JPH02245442A - Air-fuel ratio learning control method and control device and fuel supply method and device for internal combustion engine - Google Patents

Abstract

PURPOSE:To increase the control accuracy of an air-fuel ratio by obtaining the opening degree of a control valve for purging evaporated fuel reserved in a canister to the intake system of an engine depending upon an engine load and speed, and adjusting a learning value for adjusting a fuel correction amount depending upon the opening degree of the valve. CONSTITUTION:During the operation of an engine 1, a basic fuel amount is obtained in ECU 5 from an intake air amount and an engine speed. The basic fuel amount so obtained is corrected according to a correction value, depending upon cooling water temperature and the like, and an increment correction value and the like during the detection of an acceleration mode and the like. In addition, the basic fuel amount is corrected according to an air-fuel correction factor and a learning value on the basis of an air-fuel ratio detected with an oxygen sensor 1, thereby obtaining a final fuel amount. In this case, the opening of a purging control valve 17 for purging evaporated fuel reserved in a canister 16 into an engine intake system is read out via the search of the map wherein various values are set, depending upon an engine load and speed. The aforesaid valve 17 is thereby controlled and the learning value is adjusted, depending upon the valve opening.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel supply control method and apparatus for an internal combustion engine, and more particularly to a learning control method and a learning control apparatus for air-fuel ratio feedback control of an internal combustion engine.

[Conventional technology]

In conventional air-fuel ratio feedback control, the amount of fuel Ti supplied to the internal combustion engine is usually set to Ti = @ '
Calculated using rp coefficient α+2 Kl v K2: coefficient Tp; basic fuel amount α; air-fuel ratio feedback coefficient. However, this air-fuel ratio feedback control alone has a problem in that it takes time to stabilize the air-fuel ratio to the stoichiometric air-fuel ratio when the operating state of the internal combustion engine changes significantly.

Therefore, for example, in the air-fuel ratio learning control device described in Japanese Patent Application Laid-Open No. 60-90944, a learning correction value β according to the operating state of the internal combustion engine is used, and the fuel amount Ti is I'm trying to find out.

[Problem to be solved by the invention]

In internal combustion engines installed in automobiles, evaporated fuel is stored in the fuel tank and purged into the internal combustion engine intake system to prevent the evaporated fuel from being released into the atmosphere and polluting the environment. Some have a mechanism.

Even if such air-fuel ratio control of an internal combustion engine is controlled by the conventional learning control device, the amount of fuel purged from the canister is not taken into consideration, so a problem arises in that the air-fuel ratio cannot be accurately controlled.

On the other hand, Japanese Patent Application Laid-Open No. 112755/1983 discloses a technique in which a table for reading out learning values is changed depending on whether or not the canister has been purged in air-fuel ratio feedback learning control. However, this conventional technique only deals with two states, whether or not it has been purged, and there is a problem in that it cannot be directly applied to techniques that control the amount of purge with more precision, as has been the case in recent years.

An object of the present invention is to provide an air-fuel ratio learning control method and device, and a fuel supply method and device, which can accurately control the air-fuel ratio even in an internal combustion engine equipped with a canister.

[Means to solve the problem]

The above objective is achieved by detecting the amount of evaporated fuel purge from the canister to the internal combustion engine intake system, and correcting the amount of fuel supplied from the fuel injection valve, etc. to the internal combustion engine based on the purge amount. .

[Effect]

In the present invention, the canister purge is not controlled on and off by an on-off valve, but the amount of opening of the control valve is controlled, and even the amount of purge is controlled. Since the amount of fuel supplied from a fuel supply device such as a fuel injection valve is corrected according to the detected amount of purge, the air-fuel ratio can be controlled with high precision.

