JPH0260852B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a learning control device for a feedback control system for controlling the air-fuel ratio, idle speed, etc. of an internal combustion engine.

<Prior Art> Conventional learning control devices for internal combustion engines include, for example, an air-fuel ratio learning control device disclosed in Japanese Patent Application Laid-open No. 59-203828, and an air-fuel ratio learning control device disclosed in Japanese Patent Application Laid-Open No. 59-211738. There is a disclosed idle speed learning control device.

Here, in an internal combustion engine having an electronically controlled fuel injection device, a learning control device for a base air-fuel ratio will be described as an example in the case where the air-fuel ratio is feedback-controlled to the stoichiometric air-fuel ratio, which is a control target value.

A fuel injection valve used in an electronically controlled fuel injection system is opened by a drive pulse signal applied in synchronization with engine rotation, and during the valve opening period, fuel at a predetermined pressure is injected. . Therefore, the fuel injection amount is controlled by the pulse width of the drive pulse signal, and if this pulse width is set as the control signal corresponding to the fuel injection amount by T _i , then in order to obtain the stoichiometric air-fuel ratio,
T _i is determined by the following equation.

T _i =T _P・COEF・α+T _S However, T _P is the basic pulse width corresponding to the basic fuel injection amount, and is called the basic fuel injection amount for convenience. T _p =
K・Q/N, where K is a constant, Q is the intake air flow rate, and N
is the engine speed. COEF is various correction coefficients such as water temperature correction. α is an air-fuel ratio feedback correction coefficient for air-fuel ratio feedback control (λ control) to be described later. T _s is a voltage correction amount, which is used to correct changes in the injection flow rate of the fuel injector due to changes in battery voltage.

Regarding λ control, an O ₂ sensor is installed in the exhaust system to detect the actual air-fuel ratio, and whether the air-fuel ratio is richer or thinner than the stoichiometric air-fuel ratio is controlled by the slice level. A correction coefficient α is determined and the stoichiometric air-fuel ratio is maintained by varying this α.

Here, the value of the air-fuel ratio feedback correction coefficient α is changed by proportional-integral (PI) control to ensure stable control.

In other words, the output voltage of the _O2 sensor is compared with the slice level voltage, and if it is higher or lower than the slice level, the air-fuel ratio is rich (lean) without suddenly enriching or thinning the air-fuel ratio. In this case, the air-fuel ratio is first lowered (raised) by P, and then gradually lowered (raised) by I minutes to make the air-fuel ratio leaner (richer).

However, under conditions where λ control is not performed,
The desired air-fuel ratio is obtained by clamping α and setting various correction coefficients COEF.

By the way, if the base air-fuel ratio under λ control conditions, that is, the air-fuel ratio when α = 1, could be set to the stoichiometric air-fuel ratio (λ = 1), feedback control would not be necessary. (for example, air flow meters, fuel injection valves, pressure regulators, control units), variations over time, non-linearity of the fuel injection valve pulse width-flow characteristics, changes in operating conditions and environment, etc. Since the air-fuel ratio deviates from λ=1, feedback control is performed.

However, if the base air-fuel ratio deviates from λ=1, it takes time to stabilize the step in the base air-fuel ratio to λ=1 through feedback control when the operating range changes significantly. For this purpose, the proportionality and integral constants (P/I) are increased, which causes overshoot and undershoot, resulting in poor controllability. In other words, if the base air-fuel ratio deviates from λ=1, the air-fuel ratio will be controlled within a range that deviates considerably from the stoichiometric air-fuel ratio.

As a result, the three-way catalyst has to be operated at a point where its conversion efficiency is poor, which increases costs due to an increase in the amount of precious metals in the catalyst, and further deteriorates the conversion efficiency as the catalyst deteriorates, forcing the catalyst to be replaced. Ru.

