JP3593388B2 - Air-fuel ratio control device for internal combustion engine - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an air-fuel ratio control device for an internal combustion engine, and more particularly to a technique for improving the control accuracy of an air-fuel ratio detection device that performs feedback control to a target air-fuel ratio.
[0002]
[Prior art]
2. Description of the Related Art A conventional air-fuel ratio control device for an internal combustion engine is disclosed in, for example, Japanese Patent Laid-Open No. 60-240840.
In brief, the basic fuel supply amount T _P (= K · Qa / N; K is minute) corresponding to the amount of air taken into the cylinder by detecting the intake air flow rate Qa and the rotation speed N of the engine is described. The calculated basic fuel supply amount _TP is corrected by the engine temperature or the like, and feedback correction is performed by a signal from an air-fuel ratio sensor (oxygen sensor) that detects the air-fuel ratio of the air-fuel mixture by detecting the oxygen concentration in the exhaust gas. also been corrected due battery voltage finally setting the fuel supply quantity T _I and.
[0003]
Then, by outputting a driving pulse signal having a pulse width corresponding to the thus set fuel supply quantity T _I at a predetermined timing, so that injects supply a predetermined amount of fuel to the engine.
By the way, the air-fuel ratio feedback correction based on the signal from the air-fuel ratio sensor is performed so as to control the air-fuel ratio near the target air-fuel ratio (the stoichiometric air-fuel ratio). It is interposed in the exhaust system, the exhaust CO in the exhaust, HC conversion efficiency (conversion efficiency) of the three-way catalyst for purifying by reducing NO _X with oxidizes (hydrocarbon) is at the stoichiometric air-fuel ratio combustion This is because it is set to function effectively in the state.
[0004]
For example, a proportional component and an integral component are respectively set according to the deviation between the air-fuel ratio detected by the air-fuel ratio sensor and the target air-fuel ratio, and a value obtained by adding these components is used as a feedback correction coefficient α as the basic fuel supply amount T. _By multiplying _P , the air-fuel ratio is controlled near the stoichiometric air-fuel ratio.
[0005]
[Problems to be solved by the invention]
By the way, as described above, the conversion efficiency of the three-way catalyst can be increased by controlling it near the stoichiometric air-fuel ratio. However, in order to maximize the conversion efficiency, λ (excess air ratio) = 1 ± 0.02 It is necessary to suppress the fluctuation width of the change in the air-fuel ratio within a narrow range of less than about.
However, in the conventional air-fuel ratio feedback control device as described above, the control constants such as the proportional component and the integral component for setting the air-fuel ratio feedback correction coefficient α are fixed values or assigned to each engine operation region. Although a value is used, in a transient state in which the operating state of the engine changes, there is a case where a delay occurs in following the target air-fuel ratio and the λ = 1 ± 0.02 is largely deviated from the appropriate range. .
[0006]
The present invention has been made in view of such a conventional problem, and the responsiveness is improved by setting a control constant for setting a feedback correction coefficient to an appropriate value with respect to a response delay of an air-fuel ratio feedback control system. The present invention provides an air-fuel ratio control apparatus for an internal combustion engine, which can maintain an air-fuel ratio in the vicinity of a target air-fuel ratio by setting an appropriate control constant even during a transition when the engine operating state changes. The purpose is to:
[0007]
[Means for Solving the Problems]
Therefore, the invention according to claim 1 is, as shown in FIG.
Air-fuel ratio detection means for detecting the air-fuel ratio of the air-fuel mixture supplied to the engine; setting using a control constant while comparing the detected value of the air-fuel ratio by the air-fuel ratio detection means with a reference value corresponding to the target air-fuel ratio An air-fuel ratio control device for an internal combustion engine including air-fuel ratio feedback control means for controlling the air-fuel ratio to approach the target air-fuel ratio by the feedback correction coefficient
Reversal cycle detection means for detecting a cycle in which a magnitude relationship of a detection value of the air-fuel ratio detection means with respect to a reference value corresponding to the target air-fuel ratio is reversed,
A storage means for correcting and setting a control constant corresponding to a reversal cycle of the air-fuel ratio sensor detected by the reversal cycle detection means in a direction in which the reversal cycle decreases as the reversal cycle increases ,
Control constant setting means for setting a control constant by retrieving a control constant corresponding to the detected inversion cycle from the storage means,
Is characterized by comprising.
[0008]
The operation and effect of the invention according to claim 1 will be described.
