JPH0833120B2 - Electronically controlled fuel injection device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an electronically controlled fuel injection device for an internal combustion engine,
In particular, the present invention relates to a device that performs transient correction based on the change amount of the basic fuel injection amount.

<Prior Art> Conventionally, in an electronically controlled fuel injection device for an internal combustion engine, an intake air flow rate Q is detected as a state quantity of intake air, and from this and an engine speed N, a basic fuel injection amount Tp = K · Q. / N (K
Is a constant), or as the state quantity of intake air,
The intake pressure (intake negative pressure) PB is detected, and the basic fuel injection amount Tp is calculated based on this. The method based on the intake air flow rate Q is called L JETRO, and the method based on the intake pressure PB is called D JETRO. Then, the final fuel injection amount Ti = Tp * COEF * LAMBDA + Ts is calculated by making corrections by various correction coefficients COEF based on the water temperature and the like, the air-fuel ratio feedback correction coefficient LAMBDA and the voltage correction amount Ts based on the battery voltage.

Then, a drive pulse signal having a pulse width corresponding to the fuel injection amount Ti is output to the electromagnetic fuel injection valve at a predetermined timing that is a cycle of engine rotation, thereby injecting and supplying fuel to the engine.

However, the fuel injection amount Ti corresponds to the engine demand during steady operation, and during transient operation, for example, during acceleration, the air-fuel ratio becomes lean due to transport delay of liquid fuel (wall flow) adhering to the inner wall of the intake passage. Therefore, the engine output did not follow the response with good response during acceleration, and the acceleration performance deteriorated.

Therefore, as described above, the basic fuel injection amount Tp calculated based on the intake air flow rate Q or the intake pressure PB, or the change amount of the basic fuel injection amount Tp calculated from the throttle valve opening TVO and the engine speed N is used. The transient correction amount is set based on this, and the final fuel injection amount Ti is calculated using this transient correction amount, so that the air-fuel ratio control accuracy and output response during transient operation including not only acceleration but also deceleration It has been proposed to improve the above (see Japanese Patent Laid-Open No. 1-125532, etc.).

<Problems to be Solved by the Invention> However, in the system having the transient correction function based on the change amount of the basic fuel injection amount Tp, the basic fuel injection amount (engine load )
Since the transient determination is made based on the fluctuation of the above and the transient correction is performed, the following problems occur due to the transient correction at the time of starting and idling.

That is, at the time of starting, the fuel injection control is performed in which the fuel amount is gradually decreased after the fuel amount is increased, but a transient determination (deceleration determination) is performed for this fuel amount reduction, and further fuel reduction direction is performed by the deceleration amount reduction correction. Since the air-fuel ratio is controlled, it takes a long time for the air-fuel ratio to converge to the ideal air-fuel ratio, and a start-up failure easily occurs due to the lean air-fuel ratio.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electronically controlled fuel injection device for an internal combustion engine, which has a deceleration correction function based on the engine load change amount and which has good startability.

<Means for Solving the Problems> Therefore, according to the present invention, as shown in FIG. 1, an electronic control unit for an internal combustion engine in which the fuel injection amount at the time of starting the engine is increased and the fuel injection control at the time of starting is gradually reduced is performed. In the control fuel injection device, an intake air state amount detecting means for detecting a state amount of intake air sucked into the engine, a basic fuel injection amount calculating means for calculating a basic fuel injection amount based on the state amount of the intake air, A deceleration reduction control unit that performs a reduction correction of the fuel injection amount according to the deceleration state of the engine based on the change amount of the basic fuel injection amount, an engine start detection unit that detects the start of the engine, and an engine start to start time. A deceleration amount reduction correction inhibiting unit that inhibits the fuel amount reduction correction by the deceleration amount reduction correction unit is provided for a certain period including the period in which the fuel injection control is performed.

<Operation> In such a configuration, when the engine start detecting means detects the engine start, the amount of change in the basic fuel injection amount during a certain period including the period from the engine start to the start fuel injection control is performed. The deceleration / weight reduction correction based on After a lapse of a certain period, the basic fuel injection amount calculation means calculates the basic fuel injection amount based on the state quantity of the intake air drawn into the engine detected by the intake air state quantity detection means. The prohibition of fuel deceleration reduction correction
The deceleration reduction amount correction means performs the reduction correction of the fuel injection amount during deceleration.

<Example> An example of the present invention (in the case of L-JETRO) will be described below with reference to the drawings.

