JPS60128949A - Air-fuel ratio controller for engine - Google Patents

Abstract

PURPOSE:To prevent the occurrence of mismaking in an air-fuel ratio compensation value based on engine speed variations as well as to aim at improvement in air-fuel ratio control, by releasing the making of the air-fuel ratio compensation value in time of detecting a speed unstable element at idling. CONSTITUTION:In time of engine operation, a fuel injection quantity is calculated at a control device 20 of a control unit 7 on the basis of each output of a speed variation detecting device 19 receiving each output of a suction pressure sensor 14 and a speed sensor 12, and a fuel injection nozzle 6 is controlled via an air-fuel ratio changing device 18 whereby an air-fuel ratio is kept on the desired value. Furthermore, in the control unit 7, there is provided with a speed unstable element detecting device 21 receiving each output signal out of an idle switch 13, a starter switch 15, a water temperature switch 16 and an accessories switch 17 or the like. In addition, in time of detecting a speed unstable element, the making of an air-fuel ratio compensation value to be conducted in time of idling operation is stopped whereby mismaking in the air-fuel compensation value is prevented from occurring before it happens.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an air-fuel ratio control device for an engine.

(Prior Art) Various techniques have been proposed in the past to control the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber of the engine to an appropriate value depending on the operating condition. Some engines are equipped with an air sensor that detects air pressure, and control the air-fuel ratio supplied to the engine in accordance with the detection signal. However, the above-mentioned exhaust sensor has durability problems depending on its usage conditions, and it is difficult to obtain an appropriate detection signal for a long period of time1.As a result, the accuracy of air-fuel ratio control decreases, resulting in poor exhaust gas countermeasures and fuel consumption rate. There is a risk that it may not be possible to maintain the performance of the device at the desired level.

Therefore, as seen in the special public interest code Sho 56-33569@,
During steady operation such as when idling, the engine speed changes with a predetermined characteristic in response to changes in the air-fuel ratio. Therefore, during steady operation, small air-fuel ratio fluctuations are constantly applied, and the accompanying rotational speed fluctuations are detected. There is a technique that performs appropriate air-fuel ratio control by adjusting the rotational speed fluctuation width to the value of the set air-fuel ratio.

In the optical technology described above, when detecting changes in engine speed by varying the air-fuel ratio, if the engine speed at idle fluctuates due to unstable factors other than changes in the air-fuel ratio, the detection error may occur. A major problem is that if the air-fuel ratio is corrected based on this, control accuracy will decrease.

In other words, for example, the above-mentioned unstable rotational speed factors during idling include the throttle valve closing during a transient period immediately after transitioning to the idling state, immediately after starting the engine, when the engine is cold, when auxiliary equipment such as a tarp is in use, etc. Even in a no-load state, the engine speed will fluctuate as time passes or auxiliary equipment stops being used, and there is a risk that this fluctuation may be mistakenly detected as a speed change due to a change in the air-fuel ratio. .

(Object of the Invention) In view of the above circumstances, the present invention detects a signal related to a change in engine speed due to a change in air-fuel ratio during idling, creates an air-fuel ratio correction value based on the detected value, and uses Provided is an engine air-fuel ratio control device that increases detection accuracy by eliminating changes in engine speed due to factors other than the air-fuel ratio changes and performs accurate air-fuel ratio control in controlling the air-fuel ratio to a target value. The purpose is to

(Structure of the Invention) An air-fuel ratio control device for an engine according to the present invention includes a fuel supply means for supplying fuel to the engine, an air-fuel ratio changing means for changing the air-fuel ratio, and a signal related to a change in engine speed due to a change in the air-fuel ratio. a rotational speed fluctuation detection means for detecting the rotational speed fluctuation, and an air-fuel ratio correction value is created based on the detected value of the rotational speed fluctuation detection means during idling, and the air-fuel ratio in other operating regions is controlled to the target value by the air-fuel ratio correction value. and a rotation speed unstable element detection means for detecting a rotation speed unstable element during idling, and the control means receives a signal from the rotation speed unstable element detection means and determines an air-fuel ratio correction value. The invention is characterized by comprising a learning stop means for canceling the creation of the learning.

