JPH0792015B2 - Electronically controlled fuel injection type internal combustion engine idle speed controller - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an idle speed control device for an electronically controlled fuel injection internal combustion engine, and in particular, feedback control of an air-fuel ratio is stopped (clamped) in a predetermined idle operation state. To improve feedback control of idle speed in an engine configured to operate.

<Prior Art> An electronically controlled fuel injection type internal combustion engine having an air-fuel ratio feedback control function is conventionally disclosed in Japanese Patent Laid-Open No. 62-107251.

That is, an oxygen sensor that detects the oxygen concentration in the exhaust gas that is closely related to the air-fuel ratio of the engine intake air-fuel mixture is provided in the exhaust system, and the output signal of this oxygen sensor and the slice level equivalent to the target air-fuel ratio (theoretical air-fuel ratio) It is detected whether the actual air-fuel ratio is rich or lean with respect to the target air-fuel ratio by comparing with, and fuel injection is performed based on the detection result so that the actual air-fuel ratio approaches the target air-fuel ratio. The air-fuel ratio feedback correction coefficient LAMBDA for correcting the amount is set.

Here, the value of the air-fuel ratio feedback correction coefficient LAMBDA is
It is changed by proportional-plus-integral (PI) control to ensure stable control. This compares the output signal of the oxygen sensor with the slice level, and when there is a high or low with respect to the slice level, the air-fuel ratio is suddenly increased, or
If the air-fuel ratio is rich (thin) without decreasing the thickness, first decrease (raise) the air-fuel ratio feedback correction coefficient LAMBDA by a predetermined proportional amount (P minute), and then increase the predetermined integral amount (I minute). ) Gradually lowering (raising) each to control the air-fuel ratio to be thin (thick).

However, under the condition that the air-fuel ratio feedback control is not performed, such as at the time of starting when the engine is to be operated on the rich side of the target air-fuel ratio in the normal operation state, at high load operation, or in the idle operation state, the air-fuel ratio feedback correction coefficient LAMB
I try to clamp the DA. In particular, the reason why the air-fuel ratio feedback correction coefficient LAMBDA is clamped in the idle operation state is to prevent the stability of the idle rotation speed from being deteriorated due to the surge caused by the change in the air-fuel ratio accompanying the change of the correction coefficient LAMBDA. .

On the other hand, in order to stabilize the idle rotation speed, feedback control of the idle rotation speed by the auxiliary air amount control is performed independently of the air-fuel ratio feedback control (under a condition different from the condition for performing the air-fuel ratio feedback control). It is generally equipped with an idle rotation speed control device.

This is because an idle control valve that controls the amount of auxiliary air is provided in the auxiliary air passage that bypasses the throttle valve that is installed in the engine intake system, and the opening of this idle control valve is set so that the actual idle rotation speed becomes the target rotation speed. Feedback control is performed so as to approach.

<Problems to be Solved by the Invention> By the way, in the feedback control of the idle rotation speed by the above-mentioned auxiliary air amount control, if the control constant is set to a large value, the responsiveness of the control is improved and the target rotation speed can be quickly controlled. However, particularly when the air-fuel ratio feedback control is performed and the idle stability is poor, if the control constant is set to a large value, the hunting of the rotation speed becomes large. For this reason, if the control constant is set to be relatively small in order to correspond to the state in which the air-fuel ratio feedback control is being performed, then the response of the idle rotation speed control is sacrificed at the time of clamping of the air-fuel ratio control, and the idle rotation speed There is a problem that it becomes impossible to avoid fluctuations promptly.

That is, when performing the air-fuel ratio feedback control,
Hunting is more likely to occur than when air-fuel ratio feedback control is not being performed.Therefore, in order to suppress the occurrence of hunting, the control constant in the rotational speed feedback control is set to be relatively small in correspondence with air-fuel ratio feedback control. Therefore, the responsiveness of the rotation speed control at the time of stopping the air-fuel ratio feedback control with a margin for hunting cannot be improved.

The present invention has been made in view of the above problems, while suppressing hunting of the rotational speed during idle operation,
The object is to improve the responsiveness of control for bringing the rotation speed closer to the target rotation speed.

<Means for Solving the Problem> Therefore, in the present invention, as shown in FIG. 1, air-fuel ratio feedback control means for feedback-controlling the fuel injection amount so that the actual air-fuel ratio approaches the target air-fuel ratio, and the engine In an electronically controlled fuel injection internal combustion engine, which comprises an air-fuel ratio feedback control stop means for stopping the feedback control of the fuel injection amount by the air-fuel ratio feedback control means in a predetermined idle operation state, a throttle interposed in the engine intake system Idling speed control means for feedback controlling the opening degree of the idle control valve so as to bring the actual idling speed closer to the target rotational speed while having an idle control valve for controlling the amount of auxiliary air supplied by bypassing the valve And a control constant in the feedback control of the idle rotation speed control means The idle rotation speed control device is configured to include a control constant increase setting unit that increases and sets the feedback control of the fuel injection amount by the air-fuel ratio feedback control stopping unit in comparison with other operating states.

<Operation> According to this configuration, the air-fuel ratio feedback control means corrects the fuel injection amount so that the actual air-fuel ratio approaches the target air-fuel ratio, but in a predetermined idle operation state, the air-fuel ratio feedback control stop means takes effect. Feedback control is stopped.

On the other hand, the idle rotation speed control means feedback-controls the opening of the idle control valve that controls the amount of auxiliary air so that the actual idle rotation speed approaches the target rotation speed.

Here, the control constant of the feedback control of the idle rotation speed control means, when the air-fuel ratio feedback control by the air-fuel ratio feedback control means is stopped by the air-fuel ratio feedback control stop means, another operating state, that is, air-fuel ratio feedback It is set to increase compared to when control is being performed. Therefore, when the air-fuel ratio feedback control is performed and the idle stability is poor, the control constant is set to a relatively small value to prevent hunting of the rotation speed due to the idle rotation speed control, and the air-fuel ratio feedback control is performed. When the idle stability is good, hunting is suppressed even if the control constant is set to a relatively large value, so that the responsiveness of the rotational speed control can be secured to the maximum.

<Example> An example of the present invention will be described below with reference to the drawings.

FIG. 2 shows the hardware configuration of this embodiment.

In the auxiliary air passage 8 provided by bypassing the throttle valve 3 interposed in the intake passage 2 of the engine 1, an idle control in which the opening is controlled according to the duty ratio of the drive pulse signal from the control unit 6 A valve 9 is provided, and the idle control valve 9 controls the amount of auxiliary air passing through the auxiliary air passage 8.

On the other hand, an electromagnetic fuel injection valve 7 is provided on the upstream side of the throttle valve 3, and the fuel injection valve 7 is also driven and controlled by the control unit 6.

The control unit 6 contains a microcomputer, sets a fuel injection amount Ti based on signals from various sensors, drives and controls the fuel injection valve 7 according to the fuel injection amount Ti, and controls the engine 1 Engine rotation speed N at the target idle rotation speed
The opening of the idle control valve 9 is adjusted to control Ns.

As the various sensors, a throttle valve opening sensor 4 for detecting the opening α of the throttle valve 3 and an oxygen concentration in the exhaust gas, which is provided in the engine exhaust passage 11 and is closely related to the air-fuel ratio of the intake air-fuel mixture, are detected. An oxygen sensor 10, a rotation speed sensor 5 such as a crank angle sensor, and a water temperature sensor 12 that detects the cooling water temperature Tw are provided.

Here, the fuel injection control by the control unit 6 will be described with reference to the flowchart of FIG.

In step (indicated as “S” in the drawing, the same applies hereinafter) 1, the throttle valve opening α detected based on the signal from the throttle valve opening sensor 4 and the signal from the rotational speed sensor 5 are detected. The engine speed N detected by

In step 2, the throttle valve opening α and the engine speed N
And the intake air flow rate Q corresponding to the actual α and N is retrieved by referring to a map on the ROM that has been obtained and stored beforehand by experiments or the like.

In step 3, based on the engine rotation speed N detected by the rotation speed sensor 5 and the intake air flow rate Q obtained in step 2, the basic fuel injection amount Tp (= K × Q) corresponding to the intake air flow rate per unit rotation. / N; K is a constant).

In step 4, the amount of acceleration / deceleration correction by the rate of change of the throttle valve opening α detected based on the signal from the throttle valve opening sensor 4 and the cooling water temperature Tw detected based on the signal from the water temperature sensor 12 Set various correction factors COEF including the water temperature correction amount according to.

In step 5, the air-fuel ratio feedback correction coefficient set by another routine (detailed description is omitted in this embodiment) by proportional-plus-integral control according to the signal from the oxygen sensor 10.
Read LAMBDA.

To briefly describe the setting control of the air-fuel ratio feedback correction coefficient LAMBDA, first, the actual air-fuel ratio is calculated by comparing the output signal from the oxygen sensor 10 with the slice level corresponding to the theoretical air-fuel ratio which is the target air-fuel ratio. It is determined whether the air-fuel ratio is richer or leaner than the air-fuel ratio, and when the actual air-fuel ratio is lean (rich), a predetermined integral amount (I minute) is added (subtracted) to the previous value, and gradually. By increasing (decreasing) the air-fuel ratio feedback correction coefficient LAMBDA, the actual air-fuel ratio is made closer to the target air-fuel ratio. When the actual air-fuel ratio is reversed from rich to lean or lean to rich, the air-fuel ratio feedback correction coefficient LAMBDA is set by increasing or decreasing by a predetermined proportional amount (P) in order to secure control responsiveness. That is, in this embodiment, the control unit 6 also serves as the air-fuel ratio feedback control means.

On the other hand, in step 6, the voltage correction component Ts is set based on the battery voltage. This is to correct the change in the injection amount (effective valve opening time) of the fuel injection valve 7 due to the fluctuation of the battery voltage.

Then, in step 7, the fuel injection amount Ti is calculated according to the following equation.

Ti = Tp × COEF × LAMBDA + Ts In step 8, the fuel injection amount Ti calculated in step 7
Is set in the output register. As a result, at the predetermined fuel injection timing synchronized with engine rotation, Ti
A drive pulse signal having a pulse width of is given to the fuel injection valve 7 to perform fuel injection.

If the air-fuel ratio feedback control by the air-fuel ratio feedback correction coefficient LAMBDA is performed even during the idle operation,
Since the air-fuel ratio changes periodically with the periodic fluctuation of the correction coefficient LAMBDA due to the proportional-plus-integral control, and a surge phenomenon of the engine output occurs, the control unit 6 causes the air-fuel ratio to change when the predetermined condition is satisfied in the engine idle operation state. Clamp the fuel ratio feedback correction coefficient LAMBDA to a constant value.

That is, when the throttle valve opening sensor 4 detects the fully closed state (idle position) of the throttle valve 3, the control unit 6 causes the value of the air-fuel ratio feedback correction coefficient LAMBDA at that time to fall within a predetermined range including the reference value (for example, It is determined whether or not it is within the reference value ± 12%), and when LAMBDA is a value within the predetermined range, the air-fuel ratio feedback correction coefficient is added to the reference value (or a value slightly on the rich side of the reference value). It is for clamping LAMBDA. Also,
When the cooling water temperature Tw is low, the air-fuel ratio feedback correction coefficient LAMBDA is clamped even under other conditions. Therefore, in this embodiment, the control unit 6 also serves as the air-fuel ratio feedback control stopping means.

Next, the opening control of the idle control valve 9 by the control unit 6, that is, the idle rotation speed control will be described with reference to the flowchart of FIG.

The idle control valve 9 includes a valve opening coil and a valve closing coil. By sending drive pulse signals in mutually inverted states to these coils, the duty ratio of the drive pulse signal is increased. (Ratio of ON time of coil for valve opening)
The opening degree is controlled in accordance with the above. In the routine shown in the flowchart of FIG. 4, the control value ISCdy that determines this duty ratio is set.

In step (denoted as "S" in the figure, the same applies hereinafter) 11, the basic control value ISCtw is set from the cooling water temperature Tw detected by the water temperature sensor 12. In addition, this setting is done by previously setting the cooling water temperature T in the ROM in the control unit 6.
A map of the basic control value ISCtw with w as a parameter may be stored and retrieved from the map based on the actual cooling water temperature Tw, or may be calculated.

In step 12, various correction amounts ISCet including correction during deceleration to prevent the negative pressure of the manifold from increasing during deceleration and acceleration correction to prevent engine stall during start
To set.

In step 13, it is determined whether or not a condition for performing idle speed control (ISC) is satisfied. Specifically, when the throttle valve 3 is fully closed (idle position) and the transmission is in the neutral state, or when the throttle valve 3 is fully closed and the vehicle speed is below a predetermined value,
Assuming that the condition for performing the idle speed control is satisfied, the process proceeds to the next step 14.

In step 14, the air-fuel ratio feedback correction coefficient LAMBDA
It is determined whether or not the condition for clamping is satisfied.
As described above, the clamp condition means that the value of the air-fuel ratio feedback correction coefficient LAMBDA when the throttle valve 3 is fully closed is within a predetermined range including the reference value or the cooling water temperature Tw.
Is less than or equal to a predetermined value.

When it is determined in step 14 that the clamp condition of the air-fuel ratio feedback correction coefficient LAMBDA is not satisfied, the process proceeds to step 16 and the integral constant for integral control of the feedback correction amount ISCfd for controlling the idle rotation speed to the target rotation speed. When I (control constant) is set to the normal value I _nor and it is determined that the clamp condition of the air-fuel ratio feedback correction coefficient LAMBDA is satisfied, the routine proceeds to step 15, where the normal value I _nor is the predetermined correction coefficient k. Is multiplied and corrected for increase to set an integration constant I. This step 15 corresponds to the control constant increase setting means.

That is, when the air-fuel ratio feedback correction coefficient LAMBDA is clamped, the rate of change of the feedback correction amount ISCfd is increased by increasing the integration constant I as compared to when it is not clamped, and the response of the idle speed control is increased. When the feedback control of the air-fuel ratio is performed and the idle stability is poor, a large integration constant I causes hunting. The correction amount ISCfd is set. Thus, when the air-fuel ratio feedback control is being performed, idle rotation speed control is performed while suppressing hunting to ensure idle stability, and when the air-fuel ratio feedback control is clamped (stopped), the most efficient It is possible to perform good rotation speed control.

When the control constant (integral constant I) in the integral control of the feedback correction amount ISCfd is set as described above, in the next step 17, the target rotation speed Ns is calculated based on the cooling water temperature Tw detected by the water temperature sensor 12. Is set by searching or calculating from the map.

Then, in the next step 18, the target rotation speed Ns set in step 17 is compared with the actual rotation speed N (actual rotation speed N) detected by the rotation speed sensor 5 to compare the target rotation speed Ns with the actual rotation speed Ns. The magnitude relationship of the rotation speed N is determined.

Here, when the actual rotation speed N is slower than the target rotation speed Ns, the routine proceeds to step 19, where the feedback correction amount ISCfd is increased by an integral constant I from the previous value (the opening degree of the idle control valve 9 is increased by a predetermined amount). On the other hand, when the actual rotation speed N is faster than the target rotation speed Ns, the routine proceeds to step 20, where the feedback correction amount ISCfd is decreased by the integral constant I from the previous value (the opening degree of the idle control valve 9 is decreased. Decrease by a predetermined amount). Since the integration constant I used at this time is increased and corrected when the air-fuel ratio feedback control is clamped as compared with when it is not clamped, the feedback correction amount ISCfd is increased / decreased in large steps during the increase correction. It will be.

When it is determined that the actual rotation speed N and the target rotation speed Ns are substantially the same, the feedback correction amount ISCfd is left at the previous value. The above steps 18 to 20 correspond to idle speed control means.

In step 21, the control value ISCdy is calculated according to the following equation.

ISCdy = ISCtw + ISCet + ISCfd The control value ISCdy set in this way is calculated in the next step 2
2 and the drive pulse signals of the duty ratio corresponding to the control value ISCdy are applied to the valve opening coil and the valve closing coil of the idle control valve 9 in a state where they are mutually inverted to open the idle control valve 9. The degree is adjusted according to the control value ISCdy.

In this embodiment, the feedback control of the idle speed is performed by the integral control. However, even in the case of the proportional integral control, the control constants (the integral constant and the proportional constant) are similarly increased to perform the present embodiment. It is obvious that the same effect as the example can be obtained.

<Effects of the Invention> As described above, according to the present invention, when the air-fuel ratio feedback control is stopped, the control constant in the feedback control of the idle rotation speed is set to be increased. Therefore, the rotation speed in the air-fuel ratio feedback control is increased. There is an effect that the responsiveness of the idle rotation speed control can be enhanced when the air-fuel ratio feedback control is stopped, while suppressing the hunting.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing a configuration of the present invention, FIG. 2 is a system diagram showing an embodiment of the present invention, FIG. 3 is a flow chart showing a fuel injection amount control in the same embodiment, and FIG.
The figure is a flowchart showing the idle speed control in the embodiment. 1 ... Engine, 2 ... Intake passage, 3 ... Throttle valve, 4
...... Throttle valve opening sensor, 5 ...... Rotation speed sensor,
6 ... Control unit, 7 ... Fuel injection valve, 8 ...
… Auxiliary air passage, 9 …… Idle control valve, 10 …… Oxygen sensor

Claims (1)

[Claims] 1. An air-fuel ratio feedback control means for feedback-controlling a fuel injection amount so that an actual air-fuel ratio approaches a target air-fuel ratio, and feedback of the fuel injection amount by the air-fuel ratio feedback control means in a predetermined idle operation state of the engine. In an electronically controlled fuel injection type internal combustion engine equipped with an air-fuel ratio feedback control stop means for stopping control, an idle control valve for controlling an amount of auxiliary air supplied by bypassing a throttle valve interposed in an engine intake system. On the other hand, the idle rotation speed control means for feedback controlling the opening of the idle control valve so that the actual idle rotation speed approaches the target rotation speed, and the control constant in the feedback control of the idle rotation speed control means are Fuel ratio feedback control stop means Readback control stop another control variable increases setting means for increasing set compared to the operating state, the idle speed control system for electronically controlled fuel injection type internal combustion engine comprising comprise at.