JP3453815B2 - Air-fuel ratio learning control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention controls the air-fuel ratio of an internal combustion engine.
Equipment, especially air-fuel ratio feedback control and air
While performing learning control of the fuel-fuel ratio, the air-fuel ratio
Air-fuel by setting control constants in feedback control
To perform rich control by shifting the ratio in the rich direction.
And technology for improving learning accuracy. [0002] 2. Description of the Related Art Conventionally, an air-fuel ratio feedback control function has been provided.
Engine with electronically controlled fuel injection system
Is disclosed in JP-B-63-46254 and the like.
Such an air-fuel ratio learning control device is employed. this
Is the engine operating condition related to the amount of air taken into the engine.
Parameters (for example, engine intake air flow rate and engine speed)
The basic fuel injection amount calculated from
_TwoProportional / integral control based on the signal from the sensor
Correct by the set air-fuel ratio feedback correction coefficient.
To calculate the fuel injection amount and feed the air-fuel ratio to the target air-fuel ratio
The air-fuel ratio feedback system
Reduce the deviation of the current feedback correction coefficient from the reference value.
Operating area divided according to engine operating state
Determines the learning correction coefficient by learning for each region, and sets the fuel injection amount
The basic fuel injection amount with the learning correction coefficient
And without correction by the air-fuel ratio feedback correction coefficient.
Look at the base air-fuel ratio obtained from the calculated fuel injection amount.
Match the target air-fuel ratio and provide air-fuel ratio feedback.
During control, this is further compensated for by a feedback correction coefficient.
That is, the fuel injection amount is calculated. According to this, air-fuel ratio feedback control
During the transient operation, the tracking of the feedback
And quickly converge near the target air-fuel ratio
To improve exhaust purification performance.
It is. On the other hand, in high-speed / high-load areas,
The target air-fuel ratio during the feedback control
Control is performed on the rich side from the ratio.
Stop the feedback control based on the fuel ratio detection.
Rich by multiplying the fuel injection amount by the coefficient for rich correction
Side control has generally been done. On the other hand, in order to improve fuel efficiency at high speeds,
O_TwoAir-fuel ratio feedback control using sensors
As a result, the air-fuel ratio is made richer than the target air-fuel ratio.
Devices that perform feedback control have been proposed. That is, air-fuel
In the ratio feedback control, the feedback correction
Control constants (proportional constants and integral constants)
When it is determined that the air-fuel ratio is leaner than the target air-fuel ratio
To the rich direction and the richer than the target air-fuel ratio.
The value to be corrected in the lean direction when it is determined that there is
If they are set to the same value, the air-fuel ratio will be rich and lean.
Again, the control center value is controlled to approximately the target air-fuel ratio.
You. This is normal air-fuel ratio feedback control.
On the other hand, the value of the control constant to be corrected in the rich direction is
If you set a value larger than the value to be corrected in the lean direction,
The time when the fuel ratio is controlled to the rich side is controlled to the lean side
Control over the air-fuel ratio
The center value shifts to the rich side to perform rich air-fuel ratio control
It is done. In this method, the base air-fuel ratio (feed
Obtained by fixed control value set without back correction
Air-fuel ratio detection even if the (air-fuel ratio) deviates from the target value
Since the correction is made based on the value, the rich air-fuel ratio control
The accuracy is improved. Therefore, specific operating conditions such as high speed and high load
In the range, the control constant in the rich direction is increased and
Air-fuel ratio feedback control shifted to the
To improve fuel economy.
You. [0005] SUMMARY OF THE INVENTION
Fuel shifted to the rich side by switching control constants
In a system for performing ratio feedback control, the learning system
If the control is used as it is, the following problems occur.
That is, the air-fuel ratio has been shifted to a richer side than the target air-fuel ratio.
When learning is performed in the state, the learning value enriches the base air-fuel ratio
It will be corrected in the direction that you do. And after finishing the learning,
After shifting to another operating area, return to the specific operating area again.
