JPS60159347A - Air-fuel ratio controlling method of internal-combustion engine - Google Patents

Abstract

PURPOSE:To make highly accurate air-fuel ratio control come to fruition, by judging on whether an air-fuel ratio deviation valve at that time is effective or not on the basis of a fact that an adjustable speed variable is above the speccified adjustable speed variable boundary value or not at a time when a fuel compensation value in time of a transient is determined according to an adjustable speed state, and regulating the said compensation value. CONSTITUTION:A controlling method bearing the above caption seeks a fundamental fuel quantity at a control circuit CONT on the basis of each detection signal out of a suction air quantity detector 2, an engine speed sensor 3 and a water temperature sensor 4, and compensates the fuel quantity by a detection signal out of an air-fuel ratio sensor 6, thereby controlling valve opening time for a fuel injection valve 8. And, when an adjustable speed state is detected from output of a throttle sensor 91, fuel compensation in time of a transient takes place in this method. In this case, when an adjustable speed variable is more than the specified boundary value, an air-fuel ratio deviation to be found out in conformity with output of the air-fuel ratio sensor 6 is made available. On the other hand, when the adjustable speed variable is below the specified boundary value, the said air-fuel ratio deviation is made unavailable. Then, a compensation value for fuel compensation in time of a transient is regulated according to the air-fuel ratio deviation.

Description

[Detailed description of the invention] Technical field The present invention relates to an air-fuel ratio control method for an internal combustion engine.

The method according to the invention is applied to motor vehicle engines. Prior Art One type of air-fuel ratio control device for engines is known in the prior art. This type of device includes means for generating a basic fuel signal representative of the fuel demand of the engine at steady state in response to the values of predetermined engine operating parameters, including engine temperature, representative of the fuel demand of the engine; means for detecting a transient engine operating condition indicative of a demand; and in response to the measured value of engine temperature and the detected transient engine operating condition, a first value determined by the engine temperature; means for generating a reinforcement boosting signal having an initial value determined by the detected engine transient and increased by a factor varying towards unity at a rate determined by the engine temperature; and a base fuel. means for supplying fuel to the engine in accordance with the signal and the reinforcement promoting signal, thereby supplying fuel to the engine on demand during both steady state and transient conditions of the engine. This device provides a fuel supply system that always ensures an optimal air-fuel ratio not only in the steady state of the engine but also in the transient state, thereby obtaining the optimal operation of the engine (see, for example, Japanese Patent Laid-Open No. 56-6034).

In the above-mentioned type of device, changes in the engine over time, such as changes in characteristics due to deposits on the injector nozzle in pulp clearance and EFI, and deposits on the back of the cylinder intake valve, i.e., lubricating oil components and combustion Changes in properties caused by stickiness such as carbon particles derived from products, changes in gas properties, and changes in volatility due to variations in gasoline properties are not taken into account, and changes in engine properties over time and changes in properties of gasoline are not considered. Since there is no means to detect changes in the air-fuel ratio from the optimum value during acceleration due to engine acceleration, sluggishness during acceleration due to engine aging and dilution of the mixed gas may occur. On the other hand, if gasoline with good volatility is used, the mixed gas becomes richer during acceleration, which may lead to poor fuel efficiency and poor emissions. be.

The fluctuations in the air-fuel ratio in this case, particularly when deposits are attached to the back surface of the intake valve, are illustrated in FIG. In Figure 1, A/F (01) shows the changes in the air-fuel ratio before deposits are attached, and A/F (DEP) shows the changes in the air-fuel ratio after deposits are attached.

NE is the engine rotation speed, ACC is the acceleration point, DE
C is the deceleration point, A/F' (OPT) is the optimum air-fuel ratio,
A/F (LN) is on the lean side, A/F (Re
H) is on the rich side.

In addition, clogging of the injector can be corrected by feedback from the air-fuel ratio sensor in steady state, but the same problem occurs during acceleration and deceleration because there is no correction means. Similar problems also occur due to variations in the manufacturing process of the engine and air flow meter, and changes over time.