The reversal cycle of the detection value of the air-fuel ratio detection means depends on a transmission delay that is a sum of a stagnation delay due to an engine cycle delay or a combustion delay and a transport delay until exhaust reaches the air-fuel ratio detection means. Is larger, the fluctuation of the air-fuel ratio tends to be larger. However, the fluctuation can be reduced by reducing the control constant (integral gain, proportional component, etc.) for setting the feedback correction coefficient.
[0009]
However, when the control constant is reduced, the response delay time until the air-fuel ratio changes to the target air-fuel ratio (becomes a steady state) when the air-fuel ratio changes during a transition increases.
Therefore, by setting a control constant corresponding to the reversal cycle of the detected air-fuel ratio detection value from the storage means and setting the control constant, the control constant decreases as the reversal cycle increases. Therefore, it is possible to shorten the transient response delay time while keeping the fluctuation of the air-fuel ratio in the steady state within an appropriate range.
[0010]
This makes it possible to maintain the air-fuel ratio in the vicinity of the target air-fuel ratio irrespective of whether it is steady or transient, thereby improving the exhaust gas purification performance as much as possible .
[0011]
Further, by setting the control constant by retrieving it from the storage means, the control constant can be quickly set, so that the responsiveness of the transient state can be improved as much as possible.
Further, according to the invention of claim 2 , as shown by a solid line in FIG.
Air-fuel ratio detection means for detecting the air-fuel ratio of the air-fuel mixture supplied to the engine; setting using a control constant while comparing the detected value of the air-fuel ratio by the air-fuel ratio detection means with a reference value corresponding to the target air-fuel ratio An air-fuel ratio control device for an internal combustion engine including air-fuel ratio feedback control means for controlling the air-fuel ratio to approach the target air-fuel ratio by the feedback correction coefficient
A transmission delay time calculating means for calculating a transmission delay time from when the air-fuel ratio is controlled based on the engine operating state to when the controlled air-fuel ratio state is transmitted to the air-fuel ratio detecting means,
The transmission delay time calculated by the transmission delay calculating means and the air-fuel ratio controlled air-fuel ratio state detected by the air-fuel ratio detecting means are detected by the air-fuel ratio detecting means after being transmitted to the air-fuel ratio detecting means. Control delay setting means for setting a control constant used for the air-fuel ratio feedback control based on the total delay time obtained by adding
Is characterized by comprising.
[0012]
The operation and effect of the invention according to claim 2 will be described.
Fluctuations in the air-fuel ratio in a steady state depend on the total delay time obtained by adding the transmission delay time calculated based on the engine operating state and the detection delay time of the air-fuel ratio detection means. Fuel ratio tends to fluctuate.
Therefore, for the same reason as described above, by setting an appropriate control constant based on the total delay time, the transient response delay time can be reduced while keeping the steady-state air-fuel ratio fluctuation within an appropriate range. Accordingly, the air-fuel ratio can be maintained near the target air-fuel ratio regardless of whether it is steady or transient, and the exhaust gas purification performance can be improved as much as possible.
The invention according to claim 3 is, as shown by a dashed line in FIG.
Engine speed detection means for detecting the engine speed,
Intake air flow rate detection means for detecting an air flow rate sucked into the engine,
The transmission delay time calculating means includes: a stagnation delay time including a delay due to an engine cycle and a delay due to combustion estimated based on the engine rotation speed detected by the engine rotation speed detection means; The transmission delay time is calculated by adding the transport delay time until the exhaust gas estimated based on the intake air flow rate detected by the exhaust gas reaches the air-fuel ratio detecting means.
[0013]
That is, since the stagnation delay time consisting of the delay due to the engine cycle and the delay due to combustion depends on the engine rotation speed, it is calculated based on the engine rotation speed, and the transportation delay time depends on the flow rate of the exhaust gas and therefore the flow rate. Since it is substantially equal to the intake air flow rate, it can be calculated based on the detected intake air flow rate, and the transmission delay time can be obtained by adding the residence delay time and the transport delay time.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below with reference to the drawings.
In FIG. 3 showing a system configuration according to one embodiment, an intake passage 12 of an engine 11 is provided with an air flow meter 13 for detecting an intake air flow rate Qa and a throttle valve 14 for controlling the intake air flow rate Qa in conjunction with an accelerator pedal. On the downstream manifold portion, an electromagnetic fuel injection valve 15 is provided for each cylinder as fuel supply means.