When entering, the base air-fuel ratio learned in the rich direction
The air-fuel ratio using the control constant for the rich shift.
Because back control is performed, there is double enrichment.
And it becomes excessively rich, and the exhaust purification performance is improved.
This will also hinder the rolling performance. The present invention has been made in view of such a conventional problem.
Switching of control constants under specific operating conditions
Air-fuel ratio feedback control to enrich the air-fuel ratio
In the fish, the learning accuracy is improved, and the exhaust purification
Performance of the internal combustion engine that can maintain good performance
It is an object to provide an air-fuel ratio learning control device. [0007] SUMMARY OF THE INVENTION For this reason, the present invention has been described with reference to FIG.
As shown in the figure, the operating state detection method for detecting the engine operating state
Stage and air-fuel for detecting the air-fuel ratio of the mixture supplied to the engine
Air-fuel based on the ratio detection means and the detected engine operating state
Air-fuel ratio basic control value setting means for setting a basic control value of the ratio
And the air-fuel ratio so that the detected air-fuel ratio approaches the target value.
Air-fuel ratio feedback compensation to increase or decrease the control value of
Control constant and air-fuel ratio for correcting the positive value to rich air-fuel ratio
Set using a control constant that corrects
Fuel ratio feedback correction value setting means and engine operating range
Learning value for correcting the basic control value of the air-fuel ratio
Storing the stored air-fuel ratio learning value storage means;
Decrease the deviation of the fuel ratio feedback correction value from the reference value
In the direction stored in the air-fuel ratio learning value storage means.
Air-fuel ratio learning value
The new means and the machine corresponding to the set basic control value of air-fuel ratio
The value corrected with the learning value in the
Correct with the back correction value to set the final air-fuel ratio control value
Air-fuel ratio control value setting means, and the air-fuel ratio
Control for rich direction correction for feedback correction value setting
The constant and the control constant for lean direction correction are
Are set to approximately the same size, and the difference is
Control constant setting means for setting to the value held.
In the air-fuel ratio learning control device for an internal combustion engine, the air-fuel ratio
The learning updating means is configured to perform a constant
Only when the condition is satisfied, the air-fuel ratio learning value updating means
The learning value is corrected and updated, and the correction for the rich direction is performed.
Control constants for which the values for and lean direction correction are set to be approximately equal
To set the air-fuel ratio feedback correction value using
A control constant switching means for updating and updating the learning value
It is characterized by having. [0008] The intake air detected by the operating state detecting means
Basic air-fuel ratio control value setting based on flow rate, engine speed, etc.
The means is a basic control value of the air-fuel ratio, specifically, a cylinder.
A base that can achieve the target air-fuel ratio corresponding to the amount of air
The main fuel injection amount and the like are set. On the other hand, with an oxygen sensor or the like interposed in the exhaust system,
The air-fuel ratio of the air-fuel mixture is detected by the representative air-fuel ratio detecting means.
And the air-fuel ratio approaches the target value based on the detected value.
The air-fuel ratio filter for increasing or decreasing the air-fuel ratio control value
Feedback correction value is the air-fuel ratio feedback correction value setting procedure.
Set by the stage. Here, the control constant setting means
To the original target air-fuel ratio (generally, the stoichiometric air-fuel ratio).
In the normal operation area where feedback control is performed,
The value to be corrected and the value to be corrected in the lean
Control constants, but in certain operating ranges
The control constant is set with a difference in the correction value,
The air-fuel ratio in the operating region of the characteristic is shifted in the rich or lean direction.
The shifted control is performed. For example, high speed / high load
In the region, the control constant for correcting in the rich direction is larger.
Air-fuel ratio feedback control
The air-fuel ratio is shifted in the rich direction.
It is. Further, the air-fuel ratio learning value updating means includes an operating area.
Each time the air-fuel ratio feedback correction value is compared with a reference value
Learning of the same area stored in the air-fuel ratio learning value storage means.
Correct and update the value in the direction to decrease the deviation from the reference value
However, in this case, the learning is directly performed in the common use area.
