JP2004138036A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the fuel consumption reducing effect obtained by the intake air control by controlling a variable intake valve while ensuring the combustion stability. <P>SOLUTION: The throttle opening learned value GTA and the valve lift learned value GVL are set to be the throttle opening TA and the valve lift quantity VL, respectively. If the combustion instability calculated based on rotation fluctuation or the like is larger than a determination value Krough, the valve lift quantity VL is correctively increased, and if the combustion instability is not larger than the determination value Krough, the valve lift quantity VL is correctively decreased (Steps 101-108). In addition, the throttle opening TA is correctively decreased or increased so as to suppress changes in the engine speed NE (change in intake air quantity GN) caused by correction of the valve lift quantity VL (Steps 109-111), and the throttle opening learned value GTA and the valve lift learned value GVL are updated by the present throttle opening TA and valve lift quantity VL, respectively (Steps 112 and 113). <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a control device for an internal combustion engine provided with a variable intake valve mechanism capable of controlling an intake air amount by varying a control amount of an intake valve of the internal combustion engine.
[0002]
[Prior art]
2. Description of the Related Art In recent years, in internal combustion engines mounted on vehicles, a variable intake valve mechanism that varies a valve control amount such as a lift amount and an opening / closing timing of an intake valve is provided, and a valve of the intake valve is controlled according to an accelerator opening degree and an engine operating state. In some cases, the intake air amount can be controlled by varying the control amount. In the intake air amount control by the variable intake valve control, the intake air amount can be reduced without narrowing the intake passage by the throttle valve by reducing the lift amount and the valve opening period of the intake valve. There is an advantage that the fuel consumption can be reduced and the fuel efficiency can be improved.
[0003]
In the conventional intake air amount control by the general throttle valve control, the pressure of the intake air downstream of the throttle valve becomes considerably negative because the opening degree of the throttle valve is reduced at a low load to reduce the intake air amount. However, in the intake air amount control by the variable intake valve control, the amount of air in the cylinder is controlled by changing the lift amount and the valve opening period of the intake valve while the throttle valve is widely opened. Regardless of the load, the pressure of the intake air downstream of the throttle valve is maintained at approximately atmospheric pressure, and even at low load, air at approximately atmospheric pressure is drawn into the cylinder from the intake port. For this reason, in the intake air amount control by the variable intake valve control, the flow of the air flowing through the intake port at a low load becomes slower than that of the intake air amount control by the throttle valve control, and the fuel ( The vaporization characteristics of wet fuel) and the flow characteristics of the air-fuel mixture in the cylinder tend to decrease. Furthermore, at low load, the closing timing of the intake valve is advanced from the intake bottom dead center so as to shorten the opening time of the intake valve, so that the piston descends even after the intake valve is closed, causing in-cylinder mixing. The air tends to expand and the temperature tends to decrease. For these reasons, in the intake air amount control by the variable intake valve control, the combustion state may be deteriorated at a low load, which may adversely affect drivability and exhaust emission.
[0004]
As a countermeasure against this, as shown in Patent Document 1 (Japanese Patent Application Laid-Open No. 2001-159341), when the intake air amount is controlled by the variable intake valve control, there is a possibility that the combustion state may be deteriorated. (Low-load operation during cold operation), the intake air amount control mode is switched from intake air amount control by variable intake valve control to intake air amount control by throttle valve control, and the lift amount and opening period of the intake valve are changed. For example, by controlling the intake air amount by throttle valve control in a state where the intake air amount is fixed at the maximum value, the deterioration of the combustion state is prevented, and the intake air amount control by the variable intake valve control is performed under normal operation conditions other than the specific operation condition. There's something we did.
[0005]
[Patent Document 1]
JP 2001-159341 A (page 2 etc.)
[0006]
[Problems to be solved by the invention]
By the way, the operating conditions under which the combustion state deteriorates when the intake air amount is controlled by the variable intake valve control may change due to changes in the environment (temperature, humidity, atmospheric pressure, etc.) surrounding the vehicle. However, according to the method of Patent Document 1, the operation is always switched to the intake air amount control by the throttle valve control at the time of the specific operation condition set in advance. Therefore, even in the operation condition where the combustion state does not actually deteriorate due to an environmental change or the like. In some cases, the control may be switched to the intake air amount control by the throttle valve control, and the effect of the intake air amount control by the variable intake valve control cannot be fully utilized.
[0007]
In addition, in the intake air amount control by the variable intake valve control, since the lift amount of the intake valve becomes small at a low load, the variation of the actual lift amount with respect to the target lift amount in each cylinder (variation due to component tolerance or assembly tolerance of each cylinder). ) Tends to increase, and the variation in the amount of intake air between cylinders tends to increase. Therefore, when the load is low, the variation in the intake air amount between the cylinders may cause the variation in the torque and the variation in the air-fuel ratio between the cylinders, and the drivability and the exhaust emission may deteriorate. To solve this problem, switching to intake air amount control by throttle valve control at a low load may be considered.
[0008]
However, variations in the actual lift amount include individual differences and changes with time, so that the intake air amount variation among the cylinders does not always increase when the load of the intake air amount control by the variable intake valve control is low. Therefore, when the load is always switched to the control of the intake air amount by the throttle valve control at a low load, even if the adverse effect due to the variation of the intake air amount between the cylinders does not actually occur, the control is switched to the intake air amount control by the throttle valve control. And the effect of the intake air amount control by the variable intake valve control cannot be fully utilized.
[0009]
The present invention has been made in view of these circumstances, and a first object is to increase the effect of intake air amount control by variable intake valve control while ensuring combustion stability. A second object is to increase the effect of intake air amount control by variable intake valve control while reducing intake air amount variation between cylinders.
[0010]
[Means for Solving the Problems]
In order to achieve the first object, a control device for an internal combustion engine according to claim 1 of the present invention detects the combustion instability of the internal combustion engine by a combustion instability detecting means, and based on the combustion instability. In this case, the intake air amount is controlled by controlling the control amount of the intake valve and / or the control amount of the throttle valve by the intake air amount control means.
[0011]
With this configuration, the control amount of the intake valve and the control amount of the throttle valve can be controlled in accordance with the actually detected degree of combustion instability. Therefore, when the combustion state tends to deteriorate, the combustion state is stabilized. The control amount of the intake valve and the control amount of the throttle valve are controlled in the direction (direction in which the combustion instability is reduced), and when the combustion state is stable, the effect of the intake air amount control by the variable intake valve control is increased. The control amount of the intake valve and the control amount of the throttle valve can be controlled in the direction. Thus, it is possible to prevent the deterioration of the combustion state caused by the intake air amount control by the variable intake valve control, and to increase the pumping loss reduction and the fuel efficiency improvement obtained by the intake air amount control by the variable intake valve control. .
[0012]
In this case, the degree of combustion instability may be detected based on at least one of the rotation fluctuation, the in-cylinder pressure, and the ion current. Rotational fluctuations, in-cylinder pressure, and ionic current change according to the combustion state of each cylinder.Rotation fluctuations detected based on the output signal of a crank angle sensor, in-cylinder pressure detected by an in-cylinder pressure sensor, etc. By monitoring the ion current detected via the above-described method, the degree of combustion instability can be accurately detected.