Furthermore, gasoline used in internal combustion engines is generally commercially available from the same manufacturer with different characteristics for each season, such as for summer and winter use. The Reid vapor pressure and distillation characteristics are generally well known as numerical values that indicate the volatility of gasoline, but even if you look at the gasoline properties of the manufacturers, the Reid vapor pressure is 0.5 Q/Cll1~0.86 Immediate/ cf
Also, the 1O% distillation temperature varies from 40 to 58°C, and the air-fuel ratio characteristics during transient times vary greatly due to changes in volatility due to differences in the properties of the fuel. In the conventional system, no consideration is given to air-fuel ratio fluctuations caused by changes in volatility due to variations in gasoline properties. Therefore, this type of device does not have a means to optimize the air-fuel ratio during acceleration and deceleration, so if the engine changes over time such as deposits, or if low-volatility gasoline is used, acceleration may occur. During deceleration, the air-fuel ratio becomes lean, resulting in deterioration of drivability such as sluggishness, and during deceleration, the air-fuel ratio becomes rich, resulting in deterioration of driving performance and deterioration of fuel efficiency.

OBJECTS OF THE INVENTION In view of the problems with the conventional type described above, an object of the present invention is to make effective the detected air-fuel ratio deviation value when the amount of acceleration/deceleration is equal to or greater than a predetermined acceleration/deceleration boundary value when detecting the air-fuel ratio deviation. In addition, in the air-fuel ratio deviation detection value when the air-fuel ratio deviation is detected a number of consecutive times, the deviation direction is valid when the direction of deviation is the same, and invalid otherwise. The purpose of this invention is to realize highly accurate transient air-fuel ratio learning control based on the idea of detecting the air-fuel ratio deviation and adjusting the correction amount in the transient fuel correction to compensate for the air-fuel ratio deviation.

In the present invention, when the transient fuel correction amount is determined at predetermined intervals according to the acceleration/deceleration state of the internal combustion engine and the amount of fuel supplied to the internal combustion engine is corrected using the correction amount, the When the acceleration/deceleration amount of the internal combustion engine is greater than or equal to a predetermined acceleration/deceleration amount boundary value, the air-fuel ratio deviation from the optimum air-fuel ratio is validated and the air-fuel ratio deviation is detected; when it is less than the predetermined acceleration/deceleration amount boundary value, the air-fuel ratio is determined to be invalid. There is provided an air-fuel ratio control method for an internal combustion engine, which is characterized by detecting a deviation and adjusting a correction amount of transient fuel correction according to the air-fuel ratio deviation detected as valid. As the value, the amount of change in intake air amount per revolution, the amount of change in throttle opening, the amount of change in intake pipe pressure, the amount of change in engine speed, etc. can be used.

Embodiment An apparatus for performing an air-fuel ratio control method for an internal combustion engine as an embodiment of the present invention is shown in FIG. The configuration of the control circuit in the device shown in FIG. 2 is shown in FIG.

In the device shown in FIG. 2, 1 is a known electronically controlled fuel injection 6-cylinder spark ignition engine that is the power source of the automobile, 2 is a known intake air amount detection device that detects the amount of air taken into the engine 1, and 3 is a known rotation speed sensor S that detects the rotation speed of the engine L; 4 is a known water temperature sensor that measures the cooling water temperature of the engine L; 5 is an exhaust passage of the engine L; 6 is a known air-fuel ratio provided in the exhaust passage 5 It's Senna.

7 is an intake pipe of the engine l, 8 is a known electromagnetic fuel injection valve provided in the intake pipe 7, 9 is a throttle valve that controls the amount of air taken into the engine l, and 91 detects the movement of the throttle valve 9. Known throttle sensor, C0N
T is a control circuit that calculates the amount of fuel to be supplied to the engine l and operates the fuel injection valve 8.

When the engine is in a steady state, the amount of fuel supplied to the engine 1 is determined by the control circuit C0NT, the intake air amount detection device 2,
The basic fuel amount is determined from the detection signals of the rotational speed sensor 3 and the water temperature sensor 4, and the feedback correction amount determined from the signal of the air-fuel ratio sensor 6 is further corrected to determine the opening time of the fuel injection valve 8.

