JPH02123252A - Air-fuel ratio controller for engine - Google Patents

Abstract

PURPOSE:To prevent the car backing phenomenon and improve the fuel consumption and exhaust gas purifying performance by suspending the feedback correction for air-fuel ratio when an automatic transmission is in the lock-up state in the engine deceleration and carrying out correction in the nonlock-up state. CONSTITUTION:The injection pulse is calculated from the intake air quantity and the engine revolution speed. When the engine operation state is in the feedback zone of the air-fuel ratio and the engine 1 is in deceleration state, if an automatic transmission 23 is in locked-up state, the feedback correction coefficient is set to zero. Though a variety of correction coefficients are applied, the feedback correction for the air-fuel ratio is substantially suspended, since the feedback correction coefficient is zero. In case of nonlock-up, the final injection pules is calculated, and an injector 8 is operated. Since, in this case, the feedback correction coefficient is inputted into a correction equation, in the final injection pulse calculation, the feedback correction for the air-fuel ratio is executed. Therefore, in case of lock up, the engine output variation due to the variation of the air-fuel ratio is suppressed, and the car backing phenomenon can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an air-fuel ratio control device for an engine, and more particularly to an air-fuel ratio control device for an engine equipped with an automatic transmission with a lock-up mechanism.

(Prior art) In recent electronically controlled engines using computers,
As shown in Japanese Patent Publication No. 58-40009, etc., the concentration of a specific gas component in the exhaust gas is detected by a sensor, and the air-fuel ratio of the mixture being supplied to the engine is determined from this concentration. When the is operated in a predetermined operating range such as low to medium load and low to medium speed, the fuel supply amount is feedback-corrected so that the air-fuel ratio converges to the stoichiometric air-fuel ratio, and this improves fuel efficiency. Air-fuel ratio control technology that can improve exhaust gas purification performance as much as possible has been widely adopted.

Furthermore, in recent years, vehicles equipped with automatic transmissions equipped with a lock-up mechanism have become widespread. This automatic transmission with a lock-up mechanism eliminates slippage of the torque converter by directly connecting the input side and output side of the torque converter when the vehicle is in a specified driving state, thereby improving fuel efficiency as much as possible. It was designed to measure improvement.

(Problem to be Solved by the Invention) By the way, when the above air-fuel ratio control is adopted for an engine equipped with an automatic transmission with a lock-up mechanism as described above, for example, when the automatic transmission is locked up, the engine is decelerated, and if the air-fuel ratio is changed by feedback correction at this time, there is a problem in that engine output fluctuations due to this change in air-fuel ratio are directly transmitted to the drive wheels, causing a carbacking phenomenon. Here, as a measure to prevent the occurrence of this carbacking phenomenon, it may be possible to stop feedback correction of the air-fuel ratio when the engine decelerates, but if this is done, the fuel efficiency will be reduced in the non-lockup state where there is no risk of the carbacking phenomenon occurring. Therefore, there is a problem that the exhaust gas purification performance cannot be improved.

The present invention was made in view of these circumstances, and
The purpose is to create an engine with an air-fuel ratio that is suitable for use in engines equipped with automatic transmissions with a lock-up mechanism, and that can improve fuel efficiency and exhaust gas purification performance as much as possible without causing carbacking. The purpose of this invention is to provide a control device.

(Means for Solving the Problems) In order to achieve the above objects, the present invention provides an automatic transmission with a lock-up mechanism, and an air-fuel ratio correction means for feedback correcting the air-fuel ratio of the air-fuel mixture supplied to the engine to a target air-fuel ratio. and deceleration detection means for detecting a deceleration state of the engine,
lockup detection means for detecting a lockup state of the automatic transmission; and feedback correction by the air-fuel ratio correction means when a non-lockup state is detected by the lockup detection means and a deceleration state is detected by the deceleration detection means. and feedback correction stopping means for stopping the engine air-fuel ratio control device.

(Function) According to the present invention having the above configuration, if the automatic transmission is in a lock-up state during engine deceleration, feedback correction of the air-fuel ratio is stopped, thereby causing fluctuations in engine output due to changes in the air-fuel ratio. is suppressed, and the occurrence of carbacking phenomenon is prevented as much as possible. On the other hand, if the automatic transmission is in a non-lockup state when the engine is decelerating,
Feedback correction of the air-fuel ratio is performed, thereby improving fuel efficiency and exhaust gas purification performance as much as possible.
At this time, fluctuations in engine output due to air-fuel ratio changes are absorbed by the torque converter, so there is no risk of carbacking occurring due to this.

(Example) Hereinafter, a preferred example of the present invention will be described in detail based on the accompanying drawings.

FIG. 1 shows a schematic configuration diagram of an air-fuel ratio control device for an engine according to the present invention, in which 1 is an engine, 2 is a combustion chamber, and this combustion chamber 2 is connected to a cylinder 3
A piston 4 is slidably inserted into the piston 4, so that the volume can be changed. Further, 5 has one end communicating with the atmosphere and the other end opening into the combustion chamber 2 to supply intake air, and 6 having one end communicating with the combustion chamber 2 and the other end being open to the atmosphere. This is an exhaust passage for discharging exhaust gas.

