JPS59206619A - Method of controlling fuel injection amount in electronically controlled internal-combustion engine - Google Patents

Abstract

PURPOSE:To compensate variation in flow characteristics of fuel injection valves for each cylinder, by taking a mean value of coefficients of A/F ratio feedback in all cylinders and a mean value of coefficients of A/F ratio feedback in cylinders other than a specific cylinder, and computing a correction value of a fuel injection amount of the specific cylinder from both the mean values. CONSTITUTION:An electronical control unit serves to compute and correct output pulses to injectors from suction air amount, rotational speed, throttle opening degree, detection value of a water temperature sensor and detection value of an O2 sensor, etc. In step 62, the electronical control unit judges that warm-up is completed and A/F ratio is in feedback control under a normal running condition, and then in step 64, a first cylinder is determined. In step 66, a mean value Fa of correction coefficients of feedback during feedback control of A/F ratio of all cylinders is taken, and in step 68, a mean value Fb of correction coefficients of feedback during feedback control of A/F ratio of cylinders other than the first cylinder is taken. In step 70, a correction value Kn of a fuel injection amount of the first cylinder is computed from (1-Fb)/4(1- Fb/Fa), and the above steps are sequentially repeated to a fourth cylinder.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection 1-1 control method for an electronically controlled internal combustion engine, and particularly to a method for controlling fuel injection 1-1 for an electronically controlled internal combustion engine, and particularly for improving the accuracy of air-fuel ratio control in each cylinder of a multi-cylinder electronically controlled internal combustion engine. j(, i related to the control method.

In a multi-cylinder electronically controlled internal combustion engine, a fuel injection valve is provided for each cylinder, but an oxygen (02) sensor as an air-fuel ratio sensor is provided commonly for all cylinders, and a feedback signal from this oxygen sensor is used. to the feedback coefficient calculated based on,! 1 (Following all cylinder fuel injection [
11 is counted as 1 word. Since variations occur in the flow rate of each fuel injector, feedback is required in conventional multi-cylinder electronically controlled internal combustion engines to absorb the variation in the flow rate of each fuel injector and control the air-fuel ratio of each cylinder to the target value. Skip fl (the amount of discontinuity when the feedback coefficient is increased or decreased discontinuously to improve responsiveness when the output level of the oxygen sensor is reversed) or slope (the output level of the oxygen sensor is the same) as a constant in the calculation of the coefficient There is no choice but to increase the increase/decrease of the feedback coefficient between 101 and 101 maintained at This is accompanied by problems such as a decrease in the purification ability of the water.

In particular, in a multi-cylinder Kitako-controlled internal twist engine where the oxygen sensor is installed relatively downstream of the JI gas system, the +
Since there is a delay in the arrival of air scum, it is possible to control the air-fuel ratio of each cylinder by absorbing the variation in the flow rate of the fuel injector.
□In order to improve the quality, it is necessary to increase the feedback frequency by increasing the skip (1t) and the slope, but due to the problems mentioned above, there is a certain limit to the increase in the slope. .

The main feature of the present invention is that the flow ji1. It is an object of the present invention to provide a fuel injection control force method for a multi-cylinder electronically controlled internal combustion engine that can improve the accuracy of air-fuel ratio control of each cylinder by compensating for variations in air-fuel ratio control.

In order to achieve this object, according to the present invention, a fuel injection valve is provided corresponding to each cylinder, an air-fuel ratio sensor is provided in common to all the cylinders, and the fuel injection valve in the fuel injection valve is In a fuel injection amount control method for an electronically controlled internal combustion engine that is corrected in relation to a feedback coefficient calculated based on a feedback signal from a fuel ratio sensor, ζ! of all cylinders is corrected. The average value Pa of the feedback coefficient during the period when the fuel ratio is feedback-controlled is calculated, and the air-fuel ratio of one specific cylinder n is under open-loop control, and the air-fuel ratio of all remaining cylinders is the feedback coefficient during the period when the feedback control is being performed. Calculate the average value Fh of Calculate the fuel injection amount by I(n) and t.

For example, the air-fuel ratio during open loop control of each cylinder from the 1st cylinder to the 4th cylinder in a 4-cylinder FL child control internal combustion engine is A/Fl, A/F2. A/F3. It is defined as Δ/174. Since the intake air amount Q of each cylinder is equal, the air-fuel ratio of all cylinders is under feedback control. During the period, the sum fi1 of the fuel injections 1, 1 of all cylinders in one cycle is Fa-Q('-+knee+1, ]-)
... (2) 8/FI A/F2 A/F3 8/FM.

type, rectify, J (', the sum of t and the sum of the intake air amount 1
Since the crack in '4Q should be the reciprocal of the target pregnant fuel ratio (for example, the stoichiometric air-fuel ratio), the following equation holds true.

” (A/Fl+/1/F2+A/F3+A/F4)
= 1. l', 7 ''' (3) 14.7 is the stoichiometric air-fuel ratio and the specific one cylinder n1, for example, '-'1 of the first cylinder.
``The fuel ratio is under open-loop control and the fuel ratio of all remaining three cylinders is under feedback control, that is, the fuel injection J11 in the fuel injection valve of the first cylinder is not corrected by the feedback coefficient, and the remaining three cylinders are under feedback control. 'M' in the fuel rJ injectors of all three cylinders, and slant injection amount are corrected by the feedback coefficient.The fuel injection D' of all cylinders in one cycle during the period in which correction is performed using the feedback coefficient is Q°2 'l )Q (迭、＋H"−△ze山(,1)8/
11.

Since the value obtained by dividing equation (4) by 40 must be the reciprocal of the stoichiometric air-fuel ratio, the following equation holds true.

A/F I ~ Δ/F /l is the final fuel drop of 4a before making 1 (n) 0 people at (3) 2 and (5) 2.
j time 'l' a u is defined, for example, from the following equation.

Tdu = Fa゛Fc・Tp +'I'v −
J
Calculated basic fuel injection time TV: 111 of the fuel injection valve (effective injection time, therefore Δ
In order to make /PI the stoichiometric air-fuel ratio of 14.7, 1 (1) can be defined from the following equation, and the final fuel injection time Taul for the first cylinder can be calculated from the following equation.

Taul− to 1−Fa−r; e−Tp +Tv −=
・(9) From equations (6) and (8), 1 (1 is defined from the equation to /:.

The total number of cylinders is C, and the correction value for the nth cylinder among the cylinders is 1 (n can be defined as (1)2).

Note that the final fuel injection time for the 11th cylinder is 1'
When a u n is defined, it becomes as follows.

'l';+un = 1(nl'a-Fe-Tp +T
v (11) Thus, in the present invention, the skip rl as the redundancy of the feedback coefficient (and the correction value K defined as described above without increasing the slope)
By changing n, it is possible to compensate for variations in the flow of each fuel injector (k) and improve the accuracy of air-fuel ratio control.

The present invention will be explained with reference to the drawings.

FIG. 1 is a schematic diagram of a four-cylinder electronically controlled engine.

The suction bale passage 1 is provided with an air flow meter 2, an intake temperature sensor 3, a throttle valve 4, a surge tank 5, and an intake pipe 6 in this order from upstream. A fuel injection valve 7 is installed in the intake pipe 6 in correspondence with each cylinder, and injects fuel into the intake system. The combustion chamber 11 includes a spark plug 12 and a cylinder head 1.
3, Ilj is determined by the cylinder block 14 and the piston 15, and the air-fuel mixture is supplied through the intake valve 16.

The air-fuel mixture combusted in the combustion stage 11 is extracted to the exhaust pipe 20 via the exhaust valve 19. The oxygen sensor 21 detects the oxygen concentration in the atmosphere, and the water temperature sensor 22 detects the oxygen concentration in the air.
is installed to detect the cooling water temperature. The cylinder discrimination sensor 25 and the rotation angle sensor 26 detect the crank angle from the rotation of the shaft 28 of the power distribution ia 27. The cylinder discrimination sensor 25 and the rotation angle sensor 26 each have a crank angle of 7.
A pulse is generated every 20° and 30° change.

The idle switch 29 causes the throttle valve 4 to open the idle link tW
Detect whether or not there is. The electronic control device 31 receives input signals from various sensors and sends output signals to the fuel injection valve 7 and the ignition device 32.

The secondary ignition current of the ignition bag 1iffl 32 is sent to the ignition plug 12 via the power distributor 27.

FIG. 2 is a block diagram of the inside of the electronic control device 31. As shown in FIG.

RAM 35, ROM 36, CPIJ 37, input/output boats 38, 39, output capo-h 40a to 40d,
, 4] are connected to each other via a bus 42. C
LOCK43 sends a pulse to CI'U 37. The analog outputs of the air flow meter 2 and intake air temperature sensor 3 are sent to a multiplexer 47 via buffers 45, 46. The multiplexer 47 selects an input signal, and the selected input signal is A/D converted by an A/D (analog/digital) converter 48 and then sent to the input/output port 3.
Sent to 8. The output of the oxygen sensor 21 is sent to the input/output boat 39 via the buffer 50 and the comparator 51, and the output of the cylinder discrimination sensor 25 and rotation angle sensor 26 is sent to the input/output boat 39 via the shaping circuit 53. Output is sent directly to input/output boat 39. Each fuel injection valve 7a to 7d is an output boat 40a-'
The ignition device 32 receives an input signal from the output port 41 via the drive circuit 56. The ignition device 32 receives an input signal from the output boat 41 via the drive circuit 56.

FIG. 3 is a flowchart of a calculation routine for a correction value Kn for compensating for variations in the flow rates of the fuel injection valves 7a to 7d. Calculate the feedback coefficient Fa during the period when the air-fuel ratio of all cylinders is under feedback control, and calculate the feedback coefficient Fa during the period when the air-fuel ratio of one specific cylinder n is under open-loop control and the air-fuel ratio of all remaining cylinders is under feedback control. Find the average value Fb of the coefficients and use Fa + Fb as described above (
1) Kn is subtracted based on the formula.

As indicated by (+1)E above, Kn is used as a multiplication term when subtracting the final g8 fuel injection time 1'aun, and as a result, the variation in the flow rate of each fuel injection valve 7a to 7d is Nevertheless, the air-fuel ratio of each cylinder is controlled to the stoichiometric air-fuel ratio as the target air-fuel ratio. To elaborate on each step, in step 62, it is determined whether the tl' calculation condition for the correction value Kn is satisfied or not, and if the determination is positive, the step 64
Proceed to the following. The calculation conditions are that Taniso has already ended, that the air-fuel ratio feedback condition is satisfied, and that the constant state (for example, +n
/l+yp line). In step 64, 1 is assigned to n as an initial value. n is the cylinder number from which the correction value Kn is subtracted.

In step 66, the air-fuel ratios of all cylinders are subjected to feedback processing, and the average value Fa of the feedback coefficients during this period is taken. The feedback coefficient decreases or increases during the period when the oxygen sensor 21 maintains an m (rich) signal or a lean signal, and when the oxygen sensor 21 changes from a rich signal to a low signal or vice versa, it is used to improve responsiveness. 4=J skips are given. The average value may be obtained by taking in a plurality of feedback coefficients immediately before skipping and averaging them. In step 68, only the air-fuel ratio of the n-th cylinder is subjected to open-loop control (feedback control is stopped), that is, the fuel injection amount is not corrected by the feedback coefficient, and the fuel injection amount of the remaining cylinders after the n-th cylinder is is feedback controlled, and the average value Fb of the feedback coefficient during this period is
take in. In step 70, a temporary Kn is calculated according to the above-mentioned equation (1). In step 72, the temporary Kn in step 70 is substituted into the true Kn. Temporary Kn of step 70
Instead of directly assigning to the true Kn, the average value of the true Kn up to now and the temporary Kn of step 70 may be substituted to the true Kn. Note that the initial value of true I (n is set to 1.0. In step 74, n + 1 is assigned to n. In step 76, it is determined whether n > 4, and if the determination is negative, Returning to step 66, if the determination is positive, this routine is terminated.In this way, 4 is added to old.
”

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of an electronically controlled engine to which the present invention is applied, Fig. 2 is a block diagram of the electronic control device shown in Fig. 1, and Fig. 3 is a diagram for compensating for variations in the flow rate of each fuel @ side valve. 2 is a flowchart of a correction value calculation routine. 7.7a-7d... fuel f1. Injection valve, 11... Combustion chamber, 21... Acid purple sensor, 31... Electronic control device.

Claims (1)

[Claims] A fuel injection valve is provided correspondingly to each cylinder, an air-fuel ratio sensor is provided commonly to all cylinders, and the fuel injection amount in the fuel injection valve is determined based on a feedback signal from the air-fuel ratio sensor. In the fuel injection amount control method for an electronically controlled internal combustion engine that is corrected in relation to the feedback coefficient calculated by The average value Fb of the feedback coefficient during the period in which the air-fuel ratio of one cylinder n in the patent is under open-loop control and the air-fuel ratio of all remaining cylinders is under feedback control is determined, and the correction value Kn is calculated by tI from the following formula, -Fb (-(] -Fb/Fa) where C is the fuel injection amount control of an electronically controlled internal combustion engine, characterized in that the fuel injection amount of one cylinder n of the total number of cylinders is calculated based on Kn. Method.