JPS6022053A - Air-fuel ratio feedback control method for electronically controlled fuel injection engine - Google Patents

Abstract

PURPOSE:To obtain a proper air-fuel ratio promptly, for instance, at the time of decelerating operation of an engine, by interrupting feedback correction of the air-fuel ratio in case that the required injection quantity of fuel is smaller than a reference injection quantity in the neighbourhood of the minimum injection quantity determined by the minimum valve opening period of an injector. CONSTITUTION:According to the control method of this invention, the fuel injection period is calculated in an ECU40 on the basis of the oututs of a crank-angle sensor 36 and a sensor 22 for detecting the pressure in an intake pipe, and a new, required injection period is calculated by multiplying the fuel injection period by the already calculated, previous feedback correction factor that is determined by the deviation between a reference air-fuel ratio and the actual air-fuel ratio. Here, judgement is made whether or not the required injection period thus calculated is smaller than the minimum injection period dependent on the minimum valve opening period of an injector 26 that is predetermined by way of simplex evaluation or the like. In case of YES, feedback correction of the air-fuel ratio is interrupted for preventing the air-fuel ratio from becoming over-lean temporarily.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio feedback control method for an electronically controlled fuel injection type 7 engine, and particularly relates to an automobile engine in which exhaust gas purification measures are taken using an air-fuel ratio sensor and a three-way catalyst. The required injection amount is calculated by adding an 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 that is suitable for use in the engine speed and engine load, etc. This invention relates to an improvement in an air-fuel ratio feedback control method for an electronically controlled fuel injection engine.

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 sensor that detects the rich-lean state of the exhaust air-fuel ratio from the oxygen mW in the exhaust gas, and an electronically controlled fuel injection device that controls the air-fuel ratio of the air-fuel mixture by controlling the fuel injection amount. For example, fuel 1, which can be determined from engine speed and engine load, etc. First, by adding air-fuel ratio feedback correction according to the rich-lean state of the air-fuel ratio determined according to the output of the air-fuel ratio sensor and determining the required injection amount, the electronically controlled fuel injection CFI (The fuel injection amount of 4i+9, that is, the air-fuel ratio is feedback-controlled, and the oxygen moisture content in the exhaust gas is reduced to a set air-fuel ratio, for example, the mixture at the stoichiometric air-fuel ratio is combusted by 1!/
, : A device that is made to be equal to the oxygen ie trace in the case of , : has been put into practical use.

Such air-fuel ratio feedback control has the characteristic that it is possible to obtain good exhaust gas purification performance regardless of changes in engine operating conditions.

In addition, in the above-mentioned field with four electronically controlled fuel injection ports,
In order to improve exhaust gas purification performance and reduce fuel consumption, a predetermined amount of fuel is reduced during engine deceleration operation.
When the condition is satisfied, the fuel injection amount is set to zero and a so-called fuel cut is performed.

However, during deceleration operation where the fuel cut condition is not satisfied, the required injection time T
AIJ may be less than or equal to the minimum injection time T AU min determined by the mechanical or electrical minimum valve time of the injector. In this case, the fuel injection time during the deceleration operation is fixed at the minimum injection time T A U min, and the air-fuel ratio at that time is also shown in Fig. 1 as the actual PaA
As shown, the air-fuel ratio remains on the ridge side compared to the set air-fuel ratio.

Therefore, if air-fuel ratio feedback correction is executed in this state, the correction coefficient FAF will drop to its lower limit value, as shown by solid line A in FIG. Therefore, when the engine shifts from deceleration operation to steady operation or acceleration operation again, the air-fuel ratio will temporarily change as shown by the diagonal line B in Fig. 1 until the air-fuel ratio feedback correction coefficient FAF returns to the appropriate value. The problem was that the engine became over-lean, increasing exhaust emissions and deteriorating drivability.

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 quickly obtaining an appropriate air-fuel ratio when transitioning from deceleration driving or high-altitude driving to steady driving or accelerating driving, thereby preventing sluggishness, hiccups, etc. An object of the present invention is to provide an air-fuel ratio feedback control method for an electronically controlled fuel injection engine that can eliminate the discomfort caused by the engine.

The present invention provides an electronic system that adjusts the required injection time 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 31st injection hill determined from the engine rotation speed, engine load, etc. In the air-fuel ratio feedback control method for a controlled fuel injection engine, as summarized in FIG. 2, the required injection 01fi is a setting IIJ near the minimum injection m determined by the minimum amount valve time of the injector.
The above objective is achieved by including a procedure for determining whether or not the required injection amount is less than the set injection m, and a procedure for canceling the air-fuel ratio feedback correction if the required injection amount is less than the set injection m. It is something.

In the present invention, the request Ilr! Air-fuel ratio feedback correction is canceled when the injection rate is less than the set injection amount near the minimum injection m, which is determined by the injector's minimum amount valve time, so it is easier to use when driving at deceleration or when driving at high altitudes. The air-fuel ratio feedback correction coefficient does not fall abnormally, so that the appropriate air-fuel ratio can be quickly obtained when transitioning from deceleration driving or high-altitude driving to steady driving or accelerating driving.

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 control method for an electronically controlled fuel injection type engine according to the present invention is adopted will be described in detail. Explain.

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 ( Throttle valve 1 for controlling the flow rate of intake air, which opens and closes in conjunction with the valve (not shown)
6, a throttle sensor 18 for detecting the opening degree of the throttle valve 16, a surge tank 20 for preventing intake air interference, and an intake pipe pressure for detecting the pressure of intake air in the surge tank 20. A sensor 22, an injector 26 for intermittently injecting pressurized fuel toward the intake boat of each cylinder of the engine 10, which is disposed in the intake manifold 24, and an air-fuel mixture introduced into the engine combustion v1oA. A spark plug 28 for igniting the engine and an exhaust manifold 30 are provided. An oxygen concentration sensor (hereinafter referred to as 02 sensor) 31 for detecting the ridge-lean state of the exhaust air-fuel ratio, and a catalyst disposed downstream of the 02 sensor 31 and filled with, for example, a three-way catalyst. converter 32
and a distributor which rotates in conjunction with the rotation of the crankshaft of the engine 10, for distributing the high-pressure ignition secondary signal generated by the ignition oil 33 to the spark plugs 28 of each cylinder of the engine 10. An astributor 34 having a shaft 34A, a crank angle sensor 36 built into the test distributor 34 for determining the rotational state of the engine 10 from the rotational state of the distributor shaft 3/1Δ, and the engine 10. A water temperature sensor 4:)-38 disposed in the cylinder block 10B for detecting the engine cold water temperature, and an engine load detected from the output of the intake pipe pressure sensor 22 and the crank angle sensor 36.
The fuel 11 injection Q1ffi is planned according to the engine speed etc. determined from the output, and the required injection amount is calculated 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. , an electronic control unit (hereinafter referred to as EC4J) 40 that outputs a valve opening time signal to the injector 26 so that the required injection amount is obtained;
has been completed.

As shown in detail in FIG. 4, the ECLI 40 includes a central processing unit (hereinafter referred to as "CPU") 40A consisting of, for example, a microprocessor for performing various arithmetic operations;
A read-only memory (hereinafter referred to as ROM) 40B for storing control programs and various data, etc., and a random access memory (hereinafter referred to as RAM) 40C for temporarily storing calculation data etc. in the CPU 40Δ. , an analog-to-digital converter with 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 inputting the digital signals. (hereinafter referred to as A/D converter) 40E,
In addition to taking in digital signals input from the thrower 1 to the sensor 18, crank angle IQ sensor 36, etc.,
Depending on the performance of the CPtJ40A, a buffer (input/output port with multiple functions (hereinafter referred to as 110 ports) for outputting control signals to the -r range controller 26, etc.) is provided.
0'', and a common bus 40G for connecting firearms and transferring data and commands.

The action will be explained below.

In this embodiment, the determination as to whether or not to execute air-fuel ratio feedback correction is made by the air-fuel ratio open loop control motor routine in the main routine as shown in FIG. That is, first, in step 110, the fuel injection period per engine revolution or unit time is determined from the engine rotational speed determined from the output of the crank angle lens 36 and the intake pipe pressure determined from the output of the intake pipe pressure sensor 22. , has already been calculated for the fuel patrol time,
By multiplying by the previous air-fuel ratio feedback correction coefficient FAF corresponding to the deviation between the set air-fuel ratio and the actual air-fuel ratio, the current required injection time 1' AU@n is obtained. Next, the process 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, proceed to step 114, and perform step 11 mentioned above.
It is determined whether the required injection time TΔU calculated at 0 is less than or equal to the minimum injection time TAUmin determined by the minimum amount valve time of the injector 26, which is determined in advance by individual evaluation or the like. When the determination result is positive, that is, when it is determined that accurate feedback correction is not performed,
Proceeding to step 116, the air-fuel ratio feedback cancellation flag is set. On the other hand, if the determination result in step 114 is negative, that is, if it is determined that accurate feedback correction is being performed, the process proceeds to step 118 and the air-fuel ratio feedback stop flag is reset.

Depending on the state of the air-fuel ratio feedback stop flag set by the air-fuel ratio open loop control mode routine, when the air-fuel ratio feedback stop flag is set, the air-fuel ratio feedback correction coefficient is set to the set value, For example, the reference value is fixed to 1.0, and air-fuel ratio oven loop control is performed.

On the other hand, when the air-fuel ratio feedback cancellation flag is reset, the output of the above 02"122 31] i,
: Accordingly, the current air-fuel ratio feedback correction coefficient FAF
is set to 1 to be used when determining the next required injection time TAtJ.

An example of the change state of the air-fuel ratio feedback correction coefficient FAF, required injection time TAU, and air-fuel ratio when shifting from steady operation to deceleration operation and returning to steady operation in this example is shown in Fig. 1 mentioned above. Indicated by chain line E. As is clear from the figure, in this embodiment, the air-fuel ratio noise back correction coefficient FAF during deceleration operation is set at a set value, for example, 11 quasi-value 1
．． Since it is fixed at 0, when returning to steady operation,
Feedback control centering on the reference value is quickly started, and the large overlean region [1, as in the conventional example indicated by the solid line Δ in FIG. 1, is eliminated.

In this embodiment, since the minimum injection Q=I time is directly used as the set injection time, the effective control amount of the required injection time does not change, and effective control can be performed over a wide control range. . Note that the set injection time is not limited to this, and may be set to a value slightly larger than the minimum injection time, for example.

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 system that is most sensitive to intake air, and to other types of electronically controlled fuel injection engines.

As explained above, according to the present invention, an appropriate air-fuel ratio can be quickly obtained when transitioning from deceleration driving or high-altitude driving to steady driving or accelerating driving.

Therefore, while reducing exhaust emissions at that time,
It has the excellent effect of improving drivability and eliminating discomfort such as sluggishness and jerking.

[Brief explanation of drawings]

FIG. 1 shows the air-fuel ratio feedback correction coefficient, required injection time,
A diagram comparing and showing an example of the relationship between changing states of air-fuel ratio, 箪2
FIG.
3 is a sectional view including a partial block diagram, and FIG. Figure 4 shows the electronic control unit 1 used in the *example above.
Figure 5 is a block diagram showing the configuration of the air-fuel ratio oven loop control mode routine in the main routine.・Minimum injection time (set injection time), F
, A F...Air-fuel ratio two-way back correction coefficient, 10
...Engine, 22...Intake pipe pressure sensor, 26
...Injector, 31...Oxygen concentration sensor (02t sensor), 36...
Crank angle sensor 1, 40...Electronic control unit (ECU). Agent Takaya Ron (and 1 other person)

Claims (1)

[Claims] (1) 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 h1 determined from the engine speed, engine speed, engine load, etc. In the air-fuel ratio control method for electronically controlled fuel injection type engines, it is determined whether the required injection angle is less than or equal to the set injection port near the minimum injection amount determined by the minimum injection amount valve time of the injector. and a step of canceling the air-fuel ratio feedback correction when the requested injection m is less than or equal to the set injection M. .