The present invention is not limited to the method of correcting the supplied fuel amount, and one method is to correct the learned value with the purge amount.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

FIG. 5 is a block diagram of an example of an internal combustion engine equipped with a canister. An air flow sensor 3 is provided at the inlet of the intake pipe 2 of the internal combustion engine 1, and the sensor 3 detects the amount of air sucked into the intake pipe 2 through the air cleaner 4.
The intake air amount detection value is sent to an engine control unit (hereinafter referred to as ECU) 5. In the middle of the intake pipe 2 is a throttle valve 6 that is linked to an accelerator pedal (not shown).
is provided, and the opening degree of this throttle valve 6 is detected by a sensor 7.
The detected value is sent to ECUS. The throttle valve 6 is located at the position where the throttle valve 6 is installed in the intake pipe 2.
A bypass passage 8 is provided to bypass the air, and the amount of auxiliary air passing through the bypass passage 8 is controlled by an auxiliary air control valve 9 driven by a control signal from the ECU 3.

A fuel injection valve 1 is located upstream of the engine combustion chamber 1o in the intake pipe 2.
The opening time of the fuel injection valve 11, that is, the amount of fuel to be supplied is calculated by the ECU 3 as will be described in detail later, and the fuel injection valve 11 is opened by a control signal from the ECU 3. Accordingly, the fuel in the fuel tank 15 is supplied into the intake pipe 2 through the fuel injection valve 11. A canister 16 is attached to this fuel tank 15, and the fuel evaporated in the tank 15 is stored in this canister 16, and the stored fuel (referred to as evaporated fuel) is passed through a purge control valve 17 to the intake air. It is designed to be purged downstream of the throttle valve 6 in the pipe 2. This purge control valve 17 is
The valve opening amount is controlled in accordance with the valve opening amount control value from the ECU 3. The valve opening amount control value is read by the ECU 3 from the purge amount (valve opening amount) search map shown in FIG. 4 according to the engine load and engine speed.The valve opening amount control value is actually expressed numerically. However, in order to qualitatively show the valve opening amount in Fig. 4, "minimum" is used.

It is expressed as "small", "r medium", "r large". In other words, in this embodiment, the valve opening amount is controlled in five stages, including the fully closed state. When starting the engine, when the oxygen sensor is inactive, and when deceleration fuel is cut, the valve is completely closed.
Other than that, search the map shown in Figure 4. Note that the purge amount during idling is set to "minimum".

An ignition plug 12 is attached to the combustion chamber IO, and a high voltage is applied to the ignition coil 13 at the ignition timing calculated by the ECU 3, and this high voltage is applied to the distributor 14 to ignite each cylinder of the engine (only one cylinder is shown). Power is distributed to the plug 12.

An oxygen sensor 19 that detects the oxygen concentration in exhaust gas is attached to the exhaust pipe 18 of the internal combustion engine 1, and the detected oxygen concentration value is sent to the ECU 3.

Further, a water temperature sensor 20 is attached to the internal combustion engine l, and the temperature of the cooling water around the combustion chamber 10 is detected.

This coolant temperature detection value is sent to the ECU 3.

A crank angle detection sensor 22 is provided on a crankshaft (not shown) connected to a piston 21 of the internal combustion engine 1.
The detected value of the sensor 22 is sent to the ECU 3.

ECU3 has each of the above sensors 3.7.19.20°22
In addition to the detection signal, the battery voltage value and other data are taken in and various calculations are performed to determine the amount of auxiliary air bypass, ignition timing, and fuel injection amount.

Next, the procedure for calculating the supplied fuel amount Ti performed by the ECU 3 will be explained. In the present invention, the fuel amount Ti supplied from the fuel supply device (fuel injection valve) is calculated using, for example, the intake air amount Qa, the engine rotation speed N, etc. It is determined as a function of the engine operating state, the detected value corresponding to the air-fuel ratio of the air-fuel mixture supplied into the combustion chamber, and the amount of purge from the canister.In the example described below, the air-fuel ratio feedback In learning control, a learning value is determined as a function of the purge amount.

