JPH077564Y2 - Air-fuel ratio learning controller for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an air-fuel ratio learning control device for an internal combustion engine having an electronically controlled fuel injection device having an air-fuel ratio feedback control function.

<Prior Art> Conventionally, in an internal combustion engine having an electronically controlled fuel injection device having an air-fuel ratio feedback control function, Japanese Patent Laid-Open No. 63-105
An air-fuel ratio learning control device such as that disclosed in Japanese Patent No. 257 is adopted.

This is because the basic fuel injection amount calculated from the parameters of the engine operating state related to the amount of air taken into the engine (for example, throttle valve opening and engine speed) is converted into a signal from an oxygen sensor provided in the engine exhaust system. Based on the feedback correction coefficient set by proportional / integral control, etc., the fuel injection amount is calculated and the air-fuel ratio is feedback-controlled to the target air-fuel ratio. The deviation from the reference value is learned for each area of the engine operating state to determine the learning correction coefficient, and when calculating the fuel injection amount, the basic fuel injection amount is corrected by the learning correction coefficient and calculated without correction by the feedback correction coefficient. The base air-fuel ratio obtained by the fuel injection amount is adjusted to match the target air-fuel ratio, and the air-fuel ratio feedback control is Among is for calculating the fuel injection amount is corrected by further air-fuel ratio feedback correction coefficient so.

According to this, the follow-up delay of the feedback control during the transient operation can be eliminated during the air-fuel ratio feedback control, and the desired air-fuel ratio can be accurately obtained when the air-fuel ratio feedback control is stopped.

<Problems to be solved by the invention> By the way, conventionally, in learning, an engine operating state area is determined by the engine speed and the basic fuel injection amount, and a correction coefficient for the base air-fuel ratio is set and stored for each area. It was

However, in the system that determines the basic fuel injection amount Tp from the throttle valve opening α and the engine speed N (hereinafter referred to as α-N system), the throttle valve portion is mainly caused by foreign matter (dirt) that adheres to the intake pipe wall. That is, the change over time of the air-fuel ratio due to this becomes a problem, but the influence due to this tends to increase as the throttle valve opening α decreases.

Therefore, the value of the learning correction coefficient with respect to the throttle valve opening α becomes as shown in FIG.
There is a problem in that there is a large difference in learning in the low opening range and the variation in the air-fuel ratio becomes large.

The present invention has been made in view of such conventional problems, and an object of the present invention is to provide an optimum air-fuel ratio learning control device for an α-N system.

<Means for Solving the Problems> Therefore, the present invention, as shown in FIG.
By providing the means K, the learning control device for the air-fuel ratio of the internal combustion engine is configured.

(A) Throttle valve opening detection means for detecting throttle valve opening (B) Engine speed detection means for detecting engine speed (C) Throttle valve opening area calculation for calculating throttle valve opening area from throttle valve opening Means (D) Rewritable learning correction amount storage means that defines an area with the throttle valve opening as at least one learning parameter, and stores a learning correction amount for addition and subtraction correction of the throttle valve opening area for each area (E) Learning correction amount search means for searching the learning correction amount of the throttle valve opening area of the corresponding area stored in the storage means from the actual value of the learning parameter (F) Throttle valve opening, engine speed, throttle valve opening area and Basic fuel injection amount calculation means for calculating the basic fuel injection amount based on the learning correction amount (G) Detecting the engine exhaust gas component Air-fuel ratio detection means for detecting the air-fuel ratio of the intake air-fuel mixture (H) The detected air-fuel ratio is compared with the target air-fuel ratio and the air-fuel ratio feedback correction coefficient is increased or decreased so that the actual air-fuel ratio approaches the target air-fuel ratio. Air-fuel ratio feedback correction coefficient setting means to be set by (I) Fuel injection amount calculation means for calculating the fuel injection amount by multiplying the basic fuel injection amount by the air-fuel ratio feedback correction coefficient (J) Drive corresponding to the calculated fuel injection amount Fuel injection means for injecting fuel to the engine at a predetermined timing synchronized with the engine rotation according to the pulse signal (K) Learning the deviation from the reference value of the air-fuel ratio feedback correction coefficient for each area of the learning parameter Learning correction amount updating means for updating and rewriting the learning correction amount in the storage means in the direction of decreasing the operation <Operation> When the throttle valve opening is detected, the throttle valve Mouth area calculation means calculates the throttle valve opening area based on the throttle valve opening, the learning correction amount retrieval means retrieves the learning correction amount of the throttle valve opening area from the storage means based on the throttle valve opening.

