JP7523867B2 - Control device for internal combustion engine - Google Patents

Description

The present invention relates to the control of an internal combustion engine equipped with a variable valve timing mechanism that can change the timing of opening or closing the intake or exhaust valves of a cylinder, and an exhaust gas recirculation device that can recirculate a portion of the exhaust gas flowing through the exhaust passage back into the intake passage.

Internal combustion engines mounted on vehicles and the like are known to have a phase-changing VVT mechanism that can variably control the opening and closing timing of the intake valve and/or exhaust valve. This type of VVT mechanism advances or retards the opening and closing timing of the intake valve and/or exhaust valve by changing the rotational phase of the intake camshaft, which drives the intake valve to open and close, and/or the exhaust camshaft, which drives the exhaust valve to open and close, relative to the crankshaft, which is the output shaft of the internal combustion engine. The VVT mechanism mainly contributes to improving the efficiency of filling the cylinder with intake air. In addition, by adjusting the length of the valve overlap period during which both the intake valve and exhaust valve of the cylinder are open, it is also possible to perform internal EGR, which causes a portion of the combustion gas generated in the cylinder to remain in the cylinder without being exhausted.

In addition, an external EGR device is also widely used, in which the exhaust passage and the intake passage of the internal combustion engine are connected via an EGR passage, and a part of the combustion gas is returned to the intake passage via the EGR passage and mixed with the intake air. An EGR valve is provided on the EGR passage to open and close it. By manipulating the opening of the EGR valve, the amount of recirculated external EGR gas increases or decreases. By using EGR, it is possible to reduce the combustion temperature in the cylinder, reduce the amount of harmful substance _NOx emitted, and reduce pumping loss (for the above, see, for example, the following patent document).

JP 2015-105614 A

To determine the amount of fuel injected into a cylinder, the amount of air (fresh air or oxygen) drawn into the cylinder must be calculated. Basically, an intake pressure sensor is installed to detect the intake pressure in the intake passage connected to the cylinder, and the intake air volume is estimated based on the intake pressure actually measured via the intake pressure sensor and the current engine speed. However, the intake air flowing into the cylinder may contain external EGR gas in addition to air, and internal EGR gas may remain in the cylinder. Therefore, to accurately estimate the intake air volume, it is necessary to make corrections according to the amount of operation of the VVT mechanism related to the internal EGR and the amount of operation of the EGR valve related to the external EGR.

In conventional internal combustion engine operation control, the VVT mechanism and the EGR valve were not operated simultaneously. In other words, the EGR valve opening was kept constant while the valve timing realized by the VVT mechanism was changed, and the valve timing was kept constant while the EGR valve opening was expanded or contracted. Therefore, when correcting the intake air volume based on the measured intake pressure, a correction amount was used that corresponds to the valve timing experimentally determined on the premise that the EGR valve was fixed at a certain opening (particularly, fully closed), and a correction amount was used that corresponds to the EGR valve opening experimentally determined on the premise that the valve timing was fixed at a certain phase angle (for example, a phase angle at which the valve overlap amount is zero).

Recently, it has become clear that operating the VVT mechanism and the EGR valve simultaneously is effective in further improving the efficiency and fuel economy of an internal combustion engine. However, as a result of intensive research by the inventors, during the transitional period when the VVT mechanism and the EGR valve are operated simultaneously, if the intake air volume is estimated using the conventional method described above, an error will occur between the actual amount of air filling the cylinder and the true value, which will cause the fuel injection volume to be inappropriate and the air-fuel ratio of the mixture to deviate, even if only temporarily, from the target air-fuel ratio. Deviation of the air-fuel ratio from the target value leads to increased emissions of harmful substances and reduced fuel economy, which is by no means desirable.

The present invention was made with the above in mind, and its intended purpose is to minimize deviations from the target air-fuel ratio value when controlling the operation of an internal combustion engine equipped with both a VVT mechanism and an EGR device.

