JP3069212B2 - Fuel injection correction method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection correction method for determining a fuel injection amount at the time of fuel cut recovery in consideration of fuel adhesion and evaporation in an intake manifold.

[0002]

2. Description of the Related Art Conventionally, this type of fuel injection correction method includes an air-fuel ratio sensor, a fuel injection amount, and an intake air amount as in an adaptive control method for an engine described in Japanese Patent Application Laid-Open No. 2-173334. It is known that a rate of adhering to the intake pipe wall surface (adhesion rate) and a rate of evaporating per unit time (evaporation rate) are estimated from the detected amount, and the amount of fuel supplied to the cylinder is controlled based on the estimated rate. I have.

[0003]

By the way, including those having the above-described structure, in which the adhesion rate and the evaporation rate are reflected in the amount of fuel to be supplied, it is assumed that the evaporation rate is constant during fuel cut. ing. In addition, it is assumed that the adhesion rate and the evaporation rate are constant even when the fuel cut is restored. However, when the adhesion rate and the evaporation rate are estimated as described above, the return increase calculated from such an adhesion rate and an evaporation rate is apt to be insufficient in practice, and the air-fuel ratio tends to be lean. If that happens, the engine may stall, which slows down the engine and causes drivability to deteriorate.

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

[0005]

In order to achieve the above object, the present invention takes the following measures. In other words, the fuel injection correction method according to the present invention uses 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 and evaporates during fuel injection. A wet correction amount is calculated based on the evaporation time constant and the wall adhesion rate set at least according to the engine temperature and the wall adhesion amount before one injection to correct the wet correction amount, and the wet correction amount and the wall adhesion are calculated. The amount of wall adhesion after the current injection is calculated based on the rate, the amount of wall adhesion before one injection, and the evaporation time constant, and the final injection time is determined based on the wet correction amount and the required basic injection amount at that time. A fuel injection correction method for performing fuel injection by fuel injection, wherein when the fuel cut is executed, the evaporation time constant is set to be larger by adding a predetermined value than when the fuel injection is executed. , Fue At least after returning from the cut
The evaporation time constant set according to the engine temperature is
And add a predetermined value during fuel cut to increase
It is characterized in that the evaporation time constant is set to be gradually smaller by subtracting from the set evaporation time constant to increase the wet correction amount.

The engine temperature in the present invention includes an engine cooling water temperature, a lubricating oil temperature, an intake air temperature, and the like.

[0007]

[Action] as long as such a configuration, the final injection time at the time of fuel cut return, the wall surface adhesion rate of fuel, the wall adhesion amount before 1 injection, fuel cut is small
At least the evaporation time constant set according to the engine temperature.
The value is determined based on the wet correction amount calculated based on the evaporation time constant that is increased by adding a predetermined value and is gradually reduced by subtraction after returning from the fuel cut, and the required basic injection amount at that time. Since the evaporation time constant is gradually reduced after returning from the fuel cut, the wet correction amount becomes larger than when the evaporation time constant is kept constant, and is an amount that satisfies the demand for the increase after return from the fuel cut. by this,
The fall of rotation after fuel cut return can be prevented,
Stalls can be avoided.

[0008]

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

The engine schematically shown in FIG. 1 is for a motor vehicle, 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 downstream thereof. 3 are provided. Near the end of the intake manifold 4 of the intake system 1 communicating with the surge tank 3 on the cylinder head 30 side, a fuel injection valve 5 is further provided.
The fuel injection valve 5 is controlled by an electronic control unit 6. An intake valve 31 is provided in the cylinder head 30 located downstream 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 provided in a pipe leading to a muffler (not shown). I have. 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 device 8, an input interface 9, and an output interface 11, and the input interface 9 Detects the intake pressure signal a from the intake pressure sensor 13 for detecting the pressure in the surge tank 3, the rotational speed signal b output from the rotational speed sensor 14 for detecting the engine rotational speed NE, and the vehicle speed. Speed signal c output from a vehicle speed sensor 15 for output, an LL signal d output from an idle switch 16 for detecting the open / closed state of the throttle valve 2, and a water temperature sensor 17 for detecting the engine coolant temperature. Water temperature signal e, O ₂
The voltage signal h output from the sensor 21 and the like are input. On the other hand, the output interface 11 outputs a fuel injection signal f to the fuel injection valve 5 and the spark plug 1
An ignition pulse g is output for the reference numeral 8.

