JPS6017237A - Air-fuel ratio control method for internal-combustion engine - Google Patents

Abstract

PURPOSE:To improve the drivability by detecting the differential air-fuel ratio from the optimal level under deceleration, then correcting the reduced fuel on the basis of said detected level thereby preventing deterioration of emission and fuel consumption. CONSTITUTION:Under steady state of engine, the amount of fuel to be fed to an engine 1 is determined by a control circuit CONT from signals from a suction air flow detector 2, rotation sensor 3 and water temperature sensor 4, then the feedback correction obtained from a signal from an air-fuel ratio sensor 6 is corrected to produce the valve-open time of a fuel injection valve 8. When the deceleration state of engine 1 is detected by a throttle sensor 91 or a suction air flow sensor 2, the control circuit CONT will further reduce the amount of fuel. Consequently, deterioration of emission and fuel consumption can be prevented resulting in improvement of the drivability.

Description

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

DESCRIPTION OF THE PREFERRED EMBODIMENTS 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 reinforcing boost signal, which has an initial value determined by the detected engine transient and is increased by a factor that varies toward unity at a rate determined by the engine temperature;
and means for fueling the engine in accordance with the base fuel signal and the reinforcement boost signal, thereby fueling the engine on demand during both steady state and transient conditions of the engine. This device is used not only in the steady state of the engine but also in the transient state.In the above-mentioned type of device, changes in the engine over time, such as characteristic changes due to deposits on the injector nozzle in valve clearance and EFI, and changes in the cylinder intake valve. It does not take into account changes in characteristics due to deposits that adhere to the back surface, that is, sticky substances such as carbon particles derived from lubricating oil components and combustion products, and the air-fuel ratio during acceleration due to aging of the engine. Since there is no means to detect the dilution of the gas mixture, it is difficult to avoid dilution of the gas mixture during acceleration, and this may cause deterioration of drivability such as sluggishness during acceleration. was there.

The fluctuations in the air-fuel ratio in this case, particularly when deposits stick to the back surface of the intake valve, are illustrated in FIG. In Fig. 1, A/F (0) represents the change in 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, Iv'F (
OPT) indicates the optimum air-fuel ratio, A/F (LN) indicates the lean side, and A/F (RCH') indicates the rich side. Also, regarding the injector blinder. In steady state, it can be corrected by feedback from the air-fuel ratio sensor, but during acceleration and deceleration, the same problem occurs 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 summer and winter gasoline. Reed vapor pressure and distillation properties are generally well-known numerical values that indicate the volatility of gasoline, but when we look at the properties of gasoline from different manufacturers, the Reid vapor pressure is 0.5 Kylcl ~ 0.86 K.
91cr&, the temperature during 10% distillation also varies from 40 to 58°C, and the air-fuel ratio characteristics during transient changes greatly due to changes in volatility due to differences in gasoline properties. In the conventional system, no consideration is given to changes in air-fuel ratio 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 deceleration, if the engine changes over time such as deposits, or if gasoline with poor volatility is used, During deceleration, the air-fuel ratio becomes too rich, leading to poor transmission and poor fuel efficiency.

Purpose of the Invention The main purpose of the present invention is to prevent the enrichment of the air-fuel ratio during deceleration, based on the concept of adjusting the fuel loss during deceleration by correcting the fuel loss during deceleration, in view of the problems with the conventional type described above. The objective is to improve drivability while preventing deterioration of emissions and fuel efficiency.

Furthermore, the present invention prevents air-fuel ratio deviation from the optimum air-fuel ratio of the mixed gas during deceleration due not only to changes over time but also to differences in gasoline properties, variations in engine manufacturing, and variations in airflow meter manufacturing. As an ancillary purpose.

Structure of the Invention In the present invention, in order to detect deceleration of the internal combustion engine and reduce fuel during deceleration, an air-fuel ratio deviation from an optimum air-fuel ratio during deceleration of the internal combustion engine is detected, and the air-fuel ratio deviation is detected. There is provided an air-fuel ratio control method for an internal combustion engine, which is characterized in that the value of the fuel reduction during deceleration is corrected based on the above.

