JPH0637863B2 - Electronically controlled fuel injection device for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronically controlled fuel injection device for an internal combustion engine, and more specifically, intake air including a temperature-sensitive resistor provided in an intake passage of the engine. The present invention relates to an electronically controlled fuel injection device in which a basic fuel injection amount is set based on an intake air flow rate detected by a flow rate detection means.

<Prior Art> Examples of conventional electronically controlled fuel injection devices for internal combustion engines include the following (Japanese Patent Application No. 60-008128).
No.).

That is, a temperature-sensitive resistor (heat wire) installed in the intake passage of the engine
Based on the electrical signal output from the hot-wire flow meter configured to include the intake air flow rate of the engine, search (or calculate) the intake air flow rate data that is preset and stored in the control unit. The basic fuel injection amount Tp (= K × Q / N; K is a constant) is calculated from the obtained intake air flow rate Q and the engine speed N converted from the ignition signal from the crank angle sensor or the ignition coil. .

Further, after calculating various correction coefficients COEF according to the engine operating state such as the engine cooling water temperature, the air-fuel ratio feedback correction coefficient α, and the correction amount Ts by the battery voltage, the final fuel injection amount Ti (= Tp × COEF × α + Ts) is calculated.

The fuel injection amount Ti with respect to the electromagnetic fuel injection valve
The fuel injection valve is opened for a time corresponding to the fuel injection amount Ti by outputting an injection pulse signal having a pulse width corresponding to the above, and a predetermined amount of fuel is injected and supplied to the engine.

<Problems to be Solved by the Invention> As described above, in the electronically controlled fuel injection device for an internal combustion engine, the basic fuel injection amount Tp is based on the intake air flow rate of the engine.
Therefore, if the detection accuracy of the hot-wire type flowmeter deteriorates due to dirt or deterioration of the temperature-sensitive resistor, there is a fear that it will not be possible to inject and supply the optimum amount of fuel to the engine.

That is, in the hot-wire flowmeter, the temperature-sensitive resistor provided in the intake passage of the engine is cooled by the intake air when the intake air flow rate increases, and the resistance value decreases, so that the temperature-sensitive resistor is output accordingly. The electric signal (voltage) changes, and the intake air flow rate of the engine is detected by searching the data of the intake air flow rate preset and stored in the control unit corresponding to this electric signal.

Therefore, when dust or oil component adheres to the temperature sensitive resistor, the adhered substance acts to suppress the temperature decrease of the temperature sensitive resistor, and thus the temperature (resistance value) change characteristic with respect to the intake air flow rate changes, An amount smaller than the actual intake air flow rate is output as the detection value. For this reason, when the engine is stopped, a large current is supplied to the temperature-sensitive resistor to heat it and burn off the deposits (Actually No. 61-5222).
(See No. 8 etc.), but the temperature sensitive resistor deteriorates due to this burnout, and the adhered matter cannot be burned off well, and as a result, the hot wire type flow meter will not Since the amount smaller than the air flow rate is output as the detected value, the basic fuel injection amount Tp is set to be smaller than the required amount of the engine, which causes over- leaning of the air-fuel ratio and the operability of the engine. There was a risk of damaging the vehicle (acceleration failure, knocking, etc.).

In particular, in the region where the intake air flow rate is large, the detection accuracy is greatly reduced due to dirt and deterioration of the temperature sensitive resistor as shown in FIG. In the worst case, there was a fear that engine burn-in would occur.

The present invention has been made in view of the above problems, and makes it possible to correct the basic fuel injection amount by self-diagnosing a decrease in the detection accuracy of a hot-wire flow meter, and to reduce the intake air flow rate when the engine is heavily loaded, which has a particularly large influence. It is an object of the present invention to inject and supply fuel to the engine in proportion to the required amount of the engine even if the detection accuracy decreases.

<Means for Solving Problems> Therefore, according to the present invention, as shown in FIG. 1, an intake air intake system configured to include a temperature sensitive resistor interposed in an intake passage of the engine to detect an intake air flow rate of the engine. Air flow rate detection means, engine rotation speed detection means for detecting the rotation speed of the engine, basic fuel injection amount setting means for setting the basic fuel injection amount based on the intake air flow rate and engine rotation speed, and the set by this An electronically controlled fuel injection device for an internal combustion engine, comprising: a fuel injection valve drive control means for driving and controlling a fuel injection valve in accordance with a basic fuel injection amount, to detect a fully open state of a throttle valve interposed in an intake passage. Throttle valve opening detection means and a basic fuel injection amount in which the basic fuel injection amount in the fully opened state of the throttle valve detected by the throttle valve opening detection means is stored in advance according to the engine speed. When the fully opened state of the throttle valve is detected by the injection amount storage means and the throttle valve opening detection means, the basic fuel injection amount retrieved from the basic fuel injection amount storage means based on the engine speed and the basic fuel injection Basic fuel injection amount correction for calculating a ratio with the basic fuel injection amount set by the amount setting means, and correcting and setting the set basic fuel injection amount based on the ratio when the ratio is equal to or greater than a predetermined value. And means are provided.