[0013]
By the way, when the intake air amount control according to the present invention changes in a direction in which the combustion state deteriorates (in a direction in which the combustion instability increases), the intake air is controlled in a direction in which the combustion state is stabilized (in a direction in which the combustion instability decreases). In order to control the control amount of the valve and the control amount of the throttle valve, the combustion instability is usually small, but the combustion state is deteriorated to some extent by operating conditions (the combustion instability has increased to some extent). (State), if the control amount of the intake valve is largely changed, the combustion state may be further deteriorated.
[0014]
Therefore, when the combustion instability detected by the combustion instability detecting means is equal to or more than a predetermined value, the variable range of the control amount of the intake valve may be limited by the control amount restricting means. . In this way, in a state in which the combustion state is deteriorated to some extent (in a state in which the combustion instability is increased to some extent), the control amount of the intake valve is forcibly changed, and the combustion state is further deteriorated. Can be avoided, and combustion stability can be ensured.
[0015]
In this case, when the degree of combustion instability is equal to or more than a predetermined value, as means for limiting the variable range of the control amount of the intake valve, for example, the control amount of the intake valve may be subjected to guard processing with a predetermined guard value, Alternatively, the variable range of the control amount of the intake valve may be narrowed, but the control amount of the intake valve may be fixed to a predetermined value. In this case, there is an advantage that the arithmetic processing for setting the control amount of the intake valve is facilitated.
[0016]
By the way, during normal operation, in order to reduce the pumping loss and improve the fuel efficiency, the control amount (lift amount and valve opening period) of the intake valve is varied while the throttle valve is largely opened, and the intake air amount is changed. Therefore, the opening of the throttle valve is largely open. Therefore, if the opening of the throttle valve is small, it is expected that some abnormality has occurred in the components of the intake air amount control system.
[0017]
From this point of view, as in claim 5, the abnormality determination means determines whether the opening of the throttle valve is equal to or less than a predetermined abnormality determination value and determines whether there is an abnormality in a component of the intake air amount control system. May be determined. With this configuration, the function of diagnosing an abnormality of a component of the intake air amount control system can be realized without adding a new sensor.
[0018]
In this case, when an abnormality is detected by the abnormality determining means, the abnormality-time intake air amount control in which the control amount of the intake valve is fixed and the amount of intake air is controlled by controlling the opening of the throttle valve is performed. It may be executed. In other words, the drive system and control system of the throttle valve are less likely to fail than the variable intake valve mechanism. There is a high possibility that the intake air amount can be controlled more accurately than when the air amount is controlled.
[0019]
At this time, when the combustion instability detected by the combustion instability detecting means is smaller than a predetermined value during the execution of the abnormal intake air amount control, the variable intake valve mechanism may be activated. It may be determined to be abnormal. During the execution of the abnormal-time intake air amount control, the intake air amount is controlled by the throttle control. Therefore, the combustion instability is reduced by the abnormal-time intake air amount control (throttle control). This means that a stable combustion state can be obtained by the control, and that the intake air amount is accurately controlled by the throttle control (the drive system and the control system of the throttle valve are normal). Therefore, if the combustion instability decreases during execution of the abnormal intake air amount control, it can be determined that the variable intake valve mechanism is abnormal.
[0020]
Further, when the combustion instability detected by the combustion instability detecting means is equal to or more than a predetermined value during execution of the abnormal intake air amount control, the variable intake valve mechanism operates normally. Or not, and if it is determined that it is operating normally, it may be determined that a component other than the variable intake valve mechanism is abnormal. In other words, the fact that the combustion instability increases during the execution of the abnormal intake air amount control means that the combustion state is not improved even with the intake air amount control by the throttle control. Means that it may be out of order. In this case, since there is a possibility that both the drive system / control system of the throttle valve and the variable intake valve mechanism have failed, it is determined whether or not the variable intake valve mechanism is operating normally, and the normal operation is performed. If it is determined that there is an abnormality, it can be determined that a component other than the variable intake valve mechanism (drive system / control system of the throttle valve) is abnormal. Thereby, it is possible to distinguish and determine the abnormality of the variable intake valve mechanism and the abnormality of the other components.
[0021]
At this time, whether or not the variable intake valve mechanism is operating normally is determined by comparing the output of a sensor for detecting the position of the intake valve with the control amount of the intake valve. It is good to This makes it possible to accurately determine whether or not the variable intake valve mechanism is operating normally.
[0022]
In order to achieve the second object, an inter-cylinder variation detecting means detects an inter-cylinder variation value representing a variation in intake air amount between cylinders of the internal combustion engine. The intake air amount control means may control the intake valve control amount and / or the throttle valve control amount based on the value to control the intake air amount.
[0023]
In this way, the control amount of the intake valve and the control amount of the throttle valve can be controlled in accordance with the actually detected inter-cylinder variation value. The control amount of the intake valve and the control amount of the throttle valve are controlled in the direction to reduce the variation, and when the variation value between cylinders is small, the control amount of the intake valve in the direction to increase the effect of the intake air amount control by the variable intake valve control. And the control amount of the throttle valve can be controlled. Thus, the effect of the intake air amount control by the variable intake valve control can be increased while reducing the intake air amount variation between cylinders caused by the intake air amount control by the variable intake valve control.
[0024]
In this case, it is preferable to detect the inter-cylinder variation value based on at least one of the intake air amount, the intake pipe pressure, the rotation fluctuation, the in-cylinder pressure, the ion current, and the air-fuel ratio. The amount of intake air detected by an air flow meter or the like or the intake pipe pressure detected by an intake pipe pressure sensor changes in accordance with the intake stroke of each cylinder. The variation value between the cylinders reflecting the variation in the intake air amount can be detected. In addition, since the air-fuel ratio of each cylinder changes according to the intake air amount of each cylinder, monitoring the air-fuel ratio detected by an air-fuel ratio sensor, etc., makes it possible to obtain the inter-cylinder variation value reflecting the intake air amount variation between the cylinders. Can be detected. Further, the combustion state of each cylinder changes according to the intake air amount of each cylinder, and the rotation fluctuation, the in-cylinder pressure, and the ionic current change according to the combustion state. By monitoring, it is possible to detect an inter-cylinder variation value reflecting the intake air amount variation between cylinders.
[0025]
By the way, in the intake air amount control using the inter-cylinder variation value, when the intake air amount variation between cylinders (inter-cylinder variation value) increases, the intake air amount variation between cylinders (inter-cylinder variation value) changes. In order to control the control amount of the intake valve and the control amount of the throttle valve in the direction of reducing the intake air amount, the variation in the intake air amount between cylinders (inter-cylinder variation value) during normal operation is small. If the control amount of the intake valve is greatly changed in a state where the intake air amount variation between cylinders (inter-cylinder variation value) has increased to some extent, the intake air amount variation between cylinders (inter-cylinder variation value) will increase more and more. Could be.
[0026]
Therefore, when the inter-cylinder variation value detected by the inter-cylinder variation detecting means is equal to or larger than a predetermined value, the variable range of the control amount of the intake valve may be limited by the control amount restricting means. With this arrangement, the control amount of the intake valve is forcibly changed in a state where the variation in the intake air amount between cylinders (inter-cylinder variation value) has increased to some extent, and the variation in the intake air amount between the cylinders (cylinder variation) has increased. A vicious cycle of increasing the inter-variation value) can be avoided.
[0027]
In this case, when the inter-cylinder variation value is equal to or greater than a predetermined value, as means for limiting the variable range of the control amount of the intake valve, for example, the control amount of the intake valve may be guard-processed with a predetermined guard value, Alternatively, the variable range of the control amount of the intake valve may be narrowed, but the control amount of the intake valve may be fixed to a predetermined value. In this case, there is an advantage that the arithmetic processing for setting the control amount of the intake valve is facilitated.
[0028]
According to a fourteenth aspect, the abnormality determining means determines whether or not the opening of the throttle valve is equal to or less than a predetermined abnormality determination value to determine whether or not there is an abnormality in a component of the intake air amount control system. You may do it. Normally, in order to reduce pumping loss and improve fuel economy, the throttle valve is widely opened and the intake air amount is controlled by varying the control amount of the intake valve. Whether or not there is an abnormality in a component of the intake air amount control system can be easily determined based on whether or not the value is equal to or less than the abnormality determination value.
[0029]
In this case, when an abnormality is detected by the abnormality determination means, the abnormality-time intake air amount control is performed by fixing the control amount of the intake valve and controlling the intake air amount by controlling the opening of the throttle valve. It may be executed. Thus, when the abnormality is detected, controlling the intake air amount by the throttle control is more likely to control the intake air amount more accurately than controlling the intake air amount by the variable valve control.
[0030]
In this case, when the inter-cylinder variation value detected by the inter-cylinder variation detection means is smaller than a predetermined value during the execution of the abnormal intake air amount control, an abnormality in the variable intake valve mechanism is determined. The determination may be made. During the execution of the abnormal intake air amount control, the intake air amount is controlled by the throttle control. Therefore, the fact that the inter-cylinder variation value becomes small by the abnormal intake air amount control (throttle control) means that the throttle control of each cylinder is performed. This means that the intake air amount is accurately controlled (the drive system and the control system of the throttle valve are normal). Therefore, if the inter-cylinder variation value decreases during execution of the abnormal intake air amount control, it can be determined that the variable intake valve mechanism is abnormal.
[0031]
In addition, when the inter-cylinder variation value detected by the inter-cylinder variation detection means is equal to or greater than a predetermined value during execution of the abnormal intake air amount control, the variable intake valve mechanism normally operates. It may be determined whether or not it is operating, and if it is determined that it is operating normally, it may be determined that a component other than the variable intake valve mechanism is abnormal. In other words, the fact that the inter-cylinder variation value increases during execution of the abnormal intake air amount control means that the inter-cylinder intake air amount variation does not become small even by the intake air amount control by the throttle control. Means that there is a possibility that the drive system / control system has failed. In this case, since there is a possibility that both the drive system / control system of the throttle valve and the variable intake valve mechanism have failed, it is determined whether or not the variable intake valve mechanism is operating normally, and the normal operation is performed. If it is determined that there is an abnormality, it can be determined that a component other than the variable intake valve mechanism (drive system / control system of the throttle valve) is abnormal.
[0032]
At this time, whether or not the variable intake valve mechanism is operating normally is determined by comparing the output of a sensor for detecting the position of the intake valve with the control amount of the intake valve. It is good to This makes it possible to accurately determine whether or not the variable intake valve mechanism is operating normally.
[0033]
The control amount of the intake valve and / or the control amount of the throttle valve set by the intake air amount control means is learned by the learning means, and the intake air amount control means learns the control learned by the learning means. The current control amount may be set based on the amount. With this configuration, the control amount of the intake valve and the control amount of the throttle valve can be quickly controlled to appropriate values without being affected by manufacturing variations of the control system or changes over time.
[0034]
BEST MODE FOR CARRYING OUT 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. An air cleaner 13 is provided at the most upstream portion of an intake pipe 12 of an engine 11 which is an internal combustion engine, and an air flow meter 14 for detecting an intake air amount is provided downstream of the air cleaner 13. Downstream 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.
[0035]
Further, on the downstream side of the throttle valve 15, a surge tank 17 is provided. In the surge tank 17, an intake pipe pressure sensor 18 for detecting an intake pipe pressure is provided. 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 near an intake port of the intake manifold 19 of each cylinder. I have. An ignition plug 21 is attached to a cylinder head of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by spark discharge of each ignition plug 21.
[0036]
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 be provided with a variable valve timing mechanism for varying the valve timing (opening / closing timing). Note that the exhaust valve 29 may be provided with only the variable valve timing mechanism without providing the variable valve lift mechanism 31.
[0037]
On the other hand, a catalyst 23 such as a three-way catalyst for purifying CO, HC, NOx and the like in the exhaust gas is provided in an exhaust pipe 22 of the engine 11, and an air-fuel ratio of the exhaust gas is detected upstream of the catalyst 23. An air-fuel ratio sensor 24 is provided. A water temperature sensor 25 for detecting a cooling water temperature and a crank angle sensor 26 for outputting a pulse signal each time the crankshaft of the engine 11 rotates at a constant crank angle (for example, 30 ° C. A) are attached to the cylinder block of the engine 11. Has been. The crank angle and the engine speed are detected based on the output signal of the crank angle sensor 26.
[0038]
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), thereby controlling the fuel injection amount of the fuel injection valve 20 according to the engine operating state. The ignition timing of the ignition plug 21 is controlled.
[0039]
Next, the configuration of the variable valve lift mechanism (variable intake valve lift mechanism) 30 of the intake valve 28 will be described with reference to FIG. Note that the variable valve lift mechanism (variable exhaust valve lift mechanism) 31 of the exhaust valve 29 has substantially the same configuration as the variable intake valve lift mechanism 30, and a description thereof will be omitted.
[0040]
As shown in FIG. 2, a link arm 34 is provided between the camshaft 32 for driving the intake valve 28 and the rocker arm 33, and is rotated above the link arm 34 by a motor 41 such as a stepping motor. A dynamically driven control shaft 35 is provided. An eccentric cam 36 is provided on the control shaft 35 so as to be integrally rotatable. 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 movably supported. 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 camshaft 32. A pressing cam 39 is provided at the lower end of the link arm 34, and the lower end surface of the pressing cam 39 is in contact with the upper end surface of a roller 40 provided at the center of the rocker arm 33.
[0041]
Thus, when the cam 37 rotates by the rotation of the camshaft 32, the swing cam 38 of the link arm 34 moves right and left following the outer peripheral surface shape of the cam 37, and the link arm 34 swings left and right. . When the link arm 34 swings left and right, the pressing cam 39 moves left and right, so that 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 vertical movement of the rocker arm 33 causes the intake bubble 28 to move up and down.
[0042]
On the other hand, when the eccentric cam 36 rotates by the rotation of the control shaft 35, the position of the support shaft of the link arm 34 moves, 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. The lower end surface of the pressing cam 39 of the link arm 34 has a base curved surface 39a formed on the left side thereof 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). The pressing curved surface 39b is formed with a curvature such that the pressing amount of the rocker arm 33 increases toward the right from the base curved surface 39a (the valve lift amount of the intake valve 28 increases).
[0043]
In the case of the high lift mode in which the valve lift amount of the intake valve 28 is increased, the initial contact point 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 it. As a result, when the pressing cam 39 moves 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, and the maximum pressing amount of the rocker arm 33 increases. As a result, the maximum valve lift amount of the intake valve 28 increases, and the period during which the rocker arm 33 is pressed becomes longer, so that the valve opening period of the intake bubble 28 becomes longer.