[0015]
The fuel injection valve 15 is driven to open by an injection pulse signal from a control unit 16 containing a microcomputer, and injects fuel supplied from a fuel pump (not shown) under pressure and controlled to a predetermined pressure by a pressure regulator. Further, a water temperature sensor 17 for detecting a cooling water temperature Tw in a cooling jacket of the engine 11 is provided, and an air-fuel ratio sensor 19 for detecting an air-fuel ratio of an intake air-fuel mixture by detecting an oxygen concentration in exhaust gas in an exhaust passage 18. And a three-way catalyst 20 for oxidizing CO and HC in the exhaust gas on the downstream side and reducing NO _X to purify the exhaust gas.
[0016]
A distributor (not shown) has a built-in crank angle sensor 21 which counts a crank unit angle signal output from the crank angle sensor 21 in synchronization with the engine rotation for a certain period of time, or a crank reference angle signal. Is measured to detect the engine rotation speed Ne.
Here, the response delay for each factor in the air-fuel ratio feedback control system of the engine 11 will be described.
[0017]
FIG. 4 shows a model of the air-fuel ratio feedback control system. Delay due to the air-fuel ratio feedback control (the delay from when the change in the air-fuel ratio is transmitted to the air-fuel ratio sensor to when the air-fuel ratio state controlled according to the change in the air-fuel ratio detected by the air-fuel ratio sensor is transmitted to the air-fuel ratio sensor) ) Is roughly divided into a delay caused by the control system by the control unit 16, a transmission delay system until the air-fuel ratio state of the engine 11 controlled by the control system is transmitted to the air-fuel ratio sensor 19, and a change in the air-fuel ratio state. And a detection delay system until the air-fuel ratio sensor 19 detects the change.
[0018]
Control system of the control unit 16 includes an integration component obtained by integrating the integral component gain k ₁ in accordance with the air-fuel ratio state (lean or rich) detected by the air-fuel ratio sensor 19, inversion of the air-fuel ratio state (rich or from lean to rich by increasing or decreasing the fuel injection amount supplied in synchronization with the engine rotation by the feedback correction coefficient and the proportional amount K ₂ given it was obtained by adding immediately after the lean) is detected α from the target air-fuel ratio Feedback control to the air-fuel ratio (stoichiometric air-fuel ratio).
[0019]
The transmission delay system of the engine 11 has a cycle in which the control is performed, that is, a delay depending on the cycle of the engine, and a delay until the air-fuel mixture of the controlled air-fuel ratio burns and the combustion gas is discharged from the cylinder. The delay time is composed of a combined retention delay and a transportation delay until the combustion gas discharged from the cylinder reaches the air-fuel ratio sensor 19 through the exhaust passage.
As shown in FIG. 5, the lower the engine rotation speed Ne, the longer the cycle period and the combustion period, and thus the longer the residence delay, and the longer the residence delay, the smaller the engine rotation speed Ne.
[0020]
As shown in FIG. 6, the transport delay increases as the intake air flow rate Qa, that is, the exhaust flow rate decreases, because the exhaust flow velocity decreases, and the transport delay increases in proportion to an increase in the intake air flow rate Qa.
On the other hand, the delay caused by the control system will be described based on the data of the air-fuel ratio feedback control shown in FIGS.
[0021]
FIGS. 7 and 8 show the integral gain k ₁ and the proportional gain k ₁ and the delay time (dead time) of the transmission delay system of the engine 11 for L = 1.2 (sec) and L = 0.1 (sec), respectively. The fluctuation state of the air-fuel ratio (excess air ratio λ) is measured when the value of both the minute k _{2 is set} to a small value of 0.01 and when both are set to a large value of 0.1. 9, 10, like the delay time L = 1.2 (sec) and L = 0.1 for the case of (sec), the air-fuel ratio fluctuation range for the integral component gain _{k 1} and proportional portion _{k 2} (Peak to Peak).
[0022]
As is clear from the figure, if the delay time of the transmission delay system is large, the reversal cycle of the air-fuel ratio sensor increases, and the variation (amplitude) of the air-fuel ratio increases accordingly, but the integral k ₁ , it is clear that it is possible to reduce the variation of the air-fuel ratio by reducing the proportional amount k _2. However, the smaller the integral component gain k ₁ and proportional portion k ₂ is a control constant (time from changing the control amount to settle to a steady state) response delay of the air-fuel ratio feedback control system is increased. FIGS. 11 and 12 show the relationship between the respective values of the integral and the proportional component and the response delay of the air-fuel ratio feedback control system.