The control circuit C0NT is configured to perform transient fuel correction on the steady state fuel amount when the acceleration/deceleration state of the engine I is detected by the throttle sensor 91 or the intake air amount detector 2. As shown in FIG. 3, the control circuit C0NT includes a multiplexer i0 that receives signals from the intake air amount sensor 2 and the water temperature sensor 4 as an input system.
1° AD converter l 02% It has a shaping circuit 103 that receives the signal from the air-fuel ratio sensor 6, an input port 104 that receives the signal from the shaping circuit and the throttle sensor 91, and an input counter 105 that receives the signal from the rotation sensor 3. The control circuit also includes Nox 106, ROM107, CPU1
08, RAM109. It has an output counter 110 and a power driver 111.

The output of the power drive section 111 is supplied to the fuel injection valve 8.

As the control circuit C0NT, a micro combinator type circuit can be used, and for example, a Toyota TCC8 type circuit can be used. In the control circuit CONT,
An air-fuel ratio deviation detection function and a transient fuel correction function have been added.

The principle of operation of the device shown in FIG. 2 will be explained with reference to FIGS. 4-8. Figure 4 is a waveform diagram regarding the air-fuel ratio sensor signal.
FIG. 5 is an air-fuel ratio sensor signal calculation flowchart. Figure 6 is a waveform diagram explaining the situation of acceleration determination, and Figure 7 is LIM (Δ
FIG. 8 is a characteristic diagram showing the relationship between LIM (ΔQ2-N) and learning frequency.

When performing transient air-fuel ratio learning control based on the behavior of the basic injection amount correction value vV) determined in the process shown in Figs. 4 and 5 based on the signal of the air-fuel ratio sensor that detects engine exhaust gas components, As shown in Figure 6, it is necessary to detect the transient air-fuel ratio fluctuation D (A/F) from DV (Ei5-R) and determine whether the fluctuation occurs during acceleration.In this acceleration determination, Q/N A state in which the change ΔΦ in (amount of intake air per revolution) is greater than or equal to a predetermined acceleration boundary value LIM (ΔQ/N) is determined to be acceleration, and learning is performed. In other words, ΔQ/N≧LIM(Δ
When it is determined that the adjustment is correct when Q2iN), the learning accuracy improves as the LIM arm Q/N) increases, as shown in FIGS. 7 and 8. - LIM (jQ/N) cannot be set to an excessively large value because the learning frequency decreases as LIM (ΔQ/N) increases, but engine trouble due to learning malfunctions
Considering this, it is better to limit the acceleration amount judgment during learning to a certain extent above the acceleration of t to improve the learning accuracy. Also,
In this learning control, when it is determined that the amount has increased too much or not enough, the learned value can be changed immediately, but in order to improve learning accuracy, the learned value must be changed when the same judgment is made n times in a row (n≧2). By doing so, it is possible to significantly improve control accuracy by preventing learning values from being changed due to erroneous judgments. and the respective maximum deviation values D (A/F(LN)) to the rich side
, D (A/F (RCi() ), and the behavior of the air-fuel ratio sensor during acceleration/deceleration, that is, the time during which the air-fuel ratio sensor 6 during acceleration/deceleration detects the leanness and richness of the mixed gas, ''). The relationship between the duration time T (LN) and the deceleration rich duration time T (RCH) is shown in the waveform diagram of FIG. 9 and the characteristic diagram of FIG. 1O.

In Figure 9, ACC is acceleration, %DEC is deceleration, and 5(
6) represents the air-fuel ratio sensor signal.

An example of the air-fuel ratio deviation from the optimum air-fuel ratio is the deposit amount W (DEP) attached to the intake system and the air-fuel ratio firing deviation value D [A/F (LN)) during acceleration and deceleration.

The relationship of DCνF (RCH) is shown in FIGS. 11 and 12. It can be seen from FIGS. 9 to 12 that by measuring the lean duration TL6 during acceleration or the rich duration TR during deceleration, the value corresponding to the deposit amount can be detected. In investigating the data shown in Figures 9 to 12, a 5M-G type engine manufactured by Toyota Motor Corporation was used.