In the embodiment, the air-fuel ratio is detected by an oxygen sensor, but it goes without saying that it may be detected by other means. The present invention can also be applied to detection methods.

The supplied fuel amount Ti in this embodiment is calculated using the following equation (2).

Ti = 1 umbrella 'rp fist α + K2
(2) Here, 2 is a coefficient for Kl+, Tp is a basic fuel amount, and α is an air-fuel ratio feedback correction coefficient.

Coefficient Klji, KW is the fuel correction value according to the cooling water temperature, KACC is the fuel acceleration increase correction value when the operating state changes to the acceleration state, KD is the fuel increase correction value when the operating state changes from idle to normal operation, FIL the full throttle increase correction value
When.

Kl=10+KACC+KD+FUL
...Find as (6).

The coefficient 2 is a battery voltage correction value, which corrects changes in the amount of fuel supplied due to fluctuations in battery voltage.

The basic fuel amount 'rp is a value that corresponds to the load state, which is one of the operating states of the engine. for example.

T p = kl umbrella Q a / N
−(7). Here, kl is a coefficient.

The air-fuel ratio feedback correction coefficient α is calculated using the following first equation.

a=AL+K6*Ln
(1) Here, AL is the air-fuel ratio correction coefficient, and K
, are weighting coefficients, and Ln is a learning value.

The air-fuel ratio correction coefficient AL is as shown in FIG. 2(a).

When the output of the oxygen sensor changes from fuel lean to fuel rich, the proportional component P is decreased, and then the integral component ■ is gradually decreased, and when the output changes from fuel rich to fuel lean, the proportional component P is reduced.
, and then gradually increases the integral I.

The learned value Ln is a value that is stored in a predetermined storage location in the memory as shown in FIG. 2(c), and is updated as described below.
It is provided for each engine operating range, for example, each intake air amount range.

Next, a detailed procedure for determining the supplied fuel amount Ti while updating the learning value Ln will be explained according to the flowchart of FIG.

First, in step 1, it is determined whether the oxygen sensor is activated. This is because if air-fuel ratio feedback control is performed when the temperature is low and the oxygen sensor cannot yet detect an accurate value, such as when the engine is started, harmful exhaust gases will be emitted instead. Therefore, if it is determined in step 1 that the oxygen sensor is not activated, the process proceeds to step 2, where AL=1.0 is set, and the execution of this program is ended.

If the oxygen sensor is activated, the process proceeds from step 1 to step 3, and it is determined whether learning condition 1 is satisfied. For example, the cooling water temperature and the correction value K based on this
The determination is made based on whether the condition that all of W, etc. are greater than or equal to a certain value is satisfied. If not satisfied, proceed to step 4, clear the learning area OK flag, and proceed to step 7. If satisfied, proceed from step 3 to step 5, and find the learning area NO based on the value of the intake air amount Qa. For example, in FIG. If it is small, select number 0 as the learning area number.

When the learning area No. is also determined, the process proceeds to step 6, where the learning area OK flag is set to ``1°1ti-'', and the process proceeds to step 7. In step 7, it is determined whether learning condition 2 is satisfied. Whether learning condition 2 is satisfied or not is determined by whether or not conditions are met for performing air-fuel ratio feedback control based on the detected value of the oxygen sensor. If the conditions for performing air-fuel ratio feedback control are not satisfied, the process proceeds from step 7 to step 2, and this process ends.

If the conditions are met to perform air-fuel ratio feedback control, proceed from step 7 to step 8, and calculate the air-fuel ratio correction coefficient AL from the output voltage of the oxygen sensor by the proportional component P and the integral component I.
Obtained by addition/subtraction operations.

Then, in the next step 9, the peak value ALP+ALP2+ALP3+'' of the air-fuel ratio correction coefficient AL is sampled, the average value of these values is determined, and the deviation δ between this average value and the reference value 1.0 is calculated. Then, in the next step 10, from the value of this deviation δ,
The learning correction amount Xn is determined by searching the table shown in FIG. 2(b).

