JP2008115782A - Failure diagnostic method and failure diagnostic system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a failure diagnostic method improving accuracy of failure diagnostic or the like of a section relating to ion current detection and an ignition system for an internal combustion engine. <P>SOLUTION: Failure of the section relating ion current detection and the ignition system for the internal combustion engine or the like is diagnosed based on a signal after time TA longer than noise mask time NM2 elapses from monitor cylinder changeover time P1-P3 out of the signals from which noise is removed by providing noise mask time NM2 to signals provided from an ion current detection means detecting ion current generated in the monitor cylinder. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a failure diagnosis method and a failure diagnosis system, and more particularly, to a failure diagnosis method and a failure diagnosis system for diagnosing a device failure.

The internal combustion engine rotates by repeatedly performing an intake stroke, a compression stroke, an expansion stroke (combustion stroke), and an exhaust stroke, and one operation cycle is completed in these four strokes. An internal combustion engine is generally composed of a plurality of cylinders, and a mixed gas of air and fuel is combusted in the combustion chamber of each cylinder, and the piston is moved by the explosive force associated with the combustion, and thermal energy is converted into mechanical energy. By converting to (power), it is taken out as the rotational output of the internal combustion engine.

When the mixed gas burns normally in the combustion chamber of each cylinder, the combustion gas generated by the combustion causes a radical reaction or ionization (ionization), and an ionic current is generated. Since this ion current changes sensitively depending on the combustion state in the combustion chamber, the combustion state of the internal combustion engine can be detected by detecting the generation state of the ion current. For example, the following patent documents 1 to
4 discloses a technique for detecting an ionic current generated during combustion of an internal combustion engine.

FIG. 1 is a block diagram schematically showing an example of a conventional fuel injection control device having a combustion state detection function of an internal combustion engine. In FIG. 1, reference numeral 1 denotes a fuel injection control device (EFI-ECU) for controlling fuel injection of a four-cylinder internal combustion engine. The fuel injection control device 1 includes a monitor cylinder switching circuit (MPX) 2, a mask circuit 3, and the like. The latch circuit 4 includes a mask circuit 5 and a microcomputer 6.

As shown in FIG. 2, the microcomputer 6 sends ignition command signals IGT1 to IGT to the igniters A1 to A4 corresponding to the cylinders # 1 to # 4 at appropriate timing.
4 (IGT-ON signal and IGT-OFF signal) to # 1 cylinder, # 3 cylinder, # 4 cylinder, # 2
The output is in the order corresponding to the cylinder.

The igniter An (n is 1 to 4) controls energization of a primary charging current flowing in a primary coil of an ignition coil (not shown) based on an ignition command signal IGTn output from the microcomputer 6. When the ignition command signal IGTn rises from OFF to ON, the primary charging current is applied to the primary coil of the ignition coil (energization starts). After that, when the ignition command signal IGTn falls from ON to OFF, the primary charging current is cut off. (Energization cut off). When the primary charging current is cut off, a high voltage is generated in the secondary coil of the ignition coil, and a spark plug (not shown) is ignited.

The ion current detection sensors B1 to B4 detect ion currents generated in the combustion chambers of the # 1 cylinder to the # 4 cylinder. As shown in FIG. 2, the ion signal IONn based on the ion current has a low period (primary charge, T _{11 in the} figure) at the time of ignition preparation (that is, after the ignition command signal IGTn rises from OFF to ON for a while). _{, T 31, T 41, T} 21).

Further, the ion signal IONn becomes Low for a certain period of time after ignition (that is, the ignition command signal IGTn falls from ON to OFF) (combustion ions, T ₁₂ in the figure,
_{T 32, T 42, T 22} ). Combustion ions may continue to be generated up to the exhaust stroke when long.

At this time, ignition noise is generated, and the generated ignition noise is detected by the ion current detection sensor B.
n may be detected. For example, the ion current detection sensor B1 is different from the # 1 cylinder #
By detecting the ignition noise generated in the three cylinders, the ion signal ION1 becomes Low.

When pre-ignition occurs, the ignition command signal IGT
An ion current is generated before n falls from ON to OFF, and the ion signal IONn becomes Lo.
becomes w (pre-ignition, in the figure _{T 13, T 33, T 43} , T 23). In addition, pre-ignition is
In an internal combustion engine, it refers to a phenomenon in which combustion starts before ignition control and the combustion timing is advanced.

The microcomputer 6 outputs the switching signals CHa, CHb after outputting the IGT-OFF signal from the output ports 6a, 6b to the input ports 2a, 2b of the monitor cylinder switching circuit 2.
Is output. The monitor cylinder switching circuit 2 switches the cylinder to be monitored based on the switching signals CHa and CHb. As a result, the monitor cylinders are switched in the order of # 1, # 3, # 4, and # 2 at the appropriate timing.

Identification codes “00”, “0” for the # 1, # 3, # 4, and # 2 cylinders, respectively.
1 ”,“ 11 ”, and“ 10 ”are provided, and when a low (0) switching signal is input to the input ports 2a and 2b, the monitor cylinder is switched to the # 1 cylinder and the input port 2a is low.
When the switching signal CHa of (0) and the switching signal CHb of High (1) are input to the input port 2b, the monitor cylinder is switched to the # 3 cylinder, and the switching signal CHa of High (1) is input to the input ports 2a and 2b. , CHb is input, the monitor cylinder is switched to the # 4 cylinder. When a high (1) switching signal CHa is input to the input port 2a and a low (0) switching signal CHb is input to the input port 2b, the monitor cylinder is switched. The cylinder can be switched to the # 2 cylinder.

As shown in FIG. 3, the microcomputer 6 outputs a low ignition command signal IGT1 to the igniter A1, and then the high (1) switching signal CHb to the input port 2b.
Is output from the # 1 cylinder to the # 3 cylinder, and a low ignition command signal IGT3 is output to the igniter A3.
By outputting the switching signal CHa of h (1), the cylinder to be monitored is changed from # 3 cylinder to # 4.
Switch to cylinder.