The intake passage 5 is provided with a throttle valve 7 that adjusts the amount of intake air, and a fuel injection valve 8 that injects and supplies fuel downstream of the throttle valve 7.
A catalyst device 9 for purifying exhaust gas is disposed.

Further, in the combustion chamber 2, an intake valve 10 is disposed at the opening of the intake passage 5, an exhaust valve 11 is disposed at the opening of the exhaust passage 6, and the air-fuel mixture in the combustion chamber 2 is disposed at the top. A spark plug 12 is arranged as an ignition means for igniting. In addition, 13 is an ignition coil that generates high voltage;
4 is a distributor that distributes the high voltage of this ignition coil 13 to the spark plug 12 of the cylinder that undergoes the explosion stroke, and functions as a crank angle sensor that detects the crank angle (or rotational speed) and identifies the reference cylinder. It also functions as a cylinder identification sensor.

Further, 15 is an intake air temperature sensor that detects the intake air temperature on the upstream side of the throttle valve 7, 16 is an air flow sensor that detects the amount of intake air, 17 is an idle switch that closes when the throttle valve 7 is fully opened, and 18 is the opening degree of the throttle valve 7. 19 is a temperature sensor that detects the engine temperature in terms of cooling water temperature; 20 is arranged in the exhaust passage 6 upstream of the catalyst device 9; This is an air-fuel ratio sensor that detects the air-fuel ratio.

These various sensors 14 to 20 are connected to an engine control unit 21, and the engine control unit 21 controls the injector 8 according to signals from them so that the operating condition of the engine 1 is optimal. It has become.

That is, these constitute a well-known electronic @type fuel injection system, and the engine control unit 21
is the basic injection pulse T ps (synonymous with basic injection amount) of the injector 8 from the intake air amount signal and the engine rotation speed signal.
In addition to calculating the final injection pulse TI (final injection amount ) is calculated, and the injector 8 is driven with this final injection pulse TI.

On the other hand, 23 is an automatic transmission attached to engine 1,
The automatic transmission 23 includes transmission mechanisms (solenoid switches, etc.) 24a to 24c for shifting to each gear stage, and
A lock-up mechanism (such as a solenoid switch) 25 for locking up a specific gear stage is provided. Each of the transmission mechanisms 24a to 24c and the lockup mechanism 25 are controlled by an automatic transmission control unit 26. Here, 27 is a vehicle speed sensor that detects the vehicle speed, 28 is a lever position sensor that detects the position of the gear shift lever, and these sensors 27-
Both 28 are the automatic transmission control unit 26 mentioned above.
It is connected to the.

By the way, the air-fuel ratio correction means A referred to in the present invention is
It is composed of an engine control unit 21 and an air-fuel ratio sensor 2o connected thereto, and forms part of the electronically controlled fuel injection device. That is, as shown in FIG. 2, the engine control unit 21 has a starting zone (
in.

A control map divided into multiple correction control zones such as a high load zone (b), a feedback zone (c), a deceleration fuel cut zone (d), and an overspeed fuel cut zone (e) is stored, and When the operating state is within the feedback zone (c) of this control map, the engine control unit 21 controls the supply of fuel so that the air-fuel ratio detected by the air-fuel ratio sensor 20 converges to a desired target air-fuel ratio (for example, the stoichiometric air-fuel ratio). Correct the amount. That is, the basic injection pulse Tps is corrected by determining the correction coefficient Crb from the deviation between the detected air-fuel ratio and the target air-fuel ratio. Note that this is a well-known air-fuel ratio control that has been conventionally performed.

Further, the deceleration detection means B referred to in the present invention is comprised of the engine control unit 21 and the idle switch 17 in this embodiment.

That is, in this case, if the idle switch 17 is turned on, the engine control unit 21 determines that the engine 1 is in a deceleration state. Note that this deceleration state may be determined by detecting a decrease in the engine rotational speed signal from a crank angle sensor provided in the distributor 14.

Further, the lock-up detection means C referred to in the present invention is constituted by the automatic transmission control unit 26 mentioned above.

That is, signals are exchanged between the automatic transmission control unit 26 and the engine control unit 21, and output information such as a shift operation signal and a lock-up signal of the automatic transmission 23 is transmitted to and from the engine control unit 26. It is designed to be output to the unit 21.

Further, the feedback correction stop means referred to in the present invention is constituted by the engine control unit 21. That is, in the engine control unit 21, even when the operating state of the engine 1 is within the feedback zone (c) on the control map, the deceleration detecting means B detects the decelerating state of the engine 1, and the lock-up detecting means C detects the decelerating state of the engine 1. When a lock-up signal is input from the air-fuel ratio correction means, feedback correction of the air-fuel ratio by the air-fuel ratio correction means is stopped, while when a lock-up signal is not input, the air-fuel ratio feedback correction control is executed as is. .

Next, the operation of this embodiment will be explained with reference to the flowchart shown in FIG.

First, in step S10, signals from various sensors are read, and then in step S20, a basic injection pulse Tps is calculated from the intake air amount signal and the engine rotation speed signal.

