JPS6231180B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio learning control method for an internal combustion engine, and is particularly suitable for use in an automobile engine equipped with an intake pipe pressure type electronically controlled fuel injection device.
Adding an increase/decrease correction according to the engine operating condition including the deviation between the exhaust gas air-fuel ratio and the target air-fuel ratio to the basic injection amount determined according to the engine intake pipe pressure or intake air amount and engine speed, The present invention relates to an improvement in a learning control method for an internal combustion engine, which injects fuel and learns and corrects an air-fuel ratio correction term used when calculating a fuel injection amount according to the deviation.

Internal combustion engines, especially automobile engines that use three-way catalysts to purify exhaust gas,
It is necessary to maintain the air-fuel ratio of the exhaust gas strictly near the stoichiometric air-fuel ratio, so for example, the air-fuel ratio is detected from the residual oxygen concentration in the exhaust gas.
The engine intake pipe pressure or In addition to the basic injection amount determined according to the intake air amount and engine speed, engine operating conditions such as engine cooling water temperature, throttle valve opening, and the deviation between the exhaust gas air-fuel ratio output from the air-fuel ratio sensor and the target air-fuel ratio are used. By injecting the fuel with corresponding feedback and feedback increase/decrease corrections, the air-fuel ratio of the air-fuel mixture is controlled by feedforward and feedback, and the basic injection amount is adjusted according to the deviation. An air-fuel ratio learning control method for an internal combustion engine has been proposed in which an air-fuel ratio correction coefficient used when correcting an increase or decrease in feed forward is learned and corrected.

According to such an air-fuel ratio learning control method, the air-fuel ratio correction coefficient is learned and corrected according to individual differences in various sensors for detecting engine operating conditions, changes over time, weather conditions, etc. The fuel injection amount is subjected to feedforward control at an air-fuel ratio close to the target air-fuel ratio, and is characterized in that good air-fuel ratio control can be performed with little delay due to feedback control. However, in the past, only the multiplication term for the basic injection amount was learned, so as shown in Figure 1, for example, the engine load detected from the intake pipe pressure or intake air amount was relatively large, and the target Although good results can be obtained in the middle and high load range of the engine, where the required air-fuel ratio (region C) varies almost proportionally to the air-fuel ratio (solid line B) due to changes over time, on the other hand, as at idle, This has the disadvantage that good learning control cannot necessarily be performed under low engine loads where the required air-fuel ratio varies by a substantially constant amount with respect to the target air-fuel ratio due to changes over time. Furthermore, if extreme operating conditions continue, or if the control circuit fails, the learned value may become an abnormal value, causing the air-fuel ratio to deviate abnormally.

The present invention has been made to eliminate the above-mentioned conventional drawbacks, and is capable of performing good air-fuel ratio learning control over a wide operating range including idling operation, and prevents abnormal deviations in the air-fuel ratio due to learning. An object of the present invention is to provide an air-fuel ratio learning control method for an internal combustion engine.

The present invention provides an increase/decrease correction in accordance with the engine operating state, including the deviation between the air-fuel ratio of exhaust gas and the target air-fuel ratio, in the basic injection amount determined according to the intake pipe pressure or intake air amount of the engine and the engine speed. In the air-fuel ratio learning control method for an internal combustion engine, the air-fuel ratio correction term used for calculating the fuel injection amount is learned and corrected according to the deviation while injecting fuel. Then, a multiplication term for the basic injection amount is learned, and an addition term for the basic injection amount is learned in an idling state, and an allowable limit is set for the learning result of the multiplication term and/or addition term. Thus, the above objective has been achieved.

Embodiments of the present invention will be described in detail below with reference to the drawings.