[0023]
Therefore, if the response delay of the control system is reduced as much as possible while keeping the fluctuation of the air-fuel ratio in the steady state within the range in which the three-way catalyst effectively functions as described above, the deviation of the air-fuel ratio during the transition can be minimized. It is clear that the air-fuel ratio can be suppressed, a good air-fuel ratio can be maintained irrespective of steady or transient, and the exhaust gas purification performance can be improved as much as possible.
The table in FIG. 13 shows the air-fuel ratio feedback in the combination of the integral and the proportional component that can keep the fluctuation (Peak to Peak) of the air-fuel ratio (excess air ratio λ) in the steady state within an appropriate range of 0.02 or less. FIG. 14 is a graph showing the relationship between the inversion cycle of the air-fuel ratio sensor and the inversion cycle of the air-fuel ratio sensor for each integral (1) to (5). The response delay time of the fuel ratio feedback control is shown, and the selected point is plotted.
[0024]
That is, as described above, the reversal cycle of the air-fuel ratio sensor depends on the delay time of the transmission delay system. When the reversal cycle is long, that is, when the delay time of the transmission delay system is large, the air-fuel ratio tends to fluctuate. In order to suppress the fluctuation within an appropriate range, it is necessary to sufficiently reduce the integral component and the proportional component. However, when the reversal cycle is short, that is, when the delay time of the transmission delay system is small, the air-fuel ratio is difficult to fluctuate. The integral component and the proportional component for suppressing the fluctuation within an appropriate range can be increased to some extent, and the response delay of the air-fuel ratio feedback control system can be reduced accordingly.
[0025]
Accordingly, the present invention is the most air-fuel ratio feedback control system in which the fluctuation of the air-fuel ratio can be suppressed within an appropriate range in response to the delay time of the transmission delay system estimated by detecting the reversal cycle of the air-fuel ratio sensor. The control constants such as the integral gain and the proportional component are set so that the response delay of the air-fuel ratio can be shortened. This is to minimize the exhaust gas purification performance as much as possible.
[0026]
Next, a routine of the control unit 16 for setting the air-fuel ratio feedback correction coefficient α in the embodiment of the first and second aspects of the invention will be described with reference to the flowchart of FIG. This routine is executed every unit time or in a cycle synchronized with the engine rotation.
In step (denoted as S in the figure, the same applies hereinafter) In step 1, the detection value (output voltage Vs) from the air-fuel ratio sensor 19 is A / D converted and input.
[0027]
In step 2, the detected value Vs of the air-fuel ratio is compared with a reference value Vso corresponding to a target air-fuel ratio (stoichiometric air-fuel ratio).
Then, when the magnitude relationship between the detected value Vs and the reference value Vso is reversed, that is, when the detected value of the air-fuel ratio is reversed from rich to lean or from lean to rich, the routine proceeds to step 3, where the inversion cycle of the detected value (previous (Time from inversion to inversion this time) T is calculated.
[0028]
In step 4, the integral component gain k ₁ and proportional portion k ₂ for the inversion period T 13, set by search from the map of characteristic obtained from the relationship of FIG. 14. As described above, this map shows that the fluctuation of the air-fuel ratio in the steady state with respect to the reversal cycle is within an appropriate range (for example, λ = 1 ± 0.02) and minimizes the response delay time of the air-fuel ratio feedback control system. have the characteristics of integral component gain k ₁ and proportional portion k ₂ to limit, as the inversion period T becomes longer, it is smaller the integral component gain k ₁ and proportional portion k _2.
[0029]
In step 5, it is determined whether the reversal direction, that is, the direction in which the detected value of the air-fuel ratio has reversed from rich to lean or from lean to rich.
Then, when the detection value of the air-fuel ratio is inverted from lean to rich, updates the air-fuel ratio feedback correction coefficient α proceeds to step 6, a value obtained by decreasing the proportional part k ₂ set in step 4 from the current value Set.
[0030]
Further, when the detected value of the air-fuel ratio is inverted from rich to lean, updates the air-fuel ratio feedback correction coefficient α proceeds to step 7, the value obtained by adding the proportional part k ₂ set in step 4 to the current value Set.
On the other hand, if it is determined in step 2 that the magnitude relationship between the detected value Vs and the reference value Vso is not reversed, the process proceeds to step 8, where an air-fuel ratio rich state in which the detected value Vs is larger than the reference value Vso is detected. Is determined.
[0031]
When the detection value Vs is larger than the reference value Vso is updated with the value obtained by subtracting the integral component gain k ₁ the air-fuel ratio feedback correction coefficient α from the current value the program proceeds to step 9.
