JPS63120836A - Air-fuel ratio learning control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent the base air-fuel ratio from obtaining its overlean state due to an abnormal learning, by inhibiting an airfuel ratio feedback control correction coefficient from its learning, control before the predetermined period after a fuel increase means, which increases fuel in the time of transient operation, operates. CONSTITUTION:An internal combustion engine, in which a feedback control means A corrects the basic fuel injection time, obtained by an engine load, by an air-fuel ratio feedback correction coefficient determined on the basis of an output signal of an O2 sensor provided in an exhaust system, controls air-fuel ratio to the vicinity of the theoretical air-fuel ratio. While a study control means B learning, controls said correction coefficient so as to be obtained in a predetermined value. Further in the time of detecting transient operation, a fuel increase means C promotes the increase of fuel. Here the engine provides a learning, control inhibiting means D, which inhibits a study control before the predetermined period after the fuel increase means C operates, preventing the base air-fuel ratio from obtaining the overlean due to an abnormal study.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio learning control device for an internal combustion engine during air-fuel ratio feedback control.

Conventional technology A three-way catalyst has been used to simultaneously purify carbon monoxide, hydrocarbons, and nitrogen oxides in exhaust gas.In order to improve the purification rate of this three-way catalyst, an O2 sensor is used to Residual IS in gas! Air-fuel ratio feedback control is performed in which the air-fuel ratio is estimated by detecting the 1 m concentration and the air-fuel ratio is controlled to be near the stoichiometric air-fuel ratio. At the basic fuel injection time TP determined by the engine load, an air-fuel ratio feedback correction coefficient FAF, not shown in FIG. Multiply by fuel injection time T
The air-fuel ratio is controlled to be close to the stoichiometric air-fuel ratio by determining AU and opening the fuel injection valve for a time corresponding to this fuel injection time TAU. However, due to environmental changes and changes over time, changes in valve timing due to changes in tappet clearance, changes in the characteristics of the pressure sensor and air flow meter, changes in the characteristics of the fuel injection rope, etc. occur, resulting in changes in the fuel injection amount m required by the engine. The air-fuel ratio may not be able to be controlled close to the stoichiometric air-fuel ratio. For this reason, the base air-fuel ratio determined by the engine load is corrected by learning control so that the air-fuel ratio feedback correction coefficient FAF falls within a predetermined value, and control is performed so that the actual air-fuel ratio is always near the stoichiometric air-fuel ratio. This learning control uses learning terms TAUG and KG learned under predetermined conditions to control the air-fuel ratio finite back correction coefficient FAF to a predetermined value, as shown in the following equation.

r AU − (1-P + T AU G )・K
G・FAF・(1+F)...(1) However, TAU G is the learning term when the throttle valve is fully closed, KG is the learning term when the throttle valve is open, and F
is a correction coefficient during transient times such as sudden acceleration.

These learning terms TALIG and KG are used when the air-fuel ratio feedback control is in progress and the engine cooling water temperature is at a predetermined value (for example, 70°C).
), the correction coefficient FAF is learned by the following method each time it skips.

First, every time the air-fuel ratio feedback correction coefficient FAF skips, the average value of the peak value of the correction coefficient FAF FAF△■
, that is, is calculated, and when the value of FAFAV is outside a predetermined range (for example, ±2%), the learning value shown in the table below is added to the 5th term.

Table and the learning terms TAUG, KG learned as above
The value is applied to the above equation (1) according to the tm III state of the throttle valve and the magnitude of the intake pipe pressure (or the amount of intake air per engine revolution), and the fuel injection time TAU is determined. As a result, the average value FAFAV is set to a predetermined value (1,
02), the value of the learning term is increased to control the air-fuel ratio to the rich side, and when the average value FAFAV is less than the predetermined value (0,98), the value of the learning term is decreased to control the air-fuel ratio to the lean side. The average value FAFAV is 1.
In other words, the air-fuel ratio is controlled to approach the stoichiometric air-fuel ratio.

Conventional air-fuel ratio learning control devices include those that start learning control after a predetermined period of time when air-fuel ratio control is switched from oven loop control to feedback control (Japanese Patent Application Laid-Open No. 59-206637), When suddenly opening or closing,
A method has been proposed in which learning errors are prevented by prohibiting learning control for a predetermined period of time (Japanese Unexamined Patent Publication No. 136539/1983).

