JP2694272B2 - Air-fuel ratio control device for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control system for an internal combustion engine, and particularly when an operating state of a vehicle shifts to a predetermined learning correction control range, an exhaust gas feedback control is performed by an initialization function. The present invention relates to an air-fuel ratio control device for an internal combustion engine that purifies exhaust gas while making the correction coefficient zero and performing learning correction control by performing learning correction control to reduce fluctuations in air-fuel ratio and fluctuations in idle speed. . [Prior Art] In recent years, in an internal combustion engine, in order to reduce the fuel consumption rate and the harmful components of exhaust gas, an air-fuel ratio control device of a feedback control system that converges to an air-fuel ratio that should obtain the best combustion state is provided. Proposed. Air-fuel ratio control system has an exhaust system provided with a for instance O ₂ input from sensor density signal serving rich signal and the amount of supplied fuel based on the fuel-lean signal and the supply air quantity by controlling the intake mixture given by an exhaust sensor Control to air-fuel ratio. In some cases, a catalytic converter such as a three-way catalyst is provided in the exhaust system in order to reduce harmful components in the exhaust gas after combustion. Further, in order to effectively act the function of reducing harmful components of exhaust gas by these devices, it is desirable to supply fuel containing no lead or the like. [Problems to be Solved by the Invention] By the way, in a conventional air-fuel ratio control system for an internal combustion engine, as shown in FIG. 5, based on a concentration signal input from an O ₂ sensor which is an exhaust sensor provided in an exhaust system. The exhaust feedback correction coefficient (O ₂ F / B correction coefficient) is changed. That is, when the concentration signal from the O ₂ sensor is inverted from the rich side to the lean side, for example, the exhaust feedback correction coefficient is added proportionally first, and then until the lean signal is inverted from the lean side to the rich side. The integral is added. Further, in an electronic fuel injection device using a microcomputer, the injector injection time T is generally expressed by the formula T = T ₀ × (1 + K ₀ + K ₁ + K ₂ + G) T ₀ : basic injection time K ₀ : exhaust feedback correction coefficient (O ₂ F / B correction coefficient) K ₁ , K ₂ : correction coefficient G: learning correction coefficient. However, in the above-mentioned electronic fuel injection device, the basic injection time of the injector is determined by a three-dimensional map based on the engine speed and the intake air pressure. A difference occurs, and the exhaust feedback correction coefficient shifts to the rich side or the lean side by this difference (see FIG. 7 (a)). In order to correct and control the deviation S of the exhaust feedback correction coefficient, the control unit of the air-fuel ratio control device for the internal combustion engine uses the exhaust feedback correction coefficient to learn the correction coefficient when the vehicle operating state is within a predetermined learning correction control range. Is calculated and stored, and learning correction control is performed by this learning correction coefficient (see FIG. 7 (b)). The learning correction coefficient is determined so that the exhaust feedback correction coefficient increases or decreases around 0, as shown in FIG. 7 (b). Further, as shown in FIG. 6, the learning correction control is not performed in the region where the engine speed is about 4000 rpm or more and the load, for example, the intake air pressure is about 200 mmHg or less. The learning correction control area is divided into, for example, a plurality of locations, and the learning correction coefficient is updated for each divided area. However, there is a deviation S from the above-mentioned exhaust feedback correction coefficient.
When the vehicle operating state shifts from the non-learning correction control range to the learning correction control range in the state where the learning correction coefficient is calculated, the learning correction coefficient is calculated and stored by the exhaust feedback correction coefficient having the deviation S, and the learning correction coefficient is stored. Learning correction control is performed using a coefficient. For this reason, as shown in FIG. 8, the fluctuation of the exhaust feedback correction coefficient caused by the deviation S becomes large, and when the fluctuation of the exhaust feedback correction coefficient is made small, the correction control time by the learning correction coefficient becomes long. As shown in FIG. 9 (from the A position to the C position), the idling speed fluctuates greatly during idling, which deteriorates drivability, and a large amount of harmful components are discharged, causing air pollution. There is an inconvenience. Further, when the exhaust feedback correction coefficient with the deviation S is reduced, if the operating state changes at the position B in FIG. 8, that is, if the engine speed or the intake air pressure as a load changes, the learning correction coefficient becomes B. The position is updated to the rich side, the fluctuation of the idle speed becomes larger, and more harmful components are discharged, which further aggravates the above-mentioned inconvenience. Therefore, in order to eliminate the above-mentioned inconvenience, an object of the present invention is to provide an exhaust feedback correction coefficient that changes based on a concentration signal input from an exhaust sensor when the vehicle operating state is within a predetermined learning correction control range. According to the learning correction coefficient, a learning correction coefficient set to increase / decrease