JPH0746750Y2 - Air-fuel ratio controller for engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an air-fuel ratio control device for controlling the air-fuel ratio of an engine equipped with an electronically controlled fuel injection device.

[Conventional technology]

BACKGROUND ART Conventionally, some engines that adjust the fuel injection amount of an injector or the like by electronic control are provided with an air-fuel ratio control device that automatically controls the air-fuel ratio so that a good air-fuel ratio can be obtained ( See Japanese Patent Publication No. 62-12382). That is, in the above device, the basic fuel injection amount is based on the intake flow rate detected by the air flow meter, the feedback correction amount is based on the detection value of the O ₂ sensor, and the learning value is further based on the feedback correction amount. It is configured to be calculated.

Then, in the feedback control region which is a relatively low rotation and low load region excluding the starting region, the final fuel injection amount is calculated by the basic fuel injection amount, the feedback correction amount, and the learning value, and the starting region and the high fuel amount are calculated. In the open control region such as the high rotation speed region, the feedback correction amount is reset and the learning value is fixed, and the final fuel injection amount is calculated by the learning value and the basic fuel injection amount. ing. Then, the fuel injection amount of the injector is changed according to the final fuel injection amount.

[Problems to be solved by the device]

By the way, when fuel with low volatility such as heavy gasoline is used, for example, when the engine temperature is low (when the engine is cold) (when the engine is cold), the fuel injected from the injector causes the fuel to be injected into the intake passage or the inner wall of the fuel chamber. To the crankcase through the gap between the inner wall of the cylinder and the piston.
Therefore, the air-fuel ratio has a lean tendency, and the feedback correction amount is corrected so as to increase the fuel injection amount. After this, when the engine temperature rises, the fuel accumulated in the crankcase, etc. is vaporized and returns to the combustion chamber, and the specific fuel ratio tends to become rich, contrary to the above, and the feedback correction amount is corrected to reduce the fuel injection amount. Then, the learning value is also set to the lean side corresponding to this feedback correction amount.

However, in the conventional engine air-fuel ratio control device, when the learning value is set to the lean side, the engine is stopped and then restarted, the learning value remains set to the lean side. Since it is fixed, the fuel injection amount tends to decrease. On the other hand, since the engine temperature is decreasing, fuel flows out to the crankcase as described above. As a result, the air-fuel ratio becomes over lean, and the responsiveness and emission of the engine deteriorate.

The present invention solves the above problem, and an object of the present invention is to provide an air-fuel ratio control device for an engine that prevents over-lean when a fuel with poor volatility is used and has good combustion stability.

[Means for Solving the Problems]

In order to achieve the above object, the present invention calculates a fuel injection amount in a feedback control region based on a basic fuel injection amount, a feedback correction amount based on an air-fuel ratio detection signal, and a learning value set based on the feedback correction amount. Then, in the open control region, in the air-fuel ratio control device of the engine that calculates the fuel injection amount by the basic fuel injection amount and the learning value, the determination means for determining whether the learning value is set to the lean side, At least in the open control area, when the learned value is on the lean side, a limiting means for limiting the reflection of the learned value is provided.

[Action]

According to the engine air-fuel ratio control device having the above configuration, it is determined whether the learning value is set to the lean side, and at least when the learning value is set to the lean side in the open control region, the learning value is set to the lean side. The reflection of is limited. That is, it is possible to prevent over lean.

〔Example〕

FIG. 2 is an overall configuration diagram of an engine to which the air-fuel ratio control device according to the present invention is applied.

A piston 20 is provided in each cylinder of the engine body, and a combustion chamber 21 is formed above the piston 20. At a position facing the combustion chamber 21, an intake valve 22 and an exhaust valve 23
An ignition plug 24 and the like are provided, and an intake passage 25 and an exhaust passage 26 are connected to the intake valve 22 and the exhaust valve 23, respectively.

In the intake passage 25, an air flow meter 27 that detects the intake flow rate, a throttle valve 28, and an injector 29 that directly supplies fuel to the engine are sequentially arranged. The upstream side portion and the downstream side portion of the throttle valve 28 are connected by a bypass passage 30 having a control valve such as an ISC valve. The exhaust passage 26 is provided with an O ₂ sensor 31 for detecting the oxygen concentration in the exhaust gas, and the engine body is provided with a water temperature sensor 32 for detecting the engine water temperature. Then, the detection signals from the air flow meter 27, the O ₂ sensor 31, the water temperature sensor 32, etc. are input to the ECU 1.

The block configuration of the ECU 1 will be described below with reference to FIG.

The ECU 1 includes a basic amount calculation means 2, a correction amount calculation means 3, a learning value calculation means 4, a discrimination means 5, a limiting means 6, and a final amount calculation means 7.
And a control means 8.

The basic amount calculation means 2 calculates the basic fuel injection amount based on the detected amount Q of the air flow meter 27 and the engine speed N and outputs it to the final amount calculation means 7. The correction amount calculation means 3 calculates the feedback correction amount CFB based on the detection result of the O ₂ sensor 31 and outputs it to the final amount calculation means 7. The learning value calculation means 4 calculates the learning value CLRN based on the feedback correction amount CFB and outputs it to the final amount calculation means 7. The discriminating means 5 is the learning value CLRN.
This is to determine whether is on the lean side.

The limiting means 6 is a signal from the determining means 5 and the water temperature sensor 32.
Based on the signal from, when the learning value CLRN is on the lean side in a state where the engine water temperature or the like is in a specific condition, the learning value CLRN is limited (reset) to 0%, for example. The final amount calculation means 7 corrects the basic fuel injection amount based on the feedback correction amount CFB, the learned value CLRN and the like to calculate the final fuel injection amount. The control means 8 determines the final pulse width Ti from the final fuel injection amount and outputs it to the injector 29.

Next, the fuel injection amount control operation of the air-fuel ratio control device will be described with reference to the flowcharts of FIGS.
Note that FIG. 3 shows a main routine of fuel injection amount control, FIG. 4 shows a subroutine for calculating the feedback correction amount CFB, and FIG. 5 shows a subroutine for calculating the learning value CLRN. .

In step S ₁ , various signals from the air flow meter 27 and the like are read by the ECU 1, and in step S ₂ , the basic pulse width Tp corresponding to the basic fuel injection amount is obtained based on the detected flow rate Q and the engine speed N (( Tp = K · Q / N, K
Indicates a constant).

Subsequently, whether the feedback condition is satisfied in step S ₃ it is determined. In this case, for example, when the engine is in a relatively low rotation and low load region excluding the starting region and the engine water temperature is 40 ° C. or higher (feedback control region), the feedback condition is satisfied. Then, when the above feedback condition is satisfied (YE in step S ₃
S), the feedback correction amount CFB is calculated in the subroutine of step S ₄ (FIG. 4). On the other hand, when the feedback condition is not satisfied (NO in step S _3), i.e.,
For open control region, such as during engine start or high-speed and high-load region, the feedback correction amount CFB at step S ₅
Is reset to 0%.

In step S _6, the volatile poor fuel such as heavy gasoline (hereinafter, heavy gasoline that) if it is determined based on the determination flag set in advance. That is, if heavy gasoline or the like is used, the engine rotation unevenness is likely to occur at a low temperature. Therefore, for example, in the determination flag, the engine speed fluctuation (rotation unevenness) ΔN in the idle state is equal to or greater than the set value α, and , "1" when the engine water temperature is below 20 ℃
Once set, the set state is maintained unless the engine is stopped once set.

Then, when the determination flag is “1” (in step S ₆
YES), in step S _7, it is determined by the determination means 5 whether the learning value CLRN is set to the lean side, that is, whether the learning value CLRN is set to −20% or less,
If the learning value CLRN less -20% (YE in step S ₇
S), whether the engine water temperature is 50 ° C. or more is determined in step S _8. Then, (YES in step S ₈₎ when the engine water temperature is above 50 ° C., if the learning condition is satisfied is judged in step S _9. In this case, for example, the learning condition is satisfied when the engine water temperature is 80 ° C. or higher in the neutral state. When the learning condition is satisfied (YES in step S _9), the learned value CLRN calculation subroutine at step S ₁₀ (FIG. 5), the process proceeds to step S ₁₃ after this. On the other hand, if the learning condition is not satisfied (step S ₉
, NO), and the learning value CLRN obtained in the previous routine processing in step S ₁₁ is set as it is as the current learning value CLRN, and thereafter, the process proceeds to step S ₁₃ .

On the other hand, if the engine coolant temperature is cold state of 50 ° C. or less in the step S ₈ (ON in step S _8), i.e., when heavy gasoline is prone state adhered to the inner wall such as a combustion chamber, the step S
_{At 12} , the learning value CLRN is limited (reset) to 0%, and the processing as the limiting means 6 is performed. Thereafter the process proceeds to step S _13.

On the other hand, (NO in step S ₆₎ if the determination flag in step S ₆ is reset to "0" and the learned value CL in step S ₇
If RM is not less than -20% (ON in step S _7), step
Moves to S _9, whether or not the learning conditions are satisfied or not is determined.

In step S _13, other various correction amount C is determined,
Final pulse width Ti is calculated by the following equation in step S _14.

Ti = Tp · (1 + CFB + CLRN + C) + Tv Note that Tv is the invalid injection pulse width.

Subsequently, the final pulse width Ti at step S ₁₅ is outputted to the injector 29, the fuel corresponding to the final pulse width Ti is injected into the engine.

Now be described with reference to a flowchart of FIG. 4 for calculation subroutine of the feedback correction amount CFB in step S _4.

In step S ₂₁ , the output of the O ₂ sensor 31 is read, and in step S ₂₂ , it is determined whether the air-fuel ratio is in the rich state,
If rich state (YES in step S _22), step S
_{At 23} , it is judged whether or not the air-fuel ratio based on the previous output of the O ₂ sensor 31 was in the rich state.

Then, if the previous air-fuel ratio is in the rich state (step S
₂₃ YES), the feedback correction amount CFB at step S ₂₄
Is a predetermined integral value Δ for the previous feedback correction amount CFB.
It is updated to the value obtained by subtracting I. On the other hand, if the previous air-fuel ratio is in a lean state (NO at step S _23), the feedback correction amount CFB at step S ₂₅ is updated to the last feedback correction amount CFB to a value obtained by subtracting a predetermined proportional value P. In step S _26, the output of the O ₂ sensor 31 as a preceding value ECU1
It is stored in the internal memory (not shown) and then returns.

On the other hand, the air-fuel ratio in the step S ₂₂ is as long as the lean state (NO at step S _22), in step S ₂₇ is the air-fuel ratio of the preceding whether it was a lean state is determined. Then, if the previous air-fuel ratio is lean (YES in step S _27), step
In S ₂₈ , the feedback correction amount CFB is updated to a value obtained by subtracting the predetermined integral value ΔI from the previous feedback correction amount CFB. On the other hand, if the previous air-fuel ratio in the rich state (NO at step S _27), the feedback correction amount CFB at step S ₂₉
Is a predetermined proportional value P to the previous feedback correction amount CFB.
Is updated to a value obtained by adding, the detection result of the O ₂ sensor 31 is stored in the memory in the ECU 1 in step S ₂₆ , and then the process returns.

It will now be described with reference to a fifth flow chart for calculation subroutine of the learning value CLRN in step S _10. In the flowchart of FIG. 5, the count value CN is "3".
Although the count is incremented by 2 ", the count may be incremented by other than" 32 ".

Step S ₃₁ feedback correction amount CFB described above in is added to the integrated value FCFB, the count value CN is incremented in step S _32. Succeedingly, in a step S ₃₃ , it is determined whether or not the count value CN has reached “32”, that is, whether or not the count value has been counted up. Then, to be counted up (YES at step S _33), the learning value correction amount ΔCLRN is calculated by the following equation in step S _34.