(Effects of the Invention) According to the present invention, a signal related to a change in engine speed due to a change in air-fuel ratio is detected during idling, and an air-fuel ratio correction value is created based on the detected value to adjust the air-fuel ratio in other operating regions. When controlling the fuel ratio to the target value, when a change in engine speed is detected, engine speed fluctuations due to factors other than changes in the air-fuel ratio are eliminated, which prevents incorrect creation of air-fuel ratio correction values based on engine speed fluctuations. It is possible to prevent this, improve the accuracy of air-fuel ratio control, and maintain the performance of exhaust gas countermeasures and fuel consumption rate at the desired state.

(Example) Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 7 shows the overall configuration, in which an intake passage 2 that supplies intake air to the engine 1 is provided with a throttle valve 3 and an air cleaner 4, and constitutes a fuel supply means 5 that supplies fuel to the engine 1. A fuel injection nozzle 6 is interposed. A control signal from a control unit 7 is outputted to the fuel injection nozzle 6 to control the fuel injection amount and adjust the air-fuel ratio.

Further, an actuator 8 for adjusting the idle opening degree of the throttle valve 3 is connected to the throttle valve 3.
A known idle speed control device 11 (SIG) is provided for outputting a control signal from the idle speed control circuit 9 via a gate circuit 1O to control the engine speed at a constant value during idling. There is. A detection signal from a rotation speed sensor 12 that detects the rotation speed of the engine 1 and a detection signal from an idle switch 13 that detects the fully open state of the throttle valve 3 are input to the idle speed control circuit 9, and the gate circuit 1o The actuator 8 is opened and closed by the SIG stop signal from the control unit 7, and during idle time when this stop signal is not output, the actuator 8 is feedback-controlled so that the rotation speed detected by the rotation speed sensor 12 becomes the set value. .

In addition to the detection signal of the rotation speed sensor 12 and the idle switch 13, the control unit 7 includes a negative pressure sensor 1 that detects intake negative pressure in the intake passage 2.
4, a detection signal of the start switch 15 that detects when the engine is started, a detection signal of the water temperature sensor 16 that detects the cooling water temperature, and an auxiliary device that detects the on state (usage state) of auxiliary equipment such as a cooler. Detection signals of the machinery switches 17 are inputted respectively. This control unit 7
includes an air-fuel ratio changing means 18 that adjusts the fuel injection pulse output to the fuel injection nozzle 6 to change the air-fuel ratio, and receives a signal from the rotation speed sensor 12 and detects a signal related to a change in engine rotation speed. Rotation speed fluctuation detection means 19;
The rotational speed signals of the negative pressure sensor 14 and the rotational speed fluctuation detection means 19 are used to determine the fuel injection layer (fuel injection pulse width).
A control means 20 calculates the air-fuel ratio and outputs a control signal to the air-fuel ratio changing means 18 to control the air-fuel ratio to a target value, and receives detection signals from the idle switch 13, starting switch 15, water temperature sensor 16, auxiliary equipment switch 17, etc. and an unstable rotational speed element detection means 21 for detecting an unstable rotational speed element during idling, and when the control means 20 receives a signal from the idle switch 13 and creates an air-fuel ratio correction value during idling operation. To do this, an SrG stop signal is output to the gate circuit 10 of the idle speed control device 11 to stop its operation, and the air-fuel ratio is varied, and a change in engine speed due to the change in the air-fuel ratio is detected by the speed fluctuation detection means 19. Based on this signal, the air-fuel ratio correction value is created by determining the relationship between the air-fuel ratio and the fuel injection pulse.
While controlling the air-fuel ratio in other operating ranges, including idling, when lJm is not performed, the rotational speed unstable element detection means 21 detects the state immediately after starting the engine, immediately after transitioning to the idle state, and during cooling. When detecting an unstable state of the idle speed, such as a cold engine state where the water temperature is lower than the set value or a state where auxiliary equipment such as a cooler is in use, a signal from the revolution speed unstable element detection means 21 is received. The learning stop means (not shown) of the control means 20 is configured to output a stop signal and stop the creation of the air-fuel ratio correction value.

