JPH029925A - Air-fuel ratio controller for engine - Google Patents

Abstract

PURPOSE:To suppress the deterioration of the responsiveness in the air-fuel ratio feedback control irrespectively of the increase of the fuel transport delay by increasing the control gain in the air-fuel ratio feedback control according to the increase of the intake passage resistance, when the increase of the intake passage resistance through the lapse of time is detected. CONSTITUTION:The air-fuel ratio of the mixed gas supplied into an engine 1 is detected by an air-fuel ratio detecting means A, and a detection signal is inputted into an air-fuel ratio feedback control means B. The air-fuel ratio of the mixed gas is feedback-controlled to an aimed air-fuel ratio by a prescribed control gain on the basis of the deviation of the detected air-fuel ratio for an aimed air-fuel ratio. In this case, a passage resistance increase detecting mans C for detecting the increase of the passage resistance through the lapse of time in an intake passage 2 is installed, and the detection signal is inputted into a control gain varying means D. As the detected passage resistance is larger, the above-described control gain is increased, and the deterioration of the responsiveness in the air-fuel ratio feedback control due to the delay of the fuel transfer accompanied with the increase of the passage resistance is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an engine air-fuel ratio control device that performs feedback control of the engine air-fuel ratio to a target air-fuel ratio.

(Prior art) Zero in the exhaust passage of the engine. An air-fuel ratio detection means such as a sensor is provided, and the detected air-fuel ratio is compared with the target air-fuel ratio, and the fuel injection m, etc. is controlled based on the deviation, and the air-fuel ratio supplied to the engine is feedback-controlled to the target air-fuel ratio. Engine air-fuel ratio control devices configured to do this have been known in the past (see, for example, Japanese Patent Publication No. 62-59220).

By the way, carbon and the like adhere to the intake boats and intake valves of the engine due to exhaust gas being blown back during operation. As the mileage increases and the amount of carbon adhering to the intake boat increases, the flow of fuel worsens due to increased passage resistance, resulting in a large transfer delay between when the fuel is injected and when it enters the combustion chamber. Become. As a result, as the mileage increases, the responsiveness of the feedback control gradually deteriorates, and at the same time, combustion stability deteriorates, leading to problems such as deterioration of fuel efficiency. Conventional devices have been unable to maintain the responsiveness of feedback control when the fuel transfer delay increases due to such an increase in passage resistance over time.

(Object of the Invention) The present invention has been made in view of the above-mentioned problems, and is capable of ensuring the responsiveness of air-fuel ratio feedback control even if the fuel transfer delay increases due to the passage resistance of the intake passage increasing over time. The purpose of this invention is to obtain an air-fuel ratio control device for an engine that can control the air-fuel ratio of an engine.

(Structure of the Invention) The present invention recognizes the fact that the increase in passage resistance over time due to adhesion of carbon, etc. to the intake boat, etc. is a major factor in deteriorating the responsiveness of air-fuel ratio feedback control as described above. , the responsiveness is ensured by changing the control gain, and its configuration is as follows. That is, as shown in FIG. 1, the engine air-fuel ratio control device according to the present invention includes an air-fuel ratio detection means for detecting the air-fuel ratio of the air-fuel mixture supplied to the engine, and an air-fuel ratio detected by the air-fuel ratio detection means. an air-fuel ratio feedback control means for feedback-controlling the air-fuel ratio of the air-fuel mixture supplied to the engine to the target air-fuel ratio using a predetermined control gain based on a deviation of the air-fuel ratio from the target air-fuel ratio; The present invention is characterized by comprising passage resistance increase detection means for detecting an increase in resistance, and control gain changing means that receives the output of the passage resistance increase detection means and increases the control gain as the detected passage resistance increases.

(Operation) The air-fuel ratio feedback control means compares the air-fuel ratio detected by the air-fuel ratio detection means with the target air-fuel ratio, and feeds back the air-fuel ratio of the air-fuel mixture supplied to the engine to the target air-fuel ratio based on the deviation. Control. The control is performed based on a predetermined control gain. Then, as the mileage increases and the passage resistance of the intake passage increases due to adhesion of carbon, etc., the control gain is increased accordingly.
Deterioration of control responsiveness is suppressed.

(Example) Examples will be described below based on the drawings.

FIG. 2 is an overall view of an embodiment of the present invention.

In this embodiment, an injector 3 for fuel injection is provided in an intake passage 2 of an engine 1. Further, the top and side of the intake passage 2 are connected to an air cleaner 5 via a surge tank section 4. A throttle valve 6 is provided upstream of the surge tank section 4, and an air flow meter 7 for detecting the amount of intake air is provided downstream of the connection section with the air cleaner 5.
An intake air temperature sensor 8 is provided. A bypass passage 9 that bypasses the throttle valve 6 is also formed in the intake passage 2, and an idle speed control valve (abbreviated as an ISO valve) 10 is provided in the bypass passage. The injector 3 is controlled by an engine control unit 11.

The ISC valve lO and the engine's ignition system 12 are also controlled by this engine control unit 11.

The engine control unit 11 receives an engine rotation speed signal from a rotation sensor 14 attached to the engine camshaft 13, a water temperature signal from a water temperature sensor 16 provided in the water jacket 15 of the engine l, and an exhaust passage 17.
0 provided at An idle switch signal, etc. is input.

The control unit 11 calculates the basic fuel injection amount based on the intake air amount and the engine speed, multiplies it by a correction coefficient such as water temperature correction to obtain a corrected injection amount, and further calculates the corrected injection amount.
, the output of the sensor 18 is multiplied by a feedback correction coefficient to determine the final injection amount. In this example,
Feedback correction is performed using an integral term. At that time, the feedback correction coefficient is set to a value based on the value of ■, which is larger when the transfer delay is large than when the transfer delay is small, depending on the size of the fuel transfer delay due to the increase in intake passage resistance over time. Ru.

The transfer delay is detected based on the delay time of O and sensor output when fuel is returned from deceleration fuel cut (F/C). In other words, in the time chart of Figure 3,
The sensor output in a clean state is as shown by the solid line in FIG.

The time it takes for this to cross the sly level (ot TH) after the fuel returns is T. It is. On the other hand, when carbon or the like adheres to the intake passage, the sensor output becomes, for example, as shown by the broken line in FIG. A transfer delay is detected based on the magnitude of this time delay.

Note that the fuel cut during deceleration and the return to the fuel injection state upon completion of deceleration are performed as follows.

When the idle switch signal is turned on, that is, the throttle valve is fully closed, and a deceleration state in which the engine speed is equal to or higher than a predetermined value is detected, the fuel injection amount is set to zero. When the engine speed drops to a predetermined return speed, an initial value for the return/R reduction correction is set for the calculated fuel injection amount, and fuel injection is restarted with the injection amount reduced by that initial value. . and,
As time passes, the reduction value is reduced by a predetermined amount to restore the normal injection amount. Also, if the engine speed when entering the deceleration fuel cut zone is above the predetermined value above, and the fuel cut zone is entered from a high rotation speed above a certain speed, then when the fuel is restored, Observe the output of the 02 sensor 18 and compare it with the time it takes for the sensor output to rise and cross a predetermined slice level when the fuel is restored with no carbon or other deposits in the intake passage. Depending on how long there is a delay in the time it takes for the sensor output to cross the slice level upon return, a delay in fuel transfer due to increased passage resistance due to adhesion of nocobons, etc., is detected. If a transfer delay is detected, the fuel supply pattern at the time of recovery is corrected to the augmented side depending on the magnitude of the transfer delay. That is, the larger the transfer delay, the smaller the initial value of the return debt reduction correction, that is, the fuel supply is restarted with less weight loss. At the same time, we will increase the rate at which the depreciation value is reduced to speed up the return to the normal value.If the engine speed enters the fuel cut zone from a point where the engine speed is lower than the above-mentioned constant speed, the fuel If the cut time is short, a situation may occur in which the fuel recovery starts with the adhering fuel remaining from before the fuel cut, but in that case, the residual fuel is
, the increase in path resistance cannot be detected by the sensor output as described above because it affects the sensor output. Therefore, when the engine enters the fuel cut zone while the engine speed is relatively low, the fuel is restored in the normal pattern. Figure 3 (a) shows fuel cut during deceleration (, F/C
) and the fuel supply pattern at the time of fuel recovery. In the same figure (a), the solid line is the pattern in a clean state. In addition, the broken line ■ indicates the case where the initial value of the return weight loss correction is made small (and the same broken line ■ shows the case where the rate at which the weight loss value is reduced is increased. In this example, when a transfer delay is detected The return fuel pattern for is actually a combination of these ■ and ■.The dashed line ■
It is possible that the return pattern can be changed by increasing the return rotation speed. Figure 4 shows the feed bank correction coefficient (C) when the transfer delay is large (solid line) and when the transfer delay is small (broken line).
) is a comparison diagram. When the transfer delay is large, the slope of the C curve, that is, the control gain, is set large in this way, thereby suppressing a decrease in control responsiveness.

Note that in this case, since the I value is changed, the influence on control stability is minimized.

Next, the control of this embodiment will be explained in more detail with reference to the flowcharts of FIGS. 5 and 6.

FIG. 5 is a flowchart for determining transfer delay. 5l-824 shows each step.

Start the engine and first check with Sl to see if the idle switch is on.

If the idle switch is on, then go to S2 and check whether the engine rotation speed N is a constant rotation speed N6)
I see.

If N0≧N6, then fuel cut is performed in S3 (fuel injection i t i=o).

Next, the process goes to S4, and it is determined whether the engine rotational speed N0 has become equal to or less than the fuel return rotational speed N. and,
If N, ≦N, the timer starts operating in S5, and the return weight loss correction value Croe is initialized in S6 (Or, c=Cr, c(0)).

Then, in S7, the fuel injection amount t0 is calculated and injection is performed. The fuel injection amount at the time of return is determined by the return reduction correction value Cro from the basic injection amount t obtained from the engine speed, intake air amount, etc.
The value is obtained by subtracting e and adding the invalid injection time 1v.

In addition, in S8, Cr and c are decreased by a predetermined amount Creed, and in S9 it is checked whether Crac≦0, and C
Continue the return weight loss correction until rsc≦0.

If Crsc≦0, the process goes to SIO and calculates the fuel injection amount without return reduction correction.

Then, at Sll, 0. It is determined whether the output of the sensor has exceeded the slice level, and if it has exceeded the slice level, the timer is stopped in S12, and the timer value T at this time is determined.

If the slice level has not been reached, the process returns to SIO.

Next, go to S13, and compare the T obtained in S12 with the timer value T (time until the sensor output reaches the slice level or higher after the fuel is restored) obtained in advance in a clean state with no carbon adhesion in the intake passage. The difference T is calculated, and the process goes to S14 to check whether ΔT is greater than or equal to a certain value A. And ΔT
If ≧A, a flag is set because the transfer delay is large (S15), and if not, the flag is set to zero (S16).

If the engine speed N0 is not higher than N6 in S2, S1
Go to 7 and N. Determine whether ≧Nb. Here, Nb is the fuel cut rotation speed, and Nr<Nb<N. In other words, it is determined whether the fuel cut zone is entered from the relatively low rotation side. And N6≧Nb
If so, go to S+8 and cut fuel.

Then, the process goes to S+9, where it is determined whether the engine rotation speed N has become equal to or less than the return rotation speed N, and if No≦N
, return to S+8 and continue fuel cut until .

If YES in S19, the return weight loss correction value Cf is determined in S20.
Perform initial settings for @C.

Next, in S21, the fuel injection amount at the time of return is calculated in the same manner as in S7. Then, the process goes to S22, and as in S8, Croe is decreased by the predetermined ffic,,cd, and in S23, it is checked whether or not Croe≦0, and Cr
o,, S0, the fuel injection amount without return reduction correction is calculated in S24. Also, in S23 cr, ,c
Unless it is determined that ≦0, the process returns to S21 to continue the return weight loss correction.

Also, if SL is NO, which means the throttle valve is not fully closed, or if S17 is NO, which means the engine speed N6 has not reached S5, the fuel is not cut because it is not in the predetermined deceleration state, and S24 Go to and perform normal fuel injection.

FIG. 6 shows a feedback control routine.

PI-PI4 indicate each step.

When you start, first measure the amount of intake air with PI. is read, and then the engine rotation speed N is read in P2.

Then, in P3, a basic injection pulse is set by multiplying Q/N by a constant K.

Next, in P4, find the correction coefficient C6 based on water temperature, etc.
In P5, the corrected injection pulse T1 is determined (T.

-C8-To).

Next, in P6, compare the exhaust sensor (O2 sensor) output (
E), the sensor output is on the rich side (
Read whether E=1) is on the lean side (E=0).

Next, the PI determines whether the transfer delay is large. This determination is made by reading the flag set in the routine of FIG.

If the PI indicates that the transfer delay is large, a large l value (■,) is set in P8. Also, if not, P9
Then, set a relatively small ■value (I,) (rl>+2
).

Then, go to PIO and check whether it is E-1 or not, E=
1, that is, when it is said to be rich, the feedback correction coefficient C is set to be smaller by the value of l, (pH), and when E=I is not, that is, it is lean, C is made larger by I. do.

Then, the process goes to PI3, multiplies the corrected injection pulse TI by the feedback correction coefficient C to obtain the final injection pulse T, and performs injection at PI4.

In the above embodiment, the control gain is switched depending on whether the transfer delay exceeds a certain level, but it is also possible to change the control gain linearly depending on the degree of transfer delay. be.

Furthermore, the present invention is, of course, not limited to feedback correction of only the integral term, but can be applied to various types of control, such as a combination of proportional action and integral action.

(Effects of the Invention) Since the present invention is configured as described above, if the delay in fuel transfer becomes large due to an increase in passage resistance over time due to carbon etc. adhering to the intake boat, etc., the foot bank control can be adjusted. It is possible to prevent deterioration of responsiveness and perform highly accurate air-fuel ratio control.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of the present invention, FIG. 2 is an overall system diagram of an embodiment of the present invention, FIGS. 3 and 4 are time charts explaining the control of the embodiment, and FIGS. FIG. 6 is a flowchart for executing control in the same embodiment. l: Engine, 2. Intake passage, 3 Injector, 11
Control unit, 18:0. Sessa.

Claims (1)

[Claims] (1) An air-fuel ratio detection means for detecting the air-fuel ratio of the air-fuel mixture supplied to the engine; and a predetermined control gain that controls the engine based on the deviation of the air-fuel ratio detected by the air-fuel ratio detection means from the target air-fuel ratio. air-fuel ratio feedback control means for feedback controlling the air-fuel ratio of the air-fuel mixture supplied to the air-fuel mixture to a target air-fuel ratio; passage resistance increase detection means for detecting an increase in passage resistance of the intake passage over time; An air-fuel ratio control device for an engine, comprising control gain changing means that receives an output and increases the control gain as the detected passage resistance increases.