The present invention is a control device for controlling an internal combustion engine equipped with a VVT mechanism capable of changing the timing of opening or closing the intake valve or exhaust valve of a cylinder, and an EGR device capable of recirculating a portion of the exhaust gas flowing through an exhaust passage to the intake passage, the control device measuring the intake pressure in an intake passage connected to the cylinder and calculating the amount of air taken into the cylinder, A correction amount p1 corresponding to the valve timing realized by the VVT mechanism and not depending on the opening degree of the EGR valve is stored in a memory, and a correction amount p1 corresponding to the current valve timing is obtained based on the correction amount p1. A correction amount p2 corresponding to the EGR valve opening and not depending on the valve timing realized by the VVT mechanism is stored in a memory, and a correction amount p2 corresponding to the current EGR valve opening is obtained based on the correction amount p2. Further, a correction amount pEX corresponding to the valve timing realized by the VVT mechanism and the opening degree of the EGR valve is stored in a memory, and a correction amount pEX corresponding to the current valve timing and the current EGR valve opening is obtained based on the correction amount pEX. An actual measured value P of intake pressure is corrected using the correction amount p1, the correction amount p2, and the correction amount pEX to determine a partial pressure PM of air in the intake air taken into the cylinder, and an intake air amount or a fuel injection amount is calculated, and the correction amount pEX is A control device for an internal combustion engine has been configured in which an increase in deviation C, which is the difference between a deviation B of an actual air-fuel ratio from a target air-fuel ratio that occurs when an operation to change the valve timing by the VVT mechanism is performed while keeping the opening of the EGR valve constant, and a deviation A of an actual air-fuel ratio from a target air-fuel ratio that occurs when an operation to change the valve timing by the VVT mechanism is performed while changing the opening of the EGR valve, is determined to be approximately constant regardless of the valve timing .

The present invention makes it possible to reduce deviations from the target air-fuel ratio value when controlling the operation of an internal combustion engine equipped with both a VVT mechanism and an EGR device.

1 is a diagram showing a schematic configuration of an internal combustion engine and a control device according to an embodiment of the present invention; FIG. 4 is a flowchart showing an example of a processing procedure executed by the control device according to a program of the embodiment. 5 is a diagram for explaining a method for determining a correction amount of the intake air amount used by the control device of the embodiment. FIG.

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an internal combustion engine for a vehicle according to this embodiment. The internal combustion engine according to this embodiment is a spark-ignition four-stroke gasoline engine having a plurality of cylinders 1 (one of which is shown in FIG. 1). An injector 11 that injects fuel toward the intake port is provided upstream of the intake valve of each cylinder 1 and near the intake port connected to each cylinder 1. An ignition plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The ignition plug 12 generates a spark discharge between a center electrode and a ground electrode when an induced voltage generated by an ignition coil is applied to the ignition coil. The ignition coil is integrally built into the coil case together with an igniter, which is a semiconductor switching element.

The intake passage 3, which supplies intake air to the cylinders 1, takes in air from the outside and directs it to the intake port of each cylinder 1. An air cleaner 31, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order from upstream on the intake passage 3.

The exhaust passage 4 for discharging exhaust gas from the cylinders 1 guides the exhaust gas generated by burning fuel in the cylinders 1 to the outside through the exhaust port of each cylinder 1. An exhaust manifold 42 and a three-way catalyst 41 for purifying the exhaust gas are arranged on the exhaust passage 4.

The external EGR device 2 includes an external EGR passage 21 that connects the exhaust passage 4 and the intake passage 3, an EGR cooler 22 provided on the EGR passage 21, and an EGR valve 23 that opens and closes the EGR passage 21 to control the flow rate of EGR gas flowing through the EGR passage 21. The inlet of the EGR passage 21 is connected to a predetermined location downstream of the catalyst 41 in the exhaust passage 4. The outlet of the EGR passage 21 is connected to a predetermined location downstream of the throttle valve 32 in the intake passage 3 (in particular, the surge tank 33 or the intake manifold 34).

In the internal combustion engine of this embodiment, a timing chain (or belt) is wrapped around the crank sprocket (or pulley), the intake side sprocket (or pulley), and the exhaust side sprocket (or pulley), and this timing chain transmits the rotational driving force from the crankshaft to the intake camshaft via the intake side sprocket and to the exhaust camshaft via the exhaust side sprocket.

