JPH06137186A - Transient time air-fuel ratio correcting method - Google Patents

Abstract

PURPOSE:To correct a transport delay of fuel in fuel injection a transient time. CONSTITUTION:In a transient time air-fuel ratio correcting method whereby a fuel amount adhering to a wall surface of an intake pipe line in the vicinity of an intake valve and a fuel amount vaporizing when injected the fuel already adhering are corrected in a fuel injection amount in the case of transient time, in the case of detecting the transient time, based on at least a wall surface sticking rate set in accordance with an engine temperature, wall surface sticking amount before one injection, at least a vaporizing time constant set in accordance with the engine temperature, a wet correction amount is calculated by a process 54, and based on the wet correction amount, wall surface sticking rate, wall surface sticking amount before one injection and the vaporizing time constant, a wall surface sticking amount after this time injection is calculated by a process 55, so that based on the wet correction amount and a required basic injection amount at this point of time, the final injection time is determined by a process 56.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transient air-fuel ratio correction method for determining a fuel injection amount in consideration of a fuel transportation delay in an intake manifold.

[0002]

2. Description of the Related Art Conventionally, as a transient air-fuel ratio correction method of this type, for example, as in a fuel supply control method for accelerating an internal combustion engine disclosed in Japanese Patent Laid-Open No. 62-228637, for example, intake pressure (intake pipe pressure). It is known to predict the adhered fuel adhering to the inner wall of the intake pipe based on the parameter value indicating the engine load such as the change amount of) and increase the injected fuel amount according to the predicted value. In addition, JP-A-2-1733
As in the engine adaptive control method described in Japanese Patent Publication No. 34-34,
It is also known that the fuel adhering to the wall surface of the intake pipe is estimated from the detected amount including the air-fuel ratio sensor, the fuel injection amount, and the intake air amount, and the fuel amount supplied to the cylinder is controlled based on the estimated value.

[0003]

However, in the case of the former one, the change in the detected intake pressure is small and the correction amount is calculated based on the change in the intake pressure. There were times when I could not. In this case, since the correction cannot be performed with high precision, the engine becomes lean in the slow acceleration state, and it may be difficult to maintain the air-fuel ratio in a stable state. In addition, when the change in intake pressure is small, only so-called tailing correction, which is a transient correction in the latter half of acceleration, can be set to a certain amount of attenuation, which is different from the actual requirement, making adaptation difficult. It was Further, in the configuration like the latter one mentioned above, the control logic becomes complicated and the number of words is increased.

An object of the present invention is to eliminate such a problem.

[0005]

The present invention takes the following means in order to achieve such an object. That is, the transient air-fuel ratio correction method according to the present invention is
Air-fuel ratio correction at transient time to correct the amount of fuel adhering to the wall surface of the intake pipe near the intake valve and the amount of fuel already adhering to evaporate at the time of fuel injection at the fuel injection amount at the time of transition In the method, when a transient time is detected, and when the transient time is detected, the wall surface adhesion rate set at least according to the engine temperature, the wall surface adhesion amount before one injection, and at least the engine temperature A wet correction amount is calculated on the basis of the evaporation time constant set as follows, and when a transition time is detected, based on the wet correction amount, the wall surface adhesion rate, the wall surface adhesion amount before one injection, and the evaporation time constant. It is characterized in that the amount of adhered wall surface after the current injection is calculated, and the final injection time is determined based on the wet correction amount and the required basic injection amount at that time.

Examples of the engine temperature in the present invention include engine cooling water temperature, lubricating oil temperature, intake air temperature and the like.

[0007]

With such a construction, the final injection time during the transient time is the wet correction amount calculated based on the wall surface deposition rate of fuel, the wall surface deposition amount before one injection, and the evaporation time constant, and It is determined based on the required basic injection amount at the time. The wet correction amount is determined by the rate of wall adhesion and the evaporation time constant.
Since the parameter is the engine temperature that changes with the passage of time, it changes according to the detected transient state. In addition, in the transient period, the wall surface adhesion amount after the current injection is calculated based on the wet correction amount when the transient time is detected, the wall surface adhesion rate, the wall surface adhesion amount before one injection, and the evaporation time constant. In other words, when there is no wet correction amount, a part of the fuel injected into the intake pipe adheres, and the fuel already adhered to the wall surface corresponding to the adhesion evaporates, so that the required amount of fuel is Even if is injected, some amount will reach the intake valve with a substantial delay, but even if the transient state becomes long, the amount of adhered wall surface during that period is
Since it is controlled by the wet correction amount, the final injection time can be maintained at a value close to the required value even in the latter half of the transient state, that is, the tailing portion, and the delay in fuel transportation can be eliminated.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

