JPS6019942A - Method of feedback control of air-fuel ratio of electronically controlled fuel injection engine - Google Patents

Abstract

PURPOSE:To quickly return to an air-fuel ratio at the time of shifting from a decelerating or on-highland operation to a stationary or accelerating operation, by making the lower limit of a compensation coefficient equal to a normal value when a demanded injection quantity is larger than a minimum injection quantity and by making said lower limit higher than the normal value when the demanded injection quantity is smaller than the minimum injection quantity. CONSTITUTION:When an exact feedback compensation is performed as a calculated demanded injection quantity Qa is larger than a minimum injection quantity Qb determined by the minimum valve opening time of an injector 26, a normal value D is applied as the lower limit FAFmin of an air-fuel feedback compensation coefficient. When the exact feedback compensation is not performed, a value E higher than the normal value D is applied as the lower limit FAFmin of the compensation coefficient. The air- fuel ratio feedback compensation coefficient FAF is guarded by the lower limit FAFmin to complete a routine. Since the air-fuel ratio feedback compensation coefficient is thus guarded in a decelerating operation by the lower limit higher than the normal value, the compensation coefficient is quickly returned to a control region when a stationary operation is resumed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio feedback control method for an electronically controlled fuel injection engine, and particularly relates to an electronically controlled fuel injection engine in which exhaust gas purification measures are taken using an air-fuel ratio sensor and a three-way catalyst. Suitable for use in automobile engines equipped with an injection 1iFl device, the fuel injection amount is determined from engine rotational speed and engine load, and air-fuel ratio feedback correction is added in accordance with the deviation between the set air-fuel ratio and the actual air-fuel ratio. This invention relates to an improvement in an air-fuel ratio feedback control method for an electronically controlled fuel injection engine that increases the required injection.

In internal combustion engines, especially automobile engines that use three-way catalysts to purify exhaust gas, it is necessary to maintain the exhaust air-fuel ratio strictly close to the stoichiometric air-fuel ratio.
For example, an oxygen concentration sensor that detects the rich-lean state of the exhaust air-fuel ratio from the oxygen-rich eaves in the exhaust gas, and a fuel injection 9A
and an electronically controlled fuel injection device that controls the air-fuel ratio of the air-fuel mixture by controlling the amount, and the fuel injection amount is determined based on the output of the air-fuel ratio sensor, which is determined from, for example, engine rotational speed and engine load. By adding air-fuel ratio feedback correction according to the rich-lean state of the air-fuel ratio and adjusting the required injection amount, the fuel injection amount of the electronically controlled fuel injection device, that is, the air-fuel ratio, is feedback-controlled and the exhaust gas is adjusted. A device in which the oxygen concentration in the gas is made equal to the oxygen concentration when a mixture at a set air-fuel ratio, for example, a stoichiometric air-fuel ratio is combusted, has been put into practical use.

Such air-fuel ratio feedback control is characterized in that good exhaust gas purification performance can be obtained regardless of changes in engine operating conditions.

Furthermore, in the electronically controlled fuel injection device described above, in order to improve exhaust gas purification performance and reduce fuel consumption, when a predetermined fuel cut condition is met during deceleration operation of the engine, the fuel is A so-called fuel cut is performed by setting the injection amount to zero.

However, during deceleration operation where the fuel cut condition is not satisfied, the required injection amount Qa
is the minimum ejection amount determined by the minimum mechanical or electrical opening time of the injector. 1) The following may occur. In this case, during the deceleration operation, the amount of fuel supplied is fixed at the minimum tolerance level Qb, and the air-fuel ratio at that time is richer than the set air-fuel ratio, as shown by the actual hAA in Fig. 1. It will remain on the side. Therefore, if air-fuel ratio feedback correction is executed in this state, the correction coefficient FA
As shown by the solid line A in the figure, the lower limit value D and t'c decrease. Therefore, when the engine transitions from deceleration operation to steady/normal operation or acceleration operation, the air-fuel ratio will not change as indicated by the diagonal line B in Figure 1 until the air-fuel ratio feedback correction factor @FAF returns to the appropriate value. As in the previous example, the engine temporarily became over-lean, resulting in an increase in exhaust emissions and a worsening of drivability.

In order to solve this problem, when transitioning from steady operation to deceleration operation, the air-fuel ratio feedback correction coefficient FAF is changed to the reference ff11, as shown by the chain 1fAc in Fig. 1.
．． It is also conceivable to fix the value to O and stop air-fuel ratio feedback correction during deceleration operation. However, in this case, the air-fuel ratio feedback correction coefficient FAF is 1.0.
By increasing the value below to 1°0, the required injection amount Qa exceeds the minimum injection 9AIQb, which causes the air-fuel ratio feedback correction to restart and stop again, which causes the air-fuel ratio to increase. There was a risk that it would become unstable due to hunting.

Such a problem could occur not only during deceleration driving but also when driving at high altitudes.

The present invention has been made to solve the above-mentioned conventional problems, and is capable of transitioning from deceleration driving or high-altitude driving to steady or accelerated driving without destabilizing the air-fuel ratio during decelerating driving or high-altitude driving. The purpose of the present invention is to provide an air-fuel ratio feedback control method for an electronically controlled fuel@split engine that can quickly obtain an appropriate air-fuel ratio.

The present invention focuses on fuel injection that takes into account engine speed, engine load, etc. Fig. 2 shows an air-fuel ratio feedback control method for an electronically controlled fuel injection engine in which the required injection amount is adjusted by adding air-fuel ratio feedback correction according to the deviation between the set air-fuel ratio and the actual air-fuel ratio to 111. As shown in the summary, the procedure for determining whether or not the required injection 9A carton exceeds the minimum injection interval determined by the minimum opening time of the injector, and the procedure for determining whether the required injection amount exceeds the minimum injection amount. , the procedure for setting the upper limit value of the air-fuel ratio feedback correction coefficient to the normal value, and when the required injection amount eA is less than the minimum injection amount, setting the lower limit value of the air-fuel ratio feedback correction coefficient to a value larger than the normal value. a procedure for guarding the lower limit of the air-fuel ratio feedback correction coefficient using the lower limit value;
By including this, the above objective has been achieved.

In the present invention, when the required injection amount is less than the minimum injection amount, the lower limit value of the air-fuel ratio feedback correction coefficient is set to a value larger than the normal value. The air-fuel ratio feedback correction coefficient does not fall abnormally, and therefore, the appropriate air-fuel ratio can be quickly obtained when transitioning from deceleration operation 15 high altitude driving to steady operation or acceleration operation.

Below, with reference to the drawings, an embodiment of an automobile engine equipped with an intake pipe pressure sensing type electronically controlled fuel injection device in which the air-fuel ratio feedback & ILJ control method for an electronically controlled fuel injection type engine according to the present invention is adopted will be described. Explain in detail.

As shown in FIG. 3, this embodiment includes an intake temperature sensor 12 for detecting the temperature of intake air taken in from the outside, an accelerator pedal ( A throttle valve 16 for controlling the flow of intake air, a throttle sensor 18 for detecting the opening degree of the throttle valve 16, and a throttle valve 16 for controlling the intake air interference. A surge tank 20 for preventing surges, an intake pipe pressure sensor 22 for detecting the pressure of intake air in the surge tank 20, and an intake boat for each cylinder of the engine 10 disposed in the intake manifold 24. An injector 26 for intermittently injecting pressurized fuel, a spark plug 28 for igniting the air-fuel mixture introduced into the engine combustion seedling 10A, and an exhaust air-fuel ratio disposed in the exhaust manifold 3o. an M-line 21 degree sensor (hereinafter referred to as O2 sensor) 31 for detecting the rich-lean state of
2, and a detripulator shaft 34A that rotates in conjunction with the rotation of the crankshaft of the engine 1o, for distributing the high-voltage secondary ignition signal generated by the ignition coil 33 to the spark plugs 28 of each cylinder of the engine 1o. The engine 10 is determined from the rotating state of the destroyer 34 and the destroyer shaft 34A built in the destroyer 34.
Detected from the crank angle sensor 36 for detecting the rotational state of the engine, the water temperature sensor 38 disposed in the cylinder block 10B of the engine 10 for detecting the engine cooling water temperature, and the output of the intake pipe pressure sensor 22. The fuel injection amount is calculated according to the engine load and the engine rotation speed determined from the output of the crank angle sensor 36, and an air-fuel ratio feedback correction is added to the fuel injection 61 m according to the deviation between the set air-fuel ratio and the actual air-fuel ratio. An electronic control unit (hereinafter referred to as ECU) calculates a required injection amount and outputs a valve opening time signal to the injector 26 so that the required injection amount is obtained.
It is composed of a total of 40.

As shown in detail in FIG. 4, the ECtJ 40 includes a central processing unit (hereinafter referred to as CPU) 40A consisting of, for example, a microprocessor for performing various arithmetic processing;
Read-only memory (hereinafter referred to as ROM) 40B for storing control programs and various data, etc.
:, random access memory (hereinafter referred to as RAM) for temporarily storing calculation data etc. in the CPU 40Ak:.
) 40C, and a multiplexer function for converting analog signals inputted from the intake temperature sensor 12, intake pipe pressure sensor 22, 02 sensor 31, water temperature sensor 38, etc. into digital signals and sequentially importing the digital signals. Analog-
Digital converter (hereinafter referred to as A/D converter) 40
E, and receives digital signals input from the throttle sensor 18, crank angle sensor 36, etc.
An input/output port (hereinafter referred to as I10 port) 40F with a buffer function for outputting a control signal to the injector 26 etc. according to the calculation result of CPLJ40A.
and a common bus 40G for connecting the respective component devices and transferring data and instructions.

The action will be explained below.

Air-fuel ratio feedback correction coefficient FAF in this embodiment
The lower limit guard of is performed according to a flowchart as shown in FIG. That is, first, in step 110, the fuel injection amount per engine revolution or per unit time is calculated from the engine rotation speed, which is determined from the output of the crank angle sensor 36, and the intake pipe pressure, which is determined from the output of the intake pipe pressure sensor 22. , by multiplying the fuel injection amount by the previous air-fuel ratio feedback correction coefficient FAF, which corresponds to the deviation between the set air-fuel ratio and the actual air-fuel ratio, which has already been calculated, the current requested injection! ) Calculate J I Q a. The program then proceeds to step 112, in which the current air-fuel ratio feedback correction coefficient FAF is calculated according to the output of the 02 sensor 31.

Next, the process proceeds to step 114, and it is determined whether or not the required injection ff1Qa calculated in step 110 exceeds the minimum injection Q Q b determined by the minimum valve opening time of the injector 26, which has been determined in advance by individual evaluation or the like. Determine.

If the determination result is positive, that is, if it is determined that accurate feedback correction is being performed, step 11
Proceed to step 6, the lower limit value FA of the air-fuel ratio feedback correction coefficient
Enter the normal price as Fmin. On the other hand, if the determination result in step 114 is negative and it is determined that accurate feedback correction is not applied to the poem, the process proceeds to step 118, and the lower limit M of the air-fuel ratio feedback correction coefficient is
As FAFn+in, a value E larger than the above normal value
Insert ('E>D). This value E can be set, for example, to a value such that the required amount Qa and the minimum @Kenshi Ql) substantially match.

After the rescue step 116 or 118, step 120
Then, the lower limit of the air-fuel ratio feedback correction WN number FAF is guarded by the lower limit ffiFAFmin at that time, and this routine ends.

The air-fuel ratio feedback correction coefficient FAF determined by this routine is used when calculating the next required injection amount Qa.

In this embodiment, the air-fuel feedback correction coefficient FAF when transitioning from steady operation to deceleration operation and returning to steady operation again, request 1131! ) An example of how the air-fuel ratio changes is shown by the 1iftI line F in FIG. 1 mentioned above.

As is clear from the figure, in this embodiment, the air-fuel ratio feedback correction coefficient FAF during operation is guarded at a value E that is larger than the normal value, so when the steady operation is resumed, the air-fuel ratio feedback correction coefficient FAF is The fuel ratio feedback correction coefficient FAF quickly returns to the feedback control area, and as shown in Fig.
! The large over-lean region B, as in the conventional example shown in A, is eliminated. Further, unlike the comparative example shown by the dashed line C in FIG. 1, the air-fuel ratio does not become unstable due to hunting during deceleration operation.

In this embodiment, the lower limit value F A F mln of the air-fuel ratio feedback correction coefficient was set to a binary value, so 10
Gram is simple. Note that the method of changing the lower limit value of the air-fuel ratio feedback correction coefficient is not limited to this, for example, 3
It is also possible to make it greater than the value.

In the above embodiment, the present invention was applied to an automobile engine equipped with an electronically controlled fuel injection device that senses intake pipe pressure, but the scope of application of the present invention is not limited to this.
For example, it is obvious that the present invention can be similarly applied to automobile engines equipped with an electronically controlled fuel injection device that senses the amount of intake air, and other types of electronically controlled fuel injection engines.

As explained above, according to the present invention, the air-fuel ratio is not destabilized during deceleration driving or high-altitude driving, and when transitioning from decelerating driving or high-altitude driving to steady or accelerated driving, the air-fuel ratio can be quickly adjusted to the appropriate level. The air-fuel ratio can be obtained. Therefore, it has the excellent effect of reducing exhaust emissions and improving drivability.

[Brief explanation of the drawing]

Figure 1 shows the air-fuel ratio feedback correction coefficient, demand@copper amount, and air-fuel ratio when transitioning from steady operation to deceleration operation and returning to steady operation in a conventional example, a comparative example, and an example of the present invention. Fig. 2 is a flowchart showing the gist of the air-fuel ratio noise back control method for an electronically controlled fuel injection engine according to the present invention, and Fig. 3 is a pictorial diagram comparing examples of relationships between changing states. An actual example of an automobile engine equipped with an electronically controlled fuel injection system that senses intake pipe pressure!
FIG. 4 is a cross-sectional view including a partial block diagram showing the configuration of one example; FIG. 4 is a block diagram showing the configuration of the Kameko control unit used in the embodiment; FIG. FIG. 4 is a flowchart showing the main part of a routine for guarding the lower limit of the fuel ratio feedback correction coefficient. Qa...required injection amount, Qb...minimum injection amount, FAF
...Air-fuel ratio feedback correction coefficient, F A F m
in...lower limit value, D...normal value, E...value larger than the normal value, 10...engine, 22...intake pipe pressure sensor,
26... Injector, 31... Oxygen concentration sensor (02 sensor), 32...
catalytic converter, 36... crank angle sensor, 40... electronic control unit (ECU). Agent Takaya Ron (and 1 other person)

Claims (1)

[Claims] (1) Electronically controlled fuel injection in which the required injection amount is determined by adding air-fuel ratio feedback correction according to the deviation between the set air-fuel ratio and the actual air-fuel ratio to the fuel injection amount determined from engine speed, engine load, etc. In the air-fuel ratio feedback control method for a type engine, a procedure for determining whether the required injection amount exceeds the minimum injection amount determined by the minimum valve opening time of the injector; If the required injection rate is below the minimum injection amount, the lower limit value of the air-fuel ratio feedback correction coefficient should be set to a higher value than the normal value. 1. An air-fuel ratio feedback control method for an electronically controlled fuel injection engine, characterized in that the air-fuel ratio feedback control method for an electronically controlled fuel injection engine includes the steps of: overriding the air-fuel ratio feedback correction coefficient; and guarding the lower limit of the air-fuel ratio feedback correction coefficient using the lower limit value.