JPH08200120A - Control method for fuel injection - Google Patents

Abstract

PURPOSE: To eliminate that the fuel injection amount is rapidly set to the large amount corresponding to the engine speed by correcting the fuel injection amount to be taken as the reference by the gradually increased power increasing amount when the power increasing amount set on the basis of the engine speed is increased with the time. CONSTITUTION: An electronic controller 6 houses a program for taking an intake air pressure signal (a) to be output from an intake air pressure sensor 14 and a rotational number signal (b) to be output from a rotational number sensor 15 as the main information, correcting the reference injection time by various correction factors including the power increasing amount correction factor to be determined according to the engine rotating state, and setting it to the effective injection time. The program is so made that the fuel injection amount to be taken as the reference may be corrected by the gradually increased power increasing amount by setting the power increasing amount in which the fuel injection amount to be taken as the reference is set last time and the power increasing amount to be gradually increased on the basis of the engine speed detected this time when the set power increasing amount is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a fuel injection control method for a vehicle engine under high load.

[0002]

2. Description of the Related Art Conventionally, a fuel injection type engine is normally operated at a stoichiometric air-fuel ratio. However, in order to ensure output performance at high load, or in combustion at high rotation speed and high load range. In order to lower the temperature and maintain the catalyst temperature at a predetermined temperature, the operation is performed with an output air-fuel ratio or an air-fuel ratio richer than the output air-fuel ratio, a so-called power air-fuel ratio. In this case, the effective injection time is calculated by correcting the basic injection time that matches the theoretical air-fuel ratio with the power increase correction coefficient. As a fuel injection control method using such a power increase correction coefficient, for example, as described in Japanese Patent Laid-Open No. 5-39738, a large value corresponding to a low engine speed and a high engine speed is provided. It is known that the power increase correction coefficient and the power increase correction coefficient having a small value are stored, and one of them is read according to the engine speed in the case of a high load to calculate the effective injection time. There is. Generally, such a power increase correction coefficient is
The two-dimensional map is defined by the engine speed and the intake air amount, and the air-fuel ratio becomes richer as the engine speed becomes higher and the intake air amount becomes larger.

[0003]

By the way, in a vehicle equipped with an automatic transmission (hereinafter referred to as "A / T"), when the accelerator pedal is greatly depressed to accelerate, it is called a kickdown in which the engine speed rapidly changes. The phenomenon occurs. In this case, in the configuration of the above publication, the power increase correction coefficient changes abruptly as the engine speed changes, and as a result, the fuel injection amount increases.

However, even if the engine is in such a high rotation state, the temperature of the catalyst does not change following it but rises with a certain time delay. Therefore, if the fuel injection amount is corrected with the power increase correction coefficient for the purpose of suppressing the temperature rise of the catalyst and protecting the catalyst, the air-fuel ratio becomes overrich before the temperature rise is suppressed, resulting in efficient fuel consumption. May not be possible. Further, since the air-fuel ratio becomes overrich, the purification of CO and HC deteriorates, and the emission may not be maintained almost the same as the stoichiometric air-fuel ratio.

[0005] An object of the present invention is to solve such a problem.

[0006]

In order to achieve the above object, the present invention takes the following measures. That is, the fuel injection control method according to the present invention calculates the basic fuel injection amount based on at least the engine speed of the engine including the catalyst in the exhaust system, and at the time of high load operation, based on at least the engine speed. A fuel injection control method that determines the final fuel injection amount by correcting the basic fuel injection amount by the power increase set by the above, and detects the engine speed and determines the power based on the detected engine speed. When the power increase is set, it is detected that the set power increase is increasing with the passage of time, and when the power increase is increasing, the basic fuel injection amount is detected at least as the previously set power increase. Based on the power increase set based on the engine speed and the power increase that is gradually increased, the basic fuel injection is performed by the gradually increased power increase. And correcting the.

[0007]

With this structure, when the power increase set based on the engine speed increases with time, the basic fuel injection amount is corrected by the gradually increased power increase. To be done. In other words, if the engine speed suddenly rises and the power increase set with it increases from the previous time, the basic fuel injection amount is set by the power increase set based on the sharply increased engine speed. It does not correct. For this reason,
The fuel injection amount does not suddenly become large corresponding to the engine speed. As a result, wasteful fuel is not injected for cooling the catalyst, fuel efficiency does not decrease, and unnecessary overrich states can be eliminated, so emission does not deteriorate.

[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. In the vicinity of the cylinder head 30 side end of the intake manifold 4 of the intake system 1 communicating with the surge tank 3, a fuel injection valve 5 is further provided.
An intake valve 31 is provided 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). The O ₂ sensor 21 outputs a voltage signal h corresponding to the oxygen concentration. The engine is combined with an automatic transmission and mounted on a vehicle. The automatic transmission has, for example, four speeds and may be widely known in this field.

