JP2873506B2 - Engine air-fuel ratio control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an air-fuel ratio control device for an engine, and more particularly, to an air-fuel ratio of an engine, and based on a deviation between an air-fuel ratio detected in a specific learning region and a target air-fuel ratio. The present invention relates to an air-fuel ratio control device for an engine in which a learning value is calculated and learning control is performed to achieve a target air-fuel ratio.

(Prior Art) In general, the technology of detecting the air-fuel ratio of an engine, compensating for the deviation of the air-fuel ratio due to variations in injectors and changes over time of an air flow meter, and performing learning control to achieve a target air-fuel ratio is based on the engine. A well-known air-fuel ratio control method has been conventionally known (for example, see Japanese Patent Publication No. 63-1453).

The air-fuel ratio control as described above is generally performed based on a learning value obtained in an operation region where the engine speed is stable (for example, an idling operation region), and the engine speed changes. In the operating region, the air-fuel ratio control is performed by reflecting the learning value. Then, as disclosed in the above-described known example, the learning reflection ratio in an operation region (that is, a non-learning region) other than a learning region (for example, an idling operation region) is changed according to the intake air amount (that is, If the amount of intake air increases, the learning reflection ratio is reduced).

(Problems to be Solved by the Invention) However, in the case of the air-fuel ratio control as described above, there are the following problems.

That is, since the learning reflection ratio is changed according to the intake air amount, the learning reflection gradient is set in a boundary region such as when accelerating or decelerating (for example, when the idle switch is turned off → on or when on → off). The reset speed at which the learning value is reset to zero during acceleration (that is, when shifting from the learning region to the non-learning region), and at the time of deceleration (that is, when shifting from the non-learning region to the learning region). In (2), the set speed at which the learning value is returned to the previous learning value must be the same. Then, in the acceleration transition period in which the amount of intake air increases sharply, the learning reflection ratio decreases rapidly, and there is a possibility that the air-fuel ratio deviates from the target air-fuel ratio. Therefore,
In order to make the reflection slope of the learning value during acceleration gentle, it is necessary to set so that the learning reflection rate increases with the increase in the intake air amount. At the time of a large airflow meter characteristic, there is a possibility that a learning value is erroneously reflected in a non-learning region.

On the other hand, at the time of deceleration (that is, when shifting from the non-learning area to the learning area), it is not necessary to make the learning reflection gradient gentle, and it is sufficient to immediately return to the previous learning value.

The present invention has been made in view of the above points, and changes the learning reflection gradient between the case where the engine operation state shifts from the learning area to the non-learning area and the case where the engine operation state shifts from the non-learning area to the learning area. By this, it is intended to prevent the deviation of the air-fuel ratio when shifting from the learning region to the non-learning region, and to ensure the responsiveness of the air-fuel ratio control when shifting from the non-learning region to the learning region. is there.

(Means for Solving the Problems) In the present invention, as means for solving the above problems, an air-fuel ratio of an engine is detected, and based on a deviation between an air-fuel ratio detected in a specific learning region and a target air-fuel ratio. An air-fuel ratio control device for an engine having an air-fuel ratio learning control means for performing learning control by calculating a learning value to obtain a target air-fuel ratio by calculating a learning value when a transition is made from the learning region to the non-learning region. The reset speed at which the learned value is reset to zero based on the predetermined gradient characteristic, the learning value that was reset to zero when shifting from the non-learning region to the learning region was previously calculated based on the predetermined gradient characteristic. Control means for lowering the set speed for returning to the learning value is provided.

The learning region is, for example, an idle operation region.

(Operation) In the present invention, the following effects are obtained by the above means.

That is, when the engine operation state shifts from the learning region to the non-learning region, the reset speed at which the learning value calculated in the learning region is reset to zero based on the predetermined gradient characteristic shifts from the non-learning region to the learning region. The air-fuel ratio when shifting from the learning region to the non-learning region is controlled by controlling the learning value that has been reset to zero to be lower than the set speed at which the learning value is reset to the previously calculated learning value based on a predetermined gradient characteristic. Is prevented, and the responsiveness of the air-fuel ratio control when shifting from the non-learning region to the learning region is ensured.