In the next step 11 (Fig. 1 (b)), the kll search map (Fig. 3 (a)) is searched from the canister purge amount CPout and the intake air amount Qa, and the Find the limiter value kl. This purge amount CPout is 1, for example, purge control valve 1
If 7 is for duty ratio control, it is checked at that on-duty.

The limiter values set in the kll map are shown in Figure 3 (
As shown in b) (the vertical axis shows the klt value), it is set so that the larger the purge amount CPout, the smaller the value, and the larger the engine load, the larger the value. This is thought to have a large effect on the learned value Ln of evaporative fuel purge if the purge amount is large and the engine load is small. is updated to a small learned value.). When the purge amount is small and the engine load is large, it is considered that the influence on the learned value Ln is small, so the limiter value kfL is increased to reduce the limit on the intake of the learned value. The range of values taken by the limiter value kl is 1, for example, 0.05≦1 (Il≦0.95).

In the next step 12, the limiter value correction coefficient value kp is set to the third value.
Search from the kp search map shown in Figure (c). In this map, as shown in FIG. 3(d), the kp value takes on a larger value as the integrated value of the purge amount becomes larger. As the canister continues purging, the vaporized fuel stored in the canister gradually decreases until it is completely exhausted, and even if the control valve 17 is opened, it is no longer purged into the engine intake system. For this reason, controllability is improved by correcting the kl value according to the progress of purge, that is, based on the integrated value of the purge amount and the purge time CPt.

In step 13, it is determined whether kl*kρ≦1 holds true or not, and if it holds true, step I in FIG. 1(C) is performed.
Proceed to step 5, and if it does not hold, proceed to step 14,
kll=1. Set kp=1 and proceed to step 15.

In step 15, it is determined whether the learning completion flag is set to 11111 or not. Learning completion flag is “O”
”, skip steps 16 to 18 and go to step 1.
Proceed to 9, and if it is “1”, proceed to step 16. In step 16, Ln=Ln previous value 10 to 311 ktb kp.
In (3), a new learning value Ln is obtained with K3=Xn, and this is stored as a new learning value in the corresponding learning area No. in FIG. 2(e) to update the learning value.

In the next step 17, the learning value L obtained in step 16 is
Using n, its adjacent value Ln-1r Ln+1 is calculated by the following formula (
4).

The learned value is obtained by (5) and stored in the corresponding location, and the learned value is updated. This is to anticipate the next control and perform control with good responsiveness.

Ln-+=ko" (Ln+Ln- is the previous value) ・(
4) LII+l”kl (Ln+Ln++ same value as before)
-(5) Here, k is a weighting coefficient.

Since learning has been completed as described above, the next step 18 clears the learning completion flag and proceeds to step 19. In step 19, the learning value corresponding to the current learning area number, that is, the learning value updated as described above. Ln is searched and read out, and in the next step 20, the above-mentioned (1)
Calculate formula % formula % (1).

In the next step 21 (Fig. 1(d)), step (7) described above is performed.
Calculate the basic fuel amount Tp using the formula, and in the next step 22, add + (= COE F ) to the coefficient using the above-mentioned formula (6).
Calculate. And finally, the above-mentioned formula (2) % formula %
In (2), the supplied fuel amount Ti is calculated, the execution of this control procedure is ended, and this control procedure is repeated again after, for example, LOMS.

In the above embodiment, the purge amount is estimated based on the opening degree of the purge control valve, but the present invention can also be applied to a case where the purge amount is directly detected using a sensor or the like. In this case, the purge amount detection value is used instead of the integrated value or purge time.

According to the embodiments described above, the purge amount is accurately controlled based on the engine rotation speed and the engine load, and the learned value is finely adjusted and updated according to the purge amount, so that the air-fuel ratio can be accurately controlled.

〔Effect of the invention〕

According to the present invention, the air-fuel ratio can be well controlled and comfortable driving performance can be obtained regardless of the amount of purge from the canister.

