JP2024108877A - Control device for internal combustion engine - Google Patents

Abstract

[Problem] To optimize the fuel injection amount and effectively control the air-fuel ratio regardless of the operation of an EGR device associated with an internal combustion engine. [Solution] This is a control device for an internal combustion engine that is equipped with an exhaust gas recirculation device having an EGR passage that connects the exhaust passage to an intake passage, and an EGR valve that opens and closes the EGR passage, and when determining the fuel injection amount, a basic injection amount proportional to the amount of air taken into the cylinder is corrected by feedback control that causes the air-fuel ratio of the gas flowing through the exhaust passage to follow a target air-fuel ratio, and further a different correction is applied depending on whether the EGR valve is open or closed. [Selected Figure] Figure 5

Description

The present invention relates to a control device that controls an internal combustion engine mounted on a vehicle, etc.

In general, a three-way catalyst is installed in the exhaust passage of an internal combustion engine to oxidize/reduce harmful substances HC, CO, and _NOx contained in the exhaust gas to make them harmless. In order to efficiently purify all of HC, CO, and _NOx , it is necessary to keep the air-fuel ratio of the gas within a certain range near the theoretical air-fuel ratio, called a window.

To achieve this, an air-fuel ratio sensor is installed in the exhaust passage of the internal combustion engine, and a feedback loop is constructed that references the output signal of the air-fuel ratio sensor to feedback-control the air-fuel ratio of the gas. The electronic control unit, which controls the operation of the internal combustion engine, determines the amount of fuel to be injected from the injector by multiplying the basic injection amount, which corresponds to the amount of air (fresh air) drawn into the cylinder, by a feedback correction coefficient that reduces the deviation between the air-fuel ratio of the gas flowing through the exhaust passage and its target value.

An exhaust gas recirculation device is often attached to an internal combustion engine. The EGR device connects the exhaust passage and the intake passage of the internal combustion engine via an EGR passage, and recirculates part of the exhaust gas to the intake passage via the EGR passage and mixes it with the intake air. An EGR valve that opens and closes the EGR passage is arranged on the EGR passage, and the amount of EGR gas recirculated is adjusted by controlling the opening degree of the EGR valve. EGR reduces the combustion temperature of the mixture in the combustion chamber of the cylinder, reducing the amount of _NOx produced. It also reduces pumping loss (see, for example, the following patent document).

JP 2022-133865 A

The gases exhausted from the multiple cylinders of the internal combustion engine 100 each flow through the exhaust passage 4 in a geometrically different path. Therefore, as shown in FIG. 7, the exhaust gas E1 from one cylinder comes into contact with the air-fuel ratio sensors 43, 44 (particularly the sensor 44 downstream of the catalyst 41) in large amounts, while the exhaust gas E2 from another cylinder comes into contact with the air-fuel ratio sensors 43, 44 in relatively small amounts. Moreover, the flow paths of the gases E1 and E2 can change depending on whether the EGR valve is open (gas flows from the exhaust passage into the EGR passage) or closed (gas does not flow from the exhaust passage into the EGR passage).

If the air-fuel ratio of the gas that comes into contact with the air-fuel ratio sensor in large amounts is lean and the air-fuel ratio of the gas that comes into contact with the air-fuel ratio sensor in small amounts is not lean (or is rich), the ECU increases the fuel injection amount to bring the lean air-fuel ratio closer to the target value. Conversely, if the air-fuel ratio of the gas that comes into contact with the air-fuel ratio sensor in large amounts is rich and the air-fuel ratio of the gas that comes into contact with the air-fuel ratio sensor in small amounts is not rich (or is lean), the ECU decreases the fuel injection amount to bring the rich air-fuel ratio closer to the target value. In this way, simply implementing air-fuel ratio feedback control may cause the air-fuel ratio of the internal combustion engine as a whole to deviate from the target value, raising concerns about increased emissions of harmful substances.

The intended purpose of the present invention is to optimize the amount of fuel injected and effectively control the air-fuel ratio, regardless of whether the EGR device attached to the internal combustion engine is in operation.

