JPH0634595Y2 - Air-fuel ratio controller for engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to an improvement of an air-fuel ratio control device for an engine, particularly, one for performing learning control.

(Prior Art) An air-fuel ratio control device having a learning function (Japanese Patent Laid-Open No. 60-145)
In Japanese Patent No. 443), the learning value (K
_BLRC ) is added.

Ti = Tp × Co × α × K _BLRC + Ts (1) However, in the equation (1), Tp is the basic pulse width (basic injection determined by the intake air amount (Qa) and the engine speed (Ne). The air-fuel ratio determined by this Tp is called the base air-fuel ratio. Co is various correction coefficients, α is the feedback correction coefficient of the air-fuel ratio, and Ts is the voltage correction amount.

In this case, the area where the learning value (learning correction coefficient) is stored, as shown in FIG. 6, has the horizontal axis representing the engine rotation speed (N
e), the vertical axis is the basic pulse width (Tp) as an engine load equivalent, and is partitioned by a grid having a predetermined interval (this grid is referred to as a "learning grid"), and learning is different for each partitioned area. The value is stored.

FIG. 7 shows a program for updating the learning value,
It is executed every predetermined crank angle. In S1, it is determined whether the learning condition is satisfied. An example of this learning condition is as follows, and when all of these are satisfied, the learning condition is satisfied.

Tp and Ne are in the same area Air-fuel ratio feedback control is in progress Oxygen sensor output is sampled for several cycles The difference between the maximum and minimum values of oxygen sensor output is more than a certain value Oxygen sensor control The cycle is within the reference value If it is determined that the learning condition is satisfied, the process proceeds to S2, where α
The deviation (ε) from the control center (1.0) of is calculated by the following formula.

ε = (a + b) / 2−1 (2) However, in the equation (2), a is the value of α just before the air-fuel ratio is changed from lean to rich, and b is the air-fuel ratio is changed from rich to lean. The immediately preceding value of α, that is, a is the maximum value of the half cycle of α, and b is the minimum value of the half cycle.

In S3, the area to which Tp and Ne at that time belong is selected, and in S4, the learning value (K _BLRC ) that was in that area is read, and this value and this ε are used to learn this time (K _BLRC ). To calculate. If this is expressed by an equation, K _BLRC = K _BLRC + R × ε (3).

However, in the equation (3), R is a learning update rate, and an appropriate value less than 1 is selected to avoid hunting or the like.

Here, ε corresponds to the deviation from the target air-fuel ratio, that is, the air-fuel ratio deviation, and by incorporating this deviation into the learning value, the deviation from the next time is eliminated.

(Problems to be solved by the invention) By the way, there is a purge air introducing device shown in FIG. 8 for preventing the evaporated fuel from diffusing into the atmosphere. This is because the fuel vapor generated from the fuel tank 36 when the engine is stopped is adsorbed to the activated carbon 38 in the canister 37, the purge air control valve 39 is opened within a predetermined opening range of the throttle valve 28, and the atmosphere from the outside of the canister 37. Is introduced so that the adsorbed fuel is desorbed from the activated carbon 38, and the air containing the desorbed fuel (hereinafter referred to as “purge air”) is sucked into the intake passage 21.

FIG. 9 shows the purge air amount with respect to the throttle valve opening (TV0), and the purge air is introduced within a predetermined opening range from X to Y. It should be noted that the reason why the purge air is not sucked at and near the fully closed position is that the idle rotation becomes unstable if the purge air is introduced in this case, and this is avoided.

By the way, in the case where such a purge air introducing device is provided, the boundary of the purge air introducing region and the above-mentioned learning grid do not necessarily overlap with each other. As a result, a step difference in the air-fuel ratio may occur and the learning accuracy may decrease.

For example, in FIG. 10, if the center of _one area (A ₁ ) divided by four learning grid points D ₁ , D ₂ , D ₃ , and D ₄ is TV
Considering the case where the line of 0 = X (that is, the boundary of the purge air introduction region) is crossed, the purge air is not introduced in the region (A _D ) below the line of X, whereas the region above (A _U) ), Purge air is introduced.

Now, if the operating point stops for a while at U ₁ point that belongs to the upper area (A _U ), the learning condition is satisfied and the area (A ₁ )
The learning value of is updated. According to the updated learning value, the optimum value is given when the purge air is introduced, so the operating point leaves the area (A ₁ ) once, and then the U ₂ point (or U ₂ ) belonging to the area (A ₁ ) ₁ ), the optimum learning value is read when the purge air is introduced, so that the stoichiometric air-fuel mixture can be obtained from the beginning when U ₂ (U ₁ ).

