JPS60240840A - Control device of air-fuel ratio in internal-combustion engine - Google Patents

Abstract

PURPOSE:To enable a change of air-fuel ratio to be avoided in an engine when it is driven in low speed operation, by stopping feedback correction of the air-fuel ratio by proportional integration control and fixing a feedback correction quantity of the air-fuel ratio to the predetermined value when a predetermined condition of low speed operation is detected. CONSTITUTION:A captioned device equips a supply fuel quantity determining means B which determines a supply quantity of fuel by suitably correcting in accordance with a water temperature and an idle condition a basic injection quantity Tp, calculated from an intake air quantity and an engine speed, of the data obtained from the output signal of an engine operational conditiin detecting means A. And a feedback correcting means D feedback corrects the above described supply quantity of fuel by proportional integration control in accordance with the output signal of an in-exhaust oxygen concentration detecting means C. Here the captioned device equips a detecting means E detecting a predetermined low speed operational condition, and when it is detected, a feedback correction quantity fixing means F operates so as to fix a feedback correction quantity for the supply quantity of fuel to the predetermined value.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an improvement in an air-fuel ratio control device having a function of feedback controlling the air-fuel ratio of an air-fuel mixture supplied to an engine based on the oxygen concentration in engine exhaust gas.

Background Art> This type of air-fuel ratio control device is used, for example, in an electronically controlled fuel injection internal combustion engine, to increase or decrease the amount of fuel injected into the intake air flow to control the air-fuel ratio of the air-fuel mixture supplied to the engine. There is something to control.

To explain this, in an electronically controlled fuel injection type internal combustion engine, the fuel injection amount Ti (valve opening pulse width for driving the fuel injection valve) is determined by the following equation.

Ti = Tpx COEF A correction coefficient determined by various operating conditions, α is a feedback correction coefficient for air-fuel ratio feed bank control (hereinafter referred to as λ control), and Ts is a voltage correction factor, which is a correction coefficient for the fuel injection valve due to fluctuations in battery voltage. This is to correct changes in valve opening operation characteristics.

λ control is an oxygen sensor installed in the exhaust system, and determines whether the air-fuel ratio of the mixture supplied to the engine is richer or leaner than the set air-fuel ratio based on whether the output of the oxygen sensor exceeds a predetermined slice level. Based on this determination, the fuel injection amount is controlled so that the air-fuel ratio of the air-fuel mixture supplied to the engine becomes the set air-fuel ratio. That is, by changing the above-mentioned air-fuel ratio feedbank correction coefficient αΦ value based on the output of the oxygen sensor, the fuel injection amount Ti is changed,
The air-fuel ratio of the air-fuel mixture supplied to the engine is maintained at a set air-fuel ratio.

Here, the value of the air-fuel ratio feedback correction coefficient α is changed by proportional-integral control (PI control) to achieve stable control.

In other words, the output of the oxygen sensor is compared with a predetermined slice level, and if the output of the oxygen sensor is greater (smaller) than the slice level, the air-fuel ratio is richer (leaner) than the set air-fuel ratio.
In this case, without rapidly decreasing (increasing) α, first decrease (increase) by a proportional amount, and then decrease (increase) by an integral amount that is set to a smaller value than the proportional amount. The injection amount is gradually decreased (increased) without suddenly decreasing (increasing) all at once, making the air-fuel ratio leaner (richer).

However, in air-fuel ratio control using such proportional-integral control, even if the set air-fuel ratio is achieved macroscopically,
Microscopically, the value of the air-fuel ratio feedbank correction coefficient α is the first
As shown in the figure, the air-fuel ratio fluctuates finely around the value αt that gives the set air-fuel ratio, and the air-fuel ratio of the air-fuel mixture supplied to the engine fluctuates finely accordingly.

For example, during low-speed operation in a low-speed gear position such as idle self-propulsion, fluctuations in the engine output torque due to fluctuations in the air-fuel ratio become large. During operation, vibrations and hums occur due to fluctuations in the output torque (see FIG. 2), and there is a fear that drivability may deteriorate.

(Object of the Invention) The present invention has been made with attention to such problems, and an object of the present invention is to provide an air-fuel ratio control device that can avoid fluctuations in the air-fuel ratio during low-speed engine operation. The purpose is to improve drivability in this driving range.

<Summary of the Invention> For this purpose, the present invention includes means for detecting the engine operating state as shown in FIG. 3, and means for determining the amount of fuel to be supplied to the engine based on the engine operating state detected by the means. An air-fuel ratio control device comprising means for detecting an oxygen concentration in engine exhaust gas, and means for feedback correcting the amount of fuel supplied to the engine based on the oxygen concentration detected by the means, using proportional-integral control. means for detecting the operating state; and means for fixing a feed bank correction amount to a predetermined value for the amount of fuel supplied to the engine when a predetermined low speed operating state is detected by the means; The above objective is achieved by avoiding fluctuations in the air-fuel ratio of the air-fuel mixture supplied to the engine.

<Example> The present invention will be explained below based on an embodiment shown in FIG.

Note that this is an application of the present invention to an electronically controlled fuel injection type internal combustion engine.

That is, in the figure, CPUI, ROM2. Output signals from various sensors serving as engine operating state detection means are input to the CPUI of the microcomputer, which includes a RAM 3, an address decoder 4, and the like. First, the analog input interface 9 receives as analog input signals an intake air flow rate signal from the hot wire air flow meter 5, a throttle opening signal from the throttle sensor 6, an engine cooling water temperature signal from the water temperature sensor 7, and a voltage signal from the Hara Chiri 8. and is input via the A/D converter 10. Also,
The output signal of the oxygen sensor 11 as a means for detecting the oxygen concentration in the exhaust gas is also input to the cp via the analog input interface 9.
It is now entered into the ui. Here 12 is A/
This is a D conversion timing controller.

On the other hand, as a digital input signal, idle switch 1
3. There are signals from the gear position switch 14, which are input to the CPUI via a digital input interface 15.

In addition, a reference signal every 180° and a position signal every 1° from the crank angle sensor 16 are sent to CPtJl via a one-shot multi-circuit 17, and a vehicle speed signal from the vehicle speed sensor 18 is sent via a waveform shaping circuit 19 to CPtJl. is input.

As an output signal from the CPU 1 in response to these input signals, a pulse signal for driving the fuel injection valve 20 is outputted to the fuel injection valve 20 via the current waveform control circuit 21.

Next, the operation will be explained with reference to the flowchart shown in FIG.

First, the output signals of the various sensors are read in Sl. Next, in S2, the basic injection amount 'rp is calculated from the intake air flow rate Q read in Sl and the engine rotational speed N determined from the output of the crank angle sensor 16 read in <31.

In S3, the value of the coefficient C0EF is determined based on the output signals of the water temperature sensor 7 and the throttle sensor 6, and in S4, the hesostatic voltage correction numerator s is set based on the battery voltage.

The above steps 82 to S4 correspond to the supply fuel amount determining means shown in FIG.

Then, in the judgments from 35 to S8, the gear is in the low speed gear position (
S5), the idle switch 13 is turned on (S6), the engine speed is below a predetermined value (S7), and the vehicle speed is below a predetermined value (S8).
), the engine is in idle self-running state,
It is determined that the engine is in a predetermined low speed operating state and the process proceeds to S9, and if at least one of the above conditions is not satisfied, it is determined that the engine is not in the predetermined low speed operating state and the process proceeds to S910.

That is, steps S5 to S8 correspond to the low-speed driving state detection means shown in FIG. 3.

In S9, a predetermined constant value is substituted for the feedhack correction coefficient α, and the feedhack correction amount for the fuel injection amount is fixed. This process corresponds to the feed hack correction amount fixing means shown in FIG.

On the other hand, when proceeding to SIO, the feed bank correction coefficient α is set by the proportional-integral control described above.

That is, when this routine is activated immediately after the output of the oxygen sensor 11 is reversed from the rich side to the lean side, a proportional amount is added to α, and when this routine is activated for the second time or later after the output of the oxygen sensor 11 is reversed, an integral is added to α. are added sequentially. Contrary to the above case, when the output of the oxygen sensor 11 is reversed from the lean side to the rich side, the same operation is performed by changing the addition of the proportional and integral parts to subtraction.

In other words, this process SIO corresponds to the supplied fuel amount feedback correction means shown in FIG.

In sii, S2-34. The fuel injection amount Ti is calculated from T p , COE F , T s , and α determined in S9 or SIO, respectively, using the above-mentioned calculation formula. S1
In step 2, the pulse signal having the pulse width Ti calculated in step 311 is output to the current waveform shaping circuit 21, and the fuel injection valve 20 is opened.

According to the air-fuel ratio control device that operates in this way, when a predetermined low-speed operating state is detected, the feed hack correction coefficient α
Since α is fixed at a constant value, the minute fluctuations in the air-fuel ratio of the air-fuel mixture supplied to the engine, which can be seen when the value of α is determined by proportional-integral control, are eliminated (see Figure 6). .

This prevents the occurrence of vibrations and hums due to fluctuations in engine output torque in low-speed operating ranges such as idling free running, and maintains good drivability in this operating range.

Note that the detection of the predetermined low-speed driving state is not limited to that of this embodiment, and may also include detection of the treadmill speed, the amount of accelerator depression, and the like.

Furthermore, although the present embodiment controls the air-fuel ratio of an electronically controlled fuel injection type internal combustion engine, the present invention can also be applied to air-fuel ratio control of an internal combustion engine equipped with an electronically controlled carburetor, and similar effects can be achieved. It is something.

<Effects of the Invention> As explained above, in the present invention, a means for detecting a predetermined low-speed operating state is provided, and when the means detects a predetermined low-speed operating state, the air-fuel ratio feed puncture correction by proportional-integral control is stopped. However, means for fixing the air-fuel ratio feedback correction amount to a predetermined value is provided. Therefore, in low-speed operating conditions, fluctuations in the air-fuel ratio of the air-fuel mixture supplied to the engine due to feedback control are prevented, which prevents fluctuations in engine output torque and Vibrations and hums are prevented from occurring, and drivability in this area is improved.

[Brief explanation of the drawing]

FIG. 1 is a time chart showing how the feed hack correction coefficient α changes in the conventional example, and FIG. 2 is a time chart showing how the engine output torque changes corresponding to the above.
Fig. 3 is a block diagram showing the configuration of the present invention, Fig. 4 is a block diagram showing an embodiment of the present invention, Fig. 5 is a flowchart showing the operating process of the same, and Fig. 6 shows the effects of the present invention. ,(
A) is a time chart showing the fixed range of the feedback correction amount, and (B) is a time chart showing how the engine output torque changes. 1...CPU 5...Air flow meter 6...
Throttle sensor 7... Water temperature sensor 11... Oxygen sensor 13... Idle switch 14... Gear position switch 16... Crank angle sensor 18.
... Vehicle speed sensor patent applicant Japan Electronics Co., Ltd. Representative Patent attorney Fujio Sasashima Figure 1 Figure 2 Figure 6 (A) Figure 6 (B) Figure 3

Claims (1)

[Claims] A means for detecting an engine operating state, a means for determining an amount of fuel to be supplied to the engine based on the engine operating state detected by the means, and a means for detecting an oxygen concentration in the engine exhaust gas, an air-fuel ratio control device that controls the air-fuel ratio of the air-fuel mixture supplied to the engine to a predetermined value, comprising means for feedback correcting the amount of fuel supplied to the engine based on the oxygen concentration by proportion-integral control; The present invention further includes means for detecting a predetermined low-speed operating state, and means for fixing a feed bank correction amount for the amount of fuel supplied to the engine to a predetermined value when the predetermined low-speed operating state is detected by the means. Features: Air-fuel ratio control device for internal combustion engines.