The present invention controls an internal combustion engine equipped with an exhaust gas recirculation system having an EGR passage that connects the exhaust passage to the intake passage, and an EGR valve that opens and closes the EGR passage. In determining the amount of fuel injection, a control device for the internal combustion engine is configured that adds a correction by feedback control that causes the air-fuel ratio of the gas flowing through the exhaust passage to follow a target air-fuel ratio to a basic injection amount that is proportional to the amount of air taken into the cylinder, and further adds a different correction depending on whether the EGR valve is open or closed.

According to the present invention, the amount of fuel injected can be optimized and the air-fuel ratio can be well controlled regardless of the operation of the EGR device attached to the internal combustion engine.

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; 4 is a timing chart showing a change in a correction amount FAF due to air-fuel ratio feedback control performed by the control device; FIG. 4 is a diagram illustrating an example of the relationship between a correction amount FACF and delay times TDR and TDL in the air-fuel ratio feedback control performed by the control device. 4 is a timing chart showing a change in a correction amount FACF due to air-fuel ratio feedback control performed by the control device; 4 is a flowchart showing an example of a procedure of a process executed by the control device according to a program. 4 is a timing chart illustrating an example of a transition of a correction amount X set by the control device. FIG. 2 is a schematic diagram showing the flow of gas discharged from each cylinder of an internal combustion engine and flowing through an exhaust passage.

One embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an overview of an internal combustion engine 100 for a vehicle in this embodiment. The internal combustion engine 100 is a spark-ignition type four-stroke reciprocating engine having a plurality of cylinders 1 (for example, an in-line three-cylinder engine; FIG. 1 shows one of them). 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. In addition, 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, which is an intake throttle valve, a surge tank 33, and an intake manifold 34 are arranged in this order from upstream on the intake passage 3.

An exhaust passage 4 for discharging exhaust gas from the cylinders 1 guides gas generated by burning fuel inside 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 exhaust gas are disposed on the exhaust passage 4. The catalyst 41 induces an oxidation/reduction reaction of harmful substances such as HC, CO, and _NOx to render them harmless.

Air-fuel ratio sensors 43, 44 for detecting the air-fuel ratio of the gas flowing through the exhaust passage 4 are installed upstream and downstream of the catalyst 41 in the exhaust passage 4. The air-fuel ratio sensors 43, 44 may be _O2 sensors having nonlinear output characteristics with respect to the air-fuel ratio of the exhaust gas, or may be linear A/F sensors having output characteristics proportional to the air-fuel ratio of the exhaust gas, but in this embodiment, the air-fuel ratio sensor 43 upstream of the catalyst 41 and the air-fuel ratio sensor 44 downstream of the catalyst 41 are both assumed to be _O2 sensors. The output voltage of the _O2 sensors 43, 44 shows a large and steep gradient with respect to the air-fuel ratio in a certain range near the theoretical air-fuel ratio, and approaches a high saturation value when the air-fuel ratio is richer than that, and approaches a low saturation value when the air-fuel ratio is leaner than that, drawing a so-called Z characteristic curve. The O2 sensors 43, 44 may be provided with heaters for heating them to hasten their activation.

The 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.

The ECU0, which is the control device for the internal combustion engine 100 in this embodiment, is a microcomputer system having a processor, memory, an input interface, an output interface, etc. The ECU0 may be configured by connecting multiple ECUs or controllers so that they can communicate with each other via an electrical communication line such as a CAN (Controller Area Network).

The input interface of the ECU0 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 of the internal combustion engine 100 and the engine speed, an accelerator opening signal c output from a sensor that detects the amount of depression of the accelerator pedal by the driver of the vehicle as the accelerator opening (in other words, the required engine load rate or engine torque), a cooling water temperature signal d output from a water temperature sensor that detects the temperature of the cooling water of the internal combustion engine 100, an intake air temperature/intake pressure signal e output from a 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 air-fuel ratio signal f output from an air-fuel ratio sensor 43 that detects the air-fuel ratio of the gas upstream of the catalyst 41 in the exhaust passage 4, an air-fuel ratio signal g output from an air-fuel ratio sensor 44 that detects the air-fuel ratio of the gas downstream of the catalyst 41, and an atmospheric pressure signal h output from an atmospheric pressure sensor that detects the atmospheric pressure.

The output interface of ECU0 outputs an ignition signal i to an igniter associated with the spark plug 12, a fuel injection signal j to the injector 11, an opening control signal k to the electronic throttle valve 32, an opening control signal l to the EGR valve 23, etc.