A schematic flowchart of the control program of the control circuit CONT is shown in FIG. This program is for performing electronically controlled fuel injection, and steps 5100 to 81
Consists of 08. Start at 8100, 8101
In this step, memory and output ports are initialized. 8
In step 102, the basic fuel injection amount is calculated from the intake air amount data Q, the engine rotation speed data N, and the water temperature sensor data θ7. At 8103, feedback control is performed using the signal from the air-fuel ratio sensor 6 so that the air-fuel ratio is constant, and the basic fuel injection amount is corrected.

8104 detects air-fuel ratio deviation during acceleration, and 5ios
Now, calculate the transient fuel correction ratio.

At 8106, one revolution of the engine is determined, and at 8107, for each revolution of the engine, the opening time of the fuel injection valve 8 is calculated from the basic fuel amount corrected by feedback control and the transient fuel correction ratio. Finally, a detailed flowchart of the air-fuel ratio deviation detection process in the flowchart of FIG. 13, which controls the fuel injection valve at 8108, is shown in FIG.
A detailed flowchart of transient fuel correction is shown in FIG.

As shown in Figure 14, for a certain period of time (for example, 32.7ms +
). As a method to detect air-fuel ratio deviation,
Comparing the output signal of the air-fuel ratio sensor 6 with a constant voltage level,
Detects the dilute (lean) state and rich (rich) state of the mixed gas, and calculates the lean duration T (LN) during acceleration.
and a method of measuring the rich duration time T (RCH).

For example, the influence of deposits occurs only when the cooling water temperature is low, and in order to make the estimation of the amount of deposits stable and accurate, 8202.8202'.

8203.5204, cooling water temperature less than 80'C, acceleration above a certain level and within 5 seconds after acceleration, engine rotation speed 90 Orpm ~
In the case of 2000 rpm, the lean duration time T (LN) and the rich duration time T (RCH) are measured. Further, in 8205, it is limited to feedback control so that rich and lean appear alternately.

In step 5206, it is determined whether it is rich or lean. For Lean 5
At 207, the lean time counter is incremented by 1 and T(
LN) is counted in units of 32.7 ms per year.

Next, in 8208, the value of the rich time counter is set to a constant value (
It is determined whether the rich time limit (rich time limit) has been exceeded, and if so, it is considered rich and the process proceeds to 8208-A. 8208-
When BC=1 in A, the previous discrimination is rich, so 5209
The rich correction counter is incremented by 1. On the other hand, when Bc=+io in 8208-A, since the previous determination was not rich, the rich correction counter is not updated and BC=+io in 8208-B.
1 and proceed to 8210. Next, in step 8210, the rich time counter is set to 0. If 8206 is determined to be rich, 8211 to 8214°8212-A,
At 8212-B, the rich time counter is increased by 1 and lean time is determined.

Deposit adhesion and peeling can be estimated from the values of the lean correction counter and rich correction counter determined in steps 8206 to 5214- described above. That is, it is possible to estimate a change in the engine from a normal state to an abnormal state and a return from an abnormal state to a normal state.

In the transient fuel correction shown in FIG.
Determine the amount of intake air Q/N for the rotation counter. At 5302, a determination is made to perform the following process at regular intervals, for example, every 32.7 ms.

In 5303, the correction coefficient 08 and the smoothing coefficient Cb are determined as functions of the rich correction counter and the lean correction counter 6. The smoothing correction coefficient ca and the smoothing coefficient Cb are set as values corresponding to the air-fuel ratio deviation during acceleration.

In 5304, Φ(g) was smoothed, (Q/N
) 1 can be requested by the following formula.

(vN)i = (Q/N)i-1+ (Q/N-(Q
/N)i-t)/Cb However, let (vN)l calculated 32.7 ms ago be (Q/N)i-1.

8305 K:j, -ite Q/N, ('Q/N
) i, Ca, and the cooling water temperature, the transient fuel correction ratio f(AEW) is calculated using the following formula.

t (AEW) = (Q/N-(Q/N)x) x
Ca XK Here, K is a correction ratio for engine cooling and is stored in the map in advance. Also, f(AEW) is
It takes both positive and negative values depending on the change in value. Correction is performed by multiplying the basic fuel amount by the transient fuel correction ratio f (AEW).

