JPH036344B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to an engine misfire determination method for determining a misfire state of an internal combustion engine such as a gas engine based on exhaust temperature.

<Prior art> Conventionally, as a method for determining the misfire state of an engine from the exhaust gas temperature, a certain reference value for the misfire exhaust temperature is set, and when the exhaust temperature falls below this reference value, a misfire occurs. There is a way to determine that. However, the misfire exhaust temperature differs depending on the amount of load; when the load is high, the misfire exhaust temperature is high, and when the load is low, the misfire exhaust temperature is low. Therefore, in the above method, the lowest value among the misfire exhaust temperatures corresponding to the load amount must be used as the misfire reference value. Therefore, when a misfire occurs in a high load area, the actual misfire exhaust temperature at that time is at a high level, but the actual reference value is set to the lowest level, so the exhaust temperature is set to the lowest level. A misfire is determined only when the misfire falls below this value, and there is a drawback that it takes time from the occurrence of a misfire until the misfire determination is made, resulting in a delay in the misfire determination.

On the other hand, in consideration of the fact that the misfire exhaust gas temperature differs depending on the load, a means for detecting the load and a means for storing the relationship between the misfire exhaust temperature and the load as a misfire judgment number table are used. A method of determining a misfire by searching for a misfire exhaust temperature corresponding to a detected load value and comparing the misfire exhaust temperature with the detected exhaust temperature value has already been considered.

However, as shown in the waveform diagram in Figure 5, the actual exhaust gas temperature E changes with a slight delay in the change in the load L, and there is a slight delay between the change in the load L and the change in the exhaust temperature E. There is a time difference. For example, load L
When the temperature E increases rapidly, if the engine is normal, the exhaust temperature E rises with a slight time lag. In this case, immediately after the load L increases, the load L
When searching for the misfire exhaust temperature Eo corresponding to It is at a low level. If a misfire is determined by comparing this high-level misfire exhaust gas temperature Eo with the low-level detected exhaust gas temperature value E, there will be an inconvenience that it will be incorrectly determined that a misfire has occurred even though no misfire has occurred.

Furthermore, when the load L suddenly decreases, the exhaust gas temperature E decreases with a slight delay in the change. If you search for the misfire exhaust temperature Eo immediately after the load L decreases,
The misfire exhaust gas temperature Eo is a low value corresponding to the load L, whereas the actual exhaust gas temperature L has not yet decreased and remains at the same high level as before. If a misfire occurs at this point, a high level of exhaust gas temperature E and a low level of misfire exhaust temperature
A misfire is determined by comparing the misfire with Eo, and a misfire is not determined until the exhaust gas temperature E falls below a low level misfire exhaust temperature Eo, and it takes time to determine a misfire.

In this way, the method of determining a misfire simply by using a misfire determination table causes an erroneous determination or a delay in determination when the load changes suddenly. If it is determined that a misfire has occurred frequently even though no misfire has occurred, the reliability of this method decreases, and if there is a delay in determining a misfire, the air-fuel mixture may leak out to the outside during that time, which is dangerous.

<Objective of the Invention> The present invention has been made in view of the above-mentioned problems, and aims to accurately and speed up misfire determination, increase the reliability of the determination, and prevent the risk of air-fuel mixture leaking out. The purpose is to

<Structure of the Invention> In order to achieve the above object, the present invention includes means for detecting exhaust gas temperature, means for detecting load, and means for storing the relationship between misfire exhaust temperature and load as a misfire determination number table. In this method, a load variable is provided in advance as a parameter when searching for misfire exhaust temperature from the number of misfire determinations, and the load and exhaust temperature are respectively detected and each detected value is determined. a step of comparing the detected load value with the load variable and adding or subtracting a certain amount to the load variable according to the difference; and a step of searching the misfire exhaust temperature from the misfire judgment table based on the load variable. and a step of determining a misfire by comparing the misfired exhaust temperature and the detected exhaust temperature value, and outputting a misfire signal when the detected exhaust temperature value falls below the misfired exhaust temperature, By repeatedly changing the load variable to follow the detected load value with a time difference, a misfire exhaust temperature corresponding to the detected exhaust temperature value at the time of load detection is searched, and a misfire is determined based on the detected misfire exhaust temperature. It is something like that.

<Example> Hereinafter, the present invention will be described in detail based on an example shown in the drawings. FIG. 1 is a block diagram of an engine misfire determination device used to implement the method of the present invention. In the figure, reference numeral 1 is a control unit, 2 is an exhaust temperature sensor which is means for detecting exhaust temperature, and 3 is a load control unit. A load sensor such as a governor is the means of detection. The control unit 1 includes a CPU 4, a ROM 5, a RAM 6,
It includes an input/output port 7 and an A/D converter 8.

The ROM 5 stores the program of the method of the present invention as well as the relationship between the misfire exhaust gas temperature Eo and the load L as a misfire determination number table. The misfire determination number table stored in the ROM 5 is a numerical table of the relationship between the load L and the misfire exhaust temperature Eo as shown in the characteristic diagram of FIG. 2. As the load L increases, the misfire exhaust temperature It has been shown that Eo increases. In this misfire judgment number table, instead of searching for the misfire exhaust temperature Eo directly from the load detection value Ea, the load variable Lv, which will be described later, is used as a mediating variable.
The misfire exhaust temperature Eo is detected by Lv.

The A/D converter 8 includes an exhaust temperature sensor 2.
and load sensor 3 are connected via amplifiers 9 and 10, respectively, and exhaust temperature detection value Ea and load detection value La are input to CPU 4 through this A/D converter 8, respectively. Input/output port 7 is CPU
4 outputs a misfire signal indicating a misfire when it is determined that there is a misfire. This misfire signal is input to the alarm or other control section (none of which is shown) to cause the alarm or the like to take a desired action.

The method of the present invention is to determine a misfire using a misfire determining device equipped with an exhaust temperature detecting means, a load detecting means, and a means for storing a misfire determination number table as described above, and each step of the misfire is determined. This will be explained in detail based on the flowchart of FIG.

In the method of the present invention, the load variable Lv is set in advance as a parameter for searching the misfire exhaust temperature Eo with reference to the misfire determination number table, and the initial value of this load variable Lv is set to "0" in step N1. do. Then, in the next step N2, the exhaust temperature detection value Ea from the exhaust temperature sensor 2 and the load detection value La from the load sensor 3 are read, and each detection value Ea, La is read.
Store in RAM6. In step N3, the load variable
Lv is compared with the load detection value La, and if the load detection value La is larger than the load variable Lv, the process advances to step N4, where a certain amount (in this case, "1") is added to the load variable Lv, and the process proceeds to step N4. Proceed to N6. If the detected load value La is smaller than the load variable Lv, proceed to step N5, in which a certain amount "1" is subtracted from the load variable Lv, and proceed to step N6. Load detected value La and load variable Lv If they are equal, step directly without adding or subtracting as above.
Proceed to N6.

After passing steps N3 to N5 in this way, the load variable is changed according to the difference between the load variable lv and the load detection value La.
A certain amount is added or subtracted from Lv.

In step N6, the load variable Lv is set as the load value in the misfire judgment number table, and the misfire exhaust temperature Eo is searched from this load variable Lv.
In step N6, the misfire exhaust temperature Eo obtained in the previous step N6 is compared with the detected exhaust temperature Ea stored in the RAM 6 to determine whether there is a misfire. When the detected exhaust temperature value Ea is below the misfire exhaust temperature Eo, the process proceeds to step N8 and outputs a misfire signal.
Is the detected exhaust temperature value Ea equal to the misfire exhaust temperature Eo?
If it is less than that, jump to step N9. After waiting for a certain period of time at step N9, the process returns to step N2.

The load variable Lv matches the load detection value La during normal operation with a constant load, but when the load detection value La changes significantly, it follows the change with a slight delay. For example, if the load detection value La suddenly increases, the steps from step N2 to step N9
Although there is a considerable difference between the load variable Lv and the load detection value La, there is a considerable difference between the load variable Lv and the load detection value La, but from step N2 to step N9. By repeating the loop up to, a certain amount "1" is sequentially added to the load variable Lv, and the load variable Lv becomes the load detection value La.
leading to a match. The time required to repeat this loop becomes the time difference in which the load variable Lv follows the load detection value La.

In this way, the load variable Lv follows the load detection value La with a slight delay, but this load variable
The degree of delay in Lv is similar to the degree of delay in the detected exhaust temperature value Ea with respect to the detected load value La. If you search for the misfire exhaust temperature Eo using this load variable L _V , it will accurately correspond to the detected exhaust temperature value Ea at that time. The misfire exhaust temperature Eo will be searched.

Now, as shown in FIG. 4, when the load detection value La increases rapidly, the load variable Lv changes to follow this with a slight time lag. Immediately after the load detection value La increases, the misfire exhaust temperature Eo increases due to this load variable Lv.
When searching for , the misfire exhaust temperature Eo is a value that has slightly increased from the previous level. On the other hand, the detected exhaust temperature value Ea also changes as the load changes, but this detected exhaust temperature value Ea also changes with the detected load value.
It follows La with a slight time lag.
Therefore, the misfire exhaust gas temperature becomes a value that almost exactly corresponds to the detected exhaust gas temperature at that time.

<Effects of the Invention> As described above, the present invention has the following advantages:
Since the exhaust misfire exhaust temperature is searched using a load variable that changes following the load detection value with a slight time difference, it is possible to find a misfire exhaust temperature that almost exactly corresponds to the actual exhaust temperature at the time of misfire determination. There is no large difference between the detected exhaust temperature value at the time of misfire determination and the misfired exhaust temperature as in conventional methods, and a misfire is determined based on the misfired exhaust temperature corresponding to the detected exhaust temperature value. , a misfire determination can be made accurately and quickly.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a device used to carry out the method of the present invention, FIG. 2 is a characteristic diagram showing the relationship between load and misfire exhaust temperature stored as a misfire judgment number table, and FIG.
The figure is a flowchart showing the misfire judgment operation, and Figure 4 shows the load detection value and exhaust temperature detection value in the method of the present invention.
FIG. 5 is a waveform diagram showing the relationship between the misfire exhaust temperature and the load, the exhaust gas temperature, and the misfire exhaust temperature in a conventional method. 1...Control unit, 2...Exhaust temperature sensor, 3...
Load sensor, Ea... Exhaust temperature detection value, Eo... Misfire exhaust temperature, La... Load detection value, Lv... Load variable.

Claims (1)

[Claims] 1. A method for determining engine misfire using means for detecting exhaust gas temperature, means for detecting load, and means for storing the relationship between misfire exhaust temperature and load as a misfire determination number table, the method comprising: a step of providing a load variable in advance as a parameter when searching for the misfire exhaust temperature from a numerical table, detecting the load and the exhaust temperature, and storing each detected value;
A step of comparing the detected load value and the load variable and adding or subtracting a certain amount to the load variable according to the difference, a step of searching the misfire exhaust temperature from the misfire determination number table based on the load variable, and a step of searching the misfire exhaust temperature and the exhaust gas according to the load variable. The misfire is determined by comparing the detected exhaust temperature value with the detected temperature value, and a misfire signal is output when the detected exhaust temperature value falls below the misfired exhaust temperature, and each step is repeated until the load variable becomes the load detected. By changing the value with a time difference, the misfire exhaust temperature corresponding to the detected exhaust temperature value at the time of load detection is searched, and a misfire is determined based on the misfire exhaust temperature. A misfire determination method for engines with