Figure 2 shows the characteristics of changes in engine speed due to changes in the air-fuel ratio. For example, in steady operating conditions such as idling, the engine speed reaches its maximum speed when the air-fuel ratio is 13.5. , leaner than this air-fuel ratio (for example, 16
) or rich (for example, 12), the engine speed decreases, and the change characteristics are different for each air-fuel ratio. Therefore, the control means 13 controls the change ΔA/F of the air-fuel ratio to the rich side or the lean side.
Detects whether the rotational speed fluctuation Δrpm increases or decreases, and determines whether the air-fuel ratio is richer or leaner than 13.5'', and adjusts the air-fuel ratio so that the engine speed is the highest. The engine rotation speed is varied in the direction, and the point where the variation in engine speed is the least or the variation is reversed is determined to be the maximum rotation position, and the fuel injection pulse at this time is learned and detected as a value corresponding to the air-fuel ratio of 13.5, Based on this, an air-fuel ratio correction value is created to control the actual target air-fuel ratio, for example, the stoichiometric air-fuel ratio (14,7), and the air-fuel ratio is controlled by correcting the fuel injection pulse to correspond to this. .

Next, the operation of the control unit 7 will be explained with reference to flowcharts showing the main processing routine in FIG. 3, the learning processing routine in FIG. 4, and the interrupt processing routine in FIG. 5, respectively. In this example, the fluctuation of the air-fuel ratio during the air-fuel ratio learning control is determined by changing the reference value α of the air-fuel ratio (fuel injection pulse) by a predetermined amount step by step, as shown in FIG. It is designed to supplementally increase or decrease the value α, and depending on whether the change in engine speed corresponding to this supplementary variation β is in the increasing or decreasing direction, the change in the reference value α is made rich or lean. The air-fuel ratio is changed so that the engine rotational speed becomes i high rotational speed.

Figure 3 shows the main processing routine. After starting and initializing in step $1, it is determined in steps S2 to S10 whether or not the engine is in an idling state where fluctuations in engine speed due to unstable engine speed factors have not occurred. , the learning process is performed during stable idling (when each determination is YES). First, in step S2, it is determined whether the cooling water temperature by the water temperature sensor 16 is 60 degrees Celsius or higher, and if No, it is detected as the engine is cold (the engine speed increases as the water temperature rises), and in step S3, the start switch 1 is turned on.
5, the timer set after the engine starts determines whether the set time t1 seconds has elapsed, and if No, it is detected as a transition period immediately after the engine starts (a state in which the number of revolutions increases to the idle speed after a complete explosion), and step S4 In step S5, it is determined whether the idle switch 13 is on, and in step S5, it is determined whether the engine rotation speed is 800 rpm or less.
When both judgments are YES, it is detected as the idle time of the engine 1, an idle timer is set in step S6, and after the idle timer is set in step S7, it is determined whether a set time t2 seconds has elapsed; When the answer is No, it is detected as a transition period immediately after shifting to idle (a state until the number of revolutions stabilizes at idle), and in step S8 it is determined whether the auxiliary equipment switch 17 is off. When the answer is No, the use of the auxiliary equipment is detected. II (the engine speed fluctuates due to load fluctuations associated with its use), and furthermore, in step S9, the engine speed N is determined from the learning process (FIG. 4) described later.
(n) is memorized, and in step S10 it is determined whether the rotational fluctuation width, which is the absolute value of the deviation from the previous engine rotational speed N (n-1>), is less than or equal to the set value ΔN. This is detected when the engine speed fluctuates due to factors other than the above-mentioned unstable factors, such as a misfire, and the rotational speed fluctuation is larger than the rotational fluctuation caused by a normal air-fuel ratio change.