On the other hand, in order to improve responsiveness during transient operations such as during acceleration, asynchronous injection is performed that performs fuel injection regardless of the crank angle position, and an air-fuel ratio correction coefficient FTC is activated during transient operations to temporarily adjust the air-fuel ratio. Rich control is generally adopted. Some engines use only asynchronous injection, while others use FT
Some engines perform only C operation, or some engines perform both. If the air-fuel ratio temporarily becomes rich due to asynchronous injection or FTC operation during transient operation, the air-fuel ratio correction coefficient FAF will not fall within the predetermined value, so learning control will adjust the base air-fuel ratio. It is corrected to the lean side.

In addition, when the lean signal continues for a predetermined period of time or more (for example, 8 seconds or more) due to a short circuit in the 02 sensor system, the lean monitor stops feedback control and performs open-loop control of the air-fuel ratio to prevent rough engine idle. Control is generally adopted.

Problems to be Solved by the Invention However, when asynchronous injection or FTC operates continuously, the air-fuel ratio becomes rich and the air-fuel ratio feedback correction coefficient F
The state in which the AF does not fall within the predetermined value continues. Meanwhile, in the conventional device, the base air-fuel ratio is corrected to be lean by learning control. If the operating state changes from this state to a state where asynchronous injection or FTC does not operate, the base air-fuel ratio has been corrected to be lean, so the air-fuel ratio
The actual air-fuel ratio is corrected to the rich side using the dopak correction coefficient FAF. However, in engines where a guard is not set for the base air-fuel ratio, if the base air-fuel ratio is corrected to the lean side too much and the asynchronous injection or FTC does not operate, the air-fuel ratio feedback correction coefficient Feedback control by FAF does not correct the air-fuel ratio sufficiently, and the air-fuel ratio continues to be lean.
As a result, there was a problem in that the i-speed engine reached a rough idle, and in the worst case, the engine stalled.

Furthermore, in engines where a guard is set for the base air-fuel ratio, it can be sufficiently corrected by feedback control using the air-fuel ratio feedback correction coefficient FAF, but the lean monitor execution condition is entered during rich correction, and the feedback control of the air-fuel ratio is stopped. In oven loop control, the base air-fuel ratio remains in a lean state, so there is a problem that the engine reaches a rough idle and, in the case of R, the engine stalls.

The present invention was made in view of the above, and its purpose is to stop air-fuel ratio learning control for a certain period of time when asynchronous injection or FTC is activated, and to prevent malfunctions in the internal combustion engine caused by abnormal learning. An object of the present invention is to provide an air-fuel ratio learning control device that prevents the above.

Means for Solving the Problems In order to solve the problems of the prior art described above, the present invention detects the residual bacterial acid in the exhaust gas during the basic fuel injection time determined by the engine load. a feedback control means for controlling the air-fuel ratio of the air-fuel mixture to near the stoichiometric air-fuel ratio by correcting it with an air-fuel ratio feedback correction coefficient obtained based on the output signal of the two sensors; In an internal combustion engine having a learning control means for performing learning control and a fuel increase means for increasing the amount of fuel during transient operation, the learning control prohibits the learning control until a predetermined period has elapsed after the fuel increase means is activated. An air-fuel ratio learning control device for an internal combustion engine is provided, which is characterized by being provided with a prohibition means.

Operation: Until a predetermined period of time has elapsed after the asynchronous injection or FTC is activated, the learning control inhibiting means prohibits learning control for correcting the base air-fuel ratio in order to keep the air-fuel ratio feedback correction coefficient within a predetermined value.

This prevents the base air-fuel ratio from becoming over-lean due to abnormal learning when eight fuel increase means such as asynchronous injection or FTC operate continuously, and prevents the base air-fuel ratio from becoming over-lean due to abnormal learning. When the operating condition is such that the engine does not operate, it is possible to effectively prevent rough idle of the engine or engine stall.

The learning prohibition period can be defined by, for example, the number of skips of the air-fuel ratio feedback correction coefficient FAF, time, or crank angle.

Embodiments The present invention will be explained in detail below based on embodiments shown in the drawings.

FIG. 2 shows an embodiment of an internal combustion engine and its peripheral equipment to which the present invention is applied.