Therefore, as shown in Fig. 16, (when accelerating by opening the rethrottle (TH is throttle opening), C2)
(3) The (Q/N)i value also gradually increases, and (4) the transient fuel correction ratio f (AIW
) is increased with the waveform shown, (5) the fuel injection valve opening time U is determined, and fuel is supplied.

Also, if (6) the throttle is closed to decelerate, (7)
The ψ value decreases, (8) the (Q/N)l value also gradually decreases, and (9) the transient fuel correction ratio f (Aff) decreases in a waveform as shown in the figure. Then the fuel injection valve opening time U is determined and fuel is supplied. - An example of the operation results of the device shown in FIG. 2 is shown in FIG. 17 Q, ω). 17th
In Figures (4) and (6), the engine speed is 110
0Orp, and the cooling water temperature was 30°C.

Acceleration is performed by throttle operation, and the acceleration conditions are intake pressure [
The intake pressure suddenly increased from -400 lHgJ to -100 lHgJ. (4) shows the air-fuel ratio versus time when gasoline A is used. ω) shows the air-fuel ratio situation with respect to time when gasoline B is used, and shows the situation as a result of the learning control performed by the device in FIG.

As shown in Figure 17 (4), ω), the air-fuel ratio during acceleration was almost the optimum air-fuel ratio for gasoline A (10% distillation temperature 47°C, Reid vapor pressure 0.7211A); If gasoline B with different gasoline properties and poor volatility is used (10% distillation temperature 54℃, Reid vapor pressure 0.6KF15f), the air-fuel ratio during acceleration will be diluted, but the learning in the device shown in Figure 2 is not possible. As a result, it becomes possible to obtain the same air-fuel ratio characteristics as when gasoline A is used for about the seventh time. At this time, it is natural that if the amount of correction is increased, learning can be accomplished in an even smaller number of times.

Now, looking at FIGS. 7 and 8, step 820 is the limiting condition for detecting the air-fuel ratio deviation in FIG. 14.
2-A17) Acceleration amount boundary value LIM (ΔvN) and Figure 2 is a characteristic diagram showing the results of investigating the learning accuracy and learning frequency when learning was performed by driving the first mountain in LA ÷ 4 mode cold in the device. F, the amount of acceleration is the amount of change in intake air amount ΔQ/N (1
/re is detected and learning is performed when ΔΦ乍≧LIM (^ and N).

As can be seen from these characteristic diagrams, LIM (＾
By setting N) to 0.04, the learning accuracy is 9.
0% or more can be secured, and the learning frequency can be obtained as 7 times, making it possible to perform stable and accurate learning. However, in the present invention, LIM (ΔQ/N) is not particularly limited to 0.04, but can be set to 0.04 or more if learning accuracy is prioritized.

Effects of the Invention According to the present invention, when detecting an air-fuel ratio deviation, the air-fuel ratio deviation detection value when the acceleration/deceleration amount is a certain amount or more is made valid, or the air-fuel ratio deviation is detected continuously a certain number of times or more. In the air-fuel ratio deviation detected value, it is valid when the direction of the deviation is the same, and invalidated otherwise. Correction in the transient fuel correction is performed to stably and accurately detect the air-fuel ratio deviation and compensate for the air-fuel ratio deviation. The amount is adjusted, realizing more accurate transient air-fuel ratio learning control.

[Brief explanation of drawings]

FIG. 1 is a waveform diagram showing changes in air-fuel ratio during acceleration and deceleration before and after deposition of deposits, FIG. 2 is a diagram showing an apparatus for performing an air-fuel ratio control method for an internal combustion engine as an embodiment of the present invention, and FIG. , FIG. 2 is a diagram showing the configuration of a control circuit in the device, and FIG. 4 is a waveform diagram showing waveforms related to air-fuel ratio sensor signals. FIG. 5 is a flow chart of air-fuel ratio sensor signal calculation. Figure 6 is a waveform diagram explaining the situation of ore acceleration determination, Figure 7 is L
A characteristic diagram showing the relationship between IM (ΔQ/N) and learning accuracy. FIG. 8 is a characteristic diagram showing the relationship between LIM (ΔQ/N) and learning frequency. Figures 9 and 10 show air-fuel ratio behavior during acceleration and deceleration. , a waveform diagram and a characteristic diagram showing the relationship between the behavior of the air-fuel ratio sensor during acceleration and deceleration; FIGS. 13 is a flowchart showing the calculation flow in the device shown in FIG. 2; FIG. 14 is a flowchart showing details of the deposit amount corresponding value detection calculation; FIG. 15 is a flowchart showing details of transient fuel correction;
The figure is a waveform diagram showing the situation of fuel injection during deceleration, Figure 17 (4), @ is a diagram showing an example of the operation result of the device shown in Figure 2. (Explanation of symbols) ■...Engine, 2...Intake air amount detection device, 3.
... Rotation speed sensor, 4... Water temperature sensor, 5... Exhaust passage, 6... Air-fuel ratio sensor, 7... Intake pipe %8...
- Fuel injection valve, 9... Throttle valve, 91... Throttle sensor, C0NT... Control circuit. Patent Applicant Japan Auto Parts Research Institute Co., Ltd. Toyota Motor Corporation Patent Application Agent Patent Attorney Akira Aoki Patent Attorney Kazuyuki Nishidate Patent Attorney Masashi Matsushita Patent Attorney Akira Yamaguchi Masaya Nishiyama 4S Figure 6 Fig. 7 Fig. 8 -LIM (-Q/N) -LIM (=Q/N) Fig. 9 N510 (sec) Fig. 11 Figure 16 T)-1 1st ′ [Gasoline A] [Gasoline B] Before learning control 3rd time 5th time Learning completed (7 times 1)

Claims (1)

[Claims] 1. In determining the transient fuel correction amount at predetermined intervals according to the acceleration/deceleration state of the internal combustion engine and correcting the fuel lid supplied to the internal combustion engine with this correction amount, When the acceleration/deceleration amount of the internal combustion engine is above a predetermined acceleration/deceleration amount boundary value, the air-fuel ratio deviation from the optimum air-fuel ratio is considered valid and the air-fuel ratio deviation is detected, and when it is below the predetermined acceleration/deceleration amount boundary value, it is invalidated. An air-fuel ratio control method for an internal combustion engine, comprising: detecting an air-fuel ratio deviation; and adjusting a correction amount of transient fuel correction according to the air-fuel ratio deviation detected as valid. 2. The method according to claim 1, wherein the transient fuel correction is a transient fuel correction that determines a transient fuel correction amount at every predetermined time interval. 3. The method according to claim 1, wherein the transient fuel correction is a transient fuel correction that determines a transient fuel correction amount in synchronization with the rotation of the internal combustion engine. 4. The method according to claim 1, wherein the transient fuel correction is a transient fuel correction using an intake air amount as a correction amount determining factor. 5. The method according to claim 1, wherein the transient fuel correction is a transient fuel correction using throttle opening or intake pipe pressure as the correction amount determining factor. 6. The method according to claim 1, wherein the air-fuel ratio deviation detection is performed using an air-fuel ratio sensor. 7. The method according to claim 1, wherein the air-fuel ratio deviation is an air-fuel ratio deviation caused by deposits attached to the intake system of the internal combustion engine. 8. The method according to claim 1, wherein the air-fuel ratio deviation is an air-fuel ratio deviation caused by deposits attached to the nozzle part of an injector that supplies fuel to the internal combustion engine. 9. The air-fuel ratio 2. The method according to claim 1, wherein the deviation is an air-fuel ratio deviation resulting from variations in manufacturing of the intake air amount detection means for detecting the amount of intake air into the internal combustion engine or changes in characteristics due to changes over time. 10. The method of claim 1, wherein the air-fuel ratio deviation is an air-fuel ratio deviation resulting from manufacturing variations or changes over time of the internal combustion engine. 11. The air-fuel ratio deviation is an air-fuel ratio deviation resulting from variations or changes in the properties of the fuel used in the internal combustion engine;
A method according to claim 1.