JP4014013B2 - Ion current detection device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ion current detection device for an internal combustion engine having a function of diagnosing the state of the spark plug and the combustion state of the internal combustion engine by detecting an ion current flowing through the electrode of the spark plug.
[0002]
[Prior art]
In recent years, in order to detect the combustion state of an internal combustion engine (engine), a technique has been developed in which an ionic current flowing through a spark plug terminal is detected for each ignition, and ignition, misfire, etc. are detected based on the ionic current detection signal. ing. The conventional ignition / misfire determination uses the characteristic that the ion current increases at the time of ignition. The ion current detection signal is compared with a predetermined determination reference voltage. If the ion current detection signal is equal to or higher than the determination reference voltage, Judgment, otherwise, it is determined as misfire.
[0003]
[Problems to be solved by the invention]
However, since the ionic current varies greatly depending on the engine operating conditions, the method of determining ignition / misfire by comparing the ionic current detection signal with the determination reference voltage as in the above-described conventional case depends on the variation of the engine operating conditions. There is a risk of misjudgment of ignition / misfire due to the influence of fluctuations in ion current.
[0004]
In addition, since the combustion state of the internal combustion engine depends on the discharge performance of the spark plug, it is desirable to be able to detect it quickly if the discharge performance of the spark plug deteriorates due to adhesion of an insulator deposit or the like. .
[0005]
However, the conventional diagnosis of spark plug abnormality is done by removing the spark plug from the engine at the service factory and visually observing the state of the ignition part of the spark plug to determine normality / abnormality. If you do not have a vehicle, you can not diagnose the spark plug abnormality. To date, there has been a drawback in that a method for detecting an abnormality of a spark plug at an early stage during operation has not been established, and discovery and countermeasures for the abnormality of the spark plug are delayed.
[0006]
Accordingly, a first object of the present invention is to make it possible to accurately diagnose the state of the ignition plug during operation, and a second object is to accurately diagnose the combustion state of the internal combustion engine from the ion current. Is to be able to do it.
[0007]
[Means for Solving the Problems]
In order to achieve the first object, in claim 1 of the present invention, focusing on the fact that the ionic current flowing through the spark plug electrode changes depending on the state of the spark plug, the ionic current flowing through the spark plug electrode is ionized. Detected by the current detection means, the average value and standard deviation of the output value of the ion current detection means is obtained according to the lognormal distribution characteristic by the output distribution evaluation means, and the ignition plug state is ignited based on this average value and standard deviation. Diagnose with plug diagnostic means. Thus, by obtaining the average value and standard deviation of the output value of the ion current detecting means by the lognormal distribution characteristic, the diagnostic parameter (average value and the average value) that reduces the influence of the fluctuation of the ion current due to the fluctuation of the operating condition of the internal combustion engine is obtained. (Standard deviation) can be obtained, and the state of the spark plug can be accurately diagnosed based on the diagnostic parameter.
[0008]
In order to achieve the second object, according to a second aspect of the present invention, the combustion state of the internal combustion engine is diagnosed by the combustion state diagnostic unit based on the average value and the standard deviation obtained by the output distribution evaluation unit. To do. In this way, it is possible to accurately diagnose the combustion state of the internal combustion engine based on the diagnostic parameters (average value and standard deviation) in which the influence of fluctuations in ion current due to fluctuations in the operating conditions of the internal combustion engine is reduced.
[0009]
In this case, it goes without saying that both the combustion state of the internal combustion engine and the state of the spark plug may be diagnosed based on the average value and the standard deviation obtained by the output distribution evaluation means as in claim 3. Yes.
[0010]
Further, as described in claim 4, when the average value and the standard deviation obtained by the output distribution evaluation means are out of a predetermined range, that is, when a different type of plug is installed or when the ignition plug is abnormal, diagnosis is prohibited. Means may be provided. In this way, it is possible to avoid making a diagnosis of the combustion state in a state where the ion current cannot be detected with high accuracy, and the diagnosis accuracy of the combustion state can be further improved.
[0011]
Further, as in claim 5, the average value and the standard deviation may be obtained under specific operating conditions in which the ion current generation state is stable. In this way, the average value and the standard deviation can be obtained with high accuracy.
[0012]
Further, as in claim 6, when the value obtained by the output distribution evaluating means is not more than a predetermined average value and not more than a predetermined standard deviation, it may be diagnosed that the spark plug is abnormal. That is, when both the average value and the standard deviation are small, it means that the ion current detected by the ion current detection means is always small. In this case, it is considered that the ionic current is difficult to detect due to adhesion of an insulator deposit to the electrode of the spark plug, so that the value obtained by the output distribution evaluation means is below a predetermined average value and Whether or not the spark plug is abnormal can be accurately diagnosed based on whether or not it is equal to or less than a predetermined standard deviation.
[0013]
Further, as in claim 7, the first determination reference value set in advance is compared with the second determination reference value calculated by the formula of “average value−n × standard deviation (where n> 3)”. Then, the determination reference value of the combustion state may be corrected. In this way, even when the spark plug is replaced with a different type of spark plug with different ion current detection characteristics or when the spark plug is deteriorated, the judgment reference value can be corrected according to the spark plug, and the combustion state The diagnostic accuracy can be further improved.
[0014]
Further, as in the eighth aspect, a determination reference value for the combustion state may be set for each cylinder. In this way, even if the ionic current detection characteristics of the spark plug are different for each cylinder, the combustion state can be accurately diagnosed with the optimum determination reference value for each cylinder.
[0015]
Further, as in claim 9, logarithmic normal distribution of the output value of the ion current detection means is obtained for each predetermined number of ignition cycles, and the output value corresponding to the 50% cumulative frequency is taken as the average value, and the m% cumulative frequency (however, The standard deviation may be obtained from the output value corresponding to m <50). In this way, the average value and the standard deviation can be obtained very simply from the lognormal distribution characteristics.
[0016]
By the way, as the use period of the spark plug becomes longer, the insulator deposit gradually adheres to the outer peripheral surface of the center electrode of the spark plug, and the exposed area of the center electrode may be reduced. If it becomes like this, the ion current which flows into a center electrode will reduce, and the output of an ion current detection means will fall.
[0017]
As a countermeasure, a multipolar plug or a creeping discharge plug may be used as the ignition plug as in claim 10. Multi-polar plugs and creeping discharge plugs generate a spark discharge from the side toward the outer peripheral surface of the center electrode of the spark plug, so that the outer peripheral surface of the center electrode is cleaned by the discharge energy, and the insulator deposit adheres. Less is. Therefore, if the multipolar plug or the creeping discharge plug is used, it is possible to prevent the output of the ion current detecting means from being lowered due to the adhesion of the insulator deposit.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment (1) of the present invention will be described with reference to FIGS. First, the circuit configuration of the ignition control system will be described with reference to FIG. One end of the primary coil 22 of the ignition coil 21 is connected to the battery 23, and the other end of the primary coil 22 is connected to the collector of the power transistor 25 built in the igniter 24. One end of the secondary coil 26 is connected to a spark plug 27, and the other end of the secondary coil 26 is connected to the ground via two Zener diodes 28 and 29.
[0019]
The two Zener diodes 28 and 29 are connected in series in opposite directions, a capacitor 30 is connected in parallel to one Zener diode 28, and an ion current detection resistor 31 is connected in parallel to the other Zener diode 29. A potential Vin between the capacitor 30 and the ionic current detection resistor 31 is input to the inverting input terminal (−) of the inverting amplifier circuit 33 via the resistor 32 and is inverted and amplified. The output voltage V of the inverting amplifier circuit 33 is ionized. The current detection signal is input to the engine control circuit 34. The ion current detection circuit 35 (ion current detection means) is composed of Zener diodes 28 and 29, a capacitor 30, an ion current detection resistor 31, an inverting amplification circuit 33, and the like.
[0020]
During engine operation, the power transistor 25 is turned on / off at the rise / fall of the ignition command signal transmitted from the engine control circuit 34 to the igniter 24. When the power transistor 25 is turned on, a primary current flows from the battery 23 to the primary coil 22. After that, when the power transistor 25 is turned off, the primary current of the primary coil 22 is cut off and a high voltage is electromagnetically induced in the secondary coil 26. This high voltage causes spark discharge between the electrodes 36 and 37 of the spark plug 27. This spark discharge current flows from the ground electrode 37 of the spark plug 27 to the center electrode 36, is charged to the capacitor 30 via the secondary coil 26, and flows to the ground side via the Zener diodes 28 and 29. After the capacitor 30 is charged, the ion current detection circuit 35 is driven by using the charging voltage (for example, 120V) of the capacitor 30 regulated by the Zener voltage of the Zener diode 28 as a power source, and the ion current is detected as described later.
[0021]
On the other hand, the ion current flows in the opposite direction to the spark discharge current. In other words, after ignition is finished, a voltage is applied between the electrodes 36 and 37 of the spark plug 27 by the charging voltage of the capacitor 30, so that ions generated when the air-fuel mixture burns in the cylinder are connected between the electrodes 36 and 37. Although an ionic current flows, the ionic current flows from the center electrode 27 to the ground electrode 28, and further flows from the ground side through the ion current detection resistor 31 to the capacitor 30. At this time, the input potential Vin of the inverting amplifier circuit 33 changes according to the change of the ionic current flowing through the ion current detection resistor 31, and a voltage corresponding to the ionic current is output from the output terminal of the inverting amplifier circuit 33 to the engine control circuit 34. Is done.
[0022]
The engine control circuit 34 includes a noise mask 38, a peak hold circuit 39, an A / D converter 40, and a microcomputer 41. The output voltage of the ion current detection circuit 35 is input to the peak hold circuit 39 after the noise component is removed by the noise mask 38. The peak hold circuit 39 detects the peak value of the output voltage of the noise mask 38 and holds it. The output of the peak hold circuit 39 is read into the microcomputer 41 via the A / D converter 40.
[0023]
Various engine control programs for performing fuel injection control and ignition timing control are stored in a ROM (storage medium) of the microcomputer 41, and each abnormality diagnosis shown in FIGS. 2 to 4 and FIG. The program is stored. By executing each program for abnormality diagnosis by the microcomputer 41, it is diagnosed whether or not there is an abnormality in the spark plug 27 or combustion abnormality, and when the abnormality is finally diagnosed, the warning lamp 42 is turned on or blinked. Warning the driver. Hereinafter, processing contents of each program for abnormality diagnosis will be described.
[0024]
The output distribution evaluation program shown in FIG. 2 is started for each ignition and functions as output distribution evaluation in the claims. When this program is started, first, at step 101, the intake pipe pressure Pm, the engine speed Ne, and the cooling water temperature Thw are read, and then at step 102, it is suitable for evaluating the logarithmic normal distribution of ion current output described later. It is determined whether the specific operating condition is satisfied. Here, the specific operating condition is an operating condition in which the generation state of the ionic current is stable. For example, when all of the following conditions (1) to (3) are satisfied, the specific operating condition is set.
[0025]
(1) The intake pipe pressure Pm is almost at no load.
(2) The engine speed Ne is within the range of 700 to 750 rpm, for example.
(3) The cooling water temperature Thw is, for example, 70 ° C. or higher.
If any one of the conditions (1) to (3) is not satisfied, the specific operating condition is not obtained. In this case, the process proceeds to step 107 without performing the logarithmic normal distribution evaluation process (steps 103 to 106) of the ion current output.
[0026]
On the other hand, if it is a specific operating condition, the process proceeds from step 102 to step 103, where the output of the ion current detection circuit 35 (hereinafter referred to as "ion current output") Ii is set to the noise mask 38, peak hold circuit 39, A / D. Read through the converter 40. Thereafter, in step 104, the read ion current outputs Ii are written one by one in, for example, 63 data areas I1 to I63 of the table T1. Needless to say, the number of data in the table T1 may be other than 63.
[0027]
Then, in the next step 105, it is determined whether or not the value of the counter i for counting the number of times of reading of the ion current output Ii has reached 63 (that is, whether or not all data writing to I1 to I63 of the table T1 has been completed). If i <63, the process proceeds to step 109 where the counter i is incremented and the program is terminated.
[0028]
By repeating such processing, when all the data writing to I1 to I63 of the table T1 is completed, the process proceeds from step 105 to step 106, an average value / standard deviation calculation program shown in FIG. An average value X and a standard deviation σ of the output Ii are obtained by log normal distribution characteristics. Thereafter, after the counter i is reset to the initial value “1” in step 107, the data I1 to I63 of the table T1 are reset in step 108 and the program is terminated.
[0029]
Next, processing contents of the average / standard deviation calculation program of FIG. 3 executed in step 106 will be described. In this program, first, in step 111, the 63 pieces of data I1 to I63 in the table T1 are rearranged in ascending order and rewritten to 63 pieces of data I'1 to I'63 in the table T2. As a result, the size relationship of the 63 pieces of data I′1 to I′63 in the table T2 is I′1 ≦ I′2 ≦ …… ≦ I′62 ≦ I′63.
[0030]
In this case, since the total number of the data I′1 to I′63 in the table T2 is 63, the ion current output corresponding to the 50% cumulative frequency is the 32nd (median value of distribution) data I ′ corresponding to the smallest one. 32, and this I'32 becomes the average value X of the ion current output. The tenth data I′10 from the smallest is the ion current output corresponding to 15.9% cumulative frequency, and this I′10 is the standard deviation σ of the ion current output.
[0031]
Therefore, in step 112, in order to obtain the standard deviation σ and the average value X, data I′10 corresponding to 15.9% cumulative frequency is read and data I′32 corresponding to 50% cumulative frequency is read. Thereafter, in step 113, the average value X1 and the standard deviation σ1 based on the lognormal distribution characteristic are calculated by the following natural logarithmic function using I'32 and I'10, and the program is terminated.
X1 = ln (I'32)
σ1 = ln (I'32 / I'10)
A general logarithmic function (log) may be used instead of the natural logarithmic function (ln).
[0032]
The abnormal temporary flag set / reset program shown in FIG. 4 is started every time the average value X1 and the standard deviation σ1 are calculated by the program of FIG. When this program is started, first, in step 201, the average value X1 and the standard deviation σ1 are read. Thereafter, in step 202, it is determined whether the current average value X1 and standard deviation σ1 correspond to the zones A, B, or C of the X, σ map shown in FIG.
[0033]
Here, the zone A is an area that is equal to or smaller than a predetermined average value and equal to or smaller than a predetermined standard deviation, and is a spark plug abnormal zone. That is, in zone A, since both the average value X1 and the standard deviation σ1 are small, it means that the ionic current output values I′1 to I′63 are uniformly small. The cause is considered to be a state where it is difficult to detect the ionic current due to adhesion of an insulator deposit to the center electrode 36 of the spark plug 27, and therefore the zone A becomes a spark plug abnormal zone.
[0034]
Zone B is a region that is greater than or equal to a predetermined standard deviation and is a combustion abnormality zone. That is, the zone B means that the standard deviation σ1 is large, so that the ionic current output values I′1 to I′63 vary greatly. Since this cause is considered to be due to poor combustion such as misfire, zone B becomes a combustion abnormal zone.
[0035]
Zone C is a region that is not less than a predetermined average value and not greater than a predetermined standard deviation, and is a normal zone. That is, since the zone C is a zone where the ion current output values I′1 to I′63 are large overall and have little variation, a large ionic current can be obtained in a stable combustion state and with a normal spark plug 27. It means that the detection is stable.
[0036]
If the current average value X1 and the standard deviation σ1 correspond to the spark plug abnormality zone A, the process proceeds from step 203 to step 204, and the temporary flag KFP of the spark plug abnormality is set to “1” which means detection of the spark plug abnormality. After that, in step 205, the temporary combustion abnormality flag KFN is reset to "0" meaning normal combustion.
[0037]
On the other hand, if the current average value X1 and standard deviation σ1 correspond to the combustion abnormality zone B, the process proceeds from step 206 to step 207, and after setting the temporary abnormality flag KFN of combustion abnormality to “1”, which means detection of combustion abnormality, In step 209, the spark plug abnormality temporary flag KFP is reset to "0" which means that the spark plug is normal.
[0038]
On the other hand, if the current average value X1 and the standard deviation σ1 correspond to the normal zone C, the routine proceeds from step 206 to step 208, where the combustion abnormality temporary flag KFN is reset to “0” meaning normal combustion, and then step 209 Then, the temporary flag KFP of the spark plug abnormality is reset to “0” meaning that the spark plug is normal.
[0039]
When the abnormality temporary flag set / reset program is terminated as described above, the abnormality diagnosis program shown in FIG. 6 is executed. This abnormality diagnosis program functions as a spark plug diagnosis means and a combustion state diagnosis means in the claims together with the abnormality temporary flag set / reset program of FIG.
[0040]
In this abnormality diagnosis program, first, at step 301, it is determined whether or not the temporary flag KFP of the spark plug abnormality is “1” meaning ignition plug abnormality detection, and if KFP = 1 (ignition plug abnormality detection). In step 302, the abnormality detection number counter jP for counting the number of detections of the ignition plug abnormality is incremented by 1. If KFP = 0 (ignition plug is normal), the process proceeds to step 305 and the abnormality detection number counter jP is initialized. Reset to the value “1”.
[0041]
If KFP = 1 (ignition plug abnormality detection), after the abnormality detection number counter jP is incremented (step 302), whether or not the value of the abnormality detection number counter jP exceeds, for example, “3” in step 303. That is, it is determined whether or not the spark plug abnormality has been detected three times in succession. If “Yes”, it is finally determined that the spark plug abnormality has occurred, and the routine proceeds to step 304 where ignition plug diagnosis processing is performed. The spark plug abnormality information is written in the backup RAM (not shown), and the warning lamp 42 is lit to warn the driver.
[0042]
When the abnormality detection number counter jP is 3 or less, the program is terminated without making a final diagnosis.
[0043]
On the other hand, if KFP = 0 (ignition plug is normal), after resetting the abnormality detection number counter jP (step 305), it is determined in step 306 whether or not the warning lamp 42 is lit. If there is, the program is terminated without performing the subsequent processing. If the warning lamp 42 is not lit, the routine proceeds to step 307, where it is determined whether or not the temporary abnormality flag KFN of combustion abnormality is “1” which means detection of combustion abnormality, and if KFN = 0 (combustion normal). The program is terminated as it is, but if KFN = 1 (combustion abnormality detection), the process proceeds to step 308, combustion diagnosis processing is performed, combustion abnormality information is written to the backup RAM, and the warning lamp 42 is turned on. Warning the driver.
[0044]
In the embodiment (1) described above, as a spark plug, the spark plug 27 having a general structure as shown in FIG. 7A, that is, the tip of the ground electrode 37 is located on the tip end surface in the axial direction of the center electrode 36. Although the opposed spark plug 27 is used, instead of this, a multipolar plug 53 in which the tip portions of two or more ground electrodes 51 are opposed to the outer peripheral surface of the center electrode 52 as shown in FIG. Alternatively, a creeping discharge plug 56 in which the ground electrode 54 is formed in a cylindrical wall shape surrounding the periphery of the center electrode 55 may be used as shown in FIG. Of course, it goes without saying that spark plugs having various shapes other than these may be used.
[0045]
Incidentally, as shown in FIG. 7A, in a general spark plug 27 in which a spark discharge is generated in the axial direction between the axial front end surface of the center electrode 36 and the front end portion of the ground electrode 37, the spark plug 27 As the period of use increases, the insulator deposit gradually adheres to the outer peripheral surface of the center electrode 36 of the spark plug 27. Finally, as shown in FIG. The entire outer peripheral surface except the surface (discharge surface) may be covered with an insulator deposit, and the exposed area of the center electrode 36 may be extremely reduced. As a result, the ion current flowing through the center electrode 36 decreases, and the output (ion current output) of the ion current detection circuit 35 decreases.
[0046]
Incidentally, FIG. 9 shows an example of an ion current output deterioration characteristic due to adhesion of an insulator deposit to the center electrode of the spark plug. In the Ni spark plug and the Pt spark plug having the general structure shown in FIG. 7A, as the service period becomes longer, the deposit ratio of the insulator deposit to the outer peripheral surface of the center electrode increases, and the exposed area of the center electrode is reduced. The ion current output is reduced.
[0047]
On the other hand, in the multipolar plug 53 of FIG. 7B, there is almost no decrease in the ionic current output due to the adhesion of the insulator deposit to the center electrode 52 (see FIG. 9). That is, in the multipolar plug 53, the tip portions of the two or more ground electrodes 51 face the outer peripheral surface of the center electrode 52, and spark discharge is generated from the side toward the outer peripheral surface of the center electrode 52. As shown in (b), the outer peripheral surface of the center electrode 52 is cleaned by the discharge energy, and there is little adhesion of the insulator deposit. Therefore, if the multipolar plug 53 is used, it is possible to prevent a decrease in the ionic current output due to the adhesion of the insulator deposit, and the calculation accuracy of the output ratio can be favorably maintained over a long period.
[0048]
Similarly, even when the creeping discharge plug 56 of FIG. 7C is used, since a spark discharge is generated from the side toward the outer peripheral surface of the center electrode 55, the outer peripheral surface of the center electrode 52 is cleaned by the discharge energy. Therefore, it is possible to prevent a decrease in the ionic current output due to the adhesion of the insulator deposit.
[0049]
By the way, as shown in FIG. 10, the ion current detection characteristics vary depending on the type of spark plug. Therefore, if the same determination reference value is used when the spark plug is replaced with a different type of spark plug having different ion current detection characteristics or when the spark plug is deteriorated, the diagnostic accuracy may be lowered.
[0050]
Therefore, in the embodiment (2) of the present invention shown in FIGS. 11 to 14, the judgment reference value is corrected for each cylinder so that the combustion state can be accurately diagnosed with the optimum judgment reference value for each cylinder. Yes. Hereinafter, the diagnosis method of the present embodiment (2) will be described. First, the average value X # and standard deviation σ # (# is the cylinder number) of the ionic current outputs I ′ # 1 to I ′ # 63 are obtained for each cylinder by the same method as in the first embodiment.
[0051]
Thereafter, the determination reference value correction coefficient calculation program of FIG. 11 is executed. In this program, first, in step 401, the average value X # and standard deviation σ # of the ionic current outputs I ′ # 1 to I ′ # 63 are read for each cylinder. Thereafter, in step 402, a second determination reference value I ′ # J2 is obtained by the following equation.
I '# J2 = X # -4σ #
This second criterion value I ′ # J2 is 4σ point, but 5σ point (X # −5σ #), 6σ point (X # −6σ #),..., Nσ point (X # −nσ #). It is also good.
[0052]
In the next step 403, a ratio ko between the second determination reference value I '# J2 and the preset first determination reference value I'# J1 is calculated (ko = I '# J2 / I). '# J1). The relationship between these determination reference values I ′ # J1 and I ′ # J2 is shown in FIG.
[0053]
In the next step 404, it is determined whether or not ko is larger than 1 (other numerical values are acceptable) (that is, the second criterion value I '# J2 is larger than the first criterion value I'# J1). If k o ≦ 1 (when the second determination reference value I ′ # J2 is equal to or less than the first determination reference value I ′ # J1), as shown in FIG. Since it is estimated that the ion current output distribution is when the different types of plugs are attached or when the plug characteristics are deteriorated, the process proceeds to step 405, and after setting the temporary flag KFP of the ignition plug abnormality to “1” meaning detection of the ignition plug abnormality, step 406 Then, the diagnosis of the combustion state is prohibited and the program is terminated. The processing in step 406 functions as a diagnosis prohibition unit in the claims.
[0054]
On the other hand, when ko> 1 (when the second determination reference value I ′ # J2 is larger than the first determination reference value I ′ # J1), as shown in FIG. Therefore, the process proceeds from step 404 to step 407, where it is determined whether or not ko> 1.5 (other numerical values are acceptable). If k o ≦ 1.5, that is, if the difference between the second criterion value I ′ # J2 and the first criterion value I ′ # J1 is relatively small, the standard deviation σ # is small, Since a stable ion current output is obtained, the process proceeds to step 410, and the correction coefficient k # is set to “1” (that is, the determination reference value of the combustion state is not corrected).
[0055]
On the other hand, when ko> 1.5, that is, when the difference between the second determination reference value I ′ # J2 and the first determination reference value I ′ # J1 is relatively large, the standard deviation σ # is large. Since it is necessary to correct the determination reference value of the combustion state, the process proceeds to step 408, and the correction coefficient k # is calculated by multiplying k0 by the weighting coefficient k3 (k # = ko * k3). Here, the weighting coefficient k3 is set in a range of 0 <k3 <1 (normally k3 = 0.5). This weighting coefficient k3 is updated in the next step 409 according to the latest correction coefficient k #.
[0056]
The determination reference value correction coefficient calculation program of FIG. 11 described above is executed for each cylinder, and the correction coefficient k # is calculated for each cylinder.
[0057]
As shown in FIG. 13, an operation condition map of the correction coefficient k # using the engine speed Ne and the intake pipe pressure Pm as parameters is set in advance, and the current engine speed Ne and the intake pipe pressure Pm are set. Accordingly, it may be determined whether k # = 1 or k # = ko × k3 based on the operation condition map of FIG.
[0058]
On the other hand, the misfire determination program shown in FIG. 14 is executed for each cylinder, and the ignition / misfire determination is performed for each cylinder as follows. First, in step 501, the intake pipe pressure Pm, the engine speed Ne, and the cylinder number # are read, and in step 502, the correction coefficient k # and the first determination reference value I ′ # J1 are read. In the next step 503, the ion current output I ′ # i is read, and then in step 504, the determination reference value (I ′ # J1 × k #) of the combustion state is calculated and this determination reference value (I ′ # J1 × k #) and the ionic current output I ′ # i, and if I ′ # i> I ′ # J1 × k, the process proceeds to step 505, where it is determined that ignition has occurred, and the combustion flag FN is ignited. Resets to “0” which means.
If I ′ # i ≦ I ′ # J1 × k, the routine proceeds to step 506, where a misfire is determined and the combustion flag FN is set to “1” meaning misfire.
[0059]
In the embodiment (2) described above, the average value X # and standard deviation σ # of the ion current output I ′ # i are used to calculate the correction coefficient k #, and the combustion state is determined by this correction coefficient k #. The determination reference value (I ′ # J1 × k #) is corrected. Thereby, also in the present embodiment (2), misfire / ignition can be accurately determined by using the average value X # of the ionic current output I ′ # i and the standard deviation σ #.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a configuration of an ignition control system and an ion current detection circuit in an embodiment (1) of the present invention.
FIG. 2 is a flowchart showing a processing flow of an output distribution evaluation program.
FIG. 3 is a flowchart showing a processing flow of an average value / standard deviation calculation program;
FIG. 4 is a flowchart showing a process flow of an abnormal temporary flag set / reset program.
FIG. 5 is a diagram conceptually showing an X, σ map.
FIG. 6 is a flowchart showing a flow of processing of an abnormality diagnosis program
7A is an enlarged front view showing the shape of an ignition part of a general spark plug, FIG. 7B is an enlarged front view showing the shape of an ignition part of a multipolar plug, and FIG. 7C is the shape of an ignition part of a creeping discharge plug. Enlarged perspective view showing
8A is an enlarged perspective view showing the state of attachment of an insulator deposit to the center electrode of a general spark plug, and FIG. 8B is an enlarged view showing the state of attachment of an insulator deposit to the center electrode of a multipolar plug. Perspective view
FIG. 9 is a graph showing ion current output deterioration characteristics due to adhesion of an insulator deposit to the center electrode for multipolar plugs, Ni plugs, and Pt plugs.
FIG. 10 is a diagram showing a logarithmic normal distribution of ion current output for a multipolar plug, a Ni plug, and a Pt plug.
FIG. 11 is a flowchart showing a processing flow of a determination reference value correction coefficient calculation program used in the embodiment (2) of the present invention.
FIG. 12 is a diagram showing a comparison between an ion current output distribution when a different type of plug is mounted or when plug characteristics are deteriorated and a normal ion current output distribution.
FIG. 13 is a diagram conceptually showing an operation condition map of a correction coefficient k #.
FIG. 14 is a flowchart showing a process flow of a misfire determination program.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 21 ... Ignition coil, 22 ... Primary coil, 23 ... Battery, 24 ... Igniter, 25 ... Power transistor, 26 ... Secondary coil, 27 ... Spark plug, 31 ... Ion current detection resistor, 33 ... Inversion amplification circuit, 34 ... Engine Control circuit 35 ... Ion current detection circuit (ion current detection means) 36 ... Center electrode 37 ... Ground electrode 38 ... Noise mask 39 ... Peak hold circuit 41 ... Microcomputer (output distribution evaluation means, spark plug diagnosis) Means, combustion state diagnosis means, diagnosis prohibition means), 51 ... ground electrode, 52 ... center electrode, 53 ... multipolar plug, 54 ... ground electrode, 55 ... center electrode, 56 ... creeping discharge plug.

Claims (10)

Ionic current detection means for detecting ionic current flowing through the electrode of the spark plug;
An output distribution evaluation means for obtaining an average value and a standard deviation of the output values of the ion current detection means by log normal distribution characteristics;
An ionic current detection device for an internal combustion engine, comprising: an ignition plug diagnosis means for diagnosing the state of the ignition plug based on an average value and a standard deviation obtained by the output distribution evaluation means. Ionic current detection means for detecting ionic current flowing through the electrode of the spark plug;
An output distribution evaluation means for obtaining an average value and a standard deviation of the output values of the ion current detection means by log normal distribution characteristics;
An ionic current detection device for an internal combustion engine, comprising: combustion state diagnosis means for diagnosing the combustion state of the internal combustion engine based on an average value and a standard deviation obtained by the output distribution evaluation means. The ionic current detection for an internal combustion engine according to claim 2, further comprising spark plug diagnosis means for diagnosing the state of the spark plug based on an average value and a standard deviation obtained by the output distribution evaluation means. apparatus. 4. A diagnosis prohibiting means for prohibiting diagnosis of a combustion state by the combustion state diagnosing means when an average value and a standard deviation obtained by the output distribution evaluating means are out of a predetermined range. An ion current detection device for an internal combustion engine according to claim 1. 5. The internal combustion engine ion according to claim 1, wherein the output distribution evaluation unit obtains an average value and a standard deviation under a specific operating condition in which an ion current generation state is stable. Current detection device. The spark plug diagnosis means diagnoses that there is an abnormality in the spark plug when the value obtained by the output distribution evaluation means is not more than a predetermined average value and not more than a predetermined standard deviation. 4. An ion current detection device for an internal combustion engine according to 3. The combustion state diagnosing means compares the first determination reference value set in advance with the second determination reference value calculated by the equation “average value−n × standard deviation (where n> 3)”. 5. The ion current detection device for an internal combustion engine according to claim 2, wherein the determination reference value of the combustion state is corrected. The ionic current detection device for an internal combustion engine according to any one of claims 2 to 4, wherein the combustion state diagnostic means sets a reference value for determining a combustion state for each cylinder. The output distribution evaluation means obtains a logarithmic normal distribution of the output values of the ion current detection means for each predetermined number of ignition cycles, sets the output value corresponding to the 50% cumulative frequency as an average value, and calculates m% cumulative frequency (however, m The ionic current detection device for an internal combustion engine according to any one of claims 1 to 8, wherein a standard deviation is obtained from an output value corresponding to <50). The ion current detection device for an internal combustion engine according to claim 1, wherein a multipolar plug or a creeping discharge plug is used as the ignition plug.

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