based on this, the calculation accuracy of the first inter-cylinder variation value DEV1 when the throttle valve 15 is closed is ensured.
[0143]
[First Cylinder Variation Estimation Routine]
In the present embodiment (3), a first inter-cylinder variation estimation routine shown in FIG. 23 is executed. When this routine is started, first, at step 701, the count value of the crank angle counter CCRNK is read, and then the routine proceeds to step 702, where the throttle valve is determined by whether or not the throttle opening TA is smaller than the predetermined opening KTA. It is determined whether 15 is closed. Whether the throttle valve 15 is closed may be determined based on whether the intake pipe pressure PM (for example, the average intake pipe pressure of all cylinders) is smaller than a predetermined pressure KPM (for example, atmospheric pressure). .
[0144]
When it is determined that the throttle opening degree TA is smaller than the predetermined opening degree KTA (or the intake pipe pressure PM is smaller than the predetermined pressure KPM), the processing of steps 703 to 707 is executed. First, the intake pipe pressure sensor An intake pipe pressure instantaneous value PMAP corresponding to the output voltage VMAP of 18 is calculated (steps 703 and 704).
[0145]
Thereafter, the minimum intake pipe pressure value PPMmin (#i) of each cylinder is calculated, and this is smoothed to obtain the final minimum intake pipe pressure value PMmin (#i) of each cylinder. A first inter-cylinder variation value DEV1 (#i) of each cylinder is calculated based on the minimum intake pipe pressure value PMmin (#i) of the cylinder (steps 705 to 707).
[0146]
On the other hand, if it is determined in step 702 that the throttle opening degree TA is greater than or equal to the predetermined opening degree KTA (or the intake pipe pressure PM is greater than or equal to the predetermined pressure KPM), that is, the throttle valve 15 is controlled at or near the fully open position. If YES in step 706, the processing in steps 706 to 712 is executed. First, the intake air amount instantaneous value GAFM corresponding to the output voltage VAFM of the air flow meter 14 is calculated (steps 708 and 709).
[0147]
Thereafter, the maximum intake air amount GGAmax (#i) of each cylinder is calculated, and this is smoothed to obtain the final maximum intake air amount GAmax (#i) of each cylinder. Based on the maximum intake air amount GAmax (#i), the first cylinder variation value DEV1 (#i) of each cylinder is calculated (steps 710 to 712).
[0148]
In this routine, when it is determined that the throttle opening TA is equal to or larger than the predetermined opening KTA (or the intake pipe pressure PM is equal to or larger than the predetermined pressure KPM), the routine is based on the maximum intake air amount GAmax (#i) of each cylinder. The first inter-cylinder variation value DEV1 (#i) of each cylinder is calculated. However, the present invention is not limited to this, and the intake air amount average value GAave (#i) and the intake air amount maximum value GAmax (#i) are not limited thereto. ) The first inter-cylinder variation value DEV1 (#i) is calculated based on one or more of the intake air amount minimum value GAmin (#i) and the intake air amount amplitude value GAwid (#i). You may do it. Alternatively, two of the intake pipe pressure average value PMave (#i), the intake pipe pressure maximum value PMmax (#i), the intake pipe pressure minimum value PMmin (#i), and the intake pipe pressure amplitude value PMwid (#i) The first inter-cylinder variation value DEV1 (#i) may be calculated based on one or more. Instead of the intake pipe pressure average value PMave (#i), the area of the intake pipe pressure of each cylinder may be calculated.
[0149]
In the present embodiment (3) described above, when the throttle opening degree TA is smaller than the predetermined opening degree KTA (or the intake pipe pressure PM is smaller than the predetermined pressure KPM), the throttle opening 15 is disposed downstream of the throttle valve 15. Since the first cylinder-to-cylinder variation value DEV1 (#i) is calculated based on the intake pipe pressure minimum value PMmin (#i) detected by the intake pipe pressure sensor 18, it is always on the upstream side of the throttle valve 15. Compared with the case where the first cylinder variation value DEV1 (#i) is calculated based on the output of the arranged air flow meter 14, the first cylinder variation value (#i) when the throttle valve 15 is closed. ) Calculation accuracy can be improved. In addition, when the throttle valve 15 is closed, the intake pipe pressure fluctuates to the negative side due to the intake of air into each cylinder. Therefore, the first inter-cylinder variation value is obtained by using the intake pipe pressure minimum value PMmin (#i). The calculation accuracy of (#i) can be further increased.
[0150]
<< Embodiment (4) >>
In the embodiment (1), the second inter-cylinder variation value DEV2 is calculated for each cylinder based on the rotational fluctuation. However, in the embodiment (4) of the present invention shown in FIGS. Based on the air-fuel ratio, the second cylinder variation value DEV2 is calculated for each cylinder.
[0151]
In the present embodiment (4), a second inter-cylinder variation estimation routine shown in FIG. 24 and a second inter-cylinder variation correction routine shown in FIG. 26 are executed.
[0152]
[Second Cylinder Variation Estimation Routine]
The second inter-cylinder variation estimation routine shown in FIG. 24 calculates the second inter-cylinder variation value DEV2 for each cylinder based on the air-fuel ratio detected by the air-fuel ratio sensor 24 as follows.
[0153]
When this routine is started, first, at step 801, the output AF of the air-fuel ratio sensor 24 is read, and then the routine proceeds to step 802 where the count value of the crank angle counter CCRNK is read.
[0154]
Thereafter, the routine proceeds to step 803 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 intake air amount GA), the exhaust system delay time DELY shown in FIG. A delay time DELY corresponding to the engine operating state (for example, the engine speed NE and the intake air amount GA) is calculated.
[0155]
In the next step 804, 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 AAF (#i) of each cylinder is calculated.
[0156]
Thereafter, the process proceeds to step 805, and the air-fuel ratio average value AAF (#i) of each cylinder calculated in step 804 is smoothed to obtain the final air-fuel ratio average value AF (#i) of each cylinder.
AF (#i) = AF (#i) old + k * {AAF (#i) -AF (#i) old}
Here, AF (#i) old is the previous air-fuel ratio average value.
