JPH02308938A - Fuel control method for engine - Google Patents

Abstract

PURPOSE:To prevent occurrence of an engine stall and deterioration of a drivability, by holding the volume of fuel at a decreased value for deceleration or fuel cut-off for a predetermined period while inhibiting an increment compensation for the predetermined period. CONSTITUTION:After deceleration being initiated from the time of full open of a throttle valve, since the volume of fuel is held at a decreased value for deceleration or a fuel cut-off is continued for a predetermined period, fuel is sufficiently restricted or fuel is surely cut off until the engine rotational speed lowers down to a value in the vicinity of an idle rotational speed. Further, since a fuel increment compensation is inhibited during the time period even though an abrupt drop in engine rotational speed occurs, it is possible to easily restrain the air/fuel ratio from being turned into an over-rich condition at a time in the vicinity of the later half of the deceleration. Meanwhile, after the set time elapsing, a decrease in fuel volume and a fuel cut-off are inhibited at once, and a fuel increment compensation is at once made if the engine rotational speed is abruptly dropped by a value greater than a set value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an engine fuel control method that can be suitably employed in automobiles and the like equipped with automatic transmissions using torque converters and the like.

[Prior art] In an engine equipped with an electronically controlled fuel injection device, during deceleration with the throttle valve fully closed, in order to prevent catalyst overheating and save fuel, ■ If the engine speed exceeds the set speed. Usually, the fuel is decelerated and reduced or the fuel is cut.

In addition to such a configuration, as a prior art of the present invention, for example, as shown in Japanese Patent Application Laid-Open No. 6049-6049, there is a technique in which the engine speed is lower than the set speed during deceleration with the throttle valve fully open. If the amount of drop in engine speed is twice below a predetermined value in a region where the engine speed is below, the amount of fuel supplied is increased to prevent a sudden drop in engine speed near idle speed. There are also examples.

[Problem to be Solved by the Invention] However, in an engine equipped with a hydraulic automatic transmission, as schematically shown in Fig. 5, rapid deceleration is performed by returning the throttle valve to the fully open position (idle switch ON). and,
Unlike the rotation drop (see double-dashed line) in the case of an engine equipped with a manual transmission, the engine rotation speed (E/G rotation speed) rapidly drops to idle rotation. At this time, when the engine speed reaches a set rotation speed such as the prohibition speed for deceleration reduction or the fuel cut return speed, the deceleration reduction, etc. of fuel is immediately prohibited by the control (2). Then, as the engine speed decreases thereafter, the fuel increase correction is immediately started by the control (2), so that the amount of fuel supplied becomes excessive with respect to the actual required amount.

That is, during such deceleration, it is preferable to gradually increase the amount of fuel as the engine rotation approaches the idle rotation, as indicated by the dashed line in the figure.

However, in reality, the fuel is rapidly restored during deceleration, so the engine speed approaches the idle speed (as a result, the air-fuel ratio A/F becomes overrich).
(See the shaded area), CO, HC, etc. in the exhaust gas increase, worsening emissions during deceleration. Furthermore, due to misfires caused by over-rich engine speed, the engine speed easily becomes less than the idle speed, increasing the risk of engine stalling and deterioration of drivability.

The present invention aims to eliminate such problems.

[Means for Solving the Problems] In order to achieve the above object, the present invention performs deceleration reduction or fuel cut of fuel during deceleration with the throttle valve fully open, and also performs fuel deceleration reduction or fuel cut in an area where deceleration fuel reduction or fuel cut is prohibited. In the engine fuel control method, the fuel supply amount is increased when the engine speed decreases below a predetermined value, after the throttle valve returns to the idling position. The present invention is characterized in that the fuel deceleration reduction or fuel cut continues during this period, and the increase correction is prohibited during this period.

Note that the time it takes for the engine rotation to drop to idle rotation after the throttle valve is returned to the fully closed state is approximately a constant time t in a car with an automatic transmission. It becomes. Therefore, it is desirable that the set time be set near the end of the deceleration state, taking this time into account.