Further, if the detection value Vs is smaller than the reference value Vso is updated with the value obtained by adding the integral component gain k ₁ the air-fuel ratio feedback correction coefficient α to the current value the program proceeds to step 10.
[0032]
Next, an air-fuel ratio feedback control routine using the air-fuel ratio feedback correction coefficient α set as described above will be described with reference to the flowchart of FIG.
In step 21, based on the intake air flow rate Qa detected by the air flow meter 13 and the engine speed N calculated based on the signal from the crank angle sensor 21, the basic fuel injection amount corresponding to the intake air amount per unit rotation the T _P is calculated by the following equation.
[0033]
T _P = K × Qa / N (K is a constant)
In step 22, various correction coefficients COEF are set based on the cooling water temperature Tw detected by the water temperature sensor 17, and the like.
In step 23, the air-fuel ratio feedback correction coefficient α set in FIG. 15 is read.
[0034]
In step 24, it sets the voltage correction amount T _S based on the battery voltage. This is for correcting a change in the injection flow rate of the fuel injection valve 15 due to a change in the battery voltage.
In step 25, a final fuel injection amount T _I is calculated according to the following equation.
T _I = T _P × COEF × α + T _S
In step 26, set in the output register the computed fuel injection valve T _I.
[0035]
Consequently, when a fuel injection timing of a predetermined engine rotation synchronization, fuel injection is performed a drive pulse signal having a pulse width of the calculated fuel injection amount T _I is given to the fuel injection valve 15.
As described above, in the present embodiment, a control constant is set based on the reversal cycle of the air-fuel ratio sensor so as to minimize the response delay of the control system during the transition while suppressing the fluctuation of the air-fuel ratio in the steady state to an appropriate range. Since the air-fuel ratio feedback control is performed using the control constants, the air-fuel ratio can be maintained near the target air-fuel ratio (stoichiometric air-fuel ratio) regardless of whether it is steady or transient, and the exhaust purification performance can be improved as much as possible. Can be improved.
[0036]
In the above-described embodiment, the direct control constant (integral gain k ₁ , proportional component k ₂ ) is calculated directly based on the inversion cycle of the air-fuel ratio sensor. However, the transmission delay time is calculated, and the air-fuel ratio sensor is further calculated. It is also possible to calculate the total delay time by summing the detection delay times of the above and set the control constant based on the total delay time.
FIG. 17 shows a part of a flowchart of an embodiment of the invention according to claims 3 and 4 for calculating the transmission delay time and setting a control constant. That is, in the present embodiment, steps 3 and 4 in the flowchart of FIG. 15 showing the first embodiment are changed to steps 31 to 35, and only the changed portions are shown.
[0037]
In step 31, it calculates the residence time delay D ₁ of the combined delay due to the delay and combustion by-cycle engine based on the engine rotational speed Ne detected by the crank angle sensor 21 (or retrieved from the map) to.
In step 32, the exhaust gas that is estimated to calculate the transport delay time D ₂ to reach the air-fuel ratio sensor 19 (or retrieved from the map) are based on the intake air flow rate Qa detected by the air flow meter 13.
[0038]
In step 33, it calculates the propagation delay Dt by summing the residence time delay D ₁ and said transport delay time D _2.
In step 34, the total delay time D is calculated by adding the detection delay time Ds of the air-fuel ratio sensor 19 known in advance to the transmission delay time Dt.
In step 35, set by searching the integral component gain k ₁ and proportional portion k ₂ in advance a characteristic from the stored map set to the total delay time D the calculated.
[0039]
As described above, since the fluctuation of the air-fuel ratio in the steady state depends on the total delay time, it is possible to set a control constant that suppresses the fluctuation of the air-fuel ratio within an appropriate range by calculating the total delay time. Thus, similarly to the first embodiment, the exhaust gas purification performance can be improved as much as possible by maintaining the air-fuel ratio near the target air-fuel ratio regardless of whether it is steady or transient.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the configuration and functions of the invention according to claims 1 and 2;
FIG. 2 is a block diagram showing the configuration and functions of the invention according to claims 3 and 4;
FIG. 3 is a diagram showing a system configuration of an embodiment according to the present invention.
FIG. 4 is a diagram showing a model of an air-fuel ratio feedback control system of the engine.
FIG. 5 is a graph showing a relationship between an engine rotation speed Ne and a residence delay time.