[Brief explanation of drawings]

FIG. 1 (a), (b), (c) + (d) is a flowchart showing a procedure for calculating the amount of fuel to be supplied according to an embodiment of the present invention, and FIG. 2 (a), (b), (C) are explanatory diagrams of the air-fuel ratio correction coefficient, learned correction amount, and learned value, respectively. Figures 3 (a) and (b) are explanatory diagrams of the kl search map, and Figures 3 (C) and (d) are explanatory diagrams of the kp search map. FIG. 4 is an explanatory diagram of a purge amount search map, and FIG. 5 is a configuration diagram of an internal combustion engine equipped with a canister. DESCRIPTION OF SYMBOLS 1... Internal combustion engine, 2... Intake pipe, 3... Air flow sensor, 5... ECU, 10... Combustion chamber, 1
1...Fuel injection valve, 15...Fuel tank, 16...
・Canister, 17...Purge control valve, 19...
oxygen sensor. Representative patent attorney Tadashi Akimoto Younger brother (b) (C) Figure (d)

Claims (1)

[Claims] 1. Detecting a value corresponding to the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine, correcting the amount of fuel supplied to the internal combustion engine using the detected value, and feeding back the air-fuel ratio to a predetermined air-fuel ratio. In the air-fuel ratio feedback control method, the air-fuel ratio learning control method adjusts the correction amount related to the correction with a learning value determined according to the operating state of the internal combustion engine,
A map in which various valve values are set according to engine load and engine rotation speed to determine the opening amount of a control valve that purges evaporated fuel stored in a canister installed in an internal combustion engine into the intake system of the internal combustion engine. 1. An air-fuel ratio learning control method, characterized in that the control is performed by reading out a corresponding valve opening value from a valve opening amount, and the learning value is further adjusted in accordance with the valve opening amount. 2. An air-fuel ratio feedback control method in which the air-fuel ratio is feedback-controlled to a predetermined value by multiplying the basic fuel amount according to the load of the internal combustion engine by a coefficient according to the oxygen concentration in the exhaust gas, the correction coefficient being applied to the internal combustion engine. In an air-fuel ratio learning control method that corrects the air-fuel ratio using a learned value according to the operating state of the engine, the opening amount of a control valve that purges evaporated fuel stored in a canister installed in an internal combustion engine into the intake system of the internal combustion engine is The valve opening value is controlled by reading out the corresponding valve opening value from a map in which various valve opening values are set according to the load and the engine speed, and the learned value is further adjusted according to the valve opening amount. Air-fuel ratio learning control method. 3. An air-fuel ratio feedback control method for an internal combustion engine, which is equipped with a mechanism for purging evaporated fuel stored in a canister into the intake system of the internal combustion engine, and the amount of fuel supplied to the internal combustion engine is controlled by the operating state of the internal combustion engine. In the air-fuel ratio learning control method, the purge amount of vaporized fuel from the canister is controlled by controlling the opening amount of a control valve, and the learned value is updated according to the purge amount. An air-fuel ratio learning control method characterized by: 4. A control valve that purges the evaporated fuel stored in the canister to the internal combustion engine intake system, and a map that has a value for controlling the opening amount of the control valve as a value corresponding to the engine load and engine rotation speed; load state detection means for detecting the load state of the internal combustion engine; operating state detection means for detecting the operating state of the internal combustion engine; and reading out values corresponding to the engine load and engine speed from the map and controlling the above using the values. a valve control means for controlling the valve; an air-fuel ratio detection means for detecting a value corresponding to an air-fuel ratio of the air-fuel mixture supplied from the internal combustion engine; and a basic fuel amount calculation means for calculating a basic fuel amount according to the load condition. , a feedback correction means for calculating a correction value according to the air-fuel ratio and correcting the basic fuel amount using the correction value; a learning means for adjusting the amount of fuel, and determining a supply fuel amount corresponding to the fuel amount obtained by the learning means, the feedback correction means, and the basic fuel amount calculation means, so that the fuel of the supply fuel amount is supplied to the internal combustion engine. and control means for controlling a fuel supply device installed in an internal combustion engine. 5. Air-fuel ratio correction coefficient A determined based on the learned value Ln depending on the operating state of the internal combustion engine and whether the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine is larger or smaller than a predetermined air-fuel ratio.
