JPS60164634A - Air-fuel ratio control device in engine - Google Patents

Abstract

PURPOSE:To enhance the accuracy of correlation between the air-fuel ratio and rotational speed of an engine, by steppedly changing the air-fuel ratio upon detection of variations in engine rotational speed, and as well by delaying the detection of signals relating to the variations in engine rotational speed after the air-fuel ratio being varied. CONSTITUTION:A control unit 7 is composed of an air-fuel ratio changing means 11 for adjusting a fuel injection pulse to change an air-fuel ratio, a rotational speed variation detecting means 12 for detecting signals relating to variations in engine rotational speed and a control means for controlling the air-fuel ratio at a desired value. Further, the control means 13 receives a signal from an idle switch 10 and steppedly change the air-fuel ratio upon idle operation, and variations in engine rotational speed, accompanied with these air-fuel ratio variations are detected as a signal from the rotational speed variation detecting means 12 with a certain relay from the time of air-fuel ratio variation. Further in accordance with this signal, the relation between the air-fuel ratio and the engine rotational speed is obtained to control the air-fuel ratio at its desired value. With this arrangement, the correspondence between the air-fuel ratio and the fuel injection pulse may be made clear to limit detected errors to a minumum value, and as well it is possible to aim at enhancing the accuracy of detection and the control of air-fuel ratio.

Description

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

(Prior Art) Various techniques have been proposed in the past for controlling 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 that detects the exhaust gas, and the air-fuel ratio supplied to the engine is controlled according to the detected 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 time.As a result, the accuracy of air-fuel ratio control decreases, and as a result, there are problems with exhaust gas countermeasures and fuel consumption rate. There is a possibility that 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 as described above, it takes a considerable amount of time after the air-fuel ratio is varied until the engine speed actually changes correspondingly. It is very difficult to obtain a correlation between the air-fuel ratio and the engine speed when the engine speed is increased, and when implementing this method, the detection error will increase unless the detected value is processed properly. , the accuracy of air-fuel ratio control may be reduced, and the system may become effective only during long-term steady operation.

(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 the air-fuel ratio, and controls the air-fuel ratio to a target value based on the detected value. It is an object of the present invention to provide an air-fuel ratio control device for an engine that reduces the occurrence of detection errors caused by delays in changes in engine rotational speed and performs accurate air-fuel ratio control.

(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. and a control means that controls the air-fuel ratio to a target value by outputting a control signal to the air-fuel ratio changing means based on the detected value of the rotation speed fluctuation detection means, The control means changes the air-fuel ratio in stages when the rotational speed fluctuation is detected by the rotational speed fluctuation detection means, and also causes a delay in detecting a signal related to the engine rotational speed fluctuation from the change in the air-fuel ratio. It is characterized by this.

(Effects of the Invention) According to the present invention, in detecting a signal related to a change in engine speed due to a change in air-fuel ratio and controlling the air-fuel ratio to a target value based on the detected value, when a change in engine speed is detected, By changing the air-fuel ratio in stages and delaying the detection of signals related to changes in engine speed, it is possible to accurately detect changes in engine speed that correspond to changes in the air-fuel ratio. To improve the accuracy of air-fuel ratio control by reducing detection errors caused by delays in changes in engine speed due to changes in air-fuel ratio, and to maintain the performance of exhaust gas countermeasures and fuel economy ratio at the desired state. I can do it.

(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 iron and adjust the air-fuel ratio.