On the other hand, in the specific operation region, the learning condition is satisfied.
Use the above control constants when performing stand-by learning.
The amount of correction in the rich direction and the amount of correction in the lean direction.
Using the control constants set to be approximately equal, the same
Learning is performed while performing fuel ratio feedback control. With this configuration, the specific operation range
In the learning, the basic control value (base air-fuel ratio) is
It is made to approach the value equivalent to the standard air-fuel ratio,
During non-learning, the learning value is used while
Control with a difference in the correction amount between the touch direction and the lean direction.
By performing air-fuel ratio feedback control using
In the specific operation area,
Air / fuel ratio shifted to rich or lean with good response
You can take control. [0012] DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.
I will tell. In FIG. 2 showing the configuration of one embodiment,
The intake passage 12 has an air flow meter for detecting an intake air flow rate Q.
The intake air flow rate Q in conjunction with the motor 13 and the accelerator pedal.
A throttle valve 14 is provided for controlling the downstream manifold portion.
Has an electromagnetic fuel injection valve as a fuel supply means for each cylinder
15 are provided. The fuel injection valve 15 includes a microcomputer.
Injection pulse signal from built-in control unit 16
The valve is driven to open and pumped from a fuel pump (not shown).
Is controlled to a predetermined pressure by the pressure regulator.
The injected fuel is supplied. Furthermore, the cooling jacket of the engine 11
A water temperature sensor 17 for detecting a cooling water temperature Tw in the inside is provided.
You. On the other hand, the exhaust passage 18
By detecting the oxygen concentration, the air-fuel ratio
An air-fuel ratio sensor 19 is provided as air-fuel ratio detection means for detection.
And the oxidation of CO and HC in the exhaust gas
And NO_XAs an exhaust purification catalyst that purifies by reducing
A three-way catalyst 20 is provided. A distribution not shown in FIG.
The crank angle sensor 22 is built in the
Output from the crank angle sensor 22 in synchronization with the engine speed.
The unit angle signal for a certain period of time, or
The cycle of the reference angle signal is measured to detect the engine speed N.
You. The air flow meter 13, water temperature sensor 17,
The link angle sensor 22 and the like correspond to operating state detecting means. Next, air-fuel by the control unit 16
The ratio control routine is performed according to the flowcharts of FIGS.
Will be explained. FIG. 3 shows a fuel injection amount setting routine.
Is performed at predetermined intervals (for example, every 10 ms). S
In step (denoted by S in the figure) 1, the air flow meter 13
Air flow rate Q detected by the crank angle sensor
22 based on the engine speed N calculated based on the signal from
Basic fuel equivalent to the amount of intake air per unit rotation
Injection amount T_PIs calculated by the following equation. Basic fuel injection amount T
_PCorresponds to the basic control value of the air-fuel ratio.
Therefore, the function of step 1 is to set the air-fuel ratio basic control value.
It corresponds to a means. T_P= K x Q / N (K is a constant) In step 2, the cooling temperature detected by the water temperature sensor 17
Set various correction coefficients COEF based on water temperature Tw etc.
You. In step 3, a feedback correction coefficient described later is used.
Feedback correction coefficient set by setting routine
α and the corresponding operation stored in the RAM map described later.
Learning value α_LRead. This RAM map
It corresponds to an air-fuel ratio learning value storage means. In step 4, based on the battery voltage value
Voltage correction T_SSet. This is the battery voltage change.
To correct the injection flow rate change of the fuel injector 15 due to
Things. In step 5, the final fuel injection amount T_I
Is calculated according to the following equation. Final fuel injection amount T_IIs the most
This corresponds to the final air-fuel ratio control value, and
The function of step 5 corresponds to the air-fuel ratio control value setting means. T_I= T_P× COEF × α × α_L+ T_S In step 6, the calculated fuel injection valve T_IOutput for
Set it in the Vista. As a result, the predetermined organization
When the rotation-synchronous fuel injection timing comes, the calculated fuel
Injection amount T_IDrive pulse signal with pulse width of
The fuel is supplied to the valve 15 for fuel injection. Next, the air-fuel ratio feedback correction coefficient is set.