[Function] According to this configuration, after the throttle valve is fully opened and deceleration has started, fuel deceleration reduction and fuel cut continue for the set time, so the engine speed remains close to idle speed. The fuel supply amount will be sufficiently reduced or the fuel cut will be performed reliably until the vehicle descends to . During that time, even if there is a rapid drop in engine speed, fuel increase correction is prohibited, making it easier to suppress the air-fuel ratio from rapidly changing to over-rich in the latter half of deceleration.

On the other hand, once the set time has elapsed, fuel deceleration reduction and fuel cut are immediately prohibited, and if the engine speed exceeds the set value and is rapidly decreasing, fuel increase correction is performed immediately. , there will be no fuel shortage near idle speed.

"Embodiment" An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

The engine schematically shown in FIG. 1 is used in an automobile, and includes an electronically controlled fuel injection device 1 and an automatic transmission (not shown) using a torque converter or the like. The electronically controlled fuel injection device 1- includes a fuel injection valve 3 attached to an intake pipe 2, and an electronic control device 4 that adjusts the amount of fuel injected from the fuel injection valve 3 according to engine conditions. Various information for adjusting the fuel injection amount and the like is input to the electronic control device 4.

The fuel injection valve 3 has a built-in electromagnetic coil, and when the fuel injection signal a is applied to the electromagnetic coil from the electronic control device 4, it injects fuel in an amount corresponding to the application time into the vicinity of the intake port. It is structured as follows.

The electronic control device 4 includes a central processing unit 5 and a memory 6.
, an input interface 7, and an output interface 8; A signal d from the switch 11, a vehicle speed signal e from the vehicle speed sensor 12 for detecting the vehicle speed, a water temperature signal from a water temperature sensor (not shown) for detecting the warm-up state of the engine, etc. are inputted, respectively. It has become so. The crank angle sensor 9 is configured to output an electrical signal corresponding to the engine speed and crank angle, and is provided in the distributor 13. The pressure sensor 10 is attached to the surge tank 14 and is configured to output an electrical signal according to intake pipe pressure. The idle switch 11 is 0N, which is turned on when the throttle valve 15 is in the idling position and turned off when it is in the non-idling position.
- It is an OFF switch and is connected to the throttle shaft 16. On the other hand, the output interface 8 outputs a fuel injection signal a toward the fuel injection valve 3.

In addition, this electronic control device 4 is provided with a function shown schematically in FIGS. 2 and 3 in order to increase or decrease the amount of fuel supplied during a transient period in response to changes in intake pipe pressure, engine speed, etc. Set up the program as shown.

First, in step 51 in FIG. 2, the amount of change in intake pipe pressure is determined from the difference between the latest intake pipe pressure and the intake pipe pressure before a predetermined rotation, and the transient air-fuel ratio correction coefficient KF is calculated in accordance with the amount of change. Determine, and proceed to step 52. When the engine is accelerating, the transient air-fuel ratio correction coefficient KF increases in accordance with the acceleration state, and during deceleration, the transient air-fuel ratio correction coefficient KF decreases in accordance with the deceleration state. In step 52, the idle switch 11 is turned on, and the elapsed time t since the idle switch 11 is turned on is equal to the set time 1.
1 (11<1°).

If these conditions are not met, proceed to the main routine; if these conditions are met, proceed to step 5.
Proceed to step 3. In step 53, the transient air-fuel ratio correction coefficient K
Set F to O and proceed to the main routine.

-'l - On the other hand, in step 61 in FIG. 3, the amount of change in engine speed (INEN-NEO+
), and if the amount of change (l NEN - NEOl) exceeds a predetermined value (for example, 40 rpm),
The corresponding value FNE (variables before and after including 1) is set as the idle stabilization correction coefficient KL, and the process proceeds to step 62.

For example, if the amount of change (l NEN - NEOl) is twice the predetermined value when the engine speed is in a decreasing state, the idle stabilization correction coefficient KL becomes a value larger than 1, and the engine speed It is set to 1 if there is no change in .

When the engine rotation is in an increasing state, the amount of change (l
If NEN - NEOl') exceeds the predetermined value, the idle stabilization correction coefficient KL will be a value smaller than 1. In step 62, the idle switch 11- is turned to OFF.
The elapsed time t since it became N is the set time 12 (12<
1°), and if it is determined that it has reached j-, the process moves to the main routine; if it is determined that it has not reached it, the process proceeds to step 63. In step 63, the idle stabilization correction coefficient KL is set to 1.0, and the process proceeds to the main routine.