The electronic control unit 6 uses the intake pressure signal a output from the intake pressure sensor 13 and the rotational speed signal b output from the rotational speed sensor 14 as main information, and various types of information determined according to the engine conditions. The fuel injection valve opening time, that is, the final injection time TAU is determined by correcting the basic injection time TP with the correction coefficient, and the fuel injection valve 5 is controlled based on the determined time, so that fuel corresponding to the engine load is injected. A program for injecting from the valve 5 to the intake system 1 near the cylinder head 30 is stored. Further, in this program, the amount of fuel adhering to the wall surface of the intake pipe near the intake valve 31 and the amount of fuel that has already adhered and evaporates during fuel injection are corrected to the amount of fuel to be injected. , evaporation time constant that is set in accordance with at least the engine temperature τ
The wet correction amount TPWET is calculated on the basis of the WTW, the wall adhesion ratio X, and the wall adhesion amount MF _n-1 before one injection, and the wet correction amount TPWET, the wall adhesion ratio X, and the wall adhesion amount MF before one injection are calculated. calculates a wall deposit quantity MF _n after this injection, based on the _n-1 and the evaporation time constant tau, a final injection time tAU _n on the basis of the wet correction amount TPWET and the required basic injection amount tTau _n at that time The fuel injection is determined and the fuel injection is performed, and when the fuel cut is performed, the evaporation time constant τ is set to be more predetermined than when the fuel injection is performed.
Increase the value by adding the value, and after returning from fuel cut, set at least according to the engine temperature.
The fuel cut actual value is set with the evaporation time constant τm as the lower limit.
Evaporation time constant τ set large by adding a predetermined value during the line
And the evaporation time constant τ is set to be gradually reduced to increase the wet correction amount TPWET.

The outline of the fuel injection correction program is as shown in FIGS. 2, 3 and 4.

First, in FIG. 2, in step 51,
The cooling water temperature of the engine, the wall adhesion ratio X depending on the load , and the evaporation time constant τm are read. The wall surface adhesion rate X and the evaporation time constant τm are calculated in an (X, τm) calculation routine shown in FIG. In the (X, τm) calculation routine,
First, in step 61, data of the engine speed NE, the intake pressure PM, and the coolant temperature are read. In step 62, the (TX, Tτ) map and the water temperature coefficient map are searched based on the read data. As shown in FIG. 5, the (TX, Tτ) map is set in the entire operation range based on the rotational speed NE and the intake pressure PM. In addition, as shown in FIG. 6, the water temperature coefficient map defines a first water temperature coefficient K1 and a second water temperature coefficient K2 having characteristics that converge to a substantially constant value as the cooling water temperature increases. First water temperature coefficient K1
Is for the wall adhesion ratio X, and the second water temperature coefficient K2
Is for the evaporation time constant τm. Step 63
Then, (TX, T
τ) First and second water temperature coefficients obtained from the water temperature coefficient map based on the respective map values TX and Tτ of the wall surface adhesion rate X and the evaporation time constant τm obtained by searching the map and the cooling water temperature data at that time. From K1 and K2, the wall adhesion ratio X and the evaporation time constant τm corresponding to the operating state are calculated based on the following equation.

X = K1 * TX (1-1) τm = K2 * Tτ (1-2) Next, in step 52, it is determined whether or not the cooling water temperature is 75 ° C. or higher. If not, the process proceeds to step 55. In step 53,
The constant value DELτ, which is the amount of change of the evaporation time constant at the time of fuel cut return for each injection, is subtracted from the evaporation time constant τ set at this time. In step 54, the evaporation time constant τ is determined whether the following evaporation time constant τm which depends on the coolant temperature and load, if not less than the flow proceeds to step 56,
If it is below, the process moves to step 55. In step 55, the evaporation time constant τ is set to the evaporation time constant τm, and the routine proceeds to step 56.

In step 56, it is determined whether or not the fuel is being cut. If the fuel is being cut, the process proceeds to step 57, and if not, the process proceeds to step 58. In step 57, the evaporation time constant increase ADDτ during fuel cut is added to the evaporation time constant τ,
Execute the change of the evaporation time constant τ.

