JPH0129977B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in means for performing learning correction in an air-fuel ratio feedback control method using an air-fuel ratio sensor.

[Prior art]

In order to purify exhaust gas emitted from internal combustion engines, there is a wide range of methods for improving the purification efficiency of three-way catalysts by using air-fuel ratio sensors to feedback control the air-fuel ratio to near the theoretical air-fuel ratio. It is used.

Furthermore, during air-fuel ratio feedback control, so-called learning control is being introduced to detect errors in sensors, actuators, etc. and correct control errors in the entire control system.

Figure 1 shows the configuration of a conventional air-fuel ratio control method using an electronically controlled fuel injection device, where 1 is an internal combustion engine, 2 is an injector that supplies fuel to the internal combustion engine 1, and 3 is an internal combustion engine. 1 is an air flow sensor that detects the amount of air taken in, 4 is an air cleaner, 5 is a throttle valve that adjusts the amount of air taken into the internal combustion engine 1, 6 is an intake pipe, and 7 is the temperature of water that cools the internal combustion engine 1. 8 is a control device that inputs the operating state of the internal combustion engine from the air flow sensor 3 or the water temperature sensor 7, etc., calculates the required amount of fuel, and controls the drive pulse width applied to the injector 2; an exhaust pipe; 10 is an air-fuel ratio sensor provided in the exhaust pipe 9 and generates an output corresponding to the air-fuel ratio based on the components of exhaust gas; 11 is a fuel tank;
12 is a fuel pump for supplying fuel to the injector 2, and 13 is a fuel pressure regulator for maintaining the pressure of the fuel supplied to the injector 2 constant.

In the above configuration, the control device 8 uses the amount of intake air obtained by the air flow sensor 3 as main input information, and displays the operating state of the internal combustion engine, such as the signal of the water temperature sensor 7 or the signal of the engine rotation speed (not shown). The amount of fuel to be supplied to the internal combustion engine 1 is calculated based on the parameters, and the result is output as the drive pulse width of the injector 2.

Therefore, the internal combustion engine 1 is operated at a desired air-fuel ratio, but in order to efficiently purify the exhaust gas,
It is essential to accurately control the air-fuel ratio to near the theoretical air-fuel ratio.

However, since the sum of errors of the air flow sensor 3, injector 2, etc. is not small enough, feedback control using the air-fuel ratio sensor 10 is required.

As shown in FIG. 3, the characteristics of the air-fuel ratio sensor 10 are such that when the air-fuel ratio reaches the theoretical air-fuel ratio, the level of the voltage it outputs is reversed.

Conventionally, it has been widely practiced to feedback the air-fuel ratio as shown in FIG. 4b using the signal output from the air-fuel ratio sensor 10 as described above.

Also, air flow sensor 3 or injector 2
Recently, learning control has been introduced, which detects errors or secular changes in components such as air-fuel ratios as deviations during feedback control of the air-fuel ratio, and corrects them based on the results.

FIG. 4 shows an operating waveform diagram, and FIG. 5 shows a control procedure including learning control.

In FIG. 5, in step 101, a basic fuel injection amount _{Q f that} is proportional to the intake air amount information Q a from the air flow sensor 3 is calculated. Step 10
2, the RAM of the control device 8 is set to the basic fuel injection amount Q _f .
83 by the stored learning value C _L to calculate the corrected fuel injection amount Q ₁ . In step 103, it is determined whether or not the air-fuel ratio sensor 10 is active based on the output signal of the air-fuel ratio sensor 10. If it is not active, the process moves to open loop control, and if it is active, the process moves to step 104. In step 104, it is determined whether the output signal of the air-fuel ratio sensor 10 is rich or lean, and if it is rich, the output signal of the air-fuel ratio sensor 10 is integrated in step 105 to obtain an integral coefficient _CFB of a feedback smaller than 1. If lean, the output signal of the air-fuel ratio sensor 10 is integrated in step 106 to obtain an integral coefficient of feedback greater than 1.
Find C _FB . In step 107, step 1
The final fuel injection amount _Q2 is calculated by multiplying the feedback integral coefficient _CFB obtained in 05 or 106 by the above fuel injection amount _Q1 , and the calculation result _Q2 is used by the control device to drive the injector 2. 8 to the register of the output interface 84 and trigger it. In step 108, a learning value C _L is calculated by averaging the feedback integral coefficients C _FB .
In step 109, this learning value C _L is stored in the RAM 83.
Store and update.

As shown in FIGS. 4a and 4b, the air-fuel ratio sensor 10
When the signal output from is on the rich side, the air-fuel ratio is integrally controlled to the lean side, and when the output signal is on the lean side, the air-fuel ratio is integrally controlled to the rich side, so that the average value of the air-fuel ratio is adjusted to the theoretical value. The air-fuel ratio (excess air ratio 1.0) can be adjusted. but,
If there is an error in the air flow sensor 3 or the injector 2, the feedback integral coefficient _CFB repeats increasing and decreasing integrals around a value shifted by +C _L1 from the center value 1.0.