The electronic control unit 6 includes a central processing unit 7
An A / D converter (not shown) mainly composed of a microcomputer system including a memory device 8, an input interface 9, and an output interface 11 for converting an input analog signal into a digital signal. Is built in. The input interface 9 has an intake pressure sensor 1 for detecting the pressure in the surge tank 3, that is, the intake pipe negative pressure (hereinafter referred to as intake pressure).
3, an intake pressure signal a output from the engine 3, a rotational speed signal b output from the rotational speed sensor 14 to detect the engine rotational speed NE, a vehicle speed signal c output from a vehicle speed sensor 15 to detect the vehicle speed, and a throttle. A throttle switch 16 has a power switch 16a that outputs a full-open signal fs when the valve 2 is fully open, and a throttle opening signal d and a full-open signal fs output from a throttle sensor 16 for detecting the open / closed state of the throttle valve 2. The water temperature signal e output from the water temperature sensor 17 for detecting the cooling water temperature of the engine, the voltage signal h output from the O ₂ sensor 21, and the like are input. On the other hand, the output interface 11 outputs a fuel injection signal f corresponding to an effective injection time TAU described later to the fuel injection valve 5 and an ignition pulse g to the spark plug 18.

The electronic control unit 6 has an intake pressure signal a output from the intake pressure sensor 14 and a rotation speed signal b output from the rotation speed sensor 15 as main information, and is determined according to the rotation state of the engine. Various correction factors including a power increase correction factor FPOWER, for example, a post-starting amount increase correction factor FSE,
The basic injection time TP is corrected by the warm-up increase correction coefficient FWL, the air-fuel ratio feedback correction coefficient FAF, etc. to set the fuel injection valve opening time, that is, the effective injection time TAU, and the fuel injection valve 5 is controlled by the set time. The fuel corresponding to the engine load from the fuel injection valve 5 to the cylinder head 30.
A program for injecting into the nearby intake system 1 is built in. The calculation of the effective injection time TAU may be performed, for example, by the following formula.

TAU = TP * FAF * FWL * FPOWER + FSE Further, in this program, the engine speed is detected, the power increase is set based on the detected engine speed, and the set power increase increases with time. When the power increase is increasing, the basic fuel injection amount is gradually increased based on at least the previously set power increase and the power increase set based on the engine speed detected this time. Is programmed to correct the basic fuel injection amount by gradually increasing the power increase.

The outline of this fuel injection control program is as shown in FIG. However, as the program itself for calculating the effective injection time TAU in consideration of various correction factors during steady operation, a conventionally known program can be used, and therefore illustration and description thereof will be omitted. This program is provided with a power increase two-dimensional map as data in order to set the power increase correction coefficient FPOWER. The power increase two-dimensional map, as schematically shown in FIG. 3, shows the engine rotation speed in a predetermined operation range, that is, in an area exceeding the predetermined operation range of the engine speed NE and the intake pressure PM. The number NE and the intake pressure PM are set as parameters, and the higher the engine speed NE, the higher the intake pressure PM and the higher the load, the larger the basic power increase correction coefficient PWBASE is set. is there.

In step S1 of this program, the effective injection time TAU is detected to be calculated, and the engine speed NE which is stored in the storage device 8 until the next detection and can be read when necessary is read. . Similarly, in step S2, the intake pressure PM is read. Step S
In 3, the read engine speed NE and intake pressure PM
Therefore, the basic power increase correction coefficient PWBASE is determined by the power increase two-dimensional map. The method of determining the basic power increase correction coefficient PWBASE is not limited to that of this embodiment, but may be calculated by using the engine speed NE and the intake pressure PM as parameters. Next, in step S4, the previous power increase correction coefficient FPOWER is compared with the basic power increase correction coefficient PWBASE determined in step S3 this time. If the basic power increase correction coefficient PWBASE is large, the process proceeds to step S5, and the small If it is, the process proceeds to step S6.
That is, it is detected that the power increase correction coefficient FPOWER is increasing depending on whether the engine speed NE increases or the intake pressure PM increases. In step S5, the power increase correction coefficient FPOWER is calculated by the following equation.
Perform an averaging calculation.

FPOWER _m = [{FPOWER _m-1 x
(N-1)} + PWBASE _m ] ÷ n where m and n are positive integers In this embodiment, the power increase correction coefficient FPOWE of this time
R _m is multiplied by the power increase correction coefficient FPOWER _{m− 1} used in the calculation of the effective injection time TAU last time, which is 1 less than the smoothing coefficient n, and the product is multiplied by the basic power correction coefficient PWBASE _m determined this time. In addition, the sum is divided by the smoothing coefficient n to calculate. The moderation calculation method is not limited to the one shown in the above equation, and in the case of the condition in step S4, the power increase correction coefficient FPOWER
It suffices if the calculation is such that In step S6, the power increase correction coefficient FPOWER _m for this time is set as
The basic power increase correction coefficient PWBASE _m determined this time is set.

In such a structure, as shown in FIG. 4, the throttle valve 2 is suddenly opened greatly, the intake pressure PM is greatly changed stepwise, and then the engine speed NE is gradually increased and then kicked down. The operating state that sharply rises will be described. First, when the accelerator pedal is depressed to accelerate and the throttle valve 2 is opened to almost full opening, the operating state is the power air-fuel ratio for performing power increase correction from the feedback control region based on the voltage signal h output from the O ₂ sensor 21. Move to the control area. At this time, the control executes steps S1 to S3,
The basic power increase correction coefficient PWBASE _m for this time is determined. Before this time point, the intake pressure PM was in the feedback control region, so the previous power increase correction coefficient FP
OWER _{m- 1} is 0, on the other hand, the basic power boost correction coefficient PWBASE _m according to the intake pressure PM is set this time, and it is determined that the basic power boost correction coefficient PWBASE _m is large in step S4. . In the post-control, step S5 is executed, and the smoothing process is performed to determine the power increase correction coefficient FPOWER _m for this time. Then, the basic injection time TP is corrected by the power increase correction coefficient FPOWER _m this time, and the effective injection time TAU is calculated.

After that, since the engine speed NE gradually increases, the basic power increase correction coefficient PWBASE _m becomes larger than the previous power increase correction coefficient FPOWER _m-1 every time. Therefore, the control is executed by repeating steps S1 to S5, and the amount of power increase effectively acting for the smoothing process gradually increases. Then, when the engine speed NE rises to some extent, the intake pressure PM is still maintained at a high level, so that the automatic transmission undergoes kickdown, and the engine speed NE changes in a substantially stepwise manner. Even in this state, the basic power increase correction coefficient PWBASE _m of this time becomes larger than the power increase correction coefficient FPOWER _{m- 1 of the} previous time, so the control is performed by executing steps S1 to 5 and the power increase correction coefficient which is annealed. Calculate FPOWER _m .

Therefore, as shown by the dotted line in FIG. 4, when the intake pressure PM and the engine rotational speed NE change abruptly, the power increase does not change rapidly following the changes, but is indicated by the solid line. Then, the change gradually increases. Therefore, since the fuel injection amount does not suddenly increase, the three-way catalyst 22
Is no longer cooled in accordance with changes in intake pressure PM and engine speed NE, and quickly converges to a steady-state temperature. Moreover, since the amount of power increase is gradually increased, the increase in catalyst temperature can be suppressed within an allowable range that does not impair its performance even during acceleration. As a result, it is possible to prevent deterioration of fuel consumption and prevent deterioration of emission.

The present invention is not limited to the embodiment described above, but may be applied to an engine equipped with a manual mission. The power enrichment coefficient FPOWER, as described above, instead of the smoothing calculation, by adding a predetermined value to the calculated basic power enrichment coefficient PWBASE determining the current power enrichment coefficient FPOWER _m It may be one.

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.

[0021]

As described above in detail, according to the present invention, when the power increase set based on the engine speed increases with the lapse of time, the basic fuel injection amount gradually increases. Since it is corrected by increasing the power, the fuel injection amount does not suddenly become large corresponding to the engine speed, and as a result, unnecessary fuel is not injected for cooling the catalyst and fuel consumption is reduced. Can be prevented. Moreover, since unnecessary overrich can be eliminated, deterioration of emission can be prevented.

[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 graph schematically showing a power increase two-dimensional map of the same example.

FIG. 4 is an operation explanatory view of the same embodiment.

[Explanation of symbols]

 1 ... Intake system 2 ... Throttle valve 5 ... Fuel injection valve 6 ... Electronic control unit 7 ... Central processing unit 8 ... Memory device 9 ... Input interface 11 ... Output interface 20 ... Exhaust system 22 ... Three-way catalyst

Claims (1)

[Claims] 1. A basic fuel injection amount is calculated based on at least the engine speed of an engine equipped with a catalyst in an exhaust system, and during high load operation, a power increase set at least based on the engine speed is used. This is a fuel injection control method that determines the final fuel injection amount by correcting the basic fuel injection amount, detects the engine speed, and sets and sets the power increase based on the detected engine speed. It detects that the power increase is increasing with time, and when the power increase is increasing, the basic fuel injection amount is set based on at least the previously set power increase and the engine speed detected this time. It is characterized by setting a power increase that gradually increases based on the power increase that is performed and correcting the basic fuel injection amount by the gradually increasing power increase. Fuel injection control method.