Then, the basic fuel injection amount calculation means calculates the basic fuel injection amount from the throttle valve opening, the engine speed, the throttle valve opening area and the learning correction amount thereof.

The air-fuel ratio feedback correction coefficient setting means compares the detected actual air-fuel ratio with the target air-fuel ratio and sets the air-fuel ratio feedback correction coefficient by increasing or decreasing so that the actual air-fuel ratio approaches the target air-fuel ratio.

Then, the fuel injection amount calculation means calculates the fuel injection amount by multiplying the basic fuel injection amount by the air-fuel ratio feedback correction coefficient.

Then, the drive pulse signal corresponding to the fuel injection amount causes the fuel injection means to operate at a predetermined timing synchronized with the engine rotation, and the fuel is injected and supplied to the engine.

On the other hand, the learning correction amount updating means updates and rewrites the learning correction amount in the storage means so as to learn the deviation of the air-fuel ratio feedback correction coefficient from the reference value for each area of the throttle valve opening and reduce it. .

Here, the learning sets and stores a learning correction amount for performing addition / subtraction correction of the throttle valve opening area using the throttle valve opening as at least one learning parameter.

Therefore, in the α-N system, the throttle valve portion is clogged mainly by foreign substances adhering to the intake pipe wall, etc., and thus there is a problem of a change in the air-fuel ratio with time. Since the change from the solid line in FIG. 8 to the broken line is almost uniform over the entire opening range, the learning correction amount of the opening area also changes almost uniformly as shown in FIG. For this reason, it is difficult to cause a learning step difference between each area, and it is possible to reduce variations in the air-fuel ratio even if the map grid is rough.

<Example> An example of the present invention will be described below.

In FIG. 2, air is drawn into the engine 1 from an air cleaner 2 via a throttle body 3 and an intake manifold 4.

A throttle valve 5 is interposed in the throttle body 3, and a fuel injection valve 6 as fuel injection means is provided upstream of the throttle valve 5. The fuel injection valve 6 is an electromagnetic opening / closing type, which is energized by a drive pulse signal from the control unit 7 to open the valve, and is pressure-fed by a fuel pump (not shown) to inject fuel adjusted to a predetermined pressure by a pressure regulator. .

The control unit 7 includes a microcomputer including a CPU, ROM, RAM, I / O, etc., performs arithmetic processing based on input signals from various sensors, and injects the fuel injection valve 6
Control the operation of.

As the various sensors, the throttle valve 5 is provided with a potentiometer-type throttle sensor 8 as a throttle valve opening detection means, and detects the throttle valve opening α.

Further, a crank angle sensor 9 is provided and, for example, in the case of four cylinders, it outputs a reference signal REF for each crank angle of 180 ° and a unit signal POS for each crank angle of 1 °. Where the reference signal R
The engine speed N can be calculated by measuring the cycle of EF or the number of unit signals POS generated within a predetermined time. Therefore, the crank angle sensor 9 is the engine speed detecting means.

Further, the exhaust manifold 10 is provided with an oxygen sensor 11. The oxygen sensor 11 is a well-known sensor in which the output voltage changes abruptly when the air-fuel mixture is burned near the stoichiometric air-fuel ratio, which is the target air-fuel ratio. Therefore, the oxygen sensor 11 is an air-fuel ratio (rich / lean) detecting means.

In addition, a water temperature sensor 12 for detecting the engine cooling water temperature Tw and the like are provided.

Further, a battery 13 is connected to the control unit 7 via an engine key switch 14 as its operating power source and for detecting its voltage. Also internal RAM
As the memory holding power source, the battery 13 is connected not through the engine key switch 14 but through an appropriate stabilizing power source.

Here, the CPU of the microcomputer incorporated in the control unit 7 performs arithmetic processing according to a program (fuel injection amount arithmetic routine, air-fuel ratio feedback control routine, learning routine) on the ROM shown as a flowchart in FIGS. 3 to 5. And control the fuel injection.