[0044]
On the other hand, in the low lift mode in which the valve lift of the intake valve 28 is reduced, the initial contact point between the pressing cam 39 of the link arm 34 and the roller 40 of the rocker arm 33 is moved to the left by the rotation of the control shaft 35. Move to Accordingly, when the pressing cam 39 moves 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, and the maximum pressing amount of the rocker arm 33 decreases. As a result, the maximum valve lift of the intake valve 28 is reduced, and the period during which the rocker arm 33 is pressed is shortened, so that the valve opening period of the intake bubble 28 is shortened.
[0045]
In the variable intake valve lift mechanism 30 described above, the control shaft 35 is rotated by the motor 41 to continuously move the initial contact point between the pressing cam 39 of the link arm 34 and the roller 40 of the rocker arm 33. 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 cylinders can be varied continuously and collectively.
[0046]
The ECU 27 controls the variable intake valve lift mechanism 30 according to a target intake air amount set based on the accelerator opening and the like, and continuously varies the valve lift amount of the intake valve 28 to control the intake air amount. . In the case of a system using both the variable intake valve lift mechanism 30 and the variable intake valve timing mechanism, the intake air amount may be controlled by continuously varying both the valve lift amount and the valve timing.
[0047]
As described above, the intake air amount control by the variable intake valve control has an effect of reducing the pumping loss and improving the fuel efficiency, but the combustion state deteriorates at a low load when the valve lift amount is reduced, so that the driver is deteriorated. It may adversely affect the performance and exhaust emissions.
[0048]
Therefore, the ECU 27 detects the degree of combustion instability based on the rotation fluctuation and the like by executing the intake air amount control program shown in FIG. 3 stored in the ROM. When the combustion state is deteriorating, the valve lift and the throttle opening are corrected to stabilize the combustion state. On the other hand, when the combustion instability is equal to or less than the predetermined determination value and the combustion state is stable, the valve lift and the throttle opening are corrected in a direction to increase the effect of the intake air amount control by the variable intake valve control. Hereinafter, the processing content of the intake air amount control program of FIG. 3 executed by the ECU 27 will be described.
[0049]
The intake air amount control program shown in FIG. 3 is executed at a predetermined cycle after an ignition switch (not shown) is turned on, and plays a role as intake air amount control means referred to in the claims. When the program is started, first, in step 101, the warming-up of the engine 11 is completed based on whether the cooling water temperature detected by the water temperature sensor 25 is higher than a predetermined warming-up judging water temperature T0 (for example, 80 ° C.). It is determined whether or not.
[0050]
If it is determined in step 101 that the warm-up is not completed, the process proceeds to step 102, in which the intake air amount is controlled by throttle valve control. In this case, while the valve lift amount (the maximum valve lift amount and the valve opening period) of the intake valve 28 is fixed to, for example, the maximum value, only the throttle opening is varied to control the intake air amount.
[0051]
Thereafter, if it is determined in step 101 that the warm-up has been completed, the process proceeds to step 103, in which a map of the throttle opening learning value GTA shown in FIG. And the throttle opening learned value GTA in the operating region corresponding to the target intake air amount GNtg) and reads it as the throttle opening TA.
TA = GTA
[0052]
The map in FIG. 4A is divided into a plurality of operating regions using the engine speed NE and the target intake air amount GNtg as parameters, and the throttle opening learning value GTA is stored for each operating region. .
[0053]
Thereafter, the routine proceeds to step 104, where a map of the valve lift learning value GVL shown in FIG. 4B is searched, and the valve in the operating region corresponding to the current operating state (the engine rotational speed NE and the target intake air amount GNtg). The lift learning value GVL is read and set as the valve lift amount VL.
VL = GVL
[0054]
The map of FIG. 4B is divided into a plurality of operating regions using the engine speed NE and the target intake air amount GNtg as parameters, and the valve lift learning value GVL is stored for each operating region.
[0055]
Thereafter, the routine proceeds to step 105, where the degree of combustion instability is calculated. Focusing on the relationship that the value of the rotation fluctuation changes according to the combustion state of each cylinder, in this step 105, the combustion instability is calculated as follows based on the rotation fluctuation. First, a time T30 required for the crankshaft to rotate a predetermined crank angle (for example, 30 ° C. A) is calculated based on the output signal of the crank angle sensor 26, and the maximum T30 is calculated for each period corresponding to the combustion stroke of each cylinder. The rotation fluctuation ΔNE of each cylinder is calculated based on the difference between the value and the minimum value. Then, the degree of variation (for example, the standard deviation) of the rotation fluctuation ΔNE of each cylinder is calculated, and is set as the combustion instability. The processing of step 105 serves as a combustion instability detecting means referred to in the claims.
[0056]
Since the in-cylinder pressure and the ionic current change according to the combustion state of each cylinder, the degree of combustion instability may be calculated in step 105 based on the in-cylinder pressure and the ionic current.
[0057]
When calculating the combustion instability based on the in-cylinder pressure, an in-cylinder pressure sensor (not shown) is provided for each cylinder, and the in-cylinder pressure sensor for each cylinder is provided for each period corresponding to the combustion stroke of each cylinder. The in-cylinder pressure characteristic value (for example, a peak value, an average value, an area, an in-cylinder pressure detection value at a predetermined crank angle, and the like) of the in-cylinder pressure is calculated based on the in-cylinder pressure detected in (5). Then, the degree of variation (for example, the standard deviation) of the in-cylinder pressure characteristic value of each cylinder is calculated and set as the combustion instability.
[0058]
On the other hand, when the combustion instability is calculated based on the ion current, the ion current characteristic value (peak value) is calculated based on the ion current detected via the ignition plug 21 of each cylinder for each period corresponding to the combustion stroke of each cylinder. Value, average value, area, ion current detection value at a predetermined crank angle, etc.), and the degree of variation (for example, standard deviation) of the ion current characteristic value of each cylinder is calculated as the combustion instability.
Further, the combustion instability may be calculated based on two or more of the rotation fluctuation, the in-cylinder pressure, and the ion current.
[0059]
After the calculation of the combustion instability, the process proceeds to step 106, where the combustion instability is compared with a predetermined determination value Krough. If the combustion instability is larger than the determination value Krough, it is determined that the combustion state is deteriorating. Then, the routine proceeds to step 107, where the valve lift amount VL is increased by a predetermined amount kVL1 by the following equation in order to stabilize the combustion state.
VL = VL + kVL1
[0060]
On the other hand, if it is determined in step 106 that the combustion instability is equal to or smaller than the determination value Krough, it is determined that the combustion state is stable, and the process proceeds to step 108, where the variable intake valve control is performed. In order to increase the effect of the intake air amount control, the valve lift amount VL is corrected by a predetermined amount kVL2 by the following equation.
VL = VL−kVL2
[0061]
After the valve lift amount VL is increased or decreased in step 107 or 108, a change in the engine rotational speed NE (a change in the intake air amount GN) due to the correction of the valve lift amount VL is performed in steps 109 to 111 described below. The throttle opening TA is reduced or increased so as to suppress the throttle opening TA.
[0062]
First, in step 109, the engine rotation speed NE is compared with the target rotation speed NEtg. If the engine rotation speed NE is higher than the target rotation speed NEtg, the process proceeds to step 110, and the throttle opening TA is increased by a predetermined amount kTA1 according to the following equation. Correct for weight loss.
