KR102153484B1 - Misfire diagnosis method and device of Multi cylinder four-stroke engine - Google Patents

Abstract

Disclosed are a method and a device for diagnosing a misfire for each cylinder of a multi-cylinder engine using a tooth time signal (the time it takes for an engine crankshaft to rotate at a certain angle) output by a crank angle sensor that recognizes the tooth of a target wheel. The method for diagnosing a misfire of a multi-cylinder engine according to the present invention includes: a linear trend removal step of removing a linear trend from tooth signals output from the crank angle sensor during one cycle; a speed trend line generation step of generating a speed trend line for each cylinder using the tooth signals at two specific positions for each cylinder among the tooth signals from which the linear trend has been removed; a distance calculation step of calculating maximum and minimum engine speed values for each cylinder by using the tooth signals at two specific positions different for each cylinder among the tooth signals from which the linear trend has been removed, and calculating the shortest distances (D1, D2) to the speed trend line from the calculated engine speed maximum and minimum values; and a misfire diagnosis step of calculating a comparison value from the two shortest distances (D1, D2) for each cylinder calculated in the distance calculation step, and diagnosing a misfire for each cylinder by analyzing the calculated comparison value.

Description

Misfire diagnosis method and device of multi cylinder four-stroke engine

The present invention relates to a method and apparatus for diagnosing misfire of a multi-cylinder engine, and more specifically, by using speed information for each cylinder calculated from a tooth time signal (time required for the engine crankshaft to rotate at a certain angle). The present invention relates to a method and apparatus for diagnosing a misfire of a multi-cylinder engine capable of accurately diagnosing and detecting whether a misfire or a cylinder in which a misfire has occurred.

Misfire is a phenomenon in which fuel injected from an engine using fossil fuel is discharged to the outside without burning. When an engine misfire occurs, unburned fuel is discharged as it is, thereby adversely affecting air pollution, or unburned fuel may be burned in the catalyst to damage the catalyst.

Accordingly, in the case of automobiles, a misfire detection logic is installed in the ECU to diagnose misfire, thereby preventing air pollution or catalyst damage. In the case of general mass-produced vehicles, an engine roughness method of diagnosing a misfire by extracting an engine speed from a tooth time signal measured by a crank angle sensor is mainly adopted.

The engine roughness method using engine variability covers a misfire detection area specified by CARB (California Air Quality Agency), but its area is limited, so it is possible to diagnose misfire in some areas such as high RPM and low load areas. There is a disadvantage of poor accuracy.

In addition to using engine variability, a method of diagnosing a misfire by measuring ionic current generated in a spark plug circuit during an explosion stroke is also known. Also known is a method of diagnosing misfire by directly measuring the combustion pressure of the cylinder.

However, these methods (methods using ionic current or methods of using combustion pressure characteristics) increase vehicle prices because new functions or new sensors must be added to the existing vehicle, which is not applicable to mass-produced cars. There is bound to be a burden in terms of cost.

In order to solve this problem, a frequency analysis method that detects whether the engine is misfired by using the output signal measured from the crank angle sensor without the addition of a separate sensor or equipment has been proposed, but the existing frequency analysis method is mainly used for amplitude (Amplitude ) And phase information, there is a problem that the diagnostic precision in a specific driving area is poor.

Korean Patent Registration No. 10-1869324 (Registration Date 2018.06.14)

The technical problem to be solved by the present invention is to provide a method and apparatus for diagnosing misfire of a multi-cylinder engine capable of diagnosing/detecting misfire for each cylinder simply and accurately with only the output signal of the crank angle sensor without the addition of a separate sensor or equipment. I want to.

According to an aspect of the present invention as a means of solving the problem,

As a method of diagnosing whether a multi-cylinder engine misfires for each cylinder by using a tooth time signal output by a crank angle sensor that recognizes the tooth of a target wheel,

a) Linear trend removal step of removing a linear trend from the tooth signal output by the crank angle sensor during one cycle

b) a speed trend line generation step of generating a speed trend line for each cylinder using the tooth signals at two specific positions for each cylinder among the tooth signals from which the linear trend has been removed;

c) Among the tooth signals from which the linear trend has been removed, the maximum and minimum engine speed values for each cylinder are calculated using the tooth signals at two specific positions for each cylinder, and the shortest distance from the calculated maximum and minimum engine speed values to the speed trend line A distance calculation step of calculating (D1, D2);

d) a misfire diagnosis step of calculating a comparison value from the two shortest distances (D1, D2) for each cylinder calculated in step c), and diagnosing a misfire for each cylinder by analyzing the calculated comparison value; a multi-cylinder engine comprising: Provides a method for diagnosing misfires.

Here, the two specific positions for obtaining the speed trend line in step b) are the rotational positions of the target wheel set corresponding to the rotational positions of the crankshafts at the beginning of the intake stroke and the end of the exhaust stroke for each cylinder. The specific position may be a rotation position of the target wheel at which the maximum and minimum engine speed values for each cylinder appear.

In addition, the speed trend line is a point on the engine speed curve including the engine speed (TDC1_rpm) component calculated from the tooth signal at the beginning of the intake stroke for each cylinder, the rotation position component of the target wheel at the beginning of the intake stroke, and the end of the exhaust stroke for each cylinder. It may be defined as a straight line passing through another point on the engine speed curve including the engine speed (TDC3_rpm) component calculated from the tooth signal of the engine and the rotation position component of the target wheel at the end of the exhaust stroke.

In addition, the comparison value in step d) may be defined as a product of two shortest distances per cylinder.

Further, in step d), the comparison value D1XD2, which is defined as the product of the two shortest distances for each cylinder, is compared with the threshold value ₁ for each cylinder mapped to the recording device to diagnose whether a misfire for each cylinder.

As another example, in step d), the comparison value (D1XD2), which is defined as the product of the two shortest distances per cylinder, is compared with the previous comparison value (D1'XD2') of the same cylinder obtained by the same method in the previous cycle. You can also diagnose whether it is a misfire.

In this case, the difference ((D1'XD2')-(D1XD2)) between the previous comparison value (D1'XD2') and the comparison value (D1XD2) is compared with the threshold value (Threshold ₂ ) mapped to the recording device It is possible to diagnose whether or not there is a mistake.

As another embodiment according to an aspect of the present invention as a means of solving the problem,

As a method of diagnosing whether a multi-cylinder engine misfires for each cylinder by using a tooth time signal output by a crank angle sensor that recognizes the tooth of a target wheel,

a) a linear trend removal step of removing a linear trend from the tooth signal output from the crank angle sensor during one cycle;

b) Among the tooth signals from which the linear trend has been removed, the engine speed at the start and end points of each cylinder is calculated using the tooth signals at two specific positions for each cylinder, and the speed increase or decrease, which is the difference between the two engine speeds at the start and end points for each cylinder. A speed increase/decrease calculation step of calculating (D3);

c) Among the tooth signals from which the linear trend has been removed, the maximum and minimum engine speed values for each cylinder are calculated using the tooth signals at two specific positions for each cylinder, and the speed amplitude, which is the difference between the calculated maximum and minimum engine speed values for each cylinder ( A speed amplitude calculation step of calculating D4);

d) a misfire diagnosis step of diagnosing a misfire for each cylinder by analyzing the difference between the speed increase/decrease (D3) for each cylinder derived in step b) and the speed amplitude for each cylinder (D4) derived in step c). Provides a method for diagnosing misfire of a cylinder engine.

Here, the two specific positions in step b) are the rotational positions of the target wheel set corresponding to the rotational positions of the crankshafts at the beginning of the intake stroke and the end of the exhaust stroke for each cylinder, and the other two specific positions in step c) are It may be a rotation position of the target wheel at which the maximum and minimum engine speed values appear.

Further, in step d), the difference between the speed increase/decrease (D3) and the speed amplitude (D4) for each cylinder is compared with a threshold value for each cylinder mapped to the recording device to diagnose whether or not a misfire for each cylinder.

As another example, in step d), the difference between the speed increase/decrease (D3) and the speed amplitude (D4) for each cylinder is compared with the difference between the speed increase/decrease and the speed amplitude of the same cylinder obtained in the previous cycle to diagnose whether or not a misfire for each cylinder. have.

According to another aspect of the present invention as a means of solving the problem,

As a device that diagnoses whether a multi-cylinder engine is misfired for each cylinder,

A crank angle sensor disposed around a target wheel of the engine crankshaft to generate a tooth time signal required for engine speed calculation;

Including; a controller that analyzes the engine speed change of one cycle from the tooth signal of the crank angle sensor and diagnoses whether a misfire occurs using the analysis result,

The controller,

A linear trend removal unit that removes a linear trend from the tooth signal output from the crank angle sensor during one cycle;

A speed trend line generator for generating a speed trend line for each cylinder using the tooth signals at two specific positions for each cylinder among the tooth signals from which the linear trend has been removed;

Among the tooth signals from which the linear trend has been removed, the maximum and minimum engine speed values for each cylinder are calculated using the tooth signals at two specific positions for each cylinder, and the shortest distance from the calculated engine speed maximum and minimum values to the speed trend line (D1 , A distance calculation unit that calculates D2) and

Misfire diagnosis device for a multi-cylinder engine including a misfire diagnosis unit that calculates a comparison value from the two shortest distances (D1, D2) for each cylinder calculated through the distance calculation unit, and analyzes the calculated comparison value to diagnose misfire for each cylinder Provides.

Here, the speed trend line generator includes an engine speed (TDC1_rpm) component calculated from a tooth signal at the initial stage of the intake stroke for each cylinder, a point on the engine speed curve including a rotation position component of the target wheel at the initial stage of the intake stroke, and an exhaust stroke for each cylinder. The speed trend line L1 may be generated by connecting another point on the engine speed curve including the engine speed (TDC3_rpm) component calculated from the end tooth signal and the rotation position component of the target wheel at the end of the exhaust stroke.

In addition, the misfire diagnosis unit may compare a comparison value D1XD2 defined as the product of the two shortest distances for each cylinder with a threshold value ₁ for each cylinder mapped to a recording device to diagnose whether or not a misfire for each cylinder.

As another example, the misfire diagnosis unit compares the comparison value (D1XD2) defined as the product of two shortest distances per cylinder with the previous comparison value (D1'XD2') of the same cylinder obtained by the same method in the previous cycle, Whether it can be diagnosed.

In this case, the misfire diagnosis unit may determine the difference ((D1'XD2')-(D1XD2)) between the previous comparison value (D1'XD2') and the comparison value (D1XD2), which is mapped to the recording device (Threshold ₂ ). Compared with, it is possible to diagnose the misfire by cylinder.

As another embodiment according to another aspect of the present invention as a means of solving the problem,

As a device that diagnoses whether a multi-cylinder engine is misfired for each cylinder,

A crank angle sensor disposed around a target wheel of the engine crankshaft to generate a tooth time signal required for engine speed calculation;

Including; a controller that analyzes the engine speed change of one cycle from the tooth signal of the crank angle sensor and diagnoses whether a misfire occurs using the analysis result,

The controller,

A linear trend removal unit that removes a linear trend from the tooth signal output from the crank angle sensor during one cycle;

Among the tooth signals from which the linear trend has been removed, the engine speed at the start and end points of each cylinder is calculated using the tooth signals at two specific positions per cylinder, and the speed increase or decrease (the difference between the two engine speeds at the start and end points for each cylinder) A speed increase/decrease calculation unit that calculates D3),

Among the tooth signals from which the linear trend has been removed, the maximum and minimum engine speed values for each cylinder are calculated using the tooth signals at two specific positions for each cylinder, and the speed amplitude (D4), which is the difference between the calculated maximum and minimum engine speed values for each cylinder. A velocity amplitude calculator that calculates

It provides a misfire diagnosis apparatus for a multi-cylinder engine including a misfire diagnosis unit that diagnoses misfire for each cylinder by analyzing the difference between the speed increase/decrease D3 and the speed amplitude D4 for each cylinder.

In this case, the misfire diagnosis unit may diagnose a misfire for each cylinder by comparing a difference between the speed increase/decrease D3 and the speed amplitude D4 for each cylinder with a threshold for each cylinder mapped to the recording device.

Unlike this, the misfire diagnosis unit compares the difference between the speed increase/decrease (D3) and the speed amplitude (D4) for each cylinder with the difference between the speed increase/decrease (D3') and the speed amplitude (D4') of the same cylinder obtained in the previous cycle. Diagnosis of misfire can be made.

According to an embodiment of the present invention, some information on engine characteristics that can clearly distinguish between a normal ignition and a misfire (the initial engine speed of the intake stroke and the engine speed of the end of the exhaust stroke for each cylinder, which can be determined by the output signal of the crank angle sensor, Misfire can be diagnosed using only the maximum and minimum engine speed values for each cylinder.

In other words, by diagnosing/detecting a true story with only the minimum main information that can clearly determine whether a true story has been made, it is possible to diagnose and detect a true story with high accuracy while simplifying the process for diagnosing/detecting a true story, and without additional hardware configuration. Since it can be implemented only with software, it has the advantage of low development cost.

Moreover, by comparing the comparison value calculated from the shortest distance between the maximum and minimum engine speed values and the speed trend line with a threshold value, or by comparing the previous comparison value of the same cylinder extracted in the previous cycle to diagnose whether a misfire has occurred or not. Of course, there is an advantage of being able to accurately diagnose and detect the cylinder position where the misfire occurred.

1 is a conceptual diagram of a multi-cylinder engine misfire diagnosis apparatus according to an embodiment of the present invention.
2 is a graph showing engine speed fluctuations according to elapsed time before and after the linear trend is removed from tooth signal data output from the crank angle sensor.
3 is an exemplary view illustrating a process of generating a speed trend line and calculating a shortest distance applied to an embodiment of the present invention.
4 is a view for explaining a misfire diagnosis process performed by a misfire diagnosis apparatus according to an embodiment of the present invention.
5 is a flowchart illustrating a method for diagnosing a misfire of a multi-cylinder engine according to an embodiment of the present invention.
6 is a conceptual diagram schematically showing a misfire diagnosis apparatus for a multi-cylinder engine according to another embodiment of the present invention.
7 is an exemplary view for explaining the speed increase and decrease and speed amplitude applied to another embodiment of the present invention.
8 is a view for explaining a misfire diagnosis process performed by a misfire diagnosis apparatus according to another embodiment of the present invention.
9 is a flowchart illustrating a method for diagnosing a misfire of a multi-cylinder engine according to another embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

In describing the present invention, terms used in the following specification are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

In addition, in the present specification, terms such as "comprise" or "have" are intended to designate the presence of features, numbers, steps, actions, components, parts, or a combination thereof described in the specification, but one or more other It is to be understood that the presence or addition of features, numbers, steps, actions, components, parts, or combinations thereof, does not preclude in advance the possibility of being excluded.

In addition, terms such as first and second may be used to describe various elements, but the elements should not be limited by the terms. These terms are used only for the purpose of distinguishing one component from another component.

In addition, terms such as "... unit", "... unit", "... module" described in the specification mean a unit that processes at least one function or operation, which can be implemented by hardware or software or a combination of hardware and software. I can.

In the description with reference to the accompanying drawings, the same drawing reference numerals are assigned to the same elements, and duplicate descriptions of the same elements will be omitted. In addition, in describing the present invention, when it is determined that a detailed description of a related known technology may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted.

Hereinafter, the meaning of main terms used in describing an embodiment of the present invention will be briefly described.

Among the terms used in describing an embodiment of the present invention, "one cycle" refers to a section in which the engine crankshaft rotates two wheels (720ㅀ), and for each cylinder, suction-compression-explosion (combustion expansion)-exhaust stroke It means a section that includes once. For example, in the case of a four-cylinder engine, four cylinders perform suction-compression-explosion-exhaust in a predetermined order and rotate the crankshaft two times (720°) to complete one cycle.

In addition, the ``speed trend line'' refers to a straight line generated by using the tooth signals at two specific positions for each cylinder among the tooth signals output by the crank angle sensor that detects the rotation angle or rotation position of the crankshaft during the aforementioned cycle. The "two specific positions" may be a rotational position of the target wheel set corresponding to the crankshaft rotational position of each of the initial intake stroke and the end of the exhaust stroke for each cylinder.

Also, the ``shortest distance (D1, D2)'' is the maximum engine speed generated from the tooth signals at two specific positions for each cylinder among the tooth signals output by the crank angle sensor that detects the rotation angle or rotation position of the crankshaft during the aforementioned cycle. It means a straight line distance from a value and a minimum value to the'speed trend line', where the'other two specific positions' may be a rotation position of the target wheel corresponding to the crankshaft rotation position at which the maximum and minimum engine speed values for each cylinder appear. .

For reference, the tooth signal (Tooth time signal) refers to the time it takes for the engine crankshaft to rotate at a certain angle, and is formed at equal intervals around the outer surface of a target wheel concentrically installed at the crankshaft tip. Refers to a signal that the crank shaft position sensor recognizes and outputs a plurality of teeth.

1 is a conceptual diagram schematically illustrating an apparatus for diagnosing a misfire of a multi-cylinder engine according to an exemplary embodiment of the present invention. Referring to this, the apparatus for diagnosing a misfire of a multi-cylinder engine according to an exemplary embodiment of the present invention will be described.

Referring to FIG. 1, an apparatus for diagnosing misfire of a multi-cylinder engine according to an embodiment of the present invention includes a crank angle sensor 10 and a controller 20. The controller 20 may be an ECU, and the crank angle sensor 10 is disposed around the target wheel 40 on the engine crankshaft 30, and a tooth signal required for engine speed calculation according to the rotation of the target wheel 40 ( Tooth time signal) signal is generated.

A plurality of teeth are formed on the outer circumferential surface of the target wheel 40 to measure the angular velocity of the crankshaft 30, and when the target wheel 40 rotates, the crank angle sensor 20 The controller 20 calculates the angular velocity of the engine crankshaft 30 by using the time information for detecting the tooth. And the engine speed is calculated from the calculated angular speed.

The controller 20 controls the engine speed by controlling the energized state of the fuel injector 60 and the ignition coil 50 according to the driver's acceleration or deceleration request through a hand accelerator operation (not shown), as well as the crank angle. From the tooth time signal of the sensor 10, the engine speed change of one engine cycle that is the target of misfire analysis is analyzed. And, using the analysis result, it diagnoses whether there is a misfire.

Misfire, as mentioned in the background art, refers to a phenomenon in which fuel injected into the engine cylinder is discharged to the outside without burning. When a misfire occurs, the periodicity of the tooth signal (Tooth time siganal, the time it takes for the engine crankshaft to rotate at a certain angle) is impaired as the energy source that accelerates the engine speed is not generated in the explosion (combustion expansion) stroke.

Misfire is caused by no combustion of fuel in the explosion stroke -> no combustion pressure -> reduction in piston speed -> reduction in crankshaft rotational momentum, resulting in a longer tooth time and a decrease in engine speed. That is, when a misfire occurs, the energy source that drives the engine is not generated, so the engine speed decreases. Therefore, by analyzing the engine speed for each cylinder in one cycle, it is possible to diagnose the misfire for each cylinder.

The present invention enables accurate and quick diagnosis/detection of a misfire occurring in a multi-cylinder engine by using the characteristics of changes in engine speed appearing during a misfire. To this end, the controller 20 applied in the present embodiment is It includes a trend removal unit 22 and a speed trend line generation unit 24. It also includes a distance calculation unit 26 and a misfire diagnosis unit 28.

The configuration of each part constituting the controller will be described in more detail.

The linear trend removal unit 22 removes a linear trend from the tooth signal output from the crank angle sensor 10 during one cycle. This is because if the linear trend is not removed from the signal data output from the crank angle sensor 10, an overshoot occurring in normal ignition may affect the engine speed fluctuation of the cylinder where the misfire occurs, that is, the cylinder.

If the overshoot from normal ignition affects the engine speed fluctuation of the cylinder where the misfire occurs, it may be difficult to accurately and accurately diagnose whether or not the misfire occurs. Therefore, by removing the linear trend from the output signal data of the crank angle sensor 10 collected during one cycle (Linear detrend), it is desirable to remove the effect of the overshoot on the engine speed of the misfire occurrence cylinder in advance.

Removing the linear trend from all tooth signals in a cycle means in a different sense, subtracting these averages from the engine speed that is calculated from all tooth signals during one cycle. In FIG. 2, (a) is a graph showing the engine speed fluctuations according to the elapsed time before the linear trend is removed from the tooth signal data output from the crank angle sensor, and (b) is a graph showing the engine speed fluctuations after the linear trend is removed. It is a graph.

The speed trend line generator 24 generates a speed trend line for each cylinder by using the tooth signals at two specific positions for each cylinder among the tooth signals from which the linear trend has been removed. For example, in a four-cylinder engine with four cylinders, a total of four speed trend lines are generated for each cylinder in one cycle. Of course, the engine is not limited to a four-cylinder engine because it can be a two- or more-cylinder engine.

The two specific positions for collecting the tooth signals necessary for generating the speed trend line may preferably be rotation positions of the target wheel 40 set corresponding to the crankshaft rotation positions at the start and end points of the unit cycle for each cylinder.

More specifically, it may be a rotational position of the target wheel 40 set corresponding to the crankshaft rotational position at the beginning of the suction stroke and the end of the exhaust stroke of a unit cycle for each cylinder. For example, in the case of a four-cylinder engine, it may be specified as the rotational position of the target wheel 40 corresponding to the crankshaft rotational position at the beginning of the intake stroke and the end of the exhaust stroke for each cylinder in one cycle.

The distance calculation unit 26 uses the tooth signals at two specific positions different from the position to collect the tooth signals required for the generation of the speed trend line among the tooth signals from which the linear trend has been removed, and uses the maximum and minimum engine speed values for each cylinder during one cycle. Is calculated, and the shortest distances (D1, D2) from the calculated maximum and minimum engine speed values for each cylinder to the speed trend line of the corresponding cylinder are calculated.

The other two specific positions for collecting the tooth signals required to calculate the shortest distances (D1, D2) are preferably the rotational positions of the target wheel 40 at which the maximum and minimum engine speed values for each cylinder appear, such as simulation of the same simulation environment or Through repeated experiments, the target wheel rotation position at which the maximum and minimum engine speed values for each cylinder appear, and the average value of the obtained rotation positions may be derived, and may be a fixed value set for each cylinder.

Of course, it is not limited to using the rotation position of the target wheel 40 as a fixed value for calculating the shortest distances D1 and D2. Because the rotational position of the target wheel 40 at which the maximum and minimum engine speed values appear for each cycle may vary slightly due to combustion characteristics, the position at which the angular speed of the target wheel 40 for each cylinder is the maximum and the minimum at each cycle It is also possible to use the tooth signal of.

Referring to FIG. 3, a process of generating a speed trend line by a speed trend line generating unit and calculating a shortest distance by a distance calculating unit will be described in more detail.

3 is an exemplary diagram for explaining the process of generating a speed trend line and calculating the shortest distance, with four cylinders, that is, four cylinders, and no. 1 (Cyl 1) -3 (Cyl 3) -4 (Cyl 4) -2 ( Cyl 2) Engine speed according to crankshaft rotation angle change (x-axis direction) after removing the linear trend by dividing the tooth signal output from the crank angle sensor 10 for each cylinder in a four-cylinder engine in which combustion is performed in the order of cylinder (cylinder) It is an engine speed curve expressed as a change amount (y-axis direction).

Referring to FIG. 3, the speed trend line L1 is a point on the speed curve including the engine speed (TDC1_rpm) component calculated from the tooth signal at the beginning of the suction stroke for each cylinder and the rotation position component of the target wheel 40 (TDC1). And, it can be generated by connecting the engine speed (TDC3_rpm) component calculated from the tooth signal at the end of the exhaust stroke for each cylinder and another point (TDC3) on the speed curve including the rotational position component of the target wheel 40.

More specifically, in FIG. 3, TDC1 is a point including an engine speed (TDC1_rpm) component on the y-axis and a rotational position component of the target wheel 40 on the x-axis, and TDC3 is also the engine speed (TDC1_rpm) on the y-axis. TDC3_rpm) component and the x-axis contains the rotational position component of the target wheel 40 of a different value, so the speed trend line (L1) can be obtained using a simple equation (the equation of a straight line passing through two points). have.

The shortest distance (D1, D2) is the distance from the maximum engine speed value (rpm _max ) and minimum value (rpm _min ) for each cylinder to the speed trend line L1, as mentioned earlier, and the speed trend line L1 for each cylinder in FIG. The distance in the y-axis direction (D1) between one point (P1) where the maximum engine speed value (rpm _max ) appears, and the other point (P2) where the speed trend line for each cylinder (L1) and the minimum speed value (rpm _min ) appears. It means the distance in the y-axis direction (D2).

Here, P1 and P2 are points on the engine speed curve each including the engine speed (rpm _max, rpm _min ) component on the y-axis and the rotation position component of the target wheel 40 on the x-axis, so between the point and the straight line The shortest distance (D1, D2) can be quickly calculated by using a simple computational process that includes the known equations used to calculate the distance (the distance between P1 and L1 and the distance between P2 and L2). .

Information on the two shortest distances (D1, D2) for each cylinder calculated by the distance calculation unit 26 is transmitted to the misfire diagnosis unit 28, and the misfire diagnosis unit 28 is the shortest distance (D1, D2) for each cylinder. ), a comparison value (D1XD2) defined as the product of the two shortest distances (D1, D2) is calculated, and the calculated comparison value (D1XD2) is analyzed to diagnose whether a misfire for each cylinder during one cycle.

As an example, the comparison value D1XD2, defined as the product of two shortest distances _per cylinder, may be compared with a threshold value ₁ for each cylinder previously mapped to a recording device to diagnose whether or not a misfire per cylinder.

As another example, the comparison value (D1XD2), which is defined as the product of the two shortest distances per cylinder, is compared with the previous comparison value (D1'XD2') of the same cylinder obtained by the same method in the previous cycle to diagnose whether or not there is a misfire for each cylinder. It can also be configured. In this case, preferably, the difference ((D1'XD2')-(D1XD2)) between the previous comparison value (D1'XD2') and the comparison value (D1XD2) is compared with the threshold value (Threshold ₂ ) mapped to the recording device. By doing so, it is possible to diagnose whether or not a misfire by cylinder.

In normal ignition, an energy source that accelerates the engine speed is generated in the explosion stroke for each cylinder. Therefore, the comparison value D1XD2 calculated from the distance between the maximum and minimum engine speed values with respect to the speed trend line L1 is relatively small. In the case of a four-cylinder engine, if explosion (expansion combustion) occurs normally in the order of the specified order (No. 1 (Cyl 1)-3 (Cyl 3)-4 (Cyl 4)-2 (Cyl 2))) This is because the overall engine speed fluctuations are not large.

On the other hand, when a misfire occurs, the comparison value D1XD2 appears in a distinctly large width compared to the normal ignition (cylinders 1, 4, and 2 in FIG. 3) (unit cycle section of cylinder 3 in FIG. 3). When a misfire occurs in a specific cylinder (cylinder 3 in FIG. 3), there is no energy added by the explosion, so the engine speed fluctuation range of the cylinder is inevitably larger than that of other cylinders.

Therefore, by analyzing the comparison value D1XD2 for each cylinder described above, it is possible to accurately diagnose whether a misfire has occurred, as well as how many times a misfire has occurred in the cylinder. The present invention diagnoses whether a misfire occurs by using the fact that the comparison value (D1XD2) defined as the product of the shortest distance of the maximum engine speed and the minimum value to the speed trend line for each cylinder appears in distinctly different patterns depending on whether a misfire occurs. .

4 is a difference between the comparison value for each cylinder ((D1XD2) in the current cycle and the comparison value for the same cylinder (D1'XD2)' obtained by the same method in the previous cycle in the misfire diagnosis method performed by the misfire diagnosis unit (((D1 This is a diagram for explaining the process of diagnosing whether or not misfire for each cylinder is analyzed by analyzing'XD2')-(D1XD2)).

4(a) is an engine speed curve showing the amount of change in engine speed according to the crankshaft rotation angle change by dividing the tooth signal output from the crank angle sensor for each cylinder during the last cycle, and FIG. 4(b) is It is an engine speed curve expressed as the amount of engine speed change according to the crankshaft rotation angle change by dividing the tooth signal output from the crank angle sensor during the cycle by cylinder.

Referring to Fig. 4 and the previous Fig. 3 together, as mentioned above, since an energy source for accelerating the engine speed is generated in the explosion stroke for each cylinder in normal ignition, the engine speed change range for each cylinder is small, and thus the comparison value D1XD2 is not large. . On the other hand, in the true story without the addition of energy due to the explosion, the comparison value D1'XD2' appears relatively large because the engine speed change range is large.

Looking at the section excluding the unit cycle section of cylinder 1 (unit cycle section of cylinder 3, 4, and 2) in Fig. 4, the comparison value ((D1'XD2) in the previous cycle (Fig. 4(a))) ') and the comparison value (D1XD2) for each cylinder in the current cycle (Fig. 4(b)), it is intuitive that the difference between the two comparison values for each cylinder ((D1'XD2')-(D1XD2)) is not large. Can be seen as.

Therefore, when comparing the comparison value for each cylinder (D1XD2) of the current cycle with the comparison value of the same cylinder (D1'XD2') of the previous cycle, the absolute value of the difference ((D1'XD2')-(D1XD2)) is set. If the value is equal to or less than (Threshold ₂ ), the misfire diagnosis unit 29 generates an energy source for accelerating the engine speed by normally igniting the corresponding cylinder, for example, cylinders 3, 4, and 2 in FIG. It can be diagnosed as prescribed.

On the contrary, looking at the unit cycle section of cylinder 1, the comparison value D1'XD2' is defined as the product of the distance from the speed trend line L1 to the maximum and minimum engine speed values in the previous cycle (Fig. 4A). ) And the comparison value ((D1XD2) in the current cycle (Fig. 4(b)) are clearly compared, which means that the ignition was not normally ignited in cylinder 1 of the current cycle.

As such, when the comparison value of the unit cycle section of the same cylinder is significantly different, the misfire diagnosis unit 28 may diagnose that a misfire has occurred in the corresponding cylinder (Cylinder 1). Preferably, the misfire diagnosis unit 28 has an absolute value of the difference ((D1'XD2')-(D1XD2)) between the comparison value for each cylinder (D1XD2) and the comparison value for the same cylinder (D1'XD2') of the previous cycle. If it is greater than the set threshold (Threshold ₂ ), it can be diagnosed as a misfire.

On the other hand, if the same cylinder of the previous cycle is diagnosed as a misfire, for example, if cylinder 1 was diagnosed as a misfire immediately before, the difference between the comparison value in the previous unit cycle section and the comparison value in the current unit cycle section ( If the absolute value of (D1'XD2')-(D1XD2)) is greater than the threshold value (Threshold ₂ ), it is diagnosed as normal ignition, and if it is equal to or less than the threshold value (Threshold ₂ ), it can be diagnosed as continuous misfire.

If a misfire occurs in a specific cylinder in the previous unit cycle section and the same cylinder returns to normal ignition in the current unit cycle section, the comparison value difference (as opposed to the case where the previous is normal ignition and the current misfire (cylinder 1 in Fig. 4)) occurs. If the absolute value of (D1'XD2')-(D1XD2)) is relatively large, and a misfire occurs continuously in two unit cycle intervals, the absolute value of the comparison value difference ((D1'XD2')-(D1XD2)) is Because it is relatively small.

As described above, the apparatus for diagnosing misfire of a multi-cylinder engine according to an embodiment of the present invention compares the comparison value defined as the product of the shortest distance from the maximum engine speed and the minimum value to the speed trend line L1 by classifying each cylinder with a threshold value, or By diagnosing whether a misfire occurs by comparing the comparison value of the same cylinder extracted in the previous cycle, it is possible to accurately diagnose and detect not only the misfire, but also the cylinder where the misfire has occurred, that is, the position of the cylinder.

Hereinafter, a process of diagnosing a misfire for a multi-cylinder engine performed by the apparatus for diagnosing misfire of a multi-cylinder engine according to the above-described exemplary embodiment will be described with reference to the flowchart of FIG. 5.

5 is a flowchart illustrating a method for diagnosing a misfire of a multi-cylinder engine according to an embodiment of the present invention. For convenience of explanation, the configuration shown in FIG. 1 will be described with reference to the corresponding reference number.

5, the misfire diagnosis performed by the misfire diagnosis apparatus of a multi-cylinder engine according to an embodiment of the present invention includes a linear trend removal step (S100), a speed trend line generation step (S200), and a distance calculation step (S300). And a misfire diagnosis step (S400). Hereinafter, the operation or processing performed in each step will be described in detail.

In the linear trend removal step S100, the rotation of the target wheel 40 is detected during one cycle, and a linear trend is removed from the tooth signal output from the crank angle sensor 10 (Linear Detrend). This is because, if the linear trend is not removed from the signal data output from the crank angle sensor, the overshoot occurring in normal ignition can affect the engine speed fluctuation of the cylinder where the misfire occurs, that is, the cylinder.

In some cases, in the linear trend removal step (S100), the tooth signal of the crank angle sensor 10 is extracted at regular intervals to reduce the amount of signal data to be processed, thereby greatly reducing the computational load that the controller has to bear. The process may be included. In this case, the maximum down-sampling may be a case where the tooth signal is collected only at the beginning of the intake stroke and the end of the exhaust stroke for each cylinder, and only the positions where the maximum and minimum engine speed values appear.

In the speed trend line generation step (S200), a task of generating a speed trend line for each cylinder is performed using the tooth signals at two specific positions for each cylinder among the tooth signals from which the linear trend has been removed through the step S100. For example, in the case of a four-cylinder engine, a total of four speed trend lines are generated for each cylinder in one cycle. Of course, it is not limited to a four-cylinder engine, and the engine may be a two or more multi-cylinder engine.

The two specific positions for collecting the tooth signal required for generating the speed trend line may be preferably the rotational positions of the target wheel set corresponding to the crankshaft rotational positions at the beginning of the suction stroke and the end of the exhaust stroke for each cylinder. For example, in the case of a four-cylinder engine having four cylinders, it may be the rotational position of the target wheel corresponding to the crankshaft rotational position at the beginning of the intake stroke and the end of the exhaust stroke for each cylinder in one cycle.

In the distance calculation step (S300), the maximum and minimum engine speed values for each cylinder are calculated by using the tooth signals at two specific positions different from the position at which the tooth signals required for generating the speed trend line are collected among the tooth signals from which the linear trend has been removed. , From each of the calculated engine speed maximum and minimum values, the shortest distances D1 and D2 to the speed trend line are calculated.

Similarly, in the case of a four-cylinder engine as an example, a total of eight shortest distance values can be generated, two for each cylinder in one cycle.

The other two specific positions for collecting the tooth signal required for the calculation of the shortest distance (D1, D2) are preferably the rotational positions of the target wheel 40 at which the maximum and minimum engine speed values per cylinder appear, and simulation or repetition of the same simulation environment Through an experiment, a target wheel rotation position at which the maximum and minimum engine speed values for each cylinder appear, and the average value of the obtained rotation positions may be derived, and may be a fixed value set for each cylinder.

Of course, it is not limited to using the rotational position of the target wheel 40 for extracting the extreme speed value as a fixed value. Because the rotational position of the target wheel 40 at which the maximum and minimum engine speed values appear for each cycle may vary slightly due to combustion characteristics, the position at which the angular speed of the target wheel 40 for each cylinder is the maximum and the minimum at each cycle It is also possible to extract the velocity extreme value for each cylinder from the tooth signal of.

In the misfire diagnosis step (S400), the misfire for each cylinder is diagnosed using the information on the two shortest distances (D1, D2) for each cylinder calculated in the step S300. More specifically, a comparison value (D1XD2) defined as the product of two shortest distances (D1, D2) is calculated from the information on the shortest distance (D1, D2) per cylinder, and the calculated comparison value (D1XD2) is analyzed. It diagnoses whether or not there is a misfire for each cylinder during one cycle.

Preferably, the comparison value (D1XD2), which is defined as the product of the two shortest distances per cylinder, is compared with the threshold value for each cylinder (Threshold ₁ ) previously mapped to the recording device to diagnose whether or not it is misfired for each cylinder, or the two shortest distances _per cylinder. The comparison value D1XD2 defined as the product of the distance may be compared with the previous comparison value D1'XD2' of the same cylinder obtained by the same method in the previous cycle to diagnose whether or not misfire for each cylinder.

When comparing the comparison value (D1XD2) with the previous comparison value (D1'XD2') and diagnosing whether there is a misfire for each cylinder, preferably, the difference between the previous comparison value (D1'XD2') and the comparison value (D1XD2) (( By comparing D1'XD2')-(D1XD2)) with the threshold value (Threshold ₂ ) mapped to the recording device, it is possible to accurately diagnose the misfire for each cylinder.

In normal ignition, an energy source that accelerates the engine speed is generated in the explosion stroke for each cylinder. Therefore, the comparison value D1XD2 calculated from the distance between the maximum and minimum engine speed values with respect to the speed trend line L1 is relatively small. In the case of a four-cylinder engine, if explosion (expansion combustion) occurs normally in the order of the specified order (No. 1 (Cyl 1)-3 (Cyl 3)-4 (Cyl 4)-2 (Cyl 2))) This is because the overall engine speed fluctuations are not large.

On the other hand, when a misfire occurs, the comparison value D1XD2 appears in a distinctly large width compared to the normal ignition (cylinders 1, 4, and 2 in FIG. 3) (unit cycle section of cylinder 3 in FIG. 3). When a misfire occurs in a specific cylinder (cylinder 3 in FIG. 3), there is no energy added by the explosion, so the engine speed fluctuation range of the cylinder is inevitably larger than that of other cylinders.

Therefore, by analyzing the comparison value D1XD2 for each cylinder described above, it is possible to accurately diagnose whether a misfire has occurred, as well as how many times a misfire has occurred in the cylinder. The present invention diagnoses whether a misfire occurs by using the fact that the comparison value (D1XD2) defined as the product of the shortest distance of the maximum engine speed and the minimum value to the speed trend line for each cylinder appears in distinctly different patterns depending on whether a misfire occurs. .

According to an embodiment of the present invention discussed above, some information on engine characteristics that can clearly distinguish between normal firing and misfire (intake stroke for each cylinder determined by the output signal of the crank angle sensor, initial engine speed and exhaust stroke) Misfire can be diagnosed using only the end-stage engine speed and the maximum and minimum engine speed values for each cylinder.

In other words, by diagnosing/detecting a true story with only the minimum main information that can clearly determine whether a true story has been made, it is possible to diagnose and detect a true story with high accuracy while simplifying the process for diagnosing/detecting a true story, and without additional hardware configuration. Since it can be implemented only with software, it has the advantage of low development cost.

Moreover, by comparing the comparison value calculated from the shortest distance between the maximum and minimum engine speed values and the speed trend line with a threshold value, or by comparing the previous comparison value of the same cylinder extracted from the previous cycle to diagnose whether a misfire has occurred or not. Of course, there is an advantage of being able to accurately diagnose and detect the cylinder position where the misfire occurred.

6 is a conceptual diagram schematically showing an apparatus for diagnosing a misfire of a multi-cylinder engine according to another embodiment of the present invention, and referring to this, a misfire diagnosis apparatus for a multi-cylinder engine according to another embodiment of the present invention will be described. The same reference numerals are assigned to the same components as in the above-described embodiment.

First, the meaning of the main terms used in describing another embodiment of the present invention will be briefly described.

Among the terms used in describing another embodiment of the present invention, "one cycle" is a section in which the engine crankshaft rotates two wheels (720ㅀ), as in the above-described embodiment, and suction-compression-explosion for each cylinder (Combustion expansion)-refers to a section that includes one exhaust stroke. For example, in the case of a four-cylinder engine, four cylinders perform suction-compression-explosion-exhaust in a predetermined order, and rotate the crankshaft two turns (720°) to complete one cycle.

And ``speed increase or decrease'' means the difference between the two engine speeds calculated from the tooth signals at two specific positions for each cylinder among the tooth signals output by the crank angle sensor that detects the rotation angle or rotation position of the crankshaft during the aforementioned cycle. , Here, the "two specific positions" may be the rotational positions of the target wheel set corresponding to the crankshaft rotational positions at the start and end (end of the exhaust stroke) for each cylinder.

In addition, ``speed amplitude'' means the difference between the two engine speeds calculated from the tooth signals at two specific positions for each cylinder among the tooth signals output by the crank angle sensor that detects the rotation angle or rotation position of the crankshaft during the aforementioned cycle. . At this time, "the other two specific positions" may be the rotational positions of the target wheel corresponding to the crankshaft rotational positions at which the maximum and minimum engine speed values for each cylinder appear.

For reference, the tooth signal (Tooth time signal) refers to the time it takes for the engine crankshaft to rotate at a certain angle, and is formed at equal intervals around the outer surface of a target wheel concentrically installed at the crankshaft tip. Refers to a signal that the crank shaft position sensor recognizes and outputs a plurality of teeth.

Referring to FIG. 6, an apparatus for diagnosing misfire of a multi-cylinder engine according to an embodiment of the present invention includes a crank angle sensor 10 and a controller 20 ′. The controller 20' may be an ECU, and the crank angle sensor 10 is disposed around the target wheel 40 on the engine crankshaft 30, and a tooth signal required for engine speed calculation according to the rotation of the target wheel 40 (Tooth time signal) signal is generated.

A plurality of teeth are formed on the outer circumferential surface of the target wheel 40 to measure the angular velocity of the crankshaft 30, and when the target wheel 40 rotates, the crank angle sensor 20' The controller 20 ′ calculates the angular velocity of the engine crankshaft 30 using the time information for detecting the tooth. And the engine speed is calculated from the calculated angular speed.

The controller 20' controls the engine speed by controlling the energized state of the fuel injector 60 and the ignition coil 50 according to the driver's acceleration or deceleration request through a hand accelerator operation (not shown), as well as the crank. From the tooth time signal of each sensor 10, the engine speed change of one engine cycle that is the target of misfire analysis is analyzed. And, using the analysis result, it diagnoses whether there is a misfire.

Misfire, as mentioned in the background art, refers to a phenomenon in which fuel injected into the engine cylinder is discharged to the outside without burning. When a misfire occurs, the periodicity of the tooth signal (Tooth time siganal, the time it takes for the engine crankshaft to rotate at a certain angle) is impaired as the energy source that accelerates the engine speed is not generated in the explosion (combustion expansion) stroke.

Misfire is caused by no combustion of fuel in the explosion stroke -> no combustion pressure -> reduction in piston speed -> reduction in crankshaft rotational momentum, resulting in a longer tooth time and a decrease in engine speed. That is, when a misfire occurs, the energy source that drives the engine does not occur, so the engine speed decreases. Therefore, by analyzing the engine speed in one cycle, it is possible to diagnose whether the misfire occurs.

Another embodiment of the present invention is to accurately and quickly diagnose/detect a misfire occurring in a multi-cylinder engine by using the change characteristic of engine speed that appears during a misfire. For this purpose, the controller 20' applied to the present embodiment ) Includes a linear trend removal unit 22 and a speed increase/decrease calculation unit 25. It also includes a velocity amplitude calculation unit 27 and a misfire diagnosis unit 29.

The configuration of each part constituting the controller will be described in more detail.

The linear trend removal unit 22 removes a linear trend from the tooth signal output from the crank angle sensor 10 during one cycle. This is because if the linear trend is not removed from the signal data output from the crank angle sensor 10, an overshoot occurring in normal ignition may affect the engine speed fluctuation of the cylinder where the misfire occurs, that is, the cylinder.

If the overshoot from normal ignition affects the engine speed fluctuation of the cylinder where the misfire occurs, it may be difficult to accurately and accurately diagnose whether or not the misfire occurs. Therefore, by removing the linear trend from the output signal data of the crank angle sensor 10 collected during one cycle (Linear detrend), it is desirable to remove the effect of the overshoot on the engine speed of the misfire occurrence cylinder in advance.

Removing the linear trend from all tooth signals in a cycle means in a different sense, subtracting these averages from the engine speed that is calculated from all tooth signals during one cycle.

The speed increase/decrease calculation unit 25 extracts the engine speed at the start and end points for each cylinder by using the tooth signals at two specific positions per cylinder among the tooth signals from which the linear trend has been removed, and extracts the start and end points for each cylinder. Calculate the speed increase or decrease from the engine speed. Here, the speed increase or decrease means the difference between the two engine speeds at the start and end points of each cylinder, as mentioned above.

For example, in a four-cylinder engine with four cylinders, a total of four speed increases and decreases are calculated for each cylinder in one cycle. Of course, it is not limited to a four-cylinder engine, and the engine may be a two or more multi-cylinder engine.

The two specific positions for collecting the tooth signals required for calculating the speed increase or decrease may preferably be the rotational positions of the target wheel 40 set corresponding to the crankshaft rotational positions at the beginning of the suction stroke and the end of the exhaust stroke for each cylinder. For example, in the case of a four-cylinder engine, it may be specified as the rotational position of the target wheel 40 corresponding to the crankshaft rotational position at the beginning of the intake stroke and the end of the exhaust stroke for each cylinder in one cycle.

The velocity amplitude calculation unit 27 calculates the velocity amplitude for each cylinder by using the tooth signal at two specific positions different from the position at which the tooth signal required to derive the velocity increase or decrease among the tooth signals from which the linear trend is removed. Here, the speed amplitude means the difference between the maximum value and the minimum value of the engine speed calculated from the tooth signal for each cylinder, as mentioned above.

Similarly, in the case of a four-cylinder engine as an example, a total of four speed amplitudes are calculated, one per cylinder in one cycle.

The other two specific positions for collecting the tooth signal required for calculating the velocity amplitude are preferably the rotational positions of the target wheel 40 at which the maximum and minimum engine speed values for each cylinder appear, and through simulation or repeated experiments in the same simulation environment, It may be a fixed value set for each cylinder by obtaining the target wheel rotational position at which the maximum and minimum engine speed values appear, and deriving the average value of the obtained rotational positions.

Of course, it is not limited to using the rotation position of the target wheel 40 for calculating the velocity amplitude as a fixed value. Because the rotational position of the target wheel 40 at which the maximum and minimum engine speed values appear for each cycle may vary slightly due to combustion characteristics, the position at which the angular speed of the target wheel 40 for each cylinder is the maximum and the minimum at each cycle It is also possible to extract the velocity amplitude for each cylinder from the tooth signal of

The speed increase and decrease and the speed amplitude will be described in more detail with reference to FIG. 7.

7 is an exemplary diagram for explaining the speed increase/decrease and the speed amplitude, there are four cylinders, that is, the number 1 (Cyl 1) -3 (Cyl 3) -4 (Cyl 4) -2 (Cyl 2) In a four-cylinder engine in which combustion is performed in the order of cylinders (cylinders), the tooth signal output from the crank angle sensor 10 is classified for each cylinder as the engine speed change (y-axis direction) according to the crankshaft rotation angle change (x-axis direction). This is the engine speed curve shown.

Referring to FIG. 7, the speed increase/decrease (D3) is a point (TDC1) on the speed curve including the engine speed (TDC1_rpm) component calculated from the tooth signal at the initial stage of the intake stroke for each cylinder and the rotation position component of the target wheel 40. And, it can be calculated from the difference between the engine speed (TDC3_rpm) component calculated from the tooth signal at the end of the exhaust stroke for each cylinder and another point (TDC3) on the speed curve including the rotational position component of the target wheel 40.

That is, the speed increase or decrease (D3) refers to the difference between the engine speed at the start (at the beginning of the suction stroke, TDC1) and the engine speed at the end (end of the exhaust stroke, TDC3) for each cylinder on the engine speed curve of FIG. It can be specified as a linear distance in the y-axis direction between TDC1 and TDC3 per cylinder.

In addition, the speed amplitude (D4) refers to the difference between the maximum engine speed value (rpm _max ) per cylinder and the minimum value (rpm _min ) among engine speed-related information calculated from the tooth signal per cylinder. It may be specified as a linear distance in the y-axis direction between the point at which the value (rpm _max ) and the point at which the minimum value (rpm _min ) appears.

In the misfire diagnosis unit 28, the difference between the velocity increase/decrease D3 for each cylinder derived by the speed increase/decrease calculation unit 25 and the velocity amplitude D4 for each cylinder derived by the velocity amplitude calculation unit 27, that is, D3 and Analyze the difference between D4 and diagnose whether or not it is misfired by cylinder. As an example, by comparing the difference between D3 and D4 with a threshold for each cylinder mapped to a recording device, it is possible to diagnose whether or not a misfire per cylinder.

As another example, the misfire diagnosis unit 28 includes the difference between D3 and D4 for each cylinder (D4-D3) and D3' and D4' of the same cylinder obtained by the same method in the previous cycle, as illustrated in FIG. 8 to be referred to later. By comparing and analyzing the difference of (D4'-D3'), it is also possible to diagnose whether or not the misfires for each cylinder.

In normal ignition, an energy source that accelerates the engine speed is generated in the explosion stroke for each cylinder. Therefore, the difference (D4-D3) between the speed amplitude (D4), which is the difference between the maximum and minimum engine speed values for each cylinder, is the difference (D4-D3), which is the difference between the engine speed at the start and end of each cylinder, is relatively small. In the case of a four-cylinder engine, if explosion (expansion combustion) occurs normally in the order of the specified order (No. 1 (Cyl 1)-3 (Cyl 3)-4 (Cyl 4)-2 (Cyl 2))) This is because the overall engine speed fluctuations are not large.

On the other hand, when a misfire occurs, the D4-D3 appear to have a distinctly large width compared to the normal ignition (cylinders 1, 4, and 2 in FIG. 7) (unit cycle section of cylinder 3 in FIG. 7). When a misfire occurs in a specific cylinder (cylinder 3 in FIG. 7), since there is no energy addition due to the explosion, the engine speed amplitude (D4) of the cylinder is bound to be relatively large compared to the other cylinders.

Therefore, by analyzing the above-described D4-D3 for each cylinder, it is possible to accurately diagnose whether a misfire has occurred, as well as how many times a misfire has occurred in the cylinder. The present invention diagnoses whether a misfire occurs by using the fact that the difference between the engine speed increase/decrease D3 and the speed amplitude D4 for each cylinder appears in distinctly different patterns depending on whether a misfire occurs.

8 shows the difference between the speed increase/decrease (D3) and the speed amplitude (D4) for each cylinder in the current cycle among the misfire diagnosis methods performed by the misfire diagnosis unit, and the speed increase/decrease (D3') of the same cylinder obtained by the same method in the previous cycle. It is a diagram for explaining the process of diagnosing whether or not misfire for each cylinder is compared with the difference in the velocity amplitude (D4').

Figure 8 (a) is an engine speed curve showing the amount of change in engine speed according to the crankshaft rotation angle change by dividing the tooth signal output by the crank angle sensor for each cylinder during the previous cycle, and Figure 8 (b) is It is an engine speed curve expressed as the amount of engine speed change according to the crankshaft rotation angle change by dividing the tooth signal output from the crank angle sensor during the cycle by cylinder.

Referring to FIG. 8 and FIG. 7 together, as mentioned above, in normal ignition, since an energy source that accelerates the engine speed is generated in the explosion stroke for each cylinder, the engine speed amplitude for each cylinder is small, and thus the difference between the speed increase and decrease and the speed amplitude (D4 -D3) is also relatively small. On the other hand, in a true story without the addition of energy due to an explosion, since the velocity amplitude increases, the difference (D4-D3) is also relatively large.

8, the difference between D3' and D4' in the previous cycle (Fig. 8(a)) excluding the unit cycle section of cylinder 1 (unit cycle section of cylinder 3, 4, and 2). When comparing the difference between D3 and D4 by the same cylinder in the current cycle (Fig. 8(b)), it can be intuitively seen that the difference between D3' and D4' for each cylinder and between D3 and D4 is not large.

Therefore, when comparing the difference between D3 and D4 for each cylinder of the current cycle and the difference between D3' and D4' of the same cylinder of the previous cycle, the difference between D3 and D4 is similar to or set to the difference between D3' and D4' of the previous cycle. When within the error range, the misfire diagnosis unit 28 may diagnose that the cylinder, for example, cylinders 3, 4, and 2 in FIG. 4 normally ignites.

In contrast, looking at the unit cycle section of cylinder 1 in FIG. 8, compared to the difference between D3' and D4' in the previous cycle (FIG. 8(a)), D3 and D3 in the current cycle (FIG. 8(b)) It can be seen that the difference between D4s has grown to a degree that can be clearly compared. In other words, it can be interpreted that in the current cycle, cylinder 1 did not explode normally and thus did not generate an energy source that accelerates the engine speed.

Therefore, if there is a difference between D3' and D4' in the previous cycle (Fig. 8(a)) and a clear difference between D3 and D4 in the current cycle (Fig. 8(b)), the misfire diagnosis unit 28 It can be diagnosed that a misfire has occurred in the cylinder (Cylinder 1). Preferably, if the absolute value of the difference between D4-D3 and D4'-D3' for each cylinder (|(D4'-D3')-(D4-D3)|) is greater than a preset threshold, it is diagnosed as a misfire. Can be configured to

On the other hand, if the same cylinder in the previous cycle is diagnosed as a misfire, for example, if cylinder 1 was diagnosed as a misfire immediately before, on the contrary, D4'-D3' in the previous unit cycle section and D4 in the current unit cycle section. -If the absolute value of the difference between D3 (|(D4'-D3')-(D4-D3)|) is greater than the preset threshold, it is diagnosed as normal ignition, and if it is equal to or less than the threshold, It can be diagnosed as continuous misfire.

As described above, the misfire diagnosis apparatus of a multi-cylinder engine according to another embodiment of the present invention refers to a difference between a maximum value and a minimum value of an engine speed for each cylinder and a speed increase or decrease, which means the difference in engine speed at the start and end points of each cylinder. By diagnosing whether or not a misfire has occurred by comparing the speed amplitudes, it is possible to accurately diagnose and detect not only the misfire, but also the cylinder where the misfire has occurred, that is, the position of the cylinder.

Hereinafter, a misfire diagnosis process for a multi-cylinder engine performed by the misfire diagnosis apparatus for a multi-cylinder engine according to another embodiment described above will be described with reference to the flowchart of FIG. 9.

9 is a flowchart illustrating a method for diagnosing a misfire of a multi-cylinder engine according to an embodiment of the present invention. For convenience of explanation, the configuration shown in FIG. 6 will be described with reference to the corresponding reference number.

9, the misfire diagnosis performed by the misfire diagnosis apparatus of a multi-cylinder engine according to another embodiment of the present invention includes a linear trend removal step (S100'), a speed increase/decrease calculation step (S200'), and a speed amplitude calculation. It is carried out through step S300' and misfire diagnosis step S400'. Hereinafter, the operation or processing performed in each step will be described in more detail.

In the linear trend removal step S100', the rotation of the target wheel 40 is detected during one cycle, and a linear trend is removed from the tooth signal output from the crank angle sensor 10 (Linear Detrend). This is because, if the linear trend is not removed from the signal data output from the crank angle sensor, the overshoot occurring in normal ignition can affect the engine speed fluctuation of the cylinder where the misfire occurs, that is, the cylinder.

In some cases, in the linear trend removal step (S100'), the tooth signal of the crank angle sensor 10 is selected at regular intervals to reduce the amount of signal data to be processed, thereby greatly reducing the computational load that the controller has to bear. A sampling process may be included. In this case, the maximum down-sampling may be a case where the tooth signal is collected only at the beginning of the intake stroke and the end of the exhaust stroke for each cylinder, and only the positions where the maximum and minimum engine speed values appear.

In the speed increase/decrease calculation step S200', a task of calculating the speed increase/decrease for each cylinder is performed using the tooth signals at two specific positions for each cylinder among the tooth signals from which the linear trend has been removed. More specifically, the engine speed at the start and end points of each cylinder is extracted using the two tooth signals at the start and end points of each cylinder among the tooth signals from which the linear trend has been removed, and the speed increases or decreases from the difference between the extracted two engine speeds. To derive.

For example, in a four-cylinder engine with four cylinders, a total of four speed increases and decreases are calculated for each cylinder in one cycle.

The two specific positions for collecting the tooth signals required for calculating the speed increase or decrease may preferably be the rotational positions of the target wheel 40 set corresponding to the crankshaft rotational positions at the beginning of the suction stroke and the end of the exhaust stroke for each cylinder. For example, in the case of a four-cylinder engine, it may be specified as the rotational position of the target wheel 40 corresponding to the crankshaft rotational position at the beginning of the intake stroke and the end of the exhaust stroke for each cylinder in one cycle.

In the velocity amplitude calculation step S300', the velocity amplitude for each cylinder is calculated by using the tooth signal at two specific positions different from the position at which the tooth signal required to derive the velocity increase or decrease among the tooth signals from which the linear trend is removed. Here, the speed amplitude means the difference between the maximum value and the minimum value of the engine speed calculated from the tooth signal for each cylinder, as mentioned above.

Similarly, in the case of a four-cylinder engine as an example, a total of four speed amplitudes are calculated, one per cylinder in one cycle.

The other two specific positions for collecting the tooth signal required for calculating the velocity amplitude are preferably the rotational positions of the target wheel 40 at which the maximum and minimum engine speed values for each cylinder appear, and through simulation or repeated experiments in the same simulation environment, It may be a fixed value set for each cylinder by obtaining the target wheel rotational position at which the maximum and minimum engine speed values appear, and deriving the average value of the obtained rotational positions.

Of course, it is not limited to using the rotation position of the target wheel 40 for calculating the velocity amplitude as a fixed value. Because the rotational position of the target wheel 40 at which the maximum and minimum engine speed values appear for each cycle may vary slightly due to combustion characteristics, the position at which the angular speed of the target wheel 40 for each cylinder is the maximum and the minimum at each cycle It is also possible to extract the velocity amplitude for each cylinder from the tooth signal of.

In the final step, the misfire diagnosis step (S400'), the difference between the speed increase/decrease (D3) for each cylinder derived in step S200' and the velocity amplitude (D4) for each cylinder derived in step S300', that is, the difference between D3 and D4, is analyzed. Diagnose whether there is a misfire by cylinder As an example, by comparing the difference between D3 and D4 with a threshold for each cylinder mapped to the recording device, it is possible to diagnose whether or not a misfire for each cylinder has occurred.

As another example, in the misfire diagnosis step (S400'), as mentioned previously, the difference between D3 and D4 for each cylinder (D4-D3) and the difference between D3' and D4' of the same cylinder obtained by the same method in the previous cycle (D4'). -D3') can be compared and analyzed to diagnose misfire by cylinder.

In normal ignition, an energy source that accelerates the engine speed is generated in the explosion stroke for each cylinder. Therefore, the difference (D4-D3) between the speed amplitude (D4), which is the difference between the maximum and minimum engine speed values for each cylinder, is the difference (D4-D3), which is the difference between the engine speed at the start and end of each cylinder, is relatively small. In the case of a four-cylinder engine, if explosion (expansion combustion) occurs normally in the order of the specified order (No. 1 (Cyl 1)-3 (Cyl 3)-4 (Cyl 4)-2 (Cyl 2))) This is because the overall engine speed fluctuations are not large.

On the other hand, when a misfire occurs, the D4-D3 appear to have a distinctly large width compared to the normal ignition (cylinders 1, 4, and 2 in FIG. 7) (unit cycle section of cylinder 3 in FIG. 7). When a misfire occurs in a specific cylinder (cylinder 3 in FIG. 7), since there is no energy addition due to the explosion, the engine speed amplitude (D4) of the cylinder is bound to be relatively large compared to the other cylinders.

Therefore, by analyzing the above-described D4-D3 for each cylinder, it is possible to accurately diagnose whether a misfire has occurred and how many times a misfire has occurred in the cylinder. The present invention diagnoses whether a misfire occurs by using the fact that the difference between the engine speed increase/decrease (D3) and the speed amplitude (D4) for each cylinder is clearly different depending on whether a misfire occurs.

In another embodiment of the present invention discussed above, some information on engine characteristics that can clearly distinguish between normal firing and misfire (the initial engine speed of the intake stroke for each cylinder and the end of the exhaust stroke, which can be determined by the output signal of the crank angle sensor) Misfire can be diagnosed using only the engine speed and the maximum and minimum engine speed for each cylinder.

In other words, by diagnosing/detecting a true story with only the minimum main information that can clearly determine whether a true story has been made, it is possible to diagnose and detect a true story with high accuracy while simplifying the process for diagnosing/detecting a true story, and without additional hardware configuration. Since it can be implemented only with software, it has the advantage of low development cost.

In addition, another embodiment of the present invention is divided into each cylinder by comparing the speed increase or decrease, which means the difference between the engine speed at the start and end of each cylinder, and the speed amplitude, which means the difference between the maximum and minimum engine speed values for each cylinder. By diagnosing, there is an advantage of being able to accurately diagnose and detect not only the occurrence of a misfire, but also the cylinder, that is, the position of the cylinder where the misfire has occurred.

In the present invention, a four-cylinder engine has been described as an example to diagnose whether a misfire occurs and a misfire occurs, but the process of diagnosing a misfire occurrence and a misfire cylinder according to the present invention is not limited to a four-cylinder engine. It is natural that it can be applied to various types of engines such as multi-cylinder engines of more than cylinders, for example, six-cylinder, eight-cylinder, and 16-cylinder engines.

In the above detailed description of the present invention, only specific embodiments according thereto have been described. However, it should be understood that the present invention is not limited to a particular form mentioned in the detailed description, but rather, it is understood to include all modifications, equivalents, and substitutes within the spirit and scope of the present invention as defined by the appended claims. Should be.

