KR102554010B1 - Misfire diagnosis method and device of engine - Google Patents

Abstract

The present invention relates to an engine misfiring diagnosis method and apparatus for diagnosing misfiring in an engine using a tooth signal output from a crank angle sensor, wherein the engine misfiring diagnosis method includes teeth output by the crank angle sensor during one cycle. A linear trend removal step of removing the linear trend from the signal, a speed trend line generation step of generating a speed trend line from tooth signals at two specific positions preset among tooth signals from which the linear trend has been removed, and a slope of the speed trend line and a preset threshold A misfire diagnosis step of diagnosing misfire by comparing the values, and a threshold value correction step of correcting the threshold value when the slope of the generated speed trend line differs from the slope of the pre-stored speed trend line by a predetermined value or more. In this way, since the misfire diagnosis index can be corrected in correspondence with the target vehicle, an effect of more accurately diagnosing misfire can be obtained.

Description

Engine misfire diagnosis method and device {MISFIRE DIAGNOSIS METHOD AND DEVICE OF ENGINE}

The present invention relates to a method and apparatus for diagnosing a misfire in an engine, and more particularly, to a method and apparatus for diagnosing a misfire in an engine capable of correcting a misfire diagnosis indicator for determining misfire using engine speed information.

A 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 may be discharged as it is, adversely affecting air pollution, or unburned fuel may burn in the catalyst and damage the catalyst.

Accordingly, in the case of automobiles, air pollution or catalyst damage is prevented by diagnosing misfire by mounting a misfire detection logic in the ECU. In the case of general mass-produced vehicles, an engine roughness method for 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 the misfire detection area specified by CARB (California Air Quality Management Agency), but has limitations in terms of accuracy in diagnosing misfires due to post oscillation.

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

However, these methods (methods using ion current or methods using combustion pressure as a characteristic) increase vehicle prices because new functions or new sensors must be added to existing vehicles, which is why they are applied to mass-produced vehicles. It is bound to be burdensome from a cost standpoint.

In order to solve this problem, Korean Patent Registration No. 10-2163796 (hereinafter referred to as 'Patent Document 1') has a cylinder calculated from a tooth time signal (the time required for the engine crankshaft to rotate at a certain angle) Disclosed is a misfire diagnosis method and apparatus for a multi-cylinder engine capable of accurately diagnosing and detecting misfiring and a cylinder in which misfiring occurs using information on each speed.

The misfire diagnosis method and apparatus of Patent Document 1 is the slope and threshold of the speed trend line calculated from the engine speed at the beginning of the intake stroke and the engine speed at the end of the exhaust stroke for each cylinder, which can be known from the signal output by the crank angle sensor without any additional configuration. By comparing the values, misfiring can be effectively diagnosed.

However, in Patent Document 1, after calculating the slope and threshold of the speed trend line in advance in the reference vehicle, the misfire is diagnosed by fixing this value to the target vehicles as a reference value.

However, even for the same vehicle, the slope of the speed trend line may vary due to the unevenness of the reciprocating motion of the piston of the engine, torsional vibration of the crankshaft, and machining tolerance of the tooth, etc. there is

Korean Patent Registration No. 10-2163796 (2020.09.29)

The present invention has been devised to solve the above problems, and provides an engine misfire diagnosis method and apparatus capable of correcting a misfire diagnosis index for determining misfire using engine speed information in correspondence with a target vehicle. It has its purpose.

In order to achieve the above object, an engine misfire diagnosis method according to a preferred embodiment of the present invention uses a tooth time signal output from a crank angle sensor to diagnose misfire of an engine. It's about how.

More specifically, the method for diagnosing a misfire of the engine includes a linear trend detrend step of removing a linear trend from a tooth signal output by the crank angle sensor during one cycle; A speed trend line generating step of generating a speed trend line from tooth signals at two specific positions set in advance among the tooth signals from which the linear trend has been removed; a misfire diagnosis step of diagnosing misfire by comparing the slope of the speed trend line with a preset threshold; and a threshold value correction step of correcting the threshold value when the slope of the generated speed trend line differs from the slope of the pre-stored speed trend line by a predetermined value or more.

Here, in the threshold value correction step, if the slope of the speed trend line generated in the steady ignition state differs from the slope of the speed trend line in the steady ignition state stored in advance by a predetermined value or more, the threshold value is corrected accordingly.

More specifically, the threshold value correction step may be performed by adding a correction value obtained by subtracting the slope value of the speed trend line in the steady ignition state stored in advance from the slope value of the speed trend line generated in the steady ignition state to a preset threshold value for correction. there is.

In the speed trend line generation step, a point on the engine speed curve including the engine speed component calculated from the tooth signal at the beginning of the intake stroke and the time component at the beginning of the intake stroke, and the engine speed component and exhaust calculated from the tooth signal at the end of the exhaust stroke It can be made to create a speed trend line by connecting another point on the engine speed curve that includes the end-of-stroke time component.

In the misfire diagnosing step, if the slope of the speed trend line is less than the threshold value, misfire is diagnosed, and if the slope is equal to or greater than the threshold value, normal ignition is diagnosed.

In order to achieve the above object, an engine misfire diagnosis device according to a preferred embodiment of the present invention is disposed around a target wheel of an engine crankshaft to generate a tooth time signal necessary for calculating engine speed a crank angle sensor; and a controller analyzing engine speed change in one cycle from the tooth signal of the crank angle sensor and diagnosing misfire using the analysis result.

Here, the controller includes: a linear trend removal unit for removing a linear trend from a tooth signal output from the crank angle sensor during one cycle; a speed trend line generation unit for generating a speed trend line for each cylinder using tooth signals at two specific positions preset for each cylinder among tooth signals from which the linear trend has been removed; a misfire diagnosis unit for diagnosing misfire by comparing the slope of the generated speed trend line with a preset threshold; and a threshold value correction unit correcting the threshold value when the slope of the generated speed trend line is different from the slope of the pre-stored speed trend line by a predetermined value or more.

The threshold value correction unit may be configured to correct the threshold value in response to a difference between the slope of the speed trend line generated in the steady ignition state and the slope of the speed trend line in the steady ignition state stored in advance by a predetermined value or more.

More specifically, the threshold correction unit may be configured to correct by adding a correction value obtained by subtracting the slope value of the speed trend line in the steady ignition state stored in advance from the slope value of the speed trend line generated in the steady ignition state to a preset threshold value. .

The speed trend line generation unit calculates a point on the engine speed curve including the engine speed component calculated from the tooth signal at the beginning of the intake stroke and the time component at the beginning of the intake stroke, and the engine speed component and exhaust stroke calculated from the tooth signal at the end of the exhaust stroke It can be made to create a speed trend line by connecting another point on the engine speed curve that includes the terminal time component.

The misfire diagnosis unit may be configured to diagnose a misfire when the slope of the speed trend line is less than the threshold value, and to diagnose a normal ignition when the slope is equal to or greater than the threshold value.

According to the method and apparatus for diagnosing misfire of an engine according to the present invention, a misfire diagnosis index for determining misfire using engine speed information can be corrected in correspondence with a target vehicle, thereby obtaining an effect of more accurately diagnosing misfire. can

1 is a diagram schematically showing an apparatus for diagnosing a misfire of an engine according to an embodiment of the present invention;
2 is a graph showing engine speed variation according to elapsed time before and after removing the linear trend from tooth signal data output from a crank angle sensor in an engine misfire diagnosis apparatus according to an embodiment of the present invention;
3 is a graph showing a process of generating a speed trend line in a method for diagnosing a misfire of an engine according to an embodiment of the present invention;
4 is a three-dimensional graph showing the result of extracting the slope of the speed trend line for each cylinder of a 4-cylinder engine in the method for diagnosing misfiring of an engine according to an embodiment of the present invention;
5 is a graph showing a speed trend line (DL) in a pre-stored normal ignition state for cylinder No. 1 and a speed trend line (RL) in a normal ignition state actually generated in cylinder No. 1;
6 is a flowchart schematically illustrating a method for diagnosing a misfire of an engine according to an embodiment of the present invention;
7 is a flowchart schematically illustrating a threshold value correction step in a method for diagnosing a misfire of an engine according to an embodiment of the present invention.

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

Since the present invention can make various changes and have various embodiments, specific embodiments will be illustrated in the drawings and described in detail in the detailed description. This is not intended to limit the present invention to specific embodiments, and should be construed as including all changes, equivalents, or substitutes included in the spirit and technical scope of the present invention.

Terms used in this application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions may include plural expressions unless the context clearly dictates otherwise.

Unless defined otherwise, all terms used herein, including technical or scientific terms, may have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention belongs. Terms such as those defined in commonly used dictionaries may be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in the present application, interpreted in an ideal or excessively formal meaning. It may not be.

Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings.

Among the terms used in describing the embodiment of the present invention, "one cycle" is a section in which the engine crankshaft rotates two times, including intake-compression-explosion (combustion expansion)-exhaust stroke for each cylinder once. means the interval. For example, in the case of a four-cylinder engine, four cylinders perform intake-compression-explosion-exhaust in a predetermined order to rotate the crankshaft twice, completing one cycle.

In addition, among the terms used in describing the embodiment of the present invention, a "speed trend line" is a tooth signal output from a crank angle sensor that detects the rotation angle or rotation position of the crankshaft during the above-described one cycle. This means a straight line generated using a tooth signal. Here, the "two specific positions" may be the rotational positions of the target wheel set in correspondence with the respective crankshaft rotational positions at the beginning of the intake stroke and the end of the exhaust stroke for each cylinder.

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

1 is a diagram schematically showing an apparatus for diagnosing a misfire of an engine according to an embodiment of the present invention.

Referring to FIG. 1 , an engine misfire diagnosis apparatus 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 to obtain a tooth signal necessary for calculating the engine speed according to the rotation of the target wheel 40 ( tooth time signal).

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 tooth detection time information. Then, the engine speed is output from the calculated angular speed.

The controller 20 not only controls the engine speed by controlling the energized state of the fuel injector 60 and the ignition coil 50 according to the driver's demand for acceleration or deceleration through manipulation of the accelerator pedal (not shown), but also the crankshaft. From the tooth time signal of each sensor 10, a change in engine speed of one engine cycle, which is a misfire analysis target, is analyzed. Then, misfire is diagnosed using the analysis result.

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

연소압 미생성

피스톤 속도 감소

크랭크축 회전 모멘텀 감소로 나타나며, 이로 인해 투스 타임이 길어지고 엔진 속도는 감소한다. 즉, 실화가 발생하면 엔진을 구동시키는 에너지원이 발생하지 않아 엔진 속도가 감소하므로, 한 사이클에서의 엔진 속도를 분석하면 실화 여부를 진단할 수 있다.The misfire was due to unburned fuel on the explosion stroke.

No combustion pressure

reduce piston speed

It manifests as a decrease in crankshaft rotational momentum, which results in longer tooth times and reduced engine speed. That is, when a misfire occurs, since an energy source for driving the engine is not generated and the engine speed decreases, it is possible to diagnose misfire by analyzing the engine speed in one cycle.

According to the present invention, a misfire occurring in an engine can be accurately and quickly diagnosed/detected by using the characteristics of change in engine speed in the event of a misfire. In particular, in a multi-cylinder engine, it is possible to diagnose/detect whether a misfire has occurred for each cylinder.

To this end, the controller 20 includes a linear trend removal unit 21, a speed trend line generator 22, and a misfire diagnosis unit 23 for diagnosing misfire based on speed trend line information.

The linear detrend unit 21 removes a linear trend from the tooth signal output by the crank angle sensor 10 during one cycle. This is because, if the linear trend is not removed from the signal data output by the crank angle sensor 10, the post oscillation phenomenon that appears immediately after a misfire occurs may affect engine speed fluctuations for each cylinder.

If the post oscillation phenomenon that appears immediately after a misfire affects engine speed fluctuations for each maneuver, accurate and precise diagnosis may be difficult in diagnosing a misfire. Therefore, it is preferable to remove the effect of the Post Oscillation phenomenon immediately after a misfire on the engine speed in advance by removing the linear trend from the output signal data of the crank angle sensor 10 collected during one cycle.

In other words, removing the linear trend from all tooth signals in one cycle means subtracting these average values from the engine speed calculated from all tooth signals in one cycle.

Figure 2 (a) is a graph showing the engine speed change over time before removing the linear trend from the tooth signal data output from the crank angle sensor, Figure 2 (b) is the engine speed change after removing the linear trend is a graph showing

The speed trend line generation unit 22 generates a speed trend line for each cylinder using tooth signals at two specific positions preset for each cylinder among the tooth signals from which the linear trend has been removed. For example, in the case of a 4-cylinder engine having 4 cylinders, a total of 4 speed trend lines are generated for each cylinder in one cycle. In the same way, in the case of a 6-cylinder engine, a total of 6 trend lines are generated for each start in one cycle.

As a preferred example, the two specific positions at which the tooth signals necessary for generating the speed trend line are collected may be the rotational positions of the target wheel 40 set corresponding to the respective crankshaft rotational positions at the beginning of the intake stroke and the end of the exhaust stroke for each cylinder. For example, in the case of a 4-cylinder engine having 4 cylinders, the rotational position of the target wheel 40 may correspond to the rotational position of the crankshaft at the beginning of the intake stroke and the end of the exhaust stroke for each cylinder in one cycle.

Referring to FIG. 3, a process of generating a speed trend line according to a preferred example will be described.

3 is an exemplary diagram for explaining the speed trend line generation process, and the number 1 (Cyl #1), number 3 (Cyl #3), number 4 (Cyl #4), and number 2 (Cyl #2) cylinders (cylinders) Change in engine speed over time (x-axis direction) after Linear Detrend by classifying the tooth signal (crankshaft angle) output by the crank angle sensor 10 for each cylinder in a four-cylinder engine in which combustion occurs sequentially It is the experimental data shown as (y-axis direction).

In FIG. 3, the time lapse of the x-axis is represented by the crankshaft angle, which can be replaced by a tooth signal. That is, if the crankshaft angle is 180 degrees, it corresponds to the 30th tooth signal, if it is 360 degrees, it corresponds to the 60th tooth signal, if it is 540 degrees, it corresponds to the 90th tooth signal, and if it is 720 degrees, it corresponds to the 120th tooth signal.

Referring to FIG. 3, the speed trend line L1 is a point P1 on the speed curve including the engine speed component and time component calculated from the tooth signal at the beginning of the intake stroke for each cylinder, and the tooth signal at the end of the exhaust stroke for each cylinder. It can be generated by connecting another point (P2) on the speed curve including the engine speed component calculated from and the time component.

More specifically, in FIG. 3 , P1 is a point including an engine speed component on the y-axis and a time component on the x-axis, and P2 also includes an engine speed component on the y-axis and a time component of another value on the x-axis. Since it includes points, the speed trend line L1 can be obtained through a simple equation (an equation for obtaining a straight line passing through two points).

In FIG. 3, since the x-axis and the y-axis represent time and engine speed, respectively, the slope of the speed trend line L1 has a dimension of engine angular acceleration, and the slope of the speed trend line is the engine between the beginning of the intake stroke and the end of the exhaust stroke for each cylinder. It quantifies the change in speed, that is, the magnitude of the engine angular velocity.

Of course, the generation of the speed trend line described above is not limited thereto as a preferred embodiment of the present invention. That is, as a preferred example of the process of generating the speed trend line, a method of using tooth signals at the beginning of the intake stroke and the end of the exhaust stroke has been shown and described as an example, but the two points used in generating the speed trend line are illustrated in FIG. It does not mean that it is limited to points.

The two points used in generating the speed trend line are that the engine speed decrease pattern due to the non-generation of an energy source in the event of a misfire on the engine speed curve of FIG. 3 can be clearly distinguished from the engine speed increase pattern in normal ignition and can be expressed. You just have to cheat. In other words, the two points only need to be the points that can best express the decrease in speed due to misfiring.

Information on the speed trend line L1 generated by the speed trend line generation unit 22 is provided to the misfire diagnosis unit 23 . The misfire diagnosis unit 23 extracts the slope of the speed trend line L1 from the provided information (speed trend line). Then, by analyzing the slope of the extracted speed trend line (L1), misfiring for each cylinder is diagnosed. Preferably, misfiring is diagnosed by comparing the slope of the speed trend line L1 with a threshold.

The speed trend line L1 is a line connecting two different points on the engine curve. Therefore, the corresponding speed trend line L1 on the engine curve illustrated in FIG. 3 naturally includes a slope value. Therefore, the misfire diagnosis unit 23 extracts the slope of the speed trend line L1 and compares the slope of the extracted speed trend line L1 with a preset threshold value to diagnose misfire.

In normal ignition, an energy source that accelerates the engine speed is generated in the explosion stroke of each cylinder. On the other hand, if a misfire occurs, there is no additional energy to accelerate the engine speed. Therefore, the slope of the speed trend line L1 appears in a distinctly different aspect in misfiring and normal ignition, as shown in FIG. 3 . Therefore, it is possible to accurately diagnose whether a misfiring has occurred or not with only the slope information of the speed trend line for each cylinder in one cycle.

The misfire diagnosis unit 23 may diagnose a misfire when the slope of the speed trend line L1 is less than the threshold value. Conversely, if the slope of the speed trend line (L1) is equal to or greater than the threshold value, normal ignition can be diagnosed. That is, an algorithm for diagnosing a misfire according to whether the slope extracted from the speed trend line L1 is smaller than a preset threshold may be included.

The threshold value, which is the criterion for determining misfire, is determined by obtaining the slope of the speed trend line that can distinguish normal ignition and misfire by engine load and speed (rpm) through simulation or repeated experiments in the same simulated environment. The value may be a value stored in a dedicated map in the form of an MxN matrix for the two factors of the engine load and engine speed (rpm). Depending on the distribution of misfire diagnostic index values, M and N may be defined as specific integers.

That is, when the current engine load and speed are input, a threshold value stored in a cell of a matrix corresponding to the current engine load and speed condition may be selected from the dedicated map and output as the threshold value.

Meanwhile, among the two factors, engine torque may be used instead of the engine load.

4 is experimental data obtained by extracting the slope of the speed trend line for each cylinder of a 4-cylinder engine. When a misfire is artificially caused by blocking fuel injection of a predetermined cylinder (cylinder) at a preset timing while changing the engine load and speed. It is a three-dimensional graph showing the slope extracted from the star velocity trend line.

As shown in FIG. 4, looking at the distribution of points meaning the slope extracted from the speed trend line for each cylinder during engine operation, the points appearing in normal ignition (slope of the speed trend line for each cylinder during normal ignition) and the points appearing during misfiring ( In case of misfiring, it can be seen that the slope of the speed trend line for each cylinder) is divided and distributed to the extent that it can be clearly distinguished based on a specific plane.

For reference, in FIG. 4, countless points distributed in the upper region of the graph based on a specific plane indicate the slope extracted from the speed trend line for each cylinder during normal ignition, and countless points distributed in the lower region instantaneously control fuel injection. These points indicate the slope extracted from the speed trend line for each cylinder when a misfire is artificially caused by blocking.

As such, the slope of the speed trend line for each normal ignition and misfire is clearly distinguished based on a specific value (the slope value of the speed trend line constituting the plane expressed as 'Threshold plane' in FIG. 4). That is, it can be clearly seen through the experimental data of FIG. 4 that the normal ignition and misfire areas are clearly distinguished based on the specific value that varies little by little depending on the engine load and speed.

Therefore, points (slope values of the speed trend line) existing on the specific threshold plane are extracted from the experimental data of FIG. If data is converted into a matrix form, recorded on a dedicated map, and used as a threshold value, the threshold value is output according to the current engine speed and load situation, so misfires for each cylinder can be accurately diagnosed/detected.

The threshold is a value obtained through simulation or repeated experiments of a simulated environment using a reference vehicle. When these threshold values are applied to target vehicles of the same vehicle type and used, the slope of the speed trend line may vary because the threshold value is slightly different depending on the condition of the vehicle and the state of use.

Accordingly, in the present invention, a misfiring can be diagnosed more accurately because a preset threshold value can be corrected in response to a slope of a speed trend line that varies depending on the state of the target vehicle.

To this end, the controller ( ) of the engine misfire diagnosis apparatus according to an embodiment of the present invention has a threshold value correction unit that corrects the threshold value when the slope of the generated speed trend line is different from the slope of the pre-stored speed trend line by a predetermined value or more. (24) is included.

More specifically, referring to FIG. 5 , the threshold correction unit 24 calculates the slope of the speed trend line DL in the normal ignition state stored in advance and the slope of the speed trend line RL actually generated in the normal ignition state. If there is a difference of more than a certain value, the threshold value may be corrected accordingly.

That is, the inclination of the speed trend line may be different even for the same type of vehicle because the non-uniformity of the reciprocating motion of the piston of the engine, the torsional vibration of the crankshaft, and the machining tolerance of the tooth are slightly different for each vehicle.

Accordingly, the threshold value may be corrected by initially driving the target vehicle.

Alternatively, even when the vehicle is used for a long period of time, since the slope of the speed trend line may vary depending on the condition of the vehicle, the threshold value may be corrected for a certain period or mileage at a certain period.

5 is a graph showing a speed trend line DL in a pre-stored steady ignition state for cylinder #1 and a speed trend line RL in a steady ignition state actually generated in cylinder #1.

As shown in FIG. 5 , the slope of the speed trend line DL in the normal ignition state stored in advance and the speed trend line RL actually generated in the normal ignition state may vary depending on the target vehicle.

In this case, the threshold correction unit 24 subtracts the slope value of the speed trend line DL in the normal ignition state stored in advance from the slope value of the speed trend line RL generated in the normal ignition state. In addition to the threshold value, the threshold value can be calibrated.

Through this, the threshold value can be corrected according to the current state of the target vehicle, and thus misfire can be more accurately diagnosed.

According to the embodiment of the present invention reviewed above, some information on engine characteristics that can clearly distinguish normal ignition from misfire (intake stroke for each cylinder, initial engine speed and exhaust stroke, which can be known from the signal output from the crank angle sensor) It is possible to diagnose misfiring only with the final engine speed).

In other words, by diagnosing/detecting a misfire with only the minimum essential information that can clearly determine whether or not there is a misfire, it is possible to diagnose/detect a misfire with high accuracy while simplifying the process for diagnosing/detecting a misfire, and without additional configuration of the software. It has the advantage of low development cost because it can be implemented only with

Moreover, since misfires are diagnosed by comparing the slope of the speed trend line with the threshold value for each cylinder, it is possible to accurately diagnose and detect the number of misfires during one cycle of the engine as well as the cylinder where the misfire occurred, that is, the cylinder position. There are advantages.

In addition, by comparing the speed trend line in the normal ignition state actually generated in the currently running target vehicle with the pre-stored speed trend line in the normal ignition state of the reference vehicle, if the slope value differs by more than a certain value, a threshold value equal to the difference value is set. It can be corrected, so misfiring can be diagnosed more accurately.

6 is a flowchart schematically illustrating a method for diagnosing a misfire in an engine according to an embodiment of the present invention, and FIG. 7 is a flowchart schematically illustrating a threshold value correction step in the method for diagnosing a misfire in an engine.

1, 6, and 7, the method for diagnosing engine misfire according to an embodiment of the present invention is a tooth time signal output by the crank angle sensor 10 recognizing a tooth of a target wheel. ) as a method for diagnosing misfire of the engine, including a linear trend removal step (S100), a speed trend line generation step (S200), a misfire diagnosis step (S300), and a threshold correction step (S400).

In the linear trend removal step (S100), the rotation of the target wheel 40 is detected during one cycle, and the linear trend is removed from the tooth signal output by the crank angle sensor 10 (Linear Detrend). This is because, if the linear trend is not removed from the signal data output by the crank angle sensor 10, the post oscillation phenomenon that appears immediately after a misfire occurs may affect engine speed fluctuations for each cylinder.

In some cases, in the linear trend removal step (S100), the tooth signal of the crank angle sensor 10 is culled at regular intervals to reduce the amount of signal data to be processed, thereby greatly reducing the computational load to be borne by the controller Downsampling process may be included. In this case, the maximum downsampling may be a case in which tooth signals are collected only at the beginning of the intake stroke and the end of the exhaust stroke for each cylinder, and at locations where the maximum and minimum values of engine speed appear.