The routine will be described with reference to the flowchart of FIG. This
Is executed in synchronization with the engine rotation. This air fuel
The ratio feedback correction coefficient setting routine
This corresponds to a feedback correction value setting means. In step 11,
Whether it is an operating condition to perform feedback control of the air-fuel ratio
Is determined. If the operating conditions are not met,
Ends the routine. In this case, feedback correction
The coefficient α is the value at the end of the previous feedback control or
Clamped to a certain reference value, feedback control is stopped
Is stopped. In step 12, the signal from the air-fuel ratio sensor 19
Signal voltage V_O2Enter In step 13, in step 12
Input signal voltage V_O2And target air-fuel ratio (stoichiometric air-fuel ratio)
Is compared with the reference value SL to determine whether the air-fuel ratio is rich or lean.
Determine. judge. Air-fuel ratio is lean (V_O2<SL)
Time, go to step 14, and when rich → lean
It is determined whether or not it is immediately after turning).
To set the air-fuel ratio feedback correction coefficient α to the current value.
Constant proportional constant P_LIs updated with the value obtained by adding
Proceed to step 16 to set the air-fuel ratio feedback correction coefficient α
A predetermined integration constant I_LUpdate with the value obtained by adding.
Here, a proportional constant P for correcting the air-fuel ratio in the rich direction
_L, Integration constant I_LIs stored for each operation area as described later.
The target air-fuel ratio (the
Range and the target air-fuel ratio (Li
Different values depending on the specific area to be controlled to
Prepare two types of maps that have been set and stored, and
Switch and use each time. On the other hand, in the determination of step 13, the air-fuel ratio
J (V_O2> SL), go to step 17, lean →
It is determined whether or not the rich is inverted (immediately after), and
When turning, proceed to step 18 for air-fuel ratio feedback correction
The coefficient α is calculated from the current value to a predetermined proportional constant P_RWith the value obtained by subtracting
Update and go to step 19 except when reversing, and
The feedback correction coefficient α from the current value to a predetermined integration constant I_RTo
Update with the subtracted value. Also in this case, correct in the lean direction
Proportional constant P_R, I_RAvailable in two types depending on the operating area
It is determined by a search from the map. FIG. 5 is a diagram showing switching according to the operating range.
For searching for the proportional and integral constants from the saved map
To indicate In step 21, the air-fuel ratio feedback control
It is determined whether or not it is an operating condition for performing. Air-fuel ratio fee
When the feedback control condition is satisfied, the routine proceeds to step 22, where the air-fuel
Target air-fuel for which rich / lean is determined by the ratio sensor 19
Ratio (stoichiometric air-fuel ratio) in the normal operating range or below
It is determined whether or not the operation is in the specific operation region in which the control is performed on the rich side. Then, it is determined that the vehicle is in the normal operation region.
If this is the case, proceed to step 23, where the ratio in the rich direction is
Example constant P_L, Integration constant I_LAnd lean proportionality constant
P_R, Integration constant I_RAnd the first map in which
Search and read the value stored in the current operation area from the
Put in. It should be noted that simple setting such as setting the same in all operation areas
Settings may be used, in which case the fixed settings stored in memory will be used.
A constant value may be read. Further, when it is determined that the vehicle is in the specific operation region.
Proceeds to step 24, and the learning control condition described later is satisfied.
Is set in the learning value update routine to be described later.
It is determined based on the value of the learning flag FL to be executed. And
When the learning flag FL is 0, that is, the learning control condition
If the condition is not satisfied and learning is not performed, step
Proceeding to 25, the proportional constant P in the rich direction_L, Integration constant I_LTo
Lean proportional constant P_R, Integration constant I_RLarger
Current driving from the second map retrieved from the specified map
Search and read the value stored in the area. Figure 6 is proportional
Constant P_L/ P_R3 shows an example of a map stored for the.
