JPH076440B2 - Internal combustion engine control method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a control method for an internal combustion engine (hereinafter referred to as an engine), and particularly to an intake air amount sensor (hereinafter referred to as an air flow sensor) and a fuel injector (hereinafter referred to as an air flow sensor). Hereinafter, it will be referred to as an injector).

[Conventional technology]

Generally, an air-fuel ratio feedback system is used for fuel injection control. This control method calculates the basic fuel injection amount from the intake air amount detected by the air flow sensor and the engine speed, and then calculates the basic fuel injection amount to the basic fuel injection amount.
The normal fuel injection amount is calculated by multiplying the O ₂ hood back correction factor and other correction factors that return the O ₂ concentration as the feed back amount, and adding this value to the battery voltage correction amount to calculate the normal fuel injection amount. This is to control the valve opening time of the injector.

That is, the pulse width corresponding to the normal fuel injection amount (hereinafter,
It is called a normal injection pulse width. ) Ti is calculated by the following formula.

Ti = T _P × K ₂ × α × K _L + T _S (1) T _P = K ₁ × Q _A / N (2) where T _P is the basic injection pulse corresponding to the basic fuel injection amount. Width, K ₁ is a constant, Q _A is the intake air amount, N is the engine speed, K ₂ is a correction coefficient based on the engine cooling water temperature, etc., α is a correction coefficient based on the air-fuel ratio feedback (O ₂ feedback), and K _L
Is the learning value, and T _S is the reactive pulse width of the injector (battery voltage correction amount). The learning control learns the deviation from the central value (that is, the average value) of the maximum value and the minimum value of α due to the air-fuel ratio feedback and obtains the learning value K _L. As a result, a good air-fuel ratio can always be obtained.

On the other hand, it is usual that the ignition timing control is also performed at the same time in order to maximize the output of the engine. The ignition timing control is determined by interpolation calculation from the control map stored in the memory of the control processor based on the basic injection pulse width T _P and the engine speed N, and the ignition timing is controlled to match the piston position. .

Note that, as a device related to the air-fuel ratio learning control device, there is, for example, JP-A-58-172242.

[Problems to be solved by the invention]

In the above-mentioned related art, since the influence of the characteristic deviation of the air flow sensor (see FIG. 4 described later) on the ignition timing control is not taken into consideration, the deviation of the ignition timing occurs when the characteristic of the air flow sensor deviates. There was a problem. That is, (2) because it does not reflect well any learning results the basic injection pulse width T _P As seen from the equation, also varies the value of the deviation in the test of connexion basic injection pulse width T _P characteristic of the air flow sensor As a result, the incorrect ignition timing is retrieved from the map. The cause of the characteristic deviation of the air flow sensor is, for example,
There are variations during manufacturing and deterioration over time.

On the other hand, the characteristic shift due to aging does not only occur in sensors but also in actuators. A particular problem in controlling the air-fuel ratio of the engine is that the injector nozzle diameter of the injector increases over time.
This is because the change in the characteristics of the injector is directly related to the fuel injection amount and therefore has a great influence on the fluctuation of the air-fuel ratio. The change in characteristics of the injector will be described later with reference to FIG.

It is an object of the present invention to provide a control method capable of compensating for the deviation of the characteristics of the air flow sensor and the injector and drawing out the maximum capacity of the engine.

[Means for solving problems]

The above-mentioned purpose, the deviation from the target value of the actual air-fuel ratio, the correction coefficient related to the air flow sensor and the injector is learned by allocating at a predetermined ratio, and the basic injection amount related to the ignition timing is corrected, And it is achieved by correcting the normal injection amount related to the injector.

That is, according to the present invention, the basic fuel injection amount (T _P ) is calculated based on the intake air amount (Q _A ) and the rotational speed (N) of the internal combustion engine, and the ignition timing is calculated based on the rotational speed and the basic fuel injection amount. Control of the internal combustion engine that controls the fuel injection amount (Ti) in order to adjust the air-fuel ratio to the target value based on the oxygen concentration in the exhaust gas and the basic fuel injection amount (α, K _L ). In the method, the deviation (αmean−1.0) from the actual target value of the air-fuel ratio is a learning value (K _L1 ) of the basic fuel injection amount at a rate (β) according to the characteristic changes of the intake air amount detection means and the injection device. ) And the learned value (K _L2 ) of the normal fuel injection amount, respectively, to control the ignition timing and the normal fuel injection amount.

〔Example〕

 Next, an embodiment according to the present invention will be described with reference to the drawings.

FIG. 2 shows an outline of an engine control system to which the present invention is applied. The air flow sensor 2 detects the air amount Q _A drawn into the engine 1, the control circuit 3 determines the normal fuel injection amount Ti, and the injector 4 is driven. The air-fuel ratio of the burned gas is detected by the O ₂ sensor 5 provided in the exhaust pipe, and the control circuit 3 responds to this signal by the normal fuel injection amount.
Correct the Ti feed back to obtain the optimum air-fuel ratio. The normal injection pulse width Ti at this time is obtained by the following equations including the equations (1) and (2) shown above.

Where K ₁ is a constant, Q _A is the intake air amount, N is the engine speed,
K ₂ is the correction coefficient based on the engine cooling water temperature, α is the air-fuel ratio correction coefficient (O ₂ feed back correction coefficient), and T _S is the battery voltage correction. The air-fuel ratio feedback check by the O ₂ sensor is performed by the air-fuel ratio correction coefficient α of the equation (1).

The air-fuel ratio correction coefficient α has an initial value of 1.0 (that is, the same as the target value), and the output of the O ₂ sensor 5 causes the movement shown in FIG. As the air-fuel ratio correction coefficient actually used, the maximum value αmax of α and the average value αmean of the minimum value αmin are used.
Is used. Based on the average value αmean of the air-fuel ratio correction coefficient, two learning values K _L1 and K _L2 are obtained by the following formula.

δ ₁ = (αmean−1.0) × β …… (4) δ ₂ = (αmean−1.0) −δ ₁ …… (5) K _L1 = K _L1 (until the previous time) + δ ₁ × γ ₁ …… (6) K _L2 = K _L2 (until last time) + δ ₂ × γ ₂ (7) Here, equation (4) is 1.0 of the air-fuel ratio correction coefficient average value αmean.
The distribution ratio β of the deviation from is defined as the first distribution coefficient δ ₁ .
The second distribution coefficient δ ₂ is 1. of the air-fuel ratio correction coefficient average value αmean.
The remainder is obtained by subtracting the first distribution coefficient δ ₁ from the deviation from 0. The first learning value K _L1 relating to the injector is multiplied by the first distribution coefficient δ ₁ by a predetermined weighting coefficient γ ₁ and added to the first learning value K _L1 up to the previous time. On the other hand, the second learning value K _L2 related to the air flow sensor is also added to the second learning value K _L2 up to the previous time by multiplying the second distribution coefficient δ ₂ by a predetermined weighting coefficient γ ₂ . The learning values K _L1 and K _L2 are stored in a map as shown in FIG.

Next, the tendency of characteristic changes of the injector 4 and the air flow sensor 2 will be described. In the case of Injector 4, the third
As shown in the figure, the gradient indicating the relationship between the normal injection pulse width T ₁ and the injected fuel changes from a to b. on the other hand,
In the case of the air flow sensor 2, as shown in FIG. 4, the relationship between the intake air amount and the output voltage of the sensor 2 tends to shift by a certain amount. From this, in the low load region where the amount of intake air is small, the influence of the characteristic change of the air flow sensor 2 is large, and conversely, as the load increases, the influence of the air flow sensor 2 becomes smaller. Paying attention to this point, the distribution ratio β described above is set to the basic pulse width T corresponding to the load of the engine 1.
By changing it according to _P (equation (2)) as shown in FIG. 6, the deviation of αmean from 1.0 can be corrected for the changes in the characteristics of the air flow meter and the injector.

Using the first learning value K _L1 and the second learning value K _L2 , the normal injection pulse width Ti is obtained by the following equation.

Ti = Tp ₁ × K ₂ × α × K _L1 ＋ T _S・ ・ ・ (8) T _P1 ＝ K ₁ × Q _A / N × K _L2 …… (9) As can be seen from the above formula (9), a new basic injection The pulse width T _P1 includes the second learning value K _L2 , and accordingly, the pulse width T _P1 is sequentially corrected to an appropriate value according to the characteristic change of the air flow sensor 2 (FIG. 4). You can search correctly.

Also, as can be seen from equation (8), the normal injection pulse width Ti
Is based on the basic injection pulse width T _P1 of the correct value described above, and includes the first learning value K _L1 corresponding to the characteristic change of the injector 4 (FIG. 3).
It can be obtained with an accurate value according to the current situation of.

There are various types of air flow sensors as the intake air amount detecting means, such as a method of detecting from the intake pipe internal pressure and engine speed, a method of detecting from the throttle opening and engine speed, and the like. Can be applied to any of these methods, and an equivalent effect can be obtained.

Next, the above control flow is summarized and shown in FIG. 1, and will be described in order of each step. The flow of FIG. 1 is roughly divided into steps 101 to 103 for preprocessing, steps 104 to 109 for learning processing according to the present invention, step 110 for calculating a new basic injection pulse width T _P1 , and step 111 for The new normal injection pulse width Ti calculation flow, step 112, can be considered as a search flow for the ignition timing map.

First, the intake air amount Q _A is calculated from the output signals from the air flow sensor 2 and the engine speed sensor (not shown), and the engine speed N is obtained [Step 10
1].

Next, this intake air amount Q _A , engine speed N and constant
Based on K ₁ , the basic injection pulse width T _P is calculated by the above equation (2) [step 102].

Next, the output signal of the O ₂ sensor 5 is taken in [Step 10
3], it is determined in step 104 whether or not the O ₂ feedback back control is being performed [step 104]. As a result, if the feedback is not in progress (NO), there is no need to learn, so the control is skipped to step 110, and normal injection control and ignition timing control are performed as is [steps 110 to 112]. On the other hand, if the feedback is being performed (YES), it is necessary to reflect the feedback amount on the control amount for learning, so the process proceeds to the next step 105. At step 105, it is judged if the output signal of the O ₂ sensor 5 is inverted (see FIG. 5). This judgment is a premise for the calculation of the next step 106. As a result of the judgment, if it is not reversed (NO), learning cannot be performed, so the control is jumped to step 110, and the subsequent normal injection control and ignition timing control are performed [steps 110 to 11].
2]. On the other hand, if reversal is confirmed (YES), the next step
Proceed to 106.

At step 106, an average value αmean of the maximum value αmax and the minimum value αmin of the O ₂ feedback amount is calculated.

At step 107, the learning value distribution ratio β is obtained from the relationship shown in FIG. 6 in consideration of the characteristic change of the air flow sensor 2 in accordance with the basic injection pulse width T _P obtained at step 102. Note that T _P is a value corresponding to the load of the engine 1.

In step 108, the first distribution coefficient δ ₁ is calculated by the expression (4) by adding the distribution ratio β previously obtained, and then the first distribution coefficient δ ₁ is added by the expression (5) by the expression (5). The distribution coefficient δ ₂ is calculated. By this calculation, the deviation of the actual air-fuel ratio from the target value (that is, αmean−1.0) is distributed at a rate according to the intake air amount Q _A and the state of the injector.

In step 108, the obtained first and second distribution coefficients δ ₁ , δ
₂ , each weighting coefficient γ ₁ , γ ₂ is the first learning value up to the previous time
This is reflected in K _L1 and the second learning value K _L2 (see equations (6) and (7)), and new learning values are created.

In step 110, the second learned value K _L2 for the air flow sensor 2 is reflected in the basic injection pulse width to create a new basic injection pulse width T _P1 .

Step 111 is based on the new basic injection pulse width T _P1 and the first learning value K for the injector 4 is added.
_A new normal injection pulse width Ti is created by reflecting _L1 .
Thereafter, the injector 4 is controlled by the normal injection pulse width Ti until the next learning.

In step 112, the ignition timing map is searched by the new basic injection pulse width T _P1 and the engine speed N, and the searched ignition timing is controlled to the correct ignition timing.

〔The invention's effect〕

According to the present invention, since the characteristic changes of the injector and the air amount detecting means can be learned separately, there is an effect that both the air-fuel ratio and the ignition timing can be correctly controlled.

[Brief description of drawings]

FIG. 1 is a flow chart showing an embodiment according to the present invention, FIG. 2 is a block diagram showing an outline of an engine control device, and FIG.
FIG. 4 is an explanatory view showing the characteristics of the injector, FIG. 4 is an explanatory view showing the characteristics of the air flow sensor, FIG. 5 is an explanatory view showing the air-fuel ratio feedback back amount, and FIG. 6 is a distribution ratio according to the basic injection pulse. Explanatory drawing, FIG. 7 is explanatory drawing which shows the example of a map of a 1st and 2nd learning value. 1 ... Engine, 2 ... Air flow sensor, 3 ... Control circuit, 4 ... Injector, 5 ... O ₂ sensor, 104-109
...... Learning step, 110 …… Basic injection pulse width calculation step, 111 …… Normal injection pulse width calculation step, 112 ……
Ignition map search step.

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Claims (1)

[Claims] 1. A basic fuel injection amount is calculated based on an intake air amount and a rotational speed of an internal combustion engine, an ignition timing is controlled based on the rotational speed and a basic fuel injection amount, and the oxygen concentration in exhaust gas and the In a control method for an internal combustion engine, in which feedback control is performed on the normal fuel injection amount to adjust the air-fuel ratio to a target value based on the basic fuel injection amount, a deviation of the actual air-fuel ratio from the target value is detected by the intake air amount detection means and In the internal combustion engine, the ignition timing and the normal fuel injection amount are controlled by distributing to the learned value of the basic fuel injection amount and the learned value of the normal fuel injection amount at a rate according to the characteristic change of the injector. Control method.