Therefore, by setting the base air-fuel ratio to λ = 1 through learning, the deviation from λ = 1 caused by the step in the base air-fuel ratio during transient times can be eliminated, and the P/I
An air-fuel ratio learning control device that improves controllability by making it possible to reduce It was filed as No.

This is because if the base air-fuel ratio deviates from the stoichiometric air-fuel ratio during air-fuel ratio feedback control, the air-fuel ratio feedback correction coefficient α increases to fill the gap. is detected, and the learning correction coefficient Kl based on the α
is determined and memorized, and when the same operating condition returns, the base air-fuel ratio is corrected using the stored learning correction coefficient Kl so as to have good responsiveness to the stoichiometric air-fuel ratio. Here, the learning correction coefficient Kl is stored for each region of a predetermined range obtained by dividing the RAM map into a grid according to appropriate parameters of the engine operating state such as engine speed and load.

Specifically, a map of the learning correction coefficient Kl corresponding to engine operating conditions such as engine speed and load is provided in RAM, and when calculating the fuel injection amount T _i , the basic fuel injection amount T is calculated as shown in the following formula. Correct _P with Kl.

T _i =T _P・COEF・Kl・α+T _S Then, learn Kl by proceeding with the following steps.

(i) In a steady state, detect the region of the engine operating state at that time, and detect the deviation Δα from the reference value of α as an average value. The standard value is λ=
The value corresponding to 1 is generally set to 1.0.

(ii) Search for Kl that has been learned up to now corresponding to the region of the engine operating state.

(iii) Find the value of Kl+Δα/M from Kl and Δα, and update the memory with the result (learning value) as new Kl _(oew) . M is a constant.

In addition, the idle speed learning control device is provided with an idle control valve in an auxiliary air passage that bypasses the throttle valve, and controls the idle speed by adjusting the opening degree of this idle control valve.
When performing feedback correction on the basic opening degree of the idle control valve corresponding to the target idle speed for each engine cooling water temperature by comparing the target idle speed and the actual idle speed, the engine operating state parameter cooling A map of the learning correction amount according to the water temperature is provided, and the learning correction amount is corrected by learning the deviation of the feedback correction amount from the reference value, and the basic opening is corrected with this learning correction amount.
This is intended to stabilize control.

<Problems to be Solved by the Invention> By the way, in this learning control method, writing and reference to the map that stores the learning correction amount is performed without interpolation calculation (interpolation slows down the learning progress speed). .

However, in this case, in the driving state near the boundary between the driving area where the learning progress is high (hereinafter referred to as the learning area) and the area where the learning progress is low (hereinafter this area is referred to as the unlearning area), Since the difference in learning correction amount between the two regions is large, the control amount fluctuates, resulting in a problem that stable control performance cannot be obtained.

As described above, it is an object of the present invention to prevent fluctuations in the control state near the boundaries of each area where learning correction amounts are stored.

<Means for Solving the Problems> For this reason, in the present invention, when searching for a learning correction amount, the determination of the searched driving condition is made to have hysteresis with respect to the direction in which the driving condition changes.

Specifically, the learning control device according to the present invention has a first
As shown in the figure, the following means (A) to (I) are provided.