As shown, in the first map, P_L= P
_R (= 4.5), whereas the second map is fast and high
For a specific operating area of the load, the
Constant P in the switch direction_L> Lean proportional constant P_RWhen
It is set to be. On the other hand, if the learning flag FL is 1,
That is, learning is performed when the learning control condition is satisfied.
Under the condition, the process proceeds to the step 23 to specify the rich control.
Perform feedback control to the stoichiometric air-fuel ratio even in the operating range.
Values in the rich direction and the lean direction
Proportional constant P set equal_L/ P_R, Integration constant I_L/ I
_RRead the value of. Next, a routine for updating the learning value of the air-fuel ratio
Will be described with reference to the flowchart of FIG. This learning value
The updating routine corresponds to an air-fuel ratio learning value updating unit. S
In step 30, it is determined whether the learning control condition is satisfied.
Is determined. To give specific learning control conditions, for example,
For example, when all the conditions listed below are satisfied
You. In the same operation area where the learning value is stored
Staying for more than the specified time.   After entering the operation region, the opening TVO of the throttle valve 14 and
And the opening change amount ΔTVO are each within a predetermined range.
thing.   More than a predetermined distance or a predetermined time since the previous learning was performed
You are running. However, this condition depends on the specific operation
Only added for areas. If the learning control condition is not satisfied,
Go to step 31 and reset the learning flag to 0
In both cases, the count value C described later_MAPReset to 0
Thereafter, this routine ends. Also, the learning control condition is satisfied.
If so, the routine proceeds to step 32, where the learning flag FL is set to 1
After that, go to step 33 to enrich the air-fuel ratio._,
Determine whether the lean has been reversed and call this subroutine
Each time the reversal is repeated, the number of reversals is expressed in step 34
Count value C_MAP1 up. And, for example, C
_MAPProceed from step 35 to step 36 when = 3
And the current air-fuel ratio feedback correction coefficient α and the reference value 1
And the deviation (α-1)₁Temporarily memorize as
You. If it is determined in step 33 that non-inversion is performed, this routine
To end. In this way, C_MAPIf ≧ 4,
Proceed from step 35 to step 37, where the air-fuel ratio
Deviation of feedback correction coefficient α from reference value 1 (α−
1) is Δα_TwoAs temporary storage. In step 38,
-Time air-fuel ratio feedback correction coefficient α and reference value
Deviation Δα from 1₁And the deviation Δα obtained in step 37
_TwoAverage value of α_MAsk for. Next, the routine proceeds to step 39, where the current operation area is set.
Learning value α stored corresponding to_LRead. Step
Proceeding to step 40, the current learning value α is calculated according to the following equation._LTo the sky
The flatness of the deviation between the fuel ratio feedback correction coefficient α and the reference value 1
Average Δα_MIs a predetermined ratio K_aBy adding
Learning value α_LTo calculate the learning value α of the same area on the RAM._L
Modify and rewrite the data in Thereafter, at step 41, for the next learning,
Δα_TwoTo Δα₁Substitute for With such a configuration, the theory
During the air-fuel ratio feedback control, the same learning
Control eliminates deviation of base air-fuel ratio for each operation area
During transient operation to eliminate the difference in air-fuel ratio between regions
Function to eliminate deviations in air-fuel ratio_,The effect is satisfied
Of course, rich air-fuel ratio feedback system
Even when in a specific driving area
Is equal to the value for rich direction correction and the value for lean direction correction.
Stoichiometric air-fuel ratio feedback control using the
Since learning is performed while performing, the base air-fuel ratio is the learning value α_LTo
Therefore, since it is learned and corrected to a value equivalent to the stoichiometric air-fuel ratio,
When restarting the feedback control to the rich air-fuel ratio
Is the rich shift by the control constant with respect to the base air-fuel ratio
Is performed, excessive enrichment is avoided, and learning
Highly responsive and accurate rich air-fuel ratio control can be performed. In the embodiment, the rich operation is performed in a specific operation range.