the exhaust feedback correction coefficient around 0 is calculated and stored, and a learning correction control control is performed to correct the air-fuel ratio by the learning correction coefficient. When shifting from the non-learning correction control range to the predetermined learning correction control range, the exhaust feedback correction which changes based on the concentration signal input from the exhaust sensor by the initialization means having the initialization function for setting the exhaust feedback correction coefficient to zero Learning correction is performed with the learning correction coefficient calculated with the exhaust feedback correction coefficient with zero coefficient. By performing the control, the fluctuation of the air-fuel ratio can be made small and the fluctuation of the idle speed at the time of idling operation can be made small, the drivability can be improved, and the emission of harmful components in the exhaust gas can be reduced, An object is to realize an air-fuel ratio control device for an internal combustion engine that can purify exhaust gas. [Means for Solving the Problems] In order to achieve this object, the present invention provides an air-fuel ratio control device for an internal combustion engine that feedback-controls the air-fuel ratio by a concentration signal input from an exhaust sensor provided in an exhaust system of the internal combustion engine. In the learning, the learning is set so that the exhaust feedback correction coefficient is increased or decreased around 0 by the exhaust feedback correction coefficient that changes based on the concentration signal input from the exhaust sensor when the vehicle operating state is in the predetermined learning correction control range. When a control unit for calculating and storing a correction coefficient and performing learning correction control to correct the air-fuel ratio by the learning correction coefficient is provided, and the vehicle operating state shifts from the non-learning correction control range to a predetermined learning correction control range. The exhaust feedback correction coefficient that changes based on the concentration signal input from the exhaust sensor The control unit is provided with an initialization unit having an initialization function for setting the exhaust gas feedback correction coefficient to zero in order to perform learning correction control with the learning correction coefficient calculated by the feedback correction coefficient. [Operation] With the configuration described above, the initialization means having the initialization function of setting the exhaust gas feedback correction coefficient to zero when the vehicle operating state shifts from the non-learning correction control range to the predetermined learning correction control range. The exhaust feedback correction coefficient that changes based on the concentration signal input from the exhaust sensor is set to zero, and learning correction control is performed using the learning correction coefficient calculated with the exhaust feedback correction coefficient that is set to zero, and fluctuations in idle speed during idling operation This reduces the exhaust gas, reduces the emission of harmful components in the exhaust gas, and purifies the exhaust gas. Embodiment An embodiment of the present invention will be described below in detail with reference to the drawings. 1 to 4 show an embodiment of the present invention. In FIG. 1, 2 is an internal combustion engine, 4 is an air cleaner, 6 is an intake manifold, 8 is an intake passage, 10 is a throttle valve, 12 is an intake valve, 14 is a combustion chamber, 16 is a piston, 18 is an exhaust valve, and 20 is It is an exhaust passage. A fuel injection valve 22 is provided facing the intake passage 8 upstream of the throttle valve 10. This fuel injection valve 22
Is fed with the fuel in the fuel tank 24. That is,
The fuel in the fuel tank 24 passes through the fuel supply passage 28 by the fuel pump 26, is filtered by the fuel filter 30, and is fed to the fuel injection valve 22. One end of the fuel pressure passage 32 is open in the middle of the fuel supply passage 28, and the other end of the fuel pressure passage 32 is opened in the fuel tank 24. A fuel regulator 34 for adjusting the fuel pressure acting on the fuel injection valve 22 to a constant value is provided in the middle of the fuel pressure passage 32.
An intake pipe side pressure passage 36 communicating with the intake passage 8 downstream of the throttle valve 10 is connected to the fuel regulator 34. One end of the EGR passage 38 opens into the exhaust passage 20, and the other end of the EGR passage 38 communicates with a return port 40 formed in the intake manifold 6 downstream of the throttle valve 10. Also, EG
An EGR valve 42 is provided in the middle of the R passage 38. This EGR
An operating pressure passage 44 of the EGR valve 42 communicates with the valve 42. A pressure sensor 48 is provided via a detection pressure passage 46 for detecting the intake pipe pressure in the intake passage 8, and an intake air temperature sensor for detecting the intake air temperature in the intake passage 8.
50 is attached to the intake manifold 6. Also,
A water temperature sensor 54 for detecting the temperature of the cooling water in the water jacket 52 formed in the intake manifold 6 is attached to the intake manifold 6. Further, an O ₂ sensor 56 that detects the oxygen concentration in the exhaust gas is attached to the exhaust passage 20. The above-mentioned pressure sensor 48, intake air temperature sensor 50, water temperature sensor
54, and the O ₂ sensor 56 is in communication with the A / D converter 58. The A / D converter 58 communicates with the control unit (CPU) 60. The control unit (CPU) 60 asynchronously injects fuel when the internal combustion engine 2 operates an air conditioner (not shown) in an idling operation state, for example. The control unit 60 has a starter switch as an input side.
