JPS5934441A - Control method of air-fuel ratio of internal-combustion engine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio control method for correcting the air-fuel ratio of an air-fuel mixture supplied to an internal combustion engine using electronic feedback means. The present invention relates to an air-fuel ratio control method for an internal combustion engine that maintains the air-fuel ratio at an appropriate value depending on the operating state immediately before shifting to a specific operating state.

Generally, the operating conditions of an engine change in various ways, so in order to obtain the desired engine operating performance, exhaust characteristics, and fuel efficiency characteristics, the air-fuel ratio of the mixture supplied to the engine must be optimally controlled according to the operating conditions. There must be. For this reason, conventionally, a sensor placed in the engine's exhaust system detects the exhaust gas concentration along with various parameters representing the engine's operating state, and when the engine is outside of a specific operating state, the air-fuel ratio of the mixture is adjusted according to this detected value. There is a method in which feedback control is performed to maintain the stoichiometric air-fuel ratio, while feedback control is interrupted when a specific operating state is in effect, and the air-fuel ratio is oven-loop controlled using a correction coefficient and/or correction constant according to the various parameters. It is being said.

As one of the above-mentioned control methods, in particular, a first operating state (during gear shifting) and a second operating state (air-fuel mixture lean region, deceleration region, and fuel supply cutoff region) are selected as specific operating states. A method in which the air-fuel ratio correction coefficient is held at the value immediately before shifting to this state during the first operating state and at a predetermined fixed value during the second operating state (% No.) has been proposed.

However, in order to maintain the air-fuel ratio correction coefficient at a fixed value in the second operating state as described above, this method is difficult to solve due to manufacturing variations or aging of the drive system of the fuel injection device and the sensors for detecting various parameter values. This has the disadvantage that the air-fuel ratio cannot be accurately controlled to the required air-fuel ratio. In addition, if the value is simply held at the previous value during the first operating state, there is a disadvantage that the air-fuel ratio fluctuates greatly during the transition from the first operating state to the second operating state, resulting in an increase in harmful components in the exhaust gas. .

The present invention has been made to solve this problem, and includes an air-fuel ratio control method for correcting the air-fuel ratio of a mixture supplied to the engine according to the exhaust gas concentration of the internal combustion engine using electronic feedback means. detects a predetermined parameter representing the operating state of the engine, determines that the engine is in the first operating state until the detected value of the parameter is within a predetermined range for a predetermined period of time; After passing, it is determined that the engine is in the second operating state, and when in the first operating state, the correction value of the air-fuel ratio of the air-fuel mixture supplied to the engine is changed to the value immediately before shifting to the first operating state. and the first predetermined value, and by holding the correction value at the first predetermined value during the second operating state, the first operating state of the engine (mixture The above-mentioned 1. An air-fuel ratio control method for an internal combustion engine that can control the air-fuel ratio in a second operating state to a value that corresponds to the actual operating characteristics of the engine, fuel injection device, etc., and that can avoid the effects of manufacturing variations, aging, etc. It provides: In particular, according to the method of the present invention, when the average value of the air-fuel ratio correction values obtained immediately before transition to the first operating state is used as the first predetermined value, the first The control delay immediately after the transition from the second operating state to the feedback control can be further reduced, and the deviation of the air-fuel ratio from the appropriate value in the second operating state can be further suppressed.

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is an overall configuration diagram of a fuel supply control device to which the method of the present invention is applied. Engine l is, for example, a 4-cylinder internal combustion engine with four main combustion chambers and an auxiliary combustion chamber (both (not shown), and the intake pipe 2 connected to the engine 1 is composed of a main intake pipe 2a communicating with each main combustion chamber and a sub-intake pipe 2b communicating with each sub-combustion chamber. ing.

A throttle body 3 is disposed in the middle of the intake pipe 2, and a main throttle valve 3a and a sub-throttle valve 3b that control the opening degrees of the main intake pipe 2a and the sub-intake pipe 2b are interlocked with each other. ing. A throttle valve opening sensor 4 is connected to the main throttle valve 3a, which detects the valve opening θth of the main throttle valve 3a and outputs a corresponding signal to control the electronic control unit (hereinafter referred to as ECU). ).

Main fuel injection valves 6 are provided in the main intake pipe 2a and the auxiliary intake pipe 2b, respectively.
A and an auxiliary fuel injection valve 6b are arranged, and only one auxiliary fuel injection valve 6b is provided for each cylinder slightly upstream of an intake valve (not shown) in the main intake pipe 2a. tube 2
They are provided in common to each cylinder slightly downstream of the sub-throttle valve 3b. Each of these fuel injection valves 6a16
It is connected to a fuel pump (not shown). Further, each of these fuel injection valves 5a and 6b is electrically connected to the ECTJ5, and the opening time of fuel injection is controlled by a control signal from the ECU3.

The main intake pipe 28 has a pipe 7 immediately downstream of the main throttle valve 3a.
An absolute pressure sensor 8 is installed to detect the absolute pressure 1)B in the main intake pipe through the main intake pipe, and the absolute pressure signal output from the absolute pressure sensor 8 is sent to the ECU 3. For example, an engine rotation speed sensor (hereinafter referred to as Ne sensor) 9 is attached around the camshaft (not shown) of the engine 1.
A crank angle signal (hereinafter referred to as TDC signal) is outputted and sent to the ECU 3 at a predetermined crank angle position every 180° rotation of the engine crankshaft.

HC in the exhaust gas arranged in the exhaust pipe 10 of the engine 1,
Upstream of the three-way catalyst 11 that purifies CO and NOx components, an O2 sensor 12 that detects the oxygen concentration in the exhaust gas is inserted facing into the exhaust pipe 10. A signal corresponding to the oxygen concentration is output and sent to the ECU 3. An engine temperature sensor (not shown) for detecting engine temperature, for example, cooling water temperature, is attached to the main body of the engine 1, and an intake air temperature sensor (not shown) for detecting intake air temperature is attached to the main intake pipe 2a. The electrical signals output from these engine temperature sensors and intake air temperature sensors are EC
Sent to U3.

Furthermore, a sensor for detecting atmospheric pressure, an engine starter switch, and a battery electrode (all not shown) are connected to the ECU 3, and a signal corresponding to atmospheric pressure, a starter switch ON/OFF state signal, and a battery voltage are connected to the ECU 3. Signals and the like are supplied to the ECU 3.

1=: The CU 5 calculates the fuel injection times 'rotrrM and TOUTS of the main fuel injection valve 6a and the auxiliary fuel injection valve 6b given by the following formulas based on the various engine parameter signals.

TotrrM= TiMx K1 + K2
-...(1) 'I'0UTS = ', ['i s x
Kl '10 to 2' = (21 Here, 'I'iM and Tis indicate the basic injection times of the main fuel injection valve 6a and the auxiliary fuel injection valve 6b, respectively, and these basic fuel injection times are, for example, It is read from the storage device in the ECTJ 5 based on the absolute pressure FB and the engine speed Ne.

1 for the coefficient. Kl', 2. and 2' are the aforementioned sensors, namely, the throttle valve opening sensor 4 and the absolute pressure sensor 8.
．． Ne sensor 9,0! It is a correction coefficient calculated according to engine parameter signals from the sensor 12, engine temperature sensor, intake air temperature sensor, atmospheric pressure sensor, etc., and is a correction coefficient that is calculated according to engine parameter signals from the sensor 12, engine temperature sensor, intake air temperature sensor, atmospheric pressure sensor, etc. It is calculated based on a predetermined formula so that the initial characteristics such as

The coefficient 1 is the air-fuel ratio correction coefficient Ko2. +) − conversion coefficient K
r, s, intake air temperature correction coefficient KTA, engine water temperature fuel increase 1-coefficient KTW, fuel increase coefficient KAFC after fuel cut (fuel supply cutoff), atmospheric pressure correction coefficient KPA,
It is given by the following equation as a product of the enrichment coefficient KWOT, etc.