ΔCLRN = (FCFB / 32) · 1/2 Then, the learning value CLRN is in step S _35, the previous learning value CLR
It is updated to a value obtained by adding the learning value correction correction amount ΔCLRN to N. In step S ₃₆ , the feedback correction amount C B is adjusted in accordance with the learning value update, so the feedback correction amount C
FB is changed to a value obtained by subtracting the learning value correction amount ΔCLRN from the previous feedback correction amount CFB. Then step S
_{At 37} , the count value CN is reset.

On the other hand, the count value CN is "31" or less in the step S _33, namely if not counted up (Step S ₃₃ N
O), the value of the previous learning value CLRN the learning value CLRN in step S ₃₈ is set as to return later.

As described above, in the device of this embodiment, it is determined that the fuel is heavy gasoline or the like (step S ₆ ), and the learning value
CLRN is set to the lean side (step YES at S _7), further if the engine coolant temperature is cold state of 50 ° C. or less (Step S ₈
In NO), i.e. to determine the case it tends to over-lean limit the learning value CLRN (step S _12), are the so prevent over-lean.

That is, as shown in FIG. 6, when the engine temperature rises and the fuel adhering to the inner wall of the combustion chamber or the like is vaporized and the air-fuel ratio tends to become rich, the feedback correction amount CFB is reduced so that the fuel injection amount decreases. Corrected to the lean side, learning value CLR
N also corresponds to this feedback correction amount CFB, for example,
It is set to the lean side at t ₀ . Then, for example, when the engine is stopped at time t ₁ and thereafter the engine is restarted at time t ₂ when the engine water temperature drops to 50 ° C. or lower, as shown by a chain double-dashed line B in FIG. In the device, the learning value CLRN is the learning value at time t _{1 in} the open control area after time t _2.
It is fixed at C ₀ . Therefore, the fuel injection amount is reduced, and over lean may occur.

On the other hand, in this apparatus, as shown in the solid line A in FIG. 6, t ₂
Since the learning value CLRA is limited (reset) to 0% at the time point, the learning value CLRN is not reflected in the fuel injection amount, and over lean can be prevented.

In the above description, the learning value is limited in the open control region when the engine is started, but the learning value may be set to the lean side in the open control region other than when the engine is started or in the feedback control region. If determined, the learning value may be limited.

[Effect of device]

This invention limits the reflection of the learned value and prevents the fuel injection amount from becoming over-lean when the learned value is set to the lean side at least in the open control region. A good engine air-fuel ratio control device can be provided.

[Brief description of drawings]

1 is a block diagram of an ECU of an air-fuel ratio control device according to the present invention, FIG. 2 is an overall configuration diagram of an engine according to the present invention, FIG. 3 is a flowchart showing a main routine of fuel injection amount control, and FIG. FIG. 5 is a flowchart showing a subroutine for calculating a feedback correction amount, fifth
FIG. 6 is a flowchart showing a subroutine for calculating the learning value, and FIG. 6 is a graph for explaining the operation of limiting the learning value. 1 ... ECU, 2 ... Basic amount calculation means, 3 ... Correction amount calculation means,
4 ... Learned value calculating means, 5 ... Discriminating means, 6 ... Limiting means, 7
... final amount calculation means, 8 ... control means, 27 ... air flow meter, 29 ... injector, 31 ... O ₂ sensor, 32 ... water temperature sensor.

Claims (1)

[Scope of utility model registration request] 1. A feedback control region calculates a fuel injection amount based on a basic fuel injection amount, a feedback correction amount based on an air-fuel ratio detection signal, and a learning value set based on the feedback correction amount. In an air-fuel ratio control device for an engine that calculates a fuel injection amount based on a basic fuel injection amount and the learned value, a determination means that determines whether or not the learned value is set to a lean side, and at least in the open control region, An air-fuel ratio control device for an engine, comprising: a limiting unit that limits reflection of the learned value when the learned value is lean.