JPH01117958A - Air fuel ratio feedback control for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve the feedback control precision by calculating the average value of the coefficient in the air fuel ratio feedback correction by using the calculated speed corresponding to the adjusted voltage, in an engine equipped with an AC generator which can set the adjusted voltage corresponding to the operation state. CONSTITUTION:An AC generator 17 is connected with an engine body, and the adjusted voltage is switched to the high or low voltage, and the adjustment to the selected voltage value is performed on the basis of the output signals of an electric load sensor 15, ear speed sensor 16, water temperature sensor, etc. During the operation of the engine 1, in an ECU 5 into which the output signals of an absolute pressure sensor 8, engine revolution speed sensor 11, O2 sensor 14. etc., are inputted, the air fuel ratio of the mixed gas is feedbach- controlled from the average value of the correction coefficient which varies according to the O2 concentration in the exhaust gas in the air fuel ratio feedback control operation region. In this cass, the above-descried average value is calculated from the calculated speed corresponding to the above-described adjusted voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an air-fuel ratio feedback control method for an internal combustion engine, and more particularly to a control method for appropriately controlling a supplied air-fuel ratio in accordance with a regulated voltage of a ΛC generator.

(Prior art and its problems) Conventionally, when an internal combustion engine is operated in an air-fuel ratio feedback control operation region, a coefficient that changes depending on the output of an exhaust gas concentration detector disposed in the exhaust system of the engine and an average of the coefficients have been disclosed. The present applicant has already disclosed an air-fuel ratio feedback control method for an internal combustion engine that uses at least one of the values to control the air-fuel ratio of the air-fuel mixture supplied to the engine (for example, Japanese Patent Laid-Open No. 60-233328).
.

This control method determines whether the engine is operated in a feedback control operating region or a region other than the feedback control operating region, and in which region of the feedback control operating region, an idle operating region or a region other than the idle operating region. When the engine is operated in the idle operating region or in a region other than the idle operating region, calculate the average value of the coefficients obtained in each region for each region, and calculate the average value for each region. is stored, and when the engine shifts to these operating ranges, air-fuel ratio feedback control is started using the average value stored in the target operating range as the coefficient, This sets the initial value at the start of feedback control to an appropriate value,
We are trying to improve the accuracy of feedback control.

However, when this control force method is applied to an internal combustion engine equipped with a ΛC generator whose regulated voltage can be set according to the operating state of the internal combustion engine, it has the problem that good accuracy of feedback control cannot be ensured. had.

That is, in this type of internal combustion engine, when the regulated voltage of the ΛC generator changes, the load condition of the engine changes accordingly, so even within the same feedback control operating region, the coefficient and the average value of the coefficient vary. fluctuate. Therefore, in cases where the regulated voltage of the ΛC generator is different between the end of feedback control and the time of return to the feedback control operating region, the initial value of the coefficient at the start of feedback control is set to the coefficient or the average of the coefficients. When set to a value, the coefficient or the average 11α of the coefficient fluctuates, so the initial value cannot be set to an appropriate value. Therefore, the transient response of the control at this time is not good, and the accuracy of the feedback control decreases. Resulting in.

Especially when the engine is in the idle operating region, Λ
The above-mentioned problem becomes more noticeable because the engine load state changes greatly due to changes in the regulated voltage of the C generator, and the average value of the coefficients also changes greatly accordingly.

(Object of the Invention) The present invention has been made to solve the problems of the prior art described above, and is directed to a transient response at the time of transition to a feedback control operating region of an internal combustion engine equipped with a ΛC generator whose regulation voltage can be set. An object of the present invention is to provide an air-fuel ratio feedback control method for an internal combustion engine that can improve performance and thereby improve the accuracy of feedback control.

(Means for Solving the Problems) In order to achieve the above object, the present invention has a ΛC generator that can set 111 rectifying voltages according to the operating state of the internal combustion engine. An air-fuel ratio of an internal combustion engine that, during operation, feedback-controls an air-fuel ratio of a mixture supplied to the engine using at least an average value of a coefficient that changes according to the output of an exhaust gas concentration detector disposed in an exhaust system of the engine. In the fuel ratio feedback control method, the set key! The average value is calculated at a calculation speed corresponding to one voltage.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is an overall configuration diagram of a fuel supply control device to which the control method of the present invention is applied. Reference numeral 1 indicates, for example, a four-cylinder internal combustion engine, and an intake pipe 2 is connected to the engine 1. A throttle valve 3 is provided in the middle. The throttle valve 3 is equipped with a throttle valve opening sensor (rOT
ll sensor) 4 is connected to convert the valve opening of the throttle valve into an electrical signal, which is then sent to an electronic control unit (
5 (hereinafter referred to as "ECUJ").

A fuel injection valve 6 is provided in the intake pipe 2 between the engine l and the throttle valve 3. This fuel injection valve 6 is provided for each cylinder slightly upstream of an intake valve (not shown) in the intake pipe 2, and each injection valve is connected to a fuel pump (not shown) and electrically connected to the ECU 3. The valve opening time of fuel injection is controlled by a signal from the ECU 3.

On the other hand, an intake pipe absolute pressure sensor (hereinafter referred to as PB sensor J) 8 is provided downstream of the throttle valve 3 via a pipe 7, and the absolute pressure sensor 8 converts into an electrical signal. The signal is sent to the ECU 3. Further, an intake air temperature sensor (hereinafter referred to as "T^sensor") 9 is installed downstream thereof, and this 1'^ sensor 9 also converts the intake air temperature into an electrical signal and sends it to the IECU 3.

The engine 1 body has a ΛC generator (rAcGJ
) 17 are connected. The regulated voltage of G17 is switched to either a high voltage (for example, 14.5V) or a low voltage (for example, +2.5V) (7) by the ECU 3, and is adjusted to the switched voltage value by a circuit not shown. It has become so. From then on, the voltage adjustment modes of ΛCG17 are set to 14.5V mode, +2,
It's called 5V mode.

The engine body 1 has an engine cooling water temperature sensor (hereinafter [1
10 (referred to as W sensor J) is provided, and this 'l' w
The sensor 10 consists of a thermistor, etc., and is inserted into the circumferential wall of the engine cylinder filled with cooling water, and supplies the detected water temperature signal to the ECU 3.
N6 sensor) 11 is installed around the camshaft or crankshaft (not shown) of the engine 1, and the TD
C signal, that is, one pulse is output at a predetermined crank angle position every 180' rotation of the crankshaft of engine l, and this pulse (hereinafter referred to as r'roc signal pulse) is sent to ECU 3.
supply to.

A three-way catalyst 13 is arranged in the exhaust pipe 12 of the engine l,
It purifies IIC, Go, and NOx components in exhaust gas. An 02 sensor 14 as an exhaust gas concentration detector is inserted into the exhaust pipe 12 on the upstream side of the three-way catalyst 13, and this 02 sensor I4 detects the oxygen concentration in the exhaust gas and sends the detected value signal to the ECU 3. supply Furthermore, the ECU 3 includes an electrical load sensor 1 that detects the load current caused by the electrical load.
5. A vehicle speed (V) sensor 16 for detecting vehicle speed is connected, and these detection signals are supplied.

EC: U5 shapes input signal waveforms from various sensors,
An input circuit 5a having functions such as correcting the voltage level to a predetermined level and converting analog signal values into digital signal values.
, central processing circuit (hereinafter referred to as rCPUJ) 5b, C
It is composed of a storage means 5c for storing various calculation programs and calculation results executed by the PU 5b, and an output circuit 5 (1, etc.) for supplying a drive signal to the fuel injection valve 6.

The CPU 5b determines various engine operating states such as a feedback control operating region and an open loop control operating region based on the various engine parameter signals described above, and also determines the following equation (1) according to the engine operating state.
A fuel injection valve 6 synchronized with the "l'DC signal pulse"
The fuel injection time 'rouτ is calculated.