(Effects of the Invention) According to the present invention, an air-fuel ratio of an engine is detected, and a learning value is calculated based on a deviation between an air-fuel ratio detected in a specific learning region and a target air-fuel ratio to become a target air-fuel ratio. In the air-fuel ratio control device of the engine provided with the air-fuel ratio learning control means for performing learning control as described above, the learning value calculated in the learning region at the time of shifting from the learning region to the non-learning region is set to zero based on a predetermined gradient characteristic. A control means is provided for setting a reset speed at which the reset value to be reset is lower than a set speed at which the learning value reset to zero when returning from the non-learning region to the learning region returns to the previously calculated learning value based on a predetermined gradient characteristic. To prevent the occurrence of an air-fuel ratio shift when shifting from the learning region to the non-learning region, and to improve the responsiveness of air-fuel ratio control when shifting from the non-learning region to the learning region. Therefore, there is an excellent effect that the operating state of the engine during an operation transition period such as acceleration or deceleration is stabilized, for example.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

In FIG. 1, an engine 1 is a known four-cycle spark ignition type engine mounted on an automobile, and uses combustion air, an air cleaner (not shown), an intake pipe 2 and a throttle valve 3.
Inhalation via.

The fuel is supplied from a fuel system (not shown) via electromagnetic fuel injection valves 4 provided for the respective cylinders. The exhaust gas after combustion is discharged into the atmosphere via an exhaust manifold 5, an exhaust pipe 6, and a catalytic converter 7.

A hot-wire type air flow meter 8 for detecting an intake air amount Qa is provided on the upstream side of the throttle valve 3 of the intake pipe 2, and an idle switch 9 is provided on the intake pipe 2. The air flow meter 8 outputs an analog voltage signal.

Further, the exhaust manifold 5 detects the air-fuel ratio from the oxygen concentration in the exhaust gas. The air-fuel ratio is high when the air-fuel ratio is smaller than the target air-fuel ratio (that is, rich), and low when the air-fuel ratio is larger than the target air-fuel ratio (that is, lean). An O ₂ sensor 10 that outputs a voltage of a level is provided.

A distributor 13 for supplying a current to the ignition plug 12 of the engine 1 at a predetermined interval is provided with a crank angle sensor 11 for detecting a rotation speed of a crank shaft of the engine 1. A pulse signal with a frequency corresponding to the speed is output. Reference numeral 14 denotes an ignition coil.

The detection signal from each of the sensors 8 to 11 is a control unit
The control unit 15 is a circuit for calculating the fuel injection amount based on each of the detection signals, and operates so as to adjust the opening time of the electromagnetic fuel injection valve 4.

Next, the control unit 15 will be described with reference to FIG.

The control unit 15 includes a microprocessor (hereinafter, referred to as a CPU) 16 that calculates a fuel injection amount, a rotation counter 17 that counts an engine rotation Ne based on a signal from the crank angle sensor 11, a digital input port 18, An analog input port 19, a temporary storage unit (hereinafter, referred to as RAM) 20 used temporarily during a program operation, a read-only memory (hereinafter, referred to as ROM) 21 for storing programs, various constants, and the like; A time control counter 22 and a power amplifier 23 for driving the electromagnetic fuel injection valve 4
And a common bus 24 for transmitting and receiving signals to and from the CPU 16.

The digital input port 18 transmits an output signal of a comparator for comparing the output of the O ₂ sensor 10 with a predetermined comparison level and an ON / OFF signal from the idle switch 9 to the CPU 16.

The analog input port 19 includes an analog multiplexer and an A / D converter, and has a function of converting a signal from the air flow meter 8 into an A / D signal and reading the converted signal into the CPU 16.

Power is supplied to the RAM 20 via a power supply circuit 25. The power supply circuit 25 is directly connected to a battery 26, and is always supplied with power. On the other hand, a power supply circuit indicated by reference numeral 27 supplies power to parts other than the RAM 20, and is connected to a battery 26 via a key switch 28.

Then, the CPU 16 detects the air-fuel ratio of the engine 1 with the O ₂ sensor 10 and, based on the deviation between the air-fuel ratio detected in a specific learning region (idle region in the present embodiment) and the target air-fuel ratio. An air-fuel ratio learning control means for calculating a learning value to perform learning control so as to attain a target air-fuel ratio; and The reset speed at which the learning value is reset to zero based on the predetermined gradient characteristic, the learning value reset to zero when the learning region is shifted from the non-learning region to the learning region is the learning value previously calculated based on the predetermined gradient characteristic. , And also serves as control means for making the setting speed lower than the setting speed for returning to.

Hereinafter, referring to the flowchart shown in FIG.
The function of the CPU 16 will be described in detail.

Key switch 28 and starter switch (not shown)
Is turned on and the engine 1 is started, and in step S ₁ , various signals such as the intake air amount Qa from the air flow meter 8, the engine speed Ne from the crank angle sensor 11, and the output of the O ₂ sensor 10 are read. Is executed.

Next, in step S _2, the CPU 16, the basic injection pulse (i.e., the fuel injection pulse commensurate with the engine rotational revolution) Tp is calculated based on the following equation.

Tp = (Qa / Ne) × K ( where, K is a constant) Next, in step S _3, the calculation of various correction values are performed by CPU 16. That is, the correction values necessary for calculating the final injection pulse Ti such as the intake air temperature correction Ca, the post-start increase correction Cs, the warm-up increase correction Cw, the feedback property Cf, the invalid injection correction Tv, and the learning value Cl (IDLE) in the idle region. Are calculated, and these correction values are temporarily stored in the RAM 20.

Thereafter, the control by the CPU16 proceeds to step S _4, the idle switch 9 is made a determination whether or not the ON state, if the idle switch 9 is in the OFF (i.e., non-learned value region from the learning value area If) where transition is made to the control by the CPU16 proceeds to step S _5, C
It is determined whether l (IDLE) ≧ 0. Where Cl (I
When it is determined that DLE) ≧ 0 (that is, when the learning value Cl (IDLE) in the idling region is corrected to increase),
Control of CPU16 proceeds to step S _6, the time of the last learning reflection amounts Cl (i) is calculated by the following equation.

Cl (i) = Cl (i-1) -Cl (D1) Here, Cl (i-1) is the last final learning reflection amount,
(D1) is a learning reflection attenuation value when the idle switch 9 is turned ON → OFF (that is, at the time of transition from the learning region to the non-learning region), and the learning reflection attenuation value Cl (D1) is set in advance. The data is stored in the ROM 21 and read each time.

When the calculation is finished, the control of CPU16 step S ₇
The process proceeds, the calculation results Cl (i) it is determined whether it is greater than zero is made, in the case of Cl (i)> 0, the control by the CPU16 proceeds to step S _8, the calculation results Cl ( i), the basic injection pulse Tp and on the basis of the various correction value calculated in step S _3, the final injection pulse Ti of the fuel injection
Is calculated by the following equation.

Ti = Tp × Ca {1.0 + Cs + Cw + Cf + Cl (i)} + Tv A predetermined amount of fuel is injected from the electromagnetic fuel injection valve 4 based on the final injection pulse Ti thus obtained.

When the calculation of the final injection pulse Ti is completed, control of CPU16 is returned to step S _1, the same control as described above is repeated. If in the process the determination in the step S ₇ becomes NO, and the final learning reflection amount in step S ₉
Cl (i) will be reset to zero, and Cl (i) =
0 computation of the final injection pulse T ₁ in step S ₈ based on the performed.

That is, at the time of transition from the learning region to the non-learning region, if the idle learning value Cl (IDLE) is a positive value, the attenuation rate α ₁ corresponding to the learning reflection attenuation value Cl (D1) (that is, reset) At (speed), the learning value is reset to zero.

On the other hand, if it is determined that Cl (IDLE) <0 in step S ₅ (i.e., if the learning value in the idle region Cl (IDLE) is in the decreasing correction is controlled by the CPU16 proceeds to step S ₁₀ , The final learning reflection amount Cl (i) at that time is calculated by the following equation.

Cl (i) = Cl (i-1) + Cl (D2) Here, Cl (D2) is a learning reflection attenuation value when the idle switch 9 is turned ON → OFF (that is, at the time of transition from the learning region to the non-learning region). And the learning reflection attenuation value Cl (D2) is
It is set in advance and stored in the ROM 21, and is read out each time. In this embodiment, Cl (D1) <Cl (D
2)

When the calculation is finished, the control of CPU16 step S ₁₁
The process proceeds, the calculation results Cl (i) it is determined whether it is smaller than zero is performed, when the Cl (i) <0, the control by the CPU16 proceeds to step S _8, the calculation results Cl ( i), the basic injection pulse Tp and on the basis of the various correction value calculated in step S _3, the final injection pulse Ti of the fuel injection
Is calculated.

A predetermined amount of fuel is injected from the electromagnetic fuel injection valve 4 based on the final injection pulse Ti thus obtained.

When the calculation of the final injection pulse Ti is completed, control of CPU16 is returned to step S _1, the same control as described above is repeated. If in the process the determination in the step S ₁₁ becomes NO, and the final learning reflection amount Cl (i) becomes to be reset to zero in step S _9, Cl (i)
= 0 calculation of the final injection pulse T ₁ in step S ₈ based on is performed.

That is, at the time of transition from the learning region to the non-learning region, if the idle learning value Cl (IDLE) is a negative value, the attenuation rate α ₂ (that is, reset) according to the learning reflection attenuation value Cl (D2) At (speed), the learning value is reset to zero.

In this embodiment, the attenuation factor alpha ₁ when the idle learning value Cl (IDLE) is a positive value, the idle learning value
Although Cl (IDLE) is set smaller than the attenuation factor alpha ₂ in the case is a negative value, this is for the following reason.

That is, when the idle learning value Cl (IDLE) is a positive value, the attenuation is in a direction in which the air-fuel ratio becomes lean.
This is to prevent the air-fuel ratio from becoming too lean due to rapid learning reflection attenuation. The idle learning value
When Cl (IDLE) is a negative value, the air-fuel ratio is attenuated in a direction in which the air-fuel ratio becomes rich. Therefore, even if a large learning reflection attenuation is performed, the air-fuel ratio does not become lean and does not pose a problem.

Now, if the idle switch 9 is determined to be switched to ON in step S ₄ (i.e., when a transition from non-learned value area learning value region has been made), the
Control by CPU16 proceeds to step _{S 12, Cl (IDLE) ≧} 0
Is determined. Here, if it is determined that the Cl (IDLE) ≧ 0 (i.e., when the idle learning value Cl (IDLE) is in the increasing correction), the control by the CPU16 proceeds to step S _13, the final learning at that time The reflection amount Cl (i) is calculated by the following equation.

Cl (i) = min ｛Cl (IDLE), Cl (i-1) + Cl (D
3)｝ Here, Cl (D3) is the learning reflection increase value when the idle switch 9 is turned from OFF to ON (that is, when shifting to the non-learning region or the learning region), and the learning reflection increase value Cl (D3) Are stored in the ROM 21 as preset setting values, and are read out each time.

That is, in the case of this embodiment, the final learning reflection amount Cl at this time is
(I) is determined to be the smaller of the idle learning value Cl (IDLE) and the sum of the previous final learning reflection amount Cl (i-1) and the learning reflection increase amount Cl (D3). . Based on the final learning reflection amount Cl (i) determined as described above,
Final injection pulse Ti is calculated in step S _8.

That is, at the time of transition from the non-learning region to the learning region, if the idle learning value Cl (IDLE) is a positive value, the idle learning value Cl (IDLE) and the last final learning reflection amount Cl (IDLE)
This immediately returns to the smaller one of the sum of (i-1) and the learning reflection increase amount Cl (D3).

On the other hand, if it is determined that the Cl (IDLE) <0 in step S ₁₂ (i.e., when the idle learning value Cl (IDLE) is in the reduction correction) control by CPU16 step S
_Proceeding to ₁₄ , the final learning reflection amount Cl (i) at that time is calculated by the following equation.

Cl (i) = max ｛Cl (IDLE), Cl (i-1) -Cl (D
4)｝ Here, Cl (D4) is the learning reflection increase value when the idle switch 9 is turned from OFF to ON (that is, when shifting from the non-learning region to the learning region), and the learning reflection increase value Cl (D4) Is
It is stored in the ROM 21 as a preset setting value, and is read out each time. In this embodiment, Cl (D4) <Cl
(D3).

That is, in the case of this embodiment, the final learning reflection amount Cl at this time is
(I) is determined to be the larger of the idle learning value Cl (IDLE) and the sum of the last final learning reflection amount Cl (i-1) and the learning reflection increase amount Cl (D4). . Based on the final learning reflection amount Cl (i) determined as described above,
Final injection pulse Ti is calculated in step S _8.

That is, at the time of transition from the non-learning region to the learning region, if the idle learning value Cl (IDLE) is a positive value, the idle learning value Cl (IDLE) and the last final learning reflection amount Cl (IDLE)
This immediately returns to the smaller one of the sum of (i-1) and the learning reflection increase amount Cl (D3).

On the other hand, if it is determined that the Cl (IDLE) <0 in step S ₁₂ (i.e., when the idle learning value Cl (IDLE) is in the reduction correction) control by CPU16 step S
_Proceeding to ₁₄ , the final learning reflection amount Cl (i) at that time is calculated by the following equation.

Cl (i) = max ｛Cl (IDLE), Cl (i-1) -Cl (D
4)｝ Here, Cl (D4) is the learning reflection increase value when the idle switch 9 is turned from OFF to ON (that is, when shifting from the non-learning region to the learning region), and the learning reflection increase value Cl (D4) Is
It is stored in the ROM 21 as a preset setting value, and is read out each time. In this embodiment, Cl (D4) <Cl
(D3).

That is, in the case of this embodiment, the final learning reflection amount Cl at this time is
(I) is determined to be the larger of the idle learning value Cl (IDLE) and the sum of the last final learning reflection amount Cl (i-1) and the learning reflection increase amount Cl (D4). . Based on the final learning reflection amount Cl (i) determined as described above,
Final injection pulse Ti is calculated in step S _8.

That is, at the time of transition from the non-learning region to the learning region, if the idle learning value Cl (IDLE) is a negative value, the idle learning value Cl (IDLE) and the last final learning reflection amount Cl
This immediately returns to the larger of (i-1) and the sum of the learning reflection increase amount Cl (D4).

In this embodiment, the learning reflection increase amount Cl (D3) when the idle learning value Cl (IDLE) is a positive value is the learning reflection increase amount when the idle learning value Cl (IDLE) is a negative value. It is made to be larger than Cl (D4) for the following reasons.

That is, when the idle learning value Cl (IDLE) is a negative value, the control is performed in a direction in which the air-fuel ratio becomes lean.
This is to prevent the air-fuel ratio corresponding to the final learning reflection amount Cl (i) to be returned from becoming too lean. When the idle learning value Cl (IDLE) is a positive value, the control is performed in a direction in which the air-fuel ratio becomes rich, so that the air-fuel ratio corresponding to the final learning reflection amount Cl (i) to be restored is set. Will not be a problem as it will not be lean.

In the above embodiment, Cl (D4)> Cl (D2).

That is, in the case of the present embodiment, the reset speed at which the learning value calculated in the learning region is reset to zero when shifting from the learning region to the non-learning region is calculated last time when shifting from the non-learning region to the learning region. That is, the speed is set lower than the set speed for returning to the learning value.

In the above embodiment, when the idle switch 9 is turned ON → OFF,
In addition to changing the attenuation gradient and the return gradient between FF and ON, the attenuation gradient is determined by the positive / negative value of the idle learning value Cl (IDLE) when the idle switch 9 is changed from ON to OFF and when the idle switch 9 is changed from OFF to ON. Although the return gradient and the return gradient are changed, the attenuation gradient and the return gradient may be changed only when the idle switch 9 is turned ON → OFF and when the idle switch 9 is turned ON → OFF.

Further, in the above embodiment, the learning region is set to the idle operation region, but another region may be set to the learning region.

[Brief description of the drawings]

1 is an overall configuration diagram of an apparatus for explaining an embodiment of the present invention, FIG. 2 is a block diagram of a control circuit in the apparatus shown in FIG. 1, and FIG. 3 is a function of a microprocessor shown in FIG. 5 is a flowchart for explaining FIG. 1 ...... engine 4 ...... fuel injection valve 8 ...... air flow meter 9 ...... idle switch 10 ...... O ₂ sensor 11 ...... crank angle sensor 15 ...... control unit

Claims (2)

(57) [Claims] An air-fuel ratio detecting means for detecting an air-fuel ratio of an engine, calculating a learning value based on a deviation between the air-fuel ratio detected in a specific learning region and a target air-fuel ratio, and performing learning control so as to reach the target air-fuel ratio; An air-fuel ratio control device for an engine having a fuel ratio learning control means, wherein a reset value for resetting a learning value calculated in a learning region to zero based on a predetermined gradient characteristic when a transition from the learning region to a non-learning region is performed. Control means for lowering the learning speed, which has been reset to zero when shifting from the non-learning region to the learning region, to a previously calculated learning value based on a predetermined gradient characteristic, is provided. An air-fuel ratio control device for an engine. 2. The air-fuel efficiency control device for an engine according to claim 1, wherein the learning region is an idling operation region.