However, if the learning value was updated at U ₁ point, but the operating point then stopped at U ₃ point belonging to the area (A _D ), the situation would be different. In other words, assuming that U ₃ point is also in the same area (A ₁ ) as U ₁ point and U ₂ , if the optimum learning value is read when introducing purge air, that learning value will be too small as purge air is not introduced. . This means that the air-fuel ratio step is generated at the moment when the learning value is read. Therefore, in order to eliminate this air-fuel ratio step, the air-fuel ratio becomes lean until α returns to the control center.

Similarly, operating points belonging to the area (A _D ) (for example, U
_Even if the operating point reaches the operating point belonging to the area (A _U ) (for example, U ₁ point or U ₂ point) after the learning value is updated at ( ₃ points), the learning value read at that time Is too large, which causes a step difference in the air-fuel ratio, and the air-fuel ratio becomes richer until α returns to the control center.

In order to eliminate the air-fuel ratio step caused by the reading of these learning values, one area should not be divided into a region where purge air is introduced and a region where purge air is not introduced.

The present invention has been made in view of such conventional problems, and an object thereof is to provide a device in which the boundary of the purge air introduction region is overlapped with the learning grid.

(Means for Solving the Problem) As shown in FIG. 1, the present invention is directed to sensors 1 and 2 for respectively detecting an engine load (for example, intake air amount Qa) and a rotation speed (Ne), and detection of these sensors. Basic injection amount T according to the value
Means 3 for calculating p (= K × Qa / Ne, where K is a constant)
And means 4 for setting a learning grid using the engine load (for example, Tp) and rotation speed (Ne) as parameters, and means 5 for storing a learning value (K _BLRC ) for each area partitioned by the learning grid. , Means 6 for reading the learning value (K _BLRC ) of the area to which the engine load and the rotational speed at that time belong
A sensor 7 for detecting an actual air-fuel ratio, and a means 8 for measuring a deviation between the detected air-fuel ratio and a predetermined target air-fuel ratio.
And means 9 for calculating the feedback correction amount (α) of the air-fuel ratio based on this deviation, the feedback correction amount (α) and the learning value (K _BLRC ) read from the area.
At 10, means for correcting the basic injection amount (Tp) to determine the fuel injection amount (Ti) to be output, means 11 for determining whether or not a learning condition is satisfied, and if this is determined, the Means 12 for updating the learning value for the same area based on the feedback correction amount (α) of the air-fuel ratio and the learning value (K _BLRC ) read from the area, and a device 13 for introducing purge air into the intake system. In an air-fuel ratio control device for an engine, comprising: a means 14 for setting the operating region where the purge air is introduced so that its boundary overlaps the learning grid, and whether the operating point is in the operating region where the purge air is introduced. Means 15 for deciding whether or not, and means 16 for activating the purge air introducing device 13 only when this is decided
With.

(Operation) Since the purge air introduction device 13 is provided from a viewpoint different from the air-fuel ratio control having the learning function, the boundary of the purge air introduction region and the learning grid may not overlap with each other. Occurs and exhaust emission becomes worse.

However, in this invention, if attention is paid to any one of the areas, it is either that the purge air is always introduced or is not necessarily introduced, and it is divided into an area where the purge air is introduced and an area where the purge air is not introduced. There is no.

As a result, the learning value read for that area is always the optimum value from the beginning when the operating point moves to a different area, so there is no chance that an air-fuel ratio step will be generated due to reading the learning value. .

(Embodiment) FIG. 2 shows a system diagram in which the present invention is applied to a fuel injection type engine. In the figure, reference numeral 24 is an air flow meter which is provided in the intake passage upstream of the throttle valve 28, and which outputs according to the amount (Qa) of air taken in through the air cleaner, and functions as an engine load sensor.
25 is a sensor (crank angle sensor) that outputs a signal for each unit angle of the crank angle and a signal for each reference position. From the signal for each unit angle, the control unit 45 counts this sensor rotation speed (Ne) Is required.

Reference numeral 26 is an oxygen sensor having a characteristic that changes abruptly at the stoichiometric air-fuel ratio, and the signal from this sensor 26 is treated as a feedback control signal of the air-fuel ratio.

29 is a sensor for detecting the throttle valve opening (TV0), 2
7 is a water temperature sensor.

On the other hand, the purge air introducing device mainly includes a canister 37 filled with activated carbon 38 that adsorbs fuel vapor from the fuel tank 36 and a purge air control valve 39. In the type shown in the figure, the control valve 39 is opened only when the throttle valve 28 is within a predetermined opening range. Specifically, the working chamber 3 defined by the diaphragm 39A of the purge air control valve 39
A suction negative pressure in the vicinity of the throttle valve 28 is introduced into 9B through a passage 40, and a return spring 39C is housed. The diaphragm 39A is normally urged downward by the return spring 39C, so that the valve 39D is closed. On the other hand, when the throttle valve 28 is opened to a predetermined opening range, the negative pressure introduced into the working chamber 39B causes
The valve 39D is pulled upward to open against the spring force. As a result, the purge air passes through the passage 41 and the intake passage 21
Is introduced to the collector section 22 of the.

45 is a control unit to which signals from the above-mentioned sensors (24 to 27, 29) are input. In this control unit 45, fuel from the fuel injection valve 35 provided in the intake port of each cylinder is based on various operating variables. By increasing or decreasing the amount, feedback control and learning control of the air-fuel ratio are performed so that the target air-fuel ratio (theoretical air-fuel ratio) is obtained, and the passage 40
A control signal (ON / OFF signal) is output to the solenoid valve 42 interposed in the. For example, regarding the former learning control, if the control unit 45 is composed of a microcomputer, the basic pulse width Tp (= K × Qa / Ne, where K is a constant) is set in the CPU by various coefficients (Co and Ts), By _{performing the} correction calculation using the fuel ratio feedback correction coefficient (α) and the learning correction coefficient (K _BLRC ), the injection pulse width (T
i) is determined by Ti = Tp × Co × α × K _BLRC + Ts.

However, α and K _BLRC are stored in the memory (ROM) according to a known method, and values such as the basic pulse width (Tp), each coefficient in various correction coefficients (Co), and voltage correction amount (Ts) are stored. Each is obtained by searching a table.

The solenoid valve 42 is for activating or deactivating the purge air introducing device, and the control unit 45
If the solenoid valve 42 is opened by the ON signal from, purging air is introduced as in the conventional case according to the characteristics shown in FIG. 9, but if the solenoid valve 42 is closed by the OFF signal,
Even if the throttle valve 28 is within the predetermined opening range, the purge air is not introduced.

Here, the control unit 45 includes the means 3 to 3 in FIG.
It will have the functions of 6,8-12,14-16.

FIG. 3 is a program for limiting the operation of the purge air introducing device to a certain range.

In S22, learning grid points are read. FIG. 4 shows the learning grid. In the figure, (N ₀ , Tp ₀ ), (N ₁ , Tp ₀ ), (N ₂ , T
Points such as p ₀ ), (N ₀ , Tp ₁ ), and (N ₂ , Tp ₂ ) are learning grid points.

In S23, the purge air introduction area is set so that its boundary exactly overlaps the learning grid. For example, in FIG. 5, regarding Tp as the engine load equivalent amount, the lower limit at which purge air is introduced is Tp ₀ and the upper limit is Tp ₂ . Similarly, for Ne, the lower limit at which purge air is introduced is N ₀ , and the upper limit is N ₂ . That is, the purge air introduction region is (N ₀ , Tp ₀ ), (N ₂ , Tp ₀ ), (N ₀ , Tp ₂ ),
The area is surrounded by the four points (N ₂ , Tp ₂ ). If this is transferred to the learning grid of FIG. 4, four areas (A _{2 to} A ₅ ) shown by diagonal lines become purge air introduction areas, and the boundary and the learning grid overlap. In this way, the boundary of the purge air introduction area is overlapped with the learning grid in order to prevent the area where the purge air is introduced and the area where the purge air is not introduced from being divided.

These S22 and S23 are performed prior to driving. That is, it is the initial setting. Therefore, if it is determined that the control is the first time in S21 and it is not the first time, the process proceeds to S25.

In S25, N and Tp at that time are read, and it is determined in S26 whether or not the operating point determined by these N and Tp is in the purge air introduction region shown in FIG. 5, and if this is determined, S
Proceeding to 27, an ON signal is output so that the solenoid valve 42 described above is opened. If it is not in the purge air introduction region, the process proceeds to S28 and the OFF signal is output so that the solenoid valve 42 is closed.

Here, the operation of the embodiment will be described with reference to FIG. Now, when the learning value is updated at the U ₄ point belonging to one area (for example, A ₂ ) where the purge air is introduced, the learning value at that time becomes an optimum value when the purge air is introduced. Then, jump out the operation point is the area (A _2), followed by belonging to the same area (A ₂₎ U ₅ points (or
When came to U ₄ points), since the _5-point U introduces purge air, and the learning values read in this case is the optimum value at the time of introduction purge air, causing the air-fuel ratio difference in level originally came to ₅ points U There is no. This situation does not change whether U ₄ and U ₅ are in the same area (A ₂ ).

On the other hand, when looking at the area where purge air is not introduced, for example, the area (A ₆ ) next to the area (A ₂ ), the learning value performed at U ₆ belonging to area (A ₆ ) is optimal when purge air is not introduced. It becomes a value. If the operating point comes out of the area (A ₆ ) and then reaches U ₇ point (or U ₆ point) in the same area (A ₆ ), purge air is not introduced at U ₇ point, and in this case Since the learned value to be read is the optimum value when the purge air is not introduced, in this case as well, the air-fuel ratio step does not occur at the beginning when the point reaches U ₇ .

In other words, in the embodiment, in regard to any one area, either the purge air is always introduced or the purge air is not always introduced, and there is no division into the area where the purge air is introduced and the area where the purge air is not introduced. is there.

As a result, the learning value that is read for that area will always be the optimum value from the beginning when the operating point moves to a different area, so there is no chance that an air-fuel ratio step will occur due to reading the learning value. Therefore, the exhaust emission can be further improved.

Finally, it goes without saying that there are various types of purge air introducing devices other than those shown in the embodiments, and the invention can be applied to these types.

(Effects of the Invention) The present invention has means for setting the purge air introduction area so that the boundary thereof overlaps the learning grid, means for determining whether or not the operating point is in the purge air introduction area, and As long as the means for operating the purge air introducing device is provided, the introduction of the purge air and the learning function are well matched, and the exhaust emission can be further improved.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to the claims of the present invention, FIG. 2 is a system diagram of an embodiment of the present invention, FIG. 3 is a flow chart for explaining operation contents of this embodiment, and FIG. FIG. 5 is a region diagram showing the learning grid, and FIG. 5 is a diagram showing the purge air introduction region of this embodiment. FIG. 6 is a region diagram showing a learning grid of a conventional example, FIG. 7 is a flow chart for explaining calculation contents of the conventional example, FIG. 8 is a schematic diagram of a purge air introducing device of the conventional example, and FIG. 9 is a conventional example. Characteristic diagram of the purge air amount with respect to the throttle valve opening of
The figure is a region diagram for explaining the operation of the conventional example. 1 ... Engine load sensor, 2 ... Engine speed sensor, 3 ... Basic injection amount calculation means, 4 ... Learning grid setting means, 5 ... Learning value storage means, 6 ... Learning value reading means, 7 ... ... Air-fuel ratio sensor, 8 ... Deviation measuring means, 9 ...
Feedback correction amount calculating means, 10 ... Fuel injection amount determining means, 11 ... Learning condition determining means, 12 ... Learning value updating means, 13 ... Purge air introducing device, 14 ... Purge air introducing area setting means, 15 ... Judgment means, 16 ... Actuation limiting means,
21 ... Intake passage, 24 ... Air flow meter, 25 ... Crank angle sensor, 26 ... Oxygen sensor, 28 ... Throttle valve, 29 ... Throttle valve opening sensor, 38 ... Canister, 39 ... Purge air control Valve, 42 ... Solenoid valve, 45 ...
…control unit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naoki Nakata 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (72) Fumio Yukawa 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (56) References JP-A-60-145443 (JP, A) JP-A-63-131843 (JP, A)

Claims (1)

[Scope of utility model registration request] 1. A sensor for respectively detecting an engine load and a rotation speed, a means for calculating a basic injection amount according to these detection values, and a means for setting a learning grid using the engine load and the rotation speed as parameters. , Means for storing a learning value for each area partitioned by this learning grid, means for reading a learning value in an area to which the engine load and the rotational speed at that time belong, a sensor for detecting an actual air-fuel ratio, and detection Means for measuring a deviation between the determined air-fuel ratio and a predetermined target air-fuel ratio, means for calculating a feedback correction amount of the air-fuel ratio based on the deviation, and this feedback correction amount and learning read from the area Means for determining the fuel injection amount to be output by correcting the basic injection amount with a value,
Means for determining whether or not a learning condition is satisfied, and when it is determined, the learning value for the same area is updated based on the feedback correction amount of the air-fuel ratio and the learning value read from the area. In the air-fuel ratio control device of the engine, which comprises means and a device for introducing purge air into the intake system, an operating region in which the purge air is introduced,
Means for setting the boundary so as to overlap the learning grid, means for determining whether or not the operating point is in the operating region where the purge air is introduced, and means for operating the purge air introducing device only when this is determined An air-fuel ratio control device for an engine, comprising: