JP2006132334A - Misfire detection device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify determination process while keeping determination accuracy good and enable accurate misfire detection without overlooking misfire in relation to a misfire detection device for an internal combustion engine for detecting misfire and specifying misfire cylinder. <P>SOLUTION: Crank angle time T<SB>n</SB>for each cylinder right after ignition or firing each explosion cycle is acquired as engine rotation speed information. Crank angle time T<SB>n</SB>of a present explosion cylinder is defined as x coordinate value and crank angle time T<SB>n-1</SB>of a previous explosion cylinder is defined as y coordinate value and a present plot point P<SB>n</SB>is plotted on an xy plane. Determination vector P<SB>n-1</SB>P<SB>n</SB>from a previous plot point P<SB>n-1</SB>toward present plot point P<SB>n</SB>is calculated. If the determination vector P<SB>n-1</SB>P<SB>n</SB>has same direction as a predetermined determination reference vector and length of the determination reference vector or greater, it is determined that misfire occurred in a previous explosion cylinder. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a misfire detection apparatus for an internal combustion engine for detecting misfire and specifying the misfire cylinder.

  Conventionally, for example, Japanese Patent No. 3324795 discloses a technique for detecting misfire of an internal combustion engine. Specifically, in this technology, the difference in engine speed between the previous combustion stroke cylinder (difference in engine speed between the previous combustion stroke cylinder and the previous combustion stroke cylinder) and the differential rotation change of the current combustion stroke cylinder (current combustion) The difference between the difference in engine speed of the stroke cylinder and the difference in engine speed of the previous combustion stroke cylinder) and the differential rotation change of the previous combustion stroke cylinder are used as parameters for misfire determination. And in the said prior art, it is determined whether misfire has arisen in the last combustion stroke cylinder by comparing these three parameters with a predetermined determination threshold value, respectively.

Japanese Patent No. 3324795 JP-A-62-118031 JP-A-2-112646

  As described above, in the above-described conventional misfire detection method, three determinations must be made between the determination threshold and the determination threshold. As described above, the above-described conventional technique requires a complicated determination process when a misfire is detected. If the misfire determination process is complicated, the case classification in the determination process becomes complicated, and therefore misfire determination may occur.

  The present invention has been made to solve the above-described problems, and can simplify the determination process while maintaining good determination accuracy, thereby enabling accurate misfire detection with no determination omission. An object of the present invention is to provide a misfire detection device for an internal combustion engine.

In order to achieve the above object, the first aspect of the invention provides rotation speed information acquisition means for acquiring engine rotation speed information of each cylinder immediately after ignition or ignition for each explosion cycle;
The engine speed information for the current explosion cylinder is the x coordinate value, the engine speed information for the previous explosion cylinder is the y coordinate value, and the engine speed information is plotted as the current plot point on the xy plane. Means,
Determination vector calculation means for calculating a determination vector from the reference point on the xy plane toward the current plot point;
When the determination vector calculated by the determination vector calculation means is in the same direction as a predetermined determination reference vector and is larger than the determination reference vector, it is determined that misfire has occurred in the previous explosion cylinder. Misfire determination means;
It is characterized by providing.

  According to a second aspect, in the first aspect, the reference point is a previous plot point.

  According to a third aspect, in the first aspect, the reference point is an intersection of a perpendicular line drawn from the current plot point to a straight line y = x and a straight line y = x.

  In a fourth aspect based on the first aspect, the determination vector calculating means is a straight line having a gradient that is predetermined according to the operating state of the internal combustion engine and passing through the current plot point. A y-axis intercept is calculated, the reference point is set as the origin of the xy plane, and a determination vector from the origin toward the y-axis intercept is calculated.

According to a fifth aspect of the present invention, there is provided a rotational speed information acquisition means for acquiring engine rotational speed information of each cylinder immediately after ignition or ignition for each explosion cycle in order to achieve the above-mentioned object.
A rotational speed information deviation calculating means for calculating a deviation between the engine rotational speed information in the current explosion cylinder and the engine rotational speed information in the previous explosion cylinder as a deviation of the engine rotational speed information in the current explosion cylinder;
The deviation of the engine speed information in the previous explosion cylinder is the x coordinate value, the deviation of the engine speed information in the current explosion cylinder is the y coordinate value, and the deviation of the engine speed information on the xy plane is the current plot point Deviation plot means for plotting;
Plot point distance calculating means for calculating a distance between the reference point on the xy plane and the current plot point;
Misfire determination means for determining that misfire has occurred in the previous explosion cylinder when the distance calculated by the plot point distance calculation means is equal to or greater than a predetermined determination reference value;
It is characterized by providing.

  According to a sixth aspect, in the fifth aspect, the reference point is a previous plot point.

  In a seventh aspect based on the fifth aspect, the plot point distance calculating means calculates the distance between the origin and the current plot point, with the reference point being the origin of the xy plane, or x The distance from the origin to the current plot point is calculated with respect to the axial direction.

  In addition, in an eighth invention according to any one of the fifth to seventh inventions, the misfire determination means further includes the respective x-coordinate values and y-coordinate values of the previous plot point and the previous plot point. Is negative, it is determined that misfire has occurred in the previous explosion cylinder.

  According to a ninth invention, in any one of the fifth to eighth inventions, the misfire determination means looks in the x-axis direction of the current plot point plotted on the xy plane for a predetermined number of times. When it is recognized that the flatness is higher than a predetermined reference in the x-axis direction, it is determined that misfire has occurred in the previous explosion cylinder.

Further, in order to achieve the above object, the tenth aspect of the invention provides rotation speed information acquisition means for acquiring engine rotation speed information of each cylinder immediately after ignition or ignition for each explosion cycle;
The engine speed information in the present explosion cylinder is the x coordinate value, the engine speed information in the previous explosion cylinder is the y coordinate value, and the engine speed information in the previous explosion cylinder is the z coordinate value. Rotation speed information plotting means for plotting the rotation speed information as a plot point this time,
Plot point distance calculating means for calculating the distance between the current plot point and the straight line x = y = z;
When the distance calculated by the plot point distance calculation means is a predetermined determination reference value or more and the current plot point is located on the yz plane side with respect to the straight line x = y = z, First determination means for determining that misfire has occurred in the previous explosion cylinder, and the distance is equal to or greater than a predetermined determination reference value, and the current plot point is xz with respect to the straight line x = y = z Misfire determination means including at least one of second determination means for determining that misfire has occurred in the explosion cylinder of the last time when located on the plane side;
It is characterized by providing.

  The eleventh invention is the tenth invention, wherein the misfire determination means includes both the first determination means and the second determination means, and the first fire is determined in a predetermined explosion cycle. If it is determined by the determining means that the previous explosion cylinder has misfired, and the second determining means determines that the previous explosion cylinder has been misfired in the next explosion cycle, the explosion cylinder It is determined that misfire has occurred.

  In a twelfth aspect based on the tenth or eleventh aspect, the first determination means includes a perpendicular line drawn from the current plot point to a straight line x = y = z and the straight line x = y = z. The intersection point is the origin, the axis parallel to the xy plane and orthogonal to the straight line x = y = z is the x2 axis, and the current plot point is in the x2 axis direction with respect to the origin It is characterized in that it is determined that misfire has occurred in the previous explosion cylinder when the distance is more than a certain distance.

  In a thirteenth aspect based on any one of the tenth to twelfth aspects, the second determination means includes a perpendicular line drawn from the current plot point to a straight line x = y = z and the straight line x = y. = When the intersection with z is calculated, the intersection is the origin, the axis parallel to the z axis is the y2 axis, and the plot point this time is more than a certain distance from the origin in the y2 axis direction In addition, it is characterized in that it is determined that a misfire has occurred in the last explosion cylinder.

  According to the first invention, the engine speed information of two cylinders can be included in one plot point. Further, according to the present invention, by calculating the determination vector based on the relationship between the reference point on the xy plane and the current plot point, the engine speed information included in the plot point is included in the determination vector. Can be included. On the other hand, when a misfire occurs in a cylinder, the engine speed information of the misfire cylinder becomes larger than that of the previous explosion cylinder if the crank angle time, for example, and becomes smaller if the engine speed, for example. Arise. Further, since the pump work for exhausting the in-cylinder gas of the misfire cylinder becomes small, the engine speed information of the cylinder that explodes next to the misfire cylinder becomes smaller than that of the misfire cylinder if the crank angle time, for example. For example, a phenomenon occurs in which the engine rotational speed increases (hereinafter referred to simply as “the phenomenon associated with misfire” in this section). As a result, the plotted points plotted on the xy plane have a distribution with regularity related to the occurrence of misfire. According to the present invention, misfire detection is performed in a single process using a single misfire determination parameter (determination vector) by comparing the position of such a plot point on the xy plane with a determination reference value. Can do. For this reason, according to the present invention, it is possible to simplify the determination process while maintaining good determination accuracy, and thereby, it is possible to detect misfire accurately and without a determination omission.

  According to the second aspect of the invention, the determination vector from the previous plot point to the current plot point is calculated. According to the phenomenon accompanying the misfire, when misfire has occurred in the previous explosion cylinder, the previous plot point and the current plot point are distributed on the xy plane across the straight line y = x. It becomes. Therefore, according to the present invention, since the value of the determination vector becomes large, the misfire determination parameter value can be increased with respect to the variation (or dispersion) of the engine speed information, and the misfire misjudgment rate is lowered. be able to.

  According to the third and fourth inventions, only the current plot point is used as the engine speed information, that is, the determination vector based on the engine speed information of the two cylinders is calculated. For this reason, since the number of data use points is smaller than that of the second invention, the variation range included in the misfire judgment parameter can be made smaller than that of the second invention, and the misfire judgment that is strong against fluctuations in the average engine speed is made. Can be realized.

  According to the fifth aspect, the engine speed information of the three cylinders can be included in one plot point as a deviation of the engine speed information. Further, according to the present invention, by calculating the distance between the reference point on the xy plane and the current plot point, the engine speed information included in the plot point can be included in this distance. On the other hand, according to the phenomenon accompanying misfire, the plotted points plotted on the xy plane have a distribution with regularity related to the occurrence of misfire. According to the present invention, misfire detection is performed in a single process using a single misfire determination parameter (the above distance) by comparing the position of such a plot point on the xy plane with a determination reference value. Can do. For this reason, according to the present invention, it is possible to simplify the determination process while maintaining good determination accuracy, and thereby, it is possible to detect misfire accurately and without a determination omission.

  According to the sixth aspect, the distance between the previous plot point and the current plot point is calculated. According to the phenomenon accompanying the misfire, when misfire has occurred in the explosion cylinder of the last time, the distance between the previous plot point and the current plot point is the distance between other plot points on the xy plane. It will be bigger than that. For this reason, according to the present invention, the value of the misfire determination parameter can be increased, and the misfire misjudgment rate can be reduced.

  According to the seventh aspect, only the current plot point is used as the engine speed information, that is, the distance based on the engine speed information of the three cylinders is calculated. For this reason, since the number of data use points is smaller than that of the sixth invention, the variation range included in the misfire judgment parameter can be made smaller than that of the sixth invention, and misfire judgment that is strong against fluctuations in the average engine speed is made. Can be realized.

  According to the eighth aspect of the present invention, it is possible to determine that the probability of occurrence of the phenomenon associated with the misfire is very high, and it is possible to perform misfire determination with higher accuracy.

  According to the ninth aspect of the present invention, it is determined that the previous explosion cylinder has misfired when the frequency distribution of the plot points this time has a flatness higher than a certain level in the x-axis direction. When the phenomenon accompanying the misfire occurs, there is a characteristic that the variation width of the engine speed information of the misfire cylinder is smaller than that of other cylinders in which combustion is normally performed. Therefore, the variation width of the deviation of the engine speed information between the misfire cylinder and the next explosion cylinder becomes small, and as a result, the flatness tends to increase. For this reason, according to this invention, a more reliable misfire determination is attained.

  According to the tenth aspect, the engine speed information of the three cylinders can be included in one plot point. Further, according to the present invention, it is determined whether or not the variation of the plotted points is equal to or higher than a certain level by determining whether or not the distance between the current plotted point and the straight line x = y = z is equal to or larger than the determination reference value. Can be determined. According to the phenomenon accompanying the misfire, when misfire has occurred in the previous explosion cylinder, the plot point of this time is located on the yz plane side with respect to the straight line x = y = z, and When misfire occurs in the explosion cylinder, the current plot point is positioned on the xz plane side with respect to the straight line x = y = z. For this reason, according to the present invention, by comparing the position of such a plot point in the xyz space with a determination reference value, misfire detection can be performed in substantially one process using a single misfire determination parameter. It can be carried out. For this reason, according to the present invention, it is possible to simplify the determination process while maintaining good determination accuracy, and thereby, it is possible to detect misfire accurately and without a determination omission.

  According to the eleventh aspect, when the same cylinder is determined to be misfired in two consecutive processing cycles, the cylinder is determined to be misfired. Therefore, the accuracy of the misfire determination can be further improved.

  According to the twelfth invention, when the current plot point is more than a certain distance in the x2 axis direction, it is accurately determined that the current plot point is located on the yz plane side with respect to the straight line x = y = z. Can be determined.

  According to the thirteenth invention, when the current plot point is more than a certain distance in the y2 axis direction, it is accurately determined that the current plot point is located on the xz plane side with respect to the straight line x = y = z. Can be determined.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1 is a diagram for explaining a configuration of an internal combustion engine 10 according to a first embodiment of the present invention. The internal combustion engine 10 of the present embodiment is a four-cylinder engine for convenience of explanation. A piston 12 that reciprocates inside the cylinder of the internal combustion engine 10 is provided. Further, the internal combustion engine 10 includes a cylinder head 14. A combustion chamber 16 is formed between the piston 12 and the cylinder head 14. An intake passage 18 and an exhaust passage 20 communicate with the combustion chamber 16.

  A throttle valve 22 is provided in the intake passage 18. The throttle valve 22 is an electronically controlled throttle valve that can control the throttle opening independently of the accelerator opening. In the vicinity of the throttle valve 22, a throttle position sensor 24 for detecting the throttle opening degree TA is disposed. A fuel injection valve 26 for injecting fuel into the intake port of the internal combustion engine 10 is disposed downstream of the throttle valve 22. A spark plug 28 is incorporated in the combustion chamber 16.

  The system of this embodiment includes an ECU (Electronic Control Unit) 30. In addition to the throttle position sensor 24 and the like, the ECU 30 is connected to a crank angle sensor 32 (rotational speed information acquisition means) that measures engine rotational speed information. The fuel injection valve 26 and the spark plug 28 described above are controlled by the ECU 30.

[Specific Processing in Embodiment 1]
Next, with reference to FIG. 2 and FIG. 3, the content of the specific process used in order to detect misfire in the system of this embodiment is demonstrated.
FIG. 2 shows a flowchart of a routine executed by the ECU 30 shown in FIG. Note that this routine is periodically executed every time the ignition timing of each cylinder arrives.

In the routine shown in FIG. 2, first, the crank angle time T _n of the current explosion cylinder is acquired (step 100). The “crank angle time T” here means the time required for the crankshaft to rotate a predetermined crank angle width. According to the crank angle sensor 32 described above, for example, the crank angle time T for every 10 ° CA can be detected. More specifically, in this step 100, 0 ° ATDC crank angle for the section from the (compression TDC) to 20 ° ATDC time _{T n} is obtained. Incidentally, the crank angle time T _n is obtained as the engine speed information of the current explosion cylinder is not limited to those for the above interval, that for a specific section from the ignition timing to 90 ° ATDC, in other words , After ignition or ignition (more preferably immediately after them). Further, the data used as the engine speed information may be the crank angular speed ω instead of the crank angular time T.

Next, the crank angle time T _n-1 of the previous explosion cylinder and the crank angle time T _{n-2 of the} previous explosion cylinder are read out (step 102). Next, the previous plot point P _n−1 and the current plot point P _n are plotted on the xy plane (see FIG. 3 described later) in which both axes are set to the crank angle time T (step 104). Specifically, the previous plot point P _n−1 is plotted with the previous crank angle time T _n−1 as the x coordinate value and the previous crank angle time T _n−2 as the y coordinate value. The current plot point P _n is plotted with the crank angle time T _n as the x coordinate value and the previous crank angle time T _n−1 as the y coordinate value. FIG. 3 is a diagram illustrating an example of such an xy plane.

Next, a determination vector (misfire determination parameter) is calculated (step 106). Specifically, on the xy plane, using the previous plot point P _n-1 as a reference point, the distance and direction between the two points P _n-1 and P _n are calculated, that is, the previous plot P _{n. A} determination vector P _n-1 P _n is calculated in a direction from ₋₁ point to the current plot point P _n . More specifically, the direction of the determination vector used here is positive in the direction from the area below the straight line y = x to the area above the straight line y = x on the xy plane shown in FIG. The reverse direction is defined as negative.

Next, it is determined whether or not the determination vector P _n−1 P _n calculated in step 106 is in the same direction as the predetermined determination reference vector and has a magnitude greater than or equal to the determination reference vector ( Step 108). The determination reference vector used in the process of step 106 is a threshold value for determining whether or not misfire has occurred in any of the cylinders, and is obtained in advance through experiments or the like. The magnitude of the determination reference vector is changed according to the operating state of the internal combustion engine and the number of cylinders. That is, as the engine speed increases or the internal combustion engine with a larger number of cylinders, the variation in the crank angle time T becomes smaller, and accordingly, the size of the determination reference vector is also set smaller.

If it is determined in step 108 that the determination vector P _n−1 P _n has the same direction as the determination reference vector and does not have a magnitude equal to or greater than the determination reference vector, The processing cycle is quickly terminated. On the other hand, if it is determined in step 108 that the determination vector P _n−1 P _n has the same direction as the determination reference vector and has a magnitude greater than or equal to the determination reference vector, It is determined that misfire has occurred in the explosion cylinder (step 110).

  Next, it is determined whether or not the number of misfire determinations is equal to or greater than a predetermined number (step 112). When it is determined in step 110 that a misfire has occurred, the ECU 30 stores the number of misfire occurrences. If it is determined in step 112 that the number of misfire determinations is equal to or greater than a predetermined number, that is, if it is determined that the number of misfires exceeds a certain frequency, a steady misfire occurs in the misfire cylinder. (Step 114). Specifically, in this step 114, when it is determined that a predetermined number of times (for example, 30 times) misfire has occurred during a predetermined number of explosions (for example, 100 times), it is determined that a steady misfire has occurred. The

[Advantages of Processing in Embodiment 1]
Next, the advantages of the processing of the routine shown in FIG. 2 described above will be described with reference to FIGS.
FIG. 4 is a diagram for explaining the advantages of the routine shown in FIG. More specifically, FIG. 4A shows an example of a change in the crank angle time T generated between the cylinders when, for example, a misfire occurs in the # 1 cylinder, and FIG. The xy plane obtained when the process of step 104 is performed based on the crank angle time T of each cylinder shown in FIG. Note that # 1 to # 4 in FIG. 4 represent the four cylinders included in the internal combustion engine 10 in the order in which explosion occurs.

  As shown in FIG. 4A, when a misfire occurs in the # 1 cylinder, the engine speed decreases due to the misfire, so the crank angle time T of the # 1 cylinder is the # 4 cylinder that exploded before that. This causes a phenomenon that the length becomes longer (# 1> # 4). In addition, the combustion pressure of the # 1 cylinder where misfire has occurred becomes very small. For this reason, in the next stroke, the pump work for exhausting the in-cylinder gas of the # 1 cylinder is reduced. As a result, since the engine speed increases, the crank angle time T of the # 2 cylinder next to the # 1 cylinder is much shorter than that of the # 1 cylinder (# 2 <# 1). Arise.

Here, when the crank angle time T of each cylinder shown in FIG. 4 (A) is represented on the xy plane with both axes as the crank angle time T by the routine method of FIG. 2, FIG. 4 (B). As shown. That is, when the # 1 cylinder is misfired, the crank angle time T is # 1># 4 as described above, so the coordinate values of the plot points P _{# 1- # 4} are x-coordinate> y-coordinate. That is, the plot points P _{# 1- # 4} are located below the straight line y = x in the xy plane of FIG. Since the crank angle time T is # 2 <# 1, the coordinate value of the plot point P _{# 2- # 1} is x coordinate <y coordinate. That is, the plot point P _{# 2- # 1} is located above the straight line y = x in the xy plane of FIG. That is, when a change in the crank angle time T shown in FIG. 4A occurs due to a misfire, two plot points P (P _{# 1)} including information on the crank angle time T related to the misfire cylinder on the xy plane. The phenomenon that- _{# 4} and P _{# 2- # 1} ) are divided into an upper part and a lower part with respect to the straight line y = x occurs reliably.

FIG. 5 is a diagram for comparing the distribution of measured values of the crank angle time T of each cylinder when no misfire occurs and when misfire occurs. More specifically, FIG. 5 (A) shows a case where no misfire has occurred in any of the cylinders, and FIG. 5 (B) shows a case where steady misfire has occurred in the # 1 cylinder. Show. In addition, the straight line shown by the solid line in FIG. 5 shows the approximate straight line for each set of plot points P (for example, P _{# 2- # 1} ) having the crank angle time T of the same cylinder as the x coordinate and the y coordinate, respectively. A straight line indicated by a broken line is a straight line y = x. Such an approximate straight line can be obtained by, for example, the least square method.

  If it is assumed that there is no variation in the crank angle time T between the cylinders, all the plot points P are located on the straight line y = x. However, there is a variation in engine speed due to a variation in combustion between cylinders, that is, a variation in crank angle time T. For this reason, as shown in FIG. 5A, the plot points P and their approximate straight lines for each cylinder are distributed without regularity at positions near the straight line y = x.

On the other hand, when a steady misfire occurs in the # 1 cylinder, as shown in FIG. 5B, the relationship between the misfire cylinder (# 1) and the next explosion cylinder (# 2) Only the determined plot points P _{# 2- # 1} are distributed far away from the straight line y = x. Assuming that misfire has occurred in the # 1 cylinder, as described above, the crank angle time T of the # 1 cylinder in which misfire has occurred becomes longer than that of the previous explosion cylinder (# 4), and the next # The crank angle time T for the two cylinders is much shorter than that for the # 1 cylinder. Accordingly, the plot point P _{# 2- # 1} in which the crank angle time of the # 2 cylinder is the x coordinate and the crank angle time T of the # 1 cylinder is the y coordinate is above the straight line y = x in the xy plane. Therefore, it is surely distributed at a position far away from the straight line y = x.

  That is, according to the routine processing of FIG. 2 described above, only the change in the crank angle time T due to misfire can be accurately detected without being affected by the inconsistent crank angle time T that exists independently for each cylinder. In other words, only the data relating to the misfired cylinder can be accurately separated from the data relating to the other cylinders.

In the processing of the present embodiment described above, plotting the plot point P on the xy plane means that information on two changes (crank angle time T of two cylinders adjacent to each other in explosion) is information on one plot point P. Means to include. Then, calculating the determination vector P _n−1 P _n between two such plot points is equivalent to including three variations in one misfire determination parameter. In the method of determining misfire through determination with a plurality of determination thresholds as in the prior art described above, since the determination process is complicated, more specifically, the case classification in the determination process is complicated. As a result, misjudgment of misfire may occur. On the other hand, according to the process of the present embodiment, the magnitude and direction of the determination vector P _n−1 P _n are compared with the determination reference vector, so that the misfire is performed in one process using a single misfire determination parameter. Detection can be performed. That is, according to the process of the present embodiment, the determination process can be simplified while maintaining a good determination accuracy, and thereby, misfire detection can be performed accurately and without omission of determination.

  Further, since the routine method of FIG. 2 performs misfire determination based on the relationship between the relative crank angle times T (engine speed information) between the cylinders, reference engine speed information is unnecessary. Therefore, even if the engine speed is changing, it is possible to perform misfire determination with high accuracy.

  Further, the number of data points of the crank angle time T used in the processing of the routine of FIG. 2 is three points, this time, the previous time, and the last time. That is, according to the processing of the above routine, it is possible to detect misfire with a small number of data points with high accuracy. As described above, the crank angle time T of each cylinder has an independent variation. For this reason, the fact that the number of data points used for misfire detection is small means that the variation width added to the determination parameter compared with the misfire determination reference value is small, that is, the determination accuracy is improved. If the number of data points is small, the determination accuracy can be kept high even when the average engine speed changes (during acceleration, etc.).

  In addition, since the fluctuation (variation width) of the engine speed (crank angle time T) of the misfired cylinder is not combusted in the cylinder, there is a physical characteristic that it is smaller than that of a cylinder in which combustion is normally performed. is there. According to the routine processing of FIG. 2, the crank angle time T of the misfire cylinder with such a small variation and the crank angle time T of the explosion cylinder before and after that are used as misfire detection parameters. The determination sensitivity is very high, that is, the ratio (S / N ratio) between the magnitude of the misfire determination parameter value and the variation width of the parameter can be increased (N is decreased).

Further, for example, when a misfire occurs in the # 1 cylinder, as described above, a phenomenon occurs in which the crank angle time T becomes # 1># 4 and # 2 <# 1, so the plot point P _{# 1- # 4} is located below the straight line y = x, and the next plot point P _{# 2- # 1} is located above the straight line y = x. In the routine method of FIG. 2, using the distance between these two plot points, that is, the magnitude of the determination vector as the misfire determination parameter means that the misfire determination parameter can be increased. Thereby, the misjudgment rate of misfire can be lowered (S / N ratio can be increased (S is increased)).

[Modification to Embodiment 1]
In the first embodiment described above, when the determination vector P _n−1 P _n is calculated, the previous plot point P _n−1 is used as a reference point in the present invention. The calculation method is not limited to this. That is, the reference point of the determination vector may be, for example, the intersection A (see FIG. 5B) of the perpendicular line drawn from the current plot point P _n to the straight line y = x and the straight line y = x. The determination vector may be calculated as AP _n (see FIG. 5B). According to such a method, since the previous plot point P _n-1 is not used, the number of data points (crank angle time T) used for the misfire determination is two points this time and the previous time, and the processing of the first embodiment described above. In addition, the misfire determination parameter that has a smaller variation range included in the misfire determination parameter (N of the S / N ratio is small) and is resistant to fluctuations in the average engine speed can be realized.

In addition, from the viewpoint of performing the number of data points used for misfire determination with two points, the method of calculating the determination vector of the present invention is not limited to the above, but is, for example, a straight line having a predetermined gradient a and in terms of calculating the y-axis intercept b ₁ in a straight line passing through the plotted points P _n, the reference point determining vectors the origin O of xy-plane, and calculates the decision vector Ob ₁ directed from the origin to the y-axis intercept b ₁ It may be a thing. The gradient a in this case is determined in advance according to the operating state of the internal combustion engine 10, more specifically according to the engine speed.

In the first embodiment described above, the determination vector P _n−1 P _n is calculated for each unit processing cycle to determine a single misfire. However, the present invention is not limited to such a method. Plot points P (for example, P _{# 2- # 1} ) having the crank angle time T of the same cylinder as the x coordinate and y coordinate, respectively, are plotted on the xy plane for a predetermined number of times (for example, 10 times). An approximate straight line y-axis intercept b ₂ (see FIG. 5B) for the set of plot points P is calculated, and a determination vector Ob ₂ (see FIG. 5B) from the origin of the xy plane toward the y-axis intercept b ₂ is calculated. ) May be calculated.

Further, the misfire determination parameters used in the present invention are the determination vectors (P _n−1 P _n , AP _n , Ob ₁ , and so on) calculated by the method of the first embodiment described above or the methods of the three modified examples described above. or it is not limited to the Ob _2). That is, the misfire determination parameter of the present invention, taking the case of the determination vector _{P n-1 P n} as an example, the determination vector _{P n-2 P n-1} of this decision vector _{P n-1 P n} and the previous May be the difference B. According to such a method, since the misfire determination parameter can be increased as compared with the method of the first embodiment described above, the misfire misjudgment rate can be further reduced.

Further, the misfire determination parameter of the present invention further includes the above-described misfire determination parameter (determination vector (P _n-1 P _n , AP _n , Ob ₁ , or Ob ₂ ) or the difference B described above) It may be calculated as an average value M in a plurality of processing cycles, and may be a difference C between the average value M and the misfire determination parameter calculated in the current processing cycle. Specifically, taking the case of the determination vector P _n-1 P _n as an example, if the determination vector calculated in the current processing cycle is P _{# 1- # 4} P _{# 2- # 1} , , The determination vectors calculated in the previous processing cycle, that is, P _{# 4- # 3} P _{# 1- # 4} (previous), P _{# 3- # 2} P _{# 4- # 3} (previous times), and P _{# 2} The difference C between the average value M of _{# 1} P _{# 3 to # 2} ( _two times before) and the determination vector P _{# 1 to # 4} P _{# 2 to # 1} calculated in the current processing cycle The misfire determination parameter may be used.

Further, not only one of the misfire determination parameters described above, that is, the determination vector (P _n-1 P _n , AP _n , Ob ₁ , or Ob ₂ ), the difference B, or the difference C, but also a plurality of misfires. A misfire may be determined when each of the determination parameters exceeds a determination reference value.

In the first embodiment described above, the crank angle time T is acquired for the section from 0 ° ATDC (compression top dead center) to 20 ° ATDC, but the engine speed information of the present invention is as follows. It is not limited to this. That is, the data used as the engine speed information is replaced with the crank angle time T in the predetermined section immediately after ignition and the crank angle time T in the predetermined section after 90 ° CA instead of the crank angle time T acquired as described above. It may be the square value D of the difference. This square value D is a value having a correlation with the torque generated by the internal combustion engine 10. Here to a given interval crank angle time T _n and the crank angle time T _n of the predetermined section after the 90 ° CA of _'immediately after ignition to be used, a similar variation in the crank angle time T caused by the explosion of the cylinder included. Therefore, if this torque correlation value D is used, it is possible to obtain engine speed information in which variations of the explosion cylinder are offset by obtaining the difference between the crank angle times T _n and T _{n ′.} This makes it possible to make a misfire determination with high accuracy.

  In the first embodiment described above, the ECU 30 executes the process of step 104, so that the “rotational speed information plotting means” in the first invention executes the process of step 106. The “judgment determination means” in the first invention is realized by executing the processing of steps 108 and 110 by the “determination vector calculation means” in the first invention.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS.
The system of the present embodiment is realized by causing the ECU 30 to execute the routine of FIG. 6 instead of the routine of FIG. 2 using the apparatus configuration of the first embodiment described above.

[Specific Processing in Second Embodiment]
Next, with reference to FIG. 6 and FIG. 7, the content of the specific process used in order to detect misfire in the system of this embodiment is demonstrated.
FIG. 6 is a flowchart of a routine executed by the ECU 30 to detect a misfire cylinder in the second embodiment. Note that this routine is periodically executed every time the ignition timing of each cylinder arrives. In FIG. 6, the same steps as those shown in FIG. 2 in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

In the routine shown in FIG. 6, first, the crank angle time T _n of the current explosion cylinder is acquired (step 100). Next, the crank angle time T _{n-1 of} the previous explosion cylinder, the crank angle time T _{n-2 of} the previous explosion cylinder, and the crank angle time T _n-3 of the previous (previous) explosion cylinder are obtained. Each is read (step 116).

Next, based on the respective crank angle times T acquired in steps 100 and 116, a deviation dT between the crank angle times T of two cylinders adjacent to each other in the explosion order is calculated by the following equation (1) ( Step 118).
dT _n = T _n−1 −T _n (1)
Specifically, in this step 118, the current crank angle time deviation dT _n (= T _n−1 −T _n ) and the previous crank angle time deviation dT _n−1 (= T _n−2 −T _n−1). ), The crank angle time deviation dT _n−2 (= T _n−3 −T _n−2 ) of the last time is acquired.

Next, the previous plot point Q _n−1 and the current plot point Q _n are plotted on the xy plane (see FIG. 7 described later) in which both axes are crank angle time deviations dT (step 120). . Specifically, the plot point Q _n-1 is plotted on the xy plane with the crank angle time deviation dT _n-2 of the previous time as the x coordinate and the previous crank angle time deviation dT _n-1 as the y coordinate, The plot point Q _n is plotted on the xy plane with the previous crank angle time deviation dT _n−1 as the x coordinate and the current crank angle time deviation dT _n as the y coordinate. FIG. 7 is a diagram illustrating an example of such an xy plane.

Next, the inter-plot point distance E (misfire determination parameter) is calculated between the previous plot point Q _n−1 and the current plot point Q _n (step 122). Next, it is determined whether or not the distance E between plot points is equal to or greater than a predetermined determination reference value (step 124). Note that the determination reference value used here is set in advance by the same method as in the case of the size of the determination reference vector of the first embodiment described above.

If it is determined in step 124 that the inter-plot point distance E is not greater than or equal to the determination reference value, the current processing cycle is immediately terminated, while the inter-plot point distance E is determined to be greater than or equal to the determination reference value. If so, it is then determined whether or not the xy coordinate values of the plot point Q _n−2 and the plot point Q _n−3 (see FIG. 7) of the previous time and the previous time are negative (see FIG. 7). Step 126).

  If it is determined that step 126 is not established, the current processing cycle is immediately terminated. On the other hand, if the determination of step 126 is established, it is determined that a misfire has occurred in the previous explosion cylinder. (Step 128). Next, when it is determined that the number of misfires has exceeded a certain frequency (step 112), it is determined that a steady misfire has occurred in the misfire cylinder (step 114).

[Advantages of Processing in Embodiment 2]
Next, the advantages of the routine processing shown in FIG. 6 described above will be described with reference to FIG.
FIG. 8 is a diagram for explaining the advantages of the processing of the routine shown in FIG. FIG. 8A shows a case where no misfire occurs in any cylinder, and FIG. 8B shows a case where steady misfire occurs in the # 1 cylinder. (C) shows a graph in which the x-coordinate value (crank angle time deviation dT) of various plot points Q in FIG. 8B is taken on the horizontal axis, and the frequency of the various plot points Q is taken on the vertical axis. Note that FIG. 8C is referred to in a modification to the second embodiment described later.

According to the routine method of FIG. 6 described above, that is, the method of plotting the plot point Q on the xy plane with both the x coordinate value and the y coordinate value as the crank angle time deviation dT, four consecutive plot points Q (Q _n , Qn _-1 , Qn _-2 , Qn _-3 ) is zero. That is, according to this method, the four types of plot points Q are distributed with variations without regularity centered on the origin (average value) of the xy plane.

  On the other hand, when the misfire occurs in the # 1 cylinder, as already described with reference to FIG. 4A, the magnitude of the crank angle time T is # 1> # 4> # 3> # 2. Therefore, according to the processing of the routine of FIG. 6, the four types of plot points Q are obtained by using the deviation dT calculated based on the crank angle time T having such a relationship as an x or y coordinate value. When plotted on the xy plane, it can be accompanied by regularity as shown in FIG.

More specifically, for example, according to the relationship of FIG. 4A, the plot point Q _{# 12- # 23} is the crank angle time between the misfire cylinder (# 1) and the next explosion cylinder (# 2). The value of the deviation dT _{# 12} is the largest compared to the other deviations dT. Therefore, when such a relationship of the deviation dT is reflected on the xy plane, the plot points Q _{# 12- # 23} having the maximum deviation dT _{# 12} as the x coordinate value are compared with the other plot points Q. This is the point that protrudes most in the positive direction of the x-axis. With respect to the other three types of plot points Q, according to the relationship shown in FIG. 4A, the regions shown in FIG. 8B have regularity as in the case of plot points Q _{# 12- # 23} . Will be distributed.

  In the processing of the present embodiment described above, plotting the plot point Q on the xy plane with the crank angle time deviation dT as the xy coordinate value means that there are three variations (crank angle times of three cylinders adjacent to the explosion). This means that the information of T) is included in one plot point Q. And calculating the distance E between plot points between such two plot points is equivalent to including four variations in one misfire determination parameter. For this reason, according to the processing of the present embodiment, it is possible to perform misfire detection accurately and without omissions in a single process using a single misfire determination parameter having such information.

Further, according to the processing of the routine shown in FIG. 6, the previous plot point Q _n-1 (Q _{# 41- # 12 in} the case of FIG. 8B) and the current plot point Q _n (FIG. 8B). it is the case of plot points between a distance E _n between Q _{# 12- # 23)} is to be greater than the distance E between the other plot points, for processing data (engine speed information of each cylinder) Is possible. For this reason, according to the processing of the above routine, the S / N ratio for misfire determination can be increased (S increases), and it is possible to accurately determine that misfire has occurred in the previous cylinder.

In the processing of the above routine, it is further determined whether or not the xy coordinate values of the previous plot point Q _n−2 and the previous plot point Q _n−3 are negative. By performing such processing in addition to the determination of the distance E between the plot points, the distance E exceeds the determination reference value, and the xy coordinate values of the plot points Q _n−2 and Q _n−3 are both negative. In some cases, it can be determined that the probability that the relationship shown in FIG. 4A is generated is extremely high, and a more accurate misfire determination is possible.

[Modification to Embodiment 2]
By the way, in the second embodiment described above, the two types of plot point distances E for the cylinders whose explosion order is adjacent to each other are calculated. However, the present invention is not limited to such a method. the distance to be used may be one that is calculated as the distance between the origin and the present plot point Q _n of the xy plane F (see FIG. 8 (B)), or, in the x-axis direction from the origin of the xy plane the distance to the current plot point Q _n G may be (see FIG. 8 (B) refer). According to these methods, the distance value is slightly smaller (S is smaller) than the method using the distance E described above, but the number of data points is reduced. That is, since the variation range included in the misfire determination parameter is small (N is small), the misfire determination with high accuracy can be performed also by these methods.

Further, not only the above-described method but also a method of determining misfire using the above-described distance E, distance F, or distance G, and after identifying a cylinder that may cause misfire, The plot points Q used for the identification are acquired a predetermined number of times (for example, about 10 times), and the frequency distribution of the plot points Q obtained as a result is flatter than a predetermined reference in the x-axis direction. May be determined that the specific cylinder is misfired. As described above, the variation width of the crank angle time T of the misfired cylinder has a characteristic that it is smaller than that of a cylinder that normally performs combustion. Therefore, the variation range of the crank angle time deviation (dT _{# 12 in} the case of FIG. 8) between the misfire cylinder and the next explosion cylinder is also small. As a result, as shown in FIG. 8C, when the horizontal axis is the x-axis in FIG. 8B, the flatness of the frequency distribution of the plot points Q _{# 12- # 23} tends to increase. Therefore, according to such a method, a more reliable misfire determination can be performed as compared with the method of the second embodiment described above.

  In the second embodiment described above, the ECU 30 executes the process of step 118, so that the “rotational speed information deviation calculating means” in the fifth aspect of the invention executes the process of step 120. By the “deviation plotting means” in the fifth invention executing the process of step 122, the “plot point distance calculating means” in the fifth invention executes the processes of steps 124 and 128. The “misfire determination means” in the fifth aspect of the present invention is realized.

Embodiment 3 FIG.
Next, Embodiment 3 of the present invention will be described with reference to FIGS.
The system of the present embodiment is realized by causing the ECU 30 to execute the routine of FIG. 9 instead of the routine of FIG. 2 using the apparatus configuration of the first embodiment described above.

[Specific Processing in Embodiment 3]
Next, with reference to FIG. 9 and FIG. 10, the content of the specific process used in order to detect misfire in the system of this embodiment is demonstrated. FIG. 9 is a flowchart of a routine executed by the ECU 30 to detect a misfire cylinder in the third embodiment. Note that this routine is periodically executed every time the ignition timing of each cylinder arrives. 9, the same steps as those shown in FIG. 2 in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

In the routine shown in FIG. 9, first, the crank angle time T _n of the present explosion cylinder is acquired (step 100), and then the crank angle time T _n-1 of the previous explosion cylinder and the crank angle time of the previous explosion cylinder are obtained. T _n−2 is read out (step 102).

Next, the current crank angle time T _n , the previous crank angle time T _n−1 , and the previous crank angle time T _n−2 are set as the x coordinate value, the y coordinate value, and the z coordinate value, respectively. The plot point R _n is plotted on the xyz space (step 130). FIG. 10 is a diagram illustrating an example of such an xyz space.

FIG. 10 is a diagram viewed from the axial direction of the straight line x = y = z in the xyz space. Here, in the xyz space of FIG. 10, a plot point R based on the crank angle time T of each cylinder in which the relationship of FIG. For the sake of illustration, let us explain. In FIG. 10, plot points R _{# 1 to # 4 to # 3} marked with a crowbar indicate that the x coordinate value is the crank angle time T of the # 1 cylinder (current) and the y coordinate value is the crank angle time T of the # 4 cylinder. (Previous) and points plotted with the z-coordinate value as the crank angle time T of the # 3 cylinder (previous times), and other diamond-marked plot points R _{# 2- # 1- # 4} and spade-marked points Since the plot point R _{# 3- # 2- # 1} and the heart mark plot point R _{# 4- # 3- # 2} are also as shown in FIG. 10, detailed description thereof is omitted.

In the routine shown in FIG. 9, when the plot point R _n as shown in FIG. 10 is plotted on the xyz space in step 130, the shortest point between the current plot point R _n and the straight line x = y = z. A distance H is calculated (step 132). Specifically, the distance H can be calculated as the length of the perpendicular drawn from the current plot point R _n the straight line x = y = z. Next, it is determined whether or not the distance H is greater than or equal to a predetermined determination reference value (step 134). Note that the determination reference value used here is set in advance by the same method as in the case of the size of the determination reference vector of the first embodiment described above.

If it is determined in step 134 that the distance H is not greater than or equal to the determination reference value, the current processing cycle is immediately terminated. On the other hand, if it is determined that the distance H is greater than or equal to the determination reference value, Next, it is determined whether or not the current plot point R _n is located in a space surrounded by the straight line x = y = z, the y axis, and the z axis (step 136).

In step 136, if the current plot point R _n is determined to be located within the space (for diamond marks plotted points R _{# 2- # 1- # 4} in FIG. 10), i.e., time If the plot point R _n of is determined to be located on the yz plane side with respect to the straight line x = y = z is determined that a misfire has occurred in the last explosion cylinder (step 138). On the other hand, if it is determined in step 136 that the current plot point R _n is not located in the space, then the current plot point R _n is represented by the straight line x = y = z and the x axis. It is determined whether or not it is located in a space surrounded by the z axis (step 140).

If it is determined in step 140 that the current plot point R _n is located in the space (in the case of the plot point R _{# 3- # 2- # 1} of the spade mark in FIG. 10), that is, this time If the plot point R _n of is determined to be located in the xz plane side with respect to the straight line x = y = z is determined that a misfire explosive cylinders before last has occurred (step 142).

[Advantages of Processing in Embodiment 3]
Next, the advantages of the routine processing shown in FIG. 9 will be described with reference to FIG.
If it is assumed that the crank angle time T does not vary among the cylinders, all plot points R plotted in the xyz space in FIG. 10 are located on the straight line x = y = z. Become. In other words, the fact that the various plot points R are distributed apart from the straight line x = y = z as shown in FIG. 10 indicates that there are three crank angle times T that are the basis of these various plot points R. Indicates that there is variation.

The four types of plot points R in FIG. 10 are plotted based on the relationship of the crank angle time T in FIG. 4A due to misfire as described above. According to the processing of the routine shown in FIG. 9, these four types of plot points R can be distributed in the xyz space with regularity as shown in FIG. More specifically, according to the relationship shown in FIG. 4A, the diamond mark plot points R _{# 2- # 1- # 4} have small x-coordinate values and large y-coordinate values. For this reason, it is distributed at a position far away from the straight line x = y = z toward the yz plane, and far away in the positive direction of the y-axis. For this reason, according to the processing of the above routine, if the distance H between the plot point R _{# 2- # 1- # 4 of} the diamond mark and the straight line x = y = z is determined to be greater than or equal to the determination reference value, # It can be determined that misfire has occurred in one cylinder, that is, the previous explosion cylinder.

Moreover, since the plot point R _{# 3- # 2- # 1} of the spade mark has a small y coordinate value and a large z coordinate value, it is large on the xz plane side with respect to the straight line x = y = z. It is a distant position, and is distributed at positions far apart in the positive direction of the z-axis. Therefore, according to the processing of the above routine, if the distance H between the spade-marked plot point R _{# 3- # 2- # 1} and the straight line x = y = z is determined to be equal to or greater than the determination reference value, # It can be determined that a misfire has occurred in one cylinder, that is, the last explosion cylinder.

  In the processing of the routine of the present embodiment described above, after plotting the plot point R on the xyz space and calculating the distance H between the straight line x = y = z, the three variations (explosion occurs). This corresponds to including information on the crank angle time T) of three adjacent cylinders in one misfire determination parameter. For this reason, according to the processing of the present embodiment, it is possible to perform misfire detection that is accurate and free of omissions in a single determination process using a single misfire determination parameter. Further, according to the processing of the above routine, during one processing cycle performed by the ECU 30, it is possible to determine whether the cylinder in which misfire has occurred was the previous one or the previous one.

[Modification to Embodiment 3]
By the way, in Embodiment 3 mentioned above, it is determined for every processing cycle which ECU30 performs whether the cylinder which had misfired was the last thing or the thing before the last time, but it is not restricted to such a method. Absent. That is, for example, after determining that misfire has occurred in the previous explosion cylinder in a certain processing cycle, it may be determined whether misfire has occurred in the previous explosion cylinder in the next processing cycle. According to such a process, when the same cylinder is determined to be misfired in two consecutive processing cycles, the cylinder is determined to be misfired. Therefore, compared with the method of the third embodiment described above. The accuracy of misfire determination can be improved.

  Further, the method described with reference to FIG. 11 is not limited to the method of the third embodiment described above. FIG. 11 is a diagram for explaining a modification of the misfire detection method according to the third embodiment of the present invention. FIG. 11 is a diagram viewed from the axial direction of the straight line x = y = z in the xyz space. In the method of FIG. 11, after plotting a plot point R in the xyz space, an intersection I between a perpendicular drawn from the plot point R to a straight line x = y = z and the straight line x = y = z is calculated. Next, an x2y2 plane in which the intersection point I is the origin, the axis parallel to the xy plane and orthogonal to the straight line x = y = z is the x2 axis, and the axis parallel to the z axis is the y2 axis is in the xyz space. create. When the plot point R is away from the origin I in the x2 axis direction by a certain distance or more (straight line α in FIG. 11), it is determined that the previous explosion cylinder has misfired. Further, when the plot point R is away from the origin I by a certain distance or more in the y2 axis direction (straight line β in FIG. 11), it is determined that misfire has occurred in the previous explosion cylinder.

  In the method of the third embodiment and the method of the modification described above, the crank angle time T is used as each coordinate value. However, the present invention is not limited to this, and a crank angle time deviation dT may be used. .

  In the third embodiment described above, the ECU 30 executes the process of step 130, so that the “rotational speed information plotting means” in the tenth invention executes the process of step 132. The “plot point distance calculating means” in the tenth aspect of the invention executes the processes of steps 134, 136, and 138, so that the “first determination means” in the tenth aspect of the invention is the steps 134, 140, and 142. The “second determination means” in the tenth aspect of the invention is realized by executing the process of step 10, and the “misfire determination means” in the tenth aspect of the invention is realized by executing the processes of steps 134 to 142 described above. ing.

  In the description of the present specification, an example in which the present invention is applied to detection of misfire of an internal combustion engine has been described. However, the present invention is not limited to this, and may be applied to discrimination of unstable combustion cylinders. It is possible. In the above description, an example of application to a spark ignition type internal combustion engine has been shown. However, the present invention is not limited to this, and the method of the present invention can also be applied to a self ignition type internal combustion engine such as a diesel engine. It is. In the method of the present invention, the x-axis, y-axis, z-axis, etc. are merely examples of the respective axes in the orthogonal coordinate system. For example, the processing of the present invention is performed with the x-axis and y-axis reversed. Obviously, this does not give any substantial difference to the above-described processing of the present invention.

It is a figure for demonstrating the structure of the internal combustion engine of Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure which shows an example of xy plane used in Embodiment 1 of this invention. FIG. 3 is a diagram for explaining an advantage of processing of a routine shown in FIG. 2. It is a figure for comparing the distribution of the measured value of the crank angle time T of each cylinder in the case where misfire does not occur and the case where misfire occurs. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a figure which shows an example of xy plane used in Embodiment 2 of this invention. It is a figure for demonstrating the advantage of the process of the routine shown in FIG. It is a flowchart of the routine performed in Embodiment 3 of the present invention. It is a figure which shows an example of xyz space used in Embodiment 3 of this invention. It is a figure for demonstrating the modification of the misfire detection method of Embodiment 3 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 16 Combustion chamber 26 Fuel injection valve 28 Spark plug 30 ECU (Electronic Control Unit)
32 Crank angle sensor

Claims (13)

Engine speed information acquisition means for acquiring engine speed information of each cylinder immediately after ignition or ignition for each explosion cycle;
The engine speed information for the current explosion cylinder is the x coordinate value, the engine speed information for the previous explosion cylinder is the y coordinate value, and the engine speed information is plotted as the current plot point on the xy plane. Means,
Determination vector calculation means for calculating a determination vector from the reference point on the xy plane toward the current plot point;
When the determination vector calculated by the determination vector calculation means is in the same direction as a predetermined determination reference vector and is larger than the determination reference vector, it is determined that misfire has occurred in the previous explosion cylinder. Misfire determination means;
A misfire detection device for an internal combustion engine, comprising:   2. The misfire detection apparatus for an internal combustion engine according to claim 1, wherein the reference point is a previous plot point.   2. The misfire detection apparatus for an internal combustion engine according to claim 1, wherein the reference point is an intersection of a perpendicular line drawn from the current plot point to a straight line y = x and a straight line y = x. 3.   The determination vector calculating means calculates a y-axis intercept in a straight line having a predetermined gradient according to the operating state of the internal combustion engine and passing through the current plot point, and the reference point is used as the xy plane. The misfire detection apparatus for an internal combustion engine according to claim 1, wherein a determination vector from the origin to the y-axis intercept is calculated. Engine speed information acquisition means for acquiring engine speed information of each cylinder immediately after ignition or ignition for each explosion cycle;
A rotational speed information deviation calculating means for calculating a deviation between the engine rotational speed information in the current explosion cylinder and the engine rotational speed information in the previous explosion cylinder as a deviation of the engine rotational speed information in the current explosion cylinder;
The deviation of the engine speed information in the previous explosion cylinder is the x coordinate value, the deviation of the engine speed information in the current explosion cylinder is the y coordinate value, and the deviation of the engine speed information on the xy plane is the current plot point Deviation plot means for plotting;
Plot point distance calculating means for calculating a distance between the reference point on the xy plane and the current plot point;
Misfire determination means for determining that misfire has occurred in the previous explosion cylinder when the distance calculated by the plot point distance calculation means is equal to or greater than a predetermined determination reference value;
A misfire detection device for an internal combustion engine, comprising:   6. The misfire detection apparatus for an internal combustion engine according to claim 5, wherein the reference point is a previous plot point.   The plot point distance calculation means uses the reference point as the origin of the xy plane and calculates the distance between the origin and the current plot point, or from the origin to the current plot point in the x-axis direction. The misfire detection apparatus for an internal combustion engine according to claim 5, wherein the distance is calculated.   The misfire determination means further determines that a misfire has occurred in the previous explosion cylinder when the x coordinate value and the y coordinate value of the previous plot point and the previous plot point are both negative. The misfire detection apparatus for an internal combustion engine according to any one of claims 5 to 7, wherein   The misfire determination means has a flatness greater than a predetermined reference in the x-axis direction when the frequency distribution when viewed in the x-axis direction of the current plot point plotted on the xy plane over a predetermined number of times. 9. The misfire detection device for an internal combustion engine according to any one of claims 5 to 8, wherein when it is recognized that the misfire has occurred, it is determined that a misfire has occurred in the previous explosion cylinder. Engine speed information acquisition means for acquiring engine speed information of each cylinder immediately after ignition or ignition for each explosion cycle;
The engine speed information in the present explosion cylinder is the x coordinate value, the engine speed information in the previous explosion cylinder is the y coordinate value, and the engine speed information in the previous explosion cylinder is the z coordinate value. Rotation speed information plotting means for plotting the rotation speed information as a plot point this time,
Plot point distance calculating means for calculating the distance between the current plot point and the straight line x = y = z;
When the distance calculated by the plot point distance calculation means is a predetermined determination reference value or more and the current plot point is located on the yz plane side with respect to the straight line x = y = z, First determination means for determining that misfire has occurred in the previous explosion cylinder, and the distance is equal to or greater than a predetermined determination reference value, and the current plot point is xz with respect to the straight line x = y = z Misfire determination means including at least one of second determination means for determining that misfire has occurred in the explosion cylinder of the last time when located on the plane side;
A misfire detection device for an internal combustion engine, comprising:   The misfire determination means includes both the first determination means and the second determination means, and it is determined that misfire has occurred in the previous explosion cylinder by the first determination means in a predetermined explosion cycle. In addition, when it is determined by the second determination means that misfire has occurred in the previous explosion cylinder in the next explosion cycle, it is determined that misfire has occurred in the explosion cylinder. Item 13. A misfire detection device for an internal combustion engine according to Item 10.   The first determination means calculates an intersection of a perpendicular drawn from the current plot point to a straight line x = y = z and the straight line x = y = z, the intersection is the origin, and the xy plane If the x2 axis is the axis parallel to the straight line x = y = z and the current plot point is more than a certain distance in the x2 axis direction with respect to the origin, misfire occurs in the previous explosion cylinder. The misfire detection apparatus for an internal combustion engine according to claim 10 or 11, wherein it is determined that the engine has failed.   The second determination means calculates an intersection of a perpendicular drawn from the current plot point to a straight line x = y = z and the straight line x = y = z, the intersection is the origin, and the z axis The parallel axis is the y2 axis, and it is determined that a misfire has occurred in the previous explosion cylinder when the current plot point is more than a certain distance from the origin in the y2 axis direction. Item 13. The misfire detection device for an internal combustion engine according to any one of Items 10 to 12.

Images