62, an air conditioning switch 64, a throttle switch 66 for detecting the opening of the throttle valve 10, an ignition coil 68 for detecting an ignition signal, and a battery 70 for detecting a voltage state. Further, the control unit 60 communicates with the EGR valve 42, the fuel pump 26, and the fuel injection valve 22 as an output side. Further, the control unit 60
On the output side, the first negative pressure switching is provided in the middle of the bypass passage 72, one end of which opens in the intake passage 8 upstream of the throttle valve 10 and the other end of which opens in the intake passage 8 downstream of the throttle valve 10. Valve (VSV1) 74 and the first negative pressure switching valve 74 in the middle of the short circuit passage 76
And a second negative pressure switching valve (VSV2) 78, which is provided in parallel with the air conditioner and is idled up when the air conditioner operates. The control unit 60 feedback-controls the air-fuel ratio by a concentration signal input from an O ₂ sensor 56 which is an exhaust sensor provided in the exhaust system of the internal combustion engine 2. And the control part
The reference numeral 60 designates an exhaust feedback correction coefficient (O2 F that changes based on the concentration signal input from the O2 sensor 56 when the vehicle operating state is in a predetermined learning correction control range set in advance.
/ B correction coefficient), a learning correction coefficient set to increase or decrease the exhaust gas feedback correction coefficient around 0 is calculated and stored, and learning correction control is performed to correct the air-fuel ratio by the learning correction coefficient. . Further, the control unit 60 is provided with an initialization means (not shown) having an initialization function of the exhaust feedback correction coefficient. That is, the initialization means sets the exhaust gas feedback correction coefficient to zero (in other words, 0 or zero) when the vehicle operating state shifts from the non-learning correction control region to the predetermined learning correction control region. , The learning correction coefficient is calculated by the exhaust feedback correction coefficient set to zero, and the learning correction control is performed. The operation will be described with reference to the learning correction control flowchart of the air-fuel ratio control apparatus for the internal combustion engine 2 in FIG. First, the learning correction control program starts (100)
By doing so, it is judged whether or not the vehicle is in the predetermined learning correction control range set in advance (102), and if YES, the vehicle driving state is set in the predetermined learning correction control range from the non-learning correction control range. A transition to the control range, that is, a determination (104) is made as to whether or not the previous correction control was feedback control using only the exhaust feedback correction coefficient. If this determination (104) is YES, as shown in the P position in FIGS. 3 and 4, the exhaust feedback correction coefficient is set to zero (106), and the learning correction coefficient is calculated by the exhaust feedback correction coefficient set to zero ( 108). Then, learning correction control is performed using the exhaust feedback correction coefficient (11
0), end the learning correction control program (11
6). Further, if the determination (102) as to whether or not it is in the predetermined learning correction control range set in advance is NO, it is determined whether or not it is the feedback control range using only the exhaust feedback correction coefficient, that is, the non-learning correction control range. The judgment (112) is made. If this determination (112) is YES, correction control is performed using the exhaust gas feedback correction coefficient (110),
The learning correction control program is ended (116). If this judgment (112) is NO, the correction control by the exhaust feedback correction coefficient is stopped (114), and the learning correction control program is ended (116). Further, the above-mentioned vehicle operating state shifts from the non-learning correction control region to a predetermined learning correction control region set in advance, that is, it is judged whether the previous correction control is feedback control using only the exhaust feedback correction coefficient (104). In the case of NO, the process shifts to the process of calculating (108) the normal learning correction coefficient by the exhaust feedback correction coefficient. As a result, when the vehicle operating state shifts from the non-learning correction control range to the predetermined learning correction control range set in advance,
With the exhaust feedback correction coefficient set to zero, the learning correction coefficient can be calculated by using the exhaust feedback correction coefficient that is set to zero, and learning correction control can be performed, and only the difference from the proper air-fuel ratio caused by the machine difference or aging of the engine Even if the feedback correction coefficient deviates to the rich side or the lean side, the fluctuation of the air-fuel ratio can be made small, and as shown in FIG. 4, the fluctuation of the idle speed during idling can be made small, and the drivability can be reduced. Can be improved. Further, the exhaust feedback correction coefficient can be set to zero to reduce the fluctuation of the air-fuel ratio, so that the learning correction control by the learning correction coefficient calculated from the exhaust feedback correction coefficient can be rapidly performed, and the harmful components in the exhaust gas can be discharged. The amount can be reduced, exhaust gas can be purified, and air pollution can be prevented. [Effects of the Invention] As described in detail above, according to the present invention, when the vehicle operating condition is within the predetermined learning correction control range, the exhaust feedback correction coefficient which changes based on the concentration signal input from the exhaust sensor is used. A control unit for calculating and storing a learning correction coefficient set to increase or decrease the exhaust gas feedback correction coefficient around 0 and for performing learning correction control to correct the air-fuel ratio by this learning correction coefficient is provided, and the vehicle operating state is non-learning. Learning correction using a learning correction coefficient calculated by the exhaust feedback correction coefficient with zero as the exhaust feedback correction coefficient that changes based on the concentration signal input from the exhaust sensor when shifting from the correction control area to the predetermined learning correction control area Controls the initialization means having the initialization function that makes the exhaust feedback correction coefficient zero for control. The exhaust feedback correction coefficient is set to zero when the vehicle operating state shifts from the non-learning correction control area to the preset learning correction control area, and the learning correction coefficient is set to zero. It is possible to calculate and perform learning correction control, and even if the exhaust feedback correction coefficient deviates by the difference with the proper air-fuel ratio caused by engine difference or aging, the fluctuation of the air-fuel ratio can be made small and idling Fluctuations in the idle speed during operation can be reduced, and drivability can be improved. Further, by making the fluctuation of the air-fuel ratio small, the learning correction control by the learning correction coefficient calculated from the exhaust feedback correction coefficient can be quickly performed, and the emission amount of the harmful component in the exhaust gas can be reduced, The exhaust gas can be purified and contributes to the prevention of air pollution.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 4 show an embodiment of the present invention, FIG. 1 is a schematic explanatory view of an air-fuel ratio control device of an internal combustion engine, and FIG. 2 is learning of an air-fuel ratio control device of an internal combustion engine. Correction control flowchart, third
FIG. 4 is a schematic diagram showing a change state of an exhaust feedback correction coefficient in a non-learning correction control region and a learning correction control region,
The figure shows the relationship between the engine speed, the exhaust feedback correction coefficient, and the learning correction. 5 to 9 show the prior art of the present invention, FIG. 5 shows the relationship between the output signal of the O ₂ sensor and the exhaust feedback correction coefficient, and FIG. 6 is set by the intake air pressure and the engine speed. FIG. 7 (a) showing a learning correction control area
Is a diagram showing feedback control by an exhaust feedback correction coefficient and a learning correction coefficient, FIG. 7 (b) is a diagram showing learning correction control by an exhaust feedback correction coefficient and a learning correction coefficient, and FIG. 8 is a non-learning correction control region FIG. 9 is a diagram showing a variation state of the exhaust feedback correction coefficient and the learning correction coefficient when the control shifts to the learning correction control range, and FIG. 9 is a diagram showing a relationship between the engine speed, the exhaust feedback correction coefficient, and the learning correction. In the figure, 2 is an internal combustion engine, 4 is an air cleaner, 6 is an intake manifold, 8 is an intake passage, 10 is a throttle valve, 12 is an intake valve, 18 is an exhaust valve, 20 is an exhaust passage, 22 is a fuel injection valve, and 24 is Fuel tank, 26 is a fuel pump, 28 is a fuel supply passage, 32 is a fuel pressure passage, 34 is a fuel regulator, 36 is an intake pipe side pressure passage, 38 is an EGR passage, 40 is a return port, 42 is an EGR valve, 44 is An operating pressure passage, 46 is a detection pressure passage, 48 is a pressure sensor,
50 is an intake air temperature sensor, 54 is a water temperature sensor, 56 is an O ₂ sensor, 58
Is an A / D converter, 60 is a control unit (CPU), 62 is a starter switch, 64 is an air conditioning switch, 66 is a throttle switch, 68
Is an ignition coil, 70 is a battery, 72 is a bypass passage, 74 is a first negative pressure switching valve (VSV1), 76 is a short circuit passage, and 78 is a second negative pressure switching valve (VSV2).

Claims (1)

(57) [Claims] In an air-fuel ratio control device for an internal combustion engine, which feedback-controls an air-fuel ratio by a concentration signal input from an exhaust sensor provided in an exhaust system of an internal combustion engine, input from the exhaust sensor when the vehicle operating state is in a predetermined learning correction control range The learning correction coefficient set to increase or decrease the exhaust feedback correction coefficient around 0 is calculated and stored by the exhaust feedback correction coefficient that changes based on the concentration signal, and the learning correction coefficient is used to correct the air-fuel ratio. A control unit for performing correction control is provided, and the exhaust gas feedback correction coefficient that changes based on a concentration signal input from the exhaust gas sensor when the vehicle operating state shifts from a non-learning correction control region to a predetermined learning correction control region is zero. And the learning correction coefficient calculated with the exhaust feedback correction coefficient which is zero The exhaust feedback correction coefficient air-fuel ratio control apparatus for an internal combustion engine, characterized in that the initialization means is provided in the control unit having an initialization function to be zero to perform.