TA = TA-kTA1
[0063]
On the other hand, if it is determined that the engine rotation speed NE is equal to or lower than the target rotation speed NEtg, the routine proceeds to step 111, where the throttle opening TA is increased by a predetermined amount kTA2 according to the following equation.
TA = TA + kTA2
[0064]
In step 109, it may be determined whether the intake air amount GN is larger than the target intake air amount GNtg. In general, the stability of the engine speed NE is more important than the output torque during the idling operation, and the output torque (the intake air amount GN) is more important than the stability of the engine speed NE during the normal operation other than the idling operation. At the time of idling operation, it is determined in step 109 whether or not the engine speed NE is higher than the target speed NEtg. It may be determined whether or not the amount GN is larger than the target intake air amount GNtg.
[0065]
After the throttle opening TA is reduced or increased in step 110 or 111, the process proceeds to step 112, where the throttle opening learning value GTA of the operating region read in step 103 is updated with the corrected throttle opening TA. .
GTA = TA
[0066]
Thereafter, the routine proceeds to step 113, where the learned valve lift value GVL of the operating region read in step 104 is updated with the corrected valve lift amount VL.
GVL = VL
The processing of steps 112 and 113 plays a role as a learning means in the claims.
[0067]
According to the above-described embodiment (1), the degree of combustion instability is detected based on rotation fluctuation and the like. When the degree of combustion instability is larger than the determination value Krough and the combustion state is deteriorating, the combustion The valve lift amount VL is increased and corrected to stabilize the state, and when the combustion instability is equal to or less than the determination value Krough and the combustion state is stable, the effect of the intake air amount control by the variable intake valve control is increased. Then, the valve lift VL is reduced and corrected. Further, the throttle opening TA is reduced or increased so as to suppress a change in the engine rotation speed NE (a change in the intake air amount GN) due to the correction of the valve lift amount VL. This improves the drivability and exhaust emission by preventing the deterioration of the combustion state caused by the intake air amount control by the variable intake valve control, and increases the fuel efficiency improvement effect of the intake air amount control by the variable intake valve control. Can be.
[0068]
In this embodiment (1), the valve lift amount VL and the throttle opening TA set based on the combustion instability are stored as a valve lift learning value GVL and a throttle opening learning value GTA. Since the lift learning value GVL and the throttle opening learning value GTA are corrected to set the next valve lift amount VL and the throttle opening TA, the control system is not affected by manufacturing variations or changes over time, etc. The valve lift VL and the throttle opening TA can be quickly controlled to appropriate values.
[0069]
<< Embodiment (2) >>
Next, an embodiment (2) of the present invention will be described with reference to FIGS.
In the intake air amount control by the variable intake valve control, when the load is small to reduce the valve lift, the intake air amount variation among the cylinders increases, the torque variation and the air-fuel ratio variation between the cylinders increase, and the drivability and the exhaust There is concern that emissions will worsen.
[0070]
Therefore, in the present embodiment (2), by executing the intake air amount control program shown in FIG. 6, an inter-cylinder variation value representing the variation in the intake air amount between the cylinders is detected, and the inter-cylinder variation value is set to a predetermined value. When it is larger than the determination value, the valve lift and the throttle opening are corrected in a direction to reduce the variation between cylinders. On the other hand, when the inter-cylinder variation value is equal to or less than the predetermined determination value, the valve lift and the throttle opening are corrected in a direction to increase the effect of the intake air amount control by the variable intake valve control.
[0071]
The program of FIG. 6 is obtained by changing the processing of steps 105 and 106 of the program of FIG. 3 described in the embodiment (1) to the processing of steps 105a and 106a, and the other processing is the same as that of FIG. is there.
[0072]
When the intake air amount control program of FIG. 6 is started, in steps 101 to 104, after the warm-up is completed, the throttle opening learning value GTA in the operating region corresponding to the current operating state is read, and is set as the throttle opening TA. At the same time, the valve lift learning value GVL in the operation region corresponding to the current operation state is read and set as the valve lift amount VL.
[0073]
Thereafter, the routine proceeds to step 105a, where an inter-cylinder variation value representing the intake air amount variation between cylinders is calculated. As shown in FIG. 7, an intake pulsation is generated in the intake pipe 12 of the engine 11 corresponding to the intake stroke of each cylinder, so that the waveform of the intake pipe pressure detected by the intake pipe pressure sensor 18 is Of the intake stroke, that is, a pulsation waveform reflecting the intake air amount of each cylinder.
[0074]
Therefore, in step 105a, an inter-cylinder variation value is calculated based on the intake pipe pressure detected by the intake pipe pressure sensor 18. In this case, based on the intake pipe pressure detected by the intake pipe pressure sensor 18 for each period corresponding to the intake stroke of each cylinder, the intake pipe pressure characteristic value (minimum value, maximum value, average value, amplitude value, area, trajectory length) Etc.). Then, a degree of variation (for example, a standard deviation) of the intake pipe pressure characteristic value of each cylinder is calculated, and the calculated degree is set as an inter-cylinder variation value. The processing in step 105a plays a role as an inter-cylinder variation detecting means referred to in the claims.
[0075]
When the air flow meter 14 that can detect the backflow of the intake air is used, the waveform of the intake air amount detected by the air flow meter 14 also has a pulsating waveform corresponding to the intake stroke of each cylinder, that is, the waveform of each cylinder. Since the pulsation waveform reflects the intake air amount, the inter-cylinder variation value may be calculated based on the intake air amount detected by the air flow meter 14. In this case, based on the intake air amount detected by the air flow meter 14 for each period corresponding to the intake stroke of each cylinder, the intake air amount characteristic value (minimum value, maximum value, average value, amplitude value, area, trajectory length, etc.) Is calculated, and a degree of variation (for example, a standard deviation) of the intake air amount characteristic value of each cylinder is calculated to obtain an inter-cylinder variation value.
[0076]
Alternatively, an intake air amount sensor may be provided in each intake manifold 19 of each cylinder, and the inter-cylinder variation value may be calculated based on the intake air amount of each cylinder detected by the intake air amount sensor of each cylinder.
[0077]
Further, since the air-fuel ratio of the exhaust gas of each cylinder changes according to the intake air amount of each cylinder, the inter-cylinder variation value may be calculated based on the air-fuel ratio of the exhaust gas detected by the air-fuel ratio sensor 24. good. In this case, the air-fuel ratio of each cylinder is estimated based on the output signal of the air-fuel ratio sensor 24 in consideration of the delay time of the exhaust system required until the exhaust gas discharged from the engine 11 is detected by the air-fuel ratio sensor 24. Then, a degree of variation (for example, a standard deviation) of the estimated air-fuel ratio of each cylinder is calculated to obtain an inter-cylinder variation value.
[0078]
Alternatively, air-fuel ratio characteristic values (average value, area, trajectory length, etc.) are calculated based on the air-fuel ratio detected by the air-fuel ratio sensor 24 for each period corresponding to the exhaust stroke of each cylinder, and the air-fuel ratio characteristics of each cylinder are calculated. The degree of variation (for example, standard deviation) of the values may be calculated to obtain the inter-cylinder variation value.
[0079]
In addition, the combustion state of each cylinder changes according to the intake air amount of each cylinder, and the rotation fluctuation, the in-cylinder pressure, and the ionic current change according to the combustion state. The inter-cylinder variation value may be calculated based on this.