“MPX output” in the figure is a voltage signal S1 output from the monitor cylinder switching circuit 2 (FIG. 1).
Is shown. This voltage signal S1 output from the monitor cylinder switching circuit 2 becomes the ion signal IONn belonging to the monitor section.
That is, when the monitor cylinder is the # 1 cylinder (ION1 monitor section in the figure), the ion signal ION1 based on the ion current detected by the ion current detection sensor B1 is output to the mask circuits 3 and 5 as the voltage signal S1, When the monitor cylinder is the # 3 cylinder (ION3 monitor section in the figure), the ion signal ION3 based on the ion current detected by the ion current detection sensor B2
Is output to the mask circuits 3 and 5.

The mask circuit 3 and the mask circuit 5 have substantially the same configuration, and noise is removed by setting a certain period (noise mask time) as a non-detection period of the ion signal. For this reason, when the ion signal IONn belonging to the monitor section becomes Low and the Low state continues for the noise mask time or longer, the voltage signals S2 and S4 output from the mask circuits 3 and 5 become High. . However, the purpose of use of the mask circuit 3 and the mask circuit 5 is different, and here, the noise mask time in the mask circuit 3 is longer than the noise mask time in the mask circuit 5.

The upper mask circuit 3 and the latch circuit 4 are used for detection of pre-ignition, and the voltage signal S2 output from the mask circuit 3 is passed through the latch circuit 4 as a voltage signal S3 to the general port 6c of the microcomputer 6. To be output.
The latch circuit 4 latches (holds) the input state at a timing to be monitored (for example, 10 to 50 μs before the output of the IGT-OFF signal) according to an instruction from the microcomputer 6. The generation time of ion current due to pre-ignition is about 400μ.
Since it becomes 2 seconds or more, it is desirable that the noise mask time in the mask circuit 3 is 390 μsec or less, which is shorter than that.

After outputting the IGT-OFF signal, the microcomputer 6 reads the signal (voltage signal S3) latched by the latch circuit 4, and after reading the voltage signal S3, instructs the latch circuit 4 to perform clear control. It has become. Thereby, the microcomputer 6 can read the voltage signal S2 output from the mask circuit 3 as the voltage signal S3 10 to 50 μsec before the IGT-OFF signal output (that is, ignition).

When pre-ignition has occurred, the voltage signal S2 10 to 50 μs before the output of the IGT-OFF signal becomes High. Therefore, the microcomputer 6 includes the latch circuit 4.
It is possible to determine whether or not pre-ignition has occurred based on the signal read from.

On the other hand, the lower mask circuit 5 detects the primary charge, thereby detecting the ignition system (
For example, igniters A1 to A4) and parts related to ion current detection (for example, ion current detection sensors B1 to B4) are used for failure diagnosis. The voltage signal S4 output from the mask circuit 5 is a micro signal. It is output to the latch port 6d (detecting the rising edge) of the computer 6.

After outputting the IGT-OFF signal, the microcomputer 6 reads the latch state of the latch port 6d that detects the rising edge, and then clears the latch port 6d. Therefore, during the period from the previous clear to the current clear, the latch port 6d
When the High signal is input to the microcomputer 6, the microcomputer 6 connects the Hi from the latch port 6 d.
The gh signal is read.

As shown in FIG. 3, if the portion related to the ignition system and ion current detection of the internal combustion engine is normal, there is a period during which the ion signal IONn is low during preparation for ignition (T _{11 in the} figure). , T _31). As described above, when the ion signal IONn belonging to the monitor section becomes Low, the voltage signal S4 output from the mask circuit 5 after a certain time (noise mask time) is H
become high. Therefore, when the microcomputer 6 can read the high signal from the latch port 6d, the parts related to the ignition system and the ion current detection of the internal combustion engine, and the monitor cylinder switching circuit 2 and the mask circuit 5 are normal. It can be judged. The noise mask time in the mask circuit 5 is preferably set to about 40 to 60 μsec in consideration of the generation time of the ionic current due to the primary charging.

FIG. 4 is a diagram showing a circuit configuration of the mask circuits 3 and 5. Monitor cylinder switching circuit 2 (FIG. 1)
The voltage signal SA (voltage signal S1 shown in FIG. 1) selected based on the ion signal IONn is input to the inverting (−) terminal of the comparator 12 via the resistor 11. The comparison voltage TH1 obtained by dividing the reference power supply Vc by the resistors 13 and 14 is input to the non-inverted (+) terminal of the comparator 12. The comparator 12 burns in the internal combustion engine based on the ion signal IONn. A voltage signal corresponding to the state is output. The output terminal of the comparator 12 is connected to the reference power source Vc via the resistor 15 and is also connected to the OUT terminal. The OUT terminal is connected to the latch circuit 4 (FIG. 1) and the latch port 6d of the microcomputer 6 (FIG. 1).

The voltage signal SA based on the ion signal IONn is input to the inverting (−) terminal of the comparator 22 via the resistor 21. The non-inverting (+) terminal of the comparator 22 has a reference power supply Vc.
Is compared with resistors 23 and 24, and a voltage signal corresponding to the combustion state in the internal combustion engine based on the ion signal IONn is output from the comparator 22.

The output terminal of the comparator 22 is connected to the reference power source Vc via resistors 25 and 26 and is connected to the non-inverted (+) terminal of the subsequent comparator 30 via resistors 25 and 27. Further, between the resistor 25 and the resistor 27 (that is, the non-inverted (+) of the output terminal of the comparator 22 and the comparator 30).
(To the terminal), a ground (GND) is connected via a capacitor 28 for integrating the output signal from the comparator 22.
The output terminal of the comparator 30 is connected between the output terminal of the comparator 12 and the OUT terminal. The comparison voltage TH2 obtained by dividing the reference power source Vc by the resistors 31 and 32 is input to the inverting (−) terminal of the comparator 30.

FIG. 5 is a timing chart showing transition states of the voltage signals SA to SC in FIG. FIG. 5A shows the transition state of the voltage signal SA based on the ion signal IONn. FIG. 5B shows the transition state of the voltage signal SB, and FIG. 5C shows the transition state of the voltage signal SC.

