JP3201646B2 - Air-fuel ratio control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control device for performing air-fuel ratio learning control of an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, as a method of learning a correction coefficient of an air-fuel ratio, there is a method of transplanting a learning correction coefficient in a learned region to an adjacent region in accordance with an equal intake air amount line.

The contents will be described in detail with reference to FIGS. 9 and 10. FIG. 9 shows a learning area and a learning result storage area. The learning area and the storage area of the learning result are configured by a map, and correspond one-to-one. Therefore, for example, the learning area No. When learning of No. 9 is performed, the result is No. 9 in the learning result storage area. 9 is stored. When the correction coefficient learning of the air-fuel ratio progresses to some extent, a region where the learning has progressed and a region where the learning has not progressed appear. Therefore, as shown in FIG. When the learning of No. 9 has progressed very much, the correction coefficient here is set to No. No. 9 as a starting point in the equal intake air amount direction, that is, No. 9 in which learning has not progressed. 16 and N
o. 2 is stored. In the figure, the area inside the broken line is a feedback area (learning area).

[0004]

However, in such a conventional technique, the injection amount of the injector or the intake air amount measured by the air flow meter varies in accordance with the fluctuation of the rotation speed. Since the correction coefficients in the intake air amount direction are treated as the same, accurate air-fuel ratio control cannot be performed. Further, the learning region No. of the highest load and high rotation in the feedback region. Even if 37 is used, it is not possible to obtain a correction coefficient for the non-feedback region with a higher load and higher rotation. As described above, in the related art, there is a problem that precise air-fuel ratio control cannot be performed over the entire operation range.

[0005] The present invention has been made in view of such problems in the prior art.
An object of the present invention is to provide an air-fuel ratio control device capable of performing accurate air-fuel ratio control.

[0006]

An air-fuel ratio control device for achieving the above object comprises a basic fuel calculating means for calculating a basic fuel injection amount from a measured intake air flow rate and an engine speed, and an engine speed and an engine speed. Feedback region correction amount calculation means for obtaining a correction amount of air-fuel ratio control in a feedback region from a deviation between a target air-fuel ratio and a measured air-fuel ratio for each basic fuel injection amount; and for each engine speed and basic fuel injection amount. Storage means for storing the correction amount in the feedback area stored in the storage means, and correcting the correction amount in the equal intake air amount area in the feedback area with respect to a change in the basic fuel injection amount. A change tendency is obtained, and a change inclination of the correction amount with respect to a change in the intake air amount in the equal fuel injection amount region within the feedback region. A change trend calculating means for determining a from the correction amount of the variation trend in the like intake air amount region in the feedback region, the variation with respect to a change in the basic fuel injection amount correction amount in an equal amount of intake air regions in the non-feedback region Estimating the tendency and estimating the fluctuation tendency of the correction amount with respect to the change of the intake air amount in the equal fuel injection amount region in the non-feedback region from the fluctuation tendency of the correction amount in the equal fuel injection amount region in the feedback region. The fluctuation tendency estimating means, the fluctuation tendency of the correction amount in the equal intake air amount region in the non-feedback region, and the fluctuation tendency of the correction amount in the equal fuel injection amount region in the non-feedback region. calculated correction amount for each engine speed and the basic fuel injection amount in the feedback area , A non-feedback region correction amount setting means for setting the correction amount in a predetermined region of the storage means, the non-feedback region complement
The supplement set in the storage means by the positive quantity setting means.
Fuel injection amount setting means for correcting the basic fuel injection amount using at least a positive amount .

[0007]

The fuel injection amount from the fuel injection valve and the air flow rate detected by the air flow meter vary. Therefore,
In the feedback area in the storage means, an appropriate correction amount for correcting this variation is registered by learning. Therefore, from the fluctuation tendency of the correction amount in the feedback region, the fluctuation tendency of the correction amount in the non-feedback region is obtained, and the correction amount in the non-feedback region is obtained from this fluctuation trend, and this is used in calculating the fuel injection amount. Even within the feedback area, it responds to variations in the fuel injection amount from the fuel injection valve and the air flow rate detected by the air flow meter,
Accurate air-fuel ratio control is realized in all operation ranges.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an air-fuel ratio control apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG.
Shows an engine system of the present embodiment.
In the figure, air to be taken in by an engine 7 is taken in from an inlet 2 of an air cleaner 1 and accommodates a hot-wire type air flow meter 3 for detecting an intake flow rate, a duct 4, and a throttle valve 5a for controlling the intake flow rate. It passes through the throttle valve body 5 and enters the collector 6. Then, the intake air is distributed to each intake pipe 8 connected to each cylinder of the engine 7 and guided into the cylinder.

On the other hand, fuel such as gasoline is sucked and pressurized from a fuel tank 9 by a fuel pump 10, passes through a fuel damper 11, a fuel filter 12, and is provided with a fuel injection valve (for each cylinder). From the injector 13, the fuel is injected into each suction pipe 8. Fuel pressure regulator 14
Is provided in these fuel piping systems and adjusts them to a constant pressure. A signal representing the intake flow rate is output from the air flow meter 3 and input to the control unit 30.

Further, the throttle valve body 5 has a throttle valve 5a.
A throttle sensor 18 for detecting the opening of the motor is mounted, and its output is also input to the control unit 30. The distributor 16 has a built-in crank angle sensor 16a, and a reference angle signal REF representing the rotational position of the crankshaft and a rotational speed (rotational speed).
An angle signal POS for detection is output, and these signals are also input to the control unit 30. An O ₂ sensor 20 is provided in the exhaust pipe, and detects whether the actual air-fuel ratio is richer or thinner than the stoichiometric air-fuel ratio. This output signal is also input to the control unit 30.

As shown in FIG. 3, the control unit 30 includes an MPU 31 for executing various operations, a ROM 32 for storing programs for various operations, a RAM 33 for storing various data and the like, O LSI
34. The I / O LSI 34 of the control unit 30 includes an idling switch 41, a starter switch 42, a water temperature gauge 43, a battery voltmeter, in addition to the above-described hot-wire air flow meter 3, crank angle sensor 16a, O ₂ sensor 20, and throttle sensor 18. 4
4 are also connected. Output signals from these sensors 3, 16a,... Are A / D converted in the I / O LSI 34, and the MPU 3
1 executes predetermined arithmetic processing according to a program stored in the ROM 32. The various control signals calculated as the calculation results are output to the fuel injection valves 13, 13,... And the ignition coils 17, 17 via the I / O LSI 34, and the fuel supply amount control and the ignition timing control are performed. Is done.

By the way, as shown in FIG. 1, the control unit 30 configured as described above is hardware-based, that is, the basic injection based on the intake air flow rate Qa and the engine speed Ne, as shown in FIG. A basic fuel calculation function 41 for calculating the amount Tp, and an air-fuel ratio feedback coefficient calculation for obtaining a difference (air-fuel ratio feedback coefficient) α between the stoichiometric air-fuel ratio and an actual air-fuel ratio detected based on a signal from the O ₂ sensor 20. A function 42 and a correction coefficient map 43 for storing a correction coefficient αL for the air-fuel ratio feedback coefficient α for each of the engine speed Ne and the fuel injection amount Tp.
And a correction coefficient αL for the air-fuel ratio feedback coefficient α is obtained for each of the engine speed Ne and the fuel injection amount Tp, registered in the correction coefficient map 43, and sequentially corrected.
A correction coefficient setting / updating function 44 for updating L; a correction coefficient search function 45 for searching the correction coefficient αL according to the engine state from the correction coefficient map 43; and a correction in the feedback area stored in the correction coefficient map 43 A correction coefficient variation tendency calculating function 46 for obtaining a variation tendency of the correction coefficient αL with respect to the variation of the fuel injection amount Tp and a variation tendency of the correction coefficient αL with respect to the variation of the intake air amount Qa from the coefficient αL; From the tendency of the variation of the correction coefficient αL for the variation of the amount Tp and the variation of the correction coefficient αL for the variation of the intake air amount Qa, the variation tendency of the correction coefficient αL and the intake air amount Q for the variation of the fuel injection amount Tp in the non-feedback region.
a correction coefficient estimating function 47 for estimating the variation tendency of the correction coefficient αL with respect to the variation of the correction coefficient αL, and the correction coefficient αL for the variation of the fuel injection amount Tp and the variation of the intake air amount Qa within the estimated non-feedback region.
Non-feedback area correction coefficient setting function 4 for registering this in the corresponding position of the correction coefficient map 43
8 and the correction coefficient α registered in the correction coefficient map 43
An injection amount calculation function 49 for correcting the basic injection amount Tp based on L and the like, and a drive signal output function 50 for outputting an injector drive pulse signal corresponding to the obtained injection amount Ti are provided.

Next, the control unit 3 of the present embodiment
The operation of 0 will be described with reference to the flowchart shown in FIG. The air-fuel ratio feedback coefficient calculation function 42
An air-fuel ratio feedback coefficient α representing a deviation between the stoichiometric air-fuel ratio and an actual air-fuel ratio detected based on a signal from the O ₂ sensor 20 is obtained. The correction coefficient setting / updating function 44 obtains a correction coefficient αL for the air-fuel ratio feedback coefficient α for each of the engine speed Ne and the fuel injection amount Tp, and registers this in the correction coefficient map 43 shown in FIG.
The above processing is repeated several times, and it is determined whether or not the number of times of learning of all the correction coefficients in the feedback area has reached a predetermined number or more (step 100). If the number of times of learning is equal to or more than the predetermined number of times, the process proceeds to step 101;

In step 101, the correction coefficient fluctuation tendency calculating function 46 calculates the fuel injection amount T from the correction coefficient αL in the feedback area stored in the correction coefficient map 43.
The variation tendency of the correction coefficient αL with respect to the variation of p and the variation tendency of the correction coefficient αL with respect to the variation of the intake air amount Qa are determined.

Here, how to determine the tendency of the correction coefficient αL to fluctuate will be described in detail with reference to FIG. In FIG. 3A, the area inside the broken line indicates the feedback area. The variation of the correction coefficient αL with respect to the variation of the injection amount Tp of the fuel injection valve 13 can be considered as a variation of the correction coefficient in a region where the intake air amount Qa is equal in the feedback region, that is, an equal intake air amount Qa _A region. Accordingly, as shown in FIG. (B), the fuel injection amount Tp and (Ti Any Good) in the horizontal axis, to organize the correction coefficient in the region of the equal amount of intake air Qa _A, for variation of injection quantity Tp The change tendency of the correction coefficient can be obtained. The variation of the intake air volume Qa, and the words the variation of the correction coefficient αL for hot wire type air flow meter 3 for detecting variation is equal area of the fuel injection amount Tp in the feedback region, i.e. the correction in the region of equal fuel injection amount Tp _A This can be considered as a change in the coefficient αL. Accordingly, as shown in FIG. (C), the intake air amount Qa in the horizontal axis, by organizing a correction factor in the region of equal fuel injection amount Tp _A, variation of the correction factor for the variation of the intake air quantity Qa Trends can be determined.

In step 102, the correction coefficient estimating function 4
7 shows the tendency of the correction coefficient for the variation of the injection amount Tp in the feedback region and the variation tendency of the correction coefficient for the variation of the intake air amount Qa in the non-feedback region. The fluctuation tendency and the fluctuation tendency of the correction coefficient with respect to the variation of the intake air amount Qa are estimated. As shown in FIGS. 6A and 6B, the variation tendency of the correction coefficient with respect to the variation of the injection amount Tp and the variation tendency of the correction coefficient with respect to the variation of the intake air amount Qa in the feedback region are respectively shown. , By linear approximation. Note that the fluctuation tendency of the correction coefficient in the non-feedback area may be estimated by linearly approximating the fluctuation tendency of the correction coefficient in the feedback area as described above. The tendency may be grasped as a function, and this function may be applied in the non-feedback region.

In step 103, the non-feedback area correction coefficient setting function 48 sets a correction coefficient αL in the non-feedback area in the correction coefficient map 43.

The setting of the correction coefficient to the point where the basic pulse width is Tp _W and the intake air amount is Qa _{W in} the non-feedback region will be specifically described with reference to FIGS. First, as shown in FIG. 6A, the injection amount Tp in the non-feedback region obtained in step 102
The difference (−) ξTp between the reference correction coefficient αL ₀ (correction coefficient for Tp _A and Qa _A ) and the correction coefficient for Tp _W is determined from the tendency of the correction coefficient to vary with respect to the variation of the above. Similarly, as shown in FIG. 6B, a difference ΔQa between the reference correction coefficient αL ₀ and the correction coefficient in Qa _A is obtained. Then, the difference (−) ξTp, ξQa is added to the reference correction coefficient αL _0, and (αL ₀ −ξTp + ξQa) is calculated as T
It is registered in the position corresponding to the _pW and Q _aW. The above processing is executed in all the areas in the non-feedback area to obtain the correction coefficients in the entire operation area.

In step 104, the injection amount calculation function 49
Is the correction coefficient αL registered in the correction coefficient map 43.
The fuel injection amount (fuel injection pulse width) Ti is obtained by correcting the basic fuel injection amount Tp using Specifically, the fuel injection amount Ti is obtained by the following equation. Ti = Tpx (α + αL) × COEF + T S COEF = KST × (1 + KTRM + KMR + KTW +
KAS + ...) Ti: fuel injection pulse width Tp: basic fuel injection pulse width (Tp = kQ
a / Ne) COEF: Open loop fuel injection correction coefficient α: Air-fuel ratio feedback coefficient αL: Feedback correction coefficient T _S : Injector voltage correction fuel injection supplementary pulse width KST: Startup increase coefficient KTRM, KMR: Mixing ratio correction coefficient KTW: water temperature correction coefficient KAS: increase coefficient after starting As described above, in the present embodiment, a correction coefficient in the non-feedback area is obtained from the fluctuation tendency of the correction coefficient in the feedback area, and this correction coefficient is used in the non-feedback area. Since the fuel injection amount is also controlled, the deviation of the actual air-fuel ratio from the target air-fuel ratio can be reduced over the entire operation range as shown in FIG. In the drawing, a broken line indicated by a triangle indicates a conventional technique, and a solid line indicated by a circle indicates the present embodiment.

Further, in this embodiment, since the variation in the air-fuel ratio can be softly absorbed, it is not necessary to strictly manage the tolerances in manufacturing the fuel injection valve 13 and the air flow meter 3.
The cost of these parts can also be reduced.

[0021]

According to the present invention, even in the entire non-feedback region, the correction amount is set in consideration of the variation in the injection amount from the fuel injection valve and the variation in the detection of the air flow meter. Over this, accurate air-fuel ratio control can be performed.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of a control unit according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating a configuration of an engine system according to an embodiment of the present invention.

FIG. 3 is a circuit block diagram of a control unit according to one embodiment of the present invention.

FIG. 4 is an explanatory diagram for explaining a correction coefficient map and a grasp of a fluctuation tendency of the correction coefficient according to the embodiment of the present invention;

FIG. 5 is an explanatory diagram showing a correction coefficient map according to one embodiment of the present invention.

FIG. 6 is an explanatory diagram for explaining how to grasp a change tendency of a correction coefficient in a non-feedback region according to one embodiment of the present invention.

FIG. 7 is a flowchart showing an operation sequence of the control unit of one embodiment according to the present invention.

FIG. 8 is a graph showing a relationship between a rotation speed variation and an air-fuel ratio variation when an embodiment according to the present invention is applied.

FIG. 9 is an explanatory diagram showing a conventional learning area and a learning result storage area.

FIG. 10 is an explanatory diagram showing a conventional learning method.

[Explanation of symbols]

3: hot wire air flow meter, 5a: throttle valve, 7: engine,
13: fuel injection valve, 16a: crank angle sensor, 17:
Ignition coil, 18 ... throttle sensor, 20 ... O ₂ sensor, 30 ... control unit, 31 ... MPU, 32
... ROM, 33 ... RAM, 34 ... I / O LSI, 41
... Basic fuel calculation function, 42 ... Air-fuel ratio feedback coefficient calculation function, 43 ... Correction coefficient map, 44 ... Correction coefficient setting / updating function, 45 ... Correction coefficient search function, 46 ... Correction coefficient fluctuation tendency calculating function, 47 ... Correction coefficient Estimation function, 48: non-feedback area correction coefficient setting function, 49: injection amount calculation function, 50: drive signal output function.

Continuation of the front page (56) References JP-A-4-43838 (JP, A) JP-A-4-43837 (JP, A) JP-A-4-43836 (JP, A) JP-A-2-271050 (JP JP-A-63-259136 (JP, A) JP-A-62-107250 (JP, A) JP-A-2-259257 (JP, A) JP-A-60-185632 (JP, A) 62-210237 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02D 41/00-41/40 F02D 45/00

Claims (3)

(57) [Claims] 1. A basic fuel calculating means for calculating a basic fuel injection amount from a measured intake air flow rate and an engine speed, and a target air-fuel ratio and a measured air-fuel ratio for each engine speed and basic fuel injection amount. Feedback region correction amount calculation means for obtaining a correction amount of air-fuel ratio control in a feedback region from a deviation from the above, storage means for storing the correction amount for each engine speed and basic fuel injection amount, and the storage means From the stored correction amount in the feedback region, a variation tendency of the correction amount in the equal intake air amount region in the feedback region with respect to the change in the basic fuel injection amount is obtained, and in the equal fuel injection amount region in the feedback region. A change tendency calculating means for obtaining a change tendency of the correction amount with respect to the change of the intake air amount; From the fluctuation tendency of the correction amount in the equal intake air amount region, the fluctuation tendency of the correction amount in the equal intake air amount region in the non-feedback region with respect to the change in the basic fuel injection amount is estimated, and the fluctuation amount in the feedback region is estimated. from the change trend of the correction amount in the fuel injection amount region, the variation trend estimation means for estimating a change tendency to inhaled air amount of change of the correction amount in equal fuel injection amount region of the non-feedback region, the non-feedback region From the variation tendency of the correction amount in the equal intake air amount region and the variation tendency of the correction amount in the equal fuel injection amount region in the non-feedback region, the engine speed and the basic fuel injection amount in the non-feedback region. The correction amount is calculated for each area, and the non-filter for setting the correction amount in the corresponding area of the storage means. The feedback area correction amount setting means and the non-feedback area correction amount setting means.
Using at least the correction amount set in the storage means ,
An air-fuel ratio control device, comprising: fuel injection amount setting means for correcting the basic fuel injection amount. 2. The non-feedback region correction amount setting means, wherein the correction amount in the equal intake air amount region in the non-feedback region varies from the change in fuel injection amount to the fuel injection region to be set. A fuel injection correction amount deviation between a correction amount estimated for the fuel injection amount and a reference correction amount is obtained, and the deviation is set based on a change tendency of the correction amount in the equal fuel injection amount region in the non-feedback region with respect to a change in the intake air amount . Calculating an air intake correction amount deviation between the correction amount estimated for the air intake amount region and the reference correction amount, and adding the fuel injection correction amount deviation and the air intake correction amount deviation to the reference correction amount. 2. The air-fuel ratio control device according to claim 1, wherein said value is set in a corresponding area in a non-feedback area of said storage means. 3. An air-fuel ratio control device according to claim 1, wherein said intake air flow rate measuring means measures said intake air flow rate, said engine speed measuring means measures said engine speed, and said engine exhaust. An engine control device comprising: an air-fuel ratio measuring unit that measures the air-fuel ratio from gas.