The engine schematically shown in FIG. 1 is for an automobile, and its intake system 1 is provided with a throttle valve 2 which opens and closes in response to an accelerator pedal (not shown), and a surge tank is provided downstream thereof. 3 is provided. A fuel injection valve 5 is further provided near the cylinder head 30 side end of the intake manifold 4 of the intake system 1 communicating with the surge tank 3.
Is provided, and the fuel injection valve 5 is controlled by the electronic control unit 6. An intake valve 31 is arranged in the cylinder head 30 in front of the fuel injection valve 5. Further, an O ₂ sensor 21 for measuring the oxygen concentration in the exhaust gas is attached to the exhaust system 20 at a position upstream of a three-way catalyst 22 arranged in a pipe line leading to a muffler (not shown). There is. The O ₂ sensor 21 outputs a voltage signal h corresponding to the oxygen concentration.

The electronic control unit 6 is mainly composed of a microcomputer system including a central processing unit 7, a storage unit 8, an input interface 9 and an output interface 11. Is the intake pressure signal a from the intake pressure sensor 13 for detecting the pressure in the surge tank 3, the rotation speed signal b output from the rotation speed sensor 14 for detecting the engine speed NE, and the vehicle speed. For outputting a vehicle speed signal c for outputting a vehicle speed sensor 15, an LL signal d for outputting an idle switch 16 for detecting the open / closed state of the throttle valve 2, and a water temperature sensor 17 for detecting an engine cooling water temperature. Water temperature signal e, O ₂ described above
The voltage signal h or the like output from the sensor 21 is input. On the other hand, from the output interface 11, the fuel injection signal f is sent to the fuel injection valve 5, and the spark plug 1
Ignition pulse g is output to eight.

The electronic control unit 6 has an intake pressure signal a output from the intake pressure sensor 13 and a rotation speed signal b output from the rotation speed sensor 14 as main information, and various kinds of information are determined depending on the engine condition. The basic injection time TP is corrected by the correction coefficient to determine the fuel injection valve opening time, that is, the final injection time TAU, and the fuel injection valve 5 is controlled according to the determined time to inject the fuel according to the engine load. A program for injecting from the valve 5 to the intake system 1 near the cylinder head 30 is built in. In addition, in this program, the amount of fuel that adheres to the wall surface of the intake pipe near the intake valve and the amount of fuel that has already adhered to the fuel vapor during fuel injection are A method for correcting a transient air-fuel ratio, which detects a transient time, and when the transient time is detected, a wall surface adhesion rate X set according to at least the engine temperature and a wall surface adhesion amount before one injection. The wet correction amount TPWET _n is calculated based on MF _n−1 and at least the evaporation time constant τ set according to the engine temperature, and when the transition time is detected, the wet correction amount TPWET _n and the wall surface adhesion rate are calculated. X and 1
A wall deposit quantity MF _n-1 prior to injection on the basis of the evaporation time constant τ to calculate the wall surface adhesion amount MF _n after this injection, the wet correction amount TPWET _n and the required basic injection amount T of the time
It is what is programmed to determine the final injection time TAU _n based on the TAU _n.

The outline of this transient air-fuel ratio correction program is as shown in FIGS. However, considering the various correction factors during steady operation, the final injection time TA
As a program itself for calculating U can use a conventionally known program, illustration and description thereof will be omitted.

First, at step 51, the engine speed NE, the intake pressure PM, and the basic injection time TP are calculated.
The calculation itself of the basic injection time TP may be the same as the conventional one. In step 52, the required basic injection amount T
TAU _n is calculated by the following formula.

TTAU _n = TP * FTHA * KG * (1 + FWL + FPOWER) (1) where FTHA is the intake pressure temperature correction coefficient and KG is the A / F
Learning correction coefficient, FWL is warm-up increase correction coefficient, FPOWE
R is a power increase correction coefficient. These correction coefficients may be determined according to each operating state by a method widely known in the art.

In step 53, it is judged whether or not the vehicle is in a steady operation state. If the vehicle is in the steady state, the routine proceeds to step 57, and if it is the transient state, the routine proceeds to step 54. The determination of the steady state is made based on whether the wet correction amount TPWET is 0 or the change in the required basic injection amount TTAU is 0. That is, the wet correction amount TPWET has not yet been calculated at the time of transition from the steady state to the transient state, and therefore the required basic injection amount TTA for the steady state is obtained.
By judging the amount of change from U, it is checked whether or not the state has transitioned to the transient state. That is, when the difference (change) between the previous (steady state) required basic injection amount TTAU _n-1 and the required basic injection amount TTAU _n this time is not 0,
Judge as a transient state. After the transition to the transitional state, the wet correction amount TPWET is always a value other than 0. Therefore, it is determined that the wet correction amount TPWET previously determined is not 0, so that the wet correction amount TPWET is not in the steady state. .

In step 54, the wall surface adhesion rate X of the fuel adhering to the inner wall surface 1a of the intake system 1 near the intake valve 31, the wall surface adhesion amount MF _n-1 before one injection, and the evaporation time constant (rate) τ.
Then, the wet correction amount TPWET is calculated by the following formula.

TPWET _n = (X * TTAU _n -MF _n-1 / τ) / (1-X) (2) The wall surface attachment rate X and the evaporation time constant τ are (X, τ) based on a map described later. ) It is calculated and determined by the calculation routine according to the cooling water temperature, the engine speed NE and the intake pressure PM at that time.

In step 55, the wall surface adhesion rate X, the wall surface adhesion amount MF _n-1 before one injection, the evaporation time constant τ, and step 5
From the wet correction amount TPWET _n obtained by the calculation of No. 4, the wall surface adhesion amount MF _n after the current injection is calculated by the following formula.

MF _n = X * (TTAU _n + TPWET _n ) + (τ−1) * MF _n−1 / τ (3) In step 56, the required basic injection amount TTAU _n and the wet correction amount TPWET _n are reduced to The final injection time TAU _n is calculated by the formula, and the routine proceeds to the injector drive routine.

TAU _n = (TTAU _n + TPWET _n ) * FAF (4) In step 57, which proceeds when it is determined that the steady state is obtained in step 53, the current wall adhesion amount MF _n is calculated by the following equation and The wet correction amount TPWET _n is set to 0.

MF _n = X * τ * TTAU _n (5) Next, the (X, τ) calculation routine will be described with reference to FIGS.

FIG. 3 is a schematic flowchart of the (X, τ) calculation routine. First, at step 61, data of the engine speed NE, intake pressure PM, and cooling water temperature are read. In step 62, the (X, τ) map and the water temperature coefficient map are searched based on the read data. The (X, τ) map is, as shown in FIG.
It is set in the entire operating range by E and the intake pressure PM. Further, as shown in FIG. 5, the water temperature coefficient map defines a first water temperature coefficient K1 and a second water temperature coefficient K2 which have a characteristic of converging to a substantially constant value as the cooling water temperature increases. The first water temperature coefficient K1 is for the wall surface attachment rate X, and the second water temperature coefficient K2 is for the evaporation time constant τ. In step 63, the map values TX and Tτ of the wall surface adhesion rate X and the evaporation time constant τ obtained by searching the (X, τ) map by the rotation speed data and the intake pressure data, respectively.
From the first and second water temperature coefficients K1 and K2 obtained from the water temperature coefficient map based on the cooling water temperature data at that time, the wall surface adhesion rate X and the evaporation time constant τ corresponding to the operating state are calculated based on the following equation. calculate. It should be noted that this routine may be executed in steps 54 and 57 described above.

X = K1 * TX (6) τ = K2 * Tτ (7) Here, the movement of the fuel when fuel injection is performed will be described. The injected fuel is as shown in FIG. Most of the air does not come into contact with the inner wall surface 1a of the intake system 1 such as the intake manifold 4 (arrow A) and directly passes through the intake valve 31 and is sucked into the cylinder. Therefore, a small amount of fuel adheres to the inner wall surface 1a of the intake system 1 as indicated by the arrow B in the figure. While the fuel thus adheres, the fuel already adhering to the inner wall surface 1a evaporates as shown by an arrow C in the figure, is mixed with the injected fuel, and is sucked into the girinder.

A description will be given of a case where the required basic injection amount TTAU changes due to acceleration as shown in FIG. 7 in the above configuration. First, in the steady state until acceleration,
Since there is no change in the engine speed NE and the intake pressure PM, there is no change in the required basic injection amount TTAU, and the control proceeds in steps 51 → 52 → 53 → 57 → 56. Then,
Since the wet correction amount TPWET _n is set to 0, the final injection time TAU _n is _equal to the required basic injection amount TTAU _n by A / F.
It is a value obtained by multiplying the feedback correction coefficient FAF. Even in this steady state, the wall surface adhesion amount MF _n is calculated in step 57, but at this time, the wet correction amount TP _n is calculated.
WET _n is 0, and rotational speed NE and intake pressure PM
And since the cooling water temperature is not changed, as shown in FIG. 8, the wall adhesion amount _{MF n-2, MF n-} 1, MF n does not change.