The control unit 7 receives a detection signal from a rotation speed sensor 8 that detects the rotation speed of the engine 1, a detection signal from a negative pressure sensor 9 that detects intake negative pressure in the intake passage 2, and detects the fully open state of the throttle valve 3. Detection signals of the idle switch 10 are respectively input. The control unit 7 includes an air-fuel ratio changing means 11 that adjusts the fuel injection pulse output to the fuel injection nozzle 6 to change the air-fuel ratio, and an air-fuel ratio changing means 11 that changes the air-fuel ratio by adjusting the fuel injection pulse outputted to the fuel injection nozzle 6, and a control unit 7 that receives a signal from the rotation speed sensor 8 and is connected to a change in engine speed. The rotational speed fluctuation detection means 12 detects the signal, and the rotational speed signals from the negative pressure sensor 9 and the rotational speed fluctuation detection means 12 are used to calculate the fuel injection amount (fuel injection pulse width), and the air-fuel ratio changing means 11 calculates the fuel injection amount (fuel injection pulse width). The control means 13 outputs a control signal to control the air-fuel ratio to a target value, and the control means 13 receives a signal from the idle switch 10 and changes the air-fuel ratio in stages during idling operation. The engine speed change accompanying the change is detected with a delay from the air-fuel ratio change by the rotation speed fluctuation detection means 12, and based on this signal, the relationship between the air-fuel ratio and the fuel injection pulse is determined, and the air-fuel ratio is determined. It is configured to control to a target 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 in the air-fuel ratio to the rich side or the lean side.
It detects whether the rotational speed fluctuation Δrpm increases or decreases with respect to 13.5, determines whether the air-fuel ratio is richer or leaner than 13.5, and adjusts the air-fuel ratio in the direction that maximizes the engine speed. The engine speed is varied, and the point at which the fluctuation in engine speed is least or the fluctuation is reversed is determined to be the highest rotational 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, in order to control the actual target air-fuel ratio, for example, the stoichiometric air-fuel ratio (14, 7), the air-fuel ratio is corrected to a corresponding fuel injection pulse to perform 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 that occurs during the learning control of the air-fuel ratio is determined by changing the reference value α of the air-fuel ratio (fuel injection pulse) stepwise by a predetermined amount of m, as shown in Fig. 6. , this reference value α is auxiliary increased or decreased, and depending on whether the change in engine speed corresponding to this auxiliary variation β is in an increasing direction or a decreasing direction, the change in the standard value α is adjusted to be rich or rich. It determines whether the engine should be on the lean side and changes the air-fuel ratio so that the engine speed reaches its maximum speed.

FIG. 3 shows the main processing routine. After starting and initializing in step $1, it is determined in step S2 whether the idle switch 10 is on, and in step S3 the engine speed is set to 800 rpm.
It is determined whether or not the following is true, and when both determinations are YES, it is detected as the engine 1 idling time, and in step S4 it is determined whether the learning completion flag is set. This learning completion flag is set in the learning processing routine shown in Figure 4. When engine 1 is started and the air-fuel ratio learning processing is completed, this character spacing completion flag is set, and learning continues until the engine stops. I try not to.

If the judgment in step S4 is No and the learning is not completed, the learning flag is set (S5), the learning process based on the routine in FIG. 4 is performed in step S6, and the learning flag is cleared (87 ) and exit this routine.

The learning processing routine in FIG. 4 starts at step S.
Initialize in step 8 and change the pre-learning fuel injection pulse τO (air-fuel ratio) to the final target fuel injection pulse (air-fuel ratio).
At the same time, the reference value α of the fuel injection pulse is read from the memory. Then, in step S9, the fuel injection pulse is set to T=T+α to perform fuel injection, and this α is changed to determine whether the predetermined time has elapsed (810), and after the second has elapsed (YES), step S11 Proceed to and set the 8-value as the initial calculation value.

Steps S12 to 817 change the fuel injection pulse to the reference value α
The purpose is to increase the fuel injection pulse from Store in memory. The calculation in step 813 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 S15 whether the value of β has reached a predetermined value Return to 812 and β
Sequentially calculate the rotation speed fluctuation range ΔN (n>) with the increase of
Memorize each.

When the determination in step 815 is YES and β becomes X, the fuel injection pulse is decreased to the reference value α in steps 81B to 823. In step 818, n is set to n+1, and in step 819, β is set to β-1. In step 820, the fuel injection pulse is set to T=T+α+β, and in step 821, the engine speed fluctuation width ΔN
(n>, is calculated, and this value is stored in the memory in step S22. The calculation in step 821 is performed from the rotation speed N (β) when β is decreased by one step to the rotation speed N (β+1
) and then add the previous fluctuation range ΔN(n-1) to this value. It is determined in step 823 whether the value of β has become O or not. If NO, β is sequentially decreased and the above steps are repeated to calculate the rotational speed fluctuation range ΔN(n) associated with the decrease in β, and each is stored. do.

If the judgment in step 323 is YES and β=0, each rotational speed fluctuation width ΔN (n>
rps is calculated, and it is determined in step $25 whether this value is positive (greater than or equal to 0). When this judgment is YES, the air-fuel ratio is changed to the rich side and the rotational speed fluctuates in the increasing direction, so the value of the air-fuel ratio corresponding to the current fuel injection pulse T0α is leaner than 13.5. Therefore, step 82
6, the air-fuel ratio is changed to the rich side by setting α to α+1, and the air-fuel ratio is changed to the rich side, and the rotational speed is changed to the decreasing direction. Since the value of the fuel ratio is richer than 13.5, in step 827, α is changed to α-1 to vary it in the lean direction.

After storing the value of α in step 82g, step S
Similarly to 9, in step 829, the fuel injection pulse is set to T=T+
After injecting fuel by setting α, it is determined whether a predetermined time (seconds) has elapsed since changing this α (330), and if seconds have elapsed (YES), the process proceeds to step S31 and the 8 value is set as the calculation initial value. Set.

Steps S32 to 837 change the fuel injection pulse to the reference value α
In step S32, the fuel injection pulse is set to T=T+α+β, and in step 833, the engine speed fluctuation width ΔN(n> is calculated. In step 834, this value is Store it in the memory.The calculation in step S33 calculates the rotation speed N when β is reduced by one step.
The previous stage rotation speed N (β+1) is subtracted from (β), and the previous fluctuation width ΔN (n-1) is added to this value.

It is determined in step 835 whether the value of β has reached a predetermined value = × (half of all the variable stages of β), and if No, n is set to n+1 in step 836, and β is set to β-1 in step 837. , the process returns to step 832 and β
The rotational speed fluctuation width ΔN (n>) due to the decrease in dirt is sequentially calculated and stored respectively.

When the determination in step S35 is YES and β becomes -X, the fuel injection pulse is increased to the reference value α in steps S38 to 843. First, in step 838, n is
+1, and in step 839 β is set to β+1, and in step 840 the fuel injection pulse is set to T−T+α.
+β, calculate the engine speed fluctuation range ΔN (n>) in step 341, and store this value in the memory in step 842.The calculation in step 841 calculates the engine speed N when β is increased by one step. (β) to the rotation speed of the previous stage N(β-
1) and then add the previous fluctuation range ΔN(n-1). It is determined in step S43 whether the value of β has become O, and if No, β is increased sequentially and the above steps are repeated to calculate the rotational speed fluctuation range ΔN(n) due to the increase in β, and each is stored. do.

If the judgment in step 343 is YES and β=0, each rotational speed fluctuation range ΔN (n>) stored in steps 334 and 342 is integrated in step 344, and
rp1m is calculated, and it is determined in step S45 whether this value is negative (less than 0). When this judgment is YES,
Since the air-fuel ratio was changed to the lean side and the rotation speed changed in the decreasing direction, the value of the air-fuel ratio corresponding to the current fuel injection pulse T+α is leaner than 13.5, so step 8
While changing α to α+1 in 4B towards richness,
When the above judgment is No, since the air-fuel ratio has been changed to the lean side and the rotational speed has fluctuated in the increasing direction, the value of the air-fuel ratio corresponding to the current fuel injection pulse T+α is richer than 13.5. In step 847, α is changed to α-1 and is varied in the lean direction.

After storing the value of α in step 348, step 3
In step 49, 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. Returning to step S9, the above step 8
The process of changing the air-fuel ratio according to the value of α increased or decreased in step 46 or 547 is repeated.

When the above α is the same value twice and the judgment in step S49 is YES, a correction coefficient K is calculated in step S50, and a learning completion flag is set in step 851.

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 Since (for example, 14.7) is known, (T ten α): τo K −1/13.5: 1 /14
．． 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 at step 360, engine rotation speed detection processing (S 61 ), intake negative Based on the pressure detection process (862), a basic jet fA peak is calculated in step 863. Further, for this basic injection interval, in steps 864 to 867, water temperature correction, intake temperature correction, enrichment correction at 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), the learning flag is set (YES), and the learning process shown in FIG. 4 is performed. If so, step 871 sets the final fuel injection pulse to τ=
T+α+β is set, and fuel injections q and j for performing air-fuel ratio fluctuation during learning control are performed at predetermined injection timings (S74). Further, if the judgment in step 370 is NO and the learning is completed and the learning flag is cleared, the fourth
Based on the correction coefficient K obtained through the learning process shown in the figure, step 87
In step 2, the final fuel injection pulse is set to τ=τOXK, and fuel injection is performed to achieve the target air-fuel ratio. Further, if the determination in step 869 is NO and the engine is not idling, the final fuel injection pulse is set to τ=τ0XK- in step 873, and fuel is injected so that the target air-fuel ratio is achieved in an operating state other than idling.

Note that the correction coefficient in step 873 is set to a small value based on the correction coefficient determined by the learning control in order to avoid large air-fuel ratio fluctuations.

According to the above embodiment, during learning control to determine the relationship between the air-fuel ratio and the fuel injection pulse, the air-fuel ratio is changed in steps, and a delay is caused in the detection of a signal related to a change in engine speed. By clarifying the correspondence between air-fuel ratio fluctuations and corresponding rotation speed fluctuations, the occurrence of detection errors can be suppressed to a minimum, and detection accuracy and, in turn, air-fuel ratio control accuracy can be improved.

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 rotation speed is converted into an integrated variation width Σ of the rotation speed variation width ΔN(n).
Δrpa+ is used to improve its detection accuracy. However, to simplify control, the above-mentioned auxiliary fluctuation β is omitted and the rotational speed fluctuation width is determined only by the reference value α, and the air-fuel ratio is determined based on this rotational speed fluctuation width. may be controlled.

Furthermore, in the above embodiment, the air-fuel ratio is changed to 1itJ at which the engine speed becomes the maximum engine speed, and the fuel injection pulse at this point is detected in correspondence with the air-fuel ratio, and then based on this detection. This example shows an example in which the air-fuel ratio is controlled to the target air-fuel ratio by setting a correction coefficient. However, as in the previous example, the air-fuel ratio is It is applicable to various modifications, such as one in which the fuel ratio is detected, or one in which engine rotational speed fluctuations in response to fluctuations in the air-fuel ratio within a predetermined range are made to correspond to the air-fuel ratio.

[Brief explanation of drawings]

Fig. 1 is an overall configuration factor for clearly showing the structure 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 flowchart showing the main processing routine; 5 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 the air-fuel ratio variation in FIG. 4. 1...Engine 5...Fuel supply means 7...Control unit 11...Air-fuel ratio changing means 12...Rotational speed fluctuation detection means 13... Control means

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, and the rotation speed. In the air-fuel ratio control device for an engine, the control means outputs a control signal to the air-fuel ratio changing means based on the detected value of the fluctuation detecting means to control the air-fuel ratio to a target value. The engine is characterized in that the air-fuel ratio is changed in stages when the rotational speed fluctuation is detected by the detection means, and there is a delay in detecting a signal related to the engine rotational speed fluctuation from the change in the air-fuel ratio. Engine air-fuel ratio control device.