JPH0428895B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel injection amount control method for an internal combustion engine, and in particular to an internal combustion engine suitable for controlling an engine using a fuel injection amount increase value immediately after engine startup. The present invention relates to a fuel injection amount control method.

[Conventional technology]

In vehicles such as automobiles, the basic value of the fuel injection amount, that is, the basic fuel injection amount, is set from the engine load such as the intake air amount and the engine speed, and this sets the air-fuel ratio to the target air-fuel ratio, for example, the stoichiometric air-fuel ratio. It has conventionally been done to control the fuel injection amount so that

By the way, immediately after starting the engine, the temperature of the intake manifold, etc. is low, and the amount of fuel adhering to the intake manifold, etc. is small. etc., and thus,
There is a problem in that the amount of fuel injected into the engine cylinder is reduced, the air-fuel ratio becomes leaner than the target air-fuel ratio, and the engine speed decreases, resulting in poor engine startability.

Therefore, it has conventionally been done to increase the basic fuel injection amount determined from the engine load and engine speed immediately after the engine is started. For example, there is known a system that performs an increase correction in accordance with the engine water temperature immediately after the engine starts, as described in Japanese Unexamined Patent Publication No. 19962/1983.

In the above publication, at the time of starting, the fuel increase value is determined according to the engine water temperature, and after the start, the fuel increase value is changed according to the amount of change in the engine water temperature per unit time.

However, in the above method, it is difficult to appropriately determine the fuel increase value. That is, when fuel injection is repeated, fuel adhering to the intake manifold etc. accumulates, and therefore the evaporation rate from the fuel adhering to the intake manifold etc. increases, thus reducing the mixture supplied into the engine cylinders. The degree of leanness of the air-fuel ratio relative to the target air-fuel ratio decreases. By the way, in the above method, the fuel increase value is changed according to the amount of change in the engine water temperature, and changes in the amount of fuel adhering to the intake manifold etc. are not considered, so it is difficult to properly determine the fuel increase value. It was difficult. In other words, compared to the change in the amount of fuel adhering to the intake manifold, the change in engine water temperature is gradual.
The decay of the fuel increase value is slow, and thus the air-fuel ratio of the mixture supplied into the engine cylinder becomes too rich.
There was a problem in that it led to deterioration in fuel efficiency, etc.

Therefore, when increasing the amount of fuel immediately after starting the engine, as shown in Figures 1 and 2, the basic fuel injection amount determined from the intake air amount and engine rotational speed is corrected based on the engine water temperature, intake air temperature, etc. In addition, at time t ₀ when engine starting is completed, the fuel increase value is set according to the engine water temperature as shown in Figure 1, and the fuel injection amount is set as shown in Figure 2 a. The fuel increase value is decreased by a predetermined attenuation amount in synchronization with the engine rotation, so that
A method has been proposed for increasing the fuel injection amount in accordance with this fuel increase value.

According to this method, since fuel injection is performed in synchronization with engine rotation, the fuel increase value described above gradually decreases with each fuel injection, and therefore, as the amount of fuel adhering to the intake manifold increases. The fuel increase value will gradually decrease, and the fuel increase value will be appropriately determined, making it possible to start the engine smoothly.

[Problem to be solved by the invention]

However, in the above method, the predetermined attenuation amount of the fuel increase value synchronized with the engine rotation is a constant value regardless of the engine rotation speed.
As shown in Figure 3a, when a sudden racing operation is performed where the engine speed exceeds 2000 rpm immediately after the engine starts, the fuel increase value decreases rapidly due to the rapid increase in the engine speed. ,
In addition, the temperature of the intake manifold, etc. has not risen, and the rate of evaporation from the fuel adhering to the intake manifold, etc. is still small, so as shown by the chain line in Figure 3b, the air-fuel mixture supplied into the engine cylinders is decreasing. The engine would be controlled with a lean air-fuel ratio, which could lead to engine malfunction.

Therefore, an object of the present invention is to provide a fuel for an internal combustion engine that can prevent the air-fuel ratio of the air-fuel mixture supplied into an engine cylinder immediately after engine startup from becoming a lean air-fuel ratio, regardless of changes in engine speed. An object of the present invention is to provide an injection amount control method.

[Means to solve the problem]

In order to achieve the above object, the present invention detects the engine operating state, calculates the basic fuel injection amount based on the engine load and engine rotation speed, and corrects the basic fuel injection amount based on the engine warm-up state. Immediately after the engine starts, the fuel injection amount is set according to the engine water temperature and is gradually decreased by a predetermined attenuation amount in synchronization with the engine rotation after the engine start is completed. In a fuel injection amount control method for an internal combustion engine in which the fuel injection amount is set by increasing the basic fuel injection amount according to the increase value, a predetermined attenuation amount synchronized with the engine rotation of the fuel increase value is set at high engine speeds. Make it as small as possible,
Alternatively, when the engine is rotating at a high speed of a predetermined engine speed or higher, it is made smaller than when the engine is rotating at a low speed, below the predetermined speed.

[Effect]

According to the present invention, the predetermined attenuation amount of the fuel increase value that is synchronized with the engine rotation is made smaller as the engine rotates at higher speeds, or when the engine speed is higher than the predetermined engine speed and when the engine speed is lower than the predetermined speed. Therefore, even if a sudden racing operation is performed where the engine speed exceeds 2000 rpm immediately after the engine starts, the fuel increase value will gradually decrease, and at this time, the temperature of the intake manifold etc. will rise. If the rate of evaporation from the fuel adhering to the intake manifold is still low, the basic fuel injection amount will be corrected even with a large fuel increase value. It is possible to prevent the air-fuel ratio from becoming a lean air-fuel ratio.

[Embodiments of the invention]

Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 4 shows the configuration of a system to which the present invention is applied.

In FIG. 4, the intake system of the engine 10 includes:
An air flow meter 12, an intake air temperature sensor 13, a throttle valve 14, etc. are provided, and the air sucked through the air flow meter 12 flows into the throttle valve 1.
4 to the intake manifold 16 and mixes with fuel injected from the fuel injection valve 18. The air-fuel mixture is supplied to a combustion chamber 22 through an intake valve 20, is combusted by a spark plug 26 provided in a cylinder head 24, and is discharged through an exhaust valve 28 to an exhaust system.

Further, the cylinder block 32 is provided with a water temperature sensor 34 for detecting the engine water temperature.
Further, a cylinder discrimination sensor 40 and a rotation angle sensor 42 are built into the distributor 38 which distributes the ignition signal from the igniter 36 to each cylinder.

Detection outputs of sensors that detect various operating states of the engine, such as the air flow meter 12, intake temperature sensor 13, water temperature sensor 34, cylinder discrimination sensor 40, and rotation angle sensor 42, and the ignition switch 4
A starter signal based on the actuation of No. 3 is supplied to the control device 44.

FIG. 5 shows a configuration in which a microcomputer is used as the control device 44.

The control device 44, as shown in FIG.
CPU50, RAM52, ROM54, input/output ports 56, 58, output ports 60, 62, A/D converter 64, multiplexer 66, drive circuit 68,
70, consists of a waveform shaping circuit 72,
The CPU 50, RAM 52, ROM 54, input/output ports 56, 58, and output ports 60, 62 are connected by a bus line 76, respectively.

The detection outputs of the intake air temperature sensor 13, air flow meter 12, and water temperature sensor 34 are sent to the multiplexer 66,
It is supplied to the input/output port 56 via the A/D converter 64. Cylinder discrimination sensor 40, rotation angle sensor 4
The second detection output is supplied to the input/output port 58 via the waveform shaping circuit 72. Further, a starter signal generated by the operation of the ignition switch 43 is supplied to the input/output port 58.

The igniter 36 can provide an ignition signal to the distributor 38 via a control signal provided via an output port 60 and a drive circuit 68 . The fuel injection valve 18 can control the fuel injection time by a control signal supplied via the output port 62 and the drive circuit 70.

In addition, the ROM 54 stores data corresponding to the initial value of the fuel increase value immediately after engine startup, which is set according to the engine water temperature as shown in FIG. Data indicating the amount of attenuation is stored separately for when the engine is at high speed and when the engine is not at high speed.

The present embodiment has the above configuration, and its operation will be explained next.

FIG. 6 shows a flowchart for explaining a routine for calculating fuel injection time after engine startup by a system to which the present invention is applied.

In FIG. 6, first at step 100,
In order to determine whether or not the engine has just been started, it is determined whether or not a starter signal is present due to the operation of the ignition switch 43. If the engine is starting, a determination of YES is made in step 100, and the process moves to step 102. In this step, a flag f indicating when the engine is started is set to 1, and the process proceeds to step 104.
Move to. In step 104, the fuel injection time τSTA, which is determined as the fuel injection amount at startup, is calculated based on the sensor outputs of the intake air temperature sensor 13, air flow meter 12, water temperature sensor 34, etc. Proceed to step 100.

That is, after the engine has started, the determination in step 100 is NO, and the process moves to step 106. step
In step 106, the basic fuel injection time τ is calculated based on the intake air amount Q detected by the air flow meter 12 and the engine rotational speed N detected by the rotation angle sensor 42, and the process moves to step 108. In step 108, a correction value based on the detection output of various sensors such as the water temperature sensor 34 is integrated into the basic fuel injection time τ calculated in step 106, the corrected fuel injection time is calculated, and the process moves to step 110.

In step 110, it is determined whether the flag f is 1 or not. In this step 110,
Since the flag f has already been set to 1 in step 102, the determination is YES, and the process proceeds to step 112.
Move to. Here, the flag f is set to 0 and the process moves to step 114. In step 114, the fuel increase value f(ASE) is determined according to the detection output of the water temperature sensor 34.
is loaded into the ROM 454, and the process moves to step 116. In step 116, the fuel injection time τ calculated in step 108 x {1 + (fuel increase value) f in step 114 is calculated.
(ASE)}, and calculate the fuel injection time τ based on the calculated fuel injection time τ.
Control 8. After this, step 100, 106 again,
Processes 108 and 110 are performed. At this time, in step 110, the flag f is set in step 112.
has already been set to 0, the determination is NO and the process moves to step 118.

In step 118, it is determined whether the engine has rotated once or not. If the determination is YES, the process moves to step 120, and if the determination is NO, the process moves to step 116 described above.

In step 120, in order to determine whether the engine is rotating at high speed, it is determined based on the output of the rotation angle sensor 42 whether the engine rotation speed is 2000 rpm or more. If NO is determined in this step 120, and the engine speed is not high, the process moves to step 122.

In step 122, numerical data indicating the amount of attenuation determined at times other than when the engine is running at high speed, for example -1%, is fetched from the ROM 54, and this value is added to the previously calculated fuel increase value f(ASE)i-1. Then, the fuel increase value f(ASE)i after one rotation of the engine is calculated, and the process moves to step 116. In this case, the process in step 116 is to control the fuel injection valve 18 using the injection time τ that changes the fuel increase value f(ASE) in step 116 described above to the fuel increase value f(ASE)i calculated in step 122. do. After that, as the steps 100, 106, 108, 110, 118, 120, and 122 are continued, the fuel amount is increased by 1% attenuation with each engine revolution, as shown by the solid line in Figure 3b. The value controls the air/fuel ratio. While this process is continuing, as shown in Figure 3a, if a sudden racing operation occurs and the engine speed exceeds 2000 rpm, the step
If YES is determined in step 120, the process moves to step 124, which is the process performed when the engine is running at high speed.

In step 124, numerical data indicating the amount of attenuation determined for high engine speeds, for example -0.5%, is fetched from the ROM 54, and this value is added to the previously calculated fuel increase value f(ASE)i-1. , the fuel increase value f(ASE)i at high engine speed is calculated, and the process moves to step 116. In this case, the process in step 116 is to change the aforementioned fuel increase value f(ASE) to the fuel increase value f(ASE)i calculated in step 124, and to operate the fuel injection valve 18 at the changed fuel injection time τ. Control. When the processing in step 116 is carried out, even if a sudden racing operation as shown in FIG. 3a is performed, as shown by the solid line in FIG. Since the fuel increase value is gradually reduced by a small amount of attenuation at high engine speeds, it is possible to prevent the air-fuel ratio from becoming too lean, and there is no engine malfunction that would cause the engine to stop, and the engine can be controlled in an optimal state. can.

FIG. 7 shows a flowchart illustrating another embodiment of the invention.

In this embodiment, the routine for calculating the fuel injection time τ performs steps 130 and 132 after step 118 shown in FIG. 6, and as shown in FIG. The numerical value of the attenuation amount α is stored in the ROM 54 so that it varies linearly, and the other processes are the same as those shown in FIG. Omitted.

That is, in this embodiment, in step 118,
If the determination is YES, the process proceeds to step 130, where the attenuation amount α corresponding to the engine rotational speed N is fetched from the ROM 54 based on the detection output of the rotation angle sensor 42, and the process proceeds to step 132. In step 132, the attenuation amount α is subtracted from the previously calculated fuel increase value f(ASE) to calculate the fuel increase value f(ASE)i after one revolution of the engine, and the process moves to step 116.

In step 116, similar to the process in FIG. 6, the fuel increase value f calculated in step 114 is
The fuel injection valve 18 is controlled using the fuel injection time τ obtained by changing (ASE) to the fuel increase value f(ASE)i calculated in step 132.

In this embodiment, since the amount of attenuation decreases linearly, the engine can be operated smoothly from the time the engine is started until the time the engine is warmed up.

〔Effect of the invention〕

As explained above, according to the present invention, the predetermined attenuation amount of the fuel increase value that is synchronized with the engine rotation is made smaller as the engine rotates at higher speeds, or when the engine speed exceeds the predetermined engine speed, the predetermined engine speed increases. Since the fuel increase value is smaller than that at low engine speeds of less than 2,000 rpm, the fuel increase value will gradually decrease even if the engine speed exceeds 2000 rpm immediately after engine startup. Even if the temperature of the engine has not risen and the evaporation rate from the fuel adhering to the intake manifold is still at least low, the basic fuel injection amount will be corrected to increase even with a large fuel increase value. It is possible to prevent the air-fuel ratio of the supplied air-fuel mixture from becoming a lean air-fuel ratio, resulting in the effect that engine startability can be improved.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the relationship between the engine water temperature and the initial value of the fuel increase value, and Fig. 2 a and b are engine characteristic diagrams when increasing the fuel amount after the engine has started.
Figures a and b in Figure 3 are engine characteristic diagrams when sudden racing operation is performed after engine startup;
Figure 5 is a system configuration diagram of an internal combustion engine to which the present invention is applied, Figure 5 is a configuration diagram to explain the configuration of the control device shown in Figure 4, and Figure 6 is a fuel injection time calculation of the system to which the present invention is applied. FIG. 7 is a flowchart illustrating the process of a fuel injection time calculation routine according to another embodiment of the present invention; FIG. 8 is a flowchart illustrating the relationship between engine speed and damping amount α FIG. 12...Air flow meter, 13...Intake temperature sensor, 18...Fuel injection valve, 34...Water temperature sensor,
40...Cylinder discrimination sensor, 42...Rotation angle sensor, 44...Control device.

Claims (1)

[Claims] 1. Detects the engine operating state, calculates the basic fuel injection amount based on the engine load and engine rotation speed, and corrects the basic fuel injection amount based on the engine warm-up state to determine the fuel injection amount. Immediately after the engine starts, the fuel increase value is set according to the engine water temperature and is gradually decreased by a predetermined damping amount in synchronization with the engine rotation after the engine start is completed. In the fuel injection amount control method for an internal combustion engine in which the fuel injection amount is set by increasing the basic fuel injection amount, the predetermined attenuation amount synchronized with the engine rotation of the fuel increase value is made smaller as the engine speed increases; Alternatively, a fuel injection amount control method for an internal combustion engine is characterized in that the fuel injection amount is made smaller when the engine is rotating at a high speed of a predetermined engine speed or higher than when the engine is rotating at a low speed below the predetermined engine speed.