JPS6060231A - Air-fuel ratio learning control method for internal-combustion engine - Google Patents

Abstract

PURPOSE:To prevent deterioration of the driving performance and the specific fuel consumption of an engine, by executing learning control when an intake throttle valve and the engine load are feedback-controlled under specific conditions and the temperature of intake air is whithin a prescribed range. CONSTITUTION:A control circuit 61 executes learning of values to be learnt when an intake throttle valve and the engine load are feedback controlled under specific conditions. For this purpose, judgement is made at first that the intake throttle valve is not in its idling position and then judgement is made whether the pressure PM in an intake pipe has entered into learning region or not. In case that the judgement is YES, learning of values to be learnt is executed when the air-fuel ratio is under feedback control, the temperature THW of engine cooling water becomes higher than a prescribed value, the temperature of intake air is within a prescribed range and skipping of an air-fuel ratio feedback correction factor FAF is caused. By employing such a method, it is enabled to reduce the number of bits of memory and the number of words of a program and to prevent deterioration of the driving performance and the specific fuel consumption of an engine due to errors of learnt values.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an air-fuel ratio learning control method for an internal combustion engine, and in particular detects the residual oxygen concentration in exhaust gas during a basic fuel injection period determined by engine load and engine speed. The air-fuel ratio feedback correction coefficient obtained based on the output signal of the 02 sensor is used to perform feedback control so that the air-fuel ratio of the mixture becomes the target air-fuel ratio. The present invention relates to an air-fuel ratio learning control method for an internal combustion engine that learns to approach a predetermined value.

[Prior art]

Conventionally, a three-way catalyst has been used to simultaneously purify carbon monoxide, hydrocarbons, and nitrogen oxides in exhaust gas.In order to improve the purification rate of this three-way catalyst, the 02 sensor The air-fuel ratio is increased by detecting the residual oxygen concentration, estimating the air-fuel ratio, and controlling the air-fuel ratio to near the stoichiometric air-fuel ratio. In performing this foot check control, the output from the 02 sensor is determined during the basic fuel injection time TP determined by the engine load (intake pipe pressure PM and intake air amount per engine revolution Q/NE) and the engine speed. Based on the signal-processed air-fuel ratio signal, the fuel injection time TAU is determined by multiplying the air-fuel ratio feedback correction coefficient FAF'i shown in FIG. The air-fuel ratio is controlled to be close to the stoichiometric air-fuel ratio by opening the fuel injection valve for a corresponding period of time. However, due to environmental changes and changes over time, changes in the pulp timing due to changes in tabet compliance, changes in the characteristics of pressure sensors and air flow meters, and changes in the characteristics of fuel injection valves occur, resulting in changes in the fuel injection amount to the engine's required fuel injection amount. The air-fuel ratio may not be able to be controlled close to the stoichiometric air-fuel ratio. For this reason, air-fuel ratio learning control is performed to control the air-fuel ratio so that it is always near the stoichiometric air-fuel ratio. This learning control is performed using a learning value T learned at a predetermined value as shown in the following equation.
AUG and KG'i are used to control the average value FAFAV of the air-fuel ratio feedback correction coefficient to a predetermined value.

TAU=(TP ten TAUG)・KG−FAF・F(t)
...... (1) However, TAUG is the learned value when the intake throttle valve is at the idle position, T (G is the learned value when the intake throttle valve is at the idle position, and F(t) is the warm-up value. When the increase coefficient and starting power are 200-1-30 (1 + + + Hy, KG, 300-400 HP, KG2, 400
KG3 is adopted when ~500 Hp.

These learning values TAUG, KG (KG, , KG2, KG
3) is the correction coefficient F when the engine cooling water temperature exceeds a predetermined value (for example, 80°C) during air-fuel ratio feedback control.
Each time the AF is activated, it is learned by the following method.

First, every time the sudden fuel ratio feedback correction coefficient FAF skips, the arithmetic average value F of the maximum and minimum values of the correction coefficient T'AF is calculated.
AFΔ■, that is, the value of the average value FAFAv is within the run-up range (for example, +2
%) When the value outside the range is reached, the learned value TAUG is set by learning,
KG-i increases or decreases by a predetermined value. That is, the average value FAFAV
When the average value FAFAV exceeds 1.02, the learned values TAUG and KG are increased by a predetermined value, and when the average value FAFAV becomes less than 0.98, the learned values TAUG and KG are decreased by a predetermined value.

Then, the learned values TAUG, KG learned as above
The above (1
) is applied to the equation, and the fuel injection time TAU is determined. As a result, when the average value FAFAV exceeds 1.02, the learned value is increased and the air-fuel ratio is controlled to the rich side, and when the average value FAFAV is less than 0.98, the learned value is decreased and the air-fuel ratio is controlled to the lean side. Controlled, average value FAFAV
Learning control is performed so that the ratio approaches 1, that is, the stoichiometric air-fuel ratio.

