JPH0251053B2 - - Google Patents

Description

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.

BACKGROUND OF THE INVENTION One type of air-fuel ratio control device for an engine is known in the 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 transient engine operating conditions indicative of demand;
responsive to the measured value of engine temperature and the detected transient engine operating condition, the first value being equal to the first value determined by the engine temperature and determined by the detected transient engine condition; means for generating a reinforcement boost signal having an initial value of 1 and increasing by a factor that varies toward unity at a rate determined by the temperature of the engine; and means for supplying fuel to the engine, 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 valve clearance and EFI, and deposits on the back of the cylinder intake valve, such as lubricating oil components and combustion Changes in characteristics due to sticky substances such as carbon particles derived from products, changes in characteristics due to changes in volatility due to variations in gasoline properties, etc. are not taken into consideration, and these changes over time of the engine and changes in the 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 There is a problem that drivability may deteriorate, or conversely, if highly volatile gasoline is used, the mixed gas becomes rich during acceleration, resulting in poor fuel efficiency and poor emissions.

FIG. 1 illustrates the fluctuations in the air-fuel ratio in this case, particularly when deposits are attached to the back surface of the intake valve. In Figure 1, A/F(O)
A/F (DEP) represents the change in the air-fuel ratio before the deposit is deposited, and A/F (DEP) represents the change in the air-fuel ratio after the deposit is deposited. ACC is the acceleration point, DEC is the deceleration point,
A/F (OPT) represents the optimum air-fuel ratio, A/F (LN) represents the lean side, and A/F (RCH) represents 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. Further, similar problems have also occurred due to variations in manufacturing of the engine and air flow meter and changes over time.

Furthermore, the 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. Reed vapor pressure and distillation characteristics are generally well-known numerical values that indicate the volatility of gasoline, but even when examining the properties of gasoline from a certain manufacturer, the Reid vapor pressure cannot be determined.
0.5Kg/cm ² ~ 0.86Kg/cm ² Also, the 10% distillation temperature is 40 ~
It varies widely at 58℃, and the air-fuel ratio characteristics during transient times change greatly due to changes in volatility due to differences in gasoline properties. 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, since the above-mentioned type of device does not have a means to optimize the air-fuel ratio during acceleration and deceleration, if the engine changes over time such as deposits, or if gasoline with poor volatility is used, During acceleration, the air-fuel ratio becomes lean, resulting in poor drivability such as sluggishness, and during deceleration, the air-fuel ratio becomes richer, resulting in poor emissions and poor fuel efficiency.

Object of the Invention One object of the present invention is to calculate the difference between correction amount determining factors corresponding to intake conditions such as intake air amount per revolution, intake pipe negative pressure, throttle opening, etc. and their smoothed values at predetermined intervals. The purpose is to form a transient correction pattern in which the damping rate gradually decreases by taking the following values, and to perform air-fuel ratio control in which optimum correction is performed without rich/lean spikes.

Another object of the present invention is to detect rich/lean spikes with high sensitivity when transient conditions change due to changes over time, etc. by performing air-fuel ratio control that performs this optimal correction, to quickly learn, and to The objective is to improve the controllability of the temporal air-fuel ratio.

Structure of the Invention In the present invention, when an internal combustion engine is accelerating or decelerating, a transient fuel correction amount is determined at predetermined intervals according to the acceleration/deceleration state of the internal combustion engine, and the transient fuel correction amount is used to determine the internal combustion engine. In an air-fuel ratio control method for an internal combustion engine that corrects the amount of fuel supplied to the engine, the air-fuel ratio deviation from the optimum air-fuel ratio during acceleration and deceleration of the internal combustion engine is detected using the output of an air-fuel ratio sensor provided in the internal combustion engine. Then, in accordance with the detected air-fuel ratio deviation, the transient fuel correction amount obtained from the difference between the correction amount determining factor amount corresponding to the intake state of the internal combustion engine and its smoothing amount is corrected, and thereby the transient fuel correction amount is adjusted during acceleration and deceleration. Provided is an air-fuel ratio control method for an internal combustion engine, characterized in that the air-fuel ratio of the mixed gas fuel is prevented from deviating from the optimum air-fuel ratio.

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 engine 1
4 is a known water temperature sensor that measures the cooling water temperature of the engine 1; 5 is an exhaust passage of the engine 1; 6 is an exhaust passage 5;
This is a well-known air-fuel ratio sensor installed in the

7 is an intake pipe of the engine 1, 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 1, and 91 is a sensor that detects the movement of the throttle valve 9. A well-known throttle sensor CONT is a control circuit that calculates the amount of fuel to be supplied to the engine 1 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 CONT as a basic fuel amount from the detection signals of the intake air amount detection device 2, the rotation speed sensor 3, and the water temperature sensor 4. The feedback correction amount obtained from the signal of the air-fuel ratio sensor 6 is corrected to obtain the valve opening time of the fuel injection valve 8.