In FIG. 2, in the engine 1, the air cleaner 2
Air is sucked through a throttle valve 3 that interlocks with an accelerator pedal, an auxiliary air control valve 5 provided in an auxiliary air passage 4 that bypasses the throttle valve 3, and an intake manifold 6.

In each branch of the intake manifold 6, a fuel injection valve 7 is provided for each cylinder. The fuel injection valve 7 is an electromagnetic fuel injection valve that is energized by a solenoid to open the valve, is deenergized, and is closed. The fuel injection valve 7 is energized by a drive pulse signal from a control unit 8 described later to open the valve, and a fuel not shown Fuel that is pumped and adjusted to a predetermined pressure by a pressure regulator is injected.

Further, a spark plug 9 is provided in the combustion chamber of the engine 1 to spark-ignite and ignite and burn the air-fuel mixture.
Control unit 8 consists of CPU, ROM, RAM, A / D converter,
A microcomputer including an input / output interface is provided, and arithmetic processing is performed based on input signals from various sensors to control the operation of the fuel injection valve 7, the auxiliary air control valve 5, and the spark plug 9. However, in the following, the fuel injection valve 7
Only the control of the fuel injection amount by will be described.

As the various sensors, a hot-wire type air flow meter 10 is provided in the intake passage upstream of the throttle valve 3 to detect the intake air flow rate Q. In the case of D JETRO, an intake pressure sensor is provided in the intake manifold to detect the intake pressure (intake negative pressure) PB.

Further, the crank angle sensor 11 is provided, and in the case of, for example, four cylinders, it outputs the reference signal REF for each crank angle of 180 ° and the unit signal POS for each crank angle of 1 to 2 °. Here, the engine rotation speed N can be calculated by measuring the cycle of the reference signal REF or the number of generated unit signals POS within a predetermined time.

Further, the throttle valve 3 is provided with a potentiometer for detecting the throttle valve opening TVO and a throttle sensor 12 including an idle switch 12A which is turned on at its fully closed position (idle position).

Further, an O ₂ sensor 14 is provided in the exhaust manifold 13 of the engine 1 to detect rich / lean of the air-fuel ratio via the oxygen concentration in the exhaust.

A water temperature sensor 15 is provided so as to face the water jacket of the engine 1 to detect the engine cooling water temperature Tw.
Reference numeral 16 is a starter switch as an engine start detecting means for turning on the engine to start the engine when the engine is started.

In the present embodiment, the functions as the basic fuel injection amount calculation means, the deceleration reduction amount correction means, and the deceleration reduction amount prohibition means are provided by software as shown in the flowcharts of FIGS. 3 and 4. . Further, in the present embodiment, in addition to the basic fuel injection amount Tp based on the intake air flow rate detected by the air flow meter 10, the basic fuel injection amount αNTp based on the throttle valve opening TVO and the engine rotation speed N is calculated. However, the deceleration amount reduction correction is performed based on the change amount of αNTp.

Next, the fuel injection amount control of this embodiment performed by the control unit will be described with reference to the flowcharts of FIGS. 3 and 4.

In step 1 (indicated by S1 in the figure, the same applies hereinafter), various signals such as signals from various sensors and signals from the starter switch 16 are input.

In step 2, it is determined whether the starter switch 16 is ON. When the starter switch 16 is ON, it is determined that the engine has started and the routine proceeds to step 3.

In step 3, the deceleration reduction correction at the time of engine start is prohibited, and the fuel injection amount control without the deceleration reduction correction is executed.

On the other hand, the starter switch 16 is turned off in step 2.
When it is determined that the value of the value is 0, the process proceeds to step 4.

In step 4, the deceleration reduction correction prohibition time t ₀ after engine start set based on the engine cooling water temperature at this time detected based on the signal from the water temperature sensor 15 and the starter switch 16 are turned off. The time elapsed from the time point t is compared. Then, while t <t _0, the routine proceeds to step 3, where the deceleration reduction correction is prohibited, and when t ≧ t ₀ , the routine proceeds to step 5.

In step 5, the deceleration amount reduction correction is executed as shown in the flowchart of FIG.

In step 6, a pulse output corresponding to the determined final fuel injection amount Ti is generated.

Next, the deceleration / reduction correction control of this embodiment will be described with reference to the flowchart of FIG.

In step 11, various signals such as the opening degree TVO of the throttle valve 3 detected by the throttle sensor 12 and the engine speed N calculated based on the signal from the crank angle sensor 11 are input.

