JP2625984B2 - Air-fuel ratio control device for electronically controlled fuel injection type internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control apparatus for an electronically controlled fuel injection type internal combustion engine that detects an oxygen concentration in exhaust gas and controls an air-fuel ratio based on the detected value. Things.

[Prior Art] Conventionally, in an electronically controlled fuel injection type internal combustion engine, an air-fuel ratio that controls an injection amount of fuel so that an air-fuel ratio becomes a stoichiometric air-fuel ratio using an O ₂ sensor that detects an oxygen concentration in exhaust gas. Feedback control using a control device is performed. Recently, in this feedback control, learning control for setting the base air-fuel ratio to the stoichiometric air-fuel ratio based on the air-fuel ratio correction coefficient has been performed.

However, the air-fuel ratio control apparatus, when the internal combustion engine exhaust gas temperature becomes idling is reduced to an inactive state immediately before the O ₂ sensor, the output of the O ₂ sensor becomes unstable,
If learning is performed based on this unstable output, there is a risk of erroneous learning.

For this reason, Japanese Patent Application Laid-Open No. 60-50246 discloses a method in which the learning value is updated a predetermined number of times during idling in a steady operation state (not during start-up or cold), the air-fuel ratio correction coefficient is clamped, and learning is stopped. ing.

[Problems to be Solved by the Invention] However, after the O ₂ sensor is inactivated once, the load of the internal combustion engine fluctuates due to the start of the air conditioner or an increase in the electric load, and the exhaust gas temperature rises. Learning is performed when the _two sensors are activated. At this time, the output is unstable because the O ₂ sensor is in the state immediately before the inactive state, and learning is performed when the output is unstable, so there is a possibility of erroneous learning.

While this invention was made to solve the above problems, and an object when the O ₂ sensor becomes once inactive state when idle in a steady operation state, which is in its idle state, learning , The erroneous learning caused by the O ₂ sensor learning based on the unstable output immediately before the inactive state can be prevented, and the air-fuel ratio of the internal combustion engine can be accurately controlled at idle. It is to provide a fuel ratio control device.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides, as shown in FIG. 1, a basic injection amount based on an intake air amount of an internal combustion engine or a parameter related thereto and an engine speed. Air-fuel ratio correction coefficient setting for comparing the actual air-fuel ratio detected by the oxygen concentration sensor provided in the exhaust system with the stoichiometric air-fuel ratio to set the air-fuel ratio correction coefficient by proportional integral control Means, a storage means for storing an air-fuel ratio learning correction coefficient, a learning condition determining means for determining whether a learning condition for updating the learning correction coefficient stored in the storage means is satisfied, and the learning condition Learning correction coefficient updating means for updating the learning correction coefficient stored in the storage means based on the air-fuel ratio correction coefficient when the determining means determines that the learning condition is satisfied; and Injection amount calculation means for calculating an injection amount based on the output basic injection amount, the air-fuel ratio correction coefficient and the learning correction coefficient, and a drive for outputting a drive pulse signal corresponding to the calculated injection amount to the fuel injection valve Means for controlling the air-fuel ratio of an electronically controlled fuel injection type internal combustion engine, comprising: an idle state detecting means for detecting an idle operating state of the internal combustion engine; and an idle operating state detected by the idle state detecting means. If the learning condition determining means once determines that the learning condition is not satisfied, while the idle state detecting means detects the idle operation state, the determination result of the learning condition determining means The gist is air-fuel ratio control of an internal combustion engine provided with learning prohibition means for prohibiting the learning correction coefficient updating means from updating the learning correction coefficient regardless of the above.

[Operation] The basic injection amount is calculated by the basic injection amount calculating means based on the intake air amount or a parameter related thereto and the engine speed. The air-fuel ratio correction coefficient is set by the air-fuel ratio correction coefficient setting means based on the detected air-fuel ratio of the oxygen concentration sensor and the stoichiometric air-fuel ratio. When the learning condition determining means determines that the learning condition for updating the learning correction coefficient stored in the storage means is satisfied, the learning correction coefficient updating means stores the learning correction coefficient in the storage means based on the air-fuel ratio correction coefficient. The learning correction coefficient that has been updated is updated. The injection amount is calculated by the injection amount calculation means based on the calculated basic injection amount, the air-fuel ratio correction coefficient, and the learning correction coefficient, and a driving pulse signal corresponding to the injection amount is output from the driving means, Predetermined fuel is injected from the injection valve.

