JPS60128953A - 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 speed variations as well as to aim at improvements in accuracy for air-fuel ratio control, by releasing the operation of an idling speed controller in time of detecting a speed variation attendant on an air-fuel ratio change. 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 this control unit 7, there is provided with a learning stop device 21 receiving each output of an idle switch, starter switch 15, an engine cooled time detecting device 16 and auxiliaries switch 17 or the like. In addition, immediately after engine starting or shifting to an idling state, in time of detecting an idling speed unstable state at engine cooled time or use of auxiliaries, the making of an air-fuel ratio compensation value at the control device 20 is made so as to be stopped.

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 an engine to an appropriate value depending on the operating condition. Some engines are equipped with an exhaust sensor for detection 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 time, resulting in a decrease in the accuracy of air-fuel ratio control.
There is a possibility that exhaust gas countermeasures and fuel consumption performance cannot be maintained at the desired level.

Therefore, as seen in Special Publication No. 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 prior art described above, when detecting a change in engine speed by varying the air-fuel ratio, the engine is equipped with an idle speed control device that controls the engine speed at a constant value when idling. Even if the fuel ratio is varied, the engine rotational speed does not follow the variation, and accurate detection cannot be performed, and there is a problem in that the air-fuel ratio cannot be controlled satisfactorily based on this variation.

(Object of the Invention) In view of the above-mentioned 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 calculates a signal related to a change in engine rotation speed due to a change in air-fuel ratio during idling. In order to control the air-fuel ratio to the target value, the operation of the idle speed control device is stopped when creating the air-fuel ratio correction value, and the engine speed changes to follow changes in the air-fuel ratio to improve detection accuracy. It is an object of the present invention to provide an air-fuel ratio control device for an engine that performs accurate air-fuel ratio control.

(Structure of the Invention) The air-fuel ratio l1JIIl arrangement of the engine of the present invention includes a fuel supply means for supplying fuel to the engine, an idle speed control device that controls the engine speed at a constant value during idling, and an air-fuel ratio control device that controls the engine speed at a constant value. an air-fuel ratio changing means for changing the engine speed, 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, and creating an air-fuel ratio correction value based on a detected value of the rotation speed fluctuation detection means during idling. and a control means for controlling the air-fuel ratio in the operating range to a target value using the air-fuel ratio correction value, wherein the control device is configured such that when the rotation speed fluctuation detecting means detects a rotation speed fluctuation due to a change in the air-fuel ratio, , further comprising a stop means for stopping the operation of the idle speed control device.

(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, the idle speed control device is deactivated when a change in engine speed is detected, and the engine speed changes in response to the change in the air-fuel ratio. It is possible to prevent erroneous creation of an air-fuel ratio correction value based on the above, 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. 1 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 the 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.
The idle speed is IIl! A known idle speed control device 11 (SIG) is provided which outputs a control signal from the II circuit 9 via a gate circuit 1O to control the engine speed during idling to a constant value. 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 from the start switch 15 that detects when the engine is started, a detection signal from the water temperature sensor 16 that detects the cooling water temperature, and an auxiliary signal 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 of the negative pressure sensor 14 and the rotational speed fluctuation detection means 19 is multiplied by the fuel injection D (fuel injection pulse width).
A control means 2O calculates and outputs a control signal to the air-fuel ratio changing means 18 to control the air-fuel ratio to the target value, and receives detection signals from the idle switch 13, starting switch 15, water temperature sensor 16, auxiliary equipment switch 17, etc. The control means 20 also has a learning stop means 21 for detecting an unstable rotational speed element during idling, and the control means 20 receives a signal from the idle switch 13 and when creating an air-fuel ratio correction value during idling, Gate circuit 10 of rotation speed control device 11
includes a stop means (not shown) for outputting a SIG stop signal to stop the operation thereof, and varying the air-fuel ratio;
A change in engine speed due to this air-fuel ratio change is detected by a signal from the rotation speed fluctuation detection means 19, and based on this signal, the relationship between the air-fuel ratio and the fuel injection pulse is determined to create an air-fuel ratio correction value, and learning control is performed. While controlling the air-fuel ratio in other operating ranges, including idling, when the engine is not running, the learning stop means 21 controls whether the engine is in the state immediately after starting, immediately after shifting to the idling state, or when the cooling water temperature is lower than the set value. When an unstable state of the idle rotation speed is detected, such as a low cold state or a state where auxiliary equipment such as a cooler is used, the control means 2 receives the signal from the learning stop means 21.
0 is configured to stop creating the air-fuel ratio correction value.

FIG. 2 shows the characteristics of changes in engine speed due to changes in air-fuel ratio when the operation of the idle speed IIJiIII device 11 is stopped. Air fuel ratio is 13.5
The engine speed reaches its maximum speed when the air-fuel ratio is leaner (e.g., 16) or richer (e.g., 12), and the engine speed decreases from this air-fuel ratio. ing. Therefore, the control means 13 detects whether the rotational speed fluctuation Δrpl increases or decreases in response to the change ΔA/F of the air-fuel ratio toward the rich side or the lean side, and detects whether the rotational speed fluctuation Δrpl increases or decreases when the air-fuel ratio is 13. Determine whether it is on the rich side or lean side from 5, change the air-fuel ratio in the direction where the engine speed is the highest, and judge the point where the engine speed has the least fluctuation or the fluctuation is reversed as the highest rotational position. , the fuel injection pulse at this time is the air-fuel ratio of 13
．． Based on this, an air-fuel ratio correction value is created to control the actual target air-fuel ratio to the stoichiometric air-fuel ratio (14, 7), and the fuel injection pulse is corrected to correspond to this value. air-fuel ratio control.

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 the change in engine speed corresponding to this supplementary variation β is −[depending on whether the change is in the upward direction or in the downward direction, the change in the reference value α is made to be rich or lean. The air-fuel ratio is changed so that the engine speed reaches its maximum speed.

FIG. 3 shows the main processing routine. After starting and initializing in step s1, it is determined in steps S2 to 810 whether or not the engine is in an idling state where fluctuations in engine speed due to unstable engine speed factors have not occurred. Learning processing is performed during stable idling (when each judgment is YES). First, in step s2, the water temperature sensor 16
determine whether the cooling water temperature is 60°C or higher, and when NO is detected as engine cold m<engine speed increases as the water temperature rises), the timer set after the engine is started by the start switch 15 in step $3. It is determined whether or not the set time t1 seconds has elapsed, and when the answer is 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 in step S4, it is determined whether the idle switch 13 is on. In step S5, it is determined whether the engine rotation speed is 800 rpm or less, and when both judgments are YES, it is detected as the idle time of the engine 1. In step S6, an idle timer is set, and in step S7, the engine 1 is idle. After the timer is set, it is determined whether the set time t2 seconds has elapsed, and when NO is detected as a transition period immediately after shifting to idle (a state until the number of revolutions stabilizes at idle), the auxiliary equipment is It is determined whether the switch 17 is off, and when the switch 17 is off, it is detected as when the auxiliary equipment is being used (the engine speed fluctuates due to the load fluctuation caused by the use of the auxiliary equipment). Figure 4) shows the engine speed N.
(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 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 judgment in steps S2 to S10 is YES,
That is, when the vehicle is in a stable idling state, it is determined in step 811 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 the learning is continued until the engine stops +L. I try not to.

If the determination in step 811 is NO and learning is not completed, step 812 determines the idle rotation speed l1III.
S, IG stop signals are output to the gate circuit 10 of the I device 11, the gate circuit 10 is closed, the control signal to the actuator 8 is cut off, 5IGIII is disabled, and the actual While setting the learning flag (813), the learning process is performed based on the routine shown in Fig. 4 in step 814, and the learning flag is cleared (815). End the routine.

The learning processing routine in FIG. 4 starts at step 8.
Initialize in 1B and 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 set the reference value α of the fuel injection pulse to Hiki Morigara calls. In step S19, 8 values are set as the calculation initial values.

Steps S20 to 825 change the fuel injection pulse to the reference value α
to an auxiliary β, and in step 820 the fuel injection pulse is set to T=T+α+β;
In step S21, the engine speed fluctuation range ΔN (n) is calculated, and in step 822, this value is stored in the memory.

The calculation in step 321 is to subtract the rotation speed N (β-1) of the previous stage from the rotation speed N (β) when β is increased by one step, and add the previous rotation fluctuation width ΔN (n-1>) to this. It is determined in step S23 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, and β is increased in step 825. is set as β+1, and the process returns to step 820 to sequentially calculate rotational speed variation widths ΔN (n) accompanying an increase in β and store them.

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 831. In step 826, n@n+1 is set, 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 S29, the engine speed fluctuation range ΔN(
n) and stores this value in memory in step 830. The calculation in step 829 above is the result of subtracting the rotation speed N (β+1) of the previous stage from the rotation speed N (β) when β is reduced by one step, and adding the previous fluctuation range ΔN (n-1) to this. It is. It is determined in step 831 whether the value of β has become 0, and if No, β is sequentially decreased and the above steps are repeated, and the rotation speed fluctuation range ΔN as β decreases.
(-n) is calculated and stored respectively.

If the judgment in step 831 is YES and β = 0, each rotational speed fluctuation width ΔN (n) stored in steps 822 and 830 is integrated in step 832, and the cumulative fluctuation amount Σ
Δrpa+ 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 has been changed to the rich side and the rotational speed has fluctuated in the increasing direction, the air-fuel ratio corresponding to the current fuel injection pulse T'+α is leaner than 13.5. Step 8
34, while changing α to α+1 in the rich direction,
The above judgment is N.

At the time of , the current fuel injection pulse T+α is
Since the corresponding air-fuel ratio is richer than 13.5,
In step 835, α is changed to α-1 and is varied in the lean direction.

After storing the value of α in step 836, step 8
Proceed to step 37 and set the 8-value as the initial calculation value.

Steps 83g to 843 change the fuel injection pulse to the reference value α
In step 838, the fuel injection pulse is set to T=T+α+β, and in step 839, the engine speed fluctuation range ΔN (n) is calculated, and in step 84G, this value is Store in memory. The calculation in step 839 is calculated by subtracting the rotation speed N (β+1) of the previous stage from the rotation speed N (β) when β is reduced by one step, and adding the previous fluctuation width ΔN (n-1) to this value. It is. , it is determined in step 841 whether the value stored in F memory 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 β is set to β- in step 843. 1, the process returns to step 838, and sequentially calculates the rotational speed variation range ΔN(n) accompanying the decrease in β, and stores 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 (then, in step 845, β is set to β+1, and in step 846, the fuel injection pulse is set to T=T+α
+β, the engine rotation speed fluctuation range ΔN(n) is calculated in step 847, and this value is stored in the memory in step 848. 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
) is subtracted and the previous fluctuation range ΔN(n-1) is added to this. It is determined in step 849 whether or not the value of β has become 0. If NO, β is increased sequentially and the above steps are repeated to calculate the rotational speed fluctuation range ΔN (n) associated with the increase in β, and each is stored. do.

If the judgment in step S49 is YES and β=O, then in step S50T, the respective rotational speed fluctuation ranges ΔN(n) stored in steps S40 and 84B are integrated to calculate the cumulative fluctuation amount ΣΔrpm, and this value is negative. (less than 0) is determined in step 851. 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 MF4 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
Determine whether 55≠α has become the same value twice, and if it is not the same value, it means that the engine rotation speed has not changed to the fuel injection pulse (air-fuel ratio) that reaches the maximum rotation speed. , returns to step 319 and repeats the process of changing the air-fuel ratio according to the value of α increased or decreased in step 852 or 853.

When the above-mentioned α becomes the same value twice and the judgment at step 855 is YES, a correction coefficient K is calculated at step 856, and a learning completion flag is set at step 857.

The calculation for this correction coefficient is performed at the highest engine speed when α becomes the same value twice (the value of fuel injection pulse T+α with air-fuel ratio 13.5>, the value of fuel injection pulse τ0 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 a fuel injection pulse according to the operating state of the engine, and after starting and initializing in step 860, detection of the engine speed begins II! (861), and based on the intake negative pressure detection process (S62), the basic injection amount is calculated in step 863. Furthermore, for this basic injection amount, step 8
In steps 64 to 867, water temperature correction, intake temperature correction, enrichment correction during high load, and fuel cut correction during deceleration are performed, and in step 868, a basic fuel injection pulse τ0 is calculated.

Then, in step 869, it is determined whether it is in an idle state, and if it is idle (YES), it is determined whether the learning flag is set (870), and if the learning flag is set (YES>6, the learning process in FIG. 4 is executed). If so, step 871 sets the final fuel injection pulse to τ-
T+α+β is set, and fuel injection is performed at a predetermined injection timing (879) to perform the air-fuel ratio variation of the learning control mR. Further, if the judgment in step 870 is No, the learning is completed and the learning flag is cleared, then in steps 872 to 876, the fuel #4Ill injection pulse is gradually set &! Finally, based on the correction coefficient K obtained in the learning process shown in FIG. Perform injection. That is, step 8
72 is for determining whether the learning flag is cleared only when the determination at 870 becomes No, and when this determination is YES, the fuel injection pulse τ=T+α becomes the maximum engine rotation speed at idle. To change this to the target fuel injection pulse τ=τOXK set in step 877, first, in step 873, the fuel injection pulse is changed to τ−T.
+α+γ is set to vary by a slight Ω value γ, and after fuel injection is performed at a predetermined injection timing (874) r-, it is determined in step 375 whether the current fuel injection pulse τ-T+α+γ is equal to the target value τOXK. However, if they do not match, the excitation value γ is set to γ+1 in step 876, and the variation is advanced by one step, and the injection amount is gradually varied until the determination in step 875 becomes YES. When the determination in step S75 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 872 is NO and fuel injection based on step 877 is continued. do.

Further, if the judgment in step 369 is No and the state is not idle, the final fuel injection pulse is set to τ in step 87g.
-τQXK-, and fuel injection is performed to achieve the target air-fuel ratio in operating states other than idling. Note that the correction coefficient ' in step 878 is set to a small value based on the correction coefficient determined by learning control to avoid large air-fuel ratio fluctuations.

According to the embodiment described above, during learning control that determines the relationship between the air-fuel ratio and the fuel injection pulse during idling, the operation of the idle speed control device that controls the engine speed during idling to a constant value is stopped, and the learning The engine speed is varied in response to the change in air-fuel ratio for performing υ1111, and the correlation between the two is improved in accuracy, thereby improving the accuracy of air-fuel ratio control.

In addition, 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 change in the rotational speed is expressed as the integrated variation mouth ΣΔ of the rotational speed variation width ΔN (n).
rpm to improve its detection accuracy, but in order to simplify control, the above-mentioned auxiliary fluctuation β is omitted and the rotation speed fluctuation width is determined only by the reference value α, and this rotation speed fluctuation width is used to improve the detection accuracy. The fuel ratio may also be controlled.

[Brief explanation of the drawing]

Fig. 1 is a biological configuration diagram to clearly demonstrate the configuration of the present invention, Fig. 2 is a curve diagram showing the fluctuation characteristics of engine speed with respect to changes in air-fuel ratio, and Fig. 3 is a flowchart showing the main processing routine. 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 ζt 11...Idle speed control device 18...
... Air-fuel ratio changing means 19 ... Rotation speed fluctuation detecting means 20 ... Control means @1. Figure 2 Figure 1N6 Figure l1lai

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, an idle speed lll1 [l device for controlling the engine speed at a constant value at idle, and an air-fuel ratio changing means for changing the air-fuel ratio. A rotational speed fluctuation detection means detects a signal related to a change in engine rotational speed, and an air-fuel ratio correction value is created based on the detected value of the rotational speed fluctuation detection means during idling. an air-fuel ratio i of an engine equipped with a control means for controlling the air-fuel ratio to a target value;
In the engine control device, the control device comprises a stop means for stopping the operation of the idle rotation speed control device when the rotation speed fluctuation detection means detects a rotation speed fluctuation due to a change in air-fuel ratio. air-fuel ratio control device.