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 C0NT in the device shown in FIG. 2 is shown in FIG. In the device shown in FIG. 2, ■ 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;
Reference numeral 3 denotes a known rotation speed sensor that detects the engine 10 rotation speed, 4 a known water temperature sensor that measures the cooling water temperature of the engine and engine 1, 5 a known exhaust passage of the engine 1, and 6 a known engine speed sensor installed in the exhaust passage 5. It is an air fuel ratio sensor.

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 detects the movement of the throttle valve 9. Known throttle sensor, C0NT
calculates the amount of fuel to be supplied to the engine 1 and injects the fuel injector 8.
This is a control circuit that operates the

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 rotation speed sensor 3 and the water temperature sensor 4, and the fuel injection amount is corrected based on the signal of the air-fuel ratio sensor 6, and the valve opening time of the fuel injection valve 8 is determined.

Further, the control circuit C0NT is configured so that when the throttle sensor 91 or the intake air amount detection device 2 detects a deceleration state of the engine 1, the fuel amount during deceleration is reduced to a value greater than the amount of fuel determined during steady state.

As shown in FIG. 3, the control circuit C0NT includes, as an input system, a multiplexer 101 that receives signals from the intake air amount sensor 2 and the water temperature sensor 4, and an AD converter 10.
2. It has a shaping circuit 03 that receives the signal from the air-fuel ratio sensor 6, an input port 104 that receives the signal from the shaped circuit and the throttle sensor 91, and an input counter 105 that receives the signal from the rotation sensor 3. The control circuit also connects bus 106
, a ROM 107, a CPU 108, a RAM 109, 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 microcomputer type circuit can be used, for example, a Toyota TCC8 type circuit can be used. In the control circuit C0NT,
An air-fuel ratio deviation detection function and a deceleration fuel reduction correction function have been added.

The air-fuel ratio behavior during acceleration/deceleration, that is, the maximum deviation value D (A/FCLN>
E, D CA/F (RCH)), and the behavior of the air-fuel ratio sensor during acceleration and deceleration, that is, the time during which the air-fuel ratio sensor 6 detects the lean and rich mixture gas during acceleration and deceleration, and the lean duration time during acceleration T (LN) and the rich continuation time T (RCH) during deceleration are shown in the waveform diagram in Figure 4 and the characteristic diagram in Figure 5.
DEC represents deceleration, and 5 (6) represents the air-fuel ratio sensor signal. As an example of the air-fuel ratio deviation from the optimum air-fuel ratio, the deposit amount W(DEP) attached to the intake system and the maximum air-fuel ratio deviation value DCA/F(LN)), D(A/F(
RCH)) is shown in FIGS. 6 and 7.

From Figures 4 to 7, lean duration time T (LN
) or by measuring the rich continuation time T (RCH) during deceleration, it is found that the value corresponding to the deposit amount can be detected. In addition, when adjusting the data 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 C0NT is shown in FIG. This program is for performing electronically controlled fuel injection, and steps S1.00 to S51
It will be 08 years old. Start at 5100, 5101
Initialize memory and input/output ports. 5
In step 102, the basic fuel amount is calculated from the intake air amount data Q, the engine speed data N, and the water temperature sensor data θW. In 5103, using the signal of the fuel-fuel ratio sensor 6,
Feedback control is performed to correct the basic fuel amount so that the air-fuel ratio remains constant. In steps 5104 and 5105, the amount corresponding to the fuel loss during initial deceleration and the deposit is detected, and the amount corresponding to the deposit is corrected to the fuel loss during initial deceleration. In step 5106, one revolution of the engine is determined, and in step 5107, the valve opening time of the fuel injection valve 8 for each revolution of the engine is calculated from the basic fuel amount corrected by feedback control and the fuel loss during deceleration. Finally, in step 5108, fuel injection valve control is performed.