In the speed trend line generation step (S200), a speed trend line for each cylinder is generated using tooth signals at two specific positions for each cylinder among the tooth signals from which the linear trend has been removed through the linear trend removal step (S100). For example, in the case of a 4-cylinder engine, a total of 4 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-cylinder or multi-cylinder engine.

Preferably, the two specific positions at which the tooth signals necessary for generating the speed trend line are collected may be the rotational positions of the target wheel set corresponding to the respective crankshaft rotational positions at the beginning of the intake stroke and the end of the exhaust stroke for each cylinder. For example, in the case of a 4-cylinder engine having 4 cylinders, the rotational position of the target wheel may correspond to the rotational position of the crankshaft at the beginning of the intake stroke and the end of the exhaust stroke for each cylinder in one cycle.

Referring to FIG. 3, the speed trend line L1 is a point P1 on the speed curve including the engine speed component and time component calculated from the tooth signal at the beginning of the intake stroke for each cylinder, and the tooth signal at the end of the exhaust stroke for each cylinder. It can be generated by connecting another point (P2) on the speed curve including the engine speed component calculated from and the time component.

In the misfire diagnosis step (S300), a slope is extracted from the speed trend line for each cylinder generated in the speed trend line generation step (S200), and misfire is diagnosed for each cylinder by analyzing the extracted slope. Preferably, a misfire is diagnosed by comparing the slope extracted from the speed trend line for each cylinder generated in the speed trend line generation step (S200) with a threshold value recorded in a recording device (eg, a memory storing the dedicated map described above). do.

In normal ignition, an energy source that accelerates the engine speed is generated in the explosion stroke of each cylinder. On the other hand, if a misfire occurs, there is no additional energy to accelerate the engine speed. Therefore, the slope of the speed trend line, as shown in FIG. 3, appears in a distinctly different aspect in misfiring and normal ignition. Therefore, it is possible to accurately diagnose whether or not a misfire has occurred with only the slope information of the speed trend line for each maneuver.

In the misfire diagnosis step (S300), if the slope of the speed trend line extracted for each cylinder during one cycle is less than the threshold value, misfire is diagnosed, and if the slope of the speed trend line is equal to or greater than the threshold value, normal ignition is determined. can be diagnosed

The threshold value, which is the criterion for determining whether or not there is a misfire, obtains the slope of the speed trend line for distinguishing normal ignition and misfire for each engine load and speed (rpm) through simulation or repeated experiments in the same simulated environment, The obtained values may be converted into data and stored in a matrix form for the two factors of the engine load and engine speed (rpm) in a dedicated map.

The threshold value correction step (S400) is a step of correcting the threshold value when the slope of the generated speed trend line is different from the slope of the pre-stored speed trend line by a predetermined value or more.

In the threshold value correction step (S400), when the slope of the speed trend line generated in the normal ignition state differs from the slope of the speed trend line in the pre-stored normal ignition state by more than a predetermined value, the threshold value is corrected in response thereto. can

More specifically, in the threshold value correction step (S400), the slope of the speed trend line generated in the normal ignition state is calculated (S410), and the speed in the normal ignition state is stored in advance from the slope value of the speed trend line generated in the normal ignition state. If the value obtained by subtracting the slope of the trend line is greater than or equal to a preset predetermined value (eg in S420), the slope value of the speed trend line in the steady ignition state stored in advance is calculated from the slope value of the speed trend line generated in the steady ignition state at the preset threshold. It can be made to correct the threshold value by adding the subtracted correction value.

Here, if the value obtained by subtracting the slope value of the speed trend line in the steady ignition state stored in advance from the slope value of the speed trend line generated in the steady ignition state is less than a predetermined value (No in S420), the threshold value is preset without correcting Continue to use the existing threshold value.

Misfiring can be more accurately diagnosed according to the currently running target vehicle through the threshold value correction.

