JPH0772509B2 - Electronically controlled fuel injection device for internal combustion engine - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electronically controlled fuel injection device for an internal combustion engine.

<Prior Art> As a conventional electronically controlled fuel injection device for an internal combustion engine, a so-called multi-fuel injector is provided downstream of a branch portion of an intake manifold to each cylinder (manifold branch portion or intake port) for each cylinder. There is a point injection (MPI) system and a so-called single point injection (SPI) system in which a single fuel injection valve is installed in common for all cylinders upstream from the collector of the intake manifold (usually upstream of the throttle valve). In view of this, an MPI system with a short distance from the fuel injection valve to the cylinder and a short injection fuel arrival delay time is preferable.

<Problems to be Solved by the Invention> However, in the MPI system, considering a rapid acceleration pattern, although acceleration is detected immediately after acceleration to increase the fuel injection amount, acceleration detection delay time, correction calculation delay time,
During the total delay time including the fuel injection valve response delay time and the injected fuel arrival delay time, the amount of air charged in the manifold / collector section flows into the cylinder, and as shown in FIG. For this reason, poor drivability during acceleration (deterioration of response) and deterioration of emission occur, and it has been demanded to solve these problems.

In view of such circumstances, the present invention makes it possible to make the initial lean by the amount of air filled in the manifold / collector during the delay time from the acceleration to the time when the increased amount of corrected fuel reaches the cylinder. The purpose is to be able to prevent.

<Means for Solving the Problem> Therefore, according to the present invention, as shown in FIG. 1, the first manifold for each cylinder is provided downstream of the branch portion of the intake manifold 6 to each cylinder.
The fuel injection valve 7 is provided, and the second fuel injection valve 8 is provided upstream of the collector portion of the intake manifold 6.

On the other hand, an intake air flow rate detecting means a for detecting the engine intake air flow rate, an averaging means b for averaging the detected intake air flow rate, an engine speed detecting means c for detecting the engine speed, and an averaging means. A first fuel injection amount calculation for calculating a first fuel injection amount by the first fuel injection valve based on the intake air flow rate averaged by the means and the engine speed detected by the engine speed detection means. Means d, a second fuel injection amount by the second fuel injection valve is calculated based on the intake air flow rate detected by the intake air flow rate detection means and the engine speed detected by the engine speed detection means. 2 fuel injection amount calculation means e.

<Operation> In the above configuration, the first fuel injection valve provided in each cylinder downstream of the branch portion of the intake manifold to each cylinder injects the fuel in the first fuel injection amount, and the intake manifold A second fuel injection valve provided upstream of the collector section of the above section injects a second fuel injection amount of fuel. Note that these are performed at a predetermined share rate.

Therefore, the collector portion of the intake manifold is always in the premixed state with the fuel injected from the second fuel injection valve, and during the delay time from the acceleration until the fuel whose amount has been corrected to increase reaches the cylinder, When the filled portion of the manifold / collector portion flows into the cylinder, the filled portion is in a premixed state, so that the initial leaning can be prevented as much as possible.

Here, when calculating the first fuel injection amount by the first fuel injection valve, the fuel injection amount based on the amount of air flowing through the fuel injection valve portion, that is, the fuel injection amount based on the suction negative pressure is obtained. It is necessary to measure the intake air flow rate detection means (air flow meter) including the filling amount of the manifold / collector (hatched portion in FIG. 5).
In order to cancel this, the averaged intake air flow rate Q _AVE (shown by the broken line in FIG. 5) is obtained, and the fuel injection amount is calculated based on this.

Further, when the second fuel injection amount is calculated by the second fuel injection valve, it is necessary to inject fuel from the second fuel injection valve to the filling amount of the manifold / collector portion, and therefore, it is detected. Using the intake air flow rate Q (shown by the solid line in FIG. 5) as it is, the fuel injection amount is calculated.

<Example> An example of the present invention will be described below.

In FIG. 2, an air cleaner 2 is provided in each cylinder of the engine 1.
From the intake duct 3, the throttle valve 5 in the throttle chamber 4, the collector portion 6a of the intake manifold 6, and each branch portion 6b, air is sucked.

Here, each branch portion 6b of the intake manifold 6 is provided with a first fuel injection valve 7.

A second fuel injection valve 8 is provided upstream of the throttle valve 5 in the throttle chamber 4. Although the throttle valve 5 is upstream in this example, it may be upstream of the collector portion 6a of the intake manifold 6.