FIG. 9 shows a detailed flowchart of the air-fuel ratio difference detection process 5104, and FIG. 10 shows a non-detailed flowchart of the calculation process of the initial deceleration fuel loss and the deceleration fuel loss correction for this loss.

The deceleration correction shown in FIGS. 9 and 10 is performed every fixed period of time, for example, every 32.7 mS, as shown at 5201. 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 the leanness (
A method is used in which two values, a lean state and a rich state, are detected and the lean duration time T (LN) and rich duration time T (RCH) during deceleration are measured.

For example, the influence of deposits only occurs when the cooling water temperature is low, and in order to make it easier to estimate the deposit arrival time,
For 8202, 8203, and 5204, the cooling water temperature is less than 80℃, within 5 seconds after deceleration, and the engine rotation speed is 90Orpm ~ 2
In the case of 000 rpm, the limp duration time T' (LN) and the rich duration time T (RCH) are measured.

Also, in 5205, rich and lean appear alternately,
Limited to feedback control.

At 8206, rich and lean are determined. For Lean 5
At 207, the lean time counter is incremented by 1 and T(
LN) is counted in 32.7 ms units. Next, in 8208, it is determined whether the value of the rich time counter exceeds a fixed value, that is, the rich time limit. If it does, in 5209, the rich correction counter is incremented by 1. Next, in step 82.10, the time counter is set to O.

5. ．． Similarly, if it is determined to be rich in 8206, 5211~
At 5214, 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 5206 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 FIG. 10, at 8301, the intake air amount Q/' per one engine revolution is obtained by combining 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.
Calculate the rate of change Δ(Q/N) of N.

If the Δ(Q/N) is negative, the engine is decelerating. Therefore, in step 5302, if Δ(Q/N) is negative and equal to or greater than a certain value, it is regarded as deceleration, and the process proceeds to step 5303.

5303, the fuel loss value during deceleration is expressed as the cooling water temperature, Δ(Q/
N), as a function of the lean correction counter and rich correction counter. Basically, the unit Δ(
Q/N) Naoshi's weight loss ratio is stored in the map in advance, and the weight loss ratio for the water temperature is taken out and Δ(Q/N'')
The value of fuel loss during deceleration is calculated by multiplying by the values of the lean correction counter and rich correction counter. This reduction value is the initial value at the time of deceleration detection.

At 5304 and 5305, a constant value is subtracted from the fuel loss value during deceleration every engine revolution, and the value is attenuated to 0. Therefore, as shown in FIG. (2) the Q/N value also decreases, (3) the fuel deceleration ratio R during deceleration is decreased in the waveform shown in the figure, and (4) the fuel injector opening time U increases. Determined and fueled.

In carrying out the present invention, various modifications of the above-described embodiments can be made. for example.

In the embodiment described above, the initial value of the fuel loss value during deceleration when a deposit is attached is changed depending on the values of the lean correction counter and the rich correction counter. As shown in Flowchart 1, the weight loss during deceleration is determined only by the water temperature θW and Δ(Q/N'), regardless of deposit adhesion.

In addition, it is also possible to perform a correction deceleration reduction when a deposit is deposited, which is activated only when a deposit is deposited.

In FIG. 12, when deceleration is detected in 5402, the deceleration weight loss value is calculated as the cooling water temperature and Δ(Q/N) in 8403.
To confuse. Next, in step 8404, a corrected deceleration fuel loss value at the time of deposit is calculated.

In this calculation, a deceleration fuel reduction correction value corresponding to the deposit amount is calculated as a function of four variables: cooling water temperature, lean correction counter value, rich correction counter value, and Δ(Q/N). Each rotation of the engine, a constant value ('It + 3't) is subtracted from each of the deceleration loss value and the deceleration loss correction value at the time of deposit deposition, and the deceleration is attenuated to O. Reduction is performed by multiplying this deceleration reduction ratio by the deceleration reduction correction reduction ratio at the time of deposit adhesion to the basic injection amount.

In the above, we have explained how to correct air-fuel ratio deviations due to deposits, but there are also problems such as clogging of EFI injectors, deviations in air flow meter characteristics, deviations in speed density pressure sensor characteristics, and characteristics when using gasoline with different volatility. It is also possible to deal with deviations.

In the device shown in Figure 2, the air-fuel ratio deviates from the optimum air-fuel ratio of the mixed gas during deceleration due to deposits on the back of the intake pulp during cold, changes in the characteristics of the injector and air flow meter, and changes in the properties of gasoline. This prevents a decrease in engine exhaust gas emissions and fuel efficiency. In addition, the device shown in Figure 2 prevents air-fuel ratio deviation from the optimum air-fuel ratio of the mixed gas during deceleration due to not only the above-mentioned changes over time, but also variations in engine manufacturing, air flow meter manufacturing, and gasoline properties. can.

Effects of the Invention According to the present invention, enrichment of the air-fuel ratio during deceleration is prevented,
Deterioration of emissions and fuel efficiency is prevented, and drivability can be improved.

[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 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 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. Characteristic diagram, Figure 8 is a flowchart showing the calculation flow in the device shown in Figure 2, Figure 9 is a flowchart showing details of the deposit amount corresponding value detection calculation, f, Figure 16 is a flowchart showing details of the calculation of fuel loss at initial deceleration. Flowcharts: FIG. 11 is a waveform chart showing the state of fuel injection during deceleration, and FIG. 12 is a flowchart showing the calculation flow of the increase during acceleration and the correction when deposits are attached in another embodiment. (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. Figure 6 Rod 7 1 → W (DEP) Figure 10 Figure 11 T) (Continued from page 1 0 Inventor: Kunihiko Sato Toyota Motor Corporation, 1 Toyota-cho Toyota Town, Japan Applicant: Toyota Motor Corporation Company 1 Toyota-cho, Toyota City

Claims (1)

[Scope of Claims] 1. In detecting deceleration of the internal combustion engine and reducing fuel during deceleration, υ detects an air-fuel ratio deviation from the optimum air-fuel ratio during deceleration of the internal combustion engine, and detects the air-fuel ratio deviation. 1. A method for controlling an air-fuel ratio of an internal combustion engine, comprising: correcting a value of the fuel reduction during deceleration based on the value of the fuel reduction during deceleration. 2. The method according to claim 1, wherein the air-fuel ratio deviation is detected in the form of air-fuel ratio deviation detection using an air-fuel ratio sensor. Claim 1, which is a correction of the fuel loss value during deceleration by correcting one or more parameters that determine the fuel loss according to the air-fuel ratio deviation determined by the air-fuel ratio deviation detection.
The method described in section. 4. The correction of the fuel loss value during deceleration is performed by adjusting one or more parameters among the parameters that determine the correction value of the fuel loss value during deceleration according to the air-fuel ratio deviation requested by the air-fuel ratio deviation detection. Claim 1 is a correction of the fuel reduction value during deceleration by simultaneously operating the reduction during deceleration and the reduction to which the fuel reduction value during deceleration has been corrected during deceleration of the internal combustion engine. the method of. 5. The method according to claim 1, wherein the air-fuel ratio deviation is an air-fuel ratio deviation caused by deposits arriving in the intake system of the internal combustion engine. 6. The method according to claim 1, wherein the air-fuel ratio deviation is an air-fuel ratio deviation caused by deposits attached to a nozzle of an injector that supplies fuel to the internal combustion engine. 7. Claim 1, wherein the air-fuel ratio deviation is an air-fuel ratio deviation resulting from variations in the manufacturing process 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. 8. The method according to 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. 9. The air-fuel ratio deviation is an air-fuel ratio difference resulting from variations or changes in the properties of the fuel used in the internal combustion engine;
A method according to claim 1.