[0080]
When the inter-cylinder variation value is calculated based on the rotation fluctuation, the rotation fluctuation ΔNE of each cylinder is calculated based on the difference between the maximum value and the minimum value of T30 for each period corresponding to the combustion stroke of each cylinder, and each cylinder is calculated. The degree of variation (for example, the standard deviation) of the rotational fluctuation ΔNE is calculated to obtain an inter-cylinder variation value.
[0081]
When calculating the inter-cylinder variation value based on the in-cylinder pressure, the in-cylinder pressure is detected based on the in-cylinder pressure (see FIG. 5) detected by the in-cylinder pressure sensor of each cylinder for each period corresponding to the combustion stroke of each cylinder. The pressure characteristic values (peak value, average value, area, trajectory length, etc.) are calculated, and the degree of variation (for example, standard deviation) of the in-cylinder pressure characteristic value of each cylinder is calculated to be the inter-cylinder variation value.
[0082]
Alternatively, the inter-cylinder variation value may be calculated based on the in-cylinder pressure value immediately before ignition of each cylinder or the in-cylinder pressure characteristic value (average value, area, trajectory length, etc.) during a predetermined period before ignition. .
[0083]
When the inter-cylinder variation value is calculated based on the ion current, the ion current characteristic value (peak value) is calculated based on the ion current detected via the ignition plug 21 of each cylinder for each period corresponding to the combustion stroke of each cylinder. Value, average value, area, etc.), and the degree of variation (for example, standard deviation) of the ion current characteristic value of each cylinder is calculated to obtain the inter-cylinder variation value.
Further, the inter-cylinder variation value may be calculated based on two or more of the intake pipe pressure, the intake air amount, the air-fuel ratio, the rotation fluctuation, the in-cylinder pressure, and the ion current.
[0084]
After calculating the inter-cylinder variation value, the process proceeds to step 106a, where the inter-cylinder variation value is compared with a determination value Krough. If the inter-cylinder variation value is greater than the determination value Krough, the process proceeds to step 107, and the intake air amount between the cylinders In order to reduce the variation, the valve lift amount VL is increased and corrected by a predetermined amount kVL1.
[0085]
On the other hand, if it is determined in step 106a that the inter-cylinder variation value is equal to or smaller than the determination value Krough, the process proceeds to step 108, in order to increase the effect of the intake air amount control by the variable intake valve control. The valve lift amount VL is reduced and corrected by a predetermined amount kVL2.
[0086]
Thereafter, the throttle opening TA is reduced or increased so as to suppress a change in the engine speed NE (a change in the intake air amount GN) due to the correction of the valve lift amount VL (steps 109 to 111).
[0087]
Thereafter, the throttle opening learning value GTA is updated with the corrected throttle opening TA, and the valve lift learning value GVL is updated with the corrected valve lift amount VL (steps 112 and 113).
[0088]
In the above-described embodiment (2), the inter-cylinder variation value representing the variation in the intake air amount between the cylinders is detected. When the inter-cylinder variation value is equal to or smaller than the determination value Krough, the valve lift amount VL is increased and corrected so that the effect of the intake air amount control by the variable intake valve control is increased. Further, the throttle opening TA is reduced or increased so as to suppress a change in the engine rotation speed NE (a change in the intake air amount GN) due to the correction of the valve lift amount VL. This reduces the variation in intake air amount between cylinders generated by intake air amount control by variable intake valve control, thereby improving drivability and exhaust emissions, while improving the fuel efficiency of intake air amount control by variable intake valve control. Can be increased.
[0089]
In the above embodiments (1) and (2), first, the valve lift amount VL is corrected based on the combustion instability (or the inter-cylinder variation value), and then the throttle opening TA is corrected. Conversely, the valve lift amount VL may be corrected after first correcting the throttle opening TA based on the combustion instability (or the inter-cylinder variation value).
[0090]
Further, in each of the above embodiments (1) and (2), a stepping motor is used as a drive source of the variable valve lift mechanisms 30 and 31, but other electromagnetic actuators or hydraulic actuators are used. Is also good. Alternatively, the valve lift, valve timing, and the like may be varied by directly driving the intake valve 28 and the exhaust valve 29 with an electromagnetic actuator.
[0091]
<< Embodiment (3) >>
Next, an embodiment (3) of the present invention will be described with reference to FIGS. This embodiment (3) may be implemented in combination with the embodiment (1) or the embodiment (2).
[0092]
In the present embodiment (3), the execution area of the intake air amount control by the variable intake valve control is limited to an area where combustion stability can be secured to some extent (or an area where intake air amount variation between cylinders can be reduced to some extent). It has an abnormality diagnosis function and a fail-safe function. Hereinafter, processing contents of each program for realizing these functions will be described.
[0093]
[Variable intake valve control execution flag set / reset]
The variable intake valve control execution flag set / reset program shown in FIG. 8 is executed at a predetermined cycle after an ignition switch (not shown) is turned on, and also serves as a control amount limitation control means described in the claims. When the program is started, first, in step 201, it is determined whether or not the degree of combustion instability is equal to or more than a predetermined value K1 (or whether or not the inter-cylinder variation value is equal to or more than a predetermined value K2). Here, the predetermined value K1 (or K2) is a determination value that determines the boundary of the execution region of the variable intake valve control, and may be set to an appropriate value through experiments, simulations, or the like.
[0094]
When the combustion instability is smaller than the predetermined value K1 (or when the inter-cylinder variation value is smaller than the predetermined value K2), the combustion stability can be ensured even if the intake air amount control by the variable intake valve control is performed (or In step 202, the variable intake valve control execution flag is set to "1", and the intake air amount control by the variable intake valve control is executed.
[0095]
On the other hand, when the combustion instability is equal to or higher than the predetermined value K1 (or when the inter-cylinder variation value is equal to or higher than the predetermined value K2), if the intake air amount control by the variable intake valve control is performed, the combustion state is changed. It is determined that there is a possibility of deterioration (or a possibility that the variation in the intake air amount between cylinders becomes large), and the routine proceeds to step 203, where the variable intake valve control execution flag is reset to “0”, and the variable intake valve control is performed. , The valve lift amount VL is fixed at the maximum valve lift amount VLmax, and the intake air amount control by throttle control is executed. At this time, the valve lift VL may be fixed to a lift other than the maximum valve lift VLmax.
[0096]
In this program, when the combustion instability is equal to or more than a predetermined value K1 (or when the inter-cylinder variation value is equal to or more than a predetermined value K2), the intake air amount control by the variable intake valve control is prohibited and the valve lift is controlled. Although the amount VL is fixed, the intake air amount control by the variable intake valve control is prohibited when the combustion instability is equal to or more than the predetermined value K1 (or when the inter-cylinder variation value is equal to or more than the predetermined value K2). Instead, the valve lift amount VL of the variable intake valve control may be subjected to guard processing with a predetermined guard value, or the variable range of the valve lift amount VL may be narrowed. What is necessary is just to appropriately limit the variable range of VL. At this time, the intake air amount may be controlled by using both the variable intake valve control and the throttle control.
[0097]
[Abnormal diagnosis]
The abnormality diagnosis program shown in FIG. 9 is executed at a predetermined cycle after an ignition switch (not shown) is turned on, and plays a role as abnormality diagnosis in the claims. When the program is started, first, in step 211, an abnormality determination value K3 is calculated by a map or the like based on the target air amount. Thereafter, in steps 212 and 213, it is determined whether or not the following two conditions (1) and (2) are satisfied to determine whether or not the abnormality diagnosis execution condition is satisfied.
[0098]
(1) The engine speed is within a predetermined range (step 212).
(2) The engine load is within a predetermined range (step 213).
If there is a condition that does not satisfy either one of these two conditions (1) and (2), the abnormality diagnosis execution condition is not satisfied, and the program is terminated as it is.
[0099]
On the other hand, if the above two conditions (1) and (2) are satisfied at the same time, the abnormality diagnosis execution condition is satisfied, and the routine proceeds to the next step 214, where the throttle opening TA is determined by the abnormality determination calculated in the step 211. It is determined whether or not the component of the intake air amount control system is abnormal based on whether or not the value is equal to or less than the value K3. As a result, if it is determined that the throttle opening TA is equal to or less than the abnormality determination value K3, it is determined that there is an abnormality in a component of the intake air amount control system, and the routine proceeds to step 215, where the abnormality determination flag Xfail indicates that there is an abnormality. Set to “1”, reset the variable intake valve control execution flag to “0”, inhibit the intake air amount control by the variable intake valve control, and fix the valve lift amount VL to the maximum valve lift amount VLmax. Then, the abnormal-time intake air amount control for controlling the intake air amount by the throttle control is executed. At this time, the valve lift VL may be fixed to a lift other than the maximum valve lift VLmax.
[0100]
On the other hand, if it is determined in step 214 that the throttle opening TA is larger than the abnormality determination value K3, it is determined that there is no abnormality in the components of the intake air amount control system, and the process proceeds to step 216. The determination flag Xfail is reset to “0” meaning no abnormality, the variable intake valve control execution flag is set to “1”, and the intake air amount control by the variable intake valve control is executed.
[0101]
[Abnormal point judgment]
The abnormality location determination program shown in FIG. 10 is executed at a predetermined cycle after an ignition switch (not shown) is turned on, and plays a role of abnormality diagnosis in the claims together with the abnormality diagnosis program of FIG.
[0102]
When the program is started, first, in step 221, it is determined whether or not the abnormality determination flag Xfail is set to “1” indicating that there is an abnormality, and the abnormality determination flag Xfail is set to “0” which indicates that there is no abnormality. ", The program is terminated without performing the subsequent processing.
[0103]
On the other hand, if the abnormality determination flag Xfail is set to “1” indicating that there is an abnormality, the process proceeds to step 222, and determines whether the combustion instability is equal to or less than the predetermined value K4 (or the inter-cylinder variation value). Is less than or equal to a predetermined value K5). Here, the predetermined value K4 (or K5) is a determination value for determining whether or not there is a failure in the variable intake valve lift mechanism 30, and may be set to an appropriate value through experiments, simulations, or the like.
[0104]
If it is determined in step 222 that the degree of combustion instability is equal to or less than the predetermined value K4 (or the inter-cylinder variation value is equal to or less than the predetermined value K5), the process proceeds to step 223, where the failure of the variable intake valve lift mechanism 30 is determined. judge.
[0105]
On the other hand, if it is determined that the degree of combustion instability is larger than the predetermined value K4 (or the inter-cylinder variation value is larger than the predetermined value K5), the process proceeds to step 224, and the variable intake valve lift mechanism abnormality diagnosis of FIG. It is determined whether or not the variable intake valve lift mechanism 30 is normal based on the diagnosis result by the program. As a result, if it is determined that the variable intake valve lift mechanism 30 is normal, the process proceeds to step 225, and it is determined that a component other than the variable intake valve lift mechanism 30 has failed. If it is determined that the variable intake valve lift mechanism 30 is not normal, the process proceeds to step 223, and it is determined that the variable intake valve lift mechanism 30 has failed.
[0106]
[Variable intake valve lift mechanism abnormality diagnosis]
The variable intake valve lift mechanism abnormality diagnosis program shown in FIG. 11 is executed at a predetermined cycle after an ignition switch (not shown) is turned on, and serves as an abnormality diagnosis in the claims together with the programs of FIGS. 9 and 10. Fulfill. In this program, the presence or absence of a failure of the variable intake valve lift mechanism 30 is determined as follows based on the time required for the actual valve lift to converge to the target valve lift. First, in step 231, it is determined whether or not the change amount of the target valve lift amount is equal to or less than a predetermined value K6. If the change amount of the target valve lift amount is larger than the predetermined value K6, the subsequent processing is performed. Without this program, end this program.
[0107]
On the other hand, if it is determined in step 231 that the change amount of the target valve lift amount is equal to or smaller than the predetermined value K6, the process proceeds to step 232, where the actual valve lift of the intake valve 28 detected by the lift sensor (not shown) is detected. It is determined whether the amount has converged to the target valve lift amount within a predetermined time K7. Here, the predetermined time K7 corresponds to the longest time in the normal range of the time required for the actual valve lift to converge on the target valve lift when the amount of change in the target valve lift is the predetermined value K6. An appropriate value may be set by a simulation or the like.
[0108]
If it is determined in step 232 that the actual valve lift has converged to the target valve lift within the predetermined time K7, the process proceeds to step 233, where the variable intake valve lift mechanism 30 is determined to be normal. On the other hand, if it is determined that the actual valve lift has not converged to the target valve lift within the predetermined time K7, the process proceeds to step 234, and it is determined that the variable intake valve lift mechanism 30 has failed.
[0109]
According to the above-described embodiment (3), when the valve lift amount VL is changed in a state where the combustion state has deteriorated to some extent due to operating conditions or the like (or a state where the variation in the intake air amount between the cylinders has increased to some extent). When the combustion instability is equal to or more than the predetermined value K1 in consideration of the possibility that the combustion state may worsen (or the variation in the intake air amount between cylinders may increase) (or the cylinder). When the inter-variation value is equal to or more than the predetermined value K2), the valve lift amount VL is fixed, so that the combustion state deteriorates to some extent (or the intake air amount variation between cylinders increases to some extent). The vicious cycle of forcibly changing the valve lift amount VL to further deteriorate the combustion state (or increasing the variation in intake air amount between cylinders) is avoided. It is possible.
[0110]
Also, during normal operation, in order to reduce the pumping loss and improve fuel efficiency, the throttle valve 15 is widely opened and the valve lift VL is varied to control the intake air amount. In consideration of the fact that the throttle valve is largely opened, the presence or absence of an abnormality in the components of the intake air amount control system is determined based on whether or not the throttle opening is equal to or less than the abnormality determination value K3. Therefore, it is possible to realize the abnormality diagnosis function without adding new sensors while satisfying the demand for cost reduction.
[0111]
In addition, when an abnormality of a component of the intake air amount control system is detected, the intake air amount control by the variable intake valve control is prohibited, and the valve lift amount VL is fixed to the maximum valve lift amount VLmax, thereby achieving high reliability. Since the abnormal intake air amount control that controls the intake air amount by the throttle control is executed, the intake air amount can be controlled more accurately than the case where the intake air amount control by the variable intake valve control is executed when the abnormality is detected. Probability is high.
[0112]
During the execution of the abnormal-time intake air amount control, the intake air amount is controlled by the throttle control. Therefore, the combustion instability is reduced by the abnormal-time intake air amount control (throttle control) (or the inter-cylinder variation value is reduced). ) Means that a stable combustion state can be obtained by the intake air amount control by the throttle control (or the variation in the intake air amount among the cylinders becomes small), and thus the intake air amount can be accurately controlled by the throttle control. (The drive system and control system of the throttle valve 15 are normal).
[0113]
In consideration of this point, in the present embodiment (3), it is determined whether the combustion instability is equal to or less than the predetermined value K4 during the execution of the abnormal intake air amount control (or the inter-cylinder variation value is equal to or less than the predetermined value K5). ), The presence or absence of a failure in the variable intake valve lift mechanism 30 is determined. Therefore, the function of diagnosing abnormality of the variable intake valve lift mechanism 30 can be reduced at a low cost without adding new sensors. It can be realized while satisfying the requirements of
[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 processing flow of an intake air amount control program according to the embodiment (1).
4A is a diagram conceptually showing a map of a throttle opening learning value GTA, and FIG. 4B is a diagram conceptually showing a map of a valve lift learning value GVL;
FIG. 5 is a time chart showing the behavior of in-cylinder pressure.
FIG. 6 is a flowchart showing a processing flow of an intake air amount control program according to the embodiment (2).
FIG. 7 is a time chart showing the behavior of the intake pipe pressure.
FIG. 8 is a flowchart showing the flow of processing of a variable intake valve control execution flag set / reset program according to the embodiment (3).
FIG. 9 is a flowchart showing the flow of processing of an abnormality diagnosis program according to the embodiment (3).
FIG. 10 is a flowchart showing the flow of processing of an abnormal point determination program according to the embodiment (3).
FIG. 11 is a flowchart showing a processing flow of a variable intake valve lift mechanism abnormality diagnosis program according to the embodiment (3).
[Explanation 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 Sensors, 26: crank angle sensor, 27: ECU (intake air amount control means, combustion instability detection means, inter-cylinder variation detection means, learning means, control amount restriction means, abnormality determination means), 28 ... intake valve, 29 ... exhaust valve, 30, 31 ... variable valve lift mechanism.

Claims (19)

In a control device for an internal combustion engine having a variable intake valve mechanism capable of controlling an intake air amount by varying a control amount of an intake valve of the internal combustion engine,
Combustion instability detecting means for detecting the combustion instability of the internal combustion engine;
An intake air amount control means for controlling an intake air amount by controlling a control amount of the intake valve and / or a control amount of the throttle valve based on the combustion instability. Control device. The control of an internal combustion engine according to claim 1, wherein the combustion instability detecting means detects the combustion instability based on at least one of a rotation fluctuation, a cylinder pressure, and an ion current. apparatus. 2. The control device according to claim 1, further comprising a control amount limiting unit configured to limit a variable range of the control amount of the intake valve when the combustion instability detected by the combustion instability detecting unit is equal to or more than a predetermined value. 3. The control device for an internal combustion engine according to 2. The control amount limiting means fixes the control amount of the intake valve to a predetermined value when the combustion instability detected by the combustion instability detecting means is equal to or more than a predetermined value. Internal combustion engine control device. An abnormality determining means for determining whether or not there is an abnormality in a component of the intake air amount control system based on whether or not the opening of the throttle valve is equal to or less than a predetermined abnormality determination value. 5. The control device for an internal combustion engine according to any one of 4. The abnormal intake air amount control means for fixing the control amount of the intake valve and controlling the intake air amount by controlling the opening of the throttle valve when the abnormality determining means detects an abnormality. The control device for an internal combustion engine according to claim 5, wherein The abnormality determination unit determines that the variable intake valve mechanism is abnormal when the combustion instability detected by the combustion instability detection unit during execution of the abnormal intake air amount control is smaller than a predetermined value. The control device for an internal combustion engine according to claim 6, wherein the control is performed. The abnormality determination unit is configured to normally operate the variable intake valve mechanism when the combustion instability detected by the combustion instability detection unit during execution of the abnormal intake air amount control is equal to or greater than a predetermined value. 8. The internal combustion engine according to claim 6, wherein it is determined whether or not the internal combustion engine is operating, and if it is determined that the internal combustion engine is operating normally, it is determined that a component other than the variable intake valve mechanism is abnormal. Engine control device. The abnormality determining means determines whether or not the variable intake valve mechanism is operating normally by comparing an output of a sensor for detecting a position of the intake valve with a control amount of the intake valve. The control device for an internal combustion engine according to claim 8, wherein In a control device for an internal combustion engine having a variable intake valve mechanism capable of controlling an intake air amount by varying a control amount of an intake valve of the internal combustion engine,
An inter-cylinder variation detecting means for detecting an inter-cylinder variation value representing an intake air amount variation between cylinders of the internal combustion engine,
An intake air amount control means for controlling an intake air amount by controlling a control amount of the intake valve and / or a control amount of the throttle valve based on the inter-cylinder variation value. Control device. The inter-cylinder variation detecting means detects the inter-cylinder variation value based on at least one of an intake air amount, an intake pipe pressure, a rotation variation, an in-cylinder pressure, an ion current, and an air-fuel ratio. The control device for an internal combustion engine according to claim 10. 12. A control amount limiter for limiting a variable range of a control amount of the intake valve when an inter-cylinder variation value detected by the inter-cylinder variation detector is equal to or greater than a predetermined value. 3. The control device for an internal combustion engine according to claim 1. 13. The control method according to claim 12, wherein the control amount limiting unit fixes the control amount of the intake valve to a predetermined value when the inter-cylinder variation value detected by the inter-cylinder variation detection unit is equal to or more than a predetermined value. Control device for internal combustion engine. 11. An abnormality judging means for judging the presence or absence of an abnormality in a component of the intake air flow control system based on whether or not the opening of the throttle valve is equal to or less than a predetermined abnormality determination value. A control device for an internal combustion engine according to any one of claims 13 to 13. The abnormal intake air amount control means for fixing the control amount of the intake valve and controlling the intake air amount by controlling the opening of the throttle valve when the abnormality determining means detects an abnormality. The control device for an internal combustion engine according to claim 14, wherein the control is performed. The abnormality determination unit determines that the variable intake valve mechanism is abnormal when the inter-cylinder variation value detected by the inter-cylinder variation detection unit during execution of the abnormal intake air amount control is smaller than a predetermined value. The control device for an internal combustion engine according to claim 6, wherein: The abnormality determining means operates the variable intake valve mechanism normally when the inter-cylinder variation value detected by the inter-cylinder variation detecting means during execution of the abnormal intake air amount control is equal to or greater than a predetermined value. 17. The internal combustion engine according to claim 15, wherein it is determined whether or not the internal combustion engine is operating normally. If it is determined that the internal combustion engine is operating normally, it is determined that a component other than the variable intake valve mechanism is abnormal. Control device. The abnormality determining means determines whether or not the variable intake valve mechanism is operating normally by comparing an output of a sensor for detecting a position of the intake valve with a control amount of the intake valve. The control device for an internal combustion engine according to claim 17, wherein Learning means for learning a control amount of the intake valve and / or a control amount of the throttle valve set by the intake air amount control means;
19. The control device for an internal combustion engine according to claim 1, wherein the intake air amount control unit sets a next control amount based on the control amount learned by the learning unit.

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