JPH0441954A - Electronic control fuel injection device of internal combustion engine - Google Patents

Abstract

PURPOSE:To avoid an accidental fire and irregular combustion by setting a fuel injection amount according to an engine operation condition, and fixing a lower limit value as the fuel injection amount when the set value of the fuel injection amount is smaller than the lower limit value. CONSTITUTION:A fuel injection valve (a) is provided on an intake system of an engine. A fuel injection control means (b) which sets a fuel injection amount according to an engine operation condition and injects the fuel with a specified injection interval synchronized to an engine speed is also provided on the engine. In addition, a fuel injection amount comparing means (c) which compares the set value of the fuel injection amount to a specified lower limit value is arranged. When the set value is judged to be smaller than the lower limit value through the comparison, the lower limit value is fixed as the fuel injection amount by means of a fuel injection amount lower limit fixing means (d). When the lower limit value is fixed as the fuel injection amount, the injection interval according to the fuel injection valve (a) is set uncynchronizedly to the engine speed by means of a injection interval varying means (e), while the injection interval is widened corresponding to the comparison between the lower limit value and the set value.

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.

<Conventional technology> In a conventional electronically controlled fuel injection system for an internal combustion engine, an electromagnetic fuel injection valve is provided in the engine intake system, and the injection valve is injected based on the intake air flow rate Q detected by an air flow meter and a signal from a crank angle sensor. The basic fuel injection amount Tp (K - Q/N, K is a constant) is calculated from the calculated engine speed N, and this is corrected appropriately to obtain the final fuel injection amount Ti (
=Te+Ts; Te=Tp-COEF, COEF are various correction coefficients.

Ts is the voltage correction amount), and a drive pulse signal with a pulse width corresponding to this Ti is output to the fuel injection valve at a predetermined timing synchronized with the rotation of the engine to inject the optimal amount of fuel into the engine intake system. are doing.

For example, in the case of a 4-cylinder, 4-stroke engine with a single point injection system that includes a single fuel injection valve at the gathering part of the intake passage, fuel is injected four times (one injection per stroke) every two revolutions of the engine.

<Problems to be Solved by the Invention> Incidentally, in a fuel injection valve, there is a proportional relationship between the drive pulse width and the fuel injection amount, but in a region where the drive pulse width is below a predetermined lower limit value, as shown in FIG. Furthermore, the linearity of the drive pulse width vs. fuel injection amount characteristic is lost due to the effects of jumping when the valve element of the fuel injector collides with the stopper or valve seat.

Therefore, it is desirable to use the fuel injection valve with a drive pulse width equal to or greater than the lower limit value, but during deceleration or the like, a non-linear region equal to or less than the lower limit value may be used.

Therefore, as a countermeasure, when using the fuel injector in a non-linear region below the lower limit value, the drive pulse width must be stored in advance in order to obtain the desired injection amount. Convert it to width, output it to the fuel injection valve,
There is something that makes it eject
(See Publication No. 39).

However, doing so will cause wear and tear on the fuel injector parts.
Alternatively, if the non-linear characteristics change due to changes in various conditions such as temperature, there is a problem that the correction may not be completed if the non-linear characteristics are changed to a pre-stored correction pulse width.

In addition, as another countermeasure, when the fuel injection amount becomes smaller than the lower limit value, it is possible to avoid outputting the drive pulse signal (Te + Ts) as shown in ■ in Fig. 7 to the fuel injection valve. There is a method in which so-called thinning injection is performed by outputting a drive pulse signal (2Te+Ts) as shown in (2) for two times, so that the amount of injection for one time is equal to or greater than the lower limit value.

However, if you do this, there will be no change in the total injection amount, or the injection interval will become too long due to the thinning of injections, and the richness and leanness of the mixture ratio of each cylinder will vary greatly, causing If a misfire or irregular combustion occurs,
As a result, there have been problems such as deterioration of emissions, deterioration of drivability, and occurrence of afterburn.

In view of the above-mentioned problems, the present invention provides an electronic control system for an internal combustion engine that can perform proper fuel injection and obtain a good combustion state even when the fuel injection amount is smaller than the lower limit value. The purpose is to provide a fuel injection device.

