JPH051374B2 - - Google Patents

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 period of time.As a result, the accuracy of air-fuel ratio control decreases, resulting in problems with exhaust gas countermeasures and fuel consumption. There is a risk that the rate performance may not 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, even if the air-fuel ratio fluctuates within the same range, there is a difference between rich and lean air-fuel ratio regions. There is a problem in that the amount of change in the engine rotational speed is different, and irregular rotational fluctuations occur regardless of the driver's operation, giving the driver a sense of discomfort.

(Object of the Invention) In view of the above circumstances, the present invention provides a method for controlling the air-fuel ratio to a target value based on the relationship between changes in the air-fuel ratio and changes in the engine speed. It is an object of the present invention to provide an air-fuel ratio control device for an engine that eliminates the discomfort experienced by users.

(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. The air-fuel ratio is changed during idling, and the air-fuel ratio is adjusted to the maximum rotational speed air-fuel ratio based on the detected value of the rotational speed fluctuation detection means, and the fuel injection pulse is generated at this maximum rotational speed air-fuel ratio. and a control means for learning and detecting the air-fuel ratio, determining an air-fuel ratio correction value for the target air-fuel ratio, and outputting a control signal to the air-fuel ratio changing means to control the air-fuel ratio to the target value, the control means comprising:
The air-fuel ratio change amount variable means corrects the air-fuel ratio change amount based on the deviation between the engine speed fluctuation range when the air-fuel ratio changes and the set value, and keeps the engine speed change range constant with respect to the air-fuel ratio change amount. It is characterized by:

(Effects of the Invention) According to the present invention, in controlling the air-fuel ratio to a target value based on the relationship between a change in the air-fuel ratio and a change in the engine speed, when a change in the engine speed is detected, the amount of change in the air-fuel ratio is determined by the change in the engine speed. By making the width variable and constant, control can be performed without causing irregular changes in engine speed due to driver operations, eliminating discomfort for the driver and achieving good air-fuel ratio control. It is possible to maintain the performance of exhaust gas countermeasures and fuel consumption rate at the desired state.

(Example) Hereinafter, an example of the present invention will be described 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.

The control unit 7 includes an engine 1
The detection signal of the rotation speed sensor 8 which detects the rotation speed of the engine, the detection signal of the negative pressure sensor 9 which detects the intake negative pressure of the intake passage 2, and the detection signal of the idle switch 10 which detects the fully closed state of the throttle valve 3 are detected. Each is input. The control unit 7 includes an air-fuel ratio changing means 11 that adjusts the fuel injection pulse outputted 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 output to the fuel injection nozzle 6, and a control unit 11 that receives a signal from the rotation speed sensor 8 and controls the engine rotation speed. A rotation speed fluctuation detection means 12 detects a signal, and receives the rotation speed signals from the negative pressure sensor 9 and the rotation speed fluctuation detection means 12, calculates a fuel injection amount (fuel injection pulse width), and controls the air-fuel ratio changing means 11. The control means 13 outputs a 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 during idling operation, and controls the engine as a result of this air-fuel ratio change. An air-fuel ratio that detects a change in the rotational speed based on a signal from the rotational speed fluctuation detection means 12 and allows the amount of change in the air-fuel ratio to be made in accordance with the fluctuation width of the engine rotational speed so that the engine rotational speed fluctuation range is constant. It includes a change amount variable means (not shown), and is configured to determine the relationship between the air-fuel ratio and the fuel injection pulse based on the change in the air-fuel ratio, and control the air-fuel ratio to a target value.

Figure 2 shows the characteristics of changes in engine speed as the air-fuel ratio changes. For example, in steady operating conditions such as idling, the engine speed reaches its maximum when the air-fuel ratio is 13.5; The engine speed decreases whether the air-fuel ratio is leaner (for example, 16) or richer (for example, 12), and the characteristics of the change are different for each air-fuel ratio. Therefore, the control means 13 detects whether the rotational speed fluctuation Δrpm increases or decreases with respect to the change ΔA/F of the air-fuel ratio toward the rich side or the lean side, and determines whether the air-fuel ratio is richer than 13.5. This is to determine whether the engine speed is on the lean side, and the amount of change in the air-fuel ratio at this time is adjusted so that the accompanying engine speed remains at a constant set value, and based on this, the air-fuel ratio is adjusted so that the engine speed is at its highest. The time when the adjusted air-fuel ratio reverses is determined to be the highest rotational position, and the fuel injection pulse at this time is set to 13.5 of the air-fuel ratio.
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 air-fuel ratio is corrected to the corresponding fuel injection pulse. I'm trying to control it.