The processor of ECU0 interprets and executes a program stored in memory in advance, and calculates operating parameters to control the operation of internal combustion engine 100. ECU0 acquires various pieces of information a, b, c, d, e, f, g, and h required for controlling the operation of internal combustion engine 100 via an input interface, and determines various operating parameters such as the required fuel injection amount appropriate to the amount of air taken 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), and required EGR rate (or EGR gas amount). ECU0 applies various control signals i, j, k, and l corresponding to the operating parameters via an output interface.

When determining the amount of fuel to be injected from the injector 11, the ECU 0 first calculates the amount of air (fresh air) drawn into the cylinder 1, and then determines the basic amount TP of fuel injection that is proportional to the amount of intake air (so that the theoretical air-fuel ratio or a target air-fuel ratio close to the theoretical air-fuel ratio can be achieved depending on the amount of intake air). The amount of intake air is estimated based on the current engine speed and intake pressure (in the surge tank 33 or intake manifold 34), etc. The estimated value of the amount of intake air may be corrected according to the current intake temperature, atmospheric pressure, etc. The estimation method is well known.

Next, this basic injection amount TP is corrected by a feedback correction coefficient FAF corresponding to the deviation between the air-fuel ratio of the gas flowing into the catalyst 41 and its target value, various correction coefficients K determined based on environmental conditions and the like, and a correction coefficient X corresponding to the EGR described below. The feedback correction coefficients FAF, K, and X are all positive numbers that increase or decrease from 1. Thus, taking into account the invalid injection time TAUV during which no fuel is injected even when the injector 11 is opened, the final fuel injection time T, i.e., the time for which the injector 11 is opened, is calculated. The fuel injection time T is expressed as follows:
T=TP×FAF×X×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.

Air-fuel ratio feedback control converges the air-fuel ratio of the mixture filled in cylinder 1, and therefore the air-fuel ratio of the exhaust gas discharged from cylinder 1 and led to catalyst 41, to a desired target air-fuel ratio, thereby maximizing the purification efficiency of harmful substances in catalyst 41. The air-fuel ratio feedback correction coefficient FAF is determined based on the output signal f of air-fuel ratio sensor 43 upstream of catalyst 41. As shown in FIG. 2, ECU 0 compares the output voltage f of air-fuel ratio sensor 43 with a judgment voltage value corresponding to the target air-fuel ratio, and judges it to be rich if it is higher than the judgment voltage value, and lean if it is lower than the judgment voltage value. Then, ECU 0 increases or decreases the feedback correction coefficient FAF based on the judgment result of the air-fuel ratio of the gas upstream of catalyst 41.

Specifically, when the result of the determination of the air-fuel ratio of the gas upstream of the catalyst 41 reverses from rich to lean (after the delay time TDL described below has elapsed), the feedback correction coefficient FAF is increased by the skip value RSP. In addition, while the air-fuel ratio is determined to be lean, the feedback correction coefficient FAF is gradually increased by the rich integral value KIP per calculation cycle (control cycle). The period of the calculation cycle is equal to the period in which each cylinder 1 of the internal combustion engine 100 enters a new cycle (a series of intake stroke-compression stroke-expansion stroke-exhaust stroke). It is also possible to increase the absolute value of the rich integral value KIP as the absolute value of the difference or ratio between the determination voltage value and the output voltage value f of the air-fuel ratio sensor 43 increases.

On the other hand, when the result of the determination of the air-fuel ratio of the gas upstream of the catalyst 41 reverses from lean to rich (after the delay time TDR described below has elapsed), the feedback correction coefficient FAF is decreased by the skip value RSM. In addition, while the air-fuel ratio is determined to be rich, the feedback correction coefficient FAF is gradually decreased by the lean integral value KIM per calculation cycle. Note that it is also possible to increase the absolute value of the lean integral value KIM the greater the absolute value of the difference or ratio between the output voltage value f of the air-fuel ratio sensor 43 and the determination voltage value.

When the feedback correction coefficient FAF, which is multiplied by the basic injection amount TP, increases, the amount of fuel injected by the injector 11 is increased, and the air-fuel ratio of the mixture becomes richer. When the feedback correction coefficient FAF decreases, the amount of fuel injected by the injector 11 is reduced, and the air-fuel ratio of the mixture becomes leaner.