<Means for Solving the Problems> In order to achieve the above object, the present invention includes a fuel injection valve (a) in the engine intake system, as shown in FIG. In an electronically controlled fuel injection device for an internal combustion engine comprising a fuel injection control means (b) for setting a fuel injection amount and performing fuel injection at a predetermined injection interval synchronized with engine rotation, the following (C) to (e) The configuration is such that a means is provided.

(C) Fuel injection amount comparison means for comparing the set value of the fuel injection amount with a predetermined lower limit value (d) When it is determined by this comparison that the set value is smaller than the lower limit value, the fuel injection amount is Fuel injection amount lower limit fixing means (e) for fixing the fuel injection amount to the lower limit value When the fuel injection amount is fixed to the lower limit value, the injection interval by the fuel injection valve is asynchronous to the engine rotation, and the lower limit value and the set value are Injection interval variable means for extending the injection interval according to the injection ratio (for use) According to the above configuration, the fuel injection control means normally controls the engine operation through the fuel injection valve provided in the engine intake system. A fuel injection amount set according to the state is injected and supplied at a predetermined injection interval synchronized with engine rotation.

However, when the fuel injection amount comparing means compares the set value of the fuel injection amount with a predetermined lower limit value and determines that the set value is smaller than the lower limit value, the fuel injection amount lower limit value fixing means sets the fuel injection amount to While fixing the amount at the lower limit value, the injection interval variable means makes the injection interval asynchronous to the engine rotation, and extends the injection interval according to the ratio between the lower limit value and the set value.

In other words, if the normal injection interval is a fuel injection amount in a non-direct region where there is no proportional relationship between the drive pulse width and the injection amount,
The fuel injection amount is increased to the lower limit value, and while the injection amount can be accurately adjusted from the drive pulse width, the injection interval is variably extended by the increased amount. According to this, since the injection interval is extended to a minimum extent, the mixture ratio of each cylinder does not become extremely rich or lean.

<Example> Examples according to the present invention will be described below based on FIGS. 2 to 5.

First, the system will be explained with reference to FIG.

The engine 1 includes an air cleaner 2. Air is drawn in via the throttle chamber 3 and the intake manifold 4.

The throttle chamber 3 is provided with a throttle valve 5 that operates in conjunction with an accelerator pedal (not shown) to control the intake air flow rate Q, and an electromagnetic fuel injection valve 6 is provided upstream thereof. The fuel injection valve 6 opens when the solenoid is energized by a drive pulse signal from the control unit 7, and injects fuel into the engine l, which is pressure-fed from a fuel pump (not shown) and adjusted to a predetermined pressure by a pressure regulator. do.

Further, the control unit 7 receives input signals from various sensors, processes them using a built-in microcomputer, determines the fuel injection amount, and sends a drive pulse signal with a pulse width corresponding to this to the engine 1. The fuel is output to the fuel injection valve 6 at a predetermined injection interval (crank angle 720°/n (n is the number of cylinders)) synchronized with the rotation of the fuel injection valve 6 .

As the various sensors described above, a bypass type hot wire air flow meter 8 is provided in the intake passage, and outputs a voltage signal according to the intake air flow rate Q.

In addition, a crank angle sensor 9 is provided, such as built in a distributor (not shown), and a reference signal REF for each crank angle of 720°/n (n is the number of cylinders) is provided.
It outputs a unit signal PO8 every crank angle pi or 2 degrees.

Here, by measuring the period of the reference signal REF or the number of occurrences of the unit signal PO8 within a predetermined time,
The engine rotation speed N can be calculated.

Further, the throttle valve 5 is provided with a potentiometer type throttle sensor 10, and the throttle valve opening T
Outputs a signal according to VO.

In addition, a water temperature sensor 11 is installed in the water jacket of engine 1.
is provided and outputs a signal according to the cooling water temperature Tw.

Furthermore, the voltage of a battery 12 is applied to the control unit 7 via an engine key switch 13 as its operating power source and for detecting the power supply voltage.

Here, the microcomputer built into the control unit 7 executes the routine shown in the flowcharts of FIGS. 3 and 4.

First, with reference to the flowchart in FIG.
The first control routine executed every time EF occurs will be explained.

Incidentally, for a concrete explanation, reference is also made to the output timing diagram of the drive pulse signal in FIG. 5.

When the reference signal REF is generated, this normally means that the reference signal R
In order to inject at an injection interval for each EF occurrence, the fuel injection amount is set according to the engine operating state and the fuel is injected and supplied.

In step 1 (denoted as Sl in the figure, the same applies hereinafter), the intake air flow rate Q detected based on the signal from the air flow meter 8 and the engine rotation speed N calculated based on the signal from the crank angle sensor 9 are calculated. From this, the basic fuel injection amount Tp is calculated according to the following equation.

Tp=-Q/N (K is a constant) In step 2, the throttle valve opening TVO detected based on the signal from the throttle sensor 10 and the cooling water temperature Tw detected based on the signal from the water temperature sensor 11. The basic fuel injection amount Tp is corrected by the various correction coefficients C0FF, and the fuel injection amount (effective pulse width) Te is calculated as shown in the following equation.

Te-Tp-COEF In step 3, a voltage correction amount (invalid pulse width) Ts based on the voltage of the battery 12 is added to this to calculate the fuel injection amount (drive pulse width) Ti as shown in the following equation.

Ti=Te+Ts In step 4, it is determined whether or not the extension flag F is set. If it is not set, it indicates a normal control state, and in this case, the process proceeds to step 5.

In step 5, the reference signal RE calculated in step 3 is
In order to inject every time F occurs, the set value Ti of the fuel injection amount, which is set according to the engine operating state, is set to a lower limit value T1. l- (minimum value in the region where the drive pulse width of the fuel injection valve 6 and the injection amount are in a proportional relationship), when Ti≧TI+++1m, the set value Ti of the fuel injection amount is This indicates that the drive pulse width and the injection amount are in a proportional relationship range, so the process proceeds to steps 6 and 7 to inject at the normal injection interval.

In step 6, the value TIME of the injection interval timer is set to 0. This is counted up by a second control routine shown in the flowchart of FIG. 4, which will be described later.

In step 7, a drive pulse signal having a width corresponding to the set value Ti of the fuel injection amount calculated in step 3 is applied to the fuel injection valve 6.
output to and inject.

Also, by the comparison in step 5, Ti<Ti, .

When it is determined, it indicates that the drive pulse width of the fuel injection valve 6 and the injection amount are not within the range where there is a proportional relationship. Specifically, this is at time A in FIG. In such a case, in order to avoid outputting the drive pulse signal P, an extension flag F is set in step 8 to extend the injection interval, and the process proceeds to step 9.

In step 9, the fuel injection amount Ti is set to a lower limit value T1111.
Substitute 1° and fix it. Specifically, it is the drive pulse signal P2.

In step 10, the period of the reference signal REF, which is measured by a separate routine not shown, is read and substituted into the injection interval Tinj in order to be stored as a time corresponding to a predetermined injection interval synchronized with the engine rotation.

In step 11, the interval from the previous injection to the next extended injection is determined according to the following equation, that is, the extended injection interval T
Calculate and set inj'.

Tinj'=Tinj ・(Ti1., -Ts) /T
In other words, depending on the ratio of T im +a and Ti, Tin
Let j be extended as Tinj' (see Figure 5).

In step 12, the injection interval timer value TIME
is compared with the extended injection interval Tinj' and TIME< T
If it is inj, this routine ends as it is.

In other words, injection is not performed at injection intervals that are synchronized with engine rotation.

Then, according to the second control routine, the fuel is injected at injection intervals asynchronous to the engine rotation.

Here, the second control routine executed every unit time will be explained with reference to the flowchart of FIG. 4.

In step 21, the injection interval timer value TIME
Increase by 1 count. This is to measure the time since the previous injection.

In step 22, it is determined whether the extension flag F is set.

If the user is not standing, this routine ends as is, but if the user is standing, proceed to step 23 and check whether the value TIME of the injection interval timer is equal to the extended injection interval Tinj' set in step 11. Determine whether

If they are not equal, the routine ends and returns until they are counted up until they are equal, or if they are equal, the process proceeds to step 24 and the value TIME of the injection interval timer is set to zero.

In step 25, the fuel injection tkTL is the value (drive pulse signal P2) fixed to the lower limit value T1mIn in step 9, but in order to inject it, the fuel injection valve 6
This routine ends with an extended injection.

