JP3961745B2 - Misfire detection device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a misfire detection apparatus for an internal combustion engine that detects misfire occurring in the internal combustion engine.
[0002]
[Prior art]
Conventionally, when performing misfire detection of an internal combustion engine, the determination level for detecting misfire of the internal combustion engine is usually set by interpolation based on a two-dimensional map using engine speed and load as parameters. Misfire that occurs in the internal combustion engine is detected using the set determination level.
[0003]
[Problems to be solved by the invention]
By the way, even if the engine speed and load of the internal combustion engine are the same, the required value may differ depending on the operating state of the internal combustion engine as a determination level that can accurately detect misfire and does not cause erroneous detection. It was.
[0004]
For example, the engine rotational speed and load of the internal combustion engine are the same during the early catalyst warm-up control for early activation of the three-way catalyst for purifying exhaust gas and in the normal operating state during which the control is not being performed. Regardless, the combustion state is different and the required judgment level for misfire detection is not the same. For this reason, if misfire detection is performed during early catalyst warm-up control using a determination level that is set by interpolation based on the engine speed and load at that time, based on a map that has been adapted under normal operating conditions, a false or false error is detected. There was a problem that judgment occurred.
[0005]
Accordingly, the present invention has been made to solve such a problem, and an object thereof is to provide a misfire detection device for an internal combustion engine capable of accurately detecting misfire according to the operating state of the internal combustion engine.
[0006]
[Means for Solving the Problems]
According to the misfire detection apparatus for an internal combustion engine according to claim 1, the determination level for determining the misfire of the internal combustion engine is a specific operation other than the value set in the normal operation state of the internal combustion engine. The value set during the early catalyst warm-up control that affects the combustion state of the internal combustion engine as a state is set to a small value, and is set correspondingly so that only large fluctuations in the average engine speed change amount are captured. Has been. As a result, the determination level corresponding to the predetermined operating state of the internal combustion engine can be compared with the average rotational speed change amount at that time, so that it affects not only the normal operating state of the internal combustion engine but also the combustion state of the internal combustion engine. Even during catalyst early warm-up control, the presence or absence of misfire is accurately determined.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described based on examples.
[0009]
FIG. 1 is a schematic diagram showing an overall configuration of a misfire detection apparatus for an internal combustion engine according to an example of an embodiment of the present invention.
[0010]
In FIG. 1, reference numeral 10 denotes an internal combustion engine composed of four-cycle V type 6 cylinders (# 1 cylinder to # 6 cylinder), and 11 denotes an intake passage for supplying intake air introduced from an air cleaner 12 to the internal combustion engine 10 side. . Reference numeral 13 denotes an intake air amount sensor such as an air flow meter for detecting an intake air amount GN [g / rev] introduced into the intake passage 11.
[0011]
A rotational speed sensor 21 is disposed on the crankshaft 16 of the internal combustion engine 10 and outputs a signal at every predetermined crank angle to obtain an engine rotational speed NE [rpm]. 23 is incorporated in the distributor 22 and is a specific cylinder. For example, a reference position sensor for detecting a reference position G for each compression TDC (Top Dead Center) at which the piston 17 of the # 1 cylinder rises most. A water temperature sensor 24 is disposed in the cooling water passage of the internal combustion engine 10 and detects the cooling water temperature THW [° C.].
[0012]
Reference numeral 30 denotes an intake air amount GN signal from the intake air amount sensor 13, an engine rotational speed NE signal from the rotational speed sensor 21, a reference position G from the reference position sensor 23, a cooling water temperature THW signal from the water temperature sensor 24, and other various sensor signals. ECU (Electronic Control Unit: electronic control unit) that calculates optimal control amounts in the fuel system and ignition system and outputs control signals for accurately controlling the injector (fuel injection valve) 26, the igniter 27, etc. ).