Both the first and second fuel injection valves 7 and 8 are electromagnetic fuel injection valves that are opened by energizing a solenoid and closed by deenergizing a solenoid.
A valve is energized by a drive pulse signal from 20 to open the valve, and fuel is pressure-fed from a fuel pump (not shown) to inject and supply fuel adjusted to a predetermined pressure by a pressure regulator.

The control unit 20 includes a microcomputer including a CPU, a ROM, a RAM, an input / output interface, etc., receives input signals from various sensors, performs arithmetic processing as described below, and outputs the first and second signals. It controls the operation of the fuel injection valves 7 and 8.

As the various sensors, a hot-wire type air flow meter 21 is provided in the intake duct 3, and the intake air flow rate Q
And outputs a voltage signal Us corresponding to. Therefore, the air flow meter 21 is the intake air flow rate detecting means.

In addition, the crank angle sensor 22 is provided, and in the case of four cylinders, the reference signal for each crank angle of 180 ° and the crank angle 1 to
A unit signal for every 2 ° is output. Here, the engine speed N can be calculated by measuring the cycle of the reference signal or the number of unit signals generated within a predetermined time. Therefore,
The crank angle sensor 22 is an engine speed detecting means.

In addition, a water temperature sensor 23 for detecting the cooling water temperature Tw of the engine 1,
A potentiometer type throttle sensor 24 for detecting the opening TVO of the throttle valve 5 is provided.

Here, the control unit 20 controls the fuel injection amount by the first fuel injection valve 7 in accordance with a first fuel injection amount control routine shown as a flowchart in FIG. 3, and also as a flowchart shown in FIG. The fuel injection amount by the second fuel injection valve 8 is controlled according to the fuel injection amount control routine of No. 2.

First, the first fuel injection amount control routine (FIG. 3) will be described.

In step 11 (denoted as S11 in the drawing; the same applies hereinafter), the voltage signal Us from the air flow meter 21 is read, and in the next step 12, the voltage signal Us is converted into the intake air flow rate Q by referring to the map.

In step 13, based on the detected intake air flow rate Q, the moving average Q _AVE of the intake air flow rate is calculated by the following equation. The value of the weighting constant is arbitrary. This step
13 parts correspond to the averaging means.

In step 14, from the moving average Q _AVE of the intake air flow rate and the engine speed N calculated based on the signal from the crank angle sensor 22, the basic fuel injection amount Tp ₁ = K ₁ · Q _AVE / N ( However, K ₁ is a constant.

In step 15, based on the basic fuel injection amount Tp ₁ ,
This is multiplied by various correction factors COEF and the voltage correction amount Ts is added to obtain the final fuel injection amount Ti ₁ by the first fuel injection valve 7.
= Tp ₁ · COEF + Ts is calculated. Here, the steps 14 and 15 correspond to the first fuel injection amount calculation means.

The various correction coefficients COEF are determined by the cooling water temperature Tw, the throttle valve opening change amount ΔTVO, and the like, and the voltage correction amount Ts is determined by the battery voltage.

Next, the second fuel injection amount control routine (FIG. 4) will be described.

In step 21, the voltage signal Us from the air flow meter 21
In step 22, the voltage signal Us is converted into the intake air flow rate Q by referring to the map.

In step 23, from the detected intake air flow rate Q and the engine speed N calculated based on the signal from the crank angle sensor 22, the basic fuel injection amount Tp ₂ = K ₂ · Q / N (however, K ₂ is a constant).

In step 24, based on the basic fuel injection amount Tp ₂ ,
This is multiplied by various correction factors COEF and the voltage correction amount Ts is added to obtain the final fuel injection amount Ti ₂ by the second fuel injection valve 8.
= Tp ₂ · COEF + Ts is calculated. Here, steps 23 and 24 correspond to second fuel injection amount calculation means.

In this way, when the first fuel injection amount Ti ₁ and the second fuel injection amount Ti ₂ are obtained, for the first fuel injection valve 7,
Corresponding to the _first fuel injection amount Ti ₁ once per 1/2 revolution of the engine (once every 2 revolutions of the engine when viewed from each first fuel injection valve 7) at a predetermined timing and in a predetermined order. A drive pulse signal having a pulse width is output to inject fuel, and a second fuel injection amount Ti _{2 is set} to the second fuel injection valve 8 at a timing of once per 1/2 engine revolution. A drive pulse signal having a corresponding pulse width is output and fuel injection is performed.

The sharing ratio of the first fuel injection valve 7 and the second fuel injection valve 8 is set to about 8: 2 to 5: 5 and set by the K ₁ and K ₂ constants, but depending on the engine operating conditions, It is variable.