Τ = τm + ADDτ (1-3) In step 58, the calculation of the injection amount is executed by the injection amount calculation routine shown in FIG. This injection amount calculation routine will be described later in detail. In step 59, the final injection time TA calculated in the injection amount calculation routine
Executing the fuel injection based on U _n.

Next, an injection amount calculation routine will be described with reference to FIG. First, at step 71, the engine speed N
The basic injection time TP is calculated from E and the intake pressure PM. The calculation itself of the basic injection time TP may be the same as the conventional one. In step 72, the required basic injection amount TT
AU _n is calculated by the following equation.

TTAU _n = TP * FTHA * KG * (1 + FWL + FPOWER) (2-1) where FTHA is an intake pressure temperature correction coefficient, and KG is A / F
The learning correction coefficient, FWL, is a warm-up increase correction coefficient, FPOWE
R is a power increase correction coefficient. These correction coefficients may be determined according to each operation state by a method widely known in the art.

In step 73, it is determined whether or not the vehicle is in a steady operation state. If the vehicle is in a steady state, the process proceeds to step 77; 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 been calculated yet at the time of transition from the steady state to the transient state, and therefore, the required basic injection amount TTA in the steady state has been calculated.
By determining the amount of change from U, it is determined whether or not a transition has been made to the transient state. In other words, if the difference (change) between the last required basic injection amount TTAU _n-1 (steady state) and the current required basic injection amount TTAU _n is not 0, it is determined that the state is a transient state. After the transition to the transient state,
Since the wet correction amount TPWET is always a numerical value other than 0, it is determined that the vehicle is not in the steady state by determining that the previously determined wet correction amount TPWET is not 0.

In step 74, the wall 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 adhesion amount MFn _-1 before one injection, and the evaporation time constant (rate) τ
Then, the wet correction amount TPWET is calculated by the following equation.

TPWET _n = (X * TTAU _n -MF _n−1 / τ) / (1-X) (2-2) In step 75, the wall surface adhesion ratio X and the wall surface adhesion amount MF _n− before one injection are obtained. and a wet correction amount TPWET _n obtained in ₁ and the calculation of the evaporation time constant τ and step 74, calculates the wall deposit quantity MF _n after this injection by the following equation.

MF _n = X * (TTAU _n + TPWET _n ) + (τ−1) * MF _n−1 / τ (2-3) In step 76, the required basic injection amount TTAU _n and the wet correction amount TPWET _n are calculated. from the final injection time TAU _n calculated by the following equation, the process proceeds to the injector driving routine.

TAU _n = (TTAU _n + TPWET _n ) * FAF (2-4) In step 73, which proceeds when it is determined in step 73 that the state is a steady state, the current wall surface adhesion amount MF _n is calculated by the following equation. together, to set the wet correction amount TPWET _n to 0.

MF _n = X * τ * TTAU _n (2-5) Here, the movement of the fuel when fuel injection is performed will be described. As shown in FIG. Is sucked into the cylinder directly through the intake valve 31 without coming into contact with the inner wall surface 1a of the intake system 1 such as the intake manifold 4 (arrow A). Thus, a small amount of the fuel adheres to the inner wall surface 1a of the intake system 1 as shown by an arrow B in the figure. While the fuel adheres in this manner, the fuel that has already adhered to the inner wall surface 1a evaporates as shown by the arrow C in the figure, mixes with the injected fuel, and is sucked into the cylinder.

In the above configuration, first, the case where the warm-up operation is completed and the operation is performed in a steady state will be described. In this case, assuming that the cooling water temperature has risen to 75 ° C. or higher, the control proceeds to steps 51 → 52 → 53 → 54 → 5
5 → 56 → 58 → 59 and the final fuel injection time TAU
Calculate _n and execute fuel injection. In the steady state, the required basic injection amount TTAU does not change because the engine speed NE and the intake pressure PM do not change, and the evaporation time constant τ also becomes a constant value. Thus, the wet correction amount TPW
Since ET _n is set to 0, the final injection time TAU _n is a value obtained by multiplying the required basic injection amount TTAU _n by the A / F feedback correction coefficient FAF. Even in this steady state,
Since although the wall adhesion amount MF _n in step 77 is calculated, that wet correction amount TPWET _n when this is zero, and that the rotational speed NE and the intake pressure PM and the coolant temperature does not change, the wall adhesion amount _{MF n- 2} , MF _n−1 , MF
_n does not change.