In addition, a VVT mechanism 5 is interposed between the intake sprocket and the intake camshaft. The VVT mechanism 5 is a known mechanism that changes the opening and closing timing of the intake valve of cylinder 1 by changing the rotational phase of the intake camshaft relative to the crankshaft. The VVT mechanism 5 may be a vane-type VVT that uses the lubricating oil (engine oil) of the internal combustion engine as the working fluid and displaces the phase angle of the camshaft relative to the cam sprocket using the lubricating oil pressure, or it may be a motor-driven VVT that displaces the phase angle of the camshaft relative to the cam sprocket using an electric motor.

The ECU (Electronic Control Unit) 0, which is the control device for the internal combustion engine in this embodiment, is a microcomputer system having a processor, memory, an input interface, an output interface, etc. The ECU 0 may be configured by connecting multiple ECUs or controllers so that they can communicate with each other via an electric communication line such as a CAN (Controller Area Network).

The input interface of the ECU 0 receives inputs such as a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle signal b output from a crank angle sensor that detects the rotation angle of the crankshaft and the engine speed, an accelerator opening signal c output from a sensor that detects the depression amount of the accelerator pedal or the opening degree of the throttle valve 32 as the accelerator opening (in other words, the required engine load factor or engine torque), a cooling water temperature signal d output from a water temperature sensor that detects the cooling water temperature of the internal combustion engine, an intake air temperature/intake pressure signal e output from a temperature/pressure sensor that detects the intake air temperature and intake pressure in the intake passage 3 (particularly, the surge tank 33 or the intake manifold 34), an atmospheric pressure signal f output from a sensor that detects the atmospheric pressure, a cam angle signal g output from a cam angle sensor at multiple cam angles of the intake camshaft, and an air-fuel ratio signal h output from an air-fuel ratio sensor ( _O2 sensor or linear A/F sensor) that detects the air-fuel ratio of the gas flowing through the exhaust passage 4.

The output interface of ECU0 outputs an ignition signal i to the igniter of the spark ignition device that applies high voltage to the spark plug 12, a fuel injection signal j to the injector 11, an opening control signal k to the throttle valve 32, an opening control signal l to the EGR valve 23, a valve timing control signal m to the VVT mechanism 5, and the like.

The processor of ECU0 interprets and executes programs stored in memory in advance, and calculates operating parameters to control the operation of the internal combustion engine. ECU0 acquires various pieces of information a, b, c, d, e, f, g, and h required for controlling the operation of the internal combustion engine via an input interface, and determines various operating parameters such as the required fuel injection amount appropriate to the amount of air (fresh air) drawn into cylinder 1, fuel injection timing (including the number of fuel injections per combustion), fuel injection pressure, ignition timing (including the number of spark ignitions per combustion), required EGR rate (or EGR gas amount), and intake valve opening and closing timing. ECU0 applies various control signals i, j, k, l, and m corresponding to the operating parameters via an output interface.

When determining the fuel injection amount, ECU0 determines a basic amount TP of fuel injection amount that is proportional to the amount of air taken into cylinder 1 and that can realize the target air-fuel ratio for the amount of intake air. In a wide range of operating conditions, the target air-fuel ratio is the stoichiometric air-fuel ratio or close to it. However, in the high rotation range or high load range, the target air-fuel ratio may be set richer than the stoichiometric air-fuel ratio in order to increase the output of the internal combustion engine.

This basic injection amount TP is then corrected by a feedback correction coefficient FAF, which corresponds to the deviation between the air-fuel ratio of the gas flowing into the catalyst 41 and its target value, and various correction coefficients K, which are determined according to environmental conditions and other factors. The correction coefficients FAF and K are each a positive number that increases or decreases around 1. Furthermore, the final fuel injection time T, i.e., the time to energize the injector 11 to open it, is calculated taking into account the invalid injection time TAUV, during which no fuel is injected even when the injector 11 is opened. The fuel injection time T is calculated as follows:
T=TP×FAF×K+TAUV
The ECU 0 inputs a signal j to the injector 11 for the fuel injection time T, and opens the valve of the injector 11 to inject fuel.

In order to accurately control the air-fuel ratio of the mixture to the target air-fuel ratio, the ECU 0 needs to accurately estimate the amount of air (or oxygen) that is drawn into the cylinder 1. If an error occurs between the estimated amount of intake air and the actual amount, the fuel injection amount TP will be inappropriate, and the air-fuel ratio will deviate from its target value, which may lead to increased emissions of harmful substances and reduced fuel efficiency.

