JPS6047837A - Lean combustion controlling system for internal- combustion engine - Google Patents

Abstract

PURPOSE:To enable to execute lean combustion control taking inconsistency of the engine characteristics into consideration, by making the state that learning of the air-fuel ratio is already completed as a part of conditions for shifting to the stage of lean combustion control, and executing the lean combustion control on the basis of a base injection quantity of fuel after learning of the air-fuel ratio is completed. CONSTITUTION:In operation of an engine, whether learning of the air-fuel ratio is already completed or not is judged by an ECU on the basis of the fact whether or not the mean value of an air-fuel ratio correcting factor with time lies within the prescribed range larger than a reference value alpha1 that is slightly smaller than 1 and smaller than a reference value alpha2 that is slightly larger than 1. In case of YES, whether feedback conditions are satisfied or not is judged on the basis of a condition signal STS of an internal combustion engine EG. Further, in case of YES, whether the conditions for lean combustion are satisfied or not is judged when the frequency of inversion of rich/lean signals is higher than a prescribed value after completion of learning of the air-fuel ratio. When the conditions for lean combustion are thus satisfied, lean combustion control is executed on the basis of the base injection quantity of fuel after completion of the air-fuel ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a lean-burn control method for an internal combustion engine, including an air-fuel ratio learning stage, a fee-1-hack control stage, and a lean-burn control stage. be.

Conventional Technology and Problems In general, internal combustion engines use an oxygen sensor to detect the oxygen concentration in exhaust gas, and control the fuel injection amount according to this detection result to maintain the air-fuel ratio at a constant value. Hack control is in place. In this case, in consideration of variations in the characteristics of the internal combustion engine, air-fuel ratio learning is often used in preparation for situations such as when the oxygen sensor is inactive and foot hack control cannot be performed. This learning of the air-fuel ratio is performed by correcting the basic injection amount itself, whereas the control of the fuel injection amount in the feedback control described above is performed by correcting the air-fuel ratio. This air-fuel ratio learning amount (basic injection amount correction ■) is stored in the RAM using the puncture amplifier power supply, and feed pack control is performed when the oxygen sensor is in an inactive state, such as when starting the internal combustion engine. When this is not possible, by controlling the injection amount using the previously stored learning amount of the air-fuel ratio, it is possible to correct variations in the characteristics of the internal combustion engine. On the other hand, when the internal combustion engine is stable and under low load.

In order to reduce fuel consumption, lean burn control (barge kill lean control) is generally performed, which maintains the air-fuel ratio at a predetermined amount higher than the theoretical value by reducing the basic injection amount at a fixed rate. There is.

However, in the conventional lean burn control method described above, the basic injection amount before learning is reduced at a uniform rate without considering variations in the characteristics of the internal combustion engine, so depending on the characteristics of the internal combustion engine.

The air-fuel ratio becomes too high due to lean burn control.

Driving performance may deteriorate or the internal combustion engine may stop.

Alternatively, there may be a problem that the catalyst becomes overheated.

OBJECTS OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide a lean burn control system that takes into account variations in the characteristics of internal combustion engines.

Structure of the Invention The present invention achieves the above object by making it part of the condition for transitioning to the lean burn control stage that learning of the air-fuel ratio has already been completed, and completing the learning at the transitioned lean burn control stage. Further details of the present invention, which is configured to perform lean burn control based on the subsequent basic injection amount, will be explained below using examples.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a fuel injection control system for an internal combustion engine to which an embodiment of the present invention is applied. EG is internal combustion engine, ECU internal MA +2. lj related control unit, and this internal combustion engine control unit I-E CU includes a microprocessor CPU, a comparator circuit COMP, and a buffer B.
It is composed of UF.

The comparison circuit COMP receives a signal Vs indicating the oxygen concentration from an oxygen sensor installed in the internal combustion engine EC, and compares this signal with a reference value V ref to determine whether the air-fuel ratio (A/F) is lean or lean. Display whether it is high or low 2
Output the value signal to the microprocessor CPU. The microprocessor CPU receives the output of the comparison circuit C'OMP and a signal STS indicating the state of the internal combustion engine received from the internal combustion engine.
Based on this, a command signal for fuel injection of 1 TAU is supplied to the internal combustion engine CG via the buffer BUF.

FIG. 2 is a flowchart illustrating the operation of the microprocessor CPU.

When control of the fuel injection amount is started, learning of the air-fuel ratio is performed in Pro 7 Ri 10. That is, first step 11
At , it is determined whether or not learning of the air-fuel ratio has already been completed. This determination is made by determining whether the time average value FAFAV of the air-fuel ratio correction coefficient FAF is within a predetermined range that is larger than a predetermined value α1 that is slightly smaller than 1 and smaller than a predetermined value α2 that is slightly larger than 1. It will be done.

This air-fuel ratio correction coefficient FAF is determined by a comparison circuit CCI in a feedback (F/B) control block 60, which will be described later.
It is an amount that is increased or decreased according to the rich/lean signal from MP and changes in a sawtooth waveform over time, and if the basic injection amount is different from TP.

TAU=TP*’FAF is defined as

If F A F A V is not within the above-mentioned predetermined range, that is, if the learning of the air-fuel ratio has not yet been completed, it is determined in step 12 whether or not this is greater than 1. . If FΔFAV is smaller than 1, the basic injection iTP is decreased by a predetermined step in step 13;
On the other hand, if it is greater than 1, it is Ste.

In Step 14, the basic injection (iTP) is increased by a predetermined step.
This is done in the direction of convergence near .

On the other hand, if it is determined in step 11 that learning of the air-fuel ratio has already been completed, the process proceeds to the second determination step 20 without performing any further learning.

In step 20, it is determined whether a feed bank (F/B) condition is satisfied based on the internal combustion engine status signal STS. If the feed hack condition is satisfied, the process moves to block diagram 30 in which it is determined whether or not learning of the air-fuel ratio has already been completed. That is, in step 31, it is determined that learning is completed, and if it is completed, it is determined whether the edge/lean signal from the comparator circuit COMP (comparison output of COMP) has been inverted a predetermined number of times (for example, three times) or more. It will be judged. If the rotation has been reversed a predetermined number of times or more, the process moves to step 50 in which it is determined whether the conditions for partial lean (P/L) control are satisfied. 2 if either the above air-fuel ratio learning or the specified number of reversals has not been completed.
Decision step 50 is skipped.

On the other hand, if it is determined in step 20 that the conditions for feedback control are not satisfied, step 40
At this point, open control is performed to fix FAF to 1.

In step 50, based on the status signal STS of the internal combustion engine, it is determined whether the number of revolutions is greater than a predetermined value, whether the throttle opening is greater than a predetermined value, whether the acceleration/deceleration is not in progress, whether the cooling water temperature is within a predetermined range, etc. lean combustion (partial lean)
It is determined whether the condition is met. If this partial lean condition is not satisfied, the process moves to block 60, where feedbank (F/B) control is performed; on the other hand, if the partial lean condition is satisfied, the process moves to block 70, where feedbank (F/B) control is performed. Partial lean control is performed.

In the feedback control, first, in step 61, it is determined whether the oxygen concentration in the exhaust gas is lynch or lean (high/low output of the comparison circuit COMP). If lean, the air-fuel ratio correction coefficient FAF is increased by a predetermined step in step 63, and if lean, the air-fuel ratio correction coefficient FAF is decreased by a predetermined step in step 62.

In partial lean control, first, in step 71, it is determined whether the air-fuel ratio correction coefficient FAF has reached the set value KO by partial lean control. If it has not reached it yet, in step 72, FAF is decreased by a predetermined step. be done. If it has already reached the set value and is below it.

In step 73, it is clamped to the set value Ko.

Finally, in step 80, the injection amount TAU is determined by multiplying the basic injection iTP that is being learned or has been learned by the air-fuel ratio correction coefficient FAF determined as described above.

In the present invention, since block 30 is provided as a condition for starting partial lean control, the set value K is set to reach the above partial lean.

is an air-fuel ratio correction coefficient for the basic injection amount whose air-fuel ratio has been learned. In this way, partial lean control is performed based on the basic injection amount for which learning of the air-fuel ratio has been completed.

In a preferred embodiment of the present invention, during the conditions for starting partial lean control, the oxygen concentration detection result (comparison port '1lfr COM
This includes that the output (high/low) of P is inverted a predetermined number of times or more, and the reason for this is as follows.

Generally, in order to improve the responsiveness of feed hack control, as shown in Fig. 3, when the oxygen sensor is reversed, F A
The value of F is changed by skipping. FAFAV is the FA at the time of the previous skip at the time the FAF skips.
Determined by taking the average of j[i between F and the current FAF11. Ru. Therefore, at the time of transition to feed puncture control, the value of FΔrS is held at a value of 1.0 until the next skip. If the basic injection amount deviates at this time, it will take a long time to reach the first skip as shown in the third diagram.

If another partial lean condition is satisfied during this time, there is a problem that partial lean control is started with the air-fuel ratio being shifted because FAFAV is 1. This inconvenience occurs when the FA is repeated a predetermined number of times.
This can be eliminated by a configuration that does not shift to partial lean control until FAV is successfully calculated.

Detailed Description of the Invention As described above, the present invention makes it part of the condition for transitioning to the lean burn control stage that the learning of the air-fuel ratio has already been completed, and the learning is performed in the transitioned lean burn control stage. Since it is configured to perform lean burn control based on the basic injection amount after completion, there is an advantage that it is possible to realize a lean burn control method that takes into account variations in the characteristics of the internal fA engine.

[Brief explanation of drawings]

FIG. 1 is a configuration block diagram of a fuel injection control system to which an embodiment of the present invention is applied, and FIG. 2 is a flowchart for explaining the operation of the microprocessor CPU shown in FIG. BRIEF DESCRIPTION OF THE DRAWINGS It is a conceptual diagram for explaining the principle of one embodiment of the present invention.PC: internal combustion engine, ECU: internal combustion engine 1
-, CPU...Microproceno"J-, COMP...
Comparison circuit, BUF...buffer. Patent applicant: Fujitsu Ten Ltd. Representative: Patent attorney: Gobe Tamamushi (1 other person) Figure 1 Figure 3 Figure AF

Claims (2)

[Claims] (1) In a combustion control method for an internal combustion engine including an air-fuel ratio learning stage, a feed hack control stage, and a lean burn control stage. Part of the conditions for transitioning to the lean burn control stage is that the learning of the air-fuel ratio has already been completed and the transition to feedhack control is completed, and the learning of the air-fuel ratio is completed at the stage of lean burn control that has been transitioned to. A lean-burn control method for an internal combustion engine characterized by performing lean-burn control based on a subsequent basic injection amount. (2) As part of the conditions for transitioning to the lean burn control stage, the oxygen concentration comparison results must be reversed a predetermined number of times after transitioning to foot hack control.