Also, after this, when executing the first control routine (fifth
At point B in the figure), since the extension flag F is already set, no injection is performed using the drive pulse signal P3, and a new T
inj' (dotted chain line in Figure 5) and calculate this Ti
Injection is performed using the drive pulse signal P4 at an injection interval of nj'.

On the other hand, in the determination at step 12 of the first control routine, TI
When ME≧Ti, this indicates that there is no longer a need for extension, so the extension flag F is lowered in step 13 and the process proceeds to step 14.

Step 14 is the lower limit value Ti of the fuel injection amount Ti. However, if the fuel injection amount Ti remains at this level for the first time after release, the mixture ratio will become rich due to the influence of the previous extended injection. , the fuel injection amount Ti is corrected to decrease.

In step 15, the injection interval timer value TIME
Set to 0.

Then, in step 16, the fuel injection amount Ti calculated in step 14 is injected, and this routine ends.

Specifically, at time C in FIG. 5, TIME≧Tinj'
Then, the drive pulse signal P5 of ■ is set to the lower limit value T 1m1
Stop fixing it to m, reduce the drive pulse signal P to the drive pulse signal P6 of (2), and inject in synchronization with the engine rotation.

Here, steps 1 to 3.7 of the first control routine correspond to fuel injection control means, step 5 corresponds to fuel injection amount comparison means, step 9 corresponds to fuel injection amount lower limit value fixing means, and step 10.11 and the second control routine correspond to the injection interval variable means.

Although the above explanation has been made using an example of a 4-stroke engine with a single point injection system, the present invention can also be applied to a 2-stroke engine etc. in which the distance from the installation position of the fuel injection valve to the combustion chamber is relatively long. It is possible.

<Effects of the Invention> As explained above, according to the present invention, the fuel injection amount is
It is set according to the engine operating state, and normally the fuel is injected at a predetermined injection interval synchronized with the engine rotation, and when the set value of the fuel injection amount becomes smaller than the lower limit value, this fuel injection amount is set to the lower limit value. Since it is fixed at the lower limit value, it is possible to avoid fuel injection below the lower limit value.

In addition, as the amount of fuel injected is increased, the injection interval is variably lengthened by that amount, so the injection interval for each cylinder can be extended or minimized, and the mixture ratio can be extremely rich or lean. In addition to preventing misfire, irregular combustion, afterburn, etc., it is possible to obtain the best possible combustion state.

[Brief explanation of drawings]

Fig. 1 is a functional block diagram showing the configuration of the present invention, Fig. 2 is a system diagram of an embodiment of the invention, Fig. 3 is a flowchart showing the first control routine, and Fig. 4 is a flowchart showing the second control routine. 5 is a time chart showing the state of control, FIG. 6 is a line diagram showing the relationship between drive pulse width and fuel injection amount, and FIG. 7 is a time chart 1 showing the state of conventional control. be. l... Engine 6... Fuel injection valve 7... Control unit 8... Air flow meter 9
...Crank angle sensor lO...Throttle sensor Fig. 4] IL Iv YOY RyoA, known patent applicant Japan Electronics Co., Ltd. Agent Patent attorney Fujio Sasashima Fig. 7 2 Te tTs

Claims (1)

[Scope of Claims] A fuel injection valve is provided in the engine intake system, and a fuel injection control means is provided that sets the fuel injection amount according to the engine operating state and performs fuel injection at a predetermined injection interval synchronized with the engine rotation. An electronically controlled fuel injection device for an internal combustion engine comprising: fuel injection amount comparison means for comparing the set value of the fuel injection amount with a predetermined lower limit value; and as a result of this comparison, it is determined that the set value is smaller than the lower limit value. Sometimes, the fuel injection amount lower limit fixing means fixes the fuel injection amount to the lower limit value, and when the fuel injection amount is fixed to the lower limit value, the injection interval by the fuel injection valve is asynchronous to the engine rotation, and the fuel injection amount lower limit value is fixed to the lower limit value. An electronically controlled fuel injection system for an internal combustion engine, characterized in that the electronically controlled fuel injection device for an internal combustion engine is provided with: injection interval variable means for extending the injection interval according to a ratio between the injection interval and the set value.