As a result, the first branch 6b of the intake manifold 6
The fuel injection valve 7 injects a first fuel injection amount of a predetermined proportion (for example, 80%) with respect to the fuel injection amount determined according to the engine operating condition, and the second fuel is injected into the throttle chamber 4. The fuel injection valve 8 injects a second fuel injection amount of a predetermined share (for example, 20%) of the fuel injection amount determined according to the engine operating condition.

Therefore, the collector portion 6a of the intake manifold 6 is always in a premixed state with the fuel injected from the second fuel injection valve 8,
At the time of sudden acceleration, during the delay time from the acceleration to the time when the fuel whose amount has been corrected to increase reaches the cylinder, when the filled portion of the collector portion 6a flows into the cylinder, this filled portion is in a premixed state. Therefore, the initial leaning can be prevented as much as possible.

Here, when the first fuel injection amount Ti ₁ by the first fuel injection valve 7 is calculated, the fuel injection amount based on the amount of air flowing through the fuel injection valve 7, that is, the fuel based on the suction negative pressure is used. Although it is necessary to obtain the injection amount, since the air flow meter 21 measures the filling amount of the collector portion 6a of the intake manifold 6 (hatched portion in FIG. 5), the intake air averaged to cancel this is taken. Flow rate Q
_AVE (shown by the broken line in FIG. 5) is obtained, and the fuel injection amount is calculated based on this.

Further, the second fuel injection amount Ti ₂ by the second fuel injection valve 8
In the calculation of, since it is necessary to inject fuel from the second fuel injection valve 8 to the filling portion of the collector portion 6a of the intake manifold 6, the detected intake air flow rate Q (5th
The solid line (in the figure) is used as it is to calculate the fuel injection amount.

As a result, the fuel injection amount from the first and second fuel injection valves 7 and 8 can be optimized.

<Effects of the Invention> As described above, according to the present invention, in addition to the first fuel injection valve provided for each cylinder downstream of the branch portion of the intake manifold for each cylinder, the intake manifold Since the fuel is injected from the second fuel injection valve provided upstream at a predetermined share ratio, the collector portion of the intake manifold is always in a premixed state with the fuel injected from the second fuel injection valve, and acceleration is performed. During the delay time from when the fuel whose amount has been increased to the time when it reaches the cylinder is reached, when the filled portion of the manifold / collector section flows into the cylinder, this filled portion is in the state of premixing, so it is necessary to make the initial lean. It can be prevented as much as possible.

Further, when calculating the first fuel injection amount by the first fuel injection valve, the intake air flow rate that has been averaged so as to cancel the filling amount of the manifold collector portion is obtained, and the fuel injection is performed based on this. When calculating the amount and calculating the second fuel injection amount by the second fuel injection valve,
Since it is necessary to inject fuel into the manifold / collector portion as well, the detected intake air flow rate is used as it is to calculate the fuel injection amount, and the fuel injection from the first and second fuel injection valves is performed. The amount can be optimized.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing the configuration of the present invention, FIG. 2 is a system diagram showing an embodiment of the present invention, FIG. 3 is a flow chart of a first fuel injection amount control routine, and FIG.
5 is a flow chart of a fuel injection amount control routine of FIG. 5, FIG. 5 is a view showing a state of averaging processing, and FIG. 6 is a view showing an air-fuel ratio characteristic at the time of acceleration as a problem of the conventional art. 1 ... Engine, 4 ... Throttle chamber, 5 ... Throttle valve, 6 ... Intake manifold, 6a ... Collector part,
6b ... Branch part, 7 ... first fuel injection valve, 8 ... second fuel injection valve, 20 ... control unit, 21 ...
Air flow meter, 22 ... Crank angle sensor

Claims (1)

[Claims] 1. A first fuel injection valve provided for each cylinder downstream of a branch portion of the intake manifold into each cylinder, and a second fuel injection valve provided upstream for a collector portion of the intake manifold. And an intake air flow rate detecting means for detecting an engine intake air flow rate, an averaging means for averaging the detected intake air flow rate, an engine speed detecting means for detecting an engine speed, and an averaging means. By the first fuel injection valve based on the intake air flow rate averaged by the engine and the engine speed detected by the engine speed detecting means.
First fuel injection amount calculation means for calculating the fuel injection amount of
A second fuel injection that calculates a second fuel injection amount by the second fuel injection valve based on the intake air flow rate detected by the intake air flow rate detection means and the engine speed detected by the engine speed detection means. An electronically controlled fuel injection device for an internal combustion engine, comprising: an amount calculation means.