(A) Basic control amount setting means for setting basic control amounts corresponding to control target values such as air-fuel ratio and idle speed; (B) A grid axis that divides the engine operating state into a plurality of regions according to the parameters; (C) A rewritable storage means that stores learning correction amounts for correcting the basic control amount for each area surrounded by these grid axes. Learning correction amount search means (D) for searching the learning correction amount Compares the control target value and the actual value and increases or decreases the feedback correction amount by a predetermined amount to correct the basic control amount so that the actual value approaches the control target value. Feedback correction amount setting means (E) that sets the basic control amount set by the basic control amount setting means, the learning correction amount searched by the learning correction amount search means, and the feedback correction amount set by the feedback correction amount setting means Controlled amount calculation means (F) that calculates a controlled amount from the correction amount Control means (G) that operates according to the control amount and controls the air-fuel ratio, idle rotation speed, etc. A learning correction amount correction means (H) that learns the average value of the deviation and corrects and rewrites the learning correction amount corresponding to the region of the engine operating state during that time in the direction of decreasing this. Operating state change direction determining means (I) for determining the operating region in which the learning correction amount retrieved from the storage means by the learning correction amount retrieving means is determined depending on the direction in which the parameters of the engine operating state change. Operating region determination means (operation) that is performed with hysteresis so that the grid axes that divide the The learning correction amount retrieval means CC searches the storage means B for the learning correction amount in the corresponding area based on the actual engine operating state, and the feedback correction amount setting means D , the control target value and the actual value are compared, and the feedback correction amount is increased or decreased by a predetermined amount based on, for example, proportional-integral control so as to bring the actual value closer to the control target value. Then, the control amount calculation means E is
A control amount is calculated by correcting the basic control amount with a learning correction amount and further correcting it with a feedback correction amount, and the control means F operates according to this control amount to control, for example, the fuel injection amount or the auxiliary air amount. hand,
Controls the air-fuel ratio, idle speed, etc.

Here, the storage means B stores the engine operating state in a plurality of areas partitioned by one or two parameters in a rewritable state with learning correction amounts. When searching for the learning correction amount, first, the operating state change direction determining means H determines the direction in which the parameter of the engine operating state changes, and then the operating region determining means I determines when the parameter changes in one direction. When the learning correction amount is changed in the opposite direction, the position of the grid axis that partitions the driving region in which the learning correction amount is stored is determined to determine the driving region in which the search is performed, and the learning correction amount is searched based on the determination result. I do.

This makes it possible to prevent hunting of the control amount due to differences in learning correction amounts retrieved from mutually adjacent operating regions when the operating state is near the grid axis.

<Example> An example in which the learning control device of the present invention is applied to an air-fuel ratio feedback control system of an internal combustion engine having an electronically controlled fuel injection device will be described below.

In FIG. 2, air is taken into the engine 1 through an air cleaner 2, an intake duct 3, a throttle chamber 4, and an intake manifold 5. As shown in FIG.

The intake duct 3 is provided with an air flow meter 6 as means for detecting the intake air flow rate Q, and outputs a voltage signal corresponding to the intake air flow rate Q signal. The throttle chamber 4 includes primary throttle valves 7 and 2 that are linked to an accelerator pedal (not shown).
A next throttle valve 8 is provided to control the intake air flow rate Q. Further, an auxiliary air passage 9 is provided that bypasses these throttle valves 7 and 8, and an idle control valve 10 is interposed in this auxiliary air passage 9. A fuel injection valve 11 is provided in the intake manifold 5 or the intake port of the engine 1 . The fuel injection valve 11 is an electromagnetic fuel injection valve that opens when the solenoid is energized and opens when the energization is stopped. Fuel that is pressure-fed and controlled to a predetermined pressure by a pressure regulator is injected and supplied to the engine 1. Therefore, the fuel injection valve 11 is a control means for controlling the fuel injection amount through its operation and controlling the air-fuel ratio to the optimum air-fuel ratio (stoichiometric air-fuel ratio) which is the control target value.

Exhaust gas is exhausted from the engine 1 via an exhaust manifold 12, an exhaust duct 13, a three-way catalyst 14, and a muffler 15.

The exhaust manifold 12 is provided with an O ₂ sensor 16 . This O ₂ sensor 16 outputs a voltage signal according to the ratio of the oxygen concentration in the atmosphere (constant) and the oxygen concentration in the exhaust gas, and is known to cause a sudden change in electromotive force when the air-fuel mixture is combusted at the stoichiometric air-fuel ratio. It is a sensor of Therefore, the O ₂ sensor 16 is a means for detecting the air-fuel ratio (rich/lean) of the air-fuel mixture. Three-way catalyst 14
is a catalyst device that efficiently oxidizes or reduces CO, HC, and NOx in exhaust gas near the stoichiometric air-fuel ratio of the air-fuel mixture and converts them into other harmless substances.

In addition, a crank angle sensor 17 is provided. The crank angle sensor 17 is connected to the crank pulley 1
8 is provided with a signal disk plate 19,
Teeth provided on the outer circumference of the plate 19 output a reference signal every 120 degrees and a position signal every 1 degree, for example. Here, the engine rotation speed N can be calculated by measuring the period of the reference signal. Therefore, the crank angle sensor 17 is a means for detecting not only the crank angle but also the engine speed N.

The air flow meter 6 and the crank angle sensor 1
7 and the O ₂ sensor 16 are both input to a control unit 30. Furthermore, the control unit 30 is equipped with a battery 20 as its operating power source and for detecting the reduced voltage.
voltage is applied via the engine key switch 21 and directly. Furthermore, the control unit 30 includes a water temperature sensor 22 that detects the engine cooling water temperature as necessary, a throttle sensor 23 including an idle switch that detects the throttle opening of the primary throttle valve 7, and a vehicle speed sensor that detects the vehicle speed. 24, a signal from a neutral switch 25 or the like that detects the neutral position of the transmission is input. The control unit 30 performs arithmetic processing based on various input signals, outputs a drive pulse signal with an optimal pulse width to the fuel injection valve 11, and obtains the fuel injection amount for obtaining the optimal air-fuel ratio.

As shown in FIG. 3, the control unit 30 includes a CPU 31, a P-ROM 32, a CMOS-
It has a RAM 33 and an address decoder 34. Here, the RAM 33 is a rewritable storage means for learning control, and as the operating power source of this RAM 33, the battery 20 is used without going through the engine key switch 21 in order to retain the memory contents even after the engine key switch 21 is turned off. Connect via a suitable regulated power supply.

Among the input signals to the CPU 31, each voltage signal from the air flow meter 6, O ₂ sensor 16, battery 20, water temperature sensor 22, and throttle sensor 23 is an analog signal. The signal is input via a converter 36. The A/D converter 36 is connected to the address decoder 34 by the CPU 31.
and is controlled via the A/D conversion timing controller 37. The reference signal and position signal from the crank angle sensor 17 are inputted via a one-shot multi-circuit 38. The signal from the idle switch built in the throttle sensor 23 and the neutral switch 25
The signal from the digital input interface 3
9, and a signal from the vehicle speed sensor 24 is input via a waveform shaping circuit 40.

An output signal from the CPU 31 (a driving pulse signal for the fuel injection valve 11) is sent to the fuel injection valve 11 via a current waveform control circuit 41.

Here, the CPU 31 performs input/output operations, arithmetic processing, etc. according to a program (stored in the ROM 32) based on the flowchart (fuel injection amount calculation routine and learning subroutine) shown in FIG. 4, and calculates the fuel injection amount. control.

Furthermore, basic control amount (basic fuel injection amount) setting means,
As a learning correction amount (coefficient) search means, a feedback correction amount (coefficient) setting means, a control amount (fuel injection amount) calculation means, a learning correction amount (coefficient) modification means, a driving state change direction determining means, and an operating region determining means. The functions are achieved by the program.

Next, the operation will be explained with reference to the flowchart shown in FIG.

In FIG. 4, in step 1 (S1 in the figure), the basic fuel is calculated from the intake air flow rate Q obtained from the signal from the air flow meter 6 and the engine speed N obtained from the signal from the crank angle sensor 17. Calculate the injection amount T _P (=K・Q/N). This part corresponds to the basic control amount setting means.

In step 2, various correction coefficients COEF are set.

In step 3, it is determined whether the engine speed N is increasing.

If it is determined that the engine speed is increasing, the process proceeds to step ₄ , and as shown in FIG. After setting the subscript number n of ~ _N8 to 1, proceed to step 5,
The actual rotation speed N is set to a predetermined value ΔN to the rotation speed N _o of the grating axis.
(for example, 50 rpm) is compared with the value N _o +ΔN.

If N≧N _o +ΔN, proceed to step 6 and increase the value of n by 1, then proceed to step 5 again and add ΔN to the rotational speed N _o corresponding to the value of n that has been increased by 1. This value is compared with the actual rotational speed N, and this operation is repeated until N<N _o +ΔN.

When N<N _o +ΔN, the process proceeds to S7, and in the operating range in which the learning correction coefficient Kl is searched, the region of the rotational speed N is determined to satisfy N _{o -} ≦N<N _o .

If it is determined in step 3 that the actual rotational speed N is not increasing, that is, it is steady or decelerating, then proceed to step 8 and set n = 1 as in step 4, then proceed to S9, and this time set the actual rotational speed N Rotation speed N _o of axis n
Compare with.

From then on, go through step 10 until N<N _o .
After increasing by 1, return to step 9 and set N<N _o
When this occurs, in step 11, the rotational speed range in which Kl is searched is determined as N _{o -} ≦N<N _o .

Next, the basic fuel injection amount, which is another parameter that demarcates the operating region in which the learning correction coefficient Kl is memorized.
Regarding T _R , the region in which Kl is searched is determined in the same manner as in the case of rotation speed N.

That is, in step 12, it is determined whether or not the basic fuel injection amount T _P is increasing. If it is increasing, n = 1 in step 13, and in step 14, the actual T _P is determined.
is compared with the sum of T _Po and the predetermined amount ΔT _P , and T _P <
In step 15, n is incremented by 1 and the process returns to step 14 until T _Po +ΔT _P. When T _P < T _Po +ΔT _P , in step 16, the area of T _P for Kl search is set.
It is determined that T _Po-1 ≦T _P <T _Po .

Also, if T _P is not increasing, step 17
Then go through steps 18 and 19 and increase n by 1.
T _P and T _Po are compared, and when T _P <T _Po , the search area is determined to be T _Po-1 ≦T _P <T _Po .

Next, the process proceeds to _step 21, where N o-1 , N _{o -1} ,
The learning correction amount Kl stored in the operating region surrounded by the lattice axes of _No , T _Po-1 , and T _Po is searched.

Here, Step 3 and Step 12 correspond to the function of the driving state change direction determining means, and Steps 4 to 12 correspond to the function of the driving state change direction determination means.
11 and steps 13 to 20 correspond to the function of the driving range determining means, and step 21 corresponds to the learning correction amount searching means.

In step 22, a voltage correction amount T _S is set based on the voltage value of the battery 20.

In step 23, it is determined whether the λ control condition is met.

Here, if the condition is not λ control conditions, such as high rotation, high load region, etc., the air-fuel ratio feedback correction coefficient α is clamped to the previous value (or reference value α ₁ ), and the process goes from step 23 to step 28, which will be described later. move on.

For λ control conditions, steps 24 to 26
The output voltage of the O ₂ sensor 16 is compared with the slice level voltage to determine whether the air-fuel ratio is rich or lean, and the air-fuel ratio feedback correction coefficient α is set by integral control or proportional-integral control. This part corresponds to the feedback correction amount setting means. Specifically, in the case of integral control, when it is determined that the air-fuel ratio is rich as a result of the comparison in step 24, step 25 is executed.
In step 26, the air-fuel ratio feedback correction coefficient α is decreased by a predetermined integral (I) from the previous value, and conversely, when it is determined that the air-fuel ratio is lean, the air-fuel ratio feedback correction coefficient α is decreased from the previous value in step 26. given integral
Increase by (I) minutes. In the case of proportional-integral control, in addition to this, when rich←→lean is reversed, a large predetermined proportional amount (P) is increased or decreased in the same direction as the integral (I) (see FIG. 6).

In step 27, the learning correction coefficient Kl retrieved in step 21 and the air-fuel ratio feedback correction coefficient α are calculated.
A new learning correction coefficient Kl _(oew) is set from the average value of the deviation Δα from the reference value α ₁ according to the following equation, and the data of the learning correction coefficient in the same area is corrected and rewritten.

This step 27 corresponds to learning correction amount modification means.

Kl _(oew) ←Kl+/M (M is a constant, M>1) Thereafter, in step 28, the fuel injection amount T _i is calculated according to the following equation. This part corresponds to the control amount calculation means.

T _i = T _p・ COEF ・ Kl ・ α + T _S When the fuel injection amount T _i is calculated, a drive pulse signal with a pulse width of T _i is output at a predetermined timing in synchronization with the engine rotation, and the current waveform Control circuit 4
1 to the fuel injection valve 11, and fuel injection is performed.

In this way, engine speed N and basic injection amount
Even if T _P fluctuates in the vicinity of the lattice axes N _{o and} T _Po , we created hysteresis in the size of the lattice axes in the region where the learning correction coefficient Kl is searched according to the direction in which these change, so that the adjacent learning regions It is possible to prevent hunting of the air-fuel ratio due to the difference in Kl between the current range and the unlearned range, and stable controllability can be obtained.

Although this embodiment has been described as being applied to air-fuel ratio control, it goes without saying that it can also be applied to idle rotation speed control, ignition timing control, etc.

<Effects of the Invention> As explained above, according to the present invention, when searching for a learning correction amount, the lattice axes of the operating state parameters that partition the operating region to be searched are made to differ depending on the direction in which the parameters change. Since the configuration has hysteresis, it is possible to prevent hunting of the control amount when the operating state is near the grid axis, and stable controllability can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration and functions of the present invention, Fig. 2 is a block diagram showing an embodiment of the invention, Fig. 3 is a block circuit diagram of the control unit in Fig. 2, and Fig. 4 is a block diagram showing the configuration and functions of the present invention. A flowchart showing the control contents, Figure 5 is a schematic diagram of the learning correction amount map, and Figure 6 is a schematic diagram of the learning correction amount map.
The figure is a time chart showing the relationship between the O ₂ sensor output and the feedback correction amount. DESCRIPTION OF SYMBOLS 1... Engine, 6... Air flow meter, 10... Idle control valve, 11... Fuel injection valve, 16... _O2 sensor, 17... Crank angle sensor, 30... Control unit.

Claims (1)

[Claims] 1. Basic control amount setting means for setting basic control amounts corresponding to control target values such as air-fuel ratio and idle rotation speed, lattice axes that divide the engine operating state into a plurality of regions according to the parameters, and these lattices. a rewritable storage means that stores a learning correction amount for correcting the basic control amount for each region surrounded by the axis; and a learning correction amount for the corresponding region from the storage means based on the actual engine operating state. A learning correction amount search means to search, and a feedback correction amount to increase or decrease by a predetermined amount a feedback correction amount for comparing the control target value and the actual value and correcting the basic control amount so that the actual value approaches the control target value. A control amount is determined from the correction amount setting means, the basic control amount set by the basic control amount setting means, the learning correction amount searched by the learning correction amount search means, and the feedback correction amount set by the feedback correction amount setting means. a control amount calculation means for calculating the control amount; a control means for operating according to the control amount to control the air-fuel ratio, the idle rotation speed, etc.; and learning the average value of the deviation of the feedback correction amount from the reference value; learning correction amount correcting means for correcting and rewriting the learning correction amount corresponding to the area of the engine operating state during that time in a direction to decrease the learning correction amount; and operating state change direction determining means for determining the direction in which the parameter of the engine operating state changes. , hysteresis is applied to determine the operating region in which the learning correction amount retrieved from the storage means by the learning correction amount retrieval means is set such that the grid axes dividing the operating region differ depending on the direction in which the parameters of the engine operating state change. A learning control device for an internal combustion engine, comprising: operating range determining means.