Next, when the acceleration state is reached (FIG. 7, time t)
1) Since the rotational speed NE and the intake pressure PM change, the required basic injection amount TTAU _n changes. Therefore, since it is determined in step 53 that the engine is not in the steady state, the control proceeds to steps 51 → 52 → 53 → 54 → 55 → 56, and the final injection time TAU _n is the required basic injection amount TTAU.
_{n /} wet correction amount TPWET _n
It is a value obtained by multiplying the F feedback correction coefficient FAF. In such an acceleration state, the wet correction amount TPWE
T becomes a positive value, and becomes a negative value in the deceleration state at time t2 in FIG. Since the steps 51 to 56 are repeatedly executed until the acceleration is completed, the final injection time TAU _n is the wet correction amount TPWET.
_It is corrected to _n and becomes a proper value.

As described above, even when the injected fuel adheres to the wall surface and the adhered fuel evaporates, if it is detected that the fuel is in a transient state regardless of the type of acceleration, it is detected during the transient state. , Wall adhesion rate X and wall adhesion amount M before one injection
The wet correction amount TPWET _n is calculated based on F _n−1 and the evaporation time constant τ, and the wet correction amount TPWET is calculated.
_{Since the} required basic injection amount TTAU _n is corrected by _n , the delay of fuel transportation in the latter half of the transient time can be efficiently eliminated.

The present invention is not limited to the embodiments described above.

In addition, the configuration of each part is not limited to the illustrated example, and various modifications can be made without departing from the spirit of the present invention.

[0029]

As described above in detail, the present invention provides the wet correction amount with the wall surface deposition rate of fuel and the wall surface deposition amount before one injection that can theoretically calculate the fuel transportation delay in the latter half of the transient period. It is calculated based on the evaporation time constant, the final injection time during the transition is determined based on the wet correction amount and the required basic injection amount at that time, and the wall adhesion amount after the injection of that time is calculated. Therefore, even in the latter half of the transition period, the tailing portion can be controlled near the required injection amount by the wet correction amount, and the delay in fuel transportation can be eliminated. Moreover, since the wall surface adhesion amount is theoretically calculated, the configuration of the control logic can be simplified.

[Brief description of drawings]

FIG. 1 is a schematic configuration explanatory view showing an embodiment of the present invention.

FIG. 2 is a flowchart showing a control procedure of the embodiment.

FIG. 3 is a flowchart showing a control procedure of the embodiment.

FIG. 4 is an explanatory diagram showing a configuration of an (X, τ) map according to the same embodiment.

FIG. 5 is an explanatory diagram showing a configuration of a water temperature coefficient map of the embodiment.

FIG. 6 is a schematic view of a main part showing an enlarged main part of the fuel trend of the embodiment.

FIG. 7 is an operation explanatory view of the same embodiment.

FIG. 8 is an explanatory view of the operation of the same embodiment.

[Explanation of symbols]

 1 ... Intake system 2 ... Throttle valve 4 ... Intake manifold 5 ... Fuel injection valve 6 ... Electronic control device 7 ... Central processing unit 8 ... Memory device 9 ... Input interface 11 ... Output interface 13 ... Intake pressure sensor 14 ... Rotation speed sensor 17 ... Water temperature sensor

Claims (1)

[Claims] 1. The amount of fuel adhering to the wall surface of the intake pipe in the vicinity of the intake valve and the amount of fuel already adhering to evaporate during fuel injection are corrected in the fuel injection amount in the transient state. Which is a transient air-fuel ratio correction method that detects a transient time, and when a transient time is detected, at least the wall adhesion rate set according to the engine temperature and the wall adhesion amount before one injection, The wet correction amount is calculated based on at least the evaporation time constant set according to the engine temperature, and when the transient time is detected, the wet correction amount, the wall surface adhesion rate, the wall surface adhesion amount before one injection, and the evaporation time A transient air-fuel ratio correction method characterized in that a wall adhesion amount after current injection is calculated based on a constant, and a final injection time is determined based on the wet correction amount and a required basic injection amount at that time.