An embodiment of an intake pipe pressure type electronically controlled fuel injection device in which the air-fuel ratio learning control method for an internal combustion engine according to the present invention is adopted is as shown in FIGS. 1 and 2. , an intake temperature sensor 14 for detecting the temperature of intake air taken in from the air cleaner 12, and an intake passage 16.
A throttle valve 18 for controlling the flow rate of intake air, which is disposed inside the vehicle and opens and closes in conjunction with an accelerator pedal (not shown) disposed in the driver's seat.
, a throttle sensor 20 including an idle contact for detecting whether or not the throttle valve 8 is at an idle opening, and a potentiometer that generates a voltage output proportional to the opening of the throttle valve 18, and a surge tank. 2
2, an intake pipe pressure sensor 23 for detecting intake pipe pressure from the pressure in the surge tank 22, and a bypass passage 24 that bypasses the throttle valve 18.
an idle rotation control valve 26 disposed in the middle of the bypass passage 24 for controlling the idle rotation speed by controlling the opening area of the bypass passage 24; and an idle rotation control valve 26 disposed in the intake manifold 28. , an injector 30 for injecting fuel toward the intake port of the engine 10, and an oxygen concentration sensor 34 disposed in the exhaust manifold 32 for detecting the air-fuel ratio from the residual oxygen concentration in the exhaust gas.
and an exhaust pipe 36 downstream of the exhaust manifold 32.
a three-way catalytic converter 38 disposed in the middle of the
A distributor 40 has a distributor shaft that rotates in conjunction with the rotation of the crankshaft of the engine 10, and a top dead center signal and A top dead center sensor 42 and a crank angle sensor 44 that output a crank angle signal, a cooling water temperature sensor 46 disposed in the engine block for detecting engine cooling water temperature, and a transmission 4
A vehicle speed sensor 50 for detecting the running speed of the vehicle from the rotation speed of the output shaft of No. 8; The basic injection amount per engine stroke is determined from the map, and the throttle sensor 2
0 output throttle valve opening, the cooling water temperature sensor 46
Output engine cooling water temperature, the oxygen concentration sensor 3
The fuel injection amount is determined by adding feedforward and feedback increase/decrease corrections according to engine operating conditions such as the deviation between the exhaust gas air-fuel ratio detected from the four outputs and the target air-fuel ratio. A valve opening time signal is output to the injector 30, and further, an air-fuel ratio correction term used when correcting the basic injection amount by feed forward increase/decrease is corrected according to the deviation, and the engine operating state is The ignition timing is determined according to the igniter coil 5.
In the intake pipe pressure type electronically controlled fuel injection device for an automobile engine 10, the digital control circuit 54 outputs an ignition signal to the engine 2 and further includes a digital control circuit 54 that controls the idle rotation control valve 26 during idling. In the normal operating state, a multiplication term for the basic injection amount is learned, and in an idling operating state, an addition term for the basic injection amount is learned, and the learning result of the multiplication term and/or addition term is Tolerable limits are set.

As shown in detail in FIG. 3, the digital control circuit 54 is a central processing unit (hereinafter referred to as CPU) consisting of a microprocessor that performs various arithmetic operations.
60, the intake temperature sensor 14, the potentiometer of the throttle sensor 20, and the intake pipe pressure sensor 2.
3. An analog input port 62 with a multiplexer for converting analog signals input from the oxygen concentration sensor 34, cooling water temperature sensor 46, etc. into digital signals and sequentially inputting them into the CPU 60; and an idle contact point of the throttle sensor 20; Top dead center sensor 4
2. A digital input port 64 for inputting digital signals input from the crank angle sensor 44, vehicle speed sensor 50, etc. to the CPU 60 at predetermined timing, and a read-only memory (hereinafter referred to as "read-only memory" for storing programs or various constants, etc.). Random access memory (hereinafter referred to as RAM) 68 for temporarily storing calculation data etc. in the CPU 60, and random access memory (hereinafter referred to as RAM) 68 for backup that can maintain memory by being supplied with power from the auxiliary power supply even when the engine is stopped. A memory (hereinafter referred to as backup RAM) 70 and a digital output port 7 for outputting the calculation results of the CPU 60 to the idle rotation control valve 26, injector 30, coil with igniter 52, etc. at a predetermined timing.
2 and a common bus 7 that connects each of the above components.
It is composed of 4.

The action will be explained below.

First, the digital control circuit 54 calculates the intake pipe pressure PM output from the intake pipe pressure sensor 23 and the engine rotation speed NE calculated from the output of the crank angle sensor 44.
The basic injection time TP (PM, NE) is read out from the map stored in the ROM 66 in advance.

Furthermore, the fuel injection time TAU is calculated by correcting the basic injection time TP (PM, NE) using the following equation according to the signals from each sensor.

TAU=K〓TP(PM,NE)〓F+A...(1) Here, K is the multiplication term for the basic injection time TP (initial value =
1), A is an addition term (initial value =
0), F is a correction coefficient including an air-fuel ratio feedback correction coefficient FAF, which is corrected according to the engine operating state.

Fuel injection time TAU determined in this way
A fuel injection signal corresponding to this is output to the injector 30, and the injector 30 is opened for the fuel injection time TAU in synchronization with the engine rotation, and fuel is injected into the intake manifold 28 of the engine 10.

The learning of the air-fuel ratio correction term in this embodiment is performed in the fourth
This is done according to the program shown in the figure.

That is, first, in step 101, it is determined whether the idle switch is on. If the determination result is positive, the process proceeds to step 102, where it is determined whether the engine speed is below a predetermined value, which is about 200 to 300 rpm higher than the idle speed. If the determination result is positive, the process proceeds to step 103, where it is determined whether the intake pipe pressure PM is greater than or equal to a predetermined value higher than the intake pipe pressure during deceleration. If the determination result in step 103 is positive, that is, when the engine is in an idling state,
Proceeding to step 104, the addition term A to the basic injection time TP is learned. On the other hand, the above step 10
If the result of any of the determinations 1, 102, and 103 is negative, that is, if the vehicle is in a normal operating state other than an idling operating state, the process proceeds to step 105;
Learn the multiplication term K for the basic injection time TP.

Specifically, the learning of the addition term A in step 104 is performed according to a program as shown in FIG. That is, first step 201
Then, it is determined whether a predetermined period of time or more has passed since the previous learning. If the determination result is negative, the program is terminated without learning the addition term A.

This is because there is no point in learning the addition term A too frequently. On the other hand, if the determination result in step 201 is positive, step 2
Proceed to step 02 and set the air-fuel ratio feedback correction coefficient.
An average value FAFAV of FAF within a predetermined time is calculated.
Next, the process proceeds to step 203, where it is determined whether the calculated average value FAFAV is larger than the value 1 corresponding to the target air-fuel ratio by a predetermined value α or more. If the determination result is positive, the process proceeds to step 204, where the predetermined value △ is added to the addition term A (initial value = 0) up to that point.
Let the addition of A be a new addition term A. Next, proceeding to step 205, the calculated addition term A
is less than or equal to its upper limit value Amax. If the determination result is positive, the addition term A calculated in step 204 is used as the learned value and the program is terminated. On the other hand, if the determination result in step 205 is negative,
Proceeding to step 206, the upper limit value Amax of the addition term is set as addition term A, and this program ends.

If the determination result in step 203 is negative, the process proceeds to step 207, where the average value FAFAV calculated in step 202 is determined to be smaller than the value 1 corresponding to the target air-fuel ratio by a predetermined value α or more. Determine whether or not the If the determination result is positive, the process proceeds to step 208, where a new addition term A is obtained by subtracting a predetermined value ΔA from the previous addition term A. Next, the process proceeds to step 209, where it is determined whether the calculated addition term A is greater than or equal to its lower limit value Amin. If the determination result is positive, the addition term A calculated in step 208 is used as the learning value and the program is terminated. On the other hand, if the determination result in step 209 is negative, the program proceeds to step 210, sets the lower limit value Amin of the addition term to addition term A, and ends this program.

Further, if the determination result in step 207 is negative, that is, if the average value FAFAV calculated in step 202 is greater than or equal to 1-α and less than or equal to 1+α, it is determined that there is no need to perform learning correction. ,
This program ends without learning the addition term A.

Also, step 1 of the program shown in Figure 4
The learning of the multiplication term K for the basic injection time TP in step 05 is performed according to a program as shown in FIG. That is, first in step 301, it is determined whether a predetermined period of time or more has elapsed since the previous learning. If the determination result is negative, the program is terminated without learning the multiplication term K. This is because there is no point in learning the multiplication term K too frequently. On the other hand, if the determination result in step 301 is positive, step 302
Then, the average value FAFAV of the air-fuel ratio feedback correction coefficient FAF within a predetermined period of time is calculated. Next, proceed to step 303 and calculate the calculated average value.
It is determined whether FAFAV is larger than the value 1 corresponding to the target air-fuel ratio by a predetermined value β or more. If the determination result is positive, the process proceeds to step 304, where the multiplication term K (initial value = 1) up to that point is set to a predetermined value △.
The addition of K is defined as a new multiplication term K. Next, the process proceeds to step 305, where the calculated multiplication term K
is less than or equal to its upper limit value Kmax. If the determination result is positive, the multiplication term K calculated in step 304 is used as the learned value and the program is terminated. On the other hand, if the judgment result in step 305 is negative, the process proceeds to step 306, where the upper limit value of the multiplication term is
This program ends with Kmax as the multiplication term K.

