JPS6073019A - Air-fuel ratio control for engine - Google Patents

Abstract

PURPOSE:To improve the durability of the exhaust system of an engine and suppress the deterioration of fuel economic efficiency by controlling the air-fuel ratio of the mixed gas towards enrichment when the exhaust temp. exceeds a set value, in the high-load and high-revolution-number range of an engine. CONSTITUTION:When a fuel-injection control circuit 9 controls the air-fuel ratio of an engine, it is confirmed that the value of a timing counter CN for correcting the fuel injection amount which is set into a memory apparatus accords with a timing set value M set beforehand, when the engine is put into high-load and high-revolution range. When the value on the timing counter CN reaches the set value M, and an exhaust temp. is over a set value, the air-fuel ratio of the mixed gas is controlled towards enrichment with the exhaust temp.-corrected injection amount F1 added with correction injection amount f. Therefore, deterioration of fuel economic efficiency can be suppressed, and the durability of the exhaust system of the engine can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention primarily relates to an air-fuel ratio control method applied to gasoline engines for automobiles and the like.

(b) Prior art Engines installed in automobiles, etc. are used under various load conditions and in a wide range of rotational speeds, so even when operating without any abnormalities such as misfires, the exhaust temperature may vary. There is a problem that the permissible value may be temporarily exceeded, and when this occurs in a coal-fired vehicle, the durability of the exhaust system is significantly reduced.

Therefore, as a prior art developed to deal with such inconveniences, as shown in Shikkai No. 58-28560, when the temperature of the engine exceeds a preset allowable value, There is a system in which the air-fuel ratio of the air-fuel mixture supplied to the engine is controlled to be richer than the stoichiometric air-fuel ratio to lower the exhaust temperature. However, this one
Since the engine load and engine speed are controlled over the entire range, favorable results are not necessarily obtained in terms of fuel economy. In other words, it is possible for the exhaust temperature to exceed the allowable value even in the low-load, low-speed range of the engine, but it is rare for the engine to continue operating steadily for a long time in such a range, and the rise in exhaust temperature is only temporary. In most cases, it becomes something. Moreover, since the amount of waste is small in this region, the exhaust temperature will rise somewhat,
However, the thermal impact on the publishing system is small. On the other hand, high engine loads such as continuous pitching or continuous driving on expressways,
In the high rotation range, there are many opportunities for steady operation to continue for a long period of time, and there is a high possibility that the exhaust temperature will continue to exceed the permissible value for a long period of time. Therefore, the inconvenience that the durability of the exhaust system of the engine is impaired due to heat damage occurs in a high load and high rotation region as an IE. Nevertheless, the above-mentioned prior art has the problem that deterioration in fuel economy cannot be avoided because the air-fuel ratio is corrected in the direction of enrichment over the entire range of engine load and engine speed.

(c) Purpose The present invention was made with attention to such circumstances,
The first objective is to suppress the exhaust temperature while suppressing the deterioration of fuel economy, and to effectively prevent the deterioration of the durability of the exhaust system of the engine due to the rise in the sliding air temperature. An object of the present invention is to provide an air-fuel ratio control device for an engine that can prevent the above problems.

(D) Structure In order to achieve the above-mentioned object, the present invention detects the exhaust gas temperature of the engine, and detects the engine's high load and high rotation region (the "high load and high rotation region" in this specification refers to It refers to both the area of high load and high rotation, and the area of either high load or high rotation. ), when the exhaust gas temperature exceeds a set value, the air-fuel ratio of the air-fuel mixture is controlled to be richer than the standard air-fuel ratio.

(e) Examples Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic system diagram of a gasoline engine equipped with an electronically controlled fuel injection device mounted on an automobile. As shown in this drawing, in this engine, intake air taken in through an air cleaner 1 is supplied to an intake port 5 of an engine body 4 via a surge tank 2 and an intake manifold 3. Reference numeral 6 denotes a throttle valve provided in front of the surge tank 2, and the amount of intake air supplied to the engine main body 4 is controlled by the opening degree of the throttle valve 6.

8 is intake manifold 3 in front of intake port 5
This is a fuel injection injector installed in the.

This injector 8 is configured to be able to control the injection amount of fuel supplied via a fuel supply path (not shown) based on a control signal output from a fuel injection control circuit 9. On the other hand, the exhaust gas discharged from the exhaust port 1O of the engine body 4 is an exhaust gas; - Manifold 11
, and is discharged to the outside through an exhaust system such as a muffler (not shown). Further, an exhaust temperature sensor 12 for detecting the temperature of exhaust gas discharged from the engine body 4 is attached to the exhaust manifold F' 11, and a detection signal from the sensor 12 is inputted to the fuel injection control circuit 9. In addition to the above-described detection signals, the fuel injection control circuit 9 also receives a detection signal from an air flow meter 13 provided immediately after the air cleaner 1 to detect the amount of intake air, a detection signal to detect the engine rotation speed, etc. , detection signals from various sensors are respectively input. Then, the fuel injection control circuit 9 outputs a signal to the injector 8, indicating that an amount of fuel should be injected in accordance with the operating state of the engine detected by these signals. ing.

Incidentally, the fuel injection control circuit 9 is a device using a microcomputer or the like, and the control procedure of the part necessary for explaining the present invention will be explained based on the flowchart shown in FIG. First, in step 1, a basic injection amount Fo is selected based on the engine speed and intake air amount.

Next, in step 2, it is determined whether the air-fuel ratio of the air-fuel mixture is corrected to suppress the exhaust temperature from the engine body 4, that is, whether the engine is in a high load and high rotation range. The determination is made based on the opening degree of the throttle valve 6, the negative pressure of the intake manifold 3, the rotation speed of the engine body 4, etc., respectively. Then, if the engine is not operating in a high load, high rotation range, execute routine a that goes through step 3, set the basic injection amount FO selected in step 1 as the final injection amount F, and respond according to that value. Control 45
output the number to the injector 8. In other words, the air-fuel mixture is not controlled in the direction of enrichment. On the other hand, when the engine enters the operating range or high load/high rotation range, the process proceeds to step 4. In this step, it is checked whether the value of the timing counter CN for injection amount correction processing set in the storage device matches the preset timing setting value M, and the reward value of the tying counter CN is If M has not been reached, routine b consisting of step 5.6.7 is executed. here,
The reason for providing the timing counter CN is that the exhaust gas generated by the ignition is detected from the ignition timing by the exhaust temperature sensor 1.
2 and is detected by the sensor 12. In this embodiment, the air-fuel ratio is corrected every time M injections are performed. First, in step 5, Fl is set as the exhaust temperature corrected injection amount at the address where the exhaust temperature corrected injection amount Fl is to be stored.

Next, in step 6, 1 is added to the timing counter cN, and in step 7, the sum of the basic injection amount FO and the exhaust temperature correction injection amount Fl set in step 5 is set as the final injection amount F. control signal to injector 8
Output to. Thereafter, this routine b is repeatedly executed until the value of the timing counter CN reaches M.

Next, when the value of the timing counter CN reaches M, it is checked in step 8 based on the detection signal detected by the exhaust temperature sensor 12 whether or not it exceeds the #ll humidity temperature setting exhaust temperature. Then, if the exhaust temperature exceeds the set exhaust temperature, proceed to step 9 and exhaust temperature correction injection amount F1
As, the exhaust temperature correction injection amount F set in step 5 above
1 plus the corrected injection amount f per calculation process. Next, in step 10, the exhaust temperature correction injection amount F1 calculated in step 9 is calculated as correction injection fine 1 - limit value F1ma.
Determine whether or not x exceeds this J-limit value F 1 m
If it does not exceed a x, the process proceeds to step 11, where a value obtained by adding the exhaust temperature correction injection amount Fl calculated in step 9 to the basic injection amount Fo is calculated as the final injection amount. Next, after clearing the value of the timing counter CN in step 12, the value calculated in step 11 is set as the final injection iF, and a control signal is output to the injector 8.

On the other hand, in Step 2B 10, the exhaust temperature correction injection 3. calculated in Step 9 is performed. F 1 is the corrected injection amount upper limit (1
If fj F l m a x is exceeded, step 13
The process proceeds to Step 11, with the exhaust temperature correction injection lFl being suppressed to the corrected injection amount upper limit value FLmax.

By the way, in step 8, if the exhaust gas temperature has not reached the set exhaust gas temperature, the following procedure is executed. First, in step 14, it is checked whether the exhaust temperature correction injection 71)
1, the final injection fJl:F is set as the reference injection g F o and a control signal is output to the injector 8. on the other hand,
If the exhaust temperature correction injection iF1 is not zero, the process proceeds to step 15, where the correction injection Skf per calculation process is subtracted from the second exhaust temperature correction injection amount F1. If the value is within the positive range, the process proceeds to step 16, where the value of Fl-f is set as the exhaust temperature correction injection amount F1, and the process proceeds to step 11. On the other hand, in step 15, if the value of Fl-f falls within the negative range, the process proceeds to step 17, where the exhaust temperature correction injection iF1 is set to zero, and the process proceeds to step 11. Therefore, the series of steps 14, 15, 16, and 17 are provided to act in the direction of reducing the corrected injection amount F1 in a region where the exhaust gas temperature does not exceed the set exhaust temperature, so that the corrected injection amount F1 is If the target value is large, execute step 1'6 for the number of M injections, and then perform correction injection #
The corrected injection amount f per calculation process is subtracted from F1. In addition, the calculation result is constantly monitored in step 15 to ensure that it does not fall into the negative region, and if it does fall into the negative region, the corrected injection amount F1 is immediately set to zero in step 17, and then directly Step 11
will be executed.

In addition, after the engine stops, the Masu Temperature Injection M immediately before the engine stops
It is desirable to pack-amplify the FI with a battery and store it in a storage device, and in this way it is possible to eliminate the need for unnecessary control after restarting the engine.

To summarize the above control procedure, first, it is determined whether or not the operating state of the engine body 4 is in the high load, high rotation range, and control is performed to suppress the exhaust temperature in areas other than the high load and high rotation range. Do not do this.

On the other hand, when the operating state of the engine body 4 is in the high load and high rotation range, the exhaust temperature is monitored to see if it exceeds the set exhaust temperature, and if it exceeds the set exhaust temperature, the exhaust temperature correction injection iF1 is immediately performed. is calculated and the air-fuel ratio of the mixture is controlled in the direction of enrichment.

Further, in a region where the air temperature υ1 is lower than the set exhaust temperature, the exhaust temperature correction injection amount F1 is reduced, and finally becomes the exhaust temperature correction injection amount Flt-zero.

(f) Effects Since the present invention has one or more configurations, the following effects can be obtained.

First, the exhaust temperature is detected, and if the exhaust temperature exceeds the set value, the air-fuel ratio of the mixture is corrected in the direction of enrichment, so the exhaust temperature can be adjusted smoothly without causing knocking, etc. can be reduced to normal values,
The durability of the engine exhaust system can be improved.

Moreover, the correction of the air-fuel ratio in the direction of enrichment is performed only in the high load and high rotation range where there is a risk of problems with the durability of the υF gas system. There is no problem of deterioration in fuel economy.

[Brief explanation of the drawing]

Fig. 1 is a system explanatory diagram showing one embodiment of the present invention;
The figure is a flowchart showing the control procedure in the same embodiment. 1 and conflict Φ Air cleaner 2... Surge tank 301 Intake manifold 4 - Engine body 5... Intake boat 6... Throttle valve 8 @e injector 9... Fuel injection control circuit 101/Exhaust port 11 Exhaust manifold 12Φ...Exhaust temperature sensor 131/Air flow meter Representative Patent attorney Hiroshi Akazawa

Claims (1)

[Claims] This system suppresses the engine exhaust temperature by changing the air-fuel ratio of the air-fuel mixture supplied to the engine, and detects the engine exhaust temperature so that the exhaust temperature does not exceed the set value in the high load and heavy rotation region of the engine. 1. A method for controlling an air-fuel ratio of an engine, characterized in that when the air-fuel ratio exceeds the standard air-fuel ratio, the air-fuel ratio of the air-fuel mixture is controlled to be richer than the standard air-fuel ratio.