In the figure, 1 is the engine body, 2 is the piston, 3 is the cylinder,
4 is a spark plug, 5 is an intake valve, 6 is an exhaust valve, 7
is an exhaust manifold, 8 is an oxygen sensor that detects the oxygen concentration in the exhaust gas, and 9 is a water temperature sensor that detects the engine cooling water temperature.

In the intake system, 11 is an air cleaner and 12 is an air cleaner in the figure.
14 is a throttle valve installed in the intake passage 13; 15 is a bypass intake passage that bypasses the throttle valve 14; 16 is an air meter installed in the bypass intake passage 15 from the control circuit 20; Idle speed control valve whose opening degree is controlled by a pulse signal with a predetermined duty ratio according to the command of
ISCV), 17 is a throttle position sensor that outputs a signal according to the opening degree of the throttle valve 14, 18 is an intake manifold, 19 is a fuel injection valve, and 21 is an intake temperature sensor that detects the temperature of intake air.

In the ignition system, in the figure, 23 is an igniter that outputs the high voltage necessary for ignition from the secondary side of the ignition coil, and 24 is linked to a crankshaft (not shown), and the high voltage generated by the igniter 23 is connected to the spark plug of each cylinder. 25 is a rotation angle sensor that outputs a pulse signal 24 times per one revolution of the distributor 24 (82 revolutions of the crankshaft), and 26 is a cylinder that outputs a pulse signal once per one revolution of the distributor 24. Discrimination Senna. The control circuit 20 is made up of a microcomputer, which inputs signals from various sensors, performs predetermined calculations and controls based on these input signals, and outputs predetermined signals to various actuators. .

Next, FIG. 3 shows specific components of the control circuit 20. As shown in FIG.

The central processing unit <CPtJ) 30 inputs and calculates data output from each sensor according to a control program, and also performs processing to control various actuators such as the fuel injection valve 19 and igniter 23. The only memory (ROM) 31 is a storage device that stores data such as the control program and ignition timing calculation map, and the random access memory (RAM) 32
is a storage device that temporarily reads and writes data output from each sensor and data necessary for arithmetic control, and backup random access memory (backup RAM) 3
Reference numeral 3 denotes a storage device in which data necessary for driving the engine is backed up by a battery power source even when an ignition switch (not shown) is turned off.

Further, the input section 34 shapes the output signals of each sensor such as the oxygen sensor 8, the water temperature sensor 9, and the intake air temperature sensor 21 by a waveform shaping circuit (not shown), and converts this signal into A/D by a multiplexer (not shown). The data is output to the CPU 30 and RAM 32 or 33 at a predetermined time according to instructions. In the input section 34, if the output signal from each sensor is an analog signal, it is converted into a digital signal by an A/D converter built in the multiplexer. The input/output unit 35 shapes the output signals of the rotation angle sensor 25, cylinder discrimination sensor 26, etc. by a waveform shaping circuit, and sends the signals to R via the input port.
It is designed to write to AM32 etc. The input/output section 35 also controls the fuel injection valve 19 and igniter 23 by a drive circuit driven via an output boat according to a command from the CPU 30.
・It is designed to drive l5CV16 etc. at a predetermined timing. The pass line 36 is connected to the IyI CPU 30.
It connects each element such as the ROM 31 and the input section 34 and input/output section 35 to send various data.

The control circuit 20 calculates fuel injection DAffi, ignition timing, etc. according to the operating conditions based on the detection data input from each sensor, and during idling operation, adjusts the rotation speed to a preset target rotation speed depending on the operating condition. The valve opening pulse duty ratio to be output to l5CV16 is calculated so as to match the engine speed, and this calculated signal is output to l5CV16 to control the idle speed to the target rotation speed.

The fuel injection amount TAU is calculated based on the formula: TAU-kXQ/NX (ZXFAF+β, where k is a constant, Q is intake air excitation, NG,
tl function rotation speed, α is a correction coefficient for engine cooling water temperature, intake temperature, etc., FAF is an air-fuel ratio feedback correction coefficient determined based on the output signal of the oxygen sensor, and β is another correction coefficient.

Hereinafter, the operation of an embodiment of the air-fuel ratio learning control device of the present invention will be explained based on Ll-charts shown in FIGS. 4 and 5.

