JPH0729235Y2 - Fuel injection valve failure diagnostic device for electronically controlled fuel injection internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a fuel injection valve failure diagnosis device for an electronically controlled fuel injection type internal combustion engine.

<Prior Art> In a conventional electronically controlled fuel injection type internal combustion engine,
As disclosed in Japanese Patent Laid-Open No. 59-203829, the fuel injection amount is set based on the engine operating condition, and a drive pulse signal corresponding to this fuel injection amount is provided for each cylinder at a predetermined timing. The fuel is intermittently injected and supplied by outputting the fuel to each injection valve.

<Problems to be solved by the invention> By the way, since the fuel injection valve is driven to open according to the drive pulse signal as described above, if the output line of the drive pulse signal or the electromagnetic coil is disconnected, Even if the drive pulse signal is output from the control unit, the fuel injection valve is not actually driven to open and the fuel is not injected and supplied. As described above, when the fuel injection valve of the specific cylinder is disconnected, the desired combustion pressure does not occur in the specific cylinder, so that the rotational balance is deteriorated but the engine operation cannot be continued. It was difficult to notice, and even if it was noticed, it was difficult to determine in which cylinder the fuel injection valve was disconnected.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a fuel injection valve failure diagnosis device capable of detecting a cylinder in which a disconnection of a fuel injection valve has occurred.

<Means for Solving the Problems> Therefore, in the present invention, as shown in FIG. 1, a rotation synchronizing signal output means for outputting a detection signal for each predetermined reference position of the piston of each cylinder, and a predetermined low rotation stability of the engine. Judgment operation state detection means for detecting the operating state, air-fuel ratio detection means for detecting the engine exhaust gas component to detect the air-fuel ratio of the engine intake air-fuel mixture, and engine intake air-fuel mixture detected by the air-fuel ratio detection means A predetermined low rotation stable operation state of the engine is detected by the increase control state determination means for determining the state in which the fuel increase control is necessary to bring the actual air-fuel ratio closer to the target air-fuel ratio based on the air-fuel ratio, and the determination operation state detection means. And an interval time for measuring the interval time of the detection signal output from the rotation synchronization signal output means when the fuel increase control state determination means determines that the fuel increase control is required. And a fuel injection valve failure determination means for determining a fuel injection valve failure of a specific cylinder based on the ratio between the previous value and the current value of the detection signal interval time measured by the interval time measurement means. The fuel injection valve failure diagnosing device is configured.

<Operation> According to the failure diagnosis device having such a configuration, the fuel consumption increase control state determination means increases the fuel increase amount in order to bring the actual air-fuel ratio closer to the target air-fuel ratio based on the air-fuel ratio of the engine intake air-fuel mixture detected by the air-fuel ratio detection means. Determine the conditions that require control. Then, when the predetermined low rotation stable operation state of the engine is detected by the determination operation state detection means and the state in which the fuel increase control is required is determined by the increase control state determination means, the rotation synchronization signal output means outputs it. Output interval time of the detection signal for each predetermined reference position of the piston of each cylinder,
It is measured by the interval time measuring means. Then, the fuel injection valve failure determination means determines the fuel injection valve failure of the specific cylinder based on the ratio between the previous value and the current value of the measured interval time.

That is, if the fuel is not supplied due to the disconnection of the fuel injection valve of the specific cylinder, the rotation balance will be deteriorated. Therefore, if the rotation is originally stable, the rotation synchronization should be at equal time intervals. Variations will occur in the signal intervals. However, since rotational variations are also generated by misfire, pay attention to the fact that the average air-fuel ratio becomes lean unless fuel is supplied to a specific cylinder, and the fuel injection amount is adjusted to bring the actual air-fuel ratio close to the target air-fuel ratio. When it is necessary to correct the amount of increase, it is determined that the rotation variation is caused by the disconnection of the fuel injection valve instead of the misfire. Then, the rotation variation due to the disconnection of the fuel injection valve is specified to a predetermined cylinder based on the change of the interval time of the rotation synchronization signal.

The reason for making this determination on the low rotation side is to ensure that the interval time is accurately measured by the interval time measuring means.

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

In FIG. 2, air is sucked into the engine 1 from an air cleaner 2 through an intake duct 3, a throttle valve 4 and an intake manifold 5. At the 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 that is energized by a solenoid to open the valve, and deenergized to close the valve. The fuel injection valve 6 is energized by a drive pulse signal from the control unit 12 to open the valve. Fuel that is pumped from the fuel pump and adjusted to a predetermined pressure by the pressure regulator is injected and supplied.

A spark plug 7 is provided in the combustion chamber of each cylinder of the engine 1 to spark-ignite and burn the air-fuel mixture.

Then, from the engine 1, the exhaust manifold 8, the exhaust duct
Exhaust gas is discharged through the three-way catalyst 10 and the muffler 11.

The control unit 12 includes a CPU, ROM, RAM, a microcomputer including an A / D converter and an input / output interface, receives input signals from various sensors, and performs arithmetic processing as described later, The operation of the fuel injection valve 6 is controlled.

As the various sensors, a hot-wire or flap-type air flow meter 13 is provided in the intake duct 3 and outputs a voltage signal according to the intake air flow rate Q.

Also, a crank angle sensor as a rotation synchronization signal output means
With 14 cylinders and 6 cylinders, crank angle 120 °
Reference signal Ref for each (for each piston reference position of each cylinder),
The unit signal Pos for each crank angle of 1 ° or 2 ° is output. Here, the engine speed N can be calculated by measuring the cycle (interval time) of the reference signal Ref or the number of generated unit signals Pos within a predetermined time. The water jacket of the engine 1 is provided with a water temperature sensor 15 that detects the cooling water temperature Tw. The reference signal
One of the Refs can be discriminated from the other so that each reference signal Ref can be associated with a cylinder.

Further, an O ₂ sensor 16 as an air-fuel ratio detecting means is provided at the collecting portion of the exhaust manifold 8 to detect the air-fuel ratio of the air-fuel mixture sucked into the engine 1 via the O ₂ concentration in the exhaust gas. Also,
An idle switch 17 is provided which is turned on at the idle position (fully closed position) of the throttle valve 4.

Here, the CPU of the microcomputer incorporated in the control unit 12 determines the basic fuel injection amount Tp based on the intake air flow rate Q detected by the air flow meter 13 and the engine rotation speed N detected by the crank angle sensor 14. In addition to setting the
The basic fuel injection amount Tp is feedback-controlled so that the actual air-fuel ratio detected by the O ₂ sensor 16 approaches the target air-fuel ratio, and further the engine operating conditions such as the cooling water temperature Tw detected by the water temperature sensor 15 are set. Based on the correction, the final fuel injection amount Ti (expressed as the valve opening time of the fuel injection valve 6) is set. Then, a drive pulse signal having a pulse width corresponding to the fuel injection amount Ti is output to the fuel injection valve 6 at a predetermined timing to control the fuel injection supply by the fuel injection valve 6.

On the other hand, the control unit 12 detects the disconnection of the fuel injection valve 6 according to the flowchart of FIG. here,
The control unit 12 also serves as an increase control state determination means, an interval time measurement means, and a fuel injection failure determination means.

In step (denoted as "S" in the figure. The same applies hereinafter) 1, it is determined whether or not the engine is in the idle stable operation state, and if it is in the idle stable operation state, the routine proceeds to step 2. The idle stable operation state is determined under the condition that a predetermined time or more has passed since the idle switch 17 was turned on, a complete warming state (cooling water temperature Tw or more) and no external load fluctuation of the air conditioner or the like. Therefore, the determination operation state detection means in this embodiment corresponds to the idle switch 17, the water temperature sensor 15, and the like.

In step 2, air-fuel ratio feedback control of the fuel injection valve Ti is performed based on the detection value of the O ₂ sensor 16 (CLOS
It is determined whether the status is E) or the air-fuel ratio feedback control is clamped (OPEN). The operating conditions in which the air-fuel ratio feedback control is cranked include, for example, deceleration, high load operation, low water temperature, and the like.

If it is determined in step 2 that the air-fuel ratio feedback control is being performed, the process proceeds to step 3. In step 3, it is determined whether the control direction in the air-fuel ratio feedback control is the rich direction or the lean direction. Since the air-fuel ratio feedback control controls the actual air-fuel ratio to approach the target air-fuel ratio as described above, when the fuel injection amount is increased and corrected by the feedback control (the air-fuel ratio feedback correction coefficient is When it is larger than the reference value), the control is in the direction of making the air-fuel ratio rich, and conversely, when the fuel injection amount is reduced by the air-fuel ratio feedback control (the air-fuel ratio feedback correction coefficient is greater than the reference value). Control is in the direction of making the air-fuel ratio lean.

If it is determined in step 3 that the control direction is the rich direction, it means that the current base injection amount is smaller than the injection amount corresponding to the target air-fuel ratio and the fuel amount increase correction control is required by the feedback control. It is shown that the lean injection direction is in a state where the base injection amount is larger than the fuel corresponding to the target air-fuel ratio. When a part of the fuel injection valve 6 is disconnected and fuel is not supplied to some cylinders, the base injection amount before feedback control becomes smaller than the injection amount corresponding to the target air-fuel ratio. Therefore, when the feedback control is in the lean direction, even if the rotational balance is deteriorated, the cause is not the disconnection of the fuel injection valve 6, but the fuel is injected and supplied. Even if the combustion pressure cannot be obtained due to an ignition mistake, the spark plug 7
It is presumed to be caused by the misfire.

Therefore, the fuel injection valve 6 may be disconnected only when the air-fuel ratio feedback control is in the rich direction in step 3, and therefore, when it is determined in step 3 that the fuel injection valve 6 is in the rich direction, the process proceeds to step 4 and subsequent steps.

In step 4, the interval time T of the reference signal Ref output from the crank angle sensor every 120 ° is measured, and the ratio R (= this time T / previous time T) between the previous value and the current value of the interval time T is measured. calculate. Here, the detection of the interval time T
Since it is performed during idle operation, which is a low rotation operation state of the engine, the interval time T is longer than during high rotation operation, and accurate time measurement is possible.

When the engine rotation is stable, the crankshaft is 120 °
Since the time (interval time T) required to rotate only for a certain period should be constant, the ratio is maintained at approximately 1, but the fuel injection valve 6
If there is a cylinder that has a disconnection of the drive signal output line or the valve opening drive coil to the cylinder, as shown in FIG. 4, the interval between the reference signals Ref affected by the combustion pressure of the cylinder is extended. Become.

Therefore, the cylinder in which the disconnection of the fuel injection valve 6 has occurred can be specified depending on which reference signal Ref the interval time T has extended, and in the next step 5, the ratio R is equal to or greater than the predetermined value R _1. When it is determined that the current interval time T is longer than the predetermined time as compared with the previous time, it is determined in step 6 that the fuel injection valve 6 of the cylinder that affects the current interval time T has a disconnection. . In order to avoid erroneous detection, it is desirable to determine the disconnected cylinder of the fuel injection valve 6 after it is detected a plurality of times that the interval time T has been extended between the same reference signals Ref.

Which of the reference signals Ref is influenced by the combustion pressure of which cylinder is obtained in advance as shown in FIG. In the case of the one shown in FIG. 5, when a disconnection occurs in the fuel injection valve 6 of the # 6 cylinder, the interval between the reference signal Ref discrimination signal (a signal with a wide pulse width) and the next reference signal Ref is shown by the symbol ▲. Therefore, if it is determined by the measurement of the interval time T that the time between the reference signals Ref has been extended, it can be determined that the fuel injection valve 6 of the # 6 cylinder is disconnected.

When the cylinder in which the disconnection of the fuel injection valve 6 has occurred is determined in step 6, in the next step 7, for example, a panel provided on the dashboard of the vehicle displays the failure of the fuel injection valve 6 of the determined cylinder. Notify the driver.

In this embodiment, the reference signal from the crank angle sensor 14
Although the rotation variation is detected based on the Ref interval time T, the rotation variation may be similarly detected by measuring the ignition cycle. Further, in an engine configured such that the air-fuel ratio feedback control is clamped during idle operation, it is determined whether the actual air-fuel ratio detected by the O ₂ sensor 16 is lean or rich with respect to the target air-fuel ratio. Then, it is determined that the fuel injection valve 6 is disconnected when it is lean (when it is necessary to control the fuel amount increase in order to approach the target air-fuel ratio). Further, in the present embodiment, a 6-cylinder internal combustion engine is assumed, but a 4-cylinder or 8-cylinder internal combustion engine is used.
It may be an engine such as a cylinder, and the number of cylinders is not limited.

<Effect of the Invention> As described above, according to the present invention, it is possible to detect the disconnection of the fuel injection valve in the specific cylinder based on the occurrence of the rotation variation in distinction from the misfire due to the spark plug.
There is an effect that the driver can be notified of the disconnection of the fuel injection valve based on such detection.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of the present invention, FIG. 2 is a system schematic diagram showing an embodiment of the present invention, FIG. 3 is a flow chart showing a fault diagnosis control in the same embodiment, and FIG. 4 is a fuel injection. FIG. 5 is a time chart showing the reference signal output characteristic when the valve is broken, and FIG. 5 is a graph showing the change in the interval time due to the breaking of the fuel injection valve. 1 ... Engine, 6 ... Fuel injection valve, 12 ... Control unit, 14 ... Crank angle sensor, 15 ... Water temperature sensor,
16 …… O ₂ sensor, 17 …… Idle switch

Claims (1)

[Scope of utility model registration request] 1. A structure in which a drive pulse signal corresponding to a fuel injection amount set according to engine operating conditions is output to a fuel injection valve provided for each cylinder to intermittently supply fuel to the engine. In the electronically controlled fuel injection type internal combustion engine, a rotation synchronization signal output means for outputting a detection signal for each predetermined reference position of the piston of each cylinder, and a determination operation state detection means for detecting a predetermined low rotation stable operation state of the engine. , An air-fuel ratio detecting means for detecting an engine exhaust gas component and thereby detecting an air-fuel ratio of the engine intake air-fuel mixture, and an actual air-fuel ratio based on the air-fuel ratio of the engine intake air-fuel mixture detected by the air-fuel ratio detecting means. An increase control state determination means for determining a state in which a fuel increase control is required to bring the fuel ratio close to a fuel ratio, and a predetermined low rotation stable operation state of the engine is detected by the determination operation state detection means and the increase control state. Interval time measuring means for measuring the interval time of the detection signal output from the rotation synchronizing signal output means when the determining means determines that the fuel increase control is required, and the interval time measuring means measures the interval time. An electronically controlled fuel injection system characterized by comprising a fuel injection valve failure determination means for determining a fuel injection valve failure of a specific cylinder based on a ratio of a previous value and a current value of the detection signal interval time. Fuel injection valve failure diagnosis device for internal combustion engine.