As shown in FIG. 2, in estimating the intake air volume, the ECU 0 of this embodiment first obtains the current intake pressure P in the intake passage 3 (surge tank 33 or intake manifold 34) connected to the cylinder 1 (step S1). It goes without saying that the intake pressure P downstream of the throttle valve 32 in the intake passage 3, and therefore the amount of intake air flowing into the cylinder 1, depends on the opening degree of the throttle valve 32. The intake pressure P can be measured by referring to the output signal e of the intake pressure sensor.

The intake air flowing through the intake passage 3 into cylinder 1 may contain external EGR gas. Furthermore, internal EGR gas may remain in cylinder 1, which has not been completely discharged during the exhaust stroke, or has been re-inhaled into cylinder 1 during the intake stroke. The intake pressure P calculated in step S1 ignores the presence of external EGR and internal EGR. In order to accurately calculate the amount of air drawn into cylinder 1, the actually measured intake pressure P cannot be regarded as the partial pressure of the intake air as it is, but a correction must be made to subtract the partial pressure of the EGR gas from it.

Therefore, next, ECU0 determines a correction amount p1 (not depending on the opening degree of EGR valve 23) according to (only) the valve timing currently embodied by VVT mechanism 5 (step S2). The length of the valve overlap period during which both the intake valve and exhaust valve of cylinder 1 are open affects the amount of internal EGR gas remaining in cylinder 1. When the intake valve opening timing is advanced and the valve overlap amount increases, the internal EGR increases and the amount of air filled in cylinder 1 decreases accordingly. Therefore, the more the phase angle of the intake valve timing is advanced, the more it is required to reduce the intake pressure P determined in step S1 and correct it so that it approaches the true value of the partial pressure of the intake air. If the correction amount p1 is a correction coefficient multiplied by the intake pressure P, the larger the advance amount of the intake valve timing, the smaller the value of the correction coefficient will be; if the correction amount p1 is a correction term subtracted from the intake pressure P, the larger the advance amount of the intake valve timing, the larger the absolute value of the correction term will be.

Map data that specifies the relationship between the engine speed Ne and intake pressure P and the correction amount p1 is stored in advance in the memory of ECU0. The correction amount p1 related to the internal EGR is experimentally obtained by changing the valve timing with the VVT mechanism 5 while keeping the opening of the EGR valve 23 constant (particularly fully closed) under various operating conditions. The reason why [engine speed Ne, intake pressure P] are used as arguments is that the valve timing when controlling the operation of the internal combustion engine is determined according to the engine speed Ne and intake pressure P (indirectly indicating the amount of advance of the intake valve timing). ECU0 searches the map using the current engine speed Ne and intake pressure P as keys, and obtains the current correction amount p1.

The ECU 0 also determines a correction amount p2 (not depending on the valve timing realized by the VVT mechanism 5) according to the current opening degree of the EGR valve 23 (only) (step S3). The opening degree of the EGR valve 23 affects the amount of external EGR gas that flows back from the exhaust passage 4 to the intake passage 3 and into the cylinder 1. When the opening degree of the EGR valve 23 is widened, the external EGR increases, and the amount of air filled into the cylinder 1 decreases accordingly. Therefore, the larger the opening degree of the EGR valve 23, the more it is required to correct the intake pressure P obtained in step S1 by subtracting it so as to approach the true value of the partial pressure of the intake air. If the correction amount p2 is a correction coefficient by which the intake pressure P is multiplied, the larger the opening degree of the EGR valve 23, the smaller the value of the correction coefficient is, and if the correction amount p2 is a correction term to be subtracted from the intake pressure P, the larger the absolute value of the correction term is, the larger the opening degree of the EGR valve 23.

Map data that defines the relationship between the engine speed Ne and intake pressure P and the correction amount p2 is stored in advance in the memory of ECU0. The correction amount p2 related to the external EGR is experimentally obtained by controlling the opening of the EGR valve 23 while keeping the valve timing realized by the VVT mechanism 5 constant (particularly, the timing at which the valve overlap amount is 0) under various operating conditions. The reason why [engine speed Ne, intake pressure P] is used as an argument is that the opening of the EGR valve 23 when controlling the operation of the internal combustion engine is determined according to the engine speed Ne and intake pressure P (indirectly indicating the opening of the EGR valve 23). ECU0 searches the map using the current engine speed Ne and intake pressure P as keys, and obtains the current correction amount p2.

The above steps S1 to S3 are the same as those in conventional internal combustion engine control. However, the correction amounts p1 and p2 calculated in steps S2 and S3 are not determined on the assumption that both the VVT mechanism 5 and the EGR valve 23 will be operated simultaneously. Correction using only these correction amounts p1 and p2 may result in an error between the intake air volume estimated by the ECU 0 and the actual amount of air filled into the cylinder 1 during the transitional period when the VVT mechanism 5 and the EGR valve 23 are operated simultaneously.

Therefore, in this embodiment, in addition to the conventional control method, a new correction amount pEX is introduced to further reduce such errors (step S4).

Hereafter, a method for determining a new correction amount pEX in the cooperative control of the VVT mechanism 5 and the EGR device 2 will be described. Figure 3 shows the result of measuring the deviation of the air-fuel ratio of the mixture filled in the cylinder 1 (and the exhaust discharged from the cylinder 1 and flowing into the catalyst 41) from the target air-fuel ratio when the intake valve timing is changed by operating the VVT mechanism 5 under multiple accelerator opening (or intake pressure P) conditions and the intake air amount is estimated and the fuel injection amount TP is determined according to the conventional control method. The horizontal axis is the advance amount (crank angle (° CA)) of the opening and closing timing of the intake valve embodied by the VVT mechanism 5, and the valve overlap amount, which is the period during which both the intake valve and the exhaust valve are open, is 0 at a reference phase angle (for example, 10° CA) α. If the opening and closing timing of the intake valve is advanced beyond the reference phase angle α, the valve overlap amount is enlarged and the internal EGR amount is increased. The vertical axis is the deviation between the air-fuel ratio of the mixture and the target air-fuel ratio; if the deviation is zero, the air-fuel ratio of the mixture matches the target air-fuel ratio.

In FIG. 3, dashed line B represents the deviation in the air-fuel ratio that occurs when the intake valve timing is changed by the VVT mechanism 5 while the opening of the EGR valve 23 is kept constant (particularly, fully closed). In contrast, solid line A represents the deviation in the air-fuel ratio that occurs when the intake valve timing is changed by the VVT mechanism 5 while changing the opening of the EGR valve (particularly while opening the valve instead of fully closing it). Also, dashed line C represents the difference between the latter deviation and the former deviation (C=A-B). It can be seen that unless the correction amount pEX, which is introduced for the first time in this embodiment, is taken into account, the deviation in the air-fuel ratio increases in the coordinated control in which the VVT mechanism 5 and the EGR valve 23 are operated simultaneously compared to the conventional control in which only one is operated and the other is fixed. Furthermore, the increase C of the deviation is minimum (close to 0) when the valve timing realized by the VVT mechanism 5 is near the reference phase angle α, and increases as the valve timing advances or retards from the reference phase angle α. However, this tendency is the same regardless of the degree of accelerator opening. Moreover, the shape of the line C of the increase in deviation in FIG. 3 and the width (height along the vertical axis) between the maximum and minimum values are approximately uniform regardless of the degree of accelerator opening.

In cooperative control in which the VVT mechanism 5 and the EGR valve 23 are operated simultaneously, in order to further reduce the error mixed into the intake air amount estimated by the ECU 0 and further reduce the deviation of the air-fuel ratio of the mixture from the target air-fuel ratio, the correction amount pEX is determined so that at least the deviation increase amount C is approximately constant regardless of the advance amount of the valve timing, in other words, so that the line of the deviation increase amount C in FIG. 3 is approximately horizontal along the horizontal axis (in this case, the deviation line A during cooperative control and the deviation line B during non-cooperative control become approximately parallel to each other, and the difference between the two is smaller than that shown in FIG. 3). Such a correction amount pEX depends on the valve timing embodied by the VVT mechanism 5 and the opening of the EGR valve 23, but does not necessarily depend on the accelerator opening, and it is considered possible to use the same correction amount pEX even if the accelerator opening is different.

