JPH02163437A - Fail-safe device in fuel feed controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To generate the fail-safe by converting the opening degree of a throttle valve to the value corresponding to the opening area of a suction system and setting the fundamental fuel feed quantity on the basis of the value which is obtained by dividing the value corresponding to the opening area by the engine revolution speed, when an intake air sate quantity detecting sensor is in anomaly. CONSTITUTION:In ordinary case, a setting means B sets the fundamental fuel feed quantity on the basis of the intake air state quantity detected by a detecting means A, and controls a fuel feeding means D through a fuel feed control means C. When an anomaly detecting means E detects the anomaly of the intake air state detecting means A, an abnormal fuel feed quantity setting means F sets the abnormal fuel feed quantity by dividing the value corresponding to the opening area of a suction system which is obtained by the conversion from a throttle valve opening degree obtained by a detecting means G by a conversion means H, by the engine revolution speed obtained by a detecting means I. Further, when the throttle valve opening degree is converted to the value corresponding to the opening area, the opening degree of a bypass passages which is set by an auxiliary air quantity control means J is corrected by a correcting means K. Thus, the precision in the fuel feed quantity control in the fail-safe of a fuel control system can be improved.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a fail-safe device in a fuel supply control device for an internal combustion engine, and more specifically, a fail-safe device configured to set a basic fuel supply amount based on a state quantity of intake air. The present invention relates to fail-safe control of fuel supply amount when a sensor that detects the state quantity of intake air is abnormal in an engine that has been operated.

<Prior art> Conventionally, as a fuel supply control device for an internal combustion engine, a state quantity of intake air such as intake air flow rate and intake pressure is detected, a basic fuel supply amount is set based on the state quantity, and this setting is performed. An electronically controlled fuel injection device configured to drive and control a fuel injection valve based on the basic fuel supply amount is widely known (see Japanese Patent Laid-Open No. 59-49334, etc.).

By the way, in the control device that controls the fuel supply amount by detecting the amount of Bi in the intake air as described above, an abnormality may occur in the sensors such as the air flow meter and the intake pressure sensor that detect the state of the intake air t-p. If the detected value becomes an abnormal value, the fuel supply amount will be set based on this abnormal value, which may greatly disturb the air-fuel ratio of the intake air-fuel mixture, which may greatly deteriorate the operational stability of the engine. be.

For this reason, the present applicant has previously developed an electronically controlled fuel injection system that normally sets a basic fuel injection amount (supply amount) based on the intake air flow rate and engine rotational speed detected by an air flow meter. proposed a fail-safe device configured to set the basic fuel supply amount from the throttle valve opening degree and engine rotational speed in the event of an abnormality (see Japanese Utility Model Publication No. 183049/1983).

<Problems to be Solved by the Invention> However, in the fail-safe control described above, the basic fuel supply amount is stored in a map that uses the throttle valve opening degree and the engine speed as parameters, and the basic fuel supply amount is determined from this map. Since the system is configured to search and obtain the fuel supply amount, the amount of memory increases when trying to ensure fuel control accuracy during fail-safe conditions, and the amount of memory for fail-safe control that is not used during normal times increases. The problem was that it was not rational.

When setting the basic fuel supply amount from the throttle valve opening and the engine rotation speed, the gradient of the air amount change with respect to the opening change rate is large on the low opening side of the throttle valve (see Figure 4), so the fuel control In order to ensure accuracy, it is necessary to make the grid of the map of the basic fuel supply amount finer as the throttle valve opening is lower (see Figure 5), which increases the amount of memory for fail-safe control. This is what it used to be.

The present invention has been made in view of the above problems, and provides fail-safe control of fuel supply when a sensor such as an air flow meter that detects the state quantity of intake air is abnormal.
The purpose is to reduce the amount of memory for fail-safe control while ensuring fuel control accuracy during fail-safe control.

Means for Solving the Problems> Therefore, in the present invention, as shown in FIG. A basic fuel supply amount setting means for setting a basic fuel supply amount based on the air condition a quantity, and a fuel supply control means for driving and controlling the fuel supply means based on the set basic fuel supply amount. In the fuel supply control device for an internal combustion engine configured, the abnormality detection means detects an abnormality of the intake air state quantity detection means, the throttle valve opening detection means detects the opening of the throttle valve, and the rotational speed of the engine is detected. 7) an engine rotational speed detecting means for detecting the engine rotational speed, an opening area converting means for converting the throttle valve opening detected by the throttle valve opening detecting means into an opening area equivalent value, and the intake air condition detected by the abnormality detecting means. When an abnormality is detected in the amount detecting means, the basic fuel supply amount is set in place of the basic fuel supply amount setting means based on the value obtained by dividing the converted opening area equivalent value by the detected engine rotation speed, and A fail-safe device is configured to include abnormal fuel supply amount setting means for operating the fuel supply control means based on the fuel supply amount.

Further, as shown by the dotted line in FIG. 1, the internal combustion engine is supplied with air passing through the auxiliary air passage through the opening degree of an auxiliary air amount control valve installed in the auxiliary air passage that bypasses the throttle valve. When the auxiliary air amount control means is provided to control the auxiliary air amount, the opening area is obtained by converting a correction value according to the opening degree of the auxiliary air amount control valve controlled by the auxiliary air amount control means using the opening area conversion means. It is preferable to provide an opening area correction means for correcting by adding to the corresponding value and causing the abnormal fuel supply amount setting means to set the basic fuel supply amount based on the correction result.

<Operation> In the fuel supply control device for an internal combustion engine to which the fail-safe device according to the present invention is applied, the intake air state quantity detection means detects state quantities of engine intake air such as intake air flow rate and intake pressure, and The supply amount setting means sets the basic fuel supply amount based on the detected state quantity of intake air. Once the basic fuel supply amount is set, the fuel supply control means drives and controls the fuel supply means based on this basic fuel supply amount.

In the fail-safe device according to the present invention, the abnormality detection means detects an abnormality in the intake air state quantity detection means, the throttle valve opening detection means detects the opening of the throttle valve, and the engine rotation speed detection means detects an abnormality in the intake air state quantity detection means. Detects engine rotation speed. Further, the opening area converting means converts the throttle valve opening detected by the throttle valve opening detecting means into a value corresponding to the opening area of the intake passage.

Here, when the abnormality detection means detects an abnormality in the intake air state quantity detection means, the abnormality fuel supply amount setting means sets the opening area equivalent value to the engine rotational speed instead of the basic fuel supply amount setting means. A basic fuel supply amount is set based on the value divided by , and the fuel supply control means is operated based on this basic fuel supply amount. That is, when the intake air state quantity detection means is abnormal, fuel supply control is not performed according to the basic fuel supply amount set based on the intake air state quantity, and the throttle valve opening is changed to the intake passage corresponding to the opening. The basic fuel supply amount is calculated by dividing the opening area equivalent value obtained by converting from this opening degree by the engine rotation speed, assuming that the intake air flow rate increases as the opening area increases. The fuel supply control is performed according to the basic fuel supply amount determined from the opening area equivalent value.

Further, an auxiliary air amount control valve is interposed in the auxiliary air passage that bypasses the throttle valve, and the amount of auxiliary air that is supplied through the auxiliary air passage is controlled through the opening degree of this control valve. When a control means is provided, in addition to the opening area controlled by the throttle valve, the opening area of the auxiliary air passage controlled by the auxiliary air amount control valve influences the intake air flow rate.

For this reason, the opening area correction means adds a correction value corresponding to the opening degree of the auxiliary air amount control valve controlled by the auxiliary air amount control means to the opening area equivalent value converted by the opening area conversion means for correction. Then, based on this correction result, that is, the opening area controlled by the throttle valve and the auxiliary air amount control valve, the abnormal fuel supply amount setting means sets the basic fuel supply amount.

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

In FIG. 2 showing one embodiment, an air flow meter 3 such as a hot wire type as an intake air state quantity detection means for detecting an intake air flow IQ is installed in an intake passage 2 of an engine 1, and an air flow meter 3 such as a hot wire type is installed in an intake passage 2 of an engine 1. A throttle sensor 5 is provided as a throttle valve opening detection means for detecting, for example, a potentiometer. Further, a water temperature sensor 6 that detects a cooling water temperature Tw representing the engine temperature, and a rotation speed sensor 7 as an engine rotation speed detection means such as a crank angle sensor that detects an engine rotation speed N are provided.

Detection signals from each of the above sensors are manually input to a control unit 8 having a built-in microcomputer. Further, the engine l is provided with an electromagnetic fuel injection valve 9 for each cylinder as a fuel supply means. These fuel injection valves 9 are driven to open and open in an on/off manner by a drive pulse signal output from the control unit 8 in accordance with the fuel injection amount (fuel supply W), and inject and supply fuel to the engine 1.

Furthermore, an auxiliary air passage 10 bypassing the throttle valve 4
The vehicle near conditioner (which includes a compressor (not shown) driven by engine 1
When the air conditioner (hereinafter abbreviated as "air conditioner") is turned on, more specifically, a normally closed solenoid valve (auxiliary air amount control valve H1 is provided) which is turned on when the compressor is in an engine-driven state and opens the auxiliary air passage 10. By turning on this solenoid valve 11 and opening the auxiliary air passage 10 when the air conditioner is turned on, a drop in rotation due to the driving load of the compressor is prevented. A relay (not shown) is installed to turn the compressor (air conditioner) on and off.
An auxiliary air amount control means is constituted by the relay, etc., which controls ON/OFF of the electromagnetic valve 11.

Next, fuel supply control by the control unit 8 and fail-safe control according to the present invention will be explained according to the routine shown in the flowchart of FIG.

In this embodiment, basic fuel supply amount setting means.

The functions of fuel supply control means, abnormality detection means, abnormality fuel supply amount setting means, opening area conversion means, and opening area correction means are provided in the form of software as shown in the flowchart of FIG. 3 above.

The routine shown in the flowchart of FIG. 3 is a fuel injection amount setting routine, and is executed, for example, at every minute time.

Here, first in step 1 (indicated as Sl in the figure; the same applies hereinafter), an abnormality of the air flow meter 3 is determined.
This abnormality determination is performed, for example, when the output voltage output from the air flow meter 3 according to the intake air flow rate Q falls below a predetermined voltage (abnormality determination level voltage) even once during the execution cycle of this routine. It is determined that the meter 3 is abnormal. In addition, air flow meter 3 here
The abnormality determination may be performed by other methods,
This does not limit the abnormality determination method.

When it is determined in step 1 that the air flow meter 3 is normal, the process proceeds to step 2 in order to set the normal basic fuel injection amount based on the intake air flow rate Q detected by the air flow meter 3.

In step 2, the basic fuel injection amount 'rp is calculated according to the following formula.

T p = K o This is to ensure that the fuel is set in accordance with the amount of intake air per unit.

On the other hand, if it is determined in step 1 that the air flow meter 3 is abnormal and the intake air flow rate Q detected by the air flow meter 3 is unreliable, the process proceeds to step 3 and the throttle valve 4 is opened as detected by the throttle sensor 5. degree TVO is converted into a value A corresponding to the opening area of the intake passage 2 in which the throttle valve 4 is interposed.

A map of the opening area equivalent value A corresponding to the throttle valve opening degree TVO is stored in advance in the ROM of the microcomputer built in the control unit 8.
Based on the detected opening TVO, the corresponding opening area equivalent value A is searched from this map.

In the next step 4, turn on the air conditioner compressor.
- Determine OFF, that is, ON-OFF of the normally closed solenoid valve 11 that controls opening and closing of the auxiliary air passage 10. Here, when the air conditioner is ON and the solenoid valve 11 is controlled to be ON to open and air is supplied through the auxiliary air passage IO, the process proceeds to step 5.

In step 5, the throttle valve opening T
A predetermined correction value ΔA is added to the opening area equivalent value A obtained by converting VO based on the map, and a new opening area equivalent value A is set. The correction value ΔA is the throttle valve opening T
Auxiliary air passage 10 that can be treated equivalently to value A converted from VO
By adding this correction value ΔA, the opening area in the intake system of the engine 1 can be changed to the opening area of the auxiliary air passage 10 controlled by the solenoid valve 11 in addition to that controlled by the throttle valve 4. It can also be calculated including the area. When the opening area of the intake system is calculated and set only from the throttle valve opening TVO, the auxiliary air passage I
This does not include the opening area that changes as O is turned on and off, and when the solenoid valve 11 is turned on, a value smaller than the actual one is set by an amount equivalent to the opening area of the auxiliary air passage 10 relative to the total opening area of the intake system. By adding A to the correction value as described above, the opening area equivalent value A in the intake system of the engine 1 can be set with high accuracy.

When it is determined in step 4 that the air conditioner is OFF, this means that the solenoid valve 11 is OFF and the auxiliary air passage 10 is closed, so the opening area obtained by converting the throttle valve opening degree TVO in step 3 Since the equivalent value A corresponds to the total opening area of the intake system, step 5 is skipped and the process proceeds to step 6.

In step 6, the basic fuel injection amount Tp is calculated based on the intake system opening area equivalent value A obtained as described above and the engine rotation speed N detected by the rotation speed sensor 7 according to the following formula.

T p =K AXA/N Here, Kh is a constant, and assuming that a constant intake air flow rate per unit area of the intake system can be obtained, the fuel corresponding to the intake air amount per unit rotation is calculated and set. It is.

In this way, when the air flow meter 3 is abnormal, the throttle valve opening TVO is converted to the value A equivalent to the opening area of the intake system, and the O of the solenoid valve 11 installed in the auxiliary air passage 10 is
At N, the opening area equivalent value ΔA of the auxiliary air passage 10 is added to the opening area equivalent value A based on the TVO, and the opening area change of the engine 1 intake system is determined not only by the opening degree TVO of the throttle valve 4 but also by the auxiliary air passage lO. Taking this into consideration, the basic fuel injection amount Tp is set based on the opening area equivalent value A and the engine rotational speed N, thereby stabilizing the operation of the engine 1 even if the air flow meter 3 becomes abnormal. can be continued.

By the way, on the low opening side of the throttle valve 4, the gradient of the opening area change with respect to the opening change is large, so when setting the map of the opening area equivalent value A corresponding to the throttle valve opening TVO, it is necessary to If the grid of the map is not made fine, the accuracy of setting the opening area equivalent value A on the low opening side cannot be ensured.

However, in this embodiment, the throttle valve opening TVO
Since there is a one-to-one correspondence between the value A and the opening area equivalent value A, for example, the intake air flow IQ and the basic fuel injection amount Tp can be searched from a map using the throttle valve opening TVO and the engine rotational speed N as parameters. Even if the lattice state (resolution) of the throttle valve opening TVO is the same as in the case of calculation, the amount of memory is small because the parameter of the engine speed N is not included, and fail-safe control is unnecessary when the air flow meter 3 is normal. The amount of memory used can be minimized.

As mentioned above, when the air flow meter 3 is normal, the basic fuel injection amount Tp is calculated based on the intake air flow IQ detected by the air flow meter 3, and
When there is an abnormality, the basic fuel injection amount Tp is calculated based on the opening area equivalent value A retrieved from the map based on the throttle valve opening degree TVO, and in the next step 7, for example, the cooling water temperature Tw detected by the water temperature sensor 6 is calculated. The final fuel injection amount Ti is calculated by applying various corrections to the basic fuel injection amount Tp depending on the engine operating state.

Then, in the next step 8, the fuel injection amount fiTi calculated in the above step 7 is set in an output register, and when a predetermined fuel injection timing comes, the latest fuel injection amount Ti set in this output register is read out. By applying a driving pulse signal of pulse 11 corresponding to the fuel injection amount Ti to the fuel injection valve 9, the fuel injection valve 9 is opened for a predetermined period of time and fuel is supplied to the engine l.

In this embodiment, the solenoid valve 11 installed in the auxiliary air passage 10 is configured to be turned on and off in accordance with the ON and OFF of the air conditioner. The opening degree may be variably controlled by controlling the duty ratio of the pulse signal. In this case, since the opening degree of the solenoid valve 11 can be known from the duty ratio, the correction value ΔA can be variably set according to the duty ratio, so that the opening degree of the auxiliary air passage 10 can be adjusted with high accuracy. Correction can be made, and in this case, the control unit 8 serves as the auxiliary air amount control means.

Furthermore, in this embodiment, the fuel supply control device is configured to detect the intake air flow rate Q as the state quantity of the intake air and set the basic fuel injection amount Tp, but instead of the intake air flow rate Q, the intake air pressure ( The configuration may be such that the basic fuel injection amount Tp is set based on this intake pressure by detecting the intake pressure (intake negative pressure), and when the sensor that detects the intake pressure is abnormal, fail-safe control similar to this embodiment is performed. You can get the same effect by doing this.

<Effects of the Invention> As explained above, according to the present invention, state quantities of intake air such as intake air flow rate and intake pressure are detected, and the basic fuel supply amount is set based on the detected values. In the fuel supply control device, when the sensor that detects the state quantity of the intake air is abnormal, the throttle valve opening is converted to a value equivalent to the opening area of the intake system, and the value obtained by dividing this equivalent opening area by the engine rotation speed is calculated. By configuring the basic fuel supply amount to be set based on , it is possible to reduce the amount of memory for fail-safe control while ensuring the accuracy of fuel supply control during fail-safe fuel control.

In addition, when the amount of auxiliary air is controlled by an auxiliary air amount control valve installed in the auxiliary air passage that bypasses the throttle valve, the correction value corresponding to the opening degree of this auxiliary air amount control valve is Since it is configured to be added to the value equivalent to the opening area obtained by converting from the opening degree, there is an effect that fuel setting accuracy can be ensured during fail-safe control even when auxiliary air amount control is performed.

[Brief Description of the Drawings] Fig. 1 is a block diagram showing the configuration of the present invention, Fig. 2 is a system schematic diagram showing an embodiment of the present invention, and Fig. 3 is normal fuel supply amount control in the above embodiment. FIG. 4 is a diagram showing the relationship between throttle valve opening and intake air amount, and FIG. 5 is a diagram illustrating a conventional map grid for fail-safe control. . l... Engine 3... Air flow meter 4...
・Throttle valve 5...Throttle sensor 7・
...Rotational speed sensor 8...Control unit 9...Fuel injection valve 10...Auxiliary air passage 1
1... Solenoid valve (auxiliary air flow control valve) Figure 3 Patent applicant: Japan Electronics Co., Ltd. Agent Patent attorney: Fujio Sasashima

Claims (2)

[Claims] (1) Intake air state quantity detection means that detects the state quantity of engine intake air, and basic fuel supply amount setting that sets the basic fuel supply amount based on the state quantity of intake air detected by the intake air state quantity detection means. and a fuel supply control means for driving and controlling the fuel supply means based on the set basic fuel supply amount, wherein the intake air state quantity detection means includes: an abnormality detection means for detecting an abnormality; a throttle valve opening detection means for detecting the opening of the throttle valve; an engine rotational speed detection means for detecting the rotational speed of the engine; an opening area conversion means for converting the converted opening area equivalent value into an equivalent value; and an opening area conversion means for converting the converted opening area equivalent value into an equivalent value in place of the basic fuel supply amount setting means when the abnormality detection means detects an abnormality in the intake air state quantity detection means. and abnormal fuel supply amount setting means for setting a basic fuel supply amount based on a value divided by the engine rotational speed and operating the fuel supply control means based on the basic fuel supply amount. A fail-safe device in a fuel supply control device for an internal combustion engine. (2) Assisting the internal combustion engine to control the amount of auxiliary air supplied through the auxiliary air passage through the opening degree of an auxiliary air amount control valve installed in the auxiliary air passage that bypasses the throttle valve. comprising an air amount control means, which corrects by adding a correction value according to the opening degree of an auxiliary air amount control valve controlled by the auxiliary air amount control means to the opening area equivalent value converted by the opening area conversion means; 2. The fail-safe fuel supply control device for an internal combustion engine according to claim 1, further comprising an opening area correction means for causing the abnormal fuel supply amount setting means to set a basic fuel supply amount based on the correction result. Device.