The target air-fuel ratio by increasing the control constant
In the example shown above, the shift to the
The target air-fuel ratio is increased by increasing the control
It is also possible to shift to the
Even when learning in the lean shift operation area, rich
Air-fuel ratio control that makes the correction amount in the
It goes without saying that the present invention can be applied in such a manner. [0033] As described above, according to the present invention,
If the air-fuel ratio feedback control is
Values for the rich and lean directions of the control constants
And shift control of the air-fuel ratio with a difference
However, even in the specific driving range, the control
Set the numbers approximately equal to perform air-fuel ratio feedback control
This prevents the air-fuel ratio from shifting excessively
Highly responsive and accurate shift air-fuel ratio control through learning
Can be performed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a configuration of the present invention. FIG. 2 is a diagram showing a configuration of an embodiment of the present invention. FIG. 3 is a flowchart showing a fuel injection amount setting routine of the embodiment. FIG. 4 is a flowchart illustrating an air-fuel ratio feedback correction coefficient setting routine according to the embodiment; FIG. 5 is a flowchart illustrating a control constant setting routine during air-fuel ratio feedback control according to the embodiment; FIG. 6 is a diagram showing two types of control constant setting maps according to the first embodiment. FIG. 7 is a flowchart showing a routine for updating a learning value of an air-fuel ratio according to the embodiment. [Description of Signs] 11 Engine 13 Air flow meter 15 Fuel injection valve 16 Microcomputer 19 Air-fuel ratio sensor 22 Crank angle sensor

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-298640 (JP, A) JP-A-57-99246 (JP, A) JP-A-63-246432 (JP, A) JP-A-2- 102335 (JP, A) JP-A-62-267251 (JP, A) JP-A-57-171044 (JP, A) JP-A-58-25543 (JP, A) JP-A-6-294343 (JP, A) Japanese Utility Model Application Hei 2-59240 (JP, U) Japanese Utility Model Application Sho 59-150966 (JP, U) Japanese Patent Publication No. 63-46254 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02D 41/02-41/20 F02D 45/00

Claims (1)

(57) [Claims] [Claim 1] Operating state detecting means for detecting an engine operating state; air-fuel ratio detecting means for detecting an air-fuel ratio of an air-fuel mixture supplied to an engine; Air-fuel ratio basic control value setting means for setting an air-fuel ratio basic control value based on the state; and an air-fuel ratio feedback correction value for increasing or decreasing the air-fuel ratio control value so that the detected air-fuel ratio approaches a target value. Air-fuel ratio feedback correction value setting means for setting using a control constant for correcting the air-fuel ratio in the rich direction and a control constant for correcting the air-fuel ratio in the lean direction, and a basic control value of the air-fuel ratio for each operating region of the engine. An air-fuel ratio learning value storage unit storing a learning value for correcting the air-fuel ratio learning correction value stored in the air-fuel ratio learning value storage unit in a direction to reduce a deviation from a reference value of the air-fuel ratio feedback correction value for each of the operation regions. versus Air-fuel ratio learning value updating means for correcting and updating a learning value in a corresponding operating region; and an air-fuel ratio feedback correction value obtained by correcting a basic control value of a set air-fuel ratio with a learning value in a corresponding engine operating region. Air-fuel ratio control value setting means for setting a final air-fuel ratio control value by correcting the air-fuel ratio feedback control value, and a control constant for rich direction correction for setting the air-fuel ratio feedback correction value and a control for lean direction correction. And a control constant setting means for setting a constant to a substantially equal magnitude in a normal operation range and a value having a difference in a specific operation range, and an air-fuel ratio learning control device for an internal combustion engine comprising: The air-fuel ratio learning update unit performs a correction update of the learning value by the air-fuel ratio learning value update unit only when a certain condition is satisfied in the specific operation region, and performs the rich direction correction and the lean direction correction. And a control constant switching means for correcting and updating a learning value while setting an air-fuel ratio feedback correction value using a control constant in which a value for direction correction is set substantially equal. Air-fuel ratio learning control device.