The correction amount pEX may be a correction coefficient by which the intake pressure P is multiplied, or may be a correction term by which the intake pressure P is added or subtracted. Alternatively, the correction amount pEX may be a correction coefficient by which the correction amount p1 or the correction amount p2 is multiplied, or a correction term by which the correction amount p1 or the correction amount p2 is added or subtracted. In this embodiment, the correction amount pEX corrects the correction amount p2. This is because the opening and closing speed of the EGR valve 23 is slower than the speed at which the phase angle of the camshaft is changed by the VVT mechanism 5.

Map data that defines the relationship between the advance amount of the valve timing realized by the VVT mechanism 5, the opening degree of the EGR valve 23, and the correction amount pEX is stored in advance in the memory of the ECU 0. In step S4, the ECU 0 searches the map using the current advance amount of the valve timing and the opening degree of the EGR valve 23 as keys to obtain the current correction amount pEX.

Then, the ECU 0 corrects the measured intake pressure P using the correction amounts p1, p2, and pEX to obtain a partial pressure PM of the intake air that is close to the true value (step S5). For example,
PM=P×p1±(p2±pEX)
In the above formula, p1 is a correction coefficient related to the internal EGR, and p2 and pEX are correction terms related to the external EGR.

Finally, ECU0 determines the amount of air taken into cylinder 1 from the current engine speed Ne and intake air pressure PM (step S6). The current engine speed Ne can be measured by referring to the output signal b of the crank angle sensor. Map data that defines the relationship between the engine speed Ne and intake air pressure PM and the intake air amount is stored in advance in the memory of ECU0. ECU0 searches the map using the current engine speed Ne and intake air pressure PM as keys to obtain the current intake air amount. The intake air amount may be corrected according to the current intake temperature and atmospheric pressure.

As mentioned earlier, the calculated intake air volume is used to calculate the fuel injection volume TP.

In this embodiment, the control device controls an internal combustion engine equipped with a VVT mechanism 5 that can change the timing of opening or closing the intake valve of cylinder 1, and an EGR device 2 that can recirculate a portion of the exhaust gas flowing through the exhaust passage 4 to the intake passage 3. The control device measures the intake pressure P in the intake passage 3 connected to the cylinder 1 to calculate the amount of air taken into the cylinder 1. The control device stores and holds in memory a correction amount pEX that reduces the difference C between the deviation B of the actual air-fuel ratio from the target air-fuel ratio that occurs when the VVT mechanism 5 changes the timing of opening or closing the intake valve while keeping the opening of the EGR valve 23 constant, and the deviation A of the actual air-fuel ratio from the target air-fuel ratio that occurs when the VVT mechanism 5 changes the timing of opening or closing the intake valve while changing the opening of the EGR valve 23. The control device 0 for the internal combustion engine corrects the intake air amount (intake air pressure PM) using the correction amount pEX.

According to this embodiment, the deviation of the air-fuel ratio from the target value during cooperative control in which the VVT mechanism 5 and the external EGR device 2 are operated simultaneously can be reduced. If a deviation occurs between the actual air-fuel ratio known by referring to the output signal h of the air-fuel ratio sensor and the target air-fuel ratio, the deviation is corrected after the fact by feedback control (correction coefficient FAF). The control device 0 of this embodiment can more accurately estimate the amount of air taken into the cylinder 1 during a transitional period in which the valve timing embodied by the VVT mechanism 5 and the opening degree of the EGR valve 23 are changed simultaneously, and can appropriately set the basic fuel injection amount TP to prevent the deviation between the air-fuel ratio and its target value from increasing. Therefore, the convergence of the air-fuel ratio to the target value through feedback control is accelerated, an increase in the amount of harmful substances emitted can be avoided, and wasteful fuel consumption (if the state in which the air-fuel ratio is leaner than the target value continues for a long time, the fuel injection amount FAF continues to be increased during that time) is suppressed.

The control method of this embodiment can be implemented without adding new hardware, and does not result in increased costs.

The present invention is not limited to the embodiment described above in detail. For example, in the above embodiment, the correction amount pEX is set to correct the intake air amount (intake air pressure PM, more specifically, the correction amount p2), but instead, it is also possible to set it to correct the fuel injection amount TP (a correction coefficient multiplied by the fuel injection amount TP, or a correction term added to or subtracted from the fuel injection amount TP). This also makes it possible to prevent the deviation between the air-fuel ratio of the mixture and its target value from increasing.

In the above embodiment, the internal combustion engine is not equipped with an exhaust VVT mechanism for variably controlling the opening and closing timing of the exhaust valve of cylinder 1, but the internal combustion engine may be equipped with an exhaust VVT mechanism similar to the intake VVT mechanism 5. When the exhaust valve timing is advanced or retarded via the exhaust VVT mechanism, the valve overlap amount changes, and the amount of internal EGR gas increases or decreases. Therefore, it is naturally conceivable that the present invention can be applied to the coordinated control of the exhaust VVT mechanism and the external EGR device 2.

The specific form of the VVT mechanism 5 for changing the opening and closing timing of the intake valve and/or exhaust valve of the cylinder 1 of the internal combustion engine is arbitrary and is not limited to a unique form. In addition to mechanisms that advance/retard the rotational phase of the intake camshaft and/or exhaust camshaft relative to the crankshaft, mechanisms that prepare multiple cams to drive the intake valve and/or exhaust valve to open and use these cams appropriately, mechanisms that change the lever ratio of a rocker arm via an electric motor, and mechanisms that use electromagnetic solenoid valves for the intake valve and/or exhaust valve are also known, and it is permissible to select and employ from among these various mechanisms.

In addition, the specific configuration of each part and the processing procedures can be modified in various ways without departing from the spirit of the present invention.

The present invention can be used to control internal combustion engines installed in vehicles, etc.

0...Control unit (ECU)
REFERENCE SIGNS LIST 1...cylinder 11...injector 2...exhaust gas recirculation (EGR) device 23...EGR valve 3...intake passage 32...throttle valve 4...exhaust passage 5...variable valve timing (VVT) mechanism b...crank angle signal c...accelerator opening signal g...cam angle signal j...fuel injection signal k...throttle valve opening operation signal l...EGR valve opening operation signal m...valve timing control signal A...air-fuel ratio deviation occurring during cooperative control B...air-fuel ratio deviation occurring during non-cooperative control C...difference between air-fuel ratio deviation occurring during cooperative control and air-fuel ratio deviation occurring during non-cooperative control

Claims (1)

A control device for controlling an internal combustion engine equipped with a VVT mechanism capable of changing the timing of opening or closing the intake valve or exhaust valve of a cylinder, and an EGR device capable of recirculating a portion of the exhaust gas flowing through an exhaust passage to the intake passage, the control device calculating the amount of air taken into the cylinder by measuring the intake pressure in the intake passage connected to the cylinder,
A correction amount p1 corresponding to the valve timing realized by the VVT mechanism, which does not depend on the opening degree of the EGR valve, is stored in a memory, and based on this, a correction amount p1 corresponding to the current valve timing is obtained,
In addition, a correction amount p2 corresponding to the opening degree of the EGR valve, which does not depend on the valve timing realized by the VVT mechanism, is stored in a memory, and based on this, a correction amount p2 corresponding to the current opening degree of the EGR valve is obtained,
Furthermore, a correction amount pEX corresponding to the valve timing and the opening of the EGR valve realized by the VVT mechanism is stored in a memory, and based on this, a correction amount pEX corresponding to the current valve timing and the current opening of the EGR valve is obtained,
a partial pressure PM of air in the intake air taken into the cylinder is obtained by correcting the actual intake pressure P using the correction amount p1, the correction amount p2, and the correction amount pEX, and an intake air amount or a fuel injection amount is calculated;
A control device for an internal combustion engine , in which the correction amount pEX is determined so that an increase in deviation C, which is the difference between a deviation B of the actual air-fuel ratio from a target air-fuel ratio that occurs when an operation is performed to change the valve timing by the VVT mechanism while keeping the opening of the EGR valve constant, and a deviation A of the actual air-fuel ratio from a target air-fuel ratio that occurs when an operation is performed to change the valve timing by the VVT mechanism while changing the opening of the EGR valve, is approximately constant regardless of the valve timing .

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