[0157]
Thereafter, the process proceeds to step 806, and after calculating the average value AFave of the air-fuel ratio average values AF (# 1) to AF (# 4) of all the cylinders, the process proceeds to step 807 and the second inter-cylinder variation value of each cylinder. DEV2 (#i) is calculated by the following equation.
[0158]
DEV2 (#i) = {AF (#i) -AFave} / AFave
[Second Cylinder Variation Correction Routine]
The second inter-cylinder variation correction routine shown in FIG. 26 is the second inter-cylinder variation correction when the second inter-cylinder variation value DEV2 is calculated based on the air-fuel ratio of each cylinder. By correcting the fuel injection time (fuel injection amount) for each cylinder based on the inter-cylinder variation value DEV2, the air-fuel ratio variation among the cylinders is corrected.
[0159]
When this routine is started, first, in step 901, the second inter-cylinder variation value DEV2 (#i) of each cylinder is read, and then the process proceeds to step 902, where the second inter-cylinder variation value DEV2 of each cylinder. Using (#i), the fuel injection time correction coefficient KTAU1 (#i) of each cylinder is calculated by the following equation.
KTAU (#i) = DEV2 (#i) +1
[0160]
Thereafter, the process proceeds to step 903, where the average fuel injection time TAU of all cylinders before correction is multiplied by the fuel injection time correction coefficient KTAU (#i) of each cylinder, and the final fuel injection time TAU (#i) of each cylinder. Ask for.
TAU (#i) = TAU × KTAU (#i)
[0161]
By the above processing, the fuel injection amount of each cylinder is corrected according to the second inter-cylinder variation value DEV2 of each cylinder (see the parentheses in FIG. 17), thereby reducing the air-fuel ratio variation between the cylinders.
[0162]
Even in the case of the present embodiment (4) described above, the same effects as those of the embodiment (1) can be obtained.
[0163]
<< Embodiment (5) >>
In each of the above embodiments (1) to (4), the torque variation between the cylinders is corrected by correcting the ignition timing for each cylinder by the first inter-cylinder variation correction, and the second inter-cylinder variation correction is performed. The variation in the air-fuel ratio between the cylinders is corrected by correcting the fuel injection time (fuel injection amount) for each cylinder. On the contrary, the embodiment of the present invention shown in FIGS. ), The fuel injection time (fuel injection amount) is corrected for each cylinder by the first inter-cylinder variation correction, thereby correcting the air-fuel ratio variation between the cylinders, and the second inter-cylinder variation correction for each cylinder. By correcting the ignition timing, torque variation between cylinders is corrected.
[0164]
In the present embodiment (5), a first inter-cylinder variation correction routine shown in FIG. 27 and a second inter-cylinder variation correction routine shown in FIG. 28 are executed.
[0165]
[First Cylinder Variation Correction Routine]
The first inter-cylinder variation correction routine shown in FIG. 27 corrects the fuel injection time (fuel injection amount) for each cylinder on the basis of the first inter-cylinder variation value DEV1 of each cylinder. This is to correct the variation in the fuel ratio.
[0166]
When this routine is started, first, in step 1001, the first inter-cylinder variation value DEV1 (#i) of each cylinder is read, and then the process proceeds to step 1002, where the first inter-cylinder variation value DEV1 of each cylinder is read. Using (#i), the fuel injection time correction coefficient FTAU1 (#i) of each cylinder is calculated by the following equation.
FTAU (#i) = DEV1 (#i) +1
[0167]
Thereafter, the routine proceeds to step 1003, where the average fuel injection time TAU of all cylinders before correction is multiplied by the fuel injection time correction coefficient FTAU (#i) of each cylinder, and the final fuel injection time TAU (#i) of each cylinder. Ask for.
TAU (#i) = TAU × FTAU (#i)
By the above processing, the air-fuel ratio variation among the cylinders is reduced by correcting the fuel injection amount of each cylinder according to the first inter-cylinder variation value DEV1 of each cylinder.
[0168]
[Second Cylinder Variation Correction Routine]
The second cylinder-to-cylinder variation correction routine shown in FIG. 28 is the second cylinder-to-cylinder variation correction when the second cylinder-to-cylinder variation value DEV2 is calculated based on the rotation variation of each cylinder. By correcting the ignition timing for each cylinder based on the inter-cylinder variation value DEV2, the torque variation between the cylinders is corrected.
[0169]
When this routine is started, first, in step 1101, the second inter-cylinder variation value DEV2 (#i) of each cylinder is read. Then, the process proceeds to step 1102, and the second inter-cylinder variation value DEV2 of each cylinder. The minimum value DEV2min is selected from (# 1) to DEV2 (# 4).
[0170]
In the next step 1103, a map of the ignition timing basic correction amount KAOP1 having the characteristics shown in FIG. 29 is retrieved, and the second inter-cylinder variation value DEV2 (#i) and the minimum value DEV2min are calculated for each cylinder. A basic correction amount KAOP1 (#i) corresponding to the difference is calculated.
[0171]
Thereafter, the process proceeds to step 1104, and after reading the engine speed NE and the intake air amount GA, the process proceeds to step 1105, where a map of the correction coefficient KAOP2 shown in FIG. A correction coefficient KAOP2 (#i) corresponding to (for example, engine speed NE and intake air amount GA) is calculated.
[0172]
Thereafter, the process proceeds to step 1106, where the basic correction amount KAOP1 (#i) of each cylinder is multiplied by the correction coefficient KAOP2 (#i) to obtain the ignition timing correction amount KAOP (#i) of each cylinder.
KAOP (#i) = KAOP1 (#i) × KAOP2 (#i)
In the next step 1107, the ignition timing correction amount KAOP (#i) of each cylinder is added to the average ignition timing AOP of all cylinders before correction to obtain the final ignition timing AOP (#i) of each cylinder.
AOP (#i) = AOP + KAOP (#i)
[0173]
With the above processing, the torque variation between the cylinders is reduced by reducing the torque by retarding the ignition timing of each cylinder according to the second inter-cylinder variation value DEV2 of each cylinder. If there is a margin on the advance side of the ignition timing, torque variation between cylinders can be reduced by using both torque increase by ignition timing advance angle correction and torque decrease by retard angle correction. good.
[0174]
In the present embodiment (5) described above, as shown in the time chart of FIG. 31, in the first inter-cylinder variation correction, the first inter-cylinder variation values DEV1 (# 1) to DEV1 (# 4) of each cylinder. ) To calculate the fuel injection time correction coefficients FTAU (# 1) to FTAU (# 4) of each cylinder, and use these fuel injection time correction coefficients FTAU (# 1) to FTAU (# 4) to calculate each cylinder. The variation in the air-fuel ratio among the cylinders is corrected by correcting the fuel injection time.
[0175]
Thereafter, in the second cylinder variation correction, the ignition timing correction amount KAOP (# 1) to KAOP of each cylinder based on the second cylinder variation values DEV2 (# 1) to DEV2 (# 4) of each cylinder. (# 4) is calculated and the ignition timing of each cylinder is corrected using these ignition timing correction amounts KAOP (# 1) to KAOP (# 4), thereby correcting the torque variation between the cylinders.
[0176]
When the intake air amount variation between cylinders is relatively small, such as when the intake air amount control by variable intake valve control is at medium or high load or when the intake air amount control by throttle control is In the case of small), even if the air-fuel ratio variation between the cylinders is corrected by the first cylinder-to-cylinder variation correction, the torque variation between the cylinders is small. Therefore, even if the second inter-cylinder variation value DEV2 is calculated based on the rotational fluctuation of each cylinder, the second inter-cylinder variation value DEV can be calculated with high accuracy. Thus, the torque variation between cylinders can be accurately corrected by the second variation correction between cylinders. This embodiment (5) is particularly effective when it is desired to suppress torque fluctuations while giving priority to air-fuel ratio control (exhaust emission reduction).
[0177]
<< Embodiment (6) >>
In the embodiment (6) of the present invention shown in FIG. 32, the torque variation between the cylinders is corrected by correcting the ignition timing for each cylinder by the first cylinder-to-cylinder variation correction, and further the second cylinder-to-cylinder variation. By correcting, the ignition timing of each cylinder is corrected again.
In the present embodiment (6), the first inter-cylinder variation correction routine shown in FIG. 10 and the second inter-cylinder variation correction routine shown in FIG. 28 are executed.
[0178]
In this case, as shown in the time chart of FIG. 32, in the first inter-cylinder variation correction, ignition of each cylinder is performed based on the first inter-cylinder variation values DEV1 (# 1) to DEV1 (# 4) of each cylinder. The timing correction amounts FAOP (# 1) to FAOP (# 4) are calculated, and the ignition timing of each cylinder is corrected using these ignition timing correction amounts FAOP (# 1) to FAOP (# 4). Torque variation is corrected.
[0179]
Thereafter, in the second cylinder-to-cylinder variation correction, the ignition timing correction amounts KAOP (# 1) to KAOP for each cylinder based on the second cylinder-to-cylinder variation values DEV2 (# 1) to DEV2 (# 4) for each cylinder. (# 4) is calculated, and using these ignition timing correction amounts KAOP (# 1) to KAOP (# 4), the ignition timing of each cylinder corrected by the first inter-cylinder variation correction is recorrected (FIG. 28), the variation in torque between the cylinders is corrected with higher accuracy.
[0180]
Emphasis on torque fluctuation suppression (improvement of drivability) when the intake air amount variation is relatively small, such as during intake / intake control with variable intake valve control during medium / high loads or intake air amount control with throttle control In this case, as in this embodiment (6), the torque variation between the cylinders is corrected by correcting the ignition timing of each cylinder by the first inter-cylinder variation correction, and further, the second inter-cylinder variation correction is performed. If the ignition timing of each cylinder is re-corrected, the torque variation between the cylinders can be corrected in two stages of the first cylinder-to-cylinder variation correction and the second cylinder-to-cylinder variation correction. The variation can be corrected with higher accuracy, and the effect of improving drivability can be enhanced.
[0181]
<< Embodiment (7) >>
In the embodiment (7) of the present invention shown in FIG. 33, the variation in the air-fuel ratio between the cylinders is corrected by correcting the fuel injection time (fuel injection amount) for each cylinder by the first cylinder-to-cylinder variation correction. The fuel injection time of each cylinder is recorrected by the second cylinder-to-cylinder variation correction.
[0182]
In this embodiment (7), the first inter-cylinder variation correction routine shown in FIG. 27 and the second inter-cylinder variation correction routine shown in FIG. 14 (or the second inter-cylinder variation correction routine shown in FIG. 26). Execute.
[0183]
In this case, as shown in the time chart of FIG. 33, in the first inter-cylinder variation correction, the fuel of each cylinder is based on the first inter-cylinder variation values DEV1 (# 1) to DEV1 (# 4) of each cylinder. Calculate injection time correction coefficients FTAU (# 1) to FTAU (# 4), and correct the fuel injection time of each cylinder using these fuel injection time correction coefficients FTAU (# 1) to FTAU (# 4) To correct the air-fuel ratio variation between cylinders.
[0184]
Thereafter, in the second cylinder-to-cylinder correction, the fuel injection time correction coefficient KTAU (# 1) of each cylinder is calculated based on the second cylinder-to-cylinder variation value DEV2 (# 1) to DEV2 (# 4) of each cylinder. KTAU (# 4) is calculated, and the fuel injection time of each cylinder corrected by the first inter-cylinder variation correction is recorrected using these fuel injection time correction coefficients KTAU (# 1) to KTAU (# 4). By doing this (see the parentheses in step 506 in FIG. 14 or the parentheses in step 903 in FIG. 26), the air-fuel ratio variation between the cylinders is corrected with higher accuracy.
[0185]
When intake air amount control by variable intake valve control is relatively small, such as during medium / high load control or intake air amount control by throttle control, and when air-fuel ratio control (exhaust emissions reduction) is important As in this embodiment (7), by correcting the fuel injection time for each cylinder by the first inter-cylinder variation correction, the air-fuel ratio variation among the cylinders is corrected, and further, the second inter-cylinder variation is corrected. If the fuel injection time of each cylinder is corrected again by the correction, the air-fuel ratio variation between the cylinders can be corrected in two stages of the first cylinder variation correction and the second cylinder variation correction. Variations in air-fuel ratio among cylinders can be corrected with higher accuracy, and exhaust emissions can be effectively reduced.
[0186]
<< Embodiment (8) >>
By the way, the variable valve lift mechanism 30 of the intake valve 28 used in each of the above embodiments is configured to collectively change the valve lift amount (maximum valve lift amount and valve opening period) of the intake valves 28 of all cylinders. However, if the motor 41 of the variable valve lift mechanism 30 is driven at high speed for each intake stroke of each cylinder to vary the valve lift amount of the intake valve 28, the intake air amount can be varied for each cylinder.
[0187]
Therefore, in the embodiment (8) of the present invention shown in FIGS. 34 to 37, the variable valve lift mechanism 30 of the intake valve 28 is used as the intake air variable means for each cylinder. The mechanism 30 corrects the intake valve lift amount for each cylinder and corrects the intake air amount for each cylinder to correct the intake air amount variation among the cylinders. In the second inter-cylinder variation correction, In addition, by correcting the fuel injection time (fuel injection amount), variations in the intake fuel amount among the cylinders are corrected.
[0188]
In the present embodiment (8), the first inter-cylinder variation correction routine shown in FIG. 34 and the second inter-cylinder variation correction routine shown in FIG. 14 (or the second inter-cylinder variation correction routine shown in FIG. 26). ).
[0189]
[First Cylinder Variation Correction Routine]
When the first inter-cylinder variation correction routine shown in FIG. 34 is started, first, in step 1201, the first inter-cylinder variation value DEV1 (#i) of each cylinder is read, and then the process proceeds to step 1202. The basic correction amount FVVL1 (#i) corresponding to the first cylinder variation value DEV1 (#i) is calculated for each cylinder by searching the map of the basic correction amount FVVL1 of the intake valve lift amount shown in FIG.
[0190]
The map of the basic correction amount FVVL1 of the intake valve lift amount in FIG. 35 is set so that the basic correction amount FVVL1 decreases as the first inter-cylinder variation value DEV1 (#i) increases. In a predetermined region where #i) is near 0, the basic correction amount FVVL1 = 0 is set, and the intake valve lift amount is not corrected.
[0191]
Thereafter, the process proceeds to step 1203, and after reading the engine speed NE and the intake air amount GA, the process proceeds to step 1204, where a map of the correction coefficient FVVL2 shown in FIG. A correction coefficient FVVL2 (#i) corresponding to (for example, the engine speed NE and the intake air amount GA) is calculated.
[0192]
In view of the fact that when the intake air amount GA decreases (when the intake valve lift amount decreases), the correction of the valve lift amount correction tends to be affected, the map of the correction coefficient FVVL2 in FIG. 36 shows that the intake air amount GA decreases. The correction coefficient FVVL2 is set to be small.
[0193]
In the next step 1205, the basic correction amount FVVL1 (#i) of each cylinder is multiplied by the correction coefficient FVVL2 (#i) to obtain the valve lift correction amount FVVL (#i) of each cylinder.
FVVL (#i) = FVVL1 (#i) × FVVL2 (#i)
[0194]
Thereafter, the process proceeds to step 1206, and the final valve lift amount VVLM is obtained by adding the valve lift correction amount FVVL (#i) of each cylinder to the average valve lift amount VVL of all cylinders before correction.
[0195]
In this case, during 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 final valve lift correction amount FVVL (# 1) of the first cylinder # 1 is used. The target valve lift amount VVLM is calculated by the following equation.
VVLM = VVL + FVVL (# 1)
During 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 final target valve lift is calculated using the valve lift correction amount FVVL (# 2) of the second cylinder # 2. The amount VVLM is calculated by the following equation.
VVLM = VVL + FVVL (# 2)
[0196]
During the period of the crank angle counter CCRNK = 18 to 23, that is, the period corresponding to the intake stroke of the third cylinder # 3, the final target valve lift is calculated using the valve lift correction amount FVVL (# 3) of the third cylinder # 3. The amount VVLM is calculated by the following equation.
VVLM = VVL + FVVL (# 3)
[0197]
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 final target valve lift is calculated using the valve lift correction amount FVVL (# 4) of the fourth cylinder # 4. The amount VVLM is calculated by the following equation.
VVLM = VVL + FVVL (# 4)
[0198]
Thereafter, the process proceeds to step 1207, and the motor 41 of the variable valve lift mechanism 30 of the intake valve 28 is driven at a high speed according to the final target valve lift amount VVLM that changes corresponding to the intake stroke of each cylinder, and the intake stroke of each cylinder. The intake valve amount is corrected every time to correct the intake air amount. As a result, the variation in the intake air amount between the cylinders is corrected.
[0199]
Further, in the present embodiment (8), by executing the second inter-cylinder variation correction routine shown in FIG. 14 (or the second inter-cylinder variation correction routine shown in FIG. 26), the second cylinder of each cylinder is executed. By correcting the fuel injection time (fuel injection amount) for each cylinder based on the inter-variation value DEV2, the intake fuel amount variation between the cylinders is corrected.
[0200]
In the present embodiment (8) described above, as shown in the time chart of FIG. 37, in the first inter-cylinder variation correction, the first inter-cylinder variation values DEV1 (# 1) to DEV1 (# 4) of each cylinder. ) To calculate the valve lift correction amounts FVVL (# 1) to FVVL (# 4) of each cylinder, and using these valve lift correction amounts FVVL (# 1) to FVVL (# 4) By correcting the intake valve lift amount and correcting the intake air amount for each cylinder, the intake air amount variation between the cylinders is corrected.
[0201]
Thereafter, in the second cylinder variation correction, the fuel injection time correction coefficient KTAU (# 1) of each cylinder is calculated based on the second cylinder variation values DEV2 (# 1) to DEV2 (# 4) of each cylinder. KTAU (# 4) is calculated and the fuel injection time variation of each cylinder is corrected by correcting the fuel injection time of each cylinder using these fuel injection time correction coefficients KTAU (# 1) to KTAU (# 4). to correct.
[0202]
In this way, the first cylinder-to-cylinder variation correction and the second cylinder-to-cylinder variation correction directly correct the intake air amount variation between the cylinders and the intake fuel amount variation between the cylinders, respectively. Thus, the variation in the air-fuel ratio between the cylinders can be corrected, so that it is not necessary to correct the ignition timing, and the problem of a decrease in fuel consumption due to the ignition delay can be avoided.
[0203]
<< Embodiment (9) >>
A feature of the embodiment (9) of the present invention shown in FIG. 38 to FIG. 41 is the first cylinder-to-cylinder variation correction, and the variable valve lift mechanism 30 corrects the intake valve lift amount for each cylinder, for each cylinder. By correcting the intake air amount, the variation in intake air amount between the cylinders is corrected, and further, the intake valve lift amount of each cylinder is corrected again by correcting the variation between the second cylinders.
[0204]
In the present embodiment (9), the above-described first inter-cylinder variation correction routine shown in FIG. 34 and the second inter-cylinder variation correction routine shown in FIG. 38 are executed.
[0205]
[Second cylinder variation correction routine]
When the second inter-cylinder variation correction routine shown in FIG. 38 is started, first, in step 1301, the second inter-cylinder variation value DEV2 (#i) of each cylinder is read, and then the process proceeds to step 1302. The basic correction amount KVVL1 (#i) corresponding to the second cylinder variation value DEV2 (#i) is calculated for each cylinder by searching the map of the basic correction amount KVVL1 of the intake valve lift amount shown in FIG.
[0206]
Thereafter, the process proceeds to step 1303, and after reading the engine speed NE and the intake air amount GA, the process proceeds to step 1304, where a map of the correction coefficient KVVL2 shown in FIG. A correction coefficient KVVL2 (#i) corresponding to (for example, engine speed NE and intake air amount GA) is calculated.
[0207]
Thereafter, the process proceeds to step 1305, where the basic correction amount KVVL1 (#i) of each cylinder is multiplied by the correction coefficient KVVL2 (#i) to obtain the valve lift correction amount KVVL (#i) of each cylinder.
KVVL (#i) = KVVL1 (#i) × KVVL2 (#i)
[0208]
In the next step 1306, using the valve lift correction amount KVVL (#i) of each cylinder, the final target valve lift amount VVLM = VVL + FVVL (#i) calculated by the first inter-cylinder variation correction routine shown in FIG. ) Is corrected again.
[0209]
In this case, during the period corresponding to the intake stroke of the first cylinder # 1 (the period of CCRNK = 12 to 17), the final target valve lift amount is used by using the valve lift correction amount KVVL (# 1) of the first cylinder # 1. VVLM is calculated by the following equation.
VVLM = VVL + FVVL (# 1) + KVVL (# 1)
[0210]
During the period corresponding to the intake stroke of the second cylinder # 2 (the period of CCRNK = 6 to 11), the final target valve lift amount VVLM is set using the valve lift correction amount KVVL (# 2) of the second cylinder # 2. Calculated by the formula.
VVLM = VVL + FVVL (# 2) + KVVL (# 2)
[0211]
During the period corresponding to the intake stroke of the third cylinder # 3 (the period of CCRNK = 18 to 23), the final target valve lift amount VVLM is set using the valve lift correction amount KVVL (# 3) of the third cylinder # 3. Calculate by the formula.
VVLM = VVL + FVVL (# 3) + KVVL (# 3)
[0212]
During the period corresponding to the intake stroke of the fourth cylinder # 4 (the period of CCRNK = 0 to 5), the final target valve lift amount VVLM is set using the valve lift correction amount KVVL (# 4) of the fourth cylinder # 4. Calculated by the formula.
VVLM = VVL + FVVL (# 4) + KVVL (# 4)
[0213]
Thereafter, the routine proceeds to step 1307, where the motor 41 of the variable valve lift mechanism 30 is driven at a high speed in accordance with the final target valve lift amount VVLM that changes in accordance with the intake stroke of each cylinder, and the intake valve for each intake stroke of each cylinder. Correct the lift amount to correct the intake air amount.
[0214]
In the present embodiment (9) described above, as shown in the time chart of FIG. 41, in the first cylinder variation correction, the first cylinder variation values DEV1 (# 1) to DEV1 (# 4) of each cylinder. ) To calculate the valve lift correction amounts FVVL (# 1) to FVVL (# 4) of each cylinder, and using these valve lift correction amounts FVVL (# 1) to FVVL (# 4) By correcting the intake valve lift amount and correcting the intake air amount for each cylinder, the intake air amount variation between the cylinders is corrected.
[0215]
Thereafter, in the second cylinder variation correction, the valve lift correction amounts KVVL (# 1) to KVVL of the respective cylinders based on the second cylinder variation values DEV2 (# 1) to DEV2 (# 4) of the respective cylinders. (# 4) is calculated, and using these valve lift correction amounts KVVL (# 1) to KVVL (# 4), the final target valve lift amount VVLM of each cylinder corrected by the first inter-cylinder variation correction is calculated again. By correcting, the variation in intake air amount between cylinders is corrected with higher accuracy.
[0216]
When the intake fuel amount variation between the cylinders is very small (when the individual difference of the fuel injection valve 20 of each cylinder is small and the evaporative gas purge is not being executed), as in this embodiment (9), between the first cylinders By correcting the intake valve lift amount for each cylinder by variation correction, the intake air amount variation among cylinders is corrected, and further, the intake valve lift amount of each cylinder is recorrected by the second cylinder variation correction. By doing so, it is possible to correct the variation in intake air amount between the cylinders in two stages, ie, the correction between the first cylinder variation and the second cylinder variation correction, so that the intake air amount variation between the cylinders can be corrected more accurately. Therefore, it is possible to achieve both torque variation correction between cylinders and air-fuel ratio variation correction between cylinders. In addition, the ignition timing correction and the fuel injection amount correction are not necessary, and the problem of a reduction in fuel consumption can be avoided.
[0217]
<< Embodiment (10) >>
Next, Embodiment (10) of this invention is demonstrated using FIG.42 and FIG.43. In this embodiment (10), as shown in FIG. 42, each cylinder of the engine 11 is provided with electromagnetic actuators 42 and 43 (variable valve mechanisms), and the intake valve 28 and the exhaust valve 29 of each cylinder are respectively It is driven by electromagnetic actuators 42 and 43. Therefore, if the electromagnetic actuator 42 of the intake valve 28 of each cylinder is individually controlled to vary the intake valve lift amount of each cylinder individually, the intake air amount can be varied for each cylinder. These electromagnetic actuators 42 of the intake valves 28 constitute cylinder-specific intake air variable means.
[0218]
In the present embodiment (10), in the first inter-cylinder variation correction, the intake valve lift amount is corrected for each cylinder by the electromagnetic actuator 42 of the intake valve 28, and the intake air amount is corrected for each cylinder. In the second cylinder variation correction, the variation in the intake fuel amount between the cylinders is corrected by correcting the fuel injection time (fuel injection amount) for each cylinder. .
[0219]
In the present embodiment (10), the first inter-cylinder variation correction routine shown in FIG. 43 and the second inter-cylinder variation correction routine shown in FIG. 14 (or the second inter-cylinder variation correction routine shown in FIG. 26). ).
[0220]
[First Cylinder Variation Correction Routine]
In the first inter-cylinder variation correction routine shown in FIG. 43, the basic correction amount FVVL1 (#i) of the intake valve lift amount corresponding to the first inter-cylinder variation value DEV1 (#i) is set for each cylinder in FIG. After calculating using the map, the correction coefficient FVVL2 (#i) corresponding to the current engine operating state (for example, engine speed NE and intake air amount GA) is calculated for each cylinder using the map of FIG. Steps 1401-1404).
[0221]
Thereafter, the process proceeds to step 1405, where the basic correction amount FVVL1 (#i) of each cylinder is multiplied by the correction coefficient FVVL2 (#i) to obtain the valve lift correction amount FVVL (#i) of each cylinder.
FVVL (#i) = FVVL1 (#i) × FVVL2 (#i)
[0222]
In the next step 1406, the valve lift correction amount FVVL (#i) of each cylinder is added to the average valve lift amount VVL of all cylinders before correction to obtain the final target valve lift amount VVL of each cylinder.
VVL (#i) = VVL + FVVL (#i)
[0223]
According to the final target valve lift amount VVL of each cylinder calculated in this way, the electromagnetic actuator 42 of the intake valve 28 of each cylinder is individually controlled to correct the intake valve lift amount for each cylinder and to adjust the intake air amount. By correcting, the variation in intake air amount between cylinders is corrected.
[0224]
In the present embodiment (10), the second cylinder-to-cylinder variation correction routine shown in FIG. 14 (or the second cylinder-to-cylinder variation correction routine shown in FIG. 26) is executed, so that the second cylinder of each cylinder is executed. By correcting the fuel injection time (fuel injection amount) for each cylinder based on the inter-variation value DEV2, the intake fuel amount variation between the cylinders is corrected.
In the case of the present embodiment (10) described above, the same effects as those of the embodiment (8) can be obtained.
[0225]
<< Embodiment (11) >>
In the embodiment (11) of the present invention shown in FIG. 44, the intake valve lift amount is corrected for each cylinder by the electromagnetic actuator 42 in the first inter-cylinder variation correction, and the intake air amount is corrected for each cylinder. The variation in intake air amount between cylinders is corrected, and the intake valve lift amount of each cylinder is recorrected by the second variation correction between cylinders.
In the present embodiment (11), the first inter-cylinder variation correction routine shown in FIG. 43 and the second inter-cylinder variation correction routine shown in FIG. 44 are executed.
[0226]
[Second cylinder variation correction routine]
In the second inter-cylinder variation correction routine shown in FIG. 44, the basic correction amount KVVL1 (#i) of the intake valve lift amount corresponding to the second inter-cylinder variation value DEV2 (#i) is set for each cylinder in FIG. After calculating using the map, a correction coefficient KVVL2 (#i) corresponding to the current engine operating state (for example, engine speed NE and intake air amount GA) is calculated for each cylinder using the map of FIG. Steps 1501-1504).
[0227]
Thereafter, the routine proceeds to step 1505, where the basic correction amount KVVL1 (#i) of each cylinder is multiplied by the correction coefficient KVVL2 (#i) to obtain the valve lift correction amount KVVL (#i) of each cylinder.
KVVL (#i) = KVVL1 (#i) × KVVL2 (#i)
[0228]
In the next step 1506, using the valve lift correction amount KVVL (#i) of each cylinder, the final target valve lift amount VVL (#i) = calculated in the first inter-cylinder variation correction routine shown in FIG. VVL + FVVL (#i) is corrected again by the following equation.
VVL (#i) = VVL + FVVL (#i) + KVVL (#i)
[0229]
In the case of the present embodiment (11) described above, the same effects as those of the embodiment (9) can be obtained.
[0230]
In addition, you may make it implement in combination with several cylinder variation correction | amendment from said each embodiment (1)-(11), for example, said each execution according to engine operating conditions etc. during engine operation, for example. The cylinder-to-cylinder variation correction described in the embodiments (1) to (11) may be switched and executed.
[0231]
In the cylinder-to-cylinder variation correction in each of the embodiments (1) to (11), the first cylinder-to-cylinder variation correction based on the first cylinder-to-cylinder variation value DEV1 and the second cylinder-to-cylinder variation value DEV2 are used. In addition, the second-stage correction of the variation between the second cylinders is performed, but the intake air variable means for each cylinder (variable valve lift mechanism 30 and electromagnetic actuator 42) for changing the intake air amount for each cylinder of the engine 11 is provided. In this system, the inter-cylinder variation value DEV is calculated based on at least one of the intake air amount and the intake pipe pressure of the engine 11, and the intake air amount is determined for each cylinder based on the inter-cylinder variation value DEV. It is also possible to correct the variation in intake air amount between the cylinders by correcting. Even in this case, the variation in the intake air amount between the cylinders can be corrected, so that the torque variation between the cylinders and the air-fuel ratio variation between the cylinders can be corrected.