K1 ==1(02-KLS-KTA ・KTW-KA
FCIIKPA @KASTIIKWOT
(3) The air-fuel ratio correction coefficient Ko2 is obtained by a subroutine according to the oxygen concentration in the exhaust gas, and the lean coefficient KLS is a constant selected according to the operating state of the engine. For example, it is set to 1 in normal operation and 0.8 in lean region.

The ECU 3 sends each drive signal to the main fuel injector to open each of the main fuel injector 6a and the auxiliary fuel injector 6b based on the fuel injection times TOUTM and Totrrs calculated by the above equations (1) and (2). 6a and the auxiliary fuel injection valve 6b.

FIG. 2 is a block diagram showing the circuit configuration of the ECU 3 shown in FIG. 1. The 'FDC signal outputted from the Ne sensor 9 shown in FIG. 'IJ' DC signal of Me counter 502
and a central processing unit (hereinafter referred to as CPU) 503. The Me counter 502 receives each TD that is sequentially input.
C signal signal waiting time is counted sequentially, and the counted value Me
is proportional to the reciprocal of the engine speed Ne. The count value Me of this Me counter 502 is transferred to C via the data bus 510.
It is supplied to PU503.

Each input signal from the throttle valve opening sensor 4, absolute pressure sensor 8, sensor 12, and other engine parameter sensors (not shown) shown in FIG.
The signals are sequentially applied to an analog-to-digital converter (hereinafter referred to as an A-reverse converter) 506 at predetermined timing. The A-D converter 506 converts the analog signals input from each sensor into corresponding digital signals and supplies the digital signals to the CPU 503 via the data bus 510.

The CPU 503 is connected via a data bus 510 to a read-only memory (hereinafter referred to as R, OM) 507, a random access memory (hereinafter referred to as R/AM) 508, and an injection valve drive circuit 509. A basic injection time TI map, coefficient values or constant values corresponding to predetermined values of various engine parameters, etc. are stored.
A, M2O3 temporarily stores the calculation result calculated by Ci' U 503. The CPU 503 reads coefficient values or constant values corresponding to the various engine parameter signals described above from the ROM 507 according to the control program stored in the ROM 507 in synchronization with the TDC signal.
1), each fuel injection time 'I'OU based on (2)
TM.

TOUTS is calculated and each calculated value is supplied to the drive circuit 509 via the data bus. The drive circuit 509 controls the opening of the main fuel injection valve 6a and the auxiliary fuel injection valve 6b according to the input calculated value.

FIG. 3 shows a flowchart of a subroutine for calculating the air-fuel ratio correction coefficient KO2.

The lean coefficient KLS is given as a function KLS = f (Ne, PR) of the engine speed Ne and the intake pipe absolute pressure PB. (fuel supply cutoff area) is set to 0.8.

When the clutch is off during gear shifting (hereinafter referred to as the first operating state), the engine temporarily enters a no-load state, and accordingly the engine enters a predetermined range (lean range, fuel cut range, or deceleration range). Therefore, in step 1), it is determined whether the lean coefficient Kts is smaller than 1 or not, and whether or not the engine is in the lean range is determined. If the answer is negative (NO), a complete determination is made as to whether the area is a fuel cut area or a deceleration area (step 2). The determination as to whether or not the engine speed Ne is in the fuel-lecut region is given by a function f(Ne, θth) between the engine speed Ne and the throttle valve opening θth when the engine speed Ne is lower than a predetermined speed. When the rotation speed is higher than a predetermined rotation speed, it is given as a function f(Ne, I'B) of the engine rotation speed Ne and the intake pipe absolute pressure 13-Pn.

