JPH0211840A - Air-fuel ratio controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To detect deterioration with high precision by adjusting the air-fuel ratio by generating the compulsory duty ratio wave form having a certain cycle and a certain amplitude during the stationary traveling of an engine and judging the degree of deterioration according to the output duty ratio of an air-fuel ratio sensor. CONSTITUTION:When a stationary traveling judging means judges the stationary traveling state of an internal combustion engine, a compulsory duty ratio generating means outputs the duty ratio pulse signal having a certain cycle and a certain amplitude into an air-fuel ratio adjusting means, and the air-fuel ratio of the mixed gas supplied into the internal combustion engine is adjusted in accordance. At this time, the output duty ratio wave form signal supplied from an air-fuel ratio sensor is taken into a deterioration judging means through a logic circuit, and the degree of deterioration of the output characteristic of the air-fuel ratio sensor is judged. Thus, the degree of deterioration of the air-fuel ratio sensor is detected with high precision, and the deflection of the air-furl ratio in the air-fuel ratio feedback control can be corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an air-fuel ratio control device for an internal combustion engine, and in particular to an improvement in the deterioration detection function of an air-fuel ratio sensor (in this specification, 02 Senna).

[Prior Art and Problems to be Solved by the Invention] Conventionally, in an air-fuel ratio feedback control system in which a 0° sensor is installed upstream or downstream of a catalyst to feedback control the air-fuel ratio according to the output of an LJ or O2 sensor, a 0° sensor is installed. The 0° sensor was determined to be abnormal if the air-fuel ratio feedbank control was not executed for a long time due to a disconnection or other reason.

However, as mentioned above, according to the O2 sensor abnormality determination, subtle deterioration of the 0□ sensor, such as rich deviation and lean deviation in the output of the 0□ sensor, cannot be accurately determined. It was not possible to prevent rich and lean deviations in the controlled air-fuel ratio during fuel ratio feedback control.

In addition, to determine the abnormality of a single 02 sensor, a compulsory waveform such as a triangular waveform, a sine waveform, a square waveform, etc. is given as the air-fuel ratio control amount, and the resulting 02 sensor A device for evaluating the performance of the 02 sensor according to the output is known (see Japanese Patent Application Laid-Open No. 57-1
24248), which is not suitable for evaluating the 02 sensor of an actual vehicle.

Therefore, an object of the present invention is to provide an air-fuel ratio control device for an internal combustion engine that has a function of detecting deterioration of the 02 sensor which is also useful in actual vehicles.

Another object of the present invention is to provide an air-fuel ratio control device for an internal combustion engine that performs air-fuel ratio feedback control in response to deterioration of the 02 sensor and compensates for variations in the output characteristics of the 02 sensor.

[Means to solve the problem]

, the means for solving the above-mentioned problems are shown in Figures 1A to 1D.
As shown in the figure.

In the means shown in FIG. 1A, an air-fuel ratio sensor is provided in the exhaust passage upstream or downstream of a three-way catalyst provided in the exhaust passage of the internal combustion engine, and the steady running determination means determines whether the engine is in a steady running state. Determine whether As a result, when the engine is in a steady running state, the forced duty ratio generating means generates a forced duty ratio waveform with a constant period and constant amplitude, and the air fuel ratio adjusting means adjusts the air fuel ratio of the engine according to the forced duty ratio waveform FAF. adjust. On the other hand, when the engine is in a steady running state, the deterioration determining means is the output (■) of the air-fuel ratio sensor. The degree of deterioration of the air-fuel ratio sensor is determined according to the duty ratio of 8.

In the means shown in FIG. 1B, in the means shown in FIG. 1Δ, the air-fuel ratio feedback control constant, for example, the skip amount R3R (R3L
), an air-fuel ratio feedback control constant, and an output V of the air-fuel ratio sensor. An air-fuel ratio correction amount calculation means for calculating an air-fuel ratio correction amount FAF' in accordance with X is added. As a result, when the engine is not in a steady running state, the air-fuel ratio adjustment means adjusts the air-fuel ratio correction amount FAF'
The engine's air-fuel ratio is adjusted accordingly.

In the means shown in FIG. 1C, the air-fuel ratio sensor in the means shown in FIG. 1A is equipped with a heater, and instead of the steady running means,
This includes additional means for determining idle running and heater energizing means. Therefore, when the engine is in an idling state, the forced duty ratio generating means generates the forced duty ratio waveform F A F with a constant period and a constant amplitude, and the air-fuel ratio adjusting means adjusts the forced duty ratio waveform F A F of the engine according to the forced duty ratio waveform FAF. Peter energizing means for adjusting the air-fuel ratio energizes the heater of the heater stone 1 air-fuel ratio senna.

11) In the means shown in Figure 1C, in the means shown in Figure 1C,
This is the same as the means shown in FIG. 1 F3, with the addition of an asymmetrical control constant calculation means and an air-fuel ratio correction amount calculation means. Thereby, the air-fuel ratio is adjusted according to the degree of deterioration of the air-fuel ratio sensor with heater.

[For production]

According to the means shown in FIGS. 1A and 1β, the forced duty ratio waveform F is used to determine the degree of deterioration of the air-fuel ratio sensor only in the steady running state or idling state of the actual vehicle.
AF is generated. In particular, the heater is energized to prevent the sensor element temperature of the air-fuel ratio sensor from decreasing during idling.

That is, as shown in FIG. 2, the output characteristics of the air-fuel ratio sensor can be categorized into three types: standard sensor, lean deviation sensor, and rich deviation sensor. In this case, the forced duty ratio waveform FAF with a constant period T and constant amplitude A
(duty ratio 50%), as shown in Fig. 3, in the case of a lean deviation sensor, the duty ratio DR of the output VOX of the air-fuel ratio sensor (=TR/(TR
→−TL)) is thick (DR>50%), and in the case of a standard sensor, the duty ratio DR is approximately 50%, and in the case of a rich deviation sensor, the duty ratio DR is small (DI+ <
50%).

In other words, the degree of deterioration of the air-fuel ratio sensor is quantitatively detected by the duty ratio DR.

In the means shown in FIGS. 1C and 1D, air-fuel ratio foot control is further executed in accordance with the degree of deterioration of the air-fuel ratio sensor, that is, the deviation of the output characteristics.

That is, as shown in FIG. 4, from time t0 to t.

After performing forced duty ratio control in between, the output V does not indicate the degree of deterioration of the air-fuel ratio sensor. Depending on the duty ratio DR of

The amount R3l- is controlled asymmetrically to compensate for deviations in the controlled air-fuel ratio.

〔Example〕

FIG. 5 is an overall schematic diagram showing an embodiment of an air-fuel ratio control device for an internal combustion engine according to the present invention. In FIG. 5, an air flow meter 3 is provided in an intake passage 2 of an engine main body l. The air flow meter 3 directly measures the amount of intake air, has a built-in potentiometer, and generates an analog voltage output signal proportional to the amount of intake air. This output signal is supplied to an A/D converter 101 with a built-in multiplexer of the control circuit 10. The disc I/rebuter 4 includes a crank angle sensor 5 whose shaft generates a pulse signal for detecting a reference position every 720 degrees in terms of crank angle, and a crank angle sensor 5 for detecting a reference position every 30 degrees in terms of crank angle. A crank angle sensor 6 is provided which generates a pulse signal. The pulse signals of these crank angle sensors 5 and 6 are supplied to the human output interface 102 of the control circuit IO, and the output of the crank angle sensor 6 is sent to the CPU 1.
03 interrupt terminal.

Further, the intake passage 2 is provided with a fuel injection valve 7 for supplying pressurized fuel from a fuel supply system to the intake boat for each cylinder.

Further, a water temperature sensor 9 for detecting the temperature of cooling water is provided in the water jacket 8 of the cylinder block of the engine body 1. Water temperature sensor 9 indicates cooling water temperature TH
Generates an analog voltage electrical signal according to W. This output is also supplied to the A/D converter 101.

In the exhaust system in a T flow from the exhaust manifold 11, there is a catalytic converter 12 that accommodates a three-way catalyst that simultaneously purifies three harmful components 1'lc, Co, and NoX in the exhaust gas.
is provided.

An 02 sensor 13 having a built-in heater 13a is provided in the υF air manifold 11, that is, on the -L flow side of the catalytic converter 12. The 02 sensor 13 issues an electrical signal corresponding to the concentration of oxygen components in the exhaust gas. In other words,
The 02 sensor 13 outputs different output voltages to the control circuit 10 depending on whether the air-fuel ratio is lean or rich with respect to the stoichiometric air-fuel ratio.
This occurs in the A/D converter 101.

Further, the throttle valve 14 of the intake passage 2 is provided with an idle switch 15 for detecting whether the throttle valve 14 is fully closed, and this output signal is supplied to the input/output interface 102 of the control circuit IO. Ru.

An alarm 16 is activated when the 02 sensor 13 is significantly deteriorated, and is maintained by the drive circuit 111 of the control circuit 10.

Reference numeral 17 denotes a vehicle speed sensor, which is composed of a permanent magnet and a reed switch, for example, and its output is sent to the control circuit 10.
It is sent to the vehicle speed formation circuit 112.

The control circuit 10 is configured as a microcomputer, for example, and includes an A/D converter 101, an input/output interface 102, a CPU 103, and a drive circuit 111.
ROM104, ROM105, hackup RO
M106, a clock generation circuit 107, etc. are provided.

Further, in the control circuit 10, a down counter 108,
Flip-flop 109 and drive circuit 110 are for controlling fuel injection valve 7.

That is, in the routine described later, the fuel injection amount TAU
is calculated, the fuel injection amount TAU is counted down by the down counter 1.
08 and the flip flop 109 is also set. As a result, the drive circuit 110 starts energizing the fuel injection valve 7. On the other hand, when the down counter 108 calculates a clock signal (not shown) and its carrier terminal finally reaches the "1" level, the flip-flop 109 is turned on and the drive circuit 110 controls the fuel injection valve. 7. In other words, the above-mentioned fuel injection amount T'
The fuel injection valve 7 is energized by the amount AU, so that an amount of fuel corresponding to the fuel injection amount TAU is sent into the combustion chamber of the engine body 1.

Note that the CPU 1103 interrupts the input/output interface 1 when the A/D conversion of the A/D converter 101 is completed.
When 02 receives the pulse signal of the crank angle sensor 6,
For example, when the interrupt signal from the 1 cock generation circuit 107 is received.

The intake air amount data Q and cooling water temperature data T HW of the air flow meter 3 are taken in by an A/D conversion routine executed at predetermined time intervals and stored in a predetermined area of the RAM 105 . In other words, the data Q and 'I'' HW in the RAM 105 are updated at predetermined intervals.
Rotation speed data N (4 is 30°C of crank angle sensor 6
It is calculated by an interrupt for each A and stored in a predetermined area of the RAM 1050.

The operation of the control circuit 10 shown in FIG. 5 will be explained.

FIG. 6 shows an air-fuel ratio control routine for a predetermined period of time, for example 4. Executed every ms.

In step 601, it is determined whether a closed loop (feedback) condition for the air-fuel ratio by the 02 sensor 13 is satisfied. For example, the output signal of the 02 sensor 13 is never inverted when the coolant temperature is below a predetermined value, while the engine is starting, during engine startup, during engine warming, during power increase, or during OTP increase to prevent catalyst overheating. When there is no fuel cut, etc., the closed loop condition is not satisfied, and in other cases, the closed loop condition is satisfied. If the closed loop condition is not satisfied, the process proceeds to step 606 and the FAF is set to the value immediately before the end of the closed loop control. Note that it may be set to a constant value, for example, 1.0. On the other hand, if the closed loop condition is satisfied, the process proceeds to step 602.

In step 602, it is determined whether the engine is in a steady state. For example, the vehicle speed SPD is taken in from the vehicle speed forming circuit 112, and it is determined whether the vehicle speed SPD is within a predetermined range of 5PDO to SP+lI as shown in FIG. If it is in an unsteady running state, the process advances to step 603 and the 0□ sensor 13
output V. Air-fuel ratio feedback control is performed according to X. On the other hand, if the vehicle is in a steady running state, forced duty ratio control is performed in step 605 via step 604. Note that after the forced duty ratio execution flag XDTY has been carried out for a predetermined period in step 604, as shown in FIG. 7, the forced duty ratio control is not carried out again. It is pre-cleared in the initialization routine.

Then, in step 606, the routine of FIG. 6 ends.

FIG. 8 is a detailed flowchart of the fee pack control step 603 of FIG.

In step 801, the output V of the 0□ sensor 13 is converted into an A/D
Convert and import, at step 802 ■. Determine whether or not X is the comparison voltage ■8, for example, 0.45 V or less. In other words, determine whether the air-fuel ratio is rich or lean. In other words, if the air-fuel ratio is lean (Vox≦VR), step 803
It is determined whether the delay counter CDLY is negative or not, and if CDLY>O, CDLY is set to O in step 804, and the process proceeds to step 805. In step 805,
Decrease the delay counter CDLY by 1 and proceed to step 8.
06. At 807, the delay counter CDLY is guarded at the minimum value TDL. In this case, when the delay counter CDLY reaches the minimum value TDL, step 8
At 08, the air-fuel ratio flag F is set to "0" (lean). Note that the minimum value TDL is a lean delay state for maintaining the determination that the rich state is present even if there is a change from rich to lean in the output of the upstream side 02 sensor 13, and
Defined as a negative value. On the other hand, Su・7chi (VOX>VR)
If so, in step 809 the delay counter CD
It is determined whether LY is positive or not, and if CDLY<Q, CDLY is set to 0 in step 810 and the process proceeds to step 811. In step 811, the delay counter CDLY is incremented by 1, and in step 812. At 813, the delay counter CDLY is guarded at the maximum value TDR. In this case, when the delay counter CDLY reaches the maximum value TDR, the air-fuel ratio flag F is set to "1" (rich) in step 814.The maximum value TDR is "-stream side 02".
This is the rich delay time required to maintain the determination that the lean state is present even if the output of the sensor 13 changes from lean to rich, and is defined as a positive value.

In step 815, it is determined whether the sign of the air-fuel ratio flag F has been reversed, that is, it is determined whether the air-fuel ratio after the delay processing has been reversed. If the air-fuel ratio is reversed, then in step 816, it is determined based on the value of the air-fuel ratio flag F whether the reversal is from rich to lean or from lean to rich. If it is a reversal from rich to lean, it is increased in a skip manner to FAF -FAF+ll5R in step 817, and conversely, if it is a reversal from lean to rich,
In step 818, it is decreased in a skip manner to l1AF (-FAF-R3L. In other words, skip processing is performed.

If the sign of the air-fuel ratio flag F is not inverted in step 815, step 819. 820. Integration processing is performed at 821. That is, in step 819, F“0”
If F-''0'' (lean), FAF -1iAF+KIR is determined in step 820, and on the other hand, if F-``1'' (rich), FAI' = FAF KIL is determined in step 821. Here, the integral constants KIR and KIL are set sufficiently small compared to the skip amounts R3R and R3L, that is, KIR(KIL
) <R5R(R3L). Therefore, step 82
0 gradually increases the fuel injection amount in a lean state (F="0"), and step 821 gradually decreases the fuel injection amount in a rich state fi (F-'"1").

Step 817. 818. 820. The air-fuel ratio correction coefficient FAF calculated in step 821 is processed in step 822. 8
23 is guarded at a minimum value, for example 0.8, and step 824 . At 825, it is guarded at a maximum value of 1.2, for example. As a result, if the air-fuel ratio correction coefficient FAF becomes too large (or too small) for some reason, the air-fuel ratio of the engine is controlled using that value to prevent over-rich or over-lean conditions.

The FAF calculated as described above is stored in 11AM 105, and the routine ends in step 826.

FIG. 9 shows the forced duty ratio control step 605 in FIG.
This is a detailed flowchart 1.

In step 901, a duty ratio calculation execution flag XDTYEXE is set in order to execute the output duty ratio calculation of the 0□ sensor 13 shown in FIG.

Next, in step 902, the counter CDTV is amplified by 11 counts, and in step 903, the 1/2 period (period T, amplitude A) of the forced duty ratio waveform (period T, amplitude A) shown in FIG.
=T/2) has elapsed. That is, CDTY≧1′/(2·4m5) However, 4ms was introduced because the step is executed every 4ms. For example, the period T of the forced duty ratio waveform is 1 to 2.5 Hz in terms of frequency.
The amplitude A is a value corresponding to 4% to 8%, thereby making it possible to maximize the purification performance of the three-way catalyst. As a result, the flow of steps 904 to 908 is executed only when /2 has elapsed, and in other cases, the process directly proceeds to step 909.

In step 904, the counter CDTY is cleared, and in step 905, the rich flag X 11 C11 is inverted.

Next, in step 906, the rich flag Xl? CIl
It is determined whether or not is "l" (rich side). Xl'lC
If H="'l", then in step 907 the air-fuel ratio correction amount FAF is set as PAF←FAI'B→ Δ, and on the other hand, Xl? If CH-“0”, step 90
In step 8, the air-fuel ratio correction amount FAF is set to FAFlFAPR. However, FAFB is a constant value, for example, FAFB=1.0-A/2.

Then, in step 909, the routine of FIG. 9 ends.

In this way, a forced duty ratio waveform with a period of 1 and an amplitude of A as shown in FIG. 10 is obtained.

FIG. 11 shows the forced duty ratio control step 60 of FIG.
02 sensor 13 output V when 5 is being executed. X
This routine calculates the duty ratio DR of the 12th
The routine in FIG. 11 will be explained with reference to the timing diagrams 1 and 2 in the figure.

Also the time. Previously, that is, before the forced duty ratio control in step 605 in FIG. 6 was executed, the duty ratio calculation execution flag XDTYEXE in FIG.
1 and the routine of FIG. 11 is not substantially executed.

Time t. , the forced duty ratio control in step 605 of FIG. 6 is executed, and the duty ratio calculation execution flag XDTY is set in step 901 of FIG. 9.
EXE is cented. Therefore, the flow at step 1101 proceeds to step 1102 and subsequent steps.

In step 1102, the time counter CNT is counted up by +1. As a result, in step 1103, it is determined whether or not the time 3T/2 has elapsed, and in step 1104
Then, it is determined whether the time n·T+3T/2 has elapsed. In addition, 4ms in steps 1103 and 1104
was introduced because this step is executed every 4 ms. That is, the time t0 to 1. shown in FIG.
Flow then proceeds directly to step 1121, where virtually nothing is performed, and at time t1-L3, flow proceeds to steps 1105-1112, and at time L3, flow proceeds to steps 1113-1120.

Steps 1105 to 1112 will be explained. In step 1105, the output V of the 0□ sensor 13 is determined. X to A/D
Convert and import, at step 1106 ■. It is determined whether or not the comparison voltage VR is, for example, 0.45V or less, that is, it is determined whether the air-fuel ratio is rich or lean. Step 1
■ at 106. If X≦VR (lean), step 1
The process proceeds to step 107, where the air-fuel ratio flag F is set to "0", and if the sampling flag FS is "0", the process directly proceeds to step 1121. On the other hand, if VOX>VR (rich), the process proceeds to step 1108, where the air-fuel ratio flag F is set to 1'', and further, at step 1110, the sampling start flag F is set.
Set S (“l”).

In other words, the first time 02 sensor 1 after time t1 in FIG.
3 output V. Step 1 at time t2 when X becomes rich
Flows 111 and 1112 are executed. Step 1
In step 111, it is determined whether the air-fuel ratio is rich (F-“1°) or not, and only when the air-fuel ratio is rich, step 111 is performed.
2, the rich time counter CRC11 is incremented by +1. In this way, from time t2 to t3 in FIG.
Then, the transition times of n forced duty ratio waveforms are measured. In addition, time t. FS- at ~t2
Not measuring the rich time as “0'' is exactly nT
This is for measuring the rich time of a period, and is not limited to this.

Steps 1113 to 1120 will be explained. In step 1113, the output of the 02 sensor 13 is ■. The duty ratio DR of n waveforms of X is DR4-CRCII/(T-n/4 ms)
Calculate by Then, in step 1114, RO
The rich skip amount R3R is calculated by interpolation using the one-dimensional map stored in M104, and in step 1115, the lean skip amount R3L is calculated as R3R4-10%-R3.
In step 1116, the skip amount R3R is calculated as R
Store S L in backup RΔ old 06. Here,
Skip amount R8R, R according to rich duty ratio DR
3L, the rich duty ratio DR indicates the rich/lean deviation of the output characteristics of the 02 sensor 13, that is, the rich/lean deviation of the control air-fuel ratio, and the skip amount R3R
, R3L can be asymmetrically controlled to correct rich/lean deviations in the controlled air-fuel ratio. That is,
By increasing the rich skip amount R3R, the control air-fuel ratio can be shifted to the rich side, and the lean skip amount RS L
The control air-fuel ratio can be shifted to the lean side even if the amount of rich skip R3I- is decreased, and on the other hand, the control air-fuel ratio can be shifted to the lean side by increasing the lean skip 1R3I-.
Even if 3R is reduced, the control air-fuel ratio can be shifted to the lean side. Therefore, s-chide.

The air-fuel ratio can be controlled by correcting the rich skip amount R3R and the lean skip amount R3L according to the tee ratio DR. In addition to the skip amounts R3R and R3L, the air-fuel ratio control constant includes the integral constant K I
R, K I L, delay time TDRTDL, or 0
It is also possible to make the comparison voltages ■□ of the outputs ■ and of the two sensors 13 variable.

In steps 1117 and 1118, it is determined whether or not the 02 sensor 13 is abnormal based on the rich duty ratio DR.

That is, in step 1117, if the rich duty ratio DR is within a predetermined range of DR<DR<DRz, the 02 sensor 13 is considered normal and the process proceeds to step 1119, but if DR≦DR or DR≧
If it is DR2, it is assumed that the rich deviation or lean deviation of the 02 sensor 13 is large and abnormal, and the diagnostic flag XDIAG is set to 1'' in step 1118 to back up R.
It is stored in the A gate 106 and the alarm 16 is activated.

In step 1119, in order to indicate the end of forced duty ratio control and duty ratio calculation, the flag XDTY is set to "1", and the flag XDTYEXIE and flag FS are set to 0. In this case, the forced duty ratio control at step 605 in FIG. 6 is not executed, and the routine in FIG. 11 is also executed at step 11.
01, it is not actually executed.

In step 1120, after time t3, the air-fuel ratio feed control step in FIG.
The deviation in the air-fuel ratio of the control is reduced by starting from .

This routine then ends at step 1121.

In the routine shown in FIG. 11, the rich and lean deviations of the 02 sensor 13 are detected and the rich and lean deviations of the control air-fuel ratio are corrected. It may also be detected.

FIG. 13 is an embodiment of FIG. 6, in which step 602' is provided in place of step 602 in FIG. 6, and step 607 is added. That is, steady running in which the load hardly changes in the routine shown in FIG. 6 is very difficult in actual running, but it is possible in an idling state. However, since the exhaust gas temperature is low during idling, the element temperature of the 02 sensor 13 decreases, resulting in a very large measurement error. Therefore, in the routine shown in FIG. 13, forced duty ratio control is executed in the idle running state, that is, when the idle switch 15 is on (LL-''1''). 13a is energized to rotate the sensor element at an angle of about 500°, for example.
Achieve C or higher.

FIG. 14 shows an injection amount calculation routine, which is executed at every predetermined crank angle, for example, every 360° CA.

In step 1404, the intake air amount data Q and rotational speed data Ne are read from the RAM 105, and the basic injection amount T is read out.
A[Calculate IP. For example, TALII”-cx −
Let Q/Ne (α is a constant). Step 1402 reads the cooling water temperature data T HW from the RAM 105 and returns it to R.
The warm-up increase value FWL is calculated by interpolation using the one-dimensional MA knob stored in the OM 104. In step 1403, the final injection amount TAU is set as TAU←-TAUP-FAI'
- Calculate by (FWL+β)4T. Note that β and γ are correction amounts determined by other operating state parameters.

Next, in step 1404, the injection amount TAU is set in the down counter 108 and the flip-flop 1 is set.
Set 09 to start fuel injection. This routine then ends in step 1405.

As described above, when the time corresponding to the injection amount TAU has elapsed, the flip-flop 109 is reset by the carrier signal of the down counter 108, and the fuel injection ends.

In addition, in the two examples, the fuel injection amount is calculated according to the intake air amount and the engine rotation speed, but the fuel injection amount is calculated depending on the intake air pressure and the engine rotation speed, or the throttle valve opening and the engine rotation speed. The fuel injection amount may be calculated accordingly.

Further, in the above embodiment, an internal combustion engine is shown in which the amount of fuel injected into the intake system is controlled by the amount of fuel injected, but the present invention can also be applied to a carburetor type internal combustion engine. For example, the electric link air conditioner roll valve (EACV) controls the air-fuel ratio by adjusting the amount of air intake into the engine, and the electric link bleed air conditioner 1~rollhalf adjusts the air bleed amount of the gabbretor. The present invention can be applied to devices that control the air-fuel ratio by introducing atmospheric air into the main system passage and slow system passage, and those that adjust the amount of secondary air sent to the exhaust system of an engine. In this case, the basic injection amount TA[I
The basic fuel injection amount corresponding to P is determined by the carburetor itself, that is, it is determined according to the intake pipe negative pressure corresponding to the intake air amount and the rotational speed of the engine, and in step 1403, the basic fuel injection amount corresponding to the final fuel injection amount 1゛ΔU is determined. The amount of air supplied is calculated.

Further, in the above-described embodiment, a 02 sensor was used as the air-fuel ratio sensor, but a CO sensor, a lean mixer sensor, etc. may also be used.

Furthermore, although the embodiment described above is constructed from a microcomputer, that is, a digital circuit, it may also be constructed from an analog circuit.

〔Effect of the invention〕

As explained above, according to the present invention, deterioration in the output characteristics of the air-fuel ratio sensor can be detected with high accuracy, and deviations in the air-fuel ratio during air-fuel ratio feedback control can be corrected, resulting in deterioration of fuel efficiency and drivability. It is possible to prevent deterioration of energy consumption, deterioration of emissions, etc.

[Brief explanation of the drawing]

Figures 1A to 1D are overall block diagrams for explaining the present invention in detail. Figure 2 is an exhaust emission characteristic diagram showing the output characteristics of the 02 sensor. Figures 3 and 4 are detailed diagrams of the present invention. A timing diagram to be explained; FIG. 5 is an overall schematic diagram showing an embodiment of the air-fuel ratio control device for an internal combustion engine according to the present invention; FIGS. 6, 8, 9, 11, 13, 14th
The figure is a flowchart for explaining the operation of the control circuit in Figure 3. Figures 7, 10, and 12 supplement flowcharts 1 and 1 in Figures 6, 9, and 11, respectively. FIG. 2 is a timing chart for explanation. DESCRIPTION OF SYMBOLS 1... Engine body, 3... Air flow meter, 4... Dis1-rebuter, 5.6... Crank angle sensor, 10... Control circuit, 12... Catalytic converter, 13...・0□sensor, 15...Idle switch. Ward XRCH='1゛' Procedural amendment (voluntary) October 1988

Claims (1)

[Scope of Claims] 1. A three-way catalyst provided in an exhaust passage of an internal combustion engine; an air-fuel ratio sensor provided in an exhaust passage upstream or downstream of the three-way catalyst; when the engine is in a steady running state; steady running determining means for determining whether or not the engine is in a steady running state; forced duty ratio generating means for generating a forced duty ratio waveform of a constant period and constant amplitude when the engine is in a steady running state; an air-fuel ratio adjusting means for adjusting the air-fuel ratio of the engine; and a deterioration determining means for determining the degree of deterioration of the air-fuel ratio sensor according to a duty ratio of the output of the air-fuel ratio sensor when the engine is in a steady running state. An air-fuel ratio control device for an internal combustion engine, comprising: 2. Claim 1, further comprising: asymmetrical control constant calculation means for calculating an air-fuel ratio feedback control constant according to the degree of deterioration of the air-fuel ratio sensor; and according to the air-fuel ratio feedback control constant and the output of the air-fuel ratio sensor. An air-fuel ratio control device for an internal combustion engine, comprising: an air-fuel ratio correction amount calculation means for calculating an air-fuel ratio correction amount, wherein the air-fuel ratio adjustment means adjusts the air-fuel ratio of the engine according to the air-fuel ratio correction amount. 3. A three-way catalyst installed in the exhaust passage of an internal combustion engine; an air-fuel ratio sensor with a heater installed in the exhaust passage upstream or downstream of the three-way catalyst; idling determination means for determining idle running; forced duty ratio generating means for generating a forced duty ratio waveform of a constant period and constant amplitude when the engine is in an idling running state; an air-fuel ratio adjusting means for adjusting a fuel ratio; a heater energizing means for energizing the heater of the heater-equipped air-fuel ratio sensor when the engine is in an idling state; and a heater energizing means for energizing the heater-equipped air-fuel ratio sensor when the engine is in an idling state An air-fuel ratio sensor deterioration detection device for an internal combustion engine, comprising deterioration determining means for determining the degree of deterioration of the air-fuel ratio sensor according to the duty ratio of the output of the fuel ratio sensor. 4. Claim 3, further comprising: asymmetric control constant calculation means for calculating an air-fuel ratio feedback control constant according to the degree of deterioration of the air-fuel ratio sensor; and according to the air-fuel ratio feedback control constant and the output of the air-fuel ratio sensor. An air-fuel ratio control device for an internal combustion engine, comprising: an air-fuel ratio correction amount calculation means for calculating an air-fuel ratio correction amount, wherein the air-fuel ratio adjustment means adjusts the air-fuel ratio of the engine according to the air-fuel ratio correction amount.