In other words, the average value of the integral coefficient C _FB during feedback control indicates the deviation from the center value, and this +C _L1 is the value to be learned.
Stored in RAM (uniform speed access memory device) 83,
Correct the basic fuel injection amount.

However, in the conventional device, the amount of fuel remaining in the fuel tank 11 is small, and the injector 2
Even if the fuel supply is insufficient and air is mixed in, the period shown in Figure 4 c.
As shown by T ₁ , the drive pulse width of the injector 2 is increased by feedback control to adjust the air-fuel ratio to the theoretical air-fuel ratio, and the learned value becomes +C _L2 , an abnormally large value, and the RAM 83
is memorized. When fuel is supplied to the fuel tank 11 with this +C _L2 stored in the RAM 83, the basic fuel injection amount has been significantly corrected by the learned value, so the air-fuel ratio becomes extremely rich. In oven loop control, the flammability limit may be exceeded, and it becomes difficult to establish feedback control.

As described above, in conventional learning control, errors in the entire control system such as sensors, computing devices, injectors, or fuel supply devices are detected, and the detected errors are reflected in control. The amount of fuel remaining in the tank becomes small, and due to vibrations of the vehicle body, etc., the remaining amount of fuel temporarily becomes zero, and air gets mixed in, causing the air-fuel ratio to become lean, so that the signal from the air-fuel ratio sensor becomes Learning correction is performed while increasing the opening time of the fuel injector until the desired air-fuel ratio is displayed. However, there was a problem in that the learning correction was temporarily erroneously executed, and as a result, the air-fuel ratio was erroneously compensated for the rich side.

[Summary of the invention]

The present invention was made with the aim of solving the problems of the conventional example as described above, and when the remaining amount of fuel in the fuel tank is less than a predetermined amount, learning control is prohibited to prevent mistakes. It is an object of the present invention to provide an air-fuel ratio control method that does not execute air-fuel ratio correction.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 2 shows a device configuration for realizing an air-fuel ratio control method for an internal combustion engine according to an embodiment of the present invention, and the same or equivalent parts as in the conventional example are designated by the same reference numerals 1 to 13. Input interface 80, microprocessor 81, ROM 82,
The control device 8, which is composed of a RAM 83 and an output interface 84, stores the flow shown in FIG. 6 as a control program in the ROM 82. In the embodiment of the present invention, as shown in FIG. 2, in contrast to the conventional system, a signal from the fuel gauge 14 is added to the control device 8, and when the remaining amount of fuel in the fuel tank 11 is less than a predetermined amount, learning is performed. It is configured to prohibit the storage of values into the RAM 83.

As shown in FIG. 6, storage of the learned value in the RAM 83 is prohibited when the remaining amount of fuel in the fuel tank 11 is less than a predetermined amount.

In FIG. 6, steps 201 to 207 correspond to steps 101 to 107 in FIG. 5 and are exactly the same, and their explanation will be omitted. Step 207
Next, the process proceeds to step 208, where the fuel meter checks whether or not more than a predetermined amount of fuel remains in the fuel tank 11.
Compare and determine the magnitude of the 14 output signals and the threshold,
If the remaining fuel amount is less than a predetermined value, learning is prohibited, and if the remaining fuel amount is greater than or equal to the predetermined value, learning is performed in step 209. In step 209, step 1 in FIG.
The learned value C _L is obtained in the same manner as in 08, and then in step 210, the learned value C _L is stored in the RAM 83 and updated.

〔Effect of the invention〕

As explained above, the present invention enables learning values to be
Prohibits storage in RAM when the remaining amount of fuel in the fuel tank is less than a predetermined amount, and
Since the memory of the previous learning value is retained, when there is a small amount of fuel remaining and there is a risk of air being mixed in the fuel, the sensor or actuator that is a component of the control system It is possible to prevent erroneous large-scale corrections from being performed regardless of the errors in the data.

Therefore, the air-fuel ratio can always be controlled to the most appropriate value, and the excellent effect of enabling stable engine operation is achieved.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing a conventional device, Fig. 2 is a configuration diagram showing an embodiment of the present invention, Fig. 3 is a characteristic diagram showing the characteristics of the air-fuel ratio sensor, and Fig. 4 is a waveform diagram showing the operating state. FIG. 5 is a flow chart of a conventional device, and FIG. 6 is a flow chart of an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Internal combustion engine, 2... Injector, 3... Air flow sensor, 8... Control device, 10... Air-fuel ratio sensor, 11... Fuel tank, 14... Fuel gauge. In the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. Fuel is supplied by performing an increase/decrease correction based on the deviation between the air-fuel ratio detected from exhaust gas components and the target air-fuel ratio on the basic supply amount of fuel calculated from the amount of air taken into the internal combustion engine. In addition, in the air-fuel ratio control method for an internal combustion engine that learns and corrects the air-fuel ratio correction term used when calculating the fuel supply amount in response to the above-mentioned deviation, when the remaining amount of fuel in the fuel tank is less than a predetermined amount, the above-mentioned learning is performed. An air-fuel ratio control method for an internal combustion engine, characterized in that correction is prohibited.