JPH06330798A - Self-diagnostic device in assist air device for internal combustion engine - Google Patents

Abstract

PURPOSE:To judge whether or not an assist air device for atomizing fuel functions normally. CONSTITUTION:A transient operation condition of an engine is detected (S1). An average value alphaAV of fluctuation of air-fuel ratio feedback correction factors within a specified time after transient judgment (S2, S8) is obtained as a value indicating air-fuel ratio fluctuation width in the transient operation (S3 and S4, S9 and S10). When assist air is actually supplied, atomization angoe of fuel is enlarged for increasing a flow rate along a wall, accordingly the air-fuel ratio fluctuation width is increased in the transient operation. It is judged whether or not the average value alphaAV corresponds to the characteristic (S5 to S7, S11 to S13). Based on the judgment result, failure occurrence is judged in respect to the assist air device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-diagnosis device for an assist air device of an internal combustion engine, and more specifically, a part of engine intake air is ejected as assist air in the vicinity of a nozzle hole of a fuel injection valve to form a fine particle The present invention relates to a technique for diagnosing whether or not the assist air device that is intended to be realized is functioning properly.

[0002]

2. Description of the Related Art Conventionally, as an assist air supply device for an internal combustion engine, a part of intake air is guided as assist air from an intake passage upstream of a throttle valve to the vicinity of an injection hole of a fuel injection valve and injected from the injection valve. It is known that the assist air collides with the generated fuel to atomize the fuel, thereby improving combustion and improving fuel consumption and exhaust properties (Japanese Patent Publication No. 9465/1989, Japanese Utility Model Publication No. 9465/1989). 63-1
8767, etc.).

By the way, the supply of the assist air is as follows.
This is effective when the engine cannot atomize the fuel satisfactorily at low temperatures, but when atomization is sufficient without the supply of assist air, the jet of assist air disturbs the directivity of the fuel spray. As a result, the spray angle is increased, and the minimum intake air amount is increased by the supply of assist air, which causes the idle rotation speed to be increased more than necessary during warm-up when the idle request air amount is small.

Therefore, an electromagnetic on-off valve is provided in the passage for guiding the assist air to the fuel injection valve, and the on-off valve is controlled on / off based on the operating conditions such as the temperature of the cooling water to assist the engine when the engine is cold. Some are configured to supply assist air only when air is needed.

[0005]

As a method of diagnosing a failure in the above assist air device, there is a method of detecting disconnection of the electromagnetic on-off valve. Even if the energization is being controlled normally according to the control signal, it may not be possible to switch the supply / cutoff of the assist air in response to the control signal due to sticking of the valve element or clogging of the passage. However, there is a problem that the above-mentioned diagnosis method cannot be used even if the above occurs.

The present invention has been made in view of the above circumstances, and it is possible to diagnose whether or not the assist air supply / interruption control is actually functioning and the desired fuel atomization control is functioning properly. It is intended to provide a self-diagnosis device.

[0007]

Therefore, a self-diagnosis device in an assist air system for an internal combustion engine according to the present invention is
It is configured as shown in FIG. 1 or 2. In FIG.
The assist air passage is a passage for ejecting a part of the engine intake air as assist air in the vicinity of the injection hole of the fuel injection valve, and the assist air supply switching means supplies and cuts off the assist air through the assist air passage. Switch control.

On the other hand, the transient detecting means detects the transient operating state of the engine, and the air-fuel ratio detecting means detects the air-fuel ratio of the intake air-fuel mixture of the engine. Here, the air-fuel ratio fluctuation width detecting means distinguishes the switching control state of the assist air supply switching means, and in the transient operation state detected by the transient detecting means, the air-fuel ratio variation detecting means detects the air-fuel ratio variation range based on the detection result of the air-fuel ratio detecting means. Detects the fluctuation range of the fuel ratio.

The self-diagnosis means based on the air-fuel ratio makes a failure diagnosis of the assist air device based on the air-fuel ratio fluctuation width for each switching control state detected by the air-fuel ratio fluctuation width detection means. In FIG. 2, the assist air passage is a passage for ejecting a part of the engine intake air as assist air in the vicinity of the injection hole of the fuel injection valve, and the assist air supply switching means is the assist air passage through the assist air passage. Controls switching between supply and cutoff.

On the other hand, the rotational speed detecting means detects the rotational speed of the engine, and the idle detecting means detects a predetermined idle operating state of the engine. Here, the idle rotation detecting means sets the engine rotation speed detected by the rotation speed means to a switching control state by the assist air supply switching means when a predetermined idle operating state is detected by the idle detection means. The idle rotation speed is detected separately.

Then, the self-diagnosis means by idle rotation makes a failure diagnosis of the assist air device based on the idle rotation speed for each switching control state detected by the idle rotation detection means.

[0012]

[Operation] When the assist air is supplied, the assist air collides with the fuel spray from the injection valve and atomizes,
This causes an increase in the spray angle, thus increasing the wall flow rate. Therefore, when the assist air is supplied, the fluctuation range of the air-fuel ratio during the transient operation tends to be larger than that during the interruption. Therefore, by determining whether or not the fluctuation range of the air-fuel ratio during transient operation has a value corresponding to the switching control state of assist air, the atomization by assist air is actually performed in response to the switching control. It will be possible to diagnose whether the engine is being shut off or the assist air is actually shut off.

When air is supplied through the assist air passage, the amount of air supplied through the assist air passage increases as compared to when the air is shut off. Higher speed. Therefore, the rotation speed in the idle operation state where the influence of the assist air supply is large (idle rotation speed) is detected according to the switching control state of the assist air supply, and whether it matches the characteristics of the rotation speed according to the switching control state. Depending on whether
The assist air device is now diagnosed.

[0014]

EXAMPLES Examples of the present invention will be described below. In FIG. 3 showing an embodiment, air is drawn into an internal combustion engine 1 from an air cleaner 2 through an intake duct 3, a throttle valve 4 (throttle valve) and an intake manifold 5. At each branch portion of the intake manifold 5, a fuel injection valve 6 is provided for each cylinder.

The fuel injection valve 6 is an electromagnetic fuel injection valve which is energized by a solenoid to open the valve, and deenergized to close the valve, and a pulse corresponding to a required fuel amount sent from a control unit 12 described later. The fuel is intermittently driven to open by a drive pulse signal having a width, is fed by pressure from a fuel pump (not shown), and the fuel adjusted to a predetermined pressure by a pressure regulator is injected and supplied to the engine 1. The fuel injection valve 6 is installed so as to face the intake valve.

A spark plug 7 is provided in each combustion chamber of the engine 1, and spark ignition is performed by the spark plug 7 to ignite and burn the air-fuel mixture. Exhaust gas from the engine 1 is discharged through an exhaust manifold 17, an exhaust duct 18, a catalyst 19, and a muffler 20. The control unit 12 includes a CPU, ROM, RAM, A /
A microcomputer including a D converter, an input / output interface, and the like is provided, receives input signals from various sensors, calculates a fuel injection amount corresponding to the cylinder intake air amount, and operates the fuel injection valve 6. The ignition timing ADV according to operating conditions such as engine load and rotational speed
Is set and the ignition by the spark plug 7 is controlled.

As the various sensors, the intake duct 3 is used.
An air flow meter 8 is provided therein and outputs a signal according to the intake air flow rate Q of the engine 1. Further, a crank angle sensor 9 (rotation detecting means) is provided, and at each predetermined piston position in each cylinder (for example, BTDC 70 ° C).
Reference angle signal REF of A) and crank angle 1 ° or 2 °
The unit angle signal POS for each is output to each. Here, the engine rotation speed Ne can be calculated by measuring the cycle of the reference angle signal REF or the number of generated unit angle signals POS within a predetermined time.

A water temperature sensor 10 for detecting the cooling water temperature Tw of the water jacket of the engine 1 is also provided.
Further, a throttle sensor 11 for detecting the opening degree TVO of the throttle valve 4 by a potentiometer is provided. Further, an oxygen sensor 21 (air-fuel ratio detecting means) for detecting the oxygen concentration in the exhaust gas is provided at the collecting portion of the exhaust manifold 17.
Is provided. The oxygen sensor 21 is a known sensor that detects rich / lean with respect to the stoichiometric air-fuel ratio by detecting the oxygen concentration in the exhaust gas that is closely related to the air-fuel ratio of the engine intake air-fuel mixture.

Then, the control unit 12 performs proportional / integral control of the air-fuel ratio feedback correction coefficient α based on the rich / lean of the actual air-fuel ratio with respect to the stoichiometric air-fuel ratio detected by the oxygen sensor 21, and the air-fuel ratio is adjusted. It has an air-fuel ratio feedback control function for performing feedback control to the stoichiometric air-fuel ratio which is the target air-fuel ratio by correcting the basic fuel injection amount with the feedback correction coefficient α (see FIG. 5).

On the other hand, an electromagnetic idle control valve 14 is provided in a bypass passage 13 that bypasses the throttle valve 4. The idle control valve 14 is an opening adjustment valve whose opening is adjusted by duty-controlling the energization of the attached electromagnetic coil, and the control unit 12 approaches the target rotation speed during a predetermined idle operation. Thus, the opening degree of the idle control valve 14 is feedback-controlled.

Further, an assist air passage 15 is provided which branches from the intake duct 3 on the upstream side of the throttle valve 4 and bypasses the throttle valve 4 and opens near the injection holes of each fuel injection valve 6. The air (hereinafter referred to as assist air) guided by the pressure difference between the upstream and downstream sides of No. 4 is ejected near the injection hole of the fuel injection valve 6 and collides with the injected fuel to promote atomization of the injected fuel. ing.

A normally closed solenoid valve 16 for controlling the opening / closing of the assist air passage 15 is provided in the middle of the assist air passage 15. This solenoid valve 16 as an assist air supply switching means is to be on / off controlled by the control unit 12 based on information such as the cooling water temperature Tw detected by the water temperature sensor 10, and one of the engine intake air As a part, the supply / cutoff of the assist air ejected to the injection hole portion is switched and controlled.

As described above, the control unit 12 has a function of controlling the supply / cutoff of the assist air by the on / off control of the solenoid valve 16 and performing a failure diagnosis of the assist air device. The state of diagnosis will be described with reference to the flowchart of FIG. In this embodiment, the function as the air-fuel ratio fluctuation range detection means and the self-diagnosis means based on the air-fuel ratio is provided in software by the control unit 12 as shown in the flowchart of FIG.

In the flow chart of FIG. 4, first, in step 1 (denoted as S1 in the figure. The same applies hereinafter),
Throttle valve opening TV detected by the throttle sensor 11
The steady state / acceleration / deceleration of the engine 1 is determined based on the rate of change of O per unit time. In this embodiment, the throttle sensor 11 corresponds to the transient detecting means.

When it is judged in step 1 that the throttle valve 4 is operated to be opened at a predetermined ratio or more and the engine 1 is in the accelerating operation state, the routine proceeds to step 2. In step 2, it is determined whether or not the elapsed time from the initial acceleration determination is within a predetermined time. Then, when the elapsed time from the initial acceleration determination is within the predetermined time, the routine proceeds to step 3, where the air-fuel ratio feedback correction coefficient α is sampled.

The correction coefficient α in step 3 above
The pulling is a correction coefficient α in the steady state before acceleration judgment.
Was set to the latest with the average value of as the reference value (initial value)
Deviation between the correction coefficient α and the average value (α_1,α_2,...
α_n) For each proportional / integral control cycle of the correction coefficient α.
It is a ring (see FIG. 5). The sampling
Deviation (α_1,α_2,... α_n) Is the next step 4
Are sequentially integrated with, and the integrated value is divided by the sampling number
Therefore, the average value of the deviation α _AVIs calculated.

When the air-fuel ratio becomes lean due to the acceleration operation of the engine 1, the correction coefficient α is gradually increased by integral control in order to eliminate such leaning, but the degree of leaning ( The larger the fluctuation range of the air-fuel ratio, the higher the level of the required correction coefficient α, and it takes time to reach the required correction coefficient α. Therefore, if the lean degree is small, the correction coefficient α converges in a relatively short time within the predetermined time,
Although the average value α _AV takes a relatively small value, the larger the degree of leaning, the longer the correction coefficient α is controlled to increase within the predetermined time, and the average value α _AV also increases accordingly. growing. Therefore, the degree of leaning (air-fuel ratio fluctuation range) that accompanies the acceleration operation can be determined by the average value α _AV .

When the average value α _AV corresponding to the air-fuel ratio fluctuation range during acceleration is obtained as described above, in the next step 5,
The control state of assist air is determined based on ON / OFF of the control signal output to the solenoid valve 16. When the ON control signal is output to the solenoid valve 16 and the assist air supply control is being performed, the process proceeds to step 6, and the average value α _AV and the assist air is still supplied during acceleration. If it is, the corresponding judgment level α _ON (addition) is compared. In other words, it is determined whether or not the actually detected air-fuel ratio fluctuation range during acceleration is equal to or greater than a predetermined value.

The determination level α _ON (addition) is set to a level that does not fall in the acceleration state where the assist air is supplied according to the control signal and the fuel is atomized. That is, when the assist air is supplied, the fuel injected from the fuel injection valve 6 collides with the assist air to increase the spray angle and increase the amount of fuel that becomes a wall flow. Grows larger.
Therefore, although the assist air is being supplied as the control state, if the lean degree during acceleration is not a size commensurate with the assist air supply, the assist air is not actually supplied. It can be presumed that this has not been done or the amount of ethist air has decreased.

Therefore, when it is determined in step 6 that the average value α _AV is lower than the determination level α _ON (addition), in other words, the leaning degree during acceleration is lower than the desired level. In this case, the process proceeds to step 15 to determine the failure of the assist air device. On the other hand, when it is determined that the average value α _AV is equal to or higher than the determination level α _ON (additional), in other words, when the desired level of leaning has occurred, the assist air is actually supplied. Therefore, it is judged that the spray angle has increased (the wall flow rate has increased), and the step
Proceed to step 14 and determine that the assist air system is functioning normally.

When it is determined in step 5 that the control state of the assist air is the cutoff (OFF) state,
In step 7, the determination level α _OFF (addition) corresponding to acceleration in the assist air cutoff control state is compared with the average value α _AV . If the assist air is shut off as controlled, the spray angle will not increase and
Since the wall flow rate should be small, it is expected that the degree of leaning during acceleration will also be low.

Therefore, when it is determined in step 7 that the average value α _AV exceeds the determination level α _OFF (addition), the assist air which should have been cut off in the control state is actually supplied. However, it is considered that the degree of leaning at the time of acceleration is increased due to the expansion of the spray angle due to the supply of the assist air, and the process proceeds to step 15 to determine the failure of the assist air device.

If it is determined in step 7 that the average value α _AV is equal to or lower than the determination level α _OFF (addition),
Since the assist air is cut off according to the control, it is determined that the degree of leaning during acceleration is small, and the routine proceeds to step 14, where it is determined that the assist air device is functioning normally. On the other hand, when it is determined in step 1 that the vehicle is in the deceleration operation state, the air-fuel ratio fluctuates in the rich direction,
Also at this time, similarly to the time of acceleration, the average value α _AV that indicates the degree of enrichment of the air-fuel ratio is obtained,
This average value α _AV is compared with the preset judgment levels α _ON (decrease) and α _OFF (decrease) for deceleration, and whether or not the degree of enrichment corresponding to the control state of the assist air is shown. Thus, it is determined whether the assist air device is normal or not (step 8 to step 13).

As described above, according to the above-described embodiment, when the assist air is supplied, the spray angle is expanded, which increases the wall flow rate, and the air-fuel ratio fluctuation range during the transient operation is increased. Then, it is determined whether or not the assist air device is functioning properly by comparing the actually detected air-fuel ratio fluctuation range during transient operation with the determination level corresponding to the control state of the assist air.

Therefore, the diagnosis is not limited to the disconnection of the solenoid valve 16, but it is also possible to diagnose a state in which the assist air cannot be supplied or shut off in accordance with the control because the valve is stuck or the assist air passage 15 is clogged. It is possible to provide a highly reliable diagnostic result. In the above embodiment, the fluctuation range of the air-fuel ratio during the transient operation is determined based on the average value α _AV , but when an oxygen sensor capable of detecting the air-fuel ratio in a wide range is provided, The oxygen sensor may directly detect the change in the air-fuel ratio with respect to the target air-fuel ratio, and even when the result of the air-fuel ratio feedback control is used, the change in the air-fuel ratio during the control period and the transition may be detected. The fluctuation range may be detected based on the level of the correction coefficient α required to eliminate the fluctuation.

For self-diagnosis, the assist air supply control state and the shutoff control state may be forcibly created during the transient operation. By the way, when the solenoid valve 16 is controlled to be opened to supply the assist air, the effective opening area of the intake system is increased and the intake air amount of the engine is increased by the amount corresponding to the assist air. In particular, during idle operation with a small amount of air (when the engine has a low load), the influence of the change in the amount of air increases due to the supply and interruption of the assist air, and the supply of assist air greatly affects the idle rotation speed. Become.

Therefore, a second embodiment of the self-diagnosis of the assist air system utilizing the above characteristics will be described with reference to the flowchart of FIG. In this embodiment, the function as the idle rotation detecting means and the self-diagnosis means by the idle rotation is provided by the control unit 12 by software as shown in the flowchart of FIG.

In the flowchart of FIG. 6, first, at step 21, it is judged if the engine is in a predetermined idle operation state. In the predetermined idle operation state, the throttle opening TVO detected by the throttle sensor 11 is fully closed, and the idle rotation speed is sampled for each on / off control state of assist air as described later. It is preferable that the parameters that affect the idle rotation speed be constant except for the assist air. still,
The throttle sensor 11 corresponds to the idle detecting means in this embodiment.

When a predetermined idle operation state is detected in step 21, the routine proceeds to step 22 and it is determined whether the assist air control state is on or off. Then, depending on the ON / OFF discrimination, the routine proceeds to step 23 or step 24, and the engine rotation speed Ne at that time is sampled as an idle rotation speed.

Since the sampling of the rotation speed Ne in the steps 23 and 24 is for detecting the change of the idle rotation speed due to the control state of the assist air, the feedback control of the idle rotation speed is clamped. The rotation speed Ne is sampled. Then, in the next step 25, the idle speed Ne _ON in a state where performing supply control of assist air, the difference ΔN between the idle speed Ne _OFF in while performing the cutoff control of the assist air operation To do.

In step 26, the deviation ΔN is compared with a predetermined value. Here, when the supply / cutoff of the assist air is normally performed, the amount of air in the supply control state is larger than that in the cutoff control state by the amount of assist air,
Correspondingly, the deviation ΔN should be greater than or equal to a predetermined value. Therefore, if it is determined in step 26 that the deviation ΔN is greater than or equal to the predetermined value, the supply of assist air
It can be estimated that the interruption is actually performed according to the control,
In this case, the routine proceeds to step 27, where it is determined that the assist air device is functioning normally.

On the other hand, when it is determined in step 26 that the deviation ΔN is less than the predetermined value, the assist air supply / interruption switching is not actually performed for the assist air on / off control. It is estimated that the assist air is fixed in the cutoff state or the supply state. Therefore,
In this case, the process proceeds to step 28, and it is determined whether the assist air device has failed.

In the second embodiment, the on / off control of the assist air may be a normal control, or may be turned on or off in a predetermined idle operation state for self-diagnosis. Alternatively, the rotation speed at that time may be sampled by forcibly switching. Further, in the above embodiment, the assist air is supplied by the differential pressure between the upstream and downstream of the throttle valve 4, but the assist air supplied as a part of the engine intake air is supplied / shut-off switching control according to the operating condition. As long as it is configured as described above, for example, an air pump may be provided and the assist air may be supercharged and supplied.

[0044]

As described above, according to the present invention, the characteristic that the spray angle of the fuel is expanded by the supply of the assist air and the wall flow rate is increased, whereby the fluctuation range of the air-fuel ratio during the transient operation becomes large, or , By utilizing the characteristic that the amount of air increases and the rotation speed increases due to the supply of assist air, the self-diagnosis of the assist air device is performed based on the actual functional state of the assist air control. Even if a failure such as valve sticking or passage clogging occurs, diagnosis can be performed, and a highly reliable diagnosis result can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing the basic configuration of the present invention.

FIG. 2 is a block diagram showing the basic configuration of the present invention.

FIG. 3 is a system schematic diagram showing an embodiment of the present invention.

FIG. 4 is a flowchart showing a state of self-diagnosis according to the first embodiment.

FIG. 5 is a time chart showing the characteristics of air-fuel ratio feedback control.

FIG. 6 is a flowchart showing a state of self-diagnosis according to the second embodiment.

[Explanation of symbols]

 1 engine 4 throttle valve 6 fuel injection valve 8 air flow meter 9 crank angle sensor 11 throttle sensor 12 control unit 15 assist air passage 16 solenoid valve 21 oxygen sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical indication location F02M 23/04 A 23/12 Z A 69/00 310 F 8923-3G 69/46 69/04 G 8923-3G

Claims (2)

[Claims] 1. An assist air passage for ejecting a part of engine intake air as assist air in the vicinity of an injection hole of a fuel injection valve, and a supply of the assist air through the assist air passage.
In an assist air device for an internal combustion engine configured to include an assist air supply switching means for switching shutoff control, a transient detection means for detecting a transient operating state of the engine, and an air-fuel ratio of an intake air-fuel mixture of the engine are detected. By distinguishing the switching control state of the air-fuel ratio detection means and the assist air supply switching means, in the transient operating state detected by the transient detection means, the fluctuation range of the air-fuel ratio is determined based on the detection result of the air-fuel ratio detection means. An air-fuel ratio fluctuation range detecting means for detecting, and an air-fuel ratio self-diagnosis means for performing a failure diagnosis of the assist air device based on the air-fuel ratio fluctuation range for each switching control state detected by the air-fuel ratio fluctuation range detecting means, A self-diagnosis device in an assist air system for an internal combustion engine, characterized in that 2. An assist air passage for ejecting part of engine intake air as assist air in the vicinity of an injection hole of a fuel injection valve, and supply of the assist air through the assist air passage.
In an assist air device for an internal combustion engine configured to include an assist air supply switching means for switching shutoff control, a rotation speed detecting means for detecting a rotation speed of the engine, and an idle detection for detecting a predetermined idle operation state of the engine. Means, and when the predetermined idle operation state is detected by the idle detection means, the engine rotation speed detected by the rotation speed means is differentiated between the switching control state by the assist air supply switching means and the idle rotation speed. And an idle rotation self-diagnosis means for performing a failure diagnosis of the assist air device based on the idle rotation speed for each switching control state detected by the idle rotation detection means. In the assist air system of an internal combustion engine characterized by Cross-sectional devices.