FIG. 6 is a graph showing a relationship between an intake air flow rate Qa and a transport delay time.
FIG. 7 is a diagram showing a change state of the air-fuel ratio for a small value and a large control constant when the transmission delay time is long.
FIG. 8 is a diagram showing a change state of the air-fuel ratio for a small value and a large value of the control constant when the transmission delay time is short.
FIG. 9 is a diagram illustrating a relationship between a variation width of an air-fuel ratio with respect to an integral component and a proportional component when a transmission delay time is large.
FIG. 10 is a diagram illustrating a relationship between a variation width of an air-fuel ratio with respect to an integral component and a proportional component when a transmission delay time is short.
FIG. 11 is a diagram showing a relationship between a response delay time of an air-fuel ratio feedback control system and an integral.
FIG. 12 is a diagram showing a relationship between a response delay time of an air-fuel ratio feedback control system and a proportional component.
FIG. 13 shows the shortest response delay time of the air-fuel ratio feedback control among combinations of integral and proportional components that can keep the fluctuation range of the air-fuel ratio (excess air ratio λ) in a steady state within an appropriate range. Table.
FIG. 14 is a graph showing the response delay time of the air-fuel ratio feedback control with respect to the inversion cycle of the air-fuel ratio sensor for each combination of integral and proportional components.
FIG. 15 is a flowchart showing a routine for setting an air-fuel ratio feedback correction coefficient according to the embodiment of the present invention.
FIG. 16 is a flowchart showing an air-fuel ratio feedback control routine.
FIG. 17 is a flowchart showing a part of a routine for setting an air-fuel ratio feedback correction coefficient according to the embodiment of the invention according to claims 3 and 4;
[Explanation of symbols]
Reference Signs List 11 internal combustion engine 13 air flow meter 15 fuel injection valve 16 control unit 19 air-fuel ratio sensor 21 crank angle sensor

Claims (3)

Air-fuel ratio detection means for detecting the air-fuel ratio of the air-fuel mixture supplied to the engine; setting using a control constant while comparing the detected value of the air-fuel ratio by the air-fuel ratio detection means with a reference value corresponding to the target air-fuel ratio An air-fuel ratio control device for an internal combustion engine including air-fuel ratio feedback control means for controlling the air-fuel ratio to approach the target air-fuel ratio by the feedback correction coefficient
Reversal cycle detection means for detecting a cycle in which a magnitude relationship of a detection value of the air-fuel ratio detection means with respect to a reference value corresponding to the target air-fuel ratio is reversed,
A storage means for correcting and setting a control constant corresponding to a reversal cycle of the air-fuel ratio sensor detected by the reversal cycle detection means in a direction in which the reversal cycle decreases as the reversal cycle increases ,
Control constant setting means for setting a control constant by retrieving a control constant corresponding to the detected inversion cycle from the storage means,
An air-fuel ratio control device for an internal combustion engine, comprising: Air-fuel ratio detection means for detecting the air-fuel ratio of the air-fuel mixture supplied to the engine; setting using a control constant while comparing the detected value of the air-fuel ratio by the air-fuel ratio detection means with a reference value corresponding to the target air-fuel ratio An air-fuel ratio control device for an internal combustion engine including air-fuel ratio feedback control means for controlling the air-fuel ratio to approach the target air-fuel ratio by the feedback correction coefficient
A transmission delay time calculating means for calculating a transmission delay time from when the air-fuel ratio is controlled based on the engine operating state to when the controlled air-fuel ratio state is transmitted to the air-fuel ratio detecting means,
The transmission delay time calculated by the transmission delay calculating means and the air-fuel ratio controlled air-fuel ratio state detected by the air-fuel ratio detecting means are detected by the air-fuel ratio detecting means after being transmitted to the air-fuel ratio detecting means. Control delay setting means for setting a control constant used for the air-fuel ratio feedback control based on the total delay time obtained by adding
An air-fuel ratio control device for an internal combustion engine, comprising: Engine speed detection means for detecting the engine speed,
Intake air flow rate detection means for detecting an air flow rate sucked into the engine,
The transmission delay time calculating means includes: a stagnation delay time including a delay due to an engine cycle and a delay due to combustion estimated based on the engine rotation speed detected by the engine rotation speed detection means; 3. The internal combustion engine according to claim 2 , wherein a transmission delay time is calculated by adding a transport delay time until exhaust gas estimated based on the intake air flow rate detected by the exhaust gas reaches the air-fuel ratio detecting means. Air-fuel ratio control device.

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