The flowchart in Figure 4 shows asynchronous injection or FTC
(Transient air-fuel ratio correction coefficient) is a flowchart for checking whether or not it has been activated. First, in step 101,
It is determined whether or not asynchronous injection has been executed, and if asynchronous injection has been executed, the process proceeds to step 103 and the FΔF skip counter CFAF is reset. If it is determined in step 101 that asynchronous injection is not being performed, the process proceeds to step 102, where it is determined whether or not the FTC has operated. If the FTC is activated, the process advances to step 103 and the FAF skip counter CFAF is reset. That is, in this processing routine, if either asynchronous injection or FTC operates, the FAF skip counter CFAF is reset. On the other hand, if neither asynchronous injection nor FTC operates, this routine is ended without resetting the FAF skip counter CFAF.

Next, referring to the flowchart in FIG. 5, this flowchart is a processing routine for controlling the air-fuel ratio by prohibiting learning control under certain conditions.
At 01, it is determined whether or not the air-fuel ratio feedback correction coefficient FAF has been skipped. The air-fuel ratio feedback correction coefficient FAF is changed by an integral constant and a skip as is well known in the present embodiment, and when it is determined in step 201 that there is a skip in the air-fuel ratio feedback correction coefficient , the process proceeds to step 202 and the air-fuel ratio feedback correction coefficient F
The AF skip counter CFAF is incremented by one. Next, the process proceeds to step 203, where it is determined whether the FAF skip counter CFAF is greater than a predetermined value A (for example, 6), and if it is less than the predetermined value, the process proceeds to step 2.
04, the learning control of the base air-fuel ratio for keeping the air-fuel ratio feedback coefficient FAF within a predetermined value is prohibited. On the other hand, if the skip counter CFAF of the FAF becomes larger than the predetermined value A in step 203, the process proceeds to step 205, where learning inhibition is canceled and learning control of the base air-fuel ratio is restarted.

In this way, in this embodiment, learning control of the base air-fuel ratio is prohibited for a certain period of time after asynchronous injection or FTC is activated, so that if asynchronous injection or FTC is frequently activated, In addition, erroneous learning based on this can be prevented, and the base air-fuel ratio will not be learned and controlled to an extremely over-lean side, so rough idle or engine stall of the internal combustion engine can be effectively prevented. Furthermore, since erroneous learning can be effectively prevented, it is difficult to enter the lean monitor execution condition, and engine troubles such as rough idling due to lean monitor operation can be prevented.

Regarding the learning control method, please refer to Japanese Patent Application Laid-Open No. 59-20663.
Since this method is the same as the known learning control method disclosed in No. 7, the explanation thereof will be omitted in this specification.

Effects of the Invention As detailed above, the present invention prohibits learning control of the base air-fuel ratio for a certain period of time after the fuel amplification means such as asynchronous injection or FTC is activated. If the operation of the fuel increase means such as Therefore, it is possible to effectively prevent rough idling or engine stall of the internal combustion engine due to an overlean air-fuel ratio.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the basic configuration of the present invention, Figure 2 is a schematic system configuration diagram of an internal combustion engine equipped with the air-fuel ratio learning control device of the present invention, and Figure 3 is a control circuit configured with a microcomputer. A block diagram showing an example, FIGS. 4 and 5 are flow charts showing the operation of the embodiment of the present invention, and FIG. 6 shows an air-fuel ratio signal and an air-fuel ratio feedback correction coefficient F.
It is a diagram showing the relationship with AF. 1... Engine body, 2... Piston, 3...
- Cylinder, 4... Spark plug, 8... Oxygen sensor, 9... Water temperature sensor, 13... Intake passage, 14... Throttle valve, 19... Fuel injection valve, 20... control circuit.

Claims (1)

[Claims] The air-fuel ratio of the air-fuel mixture is corrected by the air-fuel ratio feedback correction coefficient obtained based on the output signal of the O_2 sensor that detects the residual oxygen concentration in the exhaust gas. In an internal combustion engine, the internal combustion engine has a feedback control means for controlling the air-fuel ratio to be near the stoichiometric air-fuel ratio, a learning control means for performing learning control so that the air-fuel ratio feedback correction coefficient falls within a predetermined value, and a fuel increase means for increasing the amount of fuel during transient operation. . An air-fuel ratio learning control device for an internal combustion engine, characterized in that a learning control inhibiting means is provided for inhibiting the learning control until a predetermined period has elapsed after the fuel increase means is activated.