JPS6329039A - Electronically controlled fuel injection system for internal combustion engine - Google Patents

Abstract

PURPOSE:To keep off any overrichness in an air-fuel ratio at the time of trouble of an on-off valve inside a bypass passage, by making an air quantity to be fed by bypassing a throttle valve accurately correctable for increment to the suction air flow retrieved according to throttle valve opening and engine speed. CONSTITUTION:In this system, there is provided with a retrieving device D which retrieves the suction air flow stored in a suction air flow memory device C on the basis of each output signal out of a throttle valve opening detecting device A and an engine speed detecting device B. And, also there is provided with a correcting device F which has the retrieved suction air flow corrected for increment as much as the specified value when on-off control over an-off valve inside a bypass passage bypassing a throttle valve, and when an air-fuel ratio comes to overrichness of more than the specified one at the time of opening control of the on-off valve, this increment correction is prohibited by a prohibiting device G. And, on the basis of the retrieved suction air flow or the incrementally corrected suction air flow, a fuel injection quantity is set by a fuel injection quantity setting device H.

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, and more specifically, a fuel injection amount is set based on detected values of throttle valve opening and engine rotation speed. The present invention relates to an electronically controlled fuel injection device.

<Prior Art> As a conventional device of this type, there is one shown in FIG. 5, for example (see Japanese Patent Application No. 6L-008127, etc.).

A throttle valve opening sensor 4 for detecting the opening degree α of a throttle valve 3 interposed in the intake passage 2 of the internal combustion engine 1, and a rotation speed sensor 5 such as a crank angle sensor for detecting the engine rotation speed N are provided. , the detection signals from these sensors 4 and 5 are input to the control unit 6. The ROM of the microcomputer built in the control unit 6 stores the intake air flow rate Q corresponding to each of a plurality of operating regions divided using the throttle valve opening α and the engine speed N as parameters. Data is stored, and based on the detected values of throttle valve opening α and engine rotational speed N, data on the intake air flow rate Q in the corresponding operating region is searched from the data.

Then, the basic fuel injection amount 'rp (=KxQ/N; is a constant) is calculated based on the retrieved intake airflow iiQ and the engine rotational speed N detected by the rotational speed sensor 5, and the engine cooling water is After calculating various correction coefficients C0EF according to engine operating conditions such as temperature, air-fuel ratio feedback correction coefficient β, and correction numerator s according to battery voltage,
Final fuel injection amount Ti (=TpxCOEFxβ+
Ts) is calculated.

When the fuel injection tTi is set, an injection pulse signal with a pulse width corresponding to the fuel injection amount Ti is output to the fuel injection valve 7, so that the engine 1 is caused to inject and supply a predetermined amount of fuel.

However, when the fuel injection amount Ti is set based on the intake air flow rate Q, which is retrieved based on the detected values of the throttle valve opening degree α and the engine speed N, as described above, the throttle valve Since the bypassed air flow rate is unrelated to the fuel injection amount setting, the fuel injection amount is set to match the intake air flow rate, which is smaller than the actual intake air flow rate, resulting in an over-lean air-fuel ratio. There was a fear that it would happen.

That is, when controlling the idle rotation speed by controlling the opening and closing of an idle control valve (electromagnetic on-off valve) installed in a bypass intake passage that bypasses the throttle valve, air that is not related to the throttle valve opening degree α is supplied. Then, air other than the intake air flow fiQ, which is uniquely determined based on the detected values of the throttle valve opening α and the engine speed N, is supplied, and is supplied bypassing this throttle valve. There is a shortage of fuel to match the air flow rate.

For this reason, conventionally, the retrieved intake air flow rate Q has been corrected to increase by a predetermined amount, for example, by turning on and off a solenoid valve that controls opening and closing of the bypass intake passage.

That is, when controlling the idle rotation speed by controlling the opening and closing of the bypass intake passage, the negative pressure in the intake passage is large and the airflow flowing through the bypass intake passage becomes a sonic flow, so the flow rate approximately decreases depending on the area of the passage. It becomes constant. Therefore, when the solenoid valve is on and the bypass intake passage is controlled to open, the fuel injection amount Ti is based on the air flow rate obtained by adding a predetermined amount (the air flow rate of the bones of the bypass intake passage) to the retrieved intake air flow rate Q. The air-fuel ratio could be controlled to a level that would cause no problems.

An example of such control will be briefly explained based on the flowchart (Ti calculation routine) in FIG. In step 2, based on these detected values, 3 of α-N-Q is input.
Search data for intake air flow rate Q from the dimensional map.

In step 3, it is determined whether the normally closed electromagnetic valve that opens and closes the bypass intake passage that bypasses the throttle valve is on or off. If it is on and the bypass intake passage is controlled to open, proceed to the next step 4. Proceed to step 2
The predetermined intake air flow rate (L
(Intake air flow rate of the bypass intake passage bone) is added and set as the final intake air flow rate Q.

Then, in step 5, the basic fuel injection iTp is calculated based on the intake air flow rate Q to which the predetermined intake airflow filQ has been added, and in step 6, this basic fuel injection ftTp is further corrected to obtain the final fuel injection amount. Set Ti.

On the other hand, when the electromagnetic valve is off and the bypass intake passage is controlled to be closed, step 4 is skipped and the process proceeds to step 5. Therefore, when the solenoid valve is off,
The final fuel injection 11Ti is set based on the intake air flow rate Q found in step 2.

<Problems to be Solved by the Invention> However, when the intake air flow rate is increased and corrected based on the on/off status of the solenoid valve that opens and closes the bypass intake passage, the valve body of the solenoid valve becomes stuck. Even when the bypass intake passage actually remains closed even if the electromagnetic valve is energized by doing so, the intake air flow rate is corrected to increase. Therefore, in the event of a failure of such a solenoid valve, the intake air flow rate used to set the fuel injection amount may be higher than the actual intake air flow rate by the amount of increase correction (therefore, there is a risk that the air-fuel ratio may become over-rich). there were.

The present invention has been made in view of the above-mentioned problems, and is based on the amount of air that is supplied by bypassing the throttle valve, with respect to the intake air flow rate that is searched based on the detected values of the throttle valve opening degree and the engine rotation speed. An object of the present invention is to provide an electronically controlled fuel injection device for an internal combustion engine that can accurately increase the amount of fuel.

Means for Solving the Problems> Therefore, in the present invention, as shown in FIG. An engine rotation speed detection means for detecting the rotation speed, an intake air flow rate storage means for storing the intake air flow rate corresponding to each operating region using the throttle valve opening degree and the engine rotation speed as parameters, and each of the above-mentioned detection means. an intake air flow rate search means for searching the intake air flow rate based on detected values of the throttle valve opening degree and the engine speed; and an on-off valve that opens and closes the bypass intake passage that bypasses the thrower valve. bypass intake passage opening/closing control detection means for detecting control, and when it is detected that the opening/closing valve is controlled to open, the intake air flow rate searched by the intake air flow rate search means is corrected to increase by a predetermined amount. an intake air flow rate correction means, an air-fuel ratio detection means for detecting the air-fuel ratio of the engine, and an increase correction by the intake air flow rate correction means when the air-fuel ratio becomes richer than a predetermined value when the on-off valve is controlled to open. a fuel injection amount setting means for setting the fuel injection amount based on the intake air flow rate searched by the air search means or the intake air flow rate corrected to increase by the intake air flow rate correction means; , and a drive control means for driving and controlling the fuel injection valve according to the fuel injection amount set thereby to constitute an electronically controlled fuel injection device for an internal combustion engine.

According to this electronically controlled fuel injection device, when the opening/closing valve that opens and closes the bypass intake passage that bypasses the throttle valve is controlled to open, for example, when a normally closed electromagnetic valve is energized, the searched The intake air flow rate is corrected by increasing the amount of air flowing through this bypass passage, but as a result of this increase correction, the air-fuel ratio becomes over-rich.
When this occurs, such increase correction is prohibited to avoid over-enrichment of the air-fuel ratio.

In other words, if the air-fuel ratio becomes excessively enriched as a result of performing an increase correction assuming that the bypass intake passage is open, the bypass intake passage may not be open for some reason (such as a malfunction of the on-off valve) and the air will flow. Since it is assumed that the amount of air flowing through the bypass passage is not increased,
The fuel injection amount is set only according to the intake air flow rate retrieved based on the detected values of the throttle/torle valve opening and the engine rotational speed.