[0232]
In the above embodiments (1) to (11), the present invention is applied to a system that performs intake air amount control by variable intake valve control. However, the present invention is applied to a system that performs only intake air amount control by throttle control. It may be applied.
[0233]
The scope of application of the present invention is not limited to a four-cylinder engine, and the present invention may be applied to a multi-cylinder engine having five or more cylinders or three or less cylinders.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an entire engine control system according to an embodiment (1) of the present invention.
FIG. 2 is a front view of a variable valve lift mechanism.
FIG. 3 is a flowchart showing a flow of processing of a cylinder-to-cylinder variation correction base routine of the embodiment (1).
FIG. 4 is a flowchart showing a processing flow of a first inter-cylinder variation estimation routine of the embodiment (1).
FIG. 5 is a flowchart showing a part of the processing flow of a modified example (No. 1) of the first inter-cylinder variation estimation routine of the embodiment (1).
FIG. 6 is a flowchart showing a part of the processing flow of a modified example (No. 2) of the first inter-cylinder variation estimation routine of the embodiment (1).
FIG. 7 is a flowchart showing a part of the processing flow of a modified example (No. 3) of the first inter-cylinder variation estimation routine of the embodiment (1).
FIG. 8 is a diagram conceptually showing a map for converting an output voltage VAFM of an air flow meter into an intake air amount instantaneous value GAFM.
FIG. 9 is a time chart showing the pulsation waveform of the intake air amount
FIG. 10 is a flowchart showing a process flow of a first inter-cylinder variation correction routine of the embodiment (1).
FIG. 11 is a diagram conceptually showing a map of a basic correction amount FAOP1 of ignition timing.
FIG. 12 is a diagram conceptually showing a map of a correction coefficient FAOP2.
FIG. 13 is a flowchart showing a process flow of a second inter-cylinder variation estimation routine of the embodiment (1).
FIG. 14 is a flowchart showing the flow of processing of a second inter-cylinder variation correction routine of the embodiment (1).
FIG. 15 is a diagram conceptually showing a map of a basic correction amount KTAU1 for fuel injection time.
FIG. 16 is a diagram conceptually showing a map of a correction coefficient KTAU2.
FIG. 17 is a time chart showing an execution example of the embodiment (1).
FIG. 18 is a flowchart showing a process flow of a first inter-cylinder variation estimation routine of the embodiment (2).
FIG. 19 is a flowchart showing a part of the processing flow of a modified example (part 1) of the first inter-cylinder variation estimation routine of the embodiment (2).
FIG. 20 is a flowchart showing a part of the processing flow of a modified example (No. 2) of the first inter-cylinder variation estimation routine of the embodiment (2).
FIG. 21 is a flowchart showing a part of the processing flow of a modified example (No. 3) of the first inter-cylinder variation estimation routine of the embodiment (2).
FIG. 22 is a diagram conceptually showing a map of an intake pipe pressure instantaneous value PMAP.
FIG. 23 is a flowchart showing a flow of processing of a first inter-cylinder variation estimation routine of the embodiment (3).
FIG. 24 is a flowchart showing the flow of processing of a second inter-cylinder variation estimation routine of the embodiment (4).
FIG. 25 is a diagram conceptually showing a map of an exhaust system delay time DELY.
FIG. 26 is a flowchart showing the flow of processing of a second inter-cylinder variation correction routine of the embodiment (4).
FIG. 27 is a flowchart showing a flow of processing of a first inter-cylinder variation correcting routine of the embodiment (5).
FIG. 28 is a flowchart showing a process flow of a second inter-cylinder variation correction routine of the embodiment (5).
FIG. 29 is a diagram conceptually showing a map of a basic correction amount KAOP1 of ignition timing.
FIG. 30 is a diagram conceptually showing a map of a correction coefficient KAOP2.
FIG. 31 is a time chart showing an execution example of the embodiment (5);
FIG. 32 is a time chart showing an execution example of the embodiment (6).
FIG. 33 is a time chart showing an execution example of the embodiment (7);
FIG. 34 is a flowchart showing the flow of processing of a first inter-cylinder variation correcting routine of the embodiment (8).
FIG. 35 is a diagram conceptually showing a map of a basic correction amount FVVL1 of the intake valve lift amount.
FIG. 36 is a diagram conceptually showing a map of the correction coefficient FVVL2.
FIG. 37 is a time chart showing an execution example of the embodiment (8).
FIG. 38 is a flowchart showing the flow of processing of a second inter-cylinder variation correcting routine of the embodiment (9).
FIG. 39 is a diagram conceptually showing a map of a basic correction amount KVVL1 of the intake valve lift amount.
FIG. 40 is a diagram conceptually showing a map of a correction coefficient KVVL2.
FIG. 41 is a time chart showing an execution example of the embodiment (9)
FIG. 42 is a schematic configuration diagram of the entire engine control system in the embodiment (10).
FIG. 43 is a flowchart showing a process flow of a first inter-cylinder variation correction routine of the embodiment (10).
FIG. 44 is a flowchart showing a process flow of a second inter-cylinder variation correction routine of the embodiment (11).
[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 26... Crank angle sensor 27. ECU (first cylinder variation estimating means, first cylinder variation correcting means, second cylinder variation estimating means, second cylinder variation correcting means, variation estimating Inhibiting means, variation correction omitting means), 28 ... intake valve, 29 ... exhaust valve, 30, 31 ... variable valve lift mechanism (intake air variable means for each cylinder), 42, 43 ... electromagnetic actuator (intake air variable means for each cylinder) .

