JPH05202799A - Combustion condition diagnostic device of internal combustion engine - Google Patents

Abstract

PURPOSE:To correctly obtain abnormal alarms or the like to the driver by obtaining the degree of the influences to the damages of the catalyst for purifying the exhaust gas caused by the abnormal combustion such as misfire of the internal combustion engine and the air pollution or the like caused by the exhaust gas. CONSTITUTION:The degree of damages of the catalyst caused by misfire or the like and the influences of the degree of the pollution of the exhaust gas are obtained from the detected results by a combustion condition detecting means 1 and from the detected results by an operational condition detecting means 2 by an influence degree evaluating means 3 and a diagnostic means 4, and when they exceed the allowable range, the diagnostic results indicating the abnormality are outputted. Thus, it becomes possible to correctly obtain the diagnosis that the combustion condition is abnormal and the degree of the adverse effects without increasing the accuracy for diagnosis required for the combustion condition detecting means and the possibility for the mistaken diagnosis by making a judgement whether or not the adverse effect due to misfire or the like exceeds the allowable range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for determining an abnormal combustion state due to misfire of an internal combustion engine, and more particularly to a combustion state diagnostic apparatus suitable for an internal combustion engine for automobiles.

[0002]

2. Description of the Related Art An abnormal combustion state of an internal combustion engine due to, for example, a misfire or the like causes air pollution because first of all, unburned gas is discharged. Furthermore, in a system equipped with an exhaust gas purification device that uses a catalyst, such as an internal combustion engine for automobiles, unburned gas discharged due to an abnormal combustion state burns in the catalyst, causing the exhaust gas purification device to reach an abnormally high temperature and performance. May decrease. Therefore,
For these measures, for example, it is necessary to detect that a misfire has occurred, warn the driver of it, and stop the fuel supply to the cylinder in which the misfire has occurred.

By the way, as a prior art relating to such a misfire detecting device, for example, Japanese Patent Publication No. 51-22568.
Japanese Patent Laid-Open No. 62-54138 and Japanese Patent Laid-Open No. 62-54138 disclose such prior arts, for example, when a misfire is detected even once, the misfire is not immediately diagnosed but a predetermined number of misfires is detected. The misfire signal (that is, the diagnosis result that the misfire has occurred) is generated only when the misfire is exceeded or when the misfire continues for a predetermined time. this is,
Even in the case of one misfire, in order to diagnose the occurrence of misfire, the detection device is required to have a considerable accuracy,
In addition, the probability of diagnosing a misfire even during normal operation increases.

Further, for example, a catalyst used in an exhaust gas purifying apparatus does not immediately deteriorate in performance even if some misfire occurs. Therefore, in the prior art, for example, from the temperature tolerance of the catalyst and the accuracy of the detection device, a predetermined threshold value is set for the determination based on the number of misfires,
The misfire is diagnosed only when this threshold value is exceeded, whereby the misfire detection device can be surely diagnosed for the number or frequency of misfires that may deteriorate the performance of the catalyst. Without increasing the accuracy of
In addition, the probability of misdiagnosis can be prevented from increasing.

[0005]

By the way, in an internal combustion engine for an automobile, in particular, exhaust gas is required to be sufficiently purified, and therefore, allowable emission values of HC, CO, NOx, etc. (exhaust gas regulation values) are required. However, the value has become lower year by year, that is, a value that is stricter to clear, and therefore an exhaust gas purifying device using a catalyst or the like is becoming more and more important.

[0006] In some cases, the law requires that a self-diagnosis function such as detection of misfire be provided.
Air Resources Board in California, USA (below,
ARB), and the law requiring the provision of a self-diagnosis function (hereinafter referred to as OBD2), which was proposed to be applied to vehicles from the 1994 model, causes exhaust gas to deteriorate to a certain extent or more, and It is required to issue a warning when a misfire occurs at a frequency (specified as the number of times per predetermined engine speed) that deteriorates the performance of the.

In order to satisfy this OBD2, however, it is necessary to use a low value of about several percent as a threshold value as the frequency of misfires, and thereby diagnose misfires (determine whether or not to generate a warning). is there. However, such misfire detection is easy when the load applied to the internal combustion engine is large, but difficult when the load is small.It is difficult to detect the misfire depending on the engine operating condition such as the load. The degree is different. Furthermore, even if some misfire occurs at low speed and low load, there is little adverse effect such as deterioration of exhaust gas and temperature rise of the catalyst, but at high speed and high load even a small misfire has a large adverse effect. Depends on engine operating conditions.

In the prior art, the operating condition is not taken into consideration. Therefore, if the OBD2 is to be satisfied, as a threshold value for diagnosis, as described above, the frequency is as low as several%, and the engine It is necessary to set the same over the entire operating range, so there is a problem that, for example, the possibility of misdiagnosis at high load increases, or the detection accuracy of the misfire detection device must be made quite high. is there.

On the other hand, the OBD 2 is described to set a threshold value for the number of misfires in accordance with the operating state, and a large threshold value is set when the load is low and the influence of the misfire is small. Therefore, the problems described above are unlikely to occur. Even in this case, however, the following problems remain. That is, the number of misfires during a predetermined rotation is measured, and the diagnosis is made based on the threshold value based on the operation state at the end of the predetermined rotation, so if the operation state changes during the predetermined rotation. , Even if the effect of misfire is great, do not diagnose misfire,
On the contrary, there remains a problem that a misfire may be diagnosed when there is almost no effect.

This does not occur when the driving state does not change during the above-described predetermined rotation, but in automobiles, the driving state generally changes, for example, due to acceleration or deceleration. Therefore, this is a problem to be solved. Remain. As a solution to this problem, there is also a method of shortening the predetermined rotation (or the predetermined period) for measuring the number of misfires so that the change in the operating state during that time does not become large.

However, in this case, as a result, the threshold value of the number of misfires has to be set to a small value, and the above-mentioned problem such as an increase in the required accuracy of the detection device occurs. Furthermore, even if the number of misfires is such that there is no adverse effect if it is true, if there are adverse effects if the misfires occur frequently in succession, then a misfire must be diagnosed.

[0012] Specifically, for example, in the case where the misfire occurs 50 times at 1000 rpm, if the number of misfires is set to 100 rpm in order to shorten the rotation section for measuring the number of misfires, there are 5 misfires. It is necessary to generate the diagnosis result of misfire. Therefore, if the misfire occurs only five times and it is 100 revolutions, the result of the diagnosis is that the misfire has occurred, even though the misfire has almost no adverse effect.

An object of the present invention is to solve the above problems. That is, without increasing the required accuracy of the combustion state detection device for detecting a misfire or the like more than necessary, and without increasing the probability of erroneous diagnosis occurrence, there is a possibility that there may be a detrimental effect (or It is to provide a combustion state diagnosis device capable of accurately diagnosing misfires such as the number of accidents.

[0014]

To achieve the above object, first, in addition to combustion state detecting means for detecting a combustion state such as misfire of an internal combustion engine, operating state detecting means for detecting an operating state of the engine, From the operating state detected by this operating state detection means, from the evaluation result by this impact degree evaluation means and the impact degree evaluation means for assessing the extent of the effect (exhaust gas deterioration, catalyst temperature rise, etc.) due to its misfire, etc. A diagnostic means for generating a diagnostic result of abnormal combustion occurrence due to misfire or the like is provided.

[0015]

Since the evaluation result of the influence degree evaluation means can represent, for example, the amount of unburned gas discharged per misfire, the evaluation result is added for a predetermined period of time to be discharged by misfire. The total amount of unburned gas can be determined. Then, the diagnosis means calculates the influence of deterioration of exhaust gas, temperature rise of the catalyst, etc. from the evaluation result of the influence degree evaluation means, and when the value exceeds an allowable value, a diagnosis result of abnormal combustion occurrence due to misfire or the like is obtained. Occur.

This influence degree evaluation means can evaluate the influence degree due to the misfire based on the operating state at the time of occurrence of the misfire, and further, by performing the arithmetic processing such as adding the evaluation result for a predetermined period, It is possible to know the effects of deterioration of exhaust gas and temperature rise of the catalyst. Therefore, the adverse effect of misfire can be accurately known even when the operating state is changing.

Further, in the low load region where it is difficult to detect misfire, since the adverse effect of misfire is small, the impact evaluation means produces a small evaluation result. As a result, there is no need to raise the detection accuracy in a region where it is difficult to detect a misfire more than necessary, and
There is no possibility of increasing the possibility of misdiagnosis,
Therefore, it is possible to accurately execute the warning to the driver and the stop of the fuel supply to the misfiring cylinder, for example.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The combustion state diagnosing device for an internal combustion engine according to the present invention will be described below in detail with reference to the illustrated embodiments. FIG. 1 is a block diagram showing an embodiment of the present invention, in which 1 is combustion state detecting means, 2 is operating state detecting means, 3
Is an impact evaluation means, and 4 is a diagnostic means.

The combustion state detecting means 1 has a function of detecting whether or not a misfire has occurred, for example, each time combustion is performed in a cylinder of an engine.
The method of detecting from the fluctuation of the rotation speed of the internal combustion engine, which is disclosed in Japanese Patent No. 206342, is used, but not limited to this, the method of detecting from the combustion pressure in the combustion chamber, the temperature, etc., the exhaust gas pressure Pulsation, a method of detecting from the temperature, a method of providing an ion gap in the combustion chamber, detecting from the ion current flowing between them, a method of measuring and detecting the combustion light in the combustion chamber, or a method of detecting from the current waveform flowing through the ignition coil, etc. There are many known methods such as the above, and any of these methods may be used.

The operating state detecting means 2 is a parameter relating to the intake air amount and the fuel supply amount of the internal combustion engine, or a parameter relating to the operating state of the engine such as the rotational speed, the load, and the exhaust gas temperature, the atmospheric pressure and the air temperature. It functions to detect at least one kind of parameter from the inside.

Based on the detection results of the combustion state detecting means 1 and the operating state detecting means 2, the influence degree evaluating means 3 abnormally raises the temperature of the catalyst due to combustion of unburned gas due to misfire, and the performance of the catalyst is improved. The function is to evaluate the degree of the effect of a misfire such as a decrease or incomplete purification of exhaust gas due to unburned gas, polluting the atmosphere, and outputting the result. The method of evaluating the degree of influence by the degree-of-effect evaluation means 3 is performed using an evaluation function that is set in advance, for example, according to the operating state of the engine.

As the evaluation function used at this time, for example, the degree of catalyst damage due to a single misfire or the degree of exhaust gas pollution is quantified for each operating state. Each time the combustion state detecting means 1 detects a misfire, it outputs the value of the evaluation function related thereto as an evaluation result. An example of the evaluation function is shown in FIG.

First, FIG. 2A shows an example of an evaluation function for the intake air amount of the engine. As the intake air amount increases, the amount of unburned gas due to misfire increases. The degree of pollution will also increase. Therefore, the evaluation function for the intake air amount is set to be substantially proportional to the increase in the intake air amount, as shown in the figure.

Next, FIG. 2 (b) also shows an example of an evaluation function for the intake air amount, but in this case, the degree of catalyst damage in the exhaust gas purifying device is taken into consideration. .. That is, since the temperature of the exhaust gas is low when the intake air amount is relatively small, the catalyst is hardly damaged even if some misfire occurs, but when the intake air amount exceeds a certain level, the exhaust gas As the temperature rises, even a slight misfire will damage the catalyst. Therefore, the evaluation function is set so as to sharply increase from the middle as the intake air amount increases as shown in the figure.

Further, FIG. 2C is an example of an evaluation function in the case where the exhaust gas temperature in the vicinity of the catalyst is taken into consideration. In this case as well, for the same reason as in the case of FIG. 2B, The evaluation function is as shown. In this case, another evaluation function for the engine load or the like may be set, and the product of these two types of evaluation functions, for example, may be output from the influence degree evaluation means 3. In this case, , The damage degree of the catalyst can be expressed more accurately.

Further, as the evaluation function, for example, the supplied fuel amount may be used instead of the intake air amount in the above example, or the intake air pressure, the fuel supply amount per combustion, or the like of the engine may be used. It is also possible to employ a parameter representing the product of the amount related to the load and the rotation speed instead of the intake air amount, and use two or more types of operating state parameters such as the throttle opening and the rotation speed, and use these parameters. It is also possible to set an evaluation function as a function, or to set an evaluation function with respect to, for example, the atmospheric pressure or the temperature, or to correct another evaluation function according to these.

By the way, the evaluation result obtained by the above-mentioned evaluation function and outputted from the influence degree evaluation means 3 does not need to be one kind, and for example, a plurality of evaluation results divided according to the kind of influence of misfire are outputted. It may be done.

Further, when the combustion state detecting means 1 is configured to detect the number of misfires during a certain predetermined period (preferably short), the operating state representative of the predetermined period is determined. The product of the same evaluation function as obtained above and the number of misfires may be used as the evaluation result. Further, when the combustion state detecting means 1 is configured to detect not only the presence or absence of misfire but also the quality of the combustion state,
An evaluation function may be set for each of the detection results from the combustion state detecting means 1. According to this,
Further, it is possible to more accurately determine the degree of adverse effects due to abnormal combustion such as misfire.

Further, as the combustion state detecting means 1, for example, a means for detecting misfire and a means for detecting abnormalities of combustion of two or more different types such as a means for detecting knocking are combined to evaluate the degree of influence. By inputting to the means 3 and applying an evaluation function to each, it is possible to comprehensively evaluate the damage of the catalyst for various kinds of abnormalities.

The diagnosing means 4 functions to output the diagnosis result based on the evaluation result of the influence degree evaluating means 3. As a method of obtaining the diagnosis result at this time, for example, a certain period
During the time (time, number of ignitions, etc.), the evaluation results from the influence degree evaluation means 3 are integrated, and when the value exceeds a predetermined threshold value, a diagnostic result indicating an abnormality is output. Instead of this, for example, if the engine is started and the integrated value is used, it is possible to know the integrated emission amount of unburned gas due to misfire, so if this value exceeds a predetermined threshold, it is considered abnormal. You can In addition, in the case where the evaluation is made with emphasis on the damage to the catalyst, a method may be adopted in which the evaluation results are integrated while being temporally weighted and compared with a predetermined threshold value.

FIG. 3 shows an example of an internal combustion engine to which an embodiment of the present invention is applied. In the figure, intake air of the engine is
It is measured from the air cleaner 5 by an intake air amount sensor 6, and is taken into the combustion chamber through an intake pipe 7, a throttle valve 8 and an intake manifold 9. An oxygen concentration sensor 11 is provided in the middle of the exhaust pipe 10, and a catalyst 12 for purifying exhaust gas is provided downstream thereof. An exhaust gas temperature sensor 13 for measuring the temperature of the exhaust gas is provided near the catalyst 12.

Next, a knock sensor 21 is attached in the vicinity of the cylinder, and an electromagnetic pickup 15, 1 for measuring rotational speed and crank position is attached to the crankshaft of the engine.
6 is provided. Each signal from the intake air amount sensor 6, the oxygen concentration sensor 11, the electromagnetic pickups 15 and 16, the knock sensor 21, and the exhaust temperature sensor 13 is input to the control unit 14, and the control unit 14 inputs these signals to the engine. The amount of fuel to be supplied is calculated, the injector 20 is driven, the ignition timing is calculated, and the current to the ignition coil 17 is controlled. The high-voltage current generated in the ignition coil is distributed to the spark plug 19 of each cylinder by the distributor 18.

The apparatus shown in FIG. 1 is incorporated in the control unit 14, and the diagnostic result by it is
The diagnostic result output terminal 22 is output. The diagnostic result output terminal 22 is connected to, for example, an abnormality warning light in the driver's seat or the like, and is turned on when an abnormality such as a misfire occurs, thereby driving the abnormality. Warn the person.

As shown in FIG. 4, the control unit 14 includes a CPU 23, an input I / O 24 for fetching signals from each sensor, a ROM 25 which is a memory for storing processing programs and data, and a data read / write operation. A RAM 26, which is a memory for performing the above, and an output I / O 27 for outputting each control signal and diagnostic result to the outside.

When the combustion state detecting device disclosed in Japanese Patent Application Laid-Open No. 3-206342 is adopted, the combustion state detecting means 1 itself also has the above-mentioned configuration and the control unit 14 has the above configuration.
Although it can be incorporated into the inside of the combustion chamber, for example, when the combustion state is detected by the pressure in the combustion chamber, a combustion state detecting means is provided outside the control unit 14 and its output signal is taken in from the input I / O 24. Is also good
A signal relating to the pressure in the combustion chamber may be fetched from the input I / O 24 and processed.

Next, the processing contents of the CPU 20 will be explained using a flow chart.

FIG. 5 shows an embodiment in which the evaluation results for each predetermined period are added, and is suitable for evaluating the deterioration of exhaust gas, for example, and this routine is carried out, for example, every ignition cycle. It is activated every time.

In step 101, the combustion state detecting means 1
Check the presence of misfire by the detection signal from. If a misfire has occurred, the process proceeds to step 102, and if not, the process proceeds to step 107. In step 102, the operating state is read from the operating state detecting means 2, and in step 10
In 3, the evaluation function according to the driving state is searched. The evaluation function is, for example, R according to the value of the parameter indicating the driving state
It should be stored in OM25. Then, the search result is stored as a variable MFAF.

Next, at step 104, the integrated value of the variable MFAF is obtained and stored as TMFAF. In step 105, the integrated value TMFAF is compared with the threshold value THAF. If it exceeds THAF, step 106 is performed.
The diagnostic result indicating abnormality is output in step S3, and when the threshold THAF is not exceeded, the process proceeds to step 107. In step 107, INT is a period for which the evaluation result is added (for example, a predetermined number of ignitions), and it is checked by the counter CINT whether or not it is within the period. If it is within the period, the counter CINT is incremented in step 108, and the predetermined period INT has elapsed. At this point, the integrated value TMFAF and the counter CINT are cleared in step 109, and the processing ends.

By the way, in this embodiment, the integrated value TMFAF and the threshold value THAF are compared for each misfire detection. However, the comparison may be made only when a predetermined period elapses. Is shown in FIG. Note that the processing contents of this embodiment are only the order of the processing in the embodiment of FIG.

Next, FIG. 7 is a flow chart of another embodiment of the present invention, which is an example in which the evaluation results are time-weighted. For example, damage to the catalyst 12 due to a rise in exhaust gas temperature is shown. It is suitable for evaluation, and in this example, even when misfire does not occur, a different evaluation function from that at the time of misfire occurrence is set, and the temperature rise of exhaust gas, etc. is obtained more accurately. You can do it.
Also in this routine, for example, it is started every ignition cycle.

First, in step 201, the operating state is read from the operating state detecting means 2. In step 202,
The presence or absence of misfire is checked by the detection signal from the combustion state detecting means 1. If a misfire has occurred, the process proceeds to step 203, and if not, the process proceeds to step 204. In step 203, the evaluation function A for occurrence of misfire is searched and the result is stored in the variable MFAF. Step 204
Then, the evaluation function B for when no misfire occurs is retrieved and the result is stored in the variable MFAF.

In step 205, the integrated value T up to the previous time is calculated.
A value obtained by adding the variable MFAF of this time to the value obtained by multiplying MFAF by the coefficient K is newly stored as the integrated value TMFAF.
At this time, by selecting a value between 0.0 and 1.0, for example, as the value of the coefficient K, the influence of past misfires will be gradually reduced and calculated. The influence of time can be reflected more accurately by changing the value of K not according to a fixed value, for example, according to the rotation speed of the internal combustion engine. Further, if K = 1, step 104 in the embodiment of FIG. 5 and step 1 in the embodiment of FIG. 6 are performed.
It is the same as 14, and it is possible to introduce K in step 104 of FIG. 5 or step 114 of FIG.

Next, at step 206, the integrated value TMF
AF is compared with a threshold value THAF, and if it exceeds the threshold value THAF, a diagnostic result indicating an abnormality is output in step 207. On the other hand, when the threshold value THAF is not exceeded, this routine is finished as it is. In this example as well, it is possible to make a diagnosis every predetermined period, as in the example of FIG. 5 or FIG.

By the way, in the above embodiment, the diagnosis result indicating the abnormality may be obtained as, for example, an ON / OFF signal, or the integrated value TMF indicating the influence of misfire.
It may be obtained as AF. Then, based on the result of this diagnosis, for example, as described above, the warning light for the driver may be turned on, or the fuel supply to the misfiring cylinder may be stopped.

Further, in the above embodiments, the detection result of the combustion state detecting means indicates whether or not there is a misfire. For example, when a value indicating the quality of the combustion state is output as the detection result, An evaluation function may be set for the detection result and the operating state.

[0047]

As described above, according to the present invention, with respect to a misfire having a frequency that has almost no adverse effect, it is not erroneously diagnosed as a misfire, and it is difficult to detect the misfire. It is possible to determine the degree of catalyst damage due to misfire and the degree of exhaust gas contamination without increasing the detection accuracy in the above. Therefore, it is possible to accurately execute a warning to the driver and, for example, stop the fuel supply to the misfiring cylinder.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating an embodiment of a combustion state diagnosis device for an internal combustion engine according to the present invention.

FIG. 2 is an explanatory diagram of an evaluation function used in an embodiment of the present invention.

FIG. 3 is a configuration diagram showing an example of an internal combustion engine to which an embodiment of the present invention is applied.

FIG. 4 is an internal configuration diagram of a control unit according to an embodiment of the present invention.

FIG. 5 is a flowchart showing the processing contents in one embodiment of the present invention.

FIG. 6 is a flowchart showing processing contents in another embodiment of the present invention.

FIG. 7 is a flowchart showing processing contents in still another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Combustion state detection means 2 Operating state detection means 3 Influence degree evaluation means 4 Diagnostic means 6 Intake air amount sensor 11 Oxygen concentration sensor 12 Catalyst 13 Exhaust temperature sensor 14 Control unit 15, 16 Electromagnetic pickup 19 Spark plug 20 Injector 22 Diagnostic result output Terminal

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kozo Kato 2520 Takaba, Katsuta City, Ibaraki Prefecture Hitachi Ltd. Automotive Equipment Division

Claims (3)

[Claims] 1. A combustion state diagnosing device for an internal combustion engine, comprising: a combustion state detecting means for detecting a combustion abnormality such as misfire of the internal combustion engine; and a diagnosing means for diagnosing the combustion state based on an output of the combustion state detecting means. An operating state detecting means for detecting an operating state of the internal combustion engine; and an impact degree evaluating means for assessing the degree of influence of combustion abnormality based on the detection results of the combustion state detecting means and the operating state detecting means. A combustion state diagnosis device for an internal combustion engine, wherein the diagnosis means is configured to perform abnormality diagnosis of a combustion state based on an evaluation result of the influence degree evaluation means. 2. The generating device according to claim 1, wherein the operating condition detecting means is configured to detect at least one of an intake air amount and a supplied fuel amount of the internal combustion engine as a parameter representing an operating condition, and the influence degree. The combustion state diagnosis device for an internal combustion engine, wherein the evaluation means is configured to generate an evaluation result based on this parameter. 3. The invention according to claim 1 or 2, wherein the diagnosis means integrates the evaluation results by the influence evaluation means for a predetermined period, and when the integration result exceeds a predetermined threshold value, the combustion state is abnormal. A combustion state diagnosis device for an internal combustion engine, which is configured to generate a diagnosis result indicating that