<Example> An embodiment of the present invention will be described below based on the drawings.

FIG. 2 shows the hardware configuration of this embodiment. Note that the same elements as in the conventional example are given the same reference numerals.

The control unit 6 includes the throttle valve opening α detected by the throttle valve opening sensor 4 as a throttle valve opening detection means, and the engine rotation speed detected by the engine rotation speed sensor 5 as an engine rotation speed detection means. The rotational speed N and the oxygen concentration in the exhaust gas, which is closely related to the air-fuel ratio detected by the oxygen concentration sensor 10 as an air-fuel ratio detection means installed in the exhaust passage 11, are input. There is. Further, the control unit 6 controls the opening and closing of a normally closed tm valve 9 and an electromagnetic fuel injection valve 7, which open and close a bypass intake passage 8 provided by bypassing the throttle valve 3, respectively, by controlling energization.

That is, the control unit 6 includes intake air flow rate storage means, intake air flow rate search means, intake air flow rate correction means, fuel injection amount setting means, and drive control means.

It serves as bypass intake passage opening/closing control detection means and increase correction prohibition means.

The operation of the electronically controlled fuel injection system having such a configuration will be explained based on the flowchart shown in FIG.

In step 1O (indicated as "S" in the figure, the same shall apply hereinafter), the detected values of throttle valve opening α and engine rotational speed N are respectively input, and the air-fuel ratio change calculation routine shown in Fig. 4 is executed. Input the calculated air-fuel ratio change amount ΔMR.

In step 11, data on the intake air flow rate Q stored in advance in the ROM of the microcomputer built in the control unit 6 is based on the detected values of the throttle valve opening α and the engine rotational speed N input in step 10. Search for.

In step 12, it is determined whether the electromagnetic valve 9 is on or off, and when it is determined that the electromagnetic valve 9 is on (that is, the electromagnetic valve 9 is energized to open the bypass intake passage 8), the process proceeds to step 13. The fuel ratio change amount ΔMR is compared with a predetermined value.

Here, the air-fuel ratio change amount ΔMR is calculated based on the oxygen concentration in the exhaust gas detected by the oxygen concentration sensor 10, and the air-fuel ratio feedback correction coefficient β, as shown in the flowchart of FIG. Reference value β of fuel ratio feedback correction coefficient β. (Step 20)
), and when this air-fuel ratio change amount ΔMR becomes larger than a predetermined value, it indicates that the air-fuel ratio is over-rich.

If it is determined that the air-fuel ratio is overrich in this way, the flag is set to 1 in step 17, and the process proceeds to step 18.

On the other hand, if it is determined in step 13 that the air-fuel ratio change amount ΔMR is less than or equal to the predetermined value, and the air-fuel ratio is not overrich, the process proceeds to step 14, where a flag is determined.

Here, when it is determined that the flag is 1, that is, ΔMR>predetermined value and over-riching of the air-fuel ratio has been determined, the process proceeds from step 13 to step 17, and the flag is set to 1. Sometimes, the process jumps to step 15 and proceeds to step 1a. Further, if it is determined that the flag is O, and the electromagnetic valve 9 is in the on state, but no overriching of the air-fuel ratio has occurred, the searched intake air flow rate Q is increased and corrected in step 15. .

Specifically, a predetermined amount Q0 corresponding to the amount of air flowing through the bypass intake passage 8 is added to the data of the intake air flow rate Q retrieved in step 11 to obtain the final intake air flow rate Q.

Incidentally, when it is determined in step 12 that the electromagnetic valve 9 is off and the electromagnetic valve 9 is not energized and therefore the bypass intake passage 8 is controlled to be closed, the flag is set to O in step 16 and the process then proceeds to step 18. .

In step 18, a basic fuel injection amount Tp (=KXQ/N; is a constant) is calculated based on the intake air flow rate Q retrieved in step 11 or the intake air flow rate Q corrected to increase in step 15.

In step 19, the air-fuel ratio feedback correction coefficient β is calculated based on the various correction coefficients C0EF depending on the engine operating state such as the engine cooling water temperature, the oxygen concentration in the exhaust gas detected by the oxygen concentration sensor 10, and the battery voltage. After calculating the correction numerator s, the final fuel injection amount Ti
(=TpXCOEF×β+Ts) is calculated.

Then, the control unit 6 controls this fuel injection amount T
The injection pulse signal with a pulse width corresponding to i is sent to the fuel injector 7.
A predetermined amount of fuel is injected and supplied to the engine 1.

As described above, the increase correction corresponding to the flow of the bypass intake passage 8 for the retrieved intake air flow rate Q is performed when the solenoid valve 9 is on and the air-fuel ratio is not overrich. As a result, even if the valve body of the solenoid valve 9 becomes stuck for some reason and the bypass intake passage 8 remains closed even if the solenoid valve 9 is energized, the air-fuel ratio will not be exceeded. This enables problem-free air-fuel ratio control by avoiding enrichment.

That is, conventionally, regardless of whether the bypass intake passage 8 is actually opened or not, if the electromagnetic valve 9 is energized, the intake air flow rate for the bypass intake passage 8 is calculated for the searched intake air flow rate Q. Since the intake air flow rate was added up, the intake air flow rate increase correction was made even when the solenoid valve 9 failed and the bypass intake passage 8 was not opened. This is indirectly detected by ΔMR, and correction to increase the intake air flow rate is prohibited. Therefore, even if the electromagnetic valve 9 fails, the engine 1 can be prevented from operating in an overrich state.

<Effects of the Invention> As explained above, according to the present invention, the intake air flow rate searched based on the detected values of the throttle valve opening degree and the engine speed can be accurately corrected to increase the amount flowing through the bypass intake passage. It will be held in In other words, there is a failure in the on-off valve that opens and closes the bypass intake passage, and as a result of increasing the intake air flow rate when the bypass intake passage is not actually opened even if the on-off valve is controlled to open, the air-fuel ratio changes. When overconcentration occurs, increasing correction of the intake air flow rate is prohibited.
This makes it possible to quickly avoid over-enrichment of the air-fuel ratio.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of the present invention, Fig. 2 is a system diagram showing an embodiment of the present invention, Fig. 3 is a flowchart showing a fuel injection amount calculation routine in the above embodiment, and Fig. 4 is a flowchart in the same embodiment. FIG. 5 is a system diagram showing an example of a conventional electronically controlled fuel injection device. FIG. 6 is a flow chart showing a conventional intake air flow rate increase correction control. 1... Engine 2... Intake passage 3... Slot 7
) Valve 4... Throat 7) Valve opening sensor 5...
・Rotation speed sensor 6...Control unit 7
...Fuel injection valve 8...Bypass intake passage 9...
・Solenoid valve 10...Oxygen concentration sensor 11...
Exhaust passage patent applicant Japan Electronics Co., Ltd. Agent Patent attorney Fujio Sasashima Figure 2, Ward 4, 5vA

Claims (1)

[Claims] A throttle valve opening detection means for detecting the opening of a throttle valve installed in the intake passage of the engine, an engine rotation speed detection means for detecting the rotation speed of the engine, and a parameter for determining the throttle valve opening and the engine rotation speed. an intake air flow rate storage means that stores an intake air flow rate corresponding to each operating region; an intake air flow rate search means that searches for an intake air flow rate based on detected values of throttle valve opening and engine rotational speed; bypass intake passage opening/closing control detection means for detecting opening/closing control of an opening/closing valve that opens/closes a bypass intake passage that bypasses a throttle valve; and increasing the intake air flow rate retrieved when the opening/closing valve is controlled to open by a predetermined amount. an intake air flow rate correction means for correcting the air-fuel ratio; an air-fuel ratio detection means for detecting the air-fuel ratio of the engine; and an air-fuel ratio detection means for detecting the air-fuel ratio of the engine; an increase correction prohibiting means for prohibiting increase correction; a fuel injection amount setting means for setting a fuel injection amount based on the retrieved intake air flow rate or the intake air flow rate corrected to increase by the intake air flow rate correction means; An electronically controlled fuel injection device for an internal combustion engine, comprising: drive control means for driving and controlling a fuel injection valve according to a fuel injection amount.