However, in this air-fuel ratio learning control method, the learning area is divided into three areas depending on the engine load and three learning values are used. Therefore, when controlling with a microcomputer, the number of memory pids increases and the number of program words increases. The problem is that there are many.

1. In order to control fuel injection fjtf according to the intake temperature, the intake temperature sensor is installed on the intake manifold.KH, the sensor output is affected by the intake manifold temperature, and when starting from an extremely low temperature, the cooling water temperature The temperature rises as shown in Figure A in Figure 2, but since the intake manifold temperature does not rise according to the cooling water temperature, the sensor detects 1.
The expanded intake air temperature rises like fiB. In such a state, the intake temperature detected by the intake temperature sensor is low, so the amount of fuel a and 6 injection is increased by intake temperature correction, and the air-fuel ratio is controlled to be rich, while the cooling water temperature is kept at a predetermined value (80"
C) If the distance is exceeded and the air ratio feedback is in progress, the learning will be canceled and the learning shift will be reduced. For this reason, the learned value becomes extremely small immediately after the intake temperature increase correction is canceled, and this learned value causes the fuel ratio to increase by 1 V.
'l A problem arises in that the vehicle is erected and the drivability deteriorates. On the other hand, the intake air temperature sensor uses a JI6 thermistor, so the resistance value decreases when the temperature gets high.
The air-fuel ratio is controlled to be richer than the intake temperature correction, and the same problem as above occurs.

We obtained the knowledge that they are almost the same.

- [Object of the Invention] The present invention has been made based on the above findings as well as solving the above-mentioned problems, and narrows the learning area and prevents the learned value from becoming abnormal at extremely low temperatures and high temperatures. The purpose of this invention is to provide an air-fuel ratio learning control method.

[Structure of the invention]

In order to achieve the above object, the present invention uses an air-fuel ratio feedback correction coefficient obtained based on the output signal of the 02 sensor that detects the residual oxygen concentration in exhaust gas for the basic fuel injection time determined by the engine load and engine speed. In the air-fuel ratio learning control method for an internal combustion engine, the air-fuel ratio learning control method for an internal combustion engine performs feedback control so that the air-fuel ratio of the mixture becomes a target air-fuel ratio by correcting the air-fuel ratio, and learns so that the average value of the air-fuel ratio feedback correction coefficient approaches a predetermined value. It is characterized in that learning occurs when the throttle valve is not in the idle position, the engine load is within a predetermined range, feedback control is in progress, and the intake air temperature is within a predetermined range.

According to the present invention, when the learning condition is satisfied in the learning region ((), the learning value is changed by learning, and learning is prohibited at extremely low temperatures and at high temperatures.

〔Effect of the invention〕

Therefore, according to the present invention, since two learning values are fully adopted (2), when controlling with a microcomputer, the number of memory pids and the number of program words can be reduced compared to conventional methods. The effect is that deterioration of drivability and fuel efficiency due to value abnormality can be prevented.

[Embodiments of the invention]

Hereinafter, one example of the present invention will be explained in detail with reference to the drawings.

FIG. 3 shows a configuration example of a white smoke engine for an automobile including an electronic fuel injection control device to which the present invention is applied. 1 air filter, connected to the throttle body 5 via the valve 3.

The throttle body 5 is provided with a fuel injection valve 7 on its upstream side, and an intake throttle valve 9 is provided downstream of the fuel injection valve 7 to adjust the amount of intake air in conjunction with an accelerator pedal (not shown). An intake pipe absolute pressure sensor 11 is provided downstream of the intake valve 9 to measure the absolute pressure at that location. Further, a valve opening position sensor 2 that measures the opening position R of the intake throttle valve 9, an idle switch 4 that is turned on only when the intake throttle valve 9 is in the idle position (when it is fully closed), and a valve opening position sensor 2 that measures the opening position R of the intake throttle valve 9; A power switch 6 that is turned on only when the opening of the intake throttle valve 9 is 30 degrees or more is attached in association with the intake throttle valve 9.

The throttle body 5 is connected to an intake manifold 13 having branch pipes connected to each cylinder of the engine,
The intake manifold 13 is provided with an intake temperature sensor 15 that measures the temperature of intake air therein. On the bottom wall 13a of the intake manifold 13 before branching, there is a riser part 17 for circulating engine cooling water and heating the air-fuel mixture.
is provided.

This is a well-known conventional engine body, and a combustion chamber 27 is formed by a piston 21, a cylinder 23, and a cylinder head 25.
The air-fuel mixture is drawn into the ignition chamber 27 via the intake valve 29 and is ignited by the ignition plug 31. A water jacket 33 is formed around fC of the cylinder 23, and engine cooling water is circulated through the water jacket 33 to cool parts including the cylinder 23. An engine cooling water temperature sensor 37 for measuring the engine cooling water temperature in the water jacket 33 is provided on the outer wall of the cylinder block 35. An exhaust manifold 39 is connected to the cylinder head 250 and an exhaust boat (not shown). On the downstream side thereof, a sensor 41 for measuring the residual oxygen concentration in the exhaust gas is provided. The exhaust manifold 39 is a three-way catalyst cone
- It is connected to the exhaust pipe 45 through a 43-metal metal.

47 is a transmission connected to the engine body 19;
A vehicle speed sensor 49 is attached to measure the speed of the vehicle based on the rotational speed of the final output shaft.

51 is a key switch, 53 is an igniter, and 55 is a distributor. The distributor 55 is provided with an Ne sensor 57 that outputs an on/off signal at every predetermined crank angle θ1, and the output signal controls the engine rotation. A G sensor 59 is provided, which outputs an on/off signal at each angle θ2, which is larger than the angle θ1, and the output signal is used to identify the cylinder. Dead center position detection is performed.

60 indicates the battery.

The control circuit 61 includes a valve opening position sensor 2, an idle switch 4, a power switch 6, an intake temperature sensor 11, an intake temperature sensor 15, an engine coolant temperature sensor 37.02 sensor 4
1, vehicle speed sensor 49, key switch 51. Ne sensor 5
7, are connected to the G sensor 59 and the battery 60, respectively, and are connected to the valve opening signal S1, idle signal s2, power (No. 8 S3, intake pressure signal s4, intake temperature signal s5, water temperature signal S6, air-fuel ratio Ig) s7, vehicle speed signal S8, ignition signal S9, engine speed signal s10, and air speed are input from each sensor.1.The control circuit 61 is also connected to the fuel injection valve 7 and the igniter 53, and performs a predetermined calculation. Based on this, a fuel injection signal S12 and an ignition signal 313 are output.

As shown in FIG. 4, the control circuit 61 includes a central processing unit (CPU) 61a that controls each device,
-1: Random "access memory" (ROM) 61b, where numerical values and flags in the calculation process are written to a predetermined area.
RAM) (i 1 r, , Al1) converting analog human input signals into digital signals (8 DC
) 61d, I/O interface (I/O) to which each Jilt digital signal is input and each digital signal G is output; 61e, Bank-up which is supplied with power from the auxiliary source and maintains memory when the engine is stopped. It is composed of a memory (BU-4ΔΔ4) 6], f, and a path line 61g to which each of these devices is connected. 1. In this embodiment, a map of the basic fuel injection time TP determined by the intake pipe pressure and the engine speed is stored in the ROM in advance.

In the above engine, fuel is injected from the fuel injection valve according to the following procedure. 1. First, read the engine speed Ne f calculated based on the engine speed signal S1, and calculate the intake pipe pressure PM based on the intake pipe pressure signal S4.
Load. Next, engine speed Ne and intake pipe pressure P
M,! 2 from the basic fuel injection time map based on :
The basic fuel injection time TPk is calculated by dimensional interpolation. Next, based on the above formula (1), the fuel injection time TA
U'z is determined, and the fuel injection valve is opened for a time corresponding to this fuel injection time TAU to inject fuel. However, in this embodiment, one learned value T AUG and one learned value KG are adopted, and the learned value T AUG is applied to the above equation (1) for all operating ranges regardless of the on/off state of the throttle switch. The learned value KG is applied to the above equation (11) for the entire operating range of the throttle switcher.

Next, FIGS. 5 and 6 regarding embodiments of the present invention? Refer to and explain.

First, it is determined whether the intake throttle valve 9 of the crank 100 is in the idle position based on the off state of the idle switch. When the idle switch is off, step 101
Intake pipe pressure PM is 200 $1111] ()
It is determined whether there is a person within the range of 400 mm Hy, that is, whether the intake pressure PM is within the learning range. The range of this intake pressure is constant 44. Intake during sparrow racing also shows output. Also, 1 of the average value FAFΔ■
- Since there are 16 in all operating ranges and they are almost the same,
The learning area is defined only for the steady state running state. If intake pipe pressure F'M is within the learning range, step 1
Judging the learning conditions of 03 or above, do not use learning 11 in 1 to 1. If the intake t1-pressure PM is not within the learning range, proceed to the first routine of learning 1. .-power, crank 10 when idle switch is on
2, the engine speed Ne is a predetermined value (for example, 1.1
(100 rpm) Not ia'i and pre-intake pressure PM
GANO"J+'iL value ((9 Sue is 200iaHP)
'e is exceeded or not. If the judgment in step 102 is negative, that is, if the judgment is negative, the learning conditions in step 103 and below are judged and the learning value is learned, and if the judgment in step 102 is negative, In other words, in the case of cranking, idle up, etc., proceed to the next routine without learning.