[0013]
The ECU 30 includes a CPU 31 as a central processing unit that executes various known arithmetic processes, a ROM 32 that stores control programs, a RAM 33 that stores various data, a B / U (backup) RAM 34, an input / output circuit 35, and a bus connecting them. It is configured as a logical operation circuit composed of lines 36 and the like. Reference numeral 29 denotes a warning lamp for notifying the driver or the like of the occurrence of misfire when the ECU 30 determines that misfire has occurred.
[0014]
Next, FIG. 3 thru | or FIG. 3-FIG. 3 based on the flowchart of FIG. 2 which shows the process sequence of the misfire presence determination in CPU31 in ECU30 used with the misfire detection apparatus of the internal combustion engine concerning one Example of embodiment of this invention. This will be described with reference to FIG. This misfire presence / absence determination routine is repeatedly executed with an interruption every predetermined crank angle, for example, 30 [° CA (Crank Angle)].
[0015]
Here, FIG. 3 is a map for calculating a determination level for determining the presence or absence of misfire in the normal operation state of the internal combustion engine 10, and FIG. 4 is a diagram showing the number of times of ignition [times] in the normal operation state of the internal combustion engine 10. FIG. 4A is a characteristic diagram showing a relationship between an average rotational speed change amount Δω [rpm] and a determination level REF1 for determining the presence or absence of misfire. FIG. 4 (a) shows a case without misfire, and FIG. 4 (b) shows a case with misfire. Show. FIG. 5 is a map for calculating a determination level for determining the presence or absence of misfire during the catalyst early warm-up control as a specific operation state of the internal combustion engine 10, and FIG. 6 is during the catalyst early warm-up control of the internal combustion engine 10. 6 is a characteristic diagram showing the relationship between the average rotational speed variation Δω [rpm] for each ignition number [times] and the determination level REF2 for determining the presence or absence of misfire. FIG. (B) shows when there is misfire.
[0016]
In FIG. 2, first, in step S101, the current time T30i required for the crankshaft 16 to rotate 30 [° CA] is calculated from the deviation between the previous interrupt time and the current interrupt time. Next, the process proceeds to step S102, and it is determined whether the current interrupt timing is compression TDC in any one of the # 1 cylinder to # 6 cylinder. If the determination condition in step S102 is not satisfied, that is, if the current interrupt timing is not compression TDC, this routine is terminated without doing anything.
[0017]
On the other hand, when the determination condition of step S102 is satisfied, that is, when the current interrupt timing is the compression TDC of the # 1 cylinder, the process proceeds to step S103, the current time T30i calculated in step S101, the previous time, the last time, and 3 The data for all four times of the times T30i-1, T30i-2 and T30i-3 calculated at the time of the previous execution are accumulated, and the time T120i required for the crankshaft 16 to rotate 120 [° CA] is calculated. Is done.
[0018]
Next, the process proceeds to step S104, and the current average rotational speed ωn of the internal combustion engine 10 is calculated by the reciprocal of the time T120i required for the crankshaft 16 calculated in step S103 to rotate 120 [° CA]. . Next, the process proceeds to step S105, and the current average rotational speed change amount Δωn is calculated by the following equation (1). Here, ωn-1 is the average rotational speed calculated at the previous time, ωn-3 is three times before, and ωn-4 is the four times before the execution. Further, (ωn-1−ωn) is the latest amount of change in rotational speed in the cylinder in which the expansion (explosion) stroke continues, and (ωn−4−ωn-3) is 360 in the cylinder in which the expansion (explosion) stroke continues. [° CA] is the amount of change in rotation speed before.
[0019]
[Expression 1]
Δωn = (ωn-1−ωn) − (ωn−4−ωn-3) (1)
[0020]
Next, the routine proceeds to step S106, where it is determined whether the catalyst early warm-up control is being performed as a specific operation state of the internal combustion engine 10. If the determination condition in step S106 is not satisfied, that is, if the catalyst early warm-up control is not being performed and the engine is in a normal operation state, the process proceeds to step S107, and as shown in FIG. 3, for example, engine speed NE = 1500 [rpm ] And a map value corresponding to the intake air amount GN = 0.8 [g / rev] as a load, that is, a determination level REF1 for determining the presence or absence of misfire in a normal operation state is calculated by interpolation calculation.
[0021]
Here, with reference to FIG. 4, the setting of the map value for calculating the determination level REF1 for determining the presence or absence of misfire in the normal operating state of the internal combustion engine 10 of FIG. 3 will be described.
[0022]
When the internal combustion engine 10 shown in FIG. 4 (a) is in a normal operation state and no misfire occurs, the variation in the average rotational speed change amount Δω is small. On the other hand, as shown in FIG. 4B, when the misfire is present in the normal operation state of the internal combustion engine 10, the variation in the average rotational speed change amount Δω is extremely at a predetermined timing corresponding to the misfire cylinder. It appears greatly. Therefore, in the normal operating state of the internal combustion engine 10, the determination level REF1 (= 200 [rpm]) indicated by a one-dot chain line in FIG. 4B is set so as to capture only a large fluctuation in the average rotational speed change amount Δω. Is done.
[0023]
Next, the routine proceeds to step S108, where it is determined whether or not the current average rotational speed change amount Δωn exceeds the determination level REF1 calculated in step S107. If the determination condition in step S108 is not satisfied, that is, if the current average rotational speed change amount Δωn is as small as the determination level REF1 or less, the process proceeds to step S109, and it is determined that there is no misfire in the normal operation state, and this routine is terminated.
[0024]
On the other hand, when the determination condition of step S106 is satisfied, that is, when the catalyst early warm-up control is being performed, the routine proceeds to step S110, and as shown in FIG. 5, for example, the engine rotational speed NE = 1500 [rpm] and the intake air as a load A map value corresponding to the amount GN = 0.8 [g / rev], that is, a determination level REF2 for determining the presence or absence of misfire during the early catalyst warm-up control is calculated by interpolation.
[0025]
Here, with reference to FIG. 6, the setting of the map value for calculating the determination level REF2 for determining the presence or absence of misfire during the early catalyst warm-up control of the internal combustion engine 10 of FIG. 5 will be described.
[0026]
In the early warm-up control of the internal combustion engine 10 shown in FIG. 6 (a), when the misfire is not present, the average rotational speed change amount Δω is larger than that in the normal operation state shown in FIG. It can be seen that the fluctuation is slightly larger. On the other hand, when the misfire is occurring during the early catalyst warm-up control of the internal combustion engine 10 shown in FIG. 6B, the variation in the average rotational speed change amount Δω is obviously large at a predetermined timing corresponding to the misfire cylinder. Appear. Therefore, during the early catalyst warm-up control of the internal combustion engine 10, a determination level REF2 (= 100 [rpm]) indicated by a one-dot chain line in FIG. Is set.
[0027]
Next, the process proceeds to step S111, where it is determined whether the current average rotational speed change amount Δωn exceeds the determination level REF2 calculated in step S110. When the determination condition of step S111 is satisfied, that is, when the current average rotational speed change amount Δωn exceeds the determination level REF2, the routine proceeds to step S112, where it is determined that misfire has occurred during the early catalyst warm-up control, and this routine ends.
[0028]
If the determination condition of step S108 is satisfied, that is, if the current average rotational speed change amount Δωn exceeds the determination level REF1, the routine proceeds to step S112, where it is determined that misfire has occurred in the normal operating state of the internal combustion engine 10, and this routine is executed. Exit. Further, when the determination condition of step S111 is not satisfied, that is, when the current average rotational speed change amount Δωn is as small as the determination level REF2 or less, the process proceeds to step S113, and there is no misfire during the early catalyst warm-up control of the internal combustion engine 10. This routine is finalized.
[0029]
As described above, the misfire detection apparatus for an internal combustion engine according to the present embodiment includes the rotational speed sensor 21 as the rotational speed detection means for detecting the engine rotational speed NE of the internal combustion engine 10 and the engine rotational speed detected by the rotational speed sensor 21. A change amount calculation means achieved by the CPU 31 in the ECU 30 for calculating the average rotation speed change amount ΔNE of the NE, and an average rotation speed change amount Δω in the normal operation state of the internal combustion engine 10 or other specific operation states In contrast, the determination level setting means achieved by the CPU 31 in the ECU 30 for setting the determination levels REF1 and REF2 for determining misfire, respectively, and the average rotational speed change amount Δω calculated by the change amount calculation means are Presence / absence of misfire in the internal combustion engine 10 as compared with a determination level corresponding to a predetermined operating state of the internal combustion engine 10 set by the determination level setting means ; And a misfire judging means is achieved by CPU31 in determining ECU 30, the specific operation state is in effect rapid catalyst warm-up control to the combustion state of the internal combustion engine 10, set by the evaluation level setting means a shall be set such that the determination level REF1, REF2 is captured only large variations in the average rotation speed variation Δω in the engine rotational speed NE calculated by the change amount calculation means.
[0030]
That is, the determination levels REF1 and REF2 for determining misfire of the internal combustion engine 10 affect the combustion state of the internal combustion engine 10 as a normal operation state of the internal combustion engine 10 or a specific operation state other than that. Each is set in advance so as to capture only a large variation in the average rotational speed change amount Δω of the engine rotational speed NE during machine control . As a result, the determination level corresponding to the predetermined operating state of the internal combustion engine 10 can be compared with the average rotation speed change amount Δω at that time, so that the combustion state of the internal combustion engine 10 is not limited to the normal operating state. Even during the catalyst early warming-up control that influences, the presence or absence of misfire can be accurately determined.
[0032]
By the way, in the said Example, although the catalyst early warming-up control was described as a specific driving | running state of the internal combustion engine 10, when implementing this invention, it is not limited to this, In addition, the internal combustion engine 10 By setting individually the determination level for determining the presence or absence of misfire corresponding to the operating state that affects the combustion state, the presence or absence of misfire can be accurately determined.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an overall configuration of a misfire detection apparatus for an internal combustion engine according to an example of an embodiment of the present invention.
FIG. 2 is a flowchart showing a misfire presence / absence determination processing procedure in a CPU in an ECU used in an internal combustion engine misfire detection apparatus according to an embodiment of the present invention;
FIG. 3 is a map for calculating a determination level for determining the presence or absence of misfire in the normal operating state of the internal combustion engine of FIG. 2;
4 is a characteristic diagram showing a relationship between a determination level for determining the presence or absence of misfire in the map of FIG. 3 and an average rotational speed change amount for each number of ignitions.
FIG. 5 is a map for calculating a determination level for determining the presence or absence of misfire during the early catalyst warm-up control of the internal combustion engine of FIG. 2;
6 is a characteristic diagram showing a relationship between a determination level for determining the presence or absence of misfire in the map of FIG. 5 and an average rotational speed change amount for each number of ignitions.
[Explanation of symbols]
10 Internal combustion engine 21 Rotational speed sensor (Rotational speed detection means)
30 ECU (Electronic Control Unit)
31 CPU

Claims (1)

Rotation speed detection means for detecting the engine rotation speed of the internal combustion engine;
A change amount calculation means for calculating an average rotation speed change amount of the engine rotation speed detected by the rotation speed detection means;
A determination level setting means for setting a determination level for determining misfire, corresponding to the amount of change in the average rotational speed in a normal operation state of the internal combustion engine or a specific operation state other than the normal operation state;
The amount of change in the average rotation speed calculated by the change amount calculation means is compared with the determination level corresponding to a predetermined operating state of the internal combustion engine set by the determination level setting means, and whether or not misfire has occurred in the internal combustion engine Misfire determination means for determining
The specific operating state is during early catalyst warm-up control that affects the combustion state of the internal combustion engine, and the determination level set by the determination level setting means is a determination level set in a normal operating state. A misfire detection device for an internal combustion engine, which is set to capture only a large fluctuation in an average rotational speed change amount of the engine rotational speed calculated by the change amount calculation means , which is a smaller value .

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