Also, the control circuit CONT is the throttle sensor 91
Alternatively, when the acceleration/deceleration state of the engine 1 is detected by the intake air amount detector 2, a transient fuel correction is performed on the fuel amount determined during the steady state.

As shown in FIG. 3, the control circuit CONT is
As an input system, a multiplexer 101 receives signals from the intake air amount sensor 2 and the water temperature sensor 4;
AD converter 102 , shaping circuit 103 that receives signals from air-fuel ratio sensor 6 , input port 1 that receives signals from the shaping circuit and throttle sensor 91
04, has an input counter 105 that receives a signal from the rotation sensor 3. The control circuit also connects the bus 106,
It has a ROM 107, a CPU 108, a RAM 109, an output counter 110, and a power driver 111. The output of the power drive unit 111 is the fuel injection valve 8
supplied to

As the control circuit CONT, a microcomputer type circuit can be used, for example, a Toyota TCCS type circuit can be used. The control circuit CONT has an air-fuel ratio deviation detection function and a transient fuel correction function added.

The air-fuel ratio behavior during acceleration/deceleration, that is, the maximum deviation value D[A/
F(LN)], D[A/F(RCH)], and the behavior of the air-fuel ratio sensor during acceleration/deceleration, that is, the time during which the air-fuel ratio sensor 6 detects the leanness and richness of the mixed gas during acceleration/deceleration, that is, during acceleration. The relationship between the lean duration time T (LN) and the deceleration rich duration time T (RCH) is shown in the waveform diagram of FIG. 4 and the characteristic diagram of FIG. 5. In FIG. 4, ACC represents acceleration, DEC represents deceleration, and S(6) represents the air-fuel ratio sensor signal.

As an example of the air-fuel ratio deviation from the optimum air-fuel ratio, the amount of deposits attached to the intake system W (DEP) and the maximum air-fuel ratio deviation value D [A/F (LN)] during acceleration and deceleration,
The relationship between D [A/F (RCH)] is shown in FIGS. 6 and 7. It can be seen from FIGS. 4 to 7 that by measuring the lean duration TL during acceleration or the rich duration TR during deceleration, it is possible to detect the value corresponding to the deposit amount. In investigating the data shown in Figures 4 to 7, 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 consists of steps S100 to S108. Starts in S100, and in S101, memory,
Initialize the input/output ports. In S102, a basic fuel injection amount is calculated from intake air amount data Q, engine rotation speed data N, and water temperature sensor data θ _W. In S103, the basic fuel injection amount is corrected by performing feedback control using the signal from the air-fuel ratio sensor 6 so that the air-fuel ratio remains constant.

In S104, the air-fuel ratio deviation during acceleration is detected,
In S105, a transient fuel correction ratio is calculated. S
106, it is determined that the engine is rotating once, and the engine 1
For each rotation, in S107, the opening time of the fuel injection valve 8 is calculated from the basic fuel amount corrected by the feedback control and the transient fuel correction ratio, and the fuel injection valve is controlled in S108. A detailed flowchart of the air-fuel ratio deviation detection process in the flowchart of FIG. 8 is shown in FIG. 9, and a detailed flowchart of the transient fuel correction is shown in FIG. 10.

In the air-fuel ratio deviation detection process shown in FIG.
As shown in S201, for a certain period of time (for example, 32.
Processing is performed every 7ms). As a method of detecting the air-fuel ratio deviation, the output signal of the air-fuel ratio sensor 6 is compared with a constant voltage level, and two values of a lean state and a rich state of the mixed gas are detected, and lean continuation during acceleration is detected. A method of measuring time T (LN) and rich duration T (RCH) is used.

For example, the influence of deposits occurs only when the cooling water temperature is low, and in order to make it easier to estimate the amount of deposits, in S202, S203, and S204, the cooling water temperature is less than 80°C, within 5 seconds after acceleration, and the engine speed is 900 rpm or more. Measure lean duration time T (LN) and rich duration time T (RCH) at 2000 rpm.
Also, rich and lean appear alternately, S20
5, it is limited to during feedback control.