Next, when the fuel cut is performed,
After the control proceeds to step 56, the control proceeds to step 57.
To increase the evaporation time constant τ by adding the evaporation time constant increment ADDτ to the evaporation time constant τ. This allows
As shown in FIG. 8, it decreases the reciprocal 1 / tau of evaporation time constant tau, wall deposit quantity MF _n is 0 decreases because the fuel will not be injected. Thus, when the fuel cut is stopped (return to fuel cut), the control executes steps 51 to 56, and thereafter proceeds to step 58 → 59, where the final injection calculated in the injection amount calculation routine (step 58). The fuel injection valve 5 is energized for the time TAU _n to execute the fuel injection. In the fuel injection amount calculation routine, after the fuel cut is restored, during the fuel cut, the evaporation time constant increase ADD at the time of the fuel cut return is added.
Since the evaporation time constant τ is increased by an amount corresponding to the addition of τ, as is apparent from the equation (2-2), 1 to the amount of the required basic injection amount TTAU _n that adheres to the inner wall surface 1a
The wall surface adhesion amount MF _{n -1} before the injection is reduced, whereby the wet correction amount TPWET _n is increased and increased as compared with the conventional case. In conjunction with the wet correction amount TPWET _n having such a large value, the equation (2-3)
As is clear from FIG. 5, as the evaporation time constant τ gradually decreases, the wall surface adhesion amount MF _n−1 increases and converges to the target value after a slight overshoot.

Thus, after returning from the fuel cut,
Since the amount of fuel adhering to the inner wall surface 1a of the intake system 1 near the intake valve 31 increases, and the amount of fuel evaporating from the inner wall surface 1a decreases, the evaporation time constant τ is gradually reduced when returning from the fuel cut. by increasing the wet correction amount TPWET _n after cut operation, to prevent a drop of the rotation, avoiding stall.

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

[0029]

According to the present invention, as described in detail above, the evaporation time constant is gradually reduced at the time of return from fuel cut. Therefore, even when the amount of adhered wall surface after return from fuel cut is large, a small amount of evaporation is compensated. It is possible to increase the wet correction amount, thereby preventing a drop in rotation after returning from fuel cut, avoiding a stall, and effectively preventing deterioration in drivability.

[Brief description of the drawings]

FIG. 1 is a schematic structural explanatory view showing one 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 a flowchart showing a control procedure of the embodiment.

FIG. 5 is an explanatory diagram showing a configuration of a (TX, Tτ) map of the embodiment.

FIG. 6 is an explanatory diagram showing a configuration of a water temperature coefficient map of the embodiment.

FIG. 7 is a schematic view of a main part, showing a trend of fuel in the embodiment in an enlarged manner.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Intake system 2 ... Throttle valve 4 ... Intake manifold 5 ... Fuel injection valve 6 ... Electronic control unit 7 ... Central processing unit 8 ... Storage device 9 ... Input interface 11 ... Output interface 13 ... Intake pressure sensor 14 ... Revolution speed sensor 17: Water temperature sensor 31: Intake valve

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F02D 41/00-41/40 F02D 45/00

Claims (1)

(57) [Claims] In order to correct the amount of fuel adhering to the wall surface of an intake pipe near an intake valve and the amount of fuel that has already adhered and evaporate during fuel injection, at least the amount of fuel to be injected is corrected. A wet correction amount is calculated based on an evaporation time constant and a wall adhesion rate set according to the engine temperature , and a wall adhesion amount before one injection, and the wet correction amount, the wall adhesion ratio, and a wall surface before one injection are calculated. Fuel injection for calculating the amount of wall adhesion after the current injection based on the amount of adhesion and the evaporation time constant, and determining the final injection time based on the wet correction amount and the required basic injection amount at that time to perform fuel injection A correction method, wherein a predetermined value is added to the evaporation time constant when fuel cut is performed, more than when fuel injection is performed .
Largely set by Rukoto, after returning from the fuel cut at least the engine temperature
The evaporation time constant set in accordance with
A fuel injection correction method, wherein a predetermined value is added during execution of the fuel cut and the evaporation time constant is set to be gradually smaller by subtracting from a large set evaporation time constant to increase the wet correction amount. .