Claims (16)

The first cylinder variation estimation Teite stage of calculating a first cylinder variation value representing the intake air amount variation among the cylinders based on at least one of the intake pipe pressure and the intake air amount of the internal combustion engine having a plurality of cylinders When,
First inter-cylinder variation correction means for performing first inter-cylinder variation correction for correcting at least one of torque variation between cylinders and air-fuel ratio variation between cylinders based on the first inter-cylinder variation value;
A second representing an intake air amount variation between cylinders and / or an intake fuel amount variation between cylinders based on at least one of a combustion state of the internal combustion engine and an air-fuel ratio of exhaust gas after execution of the first inter-cylinder variation correction. Second inter-cylinder variation estimating means for calculating the inter-cylinder variation value of
And second inter-cylinder variation correction means for performing second inter-cylinder variation correction for correcting at least one of torque variation between cylinders and air-fuel ratio variation between cylinders based on the second inter-cylinder variation value. A control device for an internal combustion engine. An air flow meter for detecting the amount of intake air of the internal combustion engine,
The first cylinder-to-cylinder variation estimation means is at least one of an average value, maximum value, minimum value, amplitude value, and area of the intake air amount detected by the air flow meter for each period corresponding to the intake stroke of each cylinder. The control apparatus for an internal combustion engine according to claim 1, wherein the first inter-cylinder variation value is calculated based on one of the two. An intake pipe pressure sensor for detecting an intake pipe pressure of the internal combustion engine;
The first inter-cylinder variation estimating means includes an average value, maximum value, minimum value, amplitude value, and area of the intake pipe pressure detected by the intake pipe pressure sensor for each period corresponding to the intake stroke of each cylinder. 3. The control device for an internal combustion engine according to claim 1, wherein the first inter-cylinder variation value is calculated based on at least one. When the throttle opening of the internal combustion engine is smaller than a predetermined opening or when the intake pipe pressure is lower than a predetermined pressure, the first cylinder-to-cylinder variation estimating means determines the intake pipe pressure detected by the intake pipe pressure sensor. 4. The control device for an internal combustion engine according to claim 3, wherein the first inter-cylinder variation value is calculated based on a local minimum value.   The second cylinder-to-cylinder variation estimation means detects a rotational fluctuation that becomes information on the combustion state of each cylinder for each period corresponding to the combustion stroke of each cylinder, and based on the rotational fluctuation, the second cylinder-to-cylinder variation. 5. The control device for an internal combustion engine according to claim 1, wherein a value is calculated. An air-fuel ratio sensor for detecting an air-fuel ratio of the exhaust gas of the internal combustion engine,
The second cylinder-to-cylinder variation estimating means detects the air-fuel ratio of the exhaust gas of each cylinder by the air-fuel ratio sensor for each period corresponding to the exhaust stroke of each cylinder, and based on the air-fuel ratio, the second cylinder The internal combustion engine control device according to any one of claims 1 to 5, wherein an interval variation value is calculated. The first inter-cylinder variation correcting unit corrects the torque variation between the cylinders by correcting the ignition timing for each cylinder based on the first inter-cylinder variation value.
The second cylinder-to-cylinder variation correcting means corrects the air-fuel ratio variation among the cylinders by correcting the fuel injection amount for each cylinder based on the second cylinder-to-cylinder variation value. The control apparatus for an internal combustion engine according to any one of 1 to 6. The first inter-cylinder variation correcting unit corrects the air-fuel ratio variation among the cylinders by correcting the fuel injection amount for each cylinder based on the first inter-cylinder variation value.
The second cylinder variation correcting means corrects torque variation between cylinders by correcting an ignition timing for each cylinder based on the second cylinder variation value. The control apparatus for an internal combustion engine according to any one of claims 6 to 10. A cylinder-specific intake air variable means for varying the intake air amount for each cylinder of the internal combustion engine;
The first inter-cylinder variation correcting unit corrects the control amount of the cylinder-specific intake air varying unit for each cylinder based on the first inter-cylinder variation value to correct the intake air amount for each cylinder. ,
The internal combustion engine according to any one of claims 1 to 6, wherein the second inter-cylinder variation correcting unit corrects the fuel injection amount for each cylinder based on the second inter-cylinder variation value. Control device. The first inter-cylinder variation correcting unit corrects the torque variation between the cylinders by correcting the ignition timing for each cylinder based on the first inter-cylinder variation value.
The second cylinder variation correcting means recorrects the ignition timing corrected by the first cylinder variation correction for each cylinder based on the second cylinder variation value. The control apparatus for an internal combustion engine according to any one of 1 to 6. The first inter-cylinder variation correcting unit corrects the air-fuel ratio variation among the cylinders by correcting the fuel injection amount for each cylinder based on the first inter-cylinder variation value.
The second cylinder variation correcting means recorrects the fuel injection amount corrected by the first cylinder variation correction for each cylinder based on the second cylinder variation value. Item 7. The control device for an internal combustion engine according to any one of Items 1 to 6. A cylinder-specific intake air variable means for varying the intake air amount for each cylinder of the internal combustion engine;
The first inter-cylinder variation correcting unit corrects the control amount of the cylinder-specific intake air varying unit for each cylinder based on the first inter-cylinder variation value to correct the intake air amount for each cylinder. ,
The second inter-cylinder variation correcting unit recorrects the control amount of the cylinder-specific intake air variable unit corrected by the first inter-cylinder variation correction for each cylinder based on the second inter-cylinder variation value. The control device for an internal combustion engine according to any one of claims 1 to 6, wherein   13. A variation estimation prohibiting unit that prohibits calculation of the second inter-cylinder variation value until a predetermined period elapses after a change in the correction amount of the first inter-cylinder variation correction. The control apparatus for an internal combustion engine according to any one of the above.   A variation correction omitting unit is provided that omits the second inter-cylinder variation correction when the variation in torque and / or air-fuel ratio becomes equal to or less than a predetermined value due to the first inter-cylinder variation correction. The control device for an internal combustion engine according to any one of claims 1 to 13. The cylinder-specific intake air variable means has a variable intake valve mechanism independent for each cylinder, and controls the variable intake valve mechanism of each cylinder to vary the intake air amount for each cylinder. the control apparatus according to claim 9 or 1 2,. The cylinder-specific intake air variable means has a variable intake valve mechanism that collectively changes the valve control amount of all cylinders or a plurality of cylinders of the internal combustion engine, and the variable valve mechanism for each intake stroke of each cylinder. the high-speed drive to control apparatus for an internal combustion engine according to claim 9 or 1 2, characterized in that for varying the intake air amount for each cylinder by varying the valve control amount.

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