The functions of the throttle valve opening area calculating means, the learning correction amount searching means, the basic fuel injection amount calculating means, the air-fuel ratio feedback correction coefficient setting means, the fuel injection amount calculating means, and the learning correction amount updating means are achieved by the program. To be done. A RAM is used as the learning correction amount storage means.

Next, referring to the flow charts of FIGS. 3 to 5, the state of the arithmetic processing of the microcomputer in the control unit 7 will be described.

Step 1 in the fuel injection amount calculation routine of FIG.
(Indicated as S1 in the figure. The same applies hereinafter), the engine speed N calculated based on the signal from the throttle valve opening α and the crank angle sensor 9 detected based on the signal from the throttle sensor 8. Read in etc.

In step 2, the throttle valve opening area A ₀ corresponding to the throttle valve opening α is previously obtained by calculation or the like is referred to, and a map on the ROM stored therein is referred to search for A ₀ corresponding to the actual α. Read in. It may be obtained by calculation without depending on the map. This portion corresponds to the throttle valve opening area calculation means.

In step 3, the map on the RAM as the learning correction amount storage means that stores the learning correction amount A _L for adding / subtracting correction of the throttle valve opening area corresponding to the throttle valve opening α is referred to Search and read A _L corresponding to α.
This portion corresponds to the learning correction amount search means. The map of the learning correction amount A _L of the throttle valve opening area is such that the throttle valve opening α, which is a learning parameter, is set at an appropriate interval (fixed interval or dense in the low opening range and coarse in the high opening range). The area is divided into a plurality of areas, and the learning correction amount A _L is stored for each area. When the learning is not started, 0 is stored as the initial value.

In step 4, the basic fuel injection amount Tp corresponding to the throttle valve opening α and the engine speed N is obtained by experiments or the like in advance and is referred to a map on the ROM, which corresponds to the actual α, N. Search and read Tp. The intake air flow rate Q may be obtained by referring to a map from α and N, and Tp = K · Q / N (K is a constant) may be obtained by calculation from this Q and N.

In step 5, the basic fuel injection amount Tp obtained in step 4
Is corrected according to the following equation.

Here, steps 4 and 5 correspond to the basic fuel injection amount calculation means.

In step 6, various correction coefficients including the mixture ratio correction coefficient K _MR according to the engine speed N and the basic fuel injection amount Tp, the water temperature increase correction coefficient K _TW according to the water temperature Tw, etc. COEF = 1 + K _MR + K _TW
Set +. Further, the voltage correction amount Ts is set based on the battery voltage.

In step 7, the fuel injection amount Ti is calculated according to the following equation.

Ti = Tp · COEF · LAMBDA + Ts Here, LAMBDA is an air-fuel ratio feedback correction coefficient, which is set by the air-fuel ratio feedback control routine of FIG. 4 described later, and its reference value is 1.

The part of step 7 corresponds to the fuel injection amount calculation means.

In step 8, the calculated Ti is set in the output register. As a result, at a predetermined fuel injection timing of engine rotation synchronization (for example, every 1/2 rotation), a drive pulse signal having the pulse width of Ti set latest is given to the fuel injection valve 6 to inject fuel. Is done.

FIG. 4 is an air-fuel ratio feedback control routine, which is executed in rotation synchronization or time synchronization, whereby the air-fuel ratio feedback correction coefficient LAMBDA is set. Therefore, this routine corresponds to the air-fuel ratio feedback correction coefficient setting means.

In step 11, the comparison value Tp 'of the basic fuel injection amount is retrieved from the engine speed N, and in step 12, the actual basic fuel injection amount is calculated.
Compare Tp with the comparison value Tp ′.

If Tp> Tp ', the routine proceeds to step 13 where the λcont flag is set to 0 and this routine is terminated. Therefore, the air-fuel ratio feedback correction coefficient LAMBDA is clamped to the previous value (or reference value 1), and the air-fuel ratio feedback control is stopped. This is because the air-fuel ratio feedback control is stopped in the high rotation and high load range, a rich output air-fuel ratio is obtained by the mixing ratio correction coefficient K _MR , and the rise in exhaust temperature is suppressed, seizure of the engine and ternary This is to prevent burning of the catalyst.