Further, if the learning condition determining means once determines that the learning condition is not satisfied while the idle state detecting means detects the idle operating state of the engine, the idle state detecting means While the state is detected, regardless of the judgment result of the learning condition judgment means,
Updating of the learning correction coefficient by the learning correction coefficient updating means is prohibited by the learning prohibiting means.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS.

As shown in FIG. 6, the combustion chamber 2 of the engine 1 as an internal combustion engine is adapted to suck air through an intake pipe 3, a surge tank 4, and an intake manifold 5 downstream of an air cleaner (not shown). A throttle valve 6 is arranged in the intake pipe 3 and is linked with the throttle valve 6 and is turned on when the throttle valve 6 is in an idle position (fully closed position) and turned off when the throttle valve 6 is opened. A throttle switch 7 as idle state detecting means is provided, and its output is provided by basic injection amount calculating means, air-fuel ratio correction coefficient setting means, learning condition determining means, learning correction coefficient updating means, learning inhibiting means, injection amount calculating means. And a control circuit 20 as a storage means. An intake air temperature sensor 8 that detects the temperature of the intake air and outputs an intake air temperature signal to the control circuit 20 is provided upstream of the throttle valve 6. The surge tank 4 has a throttle valve 6
Is provided with a pressure sensor 9 for detecting an intake pipe pressure on the downstream side of the control circuit and outputting an intake pipe pressure signal to the control circuit 20.

The intake manifold 5 is provided with a fuel injection valve 10 for each cylinder, and each fuel injection valve 10 injects fuel into each combustion chamber 2 by a fuel injection signal output from the control circuit 20. Has become.

The tip of an ignition plug 11 projects into each combustion chamber 2 of the engine 1, and a distributor 12 is connected to the ignition plug 11. The distributor 12 is provided with a cylinder discriminating sensor 13 and an engine speed sensor 14 each composed of a pickup fixed to its housing and a signal rotor fixed to the distributor shaft. The cylinder discrimination sensor 13 outputs a cylinder discrimination signal to the control circuit 20 at every crank angle 720 °, for example, and the engine speed sensor 14 outputs a crank angle signal to the control circuit 20 at every crank angle 180 °, for example. I have. An igniter 15 is connected to the distributor 12.

Each combustion chamber 2 of the engine 1 is an exhaust manifold
It is connected via 16 to a catalytic converter (not shown) filled with a three-way catalyst. Also, exhaust manifold
An O ₂ sensor 17 for detecting the concentration of residual oxygen in the exhaust gas and outputting an air-fuel ratio signal to the control circuit 20 is provided at 16.

A water temperature sensor 18 for detecting a cooling water temperature of the engine 1 and outputting a water temperature signal to the control circuit 20 is provided in the engine block 1a.
Is provided.

 Next, the control circuit 20 will be described with reference to FIG.

The control circuit 20 inputs and calculates each signal detected by each sensor described above according to a control program, and performs a process for controlling each device described above, a central processing unit (hereinafter referred to as a CPU) 21, a control program and an initial Read only memory (ROM) 2 in which data is stored in advance
2. A random access memory (RAM) 23 in which various signals input to the control circuit 20 and data necessary for arithmetic control are temporarily stored, and a key switch of the engine 1 is turned on by the driver.
A backup ram (BU-RAM) 24, an input / output interface 25, and an A / D converter 26 capable of storing various data necessary for control of the engine 1 after the FF by a battery.
And a bus 27 such as a data bus or a control bus for connecting them.

Output from the air-fuel ratio signal and the throttle switch 7 is output cylinder discrimination signals output from the cylinder discrimination sensor 13, a crank angle signal output from the engine speed sensor 14, from the O ₂ sensor 17 to the input-output interface 25 A throttle signal and the like are input, and a fuel injection signal for controlling the opening and closing time of the fuel injection valve 10 and an ignition signal for controlling the on / off time of the igniter 15 are output via a drive circuit. The A / D converter 26 includes the intake air temperature sensor 8,
An intake air temperature signal, an intake pipe pressure signal, and a water temperature signal are input from the pressure sensor 9 and the water temperature sensor 18, respectively, and are converted into digital signals.

Next, the processing executed by the control circuit 20 will be described with reference to FIGS. 3 (a) and 3 (b).

First, in step 30, a basic injection amount Tp is calculated based on signals from the pressure sensor 9 and the engine speed sensor 14, and in step 31, various correction coefficients K (for example, water temperature correction coefficient,
Intake temperature correction coefficient, acceleration / deceleration correction coefficient, etc.) are set, and in a subsequent step 32, the invalid injection time Tv of the fuel injection valve 10 is set.

In step 33, it is determined whether the air-fuel ratio feedback condition is satisfied. This determination is made to be satisfied, for example, when the O ₂ sensor is in the active state, the water temperature is greater than 40 ° C., and after the start. If it is determined in step 33 that the feedback condition is not satisfied, the process proceeds to step 47 in which the air-fuel ratio correction coefficient FAF is set to "1" in step 46. If it is determined in step 33 that the condition is satisfied, then in step 34
Read output voltage V of the O ₂ sensor 17. In step 35, the output voltage V is compared with a reference voltage Vref (for example, 0.45 volts). If V <Vref, it is determined that the air-fuel ratio is lean, and the routine proceeds to step 36, where the air-fuel ratio is changed from rich to lean. It is determined whether or not is the time of inversion. If it is determined in this step 36 that reversal is being performed, the process proceeds to step 37, where the reversal instruction flag FI is set to "1", and the process proceeds to step 38, where FIG.
As shown in (2), the air-fuel ratio correction coefficient FAF is increased (skipped) by a predetermined proportional constant P with respect to the previous value. Also step
If it is determined in step 36 that it is not the time of reversal, the process proceeds to step 39, in which the reversal instruction flag FI is set to "0". And the air-fuel ratio correction coefficient FAF is increased at a predetermined slope.

If it is determined in step 35 that the air-fuel ratio is rich (V> Vref), the routine proceeds to step 41, where it is determined whether or not the air-fuel ratio is being reversed from lean to rich. If it is determined in this step 41 that it is the time of reversal, the reversal instruction flag FI is set to "1" in step 44, and the air-fuel ratio correction coefficient FAF is set to a value in step 45 shown in FIG. Decrease (skip) by a predetermined proportional constant P. If it is determined in step 41 that it is not the time of reversal, the process proceeds to step 42, in which the reversal instruction flag FI is set to "0", and in step 43, the air-fuel ratio correction coefficient FAF is set to The air-fuel ratio correction coefficient FAF is reduced at a predetermined slope by a predetermined integration constant I.

Then, in a step 47, it is determined whether or not the throttle switch 7 is on. If the throttle switch 7 is off, the process proceeds to a step 49, where the learning inhibition flag FP
S is set to “0”, and the routine proceeds to step 50.

If it is determined in step 47 that the throttle switch 7 is on, the process proceeds to step 48, where the learning inhibition flag FPS is set to "1".
Is determined. If it is determined that the flag FPS is “1”, the process proceeds to step 56. If it is determined in step 48 that the learning prohibition flag FPS is "0", the process proceeds to step 50, where it is determined whether the learning condition is satisfied. This determination is made during the feedback of the air-fuel ratio, when the cooling water temperature is greater than 70 ° C., and when the number of skips is performed three or more times, it is determined that the condition is satisfied.

If it is determined in step 50 that the learning condition is not satisfied,
Proceeding to step 57, it is determined whether the learning condition was satisfied last time. If the previous learning condition is not satisfied in step 57, the process proceeds to step 56. If the previous learning condition is satisfied in step 57, that is, if the learning condition is reversed from being satisfied to not being satisfied, the process proceeds to step 58, where the learning inhibition flag FPS is set to "1", and the process proceeds to step 56.

If it is determined in step 50 that the learning condition is satisfied, it is determined in step 51 whether the reversal instruction flag FI is “1”. If the inversion instruction flag FI is "0", the process proceeds to step 56, and if the inversion instruction flag FI is "1", the process proceeds to step 52 to calculate the average correction coefficient FAFAV. This correction coefficient average value FAFAV is the air-fuel ratio correction coefficient FAF immediately before the current skip (for example, shown in FIG. 5B).
And the air-fuel ratio correction coefficient FAF immediately before the previous skip (for example, shown in FIG. 5 (b)).

In a succeeding step 53, it is determined whether or not the correction coefficient average value FAFAV> 1 + α. Here, α is a value representing the width of the dead zone, and is set to, for example, 0.01. This step 53
If it is determined that FAFAV> 1 + α, the routine proceeds to step 54, where the learning value Mi is set to Mi + ΔMi, and the routine proceeds to step 55. Here, the learning value Mi (M _{1 to} M ₁₆ ) is the engine speed NE as shown in FIG.
The learning value Mi is set in advance for each area of the engine operating state divided by the engine operating state and the intake pipe pressure PM, and the learning value Mi is set to “1” when learning is not started. ΔMi
Is an update width of the learning value, and is set to, for example, 0.002.

If it is determined in step 53 that FAFAV ≦ 1 + α,
Proceeding to step 59, it is determined whether FAFAV <1-α. If it is determined in step 59 that FAFAV> 1 + α, the process proceeds to step 56. If it is determined in this step 59 that FAFAV <1−α, the routine proceeds to step 60, where the learning value Mi is set to Mi−ΔMi, and the routine proceeds to step 55.

In this step 55, the learning correction coefficient FLAF is calculated by taking the average of the average value of all the learning values Mi and the learning value Mi of the corresponding area.
The drive pulse width TAU of the fuel injection valve 10 is calculated by adding the invalid injection time Tv to a value obtained by multiplying the basic injection amount Tp calculated in 30 by the various correction coefficients K, the air-fuel ratio correction coefficient FAF, and the learning correction coefficient FLAF. A predetermined amount of fuel is injected from the fuel injection valve 10 by the drive pulse width TAU.

As described above, in this embodiment, while the learning condition is satisfied, even in the idling operation state, step 47 in FIG.
Learning of the air-fuel ratio is continued via 48, 50, 51 ...
In the steady operating condition of the engine 1, enters the idling exhaust gas temperature is lowered, the O ₂ sensor 17 becomes inactive state, the air-fuel ratio feedback is stopped by the air-fuel ratio feedback condition is not to be established, the 3. The process proceeds from step 50 in FIG. 3 (b) to steps 57 and 58, and learning is prohibited. At this time, in step 58 of FIG.
S = 1, and if this FPS is 1, the next step 48
And the answer is YES, bypassing Step 50 and below, Step 5
Proceeding to 6 prohibits re-learning during idling operation. Therefore, after this, when the O ₂ sensor 17 and the exhaust gas temperature rises caused load variation due to an increase in air conditioner starting or electrical load on the engine 1 becomes active, FIG. 5 (b)
As shown in FIG. 3, the air-fuel ratio feedback condition is satisfied, and the air-fuel ratio feedback is restarted.
Even if the learning condition shown in FIG. 50 is satisfied, the throttle switch is turned on as shown in FIG. 5D, and the program goes through steps 47 and 48 in FIG. 3B, where FPS = 1. Therefore, the air-fuel ratio learning is prohibited. Therefore, the learning value of the O ₂ sensor 17 at this time is not updated in the state where the output is unstable immediately before the inactive state, so that erroneous learning can be prevented as shown by the solid line in FIG. 5 (c). Therefore, FIGS. 5 (b) and (c)
As shown in (1), accurate air-fuel ratio control can be performed during idling operation. Note that the broken line in FIG. 5 (c) shows the result when learning is performed as before, when the learning condition is satisfied.

FIG. 7 is a flowchart showing another learning process. In this another example, the learning value Mi in the above embodiment is FLAF. Then, in step 59, the average value FAFAV <1−α
If it is determined that the learning correction coefficient
FLAF is FLAF-ΔFLAF. Note that ΔFLAF is the update width of the learning value, and is set to, for example, 0.002. or,
If it is determined in step 53 that FAFAV> 1 + α, the learning value FLAF is set to FLAF + ΔFLAF in step 61.

Therefore, according to this alternative example, the learning correction coefficient FLAF can be obtained without calculating the average value of all the learning values Mi as in the above embodiment, and the control can be simplified.

In each of the above embodiments, the present invention is applied to a system for obtaining the basic injection amount based on the intake pipe pressure and the engine speed.
A system that calculates the basic injection amount based on the intake air amount detected by the air flow meter and the engine speed, and a system that calculates the basic injection amount based on the throttle opening and the engine speed detected by the throttle opening sensor The present invention can also be applied to

[Effects of the Invention] As described above in detail, according to the present invention, at the time of idling in the steady operation state, the air-fuel ratio feedback condition in which the O ₂ sensor is inactive once becomes unsatisfied, and the learning condition is satisfied. Once determined the non then, by during its idle prohibiting learning regardless the determination result of the learning conditions, be O ₂ sensor by load fluctuations during the idle becomes the active state of inactive brink , Can prevent erroneous learning by learning based on the unstable output,
There is an excellent effect that accurate air-fuel ratio control can be performed during idling.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims of the present invention, FIG. 2 is a block diagram showing an electrical configuration, FIGS. 3 (a) and 3 (b) are flow charts showing one embodiment of the present invention, FIG. Is a diagram showing a learning value set by the engine speed and the intake pipe pressure,
5 (a) to 5 (e) are waveform diagrams for explaining the operation, FIG. 6 is an overall configuration diagram of the engine, and FIG. 7 is a flowchart showing another learning process. In the figure, 1 is an engine as an internal combustion engine, 2 is a combustion chamber, 7
Is a throttle switch as idle state detecting means,
17 O ₂ sensor 20 is the basic injection amount calculating means, air-fuel ratio correction coefficient setting means, the learning condition determining means, the learning correction coefficient updating means, learning prohibition means is a control circuit of the injection amount calculating means and the memory means.

Claims (1)

(57) [Claims] 1. A basic injection amount calculating means for calculating a basic injection amount based on an intake air amount of an internal combustion engine or a parameter related thereto and an engine speed, and an actual detection by an oxygen concentration sensor provided in an exhaust system. The air-fuel ratio and the stoichiometric air-fuel ratio are compared to set an air-fuel ratio correction coefficient by proportional integral control, and an air-fuel ratio correction coefficient setting unit; a storage unit that stores an air-fuel ratio learning correction coefficient; Learning condition determining means for determining whether a learning condition for updating a learning correction coefficient is satisfied; and the air-fuel ratio correction coefficient when the learning condition determining means determines that the learning condition is satisfied. Learning correction coefficient updating means for updating the learning correction coefficient stored in the storage means on the basis of: the injection amount based on the calculated basic injection amount, air-fuel ratio correction coefficient, and learning correction coefficient. An electronically controlled fuel injection type internal combustion engine air-fuel ratio control device, comprising: an injection amount calculating unit that outputs an injection amount; and a driving unit that outputs a drive pulse signal corresponding to the calculated injection amount to the fuel injection valve. An idle state detecting means for detecting an idle operating state; and a case where the learning condition determining means once determines that the learning condition is not satisfied when the idle state detecting means detects the idle operating state. A learning prohibition unit that prohibits the learning correction coefficient updating unit from updating the learning correction coefficient while the idle state detection unit detects the idling operation state, regardless of the determination result of the learning condition determining unit. An air-fuel ratio control device for an electronically controlled fuel injection type internal combustion engine, comprising: