JPH1150941A - Ignition plug diagnostic device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately diagnose the degree of progress of carbon fouling of an igniton plug provided in a combustion chamber of an internal combustion engine. SOLUTION: Whether the magnitude of current (an AD value) to flow between electrodes of an ignition plug is larger than a value corresponding to the specified threshold value Vth or not is judged after 500 μs from the time when an ignition signal IGt is applied to the ignition plug. Moreover, the duration in which the AD value to be detected after the ignition signal Igt is off (after discharge of the ignition plug is finished) becomes a value larger than a value corresponding to 2.9 V is confirmed. After that, the degree of damping of the AD value, in which the difference ΔV between the last AD value and this time AD value becomes a value corresponding to 0.5 V or more is confirmed. Therefore, the carbon fouling state in which misfire is to be generated with some possibility is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for diagnosing a spark plug provided in a combustion chamber of an internal combustion engine, and more particularly to a device for diagnosing the degree of progress of smoldering of a spark plug. is there.

[0002]

2. Description of the Related Art An internal combustion engine generally used for an automobile engine or the like converts two reciprocating movements of a piston into two rotations of a crankshaft in four strokes of intake, compression, expansion (combustion) and exhaust, and outputs the same. Is to be obtained. In recent years, such a process of the internal combustion engine has been strictly controlled and managed by an electronic control unit.

By the way, in such an internal combustion engine,
Unless the fuel (air-fuel mixture) compressed in the compression stroke of each cylinder is optimally and reliably burned in the next expansion (combustion) stroke, an abnormal load is applied to other cylinders or unburned gas flows out. May cause various obstacles. Therefore, in order to ensure stable operation of the internal combustion engine, whether or not combustion was reliably performed in each cylinder,
That is, it is necessary to determine the presence or absence of a misfire. An ion detection circuit is known as a means for making such a misfire determination.

In the expansion (combustion) process, a fuel (air-fuel mixture) is burned by discharging an ignition plug provided in a combustion chamber based on an ignition signal IGt from an electronic control unit provided in the internal combustion engine. The ion detection circuit detects an ion generated in the combustion chamber as a result of the combustion of the fuel (air-fuel mixture) as an ion current. Then, misfire is determined based on the presence or absence of the ion current detected at this time. Note that the ignition plug forms a part of the ion detection circuit.

Next, the relationship between the ignition signal IGt and the ion current (ion detection signal Ii) will be described with reference to a time chart shown in FIG. As shown in FIG. 4A, the ignition signal IGt is turned on at a predetermined timing and then turned off. Here, the fuel (air-fuel mixture) in the combustion chamber is burned at the timing when the ignition signal IGt is turned off. The ion detection signal Ii detected at the time of combustion and after the combustion has a predetermined peak after the ignition signal IGt is turned off, as shown in FIG. have. As described above, misfire is determined based on the presence or absence of such an ion detection signal Ii. In this determination, when misfire, that is, absence of the ion detection signal Ii is recognized, the electronic control unit performs appropriate processing to cope with the misfire.

In the above-mentioned ignition plug, a substance such as carbon adheres to the surface of the insulator, so that the resistance value (insulation resistance) between the electrodes of the ignition plug is reduced, that is, so-called smoldering occurs. is there. In this case, FIG.
As shown in (d) to (i), as the ion detection signal Ii, a signal including a leakage current due to the decrease in the resistance value is detected. When the detection signal Ii including the leakage current is detected, it is considered that smoldering may have progressed until a misfire occurs. However, since the detection value is present as the ion detection signal Ii, normal combustion is not detected. It is erroneously judged that it has been performed.

Therefore, conventionally, for example, Japanese Unexamined Patent Publication No.
As can be seen in the device described in Japanese Patent Application Publication No. 1 (1994), the occurrence of smoldering of the spark plug is detected by the presence or absence of a current (leakage current) flowing between the electrodes of the spark plug when the ignition signal IGt is turned on. It is also known that the misfire determination based on the ion detection signal Ii is invalidated when the occurrence of the misfire is detected.

[0008]

As described above, smoldering may proceed until a misfire occurs. As described above, when a misfire occurs remarkably, the smolder is discharged to an exhaust passage without being used for combustion. The exhausted fuel may be burned by the catalytic converter provided in the exhaust passage. Such combustion of the fuel may lead to overheating of the catalytic converter.

However, in the above-mentioned conventional apparatus, although the presence or absence of smoldering is detected based on the leakage current, the smoldering state, that is, overheating of the catalytic converter, that is, the progress of smoldering is not detected at all. Could not.

The present invention has been made in view of the above circumstances, and has as its object to provide an ignition system for an internal combustion engine capable of accurately diagnosing the progress of smoldering of a spark plug provided in a combustion chamber of the internal combustion engine. It is to provide a plug diagnostic device.

[0011]

According to a first aspect of the present invention, there is provided a spark plug diagnostic apparatus for an internal combustion engine for diagnosing a smoldering state of a spark plug provided in a combustion chamber of the internal combustion engine. First current detection means for detecting a current flowing between the electrodes of the ignition plug when an ignition signal is supplied to the ignition plug; and second current detecting a current flowing between the electrodes of the ignition plug after the discharge of the ignition plug has been completed. The gist of the present invention is to include a detecting means and a judging means for judging the degree of progress of smoldering of the ignition plug based on the current detection mode by the first and second current detecting means.

In the above configuration, the first current detecting means includes:
A current flowing between the electrodes of the ignition plug when the ignition signal is supplied to the ignition plug (when a primary current is supplied to the ignition coil) is detected. That is, when smoldering occurs in the ignition plug and a leakage current flows between the electrodes due to the smoldering, the leakage current is detected by the first current detection means. On the other hand, the second current detecting means detects a current flowing between the electrodes of the spark plug after the discharge of the spark plug is completed. That is, when the mixture is burned by the discharge of the spark plug, ions are generated in the combustion chamber, and an ion current flows between the electrodes of the spark plug based on the generated ions. The ionic current flowing between the spark plug electrodes is detected by the second current detecting means.
However, when smoldering occurs in the spark plug and a leakage current flows, the behavior of the current detected by the second current detecting means is also different from the behavior of the current (ion current) flowing based on the generation of ions. It will be very different. The behavior of the current based on the leakage current also changes according to the degree of smoldering of the spark plug. Therefore, as in the same configuration, by simultaneously monitoring the current detection modes by the first and second current detection means, it is possible to accurately determine not only the occurrence of smoldering of the spark plug but also the degree of progress thereof. Will be able to do it.

According to a second aspect of the present invention, in the spark plug diagnostic apparatus for an internal combustion engine according to the first aspect, the determining means determines that a current value detected by the first current detecting means is equal to or greater than a first value. The gist is to determine the degree of progress of the smoldering on the basis of the duration of the current value detected by the second current detecting means when the current value becomes equal to or more than the second value. .

According to a third aspect of the present invention, in the spark plug diagnostic device for an internal combustion engine according to the first aspect, the determining means determines that a current value detected by the first current detecting means is equal to or greater than a predetermined value. The gist is to determine the magnitude of the degree of progress of the smoldering based on the magnitude of the attenuation of the current value detected by the second current detecting means.

According to a fourth aspect of the present invention, in the spark plug diagnostic device for an internal combustion engine according to the first aspect, the determining means determines that a current value detected by the first current detecting means is equal to or greater than a first value. Determining whether the degree of progress of the smoldering is greater or less based on the length of the duration of the current value detected by the second current detecting means and the magnitude of the attenuation degree when the current value exceeds the second value. It is assumed that.

The behavior of the current detected by the second current detecting means when smoldering occurs in the spark plug is such that the current value is maintained at a predetermined value (second value) or more as the smoldering progresses. It has been confirmed by the present inventors that when the smoldering period is prolonged and the smoldering is further progressing, the sustained current value is greatly attenuated according to the degree of the progress. Therefore, according to the above configurations according to the inventions described in claims 2 to 4,
In view of such characteristics of the current detected by the second current detection means, it is possible to make a more detailed determination on the degree of progress of the smoldering. Further, according to these configurations, when the current value detected by the first current detecting means is equal to or more than the predetermined value or the first value, that is, only when the smolder is actually generated in the spark plug, Because the judgment about the degree is made, the second
If the determination is performed only in the current detection mode by the current detection means, there is a risk of erroneous determination, but the determination accuracy can be improved, and unnecessary calculation related to the determination can be omitted before smoldering occurs. In addition, it is possible to reduce the calculation load as the determination means.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment embodying a spark plug diagnostic device for an internal combustion engine according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a system configuration diagram of a four-cylinder gasoline engine 1 as an internal combustion engine. The engine 1 includes a cylinder block 1a, and four (only one is shown in FIG. 1) cylinders 2 are provided in the cylinder block 1a. The pistons 3 provided in each cylinder 2 so as to be able to reciprocate are connected via a connecting rod 3a to a crankshaft 10, which is an output shaft of the engine, and the connecting rod 3a causes the piston 3 to reciprocate to rotate the crankshaft 10. Is to be converted.

A cylinder head 1b is mounted on the upper end of the cylinder block 1a. In each cylinder 2, a combustion chamber 4 is formed between the upper end of the piston 3 and the cylinder head 1b. An ignition plug 11 provided for each combustion chamber 4 ignites the mixture introduced into the combustion chamber 4. Similarly, the intake port 5a and the exhaust port 6a provided corresponding to each combustion chamber 4 constitute a part of the intake passage 5 and the exhaust passage 6, respectively. An intake valve 7 and an exhaust valve 8 provided corresponding to each combustion chamber 4 have respective ports 5a,
6a are respectively opened and closed. The valves 7 and 8 are opened and closed by rotation of cams (not shown) provided on the intake-side camshafts 31 and the exhaust-side camshafts 32 with the rotation of the camshafts 31 and 32, respectively. Timing pulleys 33, 34 provided at the tips of the camshafts 31, 32, respectively, are connected to the crankshaft 10 via a timing belt 35 (crankshaft 1).
The connection mode with 0 is not shown).

That is, when the engine 1 is operating, the rotational force of the crankshaft 10 is transmitted to each camshaft 3 via the timing belt 35 and the timing pulleys 33 and 34.
1, 32. As the camshafts 31 and 32 rotate, the valves 7 and 8 operate. Each of the valves 7, 8 is opened and closed at a predetermined timing in synchronization with the rotation of the crankshaft 10, that is, in response to the reciprocation of each piston 3.

A water temperature sensor 15 for detecting a water temperature (cooling water temperature) THW of the cooling water of the engine 1 is attached to the cylinder block 1a. A surge tank 16 for suppressing intake air pulsation is provided in a part of the intake passage 5, and a diaphragm-type intake pressure sensor 17 for detecting an intake pressure PM is attached to the surge tank 16. An upstream side of the surge tank 16 is provided with a throttle valve 18 which is opened and closed based on an operation of an accelerator pedal 21.
The amount of air taken into the intake passage 5 is adjusted by opening and closing the throttle valve 18. In the vicinity of the throttle valve 18, a throttle sensor 19 for detecting the throttle opening TA, and an idle switch 20 which is turned on when the throttle valve 18 is fully closed.
Is installed.

An air cleaner 23 is disposed upstream of the throttle valve 18 and has an air cleaner 2.
3, an intake air temperature sensor 24 for detecting the intake air temperature THA is attached.

On the other hand, the exhaust gas (H
A three-way catalytic converter 26 for purifying (C, CO, NOx) is attached. Further, the engine 1 has a rotation speed sensor 27 and a crank angle reference position sensor 28.
Is provided. The rotation speed sensor 27 is the engine 1
The rotational speed Ne of the (crankshaft 10) is detected.
The crank angle reference position sensor 28 detects a reference position (for example, compression top dead center) of the rotation angle (crank angle) of the crankshaft 10 in the specific cylinder.

A high voltage output from the igniter 13 is applied to the ignition plug 11. The ignition timing of the ignition plug 11 is determined by the high voltage output timing from the igniter 13. The engine 1 uses an ignition plug 11 to convert an air-fuel mixture composed of intake air from an intake passage 5 and fuel injected from an injector 9 into a combustion chamber 4.
After exploding in the inside to obtain the driving force, the exhaust gas is discharged to the exhaust passage 6 through the exhaust valve 8.

Incidentally, a part of an ion detection circuit described later is provided in the igniter 13, and an ion current generated after ignition is detected by the detection circuit. Next, the configuration of an electronic control unit (hereinafter, referred to as “ECU”) 61 that integrally controls such an engine system will be described with reference to the block diagram of FIG.

As shown in FIG. 2, the ECU 61 is composed of a digital computer, and is connected to a RAM (random access memory) 6 via a bus 62.
3, a ROM (Read Only Memory) 64, a CPU (Central Processing Unit) 65 composed of a microprocessor, an input port 66 and an output port 67.

The CPU 65 comprises an arithmetic processing circuit.
Various arithmetic processes are executed in accordance with a control program and initial data stored in the M64 in advance. RAM 63 is CP
The calculation result by U65 is temporarily stored.

The water temperature sensor 15, the intake pressure sensor 17,
Detection signals from the throttle sensor 19, the idle switch 20, the intake air temperature sensor 24, the rotation speed sensor 27, the crank angle reference position sensor 28, and the like are input to the input port 66. The ion current detected by the ion detection circuit, a part of which is formed in the igniter 13, is also input to the input port 66. The operating state of the engine 1 is detected by these sensors 13, 15, 17, 19, 20, 24, 27, 28.

On the other hand, the output port 67 is connected to each injector 9 and each igniter 1 via a corresponding drive circuit or the like.
3 and so on. The output port 67 is also connected to a lamp 14 that is turned on when it is determined that the smolder is dangerous in the diagnosis of the ignition plug 11 described later. The lamp 14 is mounted on the dashboard of the driver's seat, and the display of the lamp 14 allows the driver to know the diagnosis result of the ignition plug 11. Then, the ECU 61 determines each of the sensors 13, 15, 17, 19, 20, 24, 2
The injector 9, the igniter 13, the lamp 14, and the like are suitably controlled in accordance with the control program and the initial data stored in the ROM 64 based on the detection signals from the detectors 7 and 28.

Next, the above-described ion detection circuit constituted by the igniter 13 and the ignition plug 11 will be described with reference to FIG. As shown in FIG. 3, the ion detection circuit 40 is mainly composed of a power supply 41, the igniter 13, and the ignition plug 11. The igniter 13 further includes an ignition coil 42, an igniter circuit 43, and an ion detection circuit 44.
It is constituted by.

The ignition coil 42 has a primary winding 42a.
And a secondary winding 42b. The igniter circuit 43 includes a drive circuit 46 and a power transistor 47.
have. The ion detection circuit unit 44 includes a capacitor 48, Zener diodes 49 and 50, a resistor 51,
It has an inverting amplifier 52, a V / I (voltage / current) converter 53, and an output terminal 55.

In such a configuration, one end of the primary winding 42a of the ignition coil 42 is connected to the power supply 41, and the other end is connected to the power transistor 47.
It is connected to the. The drive circuit 46 is connected to a control electrode of a power transistor 47.

On the other hand, one end of the secondary winding 42b of the ignition coil 42 is connected to the ignition plug 11.
The ignition plug 11 includes a discharge electrode 11a connected to the one end of the secondary winding 42b, and a ground electrode 11b which is arranged to face the discharge electrode 11a and is grounded. The ignition plug 11 is provided so as to be exposed in the combustion chamber (not shown) of each cylinder, and its ground electrode 11b is grounded via the combustion chamber wall.

On the other hand, the other end of the secondary winding 42b is connected to the Zener diodes 49 and 50 of the ion detection circuit section 44.
Through the Zener diode 4
A capacitor 48 and a resistor 51 for detecting an ion current are connected in parallel to 9, 50, respectively. A connection point between the parallel circuit including the zener diode 49 and the capacitor 48 and the resistor 51 is further connected to an output terminal 55 of the detection circuit unit 44 via an inverting amplifier 52 and a V / I converter 53. .

Next, the operation of the ion detection circuit 40 will be described with reference to FIG. In the expansion (combustion) process of the engine 1, the power transistor 47 is turned on / off via the drive circuit 46 by the ignition signal IGt from the ECU 61, and the primary current I1 flowing through the primary winding 42a is controlled.
When the primary current I1 is interrupted,
A secondary voltage V2 consisting of a negative high voltage is induced in the secondary winding 42b. As a result, a discharge spark is generated from the ground electrode 11b of the ignition plug 11 toward the discharge electrode 11a,
Fuel (air-fuel mixture) in the combustion chamber is burned. At this time, the capacitor 48 is charged by the secondary current (arc current) I2 flowing in the manner shown in FIG. In addition,
This charging voltage is maintained at a constant voltage by a Zener diode 49 connected in parallel to the capacitor 48.

On the other hand, during the expansion (combustion) process, if combustion is performed normally, a large amount of cations are generated in the combustion chamber. Then, the generated cations are ion current I
And flows through the route shown in FIG. That is, the ion current I is supplied to the resistor 51, the capacitor 48, the secondary winding 4
It flows through the path through the ignition plug 2b and the ignition plug 11, and discharges the charge of the capacitor 48.

The voltage generated between both ends of the resistor 51 by the ion current I is inverted and amplified by an inverting amplifier 52 and converted into a current value by a V / I converter 53. It is output from the output terminal 55 as an ion detection signal Ii corresponding to the amount. This output is taken into the ECU 61 and used to determine whether or not combustion has been normally performed.

Next, the characteristics of the ignition signal IGt and the ion detection signal Ii will be described with reference to a time chart shown in FIG. FIG. 4A is a time chart showing a state in which the ignition signal IGt is turned on at a predetermined timing and then turned off. FIGS. 4B to 4I are time charts showing transitions of the ion detection signal Ii sequentially detected according to the degree of progress of smoldering. Incidentally, the reason why the detection signal Ii is saturated at a predetermined value or more is because the amplification factor of the inverting amplifier 52 is large and exceeds the detectable range. The sudden decrease in the ion detection signal Ii is caused by the fact that the capacitor 48
This is because the discharge time is short. As described above, the resistance between the two electrodes 11a and 11b of the ignition plug 11 decreases as the smoldering progresses, so that the discharge time becomes shorter as the smoldering progresses.

When the fuel (air-fuel mixture) in the combustion chamber is normally burned at the timing when the ignition signal IGt is turned off, the ion detection signal Ii shown in FIG. 4B is detected. As shown in FIG. 4B, the ion detection signal Ii is detected as a signal having a predetermined peak after the ignition signal IGt is turned off, that is, after the discharge of the ignition plug 11 is completed.
A misfire determination is made based on the presence or absence of the ion detection signal Ii at this time.

By the way, such an ion detection signal Ii
As described above, as the smoldering progresses, the resistance value (insulation resistance) between the discharge electrode 11a and the ground electrode 11b decreases, and is affected by the leakage current, as described above. The detection signal Ii including the leakage current is used for misfire determination. In particular, the resistance value decreases until it is shown in FIG.
Ω), when smoldering progresses, although misfiring is considered to have occurred with a considerable probability, there is a detection value as the ion detection signal Ii, so that it is erroneously determined that normal combustion has been performed. was there.

Therefore, in the present embodiment, the ion detection signal Ii is analyzed in the following manner, and the ignition is performed when it is considered that a misfire has occurred with a considerable probability (FIG. 4 (i)). Diagnose the condition of the plug.

FIGS. 5 and 6 show the ECU 61 for diagnosing whether the smoldering of the spark plug 11 is progressing until the detection signal Ii shown in FIG. 4 (i) is detected.
Is a flowchart showing a spark plug diagnosis routine of the engine 1 executed by the engine. This routine is periodically executed by a fixed time interruption every 4 ms (millisecond). Such time management is performed by a well-known timer counter function of the CPU 65.

When the processing shifts to this routine, the ECU
61 determines in step 101 whether the engine rotation speed Ne is less than or equal to 2000 rpm. If it is determined that the engine rotation speed Ne is higher than 2000 rpm, the process proceeds to step 1 without diagnosing the smoldering progress.
08. Here, the reason why the smoldering progress is not diagnosed when the engine rotation speed Ne is high is that the period from the ignition of one cylinder to the next ignition of the same cylinder is not long enough to diagnose the progress of the smoldering. It depends.

In step 108, the ECU 61 turns OFF the count start flag x4msad and the temporary flags 1, 2, and 3 every 4 ms in the smoldering flag xdksu.
(Off) ”, and proceeds to step 109.

Here, the smoldering flag xdksu is set according to the state of the ion detection signal Ii 500 μs (microseconds) after the ignition signal IGt is turned on (set to “ON”). ) Flag. After the ion detection signal Ii is subjected to I / V conversion in the ECU 61,
Analog / digital converted value (hereinafter, “AD value”)
It is treated as. The above determination is based on the ignition signal IGt.
Is performed in the ECU 61 by comparing the AD value at a timing 500 μs after the switch is turned on with a predetermined threshold value. If an AD value larger than the predetermined threshold value is confirmed, it is determined that smoldering is progressing at least at a level of 20 to 50 MΩ, and the smoldering flag xdksu is set to “ON”. If an AD value larger than the predetermined threshold is not confirmed, it is determined that smoldering has not progressed so much, and the smoldering flag xdksu is set to “OFF”.

On the other hand, a count start flag x4 every 4 ms
msad is a flag that is set (turned on) when the ignition signal IGt is turned off. When this flag is set, the number of times counted by the timer counter function every 4 ms is started to be counted.

The temporary flags 1, 2, and 3 are flags for determining the duration of the AD value and the degree of attenuation as described later. The ECU which turned off each flag in this way
Next, in step 109, the count number ecad4ms every 4 ms, the smoldering continuous number ecadksu every 4 ms, the misfire counter value cigt, and the ignition counter value cdkn are all set to "0", and the routine is exited once.

Here, the count ecad4 is counted every 4 ms.
ms is the number of times of counting the time every 4 ms by the timer counter function after the ignition signal IGt is turned off. In addition, the number of smoldering counts ecadksu every 4 ms
Is for determining the duration of an AD value larger than a predetermined threshold value. The magnitude of the AD value detected at the time of 4 ms by the timer counter function after the ignition signal IGt is turned off. Is the number of counts when is larger than a predetermined value.

Further, the misfire counter value cigt is
If it is determined that a misfire has occurred by the determination described below,
The ignition counter value cdkn is a count value that is incremented by “1”, and the ignition counter value cdkn is a count value that is incremented by “1” each time each cylinder is ignited.

On the other hand, if it is determined in step 101 that the engine rotation speed Ne is less than 2000 rpm,
Move to step 102. Then, the ECU 61 determines whether or not the smoldering flag xdksu and the count start flag x4msad every 4 ms are “ON”.
If it is determined that at least one of the smoldering flag xdksu and the count start flag x4msad every 4 ms is "OFF", the routine is temporarily exited.

If it is determined in step 102 that the smoldering flag xdksu and the count start flag x4msad every 4 ms are "ON", the process proceeds to step 103. In step 103, the ECU 61 increments the count ecad4ms by “1” every 4 ms and proceeds to step 104.

In step 104, the ECU 61 determines whether or not the count ecad4ms is less than 6 every 4 ms. Here, the count number ec every 4 ms
If ad4ms is determined to be less than six times, step 10
Move to 5.

In step 105, the ECU 61 sets the smoldering count number ecadksu to 3 every 4 ms.
It is determined whether or not this is the case. As described above, the smoldering count number ecadksu every 4 ms determines the duration of the AD value larger than a predetermined threshold value. Therefore, the number of smoldering counts ecadks every 4 ms
u is the number of counts when the magnitude of the AD value detected at the timing of every 4 ms by the timer counter function becomes larger than a predetermined value after the ignition signal IGt is turned off. In the present embodiment, a value corresponding to "2.9 V (volt)" is employed as the predetermined value. Here, the number of smoldering counts ecadksu every 4 ms is 3
If it is determined that the difference is less than the above, the process proceeds to step 107. Then, the ECU 61 determines in step 107 that 4 m
The AD corresponding to the count number ecad4ms for each s
After storing the value, the process once exits the routine.

On the other hand, if it is determined in step 105 that the smoldering count number ecadksu is 3 or more every 4 ms, that is, if the AD value is larger than the value equivalent to "2.9 V", it is determined that the continuation time is longer than 12 ms. If so, the process proceeds to step 106.

After setting the provisional flag 1 in step 106, the ECU 61 proceeds to step 107.
Then, in step 107, the ECU 61 stores the AD value corresponding to the count ecad4ms every 4 ms, and then temporarily exits the routine.

In step 104, 4 m
If it is determined that the count ecad4ms for each s is 6 or more, the ECU 61 proceeds to step 111 shown in FIG. 6 to determine the degree of attenuation of the AD value. Here 4
If it is determined that the count ecad4ms is less than 10, that is, 6 to 9 times per ms, step 112
Move to

In step 112, the ECU 61 determines whether the difference between the previously stored AD value and the currently detected AD value is larger than a predetermined value, and whether the temporary flag 1 is "ON". In the present embodiment, a value equivalent to “0.5 V” is adopted as the predetermined value. Here, the difference between the previously stored AD value and the currently detected AD value is equal to or smaller than a value equivalent to “0.5 V”, or the temporary flag 1 is set to “O”.
If it is determined to be "FF", the process proceeds to step 115.

After the ECU 61 sets the temporary flag 2 to "OFF" in step 115, the ECU 61 proceeds to step 107. Then, in step 107, the ECU 61 stores the AD value corresponding to the count ecad4ms every 4 ms, and then temporarily exits the routine.

In step 112, the difference between the previously stored AD value and the currently detected AD value is "0.5".
V ”and the temporary flag 1 is“ ON ”.
If it is determined, the process proceeds to step 113.

In step 113, the ECU 61 determines whether the temporary flag 2 is "ON" and the temporary flag 3 is "OFF". If it is determined that the temporary flag 2 is “OFF” or the temporary flag 3 is “ON”, the process proceeds to step 116.

The ECU 61 sets the temporary flag 2 to "ON" in step 116, and then proceeds to step 107. Then, the ECU 61 determines in step 107 that 4 m
The AD corresponding to the count number ecad4ms for each s
After storing the value, the process once exits the routine.

If it is determined in step 113 that the provisional flag 2 is “ON” and the provisional flag 3 is “OFF”, the process proceeds to step 114.
The ECU 61 sets the temporary flag 3 to “ON” in step 114, increments the misfire counter value cigt by “1”, and then proceeds to step 107. Then, the ECU 61 determines in step 107 that 4 m
The AD corresponding to the count number ecad4ms for each s
After storing the value, the process once exits the routine.

On the other hand, in step 111, the 4m
When it is determined that the count ecad4ms is 10 or more for each s, the process proceeds to step 121. In step 121, the ECU 61 determines that one expansion (combustion) stroke of a certain cylinder has been completed, and determines that the ignition counter value c
After incrementing dkn by “1”, step 122
Move to

In step 122, the ECU 61 sets the count start flag x4msad and the temporary flags 1, 2 and 3 to "OF" every 4ms.
The process moves to step 123 as "F".

The ECU 61 determines in step 123 that 4
The count number ecad4ms for every ms and the smolder count number ecadksu for every 4ms are set to "0", and the routine proceeds to step 124.

In step 124, the ECU 61 determines whether or not the ignition counter value cdkn is larger than 100. That is, it is determined whether the expansion (combustion) stroke has been performed more than 100 times in a certain cylinder. If it is determined that the ignition counter value cdkn is 100 or less, the process proceeds to step 107. And ECU
61 stores the AD value corresponding to the count ecad4ms every 4 ms in step 107,
The process once exits.

If it is determined in step 124 that the ignition counter value cdkn is larger than 100, the process proceeds to step 125. In step 125, the ECU 61 sets the misfire counter value cigt to 100.
It is determined whether or not the value divided by is greater than the misfire determination rate criterion. The misfire judgment rate criterion is
It is a value of 0 to 1 determined by the engine speed Ne and the engine load L. The misfire determination rate criterion has a smaller value as the engine rotation speed Ne is larger and the engine load L is larger. If it is determined that the value obtained by dividing the misfire counter value cigt by 100 is equal to or less than the corresponding misfire determination rate criterion, the process proceeds to step 127 described later.

If it is determined in step 125 that the value obtained by dividing the misfire counter value cigt by 100 is larger than the corresponding misfire determination rate criterion, the process proceeds to step 126.

In step 126, the ECU 61 sets the dangerous smoldering judgment to "ON". Here, when the dangerous smoldering determination is set to “ON”, the lamp 14 is turned on. Then, the process proceeds to step 127.

At step 127, the ignition counter value cdkn and the misfire counter value cigt are set to "0", and then the routine proceeds to step 107. Then, in step 107, the ECU 61 counts ec every 4 ms.
After storing the AD value corresponding to ad4ms, the routine once exits.

In the present embodiment, a spark plug diagnosis routine for the engine 1 shown in FIG. 7 is executed separately from the spark plug diagnosis routine. The ignition plug diagnosis routine will be described below.

The ignition plug diagnosis routine is executed by a rotation speed Ne interrupt based on a rotation speed signal output from the rotation speed sensor 27 when a certain cylinder advances 30 ° after passing through the top dead center.

When the processing shifts to this routine, the ECU
61 first determines in step 131 whether or not the smoldering flag xdksu has been "OFF" for two consecutive ignitions. If the smoldering flag xdksu is determined to be "ON" at least once, the routine exits from the routine.

If it is determined in step 131 that the smoldering flag xdksu has been "OFF" for two consecutive ignitions, the process proceeds to step 132. ECU
In step 132, regardless of the current state of the dangerous smoldering determination (step 126), the dangerous smoldering determination is determined to be normal and the process proceeds to step 133. If the dangerous smoldering determination is normal, the lamp 14 is turned off.

In step 133, the ECU 61 sets the misfire counter value cigt to "0" regardless of the current state of the misfire counter value cigt, and once exits the routine.

Next, the spark plug diagnosis mode of the present embodiment based on each of the above processes will be described in further detail with reference to FIG. FIG. 8 shows a time chart of the AD value when the ignition signal IGt and the smoldering are considerably advanced, and shows the relationship between the count number ecad4 ms and the like every 4 ms counted corresponding to these. As described above, in the present embodiment, a smoldering state (FIG. 4 (i)), which is considered to be caused by a considerable probability of misfiring, is detected.

First, it is determined whether or not the magnitude of the AD value 500 μs after the ignition signal IGt is turned on is larger than a predetermined threshold Vth equivalent value. Here, when the AD value is larger than the predetermined threshold Vth equivalent value, the smoldering flag xdksu is set to “ON” (FIG. 8).
(D)). In this case, it is determined that smoldering is progressing at least at a level of 20 to 50 MΩ.

In this case, the engine speed Ne
Is less than or equal to 2000 rpm, the count ecad4ms is counted every 4 ms in accordance with the timer counter function of the ECU 61 every 4 ms on condition that the ignition signal IGt is off. As shown in FIG. 8C, until the count number ecad4ms is counted 5 times every 4 ms, the time when the AD value is larger than the value equivalent to “2.9 V” is 3 times or more (12 ms or more). Is detected, and the duration of the AD value larger than the predetermined threshold value is confirmed. Here, when the continuation time of 12 ms or more is confirmed, the temporary flag 1 is set to “ON” (FIG. 8).
(E)).

On the other hand, the count number eca is counted every 4 ms.
Until d4ms is counted 6 to 9 times, the previous A
When the difference ΔV between the D value and the present AD value is larger than the value equivalent to “0.5 V”, it is detected that the difference ΔV continues twice consecutively.
Check the value attenuation. Here, when the degree of attenuation is confirmed for the first time, the temporary flag 2 is set to “ON” (FIG. 8).
(F)) When the degree of attenuation is further confirmed, the temporary flag 3 is set to "ON" (FIG. 8 (g)).

By confirming the duration and the degree of attenuation of the AD value, a smoldering state which seems to have caused misfire is detected with a considerable probability. Further, in the present embodiment, every time the smoldering state is detected, the misfire counter value cigt is set to “1” on the assumption that a misfire has occurred.
Increment by one. If more than 100 expansion (combustion) strokes of the cylinder have been completed, the value obtained by dividing the misfire counter value cigt by 100 is compared with a misfire determination rate criterion to determine whether or not the cylinder is in a dangerous smoldering state. Is confirmed. Here, if it is confirmed that a dangerous smoldering state is present, the dangerous smoldering judgment is set to “ON” and
The lamp 14 is turned on.

In the present embodiment, if the state where the smoldering flag xdksu is "OFF" is confirmed for two consecutive ignitions, it is determined that the smoldering detection is temporary and the normal judgment is made. Dangerous smoldering judgment “OF
F "), and the lamp 14 is turned off.

As described in detail above, according to the present embodiment, the following effects can be obtained. After the ignition signal IGt is turned on, the smoldering state is roughly detected at 500 μs, and the ignition signal I
Since the detection of the smoldering state is selectively performed after Gt is turned off, unnecessary calculations can be omitted in a state where smoldering is not progressing.

A state in which misfire is considered to have occurred with a considerable probability due to the influence of smoldering can be detected. When it is determined that misfire due to the influence of smoldering is severe, the lamp 14 is turned on to appropriately warn that it is time to replace the spark plug 11. Therefore, it is possible to prevent the catalyst from being overheated due to the misfire.

If it is confirmed that the user has temporarily lost power, the lamp 14 is turned off to eliminate unnecessary warnings. Note that the present embodiment is not limited to the above, and may be changed as follows.

In the present embodiment, the misfire determination rate criterion used for the dangerous smoldering determination is a variable corresponding to the engine speed Ne and the engine load L. A variable corresponding to only one may be used. The misfire determination rate criterion may be an appropriate constant.

In the present embodiment, initially, after the ignition signal IGt is turned on, it is confirmed that the AD value of 500 μs is larger than a predetermined threshold value Vth equivalent value, and at least a level of 20 to 50 MΩ. It detects that smoldering is progressing. This may be achieved by setting another timing or a threshold value and detecting that smoldering is progressing at a level other than the above.

In the present embodiment, initially, it is confirmed that the AD value of 500 μs after the ignition signal IGt is turned on is larger than a predetermined threshold Vth equivalent value. Further, in a state where the ignition signal IGt is turned off, the timer counter function detects an AD value that is timed every 4 ms. Then, it is determined that the time when the AD value is greater than the value equivalent to “2.9 V” is 12 ms or more as the duration, and the difference between the previous AD value and the present AD value is “0.5 V” as the degree of attenuation. It was determined that the case where the value was larger than the equivalent value continued twice consecutively. As a result, a smoldering state in which misfire has occurred with a considerable probability (FIG. 4)
(I)) is detected. In this case, the continuation time and the degree of attenuation are determined by adopting other appropriate setting values, whereby the smoldering state at other stages is detected. You may.

Further, A corresponding to the smoldering state of each stage.
The D value detection mode may be stored in the ROM 64 as a map in advance. Then, in a state where the ignition signal IGt is turned off, 4 ms by the timer counter function.
Detects the AD value that matches the timing of each time. And AD
The duration of the value and the degree of attenuation may be confirmed to detect the smoldering state at various stages. In this case, for example, the smoldering state before the misfire is detected, and measures such as reducing the amount of fuel increase in advance in accordance with the smoldering state can be taken to improve the smoldering state.

In the present embodiment, the ignition signal IG
It is confirmed that the leakage current of 500 μs after t is turned on is larger than a predetermined threshold value Vth equivalent value. Then, it is determined that the case where the AD value is greater than the value equivalent to “2.9 V” is 12 ms or more as the duration, and the difference between the previous AD value and the present AD value is “0.5” as the degree of attenuation.
It was determined that the case where the value was larger than the "V" equivalent value continued twice consecutively. Thus, the smoldering state in which misfire has occurred with a considerable probability (FIG. 4 (i)) is detected, but this is done by judging only one of the duration and the degree of attenuation of the AD value. The state may be detected.
The detection mode of the AD value corresponding to the smoldering state at each stage may be stored in the ROM 64 as a map in advance. Then, the AD value adjusted by measuring the time every 4 ms is detected by the timer counter function. Based on this AD value, only one of the duration and the degree of attenuation may be confirmed, and the smoldering state at various stages may be detected.

In the present embodiment, the ion detection circuit 40 is constituted by the ignition plugs 11 of the respective cylinders (combustion chambers 4) and the corresponding igniters 13 and the like. A distributor for distributing the ignition voltage to each ignition plug 11 may be provided therebetween to form an ion detection circuit.

In the present embodiment, the case where the present invention is applied to a four-cylinder engine as an internal combustion engine has been described. However, the present invention can be similarly applied to engines having other numbers of cylinders. .

[0092]

According to the present invention, it is possible to accurately determine not only the occurrence of smoldering of the spark plug but also the degree of its progress. Then, based on the result of the determination, it is possible to accurately know the timing of replacement or maintenance of the spark plug.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an outline of an engine system to which an embodiment of a spark plug diagnostic device according to the present invention is applied.

FIG. 2 is a block diagram showing an electrical configuration of the embodiment.

FIG. 3 is a circuit diagram illustrating an ion detection circuit.

FIG. 4 is a time chart showing an ignition signal and an ion detection signal according to the degree of progress of smoldering.

FIG. 5 is a flowchart showing a procedure for diagnosing a spark plug.

FIG. 6 is a flowchart showing a procedure for diagnosing a spark plug.

FIG. 7 is a flowchart showing a diagnostic procedure of a spark plug.

FIG. 8 is a time chart showing a diagnosis mode of the ignition plug.

[Explanation of symbols]

4 combustion chamber, 11 spark plug, 13 igniter, 1
DESCRIPTION OF SYMBOLS 4 ... Lamp, 26 ... Three-way catalytic converter, 27 ... Rotation speed sensor, 28 ... Crank angle reference position sensor, 40 ... Ion detection circuit, 41 ... Power supply, 42 ... Ignition coil, 43 ... Igniter circuit, 44 ... Ion detection circuit Department,
55: output terminal, 61: ECU.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hirokazu Oguro 1-1-1, Showa-cho, Kariya-shi, Aichi Pref.

Claims (4)

[Claims] 1. An ignition plug diagnosis device for an internal combustion engine for diagnosing a smoldering state of an ignition plug provided in a combustion chamber of the internal combustion engine, wherein a current flowing between electrodes of the ignition plug is detected when an ignition signal is supplied to the ignition plug. A first current detecting means, a second current detecting means for detecting a current flowing between the electrodes of the spark plug after the discharge of the spark plug is completed, and a current detecting mode by the first and second current detecting means. Determining means for determining the degree of progress of the smoldering of the spark plug based on the spark plug. 2. The method according to claim 1, wherein the determining means determines a second one of the current values detected by the second current detecting means when the current value detected by the first current detecting means is equal to or more than a first value.
The spark plug diagnostic device for an internal combustion engine according to claim 1, wherein the magnitude of the degree of progress of the smoldering is determined based on the length of the duration that is equal to or greater than the value of?. 3. The method according to claim 1, wherein the determining means determines whether the degree of attenuation of the current value detected by the second current detecting means is greater or smaller when the current value detected by the first current detecting means is equal to or greater than a predetermined value. The spark plug diagnostic device for an internal combustion engine according to claim 1, wherein the degree of progress of the smoldering is determined based on the smoldering degree. 4. The method according to claim 1, wherein the determining means determines a second current value detected by the second current detecting means when the current value detected by the first current detecting means is equal to or more than a first value.
2. The magnitude of the degree of progress of the smoldering is determined based on the length of the duration and the magnitude of the degree of attenuation to a value equal to or greater than the value of
A spark plug diagnostic device for an internal combustion engine according to claim 1.