Generally, the engine speed Ne is high during gear shifting, so in this embodiment, the intake pipe absolute pressure PB is used as a predetermined parameter representing the operating state of the engine, and this absolute pressure Pn determines whether the engine is in the fuel cut region or deceleration region. Determine whether That is, in step 2 described above, it is determined whether the intake pipe internal pressure PB shown by song II in FIG.
If the answer is negative (NO), the fluctuation time tD of the intake pipe pressure PR is set to 0 (step 3), and the air-fuel ratio correction coefficient KO2 for performing feedback control is calculated (step 4). .

Feedback control using the air-fuel ratio correction coefficient Ko2 is performed as follows. First, it is determined whether the output level of the 02 sensor 12 has reversed or not. If it is determined that the output level has reversed, it is determined whether the previous air-fuel ratio correction was an open loop, and if it is not an open loop, the Proportional control (P
term control).

The correction value Pi during this P-term control is added to or subtracted from the coefficient Koz when the output level of the q-102 sensor is inverted (read from the Ne-Pi14 table (not shown) using the engine rotation speed Ne). That is, when the output level of the 02 sensor is low level, the correction value Pi is added to the coefficient 02, and when the output level is high level, the coefficient Ko2 is added.
The correction value Pi is subtracted from. Therefore, the correction coefficient KO2 is represented by the broken line ■ in FIG. 4(b).

Next, the average value KREF is calculated based on the coefficient KO2 obtained in this way (step 5). The average value KREF is calculated by the following formula.

Here, Koz p is the value of Koz immediately before or after the proportional term (2nd term) operation, A, B ke constant (A > B), K'
REF is the average value of Koz obtained up to the previous time.

The reason why the average value KREF is calculated based on the Koz p value immediately before or after the P-term operation is because the air-fuel ratio of the engine air-fuel mixture at the time immediately before or after the P-term operation, that is, when the output level of the 02 sensor is reversed, is the theoretical one. This is because it has the value closest to the value (=] 47), and thereby it is possible to obtain the average value of Koz when the air-fuel ratio of the mixture is close to the stoichiometric mixture ratio, and it is based on the engine operating conditions. Most suitable KR
The EF value can be calculated.

Moreover, the average value of Koz can also be calculated by the following equation instead of both equations (4).

Here, KO□pj is the Ko2p that occurred during the P-term operation j times before the current P-term operation, B is a constant, and P
The term is the number of operations (the number of times the 02 sensor is reversed).

If it is determined affirmative (Yes) in step 1, that is, the lean region has entered, or if it is determined affirmative (Yes) in step 2, that is, it is determined that the fuel cut region or deceleration region has entered. In order to identify whether or not such a state is caused by a gear change operation, the elapsed time to (variation time) from the time of entering these predetermined regions is determined by a predetermined time, for example, from 1 second. It is determined whether or not the length is also long (step 6).

If the determination is negative (NO) in step 6 (Fig. 4 (a) III), it is determined that the first operating state is the shift operation, and at this time, the coefficient Ko2 is the value immediately before shifting to the shift operation. The second predetermined value (in this embodiment, the arithmetic mean of the immediately preceding value I(02i and the average value KRBF) is the value between the value Ko2i generated during the feedback operation and the first predetermined value (in this embodiment, the average value KREF). (Ko2i
10 KREF) / 2) (Step 7)
. Then, after the shift operation is completed, the feedback operation is started again from this value Ko2i (Fig. 4 (b) ■). If it is determined that the value is affirmative αes in step 6, that is, the value is within the predetermined range. Time (variable time)
If tn exceeds 1 second (Fig. 4 (a) IV), it is determined that the operating state is in the second operating state (lean region, deceleration region, or fuel cut region), and the coefficient is immediately changed after a predetermined time of 1 second has elapsed. Ko2 is set to the average value KREF (FIG. 4(b) Vl) (step 8). This average value KREF is the average value of the =17-correction coefficient values immediately before transition to the second operating state. This second operating state is Mf
As mentioned above, it shows multiple regions including the lean region, deceleration region, and fuel cut region, and when transitioning between these regions, the measurement of the fluctuation time tD is not canceled even if there is a continuous transition. Let's continue.

Similarly, in this embodiment, a case has been described in which fuel cut or deceleration is determined after determining the lean coefficient, but it goes without saying that the determination may be performed in the opposite order.

As explained above, according to the present invention, the engine is in the first operating state until the detected value of the predetermined parameter representing the operating state of the engine is within the predetermined range for a predetermined period of time. In addition, after this predetermined time has elapsed, it is determined that the engine is in the second operating state, and when in the first operating state, the air-fuel ratio correction value is set to the value immediately before shifting to the first operating state. and the first predetermined value.
The correction value of the air-fuel ratio is maintained at a predetermined value, and the correction value of the air-fuel ratio is maintained at the first predetermined value during the second operating state. It can be controlled to a value that corresponds to the operating characteristics of the fuel injection system, etc., and avoids the effects of manufacturing variations and aging.'! According to the embodiment of the present invention, the air-fuel ratio correction coefficient value in the second operating state is maintained at the average value of the air-fuel ratio correction coefficient values obtained immediately before shifting to the first operating state. So, the second
It is possible to perform air-fuel ratio control that immediately responds to the operating state of the engine in the operating state of the engine (that is, the lean region, the deceleration region, or the fuel cut region).

Furthermore, according to the embodiment of the present invention, in the first operating state, the air-fuel ratio correction coefficient value is maintained at a value equal to the arithmetic mean of the air-fuel ratio correction coefficient value immediately before shifting to the operating state and the average value. This makes it possible to reduce in a well-balanced manner both the control delay that occurs when transitioning from the first operating state to the feedback region and the control delay that occurs when transitioning from the first operating state to the second operating state. be.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing an embodiment of a fuel supply device to which the air-fuel ratio control method for an internal combustion engine according to the present invention is applied, and FIG. 2 is an embodiment of the circuit configuration of the ECU shown in FIG. 1. Block diagram, FIG. 3 is a diagram showing an example of a flowchart of the air-fuel ratio correction coefficient calculation subroutine, FIG. 4(a)
and Φ) are graphs showing changes in the absolute pressure in the intake pipe and changes in the correction coefficient. 1°°゛engine, 2・-Mfi'lf, 3°・°throttle body, 4...throttle valve opening sensor, 5
...ECU. 6a, 5b...Fuel injection valve, 8...Absolute pressure sensor,
9...Ne sesen, 11...Three-way catalyst, 12...
02 sensor. Applicant Honda Motor Co., Ltd. Agent Patent Attorney Toshihiko Watanabe

Claims (1)

[Scope of Claims] 1. In an air-fuel ratio control method for correcting the air-fuel ratio of a mixture supplied to an engine according to the exhaust gas concentration of the internal combustion engine using electronic feedback means, a predetermined parameter representing the operating state of the engine is provided. is detected, and the engine is determined to be in the first operating state while the detected value of the parameter is within a predetermined range for a predetermined period of time, and after the predetermined time has elapsed, the engine is determined to be in the first operating state. It is determined that the engine is in the second operating state, and in the first operating state, the correction value of the air-fuel ratio of the air-fuel mixture supplied to the engine is set to the value immediately before shifting to the first operating state and the first predetermined value. A method for controlling an air-fuel ratio of an internal combustion engine, characterized in that the correction value is maintained at a second predetermined value between , and the correction value is maintained at the first predetermined value during the second operating state. 2. The air-fuel ratio control method according to claim 1, wherein the second operating state is a region in which the air-fuel mixture is made lean. 3. The air-fuel ratio control method according to claim 1, wherein the second operating state is a deceleration region or a fuel supply cutoff region. 4. The air-fuel ratio control method according to any one of claims 1 to 3, wherein the first operating state is during a speed change operation. 5. According to any one of claims 1 to 4, the first predetermined value is an average value of air-fuel ratio correction values obtained immediately before shifting to the first operating state. air-fuel ratio control method. 6. The air-fuel ratio control method according to claim 5, wherein the second predetermined value is an arithmetic mean value of a value immediately before shifting to the first operating state and the average value.