Then, in the next step S30, the basic injection pulse T
ps is rounded, and the injection pulse Tpx(i) after this rounding is calculated based on the following equation (1).

Tpx(i) −fαxTps(i-1) + (10
0-α)XTps(1)l ÷1 00-----・-
(1) Note that α is a constant (0 x α<100), I represents the current value, and l-1 represents the previous value.

Next, in step S40, it is determined whether the operating state of the engine is within the air-fuel ratio feedback zone (c), and if this is YES, in the next step S50, it is determined whether the engine 1 is in a deceleration state or not. is determined. In addition,
This deceleration state may be detected, for example, by a decrease in engine speed or by turning on an idle switch.

If the determination in step S50 is also YES, then in step S60 it is determined whether or not the automatic transmission 23 is locked up, for example, when the lockup switch is set to 0.
Determined by N-OFF. And this step S
If the determination at 60 is also YES, 0 is substituted into the air-fuel ratio feedback correction coefficient Crb at the next step S70. Further, if the determination in step S40 is NO, the flow jumps to step S70.

Thereafter, in the next step S80, a final injection pulse TI is calculated by taking into account various correction coefficients in addition to the feedback correction coefficient Crb, and then the injector 8 is driven with this final injection pulse TI in the next step S90. In this case, since 0 is substituted into the air-fuel ratio feedback correction coefficient Cfb in step S70, the air-fuel ratio feedback correction is substantially stopped.

On the other hand, if the determinations in steps S50 and S60 are NO, the flow moves to step 5100, where the air-fuel ratio correction coefficient Crb is calculated, and then the flow returns to step S80, where the final injection pulse is t1 is calculated, and the injector 8 is operated in the next step S90. In this case, the air-fuel ratio feedback correction coefficient Crb calculated in step 5100 is substituted into the correction formula when calculating the final injection pulse [i in step S80, so that the air-fuel ratio feedback correction is executed. Become.

That is, as is clear from the above explanation, engine 1
When the operating state of the automatic transmission 23 is within the feedback zone (c) for feedback correction of the air-fuel ratio and the engine 1 is in a deceleration state, the lock-up state of the automatic transmission 23 is taken into consideration, and if this is in the lock-up state, the air-fuel ratio feedback correction is stopped. Therefore, fluctuations in engine output due to changes in the air-fuel ratio are suppressed as much as possible, thereby preventing carbacking phenomenon caused by fluctuations in engine output as much as possible.

On the other hand, if the automatic transmission 23 is in a non-lockup state,
Feedback correction of the air-fuel ratio is performed to improve fuel efficiency and exhaust gas purification performance as much as possible. At this time, even if the air-fuel ratio is changed by feedback correction,
Fluctuations in engine output due to changes in the air-fuel ratio are absorbed by the torque converter of the automatic transmission 23, so there is no risk of carbacking occurring.

Note that, as shown in the flowchart of FIG. 4, the basic injection pulse Tp is generated after determining whether to perform the feedback correction or to stop the feedback correction.
Steps S30a and 530b of the smoothing process for s may be provided in parallel, and the content of the smoothing process may be slightly changed. That is, in step 530a, the injection pulse Tpx(i) after the smoothing process is calculated based on the following equation (2), and in step 530b, the injection pulse Tpx(i) after the smoothing process is calculated based on the following equation (2). 3) Calculate based on the formula.

Tpx(i) = (βX Tps(1-1) +
(l Q □ - β) x Tps (1) ) + 100
・・・・・・(2) Tpx(i) = +7 XTps
(1-1) + (100-7)XTps(1)l +
100------(3) Here, β and γ are constants, and β>γ.

(Effects) In summary, according to the present invention, when the automatic transmission is in a lock-up state during engine deceleration, feedback correction of the air-fuel ratio is stopped, while feedback correction of the air-fuel ratio is stopped when the automatic transmission is in a non-lock-up state. Therefore, it is possible to prevent the occurrence of car backing during lock-up as much as possible, while improving fuel efficiency and exhaust gas purification performance as much as possible during non-lock-up.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic configuration of an engine air-fuel ratio control device according to the present invention, FIG. 2 is a diagram showing a control map that divides control regions of various correction controls for fuel supply amount, and FIG. 3 is a diagram showing this implementation. FIG. 4 is a flowchart showing an example of control, and is a modification of the flowchart shown in FIG. 3. 1...Engine 20...Air-fuel ratio sensor 21...Engine control unit 23.
... Automatic transmission 25 ... Lock-up mechanism

Claims (1)

[Scope of Claims] An automatic transmission with a lock-up mechanism, an air-fuel ratio correction means for feedback correcting the air-fuel ratio of the air-fuel mixture supplied to the engine to a target air-fuel ratio, and a deceleration detection means for detecting a deceleration state of the engine. lockup detection means for detecting a lockup state of the automatic transmission; and when the lockup detection means detects the lockup state and the deceleration detection means detects the deceleration state, the air-fuel ratio correction means An air-fuel ratio control device for an engine, comprising: feedback correction stopping means for stopping feedback correction.