<Operation> According to the electronically controlled fuel injection device having such a configuration, the basic fuel injection amount (corresponding to the actual intake air flow rate) corresponding to the required engine amount when the throttle valve is fully opened is preliminarily tested in accordance with the engine rotation speed. When the ratio of the stored basic fuel injection amount to the stored basic fuel injection amount and the basic fuel injection amount set based on the detected intake air flow rate and engine speed is calculated, The decrease in the detection accuracy of the intake air flow rate detection means can be known by the size of the ratio, and the basic fuel injection amount at that time can be corrected by correcting the basic fuel injection amount at that time based on this ratio, so that the basic fuel injection amount commensurate with the required amount of the engine can be obtained. It is set so that over leaning of the air-fuel ratio can be avoided.

Therefore, it is possible to avoid making the air-fuel ratio over lean when the engine has a high load, which is particularly susceptible to the deterioration of the detection accuracy of the intake air flow rate detection means.

<Example> An example of the present invention will be described below with reference to the drawings.

FIG. 2 shows the hardware configuration of this embodiment.

Throttle valve (not shown) installed in the intake passage of the engine
The intake air flow rate based on the ON / OFF signal of the full switch 1 as the throttle valve opening detection means that is turned on when the throttle valve is fully opened, and the resistance value change of the temperature sensitive resistor provided in the upstream intake passage of the throttle valve. Output voltage V of the hot wire type flow meter 2 as the intake air flow rate detection means output corresponding to Q
s, the engine rotation speed signal N detected by the rotation speed sensor 3 as the engine rotation speed detection means, and the cooling water temperature signal Tw detected by the water temperature sensor 4 are input / output devices,
It is adapted to be inputted to a control unit 5 having a built-in microcomputer composed of a storage device and a central processing unit, and the control unit 5 sets a fuel injection amount Ti set based on these signals as described later. The injection pulse signal corresponding to is output to the drive circuit 6 of the fuel injection valve 7.

That is, in this embodiment, the control unit 5 is
The drive circuit 6 also serves as a basic fuel injection amount setting means, a basic fuel injection amount storage means, and a basic fuel injection amount correction means.
And constitute fuel injection valve drive control means.

Next, setting of the fuel injection amount Ti by the control unit 5 will be described with reference to the flowchart of FIG.

In step (denoted as "S" in the figure, the same applies hereinafter) 1, the full switch (Full SW) 1 is turned ON / O.
Intake air flow rate Q detected by FF and each sensor,
Input the engine speed N and the cooling water temperature Tw.

In step 2, the intake air flow rate Q input in step 1
And basic engine speed Tp (←
K × Q / N; K is a constant) is calculated.

In step 3, full switch 1 input in step 1
If the signal is ON, that is, if the throttle valve is in the fully open state, proceed to step 4. If it is OFF and the throttle valve is not in the fully open state, jump to steps 4 to 7. And proceed to step 8.

In step 4, the engine speed N input in step 1
The stored value of the basic fuel injection amount Tp (hereinafter simply referred to as 4 / 4Tp) in the fully open state of the throttle valve is searched based on the above. The memory unit of the microcomputer built in the control unit 5 has a size of
Tp is stored in association with the engine speed N, and the basic fuel injection amount Tp retrieved in step 4 is an injection amount corresponding to the required amount of the engine, that is, the actual intake air flow rate.

If you search for 4/4 Tp in step 4, in the next step 5,
Ratio of 4 / 4Tp and Tp of calculation result of step 2 (4 / 4T
p / Tp) is calculated, and the calculation result is used as a correction coefficient B for correcting the intake air flow rate Q.

The calculated correction coefficient B is the predetermined value B in step 6.
_If the decrease in the detection accuracy of the hot-wire flowmeter 2 (deviation of the detected value to the negative side) is B ≧ B ₁ or more due to dirt or deterioration of the temperature-sensitive resistor, B 7
If the basic fuel injection amount Tp is newly calculated using the correction coefficient B, and the decrease in the detection accuracy of the hot-wire flow meter 2 is within the allowable range B <B ₁ , step 7 is skipped. Go to step 8.