Toor=TiXKo2XKI102-(1) T here
i indicates the basic fuel injection time, for example, the absolute pressure inside the intake pipe P
It is calculated from a Ti map (not shown) stored in the storage means 5C described above in accordance with H^ and the engine rotation speed Ne. KO2 is the KO2 calculation subroutine (Figure 2), which will be described later.
This is the 02 feedback correction coefficient calculated by Also, K! and 2 are correction coefficients and correction variables that are calculated according to various engine parameter signals, respectively, and are set to required values to optimize engine characteristics such as fuel consumption characteristics and engine acceleration characteristics according to engine operating conditions. Set.

The CPU 5b calculates the fuel injection time 'r obtained as described above.
A drive signal for opening the fuel injection valve 6 based on the signal ``our'' is supplied to the fuel injection valve 6 via the output circuit 5d.

In addition, the CPU 5b has an electric load sensor 15 and a V sensor! 6
and 80G1 according to the output signal from the Tw sensor lO, etc.
7 and supplies the switching signal to ΛCOL 7 based on the setting.

FIG. 2 shows a flowchart of a subroutine for calculating the 02 feedback correction coefficient KO2. This program is TD
This is executed in synchronization with each occurrence of a C signal pulse.

First, it is determined whether activation of the 02 sensor 14 has been completed (step 20I). That is, the internal resistance detection method of the 02 sensor 14 detects whether the output voltage of the 02 sensor 14 has reached the activation starting point Vx (for example, 0.6 V), and when it reaches Vx, it is determined that it is activated. do.

If the answer is negative (NO), set KO2 to 1.0 (step 202), terminate this program, and
If ' is constant (Yes), it is determined whether the engine 1 is being operated in the oven loop control operating region (oven region) (step 203). This open-loop control operating range covers the full load range of the internal combustion engine, the low rotation speed range,
These include high rotation speed range and lean mixture range.

If the answer to step 203 is positive (Yes), KO2 is set to 1.0 in the same manner as above (step 2o2), this program is terminated, and the equation (1
) is set to a value of 1 according to the operating condition, and this is applied to perform open-loop control.

On the other hand, if the answer to step 203 is negative (No), it is determined that the operating state of the engine I is in the feedback control operating region, and feedback control is performed. First, 02 sensor! In step 2o4), it is determined whether the output level of the O2 sensor I4 has been inverted or not. If the answer is affirmative (Yes), that is, the output level of the O2 sensor I4 has been inverted, proportional control (P-term control) is performed. That is, in step 2, it is determined whether the output level of the 02 sensor 14 is at a low level (ffOW) or not.
o5), if the answer is affirmative (Yes), the storage means 5
A predetermined time t and PR according to the engine speed Ne are determined from the Ne-LPR table stored in c (step 2).
06). This predetermined time trR is for keeping the application period of a second correction value Pg, which will be described later, constant over the entire engine rotation range, and is therefore set to a smaller value as the engine rotation speed Ne increases.

Next, it is determined whether the predetermined time LPR has elapsed since the last application of the second correction value Pv (step 207).
. When the answer is pt constant (Yes), the Ne-['R table is stored in the storage means 5c.
Second correction value Pl according to e! (step 208
), when negative (No), the Ne-PR child table calculates the first correction value P according to the engine rotation speed Ne from the Ne-P table separately stored in the storage means 5c (step 2o9).

The first correction value P is the second correction value Pl! is set to a smaller value. Next, the correction value P is added to the correction coefficient KO2.
i, that is, the first correction ((iP or the second correction value Pv) (step 21O). If the answer to step 205 is negative (No), the engine A first correction tUI' corresponding to the rotational speed Ne is determined (step 211), and the correction value P is subtracted from the correction coefficient KO2 (step 212).
.

In this way, when the output signal of the 02 sensor 14 is inverted,
A first correction value P or a second correction value PR is set as a correction coefficient KO2 according to the engine rotational speed Ne in the direction to correct this reversal.
Add or subtract from.

Using the value of the correction coefficient KO2 obtained in this manner, the average value KREF of KO2 is calculated based on the following equation (2) (step 213), and is stored in the memory. This average [KR
EF is KI! which will be described later. Based on the εF calculation subroutine (Fig. 3), if the current loop corresponds to a feedback control operation region other than the idle operation region, KREFI is set.
Or KREF2 is calculated, and when it corresponds to the idle operation region, KREFO12,5 or Ki! 1pon
, s are calculated for each voltage adjustment mode.

K*Epn=CnXKo2p+ (1-Cn)xK*i
:pn' - (2) Here, the value KO2P is the value of KO2 immediately before or after the proportional term (P term) operation, and Cn is an experimentally appropriate value for each operating region and voltage adjustment mode (0<Cn The variable Kl!εFn' set in (1) is the KO2 obtained up to the previous time in the operating region and voltage adjustment mode to which the current loop applies.
is the average value of

Kl of KO2P during each P-term operation depending on the value of variable Cn!
The proportion to EFII changes, ie the average value Kl! εF
Since the calculated speed of n changes, by setting this Cn value to an appropriate value (0<Cn<1) according to the specifications of the target air-fuel ratio feedback 111 control device, engine, ΛCG, etc. Optimal Kl! EFn(KRI:F
OI2.5. KREFO14,5,Kl! EFI or Kl! EF2) can be obtained.

The average taKt:tpn of KO2 calculated in this way is determined depending on the corresponding operating region when the engine l shifts to the feedback control operating region, and further depending on the voltage adjustment mode when the operating region is in the idle operating region. , is set as the initial value of the correction coefficient KO2 at the start of control in the feedback control operation region (not shown)
.

If the answer to step 204 is negative (No), that is, the output level of the O2 sensor 14 has not been inverted, then integral control (one-term control) is performed in steps 214 and subsequent steps. First, similarly to step 205 described in 01j, the 02 sensor 14
It is determined whether the output level of is low level (step 214). When the answer is affirmative (Yes), that is, when the output level of the 02 sensor 14 is low level, '
Step 21: Count the number of l' D C signal pulses.
5), determine whether the count number NIL has reached a predetermined value (11N1) (step 216).
If the answer to question 16 is negative (NO), the correction coefficient KO2 is held at the previous value (step 217), and F'? Fixed (Y
es), a predetermined value Δk is added to the coefficient KO2 (
At the same time as step 218), the count number NIL is reset to O (step 210), and a predetermined value Δk is added to KO2 every time NIL reaches N+.

Also, if the answer to step 214 is negative (NO), '
I″Count the number of DC signal pulses (step 220)
, the count number N! 11 has reached a predetermined value NI (step 221), and the answer is negative (NO).
), the correction coefficient KO2 is held at the immediately previous value (step 222).

When the answer to step 221 is affirmative (Yes), a predetermined value Δl( is subtracted from the correction coefficient KQ2 (step 22
3), the count number Nio is reset to 0 (step 224), and a predetermined value Δk is decremented from the coefficient KQ2 every time the count number Not reaches a predetermined value NI.

In this way, when the output of the 02 sensor 14 remains at a lean or rich level, 'I' is used to correct this.
' D A constant value Δk is added to or subtracted from the correction coefficient KO2 every time the CtR pulse is generated a predetermined number of N+ times.

FIG. 3 shows the KRE executed in step 213 of FIG.
A flowchart of the FW output subroutine is shown.

First, in step 301, it is determined whether the engine l is in the idle operating range. This determination is made, for example, by determining whether or not the engine rotational speed Ne is less than a predetermined value and the intake pipe absolute pressure PB8 is less than a predetermined value. When the answer to step 301 is affirmative (Yes), that is, when the engine l is in the idle operation region, the count value of TFRTI+timer consisting of a down counter is set for a predetermined period of time TF! Set it to T11 and make it star 1~ (
Step 302), and then it is determined whether the voltage regulation mode of ΛCGl 7 is the 12.5V mode (Step 303). This answer determines l' (Yes), that is, 80G
When the voltage adjustment mode of No. 17 is the 12.5V mode, based on the above formula (2), the voltage adjustment mode of 12.5V during idling operation is
Average value Kl of KO2 for V mode! EFOI2.5 is calculated (step 304), while negative (No), that is, Λ
When the voltage adjustment mode of CGl 7 is 14.5V mode, based on the above formula (2), 1
s of Ko2 for 4,5V mode (l average value KREFO14
, 5 (step 305), and ends this program.

As mentioned above, when engine 1 is idling, K
The average value KRεF of O2 is calculated and stored for each voltage adjustment mode of ΛCGl7 at a calculation speed according to the adjustment voltage, and the stored average value Kl! EF is set as the initial value of the correction coefficient KO2 according to the voltage adjustment mode applicable at this time when the engine I returns to the idle operating range.
Regardless of changes in the adjustment voltage, the initial value of KO2 can be set to an appropriate value, and therefore the transient response of feedback control at this time can be improved.

n: If the answer to step 301 is negative (FJo), that is, when the engine l is in a feedback control operation region other than the idle operation region, TFBTI+timer count value TFBTI+ started in step 302 is
is equal to [0 (step 306).

If the answer is negative (No), the average value KREF2 of KO2 is calculated based on the formula (2) (step 307).
) Exit this program. That is, the average of KO2 (((
KREF2 is calculated when the engine 1 shifts from the idle operating region to a feedback side control operating region other than the idle operating region, and is calculated only until a predetermined period of time j FBTI has elapsed after the shift.

0; If the answer to step 306 is affirmative (Yes), it is determined whether the throttle valve opening (?TII) is smaller than a predetermined value OFc (step 308). If the answer is negative (No), that is, 0 When 11≧Orc holds true and the throttle valve 3 is not in the fully open state, the above formula (
Calculate the average IQ K RεF+ of KO2 based on step 2). If step 309) is affirmative (Yes), that is, the throttle valve 3 is almost fully closed, the average value Kl! This program is ended without calculating εF. In other words, KO2's 11αKREFI is determined by the predetermined time t FBTI+ after the engine l shifts from the idle operation region to the feedback control operation region other than the idle operation region.
is calculated when the time period has elapsed and the throttle valve 3 is not in the fully closed state.

(Effects of the Invention) As described in detail above, the present invention provides air-fuel ratio feedback control of an engine as described in (1) above, which is equipped with a ΛC generator whose adjustment voltage can be set according to the operating state of the internal combustion engine. An internal combustion engine that feedback-controls the air-fuel ratio of the air-fuel mixture supplied to the engine using at least an average value of a coefficient that changes according to the output of an exhaust gas concentration detector disposed in the exhaust system of the engine during operation in an operating range. In the air-fuel ratio feedback control method for an engine, the average value is calculated at a calculation speed according to the set adjustment voltage, so that feedback control operation of an engine equipped with a ΛC generator whose adjustment voltage can be set is possible. By improving the transient response when transitioning to the region, the accuracy of feedback control can be improved.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram of a fuel supply control device to which the control method of the present invention is applied, and Fig. 2 is an o2 feedback correction coefficient K.
Flowchart of O2 calculation subroutine, Figure 3 shows 0
2 Average value of feedback correction coefficient KO2 1 (Flowchart of subroutine for calculating RεF) 1...Internal combustion engine, 14...O2 sensor (exhaust gas concentration detector), 17...ΛC generator (ΛCG
), KO2...02 feedback correction coefficient (coefficient), KREF...average value of KO2 (average value of coefficients).

Claims (1)

[Claims] 1. Output of an exhaust gas concentration detector disposed in the exhaust system of the engine when the engine, which is equipped with a ΛC generator whose adjustment voltage can be set according to the operating state of the internal combustion engine, is operated in an air-fuel ratio feedback control operating region. In the air-fuel ratio feedback control method for an internal combustion engine, the air-fuel ratio of an air-fuel mixture supplied to the engine is feedback-controlled using at least an average value of coefficients that changes according to the average value at a calculated speed according to the set adjustment voltage. An air-fuel ratio feedback control method for an internal combustion engine, characterized by calculating a value.