If the determination result in step 303 is negative, the process proceeds to step 307, where the average value FAFAV calculated in step 302 is smaller than the value 1 corresponding to the target air-fuel ratio by a predetermined value β or more. Determine whether or not the If the determination result is positive, the process proceeds to step 308, where a new multiplication term K is obtained by subtracting a predetermined value ΔK from the previous multiplication term K. Next, the process proceeds to step 309, where it is determined whether the calculated multiplication term K is greater than or equal to its lower limit value Kmin. If the determination result is positive, the multiplication term K calculated in step 308 is used as the learning value and the program is terminated. On the other hand, if the determination result in step 309 is negative, the program proceeds to step 310, sets the lower limit value Kmin of the multiplication term to the multiplication term K, and ends this program.

Furthermore, if the determination result in step 307 is negative, that is, if the average value FAFAV calculated in step 302 is greater than or equal to 1-β and less than or equal to 1+β, it is determined that there is no need to perform learning correction. ,
This program ends without learning the multiplication term K.

In this way, by learning the addition term A to the basic injection quantity in the idling operating state and learning the multiplication term K to the basic injection quantity in the normal operating state excluding the idling operating state, the above-mentioned figure 1 can be obtained. It is possible to perform air-fuel ratio learning control that particularly meets the required characteristics of an automobile engine equipped with an intake pipe pressure type electronically controlled fuel injection device as shown. Furthermore, since upper and lower limits are set for both the multiplication term K and the addition term A, even if extreme operating conditions continue or some abnormality occurs,
The fuel injection time TAU does not take an extremely extreme value, and abnormal deviations in the air-fuel ratio can be prevented.

Incidentally, in the embodiment described above, a permissible limit was set for both the multiplication term K and the addition term A for the basic injection quantity, but it is of course possible to set a permissible limit for only one of them.

In the above embodiment, the present invention is applied to an automobile engine equipped with an intake pipe pressure type electronically controlled fuel injection device, but the scope of application of the present invention is not limited to this, and the present invention is applied to an automobile engine equipped with an intake pipe pressure type electronically controlled fuel injection device. It is obvious that the present invention can be similarly applied to an internal combustion engine equipped with an electronically controlled fuel injection device or an internal combustion engine equipped with a general electronically controlled fuel injection device.

As described above, according to the present invention, it is possible to perform learning that matches the required characteristics of the engine, and to perform good air-fuel ratio control that corresponds to changes in the engine over time. Further, it has excellent effects such as being able to prevent abnormal deviations in the air-fuel ratio due to learning.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the variation range due to changes over time in engine load and required injection amount, for explaining the principle of the present invention, and FIG. 2 is a diagram showing the air-fuel ratio learning control for an internal combustion engine according to the present invention. FIG. 3 is a block diagram showing the configuration of an embodiment of an intake pipe pressure type electronically controlled fuel injection device for an automobile engine in which the method is adopted.
FIG. 4 is a block diagram showing the configuration of the digital control circuit used in the embodiment, FIG. 4 is a flowchart showing a program for selecting a learning target, and FIG. 5 is a flow chart showing an addition to the basic injection time. a flowchart showing a program for learning terms;
FIG. 6 is a flowchart showing a program for learning the multiplication term for the basic injection time. 10...Engine, 14...Intake temperature sensor, 1
8... Throttle valve, 20... Throttle sensor, 23
...Intake pipe pressure sensor, 30...Injector,
34... Oxygen concentration sensor, 40... Distributor, 42... Top dead center sensor, 44... Crank angle sensor, 46... Cooling water temperature sensor, 54...
Digital control circuit.

Claims (1)

[Claims] 1 The basic injection amount determined according to the engine intake pipe pressure or intake air amount and engine speed,
Fuel is injected with an increase/decrease correction based on the engine operating condition, including the deviation between the air-fuel ratio of exhaust gas and the target air-fuel ratio, and the air-fuel ratio used when calculating the fuel injection amount is injected according to the deviation. In an air-fuel ratio learning control method for an internal combustion engine in which a fuel ratio correction term is learned and corrected, a multiplication term for the basic injection quantity is learned in a normal operating state, and an addition term for the basic injection quantity is learned in an idling operating state. An air-fuel ratio learning control method for an internal combustion engine, characterized in that the learning result of the multiplication term and/or the addition term is set with an allowable limit.