In the present invention, a 4-cylinder engine has been taken as an example to diagnose whether a misfire has occurred and a misfire location has been described as an example. It should be noted that it can be extended and applied to various types of engines, such as multi-cylinder engines of 2 or more cylinders, for example, 6-cylinder, 8-cylinder, and 16-cylinder engines.

Although the present invention has been described in detail through specific examples, this is for explaining the present invention in detail, the present invention is not limited thereto, and the present invention is within the technical spirit of the present invention. It is clear that modification or improvement is possible by the person.

All simple modifications or changes of the present invention fall within the scope of the present invention, and the specific protection scope of the present invention will be clarified by the appended claims.

10: crank angle sensor
20: Controller
21: linear trend removal unit
22: speed trend line generation unit
23: misfire diagnosis unit
24: threshold correction unit
30: crankshaft
40: target wheel
50: ignition coil
60: fuel injector

Claims (10)

An engine misfire diagnosis method for diagnosing misfire of an engine using a tooth time signal output from a crank angle sensor,
a linear detrend step of removing a linear trend from a tooth signal output from the crank angle sensor during one cycle;
A speed trend line generation step of generating a speed trend line from tooth signals at two specific positions set in advance among the tooth signals from which the linear trend has been removed;
a misfire diagnosis step of diagnosing misfire by comparing the slope of the speed trend line with a preset threshold; and
a threshold value correction step of correcting the threshold value in response to a difference between the slope of the speed trend line generated in the steady ignition state and the slope of the speed trend line in the steady ignition state stored in advance by a predetermined value or more;
Misfire diagnosis method of an engine comprising a.
delete According to claim 1,
In the threshold value correction step,
A method for diagnosing a misfire of an engine, characterized in that the correction value obtained by subtracting the slope value of the speed trend line in the steady ignition state stored in advance from the slope value of the speed trend line generated in the steady ignition state is added to a preset threshold value and corrected.
According to claim 1,
The speed trend line generation step,
A point on the engine speed curve including the engine speed component calculated from the tooth signal at the beginning of the intake stroke and the time component at the beginning of the intake stroke;
A method for diagnosing a misfire of an engine, characterized in that a speed trend line is generated by connecting another point on an engine speed curve including an engine speed component calculated from a tooth signal at the end of an exhaust stroke and a time component at the end of an exhaust stroke.
According to claim 1,
The misfire diagnosis step,
Misfiring is diagnosed when the slope of the speed trend line is less than the threshold value, and normal ignition is diagnosed when the slope is equal to or greater than the threshold value.
A crank angle sensor disposed around a target wheel of an engine crankshaft to generate a tooth time signal necessary for calculating an engine speed; and
A controller that analyzes engine speed change in one cycle from the tooth signal of the crank angle sensor and diagnoses misfire using the analysis result;
The controller,
a linear trend removal unit for removing a linear trend from a tooth signal output from the crank angle sensor during one cycle;
a speed trend line generation unit for generating a speed trend line for each cylinder using tooth signals at two specific positions preset for each cylinder among tooth signals from which the linear trend has been removed;
a misfire diagnosis unit for diagnosing misfire by comparing the slope of the generated speed trend line with a preset threshold; and
a threshold correction unit correcting the threshold value in response to a difference between the slope of the speed trend line generated in the steady ignition state and the slope of the speed trend line in the steady ignition state stored in advance;
Engine misfire diagnosis device comprising a.
delete According to claim 6,
The threshold correction unit,
An engine misfire diagnosis device characterized by adding a correction value obtained by subtracting the slope value of the speed trend line in the normal ignition state stored in advance from the slope value of the speed trend line generated in the normal ignition state to a preset threshold value and correcting it.
According to claim 6,
The speed trend line generation unit,
A point on the engine speed curve including the engine speed component calculated from the tooth signal at the beginning of the intake stroke and the time component at the beginning of the intake stroke;
An engine misfire diagnosis device, characterized in that for generating a speed trend line by connecting another point on an engine speed curve including an engine speed component calculated from the tooth signal at the end of the exhaust stroke and a time component at the end of the exhaust stroke.
According to claim 6,
The misfire diagnosis unit,
Misfiring is diagnosed when the slope of the speed trend line is less than the threshold value, and normal ignition is diagnosed when the slope is equal to or greater than the threshold value.

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