Rich or lean is determined in S206. In the case of lean, in S207, the lean time counter is incremented by 1 and T (LN) is counted in units of 32.7 ms.
Next, in S208, it is determined whether the value of the rich time counter exceeds a certain value (rich time limit), and if it does, the rich correction counter is incremented by 1 in S209. Next, in step S210, the rich time counter is set to 0. If it is determined in S206 that the time is rich, the rich time counter is incremented by 1 and lean time is determined in the same manner in S211 to S214.

Deposit adhesion and peeling can be estimated from the values of the lean correction counter and rich correction counter obtained in S206 to S214 described above. That is,
It is possible to estimate the change of 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.
At 301, the intake air amount signal Q from the intake air amount detection device 2 and the rotation speed signal N from the rotation speed detection device 3 are detected.
The intake air amount Q/N per engine revolution is determined from . In S302, a determination is made to perform the following process at regular intervals, for example, every 32.7 ms.

In S303, the correction coefficient C _a and the smoothing coefficient C _b are determined as functions of the rich correction counter and the lean correction counter. In other words, the correction coefficient C _a ,
Find the smoothing coefficient C _b as a value corresponding to the air-fuel ratio deviation during acceleration.

In S304, (Q/N) _i , which is obtained by smoothing Q/N, is obtained from the following formula.

(Q/N) _i = (Q/N) _i-1 + {Q/N-(Q/N) _i-1 }/ _Cb However
Let (Q/N) _i calculated 32.7ms ago be (Q/N) _i-1 .

In S305, the Q/N, (Q/N) _i , Ca,
The transient fuel correction ratio f (AEW) is calculated from the value K determined by the cooling water temperature and the cooling water temperature using the following equation.

f(AEW) = {Q/N-(Q/N) _i }×Ca×K Here, K is the correction ratio for engine cooling, which is stored in the map in advance, and f(AEW)
takes both positive and negative values depending on the change in Q/N. Correction is performed by multiplying the basic fuel amount by the transient fuel correction ratio f (AEW).

Therefore, as shown in Fig. 11, (1) when the throttle is opened and the engine is accelerated (TH is the throttle opening), (2) the above Q/N value also increases, and (3) the above (Q/N )
_{The i} value also gradually increases, and (4) transient fuel correction ratio f
(AEW) 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 Q/N value decreases, (8) the (Q/N) _i value also gradually decreases, and (9) the transient fuel correction ratio f (AEW) decreases with a waveform as shown in the figure. , (10) 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 FIGS. 12A and 12B. In FIGS. 12A and 12B, the engine speed was 1000 rpm and the cooling water temperature was 30°C. Acceleration was performed by throttle operation, and the acceleration condition was a sudden increase in intake pressure from ``-400mmHg'' to ``-100mmHg.'' A represents the air-fuel ratio over time when gasoline A is used. B represents the state of the air-fuel ratio with respect to time when gasoline B is used, and represents the state as a result of learning control performed by the device in FIG.

As shown in Figure 12A and B, the air-fuel ratio during acceleration was almost the optimum air-fuel ratio for gasoline A (10% distillation temperature 47°C, Reid vapor pressure 0.72 kg/cm ³ ); If gasoline B with different properties and poor volatility is used (10% distillation temperature 54℃, lead vapor 0.6Kg/cm ³ ), 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 air-fuel ratio characteristics similar to those obtained 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.

In carrying out the present invention, various modifications can be made in addition to the above-described embodiments. For example, in the embodiment described above, step S302
As shown in Figure 13, the calculation of (Q/N) _i was performed at regular intervals (32.7ms), but instead, as shown in the flowchart of Figure 13, the calculation of (Q/N) _i was performed by the engine. It can also be performed synchronized with the rotation, for example, every rotation of the engine.

In FIG. 13, Q/N is calculated in S401, and determination is made for each rotation of the engine in S402. In S403, the correction coefficient Ca and the smoothing coefficient Cb are determined as functions of the rich correction counter and the lean correction counter. In other words, the correction coefficient
Calculate Ca and smoothing coefficient Cb as values corresponding to the air-fuel ratio deviation during acceleration.

In S404, (Q/N) _j obtained by smoothing Q/N is obtained from the following equation.

(Q/N) _j = (Q/N) _j-1 + {Q/N-(Q/N)
_j
-1 }/Cb However, (Q/N) _j calculated before one revolution of the engine is set as (Q/N) _j-1 .

In S405, the Q/N, (Q/N) _j , Ca,
The transient air-fuel ratio correction ratio f' (AEW) is calculated using the following equation from the value K' determined by the temperature and the cooling water temperature.

f'(AEW)={Q/N-(Q/N) _j }×Ca×K' Correction is performed by multiplying the basic fuel amount by this f'(AEW).