If Tp ≦ Tp ′, the process proceeds to step 14, the λcont flag is set to 1, and then the process proceeds to step 15 and thereafter. This is because the air-fuel ratio feedback control is performed in the low and medium rotation speed and low and medium load regions.

In step 15, read the output voltage V ₀₂ of the oxygen sensor 11,
In the next step 16, the lean rich of the air-fuel ratio is judged by comparing with the slice level voltage V _ref .

When the air-fuel ratio is lean (V ₀₂ <V _ref ), the _routine proceeds from step 16 to step 17, and it is judged whether or not it is during the reversal from rich to lean (immediately after the reversal).
After proceeding to, the deviation of the previous air-fuel ratio feedback correction coefficient LAMBDA from the reference value 1 is stored as Δa = LAMBDA-1 for the learning routine of FIG. Is increased by a predetermined proportional constant PR with respect to the previous value. Except when reversing, the routine proceeds to step 20, where the air-fuel ratio feedback correction coefficient LAMBDA is increased by a predetermined integration constant IR with respect to the previous value, and thus the air-fuel ratio feedback correction coefficient LAMBDA is increased at a constant slope. Note that PR >> IR.

When the air-fuel ratio is rich (V ₀₂ > V _ref ), the _routine proceeds from step 16 to step 21, and it is judged whether or not the lean-to-rich reversal is being performed (immediately after the reversal).
Go to step S23 and store the deviation of the previous air-fuel ratio feedback correction coefficient LAMBDA from the reference value 1 as Δb = LAMBDA-1 for the learning routine of FIG. Is decreased by a predetermined proportional constant PL from the previous value. Except when reversing, the routine proceeds to step 24, where the air-fuel ratio feedback correction coefficient LAMBDA is decreased by a predetermined integration constant IL from the previous value, and thus the air-fuel ratio feedback correction coefficient LAMBDA is decreased with a constant slope. Note that PL >> IL.

FIG. 5 shows a learning routine, which is executed as a background job, whereby the learning correction amount A _L is set / updated. Therefore, this routine corresponds to the learning correction amount updating means.

First, it is determined whether or not a predetermined learning condition is satisfied.

In step 31, it is judged whether or not the λcont flag is 1, and when it is 0, this routine is ended. This is because learning cannot be performed when the air-fuel ratio feedback control is stopped.

In step 32, it is determined whether or not it is in a steady state. The steady state is conditioned on that the area of the throttle valve opening α is defined and the number of times the lean rich signal of the oxygen sensor 11 is inverted in the same area is a predetermined value (for example, 3) or more. In addition, the rate of change of the throttle valve opening α and the rate of change of the engine speed N may be small. If this condition is not satisfied, this routine ends.

When the predetermined learning condition is satisfied, the routine proceeds to step 33, where the average value of the above-mentioned Δa and Δb is obtained. Δa and Δb stored at this time are the air-fuel ratio feedback correction coefficient
This is the peak value above and below the deviation from the standard value 1 of the air-fuel ratio feedback correction coefficient LAMBDA from the reversal of the increase / decrease direction of LAMBDA. By calculating the average of these, the standard value 1 of the air-fuel ratio feedback correction coefficient LAMBDA The average deviation ΔLAMBDA from is calculated.

Next, the routine proceeds to step 34, where the learning correction amount A _L (initial value is 0) stored in the map on the RAM corresponding to the area of the current throttle valve opening α is retrieved and read.

Next, in step 35, the current learning correction amount is calculated according to the following equation.
Calculating a new learning correction quantity A _L by adding converted to A _L a predetermined ratio deviation ΔLAMBDA from the reference value of the air-fuel ratio feedback correction coefficient in the throttle valve opening area fraction.

A _L ← A _L + a × ΔLAMBDA / M (a is a conversion constant, M is a ratio constant, M ≧ 1) Next, go to step 36 and rewrite the data of the learning correction amount A _L of the same area of the map on the RAM. It

Next, another embodiment will be described. Only the fuel injection amount calculation routine is different, which is shown in FIG.