In step 103, the air-fuel ratio is set to the stoichiometric air-fuel ratio based on the output No. 16 of the 02 sensor.
Check whether you are doing l m or not. If fee 1 bank control is not in progress, 1511-f, bank control warehouse line 7. If there are c-C, drum '7! ' + filial note 7 is performed, so the process proceeds to the next routine without learning the feed bank tlill 1lij, and in step '104, the ennon cooling water temperature T li W is set to L.
1 Check if it exceeds the constant value (2 is 80 "C")
(+ rib) Ru. When the cooling water temperature is at the T91 constant value, the engine rotates once (Ikuchu-C-4 Rirukme learning is not performed, and when the cooling water temperature II to V exceeds the standard value, the engine rotates 5 times. In step 105, if the intake temperature T I (A or Di constant 4') emitted by the intake temperature sensor is 4
0 'C <'j' HA (90"'C)" All tests are carried out to determine whether the temperature is 1. When the intake air temperature T HA is outside the specified range, that is, when the temperature is extremely low and when the temperature is l.14 VC. does not perform learning, and when the intake air temperature THA is within a predetermined range, it is determined in step 106 whether or not the air-fuel ratio feedback correction coefficient FAF has skipped, and only when it has skipped, the learned value is learned in step 107.

An example of the above learning will now be explained based on the processing routine VC shown in FIG. 1. In step 110, it is determined whether the air-fuel ratio feedback correction coefficient FAF has skipped a certain number of times, and only when it has skipped a predetermined number of times, step 111 is performed.
Average value based on formula (2) above]” A F A V
Calculate. Here, after skipping a predetermined number of times, the average value is reduced by 3 in total, which is oven loop control.
This is because immediately after shifting from to feedback control, changes in the air-fuel ratio feedback correction coefficient are uncertain. Therefore, the unstable air-fuel ratio feedback correction coefficient is not used in calculations.

In the next step 112, it is determined whether the average value F A F A V exceeds 1. If it exceeds 1, that is, if the air-fuel ratio is leaner than the stoichiometric air-fuel ratio, the idle switch is turned on in step 113. It is determined whether the idle switch is on or not, and when the idle switch is on, the learned value T is set in step 114.
AUG'e predetermined J-4, (e.g. 0.002) increase, step 1 when Id/L-nitch is off.
15, the learning value KGi is increased by a predetermined amount (for example, 8).

On the other hand, when the average value FAFA'V is less than 1, that is, when the air-fuel ratio is υ richer than the stoichiometric air-fuel ratio, it is determined in step 116 whether or not the idle switch is on. Learning value TAUG (
j predetermined amount, (e.g., o, o 02 ) reed'f;
While the idle switch is off, the learned value KG is increased to a predetermined amount (for example, 8) ξ in step 118.

The learning value learned as described above is applied to the equation (1) above according to the on/off state of the throttle switch, and the air-fuel ratio is learning-controlled.

In addition, although the engine in which the basic fuel injection time is determined by the intake pipe pressure and engine speed and uses one state-specific injection valve has been described above, the engine to which the present invention is applied is not limited to this. The basic fuel injection time is determined by the amount of intake air per engine revolution and the engine speed.It also applies to engines equipped with twisted injection valves for each air intake that protrude into the engine intake manifold.
Is it possible?

[Brief explanation of drawings]

Figure 1 is a diagram showing changes in the air-fuel ratio signal and correction coefficient FAF, Figure 2 is a diagram showing changes in cooling water temperature and intake air temperature, and Figure 3 is an example of an engine to which the present invention is applied. Figure 4 is a block diagram showing an example of the circuit;
FIG. 5 is a flowchart showing an embodiment of the first invention, and FIG. 6 is a flowchart showing the entire embodiment of the first invention. l step. This is Flow 1 Oka showing the details of 107. 7... Caustic material injection valve, 9... Intake throttle valve, 11... Pressure sensor, 15... Intake temperature sensor, 41... 02 sensor, 49... Vehicle speed sensor, 61... Control circuit . Agent Tatsuyuki Unuma (and 1 other person)

Claims (1)

[Claims] (1) Basic fuel injection time determined by engine load and engine speed 02 Detecting residual oxygen concentration in exhaust gas
Feedback control is performed so that the air-fuel ratio of the air-fuel mixture becomes the target air-fuel ratio by correction using an air-fuel ratio feedback correction coefficient obtained based on the output signal of the sensor, and the average value of the air-fuel ratio feedback correction coefficient is a predetermined value. In an air-fuel ratio learning control method for an internal combustion engine, the air-fuel ratio learning control method for an internal combustion engine learns the air-fuel ratio to approach An air-fuel ratio learning control method for an internal combustion engine, characterized in that the learning is performed when the air-fuel ratio is established.