In the predetermined routine, fuel injection ff1T to be supplied from the fuel injection valve 3 is determined based on the above processing results. That is, the basic injection -i1'P determined based on the engine speed, intake pipe pressure, etc. is corrected using the transient air-fuel ratio correction coefficient KF, the idle stabilization correction coefficient KL, and various correction coefficients determined according to the engine situation. Then, the fuel injection amount T is determined. Next, the fuel injection valve 3 is opened for a time corresponding to the determined fuel injection amount of 1'' to supply fuel to the combustion chamber 17. Note that the above control is repeatedly executed while the engine is operating.

According to such a configuration, as schematically shown in FIG. 4, when the throttle valve 15 is returned to the fully closed state (idle switch 1 is ON), the intake pipe pressure rapidly changes accordingly. Therefore, the transient air-fuel ratio correction coefficient I<F decreases according to the amount of change. During the set time t2 after the throttle valve 15 is closed, the idle stabilization correction coefficient KL is set to 1°0, so the amount of fuel supplied to the combustion chamber 17 increases as the intake air amount decreases. The amount of deceleration will be reduced.

On the other hand, when the set time t has elapsed after the throttle valve 15 was closed, the transient air-fuel ratio correction coefficient KF'' is set to 0, and deceleration reduction of fuel is prohibited. If the vehicle is descending rapidly, the idle stabilization correction coefficient KL is set to a value greater than 1 immediately after the set time t2 has elapsed, so that the fuel increase correction is immediately performed.

Therefore, according to such a configuration, during deceleration with the throttle valve fully open, the fuel supply amount can be sufficiently reduced depending on the deceleration state while the engine speed drops to near idling speed, so that during the second half of deceleration, the fuel supply amount can be sufficiently reduced depending on the deceleration state. It is possible to effectively prevent the air-fuel ratio from changing to over-rich in the vicinity. As a result, deterioration of emissions during deceleration can be suppressed, and overheating of the catalyst can be prevented and fuel can be saved.

In addition, when the engine speed drops to near the idle speed, the amount of fuel is adjusted to increase according to the degree of fall in the engine speed, which may cause problems such as the engine speed falling below the idle speed due to a delay in the return of fuel. Without a doubt,
It can be smoothly lowered to idle speed. In this case, there is a time when the air-fuel ratio becomes slightly Olverrich near the end of deceleration, but the time is very small compared to the conventional example. Therefore, in order to reliably prevent engine stall during deceleration and to ensure idle stability, a slight overrich portion near the end of deceleration as described above is necessary.

Note that although the second embodiment is a case in which the amount of fuel is reduced during deceleration within a set time during deceleration, the present invention is also applicable to a case where fuel is cut during deceleration.

Further, the time for deceleration reduction or fuel cut of fuel and the time for prohibiting fuel increase correction may be made different.

[Effects of the Invention] According to the present invention configured as described above, it is possible to effectively prevent deterioration of emissions during deceleration and deterioration of drivability when transitioning from deceleration to idle speed, and also to reduce engine speed. It is possible to provide an engine fuel control method with excellent control accuracy that can smoothly converge to idle rotation.

[Brief explanation of drawings]

1 to 4 show one embodiment of the present invention, FIG. 1 is a schematic overall configuration diagram, FIGS. 2 and 3 are flowcharts showing control procedures, and FIG. 4 is an explanatory diagram of the operation. It is. FIG. 5 is an explanatory diagram of the operation of a conventional example. 1...Electronically controlled fuel injection device 3...Fuel injection valve 4...Electronic control device 9...Crank angle sensor 10...Pressure sensor 11...Idle switch 15...Thrower I/Rubalp 1. 1. ,···set time

Claims (1)

[Claims] Deceleration reduction of fuel or fuel cut is performed during deceleration with the throttle valve fully closed, and the fuel supply amount is reduced when the amount of decrease in engine speed exceeds a predetermined value in a region where deceleration reduction of fuel or fuel cut is prohibited. In the engine fuel control method that performs an increase correction, after the throttle valve returns to an idling position, the fuel deceleration reduction or fuel cut is continued for a set time, and the increase correction is prohibited during that time. An engine fuel control method characterized by: