JPS62162747A - Time elapsing change correcting device for air-fuel ratio - Google Patents

Abstract

PURPOSE:To correct the discrepancy between air-fuel ratios which change with an elapsed time, by comparing the average outputs of O2 during a prescribed time under a same condition with its previous value at each prescribed travelling time, judging it to be the deterioration of an O2 sensor when the difference is more than a prescribed value, and setting up input shift values corresponding to the deterioration. CONSTITUTION:A timer 17 is set up at each prescribed travelling time on condition that more than a prescribed time is passed away after the starting of an engine and water temperature is more than a prescribed value, by means of the logical multiply of the outputs of a water temperature switch 2 and a timer 15 which is set up when an ignition switch 1 is put on. The timer 17 calculates the average output VB of an O2 sensor 3 from an O2 detecting portion 11 via a calculating means 12 for a prescribed time, and a deterioration judging means 13 compares it with previous average output VA. When the difference between the average value of this time and the average value of the previous time is more than a prescribed value, a correcting means 18 reads out input shift values corresponding to the average output from a memory portion 19, and outputs the input shift values to an air-fuel ratio feedback controlling means 20.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an air-fuel ratio control correction device for an automobile engine.

[Conventional technology]

In recent years, air-fuel ratio control devices using microcomputers have been adopted in automobile engines.
The basic fuel injection m is calculated based on the engine rotational speed signal, etc., and correction is made according to the cooling water temperature, atmospheric pressure, and operating conditions. Feedback control was performed to ensure that the exhaust gas was maintained at a favorable level. But 0! The sensor deteriorates as the distance traveled by the vehicle or the operating time of the engine increases, and this deterioration causes the air-fuel ratio control point to shift to the rich side, making it difficult to maintain a good exhaust gas level over a long period of time. For this reason, for example, an air-fuel ratio sub-section correction device shown in FIG.
2-1 to 22-n are comparison circuits, and 23 is a counter. In the air-fuel ratio correction device configured in this way, the mileage signal detected by the mileage meter 21 is combined with the set mileage set by the resistors R1 and R2 for each predetermined mileage, and each comparator 22- 1 to 22-n, and each time the set mileage is reached, the double amount is sequentially output, and the counter 2
3, a signal corresponding to the traveling distance is input to the air-fuel ratio feedback control circuit 20, and the feedback control constant by the OT sensor is corrected. In this way, the shift of the air-fuel ratio control point to the rich side due to deterioration of the Ox sensor is corrected and controlled,
Maintain good exhaust gas levels at all times.

[Problems to be solved by the invention]

The air-fuel ratio control correction device configured as described above is configured to correct the feedback control constant by a preset correction peak every preset predetermined travel distance, and corrects the or-sensitivity deterioration. It looked like this, but O
The deterioration of the x-sensor does not occur in proportion to only the distance traveled, that is, the engine operating time, but the degree of deterioration changes greatly depending on the engine operating conditions, such as exhaust gas concentration, so it is not always possible to provide accurate feedback. It is not possible to correct the control constant, and there is a risk that the air-fuel ratio may be controlled to a control point slightly outside the vicinity of stoichiometry. This invention was made in order to solve the problems of the conventional ones as described above. Even if a deviation in air-fuel ratio correction occurs due to deterioration of the 02 sensor, it can be accurately corrected and always maintain good exhaust gas. The purpose is to make it possible to keep up with the level.

[Means for Solving the Problems 1] The air-fuel ratio temporal change correction device according to the present invention includes an air-fuel ratio control correction device that includes a detection section for an Ox sensor output, a calculation device for calculating an average o2 output, and a calculation device for calculating an average o2 output. a first storage unit that stores the average 02 output; a determination unit that determines the inferior power of the Ox sensor; and a correction unit that changes the air-fuel ratio correction value α;
A second table that stores λ shift values according to deterioration as a table.
and a timer means, the average o2 output for a predetermined time under the same conditions is compared with the stored previous average o2 output for each predetermined running time, and if the difference is more than a predetermined value, the deterioration is detected. Then, a new λ shift value is read and set from a table stored based on the average o2 output at that time. [Operation] In the air-fuel ratio correction over time according to the present invention, when the cooling water temperature reaches a predetermined value or higher in the warm-up state, the timer means is set and the average value of the 02 sensor output within this timer time is calculated. , the previous average Ox stored for each predetermined running time
The judgment means compares the output with the output, and when the difference is greater than a predetermined value, it is judged as deterioration, and the table stored in the second storage unit is searched based on the current average 02 output, and the corresponding λ shift value is read out. , the λ shift is moved to the lean side, and the air-fuel ratio correction value α in the air-fuel ratio feedback control circuit is changed. [Embodiment 1] Fig. 1 is a block diagram of a device for correcting changes in air-fuel ratio over time, showing an embodiment of the present invention. To detect. 3 is an Ox sensor, 4 is an air flow meter that measures the amount of intake air, 5 is an engine speed sensor, 6 is a fuel injection valve drive circuit, 7 is a fuel injection valve, 10 is a temporal change correction device composed of a microcomputer, 11 is o2
12 is a calculating means for calculating the average value of the output of the Ox sensor; 13 is a determining means for determining the deterioration of the 02 sensor;
Reference numeral 14 denotes a first storage section such as a RAM, which stores the previous output of the 02 sensor. 15 is a timer means that is set when the ignition switch 1 is turned on, and 1G is an AND circuit. When the timer means 15 times up and its output becomes a torque level, and the engine starts to warm up and the water temperature switch 2 is turned on. The logical product is established,
1- Output the rubel. Reference numeral 17 denotes a timer means, which is set by the output of the AND circuit 16, whose rising signal causes the calculation means 12 to start averaging the Ox output, and a time-up signal that terminates the average value calculation. The previous average o2 output VA stored from the storage unit 14 is successively stored, and the current average Ox
The difference from the output VB is determined by the determining means 13, and the difference (
VA-VB) is compared with a predetermined value Z. Reference numeral 18 indicates a correction means, and reference numeral 19 indicates a second storage section consisting of flOM or the like, in which λ shift values corresponding to 02 sensor deterioration are stored as a table.
When S)>Z and it is determined that the Ox sensor has deteriorated, the correction means 18 calculates the corresponding λ from the current average 01 output.
Shift values PO to PntfiFA are extracted. 20 is an air-fuel ratio feedback control means, which includes an air flow meter 4;
Fuel injection f! based on No. 13 of rotation speed sensor 5, water temperature sensor 2, etc. <Injection FR>>, further performs air-fuel ratio feedback control based on the output of the 02 sensor 3, changes the air-fuel ratio correction value α by the 01 output according to the read λ shift value, and adjusts the output pulse width. Based on the signal, the amount valve time of the fuel injection valve 7 is υ controlled via the drive circuit 6. Next, the operation of the temporal change correction device configured as above will be explained with reference to the flowchart shown in FIG. The operation shown in this flowchart is performed once every certain mileage of the vehicle or every cumulative operating time of the engine, and the relationship between the 02 output and the air-fuel ratio correction (l!! (λ shift)) is determined from table data In the figure, 'lj/A is the previous average 02 output value, VB is the current average 02 output value, P is the air-fuel ratio correction value set last time, and Pn is the air fuel ratio set this time. The fuel ratio correction value, A is the set time (seconds) of the timer means 15, B is the set value of the water temperature switch 2, C is the set time of the timer means 17, and Z is the set value for determining the deterioration of the Ox sensor 3. First, the ignition switch 1 is turned on to start the engine, and the timer means 15 is set. When the timer time limit A seconds has elapsed, warm-up progresses with the start, and the engine cooling water temperature 7W reaches the setting 1a8 or higher, the water temperature switch is turned on. 2 is O
N, and the timer means 17 is set. During this timer time C, the calculation means 12 detects the Oz detection section 11.
The 02 output outputted from the 02 output is determined as an integral value, and further divided by the time C to calculate the average 02 output VB. Next, when the timer time limit C is reached, the judgment means 13 calculates the difference between the previous average 02 output vA stored in the recording section 14 and the current average 2 output Vs, and the difference is determined in advance. It is compared with a predetermined value Z, and if (to -VB)>Z, it is determined that the 01 sensor 3 has deteriorated. On the other hand, if (VA-VB)≦Z and it is determined that no deterioration has occurred, λ
If the shift value is continued to be used as it is, or if deterioration has occurred, the average 0
2 The λ shift value pn corresponding to the output 8 is read out, the previously set air-fuel ratio correction 1tlI P is changed to pn, and the λ shift value is shifted to the lean side. In addition, the first storage unit 1
The previous average 01 output value V^ stored in 4 is rewritten to Vs and stored as a new average o2 output value VA. When this series of temporal change correction operations are completed, the air-fuel ratio feedback control υO means 20 adjusts the new λ shift value pn
The air-fuel ratio correction coefficient α is changed based on this, and the normal air-fuel ratio feedback control is returned to. In addition, each setting is 1 shift A. [3, Z and λ shifts are determined by experiment. The above-described air-fuel ratio correction device for changes over time is composed of a microcomputer, and has control functions such as ignition timing control, air-fuel ratio control, swirl ratio control υ0, knocking control, etc. ! It is integrated with a functional engine υj control unit. [Effects of the Invention] As explained above, the present invention compares the average o2 output for a predetermined time under the same conditions with the previously stored average o1 output for each preset running time, and when the difference is equal to or greater than a predetermined value. If this occurs, it is determined that the O2 sensor has deteriorated and a new λ shift value is set, so even if a deviation occurs in the air-fuel ratio correction due to aging of the O2 sensor, a good exhaust gas level can always be maintained, and the exhaust gas system It is possible to obtain the effect that the reliability of the system is improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an air-fuel ratio correction device for changes over time showing an embodiment of the present invention, FIG. 2 is a flowchart showing the operation of the invention, and FIG. 3 is a main part of a conventional air-fuel ratio control correction device. It is a circuit diagram. 3...02 sensor, 7...fuel injection valve, 10...
Ship 1 hourly change correction device, 11...02 detection unit, 12...
- Calculating means, 13... Deterioration determining means, 14... First
15.17...Timer means, 18...Correction means, 19...Second memory section, 2°...Air-fuel ratio feedback control means. Patent applicant: Fuji Heavy Industries Co., Ltd. Agent: Patent attorney: Makoto Kobashi Ukiwa Patent attorney: Susumu Murai

Claims (1)

[Claims] The air-fuel ratio control correction device includes a detection unit for an O_2 sensor output, a calculation unit for calculating an average O_2 output, a first storage unit for storing the previous average O_2 output, and a judgment unit for determining deterioration of the O_2 sensor. , comprising a correction means for changing the air-fuel ratio correction value α, a second storage unit storing a λ shift value according to deterioration as a table, and a timer means, and calculates the average O_2 output for a predetermined time under the same conditions. Compare the stored previous average O_2 output every predetermined running time, and if the difference is greater than a predetermined value, it is determined that there has been deterioration, and the average O_2 output at that time is
The new λ from the table stored by the _2 output
A device for correcting changes over time in an air-fuel ratio, characterized in that a shift value is read and set.