JPH05263694A - Failure sensing device for fuel supply system - Google Patents

Abstract

PURPOSE:To sense failure in a fuel supply system at an early stage. without missing perfectly, and accurately by comparing the correcting amount of fuel injection amount with the specified failure judging value both under the engine in idling and non-idling. CONSTITUTION:A means 14 to sense the suced air amount and a means 17 to inject the fuel into each cylinder are installed in the suction passage 9 of an engine 1, while a means 36 to sense the actual air-fuel ratio of the mixture gas is furnished in the exhaust passage 11. On the basis of the sensed sucked air amount and actual air-fuel ratio, the correcting amount of the fuel injection amount is set by a fuel injection correcting amount setting means 41 so that the air-fuel ratio of the mixture gas is optimized. The set correcting amount is compared with a failure judging value when the engine 1 is idling, and failure in the fuel supply system is judged by the first failure judging means 42. Further when the engine 1 is out of idling, the set correcting amount is compared with the failure judging value followed by judgement of the fuel supply system by the second failure judging means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply system failure detection device, and more particularly to a device for detecting a failure of a fuel supply system such as an air flow meter or an injector based on an amount of deviation of an air-fuel ratio.

[0002]

2. Description of the Related Art Conventionally, as a method for detecting a failure of an air flow meter or an injector, which is a fuel supply system in an engine, for example, as disclosed in Japanese Patent Laid-Open No. 3-54345, an air-fuel ratio deviation amount is determined. It is known to detect and determine that a failure has occurred in the fuel supply system when the deviation amount of the air-fuel ratio exceeds a predetermined value. Specifically, an O ₂ sensor is arranged in the exhaust passage of the engine, the oxygen concentration in the exhaust gas is detected by the O ₂ sensor, and the fuel injection amount is feedback-corrected based on the oxygen concentration detection signal. Calculate the coefficient. If the learning value of the fuel injection amount set based on this feedback correction coefficient exceeds a predetermined value, it becomes impossible to set an appropriate air-fuel ratio, and a failure occurs in the air flow meter or injector. It is determined that it has occurred.

Such a failure detecting operation is generally performed during idle operation. The reason is that it is possible to detect the failure of the fuel supply system early because it is possible to detect the failure immediately after the engine is started. Also, since the intake air amount is small, there is a slight deviation in the fuel injection amount (clogged injector, etc.). ) Is generated, its influence greatly affects the air-fuel ratio, and failure detection can be performed, so failure detection accuracy can be increased, and further, since the intake air amount is small, Even if the bypass passage, which is arranged to bypass the air flow meter to adjust the output of the air flow meter and the intake air amount, is blocked, its influence greatly affects the air-fuel ratio. In particular, it is possible to detect clogging of the bypass passage.

[0004]

However, when the failure detection operation of the fuel supply system is performed only during the idle operation as described above, the failure of the fuel supply system may be overlooked as described below. In other words, during idle operation, the amount of intake air is small and the amount of exhaust is also small.
Due to this, uneven flow of exhaust gas is often generated in the exhaust passage. Therefore, when one of the injectors arranged in each cylinder is clogged, the exhaust from the cylinder clogged with this injector may not hit the O ₂ sensor due to the uneven flow of the exhaust. In such a case, the learning value does not exceed the predetermined value, so that the engine operation continues without failure determination.

The present invention has been made in view of this point, and an object of the present invention is to provide a failure detection device capable of detecting a failure in the fuel supply system without missing it.

[0006]

In order to achieve the above object, the present invention is designed to perform the failure detection operation of the fuel supply system even in the state where the drift of the exhaust gas does not occur in the exhaust passage. Specifically, the invention according to claim 1 is as shown in FIG.
As shown in, the intake air amount detecting means 14 arranged in the intake passage 9 of the engine 1 for detecting the intake air amount, and arranged for each cylinder of the engine 1, injecting fuel toward each cylinder. The fuel injection means 17, the actual air-fuel ratio detection means 36 for detecting the difference of the actual air-fuel ratio from the optimum air-fuel ratio of the air-fuel mixture according to the engine operating state, and the intake air amount detection means 14 and the actual air-fuel ratio detection means 36. A fuel injection correction amount setting unit 41 that receives each output and sets a correction amount of the fuel injection amount injected from the fuel injection unit 17 so that the air-fuel ratio of the air-fuel mixture becomes an optimum value according to the engine operating state. Prepare for.
Then, during the idle operation of the engine, a first failure for receiving the output signal of the fuel injection correction amount setting means 41 and comparing the output signal with a preset failure determination value to determine the failure of the fuel supply system. The determination means 42 receives the output signal of the fuel injection correction amount setting means 41 during non-idle operation of the engine, and determines the failure of the fuel supply system by comparing the output signal with a preset failure determination value. The second failure determination means 43 is provided.

According to a second aspect of the present invention, in the fuel supply system failure detection device according to the first aspect, the first failure determination means 42 outputs the output signal of the fuel injection correction amount setting means 41 during engine idle operation. In response, the output signal is compared with a preset failure determination value to determine at least the failure of the intake air amount detecting means 14. Further, the second failure determination means 43 receives the output signal of the fuel injection correction amount setting means 41 and compares the output signal with a preset failure determination value during non-idle operation of the engine, whereby the fuel injection means 17 failures are judged.

According to a third aspect of the present invention, in the fuel supply system failure detecting device according to the first or second aspect, the actual air-fuel ratio detecting means 36 is disposed in the exhaust passage 11 of the engine. An O ₂ sensor for detecting the oxygen concentration of the exhaust gas flowing through is used.

[0009]

With the above construction, the present invention provides the following actions. According to the first aspect of the present invention, the fuel injection correction amount is based on the intake air amount detected by the intake air amount detecting means 14 and the difference between the actual air-fuel ratio and the optimum air-fuel ratio detected by the actual air-fuel ratio detecting means 36. The setting unit 41 sets the correction amount of the fuel injection amount injected from the fuel injection unit 17, and the air-fuel ratio of the air-fuel mixture is set to the optimum value according to the engine operating state. Then, in the failure detection operation of the fuel supply system, the first failure determination means 42 receives the output signal of the fuel injection correction amount setting means 41 during idle operation of the engine 1, and the output signal and the failure set in advance. A failure of the fuel supply system is determined by comparing with the determination value. Further, during non-idle operation of the engine 1, the second failure determination means 43 receives the output signal of the fuel injection correction amount setting means 41 and compares the output signal with a preset failure determination value, This also determines the failure of the fuel supply system. As a result, the failure can be detected during the idle operation immediately after the engine is started, so that not only can the failure be detected early, but the failure of the fuel supply system can be detected even during the non-idle operation. Injector 1 arranged for each cylinder
Failure to overlook a failure in the case where one of the injectors 7 is clogged is compensated for, and failure detection is reliably performed.

According to the second aspect of the present invention, the first failure determination means 42 determines at least the failure of the intake air amount detection means 14 during the idle operation of the engine 1, and the second failure determination means 42 performs the second operation during the non-idle operation of the engine 1. Failure determination means 43
Determines the failure of the fuel injection means 17. This allows
Among the malfunctions of the fuel supply system, the malfunction of the intake air amount detecting means 14 and the malfunction of the fuel injection means 17 are discriminated.

According to the third aspect of the invention, the difference between the actual air-fuel ratio and the optimum air-fuel ratio is detected based on the oxygen concentration of the exhaust gas detected by the O ₂ sensor 36 arranged in the exhaust passage 11. Therefore, the correction amount of the fuel injection amount is set based on the detection signal of the oxygen concentration.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows the overall configuration of the embodiment of the present invention. In the figure, 1 is a multi-cylinder engine, and this engine 1
Is a cylinder block 3 having a plurality of (for example, four) cylinders 2 arranged in a direction perpendicular to the plane of the drawing, a cylinder head 4 assembled on the upper surface of the cylinder block 3, and a cylinder assembled on the upper surface of the cylinder head 4. Head cover 5
And a piston 6 that reciprocates in each cylinder 2,
A combustion chamber 7 defined by the lower surface of the cylinder head 4 and the top surface of the piston 6 is formed in the cylinder 2.
The piston 6 is connected to a crankshaft 8 via a connecting rod (not shown). Further, the cylinder head 4 has an intake port 4a and an exhaust port 4b.
Are formed. Further, 9 in FIG. 2 is an intake passage for supplying intake air into the combustion chamber 7, and 10 is an intake valve for opening and closing a downstream end opening of the intake port 4a. 11
Is an exhaust passage for discharging the exhaust gas in the combustion chamber 7, 12 is an exhaust valve for opening and closing the upstream end opening of the exhaust port 4b, 1
Reference numeral 3 is a catalytic converter as an exhaust gas purification device disposed in the exhaust passage 11.

In the intake passage 9, from the upstream side, in order from the upstream side, an air flow meter 14 as an intake air amount detecting means for detecting the intake air amount, a throttle valve 15 for controlling the intake air amount, and an intake pulsation. For absorption of
The injector 1 as the fuel injection means in the present invention, which is arranged in each of the cylinder 16 and each cylinder for injecting and supplying the fuel.
7 is provided, and an air cleaner 18 is provided at the upstream end of the intake passage 9.
It is connected to the. A part of the intake passage 9 on the downstream side of the surge tank 16 is branched into a primary passage 9a and a secondary passage 9b, and the secondary passage 9b is opened and closed by an actuator 9c which operates according to the internal pressure of the surge tank 16. The secondary valve 9d is provided. Further, in the intake passage 9,
An air flow meter bypass passage 9e is arranged so as to bypass the air flow meter 14, and when the engine 1 is idle, intake air also flows through the air flow meter bypass passage 9e. The output of 14 and the intake air amount are adjusted.

Reference numeral 19 denotes a bypass passage for bypassing the throttle valve 15 and supplying air to the combustion chamber 7. In the middle of the bypass passage, the amount of air flowing through the bypass passage 19 is controlled when the engine 1 is idle. An idle speed control valve (ISC valve) 20 including a proportional solenoid valve for adjusting the rotational speed (idle rotational speed) is provided.

Reference numeral 21 is a fuel tank connected to the injector 17 through a fuel supply passage 22. A fuel pump 22a is connected to the upstream end of the fuel supply passage 22 and the fuel supply passage 22 is connected to the fuel pump 22a.
A fuel filter 22b is interposed in the. Further, the injector 17 is connected to a regulator passage 23 having a pressure regulator 23a for maintaining a constant internal pressure of the injector 17 and performing stable fuel injection.

Further, 25 in FIG. 2 is a fuel tank 2
1 is an evaporative fuel supply apparatus for supplying the evaporative fuel generated in 1 to the combustion chamber 7 side, and is provided with a purge passage 26, the purge passage 26 having an upstream end opened to an upper portion in the fuel tank 21, The downstream end of the surge tank 16 opens into the intake passage 9. In the middle of the purge passage 26, a canister 27 for collecting and adsorbing the evaporated fuel and a purge passage 2 are provided.
Supplying evaporated fuel to the intake passage 9 by opening and closing 6 (page)
Of a duty solenoid valve for adjusting
And a control valve 28. Also,
An atmosphere open passage 29 is connected to the canister 27. The atmosphere opening passage 29 has a canister 27 at one end.
The other end is opened to the outside air in the internal space of the outside, and when the evaporated fuel is sent to the intake passage 9, the outside air is sucked into the canister 27 with the opening operation of the purge control valve 28. On the other hand, when the evaporated fuel overflows in the canister 27, a part of the evaporated fuel is released into the atmosphere.

Reference numeral 30 in FIG. 2 is an EGR device, which comprises an EGR passage 31 and an EGR control valve 32 interposed in the EGR passage 31,
The supply amount of EGR gas is set according to the pressure difference between the negative pressure on the downstream side of the throttle valve and the negative pressure on the upstream side of the throttle valve.

The injector 17, the idle speed control valve 20, the page control valve 28 and the like are operated and controlled by a control unit 40 having a built-in CPU. In addition, the control unit 40 has an intake air amount signal detected by the air flow meter 14, a signal of an idle switch 35 which is provided in the vicinity of the throttle valve 15 and is turned on during idle operation, and an exhaust passage 11. A detection signal of an O ₂ sensor 36 as an actual air-fuel ratio detecting means according to the present invention for detecting the oxygen concentration in the exhaust gas that is provided and is flowing through the exhaust passage 11 is input.

In this engine 1, the injector 1
Feedback control of the fuel injection amount from 7 is performed. That is, the oxygen concentration in the exhaust gas is detected by the O ₂ sensor 36, the detection signal of this oxygen concentration is transmitted to the control unit 40, and the control unit 40 calculates the feedback correction coefficient of the fuel injection amount based on this detection signal. To be done. It is well known in the art to calculate the feedback correction coefficient of the fuel injection amount based on the oxygen concentration in the exhaust gas in this way, and the correction amount of the fuel injection amount can be set with a simple configuration. .. Then, the learning value of the fuel injection amount is calculated based on this feedback correction coefficient, and the fuel injection from the injector 17 is performed by this learning value to set an appropriate air-fuel ratio of the air-fuel mixture according to the engine operating state. I am trying to do it.

The characteristic operation of this example is as follows.
This is a failure detection operation of the fuel supply system for detecting a failure of the air flow meter 14 due to clogging of the air flow meter bypass passage 9e or a failure of the injector 17 due to clogging of the injector 17. The signal processing procedure by the control unit 40 for performing the failure detection operation of the fuel supply system, which is the feature of this embodiment, will be described below with reference to the flowcharts of FIGS. 3 and 4. In the figure, first, the ignition switch is turned ON to start the operation, and in step S1, the detection signals of the respective sensors are read. Then, in step S2, it is determined whether the engine operating state is the idle operating state. Specifically, the idle switch 35 is turned on.
It is determined by operation that the engine is in an idle operation state.
Then, if YES in step S2, where the engine operating state is the idle operating state, step S2
3, the feedback correction coefficient is based on the detection signal of the oxygen concentration in the exhaust gas detected by the O ₂ sensor 36.
Calculate CFB1. Then, after the feedback correction coefficient CFB1 is calculated in this way, the process proceeds to step S4, and the learning value CLRN1 of the fuel injection amount is calculated based on the feedback correction coefficient CFB1 calculated in step S3. That is, the learned value CLRN1 corrects the fuel injection amount of the injector 17 in the idle operation state, and the fuel injection is performed with the corrected fuel injection amount. Then, in this way, the learning value CLRN
After the calculation of 1, the process proceeds to step S5, and it is determined whether the learning value CLRN1 calculated in step S4 is larger than a preset failure determination value α. That is, in step S5, when the learned value of the fuel injection amount is abnormally large, it is impossible to set an appropriate air-fuel ratio, and it is determined that a failure has occurred in the fuel supply system. I am trying to do it. If YES in step S5 when the learning value CLRN1 is larger than the failure determination value α, the process proceeds to step S6 to set the failure determination flag FLAG (A) to 1 and set it to 1 while the learning value CLRN1 is set.
If NO is less than the failure judgment value α, step S7
To 0 without turning on the failure judgment flag FLAG (A)
Set to.

On the other hand, if the engine operating condition is NO, which is not the idle operating condition in step S2, the process proceeds to step S8, in which the feedback correction coefficient is based on the detection signal of the oxygen concentration in the exhaust gas detected by the O ₂ sensor 36. Calculate CFB2. Then, after the feedback correction coefficient CFB2 is calculated in this way, step S
9, the fuel injection amount learning value CL is calculated based on the feedback correction coefficient CFB2 calculated in step S8.
Calculate RN2. That is, the learning value CLRN2 corrects the fuel injection amount of the injector 17 in the engine operating state, and the fuel injection is performed with the corrected fuel injection amount. Then, after the learning value CLRN2 is calculated in this way, it is determined in step S10 whether or not the learning value CLRN2 calculated in step S9 is larger than a preset failure determination value α. That is, in this step S10, when the learned value of the fuel injection amount is abnormally large, it is impossible to set an appropriate air-fuel ratio, and it is determined that a failure has occurred in the fuel supply system. I am trying to do it. If the learning value CLRN2 is larger than the failure determination value α in this step S10, the process proceeds to step S11 to set the failure determination flag FLAG (B) to 1 and set the learning value CLRN2 to the failure determination. In the case of NO that is less than or equal to the value α, the process proceeds to step S12 and the failure determination flag FLAG (B)
Set to 0 without starting. In this way, failure determination is performed during engine idle operation and non-idle operation, and the failure determination flags FLAG (A), FLAG
(B) is set.

After that, the process proceeds to step S13 (FIG. 4), and it is determined whether or not the failure determination flag FLAG (A) during idle operation is set to 1, and this failure determination flag FLAG (A) is set to 1. If YES is set in step S14, the process proceeds to step S14. And this step S1
4, the failure determination flag FLAG during non-idle operation
It is determined whether or not (B) is set to 1, and if this failure determination flag FLAG (B) is set to 1, in the case of YES, the routine proceeds to step S15, where the air flow meter fail flag FLAG (AFM ) Is set to 1 and then to step S16, the injector fail flag FLAG (I
Start J) and set it to 1. That is, since both the failure determination flag FLAG (A) during idle operation and the failure determination flag FLAG (B) during non-idle operation are set to 1, both the air flow meter 14 and the injector 17 have a failure. After it is determined that the airflow meter bypass passage 9e is clogged in the airflow meter 14 or at least one injector 17 is clogged in the injector 17, it is returned. ..

On the other hand, in step S14, if the failure determination flag FLAG (B) during non-idle operation is set to 0, the process proceeds to step S17, and the air flow meter fail flag FLAG (AFM) is set up. After that, the process proceeds to step S18 and the injector fail flag FLAG (IJ) is set to 0 without being raised.
That is, the failure determination flag FLAG during idle operation
Since (A) is set to 1, it is determined that a failure has occurred in the air flow meter 14, and the failure determination flag FLAG (B) during non-idle operation is set to 0. After it is determined that the injector 17 has not failed, the process is returned.

If the failure determination flag FLAG (A) during idle operation is NO in step S13, the process proceeds to step S19. Then, in this step S19, it is determined whether or not the failure determination flag FLAG (B) in the non-idle operation is set to 1, and the failure determination flag FLAG (B) is set to 1 in YES. In this case, the process proceeds to step S20 and the air flow meter fail flag FLAG (AFM) is set to 0 without being raised, and then the process proceeds to step S21 to raise the injector fail flag FLAG (IJ) to 1. That is, the failure determination flag during idle operation
Since FLAG (A) is set to 0, it is determined that no failure has occurred in the air flow meter 14, and the failure determination flag FLAG (B) during non-idle operation.
Is set to 1, and it is determined that the injector 17 has failed, and then the process returns.

On the other hand, in step S19, when the failure determination flag FLAG (B) is set to 0, NO,
In step S22, the air flow meter fail flag FLAG (AFM) is set to 0 without being raised, and then in step S23, the injector fail flag FLAG (IFM) is set.
J) is also set to 0 without starting. That is, since the failure determination flag FLAG (A) during idle operation and the failure determination flag FLAG (B) during non-idle operation are both set to 0, no failure has occurred in either the air flow meter 14 or the injector 17. After determining that
Will be returned.

Since the control operation as described above is performed, the fuel injection correction amount setting means 41 according to the present invention in step S4 and step 9 is performed in step S4.
5, the first failure determination means 42 referred to in the present invention and the second failure determination means 43 referred to in the present invention in step S10.
Is configured.

Since the failure of the fuel supply system is detected by the operation of the control unit 40 as described above, the failure can be detected during the idle operation immediately after the engine is started, so that the failure of the fuel supply system can be detected early. In addition, since it is possible to detect a failure of the injector 17 during non-idle operation in which there is no drift in the exhaust gas, one of the injectors 17 provided for each cylinder can be detected as in the conventional case.
In the case where two injectors are clogged, it is possible to compensate for a missed failure of the fuel supply system caused by the fact that the exhaust gas from the cylinder clogged with the injector 17 does not hit the O ₂ sensor due to the uneven flow of the exhaust gas during idle operation. Therefore, the failure of the fuel supply system can be accurately detected. Further, it is possible to distinguish between the failure of the air flow meter 14 and the failure of the injector 17 among the failures of the fuel supply system, and it is possible to recognize the failure location of the fuel supply system.

In the control operation of this embodiment, the failure of the air flow meter 14 is detected during the idling operation of the engine 1. However, even if the drift is generated during the idling operation, the injector is used. When the exhaust gas from the cylinder clogged with 17 hits the O ₂ sensor 36, the failure of the injector 17 can be determined. Therefore, when the failure is determined during the failure determination during idle operation, the air flow meter is used. It may be determined that a failure has occurred in at least one of 14 and the injector 17.

[0029]

As described above, according to the present invention,
The following effects are exhibited. According to the invention described in claim 1, when the engine is in the idle operation, the output signal of the fuel injection correction amount setting means is received, and the output signal is compared with a preset failure determination value, whereby the fuel supply system fails. The fuel supply system by receiving the output signal of the fuel injection correction amount setting means during non-idle operation of the engine and comparing the output signal with a preset failure determination value. And a second failure determination means for determining a failure, and the failure can be detected during idle operation immediately after the engine is started, so that the failure can be detected early.
Since the failure detection of the fuel supply system is performed even during the non-idle operation, it is possible to miss the failure when one of the injectors arranged for each cylinder is clogged during the idle operation. Therefore, the failure of the fuel supply system can be accurately detected.

According to the second aspect of the present invention, the first failure determination means determines at least the failure of the intake air amount detection means during the idle operation of the engine, and the second failure determination means.
By the failure determination means, during non-idle operation of the engine,
Since the failure of the fuel injection means is determined, it is possible to distinguish the failure of the intake air amount detection means and the failure of the fuel injection means among the failures of the fuel supply system, and recognize the failure location of the fuel supply system. be able to.

According to the third aspect of the invention, the actual air-fuel ratio detecting means is constituted by an O ₂ sensor which is arranged in the exhaust passage of the engine and detects the oxygen concentration of the exhaust gas flowing through the exhaust passage. Since the correction amount of the fuel injection amount is set based on the oxygen concentration of the exhaust gas detected by the O ₂ sensor, the correction amount of the fuel injection amount can be set with a simple configuration.

[Brief description of drawings]

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

FIG. 2 is an overall schematic diagram of an engine.

FIG. 3 is a flow chart showing a part of a failure detection operation by the control unit.

FIG. 4 is a flowchart showing a part of a failure detection operation by the control unit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 engine 9 intake passage 11 exhaust passage 14 air flow meter (intake air amount detection means) 17 injector (fuel injection means) 36 O ₂ sensor (actual air-fuel ratio detection means) 41 fuel injection correction amount setting means 42 first failure determination means 43 Second failure determination means

Claims (3)

[Claims] 1. An intake air amount detecting means arranged in an intake passage of an engine for detecting an intake air amount, and a fuel injection means arranged for each cylinder of the engine and injecting fuel toward each cylinder. , The actual air-fuel ratio detection means for detecting the difference between the actual air-fuel ratio and the optimum air-fuel ratio of the air-fuel mixture according to the engine operating state, and the respective outputs of the intake air amount detection means and the actual air-fuel ratio detection means, Fuel injection correction amount setting means for setting a correction amount of the fuel injection amount injected from the fuel injection means so that the air-fuel ratio becomes an optimum value according to the engine operating state, and the fuel injection during the idle operation of the engine. First failure determination means for determining a failure of the fuel supply system by receiving an output signal of the correction amount setting means and comparing the output signal with a preset failure determination value; A second failure determination means for receiving the output signal of the fuel injection correction amount setting means and comparing the output signal with a preset failure determination value to determine a failure of the fuel supply system. Failure detection device for fuel supply system. 2. The fuel supply system failure detection device according to claim 1, wherein the first failure determination means receives an output signal of the fuel injection correction amount setting means during idle operation of the engine,
At least a failure of the intake air amount detection means is determined by comparing the output signal with a preset failure determination value, and the second failure determination means is configured to:
A fuel supply characterized by being configured to receive an output signal of the fuel injection correction amount setting means and compare the output signal with a preset failure determination value to determine a failure of the fuel injection means. System failure detection device. 3. The failure detection device for a fuel supply system according to claim 1, wherein the actual air-fuel ratio detection means is arranged in the exhaust passage of the engine and detects the oxygen concentration of the exhaust gas flowing through the exhaust passage. A fuel supply system failure detection device comprising an O ₂ sensor.