By determining the above (Q/N) _j in synchronization with the engine rotation, the number of engine combustion cycles to which the increase/decrease due to the transient air-fuel ratio correction ratio f' (AEW) contributes is the same regardless of the engine rotation speed. They are almost the same under acceleration conditions. Therefore, it is possible to prevent the air-fuel ratio from fluctuating during transient periods under various engine conditions.

Furthermore, in the above-mentioned embodiment, air-fuel ratio deviation detection is performed in S2.
In 03, the period is limited to 5 seconds after acceleration, but as can be seen from FIGS. 4 and 5, this can be detected by measuring T (LN) and T (RCH) during deceleration.

Furthermore, in the above-mentioned embodiment, the amount is increased based on the intake air amount Q/N and its smoothing amount as the correction amount determining factor, but this is based on other intake pipe negative pressure values, throttle opening, etc. , the amount may be increased based on the amount of annealing.

Effects of the Invention According to the present invention, the difference between correction amount determining factors corresponding to intake conditions such as intake air amount per revolution, intake pipe negative pressure, throttle opening, etc. and its smoothed value is calculated at predetermined intervals. As a result, a transient correction pattern in which the damping rate gradually decreases is formed, and air-fuel ratio control can be performed in which optimum correction is performed without rich/lean spikes.

Further, according to the present invention, by performing air-fuel ratio control that performs this optimal correction, rich/lean spikes when the transient state changes due to changes over time etc. are detected with high sensitivity, and learning is performed quickly. Controllability of the transient air-fuel ratio can be improved.

Furthermore, according to the present invention, deviations from the optimum air-fuel ratio of the mixed gas during acceleration and deceleration due to deposits on the back surface of the intake valve, clogging of the injector, and changes over time in the engine and intake air amount detection device are prevented. This prevents the air-fuel ratio from diluting during acceleration,
It is possible to improve drivability while preventing deterioration in emissions and fuel efficiency.

[Brief explanation of the drawing]

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 the control circuit in the device, Figs. 4 and 5 are waveform diagrams and characteristic diagrams showing the relationship between the air-fuel ratio behavior during acceleration/deceleration and the behavior of the air-fuel ratio sensor during acceleration/deceleration, and Fig. 6 , Figure 7 is a structural diagram and characteristic diagram showing the relationship between the amount of deposits attached to the intake system and the behavior of the air-fuel ratio during acceleration and deceleration.
The figure is a flowchart showing the calculation flow in the device shown in FIG.
Fig. 9 is a flowchart showing the details of the deposit amount corresponding value detection calculation, Fig. 10 is a flowchart showing the details of transient fuel correction, Fig. 11 is a waveform chart showing the fuel injection situation during deceleration, and Fig. 12A. , B are diagrams showing an example of the operation results of the apparatus shown in FIG. 2, and FIG. 13 is a calculation flowchart showing a modification of the calculation flow in FIG. 10. Explanation of symbols, 1... 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, CONT...
control circuit.

Claims (1)

[Claims] 1. During acceleration or deceleration of the internal combustion engine, a transient fuel correction amount is determined at predetermined intervals according to the acceleration/deceleration state of the internal combustion engine, and the transient fuel correction amount is used to control the internal combustion engine. An air-fuel ratio control method for an internal combustion engine that corrects the amount of fuel supplied to an internal combustion engine, which detects an air-fuel ratio deviation from an optimal air-fuel ratio during acceleration and deceleration of the internal combustion engine using the output of an air-fuel ratio sensor provided in the internal combustion engine. , Corrects the transient fuel correction amount obtained from the difference between the correction amount determining factor amount corresponding to the intake state of the internal combustion engine and its smoothing amount in accordance with the detected air-fuel ratio deviation, and thereby corrects the transient fuel correction amount during acceleration and deceleration. An air-fuel ratio control method for an internal combustion engine, characterized in that the air-fuel ratio of a mixed gas fuel is prevented from deviating from an optimum air-fuel ratio. 2. The transient fuel correction is a transient fuel correction that determines a transient fuel correction amount at each predetermined time interval.
A method according to claim 1. 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 a correction amount determining factor. 6. Claim 1, wherein the smoothing calculation of the correction amount determining factor amount is a smoothing calculation of the correction amount determining factor amount, in which a smoothing calculation of the amount that changes due to acceleration/deceleration is performed at fixed time intervals. Method described. 7 The correction amount determining factor amount and the smoothing calculation of this amount are the smoothing calculations of the correction amount determining factor amount in which a smoothing calculation of the amount that changes due to acceleration and deceleration is performed in synchronization with the engine rotation of the internal combustion engine. A method according to claim 1.