When the determination in steps S2 to 810 is YES,
That is, when the idle link state is stable, it is determined in step S11 whether the learning completion flag is set. This learning completion flag is set in the learning processing routine shown in Fig. 4. When the engine 1 is started and the air-fuel ratio learning processing is completed, this learning completion flag is set, and learning is not performed until the engine is stopped. That's what I do.

If the determination in step 811 is No and learning is not completed, step 812
output a SIG stop signal to the gate circuit 1o of 1;
The gate circuit 1o is closed to cut off the control signal to the actuator 8, disabling 5IGIlIIItll, causing the engine speed to actually change in response to the change in air-fuel ratio, and setting the learning flag (S13). Then, in step 814, a learning process is performed based on the routine of FIG. 4, and then the learning flag is cleared (S15) and this routine is ended.

The learning processing routine in FIG. 4 starts at step 8.
Initialize in 1B to set the correction coefficient for correcting the pre-learning fuel injection pulse τ0 (air-fuel ratio) to the final target fuel injection pulse (air-fuel ratio) to 1, and store the reference value α of the fuel injection pulse in memory. Call from. Step S1
Step 9 sets the 6 value as the initial calculation value.

Steps 820 to 825 change the fuel injection pulse to the reference value α
The purpose is to increase the fuel injection pulse from Store the value in memory. The calculation in step S21 is the rotation speed N when β is increased by one step.
The rotation speed N (β-1) of the previous stage is subtracted from (β), and the previous rotation fluctuation width ΔN (n-1) is added thereto. It is determined in step 823 whether the value of β has reached a predetermined value x (half of all the variable stages of β), and if NO, n is set to n+1 in step 824, β is set to β+1 in step 825, and the step Return to 820 and β
The rotation speed fluctuation range ΔN (n>) accompanying the increase in is sequentially calculated and stored.

When the determination in step S23 is YES and β becomes X, the fuel injection pulse is decreased to the reference value α in steps 826 to S31. In step 826, n is set to n+1, and in step 827, β is set to β-1. In step 828, the fuel injection pulse is set to T=T+α+β, and in step 829, the engine speed fluctuation width ΔN
(n) and stores this value in memory in step 830. The calculation in step 829 is calculated from the rotation speed N (β) when β is reduced by one step to the rotation speed N (β+1) of the previous stage.
is subtracted, and the previous fluctuation range ΔN (n-1> is added to this. It is determined in step 831 whether the value of β has become O, and if NO, β is sequentially decreased and the above By repeating the step, the rotation speed fluctuation range Δ as β decreases.
N (n) are calculated and stored respectively.

If the determination in step S31 is YES and becomes β-O, each rotational speed fluctuation range ΔN (n) stored in steps 822 and 830 is integrated in step S32 to calculate the cumulative fluctuation amount Σ.
Δrpl is calculated, and it is determined in step 833 whether this value is positive (greater than or equal to 0). When this judgment is YES,
Since the air-fuel ratio was changed to the rich side and the rotational speed changed in the increasing direction, the air-fuel ratio corresponding to the current fuel injection pulse T+α is leaner than 13.5, so step 834
While α is changed to α+1 in the rich direction, the above judgment is N.

When , the air-fuel ratio was changed to the rich side and the rotational speed changed in the decreasing direction, so the current fuel injection pulse T+α
Since the air-fuel ratio corresponding to is richer than 13.5, in step 335, α is changed to α-1 and is varied in the lean direction.

After storing the value of α in step 836, step S
Proceed to step 31 to set each part to the initial calculation value.

Steps 8313 to 843 are for reducing the fuel injection pulse from the reference value α to the supplementary β, and in step 838 the fuel injection pulse is set to T=T+α+β;
In step 839, the engine speed fluctuation range ΔN (n>) is calculated, and in step 840, this value is stored in the memory.

The calculation in step 839 is to subtract the rotation speed N (β+1) of the previous stage from the rotation speed N (β) when β is reduced by one step, and add the previous fluctuation range -8N (n-1) to this value. This is what I did. It is determined in step 841 whether the value of β has reached a predetermined value -X (half of all the variable stages of β), and if no, n is set to n+1 in step 842, and
In step 843, β is set to β-1, and the process returns to step 338 to sequentially calculate rotational speed fluctuation widths ΔN (n) accompanying the decrease in β and store them.

When the determination in step 841 is YES and β becomes -X, the fuel injection pulse is increased to the reference value α in steps 844 to 849. First, in step 844, n is
+1, and in step 845 β is set to β+1, and in step 846 the fuel injection pulse is set to T=T+α.
+β, and in step 847 the engine revolution speed fluctuation range ΔN (n) is calculated, and in step 848 this value is stored in the memory. The calculation in step 847 is calculated from the rotational speed N (β) when β is increased by one step to the rotational speed N (β−
1) and then add the previous fluctuation range ΔN(n-1). It is determined in step 849 whether the value of β has become 0, and if No, β is increased sequentially and the above step is returned to S, and the rotation speed fluctuation width ΔN (n) accompanying the increase in β is calculated, and each Remember.

If the judgment in step 849 is YES and β=0, each rotational speed fluctuation width ΔN (n) stored in steps S40 and 848 is integrated in step 850, and the accumulated fluctuation speed Σ
ΔrpIl+ is calculated, and it is determined in step 851 whether this value is negative (less than 0). When this judgment is YES, since the air-fuel ratio has been changed to the lean side and the rotation speed has fluctuated in the decreasing direction, the air-fuel ratio corresponding to the current fuel injection pulse T+α is leaner than 13.5, so step 8
42, while changing α to α+1 in the rich direction,
The above judgment is N.

When , the air-fuel ratio was changed to the lean side and the rotational speed changed in the increasing direction, so the current fuel injection pulse T+α
Since the air-fuel ratio corresponding to is richer than 13.5, in step 853, α is changed to α-1 and is varied in the lean direction.

After storing the value of α in step 854, step 8
55, it is determined whether α has become the same value twice, and if it is not the same value, the engine speed has not changed to the fuel injection pulse (air-fuel ratio) that reaches the maximum speed. Return to step 819 and 1. The process of changing the air-fuel ratio according to the value of α increased or decreased in step 852 or S53 is repeated.

When the above α is the same value for the two marks and the judgment at step 855 is YES, a correction coefficient K is calculated at step S56, and a learning completion flag is set at step 857.

This correction coefficient is calculated based on the value of the fuel injection pulse T+α at the highest engine speed (air-fuel ratio 13.5) when α is the same value twice, the value of the fuel injection pulse τO before learning, and the target air-fuel ratio. (For example, since 14.7> is known, (T+α):τo K= 1 /13.5: 1 /1
4.7.

The interrupt processing routine shown in Fig. 5 sets the fuel injection pulse according to the operating state of the engine, and after starting and initializing in step 860, the processing routine detects the engine speed (861), and the intake negative pressure. Detection process (
862), the basic injection amount is calculated in step 863. Furthermore, for this basic injection amount, step 864
From step 867, water temperature correction, intake temperature correction, enrichment correction during high load, and fuel cut correction during deceleration are performed, and step 8
6g to calculate the basic fuel injection pulse τ0. Then, in step 869, it is determined whether the system is in an idle state, and if it is idle (YES), it is determined whether the learning flag is set (870), the learning flag is set (YES), and the learning process shown in FIG. If so, step 871 sets the final fuel injection pulse to τ-
T+α+β is set, and fuel injection for performing air-fuel ratio fluctuation during learning control is performed at a predetermined injection timing (879). Further, if the judgment in step 370 is No, the learning is completed and the learning flag is cleared, the fuel injection pulse is gradually increased or decreased to the target value in steps 872 to 876, and finally the result shown in FIG. Based on the correction coefficient K obtained in the learning process, the final fuel injection pulse is set to τ=τOXK in step 877, and fuel injection is performed to achieve the target air-fuel ratio. That is, step 872
It is only when the judgment in step 70 becomes N, 0 that it is judged whether or not the learning flag has been cleared, and this judgment is Y.
At the time of ES, the fuel injection pulse τ=T+α is changed so that the engine speed during idling becomes the maximum speed, and this is changed to the target fuel injection pulse τ−τOXK set in step 877. about,
First, in step 873, the fuel injection pulse is set to τ=T+α+
After setting γ to vary by a minute value γ and performing fuel injection at a predetermined injection timing (874), step 87
5, the current fuel injection pulse τ = T + α + γ is the target value τO
It is determined whether it is equal to
gradually vary. When the determination in step S72 is YES and the fuel injection pulse reaches the target value τOXK, fuel injection is performed at this target value, and thereafter, the determination in step S72 is NO and fuel injection based on step 877 is continued. do.

Roughly speaking, if the judgment in step S69 is No and the state is not idle, the final fuel injection pulse is set to τ in step 878.
-τ 0 A small value is used to avoid large air-fuel ratio fluctuations.

According to the above embodiment, during the learning control that determines the relationship between the air-fuel ratio and the fuel injection pulse at idle, the case where the engine speed fluctuates due to factors other than changes in the air-fuel ratio is excluded, and the idle speed is stabilized. In this state, the air-fuel ratio is varied, the corresponding variation in engine speed is detected, and the correlation between the two is accurately determined, thereby improving the accuracy of air-fuel ratio control.

In the above embodiment, the air-fuel ratio is varied by the auxiliary variation β in addition to the reference value α, and the signal related to the accompanying rotational speed change is expressed as the rotational speed fluctuation range ΔN (cumulative variation amount ΣΔr of n>
pm to improve its detection accuracy, but in order to simplify control, the auxiliary fluctuation β is omitted and the amount of rotational speed fluctuation based only on the reference value α is calculated. The fuel ratio may also be controlled.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram for clearly showing the configuration of the present invention, FIG. 2 is a curve diagram showing the fluctuation characteristics of engine speed with respect to air-fuel ratio changes, FIG. 3 is a 70-chart diagram showing the main processing routine, FIG. 4 is a flowchart showing a learning processing routine, FIG. 5 is a flowchart showing an interrupt processing routine for performing fuel injection, and FIG. 6 is an explanatory diagram showing an example of variation in the air-fuel ratio in FIG. 4. 1...Engine 5...Fuel supply means 7...Control unit 18...Air-fuel ratio changing means 19...Rotational speed fluctuation detection means 20... Control means 21... Rotation speed unstable element detection means w 1 Fig. 112 Fig. 116

Claims (1)

[Claims] (1) A fuel supply means for supplying fuel to the engine, an air-fuel ratio changing means for changing the air-fuel ratio, a rotation speed fluctuation detection means for detecting a signal related to a change in engine speed due to a change in the air-fuel ratio, An air-fuel ratio control device for an engine, comprising: a control means for creating an air-fuel ratio correction value based on the detected value of the rotation speed fluctuation detection means, and controlling the air-fuel ratio in other operating regions to a target value using the air-fuel ratio correction value. A rotational speed unstable element detection means is provided for detecting an unstable rotational speed element during idling, and the control means cancels the creation of the air-fuel ratio correction value upon receiving a signal from the rotational speed unstable element detection means. An air-fuel ratio control device for an engine, comprising: means.