When the voltage signal SA becomes smaller than the comparison voltage TH1 (that is, the input signal to the comparators 12 and 22 becomes smaller than the comparison voltage TH1), the output signal from the output terminal of the comparators 12 and 22 changes from Low to High. . On the other hand, the voltage signal SA becomes larger than the comparison voltage TH1 (
That is, when the input signal to the comparators 12 and 22 becomes larger than the comparison voltage TH1, the output signal from the output terminals of the comparators 12 and 22 changes from High to Low.

When the output signal from the output terminal of the comparator 22 changes from Low to High, the capacitor 28
Then, charging is started, and the voltage signal SB rises slowly as shown in FIG. On the other hand, when the output signal from the output terminal of the comparator 22 changes from High to Low, the capacitor 2
The discharge starts at 8 and the voltage signal SB slowly falls.

When the voltage signal SB becomes larger than the comparison voltage TH2 (that is, the input signal to the comparator 30 becomes larger than the comparison voltage TH2), the output signal from the output terminal of the comparator 30 changes from Low to High. On the other hand, when the voltage signal SB becomes smaller than the comparison voltage TH2 (that is, the input signal to the comparator 30 becomes smaller than the comparison voltage TH2), the output signal from the output terminal of the comparator 30 changes from High to Low.

When the output signal from the output terminal of the comparator 30 is High, a signal corresponding to the output signal from the output terminal of the comparator 12 is output to the OUT terminal. Therefore, the voltage signal SB is compared with the comparison voltage TH.
When it is larger than 2, as shown in FIG. 5C, a signal corresponding to the output signal from the output terminal of the comparator 12 is output to the OUT terminal as the voltage signal SC (voltage signals S2 and S4 shown in FIG. 1). Will be.

In this way, by setting the input signal to the non-inverting (+) terminal of the comparator 30 to rise slowly, the noise mask time T1 (FIG. 5) for removing noise is set, and the ion The voltage signal S1 (SA) output from the current detection sensor Bn via the monitor cylinder switching circuit 2
) Is removed. That is, the voltage signal SA is low.
A period (T1) from when switching to High to when the integrated value at the capacitor 28 exceeds the comparison voltage TH2 can be set as the noise mask time. Noise mask time T1
Can be adjusted by changing the capacitance of the capacitor 28.

FIG. 6 is a diagram showing an ion current detection sequence. “MPX output” in the figure indicates the voltage signal SA (S1) output from the monitor cylinder switching circuit 2. This voltage signal SA (S1) output from the monitor cylinder switching circuit 2 is the ion signal IONn belonging to the monitor section.
It becomes.

As shown in FIG. 6, the noise mask time NM1 (for example, 390 μsec) of the mask circuit 3
When ion current is generated longer than that (ie, when pre-ignition occurs)
The voltage signal SC (S2) output from the mask circuit 3 changes from Low to High.
By detecting the change of the voltage signal SC (S2) from Low to High, preignition can be detected.

Similarly to the above, when the ionic current is generated longer than the noise mask time NM2 (for example, 40 to 60 μsec) of the mask circuit 5 (that is, when primary charging is generated), the voltage signal output from the mask circuit 5 SC (S4) changes from Low to High. By detecting the change of the voltage signal SC (S2) from Low to High, it is possible to determine that the ignition system of the internal combustion engine and the part related to the detection of ion current are normal.

FIG. 7 is a diagram showing a sequence of a voltage signal S1 output from the monitor cylinder switching circuit 2, a voltage signal S4 input to the latch port 6d, and a latch state at the latch port 6d. At the output timing of the IGT-OFF signal, the microcomputer 6 reads the latch state (Process 1), switches the monitor cylinder (Process 2), and clears the latch (Process 3) in this order. Yes.

Process 1. Latch signal (latch state) from the latch port 6d that detects the rising edge
Is read.
Process 2. Output ports 6a and 6b with respect to the input ports 2a and 2b of the monitor cylinder switching circuit 2
Switch signals CHa and CHb to switch the cylinder to be monitored.
Process 3. The latch state of the latch port 6d is cleared.

As shown in FIG. 7, the signal is input to the latch port 6d between the monitoring cylinder switching time and the next monitoring cylinder switching time (for example, from time P1 to time P2 and from time P2 to time P3). When the signal rises from Low to High, the latch port 6d is Hi.
The gh state is latched (held). When the primary charging EV1 and EV2 occur, the signal input to the latch port 6d is changed from Low to H after the noise mask time NM2 elapses.
You will stand up to “high”.

As described above, the microcomputer 6 latches the latch port 6d when the monitor cylinder is switched.
The latch state at is read. When primary charging EV1 and EV2 are occurring, the latch state at the latch port 6d at the monitor cylinder switching time (but before latch clear) becomes High. Therefore, when the latch state at the latch port 6d read at the time of switching the monitor cylinder is High, the microcomputer 6 determines that the primary charge to be generated has been detected, and detects the ignition system and ion current of the internal combustion engine. It can be determined that the relevant site is normal.

By the way, as shown in FIG. 8, for example, when the ion signal ION3 detected from the ion current detection sensor B3 is fixed to Low due to the ground fault of the part related to the ion current detection, the ion signal ION3 is monitored. , The voltage signal S1 output from the monitor cylinder switching circuit 2 and input to the mask circuit 5 is fixed to Low. Therefore, after the noise mask time NM2 has elapsed from the monitor cylinder switching time P2, the voltage signal S4 input to the latch port 6d changes from Low to High.

When the voltage signal S4 input to the latch port 6d rises from Low to High,
The latch port 6d is latched in the high state. That is, the latch port 6d is latched in the high state regardless of whether or not primary charging has occurred. For this reason, the microcomputer 6 determines that primary charging has been detected, and misdiagnoses it as normal even if there is an abnormality in the ignition system of the internal combustion engine.