The steps 51 to 53 are the same as the steps 1 to 3 described above.

In step 54, the learning correction amount is added to the throttle valve opening area A _0.
A _L is added to obtain the true throttle valve opening area A.

In step 55, the throttle valve opening area A is divided by the engine speed N, the intake air flow rate Q ₀ is calculated corresponding to the A / N, and the stored map on the ROM is referred to. Correspond
Search for Q ₀ .

In step 56, the suction efficiency η is obtained corresponding to the throttle valve opening α and the engine speed N, and the stored rimap on the ROM is referred to search for η corresponding to α, N.

In step 57, the basic fuel injection amount Tp = Q ₀ · η is calculated from the intake air flow rate Q ₀ and the intake efficiency η.

Here, steps 54 to 57 correspond to the basic fuel injection amount calculation means.

The steps 58 to 60 are the same as the steps 6 to 8 described above.

The learning parameter may be only the throttle valve opening α or the throttle valve opening α and the engine speed N.

In this method, the learning correction amount is
It is considered that there is no appreciable difference in the A _L, for unlearned area can be learned estimated based on the learning correction amount A _L of the other areas.

<Effects of the Invention> As described above, according to the present invention, the learning correction amount for adding / subtracting the throttle valve opening area is set with the throttle valve opening as at least one learning parameter.
Since it is memorized, there is an effect that learning can be performed effectively without causing a learning step between learning areas for throttle valve clogging (dirt), which is the main change over time of the α-N method, and effective correction can be obtained. To be

[Brief description of drawings]

FIG. 1 is a functional block diagram showing the configuration of the present invention, FIG. 2 is a system diagram showing an embodiment of the present invention, FIG. 3 is a flow chart of a fuel injection amount calculation routine, and FIG. 4 is an air-fuel ratio feedback control routine. FIG. 5, FIG. 5 is a flowchart of a learning routine, FIG. 6 is a flowchart of a fuel injection amount calculation routine of another embodiment, and FIG. 7 is a state diagram of a learning correction coefficient with respect to the throttle valve opening in the conventional learning system. FIG. 8 is a diagram showing how the throttle valve opening area changes with time with respect to the throttle valve opening, and FIG. 9 is a state diagram of the learning correction amount with respect to the throttle valve opening in the learning system of the present invention. 1 ... Engine, 5 ... Throttle valve, 6 ... Fuel injection valve,
7 ... control unit, 8 ... throttle sensor, 9 ... crank angle sensor, 11 ... oxygen sensor

Claims (1)

[Scope of utility model registration request] 1. A throttle valve opening detecting means for detecting a throttle valve opening, an engine speed detecting means for detecting an engine speed, and a throttle valve opening area calculation for calculating a throttle valve opening area from the throttle valve opening. Means, a rewritable learning correction amount storage means that defines an area with the throttle valve opening as at least one learning parameter, and stores a learning correction amount for addition / subtraction correction of the throttle valve opening area for each area; Learning correction amount retrieval means for retrieving a learning correction amount of the throttle valve opening area of the corresponding area stored in the storage means from the actual value of the throttle valve opening, engine speed, throttle valve opening area and its learning correction The basic fuel injection amount calculation means for calculating the basic fuel injection amount based on the amount, and the engine exhaust component are detected and The air-fuel ratio detection unit that detects the air-fuel ratio of the air-fuel mixture is compared with the detected air-fuel ratio and the target air-fuel ratio, and the air-fuel ratio feedback correction coefficient is set to increase or decrease so that the actual air-fuel ratio approaches the target air-fuel ratio. Air-fuel ratio feedback correction coefficient setting means, fuel injection amount calculation means for calculating the fuel injection amount by multiplying the basic fuel injection amount by the air-fuel ratio feedback correction coefficient, and an engine according to the drive pulse signal corresponding to the calculated fuel injection amount. Fuel injection means for injecting fuel to the engine at a predetermined timing synchronized with rotation, and learning for a deviation of an air-fuel ratio feedback correction coefficient from a reference value for each area of the learning parameter to reduce the deviation. A learning correction amount updating means for updating and rewriting the learning correction amount of the means, and an air-fuel ratio learning control device for an internal combustion engine, comprising: