JPS58217733A - Fuel injection control method of internal-combustion method - Google Patents

Abstract

PURPOSE:To facilitate an air-fuel ratio control, by arranging such that a verification is made as to whether an O2 sensor remains activated, even after once activated, and the feedback of O2 is stopped upon the O2 sensor being rendered inactive. CONSTITUTION:In a step 601, a verification is made as to the setting of flag O2 FCG(1) to be erected upright when activated in a step 601. If activated as designed, a feedback is effected. An exhaust gas temperature may drop and an O2 sensor may become inactive, if a fuel supply cut continues for longer periods or an idling operation prolongs. The feedback is stopped when the inactivation of O2 sensor is verified by the upward rise of inpedance inside the O2 sensor. In this manner, an optimum air-fuel ratio control can be effected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a fuel injection control method for an internal combustion engine, in particular, an oxygen concentration sensor (hereinafter referred to as a 0□ sensor) that detects whether exhaust gas is in an over-rich state (hereinafter referred to as RI/NOTI) or under-fueled (hereinafter referred to as lean). Regarding the fuel injection control method that determines the state (called 02
The system determines whether the sensor is in a lean state or a rich state when the sensor is activated, thereby making it possible to properly control the air-fuel ratio.

Generally, in this type of fuel injection control device, the valve opening time of the fuel injection device of an internal combustion engine, especially a gasoline engine, is adjusted to a reference value according to the engine speed and engine load, depending on the operating state of the engine. For example, it is determined by electronically adding, subtracting, or multiplying constants and coefficients corresponding to engine speed, absolute pressure in the intake pipe, engine water temperature, throttle valve opening, exhaust oxygen concentration, etc. This controls the amount of fuel injected, thereby controlling the air-fuel ratio of the mixture supplied to the engine.

The internal impedance of the 02 sensor used in the above fuel injection control device varies greatly depending on the ambient temperature, βn■) - (α/T) -β ...
-Represented by the formula (1). Here, a and β are constants, R is the internal impedance of the 02 sensor, and T is the absolute temperature. On the other hand, the electromotive force of the 02 sensor is expressed as: Here, R is a gas constant, F is a Faraday constant, T is an absolute constant, and P 02 (e xh )
Po2(air) can be considered to be the partial pressure of oxygen in the exhaust gas, and Po2(air) is the partial pressure of oxygen in the atmosphere, which is approximately 0.21 (constant).

FIG. 1 shows a measurement system for measuring the electromotive force of the 02 sensor. In Fig. 1, 1 is the 02 sensor, 2 is a load resistor (resistance value 6 Mρ) connected in series with the 02 sensor 1, and the result of experimentally determining the voltage V between the terminals of this load resistor 2 is As shown in the figure.

FIG. 3 shows the input circuit of the 02 sensor that is actually used. In FIG. 3, 1 is an 02 sensor, 3 is a fixed resistor, and 4 is an operational amplifier (hereinafter referred to as an operational amplifier), and the input impedance of this operational amplifier 4 is approximately 5MQ. In FIG. 3, assuming that the leakage current from the operational amplifier 4 is 1, the output voltage of the operational amplifier 4 is as follows.

The oxygen partial pressure in the exhaust gas is 10 at 400'C under excessive fuel concentration (hereinafter referred to as Lynch), and 16 at 800°C.
It is about 1o in a state of fuel shortage C or less. In Fig. 3, the leakage current of the operational amplifier 4 is 100 μA, R.

to 10Ω, and a == 10.824, β=7.
78, equation (3) yields the output voltage of the operational amplifier with respect to the ambient temperature as shown in FIG.

FIG. 5 shows an example of an electronic control unit (hereinafter referred to as ECU) that performs fuel calculations. In FIG. 5, 5 is an input interface, and this input interface 5 includes 02
Various analog inputs other than sensor a, such as intake air amount sensor, intake pipe interior, absolute pressure sensor, intake air temperature sensor, water temperature sensor, throttle valve opening sensor, and switch input b
1, for example, a starter switch, a rotation speed sensor that generates a pulse at every predetermined crank angle, etc. are connected.

6 is an A/D=ff converter, and this A/D converter 6 converts analog input information from the above-mentioned sensors, switches, etc. into digital values.

The analog input information and switch inputs converted into digital quantities are input to the microcomputer 7, where various calculations are performed. Although the microcomputer 7 is shown as a 1-chip microcomputer with six blocks, the RAM, R6, etc. may be connected externally. Based on various input information, the fuel injection time signal and information on the cylinder to be opened are calculated by the microcomputer 7, and are sent to the timer module 8, converted to a pulse width, and sent to the output interface 9. The fuel is sent to the fuel injection valve C.

As can be seen from Figure 4, lean or rich cannot be determined unless the ambient temperature of the 02 sensor reaches a certain level, so after the ambient temperature rises, the output level of the 02 sensor is fed back to the fuel calculation. It is common to multiply Judgment that the ambient temperature has risen (hereinafter 0
Although various proposals have been made for 02 activation (referred to as 02 activation), it is basically based on indirectly measuring the internal impedance of the 02 sensor. -To explain an example using Fig. 4, 02
02 when a predetermined condition, such as the engine water temperature rising above a certain level, is satisfied after detecting that the output voltage of the sensor has once become lower than the predetermined level vX1.
It was 7 bases, indicating that the sensor had been activated.

However, in the conventional example described above, once activation is determined, it continues to be determined as activated until the ECU is powered off, and feedback control is not performed except in the open state (for example, when fuel is cut, power is increased, etc.). Was.

However, fuel cut due to long downhill slope,
When the idle state is connected, the temperature of the exhaust gas decreases, the ambient temperature of the 02 sensor decreases, and the internal impedance of the 02 sensor increases, and even in the idle state, the 02 sensor exceeds the lean/rich judgment level (vREF in Figure 4). The output voltage from the operational amplifier increases, leading to lean,
Lynch had the flaw of making poor decisions.

The present invention eliminates the drawbacks of the prior art, and
Even if the sensor is activated once, if the impedance inside the 02 sensor increases, it is considered inactive and the feed pump is turned off.

An embodiment of the present invention will be described below. In this embodiment, the fuel injection time span (ToUT) calculated by the microcomputer 7f is determined by the following equation.

TOUT = (KO2XK1+2) Ti+ΔTv・
...(4)" In the two notation formula (4), Ti is the standard fuel injection time duration, which is determined by the engine speed and engine load (for example, suction pipe negative pressure and intake air amount), and No. 2 is the 02 feedback. Coefficient, K1. 2 is a correction coefficient based on engine water temperature, intake air temperature, etc., and ΔTV is a voltage correction amount.

Further, KO2 in formula (4) can be expressed as shown in the following formula.

KO2(n) −KO2(n-1) + (P+Δi)
......(5) In equation (5), KO2(n
-1) is the value at the previous suction stroke, and K02(n) is the value at the current suction stroke.

- Also, P and Δi are proportional terms and integral terms, respectively, and P
, Δ1 can each take a positive value or a negative value. P is added or subtracted when changing from a lean state to a rich state, or when changing from a rich state to a lean state, and Δ1
is added or subtracted for each intake stroke.

That is, after activation is determined, the lean state or rich state is determined by the output V of the O2 sensor input circuit, and the fuel injection according to equation (4) is determined by the KO2 value determined by the result of this lean or rich determination. time d](T
oUT) is calculated, and the fuel injection device (injector) is controlled based on the calculation result.

If you drive downhill for a long time with the fuel cut and idling, the temperature of the exhaust gas will drop and the 02
The ambient temperature around the sensor may drop and the 02 sensor may become inactive.

In this embodiment, when the 02 sensor is once activated and then determined to be inactive, KO2(n) -KO2(n-1) ””
(6), or KO2(n) is set to a constant value.

This example will be explained in more detail.

First, in Figure 4, draw a horizontal line with VMAX as the maximum output voltage value in the rich state in the region where the 02 sensor is activated, and draw a vertical line from point a where it intersects with the line on the Lynch side to indicate the lean side. The output type of the intersecting points is -1a, and the pressure is Vo. Add a predetermined margin to VMAX and get 10, -j vX2. A predetermined margin is subtracted from vo to set ■x1 (■X1 may be equivalent to the determination level ■REF). First, activation is determined at step 601 in FIG. That is, in step 601, it is determined whether 02FCG(1) (a flag set when activated) is set. If not set, No - Step 6
02FCG(2) (output voltage is V in inactive state)
Since the flag that is set when the voltage is below x1 is not set, No → If the output voltage is below x1 in step 603, YES → 02F, CG (2) in step 604
is set → YES in step 605 if the other conditions are satisfied - 02FCG (1) is set in step 606, and a feedback system is entered from then on.

On the other hand, when the internal impedance of the 02 sensor increases, 02FCG (1) is set in step 601, so YES → in step 607, the output voltage is greater than vX2, so YES → in step 608, o2FL is set.
Clear G(1) and 02FLG(2) to activate
/ The system returns to the initial state of cutting and does not perform feedback control using the O2 sensor.

Note that if the output voltage of the 02 sensor continues to be equal to or higher than vx2 a plurality of times, it may be determined that the sensor is inactive, and the feed bank control may be stopped.

(Left below) Wandering Eaves 11. The reason why we chose vXl to be smaller than Vo in ゛koX is as follows.
0 02 than the temperature at which the output voltage of the sensor shows vXl
If the ambient temperature of the sensor is high, the output voltage of the 02 sensor will not exceed VMAX and exceed ■X2 even if it becomes rich, so it may be mistaken as being inactive when it is actually activated. and d2
This is to absorb variations in characteristics of sensors, etc.

The temperature that shows vREF on the lean side, and vX on the liver and chi side.
2, when the 02 sensor is considered to be activated, the output voltage will be above the judgment level VREF even if it indicates the actual exhaust gas state, so there is still a problem that the 02 sensor will be considered rich. In order to remain, step 6 in Figure 5
At 09, it is also possible to ask if it is OK to continue with the judgment that the 02 sensor is activated. For example, whether the fuel cut state has continued for more than a predetermined time or whether the idle state has not continued for more than a predetermined time.

As described above, according to the present invention, even if the 02 sensor is deemed to have been activated once, it is checked whether the determination of activation can be continued again, and if the 02 sensor cannot be considered to be activated, it is not activated. When this judgment is made and the OX is activated again, the feedback control by the 02 sensor is stopped, so it is possible to perform good air and fuel ratio control.

[Brief explanation of drawings]

Figure 1 is an electric circuit diagram of the circuit that measures the electromotive force of the oxygen concentration sensor, Figure 2 is a diagram showing the results of measurement using the circuit shown in Figure 1, and Figure 3 is the electric circuit of the input circuit of the oxygen concentration sensor. Figure 4 shows the rotation of 01...Oxygen concentration sensor (02 sensor), 2°3 as shown in Figure 3.
... Resistor, 4... Operational amplifier (op-amp), 5, Φ, e... Input interface, 6...
...Fist/A/D converter, 7...Microcomputer, 81 Cow...Timer module, 9...Output interface. Name of agent: Patent attorney Toshio Nakao (1st person)
Figure 2 Figure 3 Figure 4 M west pressure ('c)

Claims (2)

[Claims] (1) Calculating means for calculating the fuel injection duration based on predetermined input information of the internal combustion engine;
a rich state), a fuel deficient state (lean state), and an activation determining means for determining whether the lean/rich determining means is activated.
When the activation determination means determines activation, the fuel injection time width is corrected according to the lean/rich determination result by the lean/rich determination means, and the activation determination means deactivates. A fuel injection control method for an internal combustion engine, characterized in that when it is determined that the fuel injection time 1] is corrected based on the lean/rich determination result by the lean/rich determining means. (2) a lean/rich discrimination means for discriminating between a rich state and a lean state depending on the magnitude of the oxygen concentration sensor output with respect to a first predetermined level; Claim 1, further comprising activation determining means that determines activation and determines inactivity when the output of the oxygen concentration sensor is higher than a third predetermined level that is higher than the second predetermined level. A fuel injection control method for an internal combustion engine.