10: crank angle sensor
20, 20': controller
30: crankshaft
40: target wheel
50: ignition coil
60: fuel injector

Claims (19)

As a method of diagnosing whether a multi-cylinder engine misfires for each cylinder by using a tooth time signal output by a crank angle sensor that recognizes the tooth of a target wheel,
a) Linear trend removal step of removing a linear trend from the tooth signal output by the crank angle sensor during one cycle
b) a speed trend line generation step of generating a speed trend line for each cylinder using the tooth signals at two specific positions for each cylinder among the tooth signals from which the linear trend has been removed;
c) Among the tooth signals from which the linear trend has been removed, the maximum and minimum engine speed values for each cylinder are calculated using the tooth signals at two specific positions for each cylinder, and the shortest distance from the calculated maximum and minimum engine speed values to the speed trend line A distance calculation step of calculating (D1, D2);
d) a misfire diagnosis step of calculating a comparison value from the two shortest distances (D1, D2) for each cylinder calculated in step c), and diagnosing a misfire for each cylinder by analyzing the calculated comparison value; a multi-cylinder engine comprising: How to diagnose misfire.
The method of claim 1,
The two specific positions for obtaining the speed trend line in step b) are the rotational positions of the target wheel set corresponding to the rotational positions of the crankshafts at the beginning of the intake stroke and the end of the exhaust stroke for each cylinder,
In step c), the other two specific positions are the rotational positions of the target wheel at which the maximum and minimum engine speed values for each cylinder are displayed.
The method of claim 2,
The speed trend line is,
A point on the engine speed curve including the engine speed (TDC1_rpm) component calculated from the tooth signal at the beginning of the suction stroke for each cylinder and the rotation position component of the target wheel at the beginning of the suction stroke;
Misfire diagnosis method of a multi-cylinder engine defined as a straight line passing through another point on the engine speed curve including the engine speed (TDC3_rpm) component calculated from the tooth signal at the end of the exhaust stroke for each cylinder and the rotation position component of the target wheel at the end of the exhaust stroke .
The method of claim 1,
The comparison value in step d) is defined as a product comparison value (D1XD2) of two shortest distances per cylinder.
The method of claim 4,
In step d),
Misfire diagnosis method of a multi-cylinder engine for diagnosing misfire by cylinder by comparing the comparison value (D1XD2) defined as the product of two shortest distances per cylinder with a threshold value _per cylinder mapped to a recording device (Threshold ₁ ).
The method of claim 4,
In step d),
The comparison value (D1XD2), which is defined as the product of the two shortest distances per cylinder, is compared with the previous comparison value (D1'XD2') of the same cylinder obtained by the same method in the previous cycle to diagnose misfire for each cylinder. How to diagnose misfire.
The method of claim 6,
The difference ((D1'XD2')-(D1XD2)) between the previous comparison value (D1'XD2') and the comparison value (D1XD2) is compared with the threshold value (Threshold ₂ ) mapped to the recording device to see if the cylinder is misfired. Misfire diagnosis method of a multi-cylinder engine to diagnose.
As a method of diagnosing whether a multi-cylinder engine misfires for each cylinder by using a tooth time signal output by a crank angle sensor that recognizes the tooth of a target wheel,
a) a linear trend removal step of removing a linear trend from the tooth signal output from the crank angle sensor during one cycle;
b) Among the tooth signals from which the linear trend has been removed, the engine speed at the start and end points of each cylinder is calculated using the tooth signals at two specific positions for each cylinder, and the speed increase or decrease, which is the difference between the two engine speeds at the start and end points for each cylinder. A speed increase/decrease calculation step of calculating (D3);
c) Among the tooth signals from which the linear trend has been removed, the maximum and minimum engine speed values for each cylinder are calculated using the tooth signals at two specific positions for each cylinder, and the speed amplitude, which is the difference between the calculated maximum and minimum engine speed values for each cylinder ( A speed amplitude calculation step of calculating D4);
d) a misfire diagnosis step of diagnosing a misfire for each cylinder by analyzing the difference between the speed increase/decrease (D3) for each cylinder derived in step b) and the speed amplitude for each cylinder (D4) derived in step c). How to diagnose misfire of a cylinder engine.
The method of claim 8,
The two specific positions in step b) are the rotational positions of the target wheel set corresponding to the rotational positions of the crankshafts at the beginning of the intake stroke and the end of the exhaust stroke for each cylinder,
In step c), the other two specific positions are the rotational positions of the target wheel at which the maximum and minimum engine speed values for each cylinder are displayed.
The method of claim 1,
In step d),
Misfire diagnosis method of a multi-cylinder engine that diagnoses misfire for each cylinder by comparing the difference between the speed increase/decrease (D3) and the speed amplitude ((D4) for each cylinder with the threshold for each cylinder mapped to the recording device.
The method of claim 1,
In step d),
Misfire diagnosis method of a multi-cylinder engine by comparing the difference between speed increase/decrease (D3) and speed amplitude (D4) for each cylinder with the difference between the speed increase/decrease and speed amplitude of the same cylinder obtained in the previous cycle.
As a device that diagnoses whether a multi-cylinder engine is misfired for each cylinder,
A crank angle sensor disposed around a target wheel of the engine crankshaft to generate a tooth time signal required for engine speed calculation;
Including; a controller that analyzes the engine speed change of one cycle from the tooth signal of the crank angle sensor and diagnoses whether a misfire occurs using the analysis result,
The controller,
A linear trend removal unit that removes a linear trend from the tooth signal output from the crank angle sensor during one cycle;
A speed trend line generator for generating a speed trend line for each cylinder using the tooth signals at two specific positions for each cylinder among the tooth signals from which the linear trend has been removed;
Among the tooth signals from which the linear trend has been removed, the maximum and minimum engine speed values for each cylinder are calculated using the tooth signals at two specific positions for each cylinder, and the shortest distance from the calculated engine speed maximum and minimum values to the speed trend line (D1 , A distance calculation unit that calculates D2) and
Misfire diagnosis device for a multi-cylinder engine including a misfire diagnosis unit that calculates a comparison value from the two shortest distances (D1, D2) for each cylinder calculated through the distance calculation unit, and analyzes the calculated comparison value to diagnose misfire for each cylinder .
The method of claim 12,
The speed trend line generator,
A point on the engine speed curve including the engine speed (TDC1_rpm) component calculated from the tooth signal at the beginning of the suction stroke for each cylinder and the rotation position component of the target wheel at the beginning of the suction stroke;
The speed trend line (L1) is generated by connecting another point on the engine speed curve including the engine speed (TDC3_rpm) component calculated from the tooth signal at the end of the exhaust stroke for each cylinder and the rotation position component of the target wheel at the end of the exhaust stroke. Misfire diagnosis device for cylinder engines.
The method of claim 12,
The misfire diagnosis unit,
The two per cylinder of cylinder-specific threshold value map the comparison value (D1XD2) is defined as the product to the recording apparatus of the shortest distance (Threshold ₁₎ and by the diagnostic device of the multi-cylinder engine misfire diagnosing whether per cylinder misfire comparison.
The method of claim 12,
The misfire diagnosis unit,
Misfire of a multi-cylinder engine that diagnoses misfire for each cylinder by comparing the comparison value (D1XD2) defined as the product of the two shortest distances per cylinder with the previous comparison value (D1'XD2') of the same cylinder obtained by the same method in the previous cycle. Diagnostic device.
The method of claim 15,
The misfire diagnosis unit,
The difference ((D1'XD2')-(D1XD2)) between the previous comparison value (D1'XD2') and the comparison value (D1XD2) is compared with the threshold value (Threshold ₂ ) mapped to the recording device to see if the cylinder is misfired. Misfire diagnosis device of a multi-cylinder engine to diagnose.
As a device that diagnoses whether a multi-cylinder engine is misfired for each cylinder,
A crank angle sensor disposed around a target wheel of the engine crankshaft to generate a tooth time signal required for engine speed calculation;
Including; a controller that analyzes the engine speed change of one cycle from the tooth signal of the crank angle sensor and diagnoses whether a misfire occurs using the analysis result,
The controller,
A linear trend removal unit that removes a linear trend from the tooth signal output from the crank angle sensor during one cycle;
Among the tooth signals from which the linear trend has been removed, the engine speed at the start and end points of each cylinder is calculated using the tooth signals at two specific positions per cylinder, and the speed increase or decrease (the difference between the two engine speeds at the start and end points for each cylinder) A speed increase/decrease calculation unit that calculates D3),
Among the tooth signals from which the linear trend has been removed, the maximum and minimum engine speed values for each cylinder are calculated using the tooth signals at two specific positions for each cylinder, and the speed amplitude (D4), which is the difference between the calculated maximum and minimum engine speed values for each cylinder. A velocity amplitude calculator that calculates
Misfire diagnosis device for a multi-cylinder engine including a misfire diagnosis unit that diagnoses a misfire for each cylinder by analyzing the difference between the speed increase/decrease (D3) and the speed amplitude (D4) for each cylinder.
The method of claim 17,
The misfire diagnosis unit,
Misfire diagnosis device for multi-cylinder engines that diagnoses misfire by cylinder by comparing the difference between speed increase/decrease (D3) and speed amplitude (D4) for each cylinder with the threshold value for each cylinder mapped to the recording device.
The method of claim 17,
The misfire diagnosis unit,
Multi-cylinder diagnosing misfire by cylinder by comparing the difference between speed increase/decrease (D3) and speed amplitude (D4) for each cylinder with the difference between speed increase/decrease (D3') and speed amplitude (D4') of the same cylinder obtained in the previous cycle. Engine misfire diagnosis device.

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