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 system determines whether the engine speed is the same and changes the air-fuel ratio so that the engine speed reaches the maximum speed, and adjusts the above-mentioned auxiliary fluctuation β so that the accompanying engine speed fluctuation width remains constant. be.

FIG. 3 shows the main processing routine. After starting and initializing in step S1,
In step S2, it is determined whether the idle switch 10 is on or not, and in step S3, it is determined whether the engine rotation speed is 800 rpm or less, and when both judgments are YES, it is detected as the engine 1 is idling, and in step S4, the engine 1 is idle. Determine 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 judgment in step S4 above is NO and learning is not completed, a learning flag is set (S5).
Then, in step S6, a learning process is performed based on the routine shown in FIG. 4, and the learning flag is cleared (S7) to end this routine.

The learning process routine in FIG. 4 starts and initializes in step S8, and then corrects the pre-learning fuel injection pulse τ ₀ (air-fuel ratio) to the final target fuel injection pulse (air-fuel ratio) with a correction coefficient K= 1, and the reference value α of the fuel injection pulse is recalled from the memory. In step S9, each value is set as an initial value for calculation.

Steps S10 to S15 are for increasing the fuel injection pulse from the reference value α to the supplementary β, and in step S10 the fuel injection pulse is increased to T=T.
+α+β, and the engine rotational speed variation range ΔN(n) is calculated in step S11, and the value of ΔN(n) and the value of N(β) are stored in the memory in step S12. The calculation in step S11 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 range ΔN (n-1) to this. This is what I did. In step S13, it is determined whether the fluctuation range of the engine speed due to changing β with respect to α, that is, the absolute value of the difference between N(β)−N(1) has reached the set value ΔE.
If the judgment is NO, n is set to n+1 in step S14, β is set to β+1 in step S15, and the process returns to step S10 to sequentially calculate the rotational speed fluctuation range ΔN(n) as β increases, and N(β) and memorize each.

If the judgment in step S13 is YES and the rotational fluctuation width reaches the set value ΔE, step S1
6 to S21, the fuel injection pulse is decreased to the reference value α. In step S16, n is set to n+1, and in step S17, β is set to β-1, and then
In step S18, the fuel injection pulse is set to T=T+α+
.beta., the engine speed fluctuation range .DELTA.N(n) is calculated in step S19, and this value is stored in the memory in step S20. The calculation in step S19 is performed 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 previously calculated fluctuation range ΔN (n-1) to this value.
is added. It is determined in step S21 whether or not the value of β has become 0. If NO, β is sequentially decreased and the above steps are repeated.
Calculate the rotation speed fluctuation range ΔN (n) due to the decrease in
Memorize each.

If the judgment in step S21 is YES and β=0, then in step S22 the rotation speed fluctuation widths ΔN(n) stored in steps S12 and S20 are integrated to calculate the cumulative fluctuation amount ΣΔrpm, and if this value is positive ( 0 or more) is determined in step S23.
When this judgment is YES, the air-fuel ratio has changed to the rich side and the rotational speed has fluctuated in the increasing direction.
Since the value of the air-fuel ratio corresponding to the current fuel injection pulse T+α is leaner than 13.5, step S24
When the above judgment is NO, the air-fuel ratio is changed to the rich side and the rotational speed fluctuates in the decreasing direction, so the air-fuel ratio corresponding to the current fuel injection pulse T+α is Since the value of is richer than 13.5, step S
25, α is changed to α-1 and is varied in the lean direction.

After storing the value of α in step S26, the process proceeds to step S27, where each value is set as an initial value for calculation.

Steps S28 to S33 are for reducing the fuel injection pulse from the reference value α to the supplementary β, and in step S28, the fuel injection pulse is reduced to T=
T + α + β, calculate the engine speed fluctuation range ΔN (n) in step S29, and calculate this ΔN (n)
and the value of N(β) are stored in the memory in step S30. The calculation in step S29 sets β to 1.
The rotation speed N (β+1) of the previous stage is subtracted from the rotation speed N (β) when the step is decreased, and the previous fluctuation range ΔN (n-1) is added to this value. In step S3, it is determined whether the fluctuation range of the engine speed due to changing β with respect to α, that is, the absolute value of the difference between N(β)-N(1), has reached a predetermined value ΔE.
1, and if NO, then n in step S32.
is set to n+1, and β is set to β-1 in step S33, and the rotational speed fluctuation range ΔN due to the decrease of β is
(n) are sequentially calculated and stored together with N(β).

When the determination in step S31 is YES and the rotational fluctuation width becomes ΔE, the fuel injection pulse is increased to the reference value α in steps S34 to S39.
First, in step S34, n is set to n+1, and in step S35, β is set to β+1, and then in step S36, the fuel injection pulse is set to T=T+α+β.
, the engine speed fluctuation range ΔN(n) is calculated in step S37, and this value is stored in the memory in step S38. The calculation in step S37 is the result of subtracting the rotation speed N (β-1) of the previous stage from the rotation speed N (β) when β is increased by one step, and adding the previous fluctuation width ΔN (n-1) to this. It is. It is determined in step S39 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 S39 is YES and β=0, then in step S40 the rotational speed fluctuation widths ΔN(n) stored in steps S30 and S38 are integrated to calculate the cumulative fluctuation amount ΣΔrpm, and if this value is negative ( (less than 0) is determined in step S41.
When this judgment is YES, the air-fuel ratio has changed to the lean side and the rotation speed has fluctuated in the decreasing direction.
Since the value of the air-fuel ratio corresponding to the current fuel injection pulse T+α is leaner than 13.5, step S42
When the above judgment is NO, the air-fuel ratio is changed to the lean side and the rotational speed fluctuates in the increasing direction, so the air-fuel ratio corresponding to the current fuel injection pulse T+α is is richer than 13.5, so step S43
In this case, α is set to α+1 and is varied in the lean direction.

After storing the value of α in step S44, it is determined in step S45 whether α is the same value twice, and if the value is not the same, the maximum engine speed is determined as the maximum engine speed. Since the fuel injection pulse (air-fuel ratio) has not changed, the process returns to step S9 and the step S
α increased or decreased in 42 or S43
The process of changing the air-fuel ratio according to the value of is repeated.

When the above α becomes the same value twice, the step S4 is performed.
If the determination in step 5 is YES, a correction coefficient K is calculated in step S46, and a learning completion flag is set in step S47. The calculation of this correction coefficient K is
Since the value of the fuel injection pulse T+α at the maximum engine speed (air-fuel ratio 13.5) where α is the same twice (air-fuel ratio 13.5), the value of the fuel injection pulse τ0 before learning, and the target air-fuel ratio (for example, 14.7) are known. , (T+α):τ0K=1/13.5:1/14.7.

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 S60, the engine rotation speed detection processing (S6
1) Based on the intake negative pressure detection process (S62),
In step S63, a basic injection amount is calculated. Further, with respect to this basic injection amount, water temperature correction, intake temperature correction, enrichment correction during high load, and fuel cut correction during deceleration are performed in steps S64 to S67, and a basic fuel injection pulse τ0 is calculated in step S68.

Then, in step S69, it is determined whether it is in an idle state, and if it is in an idle state (YES), it is determined whether a learning flag is set (S7
0), when the learning flag is set (YES) and the learning process shown in FIG. 4 is being performed, step S
At step 71, the final fuel injection pulse is set to τ=T+α+β, and fuel injection for performing air-fuel ratio variation during learning control is performed at a predetermined injection timing (S74).
If the judgment in step S70 is NO, the learning is completed and the learning flag is cleared, the final injection pulse is adjusted in step S72 to τ=τ0× based on the correction coefficient K obtained in the learning process shown in FIG.
K and performs fuel injection to achieve the target air-fuel ratio. Further, if the determination in step S69 is NO.
When the engine is in a state other than idling, the final fuel injection pulse is set to τ=τ0×K' in step S73, and fuel is injected to achieve the target air-fuel ratio in an operating state other than idling. Note that the correction coefficient K' in step S73 is set to a smaller value than the correction coefficient K obtained by learning control 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 change in the auxiliary fluctuation β for determining the direction of fluctuation in the basic air-fuel ratio α when changing the air-fuel ratio The amount is kept constant so that the range of variation in engine speed is equal to the set value ΔE, and the air-fuel ratio is varied to a value where the engine speed reaches its maximum speed, thereby reducing the discomfort felt by the driver.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram to clarify the structure 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, Fig. 3 is a flowchart 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, 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 rotational speed fluctuation detection means for detecting a signal related to a change in engine speed due to a change in the air-fuel ratio; The air-fuel ratio is adjusted to the maximum rotational speed air-fuel ratio, the fuel injection pulse at this maximum rotational speed air-fuel ratio is learned and detected, the air-fuel ratio correction value for the target air-fuel ratio is determined, and a control signal is output to the air-fuel ratio changing means. and a control means for controlling the air-fuel ratio to a target value. 1. An air-fuel ratio control device for an engine, comprising an air-fuel ratio change amount variable means for correcting the amount of change in the engine rotational speed and making a range of fluctuation in engine speed constant with respect to an amount of change in the air-fuel ratio.