Using _L, the following formula (1) α=A_L+K_O*Ln・
...(1) K_O is calculated using the following formula (2) Ti=K_l* from means for determining the air-fuel ratio feedback coefficient α using a coefficient, the basic fuel amount Tp corresponding to the load condition of the internal combustion engine, and the air-fuel ratio feedback coefficient α. Tp*α+K_2...(2) K, K_
2 is an air-fuel ratio learning control device comprising means for determining a fuel amount Ti based on a coefficient and means for driving a fuel supply device according to the fuel amount Ti; Means for determining a limiter value kl that takes a smaller value as the amount of fuel purged into the internal combustion engine intake system increases, and the learned value Ln is calculated using the following formula (3) Ln=L
n previous value+K_3*kl (3) An air-fuel ratio learning control device characterized by comprising means for determining K_3 by a coefficient. 6. In claim 5, a storage means for storing a learned value Ln corresponding to an operating range of the internal combustion engine, and a new learned value Ln obtained by calculating the learned value Ln stored in the storage means using the equation (3) above. An air-fuel ratio learning control device comprising: means for updating the air-fuel ratio. 7. In claim 6, when updating the learning value Ln,
The learning values Ln-1 and Ln+1 of the operating area before and after that are also Ln-1 = K_4 * (Ln updated value + Ln-1 previous value) L
n+1=K_4*(Ln update value+Ln+1 previous value) where K_4 is an air-fuel ratio learning control device characterized by comprising means for updating with a weighting coefficient. 8. In any one of claims 5 to 7, a storage means having as a map a correction value kp that takes a larger value as the integrated value of the purge amount from the canister increases, and a correction value according to the integrated value of the purge amount at that time. An air-fuel ratio learning control device comprising: means for reading a value kp from the map and multiplying it by the second term on the right side of the equation (3). 9. The air-fuel ratio learning control device according to claim 8, wherein when kl*kp exceeds the numerical value "1", kl=1 and kp=1. 10. In a fuel supply method for supplying an amount of fuel to an internal combustion engine in which the basic fuel amount determined according to the load condition of the internal combustion engine is corrected according to the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine, the method is equipped to an internal combustion engine. The amount of evaporated fuel stored in the canister that is purged into the internal combustion engine intake system is controlled by the opening amount of the control valve, and the amount of fuel supplied to the internal combustion engine is corrected by the opening amount of the control valve. A method for supplying fuel to an internal combustion engine, comprising supplying a determined amount of fuel to the internal combustion engine. 11. In an internal combustion engine in which evaporative fuel stored in a canister is purged into the internal combustion engine intake system while controlling the purge amount by controlling the opening amount of a control valve, the load condition of the internal combustion engine and the supply to the internal combustion engine A fuel supply method for an internal combustion engine, characterized in that the amount of fuel to be supplied to the internal combustion engine is calculated as a function of the air-fuel ratio of the air-fuel mixture and the purge amount, and the calculated amount of fuel is supplied to the internal combustion engine. . 12. Detection means for detecting the amount of vaporized fuel stored in the canister purged into the internal combustion engine intake system; operating state detection means for detecting the operating state of the internal combustion engine; and air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine. an air-fuel ratio detection means for detecting a value according to the operating condition, and a fuel that corrects the fuel amount determined according to the operating state according to the air-fuel ratio and the purge amount and supplies the corrected fuel amount to the internal combustion engine. 1. A fuel supply device for an internal combustion engine, comprising a supply means.