However, when the output voltage f of the air-fuel ratio sensor 43 fluctuates so as to cross the judgment voltage value, the judgment result of the air-fuel ratio of the gas upstream of the catalyst 41 is not immediately reversed, but rather the judgment result is reversed after the delay times TDL and TDR have elapsed. That is, when the output voltage f of the air-fuel ratio sensor 43 switches from rich to lean (below the judgment voltage value), it is determined that the air-fuel ratio has reversed from rich to lean after the lean judgment delay time TDL has elapsed. Also, when the output voltage f of the air-fuel ratio sensor 43 switches from lean to rich (above the judgment voltage value), it is determined that the air-fuel ratio has reversed from lean to rich after the rich judgment delay time TDR has elapsed.

The lean judgment delay time TDL and rich judgment delay time TDR are provided to prevent chattering, which occurs when noise is mixed into the output signal f of the air-fuel ratio sensor 43 and the result of the lean/rich air-fuel ratio judgment is inverted multiple times in a short period of time, causing the fuel injection amount to fluctuate and increase or decrease.

The delay times TDL and TDR increase and decrease according to the correction amount FACF. FIG. 3 illustrates the relationship between the correction amount FACF and the delay times TDL and TDR. In FIG. 3, the lean judgment delay time TDL is shown by a dashed line, and the rich judgment delay time TDR is shown by a solid line. As the correction amount FACF increases, the lean judgment delay time TDL is shortened and the rich judgment delay time TDR is extended. This delays the time when the feedback correction coefficient FAF changes from an increase to a decrease, and accelerates the time when it changes from a decrease to an increase. As a result, the fuel injection amount increases on average, and the target air-fuel ratio of the gas flowing into the catalyst 41, which should be converged by air-fuel ratio feedback control, shifts to the rich side.

Conversely, the smaller the correction amount FACF, the longer the lean judgment delay time TDL and the shorter the rich judgment delay time TDR. This makes it faster for the feedback correction coefficient FAF to change from increasing to decreasing, and slows down the change from decreasing to increasing. As a result, the fuel injection amount decreases on average, and the target air-fuel ratio of the gas flowing into the catalyst 41 shifts to the lean side.

During air-fuel ratio feedback control, ECU0 also calculates the above-mentioned correction amount FACF. As shown in FIG. 4, when calculating the correction amount FACF, ECU0 compares the output voltage g of the air-fuel ratio sensor 44 that detects the air-fuel ratio of the gas downstream of the catalyst 41 with a judgment voltage value corresponding to the theoretical air-fuel ratio or a target air-fuel ratio in the vicinity thereof, and judges the air-fuel ratio to be rich if it is higher than the judgment voltage value, and lean if it is lower than the judgment voltage value. This judgment voltage value does not necessarily match the judgment voltage value compared with the output signal f of the air-fuel ratio sensor 43. Then, ECU0 increases or decreases the correction amount FACF based on the judgment result of the air-fuel ratio of the gas downstream of the catalyst 41.

Specifically, while the air-fuel ratio of the gas downstream of the catalyst 41 is judged to be rich, the correction amount FACF is gradually decreased by the lean integral value FACFKIM per calculation cycle, while while the air-fuel ratio is judged to be lean, the correction amount FACF is gradually increased by the rich integral value FACFKIP per calculation cycle. The absolute value of the lean integral value FACFKIM may be increased as the absolute value of the difference or ratio between the output voltage value g of the air-fuel ratio sensor 44 and the judgment voltage value increases, and the absolute value of the rich integral value FACFKIP may be increased as the absolute value of the difference or ratio between the judgment voltage value and the output voltage g of the air-fuel ratio sensor 44 increases. As already mentioned, when the correction amount FACF decreases, the target air-fuel ratio of the gas flowing into the catalyst 41 moves toward lean, and when the correction amount FACF increases, the target air-fuel ratio of the gas flowing into the catalyst 41 moves toward rich.

In the exhaust system of an actual internal combustion engine 100, as shown in FIG. 7, the flow of gas E1 discharged from a certain cylinder 1 comes into contact with the air-fuel ratio sensors 43, 44 (especially the sensor 44 downstream of the catalyst 41) in large amounts, while the flow of gas E2 discharged from other cylinders 1 comes into contact with the air-fuel ratio sensors 43, 44 in small amounts. Moreover, the flows of exhaust gas E1, E2 from each cylinder 1 can change depending on whether the EGR valve 23 is open (allowing gas to flow from the exhaust passage 4 to the EGR passage 21) or closed (not allowing gas to flow from the exhaust passage 4 to the EGR passage 21). Depending on the opening degree of the EGR valve 23, the amount of gas E1, E2 flowing out from each cylinder 1 that comes into contact with the air-fuel ratio sensors 43, 44 will vary. When the EGR valve 23 is closed, more gas E1 hits the air-fuel ratio sensors 43, 44 than gas E2, but when the EGR valve 23 is opened, more gas E2 hits the air-fuel ratio sensors 43, 44 than gas E1.

The air-fuel ratio of gas E1 (or E2), which comes into contact with the air-fuel ratio sensors 43, 44 in large amounts, has a large effect on the correction amounts FAF and FACF of the fuel injection amount by feedback control. Conversely, the air-fuel ratio of gas E2 (or E1), which comes into contact with the air-fuel ratio sensors 43, 44 in small amounts, has a relatively small effect on the correction amounts FAF and FACF. If the air-fuel ratio of the former gas E1 is lean but the air-fuel ratio of the latter gas E2 is not lean (or is rich), the air-fuel ratio feedback control attempts to increase the correction amounts FAF and FACF to increase the fuel injection amount. However, there is a risk that the air-fuel ratio of the internal combustion engine 100 as a whole will be biased toward the rich side compared to the target value. Conversely, if the air-fuel ratio of the former gas E1 is rich but the air-fuel ratio of the latter gas E2 is not rich (or is lean), the correction amounts FAF and FACF are decreased to reduce the fuel injection amount, but there is a risk that the air-fuel ratio of the internal combustion engine 100 as a whole will be leaner than the target value.

The correction coefficient X, which is taken into consideration when calculating the fuel injection amount T, is a correction amount intended to mitigate or suppress excessive influence due to the air-fuel ratio of gas with a large flow rate that contacts the air-fuel ratio sensors 43, 44, taking into consideration the difference in the flow paths of the gas discharged from each cylinder 1 and flowing through the exhaust passage 4. The correction coefficient X is
- A different value is set for each cylinder 1. - It is changed depending on whether the EGR valve 23 is currently open (EGR is being performed) or closed (EGR is not being performed). - It is changed depending on the current operating range of the internal combustion engine 100 [engine speed, engine load factor (or accelerator opening, intake pressure, intake amount, fuel injection amount, engine torque)].

Map data that defines the relationship between the operating range of the internal combustion engine 100 [engine speed, engine load factor] and the correction amount X for each of the multiple cylinders 1 contained in the internal combustion engine 100 is stored in the memory of the ECU 0 in advance. In the case of a three-cylinder engine, there are three map data corresponding to each of the three cylinders 1. Furthermore, map data for when the EGR valve 23 is open and EGR is being performed and map data for when the EGR valve 23 is closed and EGR is not being performed coexist separately. In total, there are six map data, and the map data to be referenced at each time is selected.

As shown in FIG. 6, ECU0 selects map data to be referenced according to the current stroke of the internal combustion engine 100, i.e., according to which cylinder 1 the gas discharged from is flowing through the exhaust passage 4 (whether it is considered to be in contact with the air-fuel ratio sensors 43, 44) when calculating FAF and FACF in the current calculation cycle (step S0). For example, if gas discharged from the second cylinder 1 is currently flowing through the exhaust passage 4, the map data corresponding to the second cylinder 1 will be selected (step S5 or S6).

Then, ECU0 selects map data to be referenced depending on whether EGR valve 23 is currently open and EGR is being performed (steps S1, S4, or S7). For example, if gas discharged from second cylinder 1 is currently flowing through exhaust passage 4 and EGR is being performed, ECU0 selects map data for second cylinder 1 when EGR is being performed (step S5). If EGR is not being performed, ECU0 selects map data for second cylinder 1 when EGR is not being performed (step S6).

Then, ECU0 searches the map data using the parameters of the current operating range of the internal combustion engine 100 [engine speed, engine load factor] as a key, obtains the correction amount X that matches the current conditions (steps S2, S3, S5, S6, S8 or S9), and uses this to calculate the fuel injection time T.

The correction coefficient X described in the map data corresponding to the cylinder 1, in which the exhaust gas is likely to hit the air-fuel ratio sensors 43 and 44 and has a relatively large effect on the air-fuel ratio feedback control, is
|1-FAF|>|1-FAF×X|
In other words, (FAF x X) is set closer to 1 than FAF to weaken the correction of the fuel injection time T by the air-fuel ratio feedback control. Alternatively, the correction coefficient X described in the map data corresponding to the cylinder 1, which is less likely to hit the air-fuel ratio sensors 43 and 44 and has a relatively small effect on the air-fuel ratio feedback control, is set as follows:
|1-FAF|>|1-FAF×X|
In other words, it is possible to set (FAF×X) so as to move it farther away from 1 than FAF, thereby strengthening the correction of the fuel injection time T by the air-fuel ratio feedback control.

The correction coefficient X may take different values depending on whether the air-fuel ratio feedback correction coefficient FAF is greater than or equal to 1 (whether the air-fuel ratio measured via the sensor 43 is lean) or less than 1 (whether the air-fuel ratio measured via the sensor 43 is rich).

In addition, the correction coefficient X may take a different value depending on the current opening degree of the EGR valve 23. In this case, if the correction coefficient that is not dependent on the opening degree of the EGR valve 23 described in the map data during EGR execution (for each cylinder 1) is denoted _{by XB} , and the correction coefficient according to the opening degree of the EGR valve 23 is denoted by γ, the correction coefficient X to be substituted into the calculation formula for the fuel injection time T is given by
X = XB x γ
Map data that defines the relationship between the opening of the EGR valve 23 and the correction amount γ is stored in advance in the memory of the ECU 0. The ECU 0 searches the map data using the current opening of the EGR valve 23 as a key, obtains the correction amount γ that matches the current conditions, and uses this to calculate the fuel injection time T.

It is preferable to gradually change the correction coefficient X used in the calculation of the fuel injection time T, rather than suddenly changing it in a stepwise manner. For example, as shown in Fig. 6, when the correction coefficient X obtained by referring to the map data changes from _X0 to _X1 at time _t1 , the value substituted as the correction coefficient X in the calculation formula of the fuel injection time T is not immediately changed from _X0 to _X1 at time _t1 , but is gradually changed from _X0 to _X1 after time t1. Similarly, when the correction coefficient X obtained by referring _to the map data changes from _X1 to _X2 at time _t2 , the value of the correction coefficient X is also gradually changed from _X1 to _X2 .

In this embodiment, the control device 0 of the internal combustion engine 100 is configured to control the EGR passage 21 that connects the exhaust passage 4 to the intake passage 3, and the EGR device 2 that has the EGR valve 23 that opens and closes the EGR passage 21. When determining the fuel injection amount T, the control device 0 adds a correction FAF by feedback control that makes the air-fuel ratio of the gas flowing through the exhaust passage 4 follow the target air-fuel ratio to the basic injection amount TP that is proportional to the amount of air taken into the cylinder 1, and further adds a correction X that differs depending on whether the EGR valve 23 is open or closed. According to this embodiment, the fuel injection amount T can be optimized to effectively control the air-fuel ratio regardless of the operation of the EGR device 2, which can contribute to further reduction in the emission of harmful substances.

The present invention is not limited to the embodiment described above. The specific configuration of each part and the processing procedure can be modified in various ways without departing from the spirit of the present invention.

100... internal combustion engine 0... control device (ECU)
REFERENCE SIGNS LIST 1 cylinder 11 injector 2 exhaust gas recirculation (EGR) device 23 EGR valve 3 intake passage 4 exhaust passage 43, 44 air-fuel ratio sensor b crank angle signal c accelerator opening signal f, g air-fuel ratio signal j fuel injection signal k throttle valve opening operation signal l EGR valve opening operation signal

Claims (1)

An internal combustion engine having an exhaust gas recirculation device including an EGR passage that connects an exhaust passage to an intake passage and an EGR valve that opens and closes the EGR passage,
A control device for an internal combustion engine, which, when determining the amount of fuel injection, applies a correction through feedback control that causes the air-fuel ratio of the gas flowing through the exhaust passage to follow a target air-fuel ratio to a basic injection amount that is proportional to the amount of air taken into the cylinder, and further applies a different correction depending on whether the EGR valve is open or closed.

Images