In step 7, the intake air flow rate Q input in step 1
Is multiplied by the correction coefficient B calculated in step 5 to correct,
A basic fuel injection amount Tp (← K × BQ / N; K is a constant) is calculated. Since the correction coefficient B is the ratio of 4 / 4Tp corresponding to the required amount of the engine to the basic fuel injection amount Tp based on the detection result of the hot-wire flow meter 2 as described above, this correction coefficient B is calculated as follows. By multiplying the intake air flow rate Q, the detected intake air flow rate Q can be approximated to the actual amount.

Therefore, the basic fuel injection amount Tp calculated in step 7 becomes a value close to the required amount of the engine even if the detection accuracy of the hot-wire flow meter 2 is reduced more than a predetermined value, and the basic wire fuel injection amount Tp detected by the hot-wire flow meter 2 is detected. It is possible to avoid engine seizure without causing the air-fuel ratio to become over lean in the throttle valve fully open state (when the engine is under a heavy load) where the decrease in accuracy is particularly significant.

In step 8, the basic fuel injection amount Tp calculated in step 2 or step 7 is set in the same manner as in the conventional case, and various correction coefficients CO depending on the engine operating state such as the cooling water temperature Tw.
The final fuel injection amount Ti (← Tp × COEP × α + Ts) is calculated by performing a correction calculation using the EF, the air-fuel ratio feedback correction coefficient α, the correction amount Ts by the battery voltage, and the like.
Then, an injection pulse signal corresponding to the set fuel injection amount Ti is output to the drive circuit 6 of the fuel injection valve 7 to inject and supply a predetermined amount of fuel to the engine.

As described above, in the case of the present embodiment, 4/4 Tp is stored in advance, and when the fully open state of the throttle valve is detected by the full switch 1, based on the detected value of the intake air flow rate Q at that time. The calculated basic fuel injection amount Tp is compared with 4 / 4Tp at the corresponding engine speed N, and whether the detection accuracy of the hot-wire flow meter 2 is lowered by a predetermined value or more depending on the ratio of the basic fuel injection amount Tp. In addition, the intake air flow rate Q detected based on this ratio is corrected to approximate the actual value. Therefore, the hot wire type flow meter 2
The detection error on the negative side of the intake air flow rate Q becomes particularly large due to the dirt and deterioration of the temperature-sensitive resistor at full throttle valve opening (when the intake air flow rate Q is large as shown in FIG. 4). In addition, the basic fuel injection amount Tp to be set can be made to correspond to the required amount of the engine, and it is possible to avoid making the air-fuel ratio over lean.

<Effect of the Invention> As described above, according to the present invention, even if the detection accuracy of the intake air flow rate decreases due to dirt or deterioration of the temperature-sensitive resistor,
It is possible to prevent the basic fuel injection amount from being set to be smaller than the engine required amount and the air-fuel ratio to become over lean when the throttle valve is fully open. Therefore, there is an effect that it is possible to avoid the risk of engine seizure at the time of high engine load.

[Brief description of drawings]

FIG. 1 is a block diagram of the configuration of the present invention, FIG. 2 is a schematic view of a system showing an embodiment of the present invention, FIG. 3 is a flow chart showing a fuel injection amount Ti setting control in the same embodiment, and FIG. It is a graph which shows the tendency for the detection accuracy of a flow meter to fall. 1 ... Full switch, 2 ... Hot wire type flow meter 3 ... Rotation speed sensor, 5 ... Control unit 6 ... Drive circuit, 7 ... Fuel injection valve

Claims (1)

[Claims] 1. An intake air flow rate detecting means for detecting an intake air flow rate of an engine, which includes a temperature sensitive resistor interposed in an intake passage of the engine, and an engine rotational speed detecting means for detecting a rotational speed of the engine. And a basic fuel injection amount setting means for setting the basic fuel injection amount based on the intake air flow rate and the engine rotation speed, and a fuel injection valve drive control means for driving and controlling the fuel injection valve according to the set basic fuel injection amount. In an electronically controlled fuel injection device for an internal combustion engine, comprising: a throttle valve opening detecting means for detecting a fully opened state of a throttle valve interposed in an intake passage; and a throttle detected by the throttle valve opening detecting means. A fully opened state of the throttle valve by the basic fuel injection amount storage means for storing in advance the basic fuel injection amount in the fully opened state of the valve according to the engine rotation speed, and the throttle valve opening degree detection means. When detected, the ratio of the basic fuel injection amount retrieved from the basic fuel injection amount storage means based on the engine speed and the basic fuel injection amount set by the basic fuel injection amount setting means is calculated, and the ratio is calculated. Is a predetermined value or more, a basic fuel injection amount correcting means for correcting and setting the set basic fuel injection amount based on the ratio is provided, and an electronically controlled fuel injection device for an internal combustion engine.