In step 12, the opening area A of the engine intake system is searched and obtained from the map preset in the ROM of the microcomputer based on the throttle valve opening TVO input in step 11. In setting the opening area A, the auxiliary air passage 4 variably controlled by the auxiliary air control valve 5 is used.
The opening area and the opening area of the passage controlled by the air regulator (not shown) are also set.

In step 13, A / N is calculated based on the value A / N obtained by dividing the opening area A obtained in step 12 by the engine rotation speed N.
The basic volumetric efficiency QHφ corresponding to is searched and obtained from the map preset in ROM.

In step 14, the basic volumetric efficiency QHφ obtained in step 13 is multiplied by the coefficient C to calculate the basic fuel injection amount αNTp based on the opening area A of the intake system.

In step 15, the current αNT obtained in step 14 above
The change amount ΔαNTp of the basic fuel injection amount αNTp is calculated from the difference between p and αNTp obtained last time.

In step 16, the reduction correction amount D corresponding to the change amount ΔαNTp of the basic fuel injection amount obtained in step 15 is preliminarily stored in the ROM.
Search from the map set in.

In step 17, the basic fuel injection amount Tp is calculated from the intake air flow rate Q obtained by the air flow meter 10 and the engine rotation speed N.

In step 18, the basic fuel injection amount Tp obtained in step 17 is obtained from various correction coefficients COEF set based on operating conditions such as engine temperature and the oxygen concentration in the exhaust gas detected by the O ₂ sensor 14. The final fuel injection amount is corrected by the feedback correction coefficient LAMBDA, which is set based on the air-fuel ratio, and is further corrected by adding the reduction correction amount D obtained in step 16 and the battery voltage correction amount Ts. Calculate Ti.

Therefore, at the time of engine start and during a certain period after start,
Since the deceleration reduction amount correction is prohibited, the fuel injection amount Ti that does not add the reduction amount correction amount D is injected and supplied, and after the lapse of the certain period, the deceleration amount reduction correction is executed and the fuel injection amount D is added. A quantity Ti will be injected and supplied.

In this way, at engine start and for a certain period after start,
If the deceleration reduction correction is prohibited, even if the fuel injection amount is reduced after the start, the deceleration reduction correction based on this will not be performed as in the conventional case, which may result in a start failure due to a lean air-fuel ratio. The engine startability is improved.

If the basic fuel injection amount obtained based on the opening area of the intake system is adopted in obtaining the reduction correction amount D as in this embodiment, the basic fuel injection amount based on the detected intake air flow rate of the air flow meter 10 is used. As compared with the case of using, the reduction correction amount can be set more accurately without being affected by the intake pulsation and the like.

<Effects of the Invention> In an internal combustion engine in which the fuel injection amount at the time of starting the engine is increased and the fuel injection control at the time of starting the engine is gradually reduced, a fixed period including the period from the engine start to the time fuel injection control at the start is performed. During this period, the deceleration reduction correction based on the amount of change in the engine load is prohibited, so that leaning of the air-fuel ratio due to the reduction in the fuel injection amount due to the fuel injection control during startup can be suppressed and engine startability can be suppressed. Can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a configuration of the present invention, FIG. 2 is a system schematic diagram showing an embodiment of the present invention, and FIGS. 3 and 4 are diagrams showing an embodiment of the present invention. It is a flow chart which shows control contents. 1 ... Engine, 3 ... Throttle valve, 7 ... Fuel injection valve,
8 ... Control unit, 10 ... Air flow meter, 11 ... Crank angle sensor, 12 ... Throttle sensor, 12A ... Idle switch, 16 ... Starter switch

Claims (1)

[Claims] 1. An electronically controlled fuel injection device for an internal combustion engine in which a fuel injection control at startup is performed in which the fuel injection amount is increased at the time of engine startup and then gradually reduced and corrected, and the state quantity of intake air drawn into the engine is detected. Intake air state quantity detection means, basic fuel injection quantity calculation means for calculating the basic fuel injection quantity based on the intake air state quantity, and fuel depending on the deceleration state of the engine based on the change quantity of the basic fuel injection quantity. Deceleration amount reduction correction means for performing injection amount reduction correction, engine start detection means for detecting engine start, and the deceleration amount reduction correction for a fixed period including a period during which the engine fuel injection control is performed after engine start. An electronically controlled fuel injection device for an internal combustion engine, comprising: deceleration reduction correction inhibiting means for inhibiting fuel reduction correction by the means.