Further, as shown in FIG. 9, a large delay occurs in the processing of the microcomputer 6, for example, the switching of the monitor cylinder from the # 1 cylinder to the # 3 cylinder is delayed, and the monitor cylinder to the # 3 cylinder after the primary charge EV2 Is switched, the voltage signal S1 output from the monitor cylinder switching circuit 2 and input to the mask circuit 5 remains High even if the primary charge EV2 is generated.

Accordingly, the voltage signal S4 input to the latch port 6d remains Low, and the voltage signal S4 input to the latch port 6d changes from Low to High during the period from the monitor cylinder switching time P2 to the monitor cylinder switching time P3. Will not. That is, primary charge EV2
Even if this occurs, the latch port 6d is not latched in the high state. For this reason, even if there is no abnormality in the ignition system of the internal combustion engine or the part related to the detection of ion current, the microcomputer 6 misdiagnoses that there is an abnormality in these parts.
JP 2004-108298 A Japanese Patent Laid-Open No. 2003-21034 JP-A-8-338298 JP-A-7-91357

Means for solving the problems and their effects

The present invention has been made in view of the above problems, and provides a failure diagnosis method and a failure diagnosis system with improved accuracy such as failure diagnosis of an ignition system of an internal combustion engine or a part related to ion current detection. It is aimed.

As shown in FIG. 8, for example, when the ion signal ION3 detected from the ion current detection sensor B3 is fixed to Low due to the ground fault of the part related to the ion current detection, the ion signal ION3 belongs to the monitor section. In this case, the voltage signal S1 output from the monitor cylinder switching circuit 2 and input to the mask circuit 5 is fixed to Low. Therefore, after the noise mask time NM2 has elapsed from the monitor cylinder switching time P2, the voltage signal S4 input to the latch port 6d changes from Low to High.

When the voltage signal S4 input to the latch port 6d rises from Low to High,
The latch port 6d is latched in the high state. That is, the latch port 6d is latched in the high state regardless of whether or not primary charging has occurred. For this reason, the microcomputer 6 determines that primary charging has been detected, and misdiagnoses it as normal even if there is an abnormality in the ignition system of the internal combustion engine.

When the noise mask time NM2 has elapsed from the monitor cylinder switching point P2, the mask circuit 5
The signal that is output from and input to the latch port 6d rises from Low to High,
The High state is latched at the latch port 6d. From then until the next monitor cylinder switching time P3, the signal input to the latch port 6d is maintained at High.

It is natural that High is maintained, but the signal input to the latch port 6d does not rise from Low to High. Therefore, monitor cylinder switching point P2
After the noise mask time NM2 elapses, the signal input to the latch port 6d rises from Low to High, and after the High state is latched at the latch port 6d, the latch state of the latch port 6d is cleared (Low). The low state is latched at the latch port 6d until the next monitor cylinder switching time P3.

Therefore, even if the ion signal ION3 detected from the ion current detection sensor B3 is fixed to Low due to a ground fault related to ion current detection, the signal output from the mask circuit 5 and input to the latch port 6d Among them, the high state is not latched at the latch port 6d in the signal after the time longer than the noise mask time NM2 has elapsed from the monitor cylinder switching time P2. That is, it is possible to prevent a situation in which the microcomputer 6 makes an erroneous determination that primary charging has been detected.

The failure diagnosis method (1) according to the present invention is an invention made on the basis of the above knowledge, and provides a non-detection period for a signal obtained from an ion current detection means for detecting an ion current generated in a monitor cylinder. Of the signal from which noise has been removed, based on the signal after the time longer than the non-detection period has elapsed since the monitoring cylinder was switched, the part related to the ignition system or ion current detection of the internal combustion engine, or the internal combustion engine It is characterized by diagnosing a failure of the ignition system and the part.

According to the failure diagnosis method (1), among the signals obtained by providing the non-detection period and removing noise with respect to the signal obtained from the ion current detecting means, not from the monitor cylinder switching time but from the monitor cylinder switching time. Since a failure diagnosis of the ignition system of the internal combustion engine or the like is performed based on a signal after a time longer than the non-detection period, an appropriate failure diagnosis with high accuracy can be realized.

Further, the failure diagnosis method (2) according to the present invention is based on a signal obtained from an ion current detection unit that detects an ionic current generated in the monitor cylinder by switching the monitor cylinder using an energization interruption to the ignition member as a trigger. The part of the internal combustion engine related to ignition system or ion current detection, or the failure of the ignition system and part of the internal combustion engine is diagnosed, and the energization stop time from the energization interruption to the ignition member to the energization start to the ignition member Is set to be equal to or longer than a predetermined time, and the predetermined time is longer than a maximum delay time that occurs from the time when the ignition member is de-energized until the monitor cylinder is switched.

As shown in FIG. 9, a large delay occurs in the processing of the microcomputer 6, for example, #
When the switching of the monitor cylinder from the 1 cylinder to the # 3 cylinder is delayed and the monitor cylinder is switched to the # 3 cylinder after the primary charge EV2, even if the primary charge EV2 is generated, the monitor cylinder switching circuit 2 The voltage signal S1 that is output and input to the mask circuit 5 remains High.

Accordingly, the voltage signal S4 input to the latch port 6d remains Low, and the voltage signal S4 input to the latch port 6d changes from Low to High during the period from the monitor cylinder switching time P2 to the monitor cylinder switching time P3. Will not. That is, primary charge EV2
Even if this occurs, the latch port 6d is not latched in the high state. For this reason, even if there is no abnormality in the ignition system of the internal combustion engine or the part related to the detection of ion current, the microcomputer 6 misdiagnoses that there is an abnormality in these parts.

However, according to the failure diagnosis method (2), the ignition switch (IGT) is cut off from the ignition member.
-OFF) until the start of energization of the ignition member (IGT-ON) is set to be equal to or longer than the predetermined time, and the predetermined time occurs from the time when the ignition member is de-energized until the monitor cylinder is switched. Make it longer than the maximum delay time.

Thereby, even if a large delay occurs in the processing of the microcomputer or the like, the start of energization of the ignition member can be surely delayed until after the monitor cylinder is switched, so that there is an abnormality in the ignition system of the internal combustion engine or the like. Although it has not occurred, it is possible to prevent the occurrence of a situation such as misdiagnosis that an abnormality has occurred in these.

Further, the failure diagnosis method (3) according to the present invention switches the monitor cylinder by using the energization interruption to the ignition member as a trigger, and does not apply to the signal obtained from the ion current detection means for detecting the ion current generated in the monitor cylinder. Based on the signal from which noise has been removed by providing a detection period, the ignition system of the internal combustion engine or a part related to ion current detection, or a failure of the ignition system of the internal combustion engine and the part is diagnosed, and the ignition member is energized. The energization stop time from the shutoff to the start of energization to the ignition member is set to a predetermined time or more, and the predetermined time is set to the maximum delay time that occurs between the energization shutoff to the ignition member and the monitor cylinder switching and the non-detection period. It is characterized by longer than the combined time.

According to the failure diagnosis method (3), the energization stop time from the energization interruption to the ignition member until the energization start to the ignition member is set to the predetermined time or more, and the predetermined time is
The delay time is longer than the maximum delay time that occurs from the time when the ignition member is deenergized until the monitor cylinder is switched.

Thereby, even if a large delay occurs in the processing of the microcomputer or the like, the start of energization of the ignition member can be surely delayed until after the monitor cylinder is switched, so that there is an abnormality in the ignition system of the internal combustion engine or the like. Although it has not occurred, it is possible to prevent the occurrence of a situation such as misdiagnosis that an abnormality has occurred in these.

By the way, in the failure diagnosis method (1), among the signals obtained by providing the non-detection period and removing noise with respect to the signal obtained from the ion current detection means, the signal is longer than the non-detection period from the monitor cylinder switching time. Although a failure of the ignition system of the internal combustion engine or the like is diagnosed based on a signal after time has elapsed, if the monitor cylinder is switched immediately before the start of the next energization, the primary charge may not be properly detected. There is.

However, according to the failure diagnosis method (3), the predetermined time is set to be longer than the total time of the maximum delay time that occurs from the time when the ignition member is deenergized until the monitor cylinder is switched and the non-detection period. The start of energization of the ignition member can be delayed until the non-detection period elapses after the monitor cylinder switching. Therefore, the accuracy of failure diagnosis when the failure diagnosis method (1) is employed can be improved.

Embodiments of a failure diagnosis method and a failure diagnosis system according to the present invention will be described below with reference to the drawings. FIG. 10 is a block diagram schematically showing a main part of a fuel injection control device adopting the failure diagnosis method (or failure diagnosis system) according to the embodiment (1). In addition, the same code | symbol is attached | subjected about the component similar to the fuel-injection control apparatus shown in FIG.

In the figure, reference numeral 41 denotes a fuel injection control device (EFI-E) for controlling fuel injection of a four-cylinder internal combustion engine.
The fuel injection control device 41 includes a monitor cylinder switching circuit (MPX) 2, a mask circuit 3, a latch circuit 4, a mask circuit 5, and a microcomputer (microcomputer) 42.
It is comprised including.

As shown in FIG. 2, the microcomputer 42 ignites the ignition command signals IGT1 to IGT4 (with appropriate timing) to the igniters A1 to A4 corresponding to the cylinders # 1 to # 4 as shown in FIG. IGT-ON signal and IGT-OFF signal) are output in the order corresponding to the # 1, # 3, # 4, and # 2 cylinders.

Similarly to the microcomputer 6, the microcomputer 42 is connected to the output port 4.
IGT-OF from 2a, 42b to the input ports 2a, 2b of the monitor cylinder switching circuit 2
The switching signals CHa and CHb are output after the F signal is output. The monitor cylinder switching circuit 2 switches the cylinder to be monitored based on the switching signals CHa and CHb. As a result, the monitor cylinders # 1, # 3, # 4, # 2 at appropriate timing.
It will be switched in the order of the cylinder.

Further, after outputting the IGT-OFF signal, the microcomputer 42 reads the signal (voltage signal S3) latched by the latch circuit 4, and after reading the voltage signal S3, instructs the latch circuit 4 to perform clear control. It is supposed to be. Thereby, the microcomputer 42 can read the voltage signal S2 output from the mask circuit 3 as the voltage signal S3 10 to 50 μsec before the IGT-OFF signal output (that is, ignition).

  When pre-ignition has occurred, the voltage signal S2 10 to 50 μs before the output of the IGT-OFF signal becomes High. Therefore, the microcomputer 42 can determine whether pre-ignition has occurred based on the signal read from the latch circuit 4.

The microcomputer 42 reads the latch state of the latch port 42d that detects the rising edge after outputting the IGT-OFF signal, and then clears the latch port 42d. Therefore, if a High signal is input to the latch port 42d between the previous clear and the current clear, the microcomputer 42 causes the latch port 4 to
A High signal is read from 2d.

Next, the processing operation [1] performed by the microcomputer 42 in the fuel injection control device 41.
Is described based on the flowchart shown in FIG. However, this processing operation [1] is IG
This operation is performed when the timing for outputting the T-OFF signal is reached. Although not shown in FIG. 10, various sensors such as an engine rotation sensor are connected to the microcomputer 42 so that the microcomputer 42 can grasp that the engine has started, the engine speed, and the like. It has become.

First, the latch state at the latch port 42d is read (step S1), and then the switching signals CHa and CHb are output from the output ports 42a and 42b to the input ports 2a and 2b of the monitor cylinder switching circuit 2. Switching the monitor cylinder (step S2)
. If the latch state read from the latch port 42d is High, it can be determined that the primary charge to be generated has been detected, and it can be determined that the parts related to the engine ignition system and ion current detection are normal.

After switching the monitor cylinder, the noise mask time NM2 (for example, 40 in the mask circuit 5)
TA (for example, 50 to 70 μsec) longer than TA (for example, 50 to 70 μsec) and wait for processing (Step S
3) After the standby time has elapsed, the latch state of the latch port 42d is cleared (Low) (step S4).

FIG. 12 shows the voltage signal S1 output from the monitor cylinder switching circuit 2 and the mask circuit 5 in the fuel injection control apparatus employing the failure diagnosis method (or failure diagnosis system) according to the embodiment (1). It is the figure which showed sequences, such as the voltage signal S4 input into the latch port 42d, and the latch state in the latch port 42d.

From the sequence shown in FIG. 12, the latch state of the latch port 42d is not the monitor cylinder switching time points P1, P2, and P3 as in the prior art, but is longer than the noise mask time NM2 from the monitor cylinder switching time points P1, P2, and P3. It can be seen that the points are cleared at the time points P1 ′, P2 ′, and P3 ′ when TA has elapsed.

According to the fuel injection control apparatus employing the failure diagnosis method (or failure diagnosis system) according to the above embodiment (1), the latch state of the latch port 42d is the monitor cylinder switching points P1, P
2. Time points P1 ′ and P2 ′ when a time TA longer than the noise mask time NM2 has elapsed from P3.
, Cleared at P3 ′.

Therefore, as shown in FIG. 12, for example, the ion signal ION3 detected from the ion current detection sensor B3 is fixed to Low due to the ground fault of the part related to the ion current detection, and the # 3 cylinder is the monitor cylinder. Sometimes, the signal output from the monitor cylinder switching circuit (MPX) 2 and input to the mask circuit 5 is fixed to Low, and after the noise mask time NM2 has elapsed from the monitor cylinder switching time point P2 (the next monitor cylinder switching time point) Up to P3), latch port 4
Even if the signal input to 2d is fixed to High, the latch state of the latch port 42d is cleared at the monitor cylinder switching time point P2 ′, so that the latch state of the latch port 42d remains High until the next monitor cylinder switching time point P3. It is not fixed by.

Therefore, the latch state of the latch port 42d read at the next monitor cylinder switching time P3 is H
Since the microcomputer 42 is not high, the microcomputer 42 does not determine that the primary charge has been detected. Therefore, it is possible to prevent the microcomputer 42 from erroneously determining that the abnormality is occurring in a portion related to the engine ignition system or ion current detection. Can do.

As is clear from the sequence shown in FIG. 12, if the latch state of the latch port 42d is cleared after the end of the primary charge, the primary charge cannot be detected. It is necessary to perform the operation before the noise mask time NM2 from the end of charging. Therefore, about time TA, IGT-OFF (energization interruption) to IGT
It is desirable to set it to be shorter than the energization stop time until -ON (energization start).

Next, a fuel injection control apparatus that employs the failure diagnosis method (or failure diagnosis system) according to Embodiment (2) will be described. However, since this fuel injection control device has the same configuration as the fuel injection control device 41 shown in FIG. 10 except for the microcomputer 42, the microcomputer is given a different reference numeral and description of the other components. Is omitted here.

In the figure, reference numeral 41A denotes a fuel injection control device (EFI-) for controlling fuel injection of a four-cylinder internal combustion engine.
ECU), the fuel injection control device 41A includes a monitor cylinder switching circuit (MPX) 2,
Mask circuit 3, latch circuit 4, mask circuit 5, microcomputer (microcomputer)
42A.

Next, processing operations performed by the microcomputer 42A in the fuel injection control device 41A [
2-1] will be described based on the flowchart shown in FIG. However, this processing operation [2
-1] is an operation performed when the timing for outputting the IGT-OFF signal is reached. Although not shown in FIG. 10, similarly to the microcomputer 42, various sensors such as an engine rotation sensor are connected to the microcomputer 42A, and the microcomputer 42A indicates that the engine has started and the engine rotation speed. Etc. can be grasped.

First, the latch state at the latch port 42d is read (step S11), and then the switching signals CHa and CHb are output from the output ports 42a and 42b to the input ports 2a and 2b of the monitor cylinder switching circuit 2. Switch the monitor cylinder (step S1)
2). If the latch state read from the latch port 42d is High, it can be determined that the primary charge to be generated has been detected, and it can be determined that the parts related to the engine ignition system and ion current detection are normal.

After switching the monitor cylinder, at the current time Tn, the noise mask time NM in the mask circuit 5
Predetermined processing (specifically, clearing the latched state of the latch port 42d) by adding a time TA (for example, 50 to 70 μsec) longer than 2 (for example, 40 to 60 μsec)
Is set (step S13).

Next, processing operations performed by the microcomputer 42A in the fuel injection control device 41A [
2-2] will be described based on the flowchart shown in FIG. However, this processing operation [2
-2] is an operation performed every predetermined period when the target time Tx is set. First, the current time Tn and the target time Tx are compared to determine whether or not the target time Tx has been reached (step S21).

If it is determined that the target time Tx has been reached, then the latch state of the latch port 42d is cleared (Low) (step S22). On the other hand, if it is determined that the target time Tx has not been reached, it is not time to clear the latched state of the latch port 42d, so the processing operation [2-2] is terminated as it is.

According to the fuel injection control device employing the failure diagnosis method (or failure diagnosis system) according to the above embodiment (2), as with the fuel injection control device 41, the latch state of the latch port 42d is the monitoring cylinder switching point. Time T longer than noise mask time NM2 from P1, P2, P3
It is cleared at time points P1 ′, P2 ′, and P3 ′ when A has elapsed. Therefore, the fuel injection control device 4
The same effect as 1 is obtained.

Next, a fuel injection control device that employs the failure diagnosis method (or failure diagnosis system) according to Embodiment (3) will be described. However, since this fuel injection control device has the same configuration as the fuel injection control device 41 shown in FIG. 10 except for the microcomputer 42, the microcomputer is given a different reference numeral and description of the other components. Is omitted here.

In the figure, reference numeral 41B denotes a fuel injection control device (EFI-) for controlling fuel injection of a four-cylinder internal combustion engine.
ECU), the fuel injection control device 41B includes a monitor cylinder switching circuit (MPX) 2,
Mask circuit 3, latch circuit 4, mask circuit 5, microcomputer (microcomputer)
42B.

The microcomputer 42B uses the output of the IGT-OFF signal as a trigger to execute the latch state reading (process 1), monitor cylinder switching (process 2), and latch clear (process 3) in this order. ing.
Process 1. A latch signal (latch state) is read from the latch port 42d that detects the rising edge.
Process 2. For the input ports 2a, 2b of the monitor cylinder switching circuit 2, output ports 42a, 4
The switching signals CHa and CHb are output from 2b to switch the cylinder to be monitored.
Process 3. The latch state of the latch port 42d is cleared.

Next, processing operations performed by the microcomputer 42B in the fuel injection control device 41B [
3] will be described based on the flowchart shown in FIG. However, this processing operation [3] is performed every predetermined period. First, a time difference D obtained by subtracting the previous energization cut-off timing T _CT 'from the next energization start timing T _ST is calculated (step S31). The energization start time _TST is the time when the IGT-ON signal is output to start energization of the primary coil of the ignition coil, and the energization cut-off time _TCT is the time when the IGT-OFF signal is output and the energization of the primary coil is performed. The ignition start timing _TST and the energization cutoff timing _TCT are calculated by comprehensively judging the engine state from the engine speed and the like.

It is determined whether or not the time difference D is greater than or equal to a preset time TB (step S3).
2). The time difference D is not more than the time TB (that is, the energization stop time is not more than the time TB,
If determined to be short, the time obtained by adding the time TB to the previous power cut-off time T _CT ′ is set as the power start time T _ST , and the power stop time (time difference D) is set to the time TB or more (step S33).
. On the other hand, if it is determined that the time difference D is greater than or equal to the time TB, the processing operation [3] is terminated as it is because the processing in step S33 is unnecessary.

As described above, the microcomputer 42B uses the output of the IGT-OFF signal (that is, interruption of energization to the primary coil of the ignition coil) as a trigger to read the latch state (process 1) and switch the monitor cylinder (process 2). , Latch clear (processing 3) processing is performed in order, such as interrupt handler activation time and task activation time.
If the processing timing of these processes 1 to 3 overlaps the process that should be performed with priority over 3,
These processes 1 to 3 are postponed, and there is a possibility that the processes are greatly delayed from the output of the IGT-OFF signal. For this reason, the time TB is set to a time longer than the maximum delay time (for example, 300 μsec) obtained by adding all the times required for the processing to be preferentially performed.

FIG. 16 shows the voltage signal S1 output from the monitor cylinder switching circuit 2 and the mask circuit 5 in the fuel injection control apparatus employing the failure diagnosis method (or failure diagnosis system) according to the embodiment (3). It is the figure which showed sequences, such as the voltage signal S4 input into the latch port 42d, and the latch state in the latch port 42d.

Since the time difference D (energization stop time) from the previous energization cut-off to the next energization start from the sequence shown in FIG. 16 is equal to or greater than the time TB, a large delay occurs in the processing of the microcomputer 42B. Even if the switching of the monitor cylinder to the third cylinder is delayed, it can be seen that the monitor cylinder is switched to the # 3 cylinder before the primary charge EV2.

According to the fuel injection control device that employs the failure diagnosis method (or failure diagnosis system) according to the above embodiment (3), the energization cutoff of the primary coil of the ignition coil (IGT-OFF)
Energization stop time (time difference D) from energization start (IGT-ON signal output)
Is set to be equal to or longer than the time TB (a time longer than the maximum delay time), the energization start can be surely delayed until after the monitor cylinder switching P1, P2, P3. Therefore, it is possible to prevent the occurrence of a situation in which an abnormality is caused in the ignition system of the engine and the like, and a misdiagnosis is caused in the abnormality. In order to improve accuracy, time TB
It is better to add a margin time, and the time TB is the maximum delay time (for example, 300
It is desirable to set a time obtained by adding a margin time (for example, 80 μsec) to (μsec).

Next, a fuel injection control device that employs the failure diagnosis method (or failure diagnosis system) according to Embodiment (4) will be described. However, since this fuel injection control device has the same configuration as the fuel injection control device 41 shown in FIG. 10 except for the microcomputer 42, the microcomputer is given a different reference numeral and description of the other components. Is omitted here.

In the figure, reference numeral 41C denotes a fuel injection control device (EFI-) for controlling fuel injection of a four-cylinder internal combustion engine.
ECU), the fuel injection control device 41C includes a monitor cylinder switching circuit (MPX) 2,
Mask circuit 3, latch circuit 4, mask circuit 5, microcomputer (microcomputer)
42C.

The microcomputer 42C performs the same processing operation as the processing operation [1] performed by the microcomputer 42, or the processing operations [2-1] and [2-2] performed by the microcomputer 42A.
The same processing operation as the processing operation [3] performed by the microcomputer 42b is performed.

The time TB used in the processing operation [3] is the maximum delay time (for example, 300 μm).
Seconds), the time TA used in the processing operation [1] or the processing operation [2-1] (for example, 50 to
70 μsec) is set to be longer than the total time.

According to the fuel injection control device employing the failure diagnosis method (or failure diagnosis system) according to the above embodiment (4), the same effects as those of the fuel injection control devices 41 and 41A can be obtained, and further the fuel injection control device. The same effect as 41B can be obtained. Further, since the time TB is set to a time longer than the time obtained by adding the time TA to the maximum delay time, even if a large delay occurs in the microcomputer 42C, not only the switching of the monitor cylinder but also the latch Port 4
The latch clear for 2d can also be completed before the next energization start (output of the IGT-ON signal).

When the monitor cylinder is switched immediately before the start of the next energization and the latch state of the latch port 42d is cleared after the start of energization, the latch state of the latch port 42d, which has been latched to the High state by the primary charge, is changed. There is a risk of clearing, but time T
By setting B as described above, such a situation can be avoided. In order to further improve the accuracy, it is better to add a margin time to the time TB, and the time TB is the time TA and the margin time (for example, 80 μsec) as the maximum delay time.
It is desirable to set a time obtained by adding to (for example, 430 to 450 μsec).

Further, when the processing operations similar to the processing operations [2-1] and [2-2] performed by the microcomputer 42A are adopted instead of the processing operations similar to the processing operation [1] performed by the microcomputer 42, Since the processing operation [2-2] may be delayed, the time TB
Is preferably set to a time obtained by adding a maximum processing delay time (for example, 60 μsec) of the processing, and a time (for example, 570 to 59) including another margin time (for example, 80 μsec).
It is more desirable to set to 0 μsec.

It is the block diagram which showed schematically an example of the conventional fuel-injection control apparatus. It is the figure which showed the ion current detection sequence. It is the figure which showed the ion current detection sequence. It is the figure which showed the circuit structure of the mask circuit. 6 is a timing chart showing transition states of each voltage signal in FIG. 4. It is the figure which showed the ion current detection sequence. It is the figure which showed sequences, such as the signal output from a monitor cylinder switching circuit, the signal input into a latch port, and the latch state in a latch port. It is the figure which showed sequences, such as the signal output from a monitor cylinder switching circuit, the signal input into a latch port, and the latch state in a latch port. It is the figure which showed sequences, such as the signal output from a monitor cylinder switching circuit, the signal input into a latch port, and the latch state in a latch port. It is the block diagram which showed roughly the principal part of the fuel-injection control apparatus which employ | adopted the failure diagnosis method (or failure diagnosis system) which concerns on embodiment (1) of this invention. It is the flowchart which showed the processing operation which the microcomputer in the fuel-injection control apparatus which employ | adopted the failure diagnosis method (or failure diagnosis system) which concerns on embodiment (1). In the fuel injection control device employing the failure diagnosis method (or failure diagnosis system) according to the embodiment (1), a signal output from the monitor cylinder switching circuit, a signal input to the latch port, and a latch at the latch port It is the figure which showed sequences, such as a state. It is the flowchart which showed the processing operation which the microcomputer in the fuel-injection control apparatus which employ | adopted the failure-diagnosis method (or failure-diagnosis system) which concerns on embodiment (2). It is the flowchart which showed the processing operation which the microcomputer in the fuel-injection control apparatus which employ | adopted the failure-diagnosis method (or failure-diagnosis system) which concerns on embodiment (2). It is the flowchart which showed the processing operation which the microcomputer in the fuel-injection control apparatus which employ | adopted the failure diagnosis method (or failure diagnosis system) which concerns on embodiment (3). In the fuel injection control apparatus employing the failure diagnosis method (or failure diagnosis system) according to the embodiment (3), a signal output from the monitor cylinder switching circuit, a signal input to the latch port, and a latch at the latch port It is the figure which showed sequences, such as a state.

Explanation of symbols

41, 41A-41C Fuel injection control device 42, 42A-42C Microcomputer

Claims (7)

Among signals obtained by removing a noise by providing a non-detection period with respect to the signal obtained from the ion current detection means for detecting the ion current generated in the monitor cylinder, a time longer than the non-detection period from when the monitor cylinder is switched. Based on the signal after it has passed,
A failure diagnosis method comprising diagnosing an ignition system of an internal combustion engine or a portion related to ion current detection, or a failure of the ignition system of the internal combustion engine and the portion. Switching the monitor cylinder using the power supply interruption to the ignition member as a trigger,
Based on a signal obtained from an ion current detecting means for detecting an ion current generated in the monitor cylinder, an ignition system of the internal combustion engine or a part related to ion current detection, or a failure of the ignition system of the internal combustion engine and the part is detected. With diagnosis,
The energization stop time from energization interruption to the ignition member until energization start to the ignition member is set to a predetermined time or more,
A failure diagnosis method characterized in that the predetermined time is made longer than a maximum delay time that occurs from the time when the ignition member is turned off until the monitor cylinder is switched. Switching the monitor cylinder using the power supply interruption to the ignition member as a trigger,
An internal combustion engine ignition system or a part related to ion current detection based on a signal obtained by removing noise by providing a non-detection period with respect to a signal obtained from ion current detection means for detecting ion current generated in the monitor cylinder Or diagnosing a failure of the ignition system and the part of the internal combustion engine,
The energization stop time from energization interruption to the ignition member until energization start to the ignition member is set to a predetermined time or more,
A failure diagnosis method characterized in that the predetermined time is made longer than a time obtained by combining a maximum delay time that occurs between energization interruption of the ignition member and monitor cylinder switching and the non-detection period. The maximum delay time may be equal to or longer than a time required to perform a process having a higher priority than the monitor cylinder switching process, because the monitor cylinder switching process and the process timing may overlap. The failure diagnosis method according to claim 2 or 3. Mask means for removing noise by providing a non-detection period for a signal obtained from ion current detection means for detecting ion current generated in the monitor cylinder;
Holding means for holding the state after the change when a change occurs in the signal from which noise has been removed by the mask means;
Release means for releasing the state held by the holding means after a time longer than the non-detection period has elapsed since the switching of the monitor cylinder;
Determining means for determining whether or not the state held by the holding means is the state after the change at the next monitor cylinder switching;
Based on a determination result by the determination means, the engine is configured to diagnose a part related to the ignition system or the ionic current detection of the internal combustion engine or a failure of the ignition system of the internal combustion engine and the part. Fault diagnosis system. A switching means for switching the monitor cylinder using a current cut-off to the ignition member as a trigger;
A setting means for setting an energization stop time from energization interruption to the ignition member to start of energization to the ignition member at a predetermined time or more,
The failure diagnosis system according to claim 5, wherein the predetermined time is longer than a time obtained by combining a maximum delay time that occurs between energization interruption of the ignition member and monitor cylinder switching and the non-detection period. The maximum delay time may be a time required for performing a process having a higher priority than a process for switching a monitor cylinder, because the process timing of the monitor cylinder may be overlapped with a process timing. 6. The fault diagnosis system according to 6.

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